JP2005232202A - Multilayer ion-exchange membrane, membrane/electrode assembly and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion-exchange membrane which has both good inhibition of methanol permeation and joining properties to electrodes and is suitably used in a fuel cell, particularly a direct methanol fuel cell, a membrane/electrode assembly using the ion-exchange membrane, and a fuel cell. <P>SOLUTION: The ion-exchange membrane is a multilayer ion-exchange membrane obtained by laminating two or more layers, and respective layers are constituted of different ion exchange resins, and at least one of the ion-exchange layers is a polyarylene ether compound containing a constituting component represented by chemical formula (1) (wherein Ar is a divalent aromatic group; Y is a sulfone group or a ketone group; and X is H or a cation species) and a constituting component represented by chemical formula (2) (wherein Ar' is a divalent aromatic group). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ion exchange membrane that can be used as a proton exchange membrane of a fuel cell and can achieve both compatibility with an electrode while suppressing the permeability of fuel such as methanol and hydrogen.

  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.

A direct methanol fuel cell uses an aqueous methanol solution as a fuel, but when methanol passes through the membrane and moves to the air electrode, the output is lowered. Therefore, when a perfluorocarbon sulfonic acid polymer membrane having a high methanol permeability is used in a direct methanol fuel cell, there is a problem that when a high concentration aqueous methanol solution is used, the amount of methanol permeated becomes large and the output is significantly reduced. Therefore, non-perfluorocarbon sulfonic acid ion exchange membranes having low methanol permeability have been studied. (For example, see Patent Documents 1 to 3)
JP 2003-288916 A JP 2003-331868 A US Patent Application Publication No. 2002/0091225

  However, although these hydrocarbon-based ion exchange membranes have methanol permeability smaller than that of perfluorocarbon sulfonic acid-based ion exchange membranes, their performance when used as fuel cells has not been satisfactory. Also, in perfluorocarbon sulfonic acid ion exchange membranes, the electrodes are usually joined by hot pressing or the like. However, if an attempt is made to join electrodes using a hydrocarbon ion exchange membrane by the same method, joint failures such as peeling often occur. It was. Therefore, a further excellent hydrocarbon ion exchange membrane is required.

  The present invention has been made against the background of the problems of the prior art, and both the methanol permeation suppressing property and the bonding property with the electrode are good, and the ion exchange membrane suitable for a fuel cell, particularly a direct methanol fuel cell, An object of the present invention is to provide a membrane / electrode assembly and a fuel cell using an ion exchange membrane.

  As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention

(1) A multilayer ion exchange membrane formed by laminating two or more layers, each of which is composed of different ion exchange resins, and at least one of the ion exchange resin layers has the chemical formula (1) An ion exchange membrane, which is a polyarylene ether compound containing a constituent represented by the chemical formula (2).

化学式（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。

Chemical 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.

化学式（２）
ただし、Ａｒ'は２価の芳香族基を示す。

Chemical formula (2)
However, Ar ′ represents a divalent aromatic group.

(2) A multilayer ion exchange membrane formed by laminating two or more layers, and each layer is composed of different ion exchange resins, and at least one of the ion exchange resin layers has the chemical formula (1) An ion exchange membrane, which is a polyarylene ether compound containing a constituent represented by the chemical formula (3).

化学式（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。

Chemical 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.

化学式（３）
ただし、Ａｒ'は２価の芳香族基を示す。

Chemical formula (3)
However, Ar ′ represents a divalent aromatic group.

(3) The ion exchange membrane according to (1) or (2), wherein the polyarylene ether compound has a sulfonic acid group content in the range of 0.3 to 3.5 meq / g.

(4) The ion exchange membrane according to any one of (1) to (3), wherein the polyarylene ether-based compound includes a constituent represented by the chemical formula (5) together with the chemical formula (4).

化学式（４）

化学式（５）
ただし、ＸはＨまたは１価のカチオン種を示す。

Chemical formula (4)

Chemical formula (5)
X represents H or a monovalent cation species.

(5) An ion comprising a plurality of ion exchange membrane resin layers, wherein the ion exchange membrane resin layer is composed of the polyarylene ether compound according to any one of (1) to (4) Exchange membrane.

(6) The ion exchange membrane according to any one of (1) to (5), wherein the ion exchange capacity of the outermost ion exchange resin layer is larger than the ion exchange capacity of the inner ion exchange resin layer .

(7) A membrane / electrode assembly using the ion exchange membrane according to any one of (1) to (6).

(8) A fuel cell using the ion exchange membrane according to any one of (1) to (6).

(9) The fuel cell according to (8), wherein methanol is used as a fuel.
It is.

  The ion exchange membrane according to the present invention is an excellent ion exchange membrane that hardly permeates methanol as a fuel and has improved bonding properties with an electrode. Therefore, it is particularly suitable for a direct methanol fuel cell.

Hereinafter, the present invention will be described in detail.
The ion exchange membrane of the present invention is a multilayer ion exchange membrane formed by laminating two or more layers, and each layer is composed of different ion exchange resins, and at least one of the ion exchange resin layers is A polyarylene ether compound having a specific structure is included. A preferable form of the polyarylene ether-based compound in the present invention includes those containing the structural component represented by the chemical formula (2) together with the chemical formula (1).

化学式（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。

Chemical 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.

化学式（２）
ただし、Ａｒ'は２価の芳香族基を示す。
化学式（２）で示される構成成分は、化学式（３）で示される構成成分であることが好ましい。

Chemical formula (2)
However, Ar ′ represents a divalent aromatic group.
The component represented by the chemical formula (2) is preferably a component represented by the chemical formula (3).

ただし、Ａｒ'は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  Moreover, the polyarylene ether compound in the present invention may contain structural units other than those represented by the chemical formulas (1) and (2). At this time, it is preferable that structural units other than those represented by the chemical formula (1) or the chemical formula (2) are 50% by weight or less of the polyarylene ether in the present invention. By setting it as 50 mass% or less, it can be set as the composition which utilized the characteristic of the polyarylene ether type compound in this invention.

  In the polyarylene ether compound in the present invention, the structural unit represented by the chemical formula (1) is preferably in the range of 10 to 60 mol%, more preferably 20 to 50 mol%. If it is less than 10 mol%, the proton conductivity is too low, which is not preferable, and if it is more than 50 mol%, it is not preferable because it exhibits water solubility or excessive swelling.

  As the polyarylene ether compound in the present invention, a compound containing a structural component represented by the chemical formula (5) together with the chemical formula (4) is particularly preferable. By having a biphenylene structure, the dimensional stability in methanol and its aqueous solution and the methanol permeation inhibiting performance are excellent, and the toughness of the film is also high.

化学式（４）

化学式（５）
ただし、ＸはＨまたは１価のカチオン種を示す。

Chemical formula (4)

Chemical formula (5)
X represents H or a monovalent cation species.

  In the polyarylene ether compound composed of the structural units represented by the chemical formula (4) and the chemical formula (5) in the present invention, the structural unit represented by the chemical formula (4) is in the range of 18 to 58 mol% of the whole. It is more preferable, and it is further more preferable that it is 20-40 mol%. If it is less than 10 mol%, the proton conductivity is too small, which is not preferable, and if it is more than 58 mol%, it is not preferable because it exhibits water solubility or excessive swelling.

  The polyarylene ether compound in the present invention can be polymerized by an aromatic nucleophilic substitution reaction containing the compounds represented by the chemical formulas (6) and (7) as monomers. Specific examples of the compound represented by the chemical formula (6) include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3,3. Examples include '-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl sulfone, and those whose sulfonic acid group is converted to a salt with a monovalent cationic species. It is done. 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 (7) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. .

化学式（６）

化学式（７）
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及び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、加工性及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。

Chemical formula (6)

Chemical formula (7)
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 with 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-described aromatic nucleophilic substitution reaction, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used in combination with the compounds represented by the chemical formulas (6) and (7) 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 component represented by the chemical formula (1) and Ar ′ in the component represented by the chemical formula (2) are generally represented by the chemical formula (6) described above in the aromatic nucleophilic substitution polymerization. It is a structure introduced from an aromatic diol component monomer used together with the compound represented by (7). 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-bi (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, etc. 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.

  When the polyarylene ether compound in the present invention is polymerized by an aromatic nucleophilic substitution reaction, an activated difluoroaromatic compound and / or a dichloroaromatic compound and an aromatic compound including compounds represented by the chemical formula (6) and the chemical formula (7) A polymer can be obtained by reacting diols 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 weight. When the amount is less than 5% by weight, the degree of polymerization 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. 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.

  The polyarylene ether compound in 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 tends to become brittle when molded as an ion exchange 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 ion exchange capacity of the polyarylene ether compound in the present invention is preferably in the range of 0.3 to 3.5 meq / g, and more preferably in the range of 1.0 to 2.5 meq / g. More preferably, it is in the range of 1.2 to 2.1 meq / g. When the ion exchange capacity is smaller than 0.3 meq / g, proton conductivity becomes too small, which is not preferable. When the ion exchange capacity is smaller than 3.5 meq / g, membrane swelling and dissolution occur, and methanol permeability is remarkably increased.
Of the ion exchange resin layers, at least one layer is in the range of 1.0 to 1.7 meq / g, and at least another layer has an ion exchange capacity of 1.4 to 2.1 meq / g. It is preferable to have. Of the respective ion exchange resins, any ion exchange resin may be a polyarylene ether compound having a specific structure in the present invention, but at least an ion exchange resin layer having a high ion exchange capacity has a specific structure in the present invention. An arylene ether-based compound is preferable from the viewpoint of suppressing membrane swelling and dissolution.

  In the ion exchange membrane of the present invention, it is preferable that all the layers contain the polyarylene ether compound having the specific structure described above, but some layers have ion exchange other than the polyarylene ether compound having the specific structure described above. You may consist of resin (other ion exchange resin). Examples of such ion exchange resins include ionomers containing at least one of polystyrenesulfonic acid, poly (trifluorostyrene) sulfonic acid, polyvinylphosphonic acid, polyvinylcarboxylic acid, and polyvinylsulfonic acid components, and aromatic polymers. As polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyphenylquinoxaline, polyaryl ketone, polyether ketone, polybenzoxazole, polybenzthiazole, polyimide, etc. A polymer in which at least one of a sulfonic acid group, a phosphonic acid group, a carboxyl group, and a derivative thereof is introduced into a polymer containing at least one component. It can be given over. Polysulfone, polyethersulfone, polyetherketone, and the like referred to here are generic names for polymers having a sulfone bond, an ether bond, and a ketone bond in the molecular chain thereof. Polyetherketoneketone, polyetheretherketone, It includes polyether ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone and the like, and is not limited to a specific polymer structure.

  Among other ion exchange resins, a polymer having a sulfonic acid group on an 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 a sulfonating agent include those using concentrated sulfuric acid or fuming sulfuric acid, which have been reported as an example of introducing a sulfonic acid group into an aromatic ring-containing polymer (for example, Solid State Ionics, 106, P.A. 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 sulfonic acid group-containing aromatic polyarylene ether compound of the present invention, it is possible to use these reagents and to select reaction conditions according to each polymer. Moreover, it is also possible to use the sulfonating agent described in Japanese Patent No. 2884189.

  Other ion exchange resins can also be synthesized using a monomer containing an acidic group in at least one of the monomers used for polymerization. For example, in a polyimide synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride, an acidified polyimide can be obtained by using a sulfonic acid group-containing diamine as at least one aromatic diamine. 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. be able to. In this case, it is preferable to use a sulfonic acid group-containing dihalide rather than using a sulfonic acid group-containing diol because the degree of polymerization tends to increase and the thermal stability of the obtained acidic group-containing polymer increases.

  Other ion exchange resins are preferably polyarylene ether compounds such as sulfonic acid group-containing polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyether ketone polymers.

  The ratio of the various ion exchange resin layers in the ion exchange membrane of the present invention can take any value depending on the purpose and is not particularly limited, but the thickness of each layer is 10% or more of the whole. Preferably there is. The thickness of each layer can be estimated from the cast thickness of the solution at the time of film formation, or the thickness of each layer can be measured by dyeing sulfonic acid groups and observing under a microscope.

  In the ion exchange membrane of the present invention, each ion exchange resin layer may contain a polymer that is not an ion exchange resin. Examples of polymers that are not ion exchange resins 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, poly Acrylate resins such as methacrylic acid esters, polymethyl acrylates, polyacrylic acid esters, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, Cellulose resins such as cellulose acetate and ethyl cellulose, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone , Polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole and other aromatic polymers, epoxy resins, phenol resins, novolac resins, benzoxazine resins, etc. There are no particular restrictions on the thermosetting resin. A combination with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving the polymer dimensionality. When a sulfonic acid group is further introduced into these basic polymers, the composition The processability is more preferable. The content of these non-ion exchange resins in the ion exchange membrane of the present invention is preferably 50% by weight or less, and more preferably 30% by weight or less. If the content is 50% by weight or more, the sulfonic acid group concentration of the ion exchange membrane tends to be low and good ion conductivity tends to be not obtained, and the unit containing the sulfonic acid group becomes a discontinuous phase and becomes conductive. There is a tendency for the mobility of ions to decrease. 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 multilayer ion exchange membrane in the present invention can be made into an ion exchange membrane by any method such as extrusion, rolling or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. For example, it can be obtained by applying and drying a solution of the second ion exchange resin on a first ion exchange resin layer prepared in advance. Application | coating of an applicator, a coater, etc. may be used for application | coating of a solution, and you may spray using a spray etc. Solvents used for dissolving the ion exchange resin include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphonamide, methanol, An appropriate alcohol can be selected from alcohols such as ethanol, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The polymer concentration in the solution is preferably in the range of 0.1 to 50% by weight. If the polymer concentration in the solution is less than 0.1% by weight, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by weight, the processability 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 compound non-solvent that can be mixed with a solvent that dissolves the compound, or the like. When the solvent is an organic solvent, it is preferable to distill off the solvent by heating or drying under reduced pressure. At this time, if necessary, it can be molded in a form combined with other compounds. 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 article thus obtained may contain a salt form with a cationic species, but it can be converted to a free sulfonic acid group by acid treatment as necessary. You can also.

  The ion exchange membrane in the present invention can have an arbitrary thickness, but if it is 20 μm or less, it becomes difficult to satisfy the predetermined characteristics, so that it is preferably 20 μm or more, and more preferably 50 μm or more. Moreover, since manufacture will become difficult when it becomes 300 micrometers or more, it is preferable that it is 300 micrometers or less.

  Casting from a solution is most preferable as a method for forming an ion exchange membrane from the polyarylene ether compound and the resin composition thereof in the present invention. Obtaining a laminated ion exchange membrane by casting the solution of the second ion exchange resin on the first ion exchange resin layer obtained by removing the solvent from the cast solution as described above and removing the solvent. Can do. 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 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 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 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, 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. 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. When used as an ion exchange membrane, the sulfonic acid group in the membrane may contain a metal salt, but 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.

  In the multilayer ion exchange membrane of the present invention, it is preferable that the ion exchange capacity of the ion exchange resin layer of the outer layer is higher than that of the inside because the bondability between the membrane and the electrode is improved. As a preferred example, a multilayer ion exchange membrane having a structure having an outer layer having a high ion exchange capacity on both surfaces of an inner layer having a low ion exchange capacity can be mentioned.

  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 polyarylene ether compound or the resin composition thereof on the electrode surface is preferable. 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 direct methanol fuel cell using methanol as a fuel, but can also be suitably used for a fuel cell using other substances such as dimethyl ether and hydrogen as a fuel. It can be used for any application known as an ion exchange membrane such as a membrane.

  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 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).

Conductivity: Constant temperature / humidity oven (80 ° C, 95% relative humidity) with a platinum wire (diameter: 0.2 mm) pressed against the surface of a strip-shaped film sample on a self-made measurement probe (manufactured by 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]

  Methanol permeation rate (M): The liquid fuel permeation rate of the ion exchange membrane was measured as the permeation rate of methanol 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 while stirring the cells on both sides at 25 ° C. was calculated using a gas chromatograph ( The area of the ion exchange membrane is 2.0 cm 2).

  Evaluation of bondability with electrode: After adding a small amount of ultrapure water and isopropyl alcohol to Pt / Ru catalyst-supporting carbon (TEC61E54, Tanaka Kikinzoku Kogyo Co., Ltd.) Was added so that the weight ratio of Pt / Ru catalyst-supported 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, which is 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 DuPont 20% Nafion solution (product number: SE-20192) is added to the Pt catalyst-supporting carbon. A cathode catalyst paste was prepared by adding carbon and Nafion at a weight ratio of 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. A membrane sample is sandwiched between the above two types of carbon papers with an electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, and is heated and pressurized at 135 ° C. and 7 MPa for 3 minutes by a hot press method. An electrode assembly was obtained. The completed membrane / electrode assembly was observed, and the bondability was evaluated from the peeling of the electrode.

  Power generation evaluation: The obtained membrane / electrode assembly 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 oxygen gas (80 ml / min) adjusted to 40 ° C. and a 5 mol / L aqueous methanol solution (1.5 ml / min) to the anode and cathode, respectively. . The output voltage at a current density of 0.05 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 measured. After stirring with an aqueous sodium hydroxide solution, the ion exchange capacity was determined by back titration with an aqueous hydrochloric acid solution. .
[Example]

Synthesis example 1
3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) 61.406 g (0.1250 mol), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 64.504 g ( 0.3750 mol), 4,4′-biphenol 88.428 g (0.4749 mol), potassium carbonate 93.105 g (0.5000 mol) and molecular sieve 52.0 g were weighed into a 2000 ml four-necked flask and flushed with nitrogen. . After adding 550 ml of N-methyl-2-pyrrolidone (abbreviation: NMP) and stirring at 150 ° C. for 70 minutes, the reaction temperature is increased to 195-200 ° C. Continued (about 8 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 2 hours and then dried. The logarithmic viscosity of the polymer was 1.53.

Synthesis example 2
A polymer having a logarithmic viscosity of 1.03 was obtained in the same manner as in Synthesis Example 1 except that 110.531 g (0.2250 mol) of S-DCDPS and 47.3037 g (0.2750 mol) of DCBN were used.

Synthesis example 3
A polymer having a logarithmic viscosity of 1.21 was obtained in the same manner as in Synthesis Example 1 except that 85.969 g (0.1750 mol) of S-DCDPS and 55.903 g (0.3250 mol) of DCBN were used.

Example 1
10.0 g of the polymers of Synthesis Example 1 and Synthesis Example 2 were each dissolved in 30 ml of NMP. First, the polymer solution of Synthesis Example 1 was cast on a glass plate on a hot plate to a thickness of about 500 μm and dried at 150 ° C. for 4 hours to obtain a film. On one side of the obtained film, the polymer solution of Synthesis Example 2 was cast to a thickness of about 250 μm, dried at 150 ° C. for 4 hours to laminate the polymer layer of Synthesis Example 2, and on the other side in the same manner. The polymer layer of Synthesis Example 2 was laminated. 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.

Comparative Example 1
10.0 g of the polymer of Synthesis Example 3 was dissolved in 30 mL of NMP, cast to a thickness of about 1000 μm on a glass plate on a hot plate, 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.

Comparative Example 2
An ion exchange membrane was prepared and evaluated in the same manner as in Comparative Example 1 except that 10.0 g of the polymer of Synthesis Example 2 was dissolved in 30 mL of NMP.

Comparative Example 3
An ion exchange membrane was prepared and evaluated in the same manner as in Comparative Example 1 except that 10.0 g of the polymer of Synthesis Example 3 was dissolved in 30 mL of NMP.

Comparative Example 4
Various evaluations were performed on Nafion (trade 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.

  As can be seen from Table 1, the ion exchange membranes of the examples are more effective in suppressing methanol permeation and proton conductivity than the ion exchange membrane of Comparative Example 1 which is a hydrocarbon ion exchange membrane having the same ion exchange capacity. It can be seen that they are equivalent or better and have excellent bonding properties with the electrodes. The ion exchange membranes of Comparative Examples 2 and 3 in which the ion exchange resins of Synthesis Examples 1 and 2 that are constituents of the ion exchange membrane of Example 1 are made into ion exchange membranes alone have poor bonding properties as in Comparative Example 2. It can be seen that methanol permeability is remarkably increased as in Comparative Example 3, which is not preferable. Further, Nafion (trade name) 117, which is a known perfluorocarbon sulfonic acid ion exchange membrane, is not preferred because of its extremely large methanol permeability.

  It has been shown that the ion exchange membrane of the present invention is an ion exchange membrane excellent in both methanol permeation suppression and electrode bonding properties. The ion exchange membrane of the present invention is suitable for use in an ion exchange membrane for a fuel cell, particularly suitable for a direct methanol fuel cell, and greatly contributes to the industry.

Claims (9)

It is a multilayer ion exchange membrane formed by laminating two or more layers, and each layer is composed of different ion exchange resins, and at least one of the ion exchange resin layers has chemical formula (2) together with chemical formula (1). An ion exchange membrane characterized in that it is a polyarylene ether-based compound containing a component represented by

Chemical 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.

Chemical formula (2)
However, Ar ′ represents a divalent aromatic group. It is a multilayer ion exchange membrane formed by laminating two or more layers, and each layer is made of a different ion exchange resin, and at least one of the ion exchange resin layers has chemical formula (3) together with chemical formula (1). An ion exchange membrane characterized in that it is a polyarylene ether-based compound containing a component represented by

Chemical 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.

Chemical formula (3)
However, Ar ′ represents a divalent aromatic group.   The ion exchange membrane according to claim 1 or 2, wherein the polyarylene ether compound has a sulfonic acid group content in the range of 0.3 to 3.5 meq / g. The ion exchange membrane according to any one of claims 1 to 3, wherein the polyarylene ether compound includes a constituent represented by the chemical formula (5) together with the chemical formula (4).

Chemical formula (4)

Chemical formula (5)
X represents H or a monovalent cation species.   An ion exchange membrane comprising a plurality of ion exchange membrane resin layers, wherein the ion exchange membrane resin layer is composed of the polyarylene ether compound according to any one of claims 1 to 4.   The ion exchange membrane according to any one of claims 1 to 5, wherein an ion exchange capacity of the outermost ion exchange resin layer is larger than an ion exchange capacity of the inner ion exchange resin layer.   7. A membrane / electrode assembly using the ion exchange membrane according to claim 1.   A fuel cell comprising the ion exchange membrane according to claim 1.   The fuel cell according to claim 8, wherein methanol is used as a fuel.