Diaphragm for alkaline water electrolysis

Abstract

To provide a diaphragm for alkaline water electrolysis capable of sufficiently suppressing falling of inorganic particles while having a sufficiently practical membrane resistance.SOLUTION: A diaphragm for alkaline water electrolysis comprising a porous support and a porous membrane provided on one or both principal surfaces of the porous support and containing inorganic particles and an organic resin, the diaphragm further comprising a coating membrane covering at least a part of one or both principal surfaces of a main body layer composed of the porous support and the porous membrane, the coating membrane containing a first resin having a neutral or basic polar functional group.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conventionally, a diaphragm for alkaline water electrolysis has been known that contains inorganic particles, an organic resin, and a porous support. One of the challenges facing such a diaphragm for alkaline water electrolysis is to prevent the inorganic particles from falling off (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-90909 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure has been made in light of the above-described current situation, and an object of the present disclosure is to provide a diaphragm for alkaline water electrolysis that has a membrane resistance that is sufficiently practical and that can sufficiently suppress separation of inorganic particles. [Means for solving the problem]

[0005] That is, the present disclosure provides the following diaphragm for alkaline water electrolysis: [1] A diaphragm for alkaline water electrolysis comprising: a porous support; and a porous membrane provided on one or both main surfaces of the porous support and comprising inorganic particles and an organic resin, the diaphragm further comprising a coating membrane covering at least part of one or both main surfaces of a main layer comprising the porous support and the porous membrane, the coating membrane comprising a first resin having a neutral or basic polar functional group. [2] The diaphragm for alkaline water electrolysis according to [1] above, wherein the neutral or basic polar functional group is at least one selected from the group consisting of an acetamide group, an acetyl group, an alcoholic hydroxyl group, a methoxy group, and an amino group. [3] The diaphragm for alkaline water electrolysis according to [1] or [2] above, wherein the first resin is at least one selected from the group consisting of vinyl resins, cellulose resins, polyether resins, and polyamine resins. [4] The diaphragm for alkaline water electrolysis according to any of [1] to [3], wherein the first resin is at least one selected from the group consisting of poly-N-vinylacetamide, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, and polyethyleneimine. [5] The diaphragm for alkaline water electrolysis according to any one of [1] to [4], wherein the coating membrane further comprises a second resin other than the first resin. [6] The diaphragm for alkaline water electrolysis according to [5], wherein the second resin comprises at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone. [7] The diaphragm for alkaline water electrolysis according to [5] or [6], wherein the ratio (A / B) of the mass (A) of the first resin to the mass (B) of the second resin in the coating membrane is 0.2 to 3.5. [8] The diaphragm for alkaline water electrolysis according to any one of [5] to [7] above, wherein the coating membrane comprises the first resin and the second resin. [9] The diaphragm for alkaline water electrolysis according to any of [1] to [8], wherein the porous membrane further comprises, in a surface portion in contact with the coating membrane, a first resin having a neutral or basic polar functional group, in addition to the organic resin.

[10] The diaphragm for alkaline water electrolysis according to any of [1] to [9] above, 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.

[11] The diaphragm for alkaline water electrolysis according to any of [1] to

[10] , wherein the inorganic particles comprise at least one selected from the group consisting of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate.

[12] The diaphragm for alkaline water electrolysis according to any of [1] to

[11] above, wherein the organic resin comprises at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone.

[13] The membrane resistance is 0.10 to 1.00 Ωcm 2 The diaphragm for alkaline water electrolysis according to any one of the above [1] to

[12] , [Effects of the Invention]

[0006] The diaphragm for alkaline water electrolysis according to the present disclosure has a membrane resistance that is sufficiently practical, and is capable of suppressing the shedding of inorganic particles. [Brief explanation of the drawings]

[0007] [Figure 1] Fig. 1 shows a backscattered electron image of a main surface of a diaphragm for alkaline water electrolysis obtained in an example, taken by FE-SEM. [Figure 2] FIG. 10 is a diagram showing a method for determining the thickness of a coating film in an example. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present disclosure will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present disclosure described below is also a preferred embodiment of the present disclosure. Note that in this description, a numerical range indicated as "X to Y" means "X or more and Y or less." For example, "0.10 to 1.00 Ωcm 2 " is "0.10cm 2 More than 1.00Ωcm 2 means "below."

[0009] 1. Diaphragms for alkaline water electrolysis The diaphragm for alkaline water electrolysis according to the present disclosure comprises a porous support and a porous membrane provided on one or both main surfaces of the porous support and comprising inorganic particles and an organic resin, and further comprises a coating membrane which covers at least a part of one or both main surfaces of a main layer formed by the porous support and the porous membrane and which comprises a first resin having a neutral or basic polar functional group.

[0010] In the diaphragm for alkaline water electrolysis according to the present disclosure, a component comprising a porous support and a porous membrane is referred to as a main layer. The main layer may comprise a porous support and a porous membrane provided on only one main surface of the porous support, or may comprise a porous support and porous membranes provided on both main surfaces of the porous support. In the latter case, the porous membranes provided on both main surfaces of the porous support may be separate from each other, or may be connected via porous membranes present in the pores of the porous support.

[0011] The diaphragm for alkaline water electrolysis according to the present disclosure further comprises a coating film covering at least a part of one or both main surfaces of the main layer, the coating film comprising a first resin having a neutral or basic polar functional group. The provision of such a specific coating film makes it possible to suppress detachment of inorganic particles contained in the porous membrane while ensuring a sufficiently low and practical membrane resistance.

[0012] It is presumed that the inorganic particles can be prevented from falling off because the coating film physically prevents the inorganic particles from falling off and the inorganic particles are held in place by interacting with the polar groups of the first resin contained in the coating film.

[0013] When a coating membrane is provided on the main layer, the thickness of the diaphragm for alkaline water electrolysis of the present disclosure increases compared to when no coating membrane is provided, and simply speaking, it is expected that the membrane resistance will increase. However, when the coating membrane contains a first resin having a neutral or basic polar functional group, the hydrophilicity of the surface of the diaphragm for alkaline water electrolysis of the present disclosure can be improved, and the membrane resistance can be sufficiently low for practical use.

[0014] The coating membrane is provided on one or both main surfaces of the main layer and is located on the outermost surface of the diaphragm for alkaline water electrolysis of the present disclosure. More specifically, when the main layer comprises a porous support and a porous membrane provided on only one main surface of the porous support, the coating membrane may be provided on the porous membrane, or may be provided on both the porous support and the porous membrane. When the main layer comprises a porous support and porous membranes provided on both main surfaces of the porous support, the coating membrane may be provided on one of the porous membranes, or may be provided on both of the porous membranes.

[0015] The coating film covers at least a portion of one or both main surfaces of the main layer. For example, the coating film preferably covers 30% or more of the area of ​​one main surface of the main layer, more preferably 50% or more, and even more preferably 70% or more. The coating film may cover 100% of the area of ​​one main surface of the main layer. When the coating film covers both main surfaces of the main layer, the coating film preferably covers 30% or more of the area of ​​each main surface, more preferably 50% or more, and even more preferably 70% or more.

[0016] The coating membrane, porous membrane, and porous support constituting the diaphragm for alkaline water electrolysis will now be described.

[0017] (Coating film) The coating film includes a first resin having a neutral or basic polar functional group. The first resin has hydrophilicity and good alkali resistance due to the neutral or basic polar functional group. Examples of the neutral or basic polar functional group include polar functional groups other than acid groups, such as acetamide groups, acetyl groups, alcoholic hydroxyl groups, methoxy groups, and amino groups. The neutral or basic polar functional group is preferably at least one selected from the group consisting of acetamide groups, acetyl groups, alcoholic hydroxyl groups, methoxy groups, and amino groups, more preferably acetamide groups and / or alcoholic hydroxyl groups, and even more preferably acetamide groups.

[0018] The first resin is preferably at least one selected from the group consisting of vinyl resins, cellulose resins, polyether resins, and polyamine resins.

[0019] Examples of the vinyl resin include poly-N-vinylacetamide, polyvinylacetyl, polyvinyl alcohol, polyvinyl ether, polyvinylamine, copolymers of two or more vinyl compounds having a neutral or basic polar functional group, and copolymers of a vinyl compound having a neutral or basic polar functional group and another unsaturated monomer polymerizable with the vinyl compound.

[0020] The other unsaturated monomer polymerizable with the vinyl compound is not particularly limited, and examples thereof include (meth)acrylic acid alkyl esters, silane group-containing unsaturated monomers, halogen atom-containing unsaturated monomers, and epoxy group-containing unsaturated monomers.

[0021] The vinyl resin preferably contains 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less of the structural units derived from the other unsaturated monomers relative to 100% by mass of all structural units (i.e., the total of the structural units derived from the monomer having the neutral or basic polar functional group and the structural units derived from the other unsaturated monomers). The vinyl resin may not contain any structural units derived from the other unsaturated monomers.

[0022] Examples of the cellulose-based resin include cellulose, carboxyalkyl cellulose such as carboxymethyl cellulose, and hydroxyalkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose.

[0023] Examples of the polyether resin include polyalkylene glycols such as polyethylene glycol and polypropylene glycol.

[0024] Examples of the polyamine resin include homopolymers of mono- or diallylamine derivatives, copolymers of two or more mono- or diallylamine derivatives, polyalkyleneimines such as polyethyleneimine, polyalkylenepolyamines, and polyamidepolyamines.

[0025] The coating film may contain only one type of such first resin, or may contain two or more types. From the viewpoint of improving hydrophilicity and alkali resistance, the first resin is preferably at least one selected from the group consisting of poly-N-vinylacetamide, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, and polyethyleneimine, more preferably poly-N-vinylacetamide and / or polyvinyl alcohol, and even more preferably poly-N-vinylacetamide.

[0026] The first resin preferably has a weight-average molecular weight of 10,000 to 3,000,000, more preferably 50,000 to 2,000,000, and even more preferably 100,000 to 1,000,000. The weight-average molecular weight of the first resin is measured by the method described in the examples below.

[0027] From the viewpoint of improving hydrophilicity and alkali resistance, the first resin is preferably one that, when made into a 5% by mass aqueous solution, exhibits a pH of 7 or more and 10 or less at 25° C. The pH of the aqueous solution at 25° C. is measured by the method described in the examples below.

[0028] The coating film preferably further includes a second resin other than the first resin. The term "the coating film includes a second resin other than the first resin" refers to the coating film including a specific resin that corresponds to a "first resin having a neutral or basic polar functional group" and a "second resin" other than the specific resin. However, the second resin may be, for example, a resin other than the first resin having a neutral or basic polar functional group, in other words, a resin that does not have a neutral or basic polar functional group.

[0029] The second resin may be the same as the organic resin contained in the porous membrane described below, for example, fluorine-based resins such as 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; olefin-based resins such as polyethylene, polypropylene, polybutene, polymethylpentene; aromatic hydrocarbon-based resins such as polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyarylate, polyetherimide, polyimide, polyamideimide; etc. The coating membrane may contain only one type of such second resin, or may contain two or more types. From the viewpoints of improving the alkali resistance of the coating membrane and improving the adhesive strength between the porous membrane and the coating membrane, the second resin preferably contains at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, and more preferably contains polysulfone. Furthermore, the second resin also preferably contains the same resin as the organic resin contained in the porous membrane described below. This improves the adhesive strength between the porous membrane and the coating membrane, which is thought to enable the diaphragm for alkaline water electrolysis to be used stably for a longer period of time.

[0030] The ratio (A / B) of the mass (A) of the first resin to the mass (B) of the second resin in the coating membrane is preferably 0.2 to 3.5, from the viewpoints of improving the alkali resistance of the coating membrane and improving the adhesive strength between the porous membrane and the coating membrane. From the viewpoint of further suppressing detachment of the inorganic particles, the ratio (A / B) is more preferably 3 or less, even more preferably 1.5 or less, still more preferably 0.9 or less, still more preferably 0.7 or less, and particularly preferably 0.5 or less. Furthermore, from the viewpoint of further reducing the membrane resistance of the diaphragm for alkaline water electrolysis of the present disclosure, the ratio (A / B) is more preferably 0.4 or more, even more preferably 0.6 or more, still more preferably 0.8 or more, and particularly preferably 2 or more.

[0031] The coating film may contain components other than the first resin and the second resin. For example, the coating film may contain inorganic particles only on the main layer side, for example, by mixing inorganic particles from the porous film. In other words, the coating film may contain inorganic particles only at the boundary with the main layer. The inorganic particles are the same as the inorganic particles contained in the porous film, which will be described later.

[0032] The mass ratio of other components in 100% by mass of the coating film is preferably 10% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. The coating film preferably does not contain other components. In other words, the coating film preferably consists of the first resin and the second resin.

[0033] The thickness of the coating film is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 4 μm, even more preferably 0.3 to 3 μm, and particularly preferably 0.5 to 2 μm, from the viewpoints of further suppressing the dropping of inorganic particles and improving the mechanical strength of the coating film while sufficiently lowering the film resistance for practical use. The thickness of the coating film is measured by the method described in the examples below.

[0034] (porous membrane) The porous film contains inorganic particles and an organic resin.

[0035] Examples of the inorganic particles include hydroxides or oxides of magnesium, zirconium, titanium, zinc, aluminum, tantalum, etc.; sulfates of calcium, barium, lead, strontium, etc.; nitrides of titanium, zirconium, hafnium, etc.; carbides of titanium, zirconium, hafnium, etc. The porous membrane may contain only one type of such inorganic particles, or may contain two or more types.

[0036] The inorganic particles preferably contain at least one selected from the group consisting of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate, more preferably at least one selected from the group consisting of magnesium hydroxide and zirconium oxide, and even more preferably magnesium hydroxide. The total content of magnesium hydroxide, zirconium oxide, titanium oxide, and barium sulfate in the inorganic particles is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0037] The inorganic particles may be surface-treated, for example, by known surface treatments using a silane coupling agent, a fatty acid such as stearic acid or oleic acid, or a phosphate ester.

[0038] The shape of the inorganic particles is not particularly limited, and may be granular, granular, plate-like, fibrous, irregular, or the like.

[0039] The average particle size of the inorganic particles is not particularly limited, but is preferably 0.01 to 1.5 μm, more preferably 0.1 to 1 μm, and even more preferably 0.2 to 0.5 μm. The average particle size of the inorganic particles is measured by the method described in the examples below.

[0040] The aspect ratio of the inorganic particles is not particularly limited, but is preferably 2 to 8, more preferably 2.5 to 7, and even more preferably 3 to 6. The aspect ratio of the inorganic particles is the ratio [(a) / (b)] of the longest diameter (a) to the shortest diameter (b), and is the average value of any 10 inorganic particles in the image obtained by observing the inorganic particles with an SEM.

[0041] The specific surface area of ​​the inorganic particles is not particularly limited, but is preferably 5 to 35 m 2 / g, and 8 to 30m 2 / g is more preferable, and 10 to 25m 2 The specific surface area of ​​the inorganic particles is measured by the method described in the examples below.

[0042] The content of inorganic particles in the porous membrane is not particularly limited, but is preferably 60 to 95 mass %, more preferably 65 to 90 mass %, and even more preferably 70 to 85 mass %, relative to 100 mass % of the porous membrane.

[0043] Examples of the organic resin include fluorine-based resins such as 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; olefin-based resins such as polyethylene, polypropylene, polybutene, and polymethylpentene; aromatic hydrocarbon-based resins such as polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polystyrene, polysulfone, polyethersulfone, polyphenylsulfone, polyarylate, polyetherimide, polyimide, and polyamideimide; and the like. The porous membrane may contain only one type of such organic resin, or may contain two or more types.

[0044] The organic resin preferably contains at least one selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone, and more preferably contains polysulfone. The total content of polysulfone, polyethersulfone, and polyphenylsulfone in the organic resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0045] The content of the organic resin in the porous membrane is not particularly limited, but is preferably 5 to 40 mass %, more preferably 10 to 35 mass %, and even more preferably 15 to 30 mass %, relative to 100 mass % of the porous membrane.

[0046] The porous film may further contain, in addition to the organic resin, a first resin having a neutral or basic polar functional group. For example, the porous film may contain, in addition to the organic resin, a first resin having a neutral or basic polar functional group in the surface portion in contact with the coating film. The first resin contained in the porous film may be a porous film in which a portion of the first resin contained in the coating film-forming composition has been slightly impregnated. This improves the adhesive strength between the porous film and the coating film, making it less likely that problems such as peeling of the coating film will occur even after long-term use.

[0047] In addition, the porous membrane containing a first resin having a neutral or basic polar functional group in addition to the organic resin means that the porous membrane contains a specific organic resin that falls under the category of "organic resin" and also contains a "first resin having a neutral or basic polar functional group" other than the specific organic resin. Thus, the first resin is not limited to anything other than the broad concept of "organic resin." In other words, the porous membrane containing a first resin having a neutral or basic polar functional group in addition to the organic resin means that the porous membrane contains one or more specific organic resins that fall under the category of "organic resin" and one or more resins that are different in the type of main chain and / or functional group from the one or more organic resins and fall under the category of "first resin having a neutral or basic polar functional group." In addition, in calculating the mass percentage and mass ratio, if the porous membrane contains a resin that falls under both the category of "organic resin" and the category of "first resin having a neutral or basic polar functional group," the resin is considered to be a "first resin having a neutral or basic polar functional group."

[0048] The first resin having a neutral or basic polar functional group contained in the porous membrane may be the same as the first resin having a neutral or basic polar functional group contained in the coating membrane. The neutral or basic polar functional group is preferably at least one selected from the group consisting of acetamide, acetyl, alcoholic hydroxyl, methoxy, and amino groups, more preferably acetamide and / or alcoholic hydroxyl, and even more preferably acetamide. The first resin is also preferably at least one selected from the group consisting of vinyl resins, cellulose resins, polyether resins, and polyamine resins. The first resin is preferably at least one selected from the group consisting of poly-N-vinylacetamide, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, and polyethyleneimine, more preferably poly-N-vinylacetamide and / or polyvinyl alcohol, and even more preferably poly-N-vinylacetamide.

[0049] The content of the first resin in the porous membrane is not particularly limited, but is preferably 0.1 to 10 mass %, more preferably 0.3 to 3 mass %, and even more preferably 0.5 to 5 mass %, relative to 100 mass % of the porous membrane.

[0050] The thickness of the porous membrane is not particularly limited, but is preferably 5 to 500 μm, more preferably 10 to 200 μm, and even more preferably 20 to 100 μm. When the porous membrane is provided separately on both main surfaces of the porous support, each preferably has the thickness described above. The thickness of the porous membrane can be measured by FE-SEM in the same manner as the method for measuring the thickness of the coating membrane described in the Examples below.

[0051] (porous support) The porous support is a sheet-like porous body and serves as a support for the diaphragm for alkaline water electrolysis.

[0052] Examples of materials for the porous support include resins such as polyethylene, polypropylene, polysulfone, polyethersulfone, polyphenylsulfone, polyphenylene sulfide, polyketone, polyimide, polyetherimide, fluorine-based resin, etc. The porous support may contain only one type of such resin, or may contain two or more types.

[0053] The porous support preferably contains at least one selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide, and more preferably contains at least one selected from the group consisting of polypropylene and polyphenylene sulfide. The total content of polypropylene, polyethylene, and polyphenylene sulfide in the porous support is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0054] Examples of the form of the porous support include nonwoven fabric, woven fabric, mesh, porous membrane, mixed fabric of nonwoven fabric and woven fabric, etc. The porous support is preferably nonwoven fabric, woven fabric, or mesh, and more preferably nonwoven fabric or mesh.

[0055] Therefore, the porous support is preferably a nonwoven fabric, a woven fabric, or a mesh containing at least one material selected from the group consisting of polypropylene, polyethylene, and polyphenylene sulfide.

[0056] The thickness of the porous support is not particularly limited, but is preferably 30 to 1000 μm, more preferably 50 to 400 μm. The thickness of the porous support is preferably measured by the method described in the Examples below, but can also be measured by FE-SEM in the same manner as the method for measuring the thickness of the coating film described in the Examples below.

[0057] The basis weight of the porous support is not particularly limited, but is preferably 20 to 200 g / m 2 It is preferable that the density is 40 to 150 g / m 2 It is more preferable that:

[0058] The thickness of the diaphragm for alkaline water electrolysis according to the present disclosure is not particularly limited, but is preferably 50 to 1200 μm, more preferably 100 to 600 μm, and even more preferably 150 to 500 μm. The thickness of the diaphragm for alkaline water electrolysis according to the present disclosure is measured by the method described in the examples below.

[0059] The membrane resistance of the diaphragm for alkaline water electrolysis according to the present disclosure is not particularly limited, but is preferably 0.10 to 1.00 Ω cm 2 Preferably, the resistance is 0.10 to 0.50 Ωcm. 2 More preferably, the resistance is 0.10 to 0.30 Ωcm. 2 The membrane resistance of the diaphragm for alkaline water electrolysis according to the present disclosure is measured by the method described in the examples below.

[0060] 2. Manufacturing method of diaphragm for alkaline water electrolysis The method for producing the diaphragm for alkaline water electrolysis according to the present disclosure preferably includes the following steps (1) to (3): (1) A step of attaching a porous membrane-forming composition containing inorganic particles and an organic resin to a porous support (2) contacting the porous support with a non-solvent to form a main layer; (3) A step of forming a coating film by applying a coating film-forming composition containing a first resin having a neutral or basic polar functional group to the main layer.

[0061] Process (1) The step (1) is a step of attaching a porous membrane-forming composition containing inorganic particles and an organic resin to a porous support. The porous membrane-forming composition is prepared by mixing the organic resin, the inorganic particles, a solvent, and other components. For example, a dispersion (slurry) in which inorganic particles are dispersed in a solvent and a resin solution in which an organic resin is dissolved in a solvent may be prepared separately, and then these may be mixed.

[0062] The solvent 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. Only one type of solvent may be used, or two or more types may be used.

[0063] The porous film forming composition may further contain other components such as a dispersant and an additive.

[0064] The porous membrane-forming composition can be prepared using known mixing means such as a mixer, a bead mill, a ball mill, a jet mill, a disper, a sand mill, a roll mill, a pot mill, or a paint shaker.

[0065] The method for attaching the porous membrane-forming composition to the porous support is not particularly limited, and known methods such as die coating, spin coating, gravure coating, curtain coating, spraying, application methods using an applicator, coater, or other device, or immersion methods can be used.

[0066] The amount of the composition for forming a porous membrane to be applied is not particularly limited as long as a porous membrane is formed on one or both main surfaces of the porous support, but it is preferably an amount that allows the composition for forming a porous membrane to be impregnated into the entire porous support.

[0067] Process (2) The step (2) is a step of contacting the porous support to which the porous membrane-forming composition has been attached in the step (1) with a non-solvent to form a main layer. By contacting the porous support to which the porous membrane-forming composition has been attached with a non-solvent, the non-solvent diffuses into the attached porous membrane-forming composition, and the organic resin that is insoluble in the non-solvent solidifies. Meanwhile, the solvent in the porous membrane-forming composition that is soluble in the non-solvent dissolves. Due to this phase separation, a porous membrane is formed, and a main layer consisting of the porous support and the porous membrane is formed.

[0068] The non-solvent is not particularly limited as long as it has the property of not substantially dissolving the organic resin, and examples thereof include water (ion-exchanged water); lower alcohols such as methanol, ethanol, and propyl alcohol; or mixed solvents thereof. In addition to the above-mentioned components, the non-solvent may contain a small amount of a solvent similar to the solvent contained in the porous membrane-forming composition.

[0069] Examples of a method for contacting the porous support with a non-solvent include a method in which the porous support is immersed in a non-solvent (coagulation bath).

[0070] The temperature of the non-solvent when the porous support is brought into contact with the non-solvent is preferably 5 to 50°C.

[0071] After contacting the porous support with a non-solvent, the porous support is dried to form a main layer. The drying method is not particularly limited and can be performed by a known method. The drying temperature is preferably 50 to 150°C. The drying time is preferably 1 to 60 minutes.

[0072] Process (3) The step (3) is a step of forming a coating film by applying a coating film-forming composition containing a first resin having a neutral or basic polar functional group to the main layer. The coating film-forming composition may further contain a solvent, the second resin as needed, and other components such as a dispersant and additives. The solid content of the coating film-forming composition can be, for example, 1 to 20 mass % relative to 100 mass % of the coating film-forming composition.

[0073] The coating film-forming composition can be prepared using known mixing means such as a mixer, a bead mill, a ball mill, a jet mill, a disper, a sand mill, a roll mill, a pot mill, or a paint shaker.

[0074] The method for adhering the coating film-forming composition to the main layer is not particularly limited, and known methods such as die coating, spin coating, gravure coating, curtain coating, application methods using devices such as sprays, applicators, and coaters, and immersion methods can be used.

[0075] The amount of the coating film-forming composition to be applied is not particularly limited, and may be adjusted appropriately so that a coating film of a desired thickness is formed.

[0076] After the coating film-forming composition is applied, it is dried to form a coating film. The drying method is not particularly limited and can be performed by a known method. The drying temperature is preferably 50 to 150°C. The drying time is preferably 1 to 60 minutes.

[0077] In this way, the diaphragm for alkaline water electrolysis according to the present disclosure can be efficiently produced by the above-described steps (1) to (3). The method for producing the diaphragm for alkaline water electrolysis may also include other known steps, as necessary.

[0078] The diaphragm for alkaline water electrolysis according to the present disclosure can suppress detachment of inorganic particles. The diaphragm for alkaline water electrolysis according to the present disclosure can be suitably used as a diaphragm for water electrolysis using an alkaline aqueous solution as the electrolyte. [Example]

[0079] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0080] In the present examples, the conditions for measuring various physical properties are as follows: <Measurement method> <Average particle size of inorganic particles> An inorganic particle dispersion was prepared by mixing inorganic particles with a 0.2% by mass aqueous solution of sodium hexametaphosphate. After dispersing the inorganic particle dispersion using an ultrasonic cleaner, the particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (HORIBA, Ltd.: LA-950) with the red laser transmittance adjusted to 90-98% and the blue laser transmittance adjusted to 85-92%. The median diameter (d50) in the volume-based particle size distribution was taken as the average particle size (μm) of the inorganic particles.

[0081] <Specific surface area of ​​inorganic particles> 1 g of inorganic particles was placed in a cell, and degassed at 200°C while nitrogen gas was circulating through the cell. While nitrogen gas was circulating through the cell, the cell was immersed in liquid nitrogen and the nitrogen gas was adsorbed onto the inorganic particles at -196°C. The cell was kept at room temperature (25-27°C), and the amount of desorbed nitrogen gas was measured to determine the specific surface area by the BET method. A BET specific surface area meter (Macsorb HM model-1210, manufactured by Mountec Co., Ltd.) was used as the measuring device. This measurement was performed three times, and the average of each measurement result was used as the specific surface area (m 2 / g).

[0082] <Weight average molecular weight of first resin> The weight average molecular weight was measured in terms of polystyrene by gel permeation chromatography (GPC) under the following conditions. Apparatus: Tosoh GPC system HCL-8220GPC Guard column: Tosoh Corporation, TSKgel guard column SuperHZ-L Column: TSKgel Super AWM-H Eluent (LiBr·H2O, NMP containing phosphoric acid): 0.01 mol / L Standard sample: TSK standard polystyrene (Tosoh Corporation: PS-oligomer kit) Column temperature: 40℃

[0083] <pH measurement of the first resin> 5 g of the first resin was added to 95 g of ion-exchanged water to prepare a 5% by mass aqueous solution. This aqueous solution was kept at room temperature (25°C) and measured using a pH meter (LAQUA F-2000PI, manufactured by Horiba, Ltd.) in accordance with JIS Z8802.

[0084] <Thickness of porous support and thickness of diaphragm for alkaline water electrolysis> The thickness of the porous support and the thickness of the diaphragm for alkaline water electrolysis were measured using a Digimatic micrometer (Coolant-proof micrometer MDC-PXT manufactured by Mitutoyo Corporation). The thickness was measured at 10 arbitrary points, and the average value of the measurement results was used as the thickness of the porous support and the thickness of the diaphragm for alkaline water electrolysis.

[0085] <Coating film thickness> The alkaline water electrolysis diaphragm was positioned with the coating film facing upward, and a backscattered electron image was obtained using a field-emission scanning electron microscope (FE-SEM). The magnification needed to capture the entire thickness of the coating film was selected; here, a magnification of 10,000x was used. In the backscattered electron image, inorganic particles are shown in white, the organic resin and coating film are shown in gray, and voids and the background are shown in black. Because inorganic particles are dispersed in the organic resin, the coating film and the organic resin are distinguished by the presence or absence of inorganic particles, shown in white. Using the image analysis software "Image Pro Premier" (Media Cybernetics), the boundary between the porous membrane and the coating film was visually determined, and boundary line A between the porous membrane and the coating film was drawn as shown in Figure 2. A perpendicular line B was drawn from boundary line A, and point C, where perpendicular line B intersected with the upper surface of the coating film, was identified. The length from boundary line A to point C was measured. This measurement was performed at five arbitrary points on boundary line A, and the average of the measurement results was used as the thickness of the coating film. The boundary between the coating film shown in gray and the background shown in black was defined as the upper surface of the coating film.

[0086] <Membrane resistance of alkaline water electrolysis membrane> Two measurement samples were cut out from the diaphragm for alkaline water electrolysis. The measurement samples were immersed overnight in a 30% by mass aqueous potassium hydroxide solution. The diaphragm for alkaline water electrolysis was installed in a cell having the cell configuration described below, and the cell was then allowed to stand in a thermostatic bath at 25°C for 30 minutes. Thereafter, AC impedance measurement was performed under the measurement conditions described below to obtain the intercept component (Ra). AC impedance measurement was also performed without the diaphragm for alkaline water electrolysis installed to obtain the intercept component (Rb). The membrane resistance was then calculated using the following formula. This measurement was performed on two measurement samples, and the average of the measurement results was taken as the membrane resistance of the diaphragm for alkaline water electrolysis. [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 Effective measurement area: 1.77cm 2 AC impedance measurement conditions Applied voltage: 10mV vs. open circuit voltage Frequency range: 100kHz~100Hz

[0087] <Particle shedding resistance test> The diaphragm for alkaline water electrolysis was cut to a size of 100 mm diameter, and its weight was measured. The main surface on the porous support side was then fixed to a 100 mm diameter acrylic plate using double-sided tape. The diaphragm for alkaline water electrolysis was immersed in ion-exchanged water for 1 hour. A 50-mesh (JIS mesh) wire mesh was cut to a size of 100 mm diameter and fixed to a stirrer using double-sided tape. The acrylic plate, diaphragm for alkaline water electrolysis, mesh, and stirrer were placed side by side in a glass petri dish in this order from the bottom up. Ion-exchanged water was added until the diaphragm for alkaline water electrolysis was immersed. The mesh was rotated at 100 rpm for 2 hours using a magnetic stirrer. The fallen material in the glass petri dish was collected and its mass was measured, and the mass loss rate of the diaphragm was calculated.

[0088] Example 1 (1. Preparation of inorganic particle dispersion) Magnesium hydroxide particles (plate-shaped, average particle diameter 0.25 μm, specific surface area 20 m 2 Magnesium hydroxide (1000 mg / g) and N-methyl-2-pyrrolidone (Mitsubishi Chemical Corporation) were mixed in a mass ratio of 1:1, and the mixture was dispersed in a pot mill containing zirconia media balls at 27°C for 6 hours. The zirconia media balls were removed to obtain a magnesium hydroxide particle dispersion.

[0089] (2. Preparation of Porous Membrane-Forming Composition) To 200 parts by mass of the magnesium hydroxide particle dispersion, 100 parts by mass of a polysulfone solution prepared by dissolving polysulfone (BASF: Ultrason S3010) in N-methyl-2-pyrrolidone (Mitsubishi Chemical Corporation) at a concentration of 35% by mass, 40 parts by mass of 2-ethyl-1-hexanol (Fujifilm Wako Pure Chemical Industries, Ltd.), and 1.5 parts by mass of polyethyleneimine (Nippon Shokubai: SP-018) were added. N-methyl-2-pyrrolidone (Mitsubishi Chemical Corporation) was added to adjust the total concentration of magnesium hydroxide and polysulfone to 35% by mass. The mixture was stirred at 27°C for 30 minutes at 1000 rpm using a planetary centrifugal mixer (Thinky Corporation: Awatori Rentaro ARE-500). A porous membrane-forming composition was thus obtained.

[0090] (3. Formation of the main layer) Polyphenylene sulfide nonwoven fabric (thickness 130 μm, basis weight 60 g / m 2 The porous membrane-forming composition was applied to one surface of the sheet using an applicator (application amount: 30 mg / cm 2 ) At this time, the porous membrane-forming composition was impregnated into the nonwoven fabric up to the opposite surface. The nonwoven fabric impregnated with the porous membrane-forming composition was placed in a water bath at 27°C for 3 minutes and dried at 130°C for 10 minutes to obtain a main layer including a porous membrane containing magnesium hydroxide and polysulfone and a nonwoven fabric.

[0091] (4. Preparation of Coating Film-Forming Composition) A 10% by weight polysulfone solution (10 parts by weight of polysulfone solution, prepared by dissolving polysulfone (BASF Ultrason S3010) in N,N-dimethylacetamide (Fujifilm Wako Pure Chemical Industries, Ltd.) at a concentration of 30% by weight) was added to a flask containing 30 parts by weight of a poly-N-vinylacetamide aqueous solution (weight average molecular weight: 800,000, pH approximately 8 when prepared as a 5% by weight aqueous solution) dissolved in water at a concentration of 10% by weight. 87 parts by weight of N,N-dimethylacetamide (Fujifilm Wako Pure Chemical Industries, Ltd.) were then added. The flask was placed in an evaporator (EYELA N-1200AV-WD) and vacuumed at 60°C for 30 minutes at 100 rpm and 25 Pa to completely remove water. This resulted in a coating film-forming composition 1 with a 50:50 (by weight) ratio of polysulfone to poly-N-vinylacetamide and a solids content of 6% by weight.

[0092] (5. Formation of coating film) The coating film-forming composition 1 was applied to the surface of the porous membrane of the main layer and dried in a dryer at 130°C for 10 minutes. In this way, a diaphragm 1 for alkaline water electrolysis was obtained, in which a coating film composed of polysulfone and poly-N-vinylacetamide was formed on the main surface of the porous membrane. As shown in Fig. 1, the coating film partially covered the main surface of the porous membrane. The diaphragm 1 for alkaline water electrolysis was subjected to measurement of the coating film thickness, measurement of membrane resistance, and a particle shedding resistance test. The results are shown in Table 1.

[0093] <Example 2> A diaphragm 2 for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amounts of the N,N-dimethylacetamide solution of polysulfone, the aqueous poly-N-vinylacetamide solution, and N,N-dimethylacetamide added in (4. Preparation of composition for forming coating film) were 14 parts by mass, 18 parts by mass, and 78 parts by mass of N,N-dimethylacetamide.

[0094] Example 3 A diaphragm 3 for alkaline water electrolysis was prepared in the same manner as in Example 1, except that the amounts of the N,N-dimethylacetamide solution of polysulfone, the aqueous poly-N-vinylacetamide solution, and N,N-dimethylacetamide added in (4. Preparation of composition for forming coating film) were 5 parts by mass, 45 parts by mass, and 90.5 parts by mass.

[0095] <Comparative Example 1> The main body layer obtained in Example 1 was used as a comparative diaphragm for alkaline water electrolysis.

[0096] [Table 1]

[0097] The results in Table 1 show that the diaphragm for alkaline water electrolysis can exhibit the effect of preventing inorganic particles from falling out while ensuring a sufficiently practical membrane resistance by providing the diaphragm for alkaline water electrolysis with a coating film that covers at least a part of one or both main surfaces of the main layer formed of the porous support and the porous membrane, and that contains a first resin having a neutral or basic polar functional group.

Claims

1. a porous support; a porous membrane provided on one or both main surfaces of the porous support, the porous membrane comprising inorganic particles and an organic resin, The porous support and the porous membrane are further provided with a coating film containing a first resin having a neutral or basic polar functional group, which covers at least a part of one or both main surfaces of the main layer. A diaphragm for alkaline water electrolysis characterized by:

2. 2. The diaphragm for alkaline water electrolysis according to claim 1, wherein the neutral or basic polar functional group is at least one selected from the group consisting of an acetamide group, an acetyl group, an alcoholic hydroxyl group, a methoxy group, and an amino group.

3. 3. The diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the first resin is at least one resin selected from the group consisting of vinyl-based resins, cellulose-based resins, polyether-based resins, and polyamine-based resins.

4. 3. The diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the first resin is at least one selected from the group consisting of poly-N-vinylacetamide, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, polyethylene glycol, and polyethyleneimine.

5. The diaphragm for alkaline water electrolysis according to claim 1, wherein the coating membrane further comprises a second resin other than the first resin.

6. The diaphragm for alkaline water electrolysis according to claim 5, wherein the second resin comprises at least one resin selected from the group consisting of polysulfone, polyethersulfone, and polyphenylsulfone.

7. The diaphragm for alkaline water electrolysis according to claim 5 or 6, wherein the ratio (A / B) of the mass (A) of the first resin to the mass (B) of the second resin in the coating membrane is 0.2 to 3.

5.

8. The diaphragm for alkaline water electrolysis according to claim 5 or 6, wherein the coating membrane comprises the first resin and the second resin.

9. The diaphragm for alkaline water electrolysis according to claim 1 or 2, wherein the porous membrane further comprises, in a surface portion in contact with the coating membrane, a first resin having a neutral or basic polar functional group, in addition to the organic resin.

10. 3. 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.

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

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

13. The membrane resistance is 0.10 to 1.00 Ωcm ２ The diaphragm for alkaline water electrolysis according to claim 1 or 2,

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