JP4512843B2 - Acid-base composite polymer electrolyte membrane - Google Patents

Description

  The present invention relates to an acid-base composite polymer electrolyte membrane comprising a polyarylene having a sulfonic acid group and a polymer having a functional group capable of interacting with the sulfonic acid group.

  The polymer electrolyte membrane is a main material constituting the fuel cell and is required to have excellent power generation performance. Therefore, there is a need for a membrane that exhibits excellent proton conductivity in a wide range of environments where fuel cells are used.

  As the polymer electrolyte membrane, a polymer having a sulfonic acid group is usually used. In order to increase the proton conductivity of the polymer electrolyte membrane, it is preferable to increase the sulfonic acid concentration in the polymer as much as possible.

  Patent Document 1 (US Pat. No. 5,403,675) discloses a solid polymer electrolyte made of sulfonated rigid polyphenylene. This polymer is mainly composed of a polymer obtained by polymerizing an aromatic compound comprising a phenylene chain, and this is reacted with a sulfonating agent to introduce a sulfonic acid group.

  However, although the proton conductivity is improved by increasing the amount of sulfonic acid groups introduced, if the concentration exceeds a certain level, the water resistance is lowered and dissolved when containing water, or the strength is reduced due to significant swelling. There is.

In the case of a fuel cell used for a portable device, it is advantageous in handling to use a methanol aqueous solution instead of hydrogen as a fuel. However, in this case as well, if the sulfonic acid concentration is increased in order to increase proton conductivity, the permeability of methanol used as a fuel increases and power generation efficiency decreases. In addition, there is a problem that the strength is reduced due to swelling of the film.
US Pat. No. 5,403,675

  An object of the present invention is to provide a polymer electrolyte membrane that exhibits excellent proton conductivity and mechanical properties in a wide temperature range and has low methanol permeability.

  As a result of intensive studies in view of the above problems, the present inventors have found that a sulfonated polyarylene that is originally excellent in water resistance and methanol resistance and can achieve a high sulfonic acid concentration, and a functional group that can interact with the sulfonic acid group. It has been found that the above-mentioned problems can be solved by forming a polyion complex with a polymer having the same.

  That is, the polymer electrolyte membrane of the present invention is characterized by comprising a polyarylene having a sulfonic acid group and a polymer having a functional group capable of interacting with the sulfonic acid group.

  The polyarylene having a sulfonic acid group is preferably composed of a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B).

(In the formula, Y represents a divalent electron-withdrawing group, Z represents a divalent electron-donating group or a direct bond, and Ar represents an aromatic group having a substituent represented by —SO ₃ H. M represents an integer of 0 to 10, n represents an integer of 0 to 10, and k represents an integer of 1 to 4.)

(Wherein R ^{1 to} R ⁸ may be the same as or different from each other, and are at least one selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group) W represents a divalent electron-withdrawing group or a single bond, T represents a single bond or a divalent organic group, and p represents 0 or a positive integer.)
The functional group capable of interacting with the sulfonic acid group is preferably a basic functional group containing a nitrogen atom.

  Hereinafter, the polymer electrolyte membrane according to the present invention will be described in detail.

  The polymer electrolyte membrane according to the present invention comprises a polyarylene having a sulfonic acid group and a polymer having a functional group capable of interacting with the sulfonic acid group.

<Polyarylene having a sulfonic acid group>
The polyarylene having a sulfonic acid group used in the present invention (hereinafter also referred to as a sulfonated polyarylene) is composed of a structural unit represented by the following general formula (A) and a structure represented by the following general formula (B). It is a polymer represented by the following general formula (C) containing a unit.

In the formula (A), Y represents a divalent electron-withdrawing group, specifically, —CO—, —SO ₂ —,
—SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (wherein l is an integer of 1 to 10), —C (CF ₃ ) ₂ — and the like can be mentioned.

Z represents a divalent electron donating group or a direct bond, and specific examples of the electron donating group include:
— (CH ₂ ) —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH═CH—, —C≡C— and

Etc. The electron-withdrawing group refers to a group having a Hammett substituent constant of 0.06 or more when the phenyl group is in the m-position and 0.01 or more when it is in the p-position.

Ar represents an aromatic group having a substituent represented by —SO ₃ H, and specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these groups, a phenyl group and a naphthyl group are preferable.

  m represents an integer of 0 to 10, preferably 0 to 2, n represents an integer of 0 to 10, preferably 0 to 2, and k represents an integer of 1 to 4.

In the formula (B), R ^{1 to} R ⁸ may be the same or different from each other, and at least selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. One atom or group is shown.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.
As the fluorine-substituted alkyl group, a trifluoromethyl group, a perfluoroethyl group,
Examples include a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group, and a trifluoromethyl group, a pentafluoroethyl group, and the like are preferable.
Examples of allyl groups include propenyl groups,
Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

  W represents a divalent electron-withdrawing group or single bond, and T represents a divalent organic group or single bond. p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

In the formula (C), W, T, Y, Z, Ar, m, n, k, p and R ^{1 to} R ⁸ are respectively W, T, Y in the general formulas (A) and (B). It is synonymous with Z, Ar, m, n, k, p and R ^{1 to} R ⁸ .

  The sulfonated polyarylene used in the present invention is represented by the formula (B) in a proportion of 0.5 to 100 mol%, preferably 10 to 99.999 mol%, of the structural unit represented by the formula (A). Are contained in a proportion of 99.5 to 0 mol%, preferably 90 to 0.001 mol%.

<Method for producing polyarylene having a sulfonic acid group>
The polyarylene having a sulfonic acid group used in the present invention becomes a structural unit represented by the monomer having a sulfonic acid ester group that can be the structural unit represented by the general formula (A) and the general formula (B). And a polyarylene having a sulfonic acid ester group is produced by hydrolyzing the polyarylene having a sulfonic acid ester group and converting the sulfonic acid ester group into a sulfonic acid group. be able to.

  The polyarylene having a sulfonic acid group is synthesized in advance from a polyarylene composed of a structural unit having no sulfonic acid group or sulfonic acid ester group in the general formula (A) and a structural unit of the general formula (B). The polymer can also be synthesized by sulfonation.

  Examples of the monomer that can be the structural unit of the general formula (A) include sulfonate esters represented by the following general formula (D) (hereinafter also referred to as monomer (D)).

In the formula (D), X is a halogen atom excluding fluorine (chlorine, bromine, iodine), -OSO ₂ G (
Here, G represents an alkyl group, a fluorine-substituted alkyl group or an aryl group. ), And Y, Z, Ar, m, n and k have the same meanings as Y, Z, Ar, m, n and k in the general formula (A), respectively.

R ^a represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 4 to 20 carbon atoms, specifically, methyl group, ethyl group, n-propyl group, iso-propyl group, tert-butyl group, iso- Butyl, n-butyl, sec-butyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, cyclopentylmethyl, cyclohexylmethyl, adamantyl, adamantanemethyl, 2-ethylhexyl, bicyclo [2.2 .1] heptyl group, bicyclo [2.2.1] heptylmethyl group, tetrahydrofurfuryl group, 2-methylbutyl group, 3,3-dimethyl-2,4-dioxolanemethyl group, cyclohexylmethyl group, adamantylmethyl group Linear hydrocarbon groups such as bicyclo [2.2.1] heptylmethyl group, branched hydrocarbon groups, alicyclic hydrocarbons Group, such as a hydrocarbon group having 5-membered heterocycles. Among these, an n-butyl group, neopentyl group, tetrahydrofurfuryl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, adamantylmethyl group, and bicyclo [2.2.1] heptylmethyl group are preferable, and a neopentyl group is particularly preferable. preferable.

Ar represents an aromatic group having a substituent represented by —SO ₃ R ^b , and specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these groups, a phenyl group and a naphthyl group are preferable.

The substituent —SO ₃ R ^b is substituted with one or more aromatic groups, and when two or more substituents —SO ₃ R ^b are substituted, these substituents are the same as each other. But it can be different.

Here, R ^b represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 4 to 20 carbon atoms, and specific examples thereof include the hydrocarbon groups having 1 to 20 carbon atoms. Among these, an n-butyl group, neopentyl group, tetrahydrofurfuryl group, cyclopentyl group, cyclohexyl group, cyclohexylmethyl group, adamantylmethyl group, and bicyclo [2.2.1] heptylmethyl group are preferable, and a neopentyl group is particularly preferable. preferable.

  m represents an integer of 0 to 10, preferably 0 to 2, n represents an integer of 0 to 10, preferably 0 to 2, and k represents an integer of 1 to 4.

  Specific examples of the sulfonic acid ester represented by the formula (D) include the following compounds.

In the above compound, a compound in which a chlorine atom is replaced by a bromine atom, a compound in which -CO- is replaced by -SO ₂ -in the above compound, a chlorine atom in the above compound is replaced by a bromine atom, and -CO- is -SO 2 Examples include compounds in which _2- is replaced.

The R ^b group in the general formula (D) is derived from a primary alcohol, and the β carbon is a tertiary or quaternary carbon, which is excellent in stability during the polymerization process, and produces sulfonic acid by deesterification. It is preferable in that it does not cause polymerization inhibition and cross-linking, and it is preferable that these ester groups are derived from primary alcohols and the β-position is a quaternary carbon.

  In the above general formula (D), specific examples of the compound having no sulfonic acid group or sulfonic acid ester group include the following compounds.

A compound in which the chlorine atom is replaced with a bromine atom in the above compound, a compound in which —CO— is replaced with —SO ₂ — in the above compound, a chlorine atom in the above compound is replaced with a bromine atom, and —CO— is —SO ₂ —. And compounds that have been replaced with.

  Examples of the oligomer that can be the structural unit of the general formula (B) include an oligomer represented by the following general formula (E) (hereinafter also referred to as oligomer (E)).

In the formula (E), R ′ and R ″ may be the same as or different from each other, and a halogen atom or —OSO ₂ G excluding a fluorine atom (where G represents an alkyl group, a fluorine-substituted alkyl group or an aryl group) The group represented by this is shown. Examples of the alkyl group represented by G include a methyl group and an ethyl group, examples of the fluorine-substituted alkyl group include a trifluoromethyl group, and examples of the aryl group include a phenyl group and a p-tolyl group.

R ^{1 to} R ⁸ may be the same or different from each other, and are at least one atom or group selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. Indicates.

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.

  Examples of the fluorine-substituted alkyl group include trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, trifluoromethyl group, pentafluoroethyl group, and the like. Etc. are preferable.

  Examples of the allyl group include a propenyl group, and examples of the aryl group include a phenyl group and a pentafluorophenyl group.

  W represents a divalent electron-withdrawing group or a single bond, and examples of the electron-withdrawing group include those described above.

  T is a divalent organic group or a single bond, and may be an electron-withdrawing group or an electron-donating group. Examples of the electron-withdrawing group and the electron-donating group include the same groups as described above.

  p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

Specifically, as the compound represented by the general formula (E), when p = 0, for example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, bis (chlorophenyl) difluoromethane, 2, 2-bis (4-chlorophenyl) hexafluoropropane, 4-chlorobenzoic acid-4-chlorophenyl, bis (4-chlorophenyl) sulfoxide, bis (4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 9,9- Bis (4-hydroxyphenyl) fluorene is mentioned. In these compounds, compounds in which a chlorine atom is replaced with a bromine atom or an iodine atom, and compounds in which at least one of halogen atoms substituted in the 4-position in these compounds are substituted in the 3-position are exemplified.

When p = 1, the specific compound represented by the general formula (E) is, for example, 4,4′-bis (4-chlorobenzoyl) diphenyl ether, 4,4′-bis (4-chloro). Benzoylamino) diphenyl ether, 4,4′-bis (4-chlorophenylsulfonyl) diphenyl ether, 4,4′-bis (4-chlorophenyl) diphenyl ether dicarboxylate, 4,4′-bis [(4-chlorophenyl) -1, 1,1,3,3,3-hexafluoropropyl] diphenyl ether, 4,4′-bis [(4-chlorophenyl) tetrafluoroethyl] diphenyl ether, compounds in which chlorine atoms are replaced by bromine atoms or iodine atoms in these compounds Further, in these compounds, compounds in which a halogen atom substituted at the 4-position is substituted at the 3-position, At least one group obtained by substituting at the 4-position of diphenyl ether in these compounds but include compounds substituted at the 3-position.

Further, the compound represented by the general formula (E) is 2,2-bis [4- {4- (4-
Chlorobenzoyl) phenoxy} phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- {4- (4-chlorobenzoyl) phenoxy} phenyl] sulfone, and the following formula Compound etc. are mentioned.

  The compound represented by the general formula (E) can be synthesized, for example, by the method shown below.

  First, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, sulfolane, diphenylsulfone, dimethylsulfoxide, etc., in order to convert the bisphenol linked with an electron-withdrawing group to the corresponding alkali metal salt of bisphenol In a polar solvent having a high dielectric constant, an alkali metal such as lithium, sodium or potassium, an alkali metal hydride, an alkali metal hydroxide, an alkali metal carbonate or the like is added.

The alkali metal is reacted in excess with respect to the hydroxyl group of phenol, and is usually used in an amount of 1.1 to 2 times equivalent, preferably 1.2 to 1.5 times equivalent. In this case, fluorine, chlorine, etc. activated with an electron-withdrawing group in the presence of water and an azeotropic solvent such as benzene, toluene, xylene, hexane, cyclohexane, octane, chlorobenzene, dioxane, tetrahydrofuran, anisole, phenetole, etc. Aromatic halogen-substituted aromatic dihalide compounds such as 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, 4,4′-chlorofluorobenzophenone, bis (4-chlorophenyl) sulfone, bis (4 -Fluorophenyl) sulfone, 4-fluorophenyl-4'-chlorophenylsulfone, bis (3-nitro-4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, hexafluorobenzene, deca Fluorobiphenyl, ,
5-difluorobenzophenone, 1,3-bis (4-chlorobenzoyl) benzene and the like are reacted. In terms of reactivity, a fluorine compound is preferable, but in consideration of the following aromatic coupling reaction, it is necessary to assemble an aromatic nucleophilic substitution reaction so that the terminal is a chlorine atom.

  The active aromatic dihalide is used in an amount of 2 to 4 times mol, preferably 2.2 to 2.8 times mol, of bisphenol. Prior to the aromatic nucleophilic substitution reaction, an alkali metal salt of bisphenol may be used. The reaction temperature is 60 ° C to 300 ° C, preferably 80 ° C to 250 ° C. The reaction time ranges from 15 minutes to 100 hours, preferably from 1 hour to 24 hours. The most preferable method is to use a chlorofluoro compound having one halogen atom having a different reactivity as the active aromatic dihalide represented by the following formula, and a nucleophilic substitution reaction with phenoxide occurs preferentially by the fluorine atom. It is convenient to obtain the desired activated terminal chloro form.

  In the formula, W is as defined for the general formula (E).

  Further, as described in JP-A-2-159, a flexible compound comprising a target electron-withdrawing group and electron-donating group may be synthesized by combining a nucleophilic substitution reaction and an electrophilic substitution reaction. .

  Specifically, an aromatic bishalide activated with an electron-withdrawing group, such as bis (4-chlorophenyl) sulfone, is subjected to a nucleophilic substitution reaction with phenol to form a bisphenoxy compound, and then this bisphenoxy compound and 4-chloro The desired compound can be obtained from Friedel-Craft reaction with benzoic acid chloride.

  Examples of the aromatic bishalide activated with the electron-withdrawing group used here include the compounds exemplified above. The phenol compound may be substituted, but an unsubstituted compound is preferable from the viewpoint of heat resistance and flexibility. In addition, it is preferable to set it as an alkali metal salt for the substitution reaction of a phenol, and the compound illustrated above is mentioned as an alkali metal compound which can be used. The amount used is 1.2 to 2 moles per mole of phenol. In the reaction, the polar solvent described above or an azeotropic solvent with water can be used.

  Chlorobenzoic acid chloride is used in an amount of 2 to 4 times mol, preferably 2.2 to 3 times mol of the bisphenoxy compound. Further, the Friedel-Craft reaction between the bisphenoxy compound and the acylating agent chlorobenzoic acid chloride is preferably performed in the presence of a Friedel-Craft activator such as aluminum chloride, boron trifluoride, or zinc chloride. . The Friedel-Craft activator is used in an amount of 1.1 to 2 times equivalent to 1 mol of an active halide compound such as chlorobenzoic acid as an acylating agent. The reaction time ranges from 15 minutes to 10 hours, and the reaction temperature ranges from -20 ° C to 80 ° C. As the solvent used, chlorobenzene, nitrobenzene and the like which are inert to Friedel-Craft reaction can be used.

Further, in the general formula (E), the compound in which p is 2 or more is, for example, a bisphenol that is a source of etheric oxygen that is the electron donating group T in the general formula (E) and an electron withdrawing group W. A compound in combination with at least one group selected from> C═O, —SO ₂ — and> C (CF ₃ ) ₂ , specifically 2,2-bis (4-hydroxyphenyl) -1 1,1,3,3,3-hexafluoropropane, alkali metal salts of bisphenols such as 2,2-bis (4-hydroxyphenyl) ketone, 2,2-bis (4-hydroxyphenyl) sulfone, and excess Substitution reaction with an active aromatic halogen compound such as 4,4-dichlorobenzophenone or bis (4-chlorophenyl) sulfone is carried out with N-methyl-2-pyrrolidone, N, N
-Obtained by sequentially polymerizing the monomer in the presence of a polar solvent such as dimethylacetamide or sulfolane.

  Examples of such compounds include compounds represented by the following formulas.

  In the above, p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

The polyarylene having a sulfonate group is synthesized by reacting the monomer (D) and the oligomer (E) in the presence of a catalyst. The catalyst used in this case is a catalyst containing a transition metal compound. This catalyst system includes (1) a transition metal salt and a compound that becomes a ligand (hereinafter referred to as “ligand component”), or a transition metal complex in which a ligand is coordinated (copper). Salt is included), and (2) a reducing agent is an essential component, and a “salt” may be added to increase the polymerization rate.

  Here, as the transition metal salt, nickel compounds such as nickel chloride, nickel bromide, nickel iodide and nickel acetylacetonate; palladium compounds such as palladium chloride, palladium bromide and palladium iodide; iron chloride and iron bromide And iron compounds such as iron iodide; cobalt compounds such as cobalt chloride, cobalt bromide, and cobalt iodide. Of these, nickel chloride, nickel bromide and the like are particularly preferable.

As the ligand component, triphenylphosphine, 2,2′-bipyridine, 1,5-
Examples include cyclooctadiene and 1,3-bis (diphenylphosphino) propane. Of these, triphenylphosphine and 2,2′-bipyridine are preferred. The compound which is the said ligand component may be used individually by 1 type, and may use 2 or more types together.

Furthermore, as the transition metal complex in which the ligand is coordinated, for example, nickel chloride bis (triphenylphosphine), nickel bromide bis (triphenylphosphine), nickel iodide bis (triphenylphosphine), nickel nitrate bis (Triphenylphosphine), nickel chloride (2,2'-bipyridine), nickel bromide (2,2'-bipyridine), nickel iodide (2,2'-bipyridine), nickel nitrate (2,2'-bipyridine) ), Bis (1,5-cyclooctadiene) nickel, tetrakis (triphenylphosphine) nickel, tetrakis (triphenylphosphite) nickel, tetrakis (triphenylphosphine) palladium and the like. Of these, nickel chloride bis (triphenylphosphine) and nickel chloride (2,2′-bipyridine) are preferred.

  Examples of the reducing agent that can be used in the catalyst system include iron, zinc, manganese, aluminum, magnesium, sodium, calcium, and the like. Of these, zinc, magnesium and manganese are preferred. These reducing agents can be used after being more activated by bringing them into contact with an acid such as an organic acid.

  “Salts” that can be used in the above catalyst system include sodium compounds such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium sulfate; potassium fluoride, potassium chloride, potassium bromide, Examples include potassium compounds such as potassium iodide and potassium sulfate; ammonium compounds such as tetraethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, and tetraethylammonium sulfate. Of these, sodium bromide, sodium iodide, potassium bromide, tetraethylammonium bromide, and tetraethylammonium iodide are preferred.

  The proportion of each component used is usually from 0.0001 to 10 mol, preferably 0.01, based on 1 mol of the total amount of the above monomers ((D) + (E), hereinafter the same) of the transition metal salt or transition metal complex. -0.5 mol. When the amount is less than 0.0001 mol, the polymerization reaction may not proceed sufficiently. On the other hand, when the amount exceeds 10 mol, the molecular weight may decrease.

  In the catalyst system, when a transition metal salt and a ligand component are used, the ratio of the ligand component used is usually 0.1 to 100 mol, preferably 1 to 10 mol, per 1 mol of the transition metal salt. . When the amount is less than 0.1 mol, the catalytic activity may be insufficient. On the other hand, when the amount exceeds 100 mol, the molecular weight may decrease.

  Moreover, the usage-amount of a reducing agent is 0.1-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 1-10 mol. If the amount is less than 0.1 mol, polymerization may not proceed sufficiently. If the amount exceeds 100 mol, purification of the resulting polymer may be difficult.

  Furthermore, when using "salt", the usage-ratio is 0.001-100 mol normally with respect to the total of 1 mol of the said monomer, Preferably it is 0.01-1 mol. If it is less than 0.001 mol, the effect of increasing the polymerization rate may be insufficient, and if it exceeds 100 mol, purification of the resulting polymer may be difficult.

Examples of the polymerization solvent that can be used when the monomer (D) and the oligomer (E) are reacted include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N,
N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N′-dimethylimidazolidinone and the like can be mentioned. Of these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and N, N′-dimethylimidazolidinone are preferable. These polymerization solvents are preferably used after sufficiently dried.

The total concentration of the monomers in the polymerization solvent is usually 1 to 90% by weight, preferably 5
-40% by weight.

  The polymerization temperature for the polymerization is usually 0 to 200 ° C, preferably 50 to 120 ° C. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.

  The polyarylene having a sulfonic acid ester group obtained using the monomer (D) can be converted into a polyarylene having a sulfonic acid group by hydrolyzing the sulfonic acid ester group and converting it to a sulfonic acid group. .

As a hydrolysis method,
(1) A method in which polyarylene having a sulfonate group is added to an excess amount of water or alcohol containing a small amount of hydrochloric acid, and the mixture is stirred for 5 minutes or longer. (2) In trifluoroacetic acid, the sulfonate group is added. (3) Method of reacting polyarylene having a temperature of about 80 to 120 ° C. for about 5 to 10 hours (3) 1 to 1 mol of sulfonic acid ester group (—SO ₃ R) in polyarylene having a sulfonic acid ester group A method of adding hydrochloric acid after reacting the polyarylene for about 3 to 10 hours at a temperature of about 80 to 150 ° C. in a solution containing 3 moles of lithium bromide such as N-methylpyrrolidone. Can be mentioned.

  The polyarylene (C) having a sulfonic acid group includes a monomer having no sulfonic acid ester group in the monomer (D) represented by the general formula (D), and an oligomer represented by the general formula (E) ( It is also possible to synthesize a polyarylene copolymer in advance by copolymerizing with E) and sulphonate the polyarylene copolymer. In this case, after producing a polyarylene having no sulfonic acid group by a method according to the above synthesis method, a sulfonic acid group is introduced into the polyarylene having no sulfonic acid group using a sulfonating agent. A polyarylene (C) having a group can be obtained.

  The introduction of the sulfonic acid group is not particularly limited, and can be performed by a general method. For example, the polyarylene having no sulfonic acid group may be prepared by using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid or sodium hydrogen sulfite in the absence of a solvent or in the presence of a solvent. Sulfonic acid groups can be introduced by sulfonation under conditions [Polymer Preprints, Japan, Vol.42, No.3, p.730 (1993); Polymer Preprints, Japan, Vol.43, No.3 , p. 736 (1994); Polymer Preprints, Japan, Vol. 42, No. 7, p. 2490-2492 (1993)].

  Examples of the solvent used for sulfonation include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide, and dimethylsulfoxide, tetrachloroethane, Halogenated hydrocarbons such as dichloroethane, chloroform, and methylene chloride. Although reaction temperature does not have a restriction | limiting in particular, Usually, -50-200 degreeC, Preferably it is -10-100 degreeC. Moreover, reaction time is 0.5 to 1,000 hours normally, Preferably it is 1 to 200 hours.

  The amount of the sulfonic acid group in the polyarylene (C) having a sulfonic acid group produced by the method as described above is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0. .8 to 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low and not practical. On the other hand, if it exceeds 5 meq / g, the water resistance may be significantly lowered.

  The amount of the sulfonic acid group can be adjusted, for example, by changing the type, usage ratio, and combination of the monomer (D) and the oligomer (E).

  The molecular weight of the polyarylene having a sulfonic acid group thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-reduced weight average molecular weight by gel permeation chromatography (GPC).

<Polymer having functional group capable of interacting with sulfonic acid group>
The polymer electrolyte membrane according to the present invention comprises a polyarylene having the sulfonic acid group and a polymer having a functional group capable of interacting with the sulfonic acid group, and these form a polyion complex, whereby high proton conductivity. And a polymer electrolyte membrane having low methanol permeability can be obtained.

  The functional group capable of interacting with the sulfonic acid group is a functional group capable of forming an acid-base composite structure with the sulfonic acid group, that is, a basic functional group.

  Examples of such basic functional groups include pyridyl group, imidazole group, benzimidazole group, diazole group, phosphonium group, primary amino group, secondary amino group, tertiary amino group, amide group, urethane group, urea group, A functional group having a nitrogen atom such as an imino group can be mentioned.

  Examples of the polymer having such a basic functional group include polyvinyl pyridine, polyvinyl pyrrolidone, polyvinyl imidazole, polyallylamine, polyacrylamide, polyethyleneimine, polypropyleneimine, polysilamine, polybenzimidazole and the like.

  The polymer having a functional group capable of interacting with the sulfonic acid group (hereinafter also referred to as a basic polymer) has a weight average molecular weight of 500 or more, preferably 1000 to 1,000,000, more preferably 5000 to 500, 000 is desirable. If the weight average molecular weight is less than 500, the effect of reducing methanol permeation and the effect of improving dimensional stability may be insufficient.

  The basic polymer may be used alone or in combination of two or more, and is 1 to 200 parts by weight, preferably 10 to 90 parts by weight, based on 100 parts by weight of the sulfonated polyarylene. It is desirable to use in proportion. By using in the said range, the effect by complex formation can fully be expressed.

<Polymer electrolyte membrane>
The polymer electrolyte membrane according to the present invention comprises the sulfonated polyarylene and the basic polymer.

As a method for producing the polymer electrolyte membrane of the present invention, for example,
(I) After dissolving the sulfonated polyarylene and the basic polymer in an organic solvent in which all of the sulfonated polyarylene, the basic polymer, and the composite of both are dissolved, and casting this solution on a substrate, Casting method to form a film by drying and removing the solvent,
(Ii) after forming the sulfonated polyarylene film by a casting method, immersing the sulfonated polyarylene film in a basic polymer solution, and impregnating the basic polymer inside the sulfonated polyarylene film; and (Iii) A method of coating the basic polymer on the surface of the sulfonated polyarylene film by, for example, spray coating a basic polymer solution after forming the film of the sulfonated polyarylene by a casting method.

The method (i) is characterized in that a film having a uniform composition can be obtained. Method (ii) above
In this case, it is necessary that the sulfonated polyarylene membrane does not dissolve in the basic polymer solution, and water is preferable as such a solvent. In the case of the above method (iii), the basic polymer solvent is not limited as in the above method (ii), and only the vicinity of the surface of the membrane can be combined.

  The substrate used in such a film forming method is not particularly limited as long as it is a substrate used in an ordinary solution casting method. For example, a substrate made of plastic or metal is used, and preferably polyethylene terephthalate ( A substrate made of a thermoplastic resin such as PET) film is used.

  Specific examples of the solvent used in these film forming methods include N-methyl-2-pyrrolidone, N, N-dimethylformamide, γ-butyrolactone, N, N-dimethylacetamide, dimethyl sulfoxide, dimethylurea, dimethyl Examples include aprotic polar solvents such as imidazolidinone. Among these, N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) is particularly preferable in terms of solubility and solution viscosity. The aprotic polar solvents may be used singly or in combination of two or more.

  Further, as the solvent, a mixture of the aprotic polar solvent and alcohol may be used. Examples of such alcohol include methanol, ethanol, propyl alcohol, iso-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like. Among these, methanol is particularly preferable because it has an effect of lowering the solution viscosity in a wide composition range. Alcohol may be used individually by 1 type, or may be used in combination of 2 or more type.

  When a mixture of the aprotic polar solvent and the alcohol is used, the aprotic polar solvent is 95 to 25% by weight, preferably 90 to 25% by weight, and the alcohol is 5 to 75% by weight, preferably 10%. -75 wt% (however, the total is 100 wt%). When the amount of alcohol is within the above range, the effect of lowering the solution viscosity is excellent.

  In addition to the alcohol, an inorganic acid such as sulfuric acid or phosphoric acid, an organic acid containing a carboxylic acid, an appropriate amount of water or the like may be used in combination.

  The polymer concentration of the solution during film formation is usually 5 to 40% by weight, preferably 7 to 25% by weight. If the polymer concentration is less than 5% by weight, it is difficult to form a thick film, and pinholes tend to be generated. On the other hand, when the polymer concentration exceeds 40% by weight, the solution viscosity is so high that it is difficult to form a film, and surface smoothness may be lacking.

The solution viscosity is usually 2,000 to 100,000 mPa · s, preferably 3,000.
˜50,000 mPa · s. When the solution viscosity is less than 2,000 mPa · s, the retention of the solution during film formation is poor and the solution may flow from the substrate. On the other hand, the solution viscosity is 100,000
If it exceeds mPa · s, the viscosity is too high, so extrusion from the die cannot be performed, and film formation by the casting method may be difficult.

After film formation as described above, when the obtained undried film is immersed in water, the organic solvent in the undried film can be replaced with water, and the amount of residual solvent in the resulting polymer electrolyte membrane is reduced. can do. In addition, you may predry an undried film before immersing an undried film in water. The preliminary drying is performed by holding the undried film at a temperature of usually 50 to 150 ° C. for 0.1 to 10 hours.

  When immersing an undried film (including a pre-dried film; the same shall apply hereinafter) in water, a batch method in which a single wafer is immersed in water may be used, and a film is formed on a substrate film (for example, PET). A continuous system may be used in which the laminated film is left as it is, or the film separated from the substrate is immersed in water and wound up. Moreover, in the case of a batch system, in order to suppress the formation of wrinkles on the treated film surface, it is preferable to immerse the film in water by a method such as placing an undried film on a frame.

  The amount of water used in immersing the undried film in water is 10 parts by weight or more, preferably 30 parts by weight or more, more preferably 50 parts by weight or more with respect to 1 part by weight of the undried film. If the amount of water used is in the above range, the amount of residual solvent in the resulting proton conducting membrane can be reduced. In addition, the amount of residual solvent in the resulting polymer electrolyte membrane can be reduced by changing the water used for immersion or allowing it to overflow to always maintain the organic solvent concentration in water below a certain level. It is effective for. Furthermore, in order to suppress the in-plane distribution of the amount of the organic solvent remaining in the polymer electrolyte membrane, it is effective to homogenize the concentration of the organic solvent in water by stirring or the like.

  The temperature of water when the undried film is immersed in water is usually in the range of 5 to 80 ° C., preferably 10 to 60 ° C., from the viewpoint of the replacement speed and ease of handling. The higher the temperature, the faster the substitution rate of the organic solvent and water, but the greater the amount of water absorbed by the film, so the surface state of the polymer electrolyte membrane obtained after drying may deteriorate. Further, the immersion time of the film is usually in the range of 10 minutes to 240 hours, preferably 30 minutes to 100 hours, although it depends on the initial residual solvent amount, the amount of water used and the treatment temperature.

  After immersing the undried film in water as described above, the film is dried at 30-100 ° C, preferably 50-80 ° C, for 10-180 minutes, preferably 15-60 minutes, and then at 50-150 ° C. The polymer electrolyte membrane can be obtained by vacuum drying for 0.5 to 24 hours, preferably under a reduced pressure of 500 mmHg to 0.1 mmHg.

  The amount of residual solvent in the polymer electrolyte membrane obtained as described above is usually reduced to 5% by weight or less, preferably 1% by weight or less.

  The polymer electrolyte membrane obtained by the method of the present invention has a dry film thickness of usually 10 to 100 μm, preferably 20 to 80 μm.

〔Example〕
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The sulfonic acid equivalent, molecular weight, proton conductivity, dimensional change rate and methanol permeability were determined as follows.

1. Sulfonic acid equivalent The polymer having the sulfonic acid group was washed with water until the water was neutral, thoroughly washed with water except for free remaining acid, dried, weighed a predetermined amount, THF / Phenolphthalein dissolved in a mixed solvent of water was used as an indicator, titration was performed using a standard solution of NaOH, and the sulfonic acid equivalent was determined from the neutralization point.

2. Measurement of molecular weight The polyarylene weight-average molecular weight having no sulfonic acid group was determined by using polystyrene (THF) as a solvent and the molecular weight in terms of polystyrene by GPC. The molecular weight of polyarylene having a sulfonic acid group was determined by GPC using polystyrene as a molecular weight using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent.

3. Measurement of proton conductivity AC resistance is obtained by pressing a platinum wire (φ = 0.5 mm) on the surface of a strip-shaped membrane sample with a width of 5 mm, holding the sample in a constant temperature and humidity device, and alternating current impedance between platinum wires. Obtained from measurement. That is, the impedance at AC 10 kHz was measured in an environment of 85 ° C. and relative humidity 90%. A chemical impedance measurement system manufactured by NF Circuit Design Block Co., Ltd. was used as the resistance measurement device, and JW241 manufactured by Yamato Scientific Co., Ltd. was used as the constant temperature and humidity device. Five platinum wires were pressed at intervals of 5 mm, the distance between the wires was changed to 5 to 20 mm, and the AC resistance was measured. The specific resistance of the membrane was calculated from the line-to-line distance and the resistance gradient, the AC impedance was calculated from the reciprocal of the specific resistance, and the proton conductivity was calculated from this impedance.
Specific resistance R (Ω · cm) = 0.5 (cm) × film thickness (cm) × resistance-to-resistance gradient (Ω / cm)
4). Dimensional change rate A plastic container (capacity: 250 mL) containing 100 mL of pure water and a 3 cm square film was placed in a pressure cooker set at 120 ° C. for 24 hours, and the dimensions of the film taken out from water were immediately measured. .

5). Methanol permeability The obtained film (polymer electrolyte membrane) was used as a pervaporation membrane and measured at 25 ° C. by a pervaporation method using an aqueous methanol solution having a concentration of 10% by weight.

[Synthesis Example 1] Preparation of Oligomer 2,2-bis (4-hydroxyphenyl) was added to a 1 L three-necked flask equipped with a stirrer, thermometer, condenser, Dean-Stark tube and nitrogen-introduced three-way cock. -1,1,1,3,3,3-hexafluoropropane (bisphenol AF) 67.3 g (0.20 mol), 4,4′-dichlorobenzophenone (4,4′-DCBP) 60.3 g (0. 24 mol), potassium carbonate 71.9 g (0.52 mol), N, N-dimethylacetamide (DMAc) 300 m
L and 150 mL of toluene were taken and heated in an oil bath under a nitrogen atmosphere and reacted at 130 ° C. with stirring. When water produced by the reaction was azeotroped with toluene and reacted while being removed from the system with a Dean-Stark tube, almost no water was produced in about 3 hours. Thereafter, most of the toluene was removed while gradually raising the reaction temperature from 130 ° C. to 150 ° C., and the reaction was continued at 150 for 10 hours. Then, 10.0 g (0.040 mol) of 4,4′-DCBP was added, and further Reacted for 5 hours. The resulting reaction solution was allowed to cool, and then the by-product inorganic compound precipitate was removed by filtration, and the filtrate was put into 4 L of methanol. The precipitated product was separated by filtration, collected, dried, and dissolved in 300 mL of tetrahydrofuran. This was reprecipitated in 4 L of methanol to obtain 95 g (yield 85%) of the target compound.

The weight average molecular weight (Mw) in terms of polystyrene determined by GPC (THF solvent) of the obtained compound was 11,200. Moreover, the obtained compound is THF, NMP, DMAc,
It was soluble in sulfolane, etc., and had a glass transition temperature (Tg) of 110 ° C. and a thermal decomposition temperature of 498 ° C.

  The obtained compound was an oligomer represented by the formula (I) (hereinafter referred to as “BCPAF oligomer”).

[Synthesis Example 2] Preparation of polyarylene having a sulfonic acid group To a 1 L three-necked flask equipped with a stirrer, a thermometer, a condenser tube, a Dean-Stark tube and a nitrogen-introduced three-way cock, 4- [4- (2,5-dichlorobenzoyl) phenoxy] 39-58 g (98.64 mmol) of benzenesulfonate neo-pentyl (A-SO ₃ neo-Pe), BCPAF oligomer obtained in Synthesis Example 1 (Mw = 11200) 15. 23 g (1.36 mmol), Ni (PPh ₃ ) ₂ Cl ₂ 1.67 g (2.55 mmol), PPh ₃ 10.49 g (40 mmol), NaI 0.45 g (3 mmol), zinc dust 15.69 g (240 mmol) and 390 mL dry NMP was added under nitrogen. The reaction system was heated with stirring (finally heated to 75 ° C.) and allowed to react for 3 hours. The polymerization reaction solution was diluted with 250 mL of THF, stirred for 30 minutes, filtered using Celite as a filter aid, and the filtrate was poured into a large excess of 1500 mL of methanol to coagulate. The coagulum was collected by filtration, air-dried, redissolved in THF / NMP (200/300 mL each), and coagulated with 1500 mL of a large excess of methanol. After air drying, 47.0 g (yield 99%) of a copolymer (PolyAB-SO ₃ neo-Pe) composed of a sulfonic acid derivative protected with a target yellow fibrous neopentyl group was obtained by heat drying. As for the molecular weight by GPC, the number average molecular weight (Mn) was 47,600, and Mw was 159,000.

5.1 g of the copolymer (PolyAB-SO ₃ neo-Pe) thus obtained was dissolved in 60 mL of NMP and heated to 90 ° C. A mixture of 50 mL of methanol and 8 mL of concentrated hydrochloric acid was added to the reaction system at one time. While in suspension, the reaction was allowed to proceed for 10 hours under mild reflux conditions. A distillation apparatus was installed, and excess methanol was distilled off to obtain a light green transparent solution. This solution was poured into a large amount of water / methanol (1: 1 weight ratio) to solidify the polymer, and then the polymer was washed with ion exchange water until the pH of the washing water reached 6 or more. From the IR spectrum of the polymer thus obtained and the quantitative analysis of the ion exchange capacity, it was found that the sulfonic acid ester group (—SO ₃ R ^a ) was quantitatively converted to the sulfonic acid group (—SO ₃ H). .

  The obtained polyarylene copolymer having a sulfonic acid group had a molecular weight by GPC of Mn of 53,200, Mw of 185,000, and a sulfonic acid equivalent of 1.9 meq / g.

[Synthesis Example 3] Synthesis of polyarylene having a sulfonic acid group 28.1 g (2.5 mmol) of BCPAF oligomer obtained in Synthesis Example 1 2,5-dichloro-4 '-(4-phenoxy) phenoxybenzophenone (DCPPB) 35.9g
(82.5 mmol), bis (triphenylphosphine) nickel dichloride 1.67
g (2.6 mmol), 1.66 g (11.1 mmol) of sodium iodide, 8.92 g (34.0 mmol) of triphenylphosphine and 13.3 g (204 mmol) of zinc dust were placed in a flask and purged with dry nitrogen. 160 ml of N-methyl-2-pyrrolidone was added, and the mixture was heated to 80 ° C. and stirred for 4 hours for polymerization. The polymerization solution was diluted with 160 mL of THF, and poured into hydrochloric acid / methanol (150/1500 mL, respectively) to solidify. After methanol washing of the solidified product was repeated, a solution dissolved in THF was added to 1500 mL of methanol to cause reprecipitation. The obtained precipitate was vacuum-dried to obtain 51.0 g (90%) of the target copolymer. The resulting copolymer has a molecular weight of 38,900 for Mn,
Mw was 160,000.

  50 g of the obtained copolymer was put into a 1000 ml separable flask equipped with a stirrer and a thermometer, 500 ml of sulfuric acid with a concentration of 98% was added, and the mixture was stirred for 24 hours under a nitrogen stream while keeping the internal temperature at 25 ° C. The obtained solution is poured into a large amount of ion-exchanged water to precipitate a polymer, and the precipitate is repeatedly washed until the pH of the washing water becomes 5, and then dried to obtain 56 g (95%) of sulfone. A polyarylene copolymer having an acid group was obtained.

The resulting polyarylene copolymer having a sulfonic acid group has a Mn of 45,50.
0, Mw was 176,000, and the sulfonic acid equivalent was 2.1 meq / g.

[Example 1]
A film was prepared by a casting method using a solution obtained by dissolving 10 g of the polyarylene copolymer obtained in Synthesis Example 2 and 2 g of polyvinylpyrrolidone in 100 mL of N-methylpyrrolidone.

[Example 2]
A film was prepared by a casting method using a solution obtained by dissolving 10 g of the polyarylene copolymer obtained in Synthesis Example 2 and 5 g of polyvinylpyrrolidone in 100 mL of N-methylpyrrolidone.

[Example 3]
A film was prepared in the same manner as in Example 1 except that 10 g of the polyarylene copolymer obtained in Synthesis Example 3 was used instead of 10 g of the polyarylene copolymer obtained in Synthesis Example 2.

[Comparative Example 1]
A film was prepared by a casting method using a solution obtained by dissolving 10 g of the polymer obtained in Synthesis Example 2 in 100 mL of N-methylpyrrolidone.

[Comparative Example 2]
A film was prepared by a casting method using a solution obtained by dissolving 10 g of the polymer obtained in Synthesis Example 3 in 100 mL of N-methylpyrrolidone.

  Table 1 shows the results of measurement of proton conductivity, dimensional change rate, and methanol permeability of each film.

  The proton conducting membranes of Examples 1 to 3 have higher proton conductivity than the proton conducting membranes of Comparative Examples 1 and 2, and the dimensional change rate and methanol permeability during immersion in hot water are suppressed. Recognize.

Claims (2)

A polymer electrolyte membrane comprising a polyarylene having a sulfonic acid group and polyvinylpyrrolidone ,
High the polyarylene having the sulfonic acid group, and wherein the constitutional unit represented by the following general formula (A), the Ru <br/> that name and a structural unit represented by the following general formula (B) Molecular electrolyte membrane.

Wherein Y is —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (l is an integer of 1 to 10) or —C (CF ₃ ) ₂ −
Z represents — (CH ₂ ) —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH═CH—, —C≡C—,

Or, it represents a direct bond, Ar represents an aromatic group having a substituent represented by —SO ₃ H, m represents an integer of 0 to 10, n represents an integer of 0 to 10, and k represents 1 to An integer of 4 is shown. )

Wherein R ^{1 to} R ⁸ may be the same or different from each other, and are at least one selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. An atom or group of
W represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CF ₃ ) ₂ —. Or a single bond,
T represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, — (CF ₂ ) ₁ — (l is an integer of 1 to 10), —C (CF ₃ ) ₂ —. , — (CH ₂ ) —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH═CH—, —C≡C—,

Or it shows a single bond, p shows 0 or a positive integer. ) 2. The polymer electrolyte membrane according to claim 1, wherein the polyvinyl pyrrolidone has a weight average molecular weight of 500 or more.