JP2009093919A - Manufacturing method for aromatic polyether electrolyte membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an electrolyte membrane that exhibits high proton conductance and high water resistance even when density of an ion exchange group is increased. <P>SOLUTION: A monomer requiring aromatic polyether having a vinyl group at an end and an ion exchange group in a molecule is impregnated into a pore of a porous base material having the swelling-resistant property. Subsequently, radical copolymerization of the vinyl group generates an electrolyte resin having ion exchange property and cross-linking in the pore of the porous base material to manufacture an electrolyte membrane filled with the electrolyte resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an electrolyte membrane, and the electrolyte membrane is a method for producing an electrolyte membrane excellent in use in an electrochemical device, particularly a fuel cell, more specifically, a direct alcohol fuel cell.

  As global environmental protection activities become more active, so-called greenhouse gas and NOx emission prevention is strongly screamed. In order to reduce the total emission amount of these gases, it is considered that practical application of a fuel cell system for automobiles is very effective.

  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 manner 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 a fuel, PEFC is divided into a reformed methanol type that uses a reformer to convert methanol into a hydrogen-based gas, 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 that is an electrolyte membrane for PEFC using conventional hydrogen as a fuel, such as a Nafion (registered trademark) membrane manufactured by Du Pont, Since methanol permeates the membrane, there is a problem that the electromotive force decreases. Furthermore, these electrolyte membranes also have an economic problem that they are very expensive.

As means for solving the above problem, Patent Document 1 proposes an electrolyte membrane in which a porous base material such as polyimide, crosslinked polyethylene, etc., which is inexpensive and hardly deformed by external force, is filled with a polymer having proton conductivity. Has been made. However, since the electrolyte membrane 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.

Furthermore, Patent Document 2 discloses an electrolyte membrane in which a first 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 first polymer is a polymer derived from 2-acrylamido-2-methylpropanoic acid. However, the durability of the electrolyte membrane described in this patent document is still insufficient.
JP 2002-83612 A International Publication No. 03/075386 Pamphlet

Among hydrocarbon-based electrolytes, a polymer in which an ion exchange group such as a sulfonic acid group is introduced into an aromatic polyether is known as a polymer excellent in oxidation resistance and heat resistance. For example, sulfonated polyether ketone (Patent Document 3), sulfonated polyethersulfone (Patent Document 4) and the like have been proposed.
Japanese National Patent Publication No. 11-502249 JP, 10-45913, A However, when the above-mentioned aromatic polyether raises ion exchange group concentration in order to raise conductivity, water resistance will fall, and film strength and adhesiveness with an electrode will also fall. There was a drawback of end. In particular, when compounding with a porous substrate, it is necessary to increase the ion exchange group concentration in the electrolyte resin to compensate for the decrease in conductivity. Therefore, in such an electrolyte membrane using the conventional electrolyte resin, water resistance is increased. The lack of sex is a significant problem.

  In the conventional electrolyte membrane, when the ion exchange group concentration is increased in order to increase proton conductivity, the electrolyte resin is easily eluted in water and the durability becomes low. In compositing with a porous base material, which is an effective technique for suppressing the swelling of the electrolyte membrane, it is necessary to further increase the ion exchange group concentration of the electrolyte membrane, and this significantly reduces the water resistance of the electrolyte resin. An object of the present invention is to provide a method for producing a composite electrolyte membrane having good proton conductivity and water resistance.

  The pores of the porous substrate are impregnated with an aromatic polyether having a vinyl group at the end and an ion exchange group in the molecule, and then the aromatic polyether is polymerized in the pores of the porous substrate Thus, an electrolyte membrane having a structure in which the pores of the porous base material are filled with the electrolyte resin is manufactured by changing the electrolyte resin to an ion-exchangeable and crosslinked electrolyte resin.

  The electrolyte membrane obtained by the above method has high water resistance even when the ion exchange group concentration is increased, and also has high proton conductivity and ability to suppress methanol permeation. As a result, an electrolyte membrane having high conductivity, high water resistance, and high durability can be realized.

Hereinafter, the present invention will be described in detail.
In the method for producing an electrolyte membrane of the present invention, the aromatic polyether (a) has a vinyl group at at least one end and an ion exchange group in the molecule. The aromatic polyether (a) reacts, for example, an aromatic polyether having a reactive group such as a hydroxyl group at a terminal with a compound having a functional group having reactivity with a hydroxyl group and a vinyl group in the molecule. Can be obtained.

（式中、Ｘ、Ｙは独立に芳香族の二価の基を表し、繰返し数ｎは１〜１００の整数である。複数あるＸおよびＹはそれぞれ２種類以上の構造単位であっても良い。）

該末端ヒドロキシ型芳香族ポリエーテルの典型的な製造方法は、構造単位Ｘを形成するジオールと、構造単位Ｙを形成する脱離基を二個持つ化合物の縮合重合である。この際の脱離基としては、ヒドロキシル基による求核置換反応で脱離し得る官能基であり、クロロ基、ブロモ基、ヨード基などのハロゲン基、ｐ−トルエンスルホニルオキシ基、メタンスルホニルオキシ基、トリフロロメタンスルホニルオキシ基などのスルホン酸エステル基が挙げられる。 <Aromatic polyether having a hydroxyl group or other reactive group at the terminal>
Among aromatic polyethers having a reactive group such as a hydroxyl group at the terminal, preferred are terminal hydroxy type aromatic polyethers having the molecular structures of the following compounds (2) to (6). The aromatic polyether (a) in the present invention is synthesized by reacting the terminal hydroxy type aromatic polyether with a compound having a vinyl group and a functional group in the molecule (hereinafter referred to as a functional vinyl compound). The

(In the formula, X and Y independently represent an aromatic divalent group, and the repetition number n is an integer of 1 to 100. Plural X and Y may each be two or more types of structural units. .)

A typical method for producing the terminal hydroxy-type aromatic polyether is condensation polymerization of a diol forming the structural unit X and a compound having two leaving groups forming the structural unit Y. The leaving group at this time is a functional group that can be eliminated by a nucleophilic substitution reaction with a hydroxyl group, a halogen group such as a chloro group, a bromo group, or an iodo group, a p-toluenesulfonyloxy group, a methanesulfonyloxy group, Examples thereof include sulfonic acid ester groups such as trifluoromethanesulfonyloxy group.

  Representative examples of the structural units X and Y include 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 2-phenyl-1,4-phenylene, 2-phenoxy-1,4-phenylene, 1 , 4-naphthylene, 2,3-naphthylene, 1,5-naphthylene, 2,6-naphthylene, 2,7-naphthylene, biphenyl-4,4′-diyl, biphenyl-3,3′-diyl, biphenyl-3 , 4′-diyl, 3,3′-diphenylbiphenyl-4,4′-diyl, 3,3′-diphenoxybiphenyl-4,4′-diyl, 2,2′-diphenylpropane-4,4′- Diyl, diphenyl ether-4,4′-diyl, diphenylsulfone-4,4′-diyl, benzophenone-4,4′-diyl and the like can be mentioned.

（式中、Ｘ、Ｙは独立に芳香族の二価の基を表し、繰返し数ｍまたはｌは１〜１００の整数である） The preferred main component of the terminal hydroxy-type aromatic polyether in the present invention is the structure of the compound (2), but it may contain components having the structures shown in the following compounds (3) and (4). . These structures are produced from a component having the structural unit Y at one or both ends, and the leaving group of Y is removed by hydrolysis and substituted with a hydroxy group. Similar to the component (2), these components can be converted into the target product by reaction with a functional vinyl compound.

(In the formula, X and Y independently represent an aromatic divalent group, and the repetition number m or l is an integer of 1 to 100)

（式中、Ｘ、Ｙは独立に芳香族の二価の基を表し、繰返し数ｍまたはｌは１〜１００の整数である）
On the other hand, the terminal hydroxy type aromatic polyether in the present invention may contain components represented by the following compounds (5) and (6). These components have a leaving group A at one or both ends, and it is difficult to convert the leaving group into a target product by reaction with a functional vinyl compound. The allowable content of these compounds is 70% or less, and preferably 50% or less. The leaving group A is a halogen group such as a chloro group, a bromo group or an iodo group, or a sulfonate group such as a p-toluenesulfonyloxy group, a methanesulfonyloxy group or a trifluoromethanesulfonyloxy group.
The average number of hydroxy groups per molecule of the terminal hydroxy-type aromatic polyether is preferably 1.2 to 2.0, and more preferably 1.5 to 2.0.

(In the formula, X and Y independently represent an aromatic divalent group, and the repetition number m or l is an integer of 1 to 100)

<Ion exchange group>
In the present invention, those containing an ion exchange group in at least one of the structural units X and Y are used. The type of ion exchange _{groups, -SO 3 M, -COOM, -PO} (OM) 2, -P (OM) 2, -SO 2 NMSO 2 - cation exchange group selected from the used rather preferred, - SO ₃ M is particularly preferably used. Here, M is selected from hydrogen, metal atoms, and ammonium. When M is a metal atom, it is preferably an alkali metal atom or an alkaline earth metal atom because the oxidation reaction is not promoted even if it is easily exchanged with a hydrogen atom and remains. As a bonding mode of the ion exchange group, a structure bonded to an aromatic ring directly or via a divalent organic group can be used. Usually, a structure directly bonded to an aromatic ring is employed for the convenience of synthesis. Ion exchange group introduction methods include introduction at the monomer stage, introduction at the terminal hydroxy-type aromatic polyether stage, introduction into the terminal vinyl-type aromatic polyether, and introduction after vinyl polymerization in the pores. Any of these methods may be used, and among them, the method of introducing at the monomer stage, the method of introducing at the terminal hydroxy type aromatic polyether stage, and the method of introducing after vinyl polymerization in the pores are preferred. In view of easy control of the amount and position of ion exchange group introduction, a method of introduction at the monomer stage is particularly recommended. The concentration of the ion exchange group in the aromatic polyether (a) is preferably 0.01 to 5 mmol / g because the higher the concentration, the better the conductivity, while the lower the concentration, the better the water resistance and durability. 0.5-5 mmol / g is more preferable. Since the volume ratio of the base material does not contribute to ionic conduction in the composite with the porous base material, it is necessary to increase the ion exchange group concentration in the electrolyte part, so that the ion exchange group of 1.5 to 5 mmol / g It is particularly preferred to have a concentration.

<Functional vinyl compound>
The functional vinyl compound in the present invention has a radical polymerizable vinyl group and a functional group having reactivity with a hydroxyl group. The functional group having reactivity with a hydroxyl group is selected from a carboxyl group, a carboxylic acid halide group, an acid anhydride group, a halomethyl group, an epoxy group, an isocyanate group, and an oxazoline group, and among these, a carboxylic acid halide group, a halomethyl group Group and isocyanate group are preferably used, and halomethyl group is particularly preferably used. Of the halomethyl groups, those activated with an allyl structure are preferably used. A specific example of the functional vinyl compound having an activated halomethyl group and a vinyl group and easily available industrially is chloromethylstyrene.

<Synthesis of aromatic polyether (a)>
The aromatic polyether (a) in the present invention can be obtained by reacting the terminal hydroxy aromatic polyether with the functional vinyl compound. The reaction conditions vary depending on the type of functional group of the functional vinyl compound. Hereinafter, typical reaction conditions when chloromethylstyrene is used as the functional vinyl compound will be described.

The terminal hydroxy aromatic polyether is used as a solution of an aprotic polar organic solvent, and an equivalent amount to an excess amount of alkali is added to the amount of terminal hydroxyl groups. If chloromethylstyrene is added here and mixed by heating, the reaction easily occurs, and an aromatic polyether having a vinylbenzyl group introduced at the terminal is obtained.
As the aprotic polar solvent used at this time, general-purpose solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, dimethylimidazolidinone, ethylene carbonate, propylene carbonate and the like can be used. The concentration of the terminal hydroxy type aromatic polyether is preferably 5 to 80%, more preferably 10 to 70%.
As the alkali, a general inorganic or organic strong base may be used. For example, an alkali hydroxide such as sodium hydroxide or potassium hydroxide can be preferably used. The alkali may be added in an amount equal to or more than the terminal hydroxyl group of the terminal hydroxy-type aromatic polyether. Typically, the target product can be obtained with a high reaction rate when used in an equivalent amount to twice the equivalent amount. .
As for chloromethylstyrene, any of commercially available 4-substituted products, 2-substituted products, 3-substituted products, and mixtures thereof can be used.
The lower the reaction temperature, the better the stability of the raw material, and the higher the reaction time, the shorter the reaction time, so 0 to 150 ° C is preferable, and 20 to 100 ° C is more preferable. Of the aromatic polyethers (a) synthesized by the method exemplified above, particularly preferred are those having the structure of (1) at the terminal. These aromatic polyethers are used as raw materials for the production of electrolyte membranes in the form of a solution or after solvent removal.
In the method for synthesizing the aromatic polyether (a) of the present invention, the reaction for introducing the terminal vinyl group is mild even under mild reaction conditions or even at low temperatures, and therefore, side reactions such as the deactivation reaction of the terminal vinyl group are rare. As a result, a highly pure telechelic oligomer having a very high terminal group introduction rate can be obtained. Therefore, the crosslinking efficiency at the time of vinyl polymerization is high, and the content of the non-crosslinkable component remains very small. Further, since it does not contain a hydrolyzable group such as an ester group, the deterioration does not proceed even in a strongly acidic atmosphere typical for a fuel cell electrolyte.

<Electrolyte membrane>
The electrolyte membrane in the present invention is produced by radical polymerization of the liquid containing the aromatic polyether (a) described above in the pores of the porous substrate. Although it is possible to radically polymerize the terminal vinyl aromatic polyether (a) alone, it is preferable to copolymerize with the vinyl monomer (b) because the polymerization is fast and the reaction is completed in a short time. In any case, as a result of polymerization in the pores, an ion exchangeable and crosslinked polymer is produced, thereby producing an electrolyte membrane having a structure in which the pores of the porous substrate are filled with the electrolyte resin. Is done. The polymer in the electrolyte membrane is called an electrolyte resin.

<Vinyl monomer (b)>
In the present invention, the vinyl monomer (b) that can be used for the above copolymerization is classified into a monomer having an ion exchange group, a crosslinkable polyfunctional vinyl monomer, and another monomer. Each is exemplified below.
A vinyl monomer having an ion exchange group is a compound having a vinyl group and an ion exchange group in the molecule. As the ion exchange group, -SO ₃ M, -COOM, -PO (OM) ₂ , -P (OM ) ₂ , a cation exchange group selected from —SO ₂ NMSO ₂ — is preferable. Here, M is preferably hydrogen, an alkali metal atom, or an alkaline earth metal. The ion exchange group is preferably a sulfonic acid having the structure —SO ₃ M or a salt thereof. Specific examples include 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- Mention may be made of monomers such as (meth) acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, (meth) allylsulfonic acid, vinylsulfone, and salts thereof.

  The crosslinkable polyfunctional vinyl monomer can be used when it is desired to make the cross-linked structure more precise. Specific examples include N, N′-ethylenebisacrylamide, triacryl formal, bisacryloylpiperazine, N, N-methylenebisacrylamide. , 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, pen Erythritol triallyl ether, divinylbenzene, bisphenol diacrylate, isocyanuric acid diacrylate, tetraallyloxyethane, triallylamine, triallyl cyanurate, triallyl isocyanurate, diallyloxy acetate, and the like. Moreover, the water-soluble vinyl monomer (b) which has a functional group which can form a crosslinked structure is also preferable 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. In addition, crosslinking can also be performed by utilizing self-crosslinking by a hydrogen abstraction reaction during polymerization, or by irradiating the polymer after polymerization with active energy rays such as an electron beam and gamma rays.

Other vinyl monomers include, for example, (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinylphosphonic acid, acidic phosphoric acid group-containing (methacrylic acid) ) Acidic monomers such as acrylates and salts thereof; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene Monomers such as glycol (meth) acrylate, N-vinylpyrrolidone, N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (Meth) acrylamide etc. And the groups of monomers and the like their quaternized compound specifically. Also, acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, vinyl acetate, vinyl propionate, styrene, substituted styrene, N-phenyl for the purpose of adjusting water absorption Hydrophobic monomers such as maleimide and N-substituted maleimide represented by N-cyclohexylmaleimide can also be used.
When the terminal vinyl group is a styryl group, the polymerization rate is improved by using a vinyl monomer with strong alternating copolymerization, and the polymerization reaction is completed in a short time despite the extremely low concentration of the polymerizable group. To do. The productivity of the electrolyte membrane can be drastically increased by a combination of high-speed polymerization and photoinitiated polymerization described later. A vinyl monomer having an e value of +2 or more in the Qe scheme which is an index of copolymerizability in radical polymerization is preferably used. Specifically, N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide and maleic anhydride are preferably used, and N-substituted maleimide is particularly preferably used.

<Use ratio of vinyl monomer (b)>
When the terminal vinyl type aromatic polyether (a) and the vinyl monomer (b) are used in combination, the higher the mass ratio of the terminal vinyl type aromatic polyether (a), the higher the proton conductivity of the electrolyte membrane. On the other hand, the larger the mass ratio of the vinyl monomer (b), the higher the polymerization rate and the polymerization reaction rate. Therefore, the mass ratio is preferably 100: 0 to 5:95, and 98: 2 ~ 20: 80 is more preferable, and 97: 3 to 40:60 is particularly preferable.
The higher the ion exchange group concentration of the electrolyte resin, the better the conductivity. On the other hand, the lower the water resistance and the higher the durability, so 0.5 mmol / g to 5 mmol / g is preferred, and 1 mmol / g to 4 mmol / g is preferred. Further preferred. The concentration of the ion exchange group of the electrolyte resin can be controlled by adjusting the concentration in the terminal vinyl type aromatic polyether (a) and the amount of the monomer having an ion exchange group in the vinyl monomer (b).

<Polymerization method>
As already mentioned, the electrolyte membrane of the present invention is typically produced by copolymerization of an aromatic polyether (a) and a vinyl monomer (b). As the polymerization method, a technique of radical polymerization can be used. Specific examples include redox-initiated polymerization, heat-initiated polymerization, electron beam-initiated polymerization, and photoinitiated polymerization such as ultraviolet rays. When the aromatic polyether (a) used is soluble in the vinyl monomer (b), bulk polymerization without using a solvent is possible, but usually solution polymerization using water or a polar organic solvent is employed. Examples of polar organic solvents include dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, dimethylimidazolidinone, ethylene carbonate, propylene carbonate and other aprotic polar solvents, methanol, ethanol, propanol, butanol, ethylene glycol, ethylene Alcohols such as glycol monoalkyl ether, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and esters such as ethyl acetate, propyl acetate, and butyl acetate can be used.

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, so when used in combination with an organic material such as polyolefin as a porous substrate, the surface of the substrate and the filled polymer It is preferable because a chemical bond can be formed between the two.

<Photoinitiated polymerization>
Among the radical polymerization initiating means, photoinitiated polymerization by ultraviolet rays is preferable because 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, it is more preferable to previously dissolve or disperse the photopolymerization initiator in the reaction solution. Examples of the photopolymerization initiator include benzoin, benzyl, acetophenone, benzophenone, quinone, thioxanthone, thioacridone, and derivatives thereof that are generally used for ultraviolet polymerization. Examples of the 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-hydroxydi-2-methyl-1-propane- 1-one; o-benzo as benzophenone Methyl benzoate, 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 ′ -Dimethylaminobenzophenone, 4,4'-diethylaminobenzophenone, etc. are mentioned.

The larger the amount of these photopolymerization initiators used, the less unreacted monomer can be reduced, while the smaller the amount, the higher the crosslink density and the higher the durability of the electrolyte membrane. The amount of the agent used is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, based on the total mass of the aromatic polyether (a) and the vinyl monomer (b).
Of these, aromatic ketone radical polymerization initiators such as benzophenone, thioxanthone, quinone, and thioacridone can generate radicals by extracting hydrogen from carbon-hydrogen bonds. When used together, a chemical bond can be formed between the substrate surface and the filled polymer, which is preferable.
<Content of non-crosslinkable component>
The copolymer of the aromatic polyether (a) and the vinyl monomer (b) described above has excellent durability because it has a crosslinked structure. The amount of the non-crosslinking component in the electrolyte resin can be easily evaluated by a washing test using the polar solvent described in the section <Polymerization method>. In the electrolyte membrane of the present invention, the residual amount of the electrolyte resin after washing for 24 hours in a polar solvent at room temperature is preferably 70% by weight or more, and more preferably 85% by weight or more.

<Porous substrate>
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 pure water at 25 ° C. for 1 hour is preferably 20% or less at the maximum compared to the time of drying. More preferably, it is 10% or less, and particularly preferably 5% or less.
In addition, the porous base material used in the present invention has a higher elastic modulus, so that the deformation is suppressed. However, a certain degree of followability is required for battery assembly processing or the like. Therefore, the tensile modulus is preferably 500 to 5000 MPa, more preferably 1000 to 5000 MPa, and the breaking strength is preferably 50 to 500 MPa, and more preferably 100 to 500 MPa.
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 the material having such a property include inorganic materials such as glass or ceramics such as alumina or silica. In addition, for organic materials, aromatic polymers such as polyimide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, polyphenylene ether, polyphenylene sulfide, and polyolefin are crosslinked or stretched by applying radiation or a crosslinking agent. And the like, which are difficult to be deformed such as extending with respect to an external force. These materials may be used alone or in combination by stacking two or more of them.
Among these porous substrates, aromatic polymers such as stretched polyolefin, cross-linked polyolefin, stretched cross-linked polyolefin, polyimide, polyamideimide, and polyethersulfone have good workability in the filling process, and the base material is available. It is preferable also from the point of easiness.

The porosity of the porous substrate used in the present invention is preferably from 5 to 95%, more preferably from 5 to 90%, since the conductivity of the electrolyte membrane is improved when the membrane strength is maintained within the range where the membrane strength is maintained. Especially preferably, it is 20 to 80%. The average pore diameter is preferably in the range of 0.001 to 100 μm, and more preferably in the range of 0.01 to 10 μm.
Furthermore, the thicker the substrate, the better the film strength, but the thinner the film, the smaller the film resistance, and the more preferable is 200 μm or less. More preferably, it is 1-150 micrometers, More preferably, it is 5-100 micrometers, Most preferably, it is 5-50 micrometers.

<Filling method>
There is no particular limitation on the method for filling the polymer of the aromatic polyether (a) into the pores of the porous substrate, and a known method can be used. For example, a method in which a porous substrate is impregnated with a solution or dispersion of an aromatic polyether (a) and a vinyl monomer (b) before polymerization, and then polymerized and crosslinked is exemplified. At that time, the mixed liquid to be filled may contain a crosslinking agent, a polymerization initiator, a catalyst, a curing agent, a surfactant and the like, if necessary.

If the mixture of the aromatic polyether (a) and the vinyl monomer (b) filled in the pores of the porous substrate is liquid and has a low viscosity, it can be used for impregnation as it is. In order to facilitate the impregnation of the porous substrate, a solution or a dispersion is preferable. In that case, the concentration is preferably 10 to 90% by mass, and more preferably 20 to 70% by mass. As the solvent used at this time, various solvents as already described in the description of the polymerization method may be used.
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.

<Surface layer formation>
The polymer of the aromatic polyether (a) is preferably chemically bonded to the surface of the porous substrate, particularly the inner surface of the pores. As a means for forming the bond, plasma is previously applied to the substrate. , UV, electron beam, gamma ray, corona discharge, etc. to generate radicals on the surface, and when the charged monomer solution is polymerized, the graft polymerization to the substrate surface occurs simultaneously, the monomer to the substrate A method in which graft polymerization onto the substrate surface and polymerization of the polymer precursor occur simultaneously by irradiating an electron beam after filling the solution, and a hydrogen abstraction-type radical polymerization initiator is blended into the polymer precursor and heated. Alternatively, a method of simultaneously irradiating ultraviolet rays to cause graft polymerization on the substrate surface and polymerization of a polymer precursor, a method using a coupling agent, and the like can be mentioned. These may be performed alone or a plurality of methods may be used in combination.

  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.

<Proton conductivity>
The conductivity of the sample at 25 ° C. was measured. An electrolyte membrane immersed 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 to measure the conductivity. The higher the conductivity, the easier the protons move in the electrolyte membrane, indicating that the fuel cell is excellent.

<Methanol permeability>
The 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. A lower permeation coefficient indicates that methanol is less likely to pass through the electrolyte membrane and is suitable for fuel cell applications.

<Crosslinking test>
100 parts by mass of aromatic polyether (a), a predetermined amount of vinyl monomer (b), 3 parts of 2-hydroxy-2-methyl-1-phenylpropan-1-one, dimethylacetamide (hereinafter abbreviated as DMAc) ) After impregnating a porous substrate (crosslinked polyethylene film, thickness 30 μm, porosity 38%) with a solution consisting of 200 parts by mass, it was irradiated with ultraviolet rays for 4 minutes with a high-pressure mercury lamp, and in an oven at 80 ° C. The electrolyte membrane was obtained by drying for 30 minutes. After measuring the weight of the membrane, it was immersed in a large excess of dimethylacetamide and stirred for 24 hours at room temperature to extract and remove soluble components in the membrane. Next, the electrolyte membrane was taken out from dimethylacetamide, air-dried for 2 hours, then dried in an oven at 80 ° C. for 30 minutes, and the weight was measured. The residual ratio of the electrolyte resin (resin residual ratio) was calculated from the weight difference between the electrolyte membranes before and after the immersion according to Equation 1.

[Formula 1] Resin residual ratio = (film weight after immersion−base material weight in film) / (film weight before immersion−base material weight in film) × 100 (%)

(The weight of the substrate in the film was calculated by multiplying the area of the film before immersion by the weight per area of the substrate.)

<Hot water durability test>
The electrolyte membrane was stirred in deionized water at 80 ° C. for 24 hours, and the resin residual rate was calculated by Equation 1 from the membrane weight before and after the test.

(Synthesis example 1) Synthesis of aromatic polyether (a) (1)
In a 500 mL four-necked flask equipped with a stirrer, a Dean Stark apparatus, and a thermometer, 10.69 g of 4,4′-biphenol (hereinafter abbreviated as BP), 4.54 g of dichlorodiphenyl sulfone (hereinafter abbreviated as DCDPS), 17.59 g of sulfonated dichlorodiphenylsulfone (hereinafter abbreviated as S-DCDPS), 9.67 g of potassium carbonate, 42.4 g of N-methylpyrrolidone (hereinafter abbreviated as NMP) and 106.14 g of toluene were charged. The flask was immersed in an oil bath and stirred at a bath temperature of 140 ° C. for 4 hours. During this time, the water separated by the Dean Stark apparatus was appropriately removed.
Next, the bath temperature was raised to 190 ° C. over about 30 minutes, and toluene was distilled off from the reaction solution. The mixture was reacted at a bath temperature of 190 ° C. for 4 hours to obtain a terminal hydroxy aromatic polyether solution.
To this solution, 113.42 g of NMP and 1.26 g of acetic acid were added and mixed. The solution was allowed to stand overnight, the precipitate was filtered, and the solution was transferred into a 1 L beaker. While stirring vigorously with a stirrer, 518 g of isopropanol was added dropwise little by little to precipitate the resin. After the entire amount of isopropanol was added, the mixture was further stirred for 2 hours. The precipitate obtained by suction filtration of this slurry was placed in a mixed solvent of isopropanol / deionized water = 5/1 (wt) and washed overnight. The solid substance obtained after suction filtration of the slurry was vacuum-dried to obtain 26.2 g of a terminal hydroxy type aromatic polyether powder. The OH concentration calculated from the area ratio of the OH proton (9.55 ppm) and the aromatic proton (6.8 to 8.5 ppm) in the H-NMR spectrum was 0.422 meq. The molecular weight was calculated to be 4739 when 100% of the product was assumed to be a both-terminal hydroxy type.

A 100 mL three-necked flask equipped with a stirrer, cooler, and thermometer was charged with 20.0 g of the terminal hydroxy aromatic polyether powder synthesized above, 40 g of NMP, and 0.75 g of 85% KOH, and an oil at 80 ° C. The resin was dissolved by stirring in a bath for 30 minutes. The oil bath was set to 60 ° C., and 2.3 g of chloromethylstyrene was charged and reacted for 7 hours. The base number determined from titration with 0.1N HCl was 0.013 meq. It became a constant value at / g, and the reaction was judged to be complete.
To this solution, 55.6 g of NMP and 0.15 g of acetic acid were added and mixed. From this solution, the resin was isolated and purified in the same manner as in the case of the terminal hydroxy type aromatic polyether, to obtain 17.8 g of terminal styryl type aromatic polyether powder as the aromatic polyether (a). The styryl group concentration calculated from the area ratio of cis-vinyl proton (5.75 to 5.9 ppm) and aromatic proton (6.8 to 8.5 ppm) in the H-NMR spectrum was 0.387 meq. / G.

(Examples 1 to 4) Crosslinkability test The vinyl monomer shown in Table 1 was added to 100 parts of the aromatic polyether obtained in Synthesis Example 1, and a crosslinkability test was conducted. Got.

(Comparative Example 1)
Instead of the terminal styryl-type aromatic polyether, 100 parts of the terminal hydroxy-type aromatic polyether, which is an intermediate of Synthesis Example 1, was used, and 6.8 parts of phenylmaleimide was added to conduct a crosslinking test. The resin residual ratio was 0%, and it was confirmed that there was no crosslinking reactivity.

Synthesis Example 2 Synthesis of Aromatic Polyether (a) (2)
A 500 mL four-necked flask equipped with a stirrer, Dean-Stark apparatus, and thermometer was charged with 10.69 g of BP, 25.13 g of S-DCDPS, 9.67 g of potassium carbonate, 42.4 g of NMP, and 106.14 g of toluene. The reaction, isolation and purification were carried out under the same conditions as in Example 1 to obtain 35.4 g of terminal hydroxy type aromatic polyether powder. The OH concentration calculated from the 1 H-NMR spectrum was 0.402 meq. / G, and the molecular weight is 4978 when 100% of the product is assumed to be a both-terminal hydroxy type.
The synthesized terminal hydroxy type aromatic polyether powder 25.0 g, NMP 50 g, and 85% KOH 0.86 g were charged and stirred in an oil bath at 80 ° C. for 30 minutes to dissolve the resin. The oil bath was set at 60 ° C., and 2.6 g of chloromethylstyrene was charged and reacted for 6 hours. The base number determined from titration with 0.1N HCl was 0.010 meq. It became a constant value at / g, and the reaction was judged to be complete.
To this solution, 74.5 g of NMP and 0.17 g of acetic acid were added and mixed. From this solution, the resin was isolated and purified in the same manner as in the case of the terminal hydroxy type aromatic polyether, and 20.5 g of terminal styryl type aromatic polyether powder was obtained as the aromatic polyether (a). The styryl group concentration calculated from the 1 H-NMR spectrum was 0.397 meq. / G.

(Example 5)
To 100 parts of the aromatic polyether of Synthesis Example 2, 6.8 parts of phenylmaleimide was added, and a crosslinkability test was performed. The resin residual ratio was 100%, and it was found that the resin had excellent crosslinking reactivity.

(Example 6) Preparation of electrolyte membrane (1)
5 g of a terminal styryl-type aromatic polyether which is the aromatic polyether (a) synthesized in Synthesis Example 1, 0.34 g of N-phenylmaleimide (hereinafter abbreviated as PMI), 2-hydroxy-2-methyl-1 -0.15 g of phenylpropan-1-one and 10 g of DMAc were mixed and heated to obtain a homogeneous solution.
A porous substrate (crosslinked polyethylene film, thickness 16 μm, porosity 38%) was immersed in this solution, and the porous film was sufficiently impregnated with the solution. Both surfaces of this film were sandwiched between polyethylene terephthalate resin films, and excess impregnating liquid adhering to the substrate surface was pushed out of the film, and then polymerized by irradiating with ultraviolet rays for 4 minutes with a high-pressure mercury lamp. The cured film was peeled off from the film and washed with deionized water. The obtained electrolyte membrane was immersed in a 1N-HCl aqueous solution three times to convert to a sulfonic acid type, and further washed twice with deionized water.
The electrolyte membrane was subjected to proton conductivity, methanol permeability test and hot water durability test. The results are shown in Table 2.

(Example 7) Preparation of electrolyte membrane (2)
4.25 g of terminal styryl type aromatic polyether synthesized in Synthesis Example 1 (a), 0.78 g of PMI, 0.3 g of styrene, 2-hydroxy-2-methyl-1-phenyl A homogeneous solution was prepared by mixing and heating 0.15 g of propan-1-one and 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 8) Preparation of electrolyte membrane (3)
3.5 g of terminal styryl-type aromatic polyether synthesized in Synthesis Example 1 (a), 1.23 g of PMI, 0.6 g of styrene, 2-hydroxy-2-methyl-1-phenyl A homogeneous solution was prepared by mixing and heating 0.15 g of propan-1-one and 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 9) Preparation of electrolyte membrane (4)
5 g of terminal styryl type aromatic polyether which is the aromatic polyether (a) synthesized in Synthesis Example 1, 0.34 g of cyclohexylmaleimide, and 0 of 2-hydroxy-2-methyl-1-phenylpropan-1-one .15 g and 10 g of DMAc were mixed and heated to obtain a uniform solution.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.
(Example 10) Preparation of electrolyte membrane (5)
5 g of terminal styryl-type aromatic polyether which is the aromatic polyether (a) synthesized in Synthesis Example 2, 0.34 g of PMI, 0. 2-hydroxy-2-methyl-1-phenylpropan-1-one 15 g and 10 g of DMAc were mixed and heated to obtain a uniform solution.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 11) Preparation of electrolyte membrane (6)
4.25 g of terminal styryl type aromatic polyether synthesized in Synthesis Example 2 (a), 0.76 g of PMI, 0.3 g of styrene, 2-hydroxy-2-methyl-1-phenyl A homogeneous solution was prepared by mixing and heating 0.15 g of propan-1-one and 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 12) Preparation of electrolyte membrane (7)
3.5 g of terminal styryl type aromatic polyether which is the aromatic polyether (a) synthesized in Synthesis Example 2, 1.21 g of PMI, 0.6 g of styrene, 2-hydroxy-2-methyl-1-phenyl A homogeneous solution was prepared by mixing and heating 0.15 g of propan-1-one and 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 13) Preparation of electrolyte membrane (8)
2.7 g of terminal styryl type aromatic polyether synthesized in Synthesis Example 2 (a), 1.73 g of PMI, 0.94 g of styrene, 2-hydroxy-2-methyl-1-phenyl A homogeneous solution was prepared by mixing and heating 0.15 g of propan-1-one and 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

(Example 14)
1.75 g of terminal styryl type aromatic polyether synthesized in Synthesis Example 1 (a), 2.1 g of cyclohexylmaleimide, 1.15 g of styrene, 2-hydroxy-2-methyl-1- A homogeneous solution was prepared by mixing and heating 0.15 g of phenylpropan-1-one and 10 g of DMAc. In this case, (a) :( b) = 35: 65.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2. Compared to Example 6, the proton conductivity was remarkably reduced to 0.84 S / cm 2, but an electrolyte membrane having no problem with methanol permeation suppression and water resistance could be produced.

(Comparative Example 2)
A homogeneous solution was prepared by mixing and heating 5 g of the aromatic polyether having a hydroxy group at the terminal, which is an intermediate product in Synthesis Example 1, with 10 g of DMAc.
An electrolyte membrane was prepared from this solution in the same manner as in Example 6, and proton conductivity, methanol permeability test, and hot water durability test were performed. The results are shown in Table 2.

As is clear from Table 2, the electrolyte membranes of the present invention (Examples 6 to 14) are superior in the balance of proton conductivity and methanol permeation suppression as compared with the uncrosslinked electrolyte membrane (Comparative Example 2), and are resistant to hot water. The sex is much better.

The electrolyte membrane produced by 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 (8)

Impregnating the pores of the porous substrate with an aromatic polyether (a) having a vinyl group at the end and having an ion exchange group in the molecule; Process for polymerizing in a pore   Impregnating the liquid containing the aromatic polyether (a) and the vinyl monomer (b) other than (a) into the pores of a porous base material having swelling resistance in an organic solvent and water; The method for producing an electrolyte membrane according to claim 1, further comprising a step of copolymerizing the (a) and (b) in the pores of the porous substrate.   The use ratio of the aromatic polyether (a) and the vinyl monomer (b) is in the range of 97: 3 to 40:60 as a mass ratio of (a) :( b). Manufacturing method of electrolyte membrane.   Use of an aromatic polyether (a) synthesized by reacting a terminal hydroxy type aromatic polyether with a functional group having reactivity with a hydroxyl group and a compound having a vinyl group (functional vinyl compound) The method for producing an electrolyte membrane according to any one of claims 1 to 3   The electrolyte membrane according to claim 4, wherein the functional vinyl compound has a functional group selected from a carboxyl group, a carboxylic acid halide group, an acid anhydride group, a halomethyl group, an epoxy group, an isocyanate group, and an oxazoline group. Production method. The method for producing an electrolyte membrane according to any one of claims 1 to 5, wherein the aromatic polyether (a) has a terminal molecular structure represented by (1).

  The method for producing an electrolyte membrane according to claim 2 or 3, wherein the vinyl monomer (b) contains N-substituted maleimide. The method for producing an electrolyte membrane according to any one of claims 2, 3, and 7, wherein the aromatic polyether (a) and the vinyl monomer (b) are copolymerized by photoinitiated polymerization.