Separator for water electrolysis, material for separator for water electrolysis, and polymer

Abstract

Provided are: a separator for water electrolysis, the separator being composed of a film that contains a polymer having at least one constitutional unit selected from a constitutional unit represented by general formula (A) and a constitutional unit represented by general formula (B); and a material and a polymer for a separator for water electrolysis, which are suitable for the formation of the separator for water electrolysis. In the formulae, L groups each independently represent a C1-20 alkylene group, X groups each independently represent a hydrogen atom, Li, Na, K, or Cs.

Description

Separator for water electrolysis, material for separator for water electrolysis, and polymer

[0001] The present invention relates to a separator for water electrolysis, a material for a separator for water electrolysis, and a polymer.

[0002] Hydrogen is 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, which uses a high-concentration alkaline aqueous solution as an electrolyte, is known. When 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, so hydrogen is attracting increasing attention as a fundamental energy for a sustainable society.

[0003] In alkaline water electrolysis, bubbly hydrogen generated at the cathode (2H ２ O + 2e － → H ２ + 2OH － ) is prevented from moving to the anode side, and bubbly oxygen generated at the anode (4OH － → O ２ + 2H ２ O + 4e － ) is prevented from moving to the cathode side, a gas-barrier separator (diaphragm) 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 pass through. Therefore, a porous membrane (microporous membrane) formed of an organic polymer material is used as a 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 above phase separation is performed in the presence of the porous support. This makes the organic polymer in the impregnated film-forming solution a porous structure, 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, it is possible to enhance the gas barrier properties while efficiently allowing alkaline aqueous solutions to penetrate into the separator, thereby further increasing ionic conductivity.

[0005] As an example of such a porous separator, Patent Document 1 describes a separator comprising a polyphenylene sulfide woven fabric (porous support) and porous layers on both sides of the porous support obtained using an N-butyl-pyrrolidone film-forming solution of polysulfone, zirconium oxide particles, and glycerol. Non-Patent Document 1 describes a separator prepared by wet phase separation using an N,N-dimethylformamide film-forming solution of polysulfone, zirconium oxide nanoparticles, and polyvinylpyrrolidone, and a polyphenylene sulfide porous support.

[0006] Special Publication No. 2023-531792

[0007] Hae In Lee et al., Journal of Membrane Science, 2020, Volume 616, 118541

[0008] As mentioned above, water electrolysis separators, such as those for alkaline water electrolysis, are required to achieve a high level of both gas barrier properties and ionic conductivity, but achieving this balance is still a work in progress. For example, Figure 1 in Non-Patent Document 1 shows a graph of separators with varying zirconium oxide nanoparticle content ratios, indicating that there is roughly a trade-off relationship between reducing ionic resistance and improving gas barrier properties, depending on the content of zirconium oxide nanoparticles, which are hydrophilic inorganic particles.

[0009] The present invention aims to provide a water electrolysis separator that can achieve a higher level of both gas barrier properties and ionic conductivity. Furthermore, the present invention aims to provide water electrolysis separator materials and polymers suitable for forming the water electrolysis separator of the present invention.

[0010] The above problems of the present invention have been solved by the following means: <1> A water electrolysis separator comprising a membrane containing a polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B). In the above formulas, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs. <2> The water electrolysis separator according to <1>, wherein the polymer further comprises a structural unit consisting of an m-phenylene group. <3> The water electrolysis separator according to <1> or <2>, wherein the polymer is a crosslinked polymer (p) having a crosslinkable group and at least one selected from the structural unit represented by the above general formula (A) and the structural unit represented by the above general formula (B). <4> The water electrolysis separator according to <3>, wherein the crosslinkable group is at least one of a vinyl group and an epoxy group. <5> The water electrolysis separator according to <3> or <4>, wherein the polymer (p) has the crosslinkable group as at least one selected from the structural unit represented by the following general formula (D) and the structural unit represented by the following general formula (E). <6> A separator material for water electrolysis, comprising a non-crosslinked polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B). In the above formulas, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs. <7> A polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B), and satisfying at least one of the following conditions 1 and 2. Condition 1: Has a constituent unit represented by the following general formula (C). Condition 2: Has a crosslinkable group. In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs. <8> The polymer according to <7>, wherein the crosslinkable group is at least one of a vinyl group and an epoxy group. <9> The polymer according to <7> or <8>, wherein the above condition 2 is the following condition 2A. Condition 2A: Having at least one selected from the constituent units represented by the following general formula (D) and the constituent units represented by the following general formula (E).

[0011] In the present invention, when there are multiple substituents or linking groups etc. (hereinafter referred to as substituents etc.) represented by a specific symbol or formula, or when multiple substituents etc. are specified simultaneously, unless otherwise specified, each substituent etc. may be identical or different from one another (regardless of whether the expression "each independently" is used or not, each substituent etc. may be identical or different from one another). The same applies to the specification of the number of substituents etc. Furthermore, when multiple substituents etc. are in close proximity (especially when adjacent), unless otherwise specified, they may be linked to each other to form a ring. Furthermore, unless otherwise specified, a ring, such as an alicyclic ring, aromatic ring, or heterocyclic ring, may be further fused to form a fused ring. In the present invention, substituents (and the same applies to linking groups and rings) that are not specified as substituted or unsubstituted may have any substituents on that group, as long as the desired effect is not impaired. For example, when referring to an "alkylene group," it includes both unsubstituted alkylene groups and substituted alkylene groups. For example, the alkylene groups having 1 to 20 carbon atoms that can be taken as L in general formulas (A) and (B) may have substituents, as will be described later. In the present invention, when the number of carbon atoms of a group is specified, this number of carbon atoms refers to the total number of carbon atoms of the group unless otherwise specified in the present invention or this specification. That is, if the group has further substituents, it refers to the total number of carbon atoms including these substituents.

[0012] In the present invention, when describing content, content ratio, conditions, physical properties, etc., by indicating numerical ranges, if the upper and lower limits of the numerical range are described separately, either upper or lower limit can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges expressed using "~", the upper and lower limits forming the numerical range are not limited to the specific combination of upper and lower limits described before and after "~" as a specific numerical range, but can be a numerical range formed by appropriately combining the upper and lower limits of each numerical range. In the present invention, a numerical range expressed using "~" means a range that includes the values ​​described before and after "~" as the lower and upper limits. In the water electrolysis separator of the present invention, each component (polymer (P), organic polymer (NP), and hydrophilic inorganic particles, etc.) may be used individually or mixed in groups of two or more, unless otherwise specified. Furthermore, each of the polymers, polymer (P), and constituent units in polymer (p) of the present invention (such as constituent units selected from constituent units represented by general formula (A) and constituent units represented by general formula (B), constituent units represented by general formula (C), and constituent units selected from constituent units represented by general formula (D) and constituent units represented by general formula (E)) may be one type or two or more types.

[0013] The water electrolysis separator of the present invention can achieve a higher level of balance between gas barrier properties and ion conductivity. Furthermore, the water electrolysis separator material and polymer of the present invention are suitable as constituent materials for the water electrolysis separator of the present invention.

[0014] Figure 1 is a schematic diagram illustrating one embodiment of an alkaline water electrolysis system. Figure 2 is a schematic diagram illustrating another embodiment of an alkaline water electrolysis system. Figure 3 is a schematic diagram illustrating yet another embodiment of an alkaline water electrolysis system.

[0015] [Water Electrolysis Separator] The water electrolysis separator of the present invention (hereinafter also referred to as "the separator of the present invention") is composed of a membrane containing a polymer (hereinafter also referred to as "polymer (P)") having at least one of the constituent units represented by the general formula (A) and the constituent units represented by the general formula (B) described below. Polymer (P) will be described in detail below.

[0016] <Polymer (P)> Polymer (P) is a polymer having at least one constituent unit selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B). In the following description, the constituent unit selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B) will also be referred to as "constituent unit (A) or (B)", the constituent unit represented by the following general formula (A) will be referred to as "constituent unit (A)", and the constituent unit represented by the following general formula (B) will be referred to as "constituent unit (B)". In constituent unit (A) or (B) of polymer (P), the hydrophilic -SO ３ X and -PO ３ X ２ Because the fluorene ring is linked via alkylene groups (L) having 1 to 20 carbon atoms, it has high mobility (mobility of substituents). Therefore, the polymer (P) contained in the film that makes up the separator has high mobility -SO ３ X and / or -PO ３ X ２ However, it is thought that the electrolyte solution (alkaline aqueous solution) can be effectively drawn into the separator during water electrolysis. As a result, ionic resistance is reduced, and the separator surface becomes more hydrophilic, reducing its affinity for gas and increasing its gas barrier properties. This is thought to allow for a higher level of balance between ionic conductivity and gas barrier properties. It should be noted that the above is merely a hypothesis, and the present invention is not limited to the above-mentioned hypothesized mechanism.

[0017] (Constituent unit (A) or (B))

[0018] In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs.

[0019] Each L independently represents an alkylene group having 1 to 20 carbon atoms. The alkylene group having 1 to 20 carbon atoms as L may be linear or branched. The number of carbon atoms in the alkylene group is preferably 2 to 15, and more preferably 2 to 10. L consists of a fluorene ring and -SO ３ X or -PO ３ X ２ The minimum number of atoms connecting the fluorene ring and -SO is preferably 1 to 20, more preferably 2 to 15, and even more preferably 2 to 10. ３ X or -PO ３ X ２ The shortest number of atoms connecting the fluorene ring and -SO ３ X or -PO ３ X ２ This refers to the number of carbon atoms that make up the connecting chain (excluding substituents) between the two. For example, if L is a 1-methyl-1,4-butylene group, then the fluorene ring and -SO ３ X or -PO ３ X ２ The shortest number of atoms connecting them is 4, which is the number of carbon atoms that make up the 1,4-butylene group (linking chain) excluding the methyl group (substituent). A preferred example of the linear alkylene group having 1 to 20 carbon atoms as L is the methylene group (-CH₂ ２ Examples of alkylene groups include ethylene, propylene, butylene, pentylene, hexylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosilene groups. A preferred example of a branched alkylene group having 1 to 20 carbon atoms is an alkylene group in a straight chain alkane having n carbon atoms, having a bond between the carbon atom at position 1 and the carbon atom at position (n-k). Hereinafter, n is an integer from 3 to 20, and k is an integer satisfying 1 ≤ k ≤ n-1. The alkylene group having 1 to 20 carbon atoms as L may have substituents such as alkoxy groups, hydroxyl groups, and amino groups.

[0020] X independently represents a hydrogen atom, Li, Na, K, or Cs. The polymer (P) contains -SO ３ X and -PO３ X ２ This is when at least a portion (or all) of X dissociates to form a monovalent cation (X ＋ ) exists as this X ＋ The remaining paired group is -SO ３ － , -PO ２ OH － or -PO ３ ２－ It may exist as an anion.

[0021] In the constituent unit (A) or (B), constituent unit (B) is preferred from the viewpoint of superior gas barrier properties. When polymer (P) has constituent unit (B), the proportion of constituent unit (B) to the total of constituent units (A) and (B) is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. Furthermore, all of constituent units (A) and (B) may be constituent unit (B).

[0022] The polymer (P) may have one or more constituent units (A) or (B). If it has two or more constituent units (A) or (B), it may have two or more constituent units (A), or two or more constituent units (B), or it may have one or more constituent units (A) and one or more constituent units (B). The total content of constituent units (A) and (B) in the total constituent units (100 mol%) of the polymer (P) is preferably 10 to 100 mol%, more preferably 20 to 90 mol%, and even more preferably 30 to 70 mol%.

[0023] (Other constituent units) The polymer (P) preferably contains constituent units other than the above constituent units (A) and (B) (also referred to as "other constituent units"). The other constituent units are not particularly limited as long as they achieve the effects of the present invention, and examples include constituent units consisting of aromatic hydrocarbon rings. "Constituent units consisting of aromatic hydrocarbon rings" means constituent units obtained by removing two hydrogen atoms from ring constituent carbon atoms that constitute a monoring (benzene ring) or a hydrocarbon condensed ring containing two or more aromatic hydrocarbon rings (naphthalene ring, anthracene ring, fluorene ring, etc.), and constituent units obtained by removing two hydrogen atoms from ring constituent carbon atoms that constitute a ring (biphenyl ring, etc.) in which two or more aromatic hydrocarbon rings (benzene ring, etc.) are linked by single bonds.

[0024] Examples of constituent units consisting of the above aromatic hydrocarbon rings include phenylene, biphenyl-diyl, naphthylene, anthracenylene, and fluorenylene (excluding those corresponding to constituent units (A) or (B) above). The position of the bonds in these constituent units is not particularly limited as long as it satisfies the requirements for constituent units consisting of the above aromatic hydrocarbon rings. For example, phenylene may be o-, m-, or p-, with m-phenylene or p-phenylene being preferred, and m-phenylene being more preferred from the viewpoint of increasing the solvent solubility of polymer (P) and suppressing solution viscosity. Furthermore, it is thought that including m-phenylene as a constituent unit imparts flexibility to polymer (P), suppresses aggregation, and creates minute voids (voids of about 0.1 to 1 nm in size) within the three-dimensional structure of the polymer, thereby contributing to improved hydrophilicity of the water electrolysis separator. In other words, it is thought that the electrolyte solution can be more easily incorporated into the separator, resulting in better ionic conductivity. Furthermore, when used as a cation exchange membrane (hereinafter, including a proton exchange membrane) as described later, it facilitates the formation of channels for cation (hereinafter, including protons) conduction. When used as an ionomer, interaction with the catalyst is promoted more than self-aggregation, the dispersibility and binding properties of the catalyst are effectively expressed, and proton conduction is not inhibited. In addition, fluorenylene only needs to have two bonds at positions 1 to 9, preferably two bonds at positions 1 to 8, more preferably 2,7-fluorenylene or 3,6-fluorenylene, and even more preferably 2,7-fluorenylene.

[0025] The above-described structural unit consisting of an aromatic hydrocarbon ring may be unsubstituted or may have substituents. Examples of substituents that may be present include the crosslinking group described later and substituents X1 to X3 described below. In particular, it is preferable that the above-described structural unit consisting of an aromatic hydrocarbon ring is either unsubstituted or has the crosslinking group described later. Note that the above-described structural unit consisting of an aromatic hydrocarbon ring having the crosslinking group described later as a substituent means that the polymer (p) described later has structural units consisting of an aromatic hydrocarbon ring having a crosslinking group as a substituent, and that the polymer (P), which is a crosslinked product of polymer (p), has a crosslinked structure formed by the reaction of at least a part (part or all) of the crosslinking group of the structural unit consisting of an aromatic hydrocarbon ring.

[0026] As substituent X1, the above-mentioned -SO is used as a substituent that can adjust the hydrophilicity of the polymer (P). ３ X and -PO ３ X ２ Other hydrophilic groups can be mentioned, and for example, groups containing a polyethylene glycol (also called polyethylene oxide) structure are preferred. The polyethylene glycol structure may be directly bonded to a structural unit consisting of an aromatic hydrocarbon ring, or it may be bonded via a linking group. Examples of linking groups include alkylene groups (preferably with 1 to 10 carbon atoms). The average number of repeating ethylene oxy units in the polyethylene glycol structure is usually 2 to 300. The end of the polyethylene glycol structure may be a hydroxyl group, or it may be protected by an alkyl group (preferably with 1 to 5 carbon atoms), etc. As an aromatic hydrocarbon ring structural unit having substituent X1, a fluorenylene structural unit having a group containing a polyethylene glycol structure is preferred. Specific examples include, but are not limited to, the structural units shown below.

[0027]

[0028] As substituent X2, a linear or branched alkyl group (without a ring structure) can be used as a substituent that can adjust the hydrophobicity of the polymer (P). The number of carbon atoms in the linear or branched alkyl group may be 1 to 25. As an aromatic hydrocarbon ring unit having substituent X2, a fluorenylene unit having a linear or branched alkyl group is preferred. Specific examples include, but are not limited to, the following units.

[0029]

[0030] As substituent X3, a bulky cyclic substituent is recommended from the viewpoint of easily forming minute voids (voids of about 0.1 to 1 nm in size) within the three-dimensional structure of the polymer. For example, an aliphatic or aromatic hydrocarbon ring group (x3) is recommended. The aliphatic or aromatic hydrocarbon ring constituting the aliphatic or aromatic hydrocarbon ring group (x3) may be a monocyclic or fused ring, and the number of carbon atoms may be 3 to 20. In addition, the aliphatic or aromatic hydrocarbon ring group (x3) is usually a monovalent group. Furthermore, the aliphatic or aromatic hydrocarbon ring group (x3) may be formed by sharing one of the carbon atoms constituting the aromatic hydrocarbon ring unit as one of the ring constituent atoms constituting the aliphatic or aromatic hydrocarbon ring group (x3). As an aromatic hydrocarbon ring unit having substituent X3, a fluorenylene unit having a bulky cyclic substituent is preferred. Specific examples include, but are not limited to, the following units.

[0031]

[0032] The content of other constituent units in the total constituent units (100 mol%) of the polymer (P) is preferably 0 to 90 mol%, more preferably 10 to 80 mol%, and even more preferably 30 to 70 mol%.

[0033] (Constituent Unit (P1)) One preferred form of the constituent unit consisting of the aromatic hydrocarbon ring described above is a constituent unit consisting of a phenylene group (also referred to as "constituent unit (P1)"). The constituent unit (P1) is preferably a constituent unit consisting of an m-phenylene group or a constituent unit consisting of a p-phenylene group, more preferably a constituent unit consisting of an m-phenylene group, and even more preferably an unsubstituted m-phenylene group (a constituent unit represented by the general formula (C) below, hereinafter referred to as "constituent unit (C)"). Note that the constituent unit consisting of a phenylene group, the constituent unit consisting of an m-phenylene group, and the constituent unit consisting of a p-phenylene group all refer to constituent units that may have substituents.

[0034] (Component unit (C))

[0035] The content of constituent unit (P1) in the total constituent units (100 mol%) of polymer (P) is preferably 10 to 50 mol%, more preferably 15 to 50 mol%, and even more preferably 20 to 50 mol%. The above description regarding the content of constituent unit (P1) can also be applied to the content of constituent units described as preferred form, more preferred form, and even more preferred form (in the case of preferred form, this means the total content). For example, the content of constituent units consisting of m-phenylene groups in the total constituent units (100 mol%) of polymer (P) is preferably 10 to 50 mol%, more preferably 15 to 50 mol%, and even more preferably 20 to 50 mol%.

[0036] (Constituent unit (P2)) Furthermore, one preferred form of the constituent unit consisting of the above aromatic hydrocarbon ring is, from the viewpoint of superior gas barrier properties, a constituent unit (P2) derived from the aromatic hydrocarbon ring constituent unit (P2p) having a crosslinkable group, which is present in the polymer (p) described later (a crosslinkable aromatic hydrocarbon ring constituent unit (P2p) that is in a crosslinked state).

[0037] The content of constituent unit (P2) in the total constituent units (100 mol%) of polymer (P) is the same as the content of crosslinkable aromatic hydrocarbon ring constituent units (P2p) in the total constituent units (100 mol%) of polymer (p) described below.

[0038] (Crosslinked polymer (p)) It is also preferable that polymer (P) is a polymer obtained by crosslinking polymer (p) having a structural unit (A) or (B) and a crosslinkable group (also referred to as "crosslinked polymer (p) having a structural unit (A) or (B) and a crosslinkable group"). Typically, this crosslinked polymer has a structure in which polymer (P) contains the above structural unit (P2). When polymer (P) is a crosslinked polymer (p) having a structural unit (A) or (B) and a crosslinkable group, polymer (P) has a crosslinked structure formed by the reaction of at least a part (part or all) of the crosslinkable groups contained in polymer (p). In this case, unreacted crosslinkable groups may be present in polymer (P). The structural units (A) and (B) contained in polymer (p) are the same as the descriptions of structural units (A) and (B) in polymer (P) above.

[0039] The crosslinkable groups of the polymer (p) are not particularly limited as long as they are groups that can react themselves to form a crosslinked structure and can form a crosslinked structure after forming structures such as water electrolysis separators, cation exchange membranes, and electrode catalysts, which will be described later. For example, ethylenically unsaturated groups can be crosslinked by electron beam (EB) irradiation. Among these, from the viewpoint of resistance to hydrolysis, it is preferable that at least one of vinyl groups and epoxy groups be present, and in this case, it is more preferable that at least a vinyl group is included. Among these, it is preferable that the crosslinkable group be a vinyl group. The conditions for EB irradiation can be appropriately adjusted so that a crosslinked structure can be formed, for example, EB irradiation at an acceleration voltage of 50 to 300 keV and a dose of 100 to 2000 kGy can be used.

[0040] When the crosslinkable group is a vinyl group, thermal radical crosslinking and / or photoradical crosslinking can be performed using a radical generator. Examples of photoradical generators include α-carbonyl compounds, acyloin ether compounds, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones, acridine compounds, phenazine compounds, oxadiazole compounds, o-acyloxime compounds, acylphosphine oxide compounds, and oxime-type polymerization initiators. Examples of commercially available photoradical generators include Irgacure 184, Irgacure 907, Irgacure 369, Irgacure 651, Irgacure 819, Irgacure OXE01, and Irgacure-OXE-02 (all trade names) from BASF. These are manufactured by IGM Resins B. V. It is also available under the company's Ominirad (trade name) series. The amount of photoradical generator used is preferably 0.01 to 30 parts by mass, and more preferably 0.1 to 15 parts by mass, per 100 parts by mass of polymer (p). For crosslinking by light irradiation, ultraviolet light is preferably used. The light irradiation dose is 10 mJ / cm². ２ ~50 J / cm ２ Preferably, 20 mJ / cm ２ ~5J / cm ２ More preferably, 30 mJ / cm ２ ~3J / cm ２ More preferably, 50 to 1000 mJ / cm ２ This is particularly preferable. In addition, to promote the crosslinking (polymerization) reaction, light irradiation may be carried out under heating conditions.

[0041] When the crosslinkable group is an epoxy group, an acid generator can be used to perform thermal cation crosslinking and / or photocation crosslinking. As the acid generator (photoacid generator and thermal acid generator), any common compound used with epoxy groups can be applied without particular limitation. Sulfonium salts or iodonium salts are particularly preferred. Nonionic acid generators or ferrocene-based (ferrocene structure) acid generators can also be used. For photoacid generators, refer to the description in the Journal of the Adhesion Society of Japan, Vol. 56, No. 10, 2020, pp. 403-414. Preferred specific examples of photoacid generators or thermal acid generators are shown below, but are not limited to these. In the following structural formulas, i-Pr represents an isopropyl group, and t-Bu represents a tert-butyl group.

[0042]

[0043]

[0044] The amount of photoacid generator or thermoacid generator used is preferably 0.5 to 15 parts by mass, more preferably 1.0 to 12 parts by mass, and even more preferably 1.5 to 9 parts by mass, per 100 parts by mass of polymer (p).

[0045] It is preferable that polymer (p) has structural units other than the above-mentioned structural units (A) and (B). The structural units other than the above-mentioned structural units (A) and (B) are not particularly limited as long as they achieve the effects of the present invention, and for example, structural units consisting of aromatic hydrocarbon rings can be mentioned. With respect to structural units consisting of aromatic hydrocarbon rings, the above-mentioned description of structural units consisting of aromatic hydrocarbon rings in polymer (P) can be applied as is, except that the crosslinkable group as a substituent that the structural unit consisting of aromatic hydrocarbon rings may have is in the state before being used in the reaction that forms the crosslinked structure.Therefore, one preferred form of structural unit consisting of aromatic hydrocarbon rings that polymer (p) may contain is structural unit (P1) in polymer (P) described above.

[0046] The part of polymer (p) having a crosslinkable group is not particularly limited, and examples include structural units other than the above-mentioned structural units (A) and (B), polymer ends, etc. Of these, it is preferable that the structural units other than the above-mentioned structural units (A) and (B) have a crosslinkable group, and it is more preferable that the structural units other than the above-mentioned structural units (A) and (B) consisting of aromatic hydrocarbon rings have a crosslinkable group. A structure in which a structural unit consisting of an aromatic hydrocarbon ring has a crosslinkable group is also called a "crosslinkable aromatic hydrocarbon ring structural unit (P2p)". The crosslinkable group may be directly bonded to the structural unit consisting of an aromatic hydrocarbon ring, or it may be bonded via a linking group. Examples of linking groups include alkylene groups (preferably with 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms) and alkylene groups containing ether bonds (preferably with 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms). The aromatic hydrocarbon ring unit (P2p) having a crosslinkable group is preferably a fluorenylene unit having a crosslinkable group (a structure in which a unit consisting of a fluorenylene group has a crosslinkable group), and more preferably at least one selected from the unit represented by the following general formula (D) and the unit represented by the following general formula (E). In the following description, the at least one unit selected from the unit represented by the following general formula (D) and the unit represented by the following general formula (E) will also be referred to as "unit (D) or (E)", the unit represented by the following general formula (D) will be referred to as "unit (D)", and the unit represented by the following general formula (E) will be referred to as "unit (E)". In particular, it is preferable that the aromatic hydrocarbon ring unit (P2p) having a crosslinkable group includes at least unit (D), and it is especially preferable that the aromatic hydrocarbon ring unit (P2p) having a crosslinkable group is unit (D).

[0047] (Constituent unit (D) or (E))

[0048] The content of aromatic hydrocarbon ring units (P2p) having a crosslinkable group in the total constituent units (100 mol%) of polymer (p) is preferably 1 to 40 mol%, more preferably 2 to 30 mol%, even more preferably 3 to 30 mol%, particularly preferably 3 to 20 mol%, and most preferably 3 to 15 mol%. The description regarding the content of aromatic hydrocarbon ring units (P2p) having a crosslinkable group can also be applied to the content of constituent units described as preferred forms of aromatic hydrocarbon ring units (P2p) having a crosslinkable group. For example, the total content of constituent units (D) or (E) in the total constituent units (100 mol%) of polymer (p) is preferably 1 to 40 mol%, more preferably 2 to 30 mol%, even more preferably 3 to 30 mol%, particularly preferably 3 to 20 mol%, and most preferably 3 to 15 mol%. Polymer (p) may have one type of constituent unit (D) or (E), or two or more types. If there are two or more constituent units (D) or (E), there may be two or more constituent units (D), or two or more constituent units (E), or there may be one or more constituent units (D) and one or more constituent units (E).

[0049] The polymer (P) is preferably a polymer containing structural unit (A) or (B) and at least one of structural unit (P1) and structural unit (P2). For example, from the viewpoint of further improving the ion conductivity and gas barrier properties of the water electrolysis separator, it is more preferable that the polymer is a polymer containing structural unit (A) or (B) containing at least structural unit (B) and at least one of structural unit (P1) and structural unit (P2), or a polymer containing structural unit (A) or (B) and structural unit (C) and structural unit (P2). In this case, it is preferable that structural unit (P2) is a structural unit derived from a fluorenylene structural unit having a crosslinkable group (a structural unit in a crosslinked state). From the viewpoint of synthesis, a preferred polymer (P) is a copolymer obtained by alternately copolymerizing structural units consisting of fluorenylene groups and structural units consisting of aromatic hydrocarbon rings other than fluorenylene groups, which contain structural unit (A) or (B).

[0050] Furthermore, the molecular structure of the polymer (P) is not particularly limited as long as it contains the constituent unit (A) or (B), and examples include linear, branched (graft structure, multi-branched structure), etc. As described above, the separator of the present invention is not limited to the molecular structure of the polymer (P), and the effects of the present invention can be achieved regardless.

[0051] Furthermore, from the viewpoint of alkali resistance and design flexibility, it is preferable that polymer (P) does not contain fluorine atoms in its molecule. Also, it is preferable that polymer (P) is not a p-doped polymer.

[0052] The mass-average molecular weight (Mw) of polymer (P) is not particularly limited, but if polymer (P) is a non-crosslinked polymer, Mw is preferably set to, for example, 10,000 to 500,000, more preferably to 20,000 to 400,000, and even more preferably to 30,000 to 300,000. The molecular weight distribution (mass-average molecular weight (Mw) / number-average molecular weight (Mn)) of polymer (P) can be, for example, 1 to 10, and preferably 2 to 5, if polymer (P) is a non-crosslinked polymer. If polymer (P) is a crosslinked polymer, it is preferable that the polymer (p) before crosslinking satisfies the above Mw and Mw / Mn values.

[0053] - Measurement of Molecular Weight - In this invention, unless otherwise specified, the mass-average molecular weight (Mw) or number-average molecular weight (Mn) of a polymer refers to the mass-average molecular weight or number-average molecular weight obtained by gel permeation chromatography (GPC) on a standard polystyrene basis. Depending on the solubility of the polymer to be measured, the eluent is appropriately selected from THF (tetrahydrofuran), NMP (N-methyl-2-pyrrolidone), water, and a mixture of aqueous phosphoric acid solution and acetonitrile. A TOSOH EcoSEC HLC-8320GPC (manufactured by Tosoh Corporation) is used as the apparatus, and an RI (Refractive Index) detector is used as the detector. The measurement is performed under temperature-controlled conditions of 40°C. The flow rate is adjusted as follows depending on the eluent. When the eluent is THF, the flow rate is set to 0.35 mL / min on the sample pump side and 0.35 mL / min on the reference pump side. When the eluent is NMP (containing 10 mM lithium bromide), the flow rates should be 0.5 mL / min on the sample pump side and 0.25 mL / min on the reference pump side. When the eluent is water (200 mM sodium nitrate aqueous solution), the flow rates should be 1 mL / min on the sample pump side and 0.25 mL / min on the reference pump side. When the eluent is a 4:1 mixture of 20 mM phosphoric acid aqueous solution and acetonitrile, the flow rates should be 1 mL / min on the sample pump side and 0.25 mL / min on the reference pump side. Alternatively, measurement can also be performed by static light scattering. This is particularly effective when the polymer does not dissolve in any of the above eluents, or when the polymer is adsorbed onto the column even if it dissolves and a chromatogram cannot be obtained. Furthermore, when GPC measurement of polymer (P) is difficult, and as described in the next paragraph, -SO4 in the constituent unit (A) or (B) is present, ３ X and -PO ３ X ２ When synthesizing polymer (P) using a protected compound in which an alkyl group is substituted for X, the molecular weight can be determined by GPC measurement of the polymer before deprotection.

[0054] (Method for synthesizing polymer (P)) Polymer (P) can be synthesized by conventional methods. For example, it can be synthesized by referring to Japanese Patent Publication No. 2021-42351, etc., and adjusting the design as appropriate. For example, a halogen-substituted fluorene compound in which two different ring constituent atoms of the fluorene ring (in compounds that derive a constituent unit (A) or (B), the ring constituent atoms at positions 2 and 7 of the fluorene ring) have Br or I as substituents, and an aromatic hydrocarbon ring (excluding the fluorene ring) in which two different ring constituent atoms have -B(OH) ２ It can be synthesized by reacting a boronic acid aromatic hydrocarbon compound having as a substituent with a Suzuki-Miyaura cross-coupling reaction to form a carbon-carbon bond. In this synthesis method, when carrying out the Suzuki-Miyaura cross-coupling reaction, -SO in the constituent unit (A) or (B) ３ X and -PO ３ X ２ A protected compound in which an alkyl group is substituted for X may be used. In this case, after polymerization in the Suzuki-Miyaura cross-coupling reaction, a deprotection reaction is carried out to -SO ３ X and -PO ３ X ２ Let's assume that.

[0055] The separator of the present invention is a separator for water electrolysis, and more preferably a separator for alkaline water electrolysis. The separator for alkaline water electrolysis is used in alkaline water electrolysis, in which an alkaline aqueous solution is electrolyzed using an electrolytic cell to produce hydrogen, by being placed between the cathode electrode and the anode electrode. The separator of the present invention is composed of a membrane containing the polymer (P) described above, and this membrane may be a porous membrane or a dense membrane as described below. The specific configuration of the separator of the present invention (porous membrane, dense membrane) will be described below.

[0056] <Porous Membrane> As the porous membrane constituting the separator of the present invention, any porous membrane containing the above-mentioned polymer (P) that can be used as a separator for water electrolysis can be used without particular limitation. For example, a porous membrane (porous membrane-I) formed by the phase separation of the above-mentioned polymer (P) (preferably further including an organic polymer other than this polymer (P) (hereinafter referred to as "organic polymer (NP)"). In this paragraph, this will be described as phase separation using the above-mentioned polymer (P) and organic polymer (NP)) can be mentioned. A combination of porous membrane-I and a porous organic polymer cloth that is a woven or nonwoven fabric (porous membrane-II) is also preferred as a porous membrane constituting the separator of the present invention. This porous membrane-II is preferably in a form in which the porous membrane-I formed by the above-mentioned 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 membrane"). Furthermore, in porous membrane-II, a form in which the above-mentioned porous organic polymer cloth is replaced with a non-organic polymer porous structure made of metal, ceramic, etc. (porous membrane-III) is also preferred as a porous membrane constituting the separator of the present invention. All of the above porous membranes are known to be used in water electrolysis separators. Furthermore, porous membrane-I in porous membranes-II and III may also preferably contain hydrophilic inorganic particles in addition to the polymer (P) and organic polymer (NP) described above. In the above composite porous membrane, "outer surface of the porous organic polymer cloth" refers to the surface of the porous organic polymer cloth when viewed from a macroscopic perspective as a single membrane of thickness, and "voids in the porous organic polymer cloth" refers to the gaps between the organic polymer fibers constituting the porous organic polymer cloth. The structure of the composite porous membrane, in which porous membrane-I containing the above-mentioned polymer (P) and organic polymer (NP) (preferably further hydrophilic inorganic particles) is disposed on at least one of the outer surface of the porous organic polymer cloth and the voids, may, for example, be a structure in which porous membrane-I is disposed only on the outer surface of the porous organic polymer cloth, or in a structure in which porous membrane-I is disposed on only one side of the porous organic polymer cloth, or on both sides.The porous membrane-I, which is disposed only on the outer surface of the porous organic polymer cloth, only needs to be disposed on at least a portion of the outer surface of the porous organic polymer cloth (at least a portion of one side, or at least a portion of both sides). Alternatively, the porous membrane-I may be disposed only in the voids of the porous organic polymer cloth. The porous membrane-I, which is disposed only in the voids of the porous organic polymer cloth, only needs to be disposed on at least a portion of the voids of the porous organic polymer cloth. Furthermore, the porous membrane-I 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 a porous membrane-I containing the above-mentioned polymer (P) and organic polymer (NP) (preferably further hydrophilic inorganic particles) is disposed on at least one of the outer surface of the porous organic polymer cloth and the voids. In particular, a structure in which the porous membrane-I is disposed on the entire outer surface of the porous organic polymer cloth and the entire voids is preferred. This is also true when the porous organic polymer cloth in the above-mentioned composite porous membrane is replaced with a non-organic polymer porous structure.

[0057] The following provides a detailed description of the porous organic polymer fabric in porous membrane-II, the non-organic polymer porous structure in porous membrane-III, porous membrane-I, and the organic polymer (NP), polymer (P), and hydrophilic inorganic particles that make up porous membrane-I.

[0058] (Porous organic polymer fabric in porous membrane-II) The porous organic polymer fabric is not particularly limited and can be used as long as it is applicable to porous separators for water electrolysis. The opening ratio of the porous organic polymer fabric is preferably 30 to 80%, more preferably 40 to 75%. 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.

[0059] 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.

[0060] 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 membrane-II, the thickness of the porous organic polymer cloth in porous membrane-II (preferably a composite porous membrane) can be measured and calculated by removing the porous organic polymer cloth from porous membrane-II using a solvent in which the above-mentioned polymer (P) and potentially contained organic polymer (NP) in porous membrane-I dissolve, and then measuring the removed porous organic polymer cloth using the method described above.

[0061] (Non-organic polymer porous structures in porous membranes - III) Non-organic polymer porous structures formed from metals, ceramics, etc. are not particularly limited as long as they are applicable to porous separators for 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 metals, ceramics, etc. can be applied to the opening ratio and thickness described above for porous organic polymer fabrics.

[0062] (Porous membrane-I) Porous membrane-I can be any membrane that is applicable to a porous separator for water electrolysis, and preferably has the function of blocking the permeation of hydrogen gas and oxygen gas and allowing hydroxyl ions to permeate. Porous membrane-I contains at least an organic polymer (NP) (preferably further a polymer (P)), and may further contain other components such as hydrophilic inorganic particles.

[0063] - Organic polymer (NP) - The organic polymer (NP) that may be included in the porous membrane-I is an organic polymer that is applicable to the wet phase separation described later, and in the phase separation step between the organic polymer (NP) and the solvent described later, the polymer (P) can be dispersed (preferably soluble) in the organic polymer (NP) phase.

[0064] The organic polymer (NP) can be selected from, for example, fluororesins, olefin resins, polyester resins, and aromatic hydrocarbon resins. 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.

[0065] Other preferred organic polymers (NPs) include polysulfone, polyethersulfone, polyphenylene sulfide, polyphenyl sulfone, polyacrylate, polyetherimide, polyimide, and polyamideimide.

[0066] Organic polymers (NPs) may be used individually or in combination of two or more types.

[0067] The organic polymer (NP) 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.

[0068] The mass-average molecular weight (Mw) of the organic polymer (NP) is not particularly limited. Considering the handling properties of the film-forming solution and the mechanical strength of the resulting separator, it can be, for example, 10,000 to 500,000, preferably 20,000 to 300,000. Mw can be determined by the conditions described above.

[0069] The content of organic polymers (NPs) in porous membrane-I is preferably 5.00 to 49.99% by mass, more preferably 5.00 to 40.00% by mass, even more preferably 7.00 to 30.00% by mass, and particularly preferably 9.00 to 25.00% by mass, when hydrophilic inorganic particles are included. The content of organic polymers (NPs) in porous membrane-I is preferably 75 to 99% by mass, more preferably 75 to 95% by mass, and even more preferably 80 to 97% by mass, when hydrophilic inorganic particles are not included.

[0070] - Polymer (P) - The porous membrane-I contains the polymer (P) described above. When hydrophilic inorganic particles are included, the polymer (P) content in the porous membrane-I 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. When hydrophilic inorganic particles are not included, the polymer (P) content in the porous membrane-I is preferably 1 to 25% by mass, more preferably 5 to 25% by mass, and even more preferably 7 to 20% by mass. In the porous membrane-I, the ratio of the polymer (P) content to the organic polymer (NP) content (polymer (P) / organic polymer (NP)) is preferably 1 / 1 to 0.05 / 1 by mass, more preferably 0.8 / 1 to 0.1 / 1, even more preferably 0.6 / 1 to 0.1 / 1, and particularly preferably 0.5 / 1 to 0.15 / 1. Furthermore, porous membrane-I may also include porous membranes that contain the aforementioned polymer (P) but do not contain organic polymer (NP).

[0071] - Hydrophilic inorganic particles - Porous membrane-I may contain hydrophilic inorganic particles. The hydrophilic inorganic particles are preferably selected from metal oxides and metal hydroxides.

[0072] The metal oxides mentioned above are preferably selected from zirconium oxide, titanium oxide, bismuth oxide, cerium oxide, and magnesium oxide.

[0073] The above metal hydroxide is preferably selected from zirconium hydroxide, titanium hydroxide, bismuth hydroxide, cerium hydroxide, and magnesium hydroxide.

[0074] In addition to particles selected from metal oxides and metal hydroxides, barium sulfate particles can also be used as hydrophilic inorganic particles.

[0075] Hydrophilic inorganic particles may be used individually or in combination of two or more types.

[0076] 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 particularly preferably 0.05 to 1.00 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%.

[0077] When porous membrane-I contains hydrophilic inorganic particles, the content of hydrophilic inorganic particles in porous membrane-I is preferably 50.00 to 94.99% by mass, more preferably 60.00 to 94.99% by mass, even more preferably 70.00 to 93.00% by mass, and particularly preferably 75.00 to 91.00% by mass.

[0078] When porous membrane-I contains hydrophilic inorganic particles, the ratio of the content of hydrophilic inorganic particles to the content of organic polymer (NP) in porous membrane-I (hydrophilic inorganic particles / organic polymer (NP)) is preferably 10 / 1 to 1 / 1 by mass, more preferably 9 / 1 to 2 / 1, even more preferably 8 / 1 to 3 / 1, particularly preferably 7 / 1 to 4 / 1, and most preferably 6.5 / 1 to 4 / 1.

[0079] (Method for manufacturing a porous membrane) The method for manufacturing a porous membrane is not particularly limited as long as the desired porous structure can be formed. For example, when the porous membrane is a porous membrane-I formed by phase separation using a polymer (P) (preferably further organic polymer (NP)), or a porous membrane-II or III containing a porous membrane-I, these porous membranes-I to III are usually manufactured by a step of forming a porous membrane-I by wet phase separation. In the method of forming a porous membrane-I by wet phase separation, the porous membrane-I contains a polymer (P) (preferably further organic polymer (NP)) as a constituent material. For example, the above-mentioned porous membrane-I can be formed by performing wet phase separation on a coating film formed with a film-forming solution obtained by dissolving the above-mentioned polymer (P) (preferably further organic polymer (NP)). Furthermore, a porous membrane-II can be obtained by including a step of further impregnating the coating film with a porous organic polymer cloth, and a porous membrane-III can be obtained by including a step of further impregnating the coating film with a non-organic polymer porous structure. Furthermore, porous membranes I to III can also be obtained by performing at least one of vapor-induced phase separation and liquid-induced phase separation as a wet phase separation, under conditions using a film-forming support. For example, a film-forming solution obtained by dissolving the above-mentioned polymer (P) (preferably further organic polymer (NP)) is cast onto a film-forming support to form a coating film, and then wet phase separation is performed with the film-forming support removed, or wet phase separation is performed with the film-forming support attached.

[0080] (Film-forming solution) The film-forming solution may be any solution of polymer (P) (and if organic polymer (NP) is included, further organic polymer (NP)) that constitutes the porous membrane-I, and may contain polymer (P) (preferably further organic polymer (NP)) and a solvent, and may also contain hydrophilic inorganic particles. The descriptions of polymer (P) and organic polymer (NP) in the porous membrane-I described above can be applied to the polymer (P) and potentially included organic polymer (NP) in the film-forming solution, respectively. Furthermore, the description of hydrophilic inorganic particles in the porous membrane-I described above can be applied to the hydrophilic inorganic particles that may be included in the film-forming solution.

[0081] - Solvent - The film-forming solution in wet phase separation can be any solvent (good solvent) that can dissolve the above-mentioned polymer (P) (and further organic polymer (NP) if it contains organic polymer (NP)), 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, DMF, γ-valerolactone, compound (2), and compound (3) shown below being more preferred.

[0082] 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 85% 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.

[0083] When the film-forming solution contains hydrophilic inorganic particles, the content of organic polymer (NP) 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 particularly preferably 6 to 15% by mass. When the film-forming solution does not contain hydrophilic inorganic particles, the content of organic polymer (NP) 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 particularly preferably 8 to 20% by mass.

[0084] If the film-forming solution contains hydrophilic inorganic particles, the polymer (P) content in the 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 film-forming solution does not contain hydrophilic inorganic particles, the polymer (P) content in the 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.

[0085] In this invention, hydrophilic inorganic particles are particles that exist dispersed in the film-forming solution without dissolving, and this dispersion state is also referred to as the film-forming solution. That is, the term "solution" in "film-forming solution" refers to the state in which the organic polymer (NP) and polymer (P) are 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.

[0086] The above film-forming solution may contain components other than those described above (solvent, polymer (P), organic polymer (NP), and hydrophilic inorganic particles). For example, 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.

[0087] - Formation of porous membranes I to III by wet phase separation - (water vapor-induced phase separation) In the manufacturing method of porous membranes I to III described above, for example, water vapor-induced phase separation is performed on the coated side of a laminate consisting of a film-forming support and a coating film containing the constituent materials of porous membrane I formed on the film-forming support (hereinafter also simply referred to as the "coated side of the laminate"). Alternatively, as will be described later, liquid-induced phase separation described later may be performed on this laminate without performing water vapor-induced phase separation. The laminate can be formed by, for example, casting a film-forming solution obtained by dissolving the above-mentioned polymer (P) (and further organic polymer (NP) if organic polymer (NP) is included) onto a film-forming support, and then appropriately drying the surface to form a coating film. In porous membranes II and III described above, after casting the 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 this porous organic polymer cloth or non-organic polymer porous structure is immersed in the film obtained by casting. When immersing a porous organic polymer cloth in a film, the porous organic polymer cloth is impregnated with the above film-forming solution, preferably completely impregnated.

[0088] 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 55 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.

[0089] (Liquid-induced phase separation) In the above-described method for producing porous membranes I to III, porous membranes I to III can be produced by impregnating a laminate that has undergone the above-described water vapor-induced phase separation, or a laminate that has not undergone the above-described water vapor-induced phase separation, 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, or a laminate that has not undergone the above-described water vapor-induced phase separation, is immersed in a solvent (poor solvent, solidification bath) that does not dissolve the above-described polymer (P) and organic polymer (NP) and is miscible with the above-described good solvent. By immersion, the proportion of the good solvent in the coating film of the film-forming solution decreases, causing the above-described polymer (P) and organic polymer (NP) to undergo phase separation (liquid-induced phase separation) from the solvent, and the polymer (P) and organic polymer (NP) to gel (solidify), forming porous membrane I, and thus porous membranes I to III can be obtained.

[0090] 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.

[0091] The temperature of the coagulation bath is preferably 0 to 90°C, more preferably 5 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.

[0092] In the above liquid derivative phase separation, after immersing the membrane in the poor solvent to form a porous membrane-I, 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.

[0093] Furthermore, if the polymer (P) described above is a crosslinked polymer (p) described above, in the production of porous membranes I to III described above, a porous membrane can be made using polymer (p) instead of polymer (P), and then polymer (P) can be formed by crosslinking the crosslinkable groups of polymer (p) to produce the separator of the present invention. The method for crosslinking the crosslinkable groups of polymer (p) is as described above for polymer (p).

[0094] When porous membranes I to III 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. The amount of residual solvent is determined by gas chromatography or after pre-drying porous membranes I to III 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 dried porous membranes -I to III.

[0095] <Dense Film> The separator of the present invention may be composed of a dense film containing the polymer (P) described above. For example, a dense film (Dense Film-I) obtained by applying a solution mainly composed of the polymer (P) described above and then drying it can be mentioned. Furthermore, a dense film (Dense Film-II) formed by combining (laminating) Dense Film-I with a porous organic polymer fabric that is a woven or nonwoven fabric is also preferred as a dense film constituting the separator of the present invention. Dense Film-II is preferred from the viewpoint of excellent mechanical strength. As for the porous organic polymer fabric that is a woven or nonwoven fabric, the description of the porous organic polymer fabric that is a woven or nonwoven fabric in the above-mentioned Porous Film-II can be applied as is.

[0096] When the separator of the present invention is composed of a porous membrane, the electrolyte solution incorporated into the voids of the porous membrane is responsible for ion conduction. When the separator of the present invention is composed of a dense membrane, the electrolyte solution incorporated between the molecular chains of the highly hydrophilic polymer (P) is responsible for ion conduction. From the viewpoint of having no macroscopic voids and having excellent gas barrier properties, it is preferable that the separator of the present invention be composed of a dense membrane.

[0097] In this invention, a dense membrane means a membrane that does not have macropores of 50 nm or more, or a membrane with a porosity of less than 10%, while a porous membrane means a membrane that has macropores of 50 nm or more and a porosity of 10% or more. A membrane formed by the phase separation method as described in the above-mentioned method for producing a porous membrane will have macropores of 50 nm or more and a porosity of 10% or more. Furthermore, a membrane obtained by the above-mentioned method for producing a dense membrane will either not have macropores of 50 nm or more, or a membrane with a porosity of less than 10%. The presence or absence of macropores can be confirmed by the mercury intrusion method, and if confirmation by the mercury intrusion method is difficult, it can be confirmed by the gas adsorption method. The porosity can be determined from the apparent density and the true density.

[0098] When the separator of the present invention is a porous membrane, the thickness of the separator can be, for example, 15 to 500 μm, more preferably 40 to 300 μm, and even more preferably 80 to 250 μm. When the separator of the present invention is a dense membrane, the thickness of the separator can be, for example, 3 to 500 μm, more preferably 5 to 300 μm, and even more preferably 10 to 250 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 (for example, 400x) that allows the cross-section of the separator of the present invention to fit in one field of view, assuming that no pores exist in the obtained cross-sectional SEM image (assuming that the pores are filled with the above-mentioned polymer (P) and organic polymer (NP)), 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.

[0099] From the viewpoint of gas barrier properties required for 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 with 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 appears in the resulting wet curve is defined as the bubble point.

[0100] When the separator of the present invention is a porous membrane, the porosity of the separator is preferably 30 to 70%, more preferably 40 to 60%, from the viewpoint of exhibiting excellent ion conductivity and excellent gas barrier properties. This porosity is the value of porosity calculated from the insertion curve by the mercury intrusion method.

[0101] The separator of the present invention has an ionic resistance of 0.07 Ω·cm, from the viewpoint of ionic conductivity required for a water electrolysis separator. ２ Preferably less than 0.05 Ω·cm ２ Less than is preferable. A practical lower limit is 0.01 Ω·cm. ２ Preferably, the range is 0.01 Ω·cm. ２ 0.07Ω・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.

[0102] The separator of the present invention satisfies the requirements for suppressing the permeability of electrolyte solutions and providing gas barrier properties for water electrolysis separators, with a water permeability of 1000 L / (bar·m). ２ Preferably less than 500 L / (bar·m) ２A 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 volume (mL) of electrolyte solution that permeates through in 8 minutes.

[0103] 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.

[0104] [Material for Water Electrolysis Separator] The material for water electrolysis separator of the present invention (also referred to as "the separator material of the present invention") includes the polymer (P) described above if the polymer (P) is not a crosslinked polymer, and includes the polymer (p) described above if the polymer (P) is a crosslinked polymer. That is, the separator material of the present invention includes a non-crosslinked polymer (also referred to as "non-crosslinked polymer (NC)") having at least one selected from the constituent units represented by the above general formula (A) and the constituent units represented by the above general formula (B). The separator material of the present invention may consist of a non-crosslinked polymer (NC), or may contain the above-mentioned organic polymer (NP) or a solvent in addition to the non-crosslinked polymer (NC). It may also contain desired additives, etc. These additives are typically components that can constitute the separator of the present invention (for example, hydrophilic inorganic particles). In the separator material of the present invention, the content of non-crosslinked polymer (NC) is preferably 1 to 100% by mass, more preferably 5 to 100% by mass, even more preferably 10 to 100% by mass, and particularly preferably 20 to 100% by mass. Alternatively, this content may be 40 to 100% by mass, 60 to 100% by mass, or 70 to 100% by mass. Depending on its component composition, the separator material of the present invention may be liquid, solid, or semi-solid. The separator material of the present invention can be used as is, or, if necessary, mixed with the above-mentioned organic polymer (NP), hydrophilic inorganic particles, etc., as a material for forming the separator of the present invention.

[0105] [Polymers] In one embodiment, the present invention provides the following polymer (hereinafter also referred to as "the polymer of the present invention") in relation to the polymer (P) described above. The polymer of the present invention is related to the polymer (P) described above when the polymer (P) is not a crosslinked polymer, and is related to the polymer (p) described above when the polymer (P) is a crosslinked polymer. The polymer of the present invention can be suitably used not only as a separator of the present invention, but also as a constituent material of a cation exchange membrane and a dispersant (ionomer) of an electrode catalyst, as described later.

[0106] The polymer of the present invention is a polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B), and satisfying at least one of the following conditions 1 and 2. Condition 1: Having a constituent unit represented by the following general formula (C). Condition 2: Having a crosslinkable group.

[0107] In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs.

[0108] The preferred chemical structure of the polymer of the present invention can be described by applying the description of the preferred chemical structure of polymer (P) or polymer (p), respectively, within the range in which the polymer of the present invention satisfies the above provisions. For example, the crosslinkable group is preferably at least one of a vinyl group and an epoxy group. Furthermore, the above condition 2 is preferably the following condition 2A. Condition 2A: Having at least one selected from the constituent units represented by the following general formula (D) and the constituent units represented by the following general formula (E).

[0109] As described above, the preferred content of at least one component selected from the constituent units represented by the general formula (D) and the constituent units represented by the general formula (E) in the polymer of the present invention is the same as the preferred content of at least one component selected from the constituent units represented by the general formula (D) and the constituent units represented by the general formula (E) in the polymer (p) described above.

[0110] [Water Electrolysis] The separator of the present invention is used in water electrolysis, placed between the cathode and the anode, and is particularly suitable for use in alkaline water electrolysis. Preferred embodiments of alkaline water electrolysis systems to which the separator of the present invention is applied will be described, but the above-mentioned alkaline water electrolysis is not limited to these embodiments.

[0111] (Alkaline Water Electrolysis) Figure 1 schematically shows a preferred embodiment of the alkaline water electrolysis system described above. In the alkaline water electrolysis system (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) 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 system (10) shown in Figure 1, the separator (11) and each electrode (12, 13) are far apart, resulting in a long travel distance for hydroxyl ions and thus limitations in improving ion conduction efficiency.

[0112] Figure 2 schematically shows another preferred embodiment of the alkaline water electrolysis system described above. The alkaline water electrolysis system (20) shown in Figure 2 is a zero-gap type in which the separator (11) and each electrode (12, 13) are in contact with each other in the alkaline water electrolysis system (10) shown in Figure 1. Because the separator (11) and each electrode (12, 13) are in contact in the alkaline water electrolysis system (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 systems are also known, which are operated under a pressure of 10 bar or more relative to atmospheric pressure (approximately 1 bar). As an example of such a pressurized alkaline water electrolysis system, an example is the alkaline water electrolysis system shown in Figure 2, in which the configuration, components, etc. of the alkaline water electrolysis system are appropriately adjusted to be able to handle pressurized operation (for example, operation under pressurized conditions of 10 bar or more).

[0113] Figure 3 schematically shows yet another preferred embodiment of the alkaline water electrolysis system described above. The alkaline water electrolysis system (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).

[0114] In the above-described alkaline water electrolysis system, 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 systems can be appropriately applied. Furthermore, as described later, it is also preferable to use the aforementioned polymer (P) as the ionomer in the cathode catalyst layer and anode catalyst layer.

[0115] Thus, in one embodiment, the present invention provides an alkaline water electrolysis system in which the separator of the present invention is incorporated as a separator in the alkaline water electrolysis system. Furthermore, in one embodiment, the present invention provides a method for manufacturing an alkaline water electrolysis system, which includes incorporating the separator of the present invention as a separator in the alkaline water electrolysis system.

[0116] [Alkaline Water Electrolysis Component] As an alkaline water electrolysis component, an alkaline water electrolysis component including the separator of the present invention is also preferred. Specifically, the above alkaline water electrolysis component 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 an alkaline water electrolysis cell as described later. Forms in which the above alkaline water electrolysis component does not include an electrode but includes a catalyst include a form in which the catalyst is on only one side of the separator of the present invention, and a form in which the catalyst is on both sides of the separator of the present invention. Forms in which the above alkaline water electrolysis component does not include a cathode electrode but includes an anode electrode include a form in which the anode electrode is 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 on only one side of the separator of the present invention, or the catalyst may be on both sides of the separator of the present invention. One embodiment of the above-mentioned alkaline water electrolysis component that does not include an anode electrode but includes a cathode electrode is one in which the cathode electrode is located on one side of the separator of the present invention. In this embodiment, a 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.

[0117] [Alkaline Water Electrolysis Cell] As an alkaline water electrolysis cell, an alkaline water electrolysis cell including the separator of the present invention or the above-mentioned alkaline water electrolysis component is also preferred. The "alkaline water electrolysis cell" includes a 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 above-mentioned alkaline water electrolysis cell includes the separator of the present invention, the above-mentioned alkaline water electrolysis cell 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 above-mentioned alkaline water electrolysis cell does not include electrodes and includes the separator of the present invention and a catalyst, the above-mentioned alkaline water electrolysis cell 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 component, or it may be included separately in combination with the alkaline water electrolytic component, similar to the anode electrode or cathode electrode. In the alkaline water electrolytic cell, 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 does not include a cathode electrode but includes the separator of the present invention and an anode electrode, it can be made into the alkaline water electrolytic cell 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 component, or it may be included separately in combination with the alkaline water electrolytic component, similar to the cathode electrode. Furthermore, if the alkaline water electrolytic cell does not include an anode electrode but includes the separator of the present invention and a cathode electrode, it can be made into the alkaline water electrolytic cell 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 electrolysis component described above, or it may be included separately in combination with the alkaline water electrolysis component, similar to the anode electrode.

[0118] [Alkaline Water Electrolysis Device] As an alkaline water electrolysis device, an alkaline water electrolysis device including the above-mentioned alkaline water electrolysis cell is also preferred. The above-mentioned alkaline water electrolysis device can produce hydrogen as described in the above-mentioned alkaline water electrolysis system by supplementing the necessary components and configurations according to the configuration of the above-mentioned alkaline water electrolysis cell.

[0119] [Method for Producing Hydrogen] Another preferred method for producing hydrogen is to electrolyze water using the alkaline water electrolysis apparatus described above. This method for producing hydrogen is the same as a conventional method for producing hydrogen (water electrolysis), except that it includes electrolyzing water using the alkaline water electrolysis apparatus described above. In particular, a preferred method for producing hydrogen is to use an alkaline aqueous solution containing 10 to 35% by mass of a metal hydroxide as the electrolyte solution and to electrolyze 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 in the aqueous solution of the metal hydroxide.

[0120] The polymer (P) contained in the separator of the present invention is, as described above, a hydrophilic -SO2 polymer with high mobility (mobility of substituents). ３ X and / or -PO ３ X ２ It is a polymer containing a constituent unit (A) or (B) having the above-mentioned polymer (P). Therefore, it is thought that it can exhibit excellent effects when used not only as a water electrolysis separator such as an alkaline water electrolysis separator, but also as a constituent material for cation exchange membranes and ionomers, as described below. [Cation exchange membrane] When the cation exchange membrane contains the above-mentioned polymer (P), it has high mobility -SO ３ X and / or -PO ３ X ２ Having this feature makes it easier for the cation exchange membrane to take in water, which is the medium for cation exchange, and also allows for the use of highly mobile -SO ３X and / or -PO ３ X ２ Contact between [the structures] is likely to occur, and cations are easily transferred. Further, X may be changed to another monovalent cation to be used as a cation exchange membrane. [Ionomer] When the ionomer of a catalyst layer in a water electrolysis system for hydrogen production, a fuel cell or the like contains the above-mentioned polymer (P), highly mobile -SO ３ X and / or -PO ３ X ２ Having X makes it easier for the catalyst to take in water that serves as an ion conduction medium, and it is considered that the catalyst can be effectively dispersed.

[0121] The present invention will be described in further detail based on Examples, but the present invention should not be construed as being limited by these Examples unless otherwise specified in the present invention.

[0122] [Polymer containing structural unit (A) or (B)] As the polymer containing structural unit (A) or (B), the following polymers 1 to 13 are used. Abbreviations in the following schemes are as follows. DMAc: N,N-dimethylacetamide DMF: N,N-dimethylformamide DMSO: dimethyl sulfoxide HClaq.: HCl aqueous solution MeOH: methanol NaOHaq.: NaOH aqueous solution Pd(dppf)Cl ２ : [1,1-bis(diphenylphosphino)ferrocene]dichloropalladium(II) Pd(OAc) ２ : palladium(II) acetate TBAB: tetrabutylammonium bromide TEA: triethylamine THF: tetrahydrofuran Further, in polymers 1 to 13, the mole percentage of each structural unit is shown on the right side of [ ]. The unit is mol%. Further, in polymers 1 to 3, 5 to 6, and 8 to 13, the neutralization rate of sulfo groups or phosphonic acid groups is approximately 100%.

[0123] (Synthesis Examples 1-4) Polymers 1-4 were synthesized according to the following scheme shown below. The mass-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of each polymer are as follows: Polymer 1 has an Mw of 100,000 and an Mw / Mn of 5; Polymer 2 has an Mw of 80,000 and an Mw / Mn of 4; Polymer 3 has an Mw of 50,000 and an Mw / Mn of 3; and Polymer 4 has an Mw of 70,000 and an Mw / Mn of 4.

[0124]

[0125]

[0126]

[0127] (Synthesis Examples 5-10) Polymers 5-10 can also be synthesized according to the following scheme. The mass-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of each polymer are as follows: Polymer 5 has an Mw of 40,000 and an Mw / Mn of 3; Polymer 6 has an Mw of 90,000 and an Mw / Mn of 5; Polymer 7 has an Mw of 50,000 and an Mw / Mn of 3; Polymer 8 has an Mw of 80,000 and an Mw / Mn of 4; Polymer 9 has an Mw of 80,000 and an Mw / Mn of 4; and Polymer 10 has an Mw of 40,000 and an Mw / Mn of 3.

[0128]

[0129]

[0130]

[0131] (Synthesis Examples 11-13) Polymer 11, described later, can be synthesized in the same manner as polymer 6, except that the blending ratio is changed in the synthesis of polymer 6. Polymers 12 and 13, described later, can be synthesized in the same manner as polymer 5, except that the blending ratio is changed in the synthesis of polymer 5. The mass-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of each polymer are as follows: polymer 11 has an Mw of 80,000 and an Mw / Mn of 5; polymer 12 has an Mw of 50,000 and an Mw / Mn of 3; and polymer 13 has an Mw of 40,000 and an Mw / Mn of 3.

[0132] [Separator Preparation] <Example 1> 8.5 g of polysulfone (product name: Udel P-3500 LCD MB7, manufactured by Solvay, Mw: 80,000) and 41.6 g of N,N-dimethylformamide (manufactured by Tokyo Chemical Industry Co., Ltd.) are mixed and stirred at 60°C for 5 hours to completely dissolve the polysulfone. Next, 2.4 g of the above polymer 1 is added as a hydrophilic polymer and stirred at 60°C for 1 hour. Then, 47.9 g of zirconium oxide particles (product name: High Purity Monoclinic Zirconia E101, manufactured by Luxfer MEL Technologies, D50: approximately 0.8 μm) is added as hydrophilic inorganic particles and stirred for 3 hours to obtain a doped solution. The doping solution described above is cast onto a glass plate using a 250 μm thick applicator to form a coating film. A woven support made of polyetheretherketone (PEEK) (manufactured by Safer, with an aperture ratio of 70% and a thickness of 54 μm) is placed on top of the coating film as a porous support, and this woven support is completely immersed in the coating film. The coating film, along with the glass plate, is gently immersed in a water bath containing water cooled to 10°C (a poor solvent) to separate the polysulfone and the polymer 1 from the solvent, forming a porous film containing polysulfone and the polymer 1 on the glass plate. This porous film with the porous support, along with the glass plate, is washed with water at 50°C for 10 minutes, and then the porous film with the porous support is peeled off the glass plate. Subsequently, the porous film with the porous support is washed with water at 90°C for 1 hour to obtain the separator (composite porous film) of Example 1, which has a thickness of 160 μm.

[0133] <Examples 2-4, 7-10> Separators (composite porous membranes) of Examples 2-4, 7-10 can be obtained in the same manner as in Example 1, except that polymer 1 is replaced with polymers 2-4, 7-10, respectively.

[0134] <Example 5> Furthermore, the separator obtained in the same manner as in Example 1, except that polymer 1 is replaced with polymer 5, can be further subjected to electron beam (EB) irradiation at an acceleration voltage of 80 keV and a dose of 1000 kGy as a post-treatment to crosslink the vinyl groups, thereby obtaining the separator (composite porous membrane) of Example 5.

[0135] <Examples 6, 11-13> Separators (composite porous membranes) of Examples 6, 11-13 can be obtained in the same manner as in Example 5, except that polymer 5 is replaced with polymers 6, 11-13, respectively.

[0136] <Comparative Example 1> A separator (composite porous membrane) of Comparative Example 1 can be obtained in the same manner as in Example 1, except that glycerol is used as a hydrophilic organic compound instead of polymer 1, following Japanese Patent Publication No. 2023-531792.

[0137] <Comparative Example 2> In the same manner as in Example 1, except that polyvinylpyrrolidone is used instead of polymer 1 as the hydrophilic polymer, following Hae In Lee et al., Journal of Membrane Science, 2020, Vol. 616, 118541, a separator (composite porous membrane) of Comparative Example 2 can be obtained.

[0138] The thickness of the separators in Examples 2 to 13 and Comparative Examples 1 and 2 is 160 μm in all cases.

[0139] The ionic conductivity and gas barrier properties, which are fundamental characteristics of the separators in Examples 1 to 13 and Comparative Examples 1 and 2, are summarized in Tables 1-1 and 1-2 below (hereinafter collectively referred to as "Table 1"). The ionic conductivity and gas barrier properties are measured and evaluated by the methods described below.

[0140] <Ionic Conductivity> 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, is in which a 28% potassium hydroxide aqueous solution is added as the electrolyte solution and maintained at 30°C. In galvanostat mode, the current density is 10 mA / cm². ２Ionic resistance is measured under the following conditions to obtain a blank value (the ionic resistance value when no separator is installed between the two chambers). Next, the separator of each of the above examples or comparative examples is sandwiched, a 28% by mass potassium hydroxide aqueous solution is filled in the same manner as above, and the ionic resistance value X is measured under the same conditions as above. The difference between the ionic resistance value X and the blank value is taken as the ionic resistance value of the separator, which is applied to the following evaluation criteria and used as an index of ionic conductivity. - Evaluation Criteria - A: 0.05Ω·cm ２ or less B: 0.05Ω·cm ２ or more and less than 0.07Ω·cm ２ C: 0.07Ω·cm ２ or more

[0141] <Gas Barrier Property> A gas diffusion layer with an anode catalyst layer (manufactured by Dioxide Material) and a gas diffusion layer with a cathode catalyst layer (manufactured by Dioxide Material) are each punched into the same shape to have an area of 1 cm ２ , and with each catalyst layer side facing inward, the separators of each of the above examples or comparative examples cut into the same shape of 1 cm ２ are sandwiched and laminated, and pressurized at a surface pressure of 4 MPa. This pressed laminate is sandwiched between two Ni bipolar plates having flow channels, and restrained with bolts so that a restraining pressure of 1 MPa is obtained. In this way, a water electrolysis cell having a layer structure of bipolar plate-gas diffusion layer-anode catalyst layer-separator-cathode catalyst layer-gas diffusion layer-bipolar plate is obtained. While supplying a 28% by mass potassium hydroxide aqueous solution heated to 95°C to each of the cathode catalyst layer and the anode catalyst layer of each of the above water electrolysis cells at a flow rate of 10 mL / min, 0.1 A / cm ２The water electrolysis cells are energized for 4 hours to obtain water electrolysis cells after initial energization. Using these water electrolysis cells after initial energization, a 28% potassium hydroxide aqueous solution heated to 95°C is supplied to the cathode catalyst layer and the anode catalyst layer at a flow rate of 10 mL / min. Sixty minutes after the start of supply, the exhaust gas generated on the anode side is measured by gas chromatography, and the amount of hydrogen gas contamination relative to oxygen gas (unit: %, a value calculated by 100 × [volume % of hydrogen gas / volume % of oxygen gas]) is applied to the following evaluation criteria and used as an indicator of gas barrier performance. - Evaluation Criteria - A: Less than 0.10% B: 0.10% or more, less than 0.20% C: 0.20% or more

[0142]

[0143]

[0144] Polymers 1 to 13 in the table correspond to polymers 1 to 13 in synthesis examples 1 to 13 described above. A summary of each polymer 1 to 10 by its constituent units is shown below. Similarly, polymers 11 to 13 in the table are also shown below. The molar percentage of each constituent unit is shown to the right of the brackets [ ]. The unit is mol%. Note that at least some or all of the vinyl groups in polymers 5, 6 and 11 to 13 are used to form a crosslinked structure in the separator.

[0145] As shown in the table above, the separator of Comparative Example 1, which is composed of a membrane containing glycerol, a hydrophilic organic compound, and the separator of Comparative Example 2, which is composed of a membrane containing polyvinylpyrrolidone, a hydrophilic polymer, both exhibit poor ion conductivity and poor gas barrier properties. In contrast, the separators of Examples 1 to 13, which satisfy the provisions of the present invention, all exhibit excellent ion conductivity and achieve excellent gas barrier properties.

[0146] 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.

[0147] This application claims priority based on Japanese Patent Application No. 2025-052715, filed in Japan on 26 March 2025, the contents of which are incorporated herein by reference as part of this specification.

[0148] 10 Alkaline water electrolysis system 11 Separator 12 Cathode electrode 13 Anode electrode 14 High-concentration alkaline aqueous solution 20 Alkaline water electrolysis system 30 Alkaline water electrolysis system 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 water electrolysis separator comprising a membrane containing a polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B). In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs.

2. The water electrolysis separator according to claim 1, wherein the polymer further comprises a structural unit consisting of an m-phenylene group.

3. The water electrolysis separator according to claim 1, wherein the polymer is a crosslinked polymer (p) having at least one selected from the constituent units represented by general formula (A) and the constituent units represented by general formula (B), and a crosslinkable group.

4. The water electrolysis separator according to claim 3, wherein the crosslinkable group is at least one of a vinyl group and an epoxy group.

5. The water electrolysis separator according to claim 4, wherein the polymer (p) has the crosslinkable group as at least one selected from the group consisting of a structural unit represented by the following general formula (D) and a structural unit represented by the following general formula (E).

6. A separator material for water electrolysis, comprising a non-crosslinked polymer having at least one component selected from the component units represented by the following general formula (A) and the component units represented by the following general formula (B). In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs.

7. A polymer having at least one selected from the constituent units represented by the following general formula (A) and the constituent units represented by the following general formula (B), and satisfying at least one of the following conditions 1 and 2: Condition 1: Having a constituent unit represented by the following general formula (C). Condition 2: Having a crosslinkable group. In the above formula, L independently represents an alkylene group having 1 to 20 carbon atoms, and X independently represents a hydrogen atom, Li, Na, K, or Cs.

8. The polymer according to claim 7, wherein the crosslinkable group is at least one of a vinyl group and an epoxy group.

9. The polymer according to claim 8, wherein condition 2 is condition 2A as follows: Condition 2A: Having at least one selected from the constituent units represented by the following general formula (D) and the constituent units represented by the following general formula (E).

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