JP2002284576A - Carbon material and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material suitable for a separator of fuel cell, etc., which has an improved bending strength and flexibility, a lowered bending modulus of elasticity, and an excellent deformability and fracture resistance. SOLUTION: The carbon material is manufactured by heat-treating an amorphous carbon obtained by forming and firing for carbonization a thermosetting resin at a temperature of 100-300 deg.C. Phenol resin, etc., are used as the thermosetting resin and graphite particles, carbon black, etc., are usable as a filler in this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon material having excellent mechanical properties, a structure such as a fuel cell separator made of the same, and a method for producing the same.

[0002]

2. Description of the Related Art Carbon materials are heat-resistant and are used as high-temperature members such as inner walls of firing furnaces and heat-resistant bricks. Used in However, since the carbon material is a brittle material, depending on the intended use, so-called cracking or cracking of the so-called material may occur due to tightening or pressing, and its use may be limited.

[0003] In order to improve the mechanical properties of carbon materials, for example, there is a method of improving the mechanical properties by incorporating a fibrous reinforcing material such as a C / C composite. However, the use of carbon fiber or the like as a reinforcing material leads to an increase in the cost of the obtained product, and also complicates the manufacturing method. In addition, it was sometimes difficult to manufacture a structure having a complicated shape. Therefore, it has been desired to improve mechanical properties by a simpler method.

[0004] Among carbon materials, there is amorphous carbon (also called glassy carbon) having excellent characteristics. Amorphous carbon is excellent in various mechanical properties as compared with graphite, but may be easily broken due to its high rigidity, and its improvement has been desired.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a carbon material having improved mechanical properties by a relatively simple method and a method for producing the same.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by subjecting a carbon material to low-temperature heat treatment for an appropriate time. Heading, the present invention has been reached. That is, after molding the thermosetting resin, carbon material obtained by heat-treating the amorphous carbon obtained by carbonization and firing at 100 to 300 ° C., and a fuel cell separator comprising the same, and after molding the thermosetting resin, A gist of the present invention is a method for producing a carbon material, which comprises heat-treating amorphous carbon obtained by carbonization and firing at 100 to 300 ° C.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The carbon material of the present invention, after molding a thermosetting resin,
It is obtained by heat-treating amorphous carbon obtained by carbonization and firing at a relatively low temperature.

[0008] The amorphous carbon used in the present invention is obtained by molding a thermosetting resin and firing it by carbonization. Examples of the thermosetting resin include a phenol resin, a polyimide, a melamine resin and a furan resin. ,
Epoxy resin, carbodiimide resin, furfuryl alcohol resin, etc. can be used. One type of thermosetting resin may be used, or a combination of different types of resins other than the main component thermosetting resin within a range that does not impair the properties. Alternatively, a mixture of two or more thermosetting resins may be used. Further, the resin mixed with the resin as the main component may be a low molecular weight product of the thermosetting resin, or may contain an additive for the purpose of improving workability, moldability, and the like. Among them, it is most preferable to use a thermosetting resin containing a phenol resin as a main component in terms of moldability and cost.

Further, graphite particles, carbon black, inorganic particles, inorganic fibers, carbon fibers, wood powder, cellulose particles, etc. may be contained for the purpose of improving other properties or as a filler. The thermosetting resin can be formed into a desired shape by molding and curing, and can be carbonized and fired in that shape.

In the present invention, the thermosetting resin is formed into a shape as close as possible to the intended use. As a result, post-processing such as cutting becomes unnecessary or can be reduced, and a target structure can be obtained more easily. Thermosetting resin molding methods include injection molding,
Press molding, transfer molding and the like can be applied, and among them, the press molding method is most preferable. When amorphous carbon obtained by carbonizing and firing a thermosetting resin obtained by a press molding method is heat-treated, a remarkable effect of improving physical properties is exhibited.

After the thermosetting resin is molded, it is carbonized and fired to obtain amorphous carbon. In order to turn into amorphous carbon, nitrogen gas,
Under an atmosphere of an inert gas such as helium gas or argon gas,
It is preferable to bake at a temperature of 700 to 1600 ° C. In the case of firing at a temperature of 700 ° C. or less, the carbonization cannot be performed sufficiently, so that the characteristics of amorphous carbon do not appear. On the other hand, 16
Even if a temperature of 00 ° C. or higher is adapted, no significant change occurs in the characteristics of the obtained amorphous carbon. From the viewpoint of effectively utilizing energy at the time of production, a more preferable firing temperature is 900 to 1200 ° C.

In the present invention, it is necessary to heat-treat the amorphous carbon obtained by carbonizing and firing the molded article of the thermosetting resin at 100 to 300 ° C. Since the constituent element of the carbon material is carbon, structural change is unlikely to occur even when heat treatment is performed at a low temperature. Conversely, when the treatment is performed at a high temperature, deterioration is promoted, and it is difficult to achieve the intended improvement in mechanical properties. Therefore, in the present invention, 100
The heat treatment is performed at a temperature of about 300C, more preferably at a temperature of about 150C to 200C. In a heat treatment at a temperature lower than 100 ° C., the effect is hardly exhibited, and in a treatment at a temperature higher than 300 ° C., deterioration of the carbon material progresses and the effect is reduced.

It is preferable that the heat treatment is performed within an appropriate heat treatment time within the above-mentioned heat treatment temperature range. The heat treatment time needs to be longer in the heat treatment at a low temperature in consideration of the heat treatment temperature, and it is possible to shorten the treatment time slightly by setting the treatment temperature higher. By performing the heat treatment at a low temperature for a long time, the effects of the present invention can be sufficiently exhibited. The atmosphere in which the heat treatment is performed is not particularly limited, but treatment in air, nitrogen, vacuum, or the like is possible. Among them, treatment in air is preferable.
The mechanical properties of the carbon material obtained by the treatment in the air are remarkably improved. This is presumably because an oxide layer was formed on the surface layer of the amorphous carbon molded body.
Further, heat treatment in air is preferable also from the viewpoint of running cost and workability. When the treatment is performed at a higher temperature, an appropriate amount of an inert gas such as nitrogen may be mixed or the pressure may be reduced in order to suppress deterioration of carbon due to oxygen.

Since the carbon material obtained by the present invention is a carbon material made of amorphous carbon, the carbon material is less deteriorated by an oxidizing atmosphere, has excellent gas barrier properties, and has excellent electrical conductivity because it is a carbon material. Good. For this reason, the fuel cell can be favorably used for various applications. In particular, in addition to the inherent corrosion resistance, gas barrier properties, and conductivity inherent to amorphous carbon, the excellent mechanical properties improved by the present invention make the fuel cell It can be suitably used as a separator for a fuel cell, and when incorporated as a separator in a fuel cell, problems such as cracking, cracking, and breakage during operation can be reduced.

[0015]

Generally, when amorphous carbon, which is a kind of carbon material, is treated at a high temperature, deterioration of the surface of the carbon material is promoted and mechanical properties are reduced. However, in the present invention, heat treatment at a low temperature allows the material to be incorporated into the material. It is presumed that the contained defects are repaired and the mechanical properties are improved.

[0016]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

Example 1 Random novolak phenolic resin (manufactured by Unitika)
(Univex N type) as raw material, using a compression molding machine NF-70 manufactured by Shinto Metal Industry Co., Ltd.
Press molding was performed under the conditions of 0 MPa and a curing time of 4 minutes to obtain a disc-shaped plate having a diameter of 20 cm. Place this plate under a nitrogen atmosphere.
It was carbonized and fired at 1,000 ° C for 20 days to obtain an amorphous carbon plate. From this plate, width x length x thickness =
A 4 mm × 40 mm × 2 mm sample piece was cut out. This sample was placed in a warm air oven set at 190 ° C, and
The treatment was performed for 0 hours and 1000 hours. Thereafter, the sample was taken out, left for 24 hours in an environment at a temperature of 23 ° C. and a humidity of 65%, and cooled. This sample was subjected to four-point bending and four-point bending elastic modulus according to the method of JIS R1601. Also,
The amount of change caused by the four-point bending deformation was also read from the stress-strain curve obtained by the four-point bending test. The flexural strength, flexural modulus, and flexural change were calculated for the untreated sample.
It was converted to a relative value when 100% was used.

Example 2 Example 1 was conducted except that the heat treatment temperature of the sample was set to 160 ° C.
A sample was prepared in the same manner as described above.

Example 3 Bisphenol A type glycidyl ether (trade name: Epikote 828, manufactured by Yuka Shell Epoxy Co.) and curing agent triphenylphosphine (TPK, manufactured by Hokuko Chemical Co., 1% by mass)
Was kneaded sufficiently at 85 ° C. to obtain an epoxy resin, and a sample was obtained in the same manner as in Example 1;
Heat treatment was performed at 1000C for 1000 hours.

Example 4 Random novolak phenolic resin (manufactured by Unitika Ltd.)
A sample was obtained in the same manner as in Example 1 by using a mixture obtained by mixing 30% by mass of graphite powder (GR-6 manufactured by Nippon Graphite Co., Ltd.) with an average particle size of 6 μm in a Univex N type). The heat treatment was performed for 1000 hours.

Example 5 Random novolak phenol resin (manufactured by Unitika Ltd.)
A sample was obtained in the same manner as in Example 1 by using a mixture obtained by mixing 30% by mass of carbon black (Seast SP manufactured by Tokai Carbon Co., Ltd.)
Heat treatment was performed at 190 ° C. for 1000 hours.

Example 6 Random novolak phenolic resin (manufactured by Unitika Ltd.)
A sample was obtained in the same manner as in Example 1 by using a raw material obtained by mixing a phenolic resin cured product (Univex C-10, Univex C-10) in a mass of 40% by mass with a Univex N type), and heat-treated at 190 ° C. for 1000 hours. Was done.

Comparative Example 1 A carbon material was obtained in the same manner as in Example 1, except that the heat treatment temperature of the sample was 90 ° C. and the processing time was 100 hours.

Comparative Example 2 A carbon material was obtained in the same manner as in Example 1, except that the heat treatment temperature of the sample was 90 ° C. and the processing time was 1,000 hours.

Comparative Example 3 A carbon material was obtained in the same manner as in Example 1, except that the heat treatment temperature of the sample was set to 320 ° C. and the processing time was set to 100 hours.

Table 1 shows the evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3.

[0027]

[Table 1]

The carbon material obtained in the examples was heat-treated to improve the bending strength and the amount of change in bending, and the flexural modulus was lowered. The carbon material obtained in the example has a small change or a low bending strength.

When the carbon material obtained in the examples was used as a fuel cell separator, cracking and cracking did not occur during assembly and operation, and the fuel cell had excellent performance as a separator material.

[0030]

According to the present invention, a carbon material having excellent mechanical properties can be obtained by heat-treating amorphous carbon at a low temperature, and can be suitably used for a fuel cell separator and the like.

[Brief description of the drawings]

FIG. 1 is a graph in which bending strength is plotted against heat treatment time among the results obtained in Examples 1 and 2 of the present invention.

FIG. 2 is a graph in which, among the results obtained in Examples 1 and 2 of the present invention, a bending elastic modulus is plotted with respect to a heat treatment time.

FIG. 3 is a graph in which, among the results obtained in Examples 1 and 2 of the present invention, an amount of bending deformation is plotted with respect to a heat treatment time.

Claims (4)

[Claims] 1. A carbon material obtained by molding a thermosetting resin and then heat-treating amorphous carbon obtained by carbonization and firing at 100 to 300 ° C. 2. A fuel cell separator comprising the carbon material according to claim 1. 3. A method for producing a carbon material, comprising forming a thermosetting resin, and heat-treating the amorphous carbon obtained by carbonizing and firing at 100 to 300 ° C. 4. The method for producing a carbon material according to claim 3, wherein the molding method of the thermosetting resin is press molding.