JP2758962B2 - Production method of raw material powder for isotropic, high density, high strength carbon materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high-density and high-strength carbon material used for jigs for semiconductors, crucibles for semiconductors or reactor wall materials for nuclear reactors, electrodes for electric discharge machining, and the like. And a method for producing a raw material powder for a carbon material for applications in which impurities are particularly problematic.

<Conventional technology> Mesophase small spheres with optical anisotropy generated in optically isotropic pitch when coal tar pitch etc. are heated at a temperature of 350 to 500 ° C are slightly extracted from benzene, tar oil, etc. Using a weak solvent, leave a part of the β component in the pitch together with the mesophase microspheres, and then calcine at a temperature of 200 to 450 ° C in an inert atmosphere for excellent self-sintering properties It is known that raw materials for carbon materials are manufactured.

If the raw material obtained by this method is used, the bulk density is 1.85 g / cm ³ or more, and the bending strength is 800 kg / cm ² or more.・ Isotropic graphite material can be easily manufactured.

However, generally, the free carbon (QI component) in the raw material pitch contains a large amount of ash, and as a result, the amount of ash in the mesophase microspheres increases.

For this reason, when manufacturing carbon blocks and graphite materials using mesophase small spheres as raw materials, it was inevitable that the ash content would increase.

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

<Problems to be Solved by the Invention> An object of the present invention is to maintain the same high density and high strength as a graphite material obtained by molding, calcining, and graphitizing a conventional mesophase spheroid containing free carbon, and ash An object of the present invention is to provide a method for producing a raw material for a high-density and high-strength carbon material with a reduced amount.

<Means for Solving the Problems> The present invention provides a heat treatment after adding and mixing 0.5 parts by weight or more of carbon powder to 100 parts by weight of a pitch substantially free of free carbon or a pitch from which free carbon is removed, and then performing heat treatment. This is a method for producing a raw material powder for an isotropic, high-density, high-strength carbon material, which comprises subjecting the generated optically anisotropic small spheres to solvent separation and calcination.

<Operation> The present invention does not substantially contain ash such as high-purity coke, artificial graphite powder, and quiche graphite with respect to a pitch not containing free carbon (QI component) or a pitch from which free carbon is removed (0.01 to 0.01%). 0.5% by weight or more, preferably 1 to 20 parts by weight, of carbon powder per 100 parts by weight of pitch. Carbon particles having a particle size of 0.1 μm to several mm can be used.

If the amount of addition and mixing is less than 0.5 parts by weight, the mesophases are united / separated during the heat treatment and small spheres cannot be produced.
If the amount is more than 20 parts by weight, the density and strength of the graphite material produced by molding, firing and graphitizing the mesophase spheres are not preferred. Therefore, in the present invention, the amount of carbon powder added and mixed is limited to 0.5 parts by weight or more.

Subsequently, heat treatment is performed to generate mesophase small spheres.

Subsequently, the mesophase microspheres generated from the pitch matrix together with the β component as a sintering component are separated using a solvent such as benzene or medium oil in tar. As a solvent, it is preferable to use a solvent such as benzene or tar medium oil having a low extraction power for the pitch 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 desirably heated at a temperature of 200 to 450 ° C. in an inert atmosphere.

In this way, uniform high density and excellent self-sintering
Raw materials for high-strength and isotropic carbon materials are manufactured.

In addition, the pitch which does not contain free carbon can be prepared as follows.

That is, free carbon is removed by treating coal tar with or without adding a solvent by a method generally employed in industry such as filtration, standing separation, and centrifugation.

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

<Example> Comparative Example 1 Coal tar pitch containing 3% of free carbon was 450
Heat treatment at ℃ for 1 hour to generate mesophase spheres,
After extraction and filtration with a six-fold amount of tar oil, the residue was calcined at 350 ° C. for 3 hours in a nitrogen atmosphere and pulverized to obtain carbonaceous mesophase microspheres.

After molding the above carbonaceous mesophase spherules to 80mmφ-30mmh, and cold isostatic molding under a pressure of 550kg / cm ^2, 1000
Table 1 shows the physical properties of the graphite material obtained by performing the graphitization treatment at a temperature of 2500 ° C. after the treatment at 3 ° C. for 3 hours.

Comparative Example 2 A heat treatment was performed at 450 ° C. for 1 hour using a pitch (QI value: 0.01 wt% or less) from which the free carbon was removed from the pitch of Comparative Example 1, and the mesophase component was coalesced and separated from the pitch matrix, resulting in a small mesophase. The sphere could not be manufactured.

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

After removing the free carbon by filtering the coal tar under pressure, distillation and heat treatment were performed to prepare a pitch.

Example 1 After adding and mixing 5 parts by weight of high-purity coke (ash content of 0.01 wt% or less) to the pitch of Comparative Example 2 (QI value of 0.01 wt% or less) per 100 parts by weight of the pitch, heat-treated at 450 ° C. for 1 hour. As a result, mesophase microspheres were produced in the same manner as in Comparative Example 1.

A graphite material was produced from the mesophase microspheres in the same manner as in Comparative Example 1.

Table 1 also shows the ash content and physical properties of the obtained graphite material.

<Effect of the Invention> The raw material for carbon material produced by the present invention has a low ash content and is a raw material for high-density, high-strength, isotropic carbon material, and is used for jigs for semiconductors, crucibles for semiconductors, and nuclear power. It is suitable as a carbon material or a raw material for an electrode for electric discharge machining.

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Claims (1)

(57) [Claims] An optical anisotropy produced by heat treatment after adding and mixing at least 0.5 parts by weight of carbon powder with respect to 100 parts by weight of a pitch substantially free of free carbon or a pitch from which free carbon has been removed. A method for producing a raw material powder for an isotropic, high-density, high-strength carbon material, wherein a sphere is subjected to solvent separation and calcination.