JP2002170580A - Diaphragm for solid polymer type fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polymer type fuel battery diaphragm of sufficient physical strength, low electric resistance, and low gas permeability. SOLUTION: The diaphragm for a solid polymer type fuel battery is provided which comprises a hydrocarbon positive ion exchange resin film whose parent material is a fluorine resin porous film which is processed to be hydrophilic, with the electric resistance in a sulfuric acid aqueous solution, 1 mol/L, preferred to be 0.20 Ω.cm2 or lower while the permeability of hydrogen gas being 3.0×10-8 cm3 (STP) cm.cm-2.s-1.cmHg-1 or below at 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane for a polymer electrolyte fuel cell, and more particularly to a membrane for a polymer electrolyte fuel cell comprising an ion-exchange resin membrane whose base material is a fluororesin porous membrane.

[0002]

2. Description of the Related Art A fuel cell is a power generation system that continuously supplies a fuel and an oxidizing agent and takes out chemical energy generated when they react as electric power. Depending on the type of electrolyte used for the fuel cell, the fuel cell has a relatively low operating temperature, a phosphoric acid type, a solid polymer type, a molten carbonate type operating at a high temperature,
It is roughly classified as a solid electrolyte type.

[0003] Among them, the polymer electrolyte fuel cell is
A gas diffusion electrode carrying a catalyst is bonded to both sides of a solid polymer membrane acting as an electrolyte, and hydrogen, which is a fuel, is placed in a chamber (fuel chamber) where one gas diffusion electrode is present, and the other gas is diffused. An oxygen-containing gas such as oxygen or air, which is an oxidizing agent, is supplied to the chamber on the side where the diffusion electrode is present, and an external load circuit is connected between the two gas diffusion electrodes to function as a fuel cell.

FIG. 1 shows the basic structure of such a polymer electrolyte fuel cell. In the figure, (1) is a cell partition, (2) is a fuel gas flow hole, (3) is an oxidant gas flow hole, (4) is a fuel chamber side gas diffusion electrode, and (5) is an oxidant chamber side gas diffusion. electrode,
(6) shows a solid polymer electrolyte membrane. In this polymer electrolyte fuel cell, in the fuel chamber (7), protons (hydrogen ions) and electrons are generated from the supplied hydrogen gas, and the protons conduct in the polymer electrolyte (6), and the other protons. It moves to the oxidant chamber (8) and reacts with oxygen in the air or oxygen gas to produce water. At this time, the electrons generated in the fuel chamber side gas diffusion electrode (4) move to the oxidant chamber side gas diffusion electrode (5) through an external load circuit to obtain electric energy.

In the polymer electrolyte fuel cell having such a structure, a cation exchange resin membrane is usually used for the membrane. The cation exchange resin membrane has low electrical resistance, high water retention, low gas permeability, stability for long-term use, and high physical strength. Required.

Conventionally, a perfluorocarbon sulfonic acid membrane has been mainly used as a cation exchange resin membrane used as a membrane for a polymer electrolyte fuel cell. However, although this membrane is excellent in chemical stability, the water retention capacity is insufficient, so that the cation exchange resin membrane is dried, and the proton conductivity is likely to decrease, and the physical strength is also poor. Since it is sufficient, it is difficult to reduce the electric resistance by thinning. Further, the perfluorocarbon sulfonic acid membrane was expensive.

[0007]

On the other hand, Japanese Patent Application Laid-Open No. 1-22
No. 932 discloses a cation exchange resin membrane in which the cation exchange resin is filled in voids of an ultra-high molecular weight polyolefin porous membrane as a polymer electrolyte fuel cell membrane. A method of dissolving and impregnating a cation exchange resin in a solvent in the pores of the base material composed of the porous membrane, and then removing the solvent or a monomer having a functional group capable of introducing a cation exchange group Is impregnated into the porous membrane, polymerized, and then a cation exchange group is introduced.

[0008] However, although the cation exchange resin membrane has very good physical strength and good heat resistance, it is not enough at this time. In addition, there has been a problem that the film shrinks and adhesion failure easily occurs.

On the other hand, as a resin material having excellent physical strength and heat resistance, a fluororesin represented by polytetrafluoroethylene is known, and a cation exchange resin membrane using this as a base material resin is known. However, for example, Japanese Patent Application Laid-Open No. 6-290
32 and JP-A-9-194609. Then, any of these cation exchange resin membranes is prepared by dissolving the cation exchange resin in a solvent and impregnating the pores of the base material formed of the porous membrane in the method for producing a cation exchange resin membrane described above. And then removing the solvent.

However, in such a production method, the cation exchange resin liquid impregnated in the base material has a high viscosity, so that it is difficult for the liquid to penetrate into the voids of the base material, and the solvent is removed after the impregnation. The volume change also occurred, and it was difficult for the cation exchange resin to be densely filled into the voids of the base material. As a result, these cation exchange resin membranes have high gas permeability, and when used as the fuel cell diaphragm, can sufficiently suppress diffusion of hydrogen gas in the fuel chamber to the oxidation chamber side. There was a problem that it was not possible to obtain a large battery output.

Further, by using such a fluororesin porous membrane and impregnating it with a monomer having a functional group capable of introducing a cation exchange group by a specific method described below, polymerization is carried out. It has been proposed to obtain a cation exchange resin membrane having low electric resistance and extremely low gas permeability (Japanese Patent Application Laid-Open No. H11-310649). But,
In this method, the above-mentioned monomer is usually a hydrocarbon-based monomer and is not well-adapted to a fluororesin. Therefore, the monomer is formed into a fluororesin porous membrane while degassing under reduced pressure. It was necessary to impregnate, and the operation was complicated. In addition, the cation exchange resin membrane obtained in this manner has a poor affinity between the base material and the cation exchange resin phase. At the time of use, the adhesion between both will decrease,
The excellent gas permeability was considerably deteriorated during the production of the fuel cell. Therefore, a sufficient battery output cannot be obtained from the start of use of the fuel cell, and there is room for further improvement in the retention of the battery output during long-term use.

From the above, it has been a major problem to develop a polymer electrolyte fuel cell membrane having sufficient physical strength, low electric resistance, and low gas permeability.

[0013]

Means for Solving the Problems The present inventors have intensively studied to solve the above problems. As a result, we succeeded in developing a membrane for a polymer electrolyte fuel cell using a fluororesin porous membrane as a base material, and having a small electric resistance and a gas permeability that does not increase over the long term, and completed the present invention. I came to.

That is, the present invention is a membrane for a polymer electrolyte fuel cell comprising a hydrocarbon-based cation-exchange resin membrane whose base material is a hydrophilic fluoropolymer-based porous membrane.

The present invention also provides a polymer electrolyte fuel cell provided with the above-mentioned membrane for a polymer electrolyte fuel cell.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The cation exchange resin membrane used in the present invention is made of a hydrophilic fluoropolymer porous membrane as a base material (substrate). That is, the hydrocarbon-based cation exchange resin is filled in the voids of the fluororesin porous membrane and adheres to the surface of the base material to form a cation-exchange resin phase to form the cation-exchange resin. It is a membrane. Such a cation exchange resin membrane is a form in which a hydrocarbon ion exchange resin having high hydration power is dispersed and adhered to a fluororesin porous membrane, and the fluororesin porous membrane is subjected to a hydrophilic treatment. In addition, the filling properties of the ion exchange resin into the voids are extremely high, and as a result, the hydrogen gas permeability coefficient is extremely small. In addition, since the compatibility between the hydrocarbon-based cation exchange resin and the fluorine-based resin porous membrane is good, the adhesion between the two is strong, and the excellent gas permeability is obtained by thermocompression bonding the membrane with a gas diffusion electrode. Or after being used for a long time after being mounted on a fuel cell.

As the fluororesin which is the raw material resin of the porous film, a known thermoplastic resin having a large number of carbon-fluorine bonds in a molecule can be used without any limitation. Usually, a polyolefin having a structure in which all or most of the hydrogen atoms, preferably at least 50 mol% of the hydrogen atoms, are replaced by fluorine atoms is used. In particular, it is most preferable to use those having a structure in which all of them are substituted by fluorine atoms. In the present invention, by using such a fluororesin as a base material of a cation exchange resin membrane, mechanical strength,
It becomes possible to obtain a cation exchange resin membrane having extremely excellent chemical stability and heat resistance.

Examples of suitable fluororesins include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (CTFE), polyvinylidene fluoride (PVdF), and tetrafluoroethylene-hexafluoropropylene copolymer ( FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-
Ethylene copolymer (ECTFE) and the like can be mentioned. Among them, in the present invention, polytetrafluoroethylene (PT
FE) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferable, and polytetrafluoroethylene (PTFE) is particularly preferable. The weight average molecular weight of these fluororesins is preferably 100,000 or more from the viewpoint of good mechanical strength.

These fluororesin porous membranes may be further backed with a cloth of fluororesin fibers such as polytetrafluoroethylene fibers.

The average pore size of the pores formed in the above-mentioned fluorine-based fat porous membrane is 0.1 to 5.0 μm, preferably 0.1 to 5.0 μm.
It is preferably 1.0 μm and has a porosity of 30 to 95%, more preferably 40 to 90%. Average pore size 0.1
When it is less than μm, the electric resistance increases, and the average pore diameter is 1.
If it is 0 μm or more, the mechanical strength may be low. When the porosity is 30% or less, the electric resistance increases, and when the porosity is 95% or more, the mechanical strength may decrease.

Further, the fluororesin porous membrane is usually 5 to 100 μm from the viewpoint of suppressing the electric resistance and imparting the mechanical strength required as a support film.
Is preferable, and more preferably 10 to
Those having a size of 70 μm are preferred.

As these porous films made of fluorine resin, those obtained by making a fluorine resin film porous by a known method are used. For example, Japanese Patent Publication Nos. 42-13560 and 58
What has been made porous by the stretching method described in US Pat.

As a method for hydrophilizing the fluororesin porous membrane used in the present invention, a known method is employed without any particular limitation. For example, corona discharge or plasma discharge treatment of a fluororesin porous membrane / irradiation with gamma rays or electron beams / treatment with a reducing agent such as an alkali metal, etc. After impregnating with a solvent, replacing with water, impregnating with an organic solution of a fluorinated surfactant, then crosslinking and fixing with an electron beam irradiation or radiation crosslinking agent, graft polymerization or impregnation of a hydrophilic monomer In general, a method of polymerizing and impregnating with an aqueous solution of a hydrophilic polymer, followed by electron beam irradiation or a method of crosslinking / fixing with a crosslinking agent, etc. Cross-linking by electron beam irradiation or cross-linking agent
The method of immobilization is preferably adopted.

The degree of hydrophilization is preferably such that the contact angle between the pure water and the fluororesin porous membrane is 120 ° or less, more preferably 60 to 100 °. Further, it is preferable that the wetting index to water is 30 dyn / cm or more, more preferably 40 to 60 dyn / cm.

In the present invention, the cation exchange resin that is present in the pores and the surface of the hydrophilic fluororesin porous membrane is a hydrocarbon cation exchange resin.
Here, in the hydrocarbon-based cation exchange resin, it is preferable that all parts other than the cation exchange group are composed of a hydrocarbon group.
It can be used if most of the side chains are formed. For example,
A small amount of other atoms such as oxygen, nitrogen, silicon, sulfur, boron, and phosphorus are interposed between the carbon-carbon bonds constituting the main chain and the side chains by an ether bond, an ester bond, an amide bond, a siloxane bond, or the like. Is also good. The amount is preferably at most 40 mol%, more preferably at most 10 mol%, based on the number of atoms constituting the main chain and side chains.

The groups other than the cation exchange groups bonded to the main chain and the side chains need not be all hydrogen, and if they are in small amounts, other atoms such as chlorine, bromine, fluorine, iodine, etc.
Alternatively, it may be substituted by a substituent containing another atom. The substitution amount is preferably such that 30 mol% or less, preferably 10 mol% or less, more preferably 5 mol% or less of the hydrogen is substituted.

The cation exchange group of the cation exchange resin is not particularly limited as long as it is a functional group that can be negatively charged in an aqueous solution.
Examples thereof include a carboxylic acid group and a phosphonic acid group, among which a sulfonic acid group is particularly preferred.

The cation exchange resin membrane used in the present invention comprises:
Since a porous membrane as thin as that described above can be used as a base material, by adjusting the cation exchange capacity and the like, 1
The electric resistance in a mol / L-sulfuric acid aqueous solution is 0.20Ω · c
m ² , preferably 0.10 Ω · cm ² or less. In such a case, it is advantageous as a membrane for a polymer electrolyte fuel cell.

The cation exchange resin membrane used in the membrane of the present invention can be a membrane having a small electric resistance as described above, and the filling property of the cation exchange resin into the voids of the porous membrane of the base material can be improved. Since it is high, the gas permeability can be extremely reduced. That is, the permeability coefficient of hydrogen gas at 50 ° C. is 3.0 × 10 ⁻⁸ cm ³ (STP) · cm · cm ^−
2 · s ⁻¹ · cmHg ⁻¹ or less, preferably 0.5 to 2.0 ×
10 ^-8 cm ³ (STP) · cm · cm ^-2 · s ^-1 · cmH
g ⁻¹ . Since the permeability coefficient of hydrogen gas is small in this way, the polymer electrolyte fuel cell membrane made of the ion exchange resin membrane can prevent the supplied hydrogen gas from diffusing into the oxygen gas through the membrane, A high output battery is obtained.

The present invention having the above hydrogen gas permeability coefficient
The cation exchange resin membrane used in Ming
The gas transmission coefficient is generally 2.0 × 10^-8cm
^Three(STP) · cm · cm^-2・ S^-1・ CmHg^-1Less than,
Furthermore, 0.3 to 1.5 × 10 ^-8cm^Three(STP) cm
・ Cm^-2・ S^-1・ CmHg^-1Has the value of Follow
And used as a membrane of a polymer electrolyte fuel cell as described above.
In this case, the penetration of oxygen gas through the diaphragm can be prevented well.
You.

Further, the cation exchange resin membrane used in the present invention has a cation exchange capacity of 0.2 to 5.0 mmol / g, preferably from the viewpoint of keeping the electric resistance in the above range.
It is preferably from 0.5 to 3.0 mmol / g.

The water content should be 30% or more, preferably 4%, so that the proton conductivity is not easily reduced by drying.
It is preferably at least 0%. Generally, the water content is 30 ~
It is kept at about 90%. In order to obtain a water content in such a range, the moisture content can be controlled by the type of cation exchange resin, cation exchange capacity, and degree of crosslinking existing in the voids of the porous membrane.

In the present invention, the cation exchange resin membrane having the above properties may be produced by any method, but is generally produced by the following method. That is, a hydrocarbon monomer having a functional group capable of introducing a cation exchange group or a hydrocarbon monomer having a cation exchange group,
After impregnating a monomer composition comprising a hydrocarbon-based crosslinkable monomer and a polymerization initiator into a hydrophilic fluoropolymer porous membrane, the monomer composition is polymerized, and A method of introducing a cation exchange group accordingly.

In this production method, as a hydrocarbon monomer having a functional group into which a cation exchange group can be introduced or a hydrocarbon monomer having a cation exchange group, a conventionally known cation exchange resin is used. What is used in the production of is used without particular limitation. Specifically, examples of the hydrocarbon monomer having a functional group into which a cation exchange group can be introduced include styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, Examples thereof include aromatic vinyl compounds such as p-tert-butylstyrene, α-halogenated styrene, and vinylnaphthalene, and one or more of these can be used.

Examples of the hydrocarbon monomer having a cation exchange group include sulfonic acid monomers such as styrene sulfonic acid, vinyl sulfonic acid and α-halogenated vinyl sulfonic acid, methacrylic acid, acrylic acid, and the like. Carboxylic acid monomers such as maleic anhydride, phosphonic acid monomers such as vinyl phosphoric acid, salts and esters thereof, and the like are used.

The hydrocarbon-based crosslinkable monomers include:
Although not particularly limited, for example, divinylbenzenes, divinylsulfone, butadiene, chloroprene, divinylbiphenyl, polyfunctional vinyl compounds such as trivinylbenzene, trimethylolmethanetrimethacrylate, methylenebisacrylamide, hexamethylene A polyfunctional methacrylic acid derivative such as dimethacrylamide is used.

In the present invention, in addition to the above-mentioned hydrocarbon monomers, if necessary, other hydrocarbon monomers and plasticizers copolymerizable with these monomers are added. Is also good. Such other hydrocarbon monomers include, for example, styrene,
Acrylonitrile, methyl styrene, acrolein, methyl vinyl ketone, vinyl biphenyl and the like are used.
As the plasticizer, dibutyl phthalate, dioctyl phthalate, dimethyl isophthalate, dibutyl adipate, triethyl citrate, acetyl tributyl citrate, dibutyl sebacate and the like are used.

As the polymerization initiator used in the above polymerization, conventionally known ones are used without any particular limitation. Specific examples of such a polymerization initiator include octanoyl peroxide,
Lauroyl peroxide, t-butylperoxy-2-
Ethylhexanoate, benzoyl peroxide, t-
Butyl peroxyisobutyrate, t-butyl peroxy laurate, t-hexyl peroxy benzoate,
An organic peroxide such as di-t-butyl peroxide is used.

In the present invention, in order to achieve the object of the present invention, the mixing ratio of each component constituting the monomer composition is generally a hydrocarbon having a functional group into which a cation exchange group can be introduced. 0.1 to 50 parts by weight, preferably 1 to 40 parts by weight of the hydrocarbon-based crosslinkable monomer with respect to 100 parts by weight of the hydrocarbon-based monomer having a cation-exchange group or a system-based monomer. It is preferable to use 0 to 100 parts by weight of other hydrocarbon monomers copolymerizable with these monomers, and 0 to 50 parts by weight based on the above monomers when adding a plasticizer. It is. The polymerization initiator is used in an amount of 0.1 to 100 parts by weight of a hydrocarbon monomer having a functional group into which a cation exchange group can be introduced or 100 parts by weight of a hydrocarbon monomer having a cation exchange group.
It is preferable to mix 1 to 20 parts by weight, preferably 0.5 to 10 parts by weight.

The method for impregnating the hydrophilic composition as the base material with the hydrophilic resin-containing porous membrane made of a fluororesin is not particularly limited, and a known method may be appropriately employed. Even if only impregnated under atmospheric pressure, the fluororesin porous membrane has been subjected to hydrophilic treatment, so that both are well-adapted, and the monomer composition penetrates into the voids with considerably high filling properties. I do. Therefore, after such impregnation, the cation exchange resin membrane obtained by polymerizing the monomer composition becomes a membrane having very low gas permeability as specified by the present invention.

In the present invention, in order to fill the monomer composition with higher filling properties, it is preferable to impregnate while degassing under reduced pressure. Specifically, it is preferable that the monomer composition is brought into contact with a hydrophilized fluororesin porous membrane under reduced pressure, and the pressure is returned to atmospheric pressure. For example, a method in which a porous film made of a fluororesin is placed in a container, the pressure is reduced by a vacuum pump, and then the monomer composition is introduced into the container until it returns to the atmospheric pressure and is immersed, or A method in which a porous film made of a fluororesin is immersed in the monomer composition, the gas in the holes is degassed under reduced pressure by a vacuum pump, and then returned to the atmospheric pressure. The pressure when depressurizing is 7.0 kPa
The pressure until the monomer boils at the working temperature is preferable, and it is particularly preferable to adopt a pressure in the range of 2.0 kPa to 0.1 kPa. According to such a method of impregnating while degassing under reduced pressure, the obtained cation exchange resin membrane has a gas permeability coefficient of the hydrogen gas of 0.3 to 1.5 × 10 ⁻⁸ cm.
³ (STP) · cm · cm ⁻² · s ⁻¹ · cmHg ⁻¹ can be obtained.

The temperature during the impregnation of the monomer composition is 25
° C or less, and the impregnation time is usually from 1 second to 60
What is necessary is just to select suitably in the range of seconds.

As a method of polymerizing the monomer composition after filling it in the above-mentioned fluororesin porous film, it is generally preferable to raise the temperature from room temperature under pressure while sandwiching a film of polyester or the like. Such polymerization conditions depend on the type of the involved polymerization initiator, the composition of the monomer composition, and the like, and are not limited at times but may be appropriately selected.

The film-like material obtained by polymerization as described above may be optionally subjected to a known cation-exchange group by a known treatment such as sulfonation, chlorosulfonation, phosphoniumation or hydrolysis. It can be introduced into a cation exchange resin membrane.

In the present invention, the cation exchange resin membrane having the above properties is used as a membrane of a polymer electrolyte fuel cell. As the polymer electrolyte fuel cell, those having a known structure can be applied without any limitation. Usually, it is generally applied to one having a structure as shown in FIG.

[0046]

The polymer electrolyte fuel cell membrane of the present invention is
Since the electric resistance is low and the cation exchange resin is filled into the voids of the fluoropolymer porous membrane which has been subjected to the hydrophilic treatment as a base material without any gaps, the gas permeability is extremely low. Also, since the fluororesin porous membrane is the base material, it is excellent in dimensional stability, heat resistance and chemical resistance.

Further, due to the good compatibility between the fluorine-based resin porous membrane and the cation exchange resin, the adhesion between the two is extremely strong. The membrane is well held even after being thermocompression bonded to the gas diffusion electrode or attached to a fuel cell and used for a long time.

Therefore, in the polymer electrolyte fuel cell equipped with the membrane of the present invention having such properties, the crossover of the fuel and the oxidant is suppressed, and a high cell output can be stably obtained for a long period of time. .

[0049]

EXAMPLES In order to explain the present invention more specifically, the following will be described.
The present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples. The properties of the cation exchange resin membranes shown in Examples and Comparative Examples indicate values measured by the following methods. (1) Impregnating property of the monomer composition into the base material When the fluororesin-based porous membrane is immersed in a glass container containing the monomer composition, the entire surface of the fluororesin-based porous membrane has a single amount. The time required for wetting with the body composition was visually observed. (2) Cation exchange capacity: 1 mol of cation exchange resin membrane
After being immersed in 1 / L-HCl for at least 10 hours to form a hydrogen ion type, the hydrogen ions released by substitution with sodium ion type with 1 mol / L-NaCl are separated by a potentiometric titrator (CO
MTITE-900, manufactured by Hiranuma Sangyo Co., Ltd.) (Amol).

Next, the same cation exchange resin membrane was dried under reduced pressure at 60 ° C. for 5 hours, and its weight was measured (Wg). The cation exchange capacity was determined by the following equation. Cation exchange capacity = A × 1000 / W [mmol / g−
Dry membrane] (3) Electric resistance A cation exchange resin membrane was placed in the center of a two-chamber cell provided with a platinum electrode, and the cell was filled with a 3 mol / L sulfuric acid aqueous solution at 25 ° C. Luggin tubes were provided on both sides of the cation exchange resin membrane, and liquid junction was performed with the reference electrode by a salt bridge. 100 across the membrane
mA / cm potential when a current of ^second current (aV) and the potential at a current of 100 mA / cm ² with no intervening film (bV) was measured. The electrical resistance of the cation exchange resin membrane was determined by the following equation. Electric resistance = 1000 × (ab) / 100 [Ω · c
m ² ] (4) Water content The cation exchange resin membrane was immersed in 1 mol / L-HCl for 4 hours or more to form a hydrogen ion type, washed sufficiently with ion-exchanged water, taken out of the membrane and taken out of the surface with Kimwipe or the like. Was wiped off and the wet weight (Wg) was measured. Next, membrane 6
It dried under reduced pressure at 0 degreeC for 5 hours, and measured the weight (Dg) at the time of drying. The water content of the cation exchange resin membrane was determined by the following equation.

Water content = 1000 × (WD) / D [%] (5) Hydrogen gas permeability As a method for measuring the hydrogen gas permeability coefficient, a gas permeability test using a U-tube mercury manometer (based on JIS Z1707). Machine was used. The cation exchange resin membrane used for the measurement was 5
It was mounted on a gas permeation tester at 0 ° C. in a water-containing state. The gas used for the measurement was oxygen or hydrogen maintained at a saturation temperature at 50 ° C. The hydrogen gas permeability coefficient was determined by the following equation.

The hydrogen gas permeation coefficient is determined not only during the production of the cation exchange resin membrane but also after the production of the cation exchange resin membrane / gas diffusion electrode assembly. The measurement was performed using a portion. P = (p / t) × (1 / A) × {1 / (Pa−Pb)} P: Gas permeability coefficient p: Gas permeation amount t; Measurement time l: Cation exchange resin membrane thickness A: Gas permeation area Pa: high-pressure gas pressure Pb: low-pressure gas pressure (6) Fuel cell output voltage 30% by weight of platinum on carbon paper having a porosity of 80%
And a mixture of a carbon black supported by the above, an alcohol of a sulfonated polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer (cation exchange capacity: 0.9) and a 5% solution of dichloroethane, and applying the mixture.
It was dried under reduced pressure at 0 ° C. for 4 hours to obtain a gas diffusion electrode.

Next, the above gas diffusion electrodes were set on both sides of the cation exchange resin membrane to be measured,
After hot pressing under pressure of 0 kg / cm ² for 100 seconds,
The mixture was left at room temperature for 2 minutes to obtain a cation exchange resin membrane / gas diffusion electrode assembly. This was assembled in the fuel cell shown in FIG. 1, and the pressure was 2 atm, the fuel cell temperature was 50 ° C., the humidification temperature was 50 ° C., and the oxygen flow rate and the hydrogen flow rate were each 200 mL / m.
A power generation test was performed at 400 mL / min in, and the terminal voltage of the cell at a current density of 0.3 A / cm ² was measured. (7) Heat resistance (shrinkage rate) After leaving the sample film for measurement preliminarily dried in a dryer at 50 ° C. for 1 hour in a dryer at 160 ° C. for 30 minutes, it was taken out of the dryer and the dimensions were measured. The shrinkage was determined by the following equation. S = 100 × (La−Lb) / La S: shrinkage ratio (%) La: length of membrane dried in a dryer at 50 ° C. (cm) Lb: left in a dryer at 160 ° C. for 30 minutes Film length (cm) (8) Durability evaluation After measuring the output voltage, 50 ° C., current density 0.3 A / c
A continuous power generation test was performed under the conditions of m ² , and the output voltage after 250 hours was measured to evaluate the durability of the cation exchange resin membrane.

Examples 1 to 6 In accordance with the composition table shown in Table 1, various monomers were mixed to obtain monomer compositions.

[0055] 400 g of the obtained monomer composition was added to 500 m
L, and impregnated and coated with polyvinyl alcohol as a hydrophilic polymer, and cross-linked and fixed with glutaraldehyde to make polytetrafluoroethylene (PTFE) porous membranes A, B, and C (all of them) A pure water contact angle of 80 ° and a water wetting index of 52 dyn /
cm: 20 cm x 20 cm) under atmospheric pressure.
It was immersed at 5 ° C. for 10 seconds to fill the voids of the porous film with the monomer composition. At that time, the impregnation property of the base material of the monomer composition was measured. Then, take out the fluorine-based resin porous membrane from a monomer composition, after coating the both sides of the fluorine-based resin porous membrane of a polyester film of 100μm as a release agent, under a nitrogen pressure of 3 kg / cm ² At 80 ° C. for 5 hours.

The obtained film was subjected to 98% concentrated sulfuric acid and a purity of 90%.
% Of chlorosulfonic acid in a 1: 1 mixture at 40 ° C. for 45 minutes to obtain a sulfonic acid type cation exchange resin membrane.

The thickness, cation exchange capacity, electric resistance, water content, hydrogen gas permeability, fuel cell output voltage, heat resistance and durability of these sulfonic acid type cation exchange resin membranes were measured. Table 2 shows the results.

Example 7 400 g of the same monomer composition as in Example 1 was placed in a 500 mL glass container, and the same hydrophilic polytetrafluoroethylene (PTFE) membrane A as in Example 1 was immersed. At that time, the impregnation property of the base material of the monomer composition was measured. Next, the glass container was 0.7 kP with a vacuum pump.
a for 10 minutes, and then degassed under reduced pressure.
FE) The pores of the porous membrane were more densely packed. Next, the same operation as in Example 1 was performed to obtain a sulfonic acid type cation exchange resin membrane.

The film thickness, cation exchange capacity, electric resistance, water content, hydrogen gas permeability, fuel cell output voltage, heat resistance and durability of these sulfonic acid type cation exchange resin membranes were measured. Table 2 shows the results.

Comparative Examples 1 and 2 400 g of the same monomer composition as in Examples 3 and 6
In a glass container L, a polytetrafluoroethylene (PTFE) porous membrane D (pure water contact angle: 131 °, water wetting index: 30 dyn / cm) was immersed. Also,
At that time, the impregnation property of the monomer composition into the base material was measured. Next, the pressure of the glass container was reduced to 0.7 kPa by a vacuum pump for 10 minutes, and the pressure was reduced. Then, the pressure was returned to normal pressure, and the monomer composition was introduced into the pores of the polytetrafluoroethylene (PTFE) porous membrane. Was charged. Next, the same operation as in Example 1 was performed to obtain a sulfonic acid type cation exchange resin membrane.

The film thickness, cation exchange capacity, electric resistance, water content, hydrogen gas permeability, fuel cell output voltage, heat resistance and durability of these sulfonic acid type cation exchange resin membranes were measured. Table 2 shows the results.

Comparative Example 3 A sulfonic acid type cation exchange resin membrane was obtained in the same manner as in Comparative Example 1 using a perfluorocarbon sulfonic acid membrane (commercially available product A).

The film thickness, cation exchange capacity, electric resistance, water content, hydrogen gas permeability, fuel cell output voltage, heat resistance and durability of this sulfonic acid type cation exchange resin membrane were measured.
Table 2 shows the results. The gas diffusion electrode has a porosity of 80 treated with water repellency with polytetrafluoroethylene.
% Carbon paper, 30% by weight of supported carbon black, 5% of alcohol and water of perfluorocarbon sulfonic acid resin (cation exchange capacity 0.9).
A solution (Aldrich) was mixed and applied.
What was dried under reduced pressure at 4 ° C. for 4 hours was used.

[0064]

[Table 1]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a basic structure of a polymer electrolyte fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Battery partition wall 2; Fuel gas flow hole 3; Oxidant gas flow hole 4; Fuel chamber side gas diffusion electrode 5; Oxidant room side gas diffusion electrode 6; Solid polymer electrolyte 7;

Claims (3)

[Claims] 1. A membrane for a polymer electrolyte fuel cell, comprising a hydrocarbon-based cation-exchange resin membrane whose base material is a hydrophilic membrane-processed fluororesin porous membrane. 2. The electric resistance in a 1 mol / L-sulfuric acid aqueous solution is 0.20 Ω · cm ² or less, and the permeability coefficient of hydrogen gas at 50 ° C. is 3.0 × 10 ⁻⁸ cm ³ (STP) cm ·
cm ^-2 · s at ^-1 · cmHg ^-1 or less claim 1, wherein the polymer electrolyte fuel cell membrane. 3. A polymer electrolyte fuel cell comprising the polymer electrolyte fuel cell diaphragm according to claim 1.