JPH03265509A - Production of powdery raw material for carbon material having isotropy, high density, and high strength - Google Patents

Abstract

PURPOSE:To produce a powdery raw material for carbon material having, isotropy, high density and high strength by adding and mixing a specific amount of carbon powder into pitch free from free carbon, exerting heat treatment, fractionating the resulting optically anisotropic microbeads with a solvent, and then carrying out calcination treatment. CONSTITUTION:Carbon powder (about 0.1mu to several millimeters grain size) practically free from ash (<=about 0.01wt.%), such as high purity coke fines, is added by >=0.5wt.%, preferably about 1-20 pts.wt., to 100 pts.wt. of pitch practically free from free carbon or pitch from which free carbon is removed, and these are mixed. Subsequently, heat treatment is exerted to form mesophase microbeads, and these mesophase microbeads are fractionated together with beta-component to be sintering component from the pitch matrix by using a solvent, such as benzene. Further, calcination treatment is carried out in an inert atmosphere at about 200-450 deg.C. Br this method, the uniform raw material for carbon material excellent in self sintering property and having high density, high strength, and isotropy can be obtained. This raw material is suitable for raw material for crucible for semiconductor use, carbon material for nuclear power use, etc.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a high-density, high-strength carbon material used for semiconductor jigs, semiconductor crucibles, nuclear reactor wall materials, electrodes for electrical discharge machining, etc. Applications in which impurities are a particular problem relate to methods for producing raw material powder for carbon materials.

<Prior art> Mesophase spherules with optical anisotropy, which are generated in optically isotropic pitch when coal tar pitch etc. is heated at a temperature of 350 to 500°C, are extracted with a small amount of benzene, oil in tar, etc. A part of the β component in the pitch remains together with the mesophase spherules using a weak solvent, and is then calcined at a temperature of 200 to 450°C in an inert atmosphere, resulting in excellent self-sintering properties. It is known that raw materials for carbon materials can be produced.

If the raw material obtained by this method is used, it can be molded, fired, and graphitized without using a binder, resulting in a bulk density of 1.85 g/cd or more and a bending strength of 800 kg/cd.
High-density, high-strength, and isotropic graphite materials of c- or higher can be easily produced.

However, -g is the free carbon in the raw material pitch (
Ql component) contains a large amount of ash, resulting in a high ash content in the mesophase spherules.

For this reason, when producing carbon blocks and graphite materials using mesophase spherules as a raw material, it was inevitable that the ash content would be high.

On the other hand, when heat treatment is performed using pitch from which free carbon has been removed as a raw material, coalescence and phase separation of mesophase components tend to occur, and the yield of small spheres becomes extremely low.

<Invention tries to solve! Im> The purpose of the present invention is to maintain high density and high strength equivalent to graphite materials obtained by molding, firing, and graphitizing mesophase small spheres containing free carbon, and to produce high density and high strength materials with reduced ash content. An object of the present invention is to provide a method for producing a raw material for high-strength carbon material.

<l [Means for solving the problem>] The present invention provides a method for adding and mixing 0.5 parts by weight or more of carbon powder to 100 parts by weight of pitch that does not substantially contain free carbon or pitch from which free carbon has been removed. , the optically anisotropic spherules produced by heat treatment are separated by solvent,
This is a method for producing raw material powder for isotropic, high-density, and high-strength carbon materials, which is characterized by a calcining treatment.

<Function> The present invention provides a pitch that does not contain free carbon (Q+ acid component) or pitch from which free carbon has been removed, and a pitch that does not substantially contain ash content (0) of high purity coke, artificial graphite powder, quiche graphite, etc. , 01 wt% or less) carbon powder is added and mixed with 0.5 parts by weight or more, preferably 1 to 20 parts by weight, per 100 parts by weight of pitch.The particle size of carbon is from 0.1 fm to several things are available.

If the amount added/mixed is less than 0.5 parts by weight, the mesophase will coalesce and phase separate during heat treatment, making it impossible to produce small spheres.
If the amount is 20 parts by weight or more, the density and strength of the graphite material produced by molding, firing, and graphitizing the mesophase small spheres will decrease, which is undesirable. Therefore, in the present invention, the amount of carbon powder added/mixed is 0.5 parts by weight. Limited to parts by weight or more.

Subsequently, heat treatment is performed to generate mesophase spherules.

Subsequently, using a solvent such as benzene or oil in tar, the mesophase spherules generated from the pitch matrix are separated together with the β component which becomes the sintered component. As the solvent, it is preferable to use a solvent having a weak extraction power for pitch, such as benzene or oil in tar, in order to leave the β component in the pitch.

Further, a calcination treatment is performed to adjust the sintering force. The calcination treatment is preferably heated at a temperature of 200 to 450°C in an inert atmosphere.

In this way, a uniform high-density, high-strength, and isotropic carbon material raw material with excellent self-sintering properties is produced.

Incidentally, a pitch that does not contain free carbon can be prepared as follows.

That is, free carbon is removed by treating coal tar with or without the addition of a solvent by a method generally practiced in industry, such as filtration, static separation, or centrifugation.

Next, the present invention will be explained in more detail with reference to specific examples.

<Example> Comparative Example 1 450% coal tar pitch containing 3% free carbon
Heat treated at ℃ for 1 hour to generate mesophase spherules,
After extraction and filtration with 6 times the amount of cool medium oil, the filtration residue was calcined at 350''C in a nitrogen atmosphere for 3 hours and pulverized to obtain carbonaceous mesophase spherules.

The above carbonaceous mesophase small spheres were molded into a 80mm φ-30mm mold, then cold isostatically molded at a pressure of 550kg/c-, treated at 1ooo''C for 3 hours, and further heated at a temperature of 2500'C. Table 1 shows the physical properties of graphite material obtained by graphitization treatment.
Shown below.

Comparative Example 2 The pitch obtained by removing free carbon from the pitch of Comparative Example 1 (Ql value 0.01 wt% or less) was used as a raw material at 450°C.
- When the heat treatment was performed for 1 hour, the mesophase components coalesced and separated from the pitch matrix, making it impossible to produce mesophase spherules.

The pitch from which free carbon was removed was prepared as follows.

After filtering the coal tar under pressure to remove free carbon,
Pitch was prepared by distillation and heat treatment.

Example 1 High-purity coke (ash content 0.01 wt% or less) was added to the pitch of Comparative Example 2 (Ql value 0.01 wt% or less) at a pitch of 100.
After adding and mixing 5 parts by weight to parts by weight, 1 at 450°C.
When heat treatment was performed for a period of time, mesophase spherules were produced as in Comparative Example 1.

Comparative example from the mesophase spherule! Graphite material was produced in the same manner as above.

The ash content and the physical properties of the graphite material obtained are also shown in Table 1.

<Effects of the Invention> The raw material for carbon materials produced by the present invention has a small ash content,
It is a raw material for high-density, high-strength, and isotropic carbon materials, and is suitable as a raw material for semiconductor jigs, semiconductor crucibles, nuclear power carbon materials, or electrodes for electrical discharge machining.

Claims (1)

[Claims] After adding and mixing 0.5 parts by weight or more of carbon powder to 100 parts by weight of pitch that does not substantially contain free carbon or pitch from which free carbon has been removed, heat treatment is performed to generate optically anisotropic small spheres in a solvent. A method for producing raw material powder for isotropic, high-density, and high-strength carbon materials, characterized by fractionation and calcining treatment.