Electrolyte membrane, electrolyte membrane with catalyst layer, membrane electrode assembly, polymer electrolyte fuel cell, and solid polymer water electrolysis device

Abstract

An electrolyte membrane comprising a porous membrane 1 and an electrolyte polymer with which pores 2 of the porous membrane 1 are filled, wherein the electrolyte polymer comprises a constituent unit A represented by formula (a1) and a constituent unit B represented by formula (a2). [In formula (a1), IExG represents an ion exchange group, L1 represents a single bond or the like, x represents an integer of 1-10, and * represents a bond.] [In formula (a2), Ar1 represents an arylene group which does not have an ion exchange group, L2 represents a single bond or the like, y represents an integer of 3-20, and * represents a bond. The number of L2s, which are single bonds, is an integer which is at least 0.5y and less than 1.0y.]

Description

Electrolyte membrane, electrolyte membrane with catalyst layer, membrane electrode assembly, polymer electrolyte fuel cell, and polymer electrolyte water electrolysis device

[0001] This disclosure relates to an electrolyte membrane, an electrolyte membrane with a catalyst layer, a membrane electrode assembly, a polymer electrolyte fuel cell, and a polymer electrolyte water electrolysis device.

[0002] In recent years, fuel cells have gained attention as a highly energy-efficient new energy technology, driven by environmental concerns. Among these, polymer electrolyte fuel cells (MLFCs), which use polymer materials as electrolytes, are particularly noteworthy due to their high maximum current density and low-temperature operation, making them suitable for powering vehicles and other mobile devices, as well as for small-capacity power sources for portable electronic devices. Furthermore, from a carbon-neutral perspective, the utilization of polymer electrolyte hydrogen energy, based on fuel cell technology, is also attracting attention.

[0003] As electrolyte membranes used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers, electrolyte membranes using fluorine-based electrolyte polymers (fluorine-based electrolyte membranes) are known (see, for example, Patent Document 1). Although fluorine-based electrolyte membranes are widely used in electrolyte applications due to their high proton conductivity, they have the problems of being expensive and having a large environmental impact.

[0004] For these reasons, the development of electrolyte polymers that do not use fluorine is also progressing. For example, Patent Document 2 discloses an invention relating to a hydrocarbon-based electrolyte membrane made of a block copolymer containing one or more segments (A1) containing ionic groups and one or more segments (A2) that do not contain ionic groups.

[0005] Japanese Patent Publication No. 11-204119, International Publication No. 2013-031675

[0006] The hydrocarbon-based electrolyte polymer obtained by block copolymerization as disclosed in the above Patent Document 2 does not necessarily have sufficient proton conductivity. In order to increase the proton conductivity, it is conceivable to increase the ratio of ion exchange groups (ionic groups). However, when the ion exchange groups increase, the swelling resistance of the electrolyte membrane decreases. Therefore, it is not easy to achieve both high proton conductivity and swelling resistance. In addition, the conventional electrolyte membrane made of an electrolyte polymer has room for improvement in terms of mechanical strength.

[0007] One aspect of the present disclosure aims to provide an electrolyte membrane that has both proton conductivity and swelling resistance and is also excellent in mechanical strength.

[0008] The present disclosure provides the following [1] to

[16] in several aspects.

[0009] [1] An electrolyte membrane including a porous membrane and an electrolyte polymer filled in the pores of the porous membrane, wherein the electrolyte polymer includes a structural unit A represented by the following formula (a1) and a structural unit B represented by the following formula (a2). [In formula (a1), IExG represents an ion exchange group, and L １ represents a single bond, -O-, -S-, or -SO ２ -, x represents an integer from 1 to 10, and * represents a bond. A plurality of IExG may be the same as or different from each other, and a plurality of L １ may be the same as or different from each other. ] [In formula (a2), Ar １ represents an arylene group having no ion exchange group, and L ２ represents a single bond, -O-, -S-, or -SO ２ -, y represents an integer from 3 to 20, and * represents a bond. A plurality of Ar １ may be the same as or different from each other, and a plurality of L ２ may be the same as or different from each other. However, the number of L ２ that is a single bond is an integer of 0.5y or more and less than 1.0y. ]

[0010] [2] The electrolyte membrane according to [1] wherein the constituent unit A comprises at least one group selected from the group consisting of a sulfonic acid group, an alkyl sulfonic acid group, and a sulfonimide group, and salts thereof, as the ion exchange group.

[0011] [3] The electrolyte membrane according to [1] or [2], wherein the constituent unit B comprises, as the arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group, which may have substituents.

[0012] [4] The electrolyte membrane according to any one of [1] to [3], wherein the constituent unit B has a structure in which at least three consecutive arylene groups are bonded together by single bonds.

[0013] [5] The electrolyte membrane according to any one of [1] to [4], wherein the content of the constituent unit B is 25 to 75 mol% of the total amount of all constituent units that make up the polymer.

[0014] [6] The electrolyte membrane according to any one of [1] to [5], wherein the electrolyte polymer contains a plurality of polymer units including the constituent unit A and the constituent unit B, and has crosslinking groups that bond to three or more of the polymer units.

[0015] [7] An electrolyte membrane according to any one of [1] to [6], having a peak in the range of 6.70 to 6.95 ppm in a 1H-NMR spectrum with tetramethylsilane as an internal standard.

[0016] [8] The electrolyte membrane according to any one of [1] to [7], wherein the weight-average molecular weight of the electrolyte polymer is 40,000 to 500,000.

[0017] [9] The electrolyte membrane according to any one of [1] to [8], wherein the porosity of the porous membrane is 30 to 95 volume%.

[0018]

[10] The electrolyte membrane according to any one of [1] to [9], wherein the porous membrane is formed of a material containing a hydrocarbon resin.

[0019]

[11] The electrolyte membrane according to any one of [1] to

[10] , having a layer containing the electrolyte polymer on one or both sides of the porous membrane.

[0020]

[12] The electrolyte membrane according to

[11] , wherein the ratio of the thickness of the porous membrane to the total thickness of the layer containing the electrolyte polymer is 0.1 to 30.

[0021]

[13] An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of [1] to

[12] and a catalyst layer disposed on one or both sides of the electrolyte membrane.

[0022]

[14] A membrane electrode assembly comprising an electrolyte membrane according to any one of [1] to

[12] and an electrode layer disposed on one or both sides of the electrolyte membrane.

[0023]

[15] A polymer electrolyte fuel cell comprising the membrane electrode assembly described in

[14] .

[0024]

[16] A solid polymer water electrolysis apparatus comprising the membrane electrode assembly described in

[14] .

[0025] According to this disclosure, it is possible to provide an electrolyte membrane that achieves both proton conductivity and swelling resistance while also possessing excellent mechanical strength.

[0026] Figure 1 is a schematic cross-sectional view of an electrolyte membrane according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view of an electrolyte membrane according to another embodiment of the present disclosure. Figure 3 is a 10,000x magnification planar SEM image of porous membrane A used in the example. Figure 4 is a 10,000x magnification planar SEM image of porous membrane B used in the example.

[0027] The following describes exemplary embodiments of this disclosure. However, this disclosure is not limited to the embodiments described below. In this specification, numerical ranges indicated using "~" indicate a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. Also, unless otherwise explicitly stated, the units of the numerical values ​​before and after "~" are the same. Furthermore, each configuration and parameter disclosed in this specification can be combined in any way, and the upper and lower limits described individually can be combined in any way.

[0028] <Electrolyte Polymer> The polymer of one embodiment (hereinafter also referred to as "polymer (P)") includes a constituent unit A represented by the following formula (a1) and a constituent unit B represented by the following formula (a2).

[0029]

[0030] In formula (a1), IExG indicates an ion exchange group, and L １ These are single bonds, -O-, -S-, or -SO ２ - indicates a hyphen, x represents an integer from 1 to 10, and * represents a combination. Multiple IExGs may be the same or different from each other, and multiple L １ They may be the same or different from one another.

[0031]

[0032] In formula (a2), Ar １ This indicates an arylene group that does not have an ion exchange group, L ２ These are single bonds, -O-, -S-, or -SO ２ - indicates a combination, y represents an integer from 3 to 20, and * indicates a combination. Multiple Ar １ These may be the same or different from each other, and there may be multiple L ２ These may be identical or different from each other. However, L is a single bond. ２ The number is an integer between 0.5y and 1.0y, inclusive. For example, if y is 10, then L is a simple combination. ２ The number is an integer between 5 and 10 (inclusive).

[0033] Polymer (P) is a so-called electrolyte polymer and possesses excellent proton conductivity. The reason for Polymer (P)'s excellent proton conductivity is not clear, but it is presumed that Polymer (P) contains a hydrophilic part composed of constituent unit A and a hydrophobic part composed of constituent unit B, and that the hydrophilic part, where ion exchange groups are densely concentrated, and the highly water-repellent hydrophobic part self-assemble in a higher-order structure, inducing a microphase separation structure, thereby forming good proton conduction paths within Polymer (P). Furthermore, because Polymer (P) contains a highly water-repellent constituent unit (constituent unit B) in its main chain, where single bonds make up a large proportion of the bonds between arylene groups containing benzene rings, the diffusion coefficient of water increases, and this is also presumed to contribute to the improvement of proton conductivity.

[0034] Polymer (P) also possesses excellent swelling resistance. The reason for this is not entirely clear, but as mentioned above, since polymer (P) contains highly water-repellent structural units (structural units B) in its main chain, it is thought that the penetration of water into the polymer is suppressed, resulting in excellent swelling resistance when formed into a film.

[0035] (Constituent Unit A) Constituent unit A contains an aromatic ring having an ion exchange group (IExG), and a linking group (L) at one end that bonds to other constituent units. １ ) has. Constituent unit A has an aromatic ring having an ion exchange group (IExG) as a linking group (L １ ) may have a continuous structure via a linkage. The linking group located at the end of constituent unit A is, for example, bonded to the aromatic ring of another constituent unit.

[0036] An ion-exchange group is a group that has the property of being able to exchange ions (e.g., cations) with other ions, and is also called an ionic group. Examples of ion-exchange groups include sulfonic acid groups, alkyl sulfonic acid groups, perfluoroalkyl sulfonic acid groups, sulfonimide groups, phosphonic acid groups, phosphate groups, and carboxyl groups, as well as their salts. As mentioned above, some of these ion-exchange groups also form salts with metal ions, etc.

[0037] Sulfonic acid groups and their salts include, for example, -SO ３ M １／ｑ(M represents H or a metal (for example, at least one selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, Al, Fe, Pt, Rh, Ru, Ir, and Pd), and q represents the valence of M (for example, an integer from 1 to 4).) The metal represented by M exists as an ion (cation), -SO ３ － It forms salt.

[0038] Alkyl sulfonic acid groups and their salts are, for example, -R １ SO ３ M １／ｑ It is represented by R １ R is an alkanediyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 12 (an integer). １ Specific examples include, for instance, a methylene group, a butane-1,4-diyl group, and a hexane-1,6-diyl group. M and q are the same as above.

[0039] Sulfonimide groups and their salts include, for example, -SO ２ NM １／ｑ SO ２ R ２ It is represented by R ２ R is an alkyl group, and from the viewpoint of obtaining better proton conductivity, its number of carbon atoms is preferably 1 to 6 (an integer). ２ Specific examples include methyl, ethyl, and propyl groups. M and q are the same as above.

[0040] From the viewpoint of obtaining better proton conductivity, constituent unit A preferably contains at least one group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, and sulfonimide groups, and their salts, as an ion exchange group, and more preferably contains at least one group selected from the group consisting of sulfonic acid groups and their salts. From a similar viewpoint, it is even more preferable that the majority of the multiple ion exchange groups present in constituent unit A are of the above-described preferred form, and it is particularly preferable that all of the multiple ion exchange groups present in constituent unit A are of the above-described preferred form.

[0041] From the viewpoint of obtaining better proton conductivity, the constituent unit A has a linking group (L １ ) as -SO ２ - is preferable. From a similar viewpoint, multiple linking groups (L) present in constituent unit A are preferable. １ It is even more preferable that the majority of these are of the above-described preferred embodiment.

[0042] Linking group (L) in constituent unit A １ ) is a linking group (L) that provides excellent flexibility. １ It is preferable that it contains -O- as ).

[0043] Linking group (L) in constituent unit A １ ) are single bonds, -O- or -SO-, from the viewpoint of improving proton conductivity and flexibility. ２ - is preferable.

[0044] Linking group (L １ The bonding position of the ion exchange group is not particularly limited, but from the viewpoint of obtaining better proton conductivity and chemical durability, it is preferable that it be located in the ortho or meta position relative to the ion exchange group. That is, it is preferable that the constituent unit A contains a 1,4-phenylene group having an ion exchange group.

[0045] The number of repeating structures (x) in the brackets [ ] in formula (a1) of constituent unit A is preferably 2 to 8, and more preferably 3 to 5, from the viewpoint of obtaining better proton conductivity and excellent resistance to hot water. The reason why proton conductivity improves when x is within the above range is not clear, but it is presumed to be due to the effect of the densely packed presence of multiple ion exchange groups.

[0046] From the viewpoint of obtaining better proton conductivity, it is preferable that the constituent unit A includes at least one structure selected from the group consisting of the structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)"), the structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)"), and the structure represented by the following formula (a1-3) (hereinafter referred to as "structure (a1-3)").

[0047]

[0048]

[0049]

[0050] In formulas (a1-1), (a1-2), and (a1-3), IExG, L １ And * are equivalent to those stated above. L in equation (a1-3) １１ x represents -O- or -S-. Multiple IExGs may be the same or different from each other. １ x represents an integer between 2 and 9, and x in equation (a1-2) ２ x represents an integer from 1 to 5, and x in equation (a1-3) ３ x represents an integer between 1 and 2. However, if the constituent unit A includes two or more structures selected from the group consisting of structures (a1-1), structures (a1-2), and structures (a1-3), x １ , 2x ２ (2 and x ２ (product of) and 4x ３ (4 and x) ３ The sum of the products of x is between 4 and 9. １ From the viewpoint of obtaining better proton conductivity and excellent resistance to hot water, the ratio is preferably 2 to 5, and more preferably 2 to 3. ２ From the viewpoint of obtaining better proton conductivity and excellent resistance to hot water, it is preferably 2 to 3, and more preferably 2. ３ From the viewpoint of obtaining better proton conductivity and excellent resistance to hot water, L is preferably 1. In formulas (a1-1), (a1-2), and (a1-3), １ From the viewpoint of improving proton conductivity and flexibility, it is preferable that it be -O-.

[0051] Constituent unit A may consist only of structure (a1-1), or it may include structure (a1-1) and structures other than structure (a1-1). Similarly, constituent unit A may consist only of structure (a1-2), or it may include structure (a1-2) and structures other than structure (a1-2). Similarly, constituent unit A may consist only of structure (a1-3), or it may include structure (a1-3) and structures other than structure (a1-3).

[0052] Constituent unit A may be a constituent unit represented by any of the following formulas (A1-1) to (A1-4).

[0053]

[0054] In formulas (A1-1) to (A1-4), IExG, * and L １ This is equivalent to the above, and L in formula (A1-2) １２ These are single bonds, -O-, -S-, or -SO ２ This indicates -. Multiple IExG may be the same or different from each other. Multiple L １ They may be the same or different from one another.

[0055] In polymer (P), the constituent unit A is preferably one of the constituent units represented by formulas (A1-1) to (A1-4), and more preferably the constituent unit represented by formula (A1-2), from the viewpoint of obtaining better proton conductivity and excellent chemical durability. １２ From the viewpoint of improving proton conductivity and chemical durability, it is preferable that it be a single bond. In this case, L in formula (A1-2) １ From the viewpoint of improving proton conductivity and chemical durability, it is preferable that it be -O-.

[0056] The multiple constituent units A in the polymer (P) may be identical or different from each other. From the viewpoint of obtaining better proton conductivity, it is preferable that the difference of x in formula (a1) among the multiple constituent units A is within 3, and it is more preferable that the multiple constituent units A are identical from each other.

[0057] From the viewpoint of obtaining better proton conductivity, the content of constituent unit A may be 20 mol% or more, 25 mol% or more, and may be 80 mol% or less, 75 mol% or less, or 50 mol% or less, relative to the total amount of all constituent units constituting the polymer (P). From a similar viewpoint, the content of constituent unit A may be 20 to 80 mol%, 25 to 75 mol%, or 25 to 50 mol%, relative to the total amount of all constituent units constituting the polymer (P).

[0058] From the viewpoint of obtaining better proton conductivity, the content of constituent unit A may be 20% by mass or more, 25% by mass or more, and may be 80% by mass or less, 75% by mass or less, or 50% by mass or less, based on the total amount of all constituent units constituting the polymer (P). From a similar viewpoint, the content of constituent unit A may be 20 to 80% by mass, 25 to 75% by mass or 25 to 50% by mass, based on the total amount of all constituent units constituting the polymer (P).

[0059] (Constituent unit B) Constituent unit B is an arylene group (Ar) that does not have an ion exchange group. １ ) is a linking group (L ２ It has a continuous structure via ) and has a linking group (L) at one end that bonds to other constituent units. ２ ) has a connecting group (L) located at the end of constituent unit B. ２ ) is, for example, bonded to the aromatic ring of another constituent unit.

[0060] The arylene group is a divalent aromatic hydrocarbon group and has a structure obtained by removing two hydrogen atoms from a monocyclic or condensed polycyclic aromatic hydrocarbon. The number of aromatic rings in the arylene group is preferably 1 to 4 from the viewpoint of solubility in solvents, film-forming ability, and further improvement of swelling resistance. The arylene group may have substituents other than ion exchange groups. Examples of substituents include aryl groups such as phenyl groups and cyano groups. When the arylene group has an aryl group as a substituent, the number of aromatic rings in the arylene group shall include the number of aromatic rings in the substituent.

[0061] An unsubstituted arylene group may be at least one group selected from the group consisting of phenylene, naphthylene, fluorene, anthracylene, phenanthrylene, triphenylene, pyrenylene, and tetracenylene groups. A substituted arylene group may be at least one group selected from the group consisting of diphenylfluorene, methylphenylene, ethylphenylene, dimethylfluorene, diethylfluorene, dipropylfluorene, diisopropylfluorene, dibutylfluorene, dipentylfluorene, dihexylfluorene, diheptylfluorene, dioctylfluorene, dinonylfluorene, didecylfluorene, diundecylfluorene, and didodecylfluorene groups. Note that a fluorene group as an arylene group means a divalent fluorene group (for example, a fluorene-2,7-diyl group).

[0062] From the viewpoint of solubility in the solvent, film-forming properties, and swelling resistance, it is preferable that the arylene group in component B contains at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have substituents, and more preferably contains at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have an aryl group as a substituent. From the viewpoint of further improving solubility in the solvent and film-forming properties, it is more preferable that component B contains a phenylene group, and even more preferable that it contains a 1,4-phenylene group. From the viewpoint of further improving swelling resistance, it is even more preferable that component B contains a diphenylfluorene group. From a similar viewpoint, it is particularly preferable that the majority of the multiple arylene groups present in component B are of the above-preferred embodiments, and it is extremely preferable that all of the multiple arylene groups present in component B are of the above-preferred embodiments.

[0063] Linking group (L) in constituent unit B ２ From the viewpoint of obtaining superior swelling resistance and flexibility, as well as excellent solubility in solvents and film-forming properties, and excellent mechanical strength of the electrolyte membrane, the following are used: single bond, -O-, or -SO ２- is preferable. However, the constituent unit B is a linking group (L ２ ) includes at least two single bonds. L is a single bond in constituent unit B. ２ The number is an integer between 0.5y and less than 1.0y, and may be an integer between 0.6y and 0.7y or more from the viewpoint of obtaining better swelling resistance, and may be an integer between 0.95y or less or 0.90y or less from the viewpoint of obtaining better flexibility. From these viewpoints, the single bond L in the constituent unit B ２ The number may be an integer between 0.6y and 0.95y or between 0.7y and 0.90y.

[0064] In the constituent unit B, the number of repeating structures (y) in the brackets [ ] in formula (a2) is an integer from 3 to 20, and is preferably 4 to 12, more preferably 5 to 10, from the viewpoint of obtaining better proton conductivity, better swelling resistance, and excellent heat and water resistance.

[0065] In the constituent unit B, the number of repeating structures (y) in the brackets [ ] in formula (a2) is preferably 2 to 7 more than the number of repeating structures (x) in formula (a1) (x + (2 to 7)), from the viewpoint of achieving both superior proton conductivity and resistance to hot water, and obtaining superior swelling resistance.

[0066] From the viewpoint of obtaining better proton conductivity, the number of aromatic rings in the main chain of constituent unit B is preferably 3 to 20, more preferably 4 to 12, and even more preferably 5 to 10.

[0067] From the viewpoint of obtaining better swelling resistance, it is preferable that constituent unit B includes a structure in which at least three consecutive arylene groups are linked by single bonds. From the viewpoint of obtaining even better swelling resistance, the number of consecutive arylene groups via single bonds may be four or more or five or more. From the viewpoint of obtaining better flexibility, the number of consecutive arylene groups via single bonds may be 10 or less, 8 or less, or 6 or less. From these viewpoints, the number of consecutive arylene groups via single bonds may be 3 to 10, 4 to 8, or 5 to 6.

[0068] Constituent unit B may be a constituent unit represented by any of the following formulas (A2-1) to (A2-5).

[0069]

[0070] * and L in equations (A2-1) to (A2-5) ２ This is equivalent to the above. R in equations (A2-3) and (A2-5) ３ R represents an alkyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 12 (an integer). ３ Specific examples include methyl, ethyl, propyl, hexyl, and dodecyl groups. In formulas (A2-3) and (A2-5), multiple R ３ They may be the same or different from one another.

[0071] In polymer (P), the constituent unit B is preferably one of the constituent units represented by formulas (A2-1) to (A2-5), and more preferably the constituent unit represented by formula (A2-4), from the viewpoint of obtaining better swelling resistance.

[0072] The multiple constituent units B in the polymer (P) may be identical or different from each other. From the viewpoint of obtaining better proton conductivity, it is preferable that the difference of y in formula (a2) among the multiple constituent units B be within 5, and it is more preferable that the multiple constituent units B are identical from each other.

[0073] From the viewpoint of obtaining better swelling resistance, the content of constituent unit B may be 25 mol% or more, 40 mol% or more, and 75 mol% or less, or 60 mol% or less, relative to the total amount of all constituent units that make up the polymer (P). From a similar viewpoint, the content of constituent unit B may be 25 to 75 mol%, and 40 to 60 mol%, relative to the total amount of all constituent units that make up the polymer (P).

[0074] From the viewpoint of obtaining better swelling resistance, the content of constituent unit B may be 25% by mass or more, 40% by mass or more, and 75% by mass or less, or 60% by mass or less, based on the total amount of all constituent units that make up the polymer (P). From a similar viewpoint, the content of constituent unit B may be 25 to 75% by mass, and 40 to 60% by mass, based on the total amount of all constituent units that make up the polymer (P).

[0075] The polymer (P) may consist only of constituent units A and B, or it may contain constituent units other than constituent units A and B. An example of a constituent unit other than constituent units A and B is constituent unit C, which is represented by the following formula (a3).

[0076]

[0077] In formula (a3), Ar ２ L indicates an arylene group. ３ These are single bonds, -O-, -S-, or -SO ２ - indicates a combination, z represents an integer from 1 to 20, and * indicates a combination. Multiple Ar ２ These may be the same or different from each other, and there may be multiple L ３ They may be the same or different from one another.

[0078] The constituent unit C is an arylene group (Ar ２ ) includes a linking group (L) that is bonded to another constituent unit at one end. ３ ) has a constituent unit C is an arylene group (Ar ２ ) is a linking group (L ３ ) may have a continuous structure via a connecting group (L) located at the end of the constituent unit C. ３ ) is, for example, bonded to the aromatic ring of another constituent unit.

[0079] The arylene group may or may not have an ion exchange group. A specific example of an arylene group having an ion exchange group is a phenylene group having one ion exchange group. Specific examples of ion exchange groups are the same as those for the ion exchange group in constituent unit A described above. Specific examples of an arylene group not having an ion exchange group are the same as those for the arylene group in constituent unit B described above.

[0080] The constituent unit C is the arylene group (Ar) in formula (a3). ２ The constituent unit may consist entirely of arylene groups that do not have ion exchange groups. In this case, the linking group (L) which is a single bond in the constituent unit C may also be a single bond. ３ The number of ) is an integer less than 0.5z or equal to 1.0z.

[0081] The content of constituent unit C may be, for example, 1 to 40 mol%, 3 to 30 mol%, or 5 to 20 mol%, relative to the total amount of all constituent units that make up the polymer (P).

[0082] The arrangement of each constituent unit in polymer (P) is not particularly limited. Each component may be arranged regularly or irregularly. For example, polymer (P) may be a so-called precisely arranged polymer in which constituent units A and B, or constituent units A, B, and C are arranged alternately, or it may be a random copolymer in which constituent units A and B, or constituent units A, B, and C are arranged irregularly. From the viewpoint of easily achieving both better proton conductivity and better swelling resistance, polymer (P) is preferably a random copolymer. From a similar viewpoint, it is preferable that each constituent unit in polymer (P) is arranged so that identical constituent units are not consecutive.

[0083] The polymer (P) may have a structure represented by, for example, the following formulas (1) to (6).

[0084]

[0085] In formulas (1) to (6), * has the same meaning as described above. A and B in formulas (1) to (6) respectively represent a structural unit A represented by formula (a1) and a structural unit B represented by formula (a2), and n represents an integer from 10 to 100. X in formulas (2) to (6) represents a structural unit X selected from a structural unit A represented by formula (a1), a structural unit B represented by formula (a2), and a structural unit C represented by formula (a3). l and m in formulas (4) to (6) each independently represent a number from 0 to 1. The plurality of A's may be the same as or different from each other, the plurality of B's may be the same as or different from each other, and the plurality of X's may be the same as or different from each other. Note that formula (4) means that a block (first block) composed of a structural unit A and a structural unit B and a block (second block) composed of a structural unit X and a structural unit B exist in a ratio of l:m, and the polymer (P) is composed of l×n first blocks and m×n second blocks. In formula (4), for convenience, (A - B) ｌ and (X - B) ｍ are described, but these do not mean that l first blocks are consecutive and m second blocks are consecutive, and the arrangement of the first block and the second block may be regular or irregular. The same applies to formulas (5) and (6).

[0086] From the viewpoint of obtaining more excellent proton conductivity and more excellent swelling resistance, the polymer (P) preferably has a structure represented by any one of formulas (1) to (6), and more preferably has a structure represented by formula (4) or formula (5).

[0087] The polymer (P) may consist of a polymer structure containing constituent units A and B, and terminal structures bonded to the structure. Examples of terminal structures include hydroxyl groups, thiol groups, halogen atoms, boronic acid groups, alkylborane groups, and boronic acid ester groups. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Examples of alkylborane groups include diethylborane, diciamilborane, dicyclohexylborane, and 9-borabicyclo[3.3.1]nonane. Examples of boronic acid ester groups include pinacol boronic acid ester, 1,3-propanediol boronic acid ester, biscyclohexyldiol boronic acid ester, neopentyl glycol boronic acid ester, and catechol boronic acid ester.

[0088] The polymer (P) may include a three-dimensional crosslinked structure formed by crosslinking a plurality of polymer units, including constituent unit A and constituent unit B, via a crosslinking group. The crosslinking group may be a group derived from a known crosslinkable compound (e.g., decafluorobiphenyl). If the crosslinking group has an aromatic ring, the polymer units may be directly crosslinked to the aromatic ring of the crosslinking group, or to -O-, -S-, or -SO ２ They may be bonded via a cross-linking group. The number of cross-linking groups may be one or more. The multiple cross-linking groups may be the same or different from each other.

[0089] The polymer (P) may contain fluorine atoms, but the fluorine content in the polymer (P) is preferably 5% by mass or less, and it is preferable that the polymer (P) does not contain fluorine atoms (the fluorine content is below the detection limit).

[0090] The number-average molecular weight of the polymer (P) may be 10,000 or more, 20,000 or more, or 22,000 or more from the viewpoint of superior proton conductivity and superior mechanical strength of the electrolyte membrane, and may be 300,000 or less, 100,000 or less, 50,000 or less, or 30,000 or less from the viewpoint of superior solubility in the solvent and film formation. From these viewpoints, the number-average molecular weight of the polymer (P) may be 10,000 to 300,000, 20,000 to 100,000, 22,000 to 50,000, or 22,000 to 30,000.

[0091] The weight-average molecular weight of polymer (P) may be 40,000 or more, 50,000 or more, 60,000 or more, or 68,000 or more, from the viewpoint of superior proton conductivity and superior mechanical strength of the electrolyte membrane, and may be 500,000 or less, 300,000 or less, or 230,000 or less, from the viewpoint of superior solubility in solvents and film formation. From these viewpoints, the weight-average molecular weight of polymer (P) may be 40,000 to 500,000, 50,000 to 300,000, 60,000 to 230,000, or 68,000 to 230,000.

[0092] The ratio of the weight-average molecular weight to the number-average molecular weight of the polymer (P) (polydispersity) may be 1.5 or higher, and may be 2.0 or higher, 2.3 or higher, 2.5 or higher, or 2.8 or higher. When the polydispersity of the polymer (P) is 2.5 or higher, better swelling resistance tends to be obtained. From the viewpoint of solubility in the solvent, the polydispersity of the polymer (P) may be 20.0 or lower, and may be 18.0 or lower, 15.0 or lower, 12.0 or lower, or 10.0 or lower. The polydispersity of the polymer (P) may be 1.5 to 20.0, 2.0 to 20.0, 2.3 to 20, 2.5 to 20.0, 2.5 to 18.0, 2.5 to 15.0, 2.5 to 12.0, or 2.8 to 10.0.

[0093] The number-average molecular weight and weight-average molecular weight of polymer (P) are measured by gel permeation chromatography (GPC) and are expressed as standard polyethylene glycol / oxide (PEG / PEO) equivalent values.

[0094] Polymer (P) uses tetramethylsilane as an internal standard. １In the 1H-NMR spectrum, a peak may be present in the range of 6.70 to 6.95 ppm. If the peak is split into a doublet or other multiplet, the median value of the peak is taken as the chemical shift value of that peak. Polymers (P) that have such a peak tend to have excellent chemical durability. The above peak may originate from the ortho hydrogen atom of the hydroxyl group in the aromatic ring at the end of polymer (P). １ The 1H-NMR spectrum can be measured by the method described in the examples below.

[0095] The ion exchange capacity (IEC) of the polymer (P) may be 1.0 mmol / g or more, 1.5 mmol / g or more, or 1.8 mmol / g or more from the viewpoint of superior proton conductivity, and may be 3.5 mmol / g or less, 3.0 mmol / g or less, or 2.8 mmol / g or less from the viewpoint of superior swelling resistance. From these viewpoints, the ion exchange capacity of the polymer (P) may be 1.0 to 3.5 mmol / g, 1.5 to 3.0 mmol / g, or 1.8 to 2.8 mmol / g.

[0096] The ion exchange capacity of the polymer (P) is a value measured by the following procedures (1) to (7). (1) Dissolve the polymer (P) in dimethyl sulfoxide (DMSO) to obtain a solution containing 15% by mass of the polymer (P). (2) Cast and apply the obtained solution onto a glass substrate and dry it at 60 °C for 12 hours to form a film. (3) After immersing the obtained film in 1 M hydrochloric acid for 24 hours, immerse it in pure water for washing. (4) Dry the washed electrolyte membrane to obtain the dry mass. Drying is carried out until the mass reduction rate when heating the electrolyte membrane at 80 °C is 1% by mass / hour or less. For example, after drying under reduced pressure, heat it at 80 °C for 12 hours or more. (5) Immerse the dried film in a 20% by mass aqueous sodium chloride solution and stir for 24 hours for ion exchange. (6) Using a 0.01 M aqueous sodium hydroxide solution, titrate the hydrochloric acid generated by the above ion exchange with the endpoint being the point where the pH reaches 7. (7) Calculate the ion exchange capacity (IEC) of the polymer (P) using the following formula. IEC (unit: mmol / g) = {concentration of aqueous sodium hydroxide solution (unit: mol / L) × dropwise addition amount (unit: mL)} / dry mass of electrolyte membrane (unit: g)

[0097] The polymer (P) can be obtained, for example, by reacting (polymerizing) monomers containing a compound represented by the following formula (b1) (hereinafter also referred to as "compound (b1)") and a compound represented by the following formula (b2) (hereinafter also referred to as "compound (b2)"). That is, the polymer (P) can be a polymer of monomers containing compound (b1) and compound (b2).

[0098]

[0099] In formula (b1), IExG, L １ and x have the same meanings as described above, and X １ｂ and X ２ｂ each independently represent a halogen atom. Examples of the halogen atom are the same as the examples of the halogen atom exemplified as the terminal structure of the polymer (P) described above.

[0100]

[0101] In formula (b2), Ar １ 、L ２And y are the same as above. Z １ｂ and Z ２ｂ Each of these independently represents a hydroxyl group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of halogen atoms, alkylborane groups, and boronic acid ester groups are the same as the examples of halogen atoms, alkylborane groups, and boronic acid ester groups exemplified above as terminal structures of polymer (P). However, Z ２ｂ When L is a hydroxyl group or a thiol group, it is a single bond. ２ The number is an integer between 0.5y and (1.0y-1), and Z ２ｂ When is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, L is a single bond. ２ The number is an integer between (0.5y-1) and (1.0y-1) inclusive.

[0102] In the above method, Z ２ｂ If it is a hydroxyl group, the terminal linking group (L ２ A constituent unit B is formed in which ) is -O-, Z ２ｂ If it is a thiol group, the terminal linking group (L ２ A constituent unit B is formed in which ) is -S-, Z ２ｂ When is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, the terminal linking group (L ２ A constituent unit B is formed, which is a single bond.

[0103] As for compound (b1), X １ｂ and / or X ２ｂ Multiple types of compounds with different properties can be used. Similarly, as compound (b2), Z １ｂ and / or Z ２ｂ Multiple types of compounds with different properties can be used.

[0104] Monomers containing compound (b1) and compound (b2) can be reacted (polymerized), for example, by aromatic nucleophilic substitution in a solvent in the presence of a base.

[0105] The solvent used in the reaction is preferably one that is a good solvent for compound (b1), compound (b2), and polymer (P), and that allows for the high molecular weight of polymer (P) during polymerization. For example, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea are preferably used. These solvents may be used individually or as a mixture of two or more.

[0106] A base is used to enhance the nucleophilicity of the monomer. The base is not particularly limited as long as it can deprotonate compound (b2). For example, alkali metal hydroxides and carbonates, alkaline earth metal hydroxides and carbonates, and organic bases such as amines can be used. The alkali metal may be lithium, sodium, potassium, rubidium, or cesium. The alkaline earth metal may be magnesium, calcium, strontium, or barium.

[0107] The reaction temperature in aromatic nucleophilic substitution reactions may be in the range of 25 to 350°C. From the viewpoint of excellent reaction rate, the reaction temperature is preferably 60°C or higher, and more preferably 100°C or higher. From the viewpoint of suppressing polymer decomposition, the reaction temperature is preferably 300°C or lower, and more preferably 250°C or lower. From these viewpoints, the reaction temperature is preferably 60 to 300°C, and more preferably 100 to 250°C.

[0108] Monomers containing compound (b1) and compound (b2) can also be subjected to cross-coupling reactions (polymerization), for example, in a solvent in the presence of a catalyst. Examples of solvents that can be used in the reaction are the same as examples of solvents that can be used in the aromatic nucleophilic substitution reaction described above.

[0109] There are no particular restrictions on the catalyst as long as it can carry out the cross-coupling reaction, and conventionally known catalysts can be used. For coupling reactions between halogens, for example, copper catalysts, nickel catalysts, or palladium catalysts can be used. For coupling reactions between halogens and boronic acid groups, alkylborane groups, or boronic acid ester groups, for example, conventionally known catalysts used in the Suzuki-Miyaura coupling reaction (palladium catalysts, nickel catalysts, etc.) can be used.

[0110] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I)hexafluorophosphate.

[0111] The nickel catalyst may be, for example, bis(1,5-cyclooctadiene)nickel(0), dibromobis(triphenylphosphine)nickel(II), or [1,1'-bis(diphenylphosphino)ferrocene]dichloronickel(II).

[0112] The palladium catalyst may be, for example, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(triphenylphosphine)palladium(II) dichloride, or [1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II).

[0113] The reaction temperature in the cross-coupling reaction may be in the range of 0 to 350°C. From the viewpoint of improving the reaction rate, the reaction temperature is preferably 30°C or higher, and more preferably 60°C or higher. From the viewpoint of suppressing polymer decomposition, the reaction temperature is preferably 300°C or lower, and more preferably 250°C or lower. From these viewpoints, the reaction temperature is preferably 30 to 300°C, and more preferably 60 to 250°C.

[0114] In the aromatic nucleophilic substitution and cross-coupling reactions described above, it is preferable to remove water from the reaction system in order to increase the molecular weight of the polymer (P). The method of dehydration is not particularly limited, but examples include azeotropic dehydration by coexisting an azeotropic solvent in the reaction system, continuous removal from the reaction system by heating above the boiling point of water, and coexisting a water-absorbing agent such as a molecular sieve. The azeotropic solvent is not particularly limited as long as it can remove water, and for example, at least one selected from the group consisting of benzene, toluene, cyclohexane, and xylene may be used.

[0115] The above aromatic nucleophilic substitution and cross-coupling reactions are preferably carried out under an inert atmosphere (for example, under a nitrogen or argon atmosphere). After the polymerization reaction is complete, the polymer can be recovered from the reaction solution and purified to obtain the desired polymer. Methods for recovering the polymer from the reaction solution include, for example, adding the reaction solution to a solvent in which the polymer has low solubility, allowing the polymer to precipitate and be recovered as a solid, and removing the solvent from the reaction solution by evaporation and recovering the polymer as a solid. Methods for purifying the polymer include, for example, washing in a solvent in which the polymer has low solubility and the by-product inorganic salts and residual monomer-derived compounds have high solubility, and washing using a Soxhlet extractor. The methods for recovering and purifying the polymer are not limited to these methods.

[0116] Polymer (P) can also be obtained by reacting (polymerizing) monomers containing compound (b1), compound (b2), and a compound represented by the following formula (b3) (hereinafter also referred to as "compound (b3)"). In other words, polymer (P) can also be a polymer of monomers containing compound (b1), compound (b2), and compound (b3).

[0117]

[0118] In formula (b3), Ar ２ Z １ｂ Z ２ｂ , L ３ And z are equivalent to those stated above.

[0119] As for compound (b3), Z １ｂ and / or Z ２ｂ Multiple types of compounds with different properties can be used. Reactions of monomers containing compound (b1), compound (b2), and compound (b3) can be carried out in the same manner as reactions of monomers containing compound (b1) and compound (b2).

[0120] While some aspects of the polymer (P) and its manufacturing method in this disclosure have been described above, the polymer (P) and its manufacturing method in this disclosure are not limited to those described above.

[0121] For example, polymer (P) can be replaced with X in formula (b1) １ｂ and X ２ｂ However, compounds that are independently a hydroxyl group, a thiol group, a boronic acid group, an alkylborane group, or a boronic acid ester group may be used. In this case, as compound (b2) and / or compound (b3), both ends (Z in formula (b2)) may be used. １ｂ and Z ２ｂ , and also Z in equation (b3) １ｂ and Z ２ｂ Either use a compound in which the (b) atom is a halogen atom, or use compounds in which one end is a halogen atom as compound (b2) and compound (b3).

[0122] Furthermore, polymer (P) can also be obtained by oxidizing a polymer (for example, a monomer polymer containing compound (b1) and compound (b2)) that includes constituent unit A represented by formula (a1) and constituent unit B represented by formula (a2). More specifically, polymer (P) is obtained by L １ or L ２ It can be an oxide of a polymer containing a -S- (sulfide group) (hereinafter referred to as "sulfide-containing polymer").

[0123] Furthermore, polymer (P) can also be obtained, for example, by reacting (polymerizing) a polymer of the monomer or its oxide with a known crosslinkable compound (e.g., decafluorobiphenyl) having three or more groups that react with the polymer or its oxide to form a crosslink. In other words, polymer (P) can be a reaction product of the polymer of the monomer or its oxide and a crosslinkable compound. This method makes it possible to obtain polymer (P) having the polymer or its oxide as a polymer unit.

[0124] The polymer (P) may be obtained by a method that includes a step of protonating the ion exchange groups that form salts with metal ions. This step may involve immersing the polymer obtained by the method described above (for example, a monomeric polymer or oxide thereof containing compound (b1) and compound (b2), or a reaction product of the polymer or oxide with a crosslinkable compound (d)) in an acid (for example, hydrochloric acid) to protonate the ion exchange groups (for example, a salt of a sulfonic acid group). By washing and drying the compound (for example, powder) after immersion, the metal ions of the polymer before immersion are replaced with protons, and a polymer (P) in which the ion exchange groups are protonated is obtained.

[0125] <Electrolyte Membrane> Figure 1 is a schematic cross-sectional view of an electrolyte membrane according to one embodiment. The electrolyte membrane 10A in Figure 1 includes a porous membrane 1 and a filler 3 containing the polymer (P) as an electrolyte polymer, which is filled into the pores 2 of the porous membrane 1. In the electrolyte membrane 10A, the porous membrane 1 is exposed on the surface of the electrolyte membrane 10A. Since the electrolyte membrane 10A contains polymer (P) as an electrolyte, it can be a hydrocarbon-based electrolyte membrane. In this specification, "hydrocarbon-based electrolyte membrane" means an electrolyte membrane that does not substantially contain fluorine atoms (i.e., the fluorine content in the electrolyte membrane is 5% by mass or less).

[0126] (Porous membrane) The porous membrane 1 contributes to improving the mechanical strength and swelling resistance of the electrolyte membrane 10A as a reinforcing material. The porous membrane 1 may be formed from a material containing a hydrocarbon resin, from the viewpoint of increasing its affinity with the polymer (P) and making it easier to obtain higher mechanical strength and swelling resistance.

[0127] Hydrocarbon resins are resins made from hydrocarbon compounds that do not contain fluorine atoms in their molecules. Examples of hydrocarbon resins include at least one selected from the group consisting of polyolefin resins, polyester resins, polyphenylene sulfide resins, polyetherimide resins, polyimide resins, polyurethane resins, and polyethersulfone resins. These resins provide sufficient stability in acidic environments in fuel cells and water electrolyzers. Examples of polyolefin resins include at least one selected from the group consisting of polyethylene resins and polypropylene resins. Examples of polyester resins include at least one selected from the group consisting of polyethylene terephthalate resins and polybutylene terephthalate resins.

[0128] From the viewpoint of reducing manufacturing costs and environmental impact, it is preferable to use polyolefin resins, and more preferable to use at least one resin selected from the group consisting of polyethylene and polypropylene. In other words, the porous membrane 1 is preferably a polyolefin porous membrane (a porous membrane mainly composed of polyolefin resin), and more preferably a polyethylene porous membrane (a porous membrane mainly composed of polyethylene) or a polypropylene porous membrane (a porous membrane mainly composed of polypropylene). Although polyolefin resins tend to have inferior mechanical strength, according to this disclosure, mechanical strength can be improved, so even when using polyolefin resins, it is easy to obtain an electrolyte membrane with sufficient mechanical strength. Furthermore, using polyolefin resins as hydrocarbon resins also tends to improve swelling resistance. Among polyolefin resins, polyethylene is most likely to provide excellent mechanical strength and excellent swelling resistance. In this specification, the main component means the component with the highest content among the contained components. The content of the main component is, for example, 60% by mass or more, and may be 80% by mass or more or 90% by mass or more.

[0129] The material containing the hydrocarbon resin may consist solely of the hydrocarbon resin, but may also contain other components other than the hydrocarbon resin, to the extent that they do not impair the effects of the present disclosure. Other components may include, for example, at least one selected from the group consisting of water-retaining inorganic substances and radical scavengers. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The total content of other components may be 0 to 10% by mass, based on the total mass of the material.

[0130] The porous membrane 1 may be a film-like membrane (porous film). The porous membrane 1 may also be a membrane formed from fibers such as nonwoven fabric. That is, the pores 2 in the porous membrane 1 may be composed of fine gaps formed by the entanglement of fibers. The porous membrane 1 may be a porous membrane having a single-pore structure or a porous membrane having a multi-pore structure.

[0131] The porosity of the porous membrane 1 may be 30 volume% or more, 40 volume% or more, 50 volume% or more, or 70 volume% or more, from the viewpoint of obtaining better proton conductivity. The porosity of the porous membrane 1 may be 95 volume% or less, 90 volume% or less, 85 volume% or less, or 80 volume% or less, from the viewpoint of improving mechanical strength. From the above viewpoint, the porosity of the porous membrane 1 may be 30 to 95 volume%, 40 to 90 volume%, 50 to 85 volume%, 70 to 85 volume%, or 70 to 80 volume%. The above porosity can be determined, for example, from the pore volume calculated by the mercury intrusion method using a POREMASTER GT (manufactured by Quantachrome Instruments).

[0132] The thickness of the porous membrane 1 may be set according to the size of the applicable device (e.g., polymer electrolyte fuel cell and polymer electrolyte water electrolysis device), and may be, for example, greater than 0 μm, 0.5 μm or more, 1 μm or more, or 5 μm or more, and may be 200 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less, or 12 μm or less. The thickness of the porous membrane 1 may be greater than 0 μm and 200 μm or less, greater than 0 μm and 100 μm or less, 0.5 to 50 μm, 1 to 25 μm, 1 to 15 μm, or 5 to 12 μm. The thicker the porous membrane, the easier it is to obtain higher mechanical strength, and the thinner the porous membrane, the easier it is to obtain better proton conductivity. Note that the thickness of the porous membrane is the average thickness measured at any five locations in the cross-section of the porous membrane.

[0133] The porous membrane 1 can be obtained by conventionally known methods. For example, when forming a membrane with a material containing a hydrocarbon resin, a template (particles, etc.) can be added, and after membrane formation, the template can be removed by performing a process such as stretching. The membrane formation method may be a known method, such as a solution casting method, a dispersion casting method, a melt press method, or a melt extrusion method. Alternatively, the porous membrane 1 (nonwoven membrane) can be formed by known methods such as the spunbond method, melt blowing method, or spunlace method. As the porous membrane 1, commercially available products such as NR2451 ultra-high molecular weight polyethylene porous sheet manufactured by Flon Chemical Co., Ltd., "Hypore" polyolefin flat membrane manufactured by Asahi Kasei Corporation, and "Poram" polyethylene microporous film manufactured by Tokuyama Corporation can also be used.

[0134] (Filler) Filler 3 contains the above polymer (P) as an electrolyte polymer. From the viewpoint of obtaining better proton conductivity, the polymer (P) content (filler amount) may be 50 parts by mass or more, 90 parts by mass or more, or 300 parts by mass or more, per 100 parts by mass of porous membrane. From the viewpoint of further improving mechanical strength, the polymer (P) content (filler amount) may be 3000 parts by mass or less, 2000 parts by mass or less, 1000 parts by mass or less, 600 parts by mass or less, 350 parts by mass or less, or 150 parts by mass or less, per 100 parts by mass of porous membrane. From the above viewpoint, the polymer (P) content (filler amount) may be 50 to 3000 parts by mass, 90 to 2000 parts by mass, 300 to 1000 parts by mass, 300 to 600 parts by mass, 50 to 350 parts by mass, or 50 to 150 parts by mass, per 100 parts by mass of porous membrane.

[0135] The filler 3 may contain other components besides the polymer (P) to the extent that they do not impair the effects of the present disclosure. These other components may include, for example, at least one selected from the group consisting of water-retaining inorganic substances and radical scavengers. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The total amount of these other components may be 0 to 10% by mass, 0 to 6% by mass, or 0 to 3% by mass, based on the total solid content of the filler.

[0136] Preferably, the filler 3 completely fills the pores 2 of the porous membrane 1, but it is not necessary for some of the pores 2 of the porous membrane 1 to be filled with the filler 3. The proportion of voids (porosity) originating from the porous membrane 1 in the electrolyte membrane 10A can be calculated by performing a cross-sectional observation of the electrolyte membrane and binarizing the void and non-void portions by image analysis. The proportion of voids (porosity) originating from the porous membrane 1 in the electrolyte membrane 10A may be 0 to 0.1 volume%, 0 to 0.01 volume%, or 0 to 0.001 volume%, from the viewpoint of obtaining higher mechanical strength and better proton conductivity.

[0137] (Electrolyte Membrane) The electrolyte membrane 10A contains polymer (P) as the electrolyte polymer, and therefore exhibits excellent proton conductivity. Furthermore, the electrolyte membrane 10A has a structure in which the porous membrane 1 and polymer (P) are composited, with polymer (P) filling the pores of the porous membrane 1, and thus has improved mechanical strength. In addition, the electrolyte membrane 10A has excellent swelling resistance due to the synergistic effect of containing polymer (P) and having the above structure. Therefore, the electrolyte membrane 10A can increase the durability of polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The electrolyte membrane 10A can also be used in redox flow batteries, electrochemical hydrogen pumps, chlor-alkali electrolyzers, solid acid catalysts, membrane humidity control devices, gas separation membranes, etc.

[0138] The electrolyte membrane 10A is obtained by filling the porous membrane 1 with a filler material 3. One method for filling the porous membrane 1 with the filler material 3 is to impregnate the porous membrane 1 with a solution containing the filler material 3, and then dry the solution.

[0139] A method for manufacturing the electrolyte membrane 10A may include, for example, a step of applying a solution containing the filler 3 onto a substrate to form a coating film (a), a step of placing the porous membrane 1 on the coating film and impregnating the porous membrane 1 with the solution (b), and a step of drying the solution (c). In this method, from the viewpoint of more thoroughly impregnating the porous membrane 1 with the solution, a step of applying the solution containing the filler 3 onto the surface of the porous membrane 1 opposite to the substrate (b-2) may be performed after step (b). The substrate may be peeled off and removed after step (c). If the ion exchange groups of the polymer (P) have metal ions, a step of substituting the metal ions with protons (d) may be performed after step (c).

[0140] For example, a glass substrate can be used as the substrate. The solvent used in the solution is not particularly limited as long as it is a solvent capable of dissolving the electrolyte polymer, and for example, at least one selected from the group consisting of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea can be used.

[0141] The method of applying the solution is not particularly limited. The application method may be, for example, the applicator method, bar coating method, spin coating method, spray coating method, dip coating method, nozzle coating method, gravure coating method, reverse roll coating method, die coating method, air doctor coating method, blade coating method, rod coating method, curtain coating method, knife coating method, transfer roll coating method, squeeze coating method, impregnation coating method, kiss coating method, calender coating method, or extrusion coating method.

[0142] The drying method is not particularly limited, as long as it can sufficiently remove the solvent from the solution. In the case of heat drying, the drying temperature may be, for example, 20 to 150°C, and the drying time may be, for example, 0.2 to 24 hours.

[0143] Step (d) may be, for example, a step of immersing the film obtained in step (c) in an acid (e.g., hydrochloric acid). By washing and drying the film after immersion, an electrolyte film is obtained in which the metal ions of the electrolyte polymer are replaced with protons.

[0144] The electrolyte membrane of this disclosure has been described above using electrolyte membrane 10A as an example, but the electrolyte membrane of this disclosure is not limited to the above.

[0145] In another embodiment, the electrolyte membrane may have layers other than the porous membrane and the layer containing the electrolyte polymer (polymer (P)) filling the pores of the porous membrane (hereinafter also referred to as the "composite layer"). For example, the electrolyte membrane may further have a layer containing the electrolyte polymer (hereinafter also referred to as the "electrolyte polymer layer") in addition to the composite layer. The electrolyte polymer is, for example, polymer (P). By having the electrolyte polymer layer on one or both sides of the porous membrane, the electrolyte membrane is more likely to achieve superior proton conductivity. In particular, by forming the outermost surface of the electrolyte membrane with the electrolyte polymer layer, the adhesion of the electrolyte membrane to the catalyst layer is improved, and the proton conductivity is improved. Hereinafter, an electrolyte membrane having an electrolyte polymer layer will be described in more detail with reference to Figure 2.

[0146] Figure 2 is a schematic cross-sectional view showing an electrolyte membrane of another embodiment. The electrolyte membrane 10B in Figure 2 has a composite layer 4 and layers containing an electrolyte polymer (a first electrolyte polymer layer 5 and a second electrolyte polymer layer 6). In the electrolyte membrane 10B, the porous membrane 1 is not exposed on the surface of the electrolyte membrane 10B, and the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are provided on the surface of the composite layer 4.

[0147] The composite layer 4 is a layer comprising a porous membrane 1 and a filler material 3 containing a polymer (P) that fills the pores 2 of the porous membrane 1. The composite layer 4 may be the electrolyte membrane 10A described above. That is, the porous membrane 1 and filler material 3 in the composite layer 4 may be the same as the porous membrane 1 and filler material 3 in the electrolyte membrane 10A.

[0148] The details of the electrolyte polymers contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are the same as the details of the electrolyte polymers contained in the electrolyte membrane 10A. The electrolyte polymers contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same as or different from the electrolyte polymer contained in the composite layer 4.

[0149] The first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be formed from a filler 3 that fills the composite layer 4. That is, the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may consist only of an electrolyte polymer, or they may contain other components that can be included in the filler 3, to the extent that they do not impede the effects of the present disclosure.

[0150] The compositions of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same or different from each other.

[0151] The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm, 0.5 μm or more, 1 μm or more, or 5 μm or more, and may be 100 μm or less, 50 μm or less, 25 μm or less, or 15 μm or less, respectively. The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm and 100 μm or less, and may be 0.5 to 50 μm, 1 to 25 μm, 5 to 25 μm, or 5 to 15 μm, respectively. Furthermore, the total thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm and 200 μm or less, and may be 1 to 50 μm or 2 to 30 μm. The thinner the electrolyte polymer layer, the easier it is to obtain better proton conductivity, and the thicker the electrolyte polymer layer, the easier it is to obtain the effect of improving mechanical strength by the composite layer. Note that the thickness of the electrolyte polymer layer is the average thickness measured at any five locations in the cross-section of the electrolyte polymer layer.

[0152] From the viewpoint of making it easier to obtain the effect of improving mechanical strength by the composite layer, the thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 is preferably thinner than the thickness of the composite layer 4.

[0153] The electrolyte polymer layers 5 and 6 in the electrolyte membrane 10B can be easily formed by adjusting the amount of solution used in the manufacturing method of the electrolyte membrane 10A described above.

[0154] In the electrolyte membrane 10B, electrolyte polymer layers are provided on both sides of the composite layer 4, but an electrolyte membrane having an electrolyte polymer layer may have the electrolyte polymer layer on only one side of the composite layer. That is, the electrolyte membrane may have only one of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6. The details (thickness, etc.) of these layers are as described above. The range of electrolyte polymer content when the electrolyte membrane has an electrolyte polymer layer is the same as the range of electrolyte polymer (polymer (P)) content in the electrolyte membrane 10A described above.

[0155] The ratio of the thickness D2 of the porous membrane to the thickness D1 of the electrolyte membrane (D2 / D1) may be 0.1 to 1. A ratio (D2 / D1) of 0.1 or higher tends to improve mechanical strength. From a similar viewpoint, the above ratio (D2 / D1) may be 0.3 or higher or 0.5 or higher. From the viewpoint of adhesion of the electrolyte membrane to the catalyst layer, the ratio (D2 / D1) may be 0.95 or lower or 0.9 or lower. From the above viewpoint, the above ratio (D2 / D1) may be 0.3 to 0.95 or 0.5 to 0.9. Note that the thickness D2 of the porous membrane may be rephrased as the thickness of the composite layer.

[0156] When the electrolyte membrane has an electrolyte polymer layer, the ratio (D2 / D3) of the thickness D2 of the porous membrane to the total thickness D3 of the electrolyte polymer layer in the electrolyte membrane is preferably 0.1 to 30. When the ratio (D2 / D3) is 0.1 or higher, the mechanical strength tends to improve, and when it is 30 or lower, the adhesion of the electrolyte membrane to the catalyst layer tends to improve. From a similar viewpoint, the above ratio (D2 / D3) may be 0.4 or higher or 1 or higher, 19 or lower, 9 or lower, 5 or lower, or 3 or lower, and may be 0.4 to 19, 1 to 9, 1 to 5, or 1 to 3. Here, the total thickness D3 of the electrolyte polymer layer means the thickness of one electrolyte polymer layer when the electrolyte polymer layer is present on only one side of the composite layer, and the sum of the thicknesses of the two electrolyte polymer layers when the electrolyte polymer layer is present on both sides of the composite layer. The thickness D2 of the porous membrane may be rephrased as the thickness of the composite layer.

[0157] If the electrolyte membrane has layers other than the composite layer, the thickness of the electrolyte membrane may be 5 to 300 μm, 10 to 200 μm, or 20 to 100 μm. The above-mentioned electrolyte membrane thickness is the average thickness measured at any five locations in the cross-section of the electrolyte membrane.

[0158] In another embodiment, the electrolyte membrane may have a plurality of the above-mentioned composite layers. The electrolyte membrane may have a structure in which, for example, two composite layers are laminated via the above-mentioned electrolyte polymer layer.

[0159] <Electrolyte membrane with catalyst layer> An electrolyte membrane with a catalyst layer according to one embodiment comprises the electrolyte membrane of the above embodiment and a catalyst layer disposed on one or both sides of the electrolyte membrane.

[0160] The catalyst layer is, for example, a layer composed of an anode catalyst or a cathode catalyst, such as in a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. Hereinafter, a layer composed of an anode catalyst will be referred to as the anode catalyst layer, and a layer composed of a cathode catalyst will be referred to as the cathode catalyst layer.

[0161] The composition of the catalyst layer is not particularly limited and can be a conventionally known configuration for catalyst layers (anode catalyst layer, cathode catalyst layer) in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The catalyst layer may be formed of a conductive composition containing, for example, an anode catalyst or cathode catalyst and a conductive material. The catalyst layer may also contain an ionomer.

[0162] As an anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of a fuel such as hydrogen can be used. As an anode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the oxygen evolution reaction can be used. For example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as two or more alloys thereof, can be used.

[0163] As a cathode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the reduction reaction of oxygen can be used, and as a cathode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting the hydrogen evolution reaction can be used. For example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, and vanadium, as well as two or more alloys thereof, can be used.

[0164] As the conductive material, at least one selected from the group consisting of furnace black, Ketjen black, channel black, acetylene black, activated carbon, and graphite can be used.

[0165] Conventional known materials can be used as the ionomer; for example, an ionomer containing a perfluoro electrolyte can be used. Alternatively, the above-mentioned polymer (P) can be used as the ionomer. It is preferable to use a material with high oxygen permeability as the ionomer. There are no particular restrictions on the amount of ionomer added to the catalyst layer, but it is preferable to adjust the amount added within a range where oxygen diffusion is not easily inhibited.

[0166] The catalyst layer may further contain additives such as water repellents like fluorinated carbon, binders like fluororesins, and hydrocarbon resins having sulfonic acid groups.

[0167] A laminate comprising an electrolyte membrane with an anode catalyst layer and a cathode catalyst layer on both sides (for example, a laminate with a layer configuration of "anode catalyst layer / electrolyte membrane / cathode catalyst layer") is also called a CCM (Catalist Coated Membrane) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0168] <Membrane electrode assembly> A membrane electrode assembly according to one embodiment comprises the electrolyte membrane of the above embodiment and an electrode layer disposed on one or both sides of the electrolyte membrane.

[0169] The electrode layer comprises, for example, the catalyst layer (anode catalyst layer or cathode catalyst layer) in the electrolyte membrane with catalyst layer of the above embodiment. Hereinafter, an electrode layer comprising an anode catalyst layer will be referred to as the anode layer, and an electrode layer comprising a cathode catalyst layer will be referred to as the cathode layer.

[0170] The configuration of the electrode layer is not particularly limited and may be a configuration conventionally known as the electrode layer (anode layer, cathode layer) of a polymer electrolyte fuel cell or polymer electrolyte water electrolysis device. The electrode layer may consist, for example, of the catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion substrate. If the catalyst layer itself has gas diffusivity, the electrode layer may consist only of the catalyst layer. As the gas diffusion substrate, for example, a porous membrane can be used. As the gas diffusion substrate, in addition to gas diffusivity, materials that have water repellency and conductivity can also be used (for example, carbon fiber substrates such as carbon nonwoven fabric or carbon paper, or titanium fiber sintered bodies).

[0171] A laminate comprising an electrolyte membrane with an anode layer and a cathode layer as electrode layers on both sides (for example, a laminate with a layer configuration of "gas diffusion substrate / anode catalyst layer / electrolyte membrane / cathode catalyst layer / gas diffusion substrate") is also called a MEA (Membrane Electrode Assembly) and is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers.

[0172] <Solid Polymer Fuel Cell> A solid polymer fuel cell according to one embodiment comprises the membrane electrode assembly of the above embodiment.

[0173] The configuration of a polymer electrolyte fuel cell is not particularly limited and may be a conventionally known configuration, except that the membrane electrode assembly of the above embodiment is used. A polymer electrolyte fuel cell may, for example, comprise two or more membrane electrode assemblies. The two or more membrane electrode assemblies may be stacked (laminated) with a separator in between. A separator conventionally known for polymer electrolyte fuel cells can be used as the separator.

[0174] <Solid Polymer Water Electrolyzer> A solid polymer water electrolyzer according to one embodiment includes the membrane electrode assembly according to the above embodiment.

[0175] The configuration of the polymer electrolyte water electrolysis apparatus is not particularly limited, and can be a conventionally known configuration except for the use of the membrane electrode assembly of the above embodiment. The polymer electrolyte water electrolysis apparatus may, for example, further include a power supply element outside the membrane electrode assembly. It may also include two or more membrane electrode assemblies.

[0176] The contents of this disclosure will be described in more detail below using examples and comparative examples, but this disclosure is not limited to the following examples.

[0177] <Synthesis Example 1> (Synthesis of hydrophilic monomer (M1)) A 10 L flask equipped with a stirrer, dropping funnel, reflux condenser, and heating device was purged with nitrogen, and 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of anhydrous tetrahydrofuran were charged in, and stirring was started. The mixture was cooled to -70°C in a methanol-dry ice bath, and 320 mL of 2.6 mol / L n-butyllithium-hexane solution was added dropwise. The mixture was stirred for 1 hour while remaining cooled in the bath. 40 mL of sulfur dioxide gas was introduced into the flask with nitrogen gas. The mixture was stirred for 30 minutes while remaining cooled in the bath. After that, the bath was removed and the internal temperature was raised to 0°C. The precipitated solid was collected by suction filtration and washed with 200 mL of tetrahydrofuran. The collected solid was dissolved in 2 L of pure water, 260 mL of 35% hydrogen peroxide solution was added, and the mixture was stirred for 18 hours. The solid was removed by suction filtration, and 600 g of sodium chloride was added to the recovered filtrate. The precipitated white solid was recovered by suction filtration and purified by recrystallization from water / isopropyl alcohol. The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer (M1) represented by the following formula (M1). The yield was 65%.

[0178] <Synthesis Example 2> (Synthesis of hydrophobic monomer (M2)) A 500 mL flask equipped with a stirring bar and condenser was purged with nitrogen. To this flask, 9.5 g of 2,7-dibromo-9,9-diphenylfluorene, 12.1 g of 4'-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)biphenyl-4-ol, 19 g of potassium carbonate, 2.0 g of tetrakis(triphenylphosphine)palladium(0), and 250 mL of tetrahydrofuran were added. The reaction mixture was heated to 90°C and stirred for 3 hours. After the reaction mixture was allowed to cool to room temperature (approximately 25°C, the same applies below), 200 mL of water and 500 mL of ethyl acetate were added and the mixture was separated, and the organic layer was recovered. The solvent was removed by evaporation using an evaporator, and the resulting crude product was purified by silica column chromatography using an ethyl acetate / hexane = 1 / 1 (volume ratio) mixed solvent as the developing solvent. The fraction containing the target substance was recovered, and the solvent was removed using an evaporator. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 53%.

[0179] <Synthesis Example 3> (Synthesis of Polymer (P1)) In a 200 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, Dean-Stark tube, and heating device, 7.87 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 0.429 g of 4,4'-dichlorodiphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.), 9.40 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 5.51 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 50 mL of dimethyl sulfoxide (DMSO) and 50 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube, and polymerization was carried out at 130 °C for 150 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified from 1800 mL of isopropyl alcohol (IPA), and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P1) having the structure represented by the following formula (P1). The yield was 93%.

[0180] In formula (P1), U1 represents the structure represented by formula (U1), U2 represents the structure represented by formula (U2), U3 represents the structure represented by formula (U3), and x, y, and n are positive numbers. In formula (U1), M represents Na, K, or H. In polymer (P1), x in formula (P1) was approximately 0.87, y was approximately 0.13, and n was approximately 21. The content of constituent units derived from hydrophobic monomer (M2) was 50 mol% of the total amount of all constituent units constituting polymer (P1). In addition, the Mn of polymer (P1) was 28000, the Mw was 72000, and the Mw / Mn was 2.6. １ When the 1H-NMR spectrum was measured, a peak was observed in the range of 6.85 to 6.87 ppm. Note that n in equation (P1) was calculated from Mn. The same applies to n in equations (P2) to (P4) described later. Furthermore, in this example, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by size exclusion chromatography (SEC) under the following conditions. １ H-NMR was measured under the following conditions.

[0181] [Molecular Weight: Measurement Conditions] The polymer was dissolved at a concentration of 1 mg / mL in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L of lithium bromide) to prepare the sample solution. A Tosoh HLC-8320GPC was used as the apparatus. Two Tosoh TSKgel SuperAWM-H columns (6.0 mm inner diameter, 15 cm length) were used. A differential refractometer was used as the detector. The flow rate was 0.6 mL / min and the temperature was 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined by converting to standard polyethylene glycol / oxide (PEG / PEO). Furthermore, the polydispersity (Mw / Mn) was determined by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0182] [ １ [H-NMR: Measurement Conditions] For 1H-NMR measurements, an AVANCE III HD 400 (400MHz, manufactured by Bruker) was used as the apparatus. １¹H-NMR was performed using heavy DMSO as the measurement solvent and tetramethylsilane (TMS) as the internal standard. Commercially available reagents were used.

[0183] <Synthesis Example 4> (Synthesis of Polymer (P2)) In a 100 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, Dean-Stark tube, and heating device, 7.47 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 0.429 g of 4,4'-dichlorodiphenyl sulfone, 9.41 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 5.52 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 50 mL of DMSO and 50 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube, and polymerization was carried out at 130 °C for 150 hours. Then, 0.052 g of decafluorobiphenyl (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and polymerization was carried out at 130 °C for 3.5 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified from 1800 mL of IPA, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain a polymer (P2) containing multiple polymer units with the structure represented by formula (P1) and having decafluorobiphenyl-derived crosslinking groups that bond to three or more of the polymer units. The yield was 93%.

[0184] Polymer (P2) is a polymer having the structure represented by the above formula (P1). In polymer (P2), x in formula (P1) was approximately 0.87 (0.83 to 0.91), y was approximately 0.13 (0.09 to 0.17), and n was approximately 16. Furthermore, the content of constituent units derived from hydrophobic monomer (M2) was 50 mol% of the total amount of all constituent units constituting polymer (P2). In addition, the Mn of polymer (P2) was 22000, Mw was 220000, and Mw / Mn was 10.0. Polymer (P2) was synthesized in the same manner as in Synthesis Example 3. １ When the 1H-NMR spectrum was measured, a peak was observed in the range of 6.85–6.87 ppm.

[0185] <Synthesis Example 5> (Synthesis of Polymer (P3)) In a 100 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, Dean-Stark tube, and heating device, 3.11 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 0.821 g of disodium diphenylsulfone-4,4'-dichloro-3,3'-disulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 3.00 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 2.59 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 20 mL of DMSO and 20 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube, and polymerization was carried out at 130 °C for 150 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified from 900 mL of IPA, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P3) having the structure represented by the following formula (P3). The yield was 81%.

[0186] In formula (P3), U1 represents the structure represented by formula (U1), U2 represents the structure represented by formula (U2), U4 represents the structure represented by formula (U4), and x, y, and n are positive numbers. In formula (U4), M represents Na, K, or H. In polymer (P3), x in formula (P3) was approximately 0.66 (0.62 to 0.70), y was approximately 0.34 (0.30 to 0.38), and n was approximately 17. The content of constituent units derived from hydrophobic monomer (M2) was 50 mol% of the total amount of all constituent units constituting polymer (P3). In addition, the Mn of polymer (P3) was 22000, Mw was 68000, and Mw / Mn was 3.1. Polymer (P3) was synthesized in the same manner as in Synthesis Example 3. １ When the 1H-NMR spectrum was measured, a peak was observed in the range of 6.85–6.87 ppm.

[0187] <Synthesis Example 6> (Synthesis of Polymer (P4)) In a 100 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, Dean-Stark tube, and heating device, 2.18 g of 4,4'-dihydroxybiphenyl (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.59 g of 4,4'-dichlorodiphenyl sulfone, 2.32 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 3.02 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 20 mL of DMSO and 20 mL of cyclohexane were added. After heating to 130 °C and reflux dehydration for 4 hours, the cyclohexane was removed from the Dean-Stark tube, and polymerization was carried out at 130 °C for 150 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified from 1000 mL of IPA, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure to obtain polymer (P4) having the structure represented by the following formula (P4). The yield was 97%.

[0188] In formula (P4), M represents Na, K, or H, and x, y, and n represent positive numbers. In polymer (P4), x was approximately 0.22, y was approximately 0.78, and n was approximately 47. In addition, the Mn of polymer (P4) was 30,000, Mw was 71,000, and Mw / Mn was 2.4.

[0189] <Preparation of Porous Membranes> The following porous membranes A and B were prepared: ・Porous membrane A (Material: Polyethylene (PE in the table), film thickness: 12 μm, porosity: 70%) ・Porous membrane B (Material: Polyethylene (PE in the table), film thickness: 12 μm, porosity: 45%) The porosity of the above porous membranes was determined from the pore volume calculated by the mercury intrusion method using a POREMASTER GT (Quantachrome Instruments). For reference, planar SEM images of porous membrane A and porous membrane B taken using a scanning electron microscope (SEM) are shown in Figures 3 and 4, respectively. The magnification of the planar SEM images in Figures 3 and 4 is 10,000x.

[0190] <Example 1> Polymer (P1) was dissolved in DMSO to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate with an applicator, and then a porous membrane A was placed on the resulting coating. Next, the polymer solution was applied to the side of the porous membrane A opposite to the glass substrate side with an applicator. After that, the electrolyte membrane of Example 1 was obtained by drying at 60°C for 6 hours. The electrolyte membrane had a composite layer containing porous membrane A and polymer (P1) filling the pores of porous membrane A, as well as an electrolyte polymer layer containing polymer (P1) on both sides of the composite layer. The thickness of the composite layer was 12 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 20 μm. The polymer (P1) content was 347 parts by mass per 100 parts by mass of porous membrane A. In this example, the thickness of the electrolyte membrane was measured with a film thickness gauge (PG-02 manufactured by TECLOCK CORPORATION).

[0191] <Example 2> An electrolyte membrane was obtained in the same manner as in Example 1, except that polymer (P2) was used instead of polymer (P1). The thickness of the composite layer was 12 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 17 μm. The content of polymer (P2) was 347 parts by mass per 100 parts by mass of porous membrane A.

[0192] <Example 3> An electrolyte membrane was obtained in the same manner as in Example 1, except that polymer (P3) was used instead of polymer (P1). The thickness of the composite layer was 12 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 23 μm. The content of polymer (P3) was 309 parts by mass per 100 parts by mass of porous membrane A.

[0193] <Example 4> An electrolyte membrane was obtained in the same manner as in Example 1, except that porous membrane B was used instead of porous membrane A. The thickness of the composite layer was 12 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 28 μm. The polymer (P1) content was 122 parts by mass per 100 parts by mass of porous membrane B.

[0194] <Comparative Example 1> Polymer (P1) was dissolved in DMSO to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate with an applicator and then dried at 60°C for 6 hours to obtain an electrolyte film with a thickness of 25 μm.

[0195] <Comparative Example 2> Polymer (P2) was dissolved in DMSO to obtain a solution containing 15% by mass of polymer (P2). The obtained solution was applied to a glass substrate with an applicator and then dried at 60°C for 6 hours to obtain an electrolyte film with a thickness of 27 μm.

[0196] <Comparative Example 3> An electrolyte membrane was obtained in the same manner as in Example 1, except that polymer (P4) was used instead of polymer (P1). The thickness of the composite layer was 12 μm, and the thickness of the electrolyte membrane (sum of the thickness of the composite layer and the electrolyte polymer layer) was 42 μm. The content of polymer (P4) was 277 parts by mass per 100 parts by mass of porous membrane A.

[0197] <Comparative Example 4> Commercially available Nafion ＴＭ A single NR211 film (thickness 25 μm) was used as the electrolyte membrane for Comparative Example 4.

[0198] <Evaluation> The mechanical strength, proton conductivity, and swelling resistance of the electrolyte membranes obtained in the examples and comparative examples were evaluated by the following method. The results are shown in Table 1.

[0199] (Mechanical Strength Evaluation) After punching out the electrolyte membrane into a dumbbell shape (JIS K 6251 type), samples were stored in a constant temperature and humidity chamber (23°C, 50% RH) for more than 12 hours and used as test specimens. In the same constant temperature and humidity chamber, the test specimens were pulled at a test speed of 10 mm / min using a universal material testing machine (UTPS-Acs(S) manufactured by TSE Corporation), and the load against strain was measured. The tensile stress was calculated by dividing the obtained load by the cross-sectional area of ​​the electrolyte membrane. The highest tensile stress value was defined as the maximum stress, and the electrolyte membrane was evaluated as having excellent mechanical strength if the maximum stress was 45 MPa or higher.

[0200] (Proton Conductivity Evaluation) Using a Teflon® measurement cell (Scribner BT-115), the electrolyte membrane was placed in contact with four platinum wires inside the cell. After maintaining the temperature at 80°C and 20% relative humidity for 2 hours, the relative humidity was increased by 10% and maintained for 30 minutes. This operation was repeated continuously until the relative humidity reached 100%, and then DC resistance was measured using the four-terminal method at 100% relative humidity. The proton conductivity of the electrolyte membrane in the planar direction under an 80°C, 100% RH environment was calculated from the obtained resistance value, the thickness of the electrolyte membrane, and the distance between terminals. The electrolyte membrane was evaluated as having excellent proton conductivity if the measured proton conductivity under an 80°C, 100% relative humidity environment was 110 mS / cm or higher.

[0201] (Swelling Resistance Evaluation) A 1.5 cm wide, 3 cm long membrane was punched out from the electrolyte membrane, and then immersed in 50 mL of 80°C pure water for 1 hour. The dimensions within the membrane plane were measured before and after immersion in pure water, and the membrane swelling rate in the direction of the membrane plane was calculated by dividing the dimensional change before and after immersion by the dimensions before immersion. If the membrane swelling rate was 27% or less, the electrolyte membrane was evaluated as having excellent swelling resistance.

[0202]

[0203] This application is based on Japanese Patent Application No. 2025-019155, filed on 7 February 2025, which is incorporated by reference in its entirety. All references cited herein are incorporated as a whole.

[0204] 1...Porous membrane, 2...Pores, 3...Filler containing electrolyte polymer, 4...Composite layer, 5...First electrolyte polymer layer, 6...Second electrolyte polymer layer, 10A, 10B...Electrolyte membrane.

Claims

1. An electrolyte membrane comprising a porous membrane and an electrolyte polymer filled in the pores of the porous membrane, wherein the electrolyte polymer includes a structural unit A represented by the following formula (a1) and a structural unit B represented by the following formula (a2). [In formula (a1), IExG represents an ion exchange group, and L １ represents a single bond, -O-, -S-, or -SO ２ -, x represents an integer from 1 to 10, and * represents a bond. A plurality of IExG may be the same as or different from each other, and a plurality of L １ may be the same as or different from each other.] [In formula (a2), Ar １ represents an arylene group having no ion exchange group, and L ２ represents a single bond, -O-, -S-, or -SO ２ -, y represents an integer from 3 to 20, and * represents a bond. A plurality of Ar １ may be the same as or different from each other, and a plurality of L ２ may be the same as or different from each other. However, the number of L ２ that is a single bond is an integer of 0.5y or more and less than 1.0y.] 2. The electrolyte membrane according to claim 1, wherein the constituent unit A comprises at least one group selected from the group consisting of a sulfonic acid group, an alkyl sulfonic acid group, a sulfonimide group, and salts thereof, as the ion exchange group.

3. The electrolyte membrane according to claim 1 or 2, wherein the constituent unit B comprises at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorene group, which may have substituents, as the arylene group.

4. The electrolyte membrane according to any one of claims 1 to 3, wherein the constituent unit B includes a structure in which at least three consecutive arylene groups are bonded together by single bonds.

5. The electrolyte membrane according to any one of claims 1 to 4, wherein the content of the constituent unit B is 25 to 75 mol% of the total amount of all constituent units that make up the polymer.

6. The electrolyte membrane according to any one of claims 1 to 5, wherein the electrolyte polymer comprises a plurality of polymer units including the constituent unit A and the constituent unit B, and has crosslinking groups that bond to three or more of the polymer units.

7. The electrolyte membrane according to any one of claims 1 to 6, having a peak in the range of 6.70 to 6.95 ppm in a 1H-NMR spectrum with tetramethylsilane as an internal standard.

8. The electrolyte membrane according to any one of claims 1 to 7, wherein the weight-average molecular weight of the electrolyte polymer is 40,000 to 500,000.

9. The electrolyte membrane according to any one of claims 1 to 8, wherein the porosity of the porous membrane is 30 to 95 volume percent.

10. The electrolyte membrane according to any one of claims 1 to 9, wherein the porous membrane is formed of a material containing a hydrocarbon resin.

11. The electrolyte membrane according to any one of claims 1 to 10, wherein the porous membrane has a layer containing the electrolyte polymer on one or both sides of the porous membrane.

12. The electrolyte membrane according to claim 11, wherein the ratio of the thickness of the porous membrane to the total thickness of the layer containing the electrolyte polymer is 0.1 to 30.

13. An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of claims 1 to 12, and a catalyst layer disposed on one or both sides of the electrolyte membrane.

14. A membrane electrode assembly comprising an electrolyte membrane according to any one of claims 1 to 12, and an electrode layer disposed on one or both sides of the electrolyte membrane.

15. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 14.

16. A polymer electrolyte water electrolysis apparatus comprising the membrane electrode assembly described in claim 14.

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