JP3060449B2 - Raw material powder for high-density and high-strength carbon material and method for producing carbon material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous powder having a self-fusing property suitable for a high-density, high-strength carbon material and a method for producing the carbon material.

[0002]

2. Description of the Related Art Conventionally, many production methods have been known for high-density carbon materials. Generally, this is obtained by kneading an aggregate such as coke powder, natural graphite, and carbon black and a binder such as coal tar pitch, followed by molding and firing. In this method, since the residual carbon ratio of the binder is very low, the density of the molded body is extremely small in one carbonization, and the density must be increased by repeating the impregnation / carbonization process many times in order to increase the density. In addition, during the carbonization process, a large amount of light components in the binder are volatilized, so that heterogeneous pores remain inside the molded body, and the molded body is expanded to easily cause tissue destruction. In order to prevent such adverse effects, the carbonization step generally involves a very slow temperature increase of 2 to 10 ° C./h, so that a production period of 3 to 4 weeks is required. The molded body that has undergone this carbonization step is further graphitized at 2500 to 3000 ° C. depending on the application, but this step also generally requires a production period of 2 to 3 weeks. Therefore, this method of producing a graphitic carbon material through a complicated process from an aggregate such as coke and a binder such as coal tar pitch requires a long production period of two to three months.

On the other hand, there is known a method in which optically anisotropic small spheres are used as a raw material for a high-density carbon material that does not require a binder. That is, in this method, mesophase microbeads obtained by separating and drying mesophase spherulites generated in the process of heat-treating coal tar pitch or petroleum heavy oil at 350 to 500 ° C from a pitch matrix with a solvent are used as raw materials. This is a method of baking after pressure molding. However, this method requires an extremely large amount of extraction solvent in the spherulite separation step, and the solvent fractionation must be repeated many times. Further, since it is difficult to completely remove the residual solvent from the obtained spherulites, it tends to cause cracks and expansion of the molded body in the subsequent carbonization step. In addition, in such a spherulite solvent extraction method, in addition to extremely low separation yield, it is not easy to control the properties of the generated spherulites, and there is an industrial problem in stably producing raw materials of a constant quality. There are many.

Further, a method of using a bulk mesophase having a specific property as a carbon precursor has also been attempted (Japanese Patent Application Publication No. Hei.
1-58124). However, a carbon material produced from such a bulk mesophase pulverized material has a low bulk density and does not always provide satisfactory performance. In addition, this method requires a step of separating the bulk mesophase obtained as a result of the coalescence of the mesocarbon microbeads from the pitch matrix, and requires many complicated steps before being processed into a bulk mesophase having a predetermined property. There must be.

[0005]

Since the process for producing a high-density carbon material is extremely complicated as described above and requires a very long production period, the carbon material produced by the conventional method is expensive. And the field of use is greatly restricted. Therefore, it is a major challenge in the carbon industry to greatly simplify the manufacturing process of the high-density carbon material and shorten the manufacturing period. An object of the present invention is to provide an excellent raw material powder for a carbon material and a method for producing the carbon material, which can produce a high-density and high-strength carbon material in a short time and at low cost.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing a high-density carbon material having the above-mentioned problems, and as a result, have found that condensed polycyclic hydrocarbon or a substance containing the same is a super-strong acid. Heat composed of a specific range of quinoline-soluble / pyridine-insoluble components and a specific range of quinoline-insoluble components, prepared by heat-treating mesophase pitch obtained by polymerization in the presence of hydrogen hydride / boron trifluoride Since the modified pitch powder has excellent fusion property while maintaining shape stability in the carbonization process, it is necessary to add a binder by using such a thermally modified mesophase pitch powder as a raw material. Without
The present inventors have found that a high-density, high-strength carbon material can be stably obtained at a low cost in a short time, and have reached the present invention.

That is, the present invention relates to a method for producing 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 a non-oxidizing atmosphere. A raw material powder for a high-density and high-strength carbon material, which is prepared by heat treatment and contains quinoline-soluble and pyridine-insoluble components in an amount of 0.5 to 1.5% by weight and a quinoline-insoluble component in an amount of 97% by weight or more; This is a method for producing a carbon material, comprising firing a raw material powder after pressure molding.

[0008] The precursor of the raw material powder for high-density and high-strength carbon material of the present invention is obtained by preparing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride / boron trifluoride which is a super strong acid. It is a mesophase pitch obtained by polymerization. This mesophase pitch is disclosed in JP-A-63-146920,
No. 1-139621, as shown in JP-A-1-254796,
It is obtained by polymerizing condensed polycyclic hydrocarbons such as naphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene, and pyrene and substances containing these in the presence of hydrogen fluoride / boron trifluoride as a super strong acid catalyst.

Hydrogen fluoride forms a strong protonic acid by coexisting with boron trifluoride, and forms a complex with a condensed polycyclic hydrocarbon which is a base. The hydrogen fluoride also acts as a solvent, and the resulting complex dissolves in excess hydrogen fluoride to form a complex solution. The polymerization reaction proceeds very smoothly in this hydrogen fluoride solution under mild conditions. The hydrogen fluoride used in excess in this way plays an important role as a reaction solvent as well as a function as a catalyst.

In the method using superstrong hydrogen oxyfluoride / boron trifluoride as a polymerization catalyst, the reaction time and temperature, the molar ratio of condensed polycyclic hydrocarbon / hydrogen fluoride / boron trifluoride,
The properties of the generated mesophase pitch can be controlled by selecting the polymerization conditions such as the kind of the raw material. Usually, the polymerization reaction is allowed to proceed for several hours at 200 to 300 ° C. using naphthalene as a starting monomer. The boiling point of this catalyst is so low that it is completely separated from the product pitch, so that the mesophase pitch obtained has a very high purity.

Since this mesophase pitch is obtained by cationic polymerization almost without dehydrogenation, it has a characteristic structure having a high content of naphthene hydrogen and aliphatic hydrogen [“Carbon” No. 155, p. 370. (1992)]. Therefore, the mesophase pitch used in the present invention is a conventional coal-based or petroleum-based mesophase pitch, i.e., a mesophase pitch obtained through condensation polymerization by heat treatment of coal tar or petroleum residue by-produced in a coal or petrochemical process, It is structurally distinct from the bulk mesophase pitch described in Japanese Patent Publication No. 1-58124.

The raw material powder for a high-density carbon material of the present invention is produced by heat-treating the above mesophase pitch in a non-oxidizing atmosphere. The heat treatment conditions at this time are not particularly limited, but the heat treatment is generally performed at a temperature of 470 to 490 ° C. 0.5 components that are soluble in quinoline and insoluble in pyridine
To 1.5% by weight, preferably 0.7 to 1.3% by weight, and the quinoline-insoluble component is 97% by weight or more, preferably 98% by weight.
It is important to select such heat treatment conditions. The fractionation with pyridine is performed by Soxhlet extraction, and the fractionation with quinoline is JIS-K2425 (centrifugation method).
It is performed based on.

In the present invention, the mesophase pitch is dissolved in quinoline and insoluble in pyridine in an amount of 0.5 to 1.5% by weight.
% And a quinoline-insoluble component in an amount of 97% by weight or more to ensure excellent moldability and achieve high density and high strength without inducing cracking or expansion in the carbonization process. . In other words, by adjusting the quinoline-soluble / pyridine-insoluble component corresponding to the binder component in the thermally modified pitch and the quinoline-insoluble component that guarantees a high carbonization yield to this range by moderate heat treatment, the following raw material characteristics are exhibited. I do.

That is, since the raw material powder of the present invention has a proper particle deformability under normal-temperature pressurization, dense packing is achieved.
Excellent moldability can be obtained even at room temperature. This molded body has strength enough to withstand normal handling even before firing. In addition, since the raw material powder shows an appropriate melt fluidity while maintaining the shape of the molded body in the initial stage of carbonization of the molded body, the raw material particles are extremely strongly bonded to each other to form a fine-mosaic structure. , High density and high strength are achieved. Furthermore, this raw material powder contains quinoline-insoluble components.
Since it contains 97% by weight or more, the carbonization yield is extremely high, and almost no pores are generated by the volatile gas in the carbonization process. As a result, as shown in the examples, the fired body has a homogeneous and dense structure, and exhibits high density and high strength.

If the amount of the component soluble in quinoline equivalent to the binder component and insoluble in pyridine in the thermally modified pitch exceeds 1.5% by weight, the melt fluidity of the raw material particles in the initial stage of carbonization of the molded product becomes excessive. And a partial flow structure is exhibited, and a large number of cracks are generated during contraction at the late stage of carbonization. Further, when the amount of components soluble in quinoline and insoluble in pyridine is significantly increased, expansion of the molded body and eventually foaming are caused. In addition, the amount of components soluble in quinoline and insoluble in pyridine and the amount of components insoluble in quinoline change in conjunction, so if the amount of components soluble in quinoline and insoluble in pyridine exceeds 1.5% by weight, insoluble in quinoline Major components will be less than 97% by weight, and the carbonization yield will be reduced at the same time. Therefore, the amount of volatile gas also increases, and the number of pores in the fired body increases. As described above, in a system in which the component soluble in quinoline and insoluble in pyridine exceeds 1.5% by weight, the number of cracks and pores in the fired body increases, so that both the bulk density and the mechanical strength of the fired body decrease (Comparative Example). 1).

On the other hand, when the amount of the component soluble in quinoline and insoluble in pyridine is less than 0.5% by weight, the melt fluidity of the raw material particles becomes insufficient in the initial stage of carbonization of the molded product,
The bonding force between the raw material particles decreases. As a result, when individual particles shrink in the later stage of carbonization, a large number of voids are generated, and at the same time, cracks are likely to occur in particles having a relatively large optically anisotropic size. Therefore, since the fired body structure becomes heterogeneous with many voids and cracks, both the bulk density and the mechanical strength decrease (Comparative Example 2).

That is, the mesophase pitch is thermally reformed so that the components soluble in quinoline and insoluble in pyridine and the components insoluble in quinoline satisfy the above-mentioned ranges. Since the moldability can be secured and the carbonization yield can be further increased,
Only one firing can produce a high-density, high-strength carbon material having a homogeneous and dense structure.

In order to obtain a high-density, high-strength carbon material from the raw material powder of the present invention, first, the mesophase pitch heat-treated in this manner is formed into a powder. The powdering method and powder shape are not particularly limited. Although there is no particular limitation on the particle size distribution, a particle size distribution that maximizes the packing density during molding is preferable, and is usually 1 to 200 μm.
More preferably, it is used for molding with a powder of 1 to 20 μm.

Next, the thermally modified pitch powder is molded under pressure. This pressure molding is preferably performed by isotropic pressure molding,
At this time, no binder is particularly required. The shape of the molded body can be freely selected according to the purpose and use.
The molding may be performed at room temperature or in a temperature range where the thermally modified powder is softened or melted, which is determined according to the required shape, performance and cost.

The desired carbon material is manufactured by subsequently firing this molded body. 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 can be graphitized at a higher temperature.

[0021]

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

Example 1 7.0 mol of naphthalene, 3.7 mol of hydrogen fluoride and 1.05 mol of boron trifluoride were charged into a 3 liter acid-resistant autoclave, and heated to 265 ° C. while maintaining the reaction pressure at 27 kgf / cm ^2.
Allowed to react for hours. Next, the discharge 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 75% by weight (based on the raw material naphthalene).
The optical anisotropic phase content of this pitch is 100%,
The softening point was 240 ° C and the H / C atomic ratio was 0.65.

This synthetic mesophase pitch was heated to 480 ° C. at a rate of 300 ° C./h in a nitrogen atmosphere and subjected to a heat treatment at this temperature for 1 hour to obtain a uniform heat-treated pitch. This heat-treated pitch contains components that are soluble in quinoline and insoluble in pyridine.
It contained 1.3 wt% and 98.1 wt% of components insoluble in quinoline. This heat-treated pitch is pulverized with a ball mill to obtain an average particle size of 6
After forming into a μm powder, the mixture was molded into a plate (35 mm × 40 mm × 10 mm) at a molding pressure of 1.5 tf / cm ² at room temperature. The molded body was heated to 1200 ° C. under a flow of argon and kept at this temperature for 2 hours. The carbonization yield at this time was 93.2%. The carbonized product was fired at 2000 ° C for 2 hours to obtain a graphitized product.
Table 1 shows the physical properties of the carbonized and graphitized products thus obtained.
Shown in

Comparative Example 1 The same mesophase pitch as in Example 1 was used under a nitrogen atmosphere.
The temperature was raised to 465 ° C. at 00 ° C./h, and heat treatment was performed at this temperature for 1 hour to obtain a uniform heat treatment pitch. The pitch of this heat treatment is 1.8wt%, which is soluble in quinoline and insoluble in pyridine.
%, And 96.4 wt% of a component insoluble in quinoline. This heat treatment pitch was fired under the same conditions as in the example. In this comparative example, there were many components soluble in quinoline and insoluble in pyridine in the heat-treated pitch, so that a high-performance carbon material could not be obtained as shown in Table 1.

COMPARATIVE EXAMPLE 2 The same mesophase pitch as in the example was applied under a nitrogen atmosphere.
The temperature was raised to 500 ° C at a rate of ° C / h, and a heat treatment was performed at this temperature for 1 hour to obtain a uniform heat treatment pitch. This heat-treated pitch contains 0.1 wt% of a component that is soluble in quinoline and insoluble in pyridine.
It contained 99.8% by weight of a component insoluble in quinoline. This heat treatment pitch was fired in the same procedure as in the example. In this comparative example, a high-performance carbon material was not obtained as shown in Table 1 because there were few components soluble in quinoline and insoluble in pyridine in the heat-treated pitch.

[0026]

[Table 1]

[0027]

The raw material powder of the present invention has good particle deformability under normal-temperature pressurization, shape stability as a molded product, moderate melt fluidity in the initial stage of carbonization, and excellent carbonization and graphitization properties. , And with an extremely high carbonization yield, it is used as a primary raw material for high-density and high-strength carbon materials.
Demonstrates particularly excellent performance. In addition, the fired body structure derived from the mesophase pitch exhibits optical anisotropy and is dense, homogeneous, and high-purity, so that the carbon bond formed is very strong. Since the degree of graphitization of the carbon bond is improved by firing at a high temperature, and densification is further promoted by shrinkage, the carbon bond is further strengthened.
Further, since the raw material powder of the present invention produced by moderate thermal reforming of the mesophase pitch has self-fusing properties, a binder is unnecessary. Therefore, a high-density and high-strength carbon material can be easily produced in a short time and at low cost using the raw material powder of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-144812 (JP, A) JP-A-6-145669 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 31/02 C08G 61/00-61/10 C10C 3/02-3/04 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A heat treatment of a mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of super-strong hydrogen oxyfluoride / boron trifluoride in a non-oxidizing atmosphere. Raw material powder for high-density and high-strength carbon materials, characterized in that the raw material powder contains 0.5 to 1.5% by weight of a quinoline-soluble and pyridine-insoluble component and 97% by weight or more of a quinoline-insoluble component. 2. A mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of super-strong hydrogen oxyfluoride / boron trifluoride and heat-treating the same in a non-oxidizing atmosphere. A raw material powder containing 0.5 to 1.5% by weight of a quinoline-soluble and pyridine-insoluble component and 97% by weight or more of a quinoline-insoluble component prepared by the method described above, followed by calcining, followed by firing.