JP3599062B2 - Method for producing carbon material having fine optically anisotropic structure - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for producing a carbon material having a fine optically anisotropic structure. More specifically, the present invention relates to a method for producing a high-density carbon material or a carbon composite material having a structure in which optically anisotropic units at a submicron level are developed randomly.
[0002]
[Prior art]
In recent years, the demand for improved performance of specialty carbon materials and carbon composite materials has become increasingly strong, and controlling the structure and organization of carbon determines the physicochemical properties of products and further enhances their performance. It is extremely important in realizing it.
In the specialty carbon materials field, in addition to increasing the density and strength of products, the shape and size of the raw material powders are controlled to achieve a fine mosaic by controlling the shape and size of the raw material powder. There is a lot of research and development going on.
[0003]
As a method for achieving such isotropic physical properties, for example, a method using mesocarbon microbeads as a raw material, that is, an optical anisotropy generated in a process of heat-treating coal tar or petroleum heavy oil, etc. There is known a method in which small spheres are separated from a pitch matrix by a solvent, dried, pressed, and then fired. However, in such a method, it is pointed out in Japanese Patent Application Laid-Open No. 1-239058 that the texture size of the obtained carbon material does not become smaller than the grain size of meso-spherulite (10 to 20 μm), and further refinement cannot be performed. .
Also, in the method using a bulk mesophase pulverized product described in Japanese Patent Publication No. 1-58124, it has been found that the anisotropic size of the bulk mesophase does not develop finely below the pulverized particle size. No. 239058.
[0004]
On the other hand, many attempts have been made to modify the raw material powder into a fine mosaic structure in advance. For example, Japanese Patent Publication No. 58-58284 discloses a method in which semi-coke having a mosaic structure composed of extremely fine units of 1 μm or less is used as a raw material for molding. However, this method requires complicated steps such as solvent extraction and separation of raw coal in the presence of hydrogen gas, followed by further heat treatment of the extract.
[0005]
Japanese Patent Publication No. 3-64448 describes a method of adding carbon black to a pitch. Japanese Patent Application Laid-Open No. 1-239058 discloses a method of blending a resin with a pitch, followed by pulverization, molding and firing without using a binder. Thus, a method for producing an isotropic graphite material having a homogeneous mosaic structure is described. However, such a method also requires complicated steps such as mixing, kneading, and re-grinding. Further, the obtained carbon material has a low bulk density, and satisfactory performance has not always been obtained.
[0006]
In the field of carbon composite materials as well, the superiority of matrix carbon having a fine mosaic structure with respect to the development of excellent thermal shock resistance and high mechanical strength is demonstrated by International Symposium on Carbon; Toyohashi, Extended Abstract, p. 196 (1982), and the pitch / phenol resin system is described in "Carbon" vol. 28, p. 559 (1990), for a pitch / carbon black system, see “Carbon” vol. 28, p. 143 (1990) and the like, extensive research has been conducted on the interaction and carbonization.
[0007]
[Problems to be solved by the invention]
Control of carbon structure is a very important factor for high performance and homogenization of products. However, the conventional method has various disadvantages as described above.
An object of the present invention is to provide a method for producing a high-performance carbon material having a fine optically anisotropic structure from a specific mesophase pitch at low cost and stably by an extremely simple method.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and consequently found that a mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of superstrong hydrogen oxyfluoride / boron trifluoride. In the process of forming a carbon material by forming a self-fusing carbonaceous powder prepared by heat-treating or oxidizing, then firing and, if necessary, graphitizing, the carbonization initial process of the molded body It has been found that the optical structure of the obtained carbon material can be modified into a uniform fine mosaic structure by controlling the heating rate in the above, and the present invention has been achieved.
[0009]
That is, the present invention is prepared by heat-treating a mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride / boron trifluoride in a non-oxidizing atmosphere. Self-fusing carbonaceous powder containing 0.5 to 1.5% by weight of a component soluble in quinoline and insoluble in pyridine and 97% by weight or more of a component insoluble in quinoline, Self-fusing carbon prepared by oxidizing under an atmosphere, containing 5.0 to 20.0% by weight of a component soluble in pyridine and insoluble in benzene and 78% by weight or more of a component insoluble in pyridine. This is a method for producing a carbon material having a fine optically anisotropic structure, characterized by firing a powder at 400 ° C. to 600 ° C. at a heating rate of 20 ° C./h or less after molding.
[0010]
The precursor of the self-fusing carbonaceous powder used in the present invention is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride / boron trifluoride which is a super strong acid. The resulting mesophase pitch. As described in JP-A-63-146920, JP-A-1-139621 and JP-A-1-254796, condensed polycyclic rings such as naphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene, and pyrene are particularly preferred. It is obtained by polymerizing a hydrocarbon and a substance containing these in the presence of hydrogen fluoride / boron trifluoride which is a super strong acid catalyst.
The self-fusing carbonaceous powder used in the present invention is prepared from this synthetic mesophase pitch by two methods, that is, heat treatment or oxidation treatment of the mesophase pitch.
[0011]
First, in the case of heat treatment, the above-mentioned synthetic mesophase pitch is successively heat-treated in a non-oxidizing atmosphere, and then crushed to obtain a self-fusing carbonaceous powder. The heat treatment conditions are not particularly limited, but treatment conditions are selected such that the components soluble in quinoline and insoluble in pyridine are 0.5 to 1.5% by weight and the components insoluble in quinoline are 97% by weight or more. You. The heat treatment temperature is generally 470-490 ° C. The heat-modified pitch thus treated is in the form of powder. The powdering method, powder shape and particle size distribution are not particularly limited.
[0012]
In the case of the oxidation treatment, the above-mentioned synthetic mesophase pitch is continuously pulverized, and then the pitch powder is subjected to an oxidation treatment in an oxidizing atmosphere to obtain a self-bonding carbonaceous powder. The powdering method and powder shape are not particularly limited. Oxidation conditions take into account the properties and oxidation reactivity of the synthesized mesophase pitch, and the components of oxidized mesophase pitch powder that are soluble in pyridine and insoluble in benzene are 5.0 to 20.0% by weight, and It is important to appropriately select the components that are insoluble in pyridine to be at least 78% by weight. Generally, the oxidation treatment is performed at a temperature in the range of 170 to 350 ° C.
[0013]
The self-fusing carbonaceous powder obtained through these operations, that is, the heat-modified mesophase pitch powder or the oxidation-modified mesophase pitch powder is molded by pressure molding, preferably isotropic pressure molding. In this case, no binder is particularly required. The shape of the molded body can be freely selected depending on the purpose, application, and the like. The molding may be performed at room temperature or in a temperature range where the self-fusing carbonaceous powder softens or melts, and is determined according to the required shape, performance and cost.
[0014]
The molded body is subsequently fired to produce a carbon material. The firing step is performed by heating the molded body to a temperature of 600 to 1700 ° C. in a non-oxidizing atmosphere to carbonize. Further, if necessary, the carbide is graphitized at a higher temperature. Therefore, the present invention includes a carbon material obtained by heating a molded body to a temperature of 600 to 1700 ° C. and carbonizing, and a carbon material obtained by graphitizing at a higher temperature.
[0015]
In order to obtain a carbon material having a fine mosaic structure after firing, when firing the green molded body made of the self-fusing carbonaceous powder, the carbonization is performed at a temperature of 20 ° C / It is very important to apply a heating rate of not more than h, preferably 5 to 15 ° C./h.
By sintering in this way, even though the particles before sintering have a domain structure, after the sintering, a submicron-level optically anisotropic unit can be modified into a homogeneous fine mosaic structure randomly developed. Since the structure thus formed has a very small optical structure size, the generation and progress of cracks during the graphitization process can be prevented, and the carbon material can be further enhanced in performance and isotropic in various physical properties.
[0016]
If the temperature rise in the initial carbonization process from 400 ° C. to 600 ° C. is faster than 20 ° C./h when firing the green molded body, a fine mosaic structure is not formed, and most of the area of the molded body is before firing. A coarse and heterogeneous structure composed of anisotropic units having a particle diameter of about Further, graphitization further generates a large number of cracks, and a desired optical structure cannot be obtained.
[0017]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples. The magnifications of the optical structure photographs (FIGS. 1 to 4) showing the results of the examples and comparative examples are all the same.
[0018]
Example 1
7.0 mol of naphthalene, 2.4 mol of hydrogen fluoride, and 0.74 mol of boron trifluoride were charged into a 3 liter acid-resistant autoclave, and the temperature was raised to 290 ° C. while maintaining the reaction pressure at 25 kg / cm ² , followed by a reaction for 4 hours. I let it. Thereafter, the release valve of the autoclave was opened, and substantially all of hydrogen fluoride and boron trifluoride were recovered in gaseous form at normal pressure. Thereafter, a mesophase pitch from which low-boiling components were removed while blowing nitrogen was obtained. The pitch yield was 70% by weight (based on the raw material naphthalene). The obtained mesophase pitch had a softening point of 250 ° C., an optically anisotropic phase content of 100%, an H / C atomic ratio of 0.60, and a carbonization yield of 87% by weight.
[0019]
The temperature of the synthesized mesophase pitch was raised to 480 ° C. in a nitrogen atmosphere, and a heat treatment was performed at this temperature for 1 hour. The resulting heat-treated pitch contained 1.0 wt% of a component soluble in quinoline and insoluble in pyridine and 98.5 wt% of a component insoluble in quinoline. This heat treatment pitch was pulverized to obtain a powder having an average particle diameter of 7 μm, and then molded into a plate (35 mm × 40 mm × 10 mm) at a molding pressure of 1.5 tf / cm ² at room temperature. The green molded body was heated at a rate of 300 ° C./h from room temperature to 400 ° C. and at a rate of 12 ° C./h from 400 ° C. to 600 ° C. under nitrogen flow, and kept at 600 ° C. for 2 hours.
[0020]
The obtained carbide was polished after filling with a resin, and optical observation was performed. As a result, as shown in FIG. 1, the structure after carbonization was homogeneous, and had a fine-mosaic structure in which anisotropic units at the submicron level were developed at random. The bulk density of the carbides 1.35 g / cm ^3, compressive strength 15.6kgf / mm ^2, bending strength was 7.8kgf / mm ^2.
Further, this carbide was heated to 1900 ° C. at a rate of 300 ° C./h under a flow of argon, and maintained at this temperature for 2 hours to obtain a graphitized product. As shown in FIG. 2, the optical structure after the graphitization was further homogenized, and the miniaturization of the anisotropic size was further promoted. No crack formation was observed. The bulk density of this graphitized product was 2.04 g / cm ³ , the compressive strength was 25.7 kgf / mm ² , and the bending strength was 13.7 kgf / mm ² .
[0021]
Example 2
The same synthetic mesophase pitch as in Example 1 was pulverized to obtain a powder having an average particle diameter of 7 μm, and then subjected to an oxidation treatment at 220 ° C. for 2 hours under flowing air. This oxidized powder contained 11.0% by weight of a component soluble in pyridine and insoluble in benzene, and 88.5% by weight of a component insoluble in pyridine. This oxidized powder was molded and carbonized under the same conditions as in Example 1. The optical structure of the obtained carbide was the same as in Example 1, and showed a fine-mosaic structure in which anisotropic units at the submicron level were developed at random. The bulk density of the carbides 1.35 g / cm ^3, compressive strength 15.6kgf / mm ^2, bending strength was 7.8kgf / mm ^2.
The optical structures of the obtained carbides and graphitized products were the same as those in Example 1, and the miniaturization of the optical structure was further promoted, and no generation of cracks was observed. The bulk density of this graphitized product was 2.01 g / cm ³ , the compressive strength was 25.1 kgf / mm ² , and the bending strength was 13.9 kgf / mm ² .
[0022]
Comparative Example 1
The same thermally modified mesophase pitch powder as in Example 1 was molded under the same conditions as in Example 1. The green molded body was heated from room temperature to 600 ° C. at a rate of 300 ° C./h, and kept at 600 ° C. for 2 hours. As shown in FIG. 3, the optical structure of the carbide thus obtained was heterogeneous, had a large anisotropic size, and many regions retaining the pulverized particle size were observed. The bulk density of this carbide was 1.32 g / cm ³ , the compressive strength was 12.9 kgf / mm ² , and the bending strength was 6.0 kgf / mm ² .
Further, this carbide was heated to 1900 ° C. at a rate of 300 ° C./h under a flow of argon and maintained at this temperature for 2 hours to obtain a graphitized product. The optical structure after graphitization was heterogeneous as shown in FIG. Further, cracks were observed in a region having a relatively large optically anisotropic size. The bulk density of this graphitized product was 1.97 g / cm ³ , the compressive strength was 14.3 kgf / mm ² , and the bending strength was 5.9 kgf / mm ² .
[0023]
Comparative Example 2
The same oxidation-modified mesophase pitch powder as in Example 2 was molded under the same conditions as in Example 1. The obtained green molded body was heated from room temperature to 600 ° C. at a rate of 300 ° C./h, and kept at 600 ° C. for 2 hours. Further, this carbide was heated to 1900 ° C. at a rate of 300 ° C./h under a flow of argon and kept at this temperature for 2 hours.
The obtained carbide structure was heterogeneous as in Comparative Example 1, the structure size was large, and the particle size at the time of pulverization was maintained. The bulk density of this carbide was 1.31 g / cm ³ , the compressive strength was 12.7 kgf / mm ² , and the bending strength was 5.9 kgf / mm ² .
The optical structure of the graphitized material was also inhomogeneous, and crack formation was observed in a region having a relatively large anisotropic size as in Comparative Example 1. The bulk density of this graphitized product was 1.97 g / cm ³ , the compressive strength was 14.0 kgf / mm ² , and the bending strength was 5.7 kgf / mm ² .
[0024]
【The invention's effect】
As described above, the optical structure of the carbon material can be easily modified into a uniform fine mosaic structure by controlling the rate of temperature rise in the initial stage of carbonization of the molded article by the method of the present invention. As a result, the carbon material product is made mechanically isotropic, and contributes to the performance improvement of the carbon material product.
[Brief description of the drawings]
FIG. 1 is a photograph of an optical structure of a carbide obtained in Example 1.
FIG. 2 is an optical structure photograph of the graphitized product obtained in Example 1.
FIG. 3 is a photograph of an optical structure of a carbide obtained in Comparative Example 1.
FIG. 4 is an optical structure photograph of the graphitized product obtained in Comparative Example 1.

Claims (1)

It is prepared by heat-treating mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride / boron trifluoride in a non-oxidizing atmosphere. Self-fusing carbonaceous powder containing 0.5 to 1.5% by weight of a soluble pyridine-insoluble component and 97% by weight or more of a quinoline-insoluble component, or oxidizes the mesophase pitch in an oxidizing atmosphere. A self-fusing carbonaceous powder prepared by the treatment and containing 5.0 to 20.0% by weight of a component soluble in pyridine and insoluble in benzene and 78% by weight or more of a component insoluble in pyridine. And then calcining at a heating rate of 400 ° C. to 600 ° C. at a rate of 20 ° C./h or less. A method for producing a carbon material having a fine optically anisotropic structure.

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