JP2017010785A - Polymer electrolyte membrane, membrane electrode assembly, and solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane having excellent mechanical strength and high chemical durability, a membrane electrode assembly, and a solid polymer fuel cell.SOLUTION: The polymer electrolyte membrane according to the present invention includes a chain polyfluoroolefin microporous membrane (A) and a polymer electrolyte (B) impregnated into the chain polyfluoroolefin microporous membrane (A). A structure of a specific formula (1) or a specific formula (2) is contained in the skeleton of the chain polyfluoroolefin microporous membrane (A). The ratio of C-H bonds in the chain polyfluoroolefin microporous membrane (A) is 0.01% or more and less than 30%. The membrane electrode assembly according to the present invention includes the polymer electrolyte membrane. The solid polymer fuel cell according to the present invention includes the membrane electrode assembly.SELECTED DRAWING: None

Description

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

  A fuel cell is one that converts the chemical energy of fuel directly into electrical energy by electrochemically oxidizing hydrogen, methanol, etc. in the battery, and is attracting attention as a clean electrical energy supply source. ing. In particular, solid polymer electrolyte fuel cells are expected to be used as alternative power sources for automobiles, household cogeneration systems, portable generators, and the like because they operate at a lower temperature than others.

  Such a solid polymer electrolyte fuel cell includes at least a membrane electrode assembly in which a gas diffusion electrode in which an electrode catalyst layer and a gas diffusion layer are laminated is bonded to both surfaces of a proton exchange membrane. The proton exchange membrane here is a membrane made of a composition having acidic groups such as a sulfonic acid group, a phosphoric acid group, and a carboxylic acid group in a polymer chain and a property of selectively transmitting protons. As a composition used for such a proton exchange membrane, a proton exchange membrane using a perfluoro proton composition typified by Nafion (registered trademark, manufactured by DuPont) having high chemical stability is preferably used. It is done.

  During operation of the fuel cell, fuel (for example, hydrogen) is supplied to the gas diffusion electrode on the anode side, and oxidant (for example, oxygen or air) is supplied to the gas diffusion electrode on the cathode side. By being connected, the operation of the fuel cell is realized. Specifically, when hydrogen is used as fuel, hydrogen is oxidized on the anode catalyst to generate protons. After passing through the proton conductive polymer in the anode catalyst layer, the protons move in the proton exchange membrane and reach the cathode catalyst through the proton conductive polymer in the cathode catalyst layer. On the other hand, electrons generated simultaneously with protons by oxidation of hydrogen reach the cathode side gas diffusion electrode through an external circuit. On the cathode catalyst, the protons react with oxygen in the oxidant to generate hydrogen. At this time, electric energy is extracted.

  At this time, the proton exchange membrane must also serve as a gas barrier partition. When the gas permeability of the proton exchange membrane is high, leakage of anode-side hydrogen to the cathode and leakage of cathode-side oxygen to the anode, that is, cross-leakage occurs. When a cross leak occurs, a so-called chemical short circuit occurs and a good voltage cannot be taken out, and hydrogen on the anode side reacts with oxygen on the cathode side. This hydrogen peroxide is decomposed by a trace amount of metal (ions such as Fe, Cr, Ni, etc.) contained in the supply pipe of the humidified gas supplied to the battery to generate hydroxy radicals and peroxide radicals. These radicals cause a problem that the deterioration of the proton exchange membrane is promoted.

On the other hand, from the viewpoint of reducing the internal resistance of the battery and increasing the output, it has been studied to reduce the thickness of the proton exchange membrane that is an electrolyte. However, if the proton exchange membrane is thinned, the effect as a gas barrier partition is reduced, and the problem of cross leak becomes more serious. Furthermore, since the mechanical strength of the membrane itself is reduced by reducing the thickness of the proton exchange membrane, it becomes difficult to handle the membrane during fabrication of the membrane electrode assembly and cell assembly, and water generated on the cathode side. There is a physical problem that the film is torn by changing the dimensions including.
In order to solve such problems, conventionally, a composite membrane for a polymer electrolyte fuel cell in which an expanded polytetrafluoroethylene membrane is filled with an electrolyte as in Patent Document 1 has been proposed. However, the cost of the polytetrafluoroethylene membrane is high, and there is a problem that the cost of the composite membrane for fuel cells is increased. Furthermore, in a fuel cell vehicle, the electrolyte membrane repeatedly swells and contracts due to load fluctuations caused by the accelerator work during operation. In response to the problem that the electrolyte membrane changes in size due to swelling and shrinkage, a reinforcing material that suppresses the dimensional change more strongly than the polytetrafluoroethylene membrane is desired.

  Therefore, as described below, a method for obtaining an electrolyte membrane by filling a microporous membrane made of a polymer compound other than polytetrafluoroethylene with an electrolyte has been proposed.

  For example, Patent Document 2 describes a technique for obtaining an electrolyte membrane by filling a hole in a porous thin film made of polyolefin such as polyethylene and polypropylene with an ion exchange resin. By using polyolefin for the porous thin film, an electrolyte membrane can be obtained at a lower cost than polytetrafluoroethylene.

  Patent Document 3 proposes a microporous membrane made of a copolymer of ultrahigh molecular weight polyethylene and 4-methyl-1-pentene, having high air permeability, excellent mechanical properties and heat resistance.

  Patent Document 4 discloses a polymer electrolyte fuel cell in which a porous body made of an ethylene-tetrafluoroethylene copolymer is impregnated with an electrolyte material and has excellent handling properties, durability, output characteristics, and dimensional stability when containing water. Electrolyte membranes have been proposed.

Japanese Patent No. 4402625 Japanese Patent Publication No. 64-22932 JP 2011-184671 A Japanese Patent No. 4857560

  However, the electrolyte membranes described in Patent Documents 2 to 3 do not have sufficient chemical durability because the microporous membrane is a hydrocarbon-based material. In the electrolyte membrane described in Patent Document 4, although the carbon-fluorine bond is present in the polymer structure, the molar ratio of ethylene to tetrafluoroethylene is 70 even in the polymer composition in which the carbon-hydrogen bond is minimized. Therefore, there is a problem that resistance to activated radicals generated during operation of the fuel cell is low and sufficient chemical durability cannot be obtained. In addition, since the heat resistance is low and the polymer electrolyte membrane is impregnated with the electrolyte, the micropores are contracted or buried in the heating process, which causes a problem that the electrical characteristics are remarkably deteriorated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a polymer electrolyte membrane, a membrane electrode assembly, and a solid polymer fuel cell having excellent mechanical strength and high chemical durability. To do.

  As a result of intensive studies to solve the above problems, the inventors of the present invention are a microporous membrane made of a chain polyfluoroolefin in which a part of the carbon-hydrogen bond is fluorinated, It has been found that the above-mentioned problems can be solved by compositing a porous membrane with an electrolyte, and the present invention has been accomplished.

That is, the present invention is as follows.
[1]
A microporous membrane (A) made of chain polyfluoroolefin;
A polymer electrolyte (B) impregnated in the chain polyfluoroolefin microporous membrane (A);
Have
The structure of the following formula (1) or the following formula (2) is included in the skeleton of the chain polyfluoroolefin microporous membrane (A),
The polymer electrolyte membrane in which the proportion of C—H bonds represented by the following formula (3) in the chain polyfluoroolefin microporous membrane (A) is 0.01% or more and less than 30%.
-CX ₁ X ₂ CX ₃ (CX ₄ X ₅ X ₆ )-(1)
(X ₁ to X ₃ each independently represents a hydrogen atom or a fluorine atom. X ₄ to X ₆ each independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. When X ₁ to X ₃ are all fluorine, the chain polyfluoroolefin microporous membrane (A) has a CX ₄ X ₅ X ₆ site in which at least one of X ₄ to X ₆ is hydrogen. One or more CX ₄ X ₅ X ₆ sites in the structure, which is an alkyl group having 1 to 5 carbon atoms, wherein at least one of X ₄ to X ₆ contains at least one carbon-hydrogen bond When any _one of X ₁ and X ₂ is hydrogen, the chain polyfluoroolefin microporous membrane (A) is CX ₃ (wherein at least one of X ₃ to X ₆ is hydrogen. containing one or more structures in CX ₄ X ₅ X ₆₎ site, or less from X ₃ of X ₆ Kutomo One Carbon - containing one or more CX ₃ is an alkyl group having 1 to 5 carbon atoms containing at least one hydrogen bond to (CX ₄ X ₅ X ₆₎ sites in the structure).
_{-CX 1 X 2 CX 3 X 4} - (2)
(X ₁ to X ₄ represent hydrogen or a fluorine atom.)
Ratio of C—H bond = (C—H bond in the chain polyfluoroolefin microporous membrane (A)) / {(C—F bond in the chain polyfluoroolefin microporous membrane (A)) ) + (CH bond in the chain polyfluoroolefin microporous membrane (A))} × 100 (%) (3)
[2]
A membrane electrode assembly comprising the polymer electrolyte membrane according to [1].
[3]
A polymer electrolyte fuel cell comprising the membrane electrode assembly according to [2].

  According to the present invention, it is possible to provide a polymer electrolyte membrane, a membrane electrode assembly, and a solid polymer fuel cell that have excellent mechanical strength and high chemical durability.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The polymer electrolyte membrane of this embodiment comprises a chain polyfluoroolefin microporous membrane (A) and a polymer electrolyte (B) impregnated in the chain polyfluoroolefin microporous membrane (A). And the structure of the following formula (1) or the following formula (2) is included in the skeleton of the chain polyfluoroolefin microporous membrane (A), and the chain polyfluoroolefin microporous membrane (A) The ratio of the C—H bond represented by the following formula (3) is 0.01% or more and less than 30%.
-CX ₁ X ₂ CX ₃ (CX ₄ X ₅ X ₆ )-(1)
(X ₁ to X ₃ each independently represents a hydrogen atom or a fluorine atom. X ₄ to X ₆ each independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. When X ₁ to X ₃ are all fluorine, the chain polyfluoroolefin microporous membrane (A) has a CX ₄ X ₅ X ₆ site in which at least one of X ₄ to X ₆ is hydrogen. One or more CX ₄ X ₅ X ₆ sites in the structure, which is an alkyl group having 1 to 5 carbon atoms, wherein at least one of X ₄ to X ₆ contains at least one carbon-hydrogen bond When any _one of X ₁ and X ₂ is hydrogen, the chain polyfluoroolefin microporous membrane (A) is CX ₃ (wherein at least one of X ₃ to X ₆ is hydrogen. containing one or more structures in CX ₄ X ₅ X ₆₎ site, or less from X ₃ of X ₆ Kutomo One Carbon - containing one or more CX ₃ is an alkyl group having 1 to 5 carbon atoms containing at least one hydrogen bond to (CX ₄ X ₅ X ₆₎ sites in the structure).
_{-CX 1 X 2 CX 3 X 4} - (2)
(X ₁ to X ₄ represent hydrogen or a fluorine atom.)
Ratio of C—H bond = (C—H bond in the chain polyfluoroolefin microporous membrane (A)) / {(C—F bond in the chain polyfluoroolefin microporous membrane (A)) ) + (CH bond in the chain polyfluoroolefin microporous membrane (A))} × 100 (%) (3)
Since it is comprised in this way, the polymer electrolyte membrane of this embodiment has the favorable balance of dimensional stability and chemical durability, and can exhibit the outstanding battery performance.

[Microporous membrane made of chain polyfluoroolefin (A)]
The microporous membrane (A) made of chain polyfluoroolefin in the present embodiment is a microporous membrane containing a polymer compound, and a part of carbon-hydrogen bonds of the microporous membrane is fluorinated. be able to. The chain polyfluoroolefin-made microporous membrane (A) may include a linear polymer compound or a branched polymer compound. By forming a carbon-fluorine bond as described above, durability against activated radicals generated during operation of the fuel cell is improved. Furthermore, as described in the above formula (1) or formula (2), by having a C—H bond in a specific range in the structure, the C—H bond site is fused with other parts in the heating step. It can be worn, and excellent mechanical strength can be obtained while ensuring good chemical durability. Furthermore, the microporous membrane (A) made of chain polyfluoroolefin in this embodiment is also excellent in electrolyte impregnation properties. As described above, the microporous membrane (A) is excellent in the balance between the impregnation property of the electrolyte, the adhesion with the electrolyte, and the mechanical strength.

  The microporous membrane (A) made of chain polyfluoroolefin in the present embodiment can be obtained using a microporous membrane (A ′) containing a polymer compound as a precursor. Examples of the microporous membrane (A ′) include, but are not limited to, microporous membranes containing a polyolefin resin, a vinyl polymerization resin, a condensation polymerization resin, a natural polymer, and the like. These may be used alone or in combination of two or more. Moreover, a microporous film can also be formed by combining monomers of different materials, such as copolymerizing a monomer constituting a polyolefin resin and a monomer constituting a vinyl polymerization resin.

  The polyolefin resin is not particularly limited, but a polymer containing propylene or ethylene as a main monomer component is preferable. This polyolefin resin may be composed of only the main monomer components described above, but in addition, monomer components such as butene, pentene, hexene, cyclohexene, 4-methyl-1-pentene, etc. may be used. You may contain.

  Specific examples of the polyolefin resin according to this embodiment include, but are not limited to, ultrahigh molecular weight polyethylene (UHMWPE), high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), and Ziegler multisite catalyst. Copolymer such as linear low-density polyethylene and ultra-low-density polyethylene obtained by using polypropylene, polypropylene, polyhexadiene, ethylene-vinyl acetate copolymer, ethylene polymer obtained using a single site catalyst, and copolymerization with propylene Copolymers with other possible monomers (propylene-ethylene copolymers, propylene-ethylene-α-olefin copolymers, etc.), norbornene-ethylene copolymers, and mixtures thereof are mentioned. Among them, a copolymer with polyethylene is preferable from the viewpoint of moldability of the microporous film, and a copolymer with ultrahigh molecular weight polyethylene is more preferable from the viewpoint of mechanical properties of the microporous film obtained by fluorination. A copolymer with high density polyethylene, more preferably a copolymer with ultrahigh molecular weight polyethylene. From the viewpoint of moldability and physical properties (mechanical strength, porosity, film thickness) of the microporous membrane, a copolymer with ultrahigh molecular weight polyethylene is particularly preferable. Further, from the viewpoint of heat resistance and mechanical properties of the microporous membrane obtained by fluorination, a copolymer with polypropylene is preferred.

  Although it does not specifically limit as vinyl polymerization resin, The polymer which contains acrylic acid ester, vinyl acetate, etc. as main monomer components is preferable. The vinyl polymer resin may be composed of only the main monomer components described above, but may be a copolymer of a polyolefin or a vinyl group and a polymerizable compound.

  Specific examples of the vinyl polymer resin according to the present embodiment are not limited to the following, but include, for example, polymethyl acrylate, polyethyl acrylate, polyvinyl acetate, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer. And a vinyl acetate-ethylene-vinyl chloride terpolymer.

  Examples of the condensation polymerization resin include, but are not limited to, polyester, epoxy resin, polyurethane, polyamide, polyimide, and copolymers thereof.

  Polyester is a compound having an ester bond and is obtained by polycondensation of a polyvalent carboxylic acid and a polyhydric alcohol. Specific examples include, but are not limited to, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like.

  The epoxy resin is a resin having an epoxy group, and is obtained by forming a crosslinked network with the epoxy group and curing it. Although the epoxy resin which concerns on this embodiment is not limited to the following, for example, an aliphatic glycidyl ether type epoxy resin, an aliphatic glycidyl ester type epoxy resin, an alicyclic glycidyl ether type epoxy resin, an alicyclic glycidyl ester type epoxy resin And non-aromatic epoxy resins. These may be used alone or in combination of two or more.

  Among these, in order to ensure chemical resistance and film strength, further, from the viewpoint of forming a uniform three-dimensional network skeleton and uniform pores on the porous sheet, an alicyclic glycidyl ether type epoxy resin, And at least one alicyclic epoxy resin selected from the group consisting of alicyclic glycidyl ester type epoxy resins. In particular, at least one alicyclic epoxy resin selected from the group consisting of an alicyclic glycidyl ether type epoxy resin having an epoxy equivalent of 6000 or less and a melting point of 170 ° C. or less, and an alicyclic glycidyl ester type epoxy resin. Is preferably used.

  Polyurethane is a polycondensate of polyhydric alcohol and polyvalent isocyanate. The polyurethane used in this embodiment is, for example, polytetramethylene oxide glycol, polyethylene adipate glycol, or polycaprolactone glycol as a polyhydric alcohol, as described in JP-A-58-52329. Can be obtained by polycondensation of at least one of diphenylmethane-4,4′-diinocyanate and 4.4′-diaminodiphenylmethane.

  The polyamide resin is a compound having an amide bond such as nylon 6, nylon 66, nylon 46, nylon 610, nylon 12, polymetaxylene adipamide, and is obtained by condensation polymerization of dicarboxylic acid and diamine. It is done.

The polyamide used in the present embodiment is preferably a polyamide having an aromatic ring from the viewpoint of improving the mechanical properties of the microporous membrane after fluorination, as described in, for example, JP-A-9-13439. It is more preferable that the polyamide resin is formed by combining a unit selected from the group consisting of the following chemical structural structural units (A-1) to (A-3) substantially as a main structural unit.
—NH—Ar ₁ —NH— (A-1)
_{-CO-Ar 2 -CO- (A-} 2)
—CO—Ar ₃ —NH— (A-3)

Here, Ar ₁ , Ar ₂ and Ar ₃ represent a divalent group having an aromatic ring structure or a structure in which a plurality of aromatic rings are linked. Further, the number of carbon atoms in Ar ₁ , Ar ₂ , and Ar ₃ can be in the range of 6 to 20, preferably in the range of 6 to 15, more preferably in the range of 6 to 12, and still more preferably. 6. Ar ₁ , Ar ₂ and Ar ₃ may be the same or different, and typical examples thereof include divalent groups represented by the following formulas (A-4) to (A-7).

（上記式において、Ｘは、−Ｏ−、−ＣＨ₂ −、−ＳＯ₂ −、−Ｓ−、−ＣＯ−、−Ｃ（ＣＨ₃ ）₂ −、−Ｃ（ＣＦ₃ ）₂ −等の二価の連結基である。）

(In the above formula, X represents _{two such as} —O—, —CH ₂ —, —SO ₂ —, —S—, —CO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, etc. Valent linking group.)

  Examples of the formula (A-7) include divalent groups represented by the following formulas (A-8) to (A-9).

（上記式において、Ｘは、前述の定義と同様である。）

(In the above formula, X is as defined above.)

（上記式において、Ｘは、前述の定義と同様である。）

(In the above formula, X is as defined above.)

Also, Ar ₁ , Ar ₂ , Ar _{3 in which} a part of hydrogen on these aromatic rings is substituted with a halogen atom such as a chlorine atom or a fluorine atom, a nitro group, a lower alkyl group, a lower alkoxy group or the like. include. In addition, the polymer in the present embodiment is a copolymer obtained by copolymerizing methylene units, pyridylene units, units such as esters, urethane, urea, ethers, thioethers, etc. There may be.

  The polyimide is composed of an acid dianhydride and a diamine, and polyimide resins composed of various acid dianhydrides and diamines can be used. As the polyimide used in the present embodiment, for example, as described in JP 2014-132057 A, a polyamic acid homopolymer or copolymer having a repeating unit having the structure of the following formula (A-10), Or what is obtained by obtaining a heating process from the polyimide precursor which is a homopolymer or copolymer of the polyamic acid partially imidized is mentioned.

  In the formula (A-10), R represents a group selected from tetravalent aromatic residues, and preferably a group selected from the structural formula shown in the following formula (A-11).

  In the formula (A-10), R ′ represents a divalent aromatic residue having 1 to 4 carbon 6-membered rings. R ′ is exemplified by a group selected from the structures represented by the following formula (A-12).

  The natural polymer in the present embodiment includes proteins, nucleic acids, lipids, polysaccharides (cellulose, starch, etc.) and natural rubber, and cellulose, natural rubber and the like can be preferably used. In addition, polymer compounds into which various functional groups are introduced using these natural polymers as raw materials can also be used.

  The cellulose resin used in the present embodiment is not limited to the following. For example, in addition to cellulose (pulp, cotton linter, regenerated cellulose, etc.), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate And cellulose acylate.

  Moreover, as a microporous film containing the cellulose resin used for this embodiment, it can be set as the nanofiber-ized cellulose compound as it describes in Unexamined-Japanese-Patent No. 2008-274525, for example.

  The microporous membrane (A ′) in the present embodiment is not limited to the following, but for example, JP-A-3-64334, JP-A-9-216964, JP-A-11-130899, Heisei 16 prepared by the Japan Patent Office. It can be obtained by the method described in the annual standard technology collection organic polymer porous body. The microporous membrane (A ′) as such a base material can be a commercially available product, and is not limited to the following. For example, Asahi Kasei “Hypore”, Ube Industries “Eupor”, Tonen Tapils “Cetella” Nitto Denko “Exepor”, Mitsui Chemicals “Hilet”, etc. can be used.

  In addition, the microporous membrane made of chain polyfluoroolefin in this embodiment (A), if necessary, metal soaps such as potassium stearate and zinc stearate, ultraviolet absorbers, light stabilizers, antistatic agents, You may contain well-known additives, such as an antifogging agent and a color pigment, in the range which does not impair the effect of this embodiment.

  The chain polyfluoroolefin microporous membrane (A) in this embodiment preferably has a porosity of 50% to 95%, more preferably 60% to 95%, and 70% to 95%. More preferably, it is more preferably 80% to 95%. When the porosity is in the range of 50% to 95%, the ion conductivity of the polymer electrolyte membrane obtained by combining the microporous membrane and the polymer electrolyte is improved, the strength is improved, and the dimensional change is suppressed. The effect tends to become more prominent. Here, the porosity of the microporous membrane refers to a value measured by a mercury porosimeter (for example, manufactured by Shimadzu Corporation, trade name: Autopore IV 9520, initial pressure of about 20 kPa) by a mercury intrusion method.

  The chain polyfluoroolefin-made microporous membrane (A) in this embodiment preferably has a thickness of 0.1 μm to 50 μm, more preferably 0.5 μm to 30 μm, and 1.0 μm to 20 μm. And more preferably 2.0 μm to 20 μm. When the film thickness is in the range of 0.1 μm to 50 μm, it becomes easy to highly fill the polymer electrolyte into the microporous membrane, and the dimensional change of the polymer electrolyte membrane tends to be further suppressed. Here, the film thickness of the chain polyfluoroolefin microporous film (A) is determined by well-known film thickness gauges (for example, inc. The value measured using the Toyo Seiki Seisakusho make, brand name "B-1").

  In the microporous membrane (A) made of chain polyfluoroolefin in the present embodiment, the pore diameter of the pores (voids) is preferably 0.03 μm to 10 μm, more preferably 0.1 μm to 10 μm, and More preferably, it is 3 μm to 5 μm, and particularly preferably 0.4 μm to 3 μm. When the pore diameter is in the range of 0.03 μm to 10 μm, the polymer electrolyte tends to fill the voids of the microporous membrane and has an effect of being difficult to escape. Here, the pore diameter of the pores of the microporous film indicates the median diameter (volume), and is a value measured by a mercury porosimeter (for example, trade name: Autopore IV 9520 manufactured by Shimadzu Corporation) by a mercury intrusion method.

[Fluorination of polymer microporous membrane]
The microporous membrane (A ′) in the present embodiment is capable of impregnating the polymer electrolyte into the microporous membrane, adhesion between the polymer electrolyte and the microporous membrane, and activating radicals generated during operation of the fuel cell. For the purpose of imparting durability, it is preferable to introduce a functional group into the polymer molecule and further convert the carbon-hydrogen bond in the molecule to a carbon-fluorine bond. In the present specification, “fluorination” means that the microporous membrane is treated so as to have at least one carbon-fluorine bond. Here, the above “fluorination” is not intended to convert all carbon-hydrogen bonds in the microporous membrane into carbon-fluorine bonds, but as described later, the microporous membrane made of chain polyfluoroolefin in this embodiment ( A) contains a specific amount of carbon-hydrogen bonds in its structure. By introducing functional groups into various microporous membranes (A ′) and forming carbon-fluorine bonds, the impregnation, adhesion and durability to activated radicals are maintained while maintaining the structure before fluorination. It becomes possible to obtain a highly porous microporous film.

  The method of fluorination of the microporous membrane (A ′) is not limited to the following, but for example, as described in JP-A-2004-143622, fluorine gas or fluorine gas is converted into an inert gas (for example, nitrogen , Argon, helium, carbon dioxide gas, etc.) can be applied by bringing the mixed gas into contact with the object to be processed.

  Further, the method for introducing the functional group while fluorinating the microporous membrane (A ′) is not limited to the following, but for example, as described in JP-A Nos. 2000-355633 and 2010-150460. It can be applied by bringing it into contact with a mixed gas containing fluorine gas and a reactive gas containing oxygen atoms and / or sulfur atoms. With this technique, for example, by introducing a proton conductive group such as a sulfonic acid group, good proton conductivity can be imparted to the microporous membrane (A) itself made of a chain polyfluoroolefin.

  The fluorination rate of the chain polyfluoroolefin microporous membrane (A) in the present embodiment can be calculated by a Fourier transform infrared absorption spectrum (FT-IR) method or a nuclear magnetic resonance (NMR) method.

For example, the measurement of the fluorination rate using FT-IR can be calculated by the method described in Japanese Patent No. 5168903. That is, the absorption area S _CH and derived from predominantly CH bonds measured by the range of the FT-IR from 3100 cm ^-1 to 2800 cm ^-1, mainly to be measured in the range from 2700 cm ^-1 to 2000 cm ^-1 calculating the absorption area S _CF of peak derived from a CF bond to. Next, the C—F group residual ratio (fluorination ratio) is calculated by the following formula (3-1).
Fluorination rate = S _CF / (S _CH + S _CF ) × 100 (%) (3-1)

  The fluorination rate of the chain polyfluoroolefin microporous membrane (A) obtained as described above is preferably 50.00% or more and 99.99% or less, more preferably 70.00% or more and 99.99% or less. 85.00% to 99.99% is more preferable. When the fluorination rate is 50.00% or more, there is a tendency that decomposition caused by activated radicals that can occur during operation of the fuel cell can be suppressed, and the durability of the polymer electrolyte membrane tends to be improved. Moreover, when the fluorination rate is 99.99% or less, it is possible to sufficiently secure the C—H bond fusion effect in the heating step and to obtain better mechanical strength.

The proportion of C—H bonds in the microporous membrane (A) made of chain polyfluoroolefin can be calculated using FT-IR similarly to the fluorination rate. That is, the absorption area S _CH and derived from predominantly CH bonds measured by the range of the FT-IR from 3100 cm ^-1 to 2800 cm ^-1, mainly to be measured in the range from 2700 cm ^-1 to 2000 cm ^-1 calculating the absorption area S _CF of peak derived from a CF bond to. Next, the C—H group residual ratio is calculated by the following formula (3).
Ratio of C—H bond = (C—H bond in the chain polyfluoroolefin microporous membrane (A)) / {(C—F bond in the chain polyfluoroolefin microporous membrane (A)) ) + (CH bond in the chain polyfluoroolefin microporous membrane (A))} × 100 (%) (3)

  The proportion of C—H bonds in the chain polyfluoroolefin microporous membrane (A) obtained as described above is 0.01% or more and less than 30% from the viewpoint of improving mechanical properties and maintaining chemical durability. And preferably 0.01% or more and less than 10%, more preferably 0.01% or more and less than 5%.

[Polymer electrolyte (B)]
The structure of the polymer electrolyte (B) in the present embodiment is not particularly limited as long as it has an ion exchange group in the molecule, but the ion exchange capacity of the polymer electrolyte (B) is 0.5-3. 0 meq / g is preferred, 0.65 to 2.0 meq / g is more preferred, and 0.8 to 1.5 meq / g is even more preferred. When the ion exchange equivalent is 3.0 meq / g or less, when used as a polymer electrolyte membrane, swelling of the polymer electrolyte membrane under high temperature and high humidity during fuel cell operation tends to be further reduced. is there. By reducing the swelling in this way, there is a tendency to reduce the problems such as a decrease in the strength of the polymer electrolyte membrane, wrinkles and peeling from the electrode, and further a problem that the gas barrier property is lowered. It is in. Further, when the ion exchange capacity is 0.5 meq / g or more, the power generation capacity of the fuel cell including the obtained polymer electrolyte membrane tends to be further improved.

  The structure of the polymer electrolyte (B) is not particularly limited as long as it has an ion exchange group in the molecule. For example, the polymer electrolyte (B) has a perfluorocarbon polymer compound having an ion exchange group or an aromatic ring in the molecule. A compound in which an ion exchange group is introduced into a partially fluorinated hydrocarbon polymer compound is preferable. Among these, a perfluorocarbon polymer compound having an ion exchange group is more preferable from the viewpoint of chemical stability.

  Here, the partially fluorinated hydrocarbon polymer compound having an aromatic ring in the molecule is not particularly limited. For example, polyphenylene sulfide, polyphenylene ether, polysulfone, polyether sulfone, polyether ether sulfone. , Polyetherketone, polyetheretherketone, polythioetherethersulfone, polythioetherketone, polythioetheretherketone, polybenzimidazole, polybenzoxazole, polyoxadiazole, polybenzoxazinone, polyxylylene, polyphenylene, polythiophene, polypyrrole, Polyaniline, polyacene, polycyanogen, polynaphthyridine, polyphenylene sulfide sulfone, polyphenylene sulfone, polyimide, polyether De, polyesterimide, polyamideimide, polyarylate, aromatic polyamide, polystyrene, polyester, a portion in the molecule of the polycarbonate, and the like are fluorinated polymer compound.

  Among these, the partially fluorinated hydrocarbon polymer compound having an aromatic ring in the molecule is not particularly limited, but from the viewpoint of heat resistance, oxidation resistance, and hydrolysis resistance, polyphenylene sulfide, Polyphenylene ether, polysulfone, polyethersulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polythioetherethersulfone, polythioetherketone, polythioetheretherketone, polybenzimidazole, polybenzoxazole, polyoxadiazole, Polybenzoxazinone, polyxylylene, polyphenylene, polythiophene, polypyrrole, polyaniline, polyacene, polycyanogen, polynaphthyridine, polyphenylene sulfide sulfone, polyphenyle Sulfone, a polyimide, polyether imide, a polymer compound in which a part of the molecule has been fluorinated polyester imide are preferable.

  In addition, although it does not specifically limit as an ion exchange group introduce | transduced into these, For example, a sulfonic acid group, a sulfonimide group, a sulfonamide group, a carboxylic acid group, a phosphoric acid group etc. are preferable. Among these, a sulfonic acid group is particularly preferable.

  Further, the perfluorocarbon polymer compound having an ion exchange group is not particularly limited. For example, perfluorocarbon sulfonic acid resin, perfluorocarbon carboxylic acid resin, perfluorocarbon sulfonimide resin, perfluorocarbon sulfonamide resin, perfluorocarbon phosphoric acid. Examples of the resin include amine salts and metal salts of these resins.

Although it does not specifically limit as a perfluorocarbon high molecular compound, More specifically, the polymer represented by following formula (4) is mentioned.
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( CF ₂ ) _f −X ⁴ )] _g − (4)
(In formula (4), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms. A and g are 0 ≦ a <1, 0 <g ≦ 1, a + g = 1, b is an integer of 0 or more and 8 or less, c is 0 or 1. d and e are integers of 0 or more and 6 or less, independently of each other. f is an integer of 0 or more and 10 or less, provided that d + e + f is not equal to 0. R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group having 1 to 10 carbon atoms, or fluorochloro X ⁴ is COOZ, SO ₃ Z, PO ₃ Z ₂ or PO ₃ HZ, where Z is a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an amine (NH ₄ , NH ₃ R ³ , NH ₂ R ³ R ⁴ , NHR ³ R ⁴ R ⁵ , NR ³ R ⁴ R ⁵ R ⁶ ), and R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups or aryl groups.

Among these, a perfluorocarbon sulfonic acid resin represented by the following formula (5) or formula (6) or a metal salt thereof is preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O- (CF 2 -CF (CF 3)) b -O- (CF 2) c -SO 3 X)] d - (5)
(In Formula (5), a and d are 0 ≦ a <1, 0 ≦ d <1, and a + d = 1. B is an integer of 1 to 8. c is an integer of 0 to 10. X is a hydrogen atom or an alkali metal atom.)
_{- [CF 2 CF 2] e} - [CF 2 -CF (-O- (CF 2) f -SO 3 Y)] g - (6)
(In Formula (6), e and g are 0 ≦ e <1, 0 ≦ g <1, and e + g = 1. F is an integer of 0 to 10. Y is a hydrogen atom or an alkali metal atom. is there.)

The perfluorocarbon polymer compound having an ion exchange group in the present embodiment is not particularly limited. For example, it is produced by polymerizing a precursor polymer represented by the following formula (7) and then performing alkali hydrolysis, acid treatment, and the like. can do.
_{^{- [CF 2 CX 1 X 2}} ] a - [CF 2 -CF (-O- (CF 2 -CF (CF 2 X 3)) b -O c - (CFR 1) d - (CFR 2) e - ( ^{_{CF 2) f -X 5)]}} g - (7)
(In the formula (7), X ¹ , X ² and X ³ are each independently a halogen element or a perfluoroalkyl group having 1 to 3 carbon atoms. A and g are 0 ≦ a <1,0. <G ≦ 1, a + g = 1, b is an integer of 0 to 8, c is 0 or 1. d and e are integers of 0 to 6 independently of each other, f Is an integer from 0 to 10. However, d + e + f is not equal to 0. R ¹ and R ² are each independently a halogen element, a perfluoroalkyl group or a fluorochloroalkyl group having 1 to 10 carbon atoms. X ⁵ is COOR ⁷ , COR ⁸ or SO ₂ R ⁸ , where R ⁷ is an alkyl group having 1 to 3 carbon atoms, and R ⁸ is a halogen element.

  Although the said precursor polymer is not specifically limited, For example, it can manufacture by copolymerizing a fluorinated olefin compound and a vinyl fluoride compound.

Here, although it does not specifically limit as a fluorinated olefin compound, For example, the compound etc. which are represented by following formula (8) are mentioned.
CF ₂ = CFZ (8)
(In the formula (8), Z represents H, Cl, F, a perfluoroalkyl group having 1 to 3 carbon atoms, or a cyclic perfluoroalkyl group that may contain oxygen.)

Moreover, it does not specifically limit as a vinyl fluoride compound, For example, the compound etc. which are represented by following formula (9)-(16) are mentioned.
_{CF 2 = CFO (CF 2)} z -SO 2 F (9)
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) z -SO 2 F (10)
_{CF 2 = CF (CF 2)} z -SO 2 F (11)
_{CF 2 = CF (OCF 2 CF} (CF 3)) z - (CF 2) z-1 -SO 2 F (12)
_{CF 2 = CFO (CF 2)} z -CO 2 R (13)
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) z -CO 2 R (14)
_{CF 2 = CF (CF 2)} z -CO 2 R (15)
_{CF 2 = CF (OCF 2 CF} (CF 3)) z - (CF 2) 2 -CO 2 R (16)
(In formulas (9) to (16), Z represents an integer of 1 to 8, and R represents an alkyl group having 1 to 3 carbon atoms.)

  Although it does not specifically limit as a copolymerization method of a fluorinated olefin compound and a vinyl fluoride compound, For example, the following methods (i)-(v) can be mentioned.

(I) Solution polymerization:
A method in which a polymerization solvent such as a fluorinated hydrocarbon is used, and polymerization is performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state where the polymerization solvent is filled and dissolved. Although it does not specifically limit as said fluorine-containing hydrocarbon, For example, trichlorotrifluoroethane, 1,1,1,2,3,4,4,5,5,5-decafluoropentane etc. are named generically as "Freon". The compound group which can be used can be used conveniently.

(Ii) Bulk polymerization:
A method of polymerizing a fluorinated olefin compound and a vinyl fluoride compound using a vinyl fluoride compound itself as a polymerization solvent without using a solvent such as a fluorinated hydrocarbon.

(Iii) Emulsion polymerization:
A method in which an aqueous solution of a surfactant is used as a polymerization solvent, and polymerization is carried out by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state of being charged and dissolved in the polymerization solvent.

(Iv) Mini emulsion polymerization, micro emulsion polymerization:
A method in which an aqueous solution of a surfactant and an auxiliary emulsifier such as alcohol is used, and polymerization is performed by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state where the aqueous solution is filled and emulsified.

(V) Suspension polymerization:
A method in which an aqueous solution of a suspension stabilizer is used and polymerization is carried out by reacting a vinyl fluoride compound and a fluorinated olefin gas in a state of being filled and suspended in the aqueous solution.

  In the present embodiment, melt mass flow rate (hereinafter abbreviated as “MFR”) can be used as an index of the polymerization degree of the precursor polymer. In the present embodiment, the MFR of the precursor polymer is preferably 0.01 g / 10 min or more, more preferably 0.1 g / 10 min or more, and further preferably 0.3 g / 10 min or more. Although the upper limit of MFR is not limited, 100 g / 10min or less is preferable and 10 g / 10min or less is more preferable. By setting the MFR to 0.01 g / 10 min or more and 100 g / 10 min or less, molding processability such as film formation of a polymer electrolyte tends to be more excellent. MFR can be measured at 270 ° C., a load of 2.16 kgf, and an orifice inner diameter of 2.09 mm based on JIS K-7210.

The precursor polymer produced as described above is hydrolyzed in a basic reaction liquid, sufficiently washed with warm water and acid-treated. By this acid treatment, the perfluorocarbon sulfonic acid resin precursor is protonated to form an SO ₃ H form.

The SO ₃ H body is dispersed in a solvent such as alcohol or water under the conditions of pressurization, heating, and stirring to form a polymer electrolyte composition. In addition, the polymer electrolyte composition in this embodiment contains said polymer electrolyte (B). In constituting the polymer electrolyte membrane of the present embodiment, when the polymer electrolyte (B) is impregnated into the microporous membrane (A) made of chain polyfluoroolefin, the polymer electrolyte composition of the present embodiment is used. Can do.

[Compound having metal ion scavenging ability (C)]
In the present embodiment, the polymer electrolyte composition may include a compound (C) having a metal ion scavenging ability. “Metal ion scavenging ability” refers to an action of inactivating metal ions that promote the decomposition of hydrogen peroxide. Here, the metal ion that promotes decomposition of hydrogen peroxide is not particularly limited, and examples thereof include Fe, Cr, Ni, and the like. The compound (C) having such a metal ion scavenging ability is not particularly limited, but for example, at least one selected from the group consisting of a phosphoric acid compound, a silicic acid compound, and a compound having a carboxyl group is preferable. .

(Phosphate compound)
Although it does not specifically limit as said phosphate compound, For example, the following compound is mentioned. The phosphoric acid compound includes a salt of the phosphoric acid compound.

(1) Phosphate esters The phosphate esters are not particularly limited, and examples thereof include esters such as phosphate esters, phosphonate esters, phosphinate esters, and phosphite esters. More specifically, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, riboflavin phosphate, phospholipid (such as reticin), starch phosphate ester, vitamin C phosphate, phytic acid (IP6: inositol six Phosphoric acid), dimethyl 4-aminobenzylphosphonate, diethyl 4-aminobenzylphosphonate, dipropyl 4-aminobenzylphosphonate, dimethyl 2-aminomethylphosphonate, diethyl 2-aminomethylphosphonate, dipropyl 2-aminomethylphosphonate, phthalimide Dimethyl methylphosphonate, diethyl phthalimidomethylphosphonate, dipropyl phthalimidomethylphosphonate, 1-hydroxymethane-1, dimethyl 1-diphosphonate, 1-hydroxyethane-1, 1-diphosphonate diethyl, -, and the like dipropyl-hydroxy-1,1-diphosphonic acid. These esters form a sparingly soluble salt with Fe ions or the like by hydrolysis, or generate an anion having a chelating ability. Of these, phytic acid and phytate are preferable. Phytic acid and its salts are acceptable as food additives, and polymer electrolyte compositions containing these are preferred from the viewpoints of toxicity and environmental burden.

(2) Compound having a phosphoric acid group The compound having a phosphoric acid group is not particularly limited, and examples thereof include orthophosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, metaphosphoric acid, tripolyphosphoric acid, hexametaphosphoric acid, and polyphosphoric acid. A compound having a phosphate group or a salt thereof may be mentioned. Phosphoric acid groups (for example, orthophosphate ion PO ₄ ³⁻ , pyrophosphate ion P ₂ O ₇ ⁴⁻ ) form a sparingly soluble salt or chelate with Fe ions and the like, and thus are preferable from the viewpoint of reducing Fenton activity.

In addition, phosphonate ion PO ₃ ³⁻ , phosphinate ion PO ₂ ^3−, and polyphosphate ion, which is a polymer of phosphoric acid, are coordinated to Fe ions to form soluble chelates, and free Fe ions This is preferable because it reduces the concentration (activity). From this viewpoint, among the compounds having a phosphate group, pyrophosphate and pyrophosphate are preferable.

  Specific compounds having the above functional groups are not particularly limited, and examples thereof include adenosine monophosphate, adenosine diphosphate, adenosine triphosphate, guanosine monophosphate, guanosine diphosphate, guanosine triphosphate, 4-aminobenzylphosphonic acid, dimethyl-4-aminomethylphosphonic acid, 2-aminomethylphosphonic acid, nitrilotris (methylenephosphonic acid), phthalimidomethylphosphonic acid, 4-amino-1-hydroxybutane-1,1-diphosphonic acid, N , N, N ', N'-ethylenediaminetetrakis (methylenephosphonic acid) and the like, and salts of these compounds.

(3) The phosphorus oxides phosphorus oxide is not particularly limited, examples thereof include P ₂ O _5. These yield PO ₄ ³⁻ and P ₂ O ₇ ²⁻ by hydrolysis. Among these, the use of phosphorous oxides capable of generating PO ₄ ^3- ion and P ₂ O ₇ ^{4 -} ion which are permitted as food additives is used from the viewpoint of toxicity and environmental load of the polymer electrolyte composition. preferable.

(Silicic acid compound)
The silicic acid compound is not particularly limited. For example, silicic acid or a heteropoly acid containing the silicic acid (for example, silicomolybdic acid or silicotungstic acid) or a salt thereof, zeolite (sodium aluminum silicate, aluminosilicate) Acid salt). Among these, silicate is preferable. Fe ions generate precipitates or chelates with silicate ions or heteropolyacid ions containing silicon, making it difficult for the Fenton reaction to occur. In addition, in the zeolite, Fe ions are exchanged with metals (for example, sodium and potassium) contained in the zeolite to be taken into the zeolite and tend not to cause the Fenton reaction.

  Although it does not specifically limit as said silicic acid compound, For example, the compound which has a functional group which makes an ionic bond with the proton conductive group of a polymer electrolyte (B) so that it may mention later is preferable. Specific examples include, but are not limited to, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ( Aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- Examples include phenyl-3-aminopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane. In these compounds, amino groups and urea groups form an ionic bond with the proton conducting group of the polymer electrolyte to be immobilized, and the alkoxy group is hydrolyzed to generate silicic acid. The silicate ions tend to cause Fe ions to form precipitates or chelates and make the Fenton reaction difficult.

(Compound having a carboxyl group)
Although it does not specifically limit as a compound which has the said carboxyl group, For example, the following compounds are mentioned. In addition, the salt of the compound which has a carboxyl group is also contained in the compound which has a carboxyl group.

(1) Aminocarboxylic acid Although it does not specifically limit as aminocarboxylic acid, For example, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraaminehexaacetic acid), HIDA (hydroxyethyliminodiacetic acid) ) And the like or salts thereof. Aminocarboxylic acids can be used as chelating agents.

(2) COO ^- compound COO having ion ^- Examples of the compound having an ion is not particularly limited, for example, oxalic acid (oxalic anhydride, oxalic acid dihydrate), gallate, or salts thereof . COO ⁻ ion as an anion (especially, oxalate ion of (COO ⁻ ) ₂ ) is a preferable anion because it easily forms a sparingly soluble salt with Fe. When these anions form a sparingly soluble salt with Fe, the Fenton reaction tends to be suppressed. Among the above, gallic acid ions allowed as food additives are more preferable from the viewpoints of toxicity and environmental burden.

(3) Carboxylic acid ester compound Although it does not specifically limit as a carboxylic acid ester compound, For example, oxalic acid ester (For example, dimethyl oxalate, diethyl oxalate, dipropyl oxalate etc.) etc. are mentioned. Carboxylic acid ester compounds form a sparingly soluble salt with Fe ions by hydrolysis, or generate an anion having a chelating ability.

(4) Polymeric carboxylic acid Although it does not specifically limit as polymeric carboxylic acid, For example, polymeric carboxylic acids, such as humic acid and tannic acid, or its salt is mentioned. Polymeric carboxylic acids also form sparingly soluble salts with Fe.

(5) Perfluorocarboxylic acid Although it does not specifically limit as perfluorocarboxylic acid, For example, perfluorocarboxylic acid or its salt, a perfluorocarbon carboxylic acid compound is mentioned. Perfluorocarboxylic acid also forms a sparingly soluble salt with Fe. Moreover, since it is a fluorine compound, it is highly resistant to radicals generated during battery operation, and can exhibit good battery performance over a long period of time.

Among these, a perfluorocarbon carboxylic acid resin represented by the following formula (16) or (17) or a metal salt thereof is particularly preferable.
_{- [CF 2 CF 2] a} - [CF 2 -CF (-O- (CF 2 -CF (CF 3)) b -O- (CF 2) c -CO 2 X)] d - (16)
(In formula (16), a and d are 0 ≦ a <1, 0 ≦ d <1, and a + d = 1. B is an integer of 1 to 8. c is an integer of 0 to 10. X is a hydrogen atom or an alkali metal atom.)
_{- [CF 2 CF 2] e} - [CF 2 -CF (-O- (CF 2) f -CO 2 Y)] g - (17)
(In the formula (17), e and g are 0 ≦ e <1, 0 ≦ g <1, and e + g = 1. F is an integer of 0 to 10. Y is a hydrogen atom or an alkali metal atom. is there.)

(Functional groups that form ionic bonds)
The compound (C) is preferably a compound having a functional group that forms an ionic bond with the polymer electrolyte (B). When the compound (C) forms an ionic bond with the proton conductive group of the polymer electrolyte (B), the compound (C) can be immobilized in the polymer electrolyte, and the elution thereof tends to be prevented.

  Although it does not specifically limit as a functional group which forms an ionic bond with the proton conductive group of a polymer electrolyte (B), For example, the functional group which has a nitrogen atom is preferable. The functional group having a nitrogen element is not particularly limited, and specific examples include amino groups, imide groups, urea groups, urethane groups, amide groups, imidazole groups, diazole groups, triazole groups, thiazole groups, triazine groups, ureas. Groups and the like. Of these, an amino group is preferable. The proton conductive group is not particularly limited, but is an acidic group such as sulfonic acid or phosphoric acid. Since the functional group having a nitrogen atom tends to be basic, the functional group having a nitrogen atom tends to form an ionic bond well with the proton conducting group.

  The content of the compound (C) is preferably 0.001 to 50000 mass%, more preferably 0.005 to 100 mass% of the total of the polymer electrolyte (B) and the compound (C). It is 20.000 mass%, More preferably, it is 0.010-10.000 mass%, More preferably, it is 0.100-5.000 mass%, More preferably, it is 0.100-2.000 mass%. When the content of the compound (C) is in the above range (0.001 to 50.000% by mass), metal ions are effectively captured while maintaining good proton conductivity, and high durability is achieved. It tends to be possible to obtain a polymer electrolyte membrane and an electrode catalyst layer.

〔solvent〕
The polymer electrolyte composition used in the present embodiment may contain a solvent. Although it does not specifically limit as a solvent used, For example, what contained at least 1 or more types in water, an organic solvent, a liquid resin monomer, and a liquid resin oligomer is mentioned.

  Although it does not specifically limit as said organic solvent, For example, alcohols, such as methanol, ethanol, 2-propanol, butanol, octanol; Ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether Esters such as acetate and γ-butyrolactone; diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, etc. Ethers; acetone, methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, Ketones such as Rohekisanon, benzene, toluene, xylene, ethylbenzene and the like; dimethylformamide, N, N- dimethyl acetoacetamide, amides such as N- methyl pyrrolidone is preferably used. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together.

  50 mass%-98 mass% are preferable with respect to 100 mass% of polymer electrolyte compositions, and, as for content of a solvent, 60 mass%-95 mass% are more preferable. When the content of the solvent is 50% by mass to 98% by mass, a polymer electrolyte composition in which various materials without precipitates are uniformly dispersed tends to be obtained.

[Radical scavenger (D)]
The polymer electrolyte composition according to the present embodiment can further contain a radical scavenger (D). As described above, the polymer electrolyte composition used in the present embodiment can efficiently suppress the generation of radical species. In addition to this, by including the radical scavenger (D), even if a radical species is generated, it can be captured by the radical scavenger (D).

  Although it does not specifically limit as a radical scavenger (D) which can be used for this embodiment, Specifically, the compound which has a functional group which enables the mechanism proposed by well-known antioxidant is mentioned. . Such a functional group is not particularly limited, and examples thereof include a functional group having a radical chain inhibiting function, a functional group having a function of decomposing radicals, and a functional group having a function of inhibiting chain initiation. Although it does not specifically limit as a functional group which has a radical chain prohibition function, For example, a phenol hydroxyl group, a primary amine, a secondary amine etc. can be mentioned. In addition, the functional group having a function of decomposing radicals is not particularly limited, and examples thereof include a mercapto group containing sulfur, phosphorus and the like, a thioether group, a disulphide group, and a phosphite group. Furthermore, the functional group having a function of inhibiting chain initiation is not particularly limited, and examples thereof include hydrazine, amide and the like (“Antioxidant Handbook” (published by Taiseisha 1978)).

  Further, examples of the radical scavenger (D) include compounds in which atoms are easily extracted by radicals, for example, hydrogen having a tertiary carbon bond or a carbon-halogen bond in the structure.

  In addition, the radical scavenger (D) that can be used in the present embodiment can also have a functional group that forms an ionic bond with the polymer electrolyte (B). Such a radical scavenger (D) is not particularly limited. For example, the compound (D-1) having at least one of a primary amine and a secondary amine in the same molecule (D-1) and / or the same molecule Selected from the group consisting of sulfur, phosphorus, hydrazine, amide, phenolic hydroxyl group, primary amine, secondary amine, hydrogen bonded to tertiary carbon, and halogen bonded to carbon. And a compound (D-2) having at least one of the above.

  Here, the functional group that forms an ionic bond with the polymer electrolyte (B) in the compound (D-1) and the compound (D-2) is not particularly limited. For example, ions in the polymer electrolyte (B) When the exchange group is a sulfonic acid group, it represents a basic functional group, and specifically includes nitrogen-containing functional groups such as primary amine, secondary amine, and tertiary amine. Therefore, if it is a primary amine or a secondary amine, it will interact with the ion exchange group of the polymer electrolyte (B) and also have a radical scavenging function (corresponding to the compound (D-1)). ). On the other hand, when the part that interacts with the ion exchange group of the polymer electrolyte (B) is a tertiary amine, the functional group that forms an ionic bond with the polymer electrolyte (B) is a part that has a radical scavenging function. In addition, there may be mentioned, for example, a phenolic hydroxyl group, a primary, secondary amine, etc. (corresponding to compound (D-2)) in the same molecule.

  More specific examples of the compound (D-1) and the compound (D-2) that can be used in the present embodiment are as follows.

  Although it does not specifically limit as a compound (D-1), For example, the aromatic compound partially substituted by said functional group like polyaniline, polybenzimidazole, polybenzoxazole, polybenzothiazole, polybenzoxazi Examples thereof include unsaturated heterocyclic compounds such as azole, phenylated polyquinoxaline, and phenylated polyquinoline.

  Although it does not specifically limit as a compound (D-2), For example, it has the tertiary nitrogen heterocyclic ring which has a sulfonic acid and an acid-base bond in a side chain, and has benzylic hydrogen which is easy to be extracted with a radical in a main chain. Examples of the compound include polyvinyl pyridine, polyvinyl carbazole, polystyrene in which an aromatic ring is introduced with a secondary amine or a group containing a tertiary amine.

  The compound (D-1) and the compound (D-2) may be a copolymer of a unit having an interaction with a polymer substance having an ion exchange group and a unit having a radical scavenging function. By having a portion having an interaction with the polymer solid electrolyte, the compatibility with the polymer electrolyte tends to be further improved. Moreover, there exists a tendency for chemical durability to improve more by having a radical capture | acquisition function.

  Content of the compound (D-1) and the compound (D-2) in the polymer electrolyte membrane of this embodiment is 100 in total of the polymer electrolyte (B), the compound (D-1), and the compound (D-2). Preferably it is 0.001-50000 mass% with respect to mass%, More preferably, it is 0.005-20.000 mass%, More preferably, it is 0.010-10.000 mass%, Still more preferably, it is 0.100-5.000 mass%, More preferably, it is 0.100-3.00 mass%.

  In this embodiment, favorable proton conductivity was maintained by setting the total content of the compound (D-1) and the compound (D-2) in the above range (0.001 to 50.000 mass%). The polymer electrolyte membrane having higher durability tends to be obtained.

〔Additive〕
In addition to the polymer electrolyte (B), the compound (C), and the radical scavenger (D), the following additives can be blended in the polymer electrolyte composition used in the present embodiment. The additives described below can be blended alone or in combination of two or more.

(Metal oxide (E))
Although it does not specifically limit as a metal oxide (E), For example, the metal oxide which has hydrogen peroxide resolution and a primary particle diameter is 1 nm-50 nm is mentioned. Here, the “primary particle size” of the metal oxide (E) means that the dispersion is adjusted so that the content of the metal oxide (E) in the solvent is 1% by mass, and the dynamic light scattering particle size is adjusted. It means the average particle diameter measured using a distribution meter (manufactured by Otsuka Electronics). The term “hydrogen peroxide resolution” means that the metal oxide (E) decomposes into water and oxygen when it comes into contact with hydrogen peroxide.

The metal oxides having a hydrogen peroxide resolution is not particularly limited, for example, zirconia (ZrO _2), titania (TiO _2), silica (SiO _2), alumina (Al ₂ O3), iron oxide (Fe ₂ O _{3, FeO, Fe 3 O 4} ), copper oxide (CuO, Cu ₂ O), zinc oxide (ZnO), yttrium oxide (Y ₂ O _3), niobium oxide (Nb ₂ O5), molybdenum oxide (MoO _3), Indium oxide (In ₂ O ₃ , In ₂ O), tin oxide (SnO ₂ ), tantalum oxide (Ta ₂ O ₅ ), tungsten oxide (WO ₃ , W ₂ O ₅ ), lead oxide (PbO, PbO ₂ ), Bismuth oxide (Bi ₂ O ₃ ), cerium oxide (CeO ₂ , Ce ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ , Sb ₂ O ₅ ), germanium oxide (GeO ₂ , GeO), lanthanum oxide (La ₂ O) _3), Ruthenium (RuO _2), and the like. These metal oxides may be used alone or as a mixture. For example, tin-added indium oxide (ITO), antimony-added tin oxide (ATO), aluminum zinc oxide (ZnO.Al ₂ O ₃ ), etc. The composite oxides listed in (1) may be used.

The metal oxide (E) used in the present embodiment prevents elution due to ionization of the metal oxide (due to heat, acid, alkali, etc.) during operation of the fuel cell, and maintains the hydrogen peroxide resolution. Zirconia (ZrO ₂ ), titania (TiO ₂ ), and yttrium oxide (Y ₂ O ₃ ) are preferable. The metal oxide (E) used in the present embodiment is preferably modified on the surface with a surface modifier having at least one reactive functional group from the viewpoint of dispersibility.

  The surface modifier of the metal oxide (E) preferably has one or more reactive functional groups. Although it does not specifically limit as this reactive functional group, For example, it is preferable to have a carbon-carbon double bond or a silicon-hydrogen bond, and an alkoxyl group, a hydroxyl group, a vinyl group, a styryl group, an acryl group, a methacryl group, One or more reactive functional groups selected from the group of acryloyl group and epoxy group are preferred. Particularly preferred in this embodiment is one or more selected from the group consisting of a silane coupling agent, a modified silicone, and a surfactant among those having a carbon-carbon double bond or silicon-hydrogen bond. .

  The silane coupling agent is not particularly limited. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyltophenoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltri Ethoxysilane, 3-glycidoxypropyltrichlorosilane, 3-glycidoxypropyltriphenoxysilane, p-styryltrimethoxysilane, p-styryltriethoxysilane, p-styryltrichlorosilane, p-styryltriphenoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropyltrichlorosilane, 3-acryloxypropyltriphenoxysilane, 3-methacryloxypropiyl Trimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrichlorosilane, 3-methacryloxypropyltriphenoxysilane, allyltrimethoxysilane, allyltriethoxysilane, allyltrichlorosilane, allyltriphenoxysilane, Vinylethyldimethoxysilane, vinylethyldiethoxysilane, vinylethyldichlorosilane, vinylethyldiphenoxysilane, 3-glycidoxypropylethyldimethoxysilane, 3-glycidoxypropyltriethyldiethoxysilane, 3-glycidoxypropyl Ethyldichlorosilane, 3-glycidoxypropylethyldiphenoxysilane, p-styrylethyldimethoxysilane, p-styrylethyldiethoxysilane, p-styryl Liethyldichlorosilane, p-styrylethyldiphenoxysilane, 3-acryloxypropylethyldimethoxysilane, 3-acryloxypropylethyldiethoxysilane, 3-acryloxypropylethyldichlorosilane, 3-acryloxypropylethyldi Phenoxysilane, 3-methacryloxypropylethyldimethoxysilane, 3-methacryloxypropylethyldiethoxysilane, 3-methacryloxypropylethyldichlorosilane, 3-methacryloxypropylethyldiphenoxysilane, allylethyldimethoxysilane, allylethyldi Ethoxysilane, allylethyldichlorosilane, allylethyldiphenoxysilane, vinyldiethylmethoxysilane, vinyldiethylethoxysilane, vinyldiethylchlorosilane, Vinyldiethylphenoxysilane, 3-glycidoxypropyldiethylmethoxysilane, 3-glycidoxypropyldiethylethoxysilane, 3-glycidoxypropyldiethylchlorosilane, 3-glycidoxypropyldiethylphenoxysilane, p-styryldiethylmethoxy Silane, p-styryldiethylethoxysilane, p-styryldiethylchlorosilane, p-styryldiethylphenoxysilane, 3-acryloxypropyldiethylmethoxysilane, 3-acryloxypropyldiethylethoxysilane, 3-acryloxypropyldiethylchlorosilane 3-acryloxypropyldiethylphenoxysilane, 3-methacryloxypropyldiethylmethoxysilane, 3-methacryloxypropyldiethylethoxysilane, 3- Taku Lilo propyl diethyl dichlorosilane, 3-methacryloxypropyl diethyl phenoxy silane, allyl diethyl silane, allyl diethyl silane, allyl diethyl chloro silane, may also be mentioned allyl diethyl phenoxy silane.

  The modified silicone is not particularly limited, and examples thereof include epoxy-modified silicone, epoxy-polyether-modified silicone, methacryl-modified silicone, phenol-modified silicone, methylstyryl-modified silicone, acrylic-modified silicone, alkoxy-modified silicone, and methylhydrogen silicone. Can be mentioned.

  Although it does not specifically limit as surfactant, For example, a nonionic surfactant is used suitably. The nonionic surfactant is not particularly limited, and examples thereof include unsaturated fatty acids such as acrylic acid, crotonic acid, oleic acid, linoleic acid, and linolenic acid.

  Examples of the method for modifying the surface of the metal oxide (E) using the surface modifier include a wet method and a dry method.

  The wet method is a method of modifying the surface of the metal oxide (E) by adding a surface modifier and the metal oxide (E) to a solvent and mixing them.

  The dry method is a method of modifying the surface of the metal oxide (E) by putting the surface modifier and the dried metal oxide (E) into a dry mixer such as a mixer and mixing them.

  The mass ratio of the modified portion of the metal oxide (E) whose surface has been modified is 5 with respect to 100% by mass of the total amount of the metal oxide (E) from the viewpoint of the mixing property with the polymer electrolyte (B). It is preferable that they are mass%-200 mass%, More preferably, they are 10 mass%-100 mass%, More preferably, they are 20 mass%-100 mass%.

  The primary particle diameter of the metal oxide (E) used in the present embodiment is preferably in the range of 1 nm to 50 nm from the balance of hydrogen peroxide resolution and dispersibility. When the primary particle diameter of the metal oxide (E) is 50 nm or less, the dispersibility of the metal oxide (E) in the polymer electrolyte composition tends to be improved. Further, when the primary particle diameter of the metal oxide (E) is 1 nm or more, the crystallinity is improved and the hydrogen peroxide tends to have a good resolution. Therefore, the more preferable range of the primary particle diameter of the metal oxide (E) is 1 nm to 30 nm, and more preferably 2 nm to 20 nm.

  The mass ratio (B / E) of the polymer electrolyte (B) to the metal oxide (E) is (B / E) = 50/50 to 99.99 / 0.00 from the viewpoint of the balance between durability and conductivity. 01 is preferable, (B / E) = 70/30 to 99.99 / 0.01 is more preferable, (B / E) = 80/20 to 99.9 / 0.1 is more preferable, and (B / E) ) = 95/5 to 99.5 / 0.5 is even more preferable.

  In addition, when mixing and dispersing the metal oxide (E), it is preferable to use it dispersed in a solvent from the viewpoint of suppressing aggregation.

  The content of the metal oxide (E) in the dispersion is preferably 1% by mass to 70% by mass, more preferably 1% by mass to 50% by mass, and still more preferably 5% by mass to 30% by mass. By setting the content of the metal oxide (E) in the dispersion to 1% by mass to 70% by mass, the metal oxide (E) maintains a good dispersion state without causing gel or precipitation in the solvent. Tend to be able to.

(Thioether compound (F))
The thioether compound (F) is not particularly limited, and is — (R—S) _n — (wherein S is a sulfur atom, R is a hydrocarbon group, and n is an integer of 1 or more). A compound containing a chemical structure, for example, a dialkyl thioether such as dimethylthioether, diethylthioether, dipropylthioether, methylethylthioether, methylbutylthioether; a cyclic thioether such as tetrahydrothiophene, tetrahydroapiran; Aromatic thioethers such as ethyl phenyl sulfide, diphenyl sulfide and dibenzyl sulfide are exemplified. These may be used as a monomer or may be used as a polymer such as polyphenylene sulfide (PPS).

  The thioether compound (F) is preferably a polymer (oligomer or polymer) of n ≧ 10 from the viewpoint of durability, and more preferably a polymer of n ≧ 1,000. A particularly preferred thioether compound (F) is polyphenylene sulfide (PPS).

  Here, polyphenylene sulfide will be described. The polyphenylene sulfide used in the present embodiment is a polyphenylene sulfide having a paraphenylene sulfide skeleton of preferably 70 mol% or more, more preferably 90 mol% or more.

  The method for producing the polyphenylene sulfide is not particularly limited. For example, a method in which a halogen-substituted aromatic compound (p-dichlorobenzene or the like) is polymerized in the presence of sulfur and sodium carbonate, a halogen-substituted aromatic compound in a polar solvent. Polymerizing in the presence of sodium sulfide or sodium hydrogen sulfide and sodium hydroxide, or polymerizing a halogen-substituted aromatic compound in the presence of hydrogen sulfide and sodium hydroxide or sodium aminoalkanoate in a polar solvent, p. -Self-condensation of chlorothiophenol and the like. Among them, a method of reacting sodium sulfide and p-dichlorobenzene in an amide solvent such as N-methylpyrrolidone or dimethylacetamide or a sulfone solvent such as sulfolane is preferable.

  In addition, the content of -SX group (herein, S is a sulfur atom and X is an alkali metal or a hydrogen atom) possessed by polyphenylene sulfide is usually 10 μmol / g or more and 10,000 μmol / g or less, Preferably they are 15 micromol / g or more and 10,000 micromol / g or less, More preferably, they are 20 micromol / g or more and 10,000 micromol / g or less.

  When the -SX group concentration is in the above range, the reactive site tends to increase. By using polyphenylene sulfide satisfying the above-mentioned range for the -SX group concentration, the dispersibility is improved by improving the miscibility with the polymer electrolyte (B) used in the present embodiment, which is higher under high temperature and low humidification conditions. Durability tends to be obtained.

  Moreover, as the thioether compound (F), those having an acidic functional group introduced at the terminal can be suitably used. The acidic functional group to be introduced is not particularly limited. For example, sulfonic acid group, phosphoric acid group, carboxylic acid group, maleic acid group, maleic anhydride group, fumaric acid group, itaconic acid group, acrylic acid group, methacrylic acid Groups are preferred. Among these, a sulfonic acid group is more preferable.

  In addition, the introduction method of an acidic functional group is not specifically limited, It implements using a general method. For example, the introduction of the sulfonic acid group can be carried out under known conditions using a sulfonating agent such as sulfuric anhydride or fuming sulfuric acid. Such an introduction method is not particularly limited. Hu, T .; Xu, W .; Yang, Y. et al. Fu, Journal of Applied Polymer Science, Vol. 91, E.E. Montoneri, Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 27, 3043-3051 (1989).

  Moreover, what substituted the introduce | transduced acidic functional group with the metal salt or amine salt is used suitably. Although it does not specifically limit as a metal salt, For example, alkaline-earth metal salts, such as alkali metal salts, such as sodium salt and potassium salt, and calcium salt, are preferable.

  Furthermore, when the thioether compound (F) is used in powder form, the average particle size of the thioether compound (F) realizes an effect such as a longer life by improving the dispersibility in the polymer electrolyte (B). From the viewpoint of making it, 0.01 to 2.0 μm is preferable, 0.01 to 1.0 μm is more preferable, 0.01 to 0.5 μm is more preferable, and 0.01 to 0.1 μm is still more preferable .

  The method for finely dispersing the thioether compound (F) in the polymer electrolyte (B) is not particularly limited. For example, the thioether compound (F) is pulverized and finely dispersed by applying high shear during melt kneading with the polymer electrolyte (B) or the like. Examples thereof include a method, a method of obtaining a polymer electrolyte solution, filtering the solution to remove coarse thioether compound (F) particles, and using the solution after filtration.

  Melt viscosity of polyphenylene sulfide suitably used for melt kneading (using a flow tester, 300 ° C., load 196 N, L / D (L: orifice length, D: orifice inner diameter) = 10/1, hold for 6 minutes Is preferably 1 to 10,000 poise, more preferably 100 to 10,000 poise from the viewpoint of moldability.

  The mass ratio (B / F) of the polymer electrolyte (B) to the thioether compound (F) is preferably (B / F) = 60/40 to 99.99 / 0.01, (B / F) = 70/30 to 99.95 / 0.05 is more preferable, (B / F) = 80/20 to 99.9 / 0.1 is more preferable, and (B / F) = 90/10 to 99.5 /0.5 is even more preferable. By setting the mass ratio of the polymer electrolyte (B) to 60 or more, good ion conductivity can be realized, and good battery characteristics tend to be realized. On the other hand, by setting the mass ratio of the thioether compound (F) to 40 or less, durability in battery operation under high temperature and low humidity conditions tends to be further improved.

  Moreover, the thioether compound (F) tends to be able to exhibit extremely high durability even under conditions of high temperature and low humidity by blending with the radical scavenger (D) according to the present embodiment.

  Here, the mass ratio (D / F) of the radical scavenger (D) to the thioether compound (F) is preferably (D / F) = 1/99 to 99/1, and (D / F) = 5/95 to 95/5 is more preferable, (D / F) = 10/90 to 90/10 is more preferable, and (D / F) = 20/80 to 80/20 is still more preferable. When the mass ratio (D / F) is within the above range, the balance between chemical stability and durability (dispersibility) tends to be excellent.

  Furthermore, the content of the total mass of the radical scavenger (D) and the thioether compound (F) in the polymer electrolyte membrane is preferably 0.01 to 50 mass%, more preferably 0.05 to 45 mass%, 0.1-40 mass% is further more preferable, 0.2-35 mass% is further more preferable, and 0.3-30 mass% is still more preferable. When the content is in the above range, the balance between ion conductivity and durability (dispersibility) tends to be excellent.

  The polymer electrolyte composition used in the present embodiment can be used in the form of a polymer electrolyte solution, a polymer electrolyte membrane, a polymer electrolyte binder, and the like.

[Polymer electrolyte solution]
The polymer electrolyte composition used in the present embodiment may be used as a polymer electrolyte solution by dissolving or dispersing the components constituting the composition simultaneously or separately and then mixing them. Furthermore, the polymer electrolyte solution can be used as a material such as a polymer electrolyte membrane or an electrode binder as it is or after being subjected to steps such as filtration and concentration, and then alone or mixed with another electrolyte solution.

  A method for producing the polymer electrolyte solution will be described. The method for producing the polymer electrolyte solution is not particularly limited. For example, first, a molded product made of the polymer electrolyte precursor is immersed in a basic reaction liquid and hydrolyzed. By this hydrolysis treatment, the polymer electrolyte precursor is converted into a polymer electrolyte (B). Next, the hydrolyzed molded product is sufficiently washed with warm water or the like, and then acid-treated.

The acid used for the acid treatment is not particularly limited, but for example, mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and organic acids such as oxalic acid, acetic acid, formic acid and trifluoroacetic acid are preferable. By this acid treatment, the polymer electrolyte precursor is protonated and becomes SO ₃ H form. The above-mentioned molded product (molded product containing a protonated polymer electrolyte) treated with an acid as described above has a good solvent (resin affinity) that can dissolve or suspend the polymer electrolyte (B). Or dissolved in a solvent). Examples of such a solvent include, but are not limited to, water; protic organic solvents such as ethanol, methanol, n-propanol, isopropyl alcohol, butanol, glycerin; N, N-dimethylformamide, N, N-dimethylacetamide And aprotic solvents such as N-methylpyrrolidone. These can be used alone or in combination of two or more. In particular, when one solvent is used, water alone is preferable. Moreover, when using 2 or more types together, the mixed solvent of water and a protic organic solvent is preferable.

  Although the method of dissolving or suspending is not particularly limited, for example, it is preferable to dissolve or disperse as it is in the above-mentioned solvent, and it is 0 to 250 ° C. under the condition of being sealed and pressurized under an atmospheric pressure or an autoclave. It is more preferable to dissolve or disperse in the temperature range. In particular, when a protic organic solvent is used as the solvent, the mixing ratio of water and the protic organic solvent is appropriately determined according to the dissolution method, dissolution conditions, type of polymer electrolyte, total solid content concentration, dissolution temperature, stirring speed, and the like. You can choose. The ratio of the mass of the protic organic solvent to water is preferably from 0.1 to 10 protic organic solvents relative to water 1, and more preferably from 0.1 to 5 protic organic solvents relative to water 1.

  The dissolution / suspension of the polymer electrolyte (B) is not particularly limited. For example, an emulsion (a liquid emulsion in which liquid particles are dispersed as colloidal particles or coarser particles in a liquid is formed. ), Suspensions (solid particles dispersed in a liquid as colloidal particles or microscopic particles), colloidal liquids (macromolecules dispersed), micellar liquids (many small molecules are intermolecular) 1 type or 2 types or more, such as a lyophilic colloidal dispersion system formed by force association.

  The polymer electrolyte solution can be concentrated or filtered according to the molding method and application. The concentration method is not particularly limited, and examples thereof include a method of evaporating the solvent by heating and a method of concentrating under reduced pressure. When the polymer electrolyte solution is used as a coating solution, the solid content ratio of the polymer electrolyte solution is preferably 0.5 to 50% by mass. When the solid content is 0.5% by mass or more, an increase in viscosity is suppressed and the handling property tends to be excellent. Moreover, it exists in the tendency for productivity to improve because a solid content rate is 50 mass% or less.

  Although it does not specifically limit as a filtration method, For example, the method of carrying out pressure filtration using a filter is mentioned typically. As for the filter, it is preferable to use a filter medium whose 90% collection particle diameter is 10 to 100 times the average particle diameter of the particles. Examples of the filter medium include paper and metal. In particular, when the filter medium is paper, the 90% collection particle size is preferably 10 to 50 times the average particle size of the particles. When using a metal filter, it is preferable that the 90% collection particle diameter is 50 to 100 times the average particle diameter of the particles. By setting the 90% collection particle size to 10 times or more of the average particle size, it is possible to prevent the pressure required for liquid feeding from becoming too high, or that the filter is blocked in a short period of time. It tends to be suppressed. On the other hand, by setting it to 100 times or less of the average particle diameter, there is a tendency that agglomerates of particles and undissolved resin that can cause foreign matters in the film can be removed satisfactorily.

[Polymer electrolyte membrane]
The polymer electrolyte membrane used in the present embodiment has the above-described chain polyfluoroolefin microporous membrane (A) and the polymer electrolyte (B), and is used for producing the polymer electrolyte membrane. Thus, the polymer electrolyte composition can be used. That is, the polymer electrolyte membrane of the present embodiment can include the polymer electrolyte composition. The thickness of the polymer electrolyte membrane is not particularly limited, but is preferably 1 μm or more and 500 μm or less, more preferably 2 μm or more and 100 μm or less, and further preferably 5 μm or more and 50 μm or less. The film thickness of 1 μm or more is preferable from the viewpoint of reducing inconveniences such as a direct reaction between hydrogen and oxygen, and further causes differential pressure, distortion, etc. during handling of the fuel cell or during operation of the fuel cell. However, it is preferable because the film is less likely to be damaged. On the other hand, when the film thickness is 500 μm or less, the ion permeability is improved and the performance as a solid polymer electrolyte membrane tends to be improved.

  Next, the manufacturing method of the polymer electrolyte membrane of this embodiment is demonstrated. The polymer electrolyte membrane of this embodiment can be obtained, for example, by filling the fine pores of the microporous membrane (A) with a fluorine-based polymer electrolyte composition.

  The method of filling the pores of the microporous membrane (A) with the fluorine-based polymer electrolyte composition is not particularly limited. For example, a method of applying the polymer electrolyte solution to the microporous membrane (A), And a method of drying the polymer electrolyte solution after impregnating the microporous membrane (A). For example, a film of a polyelectrolyte solution is formed on an elongated casting substrate (sheet) that is moving or stationary, and an elongated microporous membrane (A) is brought into contact with the solution to form a composite structure. Make it. The composite structure is dried in a hot air circulation tank. Next, there is a method in which a polymer electrolyte solution film is further formed on the dried composite structure to form a polymer electrolyte membrane. The contact between the polymer electrolyte solution and the microporous membrane (A) may be performed in a dry state, or may be performed in an undried state or a wet state. Moreover, when making it contact, you may make it press-fit with a rubber roller, controlling the tension | tensile_strength of a microporous film (A). Further, a sheet containing a polymer electrolyte may be preliminarily formed by extrusion molding, cast molding, or the like, and this sheet may be filled by hot pressing with a microporous film.

  Further, for the purpose of improving the conductivity and mechanical strength of the polymer electrolyte membrane, one or more layers containing the polymer electrolyte are laminated on at least one main surface of the polymer electrolyte membrane thus produced. May be. Moreover, in the polymer electrolyte membrane of this embodiment, you may bridge | crosslink the compounds contained there using a crosslinking agent, an ultraviolet-ray, an electron beam, a radiation.

  The polymer electrolyte membrane of the present embodiment is preferably subjected to a heat treatment after being manufactured as described above. By this heat treatment, the crystal part in the polymer electrolyte membrane and the polymer solid electrolyte part tend to be more strongly bonded, and as a result, the mechanical strength tends to be further stabilized. The temperature of this heat treatment is preferably 100 ° C to 230 ° C, more preferably 110 ° C to 230 ° C, and still more preferably 120 ° C to 200 ° C. By adjusting the temperature of the heat treatment to the above range, the adhesion between the crystal part and the polymer solid electrolyte part tends to be further improved. Moreover, the said temperature range is suitable also from a viewpoint of maintaining the moisture content and mechanical strength of a polymer electrolyte membrane. Although depending on the heat treatment temperature, the heat treatment time is preferably 5 minutes to 3 hours, more preferably 10 minutes to 2 hours from the viewpoint of obtaining a polymer electrolyte membrane having higher durability.

(Electrocatalyst layer)
The electrode catalyst layer used in the present embodiment can contain the polymer electrolyte composition. More specifically, the electrode catalyst layer may be composed of the polymer electrolyte composition, if necessary, fine particles of a catalytic metal, and a conductive agent carrying the catalyst metal. Moreover, a water repellent can also be included as needed. The catalyst used for the electrode is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron, Examples thereof include cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof. Among these, platinum is mainly used.

[Membrane electrode assembly]
The membrane electrode assembly of this embodiment has the polymer electrolyte membrane of this embodiment. More specifically, the membrane electrode assembly of the present embodiment includes the polymer electrolyte membrane and the electrode catalyst layer. The polymer electrolyte membrane according to the present embodiment can be used as a constituent member of a membrane electrode assembly and a polymer electrolyte fuel cell. A unit in which two types of electrode catalyst layers, an anode and a cathode, are bonded to both surfaces of a polymer electrolyte membrane is called a membrane electrode assembly (hereinafter sometimes abbreviated as “MEA”). A material in which a pair of gas diffusion layers are bonded to the outer side of the electrode catalyst layer so as to face each other is sometimes referred to as MEA.

  Although it does not specifically limit as a manufacturing method of MEA, For example, the following methods are performed. First, platinum-supported carbon as an electrode material is dispersed in a solution obtained by dissolving an electrode binder ion exchange resin in a mixed solution of alcohol and water to form a paste. A certain amount of this is applied to a PTFE sheet and dried. Next, the application surface of the PTFE sheet is faced to each other, and a polymer electrolyte membrane is sandwiched therebetween, and transfer joining is performed by hot pressing at 100 ° C. to 200 ° C. to obtain an MEA. In general, a binder for an electrode is prepared by dissolving an ion exchange resin in a solvent (alcohol, water, etc.). From the viewpoint of durability during operation of the fuel cell, the polymer electrolyte composition according to this embodiment is used. It is preferable.

[Solid polymer fuel cell]
The polymer electrolyte fuel cell of this embodiment has the membrane electrode assembly (MEA) of this embodiment. The MEA obtained as described above, and in some cases, the MEA having a structure in which a pair of gas diffusion electrodes are opposed to each other are further combined with components used in general polymer electrolyte fuel cells such as bipolar plates and backing plates. A solid polymer fuel cell can be constructed.

  The bipolar plate means a composite material of graphite and resin having a groove for flowing a gas such as fuel or oxidant on its surface, or a metal plate. In addition to the function of transmitting electrons to an external load circuit, the bipolar plate has a function of a flow path for supplying fuel and oxidant to the vicinity of the electrode catalyst. A fuel cell is manufactured by inserting and stacking a plurality of MEAs between such bipolar plates.

  Hereinafter, although an example explains still more concretely, this embodiment is not limited only to these examples. Measurement methods and evaluation methods for various physical properties in Examples and the like are as follows.

(C—H bond ratio)
Targeting the microporous membrane after fluorination in Production Examples 1 to 8, using a Fourier transform infrared spectrophotometer (product name: FT / IR-460 plus manufactured by JASCO Corporation), 3100 cm ⁻¹ to 2800 cm ⁻ absorption area S of peaks derived from the absorption area S _CH and 2700 cm ^-1 derived from predominantly CH bond as measured in the range up to ¹ primarily in C-F bonds measured by a range of up to 2000 cm ^-1 _CF was calculated respectively. Furthermore, the ratio of C—H bonds (C—H group residual ratio) was calculated by the following formula.
C—H group residual ratio = S _CH / (S _CH + S _CF ) × 100 (%)

(1) Fluorination treatment of microporous membrane Fluorination was performed by exposing the microporous membrane to a mixed gas composed of 5 vol% of fluorine gas and 95 vol% of nitrogen gas for 30 minutes at room temperature.

(2) Fenton test The microporous membrane was pretreated in air at 200 ° C for 2 hours. Next, an aqueous solution containing 2 ppm of iron ions and 1% of hydrogen peroxide was prepared, and the polymer electrolyte membrane after pretreatment was immersed for 1 hour in a place heated to 80 ° C. Then, the fluorine ion contained in the liquid after a test was measured with the ion chromatograph. In addition, it evaluated that it became a polymer electrolyte composition which gives a highly durable polymer electrolyte membrane, an electrode catalyst layer, etc., so that there are few amounts of fluorine ions (fluorine elution amount). That is, the microporous film in which fluorine ions were detected was evaluated as x, and the microporous film in which fluorine ions were not detected was evaluated as ◯. For non-fluorinated microporous membranes, gel permeation chromatography (GPC) measurement is performed, and the molecular weight is compared between the untreated microporous membrane and the microporous membrane after the above pretreatment. The case where there was no molecular weight reduction was marked with ◯, and the case where molecular weight reduction was observed was marked with x.

(Production Example 1)
A polyethylene microporous membrane (manufactured by DSM Solutech, grade: Solupor 3P07A porosity 83%) was fluorinated by the method described in (1). In addition, the said porosity employ | adopted the value measured using the mercury porosimeter (Autopore IV9520, the initial pressure of about 20 kPa, Shimadzu Corporation Corp.) by the mercury intrusion method (hereinafter the same). Subsequently, the Fenton test described in (2) was performed on the microporous membrane. The results are shown in Table 1.

(Production Example 2)
(Preparation of polypropylene microporous membrane)
A polypropylene (PP) resin having a density of 0.90 and a viscosity average molecular weight of 300,000 was charged into a twin screw extruder having a diameter of 25 mm and L / D = 48 via a feeder. Kneaded under the conditions of 220 ° C and 200rpm, extruded from a co-extrudable lip 3mm thick T-die installed at the tip of the extruder, immediately cooled to 25 ° C, taken up with a cast roll, and a precursor film with a thickness of 20mm Got. After this precursor film was uniaxially stretched 1.5 times at 40 ° C., this stretched film was further uniaxially stretched 2.0 times at 120 ° C. and further heat-set at 130 ° C. An 85% polypropylene microporous membrane was obtained.
This polypropylene microporous membrane was fluorinated by the method described in (1). Subsequently, the Fenton test described in (2) was performed on the microporous membrane. The results are shown in Table 1.

(Production Example 3)
(Preparation of ethylene-propylene microporous membrane)
An ethylene-propylene copolymer resin having a density of 0.88 and a viscosity average molecular weight of 400,000 was charged into a twin screw extruder having a diameter of 25 mm and L / D = 48 via a feeder. Kneaded under the conditions of 220 ° C and 200rpm, extruded from a co-extrudable lip 3mm thick T-die installed at the tip of the extruder, immediately cooled to 25 ° C, taken up with a cast roll, and a precursor film with a thickness of 20mm Got. After this precursor film was uniaxially stretched 1.5 times at 40 ° C., this stretched film was further uniaxially stretched 2.0 times at 120 ° C. and further heat-set at 130 ° C. An 82% ethylene-propylene microporous membrane was obtained.
This ethylene-propylene microporous membrane was fluorinated by the method described in (1). Subsequently, the Fenton test described in (2) was performed on the microporous membrane. The results are shown in Table 1.

(Production Example 4)
(Preparation of poly-4-methyl-1-pentene microporous membrane)
Poly (4-methyl-1-pentene) resin (DX845, manufactured by Mitsui Chemicals, Inc.) having a density of 0.83 and a melting point of 240 ° C. (catalog value) 55 parts by weight, tetra-n-octyl pyromellitate (Piromex P N- 08, manufactured by Kao Corporation), and 45 parts by weight of tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane 0.5 parts by weight are mixed. Adjusted. Next, the composition was melt-kneaded for 10 minutes after stabilization of the kneading torque at a temperature of 270 ° C. and a rotation speed of 50 rpm using a Laboplast mill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain a kneaded product. Further, the kneaded product was molded into a sheet using a compression molding machine adjusted to 270 ° C., and then cooled to room temperature with a cooling compression molding machine. A 15 mm molded body was obtained.

Tetra-n-octyl pyromellitate was extracted using 2-butanone in a state where the obtained molded body was fixed on all sides to a metal frame. Furthermore, after 2-butanone was replaced with ethanol, ethanol was volatilized and removed at room temperature to obtain a porous molded body.
Subsequently, simultaneous biaxial stretching at a stretching ratio of 3 × 3 was performed at a stretching temperature of 180 ° C. and a stretching speed of 20% / second using a test biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.). Finally, the obtained microporous membrane was fixed to a metal frame, and heat-treated for 5 minutes in a hot air oven adjusted to 170 ° C. to obtain a microporous membrane made of poly-4-methyl-1-pentene. It was.

  This poly-4-methyl-1-pentene microporous membrane was fluorinated by the method described in (1). Subsequently, the Fenton test described in (2) was performed on the microporous membrane. The results are shown in Table 1.

(Comparative Production Example 1)
The Fenton test described in (2) was performed in the same manner as in Production Example 1 except that fluorination was not performed. The results are shown in Table 1.

(Comparative Production Example 2)
The Fenton test described in (2) was carried out in the same manner as in Production Example 2 except that fluorination was not performed. The results are shown in Table 1.

(Comparative Production Example 3)
The Fenton test described in (2) was carried out in the same manner as in Production Example 3 except that fluorination was not performed. The results are shown in Table 1.

(Comparative Production Example 4)
The Fenton test described in (2) was carried out in the same manner as in Production Example 4 except that fluorination was not performed. The results are shown in Table 1.

(Reference Production Example 1)
A polytetrafluoroethylene (PTFE) film (manufactured by Donaldson, grade: # 1326 porosity 71%) as a microporous film was fluorinated by the method described in (1). Subsequently, the Fenton test described in (2) was performed on the microporous membrane. The results are shown in Table 1.

(3) Adhesiveness The polymer electrolyte membrane was cut into 5 cm × 5 cm pieces to obtain test pieces. Next, a double-sided tape (NW-K15 manufactured by Nichiban Co., Ltd.) was uniformly applied to one side of the test piece and fixed on the glass substrate. Next, cellotape (registered trademark) (CT-15 manufactured by Nichiban Co., Ltd.) was attached so as to pass through one diagonal line of the polymer electrolyte membrane, and peeled off vigorously. At this time, it was rated as x when completely peeled off at the interface between the reinforcing material and the polymer electrolyte, Δ when partially peeled, and ○ when not peeled off.

(4) Dimensional Change Measurement A dimensional change ratio (planar direction / film thickness direction) in 80 ° C. water of a polymer electrolyte membrane prepared as described below was measured as follows.

  As a membrane sample, a polymer electrolyte membrane was cut into a 4 cm × 3 cm rectangular membrane, left in a constant temperature and humidity room (23 ° C., 50% RH) for 1 hour or longer, and then the dried rectangular membrane sample in the planar direction. Each dimension was measured.

  Next, the rectangular membrane sample whose dimensions were measured was boiled in hot water at 80 ° C. for 1 hour, and water was sufficiently absorbed so that the mass change due to moisture in the electrolyte membrane was 5% or less. At this time, the film was taken out from the hot water, and it was confirmed that the amount of mass change was 5% or less with an electronic balance in a state where water on the surface was sufficiently removed. The wet membrane sample which absorbed this water and expanded was taken out from the hot water, and each dimension in the plane direction and the film thickness direction was measured. Taking each dimension in the plane direction in the dry state as a reference, taking the average of each dimension increment in the plane direction and the film thickness direction in the wet state from each dimension in the dry state was taken as the dimensional change amount (%). .

Next, the dimensional change ratio (plane direction / film thickness direction) was calculated by the following formula.
(Dimensional change ratio (plane direction / film thickness direction)) = dimensional change in plane direction (%) ÷ dimensional change in film thickness direction (%)
A: For dimensional changes, only specific numerical values are listed, and ○ and × are not judged.

(5) Durability test: OCV test In order to evaluate the chemical durability of the polymer electrolyte membrane under high-temperature and low-humidification conditions in an accelerated manner, an accelerated test using OCV was performed according to the following procedure. Note that “OCV” means an open circuit voltage.

(5) -1 Preparation of Electrocatalyst Ink 20% by mass perfluorosulfonic acid polymer solution (SS700C / 20, manufactured by Asahi Kasei E-materials, equivalent mass (EW): 740), electrode catalyst (TEC10E40E, Tanaka Kikinzoku Co., Ltd.) Made of platinum, 36.7 wt% of platinum supported) so that the platinum / perfluorosulfonic acid polymer becomes 1 / 1.15 (mass), and then the solid content (the sum of the electrode catalyst and the perfluorosulfonic acid polymer) Ethanol was added so as to be 11 wt%, and an electrode catalyst ink was obtained by stirring for 10 minutes at 3,000 rpm with a homogenizer (manufactured by ASONE).

(5) -2 Production of MEA Using an automatic screen printing machine (product name: LS-150, manufactured by Neurong Seimitsu Kogyo Co., Ltd.), the electrocatalyst ink was placed on both sides of the polymer electrolyte membrane, and the amount of platinum was 0 on the anode side. .2mg / cm ^2, was applied to the cathode side 0.3mg / cm ^2, 140 ℃, to obtain a MEA by drying and solidifying at 5 minutes condition.

(5) -3 Fabrication of a fuel cell unit cell A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) is stacked on both poles of the MEA, and then a gasket, bipolar plate, and backing plate are stacked to form a fuel cell unit cell. Obtained.

(5) -4 OCV Test The fuel cell single cell was set in an evaluation apparatus (Fuel Cell Evaluation System 890CL manufactured by Toyo Technica), and a durability test by OCV was performed.

  The OCV test conditions were such that the cell temperature was 95 ° C., the humidification bottle was 50 ° C. (relative humidity 25% RH), and hydrogen gas was supplied to the anode side and air gas was supplied to the cathode side at 50 cc / min. Further, no pressure was applied (atmospheric pressure) on both the anode side and the cathode side.

(5) -5 Degradation Determination The amount of hydrogen leak was measured every 50 hours from the start of the test using a micro gas chromatograph (CP-4900 manufactured by VARIAN). When the amount of hydrogen leaked was 1000 ppm or more, the film was judged to be broken, and the test was stopped.

  In the OCV test, the case where the film breaking time exceeded 250 hours was evaluated as ◯, and the case where the film breaking time was 250 hours or less was determined as ×.

[Example 1]
(Preparation of polymer electrolyte composition)
Perfluorosulfonic acid resin precursor obtained from tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F, which are precursors of the polymer electrolyte (B) (EW after hydrolysis and acid treatment: 740) The pellet was brought into contact with an aqueous solution in which potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times each time using a new aqueous hydrochloric acid solution, then washed with ion-exchanged water and dried. Thereby, a pellet of the polymer electrolyte (B) having a sulfonic acid group (SO ₃ H) was obtained.

  The pellet was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 66.7: 33.3 (mass ratio)), sealed, heated to 160 ° C. with stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare 5% by mass of a uniform perfluorosulfonic acid resin solution-1.

  Next, 1200 g of this solution was transferred to a 2 L eggplant flask and placed on a rotary evaporator (Rotavapor R-200 manufactured by BUCHI) with a hot water bath set to 80 ° C., and the pressure was reduced so that the solid content concentration was 20% by mass. Concentrated to prepare perfluorosulfonic acid resin solution-2.

(Production of polymer electrolyte membrane)
Using the coating machine (manufactured by Toyo Seiki Co., Ltd.), the perfluorosulfonic acid resin solution-2 obtained above is coated on Kapton 200H (product name: manufactured by Toray DuPont Co., Ltd.) so that the wet thickness is 185 μm. Worked. Before the coated surface was dried, the fluorinated polyethylene microporous membrane described in Production Example 1 was overlaid as a microporous membrane and dried at 80 ° C. for 30 minutes and then at 120 ° C. for 30 minutes. After drying, the polymer electrolyte solution-2 was applied to the microporous membrane side so that the wet thickness was 185 μm, and dried at 80 ° C. for 30 minutes and then at 120 ° C. for 30 minutes. The obtained composite membrane was washed with water and further dried at 170 ° C. for 20 minutes to obtain a polymer electrolyte membrane.

  Using this polymer electrolyte membrane, the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were carried out, and good results were obtained. The results are shown in Table 2.

[Example 2]
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the fluorinated polypropylene microporous membrane described in Production Example 2 was used as the microporous membrane.

  Using this polymer electrolyte membrane, the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were carried out, and good results were obtained. The results are shown in Table 2.

Example 3
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the fluorinated ethylene-propylene microporous membrane described in Production Example 3 was used as the microporous membrane.

Using this polymer electrolyte membrane, the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were carried out, and good results were obtained. The results are shown in Table 2.
Example 4
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the fluorinated poly-4-methyl-1-pentene microporous membrane described in Production Example 4 was used as the microporous membrane.

  Using this polymer electrolyte membrane, the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were carried out, and good results were obtained. The results are shown in Table 2.

[Comparative Example 1]
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the polyethylene microporous membrane described in Comparative Production Example 1 was used as the microporous membrane.

  Using this polymer electrolyte membrane, when the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were performed, voids were seen between the reinforcing material and the polymer electrolyte, Neither dimensional change nor durability met the standards. The results are shown in Table 2.

[Comparative Example 2]
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the polypropylene microporous membrane described in Comparative Production Example 2 was used as the microporous membrane.

  Using this polymer electrolyte membrane, when the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were performed, voids were seen between the reinforcing material and the polymer electrolyte, Neither dimensional change nor durability met the standards. The results are shown in Table 2.

[Comparative Example 3]
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the ethylene-propylene microporous membrane described in Comparative Production Example 3 was used as the microporous membrane.

  Using this polymer electrolyte membrane, when the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were performed, voids were seen between the reinforcing material and the polymer electrolyte, Neither dimensional change nor durability met the standards. The results are shown in Table 2.

[Comparative Example 4]
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the microporous membrane made of poly-4-methyl-1-pentene described in Comparative Production Example 4 was used as the microporous membrane.

  Using this polymer electrolyte membrane, when the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were performed, voids were seen between the reinforcing material and the polymer electrolyte, Neither dimensional change nor durability met the standards. The results are shown in Table 2.

[Reference Example 1]
A polymer electrolyte membrane was obtained in the same manner as in Example 1, except that a polytetrafluoroethylene (PTFE) membrane (Donaldson, grade: # 1326 porosity 71%) was used as the microporous membrane.

  Using this polymer electrolyte membrane, when the above (3) observation of impregnation, (4) dimensional change, and (5) durability test were performed, voids were seen between the reinforcing material and the polymer electrolyte, Neither dimensional change nor durability met the standards. The results are shown in Table 2.

(6) Preparation of fluorinated microporous membrane containing functional groups The microporous membrane was mixed with a mixed gas consisting of 3 vol% fluorine gas, 5 vol% oxygen gas, 5 vol% sulfur dioxide gas, and 87 vol% nitrogen gas under room temperature conditions. Fluorination was performed by exposure for 1 minute. The residual C—H group ratio of the microporous membrane after fluorination was calculated by performing measurement using FTIR in the same manner as described above.

(7) Fenton test A microporous membrane prepared as described below was pretreated in air at 200 ° C for 2 hours. Next, an aqueous solution containing 2 ppm of iron ions and 1% of hydrogen peroxide was prepared, and the polymer electrolyte membrane after pretreatment was immersed for 1 hour in a place heated to 80 ° C. Then, the fluorine ion contained in the liquid after a test was measured with the ion chromatograph. In addition, it becomes a polymer electrolyte composition which gives a highly durable polymer electrolyte membrane, an electrode catalyst layer, etc., so that there are few amounts of fluorine ions (fluorine elution amount).

(8) EW measurement A fluorine-based microporous membrane containing a functional group was cut out at 20 mm square and immersed in distilled water for 1 hour or more. Next, the fluorine-based microporous membrane was immersed in a saturated NaCl aqueous solution for 30 minutes or more with stirring. Next, titration was performed using an automatic titrator (product name: AUT-701 type, manufactured by Toa DKK). After titration, the fluorinated microporous membrane was dried at 160 ° C. and the weight was measured. EW was determined from the obtained titration result using the following formula.
EW = (W / M) −22
(In the above formula, “W” represents the mass (mg) of the microporous membrane (A) introduced with a functional group, and “M” represents the amount of sodium hydroxide (mmol) required for neutralization).

[Production Example 5]
For the polyethylene microporous membrane used in Production Example 1, a sulfonic acid group-containing fluorine-based microporous membrane was prepared by the method described in (6) above. Next, the microporous membrane was subjected to the Fenton test by the method described in (7) and the EW measurement by the method described in (8). The results are shown in Table 3.

[Production Example 6]
For the polypropylene microporous membrane prepared in Production Example 2, a sulfonic acid group-containing fluorine-based microporous membrane was prepared by the method described in (6) above. Next, the microporous membrane was subjected to the Fenton test by the method described in (7) and the EW measurement by the method described in (8). The results are shown in Table 3.

[Production Example 7]
For the ethylene-propylene microporous membrane prepared in Production Example 3, a sulfonic acid group-containing fluorine-based microporous membrane was prepared by the method described in (6) above. Next, the microporous membrane was subjected to a Fenton test by the method described in (7) and EW measurement was performed by the method described in (8). The results are shown in Table 3.

[Production Example 8]
For the poly-4-methyl-1-pentene microporous membrane prepared in Production Example 4, a sulfonic acid group-containing fluorine-based microporous membrane was prepared by the method described in (6) above. Next, the microporous membrane was subjected to a Fenton test by the method described in (7) and EW measurement was performed by the method described in (8). The results are shown in Table 3.

[Comparative Production Example 5]
A Fenton test was performed by the method described in (7) in the same manner as in Production Example 5 except that fluorination was not performed. The results are shown in Table 3.

[Comparative Production Example 6]
A Fenton test was performed by the method described in (7) in the same manner as in Production Example 6 except that fluorination was not performed. The results are shown in Table 3.

[Comparative Production Example 7]
A Fenton test was carried out by the method described in (7) in the same manner as in Production Example 7 except that fluorination was not performed. The results are shown in Table 3.

[Comparative Production Example 8]
A Fenton test was carried out by the method described in (7) in the same manner as in Production Example 8 except that fluorination was not performed. The results are shown in Table 3.

[Reference Production Example 2]
(7) In the same manner as in Production Example 5, except that a polytetrafluoroethylene (PTFE) membrane (Donaldson, grade: # 1326 porosity 71%) was used as the microporous membrane, and fluorination was not performed. The Fenton test was carried out by the method described in 1. The results are shown in Table 3.

(8) Observation of impregnation of polymer electrolyte A polymer electrolyte membrane prepared as described later was cut into 1 cm × 1 cm pieces to obtain test pieces. The cross-sectional shape of the test piece was observed with an SEM (manufactured by Hitachi, product number: S-4700, acceleration voltage: 5 kV, detector: secondary electron detector, backscattered electron detector). The cross-sectional shape was observed at a magnification of 10,000 times. The case where a void was found between the reinforcing material and the polymer electrolyte was evaluated as x, and the case where no void was observed was marked as o.

(9) Adhesiveness The polymer electrolyte membrane was cut into 5 cm × 5 cm pieces to obtain test pieces. Next, a double-sided tape (NW-K15 manufactured by Nichiban Co., Ltd.) was uniformly applied to one side of the test piece and fixed on the glass substrate. Next, cellophane (CT-15 manufactured by Nichiban Co., Ltd.) was attached so as to pass through one diagonal line of the polymer electrolyte membrane, and peeled off vigorously. At this time, it was rated as x when completely peeled off at the interface between the reinforcing material and the polymer electrolyte, Δ when partially peeled, and ○ when not peeled off.

(10) Dimensional Change Measurement The dimensional change ratio (planar direction / film thickness direction) of the polymer electrolyte membrane prepared as described later in 80 ° C. water was measured as follows.

  As a membrane sample, a polymer electrolyte membrane was cut into a 4 cm × 3 cm rectangular membrane, left in a constant temperature and humidity room (23 ° C., 50% RH) for 1 hour or longer, and then the dried rectangular membrane sample in the planar direction. Each dimension was measured.

  Next, the rectangular membrane sample whose dimensions were measured was boiled in hot water at 80 ° C. for 1 hour, and water was sufficiently absorbed so that the mass change due to moisture in the electrolyte membrane was 5% or less. At this time, the film was taken out from the hot water, and it was confirmed that the amount of mass change was 5% or less with an electronic balance in a state where water on the surface was sufficiently removed. The wet membrane sample which absorbed this water and expanded was taken out from the hot water, and each dimension in the plane direction and the film thickness direction was measured. Taking each dimension in the plane direction in the dry state as a reference, taking the average of each dimension increment in the plane direction and the film thickness direction in the wet state from each dimension in the dry state was taken as the dimensional change amount (%). .

Next, the dimensional change ratio (plane direction / film thickness direction) was calculated by the following formula.
(Dimensional change ratio (plane direction / film thickness direction)) = dimensional change in plane direction (%) ÷ dimensional change in film thickness direction (%)

(10) Durability test: OCV test In order to evaluate the chemical durability of the polymer electrolyte membrane under high-temperature and low-humidification conditions in an accelerated manner, an accelerated test using OCV was performed according to the following procedure. Note that “OCV” means an open circuit voltage.

(10) -1 Preparation of Electrocatalyst Ink 20% by mass perfluorosulfonic acid polymer solution (SS700C / 20, manufactured by Asahi Kasei E-materials, equivalent mass (EW): 740), electrode catalyst (TEC10E40E, Tanaka Kikinzoku Sales Co., Ltd.) Made of platinum, 36.7 wt% of platinum supported) so that the platinum / perfluorosulfonic acid polymer becomes 1 / 1.15 (mass), and then the solid content (the sum of the electrode catalyst and the perfluorosulfonic acid polymer) Ethanol was added so as to be 11 wt%, and an electrode catalyst ink was obtained by stirring for 10 minutes at 3,000 rpm with a homogenizer (manufactured by ASONE).

(10) -2 Fabrication of MEA Using an automatic screen printer (product name: LS-150, manufactured by Neurong Seimitsu Kogyo Co., Ltd.), the electrocatalyst ink was placed on both sides of the polymer electrolyte membrane, and the amount of platinum was 0 on the anode side. .2mg / cm ^2, was applied to the cathode side 0.3mg / cm ^2, 140 ℃, to obtain a MEA by drying and solidifying at 5 minutes condition.

(10) -3 Fabrication of a fuel cell single cell A gas diffusion layer (product name: GDL35BC, manufactured by MFC Technology) is stacked on both poles of the MEA, and then a gasket, bipolar plate, and backing plate are stacked to form a fuel cell single cell. Obtained.

(10) -4 OCV Test The fuel cell single cell was set in an evaluation apparatus (Fuel Cell Evaluation System 890CL manufactured by Toyo Technica), and a durability test by OCV was performed.

  The OCV test conditions were such that the cell temperature was 95 ° C., the humidification bottle was 50 ° C. (relative humidity 25% RH), and hydrogen gas was supplied to the anode side and air gas was supplied to the cathode side at 50 cc / min. Further, no pressure was applied (atmospheric pressure) on both the anode side and the cathode side.

(10) -5 Degradation Determination The amount of hydrogen leakage was measured every 50 hours from the start of the test using a micro gas chromatograph (CP-4900 manufactured by VARIAN). When the amount of hydrogen leaked was 1000 ppm or more, the film was judged to be broken, and the test was stopped.

  In the OCV test, the case where the film breaking time exceeded 250 hours was judged as ◯, and the case where it was 250 hours or less was judged as x.

(11) Performance evaluation A performance test was performed using a single cell of the fuel cell obtained by the methods (10) -1 to (10) -3.
The performance test conditions were a cell temperature of 80 ° C., an anode humidification bottle of 60 ° C., and a cathode humidification bottle of no humidification. Further, hydrogen gas was circulated to the anode side so that the utilization rate was 75%, and air gas was circulated to the cathode side so that the utilization rate of oxygen gas contained in the air gas was 55%. Furthermore, no pressure (atmospheric pressure) was applied to both the anode side and the cathode side. Under this condition, the cell voltage at 0.25 A / cm ² was measured.

Example 5
(Preparation of polymer electrolyte composition)
Perfluorosulfonic acid resin precursor obtained from tetrafluoroethylene and CF ₂ ═CFO (CF ₂ ) ₂ —SO ₂ F, which are precursors of the polymer electrolyte (B) (EW after hydrolysis and acid treatment: 740) The pellet was brought into contact with an aqueous solution in which potassium hydroxide (15% by mass) and methyl alcohol (50% by mass) were dissolved at 80 ° C. for 20 hours for hydrolysis treatment. Then, it was immersed in 60 degreeC water for 5 hours. Next, the treatment of immersing in a 2N hydrochloric acid aqueous solution at 60 ° C. for 1 hour was repeated 5 times each time using a new aqueous hydrochloric acid solution, then washed with ion-exchanged water and dried. Thereby, a pellet of the polymer electrolyte (B) having a sulfonic acid group (SO ₃ H) was obtained.

  The pellet was placed in a 5 L autoclave together with an aqueous ethanol solution (water: ethanol = 66.7: 33.3 (mass ratio)), sealed, heated to 160 ° C. with stirring with a stirring blade, and held for 5 hours. Thereafter, the autoclave was naturally cooled to prepare 5% by mass of a uniform perfluorosulfonic acid resin solution-1.

  Next, 1200 g of this solution was transferred to a 2 L eggplant flask and placed on a rotary evaporator (Rotavapor R-200 manufactured by BUCHI) with a hot water bath set to 80 ° C., and the pressure was reduced so that the solid content concentration was 20% by mass. Concentrated to prepare perfluorosulfonic acid resin solution-2.

(Production of polymer electrolyte membrane)
Using a coating machine (manufactured by Toyo Seiki Co., Ltd.), the perfluorosulfonic acid resin solution-2 obtained as described above is made to have a Wet thickness of 185 μm on Kapton 200H (product name, manufactured by Toray DuPont Co., Ltd.). Coated. Before the coated surface is dried, the sulfonic acid group-containing fluoropolyethylene microporous membrane described in Production Example 5 is overlaid as a microporous membrane and dried at 80 ° C. for 30 minutes and then at 120 ° C. for 30 minutes. It was. After drying, the polymer electrolyte solution-2 was applied to the microporous membrane side so that the wet thickness was 185 μm, and dried at 80 ° C. for 30 minutes and then at 120 ° C. for 30 minutes. The obtained composite membrane was washed with water and further dried at 170 ° C. for 20 minutes to obtain a polymer electrolyte membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, When the performance evaluation was performed by the method described in (11) above, good results were obtained. The results are shown in Table 4.

Example 6
A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that the sulfonic acid group-containing fluoropolypropylene microporous membrane described in Production Example 6 was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, When the performance evaluation was performed by the method described in (11) above, good results were obtained. The results are shown in Table 4.

Example 7
A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that the sulfonic acid group-containing fluoroethylene-propylene microporous membrane described in Production Example 6 was used as the microporous membrane.

Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, When the performance evaluation was performed by the method described in (11) above, good results were obtained. The results are shown in Table 4.

Example 8
A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that the sulfonic acid group-containing fluorine-based poly-4-methyl-1-pentene microporous membrane described in Production Example 8 was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, When the performance evaluation was performed by the method described in (11) above, good results were obtained. The results are shown in Table 4.

[Comparative Example 5]
A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that the polyethylene microporous membrane described in Comparative Production Example 1 was used as the microporous membrane.

  Using this polymer electrolyte membrane, a durability test was performed by the method described in (9) above, and a performance evaluation was performed by the method described in (10) above. The results are shown in Table 4.

[Comparative Example 6]
A polymer electrolyte membrane was obtained in the same manner as in Example 6 except that the polypropylene microporous membrane described in Comparative Production Example 2 was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, The performance evaluation was performed by the method described in (11) above. The results are shown in Table 4.

[Comparative Example 7]
A polymer electrolyte membrane was obtained in the same manner as in Example 7 except that the microporous membrane made of ethylene-propylene described in Comparative Production Example 3 was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, The performance evaluation was performed by the method described in (11) above. The results are shown in Table 4.

[Comparative Example 8]
A polymer electrolyte membrane was obtained in the same manner as in Example 8, except that the poly-4-methyl-1-pentene microporous membrane described in Comparative Production Example 4 was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, The performance evaluation was performed by the method described in (11) above. The results are shown in Table 4.

[Reference Example 2]
A polymer electrolyte membrane was obtained in the same manner as in Example 5 except that a polytetrafluoroethylene (PTFE) membrane (Donaldson, grade: # 1326 porosity 71%) was used as the microporous membrane.

  Using this polymer electrolyte membrane, observation of impregnation by the method described in (8) above, dimensional change by the method described in (9) above, and durability test by the method described in (10) above, The performance evaluation was performed by the method described in (11) above. The results are shown in Table 4.

Claims (3)

A microporous membrane (A) made of chain polyfluoroolefin;
A polymer electrolyte (B) impregnated in the chain polyfluoroolefin microporous membrane (A);
Have
The structure of the following formula (1) or the following formula (2) is included in the skeleton of the chain polyfluoroolefin microporous membrane (A),
The polymer electrolyte membrane in which the proportion of C—H bonds represented by the following formula (3) in the chain polyfluoroolefin microporous membrane (A) is 0.01% or more and less than 30%.
-CX ₁ X ₂ CX ₃ (CX ₄ X ₅ X ₆ )-(1)
(X ₁ to X ₃ each independently represents a hydrogen atom or a fluorine atom. X ₄ to X ₆ each independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms. When X ₁ to X ₃ are all fluorine, the chain polyfluoroolefin microporous membrane (A) has a CX ₄ X ₅ X ₆ site in which at least one of X ₄ to X ₆ is hydrogen. One or more CX ₄ X ₅ X ₆ sites in the structure, which is an alkyl group having 1 to 5 carbon atoms, wherein at least one of X ₄ to X ₆ contains at least one carbon-hydrogen bond When any _one of X ₁ and X ₂ is hydrogen, the chain polyfluoroolefin microporous membrane (A) is CX ₃ (wherein at least one of X ₃ to X ₆ is hydrogen. containing one or more structures in CX ₄ X ₅ X ₆₎ site, or less from X ₃ of X ₆ Kutomo One Carbon - containing one or more CX ₃ is an alkyl group having 1 to 5 carbon atoms containing at least one hydrogen bond to (CX ₄ X ₅ X ₆₎ sites in the structure).
_{-CX 1 X 2 CX 3 X 4} - (2)
(X ₁ to X ₄ represent hydrogen or a fluorine atom.)
Ratio of C—H bond = (C—H bond in the chain polyfluoroolefin microporous membrane (A)) / {(C—F bond in the chain polyfluoroolefin microporous membrane (A)) ) + (CH bond in the chain polyfluoroolefin microporous membrane (A))} × 100 (%) (3)   A membrane electrode assembly comprising the polymer electrolyte membrane according to claim 1.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 2.