JPH0948666A - Carbon composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon composite material having a non-permeability to gases and a high dielectric constant simultaneously. SOLUTION: This carbon composite material is obtained by blending and dispersing an expanded graphite powder having 5μm-12μm mean particle diameter and >=80% total particles of the powder belonging to the range of 0.1μm-20μm, with a thermoplastic or a thermosetting resin and press forming under a temperature from the ambient temperature to 400 deg.C. Alternatively the expanded graphite powder having 5μm-12μm mean particle diameter and >=80% total particles of the powder belonging to the range of 0.1μm-20μm is blended and dispersed with a thermosetting resin, press formed under the temperature of the ambient temperature to 400 deg.C, and the formed product is burned under a non-oxidizing atmosphere, at 700 deg.C-3000 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon composite material having gas impermeability and high conductivity, and a method for producing the same.

[0002]

2. Description of the Related Art A carbon material having gas impermeability is mainly used as a heat exchanger member, a semiconductor manufacturing member, a fuel cell component, and the like. A permeable carbon material is required.

Conventional gas-impermeable carbon materials include, for example,
A method in which a carbon material such as a glassy carbon plate or graphite is impregnated with a thermosetting resin (see Japanese Patent Application Laid-Open No. 02-153877) or a resin is applied to an expanded graphite compact, and the temperature is increased to about 2000 ° C. in an inert gas. Method of firing (JP-A-60-1)
No. 27284), or a method of impregnating an expanded graphite molded body with a thermosetting resin and then hot-pressing it (Japanese Patent Laid-Open No. Sho 6-62).
No. 0-12672).

However, the glassy carbon plate has
Although it has sufficient gas impermeability and electrical conductivity, it has a drawback that it takes a long time to fire and thus becomes expensive, and it is difficult to form a complicated shape. In addition, the method of coating a thermosetting resin on the surface of expanded graphite and firing it in an inert gas not only requires a coating step but also complicates the step, and forms a carbon layer without pinholes. However, there is a problem that sufficient gas impermeability cannot be obtained. Further, the method of impregnating the expanded graphite sheet with a resin requires an impregnation step, which complicates the step and cannot maintain sufficient gas impermeability.

In order to solve such a problem, for example, expanded graphite powder and an organic binder are mixed with a solution, which is dried and pulverized to form secondary particles of the expanded graphite powder and the organic binder. And producing an expanded graphite compact by molding the same (JP-A-54-3
No. 2517) or a method of mixing and molding expansive graphite and an organic binder (Japanese Patent Laid-Open No. 58-49).
656, JP-A-62-254363 and JP-A-1-154467).

[0006]

However, the expansive graphite generally used in the past is not well mixed with the organic binder, and it is sufficient to increase the amount of the expansive graphite in order to enhance conductivity. Since gas impermeability cannot be obtained, conversely, if the amount of expanded graphite is reduced to increase gas impermeability, sufficient conductivity cannot be obtained, so development of a carbon material that has both high gas impermeability and conductivity Was desired.

The present invention has been made for the purpose of solving the above problems and providing a carbon composite material having both gas impermeability and high conductivity and a method for producing the same.

[0008]

The structure of the carbon composite material adopted by the present invention to solve the above-mentioned object is composed of expanded graphite powder and a thermoplastic resin, or a thermosetting resin or a fired product thereof, Thermoplastic resin or thermosetting resin,
Or a molded product in which expanded graphite powder is dispersed in the fired product, wherein the expanded graphite powder has an average particle size of 5 μm.
m to 12 μm, and 80% or more of all powder particles have a particle diameter of 0.1 to 20 μm.

Similarly, in order to solve the above-mentioned object, the method of producing a carbon composite material according to the present invention has an average particle size of 5 μm to 12 μm and 80% or more of all powder particles have a particle size of 0.1 μm. To 20 μm, expanded graphite powder and thermoplastic resin or thermosetting resin are mixed and dispersed, and press-molded at a temperature of room temperature to 400 ° C., or an average particle diameter of 5 μm. ˜12 μm, 80% or more of all particles in the powder have a particle size of 0.1 μm to 20 μm, and the expanded graphite powder is mixed and dispersed.
It is characterized in that after pressure molding at a temperature of room temperature to 400 ° C., the molded product is fired at 700 ° C. to 3000 ° C. in a non-oxidizing atmosphere.

That is, the inventors of the present invention have made extensive studies as a result of achieving the above object, and when expanded graphite having a specific particle size is mixed and dispersed with a thermoplastic resin or a thermosetting resin, it is very excellent. The present invention has been completed as a result of further research, based on the idea that it may provide excellent gas impermeability and conductivity when molded or shaped to give it compatibility with other resins. It is a thing.

The present invention will be described below.

With respect to the expanded graphite used in the present invention, the raw material is not particularly limited and, for example, natural graphite, pyrolytic graphite, quiche graphite, or any other material that is commonly used in the production of expanded graphite can be used. be able to.

Expanded graphite can be produced from the above-mentioned raw material graphite by a conventionally known method, for example, after peroxomonosulfuric acid is produced by mixing concentrated sulfuric acid and hydrogen peroxide, While stirring the prepared mixed liquid, the raw material graphite was charged and allowed to react for about 1 hour to 1 day, and the reacted graphite was heated in an inert gas at 500 ° C to
It may be heated to 1000 ° C.

As the expanded graphite used in the present invention,
When producing expanded graphite from concentrated sulfuric acid and hydrogen peroxide as described above, at least one selected from perchloric acid, perchlorate, and ammonium hydrogen peroxodisulfate is added as an oxidizing agent for treatment. It may be obtained by the method described in JP-A-6-16406. Specifically, 15% ammonium hydrogen peroxodisulfate was added to a mixture of 320 parts by weight of 95 wt% concentrated sulfuric acid and 4 parts by weight of 62% hydrogen peroxide, and the mixture was mixed while cooling to 20 ° C. or lower. Expanded graphite obtained by adding natural graphite to a mixed solution, reacting it for 24 hours, and calcining this reaction product up to 1000 ° C. in nitrogen gas.

The expanded graphite obtained as described above is crushed and adjusted to have a predetermined particle size distribution and particle size if necessary, and the expanded graphite used in the present invention has an average particle size of 5 μm to 12 μm. And 80% of all powder particles
The above particle size must belong to the range of 0.1 μm to 20 μm.

When the average particle size of the expanded graphite used in the present invention is smaller than 5 μm, it becomes difficult for the thermoplastic resin or the thermosetting resin to spread among the expanded graphite particles in the mixing step described later. As a result, the gas impermeability of the resulting composite material is greatly impaired, and conversely, when the average particle size is greater than 12 μm, it is difficult for the thermoplastic resin or thermosetting resin to fill the spaces between the expanded graphite particles. In addition, not only the gas impermeability is greatly impaired, but also the packing density is lowered and the electrical connection becomes insufficient, resulting in a decrease in conductivity.

Further, in the expanded graphite used in the present invention, 80% or more of all the powder particles have a particle size of 0.1 μm to 20 μm.
It must belong to the range of m. That is, the expanded graphite, which has been pulverized and aligned to have a predetermined particle size and particle size as necessary, generally has a particle size distribution having a peak at the average particle size. When measuring the particle size,
80% or more belongs to the range of 0.1 μm to 20 μm,
2 particles belonging to the range of less than 0.1 μm and more than 20 μm
It must be less than 0%.

Of course, in the expanded graphite powder used in the present invention, 100% of all the powder particles have a particle size of 0.1 μm to 20 μm.
It may be distributed in the range of 0.1 μm, and is 0.1 μm to 20 μm.
It may be distributed within a narrower range within the range of m.

When the peak of the particle size distribution is lowered or moved in either direction, the number of particles (in the former case) or one (in the latter case) belonging to the range of less than 0.1 μm and over 20 μm increases. However, when the number of particles smaller than 0.1 μm increases, the surface area of the expanded graphite powder increases, which reduces the thickness of the resin between the expanded graphite powders, thus reducing the gas impermeability of the resulting composite material. Therefore, when the number of particles larger than 20 μm increases, not only the possibility that some of the particles are exposed on the surface of the obtained composite material, but also the number of resin layers formed between the expanded graphite powders is increased. Since the gas content is reduced, the gas impermeability of the composite material is also reduced, which is not preferable.

The expanded graphite may be pulverized by any conventionally known method, for example, a pulverizing method such as a mixer, a jet mill, a ball mill, a pin mill and a freeze pulverizing method. Particle size distribution,
Examples of the method for adjusting the particle diameter include classification methods such as a vibration sieve, a low tex cleaner, a sonic sieve, a micro classifier, and a spedic classifier.

The thermoplastic resin used in the present invention includes polyethylene, polystyrene, polypropylene,
Polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, polyoxamethylene, polyamide, polyimide, polyamide imide, polyvinyl alcohol, polyvinyl chloride, fluororesin, polyphenyl sulfone, polyether ether ketone, polysulfone Well-known resins such as polyetherketone, polyarylate, polyetherimide, polymethylpentene, etc. can be mentioned, without any particular limitation.

On the other hand, as the thermosetting resin used in the present invention, polycarbodiimide resin, phenol resin, furfuryl alcohol resin, cellulose, epoxy resin,
Well-known resins such as a urea resin and a melamine resin can be mentioned, and there is no particular limitation.

The above-mentioned thermoplastic resin or thermosetting resin is
The powder may be used as it is, or may be dissolved in an appropriate solvent to be used as a solution.

The carbon composite material of the present invention is produced by combining expanded graphite powder, which is the main component thereof, and a resin by the method described below. That is, first, the expanded graphite powder and the resin are mixed and dispersed to obtain a mixture. This mixing step is carried out by an ordinary industrial mixing method, for example, a stirring rod, a kneader, a ball mill, a sample mill, mixer,
A method using a static mixer, a ribbon mixer or the like can be adopted.

The amount ratio of the expanded graphite to the resin may be determined according to the physical properties of the intended carbon composite material and the like. For example, 10 parts by weight to 1000 parts by weight of the resin per 100 parts by weight of the expanded graphite powder. The range can be mentioned.
If the resin is smaller than this range, the strength of the composite material will be weakened, and gas impermeability will be reduced. If it is larger than this range, the conductivity will be insufficient. Happens.

Next, pressure is applied to the mixture to spread the resin between the expanded graphite powders to form a carbon composite material of the present invention.
It can be carried out by a conventionally known method such as pressure molding, hydrostatic molding, extrusion molding, injection molding, belt pressing, press heating, roll pressing and the like. In addition, even if it shape | molds in a desired shape at this time, you may improve a moldability by adding a solvent to the said mixture, for example, to granulate to a diameter of 20 micrometers-2 mm before this shaping | molding process.

The temperature in the molding step may be selected according to the resin used, but is, for example, room temperature to 400.
A range of ° C can be mentioned. In addition, in order to chemically stabilize the molded product, a heat treatment may be further performed after the molding.

Among the above mixtures, the mixture of expanded graphite and thermosetting resin can be fired in a non-oxidizing atmosphere. The firing temperature is 700 ° C to 3000 ° C,
The temperature is preferably 1000 ° C. to 2500 ° C., and there is a problem that the conductivity is not drastically improved at a firing temperature lower than 700 ° C. as compared with the above-mentioned non-fired formed body.
If the temperature is higher than 0 ° C, the firing furnace will be significantly consumed, which is not suitable for practical production.

[0029]

The present invention will be described in more detail with reference to the following examples.

Example 1 Expanded graphite and polycarbodiimide resin having an average particle diameter of 5 μm and 80% or more of all powder particles having a particle diameter in the range of 0.1 μm to 20 μm were mixed and dispersed in a combination shown in Table 1. Then, a molded product was produced at 150 ° C. and a pressure of 100 kg / cm ² . A plate material having a size of 40 mm square and a thickness of 2 mm was cut out from this molded product, and the specific resistance was measured by the 4-terminal method. or,
Cut out a 120 mm square, 1 mm thick plate material and JIS7
The gas impermeability of nitrogen gas was measured by the 126 differential pressure method. The results are shown in Table 1.

[Table 1]

Example 2 The same expanded graphite and phenolic resin as in Example 1 were mixed and dispersed in the combinations shown in Table 2, 150 ° C., 100 kg / c
Moldings were made with a pressure of m ² . Using this molded product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. Table 2 shows the results.

[Table 2]

Example 3 The same expanded graphite and polypropylene as in Example 1 were mixed and dispersed in the combinations shown in Table 3, 180 ° C., 100 kg / c.
Moldings were made with a pressure of m ² . Using this molded product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. The results are shown in Table 3.

[Table 3]

Example 4 The same expanded graphite and polytetrafluoroethylene as those in Example 1 were mixed and dispersed in the combinations shown in Table 4 at 330 ° C. and 10 ° C.
Moldings were made with a pressure of 0 kg / cm ² . Using this molded product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. The results are shown in Table 4.

[Table 4]

Example 5 Of Example 1, the composition shown in Example 1-2 (expanded graphite / polycarbodiimide resin = 100 parts by weight / 100 parts by weight) was molded under the same conditions as in Example 1, and this was molded. Firing was performed under an inert gas atmosphere up to the temperatures shown in Table 5. Using this fired product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. Table 5 shows the results.

[Table 5]

Comparative Example 1 Expanded graphite and polycarbodiimide resin having an average particle size of 100 μm and 20% of all powder particles having a particle size of 0.1 μm to 20 μm were mixed and dispersed in a combination shown in Table 6. A molded product was produced at 150 ° C. and a pressure of 100 kg / cm ² . Using this molded product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. Table 6 shows the results.

Comparative Example 2 The molded product used in Comparative Example 1 was fired up to 1000 ° C. in nitrogen gas. Using this fired product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. Table 6 shows the results.

COMPARATIVE EXAMPLE 3 Expanded graphite and polycarbodiimide resin having an average particle size of 0.5 μm and 20% of all powder particles having a particle size of 0.1 μm to 20 μm were mixed in a combination shown in Table 6. Dispersed and molded at 150 ° C. under a pressure of 100 kg / cm ² . Using this molded product, the specific resistance and the gas impermeability of nitrogen gas were measured in the same manner as in Example 1. Table 6 shows the results.

[0038]

[Table 6]

[0039]

The carbon composite material of the present invention comprises expanded graphite powder and a thermoplastic resin, or a thermosetting resin or a fired product thereof. The thermoplastic resin, the thermosetting resin, or a fired product thereof. A molded product in which expanded graphite powder is dispersed, wherein the expanded graphite powder has an average particle size of 5 μm.
.About.12 .mu.m, and 80% or more of all powder particles have a particle size of 0.
It belongs to the range of 1 μm to 20 μm and is excellent in having both gas impermeability and high conductivity.

Claims (6)

[Claims] 1. An expanded graphite powder and a thermoplastic resin, or a thermosetting resin or a fired product thereof, wherein the expanded graphite powder is dispersed in the thermoplastic resin, the thermosetting resin or a fired product thereof. The expanded graphite powder has an average particle size of 5 μm to 12 μm, and 80% or more of all powder particles have a particle size of 0.1 μm to 20 μm. And carbon composite material. 2. An expanded graphite powder having an average particle size of 5 μm to 12 μm and 80% or more of all powder particles having a particle size of 0.1 μm to 20 μm mixed with a thermoplastic resin or a thermosetting resin. A method for producing a carbon composite material, which comprises dispersing and press-molding at a temperature of room temperature to 400 ° C. 3. The ratio of expanded graphite powder to thermoplastic resin or thermosetting resin is 10 to 1000 parts by weight of thermoplastic resin or thermosetting resin to 100 parts by weight of expanded graphite powder. Of manufacturing carbon composite material of. 4. An expanded graphite powder having an average particle diameter of 5 μm to 12 μm, 80% or more of all powder particles having a particle diameter of 0.1 μm to 20 μm, and a thermosetting resin are mixed and dispersed at room temperature. A method for producing a carbon composite material, which comprises press-molding at a temperature of 400 ° C to 400 ° C and then firing the molded product at 700 ° C to 3000 ° C in a non-oxidizing atmosphere. 5. The ratio of the expanded graphite powder to the thermoplastic resin or the thermosetting resin is 10 to 1000 parts by weight of the thermoplastic resin or the thermosetting resin with respect to 100 parts by weight of the expanded graphite powder. Of manufacturing carbon composite material of. 6. The firing in a non-oxidizing atmosphere is performed at 1000
The method for producing a carbon composite material according to claim 4, wherein the method is performed at a temperature of from ℃ to 2,500 ℃.