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

Abstract

An electrolyte membrane 10A includes: a porous membrane 1 formed of a material containing a hydrocarbon-based resin; and a hydrocarbon-based electrolyte polymer filled in pores 2 of the porous membrane 1. The hydrocarbon-based electrolyte polymer has a structure represented by the following formula (1).　Formula (1): [In formula (1), A1 and A2 represent structural units represented by formula (a1) and formula (a2), L1 and L2 each independently represent a single bond or the like, n represents an integer of 10-100, and * represents a dangling bond.]　Formula (2): [In formula (a1), IExG represents an ion exchange group, L3 represents a single bond or the like, x represents an integer of 2-10, and * represents a dangling bond.]　Formula (3): [In formula (a2), Ar represents an arylene group not having an ion exchange group, L4 represents a single bond or the like, y represents an integer of 3-20, and * represents a dangling bond.]

Description

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

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

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

[0003] As an electrolyte membrane used in a polymer electrolyte fuel cell and a polymer electrolyte water electrolysis device, an electrolyte membrane (fluorine-based electrolyte membrane) using a fluorine-based electrolyte polymer as an electrolyte is known (see, for example, Patent Document 1). Although fluorine-based electrolyte membranes have high proton conductivity and are widely used for electrolyte applications, they have problems such as high cost and a large environmental load.

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

[0005] Japanese Patent Application Laid-Open No. 11-204119 International Publication No. 2013-031675

[0006] The hydrocarbon-based electrolyte polymer obtained by block copolymerization as disclosed in the above-mentioned Patent Document 2 does not necessarily have sufficient proton conductivity and does not necessarily have sufficient mechanical strength.

[0007] An object of one aspect of the present disclosure is to provide a hydrocarbon-based electrolyte membrane that is excellent in proton conductivity and mechanical strength.

[0008] In some aspects, the present disclosure provides the following [1] to

[16] .

[0009] [1] A porous membrane formed of a material containing a hydrocarbon-based resin, and a hydrocarbon-based electrolyte polymer filled in the pores of the porous membrane, wherein the hydrocarbon-based electrolyte polymer is represented by the following formula (1): [In formula (1), A １ is represented by the following formula (a1): (In formula (a1), IExG represents an ion exchange group, and L ３ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, x represents an integer of 2 to 10, * represents a bond, a plurality of IExG may be the same or different, a plurality of L ３ may be the same or different from each other.) A represents a structural unit represented by the formula: ２ is represented by the following formula (a2): (In formula (a2), Ar represents an arylene group having no ion exchange group, and L ４ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, y represents an integer of 3 to 20, * represents a bond, a plurality of Ar may be the same or different, a plurality of L ４ may be the same or different from each other.) １ and L ２ are each independently a single bond, —O—, —S— or —SO ２ -, n represents an integer of 10 to 100, * represents a bond. １ are identical to each other, and multiple A ２ are identical to each other, and multiple L １ may be the same or different, and multiple L ２ may be the same or different from each other.]

[0010] [2] Said L １ and the L ２are each independently a single bond, —O—, or —S—.

[0011] [3] Said L ３ is a single bond or —SO ２ The electrolyte membrane according to [1] or [2], wherein

[0012] [4] The electrolyte membrane according to any one of [1] to [3], wherein the structural unit represented by the formula (a1) contains, as the ion exchange group, at least one group selected from the group consisting of a sulfonic acid group, an alkylsulfonic acid group, a sulfonimide group, and salts thereof.

[0013] [5] The electrolyte membrane according to any one of [1] to [4], wherein the constitutional unit represented by the formula (a2) contains, as the arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorenylidene group, each of which may have a substituent.

[0014] [6] The constitutional unit represented by the formula (a2) is represented by the following formula (A2): [In formula (A2), Ar, L ４ and * are as defined above, and Q is a group represented by the following formula (a2-1): (In formula (a2-1), Ar and * have the same meanings as defined above. A plurality of Ars may be the same or different.) １ and y ２ Each of Ar's independently represents an integer of 2 to 4. A plurality of Ar's may be the same or different, and a plurality of L's may be the same or different. ４ may be the same or different from each other.] The electrolyte membrane according to any one of [1] to [5], comprising a structural unit represented by the following formula:

[0015] [7] The electrolyte membrane according to any one of [1] to [6], wherein the hydrocarbon-based electrolyte polymer has a weight average molecular weight of 25,000 to 500,000.

[0016] [8] The electrolyte membrane according to any one of [1] to [7], wherein the polydispersity of the hydrocarbon-based electrolyte polymer is 1.5 to 10.0.

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

[0018]

[10] The electrolyte membrane according to any one of [1] to [9], wherein the hydrocarbon-based resin is a polyolefin-based resin.

[0019]

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

[10] , which has a layer containing the hydrocarbon-based electrolyte polymer on one or both sides of the porous membrane.

[0020]

[12] The electrolyte membrane according to

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

[0021]

[13] A catalyst-layered electrolyte membrane comprising the electrolyte membrane according to any one of [1] to

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

[0022]

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

[12] and electrode layers disposed on one or both surfaces of the electrolyte membrane.

[0023]

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

[14] .

[0024]

[16] A polymer electrolyte water electrolysis device comprising the membrane electrode assembly according to

[14] .

[0025] According to the present disclosure, an electrolyte membrane having excellent proton conductivity and mechanical strength can be provided.

[0026] Fig. 1 is a schematic cross-sectional view of an electrolyte membrane according to one embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of an electrolyte membrane according to another embodiment of the present disclosure. Fig. 3 is a planar SEM image at 5000x magnification of porous membrane A used in the examples. Fig. 4 is a planar SEM image at 5000x magnification of porous membrane B used in the examples.

[0027] Exemplary embodiments of the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. Furthermore, the configurations and parameters disclosed in this specification can be combined in any manner, and the upper and lower limit values ​​individually described can be combined in any manner.

[0028] <Electrolyte Membrane> Fig. 1 is a schematic cross-sectional view of an electrolyte membrane of one embodiment. The electrolyte membrane 10A of Fig. 1 includes a porous membrane 1 and a filler 3 containing a hydrocarbon-based electrolyte polymer, which fills pores 2 of the porous membrane 1. In the electrolyte membrane 10A, the porous membrane 1 is exposed on the surface of the electrolyte membrane 10A. The electrolyte membrane 10A is a hydrocarbon-based electrolyte membrane because it contains a hydrocarbon-based electrolyte polymer as an electrolyte. In this specification, the term "hydrocarbon-based electrolyte polymer" refers to an electrolyte polymer that is substantially free of fluorine atoms (i.e., the fluorine content in the electrolyte polymer is 5% by mass or less).

[0029] (Porous Membrane) The porous membrane 1 serves as a reinforcing material for the electrolyte membrane 10A, contributing to improved mechanical strength and swelling resistance. The porous membrane 1 is made of a material containing a hydrocarbon-based resin. The hydrocarbon-based resin is a resin made of a hydrocarbon compound that does not contain fluorine atoms in its molecule.

[0030] The hydrocarbon resin may be, for example, at least one selected from the group consisting of polyolefin resins, polyester resins, polyphenylene sulfide resins, polyetherimide resins, polyimide resins, polyurethane resins, and polyethersulfone resins. These resins provide sufficient stability in the acidic environments of fuel cells and water electrolysis devices. The polyolefin resin may be, for example, at least one selected from the group consisting of polyethylene resins and polypropylene resins. The polyester resin may be, for example, at least one selected from the group consisting of polyethylene terephthalate resins and polybutylene terephthalate resins.

[0031] From the viewpoint of reducing manufacturing costs and environmental impact, it is preferable to use a polyolefin-based resin, and it is more preferable to use at least one resin selected from the group consisting of polyethylene and polypropylene. In other words, the porous membrane 1 is preferably a polyolefin-based porous membrane (a porous membrane mainly composed of a polyolefin-based resin), and more preferably a polyethylene-based porous membrane (a porous membrane mainly composed of polyethylene) or a polypropylene-based porous membrane (a porous membrane mainly composed of polypropylene). Although polyolefin-based resins tend to have poor mechanical strength, the present disclosure can improve their mechanical strength, making it easy to obtain an electrolyte membrane with sufficient mechanical strength even when using a polyolefin-based resin. In addition, the use of a polyolefin-based resin as a hydrocarbon-based resin tends to improve swelling resistance. Among polyolefin-based resins, the use of polyethylene is likely to provide excellent mechanical strength and excellent swelling resistance. In this specification, the term "main component" refers to the component with the highest content among the components contained. The content of the main component is, for example, 60% by mass or more, and may be 80% by mass or more, or 90% by mass or more.

[0032] The material containing a hydrocarbon-based resin may consist solely of a hydrocarbon-based resin, or may contain other components in addition to the hydrocarbon-based resin as long as the effects of the present disclosure are not impaired. For example, the other components may be at least one selected from the group consisting of a water-retaining inorganic substance and a radical scavenger. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The content (total amount) of the other components may be 0 to 10% by mass based on the total mass of the material.

[0033] The porous membrane 1 may be a film-like membrane (porous film). The porous membrane 1 may be a membrane formed from fibers such as nonwoven fabric. That is, the pores 2 in the porous membrane 1 may be composed of minute gaps formed by entangled fibers. The porous membrane 1 may be a porous membrane having a unidimensional pore structure or a porous membrane having a multidimensional pore structure.

[0034] The porosity of the porous membrane 1 may be 30 vol% or more, 40 vol% or more, 50 vol% or more, or 70 vol% or more, from the viewpoint of more easily obtaining superior proton conductivity. The porosity of the porous membrane 1 may be 95 vol% or less, 90 vol% or less, 85 vol% or less, or 80 vol% or less, from the viewpoint of more easily improving mechanical strength. From the above viewpoint, the porosity of the porous membrane 1 may be 30 to 95 vol%, 40 to 90 vol%, 50 to 85 vol%, 70 to 85 vol%, or 70 to 80 vol%. The porosity can be determined from the pore volume calculated by mercury intrusion porosimetry using, for example, a POREMASTER GT (manufactured by Quantachrome Instruments) apparatus.

[0035] The thickness of the porous membrane 1 may be set according to the size of the device to which it is applied (e.g., a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device), and may be, for example, greater than 0 μm, 0.5 μm or more, 1 μm or more, or 5 μm or more, and may be 200 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 15 μm or less, or 12 μm or less. The thickness of the porous membrane 1 may be greater than 0 μm and 200 μm or less, greater than 0 μm and 100 μm or less, 0.5 to 50 μm, 1 to 25 μm, 1 to 15 μm, or 5 to 12 μm. The thicker the porous membrane, the more likely it is to obtain higher mechanical strength, and the thinner the porous membrane, the more likely it is to obtain better proton conductivity. The thickness of the porous membrane is the average thickness measured at any five points on the cross section of the porous membrane.

[0036] The porous membrane 1 can be obtained by a conventionally known method. For example, when forming a membrane from a material containing a hydrocarbon resin, a template (particles, etc.) can be added, and after forming the membrane, the template can be removed by a process such as stretching to obtain the porous membrane 1. The membrane formation method can be a known method, such as a solution casting method, a dispersion casting method, a melt pressing method, or a melt extrusion method. In addition, the porous membrane 1 (nonwoven membrane) can also be formed by a known method such as a spunbonding method, a meltblowing method, or a spunlace method. As the porous membrane 1, commercially available products such as an ultra-high molecular weight polyethylene porous sheet NR2451 manufactured by Fluorochemical Corporation, a polyolefin flat membrane "Hipore" manufactured by Asahi Kasei Corporation, and a polyethylene microporous film "Porum" manufactured by Tokuyama Corporation can also be used.

[0037] (Filler) The filler 3 contains, as a hydrocarbon-based electrolyte polymer, a hydrocarbon-based electrolyte polymer (hereinafter also referred to as "polymer (P)") having a structure represented by the following formula (1).

[0038]

[0039] In formula (1), A １ represents a structural unit represented by the following formula (a1) (hereinafter referred to as "structural unit A １ ") and A ２ is a structural unit represented by the following formula (a2) (hereinafter referred to as "structural unit A２ ") and L １ and L ２ are each independently a single bond, —O—, —S— or —SO ２ -, n represents an integer of 10 to 100, and * represents a bond. １ are identical to each other, and multiple A ２ are identical to each other, and multiple L １ may be the same or different, and multiple L ２ may be the same or different from each other.

[0040]

[0041] In formula (a1), IExG represents an ion exchange group, L ３ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, x represents an integer of 2 to 10, and * represents a bond. ３ may be the same or different from each other.

[0042]

[0043] In formula (a2), Ar represents an arylene group having no ion exchange group, and L ４ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, y is an integer of 3 to 20, * is a bond. ４ may be the same or different from each other.

[0044] The polymer (P) has excellent proton conductivity. Therefore, by using the polymer (P), the proton conductivity of the electrolyte membrane can be improved. The reason why the polymer (P) has excellent proton conductivity is not clear, but it is thought that the polymer (P) has excellent proton conductivity when the polymer (P) is composed of a plurality of identical hydrophilic structural units A. １ (hydrophilic portion) and a plurality of identical hydrophobic structural units A ２It is presumed that, since the structural unit A (hydrophobic portion) is precisely arranged, the ion exchange groups are arranged at equal intervals, and the ion exchange groups are self-assembled in a higher-order structure to induce a microphase-separated structure, which in turn forms a good proton conduction path within the polymer (P). １ The presence of three or more ion-exchange groups densely packed within the polymer also contributes to the improvement of phase separation and proton conductivity. The above effect is particularly pronounced in high-humidity environments (e.g., at humidity levels of 80% RH or higher).

[0045] The polymer (P) can also improve the gas barrier properties of the electrolyte membrane. The reason for this is presumed to be as follows: Since the main chain of the polymer (P) is composed of an arylene group containing a benzene ring, the solubility of hydrogen and oxygen is low, and segment motion is restricted, thereby suppressing gas diffusion in the membrane, which is thought to improve the gas barrier properties of the electrolyte membrane.

[0046] As represented by formula (1), the polymer (P) comprises a structural unit A １ and structural unit A ２ and a linking group (L １ or L ２ ) and has a repeating structure (the structure in [ ] in formula (1)) in which the repeating number (n) of the structure is 10 to 100, and may be 15 or more or 20 or more, and may be 80 or less or 50 or less. When the repeating number (n) is 15 or more, the gas barrier property tends to be excellent, and when the repeating number (n) is 50 or less, the solubility in a solvent and the permeability into a porous membrane tend to be excellent. As the solubility in a solvent of the polymer (P) and the permeability into a porous membrane improve, the voids originating from the porous membrane in the electrolyte membrane tend to be reduced, and further excellent mechanical strength and proton conductivity tend to be obtained. From the above viewpoints, the repeating number (n) of the structure is preferably 15 to 80, and more preferably 20 to 50.

[0047] [Structural unit A １ ] Structural unit A １ is an aromatic ring having an ion exchange group (IExG) and a linking group (L ３ ) and has a continuous structure.

[0048] Ion exchange groups, also called ionic groups, have the property of releasing ions (e.g., cations) to exchange with other ions. Examples of ion exchange groups include sulfonic acid groups, alkylsulfonic acid groups, perfluoroalkylsulfonic acid groups, sulfonimide groups, phosphonic acid groups, phosphoric acid groups, and carboxy groups, as well as salts thereof. As described above, ion exchange groups also include those that form salts with metal ions, etc.

[0049] The sulfonic acid group and its salts are, 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 of 1 to 4). The metal represented by M exists as an ion (cation), and is represented by -SO ３ － and forms salts.

[0050] The alkylsulfonic acid group and its salts are, for example, —R １ SO ３ M １／ｑ It is expressed as: R １ R is an alkanediyl group, and from the viewpoint of obtaining better proton conductivity, the number of carbon atoms is preferably 1 to 12 (an integer). １ Specific examples of the group include a methylene group, a butane-1,4-diyl group, and a hexane-1,6-diyl group. M and q are as defined above.

[0051] The sulfonimide group and its salts are, for example, —SO ２ NM １／ｑ SO ２ R ２ It is expressed as: R ２ R is an alkyl group, and from the viewpoint of obtaining better proton conductivity, the number of carbon atoms is preferably 1 to 6 (an integer). ２ Specific examples of M include a methyl group, an ethyl group, and a propyl group. M and q are as defined above.

[0052] Structural unit A １From the viewpoint of obtaining better proton conductivity, the structural unit A preferably contains, as an ion exchange group, at least one group selected from the group consisting of a sulfonic acid group, an alkylsulfonic acid group, a sulfonimide group, and salts thereof, and more preferably contains at least one group selected from the group consisting of a sulfonic acid group and a salt thereof. １ It is more preferable that the majority of the ion exchange groups present in the structural unit A are those of the above-mentioned preferred embodiment. １ It is particularly preferred that all of the ion exchange groups present therein are of the above-mentioned preferred embodiment.

[0053] Structural unit A １ From the viewpoint of obtaining better proton conductivity, ３ ) as -SO ２ It is preferred that the group contains at least one group selected from the group consisting of — and —CO—, and ２ From the same viewpoint, it is more preferable that the structural unit A １ A plurality of linking groups (L ３ It is more preferable that the majority of the above-mentioned preferred embodiments.

[0054] Structural unit A １ The linking group (L ３ ) is preferably a single bond or —SO ２ It is preferable that −.

[0055] Linking group (L ３ The bonding position of the structural unit A is not particularly limited, but from the viewpoint of obtaining better proton conductivity, it is preferably located at the ortho-position or meta-position relative to the ion exchange group. １ preferably contains a 1,4-phenylene group having an ion exchange group.

[0056] Structural unit A １ The number of repetitions (x) of the structure in brackets [ ] in formula (a1) in the above formula is preferably 2 to 8, more preferably 3 to 5, from the viewpoints of obtaining better proton conductivity and excellent hot water resistance.

[0057] Structural unit A １ From the viewpoint of obtaining better proton conductivity, it is preferable that the polymerizable compound contains at least one structure selected from the group consisting of a structure represented by the following formula (a1-1) (hereinafter referred to as "structure (a1-1)"), a structure represented by the following formula (a1-2) (hereinafter referred to as "structure (a1-2)"), and a structure represented by the following formula (a1-3) (hereinafter referred to as "structure (a1-3)").

[0058]

[0059]

[0060]

[0061] IExG and * in formula (a1-1), formula (a1-2) and formula (a1-3) have the same meanings as defined above. ３１ represents —O— or —S—. Multiple IExGs may be the same or different. １ represents an integer of 2 to 10, and x in formula (a1-2) ２ represents an integer of 2 to 5, and x in formula (a1-3) ３ represents an integer of 1 or 2. １ When x contains two or more structures selected from the group consisting of structures (a1-1), (a1-2), and (a1-3), １ , 2x ２ (2 and x ２ product of ) and 4x ３ (4 and x ３ The sum of the products is 6 to 10. １ is preferably 2 to 5, more preferably 2 to 3, from the viewpoint of obtaining better proton conductivity and excellent hot water resistance. ２ is preferably 2 to 3, more preferably 2, from the viewpoint of obtaining better proton conductivity and excellent hot water resistance. ３ is preferably 1 from the viewpoint of obtaining better proton conductivity and excellent hot water resistance.

[0062] Structural unit A １may consist of only the structure (a1-1), or may contain the structure (a1-1) and a structure other than the structure (a1-1). In the latter case, the structure (a1-1) and the structure other than the structure (a1-1) are connected by a linking group (L ３ Similarly, the structural unit A １ may consist of only the structure (a1-2), or may contain the structure (a1-2) and a structure other than the structure (a1-2). In the latter case, the structure (a1-2) and the structure other than the structure (a1-2) are connected by a linking group (L ３ Similarly, the structural unit A １ may consist of only the structure (a1-3), or may contain the structure (a1-3) and a structure other than the structure (a1-3). In the latter case, the structure (a1-3) and the structure other than the structure (a1-3) are connected by a linking group (L ３ ) may be linked.

[0063] Structural unit A １ may be a structural unit represented by any one of the following formulas (A1-1) to (A1-4).

[0064]

[0065] IExG and * in formulas (A1-1) to (A1-4), and L in formulas (A1-2) to (A1-4) ３ The plural IExGs may be the same or different, and the plural L ３ may be the same or different from each other.

[0066] Structural unit A in polymer (P) １ From the viewpoint of obtaining better proton conductivity and excellent chemical durability, L is preferably any of the constitutional units represented by formula (A1-1) to formula (A1-4), and more preferably a constitutional unit represented by formula (A1-2). ３ is preferably a single bond from the viewpoint of improving proton conductivity and chemical durability.

[0067] [Structural unit A ２ ] Structural unit A ２is a group in which an arylene group (Ar) having no ion exchange group is bonded to a linking group (L ４ ) and has a continuous structure.

[0068] An arylene group is a divalent aromatic hydrocarbon group having a structure in which two hydrogen atoms have been removed from a monocyclic or fused polycyclic aromatic hydrocarbon. From the viewpoints of excellent solubility in solvents and permeability into porous membranes, the number of aromatic rings in the arylene group is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1. The arylene group may have a substituent other than an ion-exchange group. Examples of the substituent include an alkyl group and an aryl group. The alkyl group may be at least one group selected from the group consisting of a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. The aryl group may be a 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. From the viewpoints of excellent solubility in solvents and permeability into porous membranes, it is preferable that the arylene group has no substituent.

[0069] The unsubstituted arylene group may be at least one group selected from the group consisting of a phenylene group, a naphthylene group, a fluorenylidene group (fluorene group), an anthracylene group, a phenanthrylene group, a triphenylene group, a pyrenylene group, and a tetracenylene group. The substituted arylene group may be at least one group selected from the group consisting of a diphenylfluorenylidene group, a methylphenylene group, an ethylphenylene group, a dimethylfluorenylidene group, a diethylfluorenylidene group, a dipropylfluorenylidene group, a diisopropylfluorenylidene group, a dibutylfluorenylidene group, a dipentylfluorenylidene group, a dihexylfluorenylidene group, a diheptylfluorenylidene group, a dioctylfluorenylidene group, a dinonylfluorenylidene group, a didecylfluorenylidene group, a diundecylfluorenylidene group, and a didodecylfluorenylidene group.

[0070] Structural unit A ２From the viewpoint of excellent solubility in a solvent and permeability into a porous membrane, the structural unit A preferably contains, as an arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorenylidene group, which may have a substituent, more preferably contains a phenylene group which may have a substituent, even more preferably contains a phenylene group (a phenylene group having no substituent), and particularly preferably contains a 1,4-phenylene group. ２ It is more preferable that the majority of the arylene groups present in the structural unit A are those of the above-mentioned preferred embodiment. ２ It is particularly more preferred that all of the arylene groups present therein are of the above-mentioned preferred embodiments.

[0071] Structural unit A ２ is excellent in solubility in a solvent and permeability into a porous membrane, and from the viewpoint of further improving the mechanical strength of the electrolyte membrane, ４ ) as a single bond, —SO ２ It is preferred that the group contains at least one group selected from the group consisting of — and —CO—, and ２ From the same viewpoint, it is more preferable that the structural unit A contains - or -CO-. ２ A plurality of linking groups (L ４ It is more preferable that the majority of the structural units A ２ A plurality of linking groups (L ４ ) may all be the preferred embodiments described above.

[0072] Structural unit A ２ The linking group (L ４ ) is preferably a single bond, —O— or —SO 4 from the viewpoint of obtaining better proton conductivity and better mechanical strength. ２ It is preferable that −.

[0073] Structural unit A ２ The number of repetitions (y) of the structure in brackets [ ] in formula (a2) in the above formula is preferably 4 to 12, and more preferably 5 to 10, from the viewpoints of obtaining better proton conductivity and excellent hot water resistance.

[0074] Structural unit A ２ In order to achieve both better proton conductivity and hot water resistance, the number of repetitions (y) of the structure in brackets [ ] in formula (a2) in formula (a1) is preferably 2 to 7 more than the number of repetitions (x) of the structure in brackets [ ] in formula (a1) (x+(2 to 7)).

[0075] Structural unit A ２ The number of aromatic rings in the main chain of the polymer is preferably 4 to 21, more preferably 5 to 13, and even more preferably 6 to 11, from the viewpoints of achieving excellent solubility in a solvent and excellent permeability into a porous membrane, and further improving the mechanical strength of the electrolyte membrane.

[0076] Structural unit A ２ From the viewpoints of excellent solubility in a solvent and permeability into a porous membrane, and further improving the mechanical strength of the electrolyte membrane, it preferably contains at least one structure selected from the group consisting of a structure represented by the following formula (a2-1) and a structure represented by the following formula (a2-2), and more preferably contains a structure represented by the following formula (a2-1):

[0077]

[0078]

[0079] Ar and * in formula (a2-1) and formula (a2-2) have the same meanings as defined above. Multiple Ar may be the same or different.

[0080] Structural unit A ２ is particularly preferably a structural unit represented by the following formula (A2), from the viewpoints of achieving even better solubility in a solvent and permeability into a porous membrane, and further improving the mechanical strength of the electrolyte membrane.

[0081]

[0082] Ar and L in formula (A2) ４ and * are as defined above, Q represents a group having a structure represented by formula (a2-1) or formula (a2-2), and y １ and y ２ each independently represents an integer of 2 to 4. １ and y ２is preferably 2 to 3 from the viewpoint of providing excellent solubility in the solvent and permeability into the porous membrane, and further improving the mechanical strength of the electrolyte membrane. ４ may be the same or different from each other.

[0083] [Linking Group] From the viewpoint of obtaining better proton conductivity and better mechanical strength, the polymer (P) contains the structural unit A １ and structural unit A ２ The linking group (L １ or L ２ ) preferably contains at least one group selected from the group consisting of a single bond, —O—, and —S—, and more preferably contains —O—. From the same viewpoint, the structural units A present in plurality in the polymer (P) １ and structural unit A ２ The linking group (L １ and L ２ It is more preferable that the majority of the structural units A) are those of the above-mentioned preferred embodiment, and １ and structural unit A ２ The linking group (L １ and L ２ It is particularly preferred that all of the above are of the preferred embodiments.

[0084] Structural unit A in polymer (P) １ and structural unit A ２ The linking group (L １ and L ２ ) are each independently preferably a single bond, —O—, or —S—, more preferably —O—, from the viewpoint of obtaining better proton conductivity and better mechanical strength.

[0085] The polymer (P) may be composed of a structure represented by formula (1) and a terminal structure bonded to the structure. The polymer (P) may be, for example, a compound represented by any one of the following formulas (1-1) to (1-3).

[0086]

[0087] A in formula (1-1) to formula (1-3) １ , A２ , L １ , L ２ and n have the same meanings as above. However, in formula (1-1) and formula (1-2), Z ２ L binds to ２ is a single bond. １ and Z ２ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronate ester group. Examples of halogen atoms include a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I). Examples of alkylborane groups include a diethylborane group, a disiamylborane group, a dicyclohexylborane group, and a 9-borabicyclo[3.3.1]nonane group. Examples of boronate ester groups include a pinacol boronate ester group, a 1,3-propanediol boronate ester group, a biscyclohexyldiol boronate ester group, a neopentyl glycol boronate ester group, and a catechol boronate ester group.

[0088] The polymer (P) may contain a plurality of polymer units (hereinafter also referred to as "polymer units A") containing the structure represented by formula (1). For example, the polymer (P) may contain three or more polymer units A and a crosslinking group bonding the three or more polymer units A. The polymer (P) having such a crosslinking group (hereinafter also referred to as "crosslinked polymer (P')") has excellent swelling resistance.

[0089] The polymer unit A can be, for example, a compound represented by any one of the above formulas (1-1) to (1-3) having a terminal group Z １ and Z ２ Of the two terminal groups of the polymer unit A, the terminal group bonded to the crosslinking group is A １ A may be ２ The terminal group bonded to the crosslinking group may be L ２ (i.e., Z in formula (1-1) and formula (1-2) ２ L binds to ２ When the terminal group attached to the bridging group is A ２The two end groups of the polymer unit A may be bonded to different crosslinking groups. Of the two end groups of the polymer unit A, the end group opposite to the end group bonded to the crosslinking group is considered to be the end group Z １ and Z ２ The multiple polymer units A bonded to one crosslinking group may be the same or different.

[0090] 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 an aromatic ring, the polymer unit A is preferably bonded to the aromatic ring of the crosslinking group from the viewpoint of obtaining better swelling resistance. The polymer unit A may be directly bonded to the aromatic ring, and may be bonded to -O-, -S- or -SO ２ The number of aromatic rings that the crosslinking group has is preferably 1 or 2, from the viewpoint of enhancing chemical stability.

[0091] The crosslinking group may be, for example, a group represented by the following formula (c):

[0092]

[0093] In formula (c), E represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group; ５ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, L ６ represents a single bond, —O—, —S—, or —SO ２ represents -, * represents a bond bonding to the polymer unit A, p, q, r and s each represent an integer of 0 to 5, and z represents 0 or 1. However, p+q is 3 or more, p+r is 0 to 5, q+s is 0 to 5, and when z is 0, r and p are 0. When there are multiple E's, the multiple E's may be the same or different from each other. L ５ If there are multiple L ５ may be the same or different. ６may be the same or different from each other.

[0094] The group represented by formula (c) may be, for example, a group represented by any of the following formulae (c1) to (c5). The symbols in formulae (c1) to (c5) have the same meanings as above. Some or all of E in the groups represented by formulae (c1) to (c5) may be replaced with hydrogen atoms.

[0095]

[0096] The number of crosslinking groups contained in the crosslinked polymer (P') may be one or more. The multiple crosslinking groups may be the same or different from one another.

[0097] The crosslinked polymer (P') may contain a crosslinking group bonding two polymer units A. Such a crosslinking group may have the same structure as the crosslinking group bonding three or more polymer units A, except that the number of bonds bonding to the polymer unit A is different.

[0098] 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 obtaining better proton conductivity. From the same 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 but less than 100% by mass, 85% by mass or more but less than 100% by mass, or 90% by mass or more but less than 100% by mass.

[0099] From the viewpoint of achieving better proton conductivity and mechanical strength, the polymer (P) preferably does not contain fluorine atoms (the fluorine content is below the detection limit).

[0100] The number average molecular weight of the polymer (P) may be 20,000 or more, 25,000 or more, or 30,000 or more from the viewpoint of achieving superior proton conductivity and further improving the mechanical strength of the electrolyte membrane, and may be 300,000 or less, 200,000 or less, 150,000 or less, 100,000 or less, or 70,000 or less from the viewpoint of achieving superior solubility in solvents and permeability into porous films. From these viewpoints, the number average molecular weight of the polymer (P) may be 20,000 to 300,000, 25,000 to 200,000, 30,000 to 150,000, 30,000 to 100,000, or 30,000 to 70,000.

[0101] The weight average molecular weight of the polymer (P) may be 25,000 or more, 35,000 or more, 40,000 or more, or 50,000 or more from the viewpoint of achieving better proton conductivity and further improving the mechanical strength of the electrolyte membrane, and may be 60,000 or more, 100,000 or more, 150,000 or more, 200,000 or more, or 250,000 or more from the viewpoint of achieving even better proton conductivity. The weight average molecular weight of the polymer (P) may be 500,000 or less, 300,000 or less, 250,000 or less, 200,000 or less, 150,000 or less, or 100,000 or less from the viewpoint of achieving excellent solubility in solvents and permeability into porous membranes. From these viewpoints, the weight average molecular weight of the polymer (P) may be 25,000 to 500,000, 35,000 to 500,000, 40,000 to 500,000, 50,000 to 300,000, 60,000 to 200,000, 100,000 to 500,000, 150,000 to 500,000, 150,000 to 400,000, 150,000 to 300,000, 200,000 to 500,000, 250,000 to 500,000, or 25,000 to 100,000.

[0102] The ratio of the weight average molecular weight to the number average molecular weight (polydispersity) of the polymer (P) may be 1.5 or more, 2.0 or more, 2.5 or more, or 3.0 or more. When the polydispersity of the polymer (P) is 1.5 or more, excellent swelling resistance tends to be obtained. From the viewpoint of excellent solubility in solvents and permeability into porous membranes, the polydispersity of the polymer (P) may be 10.0 or less, 7.0 or less, 5.0 or less, or 3.5 or less. From these viewpoints, the polydispersity of the polymer (P) may be 1.5 to 10.0, 2.0 to 7.0, 2.5 to 5.0, 3.0 to 5.0, or 1.5 to 3.5.

[0103] The number average molecular weight and weight average molecular weight of the polymer (P) are values ​​measured by gel permeation chromatography (GPC) and calculated as standard polyethylene glycol / oxide (PEG / PEO).

[0104] The 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, the polymer (P) can be a polymer of the compound (b1) and the compound (b2).

[0105]

[0106] In formula (b1), A １ has the same meaning as above, and X １ｂ and X ２ｂ are each independently a halogen atom. Examples of halogen atoms include a fluorine atom (F), a chlorine atom (Cl), a bromine atom (Br), and an iodine atom (I).

[0107]

[0108] In formula (b2), A ２ has the same meaning as above, and Z １ｂ and Z ２ｂ each independently represents a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group. Examples of the halogen atom, the alkylborane group, and the boronic acid ester group are the same as those described above in Z １ and Z２ These are the same as the examples of the halogen atom, alkylborane group and boronic acid ester group represented by the following formula:

[0109] In the above method, the structural unit A １ and structural unit A ２ Therefore, according to the above method, the number of repetitions n in formula (1) can be easily increased to 10 or more.

[0110] According to the above method, L in formula (1) １ and L ２ is —O—, —S— or a single bond. １ｂ and Z ２ｂ When at least one of the groups is a hydroxy group, L １ and L ２ A polymer (P) is obtained in which at least one of the following is —O—, and Z １ｂ and Z ２ｂ When at least one of the groups is a thiol group, L １ and L ２ A polymer (P) is obtained in which at least one of Z １ｂ and Z ２ｂ When at least one of the groups is a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group, L in formula (1) １ and L ２ A polymer (P) is obtained in which at least one of the following is a single bond.

[0111] The compound (b1) is X １ｂ and / or X ２ｂ Similarly, as the compound (b2), a plurality of compounds having different Z １ｂ and / or Z ２ｂ It is also possible to use a plurality of compounds with different valences.

[0112] The compound (b1) and the compound (b2) can be reacted (polymerized) by, for example, an aromatic nucleophilic substitution reaction in a solvent in the presence of a base.

[0113] The solvent used in the reaction is preferably a good solvent for the compound (b1), the compound (b2), and the polymer (P) and capable of increasing the molecular weight of the polymer (P) during polymerization. For example, at least one solvent selected from the group consisting of N-methyl-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea is preferably used.

[0114] The base is used to improve the nucleophilicity of compound (b2). The base is not particularly limited as long as it can deprotonate compound (b2). For example, hydroxides and carbonates of alkali metals, hydroxides and carbonates of alkaline earth metals, 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.

[0115] The reaction temperature in the aromatic nucleophilic substitution reaction 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 decomposition of the polymer, 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.

[0116] Compound (b1) and compound (b2) can also be reacted (polymerized) by, for example, 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 the examples of solvents that can be used in the above-mentioned aromatic nucleophilic substitution reaction.

[0117] The catalyst is not particularly limited as long as it can promote a cross-coupling reaction, and conventionally known catalysts can be used. For a coupling reaction between halogens, for example, a copper catalyst, a nickel catalyst, or a palladium catalyst can be used. For a coupling reaction between a halogen and a boronic acid group, an alkylborane group, or a boronic acid ester group, for example, a conventionally known catalyst (palladium catalyst, nickel catalyst, etc.) used in the Suzuki-Miyaura coupling reaction can be used.

[0118] The copper catalyst may be, for example, copper(I) 2-thiophenecarboxylate or tetrakis(acetonitrile)copper(I) hexafluorophosphate.

[0119] 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).

[0120] The palladium catalyst may be, for example, tetrakis(triphenylphosphine)palladium(0), palladium(II) acetate, bis(triphenylphosphine)palladium(II) dichloride or [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II).

[0121] 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 decomposition of the polymer, 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.

[0122] In the aromatic nucleophilic substitution reaction and cross-coupling reaction, it is preferable to remove water from the reaction system in order to increase the molecular weight of the polymer (P). The dehydration method is not particularly limited, but examples include a method of azeotropic dehydration in which an azeotropic solvent is present in the reaction system, a method of heating the reaction system to above the boiling point of water to continuously remove it from the reaction system, and a method of using a water-absorbing agent such as a molecular sieve. The azeotropic solvent is not particularly limited as long as it can remove water, and at least one selected from the group consisting of benzene, toluene, cyclohexane, and xylene may be used.

[0123] The aromatic nucleophilic substitution reaction and cross-coupling reaction are preferably carried out under an inert atmosphere (e.g., under a nitrogen or argon atmosphere). After the polymerization reaction is completed, 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 to precipitate and recover the polymer as a solid, and removing the solvent from the reaction solution by evaporation to recover the polymer as a solid. Methods for purifying the polymer include, for example, washing the polymer in a solvent in which the polymer has low solubility but in which by-produced inorganic salts and compounds derived from residual monomers have high solubility, and washing using a Soxhlet extractor. The methods for recovering and purifying the polymer are not limited to these methods.

[0124] The polymer (P) can also be obtained by oxidizing a polymer having a structure represented by formula (1) (for example, a polymer of compound (b1) and compound (b2)). More specifically, the polymer (P) can be obtained by oxidizing a polymer having a structure represented by formula (1) in which L １ , L ２ , L ３ or L ４ The sulfide-containing polymer may be an oxide of a polymer containing —S— (sulfide group) as the group (hereinafter referred to as a “sulfide-containing polymer”). From the viewpoint of excellent chemical durability, the sulfide-containing polymer is a polymer having a structure represented by formula (1), １ , L ２ , L３ and L ４ each independently represents a single bond, —S—, or —SO ２ Preferably, the polymer is -.

[0125] The method for oxidizing the sulfide-containing polymer is not particularly limited, and may be, for example, by oxidizing a sulfide group (—S—) to form a sulfonyl group (—SO ２ The sulfide-containing polymer may be immersed in a mixed solution containing acetic acid, sulfuric acid, and hydrogen peroxide. The concentration of acetic acid in the mixed solution may be, for example, 50 to 90 mass %. The concentration of sulfuric acid in the mixed solution may be, for example, 5 to 25 mass %. The concentration of hydrogen peroxide in the mixed solution may be, for example, 1 to 15 mass %. The immersion time may be, for example, 1 to 100 hours. In the above method, heating may be performed after immersion. The heating temperature may be, for example, 30 to 120°C, and the heating time may be, for example, 0.1 to 24 hours.

[0126] The polymer (P) obtained by the above method is a polymer having a structure represented by formula (1), wherein L １ , L ２ , L ３ or L ４ As -SO ２ The polymer may be a polymer in which all of the sulfide groups in the sulfide-containing polymer have been oxidized to sulfonyl groups (complete oxide), or a polymer in which only a portion of the sulfide groups in the sulfide-containing polymer have been oxidized to sulfonyl groups (partial oxide). The degree of oxidation can be adjusted, for example, by the impregnation time, heating temperature, and heating time.

[0127] The 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 the oxide thereof to form crosslinks (hereinafter also referred to as "crosslinkable compound (d)"). That is, the polymer (P) can be a reaction product of a polymer of compound (b1) and compound (b2) or an oxide thereof with the crosslinkable compound (d).

[0128] The above method can provide a crosslinked product (e.g., the above-described crosslinked polymer (P')) having a polymer of compound (b1) and compound (b2) or an oxide thereof as a polymer unit. The above method can form a crosslinked structure while maintaining a precise array structure, thereby achieving both excellent proton conductivity and excellent swelling resistance.

[0129] The crosslinkable compound (d) may be a known crosslinkable compound, for example, a low molecular weight compound having a molecular weight of not more than 1000. The group that reacts with the polymer or its oxide to form a crosslink is, for example, a hydroxy group, a thiol group, a halogen atom, a boronic acid group, an alkylborane group, or a boronic acid ester group.

[0130] From the viewpoint of chemical stability, the crosslinkable compound (d) preferably has one or more aromatic rings. In this case, from the viewpoint of enhancing chemical stability, the group that reacts with the polymer or its oxide to form a crosslink is preferably directly bonded to the aromatic ring. From the viewpoint of enhancing chemical stability, the number of aromatic rings that the crosslinkable compound (d) has is preferably 1 or 2.

[0131] The crosslinkable compound (d) may be, for example, a compound represented by the following formula (d):

[0132]

[0133] In formula (d), E, ​​L ５ and z are as defined above, and t and u each represent an integer of 0 to 5, provided that t+u is 3 or more, and when z is 0, t is 0. The multiple E's may be the same or different. Of the multiple E's, three or more E's are terminal groups (X １ｂ , X ２ｂ , Z １ｂ or Z ２ｂ ) to form crosslinks.

[0134] The polymer of the compound (b1) and the compound (b2) and the oxide thereof, and the crosslinkable compound (d) may each be used alone or in combination of two or more kinds.

[0135] The reaction of the polymer of the compound (b1) and the compound (b2) or the oxide thereof with the crosslinkable compound (d) can be carried out in the same manner as the reaction of the compound (b1) with the compound (b2).

[0136] The polymer (P) may be obtained by a method including a step of protonating ion exchange groups that form salts with metal ions. This step may be a step of protonating the ion exchange groups (e.g., salts of sulfonic acid groups) by immersing the polymer obtained by the above-mentioned method (e.g., a polymer of compound (b1) and compound (b2) or an oxide thereof, or a reaction product of the polymer or oxide with crosslinkable compound (d)) in an acid (e.g., hydrochloric acid). After the immersion, the compound (e.g., powder) is washed and dried, whereby the metal ions of the polymer before the immersion are replaced with protons, and a polymer (P) with protonated ion exchange groups is obtained.

[0137] The content (filling amount) of the hydrocarbon-based electrolyte polymer in the electrolyte membrane 10A may be 50 parts by mass or more, 90 parts by mass or more, or 350 parts by mass or more, relative to 100 parts by mass of the porous membrane, from the viewpoint of more easily obtaining superior proton conductivity. The content (filling amount) of the hydrocarbon-based electrolyte polymer may be 3000 parts by mass or less, 2000 parts by mass or less, 1000 parts by mass or less, 600 parts by mass or less, 300 parts by mass or less, or 150 parts by mass or less, relative to 100 parts by mass of the porous membrane, from the viewpoint of more easily improving mechanical strength. From the above viewpoint, the content (filling amount) of the hydrocarbon-based electrolyte polymer may be 50 to 3000 parts by mass, 90 to 2000 parts by mass, 350 to 1000 parts by mass, 350 to 600 parts by mass, 50 to 300 parts by mass, or 50 to 150 parts by mass, relative to 100 parts by mass of the porous membrane.

[0138] The filler 3 may contain other components in addition to the hydrocarbon-based electrolyte polymer, as long as the effects of the present disclosure are not impaired. For example, the other components may be at least one selected from the group consisting of a water-retaining inorganic substance and a radical scavenger. Specifically, for example, at least one selected from the group consisting of silica, cerium oxide, and manganese oxide may be used. The content (total amount) of the other components may be 0 to 10% by mass, 0 to 6% by mass, or 0 to 3% by mass, based on the total solid content of the filler.

[0139] It is preferable that the filler 3 completely fills the pores 2 of the porous membrane 1, but some of the pores 2 of the porous membrane 1 may not be filled with the filler 3. The proportion of voids originating from the porous membrane 1 in the electrolyte membrane 10A (porosity) can be calculated by observing a cross section of the electrolyte membrane and binarizing the void and non-void portions by image analysis. The proportion of voids originating from the porous membrane 1 in the electrolyte membrane 10A (porosity) may be 0 to 0.1% by volume, 0 to 0.01% by volume, or 0 to 0.001% by volume, from the viewpoint of obtaining higher mechanical strength and better proton conductivity.

[0140] (Method for manufacturing electrolyte membrane) The electrolyte membrane 10A is obtained by filling a filler containing a hydrocarbon-based electrolyte polymer (polymer (P)) into a porous membrane 1. As a method for filling the filler 3 into the porous membrane 1, for example, a method of impregnating the porous membrane 1 with a solution containing the filler 3 and then drying the solution can be mentioned.

[0141] The method for producing the electrolyte membrane 10A may include, for example, step (a) of applying a solution containing the filler 3 onto a substrate to form a coating film, step (b) of placing the porous membrane 1 on the coating film and impregnating the porous membrane 1 with the solution, and step (c) of drying the solution. In this method, from the viewpoint of more thoroughly impregnating the porous membrane 1 with the solution, step (b-2) of applying the filler-containing solution onto the surface of the porous membrane 1 opposite the substrate may be performed after step (b). Furthermore, the substrate may be peeled off and removed after step (c). When the ion exchange group of the hydrocarbon-based electrolyte polymer has a metal ion, step (d) of substituting the metal ion with a proton may be performed after step (c).

[0142] The substrate may be, for example, a glass substrate. The solvent used for the solution is not particularly limited as long as it is a solvent capable of dissolving the hydrocarbon-based electrolyte polymer, and for example, at least one selected from the group consisting of N-methyl-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, 1,3-dimethyl-2-imidazolidinone, and tetramethylurea may be used.

[0143] The method for applying the solution is not particularly limited, and may be, for example, an applicator method, a bar coating method, a spin coating method, a spray coating method, a dip coating method, a nozzle coating method, a gravure coating method, a reverse roll coating method, a die coating method, an air doctor coating method, a blade coating method, a rod coating method, a curtain coating method, a knife coating method, a transfer roll coating method, a squeeze coating method, an impregnation coating method, a kiss coating method, a calendar coating method, or an extrusion coating method.

[0144] The drying method is not particularly limited as long as it can sufficiently remove the solvent from the solution. In the case of heat drying, the drying temperature may be, for example, 20 to 150°C, and the drying time may be, for example, 0.2 to 24 hours.

[0145] Step (d) may be, for example, a step of immersing the membrane obtained in step (c) in an acid (e.g., hydrochloric acid). After immersion, the membrane is washed and dried to obtain an electrolyte membrane in which metal ions in the hydrocarbon-based electrolyte polymer are substituted with protons.

[0146] The electrolyte membrane 10A described above has a composite structure of the porous membrane 1 and a hydrocarbon-based electrolyte polymer, and therefore has improved mechanical strength, is less likely to break during transportation or use, and tends to have excellent swelling resistance. Therefore, the electrolyte membrane 10A can enhance the durability of solid polymer fuel cells and solid polymer water electrolysis devices. Furthermore, since the electrolyte membrane 10A contains a polymer (P) as a hydrocarbon-based electrolyte polymer, it also has excellent proton conductivity. In addition to solid polymer fuel cells and solid polymer water electrolysis devices, the electrolyte membrane 10A can also be used in redox flow batteries, electrochemical hydrogen pumps, chlor-alkali electrolysis devices, solid acid catalysts, membrane humidity control devices, gas separation membranes, and the like.

[0147] Although the electrolyte membrane of the present disclosure has been described above using the electrolyte membrane 10A as an example, the electrolyte membrane of the present disclosure is not limited to the above.

[0148] In another embodiment, the electrolyte membrane may have a layer other than a layer containing a porous membrane and a hydrocarbon-based electrolyte polymer filled in the pores of the porous membrane (hereinafter also referred to as a "composite layer"). For example, the electrolyte membrane may further have a layer containing a hydrocarbon-based electrolyte polymer (hereinafter also referred to as an "electrolyte polymer layer") in addition to the composite layer. When the electrolyte membrane has the above-mentioned electrolyte polymer layer on one or both sides of the porous membrane, better proton conductivity is easily obtained. In particular, when the outermost surface of the electrolyte membrane is formed of an electrolyte polymer layer, the adhesion of the electrolyte membrane to the catalyst layer is improved, and proton conductivity is improved. Below, an electrolyte membrane having an electrolyte polymer layer will be described in more detail with reference to FIG. 2.

[0149] Fig. 2 is a schematic cross-sectional view showing an electrolyte membrane of another embodiment. The electrolyte membrane 10B in Fig. 2 has a composite layer 4 and layers containing a hydrocarbon-based electrolyte polymer (a first electrolyte polymer layer 5 and a second electrolyte polymer layer 6). In the electrolyte membrane 10B, the porous membrane 1 is not exposed on the surface of the electrolyte membrane 10B, and the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are provided on the surface of the composite layer 4.

[0150] The composite layer 4 is a layer including a porous membrane 1 and a filler 3 containing a hydrocarbon-based electrolyte polymer, which fills the pores 2 of the porous membrane 1. The composite layer 4 may be the electrolyte membrane 10A described above. That is, the porous membrane 1 and the filler 3 in the composite layer 4 may be the same as the porous membrane 1 and the filler 3 in the electrolyte membrane 10A.

[0151] The details of the hydrocarbon-based electrolyte polymer contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 are the same as the details of the hydrocarbon-based electrolyte polymer contained in the electrolyte membrane 10 A. The hydrocarbon-based electrolyte polymer contained in the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same as or different from the hydrocarbon-based electrolyte polymer contained in the composite layer 4.

[0152] The first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be formed of the filler 3 that fills the composite layer 4. That is, the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be made of only a hydrocarbon-based electrolyte polymer, and may also contain other components that can be contained in the filler 3 as long as the effects of the present disclosure are not impaired.

[0153] The compositions of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be the same as or different from each other.

[0154] The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may each be greater than 0 μm, 0.5 μm or greater, 1 μm or greater, or 5 μm or greater, and may be 100 μm or less, 50 μm or less, 25 μm or less, or 15 μm or less. The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may each be greater than 0 μm and 100 μm or less, or may be 0.5 to 50 μm, 1 to 25 μm, 5 to 25 μm, or 5 to 15 μm. Furthermore, the total thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 may be greater than 0 μm and 200 μm or less, or may be 1 to 50 μm, or 2 to 30 μm. The thinner the electrolyte polymer layer, the more likely it is that excellent proton conductivity will be obtained, and the thicker the electrolyte polymer layer, the more likely it is that the composite layer will provide improved mechanical strength. The thickness of the electrolyte polymer layer is the average thickness measured at any five points on the cross section of the electrolyte polymer layer.

[0155] The thickness of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6 is preferably thinner than the thickness of the composite layer 4, from the viewpoint of making it easier to obtain the effect of improving the mechanical strength by the composite layer.

[0156] The electrolyte polymer layers 5 and 6 in the electrolyte membrane 10B can be easily formed by adjusting the amount of solution used in the manufacturing method for the electrolyte membrane 10A described above.

[0157] In the electrolyte membrane 10B, an electrolyte polymer layer is provided on both sides of the composite layer 4, but an electrolyte membrane having an electrolyte polymer layer may have an electrolyte polymer layer only on one side of the composite layer. That is, the electrolyte membrane may have only one of the first electrolyte polymer layer 5 and the second electrolyte polymer layer 6. Details (thickness, etc.) of these layers are as described above. When the electrolyte membrane has an electrolyte polymer layer, the range of the content of the hydrocarbon-based electrolyte polymer is the same as the range of the content of the hydrocarbon-based electrolyte polymer in the electrolyte membrane 10A described above.

[0158] The ratio (D2 / D1) of the thickness D2 of the porous membrane to the thickness D1 of the electrolyte membrane may be 0.1 to 1. When the ratio (D2 / D1) is 0.1 or more, the mechanical strength is more likely to be improved. From the same viewpoint, the ratio (D2 / D1) may be 0.3 or more or 0.5 or more. From the viewpoint of the adhesion of the electrolyte membrane to the catalyst layer, the ratio (D2 / D1) may be 0.95 or less or 0.9 or less. From the above viewpoint, the ratio (D2 / D1) may be 0.3 to 0.95 or 0.5 to 0.9. The thickness D2 of the porous membrane may also be referred to as the thickness of the composite layer.

[0159] When the electrolyte membrane has an electrolyte polymer layer, the ratio (D2 / D3) of the thickness D2 of the porous membrane to the total thickness D3 of the electrolyte polymer layer in the electrolyte membrane is preferably 0.1 to 30. When the ratio (D2 / D3) is 0.1 or more, the mechanical strength is more likely to be improved, and when it is 30 or less, the adhesion of the electrolyte membrane to the catalyst layer is more likely to be improved. From the same perspective, the ratio (D2 / D3) may be 0.4 or more or 1 or more, and may be 19 or less, 9 or less, 5 or less, or 3 or less, and may be 0.4 to 19, 1 to 9, 1 to 5, or 1 to 3. Here, the total thickness D3 of the electrolyte polymer layer means the thickness of one electrolyte polymer layer when the electrolyte polymer layer is present on only one side of the composite layer, and means the sum of the thicknesses of the two electrolyte polymer layers when the electrolyte polymer layer is present on both sides of the composite layer. The thickness D2 of the porous membrane may also be referred to as the thickness of the composite layer.

[0160] When the electrolyte membrane has a layer other than the composite layer, the thickness of the electrolyte membrane may be 5 to 300 μm, 10 to 200 μm, or 20 to 100 μm. The thickness of the electrolyte membrane is the average thickness measured at any five points on the cross section of the electrolyte membrane.

[0161] In another embodiment, the electrolyte membrane may have a plurality of the composite layers. For example, the electrolyte membrane may have a structure in which two composite layers are stacked with the electrolyte polymer layer interposed therebetween.

[0162] <Catalyst-Coated Electrolyte Membrane> An electrolyte membrane with a catalyst layer of one embodiment includes the electrolyte membrane of the above-described embodiment and a catalyst layer disposed on one or both surfaces of the electrolyte membrane.

[0163] The catalyst layer is, for example, a layer composed of an anode catalyst or a cathode catalyst in a polymer electrolyte fuel cell, a polymer electrolyte water electrolysis device, etc. Hereinafter, a layer composed of an anode catalyst will be referred to as an anode catalyst layer, and a layer composed of a cathode catalyst will be referred to as a cathode catalyst layer.

[0164] The configuration of the catalyst layer is not particularly limited and may be a conventionally known configuration as a catalyst layer (anode catalyst layer, cathode catalyst layer) for a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device. The catalyst layer may be formed, for example, from a conductive composition containing an anode catalyst or a cathode catalyst and a conductive material. The catalyst layer may also contain an ionomer.

[0165] As the anode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting the oxidation reaction of a fuel such as hydrogen can be used, and as the anode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting an oxygen generation reaction can be used, and for example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys of two or more of these can be used.

[0166] As the cathode catalyst in a polymer electrolyte fuel cell, a metal catalyst capable of promoting an oxygen reduction reaction can be used, and as the cathode catalyst in a polymer electrolyte water electrolysis device, a metal catalyst capable of promoting a hydrogen generation reaction can be used, and for example, at least one selected from the group consisting of platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys of two or more of these can be used.

[0167] As the conductive material, for example, at least one selected from the group consisting of furnace black, ketjen black, channel black, acetylene black, activated carbon, and graphite can be used.

[0168] As the ionomer, a conventionally known material can be used, for example, an ionomer containing a perfluoro-based electrolyte can be used. The above-mentioned polymer (P) can also be used as the ionomer. It is preferable to use a material with high oxygen permeability as the ionomer. There is no particular limitation on the amount of ionomer added to the catalyst layer, but it is preferable to adjust the amount added within a range in which oxygen diffusion is not easily inhibited.

[0169] The catalyst layer may further contain, as additives, a water repellent such as fluorinated carbon, and a binder such as a fluorine-containing resin or a hydrocarbon resin having a sulfonic acid group.

[0170] A laminate having an anode catalyst layer and a cathode catalyst layer on both sides of an electrolyte membrane (for example, a laminate having a layer structure of "anode catalyst layer / electrolyte membrane / cathode catalyst layer") is also called a CCM (Catalyst Coated Membrane), and is suitably used in solid polymer fuel cells and solid polymer water electrolysis devices.

[0171] <Membrane Electrode Assembly> A membrane electrode assembly of one embodiment includes the electrolyte membrane of the above embodiment and electrode layers disposed on one or both surfaces of the electrolyte membrane.

[0172] The electrode layer includes, for example, the catalyst layer (anode catalyst layer or cathode catalyst layer) in the catalyst-coated electrolyte membrane of the above embodiment. Hereinafter, an electrode layer including an anode catalyst layer will be referred to as an anode layer, and an electrode layer including a cathode catalyst layer will be referred to as a cathode layer.

[0173] The configuration of the electrode layer is not particularly limited and may be a conventionally known configuration as the electrode layer (anode layer, cathode layer) of a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis device. The electrode layer may be composed of, for example, the above-mentioned catalyst layer (anode catalyst layer or cathode catalyst layer) and a gas diffusion substrate. When the catalyst layer itself has gas diffusibility, the electrode layer may be composed of only the catalyst layer. As the gas diffusion substrate, for example, a porous membrane can be used. As the gas diffusion substrate, a material having water repellency and conductivity in addition to gas diffusibility (for example, a carbon fiber substrate such as a carbon nonwoven fabric or carbon paper, or a titanium fiber sintered compact) can also be used.

[0174] A laminate comprising an anode layer and a cathode layer as electrode layers on both sides of an electrolyte membrane (for example, a laminate having a layer structure of "gas diffusion substrate / anode catalyst layer / electrolyte membrane / cathode catalyst layer / gas diffusion substrate") is also called an MEA (Membrane Electrode Assembly), and is suitably used in solid polymer fuel cells and solid polymer water electrolysis devices.

[0175] <Solid Polymer Electrolyte Fuel Cell> A solid polymer fuel cell of one embodiment includes the membrane electrode assembly of the above embodiment.

[0176] The configuration of the polymer electrolyte fuel cell is not particularly limited and may be a conventionally known configuration, except for the use of the membrane electrode assembly of the above embodiment. The polymer electrolyte fuel cell may include, for example, two or more membrane electrode assemblies. The two or more membrane electrode assemblies may be stacked (laminated) with a separator interposed therebetween. As the separator, a conventionally known separator for polymer electrolyte fuel cells can be used.

[0177] <Solid polymer water electrolysis device> A solid polymer water electrolysis device of one embodiment includes the membrane electrode assembly of the above embodiment.

[0178] The configuration of the solid polymer water electrolysis device is not particularly limited and may be a conventionally known configuration except for the use of the membrane electrode assembly of the above embodiment. The solid polymer water electrolysis device may further include, for example, a power feeder on the outside of the membrane electrode assembly. Furthermore, the solid polymer water electrolysis device may include two or more membrane electrode assemblies.

[0179] The present disclosure will be described in more detail below using examples and comparative examples, but the present disclosure is not limited to the following examples.

[0180] Synthesis Example 1 (Synthesis of Hydrophilic Monomer (M1)) A 10 L flask equipped with a dropping funnel, a reflux condenser, and a mechanical stirrer was purged with nitrogen, and 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl (101 g) and dehydrated tetrahydrofuran (4 L) were charged, and stirring was initiated. The flask was cooled to -70°C in a methanol-dry ice bath, and a 2.6 mol / L n-butyllithium-hexane solution (320 mL) was added dropwise. The mixture was stirred for 1 hour while cooled in the bath. Sulfur dioxide gas (40 mL) was introduced into the flask using nitrogen gas. The mixture was stirred for 30 minutes while cooled in the bath. The bath was then removed, and the internal temperature was raised to 0°C. The precipitated solid was filtered off by suction filtration and washed with tetrahydrofuran (200 mL). The recovered solid was dissolved in pure water (2 L), and 35% hydrogen peroxide solution (260 mL) was added, followed by stirring for 18 hours. The solid was removed by suction filtration, and sodium chloride (600 g) was added to the collected filtrate. The precipitated white solid was collected by suction filtration and purified by recrystallization from water / isopropyl alcohol. The obtained solid was dried under reduced pressure to obtain a hydrophilic monomer represented by the following formula (M1). The yield was 65%.

[0181]

[0182] Synthesis Example 2 (Synthesis of Hydrophobic Monomer (M2)) A 200 mL flask equipped with a stirrer, Dean-Stark tube, reflux condenser, and calcium chloride tube was charged with 4,4'-bis[(4-chlorophenyl)sulfonyl]-1,1'-biphenyl (4.0 g), [1,1'-biphenyl]-4,4'-diol (14.8 g), and potassium carbonate (13.2 g), and N,N-dimethylacetamide (50 mL) and toluene (50 mL) were added. The mixture was heated to 160°C in an oil bath with 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 allowing the reaction solution to cool to room temperature (approximately 25°C), the reaction solution was poured into 10% hydrochloric acid (200 mL), and the precipitated white solid was filtered off. The filtered solid was washed with ethanol (300 mL) and dried. The dried solid was purified by recrystallization from a mixed solution of N-methyl-pyrrolidone / ethanol. The obtained solid was dried under reduced pressure to obtain a hydrophobic monomer (M2) represented by the following formula (M2). The yield was 50%.

[0183]

[0184] Synthesis Example 3 (Synthesis of Hydrophobic Monomer (M3)) A 500 mL flask equipped with a stirrer and a condenser was purged with nitrogen. 2,7-dibromo-9,9-diphenylfluorene (9.5 g), 4'-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)biphenyl-4-ol (12.1 g), potassium carbonate (19 g), tetrakis(triphenylphosphine)palladium(0) (2.0 g), and tetrahydrofuran (250 mL) were added to the flask. The reaction solution was heated to 90°C and stirred for 3 hours. After allowing the reaction solution to cool to room temperature, water (200 mL) and ethyl acetate (500 mL) were added, and the mixture was separated. The organic layer was recovered. The solvent was removed using an evaporator, and the resulting crude product was purified by silica column chromatography using a mixed solvent of ethyl acetate and hexane (1 / 1 by volume) as a developing solvent. The fractions containing the target product were collected, and the solvent was removed using an evaporator. The resulting solid was dried under reduced pressure to obtain a hydrophobic monomer (M3) represented by the following formula (M3). The yield was 53%.

[0185]

[0186] Synthesis Example 4 (Synthesis of Polymer (P1)) To a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, the hydrophilic monomer (M1) (5.94 g) obtained in Synthesis Example 1, the hydrophobic monomer (M2) (4.91 g) obtained in Synthesis Example 2, and cesium carbonate (7.77 g) were added, and nitrogen substitution was performed. Thereafter, dimethyl sulfoxide (50 mL) and cyclohexane (50 mL) were added. The resulting mixture was heated to 130°C and refluxed for dehydration for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 48 hours while still heated at 130°C. The reaction solution was allowed to cool to room temperature, and then re-precipitated and purified with isopropyl alcohol (300 mL), and a solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure. The resulting polymer was immersed in 6 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ After the sulfonic acid group was protonated, the polymer (P1) was obtained. The yield was 91%.

[0187] [In formula (P1), n ​​represents a positive number.]

[0188] Polymer (P1) is a compound in which n in formula (P1) is 22. The number average molecular weight (Mn) of polymer (P1) measured by GPC was 34,000, and the weight average molecular weight (Mw) was 55,000. The GPC measurement was performed under the following conditions, and Mn, Mw, and polydispersity (Mw / Mn) were calculated using standard polyethylene glycol / oxide (PEG / PEO) equivalents. Furthermore, n in formula (P1) for polymer (P1) was calculated from the number average molecular weight (Mn). The same applies to n in formula (P1) for polymer (P2) described below. [Conditions] Sample solution: Polymer (P1) was dissolved in an eluent (DMF solvent containing 10 mmol / L of lithium bromide) at a concentration of 1 mg / mL to prepare a sample solution. Apparatus: HLC-8320GPC manufactured by Tosoh Corporation Column: Two TSKgel SuperAWM-H columns (inner diameter 6.0 mm, length 15 cm) manufactured by Tosoh Corporation were used. Detector: differential refractometer detector Flow rate: 0.6 mL / min Measurement temperature: 40°C

[0189] Synthesis Example 5 (Synthesis of Polymer (P2)) To a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, the hydrophilic monomer (M1) (3.33 g) obtained in Synthesis Example 1, the hydrophobic monomer (M2) (2.93 g) obtained in Synthesis Example 2, and cesium carbonate (4.64 g) were added, and nitrogen substitution was performed. Subsequently, dimethyl sulfoxide (20 mL) and cyclohexane (20 mL) were added. The resulting mixture was heated to 130°C and refluxed for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 48 hours while heating at 130°C. The mixture was then allowed to cool to room temperature, and 12.2 mg of decafluorobiphenyl was added. The mixture was then heated to 130°C and polymerized for 3.5 hours. After allowing the reaction solution to cool to room temperature, reprecipitation purification was performed with isopropyl alcohol (300 mL), and the solid was collected by suction filtration. The collected solid was washed with water and dried under reduced pressure. The obtained polymer was immersed in 6M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ After the sulfonic acid group was replaced with the protonated sulfonic acid group, the polymer was thoroughly washed by immersion in pure water and dried under reduced pressure to obtain a polymer in which the sulfonic acid group was protonated. The yield was 86%.

[0190] The resulting polymer (6.45 g) was dissolved in dimethyl sulfoxide (64.5 mL). This solution was transferred to a dialysis tube (molecular weight cutoff 12,000-14,000) and then transferred to a 1 L beaker to which dimethyl sulfoxide (1,000 mL) had been added in advance, and allowed to stand for dialysis. After standing at 23 ° C for 24 hours, the dimethyl sulfoxide in the beaker was discarded and replaced with fresh dimethyl sulfoxide (1,000 mL), and dialysis was performed under the same conditions. The dialyzed solution was concentrated using an evaporator, and the resulting crystals were purified by recrystallization with isopropyl alcohol (50 mL) and then dried at 80 ° C for 1 hour using a vacuum dryer to obtain a polymer (P2) containing a plurality of polymer units containing the structure represented by the above formula (P1) and having a decafluorobiphenyl-derived crosslinking group bonded to three or more of the polymer units. The yield was 88%.

[0191] The number average molecular weight of the polymer (P2), measured in the same manner as in Example 1, was 58,000, and the weight average molecular weight was 290,000.

[0192] Synthesis Example 6 (Synthesis of Polymer (P3)) To a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, the hydrophilic monomer (M1) (9.72 g) obtained in Synthesis Example 1, the hydrophobic monomer (M3) (6.99 g) obtained in Synthesis Example 3, and cesium carbonate (13.6 g) were added, and nitrogen substitution was performed. Subsequently, dimethyl sulfoxide (50 mL) and cyclohexane (50 mL) were added. The resulting mixture was heated to 130°C and refluxed for dehydration for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 48 hours while heating at 130°C. The reaction solution was allowed to cool to room temperature, and then re-precipitated and purified with isopropyl alcohol (300 mL), and a solid was recovered by suction filtration. The recovered solid was washed with water and dried under reduced pressure. The resulting polymer was immersed in 6 M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ After the sulfonic acid group was protonated, the polymer (P3) was obtained in a yield of 93%. The polymer (P3) had a structure represented by the following formula (P3) and contained protonated sulfonic acid groups.

[0193] [In formula (P3), n represents a positive number.]

[0194] Polymer (P3) is a compound in which n in formula (P3) is 16. The number average molecular weight of polymer (P3) measured in the same manner as in Example 1 was 23,000, and the weight average molecular weight was 65,000. Note that n in formula (P3) for polymer (P3) was calculated from the number average molecular weight (Mn).

[0195] Synthesis Example 7 (Synthesis of Polymer (P4)) To a 100 mL three-neck flask equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark tube, the hydrophilic monomer (M1) (9.73 g) obtained in Synthesis Example 1, the hydrophobic monomer (M3) (6.99 g) obtained in Synthesis Example 3, and cesium carbonate (3.48 g) were added, and nitrogen substitution was performed. Subsequently, dimethyl sulfoxide (50 mL) and cyclohexane (50 mL) were added. The resulting mixture was heated to 130°C and refluxed for dehydration for 4 hours, after which the cyclohexane was removed from the Dean-Stark tube. Polymerization was performed for 48 hours while heating at 130°C. The mixture was then allowed to cool to room temperature, and decafluorobiphenyl (3.57 g) was added. The mixture was then heated to 130°C and polymerized for 3.5 hours. The reaction solution was allowed to cool to room temperature, and then re-precipitated and purified with isopropyl alcohol (300 mL), and the solid was collected by suction filtration. The collected solid was washed with water and dried under reduced pressure. The obtained polymer was immersed in 6M hydrochloric acid for 24 hours to remove metal ions (Na ＋ or K ＋ ) to protons (H ＋ After the fluorine-containing polymer (P4) was substituted with fluorine-containing polymer (P3), the polymer was thoroughly washed by immersion in pure water and dried under reduced pressure to obtain a polymer (P4) containing a plurality of polymer units having a structure represented by formula (P3) and having a decafluorobiphenyl-derived crosslinking group bonded to three or more of the polymer units. The yield was 93%.

[0196] The number average molecular weight of the polymer (P4), measured in the same manner as in Example 1, was 48,000, and the weight average molecular weight was 160,000.

[0197] <Preparation of porous membranes> The following porous membranes A to C were prepared. - Porous membrane A (material: polyethylene ("PE" in the table), membrane thickness: 6 μm, porosity: 40%) - Porous membrane B (material: polyethylene ("PE" in the table), membrane thickness: 11 μm, porosity: 79%) - Porous membrane C (material: polyvinylidene fluoride ("PVDF" in the table), membrane thickness: 11 μm, porosity: 85%) The porosities of the above porous membranes were determined from the pore volumes calculated by mercury intrusion porosimetry using a POREMASTER GT (manufactured by Quantachrome Instruments). For reference, planar SEM images of porous membranes A and B taken with a scanning electron microscope (SEM) are shown in Figures 3 and 4, respectively. The planar SEM images in Figures 3 and 4 are at a magnification of 5000x.

[0198] Example 1 Polymer (P1) was dissolved in dimethyl sulfoxide to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate with an applicator, and porous membrane A was then placed on the obtained coating. Next, the polymer solution was applied to the surface of porous membrane A opposite the glass substrate with an applicator. The resulting solution was then dried at 60°C for 6 hours to obtain the electrolyte membrane of Example 1. The electrolyte membrane had a composite layer containing porous membrane A and polymer (P1) filled in the pores of porous membrane A, as well as electrolyte polymer layers containing polymer (P1) on both sides of the composite layer. The thickness of the composite layer was 6 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 9 μm. The content of polymer (P1) was 99 parts by mass relative to 100 parts by mass of porous membrane A. In this example, the thickness of the electrolyte membrane was measured with a thickness gauge (PG-02, manufactured by TECLOCK CORPORATION).

[0199] Example 2 An electrolyte membrane was obtained in the same manner as in Example 1, except that porous membrane B was used instead of porous membrane A. The thickness of the composite layer was 11 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 24 μm. The content of polymer (P2) was 558 parts by mass relative to 100 parts by mass of porous membrane B.

[0200] Example 3 An electrolyte membrane was obtained in the same manner as in Example 1, except that polymer (P2) was used instead of polymer (P1). The thickness of the composite layer was 6 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 9 μm. The content of polymer (P2) was 99 parts by mass relative to 100 parts by mass of porous membrane A.

[0201] Example 4 An electrolyte membrane was obtained in the same manner as in Example 2, except that polymer (P3) was used instead of polymer (P1). The thickness of the composite layer was 11 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 21 μm. The content of polymer (P3) was 488 parts by mass relative to 100 parts by mass of porous membrane B.

[0202] Example 5 An electrolyte membrane was obtained in the same manner as in Example 2, except that polymer (P4) was used instead of polymer (P1). The thickness of the composite layer was 11 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 31 μm. The content of polymer (P4) was 721 parts by mass relative to 100 parts by mass of porous membrane B.

[0203] Comparative Example 1: Polymer (P1) was dissolved in dimethyl sulfoxide to obtain a solution containing 15% by mass of polymer (P1). The obtained solution was applied to a glass substrate with an applicator and then dried at 60°C for 6 hours to obtain an electrolyte membrane with a thickness of 29 µm.

[0204] Comparative Example 2: Polymer (P2) was dissolved in dimethyl sulfoxide to obtain a solution containing 15% by mass of polymer (P2). The obtained solution was applied to a glass substrate with an applicator and then dried at 60°C for 6 hours to obtain an electrolyte membrane with a thickness of 29 µm.

[0205] Comparative Example 3 An electrolyte membrane was obtained in the same manner as in Example 1, except that porous membrane C was used instead of porous membrane A. The thickness of the composite layer was 11 μm, and the thickness of the electrolyte membrane (the sum of the thickness of the composite layer and the thickness of the electrolyte polymer layer) was 27 μm. The content of polymer (P1) was 842 parts by mass relative to 100 parts by mass of porous membrane C.

[0206] Comparative Example 4: Commercially available Nafion ＴＭ A single membrane of NR211 (thickness: 25 μm) was used as the electrolyte membrane of Comparative Example 4.

[0207] Comparative Example 5 Except for using polymer (P3) instead of polymer (P1), an electrolyte membrane was obtained in the same manner as in Comparative Example 1. The thickness of the electrolyte membrane was 29 μm.

[0208] Comparative Example 6 Except for using polymer (P4) instead of polymer (P1), an electrolyte membrane was obtained in the same manner as in Comparative Example 1. The thickness of the electrolyte membrane was 27 μm.

[0209] <Evaluation> The mechanical strength, proton conductivity, and swelling resistance of the electrolyte membranes of Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated by the following methods. The results are shown in Tables 1 and 2.

[0210] (Mechanical Strength Evaluation) An electrolyte membrane prepared in a dumbbell shape (JIS K 6251 type) was placed on a chuck in a thermo-hygrostat chamber of a precision universal testing machine (AG-X manufactured by Shimadzu Corporation) equipped with the thermo-hygrostat chamber. After holding the membrane at a temperature of 80°C and a relative humidity of 60°C for 3 hours, the membrane was pulled at a test speed of 10 mm / min, and the load relative to the strain was measured. The tensile stress was calculated by dividing the obtained load by the cross-sectional area of ​​the electrolyte membrane. The highest tensile stress value was defined as the maximum stress. An electrolyte membrane with a maximum stress of 50 MPa or more was evaluated as having excellent mechanical strength, and an electrolyte membrane with a maximum stress of 70 MPa or more was evaluated as having even better mechanical strength.

[0211] (Proton Conductivity Evaluation) A Teflon (registered trademark) measurement cell (BT-115, manufactured by Scribner) was prepared, and the electrolyte membrane was placed in the cell in contact with four platinum wires. After holding at 80°C and a relative humidity of 20% for 2 hours, the relative humidity was increased by 10% and then held for 30 minutes. This operation was continued until the relative humidity reached 100%, and then DC resistance measurement was performed using a four-terminal method at 100% relative humidity. From the obtained resistance value, the thickness of the electrolyte membrane, and the distance between the terminals, the proton conductivity in the in-plane direction of the electrolyte membrane in an environment of 80°C and 100% relative humidity was calculated. When the proton conductivity was 120 mS / cm or more, the electrolyte membrane was evaluated as having excellent proton conductivity.

[0212] (Swelling Resistance Evaluation) A 3 cm square membrane was punched out from the electrolyte membrane, and the punched membrane was immersed in 50 mL of pure water at 80° C. for 1 hour. The in-plane dimensions of the membrane were measured before and after immersion in pure water, and the membrane swelling ratio in the in-plane direction of the membrane was calculated by dividing the dimensional change before and after immersion by the dimension before immersion. When the membrane swelling ratio was 22% or less, the electrolyte membrane was evaluated to have excellent swelling resistance.

[0213]

[0214]

[0215] This application is based on a Japanese patent application (Patent Application No. 2024-154637) filed on September 9, 2024, the entire contents of which are incorporated herein by reference. In addition, all references cited herein are incorporated in their entirety.

[0216] 1... porous membrane, 2... pore, 3... filler containing hydrocarbon-based electrolyte polymer, 4... composite layer, 5... first electrolyte polymer layer, 6... second electrolyte polymer layer, 10A, 10B... electrolyte membrane.

Claims

1. A porous membrane formed of a material containing a hydrocarbon-based resin, and a hydrocarbon-based electrolyte polymer filled in the pores of the porous membrane, wherein the hydrocarbon-based electrolyte polymer is represented by the following formula (1): [In formula (1), A １ is represented by the following formula (a1): (In formula (a1), IExG represents an ion exchange group, and L ３ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, x represents an integer of 2 to 10, * represents a bond, a plurality of IExG may be the same or different, a plurality of L ３ may be the same or different from each other.) A represents a structural unit represented by the formula: ２ is represented by the following formula (a2): (In formula (a2), Ar represents an arylene group having no ion exchange group, and L ４ represents a single bond, —O—, —S—, or —SO ２ - or -CO-, y represents an integer of 3 to 20, * represents a bond, a plurality of Ar may be the same or different, a plurality of L ４ may be the same or different from each other.) １ and L ２ are each independently a single bond, —O—, —S— or —SO ２ -, n represents an integer of 10 to 100, * represents a bond. １ are identical to each other, and multiple A ２ are identical to each other, and multiple L １ may be the same or different, and multiple L ２ may be the same or different from each other.] 2. Said L １ and the L ２ The electrolyte membrane according to claim 1, wherein each independently represents a single bond, —O—, or —S—.

3. Said L ３ is a single bond or —SO ２ The electrolyte membrane according to claim 1 or 2, wherein 4. An electrolyte membrane according to any one of claims 1 to 3, wherein the structural unit represented by formula (a1) contains, as the ion exchange group, at least one group selected from the group consisting of a sulfonic acid group, an alkylsulfonic acid group, a sulfonimide group, and salts thereof.

5. An electrolyte membrane according to any one of claims 1 to 4, wherein the structural unit represented by formula (a2) contains, as the arylene group, at least one group selected from the group consisting of a phenylene group, a naphthylene group, and a fluorenylidene group, each of which may have a substituent.

6. The structural unit represented by the formula (a2) is a structural unit represented by the following formula (A2): [In formula (A2), Ar, L ４ and * are as defined above, and Q is a group represented by the following formula (a2-1): (In formula (a2-1), Ar and * have the same meanings as defined above. A plurality of Ars may be the same or different.) １ and y ２ Each of Ar's independently represents an integer of 2 to 4. A plurality of Ar's may be the same or different, and a plurality of L's may be the same or different. ４ The electrolyte membrane according to any one of claims 1 to 5, comprising a structural unit represented by the following formula:

7. The electrolyte membrane according to any one of claims 1 to 6, wherein the hydrocarbon-based electrolyte polymer has a weight-average molecular weight of 25,000 to 500,000.

8. The electrolyte membrane according to any one of claims 1 to 7, wherein the polydispersity of the hydrocarbon-based electrolyte polymer is 1.5 to 10.

0.

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

10. The electrolyte membrane according to any one of claims 1 to 9, wherein the hydrocarbon-based resin is a polyolefin-based resin.

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

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

13. A catalyst layer-equipped electrolyte membrane comprising the electrolyte membrane according to any one of claims 1 to 12 and a catalyst layer disposed on one or both sides of the electrolyte membrane.

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

15. A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 14.

16. A polymer electrolyte water electrolysis device comprising the membrane electrode assembly according to claim 14.

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