JP2007066743A - Conductive paste composition, conductive separator for fuel cell and manufacturing method of the conductive separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste composition capable of providing required satisfactory low volume resistivity, to provide a conductive separator for a fuel cell, and to provide a manufacturing method of the conductive separator for the fuel cell. <P>SOLUTION: The conductive paste composition contains 50-170 pts.wt. of a carbonaceous substance with respect to 100 pts.wt. of a polyimide resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a conductive paste composition, a fuel cell conductive separator, and a method for producing a fuel cell conductive separator, and in particular, a conductive paste composition having excellent conductivity and suitable for surface coating of a fuel cell separator. The present invention relates to a fuel cell conductive separator using the product, and a method for manufacturing a fuel cell conductive separator.

As a fuel cell, as shown in FIG. 1, an ion exchange membrane 1 and a unit cell 4 sandwiching the ion exchange membrane 1 between a fuel electrode 2 and an air electrode 3 serve as a hydrogen gas channel and an oxygen gas channel. It is known that a plurality are connected in series via separators 7 in which a plurality of parallel grooves 5 and 6 are formed (arrows indicate the direction of gas flow). The separator 7 in such a fuel cell functions as a current collector that electrically connects the unit fuel cells as described above, and serves as a passage for supplying hydrogen and oxygen (air). It is required to have electrical conductivity (ie low volume resistivity).
As such a separator, a mixture composition composed of a binder resin and conductive particles is molded into a predetermined shape, or a gold thin film is formed on the surface of a metal substrate formed into a predetermined shape to passivate it. (Anti-rust treatment) is known (for example, Patent Documents 1 and 2).

  However, the former separator is expensive to manufacture and it is difficult to obtain a good low volume resistivity. In addition, the latter separator cannot prevent corrosion failure caused by fine damage on the separator surface, fluctuations of constituent components, etc., and furthermore, the metal used for the surface treatment of the separator is expensive, so that the manufacturing cost is high. There is a problem that it becomes high.

In order to solve such problems, a method of coating the surface of a metal separator with a carbon-based conductive paste (for example, Patent Documents 3 and 4) has been proposed (for example, Patent Document 5).
Japanese Unexamined Patent Publication No. 2000-40517 JP 2000-311695 A JP-A-9-31402 JP 2001-19891 A JP 2002-260680 A

  However, a separator using such a conductive paste has a problem that the volume resistivity of the conductive paste is higher than that of a gold thin film, and the efficiency of the fuel cell is lowered.

  Accordingly, the present invention has been made to solve such conventional problems, and has achieved a required low volume resistivity, a conductive paste composition, a fuel cell conductive separator, and a fuel cell conductive material. It aims at providing the manufacturing method of a conductive separator.

  The conductive paste composition of the present invention includes 50 to 170 parts by weight of a carbonaceous material with respect to 100 parts by weight of a polyimide resin.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrically conductive paste composition which implement | achieved the required favorable low volume resistivity, the electrically conductive separator for fuel cells, and the electrically conductive separator for fuel cells can be provided.

  Hereinafter, the present invention will be described in detail.

  The conductive paste composition of the present invention contains a polyimide resin and a carbonaceous material as essential components, and more preferably contains a solvent.

The carbonaceous material used in the present invention functions as a conductive material. For example, carbon, carbon synthesized by heat treatment of graphite, carbon black, activated carbon, carbon fiber (carbon fiber), coke, and organic precursor in an inert atmosphere. Examples thereof include nanomaterials (carbon nanotubes, carbon nanofibers).
From the viewpoint of high conductivity, carbon black and graphite are preferred, graphite is more preferred, and particulate graphite or a mixture of particulate graphite and flake graphite is most preferred.

Since graphite has a regular structure and high conductivity among carbonaceous materials, a conductive paste composition capable of realizing low volume resistivity can be obtained by using graphite.
These carbonaceous materials preferably have an average particle size of 3 nm to 50 μm, and more preferably 3 μm to 25 μm. These average particle diameters are measured according to JIS-Z8823-2.
If the average particle diameter is less than 3 nm, the particles are too fine and the contact resistance increases, so that the volume resistivity increases. When the average particle diameter exceeds 50 μm, the surface of the cured body such as a conductive film formed becomes rough, and powder may easily fall off, possibly causing pinholes.

Particulate graphite is particulate graphite and has a particle size smaller than that of scaly graphite. In the formed conductive film etc., it fills so that the clearance gap between conductive powders, such as scale-like graphite, may be filled, and the effect | action which improves electroconductivity is carried out.
Scale-like graphite is graphite in the shape of a scale (flat plate) and has a particle diameter larger than that of particulate graphite. By reducing the number of contact points between conductive powders (particulate graphite and scaly graphite) in a conductive coating or the like, it acts to improve conductivity.
Therefore, the conductive paste composition which can implement | achieve high electroconductivity (low volume resistivity) is obtained by using what mixed particulate graphite or particulate graphite, and scale-like graphite as a carbonaceous substance.

  The particulate graphite preferably has an average particle diameter of 3 to 12 μm. When the average particle diameter is less than 3 μm, the particles are too fine and the contact resistance increases, so that the volume resistivity of the cured body such as a conductive film is increased. When the average particle diameter exceeds 12 μm, the cured body such as a conductive film. However, the filling of gaps between the conductive powders such as flake graphite is poor, and the contact of the conductive powder is not sufficient, and the volume resistivity may be increased.

  The scaly graphite preferably has an average particle size of 20 to 50 μm. If the average particle size is less than 20 μm, the particles are small, and it may not be said that the reduction in contact resistance due to scaly graphite is sufficient. When the average particle diameter exceeds 50 μm, the surface of the cured body such as a conductive film formed becomes rough, and powder may easily fall off, possibly causing pinholes.

  The compounding amount of the carbonaceous material of the present invention is 50 to 170 parts by weight, preferably 80 to 150 parts by weight, based on 100 parts by weight of the polyimide resin. If the blending amount of the carbonaceous material is less than 50 parts by weight, the amount of polyimide resin as an insulator increases, the conductivity between conductive powders (carbonaceous materials) decreases, and the volume resistivity of the cured body such as a conductive film. May increase. If the blending amount of the carbonaceous material exceeds 170 parts by weight, it becomes difficult to form a paste, and good adhesion to the substrate may not be obtained.

  The weight ratio between the particulate graphite and the flaky graphite is preferably 5:95 to 100: 0. If the ratio of the particulate graphite in the carbonaceous material is less than 5% by weight, the gap between the flaky graphite cannot be sufficiently filled with the particulate graphite, so that the contact state becomes insufficient, and the cured body such as the conductive coating film There is a possibility that the volume resistivity becomes high.

In addition to the carbonaceous material, a conductive material other than the carbonaceous material can be blended as necessary. In addition to carbonaceous materials, conductive materials that can be blended include metal powders such as gold, platinum, silver, copper, nickel, titanium, and aluminum, or conductive oxides such as conductive titanium oxide and conductive tin oxide, Or the metal compound which has another electroconductivity is mentioned.
When using these metal powders, conductive oxides or conductive metal compounds, the blending amounts are preferably 20 to 100 parts by weight based on 100 parts by weight of the carbonaceous material, respectively. The amount is more preferably 90 parts by weight, and most preferably 60 to 80 parts by weight.

The polyimide resin used in the present invention functions as a binder. By using a polyimide resin as the binder, a cured body such as a conductive film excellent in heat resistance, chemical resistance, adhesion to the substrate, and the like can be obtained.
The polyimide resin used in the present invention is represented by the following general formula.

Here, R1 in the formula is a tetravalent organic acid residue, a tetravalent aromatic group, a tetravalent aliphatic group, or two aromatic groups or aliphatic groups are a single bond, -O It represents a tetravalent organic group bonded by —, —CO—, —SO ₂ —, —CH ₂ —, —C (CF ₃ ) ₂ — or the like. R2 is a divalent diamine residue, a divalent aromatic group, a divalent aliphatic group, or two aromatic groups or aliphatic groups are a single bond, -O-, -CO-,- It represents a divalent organic group bonded by SO ₂ —, —CH ₂ —, —C (CF ₃ ) ₂ — or the like. n is an integer of 1 or more.

The polyimide resin is obtained by reacting an acid component and a diamine component.
In the formula, the acid component that becomes the Rl skeleton is, for example, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic acid, pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2, 3,3 ′, 4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 4,4′-oxydiphthalic acid, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic acid Acid, 2,2′-bis (3,4-dicarboxylphenyl) hexafluoropropane, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4 , 5,8-Naphthalenetetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, 1,2,4,5-cyclopentanetetracarboxylic acid 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3 ′, 4,4′-bicyclohexyltetracarboxylic acid, 2,3,5-tricarboxycyclopentylacetic acid, 3,4-dicarboxy-1, 2,3,4-tetrahydronaphthalene-1-succinic acid and the like, or anhydrides thereof may be mentioned, and these may be used alone or in combination of two or more.

  Examples of the diamine component having an R2 skeleton include metaphenylenediamine, paraphenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminotoluene, and 1-methoxy. -2,4-diaminobenzene, 1,4-diamino-2-methoxy-5-methylbenzene, 1,3-diamino-4,6-dimethylbenzene, 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid Acid, 1,2-diaminonaphthalene, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene 2,6-diaminonaphthalene, 1,4-diamino-2-methylnaphthalene, 1,5-diamino- -Methylnaphthalene, 1,3-diamino-2-phenylnaphthalene, 2,2-bis (4-aminophenyl) propane, 1,1bis (4-aminophenyl) ethane, 4,4'-diaminodiphenylmethane, 3, 3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-5,5'-diethyl-4, 4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetraethyl-4,4'-diaminodiphenylmethane, 4,4'-methylenebis (cyclohexylamine), 4,4'-methylenebis (3,3'-dimethyl) -Cyclohexylamine), 2,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-dia Nodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, bis (4-aminophenyl) diethylsilane, bis (4-aminophenyl) diphenylsilane, bis (4-aminophenyl) -N-methylamine, bis (4-aminophenyl) -N-phenylamine, 3,3′- Diaminobenzophenone, 4,4′-diaminobenzophenone, 4,4′-diaminobiphenyl, 3,3′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4 , 4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobi Phenyl, o-toluidine sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl Ether, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3- Bis (4-aminophenoxy) benzene, 9,10-bis (4-aminophenyl) anthracene, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 1,1-bis (4-aminophenyl) -1-phenyl 2,2,2-trifluoroethane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 2, 2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane and the like can be mentioned, and these can be used alone or in admixture of two or more.

  The acid component and the diamine component are preferably used in equimolar amounts, but can be used in the range of 0.9 to 1.2 times mol according to the purpose of use, final viscosity and molecular weight.

  The polyimide resin used in the present invention is obtained by reacting an acid component and a diamine component, and these acid component and diamine component may be contained in blocks or randomly.

In addition, the polyimide resin is a polyamic acid resin (polyimide precursor) obtained by a polycondensation reaction between a tetracarboxylic acid compound having an Rl skeleton or a dianhydride thereof and a diamine compound having an R2 skeleton. Used as a raw material for the composition. This polyimide precursor can be heated and dehydrated and closed to obtain a polyimide resin.
In addition to the polyamic acid, the polyimide precursor includes those obtained by partially imidizing the polyamic acid.

  As a synthesis solvent for the polyimide precursor (polyamic acid resin) used in the present invention, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, tetrahydrofuran, γ-butyrolactone, and the like are used. These can be used alone or in combination. It is preferable to carry out the reaction at room temperature using these solvents.

  The solvent (diluent) used in the present invention is used for adjusting the viscosity of the conductive paste composition, and is related to the control of the film forming state. As long as the solvent for diluting the conductive paste composition is a solvent having a boiling point lower than the curing temperature of the polyimide resin, either a solvent having reactivity with the polyimide resin or a solvent having no reactivity can be used. Solvents that are not reactive are preferred.

  Non-reactive solvents include ketones such as ethyl methyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene, cellosolve, methyl cellosolve, butyl cellosolve, terpineol, carbitol, methyl carbitol and butyl. Carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, glycol ethers such as tripropylene, ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol Acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, carbonate Esters such as pyrene, can pentane, hexane, heptane, octane, aliphatic hydrocarbons decane, and halogenated carbons, organic solvents etc., such as halogenated hydrocarbons.

  Among these, because of the high boiling point, for example, terpineol, butyl carbitol acetate and the like are preferable, and terpineol is more preferable.

  In consideration of the weight average molecular weight of the polyimide resin used, etc., the amount of the solvent of the present invention can be easily determined so that the viscosity of the conductive paste composition at room temperature is appropriately adjusted. it can. The viscosity of the conductive paste composition is preferably 500 to 5000 mPa · S, more preferably 800 to 3000 mPa · S at 25 ° C.

  When the viscosity of the conductive paste composition exceeds 5000 mPa · S, the viscosity is high and pinholes and the like are likely to occur, and as a result, the corrosion resistance and the adhesion to the substrate may be reduced. If it is less than 500 mPa · S, the viscosity of the conductive paste composition is low and the thickness of the conductive coating is reduced, and the gas generated during solvent removal by heating is adsorbed by the carbonaceous powder and completely removed. Failure to do so may cause pinholes, etc., which may reduce corrosion resistance.

  As described above, according to the present embodiment, by using a carbonaceous material such as graphite as the conductive material, a good low volume resistivity can be realized, and by using a polyimide resin as a binder. Thus, a conductive paste composition capable of realizing good heat resistance, chemical resistance, adhesion to a substrate, and the like can be obtained.

Below, the manufacturing method of the electrically conductive paste composition of this invention is demonstrated.
For example, a polyimide resin or polyimide precursor (polyamic acid resin), which is a liquid composition, is first put into a universal mixer, graphite powder is gradually added while mixing, and the paste composition is kneaded. Put into three rolls and knead for a long time while applying shearing force.
During kneading, it is possible to add a solvent to adjust the viscosity.
As a method of mixing while applying a shearing force, a ball mill method, a plate cone method, a mortar method, or the like can be used. The more shear force is applied, the better the electrical conductivity and mechanical strength of the resulting conductive paste composition.

The conductive separator for fuel cells of the present invention will be described. The conductive separator for a fuel cell of the present invention is obtained by forming a conductive film made of a cured product of the conductive paste composition of the present invention on the surface of a separator substrate.
The fuel cell separator base material coated with the conductive paste composition of the present invention may be made of metal or other material, for example, a material made of a resin and a carbonaceous material, A metal separator is most preferred. On the surface of the metallic separator substrate, a gas flow path composed of a plurality of parallel grooves is formed (see FIG. 1).
The conductive coating is obtained by applying the above-described conductive paste composition of the present invention to the surface of a metal separator substrate and heating and curing. As described later, the conductive coating, the heat resistance, and the chemical resistance. (For example, strong acidity), film strength, film adhesion, and other required characteristics are satisfied. 10-1000 micrometers is preferable and, as for the thickness of the film of an electrically conductive paste composition, 50-100 micrometers is more preferable.

The conductive separator for a fuel cell of the present invention is not limited to the one in which a conductive film made of a cured product of the conductive paste composition of the present invention is formed on the surface of the separator substrate. The conductive separator for a fuel cell of the present invention can be produced by molding the conductive paste composition of the present invention into a predetermined shape and heat curing. The conductive separator for a fuel cell of the present invention is formed by using a conductive metal such as aluminum as an insert material, and using the mold so that the conductive paste composition of the present invention has a predetermined shape on the outer periphery thereof. May be. You may make it further surface-treat as needed.
In the present invention, the fuel cell includes all fuel cells such as a household fuel cell, a mobile fuel cell, and an automobile fuel cell.

  Next, the manufacturing method of the electrically conductive separator for fuel cells which apply | coated the electrically conductive paste composition is demonstrated. First, for example, the surface of the stainless steel plate on which the gas flow path is formed is roughened with an abrasive, and the viscosity is adjusted on the surface (on the pretreated surface in the case where pretreatment described later is performed). The conductive paste composition of the invention is applied and heat cured. Then, by further heat treatment, a fuel cell separator coated with the conductive paste composition can be produced.

After roughening with an abrasive, the conductive paste composition of the present invention may be applied by further applying and drying a coupling agent to pretreat the substrate surface. Moreover, you may pre-bake before heat hardening. Moreover, you may abbreviate | omit subsequent heat processing by fully heat-curing.
The curing conditions are such that the curing temperature is 300 ° C. or lower, preferably 150 ° C. to 250 ° C., more preferably 160 ° C. to 200 ° C. The time for heat curing is 1 to 10 hours. Note that the heat curing may use not only one-stage heat-curing conditions but also a plurality of stages of heat-curing conditions.
The conductive paste composition can be applied by a screen printing method, a squeegee method, a dipping method, an air brush, or the like, and a dipping method is preferred.

  The conductive paste composition of the present invention can be used favorably for applications that require electrical conductivity. For example, in addition to the conductive separator for fuel cells, it can also be used for carbon electrodes for fuel cells.

  Furthermore, the glass substrate coated with the conductive resin is manufactured by applying the conductive paste composition of the present invention to the surface of the glass plate using a screen printing method, heat-curing, and then performing further heat treatment. Is possible.

  It is also possible to draw a circuit using the conductive paste composition of the present invention on the surface of the glass fiber substrate, heat and cure, and then heat treatment to form an electric circuit on the substrate. Furthermore, the conductive paste composition of the present invention can be used as a conductive paste composition for a wide range of applications such as a conductive seal and an antistatic paste.

  Hereinafter, the content of the present invention will be described using examples, but the present invention is not limited to these examples.

Example 1
First, synthesis of a polyimide resin precursor (polyamic acid resin) will be described.
In a flask equipped with a stirrer, a condenser and a nitrogen introduction tube, 36.9 g (0.09 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] propane and bis (γ-aminopropyl) tetra 2.49 g (0.01 mol) of methyldisiloxane and 279.1 g of N-methyl-2-pyrrolidone were added, and 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride was added at room temperature under a nitrogen atmosphere. 30.38 g (0.098 mol) of the product was added in portions while paying attention to an increase in the solution temperature, and stirred at room temperature for about 12 hours to prepare a polyamic acid resin solution. A part of this polyamic acid resin solution was reprecipitated with methanol, and the resulting polyamic acid resin powder was dissolved with N-methyl-2-pyrrolidone to give a solid content of 15%.

Next, preparation of a conductive paste composition will be described.
Thus obtained polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particles manufactured by SEC Co., Ltd.) (Diameter 3 μm) 2.7 parts by weight, scaly graphite (manufactured by Nippon Graphite Industry Co., Ltd., trade name SP-20, particle size 20 μm) 0.3 parts by weight were blended.
The composition thus formulated is thoroughly kneaded with a universal mixer and further kneaded with a three-roll mill for 1 hour, and then the viscosity of the paste composition is adjusted by adding terpineol to prepare a carbon-based conductive paste composition. did.

Next, preparation of a conductive film will be described.
The conductive paste composition thus obtained was applied on a stainless steel plate by a dip method. At this time, the film thickness of the coating is controlled by the viscosity of the paste to be dipped and the pulling speed at the time of dipping. After coating, a thermosetting treatment was performed at 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour to form a conductive film.

(Example 2)
Polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particle size 3 μm, manufactured by SEC Co., Ltd.) 2.1 weights Part, scaly graphite (manufactured by Nippon Graphite Industry Co., Ltd., trade name SP-20, particle size 20 μm) A conductive film was formed in the same manner as in Example 1 except that 0.9 part by weight was blended.

(Example 3)
13.3 parts by weight of polyimide resin precursor (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (manufactured by SEC, trade name SGL-3, particle size 3 μm) 1.5 parts by weight, scaly graphite (Nippon Graphite Industries Co., Ltd., trade name SP-20, particle size 20 μm) A conductive film was formed in the same manner as in Example 1 except that 1.5 parts by weight was blended.

Example 4
First, synthesis of a polyimide resin precursor (polyamic acid resin) will be described.
In a flask equipped with a stirrer, a cooler, and a nitrogen introduction tube, 46.6 g (0.09 mol) of 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane and bis (γ-aminopropyl) were added. ) 4.97 g (0.01 mol) of tetraphenyldisiloxane and 268.3 g of N-methyl-2-pyrrolidone were added, and 3,3 ′, 4,4′-bisphenyl ether tetracarboxylic acid was introduced at room temperature under a nitrogen atmosphere. Acid dianhydride 15.5 g (0.050 mol) and pyromellitic dianhydride 10.46 g (0.048 mol) were added in portions while paying attention to an increase in the solution temperature, and the mixture was stirred at room temperature for about 10 hours. A polyamic acid resin solution was produced. A part of this polyamic acid resin solution was reprecipitated with methanol, and the resulting polyamic acid resin powder was dissolved with N-methyl-2-pyrrolidone to give a solid content of 15%.

Next, preparation of a conductive paste composition will be described.
Thus obtained polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particles manufactured by SEC Co., Ltd.) (Diameter 3 μm) 0.9 parts by weight, scaly graphite (manufactured by Nippon Graphite Industry Co., Ltd., trade name SP-20, particle size 20 μm) 2.1 parts by weight were blended.
The composition thus formulated is thoroughly kneaded with a universal mixer and further kneaded with a three-roll mill for 1 hour, and then the viscosity of the paste composition is adjusted by adding terpineol to prepare a carbon-based conductive paste composition. did.

Next, preparation of a conductive film will be described.
The conductive paste composition thus obtained was applied on a stainless steel plate by a dip method. At this time, the film thickness of the coating is controlled by the viscosity of the paste to be dipped and the pulling speed at the time of dipping. After coating, a thermosetting treatment was performed at 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour to form a conductive film.

(Example 5)
Polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particle size 3 μm, manufactured by SEC Co., Ltd.) 0.3 weight Parts, scaly graphite (Nippon Graphite Industries Co., Ltd., trade name SP-20, particle size 20 μm) A conductive film was formed in the same manner as in Example 4 except that 2.7 parts by weight were blended.

(Example 6)
First, synthesis of a polyimide resin precursor (polyamic acid resin) will be described.
In a flask equipped with a stirrer, a cooler and a nitrogen inlet tube, 18.00 g (0.09 mol) of 4,4′-diaminodiphenyl ether and 2.49 g (0.01 mol) of bis (γ-aminopropyl) tetramethyldisiloxane And 167.4 g of N-methyl-2-pyrrolidone were added, 21.36 g (0.098 mol) of pyromellitic dianhydride was added at room temperature under a nitrogen atmosphere, and the mixture was stirred at room temperature for about 10 hours to obtain a polyamic acid resin. A solution was prepared. A part of this polyamic acid resin solution was reprecipitated with methanol, and the resulting polyamic acid resin powder was dissolved with N-methyl-2-pyrrolidone to give a solid content of 15%.

Next, preparation of a conductive paste composition will be described.
Thus obtained polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particles manufactured by SEC Co., Ltd.) 1.4 parts by weight was blended.
The composition thus formulated is thoroughly kneaded with a universal mixer and further kneaded with a three-roll mill for 1 hour, and then the viscosity of the paste composition is adjusted by adding terpineol to prepare a carbon-based conductive paste composition. did.

Next, preparation of a conductive film will be described.
The conductive paste composition thus obtained was applied on a stainless steel plate by a dip method. At this time, the film thickness of the coating is controlled by the viscosity of the paste to be dipped and the pulling speed at the time of dipping. After coating, a thermosetting treatment was performed at 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour to form a conductive film.

(Example 7)
Polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particle size 3 μm, manufactured by SEC Co., Ltd.) 2.1 weights A conductive film was formed in the same manner as in Example 6 except that the part was blended.

(Example 8)
First, preparation of a conductive paste composition will be described.
Bismaleimide resin (manufactured by Maruzen Petrochemical Co., Ltd., trade name BANI-H, molecular weight 488.63 g / mol) 2 parts by weight, particulate graphite (manufactured by SEC, trade name SGL-3, particle size 3 μm) 2.7 0.3 parts by weight of parts by weight and flaky graphite (manufactured by Nippon Graphite Industry Co., Ltd., trade name: SP-20, particle size: 20 μm) were blended.
The composition thus formulated is thoroughly kneaded with a universal mixer and further kneaded with a three-roll mill for 1 hour, and then the viscosity of the paste composition is adjusted by adding terpineol to prepare a carbon-based conductive paste composition. did.

Next, preparation of a conductive film will be described.
The conductive paste composition thus obtained was applied on a stainless steel plate by a dip method. At this time, the film thickness of the coating is controlled by the viscosity of the paste to be dipped and the pulling speed at the time of dipping. After the application, a heat curing treatment was performed at 160 ° C. for 1 hour and at 250 ° C. for 3 hours to form a conductive film.

Example 9
Bismaleimide resin (manufactured by Maruzen Petrochemical Co., Ltd., trade name BANI-H, molecular weight 488.63 g / mol) 2 parts by weight, particulate graphite (made by SEC Co., Ltd., trade name SGL-3, particle size 3 μm) 2.1 A conductive film was formed in the same manner as in Example 8, except that 0.9 part by weight of graphite and flaky graphite (manufactured by Nippon Graphite Industries Co., Ltd., trade name: SP-20, particle size: 20 μm) was mixed.

(Comparative Example 1)
First, preparation of a conductive paste composition will be described.
Bisphenol F-type epoxy resin (Dainippon Ink Chemical Co., Ltd., trade name EPICLON 830, molecular weight 350 g / mol) 2.5 parts by weight, epoxy curing agent (Shikoku Kasei Co., Ltd., trade name Curesol 2E4MZ-CN) 0. 025 parts by weight, particulate graphite (manufactured by SEC, trade name SGL-3, particle size 3 μm) 2.7 parts by weight, scaly graphite (manufactured by Nippon Graphite Industries Co., Ltd., trade name SP-20, particle size 20 μm) 0.3 part by weight was blended.
The composition thus formulated is thoroughly kneaded with a universal mixer and further kneaded with a three-roll mill for 1 hour, and then the viscosity of the paste composition is adjusted by adding terpineol to prepare a carbon-based conductive paste composition. did.

Next, preparation of a conductive film will be described.
The conductive paste composition thus obtained was applied on a stainless steel plate by a dip method. At this time, the film thickness of the coating is controlled by the viscosity of the paste to be dipped and the pulling speed at the time of dipping. After the application, a heat curing treatment was performed at 160 ° C. for 1 hour and at 250 ° C. for 3 hours to form a conductive film.

(Comparative Example 2)
Bisphenol F-type epoxy resin (Dainippon Ink Chemical Co., Ltd., trade name EPICLON 830, molecular weight 350 g / mol) 2.5 parts by weight, epoxy curing agent (Shikoku Kasei Co., Ltd., trade name Curesol 2E4MZ-CN) 0. 025 parts by weight, particulate graphite (manufactured by SEC Co., Ltd., trade name SGL-3, particle size 3 μm) 2.1 parts by weight, scaly graphite (manufactured by Nippon Graphite Industries Co., Ltd., trade name SP-20, particle size 20 μm) A conductive film was formed in the same manner as Comparative Example 1 except that 0.9 part by weight was blended.

(Comparative Example 3)
Bisphenol F-type epoxy resin (Dainippon Ink Chemical Co., Ltd., trade name EPICLON 830, molecular weight 350 g / mol) 2.5 parts by weight, epoxy curing agent (Shikoku Kasei Co., Ltd., trade name Curesol 2E4MZ-CN) 0. 025 parts by weight, particulate graphite (manufactured by SEC Co., Ltd., trade name SGL-3, particle size 3 μm) 1.5 parts by weight, flake graphite (manufactured by Nippon Graphite Industries Co., Ltd., trade name SP-20, particle size 20 μm) A conductive film was formed in the same manner as Comparative Example 1 except that 1.5 parts by weight was blended.

(Comparative Example 4)
Polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particle size 3 μm, manufactured by SEC Co., Ltd.) 0.7 weight A conductive film was formed in the same manner as in Example 4 except that the parts were blended.

(Comparative Example 5)
Polyimide resin precursor (polyamic acid resin) 13.3 parts by weight (corresponding to 2.0 parts by weight of polyimide resin), particulate graphite (trade name SGL-3, particle size 3 μm, manufactured by SEC Co., Ltd.) 4.0 weights A conductive film was formed in the same manner as in Example 6 except that the part was blended.

(Comparative Example 6)
Bismaleimide resin (manufactured by Maruzen Petrochemical Co., Ltd., trade name BANI-H, molecular weight 488.63 g / mol) 2 parts by weight, particulate graphite (manufactured by SEC Co., Ltd., trade name SGL-3, particle size 3 μm) 4.0 A conductive film was formed in the same manner as in Example 8 except that the parts by weight were blended.

  Table 1 shows a raw material composition table of the conductive paste compositions of the examples and comparative examples.

  Table 2 shows the performance evaluation results of the conductive coatings of the examples and comparative examples.

* ¹ : According to JIS-K7194, penetration resistance (volume resistivity) (Ω · cm) was measured using Loresta GP (manufactured by Dia Instruments Co., Ltd.).
* ² : Film strength was measured by a pencil method according to JIS-K5600.
* ³ : According to JIS-K5600, film adhesion was measured as the number of peels per 100 sheets.
* ⁴ : Acid resistance was measured with concentrated hydrochloric acid according to JIS-K8001.
* ⁵ : Film adhesion was evaluated according to JIS-K5600 for the sample left in the dryer at the set temperature, and the temperature at which the number of peels was 0 (0/100) was measured.

As shown in Table 2, the conductive coating of Comparative Example 4 in which less than 50 parts by weight of graphite, which is a carbonaceous material, is added to 100 parts by weight of polyimide resin, the penetration resistance (volume resistance) compared to the examples. The rate) was found to be slightly higher. Moreover, it was recognized that it was difficult to form the conductive coatings of Comparative Examples 5 and 6 in which graphite, which is a carbonaceous material, was blended in excess of 170 parts by weight with respect to 100 parts by weight of the polyimide resin.
On the other hand, the conductive film of the example in which 50 to 170 parts by weight of graphite, which is a carbonaceous material, is blended with 100 parts by weight of the polyimide resin has a low penetration resistance (volume resistivity) and is good. The film was confirmed to be conductive. Moreover, it was recognized that heat resistance is excellent compared with Comparative Examples 1-3 using the epoxy resin. It was also confirmed that the acid resistance, film adhesion, and film strength were good.

An electron microscope (SEM: Scanning Electron Microscope) photograph of the conductive coating film of Example 3 which is one embodiment of the present invention is shown in FIG. Note that the magnification of the photograph is 5000 times. The electron microscope used for photographing is an ABT-60 type electron microscope (SEM) having an acceleration voltage of 15 kV.
As can be seen from FIG. 2, it can be seen that the conductive coating of Example 3 of the present invention is made conductive by the connection of carbonaceous substances.

It is a figure which shows the structure of the unit cell in a fuel cell. It is a surface view by the electron micrograph of the electroconductive film of Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ion exchange membrane, 2 ... Fuel electrode, 3 ... Air electrode, 4 ... Unit cell, 5, 6 ... Concave groove, 7 ... Separator.

Claims (9)

  A conductive paste composition comprising 50 to 170 parts by weight of a carbonaceous material with respect to 100 parts by weight of a polyimide resin.   The conductive paste composition according to claim 1, wherein an average particle diameter of the carbonaceous material is 3 nm to 50 μm.   The conductive paste composition according to claim 1, wherein the carbonaceous material is made of graphite.   The graphite is composed only of particulate graphite having an average particle diameter of 3 to 12 μm, or composed of particulate graphite having an average particle diameter of 3 to 12 μm and flaky graphite having an average particle diameter of 20 to 50 μm. Item 4. The conductive paste composition according to Item 3. The polyimide resin has the following general formula
(In the formula, R1 is a tetravalent aromatic group, a tetravalent aliphatic group, or two aromatic groups or aliphatic groups are a single bond, —O—, —CO—, —SO ₂ —, Represents a tetravalent organic group bonded by —CH ₂ — or —C (CF ₃ ) ₂ —,
R2 is a divalent aromatic group, a divalent aliphatic group, or two aromatic groups or aliphatic groups is a single _{bond, -O -, - CO -,} - SO 2 -, - CH 2 -, or -C _{(CF 3) 2} - represents a divalent organic group bonded by,
n is an integer of 1 or more. )
The conductive paste composition according to claim 1, wherein the conductive paste composition is represented by:   The conductive paste composition according to any one of claims 1 to 5, further comprising a conductive powder made of at least one selected from metals and conductive oxides.   A conductive separator for a fuel cell, wherein the conductive paste composition according to any one of claims 1 to 6 is molded into a predetermined shape and cured by heating. A metal separator substrate formed in a predetermined shape;
On the surface of the metallic separator substrate, the conductive paste composition according to any one of claims 1 to 6 is applied, and a conductive film formed by heat curing;
A conductive separator for a fuel cell, comprising: A step of roughening the surface of the metal separator substrate formed in a predetermined shape;
Applying the conductive paste composition according to any one of claims 1 to 6 to the roughened surface, and heating and curing to form a conductive film;
The manufacturing method of the electrically conductive separator for fuel cells characterized by the above-mentioned.