JPWO2009104470A1 - Electrolyte membrane manufacturing method and electrolyte membrane - Google Patents

Abstract

Since the electrolyte containing a polymer having a sulfonic acid group in the molecule was insufficient in durability, the composition and the polymer with improved molecular structure of the monomer unit having an acidic group greatly improved the durability. Provides an improved electrolyte membrane. That is, a specific monomer containing an alicyclic hydrocarbon group and having at least one acidic group and / or salt thereof bonded as a substituent on the aliphatic ring of the alicyclic hydrocarbon group The electrolyte membrane is provided by polymerizing a composition containing at least one of the above.

Description

  The present invention relates to an electrolyte membrane manufacturing method and an electrolyte membrane, and the electrolyte membrane can be suitably used for electrochemical devices, particularly fuel cells, and more specifically, direct alcohol fuel cell applications. .

  A polymer electrolyte fuel cell (PEFC), which is a type of electrochemical device using a polymer electrolyte membrane, has excellent features such as low temperature operation, high output density, and low environmental impact. . Among them, PEFC, which is a methanol fuel, can be supplied as a liquid fuel in the same way as gasoline, and thus is considered promising as a power source for electric vehicles and a power source for portable devices.

  When using methanol as the fuel, PEFC is divided into a methanol reforming type that converts methanol into hydrogen-based gas using a reformer, and a direct methanol type that uses methanol directly without using a reformer (DMFC, It is divided into two types: Direct Methanol Polymer Fuel Cell). Since DMFC does not require a reformer, it has great advantages such as being able to reduce weight, and its practical use is expected.

  However, when an electrolyte membrane for DMFC is a perfluoroalkylsulfonic acid membrane which is an electrolyte membrane for PEFC using hydrogen as a fuel, for example, Nafion (registered trademark) membrane of Du Pont, etc., methanol is used. However, there is a problem that the electromotive force is lowered and the fuel efficiency is low. Furthermore, these electrolyte membranes also have an economic problem that they are very expensive.

  As means for solving the above problems, Patent Document 1 proposes an electrolyte membrane in which a porous base material that is not easily deformed by an external force is filled with a polymer having proton conductivity.

  In the PEFC or DMFC, water is generated from protons, oxygen molecules and electrons on the cathode side. However, it is widely known in the field of electrical science that the water generation route has a reaction via hydrogen peroxide in addition to the reaction that directly produces water molecules. Among these, in the case of passing through hydrogen peroxide, the hydrogen peroxide is decomposed into a hydroxyl radical inside the fuel cell, and the members constituting the battery are deteriorated. In particular, if the electrolyte used in the electrolyte membrane or electrode is a polymer composed of a hydrocarbon-based material, it is susceptible to oxidation by hydroxy radicals, and in order to improve the durability of the hydrocarbon-based electrolyte membrane, it is resistant to acid. It is important to improve the productivity.

  Patent Document 2 discloses an electrolyte membrane in which a polymer having proton conductivity is filled in pores of a porous base material that does not substantially swell with an organic solvent containing methanol and water. An electrolyte membrane has been proposed in which the polymer is a polymer derived from 2-acrylamido-2-methylpropanoic acid monomer.

  Furthermore, in Patent Document 3, instead of methylenebisacrylamide, which has been widely used as a crosslinking agent for polymers derived from 2-acrylamido-2-methylpropanoic acid and the like, a crosslinking agent such as ethylenebisacrylamide has been used. It has been proposed that the hydrolysis resistance of the polymer is greatly improved and the durability is improved.

On the other hand, Patent Document 4 describes an example of synthesizing monomers having various sulfonic acid groups from acrylonitrile, various alkenes and sulfuric acid, and also describes compounds having an aliphatic ring structure.
JP 2002-83612 A International Publication No. 2003/075385 Pamphlet International Publication No. 2006/004098 Pamphlet GB 1341104

However, since the electrolyte membrane described in Patent Document 1 includes a step of subjecting the base material to plasma irradiation and graft polymerization of the polymer, there is a problem of an increase in manufacturing equipment cost. In addition, the durability when continuously operating as a fuel cell was not sufficient. Further, the durability of the electrolyte membrane described in Patent Document 2 was also insufficient.
Moreover, in patent document 3, there is no change regarding the structure of the monomer which has an acidic group, and there was room for examination about the degradation mechanism based on the chemical decomposition | disassembly of the monomer unit which has an acidic group.
Furthermore, in Patent Document 4, a monomer that is industrially produced by the production method described in Patent Document 4 is substantially 2-acrylamide- for reasons such as ease of reaction and high yield. It has not been known that 2-methylpropanoic acid alone and a compound having an aliphatic ring structure are useful for applications requiring high durability such as fuel cell electrolyte membrane applications.
Thus, an electrolyte membrane including a polymer using 2-acrylamido-2-methylpropanoic acid monomer instead of the conventional perfluorosulfonic acid polymer has been proposed as an electrolyte membrane for DMFC. Sex was not enough.
The problem to be solved by the present invention is to provide an electrolyte membrane whose durability is greatly improved by improving the molecular structure of the monomer unit having an acidic group.

  The electrolyte membrane obtained by using the composition containing the monomer represented by the formula (1) is compared with the electrolyte membrane obtained by polymerizing 2-acrylamido-2-methylpropanesulfonic acid which has been conventionally used. It has been found that the durability is remarkably improved, and a (meth) acrylamide derivative having an aliphatic cyclic structure in one molecule and having two or more polymerizable functional groups, such as bisacryloylpiperazine, is used as a crosslinking agent. The inventors have found that the durability is further improved, and have completed the present invention.

  The electrolyte membrane obtained by polymerizing the composition according to the present invention has high proton conductivity and excellent methanol permeation prevention performance, and also has high oxidation resistance.

（式（１）において、Ｒ¹は水素原子またはメチル基を表し、Ａは脂環炭化水素基であり、かつ前記脂環炭化水素基の脂肪族環上に、少なくとも１個以上の酸性基および／またはその塩が置換基として結合している基を表す。）Hereinafter, the present invention will be described in detail.
The composition of the present invention is a composition containing at least one monomer represented by the formula (1), and the electrolyte membrane of the present invention is obtained by polymerizing the composition.

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, A is an alicyclic hydrocarbon group, and at least one acidic group on the aliphatic ring of the alicyclic hydrocarbon group and // represents a group to which a salt thereof is bonded as a substituent.)

The method for producing an electrolyte membrane of the present invention includes a step of polymerizing a composition containing at least one monomer represented by the formula (1).
Moreover, it is preferable that the manufacturing method of the electrolyte membrane of this invention further includes the process of preparing the monomer shown by said Formula (1).

（式（２）において、Ｒ¹、Ｒ²、および、Ｒ³はそれぞれ独立に、水素原子またはメチル基を表し、Ｘは水素原子または金属原子を表し、ＹおよびＺはそれぞれ独立に、カルボキシル基、スルホン酸基、および、これらの塩、並びに、エステル残基よりなる群から選択された基を表し、ＹとＺとはいずれか一方またはその両方が存在しない場合もある。）Examples of the monomer represented by the formula (1) constituting the composition of the present invention include a monomer represented by the formula (2). Specific examples thereof include 2-acrylamidocyclohexanesulfonic acid, 2- Methacrylamidocyclohexanesulfonic acid, 2-acrylamido-4-carboxycyclohexanesulfonic acid, 2-acrylamido-4,5-carboxycyclohexanesulfonic acid, 2-methacrylamideamido-4-carboxycyclohexanesulfonic acid, 2-methacrylamideamido-4,5 -Carboxycyclohexanesulfonic acid, 2-acrylamido-1-methylcyclohexanesulfonic acid, 2-acrylamido-2-methylcyclohexanesulfonic acid, 2-acrylamido-4-methoxycarbonylcyclohexanesulfonic acid, 2-acrylamido-4-meth Shi-5- carboxy cyclohexane sulfonic acid, and, salts thereof, and the like.

(In the formula (2), R ¹ , R ² and R ³ each independently represents a hydrogen atom or a methyl group, X represents a hydrogen atom or a metal atom, and Y and Z each independently represent a carboxyl group. , A sulfonic acid group, and a salt thereof, and a group selected from the group consisting of ester residues, and either Y or Z or both of them may not exist.)

A in the monomer represented by the formula (1) is preferably an alicyclic hydrocarbon group in which at least one sulfonic acid group or a salt thereof is substituted on the aliphatic ring, and the sulfonic acid group or its More preferably, the salt is a cyclohexyl group substituted with at least one.
On the aliphatic ring of the alicyclic hydrocarbon group in A, there may be a substituent other than the acidic group and / or its salt, for example, an ester residue.
The number of acidic groups and / or salts thereof on the aliphatic ring of the alicyclic hydrocarbon group in A is 1 or more, preferably 1 to 5, and preferably 1 to 3. Is more preferable.
In addition, the monomer represented by the formula (2) may have both Y and Z, may have only one of them, or may not have both. Preferably not.

  It is preferable that content of the monomer shown by Formula (1) in the said composition is the range of 20-99 mass% with respect to all the monomers contained in a composition.

<Copolymerization component of monomer represented by formula (1)>
The composition of the present invention may contain at least one monomer represented by the formula (1) and, if necessary, a monomer having an ethylenic double bond in the molecule as a copolymerization component. it can. Moreover, it is preferable that it is 1-5 types, and, as for the monomer shown by Formula (1) contained in the composition of this invention, it is more preferable that it is 1-3 types.
The monomer is not particularly limited as long as it can be copolymerized with the monomer represented by the formula (1). For example, 2-acrylamide- which is conventionally known as a sulfonic acid monomer Examples include 2-methylpropanesulfonic acid, styrenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, isoprenesulfonic acid, vinylsulfonic acid, and salts thereof.
In addition, as the water-soluble monomer, acidic monomers such as (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinylphosphonic acid, acidic phosphoric acid group-containing (meth) acrylate, Salt thereof; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, N -Monomers such as vinylpyrrolidone and N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and the like Of basic monomers and their quaternized compounds Mention may be made of the manner.
Also, for the purpose of adjusting the water absorption of the polymer, etc., acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, etc., and hydrophobic hydrophobic monomers such as vinyl acetate and vinyl propionate The body can also be used.
“(Meth) acrylate” means “acrylate and / or methacrylate”. The same applies to (meth) acrylic acid, (meth) acrylamide, and (maleic anhydride).

  Of the above copolymerization components, (meth) acrylic acid is preferable because it has the effect of improving the oxidation resistance of the polymer and thus has the effect of increasing the durability of the electrolyte membrane. Since (meth) acrylic acid has a carboxyl group, it contributes to proton conductivity in the polymer together with the component of formula (1), but its ionization degree is lower than that of the sulfonic acid group. It is good to contain in the range of 50 mass% or less. (Meth) acrylic acid is preferably used in the range of 2 to 50% by mass of the total monomers contained in the composition.

（式（３）において、Ｒ⁴およびＲ⁵はそれぞれ独立に、水素原子またはメチル基を表し、Ｒ⁶は炭素数２〜１０のアルキレン基を表し、Ｒ⁷およびＲ⁸はそれぞれ独立に、水素原子またはＲ⁷とＲ⁸とが結合して２つの窒素原子を連結する炭素数２〜４のアルキレン基を表す。）<Crosslinking component>
By including a crosslinking component in the composition of the present invention, a crosslinked structure can be introduced into a polymer obtained by polymerizing the composition. As the crosslinking component, it is preferable to use a monomer containing two or more ethylenic double bonds in one molecule because a crosslinked structure can be easily introduced. Moreover, it is preferable that it is 1-3 types, and, as for the monomer which contains 2 or more of ethylenic double bonds in 1 molecule contained in the composition of this invention, it is more preferable that it is 1 type. Further, the number of ethylenic double bonds in the monomer containing two or more ethylenic double bonds in one molecule is preferably 2 to 10, more preferably 2 to 6. More preferably, it is two.
As a monomer containing two or more ethylenic double bonds in one molecule, polyfunctional (meth) acrylamides having two or more functional groups are particularly copolymerizable with the monomer represented by the formula (1). This is preferable because the composition ratio of the monomer and the cross-linking component is easily adjusted widely.
Among these, the compound represented by the formula (3) can be particularly preferably used. Specific examples thereof include N, N′-ethylenebis (meth) acrylamide, N, N′-propylenebis (meth) acrylamide, N, N′-butylenebis (meth) acrylamide, and 1,4 di (meth) acrylamide cyclohexane. N, N′-bis (meth) acrylamide piperazine and the like.

(In Formula (3), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 2 to 10 carbon atoms, and R ⁷ and R ⁸ each independently represent hydrogen. And represents an alkylene group having 2 to 4 carbon atoms in which R ⁷ and R ⁸ are bonded to connect two nitrogen atoms.)

  Among these specific examples, N, N′-ethylenebis (meth) acrylamide and N, N′-bis (meth) acrylamide piperazine are highly water-soluble and can be represented by the formula (1) without using an organic solvent. It is preferable because the monomer shown can be dissolved in dissolved water. Further, N, N′-bis (meth) acrylamide piperazine can be combined with the monomer represented by the formula (1) to obtain a crosslinked polymer having extremely high oxidation resistance. Therefore, the electrolyte membrane of the present invention can be obtained. This is particularly preferable for increasing the durability.

  As the crosslinking component, in addition to the polyfunctional (meth) acrylamide compound, for example, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane diallyl ether, Pentaerythritol triallyl ether, divinylbenzene, bisphenol diacrylate, isocyanuric acid diacrylate, tetraallyloxye Emissions, triallylamine, triallyl cyanurate, triallyl isocyanurate, can diallyloxyacetic acid salts and preferably used.

  Of these, triallylamine, triallyl cyanurate, and triallyl isocyanurate are preferred because they can improve the hydrolysis resistance of the polymer when used as a crosslinking component. The preferable addition amount in that case is 0.5 mass% or more and 10 mass% or less in the whole composition.

Besides the polyfunctional monomer copolymerizable with the monomer represented by the formula (1) as a crosslinking component as described above, a known method can be used for the composition of the present invention. .
Specifically, a method using a crosslinking agent having two or more groups in the molecule that react with a functional group in a polymer such as a carboxyl group, a method using self-crosslinking by a hydrogen abstraction reaction during polymerization, Examples include a method of irradiating the polymer with active energy rays such as ultraviolet rays, electron beams, and gamma rays.
A method of copolymerizing a water-soluble monomer having a functional group capable of forming a crosslinked structure is also preferred from the viewpoint of easily increasing the crosslinking density. Examples of such compounds include N-methylol acrylamide, N-methoxymethyl acrylamide, N-butoxymethyl acrylamide, and the like. After radical polymerization of a polymerizable double bond, heating is performed to cause a condensation reaction. It is possible to cause the same crosslinking reaction by crosslinking or heating simultaneously with radical polymerization. These cross-linking agents can be used alone or in combination of two or more as required.

  The content of the monomer containing two or more ethylenic double bonds in one molecule in the composition is in the range of 1 to 50% by mass with respect to the total monomers contained in the composition. Preferably, it is 5-40 mass%.

<Polymerization method>
As a method used when polymerizing the composition of the present invention, a known aqueous radical polymerization technique can be used. Specific examples include redox-initiated polymerization, heat-initiated polymerization, electron beam-initiated polymerization, and photoinitiated polymerization such as ultraviolet rays.
Examples of the radical polymerization initiator for heat-initiated polymerization and redox-initiated polymerization include the following. Azo compounds such as 2,2′-azobis (2-amidinopropane) dihydrochloride; ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl peroxide, cumene hydroperoxide, di-t-butylperoxide A peroxide such as oxide; a redox initiator in which the above-mentioned peroxide is combined with a reducing agent such as sulfite, bisulfite, thiosulfate, formamidinesulfinic acid, ascorbic acid; or 2,2′-azobis -Azo radical polymerization initiators such as (2-amidinopropane) dihydrochloride and azobiscyanovaleric acid. These radical polymerization initiators may be used alone or in combination of two or more.
Among these, the peroxide radical polymerization initiator can generate radicals by extracting hydrogen from carbon-hydrogen bonds, and therefore when used in combination with an organic material such as polyolefin as a porous substrate, the surface of the substrate and the filling weight are reduced. It is preferable because a chemical bond can be formed with the coalescence.

Among the radical polymerization initiating means, photoinitiated polymerization by ultraviolet rays is desirable in that the polymerization reaction is easily controlled and a desired electrolyte membrane can be obtained with a relatively simple process and high productivity. In the case of further photoinitiating polymerization, the radical photopolymerization initiator is more preferably dissolved or dispersed in advance in the polymer precursor, its solution or dispersion.
Examples of the radical photopolymerization initiator include benzoin, benzyl, acetophenone, benzophenone, quinone, thioxanthone, thioacridone, and derivatives thereof that are generally used for ultraviolet polymerization. Examples of such derivatives include benzoin-based benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; acetophenone-based diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1- ON, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) Butanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one ; As benzophenone, o-benzoyl Methyl perfate, 4-phenylbenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-Benzoyl-N, N-dimethyl-N- [2- (1-oxy-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium chloride, 4,4′-dimethylamino Examples include benzophenone and 4,4′-diethylaminobenzophenone.

The amount of these photopolymerization initiators used is preferably 0.001 to 1% by mass, more preferably 0.001 to 0.5% by mass, based on the total mass of unsaturated monomers in the polymer precursor. Particularly preferably, it is 0.01 to 0.5% by mass. In this range, the amount of unreacted monomers is small and the crosslink density of the polymer is sufficiently high, so that the durability of the polymer is increased, and This is preferable because the durability of the electrolyte membrane is improved.
Of these, aromatic ketone radical polymerization initiators such as benzophenone, thioxanthone, quinone, and thioacridone can generate radicals by extracting hydrogen from carbon-hydrogen bonds, so that organic materials such as polyolefins can be used as porous substrates. When used together, it is preferable because a chemical bond can be formed between the substrate surface and the filled polymer.

As light irradiation conditions in the case of polymerization using light such as ultraviolet rays, 10 to 5000 mJ / cm ² is preferable in the case of ultraviolet irradiation. The compound containing a (meth) acrylamide group represented by the formula (1) is particularly polymerizable among radical polymerizable compounds, and an initiator is added by increasing the amount of energy applied even in the case of polymerization by heating or ultraviolet rays. It is possible to polymerize without it.

<Combination with porous substrate>
What filled the resin obtained by superposing | polymerizing the composition of this invention inside the void | hole of a porous base material can be preferably utilized as an electrolyte membrane. The porous substrate used in the present invention is preferably a material that does not substantially swell with respect to methanol and water, and it is particularly preferable that there is little or almost no change in area when wetted with water compared to when dried.
Although the area increase rate varies depending on the immersion time and temperature, in the present invention, the area increase rate when immersed in deionized water at 25 ° C. for 1 hour is preferably 20% or less at the maximum compared to the time of drying. .

  The porous substrate used in the present invention preferably has a tensile modulus of 500 to 5000 MPa, more preferably 1000 to 5000 MPa, and preferably has a breaking strength of 50 to 500 MPa, more preferably 100. ~ 500 MPa. Within this range, the polymer does not deform due to the force of the filled polymer being swollen by methanol or water, and the base material that is too stiff becomes brittle and is pressed during electrode bonding or tightened when assembled into a battery. It is preferable because it does not cause cracks due to the like.

Further, the porous substrate is preferably one having heat resistance against the temperature at which the fuel cell is operated, and one that does not easily extend even when an external force is applied.
Examples of materials having such properties include glass, ceramics such as alumina or silica, and the like. Examples of organic materials include engineering plastics such as aromatic polyimides, polyolefins that have been made difficult to be deformed such as being stretched against external forces by methods such as radiation irradiation and crosslinking or stretching by adding a crosslinking agent. It is done. These materials may be used alone or in combination by stacking two or more of them.

  Among these porous base materials, those made of stretched polyolefin, cross-linked polyolefin, cross-linked polyolefin after stretching, and polyimides are preferable from the viewpoint of good workability in the filling step and easy availability of the base material. Among polyolefins, those mainly composed of polyethylene are excellent in terms of hydrophobicity, chemical stability, and availability. Moreover, it is preferable that the porous substrate has at least a through hole penetrating the upper and lower surfaces.

As the porosity of the porous base material used in the present invention is larger, the amount of proton acidic groups, which are proton conductive groups per area, increases, so for example, when used in a fuel cell, the output is higher, while the smaller one is This is preferable because the film strength tends to be high. Accordingly, the porosity is preferably 5 to 95% by volume, more preferably 5 to 90% by volume, and particularly preferably 20 to 80% by volume. Moreover, it is preferable that an average hole diameter exists in the range of 0.001-100 micrometers, More preferably, it is the range of 0.01-1 micrometer.
The porous substrate is preferably in the form of a film.
Further, the thicker the substrate, the better the film strength and the lower the amount of methanol permeated, whereas the thinner the substrate, the smaller the membrane resistance as the electrolyte membrane, and the more preferable. Accordingly, the preferable film thickness is 200 μm or less, more preferably 1 to 150 μm, still more preferably 5 to 100 μm, and particularly preferably 5 to 50 μm.

  There is no particular limitation on the method for filling the crosslinked electrolyte polymer in the pores of the porous substrate, and a known method can be used. Examples thereof include a method in which a porous substrate is impregnated with the composition or polymer precursor of the present invention and / or a solution or dispersion thereof, and then the composition or polymer precursor is polymerized or crosslinked. At that time, the impregnated mixed solution may contain a crosslinking agent, a polymerization initiator, a catalyst, a curing agent, a surfactant, and the like, if necessary.

When the composition or polymer precursor impregnated in the pores of the porous substrate has a low viscosity, it can be used for impregnation as it is, but in other cases, it is preferably a solution or a dispersion. In particular, a solution with a concentration of 10 to 90% by mass is preferable, and a solution with a concentration of 20 to 70% by mass is more preferable.
In addition, if the components used are insoluble in water, some or all of the water may be replaced with an organic solvent, but when using an organic solvent, remove all the organic solvent before joining the electrodes. An aqueous solution is preferred because it is necessary. The reason for impregnation in the form of a solution is that it is easy to impregnate a porous substrate having pores when dissolved in water or a solvent and used for impregnation.
Further, for the purpose of facilitating the impregnation operation, hydrophilic treatment of the porous substrate, addition of a surfactant to the polymer precursor solution, or ultrasonic irradiation during the impregnation can be performed.

  In addition, it is preferable that a crosslinked electrolyte polymer having proton conductivity is chemically bonded to the surface of the porous substrate, particularly the inner surface of the pores. As a means for forming the bond, a polymer precursor to be filled is used. Is a radical polymerizable substance, the surface of the substrate is preliminarily generated when the substrate is polymerized by generating radicals on the surface by irradiating the substrate with plasma, ultraviolet rays, electron beams, gamma rays, corona discharge, etc. A method of causing graft polymerization to occur simultaneously, a method of causing graft polymerization to the surface of the substrate and polymerization of the polymer precursor simultaneously by irradiating an electron beam after filling the substrate with the polymer precursor, hydrogen A method of causing graft polymerization onto the substrate surface and polymerization of the polymer precursor simultaneously by blending and filling a pull-out type radical polymerization initiator into the polymer precursor, heating or irradiating with ultraviolet rays, A method using a coupling agent and the like. These may be performed alone or a plurality of methods may be used in combination.

  The electrolyte membrane of the present invention can be obtained by polymerizing the monomer represented by the formula (1), and the obtained electrolyte membrane has excellent oxidation resistance. Further, when the compound represented by the formula (3) is used in combination as a crosslinking agent, or (meth) acrylic acid is used in combination as a copolymerizable component, the oxidation resistance is further improved. Furthermore, an electrolyte membrane having a structure in which an electrolyte polymer obtained from these monomers and a crosslinking agent is impregnated into the pores of the porous substrate has a reduced methanol permeability. As a result, the present electrolyte membrane becomes an electrolyte membrane that is excellent in durability and can suppress the permeation of methanol, and is suitable for use in electrochemical devices such as DMFC.

（式（１’）において、Ｒ¹は水素原子またはメチル基を表し、Ａは脂環炭化水素基であり、かつ前記脂環炭化水素基の脂肪族環上に、少なくとも１個以上の酸性基および／またはその塩が置換基として結合している基を表す。）The electrolyte membrane of the present invention includes a resin having at least a monomer unit represented by the formula (1 ′).

(In the formula (1 ′), R ¹ represents a hydrogen atom or a methyl group, A is an alicyclic hydrocarbon group, and at least one acidic group on the aliphatic ring of the alicyclic hydrocarbon group. And / or a group to which a salt thereof is bonded as a substituent.)

R ¹ and A in the formula (1 ') has the same meaning as R ¹ and A in the formula (1), and the preferred scopes are also same.

（式（２’）において、Ｒ¹、Ｒ²、および、Ｒ³はそれぞれ独立に、水素原子またはメチル基を表し、Ｘは水素原子または金属原子を表し、ＹおよびＺはそれぞれ独立に、カルボキシル基、スルホン酸基、および、これらの塩、並びに、エステル残基よりなる群から選択された基を表し、ＹとＺとはいずれか一方またはその両方が存在しない場合もある。）In addition, the electrolyte membrane of the present invention preferably includes a monomer unit represented by the formula (2 ′) as the monomer unit represented by the formula (1 ′), and the monomer unit represented by the formula (1 ′) is represented by the formula (1 ′). The monomer unit represented by 2 ′) is more preferable.

(In the formula (2 ′), R ¹ , R ² and R ³ each independently represents a hydrogen atom or a methyl group, X represents a hydrogen atom or a metal atom, and Y and Z each independently represent a carboxyl group. Represents a group selected from the group consisting of a group, a sulfonic acid group, a salt thereof, and an ester residue, and one or both of Y and Z may not be present.)

R ^1, R ^2, R ³ in the formula (2 '), X, Y and Z, the R ¹ in the formula ^{(2), R 2, R} 3, X, have the same meaning as Y and Z, it is also preferred The range is the same.
The resin preferably has 1 to 5 monomer units represented by the formula (1 ′), more preferably 1 to 3 types.
It is preferable that content of the monomer unit shown by Formula (1) in the said resin is the range of 20-99 mass% with respect to all the monomer units of the said resin.

（式（３’）において、Ｒ⁴およびＲ⁵はそれぞれ独立に、水素原子またはメチル基を表し、Ｒ⁶は炭素数２〜１０のアルキレン基を表し、Ｒ⁷およびＲ⁸はそれぞれ独立に、水素原子またはＲ⁷とＲ⁸とが結合して２つの窒素原子を連結する炭素数２〜４のアルキレン基を表す。）The electrolyte membrane of the present invention preferably contains a resin having at least a monomer unit represented by the formula (1 ′) and a crosslinked structure.
The cross-linked structure preferably contains a monomer unit derived from a monomer containing two or more ethylenic double bonds in one molecule, and is a monomer derived from the bifunctional or higher polyfunctional (meth) acrylamides. It is more preferable to include a unit, and it is further preferable to include a monomer unit represented by the formula (3 ′).

(In Formula (3 ′), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 2 to 10 carbon atoms, and R ⁷ and R ⁸ each independently represent This represents a hydrogen atom or an alkylene group having 2 to 4 carbon atoms in which R ⁷ and R ⁸ are bonded to connect two nitrogen atoms.

^{R 4, R 5, R 6} , R 7 and R ⁸ in the formula (3 ') has the same meaning as ^{R 4, R 5, R 6} , R 7 and R ⁸ in the formula (3), it is also preferred The range is the same.
The number of monomer units derived from a monomer containing two or more ethylenic double bonds in one molecule in the resin is preferably 1 to 3, and more preferably 1 type.
The content of the monomer unit derived from containing two or more ethylenic double bonds in one molecule in the resin is preferably in the range of 1 to 50% by mass with respect to the total monomer units of the resin. More preferably, it is -40 mass%.

（式（４’）において、Ｒ⁹は水素原子またはメチル基を表す。）Moreover, it is preferable that the said resin further contains the monomer unit shown by Formula (4 '). The content of the monomer unit represented by the formula (4 ′) in the resin is preferably 2 to 50% by mass with respect to the total monomer units of the resin.

(In the formula (4 ′), R ⁹ represents a hydrogen atom or a methyl group.)

The electrolyte membrane of the present invention is preferably one in which a resin having at least a monomer unit represented by the formula (1 ′) is filled in the pores of a porous substrate such as a porous membrane.
As the porous substrate that can be used in the electrolyte membrane of the present invention, the porous substrate described above can be suitably used.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, the scope of the present invention is not limited by these examples. Moreover, the part in an Example and a comparative example shall mean a mass part unless there is particular notice. The proton conductivity, methanol permeability, and durability (forced deterioration test) of the obtained electrolyte membrane were evaluated as follows.

1. Evaluation Method for Electrolyte Membranes Produced in Examples and Comparative Examples <Proton Conductivity>
The proton conductivity of the swollen sample at 25 ° C. was measured. An electrolyte membrane that was swollen in deionized water for 1 hour was sandwiched between two platinum plates to obtain a measurement sample. Thereafter, AC impedance measurement from 100 Hz to 40 MHz was performed, and the conductivity of the sample was measured to obtain proton conductivity. The higher the proton conductivity, the easier it is for protons to move through the electrolyte membrane, indicating better fuel cell applications.

<Methanol permeability>
The methanol penetration experiment at 25 ° C. was performed as follows. The electrolyte membrane was sandwiched between glass cells, 10% by mass aqueous methanol solution was placed in one cell, and deionized water was placed in the other cell. The amount of methanol penetrating into the deionized water side was measured over time by gas chromatographic analysis, and the permeation coefficient at the steady state was measured to obtain the methanol permeation flux. The lower the permeation flux, the more difficult methanol permeates through the electrolyte membrane, indicating that it is suitable for fuel cell applications.

<Durability (Forced deterioration test)>
Durability was evaluated by forced degradation using a Fenton reagent instead of confirming the degradation phenomenon of the polymer by hydrogen peroxide generated in the battery. A mixed aqueous solution of 3.5% by mass of hydrogen peroxide and 0.01% by mass of iron (II) sulfate heptahydrate is called a Fenton reagent. An electrolyte membrane cut out to an area of 12 cm ² is immersed in 30 ml of Fenton reagent, stirred for a predetermined time at 25 ° C., and the taken-out membrane is washed three times with 1 mol / liter hydrochloric acid to remove iron. Further, it was washed twice with deionized water. The test pieces before and after the test were vacuum-dried at 70 ° C. for 3 hours, and the dry mass was measured. On the other hand, when preparing the electrolyte membrane, the mass filling rate of the polymer of the present invention with respect to the base material was obtained in advance. Since the polyethylene porous substrate has almost no mass change with respect to the Fenton reagent, the mass reduction rate of the filled polymer in the electrolyte membrane is compared by comparing the mass of the membrane before and after the Fenton test minus the mass of the substrate. Asked. It shows that durability is so high that a mass reduction rate is small, and it deteriorates easily, so that it is large.

2. Synthesis of compounds that are difficult to obtain among the reagents used in Examples and Comparative Examples (Synthesis Example 1)
A four-necked flask equipped with a stirrer was charged with 150 ml of acrylonitrile and cooled to −30 ° C. or lower in a dry ice methanol bath. While stirring the inside of the flask, 24.5 g of 97% chlorosulfuric acid was added dropwise. Next, 32 ml of cyclohexene was added dropwise. After completion of the dropwise addition, the temperature was gradually raised, and when the temperature reached 0 ° C., 300 ml of toluene was added, and the temperature was further raised to room temperature and stirring was continued until crystals were precipitated. After crystal precipitation, the four-necked flask was cooled in an ice bath, and the precipitated crystals were filtered. The crystals separated by filtration were washed with toluene to obtain a compound having a structure in which hydrochloric acid was added to the target compound (formula (4)).
Next, 17 g of the above crystals were charged into an eggplant-shaped flask, dissolved in 200 ml of distilled water, and 13.5 g of sodium carbonate was added while being careful of foaming. A stirring bar was placed in the flask, a condenser tube was attached, and the mixture was stirred at 95 ° C. for 1 hour. The content was concentrated under reduced pressure, methanol was added to dissolve, the insoluble matter was filtered, and then the steps of concentration, dissolution in methanol and filtration were repeated twice, and the filtrate was concentrated. Finally, recrystallization was performed with methanol, and the obtained crystals were dried. The yield was 14% across the two reactions. It was confirmed by NMR that it was a sodium salt of 2-acrylamidocyclohexanesulfonic acid represented by formula (4).

（式（５）において、ＸはＮａまたはメチル基を表す）(Synthesis Example 2)
A four-necked flask equipped with a stirrer and a cooling device was charged with 130 ml of acrylonitrile and cooled to −30 ° C. or lower in a dry ice methanol bath. While stirring the flask, 24.5 g of chlorosulfuric acid was added dropwise. Next, 30 ml of methyl 3-cyclohexene-1-carboxylate was added dropwise. After the dropping was completed, the temperature was gradually raised, and the temperature was raised to room temperature, followed by stirring for 3 hours. Next, the temperature was raised to 50 ° C., stirred for 2 hours, and cooled in an ice bath. Stirring was continued until crystals precipitated. After the crystals were precipitated, the four-necked flask was cooled in an ice bath, and 500 ml of toluene was added to precipitate pale yellow crystals. The crystals were filtered, washed with toluene, and dried under reduced pressure to obtain a compound having a structure in which hydrochloric acid was added to the target compound (formula (5)).
Next, 31 g of the above crystals were charged into an eggplant-shaped flask, dissolved in 150 ml of distilled water, and 20 g of sodium carbonate was added while being careful of foaming. A stirring bar was placed in the flask, a condenser tube was attached, and the mixture was stirred at 95 ° C. for 1 hour. The content was concentrated under reduced pressure, methanol was added to filter insoluble matters, and the steps of concentration, dissolution in methanol and filtration were repeated twice, and the filtrate was concentrated. Finally, recrystallization was performed with ethanol, and the obtained crystals were dried. The yield for all two reactions was 29%. It is confirmed by NMR spectrum that the mixture is a 7: 3 mixture of disodium salt of 2-acrylamido-4-carboxycyclohexanesulfonic acid represented by formula (5) and sodium salt of 2-acrylamido-4-methylcarboxycyclohexanesulfonic acid. did.

(In formula (5), X represents Na or a methyl group)

(Synthesis Example 3)
A four-necked flask equipped with a stirrer was charged with 130 ml of acrylonitrile and cooled to −30 ° C. or lower in a dry ice methanol bath under a nitrogen atmosphere. While stirring the inside of the flask, 24.5 g of 97% chlorosulfuric acid was added dropwise. Next, 32 g of 4-cyclohexene-1,2-dicarboxylic anhydride was added little by little with stirring, and the temperature was gradually raised to room temperature. After stirring at room temperature for 18 hours, the precipitated crystals were filtered. The crystal separated by filtration was washed with toluene to obtain a compound having a structure in which hydrochloric acid was added to the target compound (formula (6)).
Next, 33 g of the above crystals were charged into an eggplant-shaped flask, dissolved in 150 ml of distilled water, and 21 g of sodium carbonate was added while being careful of foaming. A stirring bar was placed in the flask, a condenser tube was attached, and the mixture was stirred at 95 ° C. for 1 hour. The contents were concentrated under reduced pressure, methanol was added and the insoluble matter was collected by filtration. Next, 60 ml of distilled water was added to the obtained insoluble matter and dissolved by heating, followed by methanol concentration, dissolution in methanol, and filtration. The filtrate was concentrated repeatedly. Finally, recrystallization was performed with methanol, and the obtained crystals were dried. The yield for the entire two reactions was 37%. It was confirmed by NMR that it was a trisodium salt of 2-acrylamide-4,5-carboxycyclohexanesulfonic acid represented by formula (6).

(Synthesis Example 4)
A four-necked flask equipped with a stirrer was charged with 360 ml of acrylonitrile and cooled to −30 ° C. or lower in a dry ice methanol bath. While stirring the flask, a mixed solution of 57.0 g of 30% fuming sulfuric acid and 29.3 g of 98% concentrated sulfuric acid was added dropwise. Next, a mixed solution of 76.9 g of 1-methylcyclohexene and 64 g of acrylonitrile was dropped. After completion of the dropwise addition, the temperature was gradually raised and stirring was continued at 40 ° C. for 3 hours to precipitate crystals. The four-necked flask was cooled in an ice bath and the crystals were filtered. The filtered crystal was washed with acetonitrile to obtain the target compound (formula (7)). The yield was 41%. It was confirmed by NMR that it was 2-acrylamido-2-methylcyclohexanesulfonic acid represented by formula (7).

(Synthesis Example 5)
A mixed solution of 200 g of acetonitrile and 90 g of acrylic acid chloride was charged into a four-necked flask and stirred while being kept at 5 ° C. or lower in an ice bath. A mixture of 400 g of acetonitrile and 39.2 g of piperazine was added dropwise thereto while keeping the mixture in the flask at 4 ° C. or lower. After completion of dropping, the ice bath was removed and the mixture was stirred at room temperature for 5 hours. The temperature was raised to 60 ° C. and the mixture was stirred for 2 hours. The precipitate formed in the reaction solution was removed by filtration, and the filtrate was concentrated to precipitate crystals. This was filtered, washed with ice-cooled acetonitrile and dried to obtain N, N′-bisacryloylpiperazine. The yield was 21%.

(Comparative Synthesis Example 1)
A four-necked flask equipped with a stirrer was charged with 660 ml of acrylonitrile and cooled to −30 ° C. or lower in a dry ice methanol bath. While stirring the flask, 108 g of 98% sulfuric acid was added dropwise. Next, 84 ml of 2,3-dimethyl-1-butene was added dropwise. After completion of the dropwise addition, the temperature was gradually raised, and the temperature was raised to 40 ° C. and stirring was continued until crystals were precipitated. After crystal precipitation, the four-necked flask was cooled in an ice bath and the crystals were filtered. The crystals separated by filtration were washed with acrylonitrile and dried at 50 ° C. under reduced pressure. When the obtained crystal was dried, the yield was 12%. It was confirmed by NMR spectrum that it was 2-acrylamide-2,3-dimethylbutanesulfonic acid represented by formula (8).

(Comparative Synthesis Example 2)
Synthesis of aromatic compound In a four-necked flask equipped with a stirrer, 44 ml of 20% aqueous sodium hydroxide solution, 50 ml of dimethylformamide and 17.3 g of sodium 4-aminobenzenesulfonate were dissolved with stirring, and ice added with sodium chloride was added. Cooled below 4 ° C. in a bath. While stirring the flask, 10 g of acrylic acid chloride was added dropwise. After completion of the dropping, stirring was continued for 2 hours. After the reaction solution was concentrated, methanol was added to precipitate sodium chloride, which was removed by filtration. This was further concentrated and dissolved in methanol to remove sodium chloride, and the obtained filtrate was concentrated to dry the crystals. The yield was 64%. It was confirmed by NMR spectrum that it was sodium 4-acrylamidobenzenesulfonate represented by formula (9).

3. Preparation of electrolyte membranes according to examples and comparative examples

Example 1
A polyethylene film (thickness 30 μm, porosity 40%) was used as the porous substrate. 98.5 parts by mass of sodium 2-acrylamidocyclohexanesulfonate synthesized in Synthesis Example 1 (Comparative Example 1 was compared with the ratio of monomer / crosslinking component having sulfonic acid and ionic conductivity in comparison with Comparative Example 1). The acid-containing monomer was adjusted to 90 parts by mass when the sulfonic acid group was ion-exchanged to form a hydrogen type), and 10 parts by mass of N, N′-ethylenebisacrylamide as a crosslinking agent, nonion An aqueous monomer solution comprising 0.5 parts by weight of a surfactant, 0.1 parts by weight of an ultraviolet radical polymerization initiator 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 100 parts by weight of water. After immersing the porous substrate and confirming that the monomer aqueous solution was sufficiently impregnated and the membrane became transparent, the membrane was taken out from the solution and quickly sandwiched between PET films. Next, ultraviolet rays were irradiated for 2 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores, and then the PET film was peeled off to obtain an Na-type electrolyte membrane. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

(Example 2)
In Example 1, except that sodium 2-acrylamidocyclohexanesulfonate is 76.6 parts by mass (when it is ion-exchanged to be 70 parts by mass), N, N'-ethylenebisacrylamide is 30 parts by mass. In the same manner as in Example 1, an electrolyte membrane was obtained. Table 1 shows the evaluation results of the obtained film.

(Example 3)
40.5 parts by mass of the compound represented by formula (5) synthesized in Synthesis Example 2 (35 parts by mass when ion-exchanged to form hydrogen), 35 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid , 30 parts by mass of N, N′-ethylenebisacrylamide as a crosslinking agent, 0.5 parts by mass of a nonionic surfactant, 0.1 parts by mass of 2-hydroxy-2-methyl-1-phenylpropan-1-one, water The same porous substrate used in Example 1 was immersed in an aqueous monomer solution consisting of 200 parts by mass, and the solution was confirmed after the aqueous monomer solution was sufficiently impregnated and the membrane became transparent. The film was taken out of the film and quickly sandwiched between PET films. Subsequently, ultraviolet rays were irradiated for 3 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores, and then the PET film was peeled off. The process of immersion in the monomer aqueous solution and ultraviolet irradiation was repeated twice to obtain a Na type electrolyte membrane. In this example, when the compound represented by the formula (5) was added, the solubility of N, N′-ethylenebisacrylamide in water was lowered, so that more water was used than in Example 1 and the monomer concentration was lowered. In order to compensate for this, the procedure from filling to polymerization was repeated three times. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

Example 4
42.2 parts by mass of the compound represented by formula (6) synthesized in Synthesis Example 3 (35 parts by mass when ion-exchanged to form hydrogen), 35 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid N, N′-ethylenebisacrylamide 30 parts by mass, nonionic surfactant 0.5 parts by mass, 2-hydroxy-2-methyl-1-phenylpropan-1-one 0.1 parts by mass, water 200 parts by mass The same porous substrate as used in Example 1 was immersed in the monomer aqueous solution, and the membrane was removed from the solution after confirming that the monomer aqueous solution was sufficiently impregnated and the membrane became transparent. It was taken out and quickly sandwiched between PET films. Subsequently, ultraviolet rays were irradiated for 3 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores, and then the PET film was peeled off. The process of immersion in the monomer aqueous solution and ultraviolet irradiation was repeated twice to obtain a Na type electrolyte membrane. In this example, when the compound represented by formula (6) was blended, the solubility of N, N′-ethylenebisacrylamide in water was lowered, so that more water was used than in Example 1 and the monomer concentration was lowered. In order to compensate for this, the procedure from filling to polymerization was repeated three times. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

(Example 5)
An electrolyte membrane was obtained in the same manner as in Example 1 except that the crosslinking agent in Example 1 was changed to 10 parts by mass of N, N′-bisacryloylpiperazine synthesized in Synthesis Example 4. Table 1 shows the evaluation results of the obtained film.

(Example 6)
An electrolyte membrane was obtained in the same manner as in Example 1 except that the crosslinking agent in Example 2 was changed to 30 parts by mass of N, N′-bisacrylamide piperazine synthesized in Synthesis Example 5. Table 1 shows the evaluation results of the obtained film.

(Example 7)
A polyethylene film (thickness 30 μm, porosity 40%) was used as the porous substrate. 76.6 parts by mass of sodium 2-acrylamidocyclohexanesulfonate synthesized in Synthesis Example 1 (70 parts by mass when ion-exchanged to form hydrogen), and N, N′-ethylenebisacrylamide 25 as a crosslinking agent Part by weight, 5 parts by weight of acrylic acid as a comonomer, 0.5 part by weight of a nonionic surfactant, an ultraviolet radical polymerization initiator 2-hydroxy-2-methyl-1-phenylpropan-1-one 0.1 The porous substrate is immersed in a monomer aqueous solution consisting of 100 parts by mass of water and 100 parts by mass of water. After confirming that the monomer aqueous solution is sufficiently impregnated and the membrane is transparent, the membrane is removed from the solution. , Quickly sandwiched with PET film. Next, ultraviolet rays were irradiated for 2 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores, and then the PET film was peeled off to obtain an Na-type electrolyte membrane. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

(Example 8)
An electrolyte membrane was obtained in the same manner as in Example 1 except that 20 parts by mass of N, N′-ethylenebisacrylamide as a crosslinking agent and 10 parts by mass of acrylic acid were used in Example 7. Table 1 shows the evaluation results of the obtained film.

Example 9
In Example 1, instead of sodium 2-acrylamidocyclohexanesulfonate, 90 parts by mass of 2-acrylamido-2-methylcyclohexanesulfonic acid obtained in Synthesis Example 4 and 10 parts by mass of N, N′-ethylenebisacrylamide were used to perform ion substitution operation. An electrolyte membrane was obtained in the same manner as in Example 1 except that the step was not performed. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 1)
90 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts by mass of N, N′-ethylenebisacrylamide as a crosslinking agent, 0.5 parts by mass of nonionic surfactant, 2-hydroxy-2-methyl-1- The same porous substrate as that used in Example 1 was immersed in a monomer aqueous solution consisting of 0.1 parts by mass of phenylpropan-1-one and 100 parts by mass of water, and the monomer aqueous solution was sufficiently impregnated. After confirming that the film became transparent, the film was taken out from the solution and quickly sandwiched between PET films. Subsequently, ultraviolet rays were irradiated for 2 minutes with a high-pressure mercury lamp to polymerize the monomers inside the pores, and then the PET film was peeled off to obtain an electrolyte membrane. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 2)
An electrolyte membrane was prepared in the same manner as in Comparative Example 1 except that 70 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid and 30 parts by mass of N, N′-ethylenebisacrylamide as a crosslinking agent were used in Comparative Example 1. Obtained. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 3)
An electrolyte membrane was prepared in the same manner as in Comparative Example 1 except that 2-acrylamido-2,3-dimethylbutanesulfonic acid synthesized in Comparative Synthesis Example 1 was used instead of 2-acrylamido-2-methylpropanesulfonic acid in Comparative Example 1. Got. Table 1 shows the evaluation results of the obtained film.

(Comparative Example 4)
An electrolyte membrane was obtained in the same manner as in Comparative Example 1 except that N, N′-methylenebisacrylamide was used instead of N, N′-ethylenebisacrylamide in Comparative Example 1. Table 1 shows the evaluation results of the obtained film. N, N′-methylenebisacrylamide has low solubility in water, and 30 parts by mass could not be added.

(Comparative Example 5)
98.7 parts by mass of sodium 4-acrylamidobenzenesulfonate synthesized in Comparative Synthesis Example 2 instead of 2-acrylamido-2-methylpropanesulfonic acid in Comparative Example 1 (90 parts by mass when ion-exchanged to form a hydrogen form) Na-type electrolyte membrane was obtained in the same manner as in Comparative Example 1 except that. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

(Comparative Example 6)
Na-type electrolyte in the same manner as in Comparative Example 2 except that 76.7 parts by mass of sodium 4-acrylamidobenzenesulfonate of Comparative Example 5 was changed to 70 parts by mass when ion-exchanged to obtain a hydrogen type. A membrane was obtained. Next, the step of immersing this membrane in 1N sulfuric acid for 1 hour was performed twice, then washed with pure water, and then the step of immersing in pure water for 1 hour was performed twice to perform ion exchange from Na type to H type. Table 1 shows the evaluation results of the film thus obtained.

In Table 1, a compound in which the synthesized monomer is a sodium salt is also expressed in terms of parts by mass converted to the acid form. Furthermore, the compound name described on the right side of the abbreviation used the name when the Na type was ion-substituted to the H type.
Abbreviations in Table 1 are shown below.
ACS: 2-acrylamide cyclohexanesulfonic acid
ACCS: 7: 3 mixture of 2-acrylamido-4-carboxycyclohexanesulfonic acid and 2-acrylamido-4-methoxycarbonylcyclohexanesulfonic acid
ACDCS: 2-acrylamide-4,5-carboxycyclohexanesulfonic acid
MACS: 2-acrylamido-2-methylcyclohexanesulfonic acid
ATBS: 2-acrylamido-2-methylpropanesulfonic acid
ADMBS: 2-acrylamide-2,3-dimethylbutanesulfonic acid
ABS: 4-acrylamidobenzenesulfonic acid
AA: Acrylic acid
EBAM: N, N'-ethylenebisacrylamide
BAP: N, N'-bisacryloylpiperazine
MBAM: N, N′-methylenebisacrylamide As is clear from Table 1, when Examples and Comparative Examples are compared, an electrolyte membrane containing a polymer using a sulfonic acid monomer having an aliphatic ring used in the present invention Is superior in oxidation resistance as compared to the case of using an aliphatic sulfonic acid monomer having no aliphatic ring structure or a sulfonic acid monomer having an aromatic ring.

  In addition, N, N′-ethylenebisacrylamide is more excellent in oxidation resistance than N, N′-methylenebisacrylamide used in Comparative Example 4. Further, in Examples 5 and 6, bisacryloylpiperazine and a sulfonic acid monomer having an aliphatic ring represented by the formula (1) or (2) are used in combination among the crosslinking agents that may be used in the present invention. This shows that the oxidation resistance is remarkably improved.

  Further, when the type of the crosslinking agent is the same, the more the crosslinking agent, the better the oxidation resistance. However, although Examples 7 and 8 have the same type of crosslinking agent as Example 1 and the amount is small. Furthermore, since the mass loss at the initial stage of the Fenton test is smaller than that in Example 1, it is shown that the oxidation resistance of the electrolyte membrane of the present invention is remarkably improved by copolymerization of acrylic acid.

  In addition, the conductivity of the electrolyte membranes obtained in the Examples was superior to that of commercially available fluorine-based electrolyte membranes, and the methanol permeation flux was small, indicating performance suitable for DMFC applications.

  The electrolyte membrane of the present invention can be applied not only to fuel cells, but also to electrochemical device elements such as various sensors and separation membranes for electrolysis.

Claims (12)

A method for producing an electrolyte membrane comprising polymerizing a composition comprising a monomer represented by formula (1) and a compound having two or more ethylenic double bonds in the molecule.

(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, A is an alicyclic hydrocarbon group, and at least one acidic group on the aliphatic ring of the alicyclic hydrocarbon group and // represents a group to which a salt thereof is bonded as a substituent.)   The manufacturing method of the electrolyte membrane of Claim 1 in which the said composition contains 2-50 mass% acrylic acid and / or methacrylic acid with respect to the whole quantity of a composition. The method for producing an electrolyte membrane according to claim 1 or 2, wherein at least one of the monomers represented by the formula (1) is a monomer represented by the formula (2).

(In the formula (2), R ¹ , R ² and R ³ each independently represents a hydrogen atom or a methyl group, X represents a hydrogen atom or a metal atom, and Y and Z each independently represent a carboxyl group. , A sulfonic acid group, and a salt thereof, and a group selected from the group consisting of ester residues, and either Y or Z or both of them may not exist.) The manufacturing method of the electrolyte membrane in any one of Claims 1-3 in which the monomer which has two or more ethylenic double bonds in the said molecule | numerator contains the compound shown by Formula (3).

(In Formula (3), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 2 to 10 carbon atoms, and R ⁷ and R ⁸ each independently represent hydrogen. And represents an alkylene group having 2 to 4 carbon atoms in which R ⁷ and R ⁸ are bonded to connect two nitrogen atoms.)   The method for producing an electrolyte membrane according to any one of claims 1 to 4, wherein the composition is polymerized in the pores of the porous membrane.   The electrolyte membrane according to claim 5, wherein the porous membrane contains polyethylene, the porosity of the porous membrane is 20 to 80% by volume, and the thickness of the porous membrane is 5 to 50 μm. Method. An electrolyte membrane comprising a resin having at least a monomer unit represented by the formula (1 ′) and a crosslinked structure.

(In the formula (1 ′), R ¹ represents a hydrogen atom or a methyl group, A is an alicyclic hydrocarbon group, and at least one acidic group on the aliphatic ring of the alicyclic hydrocarbon group. And / or a group to which a salt thereof is bonded as a substituent.) The electrolyte membrane according to claim 7, wherein the resin contains 2 to 50% by mass of a monomer unit represented by the formula (4 ′) with respect to all monomer units of the resin.

(In the formula (4 ′), R ⁹ represents a hydrogen atom or a methyl group.) The electrolyte membrane according to claim 7 or 8, wherein at least one of the monomer units represented by the formula (1 ') is a monomer unit represented by the formula (2').

(In the formula (2 ′), R ¹ , R ² and R ³ each independently represents a hydrogen atom or a methyl group, X represents a hydrogen atom or a metal atom, and Y and Z each independently represent a carboxyl group. Represents a group selected from the group consisting of a group, a sulfonic acid group, a salt thereof, and an ester residue, and one or both of Y and Z may not be present.) The electrolyte membrane according to any one of claims 7 to 9, wherein the crosslinked structure includes a monomer unit represented by the formula (3 ').

(In Formula (3 ′), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 2 to 10 carbon atoms, and R ⁷ and R ⁸ each independently represent This represents a hydrogen atom or an alkylene group having 2 to 4 carbon atoms in which R ⁷ and R ⁸ are bonded to connect two nitrogen atoms.   The electrolyte membrane according to any one of claims 7 to 10, wherein the resin is filled in pores of the porous membrane.   The electrolyte membrane according to claim 11, wherein the porous membrane contains polyethylene, the porosity of the porous membrane is 20 to 80% by volume, and the thickness of the porous membrane is 5 to 50 μm.