JP2007048557A - Method of manufacturing membrane electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a membrane electrode assembly which can offer the high-performance membrane electrode assembly by ensuring good contact performance between an aromatic solid polymer electrolyte film and catalyst film without causing any performance faults around an electrode and drop-off of the electrolyte film. <P>SOLUTION: The method includes a step where an aromatic solid polymer electrolyte film is immersed in a solvent; and a step where a catalyst paste containing an aromatic solid polymer electrolyte is applied onto the top surface of the electrolyte film, with the solvent contained within the range of 20 to 60% by weight in the electrolyte film after immersion in the solvent, then the top surface is dried, thereby forming a catalyst layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a membrane electrode assembly constituting a fuel cell, in particular, a polymer electrolyte fuel cell.

  A solid polymer electrolyte fuel cell is composed of a membrane electrode assembly in which a cathode is joined to one side of an electrolyte membrane and an anode is joined to the other side. For example, hydrogen gas is supplied to the anode as a fuel, and the cathode This is an electrochemical device in which oxygen gas is supplied as an oxidant and electrochemically reacted to obtain electric power.

  The anode and the cathode are gas diffusion electrodes, and the gas diffusion electrode includes a gas diffusion layer and a catalyst layer. The catalyst layer contains platinum group metal particles or carbon particles supporting the particles as a catalyst, and the gas diffusion layer is made of porous carbon paper having water repellency.

  As the solid polymer electrolyte membrane and electrode electrolyte used for the membrane electrode assembly, perfluorosulfonic acid polymer electrolytes represented mainly by Nafion (registered trademark, manufactured by DuPont) have been used. Here, since the power generation efficiency of the solid polymer fuel cell increases as the operating temperature of the battery increases, it is desired to increase the operating temperature. However, the perfluorosulfonic acid polymer electrolyte has a problem that it cannot be used at high temperatures because of its low heat resistance.

  Therefore, an electrolyte containing an aromatic hydrocarbon has been used so that it can be used at a high temperature. However, many aromatic polymer materials have a glass transition temperature higher than that of perfluorosulfonic acid polymer electrolytes, and below the temperature at which sulfonic acid is not eliminated, aromatic polymer materials Since the glass transition temperature is not reached, there is a problem that the bonding strength between the electrolyte membrane and the electrode is often insufficient.

  As a means for solving such a problem, a method of directly applying and forming an electrode on an electrolyte membrane has been proposed (see, for example, Patent Document 1). However, when an electrode is formed on a single electrolyte membrane, a catalyst paste containing a catalyst, an electrolyte, and a solvent is applied, so that the solvent penetrates into the electrolyte membrane, and the periphery of the electrode such as wrinkles due to changes in the size of the membrane. There arises a problem that causes poor properties.

In addition, since the content of the solvent in the electrolyte membrane is different between the portion immediately below the catalyst paste and the portion not coated, the mechanical strength of the electrode periphery that is the boundary between the two is greatly different, and the electrolyte membrane There also arises a problem that the film thickness distribution, particularly the electrolyte membrane around the electrode, is reduced.
JP 2003-100314 A

  An object of the present invention is to provide a high-performance membrane / electrode assembly that has good contact between the aromatic polymer electrolyte membrane and the catalyst layer, and does not cause defective properties around the electrode or decrease in membrane thickness of the electrolyte membrane. It is in providing the manufacturing method of the membrane electrode assembly which makes it possible to obtain.

  In view of the above problems, the present inventors conducted extensive research. As a result, it has been found that the above problems can be solved by forming an electrode by directly applying and drying a catalyst paste on the electrolyte membrane in a state where the aromatic polymer electrolyte membrane is impregnated with a solvent.

  That is, the first method for producing a membrane electrode assembly according to the present invention includes a step of immersing the aromatic polymer electrolyte membrane in a solvent, and a range of 20 to 60% by weight of the solvent in the electrolyte membrane after the solvent immersion. And a step of applying a catalyst paste containing an aromatic polymer electrolyte on the electrolyte membrane and then drying to form a catalyst layer.

  The second method for producing a membrane / electrode assembly according to the present invention comprises applying a catalyst paste containing an aromatic polymer electrolyte to one surface of an aromatic polymer electrolyte membrane and drying it. A step of forming a catalyst layer of 1, a step of immersing the electrolyte membrane on which the catalyst layer is formed, and a state in which the solvent is contained in an amount of 20 to 60% by weight in the electrolyte membrane after the immersion of the solvent And applying a catalyst paste containing an aromatic polymer electrolyte to the surface of the electrolyte membrane facing the first catalyst layer, followed by drying to form a second catalyst layer. Features.

  Before forming the first catalyst layer, the aromatic polymer electrolyte membrane is immersed in a solvent, and the solvent is contained in an amount of 20 to 60% by weight in the electrolyte membrane after the solvent immersion. It is preferable to be in a state.

  In the membrane / electrode assembly obtained by the production method of the present invention, the contact between the electrolyte membrane surface and the catalyst layer is improved, and a membrane / electrode assembly having high performance is obtained. In addition, it is possible to obtain a polymer electrolyte fuel cell having long-term reliability with respect to power generation without confirming film thickness reduction around the electrode.

Hereinafter, the manufacturing method of the membrane electrode assembly which concerns on this invention is demonstrated in detail.
The method for producing a membrane electrode assembly of the present invention comprises a step of immersing an aromatic polymer electrolyte membrane in a solvent, and directly applying a catalyst paste containing an aromatic polymer electrolyte in a state where the electrolyte membrane is impregnated with a solvent. A step of forming at least one electrode catalyst layer by processing.

(Aromatic polymer electrolyte)
The aromatic polymer electrolyte used in the present invention and the aromatic polymer electrolyte constituting the catalyst paste are not particularly limited, but are preferably made of the same polymer from the viewpoint of production efficiency and the like, particularly at high temperatures. From the viewpoint of power generation stability, a structural unit having a sulfonic acid group represented by the following general formula (A) (hereinafter also referred to as “structural unit (A)” or “sulfonic acid unit”), and the following general formula The sulfone represented by the following general formula (C) including the structural unit having no sulfonic acid group represented by (B) (hereinafter also referred to as “structural unit (B)” or “hydrophobic unit”). It is preferably made of a modified polyarylene.

  <Sulphonic acid unit>

In the above formula (A), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—.
_{, - (CF 2) i -} (i is an integer from 1 to 10.) Or -C (CF _{3) 2} - shows a. Of these, —CO— and —SO ₂ — are preferable.

Z independently represents a direct bond, — (CH ₂ ) _j — (j represents an integer of 1 to 10), —C (CH ₃ ) ₂ —, —O— or —S—. Among these, a direct bond and —O— are preferable.

Ar is —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p is 1 to
An integer of 12 is shown. The aromatic group which has a substituent represented by this is shown. Examples of the aromatic group include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and the like. In these, a phenyl group and a naphthyl group are preferable. Ar represents —SO ₃ H;
It is necessary to have at least one substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H, and two in the case of a naphthyl group It is preferable to have the above.

m is an integer of 0 to 10, preferably 0 to 2, n is an integer of 0 to 10, preferably 0 to 2, and k is an integer of 1 to 4.
As a preferred structure of the structural unit (A), in the above formula (A),
(1) a structure in which m = 0, n = 0, Y is —CO—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(2) a structure in which m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(3) A structure in which m = 1, n = 1, k = 1, Y is —CO—, Z is —O—, and Ar is a phenyl group having —SO ₃ H as a substituent;
(4) m = 1, n = 0, Y is —CO—, and Ar is two substituents —SO _3.
A structure which is a naphthyl group having H,
(5) m = 1, n = 0, Y is —CO—, Z is —O—, and Ar is a phenyl group having —O (CH ₂ ) ₄ SO ₃ H as a substituent. Examples include structures.

  <Hydrophobic unit>

In the above formula (B), A and D are each independently a direct bond, —CO—, —SO ₂ —, —
SO—, —CONH—, —COO—, — (CF ₂ ) _i — (i represents an integer of 1 to 10), — (CH ₂ ) _j — (j represents an integer of 1 to 10) , -CR _'2 -, showing cyclohexylidene group, a fluorenylidene group, -O- or -S-. Among these, a direct bond, —CO—, —SO ₂ —, —CR ′ ₂ —, a cyclohexylidene group, a fluorenylidene group, and —O— are preferable. R ′ represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group or a halogenated hydrocarbon group. For example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, A propyl group, an octyl group, a decyl group, an octadecyl group, a phenyl group, a trifluoromethyl group, etc. are mentioned.

B independently represents an oxygen atom or a sulfur atom, preferably an oxygen atom.
R ^{1 to} R ¹⁶ each independently represent a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group, an allyl group, an aryl group, a nitro group or a nitrile group, which is partially or wholly halogenated.

Examples of the alkyl group in R ^{1 to} R ¹⁶ include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, a hexyl group, a cyclohexyl group, and an octyl group. Examples of the halogenated alkyl group include a trifluoromethyl group, a pentafluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a perfluorohexyl group. Examples of the allyl group include a propenyl group. Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

s and t each represent an integer of 0 to 4. r shows 0 or an integer greater than or equal to 1, and an upper limit is 100 normally, Preferably it is 1-80.
As a preferred structure of the structural unit (B), in the above formula (B),
(1) s = 1, t = 1, A is —CR ′ ₂ —, a cyclohexylidene group or a fluorenylidene group, B is an oxygen atom, and D is —CO— or —SO ₂ —. , R ^{1 to} R ¹⁶ are hydrogen atoms or fluorine atoms,
(2) a structure in which s = 1, t = 0, B is an oxygen atom, D is —CO— or —SO ₂ —, and R ^{1 to} R ¹⁶ are hydrogen atoms or fluorine atoms,
(3) s = 0, t = 1, A is —CR ′ ₂ —, a cyclohexylidene group or a fluorenylidene group, B is an oxygen atom, and R ^{1 to} R ¹⁶ are a hydrogen atom, a fluorine atom or Examples thereof include a structure that is a nitrile group.

  <Polymer structure>

In the above formula (C), A, B, D, Y, Z, Ar, k, m, n, r, s, t and R ^{1 to} R ¹⁶ are defined in the above formulas (A) and (B). Where x and y are x + y = 10
The molar ratio in the case of 0 mol% is shown.

  The sulfonated polyarylene particularly preferably used in the present invention contains the structural unit (A), that is, the unit of x in a proportion of 0.5 to 99.999 mol%, preferably 10 to 99.99 mol%, The structural unit (B), that is, the y unit is contained in a proportion of 99.5 to 0.001 mol%, preferably 90 to 0.01 mol%.

<Method for producing sulfonated polyarylene>
Examples of the method for producing the sulfonated polyarylene include the following methods A, B, and C.

  (Method A) For example, in the method described in JP-A No. 2004-137444, a monomer having a sulfonate group that can be the structural unit (A) and a monomer or oligomer that can be the structural unit (B) are combined. A method of polymerizing to produce a polyarylene having a sulfonic acid ester group, and deesterifying the sulfonic acid ester group to convert it into a sulfonic acid group.

  (Method B) For example, in the method described in JP-A-2001-342241, a monomer having a skeleton represented by the above formula (A) but not having a sulfonic acid group or a sulfonic acid ester group, and the above structural unit (B) A method in which a monomer or an oligomer that can be used is copolymerized, and the resulting copolymer is sulfonated using a sulfonating agent.

(Method C) When Ar in the above formula (A) is an aromatic group having a substituent represented by —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H Is, for example, copolymerized a precursor monomer that can be the structural unit (A) and a monomer or oligomer that can be the structural unit (B) by the method described in JP-A-2005-60625, A method of introducing an alkyl sulfonic acid or a fluorine-substituted alkyl sulfonic acid.

  Examples of the monomer having a sulfonate group that can be the structural unit (A) that can be used in the method A include, for example, JP-A Nos. 2004-137444, 2004-345997, and 2004-346163. Examples thereof include sulfonic acid esters described in Japanese Patent Publication No. Gazette.

  Examples of the monomer that does not have a sulfonic acid group and a sulfonic acid ester group that can be used as the structural unit (A) and that can be used in the above-mentioned method B include, for example, JP-A Nos. 2001-342241 and 2002-293889. Mention may be made of the dihalides described.

  Examples of the precursor monomer that can be the structural unit (A) that can be used in the method C include dihalides described in JP-A-2005-36125.

The monomer or oligomer that can be the structural unit (B) used in any method is as follows.
In the above formula (B), when r = 0, for example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, 2,2-bis (4-chlorophenyl) difluoromethane, 2,2-bis ( 4-chlorophenyl) -1,1,1,3,3,3-hexafluoropropane, 4-chlorobenzoic acid-4-chlorophenyl ester, bis (4-chlorophenyl) sulfoxide, bis (4-chlorophenyl) sulfone, 2, Examples include 6-dichlorobenzonitrile. Among these compounds, compounds in which a chlorine atom is replaced with a bromine atom or an iodine atom can also be used.

In the above formula (B), when r = 1, for example, compounds described in JP-A-2003-113136 can be exemplified.
In the above formula (B), when r ≧ 2, for example, JP 2004-137444 A, JP 2004-244517 A, JP 2004-346164 A, Japanese Patent Application No. 2003-348523, and Japanese Patent Application No. 2003-348524. No., Japanese Patent Application No. 2004-211739, and Japanese Patent Application No. 2004- 211740.

  In order to obtain a polyarylene having a sulfonic acid group, first, a monomer that can be the structural unit (A) and a monomer or oligomer that can be the structural unit (B) are copolymerized in the presence of a catalyst, It is necessary to obtain body polyarylene. The catalyst used in carrying out the copolymerization is a catalyst system containing a transition metal compound, and this catalyst system is (i) a compound that becomes a transition metal salt and a ligand, or a ligand is coordinated. In addition, a transition metal complex (including a copper salt) and (ii) a reducing agent may be essential components, and a “salt” may be added to increase the polymerization rate. For example, the conditions described in JP-A-2001-342241 can be adopted as specific examples of these catalyst components, the use ratio of each component, the reaction solvent, concentration, temperature, time, and other polymerization conditions.

  The sulfonated polyarylene used in the present invention can be obtained by converting the precursor polyarylene obtained as described above into a polyarylene having a sulfonic acid group. As this method, there are the following three methods.

(Method a) A method of deesterifying the precursor polyarylene having a sulfonate group obtained by Method A by the method described in JP-A-2004-137444.
(Method b) A method of sulfonating the precursor polyarylene obtained in Method B by the method described in JP-A-2001-342241.

(Method c) A method of introducing an alkylsulfonic acid group into the precursor polyarylene obtained by the method C by the method described in JP-A-2005-60625.
The ion exchange capacity of the sulfonated polyarylene represented by the above formula (C) produced by the method as described above is usually 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, Preferably it is 0.8-2.8 meq / g. If the ion exchange capacity is lower than the above range, the proton conductivity tends to be low and the power generation performance tends to be reduced. On the other hand, if the ion exchange capacity exceeds the above range, the water resistance may be significantly lowered, which is not preferable.

  The ion exchange capacity can be adjusted, for example, by changing the type, use rate, and combination of the precursor monomer that can be the structural unit (A) and the monomer or oligomer that can be the structural unit (B).

  The molecular weight of the sulfonated polyarylene thus obtained is 10,000 to 1,000,000, preferably 20,000 to 800,000 in terms of polystyrene-reduced weight average molecular weight by gel permeation chromatography (GPC).

[Aromatic polymer electrolyte membrane]
The aromatic polymer electrolyte membrane (proton conductive membrane) used in the present invention is obtained by dissolving or swelling the aromatic polymer electrolyte in a solvent and casting it on a support by a known coating method. It is formed by drying and removing the solvent.

As the drying conditions, suitable conditions can be set depending on the coating speed and the material, and conditions that do not allow the sulfonic acid groups of the electrolyte to be eliminated are desirable. Specifically, the drying can be performed at a drying temperature of 20 ° C. to 180 ° C., preferably 50 ° C. to 160 ° C., and a drying time of 5 minutes to 600 minutes, preferably 30 minutes to 400 minutes.

  The solvent removal treatment can be performed by water immersion. The water temperature at this time is 5 ° C. to 120 ° C., preferably 15 ° C. to 95 ° C., and the water immersion time is 1 minute to 72 hours, preferably 5 minutes to 48 hours. Further, the solvent removal treatment may be performed by a method as disclosed in JP-A-2004-79380.

  As the support, a sheet made of a fluoropolymer such as polytetrafluoroethylene (PTFE), a glass plate or a metal plate whose surface is treated with a release agent, a sheet of polyethylene terephthalate (PET), or the like can also be used. .

<Solvent>
The solvent is not particularly limited as long as the solvent dissolves or disperses the aromatic polymer electrolyte. Moreover, you may use individually by 1 type or in combination of 2 or more types.

Specifically, water; methanol, ethanol, n-propyl alcohol, 2-propanol, 2-methyl-2-propanol, 2-butanol, n-butyl alcohol, 2-methyl-1-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl 1-propanol , Cyclohexanol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-methylcyclohexanol, 2 -Methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol, 1-octano , 2-octanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 1-methoxy-2-propanol, 1-ethoxy Alcohols such as 2-propanol; polyhydric alcohols such as ethylene glycol, propylene glycol, glycerol; dioxane, tetrahydrofuran, tetrahydropyran, diethyl ether, diisopropyl ether, di-n-propyl ether, butyl ether, phenyl ether, isopentyl Ether, 1,2-dimethoxyethane, diethoxyethane, bis (2-methoxyethyl) ether, bis (2-ethoxyethyl) ether, cineol, benzylethylether, anisole Ethers such as phenetole and acetal; acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptanone, 2,4-dimethyl-3- Ketones such as pentanone and 2-octanone; γ-butyrolactone, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, 3-methoxybutyl acetate, methyl butyrate, Esters such as ethyl butyrate, methyl lactate, ethyl lactate, butyl lactate; dimethyl sulfoxide, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2 -Pyrrolidone, tetramethi Aprotic polar solvents such as urea; toluene, xylene, heptane, hexane, heptane, etc. hydrocarbon solvents such as octane.

[Catalyst paste]
The catalyst paste used when forming the catalyst layer in the membrane electrode assembly includes a catalyst-supporting carbon, an aromatic polymer electrolyte, and a solvent, and other dispersants, carbon fibers, and the like as necessary. Ingredients may be included.

  As the aromatic polymer electrolyte constituting the catalyst paste, the same aromatic polymer electrolyte as that constituting the electrolyte membrane can be used. Moreover, the solvent which comprises the said catalyst paste can also use the thing similar to the solvent used when forming the said electrolyte membrane.

<Catalyst-supported carbon>
The catalyst in the catalyst-supported carbon used in the catalyst paste may be any catalyst that has a catalytic action on the hydrogen oxidation reaction and oxygen reduction reaction, such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, Examples thereof include metals such as lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, alloys thereof, and oxides thereof. The particle size of the catalyst is preferably 10 to 300 mm, more preferably 15 to 100 mm.

  As the carbon supporting the catalyst, carbon black such as oil furnace black, channel black, lamp black, thermal black, and acetylene black is used. Further, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin, and the like may be used.

  Examples of the oil furnace black include “Vulcan XC-72”, “Vulcan P”, “Black Pearls 880”, “Black Pearls 1100”, “Black Pearls 1300”, “Black Pearls 2000”, and “Regal 400” manufactured by Cabot Corporation. “Ketjen Black EC” manufactured by Lion Corporation, “# 3150, # 3250” manufactured by Mitsubishi Chemical Corporation, and the like. Examples of the acetylene black include “DENKA BLACK” manufactured by Denki Kagaku Kogyo.

  As the form of these carbons, in addition to particles, fibers can also be used. The amount of the catalyst supported on the carbon is not particularly limited as long as it can effectively exhibit the catalytic activity, but the supported amount is 0.1 to 9.0 g- Metal / g-carbon, preferably in the range of 0.25 to 2.4 g-metal / g-carbon.

<Carbon fiber>
Carbon fibers may be further added to the catalyst paste as necessary. As such a carbon fiber, rayon-based carbon fiber, PAN-based carbon fiber, lignin pover-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, or the like can be used, preferably vapor-grown carbon fiber. . Inclusion of carbon fiber in the catalyst paste increases the pore volume in the electrode to be formed, improving the diffusibility of fuel gas and oxygen gas, and improving the flooding caused by the generated water. Performance is improved.

<Other additives>
The catalyst paste may contain other components as required, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, dispersants, fluorine-based polymers, silicon-based polymers. You may add water repellents. When the dispersant is added, the storage stability and fluidity are excellent, and the productivity during coating is improved. Moreover, when the said water repellent is added, there exists an effect which discharges | emits the produced | generated water efficiently, and it contributes to the improvement of power generation performance.

[Production method of membrane electrode assembly]
A first method for producing a membrane / electrode assembly of the present invention includes a step of immersing an aromatic polymer electrolyte membrane formed on a support and desolvated as described above in a solvent, and in the electrolyte membrane. And applying the catalyst paste directly onto the electrolyte membrane in a state of impregnating with a solvent, followed by drying to form a catalyst layer.

  The second production method of the membrane / electrode assembly of the present invention is such that the catalyst paste is directly applied on the polymer electrolyte membrane formed on the support and subjected to the solvent removal treatment (the surface facing the support), and then dried. A step of forming a first catalyst layer, a step of peeling the support and immersing the electrolyte membrane on which the first catalyst layer is formed in a solvent, and a state in which the electrolyte membrane is impregnated with a solvent. And a step of forming a second catalyst layer by directly applying a catalyst paste on the electrolyte membrane (the surface on which the first catalyst layer is not formed) and drying it.

  In addition, the first catalyst layer has a catalyst on the electrolyte membrane (a surface facing the support) in a state where the aromatic polymer electrolyte membrane is immersed in a solvent and the electrolyte membrane is impregnated with the solvent. It is preferably formed by applying and drying a paste. In addition, you may perform peeling of a support body before the first solvent immersion.

  The solvent to be impregnated in the aromatic polymer electrolyte membrane, that is, the solvent used when immersing the electrolyte membrane is water or an alcohol aqueous solution having 6 or less carbon atoms from the viewpoint of a poor solvent that does not dissolve the electrolyte membrane. More preferred is water or an aqueous alcohol solution having 3 or less carbon atoms.

  The solvent content in the electrolyte membrane after immersion in the solvent is 20 to 60% by weight, preferably 20 to 50% by weight, based on the total weight of the electrolyte membrane. Therefore, when water is used as the immersion solvent, the water content in the electrolyte membrane after immersion in the solvent is 20 to 60% by weight, preferably 20 to 50% by weight. When an alcohol aqueous solution is used as the solvent, the alcohol content in the electrolyte membrane after immersion in the solvent is 0.01 to 10% by weight, preferably 0.1 to 10% by weight, based on the entire electrolyte membrane. The electrolyte membrane further contains water within a range that satisfies the above-mentioned conditions for the solvent content.

  If the alcohol content in the electrolyte membrane after immersion in the solvent is lower than the above range, film loss around the electrode may not be improved. On the other hand, if it exceeds the above range, part of the membrane may be dissolved. Also, if the moisture content is lower than the above range, the effect of dimensional change may remain, resulting in poor surface properties.On the other hand, if it exceeds the above range, the dimensional change after electrode formation is too large and the electrode film thickness Non-uniformity may occur.

The conditions for immersing the solvent are not particularly limited, and the immersing time, temperature, solvent concentration, or the like may be appropriately adjusted so that the solvent content in the electrolyte membrane after the immersion is within the above range.
Examples of the method for applying the catalyst paste include an intermittent coating method, a gravure coating method, a spray coating method, a screen printing method, and a blade method. In these, it is preferable that the coating method at the time of forming any one of the said 1st catalyst layer and the 2nd catalyst layer is an intermittent coating method from a viewpoint of mass productivity. Further, from the viewpoint of improving the characteristics by reducing the electrode thickness, it is also preferable to use a gravure coating method, a spray coating method or a screen printing method.

The drying treatment for removing the solvent after applying the catalyst paste is performed at a drying temperature of 20 ° C. to 180 ° C., preferably 50 ° C. to 160 ° C., and a drying time of 5 minutes to 600 minutes, preferably 30 minutes to 400 minutes. be able to. Moreover, you may remove by water immersion as needed. As conditions for water immersion, the water immersion temperature is 5 to 120 ° C., preferably 15 to 95 ° C., and the water immersion time is 1 minute to 72 hours, preferably 5 minutes to 48 hours. Although not particularly limited, the metal supported as a catalyst is 0.01 to 2.0 mg / cm ² , preferably 0.05 to 1 per unit area of the coating.
It is desirable to be present in the catalyst layer in the range of 0 mg / cm ² . Within this range, sufficiently high catalytic activity is exhibited and protons can be efficiently conducted.

  The pore volume of the catalyst layer obtained as described above is 0.05 to 3.0 ml / g, preferably 0.1 to 2.0 ml / g. When the pore volume exceeds the above range, the mechanical properties tend to be lowered, and the electron conduction and proton conduction paths are cut, and the power generation performance may be lowered. On the other hand, if the pore volume is lower than the above range, the water discharge performance is poor and the power generation performance may be lowered.

[Use]
The membrane electrode assembly obtained by the production method of the present invention can be suitably used as a membrane electrode assembly constituting a polymer electrolyte fuel cell. Further, it can be applied to hydrohalic acid electrolysis, salt electrolysis, oxygen concentrator, humidity sensor, gas sensor and the like.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. The ion exchange capacity, molecular weight, water content, and alcohol content were measured and the power generation performance was evaluated by the following method.

(Ion exchange capacity)
The resulting sulfonated polymer was thoroughly washed until the washing water became neutral to remove free remaining acid. After drying, a predetermined amount was weighed, phenolphthalein dissolved in a THF / water mixed solvent was used as an indicator, and titration was performed using a standard solution of NaOH, and the ion exchange capacity was determined from the neutralization point.

(Molecular weight)
Regarding the molecular weight of polyarylene having no sulfonic acid group, tetrahydrofuran (THF) was used as a solvent, and the molecular weight in terms of polystyrene was determined by GPC. The molecular weight of polyarylene having a sulfonic acid group was determined by GPC using polystyrene as a molecular weight using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as an eluent.

(Moisture content)
The water content was measured by leaving the electrolyte membrane immersed in water at 160 ° C. for 1 hour, and determining the difference in mass before and after heating.

(Alcohol content)
The alcohol content was measured by leaving the electrolyte membrane immersed in an aqueous alcohol solution at 160 ° C. for 1 hour, sampling the gas released at this time, and determining the alcohol content by gas chromatography. Assuming that all the alcohol in the film was released, the alcohol content in the film was calculated from this value.

(Power generation performance)
The obtained membrane electrode assembly was made into a single cell, and power was generated by supplying air to the oxygen electrode and supplying pure hydrogen to the fuel electrode. The power generation conditions were a temperature of 90 ° C., a relative humidity of 50% on the fuel electrode side, and a relative humidity of 50% on the oxygen electrode side. The power generation performance was evaluated by measuring the cell voltage at a current density of 0.5 A / cm ² .

(Evaluation of film loss around the electrode)
A 10 mm □ (A) including the electrode end and a 10 mm □ (B) including a point 20 mm away from the electrode end were cut out, the cross section was observed with a scanning electron microscope, and the thickness of the electrolyte membrane portion was measured. . The difference between the thickness of the side length (B) and the thickness of (A) was taken as the amount of film reduction. Measurement points were made at a total of 8 points, each vertex of the electrode and the middle point of each side, and the average value was calculated.

(Acupuncture evaluation)
Twenty membrane electrode assemblies were prepared, and the number of wrinkles that could be observed visually was counted and the average value was calculated.
<Synthesis Example 1>
(1) Synthesis of hydrophobic unit (I) 1,3-bis (4-chlorobenzoyl) benzene 17.8 g (50.0 mmol) was added to a 500 mL three-necked flask equipped with a stirring blade, a thermometer and a nitrogen introduction tube. , 2,2-bis (4-hydroxyphenyl) hexafluoropropane (15.1 g, 45.0 mmol), potassium carbonate (8.1 g, 58.5 mol), sulfolane (117 g), and toluene (40 g) were added at 130 ° C. under a nitrogen atmosphere. Stir. After removing water by azeotropy with toluene, toluene was removed from the system and stirred at 195 ° C. for 7 hours. The reaction solution was cooled to 100 ° C., 5.33 g (15.0 mmol) of 1,3-bis (4-chlorobenzoyl) benzene was added, and the mixture was again stirred at 195 ° C. for 3 hours. Diluted with toluene, and solid content was removed by Celite filtration. The filtrate was poured into a methanol / concentrated hydrochloric acid solution (methanol 2.0 L / concentrated hydrochloric acid 0.2 L) to coagulate the reaction product. The solid was filtered by suction filtration, and the obtained solid was washed with methanol and then air-dried. This was redissolved in tetrahydrofuran and poured into 3.0 L of methanol to solidify the reaction product. The solid was filtered by suction filtration, and the obtained solid was air-dried and further vacuum-dried to obtain 22.1 g of the desired hydrophobic unit (yield 75%). The number average molecular weight (Mn) of the product determined by GPC (polystyrene conversion) was 8,000, and the weight average molecular weight (Mw) was 14,000. It was confirmed that the obtained compound was an oligomer represented by the following formula (I).

(2) Synthesis of sulfonated polyarylene (II) In a 500 mL three-necked flask equipped with a stirring blade, a thermometer, and a nitrogen introduction tube, 31.6 g (78) of neopentyl 3- (2,5-dichlorobenzoyl) benzenesulfonate was added. 0.7 mmol), 14.1 g (1.76 mmol) of the hydrophobic unit obtained in (1), 8.39 g (32.0 mmol) of triphenylphosphine, 12.6 g (192 mmol) of zinc, bis (triphenylphosphine) nickel Weighed 2.09 g (3.2 mmol) of dichloride and 0.36 g (2.4 mmol) of sodium iodide. The flask was placed in an oil bath heated to 40 ° C. and dried in vacuum for 2 hours. After the inside was purged with dry nitrogen several times, 100 mL of dehydrated dimethylacetamide was added to initiate polymerization. The polymerization was continued for 3 hours while controlling the reaction temperature not to exceed 90 ° C. After completion of the reaction, 360 g of dimethylacetamide was added for dilution, the insoluble matter was removed by celite filtration, and the solid content was concentrated to 12%.

The obtained concentrated liquid was put into a 1 L three-necked flask equipped with a stirring blade, a thermometer, and a nitrogen introduction tube, 15.1 g (173 mmol) of lithium bromide was added, and the mixture was stirred at 120 ° C. for 7 hours. After completion of the reaction, the reaction solution was poured into 4 L of acetone to coagulate the reaction product. The solid was filtered by suction filtration, and the obtained solid was washed with methanol, then air-dried and further vacuum-dried to obtain 30.0 g of the desired polymer (yield 87%). The number average molecular weight of the product determined by GPC (polystyrene conversion) was 102,000, and the weight average molecular weight was 320,000. The obtained polymer is presumed to be a sulfonated polyarylene represented by the following formula (II). The ion exchange capacity of this sulfonated polyarylene (II) was 2.1 meq / g.

[Example 1]
(Production of proton conducting membrane)
A 15 wt% N-methyl-2-pyrrolidone (NMP) / methanol (weight ratio: 67/33) solution of the sulfonated polyarylene (II) obtained in Synthesis Example 1 above was added to a PET roll (thickness 0.125 mm, A proton conducting membrane having a film thickness of 40 μm was formed on PET by casting with a comma reverse coater on a width of 300 mm and casting and drying with a comma reverse coater, followed by desolvation by water immersion.

(Preparation of catalyst paste)
The sulfonated polyarylene (II) obtained in Synthesis Example 1 is dissolved in a water / NMP (weight ratio: 20/80) mixed solution to prepare a polymer solution, and the weight of carbon black and platinum is added to the solution. A catalyst paste was prepared by adding platinum-supported carbon particles having a ratio of 50:50 (“TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and vapor-grown carbon fiber (“VGCF” manufactured by Showa Denko), and stirring and mixing.

(Production of membrane electrode assembly)
The proton conductive membrane formed on the support (PET) and subjected to the solvent removal treatment was immersed in water (25 ° C. × 45 minutes, water content: 30% by weight). The catalyst paste was intermittently coated with a slot die on the resulting proton conductive membrane (surface facing the support) and dried to form a catalyst layer. Next, the support (PET) was peeled off and again immersed in water (25 ° C. × 45 minutes, water content: 30% by weight), and then on the proton conductive membrane (surface facing the catalyst layer) in the same manner. A membrane electrode assembly was produced by forming a catalyst layer. The power generation performance was evaluated using the membrane electrode assembly thus prepared. The evaluation results are shown in Table 1.

[Example 2]
(Production of proton conducting membrane)
A 15 weight NMP / methanol (weight ratio: 67/33) solution of the sulfonated polyarylene (II) obtained in Synthesis Example 1 above was applied to a PET roll (thickness 0.125 mm, width 300 mm) with a coating width of 250 mm. Then, a proton reverse membrane having a film thickness of 40 μm was formed on PET by casting with a comma reverse coater, forming a film, drying, and removing the solvent by immersion in water.

(Preparation of catalyst paste)
The sulfonated polyarylene (II) obtained in Synthesis Example 1 was mixed with water / NMP (weight ratio:
20/80) A polymer solution is prepared by dissolving in a mixed solution. To this solution, platinum-supported carbon particles (“TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) with a weight ratio of carbon black to platinum of 50:50 and vapor phase growth are prepared. A catalyst paste was prepared by adding carbon fiber (“VGCF” manufactured by Showa Denko) and stirring and mixing.

(Production of membrane electrode assembly)
The proton conductive membrane formed on the support (PET) and subjected to the solvent removal treatment was immersed (25 ° C. × 30 minutes) in a 5 wt% methanol aqueous solution. The catalyst paste was intermittently coated with a slot die on the resulting proton conductive membrane (surface facing the support) and dried to form a catalyst layer. Next, the support (PET) is peeled off, immersed again in the aqueous alcohol solution, and then a catalyst layer is formed on the proton conductive membrane (the surface facing the catalyst layer) by the same method, whereby a membrane electrode A joined body was produced. The alcohol content in the membrane after immersion in a methanol aqueous solution was 4% by weight as calculated by gas chromatography, and the water content was 25% by weight. The power generation performance was evaluated using the membrane electrode assembly thus prepared. The evaluation results are shown in Table 1.

[Comparative Example 1]
(Production of proton conducting membrane)
A 15 weight NMP / methanol (weight ratio: 67/33) solution of the sulfonated polyarylene (II) obtained in Synthesis Example 1 above was applied to a PET roll (thickness 0.125 mm, width 300 mm) with a coating width of 250 mm. Then, a proton reverse membrane having a film thickness of 40 μm was formed on PET by casting with a comma reverse coater, forming a film, drying, and removing the solvent by immersion in water.

(Preparation of catalyst paste)
The sulfonated polyarylene (II) obtained in Synthesis Example 1 is dissolved in a water / NMP (weight ratio: 20/80) mixed solution to prepare a polymer solution, and the weight of carbon black and platinum is added to the solution. A catalyst paste was prepared by adding platinum-supported carbon particles having a ratio of 50:50 (“TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and vapor-grown carbon fiber (“VGCF” manufactured by Showa Denko), and stirring and mixing.

(Production of membrane electrode assembly)
The catalyst paste was intermittently coated with a slot die on the proton conductive membrane (the surface facing the support) formed on the support (PET) and desolvated, and dried to form a catalyst layer. Next, the support (PET) was peeled off, and a catalyst layer was formed on the proton conductive membrane (the surface facing the catalyst layer) by the same method to produce a membrane electrode assembly. The power generation performance was evaluated using the membrane electrode assembly thus prepared. The evaluation results are shown in Table 1.

[Comparative Example 2]
(Production of proton conducting membrane)
A 15 weight NMP / methanol (weight ratio: 67/33) solution of the sulfonated polyarylene (II) obtained in Synthesis Example 1 above was applied to a PET roll (thickness 0.125 mm, width 300 mm) with a coating width of 250 mm. Then, a proton reverse membrane having a film thickness of 40 μm was formed on PET by casting with a comma reverse coater, forming a film, drying, and removing the solvent by immersion in water.

  After peeling off the support (PET), the proton conductive membrane was immersed in a 5% by weight aqueous methanol solution (25 ° C. × 30 minutes). The alcohol content in the membrane after immersion in a methanol aqueous solution was 4% by weight as calculated by gas chromatography, and the water content was 25% by weight.

(Preparation of catalyst paste)
The sulfonated polyarylene (II) obtained in Synthesis Example 1 is dissolved in a water / NMP (weight ratio: 20/80) mixed solution to prepare a polymer solution, and the weight of carbon black and platinum is added to the solution. A catalyst paste was prepared by adding platinum-supported carbon particles having a ratio of 50:50 (“TEC10E50E” manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and vapor-grown carbon fiber (“VGCF” manufactured by Showa Denko), and stirring and mixing.

(Preparation of catalyst electrode and membrane electrode assembly)
The catalyst paste was coated on carbon paper (manufactured by Toray) by bar coating and dried at 160 ° C. for 1 hour to form a catalyst electrode. It cut | disconnected to the predetermined dimension and hot-pressed in the form which pinched | interposed the said electrolyte membrane, and produced the membrane electrode assembly. Hot pressing was performed for 15 minutes under conditions of a temperature of 150 ° C. and a pressure of 100 kgf / cm ² . The power generation performance was evaluated using the membrane electrode assembly thus prepared. The evaluation results are shown in Table 1.

  As is apparent from Table 1, Examples 1 and 2 show power generation performance (high cell voltage) superior to that of Comparative Examples 1 and 2, and thus membrane electrode assemblies obtained by the production method of the present invention. It was confirmed that high power generation efficiency can be obtained by using. Further, in Examples 1 and 2, it was confirmed that long-term power generation reliability was obtained because there was no film thickness reduction around the electrode and there were very few property defects such as wrinkles.

Claims (11)

A step of immersing the aromatic polymer electrolyte membrane in a solvent;
Applying a catalyst paste containing an aromatic polymer electrolyte on the electrolyte membrane in a state where the solvent is contained in an amount of 20 to 60% by weight in the electrolyte membrane after the solvent immersion, and then drying. And a step of forming a catalyst layer by a method for producing a membrane electrode assembly. A step of forming a first catalyst layer by applying a catalyst paste containing an aromatic polymer electrolyte to one surface of the aromatic polymer electrolyte membrane and then drying;
Immersing the electrolyte membrane in which the first catalyst layer is formed in a solvent;
A catalyst containing an aromatic polymer electrolyte on the surface of the electrolyte membrane facing the first catalyst layer in a state where the solvent is contained in the range of 20 to 60% by weight in the electrolyte membrane after immersion in the solvent And a step of forming a second catalyst layer by applying and drying a paste.   Before forming the first catalyst layer, the aromatic polymer electrolyte membrane is immersed in a solvent, and the solvent is contained in the electrolyte membrane after the solvent immersion in a range of 20 to 60% by weight; The manufacturing method of the membrane electrode assembly of Claim 2 characterized by the above-mentioned.   The method for producing a membrane / electrode assembly according to any one of claims 1 to 3, wherein the solvent in which the electrolyte membrane is immersed is an aqueous alcohol solution having 6 or less carbon atoms.   The solvent for immersing the electrolyte membrane is an alcohol aqueous solution having 6 or less carbon atoms, and the alcohol content in the electrolyte membrane after immersion is 0.01 to 10% by weight. The manufacturing method of the membrane electrode assembly as described in 2.   The method for producing a membrane / electrode assembly according to any one of claims 1 to 3, wherein the solvent in which the electrolyte membrane is immersed is water.   The solvent for immersing the electrolyte membrane is water, and the moisture content of the electrolyte membrane after immersion is 20 to 60% by weight. The production of a membrane electrode assembly according to any one of claims 1 to 3 Method.   The method for producing a membrane / electrode assembly according to any one of claims 1 to 3, wherein the solvent in which the electrolyte membrane is immersed is an aqueous alcohol solution having 3 or less carbon atoms.   The solvent for immersing the electrolyte membrane is an alcohol aqueous solution having 3 or less carbon atoms, and the alcohol content in the electrolyte membrane after immersion is 0.01 to 10% by weight. A method for producing a membrane electrode assembly according to claim 1. The aromatic polymer electrolyte constituting the electrolyte membrane is composed of a sulfonated polyarylene containing a structural unit represented by the following general formula (A) and a structural unit represented by the following general formula (B). The manufacturing method of the membrane electrode assembly in any one of Claims 1-9 characterized by the above-mentioned.

[In the formula (A), Y represents —CO—, —SO ₂ —, —SO—, —CONH—, —COO—, —
(CF _{2) i} - _(i is an integer from 1 to 10.) Or -C (CF _{3) 2} - indicates,
Z is independently a direct bond, — (CH ₂ ) _j — (j represents an integer of 1 to 10), —C (CH ₃
) _2- , -O- or -S-
Ar is —SO ₃ H, —O (CH ₂ ) _p SO ₃ H or —O (CF ₂ ) _p SO ₃ H (p is 1 to 1).
An integer of 2 is shown. An aromatic group having a substituent represented by:
m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4. ]

[In the formula (B), A and D are each independently a direct bond, —CO—, —SO ₂ —, —SO
-, - CONH -, - COO -, - (CF 2) i -, (i is an integer of _{1~10.) - (CH 2)} j -, (j is an integer of 1 to 10.) —CR ′ ₂ — (R ′ is an aliphatic hydrocarbon group,
An aromatic hydrocarbon group or a halogenated hydrocarbon group is shown. ), Cyclohexylidene group, fluorenylidene group, -O- or -S-
B independently represents an oxygen atom or a sulfur atom;
R ^{1 to} R ¹⁶ each independently represent a hydrogen atom, a fluorine atom, an alkyl group, a halogenated alkyl group partially or wholly halogenated, an allyl group, an aryl group, a nitro group, or a nitrile group;
s and t each represent an integer of 0 to 4, and r represents 0 or an integer of 1 or more. ]   The aromatic polymer electrolyte that constitutes the electrolyte membrane and the aromatic polymer electrolyte that constitutes the catalyst paste are made of the same polymer. Manufacturing method of membrane electrode assembly.