JP2010040530A - Proton conductive electrolyte membrane, its forming method, and membrane-electrode conjugant, and fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane suppressed in the permeation of water and methanol and other electrolyte solutions, the permeation of gases such as hydrogen and oxygen and swelling caused by the electrolyte solution and excellent in mechanical strength, its forming method, and a membrane-electrode conjugant, and a fuel cell using the membrane. <P>SOLUTION: The electrolyte membrane contains a porous base material having a plurality of pores and proton conductive polymer compositions held in the pores. The proton conductive polymer composition contains an aromatic hydrocarbon resin having protonic acid groups. Free water contained in the electrolyte membrane is 0.5 or smaller per protonic acid group at 25°C. Bound water contained in the electrolyte membrane is 1 or smaller per protonic acid group at 25°C. The proton conductivity of the electrolyte membrane is 0.001 S/cm or higher in water at 25°C. The methanol permeability of the electrolyte membrane is 50 (kg*μm/m<SP>2</SP>*h) or lower in 30 wt.% methanol at 25°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane having a porous substrate having a plurality of pores and a proton conductive polymer composition held in the pores. In particular, the present invention relates to an electrolyte membrane used for a fuel cell.

Fuel cells are attracting attention as clean power sources for electric motors due to the depletion of petroleum resources and serious environmental problems such as global warming. Fuel cells operate at low temperatures, have high output density, and can be miniaturized, and are regarded as important and suitable for in-vehicle power supplies, household power supplies, and other applications.
As this fuel cell, a solid polymer electrolyte fuel cell using a proton conductive polymer composition, for example, a perfluorocarbon polymer having a sulfonic acid group, such as “Nafion (R)”, as an electrolyte membrane is known. . The electrolyte membrane is required to be thin to reduce electrical resistance.
However, when an attempt was made to reduce the thickness of the polymer electrolyte membrane having the sulfonic acid group, the workability and the handleability of the membrane deteriorated, and an appropriate mechanical strength could not be maintained. In addition, the effect of a short circuit (crossover) between methanol on the anode and the oxidant on the cathode through the electrolyte membrane due to swelling of the electrolyte membrane increases, and melting (creeping) of the electrolyte membrane due to temperature rise occurs. It was easy.
As a method for reducing the film thickness of another electrolyte membrane, an electrolyte membrane in which a perfluoro-based ion exchange resin is impregnated in a porous polytetrafluoroethylene film is known (see Patent Document 1). However, although perfluoro-based ion exchange resins can suppress the swelling of methanol and water to some extent, the permeation suppression of methanol is insufficient and there is a problem in the output characteristics of the electrolyte membrane.
By the way, according to the nonpatent literatures 1 and 2, the state of the water contained in the water in the electrolyte is defined as follows: free water, bound water, and antifreeze water.
Free water: Water that has the same melting and freezing temperature and enthalpy as bulk water without being affected by electrolytes or substrates.
Bound water: Water that has a melting / freezing temperature different from that of bulk water, interacts with the electrolyte or the substrate, and exhibits a phase transition (crystallization) at -20 ° C to 20 ° C.
Antifreeze water: the temperature of thawing / freezing is different from bulk water, there is a strong interaction with the electrolyte or substrate, and does not show phase transition (crystallization) at -20 ° C to 20 ° C, ie -20 ° C Water showing a phase transition (crystallization) at a lower temperature.
Of these, free water, which is the same as bulk water, can move freely in the electrolyte, causing a medium that induces methanol permeation. In addition, bound water causes methanol to permeate, although not as much as free water. Therefore, the water contained in the electrolyte is ideally composed only of antifreeze water having a strong interaction with the electrolyte or the substrate.

Japanese Patent Publication No. 5-75835 JP 2005-19055 A

H. Hatakeyama, T .; Hatakeyama, Thermochimica Acta 308, (1998) pp. 3-22 M.M. A. Hickner, B.M. S. Pivovar "FUEL CELLS" (2005), 5, no. 2 pp. 213-229

Japanese Patent Application Laid-Open No. 2005-19055 describes that the amount of free water and bound water can be reduced by mixing a proton conductive polymer and a polymer different from the polymer. However, since the amount of free water and bound water could not be reduced sufficiently, the effect of blocking the permeation of methanol was insufficient.
A first object of the present invention is to provide an electrolyte membrane that suppresses permeation of an electrolyte solution such as water and methanol, gas permeation of hydrogen and oxygen, and swelling due to the electrolyte solution, and has excellent mechanical strength, and a method for producing the same. It is in.
The second object of the present invention is to provide an electrolyte membrane that realizes an unprecedented thinning of the electrolyte membrane and has low electrical resistance, excellent dimensional stability, heat resistance, and chemical resistance, and a method for producing the same. There is to do.
The third object of the present invention is to provide a membrane-electrode assembly using the above electrolyte membrane.
A fourth object of the present invention is to provide a fuel cell using the membrane-electrode assembly.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that in a porous substrate having a plurality of pores, an aromatic having a proton acid group in all or part of each pore. The present inventors have found that an excellent electrolyte membrane that overcomes the above-mentioned drawbacks can be provided by holding a proton conductive polymer composition containing a hydrocarbon-based resin, and the present invention has been completed.
That is, the present invention
[1]. An electrolyte membrane having a porous substrate having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the proton conductive polymer composition has a proton acid group Free water contained in the electrolyte membrane at 25 ° C. containing an aromatic hydrocarbon resin is 0.5 or less per proton acid group, and in the electrolyte membrane at 25 ° C. The bound water contained is 1 or less per proton acid group, the proton conductivity of the electrolyte membrane is 0.001 S / cm or more in water at 25 ° C., and the methanol permeability of the electrolyte membrane The electrolyte membrane is characterized in that is 50 (kg · μm / m ² · h) or less in 30 wt% methanol at 25 ° C.
[2]. The electrolyte membrane according to [1] above, wherein the aromatic hydrocarbon resin is selected from the group consisting of polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, polyimide, polyquinoline, and polyquinoxaline.
[3]. The electrolyte membrane according to [1] above, wherein the aromatic hydrocarbon resin is polyethersulfone.
[4]. The electrolyte membrane according to any one of [1] to [3], wherein the protonic acid group is selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group.
[5]. The said aromatic hydrocarbon resin is related with the electrolyte membrane as described in said [1] containing the structure represented by general formula (I).

（一般式（Ｉ）中、Ｘ₁及びＸ₂は、互いに同一であっても異なっていてもよく、−（ＲＯｍ）ｎ−であり、ここで、Ｒはアルキレン基であり、ｍは０又は１、ｎは０〜２０の整数である）
［６］．前記多孔質基材が、無機材料又は耐熱性ポリマーである、上記［１］に記載の電解質膜に関する。
［７］．前記多孔質基材が、ポリイミドであり、前記芳香族系炭化水素樹脂が、ポリエーテルスルホンである、上記［１］に記載の電解質膜に関する。
［８］．前記プロトン伝導性高分子組成物が、架橋剤を含む、上記［１］ないし［７］のいずれかに記載の電解質膜に関する。
［９］．前記細孔の一部と前記芳香族系炭化水素樹脂の一部が固定されている、上記［１］ないし［８］のいずれかに記載の電解質膜に関する。
［１０］．上記［１］に記載の電解質膜の製造方法であって、以下の工程を含む、電解質膜の製造方法に関する。
（１）複数の細孔を有する多孔質基材と、前記細孔中に保持されたプロトン伝導性高分子組成物とを有する電解質膜であって、前記多孔質基材の前記細孔中に前記プロトン伝導性高分子組成物を形成するためのモノマー及び／又はオリゴマーを保持する工程；及び
（２）前記モノマー及び／又はオリゴマーを前記細孔中において重合する工程。
［１１］．前記プロトン伝導性高分子組成物を形成するためのモノマー及び／又はオリゴマーが、反応基を３個以上有することを特徴とする、上記［１０］に記載の電解質膜の製造方法に関する。
［１２］．上記［１］に記載の電解質膜の製造方法であって、以下の工程を含む、電解質膜の製造方法に関する。
（１）複数の細孔を有する多孔質基材と、前記細孔中に保持されたプロトン伝導性高分子組成物とを有する電解質膜であって、前記多孔質基材を前記プロトン伝導性高分子組成物の溶媒溶液に浸漬して前記多孔質基材の前記細孔中に前記プロトン伝導性高分子組成物を導入する工程；及び
（２）前記プロトン伝導性高分子組成物を保持した前記多孔質基材を、６０℃以上の温度で少なくとも１時間保持する工程。
［１３］．上記［１］ないし［９］のいずれかに記載の電解質膜を用いた膜−電極接合体に関する。
［１４］．上記［１３］に記載の膜−電極接合体を用いた燃料電池に関する。

(In the general formula (I), X ₁ and X ₂ may be the same or different from each other, and are — (ROm) n—, where R is an alkylene group, and m is 0 or 1, n is an integer of 0-20)
[6]. It is related with the electrolyte membrane as described in said [1] whose said porous base material is an inorganic material or a heat resistant polymer.
[7]. The electrolyte membrane according to [1] above, wherein the porous substrate is polyimide, and the aromatic hydrocarbon resin is polyethersulfone.
[8]. The proton conductive polymer composition relates to the electrolyte membrane according to any one of [1] to [7], wherein the proton conductive polymer composition includes a crosslinking agent.
[9]. The electrolyte membrane according to any one of [1] to [8], wherein a part of the pores and a part of the aromatic hydrocarbon resin are fixed.
[10]. It is a manufacturing method of the electrolyte membrane as described in said [1], Comprising: It is related with the manufacturing method of an electrolyte membrane including the following processes.
(1) An electrolyte membrane having a porous base material having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the electrolyte base material is in the pores of the porous base material. A step of holding a monomer and / or oligomer for forming the proton conductive polymer composition; and (2) a step of polymerizing the monomer and / or oligomer in the pores.
[11]. The method for producing an electrolyte membrane according to [10] above, wherein the monomer and / or oligomer for forming the proton conductive polymer composition has three or more reactive groups.
[12]. It is a manufacturing method of the electrolyte membrane as described in said [1], Comprising: It is related with the manufacturing method of an electrolyte membrane including the following processes.
(1) An electrolyte membrane having a porous substrate having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the porous substrate is Introducing the proton conductive polymer composition into the pores of the porous substrate by immersing in a solvent solution of a molecular composition; and (2) holding the proton conductive polymer composition The step of holding the porous substrate at a temperature of 60 ° C. or higher for at least 1 hour.
[13]. The present invention relates to a membrane-electrode assembly using the electrolyte membrane according to any one of [1] to [9].
[14]. The present invention relates to a fuel cell using the membrane-electrode assembly according to [13].

The electrolyte membrane of the present invention has a low electrical resistance, and can reduce the internal resistance of the fuel cell when used in a fuel cell. In the electrolyte membrane of the present invention, the proton-conductive polymer composition is filled in the pores of the porous base material without any gaps, so that the cathode oxidizing gas (for example, oxygen) or the anode methanol The permeability of is very low. Furthermore, since the electrolyte membrane of the present invention can be based on a porous base material excellent in dimensional stability, heat resistance and chemical resistance, it can suppress swelling of the electrolyte even under high temperature conditions. It is possible to provide an electrolyte membrane with stable quality by suppressing permeation of oxygen gas. Further, since it is not decomposed into radical compounds such as hydrogen peroxide generated in the electrolyte, a high battery output can be stably obtained for a long period of time.
The electrolyte membrane of the present invention is used as an electrolyte membrane for fuel cells, particularly for polymer electrolyte fuel cells and direct methanol fuel cells. By using such a fuel cell, crossover of a fuel such as methanol and an oxidant such as O ₂ gas can be suppressed, and a high cell output can be stably obtained for a long period of time.
The state of the water contained in the electrolyte membrane of the present invention is composed of water having an interaction with the electrolyte or the base material (bound water, antifreeze water). It is an electrolyte membrane that does not exist and reduces the amount of bound water as much as possible. By having such a structure, an electrolyte consisting only of antifreeze water having a strong interaction with the electrolyte or the base material hardly forms a so-called cluster structure in which water surrounds the sulfonic acid group. For this reason, the movement of water can be suppressed as much as possible, and the permeation of methanol and oxygen gas can be suppressed. Furthermore, since the infiltration of electrolytes such as hydrogen peroxide and other radical compounds generated inside the electrolyte can be suppressed, high battery output can be stably obtained for a long period of time.

The figure which shows the measurement chart of the low temperature DSC of Examples 1, 2 and Comparative Examples 1-3. The figure which shows the relationship between a filling rate and a moisture content. The figure which shows the relationship between a filling rate and bound water. The figure which shows the relationship between a filling rate and antifreeze water. The figure which shows the relationship between a filling rate and a sulfonic acid group density. The figure which shows the relationship between proton conductivity and a sulfonic acid group density. The figure which shows the relationship between proton conductivity, sulfonic acid group density, and antifreeze water.

Hereinafter, the electrolyte membrane of the present invention, the production method thereof, the membrane-electrode assembly, and the fuel cell will be described in detail.
(1) Electrolyte membrane The electrolyte membrane of this invention has the porous base material which has several pores, and the proton-conductive polymer composition hold | maintained in the said pore. The electrolyte membrane is desired to be excellent in proton conductivity, dimensional stability, heat resistance, and chemical resistance. A preferable combination of the porous substrate and the proton conductive polymer composition is a combination of materials containing both aromatics.
Here, the proton conductivity of the electrolyte membrane is 0.001 S / cm or more at 25 ° C. and 100% humidity, and more preferably 0.002 S / cm or more.
The methanol permeability may be 0 (kg · μm / m ² · h) or more and 100 (kg · μm / m ² · h) or less in 30 wt% methanol at 25 ° C., but 0 (kg · μm / m). ² · h) to 50 (kg · μm / m ² · h). When it is 100 (kg · μm / m ² · h) or more, performance deterioration due to methanol permeation becomes remarkable.
Dimensional stability and heat resistance are preferable in that the electrolyte can be prevented from swelling even under high-temperature conditions, so that permeation of methanol and oxygen gas can be suppressed.
The dimensional stability is that the electrolyte membrane is immersed in pure water for 24 hours at 25 ° C., and the area change rate (%) before and after immersion is preferably 20% or less, more preferably 10% or less, and more preferably 3% or less. It is more preferable. If the area change rate is 20% or less, sufficient adhesion between the electrolyte membrane surface and the catalyst layer is obtained, and the interface resistance between the electrolyte membrane and the catalyst layer is not excessively increased, and the swelling of the electrolyte is sufficiently suppressed. In addition, methanol permeability can be kept low.
The heat resistance is preferably such that the physical properties do not change at −30 ° C. to 150 ° C. which is the use range of the fuel cell.
It is desirable that the chemical resistance has high oxidation resistance that does not decompose into an oxidizing agent such as hydrogen peroxide generated in the electrolyte membrane.

(1-1) Porous substrate The porous substrate used in the present invention is not particularly limited, and may be selected from known inorganic materials and organic materials. These porous substrates are preferably excellent in dimensional stability, heat resistance, chemical resistance and mechanical strength.
Specifically, examples of the inorganic material include alumina-based, zirconia-based, silica-based, silicon nitride-based, silicon carbide-based ceramics, glass, alumina, and composites thereof.
As the organic material, various polymers such as a thermosetting resin and a thermoplastic resin can be selected. The porous substrate is preferably an organic material containing an aromatic. In addition, a heat resistant polymer is desirable from the viewpoint of durability. Here, the heat resistant polymer means a resin having a glass transition temperature (Tg) of 150 ° C. or higher, preferably 150 to 300 ° C. As the heat resistant polymer, polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, polyimide, polyquinoline, polyquinoxaline, cross-linked polyethylene, and a mixture thereof are preferable. Here, polyquinoline and polyquinoxaline refer to polymers having the following quinoline skeleton and quinoxaline skeleton.

本発明で使用する多孔質基材の膜厚は、例えば、０．０１〜３００μｍ、好ましくは０．０１〜２００μｍ、より好ましくは０．１〜１００μｍであることが適当である。膜厚が０．０１μｍ以上であれば、十分な強度が得られ、取扱い、作業性の面で有利であり、３００μｍ以下であれば、得られる電解質膜の電気抵抗が大きくなりすぎることもないので好適である。また、本発明の多孔質基材は、それ自身にプロトン伝導性を持たせるためのスルホン酸基を導入する必要がないので、スルホン酸基による膜の機械的強度の低下の影響を受けない。したがって、本発明の多孔質基材の膜厚は、例えば、２０μｍ未満、好ましくは、１０μｍ以下、より好ましくは、１μｍ以下としてもよい。

The film thickness of the porous substrate used in the present invention is, for example, 0.01 to 300 μm, preferably 0.01 to 200 μm, more preferably 0.1 to 100 μm. If the film thickness is 0.01 μm or more, sufficient strength is obtained, which is advantageous in terms of handling and workability. If the film thickness is 300 μm or less, the electric resistance of the obtained electrolyte film does not become too large. Is preferred. Further, since the porous substrate of the present invention does not need to introduce a sulfonic acid group for imparting proton conductivity to itself, it is not affected by a decrease in the mechanical strength of the membrane due to the sulfonic acid group. Therefore, the film thickness of the porous substrate of the present invention may be, for example, less than 20 μm, preferably 10 μm or less, more preferably 1 μm or less.

The pores present in the porous substrate used in the present invention and retaining the proton conductive polymer composition are suitably continuous pores. Here, “continuous pores” mean pores penetrating the front and back surfaces of the porous substrate, and by holding the proton conductive polymer composition in such continuous pores, It becomes possible to move from the front surface to the back surface of the porous substrate through the continuous holes. Therefore, the porous substrate of the present invention can move protons through the continuous pores without being swollen by the electrolyte.
The porosity of the porous substrate of the present invention is, for example, 10 to 95%, preferably 20 to 90%, more preferably 40 to 80%. If it is 10% or more, the proton conductive polymer composition can be sufficiently retained in the pores of the porous substrate, and sufficient ionic conductivity can be obtained. Moreover, if it is 95% or less, practical thin film strength can be obtained.
The average diameter (average through-hole diameter) of pores penetrating the front and back surfaces of the porous substrate used in the present invention is 0.001 to 100 μm, preferably 0.005 to 50 μm, more preferably 0.01 to 10 μm. It is appropriate that When the average through-hole diameter is 0.001 μm or more, the proton-conductive polymer composition can be sufficiently retained in the pores of the porous substrate, and sufficient ionic conductivity can be obtained. Moreover, if the average through-hole diameter is 100 μm or less, it is preferable because the proton-conductive polymer composition can be immobilized in the pores without leaking.

(1-2) Proton Conducting Polymer Composition The proton conducting polymer composition used in the present invention comprises an aromatic hydrocarbon resin having a proton acid group, and other resins and additives as necessary. Including.
(1-2-1) Aromatic hydrocarbon resin The aromatic hydrocarbon resin used in the present invention has an aromatic group in the main skeleton of the hydrocarbon resin. Such an aromatic hydrocarbon resin is preferable in terms of heat resistance, oxidation resistance, flexibility, and film formability. The main skeleton of this aromatic hydrocarbon resin is polyether ketone, polysulfide, polyphosphazene, polyphenylene, polybenzimidazole, polyether sulfone, polyphenylene oxide, polycarbonate, polyurethane, polyamide, polyimide, polyurea, polyquinoline, polyquinoxaline, Polysulfone, polysulfonate, polybenzoxazole, polybenzothiazole, polythiazole, polyphenylquinoxaline, polyquinoline, polysiloxane, polytriazine, polydiene, polypyridine, polypyrimidine, polyoxathiazole, polytetrazapyrene, polyoxazole, polyvinylpyridine, Polyvinylimidazole, polypyrrolidone, polyacrylate derivatives, polymethacrylate derivatives, polystyrene derivatives It is suitably a body like. Among these, from the viewpoint of heat resistance and electrolytic solution resistance (swelling resistance), it is more preferable to include any of polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, polyimide, polyquinoline, and polyquinoxaline. More preferably, it contains a sulfone. The aromatic hydrocarbon resin may be one or a mixture of the above polymers, or may be a copolymer obtained by copolymerizing two or more monomers constituting the polymer.
The number average molecular weight of the aromatic hydrocarbon resin used in the present invention is preferably 1,000 to 1,000,000. From the viewpoint of the strength and workability of the obtained electrolyte membrane, 5,000 to 500, 000 is more preferable, and 10,000 to 200,000 is particularly preferable. If the number average molecular weight is 1,000 or more, the strength of the obtained electrolyte membrane can be sufficiently maintained, and if it is 1,000,000 or less, sufficient workability can be maintained.

(1-2-2) Protonic acid group Examples of the protonic acid group present in the aromatic hydrocarbon resin include functional groups that readily release protons. For example, a sulfonic acid group (—SO ₃ H), a carboxylic acid group (—COOH), a phosphoric acid group (—PO ₃ H ₂ ), an alkyl sulfonic acid group (— (CH ₂ ) _n SO ₃ H), an alkyl carboxylic acid At least one selected from the group consisting of a group (— (CH ₂ ) _n COOH), an alkylphosphonic acid group (— (CH ₂ ) _n PO ₃ H ₂ ), and a phenolic hydroxyl group (—Ph—OH) Those included above are preferred (n is, for example, 1 to 10, preferably 1 to 5, for example).
A part of the sulfonic acid group, carboxylic acid group, and phosphoric acid group may be substituted with an alkyl group, sodium, potassium, calcium, or the like. The alkyl group and alkylene group contained in the acid-generating group have 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms.
In order to introduce the proton acid group into the main skeleton of the aromatic hydrocarbon resin, various known functional group introduction reactions can be used. For example, when introducing a sulfonic acid group, a sulfonating agent is used. Although it does not specifically limit as this sulfonating agent, For example, a concentrated sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, a sulfuric anhydride complex etc. can be used conveniently. In addition, when a carboxylic acid group is introduced, an oxidation reaction, a hydrolysis reaction of a carboxylic acid derivative, a transfer reaction, or the like can be used. In the case of introducing a phenolic hydroxyl group, a substitution reaction such as halogen, a reduction reaction such as quinone, a hydrocarbon oxidation reaction, or the like can be used.
In addition, the introduction of the proton acid group into the main skeleton of the aromatic hydrocarbon resin may be achieved by introducing the proton acid group into the monomer for producing the aromatic hydrocarbon resin before the polymerization of the aromatic hydrocarbon resin. desirable. By introducing proton acid groups at the monomer stage, sulfonic acid groups are uniformly introduced into the polymer chain, resulting in good oxidation resistance, easy control of proton conductivity, and constant quality electrolyte. Membranes can be manufactured. In addition, introduction of proton acid groups is easier than in the case of introduction into a polymer.
Protonic acid groups are contained in an amount of, for example, 0.1 to 5, preferably 0.5 to 4, and more preferably 1 to 2 per unit skeleton constituting the aromatic hydrocarbon resin. Further, the pores of the porous substrate (holes) number of moles of protonic acid group contained in 1 cm ³ (protonic acid group density (mmol / cm ³⁾⁾ is, 0.5~1.5mmol / cm ^3, preferably Is suitably 0.7 to 1.2 mmol / cm ³ , more preferably 0.8 to 1.1 mmol / cm ³ . The proton acid group density can be obtained from the following equation.

Proton acid group density (mmol / cm ³ ) = packed polymer volume density (g / cm ³ ) × ion exchange capacity IEC (meq)
Here, the filled polymer volume density (g / cm ³ ) is the mass (g) of the polymer filled per 1 cm ³ of pores (voids) of the porous substrate constituting the electrolyte membrane. Actually, it can be calculated from the mass (g) of the polymer filled in the pores having the volume determined from [1 cm × 1 cm × film thickness after polymer filling (cm) × porosity after polymer filling].

(1-2-3) Aromatic hydrocarbon resin having a protonic acid group A preferred aromatic hydrocarbon resin having a protonic acid group of the present invention has a structure represented by the following general formula (I).

一般式（Ｉ）中、Ｘ₁及びＸ₂は、互いに同一であっても異なっていてもよく、−（ＲＯ_m）_n−である。ここで、Ｒはアルキレン基、好ましくは、炭素数１〜２０、より好ましくは、炭素数１〜１０の直鎖又は分枝鎖のアルキレン基であり；ｍは０又は１であり；ｎは０〜２０、好ましくは、０〜１０、より好ましくは１〜５の整数である。上記Ｒを示すアルキレン基は、一部ハロゲン基、水酸基、フェノール等によって置換されていてもよい。
また、本発明の好ましいプロトン酸基を有する芳香族系炭化水素樹脂は、以下の一般式（ＩＩ）で表される２価のエーテル基の構造を有していてもよい。

In general formula (I), X ₁ and X ₂ may be the same or different from each other, and are — (RO _m ) _n —. Here, R is an alkylene group, preferably a linear or branched alkylene group having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms; m is 0 or 1; n is 0 -20, preferably 0-10, more preferably an integer of 1-5. The alkylene group representing R may be partially substituted with a halogen group, a hydroxyl group, phenol, or the like.
Moreover, the aromatic hydrocarbon resin which has a preferable proton acid group of this invention may have the structure of the bivalent ether group represented by the following general formula (II).

一般式（ＩＩ）中、Ｘ₃は、単結合、−Ｏ−、−ＳＯ₂−、−ＣＯ−、

In general formula (II), X ₃ represents a single bond, —O—, —SO ₂ —, —CO—,

である。

It is.

  Furthermore, a preferred aromatic hydrocarbon resin having a proton acid group of the present invention has a structure of a group obtained from a monomer / oligomer having three or more reactive groups represented by the following general formula (III). You may do it.

一般式（ＩＩＩ）中、Ｒ₁及びＲ₂は、Ｃ、Ｈ及びＯからなる基（即ち、２価の炭化水素基）である。上記一般式（ＩＩＩ）で示される基の分子量は、例えば、１０００以下、好ましくは、１００〜５００であることが適当である。具体的に、Ｒ₁及びＲ₂は、ベンゾフェノン、フラボン、アントラキノン、ピリジン、Ｒ₃（Ｐｈ−）_n（式中、Ｒ₃は、Ｃ_1〜100の飽和又は不飽和の、直鎖又は分枝鎖の脂肪族基、脂環式基又は芳香族基であり、ｎは３又は４である）から選択される化合物から３又は４つの水素基が脱離した置換基が挙げられる。より好ましくは、Ｒ₂は、ＣＨ₃Ｃ（Ｐｈ−）₃基である。
上記一般式（ＩＩＩ）で表される基は、Ａ、Ａ'及びＢの位置で架橋点を有する。一般式（ＩＩＩ）の基は、この架橋点を介して、本発明の電解質膜に含まれる樹脂又は多孔質基材と架橋することができる。この架橋により、エーテル結合、エステル結合、アミド結合、スルホン結合、ウレア結合、イミド結合、カルボニル結合又はキノキサリン結合を生成することができる。

In the general formula (III), R ₁ and R ₂ are groups consisting of C, H and O (that is, divalent hydrocarbon groups). The molecular weight of the group represented by the general formula (III) is, for example, 1000 or less, preferably 100 to 500. Specifically, R ₁ and R ₂ are benzophenone, flavone, anthraquinone, pyridine, R ₃ (Ph-) _n , wherein R ₃ is a C _1-100 saturated or unsaturated, linear or branched And a substituent in which 3 or 4 hydrogen groups are eliminated from a compound selected from the group consisting of an aliphatic group, an alicyclic group, and an aromatic group in a chain, and n is 3 or 4. More preferably, R ₂ is a CH ₃ C (Ph—) ₃ group.
The group represented by the general formula (III) has a crosslinking point at positions A, A ′ and B. The group of the general formula (III) can be crosslinked with the resin or the porous substrate contained in the electrolyte membrane of the present invention through this crosslinking point. By this crosslinking, an ether bond, an ester bond, an amide bond, a sulfone bond, a urea bond, an imide bond, a carbonyl bond, or a quinoxaline bond can be generated.

  A representative example of the synthesis of aromatic hydrocarbon resins having a protonic acid group is a method of synthesizing a polyethersulfone by MacGrath et al. (James E. McGrath, et al., “Direct polymerization of sulfonated poly (arylene). ether sulfone) random (statistical) copolymers: candidates for new proton exchange membranes ", Journal of Membrane Science 197 (2002) pp.231-242). That is, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (4,4′-dihydroxy-3,3′-disulfonic acid diphenylsulfone sodium salt) and 4,4′-dichlorodiphenylsulfone (bis ( 4-Chlorophenyl) sulfone) is used as a halogen group-containing monomer, and this is reacted with a hydroxyl group-containing monomer such as 4,4′-dihydroxybiphenyl to synthesize an aromatic hydrocarbon resin having a proton acid group. In this synthesis method, an aprotic polar solvent such as N-methyl-2-pyrrolidinone N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, hexamethylphosphonamide or the like is used for the reaction solution. Moreover, bases, such as potassium carbonate, sodium carbonate, potassium hydrogencarbonate, sodium hydrogencarbonate, sodium hydroxide, potassium hydroxide, are used as a reaction catalyst. In addition to the above monomers, sulfonic acid group-containing 4,4'-dichlorodiphenyl sulfone, sulfonic acid group-containing 4,4'-difluorodiphenyl sulfone, sulfonic acid group-containing 4,4'-dichlorobenzophenone, sulfone Acid group-containing 4,4'-difluorobenzophenone, sulfonic acid group-containing 1,3-dichloronaphthalene, sulfonic acid group-containing 1,3-difluoronaphthalene, sulfonic acid group-containing 1,5-dichloronaphthalene, sulfonic acid group-containing 1, 5-difluoronaphthalene, 4,4'-difluorodiphenylsulfone, 4,4'-dichlorobenzophenone, 4,4'-difluorobenzophenone, 1,3-dichloronaphthalene, 1,3-difluoronaphthalene, 1,5-dichloronaphthalene 1,5-difluoronaphthalene. Moreover, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl thioether, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxybenzophenone as monomers containing hydroxyl groups 1,3-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, and the like.

(1-2-4) Other Resins The proton conductive polymer composition used in the present invention may be a polymer composition composed of only one kind of the aromatic hydrocarbon resin, but is used in the present invention. A resin other than one or more of the aromatic hydrocarbon resins may be contained within a range that does not significantly deteriorate the properties of the proton conductive polymer composition. By adding these, flexibility can be added to the proton conductive polymer composition.
Moreover, the effect of suppressing the swelling of the electrolyte and preventing the proton conductive polymer composition and the like to be held in the pores of the porous substrate from segregating (eluting) outside the pores can be obtained.
Specific examples of such other resins include general-purpose resins such as polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), ABS resin and AS resin; polyacetate (POM) ), Polycarbonate (PC), polyamide (PA: nylon), engineering plastics such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); and polyacrylonitrile, polyacrylic acid, polyphenylene sulfide (PPS), polyethersulfone (PES) ), Polyketone (PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT), polyarylate (PAR), and various liquid crystal polymers (LCP); Carboxymethyl resins, phenol resins, novolak resins, and thermosetting resins such as bismaleimide resins. Further, the other resin referred to here may have a structure having a crosslinking point capable of binding to the resin or the substrate contained in the electrolyte membrane of the present invention in the structure of the resin.
The crosslinking point is preferably a reactive group capable of forming an ether bond, an ester bond, an amide bond, a sulfone bond, a urea bond, an imide bond, a carbonyl bond, or a quinoxaline bond.
The number average molecular weight of other resins is preferably 1,000 to 1,000,000, more preferably 5,000 to 500,000 from the viewpoint of the strength and workability of the obtained electrolyte membrane, It is especially preferable that it is 10,000-200,000. If the number average molecular weight is 1,000 or more, the strength of the obtained electrolyte membrane can be sufficiently maintained, and if it is 1,000,000 or less, sufficient workability can be maintained.
The other resin is preferably present in an amount of 0.01 to 90% by weight, preferably 10 to 50% by weight, based on the proton conductive polymer composition. If it is 0.01% by weight or more, it is preferable because effects such as swelling of the electrolyte and reduction of methanol permeability can be sufficiently obtained. If it is 90% or less, it is preferable because good proton conductivity can be obtained.

(1-2-5) Other Additives The proton conductive polymer composition used in the present invention may contain, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, and a crosslinker as necessary. In addition, various additives such as a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, a dispersant, and a polymerization inhibitor may be included. In particular, examples of the crosslinking agent include epoxy resins, bismaleimides, and acrylate resins.
These additives are preferably added in an amount of 0.01 to 50% by weight, more preferably 0.1 to 30% by weight, based on the proton conductive polymer composition.

(1-2-6) Composition of proton conductive polymer composition The composition of the proton conductive polymer composition is such that the aromatic hydrocarbon resin having a proton acid group is, for example, It is preferable to contain 50% by weight or more, preferably 70% by weight or more. When the amount of the aromatic hydrocarbon resin is 50% by weight or more, the proton acid group concentration in the proton conductive polymer composition can be kept sufficiently, and good proton conductivity can be obtained. Further, it is preferable because the phase of the aromatic hydrocarbon resin having a proton acid group does not become a discontinuous phase and the mobility of protons to be conducted does not decrease.

(1-2-7) Structure of water contained in proton conductive polymer composition The state of water contained in the electrolyte can be easily measured by DSC. When DSC was measured using a sample obtained by wiping off the surface of the electrolyte membrane after impregnation at 25 ° C. for 24 hours, a sharp peak near 0 ° C. was free water, and a broad peak at −20 ° C. to 20 ° C. Can be defined as bound water, and water with no peak appearing as antifreeze water.
Among these, free water is not affected by the electrolyte or the base material and is in the same state as bulk water, and therefore easily forms a cluster structure and causes methanol permeation and gas permeation. In addition, although bound water is suppressed to some extent by molecular movement of water, it still tends to form a cluster structure and causes methanol permeation and gas permeation. Therefore, it is preferable to reduce free water and bound water as much as possible, and it is preferable that only antifreeze water having strong interaction with the electrolyte or the base material is contained. The content of free water (the number of water molecules) is preferably 0 to 0.5, more preferably 0 to 0.1, per protonic acid group contained in the electrolyte membrane. The bound water is preferably 0 to 1 per proton acid group contained in the electrolyte membrane, more preferably 0 to 0.5, and still more preferably 0 to 0.1.
Antifreeze water is preferably 100 to 1 per proton acid group contained in the electrolyte membrane, more preferably 30 to 2, and even more preferably 20 to 4. If it is 1 or less, proton conduction is not sufficient, and if it is 100 or more, entry of peroxide or the like is facilitated, resulting in a shortened life.

(2) Electrolyte Membrane and Method for Producing the Same The electrolyte membrane of the present invention introduces (fills and inserts) a proton conductive polymer composition into the pores of the porous substrate, and the pores of the porous substrate. A proton-conducting polymer composition is held (fixed or supported) therein.
(2-1) Method for Producing Electrolyte Membrane The method for introducing the proton conductive polymer composition into the porous substrate is not particularly limited. For example, (a) the monomer and / or in the pores of the porous substrate A method of polymerizing oligomers, and (b) a method of introducing a proton conductive polymer composition into pores of a porous substrate by impregnating a porous substrate with a solvent solution of the proton conductive polymer composition Is mentioned.
(A) Method of polymerizing monomers and / or oligomers in the pores of the porous substrate The method of polymerizing monomers and / or oligomers in the pores of the porous substrate includes the following steps: (1) Porous Holding a monomer and / or oligomer for forming a proton conductive polymer composition in the pores of the substrate; and (2) polymerizing the monomer and / or oligomer in the pores. Is appropriate.

In this polymerization method, the proton conductive polymer composition is polymerized inside the pores of the porous substrate, and this method allows the proton conductive polymer composition to be polymerized inside the pores of the porous substrate. And the proton conductive polymer composition can be prevented from segregating (eluting) outside the pores.
Further, at the time of polymerization, the proton conductive polymer composition and the porous substrate can be reacted. For example, when using a polyethersulfone having a hydroxyl group as a reactive group serving as a crosslinking point as a proton conductive polymer composition and using a polyimide as a porous substrate, the terminal hydroxyl group of the polyethersulfone and the polyimide porous Unreacted polyamic acid in the porous substrate can react to form an ester bond and crosslink. As described above, the reaction between the pores and the proton conductive polymer composition causes crosslinking so that the proton conductive polymer composition can be prevented from being precipitated (eluted) outside the pores.
The monomer and / or oligomer used here has 3 or more, preferably 3 or 4 reactive groups. Here, examples of the reactive group include a hydroxyl group and a carboxyl group.
Moreover, it is preferable to produce | generate an ether bond, ester bond, an amide bond, a sulfone bond, a urea bond, an imide bond, a carbonyl bond, and a quinoxaline bond by bridge | crosslinking. Among these, it is desirable to generate an ether bond or an ester bond.

As this monomer, 1,1,1-tris (4-hydroxyphenyl) ethane, 1,3,5-tris (4-hydroxyphenyl) benzene, 2,4,4′-trihydroxybenzophenone, 2,3, 4-trihydroxybenzophenone, 4 ′, 5,7-trihydroxyflavanone, 3,5,7-trihydroxyflavone, 4 ′, 5,7-trihydroxyflavone, 5,6,7-trihydroxyflavone, 6- Examples thereof include those having a tri- or higher functional hydroxy group such as methyl-1,3,8-trihydroxyanthraquinone, 2,4,5-trihydroxypyridine, 2,2 ′, 4,4′-tetrahydroxybenzophenone.
Moreover, as an oligomer, the said monomer contains 2 or more molecules, Preferably the thing containing 2-100 is preferable.
The amount of the monomer and / or oligomer having 3 or more reactive groups is, for example, 0.0001 to 80 mol%, preferably 0.001 of the whole monomer and / or oligomer used in the method for producing an electrolyte membrane. It is suitable that it is -50 mol%, More preferably, it is 0.01-40 mol%. If it is 80 mol% or less, the obtained electrolyte membrane has sufficient flexibility, and if it is 0.0001 mol% or more, a sufficient effect as the electrolyte of the present invention can be obtained.

In a specific reaction method, first, monomers and / or oligomers for forming a proton conductive polymer composition are retained in the pores. That is, a solution in which the monomer and / or oligomer for forming the proton conductive polymer composition of the present invention is used as it is or in a solvent is prepared.
Here, as the solvent, for example, toluene, acetone, N-methyl-2-pyrrolidinone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc) and the like can be used. The porous substrate is immersed in the monomer and / or oligomer, or a solvent solution containing them, and the monomer and / or oligomer is held in the pores of the porous substrate.
The monomer and / or oligomer is then polymerized in the pores. As the polymerization conditions, normal conditions for polymerizing the monomers and / or oligomers may be employed. For example, after heat treatment at 60 to 200 ° C., preferably 80 to 180 ° C. for 1 to 24 hours, preferably 2 to 12 hours, the temperature is further higher to 150 to 250 ° C., preferably 160 to 200 ° C. The temperature is raised and maintained for a further 8 to 64 hours, preferably 12 to 48 hours.
During the polymerization, it is preferable to seal the pores of the porous substrate. Sealing the pores means that the solvent inside the pores is prevented from scattering. By sealing, the solvent is less likely to be scattered, and the solvent is slowly removed over the time required for the polymerization. It becomes like this. In this sense, the sealing here does not mean a complete sealing in which the solvent does not scatter at all, but the scatter of the solvent is, for example, at least 70%, preferably 80-99, compared to the completely released state. 0.9%, more preferably 90-99%. Sealing is performed by covering the both surfaces of the porous substrate with a resin film such as non-porous polyimide or a glass substrate.
After completion of the polymerization reaction, it is washed with water and vacuum dried at 40 to 120 ° C., preferably 80 to 100 ° C. for 0.5 to 10 hours, preferably 1 to 5 hours, and water is removed to obtain a polymer.

(B) Method of introducing a proton conductive polymer composition into pores of a porous substrate by impregnating the porous substrate with a solvent solution of the proton conductive polymer composition The method of impregnating the solvent solution of the polymer composition includes the following steps: (1) immersing the porous substrate in the solvent solution of the proton conductive polymer composition, and the pores of the porous substrate Introducing the proton conductive polymer composition therein; and (2) holding the porous substrate holding the proton conductive polymer composition at a temperature of 60 ° C. or higher for at least 1 hour; It is appropriate to include.
Specifically, the porous substrate is first immersed in a solvent solution of the proton conductive polymer composition. Thereby, the proton conductive polymer composition is introduced into the pores of the porous substrate.
The obtained solvent solution contains the proton conductive polymer composition in an amount of, for example, 5 to 50% by weight, preferably 10 to 40% by weight. As the solvent, for example, toluene, acetone, N-methyl-2-pyrrolidinone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc) and the like can be used. In particular, use of acetone is preferable because impurities in the porous substrate and the solvent solution can be removed. Furthermore, it is preferable to immerse the porous substrate while degassing under reduced pressure. In addition, a crosslinking agent may be added to crosslink part of the pores and part of the proton conductive polymer composition. In order to crosslink, it is preferable to use an aromatic hydrocarbon resin containing bismaleimide, an epoxy group, and an acrylate as the proton conductive polymer composition.

Next, the porous substrate holding the proton conductive polymer composition is heat-treated. By this heat treatment, the proton conductive polymer composition is further introduced into the pores of the porous substrate, the solvent is removed, and the proton conductive polymer composition is filled and fixed in the pores. It becomes.
The heat treatment temperature is suitably, for example, a heat treatment temperature of 60 to 200 ° C., preferably 80 to 180 ° C. The heat treatment time is suitably at least 1 hour, for example, 1 to 36 hours, preferably 1 to 30 hours, more preferably 2 to 24 hours. By setting the temperature to 60 ° C. or higher, the proton conductive polymer composition can be promptly introduced and fixed in the pores of the porous substrate. Moreover, if it is 1 hour or more, a proton-conductive polymer composition will fully osmose | permeate in a pore, and if it is 36 hours or less, a porous base material will not thermally decompose.
During the heat treatment, the pores of the porous substrate are preferably sealed. By sealing, the solvent is less likely to be scattered, and the solvent is slowly removed over the time required for the heat treatment. By sealing in this way, more proton conductive polymer composition is introduced into the pores of the porous substrate without the proton conductive polymer composition being deposited on the surface of the porous substrate. Will be. The sealing here does not mean a complete sealing in which the solvent does not scatter at all, and the scatter of the solvent is, for example, at least 70%, preferably 80 to 99.9%, compared to a completely released state. More preferably, it refers to a state in which 90 to 99% is suppressed. Sealing is performed by covering the both surfaces of the porous substrate with a resin film such as non-porous polyimide or a glass substrate.

  The electrolyte membrane obtained as described above is subjected to known treatments such as washing, drying, sulfonation, chlorosulfonation, phosphoniumation, hydrolysis, etc. as necessary, and the proton conductive polymer composition in the electrolyte membrane A desired cation exchange group can be introduced into the product to form a cation exchange resin membrane.

(2-2) Properties of Electrolyte Membrane The obtained electrolyte membrane is obtained by holding the proton conductive polymer composition in all or part of the pores of the porous substrate. In the retention, the pore and the proton conductive polymer composition are not chemically bonded, but the proton conductive polymer composition enters the pore and the proton conductive polymer composition does not exit from the pore. The state and immobilization refer to a state in which the pore and the proton conductive polymer composition are chemically bonded, and the proton conductive polymer composition is fixed in the pore. The latter immobilization has part of the pores of the porous substrate, for example, part of the functional group of the polymer constituting the porous substrate and the proton acid group constituting the proton conducting polymer composition. When a part of the aromatic hydrocarbon resin, for example, a part of the functional group of the polymer constituting the aromatic hydrocarbon resin is bonded, and the pores and the proton conductive polymer composition are immobilized including.

The obtained electrolyte membrane can have any film thickness depending on the purpose, but is preferably as thin as possible from the viewpoint of proton conductivity. Specifically, it is a dry film thickness, for example, 5-200 μm, preferably 5-75 μm, more preferably 5-50 μm. If the thickness of the electrolyte membrane is 5 μm or more, handling of the electrolyte membrane becomes easy, and the problem of short circuit of the fuel cell using this electrolyte membrane can be avoided. The electric resistance value can be kept low, and the power generation performance of the fuel cell using this electrolyte membrane can be improved satisfactorily. Further, a layer of a proton conductive polymer composition may be further laminated on the surface of the electrolyte membrane of the present invention.
When the electrical conductivity of the electrolyte membrane of the present invention is high, it is possible to polish both surfaces of the membrane, or to remove the surface layer of several microns by performing sandblasting or the like on both surfaces. Such polishing of the membrane and the removal of the surface layer also lead to an improvement in adhesion when the electrode catalyst layer is deposited on the electrolyte membrane of the present invention.
The electrolyte membrane of the present invention may be heterogeneous with respect to the cross section of the membrane to reduce the electrical resistance of the membrane. That is, only one surface layer portion of the membrane like a reverse osmosis membrane is a porous membrane having a dense structure (porosity 10 to 60%, preferably 20 to 50%, average pore diameter 0.001 to 10 μm, preferably 0.01 to 5 μm) and porous on the inside and on the opposite side (porosity 30 to 90%, preferably 40 to 80%, average pore diameter 0.01 to 100 μm, preferably 0.1 to 5 μm) It may be. A particularly preferable structure when the electrolyte membrane of the present invention is used as a reverse osmosis membrane is a case where both surface layer portions of the membrane are dense structures as described above and the inside is porous as described above.
The electrolyte membrane of the present invention preferably contains a sufficient amount of the proton conductive polymer composition in the porous substrate. The amount of the proton conductive polymer composition contained in the porous substrate can be evaluated by the filling rate. The filling rate means the mass ratio of the proton conductive polymer composition filled in the porous substrate, and the following formula:
[Filling rate] = [mass% of proton-conducting polymer composition actually filled] / [mass% of proton-conducting polymer composition when theoretically filled 100%] × 100
It can be obtained more. The filling rate of the electrolyte membrane of the present invention is, for example, 18 to 83%, preferably 30 to 70%, more preferably 40 to 55%. By increasing the filling rate in this way, the amount of bound water and free water contained in the electrolyte can be reduced.

(3) Membrane-electrode assembly The membrane-electrode assembly of the present invention includes the above electrolyte membrane and electrodes provided on at least one surface of the electrolyte membrane, usually both surfaces of the electrolyte membrane.
(3-1) Electrode The electrode of this invention has a gas diffusion layer and the catalyst layer provided on this gas diffusion layer and / or inside.
(3-1-1) Gas diffusion layer As the gas diffusion layer, for example, a known substrate having air permeability such as a carbon fiber woven fabric or carbon paper can be used. Preferably, those substrates and the like that have been subjected to water repellent treatment are used. The water-repellent treatment is performed, for example, by immersing these substrates in an aqueous solution of a water-repellent agent made of a fluororesin such as polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, drying, and firing. Done.

(3-1-2) Catalyst layer As the catalyst material used in the catalyst layer, for example, platinum group metals such as platinum, rhodium, ruthenium, iridium, palladium, osnium, and alloys thereof are suitable. These catalytic materials and salts of the catalytic materials may be used alone or in combination. Among them, metal salts and complexes, particularly ammine complexes represented by [Pt (NH ₃ ) ₄ ] X ₂ or [Pt (NH ₃ ) ₆ ] X ₄ (X is a monovalent anion) are preferable. Moreover, when using a metal compound as a catalyst, the mixture of several compounds may be used and double salt may be sufficient. For example, by using a mixture of a platinum compound and a ruthenium compound, formation of a platinum-ruthenium alloy can be expected by a reduction process.
The particle size of the catalyst is not particularly limited, but it is preferable that the average particle size is 0.5 to 20 nm from the viewpoint of an appropriate size that increases the catalyst activity. K.K. In a study by Kinoshita et al. (J. Electrochem. Soc., 137, 845 (1990)), it is reported that the particle size of platinum having a high activity for oxygen reduction is about 3 nm.
A cocatalyst can be further added to the catalyst used in the present invention. Examples of the cocatalyst include finely divided carbon. The finely divided carbon is preferably one in which the coexisting catalyst exhibits high activity. For example, when a platinum group metal compound is used as the catalyst, acetylene black such as Denka Black, Valcan XC-72, Black Peral 2000, etc. Is appropriate.
The amount of the catalyst varies depending on the deposition method and the like, but is deposited on the surface of the gas diffusion layer, for example, in the range of about 0.02 to about 20 mg / cm ² , preferably in the range of about 0.02 to about 20 mg / cm ^2. It is appropriate. Moreover, it is appropriate that it is present in an amount of 0.01 to 10% by weight, preferably 0.3 to 5% by weight, based on the total amount of the electrode.

(3-1-3) Binder The electrode preferably has a binder in and / or on the surface of the electrode. Such a binder promotes the bond between the gas diffusion layer and the catalyst layer and the bond between the electrode and the electrolyte membrane. As the binder, for example, all polymers that can be used in the present invention, and other fluorine-based solid polymer electrolytes such as Nafion (R) and Flemion (R) can be used.
(3-1-4) Properties of electrode The obtained electrode is porous. The average pore diameter of the porous material is, for example, 0.01 to 50 μm, preferably 0.1 to 40 μm. Furthermore, the porosity of this porous material is, for example, 10 to 99%, preferably 10 to 60%.

(3-2) Manufacture of membrane-electrode assembly The membrane-electrode assembly of the present invention is manufactured by providing the electrode on an electrolyte membrane.
Preferably, the catalyst layer side of the electrode is joined to the electrolyte membrane side. Examples of the method for producing the membrane-electrode assembly include the following three methods.
(A) A method in which a catalyst layer is directly formed on an electrolyte membrane to form a catalyst layer, and a gas diffusion layer is formed on the formed catalyst layer. For example, a catalyst material containing a perfluorocarbon polymer having an ion exchange group, a platinum group catalyst, fine carbon powder (carbon black) and other additives is applied onto an electrolyte membrane by a method described in JP-T-2000-516014, sprayed, There is a method in which a catalyst layer is formed by printing or the like, and a gas diffusion layer is heat-pressed on the catalyst layer by hot pressing or the like.
(B) A method of preparing a catalyst layer by previously applying a catalyst substance on a substrate, transferring the obtained catalyst layer onto an electrolyte membrane, and forming a gas diffusion layer on the formed catalyst layer. For example, polytetrafluoroethylene in advance and platinum black synthesized by the Thomas method or the like are uniformly mixed, applied onto a Teflon (registered trademark) sheet substrate, pressure-molded, transferred onto the electrolyte membrane, Further, there is a method in which a gas diffusion layer is disposed and the obtained laminate is pressure-bonded.
(C) A method in which an electrode is prepared in advance by immersing the gas diffusion layer in a catalyst substance solution, and the obtained electrode is provided on the electrolyte membrane. For example, the gas diffusion layer is immersed in a solution (paste) of a soluble platinum group salt to adsorb (ion exchange) the soluble platinum group salt on and in the gas diffusion layer. Next, there is a method in which a metal serving as a catalyst is deposited on a gas diffusion layer by dipping in a reducing agent solution such as hydrazine or Na ₂ BO ₄ .

A more preferable method for producing the membrane-electrode assembly of the present invention includes a method in which an electrode material containing a catalyst substance and a gas diffusion layer material is directly applied on the electrolyte membrane. Specifically, catalyst-supporting carbon particles supporting a catalyst material such as platinum-ruthenium (Pt-Ru) platinum (Pt) are used as the catalyst material, and the catalyst material is used as a solvent such as water, a solid polymer electrolyte, or the like. And a water repellent such as polytetrafluoroethylene (PTFE) particles optionally used in the manufacture of the gas diffusion layer to produce a paste. This paste is directly applied to the electrolyte membrane of the present invention by coating or spraying to form a film, followed by heating and drying to form a catalyst layer (or a part of the gas diffusion layer when a water repellent is included) on the polymer electrolyte. A water repellent layer formed).
On this catalyst layer, a gas diffusion layer such as carbon paper optionally treated with water repellency is hot-pressed to produce an electrode.
The thickness of the catalyst layer at this time is suitably, for example, 0.1 to 1000 μm, preferably 1 to 500 μm, more preferably 2 to 50 μm.

  As for the said paste, it is desirable to adjust the viscosity to the range of 0.1-1000 Pa.s. This viscosity can either (i) select each particle size, (ii) adjust the composition of the catalyst particles and binder, (iii) adjust the water content, or (iv) The viscosity can be adjusted preferably by adding viscosity modifiers such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose and cellulose, and polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, sodium polyacrylate and polymethyl vinyl ether.

(4) Fuel cell The fuel cell of the present invention uses the membrane-electrode assembly. Examples of the fuel cell of the present invention include a solid polymer type (PEFC) and a direct methanol supply type fuel cell (DMFC).
The fuel cell manufacturing method of the present invention includes a step of arranging the electrolyte membrane between two electrodes to obtain a membrane-electrode assembly.
Specifically, for example, a catalyst layer is attached on each surface of the electrolyte membrane of the present invention, and two electrodes, an anode electrode and a cathode electrode, are further provided on each surface of the membrane-electrode assembly provided with a gas diffusion layer. A fuel chamber capable of holding normal pressure or pressurized hydrogen gas, pressurized methanol gas or aqueous methanol solution is placed on one side of the resulting laminate, with the plates placed or sandwiched, and the other side of the laminate is placed. A fuel cell is manufactured by disposing a gas chamber capable of holding oxygen or air under normal pressure or pressure on the surface. The fuel cell produced in this way takes out electrical energy generated by the reaction of hydrogen or methanol and oxygen.
Further, in order to take out necessary electric power, a number of units may be arranged in series or in parallel with this membrane-electrode assembly or laminate as one unit.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
37.247 g of 4,4′-dihydroxybiphenyl, 40.208 g of bis (4-chlorophenyl) sulfone, 30,558 g of sodium 4,4′-dihydroxy-3,3′-disulfonic acid diphenylsulfone, 33.17 g of potassium carbonate, 250 ml of dimethylacetamide was charged into a 500 ml four-necked round bottom flask equipped with a Dean-Stark trap, condenser, stirrer and nitrogen feed tube. The mixture was heated to 100 ° C. on an oil bath, 200 ml of toluene was added, heated to 160 ° C. and refluxed for 4 hours to distill off the toluene. The temperature of the oil bath was raised to 180 ° C. to distill off toluene, and polymerization was continued at 180 ° C. for 80 hours. After cooling, this solution was poured into 2500 ml of water to precipitate a polymer, and the polymer was washed with water and dried (yield 99%). The obtained polymer (powder) was redissolved in N-methyl-2-pyrrolidinone to prepare a polyethersulfone solution (solid content 20% by weight). Moreover, it was 30,000 when the number average molecular weight was measured using the gel permeation chromatograph (GPC) (polystyrene conversion). When the ratio of the carbon (C) and sulfur (S) components was determined by elemental analysis (Perkin PE-2400), this polymer was found to have an EW value of 829 (g · eq ⁻¹ ).
Polyimide membrane, which is a sufficiently degassed porous substrate (trade name UPILEX-PT, manufactured by Ube Industries, Ltd.), porosity 50%, film thickness 30 μm, average through-hole diameter 0.35 μm (measured with a mercury porosimeter) ) Was immersed in N-methyl-2-pyrrolidinone and then kept at 120 ° C. for 15 minutes. After the heat treatment, the polyimide film was pulled up from N-methyl-2-pyrrolidinone, and this polyimide film was immersed in a polyethersulfone solution (20% by weight) prepared as described above.
After the immersion, the resin adhering to the surface of the porous substrate was sufficiently removed, and then the surface was covered with a glass substrate, followed by heat treatment at 130 ° C. for 5 hours to slowly remove the solvent and filling. The filled membrane was washed with water, vacuum dried at 80 ° C. for 2 hours, and water was removed to fill the pores of the polyimide membrane with sulfonated polyethersulfone (S-PES polymer). Thereafter, it was sufficiently washed with water and immersed in a 1N sulfuric acid solution for 24 hours. After the immersion, it was dried to obtain the electrolyte membrane of the present invention. From the difference in mass after filling the proton conductive polymer composition, an electrolyte membrane having a filling rate per weight of 30% and a film thickness of 30 μm was obtained.

(Example 2)
37.242 g of 4,4′-dihydroxybiphenyl, 45.952 g of bis (4-chlorophenyl) sulfone, 20.372 g of sodium diphenylsulfone 4,4′-dihydroxy-3,3′-disulfonate, 33.17 g of potassium carbonate, dimethyl 250 ml of acetamide was charged into a 500 ml four-necked round bottom flask equipped with a Dean-Stark trap, condenser, stirrer and nitrogen feed tube. This mixture was heated to 100 ° C. on an oil bath, 200 ml of toluene was added, heated to 160 ° C. and refluxed for 4 hours to distill off the toluene. The temperature of the oil bath was raised to 180 ° C. to distill off toluene, and polymerization was continued at 180 ° C. for 80 hours. After cooling, this solution was poured into 2500 ml of water to precipitate a polymer, and the polymer was washed with water and dried (yield 99%). The obtained polymer (powder) was redissolved in N-methyl-2-pyrrolidinone to prepare a polyethersulfone solution (solid content 20% by weight). Moreover, it was 30,000 when the number average molecular weight was measured using the gel permeation chromatograph (GPC) (polystyrene conversion). When the ratio of the carbon (C) and sulfur (S) components was determined by elemental analysis (Perkin PE-2000), this polymer was found to have an EW value of 1163 (g · eq ⁻¹ ).
After immersing a polyimide film (made by Ube Industries, Ltd .: trade name UPILEX-PT, porosity 50%, film thickness 30 μm), which is a sufficiently degassed porous base material, in N-methyl-2-pyrrolidinone, 120 ° C. For 15 minutes. After the heat treatment, the polyimide film was pulled up from N-methyl-2-pyrrolidinone, and this polyimide film was immersed in a polyethersulfone solution (20% by weight) prepared as described above. After the immersion, the resin adhering to the surface of the porous substrate was sufficiently removed, and then the surface was covered with a glass substrate, heat treated at 130 ° C. for 5 hours, the solvent was slowly removed and filling was performed. The filled membrane was washed with water, vacuum dried at 80 ° C. for 2 hours, and water was removed to fill the pores of the polyimide membrane with sulfonated polyethersulfone (S-PES polymer). Thereafter, it was sufficiently washed with water and immersed in a 1N sulfuric acid solution for 24 hours. After the immersion, it was dried to obtain the electrolyte membrane of the present invention. From the difference in mass after filling the proton conductive polymer composition, the filling rate per weight of the electrolyte membrane filled in the pores was 30%, and an electrolyte membrane having a thickness of 30 μm was obtained.

(Example 3)
After immersing a polyimide film (made by Ube Industries, Ltd .: trade name UPILEX-PT, porosity 50%, film thickness 30 μm), which is a sufficiently degassed porous base material, in N-methyl-2-pyrrolidinone, 120 ° C. For 15 minutes. After the heat treatment, the polyimide film was pulled up from N-methyl-2-pyrrolidinone, and this polyimide film was immersed in the polyethersulfone solution (solid content 15 wt%, N-methyl-2-pyrrolidinone solution) prepared in Example 1. The substrate surface was covered with a glass substrate, and heat treatment was performed at 130 ° C. for 5 hours to remove the solvent slowly. This operation was repeated for filling. Thereafter, the membrane was washed with water, vacuum dried at 80 ° C. for 2 hours, and water was removed to fill the pores of the polyimide membrane with sulfonated polyethersulfone (S-PES polymer). Thereafter, it was sufficiently washed with water and immersed in a 1N sulfuric acid solution for 24 hours. After the immersion, it was dried to obtain the electrolyte membrane of the present invention. The electrolyte membrane whose filling rate and film thickness are shown in Table 1 was prepared by changing the number of times of filling.

Example 4
After immersing a polyimide film (made by Ube Industries, Ltd .: trade name UPILEX-PT, porosity 50%, film thickness 30 μm), which is a sufficiently degassed porous base material, in N-methyl-2-pyrrolidinone, 120 ° C. For 15 minutes. After the heat treatment, the polyimide film was pulled up from N-methyl-2-pyrrolidinone, and the polyimide film was immersed in the polyethersulfone solution (solid content 15 wt%, N-methyl-2-pyrrolidinone solution) prepared in Example 2. The substrate surface was covered with a glass substrate, and heat treatment was performed at 130 ° C. for 5 hours to remove the solvent slowly. This operation was repeated for filling. Thereafter, the membrane was washed with water, vacuum dried at 80 ° C. for 2 hours, and water was removed to fill the pores of the polyimide membrane with sulfonated polyethersulfone (S-PES polymer). Thereafter, it was sufficiently washed with water and immersed in a 1N sulfuric acid solution for 24 hours. After the immersion, it was dried to obtain the electrolyte membrane of the present invention. The electrolyte membrane whose filling rate and film thickness are shown in Table 2 was prepared by changing the number of times of filling.

(Comparative Example 1)
Commercially available Nafion 117 (film thickness 175 μm) was used. A porous substrate was not used.

(Comparative Example 2)
The polyethersulfone solution (solid content 20% by weight) prepared in Example 1 was cast on a glass substrate, cast on a glass plate, dried at 100 ° C. for 30 minutes, and 160 ° C. for 1 hour, Was distilled off. Thereafter, the membrane was immersed in a 1N sulfuric acid solution for 24 hours to obtain an electrolyte membrane having a thickness of 50 μm. A porous substrate was not used.

(Comparative Example 3)
The polyethersulfone solution (solid content 20% by weight) prepared in Example 2 was cast on a glass substrate and cast on a glass plate, and then dried at 100 ° C. for 30 minutes and 160 ° C. for 1 hour. Was distilled off. Thereafter, the membrane was immersed in a 1N sulfuric acid solution for 24 hours to obtain an electrolyte membrane having a thickness of 50 μm. A porous substrate was not used.

<Evaluation>
The obtained electrolyte membranes of Examples and Comparative Examples were cut into dimensions of 2 cm × 2 cm, and the area change rate, oxidation resistance, shape stability, proton conductivity, and methanol permeability were evaluated by the following methods.
(I) Proton conductivity The electrolyte membrane was cut into a strip of 10 mm × 30 mm, both ends were sandwiched between platinum plates (5 mm × 50 mm), and sandwiched with a Teflon (registered trademark) measurement probe. The sandwiched laminate was measured with a 1260 FREQUENCY RESPONSE ANALYSER manufactured by SOLARTRON in a 25 ° C., 100% humidity atmosphere, and the proton conductivity was determined from the following equation.
Proton conductivity [S / cm] = Platinum plate interval [cm] / (membrane width [cm] × film thickness [cm] × resistance [Ω])
If the proton conductivity is 0.01 Sm ⁻¹ or more, preferably 0.03 Sm ⁻¹ or more, it can be said to have good proton conductivity.

(Ii) Methanol Permeability Measurement was performed at 25 ° C. using a 30 wt% aqueous methanol solution by the method of Yamaguchi et al. (J. Electrochem. Soc., 2002, 149, A1448-1453). The amount of methanol permeated through the electrolyte membrane was determined by gas chromatography, and the methanol permeation amount was plotted against the change with time. From the slope of this plot, the methanol permeation flow rate J was obtained, and from this methanol permeation flow rate J, the methanol permeation coefficient P was calculated according to the following equation considering the thickness of the electrolyte membrane.
P = J × l
(P: methanol permeation coefficient (kg · μm / m ² h), J: methanol permeation flow rate (kg · μm / m ² h), l: film thickness (μm))
When the methanol permeability coefficient P was 50 (kg · μm / m ² h) or less, it was evaluated as ○ (good methanol permeability), and when it exceeded 50 (kg · μm / m ² h), it was evaluated as x.

(Iii) Activation energy The proton conductivity was measured by changing the measurement temperature in the same manner as in (i), and the activation energy was determined. An Arrhenius plot was created by plotting the absolute temperature T as 1 / T on the horizontal axis of the graph and plotting the proton conductivity s as the common logarithm Log (s) on the vertical axis. The slope G of this Arrhenius plot was determined, and the activation energy E [J / mol] was calculated from the formula E = -2.302 × G × R.
Here, R is a gas constant of 8.314 (J / K · mol).
If the activation energy is large, the proton conduction mechanism does not depend on free water or bound water. That is, when the activation energy is large, protons move only by sulfonic acid groups. On the other hand, when the activation energy is small, protons tend to move by free water or bound water contained in the sulfonic acid.

(Iv) Structure Analysis and Content of Water in Electrolyte The electrolyte membrane was immersed in water at 25 ° C. for 24 hours, and then the water adhering to the surface was wiped off to prepare a sample for low temperature DSC. The measurement conditions for the low temperature DSC were cooling from 20 ° C. to −50 ° C. at a rate of 20 ° C./min, and then increasing the temperature to 20 ° C. at a rate of 5.0 ° C./min. A baseline was taken from −30 ° C. to 10 ° C., and the melting endothermic peak area of water during the temperature rising process was analyzed. A sharp melting endothermic peak at 0 ° C. was assigned to free water, and a broad melting endothermic peak at 0 ° C. or lower was assigned to bound water for quantitative analysis. After the measurement, the sample was vacuum-dried at 90 ° C. for 4 hours, and the dry weight excluding all free water, bound water and antifreeze water was measured to determine the total water content. The difference between the amount of free water and bound water obtained from low-temperature DSC measurement and the total water content was defined as antifreeze water. By dividing the amount of free water, bound water and antifreeze water by the number of sulfonic acid groups in the sample, the number of free water, bound water and antifreeze water molecules per sulfonic acid group was determined.

＊実施例３及び４は、図５に示すような５つの測定値の平均である。 (V) Sulfonic acid group density The protonic acid group density (sulfonic acid group density) of the protonic acid group (sulfonic acid group) in the S-PES polymers of Examples 1 to 4 was determined from the following formula.

Sulfonic acid group density (mmol / cm ³ ) = packed polymer volume density (g / cm ³ ) × ion exchange capacity IEC (meq)
Here, the filled polymer volume density (g / cm ³ ) was filled in pores having a volume determined from [1 cm × 1 cm × film thickness after polymer filling (cm) × porosity after polymer filling]. Calculated from the polymer mass (g).
The results are summarized in Table 3.

* Examples 3 and 4 are the average of five measurements as shown in FIG.

<Contrast with Examples 1 and 2 and Comparative Examples 1-3>
FIG. 1 shows DSC measurement data. From the measurement data of Comparative Example 1, Comparative Example 2, and Comparative Example 3 in FIG. 1, peaks of free water and bound water were recognized. However, from the measurement data of Example 1 and Example 2 in FIG. 1, only a small peak of bound water was observed.
Table 4 shows the structural analysis and content of water, proton conductivity, activation energy, and methanol permeability (at 25 ° C., when using 30 wt% methanol). Example 1 and Example 2 showed that there was almost no free water and the amount of bound water was very low compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3. Furthermore, it was found that Example 1 and Example 2 have proton conductivity even when the free water is 0 and the bound water is 0.5 or less, and the methanol permeability can be greatly suppressed. Moreover, when an Arrhenius plot was calculated, it turned out that Example 1 and Example 2 have high activation energy. It is estimated that Example 1 and Example 2 are different in proton conduction mechanism as compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3.

<Evaluation results of Examples 3 and 4>
Regarding the electrolyte membranes having different filling rates prepared in Example 3 and Example 4, FIG. 2 shows the relationship between the filling rate and the moisture content, FIG. 3 shows the relationship between the filling rate and the number of bound water, and FIG. FIG. 4 shows the relationship with the number of antifreeze water, and FIG. 5 shows the relationship between the filling rate and the sulfonic acid group density. As the filling rate increases, the moisture content, the number of bound water, and the number of antifreeze water tend to decrease. This is considered to be because the electrolyte swelling was suppressed by filling the pores, and the water content, the number of bound water, and the number of antifreeze water were reduced. Moreover, the moisture content was calculated | required from the following formula | equation.
[Moisture content (%)] = 100 × ([swelling film mass] − [dry film mass]) / [dry film mass]
The swelling film mass was determined after immersing the film as described above and sufficiently wiping the surface of the film.

FIG. 6 shows the relationship between the proton conductivity, the sulfonic acid group density, and the number of bound water of the electrolyte membranes produced in Example 3 and Example 4, and the proton conductivity, the sulfonic acid group density, and the number of antifreeze water are shown in FIG. FIG. 7 shows the relationship. From this figure, in the case of the electrolyte membrane of the present invention, it is the density of the sulfonic acid group that affects the proton conductivity, even if the number of bound water per sulfonic acid contained in the electrolyte membrane is 0.5 or less. It was found that proton conductivity did not decrease.
That is, as can be seen from the results of Example 3 and Example 4, the proton conductivity is not affected by water and is influenced by the sulfonic acid group, so that the proton conduction is carried through the sulfonic acid (proton). It is estimated that this is done by hopping.

以上の結果から、実施例１及び２の電解質膜は、含水率が低く、かつ、電解質溶液による膨潤を適度に抑制したものであることがわかった。 Furthermore, the water content when the electrolyte membranes of Examples 1 and 2 and Comparative Examples 1 to 3 were immersed in water and the area change rate at that time were determined. Specifically, each electrolyte membrane was immersed in pure water at 25 ° C. for 24 hours, the area change before and after immersion was measured, and the area change rate was determined from the following equation.
[Area change rate (%)] = 100 × ([swelling membrane area] · [dry membrane area]) / [swelling membrane area]
Moreover, the moisture content was calculated | required from the following formula | equation.
[Moisture content (%)] = 100 × ([swelling film mass] − [dry film mass]) / [dry film mass]
The swelling film mass was determined after immersing the film as described above and sufficiently wiping the surface of the film. The results are summarized in Table 5 below.

From the above results, it was found that the electrolyte membranes of Examples 1 and 2 had a low moisture content and moderately suppressed swelling due to the electrolyte solution.

Claims (14)

An electrolyte membrane having a porous substrate having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the proton conductive polymer composition has a proton acid group Free water contained in the electrolyte membrane at 25 ° C. containing an aromatic hydrocarbon resin is 0.5 or less per proton acid group, and in the electrolyte membrane at 25 ° C. The bound water contained is 1 or less per proton acid group, the proton conductivity of the electrolyte membrane is 0.001 S / cm or more in water at 25 ° C., and the methanol permeability of the electrolyte membrane The electrolyte membrane is characterized by having a ≦ 50 (kg · μm / m ² · h) in 30 wt% methanol at 25 ° C. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon resin is selected from the group consisting of polysulfone, polyethersulfone, polyarylate, polyamideimide, polyetherimide, polyimide, polyquinoline, and polyquinoxaline. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon resin is polyethersulfone. The electrolyte membrane according to any one of claims 1 to 3, wherein the protonic acid group is selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon resin includes a structure represented by the general formula (I).

(In the general formula (I), X ₁ and X ₂ may be the same or different and are — (ROm) n—, wherein R is an alkylene group, and m is 0 or 1, n is an integer of 0-20) The electrolyte membrane according to claim 1, wherein the porous substrate is an inorganic material or a heat-resistant polymer. The electrolyte membrane according to claim 1, wherein the porous substrate is polyimide and the aromatic hydrocarbon resin is polyethersulfone. The electrolyte membrane according to any one of claims 1 to 7, wherein the proton conductive polymer composition contains a cross-linking agent. The electrolyte membrane according to any one of claims 1 to 8, wherein a part of the pores and a part of the aromatic hydrocarbon resin are fixed. The method for producing an electrolyte membrane according to claim 1, comprising the following steps.
(1) An electrolyte membrane having a porous base material having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the electrolyte base material is in the pores of the porous base material. A step of holding a monomer and / or oligomer for forming the proton conductive polymer composition; and (2) a step of polymerizing the monomer and / or oligomer in the pores. The method for producing an electrolyte membrane according to claim 10, wherein the monomer and / or oligomer for forming the proton conductive polymer composition has three or more reactive groups. The method for producing an electrolyte membrane according to claim 1, comprising the following steps.
(1) An electrolyte membrane having a porous substrate having a plurality of pores and a proton conductive polymer composition held in the pores, wherein the porous substrate is Introducing the proton conductive polymer composition into the pores of the porous substrate by immersing in a solvent solution of a molecular composition; and (2) holding the proton conductive polymer composition The step of holding the porous substrate at a temperature of 60 ° C. or higher for at least 1 hour. A membrane-electrode assembly using the electrolyte membrane according to any one of claims 1 to 9. A fuel cell using the membrane-electrode assembly according to claim 13.

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