JPH0230666A - Carbon fiber reinforced carbon composite material and production thereof - Google Patents

Abstract

PURPOSE:To enlarge coefficient of thermal conductivity in one direction by cutting filaments of carbon fiber impregnated with a thermosetting resin, molding, curing the resin, carbonizing, impregnating the carbonized molded article with pitch or thermosetting resin and carbonizing. CONSTITUTION:Filaments of carbon fiber are impregnated with 10-70wt.% solution of thermosetting resin, the thermosetting resin is cured under heating at 50-300 deg.C for 0.2-5 hours to give a fiber/resin composite material, which is cut into pieces (5-100mm) longer than the thickness of the composite material, arranged in parallel in one direction, the arranged material is pressurized in the direction perpendicular to the long direction of the fiber and the resin is cured to give a molded article. Then the molded article is carbonized under heating at <=1,000 deg.C, further impregnated with pitch or thermosetting resin, carbonized, optionally graphitized to give the aimed composite material having >=2 ratio of coefficient of thermal conductivity in the thickness direction to that in the direction perpendicular to the thickness direction and >=3w/cm. deg.C coefficient of thermal conductivity in the thickness direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carbon fiber reinforced composite material and a method for producing the same.

(Prior Art) Carbon fiber reinforced composite materials (hereinafter referred to as C/C composite materials) are lightweight, have high strength, and have excellent heat resistance and corrosion resistance. For this reason, aerospace materials such as rocket nozzles, nose cones, and aircraft disc brakes,
It is used in heating elements, pot press molds, other mechanical parts, nuclear reactor parts, etc.

This C/C composite material is generally made of polyacrylonitrile,
Long or short carbon fibers such as pitch-based carbon fibers are impregnated or mixed with matrix materials such as CV thermosetting resins such as phenol resins, furan resins, or thermoplastic resins such as pitch, and then heated and molded using an inert gas. In a non-oxidizing atmosphere such as It is manufactured from K by graphitizing accordingly.

(Problems to be solved by the invention) However, the obtained C/C composite material is
In other words, when it is necessary to use it for purposes of effectively conducting or removing heat in the thickness direction, it is not necessarily satisfactory, and there are problems in putting it into practical use.

Therefore, the present inventors have developed a C/
In order to obtain a C/C composite material, we conducted various studies, obtained a C/C composite material with increased thermal conductivity in one direction, and arrived at the present invention.

That is, the gist of the present invention is that (1) the carbon fibers are substantially oriented in the thickness direction, and the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in the direction perpendicular to the thickness direction is greater than or equal to A carbon fiber-reinforced carbon composite material whose thermal conductivity in the thickness direction is 3 W/crrL·3 or more.

and (2) impregnate long carbon fibers in a thermosetting resin, heat this to obtain a fiber/resin composite, cut the composite into a length longer than the thickness of the desired composite material, and then The fibers are aligned in one direction so that they are substantially parallel to each other, pressure is applied in a direction perpendicular to the length of the fibers, the resin is molded, hardened, and then carbonized. A method for producing a carbon fiber-reinforced carbon composite material, which is characterized by impregnating the material with carbon fiber, followed by carbonization and, if necessary, graphitization.

(Means for solving problems) The present invention will be explained in detail below.

The carbon fiber used in the present invention is polyacrylonitrile (
Any type of carbon fiber, such as PAN) type, pitch type carbon fiber, or vapor grown carbon fiber, may be used, but pine type carbon fiber, which has high properties such as high thermal conductivity in the fiber axis direction, is particularly suitable.

The C/C composite material according to the present invention is obtained using such carbon fibers, the carbon fibers are substantially oriented in the thickness direction, and the W/C composite material in the direction perpendicular to the thickness direction is 3 or more. It is characterized by

Such a C/C composite material can be obtained by the following method.

First, long carbon fibers are impregnated with a thermosetting resin and heated to semi-cure.

Examples of thermosetting resins include phenol resins, furan resins, epoxy resins, and unsaturated polyester resins, and phenol resins, particularly resol type phenol resins, can be preferably used. These thermosetting resins are usually used after being dissolved and diluted with a solvent such as an alcohol such as ethanol, a hydrocarbon such as hexane, or acetone.

use something

Further, for those requiring a curing agent such as furan resin and eboxy resin, the curing agent is also added to the solution in an amount appropriate for each resin.

A simple method for impregnating long carbon fibers in such a thermosetting resin solution may be a simple method such as immersing the carbon fibers in the solution. From the viewpoint of processing efficiency, it is preferable to use a method in which the particles are run in a continuous manner. Also, at this time, add 1
0-! It is preferable to apply ultrasonic waves of about 0 KHz because it is possible to prevent the effects of uneven processing due to air bubbles between each single fiber or between weaves.

The carbon fibers impregnated with the thermosetting resin solution are passed through a roller to remove excess solution, and then heated.

The thermosetting resin is thermoset by the heat treatment. Appropriate conditions for heat treatment vary depending on the type of thermosetting resin used, but are usually 30 to 300°C, preferably 30 to 200°C for 0.2 to 3 hours, preferably 0.2 to 2 hours. Heat treated. At this time, it is desirable to gradually raise the temperature to a predetermined temperature in order to avoid rapid desorption of the solvent from the thermosetting resin solution applied to the carbon fibers. Further, it is preferable from the viewpoint of processing efficiency that the heat treatment is carried out by continuously running the carbon fibers in a heating furnace.

The resulting fiber/resin composite is then treated with a target C/
C It is selected from a slightly longer range than the thickness direction of the composite material, for example /3~100rr.
Selected from as. The cut composites are unidirectionally aligned substantially parallel to each other, heated and shaped by applying pressure in a direction perpendicular to the length of the fibers.

For example, when the composite is fed into a mold using a funnel-like tool, the fibers are aligned substantially parallel in the mold and the fibers are heated to the temperature required for curing of the resin. A molded body is obtained by applying pressure in a direction perpendicular to the length direction of the resin to harden the resin.

After that, the molded body 1 is placed in a container, the molded body is surrounded by coke pleat, and the container is placed in an electric furnace.
N if necessary! Carbonize by raising the temperature to about 100°C under gas flow.

If necessary, it is further placed in a graphitization furnace and heat-treated to a temperature of 2000° C. or higher in an inert atmosphere.

Next, the obtained carbide or graphitized product is impregnated with a petroleum-based or coal-based pitch or a thermosetting resin such as a phenol resin or a furan resin, and if a thermosetting resin is used, the resin is hardened. Carbonize afterwards.

In this case, it is common to use a thermosetting resin that has been dissolved in a solvent such as alcohol, acetone, anthracene oil, etc. and adjusted to an appropriate viscosity.

Moreover, in this case, a method of impregnation under pressure is preferably employed.

For example, the pitch is melted by heating the carbide or graphitide of the molded body in a vacuum in a low-pressure reaction vessel (autoclave), and the carbide or graphitide is immersed in the molten pitch. After that, N2 gas is introduced and the temperature is raised to about 50Ntoo°C under low pressure.

Thereafter, it is cooled to take out a densified carbide or graphitized product, which is carbonized to about 100° C. in the same manner as described above, and graphitized if necessary.

By repeating the so-called densification method described above, a highly densified C/C composite material with a specific gravity of 6 or more is obtained.

At this time, if the resin content or densification of the fiber/resin composite is insufficient, or if the heating rate during carbonization or graphitization is too high, the strength in the direction perpendicular to the fiber length direction will decrease. In some cases, this may lead to destruction, so it is necessary to choose appropriate conditions.

The resulting C/C composite material is an anisotropic material with high thermal conductivity and electrical conductivity in the thickness direction. Obtained C/C
Depending on the purpose, in order to improve the strength in the thickness direction and perpendicular direction, the composite material can be wrapped around the periphery using long fibers made of carbon fiber, or carbon material such as C/C composite material. can be tied into a suitable shape.

In addition, the surfaces of multiple composite materials are bonded using a resin mainly composed of phenolic resin, and this is heated again to a temperature of approximately -200°C, which is the temperature at which the C/C composite material is finally treated. /
A plurality of small pieces of C composite material may be adhered to each other to form a composite material of a desired size.

The C/C composite material of the present invention has high thermal conductivity and high electrical conductivity in the thickness direction, and can effectively remove and transmit heat. It also has high thermal shock resistance in the direction perpendicular to the thickness direction, and can withstand use in high-temperature furnaces.

That is, the C/C composite material of the present invention has a thickness direction (1
) and the thermal conductivity in the direction perpendicular to it (〃) is 7 or more, preferably 7 or more, optimally io or more, and the thermal conductivity in the thickness direction (1) is JW/am・℃ or more. For example, even if a substance heated to a high temperature is placed on one side, the heat conductivity in the thickness direction is high, so the heat will easily be transferred to the other side, and cooling water can be placed on this other side. By bringing the flowed parts into contact, this heated substance can be effectively cooled. That is, it can be effectively used when cooling multiple substances by heat exchange.

In the present invention, it is preferable to use pitch-based carbon fibers with high thermal conductivity in the fiber axial direction, particularly coal pitch-based carbon fibers with high properties, since the effect will be even greater.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

Example 1 Long wire mt5 of pitch-based carbon fiber (Mitsubishi Kasei Corporation "Dialead uooo", filament, fiber diameter 10μ)
After immersing the phenol resin in an ethanol solution and then putting it in a dryer to remove the ethanol at 70°C,
The temperature was raised to 0° C. or higher to semi-cure the phenol resin. The obtained fiber/resin composite (tow prepreg) (carbon fiber:resin=st, :egg weight ratio) was cut into a length of 'lOwa'. The fibers of this material were hardened with resin and were rod-shaped and rigid. The cut composites were arranged parallel to each other in one direction in a mold and filled into a shape larger than the intended C/C composite material.

Then, low pressure was applied at iso°C, the temperature was raised to 250°C over 7 hours, and held at 250°C for 1 hour to mold and harden.

Dimensions after molding are 108 × 1, Q, j; × I10. /
It was 0.

Next, this molded product was placed in a container filled with Coke Please, and while covered with Coke Please, the temperature was raised to 7000° C. over about 50 hours to carbonize the resin.

Next, this carbonized composite material and solid pitch were placed in an autoclave, and the temperature was raised to 250°C while maintaining the reduced pressure.
Then, after making the atmosphere positive pressure by introducing 2ft of N, the temperature was raised to 50θ℃ in 5 hours, and then heated to 200℃.
The time was maintained for 5 hours.

The pressure was kept constant during the temperature rise using the pulp attached to the autoclave.

Cool the autoclave, take out the composite material, and carbonize the molded product in the same way as too'c'! It was carbonized. After performing the above autoclave treatment and subsequent carbonization treatment three times in total, this was placed in a graphitization furnace for 1.2 hours in an argon atmosphere.
After heating up to goo'C, it was cooled to obtain a C/C composite material. The bulk density of the obtained C/C composite material was 8 Kl/cd,
Thermal conductivity in the thickness direction (same direction as the fiber axis) and in the direction perpendicular thereto was measured using a laser flash method thermal constant measuring device (manufactured by Shinku Riko).

The thermal conductivity in the thickness direction is 3. The thermal conductivity in the direction perpendicular to the thickness direction was 0.3/W/cm·°C, and the ratio was /2.0.

In addition, this one is; 1! It did not break even when rapidly placed in a graphitization furnace heated to 00°C, and had excellent thermal shock resistance.

Example In Example 1, the dimensions after molding are /, 2 x / 3 x
A C/C composite material was obtained in the same manner as in Example 1, except that G (IIw) was used, and the autoclave treatment and subsequent carbonization treatment were performed twice in total.

The bulk density of the obtained C/C composite material was 8g/d. The thermal conductivity in the thickness direction is 7. A/, thermal conductivity in the direction perpendicular to the thickness direction is 0. ! The ratio of /Ashi is 7. O
It was g.

C/C composite material with: 1! It did not break even when rapidly placed in a graphitization furnace heated to 00°C, and its thermal shock resistance was also excellent.

(Effects of the Invention) The C/C composite material according to the present invention has large thermal conductivity and electrical conductivity in the thickness direction, so it is particularly effective when used when unidirectional heat or electricity conduction is required. It can be used as a material for heat exchange such as heat removal or heat transfer, or as a switch material.

Claims (2)

[Claims] (1) The carbon fibers are substantially oriented in the thickness direction, the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in the direction perpendicular to the thickness direction is 2 or more, and the thermal conductivity in the thickness direction is A carbon fiber-reinforced carbon composite material having a temperature of 3W/cm・℃ or more. (2) Impregnate long carbon fibers in thermosetting resin, heat this to obtain a fiber/resin composite, cut this composite into a length longer than the thickness direction of the desired composite material, and The fibers are aligned in one direction so that they are parallel to each other, pressure is applied in a direction perpendicular to the length direction of the fibers, the resin is molded, hardened, and then carbonized. A method for producing a carbon fiber-reinforced carbon composite material, which is characterized by impregnating, carbonizing, and optionally graphitizing.