JP2005187249A - High-purity, high-crystallinity carbonized product and artificial graphite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a high-purity, high-crystallinity carbonized product and artificial graphite which are used as raw materials for preparing a high-quality carbon material and graphite material. <P>SOLUTION: The high-purity, high-crystallinity carbonized product is obtained by heat-treating raw material mesophase pitch at ≥500°C, wherein the raw material mesophase pitch is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride. The high-purity, high-crystallinity artificial graphite is obtained by graphitizing the carbonized product at ≥1,900°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to high purity and high crystallinity carbonized materials and artificial graphite used as raw materials for various carbon products and graphite products.

Impurities originating from the raw materials are contained in the carbon material and the graphite material. Current carbonized products (coke) and artificial graphite used as an aggregate (filler) or additive for carbon materials and graphite materials are derived from the by-products of the coal industry and petroleum refining, and therefore contain many impurities and have low chemical purity. Natural graphite is superior in crystallinity to artificial graphite, but contains many impurities such as metal. These impurities are often inconvenient when using carbon materials or graphite materials. The impurities in question vary depending on the use form of the material, but are often not preferable because they volatilize and leave structural defects, or remain and impair the function. For this reason, special treatment for high purity is required depending on the product application and grade (see, for example, Patent Documents 1 and 2). Such a complicated process for removing impurities is a factor in prolonging the production time and increasing the cost, and there is a demand for inexpensive carbonized materials and artificial graphite having high purity and high crystallinity.
Japanese Patent Laid-Open No. 2-83205 JP 2000-7313 JP

  An object of the present invention is to provide inexpensively high-purity and high-crystallinity carbonized materials and artificial graphite used as raw materials for carbon materials and graphite materials.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a synthetic mesophase pitch obtained by catalytic polymerization of a condensed polycyclic hydrocarbon monomer is a high-purity carbonized product with high carbonization yield and excellent crystallinity, and The inventors have found that artificial graphite can be stably provided with good reproducibility and have led to the present invention.

  That is, the present invention provides a raw material mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride, by heat treatment at a temperature of 500 ° C. or higher. The obtained carbonized product, which has an ash content of less than 200 ppm and has an interlayer distance d002 of less than 0.337 nm determined by X-ray diffraction when the carbonized product is graphitized at 3000 ° C. and the carbonized product It is artificial graphite obtained by graphitizing a compound at a temperature of 1900 ° C. or higher.

  According to the present invention, highly pure and highly crystalline carbonized materials and artificial graphite useful as raw materials for high-quality carbon products and graphite products can be obtained efficiently.

  The mesophase pitch (optically anisotropic pitch) used as a raw material for the carbonized material and artificial graphite in the present invention is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride. It was obtained. This synthetic mesophase pitch is composed of naphthalene, monomethylnaphthalene, dimethylnaphthalene, anthracene, phenanthrene, acenaphthene, pyrene, and the like, as shown in Japanese Patent No. 2931593, Japanese Patent No. 2612253, or Japanese Patent No. 2526585 It is obtained by polymerizing polycyclic hydrocarbons and mixtures thereof or substances containing them. The mesophase pitch used as a raw material for the carbonized material and artificial graphite in the present invention is preferably a mesophase pitch obtained by polymerizing naphthalene. In this polymerization reaction, 0.1 to 20 mol of hydrogen fluoride and 0.05 to 1.0 mol of boron trifluoride are used as a polymerization catalyst with respect to 1 mol of pitch raw material, and the temperature is 100 to 400 ° C. This is done by reacting for a minute. After completion of the polymerization reaction, the catalyst is separated, and further light components are removed. The synthetic mesophase pitch obtained in this way is extremely excellent in chemical purity, graphitization and quality stability.

The raw material mesophase pitch used in the present invention is that the pitch is embedded in a resin, and when the optical structure is observed under a polarizing microscope after polishing by a conventional method, the content of the optically anisotropic phase portion is 50% or more. It is a certain pitch. The pitch has a softening point of 200 ° C. or higher and a carbonization yield of 70% or higher.
The carbonization yield mentioned here is the yield when the mesophase pitch is heated at 5 ° C./min in an inert gas atmosphere and held for 2 hours after reaching 600 ° C.

  A carbonized product is produced by heat-treating the mesophase pitch at a temperature of 500 ° C. or higher. The heat treatment method is not particularly limited. It may be a normal pressure heat treatment under standing or stirring, or a heat treatment under pressure. For example, the heat-resistant container is charged with this mixture and heat-treated in a furnace in a nitrogen atmosphere. A conveyor type continuous heat treatment furnace or the like can also be used. From the viewpoint of productivity, the following continuous heat treatment is desirable. That is, a granular or powdered carbonized product that has been heat-treated in advance is placed in a reaction vessel maintained at a temperature of 500 ° C. or higher in an inert atmosphere, and the raw material mesophase pitch is left as it is or in a molten state with stirring. By adding it, a granular or powdered carbonized product is produced.

  In this method, the added raw material pitch first becomes a low-viscosity liquid by heating, and is dispersed on the surface of a granular or powdery pitch heat treatment (hereinafter referred to as a return medium) previously prepared. Thereafter, the polymerization by heat proceeds to finally change to an infusible carbonized product. Since the return medium is always kept in a fluid state by stirring, the gas generated by the reaction of the pitch is quickly discharged out of the system, and does not cause any significant melting and foaming as in the case of heat treatment by standing. Compared with the heat treatment in, the reactor can be continuously and efficiently carbonized in a much smaller reactor volume. Further, the pitch is dispersed on the surface of the return medium, polymerization proceeds, and solidifies while receiving shear due to the flow of the return medium, so that the optical structure of the heat-treated product obtained has a mosaic shape.

  As the return medium charged in the reactor in advance, a heat-treated product with a flow structure manufactured by a stationary method or the like must be used at first.However, as the reaction continues, almost a new heat-treated product with a mosaic structure is used. Completely substituted and the final carbonized product is systematically homogeneous.

  In the case of heat treatment using a return medium, the reactor is a vertical reactor equipped with a stirrer that can sufficiently stir the granular or powder pitch heat-treated product, and a cylindrical type equipped with a stirrable paddle Or a rotary kiln can be used. When a vertical reactor is used, for example, a reactor installed with a rotating shaft of a stirring blade inclined as described in JP-A-7-286181 can be used.

  The obtained carbonized product is pulverized as necessary. If necessary, the particle size may be adjusted by classification. For the pulverizer, an optimum model is appropriately selected from an impact pulverizer, a jet mill, a micro atomizer, and the like. As for the classifier, an optimum model is appropriately selected from a mechanical classifier, a wind classifier, and the like, and is not particularly limited.

The ash content of the carbonized product obtained by the heat treatment as described above is less than 200 ppm, preferably less than 100 ppm. The ash content in the present invention is measured as follows. A high-purity alumina crucible is placed in an electric furnace, heated at 700 ° C. for 10 minutes, allowed to cool to room temperature in a desiccator, and the mass is measured to the order of 0.1 mg. Thereafter, the carbide sample to be measured in the crucible is weighed to the order of 0.1 mg so that the mass M becomes 40 g. The crucible is put in an electric furnace and heated in an oxygen atmosphere at 700 ° C. for 48 hours, and then allowed to cool to room temperature in a desiccator, and the mass m of ash is measured to the order of 0.1 mg. Ash content A is calculated by the following equation.
A = m / M × 100
A: Ash content (mass%) m: Mass of ash (g) M: Sampling amount (g)

  The carbonized product has a lattice spacing d002 determined by X-ray diffraction when graphitized at a temperature of 3000 ° C. of less than 0.3370 nm, preferably 0.3365 nm or less. The X-ray measurement in the present invention is performed as follows. Carbonized product 0.5g and silicon powder 0.05g are mixed well in a mortar to make a measurement sample. Scan angle: 10-35 ° (2θ, CuKα), scan speed 1 ° with X-ray diffractometer Science Geigerflex. / Min, X-ray applied voltage and current are measured at 30 kV and 20 mA, respectively. The lattice spacing d002 is analyzed based on the Gakushin method.

  The carbonized product can be used as artificial graphite having a high chemical purity and a high graphitization degree by graphitizing at a temperature of 1900 ° C. or higher.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples.

Example 1
78 mol of commercially available naphthalene (manufactured by Adchemco, purity 95%), 31.2 mol of hydrogen fluoride (Morita Chemical, purity 99.9%) and boron trifluoride (manufactured by Stella Chemifa, purity 99.7%) ) 7.8 mol was charged into a 43 liter autoclave and reacted at 280 ° C. for 4 hours. Thereafter, the autoclave discharge valve was opened, and nitrogen was blown to remove substantially all of the hydrogen fluoride and boron trifluoride. Furthermore, a mesophase pitch (optical anisotropic phase content: 100%) having a softening point of 285 ° C. was obtained by performing a lighter treatment. 500 g of the mesophase pitch was put in a carbon container, heated to 600 ° C. at 10 ° C./min in a nitrogen atmosphere using an electric furnace, and kept at this temperature for 2 hours. When it was taken out after cooling to room temperature, the carbonization yield was 86%.

  As a result of ash content analysis of the carbonized product, it was 15 ppm. The carbonized product was graphitized at 3000 ° C. for 1 hour under an argon atmosphere, and then X-ray measurement was performed. The surface interval d002 was 0.3356 nm.

Example 2
The carbonized material obtained in Example 1 was coarsely pulverized to obtain a heat treatment product for return medium having an average particle size of about 0.5 mm. Next, 200 g of this heat-treated product was charged in advance in a vertical reactor equipped with a stirrer and having a diameter of 170 mm and a height of 170 mm as a return medium, and the temperature was raised to 550 ° C. under nitrogen flow while stirring. The mesophase pitch was added to the reactor at a rate of 10 g / min, and a total of 300 g was charged. After the completion of the charging, the reactor was kept at 550 ° C. for 10 minutes, and then the reactor was cooled and the contents were taken out. As a result, 400 g of granular carbonized product was obtained. The same operation was repeated 7 times to obtain a carbonized product having a substitution rate of about 99%.

  As a result of ash analysis of the carbonized product, it was 71 ppm. The carbonized product was graphitized at 3000 ° C. for 1 hour under an argon atmosphere, and then X-ray measurement was performed. The surface interval d002 was 0.3365 nm.

Comparative Example 1
Carbonized material was obtained by heat treatment under the same conditions as in Example 1 using a coal-based pitch (softening point 300 ° C.). The ash content of the carbonized product was 3%. Graphitization was performed under the same conditions as in Example 1 to obtain a graphitized product. The interplanar spacing d002 of the graphitized product was 0.3358 nm.

Comparative Example 2
A carbonized product was obtained by heat treatment under the same conditions as in Example 1 using petroleum pitch (softening point: 120 ° C.). The ash content of the carbonized product was 0.2%. Further, graphitization was performed under the same conditions as in Example 1 to obtain a graphitized product. The interplanar spacing d002 of the graphitized product was 0.3359 nm.

  The carbonized material and artificial graphite obtained by the present invention can be used as raw materials for various carbon materials and graphite materials. For example, it can be applied to bearings, sealing materials, motor brushes, machine-related members such as electric discharge machining electrodes, heat-insulating tubes, crystal growth tubes, semiconductor-related members such as heaters, and high-temperature furnace materials used in hot presses and metal heat treatment furnaces. . It is also useful as a raw material for carbon molded products and graphite molded products used in high-tech fields such as nuclear power, nuclear fusion, and aerospace. Furthermore, it is also useful as an additive modifier to the resin.

Claims (4)

  A carbonized product obtained by heat-treating a raw material mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride at a temperature of 500 ° C. or higher. A carbonized product having an ash content of less than 200 ppm and an interplanar spacing d002 of less than 0.3370 nm determined by X-ray diffraction when the carbonized product is graphitized at a temperature of 3000 ° C.   The carbonized product according to claim 1, wherein the raw material mesophase pitch is obtained by polymerizing naphthalene.   Artificial graphite obtained by graphitizing the carbonized material according to claim 1 at a temperature of 1900 ° C or higher.   2. The carbon according to claim 1, which is obtained by charging granulated or powdered carbonized material that has been heat-treated in advance into a heat treatment container and adding raw material mesophase pitch under stirring when performing carbonization. monster.