JP2015156315A - Method for manufacturing polymer electrolytic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polymer electrolytic film made of a non-fluorine-based material, flexible and hard to crack, and superior in resistance to hot water.

SOLUTION: A method for manufacturing a polymer electrolytic film comprises the steps of: molding a composition which includes a block copolymer (Z) including a polymer block (A) including a structural unit originating from an aromatic vinyl compound and having an ion-conductive group, and an amorphous polymer block (B) including a structural unit originating an unsaturated aliphatic hydrocarbon and having no ion-conductive group, and a compound (X) having, in its molecule, at least two aromatic rings with at least one hydrogen atom substituted with a hydroxyl group; and then, performing a heat treatment on the composition in a liquid at 80-150°C.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a method for producing a polymer electrolyte membrane useful for a polymer electrolyte fuel cell.

  In recent years, fuel cells have attracted attention as highly efficient power generation systems. Fuel cells are classified into molten carbonate type, solid oxide type, phosphoric acid type, solid polymer type, etc., depending on the type of electrolyte. Of these, a polymer electrolyte membrane is sandwiched between electrodes (anode and cathode), a fuel made of a reducing agent (usually hydrogen or methanol) at the anode, and an oxidant (usually air) at the cathode. Solid polymer fuel cells that generate electricity by supplying power are being considered for application to automotive power supplies, portable equipment power supplies, household cogeneration systems, and the like from the viewpoints of low temperature operability, small size, and light weight.

  Perfluorocarbon sulfonic acid polymers are often used as the material for polymer electrolyte membranes used in polymer electrolyte fuel cells because of their chemical stability. Environmental load becomes a problem.

  Under these circumstances, a polymer electrolyte membrane made of a material that does not contain fluorine (non-fluorine-based material) has recently been demanded. For example, a polymer electrolyte membrane made of polyether ether ketone (PEEK) into which a sulfonic acid group is introduced is known (see Patent Document 1). Although such a polymer electrolyte membrane is excellent in heat resistance, it is hard and brittle, so it is easily broken and lacks practical utility.

  On the other hand, there is known a polymer electrolyte membrane comprising a block unit comprising a polymer block having an ion conductive group and a flexible polymer block, which comprises a structural unit derived from an aromatic vinyl compound (Patent Document 2). reference). Such a polymer electrolyte membrane is flexible and difficult to break, and the polymer block having the ion conductive group forms an ion conductive channel by microphase separation from the flexible polymer block, and thus has excellent ion conductivity.

  On the other hand, in a polymer electrolyte fuel cell using hydrogen as a fuel, it is required to increase the operating temperature in order to increase the output, and in order to meet such a requirement, hot water of the polymer electrolyte membrane (for example, 90 ° C. or higher) Measures to improve durability (hot water resistance) against water, specifically, suppression of elution of polymer electrolyte membranes by hot water, and suppression of voltage drop during long-time operation associated with this are being studied .

  For example, a polymer electrolyte membrane comprising, as a main component, a block copolymer in which the flexible polymer block is a structural unit derived from a vinyl compound and the flexible polymer block is crosslinked with 1,2-polybutadiene or the like. It is known that the hot water resistance of water increases (see Patent Document 3).

JP-A-6-93114 International Publication No. 2006/070929 International Publication No. 2012/043400

  However, there is still room for improvement in hot water resistance toward higher output of the polymer electrolyte fuel cell.

  Accordingly, an object of the present invention is to provide a method for producing a polymer electrolyte membrane which is made of a non-fluorine material, is flexible and hardly cracked, and has excellent hot water resistance.

According to the invention, the object is
A polymer block (A) composed of a structural unit derived from an aromatic vinyl compound and having an ion conductive group (hereinafter simply referred to as “polymer block (A)”) and an unsaturated aliphatic hydrocarbon A block copolymer (Z) comprising 1 and an amorphous polymer block (B) (hereinafter simply referred to as “polymer block (B)”) having a structural unit and having no ion conductive group After molding a composition containing compound (X) (hereinafter simply referred to as “compound (X)”) having two or more aromatic rings in which one or more hydrogen atoms are substituted with hydroxyl groups in the molecule, This is achieved by providing a method for producing a polymer electrolyte membrane having a step of heat treatment in a liquid at 80 to 150 ° C.

  According to the production method of the present invention, it is possible to provide a polymer electrolyte membrane that is made of a non-fluorine-based material, is flexible and hardly cracked, and has excellent hot water resistance. The polymer electrolyte membrane obtained by the production method of the present invention is suitably used for a polymer electrolyte fuel cell.

≪Polymer electrolyte membrane≫
In the polymer electrolyte membrane obtained by the production method of the present invention, the polymer block (A) and the polymer block (B) form a microphase separation structure. As a result, since the phase containing the polymer block (A) forms an ion conductive channel, it exhibits good ion conductivity.
Here, “microphase separation” means phase separation in a microscopic sense, and more specifically, means phase separation in which the formed domain size is less than or equal to the wavelength of visible light (3800 to 7800 mm). It shall be.

  The film thickness of the polymer electrolyte membrane obtained by the production method of the present invention is preferably in the range of 4 to 170 μm, more preferably in the range of 8 to 115 μm, and more preferably in the range of 10 to 70 μm from the viewpoint of mechanical strength, handling properties, and the like. Is more preferable, and the range of 12 to 50 μm is particularly preferable. When the film thickness is 4 μm or more, the mechanical strength and fuel blocking property of the polymer electrolyte membrane are good, and when the film thickness is 170 μm or less, the ion conductivity of the polymer electrolyte film is good.

  The polymer electrolyte membrane obtained by the production method of the present invention is a composition comprising a block copolymer (Z) containing a polymer block (A) and a polymer block (B), and a compound (X). It may be a monolayer film composed only of a crosslinked body, or may be a multilayer film including at least one polymer electrolyte layer composed of the crosslinked body. As will be described later, the compound (X) acts as a cross-linking agent for the block copolymer (Z).

(Block copolymer (Z))
The block copolymer (Z) is composed of a structural unit derived from an aromatic vinyl compound and has a polymer block (A ₀ ) (hereinafter simply referred to as “polymer block (A ₀ )”) having no ion conductive group. And a block copolymer (Z ₀ ) containing the polymer block (B) by introducing an ion conductive group into the polymer block (A ₀ ).

The number average molecular weight (Mn) of the block copolymer (Z ₀ ) is not particularly limited, but is usually preferably in the range of 10,000 to 300,000, more preferably in the range of 15,000 to 250,000, and 40,000. The range of ˜200,000 is more preferred, and the range of 70,000 to 180,000 is particularly preferred. When the Mn of the block copolymer (Z ₀ ) is 10,000 or more, particularly 70,000 or more, the obtained polymer electrolyte membrane has high tensile elongation at break, and is 300,000 or less, particularly 180,000 or less. If present, the composition containing the block copolymer (Z) and the compound (X) is excellent in moldability and is advantageous in production. In addition, in this specification, Mn means the standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

  The ion exchange capacity of the block copolymer (Z) is preferably in the range of 0.4 to 4.5 meq / g, more preferably in the range of 0.8 to 3.2 meq / g, and 1.3 to 3.0 meq / g. Is more preferable, and a range of 1.8 to 2.8 meq / g is particularly preferable. The polymer electrolyte membrane obtained by the present invention has good ion conductivity when the ion exchange capacity is 0.4 meq / g or more, and hardly swells when it is 4.5 meq / g or less. The ion exchange capacity of the block copolymer (Z) can be calculated using an acid value titration method.

  Further, the block copolymer (Z) may have one or more polymer blocks (A) and polymer blocks (B). When there are a plurality of polymer blocks (A), their structures (kind of structural unit, degree of polymerization, kind of ion conductive group, introduction ratio, etc.) may be the same or different. Moreover, when it has two or more polymer blocks (B), those structures (kind of a structural unit, a polymerization degree, etc.) may mutually be the same, and may differ.

There is no restriction | limiting in particular in the coupling | bonding arrangement | sequence of the polymer block (A) and polymer block (B) in a block copolymer (Z). The polymer block (A) and the polymer block (B) may be side chains, that is, the block copolymer (Z) used in the present invention includes a graft copolymer.
In the block copolymer (Z), as an example of the bond arrangement of the polymer block (A) and the polymer block (B), an AB type diblock copolymer (A and B are each a polymer block ( A) represents a polymer block (B), the same applies hereinafter), an ABA type triblock copolymer, a BAB type triblock copolymer, an ABAB type tetrablock. Copolymer, A-B-A-B-A type pentablock copolymer, B-A-B-A-B type pentablock copolymer, (A-B) _n D-type star copolymer ( D represents a coupling agent residue, n represents an integer greater than or equal to 2. Hereinafter, the same applies to (B-A) _n D-type star copolymer, and the like. From the viewpoints of mechanical strength and ionic conductivity, an ABA type triblock copolymer, an ABBA type BA block type Data block copolymer, (A-B) _n D-type star form copolymer preferably, A-B-A type triblock copolymer is more preferable. These block copolymers may be used alone or in combination of two or more.

(Total amount of polymer block (A ₀ )) :( Total amount of polymer block (B)) in the block copolymer (Z ₀ ) is in the range of 95: 5 to 5:95 by mass ratio. Is more preferable, it is more preferably in the range of 75:25 to 15:85, still more preferably in the range of 65:35 to 20:80, and particularly preferably in the range of 45:55 to 25:75. . When the mass ratio is in the range of 95: 5 to 5:95, particularly in the range of 45:55 to 25:75, the resulting polymer electrolyte membrane has ion conductivity, mechanical strength, and activation of the polymer electrolyte fuel cell. In addition, it tends to be excellent in durability (start / stop durability) when wetting and drying are repeated with stopping.

<Polymer block (A)>
The polymer block (A) can be formed by introducing an ion conductive group into the polymer block (A ₀ ). The ion conductive group is usually introduced into the aromatic ring of the polymer block (A ₀ ).

The polymer block (A ₀ ) is composed of a structural unit derived from an aromatic vinyl compound, and the aromatic ring of the aromatic vinyl compound is a carbocyclic aromatic ring such as a benzene ring, a naphthalene ring, an anthracene ring, or a pyrene ring. Preferably, there is a benzene ring.

Examples of the aromatic vinyl compound that can form the polymer block (A ₀ ) include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 2,3-dimethylstyrene, 2, 4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, vinylbiphenyl, vinylterphenyl, vinylnaphthalene, vinylanthracene, 4-phenoxy Examples include styrene.

  Of the hydrogen atoms on the vinyl group of the aromatic vinyl compound, the hydrogen atom bonded to the α-position carbon (α-carbon) of the aromatic ring may be substituted with another substituent. Examples of the substituent include alkyl groups having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group; Group, a halogenated alkyl group having 1 to 4 carbon atoms such as a 2-chloroethyl group and a 3-chloroethyl group; or a phenyl group. Examples of the aromatic vinyl compound in which the hydrogen atom bonded to the α-carbon is substituted with these substituents include α-methylstyrene, α-methyl-4-methylstyrene, α-methyl-2-methylstyrene, α-methyl. Examples include -4-ethylstyrene, 1,1-diphenylethylene, and the like.

Among the aromatic vinyl compounds that can form the above polymer block (A ₀ ), styrene, α-methylstyrene, 4-methylstyrene, 4-ethylstyrene, α-methyl-4-methylstyrene, α-methyl-2 -Methylstyrene, vinylbiphenyl and 1,1-diphenylethylene are preferred, styrene, α-methylstyrene, 4-methylstyrene and 1,1-diphenylethylene are more preferred, and styrene and α-methylstyrene are more preferred.

A polymer block (A ₀ ) can be formed by polymerizing one of these aromatic vinyl compounds as a monomer, or a combination of two or more. Random copolymerization is preferred as the copolymerization form when two or more aromatic vinyl compounds are used in combination.

In the present invention, the polymer block (A ₀ ) may contain other structural units not derived from one or more aromatic vinyl compounds within a range not impairing the effects of the present invention. Examples of monomers that can form such other structural units include butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, and 2-ethyl-1,3. A conjugated diene having 4 to 8 carbon atoms such as butadiene and 1,3-heptadiene; 2 to 2 carbon atoms such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene and 1-octene 8 Alkenes; (Meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate And vinyl ethers such as methyl vinyl ether and isobutyl vinyl ether. In this case, the copolymerization form of these other monomers and the above-described aromatic vinyl compound is preferably random copolymerization. These other structural units are preferably 5 mol% or less of the structural units forming the polymer block (A ₀ ). That is, it is preferable that 95 mol% or more of the structural units forming the polymer block (A ₀ ) are structural units derived from an aromatic vinyl compound.

The Mn per polymer block (A ₀ ) is usually preferably in the range of 1,000 to 100,000, more preferably in the range of 2,000 to 70,000, and further in the range of 4,000 to 50,000. The range of 6,000 to 30,000 is particularly preferable. When the number average molecular weight (Mn) is 1,000 or more, particularly 6,000 or more, the polymer electrolyte membrane obtained in the present invention has good ion conductivity, and is 100,000 or less, particularly 30,000 or less. If it exists, hot water resistance will become favorable, and the said composition containing block copolymer (Z) and compound (X) is excellent in a moldability, and becomes advantageous also in manufacture.

The ion conductive group possessed by the polymer block (A ₀ ) is preferably a proton conductive group, and is —SO ₃ M or PO ₃ HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion). One or more selected from the sulfonic acid groups, phosphonic acid groups and salts thereof represented are more preferred, and sulfonic acid groups are more preferred.

<Polymer block (B)>
The polymer block (B) is an amorphous polymer block composed of a structural unit derived from an unsaturated aliphatic hydrocarbon and having no ion conductive group. In addition, the amorphous property of a polymer block (B) can be confirmed by measuring the dynamic viscoelasticity of a block copolymer (Z), and not having the change of the storage elastic modulus derived from a crystalline olefin polymer.

  Examples of the unsaturated aliphatic hydrocarbon that can form the polymer block (B) include ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene and the like having 2 to 2 carbon atoms. 8 alkenes; 7 to 10 carbon cycloalkanes such as vinyl cyclopentane, vinyl cyclohexane, vinyl cycloheptane and vinyl cyclooctane; 7 to 7 carbon atoms such as vinyl cyclopentene, vinyl cyclohexene, vinyl cycloheptene and vinyl cyclooctene 10 vinylcycloalkenes; butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc. A conjugated diene having 4 to 8 carbon atoms; cyclopentadiene, 1,3- Conjugated cycloalkadiene having 5 to 8 carbon atoms such as clohexadiene; and 2 to 2 carbon atoms such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene and 1-octene. 8 alkenes; carbons such as butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene A conjugated diene having 4 to 8 carbon atoms is preferred, a conjugated diene having 4 to 8 carbon atoms is more preferred, isobutene, butadiene and isoprene are further preferred, and butadiene and isoprene are particularly preferred. Using these unsaturated aliphatic hydrocarbons as a monomer, one type is polymerized alone or in combination of two or more types to form a polymer block (B). Random copolymerization is preferred as the copolymerization form when two or more unsaturated aliphatic hydrocarbons are used in combination.

  Further, the polymer block (B) is not derived from an unsaturated aliphatic hydrocarbon as long as the effect of the polymer block (B) that gives the block copolymer (Z) flexibility in the use temperature range is not impaired. Other structural units may be included. Examples of monomers that can form such other structural units include aromatic vinyl compounds such as styrene and vinyl naphthalene; halogen-containing vinyl compounds such as vinyl chloride; vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl pivalate. Vinyl ester; vinyl ethers such as methyl vinyl ether and isobutyl vinyl ether; In this case, the copolymerization form of these other monomers with the unsaturated aliphatic hydrocarbon described above is preferably random copolymerization. These other structural units are preferably 5 mol% or less of the structural units forming the polymer block (B). That is, it is preferable that 95 mol% or more of the structural units forming the polymer block (B) are structural units derived from unsaturated aliphatic hydrocarbons.

When the unsaturated aliphatic hydrocarbon has a plurality of carbon-carbon double bonds, any of them may be used for polymerization. For example, in the case of a conjugated diene, either 1,2-bond or 1,4-bond It may be. In the polymer block (B) formed by polymerizing the conjugated diene, a carbon-carbon double bond usually remains, but from the viewpoint of improving the heat deterioration resistance of the obtained polymer electrolyte membrane, the block block After polymerizing the polymer (Z ₀ ), a hydrogenation reaction (hereinafter referred to as “hydrogenation reaction”) is performed, and the carbon-carbon double bond is hydrogenated (hereinafter referred to as “hydrogenation”). preferable. The hydrogenation rate of such a carbon-carbon double bond (hereinafter referred to as “hydrogenation rate”) is preferably 30 mol% or more, more preferably 50 mol% or more, and further preferably 95 mol% or more.

In addition, when an ion conductive group is introduced after polymerizing the block copolymer (Z ₀ ) to form the block copolymer (Z), if the polymer block (B) is a saturated hydrocarbon structure, It is preferable because introduction of an ion conductive group into the combined block (B) hardly occurs. Therefore, when the hydrogenation reaction of the carbon-carbon double bond remaining in the polymer block (B) after polymerizing the block copolymer (Z ₀ ) is performed before introducing the ion conductive group. desirable.
The hydrogenation rate of the carbon-carbon double bond can be calculated by ¹ H-NMR measurement.

  The Mn per polymer block (B) is usually preferably in the range of 5,000 to 250,000, more preferably in the range of 7,000 to 200,000, and 15,000 to 150,000. More preferably, it is in the range of 000, particularly preferably in the range of 80,000 to 140,000. If such Mn is 5,000 or more, particularly 80,000 or more, the resulting polymer electrolyte membrane has particularly excellent mechanical strength and start / stop durability, and Mn is 250,000 or less, particularly 140,000 or less. For example, the composition containing the block copolymer (Z) and the compound (X) is excellent in moldability and is advantageous in production.

<Other polymer block (C)>
The block copolymer (Z) may further include a polymer block (C) that is composed of a structural unit derived from an aromatic vinyl compound and does not have an ion conductive group. In the polymer electrolyte membrane obtained by the production method of the present invention, the polymer block (C) forms a microphase separation structure with the polymer block (A) and the polymer block (B).

  The polymer block (C) is preferably composed of a structural unit derived from an aromatic vinyl compound represented by the following general formula (1) because of superiority in production.

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 3 to 8 carbon atoms, and R ³ and R ⁴ each independently represents a hydrogen atom or a carbon number. Represents an alkyl group of 3 to 8)

When the polymer block (C) is a structural unit derived from an aromatic vinyl compound having at least one alkyl group having 3 to 8 carbon atoms on the aromatic ring, the block copolymer (Z ₀ ) has ion conductivity. When the group is introduced to produce the polymer block (Z), an ion conductive group can be selectively introduced into the polymer block (A ₀ ).

  Examples of the aromatic vinyl compound for forming the structural unit represented by the general formula (1) include 4-propylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-isobutylstyrene, 4-tert-butylstyrene, 4-octyl styrene, α-methyl-4-tert-butyl styrene, α-methyl-4-isopropyl styrene and the like can be mentioned. 4-tert-butyl styrene, 4-isopropyl styrene, α-methyl-4-tert-butyl Styrene and α-methyl-isopropylstyrene are more preferable, and 4-tert-butylstyrene is more preferable. These may be used alone or in combination of two or more. Random copolymerization is preferred as the copolymerization form when two or more types are used in combination to form the polymer block (C).

  The polymer block (C) may contain other structural units not derived from one or more aromatic vinyl compounds within the range not impairing the effects of the present invention. Examples of the monomer capable of forming such other structural units include butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2 -Conjugated dienes having 4 to 8 carbon atoms such as ethyl-1,3-butadiene and 1,3-heptadiene; ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene Alkenes having 2 to 8 carbon atoms such as: (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate; vinyl acetate, vinyl propionate, vinyl butyrate, pivalin Vinyl esters such as vinyl acid; vinyl ethers such as methyl vinyl ether and isobutyl vinyl ether. In this case, the copolymerization form of these other monomers and the above-described aromatic vinyl compound is preferably random copolymerization. These other structural units are preferably 5 mol% or less of the structural units forming the polymer block (C). That is, it is preferable that 95 mol% or more of the structural units forming the polymer block (C) are structural units derived from an aromatic vinyl compound.

  Mn per polymer block (C) is usually preferably in the range of 1,000 to 50,000, more preferably in the range of 1,500 to 30,000, and 2,000 to 20,000. More preferably, it is in the range of 000. If such Mn is 1,000 or more, the polymer electrolyte membrane obtained by the present invention tends to be excellent in mechanical strength, and if it is 50,000 or less, the block copolymer (Z) and the compound (X) are added. The composition to be contained is excellent in moldability and advantageous in production.

  As an example of the arrangement when the block copolymer (Z) used in the present invention contains a polymer block (C), an ABC type triblock copolymer (A, B, and C are polymer blocks, respectively). (A) represents a polymer block (B) and a polymer block (C), the same shall apply hereinafter), an A-B-C-A type tetrablock copolymer, an A-B-A-C type tetrablock copolymer. Polymer, B-A-B-C type tetrablock copolymer, A-B-C-B type tetrablock copolymer, A-C-B-C type tetrablock copolymer, C-A-B- A-C type pentablock copolymer, C-B-A-B-C type pentablock copolymer, A-C-B-C-A type pentablock copolymer, A-C-B-A- C-type pentablock copolymer, A-C-B-C-A-C type hexablock copolymer, C-A-B-C-- -C-type hexablock copolymer, A-C-A-C-B-C-type hexablock copolymer, A-C-A-C-B-C-A type heptablock copolymer, A-C -B-C-B-C-A type heptablock copolymer, C-A-C-B-C-A-C type heptablock copolymer, A-C-A-C-B-C-A -C-type octablock copolymer, A-C-B-C-B-C-A-C-type octablock copolymer, A-C-B-C-A-C-B-C-type octablock copolymer A polymer etc. are mentioned. Among these, from the viewpoint of mechanical strength and ion conductivity, an ABC type triblock copolymer, an ABCA type tetrablock copolymer, an ABC type tetrablock copolymer are used. Polymer, A-C-B-C type tetrablock copolymer, C-A-B-A-C type pentablock copolymer, C-B-A-B-C type pentablock copolymer, A -C-B-C-A type pentablock copolymer, A-C-B-A-C type pentablock copolymer, A-C-B-C-A-C type hexablock copolymer, C -A-B-C-A-C type hexablock copolymer, A-C-A-C-B-C type hexablock copolymer, A-C-A-C-B-C-A type hepta Block copolymer, A-C-B-C-B-C-A type hepta block copolymer, C-A-C-B-C-A-C type hepta block copolymer Combined, A-C-A-C-B-C-A-C type octablock copolymer, A-C-B-C-B-C-A-C type octablock copolymer, A-C- B-C-A-C-B-C type octablock copolymer is preferable, A-C-B-C-type tetrablock copolymer, A-C-B-C-A type pentablock copolymer, A-C-B-C-A-C type hexablock copolymer and A-C-A-C-B-C-A-C type octablock copolymer are more preferable, and A-C-B-C -A-type pentablock copolymer and A-C-A-C-B-C-A-C type octablock copolymer are more preferable. In the polymer electrolyte membrane obtained by the production method of the present invention, these block copolymers may be used alone or in combination of two or more.

When the block copolymer (Z) constituting the polymer electrolyte membrane obtained by the production method of the present invention contains the polymer block (C), the polymer block (C) occupying the block copolymer (Z ₀ ) The content is preferably in the range of 5 to 50% by mass, more preferably in the range of 7 to 40% by mass, and still more preferably in the range of 10 to 30% by mass. When the content is 5% by mass or more, the hot water resistance of the obtained polymer electrolyte membrane is increased, and when it is 50% by mass or less, the obtained polymer electrolyte membrane tends to be excellent in start / stop durability.

<Production of block copolymer (Z ₀ )>
The block copolymer (Z) used in the production method of the present invention is a block copolymer (Z) comprising a polymer block (A ₀ ) and a polymer block (B) by polymerizing each of the aforementioned monomers. ₀ ) can be produced by a method of introducing an ion conductive group into the polymer block (A ₀ ).

A method for producing the block copolymer (Z ₀ ) can be selected as appropriate, but a method of polymerizing each monomer described above by a polymerization method selected from a living radical polymerization method, a living anion polymerization method and a living cation polymerization method is preferable. .

As a specific example of the production method of the block copolymer (Z ₀ ), a polymer block (A ₀ ) composed of a structural unit derived from an aromatic vinyl compound and a polymer block (B) composed of a structural unit derived from a conjugated diene As a method for producing a block copolymer (Z ₀ ) comprising) as an ingredient, (1) an aromatic vinyl compound under the temperature conditions of 20 to 100 ° C. using an anionic polymerization initiator in a cyclohexane solvent, A method of sequentially obtaining an ABA block copolymer by anionic polymerization of a conjugated diene and an aromatic vinyl compound;
(2) An anionic polymerization initiator is used in a cyclohexane solvent, and an aromatic vinyl compound and a conjugated diene are successively subjected to anionic polymerization under a temperature condition of 20 to 100 ° C., and then a coupling agent such as phenyl benzoate is added. To obtain an ABA type block copolymer;
(3) In a nonpolar solvent, an organolithium compound is used as an initiator, and in the presence of a polar compound having a concentration of 0.1 to 10% by mass, a fragrance having a concentration of 5 to 50% by mass at a temperature of -30 to 30 ° C A method of obtaining an ABA type block copolymer by anionic polymerization of an aromatic vinyl compound and anionic polymerization of a conjugated diene to the resulting living polymer, and then adding a coupling agent such as phenyl benzoate;
Etc.
In addition, a block copolymer (Z ₀ ) comprising a polymer block (A ₀ ) composed of a structural unit derived from an aromatic vinyl compound and a polymer block (B) composed of a structural unit derived from isobutene as components. As a way to
(4) Cationic polymerization of an aromatic vinyl compound after cationic polymerization of isobutene in the presence of a Lewis acid using a bifunctional halogenation initiator at -78 ° C in a halogen / hydrocarbon mixed solvent A method for obtaining an ABA type block copolymer;
Etc.
In addition, a polymer block (C) can be added as a component of a block copolymer by changing or adding the component made to react in the said anionic polymerization or cationic polymerization as needed.

<Production of block copolymer (Z)>
A method for producing a block copolymer (Z) by introducing an ion conductive group into the block copolymer (Z ₀ ) will be described below.

First, a method for introducing a sulfonic acid group into the block copolymer (Z ₀ ) will be described. Introduction of a sulfonic acid group (sulfonation) can be performed by a known method. For example, the block copolymer (Z ₀₎ the organic solvent solution or suspension is prepared and such solutions and a method of mixing by adding a sulfonating agent to be described later to the suspension, the block copolymer (Z ₀₎ And a method of directly adding a gaseous sulfonating agent.

  As the sulfonating agent, sulfuric acid; a mixture system of sulfuric acid and acid anhydride; chlorosulfonic acid; a mixture system of chlorosulfonic acid and trimethylsilyl chloride; sulfur trioxide; a mixture system of sulfur trioxide and triethyl phosphate; Examples thereof include aromatic organic sulfonic acids represented by 4,6-trimethylbenzenesulfonic acid. Among these, a mixture system of sulfuric acid and acid anhydride is preferable. Examples of the organic solvent to be used include halogenated hydrocarbons such as methylene chloride, linear aliphatic hydrocarbons such as hexane, cyclic aliphatic hydrocarbons such as cyclohexane, aromatic compounds having an electron withdrawing group such as nitrobenzene, etc. Can be illustrated.

Next, a method for introducing a phosphonic acid group into the block copolymer (Z ₀ ) will be described. Introduction (phosphonation) of a phosphonic acid group can be performed by a known method. For example, the aromatic ring of the polymer block (A ₀ ) is reacted with halomethyl ether in the presence of aluminum chloride to introduce a halomethyl group, and then reacted with phosphorus trichloride and aluminum chloride to be substituted with a phosphorus derivative. A method of converting to a phosphonic acid group by decomposition; and a method of converting a phosphinic acid group introduced by reacting an aromatic ring of the aromatic vinyl compound with phosphorus trichloride and anhydrous aluminum chloride to a phosphonic acid group by oxidizing with nitric acid. Can be mentioned.

In the block copolymer (Z), the introduction rate (sulfonation rate, phosphonation rate, etc.) of the ion conductive group with respect to the structural unit derived from the aromatic vinyl compound of the polymer block (A) is ¹ H-NMR. Can be used to calculate.

<Compound (X)>
Compound (X) is a compound having in its molecule two or more aromatic rings in which one or more hydrogen atoms are substituted with hydroxyl groups, and is considered to act as a crosslinking agent. It is presumed that the compound (X) has two or more aromatic rings in the molecule, so that the compound (X) is selectively present in the phase containing the hydrophilic polymer block (A). It is considered that the hot water resistance is improved without impairing the flexibility of the polymer electrolyte membrane by selectively crosslinking the polymer block (A).
The aromatic ring is preferably a hydrocarbon aromatic ring such as a benzene ring, a naphthalene ring or an anthracene ring, and more preferably a benzene ring.
In the case where the aromatic ring is a benzene ring, the benzene ring has one or more hydrogen atoms substituted with a hydroxyl group, but when the carbon on the benzene ring to which the hydroxyl group is bonded is the 1-position. In addition, it is preferable that at least one of carbons at 2, 4, and 6 positions does not have a substituent, and among these, from the viewpoint of increasing the tensile breaking elongation and tensile breaking strength of the polymer electrolyte membrane, It is more preferable that the carbon has a methyl group.

Specific examples of the compound (X) include bisphenol S, 4,4′-dihydroxybiphenyl-2,2′-disulfonic acid, 4,4′-dihydroxybiphenyl-3,3′-disulfonic acid, 2,2′- Dihydroxybiphenyl-4,4′-disulfonic acid, 5,5′-methylenebis (2-hydroxybenzoic acid), 4,4′-isopropylidenebis (2,6-dichlorophenol), 4,4′-isopropylidenebis (2,6-dibromophenol), 4,4 '-(9-fluorenylidene) diphenol, bis (2-hydroxyphenyl) methane, 2,2'-biphenol, 4,4'-biphenol, bis (4-hydroxy Phenyl) methane, bisphenol A, 4,4′-hexafluoroisopropylidenediphenol, 2,2-bis (4-hydroxy-3-methylphenol) Nyl) propane, 1,1-bis (4-hydroxy-3-methylphenyl) ethane, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 2,2′-methylenebis (6-tert) -Butyl-4-ethylphenol), 2,2'-ethylidenebis (4,6-ditert-butylphenol), 3,3'-ethylenedioxydiphenol, 1,4-bis (3-hydroxyphenoxy) benzene 1,3-bis (4-hydroxyphenoxy) benzene, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, hexestrol, dithranol, 1,1′- Bi-2-naphthol, nordihydroguaiaretic acid, bis (3,4-dihydroxy-6-methylphenyl) phenylme 9- (4-hydroxybenzyl) -10- (4-hydroxyphenyl) anthracene, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 2,6- Bis (4-hydroxy-3,5-dimethylbenzyl) -4-methylphenol, 1,1,1-tris (4-hydroxyphenyl) ethane, tris (4-hydroxyphenyl) methane, bis (4-hydroxy-3) -Methylphenyl) -4-hydroxy-3-methoxyphenylmethane, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2,4-dihydroxybenzyl)- 4-methylphenol, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, α, α, α ′, α′-tetrakis (4-hydride) Xylphenyl) paraxylene, 2,2-bis [4,4-bis (4-hydroxyphenyl) cyclohexyl] propane, C-methylcalix [4] resorcinalene, calix [4] arene, 6,6′-bis (2- Hydroxy-5-methylbenzyl) -4,4'-dimethyl-2,2'-methylenediphenol, 2,2-bis [4-hydroxy-3,5-bis (2-hydroxy-5-methylbenzyl) phenyl ] A phenol skeleton such as propane, calix [6] arene, poly-2-hydroxy-5-vinylbenzenesulfonic acid, poly-2-vinylphenol, poly-3-vinylphenol, poly-4-vinylphenol and the like as a repeating unit. Polymer to be used.
Among them, 4,4′-isopropylidenebis (2,6-dichlorophenol), 4,4′-isopropylidenebis (2,6-dibromophenol), 4,4 ′-(9-fluorenylidene) diphenol, bis (2-hydroxyphenyl) methane, 2,2′-biphenol, 4,4′-biphenol, bis (4-hydroxyphenyl) methane, bisphenol A, 4,4′-hexafluoroisopropylidenediphenol, 2,2- Bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (4-hydroxy-3-methylphenyl) ethane, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 2 , 2′-methylenebis (6-tert-butyl-4-ethylphenol), 2,2′-ethylidenebis (4,6-ditert -Butylphenol), 3,3'-ethylenedioxydiphenol, 1,4-bis (3-hydroxyphenoxy) benzene, 1,3-bis (4-hydroxyphenoxy) benzene, bis (4-hydroxy-3,5 -Dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, hexestrol, dithranol, 1,1'-bi-2-naphthol, nordihydroguaiaretic acid, bis (3,4-dihydroxy-6- Methylphenyl) phenylmethane, 9- (4-hydroxybenzyl) -10- (4-hydroxyphenyl) anthracene, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 2,6-bis (4-hydroxy-3,5-dimethylbenzyl) -4-methylphenol, 1, , 1-tris (4-hydroxyphenyl) ethane, tris (4-hydroxyphenyl) methane, bis (4-hydroxy-3-methylphenyl) -4-hydroxy-3-methoxyphenylmethane, 2,6-bis (2 -Hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2,4-dihydroxybenzyl) -4-methylphenol, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, α, α, α ′, α′-tetrakis (4-hydroxyphenyl) paraxylene, 2,2-bis [4,4-bis (4-hydroxyphenyl) cyclohexyl] propane, C-methylcalix [4] resorcinalene, Calix [4] arene, 6,6′-bis (2-hydroxy-5-methylbenzyl) -4,4′-dimethyl-2,2 ′ Methylenediphenol, 2,2-bis [4-hydroxy-3,5-bis ((2-hydroxy-5-methylbenzyl)) phenyl] propane, calix [6] arene, poly-2-vinylphenol, poly- A compound selected from 3-vinylphenol and poly-4-vinylphenol is preferable, and 2,2′-biphenol, 4,4′-biphenol, bisphenol A, 3,3′-ethylenedioxydiphenol, 1,4- Bis (3-hydroxyphenoxy) benzene, 1,3-bis (4-hydroxyphenoxy) benzene, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2 , 4-dihydroxybenzyl) -4-methylphenol, 6,6′-bis (2-hydroxy-5-methylbenzyl) -4, More preferred are compounds selected from '-dimethyl-2,2'-methylenediphenol, poly-2-vinylphenol, poly-3-vinylphenol, poly-4-vinylphenol, 2,2'-biphenol, 4, 4′-biphenol, 3,3′-ethylenedioxydiphenol, 1,4-bis (3-hydroxyphenoxy) benzene, 1,3-bis ((4-hydroxyphenoxy)) benzene, 2,6-bis ( 2-hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2,4-dihydroxybenzyl) -4-methylphenol, 6,6′-bis (2-hydroxy-5-methylbenzyl) -4,4'-dimethyl-2,2'-methylenediphenol, poly-2-vinylphenol, poly-3-vinylphenol, poly-4-vinylphenol More preferred are compounds selected from the group consisting of 2,2'-biphenol, 4,4'-biphenol, 1,4-bis (3-hydroxyphenoxy) benzene, 1,3-bis (4- Hydroxyphenoxy) benzene, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2,4-dihydroxybenzyl) -4-methylphenol, 6,6'- Selected from bis (2-hydroxy-5-methylbenzyl) -4,4′-dimethyl-2,2′-methylenediphenol, poly-2-vinylphenol, poly-3-vinylphenol, poly-4-vinylphenol Particularly preferred are compounds. Poly-4-vinylphenol is most preferable from the viewpoint of suppressing voltage drop when the polymer electrolyte membrane is incorporated in a fuel cell and operated. From the viewpoint of increasing the tensile elongation at break and tensile strength at break, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 2,6-bis (2,4-dihydroxybenzyl) Most preferred are compounds selected from -4-methylphenol and 6,6'-bis (2-hydroxy-5-methylbenzyl) -4,4'-dimethyl-2,2'-methylenediphenol.

  Compound (X) may be used alone or in combination of two or more. When the compound (X) is used in combination, it is not particularly limited, but it is preferable that at least one compound having three or more aromatic rings in which one or more hydrogen atoms are substituted with a hydroxyl group is used. It is more preferable that two or more are used. Specific combinations of compound (X) include poly-4-vinylphenol and 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, poly-4-vinylphenol and 2 , 6-Bis (2,4-dihydroxybenzyl) -4-methylphenol is preferred.

  The amount of the compound (X) used is preferably in the range of 0.01 to 25 parts by mass with respect to 100 parts by mass of the block copolymer (Z), from the viewpoint of hot water resistance of the polymer electrolyte membrane, and preferably 0.2 to 20 The range of parts by mass is more preferred, the range of 0.3 to 15 parts by mass is more preferred, and the range of 1 to 12 parts by mass is particularly preferred. Further, from the viewpoint of increasing the hot water resistance and ion conductivity, and from the viewpoint of easily setting the crosslinking density to a preferred range, the number of moles of the aromatic ring in which one or more hydrogen atoms of the compound (X) are substituted with a hydroxyl group is The range of 0.1-70 mol part is preferable with respect to 100 mol part of ion conductive groups of a polymer (Z), the range of 0.5-60 mol part is more preferable, 0.8-50 mol part is preferable. The range is more preferable, and the range of 3 to 38 mol parts is particularly preferable.

[Production method of polymer electrolyte membrane]
Next, the manufacturing method of the polymer electrolyte membrane of this invention is demonstrated.
The method for producing a polymer electrolyte membrane of the present invention comprises a step of heat-treating at 80 to 150 ° C. in a liquid after molding a composition containing the block copolymer (Z) and the compound (X). Features. A fluid composition containing a block copolymer (Z), which is a polymer electrolyte, a compound (X), and a solvent is usually used for molding the composition containing the block copolymer (Z) and the compound (X). Is used.

  Solvents that can be used in the fluid composition include halogenated hydrocarbons such as methylene chloride; aromatic hydrocarbons such as toluene, xylene, and benzene; linear aliphatic hydrocarbons such as hexane, heptane, and octane; cyclohexane And cycloaliphatic hydrocarbons such as ether; ethers such as tetrahydrofuran, alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and isobutanol. These may be used alone or in combination of two or more, but from the viewpoint of the solubility or dispersibility of the polymer block contained in each block copolymer (Z), a mixed solvent should be used. Is preferred. Preferred mixed solvents include a mixed solvent of toluene and isobutanol, a mixed solvent of xylene and isobutanol, a mixed solvent of toluene and isopropanol, a mixed solvent of cyclohexane and isopropanol, a mixed solvent of cyclohexane and isobutanol, tetrahydrofuran solvent, tetrahydrofuran Mixed solvent of methanol and methanol, mixed solvent of toluene, isobutanol and octane, mixed solvent of toluene, isopropanol and octane, mixed solvent of toluene and isobutanol, mixed solvent of xylene and isobutanol, mixed solvent of toluene and isopropanol More preferred are a mixed solvent of toluene, isobutanol and octane, and a mixed solvent of toluene, isopropanol and octane.

  The heat treatment in the production method of the present invention may be performed after the fluid composition is applied to a substrate or the like and then formed into a film by removing the solvent. Since the block copolymer (Z) is crosslinked with the compound (X) by the heat treatment, the hot water resistance of the obtained polymer electrolyte membrane can be increased. Moreover, since the block copolymer (Z) and the compound (X) can be uniformly heated by heat treatment in a liquid, the uniformity of the obtained polymer electrolyte membrane is improved.

  The fluid composition is prepared by dissolving or dispersing the block copolymer (Z) and the compound (X) in the solvent. Various stabilizers such as softeners, phenol stabilizers, sulfur stabilizers, phosphorus stabilizers, inorganic fillers, light stabilizers, antistatic agents, release agents as long as the effects of the present invention are not impaired as necessary. Various additives such as a mold, a flame retardant, a foaming agent, a pigment, a dye, a bleaching agent, and carbon fiber may be dissolved or dispersed together. The content of the block copolymer (Z) in the component (solid content) other than the solvent in the fluid composition is 50% by mass or more from the viewpoint of ion conductivity of the obtained polymer electrolyte membrane. Preferably, the content is 70% by mass or more, and more preferably 85% by mass or more.

  Examples of the softener that can be used in the fluid composition include petroleum softeners such as paraffinic, naphthenic, and aromatic process oils; liquid paraffin, vegetable oil softeners, plasticizers, and the like. These may be used alone or in combination of two or more.

  Stabilizers that can be used in the flowable composition include 2,6-ditert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-ditert-butyl-4-hydroxyphenyl). ) Propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-ditert-butyl-4-hydroxybenzyl) benzene, octadecyl-3- (3,5-ditert-butyl-) 4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3 , 5-Ditert-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-dit rt-butyl-4-hydroxyphenyl) propionate], 3,5-ditert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris- (3,5-ditert-butyl-4-hydroxybenzyl) -isocyanate Nurate, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetra Phenolic stabilizers such as oxaspiro [5.5] undecane; pentaerythrityltetrakis (3-laurylthiopropionate), distearyl 3,3′-thiodipropionate, dilauryl 3,3′-thiodipropio And sulfur stabilizers such as dimyristyl 3,3′-thiodipropionate; Le) phosphite, tris (2,4-di-tert- butylphenyl) phosphite, phosphorus-based stabilizers such as distearyl pentaerythritol phosphite. These may be used alone or in combination of two or more.

  Examples of the inorganic filler that can be used in the fluid composition include talc, calcium carbonate, silica, glass fiber, mica, kaolin, titanium oxide, montmorillonite, and alumina. These may be used alone or in combination of two or more.

  Although the density | concentration of the block copolymer (Z) in a fluid composition can be suitably selected according to molecular weight, a composition, and an ion exchange group capacity | capacitance, it is preferable that it is 5-20 mass% from a viewpoint of productivity.

  The fluid composition is usually applied on a smooth substrate made of polyethylene terephthalate (PET), glass or the like using a coater, an applicator, or the like.

  The fluid composition may be applied onto a porous substrate (porous substrate) by a dip nip method, a method using a coater, an applicator, or the like. In this case, the porous substrate is usually impregnated with at least a part of the fluid composition. The porous substrate impregnated with at least a part of the fluid composition functions as a reinforcing material by constituting a part of the polymer electrolyte membrane after crosslinking. As the porous substrate, a fibrous base material such as a woven fabric or a non-woven fabric, a film-like base material having fine through holes, or the like can be used. Examples of the film-like substrate include a fuel cell pore filling membrane. From the viewpoint of strength, the porous substrate is preferably a fibrous base material, more preferably a non-woven fabric. Examples of the fibers constituting the fibrous base material include aramid fibers, glass fibers, cellulose fibers, nylon fibers, vinylon fibers, polyester fibers, polyolefin fibers, and rayon fibers, and wholly aromatic polyesters from the viewpoint of strength. Fibers and aramid fibers are more preferable, and wholly aromatic liquid crystal polyester fibers are more preferable.

After the fluid composition is applied to the substrate or the like, the solvent is removed to obtain a film-like molded body composed of the composition containing the block copolymer (Z) and the compound (X). The temperature at which the solvent is removed can be arbitrarily selected as long as the block copolymer (Z) is not decomposed, and a plurality of temperatures may be arbitrarily combined. The removal of the solvent can be performed under ventilation conditions, vacuum conditions, or the like, and these may be combined arbitrarily. Specifically, a method of removing a solvent by drying at 60 to 120 ° C. for 4 to 10 minutes in a hot air dryer; removing a solvent by drying at 120 to 140 ° C. for 2 to 4 minutes in a hot air dryer Method of pre-drying at 25 ° C. for 1 to 3 hours and then drying in a hot air dryer at 80 to 120 ° C. for 5 to 10 minutes; pre-dried at 25 ° C. for 1 to 3 hours Thereafter, a method of drying under an atmosphere of 25 to 40 ° C. under reduced pressure for 1 to 12 hours may be mentioned.
From the viewpoint of easy preparation of a polymer electrolyte membrane having good toughness, the solvent is removed by drying at 60 to 120 ° C. for 4 to 10 minutes in a hot air dryer; at 25 ° C. for 1 to 3 hours. A method of pre-drying and then drying in a hot air dryer at about 80-120 ° C. for 5-10 minutes; after pre-drying at 25 ° C. for 1-3 hours, in an atmosphere of 25-40 ° C. A method of drying for 1 to 12 hours under a reduced pressure condition of 1.3 kPa or less is preferably used.

  When the polymer electrolyte membrane is a multi-layer membrane, for example, after applying the fluid composition to a substrate or the like, after removing the solvent to form the first layer, another polymer is further formed on the first layer. A fluid composition containing an electrolyte is applied and the solvent is removed to form a second layer. Similarly, the third and subsequent layers may be formed. Alternatively, the produced polymer electrolyte membranes may be bonded to form a multilayer film.

After coating the fluid composition on a substrate or the like, the film-like molded body obtained by removing the solvent is crosslinked by heat treatment at 80 to 150 ° C. in a liquid, and the polymer electrolyte membrane is formed. obtain.
The heating temperature at the time of heat processing is 80-150 degreeC, 85-145 degreeC is preferable and 90-140 degreeC is more preferable. When the heating temperature is less than 80 ° C, the progress of crosslinking by the compound (X) becomes insufficient, and when the heating temperature exceeds 150 ° C, the polymer electrolyte membrane tends to be thermally deteriorated. The pressure during the heat treatment is preferably from 0.1 to 0.6 MPa, more preferably from 0.1 to 0.5 MPa. The heating time is preferably 0.5 to 500 hours, more preferably 10 to 400 hours, and further preferably 80 to 300 hours.

  The liquid used in the heat treatment of the film-shaped molded body may be a liquid under the heat treatment conditions. From the viewpoint of productivity, such a liquid is preferably a liquid at 5 to 40 ° C. at normal pressure, specifically, water; alcohol such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol; hexane, Examples include alkanes such as heptane and octane; aromatic vinyl compounds such as toluene, xylene and benzene; ethers such as tetrahydrofuran and diisopropyl ether. These may be used alone or in combination of two or more. The liquid is preferably at least one selected from water, alkanes, methanol and ethanol, and more preferably water, because the film-like molded product has low solubility.

  There is no limitation in particular in the apparatus used for the said heat processing process, Well-known heating apparatuses, such as an autoclave, can be used. From the viewpoint of performing heating and pressurization simultaneously, it is preferable to use a pressure-resistant autoclave.

  In addition, it can confirm that the block copolymer (Z) is bridge | crosslinked by the improvement of the below-mentioned hot water resistance, the raise of a gel fraction, etc.

  The gel fraction of the polymer electrolyte membrane can be measured by the method described in the examples below, and is preferably 1% or more, more preferably 20% or more, further preferably 50% or more, and particularly preferably 80% or more. If the gel fraction is 80% or more, the hot water resistance tends to be particularly good.

  When the polymer electrolyte membrane is formed on a smooth substrate made of polyester (PET, PEN, etc.), glass or the like, the polymer electrolyte membrane is usually peeled from the substrate. In the case where a polymer electrolyte membrane is formed on a porous substrate and the porous substrate is used as a part of the polymer electrolyte membrane, peeling is not necessary.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not restrict | limited to these Examples.

(Measurement of ion exchange capacity of block copolymer (Z))
The block copolymer (Z) was weighed in a glass container (weighing value a (g)), an excess amount of a saturated sodium chloride aqueous solution ((300 to 500) × a (ml)) was added, and the mixture was stirred for 12 hours. . Using phenolphthalein as an indicator, hydrogen chloride generated in water was titrated (a titration b (ml)) with a 0.01 N NaOH standard aqueous solution (titer f).
The ion exchange capacity was determined by the following formula.
Ion exchange capacity (meq / g) = (0.01 × b × f) / a

(Measurement of Mn of block copolymer (Z ₀ ))
Mn was measured by the GPC method under the following conditions and calculated in terms of standard polystyrene.
Device: manufactured by Tosoh Corporation, trade name: HLC-8220GPC
Eluent: Tetrahydrofuran Column: manufactured by Tosoh Corporation, trade name: TSK-GEL (TSKgel G3000HxL (76 ml.D. × 30 cm), one TSKgel Super Multipore HZ-M (46 ml.D. × 15 cm) 3 in total)
Column temperature: 40 ° C
Detector: RI
Feed rate: 0.35 ml / min

(Measurement conditions for ¹ H-NMR)
The content of each structural unit in the block copolymer (Z ₀ ) obtained in Production Examples 1 and 2 described later, and the 1,4-bonding rate and the hydrogenation rate in the polymer block (B) are as follows. ^It calculated from the result of measuring ¹ H-NMR.
Solvent: Deuterated chloroform Measurement temperature: Room temperature Integration count: 32 times The sulfonation rate of the block copolymers (Z) obtained in Production Examples 1 to 3 was determined from the results of ¹ H-NMR measurement under the following conditions. Calculated.
Solvent: deuterated tetrahydrofuran / deuterated methanol (mass ratio 80/20) mixed solvent Measurement temperature: 50 ° C
Integration count: 32 times

(Measurement of storage modulus)
9% by mass of toluene / isobutanol / n-octane (mass ratio 3/3/4) of the block copolymer (Z-1) and the block copolymer (Z-2) obtained in Production Examples 1 and 2 Each solution is prepared, coated onto a release-treated PET film (trade name: K1504, manufactured by Toyobo Co., Ltd.) at a thickness of about 300 μm, and dried at 100 ° C. for 4 minutes in a hot air dryer. Thus, a molded body having a thickness of 20 μm was obtained.
Using the wide-range dynamic viscoelasticity measuring device (“DVE-V4FT Rheospectr” manufactured by Rheology Co., Ltd.), the resulting molded article was heated at a rate of temperature increase of 3 ° C./min in the tension mode (frequency: 11 Hz). The temperature was raised from −80 ° C. to 250 ° C., and the storage elastic modulus (E ′), loss elastic modulus (E ″), and loss tangent (tan δ) were measured. Based on the fact that there was no change in the storage elastic modulus at 80 to 100 ° C. derived from the crystallized olefin polymer, the amorphous nature of the polymer block (B) was judged. As a result, with respect to the block copolymer (Z-1) and the block copolymer (Z-2), the polymer block (B) was amorphous.

[Production Example 1]
(Production of block copolymer (Z ₀ -1))
After drying, 960 ml of dehydrated cyclohexane and 3.35 ml of sec-butyllithium (1.22 mol / L cyclohexane solution) were added to a 2 L autoclave purged with nitrogen, and then 49.5 ml of styrene while stirring at 60 ° C. , 4-tert-butylstyrene (14.3 ml), isoprene (198 ml), 4-tert-butylstyrene (14.3 ml) and styrene (49.5 ml) were sequentially added and polymerized to obtain polystyrene-b-poly (4-tert-butylstyrene)- b-Polyisoprene-b-poly (4-tert-butylstyrene) -b-polystyrene was obtained. The resulting block copolymer had an Mn of 75,300, a polyisoprene block having a 1,4-bond content of 94.0%, a styrene-derived structural unit content of 35.0% by mass, and 4-tert- The content of the structural unit derived from butylstyrene was 11.0% by mass.
Prepare a cyclohexane solution of the above block copolymer, put it in a pressure vessel that is purged with nitrogen, and use a Ni / Al Ziegler catalyst for hydrogenation at 0.5-1 MPa under hydrogen pressure at 70 ° C. for 18 hours. A polystyrene polymer block (polymer block (A ₀ )), a hydrogenated polyisoprene polymer block (polymer block (B)) and a poly (4-tert-butylstyrene) polymer block (polymer block (C )) Block copolymer (Z ₀ ) [polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene-b-poly (4-tert-butylstyrene) -b-polystyrene ( Hereinafter, referred to as “block copolymer (Z ₀ -1)”). The hydrogenation rate of the hydrogenated polyisoprene block of the obtained block copolymer (Z ₀ -1) was 99% or more.

(Production of block copolymer (Z-1))
After drying, 162 ml of methylene chloride and 81 ml of acetic anhydride were added to a 1 L three-neck flask purged with nitrogen, and 36 ml of concentrated sulfuric acid was added dropwise with stirring at 0 ° C., and the mixture was further stirred at 0 ° C. for 60 minutes for sulfonation. An agent was prepared. On the other hand, 50 g of the block copolymer (Z ₀ -1) was put into a 3 L glass reaction vessel equipped with a stirrer, the inside of the system was purged with nitrogen, 800 ml of methylene chloride was added, and the mixture was stirred at room temperature for 4 hours. And dissolved. To this solution, 279 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 100 ml of distilled water was added to stop the reaction, and 500 ml of distilled water was gradually added dropwise while stirring to precipitate a solid. After removing methylene chloride from this mixed solution by distilling off under normal pressure, the mixture was filtered, and the collected solid was transferred to a beaker, 1 L of distilled water was added, washed with stirring, and then solidified by filtration. Minutes were collected again. This washing and filtration were repeated until there was no change in the pH of the washing water, and the obtained solid content was dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a block copolymer (Z) (hereinafter “ Block copolymer (Z-1) ”). In the obtained block copolymer (Z-1), the ratio of the sulfonic acid group to the structural unit derived from styrene (sulfonation rate) was 99 mol%, and the ion exchange capacity was 2.6 meq / g.

[Production Example 2]
(Production of block copolymer (Z ₀ -2))
After drying, 737 ml of dehydrated cyclohexane and 2.06 ml of sec-butyllithium (0.70 mol / L cyclohexane solution) were added to a 2 L autoclave purged with nitrogen, and then 28.6 ml of styrene while stirring at 60 ° C. 4-tert-butyl styrene 14.4 ml, styrene 28.6 ml, 4-tert-butyl styrene 14.4 ml, isoprene 114.9 ml, 4-tert-butyl styrene 14.4 ml, styrene 28.6 ml and 4-tert- 14.4 ml of butylstyrene was sequentially added and polymerized to obtain polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-polyisoprene-b-. Poly (4-tert-butylstyrene) -b-poly Styrene -b- obtain poly (4-tert-butylstyrene). The resulting block copolymer had an Mn of 130,000, a 1,4-bond content of the polyisoprene block of 93.7%, a content of structural units derived from styrene of 35.6% by mass, 4-tert- The content rate of the structural unit derived from butylstyrene was 24.8 mass%.

Prepare a cyclohexane solution of the above block copolymer, put it in a pressure vessel that is purged with nitrogen, and use a Ni / Al Ziegler catalyst for hydrogenation at 0.5-1 MPa under hydrogen pressure at 70 ° C. for 18 hours. A polystyrene polymer block (polymer block (A ₀ )), a hydrogenated polyisoprene polymer block (polymer block (B)) and a poly (4-tert-butylstyrene) polymer block (polymer block (C )) Block copolymer (Z ₀ ) [polystyrene-b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) -b-hydrogenated polyisoprene- b-poly (4-tert-butylstyrene) -b-polystyrene-b-poly (4-tert-butylstyrene) (hereinafter “block copolymer”) Z ₀ -2) referred to as ")] was obtained.
The hydrogenation rate of the hydrogenated polyisoprene block of the obtained block copolymer (Z ₀ -2) was 99% or more.

(Production of block copolymer (Z-2))
After drying, 270 ml of methylene chloride and 149 ml of acetic anhydride were added to a 1 L three-neck flask purged with nitrogen, 67 ml of concentrated sulfuric acid was added dropwise with stirring at 0 ° C., and the mixture was further stirred at 0 ° C. for 60 minutes for sulfonation. An agent was prepared. On the other hand, 72 g of the block copolymer (Z ₀ -2) was placed in a 5 L glass reaction vessel equipped with a stirrer, the inside of the system was purged with nitrogen, 1600 ml of methylene chloride was added, and the mixture was stirred at room temperature for 4 hours. And dissolved. To this solution, 486 ml of the previously prepared sulfonating agent was added dropwise over 5 minutes. After stirring at room temperature for 48 hours, 100 ml of distilled water was added to stop the reaction, and 1 L of distilled water was gradually added dropwise while stirring to precipitate a solid. After removing methylene chloride from this mixed solution by distilling off at atmospheric pressure, the mixture was filtered, and the collected solid was transferred to a beaker, and 1 L of distilled water was added, washed with stirring, and then solidified by filtration. Minutes were collected again. This washing and filtration were repeated until there was no change in the pH of the washing water, and the obtained solid content was dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a block copolymer (Z) (hereinafter “ Block copolymer (Z-2) ”). In the obtained block copolymer (Z-2), the ratio of the sulfonic acid group to the structural unit derived from styrene (sulfonation rate) was 100 mol%, and the ion exchange capacity was 2.6 meq / g.

[Production Example 3]
(Production of sulfonated polyether ether ketone)
After 30 g of polyetheretherketone resin (PEEK, 450P, manufactured by VICTREX) was replaced with nitrogen in a glass reaction vessel equipped with a stirrer, 550 g of concentrated sulfuric acid was added and dissolved by stirring at room temperature. After stirring at room temperature for 110 hours, the reaction product was poured into ice-cooled water to coagulate and precipitate the polymer. The solid content was filtered, the obtained solid content was transferred to a beaker, 2 L of distilled water was added, and the mixture was washed with stirring, and then recovered by filtration. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the finally collected polymer was vacuum-dried to obtain a sulfonated polyetheretherketone (hereinafter referred to as “SPEEK”). The sulfonation rate of the obtained SPEEK in monomer units was 69% from ¹ H-NMR analysis, and the ion exchange capacity of the sulfonated polyetheretherketone was 2.0 meq / g.

[Example 1]
(Production of polymer electrolyte membrane)
After preparing a 9% by mass toluene / isobutanol / n-octane (mass ratio 3/3/4) solution of the block copolymer (Z-1) obtained in Production Example 1, -4-Vinylphenol (Maruzen Petrochemical Co., Ltd., product name: Marcalinker M, grade: S-1, Mn: 1100 to 1500) was converted into a block copolymer (Z-1) / poly-4-vinylphenol. Was added so that the mass ratio was 100 / 3.2 to prepare a fluid composition. Next, the fluid composition was coated on a PEN film (Teijin DuPont Films Co., Ltd., trade name: Q31M) with a thickness of about 450 μm and subjected to a hot air dryer at 100 ° C. for 6 minutes. By drying, a molded body having a thickness of 20 μm was obtained. The molded body was punched into a size of 10 cm × 10 cm, and then rolled into a pressure-resistant glass measuring bottle (capacity 110 ml). Next, 100 ml of distilled water was added to the pressure-resistant glass measuring bottle containing the molded body, and the entire molded body was immersed in water, and then stored in a pressure-resistant autoclave (manufactured by Pressure Glass Industrial Co., Ltd.). The pressure-resistant autoclave was sealed, and the compact was crosslinked by heat treatment under conditions of 0.3 MPa and 110 ° C. for 96 hours. After allowing to cool to room temperature, the crosslinked molded product was taken out, spread on a release paper, and dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a polymer electrolyte membrane.

[Example 2]
(Production of polymer electrolyte membrane)
Example 1 except that the mass ratio of block copolymer (Z-1) / poly-4-vinylphenol in the flowable composition in Example 1 was changed from 100 / 3.2 to 100 / 9.6. In the same manner as above, a polymer electrolyte membrane was obtained.

[Example 3]
(Production of polymer electrolyte membrane)
After preparing a 9.9 mass% toluene / isobutanol / n-octane (mass ratio 3/3/4) solution of the block copolymer (Z-2) obtained in Production Example 2, compound (X) Poly-4-vinylphenol (Maruzen Petrochemical Co., Ltd., product name: Marcalinker M, grade: S-1), and the mass ratio of block copolymer (Z-2) / poly-4-vinylphenol is It added so that it might become 100 / 9.6, and the fluid composition was prepared. A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the fluid composition was used.

[Example 4]
(Production of polymer electrolyte membrane)
In Example 3, a polymer electrolyte membrane was obtained in the same manner as in Example 3 except that the pressure during the heat treatment was changed to 0.5 MPa and the temperature was changed to 140 ° C.

[Example 5]
(Production of polymer electrolyte membrane)
A polymer electrolyte membrane was obtained in the same manner as in Example 3 except that the pressure during the heat treatment was 0.1 MPa, the temperature was 90 ° C., and the treatment time was changed to 270 hours.

[Example 6]
(Production of polymer electrolyte membrane)
In Example 5, except that the flowable composition was prepared by changing the mass ratio of block copolymer (Z-2) / poly-4-vinylphenol from 100 / 9.6 to 100 / 4.8. In the same manner as in Example 5, a polymer electrolyte membrane was obtained.

[Example 7]
(Production of polymer electrolyte membrane)
In Example 5, a block copolymer (Z-2) was used by using 3,3′-ethylenedioxydiphenol (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of poly-4-vinylphenol as the compound (X). ) / 3,3′-ethylenedioxydiphenol A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that a fluid composition prepared so that the mass ratio was 100 / 2.5 was used. It was.

[Example 8]
(Production of polymer electrolyte membrane)
In Example 5, 2,6-bis (2,4-dihydroxybenzyl) -4-methylphenol (manufactured by Asahi Organic Materials Co., Ltd., product name) instead of poly-4-vinylphenol as compound (X) BIR-PC) is used so that the mass ratio of the block copolymer (Z-2) / 2,6-bis (2,4-dihydroxybenzyl) -4-methylphenol is 100 / 7.0. A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that the fluid composition was used.

[Example 9]
(Production of polymer electrolyte membrane)
After preparing a 9% by mass toluene / isobutanol / n-octane (mass ratio 3/3/4) solution of the block copolymer (Z-1) obtained in Production Example 1, -4-Vinylphenol (Maruzen Petrochemical Co., Ltd., product name: Marcalinker M, grade: S-1), block copolymer (Z-1) / poly-4-vinylphenol mass ratio of 100 / It added so that it might become 3.2, and the fluid composition was prepared. Next, the fluid composition was applied on a PEN film (Teijin DuPont Films Co., Ltd., trade name: Q31M) with a thickness of about 200 μm, and then a non-woven fabric (Kuralek Laurex Co., Ltd.). , Vecrus (registered trademark), average fiber diameter of 7 μm, basis weight of 3 g / cm ² , porosity of 76.2%, thickness of 9 μm) are laminated in parallel to the coated surface so as not to cause wrinkles from above. After impregnating the fluid composition, it was dried at 100 ° C. for 6 minutes in a hot air dryer. Further, the above flowable composition was applied to a thickness of about 200 μm on this, and dried at 100 ° C. for 6 minutes in a hot air dryer to obtain the block copolymer (Z-1) and the compound (X). A 20 μm thick joined body made of the composition and the nonwoven fabric was obtained.
A 10 cm × 10 cm film is punched out from the joined body, rolled into a pressure-resistant glass bottle (capacity 110 ml), 100 ml of distilled water is added, the whole joined body is immersed in water, and then a pressure-resistant autoclave (a pressure-resistant glass). The product was stored in (Industry). The pressure-resistant autoclave was sealed, and the molded body was crosslinked by heat treatment for 96 hours under the crosslinking conditions of 0.3 MPa and 110 ° C. After allowing to cool to room temperature, the crosslinked joined product was taken out, spread on a release paper, and dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a polymer electrolyte membrane.

[Comparative Example 1]
(Production of polymer electrolyte membrane)
A 9% by mass toluene / isobutanol / n-octane (mass ratio 3/3/4) solution of the block copolymer (Z-1) obtained in Production Example 1 was prepared. A molded body having a thickness of 20 μm was obtained in the same manner as in Example 1 except that this solution was used instead of the fluid composition. A 10 cm × 10 cm film is punched from the molded body, rolled into a pressure-resistant glass bottle (capacity 110 ml), 100 ml of distilled water is added, the whole molded body is immersed in water, and then pressure-resistant autoclave (pressure-resistant glass) The product was stored in (Industry). The pressure-resistant autoclave was sealed and heat-treated at 0.3 MPa and 110 ° C. for 96 hours. After allowing to cool to room temperature, the molded article after the heat treatment was taken out, spread on a release paper, and dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a polymer electrolyte membrane.

[Comparative Example 2]
(Production of polymer electrolyte membrane)
A polymer electrolyte membrane was obtained in the same manner as in Example 2 except that the pressure during the heat treatment was 0.1 MPa, the temperature was 70 ° C., and the treatment time was changed to 270 hours.

[Comparative Example 3]
(Production of polymer electrolyte membrane)
After preparing a 5.3 mass% dimethyl sulfoxide solution of SPEEK obtained in Production Example 3, poly-4-vinylphenol (Maruzen Petrochemical Co., Ltd., product name: Marcalinker M, grade) as compound (X) : S-1) was added so that the mass ratio of SPEEK / poly-4-vinylphenol was 100 / 7.2 to prepare a fluid composition. Next, 166 mg of the flowable composition was poured into a 3 cm-high polytetrafluoroethylene container having a square bottom surface with an inner size of 8 cm × 8 cm, sufficiently dried at room temperature, and then placed in a vacuum dryer at 30 ° C. Was dried for 72 hours to obtain a molded body having a thickness of 20 μm. A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that this molded body was used.

(Performance tests and results of polymer electrolyte membranes of Examples and Comparative Examples)
The performance of the polymer electrolyte membrane was evaluated by the following measurement / evaluation method. The results are shown in Table 1.

(Hot water resistance test: residual rate of insoluble matter)
A test piece of 3 cm × 5 cm was cut out from the polymer electrolyte membranes obtained in each Example and Comparative Example, dried at 1.3 kPa and 50 ° C. for 12 hours, measured for mass (mass m ₁ ), and then 110 mL After adding 60 mL of distilled water, it was housed in a SUS metal container, sealed, and allowed to stand in a 110 ° C. constant temperature bath for 96 hours. Thereafter, the test piece in the screw tube was taken out, dried at 1.3 kPa and 50 ° C. for 12 hours, and the mass (referred to as mass m ₂ ) was measured.
The insoluble matter residual ratio (a) was determined by the following formula.
Insoluble matter residual ratio (a) (%) = m ₂ / m ₁ × 100
Moreover, another 3 cm x 5 cm test piece was cut out from the same polymer electrolyte membrane, the same test was performed, and the insoluble matter residual rate (b) was calculated | required.
The insoluble matter residual rate (a) and the insoluble matter residual rate (b) thus obtained were arithmetically averaged to obtain an insoluble content residual rate. It was judged that the higher the insoluble matter residual ratio, the better the hot water resistance.

(Measurement of gel fraction)
A test piece of 4 cm × 8 cm was cut out from the polymer electrolyte membranes obtained in each Example and Comparative Examples 1 and 2, and the mass was weighed with a precision balance. The mass at this time is M ₁ . Using a Soxhlet extractor, the test piece set on the cylindrical filter paper was refluxed with 100 ml of tetrahydrofuran for 8 hours. Thereafter, the test piece was taken out, tetrahydrofuran was distilled off under conditions of 11 kPa and 40 ° C., and further dried at 1.3 kPa and 80 ° C. for 12 hours. The mass of only the solid residue after drying was weighed with a precision balance. The mass of this time and M _2, was calculated gel fraction by the following equation.
Gel fraction = ((M ₁ −M ₂ ) / M ₁ ) × 100 (%)
For the polymer electrolyte membrane obtained in Comparative Example 3, the gel fraction was measured in the same manner except that dimethyl sulfoxide was used instead of tetrahydrofuran.

[Voltage drop rate of polymer electrolyte fuel cells]
With respect to the polymer electrolyte membranes obtained in Example 5 and Comparative Example 2, the rate of voltage drop at high temperatures was measured with an evaluation fuel cell incorporating the polymer electrolyte membrane.
First, a 9 cm × 9 cm test piece was cut out from the polymer electrolyte membrane obtained in Example 5, sandwiched between two 12.5 μm-thick PTFE films with the inside cut into 5 cm × 5 cm, and further Pt catalyst-carrying carbon. And a catalyst layer made of Nafion D1021 (manufactured by DuPont (trade name)) and two electrodes made of carbon paper, followed by heat treatment (115 ° C., 1 MPa, 8 minutes) by hot pressing to form a membrane -An electrode assembly (MEA) was prepared. Next, after the gasket is combined with the manufactured MEA, it is sandwiched between two conductive separators that also serve as gas supply channels, and the outside is sandwiched between two current collector plates and two clamping plates. A cell was produced. Load connected to the manufactured evaluation cell connected to a gas supply hose, a drain hose (a drainage recovery bottle is attached to the cathode side), a heater power supply, a thermocouple, and a power generation characteristic analyzer (manufactured by NF Circuit Design Block Co., Ltd.) A fuel cell for evaluation was assembled by connecting a current control terminal and a voltage detection terminal. One electrode (anode) of this evaluation fuel cell was supplied with hydrogen at 70 cc / min, and the other electrode (cathode) was supplied with air at 240 cc / min and operated under the following conditions to measure the voltage drop rate. .
Cell temperature: 80 ° C
Relative humidity: 100%
Current density: 0.3 A / cm ²

(Voltage drop rate 1 of polymer electrolyte fuel cell)
The evaluation fuel cell is operated for up to 1200 hours, and the voltage value is measured by a voltage detection terminal connected to the evaluation fuel cell to track the decrease in the voltage value with the operation time. The time to decrease by 10% was measured. In the polymer electrolyte membrane obtained in Example 5, the voltage value at the time of 1200 hours operation was only 1.4% lower than the voltage value at the start time, and thus decreased by 10%. The time until was judged to be over 1200 hours.

(Voltage drop rate of polymer electrolyte fuel cell 2)
The voltage value V ₁ (V) after 500 hours of operation and the voltage value V ₂ (V) after 1200 hours of operation are measured by the voltage detection terminal connected to the fuel cell for evaluation during operation, and the voltage drop rate Was calculated from the following equation.
Voltage drop rate (μV / hour) = {(V ₁ −V ₂ ) / (1200−500)} × 10 ⁶

  Since the comparative example 1 does not use the compound (X), the polymer electrolyte membrane is dissolved during the hot water treatment after molding, and the hot water resistance is poor. In addition, when the treatment temperature after molding in Comparative Example 2 is low and when a polymer electrolyte other than the block copolymer (Z) in Comparative Example 3 is used, the gel fraction is low, so that it is not crosslinked and is heat resistant. It is inferior in water. On the other hand, from Examples 1 to 9, the polymer electrolyte membrane of the present invention is excellent in hot water resistance. Further, from the comparison between Example 5 and Comparative Example 2, the polymer electrolyte membrane of the present invention has a small voltage drop when operated by being incorporated in a solid polymer fuel cell.

  According to the production method of the present invention, a polymer electrolyte membrane made of a non-fluorine material, flexible and hardly cracked, and excellent in hot water resistance can be obtained. The polymer electrolyte membrane obtained by the production method of the present invention is suitably used for a polymer electrolyte fuel cell.

Claims (7)

  Amorphous vinyl compound comprising a structural unit derived from a polymer block (A) having an ion conductive group and a structural unit derived from an unsaturated aliphatic hydrocarbon and having no ion conductive group Comprising a block copolymer (Z) containing a functional polymer block (B) and a compound (X) having two or more aromatic rings in which at least one hydrogen atom is substituted with a hydroxyl group in the molecule A process for producing a polymer electrolyte membrane comprising a step of heat-treating at 80 to 150 ° C. in a liquid after molding.   The method for producing a polymer electrolyte membrane according to claim 1, wherein the liquid is water.   The method for producing a polymer electrolyte membrane according to claim 1 or 2, wherein the pressure during the heat treatment is 0.1 to 0.6 MPa.   The method for producing a polymer electrolyte membrane according to any one of claims 1 to 3, wherein the unsaturated aliphatic hydrocarbon is a conjugated diene having 4 to 8 carbon atoms.   The polymer block (B) is obtained by hydrogenating a carbon-carbon double bond of a polymer block formed by polymerizing the conjugated diene, and the hydrogenation rate is 30 mol% or more. The manufacturing method of the polymer electrolyte membrane of description.   The said block copolymer (Z) further consists of the structural unit derived from an aromatic vinyl compound, and contains the polymer block (C) which does not have an ion conductive group in any one of Claims 1-5. A method for producing a polymer electrolyte membrane.   The production of the polymer electrolyte membrane according to any one of claims 1 to 6, wherein the amount of the compound (X) used is 0.01 to 25 parts by mass with respect to 100 parts by mass of the block copolymer (Z). Method.