JP2924062B2 - Production method of raw material powder for carbon material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a raw material powder useful as a high-density special carbon material. More specifically, the present invention relates to a method for producing a raw material powder for a special carbon material having a high density and excellent electric discharge machining characteristics.

[Conventional technology]

Conventionally, a special carbon material is produced by heating and mixing particles and powder obtained by mixing pitch coke and petroleum coke in a predetermined ratio, adding an appropriate amount of binder pitch, and then molding. Furthermore, after firing and graphitizing the green compact, it is processed to produce a special carbon material as a product. Recently, there has been reported a method for producing special carbon materials by forming mesocarbon microbeads obtained by heat treating a pitch and then treating the pitch with a solvent.

[Problems to be solved by the invention]

These methods have problems such as poor product properties such as low bulk density and low strength of products, and complicated processes and high manufacturing costs. Was desired.

In recent years, attention has been paid to the use of carbon materials as electrodes for electric discharge machining, and the demand is rapidly increasing. However, conventional carbon materials have insufficient electric discharge machining characteristics, and carbon materials having better electric discharge machining characteristics, particularly electric discharge machining Carbon materials with low consumption rate at the time are required. In addition, a carbon material manufactured from mesocarbon has a high cost due to a complicated process, has a low manufacturing cost, and is required to have high characteristics.

[Means for solving the problem]

Therefore, in view of such circumstances, the present inventors have conducted intensive studies to produce a special carbon material having high strength and good discharge characteristics, and as a result, heat-treated a coal tar-based raw material having a large proportion of an optically anisotropic structure, The present inventors have found that a raw material having certain characteristics and a finely pulverized raw material are formed into a fired graphite after forming as a raw material, and that the resulting product has high characteristics.

That is, the gist of the present invention is that a coal tar-based raw material having an optically anisotropic structure ratio of 60% or more is heat-treated while applying mechanical energy, and the volatile matter (VM) is 20% by weight.
A heat treatment step in which the average size of the optically anisotropic structure is 50 μm or less and the proportion thereof is 30% or less, and pulverization for finely pulverizing the material after the heat treatment step A method for producing a raw material powder for a carbon material, comprising the steps of: Note that the ratio of the optically anisotropic structure refers to the ratio of the area of the anisotropic structure under a polarizing microscope.

 Hereinafter, the present invention will be described in detail.

First, the coal tar-based raw material in the present invention is coal tar by-produced during coal carbonization or coal tar pitch obtained therefrom, and the VM may exceed 30% by weight.
If it exceeds 30% by weight, the heat treatment time for adjusting to the target physical properties is long, the processing capacity is reduced, and the cost is increased.
VM is desirably 30% by weight or less.

These materials have an optically anisotropic structure ratio of 60%.
If it is less than 30, the heat treatment is insufficient, so that the fraction having a light boiling point is large and the treatment is likely to be uneven due to fusion during the heat treatment. These coal tar-based raw materials can be obtained by heat treatment at 350 to 480 ° C. for about 1 to 72 hours using a delayed coker, an autoclave, or the like.

When heat treating these coal tar-based raw materials according to the present invention, it is usually selected from about 200 to 350 ° C. and about 0.5 to 24 hours, but it is more effective to apply mechanical energy during the heat treatment in order to uniformly perform the treatment. large. Examples of a method of applying mechanical energy include stirring, ultrasonic waves, and the like.

The VM of the product needs to be 3-20% by weight,
If the VM of the treated product exceeds 20% by weight, the change in weight during firing is large, and the properties are deteriorated. On the other hand, if it is less than 3% by weight, the sinterability is poor and the properties are deteriorated.

Further, when the size of the optically anisotropic structure of the processed product exceeds 50μ and the ratio exceeds 30%, the structure of the product also has many anisotropic structures, becomes non-uniform, and the characteristics are deteriorated. The size of the optically anisotropic structure is 50 μm or less, and the ratio is 30% or less. The heat treatment may be performed in an inert gas such as argon or nitrogen under autogenous pressure, or may be performed in the presence of air.

Further, the heat treatment of the coal tar-based raw material is preferably performed such that the obtained heat-treated product is pulverized to an average particle size of 15 to 20 μm, but the toluene-soluble matter is 10% by weight or less and 1% by weight or more. By reducing the amount of γ-resin to 10% by weight or less, the tendency of foam cracking during firing of the molded article is reduced.
The sintering characteristics are improved by setting the content to not less than% by weight.

Next, the heat-treated product is finely pulverized to obtain a raw material powder. In order to obtain a good molded product, the average particle size of the raw material powder is desirably 50μ or less, but in order to further improve the uniformity of the product structure, it is preferably 30μ or less, more preferably 20μ or less, and most preferably 10μ or less. It is desirable to finely pulverize.
As the molding, ordinary molding, cold isostatic pressing and the like are used. Calcination can be performed in an inert gas or in a coke breeze, and is performed at a temperature of 800 to 1300 ° C. Further, graphitization can be performed by a conventional method such as a Tamman furnace, an Acheson furnace, or induction heating, and is usually performed at 2000 to 3000 ° C.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 A coal tar-based raw material containing 24.4% by weight of VM and 90% of an optically anisotropic structure obtained by heat-treating coal tar was heated at 230 ° C. and 7 ° C. while applying mechanical energy in the presence of air.
Heat treatment was performed for 5 minutes. The amount of γ resin in the product is 5.9
%, The average size of the anisotropic structure was 20 μm, and the ratio was 10%. This product was finely pulverized to an average particle size of 18 μm, and a molded product was obtained by a mold press. After firing this molded body to 1000 ° C in coke breeze to prevent oxidation,
The product was graphitized to 2800 ° C in a Tamman furnace to obtain a product. The bulk density of graphite products is 1.87, and the wear rate during EDM is 0.8%
Met.

Example 2 The same raw material as in Example 1 was heat-treated (about 230 ° C., 85 minutes) to obtain a γ-resin having a content of 5.1% by weight. The size of the anisotropic structure of this product is an average particle size of 20μ, and its proportion is 10%
Met. This product was pulverized to an average particle size of 16 μm, and a graphite product was produced in the same manner as in Example 1. Its bulk density is
1.94, the consumption rate at the time of electric discharge machining was 1.1% by weight.

Comparative Example 1 The same raw material as in Example 1 was heat-treated to obtain a resin having a γ-resin amount of 14.7% by weight, and was finely pulverized to an average particle size of 17 μm.
A molded article was produced by the same method as that described above, but was broken due to foaming.

Comparative Example 2 The same raw material as in Example 1 was heat-treated to obtain a resin having a γ resin content of 6.9%. The size of the anisotropic structure of this product was 100 μm in average particle size, and the ratio was 80%. The product was pulverized to an average particle size of 17 μm to produce a graphite product in the same manner as in Example 1. Its bulk density was 1.77, and the consumption rate during electric discharge machining was 3.5% by weight.

Comparative Example 3 The bulk density and the consumption rate during electric discharge machining of a commercially available graphite product were simultaneously measured to be 1.84 and 4.4% by weight, respectively.

〔The invention's effect〕

The carbon material using the raw material powder according to the method of the present invention has a high bulk density and very good electric discharge machining characteristics (low consumption rate).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-126789 (JP, A) JP-A-64-81890 (JP, A) JP-A-64-29493 (JP, A) 2298 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C10C 1/19 C10C 3/00-3/18

Claims (4)

(57) [Claims] 1. A coal tar-based raw material having an optically anisotropic structure ratio of 60% or more is heat-treated while applying mechanical energy, and the volatile matter (VM) is 20% by weight or less and 3% by weight or more. And includes a heat treatment step in which the average size of the optically anisotropic structure is 50 μm or less and the proportion thereof is 30% or less, and a pulverization step of finely pulverizing the material after the heat treatment step. A method for producing a raw material powder for a carbon material, comprising: 2. The method according to claim 1, wherein the volatile content of the coal tar-based raw material is 30% by weight or less. 3. A heat treatment step, wherein the heat-treated material has an average particle size of 15 to 20.
1% when the soluble matter in toluene is 10% by weight or less
2. The method according to claim 1, wherein the concentration is set to be not less than% by weight.
Or the production method according to 2. 4. The method according to claim 1, wherein the pulverizing step is performed such that the average particle size of the obtained finely pulverized product is 30 μm or less.
4. The method according to any one of items 1 to 3.