JP2005239849A - Sulfo-containing polymer, polymer composition, ion exchange resin, ion exchange membrane, membrane/electrode conjugate, fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare an ion exchange membrane for use in a solid polymer-type fuel cell, suppressing fuel permeation and yielding high performance, to obtain a new sulfo-containing polymer usable for the ion exchange membrane, to obtain an ion exchange resin made from the polymer, and to provide a membrane/electrode conjugate and the fuel cell each using the ion exchange membrane. <P>SOLUTION: The sulfo-containing polymer is composed of recurring units with a structure represented by formula(1) or (2)[ wherein, W<SP>1</SP>and W<SP>2</SP>are each sulfur atom or oxygen atom; and Ar<SP>1</SP>is a group of formula(3)( wherein, R<SP>1</SP>and R<SP>2</SP>are each a group selected from H and a 1-4C alkyl; and n1 and n2 are each an integer of 0-2 ) ]. <P>COPYRIGHT: (C)2005,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, 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 ion exchange membranes are less permeable to methanol than perfluorocarbon sulfonic acid ion exchange membranes, their performance when used as fuel cells is not sufficient, and even better ion exchange. There is a need for membranes.

  The present invention has been made against the background of the problems of the prior art, and an ion exchange membrane that can suppress the permeation of fuel in a polymer electrolyte fuel cell and obtain excellent performance, and a novel sulfonic acid that can be used therefor An object of the present invention is to provide a group-containing polymer, an ion exchange resin comprising the polymer, a membrane / electrode assembly using the ion exchange membrane, and a fuel cell.

  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 sulfonic acid group-containing polymer comprising a repeating unit having a structure represented by the following chemical formula (1) or (2).

化学式（１）

化学式（２）
［化学式（１）又は（２）において、Ｗ１及びＷ２はＳ原子あるいはＯ原子のいずれかを、Ａｒ１は下記化学式（３）で表される基を、それぞれ表す。］

Chemical formula (1)

Chemical formula (2)
[In chemical formula (1) or (2), W1 and W2 represent either an S atom or an O atom, and Ar1 represents a group represented by the following chemical formula (3). ]

化学式（３）
［化学式（３）において、Ｒ１、Ｒ２はそれぞれ独立して、Ｈ原子及び炭素数１〜４のアルキル基からなる群より選ばれる基を、ｎ１、ｎ２はそれぞれ独立して０〜２の整数を、それぞれ表す。］

Chemical formula (3)
[In the chemical formula (3), R1 and R2 each independently represents a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n1 and n2 each independently represents an integer of 0 to 2. , Respectively. ]

化学式（４）
［化学式（４）において、Ｙ１及びＹ２はＯ又はＳ原子を、Ｚ１は−Ｓ（＝Ｏ）２−基又は−Ｃ（＝Ｏ）−基を、ＡはＨ又は１価の陽イオンを、Ａｒ２は２価の芳香族基を、それぞれ表す。］ (2) The sulfonic acid group-containing polymer according to (1), comprising a repeating unit having a structure represented by the following chemical formula (4).

Chemical formula (4)
[In the chemical formula (4), Y1 and Y2 are O or S atoms, Z1 is -S (= O) 2- group or -C (= O)-group, A is H or monovalent cation, Ar2 represents a divalent aromatic group. ]

(3) In the repeating unit having the structure represented by the chemical formula (4), part or all of Ar2 is one or more divalents selected from the group consisting of the structures represented by the chemical formulas (5) to (7). The sulfonic acid group-containing polymer according to (2), which is an aromatic group of

化学式（５）

化学式（６）

化学式（７）
［化学式（５）〜（７）において、Ｒ３、Ｒ４はそれぞれ独立して、Ｈ原子及び炭素数１〜４のアルキル基からなる群より選ばれる基を、ｎ３、ｎ４はそれぞれ独立して０〜２の整数を、それぞれ表す。］

Chemical formula (5)

Chemical formula (6)

Chemical formula (7)
[In the chemical formulas (5) to (7), R3 and R4 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 n3 and n4 are each independently 0 to 0. Each represents an integer of 2. ]

(4) The molar ratio of the repeating unit having the structure represented by the chemical formula (1) or the chemical formula (2) and the repeating unit having the structure represented by the chemical formula (4) is in the range of 5/95 to 95/5. The polymer as described in (2) or (3) above,

(5) A polymer composition comprising the polymer described in (1) to (4).

(6) An ion exchange resin containing the polymer described in (1) to (4).

(7) An ion exchange membrane comprising the polymer described in (1) to (4).

(8) A membrane / electrode assembly obtained using the ion exchange membrane according to (7).

(9) A fuel cell using the polymer according to (1) to (4) and / or the ion exchange membrane according to (7).
It is.

  The ion exchange membrane obtained from the novel sulfonic acid group-containing polymer or the composition according to the present invention is superior in permeation suppression of fuel such as methanol as compared with conventional ion exchange membranes, and is used when used as a fuel cell. In addition, it has an excellent effect that it is possible to further increase the energy use efficiency.

Hereinafter, the present invention will be described in detail.
The novel sulfonic acid group-containing polymer of the present invention comprises a repeating unit having a structure represented by the following chemical formula (1) or (2).

化学式（１）

化学式（２）
［化学式（１）又は（２）において、Ｗ１及びＷ２はＳ原子あるいはＯ原子のいずれかを、Ａｒ１は下記化学式（３）で表される基を、それぞれ表す。］

Chemical formula (1)

Chemical formula (2)
[In chemical formula (1) or (2), W1 and W2 represent either an S atom or an O atom, and Ar1 represents a group represented by the following chemical formula (3). ]

化学式（３）
［化学式（３）において、Ｒ１、Ｒ２はそれぞれ独立して、Ｈ原子及び炭素数１〜４のアルキル基からなる群より選ばれる基を、ｎ１、ｎ２はそれぞれ独立して０〜２の整数を、それぞれ表す。］

Chemical formula (3)
[In the chemical formula (3), R1 and R2 each independently represents a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n1 and n2 each independently represents an integer of 0 to 2. , Respectively. ]

  In the chemical formula (1) or (2), oxidation resistance is improved when W1 and W2 are S atoms. In the chemical formula (3), when n1 and n2 are large, it is difficult to increase the degree of polymerization of the polymer, so that the smaller one is preferable, and 0 is most preferable. When the number of carbon atoms of R1 and R2 is large, it is difficult to increase the degree of polymerization of the polymer, so that a smaller one is preferable, and a methyl group is preferable. The bonding position in the chemical formula (3) is preferably the 4-position of the phenyl group. A preferred example of chemical formula (3) is shown in chemical formula (8).

化学式（８）

化学式（９）

Chemical formula (8)

Chemical formula (9)

  The novel sulfonic acid group-containing polymer of the present invention further preferably contains a repeating unit having a structure represented by the following chemical formula (4).

化学式（４）
［化学式（４）において、Ｙ１及びＹ２はＯ又はＳ原子を、Ｚ１は−Ｓ（＝Ｏ）２−基又は−Ｃ（＝Ｏ）−基を、ＡはＨ又は１価の陽イオンを、Ａｒ２は２価の芳香族基を、それぞれ表す。］

Chemical formula (4)
[In the chemical formula (4), Y1 and Y2 are O or S atoms, Z1 is -S (= O) 2- group or -C (= O)-group, A is H or monovalent cation, Ar2 represents a divalent aromatic group. ]

  In the chemical formula (4), the oxidation resistance is improved when X and / or Y is an S atom. Z is preferably a —S (═O) 2 — group from the viewpoint of durability of the polymer. When used as an ion exchange membrane for a fuel cell, it is preferable that A is substantially H, and 90% or more of the sulfonic acid groups are preferably H. Moreover, since stability of a sulfonic acid group improves when A is a cation, it is preferable that A is a cation such as potassium, sodium or lithium in the process of forming a film from a polymer. In this case, A can be converted from metal ions to H by treatment with a strong acid such as sulfuric acid or hydrochloric acid.

The molar ratio of the repeating unit having the structure represented by the chemical formula (1) or (2) and the repeating unit having the structure represented by the chemical formula (4) is preferably in the range of 5/95 to 95/5. More preferably, it is the range of 30 / 70-85 / 15, More preferably, it is the range of 55 / 45-75 / 25. When the number of repeating units having the structure represented by the chemical formula (1) or (2) is increased, fuel permeability such as methanol can be suppressed, which is preferable. When there are many repeating units of the structure represented by the chemical formula (4), proton conductivity increases. Since suppression of fuel permeation and proton conductivity are contradictory, an appropriate point can be selected according to the purpose.
The sulfonic acid group-containing polymer of the present invention can be polymerized by an aromatic nucleophilic substitution reaction containing the compounds represented by chemical formula (10) and chemical formula (11) as monomers. 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 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 (11) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. .

化学式（１０）

化学式（１１）

Chemical formula (10)

Chemical formula (11)

  However, Z2 represents -S (= O) 2- group or -C (= O)-group, A represents a monovalent cation species, and X represents chlorine, fluorine, iodine, bromine or nitro group. 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 aromatic nucleophilic substitution reaction described above, various activated dihalogen aromatic compounds and dinitroaromatic compounds can be used in combination with the compounds represented by the chemical formulas (10) and (11) 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, the structure of Ar1 in the chemical formula (1) or (2) is obtained by replacing the diol or dimercapto compound having the structure of the chemical formula (3) with the compound represented by the chemical formula (10) or (11) or the like. It can introduce | transduce by using as a monomer made to react.
Preferred examples of the diol or dimercapto compound having the structure of the chemical formula (3) include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, -Bis (4-mercaptophenyl) fluorene, 9,9-bis (3-methyl-4-mercaptosiphenyl) fluorene and the like can be mentioned. Also, a diol or dimercapto compound other than having the structure of chemical formula (3) can be used in combination, for example, 4,4′-biphenol, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxy). Phenyl) 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′-thiobisbenzenethiol, 4,4′-thiodiphenol, 3-methyl-4,4 '-Dihydroxy-p-terphenyl, 4,4'-dihydroxy-p-terphenyl and the like can be mentioned, but in addition, various kinds which can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction. Aromatic diols can also be used. Preferred examples among the compounds used in combination include 4,4′-biphenol, 3-methyl-4,4′-dihydroxy-p-terphenyl, 4,4′-dihydroxy-p-terphenyl, and the like. . These aromatic diols or dimercapto compounds can be used by mixing a plurality of aromatic diols or dimercapto compounds.

  The molar ratio of the diol or dimercapto compound having the structure of the chemical formula (3) and the other diol or dimercapto compound is preferably in the range of 100/0 to 20/70. If the ratio of the diol or dimercapto compound having the structure of the chemical formula (3) is decreased, the fuel permeation suppression property is decreased, which is not preferable.

  When the sulfonic acid group-containing polymer in the present invention is polymerized by an aromatic nucleophilic substitution reaction, a compound represented by chemical formula (11) and / or chemical formula (10), a diol or dimercapto compound having a structure of chemical formula (3), In some cases, the polymer can be obtained by adding another activated dihalogen aromatic compound, dinitroaromatic compound, aromatic diol or aromatic dimercapto compound and reacting 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 basic compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc., which can convert aromatic diols and aromatic dimercapto compounds into an active phenoxide structure. If it is, it can be used without being limited to these. 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.

  Further, 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 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 sulfonic acid group-containing polymer in the present invention is preferably 0.1 meq / g, more preferably 3.5 meq / g or less. A small ion exchange capacity is not preferable because proton conductivity decreases. As the ion exchange capacity increases, proton conductivity increases, but at the same time, problems such as swelling of the membrane and dissolution in water easily 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 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.

  The sulfonic acid group-containing polymer in the present invention can be used as a simple substance, but can also be used as a resin 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 Thermosetting of sulfone, polyether ether ketone, polyether imide, polyimide, polyamide imide, polybenzimidazole, polybenzoxazole, polybenzthiazole and other aromatic polymers, epoxy resin, phenol resin, novolac resin, benzoxazine resin, etc. 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 dimensionality, and when a sulfonic acid group is 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 weight of the entire 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 compound concentration in the solution is preferably in the range of 0.1 to 50% by weight. If the concentration of the compound 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 workability tends to deteriorate.

  The ion exchange membrane of the present invention can be obtained from the composition containing the sulfonic acid group-containing ion exchange resin of the present invention by any method such as extrusion, rolling or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. 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, the solvent is preferably distilled off 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 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 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 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. 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.

  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 and the ion exchange membrane and the electrode are bonded, or the ion exchange membrane and the electrode are bonded. 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.

  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: 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 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).

Power generation evaluation: After adding and dampening a small amount of ultrapure water and isopropyl alcohol to Pt / Ru catalyst-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd. TEC61E54), a DuPont 20% Nafion solution (product number: SE-20192) The Pt / Ru catalyst-supported carbon and Nafion were added so that the weight ratio 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. 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 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: A sample dried for 1 hour at 100 ° C. 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
80,37 g (0.1636 mol) of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS), 42.21 g of 2,6-dichlorobenzonitrile (abbreviation: DCBN) ( 0.2454 mol), 9,9-bis (4-hydroxyphenyl) fluorene (abbreviation: BPF) 154.78 g (0.409 mol), potassium carbonate 62.18 g (0.45 mol), molecular sieve 45 g in 2000 ml four-necked The flask was weighed and flushed with nitrogen. After adding 1000 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 12 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 0.78 dL / g. The 1H-NMR spectrum measured at room temperature in deuterated dimethyl sulfoxide is shown in FIG. In FIG. 1, the signals marked NMP and DMSO are derived from the solvent, not the polymer. An enlarged view of the polymer portion is shown in FIG. 15 g of the polymer was dissolved in 45 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.

Examples 2-3
Various ion exchange membranes were prepared and evaluated in the same manner as in Example 1 except that the molar ratio of S-DCDPS and DCBN was changed.

Example 4
S-DCDPS 60.27 g (0.123 mol), DCBN 49.24 g (0.286 mol), BPF 77.39 g (0.205 mol), 4,4′-biphenol (abbreviation: BP) 38.08 g (0.205 mol) The ion exchange membrane was prepared and evaluated in the same manner as in Example 1 except that the above was used.

Comparative Examples 1-3
BP was used in place of BPF, the monomer charge ratio was changed, and various ion exchange membranes were prepared and evaluated in the same manner as in Example 1.

Comparative Example 4
A monomer charge ratio was changed using 4,4′-dichlorodiphenylsulfone (abbreviation: DCDPS) instead of DCBN, and an ion exchange membrane having a known polymer structure was prepared and evaluated in the same manner as in Example 1.

Comparative Example 5
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 had methanol conductivity and output voltage equal to or higher than those of Comparative Examples 1 to 4 having comparable ion exchange capacities, and methanol. The permeation rate is low, and it can be seen that this is an excellent membrane that can achieve both high output and proton conductivity and methanol permeation blocking properties. Moreover, even if it compares with Nafion (brand name) 117 which is a commercially available ion exchange membrane, it shows an equivalent output voltage, and it can be seen that the methanol permeation-preventing property is greatly improved. From these facts, the sulfonic acid group-containing polymer of the present invention can greatly improve its characteristics when used in an ion exchange membrane for fuel cells, and contributes greatly to the industry.

It is the 1H-NMR spectrum which measured the polymer synthesize | combined in Example 1 in this invention at room temperature in deuterated dimethyl sulfoxide.

It is an enlarged view of the polymer part of the 1H-NMR spectrum which measured the polymer synthesize | combined in Example 1 in this invention at room temperature in deuterated dimethyl sulfoxide.

Explanation of symbols

NMP: signal derived from N-methyl-2-pyrrolidone as a polymer polymerization solvent DMSO: signal derived from dimethyl sulfoxide as an NMR measurement solvent

Claims (9)

A sulfonic acid group-containing polymer comprising a repeating unit having a structure represented by the following chemical formula (1) or (2):

Chemical formula (1)

Chemical formula (2)
[In chemical formula (1) or (2), W1 and W2 represent either an S atom or an O atom, and Ar1 represents a group represented by the following chemical formula (3). ]

Chemical formula (3)
[In the chemical formula (3), R1 and R2 each independently represents a group selected from the group consisting of an H atom and an alkyl group having 1 to 4 carbon atoms, and n1 and n2 each independently represents an integer of 0 to 2. , Respectively. ] The sulfonic acid group-containing polymer according to claim 1, comprising a repeating unit having a structure represented by the following chemical formula (4).

Chemical formula (4)
[In the chemical formula (4), Y1 and Y2 are O or S atoms, Z1 is -S (= O) 2- group or -C (= O)-group, A is H or monovalent cation, Ar2 represents a divalent aromatic group. ] In the repeating unit having the structure represented by the chemical formula (4), one or more divalent aromatics in which part or all of Ar2 is selected from the group consisting of the structures represented by the chemical formulas (5) to (7) The sulfonic acid group-containing polymer according to claim 2, wherein the polymer is a group.

Chemical formula (5)

Chemical formula (6)

Chemical formula (7)
[In the chemical formulas (5) to (7), R3 and R4 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 n3 and n4 are each independently 0 to 0. Each represents an integer of 2. ]   The molar ratio of the repeating unit having the structure represented by the chemical formula (1) or the chemical formula (2) and the repeating unit having the structure represented by the chemical formula (4) is in the range of 5/95 to 95/5. The polymer according to claim 2 or 3, wherein:   A polymer composition comprising the polymer according to claim 1.   An ion exchange resin comprising the polymer according to claim 1.   An ion exchange membrane comprising the polymer according to claim 1.   A membrane / electrode assembly obtained using the ion exchange membrane according to claim 7.   A fuel cell using the polymer according to claim 1 and / or the ion exchange membrane according to claim 7.

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