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

Abstract

This polymer dispersion contains: a polymer having a structure represented by formula (1); a water-soluble organic solvent; and water. [In formula (1), A1 is a constitutional unit represented by formula (a1), A2 is a constitutional unit represented by formula (a2), L1 and L7 are each independently a single bond or the like, n is an integer of 10-100, and * is a bond.] [In formula (a1), IExG represents an ion-exchange group, L3 represents a single bond or the like, x is an integer of 2-10, and * represents a bond.] [In formula (a2), Ar represents an arylene group having no ion-exchange group, L4 represents a single bond or the like, y is an integer of 3-20, and * represents a bond.]

Description

Polymer dispersion, electrode catalyst composition, electrode catalyst layer, electrolyte membrane with electrode catalyst layer, membrane electrode assembly, polymer electrolyte fuel cell, and polymer electrolyte water electrolyzer.

[0001] This disclosure relates to polymer dispersions, electrode catalyst compositions, electrode catalyst layers, electrolyte membranes with electrode catalyst layers, membrane electrode assemblies, polymer electrolyte fuel cells, and polymer electrolyte water electrolyzers.

[0002] In recent years, fuel cells have gained attention as a highly energy-efficient new energy technology against the backdrop of environmental concerns. Among them, polymer electrolyte fuel cells, which use polymer materials as electrolytes, are attracting particular attention because they have a high maximum current density and can operate at low temperatures, making them suitable as power sources for mobile devices such as automobiles and small-capacity power sources for portable electronic devices. Furthermore, from a carbon neutrality perspective, the use of hydrogen energy in polymer electrolyte fuel cells, which is an application of fuel cell technology, is also attracting attention.

[0003] Fluorine-based polymers are known as polymers (electrolyte polymers) used in electrolytes for solid polymer fuel cells and water electrolysis (see, for example, Patent Document 1). Although fluorine-based polymers are widely used in electrolyte applications such as ionomers used in the electrode catalyst layer of fuel cells due to their high proton conductivity and excellent swelling resistance, 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 polymer 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] In order to improve the power generation efficiency of a fuel cell, it is desirable that the resistance (ionomer resistance) derived from the ionomer in the electrode catalyst layer be low. However, an electrode catalyst layer using a fluorine-based polymer such as Patent Document 1 may not exhibit a sufficiently low ionomer resistance. Further, for the formation of an electrode catalyst, a dispersion liquid in which an ionomer is dispersed in a dispersion medium containing a water-soluble organic solvent and water is used, but non-fluorine-based polymers such as Patent Document 2 tend to have low dispersibility in the above dispersion medium, and it is not always easy to form an electrode catalyst layer exhibiting a low ionomer resistance using a non-fluorine-based polymer.

[0007] One aspect of the present disclosure aims to provide a polymer dispersion liquid that contributes to the formation of an electrode catalyst layer exhibiting a low ionomer resistance.

[0008] The present invention is as described in the claims, and the present disclosure provides the following [1] to

[15] in some aspects.

[0009] [1] The following formula (1): [In formula (1), A １ is the following formula (a1): (In formula (a1), IExG represents an ion exchange group, L ３ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, x represents an integer of 2 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 ３ may be the same as or different from each other.) represents a structural unit, and A ２ is the following formula (a2): (In formula (a2), Ar represents an arylene group having no ion exchange group, L ４ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, y represents an integer of 3 to 20, and * represents a bond. A plurality of Ar may be the same as or different from each other, and a plurality of L ４ may be the same as or different from each other.) represents a structural unit, and L １ and L ２These are, independently, a single bond, -O-, -S-, or -SO-. ２ - indicates a combination, n is an integer between 10 and 100, and * indicates a combination. Multiple A １ They may be the same or different from each other, and there are multiple A ２ These may be the same or different from each other, and there are multiple L １ These may be the same or different from each other, and there are multiple L ２ They may be the same or different from each other. However, multiple A １ The difference of x in equation (a1) is 3 or less, and multiple A ２ The difference of y in formula (a2) is within 5. A polymer dispersion containing a polymer having the structure represented by ], a water-soluble organic solvent, and water.

[0010] [2] The polymer dispersion according to [1], wherein the constituent unit represented by formula (a1) 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 polymer dispersion according to [1] or [2], wherein the constituent unit represented by formula (a2) 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 a substituent.

[0012] [4] The polymer dispersion according to any one of [1] to [3], wherein the ion exchange capacity of the polymer is 1.0 to 3.5 mmol / g.

[0013] [5] The polymer dispersion according to any one of [1] to [4], wherein the octanol / water partition coefficient of the water-soluble organic solvent is 1.0 or less.

[0014] [6] The polymer dispersion according to any one of [1] to [5], wherein the content of the water-soluble organic solvent is 5 to 95 parts by mass with respect to 100 parts by mass of the total amount of the water-soluble organic solvent and the water.

[0015] [7] The polymer dispersion according to any one of [1] to [6], wherein the polymer content is 25% by mass or less based on the total mass of the polymer dispersion.

[0016] [8] The polymer dispersion according to any one of [1] to [7], wherein the weight-average molecular weight of the polymer is 10,000 to 500,000.

[0017] [9] The polymer dispersion according to any one of [1] to [8], wherein the polydispersity of the polymer is 1.5 to 20.0.

[0018]

[10] An electrode catalyst composition comprising a polymer dispersion according to any one of [1] to [9] and an electrode catalyst.

[0019]

[11] An electrode catalyst layer formed from the electrode catalyst composition described in

[10] .

[0020]

[12] An electrolyte membrane with an electrode catalyst layer, comprising an electrolyte membrane and an electrode catalyst layer according to

[11] disposed on one or both sides of the electrolyte membrane.

[0021]

[13] A membrane electrode assembly comprising an electrolyte membrane and an electrode layer having the electrode catalyst layer described in

[11] , disposed on one or both sides of the electrolyte membrane.

[0022]

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

[13] .

[0023]

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

[13] .

[0024] According to one aspect of this disclosure, it is possible to provide a polymer dispersion that contributes to the formation of an electrode catalyst layer exhibiting low ionomer resistance.

[0025] Figure 1 is a graph showing the correlation between the real and imaginary parts of the impedance in the electrode catalyst layers of Examples 1 to 6 and Comparative Example 1.

[0026] 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.

[0027] <Polymer Dispersion> The polymer dispersion of one embodiment (hereinafter also referred to as "polymer dispersion (D)") contains a polymer having the structure represented by the following formula (1) (hereinafter also referred to as "polymer (P)"), a water-soluble organic solvent, and water.

[0028]

[0029] In formula (1), A １ This is a constituent unit represented by the following formula (a1) (hereinafter referred to as "constituent unit A" １ It is also called ". ) and A ２ This is a constituent unit represented by the following formula (a2) (hereinafter referred to as "constituent unit A ２ It is also called ". ) indicates L １ and L ２ These are, independently, a single bond, -O-, -S-, or -SO-. ２ - indicates a combination, n is an integer between 10 and 100, and * indicates a combination. Multiple A １ They may be the same or different from each other, and there may be multiple A ２ These may be the same or different from each other, and there may be multiple L １ These may be the same or different from each other, and there may be multiple L ２ They may be the same or different from each other. However, multiple A １ The difference of x in equation (a1) is 3 or less, and multiple A ２ The difference of y in equation (a2) is within 5.

[0030]

[0031] In formula (a1), IExG indicates an ion exchange group, and L ３These are single bonds, -O-, -S-, -SO ２ - or -CO- is indicated, x is an integer from 2 to 10, and * is an association. Multiple IExG may be the same or different from each other, and multiple L ３ They may be the same or different from one another.

[0032]

[0033] In formula (a2), Ar represents an arylene group that does not have an ion exchange group, and L ４ These are single bonds, -O-, -S-, -SO ２ - or -CO- is indicated, y is an integer from 3 to 20, and * indicates a combination. Multiple Ars may be the same or different from each other, and multiple L ４ They may be the same or different from one another.

[0034] The polymer dispersion (D) can be used to form an electrode catalyst layer. Specifically, for example, an electrode catalyst composition can be formed by mixing the polymer dispersion (D) with an electrode catalyst, and an electrode catalyst layer can be formed using this electrode catalyst composition. Therefore, the polymer dispersion (D) can be rephrased as a polymer dispersion for electrode catalyst layer formation.

[0035] By using a polymer dispersion (D), an electrode catalyst layer exhibiting low ionomer resistance can be formed. Although the reason for this is not clear, it is presumed that the polymer (P) contained in the polymer dispersion (D) contributes to the low ionomer resistance. In other words, the polymer (P) is composed of multiple hydrophilic constituent units A １ and multiple hydrophobic constituent units A ２ Where it includes multiple A １ The difference of x in equation (a1) is 3 or less, and multiple A ２ Since the difference of y in equation (a2) is within 5, multiple hydrophilic constituent units A １ and multiple hydrophobic constituent units A ２ Each of these has the same or similar structure as the others. In other words, polymer (P) is composed of multiple hydrophilic constituent units A that have the same or similar structure as the others. １Multiple hydrophobic constituent units A having the same or similar structure as (hydrophilic part) ２ It has a structure in which the (hydrophobic portion) and are precisely arranged, and the ion exchange groups in the polymer (P) are arranged at approximately equal intervals. Therefore, when used as an electrode catalyst layer, it is presumed that the ion exchange groups self-assemble in a higher-order structure, inducing a microphase separation structure, and thereby good proton conduction paths are formed within the polymer (P), resulting in low ionomer resistance. Also, constituent unit A １ The presence of three or more densely packed ion exchange groups within the polymer is also presumed to contribute to its low ionomer resistance. Furthermore, the fact that the polymer (P) is easily dispersed in a dispersion medium containing a water-soluble organic solvent and water, allowing the electrode catalyst to be well coated with the polymer (P) during the formation of the electrode catalyst layer, is also presumed to be one of the causes of the above effect.

[0036] Furthermore, polymer dispersion (D) is less prone to instability such as sedimentation or aggregation of the polymer even after a certain period of time has elapsed since the polymer was dispersed in the dispersion medium. In other words, polymer dispersion (D) has high polymer dispersion stability. The reason for this is not clear, but it is presumed to be as follows: Since polymer (P) has a structure in which multiple hydrophilic parts and multiple hydrophobic parts are precisely arranged, it is presumed that in a dispersion medium containing a water-soluble organic solvent and water, the polymer (P) molecules align with each other with their hydrophilic parts facing outward, forming an electrical double layer and thus stably dispersed as fine particles. Thus, high dispersion stability of the polymer dispersion eliminates the need to immediately prepare the electrode catalyst composition after preparation, resulting in better workability.

[0037] (Polymer (P)) As shown in formula (1), polymer (P) is composed of constituent unit A １ and constituent unit A ２ and the linking group (L １ or L ２The structure has a continuous repeating structure (the structure in brackets in formula (1)) via a ) . The number of repeats (n) of the structure is 10 to 100, and may be 15 or more or 20 or more, or 80 or less or 50 or less. When the number of repeats (n) is 15 or more, the dispersion stability in the solvent tends to be superior, and when the number of repeats (n) is 50 or less, the film-forming properties tend to be superior. From these viewpoints, the number of repeats (n) of the structure is preferably 15 to 80, and more preferably 20 to 50.

[0038] [Construction Unit A] １ ] Component Unit A １ This is an aromatic ring having an ion exchange group (IExG) and a linking group (L ３ It has a continuous structure via ).

[0039] 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, ion-exchange groups also include those that form salts with metal ions, etc.

[0040] 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.

[0041] Alkyl sulfonic acid groups and their salts are, for example, -R １ SO ３ M １／ｑ It is represented by R １R is an alkanediyl group, and from the viewpoint of lowering ionomer resistance and further improving dispersion stability, 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 as defined above.

[0042] 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 lowering ionomer resistance and improving dispersion stability, its carbon number is preferably 1 to 6 (an integer). ２ Specific examples include methyl, ethyl, and propyl groups. M and q are the same as above.

[0043] Constituent unit A １ From the viewpoint of lowering ionomer resistance and improving dispersion stability, it is preferable that the ion exchange group contains at least one group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, and sulfonimide groups, and salts thereof, and more preferably contains at least one group selected from the group consisting of sulfonic acid groups and salts thereof. From a similar viewpoint, constituent unit A １ It is even more preferable that the majority of the multiple ion exchange groups present within are of the above preferred embodiment, and constituent unit A １ It is particularly preferable that all of the multiple ion exchange groups present therein are of the above-described preferred form.

[0044] Constituent unit A １ From the viewpoint of lowering ionomer resistance and improving dispersion stability, the linking group (L ３ ) as -SO ２ Preferably, it contains at least one group selected from the group consisting of - and -CO-, and -SO ２ - is more preferable. From a similar viewpoint, constituent unit A １ Multiple linking groups (L) present inside ３It is even more preferable that the majority of these are of the above-described preferred embodiment.

[0045] Constituent unit A １ The linking group inside (L ３ From the perspective of achieving both lower ionomer resistance and chemical durability, and from the perspective of further improving dispersion stability, single bonds or -SO ２ - is preferable.

[0046] Linking group (L ３ The bonding position of the constituent unit A is not particularly limited, but from the viewpoint of lowering the ionomer resistance and improving dispersion stability, it is preferable that it be located in the ortho or meta position relative to the ion exchange group. １ It is preferable that it contains a 1,4-phenylene group having an ion exchange group.

[0047] Constituent unit A １ In formula (a1), the number of repeats (x) of the structure in brackets [ ] is preferably 2 to 8, more preferably 3 to 5, from the viewpoint of lowering the ionomer resistance, improving dispersion stability, and having excellent heat water resistance.

[0048] Constituent unit A １ From the viewpoint of lowering ionomer resistance and further enhancing dispersion stability, it is preferable that the structure 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)").

[0049]

[0050]

[0051]

[0052] In formulas (a1-1), (a1-2), and (a1-3), IExG and * have the same meaning as described above. In formula (a1-3), L ３１represents -O- or -S-. A plurality of IExG may be the same as or different from each other. x in formula (a1-1) １ represents an integer from 2 to 10, and x in formula (a1-2) ２ represents an integer from 2 to 5, and x in formula (a1-3) ３ represents an integer from 1 to 2. However, when the structural unit A １ contains two or more structures selected from the group consisting of structure (a1-1), structure (a1-2), and structure (a1-3), x １ , 2x ２ (the product of 2 and x ２ ) and 4x ３ (the product of 4 and x ３ ) have a total of 6 to 10. x １ is preferably 2 to 5, more preferably 2 to 3, from the viewpoint of lower ionomer resistance and higher dispersion stability. x ２ is preferably 2 to 3, more preferably 2, from the viewpoint of lower ionomer resistance and higher dispersion stability. x ３ is preferably 1, from the viewpoint of lower ionomer resistance and higher dispersion stability.

[0053] The structural unit A １ may consist only of structure (a1-1), or may include structure (a1-1) and a structure other than structure (a1-1). In the latter case, structure (a1-1) and the structure other than structure (a1-1) may be linked by a linking group (L ３ ). Similarly, the structural unit A １ may consist only of structure (a1-2), or may include structure (a1-2) and a structure other than structure (a1-2). In the latter case, structure (a1-2) and the structure other than structure (a1-2) may be linked by a linking group (L ３ ). Similarly, the structural unit A １ may consist only of structure (a1-3), or may include structure (a1-3) and a structure other than structure (a1-3). In the latter case, structure (a1-3) and the structure other than structure (a1-3) may be linked by a linking group (L ３ ).

[0054] Constituent unit A １ This may be a constituent unit represented by any of the following formulas (A1-1) to (A1-4).

[0055]

[0056] IExG and * in formulas (A1-1) to (A1-4), and L in formulas (A1-2) to (A1-4). ３ This is synonymous with the above. Multiple IExG may be the same or different from each other. Multiple L ３ They may be the same or different from one another.

[0057] Constituent unit A １ From the viewpoint of lowering ionomer resistance, improving dispersion stability, and having excellent chemical durability, it is preferable that the constituent unit is one of those represented by formulas (A1-1) to (A1-4), and more preferably that it is the constituent unit represented by formula (A1-2). In formula (A1-2), L ３ From the viewpoint of further lowering ionomer resistance, further improving dispersion stability, and superior chemical durability, a single bond is preferable.

[0058] Multiple constituent units A in equation (1) １ At least one of them may be one of those exemplified above, and multiple constituent units A １ The majority of these may be those exemplified above, and multiple constituent units A １ All of these may be examples given above.

[0059] Multiple constituent units A in equation (1) １ This is a range where the difference of x in equation (a1) is 3 or less, and there are two or more constituent units A １ It may consist of multiple constituent units A. １ From the viewpoint of lowering ionomer resistance and improving dispersion stability, the number of types is preferably three or less, and more preferably two or less.

[0060] Multiple constituent units A in equation (1) １The difference of x in equation (a1) is preferably as close to 0 as possible from the viewpoint of lowering the ionomer resistance and improving dispersion stability, and may be within 2, within 1, or 0.

[0061] [Construction Unit A] ２ ] Component Unit A ２ In this case, the arylene group (Ar) which does not have an ion exchange group is linked to the L group. ４ It has a continuous structure via ).

[0062] 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, more preferably 1 to 2, and even more preferably 1, from the viewpoint of film-forming properties, lower ionomer resistance, and improved dispersion stability. The arylene group may have substituents other than ion exchange groups. Examples of substituents include alkyl groups and aryl groups. The alkyl group may be at least one group selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups. An example of an aryl group is the phenyl group. When the arylene group has an aryl group as a substituent, the number of aromatic rings in the arylene group includes the number of aromatic rings in the substituent.

[0063] 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).

[0064] Constituent unit A ２ From the viewpoint of film formation, lower ionomer resistance, and improved dispersion stability, it is preferable that the arylene group includes at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have substituents, and it is more preferable that the arylene group includes at least one group selected from the group consisting of phenylene, naphthylene, and fluorene groups, which may have an aryl group as a substituent. Constituent Unit A ２ From the viewpoint of further improving film-forming properties, it is more preferable to include a phenylene group, and even more preferable to include a 1,4-phenylene group. From a similar viewpoint, constituent unit A ２ It is particularly preferable that the majority of the multiple arylene groups present in the constituent unit A are of the above preferred embodiment. ２ It is extremely preferable that all of the multiple arylene groups present are independently phenylene groups, naphthylene groups, or fluorene groups, which may each have substituents.

[0065] Constituent unit A ２ From the viewpoint of having excellent film-forming properties and excellent mechanical strength of the film obtained by film formation, the linking group (L ４ ) as a single bond, -SO２ Preferably, it contains at least one group selected from the group consisting of - and -CO-, and -SO ２ It is more preferable to include - or -CO-. From a similar viewpoint, constituent unit A ２ Multiple linking groups (L) present inside ４ It is even more preferable that the majority of ) are of the above preferred embodiment, and constituent unit A ２ Multiple linking groups (L) present inside ４ All of the above may be in the preferred form described above.

[0066] Constituent unit A ２ From the viewpoint of lowering ionomer resistance and improving dispersion stability, the linking group (L ４ ) as a single bond, -O-, -S- or -SO ２ It is preferable to include -.

[0067] Constituent unit A ２ In formula (a2), the number of repeats (y) of the structure in brackets [ ] is preferably 4 to 12, and more preferably 5 to 10, from the viewpoint of lowering the ionomer resistance, improving dispersion stability, and having excellent heat water resistance.

[0068] Constituent unit A ２ In formula (a2), the number of repeating structures (y) in the brackets [ ] 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 lower ionomer resistance and hot water resistance, and from the viewpoint of further improving dispersion stability.

[0069] Constituent unit A ２ The number of aromatic rings in the main chain is preferably 4 to 21, more preferably 5 to 13, and even more preferably 6 to 11, from the viewpoint of lowering ionomer resistance and improving dispersion stability.

[0070] Constituent unit A ２ From the viewpoint of having excellent film-forming properties and excellent mechanical strength of the film obtained by film formation, it is preferable that the material includes at least one structure selected from the group consisting of the structure represented by the following formula (a2-1) and the structure represented by the following formula (a2-2).

[0071]

[0072]

[0073] In formulas (a2-1) and (a2-2), Ar and * have the same meanings as described above. Multiple Ars may be the same or different from one another.

[0074] Constituent unit A including the above structure ２ A concrete example of this is the constituent unit represented by the following formula (A2-1).

[0075]

[0076] Ar, L in equation (A2-1) ４ And * are the same as above, Q indicates the base of the structure represented by formula (a2-1) or formula (a2-2), and y １ and y ２ Each of these independently represents an integer between 2 and 4. １ and y ２ From the viewpoint of lowering the ionomer resistance and further improving dispersion stability, the number of Ars is preferably 2 to 3. The multiple Ars may be the same or different from each other, and the multiple Ls ４ They may be the same or different from one another.

[0077] Constituent unit A ２ From the viewpoint of obtaining excellent water repellency, the structure may include at least three consecutive arylene groups linked by single bonds. The number of consecutive arylene groups via single bonds may be four or more, or five or more, from the viewpoint of obtaining even better water repellency. The number of consecutive arylene groups via single bonds may be 10 or less, or 8 or less, or 6 or less, from the viewpoint of lowering ionomer resistance and improving dispersion stability, for example. From these viewpoints, the number of consecutive arylene groups via single bonds may be 3 to 10, or 4 to 8 or 5 to 6.

[0078] Constituent unit A including the above structure ２ This may be a constituent unit represented by any of the following formulas (A2-2) to (A2-7).

[0079]

[0080] The * in equations (A2-2) to (A2-7) has the same meaning as above. The R in equations (A2-4) and (A2-6) ３ R represents an alkyl group, and from the viewpoint of lowering ionomer resistance and further improving dispersion stability, its carbon number is preferably 1 to 12 (an integer). ３ Specific examples include methyl, ethyl, propyl, hexyl, and dodecyl groups. In formulas (A2-4) and (A2-6), multiple R ３ They may be the same or different from one another.

[0081] Multiple constituent units A in equation (1) ２ At least one of them may be one of those exemplified above, and multiple constituent units A ２ The majority of these may be those exemplified above, and multiple constituent units A ２ All of these may be examples given above.

[0082] Multiple constituent units A in equation (1) ２ This is a range where the difference of y in equation (a2) is 5 or less, and there are two or more constituent units A ２ It may consist of multiple constituent units A. ２ From the viewpoint of lowering ionomer resistance and improving dispersion stability, the number of types is preferably two or less, and more preferably one.

[0083] Multiple constituent units A in equation (1) ２ The difference of y in equation (a2) is preferably as close to 0 as possible from the viewpoint of lowering the ionomer resistance and improving dispersion stability, and may be within 4, within 3, within 2, within 1, or 0.

[0084] Multiple constituent units A in equation (1) ２ The difference in the number of aromatic rings in the main chain in formula (a2) is preferably as close to 0 as possible from the viewpoint of lowering ionomer resistance and improving dispersion stability, and may be 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or 0. From a similar viewpoint, the multiple constituent units A in formula (1) ２The difference in the number of aromatic rings in formula (a2) is preferably as close to 0 as possible, and may be 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or 0.

[0085] [Connecting group] Polymer (P) is configured as constituent unit A from the viewpoint of lowering ionomer resistance and improving dispersion stability. １ and constituent unit A ２ Linking group between (L １ or L ２ ) as single bond, -S-, -SO ２ It is preferable to include at least one group selected from the group consisting of - and -O-. From a similar viewpoint, multiple constituent units A present in the polymer (P) １ and constituent unit A ２ Linking group between (L １ and L ２ It is more preferable that the majority of these are -O- or -S-, and there are multiple constituent units A in the polymer (P). １ and constituent unit A ２ Linking group between (L １ and L ２ It is even more preferable that all of the ) are -O- or -S-. Note that polymer (P) is constituent unit A １ and constituent unit A ２ Linking group between (L １ or L ２ ) as single bonds, -S- and -SO ２ When the compound contains at least one group selected from the group consisting of the following, chemical durability tends to improve.

[0086] The polymer (P) may consist of a structure represented by formula (1) and terminal structures bonded to the structure. The polymer (P) may be, for example, a compound represented by any of the following formulas (1-1) to (1-3).

[0087]

[0088] A in equations (1-1) to (1-3) １ A ２ , L １ , L ２ and n are as defined above. However, in equations (1-1) and (1-2), Z ２L that joins ２ This is a single bond. Z １ and Z ２ 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 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.

[0089] The polymer (P) may contain multiple polymer units (hereinafter also referred to as "polymer unit A") that have the structure represented by formula (1). For example, the polymer (P) may contain three or more polymer units A and three or more crosslinking groups that bond to the polymer units A. A polymer (P) having such crosslinking groups has excellent swelling resistance.

[0090] Polymer unit A is, for example, derived from any of the compounds represented by formulas (1-1) to (1-3) above, from terminal group Z １ and Z ２ It has a structure that excludes the following. Of the two terminal groups of polymer unit A, the terminal group that bonds to the crosslinking group is A １ It is fine if A ２ It may also be the case that the terminal group that bonds to the crosslinking group is L ２ In the case of a single bond represented by (i.e., Z in equations (1-1) and (1-2)), ２ L that joins ２ In this case, the terminal group that bonds to the crosslinking group is A ２ It is assumed that the two end groups of polymer unit A may each be bonded to different crosslinking groups. Of the two end groups of polymer unit A, the end group opposite to the end group bonded to the crosslinking group is the end group Z mentioned above. １ and Z ２It may be bonded to either one of the two. Multiple polymer units A bonded to a single crosslinking group may be the same or different from one another.

[0091] The crosslinking group may be a group derived from a known crosslinkable compound (e.g., decafluorobiphenyl). From the viewpoint of chemical stability, the crosslinking group preferably has one or more aromatic rings. When the crosslinking group has aromatic rings, the polymer units are attached directly to the aromatic rings 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.

[0092] The proportion of the structure represented by formula (1) in the entire polymer (P) is preferably 80% by mass or more, from the viewpoint of lowering the ionomer resistance and further improving dispersion stability. From a similar viewpoint, the proportion of the structure represented by formula (1) in the entire polymer (P) may be 85% by mass or more, or 90% by mass or more. The proportion of the structure represented by formula (1) in the entire polymer (P) may be less than 100% by mass. The proportion of the structure represented by formula (1) in the entire polymer (P) may be 80% by mass or more and less than 100% by mass, 85% by mass or more and less than 100% by mass, or 90% by mass or more and less than 100% by mass.

[0093] 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).

[0094] The number-average molecular weight of the polymer (P) may be 8,000 or more, 9,000 or more, 10,000 or more, 20,000 or more, 25,000 or more, or 30,000 or more, from the viewpoint of lowering ionomer resistance, improving dispersion stability, and having excellent mechanical strength of the film obtained by film formation. From the viewpoint of excellent film-forming properties, it may be 300,000 or less, 200,000 or less, 100,000 or less, 80,000 or less, 60,000 or less, or 35,000 or less. From these viewpoints, the number-average molecular weight of the polymer (P) may be 8,000 to 300,000, 9,000 to 200,000, 10,000 to 100,000, 20,000 to 80,000, 25,000 to 60,000, 25,000 to 35,000, or 30,000 to 60,000.

[0095] The weight-average molecular weight of the polymer (P) may be 10,000 or more, 20,000 or more, 30,000 or more, 45,000 or more, 55,000 or more, 60,000 or more, or 70,000 or more, from the viewpoint of lowering ionomer resistance, improving dispersion stability, and having excellent mechanical strength of the film obtained by film formation, and may be 500,000 or less, 300,000 or less, 150,000 or less, 120,000 or less, 80,000 or less, or 70,000 or less, from the viewpoint of excellent film-forming properties. From these perspectives, the weight-average molecular weight of the polymer (P) may be 10,000 to 500,000, 20,000 to 300,000, 30,000 to 150,000, 45,000 to 120,000, 55,000 to 120,000, 55,000 to 80,000, 55,000 to 70,000, 70,000 to 120,000, or 60,000 to 80,000.

[0096] 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 1.8 or higher, 2.0 or higher, or 2.2 or higher. When the polydispersity of the polymer (P) is 1.5 or higher, excellent swelling resistance tends to be obtained. From the viewpoint of dispersion stability, the polydispersity of the polymer (P) may be 20.0 or lower, and may be 15.0 or lower, 10.0 or lower, 5.0 or lower, 3.0 or lower, 2.6 or lower, 2.5 or lower, or 2.3 or lower. From these perspectives, the polydispersity of the polymer (P) may be 1.5–20.0, 1.5–15.0, 1.5–10.0, 1.5–5.0, 1.5–3.0, 1.5–2.6, 1.8–5.0, 1.8–3.0, 1.8–2.6, 2.0–3.0, 2.0–2.6, 2.0–2.5, or 2.0–2.3.

[0097] 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.

[0098] The ion exchange capacity (IEC) of the polymer (P) may be 1.0 mmol / g or more, 1.5 mmol / g or more, or 2.0 mmol / g or more, from the viewpoint of lowering ionomer resistance and improving dispersion stability, and may be 3.5 mmol / g or less, 3.0 mmol / g or less, or 2.5 mmol / g or less, from the viewpoint of excellent 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 2.0 to 2.5 mmol / g.

[0099] The ion exchange capacity of polymer (P) is measured by the following procedure (1) to (7): (1) Dissolve polymer (P) in dimethyl sulfoxide (DMSO) to obtain a solution containing 15% by mass of polymer (P). (2) Cast the obtained solution onto a glass substrate and dry it at 60°C for 12 hours to produce a film. (3) Immerse the obtained film in 1 M hydrochloric acid for 24 hours, then wash it by immersing it in pure water. (4) Dry the electrolyte film after washing and determine the dry mass. Drying is carried out until the mass loss when the electrolyte film is heated 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 to perform ion exchange. (6) Using the point where the pH becomes 7 as the endpoint, titrate the hydrochloric acid produced by the above ion exchange using a 0.01 M aqueous sodium hydroxide solution. (7) The ion exchange capacity (IEC) of the polymer (P) is calculated using the following formula: IEC (unit: mmol / g) = {concentration of sodium hydroxide aqueous solution (unit: mol / L) × drop volume (unit: mL)} / dry mass of electrolyte membrane (unit: g)

[0100] Polymer (P) can be obtained, for example, by reacting (polymerizing) a compound represented by the following formula (b1) (hereinafter also referred to as "compound (b1)") with a compound represented by the following formula (b2) (hereinafter also referred to as "compound (b2)"). That is, polymer (P) can be a polymer of compound (b1) and compound (b2).

[0101]

[0102] In formula (b1), A １ This is synonymous with the above, X １ｂ and X ２ｂ Each of these independently represents a halogen atom. Examples of halogen atoms include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0103]

[0104] In formula (b2), A ２ This is synonymous with the above, Z １ｂ and Z２ｂ 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 given above, Z １ and Z ２ These are the same examples as halogen atoms, alkylborane groups, and boronic acid ester groups represented by .

[0105] In the above method, constituent unit A １ and constituent unit A ２ A structure in which these are arranged alternately (a repeating structure) can be formed throughout the polymer. Therefore, according to the above method, the number of repeats n in formula (1) can be easily set to 10 or more.

[0106] According to the above method, L in equation (1) １ and L ２ A polymer (P) is obtained in which the bonds are -O-, -S-, or single bonds. Specifically, Z １ｂ and Z ２ｂ If at least one of them is a hydroxyl group, then L in formula (1) １ and L ２ A polymer (P) is obtained in which at least one of the elements is -O-, Z １ｂ and Z ２ｂ If at least one of them is a thiol group, then L in formula (1) １ and L ２ A polymer (P) is obtained in which at least one of the elements is -S-, Z １ｂ and Z ２ｂ If at least one of them is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, then L in formula (1) １ and L ２ A polymer (P) is obtained in which at least one of the bonds is a single bond.

[0107] In the above method, A is calculated within the range where the difference of x in equation (a1) is 3 or less. １ The method involves using multiple types of compounds (b1) with different structures, and ensuring that the difference in y in formula (a2) is within 5. ２ It is permissible to use multiple types of compounds (b2) with different structures. As for compound (b1), X １ｂand / or X ２ｂ It is also possible to use multiple types of compounds with different properties. Similarly, as compound (b2), Z １ｂ and / or Z ２ｂ It is also possible to use multiple types of compounds with different properties.

[0108] Compound (b1) and compound (b2) can be reacted (polymerized) by, for example, an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0109] 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.

[0110] A base is used to enhance the nucleophilicity of compound (b2). 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.

[0111] 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.

[0112] Compound (b1) and compound (b2) can also be reacted (polymerized) by a cross-coupling reaction 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.

[0113] 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.

[0114] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I)hexafluorophosphate.

[0115] 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).

[0116] 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).

[0117] 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.

[0118] 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.

[0119] 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.

[0120] Polymer (P) can also be obtained by oxidizing a polymer having the structure represented by formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, polymer (P) is obtained from among polymers having the structure represented by formula (1), L １ , L ２ , L ３ or L ４ It can be an oxide of a polymer containing a -S- (sulfide group) (hereinafter referred to as "sulfide-containing polymer").

[0121] Polymer (P) can also be obtained by reacting (polymerizing) a polymer of compound (b1) and compound (b2) or an oxide thereof with a compound having three or more groups that react with the polymer or oxide to form a crosslink (hereinafter also referred to as "crosslinkable compound (d)"). That is, polymer (P) can be a reaction product of a polymer of compound (b1) and compound (b2) or an oxide thereof with a crosslinkable compound (d). In this method, polymer (P) having a polymer of compound (b1) and compound (b2) or an oxide thereof as polymer units can be obtained.

[0122] The crosslinkable compound (d) may be a known crosslinkable compound, and from the viewpoint of chemical stability, it is preferable that it has one or more aromatic rings. The crosslinkable compound (d) may be, for example, decafluorobiphenyl.

[0123] 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 polymer of compound (b1) and compound (b2) or an oxide thereof, or a reaction product of the polymer or oxide and 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.

[0124] (Water-soluble organic solvents) In this specification, "water-soluble organic solvent" refers to an organic solvent with an octanol / water partition coefficient of 1.5 or less. The octanol / water partition coefficient is an indicator of the hydrophobicity of a compound. A lower octanol / water partition coefficient indicates lower hydrophobicity of the compound, while a higher octanol / water partition coefficient indicates higher hydrophobicity of the compound.

[0125] The octanol / water partition coefficient of the water-soluble organic solvent is preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.4 or less, from the viewpoint of further improving dispersion stability. The octanol / water partition coefficient of the water-soluble organic solvent may be -1.5 or more, -1.0 or more, -0.5 or more, or 0.0 or more, and may be -1.5 to 1.5, -1.0 to 1.0, -0.5 to 0.5, or 0.0 to 0.4.

[0126] Examples of water-soluble organic solvents that can be used include alcohols such as ethanol, 1-propanol, 2-propanol, 1-butanol, and methanol; phenols such as phenol; ethers such as tetrahydrofuran, dimethoxyethane, and diethyl ether; ketones such as acetone and cyclohexanone; carboxylic acids such as formic acid, acetic acid, and propionic acid; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, methyl lactate, and ethyl lactate; amines such as dimethylamine, diethylamine, triethylamine, pyridine, triethanolamine, and piperazine; dimethyl sulfoxide, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and acetonitrile. These can be used individually or in combination. As a water-soluble organic solvent, it is preferable to use at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, tetrahydrofuran, acetone, and acetonitrile, from the viewpoint of further improving dispersion stability, more preferably using 1-propanol or 2-propanol, and even more preferably using 1-propanol.

[0127] (Other components) The polymer dispersion (D) may consist only of polymer (P), a water-soluble organic solvent, and water, but may also contain other components. The other components may be organic solvents other than the water-soluble organic solvent. The other components may be used individually or in combination.

[0128] (Content) From the viewpoint of further improving dispersion stability, the content of polymer (P) is preferably 25% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 8% by mass or less, and extremely preferably 5% by mass or less, based on the total mass of the polymer dispersion (D). The content of polymer (P) may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, and may be 1 to 25% by mass, 1 to 15% by mass, 2 to 10% by mass, 3 to 8% by mass, or 3 to 5% by mass, based on the total mass of the polymer dispersion (D).

[0129] The total content of polymer (P), water-soluble organic solvent, and water may be 90 to 100% by mass, 92 to 100%, 94 to 100%, 95 to 100%, or 97 to 100% by mass, based on the total mass of the polymer dispersion (D), from the viewpoint of further improving dispersion stability.

[0130] The content of the water-soluble organic solvent may be 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, 75 parts by mass or more, or 80 parts by mass or more, and may be 95 parts by mass or less, 93 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, or 25 parts by mass or less, based on 100 parts by mass of the total amount of the water-soluble organic solvent and water. From a similar viewpoint, the content of the water-soluble organic solvent may be 5 to 95 parts by mass, 10 to 95 parts by mass, 15 to 95 parts by mass, 20 to 95 parts by mass, 30 to 95 parts by mass, 40 to 95 parts by mass, 50 to 95 parts by mass, 60 to 95 parts by mass, 70 to 95 parts by mass, 75 to 95 parts by mass, or 80 to 95 parts by mass, based on 100 parts by mass of the total amount of the water-soluble organic solvent and water, and may be 10 to 93 parts by mass, 10 to 90 parts by mass, 10 to 80 parts by mass, 10 to 70 parts by mass, 10 to 60 parts by mass, 10 to 50 parts by mass, 10 to 40 parts by mass, 10 to 30 parts by mass, 10 to 25 parts by mass, 15 to 30 parts by mass, 20 to 30 parts by mass, or 25 to 30 parts by mass, based on 100 parts by mass of the total amount of the water-soluble organic solvent and water.

[0131] <Electrode Catalyst Composition> An electrode catalyst composition according to one embodiment comprises the polymer dispersion (D) and an electrode catalyst.

[0132] The electrode catalyst is not particularly limited, and conventionally known anode catalysts or cathode catalysts for solid polymer fuel cells, solid polymer water electrolyzers, etc., may be used. That is, the electrode catalyst composition may be an anode electrode catalyst composition or a cathode electrode catalyst composition. The electrode catalyst may be a metal catalyst. As the metal catalyst, 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, and two or more alloys thereof, can be used.

[0133] The electrode catalyst may include a metal catalyst and a catalyst support. In this case, the metal catalyst may be supported on the catalyst support. Conventionally known catalyst supporters can be used, for example, at least one selected from the group consisting of furnace black, Ketjen black, channel black, acetylene black, activated carbon, and graphite.

[0134] The electrode catalyst composition may contain a conductive material. The conductive material may be included as the catalyst support. Examples of conductive materials are the same as examples of catalyst support.

[0135] The electrode catalyst composition may further contain additives. Examples of additives include water repellents such as fluorinated carbon, and binders such as fluorine-containing resins and hydrocarbon resins having sulfonic acid groups.

[0136] The polymer (P) content in the electrode catalyst composition may be 10 to 98% by mass, 40 to 95% by mass, or 50 to 85% by mass, based on the total solid content of the electrode catalyst composition. The total solid content of the electrode catalyst composition refers to the amount obtained by subtracting the amount of dispersion medium from the total amount of the electrode catalyst composition.

[0137] The content of the electrode catalyst in the electrode catalyst composition may be 2 to 90% by mass, 5 to 60% by mass, or 15 to 50% by mass, based on the total amount of solids in the electrode catalyst composition.

[0138] <Electrode Catalyst Layer> The electrode catalyst layer of one embodiment is formed from the above electrode catalyst composition. That is, the electrode catalyst layer includes a polymer (P) and an electrode catalyst.

[0139] The electrode catalyst layer has low ionomer resistance because it contains polymer (P). The ionomer resistance of the electrode catalyst layer is, for example, 100 mΩ·cm. ２ The following is true: 80 mΩ·cm ２ Below or 50 mΩ·cm ２ The following are possible:

[0140] The electrode catalyst layer may contain a conductive material. Examples of conductive materials are the same as examples of conductive materials that can be included in the electrode catalyst composition described above.

[0141] The electrode catalyst layer may further contain additives. Examples of additives are the same as examples of additives that the electrode catalyst composition may further contain.

[0142] The polymer (P) content in the electrode catalyst layer may be 10 to 98% by mass, 40 to 95% by mass, or 50 to 85% by mass, based on the total amount of the electrode catalyst layer.

[0143] The content of the electrode catalyst in the electrode catalyst layer may be 2 to 90% by mass, 5 to 60% by mass, or 15 to 50% by mass, based on the total amount of the electrode catalyst layer.

[0144] The above electrode catalyst layer may be used, for example, as a layer composed of an anode catalyst or cathode catalyst in a polymer electrolyte fuel cell, polymer electrolyte water electrolysis device, etc. 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.

[0145] There are no particular limitations on the method for manufacturing the electrode catalyst layer, and it can be manufactured by conventionally known methods. For example, the electrode catalyst layer can be formed on the substrate by spray coating the electrode catalyst composition onto the substrate and then removing the dispersion medium (water and water-soluble organic solvent).

[0146] <Electrolyte membrane with electrode catalyst layer> An electrolyte membrane with an electrode catalyst layer according to one embodiment comprises an electrolyte membrane and the electrode catalyst layer of the above embodiment disposed on one or both sides of the electrolyte membrane.

[0147] The electrolyte membrane with an electrode catalyst layer may be used as an electrolyte membrane with an anode catalyst layer or an electrolyte membrane with a cathode catalyst layer, or both.

[0148] Conventional electrolyte membranes can be used; for example, an electrolyte membrane containing a fluorine-based polymer can be used. Alternatively, an electrolyte membrane containing a polymer (P) can also be used. The electrolyte membrane can also be used in combination with a microporous membrane, nonwoven fabric, mesh, etc.

[0149] 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.

[0150] In the above embodiment, instead of the electrolyte membrane, a laminate comprising an electrolyte membrane and the other membranes mentioned above (microporous membrane, nonwoven fabric, mesh, etc.) can also be used.

[0151] <Membrane electrode assembly> A membrane electrode assembly according to one embodiment comprises an electrolyte membrane and an electrode layer having the electrode catalyst layer of the above embodiment, disposed on one or both sides of the electrolyte membrane.

[0152] The electrode catalyst layer in the electrode layer of the above embodiment may be used as an anode catalyst layer or a cathode catalyst layer, or as both.

[0153] The electrode layer may consist, for example, of the electrode catalyst layer of the above embodiment and a gas diffusion substrate. If the electrode catalyst layer itself has gas diffusivity, the electrode layer may consist only of the electrode 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 (for example, carbon fiber substrates such as carbon nonwoven fabric and carbon paper, or titanium fiber sintered bodies) can also be used.

[0154] 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.

[0155] In the above embodiment, instead of the electrolyte membrane, a laminate comprising an electrolyte membrane and the other membranes mentioned above (microporous membrane, nonwoven fabric, mesh, etc.) can also be used.

[0156] <Solid Polymer Fuel Cell> A solid polymer fuel cell according to one embodiment comprises the membrane electrode assembly of the above embodiment.

[0157] 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.

[0158] <Solid Polymer Water Electrolyzer> A solid polymer water electrolyzer according to one embodiment includes the membrane electrode assembly according to the above embodiment.

[0159] 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.

[0160] 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.

[0161] <Synthesis Example 1> (Synthesis of hydrophilic monomer (M1)) A 10 L flask equipped with a dropping funnel, reflux condenser, and mechanical stirrer was purged with nitrogen, and 101 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl and 4 L of anhydrous tetrahydrofuran (THF) were charged and stirred. 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, followed by stirring under the same conditions for 1 hour. Next, 40 mL of sulfur dioxide gas was introduced into the flask with nitrogen gas, and the mixture was stirred under the same conditions for 30 minutes, after which the internal temperature was raised to 0°C. The precipitated solid was filtered off by suction filtration and washed with 200 mL of THF. The obtained 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. After removing the solid by suction filtration, 600 g of sodium chloride was added to the obtained filtrate. The precipitated white solid was removed by suction filtration and then purified by recrystallization with water / isopropyl alcohol (IPA). The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer (M1) represented by the following formula (M1). The yield was 65%.

[0162]

[0163] <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 (DMAc) and 50 mL of toluene were added. The mixture was heated to 160°C in an oil bath while stirring, and heating and stirring were continued for 4 hours. The toluene was removed from the Dean-Stark tube, and the mixture was heated to 180°C in an oil bath. After heating, heating and stirring were continued for 8 hours. After the reaction mixture was allowed to cool to room temperature (approximately 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. The dried solid was purified by recrystallization from N-methylpyrrolidone (NMP) / ethanol. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0164]

[0165] <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 THF 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, 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 product was recovered, and the solvent was removed by evaporation using an evaporator. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M3) represented by the following formula (M3). The yield was 53%.

[0166]

[0167] <Synthesis Example 4> (Synthesis of hydrophobic monomer (M4)) A 500 mL flask equipped with a stirring bar and condenser was purged with nitrogen. 41 g of 4,4'-thiobisbenzenethiol, 14 g of 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl, 80 mL of DMAc, and 4 g of potassium carbonate were added to the flask. The mixture was heated to 100°C in an oil bath while stirring, and heating and stirring were continued for 6 hours. After the reaction mixture cooled, 100 mL of 1 M hydrochloric acid was added, and the precipitated solid was collected by suction filtration. The collected solid was dissolved in dichloromethane and purified by silica column chromatography using dichloromethane as the developing solvent. The fraction containing the target product was collected, and the solvent was removed by evaporation using an evaporator. The obtained solid was purified by recrystallization from dichloromethane. The obtained solid was dried under reduced pressure to obtain the hydrophobic monomer (M4) represented by the following formula (M4). The yield was 40%.

[0168]

[0169] <Synthesis Example 5> (Synthesis of hydrophobic monomer (M5)) A 500 mL flask equipped with a stirring bar and a condenser was purged with nitrogen. 20 g of anhydrous aluminum chloride, 10 g of isophthaloyl chloride, and 240 mL of 1,2-dichlorobenzene were added to this flask. While stirring the reaction mixture, 24 g of 3-bromo-1,1'-biphenyl was added dropwise. The reaction mixture was heated to 40°C and stirred for 3 hours. After the reaction mixture cooled to room temperature, it was added to 900 mL of ice-cold 3% hydrochloric acid, and stirred at room temperature for 18 hours. The precipitated white solid was collected by suction filtration and washed with ethanol. The obtained solid was dried under reduced pressure and used in the next reaction.

[0170] 0.80 g of the obtained dried solid, 0.71 g of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol, 0.11 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloride dichloromethane adduct, and 0.57 g of sodium carbonate were added to a 100 mL flask and the flask was purged with nitrogen. 30 mL of THF was added, and the reaction mixture was heated to 50°C while stirring vigorously. Heating and stirring were continued at 50°C for 22 hours. After the reaction mixture had cooled, 100 mL of chloroform and 100 mL of 5% hydrochloric acid were added and the reaction was separated, and the organic layer was recovered. The solvent was removed using an evaporator, and 20 mL of ethyl acetate was added to suspend the mixture. The suspension was filtered by suction, and the filtrate was collected and the solvent was removed using an evaporator to obtain an orange oily substance. The resulting oily substance was dissolved in ethyl acetate and purified by silica column chromatography using a 1 / 1 (volume ratio) ethyl acetate / hexane mixed solvent as the developing solvent. The fraction containing the target substance was recovered, and the solvent was removed by evaporation. The resulting solid was purified by recrystallization from hot toluene. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M5) represented by the following formula (M5). The yield was 60%.

[0171]

[0172] <Structures represented by formulas (P1) to (P6)> Table 1 shows the structures represented by formulas (P1) to (P6) of the polymers (P1) to (P6) in Examples 1 to 6 and Comparative Example 2 described below. In formulas (P1) to (P6) below, M represents Na, K, or H, and n represents a positive number. In formulas (P4) to (P6) below, x and y represent positive numbers. The synthesis methods for polymers (P1) to (P6) are as described in Examples 1 to 6 and Comparative Example 2 described below.

[0173]

[0174] <Example 1> (Synthesis of polymer (P1)) 0.983 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.18 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.507 g of potassium 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, 10 mL of dimethyl sulfoxide (DMSO) and 10 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. 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 with 300 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 (P1) having the structure represented by the above formula (P1). The yield was 97%. n in the above formula (P1) was approximately 20. Note that n in equation (P1) was calculated from the number-average molecular weight described later. The same applies to n in equations (P2) to (P6) described later.

[0175] (Molecular Weight Measurement) The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of polymer (P1) were measured under the following conditions, and the polydispersity (Mw / Mn) was determined. Mn was 30,000, Mw was 61,000, and Mw / Mn was 2.0.

[0176] [Measurement Conditions] A sample solution was prepared by dissolving polymer (P1) at a concentration of 1 mg / mL in an eluent (N,N-dimethylformamide solvent containing 10 mmol / L of lithium bromide). The instrument used was an HLC-8320GPC (Tosoh Corporation), with two TSKgel SuperAWM-H columns (Tosoh Corporation, inner diameter 6.0 mm, length 15 cm) and a differential refractometer detector (Tosoh Corporation). The measurement conditions were an eluent flow rate of 0.6 mL / min and a column temperature of 40°C. Mn and Mw were determined in terms of standard polyethylene glycol / oxide (PEG / PEO). Polydispersity (Mw / Mn) was determined by dividing Mw by Mn.

[0177] (Ion exchange capacity measurement) The obtained polymer (P1) was dissolved in DMSO to prepare a 15% by mass solution of polymer (P1). The obtained solution was applied to a glass substrate with an applicator and dried at 60°C for 12 hours to obtain a film (film thickness 49 μm). The obtained film was immersed in 1 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to proton (H ＋ After substitution with (), an electrolyte membrane (thickness 52 μm) made of proton-substituted polymer (P1) was obtained by immersion in pure water for washing and reduced-pressure drying. The obtained electrolyte membrane was dried at 80°C for 12 hours or more to remove the contained water, and the dry mass was determined. The dried electrolyte membrane was immersed in a 20% by mass sodium chloride aqueous solution and stirred for 24 hours for ion exchange. The hydrochloric acid produced using a 0.01 M sodium hydroxide aqueous solution was titrated. The titration was performed using an automatic titrator COM-A19 (HIRANUMA Corporation), with the endpoint being the point where the pH became 7. The ion exchange capacity (IEC) was calculated using the following formula. The IEC of polymer (P1) was 2.3 mmol / g. Note that the "thickness" in this example is the value measured using PG-02 manufactured by TECLOK CORPORATION. The same applies to the "thickness" in the following examples and comparative examples. IEC (unit: mmol / g) = {Concentration of sodium hydroxide solution (unit: mol / L) × Droplet volume (mL)} / Dry mass of electrolyte membrane (unit: g)

[0178] (Preparation of polymer dispersion) 5.0 g of polymer (P1) was added to a dispersion medium consisting of 24 g of 1-propanol (octanol / water partition coefficient: 0.25) and 71 g of water, and the mixture was shaken by hand to disperse the polymer (P1). The resulting dispersion was passed through a 0.2 μm pore size filter to remove impurities, and the polymer dispersion of Example 1 (a dispersion containing 5% by mass of polymer (P1)) was prepared.

[0179] (Evaluation of Dispersion Stability of Polymer Dispersions) After preparing the polymer dispersions described above, they were allowed to stand for one hour. The dispersion stability was visually evaluated according to the following criteria, with high dispersion stability designated as "A" and low dispersion stability as "B". The results are shown in Table 2. A: The polymer separates, and no oil droplets are formed in the dispersion. B: The polymer separates, and oil droplets are formed in the dispersion.

[0180] (Evaluation of Ionomer Resistance) [Preparation of Electrode Catalyst Composition] 3 g of platinum catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: TEC10E50E, platinum loading amount: 50% by mass, catalyst support: Ketjenbrak (manufactured by Lion Specialty Chemicals Co., Ltd.)) was added to 30 g of water and sonicated for 10 minutes to uniformly disperse. 32.0 g of the polymer dispersion from Example 1 was added to the obtained dispersion to adjust the solid content concentration to 7.1%, and then mixed using a planetary ball mill at 200 rpm for 10 minutes to obtain the electrode catalyst composition.

[0181] [Fabrication of fuel cell cells] The electrode catalyst composition prepared above is coated with Pt at a rate of 0.5 mg / cm². ２ To achieve this, a gas diffusion electrode was fabricated by spray coating a gas diffusion substrate (manufactured by SGL, product name: 28BC) on a hot plate heated to 70°C. Another gas diffusion electrode was fabricated in the same manner, and the resulting pair of gas diffusion electrodes were used to create a Nafion ＴＭ By sandwiching the 211 film from both sides, Nafion ＴＭ A membrane electrode assembly was obtained, comprising an electrolyte membrane made of a 211 film and electrode layers made of gas diffusion electrodes arranged on both sides of the electrolyte membrane. Next, a fuel cell cell including this membrane electrode assembly was assembled.

[0182] [Evaluation of Ionomer Resistance] The obtained fuel cell cell was connected to an external AC power source. Impedance was measured by changing the frequency of the input AC signal, and the real part (ReZ) and imaginary part (-ImZ) of the impedance were calculated from the obtained results. The correlation between the calculated real and imaginary parts is shown in the graph in Figure 1. The impedance was measured under the following conditions: cell temperature 80°C, humidity 60% RH, anode flow rate 200 Nml / min, cathode flow rate 200 Nml / min. Hydrogen was used as the anode gas and nitrogen as the cathode gas. Ionomer resistance (unit: mΩ・cm) ２ The ionomer resistance was calculated by dividing the difference between the intersection point of the measured line with the actual axis and the intersection point of the approximate line with the actual axis by 3. The ionomer resistance was 42 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 1 has low ionomer resistance.

[0183] <Example 2> (Synthesis of polymer (P2)) 0.932 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, 1.30 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 0.593 g of potassium 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, 10 mL of DMSO and 10 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. Polymerization was carried out by heating to 150 °C for 105 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified with 300 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 (P2) having the structure represented by the above formula (P2). The yield was 90%. The polymer (P2), measured in the same manner as in Example 1, had a Mn of 51,000, a Mw of 110,000, and a Mw / Mn ratio of 2.2. The value of n in the above formula (P2) was approximately 30.

[0184] (Measurement of ion exchange capacity) An electrolyte membrane (film thickness 35 μm) made of proton-substituted polymer (P2) was prepared using the same method as in Example 1, except that polymer (P2) was used instead of polymer (P1), and the ion exchange capacity was measured using the same method as in Example 1. The IEC of polymer (P2) was 2.5 mmol / g.

[0185] (Preparation of Polymer Dispersion and Evaluation of Dispersion Stability) The polymer dispersion of Example 2 (a dispersion containing 5% by mass of polymer (P2)) was prepared in the same manner as in Example 1, except that polymer (P2) was used instead of polymer (P1). The dispersion stability of the polymer dispersion of Example 2 was evaluated using the same method as in Example 1. The results are shown in Table 2.

[0186] (Evaluation of Ionomer Resistance) Following the same procedure as in Example 1, an electrode catalyst composition and a fuel cell cell were obtained using the polymer dispersion of Example 2, and then the ionomer resistance was evaluated. The ionomer resistance was 38 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 2 has low ionomer resistance.

[0187] <Example 3> (Synthesis of polymer (P3)) 2.71 g of the hydrophobic monomer (M4) obtained in Synthesis Example 4, 2.66 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.35 g of potassium 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, 25 mL of DMSO and 25 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. Polymerization was carried out by heating to 140 °C for 260 hours. After allowing the reaction mixture to cool to room temperature, reprecipitation purification was performed with 500 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 above formula (P3). The yield was 88%. The polymer (P3), measured in the same manner as in Example 1, had a Mn of 33,000, a Mw of 75,000, and a Mw / Mn ratio of 2.3. The value of n in the above formula (P3) was approximately 20.

[0188] (Measurement of ion exchange capacity) An electrolyte membrane (film thickness 37 μm) made of proton-substituted polymer (P3) was prepared in the same manner as in Example 1, except that polymer (P3) was used instead of polymer (P1), and the ion exchange capacity was measured using the same method as in Example 1. The IEC of polymer (P3) was 2.1 mmol / g.

[0189] (Preparation of Polymer Dispersion and Evaluation of Dispersion Stability) The polymer dispersion of Example 3 (a dispersion containing 5% by mass of polymer (P3)) was prepared in the same manner as in Example 1, except that polymer (P3) was used instead of polymer (P1). The dispersion stability of the polymer dispersion of Example 3 was evaluated using the same method as in Example 1. The results are shown in Table 2.

[0190] (Evaluation of Ionomer Resistance) Following the same procedure as in Example 1, an electrode catalyst composition and a fuel cell were obtained using the polymer dispersion of Example 3, and then the ionomer resistance was evaluated. The ionomer resistance was 33 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 3 has low ionomer resistance.

[0191] <Example 4> In Example 4, polymer (P1) was used as the polymer.

[0192] (Preparation of Polymer Dispersion and Evaluation of Dispersion Stability) The polymer dispersion of Example 4 (a dispersion containing 5% by mass of polymer (P1)) was prepared in the same manner as in Example 1, except that the dispersion medium used in the preparation of the polymer dispersion was replaced with a dispersion medium consisting of 85.5 g of 1-propanol and 9.5 g of water. The dispersion stability of the polymer dispersion of Example 4 was evaluated using the same method as in Example 1. The results are shown in Table 2.

[0193] (Evaluation of Ionomer Resistance) Following the same procedure as in Example 1, an electrode catalyst composition and a fuel cell cell were obtained using the polymer dispersion of Example 4, and then the ionomer resistance was evaluated. The ionomer resistance was 23 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 4 has low ionomer resistance.

[0194] <Example 5> In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 1.48 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.28 g of the hydrophobic monomer (M3) obtained in Synthesis Example 3, 3.54 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.96 g of potassium carbonate were added, and nitrogen purging was performed. Then, 30 mL of DMSO and 30 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. Polymerization was carried out by heating to 150 °C for 118 hours. After allowing the reaction mixture to cool to room temperature, reprecipitation purification was performed with 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 above formula (P4). The yield was 90%. The polymer (P4) measured in the same manner as in Example 1 had a Mn of 20,000, a Mw of 46,000, and a Mw / Mn ratio of 2.3. In the above formula (P4), x was approximately 0.55 (0.51 to 0.59), y was approximately 0.45 (0.41 to 0.49), and n was approximately 15.

[0195] (Measurement of ion exchange capacity) An electrolyte membrane (film thickness 33 μm) made of proton-substituted polymer (P4) was prepared in the same manner as in Example 1, except that polymer (P4) was used instead of polymer (P1), and the ion exchange capacity was measured using the same method as in Example 1. The IEC of polymer (P4) was 2.4 mmol / g.

[0196] (Preparation of Polymer Dispersion and Evaluation of Dispersion Stability) The polymer dispersion of Example 5 (a dispersion containing 5% by mass of polymer (P4)) was prepared in the same manner as in Example 1, except that polymer (P4) was used instead of polymer (P1). The dispersion stability of the polymer dispersion of Example 5 was evaluated using the same method as in Example 1. The results are shown in Table 2.

[0197] (Evaluation of Ionomer Resistance) Following the same procedure as in Example 1, an electrode catalyst composition and a fuel cell cell were obtained using the polymer dispersion of Example 5, and then the ionomer resistance was evaluated. The ionomer resistance was 33 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 5 has low ionomer resistance.

[0198] <Example 6> In a 100 mL three-necked flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, 1.47 g of the hydrophobic monomer (M2) obtained in Synthesis Example 2, 1.16 g of the hydrophobic monomer (M5) obtained in Synthesis Example 5, 3.53 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.99 g of potassium carbonate were added, and the mixture was purged with nitrogen. Then, 30 mL of DMSO and 30 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. Polymerization was carried out by heating to 140 °C for 121 hours. After the reaction mixture was allowed to cool to room temperature, it was reprecipitated and purified with 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 (P5) having the structure represented by the above formula (P5). The yield was 90%. The polymer (P5) measured in the same manner as in Example 1 had a Mn of 33,000, a Mw of 77,000, and a Mw / Mn ratio of 2.3. In the above formula (P5), x was approximately 0.55 (0.51 to 0.59), y was approximately 0.45 (0.41 to 0.49), and n was approximately 20.

[0199] (Measurement of ion exchange capacity) An electrolyte membrane (film thickness 61 μm) made of proton-substituted polymer (P5) was prepared in the same manner as in Example 1, except that polymer (P5) was used instead of polymer (P1), and the ion exchange capacity was measured using the same method as in Example 1. The IEC of polymer (P5) was 2.4 mmol / g.

[0200] (Preparation of Polymer Dispersion and Evaluation of Dispersion Stability) The polymer dispersion of Example 6 (a dispersion containing 5% by mass of polymer (P5)) was prepared in the same manner as in Example 1, except that polymer (P5) was used instead of polymer (P1). The dispersion stability of the polymer dispersion of Example 6 was evaluated using the same method as in Example 1. The results are shown in Table 2.

[0201] (Evaluation of Ionomer Resistance) Following the same procedure as in Example 1, an electrode catalyst composition and a fuel cell cell were obtained using the polymer dispersion of Example 6, and then the ionomer resistance was evaluated. The ionomer resistance was 22 mΩ·cm. ２ Therefore, it was confirmed that the electrode catalyst layer of Example 6 has low ionomer resistance.

[0202] <Comparative Example 1> (Measurement of Ion Exchange Capacity) In Comparative Example 1, a commercially available Nafion was used as the sample for measuring ion exchange capacity. ＴＭ NR211 (film thickness 25 μm) was used. When the ion exchange capacity was measured using the same method as in Example 1, the IEC measured from the electrolyte membrane of Comparative Example 1 was 1.0 mmol / g.

[0203] (Evaluation of ionomer resistance) Nafion was used instead of the polymer dispersion in Example 1. ＴＭ Except for using a dispersion solution of type DE521CS (solid content: 5% by mass), an electrode catalyst composition and a fuel cell were obtained in the same manner as in Example 1, and then the ionomer resistance was evaluated. The ionomer resistance was 120 mΩ·cm. ２ That was the case.

[0204] <Comparative Example 2> (Synthesis of Polymer (P6)) 0.498 g of 4,4'-dichlorodiphenylsulfone (M6), 0.532 g of 4,4'-dihydroxybiphenyl (M7), 1.026 g of the hydrophilic monomer (M1) obtained in Synthesis Example 1, and 1.185 g of potassium 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, 10 mL of DMSO and 10 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. Polymerization was carried out at 130 °C for 72 hours. After allowing the reaction mixture to cool to room temperature, reprecipitation purification was performed with 300 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 (P6) having the structure represented by the above formula (P6). The yield was 94%. The polymer (P6) measured in the same manner as in Example 1 had a Mn of 26,000, a Mw of 69,000, and a Mw / Mn ratio of 2.7. In the above formula (P6), x was approximately 0.39 (0.35 to 0.43), y was approximately 0.61 (0.57 to 0.65), and n was approximately 40.

[0205] (Measurement of ion exchange capacity) An electrolyte membrane (film thickness 48 μm) made of proton-substituted polymer (P6) was prepared in the same manner as in Example 1, except that polymer (P6) was used instead of polymer (P1), and the ion exchange capacity was measured using the same method as in Example 1. The IEC of polymer (P6) was 2.5 mmol / g.

[0206] (Preparation of polymer dispersion) An attempt was made to prepare the polymer dispersion of Comparative Example 2 (a dispersion containing 5% by mass of polymer (P6)) in the same manner as in Example 1, except that polymer (P6) was used instead of polymer (P1). However, the polymer separated and settled as oil droplets, so it was not possible to obtain a polymer dispersion.

[0207]

[0208] This application is based on Japanese Patent Application No. 2024-169436, filed on 27 September 2024, which is incorporated by reference in its entirety. All references cited herein are incorporated as a whole.

Claims

1. The following formula (1): [In formula (1), A １ represents a structural unit represented by the following formula (a1): (In formula (a1), IExG represents an ion exchange group, L ３ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, x represents an integer from 2 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 ３ may be the same as or different from each other.)], A ２ also represents a structural unit represented by the following formula (a2): (In formula (a2), Ar represents an arylene group having no ion exchange group, L ４ represents a single bond, -O-, -S-, -SO ２ -, or -CO-, y represents an integer from 3 to 20, and * represents a bond. A plurality of Ar may be the same as or different from each other, and a plurality of L ４ may be the same as or different from each other.)], L １ and L ２ each independently represent a single bond, -O-, -S-, or -SO ２ -, n represents an integer from 10 to 100, and * represents a bond. A plurality of A １ may be the same as or different from each other, a plurality of A ２ may be the same as or different from each other, a plurality of L 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 difference in x in formula (a1) among a plurality of A １ is within 3, and the difference in y in formula (a2) among a plurality of A ２ is within 5.], a polymer dispersion containing a polymer having the structure represented by the formula, a water-soluble organic solvent, and water.

2. The polymer dispersion according to claim 1, wherein the constituent unit represented by formula (a1) comprises at least one group selected from the group consisting of sulfonic acid groups, alkyl sulfonic acid groups, sulfonimide groups, and salts thereof, as the ion exchange group.

3. The polymer dispersion according to claim 1 or 2, wherein the constituent unit represented by formula (a2) 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 a substituent.

4. The polymer dispersion according to any one of claims 1 to 3, wherein the ion exchange capacity of the polymer is 1.0 to 3.5 mmol / g.

5. The polymer dispersion according to any one of claims 1 to 4, wherein the octanol / water partition coefficient of the water-soluble organic solvent is 1.0 or less.

6. The polymer dispersion according to any one of claims 1 to 5, wherein the content of the water-soluble organic solvent is 5 to 95 parts by mass with respect to 100 parts by mass of the total amount of the water-soluble organic solvent and the water.

7. The polymer dispersion according to any one of claims 1 to 6, wherein the content of the polymer is 25% by mass or less, based on the total mass of the polymer dispersion.

8. The polymer dispersion according to any one of claims 1 to 7, wherein the weight-average molecular weight of the polymer is 10,000 to 500,000.

9. The polymer dispersion according to any one of claims 1 to 8, wherein the polydispersity of the polymer is 1.5 to 20.

0.

10. An electrode catalyst composition comprising a polymer dispersion according to any one of claims 1 to 9 and an electrode catalyst.

11. An electrode catalyst layer formed from the electrode catalyst composition according to claim 10.

12. An electrolyte membrane with an electrode catalyst layer, comprising an electrolyte membrane and an electrode catalyst layer according to claim 11, disposed on one or both sides of the electrolyte membrane.

13. A membrane electrode assembly comprising an electrolyte membrane and an electrode layer having the electrode catalyst layer described in claim 11, disposed on one or both sides of the electrolyte membrane.

14. A polymer electrolyte fuel cell comprising the membrane electrode assembly described in claim 13.

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

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