JPH0364448B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the production of high-density isotropic graphite materials used for graphite materials for nuclear reactors, electrode materials for electrical discharge machining, bearing materials for machinery, jig materials, etc. The present invention relates to a method for producing raw materials for carbon materials suitable for use in carbon materials. When the raw material for carbon material of the present invention is used, a high-density isotropic graphite material can be produced in substantially the same manner as conventional methods without using a binder.

Conventional technology The conventional method for manufacturing high-density isotropic graphite material is to use coal-based or petroleum-based coke or graphite powder crushed to a particle size of about 10 μm as aggregate, and add a binder such as binder pitch to this aggregate. death,
A common method is to knead and re-grind, then mold and sinter, further impregnate and re-sinter as necessary, and then graphitize at a high temperature.

However, this method requires a large number of steps and is time-consuming, and it is difficult to obtain a graphite material with a uniform structure because the matrix is formed from a structure made of aggregate and a structure formed by carbonization of the binder. It was hot. In addition, the binder shrinks while releasing low-boiling point substances and decomposition products as gas during carbonization, which causes the generation of pores, making it difficult to obtain a high-strength graphite material.

Therefore, in order to shorten the process and obtain a high-strength graphite material with a uniform structure, a raw material that does not require a binder and exhibits a uniform and isotropic structure during carbonization has been desired. Therefore, various studies have been made to obtain such raw materials.

For example, a method using mesocarbon microbeads extracted from mesophase spherulites precipitated by heat treatment of pitch (Special Publication No. 50-39633, Special Publication No. 39633,
No. 60-25364), after heat treating coal tar pitch, solvent extraction is carried out so that all or part of the β component remains in the insoluble pitch, and this insoluble pitch can be used as it is after baking or by finely pulverizing it without adding a binder. There is a method for obtaining a molded body (Japanese Unexamined Patent Publication No. 58-5310).

However, in this method, if the pitch is heated too much, the spherulites will coalesce and grow, making it unusable. Therefore, heat treatment must be carried out at a temperature above the temperature at which spherulites form but below the temperature at which they coalesce and grow, which not only requires difficult temperature control, but also yields only about 20% of spherulites with only one extraction. However, in order to increase the yield by repeatedly reheating the remaining pitch after extraction to generate spherulites and extraction, there is a problem that the number of steps increases and the cost increases.

This method not only requires a large number of steps, but also has high energy costs and uses a large amount of solvent, as it involves separation of insoluble matter from solvent extraction, solvent recovery, and reheating. There are some difficulties, such as:

The present invention relates to a method for producing a raw material for a high-density isotropic carbon material using a simple method that does not require a binder.

Problems to be Solved by the Invention It is an object of the present invention to provide a carbon material suitable for producing a high-density isotropic graphite material, etc., which can be molded without using a binder and has a homogeneous fine mosaic structure after firing. The objective is to produce raw materials by a simple method and at low cost.

Means for Solving the Problems In the present invention, when producing a high-density isotropic carbon material using pitch that does not substantially contain quinoline-insoluble matter as a raw material, after adding carbon black to the raw material, This is a method for producing a carbon material raw material suitable for producing high-density isotropic graphite that can be molded without using a binder and has a uniform fine mosaic structure after firing by crushing after heat treatment at a pressure of . The present invention will be explained in detail below.

Pituchi contains virtually no quinoline insoluble matter,
Virtually ash-free.

As the pitch, coal tar pitch, petroleum pitch, etc. can be used, but since coal tar pitch contains about 2 wt% of quinoline insoluble matter, this is removed. In order to obtain pitch that does not substantially contain quinoline-insoluble components from coal tar pitch, it can be obtained by pressure filtration or by adding a mixture of petroleum-based solvent and coal-tar-based solvent to soft pitch and performing liquid-liquid separation. is less than 0.1wt%.

The carbide obtained by carbonizing the pitch containing no quinoline insoluble matter shows strong anisotropy. However, by adding 10 to 100 parts by weight of carbon black to 100 parts by weight of pitch that does not contain quinoline-insoluble matter, coke having an arbitrary fine mosaic structure can be obtained.

Carbon black includes HAF, FEF,
GPF and ISAF can be used. If the amount of carbon black added is less than 10 parts by weight, the carbon black will aggregate during carbonization and will not exhibit a uniform structure. Moreover, if it exceeds 100 parts by weight, the viscosity of the mixture becomes high and it becomes impossible to knead it. It is difficult to uniformly disperse carbon black in a pitch. Particularly when a large amount of carbon black is added, the viscosity of the mixture becomes so high that it cannot be kneaded using a normal kneader. Therefore, when carrying out the present invention, it is preferable to uniformly disperse the carbon black in the pitch by using a high-torque closed-type twin-screw kneader or the like capable of heating up to around 400°C.

However, if this kneaded product is pulverized and molded as it is, it will foam and deform during the firing stage and cannot maintain a predetermined shape because of too much volatile content. Therefore, it is necessary to control the volatile content. Therefore, this kneaded material is heated to a temperature of 420°C to 560°C at a pressure below normal pressure,
Adjust so that the weight loss when increasing the temperature from room temperature to 1000°C is 5 to 25 wt% as measured using a thermobalance.

If the heat treatment time is less than 420°C, the pitch will not be sufficiently carbonized and will deform due to its own weight or cause foaming deformation during firing. When the temperature exceeds 560°C, coking progresses too much, the bonding force between particles weakens, and the strength decreases. 420 is a raw material for carbon materials that does not cause foaming deformation in the molded body during the firing stage and develops appropriate strength.
Heat treated at ℃~560℃, weight loss value on thermobalance 5~5
Limited to those adjusted within the range of 25wt%.

The weight loss value on a thermobalance referred to here is a value measured by the following method. Take 50mg to 100mg of sample into a platinum plate,
It refers to the weight loss when the temperature is raised from room temperature to 1000°C at a heating rate of 10°C/min in an argon or nitrogen atmosphere. If the weight loss value is less than 5wt%, the binding force is weak and no strength is obtained. If it exceeds 25wt%, foaming deformation will occur.

The optimum heat treatment temperature varies within the above range depending on the amount of carbon black in the starting material used and the pressure during heating. The lower the pressure and the greater the amount of carbon black, the lower the optimum heat treatment temperature tends to be.

The optimum weight loss value varies within the above range depending on the amount of carbon black in the starting material used. The higher the amount of carbon black, the higher the optimal weight loss value tends to be. Therefore, by changing the heat treatment temperature and pressure according to the starting material, the weight loss value can be adjusted to 5 to 25 wt.
Make weight reduction adjustments to obtain appropriate values between %. In this way, the raw material for the high-density isotropic carbon material of the present invention is obtained.

The raw material for the high-density isotropic carbon material of the present invention is pulverized to an appropriate particle size of 100 mesh or more using a pulverizer that causes attrition, such as a vibration mill, a vibrating ball mill, or a lightning crusher, and after pressure molding, coke powder After pressing it inside and firing it by raising the temperature to 1100℃ in a nitrogen atmosphere,
Graphite material can be obtained by heating to 2600℃ and graphitizing it. Since this graphite material does not use a binder, steps such as mixing with a binder, kneading, and re-grinding are unnecessary in the manufacturing process.

The obtained graphite material has high density without being impregnated because there are no pores caused by gas generation or contraction of the binder. Furthermore, it has many excellent features such as isotropy because it has a fine mosaic structure due to the addition of carbon black.

Example 1 25 parts by weight of carbon black (FEF) was added to 100 parts by weight of pulverized coal tar pitch that does not contain quinoline-insoluble matter and has a softening point of 85°C, and the mixture was sealed at high torque for 1 hour at 100°C. The mixture was kneaded using a two-screw kneader. The rotation speed of the kneader is 30 revolutions/min.

50g of the obtained sample was placed in a 30mmφ, 300mmL Pyrex test tube and heated under a reduced pressure of 2mmHg.
After heating from room temperature to 480°C at a temperature increase rate of 150°C/h, the material was immediately cooled in air to obtain a raw material for a carbon material of the present invention.

The weight loss of this product from room temperature to 1000°C on a thermobalance was 8.9wt%. This raw material is processed in a vibrating mill.
The material crushed to 100 meshes or less was placed in a 30 mmφ cylindrical mold, temporarily molded at a pressure of 50 kg/cm ² , and then molded using a rubber press at a pressure of 2 ton/cm ² . This is placed in coke powder and placed in a nitrogen atmosphere.
0.05℃/min up to 800℃, then 0.15 to 1100℃
The temperature was raised at a rate of °C/min for firing. Thereafter, the temperature was raised to 2600°C at a rate of 10°C/min in a Tamman furnace and maintained for 10 minutes to perform graphitization. The bulk density of graphitized products is
The weight was 1.82 g/cm ³ , the bending strength was 900 Kgf/cm ² , and the Shore hardness was 98.

Example 2 For 100 parts by weight of the same raw material pitch as Example 1,
Added 43 parts by weight of carbon black (FEF) to 190
The mixture was kneaded at ℃ for 1 hour using a high torque closed twin screw kneader. The rotation speed of the kneader is 30 revolutions/min. 100 g of the resulting sample was placed in a Pyrex test tube with a diameter of 30 mm and a length of 300 mm, and heat treated under the same conditions as in Example 1 to obtain a raw material for a carbon material of the present invention.
The weight loss of this product from room temperature to 1000°C on a thermobalance was 13 wt%. This raw material was pulverized, molded, fired, and graphitized under the same conditions as in Example 1.
The bulk density of graphitization is 1.77g/ ^cm3 and the bending strength is 900Kg.
f/cm ² and Shore hardness of 99.

Comparative Example 1 For 100 parts by weight of the same raw material pitch as in Example 1,
Add 25 parts by weight of carbon black (FEF) to 100
The mixture was kneaded at ℃ for 1 hour using a high torque closed twin screw kneader. The rotation speed of the kneader is 30 revolutions/min. 100g of the resulting sample was placed in a 30mmφ, 300mmL Pyrex test tube, heated from room temperature to 410°C at a temperature increase rate of 150°C/hr under a reduced pressure of 2mmHg, and immediately cooled in air. .

The powder was crushed, molded, and fired under the same conditions as in Example 1. The fired product was foamed and deformed and could not maintain its original shape.

Comparative Example 2 For 100 parts by weight of the same raw material pitch as in Example 1,
Add 25 parts by weight of carbon black (FEF) to 100
The mixture was kneaded at ℃ for 1 hour using a high torque closed twin screw kneader. The rotation speed of the kneader is 30 revolutions/min. 100 g of the obtained sample was placed in a 30 mmφ, 300 mm L test tube, heated from room temperature to 570° C. at a temperature increase rate of 150° C./hr under a reduced pressure of 3 mmHg, and then immediately allowed to cool in air. The weight loss of this product from room temperature to 1000°C on a thermobalance was 4wt%.

Grinding, molding, and firing graphitization were performed under the same conditions as in Example 1. The graphitized product had a bulk density of 1.62 g/cm ³ , a bending strength of 70 Kgf/cm ² and a Shore hardness of 55. Since the bulk density and bending strength values were low, it was unsuitable as a high-density isotropic carbon material.

Comparative Example 3 67 parts by weight of raw coke powder (average particle size 2.9 μm) was added to 100 parts by weight of the same raw material pitch as in Example 1, and 160 parts by weight was added.
The mixture was kneaded at ℃ for 1 hour using a high-torque closed twin-screw kneader. The rotation speed of the kneader is 30 revolutions/min. 50g of the resulting sample was placed in a 30mmφ, 300mmL test tube, heated from room temperature to 470°C at a temperature increase rate of 150°C/hr under reduced pressure of 4mmHg, and then immediately allowed to cool in air. 1000 from room temperature on a thermobalance for this thing
The weight loss to ℃ was 15wt%.

Grinding, molding, firing, and graphitization were performed under the same conditions as in Example 1. The bulk density of the graphitized product is 1.83g/ ^cm3 ,
The bending strength was 650 kgf/cm ² and the show hardness was 74.

As can be seen by comparing Examples 1 and 2 with Comparative Example 3, the graphite material made from the sample prepared by adding carbon black to the raw material pitch is different from the graphite material made from the sample prepared by adding other carbon powder such as coke powder. It has higher strength than graphite material made from. Generally, the higher the bulk density, the higher the strength, so it is necessary to compare the strength of materials with the same bulk density. Example 1 has a bulk density of 1.82 g/cm ³ , and Comparative Example 3 has a bulk density of 1.83 g/cm ³
Although they have almost the same bulk density, the material of Example 1 containing carbon black is 250Kgf/cm ² higher than the material of Comparative Example 3, which is overwhelmingly superior in terms of strength required for high-density materials. Has good value.

Effects of the Invention According to the present invention, carbon black is added to the raw material pitch and then heat-treated at a pressure below normal pressure, which is a simple method, and without going through a complicated and costly process such as solvent extraction. , it is possible to obtain a self-sintering raw material powder.

When this is further molded, fired, and graphitized, an isotropic high-density graphite material with a fine mosaic structure is obtained, which is an excellent material that exhibits much higher strength than materials prepared using carbon powder other than carbon black. Since it has dots, it can be applied to graphite materials for various purposes.

Furthermore, since the structure is fine, it is possible to process articles with more complex shapes than conventional products.

Claims (1)

[Claims] 1 Pituchi that does not substantially contain quinoline insoluble matter
Add and mix 10 to 100 parts by weight of carbon black to 100 parts by weight, and heat to 420°C to 560°C at a pressure below normal pressure.
By heating to and distilling off low boiling point substances,
A raw material for high-density isotropic carbon material whose volatile content is adjusted so that the weight loss is 5 to 25% by weight when the temperature is raised from room temperature to 1000°C as measured with a thermobalance. Manufacturing method.