JP2006206809A - Sulfonic group-containing polymer, polymer composition comprising said polymer, ion exchange resin and ion exchange membrane obtained using said polymer, and membrane/electrode assembly obtained using said ion exchange membrane, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel sulfonic group-containing polymer applicable to an ion exchange membrane, an ion exchange resin comprising the polymer, a membrane/electrode assembly obtained using the ion exchange membrane, and a fuel cell. <P>SOLUTION: The sulfonic group-containing polymer comprises a recurring unit having a structure represented by chemical formula (1). In chemical formula (1), X is an -S(=O)<SB>2</SB>- group or a -C(=O)- group; Y is H or a monovalent cation; and Ar<SP>1</SP>is a structure represented by chemical formula (2) (wherein R<SP>1</SP>and R<SP>2</SP>are each independently a group selected from the group consisting of a hydrogen atom and 1-4C alkyl groups; and n1 and n2 are each independently an integer of 0-2). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sulfonic acid group-containing polymer having a novel structure, a composition of the polymer, an ion exchange resin, an ion exchange membrane, a membrane / electrode assembly, and a fuel cell using the polymer.

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. Above all, polymer electrolyte fuel cells using polymer electrolyte membranes have high energy density, and because they have features such as being easy to start and stop because of lower operating temperatures than other types of fuel cells. Developments as power supply devices for electric vehicles and distributed power generation are advancing. Among solid polymer fuel cells, a direct methanol fuel cell that directly supplies methanol as a fuel can be miniaturized, and is being developed for applications such as power supplies for personal computers and portable devices.

  As the polymer solid electrolyte membrane, a membrane containing a proton conductive ion exchange resin is usually used. In addition to proton conductivity, the polymer solid electrolyte membrane must have characteristics such as fuel permeation deterrence and mechanical strength that prevent permeation of hydrogen and the like of the fuel. As such a polymer solid electrolyte membrane, for example, a membrane containing a perfluorocarbon sulfonic acid polymer into which a sulfonic acid group is introduced as represented by Nafion (registered trademark) manufactured by DuPont, USA is known.

  However, perfluorocarbon sulfonic acid ion exchange membranes have relatively high fuel permeability such as hydrogen and methanol, and it is necessary to suppress the permeation of fuel in order to obtain higher performance as a fuel cell.

In particular, in direct methanol fuel cells that use aqueous methanol as fuel, the output decreases when methanol passes through the membrane and moves to the air electrode. For perfluorocarbon sulfonic acid polymer membranes, methanol with a high concentration of aqueous methanol is used. There was a problem that the amount of permeated light was increased and the output was significantly reduced. Therefore, various hydrocarbon ion exchange membranes have been studied as non-perfluorocarbon sulfonic acid type having low methanol permeability. (For example, see Patent Documents 1 to 3)
JP 2003-288916 A JP 2003-331868 A However, although these hydrocarbon-based ion exchange membranes are less permeable to methanol than perfluorocarbon sulfonic acid-based ion exchange membranes, their performance as fuel cells is sufficient. There is a need for a better ion exchange membrane.

  The present invention solves the above problems, and in a polymer electrolyte fuel cell, an ion exchange membrane capable of suppressing permeation of fuel such as methanol and obtaining excellent fuel cell performance, and to be used for the ion exchange membrane It is an object of the present invention to provide a novel sulfonic acid group-containing polymer that can be produced, an ion exchange resin comprising the sulfonic acid group-containing polymer, a membrane / electrode assembly using the ion exchange membrane, and a fuel cell.

  The present invention relates to a sulfonic acid group-containing polymer comprising a repeating unit having a structure represented by the following chemical formula (1).

[In the chemical formula (1), X represents a —S (═O) ₂ — group or C (═O) — group, Y represents H or a monovalent cation, and Ar ¹ represents the following chemical formula (2). Each structure is represented. ]

[In the chemical formula (2), R ¹ and R ² are each independently a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n 1 and n 2 are each independently 0 to 2 Each represents an integer. ]
The sulfonic acid group-containing polymer of the present invention preferably contains a repeating unit having a structure represented by the following chemical formula (3).

[In the chemical formula (3), Ar ² represents one of the structures represented by the following chemical formulas (4) to (7), and Ar ³ represents the structure represented by the chemical formula (2). ]

In the sulfonic acid group-containing polymer of the present invention, X is a —S (═O) ₂ — group, Ar ¹ and Ar ² are structures represented by the following chemical formula (8), and Ar ³ is a chemical formula (6 Or a structure represented by the chemical formula (7).

  In the sulfonic acid group-containing polymer of the present invention, the number of moles (o) of the repeating unit comprising the structure represented by the chemical formula (1) and the number of moles (p) of the repeating unit comprising the structure represented by the chemical formula (3). Is preferably in the range of 5/95 to 95/5.

  The present invention relates to a polymer composition comprising the above sulfonic acid group-containing polymer.

  The present invention relates to an ion exchange resin comprising the above sulfonic acid group-containing polymer.

  The present invention relates to an ion exchange membrane comprising the above sulfonic acid group-containing polymer.

  The present invention relates to a membrane / electrode assembly using the above sulfonic acid group-containing polymer or ion exchange membrane.

  The present invention also relates to a fuel cell using the above sulfonic acid group-containing polymer or ion exchange membrane.

In the present invention, the —SO ₃ Y group in the chemical formula (1) is referred to as “sulfonic acid group” unless otherwise specified. In the present invention, the compound having a structure represented by the chemical formula also includes stereoisomers produced during synthesis due to inhibition of free rotation of the bond axis due to steric hindrance.

  In the novel sulfonic acid group-containing polymer of the present invention or the ion exchange membrane obtained from the sulfonic acid group-containing polymer, a specific structure having a terphenyl structure is contained in the sulfonic acid group-containing polymer, so that While maintaining an ion exchange capacity and proton conductivity equal to or higher than those of the exchange membrane, it is possible to improve permeation suppression of fuel such as methanol. As a result, when the ion exchange membrane is used as a fuel cell, it is possible to further increase the energy utilization efficiency.

  Hereinafter, the present invention will be described in detail.

  The present invention relates to a sulfonic acid group-containing polymer containing a repeating unit having a structure represented by the following chemical formula (1).

[In the chemical formula (1), X represents a —S (═O) ₂ — group or C (═O) — group, Y represents H or a monovalent cation, and Ar ¹ represents the following chemical formula (2). Each structure is represented. ]

[In the chemical formula (2), R ¹ and R ² are each independently a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n 1 and n 2 are each independently 0 to 2 Each represents an integer. ]
In the chemical formula (1), it is preferable that X is a —S (═O) ₂ — group because the solubility of the polymer or monomer in the solvent is increased, so that polymerization and processing are easy.

In the chemical formula (1), when Y is H (proton), it is suitable as a proton exchange resin or a proton exchange membrane. Y represents H or a monovalent cation. Examples of the monovalent cation include alkali metal ions such as Na, K, and Li, ammonium ions, and quaternary ammonium ions. When the monovalent cation is an alkali metal ion such as Na, K, or Li, the thermal stability of the sulfonic acid group is enhanced, and the polymer can be processed at a high temperature in processing processes such as film formation, dissolution, and molding. Can improve the workability. The sulfonic acid group in the form of an alkali metal salt can be converted to a free sulfonic acid group (—SO ₃ H) by treating the polymer with a strong acid such as sulfuric acid, hydrochloric acid, perchloric acid or an aqueous solution thereof. . A polymer having a sulfonic acid group exhibits high proton conductivity, and can be used as a proton exchange resin or a proton exchange membrane. Among them, the proton exchange membrane can be used as an electrolyte of a polymer electrolyte fuel cell, and a fuel cell having excellent performance can be obtained by using the polymer of the present invention.

Ar ¹ in the chemical formula (1) is a group having a structure represented by the chemical formula (2). In the chemical formula (2), R ¹ and R ² are each independently a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms. When the number of carbon atoms increases, a high molecular weight polymer is obtained. The carbon number is preferably as small as possible because it is difficult to be formed and the swelling property with water or methanol increases. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertiary butyl group, and a cyclobutyl group. preferable. n1, n2 is an integer of independently 0-2, when R ^1, R ² is an alkyl group having 1 to 4 carbon atoms, n1, the n2 increases, difficult to obtain high molecular weight polymer In addition, since the swellability due to water or methanol increases, it is preferably as small as possible, and 0 or 1 is preferable. If both n1 and n2 are 0, the solubility of the raw material monomer is lowered and it becomes difficult to obtain a high molecular weight polymer. Therefore, one of n1 and n2 is 1 and the other is 0. Preferably there is. The most preferred example is a structure in which ^one of R ¹ and R ² is a methyl group, the other one is an H atom, one of n1 and n2 is 1, and the other is 0. be able to.

  In chemical formula (2), the three phenyl groups may be covalently linked at any position. Specific examples of the chemical formula (2) are shown in the following chemical formulas (2-A) to (2-AR), but are not limited thereto.

  In the chemical formula (2), it is preferable from the viewpoint of swelling resistance that all three phenyl groups are linked at the para position. As a more preferable structure of the chemical formula (2), the structures shown in the chemical formula (2-A) and the chemical formula (2-C) to the chemical formula (2-K) are mentioned, and among them, the structure shown in the chemical formula (2-A) is the most. preferable.

  In the sulfonic acid group-containing polymer of the present invention, the repeating structure represented by the chemical formula (1) may be contained in a range of 5 to 95 mol% of the whole polymer, and more preferably 10 to 80 mol%. It is a range, More preferably, it is the range of 30-60 mol%. In the present invention, the repeating unit in the polymer represents the minimum unit structure reacted with the monomer used to synthesize the polymer. That is, when the monomer is, for example, an aromatic dihalogen compound and a bis (thio) phenol compound, the repeating unit refers to a unit structure in which an aromatic dihalogen compound and a bis (thio) phenol compound are reacted one molecule at a time. If the monomer is a compound having, for example, one aromatic halogen group and one (thio) phenol group in the molecule, it is possible to react with each other to form a polymer. The repeating unit refers to a unit structure derived from one molecule of the compound. Further, when a polymer compound synthesized separately instead of a monomer composed of a low molecular compound is used as the macromonomer, the structure of the minimum reaction unit of the monomer for synthesizing the macromonomer may be used as the repeating unit. As the repeating structure represented by the chemical formula (1) increases, proton conductivity and ionic conductivity increase, but water absorption and swelling properties also increase. Therefore, an optimum introduction amount is used according to the application and purpose. Thus, the excellent performance of the polymer of the present invention can be maximized. For example, when used as a proton exchange membrane for a fuel cell, the range is 45 to 80 mol% in the case of a fuel cell using hydrogen as a fuel, and 10 to 10 in the case of a fuel cell directly using a liquid fuel such as an aqueous methanol solution. A range of 45 moles is suitable respectively.

  In the sulfonic acid group-containing polymer of the present invention, the portion other than the repeating structure represented by the chemical formula (1) preferably has a structure not containing a sulfonic acid group. In this case, it is possible to prevent a significant increase in water absorption and swelling properties of the sulfonic acid group-containing polymer of the present invention and to impart physical strength to the polymer. A preferred example includes a structure represented by the following chemical formula (3).

[In the chemical formula (3), Ar ² represents one of the structures represented by the following chemical formulas (4) to (7), and Ar ³ represents the structure represented by the chemical formula (2). ]
When the structure represented by the chemical formula (3) is included, the water absorption and swelling properties of the sulfonic acid group-containing polymer are prevented from being significantly increased, fuel permeation deterrence is imparted, and physical strength is also improved. Moreover, since Ar < ² > has an electron withdrawing group as represented by chemical formula (4)-(7) in Chemical formula (3), oxidation resistance is provided to a sulfonic acid group containing polymer.

In chemical formula (3), Ar ² is preferably a structure represented by chemical formula (4), (6), (7), and more preferably a structure represented by chemical formula (6) or (7). preferable.

  In the sulfonic acid group-containing polymer of the present invention, other than the structure represented by the chemical formula (1) such as the repeating unit of the structure represented by the chemical formula (1) or the structure represented by the chemical formula (3). The order of arrangement of repeating units may be alternating, block, or random. If it is a block copolymer, it will show the tendency for proton conductivity and water absorption to become high.

  As specific examples of preferred structures of the sulfonic acid group-containing polymer in the present invention, chemical formula (9-A) to chemical formula (9-AU) are shown below, but the scope of the present invention is not limited to the following.

  Among the chemical formulas (9-A) to (9-AU), the chemical formulas (9-A) to (9-H) are preferable because they are excellent in proton conductivity and swelling resistance. The chemical formula (9-B) is more preferable. In the chemical formula (9-A) to chemical formula (9-AU), o and p are represented by the number of moles o of the repeating unit represented by the chemical formula (1) in the sulfonic acid group-containing polymer and the chemical formula (3). Only the number of moles p of the repeating unit is shown, and the arrangement of the repeating units of Chemical Formula (1) and Chemical Formula (3) is not limited. The arrangement of the structures represented by the chemical formula (1) and the chemical formula (3) may be either a block arrangement as represented by the chemical formula (9-A) to the chemical formula (9-AU), or an alternating or random arrangement. It may be. Here, the molar ratio o / p of o / p may satisfy the range of 5/95 to 95/5, more preferably o / p is in the range of 10/90 to 90/10, and still more preferably. O / p is in the range of 30/70 to 70/30.

  On the other hand, q in the chemical formulas (9-AO) to (9-AU) is preferably 1/2 or less of o, and more preferably 0. As the proportion of o increases, the proton conductivity and ionic conductivity increase, but the water absorption and swelling properties also increase. Therefore, the polymer of the present invention can be obtained by using the optimum introduction amount according to the application and purpose. The best performance can be demonstrated to the maximum. For example, when used as a proton exchange membrane for a fuel cell, in the case of a fuel cell using hydrogen as a fuel, a range of o / p of 45/55 to 80/20 is a fuel cell that directly uses a liquid fuel such as an aqueous methanol solution. In this case, the range of 10/90 to 45/55 is suitable. R is preferably ½ or less of p, more preferably 0. q and r represent only the number of moles of each repeating unit in the above chemical formula, and do not limit the arrangement of the repeating units. Each repeating unit in the above chemical formula is alternately arranged in addition to the block arrangement. Any arrangement may be used.

  The sulfonic acid group-containing polymer of the present invention can be polymerized by an aromatic nucleophilic substitution reaction from a mixture of monomers containing the compounds represented by chemical formula (10) and chemical formula (11) as essential components.

[In the chemical formula (10), A represents an H atom or a monovalent cation, X ¹ represents a halogen atom, and Z ² represents an —S (═O) ₂ — group or a C (═O) — group. ]

[In the chemical formula (11), R ³ and R ⁴ are each independently a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, n3 and n4 are each independently 0 to 2 Each represents an integer. ]
Specific examples of the compound represented by the chemical formula (10) 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 in which their sulfonic acid group is converted to a salt with a monovalent cationic 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 chemical formula (10) in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′- Sodium disulfonate-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone, 3, , 3′-sodium disulfonate-4,4′-difluorodiphenyl ketone, potassium 3,3′-disulfonate 4,4′-dichlorodiphenyl sulfone, potassium 3,3′-disulfonate 4,4′-difluorodiphenyl sulfone , Potassium 3,3′-disulfonate 4,4′-dichlorodiphenyl ketone, potassium 3,3′-disulfonate 4,4 ′ Difluoro diphenyl sulfone, etc. 3,3'-disulfonic acid potassium 4,4'-difluoro diphenyl ketone and the like.

  Examples of the compound represented by the chemical formula (11) include compounds represented by the following chemical formulas (11-A) to (11-E), but are not limited thereto.

  Among these, the compound of chemical formula (11-A) is preferable.

  In the aromatic nucleophilic substitution reaction described above, various activated dihalogen aromatic compounds, dinitroaromatic compounds, and bis (thio) phenol compounds are used as monomers together with the compounds represented by chemical formula (10) and chemical formula (11). You can also.

  Examples of activated dihalogen aromatic compounds include 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenyl. Examples include sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, decafluorobiphenyl, and the like. Other active aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like can also be used.

  Examples of bis (thio) phenol compounds include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 4,4′-biphenol, bis ( 4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4- Hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 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, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 4,4′-thiodiphenol, 4,4 ′ -Oxydiphenol, 4,4'-thiobisbenzenethiol, 1,3-benzenethiol, 1,4-benzenethiol, 4,4'-biphenyldithiol, etc. Various aromatic diols or various aromatic dithiols that can be used for the polymerization of polyarylene (thio) ether compounds by a substitution reaction can also be used, and are not limited to the above compounds. Preferred examples of the compound used in combination include 4,4'-biphenol and 9,9-bis (4-hydroxyphenyl) fluorene.

  When the sulfonic acid group-containing polymer in the present invention is polymerized by an aromatic nucleophilic substitution reaction, a compound having a structure represented by the chemical formula (10) and the chemical formula (11) and, if necessary, another activated dihalogen aromatic compound Or a dinitro aromatic compound, aromatic diols or aromatic dithiols, and a reaction in the presence of a basic compound to obtain a polymer. The degree of polymerization of the resulting polymer can be adjusted by adjusting the molar ratio of the reactive halogen group or nitro group to the reactive hydroxy group in the monomer to an arbitrary molar ratio. It is 8 to 1.2, more preferably 0.9 to 1.1, still more preferably 0.95 to 1.05, and a polymer having the highest degree of polymerization can be obtained when it is 1.

  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 basic compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc., but aromatic diols and aromatic dimercapto compounds can be converted into active phenoxide structures or phenylthiolates. Any structure can be used as long as it can be structured. The basic compound can be polymerized satisfactorily when used in an amount of 100 mol% or more based on the bisphenol compound, and is preferably in the range of 105 to 125 mol% based on the bisphenol compound. An excessive amount of bisphenol compound is not preferable because it causes side reactions such as decomposition.

  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 carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by mass. When the amount is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by mass, the viscosity of the reaction system becomes too high, and post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration. In addition, a polymer solution can be obtained by removing by-product salts by filtration.

  In addition, the sulfonic acid group-containing polymer in the present invention preferably has a polymer log viscosity measured by a method described later of 0.1 dL / g or more. When the logarithmic viscosity is less than 0.1 dL / g, the membrane tends to become brittle when molded as an ion exchange membrane. The logarithmic viscosity is more preferably 0.3 dL / g or more. On the other hand, when the logarithmic viscosity exceeds 5 dL / g, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  The ion exchange capacity of the sulfonic acid group-containing polymer in the present invention is preferably 0.1 meq / g or more, and preferably 3.5 meq / g or less. When the ion exchange capacity is smaller than 0.1 meq / g, proton conductivity tends to be low. On the other hand, when the ion exchange capacity is increased, proton conductivity is increased. However, when the ion exchange capacity is greater than 3.5 meq / g, there is a tendency that a problem that the membrane swells or dissolves in water tends to occur. A more preferred range is 0.5 to 3.5 meq / g, and a further preferred range is 1.0 to 2.5 meq / g.

  The ion exchange membrane in the present invention can have any thickness, but if it is smaller than 10 μm, it is difficult to satisfy predetermined characteristics such as fuel permeation deterrence and physical strength. More preferably, it is 30 μm or more. Moreover, since manufacture will become difficult when it becomes larger than 300 micrometers, it is preferable that it is 300 micrometers or less.

  The sulfonic acid group-containing polymer in the present invention can be used as a simple substance, but can also be used as a polymer composition in combination with other polymers. Examples of these polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyamides such as nylon 6, nylon 6,6, nylon 6,10 and nylon 12, polymethyl methacrylate and polymethacrylate. Acrylate resins such as polymethyl acrylate, polyacrylic acid esters, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, Cellulosic resins such as ethyl cellulose, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyether Heat curing of aromatic polymers such as sulfone, polyether ether ketone, polyether imide, polyimide, polyamide imide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There are no particular restrictions on the conductive resin. A resin composition with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving the polymer dimensional stability. When these sulfonic acid groups are further introduced into these basic polymers, The processability of the composition becomes more preferable. When used as these resin compositions, the sulfonic acid group-containing polymer of the present invention is preferably contained in an amount of 50% by mass or more and less than 100% by mass of the entire resin composition. More preferably, it is 70 mass% or more and less than 100 mass%. When the content of the sulfonic acid group-containing polymer of the present invention is less than 50% by mass of the whole resin composition, the sulfonic acid group concentration of the ion exchange membrane containing this resin composition is lowered, and good ion conductivity is obtained. In addition, the unit containing a sulfonic acid group tends to be a discontinuous phase and the mobility of ions to be conducted tends to be lowered. In addition, the composition of the present invention, if necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, Various additives such as a dispersant and a polymerization inhibitor may be included.

  The sulfonic acid group-containing polymer and the resin composition thereof in the present invention can be dissolved in an appropriate solvent to form a solution composition. Examples of the solvent include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and hexamethylphosphonamide, and alcohols such as methanol and ethanol. An appropriate one can be selected, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The solute concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the solute concentration in the solution is less than 0.1% by mass, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by mass, the workability tends to deteriorate.

The ion exchange membrane of the present invention can be obtained from the ion exchange resin containing the sulfonic acid group-containing polymer of the present invention by any method such as extrusion, rolling or casting. Among these, it is preferable to mold from a solution in which the ion exchange resin is dissolved in a suitable solvent. A method for obtaining a molded article of an ion exchange membrane from a solution can be performed using a conventionally known method. For example, in addition to heating and drying under reduced pressure, the molded product of an ion exchange membrane can be obtained by removing the solvent by immersion in a non-solvent that can be mixed with a solvent that dissolves the ion exchange resin and does not dissolve the ion exchange resin. Can do. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. At this time, if necessary, the ion exchange membrane can be molded in a form combined with another compound. When combined with a compound having a dissolution behavior similar to that of the ion exchange resin of the present invention, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded product thus obtained may contain a salt with a cationic species, but if necessary, a free sulfonic acid group (-SO ₃ H).

The most preferable method for forming an ion exchange membrane from a sulfonic acid group-containing polymer and a resin composition thereof in the present invention is casting from a solution, and the solvent is removed from the cast solution as described above to remove the ion exchange membrane. Can be obtained. Examples of the solution include a solution using an organic solvent such as N-methylpyrrolidone, N, N-dimethylformamide, and dimethyl sulfoxide, and in some cases, an alcohol solvent. The removal of the solvent is preferably by drying from the viewpoint of the uniformity of the ion exchange membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a polymer or a solvent, it can also dry at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed. The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 2000 μm. More preferably, it is 50-1500 micrometers. If the thickness of the solution is thinner than 10 μm, the form as an ion exchange membrane tends to be not maintained, and if it is thicker than 2000 μm, a non-uniform film tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled with the amount and concentration of the solution with a constant thickness using an applicator, a doctor blade, or the like, and with a cast area constant using a glass petri dish or the like. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, the evaporation rate can be reduced by lowering the temperature in the first stage. Further, when immersed in a non-solvent such as water, the solidification rate of the polymer can be adjusted by leaving the solution in air or an inert gas for an appropriate time. When used as an ion exchange membrane, the sulfonic acid group in the membrane may contain a metal salt with a cationic species, but free sulfonic acid groups (—SO ₃ H) can be obtained by appropriate acid treatment. ). In this case, it is also effective to immerse the membrane in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating.

  The membrane / electrode assembly of the present invention can be obtained by bonding the ion exchange membrane of the present invention to an electrode. As a method for producing this joined body, a conventionally known method can be used. For example, an adhesive is applied to the electrode surface to bond the ion exchange membrane and the electrode, or an ion exchange membrane and the electrode. There is a method of heating and pressurizing. Among these, the method of applying and bonding an adhesive mainly composed of the sulfonic acid group-containing polymer and the resin composition thereof to the electrode surface is preferred. This is because the adhesion between the ion exchange membrane and the electrode is improved, and it is considered that the proton conductivity of the ion exchange membrane is less impaired.

  The fuel cell of the present invention can be produced using the ion exchange membrane or the membrane / electrode assembly of the present invention. The ion exchange membrane of the present invention is suitable for a polymer electrolyte fuel cell, but is particularly suitable for a direct methanol fuel cell using methanol as a fuel. Moreover, it can be used suitably also for the fuel cell which uses other substances, such as dimethyl ether and hydrogen, as a fuel, and can be used for arbitrary uses known as ion exchange membranes, such as an electrolytic membrane and a separation membrane.

[Example]
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.

  Logarithmic viscosity: The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, and the viscosity was measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / Evaluation was made in c) (ta is the number of seconds that the sample solution was dropped, tb was the number of seconds that the solvent was dropped, and c was the polymer concentration).

Proton conductivity: A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped membrane sample on a self-made measurement probe (manufactured by Teflon (registered trademark)), and the sample is held in water at 25 ° C. The impedance between them was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. The measurement was performed while changing the distance between the electrodes, and the conductivity obtained by canceling the contact resistance between the film and the platinum wire was calculated from the gradient obtained by plotting the distance measured between the electrodes and the resistance measurement value estimated from the CC plot.
Conductivity [S / cm] = 1 / film width [cm] × film thickness [cm] × resistance interelectrode gradient [Ω / cm]
Methanol permeability: The liquid fuel permeation rate of the ion exchange membrane was measured as the methanol permeation rate by the following method. An ion exchange membrane immersed in a 5 M (mol / liter) aqueous methanol solution adjusted to 25 ° C. for 24 hours is sandwiched in an H-type cell, 100 ml of 5 M aqueous methanol solution is placed on one side of the cell, and 100 ml of ultrapure water ( 18 MΩ · cm) was injected, and the amount of methanol diffusing into the ultrapure water through the ion exchange membrane was measured using a gas chromatograph while stirring the cells on both sides at 25 ° C. (ion) The area of the exchange membrane is 2.0 cm ² ). A methanol permeability coefficient was determined from the obtained methanol permeation rate and the film thickness of the sample.

Evaluation of output voltage: After adding a small amount of ultrapure water and isopropyl alcohol to Pt / Ru catalyst-supporting carbon (TEC61E54) and moistening it, a 20 mass% Nafion (registered trademark) solution manufactured by DuPont (product number) : SE-20192) was added so that the mass ratio of Pt / Ru catalyst-carrying carbon to Nafion was 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. This catalyst paste was applied and dried by screen printing on Toray carbon paper TGPH-060 to be a gas diffusion layer so that the adhesion amount of platinum was 2 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for anode. . Further, after adding a small amount of ultrapure water and isopropyl alcohol to a Pt catalyst-supporting carbon (Tanaka Kikinzoku Kogyo Co., Ltd. TEC10V40E) and moistening it, a 20% by mass Nafion solution (product number: SE-20192) manufactured by DuPont Co. A cathode catalyst paste was prepared by adding the mass of supported carbon to Nafion so that the mass ratio was 2.5: 1 and stirring. This catalyst paste was applied to and dried on a Toray carbon paper TGPH-060 that had been subjected to water repellent treatment so that the amount of platinum deposited was 1 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for cathode. By sandwiching the membrane sample between the two types of carbon paper with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, pressurizing and heating at 130 ° C. and 8 MPa for 3 minutes by a hot press method, A membrane-electrode assembly was obtained. This joined body was incorporated into an evaluation fuel cell FC25-02SP manufactured by Electrochem, and a power generation test was performed using a fuel cell power generation tester (manufactured by Toyo Corporation). Power generation was performed at a cell temperature of 40 ° C. while supplying high purity air gas (80 ml / min) adjusted to 40 ° C. and a 5 mol / L aqueous methanol solution (1.5 ml / min) to the anode and the cathode, respectively. . The output voltage at a current density of 0.01 A / cm ² was evaluated.

  Ion exchange capacity: The weight of a sample dried at 100 ° C. for 1 hour and allowed to stand overnight at room temperature in a nitrogen atmosphere was weighed, stirred with an aqueous sodium hydroxide solution, and then ion exchange capacity was determined by back titration with an aqueous hydrochloric acid solution.

<Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: S-DCDPS) 1.595 g (3.248 mmol), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 0.911 g (5 .299 mol), 2-methyl-4,4′-dihydroxy-p-terphenyl (abbreviation: MDHTP) 2.362 g (8.546 mmol), potassium carbonate 1.299 g (9.401 mmol), dried molecular sieve 3- 1 g of A was weighed into a 50 ml four-necked flask and flushed with nitrogen. After adding 20 ml of N-methyl-2-pyrrolidone (abbreviation: NMP) and stirring at 150 ° C. for 30 minutes, the reaction temperature is increased to 195-200 ° C. Continued (about 18 hours). After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The obtained polymer was washed in boiling water for 1 hour and then dried. The logarithmic viscosity of the polymer was 0.72 dL / g. The obtained sulfonic acid group-containing polymer was subjected to ¹ H-NMR measurement in deuterated dimethyl sulfoxide at room temperature. FIG. 1 is a diagram showing a ¹ H-NMR spectrum of a sulfonic acid group-containing polymer synthesized in Example 1 and a chemical structure attributed from the spectrum. ^The signals denoted as NMP and DMSO in the ¹ H-NMR spectrum are derived from the solvent, not the polymer, and the signal denoted as NMP is a signal derived from the polymer polymerization solvent N-methyl-2-pyrrolidone, The signal indicated as DMSO is a signal derived from dimethyl sulfoxide as a solvent for NMR measurement. In addition, the signal indicated as H ₂ O is a signal derived from water adsorbed on the polymer, the signal indicated as acetone is a signal derived from the residue of the solvent used for washing the NMR tube, and indicated as a to m. The signal is a signal derived from a to m protons in the chemical formula.

  1.5 g of polymer was dissolved in 6 ml of NMP, cast on a glass plate on a hot plate to a thickness of about 400 μm, and dried at 150 ° C. for 4 hours to obtain a film. The obtained film was immersed in pure water at room temperature for 1 hour, and then immersed in a 2 mol / L sulfuric acid aqueous solution for 2 hours. Thereafter, the film was washed with pure water until the washing water became neutral, and allowed to stand in the air and dried to obtain an ion exchange membrane. The obtained ion exchange membrane was evaluated for ion exchange capacity, methanol permeability coefficient, proton conductivity, and output voltage.

<Example 2>
The amount of S-DCDPS is 2.973 g (6.052 mmol), the amount of DCBN is 0.756 g (4.382 mmol), the amount of MDHTP is 2.930 g (10.434 mmol), and the amount of potassium carbonate is 1.658 g ( Except for the change to 12 mmol), an ion exchange membrane was prepared and evaluated in the same manner as in Example 1. FIG. 2 is a diagram showing a ¹ H-NMR spectrum of a sulfonic acid group-containing polymer synthesized in Example 2 and a chemical structure attributed from the spectrum. ^The signal indicated as DMSO in the ¹ H-NMR spectrum is derived from a solvent, not a polymer, and the signal indicated as DMSO is a signal derived from dimethyl sulfoxide as an NMR measurement solvent. Further, the signal that describes the H ₂ O, the signal that describes the signal, and a~m derived from water adsorbed on the polymer is a signal derived from the protons a~m in formula.

<Comparative Example 1>
An ion exchange membrane was prepared and evaluated in the same manner as in Example 1 except that a sulfonic acid group-containing polymer having a known structure represented by the following chemical formula (12) was used.

<Comparative example 2>
An ion exchange membrane was prepared and evaluated in the same manner as in Example 1 except that a sulfonic acid group-containing polymer having a known structure represented by the following chemical formula (13) was used.

<Comparative Example 3>
An ion exchange membrane was prepared and evaluated in the same manner as in Example 1 except that a sulfonic acid group-containing polymer having a known structure represented by the following chemical formula (14) was used.

<Comparative example 4>
Evaluation similar to Example 1 was performed about Nafion (brand name) 112 which is a commercially available ion exchange membrane.

<Comparative Example 5>
Evaluation similar to Example 1 was performed about Nafion (brand name) 117 which is a commercially available ion exchange membrane.

  Table 1 shows the evaluation results of the ion exchange membranes of Examples and Comparative Examples.

  In the results shown in Table 1, as can be seen from the comparison between Example 1 and Comparative Example 1 and the comparison between Example 2 and Comparative Example 2, for example, the ion exchange membranes of the Examples have the same ion exchange capacity. As compared with an ion exchange membrane made of a polymer having a known structure with a proton conductivity and output voltage equal to or higher than that, the methanol permeability coefficient is kept small. Therefore, it can be seen that the ion exchange membrane according to the present invention is a membrane having both excellent output and proton conductivity and good methanol permeation inhibiting properties and excellent performance. In addition, compared with Nafion (trade name) 112 and Nafion (trade name) 117, which are commercially available ion exchange membranes, the ion exchange membranes of the examples show superior output voltage, and the methanol permeability coefficient is greatly improved. I understand that. From these results, it can be seen that the characteristics of the sulfonic acid group-containing polymer of the present invention can be greatly improved by using it in an ion exchange membrane for a fuel cell.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  When the sulfonic acid group-containing polymer of the present invention is used in an ion exchange membrane for a fuel cell, the fuel permeation inhibiting property can be improved without greatly reducing the output voltage and proton conductivity. Therefore, according to the present invention, it is possible to provide a fuel cell having excellent fuel utilization efficiency and high output.

1 is a diagram showing a ¹ H-NMR spectrum of a sulfonic acid group-containing polymer synthesized in Example 1 and a chemical structure assigned from the spectrum. FIG. It is a figure which shows the < ¹ > H-NMR spectrum of the sulfonic acid group containing polymer synthesize | combined in Example 2, and the chemical structure assigned from this spectrum.

Claims (11)

A sulfonic acid group-containing polymer containing a repeating unit having a structure represented by the following chemical formula (1).

[In the chemical formula (1), X represents a —S (═O) ₂ — group or C (═O) — group, Y represents H or a monovalent cation, and Ar ¹ represents the following chemical formula (2). Each structure is represented. ]

[In the chemical formula (2), R ¹ and R ² are each independently a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n 1 and n 2 are each independently 0 to 2 Each represents an integer. ] The sulfonic acid group-containing polymer according to claim 1, comprising a repeating unit having a structure represented by the following chemical formula (3).

[In the chemical formula (3), Ar ² represents one of the structures represented by the following chemical formulas (4) to (7), and Ar ³ represents the structure represented by the chemical formula (2). ]

X is a —S (═O) ₂ — group, Ar ¹ and Ar ² are structures represented by the following chemical formula (8), and Ar ³ is a structure represented by the chemical formula (6) or the chemical formula (7). The sulfonic acid group-containing polymer according to claim 2.

  The molar ratio o / p between the number of moles (o) of the repeating unit having the structure represented by the chemical formula (1) and the number of moles (p) of the repeating unit having the structure represented by the chemical formula (3) is 5 / The sulfonic acid group-containing polymer according to claim 2 or 3, which is in the range of 95 to 95/5.   A polymer composition comprising the sulfonic acid group-containing polymer according to claim 1.   An ion exchange resin comprising the sulfonic acid group-containing polymer according to claim 1.   An ion exchange membrane comprising the sulfonic acid group-containing polymer according to claim 1.   5. A membrane / electrode assembly using the sulfonic acid group-containing polymer according to claim 1.   A membrane / electrode assembly using the ion exchange membrane according to claim 7.   A fuel cell using the sulfonic acid group-containing polymer according to claim 1.   A fuel cell using the ion exchange membrane according to claim 7.

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