JP2008120956A - Sulfonic acid group-containing polymer, production method and application of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfonic acid group-containing polymer with improved physical durability, and to provide a polyelectrolyte membrane using the same, a membrane/electrode junction, a fuel cell, etc. <P>SOLUTION: The sulfonic acid group-containing polymer has at least a structural unit represented by chemical formula 1 and a structural unit represented by chemical formula 1'. X in the chemical formula 1 is -S(=O)<SB>2</SB>- group or -C(=O)- group, Y is H or a monovalent cation, R is a 1-10C alkylene group, a direct bond with a benzene ring, etc. Ar<SP>1</SP>in the chemical formula 1' is a divalent aromatic group having an electron-attracting group. n and m are each an integer more than 1 and expresses mole numbers of each structural unit, and the binding form of each structural unit may be a random, an alternating or a block form. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sulfonic acid group-containing polymer having a novel molecular structure and a production method thereof, a composition of the polymer, a polymer electrolyte membrane using the polymer, a membrane / electrode assembly, and a fuel cell.

  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.

  As the polymer solid electrolyte membrane, a proton conductive polymer electrolyte membrane 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 is known. However, since fluorine is contained in the molecule, harmful hydrofluoric acid is generated in the exhaust gas depending on the use conditions, and the environmental load is high at the time of disposal.

  Although perfluorocarbon sulfonic acid polymer electrolyte membranes have well-balanced characteristics as fuel cell electrolyte membranes, hydrocarbon polymer electrolyte membranes have been developed in order to obtain better membranes in terms of cost and performance. It is actively done.

  Many hydrocarbon polymer electrolyte membranes use a polymer in which an ionic group such as a sulfonic acid group is introduced into a heat-resistant polymer such as polyimide or polysulfone (see, for example, Patent Document 1).

  In general, hydrocarbon polymer electrolyte membranes are inferior in durability to perfluorocarbon sulfonic acid polymer electrolyte membranes, and therefore are physically or chemically reinforced. Increasing the molecular weight of the polymer that composes the polymer electrolyte membrane is one of the means to improve durability, but depending on the type of polymer, it often happens that it is difficult to obtain a polymer with a high degree of polymerization. It was.

  For example, in the case of a polymer that is polymerized by polycondensation, the number of reaction points decreases and the apparent reaction rate decreases as the degree of polymerization increases, so it is generally difficult to obtain a high molecular weight polymer (for example, patents). (Ref. 1 and 2).

JP-T-2004-509224 Japanese Patent Application Laid-Open No. 2004-149779

  An object of the present invention is to use a polymer electrolyte membrane that is capable of increasing the degree of polymerization that enables physical durability to be improved while having the same chemical characteristics as those of conventional polymers. And a polymer electrolyte membrane obtained from the polymer, a membrane / electrode assembly, and a fuel cell using the membrane / electrode assembly. is there.

  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 having at least a structural unit represented by the following chemical formula 1 and a structural unit represented by the following chemical formula 1 '.

［化学式１において、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｒは炭素数１〜１０のアルキレン基、オキシアルキレン基、アリーレン基、及びベンゼン環との直接結合からなる群より選ばれる１種以上の基を表す。化学式１’において、Ａｒ^１は電子吸引性基を有する２価の芳香族基から選ばれる１種以上の基を表す。ｎ及びｍはそれぞれの構造単位のモル数で１以上の整数を表し、化学式１及び化学式１’で表される構造単位の結合形態は、ランダム、交互、ブロック及びグラフトのいずれであってもよい。］

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, R represents an alkylene group having 1 to 10 carbon atoms, oxy It represents one or more groups selected from the group consisting of an alkylene group, an arylene group, and a direct bond with a benzene ring. In Chemical Formula 1 ′, Ar ¹ represents one or more groups selected from divalent aromatic groups having an electron-withdrawing group. n and m are the number of moles of each structural unit and represent an integer of 1 or more, and the bonding form of the structural units represented by Chemical Formula 1 and Chemical Formula 1 ′ may be random, alternating, block, or graft. . ]

(2) The sulfonic acid group-containing polymer according to (1), wherein Ar ¹ in chemical formula 1 ′ is one or more groups selected from structures represented by chemical formulas 2 to 5 below.

(3) The sulfonic acid group-containing polymer according to (2), wherein Ar ¹ in Chemical Formula 1 ′ is a structure represented by Chemical Formula 4 or 5.

(4) The sulfonic acid group-containing polymer according to any one of (1) to (3), wherein R is a direct bond between a SO ₃ Y group and a benzene ring.

(5) The sulfonic acid group-containing polymer according to any one of (1) to (4), wherein n and m in the chemical formula 1 and the chemical formula 1 ′ satisfy the following mathematical formula 1.

      0.05 ≦ n / (n + m) ≦ 0.70 (Formula 1)

(6) The sulfonic acid according to any one of (1) to (5), wherein the 0.5 g / dL N-methyl-2-pyrrolidone solution has a logarithmic viscosity at 30 ° C. of 2.0 to 5.0 dL / g. Group-containing polymer.

(7) A polymer electrolyte membrane comprising the sulfonic acid group-containing polymer as described in (1) to (6).

(8) A composition comprising the sulfonic acid group-containing polymer described in (1) to (6).

(9) A membrane / electrode assembly comprising the sulfonic acid group-containing polymer according to any one of (1) to (6) in at least one of the polymer electrolyte membrane or the electrode catalyst layer.

(10) A fuel cell having the membrane / electrode assembly according to (9).

(11) The method for producing a sulfonic acid group-containing polymer according to any one of (1) to (6), wherein a compound represented by the following chemical formula 6 is used as a raw material monomer.

である。

It is.

  The novel sulfonic acid group-containing polymer according to the present invention can obtain a polymer having a high degree of polymerization in a shorter time than conventional sulfonic acid group-containing polymers, and is highly durable when used as a polymer electrolyte membrane of a fuel cell. It has an excellent effect of making it possible.

  Hereinafter, the present invention will be described in detail. In the present invention, the weight means mass.

The sulfonic acid group-containing polymer of the present invention is a sulfonic acid group-containing polymer having a structure represented by Chemical Formula 1 and Chemical Formula 1 ′. X in Chemical Formula 1 represents a —S (═O) ₂ — group or a —C (═O) — group, and a —S (═O) ₂ — group is preferable because solubility in a solvent is increased. Moreover, it is preferable that it is -C (= O)-group since it becomes possible to give photocrosslinkability to a polymer.

  Y in Chemical Formula 1 represents H or a monovalent cation, but when used as a proton exchange membrane of a fuel cell, Y is preferably H. In processing such as dissolution, molding, and film formation, it is preferable that Y is a monovalent cation rather than H because the thermal stability of the sulfonic acid group is increased. Examples of monovalent cations include alkali metal ions such as Na, K and Li, ammonium ions and quaternary amine salts, and alkali metal ions such as Na, K and Li are preferred. The sulfonic acid group that is an alkali metal salt can be converted to a sulfonic acid group by treating the polymer with a strong acid such as sulfuric acid, hydrochloric acid, perchloric acid, or an aqueous solution thereof. A polymer having a sulfonic acid group exhibits high proton conductivity, and can be used as a proton exchange resin or a proton exchange membrane. Among them, the proton exchange membrane can be used as an electrolyte of a polymer electrolyte fuel cell, and a fuel cell having excellent performance can be obtained by using the polymer of the present invention.

  R in Chemical Formula 1 represents one or more groups selected from the group consisting of an alkylene group having 1 to 10 carbon atoms, an oxyalkylene group, an arylene group, and a direct bond with a benzene ring. Is preferable. In addition, a direct bond in which a sulfonic acid group and a benzene ring are directly bonded is more preferable because stability of the sulfonic acid group with respect to heat, radicals, and the like is increased and proton conductivity is excellent. The alkylene group is preferably a straight chain rather than a branched one. As for carbon number of an alkylene group, 1-5 are more preferable, and 3-4 are more preferable. Specifically, an n-propylene group and an n-butylene group are preferable. 1-5 are more preferable and, as for carbon number of an oxyalkylene group, 3-4 are more preferable. Specifically, an oxy-n-propylene group and an oxy-n-butylene group are preferable. Examples of the arylene group include an oxyphenylene group and a phenylene group.

  In the structural unit represented by the chemical formula 1, the following chemical formula 7;

  Specific examples of the partial structure represented by formula (1) are shown below, but are not limited thereto, and include those in which a part and all of the sulfonic acid groups form a monovalent cation. Of the following partial structures, Chemical Formulas 7A, 7B, 7C, and 7D are more preferable, and Chemical Formulas 7A and 7B are more preferable.

Ar ¹ in the chemical formula 1 ′ is an aromatic group having an electron-withdrawing group. Examples of electron withdrawing groups include sulfone groups, carbonyl groups, sulfonyl groups, phosphine groups, cyano groups, trifluoromethyl groups and other perfluoroalkyl groups, nitro groups, halogen groups, etc., cyano groups, sulfone groups A carbonyl group is preferred. The aromatic group represents a group having an aromatic ring. Examples of the group having an aromatic ring include a phenylene group, a pyridylene group, a naphthalene group, and an anthranylene group. In Ar ¹ , groups having aromatic rings may be connected to each other with an electron-withdrawing group.

Examples of Ar ¹ in Chemical Formula 1 ′ are shown below, but are not limited thereto.

Furthermore, Ar ¹ is preferably one or more groups selected from structures represented by Chemical Formulas 2 to 5. The structure of Chemical Formula 2 is preferable because solubility in a solvent is increased. Moreover, since it becomes possible to provide photocrosslinkability to a polymer, it is preferable that it is a structure of Chemical formula 3. Further, the structure of Chemical Formula 4 or 5 is preferable because the swelling property of the polymer becomes small. Among the following chemical formulas 2 to 5, the structure of chemical formula 4 or 5 is preferable, and the structure of chemical formula 5 is most preferable.

  The sulfonic acid group-containing polymer in the present invention may contain other structures other than the structure represented by Chemical Formula 1 as long as the effects of the present invention are not impaired. The other structure other than that represented by Chemical Formula 1 is preferably in the range of 0 to 50% by mass of the whole polymer, preferably in the range of 0 to 20% by mass, and in the range of 0 to 10% by mass. More preferably it is.

  Examples of other structures are shown below, but are not limited thereto.

  N and m in Chemical Formula 1 and Chemical Formula 1 ′ are each an integer of 1 or more, and n / (n + m) may be in the range of 0.01 to 1, preferably in the range of 0.05 to 0.70. The range of 0.1 to 0.6 is more preferable, and the range of 0.2 to 0.5 is more preferable. When the polymer electrolyte membrane of the present invention is used in a fuel cell using hydrogen as a fuel, n / (n + m) is preferably in the range of 0.4 to 0.6. When the polymer electrolyte membrane of the present invention is used in a fuel cell using a liquid such as methanol as a fuel, n / (n + m) is preferably in the range of 0.05 to 0.4, A range of 0.35 is more preferable. Although n + m should just exist in the range of 2-100,000, the range of 10-10000 is more preferable, and the range of 50-1000 is further more preferable. When n + m is smaller than 10, the molecular weight is small, and it may be difficult to obtain a molded body such as a film. If n + m is greater than 10,000, processing may be hindered, for example, the viscosity of the solution may increase significantly.

  The sulfonic acid group-containing polymer of the present invention can be used for an ion exchange resin, a polymer electrolyte membrane, a moisture absorbent resin, a moisture absorbent membrane, a moisture permeable membrane, an electrolyte membrane, and the like, and particularly preferably used as a polymer electrolyte membrane. Furthermore, the polymer electrolyte membrane using the sulfonic acid group-containing polymer of the present invention can be used as a proton exchange membrane by converting the sulfonic acid group to a sulfonic acid type, and is particularly suitable for a proton exchange membrane for a fuel cell. . The sulfonic acid group-containing polymer of the present invention is also suitable for use as an adhesive when a polymer electrolyte membrane or the like is bonded to an electrode or a catalyst.

  The polymer electrolyte membrane of the present invention can be made into a membrane / electrode assembly by joining an electrode or a catalyst. Moreover, the sulfonic acid group-containing polymer of the present invention can be used as an adhesive with an electrode or a catalyst for a film other than the polymer electrolyte membrane of the present invention. When the sulfonic acid group-containing polymer of the present invention is used as an adhesive, it is preferable that Y in Chemical Formula 1 is H and the sulfonic acid group is in acid form. When the sulfonic acid group is used in the form of a salt with a cation, the sulfonic acid group can be converted into an acid form by acid treatment after bonding.

  The sulfonic acid group-containing polymer of the present invention can be dissolved and dispersed in an appropriate solvent and used as a composition. Solvents that can be used include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphonamide, N-morpholine oxide, and the like. Polar solvents such as aprotic organic polar solvents, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone, ether solvents such as diethyl ether, mixtures of these organic solvents, and mixtures with water However, it is not limited to these.

  The concentration of the polymer solution is preferably in the range of 0.1 to 50% by mass. When forming a film, fiber, or the like from a solution, the concentration is more preferably in the range of 5 to 50% by mass, and further preferably in the range of 10 to 40% by mass. When the solution is used as an adhesive, the concentration is more preferably in the range of 0.1 to 20% by mass. When the solution is used as an adhesive, it may contain other components such as carbon particles carrying a catalyst such as Pt and PT-Ru, and a fluororesin.

  In the sulfonic acid group-containing polymer of the present invention, chemical formulas 10A to 10P, which are specific examples of preferred structures, are shown below, but the scope of the present invention is not limited to the following.

  The sulfonic acid group-containing polymer of the present invention can be polymerized by aromatic nucleophilic substitution reaction from a mixture of monomers containing the compounds represented by Chemical Formulas 11 to 13 as essential components.

In Chemical Formula 11, X represents a —S (═O) ₂ — group or —C (═O) — group, R represents an alkylene group having 1 to 10 carbon atoms, an oxyalkylene group, an arylene group, a SO ₃ Y group, and benzene. This represents either a direct bond with the ring, but an alkylene group is preferable because proton conductivity is improved. In addition, a direct bond in which a sulfonic acid group and a benzene ring are directly bonded is more preferable because stability of the sulfonic acid group with respect to heat, radicals, and the like is increased and proton conductivity is excellent. The alkylene group is preferably a straight chain rather than a branched one. As for carbon number of an alkylene group, 1-5 are more preferable, and 3-4 are more preferable. Specifically, an n-propylene group and an n-butylene group are preferable. 1-5 are more preferable and, as for carbon number of an oxyalkylene group, 3-4 are more preferable. Specifically, an oxy-n-propylene group and an oxy-n-butylene group are preferable. Examples of the arylene group include an oxyphenylene group and a phenylene group. Y represents H or a monovalent cation, and alkali metal ions such as Na, K, and Li are preferred. Z ¹ represents one or more groups selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and a nitro group.

  Specific examples of the compound represented by the chemical formula 11 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, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfobutyl- 4,4′-difluorodiphenyl sulfone, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl ketone, 3,3′-disulfobutyl-4,4′-difluorodiphenyl sulfone, and their sulfonic acid groups are monovalent Examples include salts with cation species. 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 in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfonic acid. Sodium-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone, 3,3 'Sodium disulfonate-4,4'-difluorodiphenyl ketone, potassium 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone, potassium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone 3,3′-Disulfonic acid potassium-4,4′-dichlorodiphenyl ketone, 3,3′-di Sulfonic acid potassium-4,4'-difluoro diphenyl sulfone, etc. 3,3'-disulfonic acid potassium-4,4'-difluoro diphenyl ketone and the like.

In Chemical Formula 12, Ar ¹ represents a divalent aromatic group having an electron-withdrawing group, and Z ² represents one or more groups selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and a nitro group. To express. Examples of the electron-withdrawing group in Ar ¹ include a sulfo group, a carbonyl group, a sulfonyl group, a phosphine group, a perfluoroalkyl group such as a cyano group and a trifluoromethyl group, a nitro group, a halogen group, and the like. Group, sulfone group and carbonyl group are preferred. The aromatic group in Ar ¹ represents a group having an aromatic ring. Examples of the group having an aromatic ring include a phenylene group, a pyridylene group, a naphthalene group, and an anthranylene group. In Ar ¹ , groups having aromatic rings may be connected to each other with an electron-withdrawing group.

  Examples of the compound represented by Chemical Formula 12 include compounds having a leaving group in a nucleophilic substitution reaction such as halogen and nitro group on the same aromatic ring, and an electron-withdrawing group for activating it. Specific examples include 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenylsulfone, 4,4 ′. -Difluorodiphenyl sulfone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, decafluorobiphenyl, and the like, but not limited thereto, other aromatics active in aromatic nucleophilic substitution reaction A group dihalogen compound, an aromatic dinitro compound, an aromatic dicyano compound, and the like can also be used.

  Specific examples of the compound represented by Chemical Formula 12 are shown below, but are not limited thereto. Among them, chemical formulas 12A, 12B, 12C, 12D, 120, 12P, 12Q, and 12R are preferable, 12C, 12D, 12Q, and 12R are more preferable, and 12D and 12R are more preferable.

  In the above aromatic nucleophilic substitution reaction, other various activated dihalogen aromatic compounds, dinitroaromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the compounds represented by Chemical Formulas 11-13. .

  Examples of other bisphenol compounds or bisthiophenol compounds include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and 4,4′-biphenol. Bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 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, hydro Non, resorcin, bis (4-hydroxyphenyl) ketone, 1,4-benzenedithiol, 1,3-benzenedithiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 2 , 2-bis (4-hydroxyphenyl) hexafluoropropane, 4,4′-thiobisbenzenethiol, 4,4′-oxybisbenzenethiol, bis (4-hydroxyphenyl) sulfide, 4,4′-dihydroxydiphenyl ether Diallyl bisphenol A, 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenolphthalein, 4-ethylresorcinol, 4-hexylresorcinol, 2-hexyl hydroquinone, 2- Octyl hydroquinone, 2-octadecyl hydroquinone, 2-tertiary butyl hydroquinone, 2,5-ditertiary butyl hydroquinone, 2,5-ditertiary amyl hydroquinone, 2,2'-dihexyl-4,4'-dihydroxybiphenyl, 1 -Octyl-2,6-dihydroxynaphthalene, 2-hexyl-1,5-dihydroxynaphthalene, and the like. In addition to these, various compounds that can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction Aromatic diols or various aromatic dithiols can also be used, and are not limited to the above compounds.

  When the sulfonic acid group-containing polymer in the present invention is polymerized by an aromatic nucleophilic substitution reaction, a compound having a structure represented by Chemical Formulas 11 to 13 and, if necessary, other activated dihalogen aromatic compounds or dinitro aromatic compounds And aromatic diols or aromatic dithiols can be added and reacted in the presence of a basic compound to obtain a polymer. By setting the molar ratio of the reactive halogen group or nitro group in the monomer to the reactive hydroxy group and thiol group to an arbitrary molar ratio, the degree of polymerization of the resulting polymer can be adjusted. 0.8 to 1.2, more preferably 0.9 to 1.1, more preferably 0.95 to 1.05, and 1 to obtain the polymer with the highest degree of polymerization. it can.

  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. The basic compound can be polymerized satisfactorily when used in an amount of 100 mol% or more with respect to the total of the bisphenol compound and the bisthiophenol compound, and preferably 105 to 105% with respect to the total of the bisphenol compound or the bisthiophenol compound. The range is 125 mol%. An excessive amount of bisphenol compound or bisthiophenol compound is not preferable because it causes side reactions such as decomposition.

  Further, in the above polymerization reaction, a bisphenol compound or bisthiophenol compound reacted with an isocyanate compound to form a carbamoylate without using a basic compound, and an activated dihalogen aromatic compound or dinitro aromatic compound are directly combined. It can also be reacted.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by mass. When the amount is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by mass, the viscosity of the reaction system becomes too high, and post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration. In addition, a polymer solution can be obtained by removing by-product salts by filtration.

  In addition, the sulfonic acid group-containing polymer in the present invention preferably has a polymer log viscosity measured by a method described later of 0.1 dL / g or more. When the logarithmic viscosity is less than 0.1 dL / g, the membrane tends to become brittle when molded as a polymer electrolyte membrane. The logarithmic viscosity is more preferably 1.0 dL / g or more, and preferably 2.0 dL / g or more. On the other hand, if the logarithmic viscosity exceeds 5 dL / g, problems in processability such as difficulty in dissolving the polymer come out. 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. As the ion exchange capacity decreases, proton conductivity decreases. As the ion exchange capacity increases, proton conductivity increases, but at the same time, problems such as membrane swelling and water dissolution are likely to occur. A more preferable range is 0.5 to 3.5 meq / g, and a further preferable range is 1.0 to 2.5 meq / g.

  The polymer electrolyte membrane in the present invention can have any thickness, but if it is 10 μm or less, it becomes difficult to satisfy the predetermined characteristics, so it is preferably 10 μm or more, and more preferably 20 μm or more. . Moreover, since manufacture will become difficult when it exceeds 300 micrometers, it is preferable that it is 300 micrometers or less.

  The sulfonic acid group-containing polymer in the present invention can be used as a simple substance, but can also be used as a 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 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 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 mass of the entire resin composition, the sulfonic acid group concentration of the polymer electrolyte membrane containing this resin composition is lowered and good ionic 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 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 polymer electrolyte 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 is converted to a free sulfonic acid group by acid treatment if necessary. You can also.

  The most preferable method for forming a polymer electrolyte membrane from a sulfonic acid group-containing polymer and a resin composition thereof in the present invention is casting from a solution, and the polymer is removed from the cast solution by removing the solvent as described above. An electrolyte 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 in view of the uniformity of the polymer electrolyte 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 less than 10 μm, the form as a polymer electrolyte membrane tends to be not maintained, and if it is more 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 by the amount and concentration of the solution by making the thickness constant using an applicator, a doctor blade or the like, or making the 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 a polymer electrolyte 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 polymer electrolyte membrane of the present invention to an electrode.
An electrode consists of an electrode material and a layer (electrode catalyst layer) containing a catalyst formed on the surface thereof, and a known material can be used as the electrode material. For example, a conductive porous material such as carbon paper or carbon cloth can be used, but is not limited thereto. As the conductive porous material such as carbon paper or carbon cloth, a material subjected to surface treatment such as water repellent treatment or hydrophilic treatment can be used. A known material can be used for the catalyst. For example, platinum, an alloy of platinum and ruthenium, and the like can be given, but the invention is not limited to them.
The catalyst can be used in any known form, and for example, carbon particles carrying catalyst fine particles can be used, but are not limited thereto.
An adhesive can be used for the catalyst and the electrode catalyst layer including the particles carrying the catalyst, and as the adhesive, a resin having proton conductivity can be used.

  As a method for producing this joined body, a conventionally known method can be used. For example, a method of applying an adhesive to the electrode surface and bonding the polymer electrolyte membrane and the electrode, or a polymer electrolyte membrane and the electrode There is a method of heating and pressurizing. As the adhesive, a known material such as a Nafion (trade name) solution may be used, or an adhesive mainly composed of the same polymer composition as that of the polymer constituting the polymer electrolyte membrane of the present invention may be used. However, other hydrocarbon-based proton conductive polymers may be used as the main component. The catalyst such as platinum and platinum-ruthenium alloy necessary for the electrode reaction can be obtained by dispersing the catalyst supported on conductive particles such as carbon in the adhesive. . The method of producing a joined body of an electrode and a polymer electrolyte membrane is preferably a method of applying and bonding to the electrode surface. Since the polymer electrolyte membrane and the polymer composition of the present invention have an appropriate softening temperature, they are particularly suitable for a method of joining a polymer electrolyte membrane and an electrode by pressure heating.

  The fuel cell of the present invention can be produced using the polymer electrolyte membrane or the polymer electrolyte membrane / electrode assembly of the present invention. The fuel cell of the present invention includes, for example, an oxygen electrode, a fuel electrode, a polymer electrolyte membrane sandwiched between the electrodes, an oxidant flow path provided on the oxygen electrode side, and a fuel electrode side. The fuel flow path is provided. A fuel cell stack can be obtained by connecting such unit cells with a conductive separator.

  The polymer electrolyte membrane of the present invention is suitable for a polymer electrolyte fuel cell. The polymer electrolyte membrane of the present invention is excellent in bondability with an electrode catalyst layer, output characteristics, and durability. The polymer electrolyte membrane of the present invention can be suitably used for a fuel cell using a liquid such as methanol, dimethyl ether or formic acid or a gas such as hydrogen as a fuel. As a polymer electrolyte membrane such as an electrolyte membrane and a separation membrane Can also be used for any known application.

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

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

<Proton conductivity>
A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped film sample on a self-made measurement probe (made of tetrafluoroethylene resin), and the sample is placed in water at 25 ° C. or in a thermostatic chamber at 80 ° C. and 95%. 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]

<Power generation evaluation of hydrogen-fueled fuel cell (PEFC)>
After adding commercially available 40% Pt catalyst-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd. Fuel Cell Catalyst TEC10V40E), a small amount of ultrapure water and isopropanol, to DuPont 20% Nafion (trade name) solution, until uniform Stir to prepare a catalyst paste. The catalyst paste was uniformly applied and dried on carbon paper (TGPH-060 manufactured by Toray Industries, Inc.) so that the amount of platinum deposited was 0.5 mg / cm ² to prepare a gas diffusion layer with an electrode catalyst layer. A polymer electrolyte membrane is sandwiched between the gas diffusion layers with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane, and the membrane is pressed and heated at 130 ° C. and 2 MPa for 3 minutes by a hot press method. -It was set as the electrode assembly. The joined body was assembled in an evaluation fuel cell FC25-02SP manufactured by Electrochem, and hydrogen and air humidified at 75 ° C. were supplied to the anode and the cathode at a cell temperature of 80 ° C., and the power generation characteristics were evaluated. The output voltage at a current density of 0.5 A / cm ² immediately after the start was taken as the initial characteristics. Moreover, as durability evaluation, continuous operation was performed on said conditions, measuring an open circuit voltage at the rate of once per hour. The time when the open circuit voltage decreased by 10% or more from the value immediately after the start was defined as the endurance time. Durability evaluation was performed with 1000 hours as the upper limit.

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

<Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: SDS) 60.00 g, 2,6-dichlorobenzonitrile (abbreviation: DCB) 26.74 g, 4,4′-dimercaptobiphenyl (Abbreviation: MBP) 60.61 g, 42.20 g of potassium carbonate, and 32 g of dried molecular sieve 3-A were weighed into a 1000 mL four-necked flask and flushed with nitrogen. 380 mL of N-methyl-2-pyrrolidone (abbreviation: NMP) was added, and while stirring, the reaction temperature was raised to 195 to 200 ° C., and the reaction was continued with the aim of sufficiently increasing the viscosity of the system (about 4). time). 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 2.44 dL / g. The ¹ H-NMR spectrum measured at room temperature in deuterated dimethyl sulfoxide of the obtained polymer is shown in FIG. 7 g of polymer is dissolved in 28 g of NMP, cast on a glass plate on a hot plate to a thickness of about 400 μm, heated at 80 ° C. for 0.5 hour, 120 ° C. for 0.5 hour, and 150 ° C. for 0.5 hour, and then glass plate The film was peeled off. The obtained film was immersed in pure water at room temperature for 1 day 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 a polymer electrolyte membrane. The obtained polymer electrolyte membrane was evaluated.

<Examples 2 to 11>
A polymer electrolyte membrane was prepared and evaluated in the same manner as in Example 1 except that the type and amount of monomer were changed.

<Example 12>
DCBN (13.37 g), MBP (16.67 g), potassium carbonate (11.61 g), and dried molecular sieve 3-A (10 g) were weighed into a 200 mL four-necked flask and flushed with nitrogen. While stirring, 70 mL of NMP was added and the reaction temperature was raised to 195 to 200 ° C. while stirring, and the reaction was continued with the aim of sufficiently increasing the viscosity of the system (about 3 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. This is polymer A. In another 200 mL four-necked flask, 25.00 g of S-DCDPS, 11.36 g of MBP, 7.91 g of potassium carbonate, and 10 g of dried molecular sieve 3-A were weighed into a 200 mL four-necked flask and flushed with nitrogen. With 100 mL of NMP added, the reaction temperature was raised to 195 to 200 ° C. while stirring, and the reaction was continued with the aim of sufficiently increasing the viscosity of the system (about 3 hours). Then, what melt | dissolved 20.31 g of polymer A previously polymerized in 60 mL NMP was added, and also it was made to react for 1 hour. After allowing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand to obtain a block copolymer. The obtained polymer was washed twice in boiling water for 1 hour and then dried. 7 g of the obtained polymer was dissolved in 28 g of NMP, cast on a glass plate on a hot plate to a thickness of about 400 μm, and heated at 80 ° C. for 0.5 hour, 120 ° C. for 0.5 hour, and 150 ° C. for 0.5 hour. The film was peeled from the glass plate. The obtained film was immersed in pure water at room temperature for 1 day 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 a polymer electrolyte membrane. The obtained polymer electrolyte membrane was evaluated.

<Comparative Examples 1-11>
A polymer electrolyte membrane was prepared and evaluated in the same manner as in Example 1 except that the type and amount of monomer were changed.

<Comparative Example 12>
A polymer electrolyte membrane was prepared and evaluated in the same manner as in Comparative Example 1 except that the polymerization time was changed to 16 hours.

  Table 1 shows the evaluation results of the polymer electrolyte membranes of Examples and Comparative Examples.

The abbreviations in Table 1 represent the following compounds.
SDS: sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone SBP: sodium 3,3′-disulfonate-4,4′-dichlorobenzophenone BSS: 3,3′-di-n-butylsulfone Sodium salt-4,4'-dichlorodiphenylsulfone DCB: 2,6-dichlorobenzonitrile DCS: 4,4'-dichlorodiphenylsulfone CBP: 4,4'-dichlorobenzophenone MBP: 4,4'-dimercaptobiphenyl BP : 4,4'-biphenol

  The structural formula of the polymer constituting the polymer electrolyte membrane in the comparative example is shown below.

  From Table 1, the sulfonic acid group-containing polymer in the present invention can obtain a polymer having a high degree of polymerization in a short time and is industrially useful. Further, when the polymer electrolyte membrane is used, the proton conductivity is equivalent to that of the polymer electrolyte membrane having a conventional structure. Further, it is apparent that the durability of the fuel cell using the polymer electrolyte membrane of the present invention is improved compared to the conventional fuel cell using the polymer electrolyte membrane.

  Since the sulfonic acid group-containing polymer of the present invention has improved the physical durability of the polymer as compared with conventional sulfonic acid group-containing polymers, the characteristics of the fuel cell can be obtained by using it as a polymer electrolyte membrane for fuel cells. Can be greatly improved, and contribute to the industry.

The polymer synthesized in Example 1 of the present invention, by using a VARIAN Co. GEMINI-200, is a ¹ H-NMR spectrum was measured at room temperature in deuterated dimethylsulfoxide.

Explanation of symbols

1. DMSO: signal derived from dimethyl sulfoxide in deuterated dimethyl sulfoxide.
2. H ₂ O: signal derived from water adsorbed on the polymer.

Claims (11)

A sulfonic acid group-containing polymer comprising at least a structural unit represented by the following chemical formula 1 and a structural unit represented by the following chemical formula 1 ′.

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, R represents an alkylene group having 1 to 10 carbon atoms, oxy It represents one or more groups selected from the group consisting of an alkylene group, an arylene group, and a direct bond with a benzene ring. In Chemical Formula 1 ′, Ar ¹ represents one or more groups selected from divalent aromatic groups having an electron-withdrawing group. n and m are the number of moles of each structural unit and represent an integer of 1 or more, and the bonding form of the structural units represented by Chemical Formula 1 and Chemical Formula 1 ′ may be random, alternating, block, or graft. . ] The sulfonic acid group-containing polymer according to claim 1, wherein Ar ¹ in Chemical Formula 1 ′ is one or more groups selected from structures represented by Chemical Formulas 2 to 5 below.

The sulfonic acid group-containing polymer according to claim 2, wherein Ar ¹ in Chemical Formula 1 ′ has a structure represented by Chemical Formula 4 or 5. R is a sulfonic acid group-containing polymer according to claim 1 is a direct bond between the SO 3 _Y group and a benzene ring. The sulfonic acid group-containing polymer according to any one of claims 1 to 4, wherein n and m in the chemical formula 1 and the chemical formula 1 'satisfy the following mathematical formula 1.
0.05 ≦ n / (n + m) ≦ 0.70 (Formula 1)   The polymer according to any one of claims 1 to 5, wherein a 0.5 g / dL N-methyl-2-pyrrolidone solution has a logarithmic viscosity at 30 ° C of 2.0 to 5.0 dL / g.   A polymer electrolyte membrane comprising the sulfonic acid group-containing polymer according to claim 1.   A composition comprising the sulfonic acid group-containing polymer according to claim 1.   A membrane / electrode assembly comprising the sulfonic acid group-containing polymer according to any one of claims 1 to 6 in at least one of a polymer electrolyte membrane and an electrode catalyst layer.   A fuel cell comprising the membrane / electrode assembly according to claim 9. 7. The method for producing a sulfonic acid group-containing polymer according to claim 1, wherein a compound represented by the following chemical formula 6 is used as a raw material monomer.

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