JP3278190B2 - Method for producing isotropic high-density graphite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably and efficiently producing an isotropic high-density graphite having excellent material strength.

[0002]

2. Description of the Related Art Isotropic high-density graphite materials are useful as various members such as electrodes for electric discharge machining, high-strength jig materials, and crucibles for aluminum deposition. Generally, isotropic high-density graphite is made of petroleum-based or coal-based coke powder, aggregated with pitch as a binder, kneaded and re-ground, and then molded by rubber press. It is produced by a method of calcining and graphitizing a body. in this case,
When manufacturing the electrode for electric discharge machining, if the average particle diameter of the aggregate coke powder is large, the unevenness of the surface becomes large due to wear, and the finished surface becomes rough, so the average particle size of the aggregate Must be adjusted to 10 μm or less. Also in the case of high-strength jig materials and crucibles for aluminum deposition, it is preferable to reduce the average particle size of the aggregate coke powder as much as possible in order to obtain high strength and high density.

However, if the average particle size of the aggregate is reduced, the oil absorption increases, and uniform kneading with the aggregate coke powder cannot be performed unless a large amount of pitch binder is used. For this reason, when the amount of the binder is increased, a large amount of volatile components contained in the firing step is generated at a time, which causes a defect phenomenon such as crack or breakage in the material structure. Therefore, it is impossible to produce a large isotropic graphite material. In order to solve such a problem, a technique for adjusting the volatile content in the kneading raw material before firing has been developed. For example, after kneading is completed, the lid of the kneading machine is opened and the generated gas is exhausted with a blower to adjust the volatile content (Japanese Patent Publication No. 1-16789).
Japanese Patent Application Laid-Open No. 62-182107, Japanese Patent Publication No. 1-272424, and a method of kneading an aggregate and a binder, coarsely pulverizing the mixture, and heating the mixture in an inert atmosphere to adjust volatile components. Japanese Patent Publication No. Hei 3-29001) has been proposed.

[0004]

These prior arts are:
Volatile components that are the main cause of cracking and breakage during firing,
In particular, the total amount of volatile components is adjusted by previously removing the toluene-soluble component having a small molecular weight contained in the pitch. However, in order to suppress material damage such as cracks and breakage in the firing stage, and to always obtain an isotropic high-density graphite material with excellent material properties, other condition factors affecting those phenomena must be considered. It needs to be clarified.

The inventor of the present invention has conducted multifaceted studies focusing on the type, blending amount, volatile content, molecular weight distribution, etc. of the binder used. As a result, not only the toluene-soluble component in the binder but also a higher Ascertain that the β-resin component is also related to material damage during firing, and adjust the β-resin content to a certain range together with the toluene-soluble component to stably achieve high strength without material damage during firing. It was clarified that an isotropic high-density graphite material could be manufactured.

The present invention has been developed on the basis of the above findings, and has as its object to provide an industrial solution for obtaining an isotropic high-density graphite material having excellent material strength and normal material structure stably and efficiently. To provide a simple manufacturing method.

[0007]

In order to achieve the above object, a method for producing an isotropic graphite material according to the present invention comprises an aggregate component mainly composed of non-graphitic carbonaceous material having a maximum particle diameter of 10 μm or less.
70 to 110 parts by weight of a pitch binder is added to and kneaded with 100 parts by weight, and the kneaded material is roughly pulverized, and then heat-treated in a temperature range of 250 to 450 ° C. to reduce the toluene soluble component and the β-resin component to 5 parts each. The composition is characterized in that the volatile content is adjusted so as to fall within the range of 重量 15% by weight, crushed again, formed into a predetermined shape by a rubber press, and then subjected to calcination carbonization and graphitization.

[0008] Examples of the non-graphitic carbonaceous aggregate component applicable to the present invention include petroleum coke, pitch coke, carbon black, anthracite, and the like. Mixtures are preferably used. It is also possible to mix and use a small amount of a graphite powder such as artificial graphite with these aggregate components. However, when the compounding ratio of the graphite powder is increased, the isotropy of the product may be reduced. The aggregate is finely pulverized by a mechanical pulverizer before use. In order to obtain a high-density structure, the maximum particle size needs to be 10 μm or less, and preferably the average particle size is in the range of 0.3 to 3 μm. Adjust the particle size.

As the binder, pitch-based binders such as coal-based hard pitch, medium pitch, soft pitch, coal tar and petroleum pitch are used. The pitch-based binder,
It is blended in an amount of 70 to 110 parts by weight with respect to 100 parts by weight of the aggregate component. If the amount of the binder is less than 70 parts by weight, the bonding strength becomes insufficient. If the amount exceeds 110 parts by weight, cracks and breakage occur in the fired material.

The kneading of the aggregate component and the binder is carried out until both components are uniformly dispersed and kneaded by using a kneading apparatus and the binder sufficiently covers the aggregate. Since the temperature during kneading must be maintained at a temperature at which the pitch binder softens, the temperature is usually increased to 150 ° C. or higher, but 250 ° C.
Exceeding the ratio is undesirable because volatile components of the pitch evaporate. Therefore, the temperature is appropriately set in the temperature range of 150 to 250 ° C. Since the kneaded material after the kneading process is a lump, it is roughly pulverized to a particle size of 10 mm or less at the maximum. Particle size 10
If there is a lump exceeding mm, it is difficult to make the amounts of the toluene-soluble component and the β-resin component in and around the surface uniform. In addition,
The toluene-insoluble content and Β-resin in the present invention have a particle size of
It was measured by extracting a sample pulverized to 212 to 500 μm with toluene or quinoline.

The coarsely ground kneaded material is then heated at 250 to 450 ° C.
The volatile component is adjusted so that the toluene-soluble component and the β-resin component are each in the range of 5 to 15% by weight. If the heat treatment temperature at this time is less than 250 ° C, it takes a long time to volatilize and remove the toluene-soluble component, while
When the temperature exceeds ℃, the toluene-soluble component and β-resin component are sharply reduced, so that the sinterability is insufficient, and the strength of the resulting isotropic graphite material is reduced. The atmosphere during the heat treatment may be an oxidizing atmosphere or an inert atmosphere. However, when an oxidizing atmosphere is employed, if the oxygen concentration becomes too high, the toluene soluble component and the β-resin component decrease very rapidly. It is necessary to lower the temperature. The heat treatment is terminated when the volatile components evaporate and the toluene-soluble component and the β-resin component both fall within the range of 5 to 15% by weight. If the toluene-soluble component and / or β-resin component exceeds 15% by weight, the removal of the volatile components becomes insufficient and the material structure cracks during firing, resulting in the structure of the produced isotropic graphite material. The density does not increase, and the expected material strength cannot be obtained. Further, as the volatilization of volatile components progresses as the toluene-soluble component and / or β-resin component becomes less than 5% by weight, the binding force decreases,
Similar material defects and insufficient properties are caused.

[0012] The kneaded material thus adjusted for volatile content is
Pulverize with a crusher The type of crusher to be used is not limited, but the average particle size of the crushed powder needs to be equal to or larger than the average particle size of the aggregate. If the pulverization is performed to the average particle size of the aggregate or less, the ratio of the aggregate having no binder component on the surface increases, so that a dense graphite material cannot be obtained. Further, the maximum particle size of the pulverized powder is preferably within three times the maximum particle size of the aggregate, and if it is more than this, large pores are generated in the structure of the graphite material, so that a dense structure cannot be obtained.

After the pulverized powder is used as a molding material and molded into a predetermined shape using a rubber press, it is calcined and carbonized in a heating furnace under a non-oxidizing atmosphere at a temperature of up to 1000 ° C., and further transferred to a graphitization furnace. Graphitization in a high temperature range of 2500 ° C. or more to obtain an isotropic high-density graphite material.

[0014]

According to the present invention, the components to be adjusted for volatile components are both the toluene-soluble component and the β-resin component. The β-resin is a component that is insoluble in toluene and soluble in quinoline, and has a binder-like binding function because it has a higher molecular weight than the toluene-soluble component, but if this adjustment is not made, material damage in the firing process Difficult to avoid. In the present invention, the kneaded product of the aggregate and the pitch-based binder is heat-treated to adjust the volatile matter so that both the toluene-soluble component and the β-resin component are in the range of 5 to 15% by weight. It is possible to produce an isotropic high-density graphite material without damage. In addition, the effect of improving the strength of the obtained graphite material is also provided. Although this mechanism has not been elucidated in detail, the molecular weight distribution of the binder component present in the kneaded material after the heat treatment is most likely to form a dense structure by sintering firmly and firmly without causing structural destruction during firing. It is presumed that this is due to the favorable state.

Such a mechanism, combined with the effect of other specific conditions such as the particle size of the aggregate and the mixing ratio of the aggregate and the pitch-based binder, is always stable and high-quality isotropic high-density graphite material. Is manufactured.

[0016]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Example 1 100 parts by weight of pitch coke powder having an average particle size of 2.5 μm and a maximum particle size of 10 μm were mixed with 110 parts by weight of a pitch, charged into a Z-type kneader, and sufficiently heated at 200 ° C. It was kneaded. After cooling, the kneaded material was roughly pulverized to a maximum particle size of 5 mm or less.
Then, the coarsely ground kneaded material was subjected to a heat treatment at a temperature of 300 ° C. for 30 minutes in an air atmosphere to adjust volatile components. This is finely pulverized by a jet pulverizer so as to have an average particle diameter of 7 μm and a maximum particle diameter of 28 μm, and then molded into a block by a rubber press.
The carbonized material was calcined at 00 ° C., transferred to a graphitization furnace, and graphitized at a temperature of 3000 ° C. The properties of the isotropic graphite material thus produced and the occurrence of cracks in the material were measured, and the results are shown in Table 1 in comparison with the toluene-soluble component and the β-resin component after the heat treatment.

Example 2 98 parts by weight of a pitch was mixed with 100 parts by weight of pitch coke powder having an average particle size of 4 μm and a maximum particle size of 14 μm, and the mixture was charged into a Z-type kneading machine and sufficiently kneaded while heating to 200 ° C. Processed. After cooling, the mixture was roughly pulverized to a maximum particle size of 5 mm or less, and then subjected to a heat treatment under the same conditions as in Example 1 to adjust volatile components. Using a jet mill, the average particle size is 8.7 μm and the maximum particle size is
It was pulverized to a size of 33 μm, formed into a block by a rubber press, calcined and carbonized under the same conditions as in Example 1 to produce an isotropic graphite material. Various properties of the obtained isotropic graphite material were measured, and the results are shown in Table 1 together with the toluene-soluble content and the β-resin content after the heat treatment.

Example 3 Pitch coke powder having an average particle size of 2.5 μm and a maximum particle size of 10 μm
100 parts by weight and 110 parts by weight of the pitch were mixed, charged into a Z-type kneading machine, and sufficiently kneaded while heating to 200 ° C. After cooling, the mixture was coarsely pulverized to a maximum particle size of 5 mm or less, and then subjected to a heat treatment at a temperature of 400 ° C. for 30 minutes in a nitrogen atmosphere to adjust volatile components. Subsequently, pulverization, molding, firing and graphitization were performed under the same conditions as in Example 1 to produce an isotropic graphite material. Various characteristics of the obtained graphite material were measured, and the results are shown in Table 2 in comparison with toluene-soluble components and β-resin components after heat treatment.

Comparative Example 1 An isotropic graphite material was produced under the same conditions as in Example 1 except that the heat treatment was carried out in an air atmosphere at a temperature of 400 ° C. for 30 minutes. The various properties of the obtained graphite material were measured, and the results were converted to the toluene soluble matter and β after heat treatment.
The results are shown in Table 1 in comparison with the resin content.

Comparative Example 2 An isotropic graphite material was manufactured under the same conditions as in Example 1 except that the heat treatment was performed in a nitrogen atmosphere at a temperature of 300 ° C. for 30 minutes. The various properties of the obtained graphite material were measured, and the results were converted to the toluene soluble matter and β after heat treatment.
The results are shown in Table 1 in comparison with the resin content.

[0022]

[Table 1]

From the results shown in Table 1, it can be seen that the isotropic graphite materials of the examples in which the amounts of the toluene-soluble component and the β-resin content after the heat treatment satisfy the requirements of the present invention have high density and excellent strength. ,
No cracking of the material is observed. On the other hand, Comparative Example 1 in which both the toluene-soluble component and the β-resin component do not satisfy the requirements of the present invention, and Comparative Example 2 in which the toluene-soluble component does not satisfy the requirements of the present invention.
The isotropic graphite material according to the present invention has a density,
The strength was low, and cracking of the material was observed.

[0024]

As described above, according to the present invention, high density,
An isotropic graphite material having a high strength and a normal material structure can be stably and efficiently manufactured. Therefore, it is useful as an industrial production technology for graphite materials for use as electrodes for electric discharge machining, high-strength jig materials, crucibles for aluminum deposition, and the like.

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Claims (1)

(57) [Claims] 1. A mixture of 100 to 100 parts by weight of a non-graphitic carbonaceous aggregate having a maximum particle size of 10 μm or less, 70 to 110 parts by weight of a pitch binder, kneading, and coarsely pulverizing the kneaded material. Heat treatment in the temperature range of 250 to 450 ° C makes toluene soluble component and β-resin component 5 to 15 wt% each.
The method for producing an isotropic high-density graphite material characterized in that volatile matter is adjusted so as to fall within the range described above, the material is ground again, molded into a predetermined shape by a rubber press, and then calcined and graphitized.