JP2775766B2 - Carbon fiber reinforced carbon composite and use thereof - Google Patents

Description

The present invention relates to a carbon fiber reinforced carbon composite material and a method for using the same.

(Prior Art) A carbon fiber reinforced carbon composite material (hereinafter, referred to as a C / C composite material) is characterized by being lightweight, high in strength, and excellent in heat resistance and corrosion resistance. For this reason, they are used for aerospace materials such as rocket nozzles, nose cones, digital brakes for aircraft, heating elements, hot press molds, other mechanical parts, and members for nuclear reactors.

This C / C composite is generally polyacrylonitrile-based,
Pitch-based carbon fibers such as long or short fibers are impregnated or mixed with a thermosetting resin such as phenolic resin or furan resin or a thermoplastic resin such as pitch, and then heated and molded into an inert gas. In a non-oxidizing atmosphere such as, firing at about 600 to 1000 ° C., firing after impregnating the pitch resin, or after densification using a method using chemical vapor deposition, or a method combining these,
It is manufactured by graphitization as needed.

(Problems to be solved by the invention) However, the obtained C / C composite material is not
That is, when it is necessary to use it for the purpose of effectively conducting or removing heat in the thickness direction, it is not always satisfactory, and there is a problem in practical use.

Therefore, the present inventors have overcome the above-mentioned insufficiency C /
Various studies were conducted to obtain a C composite material, and a C / C composite material having an increased thermal conductivity in one direction was obtained, and the present invention was achieved.

That is, the gist of the present invention is that about 50% or more of carbon fibers are substantially oriented in the thickness direction, and the thermal conductivity in the direction perpendicular to the thickness direction and perpendicular to the plane oriented in the thickness direction of the fiber. A carbon fiber reinforced carbon composite material having a thermal conductivity ratio in the thickness direction of 1.2 or more and a thermal conductivity in the thickness direction of 1.5 W / cm · ° C. or more and a method of using the same.

(Means for Solving the Problems) Hereinafter, the present invention will be described in detail.

The carbon fiber used in the present invention may be of any type such as polyacrylonitrile (PAN) -based, pitch-based carbon fiber, or vapor grown carbon fiber, and particularly high-performance pitch having high thermal conductivity in the fiber axis direction. System, especially coal-based pitch system,
Carbon fibers are preferred.

The C / C composite material according to the present invention is obtained using such a carbon fiber, and about 50% or more of the carbon fiber is substantially oriented in the thickness direction, and is perpendicular to the thickness direction and the thickness of the fiber. The ratio of the thermal conductivity in the thickness direction to the thermal conductivity in the direction perpendicular to the plane oriented in the direction is 1.2 or more, preferably 1.5 or more, and the thermal conductivity in the thickness direction is 1.5 W / cm It is characterized in that it is preferably at least 1.8 W / cm · ° C.

Then, such a C / C composite material is obtained by using a woven fabric, a short fiber, a web, a nonwoven fabric, or the like by the following method.

[A] When a woven fabric is used: As the woven fabric, ordinary plain weave, satin weave, twill weave and the like are used.

 First, these woven fabrics are impregnated with a thermosetting resin.

Examples of the thermosetting resin include a phenol resin, a furan resin, an epoxy resin, and an unsaturated polyester resin, and a phenol resin, particularly a resol-type phenol resin can be preferably used. These thermosetting resins are usually dissolved and diluted with a solvent such as alcohols such as ethanol, hydrocarbons such as hexane, or acetone.

The concentration of the thermosetting resin solution is usually in the range of 10 to 70% by weight, preferably 20 to 60% by weight.

For those requiring a curing agent such as a furan resin and an epoxy resin, the curing agent is also added to the solution, but the amount is added in an amount suitable for each resin.

As a method of impregnating such a thermosetting resin solution with a woven fabric of carbon fibers, a simple method such as immersing carbon fibers in the solution may be used. It is preferable to run continuously.

At this time, it is preferable to apply an ultrasonic wave of about 10 to 50 KHz to the tank filled with the solution, because it is possible to prevent the influence of unevenness of treatment due to bubbles or the like between the individual fibers or between the weaves.

After the above impregnation, the fiber / resin composite obtained is cut into a desired size, for example, put in a dryer to remove the solvent.

For example, a dryer in which a woven fabric is impregnated with an alcohol solution of a phenol resin by passing between rolls, and the woven fabric is passed between the rolls to remove excess resin and keep the temperature at about 10 ° C. lower than the boiling point of the alcohol. Remove alcohol. Thereafter, the woven fabric is cut with a cutter to a size slightly larger than the cross section in the thickness direction of the product intended by the cutter.

The cut composites are stacked and filled in a mold having dimensions slightly larger than the intended product, and molded. For example, the cut composites are stacked, pressure is applied in the stacking direction, and the temperature is increased to obtain a molded body in which the resin is cured by curing.

The appropriate conditions for the heat curing treatment vary depending on the type of the thermosetting resin used, but are usually 50 to 300 ° C, preferably 80 to 200 ° C for 0.2 to 5 hours, preferably 0.1 to 5 hours.
Heat treatment is performed for 2 to 2 hours.

After that, put the molded body in a container, and shape the molded body to be surrounded by coke breeze, then put the container in an electric furnace,
If necessary, the temperature is raised to about 1000 ° C. under N ₂ gas flow to carbonize.

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

Then, the obtained carbide or graphitized product is petroleum-based,
After impregnating a thermosetting resin such as coal pitch or a phenol resin or a furan resin, or in the case of a thermosetting resin, the resin is cured and then carbonized.

The recurable thermosetting resin is generally used by dissolving it in a solvent such as alcohol, acetone or anthracene oil and adjusting the viscosity to an appropriate value.

In this case, a method of impregnating under pressure is preferably employed.

For example, the carbide or graphitized material and the pitch of the molded body were put into a low-pressure reactor (autoclave) and heated in a vacuum to dissolve the pitch, and the carbide or the graphitized material was immersed in the pitch melt. Thereafter, N ₂ gas is introduced and the temperature is raised to about 550 to 600 ° C. at a low pressure.

Thereafter, it is cooled to take out a densified carbide or graphitized material, carbonized to about 1000 ° C. in the same manner as described above, and graphitized as necessary.

By repeating the above-mentioned so-called densification method, a highly dense C / C composite material having a specific gravity of 1.6 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 and graphitization is too high, the strength in the direction perpendicular to the length direction of the fiber will decrease. Therefore, it is necessary to select an appropriate condition because it may lead to destruction in some cases. In addition, a higher graphitization temperature facilitates obtaining a higher thermal conductivity.

The obtained C / C composite material is an anisotropic material having a thermal conductivity and an electrical conductivity of 1.5 W / cm · ° C. or more (usually up to less than 3.0 W / cm · ° C.) in the thickness direction.

[B] Another embodiment in which a woven fabric is used: A carbon fiber woven fabric impregnated with a thermosetting resin is stacked, then molded, cured, carbonized, and then carbonized after impregnating in a pitch or thermosetting resin. Graphite as needed to obtain the desired C / C composite.

This is cut by taking the dimension of the C / C composite material in the surface direction so as to be larger than the cross-sectional area in the thickness direction of the target product.

The cut composite is shaped so that the plane directions match,
That is, binding or bonding is performed so that the surface of the woven fabric is oriented in the thickness direction of the target product.

By wrapping around using a long fiber made of carbon fiber as a material, or by binding C / C composite material or general carbon fiber in an appropriate shape, Tied together without gaps.

In addition, the surfaces are bonded together using a resin mainly composed of phenolic resin, and the temperature is raised again to a temperature at which the C / C composite material is finally processed to cut the C / C composite material. Many pieces may be adhered to each other.

[C] When short fibers or non-woven fabrics are used: (i) A short fiber of carbon fibers is defibrated and a web is formed by an ordinary method, and this web is used in place of the woven fabric of [A] and replaced with [A]. In the same manner, a C / C composite material is prepared in which the direction in which most of the fibers of the web are oriented (the plane direction of the web) is oriented in the thickness direction of the target product.

(Ii) A carbon fiber non-woven fabric prepared from long fibers of carbon fiber by a conventional method, treated in the same manner as in [A], instead of the woven fabric in [A], and the product is oriented in the plane direction of the non-woven fabric. Create a C / C composite that is oriented in the thickness direction.

[D] When using a web formed from short fibers and needling it: Using the web obtained in [C] and needling in the thickness direction instead of the web, treating in the same manner as in [C] Thus, the C / C composite is obtained such that the plane direction of the web is oriented in the thickness direction of the target C / C composite.

The C / C composite material of the present invention has high heat conductivity and electric conductivity in the thickness direction, and can effectively remove and transmit heat. In addition, it has high thermal shock resistance in a direction perpendicular to the thickness direction, and can withstand use in a high-temperature furnace.

This C / C composite material, for example, has a high thermal conductivity in the thickness direction even if a substance heated at a high temperature is placed on one surface, so that heat is easily transmitted to the other surface, and The heated substance can be effectively cooled by contacting the parts where the cooling water has flowed. That is, it can be effectively used when cooling a substance by heat exchange.

In the present invention, it is preferable to use a pitch-based carbon fiber having a high thermal conductivity in the fiber axis direction, particularly a coal pitch-based, high-performance carbon fiber because the effect is further enhanced.

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

Example 1 Pitch fibers ("Dialead", 3000 filaments,
Eight-sheet satin weave (260 g / m ² ) with a fiber diameter of 10 μm was mixed with an ethanol solution of phenol resin (phenol resin: ethanol = 1:
After impregnating in 4) and removing ethanol in a drier maintained at a temperature of 70 ° C., it was cut into 22 × 105 mm.

The composite was stacked about 95 mm in a direction perpendicular to the plane of 22 × 105 mm so as to be larger than the size of the target C / C composite.

Then, a low pressure was applied at 150 ° C., the temperature was raised to 250 ° C. in one hour, and the temperature was held at 250 ° C. for one hour, followed by molding and curing. The dimensions of the obtained molded product were 103 × 2 × 93.4 × 21.9 mm.

Next, the molded product was placed in a container filled with coke breath, and the temperature was raised to 1000 ° C. over about 50 hours in a state covered with the coke breath to carbonize the resin.

Then, the carbonized composite and the solid pitch were put into an autoclave, and the temperature was raised to 250 ° C. in a reduced pressure state. Then, the atmosphere was made positive by adding N ₂ , and then the temperature was raised to 500 ° C. for 8 hours. After that, the temperature was kept at 500 ° C. for 5 hours.

During the heating, the pressure was kept constant using a valve attached to the autoclave.

The autoclave was cooled, the composite was taken out, and carbonized to 1000 ° C. in the same manner as the carbonization of the molded product. After the above-mentioned autoclave treatment and subsequent carbonization treatment were performed a total of three times, the mixture was placed in a graphitization furnace, heated to 2800 ° C. in an argon atmosphere, and then cooled to obtain a C / C composite material.

The bulk density of the obtained C / C composite material is 1.62 g / cm ³ , the thermal conductivity in the thickness direction is 1.63 W / cm ・ ℃, and the thermal conductivity in the direction perpendicular to it and also perpendicular to the woven fabric surface The ratio was 0.23 W / cm · ° C., and the ratio of the thermal conductivity was 7.0 (the orientation of the carbon fibers in the thickness direction was about 50%).

Example 2 The same pitch-based carbon fiber satin weave as used in Example 1 was impregnated in an ethanol solution of a phenolic resin, dried and molded on a flat plate in the same manner as in Example 1. Then, this was heated to 1000 ° C., and thereafter, it was densified by repeating a usual pitch impregnation method, and finally graphitized at 2800 ° C. Next, this 10 mm thick plate-like C / C composite material is cut into a width of 20 mm and a length of 100 mm, 20 sheets are stacked so that their planes are in contact with each other, adhered with a phenol resin, and further wound around with carbon fiber. By this, width 100 mm, length 200 m
Thus, a C / C composite material having a thickness of 20 mm and a thickness of 20 mm was obtained. The thermal conductivity in the thickness direction was 1.64 W / cm · ° C., and the ratio of the thermal conductivity in the direction perpendicular to the adhesive surface and the direction perpendicular to the adhesive surface was 7.5 (the orientation in the thickness direction was about 50%). .

Example 3 pitch fibers ("Dialead", 3000 filaments,
Short fibers were obtained by cutting fibers having a fiber diameter of 10 μm), then defibrated to form a web, cut into 30 mm × 150 mm, and impregnated with an ethanol solution of a phenol resin. Then, these were laminated so as to have a thickness of about 100 mm, and a C / C composite material was manufactured in the same manner as in Example 1.

The thermal conductivity in the thickness direction of the obtained C / C composite material was 1.64, and the ratio of the thermal conductivity in the direction perpendicular to the thickness direction and the direction parallel to the lamination direction was about 6.5 (the thickness direction). Orientation is about 100%).

Example 4 Needling was performed on the same web as that obtained in Example 3 to produce a felt in which the fibers were oriented in the thickness direction of the web.

Using this, a C / C composite material was obtained in the same manner as in Example 3, and the thermal conductivity was measured in the same manner as in Example 3. As a result, the thermal conductivity in the thickness direction was 1.64, and the ratio was 6.0 ( The equilibrium in the thickness direction is about 93%).

Example 5 In Example 1, since the size of the target C / C composite material was large, it was cut so that the size of the composite became 45 × 110 mm, and the C / C composite material finally obtained was The dimensions of the moldings obtained by stacking to increase the carbon fiber content
A C / C composite material was obtained in the same manner as in Example 1 except that the size was 112 × 105 × 46 mm, and that the autoclave treatment and the subsequent carbonization treatment were performed four times in total.

The bulk density of the resulting complex with 1.82 g / cm ^3, the thermal conductivity in the thickness direction is 2.14W / cm · ℃, it is perpendicular at and the direction of the thermal conductivity at right angles with the fabric surface 0.34 W / cm · ° C., and the ratio of the thermal conductivity was 6.0 (the orientation of the carbon fibers in the thickness direction was about 50%).

Example 6 A C / C composite material was obtained in the same manner as in Example 5, except that the heat treatment temperature was changed to 3000 ° C.

The bulk density of the obtained composite material is 1.84 g / cm ³ , the thermal conductivity in the thickness direction is 2.95 W / cm ・ ° C., and the thermal conductivity in the direction perpendicular to it and also perpendicular to the woven fabric surface is , 0.37 W / cm · ° C., and the ratio of the thermal conductivity was about 8.0.

Example 7 In Example 3, except that the thickness at the time of lamination was increased so that the carbon fiber content in the finally obtained C / C composite material was increased, C / C was performed in the same manner as in Example 2. A composite was obtained.

The bulk density of the obtained composite material was 1.85 g / cm ³ .

The thermal conductivity in the thickness direction was 1.72 W / cm · ° C., and the ratio of the thermal conductivity (0.39) perpendicular to the adhesive surface and perpendicular to the adhesive surface was about 4.4.

Example 8 A C / C composite material was obtained in the same manner as in Example 7, except that the heat treatment temperature was changed to 3000 ° C.

The bulk density of the obtained composite material was 1.83 g / cm ³ , and the ratio of the thermal conductivity was about 4.9 (2.19 / 0.45).

Example 9 The same as Example 4 except that the number of needlings was increased to increase the number of fibers oriented in the thickness direction of the web, and the autoclave treatment and the subsequent carbonization treatment were performed a total of five times. To obtain a C / C composite material.

The bulk density of the obtained composite material was 1.72 g / cm ³ , the thermal conductivity in the thickness direction was 1.66, and the thermal conductivity in the direction perpendicular to the thickness direction and parallel to the lamination direction (1.17 g) ) Ratio was about 1.4.

Example 10 A C / C composite material was obtained in the same manner as in Example 9, except that the heat treatment temperature was changed to 3000 ° C.

The bulk density of the obtained composite material was 1.73 g / cm ³ , and the ratio of the thermal conductivity was about 1.2 (1.84 / 1.53).

(Effect of the Invention) Since the C / C composite material according to the present invention has a large thermal conductivity and electrical conductivity in the thickness direction, it is particularly effective when used in a case where heat or electric conduction in one direction is required. It is.

For example, it can be used as a heat exchange material or a switch material that removes and transfers heat by bringing one plane into contact with a cooling jacket.

Continued on front page (72) Inventor Hitoshi Seki 1 Banshu-cho, Sakaide-shi, Kagawa Prefecture Mitsubishi Sakaide Co., Ltd. (72) Inventor Kimihiro Ioki 2-4-1 Shiba Park, Minato-ku, Tokyo Mitsubishi Nuclear Energy Corporation (56) References JP-A-55-3710 (JP, A) JP-A-64-5984 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/83

Claims (4)

(57) [Claims] 1. About 50% or more of carbon fibers are oriented substantially in the thickness direction, and the thickness direction with respect to the thermal conductivity in the direction perpendicular to the thickness direction and perpendicular to the plane oriented in the thickness direction of the fibers. Is a carbon fiber reinforced carbon composite material having a thermal conductivity ratio of 1.2 or more and a thermal conductivity in the thickness direction of 1.5 W / cm · ° C or more. 2. The thermal conductivity in the thickness direction is 1.5 W / cm.degree.
2. The material according to claim 1, wherein the material is less than W / cm · ° C. 3. The method according to claim 1, wherein the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in the direction perpendicular to the thickness direction and perpendicular to the plane oriented in the thickness direction of the fiber is 1.5 or more. material. 4. The thickness direction relative to the thermal conductivity in a direction in which about 50% or more of the carbon fibers are substantially oriented in the thickness direction, and are perpendicular to the thickness direction and perpendicular to the plane oriented in the thickness direction of the fiber. The ratio of the thermal conductivity of 1.2 or more, and the thermal conductivity in the thickness direction is 1.5 W / cm · ° C. or more of the carbon fiber reinforced carbon composite material, the high-temperature substance on one surface facing the thickness direction, A heat transfer method in which a low-temperature substance is brought into contact with the other surface.