JP2010067526A - Polyelectrolyte membrane for solid polymer fuel cell, membrane-electrode assembly, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyelectrolyte membrane for a solid polymer fuel cell economical, environment-friendly, excellent in moldability as well as excellent in flexibility and durability, and to provide a membrane-electrode assembly as well as a solid polymer fuel cell using the polyelectrolyte membrane. <P>SOLUTION: The polyelectrolyte membrane for a solid polymer fuel cell as well as a membrane-electrode assembly and a solid polymer fuel cell using the same have a polymer block (A) with an aromatic vinyl based compound unit as a main repetition unit and a flexible polymer block (B) as constituent elements, with a mass ratio of the polymer block (A) and the polymer block (B) of 65:35 to 10:90, the polymer block (A) containing a block copolymer with an ion-conductive group as a main constituent, with a 100% modulus of 15 MPa in a tensile test at conditions of 25°C or less and a pulling rate of 500 mm/min, a break strength of 15 MPa or more, and a breaking elongation of 300% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte membrane for a polymer electrolyte fuel cell, a membrane-electrode assembly using the electrolyte membrane, and a polymer electrolyte fuel cell.

  In recent years, fuel cell technology has been counted as one of the pillars of these new energy technologies as a fundamental solution to energy and environmental problems, and as a central energy conversion system in the future hydrogen energy era. In particular, polymer electrolyte fuel cells (PEFCs) are used for stationary power sources for electric vehicles, portable power devices, and households that use electricity and heat simultaneously from the viewpoint of miniaturization and weight reduction. Application to other power supply devices is under consideration.

  A polymer electrolyte fuel cell is generally configured as follows. First, a catalyst layer containing carbon powder carrying a white metal catalyst and an ion conductive binder made of a polymer electrolyte is formed on both sides of a polymer electrolyte membrane having proton conductivity. A gas diffusion layer, which is a porous material through which fuel gas and oxidant gas are passed, is formed outside each catalyst layer. Carbon paper, carbon cloth, or the like is used as the gas diffusion layer. A structure in which the catalyst layer and the gas diffusion layer are integrated is called a gas diffusion electrode, and a structure in which a pair of gas diffusion electrodes is bonded to the electrolyte membrane so that the catalyst layer faces the electrolyte membrane is a membrane-electrode assembly ( MEA (Mebrane Electrode Assembly). On both sides of this membrane-electrode assembly, separators having electrical conductivity and airtightness are disposed. A gas flow path for supplying a fuel gas or an oxidant gas (for example, air) to the electrode surface is formed in a contact portion of the membrane-electrode assembly and the separator or in the separator. Electric power is generated by supplying a fuel gas such as hydrogen or methanol to one electrode (fuel electrode) and an oxidant gas containing oxygen such as air to the other electrode (oxygen electrode). That is, at the fuel electrode, the fuel is ionized to produce protons and electrons, the protons pass through the electrolyte membrane, the electrons travel through an external electric circuit formed by connecting both electrodes, and are sent to the oxygen electrode, Water is produced by the reaction. In this way, the chemical energy of the fuel can be directly converted into electric energy and taken out.

  As a polymer electrolyte membrane for a polymer electrolyte fuel cell, a proton conductive ion exchange membrane having a thickness of 20 to 200 μm is usually used. Several efforts have already been made for the development of ion conductive polymers based on non-fluorine polymers. For example, polyether ether ketone (PEEK) (Patent Document 1), which is a heat-resistant aromatic polymer, has been developed. In general, membranes made from sulfonated aromatic polymers tend to be brittle, so that the membrane is not only very difficult to use, but also has a limited operating time when used in fuel cells. Tend to.

On the other hand, a structure in which a polystyrene block is made into an ion conductive channel by sulfonated a polystyrene block of a block copolymer composed of styrene and a rubber component has been proposed. For example, Patent Document 2 proposes an ion conductive membrane made of a sulfonated product of SEBS (polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer), depending on the ratio of styrene and rubber component. Since the characteristics change greatly, when this membrane is used in a fuel cell, the operable time may be limited.
JP-A-6-93114 Japanese National Patent Publication No. 10-503788

  The object of the present invention is for a polymer electrolyte fuel cell that is economical, environmentally friendly, excellent in moldability, has both strength and flexibility, and, in turn, excellent in durability between membrane and electrodes. It is an object to provide a polymer electrolyte membrane, a membrane-electrode assembly using the electrolyte membrane, and a solid polymer fuel cell.

  As a result of intensive studies to solve the above problems, the present inventors have a polymer block (A) and a flexible polymer block (B) having an aromatic vinyl compound unit as a main repeating unit as constituent components. The mass ratio of the polymer block (A) to the polymer block (B) is in a specific range, the polymer block (A) contains a block copolymer having an ion conductive group as a main component, and 25 An electrolyte membrane showing a value within a specific range of 100% modulus, breaking strength and breaking elongation in a tensile test under the condition of a tensile rate of 500 mm / min at 5 ° C. is used as a polymer electrolyte membrane for a polymer electrolyte fuel cell. The present invention was completed.

  That is, the present invention comprises a polymer block (A) and a flexible polymer block (B) having an aromatic vinyl compound unit as a main repeating unit as constituent components, and the polymer block (A) and the polymer block (B ) And a polymer block (A) containing a block copolymer having an ion conductive group as a main component, and at 25 ° C., a tensile rate of 500 mm / A polymer electrolyte for a polymer electrolyte fuel cell, characterized in that a 100% modulus in a tensile test under the condition of minutes is 15 MPa or less, a breaking strength is 15 MPa or more, and a breaking elongation is 300% or more Relates to the membrane.

In the block copolymer, the polymer block (A) and the polymer block (B) undergo microphase separation, and the polymer block (A) and the polymer block (B) are aggregated. In addition, since the polymer block (A) has an ion conductive group, an ion channel is formed by the assembly of the polymer blocks (A) and becomes a passage for protons. Further, by limiting the mass ratio of the polymer block (A) and the polymer block (B), which is the component ratio, to the polymer block (B) to 65:35 to 10:90, It becomes easy for the block copolymer to have good strength and flexibility as a whole, the 100% modulus in a tensile test at 25 ° C. and a tensile speed of 500 mm / min is 15 MPa or less, and the breaking strength is 15 MPa or more. In addition, by forming an electrolyte membrane having a property of breaking elongation of 300% or more, formability (assembly, joining, fastening, etc.) in manufacturing a membrane-electrode assembly or a polymer electrolyte fuel cell ) And durability are improved. The flexible polymer block (B) is composed of an alkene unit or a conjugated diene unit. The polymer block (A) has an aromatic vinyl compound unit as a main repeating unit. The ion conductive group is bonded to the polymer block (A), which is necessary for improving radical resistance. Ion conductive groups include sulfonic acid groups and phosphonic acid groups and salts thereof.
The present invention also relates to a method for producing the above electrolyte membrane.
The present invention also relates to a membrane-electrode assembly and a fuel cell using the above electrolyte membrane.

  The polymer electrolyte membrane, the membrane-electrode assembly and the polymer electrolyte fuel cell of the present invention are economical, environmentally friendly, flexible, and hence excellent in the bondability between the membrane and the electrode, and therefore excellent in durability. The polymer electrolyte membrane of the present invention is also excellent in moldability.

Hereinafter, the present invention will be described in detail.
The block copolymer constituting the polymer electrolyte membrane of the present invention comprises an aromatic vinyl compound unit as a main repeating unit and a polymer block (A) having at least one ion conductive group as a constituent component. .

The aromatic ring in the aromatic vinyl compound is preferably a carbocyclic aromatic ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a pyrene ring. As specific examples of these aromatic vinyl compounds, when α-carbon is tertiary carbon, styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-isopropylstyrene 4-n-propylstyrene, 4-isopropylstyrene, 4-n-butylstyrene, 4-isobutylstyrene, 4-t-butylstyrene, 4-n-octylstyrene, 2,4-dimethylstyrene, 2,5- Aromatics such as dimethylstyrene, 3,5-dimethylstyrene, 2,4,6-trimethylstyrene, 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, 1,1-diphenylethylene, vinylnaphthalene, vinylanthracene A vinyl compound is mentioned.
Further, when the α-carbon is a quaternary carbon, a hydrogen atom bonded to the α-carbon atom is an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, isopropyl group, n- An aromatic vinyl compound substituted with a butyl group, isobutyl group or tert-butyl group), a halogenated alkyl group having 1 to 4 carbon atoms (chloromethyl group, 2-chloroethyl group, 3-chloroethyl group, etc.) or a phenyl group. It is preferable that Specifically, α-methylstyrene, α-methyl-4-methylstyrene, α-methyl-4-ethylstyrene, and α-methyl-4-t-butylstyrene are preferable.
These can be used alone or in combination of two or more. Among them, styrene, α-methylstyrene, 4-methylstyrene, 4-ethylstyrene, α-methyl-4-methylstyrene, and α-methyl-2-methylstyrene are preferable. In particular, α-methylstyrene, α-methyl-4-methylstyrene, and α-methyl-2-methylstyrene are preferred from the viewpoint of improving radical resistance. The form in the case of polymerizing (copolymerizing) two or more of these may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.

The polymer block (A) may contain one or more other monomer units as long as the effects of the present invention are not impaired. Examples of such other monomers include conjugated dienes having 4 to 8 carbon atoms (specific examples are the same as those in the description of the polymer block (B) described later), alkenes having 2 to 8 carbon atoms (specific examples are described later). (Same as in the description of the polymer block (B)), (meth) acrylate (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate), vinyl ester (vinyl acetate, propion) Vinyl acid, vinyl butyrate, vinyl pivalate, etc.), vinyl ether (methyl vinyl ether, isobutyl vinyl ether, etc.) and the like. The copolymerization form of the aromatic vinyl compound and the other monomer needs to be random copolymerization.

  The aromatic vinyl compound unit in the polymer block (A) occupies 50% by mass or more of the polymer block (A) in order to impart sufficient ion conductivity to the finally obtained polymer electrolyte membrane. Preferably, it occupies 70% by mass or more, more preferably 90% by mass or more.

  The molecular weight of the polymer block (A) in the state where the ion conductive group is not introduced is appropriately selected depending on the properties of the polymer electrolyte, required performance, other polymer components, etc., but the number average molecular weight in terms of polystyrene In general, it is preferably selected from 1,000 to 500,000, and more preferably selected from 2,000 to 200,000.

  The polymer block (A) may be crosslinked by a known method within a range not impairing the effects of the present invention. By introducing crosslinks, the ion channel phase formed by the polymer block (A) is less likely to swell, and changes in mechanical properties (such as tensile properties) between drying and wetting tend to be further reduced.

Further, the polymer block (A) may be composed of a constraining block (A1) having substantially no ion conductive group and an ion conductive block (A2) having an ion conductive group.
The constraining block (A1) having substantially no ion conductive group is represented by (1) the following general formula (I)

(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ^{2 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, but at least one of them is carbon. It represents a polymer block having an aromatic vinyl compound unit represented by the formula (1 to 8) as a main repeating unit.
The alkyl group having 1 to 4 carbon atoms represented by R ¹ in the general formula (I) may be linear or branched, and is a methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group. , Isobutyl group, tert-butyl group and the like. The alkyl group having 1 to 8 carbon atoms represented by R ^{2 to} R ⁴ in the general formula (I) may be linear or branched, and is methyl, ethyl, propyl, isopropyl, butyl, sec Examples include -butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, tert-pentyl group, hexyl group, 1-methylpentyl group, heptyl group, octyl group and the like. Preferable specific examples of the aromatic vinyl compound unit represented by the general formula (I) include p-methylstyrene unit, 4-tert-butylstyrene unit, p-methyl-α-methylstyrene unit, 4-tert- Examples thereof include butyl-α-methylstyrene units, and these may be used alone or in combination. The form in the case of polymerizing (copolymerizing) two or more of these may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.

The polymer block (A1) may contain one or more other monomer units in addition to the aromatic vinyl compound unit as long as the function as a constraining phase is not hindered. Examples of the monomer that gives such other monomer units include conjugated dienes having 4 to 8 carbon atoms (specific examples are the same as those in the description of the polymer block (B) described later), and alkenes having 2 to 8 carbon atoms. (Specific examples are the same as in the description of the polymer block (B) described later), (meth) acrylate esters (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl Examples include esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ethers (methyl vinyl ether, isobutyl vinyl ether, etc.), and the like. The copolymerization form of the aromatic vinyl compound and the other monomer needs to be random copolymerization.
From the viewpoint of fulfilling the function as the constrained phase, the aromatic vinyl compound unit described above preferably occupies 50% by mass or more, more preferably 70% by mass or more, and 90% by mass of the polymer block (A1). It is even more preferable to occupy the above.

  The molecular weight of the polymer block (A1) is appropriately selected depending on the properties of the polymer electrolyte, required performance, other polymer components, and the like. When the molecular weight is large, the mechanical properties of the polymer electrolyte tend to be high, but when it is too large, it becomes difficult to mold the block copolymer, and when the molecular weight is small, the mechanical properties tend to be low, and the required performance is reduced. It is important to select the molecular weight accordingly. The number average molecular weight in terms of polystyrene is usually preferably selected from 1000 to 300,000, more preferably from 2000 to 100,000.

  The ion conductive block (A2) having an ion conductive group has the following general formula (II):

(In the formula, Ar ¹ represents an aryl group having 6 to 14 carbon atoms which may have ¹ to 3 substituents, and R ⁵ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or 1 to 3). An aromatic vinyl-based compound unit represented by a C6-C14 aryl group which may have one substituent as a main repeating unit.
Examples of the aryl group having 6 to 14 carbon atoms represented by Ar ¹ in the general formula (II) include a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, an indenyl group, a biphenylyl group, and a pyrenyl group. And a naphthyl group is preferable, and a phenyl group is more preferable. The optional 1 to 3 substituents that can be directly bonded to the aromatic ring of the aryl group are each independently a linear or branched alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, propyl group). Group, isopropyl group, butyl group, sec-butyl group, isobutyl group, tert-butyl group, etc.). R ⁵ in the general formula (II) has the same meaning as R ¹ in the general formula (I), and examples of the group and preferred examples thereof are also the same.
Specific examples of the aromatic vinyl compound that gives the aromatic vinyl compound unit represented by the general formula (II) include styrene, vinyl naphthalene, vinyl anthracene, vinyl phenanthrene, vinyl biphenyl, α-methyl styrene, 1-methyl. Examples include -1-naphthylethylene and 1-methyl-1-biphenylylethylene, and styrene and α-methylstyrene are particularly preferable.
The aromatic vinyl compound that gives the aromatic vinyl compound unit represented by the general formula (II) may be used alone or in combination of two or more. The form in the case of copolymerizing two or more types may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization.

The polymer block (A2) may contain one or more other monomer units in addition to the aromatic vinyl compound unit within a range not impairing the effects of the present invention. Examples of the monomer that gives such other monomer units include conjugated dienes having 4 to 8 carbon atoms (specific examples are the same as those in the description of the polymer block (B) described later), and alkenes having 2 to 8 carbon atoms. (Specific examples are the same as in the description of the polymer block (B) described later), (meth) acrylate esters (methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc.), vinyl Examples include esters (vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, etc.), vinyl ethers (methyl vinyl ether, isobutyl vinyl ether, etc.), and the like. The copolymerization form of the aromatic vinyl compound and the other monomer needs to be random copolymerization.
The proportion of the aromatic vinyl compound unit contained in the polymer block (A2) is preferably 50 mol% or more, more preferably 60 mol% or more from the viewpoint of imparting sufficient ion conductivity, It is still more preferable that it is 80 mol% or more.

  The molecular weight of the polymer block (A2) in the state where the ion conductive group is not introduced is appropriately selected depending on the properties of the polymer electrolyte, required performance, other polymer components, etc., but the number average molecular weight in terms of polystyrene In general, it is preferably selected from 500 to 200,000, and more preferably selected from 1000 to 100,000.

  The polymer block (A2) may be crosslinked by a known method within a range not impairing the effects of the present invention. By introducing cross-linking, changes in dimensions and mechanical properties (tensile properties) between drying and wetting tend to be further reduced.

  When the polymer block (A) constituting the polymer electrolyte membrane of the present invention is composed of the polymer block (A1) and the polymer block (A2), if the ratio of the polymer block (A1) is large, the dimensional change and dynamics are increased. Although there is a tendency that the change in mechanical properties (breaking strength etc.) tends to be small, the ionic conductivity tends to be low, and when the proportion of the polymer block (A2) is large, the ionic conductivity tends to be high, Changes in dimensions and mechanical properties (breaking strength, etc.) tend to increase. The ratio of the polymer block (A1) to the polymer block (A2) in the polymer block (A) is preferably 95: 5 to 20:80, more preferably 93: 7 to 25:75. 90:10 to 30:70 is even more preferable.

  The block copolymer used in the polymer electrolyte membrane of the present invention has a flexible polymer block (B) in addition to the polymer block (A). By limiting the mass ratio of the polymer block (A) and the polymer block (B), which is the component ratio, to 65:35 to 10:90, the polymer block (B) is present. The polymer as a whole is easy to have good strength and flexibility, and the 100% modulus in a tensile test at 25 ° C. and a tensile speed of 500 mm / min is 15 MPa or less, and the breaking strength is 15 MPa or more. In addition, by using an electrolyte membrane having a characteristic of breaking elongation of 300% or more, the moldability (assembly property, bondability, tightening property, etc.) in producing a membrane-electrode assembly or a polymer electrolyte fuel cell is improved. It is improved and durability is also improved. The flexible polymer block (B) here is a so-called rubber-like polymer block having a glass transition point or softening point of 50 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower.

  Monomers that can constitute the repeating unit constituting the flexible polymer block (B) include alkenes having 2 to 8 carbon atoms, cycloalkenes having 5 to 8 carbon atoms, and vinylcycloalkenes having 7 to 10 carbon atoms. , A conjugated diene having 4 to 8 carbon atoms and a conjugated cycloalkadiene having 5 to 8 carbon atoms, a vinyl cycloalkene having 7 to 10 carbon atoms in which part or all of the carbon-carbon double bond is hydrogenated, and carbon-carbon. A conjugated diene having 4 to 8 carbon atoms in which some or all of the double bonds are hydrogenated, a conjugated cycloalkadiene having 5 to 8 carbon atoms in which some or all of the carbon-carbon double bonds are hydrogenated, ( Examples include (meth) acrylic acid esters, vinyl esters, vinyl ethers, and the like. These may be used alone or in combination of two or more. The form in the case of polymerizing (copolymerizing) two or more kinds may be random copolymerization, block copolymerization, graft copolymerization, or tapered copolymerization. Further, when the monomer to be used for (co) polymerization has two carbon-carbon double bonds, any of them may be used for the polymerization, and in the case of a conjugated diene, it is a 1,2-bond. 1,4-bonds may be used, and the ratio of 1,2-bonds to 1,4-bonds is not particularly limited as long as the glass transition point or softening point is 50 ° C. or lower.

When the repeating unit constituting the polymer block (B) has a carbon-carbon double bond as in the case of vinylcycloalkene, conjugated diene or conjugated cycloalkadiene, the polymer of the present invention From the viewpoint of improving the power generation performance of the membrane-electrode assembly using the electrolyte membrane and improving the heat deterioration resistance, it is preferable that 80 mol% or more of such carbon-carbon double bonds are hydrogenated, and 90 mol%. The above is more preferably hydrogenated, and more preferably 95 mol% or more is hydrogenated. The hydrogenation rate of the carbon-carbon double bond can be calculated by a commonly used method such as ¹ H-NMR measurement.

The polymer block (B) is an alkene having 2 to 8 carbon atoms from the viewpoint of giving the resulting block copolymer elasticity and, in turn, good moldability in the production of a membrane-electrode assembly and a polymer electrolyte fuel cell. Units (ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, etc.), C5-C8 cycloalkene unit (cyclopentene, cyclohexene, cycloheptene, cyclooctene, etc.), C7-10 vinylcycloalkene unit (vinylcyclopentene, vinylcyclohexene, vinylcycloheptene, vinylcyclooctene, etc.), carbon Conjugated diene units having a number of 4 to 8 (1,3-butadiene, 1,3-pentadiene, isoprene 1,3-hexadiene, 2,4-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-heptadiene, 1,4-heptadiene, 3, 5-heptadiene, etc.), conjugated cycloalkadiene units having 5 to 8 carbon atoms (cyclopentadiene, 1,3-cyclohexadiene, etc.), carbon atoms having 7 to 7 carbon atoms partially or wholly hydrogenated 10 vinylcycloalkene units, 4 to 8 carbon conjugated diene units in which some or all of the carbon-carbon double bonds are hydrogenated, and some or all of the carbon-carbon double bonds are hydrogenated It is preferably a polymer block composed of at least one repeating unit selected from conjugated cycloalkadiene units having 5 to 8 carbon atoms, alkene units having 2 to 8 carbon atoms, A polymer block comprising at least one repeating unit selected from a conjugated diene unit having 4 to 8 prime atoms and a conjugated diene unit having 4 to 8 carbon atoms in which part or all of carbon-carbon double bonds have been hydrogenated. More preferably, the alkene unit having 2 to 6 carbon atoms, the conjugated diene unit having 4 to 8 carbon atoms, and the conjugated diene having 4 to 8 carbon atoms in which some or all of the carbon-carbon double bonds are hydrogenated. It is even more preferable that the polymer block is composed of at least one repeating unit selected from the units.
In the above, the most preferable alkene unit is an isobutene unit, and the most preferable conjugated diene unit is a 1,3-butadiene unit and / or an isoprene unit.

  In addition to the above monomers, the polymer block (B) may contain other monomers such as styrene and vinyl as long as the purpose of the polymer block (B) that gives elasticity to the block copolymer is not impaired. An aromatic vinyl compound such as naphthalene; a halogen-containing vinyl compound such as vinyl chloride may be included. In this case, the copolymerization form of the monomer and other monomer needs to be random copolymerization. The amount of such other monomer used is preferably less than 50% by weight, more preferably less than 30% by weight, based on the total of the above monomers and other monomers. It is still more preferable that it is less than mass%.

  The electrolyte membrane of the present invention does not have one polymer block (A), that is, a constraining block (A1) substantially having no ion conductive group, and an ion conductive block (A2) having an ion conductive group. ) Only, the mass ratio of the polymer block (A) and the polymer block (B) needs to be 65:35 to 10:90, and is 50:50 to 10:90. Is more preferable, and 45:55 to 15:85 is more preferable. When this mass ratio is 65:35 to 10:90, it becomes easy to combine good strength and flexibility, and it becomes easy to improve the bondability between the membrane and the electrode, so that the durability tends to be excellent. is there.

  Although the structure of the block copolymer which has a polymer block (A) and a polymer block (B) as a structural component is not specifically limited, ABA type | mold triblock copolymer, BAB, as an example Type triblock copolymer, ABA type triblock copolymer or a mixture of BAB type triblock copolymer and AB type diblock copolymer, ABA type B-type tetrablock copolymer, A-B-A-B-A type pentablock copolymer, B-A-B-A-B type pentablock copolymer, (AB) nX-type star copolymer Examples thereof include a polymer (X represents a coupling agent residue), (BA) nX type star copolymer (X represents a coupling agent residue), and the like. These block copolymers may be used alone or in combination of two or more.

  When the electrolyte membrane of the present invention has one polymer block (A), that is, a constraining block (A1) having substantially no ion conductive group and an ion conductive block (A2) having an ion conductive group. The mass ratio of the polymer block (A) to the polymer block (B) needs to be 65:35 to 10:90, preferably 65:35 to 15:85, and 60: More preferably, it is 40-15: 85. When this mass ratio is 65:35 to 10:90, it becomes easy to combine good strength and flexibility, and it becomes easy to improve the bondability between the membrane and the electrode, so that the durability tends to be excellent. is there.

  The structure of the block copolymer composed of the polymer block (A1), polymer block (A2), and polymer block (B) of the block copolymer used in the present invention is not particularly limited. B-A2 type triblock copolymer, A2-B-A1-A2 tetrablock copolymer, B-A2-B-A1 tetrablock copolymer, A2-B-A1-B tetrablock copolymer, A1 -B-A1-A2 tetrablock copolymer, A2-B-A2-A1 tetrablock copolymer, A2-A1-B-A1-A2 pentablock copolymer, A1-A2-B-A2-A1 penta Block copolymer, A2-A1-B-A2-A1 pentablock copolymer, A1-B-A2-B-A1 pentablock copolymer, A2-B-A1-A2-B pentablock copolymer A2-B-A1-A2-A1 pentablock copolymer, A2-B-A1-B-A1 pentablock copolymer, A2-B-A2-B-A1 pentablock copolymer, A2-B- A2-A1-B pentablock copolymer, B-A2-B-A2-A1 pentablock copolymer, B-A2-B-A1-A2 pentablock copolymer, B-A2-B-A1-B Examples thereof include a pentablock copolymer and an A1-A2-A1-B-A1 pentablock copolymer.

  The number average molecular weight of the block copolymer used in the present invention in a state where the ion conductive group is not introduced is not particularly limited, but the number average molecular weight in terms of polystyrene is usually 10,000 to 1,000,000. Preferably, 15,000-700,000 are more preferable, and 20,000-500,000 are still more preferable.

The block copolymer constituting the polymer electrolyte membrane of the present invention needs to have an ion conductive group in the polymer block (A). Examples of ions in the present invention when referring to ionic conductivity include protons. The ion conductive group is not particularly limited as long as the membrane-electrode assembly produced using the polymer electrolyte membrane can express sufficient ionic conductivity. Among them, -SO ₃ M or- A sulfonic acid group, a phosphonic acid group or a salt thereof represented by PO ₃ HM (wherein M represents a hydrogen atom, an ammonium ion or an alkali metal ion) is preferably used. As the ion conductive group, a carboxyl group or a salt thereof can also be used. The introduction position of the ion conductive group is the polymer block (A) because it is particularly effective for improving the radical resistance of the entire block copolymer.

  The introduction position of the ion conductive group into the polymer block (A) is not particularly limited and may be introduced into the aromatic vinyl compound unit or other monomer units described above. From the viewpoint of facilitating ion channel formation, it is preferably introduced into the aromatic ring of the aromatic vinyl compound unit.

  The amount of ion-conducting group introduced is appropriately selected depending on the required performance of the resulting block copolymer, etc., but exhibits sufficient ion conductivity for use as a polymer electrolyte membrane for a polymer electrolyte fuel cell. In general, the amount is preferably such that the ion exchange capacity of the block copolymer is 0.30 meq / g or more, and more preferably 0.40 meq / g or more. . The upper limit of the ion exchange capacity of the block copolymer is preferably 3.0 meq / g or less because if the ion exchange capacity is too large, the hydrophilicity tends to increase and the water resistance becomes insufficient.

  The production method of the block copolymer used in the present invention is not particularly limited, and a known method can be used, but after producing the block copolymer having no ion conductive group, the ion conductivity is improved. A method of bonding groups is preferred.

  Depending on the type, molecular weight, etc. of the monomer constituting the polymer block (A) or (B), the production method of the polymer block (A) or (B) can be a radical polymerization method, an anionic polymerization method, a cationic polymerization method, Although it is appropriately selected from coordination polymerization method and the like, radical polymerization method, anionic polymerization method and cationic polymerization method are preferably selected from the viewpoint of industrial ease. In particular, the so-called living polymerization method is preferable from the viewpoint of molecular weight, molecular weight distribution, polymer structure, ease of bonding between the polymer block (B) and the polymer block (A) made of flexible components, and specifically living Production in which a block copolymer is produced by a radical polymerization method, a living anion polymerization method or a living cation polymerization method, and then a hydrogenation reaction is carried out by a known method if desired when the polymer block (B) has a conjugated diene unit. The method is preferred.

As a specific example of the production method, a production method of a block copolymer comprising as a component a polymer block (A) made of poly (α-methylstyrene) and a polymer block (B) made of a conjugated diene will be described. In this case, it is preferable to produce by a living anionic polymerization method from the viewpoint of industrial ease, molecular weight, molecular weight distribution, ease of bonding between the polymer block (A) and the polymer block (B), and the following specific examples A typical synthesis example is shown.
(1) Method of obtaining an ABA type block copolymer by sequentially polymerizing α-methylstyrene under a temperature condition of −78 ° C. after polymerization of a conjugated diene using a dianionic initiator in a tetrahydrofuran solvent ( Macromolecules, (1969), 2 (5), 453-458),
(2) α-methylstyrene is subjected to bulk polymerization using an anionic initiator, then conjugated dienes are sequentially polymerized, and then a coupling reaction is performed with a coupling agent such as tetrachlorosilane, and (AB) nX type block Method for obtaining a copolymer (Kautsch. Gummi, Kunstst., (1984), 37 (5), 377-379; Polym. Bull., (1984), 12, 71-77),
(3) An organic lithium compound in a nonpolar solvent is used as an initiator, and a concentration of 5 to 50% by mass at a temperature of −30 ° C. to 30 ° C. in the presence of a polar compound having a concentration of 0.1 to 10% by mass. A polymer obtained by polymerizing α-methylstyrene, a conjugated diene is polymerized to the resulting living polymer, and then a coupling agent is added to obtain an ABA block copolymer.
(4) A concentration of 5 to 50% by mass at a temperature of −30 ° C. to 30 ° C. in the presence of a polar compound having a concentration of 0.1 to 10% by mass using an organolithium compound in a nonpolar solvent as an initiator. Α-methylstyrene (a monomer constituting the polymer block (A2)) is polymerized, and the resulting living polymer is polymerized with a conjugated diene. From the resulting α-methylstyrene polymer block and the conjugated diene polymer block, A method for obtaining an A2-B-A1 type block copolymer by polymerizing a monomer constituting the polymer block (A1) to a living block copolymer.

Specific examples of the production method include a polymer block (A1) having an aromatic vinyl compound such as 4-tert-butylstyrene as a main repeating unit, a polymer block (A2) comprising styrene or α-methylstyrene, and a conjugated diene. A method for producing a block copolymer or graft copolymer containing as a component a polymer block (B) composed of In this case, the living anion polymerization method is preferable from the viewpoint of industrial ease, molecular weight, molecular weight distribution, ease of bonding of the polymer blocks (A1), (B) and (A2), and the following specific synthesis examples Is shown.
(5) An anionic polymerization initiator is used in a cyclohexane solvent, and an aromatic vinyl compound such as 4-tert-butylstyrene is polymerized at a temperature of 10 to 100 ° C., and then a conjugated diene and styrene are sequentially polymerized. A method of obtaining an A1-B-A2 type block copolymer,
(6) An anionic polymerization initiator is used in a cyclohexane solvent, and an aromatic vinyl compound such as 4-tert-butylstyrene is polymerized at a temperature of 10 to 100 ° C., and then styrene and a conjugated diene are sequentially polymerized. And then adding a coupling agent such as phenyl benzoate to obtain an A1-A2-B-A2-A1 type block copolymer,
(7) Using an anionic polymerization initiator in a cyclohexane solvent, under a temperature condition of 10 to 100 ° C., an aromatic vinyl compound such as 4-tert-butylstyrene, a conjugated diene, 4-tert-butylstyrene, etc. A1-B-A1 type block copolymer is prepared by sequential polymerization of aromatic vinyl compounds and an anionic polymerization initiator system (anionic polymerization initiator / N, N, N ′, N′-tetramethylethylenediamine) is added. And then lithiating the conjugated diene unit and then polymerizing styrene to obtain an A1-B (-g-A2) -A1 type block / graft copolymer,
(8) A concentration of 5 to 50% by mass at a temperature of −30 ° C. to 30 ° C. in the presence of a polar compound having a concentration of 0.1 to 10% by mass using an organolithium compound in a nonpolar solvent as an initiator. Α-methylstyrene is polymerized and the resulting living polymer is sequentially polymerized with an aromatic vinyl compound such as conjugated diene or 4-tert-butylstyrene to obtain an A2-B-A1 type block copolymer, or , A method of sequentially polymerizing α-methylstyrene, 4-tert-butylstyrene, conjugated diene, and 4-tert-butylstyrene under the same conditions to obtain an A2-A1-B-A1 type block copolymer,
Can be adopted / applied.

  Next, a method for bonding an ion conductive group to the obtained block copolymer will be described. First, a method for introducing a sulfonic acid group into the obtained block copolymer will be described. Sulfonation can be performed by a known sulfonation method. As such a method, an organic solvent solution or suspension of a block copolymer is prepared, a sulfonating agent is added and mixed, a method of adding a gaseous sulfonating agent directly to the block copolymer, etc. Is exemplified.

  Sulfonating agents used include sulfuric acid, a mixture of sulfuric acid and aliphatic acid anhydride, chlorosulfonic acid, a mixture of chlorosulfonic acid and trimethylsilyl chloride, sulfur trioxide, a mixture of sulfur trioxide and triethyl phosphate. Examples thereof include aromatic organic sulfonic acids represented by 2,4,6-trimethylbenzenesulfonic acid. 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, and the like. You may use it, selecting suitably from several combinations.

  The method of isolating the sulfonated product from the reaction solution containing the sulfonated product of the block copolymer is a method of pouring the reaction solution into water to cause sulfonated precipitation and then distilling off the solvent at atmospheric pressure, There is a method in which the water of the stopper is gradually added and suspended, and then the sulfonated product is precipitated and then the solvent is distilled off at atmospheric pressure. The sulfonated product is finely dispersed, and then washed with water. From the viewpoint of increasing the efficiency, a method of gradually adding a stopper water to the reaction solution and suspending it, and then precipitating a sulfonated product is preferably used.

  A method for introducing a phosphonic acid group into the obtained block copolymer will be described. Phosphonation can be performed by a known phosphonation method. Specifically, for example, an organic solvent solution or suspension of a block copolymer is prepared, and the copolymer is reacted with chloromethyl ether or the like in the presence of anhydrous aluminum chloride to introduce a halomethyl group into the aromatic ring. Thereafter, there may be mentioned a method in which phosphorus trichloride and anhydrous aluminum chloride are added and reacted, followed by a hydrolysis reaction to introduce a phosphonic acid group. Alternatively, a method may be exemplified in which phosphorus trichloride and anhydrous aluminum chloride are added to the copolymer and reacted to introduce a phosphinic acid group into the aromatic ring, and then the phosphinic acid group is oxidized with nitric acid to form a phosphonic acid group.

The degree of sulfonation or phosphonation is as described above until the ion exchange capacity of the block copolymer is 0.30 meq / g or more, particularly 0.40 meq / g or more, but 3.0 meq / g or less. It is desirable to be sulfonated or phosphonated so that Thereby, practical ion conduction performance is obtained. The ion exchange capacity of the sulfonated or phosphonated block copolymer, or the sulfonation rate or phosphonation rate in the aromatic vinyl compound in the block copolymer is determined by acid value titration, infrared spectroscopic measurement, nuclear It can be calculated using an analytical means such as magnetic resonance spectrum ( ¹ H-NMR spectrum) measurement.

  The ion conductive group may be introduced in the form of a salt neutralized with a suitable metal ion (for example, alkali metal ion) or counter ion (for example, ammonium ion). For example, a desired ion conductive group can be introduced by producing a polymer using sodium o-, m- or p-styrene sulfonate, or α-methyl-o-, m or p-sodium styrene sulfonate. . Or the block copolymer which made the sulfonic acid group into the salt form can be obtained by ion-exchange by a suitable method.

  The polymer electrolyte membrane of the present invention can be added to various additives such as a softening agent, a stabilizer, a light stabilizer, an antistatic agent, a release agent, a flame retardant, a foaming agent, and a pigment as long as the effects of the present invention are not impaired. , Dyes, brighteners, carbon fibers, inorganic fillers and the like may be used alone or in combination of two or more.

Examples of the softener include petroleum softeners such as paraffinic, naphthenic or aromatic process oils, paraffin, vegetable oil softeners, plasticizers, and the like.
Stabilizers include phenol-based stabilizers, sulfur-based stabilizers, phosphorus-based stabilizers, and the like. Specific examples include 2,6-di-t-butyl-p-cresol, pentaerythryl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Benzene, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2, -thio-diethylenebi [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrodinamide), 3, 5-di-t-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 3,9-bis {2- [3 Phenolic compounds such as-(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane Stabilizer; pentaerythrityl tetrakis (3-lauryl thiopropionate), distearyl 3,3′-thiodipropionate, dilauryl 3,3′-thiodipropione And sulfur stabilizers such as dimyristyl 3,3′-thiodipropionate; trisnonylphenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, diasterylpentaerythritol diphosphite, Examples thereof include phosphorus stabilizers such as bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite.
Specific examples of the inorganic filler include talc, calcium carbonate, silica, glass fiber, mica, kaolin, titanium oxide, montmorillonite, and alumina.

In a fuel cell, when power is generated for a long time, the electrolyte membrane swells and peeling between the electrolyte membrane and the electrode tends to occur, and stable power generation may not be possible. In particular, when the tensile modulus is large when the electrolyte membrane swells and the membrane is stretched, peeling between the membrane and the electrode tends to occur. From the above viewpoint, the 100% modulus, which is the stress at the time of 100% elongation at break in the tensile test at 25 ° C. and the tensile rate of 500 mm / min, of the polymer electrolyte membrane of the present invention is 15 MPa or less. It is necessary, it is preferable that it is 0.3-13 MPa, and it is more preferable that it is 0.5-12 MPa. The 100% modulus can be reduced by increasing the mass ratio of the polymer block (B) in the block copolymer to be used.
Moreover, when the strength of the electrolyte membrane is weak and lacks flexibility, not only the durability of the electrolyte membrane is inferior, but also the bondability between the membrane and the electrode is deteriorated, and as a result, power is generated for a long time in the fuel cell. In such a case, peeling between the electrolyte membrane and the electrode tends to occur, and stable power generation tends to be impossible. From the above viewpoint, the breaking strength of the polymer electrolyte membrane of the present invention is required to be 15 MPa or more in a tensile test at 25 ° C. and a tensile speed of 500 mm / min, and is 16 to 100 MPa. The elongation at break needs to be 300% or more, preferably 320 to 1000%, and more preferably 330 to 800%. The breaking strength can be increased by increasing the number average molecular weight of the block copolymer used and increasing the mass ratio of the polymer block (A). The elongation at break can be increased by increasing the mass ratio of the polymer block (B) of the block copolymer used.

  The content of the block copolymer in the polymer electrolyte membrane of the present invention is preferably 50% by mass or more, and more preferably 70% by mass or more, from the viewpoints of the above characteristics and ion conductivity in the tensile test. 90% by mass or more is even more preferable.

  The polymer electrolyte membrane of the present invention preferably has a thickness of about 5 to 500 μm from the viewpoints of performance required as an electrolyte membrane for fuel cells, membrane strength, handling properties, and the like. When the film thickness is less than 5 μm, the mechanical strength of the film and the gas barrier property tend to be insufficient. On the contrary, when the film thickness is thicker than 500 μm, the membrane resistance increases and sufficient proton conductivity does not appear, so that the power generation characteristics of the battery tend to be lowered. The film thickness is more preferably 10 to 300 μm.

As a method for preparing the polymer electrolyte membrane of the present invention, any method can be adopted as long as it is a normal method for such preparation. For example, the block copolymer constituting the polymer electrolyte membrane of the present invention or the After the block copolymer and the above-mentioned additives are mixed with an appropriate solvent to prepare a solution or suspension of the block copolymer of 8% by mass or more, it is applied to a release-treated PET film or the like. Then, after coating using a coater or applicator, etc., a solvent coating method for obtaining an electrolyte membrane having a desired thickness by removing the solvent under appropriate conditions, or a polytetrafluoroethylene sheet or the like of 5% by mass or less After casting the solution and suspension of the block copolymer, the solvent is gradually removed over 1 to several days, thereby obtaining an electrolyte membrane having a desired thickness, and hot press molding. A method of forming a film using a known method such as roll molding or extrusion molding can be used, but the solution coating method is preferably used from the viewpoint of easily preparing an electrolyte membrane having good strength and flexibility. It is done.
Further, the same or different block copolymer solution may be newly applied on the obtained electrolyte membrane layer and dried to be laminated. Further, the same or different electrolyte membranes obtained as described above may be laminated by being pressure-bonded by hot roll molding or the like.

  The solvent used at this time is not particularly limited as long as it can prepare a solution having a viscosity capable of solution coating without destroying the structure of the block copolymer. Specifically, halogenated hydrocarbons such as methylene chloride, aromatic hydrocarbons such as toluene, xylene, and benzene, linear aliphatic hydrocarbons such as hexane and heptane, and cyclic aliphatic carbonization such as cyclohexane. Examples thereof include ethers such as hydrogen and tetrahydrofuran, alcohols such as methanol, ethanol, propanol, isopropanol, butanol and isobutyl alcohol, or mixed solvents thereof. Depending on the composition of the block copolymer, the molecular weight, the ion exchange capacity, etc., one or two or more combinations can be appropriately selected and used from the solvents exemplified above. From the viewpoint of easy preparation of a flexible electrolyte membrane, a mixed solvent system of aromatic hydrocarbons and alcohols (specifically, a mixed solvent of toluene and isobutyl alcohol, a mixed solvent of toluene and isopropyl alcohol, etc.), ring Preferred is a mixed solvent system of a formula aliphatic hydrocarbon and an alcohol (specifically, a mixed solvent of cyclohexane and isopropyl alcohol, a mixed solvent of cyclohexane and isobutyl alcohol, etc.), a tetrahydrofuran solvent, and particularly, an aromatic hydrocarbon and A mixed solvent of a mixed solvent system of alcohols is preferable. In the case of an electrolyte membrane comprising an ABA type triblock copolymer composed of a polymer block (A) and a polymer block (B), a mixed solvent system of aromatic hydrocarbons and alcohols is used. By using a mixed solvent, it is easy to form a morphology corresponding to the volume composition of the polymer block (A), or a morphology in which the phase comprising the polymer block (A) occupies a volume greater than or equal to the volume composition (for example, volume composition Therefore, when the phase of polymer block (A) forms a cylinder structure, it is easy to form a co-continuous structure and further a lamellar structure from the cylinder.) Therefore, prepare an electrolyte membrane having good strength and flexibility. Cheap.

  In addition, the solvent removal conditions in the solution coating method are arbitrarily selected as long as the conditions allow the solvent to be completely removed at a temperature equal to or lower than the temperature at which the ion conductive group such as the sulfone group of the block copolymer of the present invention is removed. It is possible. In order to express desired physical properties, a plurality of temperatures may be arbitrarily combined, or a combination of ventilation and vacuum may be arbitrarily combined. Specifically, a method of removing the solvent by hot air drying at about 60 to 100 ° C. over 4 minutes, a method of removing the solvent in 2 to 4 minutes by hot air drying at about 100 to 140 ° C., After pre-drying at about 25 ° C. for about 1 to 3 hours and then drying with hot air drying at about 100 ° C. for several minutes, or after pre-drying at about 25 ° C. for about 1 to 3 hours, 25 For example, there may be mentioned a method in which it is forced to dry for about 1 to 12 hours by vacuum drying in an atmosphere of about 40 ° C. From the viewpoint of easy adjustment of an electrolyte membrane having good strength and flexibility, a method of removing the solvent by hot air drying at about 60 to 100 ° C. over 4 minutes, or about 1 to 24 hours at about 25 ° C. After drying, follow-up drying with hot air drying at about 100 ° C. over several minutes, or pre-drying at about 25 ° C. for about 1 to 15 hours, and then vacuum drying under an atmosphere of about 25-40 ° C. For example, a method of driving and drying for about 1 to 12 hours is preferably used. In particular, in the case of an electrolyte membrane composed of an ABA type triblock copolymer composed of a polymer block (A) and a polymer block (B), a suitable drying method as described above should be adopted. Thus, it is easy to form a morphology corresponding to the volume composition of the polymer block (A) or a morphology in which the phase composed of the polymer block (A) occupies a volume greater than or equal to the volume composition (for example, from the volume composition to the polymer block ( When the phase of A) forms a cylinder structure, it is easy to form a co-continuous structure and further a lamellar structure from the cylinder. Therefore, it is easier to prepare an electrolyte membrane having good strength and flexibility.

  Next, a membrane-electrode assembly using the polymer electrolyte membrane of the present invention will be described. The production of the membrane-electrode assembly is not particularly limited, and a known method can be applied. For example, a catalyst paste containing an ion conductive binder is applied on the gas diffusion layer by a printing method or a spray method and dried. To form a joined body of the catalyst layer and the gas diffusion layer, and then to join the pair of joined bodies with the catalyst layer on the inside and to both sides of the polymer electrolyte membrane by hot pressing or the like, There is a method in which a catalyst paste is applied to both sides of a polymer electrolyte membrane by a printing method or a spray method, dried to form a catalyst layer, and a gas diffusion layer is pressure-bonded to each catalyst layer by hot pressing or the like. As another production method, a solution or suspension containing an ion conductive binder is applied to both surfaces of the polymer electrolyte membrane and / or the catalyst layer surface of a pair of gas diffusion electrodes, and the electrolyte membrane and the catalyst layer surface are bonded together. There is a method of joining by thermocompression bonding. In this case, the solution or suspension may be applied to either the electrolyte membrane or the catalyst layer surface, or may be applied to both. As another manufacturing method, first, the catalyst paste is applied to a base film made of polytetrafluoroethylene (PTFE) and dried to form a catalyst layer, and then a pair of base films on the base film is formed. The catalyst layer is transferred to both sides of the polymer electrolyte membrane by thermocompression bonding, the base film is peeled off to obtain a joined body of the electrolyte membrane and the catalyst layer, and the gas diffusion layer is crimped to each catalyst layer by hot pressing. There is a way. In these methods, these methods may be performed in a state where the ion conductive group is made into a salt with a metal such as Na, and a treatment for returning to a proton type by an acid treatment after bonding may be performed.

  Examples of the ion conductive binder constituting the membrane-electrode assembly include existing perfluorosulfones such as “Nafion” (registered trademark, manufactured by DuPont) and “Gore-select” (registered trademark, manufactured by Gore). An ion conductive binder made of an acid polymer, an ion conductive binder made of sulfonated polyethersulfone or sulfonated polyetherketone, an ion conductive binder made of polybenzimidazole impregnated with phosphoric acid or sulfuric acid can be used. . Moreover, you may produce an ion conductive binder from the block copolymer which comprises the polymer electrolyte membrane of this invention. In order to further enhance the adhesion between the electrolyte membrane and the gas diffusion electrode, it is preferable to use an ion conductive binder formed from the same material as the polymer electrolyte membrane.

  The constituent material of the catalyst layer of the membrane-electrode assembly is not particularly limited as the conductive material / catalyst support, and examples thereof include carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like. These may be used alone or in combination of two or more. The catalyst metal may be any metal that promotes the oxidation reaction of fuel such as hydrogen and methanol and the reduction reaction of oxygen, such as platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Cobalt, nickel, chromium, tungsten, manganese, palladium, etc., or alloys thereof, for example, platinum-ruthenium alloys are mentioned. Of these, platinum and platinum alloys are often used. The particle size of the metal serving as a catalyst is usually 10 to 300 angstroms. When these catalysts are supported on a conductive material such as carbon / catalyst support, the amount of catalyst used is small and it is advantageous in terms of cost. The catalyst layer may contain a water repellent as necessary. Examples of the water repellent include various thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene copolymer, and polyether ether ketone.

  The gas diffusion layer of the membrane-electrode assembly is made of a material having conductivity and gas permeability, and examples of such a material include porous materials made of carbon fibers such as carbon paper and carbon cloth. Moreover, in order to improve water repellency, this material may be subjected to water repellency treatment.

A polymer electrolyte fuel obtained by inserting the membrane-electrode assembly obtained by the above-described method between a conductive separator material that also serves as a gas supply flow path to the electrode and the electrode chamber separation. A battery is obtained. The membrane-electrode assembly of the present invention uses a pure hydrogen type using hydrogen as a fuel gas, a methanol reforming type using hydrogen obtained by reforming methanol, and hydrogen obtained by reforming natural gas. Natural gas reforming type, gasoline reforming type using hydrogen obtained by reforming gasoline, direct methanol type using methanol directly, etc. can be used as a membrane-electrode assembly for polymer electrolyte fuel cells. is there.
The fuel cell using the polymer electrolyte membrane of the present invention is excellent in durability.

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

Reference example 1
Production of block copolymer comprising poly α-methylstyrene (polymer block (A)) and hydrogenated polybutadiene (polymer block (B)) In the same manner as the previously reported method (WO 02/40611), A poly α-methylstyrene b-polybutadiene-b-poly α-methylstyrene type triblock copolymer (hereinafter abbreviated as mSBmS) was synthesized. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained mSBmS is 76000, the 1,4-bond amount determined from ¹ H-NMR measurement is 55%, and the content of α-methylstyrene unit is 28.0. It was mass%. Further, it was found by composition analysis by ¹ H-NMR spectrum measurement that α-methylstyrene was not substantially copolymerized in the polybutadiene block.
Prepare a synthesized cyclohexane solution of mSBmS, charge it into a pressure-resistant vessel that has been sufficiently purged with nitrogen, and then use a Ni / Al Ziegler-type hydrogenation catalyst for 5 hours at 80 ° C. in a hydrogen atmosphere. To obtain a poly α-methylstyrene-b-hydrogenated polybutadiene-b-polyα-methylstyrene type triblock copolymer (hereinafter abbreviated as mSEBmS). The hydrogenation proportion of the resulting mSEBmS was calculated by ¹ H-NMR spectrum measurement, it was 99.3%.

Reference example 2
Production of block copolymer consisting of polystyrene (polymer block (A)) and hydrogenated polybutadiene (polymer block (B)) In a 1400 mL autoclave, 672 ml of dehydrated cyclohexane, 1.4 ml of THF and sec-butyllithium (1.15 M) -Cyclohexane solution) 1.73 ml of styrene was charged, 16.0 ml of styrene, 114 ml of butadiene, and 16.0 ml of styrene were successively added and polymerized at 50 ° C. to obtain polystyrene-b-polybutadiene-b-polystyrene (hereinafter referred to as SBS). Abbreviated as). The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained SBS is 76000, the 1,4-bond content determined from ¹ H-NMR measurement is 55.0%, and the content of styrene units is 29.0 mass. %Met.
After preparing a cyclohexane solution of the synthesized SBS and charging it into a pressure-resistant vessel with sufficient nitrogen substitution, a hydrogenation reaction was performed at 80 ° C. for 5 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. To obtain polystyrene-b-hydrogenated polybutadiene-b-polystyrene (hereinafter abbreviated as SEBS). When the hydrogenation rate of the obtained SEBS was calculated by ¹ H-NMR spectrum measurement, it was 99.5%.

Reference example 3
Production of block copolymer consisting of polystyrene (polymer block (A)) and polyisobutylene (polymer block (B))
A polystyrene-b-polyisobutylene-b-polystyrene triblock copolymer (hereinafter abbreviated as SiBuS) was produced according to a previously reported method (WO 98/14518). SiBuS having a number average molecular weight of 65,300 and a styrene unit content of 29.0% by mass was synthesized.

Reference example 4
Production of block copolymer comprising polystyrene (polymer block (A2)), hydrogenated polyisoprene (polymer block (B)) and poly (4-tert-butylstyrene) (polymer block (A1)) 1400 mL autoclave Were charged with 768 ml of dehydrated cyclohexane and 1.95 ml of sec-butyllithium (1.0 M-cyclohexane solution), and then 36.4 ml of 4-tert-butylstyrene, 11.3 ml of styrene, 107 ml of isoprene, 11.3 ml and 4 of styrene. Poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene-b-polystyrene-b-poly (36.4 ml of tert-butylstyrene was sequentially added and polymerized successively at 50 ° C. 4-tert-butylstyrene) (hereinafter tBS) Abbreviated as SIStBS). The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 104000, the 1,4-bond content determined from ¹ H-NMR measurement is 94.0%, and the content of styrene units is 11.3 mass. %, 4-tert-butylstyrene unit content was 44.0% by mass.
A cyclohexane solution of synthesized tBSSIStBS was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen. Then, a hydrogenation reaction was performed at 50 ° C. for 8 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. And poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (tBSSEPStBS) was obtained. The hydrogenation rate of the obtained tBSSEPStBS was calculated by ¹ H-NMR spectrum measurement and found to be 99.9%.

Reference Example 5
Production of block copolymer comprising polystyrene (polymer block (A2)), hydrogenated polyisoprene (polymer block (B)) and poly (4-tert-butylstyrene) (polymer block (A1)) 1L autoclave To this, 578 ml of dehydrated cyclohexane and 1.78 ml of sec-butyllithium (1.15 M-cyclohexane solution) were charged, and then 32.2 ml of 4-tert-butylstyrene, 13.5 ml of styrene, 81.6 ml of isoprene, and 13.5 ml of styrene. And 32.2 ml of 4-tert-butylstyrene are successively added and polymerized successively at 50 ° C. to obtain poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene-b-polystyrene-b-poly. (4-tert-butylstyrene) (tBSSIStB S) was synthesized. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 103600, the 1,4-bond content determined from ¹ H-NMR measurement is 94.0%, and the content of styrene units is 17.0 mass. %, 4-tert-butylstyrene unit content was 41.0% by mass.
A cyclohexane solution of synthesized tBSSIStBS was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen. Then, a hydrogenation reaction was performed at 50 ° C. for 8 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. And poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (tBSSEPStBS) was obtained. The hydrogenation rate of the obtained tBSSEPStBS was calculated by ¹ H-NMR spectrum measurement and found to be 99.9%.

Reference Example 6
Production of block copolymer comprising polystyrene (polymer block (A2)), hydrogenated polyisoprene (polymer block (B)) and poly (4-tert-butylstyrene) (polymer block (A1)). A 4 L autoclave was charged with 768 ml of dehydrated cyclohexane and 2.70 ml of sec-butyllithium (1.00 M-cyclohexane solution), and then 50.5 ml of 4-tert-butylstyrene, 16.5 ml of styrene, 72.0 ml of isoprene, 16 Poly (4-tert-butylstyrene) -b-polystyrene-b-polyisoprene-b-polystyrene-b by sequentially adding 5 ml and 50.5 ml of 4-tert-butylstyrene and polymerizing sequentially at 50 ° C. -Poly (4-tert-butylstyrene) (tBSSIS tBS) was synthesized. The number average molecular weight (GPC measurement, polystyrene conversion) of the obtained tBSSIStBS is 80970, the 1,4-bond content determined from ¹ H-NMR measurement is 94.0%, and the content of styrene units is 17.7 mass. %, 4-tert-butylstyrene unit content was 51.3% by mass.
A cyclohexane solution of synthesized tBSSIStBS was prepared and charged into a pressure-resistant vessel that had been sufficiently purged with nitrogen. Then, a hydrogenation reaction was performed at 50 ° C. for 8 hours in a hydrogen atmosphere using a Ni / Al Ziegler hydrogenation catalyst. And poly (4-tert-butylstyrene) -b-polystyrene-b-hydrogenated polyisoprene-b-polystyrene-b-poly (4-tert-butylstyrene) (tBSSEPStBS) was obtained. The hydrogenation rate of the obtained tBSSEPStBS was calculated by ¹ H-NMR spectrum measurement and found to be 99.9%.

Example 1
(1) Synthesis of sulfonated mSEBmS 70 g of the block copolymer (mSEBmS) obtained in Reference Example 1 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen, and then 563 ml of methylene chloride. And dissolved by stirring at 35 ° C. for 2 hours. After dissolution, a sulfonation reagent obtained by reacting 20.0 ml of acetic anhydride and 8.84 ml of sulfuric acid at 0 ° C. in 38.7 ml of methylene chloride was gradually added dropwise over 20 minutes. After stirring at 35 ° C. for 5 hours, 10 ml of distilled water as a stopper was added. Thereafter, 1.2 L of distilled water was slowly poured into the polymer solution with stirring to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.2 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and the polymer collected at the end was vacuum-dried to obtain sulfonated mSEBmS. The sulfonation rate of the benzene ring of the α-methylstyrene unit of the obtained sulfonated mSEBmS was 51.5 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.06 meq / g.

(2) Preparation of electrolyte membrane for fuel cell A 16.5% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated mSEBmS obtained in (1) was prepared, and the release-treated PET film [ (Toyobo Co., Ltd. “Toyobo Ester Film K1504”) was coated with a thickness of about 300 μm, dried at 25 ° C. for 2 hours, and then sufficiently dried by vacuum drying at 30 ° C. for 10 hours. A film having a thickness of 30 μm was obtained. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed by observation with a transmission electron microscope (TEM) that the benzene ring was stained with ruthenium tetroxide to form a co-continuous structure to a lamellar structure.

(3) Production of single cell for polymer electrolyte fuel cell An electrode for a polymer electrolyte fuel cell was produced by the following procedure. A 10% by mass aqueous dispersion of Nafion is added to and mixed with Pt-Ru alloy catalyst-supporting carbon so that the mass ratio of carbon to Nafion is 1: 1, and then n-propyl alcohol is added to water / n-propyl. The mixture was added and mixed until the alcohol mass ratio became 1/1 to prepare a uniformly dispersed paste. This paste was uniformly applied to one side of the carbon paper by a spray method. The electrode for anode was produced by drying at 130 ° C. for 30 minutes. Further, a 10% by mass solution of Nafion was added to and mixed with Pt catalyst-supporting carbon so that the mass ratio of carbon to Nafion was 1: 0.75, and then n-propyl alcohol was added to water / n-propyl alcohol. Was added and mixed until the mass ratio became 1/1, to prepare a uniformly dispersed paste, and a cathode electrode was produced in the same manner as the anode side. The fuel cell electrolyte membrane prepared in (2) is sandwiched between the two kinds of electrodes so that the membrane and the catalyst surface face each other, and the outside is sandwiched in sequence between two heat-resistant films and two stainless steel plates, A membrane-electrode assembly was produced by hot pressing (130 ° C., 20 kg / cm ² , 8 min). Next, the membrane-electrode assembly produced 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. An evaluation cell for a molecular fuel cell was produced.

Example 2
(1) Synthesis of Sulfonated SEBS A sulfonating reagent was prepared by reacting 14.8 ml of acetic anhydride and 6.62 ml of sulfuric acid at 0 ° C. in 29.6 ml of methylene chloride. On the other hand, 50 g of the block copolymer (SEBS) obtained in Reference Example 2 was vacuum-dried for 1 hour in a glass reaction vessel equipped with a stirrer and then purged with nitrogen. And stirred for 4 hours to dissolve. After dissolution, the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring at 35 ° C. for 8 hours, 10 ml of distilled water as a stopper was added. Thereafter, 1.3 L of distilled water was slowly poured into the polymer solution to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.3 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated SEBS. The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated SEBS was 53.5 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.32 meq / g. (2) Preparation of electrolyte membrane for fuel cell A 12.5% by weight toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated SEBS obtained in (1) was prepared, and a release-treated PET film [Toyobo Co., Ltd., “Toyobo Ester Film K1504 ]] Was coated at a thickness of about 550 μm, dried at 25 ° C. at room temperature for 2 hours, and then sufficiently dried by vacuum drying at 30 ° C. for 10 hours to obtain a film having a thickness of 30 μm. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed by observation with a transmission electron microscope (TEM) that the benzene ring was stained with ruthenium tetroxide to form a co-continuous structure to a lamellar structure.
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated SEBS was used.

Example 3
(1) Synthesis of Sulfonated SiBuS A sulfonating reagent was prepared by reacting 20.5 ml of acetic anhydride and 9.18 ml of sulfuric acid in 41.1 ml of methylene chloride at 0 ° C. On the other hand, 60 g of the block copolymer (SiBuS) obtained in Reference Example 2 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. Then, 597 ml of methylene chloride was added and the temperature was increased to 35 ° C. And stirred for 2 hours to dissolve. After dissolution, the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring at 35 ° C. for 4 hours, 10 ml of distilled water as a stopper was added. Thereafter, 1.3 L of distilled water was slowly poured into the polymer solution to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.3 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated SEBS. The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated SEBS was 40.0 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.00 meq / g.
(2) Preparation of Fuel Cell Electrolyte Membrane A 26 mass% toluene / isobutyl alcohol (mass ratio 7/3) solution of the sulfonated SiBuS obtained in (1) was prepared, and the release-treated PET film [(stock ) "Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd.], coated at a thickness of about 200 μm, dried at room temperature at 25 ° C for 2 hours, and then sufficiently dried by vacuum drying at 30 ° C for 10 hours. A film having a thickness of 30 μm was obtained. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed by observation with a transmission electron microscope (TEM) that the benzene ring was stained with ruthenium tetroxide to form a co-continuous structure to a lamellar structure.
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated SiBuS was used.

Example 4
(1) Synthesis of Sulfonated tBSSEPStBS A sulfonating reagent was prepared by reacting 10.7 ml of acetic anhydride and 4.77 ml of sulfuric acid at 0 ° C. in 21.3 ml of methylene chloride. On the other hand, 20 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 3 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. Then, 289 ml of methylene chloride was added, and the room temperature was 25 ° C. And stirred for 2 hours to dissolve. After dissolution, the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring for 72 hours at a room temperature of 25 ° C., 5 ml of distilled water as a stopper was added. Thereafter, 0.6 L of distilled water was slowly poured into the polymer solution to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 0.6 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated tBSSEPStBS was 100 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.00 meq / g.
(2) Preparation of Fuel Cell Electrolyte Membrane A 20% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated tBSSEPStBS obtained in (1) was prepared, and the release-treated PET film [(stock ) "Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd.] was coated at a thickness of about 250 µm, and dried at 80 ° C at room temperature for 4 minutes to obtain a membrane having a thickness of 30 µm. Regarding the phase structure of the obtained electrolyte membrane, a double cylinder structure was formed by observation with a transmission electron microscope (TEM) of a benzene ring stained with ruthenium tetroxide and a sulfonic acid group stained with lead acetate. It was confirmed that
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated tBSSEPStBS was used.

Example 5
(1) Synthesis of Sulfonated tBSSEPStBS A sulfonating reagent was prepared by reacting 31.9 ml of acetic anhydride and 14.2 ml of sulfuric acid at 0 ° C. in 63.7 ml of methylene chloride. On the other hand, 50 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 3 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. And stirred for 2 hours to dissolve. After dissolution, the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring for 72 hours at room temperature of 25 ° C., 10 ml of distilled water as a stopper was added. Thereafter, 1.0 L of distilled water was slowly poured into the polymer solution to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 1.0 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The sulfonation rate of the benzene ring of the styrene unit of the obtained sulfonated tBSSEPStBS was 99 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.47 meq / g.
(2) Preparation of electrolyte membrane for fuel cell A 17% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated tBSSEPStBS obtained in (1) was prepared, and the release-treated PET film [(stock ) "Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd.] with a thickness of about 300 μm and dried at 80 ° C. for 4 minutes at room temperature to obtain a 30 μm thick film. Regarding the phase structure of the obtained electrolyte membrane, a double cylinder structure was formed by observation with a transmission electron microscope (TEM) of a benzene ring stained with ruthenium tetroxide and a sulfonic acid group stained with lead acetate. It was confirmed that
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated tBSSEPStBS was used.

Comparative Example 1
(2) Preparation of electrolyte membrane for fuel cell A 3% by mass THF / MeOH (mass ratio 8/2) solution of the sulfonated mSEBmS prepared in (1) of Example 1 was prepared and placed on a polytetrafluoroethylene sheet. The film was cast at a thickness of about 1670 μm and dried at room temperature for 2 days to obtain a film having a thickness of 50 μm. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed that a cylinder to a co-continuous structure was formed by observing a benzene ring stained with ruthenium tetroxide by transmission electron microscope (TEM).
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated mSEBmS was used.

Comparative Example 2
(2) Production of Fuel Cell Electrolyte Membrane A membrane having a thickness of 50 μm was obtained by the same method as (2) of Comparative Example 1 except that the sulfonated SEBS produced in (1) of Example 2 was used. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed that a cylinder to a co-continuous structure was formed by observing a benzene ring stained with ruthenium tetroxide by transmission electron microscope (TEM).
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated SEBS was used.

Comparative Example 3
(2) Preparation of Fuel Cell Electrolyte Membrane A membrane having a thickness of 50 μm was obtained by the same method as (2) of Comparative Example 1 except that the sulfonated SiBuS prepared in (1) of Example 3 was used. Regarding the phase structure of the obtained electrolyte membrane, it was confirmed that a cylinder to a co-continuous structure was formed by observing a benzene ring stained with ruthenium tetroxide by transmission electron microscope (TEM).
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated SiBuS was used.

Comparative Example 4
(1) Synthesis of Sulfonated tBSSEPStBS A sulfonating reagent was prepared by reacting 18.8 ml of acetic anhydride and 8.39 ml of sulfuric acid in 37.5 ml of methylene chloride at 0 ° C. On the other hand, 30 g of the block copolymer (tBSSEPStBS) obtained in Reference Example 5 was vacuum-dried in a glass reaction vessel equipped with a stirrer for 1 hour and then purged with nitrogen. Then, 360 ml of methylene chloride was added, and the room temperature was 25 ° C. And stirred for 2 hours to dissolve. After dissolution, the sulfonation reagent was gradually added dropwise over 20 minutes. After stirring for 72 hours at room temperature of 25 ° C., 10 ml of distilled water as a stopper was added. Thereafter, 0.8 L of distilled water was slowly poured into the polymer solution to solidify and precipitate the polymer. The methylene chloride was removed by distillation at atmospheric pressure, followed by filtration. The solid content obtained by filtration was transferred to a beaker, 0.8 L of distilled water was added, and washing was performed with stirring, followed by filtration and recovery. This washing and filtration operation was repeated until there was no change in the pH of the washing water, and finally the polymer collected by filtration was vacuum dried to obtain sulfonated tBSSEPStBS. The sulfonation rate of the benzene ring of the styrene unit in the obtained sulfonated tBSSEPStBS was 99 mol% from ¹ H-NMR analysis, and the ion exchange capacity was 1.49 meq / g.
(2) Preparation of Fuel Cell Electrolyte Membrane A 25% by mass toluene / isobutyl alcohol (mass ratio 8/2) solution of the sulfonated tBSSEPStBS obtained in (1) was prepared, and the release-treated PET film [(stock ) "Toyobo Ester Film K1504" manufactured by Toyobo Co., Ltd.] was coated at a thickness of about 200 µm and dried at 80 ° C for 4 minutes at room temperature to obtain a 30 µm thick membrane. Regarding the phase structure of the obtained electrolyte membrane, a double cylinder structure was formed by observation with a transmission electron microscope (TEM) of a benzene ring stained with ruthenium tetroxide and a sulfonic acid group stained with lead acetate. It was confirmed that
(3) Production of single cell for polymer electrolyte fuel cell An evaluation cell for a polymer electrolyte fuel cell was produced in the same manner as in Example 1 (3) except that the sulfonated tBSSEPStBS was used.

Performance Test of Polymer Membrane of Examples and Comparative Examples as Electrolyte Membrane for Solid Polymer Type Fuel Cell In the following tests 1) to 3), the sulfonated block obtained in each Example or Comparative Example was used as a sample. A membrane prepared from a polymer was used.
1) Measurement of ion exchange capacity A sample was weighed (a (g)) in a glass container capable of being sealed, and an excess amount of a saturated aqueous sodium chloride solution was added thereto and stirred overnight. Hydrogen chloride generated in the system was titrated (b (ml)) with a 0.01N NaOH standard aqueous solution (titer f) using a phenolphthalein solution as an indicator. The ion exchange capacity was determined by the following formula.
Ion exchange capacity = (0.01 × b × f) / a
2) Measurement of proton conductivity A sample of 1 cm × 4 cm was sandwiched between a pair of gold electrodes and attached to an open cell. The measurement cell was installed in water at a temperature of 40 ° C., and proton conductivity was measured by an AC impedance method.
3) Measurement of film strength A sample was molded into a dumbbell shape having a narrow width of 4.0 mm, and was subjected to conditions of 25 ° C., relative humidity of 50%, and tensile speed of 500 mm / min using an Instron Japan 5566 type tensile tester. The breaking strength and elongation at break were measured. The 100% modulus was defined as the stress when the distance between marked lines with an interval of 10 mm was extended to 20 mm.

4) Power generation test of single cell for fuel cell A power generation test using the prepared single cell for polymer electrolyte fuel cell was conducted.
When 3M-MeOH aqueous solution is used as the fuel and oxygen is used as the oxidant, the cell temperature is set to 60 ° C. under the condition that the 3M-MeOH aqueous solution supply rate is 0.87 ml / min and the oxygen supply rate is 250 ml / min. And tested.
Further, when hydrogen is used as the fuel and oxygen is used as the oxidant, the supply rate of oxygen is 160 ml / min and the relative humidity is 100 under conditions of a hydrogen supply rate of 250 ml / min and a relative humidity of 100%. Tested at a cell temperature of 80 ° C. under the condition of% open to the atmosphere.

  The results of the performance test are shown in Table 1 below.

As a result of the performance test as a polymer electrolyte membrane, the power generation test of the single cells for polymer electrolyte fuel cells obtained in Examples 1 to 5 and Comparative Examples 1 to 4 was carried out for 50 hours, the cell was disassembled, and the MEA In Examples 1-5, the film and the electrode were not peeled, whereas in Comparative Examples 1-3, the morphology was a cylinder structure to a co-continuous structure, and the breaking strength was insufficient. In Comparative Example 4, the mass ratio of the polymer block (A) to the polymer block (B) is not within the scope of the present invention, and the proportion of the flexible polymer block (B) is small. Since the elongation at break was insufficient, a site where the membrane and the electrode were about to peel was confirmed.
From the above, it can be said that the polymer electrolyte membrane of the present invention is excellent in durability in a power generation test.

Claims (12)

  The polymer block (A) and the flexible polymer block (B) having an aromatic vinyl compound unit as a main repeating unit are constituent components, and the mass ratio of the polymer block (A) to the polymer block (B) is 65:35 to 10:90, containing a block copolymer having an ion conductive group in the polymer block (A) as a main component, and a tensile test at 25 ° C. and a tensile speed of 500 mm / min. The polymer electrolyte membrane for a polymer electrolyte fuel cell is characterized by having a 100% modulus of 15 MPa or less, a breaking strength of 15 MPa or more, and a breaking elongation of 300% or more.   The electrolyte membrane according to claim 1, wherein the polymer block (A) comprises a constraining block (A1) having substantially no ion conductive group and an ion conductive block (A2) having an ion conductive group. In the polymer block (A), the constraining block (A1) having substantially no ion conductive group is represented by the following general formula (I):

(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ^{2 to} R ⁴ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, but at least one of them is carbon. An ion conductive block (A2) having an ion conductive group is represented by the following general formula: (II)

(In the formula, Ar ¹ represents an aryl group having 6 to 14 carbon atoms which may have ¹ to 3 substituents, and R ⁵ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or 1 to 3). 3. The electrolyte membrane according to claim 2, comprising a polymer block having as a main repeating unit an aromatic vinyl-based compound unit represented by the following formula: an aryl group having 6 to 14 carbon atoms which may have one substituent.   The electrolyte membrane according to any one of claims 1 to 3, wherein a mass ratio of the polymer block (A1) and the polymer block (A2) of the block copolymer is 95: 5 to 20:80.   The flexible polymer block (B) is an alkene unit having 2 to 8 carbon atoms, a cycloalkene unit having 5 to 8 carbon atoms, a vinylcycloalkene unit having 7 to 10 carbon atoms, a conjugated diene unit having 4 to 8 carbon atoms, and carbon. A conjugated cycloalkadiene unit having 5 to 8 carbon atoms, a vinylcycloalkene unit having 7 to 10 carbon atoms in which part or all of the carbon-carbon double bond has been hydrogenated, a conjugated diene unit having 4 to 8 carbon atoms and carbon The electrolyte membrane according to any one of claims 1 to 4, which is a polymer block composed of at least one repeating unit selected from the group consisting of conjugated cycloalkadiene units of formula 5-8.   The flexible polymer block (B) is an alkene unit having 2 to 8 carbon atoms, a conjugated diene unit having 4 to 8 carbon atoms, and 4 to 8 carbon atoms in which some or all of the carbon-carbon double bonds are hydrogenated. The electrolyte membrane according to any one of claims 1 to 5, which is a polymer block comprising at least one repeating unit selected from conjugated diene units. (Wherein, M represents a hydrogen atom, an ammonium ion or an alkali metal ion) ion-conducting group is -SO ₃ M or _-PO 3 HM to any one of claims 1 to 6, a group represented by The electrolyte membrane described.   The electrolyte membrane according to any one of claims 1 to 7, wherein an ion exchange capacity of the block copolymer is 0.30 meq / g or more.   The electrolyte membrane according to any one of claims 1 to 8, wherein the electrolyte membrane is prepared by dissolving the electrolyte in an organic solvent, and then forming the membrane on a substrate and drying it. Production method.   10. The method for producing an electrolyte membrane according to claim 9, wherein the organic solvent is a mixed solvent of an aliphatic hydrocarbon and an alcohol.   The membrane-electrode assembly using the electrolyte membrane of any one of Claims 1-8. A polymer electrolyte fuel cell using the membrane-electrode assembly according to claim 11.