JP2001335695A - Thermosettable resin molding material and molded article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosettable resin molding material having excellent moldability and electric conductivity, and to provide a molded article for a separator for a fuel cell or the like which has excellent formability, electric conductivity, mechanical strength and gas impermeability, to be more precise. SOLUTION: This thermosettable resin molding material comprises 10 to 25 wt.% of a thermoset resin, 70 to 85 wt.% of graphite and 0.1 to 3 wt.% of spherical silica having an average particle size of 1/20 or smaller than the average particle size of the graphite each based on the total weight of the molding material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly conductive thermosetting resin molding material excellent in moldability, which is obtained by adding a spherical silica having a small particle size together with graphite to a thermosetting resin, and a molded product thereof. It is about. This molding material is suitable for a separator of a fuel cell using hydrogen, alcohol, or the like as a fuel.

[0002]

2. Description of the Related Art A separator for a fuel cell is a large and thin molded article. Conventionally, as a material of this type, a binder such as a thermosetting resin is added to graphite powder, kneaded, molded, calcined, and then gas-permeable. In order to improve the properties and conductivity, the binder was impregnated with the binder, fired at a high temperature, and then cut to obtain a required shape. The method of subjecting such a carbon material to secondary processing has the advantage of good heat resistance because it is fired at a high temperature.
On the other hand, pores are likely to be generated, and a step of impregnating with a liquid thermosetting resin or the like is required. Further, since a cutting step is an essential condition, processing cost increases.

Further, there has been proposed a method in which a material obtained by kneading a graphite powder, a thermosetting resin, a reinforcing material having mechanical strength, and the like is molded, and the molded product is used as a product. As described above, the method using a resin as the binder can greatly reduce the processing cost as compared with the method of performing the secondary processing on the carbon material, but has a drawback that the conductivity of the molded body is inferior. Therefore, a method of increasing the filling amount of the graphite powder by optimizing the graphite particle size and shape to increase the conductivity of the compact has been adopted. However, in order to adjust the graphite particle size and shape, it is necessary to grind and classify the graphite, which not only complicates the process, but also increases the graphite powder loading, which decreases the fluidity of the molding material. It is difficult to obtain a compact having a large, thin, and complicated shape as described above. Therefore, the volatile organic solvent is mixed and the material is made into a paste, the viscosity of the resin,
A method of obtaining a molded body by adjusting the nonvolatile content has been adopted. Although these methods are effective, air bubbles are generated at the time of curing of the molded body, and it is difficult to maintain the shape due to insufficient curing, so a preheating step and extension of the curing time are required, and moldability and productivity are increased. Is bad.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to improve the above-mentioned drawbacks and to provide a thermosetting resin molding material having excellent moldability and conductivity. . Furthermore, since it is excellent in moldability and conductivity, it is an object to provide a large and thin conductive molded body having a complicated shape, for example, a molded product such as a fuel cell separator. is there. In the fuel cell separator, the volume resistivity indicating conductivity is 10 ⁻³ to 10 ⁻¹ Ω · c.
m or a smaller value, a complicated shape having a large number of grooves on the surface, and precise dimensional accuracy is required.

[0005]

Means for Solving the Problems The present invention has been completed as a result of intensive studies to achieve the above object, and 10 to 25% by weight of a thermosetting resin, 70% by weight of graphite, based on the whole molding material. A thermosetting resin molding material containing 0.1 to 3% by weight of spherical silica having an average particle diameter of not more than 1/20 of the average particle diameter of graphite; The present invention relates to a highly conductive thermosetting resin molding material having excellent moldability due to its excellent fluidity during molding.

Hereinafter, the present invention will be described in detail. In the present invention, the spherical silica needs to have an average particle diameter of 1/20 or less of the average particle diameter of graphite. Graphite particles usually have an aspect ratio (ratio of major axis to minor axis),
This anisotropy is one of the factors that hinder the flow of graphite and hinder the moldability of the molding material.However, when spherical silica having an average particle diameter in the above range is present, when the molding material melts and flows, Since the graphite particles slide on the spherical silica as the fulcrum along with the flow of the spherical silica, the friction between the graphite particles is suppressed,
Since the flow of graphite is smooth, the flowability of the molding material during molding is improved. On the other hand, after molding, the spherical silica exists in the voids formed between the graphite particles, and does not lower the conductivity at the contact surface between the particles. Further, since the Mohs hardness (1 to 3) of graphite is lower than that of spherical silica (Mohs hardness of 5 to 8) and the particle diameter of spherical silica is small, even if spherical silica exists on the contact surface between graphite particles, Since it is buried in the graphite surface and does not hinder contact between graphite particles, the conductivity is not significantly impaired. If the average particle size of the spherical silica is larger than 1/20 of the average particle size of the graphite, the spherical silica will not be completely buried in the graphite surface, and will not fit in the voids between the graphite particles, thus impeding the contact between graphite. It becomes difficult to maintain conductivity.

The proportion of each component in the composition is 10 to 25% by weight of a thermosetting resin, 70 to 85% by weight of graphite and 0.1 to 3% by weight of spherical silica. 10% by weight of thermosetting resin
If the amount is less than the above, the fluidity is reduced, so that the moldability becomes severe. If the amount exceeds 25% by weight, practical conductivity cannot be obtained. If the graphite content is less than 70% by weight, the conductivity is poor, and if it exceeds 85% by weight, the fluidity is reduced, so that the moldability is disadvantageous. If the content of the spherical silica is less than 0.1% by weight, the conductivity is not affected, but the fluidity is poorly improved and the moldability is not improved. If it exceeds 3% by weight, the compounding amount of graphite or resin is suppressed, and a practical level of conductivity and moldability cannot be maintained. In the present invention, in order to obtain high conductivity of 10 ⁻³ to 10 ⁻¹ Ω · cm and excellent moldability, the total blending amount of graphite and spherical silica is in the range of 75 to 85% by weight of the whole molding material. It is preferable that

[0008] The graphite that can be used in the present invention is not particularly limited. For example, natural graphite or artificial graphite such as scaly, massive, or earth-like can be used. The average particle size of the graphite can be selected according to the performance required for the molding material.
m can be used. Preferably, it is 20 to 200 μm from the viewpoint of moldability and conductivity. As the spherical silica, any average particle diameter of 1/20 or less with respect to the average particle diameter of graphite can be used, but it effectively improves the fluidity of the molding material at the time of molding and maintains conductivity. For this reason, those having a particle size of usually 0.01 to 20 μm can be used, and those having a graphite average particle size of 0.5 to 5 μm are more preferable.

As the thermosetting resin that can be used in the present invention, a resin that is solid at room temperature can be used. When it is liquid, for example, the kneading property with a pressure roll is significantly reduced, and uniform dispersion cannot be obtained. For example, a phenol resin, an epoxy resin, an unsaturated polyester resin, or the like is used. Particularly preferred are phenolic resins and epoxy resins having good heat resistance,
The phenol resin is preferably a resol-type phenol resin in that ammonia is not generated during molding and does not remain in the molded product.

Next, one example of the method for producing the thermosetting resin molding material of the present invention will be described in detail. Graphite, spherical silica, finely pulverized thermosetting resin, and a release agent are mixed with a Henschel mixer. Mix evenly. This mixed composition can be molded as it is and has high conductivity,
Further, in order to impart uniform conductivity, practical mechanical strength, and gas impermeability, the material is formed into a molding material by a heating roll and crushed to enhance moldability. If necessary, it can be granulated. It is also possible to partially use conductive fillers such as carbon black and carbon fiber instead of graphite, as long as the conductivity and moldability are not impaired, and to use some inorganic fillers other than silica together. be able to.

The thermosetting resin molding material thus obtained can be molded by a usual thermosetting resin molding machine. In particular, the thickness, which was conventionally difficult to form, is 0.5 to 5.0 mm.
A thin plate-shaped conductive molded body can be formed successfully. For example, a molded product with a groove of 220 squares x 2 mm,
Mold temperature 130-200 ° C, molding pressure 200-800k
g / cm ² and a curing time of 5 minutes.

[0012]

The present invention will be described in more detail with reference to the following examples.
However, the present invention is not limited by these examples. Further, “parts” and “%” described in Examples and Comparative Examples are all “parts by weight” and “% by weight”.
Is shown.

Examples 1-3, Comparative Examples 1-3 Artificial graphite and spherical silica shown in Table 1, stearic acid as a release agent, and dimethylene ether type resole phenol resin as a phenol resin (number average molecular weight 700, melting point 80 C.) with a Henschel mixer to obtain a composition. The obtained composition was melt-kneaded with a heating roll at 80 ° C. and then taken out and pulverized into granules to obtain a phenol molding material. This molding material is molded at a mold temperature of 170 ° C. and a molding pressure of 20
0 kg / cm ^2, compression molded 220 square × curing time of 3 minutes
A grooved molded product having a size of 2 mm was obtained. The properties of the obtained molded product are shown in the lower part of Table 1.

[0014]

[Table 1] The molded product obtained in each of the examples has good conductivity and moldability. Although the molded article obtained in Comparative Example 1 has good moldability, the conductivity is slightly lowered due to the large particle diameter of the spherical silica. In Comparative Example 2, since the amount of the spherical silica was large, the conductivity was lowered, and the moldability was also lowered. Comparative Example 3
Since spherical silica is not used, the moldability is inferior.

(Measurement method) Volume resistivity: Measured according to JIS K 7194. Formability: Good for filling and appearance were rated as good, Good for cracking of blisters / grooves in appearance, and Bad for unfilled parts, blisters and cracks in groove protruding.

[0016]

As is apparent from the above description, the thermosetting resin molding material of the present invention is a highly conductive thermosetting resin molding material having excellent moldability, and is a thin-walled material having a complicated shape. A molded article can be obtained. Therefore, a molded article such as a separator of a fuel cell using hydrogen, alcohol, or the like as a fuel can be easily produced, and thus is suitable as an industrial conductive resin molding material.

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Claims (4)

[Claims] 1. A thermosetting resin 1 for the whole molding material.
Thermosetting characterized by comprising 0 to 25% by weight, 70 to 85% by weight of graphite, and 0.1 to 3% by weight of spherical silica having an average particle size of 1/20 or less of the average particle size of graphite. Resin molding material. 2. A conductive molded article obtained by molding the molding material according to claim 1, wherein the molded article has a thickness of 0.5 to 5.0 mm. 3. The fuel cell separator according to claim 1, wherein
The thermosetting resin molding material according to the above. 4. A fuel cell separator obtained by molding the molding material according to claim 3.