JPH075367B2 - Method for producing carbon material and carbon / carbon composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon material and a carbon / carbon composite material.

Problems to be Solved by Conventional Techniques and Inventions Carbonaceous pitches are used as raw materials for high-density carbon materials because of their high carbonization yields. However, there is a problem that bubbles and cracks are generated by gas generation during carbonization, and as a method to solve this, a method of carbonizing the pitch under high pressure, Hot Isostatic Pressing (HIP under hot isostatic pressure) is used. ing. In this case, the gas generated at the time of carbonization may contaminate the internal members of the furnace such as the heater and the heat insulating material, possibly damaging the device. Therefore, in HIP for the purpose of manufacturing carbon materials, the raw materials are hermetically sealed containers such as glass or stainless steel.
The so-called canning is performed. This container also serves the purpose of maintaining the shape of the object to be processed during the heat treatment. On the other hand, the carbon / carbon composite material is 1000
It is a material that retains high strength and high elastic modulus even at high temperatures above ℃, and has unique properties such as a small coefficient of thermal expansion, and is expected to be used for parts of aerospace equipment, brakes, furnace materials, etc. ing. Due to the above characteristics, the carbonaceous pitch is also used as a precursor for a matrix of a carbon / carbon composite material, but HIP is also used in this carbonization process, and in this case, the raw material is made of glass or stainless steel. So-called canning, which is to put it in a container, is performed.

However, when using a closed container (container), a caulking process such as vacuum encapsulation is required to provide a sealing function, and it is necessary to remove the container and re-cane during re-impregnation for densification. Become. Therefore, there is a problem that the manufacturing process becomes complicated, and further, the internal pressure of the generated gas may cause cracks in the processed material, or the carbon fiber woven fabric may be deformed by the pressure of the container.

Means for Solving the Problems The present inventors have conducted research to solve the above problems and establish a simple and high-performance carbon material and carbon / carbon composite material manufacturing process, and as a result, have completed the present invention. It arrived.

According to the examination results of the inventors of the present application, when the carbonaceous pitch is heat-treated under hot isostatic pressure, the shape of the object to be treated can be maintained without using a closed container, and the open type is used. It has been found that when a container is used, the internal pressure of the generated gas can prevent cracks from entering the treated material (Japanese Patent Application No. 62-330018 (Japanese Patent Application Laid-Open No. 1-264966)).

An open container is a container that does not have a sealing function. As materials, metals such as aluminum, mild steel, stainless steel,
Glass, graphite, ceramics or the like can be appropriately selected depending on the use temperature or purpose of use. The shape of the container is not particularly limited, but it may be with or without a lid, or may be wrapped with a metal foil.

As a result of further studies, the present inventors have found that the above method can be more effectively carried out by capturing the decomposition gas generated during carbonization in the system. Further, they have found that at least one substance selected from the group consisting of refractory fibers, iron and iron-based alloys is extremely effective in capturing these decomposition gases, particularly hydrocarbon gas. The present invention is achieved by allowing these substances (capturing materials) to coexist with the object to be treated.

(1) The carbonaceous pitch is placed in an open container, and a trapping material for a decomposition gas generated when carbonizing the carbonaceous pitch is allowed to coexist in the open container without being mixed with the carbonaceous pitch, and hot isostatic pressure is applied. A method for producing a carbon material, which comprises heat-treating under pressure, and further carbonizing or graphitizing as necessary to obtain a carbon material containing no trapping material, and (2) carbon tow of carbon fiber Impregnated with a fine pitch, put the impregnated product in an open container, and allow a trapping agent for the decomposition gas generated during carbonization of the carbonaceous pitch to coexist in the open container without being mixed with the impregnated product. The present invention relates to a method for producing a carbon / carbon material, which comprises heat-treating under hydrostatic pressure and further carbonizing or graphitizing as necessary to obtain a carbon / carbon material containing no trapping agent.

Hereinafter, the method for producing the carbon material and the carbon / carbon composite material according to the present invention will be described in detail.

The carbonaceous pitch used in the present invention has a softening point of 100 to 400 ° C.,
A coal-based or petroleum-based pitch having a temperature of 150 to 350 ° C. is preferable. The carbonaceous pitch may be either an optically isotropic pitch or an anisotropic pitch, but the content of the optically anisotropic phase is 60 to 100 vol%, preferably 80 to 10 vol%.
An optically anisotropic pitch of 0 vol% is particularly preferably used.

As the carbon fiber used in the present invention, any one of pitch type, polyacrylonitrile type and rayon type can be used, but the pitch type carbon fiber is preferable. The carbon fiber tow means a unidirectional laminate of 500 to 100,000 fiber bundles of carbon fibers having a diameter of 5 to 100 μm, a two-dimensional woven fabric or its laminate, a three-dimensional woven fabric, a mat-shaped molded product, and a felt-shaped molded product. It is a two-dimensional or three-dimensional molded product.

The pitch-based carbon fiber here is a fiber obtained by melt spinning a carbonaceous pitch, infusibilizing it, carbonizing it, and graphitizing it if necessary.

The method of impregnating the carbon fiber tow with the carbonaceous pitch is, for example, heating the carbonaceous pitch under vacuum and / or pressure,
A method of melting and impregnating carbon fiber tow is used,
In order to reduce the viscosity during impregnation, it is possible to cut and back with a solvent. As the solvent, aromatic hydrocarbon, pyridine, quinoline or the like can be used. In addition, because of the densification,
The cycle of impregnation and HIP treatment described below can be performed as many times as necessary.

In the present invention, the impregnated product obtained by impregnating the carbonaceous pitch or the carbon fiber tow with the carbonaceous pitch is placed in an open-type container, and the decomposition gas capturing material is opened without being mixed with the treated object. Put in a container. As is well known, the main component of hydrocarbon gas, which is the main component of cracked gas, is methane.
Although substances that can capture these known decomposed gas components by physical adsorption or chemical adsorption are well known, refractory fibers, iron and iron-based alloys are extremely effective capturing materials as described above.

As the refractory fibers, for example, long fibers such as carbon, oxide-based ceramics and non-oxide-based ceramics, short fibers or felt can be used. Specifically, short fibers of carbon, silica, alumina or a mixture thereof are preferable.

Iron with a purity of 99% or more is used, and as an iron-based alloy, 10% or less of one or two kinds of metal selected from nickel, chromium, molybdenum, vanadium, tungsten, silica and manganese is included with respect to iron. What is done is used.

Iron and iron-based alloys can be used in the form of powder, fine wire, mesh or porous molded body.

The mode of coexisting the capturing material is not particularly limited as long as it is not mixed in the object to be treated, for example, a method of placing the object to be treated in an open container and filling the upper part with the capturing material, wrapping the object to be treated with metal foil, and further Examples thereof include a method of wrapping the outside with a capture material felt, a method of wrapping an object to be treated with a capture material in metal foil, and the like. Further, in order to prevent the capturing material from being mixed into the object to be treated, metal foil or the like can be installed between the two.

When two or more kinds of refractory fibers, iron and iron-based alloys are used in combination, these may be mixed or laminated. Refractory fiber, the amount of at least one substance selected from the group consisting of iron and iron-based alloys is arbitrarily determined by the processing conditions, usually 100 parts by weight of the object, refractory fiber Is 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, iron and iron-based alloys are 10 to 5000 parts by weight, preferably 500 to 1000 parts by weight.
Parts by weight. Note that a hydrogen trapping material, such as titanium, zirconium, or magnesium, can coexist.

The object to be treated is heat-treated under hot isostatic pressure, and carbonized or graphitized as necessary to produce a carbon material or a carbon / carbon composite material.

Conditions of heat treatment in the hot isostatic pressure is, 50~10000kg / cm ² with an inert gas, preferably pressurized to 200~2000kg / cm ^2, 100~3000 ℃, preferably, carried out at 400 to 2,000 ° C. can do. As the pressure medium gas, an inert gas such as argon, nitrogen or helium can be used.

In the present invention, the object can be sufficiently achieved by using the open type container, but if necessary, for example, when a large amount of the object to be processed is heat-treated, the HIP device with the exhaust mechanism can be preferably used. The HIP with an exhaust mechanism is a device having a mechanism capable of continuously controlling and discharging the gas components generated from the object to be processed during HIP while maintaining a high pressure, and specifically, the generated gas is a product and And / or a device equipped with a discharge mechanism capable of adjusting the amount of removal according to the diffusion rate. This gas discharge mechanism is composed of a heat exchanger with the pressure medium gas in the furnace, a cooler outside the furnace, a pressure reducing device, a flow rate control valve, and the like. Details of this HIP device with an exhaust mechanism are described in Japanese Patent Application No. 62-253171 filed by the applicant of the present application. The conditions of the pressure heat treatment in the HIP device with the exhaust mechanism also conform to the above HIP conditions.

The processed product after HIP treatment is carbonized or 2000 to 3 at 400 to 2000 ° C under normal pressure in an inert gas atmosphere, if necessary.
It can be graphitized at 000 ° C.

The volume content (Vf) of carbon fibers in the composite material is arbitrarily determined according to the purpose, but is usually 5 to 70%.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Example 1 A petroleum-based pitch having an optical anisotropic phase of 100 vol% with a softening point of 280 ° C. was placed in an open quartz container, and a ceramic short fiber composed of 50% by weight of alumina and 50% by weight of silica was placed on the upper part of the container. 100 parts by weight per 100 parts by weight of Pitch is filled with argon gas in the HIP device to 1000 kg / cm ² and 800 ° C.
In the above, pressure carbonization treatment was performed. The obtained carbide was comparable to that obtained by HIP treatment in a closed container.
Also, the dirt inside the furnace was a very slight sign.

(Example 2) The petroleum-based pitch used in Example 1 was included in stainless foil, and 1000 parts by weight of iron powder having a purity of 99% and a particle size of 5 µ was filled on the outer side thereof with 100 parts by weight of the pitch. The gas was pressurized to 1000 kg / cm ² and pressure carbonized at 800 ° C. The resulting carbide had very few cracks. Also, the dirt inside the furnace was a very slight sign.

(Comparative Example 1) The petroleum-based pitch used in Example 1 was vacuum-sealed in a stainless steel container, which was then filled with argon gas in a HIP device.
When pressure was applied to 000 kg / cm ² and pressure carbonization was performed at 1000 ° C, the inside of the furnace was slightly affected, but the obtained carbide had many cracks.

(Comparative Example 2) The petroleum-based pitch used in Example 1 was placed in an open-type stainless steel container, and was placed in an HIP device using argon gas to
When pressurized to 000 kg / cm ² and pressure carbonized at 1000 ° C., the obtained carbide had few cracks, but the inside of the furnace was contaminated.

(Example 3) A petroleum-based pitch having an optical anisotropic phase of 90 vol% with a softening point of 280 ° C was included in aluminum foil, and a ceramic fiber felt composed of 50% by weight of alumina and 50% by weight of silica was further provided on the outside thereof. , 200 for 100 parts by weight of pitch
It was filled with parts by weight, pressurized to 1000 kg / cm ² with argon gas, and pressure carbonized at 550 ° C. The resulting carbide had very few cracks. Also, the dirt inside the furnace was a very slight sign.

(Example 4) The petroleum-based pitch used in Example 1 was placed in an alumina container,
On the upper part, 50% by weight of alumina and 50% by weight of silica, a ceramic fiber felt, low carbon steel wool, and the ceramic fiber felt are 100 parts by weight, 300 parts by weight and 25 parts by weight with respect to 100 parts by weight, respectively. HIP with exhaust system filled in 3 layers each
Pressurized to 1000 kg / cm ² with argon gas in the device,
It was pressure carbonized at 800 ° C. The obtained carbide is
There were very few cracks. Also, the dirt inside the furnace was a very slight sign.

Example 5 Two-dimensional woven fabric (plain weave) of 3000 bundles of Pitch-based carbon fibers having a diameter of 10 μ (micron) was laminated and impregnated with the Pitch used in Example 1. The impregnated material was contained in aluminum oil, and 50% by weight of alumina and 50% by weight of silica were added to the outside.
Filling 100 parts by weight of ceramic fiber felt of 100% by weight with respect to 100 parts by weight of Pitch, pressurizing to 1000 kg / cm ² with nitrogen gas in a HIP device, pressurizing carbonization at 550 ° C while exhausting at ² Nm ³ / hr. did. Following carbonization under pressure, graphitization was carried out at 2500 ° C. under an inert gas atmosphere under normal pressure. When the obtained carbon / carbon composite material was observed with a scanning electron microscope and a polarization microscope, the matrix was well filled in and between the fiber bundles, and no deformation of the carbon fiber woven fabric was observed. . Also, the dirt inside the furnace was a very slight sign.

Comparative Example 3 The same impregnated material as in Example 5 was vacuum-sealed in a stainless steel container and treated in the HIP device under the same conditions as in Example 5. In the obtained product, the carbon fiber woven fabric was deformed by the pressure of the container.

(Example 6) The petroleum-based pitch used in Example 1 was impregnated into a three-dimensional orthogonal woven fabric of 3000 bundles of pitch-based carbon fibers having a diameter of 10 µ (micron). The impregnated material was filled with stainless steel foil, and 300 parts by weight of ceramic felt made of 50% by weight of alumina and 50% by weight of silica was filled in the upper part with 100 parts by weight of the pitch, and nitrogen gas was used in a HIP device with an exhaust mechanism. It was pressurized to 1000 kg / cm ² and pressure carbonized at 800 ° C. Following carbonization under pressure, graphitization was carried out at 2500 ° C. under an inert gas atmosphere under normal pressure. When the obtained carbon / carbon composite material was observed with a scanning electron microscope and a polarization microscope, the matrix was well filled in and between the fiber bundles, and no deformation of the carbon fiber woven fabric was observed. . Also, the dirt inside the furnace was a very slight sign.

(Comparative Example 4) The same impregnated material as in Example 6 was vacuum-sealed in a stainless steel container and treated in the HIP apparatus under the same conditions as in Example 6. In the obtained product, the carbon fiber woven fabric was deformed by the pressure of the container.

(Example 7) The petroleum-based pitch used in Example 1 was impregnated into a three-dimensional woven fabric of 2000 bundles of pitch-based carbon fibers having a diameter of 10 µ (micron). Iron powder with a purity of 99% and a particle size of 5μ is filled on the outside of the impregnated material, and 1000 kg /
It was pressurized to cm ² and pressure carbonized at 1000 ° C. Following pressure carbonization, carbonization was performed at 1700 ° C. under normal pressure and an inert gas atmosphere. This was again impregnated with an optically anisotropic pitch having a softening point of 280 ° C., and pressure carbonization treatment was performed under the above conditions in a HIP device with an exhaust mechanism. This cycle was repeated 5 times. The obtained carbon / carbon composite material has a bulk density of 1.74,
The bending strength was 35 kg / mm ² .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C04B 35/54 D 35/64 302 Z (72) Inventor Kiho Hayada Kosugi, Nakahara-ku, Kawasaki-shi, Kanagawa Town 2-235 (72) Inventor Taiji Ido 338 Iwai-cho, Hodogaya-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-1-264966 (JP, A)

Claims (6)

[Claims] 1. A carbonaceous pitch is placed in an open container, and a trapping agent for a decomposition gas produced when carbonizing the carbonaceous pitch is allowed to coexist in the open container without being mixed with the carbonaceous pitch. A method for producing a carbon material, which comprises heat-treating under hydrostatic pressure and further carbonizing or graphitizing as necessary to obtain a carbon material containing no trapping agent. 2. The method according to claim 1, wherein a metal foil is provided between the carbonaceous pitch and the trapping material to prevent the both from being mixed. 3. The method according to claim 1 or 2, wherein the capturing material is a refractory fiber aggregate, or a powdery substance of iron or an iron-based alloy, a fine wire, a mesh or a porous molded product. 4. A carbon fiber tow is impregnated with carbonaceous pitch,
This impregnated product is placed in an open container, and a trapping agent for a decomposition gas generated during carbonization of the carbonaceous pitch is allowed to coexist in the open container without being mixed with the impregnated product, and heat treatment is performed under hot isostatic pressure. And, if necessary, further carbonization or graphitization,
A method for producing a carbon / carbon material, characterized in that a carbon / carbon material not mixed with the capture material is obtained. 5. The method according to claim 4, wherein a metal foil is provided between the impregnated material and the capturing material to prevent the inclusion of both. 6. The method according to claim 4 or 5, wherein the capturing material is a refractory fiber aggregate, or an iron or iron-based alloy powder, fine wire, mesh or porous molded body.