JPH05279005A - Production of high-density carbon material - Google Patents

Abstract

PURPOSE:To relatively easily produce a high-density carbon material low in porosity. CONSTITUTION:A powder obtained by compacting and then crushing a carbonaceous material contg. mesophase powder is recompacted and fired. Alternatively, the powder obtained by compacting and then crushing a carbonaceous material is further mixed with a powder contg. mesophase powder to form a raw powder for the carbon material, which is recompacted and fired. Meanwhile, the pressure to compact a carbonaceous material contg. mesophase powder can be made lower than the recompacting pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high density carbon material.

[0002]

2. Description of the Related Art Carbon materials are good conductors of electricity and heat,
In a non-oxidizing atmosphere, it is stable up to ultrahigh temperatures, and has excellent properties such as high hot strength, resistance to acid and alkali, and easy machining. Among them, high-density carbon materials are particularly excellent in mechanical, electrical, and chemical properties, and are used in various fields such as graphite crucibles for semiconductor manufacturing, heaters, mechanical seal materials, sliding current collectors, electrical discharge machining electrodes, and metal melting crucibles. Used in.

The smaller the porosity of the carbon material, the more the chemical reaction from the surface of the carbon material can be suppressed, so that the oxidation resistance and the chemical resistance are remarkably improved. For this reason, with the recent development of industry, the demand level for the quality of carbon materials has become stricter, and the need for higher density carbon materials has increased.

Conventionally, in such a high-density carbon material, aggregate coke and the like are finely pulverized, coal tar pitch, a binder such as a resin are added thereto, and the mixture is hot kneaded and then pulverized again.
It was manufactured as a carbon material with a bulk density of about 1.8 by repeating molding, firing, impregnation with tar, pitch, etc., and re-firing, and the process was extremely complicated and laborious. In addition, the aggregate coke itself is porous,
Coal tar pitch used in the binder, a large amount of volatile components such as resin, to generate a large amount of pores during firing,
Although the generated pores are densified by impregnating tar and pitch, etc. and filling by re-baking, the densification is difficult because tar and pitch themselves also generate a large number of pores during baking. Further, even if the densification is attempted by repeating the above-mentioned impregnation and re-firing, the efficiency thereof tends to be decreased sequentially with each repetition.

In order to solve such a defect, the raw material powder itself has recently been self-sintering, that is, by using a carbon material raw material having both properties of an aggregate and a binder, generation of pores is prevented and high Attempts have been made to produce strong, high density graphite materials.

[0006] For example, in Japanese Examined Patent Publication No. 1-58125, a carbonaceous raw material having a specific carbon material content, volatile content, and linear shrinkage of a compact is crushed to a relatively coarse grain size, and then molded and fired. Discloses a method for producing a high-density and high-strength carbon material.

[0007]

However, if a carbon material having self-sinterability as disclosed in the above publication is used, a high-density carbon material can be obtained, but the raw material can be fired once. Since the densification is attempted to be achieved, the reaction gas cannot be fully exhausted, and fine pores are generated, so that the densification is limited.

An object of the present invention is to provide a method for solving such a conventional problem and relatively easily producing a carbon material having a higher density and a smaller porosity than the conventional one.

[0009]

Means for Solving the Problems The above problems can be solved by molding a carbonaceous raw material containing a mesophase powder, crushing the powder, and then firing the powder.

It is also possible to re-form the carbonaceous material raw material powder obtained by molding and pulverizing the carbonaceous raw material containing the mesophase powder with the powder containing the mesophase powder, and then firing it. In these cases, the molding pressure when molding the carbonaceous raw material containing the mesophase powder can be made smaller than the remolding pressure.

[0011]

The present inventor has found that when the carbon material raw material powder containing the powder obtained by molding and pulverizing the carbonaceous material containing the mesophase powder is reshaped and then fired, the density of the carbon material after firing increases. did. Further, in this case, it was also discovered that the pore distribution of the carbon material produced by the present invention is different from the pore distribution of the carbon material obtained by directly molding the carbonaceous raw material containing the mesophase powder.

FIG. 1 shows an example of pore distribution measured by a mercury porosimetry using a mercury porosimeter. In this figure, the horizontal axis shows the pore diameter, and the vertical axis shows the value obtained by integrating the volume of the pores having the pore diameter shown on the horizontal axis or more. From FIG. 1, in the carbon material manufactured by the method of the present invention, the integrated value of the pore volume decreases smoothly as the pores become larger. On the other hand, the integrated value of the pore volume of the carbon material obtained by directly molding the carbonaceous raw material containing the mesophase powder, which is shown as a comparative example, sharply decreases near a certain pore diameter.

This means that the carbon material produced by the production method of the present invention shows a smooth distribution from small pores to relatively large pores, and the comparative example shows a distribution concentrated in relatively small pore diameters. There is.

In the case where the relatively small pore diameter has a concentrated distribution as described above, the gas generated during firing has a large resistance when passing through such pores. For this reason, not only swelling and cracking are likely to occur, but also the increase in density is hindered because the gas does not escape sufficiently.

On the other hand, since the carbon material produced by the method of the present invention has a gentle distribution from small pores to relatively large pores, the gas generated during firing gradually escapes from the small pores to the large pores. Therefore, the resistance is small, gas escape is promoted, the porosity is reduced, and the density is increased.

Although it is not clear why the carbon material produced by the method of the present invention has a smooth distribution from small pores to relatively large pores, a carbonaceous material containing powder obtained by molding and grinding a carbonaceous raw material containing mesophase powder. It is considered that this is related to the fact that small continuous pores remain at the bonding interface of the carbon material raw material powder when the raw material powder is reshaped.

The average pore diameter means the value obtained from the pore distribution measured by the mercury porosimetry using a mercury porosimeter. The porosity is the volume ratio of the pores in the carbon material, and means the value obtained from the pore volume measured by the mercury porosimetry using a mercury porosimeter.

The mesophase powder is a pulverized product of a self-sintering carbonaceous raw material obtained by heat-treating a heavy oil of coal or petroleum type at about 400 to 500 ° C. The mesophase has microspheres exhibiting optical anisotropy, which are formed by layering condensed polycyclic organic aromatic compounds produced during softening and melting during solidification, or their combined phases, and have a volatile content of 7 to 20%. Is included.

In the manufacturing method using the mesophase powder, complicated steps such as impregnation of a graphite material having a small average pore diameter and repeated firing steps can be omitted.

In the present invention, it is possible to form a carbonaceous raw material containing mesophase powder, and to mix the pulverized powder with carbonaceous powder such as coke powder, graphite powder, pitch and mesophase powder to prepare a carbonaceous material raw material. However, from the viewpoint of binding particles and preventing swelling due to the generation of gas during firing, it is possible to blend mesophase powder having an appropriate volatile content and having the property of binding the particles as a binder during firing. desirable.

It is preferable that the carbonaceous raw material contains 20% or more, more preferably 50% or more of mesophase powder. If the content is less than that, the binding force of the molded body becomes weak, and it is difficult to control the particle size during pulverization. It is also possible to use only mesophase powder as a carbonaceous raw material.

It is preferable that the carbonaceous raw material containing the mesophase powder crushed after molding contains 40% or more at the time of remolding. If the blending amount is smaller than this, outgassing is less likely to be promoted, and it is difficult to obtain the pore distribution for making the fired body high density.

The crushed powder has an average particle size of 20 μm.
When a powder containing the following mesophase powder is blended, if it is blended so as to contain 20% or more, it is suitable for strengthening the binding force of the particles of the molded body and preventing swelling during firing.

The crushed particles after molding the carbonaceous raw material containing the mesophase powder have an average particle size of 20 μm or more and 100 μm or less,
The average particle size of the powder containing mesophase powder blended with this is
It is desirable that the thickness be 20 μm or less. This is to obtain an ideal pore distribution for promoting the escape of gas and increasing the density of the fired body. The average particle size of the crushed particles is 100 μm
If it exceeds, large pores are formed between particles during re-molding, and the size does not become small even by shrinkage due to firing, which is not preferable.

The molding pressure when molding the carbonaceous raw material containing the mesophase powder is preferably smaller than the remolding pressure.
This is because the carbonaceous material containing the mesophase powder is molded, and the crushed particles also shrink during remolding, improving the adhesion between the crushed particles or between the crushed particles and the mesophase powder blended before remolding. This is because the density of the fired body is also improved.

The molding pressure can be appropriately selected depending on the relationship with the target product, but the first molding pressure is 0.3 to 1.5 ton / cm ³
Is preferable, and the re-molding pressure is preferably higher than the first molding pressure, preferably 1.5 times or more.

The carbonaceous raw material containing the mesophase powder may be molded and pulverized by any of a hammer mill, a vibrating ball mill, a rotary mill, a jet mill and the like, without any particular limitation.

As for the firing temperature, the carbonization treatment at about 1000 ° C. increases the density, but the graphitization treatment at 2000 to 3000 ° C. makes the density higher, which is preferable.

As the carbonaceous raw material used in the present invention, in addition to mesophase powder, coke powder obtained by carbonizing pitch, coal, etc. at about 1000 ° C., carbon material powder obtained by carbonizing resin, carbon fiber chop, carbon Powdered carbon such as black, artificial or natural graphite powder, or graphite powder can be used.

[0030]

EXAMPLES Next, the effects of the present invention will be clarified by examples. The mesophase having a volatile content of 18.2% obtained by heat-treating coal tar at 430 ° C. at a vacuum degree of 50 Torr for about 3 hours was finely pulverized with a hammer mill to prepare mesophase powder having an average particle size of 15 μm. Next, 30 vol% artificial graphite powder with an average particle size of 16 μm was mixed with 70 vol% of this mesophase powder, filled in a rubber rubber with an inner diameter of 100 mm and a height of 100 mm, and subjected to isostatic pressing at a predetermined pressure. It was After coarsely crushing this molded body, average diameter 58 μm with a hammer mill
Crushed into In Examples 1 and 2, only the pulverized powder was filled in the rubber rubber, and hydrostatic molding was performed at a predetermined pressure. The molded body contains 30 vol% artificial graphite. Further, in Examples 3 to 5, 25 vol% of the mesophase powder was mixed with 75 vol% of the pulverized powder, the rubber rubber was filled, and the isostatic molding was performed at a predetermined pressure.

It should be noted that about 19% of the artificial graphite powder was blended in the molded body.

The obtained molded body is placed in an electric furnace in a nitrogen atmosphere and carbonized by heating to 1000 ° C., and then the obtained carbon material is heated to 2500 ° C. in a graphitizing furnace in an Ar atmosphere for graphitization. went. Table 1 shows the bulk density and porosity of the obtained graphite material.

[0033]

[Table 1]

(Comparative Example) In Table 1, as a comparative example, a raw rubber powder containing the above mesophase powder and the same artificial graphite powder in an amount of 30 vol% or 19 vol% was filled in a rubber rubber,
The bulk density and porosity of the graphite material which was subjected to isostatic pressing at a molding pressure of 1500 kg / cm ³ and similarly carbonized and graphitized are shown.

As is clear from Table 1, the graphite material manufactured by the manufacturing method of the present invention has a lower porosity and a higher density than the graphite material manufactured by the conventional manufacturing method shown in the comparative example. Is becoming

[0036]

As described above, according to the present invention, the carbonaceous raw material powder containing the mesophase powder is molded and pulverized, and the powder for the carbonaceous material raw material is reshaped and fired, so that the density is higher than ever before. A carbon material having a low porosity can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a pore distribution of a carbon material obtained by a method of the present invention in comparison with a conventional method.

Claims (3)

[Claims] 1. A method for producing a high-density carbon material, which comprises molding a carbonaceous raw material containing mesophase powder, pulverizing the powder, re-molding the powder, and then firing the powder. 2. A high-density carbon material raw material powder comprising a carbonaceous raw material containing mesophase powder, which is formed and crushed, and a powder containing carbon powder containing mesophase powder. Carbon material manufacturing method. 3. The molding pressure for molding a carbonaceous raw material containing mesophase powder is smaller than the remolding pressure.
A method for producing the high-density carbon material described.