JP2000231928A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte fuel cell having high strength even if the membrane is thin, and capable of maintaining high performance for a long time, by using a cation exchange membrane comprising per- fluorocarbon copolymer containing a sulfonic acid group as a solid high polymer electrolyte, including a reinforcement material of polyethylene fiber having a weight average molecular weight of not less than a specific value. SOLUTION: A woven cloth having 10-200 warps and 10-200 wefts/inch independently for each and a thickness of 10-80 μm is obtained by using polyethylene fabric with ultrahigh molecular weight and high density having weight average molecular weight of not less than 1 million, and the number of deniers of 0.8-50. After a gamma ray is radiated to a woven cloth flattened by applying pressure to this woven cloth, an operation to impregnate it in a solution of per-fluorocarbon copolymer containing a sulfonic acid group with concentration of 8% and dry it is repeated. A cation exchange membrane reinforced by this woven cloth consequently obtained has high tensile strength of 8.5 kg/cm and a low specific resistance of 5 Ω.cm and is used for a solid polymer electrolyte. Thereby, high performance can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art In recent years, research on a solid polymer electrolyte fuel cell using a proton conductive polymer membrane as an electrolyte has been advanced. Solid polymer electrolyte fuel cells are promising for applications such as in-vehicle power supplies because of their low operating temperature, high output density, and compact size.

[0003]

The polymer membrane used for the polymer electrolyte fuel cell usually has a thickness of 100 to 200 μm.
In particular, a cation exchange membrane comprising a perfluorocarbon polymer containing a sulfonic acid group has been widely studied because of its excellent basic characteristics. However, in order to obtain a high output density so that the fuel cell can be used for, for example, a power supply for a vehicle, the cation exchange membrane proposed at present has a resistance not sufficiently low.

In order to reduce the resistance of the cation exchange membrane, there are a method of increasing the sulfonic acid group concentration and a method of reducing the film thickness. However, when the sulfonic acid group concentration is significantly increased, the mechanical strength of the membrane decreases. In addition, there is a problem that the membrane is easily creeped due to long-term operation of the fuel cell and the durability of the fuel cell is reduced. On the other hand, when the film thickness is reduced, the mechanical strength of the film decreases, and problems such as difficulty in processing and handling when joining the gas diffusion electrode occur.

As a method for solving the above problem, a film made of a perfluorocarbon polymer containing a sulfonic acid group and polytetrafluoroethylene (hereinafter, PTF) are used.
A cation exchange membrane in which a porous body made of E (hereinafter referred to as E) is composited has been proposed (Mark W. Barbrudge et al., A.
IChE Journal, 1992, 38, 93). However, although the thickness of this film can be reduced, the porous P
The resistance does not decrease sufficiently due to the presence of TFE.

Accordingly, the present invention provides a polymer electrolyte fuel cell having a high power density over a long period of time by using a cation exchange membrane having a high strength and a low resistance even though the film thickness is small as a solid polymer electrolyte. The purpose is to:

[0007]

SUMMARY OF THE INVENTION The present invention provides a cation exchange membrane comprising a sulfonic acid group-containing perfluorocarbon polymer reinforced with ultrahigh molecular weight high density polyethylene fibers having a weight average molecular weight of 1,000,000 or more. The present invention provides a solid polymer electrolyte fuel cell having a solid polymer electrolyte.

[0008] The polyethylene fiber as a reinforcing material in the present invention has a weight average molecular weight of 1,000,000 or more, preferably 3
It is over one million. If the weight average molecular weight is less than 1,000,000, the strength of the cation exchange membrane cannot be increased.

The denier of the polyethylene fiber in the present invention is preferably 0.8 to 50. When the denier number is smaller than 0.8, the fiber strength is low, and thus it is easy to break during processing. If the denier number is larger than 50, the cation-exchange membrane becomes thicker and more resistant when formed into a composite with a sulfonic acid group-containing perfluorocarbon polymer. The denier number is particularly preferably 5 to 30.

The form of the reinforcing material in the present invention may be a woven fabric in which filaments made of polyethylene fibers are woven, a woven fabric in which yarns obtained by twisting the filaments are woven, or a nonwoven fabric. Further, a filament made of polyethylene fiber may be dispersed in a cation exchange membrane to reinforce it. The reinforcing material made of polyethylene fiber has a higher degree of freedom in the degree of reinforcement by controlling the network structure as compared with the porous PTFE material, and the increase in resistance can be reduced because the reinforcing effect is high even if the aperture ratio is high, and the dimensions There are advantages such as excellent stability.

When the reinforcing material is made of a woven fabric, the deniers of the warp and the weft are independently 0.8 to 50, especially 5
It is preferably from 30 to 30. If the denier number of the warp and weft is less than 0.8, the reinforcing effect of the membrane becomes insufficient and the
If it is larger than 0, pinholes and cracks are likely to occur at the intersections between the warp and the weft. As the warp and weft, any monofilament or multifilament can be used as long as the denier number is 0.8 to 50. The multifilament is preferable because the cross section of the yarn can be flattened, so that the resistance of the cation exchange membrane can be suppressed from increasing even if the opening ratio of the woven fabric is reduced.

[0012] The density of the warp and the weft of the woven fabric is 10-20.
0 / inch, particularly preferably 50 to 150 / inch. If less than 10 lines / inch, misalignment tends to occur,
Also, the strength of the woven fabric decreases. If the number is more than 200 / inch, the opening area of the woven fabric becomes small, and at the same time, the thickness of the cation exchange membrane becomes large.

The woven fabric is preferably flattened by a flat plate press or a roll press at a temperature of 120 ° C. or less, and the thickness of the woven fabric is 10 to 80 μm, particularly 15 to 80 μm.
It is preferably 40 μm. If the thickness is less than 10 μm, the reinforcing effect on the cation exchange membrane does not appear remarkably. On the other hand, if the thickness is more than 80 μm, the thickness of the cation exchange membrane is increased and the membrane resistance is increased.

[0014] If the reinforcing material is made of non-woven fabric, basis weight 5 to 50 g / m ^2, it is particularly preferably 20 to 40 g / m ^2. If the basis weight is less than 5 g / m ² , the strength of the nonwoven fabric decreases, and if it is more than 50 g / m ² , the opening area of the nonwoven fabric becomes small and the thickness becomes thick. The thickness of the nonwoven fabric is preferably from 10 to 80 μm, particularly preferably from 15 to 40 μm. 10
If the thickness is less than μm, the reinforcing effect on the cation exchange membrane does not significantly appear. On the other hand, if the thickness is more than 80 μm, the thickness of the cation exchange membrane is increased and the membrane resistance is increased.

When polyethylene fibers are dispersed and reinforced in the cation exchange membrane, the polyethylene fibers weigh 1 to 30 g, preferably 10 to 25 g, per m ^{2 of the} cation exchange membrane.
/ M ² . If the density of the polyethylene fibers in the cation exchange membrane is lower than 1 g / m ² , the reinforcing effect does not appear remarkably. ^{On the other hand, if} it is higher than 30 g / m ² , the film cannot be flattened when a composite film is formed from a sulfonic acid group-containing perfluorocarbon polymer and a reinforcing material.

The surface of the reinforcing material made of polyethylene fibers used in the present invention is preferably subjected to a radiation treatment, a discharge treatment, a chemical treatment, or a graft polymerization treatment. When the reinforcing material is subjected to these treatments, the adhesion between the polymer and the reinforcing material is improved when a composite film is formed from the sulfonic acid group-containing perfluorocarbon polymer and the reinforcing material, and the strength is high. A cation exchange membrane is obtained.

As a radiation treatment method, γ-rays or electron beams are used. The irradiation dose of radiation is 1 to 200 kGy,
Particularly, 10 to 100 kGy is preferable. Irradiation dose is 1k
If it is smaller than Gy, the surface treatment effect is small, and 200 k
If it is larger than Gy, cleavage of the polyethylene molecular chain proceeds,
The strength of the polyethylene fiber itself decreases. Irradiation dose is 1
In the case of ~ 200 kGy, the fiber strength is not significantly reduced, and functional groups such as carboxylic acid groups and hydroxyl groups, radicals, etc.
Active species capable of improving the adhesion to the perfluorocarbon polymer containing a sulfonic acid group are efficiently introduced into the reinforcing material.

Examples of the discharge treatment include a corona discharge treatment under normal pressure and a plasma discharge treatment under reduced pressure. As the processing conditions for corona discharge, the output is 1-3 k
W, the processing speed is preferably 3 to 30 m / min.
If the output is less than 1 kW, discharge cannot be performed. If the output is more than 3 kW, the calorific value increases and the strength of the reinforcing material decreases.
If the processing speed is lower than 3 m / min, the processing is performed excessively, and the strength of the reinforcing material is reduced. If the speed is higher than 30 m / min, there is a possibility that the treatment cannot be performed sufficiently.

The processing conditions for the plasma discharge include a pressure of 5
In the presence of a gas such as air, oxygen, or argon at a pressure of ~ 100 Pa, an output of 0.01 to 0.5 kW and a processing speed of 0.01 to 5
Processing at m / min is preferred. If the pressure is lower than 5 Pa or higher than 100 Pa, discharge cannot be performed. The gas used is not particularly limited, but a gas containing oxygen is preferable for introducing a functional group such as a carboxylic acid group or a hydroxyl group into the reinforcing material. Argon is preferable because it has an effect of stabilizing plasma. The gas may be used alone, or a mixture of two or more gases may be used.

When the output is lower than 0.01 kW, the processing effect is small. When the output is higher than 0.5 kW, heat generation is large and the strength of the reinforcing material is reduced. If the processing speed is lower than 0.01 m / min, the processing becomes excessive and the strength of the reinforcing material is reduced.
If it is faster than this, it may not be possible to process sufficiently.

Examples of the method of chemical treatment include a method of immersing a reinforcing material in chlorosulfonic acid, sulfuric acid, fuming sulfuric acid, fuming sulfuric acid / triethyl phosphate complex, or the like. Of these, chlorosulfonic acid is preferred because sulfonyl chloride groups can be efficiently introduced even at a low temperature, and sulfonic acid groups can be introduced by hydrolysis, so that adhesiveness with a sulfonic acid-type perfluorocarbon polymer can be improved. When chlorosulfonic acid is used, it may be used as it is, but in order to control the reaction of introducing a functional group into the reinforcing material, a solvent such as tetrachloroethane or trichloroethane is used.
It is preferable to use it after diluting it to about 50% by weight.

As a treatment method by the radiation graft polymerization method, the reinforcing polymer is irradiated with radiation while immersing a monomer having a functional group or a monomer capable of introducing a functional group (hereinafter collectively referred to as a monomer having a functional group) into the reinforcing material. Alternatively, the functional group-introduced monomer may be immersed in the reinforcing material after being irradiated with radiation, and then subjected to graft polymerization.
However, the method of irradiating radiation while immersing the functional group-introduced monomer in the reinforcing material is complicated, so the latter method is preferable.

The radiation treatment in the radiation graft polymerization method is preferably performed under the same conditions as the above-described radiation treatment. Further, the radiation irradiation here is preferably performed under reduced pressure or in an atmosphere of an inert gas such as nitrogen in order to protect radicals generated during the irradiation. In addition, it is preferable to keep the reinforcing material at a low temperature in order to prevent a reduction in radical concentration between the irradiation of the radiation and the immersion of the reinforcing material in the functional group-introduced monomer. The immersion of the reinforcing material in the functional group-introduced monomer is also preferably performed under reduced pressure or in an inert gas atmosphere, and the graft polymerization temperature is preferably 40 to 90 ° C.

As the functional group-introducing monomer, styrene,
α-methylstyrene, chloromethylstyrene, alkyl methacrylate, alkyl acrylate, acrylonitrile, acrolein, glycidyl methacrylate, glycidyl acrylate, vinyl acetate, styrene sulfonic acid or a salt thereof, acrylic acid or a salt thereof, methacrylic acid or a salt thereof, crotonic acid, Itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, perfluorosulfonyl fluoride, vinylbenzyltrimethylammonium chloride, arylamine or a salt thereof, 4-vinylpyridine, 2-vinylpyridine, 1-vinylimidazole, 2-vinyl Pyrazine, 4- (3-butenyl) pyridine, acrylamide, N, N-dimethylacrylamide, N- (3- (N, N-dimethyl) aminopropyl) acrylamide 2- (N, N- dimethylamino-ethyl) acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, a compound or a salt thereof having a vinyl group and a sulfonic acid group, CF ₂ = CF
_{-O- (CF 2 -CF (CF 3} )) v - (CF 2) w -CO
A fluorine-containing compound having a methoxycarbonyl group represented by OCH ₃ or the like (where v and w are integers of 0 or more;
v = w = 0 is not satisfied. ) And the like.

When the functional group-introduced monomer is a liquid, the reinforcing material may be immersed directly, or may be diluted with a solvent and then immersed in the reinforcing material. In addition to the method in which the reinforcing material is immersed in the functional group-introduced monomer, a method in which the functional group-introduced monomer is converted into a gas under reduced pressure and introduced into the reinforcing material can be adopted.In this case, the gas is diluted with an inert gas such as nitrogen. You can also. When the functional group-introduced monomer is a solid,
It is used after being dissolved in a solvent in which the functional group-introduced monomer is dissolved.

The above-described radiation treatment, discharge treatment, chemical treatment, and graft polymerization treatment may be carried out by any one of the treatments, or may be carried out by using two or more treatments in combination.

As the sulfonic acid type perfluorocarbon polymer in the present invention, conventionally known polymers are widely used. In particular, CF ₂ = CF- (OCF ₂ CFX) _{m-
O q - (CF 2) n} -SO 3 polymerized units based on fluorovinyl compound represented by H (provided that, X is fluorine atom or a trifluoromethyl group, m is an integer of from 0 to 3, n represents 0
Integer of １２12, q is 0 or 1, and m = q = n = 0. ) And a polymerization unit based on perfluoroolefin such as tetrafluoroethylene or hexafluoropropylene, chlorotrifluoroethylene, or perfluoro (alkyl vinyl ether). Among them, a copolymer containing a polymerized unit based on the fluorovinyl compound and a polymerized unit based on tetrafluoroethylene is preferable.

The sulfonic acid type functional group of the polymerized unit based on the above fluorovinyl compound is usually -SO when the fluorovinyl compound is copolymerized with tetrafluoroethylene.
It is ₂ F, -SO ₃ by hydrolysis after being copolymerized H
Is converted to

Preferred examples of the fluorovinyl compound to be copolymerized include the following. However, in the formula, r is an integer of 1 to 8, s is an integer of 1 to 8,
t is an integer of 0 to 8, and u is an integer of 1 to 3.

CF ₂ ＣＦCFO (CF ₂ ) _r SO ₂ F, CF ₂ ＣＦCFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _s SO
_{2 F, CF 2 = CF (} CF 2) t SO 2 F, CF 2 = CF (OCF 2 CF (CF 3)) u O (CF 2) 2 S
O ₂ F.

The concentration of sulfonic acid groups in the sulfonic acid type perfluorocarbon polymer, that is, the ion exchange capacity, is 0.5 to 2.0 meq / g dry resin, especially 0.7
~ 1.6 meq / gram dry resin is preferred. If the ion exchange capacity is smaller than 0.5 meq / g dry resin, the resistance of the cation exchange membrane increases. On the other hand, if it is larger than 2.0 meq / g dry resin, the mechanical strength of the cation exchange membrane may be weak.

As a method for reinforcing the cation exchange membrane with a reinforcing material composed of polyethylene fibers, a casting method using a solution or dispersion of a sulfonic acid type perfluorocarbon polymer is preferable. The reinforcing material made of a woven or non-woven fabric is preferably impregnated with the above solution, for example, and then dried and formed into a membrane to obtain a cation exchange membrane. When dispersing polyethylene fibers in a cation exchange membrane, for example, after applying a solution or dispersion of a sulfonic acid type perfluorocarbon polymer on a support film such as polyethylene terephthalate,
A method in which polyethylene fibers are sprayed and dried to obtain a cation exchange membrane is preferred.

As a film-forming method other than the above-mentioned casting method, a film-forming method by melt-thermoforming such as a heat-pressing press or a roll press can be considered. However, the reinforcing material and the sulfonic acid type perfluorocarbon polymer are sufficiently bonded. For this purpose, a high-temperature treatment of 140 ° C. or higher, which is a temperature at which the polyethylene fibers deteriorate, is required, which is not preferable.

The thickness of the reinforced cation exchange membrane obtained by the above-mentioned casting method is 15 to 100 μm, especially 20 to 100 μm.
80 μm is preferred.

The cation exchange membrane reinforced in the present invention has a gas diffusion electrode (a fuel electrode and an air electrode) closely attached to both surfaces thereof, and a separator arranged outside the gas diffusion electrodes to constitute a fuel cell.

The gas diffusion electrode is generally made of PTFE made of conductive carbon black carrying catalyst fine particles such as platinum.
And the like, a porous sheet formed using a binder made of a hydrophobic resin such as a sulfonic acid type perfluorocarbon polymer may be contained in the porous sheet. It may be contained as fine particles coated with a polymer.

The gas diffusion electrode is adhered to the cation exchange membrane by, for example, a solvent bonding method or a hot pressing method.
In the present invention, since the strength of the reinforcing material is reduced by hot pressing, it is preferable to employ a solvent bonding method. The solvent bonding method uses a solution obtained by dissolving 0.1 to 50% by weight of an ion-exchange resin composed of a perfluorocarbon polymer in one or more solvents including a fluorine-free alcohol and a fluorine-containing solvent as an adhesive. This adhesive is applied to at least one of a gas diffusion electrode and a cation exchange membrane to bond the gas diffusion electrode and the cation exchange membrane (Japanese Patent Application Laid-Open No. 07-2007).
220741).

The separator is formed with a groove serving as a passage for an oxidizing gas such as fuel gas or air, and supplies gas to the gas diffusion electrode. For example, a conductive carbon plate or the like is used.

[0039]

EXAMPLES Example 1 0.2 mol of tetrafluoroethylene and 0.1 mol of azobisisobutyronitrile were used as initiators.
045 mol CF ₂ 2CFOCF ₂ CF (CF ₃ ) O (C
F ₂ ) ₂ SO ₃ F was copolymerized at 70 ° C. for 5 hours to obtain a copolymer having an ion exchange capacity of 1.1 meq / g dry resin. This is placed in a 20% aqueous KOH solution at 90 ° C. for 1 hour.
After hydrolysis for 6 hours, 1N hydrochloric acid was added at room temperature for 1 hour.
It was converted into an acid form by immersion for 6 hours, washed with water, dried and dissolved in ethanol to obtain a solution of a perfluorocarbon polymer containing a sulfonic acid group at a concentration of 8%.

On the other hand, 10-denier polyethylene fiber (trade name: Dyneema SK-60, manufactured by Toyobo Co., Ltd., weight-average molecular weight 400) obtained by twisting nine filaments having a diameter of 12 μm.
Woven fabric having a density of 80 yarns / inch for both warp and weft yarns. The woven fabric was flattened by pressing under a pressure of 100 ° C. to have a thickness of 20 μm.

After irradiating the woven fabric with 30 kGy γ-rays, the operation of impregnating with the solution of the perfluorocarbon polymer containing sulfonic acid group and drying was repeated to form a reinforced cation exchange membrane having a thickness of 30 μm. Obtained.

(Measurement of Strength) The cation exchange membrane was heated at 90 ° C.
After immersion in pure water, the tensile strength was measured.
The width was 8.5 kg / cm.

(Measurement of membrane resistance)
After immersion in 1 M sulfuric acid at 24 ° C. for 24 hours, the specific resistance was measured by alternating current. In the measurement, 1 M sulfuric acid was used as an electrolyte and platinum was used as an electrode. The effective membrane area is 1.8
7 cm ² , and the specific resistance was measured at 25 ° C. using an LCR meter (manufactured by Yokogawa Hured Packer Co., Ltd.). The result was 5 Ω · cm.

Example 2 (Comparative Example) The solution of the sulfonic acid group-containing perfluorocarbon polymer obtained in Example 1 was cast on a polyethylene terephthalate film and dried to obtain a 30 μm-thick unreinforced resin. A cation exchange membrane was obtained.

When the tensile strength and the specific resistance were measured in the same manner as in Example 1 except that this cation exchange membrane was used, the tensile strength was 0.3 kg / cm and the specific resistance was 4.8 Ω · cm.
Met.

Example 3 The woven fabric obtained in Example 1 was applied under reduced pressure for 2 hours.
After irradiation with 0 kGy γ-rays, the woven fabric was immersed in a styrene monomer, and graft polymerization was performed at 60 ° C for 96 hours. Then, after washing with toluene and drying, a 2% solution of chlorosulfonic acid in tetrachloroethane at a concentration of 30% by weight was added.
The polymer was immersed at 5 ° C. for 16 hours to introduce a sulfonyl chloride group into a polymerized unit based on styrene of the polymer obtained by graft polymerization. Next, it was immersed in a 2M aqueous solution of potassium hydroxide at 90 ° C. for 2 hours for hydrolysis, and then immersed in a 1M aqueous solution of hydrochloric acid at 90 ° C. for 2 hours to convert the sulfonyl chloride group into a sulfonic acid group. The graft ratio (100 × (dry weight of woven fabric after sulfonation−weight of raw woven fabric) / weight of raw woven fabric) is 62%, and the thickness of the woven fabric after graft polymerization is 30%.
μm.

A reinforced cation exchange membrane having a thickness of 35 μm was obtained in the same manner as in Example 1 except that the above-mentioned woven fabric was used. When the tensile strength and the specific resistance were measured in the same manner as in Example 1 except that this cation exchange membrane was used, the tensile strength was 8.9.
kg / cm and the membrane resistance was 5.2 Ω · cm.

[Example 4] Gas diffusion electrodes for fuel electrode and oxygen electrode
As carbon black and PTFE (weight ratio: 6:
4) a thickness of about 200 μm on which platinum is supported,
Area 10cm ^TwoSheet (platinum loading 0.5mg / c
m^Two)It was used. As an adhesive, ethanol and jig
A mixed solution in which the weight ratio of lolopentafluoropropane is 1: 1
The medium containing sulfonic acid groups synthesized in Example 1
Dissolve the orocarbon polymer to make a 5% by weight solution
Was.

At room temperature, 0.05 g of an adhesive was applied to each of the two gas diffusion electrodes, and the reinforced cation exchange membrane obtained in Example 1 was sandwiched with the application surfaces facing inward. Next, this was pressed with a hand roller and dried at room temperature for 2 hours, and then dried at 60 ° C. for 2 hours to obtain a membrane electrode assembly.

Next, the above-mentioned membrane electrode assembly is sandwiched between two titanium current collectors, two sets of PTFE gas supply chambers are disposed outside the current collector, and a heater is further disposed outside the PTFE gas supply chamber. A fuel cell having a membrane area of 10 cm ² was assembled.

The temperature of the fuel cell was maintained at 80 ° C., oxygen was supplied to the oxygen electrode and hydrogen was supplied to the fuel electrode at 2 atm, and the voltage between terminals was measured at a current density of 1 A / cm ^2. there were. When the device was continuously operated under these conditions for 1500 hours, the terminal voltage did not change even after 1500 hours.

Example 5 (Comparative Example) A fuel cell was assembled in the same manner as in Example 4 except that the unreinforced cation exchange membrane produced in Example 2 was used. Example 4 using this fuel cell
When the voltage between terminals was measured at a current density of 1 A / cm ^{2 in} the same manner as in the above, it was 0.60 V. When the continuous operation was carried out in the same manner as in Example 4, the voltage between the terminals became 0.1 after 1000 hours.
It dropped to 4V. So, when you disassemble the fuel cell,
The cation exchange membrane was wrinkled at the edge of the membrane electrode assembly.

[0053]

According to the present invention, a cation exchange membrane having lower resistance and higher mechanical strength than the conventional one is used as a solid polymer electrolyte. can get.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA26 AA27 AA27X AA30 AA30X FA05 FB01 FC01 FC06 FD02 5H026 AA06 BB00 BB10 CX02 CX03 CX05 EE18 EE19 HH00 HH03 HH05

Claims (8)

[Claims] 1. A cation exchange membrane comprising a perfluorocarbon polymer containing a sulfonic acid group as a solid polymer electrolyte, wherein the cation exchange membrane is made of a polyethylene fiber having a weight average molecular weight of 1,000,000 or more. A solid polymer electrolyte fuel cell characterized by containing a material. 2. The solid polymer electrolyte fuel cell according to claim 1, wherein the polyethylene fiber has a denier of 0.8 to 50. 3. The cation exchange membrane is reinforced with a woven fabric made of the polyethylene fiber, and the woven fabric has a denier of warp and weft independently of 0.8 to 50.
And the warp and weft densities are independently 10 to 2
2. The solid polymer electrolyte fuel cell according to claim 1, wherein the number of the cells is 00 / inch and the thickness is 10 to 80 μm. 3. 4. The cation exchange membrane according to claim 1, wherein the cation exchange membrane is reinforced by a nonwoven fabric made of the polyethylene fiber, and the nonwoven fabric has a basis weight of 5 to 50 g / m ² and a thickness of 10 to 80 μm. The solid polymer electrolyte fuel cell according to the above. 5. The solid polymer electrolyte fuel cell according to claim 2, wherein the cation exchange membrane is reinforced by dispersing 1 to 30 g of the polyethylene fiber per 1 m ² . 6. The solid polymer electrolyte type according to claim 1, wherein the surface of said polyethylene fiber is treated by radiation treatment, electric discharge treatment, chemical treatment or radiation graft polymerization method treatment. Fuel cell. 7. A perfluorocarbon polymer containing a sulfonic acid group, polymer units and CF ₂ based on CF ₂ = CF _{2
= CF- (OCF 2 CFX) m} -O q - (CF 2) n -SO 3
A polymerized unit based on H (where X is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is 0 to 0)
An integer of 12, q is 0 or 1, and m = q = n = 0. And a copolymer comprising:
7. The solid polymer electrolyte fuel cell according to 4, 5, or 6. 8. The cation exchange membrane is formed by casting a solution or dispersion of a sulfonic group-containing perfluorocarbon polymer by a casting method.
8. The solid polymer electrolyte fuel cell according to 4, 5, 6, or 7.