JP2005179465A - Composition for forming solid polymer electrolyte membrane, solid polymer electrolyte membrane, its manufacturing method and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming a solid polymer electrolyte membrane, which has a high proton conductivity, high proton conductivity even in the operation under a high temperature condition, excels in film formability and can give a high-quality polymer electrolyte membrane by a simple process; to provide the polymer electrolyte membrane obtained with this and its manufacturing method; and to provide a fuel cell using the polymer electrolyte membrane. <P>SOLUTION: The composition for forming the solid polymer electrolyte membrane contains a compound showed by formula (1). The polymer electrolyte membrane composed of a cured membrane of it and the manufacturing method thereof are also provided. In the formula R<SP>1</SP>and R<SP>2</SP>are each a hydrogen atom, a fluorine atom or a 1-4C lower alkyl group; R<SP>3</SP>is a hydrogen atom, a fluorine atom or a methyl group; and Z is a divalent linear, cyclic, alicyclic or bridged alicyclic organic group, whose hydrogens bonded to carbon atoms can wholly or partially be substituted by fluorine atoms. The fuel cell is provided in which the above polymer electrolyte membrane is mounted between the fuel electrode and the air electrode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is for forming a solid polymer electrolyte membrane having a high proton conductivity, a small decrease in proton conductivity even under high temperature conditions, excellent film forming properties, and a proton conductive membrane using proton as a conductive ion species. The present invention relates to a composition, a solid polymer electrolyte membrane obtained by curing the composition, a production method thereof, and a solid electrolyte fuel cell using the same.

Substances in which ions move in solids have been actively studied as indispensable materials for electrochemical devices, and ionic conductors of conductive ionic species such as Li ⁺ , Ag ⁺ , H ⁺ , and F ⁻ have been studied. Has been found. Among them, those using proton (H ⁺ ) as a conductive ion species are expected to be applied to fuel cells, capacitors, and electrochromic display elements. In particular, the fuel cell is attracting attention as a technology that will replace the internal combustion engine of an automobile in the future because it is less likely to be in the environment.

  In addition, there is an increasing expectation as a power source for portable electronic devices typified by mobile phones that have rapidly spread in recent years. Fuel cells that have been actively researched and developed for these applications are of the solid electrolyte membrane type that operates between room temperature and 150 ° C., which is called a relatively low temperature. The solid electrolyte membrane includes “Nafion” manufactured by DuPont. A sulfonated perfluoroalkyl vinyl ether membrane represented by “(registered trademark) membrane” has been studied because of its high oxidation deterioration resistance and high proton conductivity.

  However, when the operating temperature is set to 100 ° C. or higher in order to increase the power generation efficiency, in the Nafion membrane, the domain formed by the water taken into the membrane that promotes proton conduction contracts or is destroyed, It has been pointed out that this leads to a decrease in conductivity.

  Further, a material having high proton conductivity even at a high operating temperature of 100 ° C. or higher by obtaining an electrolyte membrane from a hydrolyzate of alkoxysilane into which phosphoric acid has been introduced by a sol-gel method is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2003-260260). 2003-217339).

  However, it has been pointed out that the hydrolysis reaction of alkoxysilane is difficult to control, and if this proceeds excessively, the hardness of the electrolyte membrane increases and the membrane becomes brittle. For this reason, when forming a thin film, the condensation reaction of the hydrolyzate has been carried out at a relatively low temperature for a long time, requiring a process unsuitable for industrial production. In a system that does not involve hydrolysis and condensation reactions, it is difficult to introduce phosphoric acid that is hydrophilic. Therefore, an electrolyte membrane that has a short membrane formation process, is simple, can withstand an operating temperature under a high temperature condition of 100 ° C. or higher, and has high proton conductivity has not been proposed.

JP 2003-217339 A

  The present invention has been made in view of the above circumstances, has high proton conductivity, has high proton conductivity even in operation under high temperature conditions, has excellent film formability, and has high quality in a simple process. It is an object to provide a composition for forming a solid polymer electrolyte membrane capable of providing a solid polymer electrolyte membrane, a solid polymer electrolyte membrane obtained thereby, a method for producing the same, and a fuel cell using the solid polymer electrolyte membrane. To do.

  As a result of intensive studies to achieve the above object, the inventors of the present invention cured a composition containing a compound represented by the following general formula (1) to form a cured film, thereby achieving high proton conductivity. A solid polymer electrolyte membrane that has excellent properties and has a small decrease in proton conductivity even under operation at a high temperature of 100 ° C. or higher, and excellent film-forming properties, in a simple process and in a short time. The present inventors have found that a high-performance fuel cell can be obtained by providing the solid polymer electrolyte membrane between the fuel electrode and the air electrode, and the present invention has been made.

  Therefore, the present invention provides the following composition for forming a solid polymer electrolyte membrane, a solid polymer electrolyte membrane, a method for producing the same, and a fuel cell.

(I) A composition for forming a solid polymer electrolyte membrane, comprising a compound represented by the following general formula (1).

（式中、Ｒ¹，Ｒ²はそれぞれ水素原子、フッ素原子又は炭素数１〜４の低級アルキル基、Ｒ³は水素原子、フッ素原子又はメチル基であり、Ｚは２価の直鎖状、環式、脂環式又は有橋脂環式の有機基で、炭素原子に結合した水素原子の一部又は全てがフッ素原子で置換されていても良い。）

(Wherein R ¹ and R ² are each a hydrogen atom, a fluorine atom or a lower alkyl group having 1 to 4 carbon atoms, R ³ is a hydrogen atom, a fluorine atom or a methyl group, Z is a divalent straight chain, (In the cyclic, alicyclic or bridged alicyclic organic group, some or all of the hydrogen atoms bonded to the carbon atom may be substituted with fluorine atoms.)

(Ii) A solid polymer electrolyte membrane comprising a cured film obtained by curing the composition for forming a solid polymer electrolyte membrane.
(Iii) A fuel cell, wherein the solid polymer electrolyte membrane is provided between a fuel electrode and an air electrode.
(Iv) Solid polymer electrolyte film-forming composition containing the compound represented by the general formula (1) is cured by irradiation or heat curing to form a cured film. Manufacturing method of electrolyte membrane.

  The composition for forming a solid polymer electrolyte membrane of the present invention is a high-quality solid having high proton conductivity, small decrease in proton conductivity even under high temperature conditions, excellent film-forming properties, and high proton conductivity. The polymer electrolyte membrane can be applied in a short time by a simple process. By using this solid polymer electrolyte membrane, a very high performance solid electrolyte fuel cell can be obtained.

Hereinafter, the present invention will be described in more detail.
The composition for forming a solid polymer electrolyte membrane of the present invention is a solution-like composition from which a solid polymer electrolyte membrane can be obtained, and contains a compound represented by the following general formula (1).

In the above formula, R ¹ and R ² are each a hydrogen atom, a fluorine atom or a lower alkyl group having 1 to 4 carbon atoms. Examples of the lower alkyl group include a methyl group, an ethyl group, a propyl group, an n-butyl group, A tert-butyl group is mentioned. R ³ is a hydrogen atom, a fluorine atom or a methyl group.

Z is a divalent linear, cyclic, alicyclic or bridged alicyclic, preferably an organic group having 1 to 18 carbon atoms, and some or all of the hydrogen atoms bonded to the carbon atom are fluorine atoms. It may be replaced with. In this case, examples of the divalent linear organic group include an alkylene group having 1 to 6 carbon atoms, such as a methylene group, an ethylene group, a propylene group, and a butylene group.
Examples of the divalent cyclic substituent include a phenylene group and a tolylene group. Examples of the alicyclic substituent include a cyclohexylene group. Examples of the bridged alicyclic substituent include an adamantane-diyl group and a norbornene-diyl group. When the substituent Z is such a bridged alicyclic substituent, the hardness of the electrolyte membrane can be further improved.

  As the substituent Z, a part or all of the hydrogen atoms bonded to the carbon atoms of the linear, cyclic, alicyclic or bridged alicyclic organic group may be substituted with fluorine atoms.

In the present invention, more preferred compounds of the formula ^{(1), R 1, R} 2 is a hydrogen atom, R ³ is a methyl group, Z is composed of an alkylene group methacryloxy alkyl phosphate, R ^1, R ² and Z are the same as described above, and acryloxyalkyl phosphates in which R ³ is a hydrogen atom are exemplified. A compound in which a part or all of the hydrogen atoms bonded to the carbon atom of the substituent Z is substituted with a fluorine atom is also a more preferable compound in the present invention because it can improve oxidation resistance.

  In the composition of the present invention, a derivative of (meth) acrylic acid such as glycidyl methacrylate, N-methylol acrylamide, polytetramethylene glycol (PTMG) -urethane acrylate is added to the compound of the above formula (1), It is good also as a copolymer with (meth) acrylate.

  The composition for forming an electrolyte membrane of the present invention is mainly composed of the compound of the above formula (1), and the content thereof is 10 to 100% (mass%, the same applies hereinafter), particularly 50 to 50% of the entire composition. 100% is preferred. If the content is too small, a satisfactory blending effect cannot be obtained, and the object of the present invention may not be achieved.

  In addition to the above essential components, a solvent such as propylene glycol monomethyl ether acetate or ethyl lactate may be added to the composition of the present invention to adjust the viscosity. In addition, about 1 to 50% of the whole composition is suitable for content of a solvent.

  Furthermore, the composition may contain various surfactants such as a fluorine-based surfactant, an anionic surfactant, a cationic surfactant, and a nonionic surfactant. The blending amount is desirably in the range of 0.1 to 5% of the entire composition.

  The composition for forming a solid polymer electrolyte membrane of the present invention can be cured by irradiation with radiation, heat curing or the like to form a cured film, and this cured film can be effectively used as a solid polymer electrolyte membrane.

  In this case, the cured film (solid polymer electrolyte membrane) can be obtained by adopting an ordinary method. For example, the composition of the present invention is applied on a base film made of polyethylene or the like by a doctor blade method, a calender roll method or the like. Thereafter, it can be obtained by irradiating with radiation or by curing by heat curing, and then peeling the coating film from the base film. Alternatively, a solid polymer electrolyte membrane may be formed directly on the electrode plate by thinly applying the composition for forming a solid electrolyte membrane on an electrode plate made of carbon or the like and then curing it by irradiation or heat curing. You can choose. The film thickness is preferably 5 to 200 μm, particularly 10 to 50 μm.

  In the curing of the polymer electrolyte membrane forming composition by radiation, electron beams, gamma rays, ultraviolet rays and the like can be preferably used as the radiation, but a curing treatment using ultraviolet rays and electron beams is particularly suitable because the apparatus is simple. It is.

  The acceleration voltage of the electron beam is preferably 50 to 1,000 kV, particularly preferably 100 to 300 kV. The absorbed dose of radiation is preferably 1 kGy or more, particularly 5 to 100 kGy, and particularly preferably 10 to 30 kGy. If it is less than 1 kGy, it may not be cured satisfactorily, and if it exceeds 100 kGy, the composition may become brittle.

  Further, the irradiation with radiation is preferably performed in an inert gas atmosphere such as helium, nitrogen, and argon gas, and the oxygen concentration in the gas is preferably 100 ppm or less, more preferably 50 ppm or less, but it is not necessarily in the absence of oxygen. There is no need to do it. The temperature at which the radiation is applied may be around room temperature (20 to 40 ° C.) or lower.

  Curing of the polymer electrolyte membrane forming composition by heating adds a catalytic amount of a radical polymerization catalyst such as an organic peroxide such as benzoyl peroxide or azoisobutyronitrile to the polymer electrolyte membrane forming composition. Then, it can be cured by heating. The added amount of the catalyst is preferably 0.1 to 10%.

  In this case, although there is no restriction | limiting in particular as a heat source, an infrared lamp is preferable and heat-hardening conditions can be 10 to 180 second at 50-200 degreeC.

  The fuel cell of the present invention is provided with the solid polymer electrolyte membrane between a fuel electrode and an air electrode, and can be used as a solid electrolyte fuel cell. The configuration and material of the fuel electrode and the air electrode and the configuration of the fuel cell can be known ones, but the fuel is a mixed solution of methanol and water, and the oxidant is preferably air. .

  In a solid oxide fuel cell, a solid electrolyte is used as a diaphragm, and a catalyst layer containing a catalytic metal and an electrically conductive electrode layer are laminated or disposed on both sides of the solid electrolyte membrane, and one surface of the solid electrolyte membrane is provided. A flow path through which liquid or gas serving as fuel is supplied is provided, and liquid or gas serving as an oxidant is supplied to the other surface.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Example.

[Example 1]
Methacryloxyethyl phosphate (molecular weight 196) manufactured by Nippon Kayaku Co., Ltd. was taken in an applicator, and a film with a coating thickness of 50 μm was formed on a glass plate. This sample was irradiated with an electron beam of 30 kGy under the conditions of an acceleration voltage of 100 kV and a current of 2.5 mA in an environment with an oxygen concentration of 30 ppm or less to obtain a cured film. After immersing this membrane in pure water for 24 hours, the proton conductivity of the electrolyte membrane was measured by a four-probe method using an impedance gain phase analyzer 1260 (manufactured by Schulberger Technologies). The proton conductivity obtained was 7.7 × 10 ⁻³ S / cm.

The ion exchange capacity was measured by titration according to a conventional method. The obtained electrolyte membrane was immersed in a 5 × 10 ⁻⁴ molar sodium hydroxide solution, treated for 6 hours at 50 ° C., and the amount of residual sodium hydroxide was determined by neutralization titration with hydrochloric acid. The ion exchange capacity was calculated as the amount of sodium hydroxide consumed. The obtained ion exchange capacity was 4.25 meq / g.

[Comparative Example 1]
13 mL of tetramethoxysilane, 9 mL of distilled water, 5 mL of ethanol, and 7 mL of 0.1 mol / L hydrochloric acid aqueous solution were mixed in a beaker, and the hydrolysis reaction of tetramethoxysilane was allowed to proceed at room temperature for 1 hour, and then this mixed solution The tetramethoxyphosphoric acid 2.0mL was added to, and it stirred for further 1 hour. Thereafter, 10 mL of formamide was further added and stirred for 1 hour, and then the partial polycondensate in the beaker was placed in a plastic container. The polycondensation reaction was allowed to proceed at room temperature for 3 weeks. The polycondensate in the plastic container was taken out and dried, and then sintered at 600 ° C. for 2 hours using a muffle furnace to obtain an electrolyte material by a sol-gel method. The ionic conductivity of this glass was 2 × 10 ⁻³ S / cm. The ion exchange capacity was 1 meq / g.

From the above results, according to the present invention, by using the compound represented by the formula (1), the ionic conductivity is excellent, and the electrolyte membrane can be cured without requiring a hydrolysis reaction by a sol-gel method or the like. It was confirmed that a simple composition for forming a solid polymer electrolyte membrane can be provided.

Claims (6)

A composition for forming a solid polymer electrolyte membrane, comprising a compound represented by the following general formula (1).

(Wherein R ¹ and R ² are each a hydrogen atom, a fluorine atom or a lower alkyl group having 1 to 4 carbon atoms, R ³ is a hydrogen atom, a fluorine atom or a methyl group, Z is a divalent straight chain, (In the cyclic, alicyclic or bridged alicyclic organic group, some or all of the hydrogen atoms bonded to the carbon atom may be substituted with fluorine atoms.)   A solid polymer electrolyte membrane comprising a cured film obtained by curing the composition for forming a solid polymer electrolyte membrane according to claim 1.   The solid polymer electrolyte membrane according to claim 2, which is cured by irradiation with radiation.   The solid polymer electrolyte membrane according to claim 2, which is cured by heat curing.   5. A fuel cell, wherein the solid polymer electrolyte membrane according to claim 2, 3 or 4 is provided between a fuel electrode and an air electrode. A solid polymer electrolyte membrane comprising a compound represented by the following general formula (1) for curing a solid polymer electrolyte membrane-forming composition by irradiation or heat curing to form a cured membrane. Production method.

(Wherein R ¹ and R ² are each a hydrogen atom, a fluorine atom or a lower alkyl group having 1 to 4 carbon atoms, R ³ is a hydrogen atom, a fluorine atom or a methyl group, Z is a divalent straight chain, (In the cyclic, alicyclic or bridged alicyclic organic group, part or all of the hydrogen atoms bonded to the carbon atom may be substituted with fluorine atoms.)