Gasket for electrolysis, electrolytic cell, and electrolysis method

Abstract

The purpose of the present invention is to provide a gasket that can prevent crevice corrosion while maintaining a sealing property, which is basic performance for a gasket. The gasket for electrolysis according to the present invention is frame-shaped and has a hollow part on an inner periphery thereof, and moreover: at least one protrusion having a peripherally continuous height of 1 mm or greater is provided on one surface thereof; at least one groove having a peripherally continuous depth of 0.1 mm or greater is provided to the other surface thereof; and L1 / L2≤3 is satisfied, where L1 is the distance from the inner peripheral end to the protrusion provided most on the inner peripheral side, and L2 is the distance from the inner peripheral end to the groove provided most on the inner peripheral side.

Description

Electrolytic gaskets, electrolytic cells, and electrolytic methods

[0001] The present invention relates to an electrolytic gasket, an electrolytic cell, and an electrolytic method.

[0002] As an electrolytic cell, a structure is known in which a cathode chamber frame, to which the cathode is attached, and an anode chamber frame, to which the anode is attached, are tightly sealed together via a diaphragm and a gasket. By tightly sealing the frames and the diaphragm via the gasket, the structure prevents the electrolyte inside the electrolytic cell from leaking to the outside. Various gaskets have been conventionally known to prevent electrolyte leakage (Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 63-216990

[0004] However, conventional gaskets could not adequately prevent the electrolyte from entering the space between the electrolytic frame and the gasket, and there was a risk of corrosion occurring on the flange surface of the electrolytic frame, especially during long-term operation. As the corrosion progressed, there were concerns that the electrolytic frame would become unusable, or that damage to the flange surface could lead to mixing of gases generated at the electrodes or leakage of the internal electrolyte, making safe operation impossible.

[0005] Therefore, the object of the present invention is to provide a gasket that can suppress crevice corrosion while maintaining the basic performance of a gasket, which is sealing performance.

[0006] In other words, the present invention is as follows: [1] An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least one projection with a height of 1 mm or more extending circumferentially is provided on one surface, and at least one groove with a depth of 0.1 mm or more extending circumferentially is provided on the other surface, and when L1 is the distance from the inner circumference side end to the projection provided on the innermost side, and L2 is the distance from the inner circumference side end to the groove provided on the innermost side, the following formula (1) is satisfied: L1 / L2≦3 (1) [2] An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least one groove with a depth of 0.1 mm or more extending circumferentially is provided on the other surface, and when L2 is the distance from the inner circumference side end to the groove provided on the innermost side, in a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the innermost point on the other surface where the surface pressure is 3.0 MPa or more is within the range of L2. [3] An electrolytic gasket according to [1] or [2], wherein the other surface has a plurality of grooves, and in a cross-section in the thickness direction, when the total area of ​​the space in the region enclosed by the inner end of the innermost groove, the outer end of the outermost groove, the other surface, and a line along the shape of the one surface is W, and the total area occupied by the gasket is V, the following equation (2) is satisfied: 1 ≤ V / W ≤ 15 (2) [4] An electrolytic gasket according to any of [1] to [3], wherein it has a core material inside, and when the distance from the inner end of the core material to the inner end of the gasket is L3, the following equation (3) is satisfied: L3 ≤ L1 (3) [5] An electrolytic gasket according to any of [1] to [4], used on the anode side. [6] An electrolytic cell including an electrolytic gasket according to any of [1] to [5]. [7] The electrolytic cell according to [6], wherein the electrolytic gasket is provided between the electrolytic frame and the diaphragm, the electrolytic frame has a flange portion around its periphery where a part of the surface is a flange surface, and the distance L4 from the inner circumferential end of the electrolytic gasket to the inner circumferential end of the flange surface is 5 mm or less. [8] A method for producing hydrogen using the electrolytic cell according to [6].

[0007] The present invention provides a gasket that can suppress crevice corrosion while maintaining sealing performance.

[0008] This is a schematic diagram showing an example of the electrolytic gasket of this embodiment. This is a cross-sectional view taken along the line X-X of an example in Figure 1. This is a cross-sectional view taken along the line X-X of another example in Figure 1. This is a schematic diagram showing an enlarged view of the area near the inner circumference of the thickness cross-section. (A) is a schematic diagram illustrating area W and area V. (B) is the dashed rectangle portion of (A), and is a diagram showing only the portion used to calculate area W and area V from (A). This is a schematic diagram of a part of the outer circumference of an electrolytic cell consisting of the electrolytic gasket, electrolytic frame, and diaphragm of this embodiment. This is a side view showing the entire example of an alkaline water electrolytic cell. This is a diagram showing a cross-section of the zero-gap structure portion inside the electrolytic cell in the dashed rectangle portion of Figure 6. This is a plan view showing an example of an external header type element (electrolytic cell element). This is a diagram showing an overview of an electrolytic apparatus including an alkaline water electrolytic cell. This is a diagram illustrating the gasket of Comparative Example 2. This is a diagram illustrating the gasket of Comparative Example 3. This is a diagram illustrating the liquid filling test of the embodiment.

[0009] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following description and can be implemented in various modifications within the scope of its essence.

[0010] The electrolytic gasket of this embodiment will be explained using the drawings.

[0011] The electrolytic gasket of this embodiment is a frame-shaped electrolytic gasket 7 having a hollow portion 7b on its inner circumference (Figure 1). The electrolytic gasket of this embodiment has at least one projection with a height of 1 mm or more extending circumferentially on one surface, and at least one groove with a depth of 0.1 mm or more extending circumferentially on the other surface, and when the distance from the inner circumference side end to the projection provided on the innermost side is L1, and the distance from the inner circumference side end to the groove provided on the innermost side is L2, the following equation (1) is satisfied: L1 / L2 ≤ 3 (1) In this specification, the side with the hollow portion 7b on the inner circumference may be referred to as the "inner circumference side", and the outside of the gasket may be referred to as the "outer circumference side". Also, the direction perpendicular to the thickness of the gasket, from the inner circumference side to the outer circumference side of the gasket or the reverse direction may be referred to as the width direction of the gasket. Furthermore, the thickness-direction cross-section and thickness cross-section refer to the cross-section obtained by cutting along a line extending from the inner circumference to the outer circumference of the gasket in the thickness direction (for example, the X-X cross-section in Figure 1). Also, widening refers to the expansion in a direction perpendicular to the thickness (especially in the width direction of the gasket) when surface pressure is applied in the thickness direction.

[0012] Furthermore, another electrolytic gasket of this embodiment is a frame-shaped electrolytic gasket having a hollow portion on its inner circumference, wherein at least one groove with a depth of 0.1 mm or more is provided on the other surface, and when the distance from the inner circumference end to the innermost groove is L2, in a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the innermost point on the other surface where the surface pressure is 3.0 MPa or more is located within the range of L2 (i.e., within a distance of L2 from the inner circumference end in the direction toward the outer circumference).

[0013] The electrolytic gasket 7 described above is not limited to a rectangular tube with a square cross-section perpendicular to the thickness direction (i.e., a cross-section parallel to one surface) as shown in Figure 1, but may be a rectangular tube with a polygonal cross-section, a cylinder with a circular cross-section, etc. Also, the hollow portion 7b may be a cavity that penetrates the inside of the gasket 7, and the cross-sectional shape of the hollow portion is not limited to a square as shown in Figure 1, but may be a polygonal shape, a circle, etc. Also, the shape of the cross-section perpendicular to the thickness direction of the electrolytic gasket 7 may be the same throughout its entire thickness or may be different. The direction in which the hollow portion 7b penetrates may be considered the thickness direction. The thickness of the electrolytic gasket 7 is preferably 1.5 to 5.5 mm, more preferably 2.2 to 5.0 mm, and even more preferably 2.4 to 4.7 mm. The width of the electrolytic gasket 7 (i.e., the length in the width direction of the gasket) is preferably 18 to 40 mm, more preferably 23 to 35 mm.

[0014] The electrolytic gasket 7 described above has at least one projection 7c with a height of 1 mm or more that extends circumferentially on one of its surfaces 7e (Figure 2). "Continuing circumferentially" means that the projection 7c continues continuously or discontinuously on the surface. From the viewpoint of uniformity of the seal, it is preferable that the projection 7c continues circumferentially on one of the surfaces of the gasket 7. Figure 2 shows an example in which there are four projections 7c of the same height on one of the surfaces 7e, but the number of projections 7c provided on one of the surfaces 7e is not particularly limited and may be one or more. When multiple projections are provided on one of the surfaces 7e, the heights of each projection may be the same or different. From the viewpoint of ensuring a sufficient amount of rubber for electrolyte sealing, the height of the projection is preferably 1 mm or more, more preferably 1.2 mm or more, and even more preferably 1.3 mm or more. If the height of the projection is lower than 1 mm, there is a growing concern that the crushing and deformation of the projection during gasket compression will be insufficient, and the basic function of the gasket, which is sealing, will not be achieved. Especially during long-term use, the surface pressure on the protrusions tends to decrease due to permanent deformation of the gasket, and the concern about decreased surface pressure increases even further when the height of the protrusions is less than 1 mm. Here, for example, when the electrolytic gasket 7 is provided between the electrolytic frame and the diaphragm, one surface on which the protrusions are provided may be in contact with the diaphragm, and the other surface on which the grooves are provided may be in contact with the electrolytic frame (Figure 5). If the protrusions are too high, there is a concern that the diaphragm, which is not gripped and fixed between the inner circumference end and the innermost protrusion (i.e., between L1), may be damaged by vibration or tension due to fluctuations in liquid flow or differential pressure between electrode chambers. Therefore, from the viewpoint of protecting the diaphragm, the height of the protrusions is preferably 3.0 mm or less, and more preferably 2.0 mm or less. The height of the protrusions refers to the distance in the thickness direction from one surface 7e to a point on the surface of the protrusion 7c, and may be the longest distance (i.e., the distance to the highest point). The height of the projection 7c may be the same around the circumference or may differ, but the total height around the circumference must be 1 mm or more.

[0015] The electrolytic gasket 7 described above has at least one groove 7d with a depth of 0.1 mm or more that extends circumferentially on the other surface 7f (Figure 2). "Continuing circumferentially" means that the groove 7d continues continuously or discontinuously on the surface. From the viewpoint of uniformity of the seal, it is preferable that the groove 7d continues circumferentially on the other surface of the gasket 7. Figure 2 shows an example in which there are three grooves 7d of the same depth on the other surface 7f, but the number of grooves 7d provided on the other surface 7f is not particularly limited and may be one or more. When multiple grooves are provided on the other surface 7f, the depths of each groove may be the same or different. From the viewpoint of suppressing widening, the depth of the groove is preferably 0.1 mm or more, more preferably 0.3 mm or more, and even more preferably 0.5 mm or more. Also, from the viewpoint of preventing corrosion in the gap between the electrolytic frame and the gasket, it is preferably 1.5 mm or less, and more preferably 1.0 mm or less. The groove depth refers to the distance in the thickness direction from the other surface 7f to a point on the surface of groove 7d, and may be the longest distance (i.e., the distance to the deepest point). If there are no flat parts on one surface or the other surface, the inner circumference edge of one surface and the inner circumference edge of the other surface may be used as the reference for the height of the protrusion and the depth of the groove. The depth of the groove 7d may be the same or different around the entire circumference, but it must be 0.1 mm or more around the entire circumference. If the depth is less than 0.1 mm, the groove will be filled when the gasket is compressed, and the gasket will expand in the width direction, causing it to widen even further. If the widening progresses significantly, there is a growing concern that the diaphragm in contact with the gasket may be damaged, potentially compromising the safety of the device.

[0016] The electrolytic gasket 7 described above may have small protrusions less than 1 mm in height, protrusions that are not continuous around the circumference, small grooves less than 0.1 mm in depth, or grooves that are not continuous around the circumference on one surface 7e or the other surface 7f.

[0017] In the cross-sectional view of the electrolytic gasket 7 in the thickness direction (Figures 2 and 3), L1 is defined as the distance from the inner circumference end 7a to a projection of 1 mm or more in height that extends circumferentially on one of the innermost surfaces 7e (Figures 2 and 3). From the viewpoint of suppressing damage to the diaphragm, which is not gripped or fixed on the inner circumference, due to vibration or tension caused by fluctuations in liquid flow or differential pressure between electrode chambers, L1 is preferably 18 mm or less, more preferably 12 mm or less, and even more preferably 6 mm or less. Furthermore, from the viewpoint of the ease of the process of molding the gasket with a core material for suppressing widening inside, the lower limit of L1 is preferably greater than 0 mm, more preferably 1 mm or more, and even more preferably 1.5 mm or more. Here, "to the projection" in L1 may mean to the point where the height of the projection is highest. Also, L1 may be the distance along a straight line parallel to one of the surfaces 7e. In the electrolytic gasket of this embodiment, it is preferable that the L1 / L2, L1, L2, L3 (described later), L4 (described later), the position of the innermost point on the other surface where the surface pressure is 3.0 MPa or more, and V / W (described later) satisfy a suitable range in the thickness cross section of the entire frame of the electrolytic gasket. Here, if the cross section perpendicular to the thickness direction of the electrolytic gasket has a shape with corners (for example, a polygonal shape such as a square), it is preferable that the thickness cross section of the entire frame excluding the corners satisfies the suitable range, and it is more preferable that the thickness cross section of the entire frame satisfies the suitable range. Furthermore, if the cross section perpendicular to the thickness direction of the electrolytic gasket does not have a shape with corners (for example, a circular shape), it is preferable that the thickness cross section of the entire frame satisfies the suitable range.

[0018] In the cross-sectional view of the electrolytic gasket 7 in the thickness direction (Figures 2 and 3), L2 is defined as the distance from the inner circumference end 7a to a groove with a depth of 0.1 mm or more that extends circumferentially to the other surface 7f located on the innermost circumference (Figures 2 and 3). From the viewpoint of ensuring sealing performance on the inner circumference side of any gaps into which liquid can penetrate, L2 is preferably 0 to 10 mm, more preferably 1 to 8 mm, and even more preferably 2 to 6 mm. Here, "to the groove" in L2 may mean the point from the other surface where the depth begins to change. Also, L2 may be defined as the distance along a straight line parallel to the other surface 7f.

[0019] The electrolytic gasket 7 described above preferably satisfies the following formula (1), more preferably satisfies formula (1'), and even more preferably satisfies formula (1''), from the viewpoint of suppressing corrosion in the gap between the gasket and the electrolytic frame and suppressing widening. By satisfying the above formulas, the surface pressure on the inner circumference side becomes higher than that of the innermost groove on the other surface side, thereby suppressing the intrusion of electrolyte between the gasket and the electrolytic frame and suppressing corrosion. In addition, the presence of a groove on the other surface side can suppress widening. L1 / L2≦3 (1) L1 / L2≦1 (1') L1 / L2≦0.5 (1'')

[0020] Preferably, the electrolytic gasket 7 described above has a plurality of grooves 7d with a depth of 0.1 mm or more that extend circumferentially on the other surface 7f.

[0021] Areas W and V will now be explained. In the thickness-direction cross-section, let R be the region enclosed by the inner circumferential end of the groove located on the innermost circumference, the outer circumferential end of the groove located on the outermost circumference, the other surface 7f, and a line following the shape of the one surface 7e (i.e., the region enclosed by the dotted line in Figure 4(B)). Here, the inner circumferential end of the groove and the outer circumferential end of the groove may be defined as a straight line parallel to the thickness direction that passes through the point where the depth of groove 7d begins to change from the other surface 7f (Figures 4(A) and 4(B)). Area W is the sum of the areas of the empty space within region R (for example, the total area of ​​the white portion within region R enclosed by the dotted line in Figure 4(B), and the total area of ​​the empty space of the groove). Area V is the sum of the areas occupied by the gasket within region R (for example, the total area of ​​the shaded portion within region R enclosed by the dotted line in Figure 4(B)). In other words, the sum of area W and area V is the area of ​​region R. The electrolytic gasket 7 described above is preferably satisfied with the following equation (2), more preferably with equation (2'), and even more preferably with equation (2''), from the viewpoint of having superior sealing performance, further suppressing widening, and not creating gaps between the electrolytic frame and the gasket that could become points of corrosion. 1 ≤ V / W ≤ 15 (2) 2 ≤ V / W ≤ 14 (2') 4 ≤ V / W ≤ 12 (2'')

[0022] The electrolytic gasket 7 described above preferably has a core material 7g inside from the viewpoint of suppressing widening. The core material 7g is preferably provided continuously around the circumference of the gasket 7. The core material 7g is preferably provided substantially parallel to one surface 7e and / or the other surface 7f. The core material 7g may be provided from the outer peripheral end to the inner peripheral end in the thickness direction cross section, or it may be provided in a part between the outer peripheral end and the inner peripheral end (Figure 3). The core material 7g may be one or multiple (for example, having multiple core materials in the thickness direction, having multiple core materials intermittently in the direction from the outer peripheral to the inner peripheral, etc.).

[0023] From the viewpoint of achieving superior sealing performance and further suppressing widening, when the distance L3 is from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket, the electrolytic gasket 7 preferably satisfies the following equation (3), more preferably satisfies equation (3'), and even more preferably satisfies equation (3''): L3 ≤ L1 (3) L3 ≤ 0.85 × L1 (3') L3 ≤ 0.7 × L1 (3'')

[0024] The electrolytic gasket 7 described above has superior sealing properties and prevents the electrolyte from entering gaps between the electrolytic frame and the gasket, which can become points of corrosion. From the viewpoint of suppressing crevice corrosion, in a gasket compression test in which the electrolytic gasket 7 is compressed with an average surface pressure of 2 MPa, it is preferable that the innermost point on the other surface 7f with a surface pressure of 3.0 MPa or more is located within the range L2 from the inner circumferential edge 7a, more preferably within the range of 0.85 × L2 from the inner circumferential edge 7a, and even more preferably within the range of 0.7 × L2 from the inner circumferential edge 7a. Note that the gasket compression test refers to the test method described in the examples below.

[0025] The electrolytic gasket of this embodiment can be used as part of the outer frame of the electrolytic cell, and can be placed between the electrolytic frame and the diaphragm of the electrolytic cell. In particular, it is preferable that the electrolytic gasket of this embodiment be used as the anode-side gasket. Here, the anode side refers to the electrode chamber on the anode side of the electrode chamber 5 defined by the partition wall 1, the outer frame 3 or flange portion 8, the diaphragm 4, and the gasket 7, as described later.

[0026] The electrolytic cell of this embodiment includes the electrolytic gasket of this embodiment described above. The electrolytic cell is preferably an alkaline water electrolytic cell. In the electrolytic cell, the electrolytic gasket 7 is preferably provided between the electrolytic frame having a flange portion 8 whose surface is a flange surface and the diaphragm 4. The electrolytic gasket 7 provided in the electrolytic cell may be the electrolytic gasket of this embodiment alone, or it may be combined with other electrolytic gaskets. The example in Figure 5 shows an example in which the electrolytic gasket of this embodiment is provided in the center of three electrolytic gaskets 7, and other electrolytic gaskets of any shape are provided in the other two. In the electrolytic gasket of this embodiment, it is more preferable that the flange surface 81 of the flange portion 8 of the electrolytic frame and the other surface 7f of the electrolytic gasket 7 are arranged facing each other adjacently, and that the diaphragm 4 and one surface 7e of the electrolytic gasket 7 are arranged facing each other adjacently (Figure 5). Here, the electrolytic frame in Figure 5 consists of a flange portion 8 and a partition wall 1. From the viewpoint of suppressing the widening of the gasket, it is preferable that the flange surface 81 on which the electrolytic gasket 7 is provided is flat, and that a gap exists between the electrolytic gasket 7 and the flange surface 81 in an uncompressed state.

[0027] The distance L4 from the inner circumferential end 7a of the electrolytic gasket 7 to the inner circumferential end of the flange surface 81 of the flange portion 8 is preferably 5 mm or less, and more preferably 4 mm or less, from the viewpoint of further suppressing damage to the diaphragm. In particular, it is preferable to satisfy the above L4 in a structure in which the electrolytic frame gasket 7 and the flange surface 81 of the flange portion 8 of the electrolytic frame are in contact (Figure 5). The above L4 can be adjusted, for example, by changing the dimensions of the gasket, the dimensions of the electrolytic frame, etc.

[0028] The width of the electrolytic gasket 7 described above is preferably 50 to 150%, more preferably 70 to 130%, and even more preferably 80 to 120%, of 100% of the length of the flange surface 81 of the flange portion 8, in order to uniformly press the electrolytic frames together. Here, the length of the flange surface may be the length in the direction from the inner circumference to the outer circumference.

[0029] The electrolytic gasket 7 described above is not particularly limited, and a known insulating rubber material or resin material can be selected, and it is preferable that it contains a rubber material. From the viewpoint of preventing the rubber material of the gasket from being exposed to the electrolyte and altering or deteriorating, it is preferable that the gasket contains a fluororesin, for example, the gasket may be coated with a fluororesin. On the other hand, from the viewpoint of the moldability of the gasket, it is preferable that it does not contain a fluororesin, and whether or not to include a fluororesin can be selected depending on the purpose. In particular, from the viewpoint of suppressing gasket rupture in the electrolytic cell (especially rupture of the gasket on the anode chamber side in an alkaline water electrolytic cell), it is preferable that the fluororesin sheet covers the surface of the gasket but does not have a structure in which it is woven into the inside of the gasket. Furthermore, from the viewpoint of sealing performance between the gasket and the flange surface, it is preferable that the surface of the other surface 7f does not have a structure in which it is covered with a fluororesin sheet.

[0030] Examples of the above-mentioned rubber materials include natural rubber, isoprene rubber, styrene-butadiene rubber, butyl rubber, butadiene rubber, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), tetrafluoroethylene-propylene rubber (FEPM), chloroprene rubber, silicone rubber, fluororubber (FKM), porous PTFE (polytetrafluoroethylene), perfluoroelastomer (FFKM), acrylic rubber, acrylonitrile / butadiene rubber, chlorosulfonated polyethylene rubber, urethane rubber, polysulfurized rubber, epichlorohydrin rubber, ethylene / acrylic rubber, isobutylene-isoprene rubber, chlorosulfonated polyethylene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, polyphenylene sulfide, polyethylene, polyimide, polyacetal, and crosslinked products thereof. Among these, ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), or crosslinked versions thereof are preferred from the viewpoint of chemical resistance and hardness. Furthermore, ethylene-propylene-diene rubber (EPDM) and fluororubber (FKM) are preferred from the viewpoint of elastic modulus and alkali resistance. Depending on the type of material, known crosslinking methods such as sulfur vulcanization and peroxide crosslinking can be used, and peroxide crosslinking is preferred. The above rubber materials can be used individually or in combination of multiple types.

[0031] The electrolytic gasket 7 described above may have a portion of its surface covered with a coating layer. The coating layer preferably contains a fluororesin, but may consist only of a fluororesin. It may also not contain a fluororesin. The fluororesin can be any one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and polyvinyl fluoride, among which PTFE and PFA are preferred from the viewpoint of corrosion resistance. The fluororesin can be used individually or in combination of multiple types.

[0032] The coating layer is preferably provided on at least a portion of the surface including the surface where the gasket 7 and the flange portion 8 of the electrolytic frame are in contact, and the portion where the gasket 7 and the diaphragm 4 are in contact (Figure 5), and more preferably on at least a portion of only the surface including the portion where the gasket 7 and the diaphragm 4 are in contact.

[0033] From the viewpoint of maintaining excellent sealing performance and obtaining corrosion resistance, the thickness of the coating layer is preferably 300 μm or less.

[0034] As the core material, known materials such as polyvinylidene fluoride (PVDF) and polyethylene terephthalate (PET) can be used. In particular, the core material preferably contains PET. The mass ratio of PET to 100% by mass of the core material is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. By including PET, the sealing performance is improved, the width can be suppressed, and the degree of expansion and contraction can be increased, making it easier to install in the electrolytic cell.

[0035] The electrolytic cell of this embodiment will be described below using an alkaline water electrolytic cell as an example.

[0036] (Alkaline Water Electrolyzer) Fig. 6 shows a side view of an entire example of an alkaline water electrolyzer. Fig. 7 shows a diagram of a zero-gap structure of an example of an alkaline water electrolyzer (a cross-sectional view of the portion within the dashed square frame shown in Fig. 6). Hereinafter, the alkaline water electrolyzer may sometimes be simply referred to as an electrolyzer. As shown in Figs. 6 and 7, the electrolyzer 50 is preferably an electrolyzer (preferably a bipolar electrolyzer) in which a plurality of elements 60 including an anode 2a, a cathode 2c, a partition wall 1 that separates the anode 2a and the cathode 2c, and an outer frame 3 that encloses the partition wall 1 are stacked with a diaphragm 4 and a gasket 7 interposed therebetween. The element 60 is the above-mentioned electrolyzer element.

[0037] Also, in the electrolyzer 50, the diaphragm 4 may be in contact with the anode 2a and the cathode 2c to form a zero-gap structure Z (see Fig. 7).

[0038] The above electrolyzer may be either monopolar or bipolar. The monopolar type is a method of directly connecting one or more elements to a power source, in which a cathode terminal element is provided with a diaphragm sandwiched between the anodes of each element arranged in parallel, and an anode terminal element is provided with a diaphragm sandwiched between the cathodes, and it is a parallel circuit that connects a power source to each terminal element. The bipolar type is one of the methods of connecting a large number of bipolar elements to a power source, in which a plurality of bipolar elements with one side being the anode and the other side being the cathode are arranged in the same direction and connected in series, and only both ends are connected to the power source. The bipolar electrolyzer has the characteristic that it can reduce the current of the power source, and it can produce a large amount of compounds or predetermined substances, etc. in a short time by electrolysis. If the output of the power supply equipment is the same, a constant current and high voltage are cheaper and more compact, so industrially, the bipolar type is more preferable than the monopolar type.

[0039] (Element) Examples of the above-mentioned elements include elements used in unipolar electrolytic cells and bipolar elements used in bipolar electrolytic cells. A bipolar element 60 used in an example of a bipolar electrolytic cell 50 for alkaline water electrolysis includes a partition wall 1 that separates the anode 2a and the cathode 2c, and an outer frame 3 that surrounds the partition wall 1, as shown in Figure 7. More specifically, the partition wall 1 is conductive, and the outer frame 3 is provided to surround the partition wall 1 along its outer edge. The upper part including the outer frame 3 may be a flange portion 8. The above-mentioned element includes an anode 2a, a cathode current collector 2r, a conductive elastic body 2e, and a cathode 2c in this order, and may also include a partition wall 1, ribs 6, outer frame 3, flange portion 8, reverse current absorber, anode current collector, etc.

[0040] As shown in Figure 6, the electrolytic cell 50 is constructed by stacking the required number of elements 60. In the example shown in Figure 6, the electrolytic cell 50 is arranged with a fast head 51g, an insulating plate 51i, and an anode terminal element 51a in that order from one end, and then the anode-side gasket portion, diaphragm 4, cathode-side gasket portion, and element 60 are arranged in that order. At this time, the element 60 is positioned so that the cathode 2c faces the anode terminal element 51a. The anode gasket to element 60 is repeated as many times as required for the design production volume. After the required number of times the anode gasket to element 60 has been repeated, the anode-side gasket portion, diaphragm 4, and cathode-side gasket portion are arranged again, and finally the cathode terminal element 51c, insulating plate 51i, and loose head 51g are arranged in that order. The electrolytic cell 50 is assembled into a single unit by tightening the entire assembly with a tie rod 51r. The arrangement of components in the electrolytic cell 50 can be arbitrarily selected from either the anode side or the cathode side, and is not limited to the order described above.

[0041] As shown in Figure 6, in the electrolytic cell 50, element 60 is positioned between the anode terminal element 51a and the cathode terminal element 51c, and the diaphragm 4 is positioned between the anode terminal element 51a and element 60, between adjacent elements 60, and between element 60 and the cathode terminal element 51c.

[0042] In the electrolytic cell 50, as shown in FIG. 7, the diaphragm 4 contacts the anode 2a and the cathode 2c, and a zero-gap structure Z is formed. In particular, in the electrolytic cell 50, the portion between the adjacent two elements 60 in the mutual partition wall 1, and the portion between the adjacent element 60 and the terminal element in the mutual partition wall 1 are referred to as an electrolytic cell 65. The electrolytic cell 65 includes the diaphragm 4, the partition wall 1 of one element, the anode chamber 5a, and the anode 2a, as well as the cathode 2c, the cathode chamber 5c, and the partition wall 1 of the other element.

[0043] In alkaline water electrolysis, when there is a gap between the diaphragm 4 and the anode 2a or the cathode 2c, a large amount of bubbles generated by electrolysis in addition to the electrolytic solution will stay in this part, resulting in a very high electrical resistance. In order to significantly reduce the electrolysis voltage in the electrolytic cell 65, it is effective to make the distance between the anode 2a and the cathode 2c (hereinafter also referred to as the "inter-electrode distance") as small as possible to eliminate the influence of the electrolytic solution and bubbles existing between the anode 2a and the cathode 2c.

[0044] Therefore, a zero-gap structure is adopted that can maintain a state in which the anode 2a and the diaphragm 4 are in contact with each other over the entire electrode surface, and the cathode 2c and the diaphragm 4 are in contact with each other, or a state in which the inter-electrode distance is substantially the same as the thickness of the diaphragm 4 over the entire electrode surface, and there is almost no gap between the anode 2a and the diaphragm 4 and between the cathode 2c and the diaphragm 4.

[0045] Further, in the electrolytic cell 50, as shown in FIGS. 7 to 8, the electrode chamber 5 through which the electrolytic solution passes is defined by the partition wall 1, the outer frame 3 or the flange portion 8, the gasket 7, and the diaphragm 4. Here, the outer frame 3 may be the flange portion 8.

[0046] More specifically, the electrode chamber 5 has an electrolyte inlet 5i for introducing electrolyte into the electrode chamber 5 and an electrolyte outlet 5o for discharging electrolyte from the electrode chamber 5 at the boundary with the outer frame 3. More specifically, the anode chamber 5a is provided with an anode electrolyte inlet for introducing electrolyte into the anode chamber and an anode electrolyte outlet for discharging electrolyte discharged from the anode chamber 5a, and the cathode chamber 5c is provided with a cathode electrolyte inlet for introducing electrolyte into the cathode chamber 5c and a cathode electrolyte outlet for discharging electrolyte discharged from the cathode chamber 5c.

[0047] In the examples shown in Figures 6 to 8, the rectangular partition wall 1 and the rectangular membrane 4 are arranged in parallel, and the inner surface of the rectangular parallelepiped outer frame 3 provided at the edge of the partition wall 1 is perpendicular to the partition wall 1, so the shape of the electrode chamber 5 is a rectangular parallelepiped.

[0048] The electrolytic cell 50 is typically fitted with header pipes, which are tubes for distributing or collecting electrolyte. The lower part of the outer frame 3 at the edge of the partition wall 1 is equipped with an anode inlet header 10ai for supplying electrolyte to the anode chamber 5a and a cathode inlet header 10ci for supplying electrolyte to the cathode chamber 5c. Similarly, the upper part of the outer frame 3 at the edge of the partition wall 1 is equipped with an anode outlet header 10ao for discharging electrode solution from the anode chamber 5a and a cathode outlet header 10co for discharging electrolyte from the cathode chamber 5c. As shown in Figures 6 and 7, there are typically two types of header pipe arrangements for the electrolytic cell 50: an internal header type and an external header type, and either type may be used.

[0049] In the electrolytic cell 50, it is preferable that the electrolyte distributed by the anode inlet header 10ai is introduced into the anode chamber 5a through the anode electrolyte inlet, passes through the anode chamber 5a, is discharged from the anode chamber 5a through the anode electrolyte outlet, and is collected by the anode outlet header 10ao.

[0050] The following provides a detailed explanation of the components of the electrolytic cell and electrolytic cell used for alkaline water electrolysis.

[0051] - Partition Wall - The partition wall 1 is located between the cathode 2c and the anode 2a, and is preferably provided between the anode 2a and the cathode current collector 2r and / or between the cathode 2c and the anode current collector 2r. The shape of the partition wall may be a plate-like shape with a predetermined thickness, but is not particularly limited. The planar shape of the partition wall is not particularly limited and may be rectangular (square, rectangle, etc.) or circular (circle, ellipse, etc.), where the rectangle may have rounded corners. In one embodiment, the partition wall and the outer frame may be integrated by welding or other methods. For example, the partition wall may be provided with flange portions (anode flange portion protruding towards the anode side, cathode flange portion protruding towards the cathode side) that extend in a direction perpendicular to the plane of the partition wall, and the flange portions may be part of the outer frame.

[0052] The size of the partition wall is not particularly limited and may be designed appropriately according to the size of the electrode chamber. The thickness of the partition wall does not need to be increased if the anode rib and cathode rib are joined to the partition wall by welding or other means to form a single integrated structure, as the anode rib and cathode rib provide reinforcement. A thickness of 0.5 to 2 mm is usually sufficient.

[0053] As for the partition wall material, a material with high conductivity is preferred from the viewpoint of achieving a uniform power supply, and from the viewpoint of alkali resistance and heat resistance, nickel, nickel alloys, mild steel, and nickel alloys with nickel plating are preferred.

[0054] Here, the flange portion 8 is a portion having a flange surface that is in direct contact with an adjacent electrolytic cell element, or in contact with an adjacent electrolytic cell element via a gasket 7. For example, when the outer wall of the liquid collection tube is in contact with the outer wall of the liquid collection tube of an adjacent electrolytic cell element via a gasket 7, the liquid collection tube is also a flange portion, and the surface of the outer wall of the liquid collection tube facing the outer wall of the liquid collection tube of the adjacent electrolytic cell element is also a flange surface 81. Also, when the flange portion 8 provided at the top of the liquid collection tube is in contact with the flange portion 8 of an adjacent electrolytic cell element via a gasket 7, the surface of the outer wall of the flange portion facing the adjacent electrolytic cell element is a flange surface 81. Furthermore, when the outer wall of the liquid collection tube and the flange portion 8 provided on the upper part of the liquid collection tube are in contact with the outer wall of the liquid collection tube and the flange portion 8 provided on the upper part of the liquid collection tube of an adjacent electrolytic cell element via a gasket 7, the liquid collection tube and the flange portion are the flange portion, and the surface of the outer wall of the liquid collection tube facing the outer wall of the liquid collection tube of the adjacent electrolytic cell element and the surface of the outer wall of the flange portion facing the adjacent electrolytic cell element are the flange surface 81. The flange surface 81 may be the surface of a structure whose surface is located at the longest position in the direction perpendicular to the partition wall 1, starting from the partition wall 1 that separates the anode chamber 5a and the cathode chamber 5b. For example, if the flange portion 8 is located at the furthest position in the direction perpendicular to the partition wall 1, then the surface of the flange portion 8 may be the flange surface 81. If the anode liquid collection tube 20ao, the cathode liquid collection tube 20co, and the flange portion 8 have the surfaces furthest away in a direction perpendicular to the partition wall 1, then the surfaces of the anode liquid collection tube 20ao, the cathode liquid collection tube 20co, and the flange portion 8 may be designated as the flange surface 81.

[0055] -Electrodes- The size of electrode 2 is not particularly limited and may be determined according to the size of the electrode chamber.

[0056] In order to increase the surface area used for the electrolysis of water and to efficiently remove gases generated by the electrolysis of water from the electrode surface, it is preferable that at least one of the anode and cathode be a porous material, and more preferably that both the anode and cathode be porous materials. In particular, in the case of a zero-gap electrolytic cell, it is necessary to degas the gas generated from the back side of the contact surface with the diaphragm, so it is preferable that the surface of the electrode opposite to the surface in contact with the membrane is a through-hole.

[0057] Examples of porous materials include plain weave mesh, perforated metal, expanded metal, and metal foam.

[0058] When using perforated metal, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, it is preferable that the hole diameter be 2 mm or more and 8 mm or less, the pitch be 2 mm or more and 10 mm or less, the opening ratio be 20% or more and 80% or less, and the thickness be 0.5 mm or more and 2 mm or less.

[0059] When using expanded metal, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, it is preferable that the distance between centers in the short direction of the mesh (SW) is 2 mm or more and 5 mm or less, the distance between centers in the long direction of the mesh (LW) is 3 mm or more and 10 mm or less, the thickness is 0.5 mm or more and 2 mm or less, and the opening ratio is 20% or more and 80% or less.

[0060] When using metal foam, there are no particular restrictions on dimensions, but in order to achieve both an increase in gas generation due to an increase in electrolytic surface area and efficient removal of gas generated by electrolysis from the electrode surface, and from the viewpoint of mechanical strength, a porosity of 80% to 95% and a thickness of 0.5 mm to 2.0 mm are preferable.

[0061] The base material is not particularly limited, but mild steel, stainless steel, nickel, nickel-based alloys, etc. are preferred due to their resistance to the operating environment.

[0062] The electrode may be the substrate itself, but it is preferable that the substrate has a catalyst layer with high reaction activity on its surface.

[0063] The catalyst layer of the anode 2a is preferably formed from a material with high oxygen-evolving ability and good durability. Examples of such materials include nickel or cobalt, iron or platinum group elements. These can form the catalyst layer as elemental metals, compounds such as oxides, composite oxides or alloys composed of multiple metal elements, or mixtures thereof. The form of the catalyst layer is not particularly limited; for example, it may have pores containing metal crystals. Examples of materials that can achieve the desired catalytic activity and durability include elemental metals such as palladium, iridium, platinum, gold, ruthenium, rhodium, cerium, nickel, cobalt, tungsten, iron, molybdenum, silver, copper, zirconium, titanium, hafnium, and lanthanides, as well as nickel plating, alloy plating of nickel and cobalt, nickel and iron, and LaNiO2. ３ LaCoO ３ NiCo ２ O ４ Examples include composite oxides containing nickel and cobalt, composite oxides or alloys composed of multiple metal elements, or mixtures thereof, compounds of platinum group elements such as iridium oxide, and carbon materials such as graphene. To achieve high catalytic activity and durability, multiple catalyst layers formed from the above materials may be stacked, or multiple materials may be mixed within the catalyst layer. Furthermore, organic materials such as polymer materials may be included in the material to improve durability and adhesion to the substrate.

[0064] The catalyst layer of the cathode 2c is preferably formed from a material with high hydrogen generation capacity. Examples of such materials include nickel or cobalt, iron, or platinum group elements. These can form the catalyst layer as elemental metals, compounds such as oxides, composite oxides or alloys composed of multiple metal elements, or mixtures thereof. The form of the catalyst layer is not particularly limited; for example, it may have pores containing metal crystals. Materials that can achieve the desired catalytic activity and durability include, for example, Raney alloys consisting of a combination of multiple materials such as Raney nickel, nickel and aluminum, or nickel and tin; porous coatings made by plasma spraying using nickel compounds or cobalt compounds as raw materials; alloys or composite compounds of nickel and elements selected from cobalt, iron, molybdenum, silver, copper, etc.; platinum group metals or oxides of platinum or ruthenium, which have high hydrogen generation capacity; mixtures of these platinum group metals or oxides with compounds of other platinum group elements such as iridium and palladium, or compounds of rare earth metals such as lanthanum or cerium; and carbon materials such as graphene. To achieve high catalytic activity and durability, multiple catalyst layers formed from the above materials may be laminated, or multiple materials may be mixed within the catalyst layer. Furthermore, organic materials such as polymer materials may be included in the material to improve durability and adhesion to the substrate.

[0065] The electrolysis voltage largely depends on the performance of electrode 2. By reducing the electrolysis voltage, energy consumption can be reduced in an alkaline water electrolysis system. The electrolysis voltage includes not only the voltage theoretically required for the electrolysis of water, but also the overpotential of the anodic reaction (oxygen generation), the overpotential of the cathode reaction (hydrogen generation), and the voltage due to the distance between electrodes 2a and 2c. Here, overpotential refers to the voltage that needs to be applied in excess, exceeding the theoretical decomposition potential, when a certain current is flowing. By lowering the overpotential, the electrolysis voltage can be reduced.

[0066] Preferably, electrode 2 has properties such as high conductivity, high oxygen generation capacity or hydrogen generation capacity, and high wettability of the electrolyte on the electrode 2 surface. By having such properties, the above-mentioned overvoltage can be reduced. Furthermore, it is preferable that electrode 2 has properties that make it resistant to corrosion of the substrate and catalyst layer, detachment of the catalyst layer, dissolution into the electrolyte, and adhesion of contents to the diaphragm 4, even when unstable power such as renewable energy is supplied.

[0067] -Outer Frame- The shape of the outer frame 3 in the electrolytic cell for alkaline water electrolysis is not particularly limited as long as it can frame the partition wall 1, but it may be a shape that has an inner surface along a direction perpendicular to the plane of the partition wall 1 extending over the outer edge of the partition wall 1. The shape of the outer frame is not particularly limited and may be appropriately determined according to the plan view shape of the partition wall. The dimensions of the outer frame are not particularly limited and may be designed according to the outer dimensions of the electrode chamber. In one embodiment, the partition wall and the outer frame may be integrated by welding or other methods, for example, the partition wall may be provided with flange portions that protrude in a direction perpendicular to the plane of the partition wall (anode flange portion protruding towards the anode side, cathode flange portion protruding towards the cathode side), and the flange portions may be part of the outer frame.

[0068] For the outer frame material, conductive materials are preferred, and from the standpoint of alkali resistance and heat resistance, nickel, nickel alloys, mild steel, and nickel alloys with nickel plating are preferred.

[0069] - Diaphragm - The diaphragm 4 used in the electrolytic cell 65 for alkaline water electrolysis is not particularly limited as long as it is a membrane that can conduct ions while separating the generated hydrogen gas and oxygen gas. Examples include ion exchange membranes with ion exchange capacity and porous membranes that can permeate the electrolyte. The diaphragm 4 preferably has low gas permeability, high ionic conductivity, low electron conductivity, and high strength.

[0070] --Porous Membrane-- A porous membrane has multiple fine through-pores, allowing the electrolyte to permeate through the membrane. Since ion conduction occurs when the electrolyte penetrates the porous membrane, controlling the porous structure, such as pore size, porosity, and hydrophilicity, is extremely important. On the other hand, it is also required that the membrane not allow generated gases to pass through, i.e., that it has gas barrier properties. From this perspective as well, controlling the porous structure is important.

[0071] Porous membranes have multiple fine through-pores and include polymer porous membranes, inorganic porous membranes, woven fabrics, and nonwoven fabrics. These can be manufactured using known techniques. Examples of methods for manufacturing polymer porous membranes include phase conversion (microphase separation), extraction, stretching, and wet gel stretching.

[0072] ---Polymer Materials--- Examples of polymer materials include polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene fluoride, polycarbonate, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, polytetrafluoroethylene, perfluorosulfonic acid, perfluorocarboxylic acid, polyethylene, polypropylene, polyphenylene sulfide, polyparaphenylenebenzobisoxazole, polyketone, polyimide, and polyetherimide. Among these, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, and polytetrafluoroethylene are preferred, and polysulfone is more preferred. These may be used individually or in combination of two or more.

[0073] Since porous membranes exhibit ionic conductivity through the permeation of electrolytes, it is preferable that the porous structure, including pore size, porosity, and hydrophilicity, is appropriately controlled. By appropriately controlling the porous structure in a porous membrane, it is possible not only to allow the electrolyte to permeate but also to enhance the barrier against generated gases.

[0074] In order to obtain appropriate membrane properties such as separation ability and strength, it is preferable to control the pore size of the porous membrane. Furthermore, when used in alkaline water electrolysis, it is preferable to control the pore size of the porous membrane from the viewpoint of preventing the mixing of oxygen gas generated from the anode and hydrogen gas generated from the cathode, and from reducing voltage loss during electrolysis. The larger the average pore size of the porous membrane, the greater the amount of permeability per unit area, and in particular, in electrolysis, the ion permeability of the porous membrane tends to be good, making it easier to reduce voltage loss. Also, the larger the average pore size of the porous membrane, the smaller the contact surface area with alkaline water, so the degradation of the polymer tends to be suppressed. On the other hand, the smaller the average pore size of the porous membrane, the higher the separation accuracy of the porous membrane, and in electrolysis, the gas barrier properties of the porous membrane tend to be good. Furthermore, when hydrophilic inorganic particles with small particle sizes, as described later, are supported on the porous membrane, they can be firmly held without falling out. This allows the high retention capacity of the hydrophilic inorganic particles to be imparted, and this effect can be maintained over a long period of time.

[0075] From this viewpoint, in the porous membrane described above, the average pore size is preferably in the range of 0.1 to 1.0 μm. If the pore size is within this range, the porous membrane can achieve both excellent gas barrier properties and high ion permeability. Furthermore, it is preferable that the pore size of the porous membrane be controlled in the temperature range in which it is actually used. Therefore, for example, when used as a diaphragm 4 in an environment of 90°C, it is preferable that the above range of pore size is satisfied at 90°C. Moreover, as a diaphragm for alkaline water electrolysis, it is even more preferable that the average pore size of the porous membrane is in the range of 0.1 to 0.5 μm, which allows for even better gas barrier properties and high ion permeability.

[0076] The average pore size of a porous membrane can be measured by the following method. The average pore size of a porous membrane refers to the average water permeability pore size measured using an integrity tester (Sartorius Stedim Japan, "Sartocheck Junior BP-Plus") by the following method. First, the porous membrane, including the core material, is cut to a predetermined size to serve as a sample. This sample is placed in a pressure vessel of any size, and the vessel is filled with pure water. Next, the pressure vessel is kept in a constant temperature bath set to a predetermined temperature, and measurement is started after the inside of the pressure vessel reaches the predetermined temperature. When measurement begins, the upper surface of the sample is pressurized with nitrogen, and the pressure and permeation flow rate values ​​are recorded as pure water permeates through from the lower surface of the sample. The average water permeability pore size can be calculated using the pressure-permeation flow rate gradient between 10 kPa and 30 kPa, using the following Hagen-Poiseuille formula. Average permeable pore diameter (m) = {32ηLμ0 / (εP)} ０．５ Here, η is the viscosity of water (Pa·s), L is the thickness of the porous membrane (m), and μ0 is the apparent flow velocity, where μ0 (m / s) = flow rate (m ３ / s) / flow channel area (m ２ ) is the same. Also, ε is the porosity and P is the pressure (Pa).

[0077] For alkaline water electrolysis membranes, it is preferable to control the porosity of the porous membrane from the viewpoint of maintaining gas barrier properties and hydrophilicity, preventing a decrease in ion permeability due to bubble adhesion, and obtaining stable electrolysis performance (low voltage loss, etc.) over a long period of time. From the viewpoint of achieving a high level of both gas barrier properties and low voltage loss, the lower limit of the porosity of the porous membrane is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more. Furthermore, the upper limit of the porosity is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 55% or less. If the porosity of the porous membrane is below the above upper limit, ions can easily permeate through the membrane, and voltage loss in the membrane can be suppressed.

[0078] The porosity of a porous membrane refers to the open porosity determined by the Archimedes method, and can be calculated using the following formula: Porosity P (%) = ρ / (1 + ρ) × 100, where ρ = (W3 - W1) / (W3 - W2), where W1 is the dry mass of the porous membrane (g), W2 is the water mass of the porous membrane (g), and W3 is the saturated mass of the porous membrane (g).

[0079] To measure porosity, a porous membrane washed with pure water is cut into three 3cm x 3cm pieces to be used as measurement samples. First, W2 and W3 of each sample are measured. Then, the porous membrane is dried in a dryer set to 50°C for 12 hours or more, and W1 is measured. Finally, the porosity is calculated from the values ​​of W1, W2, and W3. The porosity of the three samples is calculated, and the arithmetic mean of these values ​​is defined as the porosity P.

[0080] The thickness of the porous membrane is not particularly limited, but is preferably 100 to 700 μm, more preferably 100 to 600 μm, and even more preferably 200 to 600 μm. If the thickness of the porous membrane is above the lower limit, it is less likely to be torn by punctures, etc., and short circuits between electrodes are less likely. Also, gas barrier properties are improved. If the thickness is below the upper limit, voltage loss is less likely to increase. Also, the influence of variations in the thickness of the porous membrane is reduced. If the thickness of the diaphragm is 100 μm or more, it is less likely to be torn by punctures, etc., and short circuits between electrodes are less likely. Also, gas barrier properties are improved. If the thickness is 600 μm or less, voltage loss is less likely to increase. Also, the influence of variations in the thickness of the porous membrane is reduced. If the thickness of the porous membrane is 250 μm or more, even better gas barrier properties are obtained, and the strength of the porous membrane against impact is further improved. From this viewpoint, the lower limit of the porous membrane thickness is more preferably 300 μm or more, even more preferably 350 μm or more, and even more preferably 400 μm or more. On the other hand, if the thickness of the porous membrane is 700 μm or less, the resistance of the electrolyte contained in the pores during operation will not easily hinder ion permeability, and even better ion permeability can be maintained. From this viewpoint, the upper limit of the porous membrane thickness is more preferably 600 μm or less, even more preferably 550 μm or less, and even more preferably 500 μm or less.

[0081] ---Hydrophilic Inorganic Particles--- It is preferable that the porous membrane contains hydrophilic inorganic particles in order to exhibit high ion permeability and high gas barrier properties. The hydrophilic inorganic particles may be attached to the surface of the porous membrane, or some of them may be embedded in the polymer material constituting the porous membrane. Furthermore, when the hydrophilic inorganic particles are embedded in the voids of the porous membrane, they become less likely to detach from the porous membrane, and the performance of the porous membrane can be maintained for a long time.

[0082] Examples of hydrophilic inorganic particles include at least one inorganic substance selected from the group consisting of oxides or hydroxides of zirconium, bismuth, and cerium; oxides of Group IV elements of the periodic table; nitrides of Group IV elements of the periodic table; and carbides of Group IV elements of the periodic table. Among these, from the viewpoint of chemical stability, oxides of zirconium, bismuth, and cerium, and oxides of Group IV elements of the periodic table are more preferred, oxides of zirconium, bismuth, and cerium are even more preferred, and zirconium oxide is even more preferred.

[0083] The hydrophilic inorganic particles are preferably in the form of fine particles.

[0084] --Porous Support-- When a porous membrane is used as a diaphragm, the porous membrane may be used together with a porous support. Preferably, the porous membrane has a structure in which the porous support is embedded, and more preferably, the porous membrane is laminated on both sides of the porous support. Alternatively, the porous membrane may be laminated symmetrically on both sides of the porous support.

[0085] Examples of porous supports include mesh, porous membranes, nonwoven fabrics, woven fabrics, and composite fabrics containing nonwoven fabrics and woven fabrics embedded within them. These may be used individually or in combination of two or more types. More preferred embodiments of the porous support include, for example, a mesh substrate composed of polyphenylene sulfide monofilaments, or a composite fabric containing nonwoven fabrics and woven fabrics embedded within them.

[0086] --Ion Exchange Membranes-- Ion exchange membranes include cation exchange membranes that selectively allow cations to pass through and anion exchange membranes that selectively allow anions to pass through, and either type of exchange membrane can be used. The material of the ion exchange membrane is not particularly limited, and known materials can be used. For example, fluorine-containing resins and modified resins of polystyrene-divinylbenzene copolymers can be suitably used. Fluorine-containing ion exchange membranes are particularly preferred due to their excellent heat resistance and chemical resistance.

[0087] Examples of fluorine-containing ion exchange membranes include those that have the function of selectively permeating ions generated during electrolysis and contain fluorine-containing polymers having ion exchange groups. Here, a fluorine-containing polymer having ion exchange groups refers to a fluorine-containing polymer having ion exchange groups, or ion exchange group precursors that can become ion exchange groups through hydrolysis. Examples include polymers having a fluorinated hydrocarbon main chain, functional groups that can be converted into ion exchange groups through hydrolysis, etc., as pendant side chains, and that are melt-processable.

[0088] The molecular weight of the fluorine-containing copolymer having ion exchange groups is not particularly limited, but is preferably 0.05 to 50 (g / 10 min) and more preferably 0.1 to 30 (g / 10 min) based on the melt flow index (MFI) value measured in accordance with ASTM:D1238 (measurement conditions: temperature 270°C, load 2160 g).

[0089] Examples of ion exchange groups found in ion exchange membranes include cation exchange groups such as sulfonic acid groups, carboxylic acid groups, and phosphate groups, and anion exchange groups such as quaternary ammonium groups.

[0090] Ion exchange membranes can be given excellent ion exchange capacity and hydrophilicity by adjusting the equivalent mass EW of the ion exchange groups. Furthermore, it is possible to control the number of smaller clusters (tiny parts in which ion exchange groups coordinate and / or adsorb water molecules), which tends to improve alkali resistance and ion selective permeability. This equivalent mass EW can be measured by salt-substituted the ion exchange membrane and back-titrating the solution with an alkaline or acidic solution. The equivalent mass EW can be adjusted by the copolymerization ratio of the raw material monomers, selection of monomer species, etc. From the viewpoint of hydrophilicity and membrane water resistance, the equivalent mass EW of the ion exchange membrane is preferably 300 or more, and from the viewpoint of hydrophilicity and ion exchange capacity, it is preferably 1300 or less.

[0091] The thickness of the ion exchange membrane is not particularly limited, but from the viewpoint of ion permeability and strength, a range of 5 to 300 μm is preferred.

[0092] Surface treatment may be applied to improve the hydrophilicity of the ion exchange membrane surface. Specifically, this may involve coating the membrane with hydrophilic inorganic particles such as zirconium oxide, or creating fine irregularities on the surface.

[0093] From the viewpoint of membrane strength, it is preferable to use the ion exchange membrane together with a reinforcing material. The reinforcing material is not particularly limited and can be a general nonwoven fabric, a woven fabric, or a porous membrane made of various materials. In this case, the porous membrane is not particularly limited, but a stretched and porous PTFE-based membrane is preferred. In the electrolytic cell of this embodiment, any of these membranes can be used without limitation.

[0094] ((Zero-gap structure)) In a zero-gap electrolytic cell 65, as a means of reducing the distance between electrodes, it is preferable to place a spring, which is an elastic body 2e, between the electrode 2 and the partition wall 1, and to support the electrode with this spring. For example, in the first example, a spring made of a conductive material may be attached to the partition wall 1, and the electrode 2 may be attached to this spring. In the second example, a spring may be attached to an electrode rib 6 attached to the partition wall 1, and the electrode 2 may be attached to that spring. When adopting such a configuration using an elastic body, it is necessary to adjust the strength of the spring, the number of springs, the shape, etc. as needed so that the pressure in contact between the electrode and the diaphragm does not become uneven.

[0095] Furthermore, by increasing the rigidity of the other electrode that is paired with the electrode supported via an elastic body (for example, by making the rigidity of the anode greater than that of the cathode), a structure that deforms less even when pressed is achieved. On the other hand, for the electrodes supported via the elastic body, by making the diaphragm a flexible structure that deforms when pressed, it is possible to absorb irregularities caused by tolerances in the manufacturing precision of the electrolytic cell and deformation of the electrodes, thereby maintaining a zero-gap structure.

[0096] More specifically, this involves attaching a current collector to the tip of a rib (rectifier plate) that is electrically in contact with the bulkhead, attaching a conductive elastic body to the upper side of the current collector, that is, the side opposite to the bulkhead, and further stacking electrodes on the upper side of the current collector, that is, the part adjacent to the conductive elastic body and facing the bulkhead, thereby forming at least a three-layer structure. The elastic body is formed by the current collector and the conductive elastic body.

[0097] The zero-gap structure Z described above includes gap structures formed between the anode terminal element 51a and the element, between elements, and between the element and the cathode terminal element 51c. In the alkaline water electrolysis cell 65, as shown in Figure 7, it is preferable that a conductive elastic body 2e and a cathode current collector 2r are provided between the cathode 2c and the partition wall 1, such that the conductive elastic body 2e is sandwiched between the cathode 2c and the cathode current collector 2r. It is also preferable that the cathode current collector 2r is in contact with the rib 6 of the cathode.

[0098] The zero-gap structure Z of the electrolytic cell 65 for alkaline water electrolysis is preferably such that, as shown in Figure 7, an element 60 is superimposed on the anode 2a side of the partition wall 1, with an anode rib 6 and anode 2a stacked in that order, and on the cathode 2c side of the partition wall 1, with a cathode rib 6, cathode current collector 2r, conductive elastic body 2e and cathode 2c stacked in that order, with a diaphragm 4 in between, so that the diaphragm 4 is in contact with the anode 2a and cathode 2c.

[0099] -Current Collector- Examples of current collectors include cathode current collectors and anode current collectors. The current collector transmits electricity to the conductive elastic material or electrodes laminated on top of it, supports the load received from them, and allows gas generated from the electrodes to pass through to the partition wall without obstruction. Therefore, the shape of the current collector is preferably expanded metal or a punched perforated plate.

[0100] The material of the current collector can be nickel, nickel alloy, stainless steel, or mild steel, depending on its conductivity and alkali resistance. However, nickel or nickel-plated mild steel or stainless steel nickel alloy is preferred for its corrosion resistance. Such current collectors are fixed to the ribs by means of spot welding, laser welding, or other methods.

[0101] -Conductive Elastic Body- The conductive elastic body is located between the current collector and the electrode and is in contact with both the current collector and the electrode. It is preferable that it transmits electricity to the electrode and does not hinder the diffusion of gas generated from the electrode. This is because if gas diffusion is hindered, the electrical resistance increases and the electrode area used for electrolysis decreases, thus reducing the electrolysis efficiency. Its most important role is to ensure tight contact between the diaphragm and the electrode by applying an appropriate and even pressure to the electrode, without damaging the diaphragm.

[0102] As the conductive elastic body, commonly known materials such as elastic bodies composed of wires can be used. The material is not limited, but nickel, nickel alloys, stainless steel, or mild steel with nickel plating are preferred in terms of conductivity and alkali resistance. For electrode substrates that can be used in zero-gap applications, electrodes with a thin wire diameter and small mesh are preferred due to their high flexibility. Commonly known substrate materials can be used for such applications.

[0103] For achieving a zero-gap structure, preferred methods of fixing electrodes include spot welding to a conductive elastic material, fixing with metal or plastic pins, or applying pressure using the elasticity of the conductive elastic material.

[0104] Furthermore, the shape of the other electrode, which is paired with the electrode supported via an elastic material, is also important. In the zero-gap configuration described above, the diaphragm is pressed more strongly against the electrode than in conventional electrolytic cells.

[0105] - Electrode Chambers - In the electrolytic cell 50, as shown in Figure 7, the electrode chambers 5 through which the electrolyte passes are defined by the partition wall 1, the outer frame 3, and the diaphragm 4. Here, the electrode chamber 5 on the anode side of the partition wall 1 is the anode chamber 5a, and the electrode chamber 5 on the cathode side is the cathode chamber 5c.

[0106] Regarding the arrangement of the header tubes in the electrolytic cell, internal header type and external header type can be adopted.

[0107] -Ribs- In the electrolytic cell 65 for alkaline water electrolysis, it is preferable that the ribs 6 are physically connected to the electrodes 2. With this configuration, the ribs 6 act as a support for the electrodes 2, making it easier to maintain the zero-gap structure Z. It is also preferable that the ribs 6 are electrically connected to the partition wall 1. Furthermore, by providing the ribs 6, it is possible to reduce the convection generated in the electrode chamber 5 due to turbulence in the flow of gas and liquid within the electrode chamber 5, thereby suppressing a local rise in the temperature of the electrolyte. Here, electrodes may be provided on the ribs, or a current collector, a conductive elastic body, and an electrode may be provided on the ribs in this order. In the example electrolytic cell for alkaline water electrolysis described above, a structure is adopted in which the cathode ribs - cathode current collector - conductive elastic body - cathode are stacked in the order of cathode ribs - cathode - cathode in the cathode chamber, and a structure is adopted in which the anode ribs - anode are stacked in the order of anode ribs - anode.

[0108] It is preferable that the ribs (anode ribs, cathode ribs) not only serve to support the anode or cathode, but also to transmit the current from the partition wall to the anode or cathode.

[0109] In an electrolytic cell for alkaline water electrolysis, it is preferable that at least a portion of the ribs be conductive, and it is even more preferable that the entire rib be conductive. With such a configuration, it is possible to suppress the rise in cell voltage due to electrode deflection.

[0110] Generally, conductive metals are used as the material for the ribs. For example, nickel-plated mild steel, stainless steel, and nickel can be used. It is especially preferable that the rib material be the same as the partition wall material, and nickel is the most preferable.

[0111] The electrodes and current collectors are usually attached to the ribs by spot welding, but other methods such as laser welding may also be used, or they may be tied together using wire or string-like materials. The ribs are fixed to the bulkhead by means of spot welding, laser welding, etc., similar to the anode or cathode.

[0112] -Gasket- In the electrolytic cell 65 for alkaline water electrolysis, as shown in Figure 7, it is preferable that a gasket 7 is sandwiched together with the diaphragm 4 between the flange portions 8 that frame the partition wall 1. The gasket 7 is used to seal the space between the element 60 and the diaphragm 4, and between the elements 60, to the electrolyte and generated gas, thereby preventing leakage of the electrolyte and generated gas to the outside of the electrolytic cell and gas mixing between the two electrode chambers.

[0113] A typical gasket structure is a rectangular or annular shape with the electrode surface cut out to match the surface in contact with the frame of the element (such as a bipolar element, anode terminal element, or cathode terminal element). Two such gaskets can be used to sandwich the diaphragm, allowing it to be stacked between elements. Furthermore, it is preferable for the gasket to have a slit portion capable of accommodating the diaphragm so that it can hold the diaphragm, and an opening that allows the accommodated diaphragm to be exposed on both surfaces of the gasket. This allows the gasket to accommodate the edge of the diaphragm within the slit portion and cover the end face of the diaphragm's edge. Therefore, leakage of electrolyte or gas from the end face of the diaphragm can be prevented more reliably.

[0114] Furthermore, it is preferable to provide a protrusion that extends from one side of the gasket. By providing such a protrusion, the protrusion is locally pressed when the device is stacked, and the diaphragm housed in the slit is pressed by the gasket at the position corresponding to the protrusion. Therefore, the gasket can hold the diaphragm more firmly, making it easier to prevent leakage of electrolyte or gas.

[0115] The gasket may have a reinforcing material (core material) embedded in it. This helps to prevent the gasket from being crushed when it is sandwiched and pressed between the frame during stacking, thus making it easier to prevent damage. Such reinforcing materials (core materials) can be made from known metal materials, resin materials, and carbon materials, specifically metals such as nickel and stainless steel, resins such as nylon, polypropylene, PVDF, PTFE, and PPS, and carbon materials such as carbon particles and carbon fibers. The shape of the reinforcing material (core material) is preferably in the form of woven fabric, nonwoven fabric, short fibers, or porous membrane. Furthermore, a protective layer may be provided on the surface of the gasket. This can improve the adhesion between the gasket and the element, and also improve the alkali resistance of the gasket. The material of such a protective layer can also be selected from the gasket material.

[0116] The thickness of a gasket is not particularly limited and is designed according to the gasket's material, modulus of elasticity, and cell area.

[0117] Adhesive may be used when attaching the gasket to the element. Adhesive can be applied to one side of the gasket and attached to one side of the outer frame of the element. It is preferable to moisten the electrode surface of the element by spraying water on it after the adhesive has dried. In the case of a gasket that has a slit portion to accommodate the edge of the diaphragm in order to hold the diaphragm, the gasket may be attached while the diaphragm is being held, or the diaphragm may be held after the gasket has been attached.

[0118] -Header- An electrolytic cell for alkaline water electrolysis preferably has a cathode chamber and an anode chamber for each electrolytic cell. In order to carry out the electrolysis reaction continuously in the electrolytic cell, it is necessary to continuously supply the cathode chamber and anode chamber of each electrolytic cell with an electrolyte solution that contains a sufficient amount of the raw materials consumed by electrolysis.

[0119] Electrolytic cells are connected to electrolyte supply and discharge piping called headers, which are common to multiple electrolytic cells. Generally, the anode distribution pipe is called the anode inlet header, the cathode distribution pipe is called the cathode inlet header, the anode collection pipe is called the anode outlet header, and the cathode collection pipe is called the cathode outlet header. Elements are connected to each electrolyte distribution pipe and each electrolyte collection pipe via hoses or similar.

[0120] The material of the header is not particularly limited, but it must be able to withstand the corrosiveness of the electrolyte used and the operating conditions such as pressure and temperature. Materials such as iron, nickel, cobalt, PTFE, ETFE, PFA, polyvinyl chloride, and polyethylene may be used for the header.

[0121] Typical configurations for the headers of electrolytic cells include internal header type and external header type.

[0122] -Internal Header- An internal header type refers to a system in which the electrolytic cell and the header (a tube for distributing or collecting the electrolyte) are integrated into a single unit.

[0123] In an internal header type electrolytic cell, more specifically, the anode inlet header and cathode inlet header are provided in the lower part of the partition wall 1 and / or the outer frame 3, and are provided to extend in a direction perpendicular to the partition wall 1, and the anode outlet header and cathode outlet header are provided in the upper part of the partition wall 1 and / or the outer frame 3, and are provided to extend in a direction perpendicular to the partition wall 1.

[0124] The anode inlet header, cathode inlet header, anode outlet header, and cathode outlet header inherently present in an internal header type electrolytic cell are collectively referred to as the internal header.

[0125] As an example of an internal header type, an anode inlet header and a cathode inlet header are provided on a portion of the lower part of the outer frame at the edge of the partition wall, and similarly, an anode outlet header and a cathode outlet header are provided on a portion of the upper part of the outer frame at the edge of the partition wall. The outer frame and the anode chamber or cathode chamber are connected by an electrolyte inlet or electrolyte outlet through which the electrolyte passes.

[0126] -External Header- An external header type refers to a configuration in which the electrolytic cell and the header (a tube for dispensing or collecting the electrolyte) are separate.

[0127] In an external header type electrolytic cell, the anode inlet header and the cathode inlet header are independently provided, running parallel to the electrolytic cell and perpendicular to the energized surface of the electrolytic cell. These anode inlet headers and cathode inlet headers are connected to each element by hoses.

[0128] The anode inlet header, cathode inlet header, anode outlet header, and cathode outlet header, which are externally connected to an external header type electrolytic cell, are collectively referred to as external headers. In the example of an external header type shown in Figure 8, a tubular member is installed in a header through-hole provided in the lower part of the outer frame 3 at the edge of the partition wall 1, and the tubular member is connected to the anode inlet header 10ai and the cathode inlet header 10ci. Similarly, a tubular member (e.g., a hose or tube) is installed in a header through-hole provided in the upper part of the outer frame 3 at the edge of the partition wall 1, and this tubular member is connected to the anode outlet header 10ao and the cathode outlet header 10co.

[0129] Furthermore, internal header type and external header type electrolytic cells may have a gas-liquid separation box inside to separate the gas generated by electrolysis from the electrolyte. The mounting position of the gas-liquid separation box is not particularly limited, but it may be installed between the anode chamber and the anode outlet header, or between the cathode chamber and the cathode outlet header.

[0130] -Electrolyte- Inside the electrolytic cell, a cathode chamber frame with the cathode attached and an anode chamber frame with the anode attached are arranged with a partition wall in between. In other words, the anode chamber and the cathode chamber are separated by a partition wall. The electrolyte is supplied to these anode chamber and cathode chamber. As the electrolyte, one that is commonly used in water electrolysis can be used. For example, potassium hydroxide aqueous solution or sodium hydroxide aqueous solution can be used. Furthermore, the electrolyte concentration is preferably 5 wt% to 35 wt%, more preferably 10 wt% to 30 wt%, and even more preferably 15 wt% to 25 wt%.

[0131] ((Method for producing hydrogen)) The method for producing hydrogen using the electrolytic cell described above will now be explained. Hydrogen is produced at the cathode by applying an electric current to an electrolytic cell equipped with the anode and cathode described above, in which the electrolyte is circulated, thereby performing water electrolysis. At this time, a fluctuating power source can be used as the power source. A fluctuating power source is a power source that, unlike a power source that outputs stably, such as grid power, is a power source that originates from a renewable energy power plant and whose output fluctuates in increments of a few seconds to a few minutes. The method of renewable energy generation is not particularly limited, but examples include solar power generation and wind power generation. For example, in the case of electrolysis using an electrolytic cell, the cationic electrolyte in the electrolyte moves from the anode chamber of one element through the diaphragm to the cathode chamber of an adjacent element, and the anionic electrolyte moves from the cathode chamber of one element through the diaphragm to the anode chamber of an adjacent element. Therefore, the current during electrolysis flows along the direction in which the elements are connected in series. In other words, the current flows from the anode chamber of one element to the cathode chamber of an adjacent element through the diaphragm. During electrolysis, oxygen gas is generated in the anode chamber and hydrogen gas is generated in the cathode chamber.

[0132] The electrolytic cell 65 for alkaline water electrolysis can be used in an electrolytic bath 50, an electrolytic device 70 for alkaline water electrolysis, etc. (Fig. 9). As the above-mentioned electrolytic device 70 for alkaline water electrolysis, for example, there are devices having an electrolytic bath 50, a liquid feed pump 71 for circulating the electrolytic solution, a gas-liquid separation tank 72 for separating the electrolytic solution from hydrogen and / or oxygen, and a water replenisher for replenishing the water consumed by electrolysis, etc. The above-mentioned electrolytic device for alkaline water electrolysis may further include a rectifier 74, an oxygen concentration meter 75, a hydrogen concentration meter 76, a flow meter 77, a pressure gauge 78, a heat exchanger 79, a pressure control valve 80, etc.

[0133] In the method for alkaline water electrolysis using the above-mentioned electrolytic device for alkaline water electrolysis, the current density applied to the electrolytic cell is preferably 4 kA / m ２ to 20 kA / m ２ and more preferably 6 kA / m ２ to 15 kA / m ２ Particularly, when using a variable power source, it is preferable to set the upper limit of the current density within the above range.

[0134] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these examples.

[0135] (Examples 1, 3, and 4) Gaskets were manufactured using the following procedure. Two types of gaskets were manufactured: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, grooves, and core material were all provided as described below. On one surface of the gasket, one small protrusion with a height of 0.4 mm was provided on the innermost side, followed by four small protrusions with a height of 1.3 mm and a continuous circumferential pattern, and then four more small protrusions with a height of 0.4 mm and a continuous circumferential pattern. The distance L1 from the inner edge 7a to the innermost protrusion with a height of 1 mm or more was 5.5 mm. The spacing between the centers of the protrusions was 2.0 mm. On the other surface, seven grooves with a depth of 0.9 mm and a continuous circumferential pattern were provided. The distance L2 from the inner circumference edge 7a to the innermost groove with a depth of 0.1 mm or more was 5.5 mm. The spacing between grooves, from the center of one groove to the center of the next groove, was 2.0 mm. The distance L3 from the inner circumference edge of the core material 7g to the inner circumference edge 7a of the gasket was 3.5 mm. In Examples 1, 3, and 4, the inner circumference dimensions of the gasket were finely adjusted so that L4 would be the desired dimension during the electrical conductivity evaluation described later.

[0136] (Example 2) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, grooves, and core material were all provided as follows. On one surface of the gasket, four protrusions with a height of 1.3 mm were provided in a continuous circumferential manner, starting from the innermost side, followed by seven small protrusions with a height of 0.4 mm in a continuous circumferential manner. The distance L1 from the inner edge 7a to the innermost protrusion with a height of 1 mm or more was 1.5 mm. The spacing between the centers of each protrusion and the centers of adjacent protrusions was 2.0 mm. On the other surface, nine grooves with a depth of 0.9 mm were provided in a continuous circumferential manner. The distance L2 from the inner edge 7a to the innermost groove with a depth of 0.1 mm or more was 3.5 mm. The distance between grooves, from the center of one groove to the center of the adjacent groove, was 2.0 mm. Furthermore, the distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 1.5 mm.

[0137] (Example 5) A gasket was manufactured in the same manner as in Example 1, except that the distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was set to 6.0 mm.

[0138] (Example 6) A gasket was manufactured in the same manner as in Example 1, except that four grooves were provided on the other surface, with their depths being 0.5 mm, 0.4 mm, 0.5 mm, and 0.2 mm from the inner circumference, the distance L2 from the inner circumference end 7a to the innermost groove with a depth of 0.1 mm or more was 5.5 mm, and the spacing between the centers of each groove and the centers of adjacent grooves was 2.0 mm.

[0139] (Example 7) A gasket was manufactured in the same manner as in Example 1, except that four grooves were provided on the other surface, with their depths being 0.4 mm, 0.3 mm, 0.4 mm, and 0.1 mm from the inner circumference, the distance L2 from the inner circumference end 7a to the innermost groove with a depth of 0.1 mm or more was 5.5 mm, and the spacing between the centers of each groove and the centers of adjacent grooves was 2.0 mm.

[0140] (Example 8) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions, grooves, and core material were all provided as described below. On one surface of the gasket, one small protrusion with a height of 0.4 mm was provided on the innermost side, followed by four small protrusions with a height of 1.3 mm and a continuous circumferential pattern, and then four more small protrusions with a height of 0.4 mm and a continuous circumferential pattern. The distance L1 from the inner edge 7a to the innermost protrusion with a height of 1 mm or more was 5.5 mm. The spacing between the centers of the protrusions was 2.0 mm. On the other surface, one groove with a depth of 0.9 mm and a continuous circumferential pattern was provided. The distance L2 from the inner circumference end 7a to the innermost groove with a depth of 0.1 mm or more was 13.5 mm. The spacing between grooves, from the center of one groove to the center of the next groove, was 2.0 mm. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 3.5 mm.

[0141] (Example 9) A gasket was manufactured in the same manner as in Comparative Example 1, except that the distance L1 from the inner circumference end 7a to the innermost projection with a height of 1 mm or more was set to 13.5 mm.

[0142] (Example 10) A gasket was manufactured in the same manner as in Comparative Example 1, except that the distance L1 from the inner circumference end 7a to the innermost projection with a height of 1 mm or more was set to 9.5 mm.

[0143] (Comparative Example 1) A gasket was manufactured using the following procedure. An EPDM gasket with an inner circumference of 50 mm square and a width of 25 mm, and an EPDM gasket with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm were manufactured. The protrusions, grooves, and core material were all provided as follows. Four protrusions, each 1.3 mm high and continuous around the circumference, were provided on one surface of the gasket. The distance L1 from the inner circumference edge 7a to the innermost protrusion with a height of 1 mm or more was 11.5 mm. The spacing between the centers of each protrusion and the centers of adjacent protrusions was 2.0 mm. On the other surface, ten grooves, each 0.9 mm deep and continuous around the circumference, were provided on the 25 mm wide gasket and twelve grooves on the 30 mm wide gasket. The distance L2 from the inner circumference edge 7a to the innermost groove with a depth of 0.1 mm or more was 3.5 mm. The distance between grooves, from the center of one groove to the center of the adjacent groove, was 2.0 mm. The distance L3 from the inner circumference end of the core material 7g to the inner circumference end 7a of the gasket was 4 mm.

[0144] (Comparative Example 2) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The protrusions and coverings were provided as follows. On one surface of the gasket, seven small protrusions with a height of 0.4 mm and continuing in a continuous circumferential manner were provided. The distance from the inner circumference edge 7a to the smallest protrusion with a height of 0.4 mm located on the inner circumference was 1 mm. The distance between the center of one protrusion and the center of the adjacent protrusion was 2.0 mm. On the other surface, seven convex shapes with a height of 0.8 mm and continuing in a continuous circumferential manner were provided. The distance from the inner circumference edge 7a to the convex shape with a height of 0.8 mm located on the inner circumference was 1.0 mm. The distance between the center of one protrusion and the center of the adjacent protrusion was 2.0 mm. A portion of the inner circumference end and a portion of the side surface of one of the surfaces are coated with fluororesin, and this coating is woven into the gasket on the inner circumference end of the other surface. Figure 10 shows the thickness cross-section of the gasket made in Comparative Example 2. In Figure 10, the shaded area that differs from gasket 7 represents the coating.

[0145] (Comparative Example 3) A gasket was manufactured using the following procedure. Two types of gaskets were manufactured: one made of EPDM with an inner circumference of 50 mm square and a width of 25 mm, and another made of EPDM with an inner circumference of approximately 1200 x 2400 mm and a width of 30 mm. The coating was provided as follows for both. No grooves or protrusions were provided on either surface of the gasket, resulting in a flat structure. A portion of the inner circumference end of one surface and a portion of the side surface of the inner circumference end were coated with fluororesin, and this coating was woven into the interior of the gasket on the inner circumference end of the other surface. Figure 11 shows the thickness cross-section of the gasket manufactured in Comparative Example 3. In Figure 11, the shaded area that differs from gasket 7 represents the coating.

[0146] (Comparative Example 4) A gasket was manufactured in the same manner as in Comparative Example 1, except that the height of the protrusion on one surface of the gasket was set to 0.8 mm.

[0147] (Comparative Example 5) A gasket was manufactured in the same manner as in Comparative Example 1, except that the depth of the groove on the other surface of the gasket was set to 0.05 mm.

[0148] (Comparative Example 6) A gasket was manufactured in the same manner as in Comparative Example 1, except that the height of the protrusion on one surface of the gasket was set to 0.8 mm and the depth of the groove on the other surface of the gasket was set to 0.05 mm.

[0149] (Evaluation) (Dimensions) The following dimensions were measured as follows: L1, L2: The gasket was measured with calipers or a ruler. L3: The gasket was cut and the cross-section was measured with calipers or a ruler. V, W: The gasket was cut, the cross-section was photographed with a microscope, and V and W were calculated from the measured dimensions. For each of L1, L2, L3, V, and W, 10 points were measured excluding the corners, and the average value was calculated. Note that V and W can also be calculated by importing the measured photographs into ImageJ and processing the images. If there is a design drawing with dimensions, they may also be calculated from the design values ​​in the drawing.

[0150] (Gasket Compression Test) In an environment with a temperature of 23±3°C and a humidity of 50±5%, a tensile and compression testing machine (Shimadzu Autograph AG-Xplus) was used to sandwich a 23mm x 60mm strip-shaped gasket and pressure-sensitive paper (Fujifilm Pressure Measurement Film Prescale Two-Sheet Type LW or LLW) between strip-shaped jigs measuring 23mm in width and 100mm in length. The gasket was compressed at an average surface pressure of 2 MPa and held for 5 minutes or more. After release, the pressure-sensitive paper was removed and analyzed using a pressure image analysis system (Fujifilm Pressure Image Analysis System FPD-8010J) to quantify the pressure. Points with a surface pressure of 3.0 MPa or higher were then analyzed, and the distance from the innermost edge of the innermost point with a surface pressure of 3.0 MPa or higher was measured.

[0151] The following crevice corrosion tests, liquid filling tests, electrical conductivity evaluations, widening evaluations, and CAE analyses were performed, and crevice corrosion, liquid filling properties, widening, and diaphragm deformation were evaluated according to the following criteria.

[0152] (Crevice Corrosion Test) A 20 x 100 mm nickel plate was prepared as a test specimen, with a 20 mm square hole drilled in the center of one end. A 20 mm wide gasket with a hole in the center was sandwiched between the 20 mm square nickel plate with a hole in the center and the test specimen, and secured with screws through the hole and tightened to 2 MPa. A potentiometer galvanostat was connected to the nickel plate to form the working electrode. A nickel mesh was used as the counter electrode, an Ag / AgCl reference electrode as the reference electrode, and 20% NaOH as the electrolyte. The specimen was maintained at a potential of +0.8 V vs. Ag / AgCl at 90°C for 50 hours. After that, the surface of the test specimen was observed visually and under a microscope to confirm the presence and extent of corrosion. The extent of crevice corrosion was evaluated by determining what percentage of the test specimen was affected.

[0153] (Liquid-filled test) A 50mm square, 25mm wide gasket was sandwiched between 150mm square stainless steel plates, with thin strips of litmus paper placed in the grooves. Eight points on the edges were tightened using spring springs (TH type, manufactured by Tokyo Hatsujo Seisakusho) to achieve an average surface pressure of 2 MPa (Figure 12). An alkaline liquid (KOH or NaOH, concentration not specified) was then placed inside, and the device was left to stand for one week at 90°C. After that, the liquid was drained and the pressure was released. The presence or absence of discoloration of the litmus paper was checked, and it was determined that the liquid had penetrated to the groove where discoloration was observed. From the perspective of suppressing crevice corrosion by preventing the electrolyte from entering the gap between the electrolytic frame and the gasket, which can be a point of corrosion, the liquid-filled test can be considered a test to measure the effect of the gasket in suppressing crevice corrosion.

[0154] (Energy Test) Energy test refers to a current density of 6 kA / m². ２ The above procedure refers to electrolysis for 1000 hours. NaOH with a concentration of 10-30 wt% was used as the electrolyte, and an ion exchange membrane was used as the diaphragm. The size of the electrodes and electrolytic cell was not specified. After 1000 hours of electrolysis, the flange surface of the electrolytic frame was visually inspected using a magnifying glass, etc., and the presence or absence of corrosion was determined by whether or not pit-like corrosion marks that were not initially observed were found. After 1000 hours of electrolysis, the diaphragm was visually inspected and palpated, and the protectiveness of the diaphragm was determined by whether or not irreversible bending, kinking, or curvature was found in the diaphragm.

[0155] (Width widening evaluation) Using a tensile and compression testing machine in warm water at a temperature of 90±3℃, a 40mm long strip-shaped gasket was placed on a U-shaped jig consisting of a strip-shaped gasket measuring 23mm wide x 60mm long with 10mm high blocks at both ends. A rectangular jig measuring 23mm wide x 40mm long x 10mm high was placed on top, and the gasket was compressed at an average surface pressure of 8 MPa for 100 hours. The amount of change in the width direction of the gasket after the pressure was released was measured.

[0156] (CAE Analysis) Computer-aided engineering (CAE) analysis, which utilizes computer simulations, was performed under the following conditions: A 23 mm wide block was placed to sandwich the width portion of a gasket with an inner circumference of 50 mm square and a width of 25 mm, and then pressed into place. The pressing pressure was set to 2 MPa based on the projected area of ​​the block, and the deformation behavior and surface pressure distribution of the gasket were evaluated. The 23 mm direction was defined as the width direction, and the displacement in the width direction was defined as the difference between the initial gasket length in the width direction (initial length) and the gasket length in the width direction after pressing (post-press length). The amount of deformation in the width direction was then calculated using the following formula: Amount of deformation in the width direction (%) = {(post-press length - initial length) / initial length} × 100

[0157] (Crevice Corrosion) ◎ (Excellent): No crevice corrosion in crevice corrosion tests or electrical evaluations. (Less than 1%) 〇〇 (Better): Almost no crevice corrosion in crevice corrosion tests or electrical evaluations. (More than 1% but less than or equal to 3%) 〇 (Good): Slight crevice corrosion in crevice corrosion tests or electrical evaluations. (More than 3% but less than or equal to 5%) × (Poor): Crevice corrosion occurs in crevice corrosion tests or electrical evaluations. (More than 5%)

[0158] (Liquid Sealing Ability) ◎ (Excellent): No liquid ingress in the liquid sealing test. 〇 (Good): Some liquid ingress in the liquid sealing test, but it is minor. × (Poor): Significant liquid ingress in the liquid sealing test.

[0159] (Sealing performance) ○ (Good): No electrolyte leakage during electrical conduction evaluation. × (Poor): Electrolyte leakage observed during electrical conduction evaluation.

[0160] (Widening) ○ (Excellent): The amount of widthwise deformation in the widening evaluation or CAE analysis is sufficiently small (5% or less) △ (Good): The amount of widthwise deformation in the widening evaluation or CAE analysis is small and acceptable (10% or less) × (Poor): The amount of widthwise deformation in the widening evaluation or CAE analysis is unacceptably large (greater than 10%)

[0161] (Diaphragm Deformation) ◎ (Excellent): No plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation. 〇 (Good): Slight plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation. △ (Poor): Significant plastic deformation in the diaphragm at the position corresponding to distance L4 after electrical evaluation.

[0162]

[0163] The gasket of Example 1 is a frame-shaped electrolytic gasket having a hollow portion on its inner circumference. One surface has at least one projection with a height of 1 mm or more that extends circumferentially, and the other surface has at least one groove with a depth of 0.1 mm or more that extends circumferentially. When L1 is the distance from the inner circumference side end to the projection on the innermost side, and L2 is the distance from the inner circumference side end to the groove on the innermost side, the relationship L1 / L2 ≤ 3 is satisfied, and it exhibits excellent crevice corrosion suppression, good liquid sealing properties, excellent widening properties, and excellent diaphragm deformation properties. Furthermore, the gasket of Example 1 is a frame-shaped electrolytic gasket having a hollow portion on its inner circumference, with at least one groove of 0.1 mm or more in the circumferential direction on the other surface. When the distance from the inner circumference side end to the innermost groove is defined as L2, in a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the innermost point on the other surface where the surface pressure is 3.0 MPa or more is within the range of L2. Therefore, it exhibited excellent crevice corrosion suppression, good liquid sealing properties, excellent widening degree, and excellent diaphragm deformation. The gasket of Example 2 had an L1 / L2 of 0.43, so its liquid sealing properties were superior to those of Example 1. The gasket of Example 3 had a distance L4 of 4 mm from the inner circumference side end of the electrolytic gasket to the inner circumference side end of the flange surface, so its diaphragm deformation was slightly inferior to that of Example 1, and it received a good evaluation. The gasket in Example 4 had a distance L4 of 8 mm from the inner circumference end of the electrolytic gasket to the inner circumference end of the flange surface, resulting in inferior diaphragm deformation compared to Examples 1 and 3, and was therefore rated as poor. The gasket in Example 5 did not satisfy the relationship L3 ≤ L1 when the distance L3 was taken from the inner circumference end of the core material to the inner circumference end of the gasket, resulting in slightly inferior widening compared to Example 1, and was rated as good. The gasket in Example 6 had a V / W of 11.4, resulting in excellent crevice corrosion suppression, good liquid sealing properties, excellent widening, and excellent diaphragm deformation. The gasket in Example 7 had a V / W of 15.5, resulting in slightly inferior widening compared to Example 1, and was rated as good. The gasket in Example 8 had a V / W of 3.23, resulting in superior liquid sealing properties compared to Example 1, and was rated as excellent.In the gasket compression test, the gasket of Comparative Example 1 had a distance of 11.5 mm from the inner edge of the innermost point where the surface pressure was 3 MPa or higher. As a result, electrolyte penetrated into the groove between the electrolytic frame and the gasket, causing crevice corrosion at that location. In other words, it failed in the categories of crevice corrosion and liquid penetration. In the gasket of Comparative Example 2, the distance from the inner edge of the innermost point where the surface pressure was 3 MPa or higher was 1.5 mm in the gasket compression test. However, because the shape of the other surface was a continuous convex shape, the contact area between the gasket and the electrolytic frame was small, and electrolyte easily penetrated between the protrusions, causing crevice corrosion at that location. In other words, it failed in the categories of crevice corrosion and liquid penetration. In the gasket of Comparative Example 3, the other surface had neither protrusions nor grooves. However, because there was no escape route for the rubber during compression, the surface pressure distribution was uneven. Furthermore, because there were neither protrusions nor grooves, the surface pressure was insufficient, resulting in liquid seeping between the gasket and the electrolytic frame and causing crevice corrosion. Specifically, it failed in the categories of crevice corrosion and liquid intrusion. Furthermore, it also failed in the widening evaluation due to the lack of escape route for the rubber during compression.

[0164] 1 Partition wall 2 Electrodes 2a Anode 2c Cathode 2e Conductive elastic body 2r Current collector 3 Outer frame 4 Diaphragm 5 Electrode chamber 5a Anode chamber 5c Cathode chamber 5i Electrolyte inlet 5o Electrolyte outlet 6 Rib 7 Gasket (Electrolytic gasket) 7a Inner edge of gasket 7b Hollow part 7c Projection 7d Groove 7e One surface 7f Other surface 7g Core material 8 Flange part 81 Flange surface 10 Header 10ai Anode inlet header 10ao Anode outlet header 10ci Cathode inlet header 10co Cathode outlet header 20ao Anode collection tube 20co Cathode collection tube 50 Electrolytic cell 51g Fast head, loose head 51i Insulating plate 51a Anode terminal element 51c Cathode terminal element 51r Tie rod 60 Electrolytic cell element (bipolar element) 65 Electrolytic cell 70 Electrolytic device 71 Liquid transfer pump 72 Gas-liquid separation tank 74 Rectifier 75 Oxygen concentration meter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve D1 Electrolyte passage direction Z Zero gap structure L1 Distance from inner circumference end 7a to projection of 1 mm or more in height that extends circumferentially on one of the innermost surfaces 7e L2 Distance from inner circumference end 7a to groove of 0.1 mm or more in depth that extends circumferentially on the other innermost surface 7f L3 Distance from inner circumference end of core material 7g to inner circumference end 7a of gasket L4 Distance from inner circumference end 7a of electrolytic gasket 7 to inner circumference end of flange surface 81 of flange portion 8 R: In the cross-section in the thickness direction, the region enclosed by the inner end of the innermost groove, the outer end of the outermost groove, the other surface, and a line following the shape of the one surface. V: The total area occupied by the gasket in region R.W is the sum of the areas of the spatial parts in region R.

Claims

1. An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least one projection with a height of 1 mm or more extending circumferentially is provided on one surface, and at least one groove with a depth of 0.1 mm or more extending circumferentially is provided on the other surface, and when L1 is the distance from the inner circumference side end to the innermost projection and L2 is the distance from the inner circumference side end to the innermost groove, the following equation (1) is satisfied: L1 / L2 ≤ 3 (1) 2. An electrolytic gasket in the shape of a frame having a hollow portion on its inner circumference, wherein at least one groove with a depth of 0.1 mm or more is provided on the other surface, and when the distance from the inner circumference end to the innermost groove is L2, in a gasket compression test in which the gasket is compressed with an average surface pressure of 2 MPa, the innermost point on the other surface where the surface pressure is 3.0 MPa or more lies within the range of L2.

3. The electrolytic gasket according to claim 1 or 2, wherein the other surface has a plurality of grooves, and in a cross-section in the thickness direction, when W is the total area of ​​the space in the region enclosed by the inner end of the innermost groove, the outer end of the outermost groove, the other surface, and a line following the shape of the one surface, and V is the total area occupied by the gasket, the following equation (2) is satisfied: 1 ≤ V / W ≤ 15 (2) 4. An electrolytic gasket according to claim 1 or 2, having a core material inside, wherein when the distance L3 is from the inner circumference end of the core material to the inner circumference end of the gasket, the following formula (3) is satisfied: L3 ≤ L1 (3) 5. An electrolytic gasket according to claim 1 or 2, used on the anode side.

6. An electrolytic cell comprising the electrolytic gasket according to claim 1 or 2.

7. The electrolytic cell according to claim 6, wherein the electrolytic gasket is provided between the electrolytic frame and the diaphragm, the electrolytic frame has a flange portion around its periphery where a part of the surface is a flange surface, and the distance L4 from the inner circumferential end of the electrolytic gasket to the inner circumferential end of the flange surface is 5 mm or less.

8. A method for producing hydrogen using the electrolytic cell described in claim 6.

Images