Separator for alkaline water electrolysis, alkaline water electrolysis member, alkaline water electrolysis cell, alkaline water electrolysis device, and method for producing hydrogen

Abstract

Provided are: a separator for alkaline water electrolysis, the separator comprising a porous base material that contains an organic polymer, and a nonionic surfactant that has an HLB value of not less than 3.0 but less than 12.0, wherein at least the outer surface of the porous base material is covered with the nonionic surfactant; an alkaline water electrolysis member; an alkaline water electrolysis cell; an alkaline water electrolysis device; and a method for producing hydrogen.

Description

Separator for alkaline water electrolysis, alkaline water electrolysis member, alkaline water electrolysis cell, alkaline water electrolysis apparatus, and hydrogen production method

[0001] The present invention relates to a separator for alkaline water electrolysis, an alkaline water electrolysis member, an alkaline water electrolysis cell, an alkaline water electrolysis apparatus, and a hydrogen production method.

[0002] Hydrogen is a clean energy that does not emit carbon dioxide and is used as a fuel for, for example, fuel cell vehicles and household fuel cells. As a method for producing hydrogen, alkaline water electrolysis using a high-concentration alkaline aqueous solution as an electrolyte is known. If alkaline water electrolysis is performed using a power generation system that utilizes renewable energy as a power source, hydrogen can be produced without emitting carbon dioxide, and thus hydrogen is attracting increasing attention as a basic energy for a sustainable society.

[0003] In alkaline water electrolysis, to prevent the bubble-like hydrogen (2H ２ O + 2e － →H ２ + 2OH － ) generated at the cathode from moving to the anode side, and to prevent the bubble-like oxygen (4OH － →O ２ + 2H ２ O + 4e － ) generated at the anode from moving to the cathode side, a separator (diaphragm) having gas barrier properties is disposed between the cathode and the anode. In addition to gas barrier properties, this separator is also required to have ion conductivity that allows OH － (hydroxide ions) to permeate from the cathode side to the anode side. Therefore, a porous membrane (micro porous membrane) formed of an organic polymer material is used as the separator for alkaline water electrolysis. ]>

[0004] It is known that porous separators for alkaline water electrolysis can be formed by a wet phase separation method. In wet phase separation, first, an organic polymer, which is a constituent material of the porous membrane, is dissolved in a solvent that dissolves the organic polymer (a good solvent) to prepare a film-forming solution, and a coating film of this film-forming solution is formed. Next, the coating film is immersed in a solvent (poor solvent, coagulation bath) that does not dissolve the organic polymer and is miscible with the good solvent. As the proportion of the good solvent in the coating film decreases due to this immersion, the organic polymer and the solvent undergo phase separation, and the organic polymer gels (coagulates), resulting in a porous membrane. To increase the mechanical strength of the porous separator, a porous support such as a nonwoven fabric or woven fabric is placed in the film-forming solution, and the phase separation is performed in the presence of the porous support. This creates a porous structure in the impregnated organic polymer in the film-forming solution, and a porous separator can be formed in which the porous support and the porous structure of the organic polymer are integrated. Furthermore, by incorporating hydrophilic inorganic particles into the separator, the gas barrier properties can be enhanced while efficiently allowing the alkaline aqueous solution to penetrate into the separator, thereby further improving ionic conductivity.

[0005] As a constituent material for alkaline water electrolysis separators, for example, Patent Document 1 describes a substrate for an alkaline water electrolysis diaphragm composed of polyphenylene sulfide fibers with a specific average single fiber fineness and crimp number, and at least its surface is treated with a hydrophilic treatment. Patent Document 1 describes introducing oxygen-containing groups or components to the surface of the polyphenylene sulfide fibers by plasma treatment or the like, from the viewpoint of reducing the adhesion of gases generated during electrolysis (which inhibits ion permeability), improving bonding with the organic polymer resin layer provided on the substrate for the alkaline water electrolysis diaphragm, and improving durability and stability during assembly. In addition, although alkali durability is not required, unlike alkaline water electrolysis separators, a technology for hydrophilizing alkaline battery separators is also known. For example, Patent Document 2 describes obtaining an alkaline battery separator consisting of a microporous film of polysulfone resin treated with a nonionic surfactant by immersing a polysulfone resin and a dope in which a nonionic surfactant is dissolved in a hydrophilic organic solvent in water. Furthermore, Patent Document 3 describes hydrophilizing a porous film made of polypropylene and / or polyethylene with a hydrophilization treatment solution containing a polyoxyethylene alkylphenyl ether-based nonionic surfactant represented by a specific general formula.

[0006] JP 2016-089197 A JP 2-276153 A JP 8-020663 A

[0007] Alkali-resistant polymers such as PS (polysulfone), PPSU (polyphenylsulfone), PPS (polyphenylene sulfide), and PEEK (polyetheretherketone), which are used as constituent materials for alkaline water electrolysis separators, are highly hydrophobic polymers. Therefore, alkaline water electrolysis separators whose surfaces are composed of these alkali-resistant polymers suffer from low electrolyte permeability and high ionic resistance. As described in Patent Document 1, by hydrophilizing the surface of the alkali-resistant polymer constituting the separator surface, ionic resistance can be kept low and an improvement in water electrolysis efficiency can be expected. However, alkaline water electrolysis separators are required to have the ability to sufficiently maintain the hydrophilic state even under alkaline water electrolysis conditions of high temperature (70°C or higher) and high alkali concentration (for example, alkaline water with a concentration of about 30% by mass) (hereinafter referred to as "high temperature high concentration alkali durability"). The present inventors have investigated and found that the surface hydrophilization treatment by plasma treatment described in the example of Patent Document 1 has poor high temperature high concentration alkali durability.

[0008] The present invention aims to provide an alkaline water electrolysis separator that has low ion resistance and can maintain this low ion resistance under high temperature and high concentration alkaline conditions. Furthermore, the present invention aims to provide an alkaline water electrolysis component, an alkaline water electrolysis cell, an alkaline water electrolysis apparatus, and a hydrogen production method using the alkaline water electrolysis separator of the present invention.

[0009] The above problems of the present invention have been solved by the following means: [1] A separator for alkaline water electrolysis comprising a porous substrate containing an organic polymer and a nonionic surfactant having an HLB value of 3.0 or more and less than 12.0, wherein at least the outer surface of the porous substrate is coated with the nonionic surfactant. [2] The separator for alkaline water electrolysis according to [1], wherein the nonionic surfactant has an ether bond and does not have an ester bond. [3] The separator for alkaline water electrolysis according to [1] or [2], wherein the HLB value of the nonionic surfactant is 5.0 or more and less than 10.0. [4] The separator for alkaline water electrolysis according to [2], wherein the HLB value of the nonionic surfactant is 6.0 or more and less than 8.7. [5] The separator for alkaline water electrolysis according to any one of [1] to [4], wherein the organic polymer contains at least one of polysulfone and polyphenylene sulfide. [6] An alkaline water electrolysis component comprising an alkaline water electrolysis separator as described in any one of [1] to [5]. [7] An alkaline water electrolysis cell comprising an alkaline water electrolysis separator as described in any one of [1] to [5], or an alkaline water electrolysis component as described in [6]. [8] An alkaline water electrolysis apparatus comprising an alkaline water electrolysis cell as described in [7]. [9] A method for producing hydrogen, comprising electrolyzing water using the alkaline water electrolysis apparatus as described in [8].

[10] A method for producing hydrogen as described in [9], comprising using an alkaline aqueous solution containing 10 to 35% by mass of a metal hydroxide as the electrolyte solution, and electrolyzing water at 70 to 95°C.

[0010] In the present invention, when describing physical properties, etc. by indicating a numerical range, when separately explaining the upper limit value and the lower limit value of the numerical range, any upper limit value and lower limit value can be appropriately combined to form a specific numerical range. On the other hand, when describing by setting a plurality of numerical ranges represented by "~", the upper limit value and the lower limit value forming the numerical range are not limited to the combination of the specific upper limit value and the specific lower limit value described before and after "~" as a specific numerical range, and can be a numerical range obtained by appropriately combining the upper limit value and the lower limit value of each numerical range. In the present invention, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0011] The separator for alkaline water electrolysis of the present invention has a low ionic resistance, and this low ionic resistance can be maintained under high-temperature and high-concentration alkaline conditions. Further, the alkaline water electrolysis member, alkaline water electrolysis cell, and alkaline water electrolysis apparatus of the present invention include the separator for alkaline water electrolysis of the present invention, and are excellent in alkaline water electrolysis efficiency and also excellent in durability. Further, according to the hydrogen production method of the present invention, it is possible to continuously perform highly efficient hydrogen production by efficient alkaline water electrolysis.

[0012] FIG. 1 is a drawing schematically showing an embodiment of an alkaline water electrolysis apparatus. FIG. 2 is a drawing schematically showing another embodiment of the alkaline water electrolysis apparatus. FIG. 3 is a drawing schematically showing yet another embodiment of the alkaline water electrolysis apparatus.

[0013] [Separator for Alkaline Water Electrolysis] The separator for alkaline water electrolysis of the present invention (hereinafter also referred to as "the separator of the present invention") comprises a porous substrate containing an organic polymer and a nonionic surfactant having an HLB value of 3.0 or more and less than 12.0 (hereinafter also referred to as "nonionic surfactant (N)"), wherein at least the outer surface of the porous substrate is coated with the nonionic surfactant (N). In the present invention, "outer surface of the porous substrate" means the surface of the film when the porous substrate is viewed from a macroscopic perspective as a film having a single thickness. This film has one surface on the front and one on the back, and both of these two surfaces together are referred to as the "outer surface of the porous substrate". In addition, the separator of the present invention may also have surfaces other than the outer surface of the porous substrate (for example, the inner wall surface of the pores of the porous substrate) coated with the nonionic surfactant (N). That is, it is preferable that the separator of the present invention has at least a part of the inner wall surface of the pores of the porous substrate coated in addition to at least the outer surface of the porous substrate. As described in the examples below, by dipping a porous substrate into a coating solution containing a nonionic surfactant (N), the nonionic surfactant (N) can coat at least the outer surface of the porous substrate while also coating part or all of the inner wall surface of the pores. In the separator of the present invention, coating with the nonionic surfactant (N) means that a layer of the nonionic surfactant (N) is formed on at least the outer surface of the porous substrate. It is preferable that the layer of the nonionic surfactant (N) is present over the entire outer surface of the porous substrate, but the layer of the nonionic surfactant (N) may not be present on a part of the outer surface of the porous substrate. It can be confirmed, for example, that at least the outer surface of the porous substrate is coated with the nonionic surfactant (N) by observing that the contact angle of the porous substrate after coating with the nonionic surfactant (N) is lower than the contact angle of the porous substrate before coating with the nonionic surfactant (N).The fact that at least the outer surface of the porous substrate is coated with the nonionic surfactant (N) may be confirmed by analysis such as TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) measurement or XPS (X-ray Photoelectron Spectroscopy) measurement, or by identification by GPC (Gel Permeation Chromatography) of the solvent extract. However, the method for confirming that at least the outer surface of the porous substrate is coated with the nonionic surfactant (N) is not limited to the above method. The present invention is satisfied if it can be confirmed that the substrate is coated with the nonionic surfactant (N) by at least one method.

[0014] The separator of the present invention has a low ionic resistance and excellent durability under high temperature and high-concentration alkali conditions, as at least the outer surface of the porous substrate is coated with a nonionic surfactant (N). This allows the low ionic resistance to be maintained even under high temperature and high-concentration alkali conditions. This is because coating at least the outer surface of the porous substrate with a nonionic surfactant (N) having an HLB value of 3.0 or more and less than 12.0 improves the hydrophilicity of the separator, suppressing ionic resistance in alkaline water electrolysis. Furthermore, the nonionic surfactant (N) is less likely to detach even under alkaline water electrolysis at high temperature (70°C or higher) and high-concentration alkali conditions (for example, alkaline water with a concentration of about 30% by mass). If the HLB value is less than 3.0, the hydrophilization of the separator is insufficient to begin with, and it is thought that the hydrophilicity cannot be maintained when exposed to high temperature and high-concentration alkali conditions, making it impossible to maintain low ionic resistance. Furthermore, if the HLB value is 12.0 or higher, the nonionic surfactant is too hydrophilic and dissolves in water, causing it to detach. This prevents the ionic resistance of the separator from being suppressed, making it impossible to maintain hydrophilicity and low ionic resistance when exposed to high temperature and high concentration alkaline conditions. The nonionic surfactant (N) and porous substrate described above are explained in detail below.

[0015] (Nonionic surfactant (N)) The nonionic surfactant (N) can be used without particular limitation as long as it is a nonionic surfactant having an HLB value of 3.0 or more and less than 12.0. The HLB (Hydrophile-Lipophile Balance) value is a value determined by the Griffin method (W.C. Griffin, J. Soc. Cosmetic Chemists., 1949, vol. 1, p. 311), and specifically, it is a value calculated by the following formula. HLB value = 20 × (sum of formula weights of hydrophilic parts of nonionic surfactant) / (molecular weight of nonionic surfactant) The HLB value of the nonionic surfactant (N) is preferably 5.0 or more and less than 10.0 from the viewpoint of further suppressing the ionic resistance. In addition, the HLB value is preferably 6.0 or more and less than 8.7. In particular, from the viewpoint of further suppressing the ionic resistance and excellent high-temperature and high-concentration alkali durability, as described later, the nonionic surfactant (N) has an ether bond and does not have an ester bond, and the HLB value is preferably 5.0 or more and less than 10.0. More preferably, the nonionic surfactant (N) has an ether bond and does not have an ester bond, and the HLB value is 6.0 or more and less than 8.7. When at least the outer surface of the alkaline water electrolysis separator is coated with two or more nonionic surfactants, at least one of the two or more nonionic surfactants may fall within the range of the HLB value shown above. In this case, in the total content of two or more nonionic surfactants covering at least the outer surface of the alkaline water electrolysis separator, the content of the nonionic surfactant (N) falling within the range of the HLB value shown above is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, and further preferably 80 to 100% by mass.

[0016] The molecular weight of the nonionic surfactant (N) is, for example, preferably 100 to 500, and more preferably 200 to 400. When the nonionic surfactant (N) has a repeating structure, the above molecular weight is the number average molecular weight.

[0017] As the nonionic surfactant (N), any nonionic surfactant from among ester-type nonionic surfactants, ether-type nonionic surfactants, and ester-ether-type nonionic surfactants may be used, as long as the above HLB value is satisfied. In other words, the nonionic surfactant (N) may contain hydrogen atoms, carbon atoms, and oxygen atoms as constituent atoms and have ether bonds or ester bonds. The nonionic surfactant (N) may contain fluorine atoms as constituent atoms, but it is preferable that it does not.

[0018] The above-mentioned ester-type nonionic surfactant refers to a structure in which a polyhydric alcohol such as glycerin, sorbitan, or sucrose is esterified with a fatty acid, i.e., fatty acid ester-type surfactants (also called polyhydric alcohol-type surfactants) such as glycerin fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters. In ester-type nonionic surfactants, the structural part derived from polyhydric alcohols such as glycerin, sorbitan, or sucrose, and the ester bond part correspond to the hydrophilic part in the above-mentioned HLB value calculation formula. In this invention, ester-type nonionic surfactants do not contain ether bonds other than cyclic ether structures such as sorbitan or sucrose. The above-mentioned ether-type nonionic surfactant refers to polyoxyalkylene alkyl ethers and polyoxyalkylene alkylphenyl ethers synthesized by ring-opening addition polymerization of alkylene oxides such as ethylene oxide to raw materials having hydroxyl groups such as alcohols and alkylphenols. In ether-type nonionic surfactants, the polyoxyalkylene structural part and the ether bond part correspond to the hydrophilic part in the above-mentioned HLB value calculation formula. In this invention, the ether-type nonionic surfactant does not contain an ester bond. The above-mentioned ether-ester-type nonionic surfactant refers to a nonionic surfactant in which a polyoxyalkylene structure is introduced into the above-mentioned ester-type nonionic surfactant. Specific examples include alkylene oxide adducts of fatty acid esters such as glycerin fatty acid esters, sorbitan fatty acid esters, and sucrose fatty acid esters. In the ether-ester-type nonionic surfactant, the structural part derived from polyhydric alcohols such as glycerin, sorbitan, and sucrose, the polyoxyalkylene structural part, and the ester bond part correspond to the hydrophilic part in the above-mentioned HLB value calculation formula. As for the nonionic surfactant (N), it is preferable to have an ether bond and not an ester bond, from the viewpoint of keeping the ionic resistance lower and having superior durability at high temperatures and high concentrations of alkali, and the above-mentioned ether-type nonionic surfactant is more preferable.

[0019] Among the raw materials having a hydroxyl group in the above ether-type nonionic surfactant, the alcohol is not particularly limited and can be a primary to tertiary alcohol (preferably a primary or secondary alcohol), and can be an alcohol having 8 to 24 carbon atoms (preferably an alcohol having 8 to 18 carbon atoms). Among the raw materials having a hydroxyl group in the above ether-type nonionic surfactant, the alkylphenol is not particularly limited and can be an alkylphenol having 8 to 24 carbon atoms, and an alkylphenol having 8 to 9 carbon atoms is preferred. Examples include (arylalkyl)phenol and alkylphenol. The polyoxyalkylene structure in the above ether-type nonionic surfactant is -(R-O) ｎ A structure represented by - is preferred. - (R-O) ｎ In the structure represented by -, R represents an alkylene group having 2 to 6 carbon atoms, preferably an alkylene group having 2 to 4 carbon atoms, and more preferably an alkylene group having 2 to 3 carbon atoms. Specific examples of R include ethylene and propylene. - (R-O) ｎ In the structure represented by -, n is a number of 1 or more, preferably 2 to 20, and more preferably 3 to 10. Specific examples of the ether-type nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene tripenzylphenyl ether, and polyoxypropylene alkyl ether. However, the polyoxyalkylene structure, alkyl ether structure, and alkylphenyl ether structure are appropriately adjusted to satisfy the above HLB value, and these are also preferred as specific examples of the ether-type nonionic surfactant.

[0020] Commercially available nonionic surfactants (N) can also be used. Examples include the Naroacty, Sannonic, Sedran, Emulmin, Ionet, and Eleminor series (all trade names) manufactured by Sanyo Chemical Industries, Ltd. For example, Naroacty CL-20, Naroacty CL-40, Naroacty ID-40, Sedran SF-506, Sannonic SS-30, and Eleminor 200L (all trade names, manufactured by Sanyo Chemical Industries, Ltd.) have a structure derived from an alcohol with 8 to 24 carbon atoms and -(R-O) ｎ It corresponds to a polyoxyalkylene alkyl ether having a polyoxyalkylene structure represented by - (R is an alkylene group having 2 to 6 carbon atoms, and n is 2 to 20 carbon atoms). In addition, Eleminor HB-29 (trade name, manufactured by Sanyo Chemical Industries, Ltd.) has a structure derived from trynzylphenol and - (CH ２ CH ２ -O) ｎ This corresponds to polyoxyethylene tripenzylphenyl ether, having a polyoxyethylene structure represented by - (n is 2 to 20).

[0021] The content of the nonionic surfactant (N) in the separator of the present invention is not particularly limited as long as the effects of the present invention are achieved, and is preferably 0.1 to 5.0% by mass, and more preferably 1.0 to 3.0% by mass. The content of the nonionic surfactant (N) in the separator of the present invention can be calculated from the change in mass before and after surface treatment of the porous substrate with the nonionic surfactant (N). Alternatively, the content of the nonionic surfactant (N) in the separator can be calculated by immersing the separator in a solvent in which the nonionic surfactant (N) can be eluted.

[0022] In the separator of the present invention, the nonionic surfactant (N) used for surface coating may be one type or two or more types.

[0023] (Porous Substrate) The porous substrate constituting the separator of the present invention can be any material containing an organic polymer that is suitable for use as a separator for alkaline water electrolysis, without any particular limitations. For example, a porous substrate made of a porous organic polymer cloth which is a woven or nonwoven fabric (Porous Substrate-I) is an example. Another example is a porous substrate formed by phase separation using an organic polymer (Porous Substrate-II). Furthermore, a combination of the above-mentioned Porous Substrate-I and Porous Substrate-II (Porous Substrate-III) is also preferred as a porous substrate constituting the separator of the present invention. This Porous Substrate-III is preferably in a form in which the above-mentioned Porous Substrate-II, formed by phase separation, is disposed on at least one of the outer surface and voids of the porous organic polymer cloth (hereinafter also referred to as "Composite Porous Substrate"). Furthermore, in Porous Substrate-III, a material in which the above-mentioned Porous Organic Polymer Cloth is replaced with a non-organic polymer porous structure made of metal, ceramic, etc. (Porous Substrate-IV) is also preferred as a porous substrate constituting the separator of the present invention. All of the above-mentioned porous substrates are known to be used as separators for alkaline water electrolysis. Furthermore, the porous substrate-II described above, and the porous substrate-II in the porous substrates-III and IV, may also preferably contain hydrophilic inorganic particles in addition to the organic polymer. In the above-mentioned composite porous substrate, "outer surface of the porous organic polymer cloth" means the surface of the film when the porous organic polymer cloth is viewed from a macroscopic perspective as a single film with a thickness, and "voids in the porous organic polymer cloth" means the gaps between the organic polymer fibers constituting the porous organic polymer cloth. The structure of the composite porous substrate, in which a porous substrate-II containing an organic polymer (preferably further hydrophilic inorganic particles) is disposed on at least one of the outer surface of the porous organic polymer cloth and the voids, can be appropriately adjusted within the range in which at least the outer surface of the composite porous substrate is covered with a nonionic surfactant (N). For example, the structure may be such that the porous substrate-II is disposed only on the outer surface of the porous organic polymer cloth, in which case the porous substrate-II may be disposed on only one side of the porous organic polymer cloth, or on both sides.Furthermore, the porous substrate-II may be disposed only in the voids of the porous organic polymer cloth. In addition, the porous substrate-II may be disposed on at least a portion of the outer surface of the porous organic polymer cloth and at least a portion of the voids. In the present invention, such forms are also included in a structure in which the porous substrate-II containing an organic polymer (preferably further hydrophilic inorganic particles) is disposed on at least one of the outer surface of the porous organic polymer cloth and the voids. Among these, a structure in which the porous substrate-II is disposed on the entire outer surface of the porous organic polymer cloth and the entire voids is preferred.

[0024] The organic polymer contained in the porous substrate is more preferably composed of at least one of polysulfone, polyphenylsulfone, polyphenylene sulfide, polyetheretherketone, and polyethersulfone, from the viewpoint of further enhancing the surface coating effect by the nonionic surfactant (N). It is even more preferably composed of at least one of the alkali-resistant polymers polysulfone, polyphenylsulfone, polyphenylene sulfide, and polyetheretherketone, and particularly preferably composed of at least one of polysulfone and polyphenylene sulfide. In porous substrate-I, "organic polymer contained in the porous substrate" means the organic polymer constituting the porous organic polymer cloth, and in porous substrate-II and porous substrate-IV, it means the organic polymer used for forming the porous substrate by phase separation. Furthermore, in porous substrate-III, "organic polymer contained in the porous substrate" means at least one of the organic polymer in porous substrate-I and the organic polymer in porous substrate-II. In particular, in porous substrate-III, it is preferable that the organic polymer in porous substrate-II, or the organic polymer in porous substrate-I and the organic polymer in porous substrate-II, is one of the organic polymers listed in the above-mentioned porous substrate.

[0025] The following provides a detailed description of the porous substrates I to IV described above, specifically: porous substrate I (porous organic polymer cloth), non-organic polymer porous structures formed from metals, ceramics, etc., porous substrate II, and the organic polymers and hydrophilic inorganic particles that constitute porous substrate II.

[0026] (Porous Substrate-I: Porous Organic Polymer Fabric) The porous organic polymer fabric is not particularly limited and can be used as long as it is applicable to porous separators for alkaline water electrolysis. The opening ratio of the porous organic polymer fabric is preferably 30 to 80%, more preferably 40 to 70%. The opening ratio is the ratio of the area of ​​voids to the area of ​​unit area when the porous organic polymer fabric is viewed in a planar manner. The porous organic polymer fabric may be either a woven fabric or a nonwoven fabric.

[0027] The organic polymers constituting the porous organic polymer fabric are not particularly limited, and examples include polypropylene, polyethylene, polysulfone, polyphenylene sulfide, polyamide, polyethersulfone, polyphenylsulfone, polyethylene terephthalate, polyetheretherketone, sulfonated polyetheretherketone, monochlorotrifluoroethylene, copolymer of ethylene and tetrafluoroethylene or chlorotrifluoroethylene, polyimide, polyetherimide, and m-aramid. Among the above, it is preferable that the organic polymer constituting the porous organic polymer fabric contains at least one of polypropylene, polysulfone, polyphenylene sulfide, polyphenylsulfone, and polyetheretherketone, and it is more preferable that it contains at least one of polyphenylene sulfide and polyetheretherketone.

[0028] The thickness of the porous organic polymer cloth is preferably 15 to 200 μm, and more preferably 15 to 150 μm. Furthermore, the thickness of the porous organic polymer cloth is also preferably 30 to 100 μm, and more preferably 30 to 75 μm. The thickness of the porous organic polymer cloth is measured using a dot-type thickness gauge. In the case of porous substrate-III, the thickness of the porous organic polymer cloth in the composite porous substrate can be measured and calculated by removing the porous organic polymer cloth from porous substrate-III using a solvent that dissolves the organic polymer contained in porous substrate-II, and then measuring the removed porous organic polymer cloth using the method described above.

[0029] (Non-organic polymer porous structures in porous substrates - IV) Non-organic polymer porous structures formed from metal, ceramic, etc. are not particularly limited as long as they are applicable to porous separators for alkaline water electrolysis, and for example, those selected from porous metal plates and porous ceramic plates can be used. The opening ratio and thickness of non-organic polymer porous structures formed from metal, ceramic, etc. can be applied to the opening ratio and thickness described above for porous organic polymer fabrics.

[0030] (Porous Substrate-II) Porous substrate-II can be any substrate that is applicable to a porous separator for alkaline water electrolysis, and preferably has the function of blocking the permeation of hydrogen gas and oxygen gas and allowing hydroxyl ions to permeate. Porous substrate-II contains at least an organic polymer and may further contain other components such as hydrophilic inorganic particles.

[0031] - Organic Polymers - Various organic polymers applicable to the wet phase separation described later can be used as the organic polymers included in the porous substrate-II.

[0032] The organic polymer can be selected from, for example, fluororesins, olefin resins, polyester resins, aromatic hydrocarbon resins, etc. As the fluororesin, a resin selected from polyvinylidene fluoride and polytetrafluoroethylene is preferred. As the olefin resin, polypropylene resin is preferred. As the polyester resin, a resin selected from polyethylene terephthalate, polybutylene terephthalate, and polybutylene naphthalate is preferred. As the aromatic hydrocarbon resin, polystyrene resin is preferred.

[0033] Other preferred organic polymers include polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylsulfone, polyacrylate, polyetherimide, polyimide, and polyamideimide.

[0034] Organic polymers may be used individually or in combination of two or more types.

[0035] The organic polymer more preferably contains at least one of polyvinylidene fluoride, polysulfone, polyethersulfone, polyphenylene sulfide, and polyphenylsulfone; even more preferably contains at least one of polysulfone, polyethersulfone, polyphenylene sulfide, and polyphenylsulfone; and particularly preferably contains at least one of polysulfone and polyphenylene sulfide.

[0036] The mass-average molecular weight (Mw) of the organic polymer is not particularly limited. Considering the handling properties of the film-forming solution described later and the mechanical strength of the resulting separator, it can be, for example, 10,000 to 500,000, and preferably 20,000 to 300,000. Mw can be determined under the following conditions. Instrument: HLC-8220GPC (Tosoh Corporation) Detector: Differential refractometer (RI (Refractive Index) detector) Pre-column: TSKGUARD COLUMN HXL-L 6mm x 40mm (Tosoh Corporation) Sample-side column: The following three columns are directly connected in order (all Tosoh Corporation): ・TSK-GEL GMHXL 7.8mm x 300mm ・TSK-GEL G4000HXL 7.8mm x 300mm ・TSK-GEL G2000HXL 7.8mm x 300mm Reference-side column: TSK-GEL G1000HXL 7.8mm x 300mm Oven temperature: 40℃ Mobile phase: THF (Tetrahydrofuran) Sample-side mobile phase flow rate: 1.0 mL / min Reference-side mobile phase flow rate: 1.0 mL / min Sample concentration: 0.1% by mass Sample injection volume: 100 μL Data acquisition time: 5 to 45 minutes after sample injection Sampling pitch: 300 milliseconds

[0037] The content of the organic polymer in the porous substrate-II can be 100% by mass. If the porous substrate-II contains other components in addition to the organic polymer, such as hydrophilic inorganic particles, the content of the organic polymer in the porous substrate-II is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, even more preferably 7 to 30% by mass, and particularly preferably 9 to 25% by mass.

[0038] - Hydrophilic inorganic particles - Porous substrate-II may contain hydrophilic inorganic particles. The hydrophilic inorganic particles are preferably selected from metal oxides and metal hydroxides.

[0039] The metal oxides mentioned above are preferably selected from zirconium oxide, titanium oxide, bismuth oxide, cerium oxide, and magnesium oxide.

[0040] The above metal hydroxide is preferably selected from zirconium hydroxide, titanium hydroxide, bismuth hydroxide, cerium hydroxide, and magnesium hydroxide.

[0041] In addition to particles selected from metal oxides and metal hydroxides, barium sulfate particles can also be used as hydrophilic inorganic particles.

[0042] Hydrophilic inorganic particles may be used individually or in combination of two or more types.

[0043] The particle size of the hydrophilic inorganic particles is preferably 0.01 to 2.00 μm, more preferably 0.02 to 1.50 μm, even more preferably 0.03 to 1.00 μm, and even more preferably 0.05 to 0.50 μm. This particle size is the median diameter (D50), and is determined by measuring the particle size distribution using laser diffraction and scattering methods, representing the particle size at which the cumulative distribution reaches 50% when the total volume of the particles is considered 100%.

[0044] When the porous substrate-II contains hydrophilic inorganic particles, the content of hydrophilic inorganic particles in the porous substrate-II is preferably 50 to 95% by mass, more preferably 60 to 95% by mass, even more preferably 70 to 93% by mass, and particularly preferably 75 to 91% by mass.

[0045] When the porous substrate-II contains hydrophilic inorganic particles, the ratio of the content of hydrophilic inorganic particles to the content of organic polymer in the porous substrate-II (hydrophilic inorganic particles / organic polymer) is preferably 10 / 1 to 1 / 1 by mass, more preferably 9 / 1 to 2 / 1, even more preferably 8 / 1 to 3 / 1, even more preferably 7 / 1 to 4 / 1, and even more preferably 6.5 / 1 to 4 / 1.

[0046] (Method for manufacturing porous substrates) The method for manufacturing porous substrates is not particularly limited. For example, if the porous substrate is a porous organic polymer fabric which is a woven or nonwoven fabric, the porous substrate-I can be obtained using an organic polymer by a general method for manufacturing woven or nonwoven fabrics. Commercially available porous organic polymer fabrics which are woven or nonwoven fabrics can also be used as the porous substrate-I.

[0047] Furthermore, when the porous substrate is a porous substrate-II formed by phase separation using an organic polymer, or a porous substrate-III or IV containing a porous substrate-II, these porous substrates-II to IV are usually manufactured by a method that includes forming the porous substrate-II by wet phase separation. Commercially available products can also be used as porous substrates-II to IV. In the method of forming the porous substrate-II by wet phase separation, an organic polymer is included as a constituent material of the porous substrate-II. For example, one method includes forming the porous substrate-II by performing wet phase separation on a coating film formed with a film-forming solution obtained by dissolving the above organic polymer. This process yields the porous substrate-II. Furthermore, a porous substrate-III can be obtained by including a step of further impregnating the coating film with a porous organic polymer cloth, and a porous substrate-IV can be obtained by including a step of further impregnating the coating film with a non-organic polymer porous structure. In addition, porous substrates-II to IV can also be obtained by performing vapor-induced phase separation and liquid-induced phase separation as wet phase separation under conditions using a film-forming support. The porous substrates II to IV can be obtained by casting a film-forming solution obtained by dissolving the above organic polymer onto a film-forming support to form a coating film, and then performing wet phase separation with the film-forming support removed, or by performing wet phase separation with the film-forming support attached.

[0048] (Film-forming solution) The film-forming solution can be any solution of the organic polymer that will be the constituent material of the porous substrate-II, and may contain the organic polymer and a solvent, and may also contain hydrophilic inorganic particles. The description of the organic polymer in the porous substrate-II described above can be applied to the organic polymer contained in the film-forming solution. The description of the hydrophilic inorganic particles in the porous substrate-II described above can be applied to the hydrophilic inorganic particles that may be contained in the film-forming solution.

[0049] - Solvent - The film-forming solution in wet phase separation can be any solvent (good solvent) that can dissolve the above organic polymer, and is preferably miscible with water. The solvent is preferably selected from N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N-butyl-2-pyrrolidone (NBP), N,N-dimethylformamide (DMF), formamide, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAC), acetonitrile, γ-valerolactone, compound (2), compound (3) shown below, and mixtures thereof, with at least one of NMP, NBP, γ-valerolactone, compound (2), and compound (3) shown below being more preferred.

[0050] If the film-forming solution contains hydrophilic inorganic particles, the solvent content in the film-forming solution is preferably 10 to 85% by mass, more preferably 15 to 80% by mass, even more preferably 25 to 70% by mass, even more preferably 30 to 65% by mass, even more preferably 32 to 60% by mass, and even more preferably 35 to 50% by mass. If the film-forming solution does not contain hydrophilic inorganic particles, the solvent content in the film-forming solution is preferably 20 to 95% by mass, more preferably 25 to 90% by mass, even more preferably 30 to 80% by mass, even more preferably 40 to 80% by mass, even more preferably 45 to 75% by mass, and even more preferably 50 to 75% by mass.

[0051] - Organic Polymers - When the film-forming solution contains hydrophilic inorganic particles, the content of organic polymers in the film-forming solution is preferably 2 to 30% by mass, more preferably 4 to 20% by mass, even more preferably 5 to 15% by mass, and still more preferably 6 to 15% by mass. When the film-forming solution does not contain hydrophilic inorganic particles, the content of organic polymers in the film-forming solution is preferably 2 to 30% by mass, more preferably 4 to 30% by mass, even more preferably 6 to 25% by mass, and still more preferably 8 to 20% by mass.

[0052] - Hydrophilic inorganic particles - Hydrophilic inorganic particles are particles that exist dispersed in the film-forming solution without dissolving, but in this invention, such a dispersion state is also referred to as the film-forming solution. In other words, the "solution" in the film-forming solution refers to the state in which the organic polymer is dissolved in the solvent. When the above film-forming solution contains hydrophilic inorganic particles, the content of hydrophilic inorganic particles in the film-forming solution is preferably 10 to 85% by mass, more preferably 15 to 80% by mass, even more preferably 20 to 70% by mass, and particularly preferably 25 to 60% by mass.

[0053] - Other Components - The above film-forming solution may contain components other than those described above (solvent, organic polymer, and hydrophilic inorganic particles). For example, in order to control pore formation in wet phase separation, it may contain polyethylene glycol, polyethylene oxide, polypropylene glycol, ethylene glycol, tripropylene glycol, glycerol, polyhydric alcohol, dibutyl phthalate, diethyl phthalate, diundecyl phthalate, isononanoic acid, neodecanoic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyethyleneimine, polyacrylic acid, methylcellulose, dextran, calcium chloride, magnesium chloride, and lithium chloride. If the above film-forming solution contains other components and hydrophilic inorganic particles, the total content of the other components in the above film-forming solution is preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, and even more preferably 0.5 to 5% by mass. If the above film-forming solution contains other components and does not contain hydrophilic inorganic particles, the total content of the other components in the above film-forming solution is preferably 1 to 25% by mass, more preferably 5 to 25% by mass, and even more preferably 7 to 20% by mass.

[0054] <Formation of Porous Substrate-II by Wet Phase Separation> (Water Vapor Induced Phase Separation) In the manufacturing method of the above-described porous substrates-II to IV, for example, water vapor induced phase separation is performed on the coated surface (hereinafter also simply referred to as "the coated surface of the laminate") of a laminate consisting of a film-forming support and a coating film containing the constituent materials of the above-described porous substrate-II formed on the film-forming support. The above laminate can be formed by, for example, casting a film-forming solution obtained by dissolving the above-described organic polymer onto the film-forming support and appropriately drying the surface. In the above-described porous substrates-III and IV, after casting the above-described film-forming solution onto the film-forming support, a porous organic polymer cloth or a non-organic polymer porous structure is placed on top and the porous organic polymer cloth or non-organic polymer porous structure is immersed in the film obtained by casting. When immersing the porous organic polymer cloth in the film, the porous organic polymer cloth is impregnated with the above-described film-forming solution, preferably completely impregnated.

[0055] In water vapor induction phase separation, it is preferable to use high-temperature, high-humidity water vapor as the poor solvent vapor in the water vapor induction phase separation. The relative humidity in the region where water vapor induction phase separation is performed can be, for example, 50 to 99%, more preferably 60 to 99%, and even more preferably 70 to 99%. The temperature in the region where water vapor induction phase separation is performed is, for example, preferably 25 to 85°C, more preferably 60 to 80°C, and even more preferably 60 to 75°C. The time for performing water vapor induction phase separation is, for example, preferably 1 to 35 seconds, more preferably 1 to 30 seconds, and even more preferably 1 to 25 seconds. The space in which water vapor induction phase separation is performed is not particularly limited in terms of specific adjustment methods, equipment, etc., as long as it can be a space in which the predetermined temperature and humidity are maintained. It is preferable that the space is provided so as to be continuous with the solidification bath in which liquid induction phase separation is performed after water vapor induction phase separation.

[0056] (Liquid-induced phase separation) In the above-described method for producing porous substrates II to IV, the laminate that has undergone the above-described water vapor-induced phase separation can be produced by impregnating it into a solidification bath, for example, with the film-forming support still attached, or after peeling off the film-forming support, and performing liquid-induced phase separation. For liquid-induced phase separation, the laminate that has undergone the above-described water vapor-induced phase separation is immersed in a solvent (poor solvent, solidification bath) that does not dissolve the organic polymer and is miscible with the good solvent. This immersion further reduces the proportion of the good solvent in the coating film of the film-forming solution, causing the organic polymer and the solvent to undergo phase separation (liquid-induced phase separation), and the organic polymer to gel (solidify), forming porous substrate II, and thus obtaining porous substrates II to IV.

[0057] As a poor solvent, for example, water, or a mixed solvent of water and a hydrophilic organic solvent (an organic solvent miscible with water) or a water-soluble polymer can be used. Examples of hydrophilic organic solvents include aprotic solvents such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMAC), and alcoholic solvents such as ethanol, propanol, or isopropanol. Examples of water-soluble polymers include water-soluble polymers such as polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA). Among the above, water is preferred as the poor solvent.

[0058] The temperature of the coagulation bath is preferably 20 to 90°C, more preferably 40 to 70°C. The duration of the coagulation bath is preferably 1 to 15 minutes, more preferably 1 to 12 minutes, and even more preferably 3 to 10 minutes.

[0059] In the above liquid derivative phase separation, after immersing the membrane in the poor solvent to form a porous substrate-II (porous membrane), immersion in glycols such as ethylene glycol and diethylene glycol, and water, or washing with the glycols and water may be performed. This step can remove any remaining solvent in the membrane.

[0060] The thickness of the separator of the present invention is, for example, 15 to 220 μm, more preferably 40 to 220 μm, and even more preferably 80 to 220 μm. This thickness is obtained by taking a cross-sectional SEM (scanning electron microscope) image of a cross-section cut from the separator of the present invention with a razor blade at a magnification (e.g., 400x) such that the entire cross-section of the separator of the present invention fits in one field of view, assuming that no pores exist in the obtained cross-sectional SEM image (assuming that the pores are filled with organic polymer), measuring the thickness at 20 equally spaced points, calculating the arithmetic mean of the 20 obtained measurements, and rounding the value to the first decimal place in μm.

[0061] When porous substrates II to IV in the separator of the present invention are manufactured by the method described above, a certain amount of the good solvent described in the film-forming solution described above inevitably remains in the separator of the present invention. As a result, the total content of the good solvent in the separator of the present invention is usually 0.01 to 5.00% by mass. Furthermore, when porous materials II to IV are manufactured by the method described above, a certain amount of other components described in the film-forming solution described above may remain in the separator of the present invention. For example, the amount of other components remaining in the separator of the present invention is preferably 0.01 to 10% by mass in total, more preferably 0.05 to 5% by mass, and even more preferably 0.1 to 1% by mass. The amount of residual solvent and the amount of residual other components are determined by gas chromatography or after pre-drying porous substrates II to IV at 40°C for 12 hours. １ By 1H-NMR (nuclear magnetic resonance) measurement, the amount can be quantified as mass% of 100% by mass in the above-mentioned porous substrate -II to IV after drying.

[0062] From the viewpoint of gas barrier properties required for alkaline water electrolysis separators, the separator of the present invention preferably has a bubble point exceeding 1 bar, and more preferably exceeding 2 bar. The bubble point is determined by measuring using a palm porometer based on the bubble point method described in ASMT (American Society for Testing and Materials) F316-86, and the pressure at which the first bubble is generated in the resulting wet curve is defined as the bubble point.

[0063] The porosity of the separator of the present invention is preferably 30 to 70%, more preferably 40 to 60%, from the viewpoint of exhibiting excellent ion permeability and excellent gas barrier properties. This porosity is the value of porosity calculated from the insertion curve by the mercury intrusion method.

[0064] The separator of the present invention has an ion resistance of 0.25 Ω·cm, from the viewpoint of ion permeability required for alkaline water electrolysis separators. ２ Preferably less than 0.20 Ω·cm ２ Less than 0.15 Ω·cm is more preferable. ２ Less than 0.10 Ω·cm is even more preferable. ２ A value less than 0.01 Ω·cm is particularly preferable. A practical lower limit is 0.01 Ω·cm. ２ Preferably, the range is 0.01 Ω·cm. ２ 0.25Ω・cm or more ２ Examples include those less than the specified value. Ion resistance is a value measured by the AC impedance method at 30°C with the separator of the present invention, punched out in a circular shape, set in a cell. Details are as described in the examples below.

[0065] The separator of the present invention satisfies the requirements for suppressing electrolyte permeability and providing gas barrier properties for alkaline water electrolysis separators, with a water permeability of 100 L / (bar·m). ２ ・hr) or more 1000L / (bar・m ２ Preferably less than 100 L / (bar·m) ２ ・hr) or more 500L / (bar・m ２ A value less than hr is more preferable. The permeability is calculated by setting a circularly punched separator of the present invention in a filter holder, supplying a 30% by mass potassium hydroxide aqueous solution heated to 85°C under a pressurized condition of 50 mbar to the circular separator from above, and measuring the amount of electrolyte (mL) that permeates through in 8 minutes.

[0066] The separator of the present invention can be used as a separator in a method for producing hydrogen by electrolyzing an alkaline aqueous solution using an electrolytic cell. In particular, it can be suitably used as an alkaline water electrolysis separator in the alkaline water electrolysis apparatus described below.

[0067] The separator of the present invention may be in the form of a long sheet wound into a roll, or it may be pre-cut into a predetermined shape according to its intended use, equipment, etc. From the viewpoint of manufacturing efficiency, it is also preferable that the separator of the present invention is in the form of a long sheet and has a thickness distribution in at least one of the width and length directions in which the thickness in the center of the sheet is greater than the thickness at both ends of the sheet. Furthermore, the separator of the present invention may be stored by immersing it in a preservation solution such as pure water. Furthermore, the separator of the present invention may be stored as a dry film without being immersed in a preservation solution.

[0068] [Method for Manufacturing an Alkaline Water Electrolysis Separator] The separator of the present invention is not particularly limited as long as at least the outer surface of the porous substrate is coated with a nonionic surfactant (N), and can be manufactured by conventional methods. For example, the separator of the present invention can be manufactured by a method that includes the step of preparing a coating agent containing a nonionic surfactant (N), and coating at least the outer surface of the porous substrate with the coating agent containing the nonionic surfactant (N) by dip coating or the like. If the coating agent contains components other than the nonionic surfactant (N), such as a solvent, the separator of the present invention can be manufactured by removing the components other than the nonionic surfactant (N), such as the solvent, by drying or the like after the coating. The method for manufacturing the separator of the present invention preferably includes a dip coating step. The content of the nonionic surfactant (N) in the dip coating solution can be adjusted according to the desired viscosity, for example, 1 to 5% by mass is preferred. Hydrophilic solvents are preferred as the solvent used in the dip coating solution, for example, alcohol solvents such as ethanol. The rate at which the porous substrate is withdrawn from the dip coating solution should be adjusted to obtain a coating layer of the desired thickness, for example, 1 to 100 mm / second. The drying conditions after preparing the nonionic surfactant (N) coating layer should be adjusted to remove solvents and other substances from the coating layer, for example, by drying in an oven or the like at 80 to 120°C for 1 to 10 minutes.

[0069] [Alkaline Water Electrolysis] The separator of the present invention is used in alkaline water electrolysis by being placed between the cathode and the anode. Preferred embodiments of an alkaline water electrolysis apparatus to which the separator of the present invention is applied (also referred to as "the alkaline water electrolysis apparatus of the present invention") will be described, but the alkaline water electrolysis of the present invention is not limited to these embodiments.

[0070] Figure 1 schematically shows a preferred embodiment of the alkaline water electrolysis apparatus of the present invention. In the alkaline water electrolysis apparatus (10) shown in Figure 1, a cathode electrode (12) is arranged on one side of the separator (11) of the present invention, and an anode electrode (13) is arranged on the other side. The separator (11) and each electrode (12, 13) are immersed in a high-concentration alkaline aqueous solution (14, preferably a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution). When an electric current flows between the electrodes, electrons are supplied to the cathode side, and bubble-like hydrogen (H) is produced from the water. ２ ) occurs (2H ２ O + 2e － →H ２ +2OH － ). Along with the generation of hydrogen, a hydroxyl ion (OH) is produced. － ) passes through the separator (11) and moves to the anode side, where electrons are removed and bubble-shaped oxygen (O ２ ) occurs (4OH － →O ２ +2H ２ O+4e － ). The cathode electrode (12) and anode electrode (13) described above are preferably composed of an electrode substrate (conductive material) and a catalyst layer on the electrode substrate. When a catalyst layer is included, the catalyst species may be the same or different between the cathode electrode (12) and the anode electrode (13). In the alkaline water electrolysis apparatus (10) shown in Figure 1, the separator (11) and each electrode (12, 13) are far apart, so the distance traveled by hydroxyl ions is long, which limits the improvement of ion conduction efficiency.

[0071] Figure 2 schematically shows another preferred embodiment of the alkaline water electrolysis apparatus of the present invention. The alkaline water electrolysis apparatus (20) shown in Figure 2 is a zero-gap type in which the separator (11) and each electrode (12, 13) are arranged in contact with each other in the alkaline water electrolysis apparatus (10) shown in Figure 1. Because the separator (11) and each electrode (12, 13) are in contact in the alkaline water electrolysis apparatus (20) shown in Figure 2, the distance traveled by hydroxyl ions is short, which is advantageous in terms of ion conduction efficiency. In addition, from the viewpoint of imparting suitability for renewable energy, pressurized alkaline water electrolysis apparatuses that are operated under a pressure of 10 bar or more relative to atmospheric pressure (approximately 1 bar) are also known. As an example of such a pressurized alkaline water electrolysis apparatus, an example is the alkaline water electrolysis apparatus shown in Figure 2, in which the configuration, components, etc. of the alkaline water electrolysis apparatus are appropriately adjusted to be able to handle pressurized operation (for example, operation under pressurized conditions of 10 bar or more).

[0072] Figure 3 schematically shows yet another preferred embodiment of the alkaline water electrolysis apparatus of the present invention. The alkaline water electrolysis apparatus (30) shown in Figure 3 is a configuration that includes a membrane electrode assembly. That is, a cathode catalyst layer (32) is arranged on one side of the separator (31) of the present invention, and an anode catalyst layer (33) is arranged on the other side. These catalyst layers are composed of a catalyst and its binder. Furthermore, a gas diffusion layer (34) is formed on the outer surface of these catalyst layers (the surface opposite to the side on which the separator (33) is arranged) to constitute a membrane electrode assembly. In Figure 3, a bipolar plate (35) is formed further outside the membrane electrode assembly. When an alkaline aqueous solution is supplied to the cathode catalyst layer (32) and the anode catalyst layer (33) of this membrane electrode assembly, and the cathode catalyst layer (32) and the anode catalyst layer (33) are electrically connected and current is passed, bubble-like hydrogen is generated from the cathode catalyst layer (32) and bubble-like oxygen is generated from the anode catalyst layer (33).

[0073] In the above-described alkaline water electrolysis apparatus, the components other than the separator, such as the cathode electrode, cathode catalyst layer, anode electrode, and anode catalyst layer, are not particularly limited, and ordinary components used in alkaline water electrolysis apparatuses can be appropriately applied.

[0074] Thus, in one embodiment, the present invention provides an alkaline water electrolysis apparatus in which the separator of the present invention is incorporated as a separator in the alkaline water electrolysis apparatus. Furthermore, in one embodiment, the present invention provides a method for manufacturing an alkaline water electrolysis apparatus, which includes incorporating the separator of the present invention as a separator in the alkaline water electrolysis apparatus.

[0075] [Alkaline Water Electrolysis Member] The alkaline water electrolysis member of the present invention includes the separator of the present invention. Specifically, the alkaline water electrolysis member of the present invention includes the separator of the present invention and at least one of a catalyst, an anode electrode, and a cathode electrode. The form including the separator of the present invention, an anode electrode, and a cathode electrode will be classified as the alkaline water electrolysis cell of the present invention, as described later. Forms in which the alkaline water electrolysis member of the present invention does not include an electrode but includes a catalyst include a form in which the catalyst is located on only one side of the separator of the present invention, and a form in which the catalyst is located on both sides of the separator of the present invention. Forms in which the alkaline water electrolysis member of the present invention does not include a cathode electrode but includes an anode electrode include a form in which the anode electrode is located on one side of the separator of the present invention. In this form, the catalyst may or may not be present. If a catalyst is present, the catalyst may be located on only one side of the separator of the present invention, or the catalyst may be located on both sides of the separator of the present invention. In the present invention, an alkaline water electrolytic member does not include an anode electrode but includes a cathode electrode. This configuration includes having a cathode electrode on one side of the separator. In this configuration, a catalyst may or may not be present. If a catalyst is present, the catalyst may be present on only one side of the separator, or on both sides of the separator.

[0076] [Alkaline Water Electrolysis Cell] The alkaline water electrolysis cell of the present invention includes the separator of the present invention or the alkaline water electrolysis component of the present invention. The "alkaline water electrolysis cell" includes the separator and two electrodes separated by the separator (anode electrode and cathode electrode). In this embodiment, an alkaline aqueous solution may be present as an electrolyte between both electrodes (including the separator of the present invention), and the anode electrode and cathode electrode may each further contain a catalyst. For example, if the alkaline water electrolysis cell of the present invention includes the separator of the present invention, the alkaline water electrolysis cell of the present invention can be made by combining the separator of the present invention with the anode electrode and cathode electrode. In this case, the anode electrode and cathode electrode may each independently contain a catalyst. Also, if the alkaline water electrolysis cell of the present invention does not include electrodes and includes the separator and catalyst of the present invention, the alkaline water electrolysis cell of the present invention can be made by combining them with the anode electrode and cathode electrode. In this case, the catalyst may be included in the alkaline water electrolytic member of the present invention, or it may be included separately in combination with the alkaline water electrolytic member of the present invention, similar to the anode electrode or cathode electrode. In the alkaline water electrolytic cell of the present invention, the catalyst may be included on at least one side of the separator of the present invention, or it may be included on both sides. Furthermore, if the alkaline water electrolytic cell of the present invention does not include a cathode electrode but includes the separator and anode electrode of the present invention, it can be made into the alkaline water electrolytic cell of the present invention by combining it with a cathode electrode. In this case, the anode electrode and cathode electrode may each independently contain the catalyst. Furthermore, the catalyst may be included in the alkaline water electrolytic member of the present invention, or it may be included separately in combination with the alkaline water electrolytic member of the present invention, similar to the cathode electrode. Furthermore, if the alkaline water electrolytic cell of the present invention does not include an anode electrode but includes the separator and cathode electrode of the present invention, it can be made into the alkaline water electrolytic cell of the present invention by combining it with an anode electrode. In this case, the anode electrode and cathode electrode may each independently contain the catalyst.Furthermore, the catalyst may be included in the alkaline water electrolytic member of the present invention, or it may be included separately in combination with the alkaline water electrolytic member of the present invention, similar to the anode electrode.

[0077] [Alkaline Water Electrolysis Apparatus] The alkaline water electrolysis apparatus of the present invention includes the alkaline water electrolysis cell of the present invention. The alkaline water electrolysis apparatus of the present invention can produce hydrogen as described above by supplementing necessary components, components, etc., according to the configuration of the alkaline water electrolysis cell of the present invention.

[0078] [Method for Producing Hydrogen] The method for producing hydrogen according to the present invention is the same as a conventional method for producing hydrogen (water electrolysis), except that it includes electrolysis of water using the alkaline water electrolysis apparatus of the present invention. In particular, a preferred method for producing hydrogen according to the present invention is one which includes using an alkaline aqueous solution containing 10 to 35% by mass of a metal hydroxide as the electrolyte solution and electrolyzing water at 70 to 95°C. Examples of metal hydroxides include sodium hydroxide and potassium hydroxide, and potassium hydroxide is preferred from the viewpoint of having a higher specific conductivity of the aqueous solution of the metal hydroxide. The content of the metal hydroxide (electrolyte) in the alkaline aqueous solution is 10 to 35% by mass, preferably 25 to 35% by mass, and more preferably 28 to 32% by mass. The temperature of the alkaline aqueous solution used when operating the alkaline water electrolysis apparatus and producing hydrogen by electrolyzing water is 70 to 95°C, preferably 70 to 90°C. This temperature may also be 75 to 85°C or 78 to 82°C. Thus, the separator of the present invention can be suitably used in the method for producing hydrogen according to the present invention that uses a high-temperature, high-concentration alkaline aqueous solution.

[0079] The present invention will be described in more detail below based on examples, but the present invention is not intended to be limited thereto. The water used is deionized water. sec means seconds, and hr means hours. The thickness of the nonwoven fabric among the porous substrates is the value measured by the method described above for the thickness of the porous organic polymer cloth, and the thickness of the porous membrane and composite porous substrate are the values ​​measured by the method described later.

[0080] [Separator Preparation] Separators No. 101-131, c15, and c16 were prepared by modifying the porous substrate with the nonionic surfactant described below. Separators No. c11-c14 were also prepared by using the porous substrate without modification with the nonionic surfactant. Separator No. c17 was prepared by performing the plasma surface treatment described below on the porous substrate. The porous substrates used are described below. The combinations of porous substrates used with the nonionic surfactant or plasma treatment are as shown in Tables 1-1 to 1-3 (hereinafter collectively referred to as "Table 1") below. Separators No. 101-131 are the separators of the present invention, and separators No. c11-c17 are for comparison.

[0081] [Porous Substrate] The following nonwoven fabrics or porous membranes were used as porous substrates as is. PPS nonwoven fabric: PS0040 (product name, manufactured by Hirose Paper Co., Ltd., polyphenylene sulfide nonwoven fabric, thickness 100 μm) PS porous membrane: Microfilter SE02 (product name, manufactured by Fujifilm Corporation, polysulfone porous membrane, thickness 140 μm) PP nonwoven fabric: U-Pore PF5500 (product name, manufactured by Ube Industries, Ltd., polypropylene nonwoven fabric, thickness 20 μm)

[0082] (Composite porous substrate I) 18 parts by mass of polysulfone (product name: Udel P-3500 LCD MB7, Mw: 80000, manufactured by Solvay), 12 parts by mass of polyvinylpyrrolidone (product name: Pitzcol K-90, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 0.5 parts by mass of lithium chloride, and 1 part by mass of water were dissolved in 68.5 parts by mass of N-methyl-2-pyrrolidone to obtain a film-forming mixture. A PPS woven fabric (product name: PPS119 / 60, manufactured by NBC Meshtec, woven fabric of polyphenylene sulfide, thickness 60 μm, aperture ratio 60%) was set on a film-forming support made of PET (polyethylene terephthalate) film, and the film-forming mixture prepared above was cast on top of it so that the total thickness of the film-forming mixture and the PPS woven fabric was 200 μm. The surface of the cast liquid film was exposed to air adjusted to 25°C and 9.9 g / kg absolute humidity (50% relative humidity) at a wind speed of 1.0 m / sec for 2 seconds (water vapor induction phase separation step). Immediately thereafter, it was immersed in a solidification bath filled with 25°C water to form a porous polysulfone structure (referred to as "PS porous structure") (condensation bath phase separation step). Subsequently, the PPS woven fabric and the PS porous structure formed in the solidification bath were peeled off from the PET film as a single unit. Next, it was washed with 80°C diethylene glycol solution for 2 minutes, then with 70°C pure water for 5 minutes, and dried at 80°C for 2 minutes to obtain a composite porous substrate I with a thickness of 200 μm.

[0083] [Treatment with Nonionic Surfactant] A nonionic surfactant was dissolved in ethanol to a concentration of 3% by mass to prepare a dip coating solution. The entire porous substrate was dipped in the solution and dried in an oven set to 100°C for 3 minutes to obtain a separator in which at least the outer surface of the porous substrate was coated (surface modified) with the nonionic surfactant. The nonionic surfactant content in all obtained separators was 1.0 to 3.0% by mass. The nonionic surfactant content in the separator was calculated from the change in mass before and after surface treatment of the porous substrate with the nonionic surfactant.

[0084] [Plasma Treatment] Plasma treatment is performed on both sides of the porous substrate under reduced atmospheric gas pressure, with a vacuum of 0.1 kPa and a treatment intensity of 150 kW·s / m. ２Vacuum plasma treatment was performed under the specified conditions. This vacuum plasma treatment introduced hydrophilic groups such as OH groups and COOH groups to the outer surface of the porous substrate.

[0085] The following measurements and evaluations were performed on each separator fabricated as described above. The results are shown in Table 1. Unless otherwise specified, the separators used for each evaluation were those that had been cut to the desired shape for the evaluation described later.

[0086] (Thickness) A cross-section cut from a porous substrate with a razor blade was captured using a cross-sectional SEM (scanning electron microscope) image at a magnification (e.g., 200x) that allowed the entire cross-section of the porous substrate to fit in a single field of view. Assuming that no pores exist in the obtained cross-sectional SEM image (assuming that the pores are filled with organic polymer), the thickness was measured at 20 equally spaced points. The arithmetic mean of the 20 measurements was calculated and rounded to the first decimal place in μm, and this value was defined as the thickness of the porous substrate. The following equipment was used for cross-sectional SEM observation: Conductive processing device: Meiwa Forsis Co., Ltd., Model: HPC-1SW osmium coater / Source: Os / Film thickness: 5 nm CIS device: JEOL Ltd., Model: IB-09060CIS / Acceleration voltage: 4 kV / Processing temperature: -130°C / As a pretreatment, the sample cut with a razor blade was attached to a Si wafer (100 μm thick) with epoxy resin and fixed in place. FE-SEM (Field Emission Scanning Electron Microscope) observation system: Carl Zeiss, model: Ultra5, measurement conditions: secondary / backscattered electron image, acceleration voltage 2kV, aperture 30μm, working distance 3.0mm (cross-section)

[0087] (Ionic Resistance) A two-chamber cell, having nickel electrodes at the current control terminal and a Lugin tube filled with 3M-KCl at the voltage control terminal, was subjected to a 30% potassium hydroxide aqueous solution as the electrolyte, and maintained at 30°C. In galvanostat mode, the current density was 10 mA / cm². ２The ion resistance was measured under the conditions described above to obtain a blank value for measurement. Next, each separator prepared above was punched out into a circular shape with a diameter of 10 mm, and these samples were used as separators. A 30% potassium hydroxide aqueous solution was filled in the same manner as the blank value measurement, and the ion resistance was measured under the same conditions as the blank value measurement. The difference between the obtained resistance value of each separator and the blank value (i.e., the value calculated by [separator resistance value] - [blank value]) was taken as the ion resistance value of that separator, and the ion resistance was determined according to the following evaluation criteria. - Evaluation Criteria - S: Ion resistance value of 0.10 Ω・cm ２ It is less than . A: Ionic resistance is 0.10 Ω·cm ２ Above, 0.15Ω・cm ２ It is less than . B: Ionic resistance is 0.15 Ω·cm ２ Above, 0.20Ω・cm ２ It is less than . C: Ionic resistance is 0.20 Ω·cm ２ Above, 0.25Ω・cm ２ It is less than . D: Ionic resistance is 0.25 Ω·cm ２ That's all.

[0088] (High temperature and high concentration alkali resistance) 1 μL of calcium chloride aqueous solution (43.75% by mass) was dropped onto the surface of each separator prepared above, and the contact angle (θ) after 1000 milliseconds was measured. Ｓ The contact angle (θ) of each separator No. 101 to 131 prepared as described above was measured. Ｓ The contact angles (θ) of each separator No. c11 to c14 fabricated as described above are all less than 80°. Ｓ Since it was smaller than ), it was confirmed that hydrophilicity was imparted to the surface of the porous substrate, and that at least the outer surface of the porous substrate was coated with a nonionic surfactant (N). Each separator prepared above was immersed in a 30% by mass KOH aqueous solution at 90°C for 24 hours, then washed with running water for about 30 seconds, wiped off the moisture with Kimwipes (product name, manufactured by Nippon Paper Crecia Co., Ltd.), and dried overnight in an oven at 40°C. 1 μL of calcium chloride aqueous solution (43.75% by mass) was dropped onto the surface of each separator after 24 hours of immersion, and the contact angle (θ) after 1000 milliseconds was measured. ２４ｈｒThe increase in contact angle due to retention in a high-temperature, high-concentration alkaline aqueous solution (i.e., [θ)) was measured. ２４ｈｒ -θ Ｓ The value calculated by [ ] was applied to the following evaluation criteria to assess the high-temperature, high-concentration alkali durability. The smaller the increase in contact angle, the less the decrease in hydrophilicity due to exposure to high-temperature, high-concentration alkaline aqueous solution, and the less likely the ionic resistance of the separator is to increase in high-temperature, high-concentration alkaline aqueous solution. Note that the above contact angle refers to the θ of the same side of the two surfaces (front and back) of the separator fabricated above. ２４ｈｒ and θ Ｓ The above increase in contact angle was determined using the following method. Furthermore, since all the separators listed in Table 1 met the same evaluation criteria for the increase in contact angle on both the front and back surfaces, the evaluation criteria for both the front and back surfaces are listed together in Table 1. - Evaluation Criteria - A: The increase in contact angle is 5° or more and less than 10°. B: The increase in contact angle is 10° or more and less than 20°. C: The increase in contact angle is 20° or more.

[0089]

[0090]

[0091]

[0092] (Porous Substrates) As described above under [Porous Substrates]. (Nonionic Surfactants: As described in the Surface Treatment column in the table) (1) Ester-type nonionic surfactant Ionet S-85: Product name, manufactured by Sanyo Chemical Industries, Ltd., sorbitan fatty acid ester (sorbitan trioleate) Ionet S-80: Product name, manufactured by Sanyo Chemical Industries, Ltd., sorbitan fatty acid ester (sorbitan monooleate) Ionet S-20: Product name, manufactured by Sanyo Chemical Industries, Ltd., sorbitan fatty acid ester (sorbitan coconut oil fatty acid ester) (2) Ether / ester-type nonionic surfactant Ionet MO-400: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene fatty acid monoester (3) Ether-type nonionic surfactant Naroacty CL-20: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether (alkylene oxide adduct of primary alcohol) Naroacty CL-40: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether Naroacty CL-85: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether Naroacty ID-40: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether (alkylene oxide adduct of primary alcohol) Sedran SF-506: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether (alkylene oxide adduct of secondary alcohol) Sannonic SS-30: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl ether (ethylene oxide adduct of secondary alcohol) Eleminol HB-29: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene tripenzylphenyl ether Eleminol 200L: Product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl ether

[0093] In the "Bonding" column for nonionic surfactants, "ester" indicates that the nonionic surfactant contains an ester bond in its chemical structure, and "ether" indicates that the nonionic surfactant contains an ether bond in its chemical structure but does not contain an ester bond. In the "HLB value" column for nonionic surfactants, the HLB value of the nonionic surfactant used should be indicated. If the nonionic surfactant used is composed of two or more compounds with different chemical structures, the HLB value range should be indicated, with the HLB value of the compound with the lowest HLB value among the compounds constituting the nonionic surfactant being the lower limit and the HLB value of the compound with the highest HLB value being the upper limit. In the columns for porous substrates and surface treatments in the table, "○" should be written in the column for the material used in each example.

[0094] From Table 1 above, the following can be seen: Separators No. c11 to c14 are not the separators of the present invention in that at least the outer surface of the porous substrate is not coated with a nonionic surfactant. These separators No. c11 to c14 have an ionic resistance of 0.25 Ω·cm. ２ The values ​​were as large as above. Separators No. c15 and c16 are not the separators of the present invention in that at least the outer surface of the porous substrate is coated with a nonionic surfactant with an HLB value of less than 3.0 or 12.0 or higher. These separators No. c15 and c16 have an ionic resistance of 0.25 Ω·cm. ２ The values ​​were as large as described above. Furthermore, the contact angle increased by more than 20° and hydrophilicity decreased significantly when exposed to high temperature and high concentration alkaline conditions, indicating that the surface became hydrophobic under high temperature and high concentration alkaline conditions. In addition, separator No. c17 is not the separator of the present invention because at least the outer surface of the porous substrate is treated with plasma as a hydrophilic treatment. Separator No. c17 has an ion resistance of 0.25 Ω·cm ２The values ​​were as large as above. Furthermore, the contact angle increased by more than 20° and hydrophilicity decreased significantly when exposed to high temperature and high concentration alkaline conditions, indicating that the plasma-treated surface was hydrophobic due to the high temperature and high concentration alkaline conditions. In contrast, separators No. 101 to 131 that satisfy the provisions of the present invention all had their ion resistance kept low to the desired level, and were able to maintain hydrophilicity and low ion resistance even when exposed to high temperature and high concentration alkaline conditions. Furthermore, from a comparison between No. 104, 114 and 124, whose porous substrates are surface-coated with the same nonionic surfactant (N), and No. 131, it can be seen that when the organic polymer contained in the porous substrate contains at least one of PS (polysulfone) and PPS (polyphenylene sulfide), the ion resistance is kept even lower and the durability of high temperature and high concentration alkaline conditions is also superior. Furthermore, No. 106 and No. 131, whose nonionic surfactant (N) HLB values ​​are similar, From comparisons with No. 107, No. 116 and No. 117, No. 126 and No. 127, No. 109 and No. 110, No. 119 and No. 120, and No. 129 and No. 130, it can be seen that when the nonionic surfactant (N) has an ether bond and no ester bond, the ionic resistance is kept lower or it is more durable at high temperatures and high concentrations of alkali. Also, from comparisons with No. 107 and No. 108, No. 117 and No. 118, and No. 127 and No. In comparison with No. 128, it can be seen that when the HLB value of nonionic surfactant (N) is 5.0 or higher and less than 10.0, the ionic resistance is kept lower and it is more durable in high temperature and high concentration alkali conditions. In particular, when the nonionic surfactant (N) has an ether bond and no ester bond, and the HLB value is 6.0 or higher and less than 8.7, it can be seen from the comparison between No. 102 and No. 103, No. 105 and No. 107, No. 112 and No. 113, No. 115 and No. 117, No. 122 and No. 123, and No. 125 and No. 127 that the ionic resistance is kept even lower.

[0095] Although we have described the present invention along with its embodiments, we do not intend to limit our invention in any detail of the description unless specifically designated, and we believe that it should be interpreted broadly without contradicting the spirit and scope of the invention as set forth in the appended claims.

[0096] This application claims priority under Japanese Patent Application No. 2024-208535, filed in Japan on 29 November 2024, the contents of which are incorporated herein by reference as part of this specification.

[0097] 10 Alkaline water electrolysis apparatus 11 Separator 12 Cathode electrode 13 Anode electrode 14 High-concentration alkaline aqueous solution 20 Alkaline water electrolysis apparatus 30 Alkaline water electrolysis apparatus 31 Separator 32 Cathode catalyst layer 33 Anode catalyst layer 34 Gas diffusion layer 35 Bipolar plate O ２ Bubble-shaped oxygen H ２ Bubble-shaped hydrogen OH － Hydroxy ion e － electronic

Claims

1. A separator for alkaline water electrolysis comprising a porous substrate containing an organic polymer and a nonionic surfactant having an HLB value of 3.0 or more and less than 12.0, wherein at least the outer surface of the porous substrate is coated with the nonionic surfactant.

2. The alkaline water electrolysis separator according to claim 1, wherein the nonionic surfactant has an ether bond and does not have an ester bond.

3. The alkaline water electrolysis separator according to claim 1, wherein the HLB value of the nonionic surfactant is 5.0 or more and less than 10.

0.

4. The alkaline water electrolysis separator according to claim 2, wherein the HLB value of the nonionic surfactant is 6.0 or more and less than 8.

7.

5. The alkaline water electrolysis separator according to claim 1, wherein the organic polymer comprises at least one of polysulfone and polyphenylene sulfide.

6. An alkaline water electrolysis component comprising the alkaline water electrolysis separator described in claim 1.

7. An alkaline water electrolysis cell comprising an alkaline water electrolysis separator according to any one of claims 1 to 5, or an alkaline water electrolysis component according to claim 6.

8. An alkaline water electrolysis apparatus comprising the alkaline water electrolysis cell described in claim 7.

9. A method for producing hydrogen, comprising electrolyzing water using the alkaline water electrolysis apparatus described in claim 8.

10. A method for producing hydrogen according to claim 9, comprising using an alkaline aqueous solution containing 10 to 35% by mass of a metal hydroxide as an electrolyte solution, and electrolyzing water at 70 to 95°C.

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