JP2003017090A - Polymer electrolyte membrane and fuel cell using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive polymer electrolyte membrane with high water resistance, high heat resistance, practical strength usable as a separator of a solid polymer electrolyte fuel cell. SOLUTION: This polymer electrolyte membrane is a composite material of a polymer electrolyte containing a block copolymer having one or more of blocks into which a sulfonic group is introduced and a block into which the sulfonic group is not practically introduced, and having at least one block among the whole blocks, which has an aromatic ring in the main chain; and a porous membrane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer electrolyte membrane,
Among them, the present invention relates to a polymer electrolyte membrane that is preferably used for fuel cells.

[0002]

2. Description of the Related Art In recent years, fuel cells have been attracting attention as a highly efficient and clean energy conversion device. Above all,
A polymer electrolyte fuel cell using a polymer membrane having proton conductivity as an electrolyte is attracting attention as a mobile power source for vehicles because it has a compact structure, high output, and can be operated with a simple system. ing.

As a proton-conducting polymer electrolyte used in a polymer electrolyte fuel cell, a perfluorosulfonic acid-based material such as Nafion (registered trademark of DuPont) has excellent characteristics as a fuel cell. Since then, it has been mainly used. However, since this material is very expensive, it is considered to be a big problem in widespread use of power generation systems using fuel cells in the future. Under these circumstances, the development of inexpensive polymer electrolytes that can replace perfluorosulfonic acid-based materials has become active in recent years. Among them, a material in which a sulfonic acid group is introduced into an aromatic polyether having excellent heat resistance and high film strength is considered to be promising.
No. 249 discloses a sulfonated polyetherketone type,
JP-A-10-45913 and JP-A-10-21
Japanese Patent Publication No. 943 describes a sulfonated polyether sulfone-based polymer electrolyte.

In these material systems, generally, the larger the amount of sulfonic acid groups introduced, the higher the proton conductivity, but at the same time, the water absorption of the polymer tends to increase. When used in a fuel cell, a film made of a highly water-absorbent polymer undergoes a large dimensional change due to the water produced during the use of the cell, causing internal stress at the bonding interface with the electrode and peeling. As a result, not only the fuel cell characteristics may not be expected, but also the strength of the membrane itself is greatly reduced by water absorption. If the strength is low, the polymer electrolyte membrane may break when it is installed in a polymer electrolyte fuel cell, water electrolysis device, etc., or the membrane may rupture due to the pressure difference between the two sides of the polymer electrolyte membrane after it is installed. There is a case that the sealing part of the torn.

On the other hand, in order to improve the membrane strength of the polymer electrolyte membrane, it has been proposed to combine a porous membrane or a non-woven fabric with the polymer electrolyte. For example, Japanese Patent Laid-Open No. 1-22932 discloses a membrane for a solid polymer electrolyte fuel cell,
A cation exchange membrane is disclosed in which pores of an ultrahigh molecular weight polyolefin porous membrane are filled with a cation exchange resin. Further, JP-A-6-29032 and JP-A-9-
Japanese Patent Publication No. 194609 discloses a cation exchange membrane using a fluorine-based resin typified by polytetrafluoroethylene as a base material resin.

However, the composite membrane using these cation exchange resins has a problem in water resistance and heat resistance of the ion exchange resin itself, and even if it is complexed with a porous membrane or a non-woven fabric, a solid polymer electrolyte fuel cell. It has not been possible to develop satisfactory properties as a diaphragm for use.

[0007]

The object of the present invention is to have excellent water resistance, high heat resistance, and practical strength which can be favorably used as a membrane of a solid polymer electrolyte fuel cell.
Another object is to provide an inexpensive polymer electrolyte membrane.

[0008]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have found that a composite membrane of a specific polymer electrolyte and a porous membrane is a solid polymer electrolyte fuel cell. They have found that they have a practical strength that can be favorably used as a diaphragm, and completed the present invention. That is, according to the present invention, each block has one or more blocks in which a sulfonic acid group is introduced and a block in which a sulfonic acid group is not substantially introduced, and at least one of all blocks has its main chain. A polymer electrolyte membrane comprising a polymer electrolyte containing a block copolymer having a block having an aromatic ring and a porous membrane, and a polymer electrolyte membrane using the membrane. A fuel cell is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail. The polymer electrolyte membrane of the present invention has at least one block in which a sulfonic acid group is introduced and a block in which a sulfonic acid group is not substantially introduced, and at least one block of all the blocks is It is a composite of a polymer electrolyte containing a block copolymer, which is a block having an aromatic ring in the main chain, and a porous membrane.

In the present invention, a block means a polymer in which two or more repeating units of one type are linked. Also,
The block copolymer refers to a polymer in which two or more blocks are directly bonded or bonded via a linking group, that is, a polymer including a plurality of blocks each composed of two or more kinds of repeating units.

In the present invention, the block having a sulfonic acid group introduced therein means that, in any part of the repeating units constituting the block, an average of 0.5 or more sulfonic acid groups (- A group represented by SO ₃ H) is bonded to the block. The binding form of the sulfonic acid group to the repeating unit constituting the block is not particularly limited, but those having a structure in which the sulfonic acid group is directly bonded to the aromatic ring are preferable because the synthesis is relatively easy.

On the other hand, in the present invention, the block in which the sulfonic acid group is not substantially introduced means a block in which the introduced amount of the sulfonic acid group per repeating unit constituting the block is 0.1 or less on average. Say.

In the present invention, the block having an aromatic ring in its main chain may be a block having the sulfonic acid group introduced or a block having substantially no sulfonic acid group introduced. Well, it may be both of these blocks.

In the present invention, examples of the block having a sulfonic acid group introduced therein include polystyrene and poly (α
-Methylstyrene), poly (allylphenyl ether), poly (phenylglycidyl ether), poly (phenylene ether), polyphenylene sulfide, polyether ether ketone, polyether ether sulfone, polysulfone, poly (phenylmethyl siloxane), poly (diphenyl) A block in which a sulfonic acid group is introduced into a block made of siloxane), poly (phenylmethylphosphazene), poly (diphenylphosphazene), an epoxy resin, or the like can be given. Above all, preferably, a sulfonic acid group is introduced into a block having a repeating unit represented by the following general formula [1], a block having a repeating unit represented by the following general formula [2], or a block made of an epoxy resin. Blocks are used.

[0015] [1] (In the formula [1], X represents —O—, —S—, —NH—, or a direct bond, R ¹ is an alkyl group having 1 to 6 carbon atoms, or 1 to 6 carbon atoms. Represents an alkoxy group or a phenyl group, and a is an integer of 0 to 3. When there are a plurality of R ¹ , they may be the same or different.

[0016] [2] (In the formula [2], Ar ¹ represents a group selected from the following structures.) (In the above formula, R ² represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a phenoxy group, b is an integer of 0 to 4, and c is 0 to 0.
It is an integer of 6. When there are a plurality of R ^2's , these may be the same or different.

Examples of the block having a repeating unit represented by the general formula [1] include poly (phenylene), poly (aniline), poly (phenylene ether), poly (phenylene sulfide), and the like.

Among them, in the general formula [1], X is —O—
The poly (phenylene ether) represented by is preferable, and specifically, poly (1,4-phenylene ether), poly (2-methyl-1,4-phenylene ether), poly (2,6-dimethyl-1). , 4-phenylene ether),
Poly (2-phenyl-1,4-phenylene ether),
Poly (2,6-diphenyl-1,4-phenylene ether), poly (2-methyl-1,3-phenylene ether), poly (2,6-dimethyl-1,3-phenylene ether), poly (2- Phenyl-1,3-phenylene ether), poly (2,6-diphenyl-1,3-phenylene ether), and the like. Among these, poly (1,4-phenylene ether), poly (2-phenyl) -1,4-phenylene ether) and poly (2,6-diphenyl-1,4-phenylene ether) are more preferable, and poly (2-phenyl-1,4-phenylene ether) is further preferable.

The block precursor having the repeating unit represented by the general formula [1] can be produced by a known method. For example, in the case of poly (phenylene ether), an oxidative polymerization method in which phenol is oxidized in the presence of a catalyst,
It can be produced by a method of condensing a halogenated phenol with a catalyst in the presence of an alkali (called Ullmann reaction).
Here, the block precursor refers to a homopolymer having a reaction site, which becomes a block by a copolymerization reaction (the same applies hereinafter).

On the other hand, the block precursor having the repeating unit represented by the above general formula [2] is, for example, the following formula.

[Chemical 1] It is obtained by ring-opening polymerization of a glycidyl ether having an aromatic ring represented by

Specifically, phenyl glycidyl ether, o-toluyl glycidyl ether, m-toluyl glycidyl ether, p-toluyl glycidyl ether,
2,3-dimethylphenyl glycidyl ether, 2,4
-Dimethylphenylglycidyl ether, 2,5-dimethylphenylglycidyl ether, 2,6-dimethylphenylglycidyl ether, 2,3,4-trimethylphenylglycidyl ether, 2,4,6-trimethylphenylglycidyl ether, 2,3 4,6-Tetramethylphenylglycidyl ether, 2-ethylphenylglycidyl ether, 4-ethylphenylglycidyl ether, 2-propylphenylglycidyl ether, 4
-N-propylphenyl glycidyl ether, 4-propylphenyl glycidyl ether, 2-butylphenyl glycidyl ether, 4-butylphenyl glycidyl ether, 4-i-propylphenyl glycidyl ether, 2-biphenyl glycidyl ether, 4-biphenyl glycidyl ether, 1-naphthyl glycidyl ether, 2-naphthyl glycidyl ether, etc. are mentioned. These may be used alone or as a copolymer using a plurality of glycidyl ethers.

If necessary, it is also possible to use a block precursor obtained by copolymerizing the above-mentioned glycidyl ether having an aromatic ring and an epoxy compound containing no aromatic ring. As the epoxy compound containing no aromatic ring, for example, ethylene oxide, propylene oxide, 1,2-
Epoxy butane, cyclohexane epoxide, epifluorohydrin, epichlorohydrin, epibromohydrin, trifluoropropylene oxide, methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether and the like can be mentioned. When such a copolymer is used as one component of the block, the heat resistance of the whole is lowered when the ratio of the epoxy component is high. Therefore, the glycidyl ether component having an aromatic ring is preferably 60% by weight or more. It is more preferable that the content is at least wt%.

A number of methods are known for ring-opening polymerization of glycidyl ether having an aromatic ring or an epoxy compound containing no aromatic ring, and any of these known polymerization methods can be used. General formula [2]
The number of repeating units represented by is preferably 2 to 20
The number is 0, and more preferably 5 to 50.

On the other hand, the block made of the above-mentioned epoxy resin means a block whose precursor is a resin (epoxy resin) having one or more epoxy groups in the molecule. However, even if the epoxy resin is not used as a precursor, a block in the form is included as a result. Among the blocks composed of an epoxy resin, a block composed of an epoxy resin having an aromatic ring in its main chain is more preferred, and a block having a repeating unit represented by the following general formula [3] is even more preferred. [3] In the formula [3], Ar ² represents a group selected from the following structures. (In the above formula, R ³ represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, d is an integer of 0 to 3, and e is an integer of 0 to 2. When there are a plurality of R ³ , these may be the same or different, Y is —O—, —S—, an alkylene group having 1 to 20 carbon atoms, a halogenated alkylene having 1 to 10 carbon atoms. Represents a group or an alkylenedioxy group having 1 to 20 carbon atoms. When there are a plurality of Zs, these may be the same or different.)

The epoxy resin having a repeating unit represented by the general formula [3] can be synthesized by a generally known method for synthesizing an epoxy resin. For example,
A method of reacting a diol compound represented by HO-Ar ² -OH with epichlorohydrin in the presence of alkali,
A method of reacting a diol compound and a diglycidyl ether compound can be mentioned.

Specific examples of the diol compound represented by HO-Ar ² -OH include hydroquinone, resorcinol, catechol, 1,2-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 2, 6-dihydroxynaphthalene,
2,7-dihydroxynaphthalene, 4,4'-dihydroxybiphenyl, 2,4'-dihydroxybiphenyl,
2,2'-dihydroxybiphenyl, 4,4'-dihydroxydiphenylmethane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4- Hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1- Bis (4-hydroxyphenyl) -1
-Phenylethane, bis (4-hydroxyphenyl) diphenylmethane, 9,9-bis (4-hydroxyphenyl) fluorene, α, α'-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene, 4,4 ' −
Dihydroxydiphenyl ether, 2,2′-dihydroxydiphenyl ether, bis (4-hydroxyphenyl) sulfide, bis (2-hydroxyphenyl) sulfide, 1,2-bis (4-hydroxyphenyl) ethane, 1,2-bis (4- Hydroxyphenoxy) ethane, 1,2-bis (3-hydroxyphenoxy) ethane, 1,2-bis (4-hydroxyphenoxy) propane, 1,3-bis (4-hydroxyphenoxy) propane, 1,4-bis ( 4-hydroxyphenoxy) butane, 1,6-bis (4-hydroxyphenoxy) hexane, diethylene glycol bis (4-hydroxyphenyl) ether and the like can be mentioned.

The number of repeating units constituting a block made of an epoxy resin having a repeating unit represented by the general formula [3] is preferably 2 to 200, more preferably 4 to 50.

The polyelectrolyte in the present invention has one or more blocks each having a sulfonic acid group introduced therein and one block having substantially no sulfonic acid group introduced therein. As the block in which is not substantially introduced, a block made of an aromatic polyether having a repeating unit represented by the general formula [4] is preferable because it has high heat resistance.

[0029] [4] In the general formula [4], R ⁴ represents an alkyl group having 1 to 6 carbon atoms, and f is an integer of 0 to 4. When there are a plurality of R ^4's, these may be the same or different. Z
It is -CO- or -SO ₂ - represent. Specific examples include blocks made of polyetherketone and blocks made of polyethersulfone.

Among them, Z in the general formula [4] is --SO.
_{A 2-} polyether sulfone is more preferable because it has high solubility in a solvent. Polyethersulfone, which is an example of the precursor of the block represented by the general formula [4], is synthesized by, for example, polycondensing 4,4′-dihydroxydiphenylsulfone and 4,4′-dichlorodiphenylsulfone. You can The weight average molecular weight of the block precursor composed of polyethersulfone is 2000 to 500.
000 is preferable, and more preferably 2000-5000.
00, and more preferably 8000 to 10000
It is 0, and particularly preferably 8000 to 100,000 is used. When the molecular weight is less than 2000, the film strength and heat resistance of the copolymer may be lowered, and when the molecular weight is more than 500000, the solubility may be lowered.

Next, the method for producing the polymer electrolyte according to the present invention will be described. The method for producing a block copolymer by chemically bonding two or more kinds of block precursors is not particularly limited, and a suitable known method can be used depending on the combination of the respective blocks.

For example, poly (phenylene ether), which is an example of the precursor of the block represented by the general formula [1],
When a polyether sulfone, which is an example of the precursor of the block represented by the general formula [4], is bonded, a poly (phenylene ether) having a hydroxyl group remaining at the terminal and a polyether sulfone having a halogen remaining at the terminal are present in an alkali. The method of condensing below is mentioned. Further, in the case of binding a poly (phenylene ether) having a hydroxyl group remaining at the terminal and a polyether sulfone having a hydroxyl group remaining at the terminal,
4,4'-difluorobenzophenone or 4,4'-
It is also possible to use a dihalogen compound such as dichlorodiphenyl sulfone as a linking agent and bond them by the same condensation reaction.

On the other hand, poly (phenylglycidyl ether) which is an example of the precursor of the block represented by the general formula [2] and polyether sulfone which is an example of the precursor of the block represented by the general formula [4] are prepared. When binding, by converting the terminal hydroxyl group of the polyethersulfone having a hydroxyl group at the terminal to an alkali metal phenolate, ring-opening polymerization of a glycidyl ether containing an aromatic ring as a polymerization initiation point is performed, and then sulfonation is performed. Can be synthesized.

Further, a block precursor obtained by copolymerizing a halogen-containing glycidyl ether, which can be used in a blocking reaction such as epichlorohydrin, with phenylglycidyl ether was first synthesized, and then polyether sulfone having a hydroxyl group remaining at the terminal was synthesized. Examples thereof include a method of condensing and in the presence of an alkali.

Further, when an epoxy resin, which is an example of the precursor of the block represented by the general formula [3], and a polyether sulfone which is an example of the precursor of the block represented by the general formula [4] are combined, There may be mentioned a method in which the glycidyl group remaining at the terminal of the epoxy resin is ring-opened and added to the hydroxyl group remaining at the terminal of the polyether sulfone to bond it.

When polyethersulfone is used as one of the block precursors, the block copolymerization reaction can be carried out in a molten state without using a solvent, but is preferably carried out in a suitable solvent. As the solvent, aromatic hydrocarbon solvents, ether solvents, ketone solvents, amide solvents, sulfone solvents, sulfoxide solvents and the like can be used, but amide solvents are preferable because of high solubility. Here, as the amide solvent, N,
Examples include N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and the like. The reaction temperature of the block copolymerization reaction is preferably 20 ° C to 250 ° C,
More preferably, it is 50 ° C to 200 ° C.

In the block copolymer used in the present invention, it is preferable that the block in which the sulfonic acid group is not substantially introduced is 60 to 95% by weight, and 70 to 90% by weight based on the whole block copolymer. It is more preferable that there is. If the block in which the sulfonic acid group is not substantially introduced is more than 95% by weight, sufficient performance as a polymer electrolyte is obtained because the sulfonic acid equivalent in the block copolymer after introducing the sulfonic acid group is small. If it is less than 60% by weight, the water resistance of the block copolymer after introduction of the sulfonic acid group may decrease.

In the block copolymer used in the present invention, the method of introducing the sulfonic acid group into a specific block is not particularly limited, but (a) the block precursor in which the sulfonic acid group is previously introduced and the sulfonic acid group are A method of copolymerizing a precursor of a block into which substantially no sulfonic acid groups have been introduced, and (b) a copolymer comprising a block into which sulfonic acid groups have been introduced and a block into which sulfonic acid groups have not been substantially introduced. , A method of selectively introducing sulfonic acid into a block of the copolymer into which a sulfonic acid group is introduced. In the block precursor into which the sulfonic acid group has been introduced, the method (b) is preferable because the sulfonic acid group may inhibit the copolymerization reaction. In the method (a), the block precursor having a sulfonic acid group introduced therein can be produced, for example, by sulfonation of the block precursor. As a sulfonating agent, the concentration is 90
A known sulfonating agent such as sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or SO ₃ can be used in an amount of at least%.

As a method for selectively introducing a sulfonic acid group into the copolymer by the method (b), (c) the sulfonic acid group is present in the block into which the sulfonic acid group is introduced, and the sulfonic acid group is substantially present. Functional groups that are not present in the unintroduced block can be utilized. As another method,
(D) It is considered to utilize the difference in reactivity for the sulfonation reaction between the block into which the sulfonic acid group is introduced and the block into which the sulfonic acid group is not substantially introduced.

As an example of the method (d), a block precursor having a repeating unit represented by the general formula [1], [2] or [3] of the present invention (2) and a general formula [ 4] and a precursor of a block having a repeating unit represented by the formula [4] to produce a block copolymer, and then sulfonate the copolymer to produce a polymer electrolyte. For example, in the sulfonation reaction of an aromatic ring using sulfuric acid as a sulfonating agent, a compound of the general formula [4]
It is known that the aromatic ring of the block having the repeating unit represented by is less reactive than the aromatic ring of the block having the repeating unit represented by the general formula [1], [2] or [3]. There is. Therefore, the precursor of the block having the repeating unit represented by the general formula [4] is reacted with the precursor of the block having the repeating unit represented by the general formula [1], [2], or [3]. The resulting block copolymer is sulfonated with sulfuric acid under appropriate conditions to selectively introduce a sulfonic acid group into a block having a repeating unit represented by the general formula [1], [2], or [3]. It is possible to produce a block copolymer in which a sulfonic acid group is not substantially introduced into the block represented by the general formula [4].

In the step of sulfonation (introducing a sulfonic acid group), a known sulfonating agent such as sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or SO ₃ having a concentration of 90% or more is used as the sulfonating agent. You can Among these, sulfuric acid having a concentration of 90% or more is preferable,
More preferred is 99 wt% sulfuric acid. In order that the sulfonation reaction of the block copolymer proceeds in a homogeneous system,
A small amount of an organic solvent that does not participate in the sulfonation reaction may be added together with sulfuric acid. These organic solvents are not included in the weight percent values for sulfuric acid noted above.

Dissolution of the block copolymer in sulfuric acid and sulfonation proceed simultaneously, and the reaction is usually completed in 2 to 20 hours at room temperature to form a uniform solution. The sulfonated block copolymer can be recovered by pouring a sulfuric acid solution into a large amount of water. The concentration of the block copolymer with respect to sulfuric acid is
It is preferably 1 to 50% by weight, more preferably 5 to 30% by weight. The reaction temperature is preferably 0 ° C to 80 ° C, more preferably 20 ° C to 40 ° C.

Thus, the polymer electrolyte is produced,
The polyelectrolyte in the present invention may also contain additives such as plasticizers, stabilizers, release agents and the like used for ordinary polymers within the range not deviating from the object of the present invention. Further, the polymer electrolyte in the present invention may have an intermolecular crosslinked structure introduced within a range not deviating from the object of the present invention.

The precursors of the blocks having the repeating units represented by the general formulas [1] to [4] are inexpensive materials which have been already used in large amounts and have already been prepared by synthetic techniques. A copolymer synthesized using this as a raw material and further sulfonated is also very inexpensive as compared with a fluorine-based material such as Nafion.

The polymer electrolyte membrane of the present invention is characterized in that the polymer electrolyte containing the above block copolymer and the porous membrane are combined. Here, the porous membrane used in the present invention serves as a base material for impregnating the polymer electrolyte, and is used for further improving the strength, flexibility and durability of the polymer electrolyte. Therefore, it can be used regardless of its shape or material as long as it meets the above purpose of use, but in consideration of good use as a membrane of a solid polymer electrolyte fuel cell, the shape of the porous membrane Has a film thickness of 1 to 100 μm, preferably 3
˜30 μm, more preferably 5 to 20 μm, pore size 0.01 to 10 μm, preferably 0.02 to 7 μm, and porosity 20 to 98%, preferably 30 to 95%.
If the thickness of the porous film is too thin, the effect of reinforcing the strength after compounding or the reinforcing effect of imparting flexibility and durability becomes insufficient, and gas leakage (cross leak) easily occurs. If the film thickness is too thick, the electric resistance will be high, and the obtained composite membrane is not preferable as a diaphragm for a polymer electrolyte fuel cell. On the other hand, if the pore size is too small, impregnation with the polymer solid electrolyte becomes very difficult, and if it is too large, the reinforcing effect on the polymer solid electrolyte becomes weak. If the porosity is too small, the resistance as a solid electrolyte membrane increases, and if it is too large, the strength of the porous membrane itself generally weakens and the reinforcing effect cannot be obtained. In addition, as the material of the porous film, an aliphatic polymer or a fluorine-containing polymer is preferable from the viewpoint of heat resistance and the effect of reinforcing physical strength.

Here, examples of the aliphatic polymer that can be preferably used include polyethylene, polypropylene, and ethylene-propylene copolymer, but are not limited thereto. The polyethylene referred to here is an ethylene-based polymer having a crystal structure of polyethylene, and includes, for example, a copolymer of ethylene and another monomer, and is specifically a linear low-density polyethylene (LLDP).
E), a copolymer of ethylene and an α-olefin, and the like are included. The polypropylene referred to here is a propylene-based polymer having a polypropylene crystal structure, and is a commonly used propylene-based block copolymer, random copolymer, etc. (These are copolymers with ethylene, 1-butene, etc. Is included).

As the fluorine-containing polymer, a known thermoplastic resin having at least one carbon-fluorine bond in the molecule is used without limitation. Usually, an aliphatic polymer having a structure in which all or most of the hydrogen atoms are replaced by fluorine atoms is preferably used.

Examples of suitable fluorine-based resins are polytrifluoroethylene, polytetrafluoroethylene, polychlorotrifluoroethylene, poly (tetrafluoroethylene-hexafluoropropylene), poly (tetrafluoroethylene-perfluoroalkyl). Ether), polyvinylidene fluoride and the like, but are not limited thereto. Of these, in the present invention, polytetrafluoroethylene and poly (tetrafluoroethylene-hexafluoropropylene) are preferable,
Polytetrafluoroethylene is particularly preferable. Further, these fluororesins preferably have an average molecular weight of 100,000 or more in terms of good mechanical strength.

The polymer electrolyte membrane of the present invention is a polymer electrolyte membrane obtained by combining the above-mentioned polymer electrolyte and the above-mentioned porous membrane. The composite method is not particularly limited, for example, a method of obtaining a composite membrane by impregnating a porous membrane in a polymer electrolyte solution, taking out the porous membrane and then drying the solvent, or a polymer electrolyte solution in the porous membrane. To obtain a composite membrane by drying the solvent, contacting the polymer electrolyte solution with the porous membrane under reduced pressure, and then returning to normal pressure to impregnate the solution into the pores of the porous membrane and dry the solvent. And a method for obtaining a composite membrane.

The solvent used for preparing the polymer electrolyte solution is not particularly limited as long as it can dissolve the polymer electrolyte and can be removed thereafter. For example, N,
Aprotic polar solvents such as N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethylsulfoxide, and chlorine-based solvents such as dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene and dichlorobenzene. Alcohols such as methanol, ethanol and propanol, and alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether are preferably used. These may be used alone, or may be used as a mixture of two or more kinds of solvents, if necessary.
Among them, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide are preferable because they have high polymer solubility.

The polymer electrolyte membrane of the present invention, which is a composite of a polymer electrolyte and a porous membrane, has improved strength, flexibility and durability of the polymer electrolyte, and is a membrane of a solid polymer electrolyte fuel cell. Can be used as well.

When the polymer electrolyte membrane of the present invention is used in a fuel cell, the thickness of the polymer electrolyte membrane is not particularly limited, but 3
-200 micrometers is preferable, 4-100 micrometers is more preferable, 5-50 micrometers is still more preferable. If the film thickness of the polymer electrolyte membrane is too thin, the film strength for practical use cannot be obtained, and if the film thickness is too thick, the electrical resistance becomes high, which is not preferable as a membrane for a polymer electrolyte fuel cell. The film thickness can be controlled by appropriately selecting the thickness of the porous membrane, the concentration of the polymer electrolyte solution, or the coating thickness of the polymer electrolyte solution on the porous membrane.

Next, the fuel cell of the present invention will be described.
The fuel cell of the present invention comprises the polymer electrolyte membrane provided by the present invention, and is produced by bonding a conductive substance as a catalyst and a current collector to both surfaces of the polymer electrolyte membrane. can do. As the catalyst,
There is no particular limitation as long as it can activate the redox reaction with hydrogen or oxygen, and known materials can be used, but it is preferable to use platinum fine particles. The platinum fine particles are preferably used by being supported on a particulate or fibrous carbon such as activated carbon or graphite. Known materials can be used for the conductive substance as the current collector, but porous carbon woven cloth or carbon paper is preferable for efficiently transporting the raw material gas to the catalyst. For the method of joining platinum fine particles or carbon carrying platinum fine particles to a porous carbon woven cloth or carbon paper, and the method of joining it to a polymer electrolyte film, see, for example, J. Electro
chem. Soc. : Electrochemical
al Science and Technology
y, 1988, 135 (9), 2209 and other known methods can be used.

[0054]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples.

Production Example 1 Production Example of Polymer Electrolyte (P1) 99 mg of anhydrous cuprous chloride and 266 mg of 2-methylbenzoxazole were stirred in 1 ml of toluene at room temperature in the air for 15 minutes. To this, 8.5 g of 2-phenylphenol and 30 ml of toluene were added, and the mixture was stirred at 50 ° C. for 5 hours in an oxygen atmosphere. After the reaction was completed, it was poured into methanol containing hydrochloric acid to precipitate a polymer, which was filtered and dried to obtain poly (2-phenylphenylene ether) (hereinafter referred to as PE1).
Add Sumika Excel PE to a flask equipped with an azeotropic distillation unit.
Add 3.0 g of S5003P (Sumitomo Chemical Co., Ltd. hydroxyl group terminated polyether sulfone), 0.75 g of PE1, 0.04 g of potassium carbonate, 15 ml of N, N-dimethylacetamide (hereinafter referred to as DMAc) and 3 ml of toluene, and heat. After stirring and dehydration under the azeotropic condition of toluene and water, toluene was distilled off. 0.05 g of 4,4'-difluorobenzophenone was added thereto, and the mixture was heated and stirred at 160 ° C for 5 hours. The reaction solution was added dropwise to a large amount of hydrochloric acid-acidic methanol, and the obtained precipitate was collected by filtration and dried under reduced pressure at 80 ° C. to obtain 3.8 g of a block copolymer.

2 g of the obtained block copolymer was stirred with 20 ml of 98% sulfuric acid at room temperature to form a uniform solution, and the stirring was continued for another 2 hours. The obtained solution was dropped into a large amount of ice water, and the obtained precipitate was collected by filtration. Further, the mixer was repeatedly washed with ion-exchanged water until the washing liquid became neutral, and then dried under reduced pressure at 40 ° C. to obtain a sulfonated block copolymer. Hereinafter, the polyelectrolyte (P
It may be abbreviated as 1).

Production Example 2 Production Example of Polymer Electrolyte (P2) Using the same catalyst as in Production Example 1 and using chlorobenzene as a solvent, 12.25 g of 2-phenylphenol and 4,4 ′ were prepared.
-Oxidative polymerization of 1.49 g of dihydroxybiphenyl as a monomer to give poly (2-
Phenylphenylene ether) (hereinafter referred to as PE2) was obtained. In a flask equipped with an azeotropic distillation apparatus, 50 g of Sumika Excel PES5003P and 0.36 of potassium carbonate were added.
g, 180 ml of DMAc and 25 ml of toluene were added. The system was replaced with nitrogen, and the mixture was heated and stirred for 2 hours under the azeotropic condition of toluene and water for dehydration, and then toluene was distilled off. Here, 4,4'-difluorobenzophenone 9.5
g was added, and the mixture was heated with stirring at 160 ° C. for 5 hours. The reaction solution was added dropwise to a large amount of methanol, and the produced precipitate was collected by filtration. The resulting precipitate was washed with a large amount of acetone under heating under reflux with stirring for 5 hours, and then taken out from acetone,
After drying under reduced pressure at 80 ° C., 45 g of chain-end fluorinated polyether sulfone was obtained.

A flask equipped with an azeotropic distillation apparatus was charged with 0.7
5 g PE2, potassium carbonate 0.03 g, DMAc15
ml and 3 ml of toluene were added. After dehydration under the azeotropic condition of toluene and water, toluene was distilled off. 3 g of the chain-end fluorinated polyether sulfone obtained above was added thereto, and the mixture was heated and stirred at 160 ° C. for 5 hours. The reaction solution was added dropwise to a large amount of acidic methanol with hydrochloric acid, and the obtained precipitate was collected by filtration and dried under reduced pressure at 40 ° C. to obtain 3.6 g of a block copolymer. The block copolymer thus obtained was used in Example 1.
In the same manner as above, sulfonation was performed using 98% sulfuric acid to obtain a sulfonated block copolymer. Hereinafter, the polymer electrolyte may be abbreviated as (P2).

Preparation Example 3 Preparation Example of Polymer Electrolyte (P3) 99 mg of anhydrous cuprous chloride and 65 mg of N, N, N ', N'-tetramethyl-1,3-propanediamine in 5 ml of chlorobenzene at room temperature in the atmosphere. It was stirred for 15 minutes. To this, 4.43 g of 2,6-diphenylphenol, 4,4'-
0.37 g of dihydroxybiphenyl and 1 of chlorobenzene
5 ml was added, and the mixture was stirred at 60 ° C. for 5 hours in an oxygen atmosphere.
After completion of the reaction, the polymer is poured into methanol containing hydrochloric acid to precipitate the polymer, which is filtered and dried to obtain poly (2
6-diphenylphenylene ether) (hereinafter referred to as PE3) was obtained. Sumika Excel PES5003P 8.0
g, PE3 2.0 g, potassium carbonate 0.2 g, 4,
0.26 g of 4'-difluorobenzophenone, DMAc
The reaction was carried out in the same manner as in Example 1 using 50 ml of toluene and 5 ml of toluene to obtain 9.8 g of a block copolymer. The obtained block copolymer is sulfonated with 98% sulfuric acid,
A sulfonated block copolymer was obtained. Hereinafter, the polymer electrolyte may be abbreviated as (P3).

Example 1 A composite of a polymer electrolyte (P1) and a polyethylene porous membrane
Production of a polymer electrolyte membrane obtained by dissolving P1 in N, N-dimethylacetamide (hereinafter, sometimes abbreviated as DMAc) at a concentration of 15% by mass, and fixing the P1 on a glass plate. Thickness 9μ
m, porosity 36%, pore diameter 0.04 μm).
The solvent was dried under normal pressure to obtain the intended polymer electrolyte membrane.

Example 2 Polymer electrolyte (P1) and polytetrafluoroethylene
Production of Polymer Electrolyte Membrane Composed of Composite with Porous Membrane Polytetrafluoroethylene Porous Membrane (Film Thickness 15 μm, Void) Dissolved P1 at a Concentration of 15% by Mass in a Mixed Solvent of Methanol / Dichloromethane Rate 90
%, Pore diameter 3.0 μm). The solvent was dried under normal pressure to obtain the intended polymer electrolyte membrane.

Examples 3, 4 Polymer electrolyte (P2) or (P3)
A polymer electrolyte formed by combining a fluoroethylene porous membrane
Production of Degraded Membrane By the same method as in Example 2, a polymer electrolyte membrane obtained by compounding the polymer electrolyte (P2) and a polytetrafluoroethylene porous membrane, or (P3) and a polytetrafluoroethylene porous membrane. A polymer electrolyte membrane was prepared by combining with the membrane.

Comparative Example 1 Production of Membrane Made of Polymer Electrolyte (P1) P1 was dissolved in DMAc at a concentration of 15 mass% and cast on a glass plate. The solvent was dried under normal pressure to obtain the intended polymer electrolyte membrane.

Comparative Examples 2 and 3 Preparation of a membrane composed of the polymer electrolyte (P2) or (P3)
In the same manner as in Comparative Example 1, the polymer electrolyte P2 or P3 was added to 1
It was dissolved in DMAc at a concentration of 5% by mass and cast on a glass plate. The solvent was dried under normal pressure to obtain the intended polymer electrolyte membrane.

Measurement of Proton Conductivity Proton conductivity was measured in a constant temperature and high temperature bath at 80 ° C. and 90% R.
SI1260 type high performance impedance under H condition
Gain / face analyzer (IMPEDANCE / GAIN-PHASE A
NALYZER, manufactured by solartoron) and 1287 type potentiostat (ELECTROCHEMICAL INTERFACE, manufactured by solartoron) were used to measure by the AC impedance method. The unit is S / cm.

Measurement of Water Absorption Rate The polymer electrolyte membrane was immersed in ion-exchanged water and boiled at 100 ° C. for 2 hours, and then the polymer electrolyte membrane was taken out from the ion-exchanged water. After wiping off the surface water, HR7
Type 3 Halogen Moisture Analyzer, MET
The water content was measured using TLER TOLEDO). (Water content) = 100 × {(water absorption film weight) − (dry film weight)} / (dry film weight)

Evaluation of Fuel Cell Characteristics A platinum catalyst supported on fibrous carbon and a porous carbon woven cloth as a current collector were bonded to both sides of the polymer electrolyte membrane. Humidified oxygen gas was supplied to one surface of the unit and humidified hydrogen gas was supplied to the other surface, and the power generation characteristics of the joined body were measured.

The proton conductivity and water absorption of the polymer electrolyte membranes obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were measured. The results are summarized in Table 1 below.

Table 1

Fuel cell characteristics of the polymer electrolyte membranes obtained in Examples 1 to 4 were evaluated. The operation and stop operations were repeated and evaluated for one week, but no deterioration in fuel cell characteristics or gas leak was observed. On the other hand, when the same fuel cell characteristic evaluation was performed on the polymer electrolyte membranes obtained in Comparative Examples 1 to 3, after one week, gas leaks occurred and deterioration of the characteristics was observed.

[0071]

EFFECTS OF THE INVENTION According to the present invention, each block has at least one block into which a sulfonic acid group is introduced and one block into which a sulfonic acid group is not substantially introduced, and at least one block among all blocks. There is provided a novel polymer electrolyte membrane comprising a polymer electrolyte containing a block copolymer, which is a block having an aromatic ring in its main chain, and a porous membrane. Since the polymer electrolyte membrane has high heat resistance and excellent water resistance and durability, it can be favorably used as a membrane of a solid polymer electrolyte fuel cell.

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[Procedure amendment]

[Submission date] May 22, 2002 (2002.5.2)
2)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Among them, Z in the general formula [4] is --SO.
_{A 2-} polyether sulfone is more preferable because it has high solubility in a solvent. Polyethersulfone, which is an example of the precursor of the block represented by the general formula [4], is synthesized by, for example, polycondensing 4,4′-dihydroxydiphenylsulfone and 4,4′-dichlorodiphenylsulfone. You can The weight average molecular weight of the block precursor composed of polyethersulfone is 2000 to 500.
000, more preferably from 8 000-1000
No. 00 is used. When the molecular weight is less than 2000, the film strength and heat resistance of the copolymer may be lowered, and when the molecular weight is more than 500000, the solubility may be lowered.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction content]

2 g of the obtained block copolymer was stirred with 20 ml of 98% sulfuric acid at room temperature to form a uniform solution, and the stirring was continued for another 2 hours. The obtained solution was dropped into a large amount of ice water, and the obtained precipitate was collected by filtration. Further, the mixer was repeatedly washed with ion-exchanged water until the washing liquid became neutral, and then dried under reduced pressure at 40 ° C. to obtain a sulfonated block copolymer. Hereinafter, the polymer electrolyte may be abbreviated as (P1).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/10 H01M 8/10 // C08L 101: 00 C08L 101: 00 F term (reference) 4F071 AA75 AA78 AF36 AF42 AH15 BA02 BB02 BC02 4J031 AA53 AA57 AA58 AB04 AC04 AC05 AD01 AF23 AF30 5G301 CA30 CD01 5H026 AA06 CX05

Claims (14)

[Claims] 1. A sulphonic acid group-introduced block and a sulfonic acid group-introduced block are each one or more, and at least one of all blocks has an aromatic fragrance in its main chain. A polymer electrolyte membrane comprising a polymer electrolyte containing a block copolymer, which is a block having a ring, and a porous membrane. 2. The polymer electrolyte membrane according to claim 1, wherein the block having a sulfonic acid group introduced has a structure in which a sulfonic acid group is directly bonded to an aromatic ring. 3. The block having a sulfonic acid group introduced thereinto is a block having a sulfonic acid group introduced into a block having a repeating unit represented by the general formula [1]. The polymer electrolyte membrane described. [1] (In the formula [1], X represents —O—, —S—, —NH—, or a direct bond, R ¹ is an alkyl group having 1 to 6 carbon atoms, or 1 to 6 carbon atoms. Represents an alkoxy group or a phenyl group, and a is an integer of 0 to 3. When there are a plurality of R ¹ , they may be the same or different. 4. The polymer electrolyte membrane according to claim 3, wherein X in the general formula [1] is —O—. 5. The block having a sulfonic acid group introduced thereinto is a block having a sulfonic acid group introduced into a block having a repeating unit represented by the general formula [2]. The polymer electrolyte membrane described. [2] (In the formula [2], Ar ¹ represents a group selected from the following structures.) (In the above formula, R ² represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a phenyl group, or a phenoxy group, b is an integer of 0 to 4, and c is 0 to 0.
It is an integer of 6. When there are a plurality of R ^2's , these may be the same or different. 6. The polymer electrolyte membrane according to claim 1, wherein the block having the sulfonic acid group introduced is a block having the sulfonic acid group introduced to a block made of an epoxy resin. 7. The polymer electrolyte according to claim 6, wherein the block made of an epoxy resin is a block having a sulfonic acid group introduced into a block having a repeating unit represented by the general formula [3]. film. [3] (In the formula [3], Ar ² represents a group selected from the following structures. (In the above formula, R ³ represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, d is an integer of 0 to 3, and e is an integer of 0 to 2. When there are a plurality of R ³ , these may be the same or different, Y is —O—, —S—, an alkylene group having 1 to 20 carbon atoms, a halogenated alkylene having 1 to 10 carbon atoms. Or a alkylenedioxy group having 1 to 20 carbon atoms. When there are a plurality of Y's, these may be the same or different.) 8. A block in which a sulfonic acid group is not substantially introduced is an aromatic polyether having a repeating unit represented by the general formula [4], and the block is any one of claims 1 to 7. The polymer electrolyte membrane according to 1. [4] (In the formula [4], R ⁴ represents an alkyl group having 1 to 6 carbon atoms, and f is an integer of 0 to ^{4. When} there are a plurality of R ^4, they may be the same or different. Good, Z is -CO
- or -SO ₂ - represents a) 9. The polymer electrolyte membrane according to claim 8, wherein Z in the general formula [4] is —SO ₂ —. 10. A block in which a sulfonic acid group is not substantially introduced is 60 to 95 with respect to the entire block copolymer.
It is weight%, The polymer electrolyte membrane of Claims 1-9 characterized by the above-mentioned. 11. A polymer electrolyte is represented by the general formula [1],
A block copolymer having a repeating unit represented by [2] or [3] is reacted with a block precursor having a repeating unit represented by the general formula [4] to produce a block copolymer. And then produced by sulfonation of the copolymer.
The polymer electrolyte membrane described. 12. The polymer electrolyte membrane according to claim 11, wherein the polymer electrolyte is produced by sulfonation of a block copolymer with sulfuric acid having a concentration of 90% or more. 13. The polymer electrolyte membrane according to claim 1, wherein the porous membrane comprises an aliphatic polymer or a fluorine-containing polymer. 14. A fuel cell comprising the polymer electrolyte membrane according to any one of claims 1 to 13.