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

Abstract

An electrolyte membrane comprising a hydrocarbon-based electrolyte polymer and a compound having a structure in which one or more groups represented by general formula (I) are bonded to an aromatic ring [in general formula (I), R1 represents an optionally substituted C1-C20 hydrocarbon group and * indicates a bond to the aromatic ring].

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 membranes using hydrocarbon-based electrolyte polymers (hydrocarbon-based electrolyte membranes) is also progressing. For example, Patent Document 2 discloses an invention relating to a hydrocarbon-based electrolyte membrane in which the electrolyte is a hydrocarbon-based electrolyte polymer consisting 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] However, hydrocarbon electrolyte membranes made of hydrocarbon electrolyte polymers, such as those disclosed in Patent Document 2, have room for improvement in terms of proton conductivity.

[0007] One aspect of this disclosure aims to improve the proton conductivity of hydrocarbon-based electrolyte membranes.

[0008] This disclosure provides, in several respects, the following [1] to

[13] .

[0009] [1] A hydrocarbon electrolyte polymer and the following general formula (I): [In general formula (I), R １ represents a hydrocarbon group having 1 to 20 carbon atoms which may have substituents, and * represents a bond to an aromatic ring. An electrolyte membrane comprising a compound having a structure in which one or more groups represented by ] are bonded to an aromatic ring.

[0010] [2] The aforementioned R １ The electrolyte membrane according to [1], wherein the alkyl group has 1 to 6 carbon atoms or the aryl group has 6 to 10 carbon atoms.

[0011] [3] The electrolyte membrane according to [1] or [2], wherein the compound has a structure in which two or more groups represented by the general formula (I) are bonded to the aromatic ring.

[0012] [4] The electrolyte membrane according to [3], wherein the compound has a structure in which two groups represented by the general formula (I) are bonded to each other's ortho positions of the aromatic ring.

[0013] [5] The electrolyte membrane according to any one of [1] to [4], wherein the aromatic ring is a benzene ring.

[0014] [6] The electrolyte membrane according to any one of [1] to [5], wherein the compound comprises at least one selected from the group consisting of diethyl phthalate and diphenyl phthalate.

[0015] [7] The hydrocarbon electrolyte polymer is of the following formula (a1): [In formula (a1), IExG represents an ion exchange group, L １ These are single bonds, -O-, -S-, -SO ２ - or -CO- is indicated, x is an integer from 1 to 10, and * indicates a combination. Multiple IExG may be the same or different from each other, and multiple L １ These may be identical or different from each other. A constituent unit A is represented by ] and the following formula (a2): [In formula (a2), Ar １represents an arylene group having no ion exchange group, and L ２ represents a single bond, a divalent aliphatic hydrocarbon group which may have a substituent, -O-, -S-, -SO ２ - or -CO-, y represents an integer of 1 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, provided that L located at the terminal ２ is not a divalent aliphatic hydrocarbon group.], and a structural unit B represented by the formula: The electrolyte membrane according to any one of [1] to [6].

[0016] [8] The electrolyte membrane according to any one of [1] to [7], wherein the hydrocarbon-based electrolyte polymer contains at least one ion exchange group selected from the group consisting of a sulfonic acid group, an alkylsulfonic acid group, a sulfonimide group, a phosphonic acid group, and salts thereof.

[0017] [9] The electrolyte membrane according to any one of [1] to [8], wherein the content of the compound is 0.000001 to 20 parts by mass relative to 100 parts by mass of the hydrocarbon-based electrolyte polymer.

[0018]

[10] An electrolyte membrane with a catalyst layer, comprising: the electrolyte membrane according to any one of [1] to [9]; and a catalyst layer disposed on one side or both sides of the electrolyte membrane.

[0019]

[11] A membrane electrode assembly comprising: the electrolyte membrane according to any one of [1] to [9]; and an electrode layer disposed on one side or both sides of the electrolyte membrane.

[0020]

[12] A polymer electrolyte fuel cell comprising the membrane electrode assembly according to

[11] .

[0021]

[13] A polymer electrolyte water electrolysis apparatus comprising the membrane electrode assembly according to

[11] .

[0022] According to the present disclosure, the proton conductivity of the hydrocarbon-based electrolyte membrane can be improved.

[0023] 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.

[0024] <Electrolyte Membrane> The electrolyte membrane of one embodiment (hereinafter also referred to as "electrolyte membrane (E)") comprises a hydrocarbon electrolyte polymer and a compound having a structure in which one or more groups represented by the following general formula (I) are bonded to an aromatic ring (hereinafter also referred to as "compound (C)"). Since electrolyte membrane (E) contains a hydrocarbon electrolyte polymer as an electrolyte, it is a hydrocarbon electrolyte membrane. In this specification, "hydrocarbon electrolyte polymer" means an electrolyte polymer that substantially does not contain fluorine atoms (i.e., the fluorine content in the electrolyte polymer is 5% by mass or less).

[0025]

[0026] In general formula (I), R １ * represents a hydrocarbon group having 1 to 20 carbon atoms, which may have substituents, and * represents a bond with an aromatic ring.

[0027] Because the electrolyte membrane (E) contains compound (C), it exhibits superior proton conductivity compared to an electrolyte membrane that does not contain compound (C).

[0028] The reason for the above effect is not clear, but it is presumed that by adding compound (C), the molecular mobility of the hydrocarbon-based electrolyte polymer in the electrolyte membrane (E) is increased, allowing for the formation of a higher-order structure that provides higher proton conductivity.

[0029] Furthermore, the electrolyte membrane (E) tends to exhibit superior mechanical strength. Although the reason for this is not clear, it is presumed that the inclusion of compound (C) between hydrocarbon electrolyte polymers increases the distance between the polymers, weakening their interactions and improving the flexibility of the electrolyte membrane.

[0030] The electrolyte membrane (E) may be an electrolyte membrane made of a resin composition (hereinafter also referred to as "resin composition (R)") comprising a hydrocarbon electrolyte polymer and compound (C), or it may be an electrolyte membrane containing resin composition (R). For example, the electrolyte membrane (E) may be an electrolyte membrane comprising a porous membrane and resin composition (R) filling the pores of the porous membrane.

[0031] If the electrolyte membrane (E) includes a porous membrane, the content (filling amount) of the resin composition (R) in the electrolyte membrane (E) may be 50 parts by mass or more, 90 parts by mass or more, or 350 parts by mass or more, per 100 parts by mass of the porous membrane, from the viewpoint of obtaining better proton conductivity. The content (filling amount) of the resin composition (R) in the electrolyte membrane (E) may be 3,000 parts by mass or less, 2,000 parts by mass or less, 1,000 parts by mass or less, or 600 parts by mass or less, per 100 parts by mass of the porous membrane, from the viewpoint of further improving mechanical strength. From the above viewpoint, the content (filling amount) of the resin composition (R) in the electrolyte membrane (E) may be 50 to 3,000 parts by mass, 90 to 2,000 parts by mass, 350 to 1,000 parts by mass or 350 to 600 parts by mass, per 100 parts by mass of the porous membrane.

[0032] The thickness (film thickness) of the electrolyte membrane (E) is not particularly limited and can be changed according to the size of the fuel cell, etc. From the viewpoint of increasing the mechanical strength of the membrane while reducing membrane resistance, the thickness of the electrolyte membrane (E) may be 1 μm or more, 5 μm or more, 7 μm or more, or 10 μm or more, and may be 200 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. From a similar viewpoint, the thickness of the electrolyte membrane (E) may be 1 to 200 μm, or 5 to 100 μm, 7 to 50 μm, or 10 to 30 μm.

[0033] The electrolyte membrane (E) is suitably used in polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. The electrolyte membrane (E) can also be used in redox flow batteries, electrochemical hydrogen pumps, chlor-alkali electrolyzers, solid acid catalysts, membrane-type humidity control devices, gas separation membranes, and the like.

[0034] The electrolyte membrane (E) can also be used in combination with a microporous membrane, nonwoven fabric, mesh, etc. That is, another embodiment of the present disclosure is a laminate comprising an electrolyte membrane (E) and another membrane (microporous membrane, nonwoven fabric, mesh, etc.).

[0035] (Hydrogen-based electrolyte polymers) Hydrocarbon-based electrolyte polymers include, for example, hydrophilic constituent units having ion exchange groups and hydrophobic constituent units not having ion exchange groups.

[0036] Ion exchange groups are groups that have the property of being able to exchange ions (e.g., cations) with other ions, and are also called ionic groups. 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. Some of these ion exchange groups also form salts with metal ions.

[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 ４ SO ３ M １／ｑ It is represented by R ４R is an alkanediyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 12. ４ Specific examples include a methylene group, a butane-1,4-diyl group, or a hexane-1,6-diyl group. M and q are as defined above.

[0039] Sulfonimide groups and their salts include, for example, -SO ２ NM １／ｑ SO ２ R ５ It is represented by R ５ R is an alkyl group, and from the viewpoint of obtaining better proton conductivity, its carbon number is preferably 1 to 6. ５ Specific examples include a methyl group, an ethyl group, or a propyl group. M and q are the same as above.

[0040] Phosphonic acid groups and their salts are, for example, -P(=O)(OM １／ｑ ) ２ It is represented as follows. M and q are the same as above.

[0041] From the viewpoint of obtaining better proton conductivity, hydrocarbon electrolyte polymers preferably contain at least one group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, sulfonimide groups, and phosphonic acid groups, and their salts, as ion exchange groups, and more preferably contain 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 the hydrocarbon electrolyte polymer are of the above-described preferred form, and it is particularly preferable that all of the multiple ion exchange groups present in the hydrocarbon electrolyte polymer are of the above-described preferred form.

[0042] From the viewpoint of superior proton conductivity, hydrocarbon electrolyte polymers may include polymers (hereinafter also referred to as "polymer (P)") comprising a constituent unit A represented by the following formula (a1) and a constituent unit B represented by the following formula (a2).

[0043]

[0044] In formula (a1), IExG indicates an ion exchange group, and L １These are single bonds, -O-, -S-, -SO ２ - or -CO- is indicated, x is an integer from 1 to 10, and * is an association. Multiple IExG may be the same or different from each other, and multiple L １ They may be the same or different from one another.

[0045]

[0046] In formula (a2), Ar １ This indicates an arylene group that does not have an ion exchange group, L ２ These include single bonds, divalent aliphatic hydrocarbon groups which may have substituents, -O-, -S-, -SO ２ - or -CO- is indicated, y is an integer from 1 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 the same or different from each other. However, the L located at the end ２ It is not a divalent aliphatic hydrocarbon group.

[0047] Polymer (P) possesses excellent proton conductivity. Therefore, by using polymer (P), the proton conductivity of the electrolyte membrane can be further improved. The reason why polymer (P) has excellent proton conductivity is not clear, but it is presumed that polymer (P) contains a hydrophilic part made up of constituent unit A and a hydrophobic part made up of constituent unit B, forming a higher-order structure in the electrolyte membrane where ion exchange groups are densely concentrated, and that this forms good proton conduction paths within polymer (P).

[0048] [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 The structure may be continuous via a linking group. The linking group located at the end of constituent unit A is, for example, bonded to the aromatic ring of another constituent unit. Details of the ion exchange group are as described above, and the preferred embodiment is similar.

[0049] From the viewpoint of obtaining even 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 more preferable that the majority of these are of the above-described preferred embodiment.

[0050] 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 a component.

[0051] Linking group (L) in constituent unit A １ From the viewpoint of obtaining even better proton conductivity and improving flexibility, the following are used: single bond, -O-, or -SO ２ - is preferable.

[0052] Linking group (L １ The bonding position of the ion exchange group is not particularly limited, but from the viewpoint of obtaining even better proton conductivity, 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.

[0053] The number of repeating structures (x) in the brackets [ ] in formula (a1) of constituent unit A is preferably 1 to 6, and more preferably 2 to 4, from the viewpoint of obtaining even better proton conductivity and excellent resistance to hot water. The reason why proton conductivity is further improved when x is within the above range is not clear, but it is presumed to be due to the effect of the dense presence of multiple ion exchange groups.

[0054] From the viewpoint of obtaining even 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)").

[0055]

[0056]

[0057]

[0058] 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 and 4x ３ The sum is between 4 and 9. １ From the viewpoint of obtaining even 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 even 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 even better proton conductivity and excellent resistance to hot water, it is preferably 1. In formulas (a1-1), (a1-2), and (a1-3), L １ From the viewpoint of improving proton conductivity and flexibility, it is preferable that it be -O-.

[0059] 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).

[0060] Constituent unit A may be a constituent unit represented by any of the following formulas (A1-1) to (A1-4).

[0061]

[0062] 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.

[0063] 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 even better proton conductivity and excellent chemical durability. １２ 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 flexibility, it is preferable that it be -O-.

[0064] The multiple constituent units A in the polymer (P) may be identical or different from each other. Furthermore, from the viewpoint of obtaining even 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.

[0065] From the viewpoint of obtaining even 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).

[0066] From the viewpoint of obtaining even 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 that make up 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 that make up the polymer (P).

[0067] [Constituent Unit B] Constituent unit B is an arylene group (Ar) that does not have an ion exchange group. １ ) includes a linking group (L) that is bonded to another constituent unit at one end. ２ ) has. Constituent unit B is Ar １ is L ２ It may have a continuous structure via L located at the end of constituent unit B. ２ For example, it is bonded to the aromatic ring of another constituent unit.

[0068] In this disclosure, the arylene group is a divalent aromatic hydrocarbon group having a structure obtained by removing two hydrogen atoms from a monocyclic or condensed polycyclic aromatic hydrocarbon. However, a divalent group obtained by removing two hydrogen atoms from the same carbon atom of a condensed polycyclic aromatic hydrocarbon (for example, a fluorenylidene group) is treated as a substituted cycloalkylidene group, not an arylene group. Furthermore, the statement that the arylene group "may have substituents other than ion exchange groups" means that the arylene group does not have at least ion exchange groups.

[0069] L ２ The divalent aliphatic hydrocarbon group may be a linear alkylene group having 1 to 6 carbon atoms. Examples of such alkylene groups include a methylene group, an ethylene group, and a hexylene group. At least one hydrogen atom in these aliphatic hydrocarbon groups may be substituted with a substituent. Examples of substituents include aryl groups (e.g., a phenyl group and a naphthyl group).

[0070] Also, L ２ The divalent aliphatic hydrocarbon group may be an alkylidene group which may have substituents. An alkylidene group which may have substituents is, for example, >C(RＸ ) (Caution Ｙ ) is represented by R Ｘ and R Ｙ Each independently represents a hydrogen atom, a substituent, or an alkyl group which may have a substituent. Ｘ and R Ｙ These groups may be bonded to each other to form a ring. Examples of substituents include aryl groups (e.g., phenyl and naphthyl groups). Specific examples of substituted alkylidene groups are phenylmethylidene and fluorenylidene.

[0071] Ar １ The number of aromatic rings present is preferably 1 to 4, from the viewpoint of solubility in the solvent, film-forming ability, and increased swelling resistance. １ Other substituents that may be present besides ion exchange groups include aryl groups such as phenyl groups. １ If it has an aryl group as a substituent, the above Ar １ The number of aromatic rings present includes the number of aromatic rings in substituents.

[0072] Ar without substituents １ Ar may be at least one group selected from the group consisting of phenylene, naphthylene, fluorene, anthracylene, phenanthrylene, triphenylene, pyrenylene, and tetrasenylene groups. １ This group may be at least one group selected from the group consisting of dialkylfluorene groups such as methylphenylene group, ethylphenylene group, dimethylfluorene group, diethylfluorene group, dipropylfluorene group, diisopropylfluorene group, dibutylfluorene group, dipentylfluorene group, dihexylfluorene group, diheptylfluorene group, dioctylfluorene group, dinonylfluorene group, didecylfluorene group, diundecylfluorene group, didodecylfluorene group, etc., and diarylfluorene groups such as diphenylfluorene group. Note that the fluorene group as an arylene group means a divalent fluorene group (for example, fluorene-2,7-diyl group).

[0073] The structural unit B, from the viewpoints of solubility in a solvent and film-forming property, as well as from the viewpoint of enhancing swelling resistance, Ar １ is preferably at least one group selected from the group consisting of a phenylene group, a naphthylene group and a fluorene group, which may have a substituent other than an ion exchange group, and more preferably contains at least one group selected from the group consisting of a phenylene group, a naphthylene group and a fluorene group which may have an aryl group as a substituent. From the viewpoint of further enhancing the solubility in a solvent and the film-forming property, the structural unit B more preferably contains a phenylene group, and still more preferably contains a 1,4-phenylene group. From the viewpoint of further enhancing the swelling resistance, the structural unit B still more preferably contains a diphenylfluorene group. From the same viewpoint, it is particularly preferable that a plurality of Ar present in the structural unit B １ are the above preferred embodiments, and it is extremely preferable that all of the plurality of Ar present in the structural unit B １ are the above preferred embodiments.

[0074] The linking group (L in the structural unit B ２ ), from the viewpoints of obtaining excellent swelling resistance and excellent flexibility, as well as from the viewpoints of excellent solubility in a solvent, excellent film-forming property, and excellent mechanical strength during film formation, is preferably a single bond, -O- or -SO ２ -. From the viewpoint of obtaining excellent swelling resistance and excellent flexibility, the structural unit B preferably contains at least two single bonds as the linking group (L ２ ). The number of L which is a single bond in the structural unit B ２ may be an integer of 0.3y or more and less than 1.0y from the viewpoint of obtaining excellent swelling resistance and excellent flexibility. For example, when y is 10, the number of L which is a single bond ２ is an integer of 3 or more and less than 10. The number of L which is a single bond in the structural unit B ２ may be an integer of 0.5y or more, 0.6y or more, or 0.7y or more from the viewpoint of obtaining more excellent swelling resistance, and may be an integer of 0.95y or less or 0.90y or less from the viewpoint of obtaining more excellent flexibility. From these viewpoints, L which is a single bond in the structural unit B ２The number of may be an integer of 0.5y or more and less than 1.0y, 0.6y or more and 0.95y or less, or 0.7y or more and 0.90y or less.

[0075] The number of repetitions (y) of the structure in [ ] in formula (a2) in structural unit B is an integer of 1 to 20, and from the viewpoint of obtaining more excellent proton conductivity, excellent swelling resistance, and excellent hot water resistance, it is preferably 2 to 20, more preferably 4 to 12, and still more preferably 5 to 10.

[0076] From the viewpoint of achieving both more excellent proton conductivity and hot water resistance, and obtaining excellent swelling resistance, the number of repetitions (y) of the structure in [ ] in formula (a2) in structural unit B is preferably a number that is 2 to 7 greater than the number of repetitions (x) of the structure in [ ] in formula (a1) (x+(2 to 7)).

[0077] Structural unit B may include a structure represented by the following formula (a2-1) from the viewpoint of excellent chemical durability.

[0078]

[0079] Ar in formula (a2-1) １ and * have the same meanings as described above. A plurality of Ar １ may be the same as or different from each other.

[0080] Specific examples of structural unit B including the structure represented by the above formula (a2-1) include the structural unit represented by the following formula (B1-1).

[0081]

[0082] Ar in formula (B1-1) １ , L ２ and * have the same meanings as described above, Q represents a group of the structure represented by the above formula (a2-1), and y １ and y ２ each independently represent an integer of 1 to 4. y １ and y ２ are preferably 2 to 3 from the viewpoint of obtaining further excellent proton conductivity. A plurality of Ar １ may be the same as or different from each other, and a plurality of L ２They may be the same or different from one another.

[0083] From the viewpoint of obtaining excellent swelling resistance, constituent unit B consists of at least three consecutive Ar １ The structure may include those connected by single bonds. １ The number may be four or more, or five or more, from the viewpoint of obtaining better swelling resistance. Ar connected via single bonds １ From the viewpoint of obtaining excellent flexibility, the number may be 10 or less, 8 or less, or 6 or less. From these viewpoints, Ar continuous via single bonds １ The number may be 3 to 10, and may be 3 to 8, 3 to 6, 4 to 8, or 5 to 6.

[0084] At least three consecutive Ar １ Specific examples of constituent unit B, which includes a structure in which the elements are linked by single bonds, include constituent units represented by any of the following formulas (B2-1) to (B2-5).

[0085]

[0086] * and L in equations (B2-1) to (B2-5) ２ This is equivalent to the above. R in equations (B2-3) and (B2-5) ３ R represents an alkyl group, and from the viewpoint of obtaining even 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 (B2-3) and (B2-5), multiple R ３ They may be the same or different from one another.

[0087] From the viewpoint of obtaining excellent swelling resistance, the polymer (P) preferably contains a structural unit represented by any of formulas (B2-1) to (B2-5), and more preferably contains a structural unit represented by formula (B2-4).

[0088] The multiple constituent units B in the polymer (P) may be identical or different from one another. 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 one another.

[0089] From the viewpoint of obtaining excellent swelling resistance, the content of constituent unit B may be 25 mol% or more, or 40 mol% or more, and 75 mol% or less, or 60 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 B may be 25 to 75 mol%, or 40 to 60 mol%, relative to the total amount of all constituent units constituting the polymer (P).

[0090] From the viewpoint of obtaining excellent 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 constituting 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 constituting the polymer (P).

[0091] 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.

[0092] 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 are arranged alternately, or it may be a random copolymer in which constituent units A and B are arranged statistically.

[0093] From the viewpoint of having even better proton conductivity, the polymer (P) may be a polymer (precisely arranged polymer) having a structure represented by the following formula (1).

[0094]

[0095] In formula (1), * has the same meaning as above, A and B represent constituent unit A represented by formula (a1) and constituent unit B represented by formula (a2), respectively, and n represents an integer from 10 to 100. Multiple A's may be the same or different from each other, and multiple B's may be the same or different from each other. However, the difference of x in formula (a1) for multiple A's is 3 or less, and the difference of y in formula (a2) for multiple B's is 5 or less.

[0096] The polymer (P) may have a structure represented by the following formula (2) from the viewpoint of superior mechanical strength.

[0097]

[0098] In equation (2), A, B, and * have the same meanings as above, X represents a constituent unit other than constituent unit A (hereinafter also referred to as "constituent unit X"), p and q each independently represent a number greater than 0 that satisfies p + q = 1, and m represents an integer from 10 to 100. Multiple A's may be the same or different from each other, multiple B's may be the same or different from each other, and multiple X's may be the same or different from each other. The constituent unit represented by X (constituent unit X) may be the same or different from the constituent unit represented by B (constituent unit B). Note that equation (2) means that a block consisting of constituent units A and B (first block) and a block consisting of constituent units X and B (second block) exist in a ratio of p:q, and that the polymer (P) is composed of p × m first blocks and q × m second blocks. In equation (2), for convenience, (A - B) ｐ and (X-B) ｑ Although it is stated as such, this does not mean that the first block consists of p consecutive blocks and the second block consists of q consecutive blocks.

[0099] 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.

[0100] The polymer (P) may include a branched structure formed by the bonding of multiple polymer units, including constituent unit A and constituent unit B, via a reactive functional group. The reactive functional group may be a group derived from a known compound (e.g., decafluorobiphenyl). If the reactive functional group has an aromatic ring, the polymer unit may be directly bonded to the aromatic ring of the reactive functional group, or to -O-, -S-, or -SO ２ They may be bonded via a -. The number of reactive functional groups may be one or more. The reactive functional groups may be identical or different from each other.

[0101] 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, polymer (P) can be a polymer of monomers containing compound (b1) and compound (b2).

[0102]

[0103] In formula (b1), IExG, L １ And x is the same as above, X １ｂ and X ２ｂEach of these independently represents a halogen atom. The examples of halogen atoms are the same as the examples of halogen atoms exemplified above as terminal structures of polymer (P).

[0104]

[0105] In formula (b2), Ar １ , L ２ And 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 those exemplified above as terminal structures of polymer (P).

[0106] 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.

[0107] As for compound (b1), X １ｂ and X ２ｂ Multiple types of compounds can be used, at least one of which is different. Similarly, Z can be used as compound (b2). １ｂ and Z ２ｂ Multiple types of compounds can be used, at least one of which is different. For example, as compound (b2), Z １ｂ and Z ２ｂ Compounds in which the atom is a halogen atom, and Z １ｂ and Z ２ｂHowever, compounds that are independently hydroxyl groups, thiol groups, boronic acid groups, alkylborane groups, or boronic acid ester groups may be used. In this case, a polymer (P) with the structure represented by formula (2) (where X represents the constituent unit B) can be easily obtained.

[0108] The amount of compound (b1) used may be adjusted so as to the content of the above-described constituent unit A, and the amount of compound (b2) used may be adjusted so as to the content of the above-described constituent unit B.

[0109] Monomers containing compound (b1) and compound (b2) can be reacted (polymerized), for example, by an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0110] 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.

[0111] 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.

[0112] 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. The reaction temperature is preferably 60 to 300°C, and more preferably 100 to 250°C.

[0113] 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.

[0114] 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.

[0115] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I)hexafluorophosphate.

[0116] 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).

[0117] 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).

[0118] 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. The reaction temperature is preferably 30 to 300°C, and more preferably 60 to 250°C.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] For example, polymer (P) can be replaced with compound (b1) by the X at both ends (in formula (b1)). １ｂ and X ２ｂ ) can also be obtained using compounds in which each is independently a hydroxyl group, a thiol group, a boronic acid group, an alkylborane group, or a boronic acid ester group. In this case, as compound (b2), at least both ends (Z in formula (b2)) １ｂ and Z ２ｂ A compound in which ) is a halogen atom is used, and further, as compound (b2), both ends (Z in formula (b2) １ｂ and Z ２ｂ Compounds in which each of these groups is independently a hydroxyl group, a thiol group, a boronic acid group, an alkylborane group, or a boronic acid ester group may be used.

[0123] 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").

[0124] 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.

[0125] 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, a 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.

[0126] The hydrocarbon electrolyte polymer may contain only polymer (P), or it may contain hydrocarbon electrolyte polymers other than polymer (P). From the viewpoint of superior proton conductivity, the content of polymer (P) may be 90 to 100% by mass, 94 to 100% by mass, or 97 to 100% by mass, or substantially 100% by mass, based on the total mass of the hydrocarbon electrolyte polymer.

[0127] From the viewpoint of reducing environmental impact, the fluorine content of the hydrocarbon electrolyte polymer is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total mass of the hydrocarbon electrolyte polymer. It is even more preferable that the hydrocarbon electrolyte polymer does not contain fluorine atoms (the fluorine content is below the detection limit).

[0128] The number-average molecular weight of the hydrocarbon electrolyte polymer may be 20,000 or more, 25,000 or more, or 30,000 or more from the viewpoint of superior proton conductivity and mechanical strength, and may be 300,000 or less, 200,000 or less, or 150,000 or less from the viewpoint of superior solubility in solvents. From these viewpoints, the number-average molecular weight of the hydrocarbon electrolyte polymer may be 20,000 to 300,000, 25,000 to 200,000, or 30,000 to 150,000.

[0129] The weight-average molecular weight of the hydrocarbon electrolyte polymer may be 40,000 or more, 50,000 or more, or 60,000 or more from the viewpoint of superior proton conductivity and mechanical strength, and may be 500,000 or less, 300,000 or less, or 250,000 or less from the viewpoint of superior solubility in solvents. From these viewpoints, the weight-average molecular weight of the hydrocarbon electrolyte polymer may be 40,000 to 500,000, 50,000 to 300,000, or 60,000 to 250,000.

[0130] The number-average molecular weight and weight-average molecular weight of hydrocarbon electrolyte polymers are measured by gel permeation chromatography (GPC) and are expressed as standard polyethylene glycol / oxide (PEG / PEO) equivalent values.

[0131] From the viewpoint of superior proton conductivity and mechanical strength, the content of hydrocarbon electrolyte polymer may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on the total solid content of the resin composition (R), and may be 99.999999% by mass or less, 99.99999% by mass or less, 99.9999% by mass or less, 99.9999% by mass or less, 99.999% by mass or less, or 99.9% by mass or less. From a similar viewpoint, the content of hydrocarbon electrolyte polymer may be 80 to 99.999999% by mass, based on the total solid content of the resin composition (R), and may be 80 to 99.99999% by mass, 80 to 99.99999% by mass, 90 to 99.9999% by mass, 95 to 99.99% by mass or 99 to 99.9% by mass, based on the total solid content of the resin composition (R). "Total solid content of the resin composition (R)" may be interpreted as "total solid content of the electrolyte membrane (E)." However, in this case, the porous membrane is not included in the solid content of the electrolyte membrane (E). The same applies hereafter.

[0132] (Compound (C)) Compound (C) is a compound having a structure in which one or more groups represented by the above general formula (I) (hereinafter referred to as "ester group (i)") are bonded to an aromatic ring. Compound (C) may be used alone or in combination of two or more.

[0133] In general formula (I), R １This represents a hydrocarbon group having 1 to 20 carbon atoms, which may have substituents. Examples of substituents include hydroxyl groups, amino groups, carbonyl groups, alkoxy groups, sulfonyl groups, and halogen atoms. Examples of halogen atoms include fluorine atoms and chlorine atoms.

[0134] The hydrocarbon group may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated, and may be linear (straight or branched) or cyclic. The aliphatic hydrocarbon group may have both an aliphatic hydrocarbon ring and an aliphatic hydrocarbon chain. The number of carbon atoms in the aliphatic hydrocarbon group may be 1 to 15, 1 to 10, or 1 to 6, from the viewpoint of superior proton conductivity and mechanical strength.

[0135] The aliphatic hydrocarbon group may be a chain-like saturated aliphatic hydrocarbon group (alkyl group) from the viewpoint of superior proton conductivity and mechanical strength. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, 3-methylpentyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, and pentadecyl groups. Some of the hydrogen atoms of these groups may be substituted with the substituents mentioned above.

[0136] The hydrocarbon group may be an aromatic hydrocarbon group. An aromatic hydrocarbon group is a group having an aromatic hydrocarbon ring. The aromatic hydrocarbon ring of the aromatic hydrocarbon group may be monocyclic or polycyclic. The number of carbon atoms in the aromatic hydrocarbon group may be 6 to 20, 6 to 18, 6 to 14, or 6 to 10, from the viewpoint of superior proton conductivity and mechanical strength.

[0137] The aromatic hydrocarbon group may be an aryl group, from the viewpoint of superior proton conductivity and mechanical strength. Examples of aryl groups include phenyl, biphenyl, naphthyl, anthracenyl, phenanthryl, fluorenyl, tetracerenyl, and pyrenyl groups. Some of the hydrogen atoms of these aryl groups may be substituted with the substituents mentioned above.

[0138] R１ From the viewpoint of superior proton conductivity and mechanical strength, it is preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and more preferably an ethyl group or a phenyl group.

[0139] The aromatic ring to which the ester group (i) is bonded (hereinafter referred to as "aromatic ring (a)") may be monocyclic or polycyclic. Aromatic ring (a) may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring. Examples of aromatic hydrocarbon rings include benzene rings, naphthalene rings, anthracene rings, phenanthrene rings, fluorene rings, tetracene rings, pyrene rings, and triphenylene rings. From the viewpoint of superior proton conductivity and mechanical strength, aromatic ring (a) is preferably a benzene ring.

[0140] The number of ester groups (i) bonded to the aromatic ring (a) may be 1 to 6, 1 to 4, or 1 to 3, and may also be 2 to 6, 2 to 4, or 2 to 3. From the viewpoint of superior mechanical strength, the number of ester groups (i) bonded to the aromatic ring (a) may be 1 to 3. When the number of ester groups (i) bonded to the aromatic ring (a) is 2 or more, the multiple ester groups (i) may be the same or different from each other.

[0141] From the viewpoint of superior proton conductivity, compound (C) preferably has a structure in which two or more ester groups (i) are bonded to the aromatic ring (a), and more preferably has a structure in which two ester groups (i) are bonded to the aromatic ring (a). In this case, from the viewpoint of superior proton conductivity and mechanical strength, compound (C) is even more preferably has a structure in which two ester groups (i) are bonded to each other's ortho positions on the aromatic ring (a).

[0142] The aromatic ring (a) may have substituents. An example of substituent is R １ The examples of substituents may be the same as those in [the relevant section].

[0143] The number of aromatic rings (a) in compound (C) may be one or more.

[0144] From the viewpoint of superior proton conductivity and mechanical strength, compound (C) is preferably a compound represented by the following general formula (II).

[0145]

[0146] In general formula (II), R １ This is synonymous with the above, and R ２ R represents a hydrogen atom or substituent, and c represents an integer from 1 to 3. If c is 2 or 3, multiple R １ These may be the same or different from each other. Multiple R ２ They may be the same or different from one another.

[0147] In general formula (II), R ２ Examples of substituents are R １ The examples of substituents may be the same as those in [the relevant section].

[0148] In general formula (II), it is preferable that c is 2 from the viewpoint of further superior proton conductivity and mechanical strength. That is, in general formula (II), -COOR is added to the benzene ring. １ It is preferable that two groups represented by are bonded. From a similar viewpoint, in general formula (II), -COOR is bonded to the ortho positions of the benzene rings. １ It is more preferable that two groups represented by are bonded together.

[0149] Compound (C) includes methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, isobutyl benzoate, pentyl benzoate, hexyl benzoate, cyclohexyl benzoate, phenyl benzoate, cis-hexen-1-yl benzoate, 2-ethylhexyl benzoate, ethyl 2-aminobenzoate, ethyl 3-aminobenzoate, ethyl 4-aminobenzoate, ethyl 2-hydroxybenzoate, ethyl 3-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl gallate, chlorobutyl benzoate, monoethyl phthalate, and Examples include aromatic monoesters such as phenethyl benzoate, polyethylene glycol benzoate, and 1,3-diphenylenedibenzoate; aromatic diesters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, di-2-ethylhexyl terephthalate, diphenyl phthalate, diphenyl isophthalate, diphenyl terephthalate, and butylbenzyl phthalate; and aromatic triesters such as trioctyl trimellitate. These may be used individually or in combination of two or more.

[0150] Compound (C) is preferably a phthalate diester, more preferably a phthalate diester, selected from the group consisting of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, and diphenyl phthalate, and even more preferably a phthalate diethyl phthalate and diphenyl phthalate.

[0151] From the viewpoint of superior proton conductivity and mechanical strength, the content of compound (C) may be 0.000001 parts by mass or more, 0.00001 parts by mass or more, 0.0001 parts by mass or more, 0.001 parts by mass or more, 0.001 parts by mass or more, 0.01 parts by mass or more, or 0.1 parts by mass or more, per 100 parts by mass of hydrocarbon electrolyte polymer, and may be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less. From a similar viewpoint, the content of compound (C) may be 0.000001 to 20 parts by mass, 0.00001 to 20 parts by mass, 0.0001 to 10 parts by mass, 0.01 to 5 parts by mass, or 0.1 to 1 part by mass, per 100 parts by mass of hydrocarbon electrolyte polymer.

[0152] From the viewpoint of superior proton conductivity and mechanical strength, the content of compound (C) may be 0.000001% by mass or more, 0.00001% by mass or more, 0.0001% by mass or more, 0.001% by mass or more, 0.001% by mass or more, 0.01% by mass or more, or 0.1% by mass or more, based on the total solid content of the resin composition (R), and may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less. From a similar viewpoint, the content of compound (C) may be 0.000001 to 20% by mass, 0.00001 to 20% by mass, 0.00001 to 20% by mass, 0.0001 to 10% by mass, 0.01 to 5% by mass, or 0.1 to 1% by mass, based on the total solid content of the resin composition (R).

[0153] The total content of hydrocarbon electrolyte polymers and compounds (C) may be 90 to 100% by mass, 96 to 100% by mass, or 98 to 100% by mass, based on the total solid content of the resin composition (R), from the viewpoint of superior proton conductivity and mechanical strength.

[0154] (Porous membrane) Porous membranes contribute to further improvement of mechanical strength and swelling resistance as reinforcing materials for electrolyte membranes. From the viewpoint of increasing affinity with hydrocarbon-based electrolyte polymers and making it easier to obtain higher mechanical strength and swelling resistance, porous membranes may be formed from materials containing hydrocarbon-based resins. Specific examples of hydrocarbon-based resins include polyolefin resins, polyester resins, polyphenylene sulfide resins, polyetherimide resins, polyimide resins, polyurethane resins, and polyethersulfone resins. These may be used individually or in combination of two or more.

[0155] (Other components) The electrolyte membrane (E) may further contain additives such as water-retaining inorganic substances and radical scavengers as other components. Specific examples of additives include water, silica, cerium oxide, and manganese oxide. The other components may be used individually or in combination. The other components may be included in the resin composition (R) or in the porous membrane.

[0156] <Method for Manufacturing an Electrolyte Membrane> Another embodiment of the present disclosure is a method for manufacturing the electrolyte membrane (electrolyte membrane (E)) of the above embodiment. The method for manufacturing the electrolyte membrane (E) of one embodiment includes, for example, a step of forming a film made of a resin composition (R) (hereinafter referred to as the "film forming step"). The film forming method in the film forming step is not particularly limited and can be manufactured by a known method for forming an electrolyte polymer film. Examples of film forming methods include the solution casting method, the dispersion casting method, the melt press method and the melt extrusion method.

[0157] In the solution casting method, for example, a solution containing a hydrocarbon electrolyte polymer and compound (C) is used, the solution is applied to a substrate, the solvent is removed, and then the film is peeled off from the substrate to obtain a film made of a resin composition (R). The method of applying the solution is not particularly limited and may be, for example, an applicator method.

[0158] The solvent used in the solution casting method is not particularly limited as long as it is capable of dissolving hydrocarbon electrolyte polymers and compound (C). For example, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea can be used. These may be used individually or in combination.

[0159] In the dispersion casting method, for example, a dispersion containing a hydrocarbon electrolyte polymer and a compound (C) is used. After applying the dispersion onto a substrate, the dispersion medium is removed, and then the film is peeled off from the substrate to obtain a film made of a resin composition (R). The method of applying the dispersion is not particularly limited and may be, for example, an applicator method.

[0160] The dispersion medium used in the dispersion casting method is not particularly limited as long as it is a dispersion medium capable of dispersing hydrocarbon electrolyte polymers and compound (C). For example, water, ethers, alcohols, ketones, esters, carboxylic acids, amines, acetonitrile, nitromethane, toluene, xylene, chlorobenzene, and chloroform can be used. Examples of ethers include tetrahydrofuran and diethyl ether. Examples of alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol, and 1-butanol. Examples of ketones include acetone and cyclohexanone. Examples of esters include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methyl lactate, and ethyl lactate. Examples of carboxylic acids include formic acid, acetic acid, and propionic acid. Examples of amines include dimethylamine, diethylamine, triethylamine, pyridine, triethanolamine, and piperazine. These may be used individually or in combination.

[0161] The method for producing the electrolyte membrane (E) of the above embodiment may further include a step of washing the obtained membrane (a membrane made of the resin composition (R)) after the membrane formation step (hereinafter referred to as the "washing step"). In the washing step, the membrane may be washed using a washing solution. In this case, the electrolyte membrane (E) is obtained by drying the membrane after the washing step by a method such as vacuum drying. As the washing solution, a known washing solution according to the purpose of washing may be used. Specific examples of washing solutions include hydrogen peroxide, sulfuric acid, hydrochloric acid, nitric acid, and pure water. These may be used individually or in combination of two or more.

[0162] In another embodiment, instead of the above-described film-forming step, the electrolyte membrane (E) may be manufactured by performing a step of filling a porous membrane with a resin composition (R) (hereinafter referred to as the "filling step"). A method for filling with the resin composition (R) is, for example, impregnating the porous membrane with a liquid (solution or dispersion) containing a hydrocarbon electrolyte polymer and a compound (C), and then drying the liquid.

[0163] <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.

[0164] 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.

[0165] 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.

[0166] As an anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of fuels 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, two or more alloys thereof, and oxides thereof can be used.

[0167] 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, two or more alloys thereof, and oxides thereof can be used.

[0168] As the conductive material, at least one selected from the group consisting of furnace black, Ketjen black, channel black, acetylene black, mesoporous carbon, activated carbon, and graphite can be used.

[0169] 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.

[0170] The catalyst layer may further contain additives such as water repellents like fluorinated carbon, binders such as fluororesins and hydrocarbon resins having sulfonic acid groups.

[0171] 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.

[0172] <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.

[0173] 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.

[0174] 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).

[0175] 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.

[0176] <Solid Polymer Fuel Cell> A solid polymer fuel cell according to one embodiment comprises the membrane electrode assembly of the above embodiment.

[0177] The configuration of a polymer electrolyte fuel cell is not particularly limited and can be a conventionally known configuration, except that it uses the membrane electrode assembly of the above embodiment. 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.

[0178] <Solid Polymer Water Electrolyzer> A solid polymer water electrolyzer according to one embodiment includes the membrane electrode assembly according to the above embodiment.

[0179] 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.

[0180] 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.

[0181] <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 added. The resulting 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. After stirring under the same conditions for 1 hour, 40 mL of sulfur dioxide gas was introduced into the flask along with nitrogen gas, and the mixture was stirred under the same conditions for 30 minutes. Then, the methanol-dry ice bath was removed and the internal temperature was raised to 0°C. The precipitated solid was filtered off by suction filtration and washed with 200 mL of tetrahydrofuran. The recovered solid was dissolved in 2 L of pure water, 260 mL of 35% hydrogen peroxide solution was added, and the mixture was stirred at 25°C 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 represented by the following formula (M1). The yield was 65%.

[0182]

[0183] <Synthesis Example 2> (Synthesis of hydrophobic monomer (M2)) In a 200 mL flask equipped with a stirring bar, Dean-Stark tube, reflux condenser, and calcium chloride tube, 4.0 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 14.8 g of [1,1'-biphenyl]-4,4'-diol, and 13.2 g of potassium carbonate were charged, and 50 mL of N,N-dimethylacetamide and 50 mL of toluene were added. The mixture was heated to 160°C in an oil bath while stirring, and stirred under the same conditions for 4 hours. After removing the toluene from the Dean-Stark tube, the mixture was heated to 180°C in an oil bath and stirred under the same conditions for 8 hours. After removing the oil bath and allowing the reaction mixture to cool to 25°C, the reaction mixture was poured into 200 mL of 10% hydrochloric acid, and the precipitated white solid was filtered off. The filtered solid was washed with 300 mL of ethanol and dried. It was purified by recrystallization from an N-methylpyrrolidone / ethanol mixed solution. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0184]

[0185] <Synthesis Example 3> (Synthesis of hydrophobic monomer (M3)) 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), 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 (M3) represented by the following formula (M3). The yield was 53%.

[0186]

[0187] <Synthesis Example 4> (Synthesis of Polymer (P1)) 8.72 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, 7.37 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, and 11.61 g of cesium carbonate were added to a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, and nitrogen purging was performed. Then, 75 mL of dimethyl sulfoxide (DMSO) and 75 mL of cyclohexane were added. The resulting mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was carried out at 130°C for 48 hours. After the reaction mixture was cooled to room temperature, it was reprecipitated and purified with 450 mL of isopropyl alcohol, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure. The obtained solid was immersed in 6 M hydrochloric acid for 24 hours, then immersed in pure water and thoroughly washed, and dried under reduced pressure to obtain polymer (P1) having the structure represented by the following formula (P1). The yield was 92%. Note that n in formula (P1) was calculated from the number-average molecular weight, as described later.

[0188]

[0189] In equation (P1), n ​​represents a positive number (approximately 19).

[0190] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of polymer (P1) were measured under the following conditions. The number-average molecular weight (Mn) of polymer (P1) was 30,000, and the weight-average molecular weight (Mw) was 61,000.

[0191] [Molecular Weight: Measurement Conditions] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by GPC. 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-8320 GPC was used as the apparatus. Two Tosoh TSKgel SuperAWM-H columns (6.0 mm inner diameter, 15 cm length) were used. A differential refractometer detector was used. 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).

[0192] <Synthesis Example 5> (Synthesis of Polymer (P2)) In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 6.99 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, 9.72 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, and 14.6 g of cesium carbonate were added, and the mixture was purged with nitrogen. Then, 50 mL of dimethyl sulfoxide (DMSO) and 50 mL of cyclohexane were added. The resulting mixture was heated to 130°C and dehydrated under reflux for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was carried out at 130°C for 48 hours. After cooling to room temperature, 3.57 g of decafluorobiphenyl was added, and polymerization was carried out at 130°C for 3.5 hours. After the reaction mixture was cooled to room temperature, it was reprecipitated and purified with 450 mL of isopropyl alcohol, and the solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure. The obtained solid was immersed in 6 M hydrochloric acid for 24 hours, then thoroughly washed by immersion in pure water, and dried under reduced pressure to obtain a polymer (P2) containing multiple polymer units having a structure represented by the following formula (P2), and having decafluorobiphenyl-derived crosslinking groups that bond to three or more of the polymer units. The yield was 96%.

[0193]

[0194] In formula (P2), M represents Na, K, or H, and n represents a positive number.

[0195] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of polymer (P2) were measured in the same manner as in Synthesis Example 4. The number-average molecular weight (Mn) of polymer (P2) was 42,000, and the weight-average molecular weight (Mw) was 200,000.

[0196] <Synthesis Example 6> (Synthesis of Polymer (P3)) In a 200 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, Dean-Stark tube, and heating device, 8.89 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, 7.36 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, 0.428 g of 4,4'-dichlorodiphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.), and 15.0 g of cesium carbonate were added, and nitrogen purging was performed. 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 cooling to room temperature, 0.0470 g of decafluorobiphenyl was added, and polymerization was carried out at 130 °C for 3.5 hours. After allowing the reaction mixture 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 a polymer (P3) containing multiple polymer units with a structure represented by the following formula (P3), and having a decafluorobiphenyl-derived crosslinking group that bonds to three or more of the polymer units. The yield was 91%.

[0197]

[0198] In formula (P3), M represents Na, K, or H, and x, y, and n represent positive numbers. The content of constituent units derived from the hydrophobic monomer (M3) was 50 mol% of the total amount of all constituent units that make up the polymer (P3). Furthermore, the Mn of the polymer (P3), measured in the same manner as in Synthesis Example 4, was 57,000, and the Mw was 280,000.

[0199] <Example 1> 1.0 g of polymer (P1), 1.0 g of a DMSO solution containing 0.00001% by mass of diethyl phthalate (DEP, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and DMSO were mixed to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate with an applicator and dried at 60°C for 6 hours to obtain the electrolyte film of Example 1 (film thickness 40 μm). The "film thickness" in this example was measured using a PG-02 manufactured by TECLOK CORPORATION. The same applies to the "film thickness" in the following examples and comparative examples.

[0200] <Example 2> An electrolyte membrane (film thickness 36 μm) of Example 2 was obtained in the same manner as in Example 1, except that a DMSO solution containing 0.0001% by mass of DEP was used instead of a DMSO solution containing 0.0001% by mass of DEP.

[0201] <Example 3> An electrolyte membrane (thickness 21 μm) of Example 3 was obtained in the same manner as in Example 1, except that 0.0010 g of DEP was used instead of a DMSO solution containing 0.00001% by mass of DEP.

[0202] <Example 4> An electrolyte membrane (thickness 19 μm) for Example 4 was obtained in the same manner as in Example 3, except that 0.0010 g of diphenyl phthalate (DPhP, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of DEP.

[0203] <Example 5> An electrolyte membrane (film thickness 39 μm) of Example 5 was obtained in the same manner as in Example 3, except that 0.10 g of DEP was used.

[0204] <Example 6> An electrolyte membrane (film thickness 31 μm) of Example 6 was obtained in the same manner as in Example 3, except that polymer (P2) was used instead of polymer (P1).

[0205] <Example 7> An electrolyte membrane (film thickness 30 μm) of Example 7 was obtained in the same manner as in Example 4, except that polymer (P2) was used instead of polymer (P1).

[0206] <Example 8> An electrolyte membrane (film thickness 31 μm) of Example 8 was obtained in the same manner as in Example 3, except that polymer (P3) was used instead of polymer (P1).

[0207] <Comparative Example 1> An electrolyte membrane (thickness 23 μm) of Comparative Example 1 was obtained in the same manner as in Example 1, except that a DMSO solution containing 0.00001% by mass of DEP was not used.

[0208] <Comparative Example 2> An electrolyte membrane (thickness 24 μm) of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that polymer (P2) was used instead of polymer (P1).

[0209] <Comparative Example 3> An electrolyte membrane (film thickness 24 μm) for Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that polymer (P3) was used instead of polymer (P1).

[0210] <Evaluation> The mechanical strength and proton conductivity of the electrolyte membranes obtained in the examples and comparative examples were evaluated by the following method. The results are shown in Tables 1 to 3.

[0211] (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 on the strain was measured. The tensile stress was calculated by dividing the obtained load by the cross-sectional area of ​​the electrolyte membrane. The elongation rate was calculated by dividing the length of the test specimen just before fracture by the length of the test specimen before the test. 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 35 MPa or higher and the elongation rate was 15% or higher.

[0212] (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 cell at 80°C and 20% relative humidity for 2 hours, DC resistance measurement was performed using the four-terminal method. The proton conductivity of the electrolyte membrane in the planar direction under an 80°C 20% RH environment was calculated from the obtained resistance value, the thickness of the electrolyte membrane, and the distance between terminals. Next, the relative humidity was increased by 10% and maintained for 30 minutes. This operation was continued until the relative humidity reached 100%, and then DC resistance measurement was performed similarly at 100% relative humidity to calculate the proton conductivity under an 80°C 100% RH environment. Furthermore, an electrolyte membrane was evaluated as having excellent proton conductivity if the measured proton conductivity was 0.8 mS / cm or higher under an environment of 80°C and 20% RH, and 150 mS / cm or higher under an environment of 80°C and 100% RH. An electrolyte membrane was evaluated as having even better proton conductivity if the measured proton conductivity was 1.3 mS / cm or higher under an environment of 80°C and 200 mS / cm or higher under an environment of 80°C and 100% RH.

[0213]

[0214]

[0215]

[0216] This application is based on Japanese Patent Application No. 2025-066198, filed on April 14, 2025, which is incorporated by reference in its entirety. All references cited herein are incorporated as a whole.

Claims

1. A hydrocarbon electrolyte polymer and the following general formula (I): [In general formula (I), R １ represents a hydrocarbon group having 1 to 20 carbon atoms which may have substituents, and * represents a bond to an aromatic ring. An electrolyte membrane comprising a compound having a structure in which one or more groups represented by ] are bonded to an aromatic ring.

2. The aforementioned R １ The electrolyte membrane according to claim 1, wherein the alkyl group has 1 to 6 carbon atoms or the aryl group has 6 to 10 carbon atoms.

3. The electrolyte membrane according to claim 1 or 2, wherein the compound has a structure in which two or more groups represented by the general formula (I) are bonded to the aromatic ring.

4. The electrolyte membrane according to claim 3, wherein the compound has a structure in which two groups represented by the general formula (I) are bonded to each other's ortho positions on the aromatic ring.

5. The electrolyte membrane according to any one of claims 1 to 4, wherein the aromatic ring is a benzene ring.

6. The electrolyte membrane according to any one of claims 1 to 5, wherein the compound comprises at least one selected from the group consisting of diethyl phthalate and diphenyl phthalate.

7. The hydrocarbon-based electrolyte polymer is represented by the following formula (a1): [In formula (a1), IExG represents an ion exchange group, L １ represents a single bond, -O-, -S-, -SO ２ - or -CO-, x represents an integer of 1 to 10, and * represents a bond. A plurality of IExG may be the same or different from each other, and a plurality of L １ may be the same or different from each other.], and a structural unit A represented by the following formula (a2): [In formula (a2), Ar １ represents an arylene group having no ion exchange group, L ２ represents a single bond, an optionally substituted divalent aliphatic hydrocarbon group, -O-, -S-, -SO ２ - or -CO-, y represents an integer of 1 to 20, and * represents a bond. A plurality of Ar １ may be the same or different from each other, and a plurality of L ２ may be the same or different from each other. However, L located at the terminal ２ is not a divalent aliphatic hydrocarbon group.], The electrolyte membrane according to any one of claims 1 to 6, comprising a structural unit B represented by the formula.

8. The electrolyte membrane according to any one of claims 1 to 7, wherein the hydrocarbon electrolyte polymer comprises at least one ion exchange group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, sulfonimide groups, and phosphonic acid groups, and salts thereof.

9. The electrolyte membrane according to any one of claims 1 to 8, wherein the content of the compound is 0.000001 to 20 parts by mass per 100 parts by mass of the hydrocarbon electrolyte polymer.

10. An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of claims 1 to 9, and a catalyst layer disposed on one or both sides of the electrolyte membrane.

11. A membrane electrode assembly comprising an electrolyte membrane according to any one of claims 1 to 9, and an electrode layer disposed on one or both sides of the electrolyte membrane.

12. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 11.

13. A solid polymer water electrolysis apparatus comprising the membrane electrode assembly described in claim 11.

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