KR970007019B1 - Process for the preparation of carbon fiber reinforced carbon composite using pitch - Google Patents

Abstract

The present invention related to a process for manufacturing carbon fiber reinforcement carbon compound material with high density using pitch as matrix material.The present invention comprised a process of impregnating pitch in carbon fiber and forming molded body; a process of ascending soften point of pitch by heat treatment under inactive atmosphere after throwing said molded body in fixed jig; a process of heating and compressing, carbonizing under inactive atmosphere.

Description

Manufacturing method of high density carbon fiber reinforced carbon composite material

The present invention relates to a method for producing a carbon fiber-reinforced carbon composite material, and more particularly, to a method for producing a high-density carbon / carbon composite using carbon fiber as a reinforcing material and pitch as a raw material of a matrix.

Carbon / carbon composites are widely used in aerospace materials such as brakes for aircrafts, rockets, heat-resistant structural materials of space shuttles, nuclear reactor materials and other mechanical parts because of their light weight, high strength, and excellent heat resistance and corrosion resistance.

Conventionally, in the production of such carbon / carbon composites, carbon fibers are impregnated with organic materials such as numerical values or pitches in a liquid phase, molded and cured, carbonized, or pyrolytic carbon between carbon fibers by chemical vapor deposition of hydrocarbon gas. It was prepared by the method of filling.

In the former method, the former has the advantages of low cost of raw materials, high carbon yield, and excellent graphitization of carbonaceous carbon obtained after carbonization, thereby improving the performance of the carbon / carbon composite material, whereas after liquid impregnation. When carbonization, some of the components contained in the pitch matrix matrix volatilize to form pores inside the carbon / carbon composite material after carbonization. Therefore, the liquid impregnation and carbonization process must be repeated several times to densify.

However, as the number of times of repeating the liquid impregnation and carbonization process increases, the time and cost required for manufacturing the carbon / carbon composite material increases, thereby reducing economic efficiency. In order to solve this problem, various approaches have been attempted to increase the carbonization yield of matrix raw materials to reduce the number of repetitions of liquid impregnation and carbonization process or to produce a dense carbon / carbon composite material at once.

First, a method of using a pressure reactor such as an autoclave or a hot isotatic press when carbonizing, European Patent No. 323750, European Patent 335736, Japanese Patent Publication No. 2-258676 And the second is coke powder having high carbonization yield (Iron and Steel, Vol. 72, No. 5, p. 306, 1986) or carbon powder (Japanese Patent Publication No. 60-200867 and Japanese Patent Publication ( Sub) 62-148366) is mixed and impregnated, and third is a method of heat treatment or extraction of solvent to use pitches having a high carbon yield as a matrix material, using anisotropic liquid crystal pitch (carbon, first 123, p. 150, 1985), methods of using self-crystallized coke (Japanese Patent Laid-Open No. 60-54974 and Japanese Patent Laid-Open No. 61-21973), and Pitch Microspheres (Japanese Patent Laid-Open No. 1-239060).

However, the first method is difficult to manufacture if the pressure reactor is expensive and the size of the carbon / carbon composite material to be manufactured is increased, the second method is added to the process of grinding by adjusting the particle size of the powder to be mixed. The viscosity of the matrix raw material rises, making it difficult to impregnate. In addition, the third method is a low production yield of the matrix raw material, the manufacturing conditions are difficult, the manufacturing cost is high, and the viscosity is high, there is a problem that the impregnation is not easy. Accordingly, an object of the present invention is to provide a more improved high-density carbon / carbon composite manufacturing method that solves the conventional problems as described above.

It is further an object of the present invention to provide a method for producing a high density carbon / carbon composite more simply by using pitch as a matrix raw material.

In the carbon fiber-reinforced carbon composite material manufacturing method according to the present invention, the pitch is impregnated in the carbon fiber, and a molded body is formed. Under heat compression and carbonization.

Hereinafter, the present invention will be described in detail.

The present inventors note that when the pitch is heat-treated, the softening point is increased, the yield of carbonization is increased while the viscosity is increased, so that impregnation is difficult. After forming the molded body and heat-treating the above-mentioned molded body to increase the softening point of the pitch and carbonize it, it was found that the viscosity can be kept low during impregnation and the yield can be increased during carbonization. Pitches with a wide range of softening points can be used as raw materials for carbon / carbon composites.

As the carbon fiber that can be used in the present invention, any known carbon fiber such as rayon-based, polyacrylonitrile-based, or pitch-based can be used, and carbon fiber can be used in the form of yarn or cloth. , Continuous fiber type such as tape, and discontinuous fiber type such as chopped fiber, mat and felt.

Pitch, which is a matrix raw material, can be used for pitches having a softening point of 25 ° C. or higher and 300 ° C. or lower among the pitches synthesized from petroleum-based heavy oil, coal tar or petroleum-based coal pitch or other organic matter.

The pitch is melted and applied to carbon fiber to be impregnated, or the pitch is pulverized into a powder form and sprinkled uniformly on the carbon fiber and then melted to impregnate. The amount of turno fibers and pitch during impregnation can be adjusted accordingly depending on the final product required.

The molded article is prepared by stacking, arranging, or dispersing the pitch-impregnated carbon fibers in a jig according to a desired use, followed by heating using a hot press, pressing at an appropriate temperature, and cooling. At this time, the heating temperature is the softening viscosity of the used pitch is 50 ℃ to 150 ℃ higher temperature is good, but if the heating temperature exceeds 350 ℃ thermal polymerization reaction of the pitch is not preferable.

The molded article is placed in a fixture and heat treated in an inert atmosphere. At this time, the role of the fixing jig is to prevent the pitch from flowing to the outside during the heat treatment and to prevent the molded body from expanding or deforming.

In addition, the heat treatment of the molded body may be performed under reduced pressure heat treatment of 1 Torr or more and 760 Torr or less, pressurized heat treatment of 1 kg / cm 2 or more and 200 kg / cm 2 or normal pressure heat treatment, and the heat treatment temperature is performed at a temperature of 300 ° C. or higher and 600 ° C. or lower. desirable. If the heat treatment at a temperature of less than 300 ℃ takes too long, while the heat treatment at 600 ℃ or more harden the pitch rapidly, it is impossible to compress during subsequent heating compression. According to the heat treatment, low-molecular-weight components having low boiling point are volatilized in the pitch component, which is a matrix raw material, and polycondensation reaction occurs, and as a result, the softening point increases as the average molecular weight increases. Can be increased.

After the heat treatment, the molded body is transferred to a fixed fixture or another suitable jig, mounted on a hot press, heated to a temperature of 450 ° C. to 700 ° C. under an inert atmosphere, compressed to a pressure of 10 kg / cm 2 to 500 kg / cm 2, and then to the original thickness of the molded body. It is compressed to 30% to 90% of and maintained for 10 minutes to 10 hours and then cooled. At this time, the compression is performed because part of the pitch inside the molded body volatilizes during the heat treatment of the molded body and flows out, or the pores formed by shrinking the pitch as a result of the polycondensation reaction can increase the density. . The carbon / carbon composite material desired by carbonization of the cooled molded body after heat-coating at a temperature of 900 ° C. or more under an inert atmosphere is produced.

Hereinafter, embodiments of the present invention will be described.

(Example 1)

Coal-based pitch powder having a softening point of 163 ° C was sprinkled on 8 sheets of woven fabric of 12,000 strands of polyacrylonitrile-based carbon fiber, and then maintained at 250 ° C for 10 minutes. I made Prepreg. Then, the prepreg was laminated in the jig and a molded product was prepared at 250 ° C. using a hot press. The molded body was placed in a fixture, and the fixture was placed in a Pyrex reactor again, and heated to 5 ° C. per minute while blowing nitrogen gas, followed by heat treatment at 480 ° C. for 70 minutes, followed by cooling. Subsequently, the molded body was removed from the fixed jig and placed in a jig made of graphite, mounted on a hot press, heated to 5 ° C. per minute while maintaining an inert atmosphere, and heated and condensed at 500 ° C. at a pressure of 50 kg / cm 2 to reach 77% of the original thickness. After maintaining for 60 minutes and cooling, it was again carbonized at 1000 ℃ for 1 hour to prepare a carbon / carbon composite material. After heat compression, the density of the cooled compact was measured to be 1.51 g / cm 2, and after carbonization, it was 1.46 g / cm 3.

(Comparative Example 1)

After the molded article was manufactured under the same conditions as in Inventive Example 1, the molded article was placed in a fixture, and the fixture was placed in a Pyrex reactor again, and heated to 5 ° C. per minute while blowing nitrogen gas at 120 ° C. at 480 ° C. After heat treatment for minutes, it cooled. After cooling, the molded product was directly carbonized at 1000 ° C. for 1 hour without undergoing a heat compression step.

The density of the molded body before carbonization was measured to be 1.43 g / cm 3, but after carbonization, it expanded and cracked between prepreg layers.

(Example 2)

The coal-based pitch powder having a softening point of 103 ° C. was sprinkled on 8 sheets of cloth-shaped cloth woven from 3,000 strands of polyacrylonitrile-based carbon fiber, and kept at 210 ° C. for 10 minutes. Pitch Prepreg was made. Next, the prepreg was laminated | stacked in the jig and the molded object was manufactured at 210 degreeC using the hot press. The molded article was placed in a fixture, and the fixture was placed again in a Pyrex reactor, heated to 5 ° C per minute under a reduced pressure of 20 Torr, heat treated at 350 ° C for 60 minutes, and cooled. Subsequently, the molded body was removed from the fixed jig and placed in a jig made of graphite, mounted on a hot press, heated to 5 ° C. per minute while maintaining an inert atmosphere, and heated and compressed at a pressure of 30 kg / cm 2 at 550 ° C. to reach 85% of the original thickness. After maintaining for 60 minutes and cooling, it was again carbonized at 1000 ℃ for 1 hour to prepare a carbon / carbon composite material.

It was 1.47 g / cm <3> as a result of measuring the density of the molded object after heat compression, and it was 1.43 g / cm <3> after carbonization.

(Example 3)

After the molded article was manufactured under the same conditions as in Inventive Example 1, the molded article was placed in a fixture, and the fixture was put again in a Pyrex reactor, and heated at 5 ° C. per minute while blowing nitrogen gas at 240 ° C. at 420 ° C. After heat treatment for minutes, it cooled. Subsequently, the molded body was removed from the fixed jig and placed in a jig made of graphite, mounted on a hot press, heated to 5 ° C. per minute while maintaining an inert atmosphere, and heated at 550 ° C. at a pressure of 100 kg / cm 2 to be 72% of the original thickness. After 60 minutes and then cooled, and then carbonized at 1100 ℃ 1 hour to prepare a carbon / carbon composite material.

The density of the molded body after heat-consolidation was measured to be 1.54 g / cm 3 and the density after carbonization was 1.50 g / cm 3.

(Comparative Example 2)

In Inventive Example 3, the carbon / carbon composite material was prepared by carbonization at 1000 ° C. for 1 hour after holding at 550 ° C. for 60 minutes without performing compression in the heat compression step. The density after carbonization was 1.27 g / cm 3.

(Comparative Example 3)

In Inventive Example 3, heat compression was performed under the same conditions as Inventive Example 3 in a direct hot press without undergoing a heat treatment step of the molded product. After cooling, the molded body had severe interlayer cracking.

As described above, according to the method of the present invention, a high-density carbon / carbon composite material can be manufactured by a simple method using a pitch having a wide range of softening points as it is, without a separate pretreatment process.

Claims (1)

A method of manufacturing a carbon fiber-reinforced carbon composite material using pitch, comprising: impregnating a pitch having a softening point in a range of 25-30 ° C. to a carbon fiber, and forming a pitch-impregnated carbon fiber; Placing the molded body in a fixture and then heat-treating it at a temperature in the range of 300-600 ° C. under an inert atmosphere to increase the softening point of the pitch; And then put the molded body in another fixed jig and heated to 450-700 ℃, compressed to 30-90% of the original thickness of the molded body at a pressure of 10-500kg / ㎠, maintained for 10 minutes-10 hours and then cooled Method for producing a high-density carbon fiber reinforced carbon composite material characterized in that.