JP2009245639A - Electrolyte membrane for polymer electrolyte fuel cell, method for manufacturing thereof, and membrane-electrode assembly for polymer electrolyte fuel cell - Google Patents

Abstract

An electrolyte membrane having excellent dimensional stability when containing water, low resistance and excellent power generation characteristics, and a manufacturing method for manufacturing these electrolyte membranes with high productivity are provided.
An electrolyte membrane for a polymer electrolyte fuel cell, the main component of which is an ion exchange resin made of a fluororesin fiber and 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 has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin, and the fluororesin is a polyvinylidene fluoride polymer having a melting point of 240 ° C. or lower. There is provided an electrolyte membrane for a polymer electrolyte fuel cell, wherein the immobilization is immobilization by fusing the fibers together.
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Description

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

  In recent years, research on polymer electrolyte fuel cells using proton-conductive polymer membranes as electrolyte membranes has been progressing. A polymer electrolyte fuel cell operates at a low temperature, has a high output density, and can be miniaturized, and is expected to be promising for uses such as an in-vehicle power source.

  As the electrolyte membrane for a polymer electrolyte fuel cell, a proton conductive ion exchange membrane having a thickness of 10 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. Fuel cell electrolyte membranes intended for actual in-vehicle use have been required to have particularly low membrane ohmic loss. The membrane ohmic loss depends on the conductivity of the electrolyte polymer used.

  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, an electrolyte membrane having a high sulfonic acid group concentration tends to increase in dimension in the length direction of the membrane when it contains water, and easily causes various adverse effects. 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, Patent Document 1 proposes a method of impregnating a porous material made of polytetrafluoroethylene (hereinafter also referred to as PTFE) with a sulfonic acid type perfluorocarbon polymer. However, since the porous body of PTFE is derived from the material and is relatively soft, it is required to perform a stretching operation with a high stretching ratio, and it is difficult to say that it is highly productive. Patent Document 2 also proposes a method of filling a porous body made of polyolefin with an ion exchange resin. However, chemical durability is insufficient, and there is a problem in long-term stability.

  In addition, a method using a fluororesin fiber has been proposed as another reinforcing method. Patent Document 3 discloses a method for producing a cation exchange membrane reinforced with a reinforcing material of a fibrillar fluorocarbon polymer, and Patent Document 4 discloses a method for producing a polymer film reinforced with short fibers of fluororesin. . However, the electrolyte membrane manufactured by these manufacturing methods has a low reinforcing efficiency because the reinforcing material itself does not have particularly positive entanglement or bonding, and it is necessary to include a relatively large amount of the reinforcing material. 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 may cause a decrease in the durability of the fuel cell. In Patent Document 5, the reinforcing effect is enhanced by using a fiber having a relatively large fiber diameter of 15 μm. However, in order to realize sufficient binding between the fibers, the reinforcing body is the number of fiber diameters. It is necessary that the thickness be double or more, and 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.

  Furthermore, Patent Document 6 discloses a configuration of the nonwoven fabric reinforced electrolyte membrane that can solve these problems and a manufacturing method. By these methods, an electrolyte membrane for a high performance and high durability fuel cell having sufficient power generation characteristics and durability can be obtained, but further improvement in productivity has been desired.

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) JP 2007-1895 A (Claims)

  The present invention has been made in view of such problems, and the present invention provides a highly polymer electrolyte membrane for a polymer electrolyte fuel cell with excellent dimensional stability when containing water, low resistance, and excellent power generation characteristics. The purpose is to do. Furthermore, it aims at providing the manufacturing method which manufactures these electrolyte membranes with high productivity. It is another object of the present invention to provide a membrane electrode assembly for a polymer electrolyte fuel cell having high output and excellent durability by having these electrolyte membranes at low cost.

  The electrolyte membrane for a polymer electrolyte fuel cell according to the present invention is a solid polymer mainly composed of an ion exchange resin made of a fluororesin fiber and reinforced with a nonwoven fabric in which at least a part of an intersection between the fibers is fixed. An electrolyte membrane for a fuel cell having an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin as an outermost layer on one or both sides, and the fluororesin has a melting point of 240 A polyvinylidene fluoride polymer having a temperature of 0 ° C. or lower, wherein the immobilization is immobilization by fusion of the fibers.

  It is preferable that the average fiber diameter of the said fiber is 0.01 micrometer-7 micrometers.

  The total thickness of the polymer electrolyte membrane for a polymer electrolyte fuel cell is preferably 7.5 μm to 25 μm.

  The thickness of the unreinforced layer is preferably equal to or greater than the radius of the average fiber diameter of the fibers.

  Further, in the method for producing an electrolyte membrane for a polymer electrolyte fuel cell according to the present invention, the electrolyte membrane for a polymer electrolyte fuel cell is composed of a polyvinylidene fluoride polymer fiber having a melting point of 240 ° C. or less. Is an electrolyte membrane mainly composed of an ion exchange resin reinforced with a nonwoven fabric in which at least a part of the intersection is fixed by fusion of fibers, and the outermost layer on one or both sides is the same as the ion exchange resin. It has an unreinforced layer made of an ion exchange resin that may be different, and the nonwoven fabric is formed through a step of adjusting the thickness by a roll-to-roll heated roll press method using a resin support. Features.

  It is preferable that the non-woven fabric is formed by obtaining the fibers by spinning by an electrospinning method.

  A melt-formable fluororesin is discharged from a spinning nozzle in a molten state, and the nonwoven fabric is formed by obtaining the fibers by drawing and spinning with a gas discharged from a gas discharge nozzle disposed in the vicinity of the spinning nozzle. Is preferred.

  It is preferable that the average fiber diameter of the said fiber is 0.01 micrometer-7 micrometers.

  The total thickness of the polymer electrolyte membrane for a polymer electrolyte fuel cell is preferably 7.5 μm to 25 μm.

  The thickness of the unreinforced layer is preferably equal to or greater than the radius of the average fiber diameter of the fibers.

  The membrane electrode assembly for a polymer electrolyte fuel cell according to the present invention includes a cathode and an anode having a catalyst layer containing a catalyst and an ion exchange resin, and a polymer electrolyte disposed between the cathode and the anode. A membrane electrode assembly for a polymer electrolyte fuel cell comprising the membrane, wherein the polymer electrolyte membrane comprises the electrolyte membrane for a polymer electrolyte fuel cell of the present invention.

  The electrolyte membrane for a polymer electrolyte fuel cell of the present invention has good dimensional stability when containing water, low resistance, excellent power generation characteristics, high productivity, and low cost.

  According to the method for producing an electrolyte membrane for a polymer electrolyte fuel cell of the present invention, the electrolyte membrane of the present invention can be produced with high productivity.

  The membrane electrode assembly of the present invention is low in cost, high in output and excellent in durability.

  Electrolyte membrane for polymer electrolyte fuel cell of the present invention (hereinafter also simply referred to as electrolyte membrane) An ion exchange resin reinforced with a non-woven fabric made of fluororesin and having at least some of the intersections between the fibers immobilized The outermost layer on one or both sides has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin, and the melting point of the fluororesin is 240. It is a polyvinylidene fluoride polymer having a temperature of 0 ° C. or lower, and at least a part of the intersections between the fibers is fixed by fusion of the fibers.

  Since the electrolyte membrane of the present invention is reinforced with the above-mentioned nonwoven fabric, there is little increase in resistance due to reinforcement, it has a sufficiently high strength even when the film thickness is thin, and is excellent in dimensional stability when containing water. Further, as an outermost layer on one side or both sides, it has a non-reinforced layer made of an ion exchange resin which may be the same as or different from the ion exchange resin, so that it can be used as a polymer electrolyte membrane for a polymer electrolyte fuel cell. Sometimes the resistance at the junction of the electrolyte membrane and the electrode can be reduced.

  Therefore, a polymer electrolyte fuel cell having a membrane electrode assembly using this electrolyte membrane can stably obtain a high output even if it is operated for a long period of time. Further, since a fluororesin having a melting point of 240 ° C. or lower is used, the thickness of the nonwoven fabric can be adjusted (thickened) at a temperature as low as 240 ° C. or lower, so a polyethylene terephthalate film (hereinafter also referred to as PET). It is possible to manufacture an electrolyte membrane by a roll-to-roll continuous process using a flexible and inexpensive resin support such as), so that extremely high productivity can be realized.

  The nonwoven fabric used for the electrolyte membrane of the present invention is a nonwoven fabric in which at least some of the intersections between the fibers are immobilized, and at least some of the intersections between the fibers are immobilized by fusion of the fibers. Yes. In addition, the intersection between the fibers in this invention includes both the intersection between the fibers of one fiber and the intersection of the fibers of different fibers.

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

  The average fiber diameter (diameter) of the fiber is preferably 0.01 μm to 7 μm, and particularly preferably 0.01 μm to 3 μm. By making the average fiber diameter of the fibers smaller than 5 μm, proton transfer can be performed more smoothly, so that an increase in resistance due to reinforcement can be suppressed. In addition, by increasing the average fiber diameter from 0.01 μm, it is possible to increase the fixing area of the intersections between fibers in the same film thickness, so that the strength of the nonwoven fabric can be further increased and the dimensional stability of the electrolyte membrane is improved. Can be made. 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. In addition, the average fiber diameter in this invention measures the fiber diameter of 200 fibers in electron microscope observation, and makes the average fiber diameter the average value except 10 data and 10 thick data among data. .

  Moreover, even if a nonwoven fabric is manufactured using fibers having a thin average fiber diameter, generally only a bulky nonwoven fabric is obtained, and it is necessary to perform a thickness adjustment step using a densification process. In this case, it is difficult to adjust the thickness of only a thin nonwoven fabric in terms of handling, and it is necessary to perform a thickness adjusting step on a support that is inexpensive and has sufficient dimensional stability and heat resistance.

  At this time, by adjusting the thickness by a continuous manufacturing process such as a roll-to-roll method, the productivity of the electrolyte membrane can be significantly increased.

  In the present invention, as the fluororesin having a melting point of 240 ° C. or lower constituting the nonwoven fabric, a polyvinylidene fluoride polymer (hereinafter sometimes simply referred to as “PVDF”), a polyvinyl fluoride polymer (hereinafter simply referred to as “PVF”). A copolymer composed of a plurality of monomer units constituting these polymers, a blend of these polymers, and the like are preferred. In particular, when PVDF is used as a fluororesin having a melting point of 240 ° C. or less that constitutes the nonwoven fabric, it is preferable because it is remarkably excellent in mechanical strength and moldability. A generally known fluororesin has a melting point in the range of approximately 260 to 270 ° C. and a high melting point.

  PVDF is a structural isomer of ETFE, but exhibits completely different properties. Due to its strong polarity, it is easily soluble in polar solvents such as dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), dimethylformamide (DMF), and acetone, and can be made into a solution relatively easily. In particular, DMAc can be made into a solution by mixing at room temperature.

  In the present invention, in order to suppress dimensional change due to swelling of the electrolyte membrane, it is preferable that mechanical properties such as tensile strength and elongation are good, and the molecular weight of PVDF is preferably 200,000 to 550,000. When the molecular weight is larger than 550,000, the solubility is lowered and it is difficult to make a solution.

  PVDF has a lower melting point than other fluororesins, but in the present invention, the temperature range expected to be used as an electrolyte membrane of a polymer electrolyte fuel cell is −40 ° C. to 120 ° C. Therefore, those having a melting point of 150 to 175 ° C are preferable, and those having a melting point of 160 to 175 ° C are more preferable. The melting point is an endotherm when heated at 10 ° C./min from room temperature to 300 ° C. in an air atmosphere using a scanning differential thermal analyzer (DSC220CU, manufactured by Seiko Instruments Inc.) as shown in the Examples below. It can be obtained from the peak.

  As a method for producing the above-mentioned fluororesin fiber, it is preferable to employ a melt blown method.

  In the melt blown method, a melt-moldable fluororesin is discharged from a spinning nozzle in a molten state, and a continuous fiber is obtained by drawing and spinning with a gas released from a gas discharge nozzle disposed in the vicinity of the spinning nozzle, and a nonwoven fabric. Is a manufacturing method in which ultrafine fibers can be formed.

  Compared to other nonwoven fabric manufacturing methods in which fibers are formed from a resin and then used as a raw material to fabricate the nonwoven fabric, the meltblown method is capable of forming fibers and fabrics at almost the same time. high. 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.

  As this type of direct nonwoven fabric manufacturing method, other methods such as the spunbond method are known. Generally, it is said that the spunbond method is also easy to obtain a nonwoven fabric composed of relatively fine fibers, but the meltblown method is generally more suitable. It is said that fine fibers are easily obtained.

  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. Although there is no restriction | limiting in particular as a film-form base material which has air permeability, A mesh, cloth, a porous body etc. are mentioned, There is no restriction | limiting in particular also about a material.

  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. In some cases, the above-mentioned fusion does not occur, and a cotton-like nonwoven fabric precursor-like material is obtained, but it is collected on a collection conveyor having an adsorption function, and the thickness is adjusted by a hot press method or the like as it is. Thus, a nonwoven fabric having a predetermined bulk 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.

  Another method for producing a nonwoven fabric made of fluororesin fibers is an electrospinning method.

  The electrospinning method is a method of spinning fibers electrically by applying a high voltage to the spinning dope.

  The electrospinning method has the following characteristics.

  (I) Compared with other methods, it can be manufactured with a simple apparatus.

  In addition to the melt-blown method, the spunbond method, papermaking method, etc. are known as methods for producing nonwoven fabrics, but all of them require large-scale nonwoven fabric production equipment. The equipment cost is high, such as the necessity of the equipment.

  (Ii) An ultrafine continuous fiber aggregate is obtained.

  Manufacturing a non-woven fabric composed of ultrafine fibers using a normal non-woven fabric facility is severe in terms of conditions and has many limitations such as the viscosity of the raw material and stretchability. On the other hand, since the electrospinning method is a spinning method using a solution, volume shrinkage occurs during the drying process, and since the raw material itself has a low viscosity, molding with an ultrafine nozzle is possible. Easy to obtain continuous fiber.

  (Iii) The fiber assembly is usually obtained as a nonwoven fabric in which fibers are combined.

  In the electrospinning method, since solidification from a solution and spinning by stretching occur simultaneously or sequentially, the fiber aggregate is obtained as a nonwoven fabric in which fibers are fused.

  FIG. 2 is a schematic configuration diagram illustrating an example of a nonwoven fabric manufacturing apparatus using an electrospinning method. The nonwoven fabric manufacturing apparatus 10 applies a high voltage between the syringe 12 filled with the spinning dope, the rotatable drum 16 disposed so as to face the needle 14 of the syringe 12, and the needle 14 and the drum 16. And a syringe pump (not shown) for discharging the spinning solution from the syringe at a constant flow rate by moving the plunger portion of the syringe 12 at a constant speed in the discharge direction.

First, the spinning solution is filled into the syringe 12. While rotating the drum 16, a high voltage is applied between the needle 14 and the drum 16 by the high voltage power source 18. The syringe pump is operated, and the spinning solution is discharged from the needle 14 at the tip of the syringe 12 at a constant speed. When a voltage is applied to the tip of the needle 14 and the electrostatic attractive force exceeds the surface tension of the spinning stock solution, the spinning stock solution is deformed into a conical shape called Taylor cone at the tip of the needle 14, and the tip of the cone is Stretched. The stretched spinning dope is refined by electrostatic repulsion of the positively charged spinning dope. The solvent instantly evaporates from the refined spinning dope, and ultrafine fibers are formed. Positively charged fibers adhere to the negatively charged drum 16. As the fibers gradually accumulate on the rotating drum 16, a fluorine-based nonwoven fabric is formed on the drum 16.
An example using PVDF is well known as an example of producing nanofibers by an electrospinning method using a fluororesin or a non-woven fabric form thereof. For example, Polymer journal. Vol. 39, no. 7, pp 670-674 (2007), J. MoI. Phys. Chem. B. 2006, 110, 23351-23364, and the like.

  As the fluorine-containing polymer having an aliphatic ring in the main chain, for example, an amorphous fluororesin (trade name: CYTOP) manufactured by Asahi Glass Co., Ltd. can be used.

  As the fluorine-containing olefin polymer, for example, a fluorine-containing olefin polymer (trade name: Lumiflon) manufactured by Asahi Glass Co., Ltd. can be scattered.

  Among the solvent-soluble fluororesins, polyvinylidene fluoride and DuPont (trade name: Teflon (registered trademark) AF) are particularly preferable because a high-temperature process can be applied to the composite process of the matrix with the electrolyte polymer.

  Although these solvent-soluble fluororesins can also be applied to the present invention, the composite process of the matrix with the electrolyte polymer is generally at 120 ° C. or higher, and among the above polymer materials, polyvinylidene fluoride is often used. Or DuPont (trade name: Teflon (registered trademark) AF) is desirable.

  When the solution containing a fluororesin is subjected to electrospinning, the solution concentration of the spinning dope is generally preferably in the range of 1 wt% to 30 wt%. The discharge amount of the spinning dope in the electrospinning method is preferably 0.1 to 50 mL / hour per discharge port. The inner diameter of the tip of the needle 14 is preferably 0.1 to 2 mm. The distance from the tip of the needle 14 to the drum 16 is preferably 5 to 40 cm. The voltage applied between the needle 14 and the drum 16 is preferably 1 to 40 kV.

  When PVDF is used, the molecular weight range is preferably Mw = 60,000 to 550,000 in the electrospinning method. Examples of the solvent for dissolving PVDF included in this range include dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), dimethylformamide (DMF), acetone, and the like. Since the electrospinning process is a process in which spinning and drying are performed simultaneously, a preferable solvent has a boiling point in the range of 100 to 200 ° C, particularly preferably in the range of 120 ° C to 160 ° C. The concentration of the spinning dope is preferably 5 wt% to 25 wt%, and the discharge amount of the spinning dope is particularly preferably 0.2 to 2 mL / hr per discharge port.

  The nonwoven fabric that can be used in the present invention is preferably subjected to at least one treatment selected from the group consisting of radiation irradiation, 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 enhanced.

  The fibers manufactured by the above-described manufacturing method can be made very thin, and the increase in resistance of the electrolyte membrane due to reinforcement can be suppressed. Therefore, an optimal nonwoven fabric can be formed as a reinforcing material for the electrolyte membrane for fuel cells. Can do.

  The method for producing an electrolyte membrane in the present invention is preferably formed through a step of adjusting the thickness by a roll-to-roll heating roll press method using a resin support. Since the electrolyte membrane of the present invention uses a fluororesin having a melting point of 240 ° C. or lower, the thickness of the nonwoven fabric can be adjusted (thickened) at a temperature of 240 ° C. or lower, so that a general-purpose polyethylene terephthalate film ( The electrolyte membrane can be continuously manufactured by a roll-to-roll method using a flexible and inexpensive resin support such as PET (hereinafter, also referred to as PET), so that extremely high productivity can be realized.

  The roll-to-roll heated roll press method 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 glass transition point is desirable, and the temperature range from (glass transition temperature −20 ° C.) to glass transition point is more desirable. Moreover, although the pressure at the time of a hot press is based also on the above-mentioned temperature conditions, generally, if it shape | molds in the pressure range of 0.5-10 MPa, thickness adjustment can be performed, without producing a big deformation | transformation to a fiber.

  Moreover, in the heated roll press method, a general purpose composed of two metal rolls-rubber rolls without using a calendering roll composed of two metal rolls-metal rolls, which has high heat resistance but high equipment cost. Using an inexpensive roll press laminating apparatus, the intersections between the continuous fibers of the fluororesin can be fixed and thickened by fusing the fibers together. Thereby, even if it is a nonwoven fabric precursor with a small basis weight, it becomes possible to perform various post-processing while minimizing deformation in handling and the like.

  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 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 is a —SO ₃ M ² group (M ² is a hydrogen atom or an alkali metal atom, the same shall apply hereinafter), a —COOM ² group or a group which is converted into these groups by hydrolysis, and B ¹ and B ² are each independently And 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.

  The thickness of the electrolyte membrane of the present invention is preferably 7.5 μm to 25 μm. 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 25 μm or less, and the lower limit is preferably 7.5 μm or more because the crossover of the raw material gas at both electrodes of the fuel cell is remarkably increased. More preferably, it is 7.5 micrometers-20 micrometers.

Moreover, from the viewpoint of the film thickness of the electrolyte membrane, the thickness of the nonwoven fabric is preferably 1 μm or more and 15 μm or less, more preferably 1 μm to 10 μm. The basis weight of the nonwoven fabric of this time, it is preferable from the viewpoint of compatibility of reinforcing effect and film resistance reduction ^{is 0.5cc / m 2 ~5cc / m 2} . For example, by performing densification on a support such as a polyethylene terephthalate film, the thickness region can be formed uniformly.

  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 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 reinforced with the above-mentioned nonwoven fabric as the outermost layer on one or both sides. Thereby, when using the electrolyte membrane of this invention as a polymer electrolyte membrane for a polymer electrolyte fuel cell, the resistance in the junction part of an electrolyte membrane and an 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. Note that the non-reinforced layer made of the ion exchange resin may contain some other component in the ion exchange resin.

  The thickness of the non-reinforced layer made of ion exchange resin is preferably 1 to 10 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 2-5 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 the electrolyte membrane of the present invention, the thickness of the unreinforced layer is preferably equal to or greater than the radius of the average fiber diameter of the fluororesin fibers. In particular, when the thickness of the unreinforced layer is smaller than half of the average fiber diameter of the fluororesin fibers, the resistance increase is significant. When the thickness of the layer that is not reinforced is equal to or greater than the average fiber radius of the continuous fibers, 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. The 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 a usual 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 diffusing the gas uniformly 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]
(Solution adjustment)
Using commercially available powdered polyvinylidene fluoride (ALDRICH, Mw: about 534000, melting point 171 ° C.), 80 g of dimethylacetamide was added to 20 g of polyvinylidene fluoride, stirred at room temperature for 16 hours, and transparent. A solution was obtained. This was used as a spinning dope for electrospinning.

[Electric field stretching]
A non-woven fabric production apparatus (manufactured by Iuchi Seisakusho Co., Ltd.) using an electrospinning method was prepared. A stainless syringe needle of 25 G (inner diameter: 0.25 mm, outer diameter: 0.5 mm, length 5 cm) was attached to the tip of a disposable syringe with a capacity of 10 mL. Using the nonwoven fabric manufacturing apparatus and the spinning solution, electrospinning was performed under the conditions of the distance from the tip of the needle to the drum: 7.5 cm, the applied voltage: 20 kV, and the discharge rate: 0.20 mL / hour. A nonwoven fabric continuous body RA1 composed of fibers having a fiber diameter of 0.3 to 0.7 μm (average fiber diameter of 0.4 μm) was obtained on the drum. The aspect ratios of the nonwoven fabric continuous body RA2 were all 10,000 or more. When an area of 2.6 cm × 2.6 cm of the nonwoven fabric continuous body RA1 was observed with a microscope, fibers having a fiber length of 13 mm or less were not observed. The fabric weight per unit area was 2 g / m ² .

[Thickness adjustment (thickening)]
Next, the non-woven fabric continuum RA1 (41) was laminated with a commercially available continuous polyethylene terephthalate support 42 having a thickness of 100 μm and thickened by using a simple laminating apparatus (VAII-700 manufactured by TAISEI LAMINATOR) shown in FIG. A continuous PET support / thickened nonwoven fabric continuum RAP1 (43) was obtained. When the thickness of the thickened nonwoven fabric continuous body RAP1 was measured with a contact-type micrometer (manufactured by Keyence Corporation: AT-005V 5 mmΦ circular Tip), the average was 5 μm. Note that the temperature of the metal roll 44 and the temperature of the rubber roll 45 at the time of densification are 140 ° C., and the force of the roll pressurization is 0.026 MPa / m with respect to the roll surface length of 600 mm. The speed was 0.15 m / min.

  The obtained temporary pressure-bonded product of continuous PET support / thickened nonwoven fabric RAP1 (43) was excellent in handling properties.

[Production of unreinforced layer made of ion exchange resin]
Next, using a solution of an ion exchange resin (Asahi Glass Co., Ltd .: Flemion) ethanol solution (FSS-2 solid content 9%) by die coating, a fluororesin film (Asahi Glass Co., Ltd .: Aflex (registered trademark) (100N (thickness)) 100 μm))) and dried at 80 ° C. for 5 minutes to obtain a 1.5 μm-thick unreinforced layer made of the above ion exchange resin.

[Electrolyte film forming method]
Next, using the simple laminating apparatus of FIG. 3 (VAII-700 manufactured by TAISEI LAMINATOR), the surface-treated continuous PET support / thickened nonwoven fabric RAP1 and the unreinforced layer having a thickness of 1.5 μm were heated. Crimping was performed to obtain a continuous PET support / intermediate laminate P1. The metal roll temperature and rubber roll temperature during densification are 120 ° C., the pressure of the roll pressurization is 0.026 MPa / m for a roll surface length of 600 mm, and the insertion speed of the continuous PET support is 0.00. It was 15 m / min.

  Next, using the continuous coating system shown in FIG. 4, using the intermediate laminate P1 (51) obtained by peeling the continuous PET support from the continuous PET support / intermediate laminate P1, an ion exchange resin (Asahi Glass) is provided on the surface. Co., Ltd .: Flemion (registered trademark) ethanol solution (FSS-2 solid content 9%), using a die coater 52, dried in a drying furnace 53, and further in a metal roll 54 and a rubber roll 55 Pressurization was performed. Then, it cut | disconnected to the sheet | seat and dried residual solvent etc. on the conditions of 140 degreeC for 30 minutes, and obtained electrolyte membrane R1 whose thickness of the whole electrolyte membrane is 8 micrometers. In addition, from the cross-sectional observation of the electron microscope, the thickness of the unreinforced layer on the surface was about 1.5 μm on both sides.

[Measurement of dimensional change rate when water is contained]
The electrolyte membrane R1 is cut into a 200 mm square, exposed to an atmosphere of a temperature of 25 ° C. and a humidity of 50% for 16 hours, and the vertical and horizontal lengths of the sample are measured. Next, after immersing the sample in ion-exchanged water at 90 ° C. for 1 hour, the vertical and horizontal lengths are measured in the same manner. An average value of the elongation in the vertical direction and the elongation in the horizontal direction of the sample was obtained and used as a dimensional change rate.

[Production of solid polymer fuel cell and measurement of electric resistance]
By sequentially adding platinum-supporting carbon in the order of water and ethanol, a catalyst dispersion (solid content 9 mass%) dispersed in a mixed dispersion medium (mass ratio of 1: 1) of ethanol and water is obtained. Thereafter, an ethanol solution (FSS-2 solid content 9%) of an ion exchange resin (Asahi Glass Co., Ltd .: Flemion (registered trademark)) and a 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 R1 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, 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 disposing a carbon plate separator having zigzag cuts on the gas channel narrow grooves on both outer sides of the membrane electrode assembly, and a heater on the outer side. The battery is assembled.

  The temperature of the fuel cell is maintained at 80 ° C., and nitrogen is supplied to the cathode and hydrogen is supplied to the anode at 0.15 MPa, respectively. At this time, the humidity of both side gases was 100% RH. In this state, the determination of electrode sheet resistance in cathode catalyst layer by AC imped. Liu, Y .; Murphy, M .; W. Baker, D .; R. Gu, W .; Ji, C .; Jorne, J .; Gasteiger, H .; A. Department of Chemical Engineering, University of Rochester, Rochester, NY, USA. ECS Transactions (2007), 11 (1, Part 1, Proton Exchange Membrane Fuel Cells 7, Part 1), 473-484. Impedance measurement exemplified by Publisher: Electrochemical Society was performed to measure the electric resistance in the thickness direction of the film. These results are shown in Table 1. In addition, about contact resistance etc., it calculated | required by extrapolating to thickness 0 using the unreinforced film | membrane from which thickness differs, and subtracted this from the cell resistance part in each measurement, and computed the electrical resistance of the thickness direction of the film | membrane single body. . The results are shown in Table 1.

[Example 2]
The electrolyte membrane R1 produced in Example 1 was laminated using the simple lamination apparatus shown in FIG. 3 to produce an electrolyte membrane R2 in which the total thickness of the electrolyte membrane was 16 μm. The roll temperature at this time was 140 ° C. both in the upper and lower directions, and the feed rate of the electrolyte membrane R2 was 0.15 m / min. The pressing force of the two rolls was about 200 N / cm. Evaluation similar to Example 1 was performed using electrolyte membrane R2. The results are shown in Table 1.

[Comparative Example 1]
Using a fluororesin having a melting point of 300 ° C. (Asahi Glass Co., Ltd .: Aflon PFA (registered trademark) (MFR 40 g / 10 min)), fibers were formed in the same manner as in the nonwoven fabric continuous body forming method of Example 1, and fluororesin (Asahi Glass) A non-woven fabric R-comp1 produced by spraying and binding a 2% solution of Cytop (registered trademark) (solvent: CTL-100) in a mist form and making a thickness adjustment (thickening) method of Example 1 At the same conditions (roll temperature 140 ° C), thickening and temporary pressure bonding were attempted on a continuous PET support, but under the same conditions, it was not sufficiently thickened and temporary pressure bonding to a continuous PET support was possible. There wasn't. The thickness of the nonwoven fabric at this time was as thick as 22 μm.

  Increasing the roll temperature did not improve the situation, and when the roll temperature exceeded 230 ° C, the polyethylene terephthalate film began to deform, and it was found that the roll press method using the polyethylene terephthalate film became impossible. .

  Therefore, the thickness of the non-woven fabric R-comp1 was abandoned, the non-woven fabric R-comp1 was cut into single sheets, and the non-woven fabric R-comp1 cut into single sheets using an adhesive-attached polyimide tape was attached to a continuous PET support. The continuous PET support / nonwoven fabric R-comp1 was prepared and fixed in the same manner as in the electrolyte membrane forming method of Example 1, except that this was used instead of the continuous PET support / thickened nonwoven fabric RAP1. A membrane R5 was produced. Evaluation similar to Example 1 was performed using electrolyte membrane R5. The results are shown in Table 1.

[Comparative Example 2]
Using a fluororesin having a melting point of 260 ° C. (Asahi Glass Co., Ltd .: Aflon ETFE (registered trademark) (MFR 40 g / 10 min)), fibers were formed in the same manner as in the nonwoven fabric continuous body forming method of Example 1 (nonwoven fabric continuous body RA3 ). This nonwoven fabric continuum RA3 was tried to be densified and temporarily pressed on a continuous PET support under the same conditions (roll temperature 140 ° C.) as the thickness adjustment (thickening) method of Example 1. However, it was not sufficiently thickened, and temporary pressing to a continuous PET support was not possible. The thickness of the nonwoven fabric at this time was as thick as 21 μm.

  Therefore, the density of the nonwoven fabric continuum RA3 was abandoned, the nonwoven fabric continuum RA3 was cut into single sheets, and the nonwoven fabric continuum RA3 cut into single sheets using an adhesive-attached polyimide tape was attached to a continuous PET support. To prepare a continuous PET support / nonwoven fabric continuity RA3, which was used in place of the continuous PET support / thickened non-woven fabric RAP1, in the same manner as in the electrolyte membrane formation method of Example 1. A film R6 was prepared. Evaluation similar to Example 1 was performed using electrolyte membrane R6. The results are shown in Table 1.

[Comparative Example 3]
Using a solution of an ion exchange resin (Asahi Glass Co., Ltd .: Flemion (registered trademark)) ethanol solution (FSS-2 solid content 9%) by die coating, a fluororesin film (Asahi Glass Co., Ltd .: Aflex (registered trademark) product number 100N (100 μm thickness)), dried at 80 ° C. for 5 minutes, and then dried at 160 ° C. for 30 minutes to remove the residual solvent, to obtain an electrolyte membrane R7 made of the above ion exchange resin and having a thickness of 25 μm. . This was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  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. The membrane / electrode assembly obtained using this electrolyte membrane provides a polymer electrolyte fuel cell having high electrical properties and high durability.

It is sectional drawing which shows one form of the nozzle cross section used with a melt blown nonwoven fabric manufacturing apparatus. It is a schematic block diagram which shows an example of the nonwoven fabric manufacturing apparatus by an electrospinning method. It is the continuous processing apparatus schematic of nonwoven fabric thickening and PET temporary pressure bonding. 1 is a schematic diagram of a continuous coating system for manufacturing a reinforced electrolyte membrane. FIG.

Explanation of symbols

1: Fluororesin 2: Gas 3: Discharge hole of spinning nozzle 4: Discharge hole of gas discharge nozzle 10: Non-woven fabric production apparatus 12: Syringe 14: Needle 16: Drum 18: High voltage power supply 31: Single screw extruder 32: Special Die 33: Melt blown nonwoven fabric manufacturing method special nozzle 34: Nonwoven fabric A1
35: Stainless steel mesh 36: Hot air for stretching 37: Drive stage 38: Air suction device 39: Excess resin outlet 41: Non-woven fabric continuum RA1
42: Continuous PET support 43: Continuous PET support / thickened non-woven fabric RAP1
44, 54: Metal roll 45, 55: Rubber roll 51: Intermediate laminate P1
52: Die coater 53: Drying furnace

Claims (11)

An electrolyte membrane for a polymer electrolyte fuel cell, the main component of which is an ion exchange resin made of a fluororesin fiber and reinforced with a nonwoven fabric in which at least a part of the intersections between the fibers is fixed,
As an outermost layer on one or both sides, it has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin,
The fluororesin is a polyvinylidene fluoride polymer having a melting point of 240 ° C. or lower,
The electrolyte membrane for a polymer electrolyte fuel cell, wherein the immobilization is immobilization by fusion of the fibers.   2. The electrolyte membrane for a polymer electrolyte fuel cell according to claim 1, wherein an average fiber diameter of the fibers is 0.01 μm to 7 μm.   3. The electrolyte membrane for a polymer electrolyte fuel cell according to claim 1, wherein a thickness of the entire electrolyte membrane for a polymer electrolyte fuel cell is 7.5 μm to 25 μm.   The electrolyte membrane for a polymer electrolyte fuel cell according to any one of claims 1 to 3, wherein a thickness of the unreinforced layer is equal to or greater than a radius of an average fiber diameter of the fibers. A method for producing an electrolyte membrane for a polymer electrolyte fuel cell, comprising:
The electrolyte membrane for a polymer electrolyte fuel cell is a non-woven fabric made of polyvinylidene fluoride polymer fibers having a melting point of 240 ° C. or less, and at least some of the intersections between the fibers are fixed by fusion of the fibers. It is an electrolyte membrane mainly composed of a reinforced ion exchange resin, and has an unreinforced layer made of an ion exchange resin that may be the same as or different from the ion exchange resin as an outermost layer on one or both sides,
The method for producing an electrolyte membrane for a polymer electrolyte fuel cell, wherein the nonwoven fabric is formed through a step of adjusting the thickness by a roll-to-roll heating roll press method using a resin support.   6. The method for producing an electrolyte membrane for a polymer electrolyte fuel cell according to claim 5, wherein the non-woven fabric is formed by obtaining the fibers by spinning by an electrospinning method.   A melt-formable fluororesin is discharged from a spinning nozzle in a molten state, and the nonwoven fabric is formed by obtaining the fibers by drawing and spinning with a gas discharged from a gas discharge nozzle disposed in the vicinity of the spinning nozzle. The method for producing an electrolyte membrane for a polymer electrolyte fuel cell according to claim 5.   The average fiber diameter of the said fiber is 0.01 micrometer-7 micrometers, The manufacturing method of the electrolyte membrane for polymer electrolyte fuel cells of any one of Claims 5-7 characterized by the above-mentioned.   The thickness of the whole electrolyte membrane for polymer electrolyte fuel cells is 7.5 micrometers-25 micrometers, The manufacture of the electrolyte membrane for polymer electrolyte fuel cells of any one of Claims 5-8 characterized by the above-mentioned. Method.   The method for producing an electrolyte membrane for a polymer electrolyte fuel cell according to any one of claims 5 to 9, wherein a thickness of the unreinforced layer is equal to or greater than a radius of an average fiber diameter of the fibers.   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. 5. The membrane electrode assembly for a polymer electrolyte fuel cell, wherein the polymer electrolyte membrane comprises the electrolyte membrane for a polymer electrolyte fuel cell according to any one of claims 1 to 4.

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