JP3138937B2 - Manufacturing method of carbon / carbon composite 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 method for producing a carbon / carbon composite material.

[0002]

2. Description of the Related Art Carbon / carbon composite materials are materials having unique properties such as maintaining high strength and high elasticity even at a high temperature of 1000 ° C. or more and having a small coefficient of thermal expansion. It is expected to be used for parts, brakes, furnace materials, etc.

[0003] The shape of the aggregate of carbon fibers used in these carbon / carbon composite materials is mainly a two-dimensional woven fabric,
Three-dimensional fabrics are also used depending on the application. Although the use of these woven fabrics provides a high-strength carbon / carbon composite material, the structure and manufacturing method of the woven fabric are complicated and expensive.

On the other hand, when short-fiber carbon fibers such as so-called chopped carbon fibers are used, a sufficient reinforcing effect cannot usually be obtained. Also, when performing the densification step of producing a carbon / carbon composite material from the above woven fabric or short fibrous carbon fiber,
It is necessary to separately perform a step of fixing carbon fibers together with a pitch or a thermosetting resin (binder).
This is one of the causes of the decrease in productivity during the carbon composite material manufacturing process.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a carbon / carbon composite material without using expensive carbon fiber fabrics.

[0006]

According to the present invention, an infusibilized fiber obtained by spinning a carbonaceous pitch and further performing an infusibilizing treatment is carbonized and molded under uniaxial pressure to form a porosity of 5 to 70%.
vol.%, bulk density of 0.1 to 1.8 g / cm ³ as a primary molded body, and densifying the primary molded body with a carbonaceous matrix, and a method of producing a carbon / carbon composite material and a carbonaceous pitch Is spun, and the infusibilized fiber obtained by the infusibilization treatment is filled into the container by forced transfer or free fall, and carbonized and molded under uniaxial pressure, with a porosity of 5 to 70 vol% and a bulk density of 0. 1 to 1.8 g / cm ³
The present invention relates to a method for producing a carbon / carbon composite material, comprising densifying a primary molded body with a matrix formed by chemical vapor deposition and / or a matrix using carbonaceous pitch as a starting material.

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

[0008] The infusibilized fibers referred to in the present invention are fibers obtained by infusibilizing pitch fibers. The pitch fiber as referred to herein is a fiber having an average diameter of usually 5 to 100 μm, preferably 7 to 30 μm, obtained by melt-spinning a carbonaceous pitch by a known method.

The carbonaceous pitch is not particularly limited, and a known pitch can be used. In particular, the softening point is usually 100 to 40.
It is desirable to use coal-based or petroleum-based pitch having 0 ° C, preferably 150 to 350 ° C. Also,
As the carbonaceous pitch, any of an optically isotropic pitch and an anisotropic pitch can be used, and an optically anisotropic pitch having an optically anisotropic phase content of 60 to 100% is particularly preferable. Used.

[0010] The infusibilization treatment can be performed in an oxidizing gas atmosphere at a temperature of usually 50 to 400 ° C, preferably 100 to 350 ° C. As the oxidizing gas, air, oxygen, nitrogen oxide, sulfur oxide, halogen, or a mixture thereof can be appropriately used. The treatment time is such a time that the fiber does not exhibit heat welding property, and is usually 10 minutes to 20 hours, preferably 30 minutes to 10 hours.

In the present invention, the infusibilized fiber is carbonized and molded under uniaxial pressure to form a primary molded body having a porosity of 5 to 70 vol% and a bulk density of 0.1 to 1.8 g / cm ³ .
Preferably, the infusibilized fiber is forcibly dropped or freely dropped into a container, and is filled in the container or the like by lamination or natural deposition. At this time, the infusible fiber is a continuous fiber or 1 to 10
Laminated or deposited in a 0 cm short fiber form.

As a method of filling the continuous fiber into a container or the like, for example, a method in which the fiber infused in a container such as a basket is directly dropped into a uniaxial pressurizing container, the infusible fiber is once sent to a pulley, Examples of the method include a method of evenly filling the container for pressure and a method of forcibly transferring and filling the infusibilized fiber into the container via an air ejector.

As a method for filling short fibers into a container or the like, for example, a method in which a short fiberized infusible fiber is freely dropped into a container for uniaxial pressurization to deposit and fill the continuous fiber, A method of feeding, cutting with a cutter or the like, and dropping is also included.

In any of the above filling methods,
It is desirable to fill evenly, and for this purpose, it is also preferable to move the filling device and / or the filling container such that, for example, the drop position or the filling position moves during filling. It is preferable to use a die or the like for uniaxial pressurization as the container for uniaxial pressurization because the process is simplified. Before or after carbonization and molding under uniaxial pressure, needle punching can be performed in the direction perpendicular to the lamination plane direction of the fibers.

The method of carbonizing and forming under uniaxial pressure is as follows:
Usually 1-100kg / c by hot press
m ² , preferably ² to 50 kg / cm ² , more preferably ^{2 to 20} kg / cm ² , usually 400 to 200 kg / cm ^2.
At 0 ° C, preferably 500-1000 ° C, usually 1
It is carried out by treating for 0 minutes to 10 hours, preferably for 30 minutes to 4 hours. The atmosphere at this time is preferably performed in a non-oxidizing atmosphere such as nitrogen, helium, neon, argon, xenon, and radon. Further, the treatment can be performed at a relatively low temperature, for example, at a temperature of about 400 to 600 ° C. for a short time, even in an oxidizing atmosphere.

The porosity of the obtained primary molded product is usually 5 to 5.
70 vol%, preferably 10 to 60%, more preferably 15 to 50%. If the porosity exceeds the above range, the shape retention of the primary molded body is reduced, and the molded body is undesirably lost or deformed in the subsequent densification step. If the porosity is less than the above range, the primary molded body will be brittlely fractured and behave like a monolithic material. Is not preferred.

The bulk density of the obtained primary molded body is
Usually 0.1 to 1.8 g / cm ³ , preferably 0.2 to 1.8 g / cm ³
1.7 g / cm ³ , more preferably 0.5 to 1.6
g / cm ³ . If the bulk density is less than the above range, the shape retention of the primary compact is reduced, and the compact is undesirably lost or deformed in the subsequent densification step. On the other hand, if the bulk density exceeds the above range, the densified carbon / carbon composite material will cause brittle fracture, behaving like a monolithic material, and exhibit the inherent characteristics of the carbon / carbon composite material. Is not preferable because it cannot be used.

Following carbonization under uniaxial pressure, carbonization or graphitization under normal pressure can be carried out. In this case, a condition of 400 to 3000 ° C., preferably 500 to 2500 ° C. in a non-oxidizing atmosphere is used. Can be implemented below.

In the present invention, a carbon / carbon composite material is produced by densifying a primary compact. The method for densification is not particularly limited as long as it is a method for producing a carbonaceous matrix, and a known method can be used. In particular, a matrix formed by chemical vapor deposition and / or a matrix using pitch as a starting material can be used. Preferably, a method for converting the compound is used.

In the case of densification by chemical vapor deposition, for example, hydrocarbons such as methane, ethane, acetylene, propane, benzene and natural gas, or at least one or more of these are diluted with an inert gas or hydrogen. The material is used as a raw material and pyrolyzed to deposit pyrolytic carbon in the primary molded body. As the inert gas, for example, helium, neon, argon, xenon, radon, or the like can be used.

The thermal decomposition temperature is usually from 700 to 3000 ° C.
Preferably it is 800-2500 degreeC. Pyrolysis pressure is
Although it can be carried out at normal pressure, reduced pressure is preferable, and specifically, usually 0.5 to 100 Torr, preferably 0.5 to 100 Torr.
~ 50 Torr.

An inert gas or a diluent gas such as hydrogen can be used for the purpose of controlling the reaction rate. In this case, these diluent gases are used with respect to the hydrocarbon gas.
Usually, it is desirable to use 0.1 to 1000 times volume, preferably 1 to 100 times volume. When the ratio of the diluent gas is less than the above range, a sufficient dilution effect cannot be obtained, and when the ratio of the diluent gas is more than the above range, the reaction rate is unnecessarily reduced. Not preferred.

In the case of densification by a matrix using pitch as a starting material, a method of impregnating a primary compact with carbonaceous pitch and then carbonizing is used. The carbonaceous pitch is not particularly limited, and a known pitch can be used. In particular, it is desirable to use a coal-based or petroleum-based pitch having a softening point of usually 100 to 400 ° C, preferably 150 to 350 ° C. As the carbonaceous pitch, any of an optically isotropic pitch and an anisotropic pitch can be used, but the content of the optically anisotropic phase is 60 to 100.
% Optically anisotropic pitch is particularly preferably used. The method of impregnation is not particularly limited, and can be performed by a known method. For example, the impregnation can be performed by sealing the primary molded body and the carbonaceous pitch in a vacuum vessel and heating and melting under reduced pressure. As the reduced pressure in this case, for example, 1 × 10 ^{−2 to} 3
It can be performed at about 00 Torr. The heating temperature is usually equal to or higher than the softening point temperature of the carbonaceous pitch and lower than the decomposition start temperature, preferably higher than the softening point temperature by 30 ° C or higher and lower than the decomposition start temperature, more preferably 180 to 450 ° C.

The carbonization is preferably performed under pressure or by pressing. Carbonization under pressure is carried out, for example, by evacuating the vessel containing the impregnated primary compacts and then, for example, by means of a non-oxidizing gas such as argon, helium, radon, neon and optionally N ₂ , preferably argon. 1000
0 kg / cm ² , preferably 100 to 2000 kg / c
pressurized to m ^2, 400~2000 ℃, preferably 500
It is performed by heating to ~ 1500C.

The carbonization under the press is usually performed by hot press at 10 to 500 kg / cm ² , preferably 20 to 500 kg / cm ² .
Uniaxially pressurized to 200 kg / cm ² , usually 400-200
It is carried out by heating to 0 ° C, preferably 500 to 1500 ° C.

[0026]

According to the present invention, it is possible to manufacture a primary molded body by a simple process, and it is possible to manufacture a carbon / carbon composite material by a simple method.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 An optically anisotropic petroleum pitch having a softening point of 280 ° C. was melt-spun to obtain a pitch fiber having an average diameter of 13 μm. An infusibilization treatment was performed on the 2,000 pitch fiber tows in the air to obtain an infusible fiber tow. The infusible fiber tow was passed through a pulley as continuous fiber, and was continuously fed into the hot press die from above. The dies were moved so that the infusibilized fibers were evenly deposited inside the dies. (FIG. 1) After infusing the infusible fiber into a die, it is hot-pressed at 700 ° C. under a pressure of 5 kg / cm ² for 1 hour, and carbonized by pressing for 1 hour to obtain a porosity of 25% and a bulk density of 1.1 g / cm ³ It was a primary molded body. The shape did not change even when the primary molded body was taken out of the die.

The primary molded body was subjected to chemical vapor deposition using methane as a raw material gas at 1200 ° C. and 1.5 Torr.
At 120 ° C. for 120 hours to produce a carbon / carbon composite material. The porosity of the obtained carbon / carbon composite material was about 4%, and no crack was observed. The obtained carbon / carbon composite material retained the shape of the primary molded body.

Example 2 An optically anisotropic petroleum pitch having a softening point of 280 ° C. was melt-spun to obtain a fiber having an average diameter of 13 μm. 2,000 pitch fibers of the tow were infusibilized in air at 300 ° C. for 1 hour. The obtained infusible fiber tow was passed through a pulley as a continuous fiber, and was continuously fed into the hot press die from above. The dies were moved so that the infusibilized fibers were evenly deposited inside the dies. After the infusibilized fiber was filled in the die, it was press-carbonized at 600 ° C. for 1 hour under a pressure of 10 kg / cm ² by hot pressing to obtain a porosity of 30% and a bulk density of 1.1 g / c.
m ³ was a primary molded body. The primary molded body was fired in nitrogen at atmospheric pressure at 1000 ° C. to obtain a molded body having a porosity of 30% and a density of 1.2 g / cm ³ . The compact maintained the shape of the primary compact.

The compact was subjected to chemical vapor deposition using methane as a source gas at 1100 ° C. and 1 Torr.
A densification treatment was performed for 20 hours to produce a carbon / carbon composite material. The porosity of the obtained carbon / carbon composite material was about 4%, and no crack was observed. The obtained carbon / carbon composite material retained the shape of the primary molded body.

(Comparative Example 1) A carbon fiber tow was passed through a pulley as a continuous fiber and continuously fed into the hot press die from above. The dies were moved so that the carbon fibers were evenly deposited inside the dies. After filling carbon fiber in the die, 10k by hot pressing
It was pressed at 600 ° C. for 1 hour under a pressure of g / cm ² , and was further fired at 1000 ° C. under nitrogen and atmospheric pressure. In the obtained fired body, the fibers were not fixed, and had a high porosity. When densification was performed at 1100 ° C. and 1 Torr for 120 hours by chemical vapor deposition using methane as a raw material gas, the molded body was swollen and deformed, and the dispersion of fibers became uneven.

[0033]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used in an example.

[Explanation of symbols]

 1. 1. Infusible fiber 2. Dies for hot press pulley

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-203267 (JP, A) JP-A-60-260469 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/83

Claims (2)

(57) [Claims] An infusibilized fiber obtained by spinning a carbonaceous pitch and further performing an infusibilization treatment is carbonized and formed under uniaxial pressure, and has a porosity of 5 to 70 vol% and a bulk density of 0.1 to 0.1%.
A method for producing a carbon / carbon composite material, comprising: forming a 1.8 g / cm ³ primary molded body, and densifying the primary molded body with a carbonaceous matrix. 2. An infusibilized fiber obtained by spinning a carbonaceous pitch and further subjecting to infusibilization treatment is filled into the container by forced transfer or free fall, and carbonized and molded under uniaxial pressure to obtain a porosity of 5%. ~ 70vol%, bulk density 0.1 ~ 1.8
g / cm ³ , wherein the primary compact is densified with a matrix formed by chemical vapor deposition and / or a matrix using carbonaceous pitch as a starting material. Law.