JP2806408B2 - Self-fusing carbonaceous powder and high density carbon 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 self-fusing carbonaceous powder suitable for a raw material for a high-density carbon material and a binder for a carbon composite material, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, many production methods for high-density carbon materials are known. These methods are roughly divided into the following two methods from the viewpoint of starting materials. One commonly used method is a method of kneading an aggregate such as coke powder, natural graphite and carbon black and a binder such as coal tar pitch, followed by molding and firing. In this method, since the residual carbon ratio of the binder is very low, the density of the molded body is extremely small in one carbonization, and the density must be increased by repeating the impregnation / carbonization process many times in order to increase the density. In the carbonization process, degassing of volatile components in the binder occurs,
The rapid escape of gas not only causes inhomogeneous pores to remain inside the molded body, but also causes expansion of the molded body and causes tissue destruction. The temperature rises very slowly at ℃ / hr, requiring a production period of 3-4 weeks. The molded body after the carbonization step is calcined at 2500 to 3000 ° C. depending on the use to produce a graphitic carbon material. This graphitization step generally requires two to three weeks. As described above, it takes a long time of two to three months to produce a graphitic carbon material from an aggregate such as coke and a binder such as coal tar pitch through a complicated process.

Another method is disclosed in Japanese Patent Application Laid-Open No. Sho.
No.49-23793, No.51-29523
And Japanese Patent Publication No. 60-25364, in which optically anisotropic small spheres are used as a raw material for a high-density carbon material without using a binder. That is, optically anisotropic small spheres (mesophase spherulites) generated during the heat treatment of coal tar pitch, petroleum heavy oil, etc. at 350-500 ° C are separated from the pitch matrix by solvent fractionation and dried. This is a method in which a mesophase spherulite is used as a raw material, which is press-molded and then fired, and a high-density and isotropic carbon material can be produced. However, in this method, a large amount of extraction solvent is required in the spherulite / separation step, and the solvent must be separated many times, and it is difficult to completely remove the residual solvent from the obtained spherulite. Therefore, it tends to cause cracks and expansion of the molded body in the subsequent carbonization step. Moreover, in such a spherulite solvent extraction method, in addition to a low separation yield, it is not easy to control the properties of the generated spherulites, and there are many industrial problems in stably producing a raw material of a constant quality.

[0004]

As described above, the process for producing a high-density carbon material is extremely complicated and requires a very long production period, so that the high-density carbon material produced by the conventional method is expensive. Therefore, at present, the field of use is greatly restricted. Therefore, in the case of a high-density carbon material, voids due to volatile gas are easily generated in the carbonized molded body, and it is a major challenge in the carbon industry to greatly simplify the production process of the obtained carbon material and shorten the production period. one of. An object of the present invention is to provide a self-fusing carbonaceous powder and a high-density carbon material capable of producing a high-density and high-strength carbon material in a short time and at low cost.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, by heat treating a specific mesophase pitch, an atomic ratio of hydrogen to carbon (H / C) and oxygen Atomic ratio of oxygen to (O /
By preparing a heat-treated pitch having (C) and using the heat-treated powder having an increased carbonization yield and excellent self-fusing property as a raw material, the heat treatment pitch can be increased in a short time and at a low cost without adding a binder. The inventors have found that a high-density carbon material can be obtained, and have reached the present invention.

That is, according to the present invention, the carbonization yield is 70% by weight or more, the softening point is 170 ° C. or more, and the optically anisotropic phase is 70% by volume.
The self-fusing carbonaceous powder obtained by heat-treating the above mesophase pitch has an atomic ratio of hydrogen to carbon in the range of 0.35 to 0.48, and an atomic ratio of oxygen to carbon of less than 0.01, and This is a high-density carbon material obtained by molding and heating it to a temperature of 600 to 1600 ° C. in a non-oxidizing atmosphere or graphitizing it at a higher temperature.

[0007] The carbon, hydrogen and oxygen contents of the self-fusing carbonaceous powder of the present invention are analyzed using an automatic analyzer to which a technique such as detection by the thermal conductivity of combustion gas is applied. Raw material pitch for producing the self-fusing carbonaceous powder of the present invention has a carbonization yield of 70% by weight or more, preferably
A mesophase pitch of 80 wt% or more is used. The carbonization yield is such that the pitch is gradually heated under an inert atmosphere,
This is the value when the temperature is maintained for about 2 hours after reaching ° C. When a pitch having a low carbonization yield is used as a raw material, voids due to volatile gas are easily generated in the carbonized molded body, which causes a reduction in the density of the obtained carbon material, and its mechanical strength, electrical conductivity, and thermal conductivity. Therefore, it is important to use a raw material pitch having a high carbonization yield since it has a bad influence on corrosion resistance and the like.

The raw material pitch has a softening point of 170 ° C. or higher by a flow tester and an optically anisotropic phase observed by a polarizing microscope of at least 70 vol%, preferably 80 vol%.
A mesophase pitch of l% or more, more preferably substantially 100 vol%, is used. If mesophase pitch which satisfies these conditions, coal-based, but may be any of petroleum, particularly JP 1-13621, aromatic described in JP-A and JP-A-3 223 391 1-254796 carbide Hydrogen superacid H
Mesophase pitch prepared by polymerizing at F-BF ₃ catalyst is suitably used in terms of high carbonization yield is obtained.

The self-fusing carbonaceous powder of the present invention is produced by heat-treating the above mesoface pitch. This heat treatment condition is the atomic ratio of hydrogen to carbon (H / C)
Is within the range of 0.35 to 0.48 and the heat treatment conditions for obtaining a self-fusing carbonaceous powder having an atomic ratio of oxygen to carbon (O / C) of less than 0.01 may be selected, and there is no particular limitation.
Generally, the above mesophase pitch is stirred under 470 ~
Heat treatment is performed at a temperature of 550 ° C.

In the present invention, good formability can be obtained only by preparing the above-mentioned mesophase pitch in this way, and high density can be achieved without inducing cracking or expansion in the subsequent carbonization step. That is, by performing such a moderate heat treatment, the initial stage of carbonization of the molded body is performed.
(400-600 ° C) good melt flowability is guaranteed,
It can be modified to a powder having a self-fusing property that exhibits excellent performance as a raw material for high-density carbon materials (Examples 1 and 2).

[0011] Excessive heat treatment lowers the fusibility of the mesoface pitch powder, and a carbon material having desired performance cannot be obtained (Comparative Example 1). On the other hand, if the heat treatment is insufficient, expansion and foaming of the molded body due to the volatile gas are likely to occur in the subsequent carbonization step, and a desired carbon material cannot be obtained (Comparative Example 2). Further, as the oxygen content of the heat-treated pitch increases, the carbonization yield decreases and the fusibility decreases, which is not preferable (Comparative Example 3).

That is, by appropriately performing heat treatment of the mesophase pitch so that H / C and O / C satisfy the above ranges, the carbonization yield is further increased, and the carbonization process is performed while maintaining the tackiness of the mesophase pitch. As a result, the gas generated in the above process can be removed as much as possible, so that a high-density and high-strength carbon material can be produced by only one firing.

In order to obtain a high-density and high-strength carbon material, the mesophase pitch heat-treated in this way is first powdered. The powdering method and powder shape are not particularly limited. Although there is no particular limitation on the particle size distribution, a particle size distribution that maximizes the packing density during molding is preferable. Generally, it is used for molding with a powder of 200 to 1 μm.

Next, the powdered heat treatment pitch is formed. At this time, a binder is not particularly required. The shape of the molded body can be freely selected depending on the purpose, application, and the like. The molding may be performed at room temperature or in a temperature range where the heat-treated powder softens or melts, and is determined according to the required shape, performance and cost. The desired carbon material is manufactured by subsequently firing the molded body. The firing conditions are generally in a non-oxidizing atmosphere, and the heating rate is 1
It is carried out by heating the molded body to a temperature of 600 to 1600 ° C. at a temperature of 300 ° C./h to carbonize it. If necessary, a step of graphitizing at a higher temperature may be included.

[0015]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited by these examples.

Example 1 Mesophase pitch AR-1 obtained by polymerizing naphthalene in the presence of superacid HF - BF ₃ (softening point> 300 ° C., carbonization yield 91 wt%, optical anisotropy Was heated to 480 ° C. at a rate of 300 ° C./h in a nitrogen atmosphere and heat-treated for 30 minutes. The H / C of this heat-treated pitch was 0.47, and the O / C was 0.006. After grinding the heat treated pitch below 74 .mu.m, the plate-shaped (50 mm × at a molding pressure 1200 kg / cm ² at room temperature
(50mm × 10mm). Thereafter, the temperature was raised to 600 ° C. at a rate of 60 ° C./h under nitrogen flow, and maintained for 2 hours. The carbonization yield was 97% by weight. Thereafter, the resultant was calcined at 1300 ° C. for 2 hours under a flow of argon to obtain a 50 mm × 50 mm × 10 mm carbide. Further, this carbide was calcined at 1900 ° C. for 2 hours. Table 1 shows the physical properties (bulk density, compressive strength, bending strength) of the obtained carbide.

Example 2 Mesophase pitch AR-2 (softening point 220 ° C., carbonization yield) obtained by polymerizing naphthalene in the presence of super strong acid HF-BF ₃
83wt%, optical anisotropy content 100vol%) under nitrogen atmosphere
The temperature was raised to 505 ° C at 300 ° C / h and heat-treated for 2 hours. The H / C of this heat treatment pitch was 0.44 and the O / C was 0.005.
After grinding the heat treated pitch below 74 .mu.m, with a molding pressure 1200 kg / cm ² at room temperature the plate-like (50mm × 50mm × 10m
m). Then 80 ℃ / h up to 600 ℃ under nitrogen flow
And kept for 2 hours. The carbonization yield was 97% by weight.
This was further calcined at 1300 ° C. and 1900 ° C., and the physical properties of the obtained carbide are shown in Table 1.

COMPARATIVE EXAMPLE 1 The same mesoface pitch AR-2 as in Example 2 was used and heated to 540 ° C. at 300 ° C./h in a nitrogen atmosphere and heat-treated for 5 hours. The H / C of this heat treatment pitch was 0.34, and the O / C was 0.005. This heat-treated powder was molded under the same conditions as in Example 2.
It was fired at 600 ° C. and further fired at 1300 ° C. and 1900 ° C. Table 1 shows the physical properties of the obtained carbide. Since the heat-treated powder had a low H / C, the self-fusing property was lost, and a large amount of black carbon powder adhered to hands.

Comparative Example 2 Mesophase pitch AR-3 (softening point 230 ° C., carbonization yield) obtained by polymerizing naphthalene in the presence of super strong acid HF-BF ₃
85wt%, optically anisotropic content 100vol%) under nitrogen atmosphere
The temperature was raised to 400 ° C. at 300 ° C./h and heat-treated for 14 hours. The H / C of this heat treatment pitch was 0.51, and the O / C was 0.005.
The heat-treated powder was fired at 600 ° C. under the same conditions as in Example 1. However, since the H / C was high, the molded product expanded, and the physical properties of the carbide could not be measured.

Comparative Example 3 Using the same mesophase pitch AR-3 as in Example 1, the temperature was raised to 450 ° C. at a rate of 300 ° C./h in a nitrogen atmosphere and heat-treated for 30 minutes. Some air was blown temporarily during this heat treatment. The H / C of this heat treatment pitch was 0.36 and the O / C was 0.02. Thereafter, firing was performed in the same procedure as in Example 1. The heat treatment pitch was high in O / C, and as shown in Table 1, a high performance carbon material could not be obtained.

[0021]

[Table 1]

[0022]

The carbonaceous powder of the present invention is a heat-treated mesophase pitch which can be easily carbonized and graphitized as a raw material for a high-density carbon material and has an extremely high carbonization yield. In addition, a sufficient high density and high strength carbon material can be obtained by only one firing. Further, the fired body structure derived from the mesophase pitch exhibits optical anisotropy and is highly dense and highly pure, so that the carbon bond formed is very strong. Since the degree of graphitization of the carbon bond is improved by firing at a high temperature, and densification is further promoted by shrinkage, the carbon bond is further strengthened. In addition, the mesophase pitch used in the present invention is provided with excellent tackiness by moderate heat treatment, so that a binder is not particularly required. Therefore, if the carbonaceous powder of the present invention is used, a high-density, high-strength carbon material can be easily produced in a short time at low cost, and the industrial significance of the present invention is extremely large.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C10C 3/02 C10C 3/10

Claims (2)

(57) [Claims] 1. A carbonization yield of 70% by weight or more and a softening point of 170 ° C.
Above, the optically anisotropic phase is obtained by heat treatment of a mesophase pitch of 70 vol% or more, the atomic ratio of hydrogen to carbon is in the range of 0.35 to 0.48, and the atomic ratio of oxygen to carbon is less than 0.01. Is a self-fusing carbonaceous powder. 2. A carbonization yield of 70% by weight or more and a softening point of 170 ° C.
Above, the optically anisotropic phase is obtained by heat treatment of a mesophase pitch of 70 vol% or more, the atomic ratio of hydrogen to carbon is in the range of 0.35 to 0.48, and the atomic ratio of oxygen to carbon is less than 0.01. After molding the self-fusing carbonaceous powder that is 600-1600 ° C under non-oxidizing atmosphere
Density carbon material obtained by carbonizing at the temperature of