JP2008300317A - Membrane electrode assembly for solid polymer fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode assembly for a solid polymer fuel cell which can materialize a high power generation performance even in a low humidity environment and has an excellent durability performance in an environment where wetness and dryness are repeated. <P>SOLUTION: The membrane electrode assembly for a solid polymer fuel cell 1 is provided with a first electrode 10 and a second electrode 20 having catalyst layers 12, 22 containing an electrode catalyst and a proton conductive polymer and gas diffusion layers 14, 24, and a solid polymer electrolyte membrane 30 arranged between the first catalyst layer 12 and the second catalyst layer 22. The solid polymer electrolyte membrane 30 has 0.05S/cm or more of an electric conductivity under an atmosphere of a temperature 80°C and a relative humidity 40% and a 90° peeling strength between the solid electrolyte membrane 30 and the first gas diffusion layer 14 is 0.03N/cm or more, and furthermore, a dimensional change ratio when the first gas diffusion layer 14 is immersed in a hot water of 80°C is less than 10%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly for a polymer electrolyte fuel cell and a method for producing the same.

  In recent years, solid polymer fuel cells have been required to operate in a low humidified environment, mainly for automotive applications. Therefore, as a proton conductive polymer contained in the solid polymer electrolyte membrane of the membrane electrode assembly, a material that exhibits high conductivity in a low humidified environment is required.

When a solid polymer fuel cell is used in an automobile and the automobile is actually driven, the solid polymer electrolyte membrane is exposed to various humidity environments. As a test for simulating this, a cycle test in which a solid polymer electrolyte membrane is repeatedly exposed to a dry environment having a relative humidity of 25% or less and a wet environment having a relative humidity of 100% or more (hereinafter referred to as a wet-dry cycle). (Referred to as non-patent document 1).
In the wet-dry cycle test, the solid polymer electrolyte membrane swells when it becomes a wet environment, shrinks when it becomes a dry environment, and repeats swelling and shrinkage with a cycle of wet and dry, In particular, it causes dimensional changes in the plane direction. Therefore, the mechanical durability performance of the membrane / electrode assembly in an environment in which wetting and drying are repeated can be evaluated by a wet-dry cycle test.
Yeh-Hung Lai, Cortney K.M. Mittelstead, Craig S. et al. Gitterman, David A.M. Dillard, "VISCOELASTIC STRESS MODEL AND MECHANICAL CHARACTERIZATION OF PERFLUOROSULFONIC ACID (PFSA) POLYMER ELECTROLYTE MEMBRANES", Proceedings of FUELCELL2005, Third International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL2005, (2005), 74120.

In order to express high conductivity in a low humidified environment, it is effective to improve the conductivity of the proton conductive polymer. For this purpose, the number of ionic groups may be increased. Moreover, in a membrane electrode assembly, the electrical conductivity in a low humidification environment can be improved by reducing the film thickness of the solid polymer electrolyte membrane.
However, increasing the ionic groups increases the water content of the proton conducting polymer. If the water content of the proton conductive polymer used for the solid polymer electrolyte membrane becomes too high, the proton conductive polymer tends to swell, and in the wet-dry cycle test, the solid polymer electrolyte membrane swells in the plane direction. And the degree of shrinkage becomes larger. Therefore, a hole may be formed in the solid polymer electrolyte membrane, and the mechanical durability performance of the membrane electrode assembly is lowered.
Further, in the membrane / electrode assembly, when the thickness of the solid polymer electrolyte membrane is reduced, the mechanical strength of the solid polymer electrolyte membrane is lowered and the durability performance is lowered.

  The present invention provides a membrane electrode assembly for a polymer electrolyte fuel cell, which can exhibit high power generation performance even in a low humidified environment, and is excellent in durability performance under repeated wet and dry environments, and a method for producing the same To do.

The membrane electrode assembly for a polymer electrolyte fuel cell of the present invention includes a first electrode having an electrode catalyst and a proton conductive polymer, a first electrode having a first gas diffusion layer, an electrode catalyst, and a proton conduction. A second electrode having a second catalyst layer containing a conductive polymer and a second gas diffusion layer, and a solid polymer electrolyte membrane disposed between the first catalyst layer and the second catalyst layer The solid polymer electrolyte membrane has a conductivity of 0.05 S / cm or more in an atmosphere at a temperature of 80 ° C. and a relative humidity of 40%. Dimensional change when the 90 ° peel strength between the molecular electrolyte membrane and the first gas diffusion layer is 0.03 N / cm or more, and the first gas diffusion layer is immersed in warm water of 80 ° C. The rate is less than 10%.
In the membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention, the solid polymer electrolyte membrane is preferably formed by casting a liquid composition in which a proton conductive polymer is dispersed in a dispersion medium.

  In the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to the present invention, the first catalyst layer formed on the first gas diffusion layer and the solid polymer electrolyte membrane are joined. Thus, the membrane electrode assembly for a polymer electrolyte fuel cell of the present invention is obtained.

  In the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to the present invention, the first catalyst layer formed on the polymer electrolyte membrane and the first gas diffusion layer are joined. Thus, the membrane electrode assembly for a polymer electrolyte fuel cell of the present invention is obtained.

The membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention can exhibit high power generation performance even in a low humidified environment, and is excellent in durability performance in an environment where wetting and drying are repeated.
According to the method for producing a membrane / electrode assembly for a polymer electrolyte fuel cell of the present invention, high power generation performance can be expressed even in a low humidified environment, and the durability performance in an environment in which wetting and drying are repeated is excellent. A membrane electrode assembly for a polymer electrolyte fuel cell can be produced.

  In the present specification, a group represented by the formula (α) is referred to as a group (α). Groups represented by other formulas are also described in the same manner. Moreover, the compound represented by Formula (1) is described as a compound (1). The same applies to compounds represented by other formulas.

<Membrane electrode assembly for polymer electrolyte fuel cell>
FIG. 1 is a schematic cross-sectional view showing an example of a membrane electrode assembly for a polymer electrolyte fuel cell (hereinafter referred to as a membrane electrode assembly).
The membrane electrode assembly 1 includes a first electrode 10 having a first catalyst layer 12 and a first gas diffusion layer 14, and a second electrode having a second catalyst layer 22 and a second gas diffusion layer 24. 20 and a solid polymer electrolyte membrane 30 disposed between the first electrode 10 and the second electrode 20 in contact with the first catalyst layer 12 and the second catalyst layer 22, respectively. .
The first electrode 10 and the second electrode 20 may be an anode or a cathode, respectively, as long as they are different from each other.

(90 ° peel strength)
In the membrane / electrode assembly 1, the 90 ° peel strength between the solid polymer electrolyte membrane 30 and the first gas diffusion layer 14 is 0.03 N / cm or more, and 0.07 N / cm or more. preferable.
If the 90 ° peel strength is 0.03 N / cm or more, the solid polymer electrolyte membrane 30 and the first gas diffusion layer 14 are bonded together with sufficient bonding strength via the first catalyst layer 12. For this reason, high power generation performance can be expressed even in a low humidified environment, and the durability performance in an environment in which wetting and drying are repeated is excellent. In particular, when the 90 ° peel strength is 0.07 N / cm or more, the deformation of the solid polymer electrolyte membrane 30 is further suppressed, and the durability performance in an environment where the membrane electrode assembly 1 is repeatedly wetted and dried is obtained. Even better.
In the membrane / electrode assembly 1, the 90 ° peel strength between the solid polymer electrolyte membrane 30 and the second gas diffusion layer 24 is also preferably 0.03 N / cm or more.

In the present invention, the “90 ° peel strength between the solid polymer electrolyte membrane 30 and the first gas diffusion layer 14” refers to the 90 ° peel strength measurement method described below in the solid polymer electrolyte membrane 30 and Of the interface with the first catalyst layer 12 and the interface between the first gas diffusion layer 14 and the first catalyst layer 12, the 90 ° peel strength of the interface that peels first is shown.
The specific measurement method of 90 degree peeling strength can be measured with the following two types of methods, for example according to the manufacturing method of the membrane electrode assembly 1. That is, after forming the catalyst layer on the solid polymer electrolyte membrane, when joining the catalyst layer and the gas diffusion layer, a 90 ° peel test (I) is performed, and after forming the catalyst layer on the gas diffusion layer, When joining the catalyst layer and the solid polymer electrolyte membrane, a 90 ° peel test (II) is performed.
Hereinafter, a description will be given with reference to FIGS.

90 ° peel test (I):
(Procedure 1) As shown in FIG. 2A, the first catalyst layer 12 is formed on one surface of the solid polymer electrolyte membrane 30, and the solid polymer electrolyte membrane 30 and the first catalyst layer 12 are separated from each other. A test piece 90 is prepared.
(Procedure 2) 80 mm in the longitudinal direction from the end 90 a of the test piece 90 and 80 mm in the longitudinal direction from the end 14 a of the first gas diffusion layer 14, the first gas diffusion layer 14 and the solid polymer electrolyte membrane The test piece 91 having a width of 20 mm and a length of 220 mm is manufactured by bonding the first catalyst layer 12 to 30.
(Procedure 3) As shown in FIG. 2B, the entire surface of the solid polymer electrolyte membrane 30 opposite to the first catalyst layer 12 side is an aluminum plate 94 having a width of 25 mm, a length of 150 mm, and a thickness of 3 mm. A sample mounting portion of a tensile tester (not shown) is attached to the end 14b of the first gas diffusion layer 14 which is bonded to the end of the first gas diffusion layer 14 via a stainless steel roller 92 having a diameter of 6 mm. Pinch.
In addition, as the double-sided tape 96, the peel strength at the interface between the first gas diffusion layer 14 and the first catalyst layer 12 of the test piece 91 and the interface between the first catalyst layer 12 and the solid polymer electrolyte membrane 30 are used. Those having an adhesive strength sufficiently higher than any of the above peel strengths are used.
(Procedure 4) The pinched end 14b is pulled at a speed of 50 mm / min in the direction perpendicular to the solid polymer electrolyte membrane 30 (arrow), and the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12 is pulled. Of the interfaces between the first gas diffusion layer 14 and the first catalyst layer 12, the peel strength of the interface that peels first is measured.

The 90 ° peel test (I) is performed on the three test pieces 91 produced by the procedure 1 and the procedure 2.
The “90 ° peel strength” is the first of the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12 and the interface between the first gas diffusion layer 14 and the first catalyst layer 12. The strength until the other interface peels is measured through a load cell and recorded on a personal computer. Among the measured strengths, the portion where the strength value is stable, that is, at the start of the peel strength measurement The average value is obtained for the portion excluding the value at the end, and this is taken as the peel strength, the average value of the peel strength is calculated three times, and this average value is obtained by dividing the test piece 91 by the width of 20 mm.

90 ° peel test (II):
(Procedure 1) As shown in FIG. 3A, the first catalyst layer 12 is formed on the surface of the first gas diffusion layer 14, and the first gas diffusion layer 14 and the first catalyst layer 12 are And the first electrode 10 and the solid polymer electrolyte membrane 30 are further provided between the first gas diffusion layer 14 and the solid polymer electrolyte membrane 30. The test piece 91 having a width of 20 mm and a length of 150 mm is produced by bonding so that 12 is located.
(Procedure 2) The single-sided adhesive tape 98 is adhered to the surface of the first gas diffusion layer 14 for 80 mm from the end 91a of the test piece 91 in the longitudinal direction.
As the single-sided adhesive tape 98, the peel strength at the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12, and the peel strength at the interface between the first catalyst layer 12 and the first gas diffusion layer 14 are used. Those having a sufficiently high adhesive strength are used.
(Procedure 3) As shown in FIG. 3B, the entire surface of the solid polymer electrolyte membrane 30 opposite to the first catalyst layer 12 side is an aluminum plate 94 having a width of 25 mm × a length of 150 mm × a thickness of 3 mm. Affixed with double-sided tape 96.
The double-sided tape 96 is based on the peel strength at the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12 and the peel strength at the interface between the first catalyst layer 12 and the first gas diffusion layer 14. Also, those having sufficiently high adhesive strength are used.
And the end 98b of the single-sided adhesive tape 98 is pinched | interposed into the sample attachment part of a tensile tester (not shown) through the stainless steel roller 92 with a diameter of 6 mm.
(Procedure 4) The clamped end 98b is pulled at a speed of 50 mm / min in the direction perpendicular to the test piece 91 (arrow), and the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12 and the first Of the interface between the first gas diffusion layer 14 and the first catalyst layer 12, the peel strength of the interface that peels first is measured.

The 90 ° peel test (II) is performed on the three test pieces 91 produced by the procedure 1.
The “90 ° peel strength” is the first of the interface between the solid polymer electrolyte membrane 30 and the first catalyst layer 12 and the interface between the first gas diffusion layer 14 and the first catalyst layer 12. The strength until the other interface peels is measured through a load cell and recorded on a personal computer. Among the measured strengths, the portion where the strength value is stable, that is, at the start of the peel strength measurement The average value is obtained for the portion excluding the value at the end, and this is taken as the peel strength, the average value of the peel strength is calculated three times, and this average value is obtained by dividing the test piece 91 by the width of 20 mm.

When the 90 ° peel strength is measured in the membrane / electrode assembly 1 in which the first catalyst layer 12 is already bonded to the solid polymer electrolyte membrane 30 and the first gas diffusion layer 14, For example, it can be measured by the following measuring method.
First, a sample having a width of 20 mm and a length of 200 mm is cut out from the membrane electrode assembly 1 and the second gas diffusion layer 24 on the non-measurement side is peeled off. Then, the surface on which the second gas diffusion layer 24 is peeled off is attached to the aluminum plate 94 with a double-sided tape 96.
The double-sided tape 96 to be used is the peeling strength at the interface between the sample solid polymer electrolyte membrane 30 and the first catalyst layer 12 and the peeling at the interface between the first catalyst layer 12 and the first gas diffusion layer 14. A material having an adhesive strength sufficiently higher than the strength is used.
Next, the single-sided adhesive tape 98 is adhered to the surface of the first gas diffusion layer 14 in the same manner as in Procedure 2 of the 90 ° peel test (II). Next, according to the procedure 3 of the 90 ° peel test (II), the end 98b of the single-sided adhesive tape 98 is sandwiched between the sample mounting portions of the tensile tester. Then, according to the procedure 4 of the 90 ° peel test (II), the clamped end 98b is pulled at a speed of 50 mm / min in the direction perpendicular to the solid polymer electrolyte membrane 30 (arrow), and the solid polymer electrolyte is obtained. Of the interface between the membrane 30 and the first catalyst layer 12 and the interface between the first gas diffusion layer 14 and the first catalyst layer 12, the peel strength of the interface that peels first is measured.

(Gas diffusion layer)
In the membrane electrode assembly 1, the first gas diffusion layer 14 has a dimensional change rate of less than 10% when immersed in 80 ° C. warm water, which is obtained by the following (Procedure 1) to (Procedure 4). It is preferable that it is less than%.
If the dimensional change rate is less than 10%, the function of suppressing the deformation of the solid polymer electrolyte membrane 30 particularly in the planar direction is exhibited when the membrane electrode assembly 1 is exposed to a wet or dry environment. . In particular, when the dimensional change rate is less than 5%, the mechanical durability of the solid polymer electrolyte membrane 30 is further improved. On the other hand, if the dimensional change rate is 10% or more, the effect of suppressing deformation of the solid polymer electrolyte membrane 30 is not sufficient, and breakage of the solid polymer electrolyte membrane 30 due to mechanical deterioration cannot be suppressed.
In the membrane electrode assembly 1, the dimensional change rate of the second gas diffusion layer 24 is also preferably less than 10%.

The dimensional change rate of the first gas diffusion layer 14 is obtained by the following (Procedure 1) to (Procedure 4).
(Procedure 1) The first gas diffusion layer 14 is placed in an atmosphere having a temperature of 25 ° C. and a relative humidity of 50% for 16 hours or more, and then the dimension (a) is measured.
(Procedure 2) Next, the gas diffusion layer 14 is immersed in warm water at 80 ° C. for 16 hours.
(Procedure 3) Thereafter, the gas diffusion layer 14 is cooled to room temperature while being immersed in warm water, taken out from the water, and the dimension (b) is measured.
(Procedure 4) The dimensional change rate is calculated from the following equation.
Dimensional change rate (%) = [dimension (b) −dimension (a)] / dimension (a) × 100

The material of the first gas diffusion layer 14 and the second gas diffusion layer 24 (hereinafter also collectively referred to as a gas diffusion layer) is not particularly limited, and includes carbon fiber woven fabric, carbon paper, carbon felt, and the like. These conductive materials can be mentioned.
The thickness of the gas diffusion layer is preferably 100 to 400 μm, and more preferably 140 to 350 μm.

The gas diffusion layer may have a porous layer (surface treatment layer) mainly composed of carbon on the surface of the layer made of the conductive material.
Since the porous layer can improve the water repellency of the first catalyst layer 12 and the second catalyst layer 22, the porous layer preferably contains a fluorine-based resin component such as polytetrafluoroethylene. The porous layer is preferably used in close contact with the first catalyst layer 12 and the second catalyst layer 22.

(Solid polymer electrolyte membrane)
The solid polymer electrolyte membrane 30 is a membrane containing a proton conductive polymer.
In the solid polymer electrolyte membrane 30, the electrical conductivity in an atmosphere at a temperature of 80 ° C. and a relative humidity of 40% needs to be 0.05 S / cm or more, and preferably 0.07 S / cm or more. When the electrical conductivity is 0.05 S / cm or more, the membrane / electrode assembly 1 can exhibit high power generation performance even when power generation is performed in a high temperature and low humidity environment.

The conductivity of the solid polymer electrolyte membrane 30 is determined by the following method.
A substrate on which 4 terminal electrodes are arranged at intervals of 5 mm is brought into close contact with a 5 mm wide film (solid polymer electrolyte membrane 30), and a constant temperature and humidity condition at a temperature of 80 ° C. and a relative humidity of 40% by a known 4 terminal method. Then, the resistance of the film is measured at a voltage of 10 kHz AC and 1 V, and the conductivity is calculated from the result.

In the solid polymer electrolyte membrane 30, the water content when immersed in warm water at 80 ° C. is preferably less than 180% by mass, and more preferably less than 150% by mass.
In order to increase the conductivity of the solid polymer electrolyte membrane 30, it is effective to increase the ion exchange capacity of the proton conductive polymer. However, in general, as the ion exchange capacity of the proton conducting polymer is increased, the moisture content when immersed in warm water increases and the dimensional change rate during moisture inclusion increases. Therefore, the mechanical durability performance with respect to humidity change that repeats wetting and drying tends to decrease. When the moisture content is less than 180% by mass, the durability performance in an environment in which wetting and drying are repeated is further improved.

The water content of the solid polymer electrolyte membrane 30 is determined by the following method.
After immersing the solid polymer electrolyte membrane 30 in warm water at 80 ° C. for 16 hours, the solid polymer electrolyte membrane 30 is cooled to room temperature while being immersed in warm water. Thereafter, the solid polymer electrolyte membrane 30 is taken out of the water, water droplets adhering to the surface of the solid polymer electrolyte membrane 30 are wiped off, and the mass at the time of water content is immediately measured. Next, the solid polymer electrolyte membrane 30 is put in a glove box and left to dry for 24 hours or more in an atmosphere of flowing dry nitrogen. Then, the dry mass of the solid polymer electrolyte membrane 30 is measured in the glove box.
The difference between the water-containing mass and the dry mass is the mass of water absorbed by the solid polymer electrolyte membrane 30 when it contains water. And the moisture content of the solid polymer electrolyte membrane 30 is calculated | required from the following Formula.
Moisture content (%) = (mass of water absorbed when the solid polymer electrolyte membrane 30 contains water / dry mass of the solid polymer electrolyte membrane 30) × 100.

  Examples of the proton conductive polymer include a fluorine-based polymer having an ionic group, a hydrocarbon-based polymer having an ionic group, and the like. From the viewpoint of chemical durability, a fluorine-based polymer having an ionic group is preferable. . Examples of the ionic group include a sulfonic acid group, a sulfonimide group, and a sulfonemethide group.

As the fluorine-based polymer having an ionic group, a polymer having a sulfonic acid group (hereinafter referred to as polymer H) obtained by hydrolyzing and acidifying a polymer having a repeating unit based on the compound (1), a group ( A polymer having a repeating unit having α) (hereinafter referred to as polymer Q) is preferred, and polymer Q is more preferred.
^{_{CF 2 = CF (OCF 2 CFX}} 1) m -O p - (CF 2) n -SO 2 F ··· (1).

However, the symbol in a formula shows the following meaning.
In Formula (1), X ¹ is a fluorine atom or a trifluoromethyl group, m is an integer of 0 to 3, n is an integer of 1 to 12, and p is 0 or 1.
In the group (α), Q ¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ² is a perfluoro which may have a single bond or an etheric oxygen atom. An alkylene group, R ^f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, and a is a group in which X is an oxygen atom. 0 in the case, 1 in the case where X is a nitrogen atom, 2 in the case where X is a carbon atom, and Y is a fluorine atom or a monovalent perfluoro organic group.

Polymer H:
As the compound (1), compounds (11) to (14) are preferable.
CF ₂ = CFO (CF ₂ ) _q SO ₂ F (11),
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _r SO ₂ F (12),
CF ₂ = CF (CF ₂ ) _s SO ₂ F (13),
_{CF 2 = CF (OCF 2 CF} (CF 3)) t O (CF 2) 2 SO 2 F ··· (14).
However, q is an integer of 1-8, r is an integer of 1-8, s is an integer of 1-8, and t is an integer of 1-5.

The polymer H may further have a repeating unit based on another monomer described later. Among the repeating units based on other monomers, a repeating unit based on a perfluoromonomer is preferable from the viewpoint of chemical durability, and a repeating unit based on tetrafluoroethylene is preferable from the viewpoint of chemical durability and mechanical strength. More preferred.
The polymer H is preferably a perfluorocarbon polymer from the viewpoint of chemical durability. The perfluorocarbon polymer may have an etheric oxygen atom.

Polymer Q:
In the group (α), when the perfluoroalkylene group of Q ¹ and Q ² has an etheric oxygen atom, the oxygen atom may be 1 or 2 or more. The oxygen atom may be inserted between the carbon atom-carbon atom bonds of the perfluoroalkylene group or may be inserted at the carbon atom bond terminal.
The perfluoroalkylene group may be linear or branched, and is preferably linear.
1-6 are preferable and, as for carbon number of a perfluoroalkylene group, 1-4 are more preferable. When there are too many carbon numbers, the boiling point of a fluorine-containing monomer will become high and distillation purification will become difficult. Moreover, when there are too many carbon numbers, the ion exchange capacity of the polymer Q will fall.

Q ² is preferably a C 1-6 perfluoroalkylene group which may have an etheric oxygen atom. When Q ² is a perfluoroalkylene group having 1 to 6 carbon atoms which may have an etheric oxygen atom, the polymer electrolyte fuel cell can be operated over a longer period than when Q ² is a single bond. The output voltage is stable.
At least one of Q ¹ and Q ² is preferably a C 1-6 perfluoroalkylene group having an etheric oxygen atom. Since the fluorine-containing monomer having a C 1-6 perfluoroalkylene group having an etheric oxygen atom can be synthesized without undergoing a fluorination reaction with a fluorine gas, the yield is good and the production is easy.

The ^{H +} group, a sulfonic acid group ^{_{- -SO 2 X (SO 2 R}} f1) a (-SO 3 - H + group), a sulfonimide group ^{_{(-SO 2 N (SO 2 R}} f1) - H + group) , sulfonmethide group ^{_{(-SO 2 C (SO 2 R}} f1) 2 - H + group).
The perfluoroalkyl group for R ^f1 may be linear or branched, and is preferably linear. The number of carbon atoms of R ^f1 is 1 to 6 preferably 1 to 4 is more preferred. R ^f1 is preferably a perfluoromethyl group, a perfluoroethyl group, or the like.
In the case of a sulfonemethide group, the two R ^f1 groups may be the same group or different groups.
Y is preferably a fluorine atom or a linear perfluoroalkyl group having 1 to 6 carbon atoms which may have an etheric oxygen atom.

The polymer Q may further have repeating units based on other monomers described later. Among the repeating units based on other monomers, a repeating unit based on a perfluoromonomer is preferable from the viewpoint of chemical durability, and a repeating unit based on tetrafluoroethylene is preferable from the viewpoint of chemical durability and mechanical strength. More preferred.
The polymer Q is preferably a perfluorocarbon polymer from the viewpoint of chemical durability. The perfluorocarbon polymer may have an etheric oxygen atom.

The polymer Q can be manufactured through the following steps, for example.
(I) A monomer having a group (β) (hereinafter referred to as a compound (m1)) and another monomer as required, and a precursor polymer having a —SO ₂ F group (hereinafter referred to as a polymer P). Step to obtain.

(II) A step of bringing the polymer P and fluorine gas into contact with each other as necessary to fluorinate unstable terminal groups of the polymer P.
(III) A step of obtaining a polymer Q by converting the —SO ₂ F group of the polymer P into a sulfonic acid group, a sulfonimide group, or a sulfonemethide group.

(I) Process:
Compound (m1) can be obtained, for example, by the synthesis route shown in <Synthesis of Proton Conducting Polymer (1)> described later.

Other monomers include, for example, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene, trifluoroethylene, vinyl fluoride, ethylene, CF ₂ = CFOR ^f2 , CH ₂ = CHR ^f3 , CH ₂ = CHCH ₂ R ^f3, and the like. However, ^Rf2 is a C1-C12 perfluoroalkyl group which may contain an etheric oxygen atom, and ^Rf3 is a C1-C12 perfluoroalkyl group.
Of the other monomers, perfluoromonomer is preferable and tetrafluoroethylene is more preferable from the viewpoint of chemical durability.

Examples of the polymerization method include known polymerization methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method.
Polymerization is performed under conditions where radicals occur. Examples of the method for generating radicals include a method of irradiating radiation such as ultraviolet rays, γ rays, and electron beams, a method of adding an initiator, and the like.

The polymerization temperature is usually 20 to 150 ° C.
Examples of the initiator include bis (fluoroacyl) peroxides, bis (chlorofluoroacyl) peroxides, dialkyl peroxydicarbonates, diacyl peroxides, peroxyesters, azo compounds, persulfates, and the like. Perfluoro compounds such as bis (fluoroacyl) peroxides are preferred from the viewpoint of obtaining a precursor polymer P with few unstable terminal groups.

  Solvents used in the solution polymerization method include polyfluorotrialkylamine compounds, perfluoroalkanes, hydrofluoroalkanes, chlorofluoroalkanes, fluoroolefins that do not have double bonds at the molecular chain ends, polyfluorocycloalkanes, and polyfluorocyclics. Examples include ether compounds, hydrofluoroethers, fluorine-containing low molecular weight polyethers, and tert-butanol.

(II) Process:
The unstable terminal group is a group formed by a chain transfer reaction, a group based on a radical initiator, or the like. Specifically, a —COOH group, —CF═CF ₂ group, —COF group, —CF ₂ H Group. By fluorinating the unstable terminal groups, the decomposition of the polymer Q can be suppressed.

The fluorine gas may be diluted with an inert gas such as nitrogen, helium or carbon dioxide, or may be used as it is without being diluted.
The temperature at which the polymer P and the fluorine gas are brought into contact is preferably room temperature to 300 ° C, more preferably 50 to 250 ° C, further preferably 100 to 220 ° C, and particularly preferably 150 to 200 ° C.
The contact time between the polymer P and the fluorine gas is preferably 1 minute to 1 week, and more preferably 1 to 50 hours.

(III) Process:
For example, when converting a —SO ₂ F group into a sulfonic acid group, the step (III-1) is performed. When converting a —SO ₂ F group into a sulfonimide group, the step (III-2) is performed.
(III-1) A step of hydrolyzing the —SO ₂ F group of the polymer P to form a sulfonate, converting the sulfonate into an acid form and converting it to a sulfonate group.
(III-2) A step of sulfonating the —SO ₂ F group of the polymer P to convert it to a sulfonimide group.

(III-1) Step:
The hydrolysis is performed, for example, by bringing the polymer P and the basic compound into contact in a solvent.
Examples of the basic compound include sodium hydroxide and potassium hydroxide. Examples of the solvent include water, a mixed solvent of water and a polar solvent, and the like. Examples of the polar solvent include alcohols (methanol, ethanol, etc.), dimethyl sulfoxide and the like.
The acidification is performed, for example, by bringing the polymer P in which —SO ₂ F group is hydrolyzed into contact with an aqueous solution such as hydrochloric acid or sulfuric acid.
Hydrolysis and acidification are usually performed at 0 to 120 ° C.

(III-2) Step:
As the sulfonimide, a method described in US Pat. No. 5,463,005, Inorg. Chem. 32 (23), page 5007 (1993), and the like.

  Hydrocarbon polymers include sulfonated polyarylene, sulfonated polybenzoxazole, sulfonated polybenzothiazole, sulfonated polybenzimidazole, sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, and sulfonated polyphenylene. Examples include sulfone, sulfonated polyphenylene oxide, sulfonated polyphenylene sulfoxide, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyether ketone, sulfonated polyether ether ketone, sulfonated polyether ketone ketone, and sulfonated polyimide. .

  The thickness of the solid polymer electrolyte membrane 30 is preferably 50 μm or less, particularly preferably 5 to 30 μm. By setting the thickness of the solid polymer electrolyte membrane 30 to 50 μm or less, particularly 30 μm or less, it is possible to further suppress a decrease in power generation performance of the solid polymer fuel cell in a low humidified environment. By setting the thickness of the solid polymer electrolyte membrane 30 to 5 μm or more, a short circuit does not occur.

The solid polymer electrolyte membrane 30 may include a reinforcing material as necessary.
Examples of the reinforcing material include porous bodies, fibers, woven fabrics, and nonwoven fabrics.
Examples of the reinforcing material include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, polyethylene, polypropylene, polyphenylene sulfide, and polyimide.

(Catalyst layer)
The first catalyst layer 12 and the second catalyst layer 22 (hereinafter collectively referred to as a catalyst layer) are layers containing an electrode catalyst and a proton conductive polymer.

A preferred example of the electrode catalyst is a supported catalyst in which platinum or a platinum alloy is supported on a carbon support.
Examples of the carbon carrier include activated carbon and carbon black.
The specific surface area of the carbon support is preferably 200 m ² / g or more. The specific surface area of the carbon support is measured by nitrogen adsorption on the carbon surface with a BET specific surface area apparatus.
Moreover, in order to improve the chemical durability of the carbon support, those graphitized by heat treatment or the like are preferable.

Platinum alloys include platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, An alloy of platinum and one or more metals selected from the group consisting of tin and platinum is preferable. The platinum alloy may contain a metal alloyed with platinum and an intermetallic compound of platinum.
The supported amount of platinum or platinum alloy is preferably 10 to 70% by mass in the electrode catalyst (100% by mass).

  Examples of the proton conductive polymer include those similar to the proton conductive polymer contained in the solid polymer electrolyte membrane 30.

When the proton conductive polymer is a fluorine-based polymer, the ratio of the electrode catalyst to the fluorine-based polymer (electrode catalyst / proton conductive polymer) is 4/6 to 9.5 / from the viewpoint of electrode conductivity and water repellency. 0.5 (mass ratio) is preferable, and 6/4 to 8/2 is particularly preferable.
Amount of platinum contained in the catalyst layer, from the viewpoint of optimum thickness for conducting an electrode reaction efficiently, preferably 0.01 to 0.5 / cm ^2, more preferably 0.05~0.35mg / cm ² .

  The thickness of the catalyst layer is preferably 20 μm or less and more preferably 1 to 15 μm from the viewpoint of facilitating gas diffusion in the catalyst layer and improving the power generation performance of the polymer electrolyte fuel cell. Moreover, it is preferable that the thickness of a catalyst layer is uniform. If the thickness of the catalyst layer is reduced, the amount of the electrode catalyst present per unit area may be reduced and the reaction activity may be lowered. If the supported catalyst is used, the reaction activity of the electrode can be maintained high without a shortage of the amount of the electrode catalyst even if it is thin.

The catalyst layer may contain a water repellent agent from the viewpoint that the effect of suppressing flooding is enhanced. Examples of the water repellent include a copolymer of tetrafluoroethylene and hexafluoropropylene, a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and polytetrafluoroethylene. As the water repellent, a fluorine-based polymer that can be dissolved in a solvent is preferable because the catalyst layer can be easily subjected to a water repellent treatment.
The amount of the water repellent agent is preferably 0.01 to 30% by mass in the catalyst layer (100% by mass).

In the membrane electrode assembly 1 described above, the solid polymer electrolyte membrane 30 has an electrical conductivity of 0.05 S / cm or more in an atmosphere at a temperature of 80 ° C. and a relative humidity of 40%. The 90 ° peel strength with respect to the first gas diffusion layer 14 is 0.03 N / cm or more, and the dimensional change rate when the first gas diffusion layer 14 is immersed in warm water at 80 ° C. is 10%. Is less than.
Since the membrane electrode assembly 1 has a solid polymer electrolyte membrane 30 having a conductivity of 0.05 S / cm or more, the membrane electrode assembly 1 has good conductivity and can exhibit high power generation performance.
When the membrane / electrode assembly 1 is exposed to various humidity environments, the solid polymer electrolyte membrane 30 inherently contains water according to the humidity environment, and its dimensions change isotropically in the planar direction and the thickness direction. To do. When the humidity environment repeats wetting and drying, the solid polymer electrolyte membrane 30 repeats swelling and shrinking, and the repetition in the planar direction may cause mechanical fatigue and break.
The first gas diffusion layer 14 in the membrane electrode assembly 1 has a dimensional change rate of less than 10% when immersed in warm water at 80 ° C., and therefore hardly undergoes a dimensional change even when the humidity environment changes. Therefore, by setting the 90 ° peel strength between the first gas diffusion layer 14 and the solid polymer electrolyte membrane 30 to 0.03 N / cm or more, the first gas diffusion layer 14 and the solid polymer electrolyte membrane are provided. 30 is firmly joined to the solid polymer electrolyte membrane 30, in particular, deformation in the plane direction is suppressed. Since the deformation of the solid polymer electrolyte membrane 30 is suppressed, the first electrode 10 and the solid polymer electrolyte membrane 30 do not peel off. Therefore, according to the membrane electrode assembly 1 of the present invention, high power generation performance can be exhibited even in a low humidified environment, and durability performance in an environment where wetting and drying are repeated can be dramatically improved.

In addition, as shown in FIG. 4, the membrane electrode assembly of the present invention is provided between the first catalyst layer 12 and the first gas diffusion layer 14 and between the second catalyst layer 22 and the second gas diffusion layer. 24 may each have an intermediate layer 84. By having the intermediate layer 84, the bonding strength between the gas diffusion layer and the catalyst layer is increased, the adhesion thereof is further increased, and the effects of the present invention are further improved.
The intermediate layer 84 may be provided only on one electrode side of the first electrode 10 and the second electrode 20.

Examples of the intermediate layer 84 include a layer made of a proton conductive polymer and a carbon material. The proton conductive polymer has a function of improving the adhesion with the catalyst layer, and the carbon material has a function of ensuring the conductivity between the gas diffusion layer and the catalyst layer.
The proton conductive polymer is not particularly limited, and examples thereof include the same proton conductive polymers as those contained in the solid polymer electrolyte membrane 30 and the catalyst layer. Thus, the joint strength between the catalyst layer and the gas diffusion layer can be further increased by providing the intermediate layer 84 containing the same proton conductive polymer contained in the catalyst layer.

As the carbon material, carbon fiber is particularly preferable, and carbon nanofiber is preferable because it is fine and has electron conductivity. Examples of the carbon nanofiber include vapor grown carbon fiber, carbon nanotube (single wall, double wall, multiwall, cup laminated type, etc.) and the like.
The fiber diameter of the carbon fiber is preferably 50 to 200 nm, and the fiber length is preferably 1 to 50 μm. By using the carbon fiber, at the interface between the intermediate layer 84 and the catalyst layer, entangled with the electron conductive material (platinum or platinum alloy and carbon support) contained in the catalyst layer, and by the point contact of the electron conductive material. Since a new conductive path is developed in addition to the conductive path, the electronic conductivity of the catalyst layer is improved. In addition, when the coating liquid containing the carbon fiber is applied, the carbon fibers are easily entangled with each other to form a void, and the void functions as a gas channel.

  The ratio of the carbon material to the proton conductive polymer (carbon material / proton conductive polymer) is preferably 1 / 0.1 to 1/5 (mass ratio), more preferably 1 / 0.2 to 1/1. By setting this range, the dispersibility of the carbon material, the adhesion between the intermediate layer 84 and the gas diffusion layer, the gas diffusion property and the drainage of the intermediate layer 84 are improved.

  The thickness of the intermediate layer 84 is preferably 2 to 20 μm. By setting it in this range, the adhesion between the intermediate layer 84 and the gas diffusion layer becomes good, the contact resistance between the gas diffusion layer and the catalyst layer can be sufficiently reduced, and the membrane electrode assembly 1 can be made thin.

  In the polymer electrolyte fuel cell, water (water vapor) is generated in the catalyst layer on the cathode side, and the water is discharged out of the system through a gas diffusion layer disposed adjacent to the catalyst layer. By providing the intermediate layer 84 mainly composed of carbon fibers between the catalyst layer and the gas diffusion layer, water quickly moves from the catalyst layer to the intermediate layer 84 by capillary action, so that the polymer electrolyte fuel cell is operated. The problem of flooding at times is easily solved.

<Method for Producing Membrane Electrode Assembly for Solid Polymer Fuel Cell>
The manufacturing method of the membrane electrode assembly 1 of the present invention includes a method of bonding the first catalyst layer 12 formed on the first gas diffusion layer 14 and the solid polymer electrolyte membrane 30, or a solid polymer. In this method, the first catalyst layer 12 and the first gas diffusion layer 14 formed on the electrolyte membrane 30 are joined.

Specifically as a manufacturing method of the membrane electrode assembly 1, the following method is mentioned.
(I) the first catalyst layer 12 formed on the first gas diffusion layer 14, the second catalyst layer 22 formed on the second gas diffusion layer 24, the solid polymer electrolyte membrane 30, The method of joining each.
(II) The first catalyst layer 12 and the second catalyst layer 22 respectively formed on the solid polymer electrolyte membrane 30 are joined to the first gas diffusion layer 14 and the second gas diffusion layer 24, respectively. Method.

[Method (I)]
Examples of the method (I) include a method having the following steps (I-1) to (I-4). This will be described with reference to FIG.
(I-1) A step of forming the solid polymer electrolyte membrane 30 on the surface of a separately prepared substrate (hereinafter referred to as “peeling substrate”).
(I-2) The process of producing the 1st intermediate body 50 (namely, 1st electrode 10) which consists of the 1st gas diffusion layer 14 and the 1st catalyst layer 12.
(I-3) The process of producing the 2nd intermediate body 60 (namely, 2nd electrode 20) which consists of the 2nd gas diffusion layer 24 and the 2nd catalyst layer 22. FIG.
(I-4) The first catalyst layer 12 is located between the first gas diffusion layer 14 and the solid polymer electrolyte membrane 30, and the second gas diffusion layer 24 and the solid polymer electrolyte membrane 30 A step of joining the first intermediate 50, the solid polymer electrolyte membrane 30, and the second intermediate 60 to form the membrane electrode assembly 1 so that the second catalyst layer 22 is positioned between them.

(I-1) Process:
The solid polymer electrolyte membrane 30 can be formed by applying a liquid composition containing a proton conductive polymer to the surface of the release substrate and drying it. In particular, the solid polymer electrolyte membrane 30 is preferably formed by casting a liquid composition in which a proton conductive polymer is dispersed in a dispersion medium on the surface of a release substrate. More preferably it is formed. Thereby, it becomes easy to obtain the solid polymer electrolyte membrane 30 which is a thin film and has a uniform thickness.

A resin film is mentioned as a peeling base material.
Resin film materials include non-fluorinated resins such as polyethylene terephthalate, polyethylene, polypropylene, and polyimide; polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-hexafluoropropylene copolymer, tetrafluoro Examples thereof include fluorine-containing resins such as ethylene-perfluoro (alkyl vinyl ether) copolymers and polyvinylidene fluoride.
The non-fluorinated resin film is preferably surface-treated with a release agent.

The liquid composition is prepared by dissolving the proton conductive polymer in a solvent or dispersing it in a dispersion medium.
The liquid composition is preferably a dispersion in which a proton conductive polymer is dispersed in a dispersion medium.
As the dispersion medium, a dispersion medium containing an organic solvent having a hydroxyl group and water is preferable.
The organic solvent having a hydroxyl group is preferably an alcohol having 1 to 4 carbon atoms in the main chain, and examples thereof include methanol, ethanol, n-propanol, isopropanol, tert-butanol, and n-butanol. The organic solvent which has a hydroxyl group may be used individually by 1 type, and 2 or more types may be mixed and used for it.
The dispersion medium may contain a fluorine-containing solvent.
Examples of the fluorine-containing solvent include the following compounds.
Hydrofluorocarbon: 2H-perfluoropropane, 1H, 4H-perfluorobutane, 2H, 3H-perfluoropentane, 3H, 4H-perfluoro (2-methylpentane), 2H, 5H-perfluorohexane, 3H-perfluoro (2-methylpentane) and the like.
Fluorocarbon: perfluoro (1,2-dimethylcyclobutane), perfluorooctane, perfluoroheptane, perfluorohexane and the like.
Hydrochlorofluorocarbon: 1,1-dichloro-1-fluoroethane, 1,1,1-trifluoro-2,2-dichloroethane, 3,3-dichloro-1,1,1,2,2-pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane and the like.
Fluoroether: 1H, 4H, 4H-perfluoro (3-oxapentane), 3-methoxy-1,1,1,2,3,3-hexafluoropropane and the like.
Fluorine-containing alcohol: 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, etc. .

The proportion of the organic solvent having a hydroxyl group in the liquid composition is preferably 1 to 90% by mass and more preferably 1 to 60% by mass in the dispersion medium (100% by mass).
The proportion of water in the liquid composition is preferably from 10 to 99 mass%, more preferably from 40 to 99 mass%, in the dispersion medium (100 mass%). By increasing the proportion of water, the dispersibility of the proton conductive polymer in the dispersion medium can be improved.
1-50 mass% is preferable among liquid compositions (100 mass%), and, as for the ratio of the proton conductive polymer in a liquid composition, 3-30 mass% is more preferable.

Examples of the method for preparing the liquid composition include a method in which shear is applied to the proton conductive polymer in the dispersion medium under atmospheric pressure or in a state sealed with an autoclave or the like.
The preparation temperature is preferably 0 to 250 ° C, more preferably 20 to 150 ° C. You may provide shearing, such as an ultrasonic wave, as needed.

The coating method is not particularly limited, and examples thereof include a batch method and a continuous method.
Examples of the batch method include a bar coater method, a spin coat method, and a screen printing method.
Examples of the continuous method include a post-measuring method and a pre-measuring method. The post-measuring method is a method in which an excess coating solution is applied and the coating solution is removed so that a predetermined film pressure is obtained later. The pre-weighing method is a method of applying a coating liquid in an amount necessary to obtain a predetermined film thickness.
Examples of the post-measuring method include an air doctor coater method, a blade coater method, a rod coater method, a knife coater method, a squeeze coater method, an impregnation coater method, and a comma coater method.
Examples of the pre-weighing method include die coater method, reverse roll coater method, transfer roll coater method, gravure coater method, kiss roll coater method, cast coater method, spray coater method, curtain coater method, calendar coater method, extrusion coater method, etc. It is done.
In order to form the uniform solid polymer electrolyte membrane 30, a screen printing method or a die coater method is preferable, and a continuous die coater method is more preferable in consideration of economy.

The drying temperature after coating the liquid composition is preferably 70 to 170 ° C.
As for the temperature of heat processing, 130-220 degreeC is preferable. If the temperature of the heat treatment is too low, depending on the type of proton conductive polymer, the polymer skeleton may not be stable, and the moisture content may be higher than the original moisture content. If the temperature of the heat treatment is too high, thermal decomposition of the ionic group starts and there is a possibility that the moisture content is lower than the original moisture content.

(I-2) Step:
The method for forming the first catalyst layer 12 on the first gas diffusion layer 14 is not particularly limited, and an electrode catalyst and a proton conductive polymer are included on the first gas diffusion layer 14. A method in which the first catalyst layer forming coating solution is applied and dried is preferred, and a method in which the catalyst layer forming coating solution is applied and dried and then heat treated is more preferred.
Thereby, since the 1st gas diffusion layer 14 and the 1st catalyst layer 12 can be joined by high joining strength, a deformation | transformation of the solid polymer electrolyte membrane 30 is suppressed and it becomes easier to obtain the effect of this invention.

As the first gas diffusion layer 14, a conductive material such as a carbon fiber woven fabric, carbon paper, or carbon felt can be used as it is.
When the surface of the first gas diffusion layer 14 has a porous layer (surface treatment layer) containing carbon as a main component, the porous layer is preferably disposed on the first catalyst layer 12 side.

The first catalyst layer forming coating solution is a dispersion in which an electrode catalyst and a proton conductive polymer are dispersed in a dispersion medium.
Examples of the dispersion medium include those similar to the dispersion medium in the liquid composition.
The coating liquid for forming the catalyst layer can be prepared, for example, by mixing the liquid composition and the electrode catalyst dispersion.
Since the viscosity of the coating solution for forming the catalyst layer varies depending on the method of forming the first catalyst layer 12, it may be a dispersion of about several tens of cP or a paste-like dispersion of about 20,000 cP. .
Further, the catalyst layer forming coating solution may contain a thickener in order to adjust the viscosity. Examples of the thickener include ethyl cellulose, methyl cellulose, cellosolve thickener, and fluorinated solvents (pentafluoropropanol, chlorofluorocarbon, etc.).

The coating method is not particularly limited, and the same method as the coating method of the liquid composition in the solid polymer electrolyte membrane 30 is used.
The drying temperature is preferably 70 to 170 ° C.
The heat treatment temperature is preferably 130 to 220 ° C. If the temperature of the heat treatment is too low, depending on the type of proton conductive polymer, the polymer skeleton may not be stable, and the moisture content may be higher than the original moisture content. On the other hand, if the temperature of the heat treatment is too high, thermal decomposition of the ionic group starts, and the moisture content may be lower than the original moisture content. However, depending on the temperature of the heat treatment, the carbon support of the catalyst may be oxidatively decomposed. Accordingly, the heat treatment is preferably performed in a nitrogen atmosphere, under reduced pressure, or in an environment in which oxygen in the catalyst layer is reduced by pressure such as pressing. In order to suppress oxidative decomposition, a carbon support graphitized by heat treatment or the like may be used as the carbon support.

(I-3) Step:
A method for forming the second catalyst layer 22 on the second gas diffusion layer 24 is not particularly limited, and an electrode catalyst and a proton conductive polymer are included on the second gas diffusion layer 24. A method in which the second catalyst layer forming coating solution is applied and dried is preferred, and a method in which the catalyst layer forming coating solution is applied, dried and then heat treated is more preferred.
Thereby, since the 2nd gas diffusion layer 24 and the 2nd catalyst layer 22 can be joined by high joining strength, a deformation | transformation of the solid polymer electrolyte membrane 30 is suppressed and it becomes easier to obtain the effect of this invention.
The specific production method is the same as that in the step (I-2) except that in the step (I-2), the first catalyst layer forming coating solution is changed to the second catalyst layer forming coating solution. It should be a method.

(I-4) Step:
Examples of the bonding method include a hot press method, a hot roll press, ultrasonic fusion, and the like, and the hot press method is preferable from the viewpoint of in-plane uniformity.
The temperature of the press plate in the press machine is preferably 100 to 150 ° C., and the press pressure is preferably 0.5 to 2.0 MPa.

[Method (II)]
Examples of the method (II) include a method having the following steps (II-1) to (II-4). This will be described with reference to FIG.
(II-1) A step of forming the solid polymer electrolyte membrane 30 on the surface of a separately prepared release substrate.
(II-2) The first catalyst layer 12 is formed on one surface of the solid polymer electrolyte membrane 30 to produce the first intermediate 50 composed of the solid polymer electrolyte membrane 30 and the first catalyst layer 12. Process.
(II-3) peeling the release substrate from the first intermediate 50, forming the second catalyst layer 22 on the surface of the solid polymer electrolyte membrane 30 opposite to the first catalyst layer 12, A step of producing a second intermediate 60 composed of the first catalyst layer 12, the solid polymer electrolyte membrane 30, and the second catalyst layer 22.
(II-4) The first catalyst layer 12 is located between the first gas diffusion layer 14 and the solid polymer electrolyte membrane 30, and the second gas diffusion layer 24 and the solid polymer electrolyte membrane 30 are A step of joining the first gas diffusion layer 14, the second intermediate 60, and the second gas diffusion layer 24 so that the second catalyst layer 22 is positioned between them to form the membrane electrode assembly 1 .

(II-1) Step:
What is necessary is just to carry out like the (I-1) process.

(II-2) Step:
The method for forming the first catalyst layer 12 on one surface of the solid polymer electrolyte membrane 30 is not particularly limited, and can be formed by the following method, for example.
1) A method in which the first catalyst layer forming coating solution is applied onto an appropriate release substrate, dried and heat-treated, and then transferred onto the solid polymer electrolyte membrane 30.
2) A method in which the first catalyst layer forming coating solution is applied onto the solid polymer electrolyte membrane 30 and dried and heat-treated.
In the two methods, the drying temperature after applying the first catalyst layer forming coating solution and the temperature and conditions of the heat treatment may be the same as those in the step (I-2).
Particularly, in the method 2), since the solid polymer electrolyte membrane 30 and the first catalyst layer 12 can be bonded with high bonding strength, deformation of the solid polymer electrolyte membrane 30 is suppressed, and the effects of the present invention can be further obtained. This is preferable because it is easily formed.

(II-3) Step:
The second intermediate 60 peels the release substrate from the first intermediate 50 and forms the second catalyst layer 22 on the surface of the solid polymer electrolyte membrane 30 opposite to the first catalyst layer 12. It is produced by doing.
The method and conditions for forming the second catalyst layer 22 on the surface of the solid polymer electrolyte membrane 30 are as follows. In the step (II-2), the first catalyst layer forming coating solution is used as the second catalyst layer forming coating solution. Except for changing to (II-2), the method and conditions may be the same as those in the step (II-2).
When the method 1) is used in the step (II-2), the release substrate is peeled off from the solid polymer electrolyte membrane 30 without passing through the first intermediate 50, and each of the solid polymer electrolyte membranes 30 is removed. The second intermediate body 60 can also be directly produced by simultaneously transferring the first catalyst layer 12 and the second catalyst layer 22 to the surface.
In the step (II-2), the second catalyst layer 22 is first formed on one surface of the solid polymer electrolyte membrane 30, and in the step (II-3), the second catalyst layer 22 is opposite. The first catalyst layer 12 may be formed later on the surface of the solid polymer electrolyte membrane 30 on the side.

(II-4) Step:
The manufacturing method of the first gas diffusion layer 14 and the second gas diffusion layer 24 may be the same method and conditions as in step (I-2).
The joining method and conditions may be the same methods and conditions as in step (I-4).

Further, in the membrane electrode assembly manufactured by the manufacturing method of the present invention, in order to increase the bonding strength between the gas diffusion layer and the catalyst layer and improve the adhesion between them, as shown in FIG. An intermediate layer 84 can be provided between the layer and the catalyst layer. In particular, the intermediate layer 84 is preferably provided when the gas diffusion layer and the catalyst layer are bonded together by hot pressing or the like.
The membrane / electrode assembly shown in FIG. 4 is obtained by, for example, previously forming an intermediate layer on the surface of the gas diffusion layer on the catalyst layer side in the production method ((I-2), (I-3) or (II-4)). 84, and can be manufactured by using a laminate composed of a gas diffusion layer and an intermediate layer 84.
The intermediate layer 84 can be formed, for example, by applying an intermediate layer forming coating solution prepared by mixing carbon particles or carbon fibers and the liquid composition onto the gas diffusion layer and drying.

<Solid polymer fuel cell>
By disposing, for example, separators 80 in which grooves 100 serving as gas flow paths are formed on both surfaces of the membrane electrode assembly 1 of the present invention, a polymer electrolyte fuel cell as shown in FIG. 7 is obtained.
Examples of the separator 80 include a separator made of various conductive materials such as a metal separator, a carbon separator, and a separator made of a material in which graphite and a resin are mixed.
In the polymer electrolyte fuel cell, power is generated by supplying a gas containing oxygen to the cathode and a gas containing hydrogen to the anode. The membrane electrode assembly 1 of the present invention can also be applied to a methanol fuel cell that generates power by supplying methanol to the anode.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Examples 1, 3, and 4 are examples, and examples 2, 5, and 6 are comparative examples.

(Ion exchange capacity)
The ion exchange capacity of the polymer was determined by the following method.
The polymer was immersed in a fixed concentration sodium hydroxide solution using water and methanol as a solvent for hydrolysis, and the ion exchange capacity was determined by back titrating the solution.

(TQ value)
The TQ value (unit: ° C.) is an index of the molecular weight of the polymer, and the extrusion amount when the polymer is melt-extruded under the condition of the extrusion pressure of 2.94 MPa using a nozzle having a length of 1 mm and an inner diameter of 1 mm is 100 mm. ^The temperature is ³ / sec.
Using a flow tester CFT-500A (manufactured by Shimadzu Corporation), the extrusion amount of the polymer was measured while changing the temperature, and the TQ value at which the extrusion amount was 100 mm ³ / second was determined.

(conductivity)
The conductivity of the polymer was determined by the following method.
A substrate on which 4 terminal electrodes are arranged at intervals of 5 mm is adhered to a 5 mm width film made of a polymer, and an alternating current of 10 kHz under a constant temperature and humidity condition of a temperature of 80 ° C. and a relative humidity of 40% by a known 4 terminal method, The resistance of the film was measured at a voltage of 1 V, and the conductivity was calculated from the result.

(Moisture content)
The water content of the polymer was determined by the following method.
After the polymer was immersed in warm water at 80 ° C. for 16 hours, the polymer was cooled to room temperature together with the warm water. The polymer was taken out from the water, water droplets adhering to the surface were wiped off, and the mass of the polymer when it was wet was measured immediately. Then, the polymer was put in a glove box and left in an atmosphere of flowing dry nitrogen for 24 hours or more to dry the polymer. And the dry mass of the polymer was measured in the glove box. From the difference between the weight of the polymer when wet and the dry weight, the weight of water absorbed by the polymer when wet was determined. And the moisture content of the polymer was calculated | required from the following Formula.
Moisture content = (mass of water absorbed when polymer is hydrated / dry mass of polymer) × 100

[90 ° peel test]
The 90 ° peel strength between the solid polymer electrolyte membrane and the cathode or anode gas diffusion layer depends on the 90 ° peel test (I) or 90 ° peel test ( Determined by performing II).
NW-20 (trade name: Nystack, manufactured by Nichiban) was used as the double-sided tape.
For the single-sided tape, Kapton adhesive tape (trade name: Kapton adhesive tape No. 6564S # 25, manufactured by Teraoka Seisakusho) was used.
As the tensile tester, RTE-1210 (product name: universal tester (Tensilon), manufactured by Orientec Co., Ltd.) was used.

[Dimensional change rate of gas diffusion layer]
The dimensional change rate of the gas diffusion layer was determined by the following (Procedure 1) to (Procedure 4).
(Procedure 1) The gas diffusion layer was placed in an atmosphere at a temperature of 25 ° C. and a relative humidity of 50% for 16 hours or more, and then the dimension (a) was measured.
(Procedure 2) Next, the gas diffusion layer was immersed in warm water at 80 ° C. for 16 hours.
(Procedure 3) Thereafter, the gas diffusion layer was cooled to room temperature in a state of being immersed in warm water, taken out from the water, and dimension (b) was measured.
(Procedure 4) The dimensional change rate was calculated from the following equation.
Dimensional change rate (%) = [dimension (b) −dimension (a)] / dimension (a) × 100

[Power generation characteristics]
The power generation characteristics were tested by the following method.
The membrane / electrode assembly is incorporated into a power generation cell, the temperature of the membrane / electrode assembly is maintained at 80 ° C., hydrogen (utilization rate 50%) at the anode and air (utilization rate 50%) at the cathode are each 200 kPa (absolute pressure). ) Under pressure. The cell voltage was recorded when the gas humidity was 50% relative humidity for hydrogen and 0% relative humidity for air, and the current density was 1.0 A / cm ² .

[Wet-dry cycle test]
The wet-dry cycle test was performed by the following method according to the method described in Non-Patent Document 1.
The membrane electrode assembly was incorporated into a power generation cell (electrode area 25 cm ² ), and the cell temperature was 80 ° C., and nitrogen was supplied to the anode and cathode at 1 L / min. At that time, the process of supplying the gas with a relative humidity of 150% and supplying the humidified gas for 2 minutes at a relative humidity of 0% was repeated as one cycle. Every 100 cycles, a pressure difference was produced between the anode and the cathode, and the presence or absence of a physical gas leak was determined. The point of time when gas leak occurred and the gas crossover speed became 10 sccm or more was judged as the life. The number of cycles at that time was used as an index of durability performance.
When the number of cycles is less than 10,000 cycles, × is defined as 10000 cycles or more and less than 20000 cycles, and ○ is set as 20,000 cycles or more.

<Synthesis of proton conducting polymer (1)>
A compound (m11) was synthesized by the synthesis route shown below, and a proton conductive polymer (copolymer A) was synthesized using the compound (m11).

Synthesis of compound (a1):
Compound (a1) was synthesized in the same manner as described in Example 2 of JP-A-57-176773.

Synthesis of compound (c1):
To a 300 cm ³ four-necked round bottom flask equipped with a Dimroth condenser, thermometer, dropping funnel, and glass rod with stirring blade, potassium fluoride (made by Morita Chemical Co., Ltd., trade name: Crocat F) 1 under a nitrogen atmosphere .6 g and 15.9 g of dimethoxyethane were added. Next, the round bottom flask was cooled in an ice bath, and 49.1 g of compound (b1) was added dropwise from the dropping funnel over 32 minutes at an internal temperature of 10 ° C. or lower. After the completion of dropping, 82.0 g of the compound (a1) was added dropwise over 15 minutes from the dropping funnel. Little increase in internal temperature was observed. After completion of the dropwise addition, the internal temperature was returned to room temperature and stirred for about 90 hours. The lower layer was collected with a separatory funnel. The recovered amount was 127.6 g and the GC purity was 55%. The recovered liquid was transferred to a 200 cm ³ 4-neck round bottom flask and distilled. 97.7 g of compound (c1) was obtained as a fraction having a degree of vacuum of 1.0 to 1.1 kPa (absolute pressure). The GC purity was 98% and the yield was 80%.

Synthesis of compound (d1):
In a 200 cm ³ stainless steel autoclave, 1.1 g of potassium fluoride (Morita Chemical Co., Ltd., trade name: Crocat F) was added. After deaeration, under reduced pressure, 5.3 g of dimethoxyethane, 5.3 g of acetonitrile and 95.8 g of compound (c1) were placed in an autoclave.
Next, the autoclave was cooled in an ice bath, and 27.2 g of hexafluoropropene oxide was added over 27 minutes at an internal temperature of 0 to 5 ° C. Then, the internal temperature was returned to room temperature while stirring and stirred overnight. . The lower layer was collected with a separatory funnel. The recovered amount was 121.9 g, and the GC purity was 63%. The recovered liquid was distilled to obtain 72.0 g of compound (d1) as a fraction having a boiling point of 80 to 84 ° C./0.67 to 0.80 kPa (absolute pressure). The GC purity was 98% and the yield was 56%.

Synthesis of compound (m11):
Using a stainless steel tube having an inner diameter of 1.6 cm, a U-shaped tube having a length of 40 cm was produced. One side of the U-shaped tube was filled with glass wool, and the other side was filled with glass beads using a stainless sintered metal as the eye plate to prepare a fluidized bed reactor. Nitrogen gas was used as the fluidizing gas, and the raw material could be continuously supplied using a metering pump. The outlet gas was collected with liquid nitrogen using a trap tube.

The fluidized bed reactor is placed in a salt bath, and the compound (d1) is added to the fluidized bed reactor so that the molar ratio of the compound (d1) / N ₂ is 1/20 while maintaining the reaction temperature at 340 ° C. 34.6 g was fed over 1.5 hours. After completion of the reaction, 27 g of liquid was obtained from a liquid nitrogen trap. The GC purity was 84%. Distillation of the liquid gave compound (m11) as a fraction having a boiling point of 69 ° C./0.40 kPa (absolute pressure). The GC purity was 98%.

¹⁹ F-NMR (282.7 MHz, solvent CDCl ₃ , standard: CFCl ₃ ) of the compound (m11).
δ (ppm): 45.5 (1F), 45.2 (1F), -79.5 (2F), -82.4 (4F), -84.1 (2F), -112.4 (2F) , −112.6 (2F), −112.9 (dd, J = 82.4 Hz, 67.1 Hz, 1F), −121.6 (dd, J = 112.9 Hz, 82.4 Hz, 1F), − 136.0 (ddt, J = 112.9 Hz, 67.1 Hz, 6.1 Hz, 1F), -144.9 (1F).

Synthesis of proton conducting polymer:
In a 30 cm ³ stainless steel autoclave, 9.84 g of the compound (m11), 3.09 g of the compound (3-1) as a solvent and 1.3 g of the compound (4-1) as an initiator were cooled with liquid nitrogen. And deaerated.
CClF ₂ CF ₂ CHClF (3-1),
(CH ₃ ) ₂ C (CN) N = NC (CH ₃ ) ₂ (CN) (4-1).

The internal temperature was raised to 70 ° C., tetrafluoroethylene was introduced into the autoclave, and the pressure was 1.31 MPaG (gauge pressure). Polymerization was carried out for 5.7 hours while keeping the temperature and pressure constant. Subsequently, the inside of the autoclave was cooled to stop the polymerization, and the gas in the system was purged. After the reaction solution was diluted with compound (3-1), compound (3-2) was added, the polymer was aggregated and filtered.
CH ₃ CCl ₂ F (3-2).

  After stirring the polymer in compound (3-1), compound (3-2) was added, and the polymer was re-agglomerated and filtered. The polymer was dried under reduced pressure at 80 ° C. overnight to obtain a proton conductive polymer (hereinafter referred to as copolymer A) which is a copolymer of tetrafluoroethylene and the compound (m11). The yield of copolymer A was 1.2 g. The properties of copolymer A are shown in Table 1.

<Synthesis of proton conductive polymer (2)>
Tetrafluoroethylene (CF ₂ = CF ₂ ) and compound (2-1) were copolymerized to obtain a proton conductive polymer (hereinafter referred to as copolymer B). The properties of copolymer B are shown in Table 1.
_{CF 2 = CFOCF 2 CF (CF} 3) O (CF 2) 2 SO 2 F ··· (2-1).

<Preparation of liquid composition (1)>
A mixed solvent of ethanol, water and 1-butanol (ethanol / water / 1-butanol = 35/50/15 mass ratio) is added to the polymer in which copolymer A is converted to the acid form by the following [acid type treatment]. The solid content concentration was adjusted to 15% by mass, and the mixture was stirred at 125 ° C. for 8 hours using an autoclave. Thereafter, water was further added to adjust the solid content concentration to 9% by mass to prepare a liquid composition (hereinafter referred to as a liquid composition SA) in which the polymer was dispersed in a dispersion medium. The composition of the dispersion medium was ethanol / water / 1-butanol = 21/70/9 (mass ratio).
[Acid type treatment]
First, the copolymer A was processed into a film having a thickness of 100 to 200 μm by pressure press molding at the TQ temperature of the copolymer A.
Next, the film was immersed in an aqueous solution containing 30% by mass of dimethyl sulfoxide and 15% by mass of potassium hydroxide at 80 ° C. for 16 hours, whereby —SO ₂ F groups in the film were hydrolyzed, Converted to SO ₃ K group.
Then, the film was immersed in a 3 mol / L hydrochloric acid aqueous solution at 50 ° C. for 2 hours. The hydrochloric acid aqueous solution was replaced, and the same treatment was repeated four more times. The film was sufficiently washed with ion-exchanged water to obtain a film-like polymer in which —SO ₃ K groups in the film were converted to sulfonic acid groups.

<Preparation of liquid composition (2)>
A mixed solvent of ethanol and water (ethanol / water = 40/60 mass ratio) is added to the polymer in which the copolymer B is converted to the acid form by the [acid type treatment], so that the solid content concentration is 25 mass%. The mixture was adjusted and stirred at 110 ° C. for 8 hours using an autoclave to prepare a liquid composition (hereinafter referred to as “liquid composition SB”).

<Manufacture of membrane electrode assembly>.
(Example 1)
A membrane electrode assembly was produced by the production method (I).

(I-1) Process:
The liquid composition SA is coated on a sheet (trade name: Aflex 100N, manufactured by Asahi Glass; hereinafter referred to as an ETFE sheet) made of an ethylene / tetrafluoroethylene copolymer having a thickness of 100 μm using a die coater. The film was dried at 80 ° C. for 30 minutes, and further subjected to heat treatment at 190 ° C. for 30 minutes to obtain a solid polymer electrolyte membrane having a film thickness of 25 μm (conductivity: 0.105 S / cm) (hereinafter referred to as solid polymer electrolyte membrane MA25). .) Was formed.

(I-2) Step:
20 g of a catalyst in which 50% by mass of platinum was supported by mass ratio on the heat-treated carbon black powder was added to 70 g of water, and ultrasonic waves were uniformly dispersed over 10 minutes. To this, 80 g of liquid composition SA was added, and 100 g of ethanol was further added to adjust the solid content concentration to 10% by mass. This was used as a coating solution for forming a catalyst layer (hereinafter referred to as coating solution CA).

A gas diffusion layer made of carbon paper (trade name: H2315T10AC1, manufactured by NOK) (hereinafter referred to as carbon paper) whose surface was treated with a dispersion containing carbon black particles and polytetrafluoroethylene was prepared.
The dimensional change rate of the gas diffusion layer was 1%. The results are shown in Table 2.
On the gas diffusion layer, the coating liquid CA was applied using a die coater so that the platinum amount was 0.2 mg / cm ² , dried for 15 minutes in an oven at 80 ° C., and further under a reduced pressure atmosphere ( A heat treatment at 190 ° C. was performed at 5 mmHg) to stabilize the proton conductive polymer in the catalyst layer to form a catalyst layer, thereby producing a first intermediate.

(I-3) Step:
A second intermediate was produced by the same method as in step (I-2).

(I-4) Step:
The ETFE sheet was peeled from the solid polymer electrolyte membrane MA25.
The solid polymer electrolyte membrane MA25 is interposed between the first intermediate and the second intermediate so that the catalyst layer is located between the gas diffusion layer and the solid polymer electrolyte membrane on both the cathode side and the anode side. Was put in a press machine preheated to 140 ° C. and hot-pressed for 5 minutes at a pressing pressure of 1.5 MPa to obtain a membrane electrode assembly having an electrode area of 25 cm ² .
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
A test piece was prepared according to procedures 1 and 2 of the 90 ° peel test (II).
Using the solid polymer electrolyte membrane MA25 obtained in Example 1 and the first intermediate, the first intermediate and the solid polymer electrolyte membrane MA25 are catalyzed between the gas diffusion layer and the solid polymer electrolyte membrane MA25. A test piece having a width of 20 mm and a length of 150 mm was prepared by bonding the layers in the same manner and under the same conditions and conditions as in step (I-4) of Example 1. A 90 ° peel test (II) was performed on this test piece. The results are shown in Table 2.

(Example 2)
A membrane electrode assembly was produced by the production method (I).

(I-1) Process:
The liquid composition SB was applied onto an ETFE sheet having a thickness of 100 μm using a die coater, dried at 80 ° C. for 30 minutes, further subjected to heat treatment at 150 ° C. for 30 minutes, and a solid polymer electrolyte having a thickness of 15 μm. A film (conductivity 0.04 S / cm) (hereinafter referred to as solid polymer electrolyte membrane MB15) was formed.

Steps (I-2) to (I-4):
A membrane / electrode assembly was obtained in the same manner as in Example 1 except that the solid polymer electrolyte membrane MA25 was changed to the solid polymer electrolyte membrane MB15 in Example 1.
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
A test piece was prepared according to procedures 1 and 2 of the 90 ° peel test (II).
That is, a test piece was produced in the same manner as in Example 1 except that the solid polymer electrolyte membrane MA25 was changed to the solid polymer electrolyte membrane MB15 in Example 1. A 90 ° peel test (II) was performed on this test piece. The results are shown in Table 2.

(Example 3)
A membrane electrode assembly was produced by the production method (II).

(II-1) Step:
In the same manner as in Example 1, solid polymer electrolyte membrane MA25 was formed.

Steps (II-2) to (II-3):
A coating solution CA was prepared by the same method as in Example 1.

The coating solution CA is coated on a separately prepared ETFE sheet using a die coater so that the amount of platinum is 0.2 mg / cm ² , dried in an oven at 80 ° C. for 15 minutes, and further in a reduced pressure atmosphere A heat treatment at 190 ° C. was performed under (5 mmHg) to stabilize the proton conductive polymer in the catalyst layer to form two catalyst layers (hereinafter referred to as catalyst layer EA).

The ETFE sheet was peeled from the solid polymer electrolyte membrane MA25.
A solid polymer electrolyte membrane MA25 is sandwiched between two catalyst layers EA, and this is heated and pressed under the conditions of a press temperature of 140 ° C., a press time of 5 minutes, and a pressure of 1.5 MPa to form the solid polymer electrolyte membrane MA25. A catalyst layer was bonded to each side.
The ETFE sheet was peeled from the catalyst layer to produce a second intermediate (membrane / catalyst layer assembly) having an electrode area of 25 cm ² .

(II-4) Step:
27 g of ethanol and 153 g of distilled water were added to 20 g of vapor grown carbon fiber (trade name: VGCF-H, manufactured by Showa Denko KK; fiber diameter: about 150 nm, fiber length: 10 to 20 μm), and stirred well. To this, 140 g of the liquid composition SB was added and stirred well, and further mixed and pulverized using a homogenizer to prepare a coating liquid FB for forming an intermediate layer.
The intermediate layer forming coating solution FB was applied to the surface of the carbon paper produced by the same method as in Example 1 using a die coater so that the solid content was 0.8 mg / cm ^2. The laminate was dried for 15 minutes to produce two laminates (hereinafter referred to as gas diffusion layers GDB) in which an intermediate layer was formed on the surface of carbon paper.

A second intermediate is sandwiched between the two gas diffusion layers GDB so that the intermediate layer is located between the gas diffusion layer GDB and the catalyst layer on both the cathode side and the anode side, A membrane electrode assembly having an electrode area of 25 cm ² was obtained by heating and pressing at 130 ° C. for 2 minutes under a pressure of 3 MPa.
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
Test pieces were prepared according to procedures 1 and 2 of the 90 ° peel test (I).
Using the solid polymer electrolyte membrane MA25 obtained in Example 3, the catalyst layer, and the gas diffusion layer GDB, a catalyst layer was formed on one surface of the solid polymer electrolyte membrane MA25 in (II-2) to (II-3) of Example 3 The test piece 90 was produced by bonding using the same method and conditions as in the process.
The catalyst layer is positioned between the gas diffusion layer GDB and the solid polymer electrolyte membrane MA25 at 80 mm in the longitudinal direction from the end of the test piece 90 and 80 mm in the longitudinal direction from the end of the gas diffusion layer GDB. The test piece of width 20mm x length 220mm was produced. A 90 ° peel test (I) was performed on this test piece. The results are shown in Table 2.

(Example 4)
A membrane electrode assembly was produced by the production method (II).

(II-1) Step:
In the same manner as in Example 1, solid polymer electrolyte membrane MA25 was formed.

(II-2) Step:
A coating solution CA was prepared by the same method as in Example 1.

The coating solution CA is applied to one surface of the solid polymer electrolyte membrane MA25 using a die coater so that the amount of platinum is 0.2 mg / cm ^2, and is dried in an oven at 80 ° C. for 15 minutes. Further, a heat treatment at 190 ° C. was performed under a reduced pressure atmosphere (5 mmHg) to stabilize the proton conductive polymer in the catalyst layer to form a catalyst layer, thereby producing a first intermediate.

(II-3) Step:
The ETFE sheet was peeled from the first intermediate.
A catalyst layer was formed on the surface of the solid polymer electrolyte membrane opposite to the catalyst layer at the same temperature and conditions as in the step (II-2), and a second intermediate (membrane catalyst layer assembly) was produced. .

(II-4) Step:
In the same manner as in Example 3, two gas diffusion layers GDB and the second intermediate were joined to obtain a membrane electrode assembly.
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
Test pieces were prepared according to procedures 1 and 2 of the 90 ° peel test (I).
Using the first intermediate and the gas diffusion layer GDB obtained in Example 4, 80 mm in the longitudinal direction from the end of the first intermediate and 80 mm in the longitudinal direction from the end of the gas diffusion layer GDB A test piece having a width of 20 mm and a length of 220 mm was prepared by joining the diffusion layer GDB and the solid polymer electrolyte membrane MA25 so that the catalyst layer was located. A 90 ° peel test (I) was performed on this test piece. The results are shown in Table 2.

(Example 5)
A membrane electrode assembly was produced by the production method (II).

Steps (II-1) to (II-3):
In the same manner as in Example 3, a second intermediate (membrane / catalyst layer assembly) was produced.

(II-4) Step:
In the same manner as in Example 1, two gas diffusion layers made of carbon paper were produced.
A second intermediate was sandwiched between the two gas diffusion layers and joined in the same manner as in Example 3 to obtain a membrane electrode assembly.
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
Test pieces were prepared according to procedures 1 and 2 of the 90 ° peel test (I).
That is, a test piece was prepared in the same manner as in Example 3 except that the gas diffusion layer GDB was changed to only carbon paper in Example 3. A 90 ° peel test (I) was performed on this test piece. The results are shown in Table 2.

(Example 6)
A membrane electrode assembly was produced by the production method (II).

(II-1) Step:
In the same manner as in Example 2, solid polymer electrolyte membrane MB15 was formed.

Steps (II-2) to (II-4):
A membrane / electrode assembly was obtained in the same manner as in Example 5 except that the solid polymer electrolyte membrane MA25 was changed to the solid polymer electrolyte membrane MB15 in Example 5.
The membrane electrode assembly was subjected to power generation characteristics and a wet-dry cycle test. The results are shown in Table 2.

[Preparation of specimen for 90 ° peel test]
Test pieces were prepared according to procedures 1 and 2 of the 90 ° peel test (I).
That is, a test piece was produced in the same manner as in Example 5 except that the solid polymer electrolyte membrane MA25 was changed to the solid polymer electrolyte membrane MB15 in Example 5. A 90 ° peel test (I) was performed on this test piece. The results are shown in Table 2.

  From the results of Table 2, by using the membrane electrode assembly of the present invention, it is possible to express high power generation performance even in a low humidified environment, and it is excellent in durability performance in an environment where wetting and drying are repeated. Recognize.

  The membrane electrode assembly of the present invention can exhibit high power generation performance even in a low humidified environment and has excellent durability performance in an environment of repeated wetting and drying. This is extremely useful for polymer electrolyte fuel cells used as systems, household cogeneration systems, and the like.

It is a schematic sectional drawing which shows an example of the membrane electrode assembly for polymer electrolyte fuel cells of this invention. FIG. 2A is a schematic diagram showing a test piece subjected to a 90 ° peel test (I), and FIG. 2B is a schematic diagram showing an apparatus for the 90 ° peel test (I). FIG. 3A is a schematic view showing a test piece subjected to a 90 ° peel test (II), and FIG. 3B is a schematic view showing an apparatus for a 90 ° peel test (II). It is a schematic sectional drawing which shows the other example of the membrane electrode assembly for polymer electrolyte fuel cells of this invention. It is a schematic sectional drawing which shows 1 process of the manufacturing method of the membrane electrode assembly for polymer electrolyte fuel cells of this invention. It is a schematic sectional drawing which shows 1 process of the manufacturing method of the membrane electrode assembly for polymer electrolyte fuel cells of this invention. It is a schematic sectional drawing which shows an example of the polymer electrolyte fuel cell using the membrane electrode assembly for polymer electrolyte fuel cells of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Membrane electrode assembly 10 1st electrode 12 1st catalyst layer 14 1st gas diffusion layer 20 2nd electrode 22 2nd catalyst layer 24 2nd gas diffusion layer 30 Solid polymer electrolyte membrane 50 1st Intermediate body 60 second intermediate body 80 separator 91 test piece

Claims (4)

A first electrode having a first catalyst layer and a first gas diffusion layer comprising an electrode catalyst and a proton conducting polymer;
A second electrode having a second catalyst layer comprising an electrode catalyst and a proton conducting polymer and a second gas diffusion layer;
In a membrane electrode assembly for a polymer electrolyte fuel cell comprising a solid polymer electrolyte membrane disposed between the first catalyst layer and the second catalyst layer,
The solid polymer electrolyte membrane has an electrical conductivity of 0.05 S / cm or more in an atmosphere at a temperature of 80 ° C. and a relative humidity of 40%, and is between the solid polymer electrolyte membrane and the first gas diffusion layer. Solid polymer having a 90 ° peel strength of 0.03 N / cm or more and a dimensional change rate of less than 10% when the first gas diffusion layer is immersed in hot water at 80 ° C. -Type fuel cell membrane electrode assembly.   The membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte membrane is formed by casting a liquid composition in which a proton conductive polymer is dispersed in a dispersion medium.   The membrane electrode for a polymer electrolyte fuel cell according to claim 1 or 2, wherein the first catalyst layer formed on the first gas diffusion layer and the solid polymer electrolyte membrane are joined. A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell, comprising obtaining the assembly.   The membrane electrode for a polymer electrolyte fuel cell according to claim 1 or 2, by joining the first catalyst layer formed on the polymer electrolyte membrane and the first gas diffusion layer. A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell, comprising obtaining the assembly.

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