JPH07157548A - Starting powder for carbonaceous material of high density and high strength and production of carbonaceous material - Google Patents

Abstract

PURPOSE:To prepare a carbonaceous powder for producing carbonaceous material of high density and high strength which has good moldability, can be readily carbonized and graphitized with extremely increased carbonization yield and can be completely fired in a shortened time, attains sufficiently high density and high strength with only single firing in no need of any binder because of its excellent self-welding properties. CONSTITUTION:A condensed polycyclic hydrocarbon or a substance containing the same is polymerized in the presence of a superstrong acid (hydrogen fluoride)-boron trifluoride to prepare a meso-phase pitch. Then, the product is heat-treated in an oxidative atmosphere to give a starting powder for high- density and high strength carbon aceous material containing more than 78wt.% of the fraction insoluble in pyridine and 5.0 to 20.0wt.% of the fraction soluble in pyridine but insoluble in benzene. The powder is molded by compression and fired to give the objective carbonaceous material.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, many methods for producing a high-density carbon material are known, but these can be roughly classified into two methods from the viewpoint of starting raw materials. One of the methods is to knead aggregates such as coke powder, natural graphite, and carbon black with a binder such as coal tar pitch, and then mold and fire the mixture. In this method, since the residual carbon ratio of the binder is very low, the density of the molded body is very small in one carbonization, and in order to increase the density, the impregnation / carbonization process must be repeated many times to densify. Further, in the carbonization process, a large amount of the light component in the binder is volatilized, so that not only the heterogeneous pores remain in the inside of the molded body but also the molded body is likely to expand to cause tissue destruction. In order to prevent such adverse effects, the carbonization process is generally performed at 2-10 ° C.
A very slow temperature rise of / h is required, so a manufacturing 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 takes 2 to 3 weeks. Therefore, this method of producing graphitic carbon material from complex materials such as coke and binder such as coal tar pitch through a complicated process requires a long time of 2 to 3 months.

Another method is to use optically anisotropic small spheres as a raw material for a high-density carbon material without using a binder. That is, mesocarbon microbeads obtained by separating mesophase spherulites generated in the process of heat treatment of coal tar pitch or heavy petroleum oil at 350 to 500 ° C from the pitch matrix with a solvent and drying it are used as raw materials. Is a method of firing after pressure molding.
However, this method requires an extremely large amount of extraction solvent in the spherulite separation step, and solvent separation must be repeated many times. Furthermore, since it is difficult to completely remove the residual solvent from the obtained spherulite, it tends to cause cracking or expansion of the molded body in the subsequent carbonization step. Moreover, in such a spherulite solvent extraction method, the separation yield is extremely low, and it is not easy to control the properties of the spherulites formed, and it is industrially problematic to stably produce raw materials of constant quality. There are many.

Further, a method utilizing a bulk mesophase having a specific property as a carbon precursor has also been attempted (Japanese Patent Publication No.
1-58124). However, the carbon material produced by using such a pulverized material of bulk mesophase as a raw material has a low bulk density, so that satisfactory performance is not always obtained. In addition, this method requires a step of separating the bulk mesophase obtained as a result of coalescence aggregation of mesocarbon microbeads from the pitch matrix, and many complicated steps are required until the bulk mesophase having a predetermined property is processed. There must be.

[0005]

The process for producing a high-density carbon material is extremely complicated as described above, and requires a very long production period. Therefore, the carbon material produced by the conventional method is expensive. However, the field of use is severely restricted. Therefore, greatly simplifying the manufacturing process of the high-density carbon material and shortening the manufacturing period are major problems in the carbon industry. 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] As a result of diligent studies on the method for producing a high-density carbon material having the above-mentioned problems, the present inventors have found that condensed polycyclic rings are present in the presence of superhydrofluoric acid fluoride / boron trifluoride. A modified compound consisting of a benzene-insoluble component and a benzene-insoluble component in a specific range obtained by oxidizing mesophase pitch obtained by polymerizing a hydrocarbon or a substance containing the same. The fine pitch powder shows excellent moldability, has excellent fusion property while maintaining the shape stability in the carbonization process, and the appropriate oxidation treatment according to the properties of the mesophase pitch is Since it further improves and retains excellent carbonization and graphitization properties, by using a modified mesophase pitch powder by such oxidation as a raw material,
The present inventors have found that a high-density and high-strength carbon material can be obtained stably at low cost in a short time without the need to add a binder, and the present invention has been completed.

That is, the present invention oxidizes mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the condensed polycyclic hydrocarbon in the presence of super strong hydrogen fluoride / boron trifluoride in an oxidizing atmosphere. 5.0 to 2% of pyridine-soluble and benzene-insoluble components prepared by the treatment.
0.0% by weight, 78% by weight or more of a component insoluble in pyridine, and a raw material powder for high-density carbon material, and a carbon material characterized by being pressure-molded and then fired. Is a manufacturing method of. The details of the present invention will be described below.

The precursor of the raw material powder for high density carbon material of the present invention is prepared 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. It is the mesophase pitch obtained as a result. This mesophase pitch is disclosed in JP-A-63-146920 and JP-A-1-1396.
No. 21, as disclosed in JP-A 1-254796, naphthalene, anthracene, phenanthrene, acenaphthene,
Condensed polycyclic hydrocarbons such as acenaphthylene and pyrene and substances containing them are treated with hydrogen fluoride, which is a super strong acid catalyst.
Obtained by polymerizing in the presence of boron trifluoride.

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 produced complex is dissolved in excess hydrogen fluoride to form a complex solution. The polymerization reaction proceeds extremely smoothly in this hydrogen fluoride solution under mild conditions. The hydrogen fluoride used in excess as described above plays an important function as a reaction solvent together with the function as a catalyst.

Further, in the method of using super strong hydrogen fluoride / boron trifluoride as a polymerization catalyst, the reaction time and temperature, the molar ratio of condensed polycyclic hydrocarbon / hydrogen fluoride / boron trifluoride of the raw material, the raw material species, etc. The properties of the generated mesophase pitch can be controlled by selecting the polymerization conditions. Usually, naphthalene is used as a raw material monomer and the polymerization reaction is allowed to proceed at 200 to 300 ° C for several hours. Since the boiling point of this catalyst is extremely low, it is completely separated from the produced pitch, and thus the obtained mesophase pitch shows extremely high purity.

Since this mesophase pitch can be obtained by cationic polymerization with almost no dehydrogenation, it has a characteristic structure with a high content of naphthene hydrogen and aliphatic hydrogen ["Carbon" 155, p.370. (1992)]. Therefore, the mesophase pitch used in the present invention is a conventional coal-based or petroleum-based mesophase pitch, that is, a mesophase pitch obtained through condensation polymerization by heat treatment of coal tar or petroleum residue produced as a by-product in a coal / petrochemical process, It is structurally distinct from the bulk mesophase described in Japanese Patent Publication No. 1-58124, and has new excellent properties not found in conventional mesophase pitches.

As the precursor pitch for producing the raw material powder for high density carbon material of the present invention, mesophase pitch having a carbonization yield of 70% by weight or more, preferably 80% by weight or more is suitably used. The carbonization yield is a value when the pitch powder is gradually heated in an inert atmosphere and reaches 600 ° C and is held for 2 hours. When a pitch with a low carbonization yield is used, voids are easily generated by volatile gas in the carbonization process of the molded body, which causes a decrease in the density of the obtained carbon material, its mechanical strength, thermal conductivity, and electrical conductivity. , It has a bad effect on corrosion resistance.

The precursor pitch has a softening point of 170 ° C. or higher by a flow tester, and the optically anisotropic phase observed by a polarization microscope is at least 70 vol% or higher, preferably 80 vol% or higher, and more preferably substantially. A mesophase pitch of 100 vol% is suitably used. Soxhlet extraction is used to separate the raw material powder for a high-density carbon material of the present invention with pyridine and benzene.

In order to produce the raw material powder for high density carbon material of the present invention, first, the above mesophase pitch is pulverized. The powdering method and the powder shape are not particularly limited.
The particle size distribution is also not particularly limited, but a particle size distribution that maximizes the packing density during molding is preferable. Generally, it is oxidized in a powder state of 1 to 200 μm, preferably 1 to 20 μm.

Next, the mesophase pitch powder is subjected to oxidation treatment under air circulation or under oxygen circulation. The oxidizing conditions at this time are 5.0 to 20.0% by weight of benzene-insoluble components soluble in pyridine of the oxidized mesophase pitch powder, with due consideration of the properties and oxidation reactivity of the precursor mesophase pitch. And the pyridine-insoluble component is 78
It is important to select appropriately so that the amount is not less than weight%. That is, by preparing a mesophase pitch powder in which the amount of pyridine-soluble and benzene-insoluble components and the amount of pyridine-soluble components satisfy the above range,
Excellent self-bonding property is provided, and high density and high strength are achieved without inducing cracking or expansion in the subsequent carbonization step.

The conditions for such an oxidation treatment are not particularly limited, but generally 170-350 in industrial practice.
C., preferably 210 to 300.degree. At 350 ° C or higher, it becomes difficult to control the oxygen absorption amount because the oxidation reaction proceeds extremely fast. Further, depending on the properties of the mesophase pitch, if the oxidation temperature is too high, the mesophase particles may be wholly or partially fused to each other, resulting in a marked decrease in operability. On the other hand, below 170 ℃, the oxidation reaction is extremely slow and not practical.

As described above, the pyridine-soluble-benzene-insoluble component corresponding to the binder component in the modified pitch is in the range of 5.0 to 20.0% by weight by the appropriate oxidation treatment in consideration of the properties of the raw material mesophase pitch and the reactivity with oxygen. To
And 78% by weight of pyridine-insoluble component that guarantees high carbonization yield
By adjusting the above, the following excellent raw material characteristics are exhibited. That is, since the raw material powder of the present invention has good particle deformability under pressure, close packing is achieved and excellent moldability is obtained even at room temperature. This molded body has sufficient strength to withstand ordinary handling even before firing. Further, since the raw material powder of the present invention exhibits 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 bonded very firmly to each other, resulting in an extremely fine mosaic. The structure is formed and high density and high strength are achieved. Further, since the raw material powder of the present invention contains 78% by weight or more of the pyridine-insoluble component, the carbonization yield is extremely high, and pores due to volatile gas are hardly generated during the carbonization process. As a result, the fired body has a uniform and dense structure, and a high-density and high-strength carbon material can be obtained as seen in the examples.

If the content of pyridine, which is equivalent to the binder component in the modified pitch, and that is insoluble in benzene exceeds 20.0% by weight, the melt fluidity of the raw material particles becomes excessive during the initial carbonization process of the molded body. Since it partially shows a flow structure, a large number of cracks are generated during contraction in the latter part of carbonization. Further, when the amount of a component soluble in pyridine but insoluble in benzene significantly increases, expansion and foaming of the molded body occur (Comparative Example 1). Also, since the amount of pyridine-soluble and benzene-insoluble components and that of pyridine-insoluble components change in tandem, the amount of pyridine-soluble and benzene-insoluble components is 20.0%.
78% by weight of pyridine-insoluble components when the content exceeds 50%
%, And the carbonization yield also decreases at the same time. Therefore, the amount of volatile gas also increases, and the number of pores in the fired body also increases. Therefore, in a system in which the content of pyridine-soluble and benzene-insoluble components exceeds 20.0% by weight, both the number of cracks and the number of pores in the fired body increase, and the bulk density and mechanical strength of the fired body decrease (Comparative Example 2).

On the other hand, when the content of pyridine-soluble and benzene-insoluble components is less than 5.0% by weight, the melt flowability of the raw material particles becomes insufficient in the initial stage of carbonization of the molded body,
The binding force between the raw material particles is reduced. As a result, a large number of voids are generated when the individual particles shrink in the latter stage of carbonization, and at the same time, cracks are likely to occur in the particles having a relatively large optically anisotropic size. Therefore, the structure of the fired body becomes inhomogeneous with many voids and cracks, and both bulk density and mechanical strength decrease (Comparative Example 3).

As described above, by oxidizing and modifying the mesophase pitch so that the pyridine-soluble and benzene-insoluble components and the pyridine-insoluble component satisfy the claims of the present invention, High self-bonding property and moldability can be ensured, and the carbonization yield can be further increased. Therefore, a high density that has a homogeneous and dense structure with only one firing without complicated and costly steps.・ Can manufacture high-strength carbon materials.

In order to produce a high-density and high-strength carbon material from the raw material powder of the present invention, first, the mesophase pitch powder thus appropriately oxidized is pressure-molded. This pressure molding is preferably isotropic pressure molding,
No binder is needed. The shape of the molded body can be freely selected according to the purpose, application and the like. The molding may be carried out at room temperature or in a temperature range where the oxidation-modified powder softens or melts, which is determined according to the required shape, performance and cost.

The molded body thus obtained is subsequently fired to produce a desired carbon material. The firing step is performed by heating the molded body to a temperature of 600 to 1700 ° C. and carbonizing it in a non-oxidizing atmosphere. If necessary,
This carbide can also be graphitized at higher temperatures.

[0023]

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

Example 1 7.0 mol of naphthalene, 3.4 mol of hydrogen fluoride, and 1.06 mol of boron trifluoride were charged into a 3 liter acid-resistant autoclave, and the temperature was raised to 265 ° C. while maintaining the reaction pressure at 25 kgf / cm ² 4
Reacted for hours. Next, the discharge valve of the autoclave was opened, and under atmospheric pressure, substantially all amounts of hydrogen fluoride and boron trifluoride were recovered in a gaseous state. Then, a mesophase pitch from which light components were removed while blowing nitrogen was obtained. The pitch yield was 79% by weight (based on raw material naphthalene). The optically anisotropic phase content of this mesophase pitch is 100%, the softening point is 235 ° C, the H / C atomic ratio is 0.66, and the carbonization yield is
It was 83% by weight. The solubility of this mesophase pitch is 18.0% by weight of pyridine-soluble-benzene-insoluble component,
The pyridine-insoluble component was 42.0% by weight.

The obtained mesophase pitch was pulverized with a ball mill to obtain a powder having an average particle size of 7 μm, and the mesophase pitch powder was oxidized at 220 ° C. for 2 hours under air flow to obtain a uniform oxidized powder. Obtained. This oxidised powder contains 13.1% by weight of pyridine soluble and benzene insoluble components.
%, And 85.9% by weight of a component insoluble in pyridine.
The oxidation-treated powder was molded into a plate shape (35 mm × 40 mm × 10 mm) at a molding pressure of 1.5 tf / cm ² at room temperature. This molded body was heated to 1000 ° C under argon flow and held for 2 hours. Further, this carbonized product was fired at 2000 ° C. for 2 hours to obtain a graphitized product.
Table 1 shows the physical properties of the carbonized products and graphitized products thus obtained.
Shown in.

Example 2 7.0 mol of naphthalene, 3.5 mol of hydrogen fluoride and 1.4 mol of boron trifluoride were charged into a 3 liter acid-resistant autoclave, and the temperature was raised to 270 ° C. while maintaining the reaction pressure at 28 kgf / cm ² 4
Reacted for hours. Next, the discharge valve of the autoclave was opened, and under atmospheric pressure, substantially all amounts of hydrogen fluoride and boron trifluoride were recovered in a gaseous state. Then, the light fraction was removed while blowing nitrogen. Furthermore, the temperature was raised to 400 ° C and heat treatment was performed for 5 hours under autogenous pressure to obtain mesophase pitch with a high softening point. The pitch yield was 68% by weight (based on raw material naphthalene). The mesophase pitch has an optically anisotropic phase content of 100%, a softening point of 300 ° C or higher, and H
The / C atomic ratio was 0.53, and the carbonization yield was 90% by weight. The solubility of this mesophase pitch is 3.9% by weight of pyridine soluble-benzene insoluble component and 93.0% of pyridine insoluble component.
It was weight%.

The obtained mesophase pitch was pulverized with a ball mill to obtain a powder having an average particle size of 8 μm, and the mesophase pitch powder was oxidized at 220 ° C. for 1 hour under air flow to obtain a uniform oxidized powder. It was This oxidation treated powder is
8.2% by weight of components that are soluble in pyridine and insoluble in benzene,
It contained 91.4% by weight of a component insoluble in pyridine. The oxidation-treated powder was fired under the same conditions as in Example 1. The physical properties of the obtained carbonized product and graphitized product are shown in Table 1.

Comparative Example 1 The same mesophase pitch powder as in Example 1 was used, and this was subjected to an oxidation treatment at 220 ° C. for 30 minutes under air circulation. This oxidation-treated powder contains 27.1% by weight of pyridine-insoluble components and 65.9% by weight of pyridine-insoluble components.
Contained. This oxidation-treated pitch powder, which is soluble in pyridine and contains a large amount of components insoluble in benzene, was molded under the same conditions as in Example 1 and tried to be calcined. The strength of the chemical products could not be measured.

Comparative Example 2 The same mesophase pitch powder as in Example 1 was used, and this was oxidized for 1 hour at 220 ° C. under air flow. This oxidation-treated powder contained 21.0% by weight of a component soluble in pyridine and insoluble in benzene, and 77.1% by weight of a component insoluble in pyridine. The oxidized pitch powder was molded and fired under the same conditions as in Example 1. Since a large amount of pyridine-soluble and benzene-insoluble components in the oxidation-treated powder, a high-performance carbon material as shown in Table 1 could not be obtained.

Comparative Example 3 The same mesophase pitch powder as in Example 2 was used, and this was oxidized for 12 hours at 220 ° C. under air flow. This oxidation-treated powder contained 3.7% by weight of a component soluble in pyridine and insoluble in benzene, and 96.2% by weight of a component insoluble in pyridine. This oxidation-treated powder was molded under the same conditions as in Example 1.
Baked. As shown in Table 1, a high-performance carbon material could not be obtained, because the oxidant-treated powder contained a small amount of pyridine-insoluble and benzene-insoluble components.

[0031]

[Table 1]

[0032]

The raw material powder of the present invention is excellent in carbonization and graphitization as a raw material for a high-density carbon material, and has an extremely high carbonization yield. Sufficiently high density and high strength carbon material can be obtained only by firing. Further, the fired body structure derived from the mesophase pitch of the raw material powder of the present invention exhibits optical anisotropy, has a dense and homogeneous structure, and has high purity, so that the carbon bond formed is very strong. The carbon bond has a higher degree of graphitization by firing at a high temperature, and the shrinkage further promotes densification, so that the carbon bond is further strengthened. In addition, the mesophase pitch powder used in the present invention is imparted with excellent self-fusing property by an appropriate oxidation treatment, so that a binder is not particularly necessary. Therefore, by using the carbonaceous powder of the present invention, a high-density / high-strength carbon material can be easily manufactured in a short time and at low cost.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C04B 35/52 // C10C 3/04 A 6958-4H

Claims (2)

[Claims] 1. Mesophase pitch obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of a super strong hydrogen fluoride / boron trifluoride is subjected to an oxidation treatment in an oxidizing atmosphere. A raw material powder for a high-density carbon material, characterized by containing 5.0 to 20.0% by weight of a pyridine-soluble component and benzene-insoluble component, and 78% by weight or more of a pyridine-insoluble component. 2. Mesophase pitch obtained by polymerizing condensed polycyclic hydrocarbon or a substance containing the same in the presence of super-strong hydrogen fluoride / boron trifluoride is subjected to an oxidation treatment in an oxidizing atmosphere. The raw material powder for high-density carbon material, which is prepared by the method and contains 5.0 to 20.0% by weight of pyridine-insoluble components and 78% by weight or more of pyridine-insoluble components, is pressed and fired. A method for producing a carbon material characterized by: