JPS61251505A - Production of formed graphite - Google Patents

Abstract

PURPOSE:Formed graphite of high strength, high-rate carbonization, high dimensional stability, high conductivity is obtained from graphite powder and tar containing meso-phase precursor through a simplified process. CONSTITUTION:The objective formed graphite is obtained by (a) suspending graphite powder in a tar fraction containing meso-phase pitch precursor, (2) heat-treating the suspension at 350-550 deg.C as an inert gas such as N2 or Ar gas is passed through the suspension, or under reduced pressure such as 10-100mmHg to form meso-phase pitch on the graphite particles, (3) effecting compression molding of the carbon precursor at 400-800 deg.C and (4) carbonizing or graphitizing the formed product in an inert atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a graphite molded body comprising graphite powder and mesophase pitch.

[Conventional technology]

Generally, when manufacturing carbon materials such as graphite electrodes, a mixture of coke and other aggregates, which do not have viscosity by themselves and cannot be made into a press-molded product, is added to 100 parts by weight of the aggregate. A widely used method is to add 30 to 4 Qxt parts of pitch as a binder, and then go through the steps of kneading, molding, and firing. However, in this case, a slow heating rate of about IC/hr is necessary in the temperature range of 300 to 600°C where the binder pitch melts and carbonizes, and since the pitch carbonization yield is as low as 50 to 601°C, a large amount of There are problems such as the formation of pores and the need for re-impregnation with binder pitch and secondary firing in order to impart density.

In order to solve these problems, various improvement methods have been proposed. For example, Japanese Patent Application Laid-Open No. 52-24211 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 as it is, and firing the mesophase. , or during heat treatment of the pitches, the carbonaceous or graphitic material and mesophase obtained after the heat treatment so that almost the entire amount of the pitches transfers to menphase are pulverized, pressure-formed as they are, and fired. A method for producing a carbon molded body made of carbon or graphite to which mesophase is attached is disclosed.

The method has the following characteristics: (i) Menphase adheres to the periphery of the additive, so no kneading step is required.

(11) Menphase has a high carbonization yield, does not pass through a softened and molten state during carbonization, and can achieve a heating rate of 100° C./hr or more.

(i) Since the mesophase generated in the pitch penetrates into small gaps in the carbon, graphite, and graphite, the porosity of the carbon and graphite 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 this 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 materials used as binders include 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 with all or a part of the benzene soluble content removed.

Because it is difficult to spread the binder pitch sufficiently over the surface of the carbonaceous fine powder, it has not been possible to obtain a homogeneous molded product even if fine powder is blended in order to obtain a dense and strong product. Compared to conventional methods, this method makes it easier to uniformly disperse the effective caking 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, but the method of the invention allows for simultaneous immersion, etc. There are advantages. Also, conventionally 3 to 6
The process that used to take several months can be shortened to 7 to 10 days by using this method, which 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. 52-24211,
Among the graphite substances that are said to be unable to form compacted bodies as they are, we focused on the fact that some graphite substances can be formed into compact bodies by pressurization.
Pressure molding of a powder obtained by mixing a mesophase-containing pitch powder with a mesophase content of 404 or more, a heating melting temperature upper limit of 400°C, and a carbonization yield of at least 700 parts by weight at 100OC. to obtain a green body, and further sinter the green body at 700°C or higher in an inert atmosphere. In the following, we will propose and discuss a method for producing a molded article with a weight change of 3 mm or less (Japanese Patent Application No. 59-199737).

Furthermore, in order to solve the problem of the long process to obtain the layered mesophase-containing pitch powder left behind in the above method, the present inventors have developed the following methods: (1) graphitic carbon, carbonaceous carbon, inorganic compounds, metals; and a step of suspending one or more materials selected from metal compounds in a tar fraction containing a mesophase pitch precursor, (2) heating the suspension system to contain the mesophase pitch precursor in the tar fraction; The mesophase pitch precursor is heat-treated at 350 to 500°C to produce menphase-containing pitch containing 5 to 90 quinoline solubles. a step of obtaining a carbonaceous precursor formed on the surface of the material; (3) a step of molding the carbonaceous precursor into a formed body containing mesophase-containing pitch; (4) a step of forming the formed body into a carbonaceous body in an inert atmosphere The present invention proposes a method for manufacturing a carbon-based composite molded body, which comprises four steps: a step of subjecting the pitch to a carbonization or graphitization reaction to contain carbon or graphite derived from the menphase-containing pitch. (fF Application No. 59-255270) [Problems to be Solved by the Invention] The method described in JP-A-52-24211 requires a step of separating a large amount of pitch with an organic solvent such as quinoline after mesophase formation. The example discloses that the separated mesophase and coke must be washed with benzene and acetone and then subjected to a vacuum drying process, and from a process perspective, a complicated treatment process is required in place of the crosstalk process. It is.

On the other hand, in the method described in Japanese Patent Publication No. 58-39770,
It is clear that new problems arise in the process, such as the need for organic solvents such as benzene and toluene, which are 20 to 50 times more expensive than aggregates, and the need for a recovery process for γ-resin. be.

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 appropriate graphite powder as a filler. By selecting an appropriate ratio of pitch to graphite, graphite molding with characteristics such as high conductivity and low shrinkage during carbonization, similar to that obtained by the method of Japanese Patent Application No. 199737/1984. You can get a body. However, in this method, the quinoline soluble content in the mesophase-containing pitch needs to be in the range of 5 to 90, preferably 20 to 704. In many cases, it is necessary to modify the material in advance through processing, etc., leaving room for process shortening.

[Means for solving problems]

(Objective of the Invention) The object of the present invention is to produce high-strength 14i from tar containing graphite powder and mesophase precursor by a simpler method.
Another object of the present invention is to provide a method for producing a graphite molded body that is excellent in high-speed carbonization, dimensional stability, and high electrical conductivity.

(Structure of the Invention) As a result of intensive studies to achieve this objective, the present inventors have found that graphite powder is prepared from tar containing a mesophase precursor by the method of Japanese Patent Application No. 59-255270 under inert gas blowing or The black smoke-mesophase pitch mixed powder obtained by heat treatment under reduced pressure does not generate cracks that are observed with other carbon precursors even when pressure molded at 400 to 800°C, and is a dense carbon material. It has been found that a molded body can be obtained. In addition, when using such a molding temperature, it is not necessary to limit the quinoline soluble content in the mesophase pitch to 5 to 90%, and graphite with excellent properties can be used even when the quinoline soluble content is 54% or less. We produced molded objects and discovered scales. Therefore, a wider range of raw materials and reaction conditions can be used, making it possible to further simplify the process. for example,
When using naphtha decomposition residue as a raw material, in conventional methods it was desired to reform it by hydrogen treatment in advance, but in the method of the present invention, this is no longer necessary, and the heat treatment conditions can be applied in a wider range. That became 'oJ Noh.

That is, the present invention provides the following steps: 1. Suspending graphite powder in a tar fraction containing a mesophase pitch precursor; 2. Suspending graphite powder at 350 to 550°C while blowing an inert gas into the suspension system or under reduced pressure. obtaining a carbonaceous precursor in which mesophase pitch is produced on graphite particles by heat treatment; 3. Pressure molding the carbonaceous precursor at 400 to 800°C;
This is a method for producing a graphite molded body, comprising the steps of: forming a green body; 4. carbonizing or graphitizing the green body in an inert atmosphere.

(Detailed Description of the Invention) (1) Step of suspending graphite powder in tar fraction As the graphite powder, for example, scaly natural graphite, earthy 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 vine graphite powder (for example, Nippon Graphite Industries ■) gCPB and ASP-1000 (trade name) or LONzA #KS to form a compact by pressure molding at room temperature. -2,5 (trade name)) is preferred, and there is no need to limit the type of tar fraction used as the raw material for h0 meso7Azebitsch, and a wide range of coal-based, petroleum-based, etc. can be used. Furthermore, since there is no need to limit the characteristics of the mesophase pitch produced, it is possible to omit the step of previously modifying the tar fraction by hydrogen treatment or the like. 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. t#1, if necessary, it is also possible to add a suitable solvent to facilitate suspension.

The amount of tar fraction relative to graphite powder varies depending on the tar composition, and the amount of mesophase pitch formed on graphite powder is 3 to 30' Ooz per 100 parts by weight of graphite.
Selected to be in the t section. However, if volume shrinkage during carbonization is to be kept small, the amount is selected to be 3 to 50]ii1 part, preferably 5 to 40 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 the flow of an inert gas such as nitrogen gas, carbon dioxide gas, or argon, or under a reduced pressure of, for example, 1O to 100 ynmHf, and after being maintained for a predetermined time, it is cooled to form a composite of graphite and mesophase pitch. get.

Since it is not necessary to strictly control the amount of quinoline soluble in the mesophase pitch, it is possible to use a wide range of conditions, and it is also possible to omit the injection of a compound having hydrogen donating ability. In this case, since the heat treatment is performed 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 uniform specific composition is converted into mesophase. The generated mesophase is relatively homogeneous, highly sticky, and has a high carbonization yield. The quinoline soluble content in mesophase pitch varies depending on the raw material and heat treatment conditions, but is usually 0.
~ 50 people. The soluble amount of quinoline was measured by JIS-2425 centrifugation method.

Further, 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 step of carbonaceous precursor In the composite of graphite and mesophase pitch obtained by heat treatment, the quinoline soluble content in the mesophase may be smaller than 54 depending on the type of mesophase precursor and heat treatment conditions. In this case, there was a problem that a dense carbon molded body could not be obtained at a molding temperature lower than 400°C. On the other hand, if pressure molding is performed at a temperature of 400 to 800°C, a dense carbon composite can be obtained from such a composite.

Until now, when heat forming other carbon precursors, 50°
It was believed that at temperatures above 600°C or above, cracks would occur and a firm molded product could not be obtained. (Proceedings of the 11th Annual Meeting of the Carbon Materials Science Society, P146 (19841)) On the other hand, in the case of the graphite-mesophase pitch composite of the present invention, a dense carbonaceous material can be obtained without cracking. This shows the characteristics of the raw material composite of the present invention.

In addition, when the mesophase pitch ratio of the graphite-mesophase pitch composite is high, when molding is performed at a temperature lower than 400 tl, there is a problem that blistering occurs in the subsequent carbonization process, making it impossible to obtain a satisfactory molded product. .

On the other hand, this problem is also solved in molding at 400'C or higher, preferably 550C or higher.

Furthermore, even if a dense molded body can be obtained by molding at a temperature lower than 400° C., a higher performance carbon molded body can be obtained by increasing the molding temperature. In addition, 8
It is difficult to use metal molds at molding temperatures higher than 00℃.
Well, it is not suitable because it requires special equipment.

Pressure molding can be carried out according to a conventional method.

The pressure is preferably in the range of 10 to aooo oh/ca (gauge), and more preferably in the range of 100 to 2000 Kf/ctd (gauge). In addition, when using a mold such as the 5UCH mold, which has a larger coefficient of thermal expansion than the molded product, in order to prevent cracks from occurring due to stress during cooling, measures must be taken to release the stress, such as adjusting the dimensions of the outer part of the mold. It is desirable to apply

(4) Carbonization/graphitization step of molded body The formed body obtained by the method of the present invention is heated in an inert atmosphere at a temperature of 4151 to 1500°C/hour, preferably for a temperature time of 10 to 150°C, preferably at least SOO°C. can be made into a graphite-carbon composite molded body by heating to 900°C or higher. Furthermore, if necessary, 5 to 100℃ up to about 3000℃
Graphitization can be achieved by heating at a heating rate of /hour.

(Features and application examples of the method of the present invention) By the method of the present invention, ■ carbon molding with improved characteristics is achieved without cracking even at molding temperatures that are considered to cause cracks in molding other carbon precursors. You get a body. (2) Since there is no need to limit the quinoline-soluble content of meso-7Aze pitch, a wide range of raw materials and preparation conditions can be used, and pretreatment of tar is also omitted, resulting in a shortened process. ■Even when the mesophase pitch ratio is high, a dense compact can be obtained without carving during carbonization.

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

[Embodiments of the invention]

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

Example 1 Scale-like graphite (
Nippon Graphite Kogyo ■, trade name CP B) 30.02 was charged into a reactor equipped with an inner cylinder with a immersion capacity of 250 d to prevent the distillate from flowing back into the pitch. A slurry was formed by adding 39.6 f of naphtha decomposition residue tar (boiling point of 170° C. or higher when converted to normal pressure) and 12.1 f of quinoline. Argon is supplied to the bottom of the reactor inner cylinder at a rate of 1.7 per minute.
The reactor was immersed in a molten salt bath previously maintained at 455° C. while supplying sl (STP). After 18 minutes, the reaction temperature was 450℃.
After reaching the temperature, the mixture was held for 30 minutes and cooled to obtain a natural graphite-mesophase pitch mixed powder that contained 10.4 weight meso7Aze pitches. The quinoline dissolved content of mesophase pitch contained in the mixed powder was determined by JIS-2425 centrifugation method to be 96.0'1.

1.7 tons of the mixed powder is placed in a vertical 63.5 ton machine with a stress release mechanism.
Fill a 1111% SO8 mold with a width of 12.7 m, 1.
4 while applying a pressure of s TON/di (gauge).
The temperature was raised to 20°C and held for 5 minutes. After the temperature was lowered to 2 sO'ct, the pressure was released and the mixture was cooled to room temperature to obtain a formed product. The resulting green body was heated to 1000° C. at a rate of 5° C./min in an argon stream in a carbonization furnace, held for 30 minutes, and then cooled to room temperature to obtain a graphite green body. The molded body has a length of 6
It is 3.9 m long, 12.9 m wide, 1.11 m thick, with a smooth surface, a volumetric shrinkage rate of 0.7% based on the formed shape, a weight loss rate of 1.2%, and a lengthwise measurement using the four-terminal method. Volume resistivity 0
．． It had a wet resistance of 8 mΩ and a bending strength of 400 Kp/-.

Example 2 Natural graphite-memphazine pitch mixed powder obtained in the same manner as in Example 17. Of was placed in a SUS mourning mold with a diameter of 50.1 l, -il, and 50.3 mm equipped with a stress release mechanism, and heated to 650 °C while applying a pressure of 0.4 TON/i (gauge). Warm and hold for 1 minute.

After the temperature was lowered to SOO°C, the pressure was released and the mixture was cooled to room temperature to obtain a formed body. The formed body was carbonized in the same manner as in Example 1 to obtain a graphite shaped body. The diameter of the molded body is 50.3ttm
It has a smooth surface with a thickness of 1.7+a, a volume shrinkage rate of 1.54 based on the formed shape, a weight loss rate of 1.3 壬, a volume resistivity in the plane direction of 0.8 mΩ by the four-terminal method, and a bending strength of 400 kg. /,-,i.

Examples 3 to 5 In an experiment similar to Example 2, heat treatment was performed by changing the amount of graphite scale and naphtha decomposition residue tar, heat treatment temperature, and time without adding quinoline, and a graphite molded body was prepared in the same manner as above. I got it. The conditions and results obtained are shown in Table 1.

(Leaving space below) Table 1 Patent Applicant Mitsubishi Oil & Chemical Co., Ltd. Agent Patent Attorney Hidetoshi Furukawa Agent Patent Attorney Masahisa Hase Procedural Amendment (Voluntary) May 1985 98 1. Indication of the Case 1985 Patent Application No. 63329 2 Name of the invention Process for producing a graphite molded body 3 Relationship with the case of the person making the amendment Patent applicant address 2-5-2 Marunouchi, Chiyoda-ku, Tokyo Name (
605) Mitsubishi Yuka Co., Ltd. 4, Agent 7, amend the statement of contents of the amendment as follows.

(1) Page 16, line 1 "5~b /hour”.

that's all

Claims (1)

[Scope of Claims] A method for producing a carbon-based composite molded body made of carbon or graphite derived from graphitic carbon and 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) Pressure molding the carbonaceous precursor at 400 to 800°C to obtain a green body; (4) Carbonizing or graphitizing the green body in an inert atmosphere. A method for producing a graphite molded body characterized by: