Diaphragm for alkaline water electrolysis

Abstract

To provide a diaphragm for alkaline water electrolysis with excellent crack resistance against tensile stress.SOLUTION: A diaphragm for alkaline water electrolysis comprises a porous membrane containing an organic resin and inorganic particles, and a porous support. The porous membrane is formed on one or both main surfaces of the porous support and within pores of the porous support. The content of the organic resin is 30 to 42 pts.mass relative to 100 pts.mass of the inorganic particles. From the diaphragm for alkaline water electrolysis, a rectangular test specimen having a length of 10 cm along a cut-out direction and a width of 3 cm is cut out, and two ends of the test specimen in a longitudinal direction are each gripped by jigs. When the test specimen is stretched in the longitudinal direction at a speed of 10 mm / min at 25°C, a distance between the two jigs before stretching is defined as X mm. When a crack having a length of 1.0 mm or more occurs in the test specimen from one end to the other end, a displacement amount of the distance between the two jigs before and after stretching is defined as Y mm. In the test specimen cut out in any direction, (Y / X) is 0.08 to 0.20.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a diaphragm for alkaline water electrolysis. [Background technology]

[0002] The use of alkaline water electrolysis devices to produce hydrogen gas as an energy resource is being considered. Alkaline water electrolysis devices are equipped with an alkaline water electrolysis diaphragm that separates the anode chamber and the cathode chamber in the electrolytic cell.

[0003] When the diaphragm for alkaline water electrolysis is installed in the apparatus or during operation of the apparatus, the diaphragm is subjected to various forces such as tension. Therefore, if the mechanical strength of the diaphragm is insufficient, cracks may occur in the diaphragm, and the diaphragm may not be able to fully function as a diaphragm.

[0004] Various studies have been conducted to improve the mechanical strength of diaphragms for alkaline water electrolysis. For example, Patent Document 1 describes a diaphragm for alkaline water electrolysis that maintains gas barrier properties and has high ion permeability even when physical damage occurs to the membrane surface, by adjusting the average pore sizes on a predetermined membrane surface to a specific relationship. Furthermore, Patent Document 2 describes an inorganic-organic composite membrane that has high membrane strength and excellent flexibility, achieved by using a nonwoven fabric having an average fiber diameter within a specific range as a support. Furthermore, Patent Document 3 describes a diaphragm for alkaline water electrolysis that has a membrane structure that suppresses the formation of macrovoids inside the membrane by adding lithium chloride, and that has excellent membrane strength and ion conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-129563 [Patent Document 2] Japanese Patent Publication No. 2020-7574 [Patent Document 3] Patent Publication No. 2021-25076 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional diaphragms for alkaline water electrolysis have only been evaluated based on their strength when the diaphragm breaks due to tensile stress, and the occurrence of cracks due to tensile stress has not been considered. During use of the diaphragm, the performance of the diaphragm may be degraded even when cracks occur rather than when rupture occurs. Therefore, further improvement in the crack resistance of diaphragms is desired.

[0007] The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a diaphragm for alkaline water electrolysis that has excellent resistance to cracking against tensile stress. [Means for solving the problem]

[0008] The present inventors have conducted extensive studies on diaphragms for alkaline water electrolysis and have found that a diaphragm for alkaline water electrolysis comprising a porous membrane containing an organic resin and inorganic particles and a porous support, where the porous membrane is formed on one or both main surfaces of the porous support and in pores in the porous support, can have excellent resistance to cracking against tensile stress by containing the organic resin and the inorganic particles in a specific range of ratio and having a specific value related to tensile stress, thereby completing the present invention.

[0009] That is, the present invention provides the following aspects. [1] A diaphragm for alkaline water electrolysis comprising: a porous membrane containing an organic resin and inorganic particles; and a porous support, the porous membrane being formed on one or both main surfaces of the porous support and in pores in the porous support, wherein the organic resin content is 30 to 42 parts by mass per 100 parts by mass of the inorganic particles. A rectangular test piece measuring 10 cm in the cutting direction and 3 cm in width is cut from the diaphragm for alkaline water electrolysis, and the thickness of the test piece in the longitudinal direction is measured. a diaphragm for alkaline water electrolysis, characterized in that when the test piece is stretched in the longitudinal direction at a rate of 10 mm / min at 25°C, and the distance between the two jigs before stretching is X mm, and the amount of displacement in the distance between the two jigs before and after stretching at which a crack measuring 1.0 mm or more from one end to the other occurs in the test piece after stretching is Y mm, the ratio (Y / X) of the test piece cut out in either direction is 0.08 to 0.20. [2] The diaphragm for alkaline water electrolysis according to [1] above, wherein the organic resin comprises at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone. [3] The diaphragm for alkaline water electrolysis according to [1] or [2] above, wherein the inorganic particles comprise at least one selected from the group consisting of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate. [4] The diaphragm for alkaline water electrolysis according to any of [1] to [3] above, wherein the porous support is a nonwoven fabric, woven fabric, or mesh comprising at least one material selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide. [Effects of the Invention]

[0010] The diaphragm for alkaline water electrolysis of the present invention has excellent resistance to cracking against tensile stress. Use of the diaphragm for alkaline water electrolysis of the present invention enables efficient alkaline water electrolysis. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 10 is a diagram showing an example of a direction in which a test piece is cut out from a diaphragm for alkaline water electrolysis. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. A combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention. In this description, a numerical range indicated as "X to Y" means "at least X and at most Y." For example, "30 to 42 parts by mass" means "at least 30 parts by mass and at most 42 parts by mass."

[0013] <Diaphragm for alkaline water electrolysis> The present invention provides a diaphragm for alkaline water electrolysis, comprising: a porous membrane containing an organic resin and inorganic particles; and a porous support, the porous membrane being formed on one or both main surfaces of the porous support and in pores in the porous support, wherein the content of the organic resin is 30 to 42 parts by mass relative to 100 parts by mass of the inorganic particles. When a rectangular test piece having a length of 10 cm in the cutting direction and a width of 3 cm is cut from the diaphragm for alkaline water electrolysis and the test piece is stretched in the longitudinal direction at a rate of 10 mm / min at 25°C while each of two longitudinal ends of the test piece is held by a jig, the distance between the two jigs before stretching is X mm, and the amount of displacement in the distance between the two jigs before and after stretching when a crack measuring 1.0 mm or more from one end to the other occurs in the test piece is Y mm, the ratio (Y / X) of the test piece cut in either direction is 0.08 to 0.20.

[0014] The diaphragm for alkaline water electrolysis of the present invention comprises a porous membrane containing an organic resin and inorganic particles, and a porous support, wherein the porous membrane is formed on one or both main surfaces of the porous support and in pores of the porous support. "The porous membrane is formed in the pores of the porous support" means that the porous support is porous and has pores, and components constituting the porous membrane are impregnated into the pores to form the porous membrane.

[0015] In the diaphragm for alkaline water electrolysis, the content of the organic resin is 30 to 42 parts by mass relative to 100 parts by mass of the inorganic particles. When the content of the organic resin is 30 parts by mass or more relative to 100 parts by mass of the inorganic particles, the diaphragm has excellent resistance to cracking against tensile stress. When the content of the organic resin is 42 parts by mass or less relative to 100 parts by mass of the inorganic particles, the diaphragm has excellent resistance to cracking against tensile stress without excessively increasing membrane resistance. In order to achieve a better balance between crack resistance and membrane resistance, the content of the organic resin is preferably 32 to 40 parts by mass relative to 100 parts by mass of the inorganic particles.

[0016] In the diaphragm for alkaline water electrolysis, when a rectangular test piece 10 cm long and 3 cm wide is cut from the diaphragm, and the two longitudinal ends of the test piece are gripped with jigs and stretched in the longitudinal direction at a rate of 10 mm / min at 25°C, the ratio (Y / X) is 0.08 to 0.20, where X mm is the distance between the two jigs before stretching and Y mm is the amount of change in the distance between the two jigs before and after stretching when a crack measuring 1.0 cm or more from one end to the other occurs in the test piece after stretching. When (Y / X) is in the above range, the diaphragm has excellent crack resistance against tensile stress. The ratio (Y / X) is preferably 0.13 to 0.20, more preferably 0.15 to 0.20, and even more preferably 0.17 to 0.20.

[0017] Y and X are determined by the method described below using a rectangular test piece cut from a diaphragm for alkaline water electrolysis, the test piece having a length of 10 cm along the cutting direction and a width of 3 cm. That is, the test piece has a rectangular shape of 10 cm long x 3 cm wide. The test piece may have a dimensional error of several millimeters in both length and width. The direction in which the rectangular test piece is cut from the diaphragm is not particularly limited, and any direction may be used. Fig. 1 shows an example of a direction in which a test piece may be cut from a diaphragm for alkaline water electrolysis. For example, as shown in Fig. 1, when the main surface of the diaphragm for alkaline water electrolysis has a rectangular shape, the cutting direction of the test piece may be the same as the lateral direction of the diaphragm, or may be oblique to the lateral direction (for example, a direction at an angle of 45° to the lateral direction), or may be perpendicular to the lateral direction. Even when the main surfaces of the diaphragm for alkaline water electrolysis have other rectangular or circular shapes, the cut-out direction of the test specimen may be parallel to, oblique to (for example, at an angle of 45° to the horizontal direction), or perpendicular to an arbitrarily selected reference direction. Thus, the diaphragm for alkaline water electrolysis of the present invention may be any test specimen cut in any direction from the diaphragm so long as the (Y / X) value falls within the above-mentioned range.

[0018] The test piece cut out from the diaphragm is held at two longitudinal ends with jigs and stretched at 25°C in the longitudinal direction at a speed of 10 mm / min. When the two longitudinal ends of the test piece are held with jigs, the test piece is fixed so that there is no slack. The distance between the two jigs before stretching is defined as X mm. X is not particularly limited, but is preferably 45 to 55 mm.

[0019] The stretching is carried out in an environment at 25°C, but it is preferably carried out in an environment at 25°C and a relative humidity of 40 to 60% in order to keep the moisture absorption amount of the test piece constant.

[0020] The test piece is stretched until a crack appears on the test piece, the distance from one end to the other being 1.0 cm or more, which distance can be measured by a known method.

[0021] The occurrence of cracks is confirmed visually. Therefore, it is preferable to check for the occurrence of cracks under bright conditions, such as by illuminating the test piece with light. For example, the illuminance when checking for cracks is preferably 500 to 2500 lx (lux) when an illuminance meter is placed 5 mm from the surface of the test piece, and the light intensity indicated by the illuminance meter is 750 to 2000 lx, more preferably 900 to 1500 lx.

[0022] The porous membrane and porous support constituting the diaphragm for alkaline water electrolysis of the present invention are described below.

[0023] (porous membrane) The porous membrane is a membrane having pores and contains an organic resin and inorganic particles.

[0024] Examples of the organic resin include fluorine-based resins, olefin-based resins, and aromatic hydrocarbon-based resins.

[0025] Examples of the fluorine-based resin include ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, and the like.

[0026] Examples of the olefin resin include polyethylene, polypropylene, polybutene, and polymethylpentene.

[0027] Examples of the aromatic hydrocarbon resin include polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyarylate, polyetherimide, polyimide, and polyamideimide.

[0028] The organic resin preferably contains an aromatic hydrocarbon resin, more preferably at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, and even more preferably polysulfone, in view of its excellent heat resistance, alkali resistance, and solubility in solvents. The organic resin may contain only one type, or may contain two or more types.

[0029] The content of the organic resin is preferably 20 to 30 mass %, more preferably 22 to 28 mass %, based on 100 mass % of the porous membrane.

[0030] Examples of the inorganic particles include metal hydroxides or oxides such as magnesium, zirconium, titanium, zinc, aluminum, and tantalum; sulfates such as calcium, barium, lead, and strontium; nitrides such as titanium, zirconium, and hafnium; and carbides such as titanium, zirconium, and hafnium. To further improve ion permeability, the inorganic particles preferably contain at least one selected from the group consisting of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate, and more preferably contain at least one selected from the group consisting of magnesium hydroxide and zirconium oxide. The inorganic particles may contain only one type, or two or more types.

[0031] The inorganic particles may be surface-untreated or surface-treated, for example, by known surface treatments using a silane coupling agent, stearic acid, oleic acid, phosphate ester, or the like.

[0032] The shape of the inorganic particles is not particularly limited, and may be any of amorphous, granular, granular, plate-like (e.g., flaky, hexagonal plate-like), fibrous, etc. Among these, granular, plate-like, and fibrous shapes are preferred in terms of ease of dispersion in a solution to prepare a coating solution, and granular and plate-like shapes are more preferred, plate-like shapes are even more preferred, and flaky shapes are particularly preferred in terms of adhesion to a resin and ion permeability.

[0033] The inorganic particles preferably have an average particle size of 0.01 to 1.5 μm. When the average particle size of the inorganic particles is within the above range, the ion permeability and gas barrier properties are excellent. In order to further improve the ion permeability and gas barrier properties, the average particle size of the inorganic particles is more preferably 0.1 to 1.0 μm, and even more preferably 0.2 to 0.5 μm.

[0034] The average particle size is the volume-average particle size (D50) determined by measuring particle size distribution using a laser diffraction method. Specifically, the average particle size is determined by measuring particle size distribution using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd., Model LA-950), and the median diameter (D50) in the volume-based particle size distribution is taken as the average particle size. The inorganic particles are mixed with a 0.2% by mass aqueous solution of sodium hexametaphosphate and dispersed by ultrasonic irradiation to prepare a measurement sample. Specifically, the average particle size can be determined by the method described in the Examples below.

[0035] The aspect ratio of the inorganic particles is preferably 2.0 to 8.0. When the aspect ratio of the inorganic particles is within the above range, the ion permeability and gas barrier properties are excellent. In order to further improve the ion permeability and gas barrier properties, the aspect ratio of the inorganic particles is more preferably 2.5 to 7.0, and even more preferably 3.0 to 6.0.

[0036] In this specification, the aspect ratio refers to the ratio [(a) / (b)] of the longest diameter (a) to the shortest diameter (b). Inorganic particles are observed using an SEM, and the ratio [(a) / (b)] is measured for each of any 10 inorganic particles in the obtained image using analysis software. The average value of the ratios [(a) / (b)] for the 10 inorganic particles is taken as the aspect ratio of the inorganic particle. Usually, the shortest diameter (b) is taken as the diameter perpendicular to the longest diameter.

[0037] The specific surface area of ​​the inorganic particles is 5 to 35 m 2 / g. When the specific surface area of ​​the inorganic particles is in the above range, the particles have excellent ion permeability. The specific surface area of ​​the inorganic particles is preferably 5.5 to 25 m 2 / g is more preferable, and 6 to 20m 2 The specific surface area can be determined by measurement using a BET specific surface area meter, and specifically, by the method described in the examples below.

[0038] The content of the inorganic particles is preferably 60 to 95 mass %, more preferably 65 to 92 mass %, and even more preferably 75 to 90 mass %, based on 100 mass % of the porous membrane.

[0039] The porous film may contain other components in addition to the organic resin and inorganic particles described above.

[0040] The thickness of the porous membrane is preferably 50 to 1000 μm, more preferably 100 to 500 μm, in order to further improve ion permeability, gas barrier properties, and strength.

[0041] (porous support) The porous support is a porous member that serves as a support for the diaphragm for alkaline water electrolysis. The porous support is preferably a sheet-like member.

[0042] Examples of materials for the porous support include resins such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyketone, polyimide, polyetherimide, and fluorine-based resins. These may be used alone or in combination of two or more. Among these, at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide is preferred, as it can exhibit excellent heat resistance and alkali resistance, and at least one resin selected from the group consisting of polypropylene and polyphenylene sulfide is more preferred.

[0043] Examples of the form of the porous support include nonwoven fabric, woven fabric, mesh, porous membrane, and a mixed fabric of nonwoven fabric and woven fabric. Preferably, nonwoven fabric, woven fabric, or mesh is used, more preferably nonwoven fabric or mesh, and even more preferably nonwoven fabric.

[0044] The porous support used in the present invention is preferably a nonwoven fabric, woven fabric, or mesh containing at least one resin selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide, and more preferably a nonwoven fabric or mesh containing polyphenylene sulfide.

[0045] When the porous support is in the form of a sheet, the thickness of the porous support is not particularly limited as long as the diaphragm for alkaline water electrolysis of the present invention can exhibit the effects of the present invention; however, the thickness is preferably 30 to 1000 μm, and more preferably 50 to 500 μm.

[0046] When the porous support is in the form of a sheet, the mass per unit area is 20 to 200 g / m 2 When the mass per unit area is within the above range, the ion permeability and gas barrier properties are excellent. The mass per unit area of ​​the porous support is more preferably 40 to 150 g / m 2 , more preferably 60 to 100 g / m2 is.

[0047] The porous support may have anisotropy in mechanical strength. That is, when the porous support is in the form of a sheet, the mechanical strength may be different in one direction from that in a direction perpendicular to the one direction.

[0048] The thickness of the diaphragm for alkaline water electrolysis is not particularly limited and may be appropriately selected depending on the size and handleability of the equipment to be used, etc.; however, from the viewpoints of the balance between membrane resistance and crack resistance of the diaphragm, gas barrier property, ion permeability, etc., the thickness is preferably 50 to 1000 μm, and more preferably 100 to 500 μm.

[0049] The porosity of the diaphragm for alkaline water electrolysis is preferably 20 to 80% by volume, more preferably 25 to 75% by volume, and even more preferably 30 to 70% by volume. When the porosity is within the above range, the pores in the membrane are continuously filled with the electrolytic solution, resulting in a membrane with excellent ion permeability and gas barrier properties. The porosity can be determined by immersing the diaphragm for alkaline water electrolysis in the electrolytic solution overnight and measuring the mass of the diaphragm before and after absorbing the electrolytic solution. Specifically, it can be determined using the following formula: Porosity (volume %) = [(mass of diaphragm after immersion - mass of diaphragm before immersion) / density of electrolyte] × 100

[0050] The membrane resistance of the diaphragm for alkaline water electrolysis is preferably 0.1 to 0.25 Ωcm in order to provide good electrolysis efficiency. 2 Preferably, the resistance is 0.1 to 0.22 Ωcm. 2 It is more preferable that:

[0051] The diaphragm for alkaline water electrolysis can be suitably used in an alkaline water electrolysis apparatus, and can be suitably used as a diaphragm separating an anode chamber from a cathode chamber in an alkaline water electrolysis apparatus.

[0052] <Method of manufacturing diaphragms for alkaline water electrolysis> The method for producing the diaphragm for alkaline water electrolysis of the present invention is not particularly limited and includes known methods. However, in terms of efficient production, a method including step (1) of mixing an organic resin and inorganic particles to prepare a porous membrane-forming composition, and step (2) of bringing the porous membrane-forming composition into contact with a porous support to form a porous membrane is preferred.

[0053] Step (1) is a step of preparing a composition for forming a porous film. The composition for forming a porous film is prepared by mixing the organic resin and inorganic particles described above in the content ratio described above. The mixing of the organic resin and inorganic particles is not particularly limited, and for example, the inorganic particles may be mixed with a resin solution in which the organic resin is dissolved in a solvent, or the organic resin may be mixed with a dispersion (slurry) in which the inorganic particles are dispersed in a solvent, or the resin solution and the dispersion may be mixed.

[0054] The solvent used for the resin solution or dispersion is not particularly limited as long as it has the property of being able to dissolve the organic resin, and examples thereof include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, etc. These solvents may be used alone or in combination of two or more.

[0055] The content of the organic resin in the resin solution is not particularly limited, but is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and even more preferably 20 to 40% by mass.

[0056] The content of inorganic particles in the dispersion is not particularly limited, but is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 40 to 60% by mass.

[0057] The dispersion may further contain a dispersant to improve the dispersibility of the inorganic particles. Examples of the dispersant include known dispersants such as polyester phosphate, polyvinylpyrrolidone, and polyacrylic acid.

[0058] The porous membrane-forming composition preferably does not contain lithium chloride. In the production of a diaphragm for alkaline water electrolysis, lithium chloride is sometimes added to suppress the formation of macrovoids, but in the present invention, the addition of lithium chloride may cause aggregation of the organic resin, which may reduce the crack resistance of the diaphragm against tensile stress, and therefore it is preferable not to use lithium chloride.

[0059] When preparing the resin solution and the dispersion or when mixing them, known devices can be used, such as a mixer, bead mill, ball mill, jet mill, disperser, sand mill, roll mill, pot mill, paint shaker, etc. Among them, a mixer and a disperser are preferred because they facilitate uniform mixing of the organic resin and the inorganic particles. If the organic resin and the inorganic particles can be mixed more uniformly, the crack resistance against tensile stress can be further improved.

[0060] The temperature during mixing may be set appropriately depending on the type of solvent used, etc., but in order to mix the organic resin and inorganic particles more uniformly, it is preferably 35°C or higher, more preferably 37 to 50°C, and even more preferably 40 to 45°C.

[0061] The mixing time is not particularly limited, but is preferably 45 minutes or more, more preferably 60 to 180 minutes, and even more preferably 60 to 120 minutes, in order to mix the organic resin and inorganic particles more uniformly.

[0062] The mixing is preferably carried out at a rotation speed of 50 rpm or more, more preferably 100 to 1500 rpm, and even more preferably 150 to 1000 rpm per minute.

[0063] Step (2) is a step of contacting the porous membrane-forming composition obtained in step (1) with a porous support to form a porous membrane. The step of forming the porous membrane is not particularly limited, but preferably includes the following steps (2-1) to (2-3) in terms of efficient production. (2-1) Step of applying the porous membrane-forming composition to a porous support (2-2) A step of contacting the coated porous support with a non-solvent (2-3) Step of drying the porous support after the contact

[0064] Step (2-1) is a step of applying the porous membrane forming composition obtained in the above step (1) to a porous support.

[0065] The coating method is not particularly limited, and includes known methods such as die coating, spin coating, gravure coating, curtain coating, spraying, and methods using an applicator or coater.

[0066] The amount of the porous membrane-forming composition to be applied is not particularly limited, but is preferably an amount that allows the porous membrane-forming composition to be impregnated into the entire porous support. For example, when a sheet-like porous support is used, it is preferable to apply the porous membrane-forming composition to one surface of the porous support and allow it to be impregnated into the other surface of the porous support. The amount of the porous membrane-forming composition to be applied may be appropriately determined depending on the thickness of the porous support, but is preferably 60 to 400 g / m 2 It is preferable that the density is 80 to 350 g / m 2 More preferably, it is 100 to 300 g / m 2 It is more preferable that:

[0067] Step (2-2) is a step of contacting the porous support with a non-solvent after the porous film-forming composition has been applied in step (2-1). By contacting the applied porous support with a non-solvent, the non-solvent diffuses into the applied porous film-forming composition, and the organic resin that is not soluble in the non-solvent solidifies. Meanwhile, the solvent in the porous film-forming composition that is soluble in the non-solvent dissolves. Such phase separation causes the organic resin to solidify, forming a film (porous film) containing inorganic particles and having pores.

[0068] Examples of the method for contacting the porous support with the non-solvent include a method in which the porous support is immersed in the non-solvent (coagulation bath).

[0069] The non-solvent is not particularly limited as long as it is a solvent that does not substantially dissolve the organic resin, and examples thereof include water (ion-exchanged water); lower alcohols such as methanol, ethanol, and propyl alcohol; or mixed solvents thereof, among which water is preferred from the viewpoints of economy and wastewater treatment. In addition to the above-mentioned components, the non-solvent may also contain a small amount of the same solvent as the solvent contained in the coating film.

[0070] Step (2-3) is a step of drying the porous support after contacting with the non-solvent in the above step (2-2). The coating film solidified in the above step (2-2) is dried to remove the non-solvent, thereby forming a porous film.

[0071] The drying method is not particularly limited and can be performed by a known method. The drying temperature is preferably 60 to 150° C., more preferably 70 to 140° C. The drying time is preferably 0.5 to 120 minutes, more preferably 1 to 60 minutes, and even more preferably 1 to 30 minutes.

[0072] The diaphragm for alkaline water electrolysis can be efficiently produced by the non-solvent induced phase separation (NIPS) method including the above-described step (1) and steps (2-1) to (2-3). [Example]

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] The conditions for measuring various physical properties in the present examples are as follows: <Measurement method> (1) Particle size of inorganic particles Inorganic particles (powder) were mixed with a 0.2 mass% aqueous solution of sodium hexametaphosphate and dispersed using an ultrasonic cleaner to obtain an inorganic particle dispersion. The particle size distribution of the inorganic particle dispersion was measured using a laser diffraction / scattering particle size distribution analyzer (product name: LA-950, manufactured by Horiba, Ltd.) by adjusting the red laser transmittance to 90-98% and the blue laser transmittance to 85-92%, and the median diameter (d50) in the obtained volume-based particle size distribution was taken as the average particle size (μm) of the inorganic particles.

[0075] (2) Specific surface area of ​​inorganic particles The specific surface area of ​​the inorganic particles was measured using a BET specific surface area meter (trade name: Macsorb HM model-1210, manufactured by Mountec Co., Ltd.). Specifically, 1 g of inorganic particles (powder) was placed in a cell as a measurement sample, and degassing was performed at 200°C while nitrogen gas was circulating through the cell. After degassing, the cell was immersed in liquid nitrogen while nitrogen gas was circulating through the cell, and nitrogen was adsorbed onto the measurement sample at a temperature of -196°C. Next, the cell was kept at room temperature, and the amount of desorbed nitrogen was measured to measure the specific surface area by the BET method. Measurements were performed three times for each sample, and the average value was used as the specific surface area (m 2 / g).

[0076] (3) Thickness of diaphragm for alkaline water electrolysis The thicknesses of the porous support and the diaphragm for alkaline water electrolysis were measured using a Digimatic micrometer (product name: Coolant Proof Micrometer MDC-PXT, manufactured by Mitutoyo Corporation). Measurements were taken at 10 random points, and the average value was defined as the membrane thickness.

[0077] (4) Crack resistance Three test pieces measuring 10 cm in length and 3 cm in width were cut from the alkaline water electrolysis diaphragm. The test pieces were mounted on a Shimadzu AG-1kNXPlus autograph. The porous membrane side was positioned toward the user, and the short edge was gripped with a jig. The distance between the grippers was 50 mm (X). An LED light was installed 10 cm away from the porous support, illuminating the test piece so that the light intensity at a position 5 mm from the surface of the test piece was 1200 lx. The test piece was stretched at a sweep rate of 10 mm / min and a temperature of 25°C. During stretching, the occurrence of a crack with a distance of 1.0 mm or more between the end points was visually determined by transmitted light observation, and the displacement (Y) of the jig distance until the crack occurred was measured. The Y / X value was calculated using the following formula. The remaining two test pieces were similarly measured, and the average Y / X value was calculated. Y / X = (displacement of jig distance until crack occurs, Y) / (distance between jigs before stretching, X)

[0078] (5) Membrane resistance For each of the diaphragms for alkaline water electrolysis obtained in each Example, etc., two diaphragm samples for measurement were prepared. Cells formed using each diaphragm sample with the following cell configuration were allowed to stand in a thermostatic bath at 25°C for 30 minutes, and then AC impedance measurements were performed under the following measurement conditions. The membrane resistance was calculated from the obtained intercept component (Ra) and the intercept component (Rb) when no measurement sample was placed in the cell, using the following formula. The above measurements were performed on two diaphragm samples, and the average of the obtained measured values ​​(at two points) was calculated and defined as the membrane resistance of the diaphragm. [Membrane resistance (Ωcm 2 )] = (Ra - Rb) × 1.77 (Measurement conditions) Cell configuration Working electrode: Ni plate Counter electrode: Ni plate Electrolyte: 30% by mass potassium hydroxide aqueous solution Sample pretreatment: Immerse in the above electrolyte overnight Effective measurement area: 1.77cm 2 AC impedance measurement conditions Applied voltage: 10mV vs. open circuit voltage Frequency range: 100kHz to 100Hz

[0079] Example 1 (1. Inorganic particle dispersion) Magnesium hydroxide (plate-shaped, average particle size and specific surface area specified) with an average particle size of 0.25 μm and N-methyl-2-pyrrolidone (Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed in a mass ratio of 1:1, and the mixture was dispersed in a paint shaker equipped with zirconia media balls at 50°C for 2 hours to obtain an inorganic particle dispersion.

[0080] (2. Coating liquid) The inorganic particle dispersion and polysulfone (PSU) (Ultrason S3010 manufactured by BASF) were mixed so that the ratio was 35 parts by mass per 100 parts by mass of magnesium hydroxide. The solid content of this mixture was 45% by mass. The resulting mixture was stirred four times using a planetary centrifugal mixer (Thinky Corporation's Awatori Rentaro ARE-500) at 40°C and 1000 rpm for 30 minutes each time. In this way, a coating liquid was obtained.

[0081] (3. Diaphragms for alkaline water electrolysis) Nonwoven fabric made of polyphenylene sulfide fiber (basis weight: 100 g / m 2 , film thickness: 190 μm) on one side of the surface, using an applicator, the amount of coating was 260 g / m 2 The coating solution was applied to the substrate. The substrate was then immersed in a water tank filled with ion-exchanged water at room temperature (25°C) for 3 minutes to solidify the coating solution. The resulting membrane was dried in a dryer at 80°C for 30 minutes to obtain a diaphragm for alkaline water electrolysis. The resulting diaphragm for alkaline water electrolysis had a membrane thickness of 260 μm.

[0082] <Example 2> A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amount of polysulfone was 30 parts by mass per 100 parts by mass of magnesium hydroxide. The membrane thickness was 240 μm.

[0083] Example 3 A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amount of polysulfone was 42 parts by mass per 100 parts by mass of magnesium hydroxide. The membrane thickness was 280 μm.

[0084] <Comparative Example 1> A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amount of polysulfone was 50 parts by mass per 100 parts by mass of magnesium hydroxide. The membrane thickness was 270 μm.

[0085] <Comparative Example 2> A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amount of polysulfone was 25 parts by mass per 100 parts by mass of magnesium hydroxide. The membrane thickness was 260 μm.

[0086] <Comparative Example 3> A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amount of polysulfone was changed to 30 parts by mass per 100 parts by mass of magnesium hydroxide, and the mixed liquid of the inorganic particle dispersion and polysulfone was stirred once at 1,000 rpm for 5 minutes at room temperature. The membrane thickness was 280 μm.

[0087] <Comparative Example 4> A diaphragm for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the content of polysulfone was 33 parts by mass relative to 100 parts by mass of magnesium hydroxide, lithium chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added in an amount of 5% by mass relative to 100% by mass of magnesium hydroxide, and the solids content of the mixed solution was 45% by mass. The membrane thickness was 250 μm.

[0088] Table 1 shows the results of the crack resistance and membrane resistance of the diaphragms for alkaline water electrolysis obtained in the above Examples and Comparative Examples.

[0089] [Table 1]

[0090] Table 1 shows that a diaphragm for alkaline water electrolysis containing 30 to 42 parts by mass of polysulfone per 100 parts by mass of magnesium hydroxide has a Y / X ratio of 0.08 or more, is excellent in crack resistance, and has low membrane resistance.

[0091] The results of Comparative Examples 3 and 4 revealed that even when the diaphragm for alkaline water electrolysis contains 30 to 42 parts by mass of polysulfone per 100 parts by mass of magnesium hydroxide, the Y / X ratio may be less than 0.08 depending on the production method, and the crack resistance may be insufficient. [Explanation of symbols]

[0092] 1. Diaphragms for alkaline water electrolysis 2 test specimens

Claims

1. A porous membrane containing an organic resin and inorganic particles and a porous support, a diaphragm for alkaline water electrolysis, the porous membrane being formed on one or both main surfaces of the porous support and in pores of the porous support, the content of the organic resin is 30 to 42 parts by mass relative to 100 parts by mass of the inorganic particles, a diaphragm for alkaline water electrolysis wherein a rectangular test piece having a length of 10 cm in the cutting direction and a width of 3 cm is cut from the diaphragm for alkaline water electrolysis, the test piece is held at two longitudinal ends with jigs and stretched in the longitudinal direction at 25°C at a rate of 10 mm / min, where X mm is the distance between the two jigs before stretching and Y mm is the amount of displacement in the distance between the two jigs before and after stretching when a crack measuring 1.0 mm or more from one end to the other occurs in the test piece after stretching, such that (Y / X) is 0.08 to 0.20 for the test piece cut out in either direction.

2. The diaphragm for alkaline water electrolysis according to claim 1, wherein the organic resin comprises at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone.

3. The diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the inorganic particles comprise at least one selected from the group consisting of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate.

4. The diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the porous support is a nonwoven fabric, a woven fabric, or a mesh comprising at least one material selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide.

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