JPH04349114A - Production of carbon material - Google Patents

Abstract

PURPOSE:To improve the strength of a carbon material by heat-treating, then micronizing and oxidizing hydrogenated pitch, forming the obtained self- sinterable material, carbonizing, sintering and then graphitizing the formed material. CONSTITUTION:A pitch material such as petroleum bottoms having 40-250 deg.C softening point is charged into an autoclave and catalytically hydrogenated at 350-450 deg.C in a hydrogen gas atmosphere. The hydrogenated pitch is heat- treated to control its softening point to 250-380 deg.C and then atomized at high temp. to obtain the fine particles of the self-sinterable material. The fine particles are oxidized at 180-350 deg.C in the air to adjust the relative oxidation weight increase to >=1.0 and the relative oxygen content to >=1.0, and the hydrogenation degree is recognized. The hydrogenated pitch is placed in a die and press-formed, and the formed body is fired in a carbonization furnace and then graphitized at 2000-3000 deg.C in a graphitization furnace to obtain a carbon material high in density and strength.

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, high-strength, isotropic carbon material using self-sintering raw materials.

0002

BACKGROUND OF THE INVENTION High-density isotropic carbon materials are used as electrode materials for electrical discharge machining, crucibles for aluminum evaporation, and wall materials for nuclear fusion reactors. When producing this high-density isotropic carbon material, petroleum-based coke or coal-based coke is generally finely pulverized to form aggregate, and a binder is added to the aggregate to form it. Molding is usually performed using cold isostatic pressing (CIP) in order to homogenize the properties. The obtained molded body is 1~
It is carbonized at a very slow temperature increase rate of 10° C./Hr, and then heated to 2000 to 3000° C. and subjected to graphitization treatment.

In contrast to this binary raw material using aggregate and binder pitch, a self-sintering raw material has recently been developed in which one type of particle has both filler and binder functions. Among them, bulk mesophase is obtained by heat-treating petroleum-based or coal-based pitch in the range of 350°C to 500°C, and has an optically anisotropic structure (liquid crystal) fully developed. When this is used as a raw material for a high-density isotropic carbon material, it is used after being finely pulverized (Japanese Patent Application Laid-Open No. 164604/1983). Since such raw materials maintain self-sintering properties, they fuse themselves to each other when molded, and there is no need to add an adhesive such as a binder.

[0004] A method using mesocarbon microbeads (MCB) as the self-sintering raw material has also been proposed (Japanese Patent Laid-Open No. 49-2379). MCBs are optically anisotropic small spheres with a diameter of about 10 μm that are generated during the heat treatment process of various pitches. M.C.
B is generated in an optically isotropic pitch matrix by heat treating the pitch. If the generated MCB is continued to be heated, the MCB will coalesce into a bulk mesophase, so the heat treatment is stopped when minute MCB is generated, and a large amount of solvent is added to take out the generated MCB. However, since MCB alone does not have sufficient self-sintering properties, a solvent is used to convert matrix pitch to MCB.
It has been proposed that when extracting CB, a portion of matrix pitch consisting mainly of β component consisting of quinoline soluble material is attached to the surface of MCB (Japanese Patent Laid-Open No. 62-417).
07).

[0005]

[Problems to be Solved by the Invention] In the method of finely pulverizing coke to make aggregate, adding a binder to it, and subjecting it to CIP molding, carbonization, and graphitization, in order to make the properties of the obtained carbon material uniform, There is a tendency to use aggregate coke with the particle size as fine as possible. However, along with this, the required amount of binder added to bond the fine particles to each other increases. If the amount of binder added increases, the binder component will decompose and volatilize from the compact during the carbonization process, resulting in a decrease in the residual carbon yield after carbonization and a decrease in the density of the compact after firing. be.

[0006] Such a tendency is also seen in a method in which a portion mainly consisting of the β component of the matrix pitch is attached as a binder around the MCB. In other words, M.C.B.
The smaller the grain size of MCB is made for homogenization, the more matrix pitch consisting mainly of β component that acts as a binder for bonding MCBs must remain, but as a result, the residual carbon yield after carbonization decreases. However, the density of the compact after firing is reduced. Such a decrease in density corresponds to an increase in porosity and is also linked to a decrease in strength.

[0007] In order to improve the above-mentioned decrease in density, ie, increase in porosity, pitch is often impregnated into the treated body during the carbonization or graphitization process, followed by reheating. However, this method is complicated and uneconomical.

[0008] The present invention was made in view of the above circumstances, and an object thereof is to provide a method for producing a carbon material that can reliably achieve high density and high strength through a relatively simple process. do.

[0009]

[Means and effects for solving the problems] In order to achieve the above object, the present invention comprises a process of producing a self-sintering raw material, a process of molding this raw material, and a process of carbonizing and firing a molded body. , a method for producing a carbon material comprising the steps of graphitizing the sintered body, wherein the raw material is obtained by subjecting hydrogenated pitch to heat treatment, and further subjecting it to refinement treatment and oxidation treatment. The present invention provides a method for producing a carbon material, which comprises a step of determining whether or not the raw material is properly hydrogenated.

[0010] As a result of intensive studies by the inventors of the present application to achieve higher density and higher strength of carbon materials through a relatively simple process, the pitch was subjected to hydrogenation heat treatment, then atomized, and further oxidized. I discovered what I could achieve by doing this. In addition, by understanding whether hydrogenation is being carried out properly, it is possible to judge whether or not the carbon material is sufficiently densified and strengthened, and to ensure that the densification is achieved properly. It has been found that it is possible to achieve high strength. This invention was made based on such knowledge. This invention will be explained in detail below.

The pitch raw material used as the self-sintering raw material for producing the carbon material of the present invention may be either coal-based residual oil or petroleum-based residual oil. The softening point of the pitch raw material used is preferably 40°C or more and 250°C or less. If the temperature is lower than this range, the yield of heat-treated pitch will decrease, and if it is higher than this range, the pitch raw material will not dissolve until the temperature is high, so it may be necessary to mix it with a solvent or fluidize it in the reactor. It becomes difficult to plan. A more preferable range of softening point is 80°C to 150°C.

[0012] The hydrogenation treatment is preferably carried out under a hydrogen gas atmosphere at a temperature of 350 to 450°C for a period of up to 3 hours. After raising the temperature to this range, the temperature may be lowered immediately without being held. In this case, as a catalyst, one composed of Ni, Co, Mo, etc., or red mud, sulfur, etc. may be used. In this case, as long as it is a hydrogen gas atmosphere, either atmospheric pressure or pressurized conditions may be used, and effects corresponding to each can be obtained.

[0013] In addition, this hydrogenation treatment is carried out by mixing the pitch with a solvent that holds transferable hydrogen in advance, and
It may be held at a temperature of 450° C. for 3 hours or less (including cases where it is not held).

[0014] Regardless of whether hydrogen gas or a solvent containing transferable hydrogen is used, sufficient hydrogen will not transfer to the pitch raw material at temperatures below the above range, and will not transfer to the pitch at temperatures above this range. This is not preferable because the hydrogen that has been released will be desorbed again.

The obtained hydrogenated pitch is further heat-treated to preferably have a softening point of 250°C or more and 380°C or less. More preferably, the temperature is adjusted to 280 to 350°C. This is to improve the residual carbon yield during carbonization firing and at the same time maintain appropriate binder performance.

The pitch obtained by heat treatment in this manner is finely divided into a predetermined particle size. The method in this case is not particularly limited, and methods such as mechanical pulverization and atomization under high temperature can be adopted, but in order to improve the filling performance during molding, it is possible to make the particles more spherical. A method by atomization is preferred.

Next, this finely divided pitch is subjected to an oxidation treatment. The temperature at this time is preferably in the range of 180 to 350°C. This is because if the temperature is lower than this, the oxidation will not be sufficient, and if the temperature is higher than this, the oxidation will proceed too much, making it impossible to ensure sufficient particle adhesion performance. This oxidation treatment may be performed in air or in an oxygen atmosphere.

Whether or not the self-sintering pitch produced in this manner can satisfy the requirements for increasing the density and strength of the carbon material depends on whether or not the pitch raw material is properly hydrogenated. Whether or not the pitch raw material has been properly hydrogenated can be determined by measuring the weight increase during the oxidation treatment of the refined pitch that has been subjected to the hydrogenation heat treatment. It can also be determined by measuring the rate of increase in oxygen content after oxidation treatment. Specifically, 180-350℃
It is preferable to understand and evaluate whether or not pitch used as a raw material for carbon material is properly hydrogenated by measuring the weight increase rate obtained by air oxidation treatment at a specific temperature within the range of . Outside this temperature range, it is difficult to understand the significant difference in weight increase between raw materials due to oxidation treatment. Even when determining the suitability of hydrogenation by measuring the rate of increase in oxygen content, it is preferable to measure the oxygen content after air oxidation treatment at a specific temperature within the same temperature range. In this case as well, it is difficult to grasp any significant difference in oxygen content between raw materials outside this temperature range.

When measuring the weight increase, the suitability of the actual hydrotreating is determined by the relative oxidation weight increase of the hydrothermally treated raw material at the same temperature with respect to the oxidized weight increase of the unhydrogenated pitch having the same softening point as the hydrothermally treated raw material. It is preferable to judge by weight increase, and if this value exceeds 1.0, it can be judged that hydrogenation is being carried out appropriately. In addition, when measuring the oxygen content, it is preferable to judge by the relative oxygen content of the hydrothermally treated raw material at the same temperature with respect to the oxygen content of the unhydrogenated heat treated pitch having the same softening point as the hydrothermally treated raw material, This value is 1.
If the value exceeds 0, it can be determined that hydrogenation is being performed appropriately. When these values are 1.0 or less, hydrogenation is insufficient, and high density and high strength cannot be achieved as a high density isotropic carbon material. The self-sintering raw material thus obtained is shaped by a known method, carbonized and fired, and graphitized, thereby obtaining the desired isotropic carbon material. In addition, the softening point here is the softening point obtained by the Mettler method. By manufacturing the carbon material as described above, high density and high strength can be reliably achieved despite the relatively simple process.

[0020]

【Example】

(Example 1)

50 parts by weight of a petroleum-based FCC residual oil was mixed with 50 parts by weight of pitch having a softening point of 120° C. according to the Mettler method. This mixture was charged into an autoclave and placed under autogenous pressure for 4 hours.
The temperature was raised to 20°C and held at that temperature for 30 minutes. Thereafter, all the collected samples were placed in a heat treatment apparatus, heated to 420°C under nitrogen gas flow, and heat-treated by holding at that temperature for 85 minutes to achieve a softening point of about 300°C. The heat-treated pitch was atomized into fine particles with an average particle diameter of 10 μm. The resulting fine particle pitch was oxidized at 250° C. for 15 minutes, and the weight increase after the oxidation treatment was measured, as well as the oxygen content of the oxidized sample. A part of the obtained sample was used as a raw material for producing carbon material.

[0022] Next, the obtained oxidized fine pitch was charged into a rubber mold and CIP molded at 1.5 T/cm2. This compact was placed in a carbonization furnace and fired at 1000°C, and then further heated to 2200°C in a graphitization furnace to perform graphitization treatment. The final product is 50mmφ x 50m
The size was m. The bulk density and bending strength of the obtained samples were evaluated. The results are shown in Table 1. Table 1 also shows the relative oxidation weight increase and relative oxygen content. Note that the relative oxidation weight increase is expressed as the weight increase rate of hydrotreated pitch/weight increase rate of unhydrogenated heat treated pitch, and the relative oxygen content is expressed as: oxygen content of hydrogenated heat treated pitch/unhydrogenated heat treated pitch It is expressed as the oxygen content (both weight % of dry base). (Example 2)

[0023] 50 parts by weight of a petroleum-based FCC residual oil was mixed with 50 parts by weight of pitch having a softening point of 120°C by the Mettler method. This mixture was charged into an autoclave, and while maintaining the inside of the autoclave at 5 kg/cm 2 G, the temperature was raised to 420° C. and held at that temperature for 30 minutes. Thereafter, all the collected samples were placed in a heat treatment apparatus, heated to 420°C under nitrogen gas flow, and heat-treated by holding at that temperature for 100 minutes to achieve a softening point of about 300°C. The heat-treated pitch was atomized into fine particles with an average particle size of 10 μm. The resulting fine particle pitch was oxidized at 250° C. for 15 minutes, and the weight increase after the oxidation treatment was measured, as well as the oxygen content of the oxidized sample. A part of the obtained sample was used as a raw material for producing carbon material.

Next, the obtained oxidized fine pitch was charged into a rubber mold and CIP molded at 1.5 T/cm2. This compact was placed in a carbonization furnace and fired at 1000°C, and then further heated to 2200°C in a graphitization furnace to undergo graphitization treatment. The final product is 50mmφ×50
The size was mm. The bulk density and bending strength of the obtained samples were evaluated. The results are shown in Table 1. Table 1 also shows the relative oxidation weight increase and relative oxygen content. (Comparative example 1)

Pitch with a softening point of 120°C determined by the Mettler method was charged into a heat treatment equipment, heated to 420°C under nitrogen gas flow, and heat-treated by holding at that temperature for 55 minutes until the softening point reached approximately 300°C. It was heat treated to The heat-treated pitch was atomized into fine particles with an average particle size of 10 μm. The resulting fine particle pitch was oxidized at 250° C. for 15 minutes, and the weight increase after the oxidation treatment was measured, as well as the oxygen content of the oxidized sample. A part of the obtained sample was used as a raw material for producing carbon material.

Next, the obtained oxidized fine pitch was charged into a rubber mold and CIP molded at 1.5 T/cm2. This compact was placed in a carbonization furnace and fired at 1000°C, and then further heated to 2200°C in a graphitization furnace to undergo graphitization treatment. The final product is 50mmφ×50
The size was mm. The bulk density and bending strength of the obtained samples were evaluated. The results are shown in Table 1. Table 1 also shows the relative oxidation weight increase and relative oxygen content.

[0027]

[Table 1]

As shown in Table 1, in both Examples 1 and 2, the relative oxidation weight increase and relative oxygen content exceeded 1.0, and as a result, the bulk density was 1.95 g/cm.
3 and the bending strength exceeded 1000 kg/cm2, both of which were high values.

On the other hand, in Comparative Example 1 in which no hydrogenation treatment was performed, the relative oxidation weight increase and relative oxygen content were 1.
．． As a result, the bulk density was lower than that of the example, and the bending strength was also less than half of that of the example. From this result, the effectiveness of the present invention was confirmed.

In the above example, the hydrogenation treatment was carried out using petroleum-based FCC residual oil as a solvent holding transferable hydrogen, but the same effect can be obtained by hydrogenation treatment in a hydrogen gas atmosphere. I was able to do that.

[0031]

According to the present invention, there is provided a method for manufacturing a carbon material that can easily and reliably increase density and strength through relatively simple steps.

Claims (7)

[Claims] 1. Production of a carbon material comprising the steps of producing a self-sintering raw material, molding the raw material, carbonizing and firing the molded body, and graphitizing the sintered body. A method, wherein the raw material is obtained by heat-treating hydrogenated pitch, followed by micronization treatment, and oxidation treatment, and determining whether or not this raw material has been properly hydrogenated. A method for producing a carbon material, comprising the step of: 2. The method for producing a carbon material according to claim 1, wherein whether or not hydrogenation is being performed appropriately is determined based on an increase in weight of the raw material during oxidation treatment. 3. The method for producing a carbon material according to claim 1, wherein whether or not hydrogenation has been carried out appropriately is determined based on an increase in oxygen content of the raw material after oxidation treatment. Claim 4: The weight increase due to oxidation treatment is reduced to 180
3. The method for producing a carbon material according to claim 2, wherein the method is determined from a weight increase rate obtained by air oxidation treatment at a specific temperature within the range of ~350°C. [Claim 5] Increase in oxygen content after oxidation treatment by 1
4. The method for producing a carbon material according to claim 3, wherein the method is determined from a weight increase rate obtained by air oxidation treatment at a specific temperature within the range of 80 to 350C. 6. The relative oxidation weight increase of the hydroheat-treated raw material at the same temperature with respect to the oxidation weight increase of unhydrogenated heat-treated pitch having the same softening point as the hydroheat-treated raw material is 1.
．． The method for producing a carbon material according to claim 2, wherein the value exceeds 0. 7. The relative oxygen content of the hydrothermally treated raw material at the same temperature with respect to the oxygen content of the unhydrogenated pitch having the same softening point as the hydrothermally treated raw material is 1.0.
4. The method for producing a carbon material according to claim 3, wherein the carbon material has a value exceeding .