JP3094502B2 - Manufacturing method of 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 method for producing a high-density and high-strength isotropic carbon material using a self-sintering raw material.

[0002]

2. Description of the Related Art A high density isotropic carbon material is used as an electrode material for electric discharge machining, a crucible for aluminum deposition, or a wall material for a nuclear fusion reactor. In the case of producing this high-density isotropic carbon material, generally, petroleum-based coke or coal-based coke is finely pulverized into an aggregate, and a binder is added to the aggregate to form the aggregate. The molding is usually performed by using a cold isostatic press (CIP) to homogenize properties. The obtained molded body is 1
It is carbonized at a very low temperature rising rate of -10 ° C / Hr, and then heated to 2000-3000 ° C and subjected to a graphitization treatment.

With respect to a binary raw material using the aggregate and the binder pitch, a self-sinterable raw material having both the function of a filler and the function of a binder in one kind of particles has recently been developed. Among them, the bulk mesophase is obtained by heat-treating a petroleum-based or coal-based pitch in a range of 350 ° C to 500 ° C, and is 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 (JP-A-59-164604). Since such a raw material retains self-sintering properties, it is fused to itself by molding, and it is not necessary to add an adhesive such as a binder.

A method using mesocarbon microbeads (MCB) as a self-sintering raw material has been proposed (JP-A-49-2379). The MCB is a small optically anisotropic sphere having a diameter of about 10 μm, which is generated in the process of heat treating various pitches. MCB
Is generated in an optically isotropic pitch matrix by heat-treating the pitch. If the generated MCB continues to be heated as it is, the MCBs are united to form a bulk mesophase. Therefore, the heat treatment is stopped at the stage when the minute MCB is generated, and M generated by adding a large amount of solvent.
Take out the CB. However, it is assumed that MCB alone does not have sufficient self-sintering properties,
When taking out B, it has been proposed to attach a portion mainly composed of a β component consisting of a quinoline-soluble component of a matrix pitch to the surface of the MCB (JP-A-62-4170).
7).

[0005]

In a method in which coke is finely pulverized into aggregate and a binder is added thereto to perform CIP molding, carbonization and graphitization, the properties of the carbon material obtained are made uniform. Aggregate coke tends to be as fine as possible. However, the required amount of the binder to be added for bonding the fine particles increases accordingly. When the amount of binder added increases, the binder component decomposes during the carbonization process and volatilizes from the molded product, so that the residual coal yield after the carbonization process decreases, and the density of the molded product after firing decreases. is there.

[0006] Such a tendency is similarly observed in a method of attaching a portion mainly composed of the β component of the matrix pitch as a binder around the MCB. That is, MCB
The smaller the particle size of the steel for homogenization, the more the matrix pitch mainly composed of β component, which serves as a binder for bonding the MCBs, needs to remain, but the residual coal yield after carbonization decreases accordingly. Then, the density of the formed body after firing decreases. Such a decrease in density corresponds to an increase in porosity, which also leads to a decrease in strength.

[0007] In order to improve the decrease in density, that is, the increase in porosity, as described above, it is often practiced to impregnate the treated body with pitch in a carbonization step or a graphitization step and to perform a reheating treatment. However, this method is complicated and uneconomical as a process.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a carbon material capable of reliably achieving high density and high strength by relatively simple steps. I do.

[0009]

In order to achieve the above object, the present invention provides a process for producing a self-sintering raw material, a process for molding this raw material, and a process for carbonizing and firing a compact. And a step of graphitizing the sintered body, wherein the raw material is obtained by subjecting the hydrogenated pitch to a heat treatment, and further performing a finer treatment and an oxidation treatment. A method for producing a carbon material, comprising a step of determining whether or not hydrogenation of the raw material has been properly performed.

As a result of extensive studies by the inventors of the present invention in order to achieve a high density and high strength carbon material by relatively simple steps, pitch is subjected to hydrogenation heat treatment, then atomized and further oxidized. It has been found that this can be achieved. In addition, by grasping whether or not hydrogenation is appropriately performed, it can be determined whether or not the carbon material has been sufficiently densified and strengthened, and the densification can be reliably performed. And that high strength can be achieved.
The present invention has been made based on such knowledge. Hereinafter, the present invention will be described in detail.

The pitch raw material used as the self-sintering raw material for producing the carbon material of the present invention may be any of coal-based residual oil and petroleum-based residual oil. The softening point of the pitch raw material used is preferably from 40 ° C. to 250 ° C. If the temperature is lower than this range, the yield of the heat-treated pitch decreases, and if the temperature is higher than this range, the pitch raw material does not dissolve until a high temperature is reached, so that it is mixed with a solvent or fluidized in a reactor. It is difficult to achieve. A more preferable range of the softening point is 80 ° C to 150 ° C.

[0012] The hydrogenation treatment is achieved by holding at a temperature of preferably 350 to 450 ° C for 3 hours or less in a hydrogen gas atmosphere. After raising the temperature to the temperature in this range, the temperature may be lowered immediately without holding. At this time, a catalyst composed of Ni, Co, Mo, or the like, or red mud, sulfur, or the like may be used as the catalyst. In this case, as long as the atmosphere is a hydrogen gas atmosphere, either under atmospheric pressure or under pressure may be used, and effects corresponding to the respective conditions can be obtained.

[0013] In this hydrogenation treatment, the pitch is mixed with a solvent holding hydrogen that can be transferred in advance, and the mixture is mixed with a solvent of 350 to 350 to
The temperature may be held at a temperature of 450 ° C. for 3 hours or less (including the case where the temperature is not held).

In both the case of using hydrogen gas and the case of using a solvent which can transfer hydrogen, a sufficient amount of hydrogen does not transfer to the pitch raw material at a temperature lower than the above range, and at a temperature higher than this range, it does not transfer to the pitch. Undesired hydrogen is desorbed again, which is not preferable.

The obtained hydrogenated pitch is further heat-treated so that its softening point is preferably 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 coal yield during carbonization and firing while maintaining proper binder performance.

The pitch obtained by the heat treatment in this manner is finely divided into a predetermined particle size. The method at this time is not particularly limited, and a method such as mechanical pulverization or atomization under high temperature can be employed.However, in order to improve the filling performance during molding, the particles can be made more spherical. The atomization method is preferred.

Next, this finely divided pitch is oxidized. 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 temperature, the oxidation is not sufficiently performed, and if the temperature is higher than this temperature, the oxidation proceeds excessively, and sufficient adhesion performance of the particles cannot be secured. This oxidation treatment may be performed in air or an oxygen atmosphere.

Whether the self-sintering pitch manufactured in this way can satisfy the densification and strength enhancement of the carbon material depends on whether the hydrogenation of the pitch raw material is properly performed. Whether or not the pitch raw material is appropriately hydrogenated can be grasped by measuring the weight increase in the oxidation treatment of the micronized hydrogenated heat treatment pitch. It can also be grasped by measuring the increase rate of the oxygen content after the oxidation treatment. Specifically, 180-350
It is preferable to measure and evaluate whether or not the hydrogenation of the pitch used as the raw material for the carbon material is appropriately performed by measuring the weight increase rate obtained by the air oxidation treatment at a specific temperature in the range of ° C. Outside this temperature range, it is difficult to ascertain the significant difference between the raw materials in the weight increase due to the oxidation treatment. When determining the suitability of hydrogenation by measuring the increase rate of the oxygen content, it is preferable to measure the oxygen content after the air oxidation treatment at a specific temperature within the same temperature range. Also in this case, it is difficult to grasp a significant difference in oxygen content between raw materials outside this temperature range.

Whether the actual hydrogenation treatment is appropriate or not is determined by measuring the relative oxidation of the hydrogenated heat-treated material at the same temperature with respect to the increase in the oxidized weight of the unhydrogenated heat-treated pitch having the same softening point as that of the hydrogenated heat-treated material. The determination is preferably made based on the weight increase, and if this value exceeds 1.0, it can be determined that the hydrogenation is appropriately performed. Further, when measuring the oxygen content, it is preferable to determine by the relative oxygen content at the same temperature of the hydrogenation heat treatment raw material with respect to the oxygen content of the unhydrogenated heat treatment pitch of the same softening point as the hydrogenation heat treatment raw material, If this value exceeds 1.0, it can be determined that the hydrogenation is appropriately performed. 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 formed by a known method, carbonized and fired, and graphitized, whereby a desired isotropic carbon material is obtained. Here, the softening point is a softening point obtained by the Metra method. By manufacturing the carbon material as described above, it is possible to surely achieve high density and high strength despite relatively simple steps.

[0020]

【Example】

 (Example 1)

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

Next, the obtained oxidized fine-grain pitch was charged into a rubber mold, and 1.5 T / cm ² Was CIP molded. This compact was placed in a carbonization furnace and fired at 1000 ° C., and then heated to 2200 ° C. in a graphitization furnace to be graphitized. The finally obtained product had a size of 50 mmφ × 50 mm. The bulk density and bending strength of the obtained sample were evaluated. Table 1 shows the results. Table 1 also shows the relative oxidation weight increase and the relative oxygen content. The relative oxidation weight increase is expressed by the weight increase rate of the hydrogenated heat treatment pitch / the weight increase rate of the non-hydrogenated heat treatment pitch. The relative oxygen content is represented by the oxygen content of the hydrogenated heat treatment pitch / the non-hydrogenated heat treatment pitch. (Both in% by weight of dry base). (Example 2)

50 parts by weight of petroleum-based FCC resid was mixed with 50 parts by weight of a pitch having a softening point of 120 ° C. according to the Mettler method. This mixture was charged into an autoclave, and the inside of the autoclave was filled with 5 kg / cm ^2. While maintaining the temperature at G, the temperature was raised to 420 ° C., and the temperature was maintained for 30 minutes. Thereafter, all the collected samples were charged into a heat treatment apparatus, and the samples were collected under nitrogen gas flow.
The temperature was raised to 20 ° C., and heat treatment was performed at that temperature for 100 minutes so that the softening point was about 300 ° C. The pitch subjected to this heat treatment was atomized to an average particle diameter of 10 μm by atomization. The obtained fine particle pitch is 2
The sample was oxidized at 50 ° C. for 15 minutes, the weight increase after the oxidization was measured, and the oxygen content of the oxidized sample was measured. A part of the obtained sample was used as a raw material for producing a carbon material.

Next, the obtained oxidized fine particle pitch was charged into a rubber mold, and 1.5 T / cm ² Was CIP molded. 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 be graphitized. The finally obtained product had a size of 50 mmφ × 50 mm. The bulk density and bending strength of the obtained sample were evaluated. Table 1 shows the results. Table 1 also shows the relative oxidation weight increase and the relative oxygen content. (Comparative Example 1)

A pitch having a softening point of 120 ° C. according to the Mettler method is charged into a heat treatment apparatus, and the temperature is raised to 420 ° C. under flowing nitrogen gas, and a heat treatment is performed for 55 minutes to maintain the softening point at about 300 ° C. Heat treatment was performed. The heat treatment pitch was atomized to an average particle diameter of 10 μm by atomization. The obtained fine particle pitch was oxidized at 250 ° C. for 15 minutes, the weight increase after the oxidizing treatment was measured, and the oxygen content of the oxidized sample was measured. A part of the obtained sample was used as a raw material for producing a carbon material.

Next, the obtained oxidized fine-grain pitch was charged into a rubber mold and 1.5 T / cm ² Was CIP molded. 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 be graphitized. The finally obtained product had a size of 50 mmφ × 50 mm. The bulk density and bending strength of the obtained sample were evaluated. Table 1 shows the results. Table 1 also shows the relative oxidation weight increase and the relative oxygen content.

[0027]

[Table 1]

As shown in Table 1, in Examples 1 and 2, the relative oxidation weight increase and the relative oxygen content exceeded 1.0, and as a result, the bulk density was 1.95 g / cm ^3.
And the bending strength is 1000 kg / cm ² , And all became high values.

On the other hand, in Comparative Example 1 in which no hydrogenation treatment was performed, the relative oxidation weight increase and the relative oxygen content were 1.0, and as a result, the bulk density was lower than that of the Example, and The strength was also less than half the value of the example. From these results, the effectiveness of the present invention was confirmed.

In the above embodiment, the hydrogenation treatment was performed using petroleum-based FCC residual oil as a solvent holding hydrogen that can be transferred. However, the same effect can be obtained by hydrogenation treatment in a hydrogen gas atmosphere. I was able to.

[0031]

According to the present invention, there is provided a method for producing a carbon material capable of easily and surely increasing the density and the strength by a relatively simple process.

Continuation of the front page (56) References JP-A-3-170311 (JP, A) JP-A-1-111706 (JP, A) JP-A-63-69756 (JP, A) JP-A-3-167318 (JP) JP-A-63-256690 (JP, A) JP-A-63-150376 (JP, A) JP-A-58-213609 (JP, A) JP-A-59-164604 (JP, A) 49-2379 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/52 C01B 31/04 101

Claims (7)

(57) [Claims] 1. A step of producing a self-sintering raw material, a step of forming the raw material, and a step of carbonizing and firing a molded body.
And carbonizing the sintered body, wherein the raw material is obtained by performing a heat treatment on the hydrogenated pitch, further performing a finer treatment, and an oxidation treatment. And a step of determining whether or not the hydrogenation of the raw material has been properly performed. 2. The method for producing a carbon material according to claim 1, wherein whether or not hydrogenation is appropriately performed is determined based on an increase in the weight of the raw material in the oxidation treatment. 3. The method for producing a carbon material according to claim 1, wherein whether or not hydrogenation is appropriately performed is determined based on an increase in the oxygen content of the raw material after the oxidation treatment. 4. The weight increase in the oxidation treatment is from 180 to
The method for producing a carbon material according to claim 2, wherein the weight is obtained from a weight increase rate obtained by an air oxidation treatment at a specific temperature within a range of 350 ° C. 5. An increase in the oxygen content after the oxidation treatment,
The method for producing a carbon material according to claim 3, wherein the weight is obtained from a weight increase rate obtained by an air oxidation treatment at a specific temperature within a range of 0 to 350 ° C. 6. The relative oxidation weight increase of the hydrogenated heat treatment material at the same temperature with respect to the increased oxidation weight of the unhydrogenated heat treatment pitch having the same softening point as that of the hydrogenated heat treatment raw material is 1.
The method for producing a carbon material according to claim 2, wherein the value is more than 0. 7. The relative oxygen content at the same temperature of the hydrogenation heat treatment raw material with respect to the oxygen content of the unhydrogenated heat treatment pitch having the same softening point as the hydrogenation heat treatment raw material is more than 1.0. The method for producing a carbon material according to claim 3.