WO2015125697A1

WO2015125697A1 - Polyelectrolyte film

Info

Publication number: WO2015125697A1
Application number: PCT/JP2015/053909
Authority: WO
Inventors: 謙太俊成; 小野　友裕; 須郷　望
Original assignee: 株式会社クラレ
Priority date: 2014-02-20
Filing date: 2015-02-13
Publication date: 2015-08-27
Also published as: TW201537817A

Abstract

Provided is a polyelectrolyte film that is obtained by performing a crosslinking treatment after forming a composition that contains: a block copolymer (Z) comprising a polymer block (A) that has an ion-conducting group and that comprises a structural unit that is derived from an aromatic vinyl compound and an amorphous polymer block (B) that does not have an ion-conducting group and that comprises a structural unit that is derived from an unsaturated aliphatic hydrocarbon; and a compound (X) that is represented by formula (1) (in the formula, R¹ represents a hydrogen atom, a hydroxyl group, or an alkyl group that has 1-4 carbon atoms, R² represents a hydrogen atom, a hydroxyl group, an alkyl group that has 1-4 carbon atoms, or an alkoxy group that has 1-4 carbon atoms, and R³ represents a hydroxyalkyl group that has 1-4 carbon atoms).

Description

Polymer electrolyte membrane

The present invention relates to 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.

For these reasons, in recent years, a polymer electrolyte membrane made of a material not containing fluorine (non-fluorine-based material) has 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 for higher output of the polymer electrolyte fuel cell.

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

According to the present invention, the above object is a polymer block (A) (hereinafter simply referred to as “polymer block (A)”) comprising a structural unit derived from an aromatic vinyl compound and having an ion conductive group. An amorphous polymer block (B) comprising a structural unit derived from an unsaturated aliphatic hydrocarbon and having no ion conductive group (hereinafter simply referred to as “polymer block (B)”) A composition comprising a block copolymer (Z) containing and a compound (X) represented by the following general formula (1) (hereinafter simply referred to as “compound (X)”) is subjected to a crosslinking treatment after molding. This is accomplished by providing a molecular electrolyte membrane.

Wherein R ¹ represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms, and R ² represents a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. R ³ represents a hydroxyalkyl group having 1 to 4 carbon atoms.)

According to the present invention, it is possible to provide a polymer electrolyte membrane which is made of a non-fluorine material and is flexible, hard to break and excellent in hot water resistance.

It is a graph showing the relationship between operation time and a voltage of the polymer electrolyte fuel cell of this invention.

[Polymer electrolyte membrane]
The polymer electrolyte membrane of the present invention is obtained by subjecting a composition containing a block copolymer (Z) containing a polymer block (A) and a polymer block (B) and a compound (X) to a crosslinking treatment after molding. Become.

In the polymer electrolyte membrane 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 of the present invention is preferably in the range of 4 to 170 μm, more preferably in the range of 8 to 115 μm, still more preferably in the range of 10 to 70 μm, from the viewpoint of mechanical strength, handling properties, and the like. A range of ˜50 μm is particularly preferred. If the film thickness is 4 μm or more, the mechanical strength of the polymer electrolyte membrane, the fuel blocking property and the handling property are good, and if the film thickness is 170 μm or less, the ion conductivity of the polymer electrolyte membrane is good. is there.

The polymer electrolyte membrane of the present invention is obtained by subjecting a composition containing a block copolymer (Z) containing a polymer block (A) and a polymer block (B) and a compound (X) to a crosslinking treatment after molding. It may be a multilayer film including at least one polymer electrolyte layer.

(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 an ion conductive group introduced into the polymer block (A ₀ ) of the block copolymer (Z ₀ ) containing the polymer block (B).

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, especially 70,000 or more, the resulting 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), respectively. 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) 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, ABABABA type pentablock copolymer, BABBAB type pentablock copolymer, (AB) _n D type star copolymer ( D represents a coupling agent residue, n represents an integer of 2 or more, the same applies hereinafter), (BA) _n D-type star copolymer, and the like. From the viewpoint of mechanical strength and ionic conductivity, ABA type triblock copolymer, ABABABA type A pentablock copolymer, (AB) _n D type star copolymer is preferred, and an AB type triblock copolymer is more preferred. In the polymer electrolyte membrane of the present invention, these block copolymers may be used alone or in combination of two or more.

In the block copolymer (Z ₀ ), (total amount of polymer block (A ₀ )) :( total amount of polymer block (B)) is in the range of 95: 5 to 5:95 by mass ratio. Preferably, it is in the range of 75:25 to 15:85, more preferably in the range of 65:35 to 20:80, and particularly preferably in the range of 50:50 to 25:75. If the mass ratio is within the above range, the obtained polymer electrolyte membrane has ion conductivity, mechanical strength, and durability when it is repeatedly wetted and dried along with starting and stopping of the polymer electrolyte fuel cell (starting and stopping) Durability) tends to be excellent.

<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.

In addition, among 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 such substituents include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, sec-butyl groups, tert-butyl groups and other alkyl groups having 1 to 4 carbon atoms; chloromethyl 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. Aromatic vinyl compounds 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 and 1,1-diphenylethylene.

Of the aromatic vinyl compounds that can form the 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 these aromatic vinyl compounds as monomers and using one kind alone or two or more kinds in combination. 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 the monomer capable of forming such other structural units include butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3. A conjugated diene having 4 to 8 carbon atoms such as butadiene and 1,3-heptadiene; 2 or more 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, it is preferable that these other monomers and the above-described aromatic vinyl compound are mixed and then subjected to polymerization. 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 ) is a structural unit 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 Mn is 1,000 or more, particularly 6,000 or more, the ion conductivity is good. When Mn is 100,000 or less, particularly 30,000 or less, the hot water resistance is good, and the composition containing the block copolymer (Z) and the compound (X) is excellent in moldability and advantageous in production. It becomes.

The ion conductive group possessed by the polymer block (A ₀ ) is preferably a proton conductive group, and —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 cyclohexadiene; and the like, and 2 carbon atoms such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 1-hexene, 1-heptene, 1-octene ~ 8 alkenes; butadiene, 1,3-pentadiene, isoprene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, etc. Conjugated dienes having 4 to 8 carbon atoms are preferred, alkenes having 4 to 8 carbon atoms and conjugated dienes having 4 to 8 carbon atoms are more preferred, isobutene, butadiene and isoprene are more 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 esters; vinyl ethers such as methyl vinyl ether and isobutyl vinyl ether; and the like. In this case, it is preferable that these other monomers and the unsaturated aliphatic hydrocarbon described above are mixed and then subjected to polymerization. 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, carbon-carbon double bonds usually remain, but from the viewpoint of improving the heat resistance deterioration of the resulting polymer electrolyte membrane, the block copolymer 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 even more preferably 95 mol% or more.

Further, 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 carried out 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, and particularly preferably in the range of 30,000 to 100,000. When the Mn is 5,000 or more, particularly 30,000 or more, the mechanical strength is particularly good, and the start / stop durability of repeating wet (start) and dry (stop) in the fuel cell is excellent. When Mn is 250,000 or less, particularly 100,000 or less, the block copolymer (Z) is excellent in moldability and advantageous in production.

<Other polymer block (C)>
The block copolymer (Z) is composed of a structural unit derived from an aromatic vinyl compound, and may further include a polymer block (C) having no ion conductive group. In the polymer electrolyte membrane 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 (2) because of superiority in production.

(Wherein R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁵ represents an alkyl group having 3 to 8 carbon atoms, and R ⁶ and R ⁷ 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 block copolymer (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 (2) include 4-propylstyrene, 4-isopropylstyrene, 4-butylstyrene, 4-isobutylstyrene, 4-tert-butylstyrene, Examples include 4-octylstyrene, α-methyl-4-tert-butylstyrene, α-methyl-4-isopropylstyrene, and the like. 4-tert-butylstyrene, 4-isopropylstyrene, 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 aromatic vinyl compounds are used in combination.

The polymer block (C) 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, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2 Conjugated diene having 4 to 8 carbon atoms such as ethyl-1,3-butadiene, 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.

The 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 the Mn is 1,000 or more, the mechanical strength of the polymer electrolyte membrane obtained in the present invention tends to be excellent, 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 in the case where the block copolymer (Z) used in the present invention contains a polymer block (C), ABC type triblock copolymer (A, B and C are each a polymer block) (A) represents a polymer block (B) and a polymer block (C), the same shall apply hereinafter), an ABCA type tetrablock copolymer, an ABCA type tetrablock copolymer. Polymer, BABC type tetrablock copolymer, ABCBC type tetrablock copolymer, ABCBC type tetrablock copolymer, CABB AC type pentablock copolymer, CBABC type pentablock copolymer, ABCBC type pentablock copolymer, ACBAA- C-type pentablock copolymer, ABCBCAC type hexablock copolymer, CABC AC type hexablock copolymer, ACCABCBC type hexablock copolymer, ACCABCBC type heptablock copolymer, A- CBCBCBC type heptablock copolymer, CACBCBCAC type heptablock copolymer, ACACABCBC A-C type octablock copolymer, ACBCCBCCAC type octablock copolymer, ABCBCCABCBC type octablock A copolymer etc. are mentioned. Among these, from the viewpoint of mechanical strength and ion conductivity, ABC type triblock copolymer, ABCA type tetrablock copolymer, and ABC type tetrablock copolymer are used. Polymer, ABCBC tetrablock copolymer, CABBC type pentablock copolymer, CBABC type pentablock copolymer, A -C—B—C—A type pentablock copolymer, A—C—B—A—C type penta block copolymer, A—C—B—C—A—C type hexablock copolymer, C -ABCCA type hexablock copolymer, ACCABCBC type hexablock copolymer, ACCABCBC type hepta Block copolymer, ACCBBCCA type heptablock copolymer, CABCBCCA type heptablock copolymer Copolymer, ACACBCBCAC type octablock copolymer, ACCBBCBCAC type octablock copolymer, AC- B-C-A-C-B-C type octablock copolymer is preferable, and A-C-B-C-C type tetra-block copolymer, A-C-B-C-A type penta-block copolymer, ABCBCAC type hexablock copolymer and ACCABCBC type AC block octablock copolymer are more preferable, and ABCBC An -A type pentablock copolymer and an ACCABCBC type octablock copolymer are more preferable. In the polymer electrolyte membrane 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 of the present invention contains the polymer block (C), the content of the polymer block (C) in the block copolymer (Z ₀ ) is from 5 to It is preferably in the range of 50% by mass, more preferably in the range of 7-40% by mass, and still more preferably in the range of 10-30% by mass. When the content is 5% by mass or more, the obtained polymer electrolyte membrane tends to be excellent in hot water resistance, 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) constituting the polymer electrolyte membrane of the present invention is a block copolymer comprising a polymer block (A ₀ ) and a polymer block (B) by polymerizing each of the aforementioned monomers. After producing the coalescence (Z ₀ ), it can be produced by a method of introducing an ion conductive group into the polymer block (A ₀ ).

The production method of 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 ) containing as a component,
(1) An aromatic vinyl compound, a conjugated diene, and an aromatic vinyl compound are sequentially anionic polymerized using an anionic polymerization initiator in a cyclohexane solvent at a temperature of 20 to 100 ° C. A method of obtaining a polymer;
(2) An anionic polymerization initiator is used in a cyclohexane solvent, and an aromatic vinyl compound and a conjugated diene are sequentially anionic polymerized at a temperature of 20 to 100 ° C., and then a coupling agent such as phenyl benzoate is added. To obtain an ABA type block copolymer;
(3) An aromatic compound having a concentration of 5 to 50% by mass in a nonpolar solvent using an organolithium compound as an initiator and in the presence of a polar compound having a concentration of 0.1 to 10% 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, 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 isobutene in the presence of Lewis acid using a bifunctional halogenation initiator in a halogen / hydrocarbon mixed solvent at −78 ° C., followed by cationic polymerization of an aromatic vinyl compound A method of 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. Of 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 represented by the following general formula (1).

Examples of the hydroxyalkyl group having 1 to 4 carbon atoms include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, 1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 1-hydroxy- 1-methylethyl group, 2-hydroxy-1-methylethyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group, and the like. A hydroxyalkyl group is preferred, and a hydroxymethyl group, a 1-hydroxyethyl group and a 2-hydroxyethyl group are preferred.

Since the compound (X) has a hydroxyphenyl group and a hydroxyalkyl group having 1 to 4 carbon atoms, preferably a hydroxyalkyl group having 1 or 2 carbon atoms, the compound (X) is selectively added to the phase containing the hydrophilic polymer block (A). For this reason, it is considered that the hot water resistance is improved without deteriorating the flexibility of the polymer electrolyte membrane by selectively crosslinking the hydrophilic polymer block (A).

Specific examples of the compound (X) include 4-hydroxybenzyl alcohol, vanillyl alcohol, 3,4-dihydroxybenzyl alcohol, 2,6-ditert-butyl-4-hydroxymethylphenol, 2- (4-hydroxyphenyl) ) Ethanol, 2- (3,4-dihydroxyphenyl) ethyl alcohol, 4-hydroxy-3-methoxy-α-methylbenzyl alcohol, 3- (4-hydroxyphenyl) -1-propanol, 1- (4-hydroxyphenyl) ) -2-propanol, 1- (4-hydroxyphenyl) -1-propanol, 2- (4-hydroxyphenyl) -2-propanol, 4- (4-hydroxyphenyl) -1-butanol, 4- (4- Hydroxyphenyl) -2-butanol, 3- (4-hydroxyphenyl) 2-methylpropanol, 3- (4-hydroxyphenyl) -1-butanol, 1- (4-hydroxyphenyl) -2-methyl-2-propanol, 3- (4-hydroxyphenyl) -2-butanol, 2- (4-hydroxyphenyl) -2-methyl-1-propanol and the like.
Among them, from the viewpoint of hot water resistance of the polymer electrolyte membrane, 4-hydroxybenzyl alcohol, vanillyl alcohol, 3,4-dihydroxybenzyl alcohol, 2,6-ditert-butyl-4-hydroxymethylphenol, 2- (3 , 4-dihydroxyphenyl) ethyl alcohol, 2- (4-hydroxyphenyl) ethanol, 4-hydroxy-3-methoxy-α-methylbenzyl alcohol are preferred, and vanillyl alcohol or 2- (4-hydroxyphenyl) ethanol is more preferred. preferable.

Compound (X) may be used alone or in combination of two or more.
The content of the compound (X) in the composition 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. The range of 1 to 20 parts by mass is more preferable, the range of 1 to 10 parts by mass is more preferable, and the range of 4 to 6 parts by mass is particularly preferable.

<Method for producing polymer electrolyte membrane>
Next, the manufacturing method of the polymer electrolyte membrane of this invention is demonstrated. Usually, a polymer electrolyte membrane is prepared by preparing a fluid composition containing a block copolymer (Z), a compound (X), and a solvent, which are polymer electrolytes, and coating the fluid composition on a substrate. By removing the solvent, a molded product comprising the composition containing the block copolymer (Z) and the compound (X) is obtained, and the molded product is obtained by crosslinking treatment.

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 fluid composition is prepared by dissolving or dispersing the block copolymer (Z) and the compound (X) in a solvent. As necessary, various stabilizers such as a crosslinking agent, a softening agent, a phenol-based stabilizer, a sulfur-based stabilizer, and a phosphorus-based stabilizer, an inorganic filler, a light stabilizer, and a charge, as long as the effects of the present invention are not impaired. Various additives such as an inhibitor, a release agent, 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 preferably 50% by mass or more from the viewpoint of ion conductivity of the obtained polymer electrolyte membrane. 70% by mass or more, more preferably 85% by mass or more.

Examples of softeners 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-di ert-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; Yl) 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 for 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.

The concentration of the block copolymer (Z) in the fluid composition can be appropriately selected depending on the molecular weight, composition, and ion exchange group capacity, but is preferably 5 to 20% by mass from the viewpoint of productivity. .

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

Further, the fluid composition may be applied onto a porous substrate (porous substrate) by, for example, 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 onto the substrate as described above, it can be formed into a film by removing the solvent. 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 a ventilation condition or a vacuum condition, and these may be combined arbitrarily. Specifically, the solvent is removed by drying at 60 to 120 ° C. for 4 minutes or longer in a hot air dryer; the solvent is removed by drying at 120 to 140 ° C. for 2 to 4 minutes in a hot air dryer. Method: Pre-drying at 25 ° C. for 1 to 3 hours, followed by drying in a hot air dryer at 80 to 120 ° C. for 5 to 10 minutes; After pre-drying at 25 ° C. for 1 to 3 hours And a method of drying under a reduced pressure condition for 1 to 12 hours in an atmosphere of 25 to 40 ° C.
From the viewpoint of easy preparation of a polymer electrolyte membrane having good toughness, the solvent is removed by drying in a hot air dryer at 60 to 120 ° C. over 4 minutes; 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, under 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 multilayer membrane, for example, after applying the fluid composition to the substrate, after removing the solvent to form the first layer, another polymer electrolyte is further formed on the first layer. The second layer is formed by applying a fluid composition containing, and removing the solvent. Similarly, the third and subsequent layers may be formed. Alternatively, the produced polymer electrolyte membranes may be bonded to form a multilayer film.

The polymer electrolyte membrane of the present invention can be formed by coating the fluid composition on a substrate and subjecting the membrane-like molded product obtained by removing the solvent to a crosslinking treatment. As the crosslinking treatment method, heating, irradiation with active energy rays such as an electron beam, and the like can be suitably employed. The crosslinking treatment by heating or active energy ray irradiation may be performed simultaneously with the removal of the solvent or after the removal of the solvent. Further, after removing the solvent while performing a crosslinking treatment by heating or active energy ray irradiation, heating or active energy ray irradiation may be further performed.
When crosslinking is performed by heating, the heating temperature is preferably 50 to 250 ° C, more preferably 60 to 200 ° C, further preferably 70 to 180 ° C, and particularly preferably 100 to 150 ° C. The heating time is preferably 0.1 to 400 hours, more preferably 0.2 to 200 hours, further preferably 0.4 to 100 hours, and particularly preferably 0.5 to 30 hours. Heating can be performed in the air, in a nitrogen atmosphere, or the like, and is preferably performed in a nitrogen atmosphere.
As the active energy irradiation, for example, when crosslinking is performed with an electron beam, the acceleration voltage is preferably in the range of 50 to 250 kV, and the dose is preferably in the range of 100 to 800 kGy.
In addition, it can confirm that the obtained polymer electrolyte membrane is bridge | crosslinked by the improvement of below-mentioned hot water resistance, the raise of a gel fraction, the raise of a crosslinking density, etc.

The gel fraction of the polymer electrolyte membrane can be measured by the method described in 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.

The crosslink density of the polymer electrolyte membrane can be calculated by the method described in Examples below, and is preferably in the range of 0.1 × 10 ⁻⁵ to 100 × 10 ⁻⁵ mol / ml, and 0.5 × 10 ⁻⁵ to 50 The range of × 10 ⁻⁵ mol / ml is more preferable, the range of 1 × 10 ⁻⁵ to 40 × 10 ⁻⁵ mol / ml is more preferable, and the range of 2 × 10 ⁻⁵ to 30 × 10 ⁻⁵ mol / ml is more preferable. Particularly preferred is a range of 3 × 10 ⁻⁵ to 15 × 10 ⁻⁵ mol / ml. If the crosslinking density is 3 × 10 ⁻⁵ mol / ml or more, the hot water resistance tends to be good, and if it is 15 × 10 ⁻⁵ mol / ml or less, the tensile elongation at break after crosslinking tends to improve. Thus, the start / stop durability tends to be good.

When the polymer electrolyte membrane is formed on a smooth substrate made of polyethylene terephthalate (PET), 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.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not 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 aqueous sodium chloride 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: 1 TSK-GEL (TSKgel G3000HxL (76 ml.D. × 30 cm), 2 TSKgel Supermultipore 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 copolymers (Z ₀ ) obtained in Production Examples 1 to 3 described later, and the 1,4-bonding rate and hydrogenation rate in the polymer block (B) are as follows. ^It was calculated from the result of measuring ¹ H-NMR.
Solvent: Deuterated chloroform Measurement temperature: Room temperature Accumulation count: 32 times The sulfonation rate of the block copolymers (Z) obtained in the above production examples 1 to 3 is based on the result 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
Accumulation count: 32 times The sulfonation rate of the sulfonated polyetheretherketone obtained in Production Example 4 was calculated from the result of ¹ H-NMR measurement under the following conditions.
Solvent: heavy dimethyl sulfoxide Measurement temperature: 30 ° C
Integration count: 32 times

(Measurement of storage modulus)
Prepare 11.5 mass% toluene / isobutanol (mass ratio 65/35) solutions of the block copolymer (Z-1) and the block copolymer (Z-2) obtained in Production Examples 1 and 2, respectively. Then, it is coated on the release-treated PET film (trade name: K1504, manufactured by Toyobo Co., Ltd.) with a thickness of about 300 μm, and dried at 100 ° C. for 4 minutes with a hot air dryer. A 20 μm shaped body was obtained.
Using the wide-range dynamic viscoelasticity measuring device (“DVE-V4FT Rheospectr” manufactured by Rheology Co., Ltd.), the resulting molded body 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 storage 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, regarding 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, 461 ml of dehydrated cyclohexane and 2.60 ml of sec-butyllithium (1.0 mol / L cyclohexane solution) were added to an autoclave with an internal volume of 1.4 L purged with nitrogen, and then stirred at 60 ° C. 19.8 ml, butadiene 135 ml and styrene 19.8 ml were sequentially added and polymerized to synthesize polystyrene-b-polybutadiene-b-polystyrene. The obtained block copolymer had an Mn of 76,000, a 1,4-bond content of the polybutadiene block of 59.9%, and a content of structural units derived from styrene of 30.0% 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 reaction at 0.5 to 1 MPa under hydrogen pressure at 70 ° C. for 15 hours. A block copolymer (Z ₀ ) [polystyrene-b-hydrogenated polybutadiene-b comprising a polystyrene polymer block (polymer block (A ₀ )) and a hydrogenated polybutadiene polymer block (polymer block (B)). -Polystyrene (hereinafter referred to as "block copolymer (Z ₀ -1)") was obtained.
The hydrogenation rate of the hydrogenated polybutadiene block of the obtained block copolymer (Z ₀ -1) was 99% or more.

(Production of block copolymer (Z-1))
In 389 ml of methylene chloride, 195 ml of acetic anhydride and 87.0 ml of sulfuric acid were mixed at 0 ° C. to prepare a sulfonating agent. On the other hand, 100 g of block copolymer (Z ₀ -1) was put into a 5 L glass reaction vessel equipped with a stirrer, and the operation of evacuating the system and introducing nitrogen was repeated three times, and then nitrogen was introduced. After adding 1000 ml of methylene chloride and stirring for 4 hours at room temperature to dissolve, 610 ml of the sulfonating agent was added dropwise over 5 minutes. After completion of the dropping, the mixture was stirred at room temperature for 48 hours, and then 720 ml of distilled water was added dropwise with stirring to stop the reaction and solidify and precipitate the solid content.
Methylene chloride was removed by distillation at normal pressure, followed by filtration. The obtained solid content was transferred to a beaker, 1 L of distilled water was added and washing was performed with stirring, and then the solid content was collected by filtration. After repeating such washing and filtration until there is no change in the pH of the washing water, the recovered solid content is dried at 1.3 kPa, 30 ° C. for 24 hours, and used for the polymer electrolyte membrane of the present invention. (Z) was obtained (hereinafter referred to as “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 100 mol%, and the ion exchange capacity was 2.3 meq / g.

[Production Example 2]
(Production of block copolymer (Z ₀ -2))
After drying, 737 ml of dehydrated cyclohexane and 2.06 ml of dehydrated cyclohexane (0.70 mol / L cyclohexane solution) were added to an autoclave with an internal volume of 2 L, which was purged with nitrogen, and then stirred at 60 ° C. with 28.styrene. 6 ml, 4-tert-butylstyrene 14.4 ml, styrene 28.6 ml, 4-tert-butylstyrene 14.4 ml, isoprene 114.9 ml, 4-tert-butylstyrene 14.4 ml, styrene 28.6 ml and 4-tert -14.4 ml of butyl styrene are 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-Po To obtain a styrene -b- 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%.

A cyclohexane solution of the above block copolymer is prepared and placed in a pressure vessel that is purged with nitrogen. Using a Ni / Al Ziegler catalyst, a hydrogenation reaction is performed at 0.5 to 1 MPa at 70 ° C. under hydrogen pressure for 18 hours. Polystyrene polymer block (polymer block (A ₀ )), hydrogenated polyisoprene polymer block (polymer block (B)) and 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 copolymerization”) (Referred to as the body (Z ₀ -2) ”).
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 three-necked flask with an internal volume of 1 L 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. 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 1000 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 is repeated until there is no change in the pH of the washing water, and the obtained solid content is dried at 1.3 kPa and 30 ° C. for 24 hours to obtain a block copolymer used for the polymer electrolyte membrane of the present invention. (Z) was obtained (hereinafter referred to as “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 the mixture was stirred and dissolved 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 polyether ether ketone (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 11.7% by mass toluene / isobutanol (mass ratio 65/35) solution of the block copolymer (Z-1) obtained in Production Example 1, vanillyl alcohol (Tokyo) Kasei Kogyo Co., Ltd.) was added so that the mass ratio of block copolymer (Z-1) / vanillyl alcohol was 100/5 to prepare a fluid composition. Next, the flowable composition was applied to a release-treated PET film (trade name: K1504, manufactured by Toyobo Co., Ltd.) with a thickness of about 300 μm, and dried at 100 ° C. for 4 minutes in a hot air dryer. As a result, a molded body having a thickness of 20 μm was obtained. The obtained molded body was crosslinked by heat treatment in a constant temperature bath at 140 ° C. for 3 hours to produce a polymer electrolyte membrane of the present invention.

[Example 2]
(Production of polymer electrolyte membrane)
After preparing a 11.5 mass% toluene / isobutanol (mass ratio 77/23) solution of the block copolymer (Z-2) obtained in Production Example 2, vanillyl alcohol (Tokyo Chemical Industry Co., Ltd.) Was added so that the mass ratio of the block copolymer (Z-2) / vanillyl alcohol was 100/5 to prepare a fluid composition. Next, the flowable composition was coated on a release-treated PET film (trade name: MRV, manufactured by Mitsubishi Resin Co., Ltd.) with a thickness of about 300 μm, and dried at 100 ° C. for 4 minutes with a hot air dryer. As a result, a molded body having a thickness of 20 μm was obtained. The obtained molded body was crosslinked by heat treatment in a constant temperature bath at 140 ° C. for 3 hours to produce a polymer electrolyte membrane of the present invention.

[Example 3]
(Production of polymer electrolyte membrane)
Instead of vanillyl alcohol, 2- (4-hydroxyphenyl) ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) is used, and the mass ratio of block copolymer (Z-2) / 2- (4-hydroxyphenyl) ethanol is A molded body having a thickness of 20 μm was obtained in the same manner as in Example 2 except that it was added so as to be 100/5. The obtained molded body was cross-linked by heat treatment for 1 hour in a 140 ° C. constant temperature bath to produce a polymer electrolyte membrane of the present invention.

[Example 4]
(Production of polymer electrolyte membrane)
After preparing a 11.7% by mass toluene / isobutanol (mass ratio 65/35) solution of the block copolymer (Z-1) obtained in Production Example 1, vanillyl alcohol (Tokyo) Kasei Kogyo Co., Ltd.) was added so that the mass ratio of block copolymer (Z-1) / vanillyl alcohol was 100/5 to prepare a fluid composition.
Next, the flowable composition was coated on a release-treated PET film (product name: K1504, manufactured by Toyobo Co., Ltd.) with a thickness of about 150 μm, and then a non-woven fabric (manufactured by 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 with the coated surface so as not to cause wrinkles from above, After impregnating the fluid composition, it was dried with a hot air dryer at 100 ° C. for 4 minutes. The flowable composition was further coated thereon with a thickness of about 125 μm, and dried at 100 ° C. for 4 minutes with a hot air dryer to obtain the block copolymer (Z-1) and the compound (X). A polymer electrolyte composed of a molded body of the contained composition and a 20 μm thick joined body composed of a nonwoven fabric were obtained. The obtained joined body was heat-treated under a nitrogen stream at 140 ° C. for 3 hours to crosslink the molded body, thereby producing a polymer electrolyte membrane of the present invention.

[Comparative Example 1]
(Production of polymer electrolyte membrane)
After preparing a 16% by mass toluene / isobutanol (mass ratio 70/30) solution of the block copolymer (Z-1) obtained in Production Example 1, 1,2-polybutadiene (Nippon Soda ( Co., Ltd., trade name: PB-1000; Mn 1,000, degree of polymerization 19) in a 40% by weight toluene solution with a mass ratio of block copolymer (Z-1) / 1,2-polybutadiene of 100/5 Was added to prepare a flowable composition. Next, the fluid composition was coated on a release-treated PET film (trade name: K1504, manufactured by Toyobo Co., Ltd.) at a thickness of about 350 μm, and then heated at 100 ° C. for 4 minutes with a hot air dryer. By drying, a molded body having a thickness of 30 μm was obtained. The obtained molded body was irradiated with an electron beam at an acceleration voltage of 150 kV, a beam current of 8.6 mA, and a dose of 300 kGy using an electro curtain type electron beam irradiation apparatus (trade name: CB250 / 30/20 mA, manufactured by Iwasaki Electric Co., Ltd.). The polymer electrolyte membrane of Comparative Example 1 was produced.

[Comparative Example 2]
(Production of polymer electrolyte membrane)
Instead of vanillyl alcohol, α, α'-dihydroxy-1,4-diisopropylbenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) is used as a block copolymer (Z-2) / α, α'-dihydroxy-1,4. A molded body having a thickness of 20 μm was obtained in the same manner as in Example 2 except that the mass ratio of diisopropylbenzene was 100/7. The obtained molded body was heat-treated in a 140 ° C. constant temperature bath for 5 hours to produce a polymer electrolyte membrane of Comparative Example 2.

[Comparative Example 3]
(Production of polymer electrolyte membrane)
Instead of vanillyl alcohol, 1,3-diphenoxybenzene (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and the block copolymer (Z-2) / 1,3-diphenoxybenzene had a mass ratio of 100 / 9.3. A molded body having a thickness of 20 μm was obtained in the same manner as in Example 2 except that the addition was performed. The obtained molded body was heat-treated in a constant temperature bath at 140 ° C. for 1 hour to produce a polymer electrolyte membrane of Comparative Example 3.

[Comparative Example 4]
(Production of polymer electrolyte membrane)
Example 2 except that diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added in place of vanillyl alcohol so that the mass ratio of block copolymer (Z-2) / diethylene glycol was 100/4. Thus, a molded body having a thickness of 20 μm was obtained. The obtained molded body was heat-treated in a constant temperature bath at 140 ° C. for 1 hour, thereby producing a polymer electrolyte membrane of Comparative Example 4.

[Comparative Example 5]
(Production of polymer electrolyte membrane)
After preparing a 5.3 mass% dimethyl sulfoxide solution of SPEEK obtained in Production Example 3, 2- (4-hydroxyphenyl) ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to SPEEK / 2- (4- Hydroxyphenyl) ethanol was added so that the mass ratio 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 internal size of 8 cm × 8 cm, sufficiently dried at room temperature, and then dried at 30 ° C. with a vacuum dryer. A molded body having a thickness of 20 μm was obtained by drying for 72 hours. The obtained molded body was heat-treated in a constant temperature bath at 140 ° C. for 24 hours to produce a polymer electrolyte membrane of Comparative Example 5.

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

(Heat resistance test)
A 3 cm × 5 cm test piece was cut out from the polymer electrolyte membranes obtained in Examples 1 to 4 and Comparative Examples 1 to 5, dried at 1.3 kPa and 50 ° C. for 12 hours, and mass (referred to as mass m ₁ ). After the measurement, the solution was placed in a 110 mL screw tube, and 60 mL of distilled water was added. The sample was then housed in a SUS metal container, sealed, and allowed to stand in a 110 ° C. constant temperature bath for 96 hours. Next, the surface state of the test piece in the screw tube was visually confirmed (visual test), and then 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 was determined by the following formula.
Insoluble matter residual ratio (a) (%) = m ₂ / m ₁ × 100
Moreover, the same test was implemented using another test piece obtained from the same polymer electrolyte membrane, and insoluble matter residual ratio (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 crosslink density and gel fraction)
A 3 cm × 5 cm test piece was cut out from the polymer electrolyte membranes obtained in Examples 1 to 4 and Comparative Examples 1 to 5, dried at 1.3 kPa and 50 ° C. for 12 hours, and mass (assumed to be mass m ₃ ). After being measured, the film was immersed in 30 ml of solvent for 3 hours, the film was taken out, and the mass of the film (mass m ₄ ) was measured in a state containing the solvent. Thereafter, 1.3 kPa, and dried 12 hours at 50 ° C., the mass was measured (the mass _{m 5).}
The crosslinking density (ν) was calculated from the Flory Rehner equation.
ν = {ln (1-m ₅ / m ₄ ) + m ₅ / m ₄ + 0.4 × (m ₅ / m ₄ ) ² } / [102 × {(m ₅ / m ₄ ) ^1/3 − (m ₅ / M ₄ ) / 2}]
Moreover, the gel fraction was computed by the following formula.
Gel fraction = m ₅ / m ₃ × 100 (%)
As the solvent, it is necessary to select a solvent in which the uncrosslinked polymer electrolyte membrane exhibits good solubility. Therefore, in Examples 1 to 4 and Comparative Examples 1 to 4, toluene / isobutanol (mass In the comparative example 5, dimethyl sulfoxide was used as the mixed solvent.

(Tensile fracture test)
For the purpose of confirming that the polymer electrolyte membrane of the present invention is flexible and difficult to break, the tensile break strength and tensile break elongation of the obtained polymer electrolyte membrane were measured by the following methods.
A dumbbell-shaped test piece is cut out from the polymer electrolyte membrane, adjusted to a humidity of 25 ° C. and a relative humidity of 40%, and set in a tensile tester (5566 type manufactured by Instron Japan). Under the conditions of 40% and a tensile speed of 500 mm / min, the tensile breaking strength and the tensile breaking elongation were measured.

(Fuel cell voltage drop rate)
For the purpose of evaluating the influence of the obtained polymer electrolyte membrane on the performance of the fuel cell, the rate of voltage drop at high temperature was measured with an evaluation fuel cell incorporating the polymer electrolyte membrane.
First, the obtained polymer electrolyte membrane was cut out into 9 cm × 9 cm, and sandwiched between two 9 cm × 9 cm PET films UTS-20BAF (Nitto Denko Corporation (trade name)) cut out inside to 5 cm × 5 cm .
Next, after sandwiching between two re-peeled films CT100 (manufactured by Panac Co., Ltd. (trade name)) of 9 cm × 9 cm with the inside cut out to 5.3 cm × 5.3 cm, a Pt catalyst of 5.3 cm × 5.3 cm A PTFE sheet with a catalyst layer containing supported carbon (manufactured by Johnson Matthey) was sandwiched so that the catalyst layer surface and the polymer electrolyte membrane face each other, and a 9 cm × 9 cm re-peeling film CT100 (manufactured by Panac Corporation (product) Name)). Next, sandwiched between two PTFE sheets having a thickness of 100 μm, sandwiched between two mirror plates, and subjected to heat treatment by hot pressing (150 ° C., 40 kg / cm ² , 10 minutes) to form the catalyst layer as a polymer electrolyte. The film was transferred to a membrane to prepare a membrane-electrode assembly (MEA). Next, the obtained MEA was sandwiched between two 200-μm-thick gaskets of 9 cm × 9 cm with the inside cut out to 5.3 cm × 5.3 cm, and then the GDL with MPL of 5.3 cm × 5.3 cm (JNT20− (A1, manufactured by Sato Light Industry Co., Ltd.) After sandwiching the MPL surface and the catalyst layer surface so that they face each other, sandwich them with two conductive separators that also serve as the gas supply flow path. An evaluation cell was fabricated by sandwiching the two clamping plates.
Connect the load current control terminal and voltage detection terminal connected to the gas supply hose, drain hose, heater power supply, thermocouple, and power generation characteristic analyzer (manufactured by NF Circuit Design Block Co., Ltd.) to the manufactured evaluation cell. A fuel cell for evaluation was assembled.
Hydrogen was supplied to one electrode (anode) of this evaluation fuel cell at 261 cc / min, and air was supplied to the other electrode (cathode) at 878 cc / min, and the fuel cell was operated under the following conditions. The relationship between operation time and voltage is shown in FIG.
Cell temperature: 80 ° C
Relative humidity: 80%
Current density: 1.0 A / cm ²

The voltage value V ₁ (V) after 50 hours of operation and the voltage value V ₂ (V) after 84 hours of operation are measured by the voltage detection terminal connected to the evaluation fuel cell during operation, and the voltage drop rate Was calculated from the following equation.
Voltage drop rate (mV / hour) = {(V ₁ −V ₂ ) / (84−50)} × 10 ³

As shown in Table 1, the polymer electrolyte membrane of the present invention is excellent in hot water resistance.
Since the polymer electrolyte membranes of Comparative Examples 1 to 4 are polymer electrolyte membranes containing a compound other than the compound (X), they are inferior in hot water resistance to the polymer electrolyte membrane of the present invention.
It can be seen that the polymer electrolyte membrane of Comparative Example 5 cannot be crosslinked because it uses a polymer electrolyte other than the block copolymer (Z).
From Example 1, it can be seen that the polymer electrolyte membrane of the present invention shows little decrease in voltage when operated by being incorporated in a fuel cell. This can be presumed to be based on the excellent hot water resistance of the polymer electrolyte membrane of the present invention.

The polymer electrolyte membrane of the present invention is made of a non-fluorine material, has a low environmental impact during production and disposal, and is flexible, resistant to cracking and excellent in hot water resistance. Therefore, the polymer electrolyte membrane for a solid polymer fuel cell Is preferably used.

Claims

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 Polymer block membrane (Z) containing a functional polymer block (B) and a composition containing a compound (X) represented by the following general formula (1), followed by a crosslinking treatment after molding .

Wherein R 1 represents a hydrogen atom, a hydroxyl group or an alkyl group having 1 to 4 carbon atoms, and R 2 represents a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. R 3 represents a hydroxyalkyl group having 1 to 4 carbon atoms.)
2. The polymer electrolyte membrane according to claim 1, wherein the unsaturated aliphatic hydrocarbon is a conjugated diene having 4 to 8 carbon atoms.
The ion conductive group is selected from a sulfonic acid group, a phosphonic acid group and a salt thereof represented by —SO 3 M or PO 3 HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion). The polymer electrolyte membrane according to claim 1 or 2, wherein the polymer electrolyte membrane is one or more.
The polymer electrolyte membrane according to any one of claims 1 to 3, wherein R 3 in the general formula (1) is a hydroxymethyl group, a 1-hydroxyethyl group or a 2-hydroxyethyl group.
The polymer according to any one of claims 1 to 4, wherein the content of the compound (X) in the composition is 0.01 to 25 parts by mass with respect to 100 parts by mass of the block copolymer (Z). Electrolyte membrane.
The block copolymer (Z) further comprises a polymer block (C) made of a structural unit derived from an aromatic vinyl compound and having no ion conductive group. The polymer electrolyte membrane as described.
A solid polymer fuel cell having the polymer electrolyte membrane according to any one of claims 1 to 6.