JPH04228411A - Composition for specific carbon material - Google Patents

Abstract

PURPOSE:To provide a composition for producing a specific carbon material having high density, high strength and high purity. CONSTITUTION:A coal tar pitch is added to a composition consisting mainly of a raw pitch coke having an average particle diameter of <=15mum and a calcined pitch coke having an average particle diameter of <=44mum to provide a composition for specific carbon materials. The composition is heated, kneaded, pulverized, molded and calcined by conventional methods and, if necessary, graphitized to provide a specific carbon material having high density, high strength, high purity and high oxidation resistance.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a composition for special carbon materials for obtaining special carbon materials with high density, high strength, high purity, and high oxidation resistance. This relates to a composition whose main composition is a mixture with coke and to which coal tar pitch is added. After this composition is heated and kneaded, it is pulverized, molded, and fired by conventional methods, and if necessary, It is graphitized to obtain a special carbon material.

The carbon material obtained from the composition of the present invention can be used for mechanical purposes such as mechanical seals and packing materials, for electrical purposes such as electrodes for electrical discharge machining, for heat-resistant purposes such as molds, crucibles, and heaters, for chemical purposes, for semiconductor purposes, Alternatively, it can be used in a wide range of fields such as nuclear power.

0003

BACKGROUND OF THE INVENTION Conventionally, calcined petroleum coke, calcined pitch coke, and their mixtures with carbon black have been used as carbon material aggregates. However, carbon materials mainly composed of calcined petroleum coke and calcined pitch coke are expensive because their bulk specific gravity and strength are improved by repeatedly performing pitch impregnation and carbonization firing. In addition, since the pitch-impregnated portion is difficult to graphitize, it is necessary to increase the graphitization temperature, resulting in poor machinability.

In order to eliminate such drawbacks of the conventional method, the present inventors previously filed Japanese Patent Application No. 51-52910 (Japanese Unexamined Patent Publication No. 52-529)
-133098), a patent application has been filed with the gist of the invention as follows. That is, the method proposed by the present inventors in the patent application is to add a binder to a mixture mainly consisting of raw petroleum coke with an average particle size of 15 microns or less and calcined pitch coke with an average particle size of 44 microns or less. This is a method for producing a special carbon material, which involves adding and kneading the carbon material, pulverizing it by a conventional method, pressing it, firing it, and graphitizing it if necessary.

[0005] This already proposed method requires that carbon or graphite products using raw petroleum coke as the main raw material have large shrinkage properties during calcination, and that calcined coke has stability during calcination. It was developed with a focus on raw petroleum coke and calcined coke as the aggregate, and coal tar pitch, petroleum pitch, phenolic resin, furan resin,
By adding a synthetic resin binder such as polyethylene resin, kneading it, crushing it, molding it, firing it, and graphitizing it if necessary, it has high density, high strength, and excellent machinability. This is to obtain a special carbon material.

[0006]

[Problems to be Solved by the Invention] However, since raw petroleum coke, which is the main raw material in the already proposed method, is produced by high-temperature pyrolysis of heavy petroleum oil, this kind of The content of aromatic carbon compounds necessary as constituents of the special carbon material is small, and the content of aliphatic carbon compounds, which are not preferred as constituents, is relatively high. Therefore, when raw petroleum coke is used to produce special carbon materials, the compatibility at the interface between raw petroleum coke and coal tar pitch is poor during kneading or calcination, making molding difficult and causing problems during calcination. It was found that higher density and strength could not be obtained unless the amount of coal tar pitch, which tends to cause cracks, was increased.

It has also been found that since heavy petroleum oil is used as a starting material, the content of ash such as sulfur, titanium, vanadium, etc. is relatively high, resulting in the following drawbacks. In other words, the presence of compounds such as sulfur partially inhibits the formation of a uniform graphite structure, and the use of this type of special carbon material has recently attracted attention and its demand is increasing for semiconductor manufacturing. In crucibles and jigs, it is necessary to avoid as much as possible the inclusion of impurities such as ash, and since they contain vanadium, which is one of the causes of reduced oxidation resistance,
It was necessary to perform more purification treatment than necessary.

[0008] Therefore, the present inventors came up with the idea of using raw pitch coke and calcined pitch coke as raw materials of this kind that do not have these drawbacks in place of the above-mentioned raw petroleum coke, and as a result of experiments, it was found that fine particulate A special carbon material was discovered from a composition in which coal tar pitch was added to a blend of raw pitch coke and calcined pitch coke.

An object of the present invention is to provide a new composition for special carbon materials that can eliminate all the drawbacks of conventional methods.

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a blend mainly consisting of raw pitch coke with an average particle size of 15 microns or less and calcined pitch coke with an average particle size of 44 microns or less. The purpose of the present invention is to provide a composition for a special carbon material, which is made by adding coal tar pitch to a carbon material.

A feature of the present invention is that by using raw pitch coke and calcined pitch coke as the main raw materials for the special carbon material, the fine particles of both raw materials are compatible with coal tar pitch. By improving properties such as graphite structure formation and uniformity within the material, we have achieved high oxidation resistance and high strength that could not be obtained with the raw petroleum coke and calcined coke combination raw materials used in the previously proposed method. Moreover, we succeeded in obtaining a special carbon material with high density and high purity.

0012

[Operation] The raw pitch coke used in the present invention is produced by heating coal tar recovered by high-temperature carbonization of coal to a coking temperature in a delayed coker.

[0013] In high-temperature carbonization of coal, most of the ash remains in the coal coke, and the recovered coal tar contains almost no ash. Therefore, the coal tar pitch binder prepared from this coal tar has a low ash content and is rich in aromatic carbon compounds which are preferable as substances forming a graphite structure.

[0014] Also, raw pitch coke obtained from coal tar is calcined by calciner to produce calcined pitch coke. Therefore, coal tar pitch, raw pitch coke, and calcined pitch coke all exhibit very similar structures. During the heating and mixing process of adding and mixing coal tar pitch to raw pitch coke and calcined pitch coke, the compatibility at the interface between the fine particles of both cokes and the binder pitch is much better than in the case of raw petroleum coke. In other words, aromatic carbon compounds etc. in the raw pitch coke are distilled out during kneading or calcination, that is, compatibility occurs, and the bonds at the interface of each particle become stronger, making the coal tar pitch more uniform and having more side effects. It is considered that a carbon material with high density and high strength can be obtained even if the amount of addition is reduced.

[0015] The above compatibility will be considered in more detail below. In other words, the value of β-resin, an aromatic carbon compound contained in binders such as coal tar pitch, has traditionally been used as a guideline to measure the degree of bonding between carbon filler and binder. The various physical properties of the final carbon material were roughly predicted based on the content of β-resin in the binder. However, this did not go beyond the range of binders such as coal tar pitch.

[0016] β-resin is a complex and diverse organic compound contained in pitches, and its exact chemical structure has not yet been identified. However, qualitatively speaking, the so-called benzene-insoluble matter (B
I) percent of not extracted by quinoline;
It is quantified by the difference in percentage of so-called quinoline insoluble content (QI).

[0017] Conventional carbon materials have been made to have high density and high strength by pursuing only the effects such as high carbon yield using an aromatic carbon compound as a binder such as coal tar pitch. Therefore, as a filler, the temperature is about 1300℃.
Even if only calcined pitch coke treated at ~1400°C is used, aromatic carbon compounds are already decomposed during coking, and no effect can be expected.

However, when raw pitch coke treated at about 300°C to 500°C is used as a filler, the aromatic carbon compound (β resin) contained in the coal tar pitch as a binder and the raw pitch coke as a filler are mixed. The aromatic carbon compound (β resin) contained is about 2
During the kneading process at 00°C to 300°C, or about 10°C
During the firing process of heating to around 00° C., the aromatic carbon compounds undergo a polycondensation reaction with each other at the filler-binder interface and become integrated, forming giant aromatic molecules and carbonizing. This series of processes is the meaning of compatibility. By doing this, it is possible to create a precursor state in which a graphite structure having a layered structure of hexagonal network connections is easily formed in the final treatment.

As a result, compared to the conventional calcined coke binder-based carbon material or raw petroleum coke binder-based carbon material with relatively high aliphatic carbon compounds, the interfacial bond between the filler and the binder portion is strong, high density, A high-strength carbon material can be obtained. These effects are accelerated by the large shrinkage phenomenon caused by the dissipation of volatile matter during firing of raw pitch coke, and the high density of raw pitch coke - calcined pitch coke - coal tar pitch carbon material. , to further ensure high strength.

Furthermore, according to the present invention, since both the raw pitch coke and the calcined pitch coke contain little ash such as sulfur, it is easy to form a graphite structure with few defects. Furthermore, when a special carbon material is produced using raw pitch coke and calcined pitch coke with extremely low ash content as main raw materials as in the present invention, a material with high purity and high oxidation resistance can be obtained. As described above, according to the present invention, a special carbon material having high density, high strength, high purity, and high oxidation resistance with very few defects can be obtained.

[0021] The reason why the average particle size of the raw pitch coke is set to 15 microns or less in the present invention is that when the average particle size of the raw pitch coke exceeds 15 microns, the particles themselves shrink, resulting in high density and high strength. This is because carbon materials or graphite materials cannot be obtained. On the other hand, the reason why the average particle size of calcined pitch coke is set to 44 microns or less is that if the particle size is larger than this, uniform contraction of the structure will be inhibited, making it impossible to obtain high density and high strength. .

[0022]

[Examples] Examples of the present invention will be described below. Example 1 A composition in which 52 parts by weight of coal tar pitch was added to a blend of 80 parts by weight of raw pitch coke with an average particle size of 5 microns and 20 parts by weight of calcined pitch coke with an average particle size of 44 microns was prepared in a kneader at 220°C. The mixture was heated and kneaded for 1 hour. This kneaded material was pulverized, molded, fired, and graphitized by a conventional method. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Example 2 A composition was prepared by adding 49 parts by weight of coal tar pitch to a blend of 80 parts by weight of raw pitch coke with an average particle size of 10 microns and 20 parts by weight of calcined pitch coke with an average particle size of 43 microns. . A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Example 3 A composition was prepared by adding 47 parts by weight of coal tar pitch to a blend of 20 parts by weight of raw pitch coke with an average particle size of 5 microns and 80 parts by weight of calcined pitch coke with an average particle size of 44 microns. . A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Comparative Example 1 A composition was prepared by adding 58 parts by weight of coal tar pitch to a blend of 80 parts by weight of raw petroleum coke having an average particle size of 5 microns and 20 parts by weight of petroleum coke having an average particle size of 44 microns. A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Comparative Example 2 A composition was prepared by adding 52 parts by weight of coal tar pitch to a blend of 80 parts by weight of raw petroleum coke having an average particle size of 5 microns and 20 parts by weight of petroleum coke having an average particle size of 44 microns. A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Comparative Example 3 A composition was prepared by adding 49 parts by weight of coal tar pitch to a blend of 80 parts by weight of raw petroleum coke having an average particle diameter of 10 microns and 20 parts by weight of petroleum coke having an average particle diameter of 43 microns. A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

Comparative Example 4 A composition was prepared by adding 47 parts by weight of coal tar pitch to a blend of 20 parts by weight of raw petroleum coke having an average particle size of 5 microns and 80 parts by weight of petroleum coke having an average particle size of 44 microns. A product was obtained in the same manner as in Example 1. The physical properties and characteristic values of the product thus obtained are shown in the table below.

[0029]

[Table 1]

[0030]

Effects of the Invention As is clear from the above results, the special carbon material obtained from the composition of the present invention has a combination of aromatic carbon compounds specific to raw pitch coke and aromatic carbon compounds of coal tar pitch. It is thought that the polycondensation reaction at the filler-binder interface dramatically improved the bonding strength between the fillers, and at the same time, the apparent specific gravity (
density) becomes large, and the transverse rupture strength reaches 1t/cm2 or more,
We were able to achieve the industry's long-standing goal of obtaining a special carbon material with optimal values for each application.

[0031] Furthermore, the content of impurities such as vanadium (ash), which is a general feature of pitch coke, is low, and when the special carbon material of the present invention is used in a high-temperature oxidizing atmosphere, oxidative consumption can be suppressed. It is possible to minimize the deterioration of the characteristics of high density and high strength.

Claims (1)

[Claims] 1. A composition for a special carbon material, which is obtained by adding coal tar pitch to a mixture mainly consisting of raw pitch coke with an average particle size of 15 microns or less and calcined pitch coke with an average particle size of 44 microns or less.