JPS61251504A - Production of formed graphite - Google Patents

Abstract

PURPOSE:Graphite powder and tar containing meso-phase pitch precursor are heat-treated by a specific method to give formed graphite of high strength, high-rate carbonization, high dimensional stability and high conductivity through a simplified process in no need of preliminary roasting. CONSTITUTION:(1) Graphite powder is suspended in the tar fraction containing meso-phase pitch precursor. (2) The suspension is heat treated at 350-550 deg.C, as an inert gas such as N2 or Ar is passed through or under reduced pressure such as 10-100mmHg, to give a complex of graphite and meso-phase pitch. Then, (3) the resultant complex is crushed, without preliminary roasting and subjected to compression molding using a graphite mold under vacuum or in an inert gas atmosphere at 800-3,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a black stone compact made of graphite powder and mesophase pitch.

[Prior art]

In general, when producing carbon materials such as graphite electrodes, aggregates such as coke, which do not have viscosity by themselves and cannot be pressed into compacts as they are, are added to the aggregate ioo weight part. A widely used method is to add 30 to 40 parts by weight of pitch as a binder, and to perform the steps of cross-wiring, molding, and firing. However, in this case, a slow temperature increase rate of about 1°C/hr is required in the 300-600°C range where the binder pitch melts and carbonizes, and the pitch carbonization yield is as low as 50-60%. There are problems such as a large amount of pores are generated in the material, and re-impregnation with binder pitch and secondary firing are required to impart density.

In order to solve these problems, various improvement methods have been proposed. For example, Japanese Patent Laid-Open No. 52-2421) describes an improved technique for mixing aggregate and binder pitch.

The publication states that carbonaceous or graphite powder is mixed with pitch, this mixture is heated at 350 to 450°C, and the mesophase produced from the pitch is added to 1 part by weight of carbonaceous or graphite. A method for producing a carbonaceous molded body, which comprises separating the carbonaceous or graphite powder and mesophase from the pitch, press-molding the pitch, and firing the pitch. Or, during heat treatment of the pitches, the carbonaceous or graphite material and mesophase obtained after the heat treatment so that almost the entire amount of the pitches transfers to mesophase are crushed, and then pressure molded and fired as they are. A method for manufacturing a carbon molded body made of carbon or graphite to which menphase is attached is disclosed.

The method has the following characteristics: (i) Since the mesophase adheres around the additive, there is no need for a crosstalk step.

(1)) Menphase has a high carbonization yield and does not pass through a softening medium during carbonization, so a temperature increase rate of 100° C./hr or more can be achieved.

(iiD) Since the mesophase generated in the pitch penetrates into the small gaps in the carbonaceous material and graphite material, the porosity of the carbonaceous material and graphite material itself does not affect the carbonized compact.

etc. are listed.

In addition, in Japanese Patent Publication No. 58-39770, carbonaceous aggregate,
Filtering all or part of the liquid medium soluble content from a slurry consisting of bituminous material and liquid medium to separate solid matter,
A method for producing a carbonaceous molded body is disclosed, which comprises heat-treating the solid material after pressure molding. The aggregates used are various types of coke, natural graphite, artificial graphite, carbon black, carbon fiber, etc., and preferably contain at least half of the powder that passes through a 200 micron sieve. The bituminous material used as a binder is coal tar, coal tar pitch, petroleum pitch, asphalt, and mixtures thereof.In the present invention, these bituminous materials are converted into so-called γ-resin (quinoline resin) by physical and chemical methods. It is characterized by using a product from which all or a part of the benzene soluble content has been removed.

Conventionally, it was difficult to spread the binder pitch sufficiently over the surface of the carbonaceous fine powder, so even if fine powder was blended to obtain a dense and strong product, it was not possible to obtain a homogeneous molded product. Using this method, it is easier to uniformly disperse the effective adhesive components in the bituminous material into the fine powder. When using ultrafine powder such as carbon black, the conventional method required a separate process to spread the viscous component over the surface of the carbon black, whereas the method of the present invention allows for simultaneous immersion. There are advantages such as Also, conventionally 3 to 6
This process, which takes several months, can be shortened to 7 to 10 days by using this method, which also allows direct graphitization, and the harmful dust and mist generated in conventional processes such as kneading, cooling, and secondary grinding can be removed using organic media. It has also been shown that the work environment can be maintained in a good condition because it can be dissolved and removed.

In addition, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 52-2421),
Graphite powder and quinoline dissolved content is 70% by weight or less, mesophase content is 40% or more, upper limit of heating melting temperature is 400℃
, and a mesophase-containing pitch powder having a carbonization yield of at least 70% at 1000° C., the resulting powder is pressure-molded to obtain a green body, and the green body is further placed in an inert atmosphere. To produce a molded body which is characterized by being fired at 700°C or higher and has a volume resistivity of 5 inertia Ω or less, a bending strength of 2GQA9/ad or more, a volume change before and after firing of 3% or less, and a weight change of 3% or less. proposed a method (patent application 1983)
-199737).

Furthermore, the present inventors aimed to solve the problem of the long process to obtain mesophase-containing pitch powder, which remained in the above method. (1) Graphitic carbon, carbonaceous carbon, inorganic compounds, metals, and metal compounds. A step of suspending one or more materials selected from the following in a tar fraction containing a mesophase pitch precursor.

(2) The suspension system is heated, the light fraction contained in the tar fraction is distilled off by blowing inert gas or vacuum suction, and the mesophase pitch precursor is heat-treated at 350 to 500°C. A step of obtaining a carbonaceous precursor in which mesophase-containing pitch containing 5 to 90% of quinoline dissolved matter is produced on the surface of the material.

(3) A step of molding the carbonaceous precursor into a formed body containing metsuphase-containing pitch.

(4) A step of subjecting the formed body to a carbonization or graphitization reaction in an inert atmosphere to contain carbon or graphite derived from the mesophase-containing pitch.

We propose a method for manufacturing carbon-based composite molded bodies that consists of the following four steps. (Japanese Patent Application No. 59-255270) Furthermore, for the production of carbon-based composite molded bodies made of graphitic carbon and carbonaceous or graphite derived from mesophase pitch, a wider range of mesophase pitch raw materials and heat treatment conditions are used. (1) A step of suspending graphite powder in a tar fraction containing a mesophase pitch precursor.

(2) A step of heat-treating the suspension system at 350 to 550° C. while blowing an inert gas or under reduced pressure to obtain a carbonaceous precursor in which Men7Aze pitch is formed on graphite particles.

(3) A step of press-molding the carbonaceous precursor at 400 to 800°C to form a formed body.

(4) A step of carbonizing or graphitizing the formed body under an inert atmosphere.

We propose a method for producing graphite molded bodies that consists of the following four steps. (Patent Application No. 60-63329) [Problems to be Solved by the Invention] The method described in Japanese Patent Application Laid-Open No. 52-2421 is to separate a large amount of pitch with an organic solvent such as quinoline after the formation of buds + 7 azes. The example discloses that the separated mesophase and coke must be washed with benzene and acetone and then subjected to a vacuum drying process, which is a complicated process that replaces the crosstalk process. A processing step is required.

On the other hand, it is clear that new problems arise in the process, such as the need for the process of recovering the ginseng described in Japanese Patent Publication No. 58-39770.

The method previously proposed by the inventors in Japanese Patent Application No. 59-255270 has a shorter process process than the method in Japanese Patent Application No. 59-199737, and also uses graphite powder suitable as the filler material. By using graphite and selecting an appropriate pitch ratio to graphite, it has characteristics such as high conductivity and small shrinkage during disasters, similar to that obtained by the method of patent application No. 1@59-199737. Although it is possible to obtain a graphite molded body with
However, there were still some complications in terms of limitations on the amount of quinoline dissolved in mesophase pitch.

The method proposed by the present inventors in Japanese Patent Application No. 60-63329 eliminates the above-mentioned complexity and makes it possible to use a wide range of met phase pitches and heat treatment conditions. However, since four steps are required, it has been desired to further shorten the steps and improve the performance of the resulting molded product.

[Means for solving problems]

(Objective of the Invention) The object of the present invention is to form nine graphite particles with excellent strength, rapid carbonization, dimensional stability, and high conductivity by a simpler method from tar containing graphite powder and mesophase precursor. Our goal is to provide methods for preparing the body.

(Structure of the Invention) As a result of intensive studies to achieve this objective, the inventors of the present invention have found that the present inventors have obtained a method of l\l application No. 1) i0-63329 from graphite powder and tar containing a mesophase precursor. Graphite-Mesophase Bite mixed powder does not require pre-firing and can be directly pressure-molded (hot-pressed) at 800°C or higher to produce a high-strength, dense graphite compact without cracking. I found that it gives The molded body obtained by the method of the present invention is disclosed in Japanese Patent Application No. 60-63329.
In addition to having strength and conductivity that are equal to or higher than those of the method in issue 2, it also has excellent gas impermeability. Furthermore, even when molding is performed using a mold material with an uneven surface, cracks do not occur, making it possible to produce molded products with complex shapes. That is, the present invention is a step of suspending L graphite powder in a tar fraction containing a mesophase pitch precursor.

2. A step of obtaining a carbonaceous precursor in which mesophase pitch is produced on graphite particles by heat treatment at 350 to 550° C. while blowing an inert gas into the nuclear suspension system or under reduced pressure.

λ A step of press-molding the carbonaceous precursor at 800 to 3000°C.

This is a method for producing a graphite molded body consisting of.

(Detailed Description of the Invention) (1) Step of suspending graphite powder in tar fraction As the graphite powder, scale-like natural graphite, earth-like natural graphite, artificial graphite, etc. can be used. Furthermore, in order to make the method of the present invention effective, it is necessary to use graphite powder that can be formed into a compact by pressure molding at room temperature (for example, CPB and A S P-1000 (trade name) manufactured by Nippon Graphite Industries, Ltd., or manufactured by LONZA Co., Ltd.). Made by KS
-2,5 (m product name)) is preferably used.

There is no need to limit the type of tar fraction used as a raw material for mesophase pitch, and a wide range of coal-based, petroleum-based, etc. can be used. However, if contamination of heavy metals, sulfur, etc. into the final compact is to be avoided, ethylene heavy end tar obtained by naphtha decomposition is preferable to coal tar or petroleum heavy component tar. In addition, if necessary, add an appropriate solvent! ! ! It is also possible to facilitate clouding.

The amount of tar fraction relative to graphite powder varies depending on the tar composition, and the amount of mesophase pitch generated on graphite powder is 3 to 150 parts by weight per 100 parts by weight of graphite.
Preferably, the amount is selected from 5 to 50 parts by weight.

(2) Mesophase generation process on the surface of the material A slurry consisting of graphite powder and tar fraction is heated at 350 to 550°C.
Preferably, mesophase pitch is generated on the graphite surface by heat treatment at 400 to 500°C. On this occasion,
The slurry is heated to the reaction temperature under a flow of an inert gas such as nitrogen gas, carbon dioxide gas, or argon, or under a reduced pressure of, for example, 10 to 100 mklsz, maintained for a predetermined period of time, and then cooled.
A composite of graphite and mesophase pitch is obtained.

Since the heat treatment is carried out under an inert gas flow or under reduced pressure, the light fraction in the tar is distilled off, and only the menphase precursor with a relatively uniform composition is converted into menphase, and the mesophase produced is comparatively homogeneous and sticky,
Moreover, the carbonization yield is high. A more homogeneous mesophase can be obtained by carrying out the heat treatment while supplying a hydrogen donor, but this is not necessary. The quinoline soluble content in mesophase pitch is suitably 40% or less.

Note that if the heat treatment temperature is lower than 350°C, it will take a long time to form the mesophase, and if it is higher than 550°C, the adhesive component will be significantly reduced, which is not preferable.

(3) Molding process of carbonaceous precursor The composite of graphite and mesophase pitch obtained by heat treatment is crushed and heated to 800°C or higher, preferably 900°C, using a graphite mold or the like under vacuum or an inert gas atmosphere.
A graphite molded body can be obtained by hot press molding at a temperature of ℃ or higher. Other carbon precursors cannot be hot-pressed directly, and a method of pre-firing has been taken.

(Carbon Materials Society 1st) Annual Meeting Proceedings $p, 146 (198
4)) On the other hand, the graphite-mesophase pitch composite of the present invention does not require pre-firing and does not produce cracks not only when the pressed surface is smooth but also when it has irregularities. Further, direct hot press molding is possible without fusion, which is a major feature of the method of the present invention.

The obtained molded product has excellent strength and conductivity, and is also gas-impermeable. These characteristics range from 800 to 150
This is achieved by molding at 0°C, but temperatures up to 3000°C can be used depending on further desired properties. The heating rate to reach the predetermined temperature can be 150-3000° C./hour, and the pressure can be 50-2000 d/eIi (gauge).

(Features and Application Examples of the Method of the Present Invention) According to the method of the present invention, (1) a molded article having a complex shape can be obtained by direct hot press molding without requiring preliminary firing. In addition, (2) the obtained molded product has excellent strength and conductivity, and is also gas-impermeable.

The graphite molded body obtained by the method of the present invention can be used for various bipolar plates including gas separation plates for fuel cells, graphite electrodes for electrolysis, graphite lubrication and ports, jigs for semiconductor manufacturing, etc. .

[Embodiments of the invention]

The content of the present invention will be explained in more detail below with reference to Examples.

Example 1 Scaled graphite (
Nippon Graphite Industries ■, trade name CP B) 23.62 was charged into a reactor equipped with an inner cylinder with an internal volume of 250 d to prevent the distillate from refluxing into the pitch. A slurry was formed by adding 75.7 f of naphtha decomposition residue tar (boiling point 170° C. or higher when converted to normal pressure). The reactor was immersed in a molten salt bath previously maintained at 475° C. while supplying argon at 1.7 t per minute (STP) to the bottom of the inner cylinder of the reactor. After 16 minutes, the reaction temperature reached 473°C, which was held for 15 minutes, and then cooled to obtain a natural graphite-mesophase pitch composite containing 24.3% by weight of mesophase pitch.

The quinoline solubility of mesophase pitch contained in the complex was determined by the JIS-2425 centrifugation method to be 92.0%.

After crushing the 4t composite material, it was packed into a graphite mold with an inner diameter of about 50m, and heated to
1) The temperature was raised to 00°C in 05 minutes and held for 5 minutes. 5
After cooling down to 00°C, the pressure was released and the mixture was cooled to room temperature to obtain a graphite molded body. The molded body has a diameter of 50.2 m and a thickness of 1.
0 ■, bulk density 1.96, volume resistivity in the plane direction by four-probe method 0.8 mΩ・, bending strength 588#/cl
It was i. In addition, a nitrogen pressure of 1 kf/cd (gauge) was applied to the 8.6 cd range of the molded body at room temperature, and gas permeation to the opposite side was observed for 10 minutes using a soap flow meter, but gas permeation was very small. I couldn't.

Example 2-5 In an experiment similar to Example 1, a graphite molded body was obtained in the same manner except that the amounts of graphite scales and naphtha decomposition residue tar, heat treatment temperature and time were changed, and the other conditions were the same. However, in Example 2, quinoline was added to the raw materials for heat treatment, and in Examples 2 and 3, the amount of mixed powder charged into the graphite mold was approximately 6 f. In addition, in Example 5, the hot press temperature was 1050°C.
And so.

The conditions and results obtained are shown in Table 1.

Example 6-9 Grooves with a triangular cross section (base 1.5 m, height 1.5 m) were inserted at intervals of 1.5 m on the bottom of the graphite-shaped sample filling part used in the experiment of Example 1-5. Graphite plates having a diameter of 50 cm and a thickness of 5 particles were charged, each of which was filled with about 8 pieces of the graphite-mesophase pitch mixed powder obtained in Examples 1-4, and hot press molded under the same conditions. As a result, in all experiments, a graphite molded body having protrusions with a triangular cross section was obtained without cracking, and could be easily separated from the graphite plate.

Table 1

Claims (1)

[Claims] A method for producing a carbon-based composite molded body made of graphite carbon and carbon or graphite derived from mesophase pitch, comprising: (1) suspending graphite powder in a tar fraction containing a mesophase pitch precursor; (2) A step of heat-treating the suspension system at 350 to 550° C. while blowing an inert gas or under reduced pressure to obtain a carbonaceous precursor in which mesophase pitch is produced on graphite particles. 3) A method for producing a graphite molded body, comprising the following three steps: 3) Pressure molding the carbonaceous precursor at 800 to 3000°C.