JP2007059376A - Proton conductive polymer composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductive polymer composite of an aromatic hydrocarbon system which can draw out the excellent performance of a fuel cell catalyst especially when used between electrodes of a fuel cell. <P>SOLUTION: A solvent composite contains a range of 1 to 30 mass% of a proton conductive polymer of at least an aromatic hydrocarbon system. A component having a polyethylene glycol conversion molecular weight in a range of 2,000 to 23,000 in the proton conductive polymer is 10 wt.% or more of the total weight of the proton conductive polymer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composition in which an aromatic hydrocarbon proton-conducting polymer is dissolved or dispersed, and particularly when added to a fuel cell electrode, the composition in which the catalytic performance in the electrode works effectively. is there.

  Examples of electrochemical devices that use a polymer solid electrolyte as an ionic conductor instead of a liquid electrolyte include a polymer electrolyte fuel cell and a water electrolyzer. The polymer electrolyte fuel cell includes a fuel cell of a type using hydrogen gas as a fuel and a fuel cell of a type using a mixed solution of a hydrocarbon-based fuel and water typified by methanol as a fuel. . The structure is composed of an electrode / electrolyte membrane assembly in which an electrolyte membrane having proton conductivity (also referred to as a polymer electrolyte membrane, an ion exchange membrane, a proton exchange membrane, or a proton conductive polymer membrane) is sandwiched between a pair of electrodes. One electrode undergoes an oxidation reaction and the other electrode undergoes a reduction reaction, and is operated as a battery or a water electrolysis tank.

  The diversification of polymer electrolyte membranes is progressing, and in addition to perfluorocarbon sulfonic acid membranes (fluorinated proton conductive polymer membranes), which are typical examples of conventional Nafion (registered trademark), aromatic hydrocarbon polymers include sulfone. A polymer electrolyte membrane made of an aromatic hydrocarbon proton conductive polymer into which proton conductive functional groups such as acid groups, phosphonic acid groups, and phosphoric acid groups are introduced (for example, Patent Document 1, Patent Document 2, Non-Patent Document 1) ) Has been studied in various ways. Unlike the fluorinated proton conducting polymer membrane, the latter membrane has little membrane deformation at high temperatures, and less methanol permeation when used in fuel cells that use liquid fuels such as methanol. It is promising because it is expected to be cheaper than fluorine-based proton conductive polymers. In the future, developments that take advantage of the characteristics of each polymer are expected.

  An electrode used in an electrode / electrolyte membrane assembly produced by laminating an electrode on the electrolyte membrane is generally suitable for a fuel cell reaction with a composition in which a proton conductive polymer is dissolved or dispersed in a solvent or the like. The catalyst ink mixed with the catalyst is applied on the gas diffusion layer or film, and the solvent is removed. Thereafter, the electrode / electrolyte membrane assembly is formed by transferring the electrode to the electrolyte membrane (for example, Patent Document 3). In addition, a method of forming the catalyst ink directly on the electrolyte membrane or by indirect application such as spraying has been studied.

  Regardless of the method, it is important for the electrode / electrolyte membrane assembly to draw out the characteristics of the electrode or electrolyte membrane in a good shape. With regard to the electrode, the mass transfer of protons and reaction gases inside the electrode is smooth. In addition, it is desired that the catalyst performance is also satisfactorily drawn out, and the bonding property with the electrolyte membrane needs to be good.

  From this point of view, conventional fluorine-based proton-conductive polymer membranes have a technique in which a composition of a fluorine-based proton-conductive polymer having a similar structure is interposed in the electrode, and a fluorine-based proton suitable for that purpose. Compositions containing conductive polymers or catalyst inks have also been prepared (for example, Patent Document 4, Patent Document 5, and Patent Document 6). In this case, since the polymers have similar physical properties, the electrode and the electrolyte The bondability of the film can also be kept good.

  On the other hand, it is more stable in the long term for an electrolyte membrane made of an aromatic hydrocarbon proton conductive polymer to be joined to an electrode having an aromatic hydrocarbon proton conductive polymer interposed between the electrodes. Although it has been studied from the viewpoint that it can operate, it has not been sufficiently studied as a composition for interposing in an electrode. For example, Patent Document 7 discloses a composition in which a non-fluorine proton conductive polymer is dissolved, but this composition has improved durability when formed into an electrolyte membrane by a method of coating and forming on an electrode. (A commercially available electrode containing Nafion (registered trademark) is used for the electrode), and the composition in Patent Document 8 is a composition suitable for forming an electrolyte membrane by a casting method, This is also not intended to intervene in the electrode.

US Patent Application Publication No. 2002/0091225 JP-A-6-93114 Japanese Patent No. 3516055 JP 2005-10827 A JP 2000-188110 A JP 2004-273434 A JP 2003-317749 A JP 2003-249244 A Journal of Membrane Science (Netherlands) 1993, 83, 211-220)

  An object of the present invention is to dissolve or disperse an aromatic hydrocarbon proton conductive polymer suitable for interposition in an electrode of a fuel cell in which an aromatic hydrocarbon proton conductive polymer is configured as an electrolyte membrane. It is possible to maintain good bonding properties with an electrolyte membrane made of an aromatic hydrocarbon proton-conducting polymer and to draw out the characteristics of a fuel cell catalyst.

  In order to achieve the above object, the present inventors have proposed an aromatic hydrocarbon-based proton-conducting polymer that can satisfactorily bring out the performance of a catalyst for a fuel cell, particularly when interposed in an electrode of a fuel cell. And the present invention has the following constitution.

1. A solvent composition containing at least an aromatic hydrocarbon-based proton conductive polymer in the range of 1 to 30% by weight, wherein the component having a molecular weight in terms of polyethylene glycol in the range of 2000 to 23000 in the proton conductive polymer is , 10% by weight or more based on the total amount of the proton conductive polymer.

2. The molecular weight distribution of the aromatic hydrocarbon-based proton conductive polymer has two or more maximum values, and at least one of the maximum values is in the range of 2000 to 23000 in terms of polyethylene glycol equivalent molecular weight. 2. The composition according to 1 above, wherein at least one of the values is in a region larger than 23000 in terms of polyethylene glycol equivalent molecular weight.

3. 2. The maximum value in the region where the molecular weight in terms of polyethylene glycol is larger than 23,000 in the molecular weight distribution of the aromatic hydrocarbon proton conductive polymer is in the range of 50,000 to 120,000 in terms of polyethylene glycol. The composition described.

4). 4. The composition according to any one of 1 to 3, wherein the solvent contained in the composition contains at least water in the range of 1 to 85% by weight.

5. 5. The composition according to any one of 1 to 4, wherein an extinction coefficient at 750 nm in a visible light absorption spectrum of the composition is in a range of ^{0 to} 0.3 cm ⁻¹ ·% ^−1. It is a composition.

6). 6. A catalyst ink comprising the composition according to any one of 1 to 5 above and a catalyst.

7). An electrode / electrolyte membrane assembly comprising an electrode produced by using the catalyst ink described in 6 above and laminated with a polymer electrolyte membrane comprising an aromatic hydrocarbon proton conductive polymer Is a fuel cell with built-in.

  The composition containing the aromatic hydrocarbon proton-conducting polymer of the present invention can be prepared by mixing with a fuel cell catalyst or the like, and an electrode prepared using the catalyst ink of the present invention Expresses good catalytic performance. Also, it is satisfactorily bonded to an electrolyte membrane made of an aromatic hydrocarbon proton conductive polymer.

Hereinafter, the present invention will be described in detail.
First, the aromatic hydrocarbon proton conductive polymer in the present invention will be described. The aromatic hydrocarbon proton conductive polymer in the present invention is a non-fluorine proton conductive polymer having a structure having an aromatic or aromatic ring in the polymer main chain, such as polysulfone, polyethersulfone, polyphenylene oxide. , Polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene, polyarylene ether, polyarylene sulfide, polyarylene sulfide sulfone, polyphenylquinoxaline, polyaryl ketone, polyether ketone, polyether ether ketone, polybenzoxazole, poly A polymer in which at least one or more ionic groups are introduced into a polymer containing at least one constituent component such as benzthiazole and polyimide can be given. Examples of the ionic group include at least one of a sulfonic acid group, a phosphonic acid group, a carboxyl group, a phosphoric acid group, and derivatives thereof. In addition, the proton conductivity of a polymer is expressed by including in the polymer a functional group such as a sulfonic acid group, a phosphonic acid group, a carboxyl group, or a phosphoric acid group. Among these, a functional group that acts particularly effectively is a sulfonic acid group. In addition, polysulfone, polyethersulfone, polyetherketone, etc. as used herein do not mean only a specific polymer structure, but a polymer having a structure such as a sulfone group, an ether group, a sulfide group, or a ketone group in the molecule. Represents a generic name. These polymers may be linear, or may have a side chain or a branched structure. In the case of a copolymer, any of random, alternating, and block copolymers may be used. Furthermore, these polymers may contain an aliphatic group in a part of the molecular chain.

  Among the polymers containing the functional group, a polymer having a sulfonic acid group on the aromatic ring can be obtained by reacting a polymer having a skeleton as in the above example with an appropriate sulfonating agent. Examples of such sulfonating agents include those using concentrated sulfuric acid or fuming sulfuric acid that have been reported as examples of introducing sulfonic acid groups into aromatic hydrocarbon polymers (for example, Solid State Ionics, 106, P.219 (1998)), those using chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P.295 (1984)), those using anhydrous sulfuric acid complex (for example, J Polym. Sci., Polym. Chem., 22, P. 721 (1984), J. Polym. Sci., Polym. Chem., 23, P. 1231 (1985)) and the like are effective. In order to obtain the proton conductive polymer of the present invention, particularly a polymer in which proton conductivity is expressed by a sulfonic acid group, it is possible to carry out by using these reagents and selecting reaction conditions according to each polymer. it can. Moreover, it is also possible to use the sulfonating agent described in Japanese Patent No. 2884189.

  The aromatic hydrocarbon proton conductive polymer can also be synthesized using a monomer containing an acidic group in at least one of the monomers used for polymerization. The acidic group may be bonded to the main chain or may be bonded to the side chain. For example, in a polyimide synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride, an acidic group-containing polyimide can be obtained by using a sulfonic acid group-containing diamine as at least one of the aromatic diamines. In the case of polybenzoxazole synthesized from aromatic diamine diol and aromatic dicarboxylic acid, and polybenzthiazole synthesized from aromatic diamine dithiol and aromatic dicarboxylic acid, at least one kind of aromatic dicarboxylic acid contains sulfonic acid group By using dicarboxylic acid or phosphonic acid group-containing dicarboxylic acid, an acidic group-containing polybenzoxazole or polybenzthiazole can be obtained. Polysulfone, polyethersulfone, polyetherketone, etc. synthesized from aromatic dihalide and aromatic diol are synthesized by using sulfonic acid group-containing aromatic dihalide or sulfonic acid group-containing aromatic diol as at least one monomer. I can do it. A sulfide group can be introduced by using an aromatic dithiol instead of an aromatic diol. At this time, it is easier to use a sulfonic acid group-containing dihalide than to use a sulfonic acid group-containing diol (or dithiol) because the degree of polymerization tends to be high and the thermal stability of the obtained acidic group-containing polymer is high. It can be said that it is preferable. The site of the sulfonic acid group can be controlled by bonding the sulfonic acid group to the main chain or side chain depending on the substitution position of the dihalide in the dihalide monomer containing the sulfonic acid group.

  The aromatic hydrocarbon proton conductive polymer in the present invention includes sulfonic acid group-containing polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, polyether ketone-based polymers such as polyarylene ether compounds and sulfonic acid groups. More preferably, it is a polyarylene compound. In these polymers, the ether group is preferably a sulfide group.

  Further, among these polymers, aromatic hydrocarbon proton conductive polymers containing a polyarylene ether structure are particularly preferable. By including a polyarylene ether structure, it is easy to disperse in a mixed solvent containing water and is excellent in handleability. Although it is not clear, it is considered that the affinity with a mixed solvent containing water is improved by the ether group. Moreover, since it has the toughness as a polymer by having a polyarylene ether structure in a polymer, there exists a tendency for durability at the time of setting it as a fuel cell to be especially preferable. The ether group is preferably a sulfide group.

  What contains the structural component shown by following General formula (1) is a preferable example.

  However, Ar is a divalent aromatic group, Y is a sulfone group or a carbonyl group, X is H and / or a monovalent cationic species, Z is any bonding mode that bonds an aromatic ring, but is directly bonded , O atoms and / or S atoms are preferable, and O atoms are more preferable.

  Furthermore, what contains the structural component shown by following General formula (2) is more preferable.

  However, Ar ′ is a divalent aromatic group, and Z is an arbitrary bonding mode for bonding an aromatic ring, but is preferably a direct bond, an O atom and / or an S atom, and more preferably an O atom. .

  The component represented by the general formula (2) is preferably a component represented by the following general formula (3).

  However, Ar ′ is a divalent aromatic group, and Z is an arbitrary bonding mode for bonding an aromatic ring, but is preferably a direct bond, an O atom and / or an S atom, and more preferably an O atom. .

  The sulfonic acid group-containing polyarylene ether compound may contain structural units other than those represented by the general formula (1) and the general formula (2). At this time, the structural units other than those represented by the general formula (1) or the general formula (2) are preferably 50% by weight or less of the polyarylene ether introduced with the sulfonic acid of the present invention. By setting the content to 50% by weight or less, a composition utilizing the characteristics of the sulfonic acid group-containing polyarylene ether compound can be obtained.

  The aromatic hydrocarbon proton conductive polymer preferably has a sulfonic acid group content in the range of 0.3 to 2.8 meq / g. When it is less than 0.3 meq / g, there is a tendency that sufficient proton conductivity is not exhibited, and when it is greater than 2.8 meq / g, the swelling of the polymer becomes too large to be suitable for use. . This tendency is particularly noticeable in fuel cells using organic fuels such as methanol. More preferably, it is 0.6-2.4 meq / g. The sulfonic acid group content can be calculated from the polymer composition.

  In addition, the sulfonic acid group-containing polyarylene ether compound can be polymerized by an aromatic nucleophilic substitution reaction containing the compounds represented by the following general formulas (4) and (5) as monomers. Specific examples of the compound represented by the general formula (4) include 3,3′-disulfo-4,4′-dichlorodiphenylsulfone, 3,3′-disulfo-4,4′-difluorodiphenylsulfone, 3, 3'-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl sulfone, and those whose sulfonic acid groups are converted to salts with monovalent cation species Can be mentioned. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound represented by the general formula (5) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. it can.

  However, Y is a sulfone group or a carbonyl group, X is a monovalent cation species, and W is chlorine or fluorine.

  In the present invention, the above 2,6-dichlorobenzonitrile and 2,4-dichlorobenzonitrile are in an isomer relationship, and any of them is used for good proton conductivity, heat resistance, workability and dimensional stability. Can be achieved. The reason is considered that both monomers are excellent in reactivity and that the structure of the whole molecule is made harder by constituting a small repeating unit.

  In the aromatic nucleophilic substitution reaction described above, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used in combination with the compounds represented by the general formulas (4) and (5) as monomers. Examples of these compounds include 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, decafluorobiphenyl, and the like. However, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  In addition, Ar in the structural component represented by the general formula (1) and Ar ′ in the structural component represented by the general formula (2) are generally the same as those described above in the aromatic nucleophilic substitution polymerization. It is a structure introduced from an aromatic diol component monomer used together with the compounds represented by formulas (4) and (5). Examples of such aromatic diol monomers include 4,4′-biphenol, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy). Phenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, terminal hydroxyl group-containing polyphenylene ether oligomer, 4,4 '-Thiobisbenzenethiol, 1,4-benzenedithiol, 1,3-benzenedithiol, 4,4'-biphenyldithiol, 1,4-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,2-bis (4 -Hydroxy-3,5-dimethylphenyl) propane, bis (4-hydroxy) 3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, bis (4-hydroxyphenyl) diphenylmethane, 9,9-bis (4 -Hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, bis (4-hydroxyphenyl) ether, bis (4-hydroxy Phenyl) sulfide Bis (4-hydroxyphenoxy) -1,4-benzene, bis (4-hydroxyphenoxy) -1,3-benzene, 1,4-bis (hydroxyphenyl) butane, 1,1-bis (hydroxyphenyl) methane, 1,2-bis (hydroxyphenyl) ethane, 1,3-bis (hydroxyphenyl) propane, 1,5-bis (hydroxyphenyl) heptane, 1,6-bis (hydroxyphenyl) hexane, and the like. In addition to these, various aromatic diols that can be used for the polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction can also be used. In addition, these aromatic diols are bonded to substituents such as alkyl groups having 1 to 30 carbon atoms, aromatic substituents such as phenyl groups, halogens, cyano groups, sulfonic acid groups and their salt compounds. You may do it. A substituent such as a halogen, a cyano group, or a sulfonic acid group may be bonded to an alkyl group or an aromatic substituent. The kind of substituent is not particularly limited, and is preferably 0 to 2 per aromatic ring. These aromatic diols can be used alone, but a plurality of aromatic diols can be used in combination.

  When polymerizing a sulfonic acid group-containing polyarylene ether compound by an aromatic nucleophilic substitution reaction, an activated difluoroaromatic compound and / or a dichloroaromatic compound including the compounds represented by the above general formula (4) and general formula (5) A polymer can be obtained by reacting a compound with an aromatic diol in the presence of a basic compound.

  The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more. Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and those that can convert an aromatic diol into an active phenoxide structure may be used. It can use without being limited to. In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used.

  When the aromatic nucleophilic substitution reaction is performed in a solvent, the molecular weight of the polymer obtained can be adjusted by controlling the reaction temperature, polymer concentration, reaction time, and the like. As described above, the reaction temperature is particularly preferably in the range of 50 ° C. to 250 ° C., and the higher the temperature, the faster the molecular weight increases, so the productivity is excellent. The polymer concentration is preferably charged so that the monomer concentration is 2 to 50% by weight. When the amount is less than 2% by weight, the molecular weight tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. The reaction time is 0.2 hours to 500 hours, preferably 1 to 80 hours. If the reaction time is shorter than 0.2 hours, the temperature of the system does not become constant, so that uniform reaction tends to be difficult, and if it exceeds 500 hours, it is not preferable from the viewpoint of productivity. The molecular weight tends to increase as the reaction time increases.

  Further, as a method for controlling the molecular weight, it is possible to prevent the polymerization reaction from proceeding more than necessary by blocking the ends of the polymer. For example, a method of adding a monomer having a single reactive site can be mentioned, but it is not particularly limited.

  The molecular weight in terms of polyethylene glycol of the aromatic hydrocarbon proton conductive polymer in the composition of the present invention preferably includes a component in the range of 2000 to 23000. Although the detailed reason is not known, an electrode made of a catalyst ink prepared by mixing a fuel cell catalyst with a composition containing an aromatic hydrocarbon proton conductive polymer having a molecular weight within this range is used for a fuel cell. Then, it is possible to maintain a high voltage in a low current density region where a voltage drop due to catalytic activity is likely to occur in fuel cell power generation. It is speculated that the adsorption state of the aromatic hydrocarbon proton conducting polymer on the catalyst is involved. In addition, a component having a molecular weight less than 2000 in terms of polyethylene glycol has a tendency to be unable to be used stably, such as being soluble in water, while a component having a molecular weight greater than 23,000 in terms of polyethylene glycol is in the low current density region. The contribution to the suppression of voltage drop tends to decrease and the voltage tends to decrease. More preferably, it contains a component having a molecular weight in terms of polyethylene glycol in the range of 2500 to 23000, more preferably in the range of 3000 to 20000, and still more preferably in the range of 3000 to 15000. Further, it is preferably contained in an amount of 10% by weight or more, more preferably 15% by weight or more, and further preferably 20% by weight or more, as a ratio to the total amount of the aromatic hydrocarbon proton conductive polymer. . When the content relative to the aromatic hydrocarbon proton conductive polymer is less than 5% by weight, the effect of suppressing the voltage drop tends to be canceled due to the influence of a component having a higher molecular weight.

  Since the molecular weight at the time of polymerization of the proton conductive polymer has a molecular weight distribution represented by a normal distribution, an aromatic hydrocarbon proton conductive polymer containing 10% by weight or more of a component having a polyethylene glycol equivalent molecular weight of 2000 to 23000 is used. When obtained by a polymerization reaction, the maximum value of the molecular weight distribution tends to be relatively small. When the molecular weight is small, the chemical / physical stability is lowered, so that when used as a fuel cell, the physical / chemical stability as an electrode tends to be somewhat lowered. The tendency is also more problematic than fluorine-based proton conductive polymers due to the intrinsic chemical stability. Therefore, even if the molecular weight can be reduced and the catalyst performance can be sufficiently extracted, if the power generation conditions are severe, such as the fuel cell temperature becomes high, the durability tends to be lowered. Therefore, as a composition containing an aromatic hydrocarbon proton conductive polymer, in addition to an aromatic hydrocarbon proton conductive polymer component having a maximum molecular weight distribution in the range of at least a polyethylene glycol equivalent molecular weight of 2000 to 23000, polyethylene A mixed composition containing one or more aromatic hydrocarbon proton-conducting polymers having a maximum molecular weight distribution in the range where the molecular weight in terms of glycol is larger than 23,000 is preferable as a measure for improving chemical and physical stability. It is. More preferably, when a component having a maximum value of polyethylene glycol equivalent molecular weight in the range of 50,000 to 120,000 is contained together with a proton conductive polymer component having a molecular weight maximum value of polyethylene glycol equivalent molecular weight of 2000 to 23000, catalyst performance and durability are improved. It can be compatible in the relationship. More preferably, the molecular weight maximum value of the component having the larger molecular weight maximum value is in the range of 60000 to 90000. When the maximum value of the molecular weight in terms of polyethylene glycol exceeds 120,000, the viscosity of the composition increases, which tends to be undesirable for handling. In addition, the adjustment method of the polymer composition having a plurality of such molecular weight maximum values is not particularly limited and can be a known method. A method of simply mixing proton conductive polymers having different molecular weight distributions at an arbitrary ratio is simple.

  Since the aromatic hydrocarbon proton conductive polymer of the present invention is a proton conductive polymer having an aromatic or aromatic ring, immediately after polymerization, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N , N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, etc., and can be obtained in a form dissolved in a solvent, but can be replaced with another solvent if necessary. If the solvent used at the time of polymerization is used as it is, it remains in the electrode even when the fuel cell is formed, and there is a tendency to adversely affect the initial performance. Therefore, substitution with another solvent is more preferable.

  As the type of organic solvent that can be used in the composition of the present invention, it is preferable to select an organic solvent having a polarity selected from alcohols, ethers, ketones, etc. (excluding impurities contained in trace amounts). .) In addition to the organic solvent selected from alcohols, ethers and ketones, it is more preferable to use a solvent containing water. By containing water, the solubility or dispersibility of the proton conducting polymer in the composition tends to be improved. In addition, moisture reduces the risk of fire and the like when mixed with the catalyst.

  Alcohols, ethers, and ketones that can be used as a more preferable solvent are more preferably those having 6 or less carbon atoms in consideration of the influence on the catalyst and the handling property as a catalyst ink. As methanol, ethanol, propanol, butanol, pentanol, hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-methyl-1-propanol, 3-methyl-1-butanol, 1-ethoxy-2-propanol 3-methoxybutanol and its derivatives are examples that can be suitably used. Examples of ether solvents that can be suitably used include diethyl ether, ethyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, methylal, and 1,4 dioxane. Examples of ketone solvents that can be selected include acetone, diethyl ketone, cyclohexanone, cyclopentanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptanone, and the like. It is. In particular, organic solvents selected from ketones or ethers, or the combined use of ketones or ethers and alcohols tend to make the composition easy to handle even when the concentration of the proton conductive polymer is high. In addition, the solvent containing water can be handled better.

  As a method for substituting the solvent at the time of polymerization with another solvent, for example, after obtaining a solid proton-conductive polymer, it can be dissolved and dispersed in a solvent suitable for the composition of the present invention. As a method for removing the solvent at the time of polymerization, there is a method of removing the solvent by evaporation from the reaction solution after completion of the polymerization reaction and washing the residue as necessary. Further, by adding the reaction solution in a solvent having a low solubility of the proton conductive polymer, the polymer can be precipitated as a solid, and the polymer can be obtained by filtering the precipitate. When the latter method is used for precipitation in water, for example, the salt generated during the polymerization reaction can be dissolved and removed in water, which is a good technique for purifying the proton conductive polymer. As a method for removing the residue, it can be removed by filtration in addition to the washing operation.

  The obtained aromatic hydrocarbon proton conductive polymer can be dissolved and dispersed in a mixed solution composed of a polymerization solvent or other organic solvent in the form of a salt such as a sulfonate, for example. It is also possible to treat the polymer in an acidic solvent such as an aqueous sulfuric acid solution or an aqueous hydrochloric acid solution and then wash it with water to convert it into an acid form and then dissolve and disperse it in an arbitrary solvent. When converting to the acid form, it is common to treat with an excess of acid, so the polymer may contain an excess of acid. Therefore, it is desirable to remove the excess acid component by repeating washing with water after conversion to the acid form. At this time, if the water used for washing contains salt, the acid functional group may be converted to the salt form, so use water that has been treated to at least remove ions such as ion-exchanged water. It is preferable to do.

  The proportion of water in the above composition is preferably such that when the solvent is a mixture of a combination selected from water and alcohol, water is in the range of 1 to 45% by weight, and the composition is more manageable. In order to improve the water content, the water content is preferably in the range of 1 to 40% by weight, more preferably in the range of 1 to 20% by weight, and still more preferably in the range of 2 to 15% by weight. It is. When the amount of water in the mixed solvent is large and exceeds 45% by weight, particularly when a composition containing a high concentration proton-conducting polymer is obtained, the composition tends to be high and difficult to handle. On the other hand, when the ratio of water is less than 1% by weight, it is difficult to obtain a homogeneous composition because the proton conductive polymer remains in a solid state. This tendency tends to be a problem when obtaining a dispersion of a proton conductive polymer having a relatively high concentration.

  The proportion of the alcohol solvent in the mixed solvent selected from water and alcohol solvents is preferably in the range of 50 to 98% by weight. When the proportion of the alcohol solvent is less than 50% by weight, it is not preferable because the viscosity of the composition is high and difficult to handle, and particularly the tendency to gel is strong. On the other hand, when the proportion of the alcohol solvent exceeds 98% by weight, the concentration of the proton conductive polymer becomes low, which is not effective when producing a catalyst ink. More preferably, it is in the range of 60 to 95% by weight.

  On the other hand, in the case of a combination other than a two-component solvent consisting of water and alcohol, such as a case where an ether or ketone solvent is included in addition to water and alcohol as the solvent of the above composition, depending on the amount of water in the solvent or a combination of organic solvents It is possible to expand the range in which the solvent can be selected. In that case, water is preferably in the range of 1 to 85% by weight, more preferably in the range of 15 to 75% by weight, and still more preferably in the range of 40 to 65% by weight. Even if the amount of water in the composition increases, the viscosity of the solution can be kept low.

  The concentration of the proton conductive polymer in the composition of the present invention is preferably in the range of 1 to 30% by weight. When the concentration of the proton conductive polymer is less than 1% by weight, the amount of the polymer in the composition is small, which is not effective when preparing a catalyst ink. Conversely, when the concentration exceeds 30% by weight, the viscosity becomes high and handling is difficult. It tends to be difficult. When the concentration of the proton conductive polymer is in the range of 1 to 25% by weight, it can be handled particularly well, more preferably in the range of 2 to 20% by weight, still more preferably in the range of 3 to 15% by weight. It is a range.

  In the composition of the present invention, the structure of the aromatic hydrocarbon-based proton conductive polymer in the composition is a dissolved (uniformly spread state) or dispersed (a part composed only of a polymer-containing part and a solvent). They exist separately) or are in an intermediate state. The structure in the composition is considered to change depending on the combination of the type and amount of water and organic solvent. Considering the behavior when dissolving / dispersing in a mixed solvent, the aromatic hydrocarbon-based proton conductive polymer is swollen with water, and then the dissolution / dispersion is promoted by adding an organic solvent. When taking a structure in which an aromatic hydrocarbon proton conductive polymer is dispersed in a solvent, it is presumed that the structure has a micelle structure swollen mainly by water, and the micelle is dispersed in an organic solvent. In addition, due to the characteristics of the organic solvent, it is presumed that as the compatibility between the organic solvent and the polymer / water increases, it approaches a dissolved state.

The composition of the present invention tends to be more preferably dissolved and dispersed uniformly so that there is no separation such as precipitation. As a technique for that purpose, a method of adding a preliminarily prepared mixed solution of water and one kind of organic solvent, or adding water to a proton conductive polymer to swell once, adding an organic solvent, and representative of stirring, etc. Can be mixed or heated by physical methods. The latter is superior in terms of ease of adjustment of the composition.
In addition, as an aromatic hydrocarbon polymer used when preparing the composition of the present invention, a solvent having a larger apparent surface area such as a fine powder than a large block-shaped polymer is more easily spread. Can be handled well. In water or an organic solvent used as a solvent, attention must be paid to purity so that impurities that poison the catalyst are not included. There is also a possibility that the solvent used during the polymerization of the polymer remains in the polymer. Since the solvent during the polymerization may adversely affect the performance of the fuel cell, it is preferable to remove it as much as possible, and it is preferable to remove it up to 5% by weight or less, and optimally 1% by weight or less based on the polymer weight.

Furthermore, as a result of investigations for obtaining better power generation performance, the present inventors have found that in a composition containing a proton-conducting polymer component contained in a polyethylene glycol equivalent molecular weight range of 2000 to 23000, the composition at 750 nm It has been found that particularly good fuel cell performance can be obtained when the extinction coefficient of the visible light absorption spectrum is in the range of ⁰ to 0.3 cm ⁻¹ ·% ⁻¹ . In a fuel cell made using a composition having a light absorption coefficient greater than 0.3 cm ⁻¹ ·% ^{−1 in the} composition, the voltage drop in the high current density region is large, and good performance tends not to be obtained. is there. More preferably, the extinction coefficient is in the range of ⁰ to 0.15 cm ⁻¹ ·% ⁻¹ , and further preferably in the range of 0.0001 to 0.05 cm ⁻¹ ·% ⁻¹ . The voltage drop at a high current density is estimated from the fact that it is generally considered to be diffusion controlled by fuel or oxygen, and when a composition having an extinction coefficient exceeding 0.3 cm ⁻¹ ·% ⁻¹ is used, It is speculated that the electrodes tend to be tightly packed. However, even in this case, it is possible to show good power generation performance in the low current density region.

  Furthermore, the composition of the present invention may contain an antioxidant and can improve the durability of the fuel cell. The type and amount of the antioxidant are not particularly limited, but from the viewpoint of affinity with the polymer, an antioxidant containing an aromatic structure in the molecule, for example, a hindered phenol-based oxidation. Inhibitors and hindered amine antioxidants can be used satisfactorily. In addition, it is particularly good when mixed in the range of 0.01 to 10% by weight with respect to the proton conductive polymer. When the content is less than 0.01% by weight, the effect of preventing oxidation is small, while from 10% by weight. If the amount is too large, the ratio to the polymer increases, and cracks are likely to occur when an electrode for a fuel cell is produced. Another example of the antioxidant includes an antioxidant described in JP-A No. 2003-201403 and the like. Note that the composition of the present invention can contain, for example, a heat stabilizer, a crosslinking agent, an antistatic agent, an antifoaming agent, a polymerization inhibitor, silica particles, alumina particles, and titania as necessary, in addition to the antioxidant. Various additives such as inorganic compounds such as particles and phosphotungstic acid particles, inorganic-organic hybrid compounds, ionic liquids, and nanocarbon materials such as carbon nanofibers may be included.

  Using the composition of the present invention, it is possible to produce a catalyst ink for use in producing a fuel cell electrode. The method for adjusting the catalyst ink is not particularly limited, and a known technique can be used. The catalyst used in the catalyst ink can be appropriately selected from the viewpoint of acid resistance and catalytic activity, but platinum group metals and alloys and oxides thereof are particularly preferable. For example, platinum or a platinum-based alloy is suitable for application to a cathode electrode, and platinum or a platinum-based alloy or an alloy of platinum and ruthenium is suitable for high-efficiency power generation when considering application to an anode electrode. As these catalyst fine particles, those supported on particulate or fibrous carbon such as activated carbon or graphite are preferably used. Even if it is supported on a nanocarbon material such as carbon nanotube or carbon nanohorn, it can be used satisfactorily. Thus, a catalyst ink can be produced by mixing the catalyst appropriately selected and the composition of the present invention. At this time, after preparing the mixed ink of the catalyst and the composition, it is possible to remove the solvent once to form catalyst particles with the catalyst surface covered with the proton conductive polymer, and then make the catalyst ink dissolved again in the solvent It is. When the amount of water in the composition is particularly small, depending on the type of catalyst, there is a possibility of ignition, so it is also possible to add a trace amount of water to the catalyst in advance, and then add the composition of the present invention. It is valid. Cooling is also effective. Components other than the catalyst and the composition of the present invention may be contained.

  In addition, an electrode / electrolyte membrane assembly can be produced by forming a catalyst layer (electrode) obtained by spreading and drying the catalyst ink thus prepared on a proton conductive electrolyte membrane. . Under the present circumstances, it is preferable that the porous carbon nonwoven fabric or carbon paper which has a role which transports an electrical power collector and a fuel effectively exists in the outer side of a catalyst layer. As the type of the electrolyte membrane, an electrolyte membrane having a structure shown by the aromatic hydrocarbon proton conductive polymer in the present invention, that is, made of a proton conductive polymer having an aromatic or aromatic ring is preferable. When a fluorine-based proton electrolyte membrane is used, the interface between the electrode and the electrolyte membrane tends to peel off due to the difference in characteristics. The electrode produced using the composition of the present invention can bring out the catalyst performance satisfactorily and is excellent for a proton-conducting polymer electrolyte membrane having an aromatic or aromatic ring that attracts attention. It is excellent in that it has adhesiveness. For electrode / electrolyte membrane assemblies, it is important to prevent large resistance from being generated between the membrane and the electrode, and it is also important to prevent peeling or peeling of the electrode catalyst due to mechanical force. is there.

  As a method for producing this joined body, for example, the catalyst ink of the present invention is uniformly applied on carbon paper, dried, and then thermocompression bonded to an electrolyte membrane, or a catalyst layer on various films instead of carbon paper. After forming, heat transfer to the electrolyte membrane and further superposition with a porous carbon layer can be taken. When thermocompression bonding or thermal transfer is performed under a condition in which the moisture content of the electrolyte membrane and / or electrode layer is controlled, a better electrode / electrolyte membrane assembly can be obtained. Also, the gas diffusibility of the catalyst layer is improved by adding a hydrophobic substance or foaming agent to the catalyst layer as appropriate, or by forming a catalyst layer on the electrolyte membrane and then performing a hydrophobic treatment on the surface. Taking a technique is also one of the techniques for producing a good electrode / electrolyte membrane assembly.

  Moreover, a fuel cell can also be produced using the electrode / electrolyte membrane assembly of the present invention, and the produced fuel cell is particularly excellent in that it maintains good performance and bondability over a long period of time.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

<Ion exchange capacity of proton conducting polymer (acid type)>
As the ion exchange capacity (IEC), the amount of acid type functional groups present in the proton conducting polymer was measured. First, as a sample preparation, the polymer powder was dried in an oven at 80 ° C. under a nitrogen stream for 2 hours, further allowed to cool in a desiccator filled with silica gel for 30 minutes, and then the dry weight was measured (Ws). Next, 200 ml of a 1 mol / l sodium chloride ultrapure aqueous solution and the weighed sample were placed in a 200 ml sealed glass bottle and stirred at room temperature for 24 hours while being sealed. It was then filtered through a glass filter. 30 ml of the filtrate was taken out and neutralized with a 10 mM sodium hydroxide aqueous solution (commercial standard solution), and IEC was determined from the titration (T) using the following formula.
IEC (meq / g) = 10 T / (30 Ws) × 0.2
(Unit of T: ml, unit of Ws: g)

<Method of measuring molecular weight in terms of polyethylene glycol>
The molecular weight of the proton conductive polymer was measured by GPC as the molecular weight in terms of polyethylene glycol. As a measuring apparatus, Shodex GPC SYSTEM-21 was used. The column used was a TSKgel G2000H _XL column connected to two TSKgel GMX _XL columns (manufactured by TOSOH). The solvent used was N, N-dimethylformamide in which 30 mM LiBr and 60 mM phosphoric acid were dissolved, the temperature was 40 ° C., and the flow rate was 0.7 ml / min. The detector used was an RI detector. The molecular weight was calculated and calculated in terms of standard polyethylene glycol. As a sample, 20 μl was injected after dissolving in 0.05% in terms of polymer solid content.

<Visible light absorption spectrum measurement>
Absorbance (E) for visible light at 750 nm was measured with a HITACHI U-2001 type double beam spectrophotometer in accordance with JIS K0115 (2004) “General Rules for Absorption Spectrophotometry”. The blank was measured using a solvent-only mixture containing no proton conducting polymer. An iodine tungsten lamp was used as the light source.
E = log (Io / It) (Io: intensity of incident light It: intensity of transmitted light)
Next, the extinction coefficient (ε [cm ⁻¹ ·% ⁻¹ ]) was calculated by the following formula.
Absorption coefficient (ε) = E (absorbance) / [l (cell length) · C (polymer concentration%)]

<Logarithmic viscosity of composition>
The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using a Ubbelohde viscometer in a thermostatic bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / c was evaluated. (Ta is the drop time of the sample solution, tb is the drop time of the solvent only, and c is the polymer concentration).

<Power generation characteristics>
The electrode / electrolyte membrane assembly is incorporated into a cell for fuel cell evaluation made by itself, and a fuel cell evaluation device manufactured by NF Circuit Design Block Co., Ltd. is used. Performed aging by generating electricity for 16 hours while supplying air. The initial performance was then evaluated by examining the current-potential curve. Further, the durability was measured by investigating the stability of the voltage while conducting a constant current continuous discharge test for 500 hours at a current density of 500 mA / cm ² .

  Samples used in Examples and Comparative Examples were produced by the following method.

(Proton conductive polymer synthesis example 1)
3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS), 2,6-dichlorobenzonitrile (abbreviation: DCBN), 4,4′-biphenol, potassium carbonate, 14 g of a mixture having a molar ratio of 1.00: 1.99: 2.99: 2.5 was weighed into a 100 ml four-necked flask together with 2.5 g of molecular sieves and flushed with nitrogen. After adding 50 ml of NMP and stirring at 151 ° C. for 2 hours, the reaction was continued by raising the reaction temperature to 190 to 200 ° C. and increasing the viscosity of the system. Proton conducting polymers with different molecular weight distributions were synthesized by changing the reaction time. After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The operation of washing the obtained polymer in boiling water for 1 hour was repeated twice. Next, after being immersed in 1 liter of 1 mol / liter hydrochloric acid aqueous solution with stirring overnight, the operation of washing again in boiling water for 1 hour was repeated 7 times, and then dried under reduced pressure, and converted into polyethylene glycol as shown in Table 1. Aromatic hydrocarbon proton conducting polymers with different molecular weights were prepared.

(Production of composition)
Dissolve and disperse each of polymers A, B, and C, which are aromatic hydrocarbon-based proton conductive materials shown in Table 1, and a one-to-two mixture of polymer A and polymer C in the following three weight ratios. A composition containing 5% by weight of a proton conductive polymer was obtained. The water used was ultrapure water, and the organic solvent was a reagent-grade grade.
(1) Proton conductive polymer / water / 1,2-dimethoxyethane = 5/10/85
(2) Proton conductive polymer / water / 1,2-dimethoxyethane / methanol = 5/5/23/67
(3) Proton conductive polymer / water / cyclohexanone = 5/5/90
Table 2 shows the values obtained by measuring the extinction coefficient for each composition. Moreover, each composition was divided into the composition of Examples 1-9 and the composition of Comparative Examples 1-3.

(Preparation of catalyst ink)
The composition was added to a commercially available 40% platinum-supported carbon catalyst (Tanaka Kikinzoku Kogyo Co., Ltd.), and stirred until uniform to obtain catalyst inks for fuel cells of Examples and Comparative Examples. In addition, the electrode produced using the composition of the number of an Example is made into the electrode of the number of an Example as it is. For example, an electrode produced using the composition of Example 1 is referred to as the electrode of Example 1. The weight ratio of the catalyst-carrying carbon and the proton conductive polymer contained in the composition was adjusted to be 1: 0.28.

(Production of electrodes)
The catalyst ink was applied to a commercially available carbon paper (E-Tek) and dried to produce a fuel cell electrode. At this time, hydrophilic carbon paper was used for the anode electrode carbon paper, and hydrophobic carbon paper was used for the cathode electrode carbon paper.

(Preparation of electrolyte membrane)
The proton conductive polymer C shown in Table 1 was dissolved in NMP (25%), cast on a glass plate on a hot plate by casting, and NMP was distilled off until it became a film, and then immersed in water overnight. did. Further, the operation of washing with ultrapure water for 1 hour was repeated 5 times. Thereafter, it was put in a frame and dried at room temperature to obtain an aromatic hydrocarbon polymer electrolyte membrane.

(Preparation of electrode / electrolyte membrane assembly)
The above electrolyte membrane was equilibrated with moisture in an atmosphere of 20 ° C. and humidity of 80 RH%, and then sandwiched between the two types of electrodes in the same environment (an anode electrode and a cathode electrode. The catalyst ink application surface is in contact with the electrolyte membrane) Arrange so that.) The laminate of this electrode and electrolyte membrane was sandwiched between two stainless steel plates together with a gasket. Subsequently, the electrode and the electrolyte membrane were joined by hot pressing at 130 ° C. under pressure. It took out with the state pinched | interposed with the stainless steel plate, naturally cooled until it became room temperature, and taken out after that, and the electrode-electrolyte membrane assembly of the Example and the comparative example was obtained. The electrode / electrolyte membrane assembly produced using the electrode of the example number is directly used as the electrode / electrolyte membrane assembly of the example number. For example, an electrode produced using the electrode of Example 1 is the electrode / electrolyte membrane assembly of Example 1.

Fuel cell power generation tests were performed on the electrode / electrolyte membrane assemblies of Examples 1 to 9 and Comparative Examples 1 to 3. At that time, along with the measurement of the current-voltage curve, the internal resistance of the battery was measured by a current interruption method. The quality of the catalyst activity can be judged from the voltage value in the low current density region of the current-voltage curve, but the voltage drop due to the internal resistance of the battery can be mistakenly considered as the voltage drop due to poor catalyst performance. Therefore, the resistance-free voltage when the resistance component of the battery was removed was used as an index of the catalyst activity, and was obtained by the following formula.
E (resistance free voltage) = Ereal (measured voltage) −R (internal resistance) I (current density)
The results of measuring the resistance-free voltage at a current density of 0.1 A / cm ² are summarized in Table 3.

From Table 3, in the fuel cell produced using the composition containing the proton conductive polymer containing 10% by weight or more of the component having a molecular weight of 2000 to 23000 in terms of polyethylene glycol in Examples, the resistance at 0.1 A / cm ² is used. It can be seen that the free voltage is high and good catalytic performance is expressed. On the other hand, in the fuel cell of the comparative example, sufficient catalyst performance was not obtained. The value of the extinction coefficient in Table 2 serves as an indicator of the dispersion or dissolution state of the proton conductive polymer in the composition, but there was a tendency that none was involved in the expression of the catalyst performance. Therefore, as a composition containing an aromatic hydrocarbon-based proton conductive polymer, it is particularly important to adjust the molecular weight of the aromatic hydrocarbon-based proton conductive polymer within the scope of the present invention.

  Moreover, in the electrode of a fuel cell, it is important depending on the usage method of a fuel cell to keep the gas diffusivity in an electrode favorable with catalyst activity. If the gas diffusibility in the electrode is poor, it tends to be difficult to pass a high current, which is not preferable in this case. From such a viewpoint, the value of the current density when the voltage was 0.2 V was investigated in the current-potential curves of the fuel cells of Examples 1 to 9 having good catalytic activity. The results are shown in Table 4.

From Table 4, there is a difference in the value of current density at 0.2 V among the examples, and the tendency is particularly good in Examples 3, 5, 6, 7, 8, and 9 where the light absorption coefficient of the composition is small. I understand. Therefore, when a composition having an extinction coefficient in the range of ^{0 to} 0.3 cm ⁻¹ ·% ⁻¹ is used, the fuel cell can be operated more favorably. At this time, as the proton conductive polymer having a smaller molecular weight is used, the extinction coefficient tends to increase, so that the adjustment of the composition tends to be difficult.

Further, the fuel cells of Examples 3 and 9 were subjected to continuous power generation for 500 hours, and the durability was compared. As a result, in the fuel cell of Example 3, the voltage at 0.5 A / cm ² was initially 0.72 V, but slightly decreased to 0.68 V. However, in the fuel cell of Example 9, Was almost constant within the initial range of 0.71V to 0.72V. Therefore, when a composition in which a proton conductive polymer having a higher molecular weight component is mixed together with a component having a molecular weight in terms of polyethylene glycol of 2000 to 23000, the fuel cell can be operated more favorably.

  The composition of the present invention is a composition in which an aromatic hydrocarbon-based proton conductive polymer is dispersed or dissolved, and has particularly good bonding properties with an aromatic hydrocarbon-based polymer electrolyte membrane. As Comparative Example 4, a similar durability test was performed on a fuel cell manufactured using a commercially available Nafion (registered trademark) solution (5%) which is a composition in which a fluorine-based proton conductive polymer is dispersed. . As a result, the initial voltage was as good as 0.72 V, but after 500 hours, the voltage dropped to 0.61 V. When the internal resistance of the fuel cell was measured by the current interruption method in order to identify the cause, an increase in resistance that was not observed when the composition of the present invention was used was observed. This is presumed to be due to a decrease in the bondability at the interface between the electrode and the polymer electrolyte membrane.

  Similar investigations were also conducted for aromatic hydrocarbon polymers having different molecular structures.

(Proton conductive polymer synthesis example 2)
In the synthesis 1 of the proton-conducting polymer, 3,3′-disulfo-4,4′-dichlorodiphenyl ketone disodium salt is used instead of S-DCDPS, and the procedure differs according to the method of the synthesis of the proton-conducting polymer 1. Proton conducting polymers D and E having molecular weight distribution were synthesized.

(Proton conductive polymer synthesis example 3)
In a four-necked flask, 0.12 mol of DCBN, 0.1 mol of 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 0.27 mol of potassium carbonate , 200 ml of NMP was taken, heated in an oil bath in a nitrogen atmosphere, and reacted with 30 g of molecular sieve at 130 ° C. with stirring. Thereafter, the reaction was carried out at 200 ° C. for 3 hours. Thereafter, 0.02 mol of DCBN was further added and reacted for another 4 hours. The resulting reaction solution was allowed to cool, the precipitate was removed by filtration, and the filtrate was poured into 4 l of methanol. The precipitated product was separated by filtration, collected, dried, and dissolved in NMP. This was reprecipitated in 4 l of methanol and dried. Then, 0.03 mol of the obtained oligomer, 0.068 mol of 2,5-dichloro-4 ′-(4-phenoxy) phenoxybenzophenone (DCPPB), 0.02 mol of bis (triphenylphosphine) nickel dichloride, iodide 0.01 mol of sodium, 0.028 mol of triphenylphosphine, and 0.18 mol of zinc powder were placed in a flask and purged with dry nitrogen. NMP100ml was added, it heated at 90 degreeC, and it superposed | polymerized by changing reaction time. Proton conducting polymers F and G having different molecular weight distributions having a polyarylene ether structure in the main chain and a sulfonated polyarylene structure in the side chain by reprecipitation by adding the polymerization solution to water, washing and drying. Got.

(Proton conductive polymer synthesis example 4)
S-DCDPS 0.014 mol, DCBN 0.036 mol, terminal hydroxyl group-containing polyphenylene ether oligomer (abbreviation: DPE) (Dai Nippon Ink's SPECIANOL DPE-PL, lot C106) (n = 1-7 as repeating units of phenylene ether monomer A mixture containing the components (average composition n = 4.0) 0.05 mol, potassium carbonate 0.065 mol, and dried molecular sieve 13 g were weighed into a 200 ml four-necked flask and flushed with nitrogen. 110 ml of N-methyl-2-pyrrolidone was added, the mixture was heated and stirred, and the reaction temperature was raised to 190 to 200 ° C. to cause the reaction. The polymerization degree of the polymer was adjusted by changing the reaction time. After allowing to cool, the polymerization solution was poured into water to precipitate the polymer into strands. The obtained polymer was washed in boiling water for 1 hour and then dried. Next, after immersing in 1 liter of 1 mol / liter sulfuric acid aqueous solution with stirring overnight, the operation of washing again in boiling water for 1 hour is repeated three times, followed by drying under reduced pressure, so that proton conduction having different molecular weight distribution is achieved. Polymers H and I were obtained.

  The properties of the proton conducting polymers D, E, F, G, H and I are shown in Table 5.

  A composition containing polymers D, E, F, G, H, I was prepared. All the compositions were adjusted so that proton conductive polymer / water / 1-propanol / 1,2-diethoxyethane = 5/62/18/15 (weight ratio). All of the obtained compositions were transparent, and it was confirmed that the polymer could be dissolved (dispersed) well. Using electrodes prepared using the respective compositions, an electrode / electrolyte membrane assembly was prepared according to the above-described method, incorporated into a fuel cell, and resistance-free voltage was measured. Table 6 shows the characteristics of the composition and the power generation result of the fuel cell.

  In Table 6, the comparison of the fuel cell using the composition produced using the polymer of the same system of Example (Comparison between Example 10 and Comparative Example 4, Comparison between Example 11 and Comparative Example 5, Example 12 and From the comparison of Comparative Example 6, it can be seen that the fuel cell of Example shows a higher resistance-free voltage than that of Comparative Example and has excellent fuel cell characteristics. Thus, even when the structure of the proton conductive polymer was changed, it was confirmed that the power generation performance was different due to the influence of the molecular weight. Therefore, the absolute value of the electrode performance may change depending on the molecular structure of the proton conducting polymer (somewhat lower in the proton conducting polymer 4), but when compared with essentially the same series of polymers, By suppressing the molecular weight within the range of the present invention, the catalyst performance can be satisfactorily extracted.

  The power generation performance shown in the embodiment is related to a fuel cell using hydrogen as a fuel as an example. However, it can be used in a fuel cell using a hydrocarbon fuel such as methanol. it can.

  The fuel cell produced using the composition containing the aromatic hydrocarbon proton conductive polymer of the present invention can exhibit good fuel cell catalytic performance. Moreover, the joined body with the polymer electrolyte membrane made of an aromatic hydrocarbon proton conductive polymer can improve the problem of poor connectivity between the electrode and the electrolyte membrane. Therefore, it can be used effectively for a fuel cell.

Claims (7)

  A solvent composition containing at least an aromatic hydrocarbon-based proton conductive polymer in the range of 1 to 30% by weight, wherein the component having a molecular weight in terms of polyethylene glycol in the range of 2000 to 23000 in the proton conductive polymer is A composition containing 10% by weight or more based on the total amount of the proton conductive polymer.   The molecular weight distribution of the aromatic hydrocarbon-based proton conductive polymer has two or more maximum values, and at least one of the maximum values is in the range of 2000 to 23000 in terms of polyethylene glycol equivalent molecular weight. The composition according to claim 1, wherein at least one of the values is in a region larger than 23000 in terms of polyethylene glycol equivalent molecular weight.   3. The maximum value in the region where the molecular weight in terms of polyethylene glycol is greater than 23,000 in the molecular weight distribution of the aromatic hydrocarbon proton conductive polymer is in the range of 50,000 to 120,000 in terms of polyethylene glycol. A composition according to 1.   The composition according to claim 1, wherein the solvent contained in the composition contains at least water in the range of 1 to 85% by weight. A composition according to claim 1, an extinction coefficient at 750nm in the visible light absorption spectrum of the composition, to be in the range of 0~0.3cm ^-1 ·% ^-1 Characteristic composition.   A catalyst ink comprising the composition according to any one of claims 1 to 5 and a catalyst.   An electrode / electrolyte membrane joint comprising an electrode produced using the catalyst ink according to claim 6 and laminated with a polymer electrolyte membrane made of an aromatic hydrocarbon proton conductive polymer. A fuel cell with a built-in body.