JPH0524919A - Production of carbon material - Google Patents

Abstract

PURPOSE:To surely obtain the high-density carbon material having a uniformly fine structure by packing a powder mixture composed of carbonaceous aggregate and binder into a forming mold, deaerating the inside of the mold, heating and pressurizing the powder mixture under a reduced pressure and calcining the molding. CONSTITUTION:The carbonaceous aggregate (e.g.: pitch coke powder) and the binder (e.g.: coal tar pitch) are kneaded or mixed and the mixture is ground at need, by which carbonaceous raw material powder 5 is produced. This carbonaceous raw material powder 5 is then packed into the forming mold for hot pressing and the inside of the forming mold is deaerated via a deaeration pipe 6. The mold is simultaneously heated by a heater 2 and the carbonaceous raw material powder 5 is molded by heating and pressurizing under the reduced pressure. The resultant molding is taken out of the forming mold, is calcined in accordance with the conventional method and is further graphitized at need to afford the carbon material. Open cells are formed on the surface layer of the molding in this way and, therefore, the gases generated in the mold are effectively dissipated to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon material by a hot pressing method.

[0002]

2. Description of the Related Art Carbon materials used for carbon electrodes, sliding members, machine seals, etc. are generally formed by kneading and crushing carbonaceous aggregate such as coke powder and a binder such as coal tar pitch. It is obtained by carbonizing or further graphitizing the obtained molded body. However, since the conventional manufacturing method requires a long process time for carbonization, improvement has been desired. Further, recently, high density and high strength of carbon materials have been required. From these things, Japanese Examined Patent Publication No. 51-20197 and Japanese Examined Patent Publication 1
As disclosed in Japanese Patent Laid-Open No. 32162, a method of manufacturing a carbon material by a hot press method in which a carbonaceous raw material powder is filled in a mold and heating and pressing are performed at the same time is proposed.

[0003]

The hot pressing method described above simplifies the manufacturing process by performing the pressure molding and firing steps of the conventional method in one step, and shortens the carbonization firing step time by applying pressure in the carbonization process. It has advantages such as shortening and obtaining a high-density carbon material. However, since the conventional hot pressing method has a closed structure and the molded body is in a pressurized state, the gas generated by the carbonization reaction remains inside the molded body, and the product after the carbonization can be visually confirmed. There is a problem that a non-uniform fine structure including large pores is formed.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a method for producing a high-density carbon material having a uniform fine structure.

[0005]

According to the present invention, a carbonaceous raw material powder obtained by kneading or mixing a carbonaceous aggregate and a binder is filled in a molding die, and the interior of the molding die is deaerated and heated under reduced pressure. The present invention relates to a method for producing a carbon material which is pressed and then fired.

In the present invention, the carbonaceous raw material powder is a mixture of a carbonaceous aggregate such as coke powder and a powder of a binder such as coal tar pitch, or a pulverized mixture of the aggregate and the binder. The type of carbonaceous aggregate and the type of binder are not particularly limited. The average particle size of this carbonaceous raw material powder is 15 to
It is preferably 30 μm.

In the present invention, the carbonaceous raw material powder is heated and pressed by the hot pressing method. It is necessary to shield the parts of the hot-pressing die that are in contact with the punch, die, spacer, and other members with a material that can withstand a sufficiently high temperature. The carbonaceous raw material powder is uniformly filled in a hot pressing mold and heated under atmospheric pressure to a temperature at which the carbonaceous raw material powder starts to soften. The heating rate in heating is not particularly limited, but is preferably 3 ° C./min or less.
Simultaneously with this heating, deaeration in the hot press molding die shielded from the outside air is performed. It is preferable that the degassing is sufficiently performed in the temperature range of 300 to 500 ° C., which has the largest amount of generated gas, in the temperature range in which the carbonaceous raw material powder undergoes the carbonization reaction to volatilize the generated gas inside the compact. .. Generally, in the carbon material production by the hot pressing method, the heating method is heating from the outside, and the temperature in the vicinity of the surface of the molded body during the temperature rising process is higher than the central temperature. Therefore, if degassing is insufficient, no openings are formed in the surface layer of the molded body, and the gas generated at the center of the molded body cannot be vaporized. Also,
If degassing is excessive, the porosity of the entire molded body will increase,
High density carbon material cannot be obtained. Deaeration is performed in the mold by 10
It is preferable that the pressure is reduced to about 100 Torr. Furthermore, in the temperature range where the carbonaceous raw material powder is softened and solidified,
By gradually pressurizing at a constant pressurizing rate, the volatilization of the gas generated inside the molded body becomes more effective. The pressure is maintained at the maximum pressure up to a temperature at which the molded body is solidified, and then the pressure is gradually reduced to obtain a heated and pressed molded body.

The above-obtained molded body is taken out of the molding die, fired according to a conventional method, and further 2500 if necessary.
Graphitize at a temperature of ℃ or more to obtain a carbon material.

[0009]

When the carbon material is manufactured by the hot pressing method in which heating and pressing are performed simultaneously, the gas generated from the carbonaceous raw material powder is
It easily remains inside the molded body. In the present invention, degassing is performed in the molding die within a temperature range where gas is generated, and pressure is gradually applied to form an opening in the surface layer of the molding, thereby generating gas inside the molding. It effectively vaporizes to the outside.

[0010]

EXAMPLES Next, examples of the present invention will be described.

Example 1 60% of pitch coke powder having an average particle size of 15 μm by weight and 40% of coal tar pitch were kneaded to obtain an average particle size of 30 μ.
The carbonaceous raw material powder of m was uniformly filled in the hot press mold shown in FIG. 1 for molding. In FIG. 1, 1 is a furnace frame, 2 is a heater, 3 is a shield material, and 4 is a ventilation material for preventing the discharge of the carbonaceous raw material powder sample 5 when degassing from the lower degassing pipe 6. After heating the sample 5 to 310 ° C. by the heater 2 under atmospheric pressure, degassing was performed under reduced pressure to 30 Torr,
Then, the sample 5 was pressurized to 300 kgf / cm ² and simultaneously heated to 550 ° C. at a rate of 1.0 ° C./min. In addition,
The deaeration operation was performed up to 450 ° C., and the pressure applied by the hot press machine was maintained up to 550 ° C. with the maximum pressure, and then the pressure was gradually reduced. The molded body thus obtained is baked at 1000 ° C. under atmospheric pressure in a non-oxidizing atmosphere,
Graphitized at 00 ℃, does not contain pores above 30μm,
A high density carbon material having a fine structure in which pores of less than 30 μm are uniformly dispersed and a bulk density of 1.81 g / cm ³ was obtained.

Example 2 A mixture having the same composition as in Example 1 was ground to give an average particle size of 20 μm.
Using the carbonaceous raw material powder of m as a sample, heating and pressing were performed in the same manner as in Example 1 by the hot pressing apparatus shown in FIG. 2, and firing and graphitization were performed in the same manner as in Example 1. The apparatus shown in FIG. 2 performs degassing from above and below, and is otherwise the same as FIG. The obtained carbon material has a dense fine structure in which pores of less than 30 μm are uniformly dispersed, and the bulk density is 1.8.
It is 1 g / cm ³ .

Example 3 The maximum pressure in the hot press was 100 kgf / cm ² ,
In the same manner as in Example 1 except that heating was performed at a temperature rising rate of 5 ° C. per minute, heating and pressurization was performed by the hot press device shown in FIG.
Firing and graphitization were carried out in the same manner as in Example 1. The apparatus shown in FIG. 3 is for degassing from the side, and other than that shown in FIG.
Is the same as. The obtained carbon material has a fine structure in which pores of less than 30 μm are uniformly dispersed and has a bulk density of 1.8.
It is of 0 g / cm ³ .

Comparative Example 1 The same carbonaceous raw material powder as in Example 1 above was used, and heating and pressurization were carried out in the same manner as in Example 1 except that deaeration was not performed.
Firing and graphitization were carried out in the same manner as in. The obtained carbon material has a large number of pores of 10 to 100 μm remaining in the center,
It has a non-uniform fine structure.

[0015]

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to eliminate the pores of 30 μm or more remaining in the central portion of the carbon material by the conventional hot pressing method, and to obtain a high density coal having a uniform fine structure. Material is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a hot pressing device used in an example of the present invention.

FIG. 2 is a schematic view of a hot press device used in an example of the present invention.

FIG. 3 is a schematic view of a hot press device used in an example of the present invention.

[Explanation of symbols]

 1 Furnace frame 2 Heater 3 Shielding material 4 Venting material 5 Sample 6 Degassing tube

Claims (1)

Claims: 1. A carbonaceous raw material powder obtained by kneading or mixing a carbonaceous aggregate and a binder is filled in a molding die, and the interior of the molding die is deaerated and heated and pressurized under reduced pressure. And a method for producing a carbon material, which comprises firing.