Electrode for electrolysis, laminate, wound body, electrolyzer, method for producing electrolyzer, method for renewing electrode, method for renewing laminate, and method for producing wound body

Abstract

The present invention relates to an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body. An electrode for electrolysis according to one aspect of the present invention has a mass per unit area of 48 mg / cm2 or less and a force applied per unit mass-unit area of 0.08 N / mg·cm2 or more.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No. 16 / 495,571, which is a U.S. National Stage Entry of PCT / JP2018 / 011535, filed Mar. 22, 2018, which claims priority to JP App. Nos. 2017-056524 and 2017-056525, each filed Mar. 22, 2017, and JP App. Nos. 2018-053146, 2018-053139, 2018-053145, 2018-053231, 2018-053144, 2018-053217, and 2018-053149, each filed Mar. 20, 2018. The disclosure of each of these documents is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body.BACKGROUND ART

[0003] For electrolysis of an alkali metal chloride aqueous solution such as salt solution and electrolysis of water, methods by use of an electrolyzer including a membrane, more specifically an ion exchange membrane or microporous membrane have been employed. This electrolyzer includes many electrolytic cells connected in series therein, in many cases. A membrane is interposed between each of electrolytic cell to perform electrolysis. In an electrolytic cell, a cathode chamber including a cathode and an anode chamber including an anode are disposed back to back with a partition wall (back plate) interposed therebetween or via pressing by means of press pressure, bolt tightening, or the like.

[0004] The anode and the cathode for use in these electrolyzers now are each fixed to the anode chamber or the cathode chamber of an electrolytic cell by a method such as welding and folding, and thereafter, stored or transported to customers. Meanwhile, each membrane in a state of being singly wound around a vinyl chloride (VC) pipe is stored or transported to customers. Each customer arranges the electrolytic cell on the frame of an electrolyzer and interposes the membrane between electrolytic cells to assemble the electrolyzer. In this manner, electrolytic cells are produced, and an electrolyzer is assembled by each customer. Patent Literatures 1 and 2 each disclose a structure formed by integrating a membrane and an electrode as a structure applicable to such an electrolyzer.CITATION LISTPatent LiteraturePatent Literature 1

[0005] Japanese Patent Laid-Open No. 58-048686Patent Literature 2

[0006] Japanese Patent Laid-Open No. 55-148775SUMMARY OF INVENTIONTechnical Problem

[0007] When electrolysis operation is started and continued, each part deteriorates and electrolytic performance are lowered due to various factors, and each part is replaced at a certain time point. The membrane can be easily renewed by extracting from an electrolytic cell and inserting a new membrane. In contrast, the anode and the cathode are fixed to the electrolytic cell, and thus, there is a problem of occurrence of an extremely complicated work on renewing the electrode, in which the electrolytic cell is removed from the electrolyzer and conveyed to a dedicated renewing plant, fixing such as welding is removed and the old electrode is striped off, then a new electrode is placed and fixed by a method such as welding, and the cell is conveyed to the electrolysis plant and placed back to the electrolyzer. It is considered herein that the structure formed by integrating a membrane and an electrode via thermal compression described in Patent Literatures 1 and 2 is used for the renewing described above, but the structure, which can be produced at a laboratory level relatively easily, is not easily produced so as to be adapted to an electrolytic cell in an actual commercially-available size (e.g., 1.5 m in length, 3 m in width). Moreover, electrolytic performance (such as electrolysis voltage, current efficiency, and common salt concentration in caustic soda) and durability are extremely poor, and chlorine gas and hydrogen gas are generated on the electrode interfacing the membrane. Thus, when used in electrolysis for a long period, complete delamination occurs, and the structure cannot be practically used.

[0008] The present invention has been made in view of the above problems possessed by the conventional art and is intended to provide an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body below.(First Object)

[0009] It is an object of the present invention to provide an electrode for electrolysis, a laminate, and a wound body that make transport and handling easier, markedly simplify a work when a new electrolyzer is started or a degraded electrode is renewed, and furthermore also can maintain or improve the electrolytic performance.(Second Object)

[0010] It is an object of the present invention to provide a laminate that can improve the work efficiency during electrode renewing in an electrolyzer and further can exhibit excellent electrolytic performance also after renewing.(Third Object)

[0011] It is an object of the present invention to provide a laminate that can improve the work efficiency during electrode renewing in an electrolyzer and further can exhibit excellent electrolytic performance also after renewing, from a viewpoint different from the second object described above.(Fourth Object)

[0012] It is a fourth object of the present invention to provide an electrolyzer, a method for producing an electrolyzer, and a method for renewing a laminate that have excellent electrolytic performance as well as can prevent damage of a membrane.(Fifth Object)

[0013] It is an object of the present invention to provide a method for producing an electrolyzer, a method for renewing an electrode, and a method for producing a wound body that can improve the work efficiency during electrode renewing in an electrolyzer.(Sixth Object)

[0014] It is an object of the present invention to provide a method for producing an electrolyzer that can improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from the fifth object described above.(Seventh Object)

[0015] It is an object of the present invention to provide a method for producing an electrolyzer that can improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from the fifth and sixth objects described above.Solution to Problem

[0016] As a result of the intensive studies by the present inventors to achieve the first object, production of an electrode for electrolysis that has a small mass per unit area and can be bonded to a membrane such as an ion exchange membrane and a microporous membrane or a degraded electrode with a weak force makes transport and handling easier, can markedly simplify a work when a new electrolyzer is started or a degraded part is renewed, and furthermore can markedly improve the characteristics in comparison with the electrolytic performance in the conventional art. Additionally, the present inventors have found that the characteristics can be equivalent to or be improved than the electrolytic performance of a conventional electrolytic cell, for which renewing work is complicated, thereby having completed the present invention.

[0017] That is, the present invention includes the following.[1]

[0018] An electrode for electrolysis having a mass per unit area of 48 mg / cm2 or less and a force applied per unit mass-unit area of 0.08 N / mg·cm2 or more.[2]

[0019] The electrode for electrolysis according to [1], wherein the electrode for electrolysis comprises a substrate for electrode for electrolysis and a catalytic layer, and the substrate for electrode for electrolysis has a thickness of 300 μm or less.[3]

[0020] The electrode for electrolysis according to [1] or [2], wherein a proportion measured by a method (3) below is 75% or more:[Method (3)]

[0021] A membrane (170 mm square), which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced, and a sample of electrode for electrolysis (130 mm square) are laminated in this order; and the laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then a proportion (%) of an area of a portion, in which the sample of electrode for electrolysis is in close contact with the membrane obtained by applying the inorganic material particles and the binder to both the surfaces of the membrane of the perfluorocarbon polymer into which the ion exchange group is introduced, is measured.[4]

[0022] The electrode for electrolysis according to any of [1] to [3], wherein the electrode for electrolysis has a porous structure and has an opening ratio of 5 to 90%.[5]

[0023] The electrode for electrolysis according to any of [1] to [4], wherein the electrode has a porous structure and has an opening ratio of 10 to 80%.[6]

[0024] The electrode for electrolysis according to any of [1] to [5], wherein the electrode for electrolysis has a thickness of 315 μm or less.[7]

[0025] The electrode for electrolysis according to any of [1] to [6], wherein a value obtained by measuring the electrode for electrolysis by a method (A) below is 40 mm or less:[Method (A)]

[0026] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.[8]

[0027] The electrode for electrolysis according to any one of [1] to [7], wherein a ventilation resistance is 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s.[9]

[0028] The electrode for electrolysis according to any of [1] to [8], wherein the electrode comprises at least one element selected from nickel (Ni) and titanium (Ti).

[10]

[0029] A laminate comprising the electrode for electrolysis according to any of [1] to [9].

[11]

[0030] A wound body comprising the electrode for electrolysis according to any of [1] to [9] or the laminate according to

[10] .

[0031] As a result of the intensive studies to achieve the second object, the present inventors have found that a laminate that includes an electrode to be bonded to a membrane such as an ion exchange membrane and a microporous membrane and to a feed conductor such as a degraded existing electrode with a weak force makes transport and handling easier, can markedly simplify a work when a new electrolyzer is started or a degraded part is renewed, and furthermore can also maintain or improve the electrolytic performance, thereby having completed the present invention.

[0032] That is, the present invention includes the following aspects.[2-1]

[0033] A laminate comprising:

[0034] an electrode for electrolysis, and

[0035] a membrane or feed conductor in contact with the electrode for electrolysis,

[0036] wherein a force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2.[2-2]

[0037] The laminate according to [2-1], wherein the force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is more than 0.005 N / mg·cm2.[2-3]

[0038] The laminate according to [2-1] or [2-2], wherein the feed conductor is a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, or a foamed metal.[2-4]

[0039] The laminate according to any of [2-1] to [2-3], comprising, as at least one surface layer of the membrane, a layer comprising a mixture of hydrophilic oxide particles and a polymer into which ion exchange groups are introduced.[2-5]

[0040] The laminate according to any of [2-1] to [2-4], wherein a liquid is interposed between the electrode for electrolysis and the membrane or feed conductor.

[0041] As a result of the intensive studies to achieve the third object, the present inventors have found that the problems described above can be solved by a laminate in which a membrane and an electrode for electrolysis are partially fixed, thereby having completed the present invention.

[0042] That is, the present invention includes the following aspects.[3-1]

[0043] A laminate comprising:

[0044] a membrane, and

[0045] an electrode for electrolysis fixed in at least one region of a surface of the membrane,

[0046] wherein a proportion of the region on the surface of the membrane is more than 0% and less than 93%.[3-2]

[0047] The laminate according to [3-1], wherein the electrode for electrolysis comprises at least one catalytic component selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy.[3-3]

[0048] The laminate according to [3-1] or [3-2], wherein at least a portion of the electrode for electrolysis penetrates the membrane and thereby is fixed in the region.[3-4]

[0049] The laminate according to any one of [3-1] to [3-3], wherein at least a portion of the electrode for electrolysis is located inside the membrane and thereby fixed in the region.[3-5]

[0050] The laminate according to any one of [3-1] to [3-4], further comprising a fixing member for fixing the membrane and the electrode for electrolysis.[3-6]

[0051] The laminate according to [3-5], wherein at least a portion of the fixing member externally grips the membrane and the electrode for electrolysis.[3-7]

[0052] The laminate according to [3-5] or [3-6], wherein at least a portion of the fixing member fixes the membrane and the electrode for electrolysis by magnetic force.[3-8]

[0053] The laminate according to any one of [3-1] to [3-7], wherein the membrane comprises an ion exchange membrane comprising a surface layer comprising an organic resin, and the organic resin is present in the region.[3-9]

[0054] The laminate according to any one of [3-1] to [3-8], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having an EW different from that of the first ion exchange resin layer.[3-10]

[0055] The laminate according to any one of [3-1] to [3-8], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having a functional group different from that of the first ion exchange resin layer.

[0056] As a result of the intensive studies to achieve the fourth object, the present inventors have found that the problems described above can be solved by sandwiching at least a portion of a laminate of a membrane and an electrode for electrolysis between an anode side gasket and a cathode side gasket, thereby having completed the present invention.

[0057] That is, the present invention includes the following aspects.[4-1]

[0058] An electrolyzer comprising:

[0059] an anode,

[0060] an anode frame that supports the anode,

[0061] an anode side gasket that is arranged on the anode frame,

[0062] a cathode that is opposed to the anode,

[0063] a cathode frame that supports the cathode,

[0064] a cathode side gasket that is arranged on the cathode frame and is opposed to the anode side gasket, and

[0065] a laminate of a membrane and an electrode for electrolysis, the laminate being arranged between the anode side gasket and the cathode side gasket,

[0066] wherein at least a portion of the laminate is sandwiched between the anode side gasket and the cathode side gasket, and

[0067] a ventilation resistance is 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of a temperature of 24° C., a relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s.[4-2]

[0068] The electrolyzer according to [4-1], wherein the electrode for electrolysis has a thickness of 315 μm or less.[4-3]

[0069] The electrolyzer according to [4-1] or [4-2], wherein a value obtained by measuring the electrode for electrolysis by a method (A) below is 40 mm or less:[4-Method (A)]

[0070] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.[4-4]

[0071] The electrolyzer according to any of [4-1] to [4-3], wherein a mass per unit area of the electrode for electrolysis is 48 mg / cm2 or less.[4-5]

[0072] The electrolyzer according to any of [4-1] to [4-4], wherein a force applied per unit mass-unit area of the electrode for electrolysis is more than 0.005 N / mg·cm2.[4-6]

[0073] The electrolyzer according to any of [4-1] to [4-5], wherein an outermost perimeter of the laminate is located farther outside than an outermost perimeter each of the anode side gasket and the cathode side gasket in a direction of a conducting surface.[4-7]

[0074] The electrolyzer according to any of [4-1] to [4-6], wherein the electrode for electrolysis comprises at least one catalytic component selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy.[4-8]

[0075] The electrolyzer according to any of [4-1] to [4-7], wherein at least a portion of the electrode for electrolysis penetrates the membrane and thereby is fixed in the laminate.[4-9]

[0076] The electrolyzer according to any of [4-1] to [4-7], wherein at least a portion of the electrode for electrolysis is located inside the membrane and thereby fixed in the laminate.[4-10]

[0077] The electrolyzer according to any of [4-1] to [4-9], wherein the laminate further comprises a fixing member for fixing the membrane and the electrode for electrolysis.[4-11]

[0078] The electrolyzer according to [4-10], wherein, in the laminate, at least a portion of the fixing member penetrates and thereby fixes the membrane and the electrode for electrolysis.[4-12]

[0079] The electrolyzer according to [4-10] or [4-11], wherein, in the laminate, the fixing member comprises a soluble material that is soluble in a electrolyte solution.[4-13]

[0080] The electrolyzer according to any of [4-10] to [4-12], wherein, in the laminate, at least a portion of the fixing member externally grips the membrane and the electrode for electrolysis.[4-14]

[0081] The electrolyzer according to any of [4-10] to [4-13], wherein, in the laminate, at least a portion of the fixing member fixes the membrane and the electrode for electrolysis by magnetic force.[4-15]

[0082] The electrolyzer according to any of [4-1] to [4-14], wherein the membrane comprises an ion exchange membrane comprising a surface layer comprising an organic resin, and the electrode for electrolysis is fixed by the organic resin.[4-16]

[0083] The electrolyzer according to any of [4-1] to [4-15], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having an EW different from that of the first ion exchange resin layer.[4-17]

[0084] A method for producing the electrolyzer according to any of [4-1] to [4-16], the method comprising:

[0085] a step of sandwiching the laminate between the anode side gasket and the cathode side gasket.[4-18]

[0086] A method for renewing the laminate in the electrolyzer according to any of [4-1] to [4-16], the method comprising:

[0087] a step of separating the laminate from the anode side gasket and the cathode side gasket to thereby remove the laminate from the electrolyzer, and

[0088] a step of sandwiching a new laminate between the anode side gasket and the cathode side gasket.

[0089] As a result of the intensive studies to achieve the fifth object, the present inventors have found that the problems described above can be solved by use of an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane, being in a wound body form, thereby having completed the present invention.

[0090] That is, the present invention includes the following aspects.[5-1]

[0091] A method for producing a new electrolyzer by arranging an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode,

[0092] wherein the electrode for electrolysis or the laminate, being in a wound body form, is used.[5-2]

[0093] The method for producing the electrolyzer according to [5-1], comprising a step (A) of retaining the electrode for electrolysis or the laminate in a wound state to thereby obtain the wound body.[5-3]

[0094] The method for producing the electrolyzer according to [5-1] or [5-2], comprising a step (B) of releasing the wound state of the wound body.[5-4]

[0095] The method for producing the electrolyzer according to [5-3], comprising a step (C) of arranging the electrode for electrolysis or the laminate on a surface of at least one of the anode and the cathode after the step (B).[5-5]

[0096] A method for renewing an existing electrode by using an electrode for electrolysis, wherein the electrode for electrolysis being in a wound body form is used.[5-6]

[0097] The method for renewing the electrode according to [5-5], comprising a step (A′) of retaining the electrode for electrolysis in a wound state to thereby obtain the wound body.[5-7]

[0098] The method for renewing the electrode according to [5-5] or [5-6], comprising a step (B′) of releasing the wound state of the wound body.[5-8]

[0099] The method for renewing the electrode according to [5-7], comprising a step (C′) of arranging the electrode for electrolysis on a surface of the existing electrode after the step (B′).[5-9]

[0100] A method for producing a wound body to be used for renewing an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode, the method comprising:

[0101] a step of winding an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane to thereby obtain the wound body.

[0102] As a result of the intensive studies to achieve the sixth object, the present inventors have found that the problems described above can be solved by integrating an electrode for electrolysis with a new membrane at a temperature at which the membrane does not melt, thereby having completed the present invention.

[0103] That is, the present invention includes the following aspects.[6-1]

[0104] A method for producing a new electrolyzer by arranging a laminate in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode, the method comprising:

[0105] a step (A) of integrating an electrode for electrolysis with a new membrane at a temperature at which the membrane does not melt to thereby obtain the laminate, and

[0106] a step (B) of replacing the membrane in the existing electrolyzer by the laminate after the step (A).[6-2]

[0107] The method for producing the electrolyzer according to [6-1], wherein the integration is carried out under normal pressure.

[0108] As a result of the intensive studies to achieve the seventh object, the present inventors have found that the problems described above can be solved by an operation in an electrolyzer frame, thereby having completed the present invention.

[0109] That is, the present invention includes the following aspects.[7-1]

[0110] A method for producing a new electrolyzer by arranging a laminate comprising an electrode for electrolysis and a new membrane in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, a membrane that is fixed between the anode and the cathode, and an electrolyzer frame that supports the anode, the cathode, and the membrane, the method comprising:

[0111] a step (A) of releasing a fixing of the membrane in the electrolyzer frame, and

[0112] a step (B) of replacing the membrane by the laminate after the step (A).[7-2]

[0113] The method for producing the electrolyzer according to [7-1], wherein the step (A) is carried out by sliding the anode and the cathode in an arrangement direction thereof, respectively.[7-3]

[0114] The method for producing the electrolyzer according to [7-1] or [7-2], wherein the laminate is fixed in the electrolyzer frame by pressing from the anode and the cathode after the step (B).[7-4]

[0115] The method for producing the electrolyzer according to any of [7-1] to [7-3], wherein the laminate is fixed on a surface of at least one of the anode and the cathode at a temperature at which the laminate does not melt in the step (B).[7-5]

[0116] A method for producing a new electrolyzer by arranging an electrode for electrolysis in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, a membrane that is fixed between the anode and the cathode, and an electrolyzer frame that supports the anode, the cathode, and the membrane, the method comprising:

[0117] a step (A) of releasing a fixing of the membrane in the electrolyzer frame, and

[0118] a step (B′) of arranging the electrode for electrolysis between the membrane and the anode or the cathode after the step (A).Advantageous Effects of Invention

[0119] (1) According to the electrode for electrolysis of the present invention, it is possible to make transport and handling easier, to markedly simplify a work when a new electrolyzer is started or a degraded electrode is renewed, and furthermore, to also maintain or improve the electrolytic performance.

[0120] (2) According to the laminate of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer and furthermore, to exhibit excellent electrolytic performance also after renewing.

[0121] (3) According to the laminate of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer and further, to develop excellent electrolytic performance also after renewing, from a viewpoint different from (2) described above.

[0122] (4) According to electrolyzer of the present invention, the electrolyzer has excellent electrolytic performance as well as can prevent damage of the membrane.

[0123] (5) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer.

[0124] (6) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from (5) described above.

[0125] (7) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from (5) and (6) described above.BRIEF DESCRIPTION OF DRAWINGS

[0126] FIG. 1 illustrates a cross-sectional schematic view of an electrode for electrolysis according to one embodiment of the present invention.

[0127] FIG. 2 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane.

[0128] FIG. 3 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0129] FIG. 4 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0130] FIG. 5 illustrates a cross-sectional schematic view of an electrolytic cell.

[0131] FIG. 6 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0132] FIG. 7 illustrates a schematic view of an electrolyzer.

[0133] FIG. 8 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0134] FIG. 9 illustrates a cross-sectional schematic view of a reverse current absorber included in the electrolytic cell.

[0135] FIG. 10 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0136] FIG. 11 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0137] FIG. 12 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0138] FIG. 13 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0139] FIG. 14 illustrates a schematic view of elastic deformation test of the electrode described in Examples.

[0140] FIG. 15 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0141] FIG. 16 illustrates a schematic view of an electrode produced in Comparative Example 13.

[0142] FIG. 17 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 13 on a nickel mesh feed conductor.

[0143] FIG. 18 illustrates a schematic view of an electrode produced in Comparative Example 14.

[0144] FIG. 19 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 14 on a nickel mesh feed conductor.

[0145] FIG. 20 illustrates a schematic view of an electrode produced in Comparative Example 15.

[0146] FIG. 21 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 15 on a nickel mesh feed conductor.

[0147] FIG. 22 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0148] FIG. 23 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane.

[0149] FIG. 24 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0150] FIG. 25 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0151] FIG. 26 illustrates a cross-sectional schematic view of an electrolytic cell.

[0152] FIG. 27 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0153] FIG. 28 illustrates a schematic view of an electrolyzer.

[0154] FIG. 29 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0155] FIG. 30 illustrates a cross-sectional schematic view of a reverse current absorber included in the electrolytic cell.

[0156] FIG. 31 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0157] FIG. 32 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0158] FIG. 33 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0159] FIG. 34 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0160] FIG. 35 illustrates a schematic view of elastic deformation test of the electrode described in Examples.

[0161] FIG. 36 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0162] FIG. 37 illustrates a schematic view of an electrode produced in Example 34.

[0163] FIG. 38 illustrates a schematic view of a structure used for placing the electrode produced in Example 34 on a nickel mesh feed conductor.

[0164] FIG. 39 illustrates a schematic view of an electrode produced in Example 35.

[0165] FIG. 40 illustrates a schematic view of a structure used for placing the electrode produced in Example 35 on a nickel mesh feed conductor.

[0166] FIG. 41 illustrates a schematic view of an electrode produced in Example 36.

[0167] FIG. 42 illustrates a schematic view of a structure used for placing the electrode produced in Example 36 on a nickel mesh feed conductor.

[0168] FIG. 43 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0169] FIG. 44 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0170] FIG. 45 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0171] FIG. 46 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0172] FIG. 47A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis penetrates a membrane and thereby is fixed. FIG. 47B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 47A.

[0173] FIG. 48A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis is located inside the membrane and thereby fixed. FIG. 48B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 48A.

[0174] FIGS. 49A to 49C illustrate cross-sectional schematic views of a laminate illustrating an aspect in which a yarn-like fixing member is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0175] FIG. 50 illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which an organic resin is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0176] FIG. 51A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of a fixing member externally grips a membrane and an electrode for electrolysis to fix them. FIG. 51B illustrates a cross-sectional schematic view of the laminate illustrating an aspect in which at least a portion of a fixing member fixes the membrane and the electrode for electrolysis by magnetic force.

[0177] FIG. 52 illustrates a cross-sectional schematic view of an electrolytic cell.

[0178] FIG. 53 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0179] FIG. 54 illustrates a schematic view of an electrolyzer.

[0180] FIG. 55 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0181] FIG. 56 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0182] FIG. 57 illustrates an explanatory view showing a laminate in Example 1.

[0183] FIG. 58 illustrates an explanatory view showing a laminate in Example 2.

[0184] FIG. 59 illustrates an explanatory view showing a laminate in Example 3.

[0185] FIG. 60 illustrates an explanatory view showing a laminate in Example 4.

[0186] FIG. 61 illustrates an explanatory view showing a laminate in Example 5.

[0187] FIG. 62 illustrates an explanatory view showing a laminate in Example 6.

[0188] FIG. 63 illustrates a cross-sectional schematic view of an electrolytic cell.

[0189] FIG. 64A illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series in a conventional electrolyzer. FIG. 64B illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series in the electrolyzer of the present embodiment.

[0190] FIG. 65 illustrates a schematic view of an electrolyzer.

[0191] FIG. 66 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0192] FIG. 67 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0193] FIG. 68 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0194] FIG. 69 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0195] FIG. 70 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0196] FIG. 71 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0197] FIG. 72 illustrates an explanatory view for explaining the positional relation between the laminate and the gaskets.

[0198] FIG. 73 illustrates an explanatory view for explaining the positional relation between the laminate and the gaskets.

[0199] FIG. 74A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis penetrates a membrane and thereby is fixed. FIG. 74B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 12A.

[0200] FIG. 75A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis is located inside the membrane and thereby fixed. FIG. 75B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 75A.

[0201] FIGS. 76A to 76C illustrate cross-sectional schematic views of a laminate illustrating an aspect in which a yarn-like fixing member is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0202] FIG. 77 illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which an organic resin is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0203] FIG. 78A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of a fixing member externally grips a membrane and an electrode for electrolysis to fix them. FIG. 78B illustrates a cross-sectional schematic view of the laminate illustrating an aspect in which at least a portion of a fixing member fixes the membrane and the electrode for electrolysis by magnetic force.

[0204] FIG. 79 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0205] FIG. 80 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0206] FIG. 81 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0207] FIG. 82 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0208] FIG. 83 illustrates a schematic view of flexibility evaluation of the electrode described in Examples.

[0209] FIG. 84 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0210] FIG. 85 illustrates a schematic view of an electrode produced in Example 35.

[0211] FIG. 86 illustrates a schematic view of a structure used for placing the electrode produced in Example 35 on a nickel mesh feed conductor.

[0212] FIG. 87 illustrates a schematic view of an electrode produced in Example 36.

[0213] FIG. 88 illustrates a schematic view of a structure used for placing the electrode produced in Example 36 on a nickel mesh feed conductor.

[0214] FIG. 89 illustrates a schematic view of an electrode produced in Example 37.

[0215] FIG. 90 illustrates a schematic view of a structure used for placing the electrode produced in Example 37 on a nickel mesh feed conductor.

[0216] FIG. 91 illustrates a cross-sectional schematic view of an electrolytic cell.

[0217] FIG. 92 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0218] FIG. 93 illustrates a schematic view of an electrolyzer.

[0219] FIG. 94 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0220] FIG. 95 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0221] FIG. 96 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0222] FIG. 97 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0223] FIG. 98 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0224] FIG. 99 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0225] FIG. 100 illustrates a schematic view of a laminate produced in Example 1.

[0226] FIG. 101 illustrates a schematic view of the case where the laminate produced in Example 1 is wound to form a wound body.

[0227] FIG. 102 illustrates a schematic view of a laminate produced in Example 4.

[0228] FIG. 103 illustrates a cross-sectional schematic view of an electrolytic cell.

[0229] FIG. 104 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0230] FIG. 105 illustrates a schematic view of an electrolyzer.

[0231] FIG. 106 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0232] FIG. 107 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0233] FIG. 108 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0234] FIG. 109 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0235] FIG. 110 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0236] FIG. 111 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0237] FIG. 112 illustrates a cross-sectional schematic view of an electrolytic cell.

[0238] FIG. 113 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0239] FIG. 114 illustrates a schematic view of an electrolyzer.

[0240] FIG. 115 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0241] FIG. 116 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0242] FIG. 117(A) illustrates a schematic view of an electrolyzer for explaining one example of each step according to a first aspect of the present embodiment.

[0243] FIG. 117(B) illustrates a schematic perspective view corresponding to FIG. 117(A).

[0244] FIG. 118(A) illustrates a schematic view of an electrolyzer for explaining one example of each step according to a second aspect of the present embodiment.

[0245] FIG. 118(B) illustrates a schematic perspective view corresponding to FIG. 118(A).

[0246] FIG. 119 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0247] FIG. 120 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0248] FIG. 121 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0249] FIG. 122 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.DESCRIPTION OF EMBODIMENTS

[0250] Hereinbelow, as for embodiments of the present invention (hereinbelow, may be referred to as the present embodiments), <First embodiment> to <Seventh embodiment> will be each described in detail, with reference to drawings as required. The embodiments below are illustration for explaining the present invention, and the present invention is not limited to the contents below. The accompanying drawings illustrate one example of the embodiments, and embodiments should not be construed to be limited thereto. The present invention may be appropriately modified and carried out within the spirit thereof. In the drawings, positional relations such as top, bottom, left, and right are based on the positional relations shown in the drawing unless otherwise noted. The dimensions and ratios in the drawings are not limited to those shown.First Embodiment

[0251] Here, a first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 21.[Electrode for Electrolysis]

[0252] An electrode for electrolysis of the first embodiment (hereinafter, in the section of <First embodiment>, simply referred to as “the present embodiment”) can provide a good handling property, has a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, and further, has a mass per unit area of 48 mg / cm2 or less from the viewpoint of economy. The mass per unit area is preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less in respect of the above, and furthermore is preferably 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0253] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0254] The electrode for electrolysis of the present embodiment has a force applied per unit mass-unit area of 0.08 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like. The force applied per unit mass-unit area is preferably 0.1 N / (mg·cm2) or more, more preferably 0.14 N / (mg·cm2) or more in respect of the above, and more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0255] From the viewpoint that the electrode for electrolysis of the present embodiment, if being an electrode having a broad elastic deformation region, can provide a better handling property and has a better adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, the thickness of the electrode for electrolysis is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. In the present embodiment, “having a broad elastic deformation region” means that, when an electrode for electrolysis is wound to form a wound body, warpage derived from winding is unlikely to occur after the wound state is released. The thickness of the electrode for electrolysis refers to, when a catalyst layer mentioned below is included, the total thickness of both the substrate for electrode for electrolysis and the catalyst layer.

[0256] The electrode for electrolysis of the present embodiment, which has a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, as described above, can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. For this reason, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated substituting work such as stripping off the electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved. Even in the case where only a feed conductor is placed in a new electrolytic cell (i.e., an electrode including no catalyst layer placed), only attaching the electrode for electrolysis of the present embodiment to the feed conductor enables the electrode to function. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0257] Further, according to the electrode for electrolysis of the present embodiment, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0258] The electrode for electrolysis of the present embodiment can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0259] The force applied can be measured by methods (i) or (ii) described below, which are as described in Examples in detail. As for the force applied, the value obtained by the measurement of the method (i) (also referred to as “the force applied (1)”) and the value obtained by the measurement of the method (ii) (also referred to as “the force applied (2)”) may be the same or different, and either of the values is 0.08 N / (mg·cm2) or more.

[0260] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.[Method (i)]

[0261] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion exchange membrane which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced (170 mm square, the detail of the ion exchange membrane referred to herein is as described in Examples), and a sample of electrode for electrolysis (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. The arithmetic average surface roughness (Ra) of the nickel plate after the blast treatment was 0.7 μm. The specific method for calculating the arithmetic average surface roughness (Ra) is as described in Examples.

[0262] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode for electrolysis in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode for electrolysis is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0263] This average value is divided by the area of the overlapping portion of the sample of electrode for electrolysis and the ion exchange membrane and the mass of the portion overlapping the ion exchange membrane in the sample of electrode for electrolysis to calculate the force applied per unit mass-unit area (1) (N / mg·cm2).

[0264] The force applied per unit mass-unit area (1) obtained by the method (i) is 0.08 N / (mg·cm2) or more, preferably 0.1 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0265] When the electrode for electrolysis of the present embodiment satisfies the force applied (1), the electrode can be integrated with a membrane such as an ion exchange membrane and a microporous membrane, for example, and used. Thus, on renewing the electrode, the substituting work for the cathode and anode fixed on the electrolytic cell by a method such as welding is eliminated, and the work efficiency is markedly improved. Additionally, by use of the electrode for electrolysis of the present embodiment as an electrode integrated with the ion exchange membrane, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0266] On shipping a new electrolytic cell, an electrode fixed on an electrolytic cell has been subjected to catalyst coating conventionally. Since only combination of an electrode having no catalyst coating with the electrode for electrolysis of the present embodiment can allow the electrode to function as an electrode, it is possible to markedly reduce or eliminate the production step and the amount of the catalyst for catalyst coating. A conventional electrode of which catalyst coating is markedly reduced or eliminated can be electrically connected to the electrode for electrolysis of the present embodiment and allowed to serve as a feed conductor for passage of an electric current.[Method (ii)]

[0267] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar to that of the method (i) above) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode for electrolysis in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode for electrolysis is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0268] This average value is divided by the area of the overlapping portion of the sample of electrode for electrolysis and the nickel plate and the mass of the sample of electrode for electrolysis in the portion overlapping the nickel plate to calculate the adhesive force per unit mass-unit area (2)(N / mg·cm2).

[0269] The force applied per unit mass-unit area (2) obtained by the method (ii) is 0.08 N / (mg·cm2) or more, preferably 0.1 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and more preferably 0.14 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0270] The electrode for electrolysis of the present embodiment, if satisfies the force applied (2), can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier. By attaching the electrode for electrolysis of the present embodiment to a degraded electrode, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0271] In the present embodiment, as the liquid included between the membrane such as an ion exchange membrane and a microporous membrane, the electrode for electrolysis or the feed conductor (degraded electrode or electrode having no catalyst coating) and the electrode for electrolysis, any liquid, such as water and organic solvents, can be used as long as the liquid generates a surface tension. The larger the surface tension of the liquid, the larger the force applied between the membrane and the electrode for electrolysis or the metal plate and the electrode for electrolysis. Thus, a liquid having a larger surface tension is preferred. Examples of the liquid include the following (the numerical value in the parentheses is the surface tension of the liquid):

[0272] hexane (20.44 mN / m), acetone (23.30 mN / m), methanol (24.00 mN / m), ethanol (24.05 mN / m), ethylene glycol (50.21 mN / m), and water (72.76 mN / m).

[0273] A liquid having a large surface tension allows the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis to be integrated (to be a laminate) to thereby facilitate renewing of the electrode. The liquid between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis may be present in an amount such that the both adhere to each other by the surface tension. As a result, after the laminate is placed in an electrolytic cell, the liquid, if mixed into the electrolyte solution, does not affect electrolysis itself due to the small amount of the liquid.

[0274] From a practical viewpoint, a liquid having a surface tension of 20 mN / m to 80 mN / m, such as ethanol, ethylene glycol, and water, is preferably used as the liquid. Particularly preferred is water or an alkaline aqueous solution prepared by dissolving caustic soda, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, or the like in water. Alternatively, the surface tension can be adjusted by allowing these liquids to contain a surfactant. When a surfactant is contained, the adhesion between the membrane and the electrode for electrolysis or the metal plate and the electrode for electrolysis varies to enable the handling property to be adjusted. The surfactant is not particularly limited, and both ionic surfactants and nonionic surfactants may be used.

[0275] The electrode for electrolysis of the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The thickness of the substrate for electrode for electrolysis (gauge thickness) is not particularly limited, but is preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further preferably 135 μm or less, further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, being capable of being suitably rolled in a roll and satisfactorily folded, and facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0276] The proportion measured by the following method (2) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 90% or more, more preferably 92% or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and further preferably 95% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (2)]

[0277] An ion exchange membrane (170 mm square) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 280 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode for electrolysis is measured.

[0278] The proportion measured by the following method (3) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 75% or more, more preferably 80% or more from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating and being capable of being suitably rolled in a roll and satisfactorily folded, and is further preferably 90% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (3)]

[0279] An ion exchange membrane (170 mm square) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode for electrolysis is measured.

[0280] The electrode for electrolysis of the present embodiment preferably has, but is not particularly limited to, a porous structure and an opening ratio or void ratio of 5 to 90% or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and preventing accumulation of gas to be generated during electrolysis. The opening ratio is more preferably 10 to 80% or less, further preferably 20 to 75%.

[0281] The opening ratio is a proportion of the opening portions per unit volume. The calculation method may differ depending on that opening portions in submicron size are considered or that only visible openings are considered. In the present embodiment, a volume V was calculated from the values of the gauge thickness, width, and length of the electrode, and further, a weight W was measured to thereby calculate an opening ratio A by the following formula.A=(1-(W / (V×ρ))×100

[0282] ρ is the density of the electrode material (g / cm3). For example, ρ of nickel is 8.908 g / cm3, and ρ of titanium is 4.506 g / cm3. The opening ratio is appropriately adjusted by changing the area of metal to be perforated per unit area in the case of perforated metal, changing the values of the SW (short diameter), LW (long diameter), and feed in the case of expanded metal, changing the line diameter of metal fiber and mesh number in the case of mesh, changing the pattern of a photoresist to be used in the case of electroforming, changing the metal fiber diameter and fiber density in the case of nonwoven fabric, changing the mold for forming voids in the case of foamed metal, or the like.

[0283] The value obtained by measurement by the following method (A) of the electrode for electrolysis in the present embodiment is preferably 40 mm or less, more preferably 29 mm or less, further preferably 10 mm or less, further more preferably 6.5 mm or less from the viewpoint of the handling property. The specific measuring method is as described in Examples.[Method (A)]

[0284] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.

[0285] In the electrode for electrolysis in the present embodiment, the ventilation resistance is preferably 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under the conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s (hereinbelow, also referred to as “measurement condition 1”) (hereinbelow, also referred to as “ventilation resistance 1”). A larger ventilation resistance means that air is unlikely to flow and refers to a state of a high density. In this state, the product from electrolysis remains in the electrode and the reaction substrate is more unlikely to diffuse inside the electrode, and thus, the electrolytic performance (such as voltage) tends to deteriorate. The concentration on the membrane surface tends to increase. Specifically, the caustic concentration increases on the cathode surface, and the supply of brine tends to decrease on the anode surface. As a result, the product accumulates at a high concentration on the interface at which the membrane is in contact with the electrode. This accumulation leads to damage of the membrane and tends to also lead to increase in the voltage and damage of the membrane on the cathode surface and damage of the membrane on the anode surface. In the present embodiment, in order to prevent these defects, the ventilation resistance is preferably set at 24 kPa·s / m or less. From a similar viewpoint as above, the ventilation resistance is more preferably less than 0.19 kPa·s / m, further preferably 0.15 kPa·s / m or less, further more preferably 0.07 kPa·s / m or less.

[0286] In the present embodiment, when the ventilation resistance is larger than a certain value, NaOH generated in the electrode tends to accumulate on the interface between the electrode and the membrane to result in a high concentration in the case of the cathode, and the supply of brine tends to decrease to cause the brine concentration to be lower in the case of the anode. In order to prevent damage to the membrane that may be caused by such accumulation, the ventilation resistance is preferably less than 0.19 kPa·s / m, more preferably 0.15 kPa·s / m or less, further preferably 0.07 kPa·s / m or less.

[0287] In contrast, when the ventilation resistance is low, the area of the electrode is reduced and the electrolysis area is reduced. Thus, the electrolytic performance (such as voltage) tends to deteriorate. When the ventilation resistance is zero, the feed conductor functions as the electrode because no electrode for electrolysis is provided, and the electrolytic performance (such as voltage) tends to markedly deteriorate. From this viewpoint, a preferable lower limit value identified as the ventilation resistance 1 is not particularly limited, but is preferably more than 0 kPa·s / m, more preferably 0.0001 kPa·s / m or more, further preferably 0.001 kPa·s / m or more.

[0288] When the ventilation resistance 1 is 0.07 kPa·s / m or less, a sufficient measurement accuracy may not be achieved because of the measurement method therefor. From this viewpoint, it is also possible to evaluate an electrode for electrolysis having a ventilation resistance 1 of 0.07 kPa·s / m or less by means of a ventilation resistance (hereinbelow, also referred to as “ventilation resistance 2”) obtained by the following measurement method (hereinbelow, also referred to as “measurement condition 2”). That is, the ventilation resistance 2 is a ventilation resistance measured, when the electrode for electrolysis has a size of 50 mm×50 mm, under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 2 cm / s, and a ventilation volume of 4 cc / cm2 / s.

[0289] The specific methods for measuring the ventilation resistances 1 and 2 are described in Examples.

[0290] The ventilation resistances 1 and 2 can be within the range described above by appropriately adjusting an opening ratio, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to smaller ventilation resistances 1 and 2, and a lower opening ratio tends to lead to larger ventilation resistances 1 and 2.

[0291] Hereinbelow, one aspect of the electrode for electrolysis of the present embodiment will be described.

[0292] The electrode for electrolysis according to the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The catalyst layer may be composed of a plurality of layers as shown below or may be a single-layer configuration.

[0293] As shown in FIG. 1, an electrode for electrolysis 100 according to the present embodiment includes a substrate for electrode for electrolysis 10 and a pair of first layers 20 with which both the surfaces of the substrate for electrode for electrolysis 10 are covered. The entire substrate for electrode for electrolysis 10 is preferably covered with the first layers 20. This covering is likely to improve the catalyst activity and durability of the electrode. One first layer 20 may be laminated only on one surface of the substrate for electrode for electrolysis 10.

[0294] Also shown in FIG. 1, the surfaces of the first layers 20 may be covered with second layers 30. The entire first layers 20 are preferably covered by the second layers 30. Alternatively, one second layer 30 may be laminated only one surface of the first layer 20.(Substrate for Electrode for Electrolysis)

[0295] As the substrate for electrode for electrolysis 10, for example, nickel, nickel alloys, stainless steel, and further, valve metals including titanium can be used, although not limited thereto. At least one element selected from nickel (Ni) and titanium (Ti) is preferably included. That is, the substrate for electrode for electrolysis preferably includes at least one element selected from nickel (Ni) and titanium (Ti).

[0296] When stainless steel is used in an alkali aqueous solution of a high concentration, iron and chromium are eluted and the electrical conductivity of stainless steel is of the order of one-tenth of that of nickel. In consideration of the foregoing, a substrate containing nickel (Ni) is preferable as the substrate for electrode for electrolysis.

[0297] Alternatively, when the substrate for electrode for electrolysis 10 is used in a salt solution of a high concentration near the saturation under an atmosphere in which chlorine gas is generated, the material of the substrate for electrode 10 is also preferably titanium having high corrosion resistance.

[0298] The form of the substrate for electrode for electrolysis 10 is not particularly limited, and a form suitable for the purpose can be selected. As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used. Among these, a perforated metal or expanded metal is preferable. Electroforming is a technique for producing a metal thin film having a precise pattern by using photolithography and electroplating in combination. It is a method including forming a pattern on a substrate with a photoresist and electroplating the portion not protected by the resist to provide a metal thin film.

[0299] As for the form of the substrate for electrode for electrolysis, a suitable specification depends on the distance between the anode and the cathode in the electrolyzer. In the case where the distance between the anode and the cathode is finite, an expanded metal or perforated metal form can be used, and in the case of a so-called zero-gap base electrolyzer, in which the ion exchange membrane is in contact with the electrode, a woven mesh produced by knitting thin lines, foamed metal, metal nonwoven fabric, expanded metal, perforated metal, metal porous foil, and the like can be used, although not limited thereto.

[0300] Examples of the substrate for electrode for electrolysis 10 include a metal foil, a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, or a foamed metal.

[0301] As a plate material before processed into a perforated metal or expanded metal, rolled plate materials and electrolytic foils are preferable. An electrolytic foil is preferably further subjected to a plating treatment by use of the same element as the base material thereof, as the post-treatment, to thereby form asperities on the surface thereof.

[0302] The thickness of the substrate for electrode for electrolysis 10 is, as mentioned above, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less, and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0303] In the substrate for electrode for electrolysis, the residual stress during processing is preferably relaxed by annealing the substrate for electrode for electrolysis in an oxidizing atmosphere. It is preferable to form asperities using a steel grid, alumina grid, or the like on the surface of the substrate for electrode for electrolysis followed by an acid treatment to increase the surface area thereof, in order to improve the adhesion to a catalyst layer with which the surface is covered. It is preferable to give a plating treatment by use of the same element as the substrate to increase the surface area.

[0304] To bring the first layer 20 into close contact with the surface of the substrate for electrode for electrolysis 10, the substrate for electrode for electrolysis 10 is preferably subjected to a treatment of increasing the surface area. Examples of the treatment of increasing the surface area include a blast treatment using a cut wire, steel grid, alumina grid or the like, an acid treatment using sulfuric acid or hydrochloric acid, and a plating treatment using the same element to that of the substrate. The arithmetic average surface roughness (Ra) of the substrate surface is not particularly limited, but is preferably 0.05 μm to 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 5 μm.

[0305] Next, a case where the electrode for electrolysis of the present embodiment is used as an anode for common salt electrolysis will be described.(First Layer)

[0306] In FIG. 1, a first layer 20 as a catalyst layer contains at least one of ruthenium oxides, iridium oxides, and titanium oxides. Examples of the ruthenium oxide include RuO2. Examples of the iridium oxide include IrO2. Examples of the titanium oxide include TiO2. The first layer 20 preferably contains two oxides: a ruthenium oxide and a titanium oxide or three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide. This makes the first layer 20 more stable and additionally improves the adhesion with the second layer 30.

[0307] When the first layer 20 contains two oxides: a ruthenium oxide and a titanium oxide, the first layer 20 contains preferably 1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the two oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0308] When the first layer 20 contains three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide, the first layer 20 contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the three oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0309] When the first layer 20 contains at least two of a ruthenium oxide, an iridium oxide, and a titanium oxide, these oxides preferably form a solid solution. Formation of the oxide solid solution allows the electrode for electrolysis 100 to exhibit excellent durability.

[0310] In addition to the compositions described above, oxides of various compositions can be used as long as at least one oxide of a ruthenium oxide, an iridium oxide, and titanium oxide is contained. For example, an oxide coating called DSA®, which contains ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and the like, can be used as the first layer 20.

[0311] The first layer 20 need not be a single layer and may include a plurality of layers. For example, the first layer 20 may include a layer containing three oxides and a layer containing two oxides. The thickness of the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1 to 8 μm.(Second Layer)

[0312] The second layer 30 preferably contains ruthenium and titanium. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0313] The second layer 30 preferably contains a palladium oxide, a solid solution of a palladium oxide and platinum, or an alloy of palladium and platinum. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0314] A thicker second layer 30 can maintain the electrolytic performance for a longer period, but from the viewpoint of economy, the thickness is preferably 0.05 to 3 μm.

[0315] Next, a case where the electrode for electrolysis of the present embodiment is used as a cathode for common salt electrolysis will be described.(First Layer)

[0316] Examples of components of the first layer 20 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0317] When the first layer 20 contains at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal, the platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal preferably contain at least one platinum group metal of platinum, palladium, rhodium, ruthenium, and iridium.

[0318] As the platinum group metal, platinum is preferably contained.

[0319] As the platinum group metal oxide, a ruthenium oxide is preferably contained.

[0320] As the platinum group metal hydroxide, a ruthenium hydroxide is preferably contained.

[0321] As the platinum group metal alloy, an alloy of platinum with nickel, iron, and cobalt is preferably contained.

[0322] Further, as required, an oxide or hydroxide of a lanthanoid element is preferably contained as a second component. This allows the electrode for electrolysis 100 to exhibit excellent durability.

[0323] As the oxide or hydroxide of a lanthanoid element, at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, and dysprosium is preferably contained.

[0324] Further, as required, an oxide or hydroxide of a transition metal is preferably contained as a third component.

[0325] Addition of the third component enables the electrode for electrolysis 100 to exhibit more excellent durability and the electrolysis voltage to be lowered.

[0326] Examples of a preferable combination include ruthenium only, ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum, ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium, ruthenium+praseodymium, ruthenium+praseodymium+platinum, ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium, ruthenium+neodymium+platinum, ruthenium+neodymium+manganese, ruthenium+neodymium+iron, ruthenium+neodymium+cobalt, ruthenium+neodymium+zinc, ruthenium+neodymium+gallium, ruthenium+neodymium+sulfur, ruthenium+neodymium+lead, ruthenium+neodymium+nickel, ruthenium+neodymium+copper, ruthenium+samarium, ruthenium+samarium+manganese, ruthenium+samarium+iron, ruthenium+samarium+cobalt, ruthenium+samarium+zinc, ruthenium+samarium+gallium, ruthenium+samarium+sulfur, ruthenium+samarium+lead, ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium, platinum+palladium+lanthanum+cerium, platinum+iridium, platinum+palladium, platinum+iridium+palladium, platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinum and nickel, alloys of platinum and cobalt, and alloys of platinum and iron.

[0327] When platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal are not contained, the main component of the catalyst is preferably nickel element.

[0328] At least one of nickel metal, oxides, and hydroxides is preferably contained.

[0329] As the second component, a transition metal may be added. As the second component to be added, at least one element of titanium, tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon is preferably contained.

[0330] Examples of a preferable combination include nickel+tin, nickel+titanium, nickel+molybdenum, and nickel+cobalt.

[0331] As required, an intermediate layer can be placed between the first layer 20 and the substrate for electrode for electrolysis 10. The durability of the electrode for electrolysis 100 can be improved by placing the intermediate layer.

[0332] As the intermediate layer, those having affinity to both the first layer 20 and the substrate for electrode for electrolysis 10 are preferable. As the intermediate layer, nickel oxides, platinum group metals, platinum group metal oxides, and platinum group metal hydroxides are preferable. The intermediate layer can be formed by applying and baking a solution containing a component that forms the intermediate layer. Alternatively, a surface oxide layer also can be formed by subjecting a substrate to a thermal treatment at a temperature of 300 to 600° C. in an air atmosphere. Besides, the layer can be formed by a known method such as a thermal spraying method and ion plating method.(Second Layer)

[0333] Examples of components of the first layer 30 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. The first layer 30 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal. Examples of a preferable combination of elements contained in the second layer include the combinations enumerated for the first layer. The combination of the first layer and the second layer may be a combination in which the compositions are the same and the composition ratios are different or may be a combination of different compositions.

[0334] As the thickness of the catalyst layer, the total thickness of the catalyst layer formed and the intermediate layer is preferably 0.01 μm to 20 μm. With a thickness of 0.01 μm or more, the catalyst layer can sufficiently serve as the catalyst. With a thickness of 20 μm or less, it is possible to form a robust catalyst layer that is unlikely to fall off from the substrate. The thickness is more preferably 0.05 μm to 15 μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness is further preferably 0.2 μm to 8 μm.

[0335] The thickness of the electrode, that is, the total thickness of the substrate for electrode for electrolysis and the catalyst layer is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less in respect of the handling property of the electrode. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. The thickness of the electrode can be determined by measurement with a digimatic thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of the substrate for electrode for electrolysis was measured in the same manner as the thickness of the electrode. The thickness of the catalyst layer can be determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode.(Method for Producing Electrode for Electrolysis)

[0336] Next, one embodiment of the method for producing the electrode for electrolysis 100 will be described in detail.

[0337] In the present embodiment, the electrode for electrolysis 100 can be produced by forming the first layer 20, preferably the second layer 30, on the substrate for electrode for electrolysis by a method such as baking of a coating film under an oxygen atmosphere (pyrolysis), or ion plating, plating, or thermal spraying. Among these, the pyrolysis method, plating method, and ion plating method are preferable because the catalyst layer can be formed while deformation of the substrate for electrode for electrolysis is prevented. When the viewpoint of productivity is added, the plating method and pyrolysis method are further preferable. The production method of the present embodiment as mentioned can achieve a high productivity of the electrode for electrolysis 100. Specifically, in the pyrolysis method, a catalyst layer is formed on the substrate for electrode for electrolysis by an application step of applying a coating liquid containing a catalyst, a drying step of drying the coating liquid, and a pyrolysis step of performing pyrolysis. Pyrolysis herein means that a metal salt which is to be a precursor is decomposed by heating into a metal or metal oxide and a gaseous substance. The decomposition product depends on the metal species to be used, type of the salt, and the atmosphere under which pyrolysis is performed, and many metals tend to form oxides in an oxidizing atmosphere. In an industrial process of producing an electrode for electrolysis, pyrolysis is usually performed in air, and a metal oxide or a metal hydroxide is formed in many cases.(Formation of First Layer of Anode)(Application Step)

[0338] The first layer 20 is obtained by applying a solution in which at least one metal salt of ruthenium, iridium, and titanium is dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of ruthenium, iridium, and titanium in the first coating liquid is substantially equivalent to that of the first layer 20.

[0339] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0340] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0341] After being applied onto the substrate for electrode for electrolysis 100, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0342] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Second Layer of Anode)

[0343] The second layer 30, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound and a platinum compound or a solution containing a ruthenium compound and a titanium compound (second coating liquid) onto the first layer 20 and then pyrolyzing the coating liquid in the presence of oxygen.(Formation of First Layer of Cathode by Pyrolysis Method)(Application Step)

[0344] The first layer 20 is obtained by applying a solution in which metal salts of various combination are dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of the metal in the first coating liquid is substantially equivalent to that in the first layer 20. The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as ethanol and butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is, but is not particularly limited to, preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0345] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0346] After being applied onto the substrate for electrode for electrolysis 10, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0347] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further baked for a long period as required, heating in the range of 350° C. to 650° C. for one minute to 90 minutes can further improve the stability of the first layer 20.(Formation of Intermediate Layer)

[0348] The intermediate layer, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound or platinum compound (second coating liquid) onto the substrate and then pyrolyzing the coating liquid in the presence of oxygen. Alternatively, a nickel oxide intermediate layer may be formed on the substrate surface only by heating the substrate, with no solution applied thereon, in the range of 300° C. to 580° C. for one minute to 60 minutes.(Formation of First Layer of Cathode by Ion Plating)

[0349] The first layer 20 can be formed also by ion plating.

[0350] An example includes a method in which the substrate is fixed in a chamber and the metal ruthenium target is irradiated with an electron beam. Evaporated metal ruthenium particles are positively charged in plasma in the chamber to deposit on the substrate negatively charged. The plasma atmosphere is argon and oxygen, and ruthenium deposits as ruthenium oxide on the substrate.(Formation of First Layer of Cathode by Plating)

[0351] The first layer 20 can be formed also by a plating method.

[0352] As an example, when the substrate is used as the cathode and subjected to electrolytic plating in an electrolyte solution containing nickel and tin, alloy plating of nickel and tin can be formed.(Formation of First Layer of Cathode by Thermal Spraying)

[0353] The first layer 20 can be formed also by thermal spraying.

[0354] As an example, plasma spraying nickel oxide particles onto the substrate can form a catalyst layer in which metal nickel and nickel oxide are mixed.

[0355] The electrode for electrolysis of the present embodiment can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. Thus, the electrode can be used as a membrane-integrated electrode. Then, the substituting work for the cathode and anode on renewing the electrode is eliminated, and the work efficiency is markedly improved.

[0356] The electrode for electrolysis of the present embodiment forms a laminate with a membrane such as an ion exchange membrane and a microporous membrane to be an integrated piece of the membrane and the electrode, and then can make the electrolytic performance comparable to or higher than those of a new electrode. The membrane is not particularly limited as long as the membrane can be laminated with the electrode, and will be described in detail below.[Ion Exchange Membrane]

[0357] The ion exchange membrane has a membrane body containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and a coating layer provided on at least one surface of the membrane body. The coating layer contains inorganic material particles and a binder, and the specific surface area of the coating layer is 0.1 to 10 m2 / g. In the ion exchange membrane having such a structure, the influence of gas generated during electrolysis on electrolytic performance is small, and stable electrolytic performance can be exhibited.

[0358] The ion exchange membrane described above includes either one of a sulfonic acid layer having an ion exchange group derived from a sulfo group (a group represented by —SO3−, hereinbelow also referred to as a “sulfonic acid group”) or a carboxylic acid layer having an ion exchange group derived from a carboxyl group (a group represented by —CO2−, hereinbelow also referred to as a “carboxylic acid group”). From the viewpoint of strength and dimension stability, reinforcement core materials are preferably further included.

[0359] The inorganic material particles and binder will be described in detail in the section of description of the coating layer below.

[0360] FIG. 2 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane. An ion exchange membrane 1 has a membrane body 10 containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and coating layers 11a and 11b formed on both the surfaces of the membrane body 10.

[0361] In the ion exchange membrane 1, the membrane body 10 includes a sulfonic acid layer 3 and a carboxylic acid layer 2, and reinforcement core materials 4 enhance the strength and dimension stability. The ion exchange membrane 1, including the sulfonic acid layer 3 and the carboxylic acid layer 2, is suitably used as an ion exchange membrane.

[0362] The ion exchange membrane may include either one of the sulfonic acid layer and the carboxylic acid layer. The ion exchange membrane may not be necessarily reinforced by reinforcement core materials, and the arrangement of the reinforcement core materials is not limited to the example in FIG. 2.(Membrane Body)

[0363] First, the membrane body 10 constituting the ion exchange membrane 1 will be described.

[0364] The membrane body 10 should be one that has a function of selectively allowing cations to permeate and comprises a hydrocarbon polymer or a fluorine-containing polymer having an ion exchange group. Its configuration and material are not particularly limited, and preferred ones can be appropriately selected.

[0365] The hydrocarbon polymer or fluorine-containing polymer having an ion exchange group in the membrane body 10 can be obtained from a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group precursor capable of forming an ion exchange group by hydrolysis or the like. Specifically, for example, after a polymer comprising a main chain of a fluorinated hydrocarbon, having, as a pendant side chain, a group convertible into an ion exchange group by hydrolysis or the like (ion exchange group precursor), and being melt-processable (hereinbelow, referred to as the “fluorine-containing polymer (a)” in some cases) is used to prepare a precursor of the membrane body 10, the membrane body 10 can be obtained by converting the ion exchange group precursor into an ion exchange group.

[0366] The fluorine-containing polymer (a) can be produced, for example, by copolymerizing at least one monomer selected from the following first group and at least one monomer selected from the following second group and / or the following third group. The fluorine-containing polymer (a) can be also produced by homopolymerization of one monomer selected from any of the following first group, the following second group, and the following third group.

[0367] Examples of the monomers of the first group include vinyl fluoride compounds. Examples of the vinyl fluoride compounds include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinyl ethers. Particularly when the ion exchange membrane is used as a membrane for alkali electrolysis, the vinyl fluoride compound is preferably a perfluoro monomer, and a perfluoro monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl ethers is preferable.

[0368] Examples of the monomers of the second group include vinyl compounds having a functional group convertible into a carboxylic acid-type ion exchange group (carboxylic acid group). Examples of the vinyl compounds having a functional group convertible into a carboxylic acid group include monomers represented by CF2═CF(OCF2CYF)s—O(CZF)t—COOR, wherein s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represent F or CF3, and R represents a lower alkyl group (a lower alkyl group is an alkyl group having 1 to 3 carbon atoms, for example).

[0369] Among these, compounds represented by CF2═CF(OCF2CYF)n—O(CF2)m—COOR are preferable. Wherein n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF3, and R represents CH3, C2H5, or C3H7.

[0370] When the ion exchange membrane is used as a cation exchange membrane for alkali electrolysis, a perfluoro compound is preferably at least used as the monomer, but the alkyl group (see the above R) of the ester group is lost from the polymer at the time of hydrolysis, and therefore the alkyl group (R) need not be a perfluoroalkyl group in which all hydrogen atoms are replaced by fluorine atoms.

[0371] Of the above monomers, the monomers represented below are more preferable as the monomers of the second group:

[0372] Examples of the monomers of the third group include vinyl compounds having a functional group convertible into a sulfone-type ion exchange group (sulfonic acid group). As the vinyl compounds having a functional group convertible into a sulfonic acid group, for example, monomers represented by CF2═CFO—X—CF2—SO2F are preferable, wherein X represents a perfluoroalkylene group. Specific examples of these include the monomers represented below:

[0373] Among these, CF2═CFOCF2CF(CF3)OCF2CF2CF2SO2F and CF2═CFOCF2CF(CF3)OCF2CF2SO2F are more preferable.

[0374] The copolymer obtained from these monomers can be produced by a polymerization method developed for homopolymerization and copolymerization of ethylene fluoride, particularly a general polymerization method used for tetrafluoroethylene. For example, in a non-aqueous method, a polymerization reaction can be performed in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound under the conditions of a temperature of 0 to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent such as a perfluorohydrocarbon or a chlorofluorocarbon.

[0375] In the above copolymerization, the type of combination of the above monomers and their proportion are not particularly limited and are selected and determined depending on the type and amount of the functional group desired to be imparted to the fluorine-containing polymer to be obtained. For example, when a fluorine-containing polymer containing only a carboxylic acid group is formed, at least one monomer should be selected from each of the first group and the second group described above and copolymerized. In addition, when a fluorine-containing polymer containing only a sulfonic acid group is formed, at least one monomer should be selected from each of the first group and the third group and copolymerized. Further, when a fluorine-containing polymer having a carboxylic acid group and a sulfonic acid group is formed, at least one monomer should be selected from each of the first group, the second group, and the third group described above and copolymerized. In this case, the target fluorine-containing polymer can be obtained also by separately preparing a copolymer comprising the monomers of the first group and the second group described above and a copolymer comprising the monomers of the first group and the third group described above, and then mixing the copolymers. The mixing proportion of the monomers is not particularly limited, and when the amount of the functional groups per unit polymer is increased, the proportion of the monomers selected from the second group and the third group described above should be increased.

[0376] The total ion exchange capacity of the fluorine-containing copolymer is not particularly limited, but is preferably 0.5 to 2.0 mg equivalent / g, more preferably 0.6 to 1.5 mg equivalent / g. The total ion exchange capacity herein refers to the equivalent of the exchange group per unit weight of the dry resin and can be measured by neutralization titration or the like.

[0377] In the membrane body 10 of the ion exchange membrane 1, a sulfonic acid layer 3 containing a fluorine-containing polymer having a sulfonic acid group and a carboxylic acid layer 2 containing a fluorine-containing polymer having a carboxylic acid group are laminated. By providing the membrane body 10 having such a layer configuration, selective permeability for cations such as sodium ions can be further improved.

[0378] The ion exchange membrane 1 is arranged in an electrolyzer such that, usually, the sulfonic acid layer 3 is located on the anode side of the electrolyzer and the carboxylic acid layer 2 is located on the cathode side of the electrolyzer.

[0379] The sulfonic acid layer 3 is preferably constituted by a material having low electrical resistance and has a membrane thickness larger than that of the carboxylic acid layer 2 from the viewpoint of membrane strength. The membrane thickness of the sulfonic acid layer 3 is preferably 2 to 25 times, more preferably 3 to 15 times that of the carboxylic acid layer 2. The carboxylic acid layer 2 preferably has high anion exclusion properties even if it has a small membrane thickness. The anion exclusion properties here refer to the property of trying to hinder intrusion and permeation of anions into and through the ion exchange membrane 1. In order to raise the anion exclusion properties, it is effective to dispose a carboxylic acid layer having a small ion exchange capacity to the sulfonic acid layer.

[0380] As the fluorine-containing polymer for use in the sulfonic acid layer 3, preferable is a polymer obtained by using CF2═CFOCF2CF(CF3)OCF2CF2SO2F as the monomer of the third group.

[0381] As the fluorine-containing polymer for use in the carboxylic acid layer 2, preferable is a polymer obtained by using CF2═CFOCF2CF(CF2)O(CF2)2COOCH3 as the monomer of the second group.(Coating Layer)

[0382] The ion exchange membrane has a coating layer on at least one surface of the membrane body. As shown in FIG. 2, in the ion exchange membrane 1, coating layers 11a and 11b are formed on both the surfaces of the membrane body 10.

[0383] The coating layers contain inorganic material particles and a binder.

[0384] The average particle size of the inorganic material particles is preferably 0.90 μm or more. When the average particle size of the inorganic material particles is 0.90 μm or more, durability to impurities is extremely improved, in addition to attachment of gas. That is, enlarging the average particle size of the inorganic material particles as well as satisfying the value of the specific surface area mentioned above can achieve a particularly marked effect. Irregular inorganic material particles are preferable because the average particle size and specific surface area as above are satisfied. Inorganic material particles obtained by melting and inorganic material particles obtained by grinding raw ore can be used. Inorganic material particles obtained by grinding raw ore can preferably be used.

[0385] The average particle size of the inorganic material particles can be 2 μm or less. When the average particle size of the inorganic material particles is 2 μm or less, it is possible to prevent damage of the membrane due to the inorganic material particles. The average particle size of the inorganic material particle is more preferably 0.90 to 1.2 μm.

[0386] Here, the average particle size can be measured by a particle size analyzer (“SALD2200”, SHIMADZU CORPORATION).

[0387] The inorganic material particles preferably have irregular shapes. Such shapes improve resistance to impurities further. The inorganic material particles preferably have a broad particle size distribution.

[0388] The inorganic material particles preferably contain at least one inorganic material selected from the group consisting of oxides of Group IV elements in the Periodic Table, nitrides of Group IV elements in the Periodic Table, and carbides of Group IV elements in the Periodic Table. From the viewpoint of durability, zirconium oxide particle is more preferable.

[0389] The inorganic material particles are preferably inorganic material particles produced by grinding the raw ore of the inorganic material particles or inorganic material particles, as spherical particles having a uniform diameter, obtained by melt-purifying the raw ore of the inorganic material particles.

[0390] Examples of means for grinding raw ore include, but are not particularly limited to, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, grain mills, hammer mills, pellet mills, VSI mills, Wiley mills, roller mills, and jet mills. After grinding, the particles are preferably washed. As the washing method, the particles are preferably treated with acid. This treatment can reduce impurities such as iron attached to the surface of the inorganic material particles.

[0391] The coating layer preferably contains a binder. The binder is a component that forms the coating layers by retaining the inorganic material particles on the surface of the ion exchange membrane. The binder preferably contains a fluorine-containing polymer from the viewpoint of durability to the electrolyte solution and products from electrolysis.

[0392] As the binder, a fluorine-containing polymer having a carboxylic acid group or sulfonic acid group is more preferable, from the viewpoint of durability to the electrolyte solution and products from electrolysis and adhesion to the surface of the ion exchange membrane. When a coating layer is provided on a layer containing a fluorine-containing polymer having a sulfonic acid group (sulfonic acid layer), a fluorine-containing polymer having a sulfonic acid group is further preferably used as the binder of the coating layer. Alternatively, when a coating layer is provided on a layer containing a fluorine-containing polymer having a carboxylic acid group (carboxylic acid layer), a fluorine-containing polymer having a carboxylic acid group is further preferably used as the binder of the coating layer.

[0393] In the coating layer, the content of the inorganic material particles is preferably 40 to 90% by mass, more preferably 50 to 90% by mass. The content of the binder is preferably 10 to 60% by mass, more preferably 10 to 50% by mass.

[0394] The distribution density of the coating layer in the ion exchange membrane is preferably 0.05 to 2 mg per 1 cm2. When the ion exchange membrane has asperities on the surface thereof, the distribution density of the coating layer is preferably 0.5 to 2 mg per 1 cm2.

[0395] As the method for forming the coating layer, which is not particularly limited, a known method can be used. An example is a method including applying by a spray or the like a coating liquid obtained by dispersing inorganic material particles in a solution containing a binder.(Reinforcement Core Materials)

[0396] The ion exchange membrane preferably has reinforcement core materials arranged inside the membrane body.

[0397] The reinforcement core materials are members that enhance the strength and dimensional stability of the ion exchange membrane. By arranging the reinforcement core materials inside the membrane body, particularly expansion and contraction of the ion exchange membrane can be controlled in the desired range. Such an ion exchange membrane does not expand or contract more than necessary during electrolysis and the like and can maintain excellent dimensional stability for a long term.

[0398] The configuration of the reinforcement core materials is not particularly limited, and, for example, the reinforcement core materials may be formed by spinning yarns referred to as reinforcement yarns. The reinforcement yarns here refer to yarns that are members constituting the reinforcement core materials, can provide the desired dimensional stability and mechanical strength to the ion exchange membrane, and can be stably present in the ion exchange membrane. By using the reinforcement core materials obtained by spinning such reinforcement yarns, better dimensional stability and mechanical strength can be provided to the ion exchange membrane.

[0399] The material of the reinforcement core materials and the reinforcement yarns used for these is not particularly limited but is preferably a material resistant to acids, alkalis, etc., and a fiber comprising a fluorine-containing polymer is preferable because long-term heat resistance and chemical resistance are required.

[0400] Examples of the fluorine-containing polymer to be used in the reinforcement core materials include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-ethylene copolymers (ETFE), tetrafluoroethylene-hexafluoropropylene copolymers, trifluorochloroethylene-ethylene copolymers, and vinylidene fluoride polymers (PVDF). Among these, fibers comprising polytetrafluoroethylene are preferably used from the viewpoint of heat resistance and chemical resistance.

[0401] The yarn diameter of the reinforcement yarns used for the reinforcement core materials is not particularly limited, but is preferably 20 to 300 deniers, more preferably 50 to 250 deniers. The weave density (fabric count per unit length) is preferably 5 to 50 / inch. The form of the reinforcement core materials is not particularly limited, for example, a woven fabric, a nonwoven fabric, and a knitted fabric are used, but is preferably in the form of a woven fabric. The thickness of the woven fabric to be used is preferably 30 to 250 μm, more preferably 30 to 150 μm.

[0402] As the woven fabric or knitted fabric, monofilaments, multifilaments, or yarns thereof, a slit yarn, or the like can be used, and various types of weaving methods such as a plain weave, a leno weave, a knit weave, a cord weave, and a seersucker can be used.

[0403] The weave and arrangement of the reinforcement core materials in the membrane body are not particularly limited, and preferred arrangement can be appropriately provided considering the size and form of the ion exchange membrane, physical properties desired for the ion exchange membrane, the use environment, and the like.

[0404] For example, the reinforcement core materials may be arranged along one predetermined direction of the membrane body, but from the viewpoint of dimensional stability, it is preferred that the reinforcement core materials be arranged along a predetermined first direction, and other reinforcement core materials be arranged along a second direction substantially perpendicular to the first direction. By arranging the plurality of reinforcement core materials substantially orthogonally inside the membrane body, it is possible to impart better dimensional stability and mechanical strength in many directions. For example, arrangement in which the reinforcement core materials arranged along the longitudinal direction (warp yarns) and the reinforcement core materials arranged along the transverse direction (weft yarns) are woven on the surface side of the membrane body is preferred. The arrangement is more preferably in the form of plain weave driven and woven by allowing warps and wefts to run over and under each other alternately, leno weave in which two warps are woven into wefts while twisted, basket weave driven and woven by inserting, into two or more parallelly-arranged warps, wefts of the same number, or the like, from the viewpoint of dimension stability, mechanical strength and easy-production.

[0405] It is preferred that particularly, the reinforcement core materials be arranged along both directions, the MD (Machine Direction) and TD (Transverse Direction) of the ion exchange membrane. In other words, the reinforcement core materials are preferably plain-woven in the MD and TD. Here, the MD refers to the direction in which the membrane body and various core materials (for example, the reinforcement core materials, reinforcement yarns, and sacrifice yarns described later) are conveyed in an ion exchange membrane production step described later (flow direction), and the TD refers to the direction substantially perpendicular to the MD. Yarns woven along the MD are referred to as MD yarns, and yarns woven along the TD are referred to as TD yarns. Usually, the ion exchange membrane used for electrolysis is rectangular, and in many cases, the longitudinal direction is the MD, and the width direction is the TD. By weaving the reinforcement core materials that are MD yarns and the reinforcement core materials that are TD yarns, it is possible to impart better dimensional stability and mechanical strength in many directions.

[0406] The arrangement interval of the reinforcement core materials is not particularly limited, and preferred arrangement can be appropriately provided considering physical properties desired for the ion exchange membrane, the use environment, and the like.

[0407] The aperture ratio for the reinforcement core materials is not particularly limited, but is preferably 30% or more, more preferably 50% or more and 90% or less. The aperture ratio is preferably 30% or more from the viewpoint of the electrochemical properties of the ion exchange membrane, and preferably 90% or less from the viewpoint of the mechanical strength of the ion exchange membrane.

[0408] The aperture ratio for the reinforcement core materials herein refers to a ratio of a total area of a surface through which substances such as ions (an electrolyte solution and cations contained therein (e.g., sodium ions)) can pass (B) to the area of either one surface of the membrane body (A) (B / A). The total area of the surface through which substances such as ions can pass (B) can refer to the total areas of regions in which in the ion exchange membrane, cations, an electrolytic solution, and the like are not blocked by the reinforcement core materials and the like contained in the ion exchange membrane.

[0409] FIG. 3 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane. FIG. 3, in which a portion of the ion exchange membrane is enlarged, shows only the arrangement of the reinforcement core materials 21 and 22 in the regions, omitting illustration of the other members.

[0410] By subtracting the total area of the reinforcement core materials (C) from the area of the region surrounded by the reinforcement core materials 21 arranged along the longitudinal direction and the reinforcement core materials 22 arranged along the transverse direction, the region including the area of the reinforcement core materials (A), the total area of regions through which substances such as ions can pass (B) in the area of the above-described region (A) can be obtained. That is, the aperture ratio can be determined by the following formula (I):Aperture⁢ ratio=(B) / (A)=((A)-(C)) / (A)(I)

[0411] Among the reinforcement core materials, a particularly preferred form is tape yarns or highly oriented monofilaments comprising PTFE from the viewpoint of chemical resistance and heat resistance. Specifically, reinforcement core materials forming a plain weave in which 50 to 300 denier tape yarns obtained by slitting a high strength porous sheet comprising PTFE into a tape form, or 50 to 300 denier highly oriented monofilaments comprising PTFE are used and which has a weave density of 10 to 50 yarns or monofilaments / inch and has a thickness in the range of 50 to 100 μm are more preferred. The aperture ratio of an ion exchange membrane comprising such reinforcement core materials is further preferably 60% or more.

[0412] Examples of the shape of the reinforcement yarns include round yarns and tape yarns.(Continuous Holes)

[0413] The ion exchange membrane preferably has continuous holes inside the membrane body.

[0414] The continuous holes refer to holes that can be flow paths for ions generated in electrolysis and an electrolyte solution. The continuous holes, which are tubular holes formed inside the membrane body, are formed by dissolution of sacrifice core materials (or sacrifice yarns) described below. The shape, diameter, or the like of the continuous holes can be controlled by selecting the shape or diameter of the sacrifice core materials (sacrifice yarns).

[0415] Forming the continuous holes inside the ion exchange membrane can ensure the mobility of an electrolyte solution on electrolysis. The shape of the continuous holes is not particularly limited, but may be the shape of sacrifice core materials to be used for formation of the continuous holes in accordance with the production method described below.

[0416] The continuous holes are preferably formed so as to alternately pass on the anode side (sulfonic acid layer side) and the cathode side (carboxylic acid layer side) of the reinforcement core materials. With such a structure, in a portion in which continuous holes are formed on the cathode side of the reinforcement core materials, ions (e.g., sodium ions) transported through the electrolyte solution with which the continuous holes are filled can flow also on the cathode side of the reinforcement core materials. As a result, the flow of cations is not interrupted, and thus, it is possible to further reduce the electrical resistance of the ion exchange membrane.

[0417] The continuous holes may be formed along only one predetermined direction of the membrane body constituting the ion exchange membrane, but are preferably formed in both the longitudinal direction and the transverse direction of the membrane body from the viewpoint of exhibiting more stable electrolytic performance.[Production Method]

[0418] A suitable example of a method for producing an ion exchange membrane includes a method including the following steps (1) to (6):

[0419] Step (1): the step of producing a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0420] Step (2): the step of weaving at least a plurality of reinforcement core materials, as required, and sacrifice yarns having a property of dissolving in an acid or an alkali, and forming continuous holes, to obtain a reinforcing material in which the sacrifice yarns are arranged between the reinforcement core materials adjacent to each other,

[0421] Step (3): the step of forming into a film the above fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0422] Step (4): the step of embedding the above reinforcing materials, as required, in the above film to obtain a membrane body inside which the reinforcing materials are arranged,

[0423] Step (5): the step of hydrolyzing the membrane body obtained in the step (4) (hydrolysis step), and

[0424] Step (6): the step of providing a coating layer on the membrane body obtained in the step (5) (application step).

[0425] Hereinafter, each of the steps will be described in detail.Step (1): Step of Producing Fluorine-Containing Polymer

[0426] In the step (1), raw material monomers described in the first group to the third group above are used to produce a fluorine-containing polymer. In order to control the ion exchange capacity of the fluorine-containing polymer, the mixture ratio of the raw material monomers should be adjusted in the production of the fluorine-containing polymer forming the layers.Step (2): Step of Producing Reinforcing Materials

[0427] The reinforcing material is a woven fabric obtained by weaving reinforcement yarns or the like. The reinforcing material is embedded in the membrane to thereby form reinforcement core materials. When an ion exchange membrane having continuous holes is formed, sacrifice yarns are additionally woven into the reinforcing material. The amount of the sacrifice yarns contained in this case is preferably 10 to 80% by mass, more preferably 30 to 70% by mass based on the entire reinforcing material. Weaving the sacrifice yarns can also prevent yarn slippage of the reinforcement core materials.

[0428] As the sacrifice yarns, which have solubility in the membrane production step or under an electrolysis environment, rayon, polyethylene terephthalate (PET), cellulose, polyamide, and the like are used. Monofilaments or multifilaments having a thickness of 20 to 50 deniers and comprising polyvinyl alcohol and the like are also preferred.

[0429] In the step (2), the aperture ratio, arrangement of the continuous holes, and the like can be controlled by adjusting the arrangement of the reinforcement core materials and the sacrifice yarns.Step (3): Step of Film Formation

[0430] In the step (3), the fluorine-containing polymer obtained in the step (1) is formed into a film by using an extruder. The film may be a single-layer configuration, a two-layer configuration of a sulfonic acid layer and a carboxylic acid layer as mentioned above, or a multilayer configuration of three layers or more.

[0431] Examples of the film forming method include the following:

[0432] a method in which a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are separately formed into films; and

[0433] a method in which fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are coextruded into a composite film.

[0434] The number of each film may be more than one. Coextrusion of different films is preferred because of its contribution to an increase in the adhesive strength in the interface.Step (4): Step of Obtaining Membrane Body

[0435] In the step (4), the reinforcing material obtained in the step (2) is embedded in the film obtained in the step (3) to provide a membrane body including the reinforcing material therein. Preferable examples of the method for forming a membrane body include (i) a method in which a fluorine-containing polymer having a carboxylic acid group precursor (e.g., carboxylate functional group) (hereinafter, a layer comprising the same is referred to as the first layer) located on the cathode side and a fluorine-containing polymer having a sulfonic acid group precursor (e.g., sulfonyl fluoride functional group) (hereinafter, a layer comprising the same is referred to as the second layer) are formed into a film by a coextrusion method, and, by using a heat source and a vacuum source as required, a reinforcing material and the second layer / first layer composite film are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure; and (ii) a method in which, in addition to the second layer / first layer composite film, a fluorine-containing polymer having a sulfonic acid group precursor is singly formed into a film (the third layer) in advance, and, by using a heat source and a vacuum source as required, the third layer film, the reinforcement core materials, and the composite film comprising the second layer / first layer are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure.

[0436] Coextrusion of the first layer and the second layer herein contributes to an increase in the adhesive strength at the interface.

[0437] The method including integration under a reduced pressure is characterized by making the third layer on the reinforcing material thicker than that of a pressure-application press method. Further, since the reinforcing material is fixed on the inner surface of the membrane body, the method has a property of sufficiently retaining the mechanical strength of the ion exchange membrane.

[0438] The variations of lamination described here are exemplary, and coextrusion can be performed after a preferred lamination pattern (for example, the combination of layers) is appropriately selected considering the desired layer configuration of the membrane body and physical properties, and the like.

[0439] For the purpose of further improving the electric properties of the ion exchange membrane, it is also possible to additionally interpose a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor between the first layer and the second layer or to use a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor instead of the second layer.

[0440] The method for forming the fourth layer may be a method in which a fluorine-containing polymer having a carboxylic acid group precursor and a fluorine-containing polymer having a sulfonic acid group precursor are separately produced and then mixed or may be a method in which a monomer having a carboxylic acid group precursor and a monomer having a sulfonic acid group precursor are copolymerized.

[0441] When the fourth layer is used as a component of the ion exchange membrane, a coextruded film of the first layer and the fourth layer is formed, in addition to this, the third layer and the second layer are separately formed into films, and lamination may be performed by the method mentioned above. Alternatively, the three layers of the first layer / fourth layer / second layer may be simultaneously formed into a film by coextrusion.

[0442] In this case, the direction in which the extruded film flows is the MD. As mentioned above, it is possible to form a membrane body containing a fluorine-containing polymer having an ion exchange group on a reinforcing material.

[0443] Additionally, the ion exchange membrane preferably has protruded portions composed of the fluorine-containing polymer having a sulfonic acid group, that is, projections, on the surface side composed of the sulfonic acid layer. As a method for forming such projections, which is not particularly limited, a known method also can be employed including forming projections on a resin surface. A specific example of the method is a method of embossing the surface of the membrane body. For example, the above projections can be formed by using release paper embossed in advance when the composite film mentioned above, reinforcing material, and the like are integrated. In the case where projections are formed by embossing, the height and arrangement density of the projections can be controlled by controlling the emboss shape to be transferred (shape of the release paper).(5) Hydrolysis Step

[0444] In the step (5), a step of hydrolyzing the membrane body obtained in the step (4) to convert the ion exchange group precursor into an ion exchange group (hydrolysis step) is performed.

[0445] In the step (5), it is also possible to form dissolution holes in the membrane body by dissolving and removing the sacrifice yarns included in the membrane body with acid or alkali. The sacrifice yarns may remain in the continuous holes without being completely dissolved and removed. The sacrifice yarns remaining in the continuous holes may be dissolved and removed by the electrolyte solution when the ion exchange membrane is subjected to electrolysis.

[0446] The sacrifice yarn has solubility in acid or alkali in the step of producing an ion exchange membrane or under an electrolysis environment. The sacrifice yarns are eluted out to thereby form continuous holes at corresponding sites.

[0447] The step (5) can be performed by immersing the membrane body obtained in the step (4) in a hydrolysis solution containing acid or alkali. An example of the hydrolysis solution that can be used is a mixed solution containing KOH and dimethyl sulfoxide (DMSO).

[0448] The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of 25 to 35% by mass.

[0449] The temperature for hydrolysis is preferably 70 to 100° C. The higher the temperature, the larger can be the apparent thickness. The temperature is more preferably 75 to 100° C.

[0450] The time for hydrolysis is preferably 10 to 120 minutes. The longer the time, the larger can be the apparent thickness. The time is more preferably 20 to 120 minutes.

[0451] The step of forming continuous holes by eluting the sacrifice yarn will be now described in more detail. FIGS. 4(a) and (b) are schematic views for explaining a method for forming the continuous holes of the ion exchange membrane.

[0452] FIGS. 4(a) and (b) show reinforcement yarns 52, sacrifice yarns 504a, and continuous holes 504 formed by the sacrifice yarns 504a only, omitting illustration of the other members such as a membrane body.

[0453] First, the reinforcement yarns 52 that are to constitute reinforcement core materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane are used as interwoven reinforcing materials. Then, in the step (5), the sacrifice yarns 504a are eluted to form the continuous holes 504.

[0454] The above method is simple because the method for interweaving the reinforcement yarns 52 and the sacrifice yarns 504a may be adjusted depending on the arrangement of the reinforcement core materials and continuous holes in the membrane body of the ion exchange membrane.

[0455] FIG. 4(a) exemplifies the plain-woven reinforcing material in which the reinforcement yarns 52 and sacrifice yarns 504a are interwoven along both the longitudinal direction and the lateral direction in the paper, and the arrangement of the reinforcement yarns 52 and the sacrifice yarns 504a in the reinforcing material may be varied as required.(6) Application Step

[0456] In the step (6), a coating layer can be formed by preparing a coating liquid containing inorganic material particles obtained by grinding raw ore or melting raw ore and a binder, applying the coating liquid onto the surface of the ion exchange membrane obtained in the step (5), and drying the coating liquid.

[0457] A preferable binder is a binder obtained by hydrolyzing a fluorine-containing polymer having an ion exchange group precursor with an aqueous solution containing dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) and then immersing the polymer in hydrochloric acid to replace the counterion of the ion exchange group by H+ (e.g., a fluorine-containing polymer having a carboxyl group or sulfo group). Thereby, the polymer is more likely to dissolve in water or ethanol mentioned below, which is preferable.

[0458] This binder is dissolved in a mixed solution of water and ethanol. The volume ratio between water and ethanol is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganic material particles are dispersed with a ball mill into the dissolution liquid thus obtained to thereby provide a coating liquid. In this case, it is also possible to adjust the average particle size and the like of the particles by adjusting the time and rotation speed during the dispersion. The preferable amount of the inorganic material particles and the binder to be blended is as mentioned above.

[0459] The concentration of the inorganic material particles and the binder in the coating liquid is not particularly limited, but a thin coating liquid is preferable. This enables uniform application onto the surface of the ion exchange membrane.

[0460] Additionally, a surfactant may be added to the dispersion when the inorganic material particles are dispersed. As the surfactant, nonionic surfactants are preferable, and examples thereof include HS-210, NS-210, P-210, and E-212 manufactured by NOF CORPORATION.

[0461] The coating liquid obtained is applied onto the surface of the ion exchange membrane by spray application or roll coating to thereby provide an ion exchange membrane.[Microporous Membrane]

[0462] The microporous membrane of the present embodiment is not particularly limited as long as the membrane can be formed into a laminate with the electrode for electrolysis, as mentioned above. Various microporous membranes may be employed.

[0463] The porosity of the microporous membrane of the present embodiment is not particularly limited, but can be 20 to 90, for example, and is preferably 30 to 85. The above porosity can be calculated by the following formula:Porosity=(1-(the⁢ weight⁢ of⁢ the⁢ membrane⁢ in⁢ a⁢ dried⁢ state) / (the⁢ weight⁢ calculated⁢ from⁢ the⁢ volume⁢ calculated⁢ from⁢ the⁢ thickness,width,and⁢ length⁢ of⁢ the⁢ membrane⁢ and⁢ the⁢ density⁢ of⁢ the⁢ membrane⁢ material))×100

[0464] The average pore size of the microporous membrane of the present embodiment is not particularly limited, and can be 0.01 μm to 10 μm, for example, preferably 0.05 μm to 5 μm. With respect to the average pore size, for example, the membrane is cut vertically to the thickness direction, and the section is observed with an FE-SEM. The average pore size can be obtained by measuring the diameter of about 100 pores observed and averaging the measurements.

[0465] The thickness of the microporous membrane of the present embodiment is not particularly limited, and can be 10 μm to 1000 μm, for example, preferably 50 μm to 600 μm. The above thickness can be measured by using a micrometer (manufactured by Mitutoyo Corporation) or the like, for example.

[0466] Specific examples of the microporous membrane as mentioned above include Zirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfon membrane in the present embodiment) and those described in International Publication No. WO 2013-183584 and International Publication No. WO 2016-203701.[Laminate]

[0467] The laminate of the present embodiment comprises the electrode for electrolysis of the present embodiment, and a membrane or feed conductor in contact with the electrode for electrolysis. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0468] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0469] Further, according to the laminate of the present invention, it is possible to maintain the electrolytic performance comparable to those of a new electrode or improve the electrolytic performance. Even in the case where only a feed conductor is placed in a new electrolytic cell (i.e., an electrode including no catalyst layer placed), only attaching the electrode for electrolysis of the present embodiment to the feed conductor enables the electrode to function. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0470] The laminate of the present embodiment can be stored or transported to customers in a state where the laminate is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0471] As the feed conductor of the present embodiment, various substrates mentioned below such as a degraded electrode (i.e., the existing electrode) and an electrode having no catalyst coating can be employed.

[0472] In the laminate of the present embodiment, the force applied per unit mass·unit area of the electrode for electrolysis on the membrane or feed conductor is preferably 0.08 N / (mg·cm2) or more, more preferably 0.1 N / (mg·cm2) or more, further preferably 0.14 N / (mg·cm2) or more, and further more preferably, from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), is 0.2 N / (mg·cm2) or more. The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.[Wound Body]

[0473] The wound body of the present embodiment includes the electrode for electrolysis of the present embodiment or the laminate of the present embodiment. That is, the wound body of the present embodiment is obtained by winding the electrode for electrolysis of the present embodiment or the laminate of the present embodiment. Downsizing the electrode for electrolysis of the present embodiment or the laminate of the present embodiment by winding, as the wound body of the present embodiment, can further improve the handling property.[Electrolyzer]

[0474] The electrolyzer of the present embodiment includes the electrode for electrolysis of the present embodiment. Hereinafter, the case of performing common salt electrolysis by using an ion exchange membrane as the membrane is taken as an example, and one embodiment of the electrolyzer will be described in detail.[Electrolytic Cell]

[0475] FIG. 5 illustrates a cross-sectional view of an electrolytic cell 1.

[0476] The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber 20, a partition wall 30 placed between the anode chamber 10 and the cathode chamber 20, an anode 11 placed in the anode chamber 10, and a cathode 21 placed in the cathode chamber 20. As required, the electrolytic cell 1 has a substrate 18a and a reverse current absorbing layer 18b formed on the substrate 18a and may comprise a reverse current absorber 18 placed in the cathode chamber. The anode 11 and the cathode 21 belonging to the electrolytic cell 1 are electrically connected to each other. In other words, the electrolytic cell 1 comprises the following cathode structure. The cathode structure 40 comprises the cathode chamber 20, the cathode 21 placed in the cathode chamber 20, and the reverse current absorber 18 placed in the cathode chamber 20, the reverse current absorber 18 has the substrate 18a and the reverse current absorbing layer 18b formed on the substrate 18a, as shown in FIG. 9, and the cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode chamber 20 further has a collector 23, a support 24 supporting the collector, and a metal elastic body 22. The metal elastic body 22 is placed between the collector 23 and the cathode 21. The support 24 is placed between the collector 23 and the partition wall 30. The collector 23 is electrically connected to the cathode 21 via the metal elastic body 22. The partition wall 30 is electrically connected to the collector 23 via the support 24. Accordingly, the partition wall 30, the support 24, the collector 23, the metal elastic body 22, and the cathode 21 are electrically connected. The cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode 21 and the reverse current absorbing layer may be directly connected or may be indirectly connected via the collector, the support, the metal elastic body, the partition wall, or the like. The entire surface of the cathode 21 is preferably covered with a catalyst layer for reduction reaction. The form of electrical connection may be a form in which the partition wall 30 and the support 24, the support 24 and the collector 23, and the collector 23 and the metal elastic body 22 are each directly attached and the cathode 21 is laminated on the metal elastic body 22. Examples of a method for directly attaching these constituent members to one another include welding and the like. Alternatively, the reverse current absorber 18, the cathode 21, and the collector 23 may be collectively referred to as a cathode structure 40.

[0477] FIG. 6 illustrates a cross-sectional view of two electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG. 7 shows an electrolyzer 4. FIG. 8 shows a step of assembling the electrolyzer 4. As shown in FIG. 6, an electrolytic cell 1, a cation exchange membrane 2, and an electrolytic cell 1 are arranged in series in the order mentioned. An ion exchange membrane 2 is arranged between the anode chamber of one electrolytic cell 1 among the two electrolytic cells that are adjacent in the electrolyzer and the cathode chamber of the other electrolytic cell 1. That is, the anode chamber 10 of the electrolytic cell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacent thereto is separated by the cation exchange membrane 2. As shown in FIG. 7, the electrolyzer 4 is composed of a plurality of electrolytic cells 1 connected in series via the ion exchange membrane 2. That is, the electrolyzer 4 is a bipolar electrolyzer comprising the plurality of electrolytic cells 1 arranged in series and ion exchange membranes 2 each arranged between adjacent electrolytic cells 1. As shown in FIG. 8, the electrolyzer 4 is assembled by arranging the plurality of electrolytic cells 1 in series via the ion exchange membrane 2 and coupling the cells by means of a press device 5.

[0478] The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 to be connected to a power supply. The anode 11 of the electrolytic cell 1 located at farthest end among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the anode terminal 7. The cathode 21 of the electrolytic cell located at the end opposite to the anode terminal 7 among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the cathode terminal 6. The electric current during electrolysis flows from the side of the anode terminal 7, through the anode and cathode of each electrolytic cell 1, toward the cathode terminal 6. At the both ends of the coupled electrolytic cells 1, an electrolytic cell having an anode chamber only (anode terminal cell) and an electrolytic cell having a cathode chamber only (cathode terminal cell) may be arranged. In this case, the anode terminal 7 is connected to the anode terminal cell arranged at the one end, and the cathode terminal 6 is connected to the cathode terminal cell arranged at the other end.

[0479] In the case of electrolyzing brine, brine is supplied to each anode chamber 10, and pure water or a low-concentration sodium hydroxide aqueous solution is supplied to each cathode chamber 20. Each liquid is supplied from an electrolyte solution supply pipe (not shown in Figure), through an electrolyte solution supply hose (not shown in Figure), to each electrolytic cell 1. The electrolyte solution and products from electrolysis are recovered from an electrolyte solution recovery pipe (not shown in Figure). During electrolysis, sodium ions in the brine migrate from the anode chamber 10 of the one electrolytic cell 1, through the ion exchange membrane 2, to the cathode chamber 20 of the adjacent electrolytic cell 1. Thus, the electric current during electrolysis flows in the direction in which the electrolytic cells 1 are coupled in series. That is, the electric current flows, through the cation exchange membrane 2, from the anode chamber 10 toward the cathode chamber 20. As the brine is electrolyzed, chlorine gas is generated on the side of the anode 11, and sodium hydroxide (solute) and hydrogen gas are generated on the side of the cathode 21.(Anode Chamber)

[0480] The anode chamber 10 has the anode 11 or anode feed conductor 11. When the electrode for electrolysis of the present embodiment is inserted to the anode side, 11 serves as the anode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the anode side, 11 serves as the anode. The anode chamber 10 has an anode-side electrolyte solution supply unit that supplies an electrolyte solution to the anode chamber 10, a baffle plate that is arranged above the anode-side electrolyte solution supply unit so as to be substantially parallel or oblique to the partition wall 30, and an anode-side gas liquid separation unit arranged above the baffle plate to separate gas from the electrolyte solution including the gas mixed.(Anode)

[0481] When the electrode for electrolysis of the present embodiment is not inserted to the anode side, the anode 11 is provided in the frame of the anode chamber 10. As the anode 11, a metal electrode such as so-called DSA® can be used. DSA is an electrode including a titanium substrate of which surface is covered with an oxide comprising ruthenium, iridium, and titanium as components.

[0482] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode Feed Conductor)

[0483] When the electrode for electrolysis of the present embodiment is inserted to the anode side, the anode feed conductor 11 is provided in the frame of the anode chamber 10. As the anode feed conductor 11, a metal electrode such as so-called DSA® can be used, and titanium having no catalyst coating can be also used. Alternatively, DSA having a thinner catalyst coating can be also used. Further, a used anode can be also used.

[0484] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode-Side Electrolyte Solution Supply Unit)

[0485] The anode-side electrolyte solution supply unit, which supplies the electrolyte solution to the anode chamber 10, is connected to the electrolyte solution supply pipe. The anode-side electrolyte solution supply unit is preferably arranged below the anode chamber 10. As the anode-side electrolyte solution supply unit, for example, a pipe on the surface of which aperture portions are formed (dispersion pipe) and the like can be used. Such a pipe is more preferably arranged along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell. This pipe is connected to an electrolyte solution supply pipe (liquid supply nozzle) that supplies the electrolyte solution into the electrolytic cell 1. The electrolyte solution supplied from the liquid supply nozzle is conveyed with a pipe into the electrolytic cell 1 and supplied from the aperture portions provided on the surface of the pipe to inside the anode chamber 10. Arranging the pipe along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell is preferable because the electrolyte solution can be uniformly supplied to inside the anode chamber 10.(Anode-Side Gas Liquid Separation Unit)

[0486] The anode-side gas liquid separation unit is preferably arranged above the baffle plate. The anode-side gas liquid separation unit has a function of separating produced gas such as chlorine gas from the electrolyte solution during electrolysis. Unless otherwise specified, above means the upper direction in the electrolytic cell 1 in FIG. 5, and below means the lower direction in the electrolytic cell 1 in FIG. 5.

[0487] During electrolysis, produced gas generated in the electrolytic cell 1 and the electrolyte solution form a mixed phase (gas-liquid mixed phase), which is then emitted out of the system. Subsequently, pressure fluctuations inside the electrolytic cell 1 cause vibration, which may result in physical damage of the ion exchange membrane. In order to prevent this event, the electrolytic cell 1 of the present embodiment is preferably provided with an anode-side gas liquid separation unit to separate the gas from the liquid. The anode-side gas liquid separation unit is preferably provided with a defoaming plate to eliminate bubbles. When the gas-liquid mixed phase flow passes through the defoaming plate, bubbles burst to thereby enable the electrolyte solution and the gas to be separated. As a result, vibration during electrolysis can be prevented.(Baffle Plate)

[0488] The baffle plate is preferably arranged above the anode-side electrolyte solution supply unit and arranged substantially in parallel with or obliquely to the partition wall 30. The baffle plate is a partition plate that controls the flow of the electrolyte solution in the anode chamber 10. When the baffle plate is provided, it is possible to cause the electrolyte solution (brine or the like) to circulate internally in the anode chamber 10 to thereby make the concentration uniform. In order to cause internal circulation, the baffle plate is preferably arranged so as to separate the space in proximity to the anode 11 from the space in proximity to the partition wall 30. From such a viewpoint, the baffle plate is preferably placed so as to be opposed to the surface of the anode 11 and to the surface of the partition wall 30. In the space in proximity to the anode partitioned by the baffle plate, as electrolysis proceeds, the electrolyte solution concentration (brine concentration) is lowered, and produced gas such as chlorine gas is generated. This results in a difference in the gas-liquid specific gravity between the space in proximity to anode 11 and the space in proximity to the partition wall 30 partitioned by the baffle plate. By use of the difference, it is possible to promote the internal circulation of the electrolyte solution in the anode chamber 10 to thereby make the concentration distribution of the electrolyte solution in the anode chamber 10 more uniform.

[0489] Although not shown in FIG. 5, a collector may be additionally provided inside the anode chamber 10. The material and configuration of such a collector may be the same as those of the collector of the cathode chamber mentioned below. In the anode chamber 10, the anode 11 per se may also serve as the collector.(Partition Wall)

[0490] The partition wall 30 is arranged between the anode chamber 10 and the cathode chamber 20. The partition wall 30 may be referred to as a separator, and the anode chamber 10 and the cathode chamber 20 are partitioned by the partition wall 30. As the partition wall 30, one known as a separator for electrolysis can be used, and an example thereof includes a partition wall formed by welding a plate comprising nickel to the cathode side and a plate comprising titanium to the anode side.(Cathode Chamber)

[0491] In the cathode chamber 20, when the electrode for electrolysis of the present embodiment is inserted to the cathode side, 21 serves as a cathode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, 21 serves as a cathode. When a reverse current absorber is included, the cathode or cathode feed conductor 21 is electrically connected to the reverse current absorber. The cathode chamber 20, similarly to the anode chamber 10, preferably has a cathode-side electrolyte solution supply unit and a cathode-side gas liquid separation unit. Among the components constituting the cathode chamber 20, components similar to those constituting the anode chamber 10 will be not described.(Cathode)

[0492] When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, a cathode 21 is provided in the frame of the cathode chamber 20. The cathode 21 preferably has a nickel substrate and a catalyst layer that covers the nickel substrate. Examples of the components of the catalyst layer on the nickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. The cathode 21 may be subjected to a reduction treatment, as required. As the substrate of the cathode 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0493] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Cathode Feed Conductor)

[0494] When the electrode for electrolysis of the present embodiment is inserted to the cathode side, a cathode feed conductor 21 is provided in the frame of the cathode chamber 20. The cathode feed conductor 21 may be covered with a catalytic component. The catalytic component may be a component that is originally used as the cathode and remains. Examples of the components of the catalyst layer include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. As the substrate of the cathode feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0495] As the feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless, having no catalyst coating may be used.

[0496] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Reverse Current Absorbing Layer)

[0497] A material having a redox potential less noble than the redox potential of the element for the catalyst layer of the cathode mentioned above may be selected as a material for the reverse current absorbing layer. Examples thereof include nickel and iron.(Collector)

[0498] The cathode chamber 20 preferably comprises the collector 23. The collector 23 improves current collection efficiency. In the present embodiment, the collector 23 is a porous plate and is preferably arranged in substantially parallel to the surface of the cathode 21.

[0499] The collector 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The collector 23 may be a mixture, alloy, or composite oxide of these metals. The collector 23 may have any form as long as the form enables the function of the collector and may have a plate or net form.(Metal Elastic Body)

[0500] Placing the metal elastic body 22 between the collector 23 and the cathode 21 presses each cathode 21 of the plurality of electrolytic cells 1 connected in series onto the ion exchange membrane 2 to reduce the distance between each anode 11 and each cathode 21. Then, it is possible to lower the voltage to be applied entirely across the plurality of electrolytic cells 1 connected in series. Lowering of the voltage enables the power consumption to be reduced. With the metal elastic body 22 placed, the pressing pressure caused by the metal elastic body 22 enables the electrode for electrolysis to be stably maintained in place when the laminate including the electrode for electrolysis according to the present invention is placed in the electrolytic cell.

[0501] As the metal elastic body 22, spring members such as spiral springs and coils and cushioning mats may be used. As the metal elastic body 22, a suitable one may be appropriately employed, in consideration of a stress to press the ion exchange membrane and the like. The metal elastic body 22 may be provided on the surface of the collector 23 on the side of the cathode chamber 20 or may be provided on the surface of the partition wall on the side of the anode chamber 10. Both the chambers are usually partitioned such that the cathode chamber 20 becomes smaller than the anode chamber 10. Thus, from the viewpoint of the strength of the frame and the like, the metal elastic body 22 is preferably provided between the collector 23 and the cathode 21 in the cathode chamber 20. The metal elastic body 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium.(Support)

[0502] The cathode chamber 20 preferably comprises the support 24 that electrically connects the collector 23 to the partition wall 30. This can achieve an efficient current flow.

[0503] The support 24 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The support 24 may have any shape as long as the support can support the collector 23 and may have a rod, plate, or net shape. The support 24 has a plate shape, for example. A plurality of supports 24 are arranged between the partition wall 30 and the collector 23. The plurality of supports 24 are aligned such that the surfaces thereof are in parallel to each other. The supports 24 are arranged substantially perpendicular to the partition wall 30 and the collector 23.(Anode Side Gasket and Cathode Side Gasket)

[0504] The anode side gasket is preferably arranged on the frame surface constituting the anode chamber 10. The cathode side gasket is preferably arranged on the frame surface constituting the cathode chamber 20. Electrolytic cells are connected to each other such that the anode side gasket included in one electrolytic cell and the cathode side gasket of an electrolytic cell adjacent to the cell sandwich the ion exchange membrane 2 (see FIGS. 5 and 6). These gaskets can impart airtightness to connecting points when the plurality of electrolytic cells 1 is connected in series via the ion exchange membrane 2.

[0505] The gaskets form a seal between the ion exchange membrane and electrolytic cells. Specific examples of the gaskets include picture frame-like rubber sheets at the center of which an aperture portion is formed. The gaskets are required to have resistance against corrosive electrolyte solutions or produced gas and be usable for a long period. Thus, in respect of chemical resistance and hardness, vulcanized products and peroxide-crosslinked products of ethylene-propylene-diene rubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) are usually used as the gaskets. Alternatively, gaskets of which region to be in contact with liquid (liquid contact portion) is covered with a fluorine-containing resin such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may be employed as required. These gaskets each may have an aperture portion so as not to inhibit the flow of the electrolyte solution, and the shape of the aperture portion is not particularly limited. For example, a picture frame-like gasket is attached with an adhesive or the like along the peripheral edge of each aperture portion of the anode chamber frame constituting the anode chamber 10 or the cathode chamber frame constituting the cathode chamber 20. Then, for example, in the case where the two electrolytic cells 1 are connected via the ion exchange membrane 2 (see FIG. 6), each electrolytic cell 1 onto which the gasket is attached should be tightened via ion exchange membrane 2. This tightening can prevent the electrolyte solution, alkali metal hydroxide, chlorine gas, hydrogen gas, and the like generated from electrolysis from leaking out of the electrolytic cells 1.(Ion Exchange Membrane 2)

[0506] The ion exchange membrane 2 is as described in the section of the ion exchange membrane described above.(Water Electrolysis)

[0507] The electrolyzer of the present embodiment, as an electrolyzer in the case of electrolyzing water, has a configuration in which the ion exchange membrane in an electrolyzer for use in the case of electrolyzing common salt mentioned above is replaced by a microporous membrane. The raw material to be supplied, which is water, is different from that for the electrolyzer in the case of electrolyzing common salt mentioned above. As for the other components, components similar to that of the electrolyzer in the case of electrolyzing common salt can be employed also in the electrolyzer in the case of electrolyzing water. Since chlorine gas is generated in the anode chamber in the case of common salt electrolysis, titanium is used as the material of the anode chamber, but in the case of water electrolysis, only oxygen gas is generated in the anode chamber. Thus, a material identical to that of the cathode chamber can be used. An example thereof is nickel. For anode coating, catalyst coating for oxygen generation is suitable. Examples of the catalyst coating include metals, oxides, and hydroxides of the platinum group metals and transition metal group metals. For example, elements such as platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron can be used.Second Embodiment

[0508] Here, a second embodiment of the present invention will be described in detail with reference to FIGS. 22 to 42.[Laminate]

[0509] A laminate of the second embodiment (hereinafter, in the section of <Second embodiment>, simply referred to as “the present embodiment”) comprises an electrode for electrolysis and a membrane or feed conductor in contact with the electrode for electrolysis, wherein a force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0510] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the existing electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0511] Further, according to the laminate of the present invention, it is possible to maintain or improve the electrolytic performance of a new electrode. Thus, the electrode fixed on a conventional new electrolytic cell and serving as an anode and / or a cathode is only required to serve as a feed conductor. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0512] The laminate of the present embodiment can be stored or transported to customers in a state where the laminate is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0513] As the feed conductor of the present embodiment, various substrates mentioned below such as a degraded electrode (i.e., the existing electrode) and an electrode having no catalyst coating can be employed.

[0514] The laminate of the present embodiment may have partially a fixed portion as long as the laminate has the configuration described above. That is, in the case where the laminate of the present embodiment has a fixed portion, a portion not having the fixing is subjected to measurement, and the resulting force applied per unit mass-unit area of the electrode for electrolysis should be less than 1.5 N / mg·cm2.[Electrode for Electrolysis]

[0515] The electrode for electrolysis of the present embodiment has a force applied per unit mass-unit area of less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a feed conductor (a degraded electrode and an electrode having no catalyst coating), and the like. The force is further preferably 1.1 N / mg·cm2 or less, further preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less.

[0516] From the viewpoint of further improving the electrolytic performance, the force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / mg·cm2 or more, further more preferably 0.14 N / (mg·cm2) or more. The force is further more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0517] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.

[0518] The mass per unit area is preferably 48 mg / cm2 or less, more preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and economy, and furthermore is preferably 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0519] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0520] The force applied can be measured by methods (i) or (ii) described below, which are as described in Examples, specifically. As for the force applied, the value obtained by the measurement of the method (i) (also referred to as “the force applied (1)”) and the value obtained by the measurement of the method (ii) (also referred to as “the force applied (2)”) may be the same or different, and either of the values is less than 1.5 N / mg·cm2.[Method (i)]

[0521] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion exchange membrane which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced (170 mm square, the detail of the ion exchange membrane referred to herein is as described in Examples), and a sample of electrode (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. The arithmetic average surface roughness (Ra) of the nickel plate after the blast treatment is 0.5 to 0.8 μm. The specific method for calculating the arithmetic average surface roughness (Ra) is as described in Examples.

[0522] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0523] This average value is divided by the area of the overlapping portion of the sample of electrode and the ion exchange membrane and the mass of the portion overlapping the ion exchange membrane in the sample of electrode to calculate the force applied per unit mass-unit area (1) (N / mg·cm2).

[0524] The force applied per unit mass-unit area (1) obtained by the method (i) is less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less, further preferably 1.1 N / mg·cm2 or less, further more preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating. The force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / (mg·cm2) or more from the viewpoint of further improving the electrolytic performance, and furthermore, is further more preferably 0.14 N / (mg·cm2), still more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0525] When the electrode for electrolysis of the present embodiment satisfies the force applied (1), the electrode can be integrated with a membrane such as an ion exchange membrane and a microporous membrane or a feed conductor, for example, and used (i.e., as a laminate). Thus, on renewing the electrode, the substituting work for the cathode and anode fixed on the electrolytic cell by a method such as welding is eliminated, and the work efficiency is markedly improved. Additionally, by use of the electrode for electrolysis of the present embodiment as a laminate integrated with the ion exchange membrane, microporous membrane, or feed conductor, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0526] On shipping a new electrolytic cell, an electrode fixed on an electrolytic cell has been subjected to catalyst coating conventionally. Since only combination of an electrode having no catalyst coating with the electrode for electrolysis of the present embodiment can allow the electrode to function as an electrode, it is possible to markedly reduce or eliminate the production step and the amount of the catalyst for catalyst coating. A conventional electrode of which catalyst coating is markedly reduced or eliminated can be electrically connected to the electrode for electrolysis of the present embodiment and allowed to serve as a feed conductor for passage of an electric current.[Method (ii)]

[0527] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar to that of the method (i) above) and a sample of electrode (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0528] This average value is divided by the area of the overlapping portion of the sample of electrode and the nickel plate and the mass of the sample of electrode in the portion overlapping the nickel plate to calculate the adhesive force per unit mass-unit area (2) (N / mg·cm2). The force applied per unit mass-unit area (2) obtained by the method (ii) is less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less, further preferably 1.1 N / mg·cm2 or less, further more preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating. The force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / (mg·cm2) or more from the viewpoint of further improving the electrolytic performance, and is further more preferably 0.14 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0529] The electrode for electrolysis of the present embodiment, if satisfies the force applied (2), can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier. By attaching the electrode for electrolysis of the present embodiment to a degraded existing electrode to provide a laminate, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0530] From the viewpoint that the electrode for electrolysis of the present embodiment, if being an electrode having a broad elastic deformation region, can provide a better handling property and has a better adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, the thickness of the electrode for electrolysis is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. In the present embodiment, “having a broad elastic deformation region” means that, when an electrode for electrolysis is wound to form a wound body, warpage derived from winding is unlikely to occur after the wound state is released. The thickness of the electrode for electrolysis refers to, when a catalyst layer mentioned below is included, the total thickness of both the substrate for electrode for electrolysis and the catalyst layer.

[0531] The electrode for electrolysis of the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The thickness of the substrate for electrode for electrolysis (gauge thickness) is, but is not particularly limited to, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, being capable of being suitably rolled in a roll and satisfactorily folded, and facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), and is further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0532] In the present embodiment, a liquid is preferably interposed between the membrane such as an ion exchange membrane and a microporous membrane and the electrode, or the metal porous plate or metal plate (i.e., feed conductor) such as a degraded existing electrode and electrode having no catalyst coating and the electrode for electrolysis. As the liquid, any liquid, such as water and organic solvents, can be used as long as the liquid generates a surface tension. The larger the surface tension of the liquid, the larger the force applied between the membrane and the electrode for electrolysis or the metal porous plate or metal plate and the electrode for electrolysis. Thus, a liquid having a larger surface tension is preferred. Examples of the liquid include the following (the numerical value in the parentheses is the surface tension of the liquid at 20° C.):

[0533] hexane (20.44 mN / m), acetone (23.30 mN / m), methanol (24.00 mN / m), ethanol (24.05 mN / m), ethylene glycol (50.21 mN / m), and water (72.76 mN / m).

[0534] A liquid having a large surface tension allows the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis to be integrated (to be a laminate) to thereby facilitate renewing of the electrode. The liquid between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis may be present in an amount such that the both adhere to each other by the surface tension. As a result, after the laminate is placed in an electrolytic cell, the liquid, if mixed into the electrolyte solution, does not affect electrolysis itself due to the small amount of the liquid.

[0535] From a practical viewpoint, a liquid having a surface tension of 24 mN / m to 80 mN / m, such as ethanol, ethylene glycol, and water, is preferably used as the liquid. Particularly preferred is water or an alkaline aqueous solution prepared by dissolving caustic soda, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, or the like in water. Alternatively, the surface tension can be adjusted by allowing these liquids to contain a surfactant. When a surfactant is contained, the adhesion between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis varies to enable the handling property to be adjusted. The surfactant is not particularly limited, and both ionic surfactants and nonionic surfactants may be used.

[0536] The proportion measured by the following method (2) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 90% or more, more preferably 92% or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and further preferably 95% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (2)]

[0537] An ion exchange membrane (170 mm square) and a sample of electrode (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 280 mm) such that the sample of electrode in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode is measured.

[0538] The proportion measured by the following method (3) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 75% or more, more preferably 80% or more from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and being capable of being suitably rolled in a roll and satisfactorily folded, and is further preferably 90% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (3)]

[0539] An ion exchange membrane (170 mm square) and a sample of electrode (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode is measured.

[0540] The electrode for electrolysis of the present embodiment preferably has a porous structure and an opening ratio or void ratio of 5 to 90% or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and preventing accumulation of gas to be generated during electrolysis, although not particularly limited. The opening ratio is more preferably 10 to 80% or less, further preferably 20 to 75%.

[0541] The opening ratio is a proportion of the opening portions per unit volume. The calculation method may differ depending on that opening portions in submicron size are considered or that only visible openings are considered. In the present embodiment, a volume V was calculated from the values of the gauge thickness, width, and length of the electrode, and further, a weight W was measured to thereby calculate an opening ratio A by the following formula.A=(1-(W / (V×ρ))×100

[0542] ρ is the density of the electrode material (g / cm3). For example, ρ of nickel is 8.908 g / cm3, and ρ of titanium is 4.506 g / cm3. The opening ratio is appropriately adjusted by changing the area of metal to be perforated per unit area in the case of perforated metal, changing the values of the SW (short diameter), LW (long diameter), and feed in the case of expanded metal, changing the line diameter of metal fiber and mesh number in the case of mesh, changing the pattern of a photoresist to be used in the case of electroforming, changing the metal fiber diameter and fiber density in the case of nonwoven fabric, changing the mold for forming voids in the case of foamed metal, or the like.

[0543] The value obtained by measurement by the following method (A) of the electrode for electrolysis in the present embodiment is preferably 40 mm or less, more preferably 29 mm or less, further preferably 10 mm or less, further more preferably 6.5 mm or less from the viewpoint of the handling property. The specific measuring method is as described in Examples.[Method (A)]

[0544] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.

[0545] In the electrode for electrolysis in the present embodiment, the ventilation resistance is preferably 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s (hereinbelow, also referred to as “measurement condition 1”) (hereinbelow, also referred to as “ventilation resistance 1”). A larger ventilation resistance means that air is unlikely to flow and refers to a state of a high density. In this state, the product from electrolysis remains in the electrode and the reaction substrate is more unlikely to diffuse inside the electrode, and thus, the electrolytic performance (such as voltage) tends to deteriorate. The concentration on the membrane surface tends to increase. Specifically, the caustic concentration increases on the cathode surface, and the supply of brine tends to decrease on the anode surface. As a result, the product accumulates at a high concentration on the interface at which the membrane is in contact with the electrode. This accumulation leads to damage of the membrane and tends to also lead to increase in the voltage and damage of the membrane on the cathode surface and damage of the membrane on the anode surface. In the present embodiment, in order to prevent these defects, the ventilation resistance is preferably set at 24 kPa·s / m or less. From a similar viewpoint as above, the ventilation resistance is more preferably less than 0.19 kPa·s / m, further preferably 0.15 kPa·s / m or less, further more preferably 0.07 kPa·s / m or less.

[0546] In the present embodiment, when the ventilation resistance is larger than a certain value, NaOH generated in the electrode tends to accumulate on the interface between the electrode and the membrane to result in a high concentration in the case of the cathode, and the supply of brine tends to decrease to cause the brine concentration to be lower in the case of the anode. In order to prevent damage to the membrane that may be caused by such accumulation, the ventilation resistance is preferably less than 0.19 kPa·s / m, more preferably 0.15 kPa·s / m or less, further preferably 0.07 kPa·s / m or less.

[0547] In contrast, when the ventilation resistance is low, the area of the electrode is reduced and the electrolysis area is reduced. Thus, the electrolytic performance (such as voltage) tends to deteriorate. When the ventilation resistance is zero, the feed conductor functions as the electrode because no electrode for electrolysis is provided, and the electrolytic performance (such as voltage) tends to markedly deteriorate. From this viewpoint, a preferable lower limit value identified as the ventilation resistance 1 is not particularly limited, but is preferably more than 0 kPa·s / m, more preferably 0.0001 kPa·s / m or more, further preferably 0.001 kPa·s / m or more.

[0548] When the ventilation resistance 1 is 0.07 kPa·s / m or less, a sufficient measurement accuracy may not be achieved because of the measurement method therefor. From this viewpoint, it is also possible to evaluate an electrode for electrolysis having a ventilation resistance 1 of 0.07 kPa·s / m or less by means of a ventilation resistance (hereinbelow, also referred to as “ventilation resistance 2”) obtained by the following measurement method (hereinbelow, also referred to as “measurement condition 2”). That is, the ventilation resistance 2 is a ventilation resistance measured, when the electrode for electrolysis has a size of 50 mm×50 mm, under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 2 cm / s, and a ventilation volume of 4 cc / cm2 / s.

[0549] The specific methods for measuring the ventilation resistances 1 and 2 are described in Examples.

[0550] The ventilation resistances 1 and 2 can be within the range described above by appropriately adjusting an opening ratio, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to smaller ventilation resistances 1 and 2, and a lower opening ratio tends to lead to larger ventilation resistances 1 and 2.

[0551] In the electrode for electrolysis of the present embodiment, as mentioned above, the force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2. In this manner, the electrode for electrolysis of the present embodiment abuts with a moderate adhesive force on the membrane or feed conductor (e.g., the existing anode or cathode in the electrolyzer) to thereby enable a laminate with the membrane or feed conductor to be constituted. That is, it is not necessary to cause the membrane or feed conductor to firmly adhere to the electrode for electrolysis by a complicated method such as thermal compression. The laminate is formed only by a relatively weak force, for example, a surface tension derived from moisture contained in the membrane such as an ion exchange membrane and a microporous membrane, and thus, a laminate of any scale can be easily constituted. Additionally, such a laminate exhibits excellent electrolytic performance. Thus, the laminate of the present embodiment is suitable for electrolysis applications, and can be particularly preferably used for applications related to members of electrolyzers and renewing the members.

[0552] Hereinbelow, one aspect of the electrode for electrolysis of the present embodiment will be described.

[0553] The electrode for electrolysis according to the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The catalyst layer may be composed of a plurality of layers as shown below or may be a single-layer configuration.

[0554] As shown in FIG. 22, an electrode for electrolysis 100 according to the present embodiment includes a substrate for electrode for electrolysis 10 and a pair of first layers 20 with which both the surfaces of the substrate for electrode for electrolysis 10 are covered. The entire substrate for electrode for electrolysis 10 is preferably covered with the first layers 20. This covering is likely to improve the catalyst activity and durability of the electrode for electrolysis. One first layer 20 may be laminated only on one surface of the substrate for electrode for electrolysis 10.

[0555] Also shown in FIG. 22, the surfaces of the first layers 20 may be covered with second layers 30. The entire first layers 20 are preferably covered by the second layers 30. Alternatively, one second layer 30 may be laminated only one surface of the first layer 20.(Substrate for Electrode for Electrolysis)

[0556] As the substrate for electrode for electrolysis 10, for example, nickel, nickel alloys, stainless steel, or valve metals including titanium can be used, although not limited thereto. The substrate 10 preferably contains at least one element selected from nickel (Ni) and titanium (Ti).

[0557] When stainless steel is used in an alkali aqueous solution of a high concentration, iron and chromium are eluted and the electrical conductivity of stainless steel is of the order of one-tenth of that of nickel. In consideration of the foregoing, a substrate containing nickel (Ni) is preferable as the substrate for electrode for electrolysis.

[0558] Alternatively, when the substrate for electrode for electrolysis 10 is used in a salt solution of a high concentration near the saturation under an atmosphere in which chlorine gas is generated, the material of the substrate for electrode 10 is also preferably titanium having high corrosion resistance.

[0559] The form of the substrate for electrode for electrolysis 10 is not particularly limited, and a form suitable for the purpose can be selected. As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used. Among these, a perforated metal or expanded metal is preferable. Electroforming is a technique for producing a metal thin film having a precise pattern by using photolithography and electroplating in combination. It is a method including forming a pattern on a substrate with a photoresist and electroplating the portion not protected by the resist to provide a metal thin film.

[0560] As for the form of the substrate for electrode for electrolysis, a suitable specification depends on the distance between the anode and the cathode in the electrolyzer. In the case where the distance between the anode and the cathode is finite, an expanded metal or perforated metal form can be used, and in the case of a so-called zero-gap base electrolyzer, in which the ion exchange membrane is in contact with the electrode, a woven mesh produced by knitting thin lines, wire mesh, foamed metal, metal nonwoven fabric, expanded metal, perforated metal, metal porous foil, and the like can be used, although not limited thereto.

[0561] Examples of the substrate for electrode for electrolysis 10 include a metal porous foil, a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, and a foamed metal.

[0562] As a plate material before processed into a perforated metal or expanded metal, rolled plate materials and electrolytic foils are preferable. An electrolytic foil is preferably further subjected to a plating treatment by use of the same element as the base material thereof, as the post-treatment, to thereby form asperities on one or both of the surfaces.

[0563] The thickness of the substrate for electrode for electrolysis 10 is, as mentioned above, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less, and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0564] In the substrate for electrode for electrolysis, the residual stress during processing is preferably relaxed by annealing the substrate for electrode for electrolysis in an oxidizing atmosphere. It is preferable to form asperities using a steel grid, alumina powder, or the like on the surface of the substrate for electrode for electrolysis followed by an acid treatment to increase the surface area thereof, in order to improve the adhesion to a catalyst layer with which the surface is covered. Alternatively, it is preferable to give a plating treatment by use of the same element as the substrate to increase the surface area.

[0565] To bring the first layer 20 into close contact with the surface of the substrate for electrode for electrolysis 10, the substrate for electrode for electrolysis 10 is preferably subjected to a treatment of increasing the surface area. Examples of the treatment of increasing the surface area include a blast treatment using a cut wire, steel grid, alumina grid or the like, an acid treatment using sulfuric acid or hydrochloric acid, and a plating treatment using the same element to that of the substrate. The arithmetic average surface roughness (Ra) of the substrate surface is not particularly limited, but is preferably 0.05 μm to 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

[0566] Next, a case where the electrode for electrolysis of the present embodiment is used as an anode for common salt electrolysis will be described.(First Layer)

[0567] In FIG. 22, a first layer 20 as a catalyst layer contains at least one of ruthenium oxides, iridium oxides, and titanium oxides. Examples of the ruthenium oxide include RuO2. Examples of the iridium oxide include IrO2. Examples of the titanium oxide include TiO2. The first layer 20 preferably contains two oxides: a ruthenium oxide and a titanium oxide or three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide. This makes the first layer 20 more stable and additionally improves the adhesion with the second layer 30.

[0568] When the first layer 20 contains two oxides: a ruthenium oxide and a titanium oxide, the first layer 20 contains preferably 1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the two oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0569] When the first layer 20 contains three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide, the first layer 20 contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the three oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0570] When the first layer 20 contains at least two of a ruthenium oxide, an iridium oxide, and a titanium oxide, these oxides preferably form a solid solution. Formation of the oxide solid solution allows the electrode for electrolysis 100 to exhibit excellent durability.

[0571] In addition to the compositions described above, oxides of various compositions can be used as long as at least one oxide of a ruthenium oxide, an iridium oxide, and titanium oxide is contained. For example, an oxide coating called DSA®, which contains ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and the like, can be used as the first layer 20.

[0572] The first layer 20 need not be a single layer and may include a plurality of layers. For example, the first layer 20 may include a layer containing three oxides and a layer containing two oxides. The thickness of the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1 to 8 μm.(Second Layer)

[0573] The second layer 30 preferably contains ruthenium and titanium. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0574] The second layer 30 preferably contains a palladium oxide, a solid solution of a palladium oxide and platinum, or an alloy of palladium and platinum. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0575] A thicker second layer 30 can maintain the electrolytic performance for a longer period, but from the viewpoint of economy, the thickness is preferably 0.05 to 3 μm.

[0576] Next, a case where the electrode for electrolysis of the present embodiment is used as a cathode for common salt electrolysis will be described.(First Layer)

[0577] Examples of components of the first layer 20 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0578] The first layer 20 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal.

[0579] When the first layer 20 contains at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal, the platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal preferably contain at least one platinum group metal of platinum, palladium, rhodium, ruthenium, and iridium.

[0580] As the platinum group metal, platinum is preferably contained.

[0581] As the platinum group metal oxide, a ruthenium oxide is preferably contained.

[0582] As the platinum group metal hydroxide, a ruthenium hydroxide is preferably contained.

[0583] As the platinum group metal alloy, an alloy of platinum with nickel, iron, and cobalt is preferably contained.

[0584] Further, as required, an oxide or hydroxide of a lanthanoid element is preferably contained as a second component. This allows the electrode for electrolysis 100 to exhibit excellent durability.

[0585] As the oxide or hydroxide of a lanthanoid element, at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, and dysprosium is preferably contained.

[0586] Further, as required, an oxide or hydroxide of a transition metal is preferably contained as a third component.

[0587] Addition of the third component enables the electrode for electrolysis 100 to exhibit more excellent durability and the electrolysis voltage to be lowered.

[0588] Examples of a preferable combination include ruthenium only, ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum, ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium, ruthenium+praseodymium, ruthenium+praseodymium+platinum, ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium, ruthenium+neodymium+platinum, ruthenium+neodymium+manganese, ruthenium+neodymium+iron, ruthenium+neodymium+cobalt, ruthenium+neodymium+zinc, ruthenium+neodymium+gallium, ruthenium+neodymium+sulfur, ruthenium+neodymium+lead, ruthenium+neodymium+nickel, ruthenium+neodymium+copper, ruthenium+samarium, ruthenium+samarium+manganese, ruthenium+samarium+iron, ruthenium+samarium+cobalt, ruthenium+samarium+zinc, ruthenium+samarium+gallium, ruthenium+samarium+sulfur, ruthenium+samarium+lead, ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium, platinum+palladium+lanthanum+cerium, platinum+iridium, platinum+palladium, platinum+iridium+palladium, platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinum and nickel, alloys of platinum and cobalt, and alloys of platinum and iron.

[0589] When platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal are not contained, the main component of the catalyst is preferably nickel element.

[0590] At least one of nickel metal, oxides, and hydroxides is preferably contained.

[0591] As the second component, a transition metal may be added. As the second component to be added, at least one element of titanium, tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon is preferably contained.

[0592] Examples of a preferable combination include nickel+tin, nickel+titanium, nickel+molybdenum, and nickel+cobalt.

[0593] As required, an intermediate layer can be placed between the first layer 20 and the substrate for electrode for electrolysis 10. The durability of the electrode for electrolysis 100 can be improved by placing the intermediate layer.

[0594] As the intermediate layer, those having affinity to both the first layer 20 and the substrate for electrode for electrolysis 10 are preferable. As the intermediate layer, nickel oxides, platinum group metals, platinum group metal oxides, and platinum group metal hydroxides are preferable. The intermediate layer can be formed by applying and baking a solution containing a component that forms the intermediate layer. Alternatively, a surface oxide layer also can be formed by subjecting a substrate to a thermal treatment at a temperature of 300 to 600° C. in an air atmosphere. Besides, the layer can be formed by a known method such as a thermal spraying method and ion plating method.(Second Layer)

[0595] Examples of components of the first layer 30 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0596] The first layer 30 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal. Examples of a preferable combination of elements contained in the second layer include the combinations enumerated for the first layer. The combination of the first layer and the second layer may be a combination in which the compositions are the same and the composition ratios are different or may be a combination of different compositions.

[0597] As the thickness of the catalyst layer, the total thickness of the catalyst layer formed and the intermediate layer is preferably 0.01 μm to 20 μm. With a thickness of 0.01 μm or more, the catalyst layer can sufficiently serve as the catalyst. With a thickness of 20 μm or less, it is possible to form a robust catalyst layer that is unlikely to fall off from the substrate. The thickness is more preferably 0.05 μm to 15 μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness is further preferably 0.2 μm to 8 μm.

[0598] The thickness of the electrode for electrolysis, that is, the total thickness of the substrate for electrode for electrolysis and the catalyst layer is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less in respect of the handling property of the electrode for electrolysis. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. The thickness of the electrode can be determined by measurement with a digimatic thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of the substrate for electrode for electrolysis can be measured in the same manner as in the case of the electrode for electrolysis. The thickness of the catalyst layer can be determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode for electrolysis.(Method for Producing Electrode for Electrolysis)

[0599] Next, one embodiment of the method for producing the electrode for electrolysis 100 will be described in detail.

[0600] In the present embodiment, the electrode for electrolysis 100 can be produced by forming the first layer 20, preferably the second layer 30, on the substrate for electrode for electrolysis by a method such as baking of a coating film under an oxygen atmosphere (pyrolysis), or ion plating, plating, or thermal spraying. The production method of the present embodiment as mentioned can achieve a high productivity of the electrode for electrolysis 100. Specifically, a catalyst layer is formed on the substrate for electrode for electrolysis by an application step of applying a coating liquid containing a catalyst, a drying step of drying the coating liquid, and a pyrolysis step of performing pyrolysis. Pyrolysis herein means that a metal salt which is to be a precursor is decomposed by heating into a metal or metal oxide and a gaseous substance. The decomposition product depends on the metal species to be used, type of the salt, and the atmosphere under which pyrolysis is performed, and many metals tend to form oxides in an oxidizing atmosphere. In an industrial process of producing an electrode, pyrolysis is usually performed in air, and a metal oxide or a metal hydroxide is formed in many cases.(Formation of First Layer of Anode)(Application Step)

[0601] The first layer 20 is obtained by applying a solution in which at least one metal salt of ruthenium, iridium, and titanium is dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of ruthenium, iridium, and titanium in the first coating liquid is substantially equivalent to that of the first layer 20.

[0602] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0603] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0604] After being applied onto the substrate for electrode for electrolysis 100, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0605] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Second Layer)

[0606] The second layer 30, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound and a platinum compound or a solution containing a ruthenium compound and a titanium compound (second coating liquid) onto the first layer 20 and then pyrolyzing the coating liquid in the presence of oxygen.(Formation of First Layer of Cathode by Pyrolysis Method)(Application Step)

[0607] The first layer 20 is obtained by applying a solution in which metal salts of various combination are dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of the metal in the first coating liquid is substantially equivalent to that in the first layer 20.

[0608] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0609] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0610] After being applied onto the substrate for electrode for electrolysis 10, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0611] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Intermediate Layer)

[0612] The intermediate layer, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound or platinum compound (second coating liquid) onto the substrate and then pyrolyzing the coating liquid in the presence of oxygen. Alternatively, a nickel oxide intermediate layer may be formed on the substrate surface only by heating the substrate, without applying a solution thereon.(Formation of First Layer of Cathode by Ion Plating)

[0613] The first layer 20 can be formed also by ion plating.

[0614] An example includes a method in which the substrate is fixed in a chamber and the metal ruthenium target is irradiated with an electron beam. Evaporated metal ruthenium particles are positively charged in plasma in the chamber to deposit on the substrate negatively charged. The plasma atmosphere is argon and oxygen, and ruthenium deposits as ruthenium oxide on the substrate.(Formation of First Layer of Cathode by Plating)

[0615] The first layer 20 can be formed also by a plating method.

[0616] As an example, when the substrate is used as the cathode and subjected to electrolytic plating in an electrolyte solution containing nickel and tin, alloy plating of nickel and tin can be formed.(Formation of First Layer of Cathode by Thermal Spraying)

[0617] The first layer 20 can be formed also by thermal spraying.

[0618] As an example, plasma spraying nickel oxide particles onto the substrate can form a catalyst layer in which metal nickel and nickel oxide are mixed.

[0619] The electrode for electrolysis of the present embodiment can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. Thus, the electrode can be used as a membrane-integrated electrode. Then, the substituting work for the cathode and anode on renewing the electrode is eliminated, and the work efficiency is markedly improved.

[0620] The electrode integrated with the membrane such as an ion exchange membrane and a microporous membrane can make the electrolytic performance comparable to or higher than those of a new electrode.

[0621] Hereinafter, the ion exchange membrane will be described in detail.[Ion Exchange Membrane]

[0622] The ion exchange membrane has a membrane body containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and a coating layer provided on at least one surface of the membrane body. The coating layer contains inorganic material particles and a binder, and the specific surface area of the coating layer is 0.1 to 10 m2 / g. In the ion exchange membrane having such a structure, the influence of gas generated during electrolysis on electrolytic performance is small, and stable electrolytic performance can be exhibited.

[0623] The membrane of a perfluorocarbon polymer into which an ion exchange group is introduced described above includes either one of a sulfonic acid layer having an ion exchange group derived from a sulfo group (a group represented by —SO3−, hereinbelow also referred to as a “sulfonic acid group”) or a carboxylic acid layer having an ion exchange group derived from a carboxyl group (a group represented by —CO2−, hereinbelow also referred to as a “carboxylic acid group”). From the viewpoint of strength and dimension stability, reinforcement core materials are preferably further included.

[0624] The inorganic material particles and binder will be described in detail in the section of description of the coating layer below.

[0625] FIG. 23 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane. An ion exchange membrane 1 has a membrane body 10 containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and coating layers 11a and 11b formed on both the surfaces of the membrane body 10.

[0626] In the ion exchange membrane 1, the membrane body 10 comprises a sulfonic acid layer 3 having an ion exchange group derived from a sulfo group (a group represented by —SO3—, hereinbelow also referred to as a “sulfonic acid group”) and a carboxylic acid layer 2 having an ion exchange group derived from a carboxyl group (a group represented by —CO2—, hereinbelow also referred to as a “carboxylic acid group”), and the reinforcement core materials 4 enhance the strength and dimension stability. The ion exchange membrane 1, as comprising the sulfonic acid layer 3 and the carboxylic acid layer 2, is suitably used as an anion exchange membrane.

[0627] The ion exchange membrane may include either one of the sulfonic acid layer and the carboxylic acid layer. The ion exchange membrane may not be necessarily reinforced by reinforcement core materials, and the arrangement of the reinforcement core materials is not limited to the example in FIG. 23.(Membrane Body)

[0628] First, the membrane body 10 constituting the ion exchange membrane 1 will be described.

[0629] The membrane body 10 should be one that has a function of selectively allowing cations to permeate and comprises a hydrocarbon polymer or a fluorine-containing polymer having an ion exchange group. Its configuration and material are not particularly limited, and preferred ones can be appropriately selected.

[0630] The hydrocarbon polymer or fluorine-containing polymer having an ion exchange group in the membrane body 10 can be obtained from a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group precursor capable of forming an ion exchange group by hydrolysis or the like. Specifically, for example, after a polymer comprising a main chain of a fluorinated hydrocarbon, having, as a pendant side chain, a group convertible into an ion exchange group by hydrolysis or the like (ion exchange group precursor), and being melt-processable (hereinbelow, referred to as the “fluorine-containing polymer (a)” in some cases) is used to prepare a precursor of the membrane body 10, the membrane body 10 can be obtained by converting the ion exchange group precursor into an ion exchange group.

[0631] The fluorine-containing polymer (a) can be produced, for example, by copolymerizing at least one monomer selected from the following first group and at least one monomer selected from the following second group and / or the following third group. The fluorine-containing polymer (a) can be also produced by homopolymerization of one monomer selected from any of the following first group, the following second group, and the following third group.

[0632] Examples of the monomers of the first group include vinyl fluoride compounds. Examples of the vinyl fluoride compounds include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinyl ethers. Particularly when the ion exchange membrane is used as a membrane for alkali electrolysis, the vinyl fluoride compound is preferably a perfluoro monomer, and a perfluoro monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl ethers is preferable.

[0633] Examples of the monomers of the second group include vinyl compounds having a functional group convertible into a carboxylic acid-type ion exchange group (carboxylic acid group). Examples of the vinyl compounds having a functional group convertible into a carboxylic acid group include monomers represented by CF2=CF(OCF2CYF)s—O(CZF)t—COOR, wherein s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represent F or CF3, and R represents a lower alkyl group (a lower alkyl group is an alkyl group having 1 to 3 carbon atoms, for example).

[0634] Among these, compounds represented by CF2=CF(OCF2CYF)n—O(CF2)m—COOR are preferable. Wherein n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF3, and R represents CH3, C2H5, or C3H7.

[0635] When the ion exchange membrane is used as a cation exchange membrane for alkali electrolysis, a perfluoro compound is preferably at least used as the monomer, but the alkyl group (see the above R) of the ester group is lost from the polymer at the time of hydrolysis, and therefore the alkyl group (R) need not be a perfluoroalkyl group in which all hydrogen atoms are replaced by fluorine atoms.

[0636] Of the above monomers, the monomers represented below are more preferable as the monomers of the second group:

[0637] Examples of the monomers of the third group include vinyl compounds having a functional group convertible into a sulfone-type ion exchange group (sulfonic acid group). As the vinyl compounds having a functional group convertible into a sulfonic acid group, for example, monomers represented by CF2=CFO—X—CF2—SO2F are preferable, wherein X represents a perfluoroalkylene group. Specific examples of these include the monomers represented below:

[0638] Among these, CF2=CFOCF2CF(CF3)OCF2CF2CF2SO2F and CF2=CFOCF2CF(CF3)OCF2CF2SO2F are more preferable.

[0639] The copolymer obtained from these monomers can be produced by a polymerization method developed for homopolymerization and copolymerization of ethylene fluoride, particularly a general polymerization method used for tetrafluoroethylene. For example, in a non-aqueous method, a polymerization reaction can be performed in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound under the conditions of a temperature of 0 to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent such as a perfluorohydrocarbon or a chlorofluorocarbon.

[0640] In the above copolymerization, the type of combination of the above monomers and their proportion are not particularly limited and are selected and determined depending on the type and amount of the functional group desired to be imparted to the fluorine-containing polymer to be obtained. For example, when a fluorine-containing polymer containing only a carboxylic acid group is formed, at least one monomer should be selected from each of the first group and the second group described above and copolymerized. In addition, when a fluorine-containing polymer containing only a sulfonic acid group is formed, at least one monomer should be selected from each of the first group and the third group and copolymerized. Further, when a fluorine-containing polymer having a carboxylic acid group and a sulfonic acid group is formed, at least one monomer should be selected from each of the first group, the second group, and the third group described above and copolymerized. In this case, the target fluorine-containing polymer can be obtained also by separately preparing a copolymer comprising the monomers of the first group and the second group described above and a copolymer comprising the monomers of the first group and the third group described above, and then mixing the copolymers. The mixing proportion of the monomers is not particularly limited, and when the amount of the functional groups per unit polymer is increased, the proportion of the monomers selected from the second group and the third group described above should be increased.

[0641] The total ion exchange capacity of the fluorine-containing copolymer is not particularly limited, but is preferably 0.5 to 2.0 mg equivalent / g, more preferably 0.6 to 1.5 mg equivalent / g. The total ion exchange capacity herein refers to the equivalent of the exchange group per unit weight of the dry resin and can be measured by neutralization titration or the like.

[0642] In the membrane body 10 of the ion exchange membrane 1, a sulfonic acid layer 3 containing a fluorine-containing polymer having a sulfonic acid group and a carboxylic acid layer 2 containing a fluorine-containing polymer having a carboxylic acid group are laminated. By providing the membrane body 10 having such a layer configuration, selective permeability for cations such as sodium ions can be further improved.

[0643] The ion exchange membrane 1 is arranged in an electrolyzer such that, usually, the sulfonic acid layer 3 is located on the anode side of the electrolyzer and the carboxylic acid layer 2 is located on the cathode side of the electrolyzer.

[0644] The sulfonic acid layer 3 is preferably constituted by a material having low electrical resistance and has a membrane thickness larger than that of the carboxylic acid layer 2 from the viewpoint of membrane strength. The membrane thickness of the sulfonic acid layer 3 is preferably 2 to 25 times, more preferably 3 to 15 times that of the carboxylic acid layer 2.

[0645] The carboxylic acid layer 2 preferably has high anion exclusion properties even if it has a small membrane thickness. The anion exclusion properties here refer to the property of trying to hinder intrusion and permeation of anions into and through the ion exchange membrane 1. In order to raise the anion exclusion properties, it is effective to dispose a carboxylic acid layer having a small ion exchange capacity to the sulfonic acid layer.

[0646] As the fluorine-containing polymer for use in the sulfonic acid layer 3, preferable is a polymer obtained by using CF2=CFOCF2CF(CF3)OCF2CF2SO2F as the monomer of the third group.

[0647] As the fluorine-containing polymer for use in the carboxylic acid layer 2, preferable is a polymer obtained by using CF2=CFOCF2CF(CF2)O(CF2)2COOCH3 as the monomer of the second group.(Coating Layer)

[0648] The ion exchange membrane has a coating layer on at least one surface of the membrane body. As shown in FIG. 23, in the ion exchange membrane 1, coating layers 11a and 11b are formed on both the surfaces of the membrane body 10.

[0649] The coating layers contain inorganic material particles and a binder.

[0650] The average particle size of the inorganic material particles is preferably 0.90 μm or more. When the average particle size of the inorganic material particles is 0.90 μm or more, durability to impurities is extremely improved, in addition to attachment of gas. That is, enlarging the average particle size of the inorganic material particles as well as satisfying the value of the specific surface area mentioned above can achieve a particularly marked effect. Irregular inorganic material particles are preferable because the average particle size and specific surface area as above are satisfied. Inorganic material particles obtained by melting and inorganic material particles obtained by grinding raw ore can be used. Inorganic material particles obtained by grinding raw ore can preferably be used.

[0651] The average particle size of the inorganic material particles can be 2 μm or less. When the average particle size of the inorganic material particles is 2 μm or less, it is possible to prevent damage of the membrane due to the inorganic material particles. The average particle size of the inorganic material particle is more preferably 0.90 to 1.2 μm.

[0652] Here, the average particle size can be measured by a particle size analyzer (“SALD2200”, SHIMADZU CORPORATION).

[0653] The inorganic material particles preferably have irregular shapes. Such shapes improve resistance to impurities further. The inorganic material particles preferably have a broad particle size distribution.

[0654] The inorganic material particles preferably contain at least one inorganic material selected from the group consisting of oxides of Group IV elements in the Periodic Table, nitrides of Group IV elements in the Periodic Table, and carbides of Group IV elements in the Periodic Table. From the viewpoint of durability, zirconium oxide particle is more preferable.

[0655] The inorganic material particles are preferably inorganic material particles produced by grinding the raw ore of the inorganic material particles or inorganic material particles, as spherical particles having a uniform diameter, obtained by melt-purifying the raw ore of the inorganic material particles.

[0656] Examples of means for grinding raw ore include, but are not particularly limited to, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, grain mills, hammer mills, pellet mills, VSI mills, Wiley mills, roller mills, and jet mills. After grinding, the particles are preferably washed. As the washing method, the particles are preferably treated with acid. This treatment can reduce impurities such as iron attached to the surface of the inorganic material particles.

[0657] The coating layer preferably contains a binder. The binder is a component that forms the coating layers by retaining the inorganic material particles on the surface of the ion exchange membrane. The binder preferably contains a fluorine-containing polymer from the viewpoint of durability to the electrolyte solution and products from electrolysis.

[0658] As the binder, a fluorine-containing polymer having a carboxylic acid group or sulfonic acid group is more preferable, from the viewpoint of durability to the electrolyte solution and products from electrolysis and adhesion to the surface of the ion exchange membrane. When a coating layer is provided on a layer containing a fluorine-containing polymer having a sulfonic acid group (sulfonic acid layer), a fluorine-containing polymer having a sulfonic acid group is further preferably used as the binder of the coating layer. Alternatively, when a coating layer is provided on a layer containing a fluorine-containing polymer having a carboxylic acid group (carboxylic acid layer), a fluorine-containing polymer having a carboxylic acid group is further preferably used as the binder of the coating layer.

[0659] In the coating layer, the content of the inorganic material particles is preferably 40 to 90% by mass, more preferably 50 to 90% by mass. The content of the binder is preferably 10 to 60% by mass, more preferably 10 to 50% by mass.

[0660] The distribution density of the coating layer in the ion exchange membrane is preferably 0.05 to 2 mg per 1 cm2. When the ion exchange membrane has asperities on the surface thereof, the distribution density of the coating layer is preferably 0.5 to 2 mg per 1 cm2.

[0661] As the method for forming the coating layer, which is not particularly limited, a known method can be used. An example is a method including applying by a spray or the like a coating liquid obtained by dispersing inorganic material particles in a solution containing a binder.(Reinforcement Core Materials)

[0662] The ion exchange membrane preferably has reinforcement core materials arranged inside the membrane body.

[0663] The reinforcement core materials are members that enhance the strength and dimensional stability of the ion exchange membrane. By arranging the reinforcement core materials inside the membrane body, particularly expansion and contraction of the ion exchange membrane can be controlled in the desired range. Such an ion exchange membrane does not expand or contract more than necessary during electrolysis and the like and can maintain excellent dimensional stability for a long term.

[0664] The configuration of the reinforcement core materials is not particularly limited, and, for example, the reinforcement core materials may be formed by spinning yarns referred to as reinforcement yarns. The reinforcement yarns here refer to yarns that are members constituting the reinforcement core materials, can provide the desired dimensional stability and mechanical strength to the ion exchange membrane, and can be stably present in the ion exchange membrane. By using the reinforcement core materials obtained by spinning such reinforcement yarns, better dimensional stability and mechanical strength can be provided to the ion exchange membrane.

[0665] The material of the reinforcement core materials and the reinforcement yarns used for these is not particularly limited but is preferably a material resistant to acids, alkalis, etc., and a fiber comprising a fluorine-containing polymer is preferable because long-term heat resistance and chemical resistance are required.

[0666] Examples of the fluorine-containing polymer to be used in the reinforcement core materials include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-ethylene copolymers (ETFE), tetrafluoroethylene-hexafluoropropylene copolymers, trifluorochloroethylene-ethylene copolymers, and vinylidene fluoride polymers (PVDF). Among these, fibers comprising polytetrafluoroethylene are preferably used from the viewpoint of heat resistance and chemical resistance.

[0667] The yarn diameter of the reinforcement yarns used for the reinforcement core materials is not particularly limited, but is preferably 20 to 300 deniers, more preferably 50 to 250 deniers. The weave density (fabric count per unit length) is preferably 5 to 50 / inch. The form of the reinforcement core materials is not particularly limited, for example, a woven fabric, a nonwoven fabric, and a knitted fabric are used, but is preferably in the form of a woven fabric. The thickness of the woven fabric to be used is preferably 30 to 250 μm, more preferably 30 to 150 μm.

[0668] As the woven fabric or knitted fabric, monofilaments, multifilaments, or yarns thereof, a slit yarn, or the like can be used, and various types of weaving methods such as a plain weave, a leno weave, a knit weave, a cord weave, and a seersucker can be used.

[0669] The weave and arrangement of the reinforcement core materials in the membrane body are not particularly limited, and preferred arrangement can be appropriately provided considering the size and form of the ion exchange membrane, physical properties desired for the ion exchange membrane, the use environment, and the like.

[0670] For example, the reinforcement core materials may be arranged along one predetermined direction of the membrane body, but from the viewpoint of dimensional stability, it is preferred that the reinforcement core materials be arranged along a predetermined first direction, and other reinforcement core materials be arranged along a second direction substantially perpendicular to the first direction. By arranging the plurality of reinforcement core materials substantially orthogonally inside the membrane body, it is possible to impart better dimensional stability and mechanical strength in many directions. For example, arrangement in which the reinforcement core materials arranged along the longitudinal direction (warp yarns) and the reinforcement core materials arranged along the transverse direction (weft yarns) are woven on the surface side of the membrane body is preferred. The arrangement is more preferably in the form of plain weave driven and woven by allowing warps and wefts to run over and under each other alternately, leno weave in which two warps are woven into wefts while twisted, basket weave driven and woven by inserting, into two or more parallelly-arranged warps, wefts of the same number, or the like, from the viewpoint of dimension stability, mechanical strength and easy-production.

[0671] It is preferred that particularly, the reinforcement core materials be arranged along both directions, the MD (Machine Direction) and TD (Transverse Direction) of the ion exchange membrane. In other words, the reinforcement core materials are preferably plain-woven in the MD and TD. Here, the MD refers to the direction in which the membrane body and various core materials (for example, the reinforcement core materials, reinforcement yarns, and sacrifice yarns described later) are conveyed in an ion exchange membrane production step described later (flow direction), and the TD refers to the direction substantially perpendicular to the MD. Yarns woven along the MD are referred to as MD yarns, and yarns woven along the TD are referred to as TD yarns. Usually, the ion exchange membrane used for electrolysis is rectangular, and in many cases, the longitudinal direction is the MD, and the width direction is the TD. By weaving the reinforcement core materials that are MD yarns and the reinforcement core materials that are TD yarns, it is possible to impart better dimensional stability and mechanical strength in many directions.

[0672] The arrangement interval of the reinforcement core materials is not particularly limited, and preferred arrangement can be appropriately provided considering physical properties desired for the ion exchange membrane, the use environment, and the like.

[0673] The aperture ratio for the reinforcement core materials is not particularly limited, but is preferably 30% or more, more preferably 50% or more and 90% or less. The aperture ratio is preferably 30% or more from the viewpoint of the electrochemical properties of the ion exchange membrane, and preferably 90% or less from the viewpoint of the mechanical strength of the ion exchange membrane.

[0674] The aperture ratio for the reinforcement core materials herein refers to a ratio of a total area of a surface through which substances such as ions (an electrolyte solution and cations contained therein (e.g., sodium ions)) can pass (B) to the area of either one surface of the membrane body (A) (B / A). The total area of the surface through which substances such as ions can pass (B) can refer to the total areas of regions in which in the ion exchange membrane, cations, an electrolytic solution, and the like are not blocked by the reinforcement core materials and the like contained in the ion exchange membrane.

[0675] FIG. 24 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane. FIG. 24, in which a portion of the ion exchange membrane is enlarged, shows only the arrangement of the reinforcement core materials 21 and 22 in the regions, omitting illustration of the other members.

[0676] By subtracting the total area of the reinforcement core materials (C) from the area of the region surrounded by the reinforcement core materials 21 arranged along the longitudinal direction and the reinforcement core materials 22 arranged along the transverse direction, the region including the area of the reinforcement core materials (A), the total area of regions through which substances such as ions can pass (B) in the area of the above-described region (A) can be obtained. That is, the aperture ratio can be determined by the following formula (I):Aperture⁢ ratio=(B) / (A)=((A)-(C)) / (A)(I)

[0677] Among the reinforcement core materials, a particularly preferred form is tape yarns or highly oriented monofilaments comprising PTFE from the viewpoint of chemical resistance and heat resistance. Specifically, reinforcement core materials forming a plain weave in which 50 to 300 denier tape yarns obtained by slitting a high strength porous sheet comprising PTFE into a tape form, or 50 to 300 denier highly oriented monofilaments comprising PTFE are used and which has a weave density of 10 to 50 yarns or monofilaments / inch and has a thickness in the range of 50 to 100 μm are more preferred. The aperture ratio of an ion exchange membrane comprising such reinforcement core materials is further preferably 60% or more.

[0678] Examples of the shape of the reinforcement yarns include round yarns and tape yarns.(Continuous Holes)

[0679] The ion exchange membrane preferably has continuous holes inside the membrane body.

[0680] The continuous holes refer to holes that can be flow paths for ions generated in electrolysis and an electrolyte solution. The continuous holes, which are tubular holes formed inside the membrane body, are formed by dissolution of sacrifice core materials (or sacrifice yarns) described below. The shape, diameter, or the like of the continuous holes can be controlled by selecting the shape or diameter of the sacrifice core materials (sacrifice yarns).

[0681] Forming the continuous holes inside the ion exchange membrane can ensure the mobility of an electrolyte solution on electrolysis. The shape of the continuous holes is not particularly limited, but may be the shape of sacrifice core materials to be used for formation of the continuous holes in accordance with the production method described below.

[0682] The continuous holes are preferably formed so as to alternately pass on the anode side (sulfonic acid layer side) and the cathode side (carboxylic acid layer side) of the reinforcement core materials. With such a structure, in a portion in which continuous holes are formed on the cathode side of the reinforcement core materials, ions (e.g., sodium ions) transported through the electrolyte solution with which the continuous holes are filled can flow also on the cathode side of the reinforcement core materials. As a result, the flow of cations is not interrupted, and thus, it is possible to further reduce the electrical resistance of the ion exchange membrane.

[0683] The continuous holes may be formed along only one predetermined direction of the membrane body constituting the ion exchange membrane, but are preferably formed in both the longitudinal direction and the transverse direction of the membrane body from the viewpoint of exhibiting more stable electrolytic performance.[Production Method]

[0684] A suitable example of a method for producing an ion exchange membrane includes a method including the following steps (1) to (6):

[0685] Step (1): the step of producing a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0686] Step (2): the step of weaving at least a plurality of reinforcement core materials, as required, and sacrifice yarns having a property of dissolving in an acid or an alkali, and forming continuous holes, to obtain a reinforcing material in which the sacrifice yarns are arranged between the reinforcement core materials adjacent to each other,

[0687] Step (3): the step of forming into a film the above fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0688] Step (4): the step of embedding the above reinforcing materials, as required, in the above film to obtain a membrane body inside which the reinforcing materials are arranged,

[0689] Step (5): the step of hydrolyzing the membrane body obtained in the step (4) (hydrolysis step), and

[0690] Step (6): the step of providing a coating layer on the membrane body obtained in the step (5) (application step).

[0691] Hereinafter, each of the steps will be described in detail.Step (1): Step of Producing Fluorine-Containing Polymer

[0692] In the step (1), raw material monomers described in the first group to the third group above are used to produce a fluorine-containing polymer. In order to control the ion exchange capacity of the fluorine-containing polymer, the mixture ratio of the raw material monomers should be adjusted in the production of the fluorine-containing polymer forming the layers.Step (2): Step of Producing Reinforcing Materials

[0693] The reinforcing material is a woven fabric obtained by weaving reinforcement yarns or the like. The reinforcing material is embedded in the membrane to thereby form reinforcement core materials. When an ion exchange membrane having continuous holes is formed, sacrifice yarns are additionally woven into the reinforcing material. The amount of the sacrifice yarns contained in this case is preferably 10 to 80% by mass, more preferably 30 to 70% by mass based on the entire reinforcing material. Weaving the sacrifice yarns can also prevent yarn slippage of the reinforcement core materials.

[0694] As the sacrifice yarns, which have solubility in the membrane production step or under an electrolysis environment, rayon, polyethylene terephthalate (PET), cellulose, polyamide, and the like are used. Monofilaments or multifilaments having a thickness of 20 to 50 deniers and comprising polyvinyl alcohol and the like are also preferred.

[0695] In the step (2), the aperture ratio, arrangement of the continuous holes, and the like can be controlled by adjusting the arrangement of the reinforcement core materials and the sacrifice yarns.Step (3): Step of Film Formation

[0696] In the step (3), the fluorine-containing polymer obtained in the step (1) is formed into a film by using an extruder. The film may be a single-layer configuration, a two-layer configuration of a sulfonic acid layer and a carboxylic acid layer as mentioned above, or a multilayer configuration of three layers or more.

[0697] Examples of the film forming method include the following:

[0698] a method in which a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are separately formed into films; and

[0699] a method in which fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are coextruded into a composite film.

[0700] The number of each film may be more than one. Coextrusion of different films is preferred because of its contribution to an increase in the adhesive strength in the interface.Step (4): Step of Obtaining Membrane Body

[0701] In the step (4), the reinforcing material obtained in the step (2) is embedded in the film obtained in the step (3) to provide a membrane body including the reinforcing material therein.

[0702] Preferable examples of the method for forming a membrane body include (i) a method in which a fluorine-containing polymer having a carboxylic acid group precursor (e.g., carboxylate functional group) (hereinafter, a layer comprising the same is referred to as the first layer) located on the cathode side and a fluorine-containing polymer having a sulfonic acid group precursor (e.g., sulfonyl fluoride functional group) (hereinafter, a layer comprising the same is referred to as the second layer) are formed into a film by a coextrusion method, and, by using a heat source and a vacuum source as required, a reinforcing material and the second layer / first layer composite film are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure; and (ii) a method in which, in addition to the second layer / first layer composite film, a fluorine-containing polymer having a sulfonic acid group precursor is singly formed into a film (the third layer) in advance, and, by using a heat source and a vacuum source as required, the third layer film, the reinforcement core materials, and the composite film comprising the second layer / first layer are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure.

[0703] Coextrusion of the first layer and the second layer herein contributes to an increase in the adhesive strength at the interface.

[0704] The method including integration under a reduced pressure is characterized by making the third layer on the reinforcing material thicker than that of a pressure-application press method. Further, since the reinforcing material is fixed on the inner surface of the membrane body, the method has a property of sufficiently retaining the mechanical strength of the ion exchange membrane.

[0705] The variations of lamination described here are exemplary, and coextrusion can be performed after a preferred lamination pattern (for example, the combination of layers) is appropriately selected considering the desired layer configuration of the membrane body and physical properties, and the like.

[0706] For the purpose of further improving the electric properties of the ion exchange membrane, it is also possible to additionally interpose a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor between the first layer and the second layer or to use a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor instead of the second layer.

[0707] The method for forming the fourth layer may be a method in which a fluorine-containing polymer having a carboxylic acid group precursor and a fluorine-containing polymer having a sulfonic acid group precursor are separately produced and then mixed or may be a method in which a monomer having a carboxylic acid group precursor and a monomer having a sulfonic acid group precursor are copolymerized.

[0708] When the fourth layer is used as a component of the ion exchange membrane, a coextruded film of the first layer and the fourth layer is formed, in addition to this, the third layer and the second layer are separately formed into films, and lamination may be performed by the method mentioned above. Alternatively, the three layers of the first layer / fourth layer / second layer may be simultaneously formed into a film by coextrusion.

[0709] In this case, the direction in which the extruded film flows is the MD. As mentioned above, it is possible to form a membrane body containing a fluorine-containing polymer having an ion exchange group on a reinforcing material.

[0710] Additionally, the ion exchange membrane preferably has protruded portions composed of the fluorine-containing polymer having a sulfonic acid group, that is, projections, on the surface side composed of the sulfonic acid layer. As a method for forming such projections, which is not particularly limited, a known method also can be employed including forming projections on a resin surface. A specific example of the method is a method of embossing the surface of the membrane body. For example, the above projections can be formed by using release paper embossed in advance when the composite film mentioned above, reinforcing material, and the like are integrated. In the case where projections are formed by embossing, the height and arrangement density of the projections can be controlled by controlling the emboss shape to be transferred (shape of the release paper).(5) Hydrolysis Step

[0711] In the step (5), a step of hydrolyzing the membrane body obtained in the step (4) to convert the ion exchange group precursor into an ion exchange group (hydrolysis step) is performed.

[0712] In the step (5), it is also possible to form dissolution holes in the membrane body by dissolving and removing the sacrifice yarns included in the membrane body with acid or alkali. The sacrifice yarns may remain in the continuous holes without being completely dissolved and removed. The sacrifice yarns remaining in the continuous holes may be dissolved and removed by the electrolyte solution when the ion exchange membrane is subjected to electrolysis.

[0713] The sacrifice yarn has solubility in acid or alkali in the step of producing an ion exchange membrane or under an electrolysis environment. The sacrifice yarns are eluted out to thereby form continuous holes at corresponding sites.

[0714] The step (5) can be performed by immersing the membrane body obtained in the step (4) in a hydrolysis solution containing acid or alkali. An example of the hydrolysis solution that can be used is a mixed solution containing KOH and dimethyl sulfoxide (DMSO).

[0715] The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of 25 to 35% by mass.

[0716] The temperature for hydrolysis is preferably 70 to 100° C. The higher the temperature, the larger can be the apparent thickness. The temperature is more preferably 75 to 100° C.

[0717] The time for hydrolysis is preferably 10 to 120 minutes. The longer the time, the larger can be the apparent thickness. The time is more preferably 20 to 120 minutes.

[0718] The step of forming continuous holes by eluting the sacrifice yarn will be now described in more detail. FIGS. 25(a) and (b) are schematic views for explaining a method for forming the continuous holes of the ion exchange membrane.

[0719] FIGS. 25(a) and (b) show reinforcement yarns 52, sacrifice yarns 504a, and continuous holes 504 formed by the sacrifice yarns 504a only, omitting illustration of the other members such as a membrane body.

[0720] First, the reinforcement yarns 52 that are to constitute reinforcement core materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane are used as interwoven reinforcing materials. Then, in the step (5), the sacrifice yarns 504a are eluted to form the continuous holes 504.

[0721] The above method is simple because the method for interweaving the reinforcement yarns 52 and the sacrifice yarns 504a may be adjusted depending on the arrangement of the reinforcement core materials and continuous holes in the membrane body of the ion exchange membrane.

[0722] FIG. 25(a) exemplifies the plain-woven reinforcing material in which the reinforcement yarns 52 and sacrifice yarns 504a are interwoven along both the longitudinal direction and the lateral direction in the paper, and the arrangement of the reinforcement yarns 52 and the sacrifice yarns 504a in the reinforcing material may be varied as required.(6) Application Step

[0723] In the step (6), a coating layer can be formed by preparing a coating liquid containing inorganic material particles obtained by grinding raw ore or melting raw ore and a binder, applying the coating liquid onto the surface of the ion exchange membrane obtained in the step (5), and drying the coating liquid.

[0724] A preferable binder is a binder obtained by hydrolyzing a fluorine-containing polymer having an ion exchange group precursor with an aqueous solution containing dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) and then immersing the polymer in hydrochloric acid to replace the counterion of the ion exchange group by H+(e.g., a fluorine-containing polymer having a carboxyl group or sulfo group). Thereby, the polymer is more likely to dissolve in water or ethanol mentioned below, which is preferable.

[0725] This binder is dissolved in a mixed solution of water and ethanol. The volume ratio between water and ethanol is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganic material particles are dispersed with a ball mill into the dissolution liquid thus obtained to thereby provide a coating liquid. In this case, it is also possible to adjust the average particle size and the like of the particles by adjusting the time and rotation speed during the dispersion. The preferable amount of the inorganic material particles and the binder to be blended is as mentioned above.

[0726] The concentration of the inorganic material particles and the binder in the coating liquid is not particularly limited, but a thin coating liquid is preferable. This enables uniform application onto the surface of the ion exchange membrane.

[0727] Additionally, a surfactant may be added to the dispersion when the inorganic material particles are dispersed. As the surfactant, nonionic surfactants are preferable, and examples thereof include HS-210, NS-210, P-210, and E-212 manufactured by NOF CORPORATION.

[0728] The coating liquid obtained is applied onto the surface of the ion exchange membrane by spray application or roll coating to thereby provide an ion exchange membrane.[Microporous Membrane]

[0729] The microporous membrane of the present embodiment is not particularly limited as long as the membrane can be formed into a laminate with the electrode for electrolysis, as mentioned above. Various microporous membranes may be employed.

[0730] The porosity of the microporous membrane of the present embodiment is not particularly limited, but can be 20 to 90, for example, and is preferably 30 to 85. The above porosity can be calculated by the following formula:Porosity=(1-(the⁢ weight⁢ of⁢ the⁢ membrane⁢ in⁢ a⁢ dried⁢ state) / (the⁢ weight⁢ calculated⁢ from⁢ the⁢ volume⁢ calculated⁢ from⁢ the⁢ thickness,width,and⁢ length⁢ of⁢ the⁢ membrane⁢ and⁢ the⁢ density⁢ of⁢ the⁢ membrane⁢ material))×100

[0731] The average pore size of the microporous membrane of the present embodiment is not particularly limited, and can be 0.01 μm to 10 μm, for example, preferably 0.05 μm to 5 μm. With respect to the average pore size, for example, the membrane is cut vertically to the thickness direction, and the section is observed with an FE-SEM. The average pore size can be obtained by measuring the diameter of about 100 pores observed and averaging the measurements.

[0732] The thickness of the microporous membrane of the present embodiment is not particularly limited, and can be 10 μm to 1000 μm, for example, preferably 50 μm to 600 μm. The above thickness can be measured by using a micrometer (manufactured by Mitutoyo Corporation) or the like, for example.

[0733] Specific examples of the microporous membrane as mentioned above include Zirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfon membrane in the present embodiment) and those described in International Publication No. WO 2013-183584 and International Publication No. WO 2016-203701.

[0734] The reason why the laminate with the membrane of the present embodiment develops excellent electrolytic performance is presumed as follows. When the membrane and the electrode firmly adhere to each other by a method such as thermal compression, which is a conventional technique, the electrode sinks into the membrane to thereby physically adhere thereto. This adhesion portion inhibits sodium ions from migrating in the membrane to thereby markedly raise the voltage. Meanwhile, inhibition of migration of sodium ions in the membrane, which has been a problem in the conventional art, is eliminated by allowing the electrode for electrolysis to abut with a moderate adhesive force on the membrane or feed conductor, as in the present embodiment. According to the foregoing, when the membrane or feed conductor abuts on the electrode for electrolysis with a moderate adhesive force, the membrane or feed conductor and the electrode for electrolysis, despite of being an integrated piece, can develop excellent electrolytic performance.[Wound Body]

[0735] The wound body of the present embodiment includes the laminate of the present embodiment. That is, the wound body of the present embodiment is obtained by winding the laminate of the present embodiment. Downsizing the laminate of the present embodiment by winding, like the wound body of the present embodiment, can further improve the handling property.[Electrolyzer]

[0736] The electrolyzer of the present embodiment includes the laminate of the present embodiment. Hereinafter, the case of performing common salt electrolysis by using an ion exchange membrane as the membrane is taken as an example, and one embodiment of the electrolyzer will be described in detail.[Electrolytic Cell]

[0737] FIG. 26 illustrates a cross-sectional view of an electrolytic cell 1.

[0738] The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber 20, a partition wall 30 placed between the anode chamber 10 and the cathode chamber 20, an anode 11 placed in the anode chamber 10, and a cathode 21 placed in the cathode chamber 20. As required, the electrolytic cell 1 has a substrate 18a and a reverse current absorbing layer 18b formed on the substrate 18a and may comprise a reverse current absorber 18 placed in the cathode chamber. The anode 11 and the cathode 21 belonging to the electrolytic cell 1 are electrically connected to each other. In other words, the electrolytic cell 1 comprises the following cathode structure. The cathode structure 40 comprises the cathode chamber 20, the cathode 21 placed in the cathode chamber 20, and the reverse current absorber 18 placed in the cathode chamber 20, the reverse current absorber 18 has the substrate 18a and the reverse current absorbing layer 18b formed on the substrate 18a, as shown in FIG. 30, and the cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode chamber 20 further has a collector 23, a support 24 supporting the collector, and a metal elastic body 22. The metal elastic body 22 is placed between the collector 23 and the cathode 21. The support 24 is placed between the collector 23 and the partition wall 30. The collector 23 is electrically connected to the cathode 21 via the metal elastic body 22. The partition wall 30 is electrically connected to the collector 23 via the support 24. Accordingly, the partition wall 30, the support 24, the collector 23, the metal elastic body 22, and the cathode 21 are electrically connected. The cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode 21 and the reverse current absorbing layer may be directly connected or may be indirectly connected via the collector, the support, the metal elastic body, the partition wall, or the like. The entire surface of the cathode 21 is preferably covered with a catalyst layer for reduction reaction. The form of electrical connection may be a form in which the partition wall 30 and the support 24, the support 24 and the collector 23, and the collector 23 and the metal elastic body 22 are each directly attached and the cathode 21 is laminated on the metal elastic body 22. Examples of a method for directly attaching these constituent members to one another include welding and the like. Alternatively, the reverse current absorber 18, the cathode 21, and the collector 23 may be collectively referred to as a cathode structure 40.

[0739] FIG. 27 illustrates a cross-sectional view of two electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG. 28 shows an electrolyzer 4. FIG. 29 shows a step of assembling the electrolyzer 4. As shown in FIG. 27, an electrolytic cell 1, a cation exchange membrane 2, and an electrolytic cell 1 are arranged in series in the order mentioned. An ion exchange membrane 2 is arranged between the anode chamber of one electrolytic cell 1 among the two electrolytic cells that are adjacent in the electrolyzer and the cathode chamber of the other electrolytic cell 1. That is, the anode chamber 10 of the electrolytic cell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacent thereto is separated by the cation exchange membrane 2. As shown in FIG. 28, the electrolyzer 4 is composed of a plurality of electrolytic cells 1 connected in series via the ion exchange membrane 2. That is, the electrolyzer 4 is a bipolar electrolyzer comprising the plurality of electrolytic cells 1 arranged in series and ion exchange membranes 2 each arranged between adjacent electrolytic cells 1. As shown in FIG. 29, the electrolyzer 4 is assembled by arranging the plurality of electrolytic cells 1 in series via the ion exchange membrane 2 and coupling the cells by means of a press device 5.

[0740] The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 to be connected to a power supply. The anode 11 of the electrolytic cell 1 located at farthest end among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the anode terminal 7. The cathode 21 of the electrolytic cell located at the end opposite to the anode terminal 7 among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the cathode terminal 6. The electric current during electrolysis flows from the side of the anode terminal 7, through the anode and cathode of each electrolytic cell 1, toward the cathode terminal 6. At the both ends of the coupled electrolytic cells 1, an electrolytic cell having an anode chamber only (anode terminal cell) and an electrolytic cell having a cathode chamber only (cathode terminal cell) may be arranged. In this case, the anode terminal 7 is connected to the anode terminal cell arranged at the one end, and the cathode terminal 6 is connected to the cathode terminal cell arranged at the other end.

[0741] In the case of electrolyzing brine, brine is supplied to each anode chamber 10, and pure water or a low-concentration sodium hydroxide aqueous solution is supplied to each cathode chamber 20. Each liquid is supplied from an electrolyte solution supply pipe (not shown in Figure), through an electrolyte solution supply hose (not shown in Figure), to each electrolytic cell 1. The electrolyte solution and products from electrolysis are recovered from an electrolyte solution recovery pipe (not shown in Figure). During electrolysis, sodium ions in the brine migrate from the anode chamber 10 of the one electrolytic cell 1, through the ion exchange membrane 2, to the cathode chamber 20 of the adjacent electrolytic cell 1. Thus, the electric current during electrolysis flows in the direction in which the electrolytic cells 1 are coupled in series. That is, the electric current flows, through the cation exchange membrane 2, from the anode chamber 10 toward the cathode chamber 20. As the brine is electrolyzed, chlorine gas is generated on the side of the anode 11, and sodium hydroxide (solute) and hydrogen gas are generated on the side of the cathode 21.(Anode Chamber)

[0742] The anode chamber 10 has the anode 11 or anode feed conductor 11. When the electrode for electrolysis of the present embodiment is inserted to the anode side, 11 serves as the anode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the anode side, 11 serves as the anode. The anode chamber 10 has an anode-side electrolyte solution supply unit that supplies an electrolyte solution to the anode chamber 10, a baffle plate that is arranged above the anode-side electrolyte solution supply unit so as to be substantially parallel or oblique to the partition wall 30, and an anode-side gas liquid separation unit arranged above the baffle plate to separate gas from the electrolyte solution including the gas mixed.(Anode)

[0743] When the electrode for electrolysis of the present embodiment is not inserted to the anode side, the anode 11 is provided in the frame of the anode chamber 10. As the anode 11, a metal electrode such as so-called DSA® can be used. DSA is an electrode including a titanium substrate of which surface is covered with an oxide comprising ruthenium, iridium, and titanium as components.

[0744] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode Feed Conductor)

[0745] When the electrode for electrolysis of the present embodiment is inserted to the anode side, the anode feed conductor 11 is provided in the frame of the anode chamber 10. As the anode feed conductor 11, a metal electrode such as so-called DSA® can be used, and titanium having no catalyst coating can be also used. Alternatively, DSA having a thinner catalyst coating can be also used. Further, a used anode can be also used.

[0746] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode-Side Electrolyte Solution Supply Unit)

[0747] The anode-side electrolyte solution supply unit, which supplies the electrolyte solution to the anode chamber 10, is connected to the electrolyte solution supply pipe. The anode-side electrolyte solution supply unit is preferably arranged below the anode chamber 10. As the anode-side electrolyte solution supply unit, for example, a pipe on the surface of which aperture portions are formed (dispersion pipe) and the like can be used. Such a pipe is more preferably arranged along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell. This pipe is connected to an electrolyte solution supply pipe (liquid supply nozzle) that supplies the electrolyte solution into the electrolytic cell 1. The electrolyte solution supplied from the liquid supply nozzle is conveyed with a pipe into the electrolytic cell 1 and supplied from the aperture portions provided on the surface of the pipe to inside the anode chamber 10. Arranging the pipe along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell is preferable because the electrolyte solution can be uniformly supplied to inside the anode chamber 10.(Anode-Side Gas Liquid Separation Unit)

[0748] The anode-side gas liquid separation unit is preferably arranged above the baffle plate. The anode-side gas liquid separation unit has a function of separating produced gas such as chlorine gas from the electrolyte solution during electrolysis. Unless otherwise specified, above means the upper direction in the electrolytic cell 1 in FIG. 26, and below means the lower direction in the electrolytic cell 1 in FIG. 26.

[0749] During electrolysis, produced gas generated in the electrolytic cell 1 and the electrolyte solution form a mixed phase (gas-liquid mixed phase), which is then emitted out of the system. Subsequently, pressure fluctuations inside the electrolytic cell 1 cause vibration, which may result in physical damage of the ion exchange membrane. In order to prevent this event, the electrolytic cell 1 of the present embodiment is preferably provided with an anode-side gas liquid separation unit to separate the gas from the liquid. The anode-side gas liquid separation unit is preferably provided with a defoaming plate to eliminate bubbles. When the gas-liquid mixed phase flow passes through the defoaming plate, bubbles burst to thereby enable the electrolyte solution and the gas to be separated. As a result, vibration during electrolysis can be prevented.(Baffle Plate)

[0750] The baffle plate is preferably arranged above the anode-side electrolyte solution supply unit and arranged substantially in parallel with or obliquely to the partition wall 30. The baffle plate is a partition plate that controls the flow of the electrolyte solution in the anode chamber 10. When the baffle plate is provided, it is possible to cause the electrolyte solution (brine or the like) to circulate internally in the anode chamber 10 to thereby make the concentration uniform. In order to cause internal circulation, the baffle plate is preferably arranged so as to separate the space in proximity to the anode 11 from the space in proximity to the partition wall 30. From such a viewpoint, the baffle plate is preferably placed so as to be opposed to the surface of the anode 11 and to the surface of the partition wall 30. In the space in proximity to the anode partitioned by the baffle plate, as electrolysis proceeds, the electrolyte solution concentration (brine concentration) is lowered, and produced gas such as chlorine gas is generated. This results in a difference in the gas-liquid specific gravity between the space in proximity to anode 11 and the space in proximity to the partition wall 30 partitioned by the baffle plate. By use of the difference, it is possible to promote the internal circulation of the electrolyte solution in the anode chamber 10 to thereby make the concentration distribution of the electrolyte solution in the anode chamber 10 more uniform.

[0751] Although not shown in FIG. 26, a collector may be additionally provided inside the anode chamber 10. The material and configuration of such a collector may be the same as those of the collector of the cathode chamber mentioned below. In the anode chamber 10, the anode 11 per se may also serve as the collector.(Partition Wall)

[0752] The partition wall 30 is arranged between the anode chamber 10 and the cathode chamber 20. The partition wall 30 may be referred to as a separator, and the anode chamber 10 and the cathode chamber 20 are partitioned by the partition wall 30. As the partition wall 30, one known as a separator for electrolysis can be used, and an example thereof includes a partition wall formed by welding a plate comprising nickel to the cathode side and a plate comprising titanium to the anode side.(Cathode Chamber)

[0753] In the cathode chamber 20, when the electrode for electrolysis of the present embodiment is inserted to the cathode side, 21 serves as a cathode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, 21 serves as a cathode. When a reverse current absorber is included, the cathode or cathode feed conductor 21 is electrically connected to the reverse current absorber. The cathode chamber 20, similarly to the anode chamber 10, preferably has a cathode-side electrolyte solution supply unit and a cathode-side gas liquid separation unit. Among the components constituting the cathode chamber 20, components similar to those constituting the anode chamber 10 will be not described.(Cathode)

[0754] When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, a cathode 21 is provided in the frame of the cathode chamber 20. The cathode 21 preferably has a nickel substrate and a catalyst layer that covers the nickel substrate. Examples of the components of the catalyst layer on the nickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. The cathode 21 may be subjected to a reduction treatment, as required. As the substrate of the cathode 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0755] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Cathode Feed Conductor)

[0756] When the electrode for electrolysis of the present embodiment is inserted to the cathode side, a cathode feed conductor 21 is provided in the frame of the cathode chamber 20. The cathode feed conductor 21 may be covered with a catalytic component. The catalytic component may be a component that is originally used as the cathode and remains. Examples of the components of the catalyst layer include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. Alternatively, nickel, nickel alloys, and nickel-plated iron or stainless, having no catalyst coating, may be used. As the substrate of the cathode feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0757] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Reverse Current Absorbing Layer)

[0758] A material having a redox potential less noble than the redox potential of the element for the catalyst layer of the cathode mentioned above may be selected as a material for the reverse current absorbing layer. Examples thereof include nickel and iron.(Collector)

[0759] The cathode chamber 20 preferably comprises the collector 23. The collector 23 improves current collection efficiency. In the present embodiment, the collector 23 is a porous plate and is preferably arranged in substantially parallel to the surface of the cathode 21.

[0760] The collector 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The collector 23 may be a mixture, alloy, or composite oxide of these metals. The collector 23 may have any form as long as the form enables the function of the collector and may have a plate or net form.(Metal Elastic Body)

[0761] Placing the metal elastic body 22 between the collector 23 and the cathode 21 presses each cathode 21 of the plurality of electrolytic cells 1 connected in series onto the ion exchange membrane 2 to reduce the distance between each anode 11 and each cathode 21. Then, it is possible to lower the voltage to be applied entirely across the plurality of electrolytic cells 1 connected in series. Lowering of the voltage enables the power consumption to be reduced. With the metal elastic body 22 placed, the pressing pressure caused by the metal elastic body 22 enables the electrode for electrolysis to be stably maintained in place when the laminate including the electrode for electrolysis according to the present embodiment is placed in the electrolytic cell.

[0762] As the metal elastic body 22, spring members such as spiral springs and coils and cushioning mats may be used. As the metal elastic body 22, a suitable one may be appropriately employed, in consideration of a stress to press the ion exchange membrane and the like. The metal elastic body 22 may be provided on the surface of the collector 23 on the side of the cathode chamber 20 or may be provided on the surface of the partition wall on the side of the anode chamber 10. Both the chambers are usually partitioned such that the cathode chamber 20 becomes smaller than the anode chamber 10. Thus, from the viewpoint of the strength of the frame and the like, the metal elastic body 22 is preferably provided between the collector 23 and the cathode 21 in the cathode chamber 20. The metal elastic body 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium.(Support)

[0763] The cathode chamber 20 preferably comprises the support 24 that electrically connects the collector 23 to the partition wall 30. This can achieve an efficient current flow.

[0764] The support 24 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The support 24 may have any shape as long as the support can support the collector 23 and may have a rod, plate, or net shape. The support 24 has a plate shape, for example. A plurality of supports 24 are arranged between the partition wall 30 and the collector 23. The plurality of supports 24 are aligned such that the surfaces thereof are in parallel to each other. The supports 24 are arranged substantially perpendicular to the partition wall 30 and the collector 23.(Anode Side Gasket and Cathode Side Gasket)

[0765] The anode side gasket is preferably arranged on the frame surface constituting the anode chamber 10. The cathode side gasket is preferably arranged on the frame surface constituting the cathode chamber 20. Electrolytic cells are connected to each other such that the anode side gasket included in one electrolytic cell and the cathode side gasket of an electrolytic cell adjacent to the cell sandwich the ion exchange membrane 2 (see FIGS. 26 and 27). These gaskets can impart airtightness to connecting points when the plurality of electrolytic cells 1 is connected in series via the ion exchange membrane 2.

[0766] The gaskets form a seal between the ion exchange membrane and electrolytic cells. Specific examples of the gaskets include picture frame-like rubber sheets at the center of which an aperture portion is formed. The gaskets are required to have resistance against corrosive electrolyte solutions or produced gas and be usable for a long period. Thus, in respect of chemical resistance and hardness, vulcanized products and peroxide-crosslinked products of ethylene-propylene-diene rubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) are usually used as the gaskets. Alternatively, gaskets of which region to be in contact with liquid (liquid contact portion) is covered with a fluorine-containing resin such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may be employed as required. These gaskets each may have an aperture portion so as not to inhibit the flow of the electrolyte solution, and the shape of the aperture portion is not particularly limited. For example, a picture frame-like gasket is attached with an adhesive or the like along the peripheral edge of each aperture portion of the anode chamber frame constituting the anode chamber 10 or the cathode chamber frame constituting the cathode chamber 20. Then, for example, in the case where the two electrolytic cells 1 are connected via the ion exchange membrane 2 (see FIG. 27), each electrolytic cell 1 onto which the gasket is attached should be tightened via ion exchange membrane 2. This tightening can prevent the electrolyte solution, alkali metal hydroxide, chlorine gas, hydrogen gas, and the like generated from electrolysis from leaking out of the electrolytic cells 1.(Ion Exchange Membrane)

[0767] The ion exchange membrane 2 is as described in the section of the ion exchange membrane described above.(Water Electrolysis)

[0768] The electrolyzer of the present embodiment, as an electrolyzer in the case of electrolyzing water, has a configuration in which the ion exchange membrane in an electrolyzer for use in the case of electrolyzing common salt mentioned above is replaced by a microporous membrane. The raw material to be supplied, which is water, is different from that for the electrolyzer in the case of electrolyzing common salt mentioned above. As for the other components, components similar to that of the electrolyzer in the case of electrolyzing common salt can be employed also in the electrolyzer in the case of electrolyzing water. Since chlorine gas is generated in the anode chamber in the case of common salt electrolysis, titanium is used as the material of the anode chamber, but in the case of water electrolysis, only oxygen gas is generated in the anode chamber. Thus, a material identical to that of the cathode chamber can be used. An example thereof is nickel. For anode coating, catalyst coating for oxygen generation is suitable. Examples of the catalyst coating include metals, oxides, and hydroxides of the platinum group metals and transition metal group metals. For example, elements such as platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron can be used.(Application of Laminate)

[0769] The laminate of the present embodiment can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing as mentioned above. In other words, the laminate of the present embodiment can be suitably used as a laminate for replacement of a member of an electrolyzer. A laminate to be used in such an application is specifically referred to as a “membrane electrode assembly”.(Package)

[0770] The laminate of the present embodiment is preferably transported or the like while enclosed in a packaging material. That is, the package of the present embodiment comprises the laminate of the present embodiment and a packaging material that packages the laminate. The package of the present embodiment, configured as described above, can prevent adhesion of stain and damage that may occur during transport or the like of the laminate of the present embodiment. When used for member replacement of the electrolyzer, the laminate is particularly preferably transported or the like as the package of the present embodiment. As the packaging material of the present embodiment, which is not particularly limited, known various packaging materials can be employed. Alternatively, the package of the present embodiment can be produced by, for example, a method including packaging the laminate of the present embodiment with a clean packaging material followed by encapsulation or the like, although not limited thereto.Third Embodiment

[0771] Here, a third embodiment of the present invention will be described in detail with reference to FIGS. 43 to 62.[Laminate]

[0772] The laminate of the third embodiment (hereinafter, in the section of <Third embodiment>, simply referred to as “the present embodiment”) has a membrane and an electrode for electrolysis fixed at least one region of the surface of the “membrane” (hereinafter, simply also referred to as a “fixed region”), and the proportion of the region on the surface of the membrane is more than 0% and less than 93%. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0773] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the existing electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0774] Further, according to the laminate of the present embodiment, it is possible to maintain the electrolytic performance of the existing electrolytic cell comparable to those of a new electrode or improve the electrolytic performance. Thus, the electrode fixed on the existing electrolytic cell and serving as an anode and / or a cathode is only required to serve as a feed conductor. Thus, it may be also possible to markedly reduce or eliminate catalyst coating. The feed conductor herein means a degraded electrode (i.e., the existing electrode), an electrode having no catalyst coating, and the like.[Electrode for Electrolysis]

[0775] The electrode for electrolysis in the present embodiment is not particularly limited as long as the electrode is an electrode to be used for electrolysis, and preferably has an area of the surface opposed to the membrane of the electrode for electrolysis (corresponds to an area of the conducting surface S2 mentioned below) of 0.01 m2 or more. The “surface opposed to the membrane” means the surface on which the membrane is located of the surfaces possessed by the electrode for electrolysis. That is, the surface opposed to the membrane in the electrode for electrolysis also can be the surface that abuts on the surface of the membrane. When the area of the surface opposed to the membrane in the electrode for electrolysis is 0.01 m2 or more, sufficient productivity can be achieved, and especially when industrial electrolysis is performed, sufficient productivity tends to be obtained. In this manner, from the viewpoint of achieving sufficient productivity and achieving practicality for a laminate to be used in renewing of the electrolytic cell, the area of the surface opposed to the membrane in the electrode for electrolysis is more preferably 0.1 m2 or more, further preferably 1 m2 or more. The area can be measured by, for example, a method described in Examples.

[0776] The electrode for electrolysis in the present embodiment has a force applied per unit mass-unit area of preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a feed conductor (a degraded electrode and an electrode having no catalyst coating), and the like. The force applied is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0777] From the viewpoint of further improving the electrolytic performance, the force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / mg·cm2 or more, further more preferably 0.14 N / (mg·cm2) or more. The force is further more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0778] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.

[0779] The mass per unit is preferably 48 mg / cm2 or less, more preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and of economy, and furthermore is 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0780] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0781] The force applied can be measured by the following method (i) or (ii). The value obtained by the measure...

Examples

example 1

[2206]As a substrate for electrode for cathode electrolysis, an electrolytic nickel foil having a gauge thickness of 16 μm was provided. One surface of this nickel foil was subjected to a roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 0.71 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment.

[2207]A porous foil was formed by perforating this nickel foil with circular holes by punching. The opening ratio was 49%.

[2208]A coating liquid for use in forming an electrode catalyst was prepared by the following procedure. A ruthenium nitrate solution having a ruthenium concentration of 100 g / L (FURUYA METAL Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molar ratio between the ruthenium element and the cerium element was 1:0.25. This mixed solution was...

example 2

[2219]In Example 2, an electrolytic nickel foil having a gauge thickness of 22 μm was used as the substrate for electrode for cathode electrolysis. One surface of this nickel foil was subjected to roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 0.96 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment. The opening ratio was 44%. Except for the above described, evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

[2220]The thickness of the electrode was 29 μm. The thickness of the catalytic layer, which was determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode, was 7 μm. The coating was formed also on the surface not roughened.

[2221]A sufficient adhesive force was obser...

example 3

[2226]In Example 3, an electrolytic nickel foil having a gauge thickness of 30 μm was used as the substrate for electrode for cathode electrolysis. One surface of this nickel foil was subjected to roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 1.38 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment. The opening ratio was 44%. Except for the above described, evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

[2227]The thickness of the electrode was 38 μm. The thickness of the catalytic layer, which was determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode, was 8 μm. The coating was formed also on the surface not roughened.

[2228]A sufficient adhesive force was obser...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No. 16 / 495,571, which is a U.S. National Stage Entry of PCT / JP2018 / 011535, filed Mar. 22, 2018, which claims priority to JP App. Nos. 2017-056524 and 2017-056525, each filed Mar. 22, 2017, and JP App. Nos. 2018-053146, 2018-053139, 2018-053145, 2018-053231, 2018-053144, 2018-053217, and 2018-053149, each filed Mar. 20, 2018. The disclosure of each of these documents is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body.BACKGROUND ART

[0003] For electrolysis of an alkali metal chloride aqueous solution such as salt solution and electrolysis of water, methods by use of an electrolyzer including a membrane, more specifically an ion exchange membrane or microporous membrane have been employed. This electrolyzer includes many electrolytic cells connected in series therein, in many cases. A membrane is interposed between each of electrolytic cell to perform electrolysis. In an electrolytic cell, a cathode chamber including a cathode and an anode chamber including an anode are disposed back to back with a partition wall (back plate) interposed therebetween or via pressing by means of press pressure, bolt tightening, or the like.

[0004] The anode and the cathode for use in these electrolyzers now are each fixed to the anode chamber or the cathode chamber of an electrolytic cell by a method such as welding and folding, and thereafter, stored or transported to customers. Meanwhile, each membrane in a state of being singly wound around a vinyl chloride (VC) pipe is stored or transported to customers. Each customer arranges the electrolytic cell on the frame of an electrolyzer and interposes the membrane between electrolytic cells to assemble the electrolyzer. In this manner, electrolytic cells are produced, and an electrolyzer is assembled by each customer. Patent Literatures 1 and 2 each disclose a structure formed by integrating a membrane and an electrode as a structure applicable to such an electrolyzer.CITATION LISTPatent LiteraturePatent Literature 1

[0005] Japanese Patent Laid-Open No. 58-048686Patent Literature 2

[0006] Japanese Patent Laid-Open No. 55-148775SUMMARY OF INVENTIONTechnical Problem

[0007] When electrolysis operation is started and continued, each part deteriorates and electrolytic performance are lowered due to various factors, and each part is replaced at a certain time point. The membrane can be easily renewed by extracting from an electrolytic cell and inserting a new membrane. In contrast, the anode and the cathode are fixed to the electrolytic cell, and thus, there is a problem of occurrence of an extremely complicated work on renewing the electrode, in which the electrolytic cell is removed from the electrolyzer and conveyed to a dedicated renewing plant, fixing such as welding is removed and the old electrode is striped off, then a new electrode is placed and fixed by a method such as welding, and the cell is conveyed to the electrolysis plant and placed back to the electrolyzer. It is considered herein that the structure formed by integrating a membrane and an electrode via thermal compression described in Patent Literatures 1 and 2 is used for the renewing described above, but the structure, which can be produced at a laboratory level relatively easily, is not easily produced so as to be adapted to an electrolytic cell in an actual commercially-available size (e.g., 1.5 m in length, 3 m in width). Moreover, electrolytic performance (such as electrolysis voltage, current efficiency, and common salt concentration in caustic soda) and durability are extremely poor, and chlorine gas and hydrogen gas are generated on the electrode interfacing the membrane. Thus, when used in electrolysis for a long period, complete delamination occurs, and the structure cannot be practically used.

[0008] The present invention has been made in view of the above problems possessed by the conventional art and is intended to provide an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body below.(First Object)

[0009] It is an object of the present invention to provide an electrode for electrolysis, a laminate, and a wound body that make transport and handling easier, markedly simplify a work when a new electrolyzer is started or a degraded electrode is renewed, and furthermore also can maintain or improve the electrolytic performance.(Second Object)

[0010] It is an object of the present invention to provide a laminate that can improve the work efficiency during electrode renewing in an electrolyzer and further can exhibit excellent electrolytic performance also after renewing.(Third Object)

[0011] It is an object of the present invention to provide a laminate that can improve the work efficiency during electrode renewing in an electrolyzer and further can exhibit excellent electrolytic performance also after renewing, from a viewpoint different from the second object described above.(Fourth Object)

[0012] It is a fourth object of the present invention to provide an electrolyzer, a method for producing an electrolyzer, and a method for renewing a laminate that have excellent electrolytic performance as well as can prevent damage of a membrane.(Fifth Object)

[0013] It is an object of the present invention to provide a method for producing an electrolyzer, a method for renewing an electrode, and a method for producing a wound body that can improve the work efficiency during electrode renewing in an electrolyzer.(Sixth Object)

[0014] It is an object of the present invention to provide a method for producing an electrolyzer that can improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from the fifth object described above.(Seventh Object)

[0015] It is an object of the present invention to provide a method for producing an electrolyzer that can improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from the fifth and sixth objects described above.Solution to Problem

[0016] As a result of the intensive studies by the present inventors to achieve the first object, production of an electrode for electrolysis that has a small mass per unit area and can be bonded to a membrane such as an ion exchange membrane and a microporous membrane or a degraded electrode with a weak force makes transport and handling easier, can markedly simplify a work when a new electrolyzer is started or a degraded part is renewed, and furthermore can markedly improve the characteristics in comparison with the electrolytic performance in the conventional art. Additionally, the present inventors have found that the characteristics can be equivalent to or be improved than the electrolytic performance of a conventional electrolytic cell, for which renewing work is complicated, thereby having completed the present invention.

[0017] That is, the present invention includes the following.[1]

[0018] An electrode for electrolysis having a mass per unit area of 48 mg / cm2 or less and a force applied per unit mass-unit area of 0.08 N / mg·cm2 or more.[2]

[0019] The electrode for electrolysis according to [1], wherein the electrode for electrolysis comprises a substrate for electrode for electrolysis and a catalytic layer, and the substrate for electrode for electrolysis has a thickness of 300 μm or less.[3]

[0020] The electrode for electrolysis according to [1] or [2], wherein a proportion measured by a method (3) below is 75% or more:[Method (3)]

[0021] A membrane (170 mm square), which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced, and a sample of electrode for electrolysis (130 mm square) are laminated in this order; and the laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then a proportion (%) of an area of a portion, in which the sample of electrode for electrolysis is in close contact with the membrane obtained by applying the inorganic material particles and the binder to both the surfaces of the membrane of the perfluorocarbon polymer into which the ion exchange group is introduced, is measured.[4]

[0022] The electrode for electrolysis according to any of [1] to [3], wherein the electrode for electrolysis has a porous structure and has an opening ratio of 5 to 90%.[5]

[0023] The electrode for electrolysis according to any of [1] to [4], wherein the electrode has a porous structure and has an opening ratio of 10 to 80%.[6]

[0024] The electrode for electrolysis according to any of [1] to [5], wherein the electrode for electrolysis has a thickness of 315 μm or less.[7]

[0025] The electrode for electrolysis according to any of [1] to [6], wherein a value obtained by measuring the electrode for electrolysis by a method (A) below is 40 mm or less:[Method (A)]

[0026] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.[8]

[0027] The electrode for electrolysis according to any one of [1] to [7], wherein a ventilation resistance is 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s.[9]

[0028] The electrode for electrolysis according to any of [1] to [8], wherein the electrode comprises at least one element selected from nickel (Ni) and titanium (Ti).

[10]

[0029] A laminate comprising the electrode for electrolysis according to any of [1] to [9].

[11]

[0030] A wound body comprising the electrode for electrolysis according to any of [1] to [9] or the laminate according to

[10] .

[0031] As a result of the intensive studies to achieve the second object, the present inventors have found that a laminate that includes an electrode to be bonded to a membrane such as an ion exchange membrane and a microporous membrane and to a feed conductor such as a degraded existing electrode with a weak force makes transport and handling easier, can markedly simplify a work when a new electrolyzer is started or a degraded part is renewed, and furthermore can also maintain or improve the electrolytic performance, thereby having completed the present invention.

[0032] That is, the present invention includes the following aspects.[2-1]

[0033] A laminate comprising:

[0034] an electrode for electrolysis, and

[0035] a membrane or feed conductor in contact with the electrode for electrolysis,

[0036] wherein a force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2.[2-2]

[0037] The laminate according to [2-1], wherein the force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is more than 0.005 N / mg·cm2.[2-3]

[0038] The laminate according to [2-1] or [2-2], wherein the feed conductor is a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, or a foamed metal.[2-4]

[0039] The laminate according to any of [2-1] to [2-3], comprising, as at least one surface layer of the membrane, a layer comprising a mixture of hydrophilic oxide particles and a polymer into which ion exchange groups are introduced.[2-5]

[0040] The laminate according to any of [2-1] to [2-4], wherein a liquid is interposed between the electrode for electrolysis and the membrane or feed conductor.

[0041] As a result of the intensive studies to achieve the third object, the present inventors have found that the problems described above can be solved by a laminate in which a membrane and an electrode for electrolysis are partially fixed, thereby having completed the present invention.

[0042] That is, the present invention includes the following aspects.[3-1]

[0043] A laminate comprising:

[0044] a membrane, and

[0045] an electrode for electrolysis fixed in at least one region of a surface of the membrane,

[0046] wherein a proportion of the region on the surface of the membrane is more than 0% and less than 93%.[3-2]

[0047] The laminate according to [3-1], wherein the electrode for electrolysis comprises at least one catalytic component selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy.[3-3]

[0048] The laminate according to [3-1] or [3-2], wherein at least a portion of the electrode for electrolysis penetrates the membrane and thereby is fixed in the region.[3-4]

[0049] The laminate according to any one of [3-1] to [3-3], wherein at least a portion of the electrode for electrolysis is located inside the membrane and thereby fixed in the region.[3-5]

[0050] The laminate according to any one of [3-1] to [3-4], further comprising a fixing member for fixing the membrane and the electrode for electrolysis.[3-6]

[0051] The laminate according to [3-5], wherein at least a portion of the fixing member externally grips the membrane and the electrode for electrolysis.[3-7]

[0052] The laminate according to [3-5] or [3-6], wherein at least a portion of the fixing member fixes the membrane and the electrode for electrolysis by magnetic force.[3-8]

[0053] The laminate according to any one of [3-1] to [3-7], wherein the membrane comprises an ion exchange membrane comprising a surface layer comprising an organic resin, and the organic resin is present in the region.[3-9]

[0054] The laminate according to any one of [3-1] to [3-8], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having an EW different from that of the first ion exchange resin layer.[3-10]

[0055] The laminate according to any one of [3-1] to [3-8], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having a functional group different from that of the first ion exchange resin layer.

[0056] As a result of the intensive studies to achieve the fourth object, the present inventors have found that the problems described above can be solved by sandwiching at least a portion of a laminate of a membrane and an electrode for electrolysis between an anode side gasket and a cathode side gasket, thereby having completed the present invention.

[0057] That is, the present invention includes the following aspects.[4-1]

[0058] An electrolyzer comprising:

[0059] an anode,

[0060] an anode frame that supports the anode,

[0061] an anode side gasket that is arranged on the anode frame,

[0062] a cathode that is opposed to the anode,

[0063] a cathode frame that supports the cathode,

[0064] a cathode side gasket that is arranged on the cathode frame and is opposed to the anode side gasket, and

[0065] a laminate of a membrane and an electrode for electrolysis, the laminate being arranged between the anode side gasket and the cathode side gasket,

[0066] wherein at least a portion of the laminate is sandwiched between the anode side gasket and the cathode side gasket, and

[0067] a ventilation resistance is 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of a temperature of 24° C., a relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s.[4-2]

[0068] The electrolyzer according to [4-1], wherein the electrode for electrolysis has a thickness of 315 μm or less.[4-3]

[0069] The electrolyzer according to [4-1] or [4-2], wherein a value obtained by measuring the electrode for electrolysis by a method (A) below is 40 mm or less:[4-Method (A)]

[0070] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.[4-4]

[0071] The electrolyzer according to any of [4-1] to [4-3], wherein a mass per unit area of the electrode for electrolysis is 48 mg / cm2 or less.[4-5]

[0072] The electrolyzer according to any of [4-1] to [4-4], wherein a force applied per unit mass-unit area of the electrode for electrolysis is more than 0.005 N / mg·cm2.[4-6]

[0073] The electrolyzer according to any of [4-1] to [4-5], wherein an outermost perimeter of the laminate is located farther outside than an outermost perimeter each of the anode side gasket and the cathode side gasket in a direction of a conducting surface.[4-7]

[0074] The electrolyzer according to any of [4-1] to [4-6], wherein the electrode for electrolysis comprises at least one catalytic component selected from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy.[4-8]

[0075] The electrolyzer according to any of [4-1] to [4-7], wherein at least a portion of the electrode for electrolysis penetrates the membrane and thereby is fixed in the laminate.[4-9]

[0076] The electrolyzer according to any of [4-1] to [4-7], wherein at least a portion of the electrode for electrolysis is located inside the membrane and thereby fixed in the laminate.[4-10]

[0077] The electrolyzer according to any of [4-1] to [4-9], wherein the laminate further comprises a fixing member for fixing the membrane and the electrode for electrolysis.[4-11]

[0078] The electrolyzer according to [4-10], wherein, in the laminate, at least a portion of the fixing member penetrates and thereby fixes the membrane and the electrode for electrolysis.[4-12]

[0079] The electrolyzer according to [4-10] or [4-11], wherein, in the laminate, the fixing member comprises a soluble material that is soluble in a electrolyte solution.[4-13]

[0080] The electrolyzer according to any of [4-10] to [4-12], wherein, in the laminate, at least a portion of the fixing member externally grips the membrane and the electrode for electrolysis.[4-14]

[0081] The electrolyzer according to any of [4-10] to [4-13], wherein, in the laminate, at least a portion of the fixing member fixes the membrane and the electrode for electrolysis by magnetic force.[4-15]

[0082] The electrolyzer according to any of [4-1] to [4-14], wherein the membrane comprises an ion exchange membrane comprising a surface layer comprising an organic resin, and the electrode for electrolysis is fixed by the organic resin.[4-16]

[0083] The electrolyzer according to any of [4-1] to [4-15], wherein the membrane comprises a first ion exchange resin layer and a second ion exchange resin layer having an EW different from that of the first ion exchange resin layer.[4-17]

[0084] A method for producing the electrolyzer according to any of [4-1] to [4-16], the method comprising:

[0085] a step of sandwiching the laminate between the anode side gasket and the cathode side gasket.[4-18]

[0086] A method for renewing the laminate in the electrolyzer according to any of [4-1] to [4-16], the method comprising:

[0087] a step of separating the laminate from the anode side gasket and the cathode side gasket to thereby remove the laminate from the electrolyzer, and

[0088] a step of sandwiching a new laminate between the anode side gasket and the cathode side gasket.

[0089] As a result of the intensive studies to achieve the fifth object, the present inventors have found that the problems described above can be solved by use of an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane, being in a wound body form, thereby having completed the present invention.

[0090] That is, the present invention includes the following aspects.[5-1]

[0091] A method for producing a new electrolyzer by arranging an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode,

[0092] wherein the electrode for electrolysis or the laminate, being in a wound body form, is used.[5-2]

[0093] The method for producing the electrolyzer according to [5-1], comprising a step (A) of retaining the electrode for electrolysis or the laminate in a wound state to thereby obtain the wound body.[5-3]

[0094] The method for producing the electrolyzer according to [5-1] or [5-2], comprising a step (B) of releasing the wound state of the wound body.[5-4]

[0095] The method for producing the electrolyzer according to [5-3], comprising a step (C) of arranging the electrode for electrolysis or the laminate on a surface of at least one of the anode and the cathode after the step (B).[5-5]

[0096] A method for renewing an existing electrode by using an electrode for electrolysis, wherein the electrode for electrolysis being in a wound body form is used.[5-6]

[0097] The method for renewing the electrode according to [5-5], comprising a step (A′) of retaining the electrode for electrolysis in a wound state to thereby obtain the wound body.[5-7]

[0098] The method for renewing the electrode according to [5-5] or [5-6], comprising a step (B′) of releasing the wound state of the wound body.[5-8]

[0099] The method for renewing the electrode according to [5-7], comprising a step (C′) of arranging the electrode for electrolysis on a surface of the existing electrode after the step (B′).[5-9]

[0100] A method for producing a wound body to be used for renewing an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode, the method comprising:

[0101] a step of winding an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane to thereby obtain the wound body.

[0102] As a result of the intensive studies to achieve the sixth object, the present inventors have found that the problems described above can be solved by integrating an electrode for electrolysis with a new membrane at a temperature at which the membrane does not melt, thereby having completed the present invention.

[0103] That is, the present invention includes the following aspects.[6-1]

[0104] A method for producing a new electrolyzer by arranging a laminate in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode, the method comprising:

[0105] a step (A) of integrating an electrode for electrolysis with a new membrane at a temperature at which the membrane does not melt to thereby obtain the laminate, and

[0106] a step (B) of replacing the membrane in the existing electrolyzer by the laminate after the step (A).[6-2]

[0107] The method for producing the electrolyzer according to [6-1], wherein the integration is carried out under normal pressure.

[0108] As a result of the intensive studies to achieve the seventh object, the present inventors have found that the problems described above can be solved by an operation in an electrolyzer frame, thereby having completed the present invention.

[0109] That is, the present invention includes the following aspects.[7-1]

[0110] A method for producing a new electrolyzer by arranging a laminate comprising an electrode for electrolysis and a new membrane in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, a membrane that is fixed between the anode and the cathode, and an electrolyzer frame that supports the anode, the cathode, and the membrane, the method comprising:

[0111] a step (A) of releasing a fixing of the membrane in the electrolyzer frame, and

[0112] a step (B) of replacing the membrane by the laminate after the step (A).[7-2]

[0113] The method for producing the electrolyzer according to [7-1], wherein the step (A) is carried out by sliding the anode and the cathode in an arrangement direction thereof, respectively.[7-3]

[0114] The method for producing the electrolyzer according to [7-1] or [7-2], wherein the laminate is fixed in the electrolyzer frame by pressing from the anode and the cathode after the step (B).[7-4]

[0115] The method for producing the electrolyzer according to any of [7-1] to [7-3], wherein the laminate is fixed on a surface of at least one of the anode and the cathode at a temperature at which the laminate does not melt in the step (B).[7-5]

[0116] A method for producing a new electrolyzer by arranging an electrode for electrolysis in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, a membrane that is fixed between the anode and the cathode, and an electrolyzer frame that supports the anode, the cathode, and the membrane, the method comprising:

[0117] a step (A) of releasing a fixing of the membrane in the electrolyzer frame, and

[0118] a step (B′) of arranging the electrode for electrolysis between the membrane and the anode or the cathode after the step (A).Advantageous Effects of Invention

[0119] (1) According to the electrode for electrolysis of the present invention, it is possible to make transport and handling easier, to markedly simplify a work when a new electrolyzer is started or a degraded electrode is renewed, and furthermore, to also maintain or improve the electrolytic performance.

[0120] (2) According to the laminate of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer and furthermore, to exhibit excellent electrolytic performance also after renewing.

[0121] (3) According to the laminate of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer and further, to develop excellent electrolytic performance also after renewing, from a viewpoint different from (2) described above.

[0122] (4) According to electrolyzer of the present invention, the electrolyzer has excellent electrolytic performance as well as can prevent damage of the membrane.

[0123] (5) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer.

[0124] (6) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from (5) described above.

[0125] (7) According to the method for producing an electrolyzer of the present invention, it is possible to improve the work efficiency during electrode renewing in an electrolyzer, from a viewpoint different from (5) and (6) described above.BRIEF DESCRIPTION OF DRAWINGS

[0126] FIG. 1 illustrates a cross-sectional schematic view of an electrode for electrolysis according to one embodiment of the present invention.

[0127] FIG. 2 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane.

[0128] FIG. 3 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0129] FIG. 4 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0130] FIG. 5 illustrates a cross-sectional schematic view of an electrolytic cell.

[0131] FIG. 6 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0132] FIG. 7 illustrates a schematic view of an electrolyzer.

[0133] FIG. 8 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0134] FIG. 9 illustrates a cross-sectional schematic view of a reverse current absorber included in the electrolytic cell.

[0135] FIG. 10 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0136] FIG. 11 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0137] FIG. 12 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0138] FIG. 13 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0139] FIG. 14 illustrates a schematic view of elastic deformation test of the electrode described in Examples.

[0140] FIG. 15 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0141] FIG. 16 illustrates a schematic view of an electrode produced in Comparative Example 13.

[0142] FIG. 17 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 13 on a nickel mesh feed conductor.

[0143] FIG. 18 illustrates a schematic view of an electrode produced in Comparative Example 14.

[0144] FIG. 19 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 14 on a nickel mesh feed conductor.

[0145] FIG. 20 illustrates a schematic view of an electrode produced in Comparative Example 15.

[0146] FIG. 21 illustrates a schematic view of a structure used for placing the electrode produced in Comparative Example 15 on a nickel mesh feed conductor.

[0147] FIG. 22 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0148] FIG. 23 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane.

[0149] FIG. 24 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0150] FIG. 25 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0151] FIG. 26 illustrates a cross-sectional schematic view of an electrolytic cell.

[0152] FIG. 27 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0153] FIG. 28 illustrates a schematic view of an electrolyzer.

[0154] FIG. 29 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0155] FIG. 30 illustrates a cross-sectional schematic view of a reverse current absorber included in the electrolytic cell.

[0156] FIG. 31 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0157] FIG. 32 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0158] FIG. 33 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0159] FIG. 34 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0160] FIG. 35 illustrates a schematic view of elastic deformation test of the electrode described in Examples.

[0161] FIG. 36 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0162] FIG. 37 illustrates a schematic view of an electrode produced in Example 34.

[0163] FIG. 38 illustrates a schematic view of a structure used for placing the electrode produced in Example 34 on a nickel mesh feed conductor.

[0164] FIG. 39 illustrates a schematic view of an electrode produced in Example 35.

[0165] FIG. 40 illustrates a schematic view of a structure used for placing the electrode produced in Example 35 on a nickel mesh feed conductor.

[0166] FIG. 41 illustrates a schematic view of an electrode produced in Example 36.

[0167] FIG. 42 illustrates a schematic view of a structure used for placing the electrode produced in Example 36 on a nickel mesh feed conductor.

[0168] FIG. 43 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0169] FIG. 44 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0170] FIG. 45 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0171] FIG. 46 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0172] FIG. 47A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis penetrates a membrane and thereby is fixed. FIG. 47B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 47A.

[0173] FIG. 48A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis is located inside the membrane and thereby fixed. FIG. 48B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 48A.

[0174] FIGS. 49A to 49C illustrate cross-sectional schematic views of a laminate illustrating an aspect in which a yarn-like fixing member is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0175] FIG. 50 illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which an organic resin is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0176] FIG. 51A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of a fixing member externally grips a membrane and an electrode for electrolysis to fix them. FIG. 51B illustrates a cross-sectional schematic view of the laminate illustrating an aspect in which at least a portion of a fixing member fixes the membrane and the electrode for electrolysis by magnetic force.

[0177] FIG. 52 illustrates a cross-sectional schematic view of an electrolytic cell.

[0178] FIG. 53 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0179] FIG. 54 illustrates a schematic view of an electrolyzer.

[0180] FIG. 55 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0181] FIG. 56 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0182] FIG. 57 illustrates an explanatory view showing a laminate in Example 1.

[0183] FIG. 58 illustrates an explanatory view showing a laminate in Example 2.

[0184] FIG. 59 illustrates an explanatory view showing a laminate in Example 3.

[0185] FIG. 60 illustrates an explanatory view showing a laminate in Example 4.

[0186] FIG. 61 illustrates an explanatory view showing a laminate in Example 5.

[0187] FIG. 62 illustrates an explanatory view showing a laminate in Example 6.

[0188] FIG. 63 illustrates a cross-sectional schematic view of an electrolytic cell.

[0189] FIG. 64A illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series in a conventional electrolyzer. FIG. 64B illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series in the electrolyzer of the present embodiment.

[0190] FIG. 65 illustrates a schematic view of an electrolyzer.

[0191] FIG. 66 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0192] FIG. 67 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0193] FIG. 68 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0194] FIG. 69 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0195] FIG. 70 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0196] FIG. 71 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0197] FIG. 72 illustrates an explanatory view for explaining the positional relation between the laminate and the gaskets.

[0198] FIG. 73 illustrates an explanatory view for explaining the positional relation between the laminate and the gaskets.

[0199] FIG. 74A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis penetrates a membrane and thereby is fixed. FIG. 74B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 12A.

[0200] FIG. 75A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of an electrode for electrolysis is located inside the membrane and thereby fixed. FIG. 75B illustrates an explanatory view illustrating a step of obtaining the structure of FIG. 75A.

[0201] FIGS. 76A to 76C illustrate cross-sectional schematic views of a laminate illustrating an aspect in which a yarn-like fixing member is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0202] FIG. 77 illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which an organic resin is used for fixing as a fixing member for fixing a membrane and an electrode for electrolysis.

[0203] FIG. 78A illustrates a cross-sectional schematic view of a laminate illustrating an aspect in which at least a portion of a fixing member externally grips a membrane and an electrode for electrolysis to fix them. FIG. 78B illustrates a cross-sectional schematic view of the laminate illustrating an aspect in which at least a portion of a fixing member fixes the membrane and the electrode for electrolysis by magnetic force.

[0204] FIG. 79 illustrates a schematic view of a method for evaluating a force applied per unit mass-unit area (1) described in Examples.

[0205] FIG. 80 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (1) described in Examples.

[0206] FIG. 81 illustrates a schematic view of a method for evaluating winding around a column of 280 mm in diameter (2) described in Examples.

[0207] FIG. 82 illustrates a schematic view of a method for evaluating winding around a column of 145 mm in diameter (3) described in Examples.

[0208] FIG. 83 illustrates a schematic view of flexibility evaluation of the electrode described in Examples.

[0209] FIG. 84 illustrates a schematic view of a method for evaluating softness after plastic deformation.

[0210] FIG. 85 illustrates a schematic view of an electrode produced in Example 35.

[0211] FIG. 86 illustrates a schematic view of a structure used for placing the electrode produced in Example 35 on a nickel mesh feed conductor.

[0212] FIG. 87 illustrates a schematic view of an electrode produced in Example 36.

[0213] FIG. 88 illustrates a schematic view of a structure used for placing the electrode produced in Example 36 on a nickel mesh feed conductor.

[0214] FIG. 89 illustrates a schematic view of an electrode produced in Example 37.

[0215] FIG. 90 illustrates a schematic view of a structure used for placing the electrode produced in Example 37 on a nickel mesh feed conductor.

[0216] FIG. 91 illustrates a cross-sectional schematic view of an electrolytic cell.

[0217] FIG. 92 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0218] FIG. 93 illustrates a schematic view of an electrolyzer.

[0219] FIG. 94 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0220] FIG. 95 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0221] FIG. 96 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0222] FIG. 97 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0223] FIG. 98 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0224] FIG. 99 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0225] FIG. 100 illustrates a schematic view of a laminate produced in Example 1.

[0226] FIG. 101 illustrates a schematic view of the case where the laminate produced in Example 1 is wound to form a wound body.

[0227] FIG. 102 illustrates a schematic view of a laminate produced in Example 4.

[0228] FIG. 103 illustrates a cross-sectional schematic view of an electrolytic cell.

[0229] FIG. 104 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0230] FIG. 105 illustrates a schematic view of an electrolyzer.

[0231] FIG. 106 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0232] FIG. 107 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0233] FIG. 108 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0234] FIG. 109 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0235] FIG. 110 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0236] FIG. 111 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.

[0237] FIG. 112 illustrates a cross-sectional schematic view of an electrolytic cell.

[0238] FIG. 113 illustrates a cross-sectional schematic view showing a state of two electrolytic cells connected in series.

[0239] FIG. 114 illustrates a schematic view of an electrolyzer.

[0240] FIG. 115 illustrates a schematic perspective view showing a step of assembling the electrolyzer.

[0241] FIG. 116 illustrates a cross-sectional schematic view of a reverse current absorber that may be included in an electrolytic cell.

[0242] FIG. 117(A) illustrates a schematic view of an electrolyzer for explaining one example of each step according to a first aspect of the present embodiment.

[0243] FIG. 117(B) illustrates a schematic perspective view corresponding to FIG. 117(A).

[0244] FIG. 118(A) illustrates a schematic view of an electrolyzer for explaining one example of each step according to a second aspect of the present embodiment.

[0245] FIG. 118(B) illustrates a schematic perspective view corresponding to FIG. 118(A).

[0246] FIG. 119 illustrates a cross-sectional schematic view of an electrode for electrolysis in one embodiment of the present invention.

[0247] FIG. 120 illustrates a cross-sectional schematic view illustrating one embodiment of an ion exchange membrane.

[0248] FIG. 121 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane.

[0249] FIG. 122 illustrates a schematic view for explaining a method for forming the continuous holes of the ion exchange membrane.DESCRIPTION OF EMBODIMENTS

[0250] Hereinbelow, as for embodiments of the present invention (hereinbelow, may be referred to as the present embodiments), <First embodiment> to <Seventh embodiment> will be each described in detail, with reference to drawings as required. The embodiments below are illustration for explaining the present invention, and the present invention is not limited to the contents below. The accompanying drawings illustrate one example of the embodiments, and embodiments should not be construed to be limited thereto. The present invention may be appropriately modified and carried out within the spirit thereof. In the drawings, positional relations such as top, bottom, left, and right are based on the positional relations shown in the drawing unless otherwise noted. The dimensions and ratios in the drawings are not limited to those shown.First Embodiment

[0251] Here, a first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 21.[Electrode for Electrolysis]

[0252] An electrode for electrolysis of the first embodiment (hereinafter, in the section of <First embodiment>, simply referred to as “the present embodiment”) can provide a good handling property, has a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, and further, has a mass per unit area of 48 mg / cm2 or less from the viewpoint of economy. The mass per unit area is preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less in respect of the above, and furthermore is preferably 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0253] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0254] The electrode for electrolysis of the present embodiment has a force applied per unit mass-unit area of 0.08 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like. The force applied per unit mass-unit area is preferably 0.1 N / (mg·cm2) or more, more preferably 0.14 N / (mg·cm2) or more in respect of the above, and more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0255] From the viewpoint that the electrode for electrolysis of the present embodiment, if being an electrode having a broad elastic deformation region, can provide a better handling property and has a better adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, the thickness of the electrode for electrolysis is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. In the present embodiment, “having a broad elastic deformation region” means that, when an electrode for electrolysis is wound to form a wound body, warpage derived from winding is unlikely to occur after the wound state is released. The thickness of the electrode for electrolysis refers to, when a catalyst layer mentioned below is included, the total thickness of both the substrate for electrode for electrolysis and the catalyst layer.

[0256] The electrode for electrolysis of the present embodiment, which has a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, as described above, can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. For this reason, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated substituting work such as stripping off the electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved. Even in the case where only a feed conductor is placed in a new electrolytic cell (i.e., an electrode including no catalyst layer placed), only attaching the electrode for electrolysis of the present embodiment to the feed conductor enables the electrode to function. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0257] Further, according to the electrode for electrolysis of the present embodiment, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0258] The electrode for electrolysis of the present embodiment can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0259] The force applied can be measured by methods (i) or (ii) described below, which are as described in Examples in detail. As for the force applied, the value obtained by the measurement of the method (i) (also referred to as “the force applied (1)”) and the value obtained by the measurement of the method (ii) (also referred to as “the force applied (2)”) may be the same or different, and either of the values is 0.08 N / (mg·cm2) or more.

[0260] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.[Method (i)]

[0261] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion exchange membrane which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced (170 mm square, the detail of the ion exchange membrane referred to herein is as described in Examples), and a sample of electrode for electrolysis (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. The arithmetic average surface roughness (Ra) of the nickel plate after the blast treatment was 0.7 μm. The specific method for calculating the arithmetic average surface roughness (Ra) is as described in Examples.

[0262] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode for electrolysis in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode for electrolysis is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0263] This average value is divided by the area of the overlapping portion of the sample of electrode for electrolysis and the ion exchange membrane and the mass of the portion overlapping the ion exchange membrane in the sample of electrode for electrolysis to calculate the force applied per unit mass-unit area (1) (N / mg·cm2).

[0264] The force applied per unit mass-unit area (1) obtained by the method (i) is 0.08 N / (mg·cm2) or more, preferably 0.1 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0265] When the electrode for electrolysis of the present embodiment satisfies the force applied (1), the electrode can be integrated with a membrane such as an ion exchange membrane and a microporous membrane, for example, and used. Thus, on renewing the electrode, the substituting work for the cathode and anode fixed on the electrolytic cell by a method such as welding is eliminated, and the work efficiency is markedly improved. Additionally, by use of the electrode for electrolysis of the present embodiment as an electrode integrated with the ion exchange membrane, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0266] On shipping a new electrolytic cell, an electrode fixed on an electrolytic cell has been subjected to catalyst coating conventionally. Since only combination of an electrode having no catalyst coating with the electrode for electrolysis of the present embodiment can allow the electrode to function as an electrode, it is possible to markedly reduce or eliminate the production step and the amount of the catalyst for catalyst coating. A conventional electrode of which catalyst coating is markedly reduced or eliminated can be electrically connected to the electrode for electrolysis of the present embodiment and allowed to serve as a feed conductor for passage of an electric current.[Method (ii)]

[0267] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar to that of the method (i) above) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode for electrolysis in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode for electrolysis is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0268] This average value is divided by the area of the overlapping portion of the sample of electrode for electrolysis and the nickel plate and the mass of the sample of electrode for electrolysis in the portion overlapping the nickel plate to calculate the adhesive force per unit mass-unit area (2)(N / mg·cm2).

[0269] The force applied per unit mass-unit area (2) obtained by the method (ii) is 0.08 N / (mg·cm2) or more, preferably 0.1 N / (mg·cm2) or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and more preferably 0.14 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0270] The electrode for electrolysis of the present embodiment, if satisfies the force applied (2), can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier. By attaching the electrode for electrolysis of the present embodiment to a degraded electrode, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0271] In the present embodiment, as the liquid included between the membrane such as an ion exchange membrane and a microporous membrane, the electrode for electrolysis or the feed conductor (degraded electrode or electrode having no catalyst coating) and the electrode for electrolysis, any liquid, such as water and organic solvents, can be used as long as the liquid generates a surface tension. The larger the surface tension of the liquid, the larger the force applied between the membrane and the electrode for electrolysis or the metal plate and the electrode for electrolysis. Thus, a liquid having a larger surface tension is preferred. Examples of the liquid include the following (the numerical value in the parentheses is the surface tension of the liquid):

[0272] hexane (20.44 mN / m), acetone (23.30 mN / m), methanol (24.00 mN / m), ethanol (24.05 mN / m), ethylene glycol (50.21 mN / m), and water (72.76 mN / m).

[0273] A liquid having a large surface tension allows the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis to be integrated (to be a laminate) to thereby facilitate renewing of the electrode. The liquid between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis may be present in an amount such that the both adhere to each other by the surface tension. As a result, after the laminate is placed in an electrolytic cell, the liquid, if mixed into the electrolyte solution, does not affect electrolysis itself due to the small amount of the liquid.

[0274] From a practical viewpoint, a liquid having a surface tension of 20 mN / m to 80 mN / m, such as ethanol, ethylene glycol, and water, is preferably used as the liquid. Particularly preferred is water or an alkaline aqueous solution prepared by dissolving caustic soda, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, or the like in water. Alternatively, the surface tension can be adjusted by allowing these liquids to contain a surfactant. When a surfactant is contained, the adhesion between the membrane and the electrode for electrolysis or the metal plate and the electrode for electrolysis varies to enable the handling property to be adjusted. The surfactant is not particularly limited, and both ionic surfactants and nonionic surfactants may be used.

[0275] The electrode for electrolysis of the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The thickness of the substrate for electrode for electrolysis (gauge thickness) is not particularly limited, but is preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further preferably 135 μm or less, further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, being capable of being suitably rolled in a roll and satisfactorily folded, and facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0276] The proportion measured by the following method (2) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 90% or more, more preferably 92% or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and further preferably 95% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (2)]

[0277] An ion exchange membrane (170 mm square) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 280 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode for electrolysis is measured.

[0278] The proportion measured by the following method (3) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 75% or more, more preferably 80% or more from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating and being capable of being suitably rolled in a roll and satisfactorily folded, and is further preferably 90% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (3)]

[0279] An ion exchange membrane (170 mm square) and a sample of electrode for electrolysis (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode for electrolysis is measured.

[0280] The electrode for electrolysis of the present embodiment preferably has, but is not particularly limited to, a porous structure and an opening ratio or void ratio of 5 to 90% or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating, and preventing accumulation of gas to be generated during electrolysis. The opening ratio is more preferably 10 to 80% or less, further preferably 20 to 75%.

[0281] The opening ratio is a proportion of the opening portions per unit volume. The calculation method may differ depending on that opening portions in submicron size are considered or that only visible openings are considered. In the present embodiment, a volume V was calculated from the values of the gauge thickness, width, and length of the electrode, and further, a weight W was measured to thereby calculate an opening ratio A by the following formula.A=(1-(W / (V×ρ))×100

[0282] ρ is the density of the electrode material (g / cm3). For example, ρ of nickel is 8.908 g / cm3, and ρ of titanium is 4.506 g / cm3. The opening ratio is appropriately adjusted by changing the area of metal to be perforated per unit area in the case of perforated metal, changing the values of the SW (short diameter), LW (long diameter), and feed in the case of expanded metal, changing the line diameter of metal fiber and mesh number in the case of mesh, changing the pattern of a photoresist to be used in the case of electroforming, changing the metal fiber diameter and fiber density in the case of nonwoven fabric, changing the mold for forming voids in the case of foamed metal, or the like.

[0283] The value obtained by measurement by the following method (A) of the electrode for electrolysis in the present embodiment is preferably 40 mm or less, more preferably 29 mm or less, further preferably 10 mm or less, further more preferably 6.5 mm or less from the viewpoint of the handling property. The specific measuring method is as described in Examples.[Method (A)]

[0284] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.

[0285] In the electrode for electrolysis in the present embodiment, the ventilation resistance is preferably 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under the conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s (hereinbelow, also referred to as “measurement condition 1”) (hereinbelow, also referred to as “ventilation resistance 1”). A larger ventilation resistance means that air is unlikely to flow and refers to a state of a high density. In this state, the product from electrolysis remains in the electrode and the reaction substrate is more unlikely to diffuse inside the electrode, and thus, the electrolytic performance (such as voltage) tends to deteriorate. The concentration on the membrane surface tends to increase. Specifically, the caustic concentration increases on the cathode surface, and the supply of brine tends to decrease on the anode surface. As a result, the product accumulates at a high concentration on the interface at which the membrane is in contact with the electrode. This accumulation leads to damage of the membrane and tends to also lead to increase in the voltage and damage of the membrane on the cathode surface and damage of the membrane on the anode surface. In the present embodiment, in order to prevent these defects, the ventilation resistance is preferably set at 24 kPa·s / m or less. From a similar viewpoint as above, the ventilation resistance is more preferably less than 0.19 kPa·s / m, further preferably 0.15 kPa·s / m or less, further more preferably 0.07 kPa·s / m or less.

[0286] In the present embodiment, when the ventilation resistance is larger than a certain value, NaOH generated in the electrode tends to accumulate on the interface between the electrode and the membrane to result in a high concentration in the case of the cathode, and the supply of brine tends to decrease to cause the brine concentration to be lower in the case of the anode. In order to prevent damage to the membrane that may be caused by such accumulation, the ventilation resistance is preferably less than 0.19 kPa·s / m, more preferably 0.15 kPa·s / m or less, further preferably 0.07 kPa·s / m or less.

[0287] In contrast, when the ventilation resistance is low, the area of the electrode is reduced and the electrolysis area is reduced. Thus, the electrolytic performance (such as voltage) tends to deteriorate. When the ventilation resistance is zero, the feed conductor functions as the electrode because no electrode for electrolysis is provided, and the electrolytic performance (such as voltage) tends to markedly deteriorate. From this viewpoint, a preferable lower limit value identified as the ventilation resistance 1 is not particularly limited, but is preferably more than 0 kPa·s / m, more preferably 0.0001 kPa·s / m or more, further preferably 0.001 kPa·s / m or more.

[0288] When the ventilation resistance 1 is 0.07 kPa·s / m or less, a sufficient measurement accuracy may not be achieved because of the measurement method therefor. From this viewpoint, it is also possible to evaluate an electrode for electrolysis having a ventilation resistance 1 of 0.07 kPa·s / m or less by means of a ventilation resistance (hereinbelow, also referred to as “ventilation resistance 2”) obtained by the following measurement method (hereinbelow, also referred to as “measurement condition 2”). That is, the ventilation resistance 2 is a ventilation resistance measured, when the electrode for electrolysis has a size of 50 mm×50 mm, under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 2 cm / s, and a ventilation volume of 4 cc / cm2 / s.

[0289] The specific methods for measuring the ventilation resistances 1 and 2 are described in Examples.

[0290] The ventilation resistances 1 and 2 can be within the range described above by appropriately adjusting an opening ratio, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to smaller ventilation resistances 1 and 2, and a lower opening ratio tends to lead to larger ventilation resistances 1 and 2.

[0291] Hereinbelow, one aspect of the electrode for electrolysis of the present embodiment will be described.

[0292] The electrode for electrolysis according to the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The catalyst layer may be composed of a plurality of layers as shown below or may be a single-layer configuration.

[0293] As shown in FIG. 1, an electrode for electrolysis 100 according to the present embodiment includes a substrate for electrode for electrolysis 10 and a pair of first layers 20 with which both the surfaces of the substrate for electrode for electrolysis 10 are covered. The entire substrate for electrode for electrolysis 10 is preferably covered with the first layers 20. This covering is likely to improve the catalyst activity and durability of the electrode. One first layer 20 may be laminated only on one surface of the substrate for electrode for electrolysis 10.

[0294] Also shown in FIG. 1, the surfaces of the first layers 20 may be covered with second layers 30. The entire first layers 20 are preferably covered by the second layers 30. Alternatively, one second layer 30 may be laminated only one surface of the first layer 20.(Substrate for Electrode for Electrolysis)

[0295] As the substrate for electrode for electrolysis 10, for example, nickel, nickel alloys, stainless steel, and further, valve metals including titanium can be used, although not limited thereto. At least one element selected from nickel (Ni) and titanium (Ti) is preferably included. That is, the substrate for electrode for electrolysis preferably includes at least one element selected from nickel (Ni) and titanium (Ti).

[0296] When stainless steel is used in an alkali aqueous solution of a high concentration, iron and chromium are eluted and the electrical conductivity of stainless steel is of the order of one-tenth of that of nickel. In consideration of the foregoing, a substrate containing nickel (Ni) is preferable as the substrate for electrode for electrolysis.

[0297] Alternatively, when the substrate for electrode for electrolysis 10 is used in a salt solution of a high concentration near the saturation under an atmosphere in which chlorine gas is generated, the material of the substrate for electrode 10 is also preferably titanium having high corrosion resistance.

[0298] The form of the substrate for electrode for electrolysis 10 is not particularly limited, and a form suitable for the purpose can be selected. As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used. Among these, a perforated metal or expanded metal is preferable. Electroforming is a technique for producing a metal thin film having a precise pattern by using photolithography and electroplating in combination. It is a method including forming a pattern on a substrate with a photoresist and electroplating the portion not protected by the resist to provide a metal thin film.

[0299] As for the form of the substrate for electrode for electrolysis, a suitable specification depends on the distance between the anode and the cathode in the electrolyzer. In the case where the distance between the anode and the cathode is finite, an expanded metal or perforated metal form can be used, and in the case of a so-called zero-gap base electrolyzer, in which the ion exchange membrane is in contact with the electrode, a woven mesh produced by knitting thin lines, foamed metal, metal nonwoven fabric, expanded metal, perforated metal, metal porous foil, and the like can be used, although not limited thereto.

[0300] Examples of the substrate for electrode for electrolysis 10 include a metal foil, a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, or a foamed metal.

[0301] As a plate material before processed into a perforated metal or expanded metal, rolled plate materials and electrolytic foils are preferable. An electrolytic foil is preferably further subjected to a plating treatment by use of the same element as the base material thereof, as the post-treatment, to thereby form asperities on the surface thereof.

[0302] The thickness of the substrate for electrode for electrolysis 10 is, as mentioned above, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less, and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0303] In the substrate for electrode for electrolysis, the residual stress during processing is preferably relaxed by annealing the substrate for electrode for electrolysis in an oxidizing atmosphere. It is preferable to form asperities using a steel grid, alumina grid, or the like on the surface of the substrate for electrode for electrolysis followed by an acid treatment to increase the surface area thereof, in order to improve the adhesion to a catalyst layer with which the surface is covered. It is preferable to give a plating treatment by use of the same element as the substrate to increase the surface area.

[0304] To bring the first layer 20 into close contact with the surface of the substrate for electrode for electrolysis 10, the substrate for electrode for electrolysis 10 is preferably subjected to a treatment of increasing the surface area. Examples of the treatment of increasing the surface area include a blast treatment using a cut wire, steel grid, alumina grid or the like, an acid treatment using sulfuric acid or hydrochloric acid, and a plating treatment using the same element to that of the substrate. The arithmetic average surface roughness (Ra) of the substrate surface is not particularly limited, but is preferably 0.05 μm to 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 5 μm.

[0305] Next, a case where the electrode for electrolysis of the present embodiment is used as an anode for common salt electrolysis will be described.(First Layer)

[0306] In FIG. 1, a first layer 20 as a catalyst layer contains at least one of ruthenium oxides, iridium oxides, and titanium oxides. Examples of the ruthenium oxide include RuO2. Examples of the iridium oxide include IrO2. Examples of the titanium oxide include TiO2. The first layer 20 preferably contains two oxides: a ruthenium oxide and a titanium oxide or three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide. This makes the first layer 20 more stable and additionally improves the adhesion with the second layer 30.

[0307] When the first layer 20 contains two oxides: a ruthenium oxide and a titanium oxide, the first layer 20 contains preferably 1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the two oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0308] When the first layer 20 contains three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide, the first layer 20 contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the three oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0309] When the first layer 20 contains at least two of a ruthenium oxide, an iridium oxide, and a titanium oxide, these oxides preferably form a solid solution. Formation of the oxide solid solution allows the electrode for electrolysis 100 to exhibit excellent durability.

[0310] In addition to the compositions described above, oxides of various compositions can be used as long as at least one oxide of a ruthenium oxide, an iridium oxide, and titanium oxide is contained. For example, an oxide coating called DSA®, which contains ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and the like, can be used as the first layer 20.

[0311] The first layer 20 need not be a single layer and may include a plurality of layers. For example, the first layer 20 may include a layer containing three oxides and a layer containing two oxides. The thickness of the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1 to 8 μm.(Second Layer)

[0312] The second layer 30 preferably contains ruthenium and titanium. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0313] The second layer 30 preferably contains a palladium oxide, a solid solution of a palladium oxide and platinum, or an alloy of palladium and platinum. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0314] A thicker second layer 30 can maintain the electrolytic performance for a longer period, but from the viewpoint of economy, the thickness is preferably 0.05 to 3 μm.

[0315] Next, a case where the electrode for electrolysis of the present embodiment is used as a cathode for common salt electrolysis will be described.(First Layer)

[0316] Examples of components of the first layer 20 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0317] When the first layer 20 contains at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal, the platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal preferably contain at least one platinum group metal of platinum, palladium, rhodium, ruthenium, and iridium.

[0318] As the platinum group metal, platinum is preferably contained.

[0319] As the platinum group metal oxide, a ruthenium oxide is preferably contained.

[0320] As the platinum group metal hydroxide, a ruthenium hydroxide is preferably contained.

[0321] As the platinum group metal alloy, an alloy of platinum with nickel, iron, and cobalt is preferably contained.

[0322] Further, as required, an oxide or hydroxide of a lanthanoid element is preferably contained as a second component. This allows the electrode for electrolysis 100 to exhibit excellent durability.

[0323] As the oxide or hydroxide of a lanthanoid element, at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, and dysprosium is preferably contained.

[0324] Further, as required, an oxide or hydroxide of a transition metal is preferably contained as a third component.

[0325] Addition of the third component enables the electrode for electrolysis 100 to exhibit more excellent durability and the electrolysis voltage to be lowered.

[0326] Examples of a preferable combination include ruthenium only, ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum, ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium, ruthenium+praseodymium, ruthenium+praseodymium+platinum, ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium, ruthenium+neodymium+platinum, ruthenium+neodymium+manganese, ruthenium+neodymium+iron, ruthenium+neodymium+cobalt, ruthenium+neodymium+zinc, ruthenium+neodymium+gallium, ruthenium+neodymium+sulfur, ruthenium+neodymium+lead, ruthenium+neodymium+nickel, ruthenium+neodymium+copper, ruthenium+samarium, ruthenium+samarium+manganese, ruthenium+samarium+iron, ruthenium+samarium+cobalt, ruthenium+samarium+zinc, ruthenium+samarium+gallium, ruthenium+samarium+sulfur, ruthenium+samarium+lead, ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium, platinum+palladium+lanthanum+cerium, platinum+iridium, platinum+palladium, platinum+iridium+palladium, platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinum and nickel, alloys of platinum and cobalt, and alloys of platinum and iron.

[0327] When platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal are not contained, the main component of the catalyst is preferably nickel element.

[0328] At least one of nickel metal, oxides, and hydroxides is preferably contained.

[0329] As the second component, a transition metal may be added. As the second component to be added, at least one element of titanium, tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon is preferably contained.

[0330] Examples of a preferable combination include nickel+tin, nickel+titanium, nickel+molybdenum, and nickel+cobalt.

[0331] As required, an intermediate layer can be placed between the first layer 20 and the substrate for electrode for electrolysis 10. The durability of the electrode for electrolysis 100 can be improved by placing the intermediate layer.

[0332] As the intermediate layer, those having affinity to both the first layer 20 and the substrate for electrode for electrolysis 10 are preferable. As the intermediate layer, nickel oxides, platinum group metals, platinum group metal oxides, and platinum group metal hydroxides are preferable. The intermediate layer can be formed by applying and baking a solution containing a component that forms the intermediate layer. Alternatively, a surface oxide layer also can be formed by subjecting a substrate to a thermal treatment at a temperature of 300 to 600° C. in an air atmosphere. Besides, the layer can be formed by a known method such as a thermal spraying method and ion plating method.(Second Layer)

[0333] Examples of components of the first layer 30 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. The first layer 30 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal. Examples of a preferable combination of elements contained in the second layer include the combinations enumerated for the first layer. The combination of the first layer and the second layer may be a combination in which the compositions are the same and the composition ratios are different or may be a combination of different compositions.

[0334] As the thickness of the catalyst layer, the total thickness of the catalyst layer formed and the intermediate layer is preferably 0.01 μm to 20 μm. With a thickness of 0.01 μm or more, the catalyst layer can sufficiently serve as the catalyst. With a thickness of 20 μm or less, it is possible to form a robust catalyst layer that is unlikely to fall off from the substrate. The thickness is more preferably 0.05 μm to 15 μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness is further preferably 0.2 μm to 8 μm.

[0335] The thickness of the electrode, that is, the total thickness of the substrate for electrode for electrolysis and the catalyst layer is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less in respect of the handling property of the electrode. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. The thickness of the electrode can be determined by measurement with a digimatic thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of the substrate for electrode for electrolysis was measured in the same manner as the thickness of the electrode. The thickness of the catalyst layer can be determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode.(Method for Producing Electrode for Electrolysis)

[0336] Next, one embodiment of the method for producing the electrode for electrolysis 100 will be described in detail.

[0337] In the present embodiment, the electrode for electrolysis 100 can be produced by forming the first layer 20, preferably the second layer 30, on the substrate for electrode for electrolysis by a method such as baking of a coating film under an oxygen atmosphere (pyrolysis), or ion plating, plating, or thermal spraying. Among these, the pyrolysis method, plating method, and ion plating method are preferable because the catalyst layer can be formed while deformation of the substrate for electrode for electrolysis is prevented. When the viewpoint of productivity is added, the plating method and pyrolysis method are further preferable. The production method of the present embodiment as mentioned can achieve a high productivity of the electrode for electrolysis 100. Specifically, in the pyrolysis method, a catalyst layer is formed on the substrate for electrode for electrolysis by an application step of applying a coating liquid containing a catalyst, a drying step of drying the coating liquid, and a pyrolysis step of performing pyrolysis. Pyrolysis herein means that a metal salt which is to be a precursor is decomposed by heating into a metal or metal oxide and a gaseous substance. The decomposition product depends on the metal species to be used, type of the salt, and the atmosphere under which pyrolysis is performed, and many metals tend to form oxides in an oxidizing atmosphere. In an industrial process of producing an electrode for electrolysis, pyrolysis is usually performed in air, and a metal oxide or a metal hydroxide is formed in many cases.(Formation of First Layer of Anode)(Application Step)

[0338] The first layer 20 is obtained by applying a solution in which at least one metal salt of ruthenium, iridium, and titanium is dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of ruthenium, iridium, and titanium in the first coating liquid is substantially equivalent to that of the first layer 20.

[0339] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0340] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0341] After being applied onto the substrate for electrode for electrolysis 100, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0342] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Second Layer of Anode)

[0343] The second layer 30, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound and a platinum compound or a solution containing a ruthenium compound and a titanium compound (second coating liquid) onto the first layer 20 and then pyrolyzing the coating liquid in the presence of oxygen.(Formation of First Layer of Cathode by Pyrolysis Method)(Application Step)

[0344] The first layer 20 is obtained by applying a solution in which metal salts of various combination are dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of the metal in the first coating liquid is substantially equivalent to that in the first layer 20. The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as ethanol and butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is, but is not particularly limited to, preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0345] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0346] After being applied onto the substrate for electrode for electrolysis 10, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0347] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further baked for a long period as required, heating in the range of 350° C. to 650° C. for one minute to 90 minutes can further improve the stability of the first layer 20.(Formation of Intermediate Layer)

[0348] The intermediate layer, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound or platinum compound (second coating liquid) onto the substrate and then pyrolyzing the coating liquid in the presence of oxygen. Alternatively, a nickel oxide intermediate layer may be formed on the substrate surface only by heating the substrate, with no solution applied thereon, in the range of 300° C. to 580° C. for one minute to 60 minutes.(Formation of First Layer of Cathode by Ion Plating)

[0349] The first layer 20 can be formed also by ion plating.

[0350] An example includes a method in which the substrate is fixed in a chamber and the metal ruthenium target is irradiated with an electron beam. Evaporated metal ruthenium particles are positively charged in plasma in the chamber to deposit on the substrate negatively charged. The plasma atmosphere is argon and oxygen, and ruthenium deposits as ruthenium oxide on the substrate.(Formation of First Layer of Cathode by Plating)

[0351] The first layer 20 can be formed also by a plating method.

[0352] As an example, when the substrate is used as the cathode and subjected to electrolytic plating in an electrolyte solution containing nickel and tin, alloy plating of nickel and tin can be formed.(Formation of First Layer of Cathode by Thermal Spraying)

[0353] The first layer 20 can be formed also by thermal spraying.

[0354] As an example, plasma spraying nickel oxide particles onto the substrate can form a catalyst layer in which metal nickel and nickel oxide are mixed.

[0355] The electrode for electrolysis of the present embodiment can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. Thus, the electrode can be used as a membrane-integrated electrode. Then, the substituting work for the cathode and anode on renewing the electrode is eliminated, and the work efficiency is markedly improved.

[0356] The electrode for electrolysis of the present embodiment forms a laminate with a membrane such as an ion exchange membrane and a microporous membrane to be an integrated piece of the membrane and the electrode, and then can make the electrolytic performance comparable to or higher than those of a new electrode. The membrane is not particularly limited as long as the membrane can be laminated with the electrode, and will be described in detail below.[Ion Exchange Membrane]

[0357] The ion exchange membrane has a membrane body containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and a coating layer provided on at least one surface of the membrane body. The coating layer contains inorganic material particles and a binder, and the specific surface area of the coating layer is 0.1 to 10 m2 / g. In the ion exchange membrane having such a structure, the influence of gas generated during electrolysis on electrolytic performance is small, and stable electrolytic performance can be exhibited.

[0358] The ion exchange membrane described above includes either one of a sulfonic acid layer having an ion exchange group derived from a sulfo group (a group represented by —SO3−, hereinbelow also referred to as a “sulfonic acid group”) or a carboxylic acid layer having an ion exchange group derived from a carboxyl group (a group represented by —CO2−, hereinbelow also referred to as a “carboxylic acid group”). From the viewpoint of strength and dimension stability, reinforcement core materials are preferably further included.

[0359] The inorganic material particles and binder will be described in detail in the section of description of the coating layer below.

[0360] FIG. 2 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane. An ion exchange membrane 1 has a membrane body 10 containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and coating layers 11a and 11b formed on both the surfaces of the membrane body 10.

[0361] In the ion exchange membrane 1, the membrane body 10 includes a sulfonic acid layer 3 and a carboxylic acid layer 2, and reinforcement core materials 4 enhance the strength and dimension stability. The ion exchange membrane 1, including the sulfonic acid layer 3 and the carboxylic acid layer 2, is suitably used as an ion exchange membrane.

[0362] The ion exchange membrane may include either one of the sulfonic acid layer and the carboxylic acid layer. The ion exchange membrane may not be necessarily reinforced by reinforcement core materials, and the arrangement of the reinforcement core materials is not limited to the example in FIG. 2.(Membrane Body)

[0363] First, the membrane body 10 constituting the ion exchange membrane 1 will be described.

[0364] The membrane body 10 should be one that has a function of selectively allowing cations to permeate and comprises a hydrocarbon polymer or a fluorine-containing polymer having an ion exchange group. Its configuration and material are not particularly limited, and preferred ones can be appropriately selected.

[0365] The hydrocarbon polymer or fluorine-containing polymer having an ion exchange group in the membrane body 10 can be obtained from a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group precursor capable of forming an ion exchange group by hydrolysis or the like. Specifically, for example, after a polymer comprising a main chain of a fluorinated hydrocarbon, having, as a pendant side chain, a group convertible into an ion exchange group by hydrolysis or the like (ion exchange group precursor), and being melt-processable (hereinbelow, referred to as the “fluorine-containing polymer (a)” in some cases) is used to prepare a precursor of the membrane body 10, the membrane body 10 can be obtained by converting the ion exchange group precursor into an ion exchange group.

[0366] The fluorine-containing polymer (a) can be produced, for example, by copolymerizing at least one monomer selected from the following first group and at least one monomer selected from the following second group and / or the following third group. The fluorine-containing polymer (a) can be also produced by homopolymerization of one monomer selected from any of the following first group, the following second group, and the following third group.

[0367] Examples of the monomers of the first group include vinyl fluoride compounds. Examples of the vinyl fluoride compounds include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinyl ethers. Particularly when the ion exchange membrane is used as a membrane for alkali electrolysis, the vinyl fluoride compound is preferably a perfluoro monomer, and a perfluoro monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl ethers is preferable.

[0368] Examples of the monomers of the second group include vinyl compounds having a functional group convertible into a carboxylic acid-type ion exchange group (carboxylic acid group). Examples of the vinyl compounds having a functional group convertible into a carboxylic acid group include monomers represented by CF2═CF(OCF2CYF)s—O(CZF)t—COOR, wherein s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represent F or CF3, and R represents a lower alkyl group (a lower alkyl group is an alkyl group having 1 to 3 carbon atoms, for example).

[0369] Among these, compounds represented by CF2═CF(OCF2CYF)n—O(CF2)m—COOR are preferable. Wherein n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF3, and R represents CH3, C2H5, or C3H7.

[0370] When the ion exchange membrane is used as a cation exchange membrane for alkali electrolysis, a perfluoro compound is preferably at least used as the monomer, but the alkyl group (see the above R) of the ester group is lost from the polymer at the time of hydrolysis, and therefore the alkyl group (R) need not be a perfluoroalkyl group in which all hydrogen atoms are replaced by fluorine atoms.

[0371] Of the above monomers, the monomers represented below are more preferable as the monomers of the second group:

[0372] Examples of the monomers of the third group include vinyl compounds having a functional group convertible into a sulfone-type ion exchange group (sulfonic acid group). As the vinyl compounds having a functional group convertible into a sulfonic acid group, for example, monomers represented by CF2═CFO—X—CF2—SO2F are preferable, wherein X represents a perfluoroalkylene group. Specific examples of these include the monomers represented below:

[0373] Among these, CF2═CFOCF2CF(CF3)OCF2CF2CF2SO2F and CF2═CFOCF2CF(CF3)OCF2CF2SO2F are more preferable.

[0374] The copolymer obtained from these monomers can be produced by a polymerization method developed for homopolymerization and copolymerization of ethylene fluoride, particularly a general polymerization method used for tetrafluoroethylene. For example, in a non-aqueous method, a polymerization reaction can be performed in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound under the conditions of a temperature of 0 to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent such as a perfluorohydrocarbon or a chlorofluorocarbon.

[0375] In the above copolymerization, the type of combination of the above monomers and their proportion are not particularly limited and are selected and determined depending on the type and amount of the functional group desired to be imparted to the fluorine-containing polymer to be obtained. For example, when a fluorine-containing polymer containing only a carboxylic acid group is formed, at least one monomer should be selected from each of the first group and the second group described above and copolymerized. In addition, when a fluorine-containing polymer containing only a sulfonic acid group is formed, at least one monomer should be selected from each of the first group and the third group and copolymerized. Further, when a fluorine-containing polymer having a carboxylic acid group and a sulfonic acid group is formed, at least one monomer should be selected from each of the first group, the second group, and the third group described above and copolymerized. In this case, the target fluorine-containing polymer can be obtained also by separately preparing a copolymer comprising the monomers of the first group and the second group described above and a copolymer comprising the monomers of the first group and the third group described above, and then mixing the copolymers. The mixing proportion of the monomers is not particularly limited, and when the amount of the functional groups per unit polymer is increased, the proportion of the monomers selected from the second group and the third group described above should be increased.

[0376] The total ion exchange capacity of the fluorine-containing copolymer is not particularly limited, but is preferably 0.5 to 2.0 mg equivalent / g, more preferably 0.6 to 1.5 mg equivalent / g. The total ion exchange capacity herein refers to the equivalent of the exchange group per unit weight of the dry resin and can be measured by neutralization titration or the like.

[0377] In the membrane body 10 of the ion exchange membrane 1, a sulfonic acid layer 3 containing a fluorine-containing polymer having a sulfonic acid group and a carboxylic acid layer 2 containing a fluorine-containing polymer having a carboxylic acid group are laminated. By providing the membrane body 10 having such a layer configuration, selective permeability for cations such as sodium ions can be further improved.

[0378] The ion exchange membrane 1 is arranged in an electrolyzer such that, usually, the sulfonic acid layer 3 is located on the anode side of the electrolyzer and the carboxylic acid layer 2 is located on the cathode side of the electrolyzer.

[0379] The sulfonic acid layer 3 is preferably constituted by a material having low electrical resistance and has a membrane thickness larger than that of the carboxylic acid layer 2 from the viewpoint of membrane strength. The membrane thickness of the sulfonic acid layer 3 is preferably 2 to 25 times, more preferably 3 to 15 times that of the carboxylic acid layer 2. The carboxylic acid layer 2 preferably has high anion exclusion properties even if it has a small membrane thickness. The anion exclusion properties here refer to the property of trying to hinder intrusion and permeation of anions into and through the ion exchange membrane 1. In order to raise the anion exclusion properties, it is effective to dispose a carboxylic acid layer having a small ion exchange capacity to the sulfonic acid layer.

[0380] As the fluorine-containing polymer for use in the sulfonic acid layer 3, preferable is a polymer obtained by using CF2═CFOCF2CF(CF3)OCF2CF2SO2F as the monomer of the third group.

[0381] As the fluorine-containing polymer for use in the carboxylic acid layer 2, preferable is a polymer obtained by using CF2═CFOCF2CF(CF2)O(CF2)2COOCH3 as the monomer of the second group.(Coating Layer)

[0382] The ion exchange membrane has a coating layer on at least one surface of the membrane body. As shown in FIG. 2, in the ion exchange membrane 1, coating layers 11a and 11b are formed on both the surfaces of the membrane body 10.

[0383] The coating layers contain inorganic material particles and a binder.

[0384] The average particle size of the inorganic material particles is preferably 0.90 μm or more. When the average particle size of the inorganic material particles is 0.90 μm or more, durability to impurities is extremely improved, in addition to attachment of gas. That is, enlarging the average particle size of the inorganic material particles as well as satisfying the value of the specific surface area mentioned above can achieve a particularly marked effect. Irregular inorganic material particles are preferable because the average particle size and specific surface area as above are satisfied. Inorganic material particles obtained by melting and inorganic material particles obtained by grinding raw ore can be used. Inorganic material particles obtained by grinding raw ore can preferably be used.

[0385] The average particle size of the inorganic material particles can be 2 μm or less. When the average particle size of the inorganic material particles is 2 μm or less, it is possible to prevent damage of the membrane due to the inorganic material particles. The average particle size of the inorganic material particle is more preferably 0.90 to 1.2 μm.

[0386] Here, the average particle size can be measured by a particle size analyzer (“SALD2200”, SHIMADZU CORPORATION).

[0387] The inorganic material particles preferably have irregular shapes. Such shapes improve resistance to impurities further. The inorganic material particles preferably have a broad particle size distribution.

[0388] The inorganic material particles preferably contain at least one inorganic material selected from the group consisting of oxides of Group IV elements in the Periodic Table, nitrides of Group IV elements in the Periodic Table, and carbides of Group IV elements in the Periodic Table. From the viewpoint of durability, zirconium oxide particle is more preferable.

[0389] The inorganic material particles are preferably inorganic material particles produced by grinding the raw ore of the inorganic material particles or inorganic material particles, as spherical particles having a uniform diameter, obtained by melt-purifying the raw ore of the inorganic material particles.

[0390] Examples of means for grinding raw ore include, but are not particularly limited to, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, grain mills, hammer mills, pellet mills, VSI mills, Wiley mills, roller mills, and jet mills. After grinding, the particles are preferably washed. As the washing method, the particles are preferably treated with acid. This treatment can reduce impurities such as iron attached to the surface of the inorganic material particles.

[0391] The coating layer preferably contains a binder. The binder is a component that forms the coating layers by retaining the inorganic material particles on the surface of the ion exchange membrane. The binder preferably contains a fluorine-containing polymer from the viewpoint of durability to the electrolyte solution and products from electrolysis.

[0392] As the binder, a fluorine-containing polymer having a carboxylic acid group or sulfonic acid group is more preferable, from the viewpoint of durability to the electrolyte solution and products from electrolysis and adhesion to the surface of the ion exchange membrane. When a coating layer is provided on a layer containing a fluorine-containing polymer having a sulfonic acid group (sulfonic acid layer), a fluorine-containing polymer having a sulfonic acid group is further preferably used as the binder of the coating layer. Alternatively, when a coating layer is provided on a layer containing a fluorine-containing polymer having a carboxylic acid group (carboxylic acid layer), a fluorine-containing polymer having a carboxylic acid group is further preferably used as the binder of the coating layer.

[0393] In the coating layer, the content of the inorganic material particles is preferably 40 to 90% by mass, more preferably 50 to 90% by mass. The content of the binder is preferably 10 to 60% by mass, more preferably 10 to 50% by mass.

[0394] The distribution density of the coating layer in the ion exchange membrane is preferably 0.05 to 2 mg per 1 cm2. When the ion exchange membrane has asperities on the surface thereof, the distribution density of the coating layer is preferably 0.5 to 2 mg per 1 cm2.

[0395] As the method for forming the coating layer, which is not particularly limited, a known method can be used. An example is a method including applying by a spray or the like a coating liquid obtained by dispersing inorganic material particles in a solution containing a binder.(Reinforcement Core Materials)

[0396] The ion exchange membrane preferably has reinforcement core materials arranged inside the membrane body.

[0397] The reinforcement core materials are members that enhance the strength and dimensional stability of the ion exchange membrane. By arranging the reinforcement core materials inside the membrane body, particularly expansion and contraction of the ion exchange membrane can be controlled in the desired range. Such an ion exchange membrane does not expand or contract more than necessary during electrolysis and the like and can maintain excellent dimensional stability for a long term.

[0398] The configuration of the reinforcement core materials is not particularly limited, and, for example, the reinforcement core materials may be formed by spinning yarns referred to as reinforcement yarns. The reinforcement yarns here refer to yarns that are members constituting the reinforcement core materials, can provide the desired dimensional stability and mechanical strength to the ion exchange membrane, and can be stably present in the ion exchange membrane. By using the reinforcement core materials obtained by spinning such reinforcement yarns, better dimensional stability and mechanical strength can be provided to the ion exchange membrane.

[0399] The material of the reinforcement core materials and the reinforcement yarns used for these is not particularly limited but is preferably a material resistant to acids, alkalis, etc., and a fiber comprising a fluorine-containing polymer is preferable because long-term heat resistance and chemical resistance are required.

[0400] Examples of the fluorine-containing polymer to be used in the reinforcement core materials include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-ethylene copolymers (ETFE), tetrafluoroethylene-hexafluoropropylene copolymers, trifluorochloroethylene-ethylene copolymers, and vinylidene fluoride polymers (PVDF). Among these, fibers comprising polytetrafluoroethylene are preferably used from the viewpoint of heat resistance and chemical resistance.

[0401] The yarn diameter of the reinforcement yarns used for the reinforcement core materials is not particularly limited, but is preferably 20 to 300 deniers, more preferably 50 to 250 deniers. The weave density (fabric count per unit length) is preferably 5 to 50 / inch. The form of the reinforcement core materials is not particularly limited, for example, a woven fabric, a nonwoven fabric, and a knitted fabric are used, but is preferably in the form of a woven fabric. The thickness of the woven fabric to be used is preferably 30 to 250 μm, more preferably 30 to 150 μm.

[0402] As the woven fabric or knitted fabric, monofilaments, multifilaments, or yarns thereof, a slit yarn, or the like can be used, and various types of weaving methods such as a plain weave, a leno weave, a knit weave, a cord weave, and a seersucker can be used.

[0403] The weave and arrangement of the reinforcement core materials in the membrane body are not particularly limited, and preferred arrangement can be appropriately provided considering the size and form of the ion exchange membrane, physical properties desired for the ion exchange membrane, the use environment, and the like.

[0404] For example, the reinforcement core materials may be arranged along one predetermined direction of the membrane body, but from the viewpoint of dimensional stability, it is preferred that the reinforcement core materials be arranged along a predetermined first direction, and other reinforcement core materials be arranged along a second direction substantially perpendicular to the first direction. By arranging the plurality of reinforcement core materials substantially orthogonally inside the membrane body, it is possible to impart better dimensional stability and mechanical strength in many directions. For example, arrangement in which the reinforcement core materials arranged along the longitudinal direction (warp yarns) and the reinforcement core materials arranged along the transverse direction (weft yarns) are woven on the surface side of the membrane body is preferred. The arrangement is more preferably in the form of plain weave driven and woven by allowing warps and wefts to run over and under each other alternately, leno weave in which two warps are woven into wefts while twisted, basket weave driven and woven by inserting, into two or more parallelly-arranged warps, wefts of the same number, or the like, from the viewpoint of dimension stability, mechanical strength and easy-production.

[0405] It is preferred that particularly, the reinforcement core materials be arranged along both directions, the MD (Machine Direction) and TD (Transverse Direction) of the ion exchange membrane. In other words, the reinforcement core materials are preferably plain-woven in the MD and TD. Here, the MD refers to the direction in which the membrane body and various core materials (for example, the reinforcement core materials, reinforcement yarns, and sacrifice yarns described later) are conveyed in an ion exchange membrane production step described later (flow direction), and the TD refers to the direction substantially perpendicular to the MD. Yarns woven along the MD are referred to as MD yarns, and yarns woven along the TD are referred to as TD yarns. Usually, the ion exchange membrane used for electrolysis is rectangular, and in many cases, the longitudinal direction is the MD, and the width direction is the TD. By weaving the reinforcement core materials that are MD yarns and the reinforcement core materials that are TD yarns, it is possible to impart better dimensional stability and mechanical strength in many directions.

[0406] The arrangement interval of the reinforcement core materials is not particularly limited, and preferred arrangement can be appropriately provided considering physical properties desired for the ion exchange membrane, the use environment, and the like.

[0407] The aperture ratio for the reinforcement core materials is not particularly limited, but is preferably 30% or more, more preferably 50% or more and 90% or less. The aperture ratio is preferably 30% or more from the viewpoint of the electrochemical properties of the ion exchange membrane, and preferably 90% or less from the viewpoint of the mechanical strength of the ion exchange membrane.

[0408] The aperture ratio for the reinforcement core materials herein refers to a ratio of a total area of a surface through which substances such as ions (an electrolyte solution and cations contained therein (e.g., sodium ions)) can pass (B) to the area of either one surface of the membrane body (A) (B / A). The total area of the surface through which substances such as ions can pass (B) can refer to the total areas of regions in which in the ion exchange membrane, cations, an electrolytic solution, and the like are not blocked by the reinforcement core materials and the like contained in the ion exchange membrane.

[0409] FIG. 3 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane. FIG. 3, in which a portion of the ion exchange membrane is enlarged, shows only the arrangement of the reinforcement core materials 21 and 22 in the regions, omitting illustration of the other members.

[0410] By subtracting the total area of the reinforcement core materials (C) from the area of the region surrounded by the reinforcement core materials 21 arranged along the longitudinal direction and the reinforcement core materials 22 arranged along the transverse direction, the region including the area of the reinforcement core materials (A), the total area of regions through which substances such as ions can pass (B) in the area of the above-described region (A) can be obtained. That is, the aperture ratio can be determined by the following formula (I):Aperture⁢ ratio=(B) / (A)=((A)-(C)) / (A)(I)

[0411] Among the reinforcement core materials, a particularly preferred form is tape yarns or highly oriented monofilaments comprising PTFE from the viewpoint of chemical resistance and heat resistance. Specifically, reinforcement core materials forming a plain weave in which 50 to 300 denier tape yarns obtained by slitting a high strength porous sheet comprising PTFE into a tape form, or 50 to 300 denier highly oriented monofilaments comprising PTFE are used and which has a weave density of 10 to 50 yarns or monofilaments / inch and has a thickness in the range of 50 to 100 μm are more preferred. The aperture ratio of an ion exchange membrane comprising such reinforcement core materials is further preferably 60% or more.

[0412] Examples of the shape of the reinforcement yarns include round yarns and tape yarns.(Continuous Holes)

[0413] The ion exchange membrane preferably has continuous holes inside the membrane body.

[0414] The continuous holes refer to holes that can be flow paths for ions generated in electrolysis and an electrolyte solution. The continuous holes, which are tubular holes formed inside the membrane body, are formed by dissolution of sacrifice core materials (or sacrifice yarns) described below. The shape, diameter, or the like of the continuous holes can be controlled by selecting the shape or diameter of the sacrifice core materials (sacrifice yarns).

[0415] Forming the continuous holes inside the ion exchange membrane can ensure the mobility of an electrolyte solution on electrolysis. The shape of the continuous holes is not particularly limited, but may be the shape of sacrifice core materials to be used for formation of the continuous holes in accordance with the production method described below.

[0416] The continuous holes are preferably formed so as to alternately pass on the anode side (sulfonic acid layer side) and the cathode side (carboxylic acid layer side) of the reinforcement core materials. With such a structure, in a portion in which continuous holes are formed on the cathode side of the reinforcement core materials, ions (e.g., sodium ions) transported through the electrolyte solution with which the continuous holes are filled can flow also on the cathode side of the reinforcement core materials. As a result, the flow of cations is not interrupted, and thus, it is possible to further reduce the electrical resistance of the ion exchange membrane.

[0417] The continuous holes may be formed along only one predetermined direction of the membrane body constituting the ion exchange membrane, but are preferably formed in both the longitudinal direction and the transverse direction of the membrane body from the viewpoint of exhibiting more stable electrolytic performance.[Production Method]

[0418] A suitable example of a method for producing an ion exchange membrane includes a method including the following steps (1) to (6):

[0419] Step (1): the step of producing a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0420] Step (2): the step of weaving at least a plurality of reinforcement core materials, as required, and sacrifice yarns having a property of dissolving in an acid or an alkali, and forming continuous holes, to obtain a reinforcing material in which the sacrifice yarns are arranged between the reinforcement core materials adjacent to each other,

[0421] Step (3): the step of forming into a film the above fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0422] Step (4): the step of embedding the above reinforcing materials, as required, in the above film to obtain a membrane body inside which the reinforcing materials are arranged,

[0423] Step (5): the step of hydrolyzing the membrane body obtained in the step (4) (hydrolysis step), and

[0424] Step (6): the step of providing a coating layer on the membrane body obtained in the step (5) (application step).

[0425] Hereinafter, each of the steps will be described in detail.Step (1): Step of Producing Fluorine-Containing Polymer

[0426] In the step (1), raw material monomers described in the first group to the third group above are used to produce a fluorine-containing polymer. In order to control the ion exchange capacity of the fluorine-containing polymer, the mixture ratio of the raw material monomers should be adjusted in the production of the fluorine-containing polymer forming the layers.Step (2): Step of Producing Reinforcing Materials

[0427] The reinforcing material is a woven fabric obtained by weaving reinforcement yarns or the like. The reinforcing material is embedded in the membrane to thereby form reinforcement core materials. When an ion exchange membrane having continuous holes is formed, sacrifice yarns are additionally woven into the reinforcing material. The amount of the sacrifice yarns contained in this case is preferably 10 to 80% by mass, more preferably 30 to 70% by mass based on the entire reinforcing material. Weaving the sacrifice yarns can also prevent yarn slippage of the reinforcement core materials.

[0428] As the sacrifice yarns, which have solubility in the membrane production step or under an electrolysis environment, rayon, polyethylene terephthalate (PET), cellulose, polyamide, and the like are used. Monofilaments or multifilaments having a thickness of 20 to 50 deniers and comprising polyvinyl alcohol and the like are also preferred.

[0429] In the step (2), the aperture ratio, arrangement of the continuous holes, and the like can be controlled by adjusting the arrangement of the reinforcement core materials and the sacrifice yarns.Step (3): Step of Film Formation

[0430] In the step (3), the fluorine-containing polymer obtained in the step (1) is formed into a film by using an extruder. The film may be a single-layer configuration, a two-layer configuration of a sulfonic acid layer and a carboxylic acid layer as mentioned above, or a multilayer configuration of three layers or more.

[0431] Examples of the film forming method include the following:

[0432] a method in which a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are separately formed into films; and

[0433] a method in which fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are coextruded into a composite film.

[0434] The number of each film may be more than one. Coextrusion of different films is preferred because of its contribution to an increase in the adhesive strength in the interface.Step (4): Step of Obtaining Membrane Body

[0435] In the step (4), the reinforcing material obtained in the step (2) is embedded in the film obtained in the step (3) to provide a membrane body including the reinforcing material therein. Preferable examples of the method for forming a membrane body include (i) a method in which a fluorine-containing polymer having a carboxylic acid group precursor (e.g., carboxylate functional group) (hereinafter, a layer comprising the same is referred to as the first layer) located on the cathode side and a fluorine-containing polymer having a sulfonic acid group precursor (e.g., sulfonyl fluoride functional group) (hereinafter, a layer comprising the same is referred to as the second layer) are formed into a film by a coextrusion method, and, by using a heat source and a vacuum source as required, a reinforcing material and the second layer / first layer composite film are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure; and (ii) a method in which, in addition to the second layer / first layer composite film, a fluorine-containing polymer having a sulfonic acid group precursor is singly formed into a film (the third layer) in advance, and, by using a heat source and a vacuum source as required, the third layer film, the reinforcement core materials, and the composite film comprising the second layer / first layer are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure.

[0436] Coextrusion of the first layer and the second layer herein contributes to an increase in the adhesive strength at the interface.

[0437] The method including integration under a reduced pressure is characterized by making the third layer on the reinforcing material thicker than that of a pressure-application press method. Further, since the reinforcing material is fixed on the inner surface of the membrane body, the method has a property of sufficiently retaining the mechanical strength of the ion exchange membrane.

[0438] The variations of lamination described here are exemplary, and coextrusion can be performed after a preferred lamination pattern (for example, the combination of layers) is appropriately selected considering the desired layer configuration of the membrane body and physical properties, and the like.

[0439] For the purpose of further improving the electric properties of the ion exchange membrane, it is also possible to additionally interpose a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor between the first layer and the second layer or to use a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor instead of the second layer.

[0440] The method for forming the fourth layer may be a method in which a fluorine-containing polymer having a carboxylic acid group precursor and a fluorine-containing polymer having a sulfonic acid group precursor are separately produced and then mixed or may be a method in which a monomer having a carboxylic acid group precursor and a monomer having a sulfonic acid group precursor are copolymerized.

[0441] When the fourth layer is used as a component of the ion exchange membrane, a coextruded film of the first layer and the fourth layer is formed, in addition to this, the third layer and the second layer are separately formed into films, and lamination may be performed by the method mentioned above. Alternatively, the three layers of the first layer / fourth layer / second layer may be simultaneously formed into a film by coextrusion.

[0442] In this case, the direction in which the extruded film flows is the MD. As mentioned above, it is possible to form a membrane body containing a fluorine-containing polymer having an ion exchange group on a reinforcing material.

[0443] Additionally, the ion exchange membrane preferably has protruded portions composed of the fluorine-containing polymer having a sulfonic acid group, that is, projections, on the surface side composed of the sulfonic acid layer. As a method for forming such projections, which is not particularly limited, a known method also can be employed including forming projections on a resin surface. A specific example of the method is a method of embossing the surface of the membrane body. For example, the above projections can be formed by using release paper embossed in advance when the composite film mentioned above, reinforcing material, and the like are integrated. In the case where projections are formed by embossing, the height and arrangement density of the projections can be controlled by controlling the emboss shape to be transferred (shape of the release paper).(5) Hydrolysis Step

[0444] In the step (5), a step of hydrolyzing the membrane body obtained in the step (4) to convert the ion exchange group precursor into an ion exchange group (hydrolysis step) is performed.

[0445] In the step (5), it is also possible to form dissolution holes in the membrane body by dissolving and removing the sacrifice yarns included in the membrane body with acid or alkali. The sacrifice yarns may remain in the continuous holes without being completely dissolved and removed. The sacrifice yarns remaining in the continuous holes may be dissolved and removed by the electrolyte solution when the ion exchange membrane is subjected to electrolysis.

[0446] The sacrifice yarn has solubility in acid or alkali in the step of producing an ion exchange membrane or under an electrolysis environment. The sacrifice yarns are eluted out to thereby form continuous holes at corresponding sites.

[0447] The step (5) can be performed by immersing the membrane body obtained in the step (4) in a hydrolysis solution containing acid or alkali. An example of the hydrolysis solution that can be used is a mixed solution containing KOH and dimethyl sulfoxide (DMSO).

[0448] The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of 25 to 35% by mass.

[0449] The temperature for hydrolysis is preferably 70 to 100° C. The higher the temperature, the larger can be the apparent thickness. The temperature is more preferably 75 to 100° C.

[0450] The time for hydrolysis is preferably 10 to 120 minutes. The longer the time, the larger can be the apparent thickness. The time is more preferably 20 to 120 minutes.

[0451] The step of forming continuous holes by eluting the sacrifice yarn will be now described in more detail. FIGS. 4(a) and (b) are schematic views for explaining a method for forming the continuous holes of the ion exchange membrane.

[0452] FIGS. 4(a) and (b) show reinforcement yarns 52, sacrifice yarns 504a, and continuous holes 504 formed by the sacrifice yarns 504a only, omitting illustration of the other members such as a membrane body.

[0453] First, the reinforcement yarns 52 that are to constitute reinforcement core materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane are used as interwoven reinforcing materials. Then, in the step (5), the sacrifice yarns 504a are eluted to form the continuous holes 504.

[0454] The above method is simple because the method for interweaving the reinforcement yarns 52 and the sacrifice yarns 504a may be adjusted depending on the arrangement of the reinforcement core materials and continuous holes in the membrane body of the ion exchange membrane.

[0455] FIG. 4(a) exemplifies the plain-woven reinforcing material in which the reinforcement yarns 52 and sacrifice yarns 504a are interwoven along both the longitudinal direction and the lateral direction in the paper, and the arrangement of the reinforcement yarns 52 and the sacrifice yarns 504a in the reinforcing material may be varied as required.(6) Application Step

[0456] In the step (6), a coating layer can be formed by preparing a coating liquid containing inorganic material particles obtained by grinding raw ore or melting raw ore and a binder, applying the coating liquid onto the surface of the ion exchange membrane obtained in the step (5), and drying the coating liquid.

[0457] A preferable binder is a binder obtained by hydrolyzing a fluorine-containing polymer having an ion exchange group precursor with an aqueous solution containing dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) and then immersing the polymer in hydrochloric acid to replace the counterion of the ion exchange group by H+ (e.g., a fluorine-containing polymer having a carboxyl group or sulfo group). Thereby, the polymer is more likely to dissolve in water or ethanol mentioned below, which is preferable.

[0458] This binder is dissolved in a mixed solution of water and ethanol. The volume ratio between water and ethanol is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganic material particles are dispersed with a ball mill into the dissolution liquid thus obtained to thereby provide a coating liquid. In this case, it is also possible to adjust the average particle size and the like of the particles by adjusting the time and rotation speed during the dispersion. The preferable amount of the inorganic material particles and the binder to be blended is as mentioned above.

[0459] The concentration of the inorganic material particles and the binder in the coating liquid is not particularly limited, but a thin coating liquid is preferable. This enables uniform application onto the surface of the ion exchange membrane.

[0460] Additionally, a surfactant may be added to the dispersion when the inorganic material particles are dispersed. As the surfactant, nonionic surfactants are preferable, and examples thereof include HS-210, NS-210, P-210, and E-212 manufactured by NOF CORPORATION.

[0461] The coating liquid obtained is applied onto the surface of the ion exchange membrane by spray application or roll coating to thereby provide an ion exchange membrane.[Microporous Membrane]

[0462] The microporous membrane of the present embodiment is not particularly limited as long as the membrane can be formed into a laminate with the electrode for electrolysis, as mentioned above. Various microporous membranes may be employed.

[0463] The porosity of the microporous membrane of the present embodiment is not particularly limited, but can be 20 to 90, for example, and is preferably 30 to 85. The above porosity can be calculated by the following formula:Porosity=(1-(the⁢ weight⁢ of⁢ the⁢ membrane⁢ in⁢ a⁢ dried⁢ state) / (the⁢ weight⁢ calculated⁢ from⁢ the⁢ volume⁢ calculated⁢ from⁢ the⁢ thickness,width,and⁢ length⁢ of⁢ the⁢ membrane⁢ and⁢ the⁢ density⁢ of⁢ the⁢ membrane⁢ material))×100

[0464] The average pore size of the microporous membrane of the present embodiment is not particularly limited, and can be 0.01 μm to 10 μm, for example, preferably 0.05 μm to 5 μm. With respect to the average pore size, for example, the membrane is cut vertically to the thickness direction, and the section is observed with an FE-SEM. The average pore size can be obtained by measuring the diameter of about 100 pores observed and averaging the measurements.

[0465] The thickness of the microporous membrane of the present embodiment is not particularly limited, and can be 10 μm to 1000 μm, for example, preferably 50 μm to 600 μm. The above thickness can be measured by using a micrometer (manufactured by Mitutoyo Corporation) or the like, for example.

[0466] Specific examples of the microporous membrane as mentioned above include Zirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfon membrane in the present embodiment) and those described in International Publication No. WO 2013-183584 and International Publication No. WO 2016-203701.[Laminate]

[0467] The laminate of the present embodiment comprises the electrode for electrolysis of the present embodiment, and a membrane or feed conductor in contact with the electrode for electrolysis. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0468] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0469] Further, according to the laminate of the present invention, it is possible to maintain the electrolytic performance comparable to those of a new electrode or improve the electrolytic performance. Even in the case where only a feed conductor is placed in a new electrolytic cell (i.e., an electrode including no catalyst layer placed), only attaching the electrode for electrolysis of the present embodiment to the feed conductor enables the electrode to function. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0470] The laminate of the present embodiment can be stored or transported to customers in a state where the laminate is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0471] As the feed conductor of the present embodiment, various substrates mentioned below such as a degraded electrode (i.e., the existing electrode) and an electrode having no catalyst coating can be employed.

[0472] In the laminate of the present embodiment, the force applied per unit mass·unit area of the electrode for electrolysis on the membrane or feed conductor is preferably 0.08 N / (mg·cm2) or more, more preferably 0.1 N / (mg·cm2) or more, further preferably 0.14 N / (mg·cm2) or more, and further more preferably, from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), is 0.2 N / (mg·cm2) or more. The upper limit value is not particularly limited, but is preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less. The upper limit value is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.[Wound Body]

[0473] The wound body of the present embodiment includes the electrode for electrolysis of the present embodiment or the laminate of the present embodiment. That is, the wound body of the present embodiment is obtained by winding the electrode for electrolysis of the present embodiment or the laminate of the present embodiment. Downsizing the electrode for electrolysis of the present embodiment or the laminate of the present embodiment by winding, as the wound body of the present embodiment, can further improve the handling property.[Electrolyzer]

[0474] The electrolyzer of the present embodiment includes the electrode for electrolysis of the present embodiment. Hereinafter, the case of performing common salt electrolysis by using an ion exchange membrane as the membrane is taken as an example, and one embodiment of the electrolyzer will be described in detail.[Electrolytic Cell]

[0475] FIG. 5 illustrates a cross-sectional view of an electrolytic cell 1.

[0476] The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber 20, a partition wall 30 placed between the anode chamber 10 and the cathode chamber 20, an anode 11 placed in the anode chamber 10, and a cathode 21 placed in the cathode chamber 20. As required, the electrolytic cell 1 has a substrate 18a and a reverse current absorbing layer 18b formed on the substrate 18a and may comprise a reverse current absorber 18 placed in the cathode chamber. The anode 11 and the cathode 21 belonging to the electrolytic cell 1 are electrically connected to each other. In other words, the electrolytic cell 1 comprises the following cathode structure. The cathode structure 40 comprises the cathode chamber 20, the cathode 21 placed in the cathode chamber 20, and the reverse current absorber 18 placed in the cathode chamber 20, the reverse current absorber 18 has the substrate 18a and the reverse current absorbing layer 18b formed on the substrate 18a, as shown in FIG. 9, and the cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode chamber 20 further has a collector 23, a support 24 supporting the collector, and a metal elastic body 22. The metal elastic body 22 is placed between the collector 23 and the cathode 21. The support 24 is placed between the collector 23 and the partition wall 30. The collector 23 is electrically connected to the cathode 21 via the metal elastic body 22. The partition wall 30 is electrically connected to the collector 23 via the support 24. Accordingly, the partition wall 30, the support 24, the collector 23, the metal elastic body 22, and the cathode 21 are electrically connected. The cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode 21 and the reverse current absorbing layer may be directly connected or may be indirectly connected via the collector, the support, the metal elastic body, the partition wall, or the like. The entire surface of the cathode 21 is preferably covered with a catalyst layer for reduction reaction. The form of electrical connection may be a form in which the partition wall 30 and the support 24, the support 24 and the collector 23, and the collector 23 and the metal elastic body 22 are each directly attached and the cathode 21 is laminated on the metal elastic body 22. Examples of a method for directly attaching these constituent members to one another include welding and the like. Alternatively, the reverse current absorber 18, the cathode 21, and the collector 23 may be collectively referred to as a cathode structure 40.

[0477] FIG. 6 illustrates a cross-sectional view of two electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG. 7 shows an electrolyzer 4. FIG. 8 shows a step of assembling the electrolyzer 4. As shown in FIG. 6, an electrolytic cell 1, a cation exchange membrane 2, and an electrolytic cell 1 are arranged in series in the order mentioned. An ion exchange membrane 2 is arranged between the anode chamber of one electrolytic cell 1 among the two electrolytic cells that are adjacent in the electrolyzer and the cathode chamber of the other electrolytic cell 1. That is, the anode chamber 10 of the electrolytic cell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacent thereto is separated by the cation exchange membrane 2. As shown in FIG. 7, the electrolyzer 4 is composed of a plurality of electrolytic cells 1 connected in series via the ion exchange membrane 2. That is, the electrolyzer 4 is a bipolar electrolyzer comprising the plurality of electrolytic cells 1 arranged in series and ion exchange membranes 2 each arranged between adjacent electrolytic cells 1. As shown in FIG. 8, the electrolyzer 4 is assembled by arranging the plurality of electrolytic cells 1 in series via the ion exchange membrane 2 and coupling the cells by means of a press device 5.

[0478] The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 to be connected to a power supply. The anode 11 of the electrolytic cell 1 located at farthest end among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the anode terminal 7. The cathode 21 of the electrolytic cell located at the end opposite to the anode terminal 7 among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the cathode terminal 6. The electric current during electrolysis flows from the side of the anode terminal 7, through the anode and cathode of each electrolytic cell 1, toward the cathode terminal 6. At the both ends of the coupled electrolytic cells 1, an electrolytic cell having an anode chamber only (anode terminal cell) and an electrolytic cell having a cathode chamber only (cathode terminal cell) may be arranged. In this case, the anode terminal 7 is connected to the anode terminal cell arranged at the one end, and the cathode terminal 6 is connected to the cathode terminal cell arranged at the other end.

[0479] In the case of electrolyzing brine, brine is supplied to each anode chamber 10, and pure water or a low-concentration sodium hydroxide aqueous solution is supplied to each cathode chamber 20. Each liquid is supplied from an electrolyte solution supply pipe (not shown in Figure), through an electrolyte solution supply hose (not shown in Figure), to each electrolytic cell 1. The electrolyte solution and products from electrolysis are recovered from an electrolyte solution recovery pipe (not shown in Figure). During electrolysis, sodium ions in the brine migrate from the anode chamber 10 of the one electrolytic cell 1, through the ion exchange membrane 2, to the cathode chamber 20 of the adjacent electrolytic cell 1. Thus, the electric current during electrolysis flows in the direction in which the electrolytic cells 1 are coupled in series. That is, the electric current flows, through the cation exchange membrane 2, from the anode chamber 10 toward the cathode chamber 20. As the brine is electrolyzed, chlorine gas is generated on the side of the anode 11, and sodium hydroxide (solute) and hydrogen gas are generated on the side of the cathode 21.(Anode Chamber)

[0480] The anode chamber 10 has the anode 11 or anode feed conductor 11. When the electrode for electrolysis of the present embodiment is inserted to the anode side, 11 serves as the anode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the anode side, 11 serves as the anode. The anode chamber 10 has an anode-side electrolyte solution supply unit that supplies an electrolyte solution to the anode chamber 10, a baffle plate that is arranged above the anode-side electrolyte solution supply unit so as to be substantially parallel or oblique to the partition wall 30, and an anode-side gas liquid separation unit arranged above the baffle plate to separate gas from the electrolyte solution including the gas mixed.(Anode)

[0481] When the electrode for electrolysis of the present embodiment is not inserted to the anode side, the anode 11 is provided in the frame of the anode chamber 10. As the anode 11, a metal electrode such as so-called DSA® can be used. DSA is an electrode including a titanium substrate of which surface is covered with an oxide comprising ruthenium, iridium, and titanium as components.

[0482] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode Feed Conductor)

[0483] When the electrode for electrolysis of the present embodiment is inserted to the anode side, the anode feed conductor 11 is provided in the frame of the anode chamber 10. As the anode feed conductor 11, a metal electrode such as so-called DSA® can be used, and titanium having no catalyst coating can be also used. Alternatively, DSA having a thinner catalyst coating can be also used. Further, a used anode can be also used.

[0484] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode-Side Electrolyte Solution Supply Unit)

[0485] The anode-side electrolyte solution supply unit, which supplies the electrolyte solution to the anode chamber 10, is connected to the electrolyte solution supply pipe. The anode-side electrolyte solution supply unit is preferably arranged below the anode chamber 10. As the anode-side electrolyte solution supply unit, for example, a pipe on the surface of which aperture portions are formed (dispersion pipe) and the like can be used. Such a pipe is more preferably arranged along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell. This pipe is connected to an electrolyte solution supply pipe (liquid supply nozzle) that supplies the electrolyte solution into the electrolytic cell 1. The electrolyte solution supplied from the liquid supply nozzle is conveyed with a pipe into the electrolytic cell 1 and supplied from the aperture portions provided on the surface of the pipe to inside the anode chamber 10. Arranging the pipe along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell is preferable because the electrolyte solution can be uniformly supplied to inside the anode chamber 10.(Anode-Side Gas Liquid Separation Unit)

[0486] The anode-side gas liquid separation unit is preferably arranged above the baffle plate. The anode-side gas liquid separation unit has a function of separating produced gas such as chlorine gas from the electrolyte solution during electrolysis. Unless otherwise specified, above means the upper direction in the electrolytic cell 1 in FIG. 5, and below means the lower direction in the electrolytic cell 1 in FIG. 5.

[0487] During electrolysis, produced gas generated in the electrolytic cell 1 and the electrolyte solution form a mixed phase (gas-liquid mixed phase), which is then emitted out of the system. Subsequently, pressure fluctuations inside the electrolytic cell 1 cause vibration, which may result in physical damage of the ion exchange membrane. In order to prevent this event, the electrolytic cell 1 of the present embodiment is preferably provided with an anode-side gas liquid separation unit to separate the gas from the liquid. The anode-side gas liquid separation unit is preferably provided with a defoaming plate to eliminate bubbles. When the gas-liquid mixed phase flow passes through the defoaming plate, bubbles burst to thereby enable the electrolyte solution and the gas to be separated. As a result, vibration during electrolysis can be prevented.(Baffle Plate)

[0488] The baffle plate is preferably arranged above the anode-side electrolyte solution supply unit and arranged substantially in parallel with or obliquely to the partition wall 30. The baffle plate is a partition plate that controls the flow of the electrolyte solution in the anode chamber 10. When the baffle plate is provided, it is possible to cause the electrolyte solution (brine or the like) to circulate internally in the anode chamber 10 to thereby make the concentration uniform. In order to cause internal circulation, the baffle plate is preferably arranged so as to separate the space in proximity to the anode 11 from the space in proximity to the partition wall 30. From such a viewpoint, the baffle plate is preferably placed so as to be opposed to the surface of the anode 11 and to the surface of the partition wall 30. In the space in proximity to the anode partitioned by the baffle plate, as electrolysis proceeds, the electrolyte solution concentration (brine concentration) is lowered, and produced gas such as chlorine gas is generated. This results in a difference in the gas-liquid specific gravity between the space in proximity to anode 11 and the space in proximity to the partition wall 30 partitioned by the baffle plate. By use of the difference, it is possible to promote the internal circulation of the electrolyte solution in the anode chamber 10 to thereby make the concentration distribution of the electrolyte solution in the anode chamber 10 more uniform.

[0489] Although not shown in FIG. 5, a collector may be additionally provided inside the anode chamber 10. The material and configuration of such a collector may be the same as those of the collector of the cathode chamber mentioned below. In the anode chamber 10, the anode 11 per se may also serve as the collector.(Partition Wall)

[0490] The partition wall 30 is arranged between the anode chamber 10 and the cathode chamber 20. The partition wall 30 may be referred to as a separator, and the anode chamber 10 and the cathode chamber 20 are partitioned by the partition wall 30. As the partition wall 30, one known as a separator for electrolysis can be used, and an example thereof includes a partition wall formed by welding a plate comprising nickel to the cathode side and a plate comprising titanium to the anode side.(Cathode Chamber)

[0491] In the cathode chamber 20, when the electrode for electrolysis of the present embodiment is inserted to the cathode side, 21 serves as a cathode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, 21 serves as a cathode. When a reverse current absorber is included, the cathode or cathode feed conductor 21 is electrically connected to the reverse current absorber. The cathode chamber 20, similarly to the anode chamber 10, preferably has a cathode-side electrolyte solution supply unit and a cathode-side gas liquid separation unit. Among the components constituting the cathode chamber 20, components similar to those constituting the anode chamber 10 will be not described.(Cathode)

[0492] When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, a cathode 21 is provided in the frame of the cathode chamber 20. The cathode 21 preferably has a nickel substrate and a catalyst layer that covers the nickel substrate. Examples of the components of the catalyst layer on the nickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. The cathode 21 may be subjected to a reduction treatment, as required. As the substrate of the cathode 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0493] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Cathode Feed Conductor)

[0494] When the electrode for electrolysis of the present embodiment is inserted to the cathode side, a cathode feed conductor 21 is provided in the frame of the cathode chamber 20. The cathode feed conductor 21 may be covered with a catalytic component. The catalytic component may be a component that is originally used as the cathode and remains. Examples of the components of the catalyst layer include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. As the substrate of the cathode feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0495] As the feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless, having no catalyst coating may be used.

[0496] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Reverse Current Absorbing Layer)

[0497] A material having a redox potential less noble than the redox potential of the element for the catalyst layer of the cathode mentioned above may be selected as a material for the reverse current absorbing layer. Examples thereof include nickel and iron.(Collector)

[0498] The cathode chamber 20 preferably comprises the collector 23. The collector 23 improves current collection efficiency. In the present embodiment, the collector 23 is a porous plate and is preferably arranged in substantially parallel to the surface of the cathode 21.

[0499] The collector 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The collector 23 may be a mixture, alloy, or composite oxide of these metals. The collector 23 may have any form as long as the form enables the function of the collector and may have a plate or net form.(Metal Elastic Body)

[0500] Placing the metal elastic body 22 between the collector 23 and the cathode 21 presses each cathode 21 of the plurality of electrolytic cells 1 connected in series onto the ion exchange membrane 2 to reduce the distance between each anode 11 and each cathode 21. Then, it is possible to lower the voltage to be applied entirely across the plurality of electrolytic cells 1 connected in series. Lowering of the voltage enables the power consumption to be reduced. With the metal elastic body 22 placed, the pressing pressure caused by the metal elastic body 22 enables the electrode for electrolysis to be stably maintained in place when the laminate including the electrode for electrolysis according to the present invention is placed in the electrolytic cell.

[0501] As the metal elastic body 22, spring members such as spiral springs and coils and cushioning mats may be used. As the metal elastic body 22, a suitable one may be appropriately employed, in consideration of a stress to press the ion exchange membrane and the like. The metal elastic body 22 may be provided on the surface of the collector 23 on the side of the cathode chamber 20 or may be provided on the surface of the partition wall on the side of the anode chamber 10. Both the chambers are usually partitioned such that the cathode chamber 20 becomes smaller than the anode chamber 10. Thus, from the viewpoint of the strength of the frame and the like, the metal elastic body 22 is preferably provided between the collector 23 and the cathode 21 in the cathode chamber 20. The metal elastic body 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium.(Support)

[0502] The cathode chamber 20 preferably comprises the support 24 that electrically connects the collector 23 to the partition wall 30. This can achieve an efficient current flow.

[0503] The support 24 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The support 24 may have any shape as long as the support can support the collector 23 and may have a rod, plate, or net shape. The support 24 has a plate shape, for example. A plurality of supports 24 are arranged between the partition wall 30 and the collector 23. The plurality of supports 24 are aligned such that the surfaces thereof are in parallel to each other. The supports 24 are arranged substantially perpendicular to the partition wall 30 and the collector 23.(Anode Side Gasket and Cathode Side Gasket)

[0504] The anode side gasket is preferably arranged on the frame surface constituting the anode chamber 10. The cathode side gasket is preferably arranged on the frame surface constituting the cathode chamber 20. Electrolytic cells are connected to each other such that the anode side gasket included in one electrolytic cell and the cathode side gasket of an electrolytic cell adjacent to the cell sandwich the ion exchange membrane 2 (see FIGS. 5 and 6). These gaskets can impart airtightness to connecting points when the plurality of electrolytic cells 1 is connected in series via the ion exchange membrane 2.

[0505] The gaskets form a seal between the ion exchange membrane and electrolytic cells. Specific examples of the gaskets include picture frame-like rubber sheets at the center of which an aperture portion is formed. The gaskets are required to have resistance against corrosive electrolyte solutions or produced gas and be usable for a long period. Thus, in respect of chemical resistance and hardness, vulcanized products and peroxide-crosslinked products of ethylene-propylene-diene rubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) are usually used as the gaskets. Alternatively, gaskets of which region to be in contact with liquid (liquid contact portion) is covered with a fluorine-containing resin such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may be employed as required. These gaskets each may have an aperture portion so as not to inhibit the flow of the electrolyte solution, and the shape of the aperture portion is not particularly limited. For example, a picture frame-like gasket is attached with an adhesive or the like along the peripheral edge of each aperture portion of the anode chamber frame constituting the anode chamber 10 or the cathode chamber frame constituting the cathode chamber 20. Then, for example, in the case where the two electrolytic cells 1 are connected via the ion exchange membrane 2 (see FIG. 6), each electrolytic cell 1 onto which the gasket is attached should be tightened via ion exchange membrane 2. This tightening can prevent the electrolyte solution, alkali metal hydroxide, chlorine gas, hydrogen gas, and the like generated from electrolysis from leaking out of the electrolytic cells 1.(Ion Exchange Membrane 2)

[0506] The ion exchange membrane 2 is as described in the section of the ion exchange membrane described above.(Water Electrolysis)

[0507] The electrolyzer of the present embodiment, as an electrolyzer in the case of electrolyzing water, has a configuration in which the ion exchange membrane in an electrolyzer for use in the case of electrolyzing common salt mentioned above is replaced by a microporous membrane. The raw material to be supplied, which is water, is different from that for the electrolyzer in the case of electrolyzing common salt mentioned above. As for the other components, components similar to that of the electrolyzer in the case of electrolyzing common salt can be employed also in the electrolyzer in the case of electrolyzing water. Since chlorine gas is generated in the anode chamber in the case of common salt electrolysis, titanium is used as the material of the anode chamber, but in the case of water electrolysis, only oxygen gas is generated in the anode chamber. Thus, a material identical to that of the cathode chamber can be used. An example thereof is nickel. For anode coating, catalyst coating for oxygen generation is suitable. Examples of the catalyst coating include metals, oxides, and hydroxides of the platinum group metals and transition metal group metals. For example, elements such as platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron can be used.Second Embodiment

[0508] Here, a second embodiment of the present invention will be described in detail with reference to FIGS. 22 to 42.[Laminate]

[0509] A laminate of the second embodiment (hereinafter, in the section of <Second embodiment>, simply referred to as “the present embodiment”) comprises an electrode for electrolysis and a membrane or feed conductor in contact with the electrode for electrolysis, wherein a force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0510] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the existing electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0511] Further, according to the laminate of the present invention, it is possible to maintain or improve the electrolytic performance of a new electrode. Thus, the electrode fixed on a conventional new electrolytic cell and serving as an anode and / or a cathode is only required to serve as a feed conductor. Thus, it may be also possible to markedly reduce or eliminate catalyst coating.

[0512] The laminate of the present embodiment can be stored or transported to customers in a state where the laminate is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier.

[0513] As the feed conductor of the present embodiment, various substrates mentioned below such as a degraded electrode (i.e., the existing electrode) and an electrode having no catalyst coating can be employed.

[0514] The laminate of the present embodiment may have partially a fixed portion as long as the laminate has the configuration described above. That is, in the case where the laminate of the present embodiment has a fixed portion, a portion not having the fixing is subjected to measurement, and the resulting force applied per unit mass-unit area of the electrode for electrolysis should be less than 1.5 N / mg·cm2.[Electrode for Electrolysis]

[0515] The electrode for electrolysis of the present embodiment has a force applied per unit mass-unit area of less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a feed conductor (a degraded electrode and an electrode having no catalyst coating), and the like. The force is further preferably 1.1 N / mg·cm2 or less, further preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less.

[0516] From the viewpoint of further improving the electrolytic performance, the force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / mg·cm2 or more, further more preferably 0.14 N / (mg·cm2) or more. The force is further more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0517] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.

[0518] The mass per unit area is preferably 48 mg / cm2 or less, more preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and economy, and furthermore is preferably 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0519] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0520] The force applied can be measured by methods (i) or (ii) described below, which are as described in Examples, specifically. As for the force applied, the value obtained by the measurement of the method (i) (also referred to as “the force applied (1)”) and the value obtained by the measurement of the method (ii) (also referred to as “the force applied (2)”) may be the same or different, and either of the values is less than 1.5 N / mg·cm2.[Method (i)]

[0521] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square), an ion exchange membrane which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced (170 mm square, the detail of the ion exchange membrane referred to herein is as described in Examples), and a sample of electrode (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. The arithmetic average surface roughness (Ra) of the nickel plate after the blast treatment is 0.5 to 0.8 μm. The specific method for calculating the arithmetic average surface roughness (Ra) is as described in Examples.

[0522] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0523] This average value is divided by the area of the overlapping portion of the sample of electrode and the ion exchange membrane and the mass of the portion overlapping the ion exchange membrane in the sample of electrode to calculate the force applied per unit mass-unit area (1) (N / mg·cm2).

[0524] The force applied per unit mass-unit area (1) obtained by the method (i) is less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less, further preferably 1.1 N / mg·cm2 or less, further more preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating. The force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / (mg·cm2) or more from the viewpoint of further improving the electrolytic performance, and furthermore, is further more preferably 0.14 N / (mg·cm2), still more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0525] When the electrode for electrolysis of the present embodiment satisfies the force applied (1), the electrode can be integrated with a membrane such as an ion exchange membrane and a microporous membrane or a feed conductor, for example, and used (i.e., as a laminate). Thus, on renewing the electrode, the substituting work for the cathode and anode fixed on the electrolytic cell by a method such as welding is eliminated, and the work efficiency is markedly improved. Additionally, by use of the electrode for electrolysis of the present embodiment as a laminate integrated with the ion exchange membrane, microporous membrane, or feed conductor, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0526] On shipping a new electrolytic cell, an electrode fixed on an electrolytic cell has been subjected to catalyst coating conventionally. Since only combination of an electrode having no catalyst coating with the electrode for electrolysis of the present embodiment can allow the electrode to function as an electrode, it is possible to markedly reduce or eliminate the production step and the amount of the catalyst for catalyst coating. A conventional electrode of which catalyst coating is markedly reduced or eliminated can be electrically connected to the electrode for electrolysis of the present embodiment and allowed to serve as a feed conductor for passage of an electric current.[Method (ii)]

[0527] A nickel plate obtained by blast processing with alumina of grain-size number 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar to that of the method (i) above) and a sample of electrode (130 mm square) are laminated in this order. After this laminate is sufficiently immersed in pure water, excess water deposited on the surface of the laminate is removed to obtain a sample for measurement. Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, only the sample of electrode in this sample for measurement is raised in a vertical direction at 10 mm / minute using a tensile and compression testing machine, and the load when the sample of electrode is raised by 10 mm in a vertical direction is measured. This measurement is repeated three times, and the average value is calculated.

[0528] This average value is divided by the area of the overlapping portion of the sample of electrode and the nickel plate and the mass of the sample of electrode in the portion overlapping the nickel plate to calculate the adhesive force per unit mass-unit area (2) (N / mg·cm2). The force applied per unit mass-unit area (2) obtained by the method (ii) is less than 1.5 N / mg·cm2, preferably 1.2 N / mg·cm2 or less, more preferably 1.20 N / mg·cm2 or less, further preferably 1.1 N / mg·cm2 or less, further more preferably 1.10 N / mg·cm2 or less, still more preferably 1.0 N / mg·cm2 or less, even still more preferably 1.00 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, and a feed conductor having no catalyst coating. The force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / (mg·cm2) or more from the viewpoint of further improving the electrolytic performance, and is further more preferably 0.14 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0529] The electrode for electrolysis of the present embodiment, if satisfies the force applied (2), can be stored or transported to customers in a state where the electrode is wound around a vinyl chloride pipe or the like (in a rolled state or the like), making handling markedly easier. By attaching the electrode for electrolysis of the present embodiment to a degraded existing electrode to provide a laminate, it is possible to make the electrolytic performance comparable to or higher than those of a new electrode.

[0530] From the viewpoint that the electrode for electrolysis of the present embodiment, if being an electrode having a broad elastic deformation region, can provide a better handling property and has a better adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and the like, the thickness of the electrode for electrolysis is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. In the present embodiment, “having a broad elastic deformation region” means that, when an electrode for electrolysis is wound to form a wound body, warpage derived from winding is unlikely to occur after the wound state is released. The thickness of the electrode for electrolysis refers to, when a catalyst layer mentioned below is included, the total thickness of both the substrate for electrode for electrolysis and the catalyst layer.

[0531] The electrode for electrolysis of the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The thickness of the substrate for electrode for electrolysis (gauge thickness) is, but is not particularly limited to, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, being capable of being suitably rolled in a roll and satisfactorily folded, and facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m), and is further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0532] In the present embodiment, a liquid is preferably interposed between the membrane such as an ion exchange membrane and a microporous membrane and the electrode, or the metal porous plate or metal plate (i.e., feed conductor) such as a degraded existing electrode and electrode having no catalyst coating and the electrode for electrolysis. As the liquid, any liquid, such as water and organic solvents, can be used as long as the liquid generates a surface tension. The larger the surface tension of the liquid, the larger the force applied between the membrane and the electrode for electrolysis or the metal porous plate or metal plate and the electrode for electrolysis. Thus, a liquid having a larger surface tension is preferred. Examples of the liquid include the following (the numerical value in the parentheses is the surface tension of the liquid at 20° C.):

[0533] hexane (20.44 mN / m), acetone (23.30 mN / m), methanol (24.00 mN / m), ethanol (24.05 mN / m), ethylene glycol (50.21 mN / m), and water (72.76 mN / m).

[0534] A liquid having a large surface tension allows the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis to be integrated (to be a laminate) to thereby facilitate renewing of the electrode. The liquid between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis may be present in an amount such that the both adhere to each other by the surface tension. As a result, after the laminate is placed in an electrolytic cell, the liquid, if mixed into the electrolyte solution, does not affect electrolysis itself due to the small amount of the liquid.

[0535] From a practical viewpoint, a liquid having a surface tension of 24 mN / m to 80 mN / m, such as ethanol, ethylene glycol, and water, is preferably used as the liquid. Particularly preferred is water or an alkaline aqueous solution prepared by dissolving caustic soda, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, or the like in water. Alternatively, the surface tension can be adjusted by allowing these liquids to contain a surfactant. When a surfactant is contained, the adhesion between the membrane and the electrode for electrolysis or the metal porous plate or metal plate (feed conductor) and the electrode for electrolysis varies to enable the handling property to be adjusted. The surfactant is not particularly limited, and both ionic surfactants and nonionic surfactants may be used.

[0536] The proportion measured by the following method (2) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 90% or more, more preferably 92% or more from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and further preferably 95% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (2)]

[0537] An ion exchange membrane (170 mm square) and a sample of electrode (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 280 mm) such that the sample of electrode in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode is measured.

[0538] The proportion measured by the following method (3) of the electrode for electrolysis of the present embodiment is not particularly limited, but is preferably 75% or more, more preferably 80% or more from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and being capable of being suitably rolled in a roll and satisfactorily folded, and is further preferably 90% or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value is 100%.[Method (3)]

[0539] An ion exchange membrane (170 mm square) and a sample of electrode (130 mm square) are laminated in this order. The laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then the proportion (%) of an area of a portion in which the ion exchange membrane (170 mm square) is in close contact with the sample of electrode is measured.

[0540] The electrode for electrolysis of the present embodiment preferably has a porous structure and an opening ratio or void ratio of 5 to 90% or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode (feed conductor), and an electrode (feed conductor) having no catalyst coating, and preventing accumulation of gas to be generated during electrolysis, although not particularly limited. The opening ratio is more preferably 10 to 80% or less, further preferably 20 to 75%.

[0541] The opening ratio is a proportion of the opening portions per unit volume. The calculation method may differ depending on that opening portions in submicron size are considered or that only visible openings are considered. In the present embodiment, a volume V was calculated from the values of the gauge thickness, width, and length of the electrode, and further, a weight W was measured to thereby calculate an opening ratio A by the following formula.A=(1-(W / (V×ρ))×100

[0542] ρ is the density of the electrode material (g / cm3). For example, ρ of nickel is 8.908 g / cm3, and ρ of titanium is 4.506 g / cm3. The opening ratio is appropriately adjusted by changing the area of metal to be perforated per unit area in the case of perforated metal, changing the values of the SW (short diameter), LW (long diameter), and feed in the case of expanded metal, changing the line diameter of metal fiber and mesh number in the case of mesh, changing the pattern of a photoresist to be used in the case of electroforming, changing the metal fiber diameter and fiber density in the case of nonwoven fabric, changing the mold for forming voids in the case of foamed metal, or the like.

[0543] The value obtained by measurement by the following method (A) of the electrode for electrolysis in the present embodiment is preferably 40 mm or less, more preferably 29 mm or less, further preferably 10 mm or less, further more preferably 6.5 mm or less from the viewpoint of the handling property. The specific measuring method is as described in Examples.[Method (A)]

[0544] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L1 and L2 are measured, and an average value thereof is used as a measurement value.

[0545] In the electrode for electrolysis in the present embodiment, the ventilation resistance is preferably 24 kPa·s / m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm / s, and a ventilation volume of 0.4 cc / cm2 / s (hereinbelow, also referred to as “measurement condition 1”) (hereinbelow, also referred to as “ventilation resistance 1”). A larger ventilation resistance means that air is unlikely to flow and refers to a state of a high density. In this state, the product from electrolysis remains in the electrode and the reaction substrate is more unlikely to diffuse inside the electrode, and thus, the electrolytic performance (such as voltage) tends to deteriorate. The concentration on the membrane surface tends to increase. Specifically, the caustic concentration increases on the cathode surface, and the supply of brine tends to decrease on the anode surface. As a result, the product accumulates at a high concentration on the interface at which the membrane is in contact with the electrode. This accumulation leads to damage of the membrane and tends to also lead to increase in the voltage and damage of the membrane on the cathode surface and damage of the membrane on the anode surface. In the present embodiment, in order to prevent these defects, the ventilation resistance is preferably set at 24 kPa·s / m or less. From a similar viewpoint as above, the ventilation resistance is more preferably less than 0.19 kPa·s / m, further preferably 0.15 kPa·s / m or less, further more preferably 0.07 kPa·s / m or less.

[0546] In the present embodiment, when the ventilation resistance is larger than a certain value, NaOH generated in the electrode tends to accumulate on the interface between the electrode and the membrane to result in a high concentration in the case of the cathode, and the supply of brine tends to decrease to cause the brine concentration to be lower in the case of the anode. In order to prevent damage to the membrane that may be caused by such accumulation, the ventilation resistance is preferably less than 0.19 kPa·s / m, more preferably 0.15 kPa·s / m or less, further preferably 0.07 kPa·s / m or less.

[0547] In contrast, when the ventilation resistance is low, the area of the electrode is reduced and the electrolysis area is reduced. Thus, the electrolytic performance (such as voltage) tends to deteriorate. When the ventilation resistance is zero, the feed conductor functions as the electrode because no electrode for electrolysis is provided, and the electrolytic performance (such as voltage) tends to markedly deteriorate. From this viewpoint, a preferable lower limit value identified as the ventilation resistance 1 is not particularly limited, but is preferably more than 0 kPa·s / m, more preferably 0.0001 kPa·s / m or more, further preferably 0.001 kPa·s / m or more.

[0548] When the ventilation resistance 1 is 0.07 kPa·s / m or less, a sufficient measurement accuracy may not be achieved because of the measurement method therefor. From this viewpoint, it is also possible to evaluate an electrode for electrolysis having a ventilation resistance 1 of 0.07 kPa·s / m or less by means of a ventilation resistance (hereinbelow, also referred to as “ventilation resistance 2”) obtained by the following measurement method (hereinbelow, also referred to as “measurement condition 2”). That is, the ventilation resistance 2 is a ventilation resistance measured, when the electrode for electrolysis has a size of 50 mm×50 mm, under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 2 cm / s, and a ventilation volume of 4 cc / cm2 / s.

[0549] The specific methods for measuring the ventilation resistances 1 and 2 are described in Examples.

[0550] The ventilation resistances 1 and 2 can be within the range described above by appropriately adjusting an opening ratio, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to smaller ventilation resistances 1 and 2, and a lower opening ratio tends to lead to larger ventilation resistances 1 and 2.

[0551] In the electrode for electrolysis of the present embodiment, as mentioned above, the force applied per unit mass-unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N / mg·cm2. In this manner, the electrode for electrolysis of the present embodiment abuts with a moderate adhesive force on the membrane or feed conductor (e.g., the existing anode or cathode in the electrolyzer) to thereby enable a laminate with the membrane or feed conductor to be constituted. That is, it is not necessary to cause the membrane or feed conductor to firmly adhere to the electrode for electrolysis by a complicated method such as thermal compression. The laminate is formed only by a relatively weak force, for example, a surface tension derived from moisture contained in the membrane such as an ion exchange membrane and a microporous membrane, and thus, a laminate of any scale can be easily constituted. Additionally, such a laminate exhibits excellent electrolytic performance. Thus, the laminate of the present embodiment is suitable for electrolysis applications, and can be particularly preferably used for applications related to members of electrolyzers and renewing the members.

[0552] Hereinbelow, one aspect of the electrode for electrolysis of the present embodiment will be described.

[0553] The electrode for electrolysis according to the present embodiment preferably includes a substrate for electrode for electrolysis and a catalyst layer. The catalyst layer may be composed of a plurality of layers as shown below or may be a single-layer configuration.

[0554] As shown in FIG. 22, an electrode for electrolysis 100 according to the present embodiment includes a substrate for electrode for electrolysis 10 and a pair of first layers 20 with which both the surfaces of the substrate for electrode for electrolysis 10 are covered. The entire substrate for electrode for electrolysis 10 is preferably covered with the first layers 20. This covering is likely to improve the catalyst activity and durability of the electrode for electrolysis. One first layer 20 may be laminated only on one surface of the substrate for electrode for electrolysis 10.

[0555] Also shown in FIG. 22, the surfaces of the first layers 20 may be covered with second layers 30. The entire first layers 20 are preferably covered by the second layers 30. Alternatively, one second layer 30 may be laminated only one surface of the first layer 20.(Substrate for Electrode for Electrolysis)

[0556] As the substrate for electrode for electrolysis 10, for example, nickel, nickel alloys, stainless steel, or valve metals including titanium can be used, although not limited thereto. The substrate 10 preferably contains at least one element selected from nickel (Ni) and titanium (Ti).

[0557] When stainless steel is used in an alkali aqueous solution of a high concentration, iron and chromium are eluted and the electrical conductivity of stainless steel is of the order of one-tenth of that of nickel. In consideration of the foregoing, a substrate containing nickel (Ni) is preferable as the substrate for electrode for electrolysis.

[0558] Alternatively, when the substrate for electrode for electrolysis 10 is used in a salt solution of a high concentration near the saturation under an atmosphere in which chlorine gas is generated, the material of the substrate for electrode 10 is also preferably titanium having high corrosion resistance.

[0559] The form of the substrate for electrode for electrolysis 10 is not particularly limited, and a form suitable for the purpose can be selected. As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used. Among these, a perforated metal or expanded metal is preferable. Electroforming is a technique for producing a metal thin film having a precise pattern by using photolithography and electroplating in combination. It is a method including forming a pattern on a substrate with a photoresist and electroplating the portion not protected by the resist to provide a metal thin film.

[0560] As for the form of the substrate for electrode for electrolysis, a suitable specification depends on the distance between the anode and the cathode in the electrolyzer. In the case where the distance between the anode and the cathode is finite, an expanded metal or perforated metal form can be used, and in the case of a so-called zero-gap base electrolyzer, in which the ion exchange membrane is in contact with the electrode, a woven mesh produced by knitting thin lines, wire mesh, foamed metal, metal nonwoven fabric, expanded metal, perforated metal, metal porous foil, and the like can be used, although not limited thereto.

[0561] Examples of the substrate for electrode for electrolysis 10 include a metal porous foil, a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, and a foamed metal.

[0562] As a plate material before processed into a perforated metal or expanded metal, rolled plate materials and electrolytic foils are preferable. An electrolytic foil is preferably further subjected to a plating treatment by use of the same element as the base material thereof, as the post-treatment, to thereby form asperities on one or both of the surfaces.

[0563] The thickness of the substrate for electrode for electrolysis 10 is, as mentioned above, preferably 300 μm or less, more preferably 205 μm or less, further preferably 155 μm or less, further more preferably 135 μm or less, even further more preferably 125 μm or less, still more preferably 120 μm or less, even still more preferably 100 μm or less, and further still more preferably 50 μm or less from the viewpoint of a handling property and economy. The lower limit value is not particularly limited, but is 1 μm, for example, preferably 5 μm, more preferably 15 μm.

[0564] In the substrate for electrode for electrolysis, the residual stress during processing is preferably relaxed by annealing the substrate for electrode for electrolysis in an oxidizing atmosphere. It is preferable to form asperities using a steel grid, alumina powder, or the like on the surface of the substrate for electrode for electrolysis followed by an acid treatment to increase the surface area thereof, in order to improve the adhesion to a catalyst layer with which the surface is covered. Alternatively, it is preferable to give a plating treatment by use of the same element as the substrate to increase the surface area.

[0565] To bring the first layer 20 into close contact with the surface of the substrate for electrode for electrolysis 10, the substrate for electrode for electrolysis 10 is preferably subjected to a treatment of increasing the surface area. Examples of the treatment of increasing the surface area include a blast treatment using a cut wire, steel grid, alumina grid or the like, an acid treatment using sulfuric acid or hydrochloric acid, and a plating treatment using the same element to that of the substrate. The arithmetic average surface roughness (Ra) of the substrate surface is not particularly limited, but is preferably 0.05 μm to 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

[0566] Next, a case where the electrode for electrolysis of the present embodiment is used as an anode for common salt electrolysis will be described.(First Layer)

[0567] In FIG. 22, a first layer 20 as a catalyst layer contains at least one of ruthenium oxides, iridium oxides, and titanium oxides. Examples of the ruthenium oxide include RuO2. Examples of the iridium oxide include IrO2. Examples of the titanium oxide include TiO2. The first layer 20 preferably contains two oxides: a ruthenium oxide and a titanium oxide or three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide. This makes the first layer 20 more stable and additionally improves the adhesion with the second layer 30.

[0568] When the first layer 20 contains two oxides: a ruthenium oxide and a titanium oxide, the first layer 20 contains preferably 1 to 9 mol, more preferably 1 to 4 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the two oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0569] When the first layer 20 contains three oxides: a ruthenium oxide, an iridium oxide, and a titanium oxide, the first layer 20 contains preferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably 1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxide contained in the first layer 20. With the composition ratio of the three oxides in this range, the electrode for electrolysis 100 exhibits excellent durability.

[0570] When the first layer 20 contains at least two of a ruthenium oxide, an iridium oxide, and a titanium oxide, these oxides preferably form a solid solution. Formation of the oxide solid solution allows the electrode for electrolysis 100 to exhibit excellent durability.

[0571] In addition to the compositions described above, oxides of various compositions can be used as long as at least one oxide of a ruthenium oxide, an iridium oxide, and titanium oxide is contained. For example, an oxide coating called DSA®, which contains ruthenium, iridium, tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and the like, can be used as the first layer 20.

[0572] The first layer 20 need not be a single layer and may include a plurality of layers. For example, the first layer 20 may include a layer containing three oxides and a layer containing two oxides. The thickness of the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1 to 8 μm.(Second Layer)

[0573] The second layer 30 preferably contains ruthenium and titanium. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0574] The second layer 30 preferably contains a palladium oxide, a solid solution of a palladium oxide and platinum, or an alloy of palladium and platinum. This enables the chlorine overvoltage immediately after electrolysis to be further lowered.

[0575] A thicker second layer 30 can maintain the electrolytic performance for a longer period, but from the viewpoint of economy, the thickness is preferably 0.05 to 3 μm.

[0576] Next, a case where the electrode for electrolysis of the present embodiment is used as a cathode for common salt electrolysis will be described.(First Layer)

[0577] Examples of components of the first layer 20 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0578] The first layer 20 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal.

[0579] When the first layer 20 contains at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal, the platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal preferably contain at least one platinum group metal of platinum, palladium, rhodium, ruthenium, and iridium.

[0580] As the platinum group metal, platinum is preferably contained.

[0581] As the platinum group metal oxide, a ruthenium oxide is preferably contained.

[0582] As the platinum group metal hydroxide, a ruthenium hydroxide is preferably contained.

[0583] As the platinum group metal alloy, an alloy of platinum with nickel, iron, and cobalt is preferably contained.

[0584] Further, as required, an oxide or hydroxide of a lanthanoid element is preferably contained as a second component. This allows the electrode for electrolysis 100 to exhibit excellent durability.

[0585] As the oxide or hydroxide of a lanthanoid element, at least one selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, and dysprosium is preferably contained.

[0586] Further, as required, an oxide or hydroxide of a transition metal is preferably contained as a third component.

[0587] Addition of the third component enables the electrode for electrolysis 100 to exhibit more excellent durability and the electrolysis voltage to be lowered.

[0588] Examples of a preferable combination include ruthenium only, ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum, ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium, ruthenium+praseodymium, ruthenium+praseodymium+platinum, ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium, ruthenium+neodymium+platinum, ruthenium+neodymium+manganese, ruthenium+neodymium+iron, ruthenium+neodymium+cobalt, ruthenium+neodymium+zinc, ruthenium+neodymium+gallium, ruthenium+neodymium+sulfur, ruthenium+neodymium+lead, ruthenium+neodymium+nickel, ruthenium+neodymium+copper, ruthenium+samarium, ruthenium+samarium+manganese, ruthenium+samarium+iron, ruthenium+samarium+cobalt, ruthenium+samarium+zinc, ruthenium+samarium+gallium, ruthenium+samarium+sulfur, ruthenium+samarium+lead, ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium, platinum+palladium+lanthanum+cerium, platinum+iridium, platinum+palladium, platinum+iridium+palladium, platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinum and nickel, alloys of platinum and cobalt, and alloys of platinum and iron.

[0589] When platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal are not contained, the main component of the catalyst is preferably nickel element.

[0590] At least one of nickel metal, oxides, and hydroxides is preferably contained.

[0591] As the second component, a transition metal may be added. As the second component to be added, at least one element of titanium, tin, molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon is preferably contained.

[0592] Examples of a preferable combination include nickel+tin, nickel+titanium, nickel+molybdenum, and nickel+cobalt.

[0593] As required, an intermediate layer can be placed between the first layer 20 and the substrate for electrode for electrolysis 10. The durability of the electrode for electrolysis 100 can be improved by placing the intermediate layer.

[0594] As the intermediate layer, those having affinity to both the first layer 20 and the substrate for electrode for electrolysis 10 are preferable. As the intermediate layer, nickel oxides, platinum group metals, platinum group metal oxides, and platinum group metal hydroxides are preferable. The intermediate layer can be formed by applying and baking a solution containing a component that forms the intermediate layer. Alternatively, a surface oxide layer also can be formed by subjecting a substrate to a thermal treatment at a temperature of 300 to 600° C. in an air atmosphere. Besides, the layer can be formed by a known method such as a thermal spraying method and ion plating method.(Second Layer)

[0595] Examples of components of the first layer 30 as the catalyst layer include metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.

[0596] The first layer 30 may or may not contain at least one of platinum group metals, platinum group metal oxides, platinum group metal hydroxides, and alloys containing a platinum group metal. Examples of a preferable combination of elements contained in the second layer include the combinations enumerated for the first layer. The combination of the first layer and the second layer may be a combination in which the compositions are the same and the composition ratios are different or may be a combination of different compositions.

[0597] As the thickness of the catalyst layer, the total thickness of the catalyst layer formed and the intermediate layer is preferably 0.01 μm to 20 μm. With a thickness of 0.01 μm or more, the catalyst layer can sufficiently serve as the catalyst. With a thickness of 20 μm or less, it is possible to form a robust catalyst layer that is unlikely to fall off from the substrate. The thickness is more preferably 0.05 μm to 15 μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness is further preferably 0.2 μm to 8 μm.

[0598] The thickness of the electrode for electrolysis, that is, the total thickness of the substrate for electrode for electrolysis and the catalyst layer is preferably 315 μm or less, more preferably 220 μm or less, further preferably 170 μm or less, further more preferably 150 μm or less, particularly preferably 145 μm or less, still more preferably 140 μm or less, even still more preferably 138 μm or less, further still more preferably 135 μm or less in respect of the handling property of the electrode for electrolysis. A thickness of 135 μm or less can provide a good handling property. Further, from a similar viewpoint as above, the thickness is preferably 130 μm or less, more preferably less than 130 μm, further preferably 115 μm or less, further more preferably 65 μm or less. The lower limit value is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more for practical reasons, more preferably 20 μm or more. The thickness of the electrode can be determined by measurement with a digimatic thickness gauge (Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of the substrate for electrode for electrolysis can be measured in the same manner as in the case of the electrode for electrolysis. The thickness of the catalyst layer can be determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode for electrolysis.(Method for Producing Electrode for Electrolysis)

[0599] Next, one embodiment of the method for producing the electrode for electrolysis 100 will be described in detail.

[0600] In the present embodiment, the electrode for electrolysis 100 can be produced by forming the first layer 20, preferably the second layer 30, on the substrate for electrode for electrolysis by a method such as baking of a coating film under an oxygen atmosphere (pyrolysis), or ion plating, plating, or thermal spraying. The production method of the present embodiment as mentioned can achieve a high productivity of the electrode for electrolysis 100. Specifically, a catalyst layer is formed on the substrate for electrode for electrolysis by an application step of applying a coating liquid containing a catalyst, a drying step of drying the coating liquid, and a pyrolysis step of performing pyrolysis. Pyrolysis herein means that a metal salt which is to be a precursor is decomposed by heating into a metal or metal oxide and a gaseous substance. The decomposition product depends on the metal species to be used, type of the salt, and the atmosphere under which pyrolysis is performed, and many metals tend to form oxides in an oxidizing atmosphere. In an industrial process of producing an electrode, pyrolysis is usually performed in air, and a metal oxide or a metal hydroxide is formed in many cases.(Formation of First Layer of Anode)(Application Step)

[0601] The first layer 20 is obtained by applying a solution in which at least one metal salt of ruthenium, iridium, and titanium is dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of ruthenium, iridium, and titanium in the first coating liquid is substantially equivalent to that of the first layer 20.

[0602] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0603] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0604] After being applied onto the substrate for electrode for electrolysis 100, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0605] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Second Layer)

[0606] The second layer 30, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound and a platinum compound or a solution containing a ruthenium compound and a titanium compound (second coating liquid) onto the first layer 20 and then pyrolyzing the coating liquid in the presence of oxygen.(Formation of First Layer of Cathode by Pyrolysis Method)(Application Step)

[0607] The first layer 20 is obtained by applying a solution in which metal salts of various combination are dissolved (first coating liquid) onto the substrate for electrode for electrolysis and then pyrolyzing (baking) the coating liquid in the presence of oxygen. The content of the metal in the first coating liquid is substantially equivalent to that in the first layer 20.

[0608] The metal salts may be chlorides, nitrates, sulfates, metal alkoxides, and any other forms. The solvent of the first coating liquid can be selected depending on the type of the metal salt, and water and alcohols such as butanol can be used. As the solvent, water or a mixed solvent of water and an alcohol is preferable. The total metal concentration in the first coating liquid in which the metal salts are dissolved is not particularly limited, but is preferably in the range of 10 to 150 g / L in association with the thickness of the coating film to be formed by a single coating.

[0609] Examples of a method used as the method for applying the first coating liquid onto the substrate for electrode for electrolysis 10 include a dipping method of immersing the substrate for electrode for electrolysis 10 in the first coating liquid, a method of brushing the first coating liquid, a roll method using a sponge roll impregnated with the first coating liquid, and an electrostatic coating method in which the substrate for electrode for electrolysis 10 and the first coating liquid are oppositely charged and spraying is performed. Among these, preferable is the roll method or electrostatic coating method, which has an excellent industrial productivity.(Drying Step and Pyrolysis Step)

[0610] After being applied onto the substrate for electrode for electrolysis 10, the first coating liquid is dried at a temperature of 10 to 90° C. and pyrolyzed in a baking furnace heated to 350 to 650° C. Between the drying and pyrolysis, preliminary baking at 100 to 350° C. may be performed as required. The drying, preliminary baking, and pyrolysis temperature can be appropriately selected depending on the composition and the solvent type of the first coating liquid. A longer time period of pyrolysis per step is preferable, but from the viewpoint of the productivity of the electrode, 3 to 60 minutes is preferable, 5 to 20 minutes is more preferable.

[0611] The cycle of application, drying, and pyrolysis described above is repeated to form a covering (the first layer 20) to a predetermined thickness. After the first layer 20 is formed and then further post-baked for a long period as required can further improve the stability of the first layer 20.(Formation of Intermediate Layer)

[0612] The intermediate layer, which is formed as required, is obtained, for example, by applying a solution containing a palladium compound or platinum compound (second coating liquid) onto the substrate and then pyrolyzing the coating liquid in the presence of oxygen. Alternatively, a nickel oxide intermediate layer may be formed on the substrate surface only by heating the substrate, without applying a solution thereon.(Formation of First Layer of Cathode by Ion Plating)

[0613] The first layer 20 can be formed also by ion plating.

[0614] An example includes a method in which the substrate is fixed in a chamber and the metal ruthenium target is irradiated with an electron beam. Evaporated metal ruthenium particles are positively charged in plasma in the chamber to deposit on the substrate negatively charged. The plasma atmosphere is argon and oxygen, and ruthenium deposits as ruthenium oxide on the substrate.(Formation of First Layer of Cathode by Plating)

[0615] The first layer 20 can be formed also by a plating method.

[0616] As an example, when the substrate is used as the cathode and subjected to electrolytic plating in an electrolyte solution containing nickel and tin, alloy plating of nickel and tin can be formed.(Formation of First Layer of Cathode by Thermal Spraying)

[0617] The first layer 20 can be formed also by thermal spraying.

[0618] As an example, plasma spraying nickel oxide particles onto the substrate can form a catalyst layer in which metal nickel and nickel oxide are mixed.

[0619] The electrode for electrolysis of the present embodiment can be integrated with a membrane such as an ion exchange membrane and a microporous membrane and used. Thus, the electrode can be used as a membrane-integrated electrode. Then, the substituting work for the cathode and anode on renewing the electrode is eliminated, and the work efficiency is markedly improved.

[0620] The electrode integrated with the membrane such as an ion exchange membrane and a microporous membrane can make the electrolytic performance comparable to or higher than those of a new electrode.

[0621] Hereinafter, the ion exchange membrane will be described in detail.[Ion Exchange Membrane]

[0622] The ion exchange membrane has a membrane body containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and a coating layer provided on at least one surface of the membrane body. The coating layer contains inorganic material particles and a binder, and the specific surface area of the coating layer is 0.1 to 10 m2 / g. In the ion exchange membrane having such a structure, the influence of gas generated during electrolysis on electrolytic performance is small, and stable electrolytic performance can be exhibited.

[0623] The membrane of a perfluorocarbon polymer into which an ion exchange group is introduced described above includes either one of a sulfonic acid layer having an ion exchange group derived from a sulfo group (a group represented by —SO3−, hereinbelow also referred to as a “sulfonic acid group”) or a carboxylic acid layer having an ion exchange group derived from a carboxyl group (a group represented by —CO2−, hereinbelow also referred to as a “carboxylic acid group”). From the viewpoint of strength and dimension stability, reinforcement core materials are preferably further included.

[0624] The inorganic material particles and binder will be described in detail in the section of description of the coating layer below.

[0625] FIG. 23 illustrates a cross-sectional schematic view showing one embodiment of an ion exchange membrane. An ion exchange membrane 1 has a membrane body 10 containing a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group and coating layers 11a and 11b formed on both the surfaces of the membrane body 10.

[0626] In the ion exchange membrane 1, the membrane body 10 comprises a sulfonic acid layer 3 having an ion exchange group derived from a sulfo group (a group represented by —SO3—, hereinbelow also referred to as a “sulfonic acid group”) and a carboxylic acid layer 2 having an ion exchange group derived from a carboxyl group (a group represented by —CO2—, hereinbelow also referred to as a “carboxylic acid group”), and the reinforcement core materials 4 enhance the strength and dimension stability. The ion exchange membrane 1, as comprising the sulfonic acid layer 3 and the carboxylic acid layer 2, is suitably used as an anion exchange membrane.

[0627] The ion exchange membrane may include either one of the sulfonic acid layer and the carboxylic acid layer. The ion exchange membrane may not be necessarily reinforced by reinforcement core materials, and the arrangement of the reinforcement core materials is not limited to the example in FIG. 23.(Membrane Body)

[0628] First, the membrane body 10 constituting the ion exchange membrane 1 will be described.

[0629] The membrane body 10 should be one that has a function of selectively allowing cations to permeate and comprises a hydrocarbon polymer or a fluorine-containing polymer having an ion exchange group. Its configuration and material are not particularly limited, and preferred ones can be appropriately selected.

[0630] The hydrocarbon polymer or fluorine-containing polymer having an ion exchange group in the membrane body 10 can be obtained from a hydrocarbon polymer or fluorine-containing polymer having an ion exchange group precursor capable of forming an ion exchange group by hydrolysis or the like. Specifically, for example, after a polymer comprising a main chain of a fluorinated hydrocarbon, having, as a pendant side chain, a group convertible into an ion exchange group by hydrolysis or the like (ion exchange group precursor), and being melt-processable (hereinbelow, referred to as the “fluorine-containing polymer (a)” in some cases) is used to prepare a precursor of the membrane body 10, the membrane body 10 can be obtained by converting the ion exchange group precursor into an ion exchange group.

[0631] The fluorine-containing polymer (a) can be produced, for example, by copolymerizing at least one monomer selected from the following first group and at least one monomer selected from the following second group and / or the following third group. The fluorine-containing polymer (a) can be also produced by homopolymerization of one monomer selected from any of the following first group, the following second group, and the following third group.

[0632] Examples of the monomers of the first group include vinyl fluoride compounds. Examples of the vinyl fluoride compounds include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinyl ethers. Particularly when the ion exchange membrane is used as a membrane for alkali electrolysis, the vinyl fluoride compound is preferably a perfluoro monomer, and a perfluoro monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and perfluoro alkyl vinyl ethers is preferable.

[0633] Examples of the monomers of the second group include vinyl compounds having a functional group convertible into a carboxylic acid-type ion exchange group (carboxylic acid group). Examples of the vinyl compounds having a functional group convertible into a carboxylic acid group include monomers represented by CF2=CF(OCF2CYF)s—O(CZF)t—COOR, wherein s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represent F or CF3, and R represents a lower alkyl group (a lower alkyl group is an alkyl group having 1 to 3 carbon atoms, for example).

[0634] Among these, compounds represented by CF2=CF(OCF2CYF)n—O(CF2)m—COOR are preferable. Wherein n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF3, and R represents CH3, C2H5, or C3H7.

[0635] When the ion exchange membrane is used as a cation exchange membrane for alkali electrolysis, a perfluoro compound is preferably at least used as the monomer, but the alkyl group (see the above R) of the ester group is lost from the polymer at the time of hydrolysis, and therefore the alkyl group (R) need not be a perfluoroalkyl group in which all hydrogen atoms are replaced by fluorine atoms.

[0636] Of the above monomers, the monomers represented below are more preferable as the monomers of the second group:

[0637] Examples of the monomers of the third group include vinyl compounds having a functional group convertible into a sulfone-type ion exchange group (sulfonic acid group). As the vinyl compounds having a functional group convertible into a sulfonic acid group, for example, monomers represented by CF2=CFO—X—CF2—SO2F are preferable, wherein X represents a perfluoroalkylene group. Specific examples of these include the monomers represented below:

[0638] Among these, CF2=CFOCF2CF(CF3)OCF2CF2CF2SO2F and CF2=CFOCF2CF(CF3)OCF2CF2SO2F are more preferable.

[0639] The copolymer obtained from these monomers can be produced by a polymerization method developed for homopolymerization and copolymerization of ethylene fluoride, particularly a general polymerization method used for tetrafluoroethylene. For example, in a non-aqueous method, a polymerization reaction can be performed in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound under the conditions of a temperature of 0 to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent such as a perfluorohydrocarbon or a chlorofluorocarbon.

[0640] In the above copolymerization, the type of combination of the above monomers and their proportion are not particularly limited and are selected and determined depending on the type and amount of the functional group desired to be imparted to the fluorine-containing polymer to be obtained. For example, when a fluorine-containing polymer containing only a carboxylic acid group is formed, at least one monomer should be selected from each of the first group and the second group described above and copolymerized. In addition, when a fluorine-containing polymer containing only a sulfonic acid group is formed, at least one monomer should be selected from each of the first group and the third group and copolymerized. Further, when a fluorine-containing polymer having a carboxylic acid group and a sulfonic acid group is formed, at least one monomer should be selected from each of the first group, the second group, and the third group described above and copolymerized. In this case, the target fluorine-containing polymer can be obtained also by separately preparing a copolymer comprising the monomers of the first group and the second group described above and a copolymer comprising the monomers of the first group and the third group described above, and then mixing the copolymers. The mixing proportion of the monomers is not particularly limited, and when the amount of the functional groups per unit polymer is increased, the proportion of the monomers selected from the second group and the third group described above should be increased.

[0641] The total ion exchange capacity of the fluorine-containing copolymer is not particularly limited, but is preferably 0.5 to 2.0 mg equivalent / g, more preferably 0.6 to 1.5 mg equivalent / g. The total ion exchange capacity herein refers to the equivalent of the exchange group per unit weight of the dry resin and can be measured by neutralization titration or the like.

[0642] In the membrane body 10 of the ion exchange membrane 1, a sulfonic acid layer 3 containing a fluorine-containing polymer having a sulfonic acid group and a carboxylic acid layer 2 containing a fluorine-containing polymer having a carboxylic acid group are laminated. By providing the membrane body 10 having such a layer configuration, selective permeability for cations such as sodium ions can be further improved.

[0643] The ion exchange membrane 1 is arranged in an electrolyzer such that, usually, the sulfonic acid layer 3 is located on the anode side of the electrolyzer and the carboxylic acid layer 2 is located on the cathode side of the electrolyzer.

[0644] The sulfonic acid layer 3 is preferably constituted by a material having low electrical resistance and has a membrane thickness larger than that of the carboxylic acid layer 2 from the viewpoint of membrane strength. The membrane thickness of the sulfonic acid layer 3 is preferably 2 to 25 times, more preferably 3 to 15 times that of the carboxylic acid layer 2.

[0645] The carboxylic acid layer 2 preferably has high anion exclusion properties even if it has a small membrane thickness. The anion exclusion properties here refer to the property of trying to hinder intrusion and permeation of anions into and through the ion exchange membrane 1. In order to raise the anion exclusion properties, it is effective to dispose a carboxylic acid layer having a small ion exchange capacity to the sulfonic acid layer.

[0646] As the fluorine-containing polymer for use in the sulfonic acid layer 3, preferable is a polymer obtained by using CF2=CFOCF2CF(CF3)OCF2CF2SO2F as the monomer of the third group.

[0647] As the fluorine-containing polymer for use in the carboxylic acid layer 2, preferable is a polymer obtained by using CF2=CFOCF2CF(CF2)O(CF2)2COOCH3 as the monomer of the second group.(Coating Layer)

[0648] The ion exchange membrane has a coating layer on at least one surface of the membrane body. As shown in FIG. 23, in the ion exchange membrane 1, coating layers 11a and 11b are formed on both the surfaces of the membrane body 10.

[0649] The coating layers contain inorganic material particles and a binder.

[0650] The average particle size of the inorganic material particles is preferably 0.90 μm or more. When the average particle size of the inorganic material particles is 0.90 μm or more, durability to impurities is extremely improved, in addition to attachment of gas. That is, enlarging the average particle size of the inorganic material particles as well as satisfying the value of the specific surface area mentioned above can achieve a particularly marked effect. Irregular inorganic material particles are preferable because the average particle size and specific surface area as above are satisfied. Inorganic material particles obtained by melting and inorganic material particles obtained by grinding raw ore can be used. Inorganic material particles obtained by grinding raw ore can preferably be used.

[0651] The average particle size of the inorganic material particles can be 2 μm or less. When the average particle size of the inorganic material particles is 2 μm or less, it is possible to prevent damage of the membrane due to the inorganic material particles. The average particle size of the inorganic material particle is more preferably 0.90 to 1.2 μm.

[0652] Here, the average particle size can be measured by a particle size analyzer (“SALD2200”, SHIMADZU CORPORATION).

[0653] The inorganic material particles preferably have irregular shapes. Such shapes improve resistance to impurities further. The inorganic material particles preferably have a broad particle size distribution.

[0654] The inorganic material particles preferably contain at least one inorganic material selected from the group consisting of oxides of Group IV elements in the Periodic Table, nitrides of Group IV elements in the Periodic Table, and carbides of Group IV elements in the Periodic Table. From the viewpoint of durability, zirconium oxide particle is more preferable.

[0655] The inorganic material particles are preferably inorganic material particles produced by grinding the raw ore of the inorganic material particles or inorganic material particles, as spherical particles having a uniform diameter, obtained by melt-purifying the raw ore of the inorganic material particles.

[0656] Examples of means for grinding raw ore include, but are not particularly limited to, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, grain mills, hammer mills, pellet mills, VSI mills, Wiley mills, roller mills, and jet mills. After grinding, the particles are preferably washed. As the washing method, the particles are preferably treated with acid. This treatment can reduce impurities such as iron attached to the surface of the inorganic material particles.

[0657] The coating layer preferably contains a binder. The binder is a component that forms the coating layers by retaining the inorganic material particles on the surface of the ion exchange membrane. The binder preferably contains a fluorine-containing polymer from the viewpoint of durability to the electrolyte solution and products from electrolysis.

[0658] As the binder, a fluorine-containing polymer having a carboxylic acid group or sulfonic acid group is more preferable, from the viewpoint of durability to the electrolyte solution and products from electrolysis and adhesion to the surface of the ion exchange membrane. When a coating layer is provided on a layer containing a fluorine-containing polymer having a sulfonic acid group (sulfonic acid layer), a fluorine-containing polymer having a sulfonic acid group is further preferably used as the binder of the coating layer. Alternatively, when a coating layer is provided on a layer containing a fluorine-containing polymer having a carboxylic acid group (carboxylic acid layer), a fluorine-containing polymer having a carboxylic acid group is further preferably used as the binder of the coating layer.

[0659] In the coating layer, the content of the inorganic material particles is preferably 40 to 90% by mass, more preferably 50 to 90% by mass. The content of the binder is preferably 10 to 60% by mass, more preferably 10 to 50% by mass.

[0660] The distribution density of the coating layer in the ion exchange membrane is preferably 0.05 to 2 mg per 1 cm2. When the ion exchange membrane has asperities on the surface thereof, the distribution density of the coating layer is preferably 0.5 to 2 mg per 1 cm2.

[0661] As the method for forming the coating layer, which is not particularly limited, a known method can be used. An example is a method including applying by a spray or the like a coating liquid obtained by dispersing inorganic material particles in a solution containing a binder.(Reinforcement Core Materials)

[0662] The ion exchange membrane preferably has reinforcement core materials arranged inside the membrane body.

[0663] The reinforcement core materials are members that enhance the strength and dimensional stability of the ion exchange membrane. By arranging the reinforcement core materials inside the membrane body, particularly expansion and contraction of the ion exchange membrane can be controlled in the desired range. Such an ion exchange membrane does not expand or contract more than necessary during electrolysis and the like and can maintain excellent dimensional stability for a long term.

[0664] The configuration of the reinforcement core materials is not particularly limited, and, for example, the reinforcement core materials may be formed by spinning yarns referred to as reinforcement yarns. The reinforcement yarns here refer to yarns that are members constituting the reinforcement core materials, can provide the desired dimensional stability and mechanical strength to the ion exchange membrane, and can be stably present in the ion exchange membrane. By using the reinforcement core materials obtained by spinning such reinforcement yarns, better dimensional stability and mechanical strength can be provided to the ion exchange membrane.

[0665] The material of the reinforcement core materials and the reinforcement yarns used for these is not particularly limited but is preferably a material resistant to acids, alkalis, etc., and a fiber comprising a fluorine-containing polymer is preferable because long-term heat resistance and chemical resistance are required.

[0666] Examples of the fluorine-containing polymer to be used in the reinforcement core materials include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-ethylene copolymers (ETFE), tetrafluoroethylene-hexafluoropropylene copolymers, trifluorochloroethylene-ethylene copolymers, and vinylidene fluoride polymers (PVDF). Among these, fibers comprising polytetrafluoroethylene are preferably used from the viewpoint of heat resistance and chemical resistance.

[0667] The yarn diameter of the reinforcement yarns used for the reinforcement core materials is not particularly limited, but is preferably 20 to 300 deniers, more preferably 50 to 250 deniers. The weave density (fabric count per unit length) is preferably 5 to 50 / inch. The form of the reinforcement core materials is not particularly limited, for example, a woven fabric, a nonwoven fabric, and a knitted fabric are used, but is preferably in the form of a woven fabric. The thickness of the woven fabric to be used is preferably 30 to 250 μm, more preferably 30 to 150 μm.

[0668] As the woven fabric or knitted fabric, monofilaments, multifilaments, or yarns thereof, a slit yarn, or the like can be used, and various types of weaving methods such as a plain weave, a leno weave, a knit weave, a cord weave, and a seersucker can be used.

[0669] The weave and arrangement of the reinforcement core materials in the membrane body are not particularly limited, and preferred arrangement can be appropriately provided considering the size and form of the ion exchange membrane, physical properties desired for the ion exchange membrane, the use environment, and the like.

[0670] For example, the reinforcement core materials may be arranged along one predetermined direction of the membrane body, but from the viewpoint of dimensional stability, it is preferred that the reinforcement core materials be arranged along a predetermined first direction, and other reinforcement core materials be arranged along a second direction substantially perpendicular to the first direction. By arranging the plurality of reinforcement core materials substantially orthogonally inside the membrane body, it is possible to impart better dimensional stability and mechanical strength in many directions. For example, arrangement in which the reinforcement core materials arranged along the longitudinal direction (warp yarns) and the reinforcement core materials arranged along the transverse direction (weft yarns) are woven on the surface side of the membrane body is preferred. The arrangement is more preferably in the form of plain weave driven and woven by allowing warps and wefts to run over and under each other alternately, leno weave in which two warps are woven into wefts while twisted, basket weave driven and woven by inserting, into two or more parallelly-arranged warps, wefts of the same number, or the like, from the viewpoint of dimension stability, mechanical strength and easy-production.

[0671] It is preferred that particularly, the reinforcement core materials be arranged along both directions, the MD (Machine Direction) and TD (Transverse Direction) of the ion exchange membrane. In other words, the reinforcement core materials are preferably plain-woven in the MD and TD. Here, the MD refers to the direction in which the membrane body and various core materials (for example, the reinforcement core materials, reinforcement yarns, and sacrifice yarns described later) are conveyed in an ion exchange membrane production step described later (flow direction), and the TD refers to the direction substantially perpendicular to the MD. Yarns woven along the MD are referred to as MD yarns, and yarns woven along the TD are referred to as TD yarns. Usually, the ion exchange membrane used for electrolysis is rectangular, and in many cases, the longitudinal direction is the MD, and the width direction is the TD. By weaving the reinforcement core materials that are MD yarns and the reinforcement core materials that are TD yarns, it is possible to impart better dimensional stability and mechanical strength in many directions.

[0672] The arrangement interval of the reinforcement core materials is not particularly limited, and preferred arrangement can be appropriately provided considering physical properties desired for the ion exchange membrane, the use environment, and the like.

[0673] The aperture ratio for the reinforcement core materials is not particularly limited, but is preferably 30% or more, more preferably 50% or more and 90% or less. The aperture ratio is preferably 30% or more from the viewpoint of the electrochemical properties of the ion exchange membrane, and preferably 90% or less from the viewpoint of the mechanical strength of the ion exchange membrane.

[0674] The aperture ratio for the reinforcement core materials herein refers to a ratio of a total area of a surface through which substances such as ions (an electrolyte solution and cations contained therein (e.g., sodium ions)) can pass (B) to the area of either one surface of the membrane body (A) (B / A). The total area of the surface through which substances such as ions can pass (B) can refer to the total areas of regions in which in the ion exchange membrane, cations, an electrolytic solution, and the like are not blocked by the reinforcement core materials and the like contained in the ion exchange membrane.

[0675] FIG. 24 illustrates a schematic view for explaining the aperture ratio of reinforcement core materials constituting the ion exchange membrane. FIG. 24, in which a portion of the ion exchange membrane is enlarged, shows only the arrangement of the reinforcement core materials 21 and 22 in the regions, omitting illustration of the other members.

[0676] By subtracting the total area of the reinforcement core materials (C) from the area of the region surrounded by the reinforcement core materials 21 arranged along the longitudinal direction and the reinforcement core materials 22 arranged along the transverse direction, the region including the area of the reinforcement core materials (A), the total area of regions through which substances such as ions can pass (B) in the area of the above-described region (A) can be obtained. That is, the aperture ratio can be determined by the following formula (I):Aperture⁢ ratio=(B) / (A)=((A)-(C)) / (A)(I)

[0677] Among the reinforcement core materials, a particularly preferred form is tape yarns or highly oriented monofilaments comprising PTFE from the viewpoint of chemical resistance and heat resistance. Specifically, reinforcement core materials forming a plain weave in which 50 to 300 denier tape yarns obtained by slitting a high strength porous sheet comprising PTFE into a tape form, or 50 to 300 denier highly oriented monofilaments comprising PTFE are used and which has a weave density of 10 to 50 yarns or monofilaments / inch and has a thickness in the range of 50 to 100 μm are more preferred. The aperture ratio of an ion exchange membrane comprising such reinforcement core materials is further preferably 60% or more.

[0678] Examples of the shape of the reinforcement yarns include round yarns and tape yarns.(Continuous Holes)

[0679] The ion exchange membrane preferably has continuous holes inside the membrane body.

[0680] The continuous holes refer to holes that can be flow paths for ions generated in electrolysis and an electrolyte solution. The continuous holes, which are tubular holes formed inside the membrane body, are formed by dissolution of sacrifice core materials (or sacrifice yarns) described below. The shape, diameter, or the like of the continuous holes can be controlled by selecting the shape or diameter of the sacrifice core materials (sacrifice yarns).

[0681] Forming the continuous holes inside the ion exchange membrane can ensure the mobility of an electrolyte solution on electrolysis. The shape of the continuous holes is not particularly limited, but may be the shape of sacrifice core materials to be used for formation of the continuous holes in accordance with the production method described below.

[0682] The continuous holes are preferably formed so as to alternately pass on the anode side (sulfonic acid layer side) and the cathode side (carboxylic acid layer side) of the reinforcement core materials. With such a structure, in a portion in which continuous holes are formed on the cathode side of the reinforcement core materials, ions (e.g., sodium ions) transported through the electrolyte solution with which the continuous holes are filled can flow also on the cathode side of the reinforcement core materials. As a result, the flow of cations is not interrupted, and thus, it is possible to further reduce the electrical resistance of the ion exchange membrane.

[0683] The continuous holes may be formed along only one predetermined direction of the membrane body constituting the ion exchange membrane, but are preferably formed in both the longitudinal direction and the transverse direction of the membrane body from the viewpoint of exhibiting more stable electrolytic performance.[Production Method]

[0684] A suitable example of a method for producing an ion exchange membrane includes a method including the following steps (1) to (6):

[0685] Step (1): the step of producing a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0686] Step (2): the step of weaving at least a plurality of reinforcement core materials, as required, and sacrifice yarns having a property of dissolving in an acid or an alkali, and forming continuous holes, to obtain a reinforcing material in which the sacrifice yarns are arranged between the reinforcement core materials adjacent to each other,

[0687] Step (3): the step of forming into a film the above fluorine-containing polymer having an ion exchange group or an ion exchange group precursor capable of forming an ion exchange group by hydrolysis,

[0688] Step (4): the step of embedding the above reinforcing materials, as required, in the above film to obtain a membrane body inside which the reinforcing materials are arranged,

[0689] Step (5): the step of hydrolyzing the membrane body obtained in the step (4) (hydrolysis step), and

[0690] Step (6): the step of providing a coating layer on the membrane body obtained in the step (5) (application step).

[0691] Hereinafter, each of the steps will be described in detail.Step (1): Step of Producing Fluorine-Containing Polymer

[0692] In the step (1), raw material monomers described in the first group to the third group above are used to produce a fluorine-containing polymer. In order to control the ion exchange capacity of the fluorine-containing polymer, the mixture ratio of the raw material monomers should be adjusted in the production of the fluorine-containing polymer forming the layers.Step (2): Step of Producing Reinforcing Materials

[0693] The reinforcing material is a woven fabric obtained by weaving reinforcement yarns or the like. The reinforcing material is embedded in the membrane to thereby form reinforcement core materials. When an ion exchange membrane having continuous holes is formed, sacrifice yarns are additionally woven into the reinforcing material. The amount of the sacrifice yarns contained in this case is preferably 10 to 80% by mass, more preferably 30 to 70% by mass based on the entire reinforcing material. Weaving the sacrifice yarns can also prevent yarn slippage of the reinforcement core materials.

[0694] As the sacrifice yarns, which have solubility in the membrane production step or under an electrolysis environment, rayon, polyethylene terephthalate (PET), cellulose, polyamide, and the like are used. Monofilaments or multifilaments having a thickness of 20 to 50 deniers and comprising polyvinyl alcohol and the like are also preferred.

[0695] In the step (2), the aperture ratio, arrangement of the continuous holes, and the like can be controlled by adjusting the arrangement of the reinforcement core materials and the sacrifice yarns.Step (3): Step of Film Formation

[0696] In the step (3), the fluorine-containing polymer obtained in the step (1) is formed into a film by using an extruder. The film may be a single-layer configuration, a two-layer configuration of a sulfonic acid layer and a carboxylic acid layer as mentioned above, or a multilayer configuration of three layers or more.

[0697] Examples of the film forming method include the following:

[0698] a method in which a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are separately formed into films; and

[0699] a method in which fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are coextruded into a composite film.

[0700] The number of each film may be more than one. Coextrusion of different films is preferred because of its contribution to an increase in the adhesive strength in the interface.Step (4): Step of Obtaining Membrane Body

[0701] In the step (4), the reinforcing material obtained in the step (2) is embedded in the film obtained in the step (3) to provide a membrane body including the reinforcing material therein.

[0702] Preferable examples of the method for forming a membrane body include (i) a method in which a fluorine-containing polymer having a carboxylic acid group precursor (e.g., carboxylate functional group) (hereinafter, a layer comprising the same is referred to as the first layer) located on the cathode side and a fluorine-containing polymer having a sulfonic acid group precursor (e.g., sulfonyl fluoride functional group) (hereinafter, a layer comprising the same is referred to as the second layer) are formed into a film by a coextrusion method, and, by using a heat source and a vacuum source as required, a reinforcing material and the second layer / first layer composite film are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure; and (ii) a method in which, in addition to the second layer / first layer composite film, a fluorine-containing polymer having a sulfonic acid group precursor is singly formed into a film (the third layer) in advance, and, by using a heat source and a vacuum source as required, the third layer film, the reinforcement core materials, and the composite film comprising the second layer / first layer are laminated in this order on breathable heat-resistant release paper on a flat plate or drum having many pores on the surface thereof and integrated at a temperature at which each polymer melts while air among each of the layers was evacuated by reduced pressure.

[0703] Coextrusion of the first layer and the second layer herein contributes to an increase in the adhesive strength at the interface.

[0704] The method including integration under a reduced pressure is characterized by making the third layer on the reinforcing material thicker than that of a pressure-application press method. Further, since the reinforcing material is fixed on the inner surface of the membrane body, the method has a property of sufficiently retaining the mechanical strength of the ion exchange membrane.

[0705] The variations of lamination described here are exemplary, and coextrusion can be performed after a preferred lamination pattern (for example, the combination of layers) is appropriately selected considering the desired layer configuration of the membrane body and physical properties, and the like.

[0706] For the purpose of further improving the electric properties of the ion exchange membrane, it is also possible to additionally interpose a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor between the first layer and the second layer or to use a fourth layer comprising a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor instead of the second layer.

[0707] The method for forming the fourth layer may be a method in which a fluorine-containing polymer having a carboxylic acid group precursor and a fluorine-containing polymer having a sulfonic acid group precursor are separately produced and then mixed or may be a method in which a monomer having a carboxylic acid group precursor and a monomer having a sulfonic acid group precursor are copolymerized.

[0708] When the fourth layer is used as a component of the ion exchange membrane, a coextruded film of the first layer and the fourth layer is formed, in addition to this, the third layer and the second layer are separately formed into films, and lamination may be performed by the method mentioned above. Alternatively, the three layers of the first layer / fourth layer / second layer may be simultaneously formed into a film by coextrusion.

[0709] In this case, the direction in which the extruded film flows is the MD. As mentioned above, it is possible to form a membrane body containing a fluorine-containing polymer having an ion exchange group on a reinforcing material.

[0710] Additionally, the ion exchange membrane preferably has protruded portions composed of the fluorine-containing polymer having a sulfonic acid group, that is, projections, on the surface side composed of the sulfonic acid layer. As a method for forming such projections, which is not particularly limited, a known method also can be employed including forming projections on a resin surface. A specific example of the method is a method of embossing the surface of the membrane body. For example, the above projections can be formed by using release paper embossed in advance when the composite film mentioned above, reinforcing material, and the like are integrated. In the case where projections are formed by embossing, the height and arrangement density of the projections can be controlled by controlling the emboss shape to be transferred (shape of the release paper).(5) Hydrolysis Step

[0711] In the step (5), a step of hydrolyzing the membrane body obtained in the step (4) to convert the ion exchange group precursor into an ion exchange group (hydrolysis step) is performed.

[0712] In the step (5), it is also possible to form dissolution holes in the membrane body by dissolving and removing the sacrifice yarns included in the membrane body with acid or alkali. The sacrifice yarns may remain in the continuous holes without being completely dissolved and removed. The sacrifice yarns remaining in the continuous holes may be dissolved and removed by the electrolyte solution when the ion exchange membrane is subjected to electrolysis.

[0713] The sacrifice yarn has solubility in acid or alkali in the step of producing an ion exchange membrane or under an electrolysis environment. The sacrifice yarns are eluted out to thereby form continuous holes at corresponding sites.

[0714] The step (5) can be performed by immersing the membrane body obtained in the step (4) in a hydrolysis solution containing acid or alkali. An example of the hydrolysis solution that can be used is a mixed solution containing KOH and dimethyl sulfoxide (DMSO).

[0715] The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of 25 to 35% by mass.

[0716] The temperature for hydrolysis is preferably 70 to 100° C. The higher the temperature, the larger can be the apparent thickness. The temperature is more preferably 75 to 100° C.

[0717] The time for hydrolysis is preferably 10 to 120 minutes. The longer the time, the larger can be the apparent thickness. The time is more preferably 20 to 120 minutes.

[0718] The step of forming continuous holes by eluting the sacrifice yarn will be now described in more detail. FIGS. 25(a) and (b) are schematic views for explaining a method for forming the continuous holes of the ion exchange membrane.

[0719] FIGS. 25(a) and (b) show reinforcement yarns 52, sacrifice yarns 504a, and continuous holes 504 formed by the sacrifice yarns 504a only, omitting illustration of the other members such as a membrane body.

[0720] First, the reinforcement yarns 52 that are to constitute reinforcement core materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane are used as interwoven reinforcing materials. Then, in the step (5), the sacrifice yarns 504a are eluted to form the continuous holes 504.

[0721] The above method is simple because the method for interweaving the reinforcement yarns 52 and the sacrifice yarns 504a may be adjusted depending on the arrangement of the reinforcement core materials and continuous holes in the membrane body of the ion exchange membrane.

[0722] FIG. 25(a) exemplifies the plain-woven reinforcing material in which the reinforcement yarns 52 and sacrifice yarns 504a are interwoven along both the longitudinal direction and the lateral direction in the paper, and the arrangement of the reinforcement yarns 52 and the sacrifice yarns 504a in the reinforcing material may be varied as required.(6) Application Step

[0723] In the step (6), a coating layer can be formed by preparing a coating liquid containing inorganic material particles obtained by grinding raw ore or melting raw ore and a binder, applying the coating liquid onto the surface of the ion exchange membrane obtained in the step (5), and drying the coating liquid.

[0724] A preferable binder is a binder obtained by hydrolyzing a fluorine-containing polymer having an ion exchange group precursor with an aqueous solution containing dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) and then immersing the polymer in hydrochloric acid to replace the counterion of the ion exchange group by H+(e.g., a fluorine-containing polymer having a carboxyl group or sulfo group). Thereby, the polymer is more likely to dissolve in water or ethanol mentioned below, which is preferable.

[0725] This binder is dissolved in a mixed solution of water and ethanol. The volume ratio between water and ethanol is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganic material particles are dispersed with a ball mill into the dissolution liquid thus obtained to thereby provide a coating liquid. In this case, it is also possible to adjust the average particle size and the like of the particles by adjusting the time and rotation speed during the dispersion. The preferable amount of the inorganic material particles and the binder to be blended is as mentioned above.

[0726] The concentration of the inorganic material particles and the binder in the coating liquid is not particularly limited, but a thin coating liquid is preferable. This enables uniform application onto the surface of the ion exchange membrane.

[0727] Additionally, a surfactant may be added to the dispersion when the inorganic material particles are dispersed. As the surfactant, nonionic surfactants are preferable, and examples thereof include HS-210, NS-210, P-210, and E-212 manufactured by NOF CORPORATION.

[0728] The coating liquid obtained is applied onto the surface of the ion exchange membrane by spray application or roll coating to thereby provide an ion exchange membrane.[Microporous Membrane]

[0729] The microporous membrane of the present embodiment is not particularly limited as long as the membrane can be formed into a laminate with the electrode for electrolysis, as mentioned above. Various microporous membranes may be employed.

[0730] The porosity of the microporous membrane of the present embodiment is not particularly limited, but can be 20 to 90, for example, and is preferably 30 to 85. The above porosity can be calculated by the following formula:Porosity=(1-(the⁢ weight⁢ of⁢ the⁢ membrane⁢ in⁢ a⁢ dried⁢ state) / (the⁢ weight⁢ calculated⁢ from⁢ the⁢ volume⁢ calculated⁢ from⁢ the⁢ thickness,width,and⁢ length⁢ of⁢ the⁢ membrane⁢ and⁢ the⁢ density⁢ of⁢ the⁢ membrane⁢ material))×100

[0731] The average pore size of the microporous membrane of the present embodiment is not particularly limited, and can be 0.01 μm to 10 μm, for example, preferably 0.05 μm to 5 μm. With respect to the average pore size, for example, the membrane is cut vertically to the thickness direction, and the section is observed with an FE-SEM. The average pore size can be obtained by measuring the diameter of about 100 pores observed and averaging the measurements.

[0732] The thickness of the microporous membrane of the present embodiment is not particularly limited, and can be 10 μm to 1000 μm, for example, preferably 50 μm to 600 μm. The above thickness can be measured by using a micrometer (manufactured by Mitutoyo Corporation) or the like, for example.

[0733] Specific examples of the microporous membrane as mentioned above include Zirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfon membrane in the present embodiment) and those described in International Publication No. WO 2013-183584 and International Publication No. WO 2016-203701.

[0734] The reason why the laminate with the membrane of the present embodiment develops excellent electrolytic performance is presumed as follows. When the membrane and the electrode firmly adhere to each other by a method such as thermal compression, which is a conventional technique, the electrode sinks into the membrane to thereby physically adhere thereto. This adhesion portion inhibits sodium ions from migrating in the membrane to thereby markedly raise the voltage. Meanwhile, inhibition of migration of sodium ions in the membrane, which has been a problem in the conventional art, is eliminated by allowing the electrode for electrolysis to abut with a moderate adhesive force on the membrane or feed conductor, as in the present embodiment. According to the foregoing, when the membrane or feed conductor abuts on the electrode for electrolysis with a moderate adhesive force, the membrane or feed conductor and the electrode for electrolysis, despite of being an integrated piece, can develop excellent electrolytic performance.[Wound Body]

[0735] The wound body of the present embodiment includes the laminate of the present embodiment. That is, the wound body of the present embodiment is obtained by winding the laminate of the present embodiment. Downsizing the laminate of the present embodiment by winding, like the wound body of the present embodiment, can further improve the handling property.[Electrolyzer]

[0736] The electrolyzer of the present embodiment includes the laminate of the present embodiment. Hereinafter, the case of performing common salt electrolysis by using an ion exchange membrane as the membrane is taken as an example, and one embodiment of the electrolyzer will be described in detail.[Electrolytic Cell]

[0737] FIG. 26 illustrates a cross-sectional view of an electrolytic cell 1.

[0738] The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber 20, a partition wall 30 placed between the anode chamber 10 and the cathode chamber 20, an anode 11 placed in the anode chamber 10, and a cathode 21 placed in the cathode chamber 20. As required, the electrolytic cell 1 has a substrate 18a and a reverse current absorbing layer 18b formed on the substrate 18a and may comprise a reverse current absorber 18 placed in the cathode chamber. The anode 11 and the cathode 21 belonging to the electrolytic cell 1 are electrically connected to each other. In other words, the electrolytic cell 1 comprises the following cathode structure. The cathode structure 40 comprises the cathode chamber 20, the cathode 21 placed in the cathode chamber 20, and the reverse current absorber 18 placed in the cathode chamber 20, the reverse current absorber 18 has the substrate 18a and the reverse current absorbing layer 18b formed on the substrate 18a, as shown in FIG. 30, and the cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode chamber 20 further has a collector 23, a support 24 supporting the collector, and a metal elastic body 22. The metal elastic body 22 is placed between the collector 23 and the cathode 21. The support 24 is placed between the collector 23 and the partition wall 30. The collector 23 is electrically connected to the cathode 21 via the metal elastic body 22. The partition wall 30 is electrically connected to the collector 23 via the support 24. Accordingly, the partition wall 30, the support 24, the collector 23, the metal elastic body 22, and the cathode 21 are electrically connected. The cathode 21 and the reverse current absorbing layer 18b are electrically connected. The cathode 21 and the reverse current absorbing layer may be directly connected or may be indirectly connected via the collector, the support, the metal elastic body, the partition wall, or the like. The entire surface of the cathode 21 is preferably covered with a catalyst layer for reduction reaction. The form of electrical connection may be a form in which the partition wall 30 and the support 24, the support 24 and the collector 23, and the collector 23 and the metal elastic body 22 are each directly attached and the cathode 21 is laminated on the metal elastic body 22. Examples of a method for directly attaching these constituent members to one another include welding and the like. Alternatively, the reverse current absorber 18, the cathode 21, and the collector 23 may be collectively referred to as a cathode structure 40.

[0739] FIG. 27 illustrates a cross-sectional view of two electrolytic cells 1 that are adjacent in the electrolyzer 4. FIG. 28 shows an electrolyzer 4. FIG. 29 shows a step of assembling the electrolyzer 4. As shown in FIG. 27, an electrolytic cell 1, a cation exchange membrane 2, and an electrolytic cell 1 are arranged in series in the order mentioned. An ion exchange membrane 2 is arranged between the anode chamber of one electrolytic cell 1 among the two electrolytic cells that are adjacent in the electrolyzer and the cathode chamber of the other electrolytic cell 1. That is, the anode chamber 10 of the electrolytic cell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacent thereto is separated by the cation exchange membrane 2. As shown in FIG. 28, the electrolyzer 4 is composed of a plurality of electrolytic cells 1 connected in series via the ion exchange membrane 2. That is, the electrolyzer 4 is a bipolar electrolyzer comprising the plurality of electrolytic cells 1 arranged in series and ion exchange membranes 2 each arranged between adjacent electrolytic cells 1. As shown in FIG. 29, the electrolyzer 4 is assembled by arranging the plurality of electrolytic cells 1 in series via the ion exchange membrane 2 and coupling the cells by means of a press device 5.

[0740] The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 to be connected to a power supply. The anode 11 of the electrolytic cell 1 located at farthest end among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the anode terminal 7. The cathode 21 of the electrolytic cell located at the end opposite to the anode terminal 7 among the plurality of electrolytic cells 1 coupled in series in the electrolyzer 4 is electrically connected to the cathode terminal 6. The electric current during electrolysis flows from the side of the anode terminal 7, through the anode and cathode of each electrolytic cell 1, toward the cathode terminal 6. At the both ends of the coupled electrolytic cells 1, an electrolytic cell having an anode chamber only (anode terminal cell) and an electrolytic cell having a cathode chamber only (cathode terminal cell) may be arranged. In this case, the anode terminal 7 is connected to the anode terminal cell arranged at the one end, and the cathode terminal 6 is connected to the cathode terminal cell arranged at the other end.

[0741] In the case of electrolyzing brine, brine is supplied to each anode chamber 10, and pure water or a low-concentration sodium hydroxide aqueous solution is supplied to each cathode chamber 20. Each liquid is supplied from an electrolyte solution supply pipe (not shown in Figure), through an electrolyte solution supply hose (not shown in Figure), to each electrolytic cell 1. The electrolyte solution and products from electrolysis are recovered from an electrolyte solution recovery pipe (not shown in Figure). During electrolysis, sodium ions in the brine migrate from the anode chamber 10 of the one electrolytic cell 1, through the ion exchange membrane 2, to the cathode chamber 20 of the adjacent electrolytic cell 1. Thus, the electric current during electrolysis flows in the direction in which the electrolytic cells 1 are coupled in series. That is, the electric current flows, through the cation exchange membrane 2, from the anode chamber 10 toward the cathode chamber 20. As the brine is electrolyzed, chlorine gas is generated on the side of the anode 11, and sodium hydroxide (solute) and hydrogen gas are generated on the side of the cathode 21.(Anode Chamber)

[0742] The anode chamber 10 has the anode 11 or anode feed conductor 11. When the electrode for electrolysis of the present embodiment is inserted to the anode side, 11 serves as the anode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the anode side, 11 serves as the anode. The anode chamber 10 has an anode-side electrolyte solution supply unit that supplies an electrolyte solution to the anode chamber 10, a baffle plate that is arranged above the anode-side electrolyte solution supply unit so as to be substantially parallel or oblique to the partition wall 30, and an anode-side gas liquid separation unit arranged above the baffle plate to separate gas from the electrolyte solution including the gas mixed.(Anode)

[0743] When the electrode for electrolysis of the present embodiment is not inserted to the anode side, the anode 11 is provided in the frame of the anode chamber 10. As the anode 11, a metal electrode such as so-called DSA® can be used. DSA is an electrode including a titanium substrate of which surface is covered with an oxide comprising ruthenium, iridium, and titanium as components.

[0744] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode Feed Conductor)

[0745] When the electrode for electrolysis of the present embodiment is inserted to the anode side, the anode feed conductor 11 is provided in the frame of the anode chamber 10. As the anode feed conductor 11, a metal electrode such as so-called DSA® can be used, and titanium having no catalyst coating can be also used. Alternatively, DSA having a thinner catalyst coating can be also used. Further, a used anode can be also used.

[0746] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Anode-Side Electrolyte Solution Supply Unit)

[0747] The anode-side electrolyte solution supply unit, which supplies the electrolyte solution to the anode chamber 10, is connected to the electrolyte solution supply pipe. The anode-side electrolyte solution supply unit is preferably arranged below the anode chamber 10. As the anode-side electrolyte solution supply unit, for example, a pipe on the surface of which aperture portions are formed (dispersion pipe) and the like can be used. Such a pipe is more preferably arranged along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell. This pipe is connected to an electrolyte solution supply pipe (liquid supply nozzle) that supplies the electrolyte solution into the electrolytic cell 1. The electrolyte solution supplied from the liquid supply nozzle is conveyed with a pipe into the electrolytic cell 1 and supplied from the aperture portions provided on the surface of the pipe to inside the anode chamber 10. Arranging the pipe along the surface of the anode 11 and parallel to the bottom 19 of the electrolytic cell is preferable because the electrolyte solution can be uniformly supplied to inside the anode chamber 10.(Anode-Side Gas Liquid Separation Unit)

[0748] The anode-side gas liquid separation unit is preferably arranged above the baffle plate. The anode-side gas liquid separation unit has a function of separating produced gas such as chlorine gas from the electrolyte solution during electrolysis. Unless otherwise specified, above means the upper direction in the electrolytic cell 1 in FIG. 26, and below means the lower direction in the electrolytic cell 1 in FIG. 26.

[0749] During electrolysis, produced gas generated in the electrolytic cell 1 and the electrolyte solution form a mixed phase (gas-liquid mixed phase), which is then emitted out of the system. Subsequently, pressure fluctuations inside the electrolytic cell 1 cause vibration, which may result in physical damage of the ion exchange membrane. In order to prevent this event, the electrolytic cell 1 of the present embodiment is preferably provided with an anode-side gas liquid separation unit to separate the gas from the liquid. The anode-side gas liquid separation unit is preferably provided with a defoaming plate to eliminate bubbles. When the gas-liquid mixed phase flow passes through the defoaming plate, bubbles burst to thereby enable the electrolyte solution and the gas to be separated. As a result, vibration during electrolysis can be prevented.(Baffle Plate)

[0750] The baffle plate is preferably arranged above the anode-side electrolyte solution supply unit and arranged substantially in parallel with or obliquely to the partition wall 30. The baffle plate is a partition plate that controls the flow of the electrolyte solution in the anode chamber 10. When the baffle plate is provided, it is possible to cause the electrolyte solution (brine or the like) to circulate internally in the anode chamber 10 to thereby make the concentration uniform. In order to cause internal circulation, the baffle plate is preferably arranged so as to separate the space in proximity to the anode 11 from the space in proximity to the partition wall 30. From such a viewpoint, the baffle plate is preferably placed so as to be opposed to the surface of the anode 11 and to the surface of the partition wall 30. In the space in proximity to the anode partitioned by the baffle plate, as electrolysis proceeds, the electrolyte solution concentration (brine concentration) is lowered, and produced gas such as chlorine gas is generated. This results in a difference in the gas-liquid specific gravity between the space in proximity to anode 11 and the space in proximity to the partition wall 30 partitioned by the baffle plate. By use of the difference, it is possible to promote the internal circulation of the electrolyte solution in the anode chamber 10 to thereby make the concentration distribution of the electrolyte solution in the anode chamber 10 more uniform.

[0751] Although not shown in FIG. 26, a collector may be additionally provided inside the anode chamber 10. The material and configuration of such a collector may be the same as those of the collector of the cathode chamber mentioned below. In the anode chamber 10, the anode 11 per se may also serve as the collector.(Partition Wall)

[0752] The partition wall 30 is arranged between the anode chamber 10 and the cathode chamber 20. The partition wall 30 may be referred to as a separator, and the anode chamber 10 and the cathode chamber 20 are partitioned by the partition wall 30. As the partition wall 30, one known as a separator for electrolysis can be used, and an example thereof includes a partition wall formed by welding a plate comprising nickel to the cathode side and a plate comprising titanium to the anode side.(Cathode Chamber)

[0753] In the cathode chamber 20, when the electrode for electrolysis of the present embodiment is inserted to the cathode side, 21 serves as a cathode feed conductor. When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, 21 serves as a cathode. When a reverse current absorber is included, the cathode or cathode feed conductor 21 is electrically connected to the reverse current absorber. The cathode chamber 20, similarly to the anode chamber 10, preferably has a cathode-side electrolyte solution supply unit and a cathode-side gas liquid separation unit. Among the components constituting the cathode chamber 20, components similar to those constituting the anode chamber 10 will be not described.(Cathode)

[0754] When the electrode for electrolysis of the present embodiment is not inserted to the cathode side, a cathode 21 is provided in the frame of the cathode chamber 20. The cathode 21 preferably has a nickel substrate and a catalyst layer that covers the nickel substrate. Examples of the components of the catalyst layer on the nickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. The cathode 21 may be subjected to a reduction treatment, as required. As the substrate of the cathode 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0755] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Cathode Feed Conductor)

[0756] When the electrode for electrolysis of the present embodiment is inserted to the cathode side, a cathode feed conductor 21 is provided in the frame of the cathode chamber 20. The cathode feed conductor 21 may be covered with a catalytic component. The catalytic component may be a component that is originally used as the cathode and remains. Examples of the components of the catalyst layer include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals. Examples of the method for forming the catalyst layer include plating, alloy plating, dispersion / composite plating, CVD, PVD, pyrolysis, and spraying. These methods may be used in combination. The catalyst layer may have a plurality of layers and a plurality of elements, as required. Alternatively, nickel, nickel alloys, and nickel-plated iron or stainless, having no catalyst coating, may be used. As the substrate of the cathode feed conductor 21, nickel, nickel alloys, and nickel-plated iron or stainless may be used.

[0757] As the form, any of a perforated metal, nonwoven fabric, foamed metal, expanded metal, metal porous foil formed by electroforming, so-called woven mesh produced by knitting metal lines, and the like can be used.(Reverse Current Absorbing Layer)

[0758] A material having a redox potential less noble than the redox potential of the element for the catalyst layer of the cathode mentioned above may be selected as a material for the reverse current absorbing layer. Examples thereof include nickel and iron.(Collector)

[0759] The cathode chamber 20 preferably comprises the collector 23. The collector 23 improves current collection efficiency. In the present embodiment, the collector 23 is a porous plate and is preferably arranged in substantially parallel to the surface of the cathode 21.

[0760] The collector 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The collector 23 may be a mixture, alloy, or composite oxide of these metals. The collector 23 may have any form as long as the form enables the function of the collector and may have a plate or net form.(Metal Elastic Body)

[0761] Placing the metal elastic body 22 between the collector 23 and the cathode 21 presses each cathode 21 of the plurality of electrolytic cells 1 connected in series onto the ion exchange membrane 2 to reduce the distance between each anode 11 and each cathode 21. Then, it is possible to lower the voltage to be applied entirely across the plurality of electrolytic cells 1 connected in series. Lowering of the voltage enables the power consumption to be reduced. With the metal elastic body 22 placed, the pressing pressure caused by the metal elastic body 22 enables the electrode for electrolysis to be stably maintained in place when the laminate including the electrode for electrolysis according to the present embodiment is placed in the electrolytic cell.

[0762] As the metal elastic body 22, spring members such as spiral springs and coils and cushioning mats may be used. As the metal elastic body 22, a suitable one may be appropriately employed, in consideration of a stress to press the ion exchange membrane and the like. The metal elastic body 22 may be provided on the surface of the collector 23 on the side of the cathode chamber 20 or may be provided on the surface of the partition wall on the side of the anode chamber 10. Both the chambers are usually partitioned such that the cathode chamber 20 becomes smaller than the anode chamber 10. Thus, from the viewpoint of the strength of the frame and the like, the metal elastic body 22 is preferably provided between the collector 23 and the cathode 21 in the cathode chamber 20. The metal elastic body 23 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium.(Support)

[0763] The cathode chamber 20 preferably comprises the support 24 that electrically connects the collector 23 to the partition wall 30. This can achieve an efficient current flow.

[0764] The support 24 preferably comprises an electrically conductive metal such as nickel, iron, copper, silver, and titanium. The support 24 may have any shape as long as the support can support the collector 23 and may have a rod, plate, or net shape. The support 24 has a plate shape, for example. A plurality of supports 24 are arranged between the partition wall 30 and the collector 23. The plurality of supports 24 are aligned such that the surfaces thereof are in parallel to each other. The supports 24 are arranged substantially perpendicular to the partition wall 30 and the collector 23.(Anode Side Gasket and Cathode Side Gasket)

[0765] The anode side gasket is preferably arranged on the frame surface constituting the anode chamber 10. The cathode side gasket is preferably arranged on the frame surface constituting the cathode chamber 20. Electrolytic cells are connected to each other such that the anode side gasket included in one electrolytic cell and the cathode side gasket of an electrolytic cell adjacent to the cell sandwich the ion exchange membrane 2 (see FIGS. 26 and 27). These gaskets can impart airtightness to connecting points when the plurality of electrolytic cells 1 is connected in series via the ion exchange membrane 2.

[0766] The gaskets form a seal between the ion exchange membrane and electrolytic cells. Specific examples of the gaskets include picture frame-like rubber sheets at the center of which an aperture portion is formed. The gaskets are required to have resistance against corrosive electrolyte solutions or produced gas and be usable for a long period. Thus, in respect of chemical resistance and hardness, vulcanized products and peroxide-crosslinked products of ethylene-propylene-diene rubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) are usually used as the gaskets. Alternatively, gaskets of which region to be in contact with liquid (liquid contact portion) is covered with a fluorine-containing resin such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may be employed as required. These gaskets each may have an aperture portion so as not to inhibit the flow of the electrolyte solution, and the shape of the aperture portion is not particularly limited. For example, a picture frame-like gasket is attached with an adhesive or the like along the peripheral edge of each aperture portion of the anode chamber frame constituting the anode chamber 10 or the cathode chamber frame constituting the cathode chamber 20. Then, for example, in the case where the two electrolytic cells 1 are connected via the ion exchange membrane 2 (see FIG. 27), each electrolytic cell 1 onto which the gasket is attached should be tightened via ion exchange membrane 2. This tightening can prevent the electrolyte solution, alkali metal hydroxide, chlorine gas, hydrogen gas, and the like generated from electrolysis from leaking out of the electrolytic cells 1.(Ion Exchange Membrane)

[0767] The ion exchange membrane 2 is as described in the section of the ion exchange membrane described above.(Water Electrolysis)

[0768] The electrolyzer of the present embodiment, as an electrolyzer in the case of electrolyzing water, has a configuration in which the ion exchange membrane in an electrolyzer for use in the case of electrolyzing common salt mentioned above is replaced by a microporous membrane. The raw material to be supplied, which is water, is different from that for the electrolyzer in the case of electrolyzing common salt mentioned above. As for the other components, components similar to that of the electrolyzer in the case of electrolyzing common salt can be employed also in the electrolyzer in the case of electrolyzing water. Since chlorine gas is generated in the anode chamber in the case of common salt electrolysis, titanium is used as the material of the anode chamber, but in the case of water electrolysis, only oxygen gas is generated in the anode chamber. Thus, a material identical to that of the cathode chamber can be used. An example thereof is nickel. For anode coating, catalyst coating for oxygen generation is suitable. Examples of the catalyst coating include metals, oxides, and hydroxides of the platinum group metals and transition metal group metals. For example, elements such as platinum, iridium, palladium, ruthenium, nickel, cobalt, and iron can be used.(Application of Laminate)

[0769] The laminate of the present embodiment can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing as mentioned above. In other words, the laminate of the present embodiment can be suitably used as a laminate for replacement of a member of an electrolyzer. A laminate to be used in such an application is specifically referred to as a “membrane electrode assembly”.(Package)

[0770] The laminate of the present embodiment is preferably transported or the like while enclosed in a packaging material. That is, the package of the present embodiment comprises the laminate of the present embodiment and a packaging material that packages the laminate. The package of the present embodiment, configured as described above, can prevent adhesion of stain and damage that may occur during transport or the like of the laminate of the present embodiment. When used for member replacement of the electrolyzer, the laminate is particularly preferably transported or the like as the package of the present embodiment. As the packaging material of the present embodiment, which is not particularly limited, known various packaging materials can be employed. Alternatively, the package of the present embodiment can be produced by, for example, a method including packaging the laminate of the present embodiment with a clean packaging material followed by encapsulation or the like, although not limited thereto.Third Embodiment

[0771] Here, a third embodiment of the present invention will be described in detail with reference to FIGS. 43 to 62.[Laminate]

[0772] The laminate of the third embodiment (hereinafter, in the section of <Third embodiment>, simply referred to as “the present embodiment”) has a membrane and an electrode for electrolysis fixed at least one region of the surface of the “membrane” (hereinafter, simply also referred to as a “fixed region”), and the proportion of the region on the surface of the membrane is more than 0% and less than 93%. The laminate of the present embodiment, as configured as described above, can improve the work efficiency during electrode renewing in an electrolyzer and further, can exhibit excellent electrolytic performance also after renewing.

[0773] That is, according to the laminate of the present embodiment, on renewing the electrode, the electrode can be renewed by a work as simple as renewing the membrane, without a complicated work such as stripping off the existing electrode fixed on the electrolytic cell, and thus, the work efficiency is markedly improved.

[0774] Further, according to the laminate of the present embodiment, it is possible to maintain the electrolytic performance of the existing electrolytic cell comparable to those of a new electrode or improve the electrolytic performance. Thus, the electrode fixed on the existing electrolytic cell and serving as an anode and / or a cathode is only required to serve as a feed conductor. Thus, it may be also possible to markedly reduce or eliminate catalyst coating. The feed conductor herein means a degraded electrode (i.e., the existing electrode), an electrode having no catalyst coating, and the like.[Electrode for Electrolysis]

[0775] The electrode for electrolysis in the present embodiment is not particularly limited as long as the electrode is an electrode to be used for electrolysis, and preferably has an area of the surface opposed to the membrane of the electrode for electrolysis (corresponds to an area of the conducting surface S2 mentioned below) of 0.01 m2 or more. The “surface opposed to the membrane” means the surface on which the membrane is located of the surfaces possessed by the electrode for electrolysis. That is, the surface opposed to the membrane in the electrode for electrolysis also can be the surface that abuts on the surface of the membrane. When the area of the surface opposed to the membrane in the electrode for electrolysis is 0.01 m2 or more, sufficient productivity can be achieved, and especially when industrial electrolysis is performed, sufficient productivity tends to be obtained. In this manner, from the viewpoint of achieving sufficient productivity and achieving practicality for a laminate to be used in renewing of the electrolytic cell, the area of the surface opposed to the membrane in the electrode for electrolysis is more preferably 0.1 m2 or more, further preferably 1 m2 or more. The area can be measured by, for example, a method described in Examples.

[0776] The electrode for electrolysis in the present embodiment has a force applied per unit mass-unit area of preferably 1.6 N / (mg·cm2) or less, more preferably less than 1.6 N / (mg·cm2), further preferably less than 1.5 N / (mg·cm2), even further preferably 1.2 N / mg·cm2 or less, still more preferably 1.20 N / mg·cm2 or less from the viewpoint of enabling a good handling property to be provided and having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a feed conductor (a degraded electrode and an electrode having no catalyst coating), and the like. The force applied is even still more preferably 1.1 N / mg·cm2 or less, further still more preferably 1.10 N / mg·cm2 or less, particularly preferably 1.0 N / mg·cm2 or less, especially preferably 1.00 N / mg·cm2 or less.

[0777] From the viewpoint of further improving the electrolytic performance, the force is preferably more than 0.005 N / (mg·cm2), more preferably 0.08 N / (mg·cm2) or more, further preferably 0.1 N / mg·cm2 or more, further more preferably 0.14 N / (mg·cm2) or more. The force is further more preferably 0.2 N / (mg·cm2) or more from the viewpoint of further facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

[0778] The force applied described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, arithmetic average surface roughness, and the like, for example. More specifically, for example, a higher opening ratio tends to lead to a smaller force applied, and a lower opening ratio tends to lead to a larger force applied.

[0779] The mass per unit is preferably 48 mg / cm2 or less, more preferably 30 mg / cm2 or less, further preferably 20 mg / cm2 or less from the viewpoint of enabling a good handling property to be provided, having a good adhesive force to a membrane such as an ion exchange membrane and a microporous membrane, a degraded electrode, a feed conductor having no catalyst coating, and of economy, and furthermore is 15 mg / cm2 or less from the comprehensive viewpoint including handling property, adhesion, and economy. The lower limit value is not particularly limited but is of the order of 1 mg / cm2, for example.

[0780] The mass per unit area described above can be within the range described above by appropriately adjusting an opening ratio described below, thickness of the electrode, and the like, for example. More specifically, for example, when the thickness is constant, a higher opening ratio tends to lead to a smaller mass per unit area, and a lower opening ratio tends to lead to a larger mass per unit area.

[0781] The force applied can be measured by the following method (i) or (ii). The value obtained by the measure...

Examples

example 1

[2206]As a substrate for electrode for cathode electrolysis, an electrolytic nickel foil having a gauge thickness of 16 μm was provided. One surface of this nickel foil was subjected to a roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 0.71 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment.

[2207]A porous foil was formed by perforating this nickel foil with circular holes by punching. The opening ratio was 49%.

[2208]A coating liquid for use in forming an electrode catalyst was prepared by the following procedure. A ruthenium nitrate solution having a ruthenium concentration of 100 g / L (FURUYA METAL Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molar ratio between the ruthenium element and the cerium element was 1:0.25. This mixed solution was...

example 2

[2219]In Example 2, an electrolytic nickel foil having a gauge thickness of 22 μm was used as the substrate for electrode for cathode electrolysis. One surface of this nickel foil was subjected to roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 0.96 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment. The opening ratio was 44%. Except for the above described, evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

[2220]The thickness of the electrode was 29 μm. The thickness of the catalytic layer, which was determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode, was 7 μm. The coating was formed also on the surface not roughened.

[2221]A sufficient adhesive force was obser...

example 3

[2226]In Example 3, an electrolytic nickel foil having a gauge thickness of 30 μm was used as the substrate for electrode for cathode electrolysis. One surface of this nickel foil was subjected to roughening treatment by means of electrolytic nickel plating. The arithmetic average roughness Ra of the roughened surface was 1.38 μm. The measurement of the surface roughness was performed under the same conditions as for the surface roughness measurement of the nickel plate subjected to the blast treatment. The opening ratio was 44%. Except for the above described, evaluation was performed in the same manner as in Example 1, and the results are shown in Table 2.

[2227]The thickness of the electrode was 38 μm. The thickness of the catalytic layer, which was determined by subtracting the thickness of the substrate for electrode for electrolysis from the thickness of the electrode, was 8 μm. The coating was formed also on the surface not roughened.

[2228]A sufficient adhesive force was obser...

Claims

1. A method for producing a new electrolyzer by arranging an electrode for electrolysis or a laminate of the electrode for electrolysis and a new membrane in an existing electrolyzer comprising an anode, a cathode that is opposed to the anode, and a membrane that is arranged between the anode and the cathode,wherein the electrode for electrolysis is provided to have a mass per unit area of 48 mg / cm2 or less and a force applied per unit mass-unit area of 0.08 N / mg·cm2 or more.

2. The method for producing the new electrolyzer according to claim 1, comprising retaining the electrode for electrolysis or the laminate in a wound state.

3. The method for producing the new electrolyzer according to claim 1, comprising releasing the wound state of the electrode for electrolysis or the laminate.

4. The method for producing the new electrolyzer according to claim 3, comprising arranging the electrode for electrolysis or the laminate on a surface of at least one of the anode and the cathode after releasing the wound state of the electrode for electrolysis or the laminate.

5. A method for renewing an existing electrode by using an electrode for electrolysis,wherein the electrode for electrolysis is provided to have a mass per unit area of 48 mg / cm2 or less and a force applied per unit mass-unit area of 0.08 N / mg·cm2 or more.

6. The method for renewing the electrode according to claim 5, comprising retaining the electrode for electrolysis in a wound state.

7. The method for renewing the electrode according to claim 5, comprising releasing the wound state of the electrode for electrolysis.

8. The method for renewing the electrode according to claim 7, comprising arranging the electrode for electrolysis on a surface of the existing electrode after releasing the wound state of the electrode for electrolysis.

Images