JP2005123108A - Polymer electrolyte fuel cell separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte fuel cell separator endowed with an insulation film improved from an insulation film material enabling a rubber layer with an insulation property to be adhered without the use of an adhesive. <P>SOLUTION: The polymer electrolyte fuel cell separator has the insulation film formed consisting of a vulcanizate of an insulation film material containing (A) polyol vulcanizable fluororubber, (B) a non-conductive reinforcing agent, (C) a polyol based vulcanizing agent, (D) a quaternary onium salt vulcanizing agent, and (E) a basic magnesium aluminum hydroxy carbonate hydrate oxide receiving agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte fuel cell separator. More specifically, the present invention relates to a polymer electrolyte fuel cell separator provided with an improved insulating film.

A fuel cell is a battery that generates electricity using the principle of extracting electricity in the process of obtaining water by reacting hydrogen and oxygen (air). In one type of polymer electrolyte fuel cell, the basic unit is generally a cell in which two separators are sandwiched by a hydrogen ion permeable polymer electrolyte membrane carrying a catalyst electrode layer on both sides via a gasket. The fuel cell stack is configured in such a state that these layers are stacked in layers. Here, the separator has an action of blocking various gases such as hydrogen and oxygen in the cell and an action of a current collecting plate for taking out electricity. For this reason, when the separator surface holding the electrolyte membrane contacts between the hydrogen side and the air side, a short circuit occurs, resulting in a problem that electricity cannot be taken out. Therefore, many means for providing an insulating film are employed on the peripheral edge of the separator excluding the power generation surface.
JP 2001-283893 A JP 2002-158018 A

  However, in these methods, it is necessary to increase the film thickness to such an extent that the film thickness can be handled beyond the originally required film thickness from the workability when the insulating film is provided on the separator, which is disadvantageous for the thinning of the fuel cell. It was. In addition, these insulating films are often fixed to the separator via an adhesive from the viewpoint of ensuring the displacement of the insulating film and sealing properties, and the elution of the adhesive component may adversely affect the fuel cell. .

In order to solve such problems, a means for directly molding a resin insulating film on a separator has been proposed, but in a general mold, the film thickness tends to be as thick as several millimeters. Also, due to the difference in shrinkage between resin and carbon after molding, there is a problem that the separator warps or the insulating film peels off. Especially in the integral molding of the resin layer on the thin separator, the resin insulating film There is a tendency for the separator to break due to the molding pressure.
JP 2002-352817 A

On the other hand, although the method of screen printing the rubber layer on the separator is disclosed in the following documents, these techniques are intended to form a gasket by screen printing, and are excellent materials for insulating films. Is not mentioned at all, and the use of the gasket materials disclosed in these documents does not lead to the formation of an insulating film having a uniform insulating ability over the entire peripheral edge where the separator needs to be insulated.
JP 2001-319669 A JP 2002-042835 A JP 2002-228001 A

  An object of the present invention is to provide a polymer electrolyte fuel cell separator in which an improved insulating film is formed from an insulating film material capable of adhering an insulating rubber layer without using an adhesive, for example. It is to provide.

  The object of the present invention is that (A) polyol vulcanizable fluororubber, (B) non-conductive reinforcing agent, (C Insulation comprising a vulcanizate of an insulating film material containing a) a polyol-based vulcanizing agent, (D) a quaternary onium salt vulcanizing agent, and (E) a basic magnesium, aluminum, hydroxy, carbonate, hydrate acceptor This is achieved by a polymer electrolyte fuel cell separator having a film formed thereon.

  The fluororubber compound, which is an insulating film material used in the present invention, can form a homogeneous and thin insulating film on the peripheral edge of the separator other than the power generation section by using it as an organic solvent solution by a screen printing method or the like. In addition, for thermosetting resins, preferably phenol resin mixed carbon separators, it is possible to bond fluororubber insulation films to separators without using adhesives, which alleviates the problem of adhesive component elution. Is done.

  In addition, when a gasket is insert-molded on a separator formed with an elastic insulating film, the elastic body absorbs the waviness and roughness of the separator, eliminating the generation of burrs, thereby reducing the burr removal process. It becomes possible to do.

  As a resin-mixed carbon separator using a thermosetting resin as a binder, a thermosetting resin composed of at least one of a phenol resin, an epoxy resin, an unsaturated polyester resin, a polyimide resin, etc., preferably 10 to 28 wt. %, Preferably 15 to 25% by weight, with graphite being 90 to 72% by weight, preferably 85 to 75% by weight. If the resin component is used in a smaller proportion, the material fluidity at the time of molding is remarkably deteriorated and molding becomes difficult. On the other hand, if the resin component is used in a proportion higher than this, the graphite becomes relatively small, and the intended electrical property is reduced. It becomes impossible to obtain conductivity.

  Fluororubber compound, which is an insulating film material, includes (A) polyol vulcanized fluororubber, (B) non-conductive reinforcing agent, (C) polyol vulcanizing agent, (D) quaternary onium salt vulcanizing agent and (E) Containing basic magnesium, aluminum, hydroxy, carbonate, hydrate acid acceptor.

  The polyol vulcanized fluororubber of component (A) is a vinylidene fluoride copolymer such as vinylidene fluoride-hexafluoropropene copolymer, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer. In order to form a solution, those having a low viscosity are preferably used. The polyol vulcanized fluororubber has good adhesiveness in the state where no adhesive is used with respect to the resin-mixed carbon separator, and also has an effect of preventing problems due to elution of the adhesive component. Furthermore, it can be said that it is a material excellent in adaptability as a component of a fuel cell because it has non-eluting properties with respect to water inherent in fluororubber and acid resistance. It should be noted that it is not preferable to use peroxide crosslinkable fluororubber instead of polyol vulcanizable fluororubber because the adhesiveness to the separator is poor and oven vulcanization in air cannot be performed.

  As the non-conductive reinforcing agent of component (B), silica, calcium silicate, hydrous silicic acid, calcium carbonate and the like are used, and silica is preferably used. These non-conductive reinforcing agents are used in a proportion of 5 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the fluororubber. Such a blending ratio is determined from the balance between the strength and hardness of the insulating film formed in the same manner as in a normal reinforcing agent. Carbon black, which is generally used as a reinforcing agent for fluororubber, impairs insulation properties when added in excess. Therefore, in the present invention, it can be added only in a proportion of 5 parts by weight or less.

  Examples of the polyol vulcanizing agent of the component (C) include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 2,2-bis (4-hydroxyphenyl) perfluoropropane (bisphenol AF), Hydroquinone, catechol, resorcin, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxyphenylmethane, 4,4′-dihydroxyphenylsulfone, 2,2-bis (4-hydroxyphenyl) butane are preferably used. Bisphenol A, bisphenol AF, hydroquinone and the like are used. These may also be in the form of alkali metal salts or alkaline earth metal salts.

As the quaternary onium salt of the component (D) used in combination with these polyol vulcanizing agents, at least one of a quaternary ammonium salt or a quaternary phosphonium salt represented by the following general formula is used.

_{(R 1 R 2 R 3 R} 4) + N - (R 1 R 2 R 3 R 4) + P -

R _{1 to} R ₄ : alkyl group having 1 to 25 carbon atoms, alkoxy group, aryl group, alkyl
A ruaryl group, an aralkyl group or a polyoxyalkylene group.
Can also be formed
X ⁻ : Cl ⁻ , Br ⁻ , I ⁻ , HSO ₄ ⁻ , H ₂ PO ₄ ⁻ , RCOO ⁻ , ROSO ₂ ⁻ , RSO ⁻ ,
ROPO ₂ H ^-, CO ₃ ^-, etc. anion

  Specifically, for example, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, n-dodecyltrimethylammonium bromide, cetyldimethylbenzylammonium chloride, methylcetyldibenzylammonium bromide, cetyldimethylethylammonium Bromide, octadecyltrimethylammonium bromide, cetylpyridinium chloride, cetylpyridinium bromide, cetylpyridinium iodide, cetylpyridinium sulfate, 1-benzylpyridinium chloride, 1-benzyl-3,5-dimethylpyridinium chloride, 1-benzyl-4-phenylpyridinium Chloride, 1,4-dibenzylpyridinium chlora 1-benzyl-4- (pyrrolidinyl) pyridinium chloride, 1-benzyl-4-pyridinopyridinium chloride, tetraethylammonium acetate, trimethylbenzylammonium benzoate, trimethylbenzylammonium-p-toluenesulfonate, trimethylbenzylammonium borate, 8- Benzyl-1,8-diazabicyclo [5,4,0] -undec-7-enium chloride, 1,8-diazabicyclo [5,4,0] -undecene-7-methylammonium methosulfate, 5-benzyl-1 , 5-diazabicyclo [4,3,0] -5-nonenium chloride, 5-benzyl-1,5-diazabicyclo [4,3,0] -5-nonenium bromide, 5-benzyl-1,5-diazabicyclo Quaternary ammonia such as [4,3,0] -5-nonenium tetrafluoroborate, 5-benzyl-1,5-diazabicyclo [4,3,0] -5-nonenium hexafluorophosphate Or salt such as tetraphenylphosphonium chloride, triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride And quaternary phosphonium salts such as trioctylmethylphosphonium bromide, trioctylethylphosphonium acetate, trioctylethylphosphonium dimethyl phosphate, tetraoctylphosphonium chloride, and cetyldimethylbenzylphosphonium chloride.

  These polyol-based and quaternary onium salt-based vulcanizing agents are used at a ratio of about 2-10 parts by weight, preferably about 3-8 parts by weight, per 100 parts by weight of the fluororubber. If the polyol-based and quaternary onium salt-based vulcanizing agent is used in a proportion higher than this, the gelation of the rubber solution is accelerated, whereas if it is used in a proportion lower than this, the vulcanization is insufficient.

As the component (E) acid acceptor that acts as an anti-gelling agent, basic magnesium, aluminum, hydroxy, carbonate, hydrate is used, and magnesium oxide or the like is preferably used in combination. Basic magnesium, aluminum, hydroxy, carbonate, hydrate is represented by the formula Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O, but the molar ratio of Mg to Al is free within a certain range. It can be taken. This compound is obtained as a white precipitate, for example, by adding an aqueous sodium hydroxide solution and an aqueous sodium carbonate solution to a mixed aqueous solution of MgCl ₂ and AlCl ₃ under stirring conditions and adjusting the pH to around 10. The acid acceptor is used in a ratio of about 0.5 to 20 parts by weight, preferably about 2 to 5 parts by weight, per 100 parts by weight of the fluororubber. If basic magnesium, aluminum, hydroxy, carbonate, hydrate is used in a higher ratio, it will cause insufficient vulcanization and a reduction in gelation prevention effect. On the other hand, if it is used in a lower ratio, gelation will occur. Becomes faster. When magnesium oxide is used in combination, magnesium oxide is further used in an amount of about 2 to 10 parts by weight, preferably about 6 to 8 parts by weight. In the fuel cell, the ammonia component is a major obstacle, and therefore it is not preferable to use an amine acid acceptor.

  In addition to the above essential components, as the filler, a non-conductive inorganic filler such as calcium carbonate, clay (aluminum silicate), talc or the like is appropriately blended and used.

  The fluororubber compound composed of the above components is a 25 to 50% by weight solid content concentration using a high boiling point organic solvent such as isophorone in order to perform its stability (anti-gelling) and uniform coating. Make adjustments by dissolving. If it is used in a state where the solid content concentration is lower than this, the film thickness required for insulation cannot be obtained. On the other hand, if it is used in a state where the solid content concentration is higher than this, the viscosity of the fluororubber solution becomes too high. It becomes difficult.

  The fluororubber insulating film is formed in a portion that requires insulation except for the power generation portion on the separator. FIG. 1 shows an embodiment of a separator formed with a gasket. An insulating film 4 and a linear gasket 5 are formed in the peripheral portion of the power generation section and the fuel gas, air, and cooling water manifold 3 having the gas flow path 2 on the separator 1 and the gas flow path 2 ′ that crosses the gas flow path 2 ′. Has been. The linear gasket 5 is disposed on the insulating film 4 formed on the separator 1 as shown in FIG. 2, or directly on the separator 1 surface between the insulating films 3 and 3 ′ as shown in FIG. The

  The fluororubber insulating film is formed by screen-printing the fluororubber solution on the peripheral edge of the separator that requires insulation, drying, and then oven vulcanizing. The insulating film is provided on both sides or one side of the separator, and the thickness thereof is 5 to 50 μm, preferably 10 to 30 μm. The total thickness of the insulating films provided on both sides of the separator is 20 μm or more (the insulating film is provided on one side). In the case where it is provided only on the surface, the thickness is 20 μm or more.

  On the separator on which the insulating film is vulcanized, a gasket is further pasted using insert molding or an adhesive. As the gasket material, normally used silicone rubber, EPDM, etc. are used. As shown in FIG. 2, when the gasket is disposed on the insulating film, the polyol vulcanized fluoro rubber of the same material as the insulating film is used. By using gasket, insert molding of the gasket material on the unvulcanized insulating film, vulcanizing the insulating film partly to obtain adhesion to the gasket, and then vulcanizing the whole in an oven A separator in which the insulating film and the gasket are integrally formed can be obtained. Further, as illustrated in FIG. 3, when a gasket is provided on the separator surface between the insulating films, a separator can be obtained by the same method using polyol vulcanized fluoro rubber made of the same material as the insulating film. it can.

  Next, the present invention will be described with reference to examples.

Example 1
100 parts by weight of a fluororubber compound having the following composition was dissolved in 150 parts by weight of isophorone to obtain a fluororubber solution for screen printing (solid content concentration 40% by weight, viscosity 50 Pa · s).
(Fluoro rubber compound)
Fluoro rubber (DuPont product Viton A-100) 100 parts by weight Silica 10 〃
MT carbon black 2 〃
Talc 20 〃
Magnesium oxide 8 〃
Basic Mg, Al, Hydroxy, Carbonate, Hydrate 2 〃
Sodium stearate 0.5 〃
Bisphenol AF 3 〃
Triphenylbenzylphosphonium chloride 2 〃

  After applying this fluororubber solution to the periphery of the 15% by weight phenol resin mixed carbon separator by the screen printing method other than the power generation part, using the fluororubber compound of the same material as the insulating film, unvulcanized insulation Gasket material was insert molded onto the membrane. This was dried at 120 ° C. for 10 minutes, and further heated and vulcanized at 180 ° C. for 10 minutes to obtain a gasket-integrated separator in which a fluororubber vulcanizate having a thickness of about 20 μm was formed as an insulating film as shown in FIG. Obtained.

  The insulating film of the obtained separator was free from defects such as pinholes and was in a homogeneous state. Moreover, while having a practically sufficient insulating property, the eluted components were also reduced to such an extent that they did not affect the fuel cell.

Example 2
In Example 1, as shown in FIG. 3, the fluororubber solution was applied to the peripheral edge other than the power generation part of the separator by screen printing, then dried at 120 ° C. for 10 minutes, and further heated at 180 ° C. for 10 minutes. By vulcanization, a separator in which a fluororubber vulcanizate having a thickness of about 20 μm was formed as an insulating film was obtained.

Next, a gasket having the following composition was formed between the insulating films by injection molding to obtain a gasket-integrated separator. Note that no adhesive was applied to the separator surface during the molding of the gasket.
(Gasket material)
Fluoro rubber (Daikin Industrial Product Daiel G-702) 100 〃
SRF carbon black 2 〃
Magnesium oxide 3 〃
Calcium hydroxide 3 〃

  The insulating film of the obtained separator was free from defects such as pinholes and was in a homogeneous state. Moreover, while having a practically sufficient insulating property, the eluted components were also reduced to such an extent that they did not affect the fuel cell.

  The separator according to the present invention can be effectively used as a separator for a polymer electrolyte fuel cell because the fluororubber insulating film can be bonded to the separator without using an adhesive.

It is one aspect | mode of the separator for fuel cells which shape | molded the insulating film and the gasket. 1 is an embodiment of a cross-sectional view taken along line AA of a fuel cell separator. FIG. 5 is another embodiment of a cross-sectional view taken along line AA of the fuel cell separator.

Explanation of symbols

1 Separator 2, 2 'Gas flow path (power generation part)
3, 3 'insulating film 4 linear gasket 5 manifold

Claims (8)

  In the peripheral part excluding the power generation part of the resin-mixed carbon separator using a thermosetting resin as a binder, (A) polyol vulcanizable fluororubber, (B) non-conductive reinforcing agent, (C) polyol-based vulcanizing agent, A solid formed by forming an insulating film made of a vulcanized material of an insulating film material containing (D) quaternary onium salt vulcanizing agent and (E) basic magnesium, aluminum, hydroxy, carbonate, hydrate acceptor Polymer fuel cell separator.   2. The polymer electrolyte fuel cell separator according to claim 1, wherein the non-conductive reinforcing agent is silica.   2. The polymer electrolyte fuel cell separator according to claim 1, wherein magnesium oxide is used in combination as an acid acceptor.   (A) 100 parts by weight of component (B) 3-50 parts by weight, (C) 2-10 parts by weight, (D) 2-10 parts by weight and (E) 0.5-20 parts The separator for a polymer electrolyte fuel cell according to claim 1 or 2, which is used in a proportion by weight.   The separator for a polymer electrolyte fuel cell according to claim 1, 3 or 4, wherein the insulating film material is used as a fluororubber solution and an insulating film shape is formed by a screen printing method.   5. The polymer electrolyte fuel cell separator according to claim 1, wherein a gasket is further formed on the insulating film.   The separator for a polymer electrolyte fuel cell according to claim 1, 3 or 4, wherein a gasket is formed on the separator surface between the insulating films. The separator for a polymer electrolyte fuel cell according to claim 6 or 7, wherein the insulating film and the gasket are integrally formed.

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