JPS61122110A - Production of high-density carbon material - Google Patents

Abstract

PURPOSE:To improve the bulk density and strength of carbon, by heating a raw material of carbon at a specific temperature under atmospheric pressure, and forming the material by pressing at the temperature for a short time. CONSTITUTION:A raw material of carbon composed of carbonaceous powder is heated at 400-600 deg.C under atmospheric pressure, and pressed under a pressure of 50-400kg/cm<2> for a short time (about <=10min) while keeping the material at a temperature within the above range. If necessary, the obtained formed article is further baked and graphitized. The above raw material of carbon is preferably self-sinterable carbonaceous powder such as bulk mesophase, meso- carbon microbead, petroleum or coal-based coke, or their mixture. The carbona ceous powder is preferably the one having a volatile content of about 6-14wt%, a quinoline insoluble content of about >=70wt%, and particle diameter of about <=10mu.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for producing a carbon material, and more specifically,
This invention relates to a method for producing high-density carbon material using a hot press method.

[Background of the invention]

Conventionally, high-density carbon materials used for mechanical parts such as sliding members and mechanical seals, or carbon electrodes, etc., have been produced by converting carbonaceous raw materials such as petroleum coke and coal pitch coke into coal tar pitch and other materials. A commonly used method is to knead the material with a binder, pressure mold it, and then fire the resulting molded product to carbonize or graphitize it. However, recently,
As carbon parts become more precise and their usage conditions become more severe, there is an increasing demand for higher strength carbon materials. Since the strength of a carbon material mainly depends on its density, it is also required to increase the density of the carbon material.

In order to meet the demand for higher density carbon materials, conventionally, (a) carbonaceous powder with self-sintering properties, such as raw coke, was used as a raw material and pressure-molded without containing a binder. , further firing and carbonization method (Special Publication Act 1983)
-46968, etc.) (b) A method of obtaining a carbon material by the so-called hot press method in which a mold of a desired shape is filled with carbonaceous powder and heating and pressurization are performed simultaneously (Japanese Patent Publication No. 57
-25481, Japanese Patent Publication No. 54-30677, etc.) have been proposed.

The above method (a) is excellent in that it does not use a binder and can, in principle, produce a high-density, homogeneous carbon material with low porosity through a simplified process. However, according to research conducted by the present inventors, in actual manufacturing, if raw materials with a high volatile content are used, ceiling gas is generated during firing, making them more likely to swell and crack. There's a problem. On the other hand, when a material with a low volatile content is used as a raw material, there is a problem that the caking property is insufficient, and therefore it is extremely difficult to select an appropriate raw material.

In addition, in the hot press method mentioned above, instead of producing a strong molded body by carrier molding or isostatic pressing and then heating and firing, as in the conventional method, pressure molding and firing are performed. Since it is carried out in one step, the manufacturing process is further simplified, and it is also superior in that it is easier to obtain a carbon material with higher density than normal pressure firing. Depending on the quality of the raw carbon material used, it may not always be possible to obtain a good molded product due to gas generation and shrinkage that inevitably occur during the heating process, and in extreme cases, the resulting molded product may deteriorate. Cracks may occur or breakage may occur.It is recognized that such a tendency is stronger for carbon material raw materials that have a high self-sintering property.

The present inventors have conducted various studies in view of the above-mentioned problems of the conventional method, and have found that when a carbon material raw material is fired under atmospheric pressure, it first expands and then contracts in the initial stage of firing. It is recognized that the temperature at which this expansion changes to contraction varies slightly depending on the raw material, but it is approximately 400 to 600℃.
It was found that the temperature was in the range of 00°C. It was also found that in the process of pressure forming and firing in the entire range from room temperature to high temperature using a hot press, cracks occur due to the transition from expansion to contraction in this temperature range.

Therefore, when attempting to obtain a crack-free, high-density molded product using the hot press method, it is necessary to press while avoiding this temperature range.

The first possible method is to
This is a method of pre-firing under pressure with a hot press down to 0°C, and then firing at normal pressure at a temperature thereafter.The second method is to convert the expansion to contraction of the pre-formed product using molding, etc. This is a method in which preliminary firing is performed under atmospheric pressure up to the final temperature, that is, 600° C., and then pressure firing is performed in the high temperature region without hops.

However, with these methods, it is not possible to obtain high-density and high-strength carbon materials, which are the original characteristics of the hot pressing method.Especially, when carbonaceous powder with self-sintering ability is used as a raw material, the above-mentioned It was found that the method did not yield molded bodies of satisfactory quality.

The reason can be considered as follows. Originally, carbonaceous powder with self-sintering ability such as bulk mesophase contains components that act as a binder, so it is possible to mold it by pressurizing it even at room temperature. When heated to ~600°C, the binder component contained inside oozes out onto the surface of the particles, and moreover, the particles become slightly plastic.

Therefore, by applying pressure under heat, the raw material particles are deformed and packed more densely, and the binder component that oozes out onto the surface causes the particles to bond firmly to each other, resulting in a molded product with higher density and higher strength. It is thought that it is possible to obtain

However, in the first method described above, the bonding between grains is insufficient in the pot press up to 400°C, so the progress of sintering in the atmospheric pressure firing C is insufficient. A molded body cannot be obtained. On the other hand, in the second method, since the pressure is applied at a temperature of 600° C. or higher, at which the particles have lost their plasticity, there is a drawback that the densification effect is small and, on the contrary, brittle fracture occurs and strength is not improved.

[Summary of the invention]

The present invention has been made in view of the above-mentioned problems of the conventional method and the findings of the present inventors, and aims to provide a method for obtaining a high-density and high-strength carbon material.

In order to achieve the above object, the method for producing a high-density carbon material according to the present invention involves heating a carbon material raw material consisting essentially of carbonaceous powder to 400 to 600'C under atmospheric pressure, and then heating the heated carbon material to 400 to 600'C. 5 while maintaining the carbon material raw material at the above temperature.
It is characterized in that it is molded into a desired shape by pressurizing at a pressure of 0 to 400 kg/ci, and then the resulting molded product is fired and graphitized as required.

According to the method of the present invention, it is possible to produce a carbon material with even higher density and superior mechanical strength than those obtained by conventional methods.

The high-density carbon material obtained by the present invention can be widely used as mechanical carbon parts, carbon electrodes, and other shaped carbon material products.

[Detailed description of the invention]

The present invention will be explained in more detail below. In the following description, "%" representing the composition is based on weight unless otherwise specified.

As raw materials for the carbon material in the present invention, carbonaceous powders having self-sintering ability such as bulk mesophase, mesocarbon micro-layer, petroleum-based or coal-based raw coke, or mixtures of these carbonaceous powders are preferably used. It will be done. Moreover, in order to further improve the caking property, a binder such as coal tar pitch can be included in the carbon material raw material as necessary.

Bulk mesophase is more preferably used as a carbonaceous powder as a carbon material raw material, but this bulk mesophase is a petroleum-based material such as atmospheric residual oil of petroleum, vacuum residual oil, decant oil of catalytic cracking, and pyrolysis tar. 400% of hydrocarbon heavy oil such as heavy oil, coal tar, oil sand oil, etc.
Mesophase small spheres (mesocarbon microbeads) that are generated in heat-treated pitch when heat-treated to a temperature of ~500℃ are aggregated and separated from the matrix pitch, and are chemically and physically active. It is a rich substance.

Regarding the manufacturing method of such bulk mesophase,
It is disclosed in JP-A-57-200213 or JP-A-59-30887 filed by the present applicant, in which heavy oil is heated to a temperature of 400 to 500°C to carry out a polycondensation reaction to form a mesophase. Once the pitch containing small spheres is obtained, the pitch is 250-40
By cooling to 0'C and applying some turbulence, mesophase spherules are aggregated and coalesced, and 1q of bulk mesophase is obtained by separating them from the parent phase. Incidentally, an apparatus for producing such a bulk mesophase is disclosed in Japanese Patent Application Laid-Open No. 1983-30887, filed by the present applicant. As a carbonaceous powder, the volatile content contained in the raw material powder is 6 to 14%, preferably 8 to 12%, and the quinoline soluble content is 70% or more, preferably 90 to 9%.
It is desirable that it be 9%. Further, the particle size of the carbonaceous powder is preferably about 10 μm or smaller in order to improve density and strength. The pulverization method for obtaining such carbonaceous powder is not particularly limited, but it is better to use a grinding method such as a dynamic ball mill than with a three-stroke type pulverizer such as a jet mill. More preferred.

Next, the carbon material raw material as described above is heated and pressure-molded by a hot press method. In the method of the present invention, the above-mentioned carbon material raw material is filled into a desired hot press mold, first heated under atmospheric pressure (under no pressure > r400 to 600°C, preferably 450 to 550°C, Next, while maintaining this temperature, it is pressurized at a pressure of 50 to 400 kg/cm, held for a certain period of time, and then returned to normal pressure to complete the molding.

In the above operation, heating to 400 to 600'C without pressure is essential to prevent cracks from occurring due to expansion to contraction in this temperature range. The heating temperature and heating time at this time can be optimally selected depending on the material of the carbon material raw material, the shape and size of the molded body to be obtained, and the like.

Furthermore, the temperature, pressurizing pressure, and pressurizing time in the subsequent heating and pressurizing step are also selected to values suitable for the material, shape, and size of the raw material. It is preferable that the pressurization time is short,
For example, it may take less than 10 minutes.

Thus, the method of the present invention does not involve raising the temperature to a temperature of 1000° C. or higher and simultaneously applying pressure, as in conventional hot press operations, but instead involves heating to a predetermined temperature under old human pressure and then applying pressure at the same time. The hot pressing operation is performed by applying pressure for a short time and then returning to normal pressure. In other words, pressure to strengthen sintering is not necessary from the beginning, but only needs to be applied in the temperature range where the raw material powder is slightly softened and exhibits plasticity, and that temperature is the temperature range defined by the present invention. The temperature is 400-600°C.

In addition, in the above hot press operation, the temperature
It is not preferable to continue applying pressure beyond this point because it may cause cracks to occur due to subsequent shrinkage or a decrease in strength due to brittle fracture.

After obtaining the molded body in this manner, the molded body is further fired at a high temperature (for example, 1000° C.) under atmospheric pressure according to a conventional method, if necessary. If necessary, a high-density, high-strength carbon material with a bulk density of 1°98/cd or more can be obtained by heating and graphitizing in a high-temperature furnace.

[Examples and comparative examples of the invention]

EXAMPLES Hereinafter, the effects of the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

1 Feng 1 Bulk mesophase obtained from catalytic cracking oil of petroleum is heat treated and further finely pulverized, resulting in a volatile content of 8.0%,
A carbon material raw material having a quinoline soluble content of 98.0% and an average particle size of 2.2 μm was prepared. This raw material powder was filled into a hot press mold with an inner diameter of 3011Ii, and the temperature was raised to 500° C. in 1 hour under atmospheric pressure without applying pressure. 500
When the temperature reached °C, pressure was applied for 2 minutes at a pressure of 200 K9/cM, and then the pressure was stopped and the mixture was allowed to cool to room temperature.

This compact was taken out of the mold, buried in coke, fired in an electric furnace to 100°C, and further heated in a high-temperature furnace to 2°C.
It was fired at 000°C. The bulk density of the obtained carbon material was 1
, 95 g/ctd, bending strength 950 to 9/cI11
It had high lightning resistance and high strength, with an electrical resistance of 1.0 x 10 -3 Ω·cIR.

Fill a hot press mold with the same raw material powder as in the above example and pressurize it to 200 to 9/cIli.
The temperature was raised to 000°C. When the sample was taken out after cooling, it was found to have broken into pieces due to cracks caused by shrinkage.

Comparative Example 2 The same raw material powder as in the above example was filled into a hot press mold and pressurized to 20ON5F/i to 400''C.Then, it was taken out of the mold and fired at 2000°C under atmospheric pressure. Obtained The carbon material has a bulk density of 1
．． 7 (1/l-d, bending strength of 520 Kg/cm, electrical resistance of 4.9×10-"Ω" cm, and was of low quality.

L comparison
Pre-calcination was carried out at °C under atmospheric pressure. After that, this molded body was set in a hot press mold and weighed 200 kg.
Pressure firing was performed at a temperature of 2000° C. by applying a pressure of /d.

The obtained carbon material had a relatively good bulk density of 1.85y/7, but had a low bending strength of 410 kg/-.

Comparative Example 4 The same raw material powder as in the above example was molded in advance by cold isostatic pressing, and then fired at a temperature of 2000° C. under atmospheric pressure. The obtained carbon material had a bulk density of 1.74 g/
Cd and bending strength were 3451 (g/cj1), which was lower quality than that obtained by the hot press method.

'Continued from page 1/Inventor 1) Sansho 2-121 Takashihama, Snoring City Invention
Person: Sakae Kitajima 2 3-151 Yayoi-cho, Izumi City
Author: Fumi Ishihito 2-29 Yayoi-cho, Izumi City
Procedural amendment document 1982 Patent application No. 2426-00 2 Name of the invention Method for manufacturing high-density carbon material 3 Relationship to the case of the person making the amendment Patent applicant Director of the Agency of Industrial Science and Technology Tatsu Todoroki (and 1 other person) 4th generationり人't w: Contents of r Book ll, page 11, 3rd line from the bottom, ``wasgaka ``slightly''
I am corrected.

rl, 98/cd or more on page 12, line 9 of the specification book, rl
, 95/cId or higher.''

(3) “Limited” on page 12, line 14 of the specification
be corrected to "limited".

(4) “By contraction” in the 6th line from the bottom of page 13 of the specification
is corrected to "due to contraction."

Claims (1)

[Claims] 1. A carbon material raw material consisting essentially of carbonaceous powder is heated to 400 to 600°C under atmospheric pressure, and then this heated carbon material raw material is heated for 50 minutes while being maintained in the above temperature range. ~400
A method for producing a high-density carbon material, which comprises molding it into a desired shape by pressurizing it at a pressure of Kg/cm^2, and further firing and graphitizing the obtained molded body as necessary. 2. The method according to claim 1, wherein the heating temperature of the carbon material raw material is 450 to 550°C. 3. Claim 1 or 2, wherein the carbon material raw material is bulk mesophase, mesocarbon microbeads, carbonaceous powder having self-sintering ability such as petroleum-based or coal-based coke, or a mixture thereof. The method described in section. 4. The method according to any one of claims 1 to 3, wherein the carbon material raw material contains a binder. 5. The method according to claim 1 or 2, wherein the carbon material raw material is bulk mesophase.