JP2018073810A - Polymer electrolyte membrane, method for manufacturing the same, membrane-electrode assembly including the same, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a polymer electrolyte membrane which develops high proton conductivity, which is improved in resistance against expansion, and which is superior in chemical stability; a method for manufacturing the polymer electrolyte membrane; and a membrane-electrode assembly including the polymer electrolyte membrane; and a fuel cell.SOLUTION: The present invention relates to a polymer electrolyte membrane comprising a copolymer having a plurality of aromatic rings in its main chain. The copolymer includes: a hydrophilic segment having a sulfonic group; and a hydrophobic segment substantially not having a sulfonic group. In the hydrophilic segment, the sulfonic group is directly coupled to the aromatic ring. In the polymer electrolyte membrane, the hydrophilic segment is bound to the hydrophobic segment by a carbon-carbon bond of the aromatic ring included in the hydrophilic segment, and the aromatic ring included in the hydrophobic segment; and the copolymer is crosslinked in a portion other than the sulfonic group.SELECTED DRAWING: None

Description

  The present invention relates to a polymer electrolyte membrane suitable for a solid polymer fuel cell, a production method thereof, a membrane / electrode assembly including the same, and a fuel cell.

  In recent years, development of highly efficient and clean energy sources has been demanded from the viewpoint of environmental problems such as global warming. Fuel cells are attracting attention as one candidate for that requirement. A fuel cell directly supplies power by supplying a fuel such as hydrogen gas or methanol and an oxidant such as oxygen to electrodes separated by an electrolyte, while oxidizing the fuel on the one hand and reducing the oxidant on the other. is there. Among the fuel cell materials described above, one of the most important materials is an electrolyte. Various types of electrolyte membranes have been developed so far to separate the electrolyte fuel and oxidant, and in recent years, the electrolyte membrane is composed of a polymer compound containing a proton conductive functional group such as a sulfonic acid group. The development of polymer electrolytes is thriving. In addition to the solid polymer fuel cell, such a polymer electrolyte is used as a raw material for electrochemical elements such as a humidity sensor, a gas sensor, and an electrochromic display element. Among these polymer electrolyte utilization methods, in particular, polymer electrolyte fuel cells are expected as one of the pillars of new energy technology. For example, a polymer electrolyte fuel cell using an electrolyte membrane made of a polymer compound having a proton-conducting functional group has features such as operation at a low temperature and reduction in size and weight. It has already been put to practical use in applications such as cogeneration systems for automobiles, and its application to consumer small portable devices and emergency power supplies is under consideration.

  As an electrolyte membrane used in a polymer electrolyte fuel cell, there is a polystyrene-based cation exchange membrane developed in the 1950s. However, the fuel cell has poor stability under a fuel cell operating environment and has a sufficient lifetime. Has not yet been manufactured. On the other hand, as an electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. Perfluorocarbon sulfonic acid membranes are said to have high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, Nafion (registered trademark) has a drawback that it is very expensive because it uses high raw materials and undergoes complicated manufacturing processes. In addition, it has been pointed out that it is deteriorated by hydrogen peroxide generated by the electrode reaction and by-product hydroxy radical. Furthermore, due to its structure, there is a limit to the introduction of sulfonic acid groups that are proton conducting groups.

  Against this background, the development of hydrocarbon electrolyte membranes has come to be expected. The reason for this is that the hydrocarbon-based electrolyte membrane is easy to have a variety of chemical structures, the range of introduction of proton conducting groups such as sulfonic acid groups can be adjusted widely, and it is relatively easy to combine with other materials. This is because there is a characteristic of being.

  In recent years, many examples have been reported in which proton conductivity is improved by introducing many sulfonic acid groups into an electrolyte membrane. Aromatic polymers such as polyethersulfone, polyphenylene sulfide, and polyetheretherketone have been studied as hydrocarbon polymers for introducing sulfonic acid groups. However, in these polymer electrolytes, since sulfonic acid groups are randomly introduced into the main chain, the swelling in the water-containing state is large, and the strength of the membrane is impaired by repeating the water-containing state and the dry state. There has been a problem in using it as an electrolyte membrane for fuel cells.

  In order to solve this problem, various block copolymers composed of a hydrophilic segment having a sulfonic acid group and a hydrophobic segment not having a sulfonic acid group have been studied, and the morphology in which the hydrophilic segment and the hydrophobic segment are phase-separated. Although the swelling resistance was improved by forming, the degree of improvement was limited.

  As a method for improving the mechanical strength of the hydrocarbon-based polymer electrolyte membrane in the swollen state, introduction of a crosslinked structure into the electrolyte resin has been studied. In Patent Document 1, a polymer electrolyte composed of a block having a proton acid group and a block having no proton acid group and having an alkyl group on an aromatic ring is introduced with a cross-linked structure by irradiating with ultraviolet rays, thereby absorbing water. It has been proposed to obtain a polymer electrolyte membrane with low rate and methanol permeability. Patent Document 2 proposes a crosslinked polymer electrolyte membrane obtained by crosslinking a proton conductive polymer and a crosslinking agent at a portion other than the proton acid group.

JP 2007-31573 A JP 2010-103079 A

  However, in Patent Document 1, the polymer electrolyte is a block in which a block having a proton acid group and a block having no proton acid group are connected by an ether bond. There is concern about stability. In Patent Document 2, the polymer electrolyte is obtained by sulfonating polyethersulfone or polyphenylene sulfide, and sulfonic acid groups are randomly introduced. Moreover, since an ether bond exists in the vicinity of the sulfonic acid group, there is still a concern about chemical stability.

  The present invention provides a polymer electrolyte membrane that exhibits high proton conductivity, improved swelling resistance, and excellent chemical stability, a method for producing the same, and a membrane / electrode assembly including the same and a fuel cell. .

  The present invention provides a polymer electrolyte membrane comprising a copolymer having a plurality of aromatic rings in the main chain, wherein the copolymer substantially comprises a hydrophilic segment having a sulfonic acid group and a sulfonic acid group. In the hydrophilic segment, the sulfonic acid group is directly bonded to an aromatic ring, and the hydrophilic segment and the hydrophobic segment are aromatic components constituting the hydrophilic segment. The present invention relates to a polymer electrolyte membrane characterized in that it is connected to a ring by a carbon-carbon bond of an aromatic ring constituting the hydrophobic segment, and the copolymer is crosslinked at a portion other than a sulfonic acid group. .

  The present invention also relates to a method for producing the above-described polymer electrolyte membrane, wherein a precursor of a hydrophilic segment having a sulfonic acid group directly bonded to an aromatic ring, and a hydrophobic having substantially no sulfonic acid group The segment precursor is subjected to a carbon-carbon bond formation reaction so that the aromatic ring of the hydrophilic segment precursor and the aromatic ring of the hydrophobic segment precursor are carbon-carbon bonded, and the hydrophilic segment and the hydrophobic segment. The polymer electrolyte is obtained by obtaining a copolymer having a plurality of aromatic rings in the main chain and then crosslinking the hydrophobic segment in the copolymer with a crosslinking agent and / or a crosslinking catalyst. The present invention relates to a film manufacturing method.

  The present invention also relates to a method for producing the above-described polymer electrolyte membrane, wherein a precursor of a hydrophilic segment having a sulfonic acid group directly bonded to an aromatic ring, and a hydrophobic having substantially no sulfonic acid group The segment precursor is subjected to a carbon-carbon bond formation reaction so that the aromatic ring of the hydrophilic segment precursor and the aromatic ring of the hydrophobic segment precursor are carbon-carbon bonded, and the hydrophilic segment and the hydrophobic segment. After obtaining a copolymer having a plurality of aromatic rings in the main chain, the copolymer is heated to crosslink portions other than the sulfonic acid groups in the copolymer. The present invention relates to a method for producing a polymer electrolyte membrane.

  The present invention also relates to a membrane / electrode assembly comprising the polymer electrolyte membrane.

  The present invention also relates to a fuel cell comprising the polymer electrolyte membrane.

  According to the present invention, a polymer electrolyte membrane that exhibits high proton conductivity, improved swelling resistance, and excellent chemical stability, a method for producing the same, and a membrane / electrode assembly including the same and a fuel cell are provided. Can be provided.

2 is a graph comparing the proton conductivity of the polymer electrolyte membrane of Example 1 and the polymer electrolyte membrane of Comparative Example 1. FIG. 4 is a graph comparing the proton conductivity of the polymer electrolyte membranes of Examples 2 and 3 and the polymer electrolyte membrane of Comparative Example 2. FIG. 6 is a graph comparing the proton conductivity of the polymer electrolyte membrane of Example 4 and the polymer electrolyte membrane of Comparative Example 3. FIG.

  As a result of intensive studies to solve the above problems, the inventors of the present invention, in a polymer electrolyte membrane comprising a copolymer composed of a hydrophilic segment and a hydrophobic segment and having a plurality of aromatic rings in the main chain, The hydrophilic segment has a sulfonic acid group, the sulfonic acid group is directly bonded to an aromatic ring, the hydrophobic segment is substantially free of a sulfonic acid group, and the hydrophilic segment and the The hydrophobic segment is connected to the aromatic ring constituting the hydrophilic segment and the carbon-carbon bond of the aromatic ring constituting the hydrophobic segment, and the copolymer is crosslinked at a portion other than the sulfonic acid group. As a result, it was found that high proton conductivity was exhibited, the swelling resistance was improved, and the chemical stability was excellent, and the present invention was completed.

  The polymer electrolyte membrane of the present invention is composed of a hydrophilic segment having a sulfonic acid group and a hydrophobic segment having substantially no sulfonic acid group and having an aromatic ring in the main chain (in the following, The copolymer is crosslinked at a portion other than the sulfonic acid group, and the copolymer has a hydrophilic segment having a sulfonic acid group and a sulfonic acid group. The hydrophobic segment that does not substantially contain is connected to the aromatic ring constituting the hydrophilic segment and the carbon-carbon bond of the aromatic ring constituting the hydrophobic segment. By adopting such a structure, there is no hetero bond such as an ether bond or a sulfide bond in the vicinity of the sulfonic acid group, and the durability of the polymer electrolyte membrane against peroxide, that is, chemical under fuel cell operating conditions. Increases durability.

  In the present invention, examples of the aromatic ring include benzene, naphthalene, anthracene, biphenyl, aromatic heterocycles containing sulfur, nitrogen and the like. When the main chain has an aromatic ring, chemical and thermal stability is high.

  The hydrophilic segment has a main chain mainly composed of an aromatic ring and a sulfonic acid group. Here, “the main chain is mainly composed of an aromatic ring” means that the molecular weight of the portion other than the main chain linking group (ether group, thioether group, sulfone group, ketone group, sulfide group, etc.) in the hydrophilic segment is 100. % Means that 70% or more of them are composed of aromatic rings. When the main chain is mainly composed of an aromatic ring, chemical and thermal stability is high.

  The structure of the hydrophilic segment is not particularly limited as long as the aromatic ring of the hydrophilic segment and the aromatic ring of the hydrophobic segment are connected by a carbon-carbon bond. It is preferable to have at least one structure represented by the following general formula group (1) as a repeating unit from the viewpoint of easy carbon-carbon bond formation, high sulfonic acid group density, and availability. . The hydrophilic segment is preferably formed by using a hydrophilic segment precursor having a sulfonic acid group directly bonded to an aromatic ring and copolymerizing with a hydrophobic segment precursor described later. In the present invention, the hydrophilic segment precursor refers to a repeating unit having a reactive site, which becomes a hydrophilic segment by a copolymerization reaction described later, and the hydrophobic segment precursor is a copolymerization reaction described later. This means a repeating unit having a reactive site that becomes a hydrophobic segment. The precursor of the hydrophilic segment has an aromatic ring and a sulfonic acid group directly bonded to the aromatic ring.

（式中、ｕは１〜４の整数、ｋ、ｌは０〜４の整数を表し、ｋ＋ｌは１以上の整数である。ｐは０〜１０の整数、ｑは０〜１０の整数、ｒは１〜４の整数を表す。Ｘは、−ＣＯ−、−ＳＯ₂−、−Ｃ（ＣＦ₃）₂−からなる群より選ばれた少なくとも１種の構造を表す。Ｙは、−ＣＯ−、−ＳＯ₂−、−ＳＯ−、−ＣＯＮＨ−、−ＣＯＯ−、−（ＣＦ₂）_t−（ｔは１〜１０の整数）、−Ｃ（ＣＦ₃）₂−からなる群より選ばれた少なくとも１種の構造を表し、Ｚは直接結合又は、−（ＣＨ₂）_o−（ｏは１〜１０の整数）、−Ｃ（ＣＨ₃）₂−、−Ｏ−、−Ｓ−からなる群より選ばれた少なくとも１種の構造を表す。Ａｒ¹は、−ＳＯ₃Ｈ又は−Ｏ（ＣＨ₂）_sＳＯ₃Ｈ（ｓは１〜１２の整数）で表される置換基を有する芳香族基を表す。）

(In the formula, u represents an integer of 1 to 4, k and l represent an integer of 0 to 4, k + 1 represents an integer of 1 or more, p represents an integer of 0 to 10, q represents an integer of 0 to 10, r Represents an integer of 1 to 4. X represents at least one structure selected from the group consisting of —CO—, —SO ₂ —, and —C (CF ₃ ) ₂ —, and Y represents —CO—. , —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _t — (t is an integer of 1 to 10), —C (CF ₃ ) ₂ —. Represents at least one structure, and Z is a direct bond or a group consisting of — (CH ₂ ) _o — (o is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O—, —S—. Ar ¹ represents an aromatic having a substituent represented by —SO ₃ H or —O (CH ₂ ) _S SO ₃ H (s is an integer of 1 to 12). Represents a group.

  By using a copolymer composed of a hydrophilic segment having a sulfonic acid group as described above and a hydrophobic segment having substantially no sulfonic acid group, which will be described later, the morphology of the polymer electrolyte membrane is microscopic. Since a phase separation structure is formed and the hydrophilic segment forms a continuous proton conduction path, proton conductivity, particularly proton conductivity under low humidification is improved.

  Since the hydrophilic segment has a sulfonic acid group, the proton conductivity of the polymer electrolyte membrane is expressed, and the main chain of the hydrophilic segment is mainly composed of an aromatic ring, so the polymer electrolyte is heat resistant and chemically durable. It will be excellent.

  In the embodiment of the present invention, examples of the sulfonic acid group include a sulfonic acid group, a sulfonate group, a sulfonic acid ester group, and the like. That is, the sulfonic acid group may be a salt such as sodium or potassium, or may be protected with an ester group such as neopentyl ester, methyl ester or propyl ester. In particular, during the synthesis of the copolymer or the formation of the polymer electrolyte membrane, it is often preferable to have a protective group such as a salt or an ester group. When used as an electrolyte membrane, it is often used after being converted into a sulfonic acid group by immersing in an aqueous solution of an inorganic acid. Therefore, in the embodiment of the present invention, the sulfonic acid group includes a group having a protective group such as a salt or an ester as long as it is a group that easily becomes a sulfonic acid group.

  The amount of the sulfonic acid group is preferably 1 to 6 and more preferably 1 to 4 per repeating unit forming the hydrophilic segment. When the amount of the sulfonic acid group is more than 6, the hydrophilicity of the hydrophilic segment becomes high and handling during synthesis tends to be difficult. When the amount of the sulfonic acid group is less than one, sufficient proton conductivity tends to be hardly exhibited.

  As the hydrophilic segment exemplified above, a commercially available product can be used as it is, or it can be obtained by sulfonating a corresponding aromatic compound with a sulfonating agent.

  Examples of the sulfonating agent include chlorosulfonic acid, sulfuric anhydride, fuming sulfuric acid, sulfuric acid, acetyl sulfuric acid and the like. Chlorosulfonic acid and fuming sulfuric acid are preferable because they have appropriate reactivity.

  In the sulfonation reaction, a solvent may or may not be used. In the case of using a solvent, the solvent is not particularly limited as long as it is inert with respect to the sulfonated agent, and examples thereof include hydrocarbon solvents and halogenated hydrocarbons. Examples of the hydrocarbon solvent include saturated aliphatic hydrocarbons, and linear or branched hydrocarbons having 5 to 15 carbon atoms are particularly preferable. From the viewpoint of solubility, pentane, hexane, heptane, octane and decane are preferable. More preferred. Examples of halogenated hydrocarbons include halogenated saturated aliphatic hydrocarbons and halogenated aromatic hydrocarbons. Examples of the halogenated saturated aliphatic hydrocarbon include monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, dichloroethane, trichloroethane, tetrachloroethane, and the like. Dichloromethane is preferable because of easy handling. Examples of the halogenated aromatic hydrocarbon include chlorobenzene, dichlorobenzene, trichlorobenzene, and the like, and chlorobenzene is preferable because of easy handling.

  The reaction temperature of the sulfonation process may be set as appropriate according to the reaction, specifically, it may be set to −80 ° C. to 200 ° C. which is the optimum use range of the sulfonation agent, more preferably −50 ° C. It is 150 degreeC, More preferably, it is -20 degreeC-130 degreeC. When the temperature is lower than −80 ° C., the reaction is slow, and the target sulfonation tends not to proceed to 100%. When the temperature is higher than 200 ° C., side reaction tends to occur.

  The reaction time of the sulfonation step can be appropriately selected depending on the structure of the aromatic compound to be sulfonated, but it is usually sufficient if it is within the range of about 1 minute to 50 hours. When it is shorter than 1 minute, uniform sulfonation tends not to proceed, and when it is longer than 50 hours, side reaction tends to occur.

  The addition amount of the sulfonated agent in the sulfonation process is preferably 1 equivalent to 50 equivalents when the total amount of the sulfonated aromatic compound is 1 equivalent. When the amount is less than 1 equivalent, the sulfonated site tends to be non-uniform, while when it exceeds 50 equivalents, the sulfonated aromatic compound main chain tends to be cleaved.

  The concentration of the aromatic compound in the sulfonating step is not particularly limited as long as the reaction proceeds uniformly when brought into contact with the sulfonating agent, but the aromatic compound does not cause side reactions such as low molecular weight, and the solvent. From the viewpoint of cost advantage due to the suppression of the amount, it is preferably 1 to 30% by weight based on the weight of the whole compound used in the sulfonation reaction.

  The ion exchange capacity of only the hydrophilic segment (hereinafter, the ion exchange capacity may be referred to as IEC) can be set to high IEC as a polymer electrolyte membrane, and express high proton conductivity under low humidification. 4.0 meq. / G or more is preferable. In the present invention, the IEC of the hydrophilic segment is determined by dividing the IEC of the polymer electrolyte membrane (which is easily determined by a conventionally known method such as titration) by the weight ratio of the hydrophilic segment. That is, the IEC of the hydrophilic segment is obtained by dividing the IEC of the polymer electrolyte obtained in the same manner as the IEC measurement method of the polymer electrolyte membrane described in the examples by the weight ratio of the hydrophilic segment. meq. / G means milliequivalent / g.

  When the structure represented by the general formula group (1) is specifically exemplified as the repeating unit forming the hydrophilic segment, a structure represented by the following chemical formula group (2) may be mentioned.

  In order to connect a hydrophilic segment to a hydrophobic segment by a carbon-carbon bond between aromatic rings, a precursor of a hydrophilic segment (having a reactive site that reacts with a precursor of a hydrophobic segment to form a hydrophilic segment) The compound preferably has halogen as a reactive site. The precursor of the hydrophilic segment preferably has an aromatic ring and a sulfonic acid group directly bonded to the aromatic ring, and has a halogen on the aromatic ring. Specific examples of such compounds include those having a structure represented by the following chemical formula group (3).

（式中、Ｈａｌはハロゲンを表す）

(In the formula, Hal represents halogen)

  In the chemical formula group (3), examples of the halogen include fluorine, chlorine, bromine, and iodine. Chlorine, bromine, and iodine are preferable because of high reactivity, and chlorine is particularly preferable because of high availability.

  In the polymer electrolyte membrane of the present invention, the hydrophobic segment has substantially no sulfonic acid group. Thereby, phase separation from the hydrophilic segment is clarified, the proton conductivity of the polymer electrolyte membrane under low humidity is improved, and the strength of the polymer electrolyte membrane is improved. In the present invention, “substantially having no sulfonic acid group” means that the hydrophobic segment has no sulfonic acid group or the number of sulfonic acid groups per repeating unit in the hydrophobic segment is hydrophilic. It means 1/10 or less of the number of sulfonic acid groups per repeating unit in the segment. From the viewpoint of further improving the proton conductivity of the polymer electrolyte membrane under low humidification and further increasing the strength of the polymer electrolyte membrane, it is preferable that the sulfonic acid group is not introduced at all in the hydrophobic segment.

  The hydrophobic segment has a main chain mainly composed of an aromatic ring. Here, “the main chain is mainly composed of an aromatic ring” means that the molecular weight of the portion other than the linking group (ether group, thioether group, sulfone group, ketone group, sulfide group, etc.) of the main chain in the hydrophobic segment is 100. % Means that 70% or more of them are composed of aromatic rings. When the main chain is mainly composed of an aromatic ring, chemical and thermal stability is high. From the viewpoint of heat resistance, a structure in which the main chain such as polyimide, polybenzimidazole, polyether or polyphenylene is mainly composed of an aromatic ring is preferred, and the main chain such as polyether or polyphenylene is mainly aromatic. A structure composed of a ring is more preferable from the viewpoint of ease of synthesis. Although it does not specifically limit as said hydrophobic segment, It is preferable to have at least 1 of the structure represented by the following general formula group (4) as a repeating unit.

（式中、Ａｒは２価の芳香族基を表し、ｎは１〜５０の整数を表す。ａ,ｂ,ｃは０〜５０の整数を表し、但し、２≦ａ＋ｂ＋ｃ≦５０を満足する。）

(In the formula, Ar represents a divalent aromatic group, n represents an integer of 1 to 50, a, b, and c represent an integer of 0 to 50, provided that 2 ≦ a + b + c ≦ 50 is satisfied. )

  In the hydrophobic segment, when the repeating unit having the structure represented by the general formula group (4) is repeated a plurality of times, the plurality of Ars may be the same as or different from each other. Preferred examples of the divalent aromatic group for Ar include a group having any structure represented by the following chemical formula group (5).

  In addition, the divalent aromatic group of Ar may have one or more substituents, and when it has two or more substituents, the plurality of substituents may be the same as each other. May be different. As said substituent, a C1-C6 alkyl group, a C1-C6 alkoxy group, a phenyl group, a cyano group etc. are mentioned, for example. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, and a hexyloxy group.

  As for the monomer which comprises the repeating unit in the said hydrophobic segment, the monomer etc. which can comprise the structure represented by the said General formula group (4) are mentioned, for example. Specifically, a monomer having a structure represented by the following chemical formula group (6) is preferably exemplified.

  Moreover, what has a thiol group instead of the hydroxyl group of the compound which has said phenolic hydroxyl group can be used suitably as a monomer which comprises the repeating unit in the said hydrophobic segment.

  In order to synthesize the precursor of the hydrophobic segment using the above monomer, a known method may be used. For example, a method of polycondensing a monomer having a nucleophilic substituent such as a hydroxyl group or a thiol group and another monomer having a leaving group such as halogen can be used. Specific reaction conditions for synthesizing the precursor of the hydrophobic segment are as described later.

  In order to connect a hydrophobic segment to a hydrophilic segment by a carbon-carbon bond between aromatic rings, in the above polycondensation reaction, a monomer having halogen is compared with a monomer having a nucleophilic substituent such as a hydroxyl group. It is preferred to use an excess, synthesize a precursor of a hydrophobic segment having a halogen at the terminal, and react with the precursor of a hydrophilic segment containing a halogen described above, as described later. The precursor of the hydrophobic segment preferably has an aromatic ring, has substantially no sulfonic acid group, and has a halogen at the terminal.

  Examples of the precursor of the hydrophobic segment having a halogen at the terminal include compounds having at least one structure represented by the following general formula group (7).

（式中、Ａｒは２価の芳香族基を表し、Ｈａｌはハロゲンを表す。ｎは１〜５０の整数を表し、ａ,ｂ,ｃは０〜５０の整数を表し、但し、２≦ａ＋ｂ＋ｃ≦５０を満足する。）

(In the formula, Ar represents a divalent aromatic group, Hal represents halogen, n represents an integer of 1 to 50, a, b, and c represent integers of 0 to 50, provided that 2 ≦ a + b + c. ≦ 50 is satisfied.)

  In the general formula group (7), examples of the halogen include fluorine, chlorine, bromine, and iodine. Chlorine, bromine, and iodine are preferable because of high reactivity, and chlorine is particularly preferable because of high availability.

  In the copolymer, the hydrophobic segment preferably has a crosslinkable functional group from the viewpoint of increasing the crosslink efficiency at a portion other than the sulfonic acid. The crosslinkable functional group reacts in the presence of a crosslinking agent and / or a crosslinking catalyst or in the absence of a crosslinking agent and a crosslinking catalyst under heating, moisture absorption, irradiation of ionizing radiation such as ultraviolet rays and electron beams, and the like. A bridge structure is formed between sex segments. The kind of the crosslinkable functional group is not particularly limited, and known ones can be used. Examples include alcoholic hydroxyl groups, phenolic hydroxyl groups, amino groups, carboxyl groups, alkenyl groups, acryloyl groups, methacryloyl groups, epoxy groups, phenyl groups, hydrolyzable silyl groups, and the like. The hydrophobic segment may contain one kind of these crosslinkable functional groups, or may contain two or more kinds.

  The precursor of the hydrophobic segment having a crosslinkable functional group is not particularly limited. For example, from the viewpoint of controlling the introduction position and amount of the crosslinkable functional group, a monomer having a crosslinkable functional group is polymerized with another monomer. It is preferable that it is obtained. Further, by using a precursor oligomerized in advance in this manner, it has a phase separation structure in which a hydrophilic segment and a hydrophobic segment are developed, and is further preferable because the strength when a polymer electrolyte membrane is obtained is improved. .

  It does not specifically limit as a monomer which has a crosslinkable functional group, A various thing can be used. For example, a compound having a structure represented by the following chemical formula group (8) can be used.

  Although there is no limitation in particular as a monomer copolymerized with a crosslinkable functional group containing monomer, For example, the monomer etc. which have a structure represented by following Chemical formula group (6) are mentioned preferably.

  A known method may be used to copolymerize the crosslinkable functional group-containing monomer and other monomers to produce a precursor of the hydrophobic segment. For example, a method of polycondensing a crosslinkable functional group-containing monomer having a nucleophilic substituent such as a hydroxyl group or a thiol group and another monomer having a leaving group such as a halogen can be mentioned.

In the present invention, a crosslinkable functional group-containing monomer having a nucleophilic substituent such as a hydroxyl group or a thiol group, or a monomer having a nucleophilic substituent such as a hydroxyl group or a thiol group, and another group having a leaving group such as halogen. When a monomer is polymerized to produce a hydrophobic segment precursor, a basic compound is usually used to accelerate the polymerization reaction. As the basic compound, for example, alkali metal salts, alkaline earth metal salts and the like are preferably used. Specifically, LiOH, NaOH, KOH, Li ₂ CO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , LiHCO ₃ , NaHCO ₃ , KHCO _{3 and the} like can be mentioned. The polycondensation reaction may be performed in a molten state without using a solvent, and is preferably performed in a suitable solvent from the viewpoint of increasing the reaction efficiency. As the solvent, those that dissolve both the reactant (monomer) and the polymer to be produced are preferable. Specific examples include aromatic hydrocarbon solvents, halogen solvents, ether solvents, ketone solvents, amide solvents. , Sulfone solvents, sulfoxide solvents and the like. Among them, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dichlorobenzene, trichlorobenzene, etc. Halogen solvents and sulfoxide solvents such as dimethyl sulfoxide are preferred. These solvents may be used alone or in combination of two or more. The reaction temperature of the polycondensation may be appropriately set according to the reactivity of the monomer used, and is preferably 20 ° C to 250 ° C, more preferably 40 to 200 ° C. If the temperature is too low, the reaction rate may be slow, and if the temperature is too high, the main chain may be cleaved. In order to accelerate the polymerization reaction, it is preferable to discharge the by-product water out of the system. In that case, a method of adding a small amount of toluene or the like as a cosolvent and performing azeotropic dehydration is used.

  One type of monomer may be copolymerized with the monomer having a crosslinkable functional group, or two or more types may be used in order to control the amount of the crosslinkable functional group introduced.

  In order to connect a hydrophobic segment to a hydrophilic segment by a carbon-carbon bond between aromatic rings, in the above polycondensation reaction, a monomer having halogen is compared with a monomer having a nucleophilic substituent such as a hydroxyl group. It is preferred to use an excess, synthesize a precursor of a hydrophobic segment having a halogen at the terminal, and react with the precursor of a hydrophilic segment containing a halogen described above, as described later.

  As the precursor of the hydrophobic segment having a crosslinkable functional group, there are many types depending on the combination of monomers used. From the viewpoint of availability of monomers, the precursor is represented by the following general formula group (9). Those having at least one structure are preferred. In addition, since the compound having at least one structure represented by the following general formula group (9) has a halogen at the terminal, the hydrophobic segment is connected to the hydrophilic segment by a carbon-carbon bond between aromatic rings. It is suitable for.

（式中、ｍは1〜５０の整数、ｎは１〜５０の整数である。Ｈａｌはハロゲンを表す。）

(In the formula, m is an integer of 1 to 50, and n is an integer of 1 to 50. Hal represents halogen.)

  In the general formula group (9), examples of the halogen include fluorine, chlorine, bromine, and iodine. Chlorine, bromine, and iodine are preferable because of high reactivity, and chlorine is particularly preferable because of high availability.

  In the present invention, the molecular weight of the precursor of the hydrophobic segment varies depending on its chemical structure, ease of synthesis, etc., but the number average molecular weight is preferably 700 to 30,000, more preferably 2000 to 10,000. If it is smaller than 700, the strength of the polymer electrolyte membrane tends to be low, and if it is larger than 30,000, synthesis of the polymer electrolyte membrane tends to be difficult due to problems such as solubility.

  In the present invention, when a precursor having at least one structure represented by the general formula group (9) is used as a precursor of the hydrophobic segment, the hydrophobic segment is represented by the following general formula group (10). It has a repeating unit having at least one structure.

（式中、ｍは１〜５０の整数、ｎは１〜５０の整数である。）

(In the formula, m is an integer of 1 to 50, and n is an integer of 1 to 50.)

  In the present invention, the crosslinkable functional group is preferably more than one per molecule of the copolymer. If it is 1 or less, there is a possibility that the crosslinking is difficult to proceed. In the present invention, in order to introduce more than one crosslinkable functional group per copolymer molecule, more than one crosslinkable functional group is introduced into the hydrophobic segment per copolymer molecule. It is preferable.

  The copolymer constituting the polymer electrolyte membrane of the present invention can be obtained by linking a hydrophilic segment precursor and a hydrophobic segment precursor with a carbon-carbon bond between aromatic rings. As described above, preferred hydrophilic segment precursors and hydrophobic segment precursors have halogen, particularly chlorine as a reactive site. As such a linking method, it is preferable to use a known method, that is, a carbon-carbon bond forming reaction using a transition metal compound.

  As the transition metal compound, nickel compounds, palladium compounds, and copper compounds are preferably used, and nickel compounds are more preferably used. As the nickel compound, zerovalent nickel complexes such as bis (1,5-cyclooctadiene) nickel and tetrakistriphenylphosphine nickel are preferably used. Further, a divalent nickel complex such as nickel chloride, nickel bromide, dichlorobistriphenylphosphine nickel or the like may be used in the presence of a reducing agent such as zinc. Further, when using a nickel-based compound, it is preferable to use a ligand such as 2,2'-bipyridyl because the carbon-carbon bond forming activity is improved.

  Examples of the solvent used for the carbon-carbon bond formation reaction include aromatic hydrocarbon solvents, halogen solvents, ether solvents, ketone solvents, amide solvents, sulfone solvents, sulfoxide solvents, and the like. Amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone from the viewpoint of dissolving both substances and products Halogen solvents such as dichlorobenzene and trichlorobenzene, and sulfoxide solvents such as dimethyl sulfoxide are preferred. These solvents may be used alone or in combination of two or more. What is necessary is just to set reaction temperature suitably, It is preferable that it is 20 to 200 degreeC, More preferably, it is 40 to 150 degreeC. If it is lower than 20 ° C, the reaction rate is slow, and if it is higher than 200 ° C, the main chain may be cleaved.

  Since the zerovalent nickel complex is unstable in water, the reaction system is preferably dehydrated. In addition to using a previously dehydrated solvent as a raw material, azeotropic dehydration using an azeotropic solvent such as toluene before addition of the zerovalent nickel compound is easy to operate and is preferably used. The reaction is preferably performed in an inert gas atmosphere.

  The time required for the carbon-carbon bond formation reaction is not particularly limited, but is preferably 10 minutes to 10 hours, and more preferably 30 minutes to 3 hours. If it is shorter than 10 minutes, the reaction may not be completed, and if it is longer than 10 hours, productivity is unnecessarily lowered.

  The molecular weight of the copolymer (polymer electrolyte A) is preferably 10,000 to 300,000 in terms of number average molecular weight, and more preferably 30,000 to 150,000 in terms of the balance between ease of synthesis and solubility in a solvent. . If the number average molecular weight is less than 10,000, the amount of sulfonic acid groups introduced is low, and sufficient proton conductivity tends to be not obtained or the strength as a membrane tends to be insufficient. When the number average molecular weight exceeds 300,000, handling tends to be difficult, for example, solubility in a solvent is lowered. The molecular weights of the oligomers such as the precursor of the hydrophobic segment and the polymer electrolyte can be determined by the measurement methods described in the examples.

  In the present invention, the IEC of the polymer electrolyte A is 1.5 to 3.5 meq. / G in order to express sufficiently high proton conductivity, preferably 1.6 to 3.0 meq. / G is more preferable because it provides an excellent balance between proton conductivity and mechanical strength under low humidification. IEC is 1.5 meq. If it is less than / g, the proton conductivity of the polymer electrolyte membrane tends to be low, and 3.5 meq. When it is larger than / g, mechanical strength decreases due to swelling with water, and it tends to be difficult to have sufficient strength. In the present invention, the ion exchange capacity of the polymer electrolyte A can be determined in the same manner as in the method for measuring the ion exchange capacity of the polymer electrolyte membrane described in the Examples.

  Subsequently, a polymer electrolyte membrane can be obtained by crosslinking the copolymer at a portion other than the sulfonic acid group. In the present invention, the polymer electrolyte membrane is composed of a crosslinked copolymer obtained by crosslinking the copolymer.

  In the copolymer, when the hydrophobic segment has a crosslinkable functional group, the polymer electrolyte membrane of the present invention is obtained by crosslinking using a suitable crosslinking method according to the type of the crosslinkable functional group. Can do. Depending on the type of the crosslinkable functional group, the hydrophobic segment can be crosslinked using a crosslinking agent and / or a crosslinking catalyst. Depending on the type of the crosslinkable functional group, neither the crosslinking agent nor the crosslinking catalyst may be used.

  When the crosslinkable functional group is an alcoholic hydroxyl group or a phenolic hydroxyl group, as the crosslinking agent, a compound having an isocyanate group, a compound having an epoxy group, or the like is preferably used.

  The compound having an isocyanate group is not particularly limited, and known compounds can be used. Specific examples include diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophoroin diisocyanate, blocked isocyanate and the like.

  The compound having an epoxy group is not particularly limited, and known compounds can be used. Specific examples include bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins, glycidyl ether type epoxy resins of bisphenol A propylene oxide adducts, hydrogenated bisphenol A type epoxy resins, and the like.

  When the crosslinkable functional group is an amino group, a compound having an isocyanate group, a compound having an epoxy group, or the like is used as a crosslinking agent. Specific examples of the compound having an isocyanate group and the compound having an epoxy group are as described above.

  When the crosslinkable functional group is a carboxyl group, a compound having an epoxy group, a compound having an isocyanate group, or the like is used as a crosslinking agent. Specific examples of the compound having an epoxy group and the compound having an isocyanate group are as described above.

  When the crosslinkable functional group is an alkenyl group, various radical initiators can be used for crosslinking, and a compound having a hydrosilyl group may be used together with a transition metal catalyst such as chloroplatinic acid. Furthermore, you may use ionizing radiations, such as an electron beam and an ultraviolet-ray.

  The radical initiator is not particularly limited, and known ones can be used. Specific examples include di-tert-butyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, benzoyl peroxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvalero). Nitrile), 2,2′-azobis (2-methylbutyronitrile), and the like.

  Specific examples of the compound having a hydrosilyl group include 1,3,5-trimethylcyclotrisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, polymethylhydrogenpolysiloxane, and the like.

  When the crosslinkable functional group is an acryloyl group or a methacryloyl group, the above-mentioned various radical initiators can be used, and crosslinking can also be performed by irradiating ultraviolet rays in the presence of a photopolymerization initiator.

  Specific examples of the photopolymerization initiator include benzophenone, o-benzoylbenzoic acid, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide. 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, bis (2,4,6-trimethyl) phenylphosphine oxide, and the like.

  When the crosslinkable functional group is an epoxy group, a compound having a carboxyl group or the like can be used as a crosslinking agent. Moreover, it can also bridge | crosslink under ultraviolet irradiation using a photo-acid generator.

  Examples of the compound having a carboxyl group include phthalic acid, 1,3-benzenedicarboxylic acid, terephthalic acid, 1,3,5-benzenetricarboxylic acid, 4,4′-oxybisbenzoic acid, and 4,4′-thiobisbenzoic acid. An acid etc. are mentioned.

  Examples of the photoacid generator include bis (cyclohexylsulfonyl) diazomethane, bis (tert-butylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, triphenylsulfonium trifluoromethanesulfonate, diphenyl-4-methylphenyl Examples thereof include sulfonium trifluoromethane sulfonate.

  When the crosslinkable functional group is a phenyl group, the crosslinking can be advanced by a Friedel-Crafts reaction using a compound having a carboxyl group.

  Specific examples of the compound having a carboxyl group are as described above. The Friedel-Crafts reaction usually proceeds in the presence of a Lewis acid, but the polymer electrolyte membrane in the present invention has a sulfonic acid group, which serves as an autocatalyst, so that it is not always necessary to add the Lewis acid. .

  When the crosslinkable functional group is a hydrolyzable silyl group, a tetravalent tin compound, a divalent tin compound, or the like is used as a hydrolysis condensation catalyst. Specific examples of the tetravalent tin compound include dibutyltin bis (acetylacetonate), dioctyltin bis (acetylacetonate), dimethyltin bis (acetylacetonate), and dibutyltin dimethoxide. Specific examples of the divalent tin compound include tin dibutanoate, tin dioctylate, and tin dodecanoate. When a divalent tin compound is used, it is preferable to use an amine compound such as octylamine or dodecylamine in combination because the catalytic activity is improved.

  In the present invention, when the hydrophobic segment has a crosslinkable functional group, the method for producing the polymer electrolyte membrane is not particularly limited, but a solution of a copolymer in which the hydrophobic segment has a crosslinkable functional group is prepared. In addition, there is a method of adding a cross-linking agent and / or a cross-linking catalyst as necessary, casting on a substrate such as a glass plate, removing the solvent (or while removing it), and applying a stimulus such as heating or ultraviolet irradiation. It is preferable because a uniform film thickness can be obtained. A polyethylene terephthalate (PET) film or the like may be attached to the glass plate. Examples of the solvent used for preparing the solution of the copolymer having a crosslinkable functional group in the hydrophobic segment include dimethyl sulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2- Examples include imidazolidinone and N-methylpyrrolidone. The removal of the solvent is preferably performed by drying at a temperature of 10 to 150 ° C, more preferably 40 to 130 ° C. When crosslinking proceeds by heating, the copolymer is crosslinked simultaneously with the removal of the solvent, and a polymer electrolyte membrane is obtained.

  When the hydrophobic segment does not have a crosslinkable functional group, the copolymer is heated to crosslink the copolymer at a portion other than the sulfonic acid group. In this method, a polymer electrolyte membrane composed of a crosslinked copolymer can be obtained by crosslinking a copolymer only by heating without using a crosslinking agent and / or a crosslinking catalyst.

  In the present invention, when the hydrophobic segment does not have a crosslinkable functional group, the method for producing the polymer electrolyte membrane is not particularly limited, but a copolymer solution in which the hydrophobic segment does not have a crosslinkable functional group is prepared. A method of heating after removing the solvent (or while removing it) on a substrate such as a glass plate is preferable because a uniform film thickness can be obtained. A polyethylene terephthalate (PET) film or the like may be attached to the glass plate. Examples of the solvent used when the copolymer is used as a solution include dimethyl sulfoxide, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, and N-methyl. Examples include pyrrolidone and the like. The removal of the solvent is preferably performed by drying at a temperature of 10 to 150 ° C, more preferably 40 to 130 ° C.

  After removing the solvent, the crosslinking reaction is performed by further heating. It is preferable that the temperature at the time of bridge | crosslinking is the range of 80 to 200 degreeC, and 100 to 180 degreeC is more preferable. If it is less than 80 degreeC, bridge | crosslinking does not fully advance, and when it exceeds 200 degreeC, electrolyte may decompose | disassemble. In addition, when removing a solvent at 80 degreeC or more, although crosslinking also advances with the removal of a solvent, after removing a solvent, it is preferable to accelerate | stimulate a crosslinking reaction by the heating bridge | crosslinking on the conditions which raised temperature.

  The heat crosslinking is preferably performed under reduced pressure because a trace amount of the solvent remaining in the electrolyte is removed and oxidation deterioration of the electrolyte during heating can be suppressed. The degree of vacuum is preferably 0 to 10 mmHg (0 to 1333.2 Pa), and more preferably 0 to 5 mmHg (0 to 666.2 Pa).

  The polymer electrolyte constituting the polymer electrolyte membrane of the present invention may be only the polymer electrolyte A described above, or may contain other polymer electrolytes in addition to the polymer electrolyte A. The polymer electrolyte membrane of the present invention may contain additives other than the polymer electrolyte A and the crosslinking agent described above.

  From the viewpoint of proton conductivity, in the polymer electrolyte membrane of the present invention, the above-described polymer electrolyte A is preferably a main component that accounts for 70% by weight or more of the entire polymer electrolyte membrane. In addition, after obtaining the polymer electrolyte membrane, a treatment such as biaxial stretching may be performed to control molecular orientation or the like, or a heat treatment may be performed to control crystallinity and residual stress. Furthermore, an appropriate chemical treatment may be performed during film formation. The chemical treatment includes, for example, addition of a protic compound for increasing conductivity and addition of a trace amount of polyvalent metal for improving durability.

  In addition, in the polymer electrolyte membrane of the present invention, various commonly used additives, antioxidants for preventing resin deterioration, antistatic agents and lubricants for improving the handleability in the molding process as a film are electrolytes. It can be used appropriately within a range that does not affect the processing and performance as a film.

  In the present invention, the thickness of the polymer electrolyte membrane can be appropriately selected depending on the application. For example, when it is considered to reduce the resistance of the polymer electrolyte membrane when used in a fuel cell, the thinner the polymer electrolyte membrane, the better. On the other hand, considering the gas barrier properties, handling properties, and resistance to tearing when bonded to the electrode, the polymer electrolyte membrane may be undesirably too thin. Considering these, the thickness of the polymer electrolyte membrane is preferably 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 100 μm or less. Moreover, when importance is attached to the output as a fuel cell, 10 μm or more and 50 μm or less are particularly preferable. If the thickness of the polymer electrolyte membrane is 5 μm or more and 300 μm or less, the production is easy, the membrane resistance and mechanical properties are balanced, and the handling property when processing as a fuel cell material is excellent. In the present invention, the thickness of the polymer electrolyte membrane can be determined by the measurement method described in the examples.

  In the present invention, the ion exchange equivalent (IEC) of the polymer electrolyte membrane can be adjusted by the IEC of the polymer electrolyte A. For example, when the polymer electrolyte membrane includes a material other than the polymer electrolyte A, the IEC as the polymer electrolyte membrane is thereby lowered. Therefore, the polymer electrolyte membrane A is adjusted as appropriate by setting the IEC of the polymer electrolyte A higher. sell.

  In the present invention, the IEC of the polymer electrolyte membrane is 1.0 to 3.5 meq. / G, preferably 1.5 to 3.0 meq. / G is more preferable. The IEC of the polymer electrolyte membrane is 1.0 eq. If it is smaller than / g, there is a tendency that preferable proton conductivity is hardly expressed, and 3.5 meq. When it is larger than / g, mechanical strength decreases due to swelling with water, and it tends to be difficult to have sufficient strength.

  The membrane / electrode assembly according to the present invention (hereinafter also referred to as “MEA”) includes the polymer electrolyte membrane of the present invention, and can be obtained by applying an electrode catalyst to the polymer electrolyte membrane.

  The electrode catalyst used in the present invention may be any conventionally known electrode catalyst for those skilled in the art. For example, any material may be used as long as it contains a conductive catalyst carrier and a catalytically active substance supported on the conductive catalyst carrier, and other specific configurations are not particularly limited. Specifically, a catalyst having activity for the electrode reaction of the fuel cell can be used. On the anode side, a catalyst having the ability to oxidize fuel (hydrogen, methanol, etc.) is used. On the cathode side, a catalyst for the reaction of generating water from supplied oxygen, protons generated at the anode, and electrons is used.

  Specific examples of the conductive catalyst carrier include carbon carriers having a high surface area such as carbon black, ketjen black, activated carbon, carbon nanohorn, and carbon nanotube, and include catalyst supporting ability, electronic conductivity, and electrochemical stability. Therefore, these materials are preferable.

  Specific examples of the catalytically active substance include platinum, cobalt, ruthenium, and the like, and these may be used alone or as an alloy containing at least one of them or as an arbitrary mixture. In particular, when considering the oxidizing ability of the fuel, the reducing ability of the oxidizing agent, and durability, platinum or an alloy containing platinum is preferable. If necessary, the catalytically active substance may be composed of three or more components using iron, tin, rare earth elements, etc. for stabilization and long life.

  MEA is a catalyst ink containing an electrode catalyst, a solvent, and a suitable polymer electrolyte. As described later, the MEA forms an electrode catalyst layer by removing the solvent after coating the catalyst ink on a substrate as a support, You may produce by making it crimp on the said polymer electrolyte membrane.

  The solvent can be used without any limitation as long as it can dissolve the polymer electrolyte and does not poison the fuel cell catalyst. In addition, as the polymer electrolyte for the catalyst ink, conventionally known perfluorocarbon sulfonic acid polymer electrolytes, hydrocarbon polymer electrolytes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated polysulfone, Sulfonated polyimide, sulfonated polyphenylene sulfide, etc.) can be used. You may use the polymer electrolyte A mentioned above.

  The catalyst ink may contain additives such as a non-electrolyte binder, a water repellent, a dispersant, a thickener, and a pore former as necessary. In addition, those additives conventionally known to those skilled in the art can be used, and other specific configurations are not particularly limited.

  Depending on the viscosity and the type of substrate, the catalyst ink may be a coating method known to those skilled in the art, for example, knife coater, bar coater, spray, dip coater, spin coater, roll coater, die coater, curtain coater, screen. It can apply | coat to a base material using printing etc.

  When a polymer film is used as the substrate, a fuel cell catalyst layer transfer sheet can be produced, and when a conductive porous sheet is used as the substrate, a fuel cell gas diffusion electrode can be produced.

  The MEA can be used, for example, in a fuel cell, particularly in a polymer electrolyte fuel cell.

  Hereinafter, examples will be shown, and the embodiment of the present invention will be described in more detail. The present invention is not limited to the following examples, and it goes without saying that various modes are possible for details. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  Each measurement was performed as follows.

(Measurement of molecular weight)
The molecular weight was measured by the GPC method under the following conditions.
GPC measuring device: HLC-8220 (manufactured by Tosoh Corporation)
Column: Super AW 4000 and Super AW 2500 (Showa Denko Co., Ltd.) connected in series Column temperature: 40 ° C
Mobile phase solvent: NMP (N-methylpyrrolidone, LiBr added to 10 mmol / dm ³ )
Solvent flow rate: 0.3 mL / min
Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation)
Hereinafter, the number average molecular weight converted with standard polystyrene is expressed as Mn, and the weight average molecular weight converted with standard polystyrene is expressed as Mw.

(Measurement of film thickness)
The film thickness after the acid treatment was measured using a digital gauge (Model PDN-20) manufactured by Ozaki Seisakusho.

(Measurement of ion exchange capacity)
As a measurement sample, 10 to 20 mg of the polymer electrolyte membrane after acid treatment was cut out and dried under reduced pressure at 80 ° C., and the dry weight (W _dry ) was measured. The polymer electrolyte membrane after drying was immersed in a saturated NaCl aqueous solution (30 mL) at room temperature for 24 hours to convert the ionic group from H ⁺ type to Na ⁺ type. Thereafter, HCl contained in the obtained solution was quantified with a 0.01 M NaOH aqueous solution using an automatic potentiometric titrator AT-510 (manufactured by Kyoto Electronics Industry Co., Ltd.), and the ion exchange capacity ( IEC) values were calculated. Two samples were prepared for the same polymer electrolyte membrane, and the average value of the two measurements was taken as the calculated IEC value by titration.

(Measurement of insoluble matter)
A polymer electrolyte membrane sample cut to about 2 cm × 3 cm was prepared, and the sample was vacuum dried at 105 ° C. for 12 hours, and then the mass was measured. The sample was immersed in dimethyl sulfoxide for 12 hours at room temperature. Then, the sample was taken out, the solvent on the surface was wiped off, and after vacuum drying at 105 ° C. for 12 hours, the mass was measured. The mass of the sample after immersion was divided by the mass of the sample before immersion and multiplied by 100 to calculate the insoluble content (%) of the sample.

(Measurement of swelling rate)
A polymer electrolyte membrane sample cut to about 2 cm × 3 cm was prepared, and the sample was immersed in pure water for 6 hours at room temperature. The dimensional change and weight in the planar direction of the sample immediately after immersion and the sample which was vacuum-dried at 100 ° C. for 2 hours were measured, and the rate of change was calculated. Regarding the planar direction, the dimensional change of the four sides was measured, and the average value was taken as the result.

(Measurement of proton conductivity)
The proton conductivity measurement of the polymer electrolyte membrane was performed using an electrolyte evaluation apparatus (MSB-AD-V-FC) manufactured by Nippon Bell Co., Ltd. The temperature in the chamber was constant at 80 ° C., and the relative humidity (RH) was 20%, 40%, 60%, 80%, and 90%. Measurement is RH = 20% → 40% → 60% → 80% → 90% → 80% → 60% → 40% → 20%, and the value at the second cycle of humidity drop is used as the measurement result. It was. The sample size is 1.0 cm × 3.0 cm, the distance between the Au probes is 1.0 cm, and using the Solartron 1255B / 1287 (manufactured by Toyo Corporation), the AC four-terminal method (300 mV, 1-100,000 Hz) Measurements were made. As the impedance Z, a value with a phase angle close to 0 ° and a value close to 1000 Hz was used according to the board plot. The conductivity σ (S / cm) was calculated by the following formula.
σ = (L / Z) × 1 / A
Here, L is the distance between Au probes (1.0 cm), and A is the cross-sectional area of the sample (1 cm × film thickness (cm)).

(Production Example 1)
To a 500 mL three-necked flask equipped with a thermometer and a stir bar, 4,4′-dichlorobenzophenone (75 g, 300 mmol) and 30% fuming sulfuric acid (400 g, 1.5 mol) were added. The mixture was heated to 130 ° C. and stirring was continued for 6 hours. After cooling to room temperature, the reaction solution was added to ice water little by little. After neutralizing with an aqueous NaOH solution, the precipitated white solid was collected by filtration. By drying at 105 ° C. under reduced pressure, 112 g of a sulfonic acid group-containing monomer (precursor of a hydrophilic segment) represented by the following formula was obtained.

(Production Example 2)
2,5-Dichlorobenzenesulfonic acid dihydrate (25 g, 95 mmol) and pure water (100 mL) were added to a 200 mL three-necked flask. At room temperature, sodium hydroxide (3.99 g, 99.8 mmol) dissolved in pure water (20 mL) was added. The mixture was cooled in an ice bath to promote crystal precipitation. The mixture was filtered to give a white solid. The filtrate was further cooled in an ice bath to precipitate crystals. The obtained white solid was mixed and dried at 60 ° C. under reduced pressure for 6 hours to obtain sodium 2,5-dichlorobenzenesulfonate (precursor of hydrophilic segment) (15.7 g, yield 60%). .

(Production Example 3)
A 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube was charged with 4,4′-dichlorodiphenylsulfone (31.6 g, 110 mmol), 4,4′-dihydroxybenzophenone (21.4 g, 100 mmol), potassium carbonate ( 20.7 g, 150 mmol), dimethylacetamide (DMAc, 200 mL), and toluene (50 mL) were added. The mixture was heated to 170 ° C. and stirring was continued for 35 hours while removing generated water. 4,4′-Dichlorodiphenylsulfone (0.5 g) was added, and the mixture was further stirred for 5 hours. The mixture was filtered using filter paper to remove excess potassium carbonate, and then the filtrate was poured into 500 mL of methanol to reprecipitate the product. The product was dried at 70 ° C. for 4 hours under reduced pressure, then washed twice with 500 mL of pure water at 60 ° C., further washed once with 500 mL of methanol at 60 ° C., and dried overnight at 70 ° C. under reduced pressure. As a result, 41.5 g of a hydrophobic part oligomer (hydrophobic segment precursor) represented by the following formula was obtained. The molecular weight by GPC was Mn = 5,400 and Mw = 13,900.

(Production Example 4)
To a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube, 4,4′-dichlorodiphenylsulfone (21.76 g, 75.8 mmol), 4,4-bis (4-hydroxyphenyl) valeric acid (9. 86 g, 34.4 mmol), 4,4′-dihydroxybenzophenone (7.38 g, 34.4 mmol), potassium carbonate (18.99 g, 137 mmol), dimethylacetamide (160 mL), and toluene (40 mL) were added. The mixture was heated to 170 ° C. and stirring was continued for 32 hours while removing generated water. As the reaction proceeded, a white solid insoluble in the solvent precipitated. 4N hydrochloric acid (200 mL) was added to remove excess potassium carbonate. The remaining solid was washed twice with pure water (250 mL) at 70 ° C., further washed once with methanol (250 mL) at 60 ° C., and then dried under reduced pressure at 70 ° C. 16.9 g of an oligomer having a carboxyl group (hydrophobic segment precursor) was obtained. The molecular weight by GPC was Mn = 6,600 and Mw = 17,800.

(Production Example 5)
To a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube was added 4,4′-dichlorodiphenylsulfone (21.76 g, 75.8 mmol), 4,4 ′-(1-phenylethylidene) bisphenol (10 g, 34). .4 mmol), 4,4′-dihydroxybenzophenone (7.38 g, 34.4 mmol), potassium carbonate (14.28 g, 103 mmol), dimethylacetamide (150 mL), and toluene (37 mL) were added. The mixture was heated to 170 ° C. and stirring was continued for 48 hours while removing the produced water. The mixture was filtered to remove excess potassium carbonate, and the filtrate was added to methanol (1 L) to reprecipitate the copolymer. The produced solid was collected, dried under reduced pressure at 70 ° C. for 12 hours, washed twice with pure water (500 mL) at 60 ° C., and further washed once with methanol (500 mL) at 60 ° C. It dried under reduced pressure at 70 degreeC for 12 hours, and obtained 28.7g of oligomers (precursor of a hydrophobic segment) represented by the following Formula. The molecular weight by GPC was Mn = 5,000 and Mw = 13,000.

(Example 1)
<Preparation of polymer electrolyte A1>
In a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 1 (precursor of hydrophilic segment, 12 g, 26.3 mol), obtained in Production Example 4 Oligomer (Precursor of hydrophobic segment, 8 g), potassium carbonate (2.28 g, 16.5 mmol), 2,2′-bipyridyl (11.56 g, 74.1 mmol), dimethyl sulfoxide (240 mL), and toluene (60 mL) ) Was added. Under a nitrogen atmosphere, the mixture was heated to 170 ° C. for 3 hours for azeotropic dehydration. After toluene was distilled off at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (10 g, 36.4 mmol) was added, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was poured into 1 L of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (500 mL), and further washed with pure water until the pH of the washing solution became 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain 14.0 g of a polymer electrolyte A1 represented by the following formula. The molecular weight by GPC was Mn = 77,000 and Mw = 165,000. The polymer electrolyte A1 was pulverized using a pulverizer, washed with methylene chloride and methanol, and dissolved in dimethyl sulfoxide to obtain a solution of polymer electrolyte A1 having a solid concentration of about 22% by weight. .

<Crosslinking process>
A dimethyl sulfoxide solution (5.08 g, solid content concentration 22 wt%) of the polymer electrolyte A1 obtained above was weighed into a screw tube, and bisphenol A diglycidyl ether (116.5 mg of 2.6 g of a crosslinking agent) was weighed. (Dissolved in dimethyl sulfoxide) was added and stirred with a stirrer chip for 15 minutes at room temperature. The obtained solution was coated on a PET film (East Lerre mirror, thickness 188 μm) affixed on a glass plate using an applicator whose clearance was set to 15 mil. The obtained coated film was heated at 120 ° C. for 12 hours using a hot plate to crosslink the polymer electrolyte A1 to obtain a polymer electrolyte membrane in which the polymer electrolyte A1 was crosslinked. After washing with 6N hydrochloric acid and pure water, the polymer electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1. The results of measuring proton conductivity are shown in Table 2 and FIG.

(Comparative Example 1)
A PET film in which a dimethyl sulfoxide solution (solid content concentration: 22% by weight) of polymer electrolyte A1 obtained in the same manner as in Example 1 was pasted on a glass plate using an applicator with a clearance set to 15 mil. The coating was carried out on (Tohrel mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate to obtain a non-crosslinked electrolyte membrane. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled off from the PET film, and the film thickness, insoluble matter, swelling degree, IEC, and proton conductivity were measured. The results are shown in Table 1, Table 2, and FIG.

(Example 2)
<Preparation of polymer electrolyte A2>
In a 500 mL four-necked flask equipped with a reflux tube and a DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 1 (precursor of hydrophilic segment, 12 g, 26.3 mmol), obtained in Production Example 5 Oligomer (precursor of hydrophobic segment, 8 g), 2,2′-bipyridyl (11.56 g, 74.1 mmol), dimethyl sulfoxide (240 mL), and toluene (60 mL) were added. Under a nitrogen atmosphere, the mixture was heated to 170 ° C. for 3 hours for azeotropic dehydration. After toluene was distilled off at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (10 g, 36.4 mmol) was added, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was poured into 1 L of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (500 mL), and further washed with pure water until the pH of the washing solution became 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain a polymer electrolyte A2 (13.5 g) of the following formula. The molecular weight by GPC was Mn = 47,000 and Mw = 383,000. The polymer electrolyte A2 is pulverized using a pulverizer, washed with methylene chloride and methanol, dissolved in dimethyl sulfoxide, and a solution of polymer electrolyte A2 having a solid content concentration of about 14.3% by weight is obtained. Obtained.

(Crosslinking process)
The dimethyl sulfoxide solution (5.14 g, solid content concentration 14.3% by weight) of the polymer electrolyte A2 obtained above was weighed into a screw tube, and 4,4′-oxybisbenzoic acid (51.1 mg as a crosslinking agent). Was dissolved in 2.6 g of dimethyl sulfoxide) and stirred with a stirrer chip for 15 minutes. The obtained solution was coated on a PET film (East Lerre mirror, thickness 188 μm) affixed on a glass plate using an applicator whose clearance was set to 15 mil. The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate. Thereafter, the pressure was further reduced to a vacuum (0 mmHg) in a vacuum drier and heated at 160 ° C. for 15 hours to obtain a polymer electrolyte membrane crosslinked with the polymer electrolyte A2. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled off from the PET film, and the film thickness, insoluble matter, swelling degree, IEC, and proton conductivity were measured. The results are shown in Table 1, Table 2, and FIG.

(Example 3)
A PET film obtained by sticking a dimethyl sulfoxide solution (solid content concentration: 14.3% by weight) of polymer electrolyte A2 obtained in the same manner as in Example 2 onto a glass plate using an applicator with a clearance set to 15 mil. The coating was carried out on (Tohrel mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate. Thereafter, the pressure was reduced to a vacuum (0 mmHg) in a vacuum drier and heated at 160 ° C. for 12 hours to obtain a polymer electrolyte membrane crosslinked with the polymer electrolyte A2. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1. The results of measuring proton conductivity are shown in Table 2 and FIG.

(Comparative Example 2)
A PET film obtained by sticking a dimethyl sulfoxide solution (solid content concentration: 14.3% by weight) of polymer electrolyte A2 obtained in the same manner as in Example 2 onto a glass plate using an applicator with a clearance set to 15 mil. The coating was carried out on (Tohrel mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate to obtain a non-crosslinked electrolyte membrane. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled off from the PET film, and insoluble matter, swelling degree, IEC, and proton conductivity were measured. The results are shown in Table 1, Table 2, and FIG.

Example 4
<Preparation of polymer electrolyte A3>
In a 1 L four-necked flask equipped with a mechanical stirrer, reflux tube, and DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 1 (precursor of hydrophilic segment, 24 g, 52.7 mmol), Production Example 3 The obtained oligomer (hydrophobic segment precursor 16 g), 2,2′-bipyridyl (23.1 g, 148 mmol), dimethyl sulfoxide (480 mL), and toluene (120 mL) were added to the nitrogen atmosphere, and the temperature was increased to 170 ° C. Azeotropic dehydration was performed by heating for a period of time. After toluene was distilled off at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (20 g, 72.8 mmol) was added, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was poured into 700 mL of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (600 mL), and further repeatedly washed with pure water until the pH of the washing solution became 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain a polymer electrolyte A3 (33.2 g) of the following formula. The average molecular weight by GPC was Mn = 85,100 and Mw = 177,000. The polymer electrolyte A3 was pulverized using a pulverizer, washed with methylene chloride and methanol, and dissolved in dimethyl sulfoxide to obtain a solution of polymer electrolyte A3 having a solid concentration of about 12% by weight. .

<Crosslinking process>
A PET film (East Reel Mirror, thickness 188 μm) obtained by pasting the dimethyl sulfoxide solution of the polymer electrolyte A3 obtained above (solid content concentration 12% by weight) on a glass plate using an applicator with a clearance set to 15 mil. ) Coated on top. The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate. Thereafter, the pressure was further reduced to a vacuum (0 mmHg) in a vacuum drier and heated at 160 ° C. for 12 hours to obtain a polymer electrolyte membrane in which the polymer electrolyte A3 was crosslinked. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1. The results of measuring proton conductivity are shown in Table 2 and FIG.

(Comparative Example 3)
A PET film in which a dimethyl sulfoxide solution (solid content concentration: 12% by weight) of polymer electrolyte A3 obtained in the same manner as in Example 4 was pasted on a glass plate using an applicator with a clearance set to 15 mil. The coating was carried out on (Tohrel mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate to obtain a non-crosslinked electrolyte membrane. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled off from the PET film, and the film thickness, insoluble matter, swelling degree, IEC, and proton conductivity were measured. The results are shown in Table 1, Table 2, and FIG.

(Example 5)
<Preparation of polymer electrolyte A4>
In a 1 L four-necked flask equipped with a reflux tube and a DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 2 (hydrophilic segment precursor, 15.68 g, 63 mmol), obtained in Production Example 4 Oligomer (precursor of hydrophobic segment, 8 g), potassium carbonate (1.92 g, 13.9 mmol), 2,2′-bipyridyl (23.84 g, 153 mmol), dimethyl sulfoxide (350 mL), and toluene (90 mL) added. Under a nitrogen atmosphere, the mixture was heated to 170 ° C. for 3 hours for azeotropic dehydration. After toluene was distilled off at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (20 g, 72.8 mmol) was added, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was poured into 1 L of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (1 mL), and further repeatedly washed with pure water until the pH of the washing solution reached 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain 11.6 g of polymer electrolyte A4 represented by the following formula. The molecular weight by GPC was Mn = 73,000 and Mw = 182,000. The polymer electrolyte A4 is pulverized using a pulverizer, washed with methylene chloride and methanol, and dissolved in dimethyl sulfoxide to obtain a solution of polymer electrolyte A4 having a solid content concentration of 14.6% by weight. It was.

<Crosslinking process>
The dimethyl sulfoxide solution of polyelectrolyte A4 obtained above (5.93 g, solid content concentration 14.6 wt%) was weighed into a screw tube, and bisphenol A diglycidyl ether (86.7 mg as a cross-linking agent was added to 250 mg of (Dissolved in dimethyl sulfoxide) was added and stirred with a stirrer chip for 15 minutes at room temperature. The obtained solution was coated on a PET film (East Lerre mirror, thickness 188 μm) affixed on a glass plate using an applicator with a clearance set to 10 mil. The obtained coated film was heated at 120 ° C. for 12 hours using a hot plate to crosslink the polymer electrolyte A4, thereby obtaining a polymer electrolyte membrane in which the polymer electrolyte A4 was crosslinked. After washing with 6N hydrochloric acid and pure water, the polymer electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1.

(Comparative Example 4)
A dimethylsulfoxide solution (solid content concentration: 14.6% by weight) of polymer electrolyte A4 obtained in the same manner as in Example 5 was attached on a glass plate using an applicator with a clearance set to 10 mil. Coating was carried out on a PET film (East Reel Mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate to obtain a non-crosslinked electrolyte membrane. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1.

(Example 6)
<Preparation of polymer electrolyte A5>
In a 1 L four-necked flask equipped with a reflux tube and a DeanStark tube, the sulfonic acid group-containing monomer obtained in Production Example 2 (hydrophilic segment precursor, 15.68 g, 63 mmol), obtained in Production Example 5 Oligomer (precursor of hydrophobic segment, 8 g, 1.39 mmol), 2,2′-bipyridyl (23.84 g, 153 mmol), dimethyl sulfoxide (350 mL), and toluene (90 mL) were added. Under a nitrogen atmosphere, the mixture was heated to 170 ° C. for 3 hours for azeotropic dehydration. After toluene was distilled off at 170 ° C., the mixture was cooled to 80 ° C., bis (1,5-cyclooctadiene) nickel (20 g, 72.8 mmol) was added, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was poured into 1 L of methanol and reprecipitated, and the solid content was washed twice with 6N hydrochloric acid (1 L), and further washed with pure water until the pH of the washing solution became 7. The solid content was dried overnight at 105 ° C. under reduced pressure to obtain a polymer electrolyte A5 (13.75 g) of the following formula. The molecular weight by GPC was Mn = 45,000 and Mw = 12,000. The polymer electrolyte A5 was made into a fine powder using a pulverizer, washed with methylene chloride and methanol, and dissolved in dimethyl sulfoxide to obtain a polymer electrolyte A5 solution having a solid content concentration of 15% by weight.

<Crosslinking process>
The dimethyl sulfoxide solution of the above polyelectrolyte A5 (solid content concentration 15% by weight) is coated on a PET film (East Lerre Miller, thickness 188 μm) pasted on a glass plate using an applicator with a clearance set to 10 mil. Worked. The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate. Thereafter, the pressure was reduced to a vacuum (0 mmHg) in a vacuum drier and heated at 160 ° C. for 12 hours to obtain a polymer electrolyte membrane in which the polymer electrolyte A5 was crosslinked. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled from the PET film, and the film thickness, insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1.

(Comparative Example 5)
A PET film (East) obtained by applying a dimethyl sulfoxide solution (solid concentration 15% by weight) of polymer electrolyte A5 obtained in the same manner as in Example 6 on a glass plate using an applicator with a clearance set to 15 mil. It was coated on a rel mirror, thickness 188 μm). The obtained coated film was dried at 120 ° C. for 12 hours using a hot plate to obtain a non-crosslinked electrolyte membrane. After washing with 6N hydrochloric acid and pure water, the electrolyte membrane was peeled off from the PET film, and insoluble matter, swelling degree, and IEC were measured. The results are shown in Table 1.

  As can be seen from the results in Table 1 above, the polymer electrolyte membranes composed of the crosslinked polymer electrolytes of the examples had improved swelling resistance compared to the corresponding non-crosslinked electrolyte membranes. Moreover, when the comparative example corresponding to an Example is contrasted, since the fall of the ion exchange equivalent by bridge | crosslinking is slight, it turns out that a sulfonic acid group hardly participates in bridge | crosslinking. Moreover, as can be seen from the results in Table 2 and FIGS. 1 to 3, the polymer electrolyte membrane of the example constituted by the crosslinked polymer electrolyte had high proton conductivity.

Claims (14)

A polymer electrolyte membrane comprising a copolymer having a plurality of aromatic rings in the main chain,
The copolymer is composed of a hydrophilic segment having a sulfonic acid group and a hydrophobic segment substantially having no sulfonic acid group,
In the hydrophilic segment, the sulfonic acid group is directly bonded to the aromatic ring,
The hydrophilic segment and the hydrophobic segment are connected by an aromatic ring constituting the hydrophilic segment and a carbon-carbon bond of the aromatic ring constituting the hydrophobic segment, and the copolymer is a sulfonic acid A polymer electrolyte membrane characterized by being crosslinked at a portion other than a group. The polymer electrolyte membrane according to claim 1, wherein the hydrophilic segment has at least one structure represented by the following general formula group (1) as a repeating unit.

(In the formula, u represents an integer of 1 to 4, k and l represent an integer of 0 to 4, k + 1 represents an integer of 1 or more, p represents an integer of 0 to 10, q represents an integer of 0 to 10, r Represents an integer of 1 to 4. X represents at least one structure selected from the group consisting of —CO—, —SO ₂ —, and —C (CF ₃ ) ₂ —, and Y represents —CO—, At least one selected from the group consisting of —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) _t — (t is an integer of 1 to 10), —C (CF ₃ ) ₂ —. Z represents a direct structure or selected from the group consisting of — (CH ₂ ) _o — (o is an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O—, and —S—. Ar ¹ represents an aromatic group having a substituent represented by —SO ₃ H or —O (CH ₂ ) _s SO ₃ H (s is an integer of 1 to 12). .)   The polymer electrolyte membrane according to claim 1, wherein the hydrophobic segment is crosslinked with a crosslinkable functional group.   The crosslinkable functional group is at least one selected from the group consisting of alcoholic hydroxyl groups, phenolic hydroxyl groups, amino groups, carboxyl groups, alkenyl groups, acryloyl groups, methacryloyl groups, epoxy groups, phenyl groups and hydrolyzable silyl groups. The polymer electrolyte membrane according to claim 3. The polymer electrolyte membrane according to claim 3 or 4, wherein the hydrophobic segment has at least one structure represented by the following general formula group (10) as a repeating unit.

(In the formula, m is an integer of 1 to 50, and n is an integer of 1 to 50.)   The polymer electrolyte membrane according to any one of claims 3 to 5, wherein the number of crosslinkable functional groups in the hydrophobic segment is more than one per molecule of the copolymer. The polymer electrolyte membrane according to claim 1 or 2, wherein the hydrophobic segment has at least one structure represented by the following general formula group (4) as a repeating unit.

(In the formula, Ar represents a divalent aromatic group, n represents an integer of 1 to 50, a, b, and c represent an integer of 0 to 50, provided that 2 ≦ a + b + c ≦ 50 is satisfied. ) A method for producing a polymer electrolyte membrane according to any one of claims 1 to 6,
A hydrophilic segment precursor having a sulfonic acid group directly bonded to an aromatic ring, a hydrophobic segment precursor having substantially no sulfonic acid group, an aromatic ring of a hydrophilic segment precursor, and a hydrophobic A carbon-carbon bond formation reaction was performed so that the aromatic ring of the segment precursor was carbon-carbon bonded to obtain a copolymer composed of a hydrophilic segment and a hydrophobic segment and having a plurality of aromatic rings in the main chain. rear,
A method for producing a polymer electrolyte membrane, wherein the hydrophobic segment in the copolymer is crosslinked with a crosslinking agent and / or a crosslinking catalyst.   The method for producing a polymer electrolyte membrane according to claim 8, wherein both the precursor of the hydrophobic segment and the precursor of the hydrophilic segment have halogen as a reactive site. A method for producing a polymer electrolyte membrane according to any one of claims 1 to 7,
A hydrophilic segment precursor having a sulfonic acid group directly bonded to an aromatic ring, a hydrophobic segment precursor having substantially no sulfonic acid group, an aromatic ring of a hydrophilic segment precursor, and a hydrophobic A carbon-carbon bond formation reaction was performed so that the aromatic ring of the segment precursor was carbon-carbon bonded to obtain a copolymer composed of a hydrophilic segment and a hydrophobic segment and having a plurality of aromatic rings in the main chain. rear,
A method for producing a polymer electrolyte membrane, wherein the copolymer is heated to crosslink a portion other than the sulfonic acid group in the copolymer.   The method for producing a polymer electrolyte membrane according to claim 10, wherein both the precursor of the hydrophobic segment and the precursor of the hydrophilic segment have halogen as a reactive site.   The method for producing a polymer electrolyte membrane according to claim 10 or 11, wherein the heat crosslinking is performed at a temperature of 80 ° C or higher and 200 ° C or lower in a reduced pressure state.   A membrane / electrode assembly comprising the polymer electrolyte membrane according to any one of claims 1 to 7.   A fuel cell comprising the polymer electrolyte membrane according to claim 1.

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