JP3651683B1 - Sulfonic acid group-containing polymer compound, ion conductive membrane obtained thereby, and article using the same - Google Patents

Abstract

Provided is a polymer electrolyte membrane that exhibits high ionic conductivity and exhibits excellent dimensional stability especially when wet.
A sulfonic acid group-containing polymer having an ion exchange capacity (IEC) of 2.0 meq / g or more, and a moisture absorption rate as the number of water molecules per sulfonic acid group in an atmosphere at 80 ° C. and a relative humidity of 95%. (Λ) shows a value smaller than the relational expression of IEC × 6-2, a sulfonic acid group-containing polymer compound, an ion conductive membrane using the sulfonic acid group-containing polymer compound, and the ion conduction Articles such as a composite of a membrane and an electrode and a fuel cell using the composite.
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Description

  The present invention relates to a sulfonic acid group-containing polymer compound, and more specifically, is a sulfonic acid group-containing polymer compound useful as a polymer electrolyte membrane having excellent moisture resistance, and further, a composite using the ion conductive membrane, The present invention relates to articles such as fuel cells.

  As an example of an electrochemical device using a polymer solid electrolyte as an ionic conductor instead of a liquid electrolyte, a water electrolyzer and a fuel cell can be raised. The polymer membrane used for these must be sufficiently stable chemically, thermally, electrochemically and mechanically with proton conductivity as a cation exchange membrane. For this reason, perfluorocarbon sulfonic acid membranes, typically “Nafion (registered trademark)” manufactured by DuPont of the United States, have been used. However, when the Nafion membrane is operated under conditions exceeding 100 ° C., the moisture content of the membrane is drastically lowered, and the membrane is significantly softened. In addition, even when operating under low humidification conditions, the moisture content of the membrane decreases, and sufficient power generation characteristics cannot be obtained. Furthermore, it is pointed out that the cost of the membrane is too high as an obstacle to the establishment of fuel cell technology.

In order to overcome such drawbacks, various polymer electrolyte membranes in which a sulfonic acid group is introduced into a non-fluorinated aromatic ring-containing polymer have been studied. As a polymer skeleton, considering heat resistance and chemical stability, aromatic polyarylene ether compounds such as aromatic polyarylene ether ketones and aromatic polyarylene ether sulfones can be regarded as promising structures, A sulfonated polyarylethersulfone (for example, see Non-Patent Document 1), a sulfonated polyetheretherketone (for example, see Patent Document 1), sulfonated polystyrene, and the like have been proposed. However, sulfonic acid groups introduced onto aromatic rings by sulfonation reaction of these polymers generally tend to be easily removed by heat, and as a method for improving this, sulfonic acid groups are introduced onto electron-withdrawing aromatic rings. A sulfonated polyarylether sulfone compound having high thermal stability has been proposed by polymerization using a monomer (see, for example, Patent Document 2). In this case, since the reactivity of a monomer is low, the problem which requires superposition | polymerization for a long time in order to obtain a polymer has arisen (for example, refer nonpatent literature 2). These non-fluorinated polymer electrolytes may have a low sulfonic acid group acidity, and in order to develop proton conductivity at the same level as that of the fluorinated polymer electrolyte membranes, the non-fluorinated polymer electrolytes are more suitable than those of fluorinated polymer electrolytes. It is necessary to introduce many sulfonic acid groups into the polymer chain. However, when the amount of the sulfonic acid group is increased, the swelling of the membrane when wetted tends to increase. In particular, there is a problem that becomes a hindrance during power generation on the high temperature side, and a membrane with more excellent dimensional stability is demanded.
JP-A-6-93114 (pages 15-17) US Patent Application Publication No. 2002/0091225 (page 1-2) Journal of Membrane Science (Netherlands) 1993, 83, p. 211-220 ACS Polymer Preprints, (USA), 2000, 41 (2), P.C. 1388-1389

  The object of the present invention is to provide proton conductivity at the same level as that of a fluorinated polymer while being a non-fluorinated polymer, have good processability and moisture resistance, and are wet even when a polymer electrolyte membrane is formed. An object of the present invention is to provide a sulfonic acid group-containing polymer compound capable of exhibiting excellent dimensional stability at the time, and further, an ion conductive membrane utilizing the characteristics of the sulfonic acid group-containing polymer compound and the ion conductive membrane An object of the present invention is to provide an article such as a fuel cell using the composite of the electrode and the electrode and the composite.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by examining the polymer characteristics of a polymer electrolyte in which a sulfonic acid is introduced onto an aromatic ring.

  That is, the present invention is achieved by the following (1) to (6).

  (1) Moisture absorption as a number of water molecules per sulfonic acid group in an atmosphere of 80 ° C. and 95% relative humidity in a sulfonic acid group-containing polymer having an ion exchange capacity (IEC) of 2.0 meq / g or more ( A sulfonic acid group-containing polymer compound, wherein λ) is smaller than the relational expression of IEC × 6-2.

  (2) The sulfonic acid group-containing polymer according to the first invention, which has the structural unit represented by the general formula (2) together with the general formula (1).

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、ＸはＨまたは１価のカチオン種を示す。

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  (3) A composition comprising 50 to 100% by mass of the polyarylene ether compound according to either the first invention or the second invention.

  (4) An ion conductive membrane comprising the compound according to any one of the first invention and the second invention and / or the composition according to the third invention.

  (5) A composite comprising the ion conductive membrane according to the fourth invention and an electrode.

  (6) A fuel cell comprising the composite according to the fifth invention.

  The sulfonic acid group-containing polymer compound of the present invention is excellent in moisture resistance, and the polymer electrolyte membrane using the sulfonic acid group-containing polymer compound is excellent in moisture resistance and dimensional stability. The polymer electrolyte membrane for fuel cells is also suitable.

Hereinafter, the present invention will be described in detail.
The present invention provides a polymer electrolyte membrane containing a sulfonic acid group, which has excellent dimensional stability, particularly dimensional stability when wet. The polymer electrolyte membrane containing a sulfonic acid group has a highly hydrophilic structure because of the sulfonic acid group, and the hygroscopic property increases as the amount of sulfonic acid group introduced is increased in order to enhance the ion conduction characteristics. Therefore, the resistance to swelling and shrinkage when the film absorbs and releases moisture tends to decrease. The present inventors have succeeded in obtaining a polymer electrolyte membrane that exhibits high ionic conductivity even under low humidity and has little dimensional deformation even during moisture absorption, while examining various properties possessed by the polymer electrolyte. . That is, a sulfonic acid group-containing polymer having an ion exchange capacity (IEC) of 2.0 meq / g or more, and a moisture absorption rate (λ) as the number of water molecules per sulfonic acid group in an atmosphere at 80 ° C. and a relative humidity of 95%. ) Exhibits a value smaller than the relational expression of IEC × 6-2, the object of the present invention can be achieved by the sulfonic acid group-containing polymer compound. In general, when sulfonic acid groups are introduced into the polymer electrolyte membrane in an amount of 2.0 meq / g or more in order to increase the ion conductivity, λ becomes a value larger than IEC × 6-2, and the membrane swelling at the time of moisture absorption is large. turn into. By setting λ to a value smaller than the relational expression of IEC × 6-2, it can be used as a polymer electrolyte membrane having good membrane dimensional stability when wet. It can be said that λ is more preferable if it is a value smaller than the relational expression of IEC × 6-3.

  The structure of the polymer electrolyte of the present invention is preferably an aromatic sulfonic acid group-containing polymer. Examples of such polymer skeletons include polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyphenylquinoxaline, polyaryl ketone, polyether ketone, polybenzoxazole, Examples thereof include polymers containing at least one component such as polybenzthiazole and polyimide. Polysulfone, polyethersulfone, polyetherketone, etc. as used herein are generic names for polymers having a sulfone bond, an ether bond, and a ketone bond in their molecular chains. In addition to a polymer skeleton structure called polyether ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone, etc., the specific polymer structure is not limited.

  Among the aromatic polymers, polymers such as polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone are preferable in terms of processability and stability. It is particularly preferable that the polymer is an aromatic polymer containing a constituent represented by the general formula (2).

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、ＸはＨまたは１価のカチオン種を示す。

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  The aromatic polymer containing the structural units represented by the general formula (1) and the general formula (2) may contain structural units other than those represented by the general formula (1) and the general formula (2). However, the structural units other than those represented by the general formula (1) or (2) are preferably 50% by mass or more, and particularly preferably 70% by mass in the polymer.

  In the sulfonic acid group-containing polymer compound of the present invention, the sulfonic acid group content is preferably 2.0 meq / g or more in terms of ion exchange capacity (IEC) in order to exhibit good ionic conductivity. From the viewpoint of ion conductivity, it can be said that IEC is preferably 2.2 or more, and more preferably 2.4 or more.

  The above-mentioned sulfonic acid group-containing polymer compound particularly preferably includes a constituent represented by the general formula (4) together with the following general formula (3). By having a biphenylene structure, the film has excellent dimensional stability under high-temperature and high-humidity conditions, and the film has higher toughness.

ただし、ＸはＨまたは１価のカチオン種を示す。

X represents H or a monovalent cation species.

  The above sulfonic acid group-containing polymer compound can be polymerized by an aromatic nucleophilic substitution reaction containing the compounds represented by the following general formulas (5) and (6) as monomers. Specific examples of the compound represented by the general formula (5) include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 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 (6) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. it can.

ただし、Ｙはスルホン基またはケトン基、Ｘは１価のカチオン種、Ｚは塩素またはフッ素を示す。本発明において、上記２，６−ジクロロベンゾニトリルおよび２，４−ジクロロベンゾニトリルは、異性体の関係にあり、いずれを用いたとしても良好なイオン伝導性、耐熱性、加工性および寸法安定性を達成することができる。その理由としては両モノマーとも反応性に優れるとともに、小さな繰り返し単位を構成することで分子全体の構造をより硬いものとしていると考えられている。

Y represents a sulfone group or a ketone group, X represents a monovalent cation species, and Z represents 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, good ion 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 above aromatic nucleophilic substitution reaction, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used in combination with the compounds represented by the general formulas (5) and (6) 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 unit represented by the general formula (1) and Ar ′ in the structural unit 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 (5) and (6). 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, 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- (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, 1,6-naphthalenediol, 2,7-naphthalenediol, bis (4- Hydroxyphenyl) ketone and the like can be mentioned, but various aromatic diols that can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction can also be used. These aromatic diols can be used alone, but a plurality of aromatic diols can be used in combination. Further, for example, it is possible to partially copolymerize monomer components having photoreactivity and heat reactivity so that a crosslinked structure can be introduced by light irradiation treatment or heat treatment after film formation.

  When the above sulfonic acid group-containing polymer compound is polymerized by aromatic nucleophilic substitution reaction, the activated difluoroaromatic compound and / or dichloroaromatic compound including the compounds represented by the above general formula (5) and general formula (6) 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 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 the post-treatment of the reaction product tends to be difficult. After the completion of the polymerization reaction, the polymer is precipitated as a solid by pouring the reaction solution into a solvent having low polymer solubility, and the polymer can be obtained by filtering the precipitate. Further, the desired polymer can be obtained by removing the solvent from the reaction solution by evaporation and washing the residue as necessary.

  The sulfonic acid group-containing polymer compound of the present invention preferably has a polymer log viscosity measured by a method described later of 0.1 or more. When the logarithmic viscosity is less than 0.1, the membrane is likely to be brittle when formed as an ion conductive membrane. The reduced specific viscosity is more preferably 0.3 or more. On the other hand, if the reduced specific viscosity exceeds 5, 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 sulfonic acid group-containing polymer compound of the present invention can also be used as a composition with other resin compounds. Examples of these polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon 6, nylon 66, nylon 610, and nylon 12, polymethyl methacrylate, polymethacrylates, and polymethyl. Acrylate resins such as acrylates and polyacrylates, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, cellulose such as ethyl cellulose Resin, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethers Thermal curing of aromatic polymers such as phon, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There is no particular limitation 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 polymer dimensional stability, and when a sulfonic acid group is further introduced into these basic polymers. The processability of the composition becomes more preferable. When using as these resin compositions, it is preferable that the compound which can be used for the polymer electrolyte of this invention is contained 50 to 100 mass% of the whole resin composition. More preferably, it is 70 mass% or more and less than 100 mass%. When the content of the compound that can be used in the polymer electrolyte of the present invention is less than 50% by mass of the entire resin composition, the sulfonic acid group concentration of the ion conductive membrane containing this resin composition is lowered, and good ion conductivity In addition, the unit containing a sulfonic acid group becomes a discontinuous phase, and the mobility of ions to be conducted tends to be lowered. In addition, the electrolyte membrane 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 compound of the present invention and the composition thereof can be formed into a molded body such as a fiber or a film by any method such as extrusion, spinning, rolling, or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. 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 compound concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the compound 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. A method of obtaining a molded body from a solution can be performed using a conventionally known method. For example, the molded product can be obtained by removing the solvent by heating, drying under reduced pressure, immersion in a solvent that is compatible with the solvent that dissolves the compound but not the compound itself, and the like. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. At this time, it can be formed into various shapes such as a fiber shape, a film shape, a pellet shape, a plate shape, a rod shape, a pipe shape, a ball shape, and a block shape by mixing with other compounds as necessary. . When combined with a compound having a similar dissolution behavior, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded body thus obtained may contain a salt formed with a cationic species, but may be converted to a free sulfonic acid group by acid treatment as necessary. it can.

  An ion conductive membrane can be produced from the sulfonic acid group-containing polymer compound of the present invention and the resin composition thereof. The most preferable method for forming the ion conductive membrane is casting from a solution, and the ion conductive membrane can be obtained by removing the solvent from the cast solution as described above. 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 evaporation of the solvent from the uniformity of the ion conductive membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a compound 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 1500 μm. More preferably, it is 50-500 micrometers. If the thickness of the solution is thinner than 10 μm, the form as an ion conductive membrane tends to be not maintained, and if it is thicker than 1500 μm, a non-uniform polymer electrolyte membrane tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, it can be applied on a substrate such as a glass plate, a polymer sheet, or a metal plate with a constant thickness using an applicator, a doctor blade, or the like, or a polymer solution such as a glass petri dish is poured to keep the solution area constant, The thickness can also be controlled by the concentration. 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. In addition, when immersed in a non-solvent such as water, the coagulation rate of the compound can be adjusted by leaving the solution in air or an inert gas for an appropriate time. The ion conductive film of the present invention can have any film thickness depending on the purpose, but it is preferably as thin as possible from the viewpoint of ion conductivity. Specifically, it is preferably 5 to 250 μm, more preferably 5 to 50 μm, and most preferably 5 to 20 μm. If the thickness of the ion conductive membrane is less than 5 μm, handling of the ion conductive membrane is difficult and a short circuit or the like tends to occur when a fuel cell is produced. The power generation performance tends to decrease. The obtained film may be subjected to post-treatment such as heat treatment or light irradiation as necessary to fix the film structure. When used as an ion conductive membrane, the sulfonic acid group in the membrane may contain a metal salt, but it can be converted to free sulfonic acid by an 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.

  Moreover, by installing an electrode on the above-described ion conductive membrane or film of the present invention, a joined body of the ion conductive membrane or film of the present invention and the electrode can be obtained. As a method for producing this composite, a conventionally known method can be used. For example, an adhesive is applied to the electrode surface and the ion conductive film and the electrode are bonded, or the ion conductive film and the electrode are combined. There is a method of heating and pressurizing. Among these, a method of applying and bonding an adhesive mainly composed of the sulfonic acid group-containing polymer compound of the present invention and the resin composition thereof to the electrode surface is preferable. This is because it is considered that the adhesion between the ion conductive film and the electrode is improved, and that the ion conductivity of the ion conductive film is less impaired.

  A fuel cell can also be produced using the above-described joined body of an ion conductive membrane or film and an electrode. Since the ion conductive membrane or film of the present invention is excellent in heat resistance, processability, ion conductivity and dimensional stability, it can withstand operation at high temperatures, is easy to produce, and has good output. A fuel cell can be provided. It is also preferable to use it as a fuel cell using methanol as a direct fuel.

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.
Solution viscosity: The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using an Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / C) (ta is the drop time of the sample solution, tb is the drop time of the solvent only, and c is the polymer concentration).
・ Ion conductivity measurement: Constant temperature / humidity oven at 80 ° C. and 95% RH by pressing a platinum wire (diameter: 0.2 mm) on the surface of a strip-shaped membrane sample on a self-made measurement probe (Teflon (R)) The sample was held in (Nagano Scientific Machinery Co., Ltd., LH-20-01), and the impedance between the platinum wires 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]
Moisture absorption: A film sample whose dry mass was measured was placed in a glass sample bottle capable of sealing, and a constant temperature / humidity oven set at 80 ° C. and a relative humidity of 95% (Nagano Scientific Machinery Co., Ltd., LH-20-01) ) For 1 hour, and the sample was taken out and sealed at the same time and allowed to cool to room temperature. Measure the mass of each sample bottle, measure the amount of moisture absorption from the increase in mass from the dry mass, and calculate the number of water molecules (λ) relative to the amount of sulfonic acid groups set at the time of polymer synthesis. In the case of a polymer having a sulfonic acid group introduced, it can be calculated using the amount of sulfonic acid group measured by titration).

Power generation evaluation: After adding a small amount of ultrapure water and isopropyl alcohol to a Pt / Ru catalyst-supporting carbon (TEC61E54) and moistening it, a 20% Nafion solution (product number: SE-20192) manufactured by DuPont is used. The Pt / Ru catalyst-carrying carbon and Nafion were added at a mass ratio of 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. The catalyst paste was applied and dried by screen printing on carbon paper TGPH-060 manufactured by Toray as a gas diffusion layer so that the amount of platinum deposited 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% Nafion solution (product number: SE-20192) manufactured by DuPont is used. A cathode catalyst paste was prepared by adding carbon and Nafion at a mass ratio of 2.5: 1 and stirring. This catalyst paste was applied and dried on carbon paper TGPH-060 manufactured by Toray Industries, Ltd., which had been subjected to water repellent finish, 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, by 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 a 2 mol / l aqueous methanol solution (1.5 ml / min) and high-purity oxygen gas (80 ml / min) adjusted to 40 ° C. to the anode and cathode, respectively.
Titration IEC: The weight of a sample dried overnight under a nitrogen atmosphere was weighed, stirred with an aqueous sodium hydroxide solution, and then ion exchange capacity (IEC) was determined by back titration with an aqueous hydrochloric acid solution.

Example 1
3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS 6.5411 g (0.01332 mol), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 1.8739 g (0. 01089 mol), 4.580 g (0.02421 mol) of 4,4′-biphenol, 3.8484 g (0.02784 mol) of potassium carbonate, and 2.61 g of molecular sieve were weighed into a 100 ml four-necked flask and flushed with nitrogen. The NMP was added and stirred at 150 ° C. for 1 hour, and then the reaction was continued by raising the reaction temperature to 195-200 ° C. to sufficiently increase the viscosity of the system (about 5 hours). The polymer obtained in the form of strands was precipitated in water except for the molecular sieve that had settled. After washing for 1 hour, dried. Amount of sulfonic acid group of the present polymer is a polymer which becomes 2.52 as the ion exchange capacity (IEC). The inherent viscosity of the polymer showed 1.43.
1 g of the polymer was dissolved in 5 ml of NMP, cast on a glass plate on a hot plate to a thickness of about 200 μm, NMP was distilled off until it became a film, and then immersed in water overnight. The obtained film was treated with boiling water in dilute sulfuric acid (concentrated sulfuric acid 6 ml, water 300 ml) for 1 hour to remove the salt, and then boiled with pure water for 1 hour to remove the acid component. When the ionic conductivity of this film was measured, it showed a value of 0.38 S / cm. The IEC determined by titration was 2.31. The moisture absorption rate (λ) of this film at 80 ° C. and a relative humidity of 95% contained 9.85 water molecules per sulfonic acid group. This film showed good dimensional stability with no change in form even after repeated immersion and extraction in hot water.

Examples 2-4
Polymers having different compositions were synthesized and evaluated in the same manner as in Example 1 except that the mixing ratio of S-DCDPS and DCBN was changed. Table 1 shows the results of moisture absorption measurement. All films showed good dimensional stability with no change in form even after repeated immersion and extraction in hot water.

Comparative Examples 1 and 2
In Example 2, polymers having different compositions were synthesized using 4,4′-dichlorodiphenylsulfone (DCDPS) instead of DCBN, and evaluated. Table 2 shows the results of moisture absorption measurement. Both films were deformed and wrinkled when they were repeatedly immersed in hot water and removed.

Example 4
When the power generation evaluation was performed using the film obtained in Example 2, good power generation characteristics of 0.32 V at a current density of 100 mA were obtained.

Example 5
3,3 ′, 4,4′-tetraaminodiphenylsulfone (abbreviation: TAS) 1.500 g (5.389 × 10 ⁻³ mole), terephthalic acid (abbreviation: TPA) 0.895 g (5.389 × 10 ⁻³ mole), 20.48 g of polyphosphoric acid (phosphorus pentoxide content 75%) and 16.41 g of phosphorus pentoxide are weighed into a polymerization vessel. Flow nitrogen and raise the temperature to 100 ° C while stirring gently on an oil bath. After maintaining at 100 ° C. for 1 hour, the temperature was raised to 150 ° C. for 1 hour, and the temperature was raised to 200 ° C. and polymerized for 4 hours. After completion of the polymerization, the mixture was allowed to cool, and water was added to take out the polymerized product, followed by repeated washing with a home mixer until the pH test paper was neutral. The obtained polymer was dried under reduced pressure at 80 ° C. overnight. The logarithmic viscosity of the polymer was 2.02. 0.3 g of this polymer and 2.7 g of the polymer obtained in Example 1 were dissolved in 20 ml of NMP, cast on a heated glass plate to a thickness of about 350 μm, and NMP was distilled off until a film was formed. Soaked over night. The obtained film was treated in dilute sulfuric acid at 70 ° C. (concentrated sulfuric acid 6 ml, water 300 ml) for 1 hour to remove the salt, and then left overnight in pure water to remove the acid component. The amount of sulfonic acid group of this film is a polymer having an ion exchange capacity (IEC) of 2.27. The ion conductivity of this film showed a value of 0.26 S / cm. The IEC determined by titration was 2.19. The moisture absorption rate of this film at 80 ° C. and a relative humidity of 95% contained 9.7 water molecules per sulfonic acid group. The film showed good dimensional stability with no change in form even after repeated immersion and extraction in hot water.

  The sulfonic acid group-containing polymer compound of the present invention can provide a polymer electrolyte material that is excellent in ion conductivity and particularly excellent in dimensional stability when wet. These can be used as ion-conducting membranes in fuel cells and water electrolyzers using hydrogen or methanol as raw materials, and can also be used as various battery electrolytes, display elements, sensors, binders, additives, etc. I can expect.

Claims (6)

A sulfone having an ion exchange capacity (IEC) of 2.0 meq / g or more, comprising an aromatic polymer obtained by copolymerizing at least one of polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone. It is an acid group-containing polymer, and the moisture absorption rate (λ) as the number of water molecules per sulfonic acid group in an atmosphere of 80 ° C. and relative humidity of 95% shows a value smaller than the relational expression of IEC × 6-2. A sulfonic acid group-containing polymer compound characterized by the above. The sulfonic acid group-containing polymer compound according to claim 1, which has a structural unit represented by the general formula (2) together with the general formula (1).

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

However, Ar ′ represents a divalent aromatic group. A composition comprising 50 to 100% by mass of the sulfonic acid group-containing polymer compound according to claim 1. An ion conductive membrane comprising the compound according to claim 1 and / or the composition according to claim 3. A composite comprising the ion conductive membrane according to claim 4 and an electrode. A fuel cell comprising the composite according to claim 5.