JP2630602B2 - Manufacturing method of high density carbon material - Google Patents

Description

The present invention relates to a method for producing a high-density carbon material.

[Conventional technology]

Carbon materials, one of non-oxide ceramics, are used in many fields such as sliding materials for mechanical seals and electrical contacts, crucibles, chemical reaction vessels, and moderators for nuclear reactors.

Carbon materials are produced by various methods depending on the application.However, most commonly, carbonaceous binders such as tar and pitch are added to fine powder of coke, carbon black, graphite, etc. About 1000 in non-oxidizing gas such as
A method of firing at ~ 1500C to carbonize the binder is employed. In addition, the product by this manufacturing method is about 2500 ~
When heated to 3000 ° C, it becomes entirely graphite. Carbon materials made by such general manufacturing methods, especially non-graphitic materials with low firing temperatures, have fine pores, allow gas to permeate freely, and also absorb liquids such as water and oil well. .

Although the properties of the porous carbon material as described above can be advantageously used in some cases, it is often a disadvantage. For example, in the case of a sealed end face material used in liquids such as mechanical seals, the liquid to be sealed may enter the pores and cause leakage if severe, and even in the case of slight penetration, corrosion or swelling may occur depending on the type of liquid. . In the case of being porous, it is difficult to use it for precision mechanical parts because the density tends to vary even within the same block, and the deformation tends to occur due to uneven thermal expansion.

Conventionally, the method of eliminating the fine pores of the porous carbon material and making it difficult for gas and liquid to pass therethrough is conventionally carried out by impregnating a carbonizable organic material such as a thermosetting synthetic resin and then re-baking to carbonize the organic material. There was a way. However, in this method, the carbide generated from the impregnated organic substance also has fine pores, and in addition, in the case of a large material, it is difficult to impregnate the organic substance up to the core.
There was a limit to the treatment effect.

Therefore, especially when a high-density product having a high gas / liquid blocking performance is required, a method of impregnating with a metal or repeating resin impregnation and firing many times has been used.

As for ceramics other than carbon materials, there is known a method of processing and sintering by hot isostatic pressing in the final step of production to increase the density (Japanese Patent Laid-Open No. 57-18 / 1982).
8468, JP-A-59-41954, etc.). However, since porous materials cannot be directly pressed and compressed, most of them use a closed metal container or a vitreous coating equivalent to it and compress the ceramic material indirectly through them. The direct pressurization of the body is extremely dense (theoretical density) without hot isostatic pressing.
This process is only performed on silicon nitride sintered bodies from which compacts (over 90%) can be obtained.

[Problems to be solved by the invention]

Accordingly, an object of the present invention is to provide a method for modifying a porous carbon material into a high-density product by a method more effective than the above-described conventional method, thereby providing a method for producing a high-density carbon material more easily than before. Things.

[Means for solving the problem]

The present invention, which succeeded in achieving the above object, comprises two inventions. First, a carbonaceous molded body having fine pores therein is produced by an arbitrary production method, and then the molded body is heated to a high temperature. And a pressure treatment by a hot isostatic pressing method in a high-pressure non-oxidizing gas.

Further, the second aspect of the present invention is to produce a carbonaceous molded article having fine pores therein by an optional production method, then impregnating the molded article with a carbonizable organic substance, and calcining the impregnated carbon dioxide in a non-oxidizing gas. This is a method for producing a high-density carbon material, which comprises carbonizing the carbonized organic material, and then subjecting the carbonized organic material to a high-temperature and high-pressure non-oxidizing gas treatment by a hot isostatic pressing method. .

Hereinafter, the production method of the present invention will be described in more detail.

In the production method of the present invention, first, micropores are formed by the above-described ordinary method or any other production method (that is, micropores which cannot be completely eliminated in the sintering step remain).
Manufacture carbon materials. That is, a mixture of carbonaceous fine powder such as coke, carbon black, and graphite and a carbonizable binder is formed, and further mixed with a non-oxidizing gas such as nitrogen for about 1000.
Baking at ~ 1500C to carbonize the binder. In this step, it is not necessary to particularly aim at densification, and the fired compact has an apparent specific gravity in which fine pores are distributed throughout.
Even a low density of 1.7 to 1.8 is acceptable. In the production method of the first invention, this is subjected to a pressing treatment by a hot isostatic pressing method as it is. In the method of the second invention,
Prior to the pressure treatment, a carbonizing organic substance impregnation treatment and firing are performed. As the carbonizable organic material, a phenol resin, a furan resin, a thermoplastic synthetic resin such as an epoxy resin, tar, pitch, and the like can be used. The impregnation treatment is performed by, for example, deaeration in a vacuum using a vacuum impregnation apparatus and then immersion in an impregnation liquid. As described above, when the object to be treated is large, impregnation up to the core is extremely difficult. However, in the impregnation in the production method of the present invention, pores may remain in the core.
The impregnated molded body is fired at 800 ° C. or higher in a non-oxidizing atmosphere to carbonize the carbonizable organic matter.

Regardless of the presence or absence of the preliminary treatment of impregnating and firing the carbonizable organic material, the hot isostatic pressing treatment in the production method of the present invention is performed by a direct pressing method without using a mold or a gas impermeable coating. The processing temperature is suitably about 1000-1500 ° C. It has been confirmed that the pressure is effective from about 500 kg / cm ^2, but a remarkable treatment effect is achieved at a high pressure of about 1000 kg / cm ² or more. As a method of heating and pressurizing, a method of performing heating first and increasing the pressure with a slight delay, a reverse method, or a method of simultaneously performing heating and pressurizing can be arbitrarily adopted.

Even those that have been impregnated and fired with carbonizable organic matter,
The carbon material has a large number of fine interconnected pores. Therefore, it is generally considered that the compact is not compressed even when the high-pressure gas is directly applied to the pores. However, as a phenomenon peculiar to the carbon material, regardless of the presence or absence of the carbonizing organic material impregnated calcination treatment (that is, even with an apparent specific gravity of about 1.7 to 1.8 leaving a large number of pores), the reason is not obvious. When subjected to the hot isostatic pressing method, a significant decrease in porosity is exhibited, and the density increases. Producing such a surprising result has never been known before.

〔The invention's effect〕

The high-density carbon material obtained by the production method of the present invention in which the above-described hot isostatic pressing is performed has a dense structure in which the surface layer and the core have almost no pores. When a large material is processed, the core part has a small amount of pores, but since it is extremely fine independent pores, even if focusing only on the core part, it is very different from the material before processing .

A particular advantage of the production method of the present invention is that there is no need to be aware of densification in the selection of carbonaceous raw materials and the first firing after raw material molding, and therefore, there is no need for expensive special raw materials, and strength Sintering conditions at a relatively low temperature (that is, about 1200 to 1300 ° C.) that can obtain a molded article having excellent heat resistance.

Further, the hot isostatic pressing is also a direct gas pressurization without using a closed metal container or a vitreous coating, so that it is possible to easily process a molded article having a complicated shape and to reduce the processing cost.

Therefore, the present invention makes it possible to easily produce high-density carbon materials with high physical properties via ordinary low-density carbon materials, and to utilize the excellent properties of carbon materials in a wider field than before. It is extremely significant.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 Natural graphite (average particle size: 2μ) 20% by weight Needle coke (average particle size: 1μ) 30 〃 phenolic resin 10 〃 altered coal tar pitch 40 原料 The raw materials having the above composition were mixed by a ball mill, and further kneaded with a kneader. After cooling, it was pulverized to obtain a molding powder. This was molded by a conventional method and fired at 1200 ° C. The obtained molded body was cut to remove a so-called black scale portion on its surface, thereby producing a 300 mm x 220 mm x 50 mm annular test molded body.

This molded body was subjected to a furan resin impregnation treatment and fired at 800 ° C.

Next, the fired molded body is directly placed in a pressure vessel of a hot isostatic pressing apparatus, and pressurized with argon (maximum pressure of 10).
00kg f / cm ² ) and a heat treatment at 1350 ° C. for 1 hour.

Example 2 A test compact formed in the same manner as in Example 1 was subjected to a coal tar pitch impregnation treatment and a calcination treatment at 1200 ° C., and then subjected to hot isostatic pressing as in Example 1. Processing was performed.

COMPARATIVE EXAMPLE 1 A test compact produced in the same manner as in Example 1
A refiring treatment was performed at 50 ° C. for 1 hour.

Table 1 summarizes the dimensional shrinkage ratio and the characteristic values of the products in the final firing step for each of the above examples. Among the characteristic values, the water absorption is determined by measuring the product so that the cross section passes through the center.
cut into mm thickness be those measured then 20 mm × make a test piece of 10 8 mm × 5 mm, when the pressure 2 hours pressurized test pieces were placed in water at the nitrogen of the closed vessel 5 kg / cm ² This is a value obtained from weight increase.

Table 1 Comparative Example 1 Example 1 Example 2 Shrinkage (%) 0.5 1.2 1.1 Apparent specific gravity 1.79 1.88 1.89 Shore hardness 89 93 93 Water absorption 3.4 0.54 0.81 Further, the products of Examples 1 and Comparative Example 1 About the cut surface, the pore distribution state was examined using a coloring test solution. The result is shown in the drawing (the pore existing portion is colored).

Example 3 A carbon material of 60% by weight of artificial graphite and 40% by weight of altered coal tar pitch was mixed by a ball mill, kneaded with a kneader, cooled and pulverized to obtain a molding powder. This was molded at normal temperature under a pressure of 1.5 ton / cm ² and fired at 1200 ° C. The obtained molded body is cut and processed to 300φ × 220φ × 50
An annular test molded body of mm was prepared.

Next, this is directly put into a pressure vessel of a hot isostatic pressurizing apparatus, and pressurized with argon (maximum pressure 1000 kg f / cm ² )
And 1350 ° C. for 1 hour.

COMPARATIVE EXAMPLE 2 A test molded body made in the same manner as in Example 3
A refiring treatment was performed at 50 ° C. for 1 hour.

Table 2 summarizes the dimensional reduction ratios and the characteristic values of the products in the final firing step for Example 3 and Comparative Example 2.
Shown in

Table 2 Comparative Example 2 Example 3 Shrinkage (%) 0.0 0.9 Apparent specific gravity 1.70 1.75 Shore hardness 55 62 Water absorption (%) 15 12

[Brief description of the drawings]

The drawing is a photograph of a cut surface colored sample showing the amount of pores remaining in the core of the products according to Example 1 and Comparative Example 1. FIG. 1: Example 1 FIG. 2: Comparative Example 1

Claims (6)

(57) [Claims] 1. A hot isostatic pressing method in which a carbonaceous molded body having fine pores therein is produced by an arbitrary production method, and then the molded body is heated to a high temperature and placed in a high-pressure non-oxidizing gas. A method for producing a high-density carbon material, comprising: 2. A carbonaceous molded article having fine pores therein,
2. The production method according to claim 1, wherein the production is performed by firing at a firing temperature of 1500 ° C. or lower. 3. A pressure treatment by a hot isostatic pressing method at a temperature of 10
2. The method according to claim 1, wherein the method is carried out at a temperature of from 00 to 1500 [deg.] C. and an atmospheric pressure of 500 kg f / cm < ² > or more. 4. A carbonaceous molded article having fine pores therein is produced by an arbitrary production method, and then the molded article is impregnated with a carbonizable organic substance, and calcined in a non-oxidizing gas to obtain the carbonized article. A method for producing a high-density carbon material, comprising: carbonizing a volatile organic substance; thereafter, heating the mixture to a high temperature and subjecting it to a pressure treatment by a hot isostatic pressing method in a high-pressure non-oxidizing gas. 5. A carbonaceous molded article having fine pores therein,
2. The production method according to claim 1, wherein the production is performed by firing at a firing temperature of 1500 ° C. or lower. 6. A pressure treatment by a hot isostatic pressing method at a temperature of 10
2. The method according to claim 1, wherein the method is carried out at a temperature of from 00 to 1500 [deg.] C. and an atmospheric pressure of 500 kg f / cm < ² > or more.