JPH05330915A - Production of carbon/carbon composite material - Google Patents

Abstract

PURPOSE:To produce a carbon/carbon composite material, capable of graphitizing at a high level and having excellent physical and mechanical characteristics by using monofilamentous or fine-cut carbon fiber. CONSTITUTION:The carbon/carbon composite material is obtained by dispersing carbon fiber having 10-1000 ratio of the length to the diameter of fiber (aspect ratio) in a solvent containing a readily graphitizable resin dispersed or dissolved therein, forming and providing sheets of carbonaceous paper having <=2mm thickness, hot-pressing the resultant carbonaceous paper, converting the carbonaceous paper into a composite material of the carbon fiber with the readily graphitizable resin, performing infusibilizing treatment or without carrying out the infusibilizing treatment, heat-treating the composite material at >=500 deg.C temperature or further Iaminating at least two or more sheets of the formed carbon/carbon composite materials, hot-pressing the laminate under reduced pressure, heat-treating the pressed laminate at >=500 deg.C temperature and, as necessary, graphitizing the heat-treated laminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a reinforcing member, a conductive member,
The present invention relates to a carbon / carbon composite material suitable for use as a battery electrode material and the like and a method for producing the same.

[0002]

2. Description of the Related Art Since a carbon material is lightweight and excellent in strength characteristics, conductivity, heat resistance and radiation resistance, a prepreg obtained by impregnating a woven carbon fiber cloth with a resin is subjected to a high temperature heat treatment at 500 ° C. or higher. The obtained carbon / carbon composite material is used as a sliding member, a battery electrode material, a structural member in the space field, a reactor partition material, and the like. It is known that the properties of this carbon / carbon composite material are determined by the degree of graphitization of the carbon material, and the more highly graphitized carbon material is, the more excellent strength property, conductivity, heat resistance property, and radiation resistance property are. Is shown.

Currently, the carbon fiber as the base material of the carbon / carbon composite material is a PAN-based carbon fiber characterized by high strength obtained by spinning polyacrylonitrile and then subjecting it to high temperature heat treatment.
Pitch-based carbon fibers characterized by high elastic modulus obtained by spinning from pitch of petroleum or coal and subjected to high-temperature heat treatment, or a combination thereof is used. However, since carbon fibers using these polymer precursors have a limited degree of graphitization even when subjected to high temperature heat treatment, carbon / carbon composite materials using these carbon fibers do not have the excellent properties of graphite. Is not working.

In recent years, the so-called vapor phase growth in which the graphite structure has grown to a high temperature by vapor phase pyrolysis of hydrocarbons in the presence of fine particles of transition metals such as iron and nickel or catalysts such as sulfur and sulfur compounds Methods for obtaining carbon fibers have been proposed (Japanese Patent Publication No. 3-61768, Japanese Patent Publication No. 4-1165).
1). However, the vapor-grown carbon fiber produced by such a method is a fine and bulky whisker-like single fiber, and a method for producing a carbon / carbon composite material using this vapor-grown carbon fiber is as follows: Conventionally known method of pressing in the state and impregnating with molten resin and then performing high temperature heat treatment, or beating treatment of carbon fibers made of short fibers in a solvent to uniformly disperse the short fibers in the solvent, and filter with a screen To obtain a carbon fiber aggregate, which is then impregnated with a resin, hot pressed and carbonized by heating (JP-A-62-96).
364) and so on. However, in these conventional methods, since the vapor grown carbon fiber has a high elastic modulus and is bulky, it is difficult to uniformly impregnate the resin, and not only the carbon / carbon composite material has a microporous structure but also the carbon / carbon composite material. There is a problem that the orientation of the vapor-grown carbon fibers in the inside becomes three-dimensionally random and the required characteristics cannot be obtained.

[0005]

In order to solve the problems in the carbon / carbon composite material, the present invention is capable of highly graphitizing using single-fiber-shaped or fine carbon fibers. And, it is an object of the present invention to provide a method for producing a carbon / carbon composite material having excellent physical and mechanical properties.

[0006]

The object of the present invention is to provide a carbon fiber having a fiber length to diameter ratio (aspect ratio) of 10 to 1000 in a solvent in which a graphitizable resin is dispersed or dissolved. Dispersion and papermaking to obtain a carbonaceous paper having a thickness of 2 mm or less, and heat-pressing the carbonaceous paper to convert it into a composite material of carbon fiber and graphitizable resin, or to perform infusibilization treatment Without heat treatment at a temperature of 500 ° C. or higher, or at least 2 times the carbon / carbon composite material thus obtained.
It is achieved by stacking one or more sheets, hot pressing under reduced pressure, and heat-treating at a temperature of 500 ° C. or more.

As the carbon fiber which is the base material of the carbon / carbon composite material of the present invention, vapor grown carbon fiber and its graphitized product are preferably used. Such vapor-grown carbon fibers are, for example, methane, ethane, propane, propylene and other aliphatic hydrocarbons, ethylene, propylene, allene, acetylene and other unsaturated aliphatic hydrocarbons, benzene, toluene and other aromatic hydrocarbons. Alicyclic hydrocarbons such as cyclohexane and cyclooctane, alcohols such as ethanol, butanol and octanol, organic acids such as lauric acid and phthalic acid, and esters such as butyl phthalate, ethyl isobutyl ketone and cyclohexanone Ketones, other nitrogen-containing organic compounds such as hexylamine, sulfur-containing organic compounds such as occlumercaptan, chlorine-containing organic compounds such as carbon tetrachloride, etc. are used as a carbon source, and these raw materials are gasified to be carriers such as hydrogen. 900-1 with gas
In a reaction zone of 500 ° C., a catalyst composed of an ultrafine metal or a metal organic compound (made of a transition metal such as iron, nickel and cobalt, and having a particle size of 3 when the metal is a simple substance)
Ultrafine particles of 00 Å or less, and those that can be used in liquid or solution form when they are metal organic compounds, of which vaporizable substances such as metallocene etc.)
It is a carbon fiber obtained by contacting with and decomposing.

The vapor-grown carbon fiber thus obtained is heated at a temperature of 1500 to 3500 ° C., preferably 2500 ° C. or higher for 3 to 120 minutes, preferably 30 minutes or longer in an atmosphere of an inert gas such as argon. Graphite fibers having a highly developed graphite structure obtained by heat treatment are particularly suitable. This high-temperature heat treatment prevents the release of elements other than carbon from the vapor-grown carbon fiber as the base material and the carbonization of the graphitizable resin as the binder in the subsequent carbonization heat treatment of the carbon / carbon composite material. Also, the effect of promoting graphitization is brought about in graphitization.

Further, polyacrylonitrile, rayon,
PAN-based carbon fibers, rayon-based carbon fibers, pitch-based carbon obtained by spinning organic compounds such as petroleum pitch and coal pitch, heating them in an oxidizing atmosphere to infusibilize them, and heat-treating them at high temperatures to carbonize and graphitize them. Fibers, milled fibers, chopped fibers, etc. obtained by cutting these graphite fibers and the like into lengths of 100 to 5000 μm can also be used.
Further, these carbon fibers may be subjected to a surface treatment such as an acid treatment with nitric acid, a fluorination treatment, a gas plasma treatment or the like in order to improve hydrophilicity and lipophilicity in papermaking, if necessary.

As the graphitizable resin which is the binder in the carbon / carbon composite material of the present invention, coal-based or petroleum-based mesophase pitch having optical anisotropy is preferably used, of which 90% or more, preferably 100. %, And those having a softening point in the temperature range of 400 ° C. or lower, preferably 370 ° C. or lower are suitable.

The bulky short-fiber carbon fiber and the graphitizable resin are dispersed in a solvent such as water or an organic solvent using a mixer or the like, but the resin may be dissolved. And by making this paper, a thickness of 2 mm or less, preferably 1
A felt composed of carbon fibers having a size of not more than mm and a graphitizable resin is obtained. Here, the mixing ratio of the carbon fiber and the graphitizable resin is preferably 10:90 to 90:10 by weight. If the amount of carbon fibers is less than this range, the effect of improving the properties of the resulting carbon / carbon composite material is reduced, and if it is more than this range, defective molding occurs due to insufficient binder. Further, when the felt thickness is 2 mm or more, the resin in the composite material is insufficiently dispersed, and the carbon / carbon composite material becomes in a microporous state, or cracks occur during high temperature heat treatment of carbonization and graphitization. Cracking occurs and the performance of the carbon / carbon composite material deteriorates. Therefore, when manufacturing a carbon / carbon composite material having a thickness of 2 mm or more, a thickness of 2 mm
It is recommended to stack two or more of the following felts.

In the production of felt, carbon fibers and resin may be premixed by using a planetary ball mill or the like before the base material is dispersed in the solvent. Such premixing is useful for the carbon fibers to loosen the intertwined aggregates, and for the resin, it is useful to uniformly disperse the aggregates in the carbon fiber aggregates by reducing the particle size. The obtained felt is pressed if necessary. Although such a pressing step is not always essential, it has the effect of orienting the carbon fibers in the felt in a direction parallel to the plane, and anisotropy appears in the properties of the resulting carbon / carbon composite material. The solvent remaining in the felt is removed by natural vaporization, heating, vacuum or vacuum heating. Further, the pressing step and the solvent removing step may be performed at the same time. The felt-like mixture of the obtained carbon fiber and the graphitizable resin is charged into a mold and heated to a temperature above the melting temperature of the resin while compressing the felt under reduced pressure or normal pressure,
A composite material in which a graphitizable resin is uniformly dispersed in carbon fibers is obtained. Here, the composite material can have various shapes such as a plate shape and a cylindrical shape depending on the mold used.

The obtained composite material is treated in a non-oxidizing atmosphere for 5 to 5 minutes.
It is carbonized at a temperature of 500 to 2000 ° C. at a temperature rising rate of about 0.5 to 50 ° C./minute under a pressure of about 25 MPa, and if necessary, held as it is for up to about 1 hour.
Here, the temperature rising rate is 5 to 10 ° C at a temperature of 1000 ° C or less.
/ Minute is preferable. Also, in the carbonization heat treatment, 50
The first stage heat treatment is performed at 0 to 800 ° C., and then 80
The carbonization heat treatment may be performed in several stages, such as performing the second stage heat treatment at 0 to 2000 ° C. When the carbon / carbon composite material after carbonization has open pores and desired physical properties cannot be obtained, the carbon / carbon composite material is impregnated with a graphitizable resin and further carbonized. The physical properties can be improved by repeating the process once or several times.

Here, in order to increase the thickness of the carbon / carbon composite material, it is possible to stack two to several obtained carbon / carbon composite materials, repeat impregnation with a graphitizable resin, and repeat carbonization. Is. Further, the obtained carbon / carbon composite material is further heated in an inert gas atmosphere at a heating rate of about 5 to 50 ° C./min for 2
Heat to about 500-3200 ° C, and further 1 if necessary
A graphite fiber / graphite composite material can also be obtained by holding it for about 0 minutes. This heat treatment for graphitization is performed by using carbon / carbon using a vapor-grown carbon fiber having high graphitization as a base material.
Effective for carbon composite materials.

[0015]

【Example】

(First Example) Benzene as a carbon source of carbon fiber,
Hydrogen was used as a carrier gas, and ferrocene was used as a catalyst. A vapor-grown carbon fiber having a length of 50 μm or less and a diameter of 0.01 to 0.5 μm produced by catalytic decomposition at a temperature of 1100 ° C. was 3000 ° C. in an argon gas. Was heat treated in order to obtain graphitized vapor grown carbon fiber. This vapor grown carbon fiber 1
0 parts by weight and 10 parts by weight of a mesophase pitch having a softening point of 280 ° C. and an optically anisotropic phase of 100% were pulverized and mixed in a planetary ball mill at room temperature and mixed to form a powder of vapor grown carbon fiber and mesophase pitch. A body mixture was obtained. The particle size of the mesophase pitch at this time was 0.01 to 0.1 mm.
Disperse the obtained mixture in toluene, 150 mm x 1
Paper is made to a size of 50 mm and a thickness of about 1 mm, and 2M at 40 ° C.
The felt was pressed at a pressure of Pa for 30 minutes to obtain a felt having a thickness of 0.5 mm. Then, the residual toluene was removed under reduced pressure at room temperature.

The felt thus obtained is set in a mold, and 15
A vapor-grown carbon fiber having a weight ratio of vapor-grown carbon fiber and pitch of 50:50, which was heated to 330 ° C. at a temperature rising rate of 10 ° C./min while being pressed at a pressure of 0 MPa and held for 1 hour. A composite with pitch was obtained. Then, the composite material is put into an electric furnace and the mixture is heated to 1000 at a rate of 1 ° C./min in a nitrogen gas atmosphere.
The temperature was raised to 0 ° C. and kept for 30 minutes to obtain carbon / carbon composite material A1.

(Second Embodiment) The carbon / carbon composite material A1 obtained in the first embodiment is placed in an electric furnace, heated to 3000 ° C. at a rate of 30 ° C./min in an argon gas atmosphere, and kept as it is. After holding for a minute, a graphite fiber / graphite composite material A2 was obtained.

(Third Example) 10 parts by weight of graphitized grade pitch-based carbon fiber chopped fiber (length: 0.5 mm, diameter: 10 μm) and 10 parts by weight of the same mesophase pitch as used in the first embodiment were used. The mixture was pulverized and mixed with a planetary ball mill at room temperature to obtain a powder mixture of pitch-based carbon fiber and mesophase pitch. The obtained mixture was subjected to papermaking, pressing, and solvent removal in the same manner as in Example 1,
A felt having a thickness of 0.5 mm was obtained. The obtained felt was heat treated in the same manner as in Example 1 to obtain a carbon / carbon composite material,
Further, this is heat treated in the same manner as in the second embodiment to obtain graphite fiber /
A graphite composite material B was obtained.

(First Comparative Example) The same vapor-grown carbon fiber used in the first example was dispersed in toluene to obtain 150 mm ×
Paper is made to a size of 150 mm and a thickness of about 1 mm, and 2
The felt was pressed at a pressure of MPa for 30 minutes to obtain a felt having a thickness of 0.5 mm. Then, the residual toluene was removed under reduced pressure at room temperature.

The felt of the vapor-grown carbon fiber thus obtained was set in a mold, and the same mesophase pitch as used in the first embodiment was added to the felt in an equal weight to 330 in a reduced pressure state.
Impregnation was performed while applying a pressure of 150 MPa to the mold at 50 ° C. to obtain a composite material of vapor grown carbon fiber and mesophase pitch having a weight ratio of 50:50. This composite is then first
Heat treatment was performed in the same manner as in the example to obtain a carbon / carbon composite material C1.

(Second Comparative Example) The carbon / carbon composite material C1 obtained in the first comparative example was heat-treated at a high temperature as in the second example,
Graphite fiber / graphite composite material C2 was obtained.

(Third Comparative Example) Using the same pitch-based carbon fiber chopped fibers used in the third example, a carbon / carbon composite material was obtained in the same manner as in the first comparative example, impregnation of pitch and 1000 ° C. After repeating the heat treatment of 2 times, 3
Heat treatment was performed at 000 ° C. to obtain graphite fiber / graphite composite material D.

(Fourth Comparative Example) The same as the first comparative example except that 10 parts by weight of the same vapor-grown carbon fiber as that used in the first example was set in a mold in a powder state without making a paper. In the same manner, 10 parts by weight of the same mesophase pitch used in the first example was impregnated. Next, this composite material was heat treated in the same manner as in Example 1 to obtain a carbon / carbon composite material. However, since this carbon / carbon composite material was in a porous state, pitch impregnation and 1000 ° C. heat treatment were performed again. To obtain a carbon / carbon composite material E.

Carbon obtained in each of the above Examples and Comparative Examples
The results of measuring the physical properties of the carbon composite material and the graphite fiber / graphite composite material are shown in Table 1. From these results, it can be seen that the composite material of the present invention has excellent properties.

[0025]

TABLE 1 ──────────────────────────────────── composite bulk density (g / cm ³⁾ Bending strength (MPa) Volume resistivity (μΩcm) ───────────────────────────────────── A1 1.7 110 850 A2 2.0 170 170 200 B 2.0 170 500 C1 1.5 75 75 200 C2 1.7 90 2800 D 2.0 110 110 1500 E 1.5 55 3300 ───────── ──────────────────────────── Composite materials A1, A2 and B are examples of the present invention Composite materials C1, C2, D and E Is a comparative example

[0026]

EFFECTS OF THE INVENTION According to the method for producing a carbon / carbon composite material of the present invention, it is suitable for use as a conductive member, a reinforcing member, a battery electrode member, a reactor partition wall material, or a host material for a graphite intercalation compound. A functional carbon / carbon composite is obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Ushijima 252 Kawashimada, Gotemba City, Shizuoka Prefecture Yazaki Parts Co., Ltd.

Claims (3)

[Claims] 1. The ratio of fiber length to diameter (aspect ratio) is 10 to 10 in a solvent in which a graphitizable resin is dispersed or dissolved.
1000 carbon fibers are dispersed and paper-made to obtain a carbonaceous paper having a thickness of 2 mm or less, and the carbonaceous paper is hot-pressed to be converted into a composite material of carbon fibers and a graphitizable resin, followed by infusibilization treatment. A method for producing a carbon / carbon composite material, which is performed with or without heat treatment at a temperature of 500 ° C. or higher. 2. The ratio of fiber length to diameter (aspect ratio) is 10 to 10 in a solvent in which a graphitizable resin is dispersed or dissolved.
1000 carbon fibers are dispersed and paper-made to obtain a carbonaceous paper having a thickness of 2 mm or less, and the carbonaceous paper is hot-pressed to be converted into a composite material of carbon fibers and a graphitizable resin, followed by infusibilization treatment. With or without heat treatment at a temperature of 500 ° C. or higher, a carbon / carbon composite material is obtained. At least two carbon / carbon composite materials are laminated and hot-pressed under reduced pressure at a temperature of 500 ° C. or higher. A method for producing a carbon / carbon composite material, which comprises heat treatment. 3. A vapor-grown carbon fiber obtained by contacting an ultrafine metal catalyst in which carbon fiber is suspended in a high temperature zone with a hydrocarbon compound, or heat-treated at a temperature of 1000 ° C. or higher. The method for producing a carbon / carbon composite material according to claim 1 or 2, wherein the graphite fiber is obtained.