JP2007018995A - ELECTROLYTE MEMBRANE, METHOD FOR PRODUCING THE SAME, AND MEMBRANE ELECTRODE ASSEMBLY FOR SOLID POLYMER FUEL CELL - Google Patents

Abstract

Disclosed is an electrolyte membrane that has high strength even when it is thin, has excellent dimensional stability when containing water, has low resistance, a method for manufacturing the electrolyte membrane, and the electrolyte membrane. Providing an excellent membrane electrode assembly for a polymer electrolyte fuel cell.
An electrolyte membrane comprising a continuous fiber of fluororesin, the main component of which is an ion exchange resin, reinforced with a nonwoven fabric in which at least a part of the intersections between the fibers is fixed, the outermost layer on one or both sides An electrolyte membrane comprising an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin. Nonwoven fabrics are manufactured by the melt blown method.
[Selection figure] None

Description

  The present invention relates to an electrolyte membrane reinforced with a nonwoven fabric, a method for producing the same, and a membrane electrode assembly for a polymer electrolyte fuel cell having the electrolyte membrane.

  In recent years, research on solid polymer fuel cells using proton-conducting polymer membranes as electrolytes has progressed. Solid polymer fuel cells operate at low temperatures, have high output density and can be miniaturized, and are promising for applications such as in-vehicle power supplies.

  As the electrolyte membrane for a polymer electrolyte fuel cell, a proton conductive ion exchange membrane having a thickness of 20 to 200 μm is usually used. In particular, a perfluorocarbon polymer having a sulfonic acid group (hereinafter referred to as a sulfonic acid type perfluorocarbon polymer). The cation exchange membrane consisting of) is widely studied because of its excellent basic properties.

  Methods for reducing the electrical resistance of the cation exchange membrane include increasing the sulfonic acid group concentration and reducing the film thickness. However, when the concentration of the sulfonic acid group is remarkably increased, the mechanical strength of the membrane is lowered, and the membrane is likely to creep during the long-term operation of the fuel cell, resulting in a decrease in the durability of the fuel cell. On the other hand, when the film thickness is reduced, the mechanical strength of the film is lowered, and when a membrane electrode assembly is produced by joining the membrane to the gas diffusion electrode, problems such as difficulty in processing and handling are caused.

  In addition, the above electrolyte membrane tends to increase in dimension in the length direction of the membrane when it contains water, and various problems are likely to occur. For example, when the membrane electrode assembly is assembled in a fuel cell and operated, the membrane swells due to water generated by the reaction, water vapor supplied together with the fuel gas, etc., and the size of the membrane increases. Usually, since the membrane and the electrode are joined, the electrode follows the dimensional change of the membrane. Since the membrane electrode assembly is usually restrained by a separator or the like in which grooves are formed as gas flow paths, the increase in the dimension of the membrane becomes “wrinkles”. And the wrinkle may fill the groove of the separator and obstruct the gas flow.

  As a method for solving the above problem, a method of impregnating a porous body made of polytetrafluoroethylene (hereinafter referred to as PTFE) with a sulfonic acid type perfluorocarbon polymer has been proposed (Patent Document 1). However, since the porous body of PTFE is derived from the material and is relatively soft, the reinforcing effect is not sufficient, and the above problems have not been solved. Moreover, although the method of filling the porous body which consists of polyolefin with the ion exchange resin is also proposed (patent document 2), the chemical durability was insufficient and there existed a problem in long-term stability.

  In addition, a method using a fluororesin fiber has been proposed as another reinforcing method. There are a method for producing a cation exchange membrane reinforced with a reinforcing material of fibrillar fluorocarbon polymer (Patent Document 3) and a method for producing a polymer membrane reinforced with short fibers of a fluororesin (Patent Document 4). In these final products, the reinforcing material itself has no particularly positive entanglement or bonding, so that the reinforcing efficiency is low and a relatively large amount of reinforcing material needs to be contained. In this case, it is difficult to shape the electrolyte membrane, and the membrane resistance may be increased.

  In Patent Document 5, a solid fiber reinforced with a fluorine fiber sheet in which the discontinuous short fibers having a length of 15 mm or less are bonded together with a binder such as viscose, carboxymethyl cellulose, or polyvinyl alcohol. An electrolyte membrane for a molecular fuel cell has been proposed. These binders are impurities for the fuel cell electrolyte membrane, and the residual binder significantly impairs the durability of the fuel cell. Further, in this proposal, a fiber having a relatively large fiber diameter of 15 μm is used, and in order to realize sufficient binding between the fibers, the reinforcing body has a thickness several times the fiber diameter or more. Therefore, it is considered that the film resistance is easily increased. Further, in the method of processing discontinuous short fibers by a method such as a papermaking method, there is a problem in thinning that it is practically difficult to handle with extremely fine fibers.

Japanese Patent Publication No. 5-75835 (Claims) Japanese Patent Publication No. 7-68377 (Claims) Japanese Patent Laid-Open No. 6-231777 (Claims) International Publication No. 04/011535 (claims) JP 2003-297394 A (claims, paragraph 0012, paragraph 0026)

  Accordingly, an object of the present invention is to provide an electrolyte membrane having a high strength even when the thickness is small, an excellent dimensional stability when containing water, and a low resistance. It is another object of the present invention to provide a membrane electrode assembly for a polymer electrolyte fuel cell that has such an electrolyte membrane and has high output and excellent durability.

  The present invention is an electrolyte membrane reinforced with a non-woven fabric composed of continuous fibers of a fluororesin, the main component of which is an ion exchange resin, in which at least a part of the intersections between the fibers is fixed, and the outermost layer on one or both sides The present invention provides an electrolyte membrane comprising an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin.

  Since the nonwoven fabric in the present invention is composed of continuous fibers, sufficient entanglement between the fibers is formed, and the number of fiber ends that can be mechanical defects is extremely small. Moreover, since at least a part of the intersections between the fibers is fixed, the elastic modulus is high. Therefore, the electrolyte membrane reinforced by this nonwoven fabric is excellent in mechanical strength.

  The electrolyte membrane of the present invention has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin as the outermost layer on one or both sides. Thereby, when the electrolyte membrane of the present invention is used as a polymer electrolyte membrane for a polymer electrolyte fuel cell, the resistance at the junction between the electrolyte membrane and the electrode can be reduced.

  The present invention is also a method for producing the above electrolyte membrane, in which a melt-moldable fluororesin is discharged from a spinning nozzle in a molten state, and stretched by a gas released from a gas discharge nozzle disposed in the vicinity of the spinning nozzle. The present invention provides a method for producing an electrolyte membrane, wherein continuous fibers are obtained by spinning to form a nonwoven fabric.

  In the production method of the present invention, the fibers constituting the nonwoven fabric can be made very thin, and an increase in the resistance of the electrolyte membrane due to reinforcement can be suppressed. Therefore, an optimum nonwoven fabric is formed as a reinforcing material for the electrolyte membrane for fuel cells. be able to.

  By collecting continuous fibers on a surface having an adsorption function to form a non-woven fabric and then hot pressing, or by applying a solution containing a binder composed of a solvent-soluble fluoropolymer, an intersection between the fibers It is preferable to bind.

  The present invention also provides a membrane for a polymer electrolyte fuel cell comprising a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin, and a polymer electrolyte membrane disposed between the cathode and the anode. In the electrode assembly, a membrane electrode assembly for a polymer electrolyte fuel cell is provided, wherein the polymer electrolyte membrane comprises the above electrolyte membrane.

  Since the electrolyte membrane of the present invention is reinforced with a nonwoven fabric made of continuous fibers of fluororesin, there is little increase in resistance due to reinforcement, and it has sufficiently high strength even when the film thickness is thin. Furthermore, since the dimensional stability when containing water is excellent, the polymer electrolyte fuel cell having this electrolyte membrane can obtain a stable high output even if it is operated for a long period of time.

  The nonwoven fabric in this invention consists of a continuous fiber of a fluororesin. The continuous fiber in the present invention means having an aspect ratio of 10,000 or more. The fiber length is desirably 20 mm or more.

  The fiber diameter (diameter) of the continuous fiber is preferably 0.01 to 13 μm. As the fiber diameter of the continuous fiber is thinner, proton transfer is performed more smoothly, so that an increase in resistance due to reinforcement can be suppressed. In addition, when the fiber diameter is small, the number of intersections between fibers at the same film thickness can be increased, so that the strength of the nonwoven fabric can be increased and the dimensional stability of the electrolyte membrane can be improved. On the other hand, if the fiber diameter is too thin, the tensile strength per fiber becomes weak, making it difficult to use practically in terms of handling. The fiber diameter is more preferably from 0.01 to 5 μm, particularly preferably from 0.01 to 3 μm.

  In the present invention, the fluororesin constituting the nonwoven fabric is a single resin containing one or more monomer units based on monomers such as perfluoroolefins such as tetrafluoroethylene and hexafluoropropylene, chlorotrifluoroethylene, and perfluoro (alkyl vinyl ether). A blend or copolymer is preferred.

  Specifically, tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polychloro From monomer units constituting these polymers such as trifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride polymer (PVdF), polyvinyl fluoride polymer (PVF), etc. And a blend of these polymers.

  Among these fluororesins, melt-moldable fluororesins such as ETFE, PFA, FEP, and PVDF are preferable, and PFA and ETFE are particularly preferable because of excellent mechanical strength and moldability. As ETFE, the molar ratio of monomer units based on tetrafluoroethylene (hereinafter referred to as TFE) / monomer units based on ethylene is preferably 70/30 to 30/70, and more preferably 65/35 to 40/60.

The above-mentioned ETFE, PFA, FEP, PVDF may contain monomer units based on a small amount of comonomer. As the _comonomers, (excluding _TFE) CF 2 = fluoroethylene such as _{CFCl; CF 2 = CFCF 3,} CF 2 = hexafluoropropylene such as _{CHCF 3; CF 3 CF 2 CF} 2 CF 2 CH = CH 2, fluoro ethylenes _{CF 3 CF 2 CF 2 CF 2} CF = CH carbon atoms, such as ₂ having from 2 to 12 perfluoroalkyl ^{_{group; R f (OCFXCF 2) k}} OCF = CF 2 ( wherein ^{R f} carbon Perfluorovinyl ethers such as a perfluoroalkyl group of formulas 1 to 6, X is a fluorine atom or a trifluoromethyl group, and k is an integer of 0 to 5); CH ₃ OC (═O) CF ₂ CF ₂ CF ₂ OCF = CF ₂ or _{FSO 2 CF 2 CF 2 OCF (} CF 3) CF 2, etc. OCF = CF _2, easily variable to a carboxylic acid group or a sulfonic acid group Perfluorovinylethers having groups; C3 olefins such as propylene, the C4 olefins such as butylene or isobutylene, olefins such as excluding ethylene. Comonomers of _{ETFE, CF 3 CF 2 CF 2} CF 2 CH = CH 2 . Examples of the comonomer _{PFA, CF 3 CF 2 OCF =} CF 2, CF 3 CF 2 CF 2 OCF = CF 2, CF 3 CF 2 CF ₂ OCF (CF ₃ ) CF ₂ OCF═CF ₂ is particularly preferred.

  When the monomer unit based on the comonomer is contained, the content ratio is usually preferably 30 mol% or less, more preferably 0.1 to 15 mol%, based on the whole monomer units of ETFE, PFA, FEP, and PVDF. More preferably, it is 2 to 10 mol%.

  As the melt flow rate (MFR) of the melt-moldable fluororesin, in the case of PFA, the MFR according to ASTM D3307 is preferably 40 to 300 g / 10 min. When forming ultrafine fibers, the lower the pressure loss of the spinning die, the better the productivity, so 60 g / 10 min or more is more preferable. Moreover, since the intensity | strength of the fiber obtained when MFR is large falls, 150 g / 10min or less is more preferable. In the case of ETFE, MFR according to ASTM D3159 = 40 g / 10 min or more is preferable.

  The nonwoven fabric in the present invention is preferably subjected to at least one treatment selected from the group consisting of irradiation with radiation, plasma irradiation and chemical treatment with metallic sodium. By performing these treatments, polar groups such as —COOH groups, —OH groups, and —COF groups are introduced on the fiber surface, and the adhesion at the interface between the ion exchange resin as a matrix and the nonwoven fabric as a reinforcing material is improved. As a result, the reinforcing effect can be increased.

  As a method for producing a nonwoven fabric when the fluororesin is a melt-moldable fluororesin such as PFA or ETFE, it is preferable to employ a melt blown method. Compared to other nonwoven fabric manufacturing methods in which fibers are formed from a resin and then made into a nonwoven fabric using the raw material as a raw material, the melt blown method is highly productive because it can form fibers and fabrics almost simultaneously. . Moreover, since the fiber which comprises a nonwoven fabric can be made very thin and the raise of the resistance of the electrolyte membrane by reinforcement can be suppressed, the nonwoven fabric most suitable as a reinforcing material of the electrolyte membrane for fuel cells can be formed especially.

  Drawing 1 is a sectional view showing one form of a nozzle section used with a melt blown nonwoven fabric manufacturing device. In the melt blown method, the melt-moldable fluororesin 1 is discharged from the discharge hole 3 of the spinning nozzle in a molten state and stretched by the gas 2 discharged from the discharge hole 4 of the gas discharge nozzle disposed in the vicinity of the spinning nozzle. A continuous fiber can be obtained by spinning. The continuous fibers can be collected on a surface having an adsorption function to form a nonwoven fabric.

  The surface having an adsorption function refers to a device that can form discharged ultrafine fibers in a cloth shape by maintaining one side of a film-like substrate having air permeability in a reduced pressure state, for example. The film-like base material having air permeability is not particularly limited, and examples thereof include meshes, cloths, porous bodies, etc., and the material is not particularly limited. Therefore, a mesh made of metal is desirable.

  As an adsorption function, it is desired to have an adsorption ability capable of sufficiently adsorbing and maintaining the spun continuous fiber in the form of a cloth. Therefore, it is preferable that the surface having the adsorption function has a wind speed of 0.1 m / second or more at a distance within 1 cm from the surface. In addition, if the surface holding the adsorption is too large, the fibers themselves are drawn inside the mesh and cannot be peeled off or the smoothness may be lost. Therefore, the mesh opening is preferably 2 mm or less, more preferably 0.15 mm or less, still more preferably 0.06 mm or less, and particularly preferably 0.03 mm or less.

  When the film-like base material having air permeability has flexibility, it can be used as a collection conveyor having an adsorption function by placing it on a conveyor that can be continuously rotated. For example, it is possible to continuously roll out a film-like base material in a roll shape, form a non-woven fabric on one side, separate and wind up, and simplify the manufacturing method.

  The bulk density of the resulting nonwoven fabric depends on the hardness and thermal properties of the resin used. In the melt blown method, it is generally possible to directly obtain a nonwoven fabric in which the intersections of fibers are partially fused by using a low-viscosity resin. Further, in some cases, the above-mentioned fusion does not occur and a cotton-like non-woven fabric precursor-like material is obtained, but it is collected by a collecting conveyor having an adsorption function and directly pressed and pressed to obtain a predetermined volume. A non-woven fabric having a density can be obtained.

  In the manufacturing method for forming the above-described nonwoven fabric, when the intersections between the fibers are not fixed, operations such as winding and handling are difficult. When at least some of the intersections between the fibers are fixed, the elastic modulus and strength can be expressed as a nonwoven fabric alone. As a result, the nonwoven fabric itself is self-supporting, handling properties are improved, and an electrolyte membrane having the nonwoven fabric can be easily manufactured. As an aspect in which at least a part of the intersections between the fibers is fixed, as described above, [1] When the fibers are fused at the time when the continuous fibers are collected and the nonwoven fabric is formed, 2] In addition to the case where the fibers are fused with each other by hot pressing the nonwoven fabric, in addition to [3] the intersection between the fibers by applying a solution containing a solvent-soluble fluoropolymer to the nonwoven fabric. And the like may be mentioned.

  The hot pressing in the above aspect [2] is desirably performed in a temperature range in which the fibers are not melted and deformed and have fusion properties. Depending on the thermophysical properties of the fluororesin constituting the fiber, in the case of a crystalline fluororesin, the temperature range from (melting point−50 ° C.) to the melting point is desirable, and the temperature range from (melting point−20 ° C.) to the melting point is more desirable. . In the case of an amorphous fluororesin, the temperature range from (glass transition temperature −50 ° C.) to the glass point transition point is desirable, and the temperature range from (glass transition temperature −20 ° C.) to the glass point transition point is more desirable. Moreover, although the pressure at the time of hot press depends on the above-mentioned temperature condition, generally, if the molding is performed in a pressure range of 0.5 to 10 MPa, the fibers can be fused without causing a large deformation.

  In the above aspect [3], the solvent-soluble fluoropolymer used for binding the intersections between fibers refers to a fluoropolymer in which a solvent capable of dissolving the fluoropolymer exists, and is 0.1% or more at room temperature. It can be present as a concentrated solution. In addition, the solution referred to in this specification includes a liquid in which the fluoropolymer is present in a dispersed or swollen state but is macroscopically recognized as a solution.

Since the binder is made of a fluorine-containing polymer, it is excellent in chemical durability in the environment where the fuel cell is used. The hydrogen bonded to the carbon atom of the fluorinated polymer is preferably a polymer substituted with all fluorine atoms. Moreover, since the elasticity modulus and intensity | strength of the nonwoven fabric bound with the binder improve, the one where the elasticity modulus of a solvent soluble fluoropolymer is higher is preferable. The fluoropolymer preferably has an elastic modulus of 10 ⁵ Pa or higher at room temperature, and more preferably has an elastic modulus of 10 ⁸ Pa or higher at room temperature. This means that the glass transition temperature of the fluoropolymer is room temperature or higher in terms of the glass transition temperature, and it has a glass transition point of 40 ° C. or higher which is considered to be an industrial room temperature range. preferable.

Preferable examples of the solvent-soluble fluorine-containing polymer constituting the binder include the following polymers [i] to [iii].
[I] Fluoropolymer having an ion exchange group or a precursor group thereof in the molecule Examples of the ion exchange group include a sulfonic acid group (—SO ₃ H) and a sulfonimide group (—SO ₂ NHSO ₂ R ^f , R ^f). Is a perfluoroalkyl group). Examples of the group that serves as a precursor of the ion exchange group include a —SO ₂ F group. In particular, a fluorine-containing polymer having an ion exchange group is preferable because it becomes an electrolyte and does not cause an increase in resistance of the electrolyte membrane without lowering the opening ratio of the nonwoven fabric. The fluorine-containing polymer having an ion exchange group may be the same as or different from the ion exchange resin constituting the electrolyte membrane.

As an example of a fluorocarbon polymer having an ion exchange group or its precursor group in the molecule and an aliphatic structure in the main chain, CF ₂ = CF— (OCF ₂ CFX) _m —O _p — (CF ₂ ) _n -SO ₂ perfluoro compound represented by F (wherein, X is a fluorine atom or a trifluoromethyl group, m is an integer of from 0 to 3, n represents 0 to 12 integer, p is 0 or 1 And in the case of n = 0, p = 0 and m = 1-3.) A copolymer containing a repeating unit based on tetrafluoroethylene and a repeating unit based on tetrafluoroethylene, and hydrolyzing and acid-forming the polymer A polymer obtained by converting a —SO ₂ F group into a —SO ₃ H group is preferred. Among these, fluorine-containing polymer having -SO 2 _F groups are soluble in HCFC solvents such ASAHIKLIN AK-225 (manufactured by Asahi Glass Co., Ltd.), fluorine-containing polymer having -SO 3 _H groups It is generally known that it is soluble in ethanol.

[Ii] Fluoropolymer having substantially no ion-exchange group and having an aliphatic ring structure in the main chain Such a fluoropolymer is difficult to crystallize due to molecular twisting due to its molecular structure, It is soluble. Examples of the fluorine-containing polymer having an aliphatic ring structure in the main chain include a polymer containing a repeating unit represented by any of the following formulas (a), (b), and (c). The polymer can be dissolved in, for example, perfluorobenzene, trifluoroethane, perfluoro (2-butyltetrahydrofuran), Fluorinert FC-77 (manufactured by 3M).

[Iii] Fluoroolefin-based fluorinated polymer having substantially no ion-exchange group Examples of the fluorinated polymer include tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer, tetrafluoroethylene, and hexafluoropropylene. , A repeating unit based on at least one monomer of a fluoroolefin selected from the group consisting of vinylidene fluoride and chlorotrifluoroethylene, vinyl ether, vinyl ester, allyl ether, allyl ester, isopropenyl ether, isopropenyl ester, methacryl ether And a copolymer with a repeating unit based on at least one monomer selected from the group consisting of methacrylic ester, acrylic ester and methacrylic ester.
These fluoropolymers are soluble in ketones, esters, chloroethanes, benzene derivatives and the like.

  The solvent of the solution containing the binder is preferably one having a boiling point of 150 ° C. or lower because it is desirable to dry and solidify on the surface having the adsorption function, and further includes one having a boiling point of 100 ° C. or lower. It is preferable. In order to ensure early binding of the intersections between the fibers of the nonwoven fabric, the solvent having the above boiling point is preferably 75% or more, more preferably 95% or more, more preferably 98% or more of the total mass of all the solvents. % Or more is preferable.

  The solution containing the binder is preferably applied by a spray coating method. The solution containing the binder is sprayed by the spray coating method, and the nonwoven fabric is passed through the sprayed state of the solution containing the binder while holding the nonwoven fabric adsorbed on the surface having the adsorption function. The binder can be selectively applied to the fiber without blocking the opening.

  The spray coating method is a coating method in which a carrier gas and a solution to be applied are sprayed simultaneously through a small gap, and the spray state is particularly affected by the viscosity of the solution to be applied. It is known that the spray system of the commonly used air spray system deforms the solution into fine droplets due to the shear stress applied from the air at the tip of the spray nozzle, so that the lower the solution viscosity, the more fine droplets can be obtained. Yes. Further, in a so-called airless spray system that does not use an injection medium such as air, it is preferable that the viscosity be low because the microfabrication is performed by the shear stress accompanying the injection of the solution itself at the nozzle tip. When the droplets are large, the binder tends to block the opening of the nonwoven fabric. Therefore, the viscosity of the solution containing the binder is preferably 10 Pa · s or less, more preferably 1 Pa · s or less, and particularly preferably 0.1 Pa · s or less.

  In the present invention, the ion exchange resin that is the main component of the electrolyte membrane may be a cation exchange resin, such as a cation exchange resin made of a hydrocarbon polymer or a partially fluorinated hydrocarbon polymer. it can. When used in a fuel cell, a cation exchange resin comprising a sulfonic acid type perfluorocarbon polymer having excellent durability is preferred. The ion exchange resin in the electrolyte membrane may consist of a single ion exchange resin or a mixture of two or more ion exchange resins.

As the sulfonic acid type perfluorocarbon polymer, conventionally known polymers are widely used. For example, a sulfonic acid type perfluorocarbon polymer can be obtained by hydrolyzing and acidifying a precursor composed of a resin having a terminal SO ₂ F. In the present specification, the perfluorocarbon polymer may contain an etheric oxygen atom or the like.

Precursors which the terminal is made of a resin which is _{SO 2 F, CF 2 = CF-} (OCF 2 CFX) m -O p - (CF 2) perfluoro compound represented by n -SO ₂ F (wherein , X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 0 to 12, p is 0 or 1, and when n = 0, p = 0 and m = 1 Preferred are copolymers comprising monomer units based on ˜3) and monomer units based on perfluoroolefins such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene or perfluoro (alkyl vinyl ether). Particularly preferred is a copolymer comprising a monomer unit based on the perfluoro compound and a monomer unit based on tetrafluoroethylene.

Preferable examples of the perfluoro compound include compounds represented by any of the following formulas. However, in the following formula, q is an integer of 1 to 8, r is an integer of 1 to 8, s is an integer of 1 to 8, and t is an integer of 1 to 5.
CF ₂ = CFO (CF ₂ ) _q SO ₂ F
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _r SO ₂ F
CF ₂ = CF (CF ₂ ) _s SO ₂ F
_{CF 2 = CF (OCF 2 CF} (CF 3)) t O (CF 2) 2 SO 2 F.

Moreover, as a cation exchange resin of polymers other than a perfluorocarbon polymer, the polymer containing the monomer unit represented, for example by following formula (1), and the monomer unit represented by following formula (2) is mentioned. . Here, P ¹ is a phenyltolyl group, a biphenyltolyl group, a naphthalene reel group, a phenanthrene reel group, and an anthracylene group, P ² is a phenylene group, a biphenylene group, a naphthylene group, a phenanthrylene group, and an anthracylene group, and A ¹ _-SO 3 ^{M 2} group ^{(M 2} represents a hydrogen atom or an alkali metal atom, hereinafter the same), - COOM ² group or by hydrolysis is a group convertible into these ^groups, B 1, ^{B 2} are each independently An oxygen atom, a sulfur atom, a sulfonyl group or an isopropylidene group; Structural isomers of P ¹ and P ² is not particularly limited, one or more fluorine atoms of the hydrogen atom of the P ¹ and P ^2, a chlorine atom, be substituted by a bromine atom or an alkyl group having 1 to 3 carbon atoms Good.

  The ion exchange capacity of the ion exchange resin in the present invention is 0.5 to 2.0 meq / g dry resin, particularly 0.7 to 1.6 meq when used as a polymer electrolyte membrane for a fuel cell. / G dry resin is preferred. If the ion exchange capacity is too low, the resistance increases. On the other hand, if the ion exchange capacity is too high, the affinity for water is too strong, and thus the electrolyte membrane may be dissolved during power generation.

  If the thickness of the electrolyte membrane is too thick, the resistance of the membrane increases. Further, when used as a polymer electrolyte membrane of a fuel cell, a thinner one is preferable because it tends to cause reverse diffusion of generated water generated on the cathode side. On the other hand, if the thickness of the electrolyte membrane is too thin, it will be difficult to develop mechanical strength, and problems such as gas leakage will easily occur. Therefore, the upper limit of the thickness of the electrolyte membrane of the present invention is preferably 100 μm or less, more preferably 50 μm or less, particularly preferably 30 μm or less, and the lower limit is preferably 5 μm or more, more preferably 20 μm or more.

From the viewpoint of the thickness of the electrolyte membrane, the thickness of the nonwoven fabric is preferably 50 μm or less, more preferably 30 μm or less, and particularly preferably 20 μm or less. The basis weight of the nonwoven fabric at this time is preferably 5 to 50 g / m ² (2.5 to 25 cc / m ² ) from the viewpoint of achieving both a reinforcing effect and a reduction in membrane resistance.

  Examples of a method for producing an electrolyte membrane mainly composed of an ion exchange resin reinforced with a non-woven fabric include (1) coating or impregnating a non-woven fabric with a solution or dispersion of an ion exchange resin, followed by drying and manufacturing. Examples thereof include a casting method for forming a film, and (2) a method in which an ion-exchange resin film-form formed in advance is laminated on a non-woven fabric by heat lamination. You may reinforce the composite film of this nonwoven fabric and ion exchange resin by an extending | stretching process etc.

  The electrolyte membrane has, as an outermost layer on one or both sides, an unreinforced layer made of an ion exchange resin that may be the same as or different from the above-described ion exchange resin reinforced with a nonwoven fabric. Thereby, when the electrolyte membrane of the present invention is used as a polymer electrolyte membrane for a polymer electrolyte fuel cell, the resistance at the junction between the electrolyte membrane and the electrode can be reduced. As described above, when the composite membrane of the nonwoven fabric and the ion exchange resin is formed, an unreinforced layer made of the ion exchange resin may be formed as the outermost layer. In addition, after the formation of the composite membrane, the surface of the composite membrane is not reinforced with an ion exchange resin by coating with a solution or dispersion of the ion exchange resin or by laminating a single membrane of the ion exchange resin. A layer can be formed. It is preferable to have an unreinforced layer as the outermost layer on both sides. The non-reinforced layer made of ion exchange resin may contain a component that does not cause an increase in resistance other than the reinforcing material.

  The thickness of the unreinforced layer is preferably 1 to 20 μm per side. This is because the fuel cell has excellent fuel gas barrier properties and membrane resistance can be suppressed. More preferably, it is 2-15 micrometers, More preferably, it is 2-10 micrometers. In addition, the thickness of the layer which is not reinforced in this specification can be measured by cross-sectional observations such as an optical microscope, a laser microscope, and an SEM. The thickness of the unreinforced layer means the shortest distance between the electrolyte membrane surface and the nonwoven fabric fibers.

  When the electrolyte membrane of the present invention is used as a polymer electrolyte membrane for a polymer electrolyte fuel cell, proton movement is shielded by non-woven fibers. If the thickness of the layer that is not reinforced is too thin, the distance for the current to bypass the fiber and bypass it becomes large, which may cause an unnecessary increase in resistance. In particular, when the thickness of the unreinforced layer is smaller than half the fiber diameter, the resistance increase is significant. When the thickness of the layer that is not reinforced is equal to or greater than the fiber radius of the continuous fiber, it is preferable to reduce the current detour distance and consequently avoid unnecessary increase in resistance.

  The electrolyte membrane of the present invention is used as a polymer electrolyte membrane of a membrane electrode assembly for a polymer electrolyte fuel cell. A membrane electrode assembly for a polymer electrolyte fuel cell includes a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin, and a polymer electrolyte membrane disposed between the cathode and the anode. .

  The membrane / electrode assembly for a polymer electrolyte fuel cell can be obtained in the following manner, for example, according to an ordinary method. First, obtain a uniform dispersion composed of a liquid composition containing a conductive carbon black powder carrying platinum catalyst or platinum alloy catalyst fine particles and an electrolyte material, and form a gas diffusion electrode by one of the following methods: Thus, a membrane electrode assembly is obtained.

  The first method is a method in which the dispersion liquid is applied to both surfaces of the electrolyte membrane, dried, and then both surfaces are adhered to each other with two carbon cloths or carbon paper. The second method is a method in which the dispersion liquid is applied and dried on two sheets of carbon cloth or carbon paper and then sandwiched from both surfaces of the electrolyte membrane so that the surface to which the dispersion solution is applied is in close contact with the electrolyte membrane. . The third method is to apply the above dispersion on a separately prepared substrate film and dry it to form a catalyst layer, then transfer the electrode layer to both sides of the electrolyte membrane, and then add two sheets of carbon cloth or carbon paper This is a method of sticking both sides together. Here, the carbon cloth or the carbon paper has a function as a gas diffusion layer and a function as a current collector for uniformly diffusing the gas by the layer containing the catalyst.

  The obtained membrane electrode assembly is formed with a groove serving as a passage for fuel gas or oxidant gas, and is sandwiched between separators. Hydrogen gas is supplied to the anode side of the membrane electrode assembly, and oxygen is supplied to the cathode side. Or air is supplied and a polymer electrolyte fuel cell is obtained.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Example 1]
Using melt blown non-woven fabric manufacturing apparatus (manufactured by Nippon Nozzle Co., Ltd.), using PFA (product name: Full-on PFA P-61XP, manufactured by Asahi Glass Co., Ltd., MFR = 40 g / 10 min), die temperature 330 ° C., stretching hot air temperature 360 ° C. Under these conditions, a nonwoven fabric is formed on a conveyor having suction capability. The fluororesin constituting the nonwoven fabric is a continuous fiber, and the aspect ratio is at least 10,000. When the area of 2.6 cm × 2.6 cm of the nonwoven fabric was observed with a microscope, a fiber length of 13 mm or less was not observed. Next, the nonwoven fabric is consolidated by hot pressing (290 ° C., 10 MPa). The fiber diameter of the spun fiber is 10 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ).

Thereafter, CF ₂ = CF ₂ and CF ₂ = CF-OC ₂ FCF (CF ₃ ) -OCF ₂ CF ₂ SO, which are dry resins with an ion exchange capacity of 1.1 meq / g with the edges of the nonwoven fabric restrained. Immersion in a solution (solid content concentration of 5% by mass) of an ion exchange resin (hereinafter referred to as ion exchange resin (A)) composed of a copolymer with ₃ H as a solvent, and pulling it up at a rate of 100 mm per minute, The nonwoven fabric is impregnated with the ion exchange resin (A). This dipping and lifting operation is repeated three times, and then dried at 55 ° C. for 1 hour in a restrained state to obtain a composite film.

On the other hand, a solution of the above ion exchange resin (A) in ethanol as a solvent is applied on a PET film by die coating and dried at 140 ° C. for 1 hour to form a single membrane 1 made of the above ion exchange resin (A) having a thickness of 10 μm. obtain.
The single membrane 1 is disposed on both sides of the composite membrane, and an electrolyte membrane is obtained by hot pressing (160 ° C., 5 Pa, 15 minutes). The electrolyte membrane was evaluated by the following method, and the results obtained are shown in Table 1. In addition, the thickness of the layer which is not reinforced is 10 micrometers from cross-sectional observation with a laser microscope.

[Measurement of tear strength]
First, a square strength measurement sample having a width of 100 mm and a length of 100 mm is cut out from the electrolyte membrane. A 50 mm incision is made with a knife from one end of the sample to the center of the membrane. Next, each end is separated up and down so that the cutting tip is torn, and is gripped by upper and lower chucking of a tensile tester, and is torn at a speed of 500 mm per minute. The value obtained by dividing the force required for tearing by the thickness of the electrolyte membrane is measured in both the longitudinal direction and the transverse direction of the membrane, and the average value is obtained to obtain the tear strength.

[Measurement of dimensional change rate when water is contained]
The electrolyte membrane is cut into 200 mm squares, exposed to an atmosphere of temperature 25 ° C. and humidity 50% for 16 hours, and the length and width of the sample are measured. Next, after immersing a sample in 25 degreeC ion-exchange water for 1 hour, length and a horizontal length are measured similarly. The average value of the elongation in the longitudinal direction and the elongation in the lateral direction of the sample is determined and used as the dimensional change rate.

[Production and evaluation of fuel cells]
The fuel cell is assembled as follows. First, the ion exchange resin (A) is charged into a mixed solvent of ethanol and water (mass ratio of 1: 1), dissolved in a flask having a reflux function by stirring at 60 ° C. for 16 hours, and a polymer having a solid content of 9%. Obtain a solution. Next, a platinum-supported carbon is sequentially added in the order of water and ethanol to obtain a catalyst dispersion liquid (solid content 9 mass%) dispersed in a mixed dispersion medium (mass ratio of 1: 1) of ethanol and water. Thereafter, the polymer solution and the catalyst dispersion are mixed at a mass ratio of 11: 3 to prepare a coating solution. Next, this coating solution is applied to both surfaces of the electrolyte membrane by a die coating method and dried to form a catalyst layer having a thickness of 10 μm and a platinum loading of 0.5 mg / cm ² on both surfaces of the membrane. Furthermore, a membrane electrode assembly is obtained by disposing carbon cloth as a gas diffusion layer on both outer sides. A solid polymer fuel having an effective membrane area of 25 cm ² by arranging a separator made of carbon plate in which gas channel narrow grooves are zigzag cut on both outer sides of the membrane electrode assembly and a heater on the outer side thereof. The battery is assembled.

The temperature of the fuel cell is maintained at 80 ° C., and air is supplied to the cathode and hydrogen is supplied to the anode at 0.15 MPa, respectively. Current density 0.1 A / cm ^2, and 1A / cm ² of the cell voltage when measuring respectively. The results are as shown in Table 1.

[Example 2]
Using a melt blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having suction capability using the same PFA as in Example 1 under conditions of a die temperature of 350 ° C. and a stretching hot air temperature of 380 ° C. Next, the nonwoven fabric is consolidated by hot pressing (290 ° C., 10 MPa). The fiber diameter of the spun fiber is 5 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ). Thereafter, an electrolyte membrane was prepared by the same method as in Example 1, the same evaluation was performed, and the results obtained are shown in Table 1.

Example 3
Using a melt blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having suction capability using the same PFA as in Example 1 under the conditions of a die temperature of 380 ° C. and a stretching hot air temperature of 400 ° C. Next, the nonwoven fabric is consolidated by hot pressing (290 ° C., 10 MPa). The fiber diameter of the spun fiber is 0.5 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ). Thereafter, an electrolyte membrane was prepared by the same method as in Example 1, the same evaluation was performed, and the results obtained are shown in Table 1.

Example 4
Using a melt blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having suction capability using the same PFA as in Example 1 under conditions of a die temperature of 330 ° C. and a stretching hot air temperature of 360 ° C. Next, the nonwoven fabric is consolidated by hot pressing (290 ° C., 10 MPa). The fiber diameter of the spun fiber is 0.5 μm, the thickness of the nonwoven fabric is 200 μm, and the basis weight is 100 g / m ² (50 cc / m ² ).

As in Example 1, this nonwoven fabric impregnated with the ion exchange resin (A) was biaxially stretched until the area ratio was 10 times, and the fiber diameter was 0.05 μm, the thickness was 20 μm, and the basis weight was 10 g. / ^m 2 to prepare (5 cc / ^{m 2)} composite membrane. Thereafter, an electrolyte membrane was prepared by the same method as in Example 1, the same evaluation was performed, and the results obtained are shown in Table 1.

Example 5
Using a melt blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having a suction capability under the conditions of a die temperature of 330 ° C. and a stretching hot air temperature of 330 ° C. using the same PFA as in Example 1. Next, this nonwoven fabric is consolidated by hot pressing (302 ° C., 5 MPa). The fiber diameter of the spun fiber is 15 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ). Thereafter, an electrolyte membrane was prepared by the same method as in Example 1, the same evaluation was performed, and the results obtained are shown in Table 1.

Example 6
Using a melt-blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having a suction capability using the same PFA as in Example 1 under conditions of a die temperature of 330 ° C. and a stretching hot air temperature of 260 ° C. Next, this nonwoven fabric is consolidated by hot pressing (302 ° C., 5 MPa). The fiber diameter of the spun fiber is 10 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ). Thereafter, an electrolyte membrane is produced in the same manner as in Example 1 except that the single membrane 2 made of ion exchange resin (A) and having a thickness of 5 μm is used. The same evaluation was performed and the results obtained are shown in Table 1.

Example 7
Using a melt-blown nonwoven fabric manufacturing apparatus, a nonwoven fabric is formed on a conveyor having a suction capability using the same PFA as in Example 1 under conditions of a die temperature of 330 ° C. and a stretching hot air temperature of 260 ° C. Next, this nonwoven fabric is consolidated by hot pressing (302 ° C., 5 MPa). The fiber diameter of the spun fiber is 10 μm, the thickness of the nonwoven fabric is 20 μm, and the basis weight is 10 g / m ² (5 cc / m ² ).

On the other hand, a solution of the above ion exchange resin (A) in ethanol as a solvent is applied on a PET film by die coating and dried at 140 ° C. for 1 hour to form a single membrane 3 made of the above ion exchange resin (A) having a thickness of 15 μm. obtain.
The single membrane 3 is disposed on both sides of the nonwoven fabric, and an electrolyte membrane is obtained by a hot press method (165 ° C., 5 MPa, 5 minutes). The same evaluation was performed and the results obtained are shown in Table 1.

[Comparative Example 1]
A monofilament die is attached to a general-purpose extruder, and PFA fibers (cross-sectional diameter of 15 μm) are obtained by melt-molding PFA similar to Example 1 at a die temperature of 380 ° C. using a general-purpose fiber take-up machine. This PFA fiber is cut with scissors so that the fiber length becomes 1 mm, mixed with a solution of ethanol of ion exchange resin (A) in a solvent (solid content concentration 9% by mass), and a solution in which short fibers are dispersed is obtained. obtain. Next, this is apply | coated so that dry thickness may be set to 20 micrometers on a base material, it is made to dry and a composite film is obtained. Thereafter, an electrolyte membrane was prepared by the same method as in Example 1, the same evaluation was performed, and the results obtained are shown in Table 2.

[Comparative Example 2]
A composite membrane is produced in the same manner as in Example 1, and an electrolyte membrane is produced without laminating a non-reinforced layer. The same evaluation was performed and the results obtained are shown in Table 2.

[Comparative Example 3]
A solution of the ion exchange resin (A) in ethanol as a solvent is applied onto a PET film by die coating and dried at 140 ° C. for 1 hour to obtain a single membrane 4 made of the ion exchange resin and having a thickness of 50 μm. The same evaluation was performed and the results obtained are shown in Table 2.

In the following Examples 8 to 10 and Comparative Example 4, the physical properties of the binder and the physical properties of the nonwoven fabric were measured as follows.
[Elastic modulus of binder, glass transition temperature]
A film-like test body having a thickness of about 200 μm was prepared by hot-pressing the solvent-soluble fluoropolymer constituting the binder (temperature 200 ° C., pressure 5 MPa). Next, 5 mm × 35 mm is cut out from this film-like test body, and using a general-purpose dynamic viscoelasticity measuring device DVA-200 (made by IT Measurement Control Co., Ltd.), a tensile mode, a frequency of 1 Hz, a scanning temperature of 2 The measurement was carried out at a rate of C / min, and the complex elastic modulus was measured from -50C to 150C. The value of the complex elastic modulus at 25 ° C. was determined. Further, the glass transition temperature (Tg) was defined as the temperature having the maximum point of the loss elastic modulus between the temperature region where the complex elastic modulus exceeds 10 ⁸ Pa and the region where the complex elastic modulus decreases to 10 ⁷ Pa due to temperature rise.

[Amount of nonwoven fabric, opening ratio, fiber diameter]
A PET film with an adhesive was pressed against the nonwoven fabric, the nonwoven fabric was transferred, and the basis weight of the nonwoven fabric was measured from the transferred area and the weight increase. Moreover, the thickness of the nonwoven fabric and the fiber diameter were measured from a cross-sectional micrograph. The aperture ratio was calculated by the following formula.
Opening ratio (%) = 100−A × 100 / (B × C)
A: The basis weight (g / m ² ) of a portion made of a material that is not an electrolyte among materials constituting the nonwoven fabric
B: Density of non-electrolyte material (g / m ³ ) among materials constituting the nonwoven fabric
C: The thickness (m) of the nonwoven fabric.

[Tensile strength of nonwoven fabric]
Within 1 hour after formation of the bonded nonwoven fabric, it was cut into a width of 10 mm and a length of 70 mm, a tensile test was carried out at a chuck distance of 50 mm, and a tensile speed of 50 mm / min, and the tensile strength was measured.

Example 8
Using a melt blown nonwoven fabric manufacturing apparatus, a nonwoven fabric was formed on a collecting conveyor having adsorption capability under the conditions of a die temperature of 390 ° C. and a stretching hot air temperature of 480 ° C. using the same PFA as in Example 1. The collecting conveyor had a 1 mm mesh SUS mesh in a band shape, and had a wind speed of 1 m / sec within 1 cm from the mesh surface. When the opening ratio of the nonwoven fabric before fixing the intersection between the fibers was measured, it was 70%.

  Next, as a solution containing a binder, a CYTOP solution (product name: CTL-109S, manufactured by Asahi Glass Co., Ltd.) was diluted with Fluorinert FC-77 (manufactured by 3M, boiling point 100 ° C.), concentration 0.5%, viscosity A solution of 0.003 Pa · s (25 ° C.) was prepared. Using a commercially available handy type sprayer, the solution was sprayed several times on the nonwoven fabric, allowed to stand for 1 minute, and the solvent was air-dried. Thereafter, the suction of the conveyor was stopped and the nonwoven fabric formed on the mesh was peeled off. As a result, a self-supporting nonwoven fabric was obtained. Table 3 shows the results of evaluating the physical properties of the nonwoven fabric after fixing the intersections between the fibers.

In a state where the edge of the nonwoven fabric is held using a four-sided restraint frame made of PTFE, the nonwoven fabric is immersed in a solution (solid content concentration of 5% by mass) of ethanol of the ion exchange resin (A) and pulled up at a rate of 100 mm per minute. The nonwoven fabric was impregnated with the ion exchange resin (A). This dipping and lifting operation was repeated three times, and then dried at 55 ° C. for 1 hour in a restrained state to obtain a composite film.
The single membrane 2 having a thickness of 5 μm used in Example 6 was disposed on both sides of the composite membrane, and an electrolyte membrane was obtained by hot pressing (160 ° C., 5 Pa, 15 minutes).

[Production and evaluation of fuel cells]
The ion exchange resin (A) is charged into a mixed solvent of ethanol and water (mass ratio of 1: 1), dissolved in a flask having a reflux function by stirring at 60 ° C. for 16 hours, and a polymer solution having a solid content of 9%. Got. Next, platinum-supported carbon was sequentially added in the order of water and ethanol to obtain a catalyst dispersion liquid (solid content: 9% by mass) dispersed in a mixed dispersion medium (mass ratio of 1: 1) of ethanol and water. Thereafter, the polymer solution and the catalyst dispersion were mixed at a mass ratio of 11: 3 to prepare a coating solution. Next, this coating solution was applied to both surfaces of the electrolyte membrane by a die coating method and dried to form a catalyst layer having a thickness of 10 μm and a platinum carrying amount of 0.5 mg / cm ² on both surfaces of the membrane. Furthermore, the membrane electrode assembly was obtained by disposing carbon cloth as a gas diffusion layer on both outer sides. A solid polymer fuel having an effective membrane area of 25 cm ² by disposing a carbon plate separator in which gas channel narrow grooves are cut in a zigzag manner on both outer sides of the membrane electrode assembly, and a heater on the outer side. I assembled the battery.
Maintaining the temperature of the fuel cell 80 ° C., air, anode and hydrogen was supplied at each 0.15MPa to the cathode was measured current density 0.1 A / cm ^2, and 1A / cm ² of the cell voltage when each. The results are shown in Table 3.

Example 9
As a solution containing a binder in Example 8, a copolymer of CF ₂ ═CF ₂ and CF ₂ ═CF—OC ₂ FCF (CF ₃ ) —OCF ₂ CF ₂ SO ₂ F (in the —SO ₃ H type) The solid content obtained by dissolving ion exchange capacity at the time of conversion: 1.1 milliequivalent / gram dry resin) in Asahiklin AK-225 (Asahi Glass Co., Ltd., boiling point: 58 ° C.) by heating at 58 ° C. for 16 hours. A nonwoven fabric was produced in the same manner as in Example 8, except that a solution having a content of 0.5% and a viscosity of 0.01 Pa · s (25 ° C.) was used. The same evaluation as in Example 8 was performed, and the results are shown in Table 3.
Further, when an electrolyte membrane and a fuel cell were produced in the same manner as in Example 8 and the cell voltage was measured, the results shown in Table 3 were obtained.

Example 10
As a solution containing a binder in Example _8, CF ₂ = CF 2 and _{CF 2 = CF-OC 2 FCF} (CF 3) -OCF 2 CF 2 SO 3 solution of a copolymer of H (product name: FSS -1, manufactured by Asahi Glass Co., Ltd.) in the same manner as in Example 8, except that a solution having a concentration of 0.5% and a viscosity of 0.01 Pa · s (25 ° C.) diluted with ethanol (boiling point 78 ° C.) was used. Produced. The same evaluation as in Example 8 was performed, and the results are shown in Table 3.
Further, when an electrolyte membrane and a fuel cell were produced in the same manner as in Example 8 and the cell voltage was measured, the results shown in Table 3 were obtained.

[Comparative Example 4]
In the same manner as in Example 8, a nonwoven fabric was formed on the collecting conveyor, and when it was attempted to stop and handle the adhering without fixing the intersections between the fibers, some fraying of the fibers occurred and stable self-supporting occurred. A reinforcement was not obtained. When a tensile test was conducted in the same manner as in Example 8, the strength was less than 10 N / m.

  According to the present invention, it is possible to efficiently produce a nonwoven fabric used for reinforcement, and it is possible to obtain an electrolyte membrane having high mechanical strength even when the thickness is thin, excellent dimensional stability when containing water, and low resistance. it can. And the membrane electrode assembly obtained using this electrolyte membrane is excellent in handling property and stability, and a polymer electrolyte fuel cell having high durability performance can be obtained.

Sectional drawing which shows one form of the nozzle cross section used with a melt blown nonwoven fabric manufacturing apparatus.

Explanation of symbols

1: Fluororesin 2: Gas 3: Discharge hole of spinning nozzle 4: Discharge hole of gas discharge nozzle

Claims (15)

  An electrolyte membrane mainly composed of an ion exchange resin, made of a continuous fiber of fluororesin and reinforced with a nonwoven fabric in which at least a part of the intersections between the fibers is fixed, and the ion as the outermost layer on one or both sides An electrolyte membrane comprising an unreinforced layer of an ion exchange resin that may be the same as or different from the exchange resin.   The fluororesin is selected from the group consisting of a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer, an ethylene / tetrafluoroethylene copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, and a polyvinylidene fluoride polymer. The electrolyte membrane according to claim 1, wherein the electrolyte membrane is one or more.   The electrolyte membrane according to claim 1 or 2, wherein the continuous fiber has a fiber diameter of 0.01 to 13 µm.   The electrolyte membrane according to any one of claims 1 to 3, wherein the unreinforced layer has a thickness equal to or greater than a fiber radius of continuous fibers.   The electrolyte membrane according to any one of claims 1 to 4, wherein an intersection between the fibers is fixed by fusion of the fibers.   The electrolyte membrane according to any one of claims 1 to 4, wherein an intersection between the fibers is fixed by a binder made of a solvent-soluble fluoropolymer.   The method for producing an electrolyte membrane according to any one of claims 1 to 6, wherein a melt-moldable fluororesin is discharged from a spinning nozzle in a molten state and discharged from a gas discharge nozzle disposed in the vicinity of the spinning nozzle. A method for producing an electrolyte membrane, characterized in that continuous fibers are obtained by drawing and spinning with a gas to form a nonwoven fabric.   The method for producing an electrolyte membrane according to claim 7, wherein the continuous fibers are collected on a surface having an adsorption function to form a nonwoven fabric, and then hot-pressed to fuse the intersections between the fibers.   The continuous fibers are collected on a surface having an adsorption function to form a nonwoven fabric, and then a solution containing a binder composed of a solvent-soluble fluoropolymer is applied to bind the intersections between the fibers. 8. A method for producing an electrolyte membrane according to item 7. The method for producing an electrolyte membrane according to claim 9, wherein the solvent-soluble fluoropolymer has an elastic modulus of 10 ⁵ Pa or more at room temperature.   The method for producing an electrolyte membrane according to claim 9 or 10, wherein the solvent-soluble fluoropolymer has an ion exchange group.   The method for producing an electrolyte membrane according to claim 9, wherein the solution containing the binder is applied by a spray coating method.   The method for producing an electrolyte membrane according to any one of claims 9 to 12, wherein the surface having the adsorption function is a mesh having an opening of 2 mm or less.   The method for producing an electrolyte membrane according to any one of claims 9 to 13, wherein the surface having the adsorption function has a wind speed of 0.1 m / second or more at a distance within 1 cm from the surface. In a membrane electrode assembly for a polymer electrolyte fuel cell, comprising: a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin; and a polymer electrolyte membrane disposed between the cathode and the anode. The said polymer electrolyte membrane consists of the electrolyte membrane in any one of Claims 1-6, The membrane electrode assembly for polymer electrolyte fuel cells characterized by the above-mentioned.

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