JPH09278553A - Production of carbon composite material reinforced with carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a brake slide material of carbon fiber-carbon composite material excellent in friction and slide characteristics. SOLUTION: This method for producing a brake slide material of carbon fiber-reinforced carbon composite material excellent in friction and slide characteristics comprises using carbon fibers, orienting the fibers in a two-dimensional random state, impregnating the obtained sheets with a resin or pitch, laminating and molding the treated sheets, subjecting the molded product to a primary calcination treatment at a temperature of <=200 deg.C, subjecting the calcined product to a CVD treatment, repeating a pitch or resin-impregnating treatment and a calcination treatment at a final thermal treatment temperature, and subsequently subjecting the densified product to a final thermal treatment at a lower temperature than the primary calcination temperature.

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 fiber reinforced carbon composite material (hereinafter referred to as C / C composite material) which is excellent in strength, friction and sliding characteristics and is suitable for a brake sliding material.

[0002]

2. Description of the Related Art A general brake material has a function of converting kinetic energy into heat energy by frictionally connecting a rotating body and a fixed body, and decelerating and stopping a moving object. . In recent years, due to the increase in weight due to the increase in speed and size, the C / C composite material has been put to practical use in many airplanes, especially as an aircraft brake material because of its excellent thermal conductivity, large heat capacity, high strength and the like. Is becoming more and more popular.

In general, a C / C composite material is prepared by impregnating a long or short carbon fiber such as PAN, pitch or rayon with a thermosetting resin such as phenol resin or furan resin or a thermoplastic resin such as pitch. It is manufactured by baking in a non-oxidizing gas atmosphere, mixing and heat-molding, and further densifying and graphitizing.

[0004]

The characteristics desired as a C / C brake material include a material having a braking ability capable of stopping within a first predetermined stopping distance, that is, a material having an appropriate friction coefficient. Material. Second, an excessive braking torque value is generated during braking,
It is desired not to have a property that does not cause a so-called galling effect and does not impose an excessive load around the brake material. That is, it is a material that does not have an excessive coefficient of friction and that has an appropriate instantaneous coefficient of friction.

Third, the amount of wear must be small. The C / C composite material is composed of matrix carbon and carbon fiber, but when used as a brake material, the carbon fiber or matrix carbon peels off from the sliding surface and wears out, limiting the number of uses. To greatly improve the life of the brakes.

[0006]

Therefore, as a result of repeated studies to solve the above-mentioned problems, the inventors have used pitch-based carbon fibers, orienting the fibers in a two-dimensional random manner, and After the subsequent firing, densification using CVD as a matrix, followed by impregnation of pitch or resin and firing at a temperature lower than the final heat treatment temperature are repeated to densify, and the final heat treatment is performed at a temperature lower than the primary firing temperature. Solved the problem.

Hereinafter, the present invention will be described in detail. As the carbon fiber used in the present invention, known pitch-based carbon fiber can be used, but the tensile modulus of the carbon fiber is preferably 10 or less.
~ 25t / mm ² 16 in an inert gas atmosphere
Tensile modulus of elasticity is 50 t / mm after firing at 00-2000 ° C
It is more desirable that it has a property of being converted into ^two or more.

The carbon fiber used may be in the form of tows, strands, rovings, yarns or the like composed of a plurality of single fibers, and it is preferable to use short fibers obtained by cutting the carbon fibers. These short fibers are formed from a bundle of a plurality of short fibers, and in the present invention, usually 0.3 to 100 mm, preferably 5 to 50 mm.
When a short fiber of about mm is used to form a C / C composite material, the short fiber is preferably opened and dispersed to prepare a two-dimensional random sheet, and a matrix substance is filled between them.

[0009] Here, as a specific method for producing a dry-opened and two-dimensionally randomly oriented sheet, for example, a random weber is used which is commonly used in spinning to mechanically convert carbon fibers into monofilaments to produce a sheet. Or a method of opening the sheet by air to produce a sheet. As a method for producing a sheet that is wet-opened and randomly oriented two-dimensionally, for example, a beater that is usually used for beating of pulp or a pulper that is used for opening is used, and short fibers are used in a solvent. After the filamentous carbon fiber is opened, for example, it is supplied little by little to a mold or the like having a screen at the bottom, or evenly dispersed by means such as stirring after opening, papermaking with a wire mesh or the like, followed by drying to produce. is there. As the solvent for uniformly dispersing the short fibrous carbon fibers, water, acetone, alcohol having 1 to 5 carbon atoms, anthracene oil or the like is preferably used, but other organic solvents may be used. If the phenol resin, furan resin, pitch, or the like is dispersed or dissolved in the solvent, the carbon fibers are bonded to each other,
It is preferable because handling in the next step is easier. Furthermore,
It is preferable to add a thickening agent such as fiber-based sodium glycolate, polyvinyl alcohol, or hydroxycellulose to the solvent because the effect thereof is further increased.

Various weights (weight per 1 m ² ) of the sheet can be taken, but 10 to 500 g / m ² is optimal in view of handleability, impregnation property and uniformity. The two-dimensional randomly oriented sheet thus obtained is impregnated with a phenol resin, furan resin, or a matrix such as petroleum-based or coal-based pitch, and then dried.
At this time, the matrix used is one dissolved in a solvent such as alcohol, acetone, anthracene oil or the like and adjusted to an appropriate viscosity.

Next, the dried sheets are laminated, filled in a mold, and pressure-molded in a temperature range of 100 to 500 ° C., and Vf (carbon fiber content) = 5 to 65%, preferably 10 to 50%. A molded product of 65%, more preferably 35 to 50% is obtained. Then, in an inert gas atmosphere such as N ₂ gas, at a temperature rising rate of 1 to 200 ° C./hr, 800 to 2200
A C / C composite material is obtained through primary firing at a temperature of up to 1800C, preferably 1800 to 2200C.

The above-mentioned fired C / C composite material has a large number of voids and cannot be practically used as it is. Therefore, in order to reduce the voids, densification treatment is performed using CVD and pitch or resin as a matrix, but the present invention precedes densification by CVD (chemical vapor deposition). The densification treatment by CVD heats the above C / C composite material placed in the reactor by an induction heating coil or resistance heating, and vapors of hydrocarbons such as methane or propane or halogenated hydrocarbons. Is supplied together with H ₂ gas, Ar gas or N ₂ gas into the reactor to impregnate the voids with the pyrolytic carbon produced and densify. Volume% of CVD
Is 10 to 35%, preferably 10 to 25%. When the densification is advanced by CVD, the densification speed gradually decreases and the processing time increases. In addition, the voids become closed pores, making it difficult to impregnate the pitch in the next step. On the other hand, if the densification in CVD is insufficient, the friction characteristics deteriorate as described in the examples.

The subsequent densification treatment with pitch or resin is
The tank in which the C / C composite material is placed is heated to a predetermined temperature, the inside of the tank is evacuated, and then molten pitch or resin is supplied and pressurized to impregnate the voids. After that, firing is performed at a temperature lower than the final heat treatment temperature, preferably 100 ° C. or more. Specific preferable temperature is 700 to 1000
℃ is mentioned. This densification treatment is repeated until the bulk density becomes 1.60 to 1.80, preferably 1.65 to 1.75.

When the final heat treatment is performed after the densification treatment, the bulk density after the final heat treatment is 1.60 to 1.80,
It is preferably densified to 1.65 to 1.75. The final heat treatment temperature is lower than the primary firing temperature,
The temperature is preferably at least 100 ° C. or lower, and a specific temperature is 1400 to 2100 ° C., preferably 15
It is carried out at 00 to 1800 ° C. The maximum temperature after such a densification treatment step needs to be the temperature at the time of the final heat treatment. The final heat treatment may be a densification step or may be separately provided after the densification step.

The C / C composite material thus produced has a hardness of 70 to 12 as measured by a Rockwell hardness tester.
5 HRP, preferably 85 to 120 HRP, and Vf (volume content of carbon fiber) of 10 to 50%, preferably 30 to 45%. The evaluation method of the C / C composite material will be described below. (Brake performance test) Using an inertial friction tester, C
A friction test is carried out by sliding a test piece (Fig. 1) (average sliding surface diameter 83.5 mm) consisting of a fixed disk (stator) and a rotating disk (rotor) formed of a / C composite material. The test conditions are: brake pressure (as sliding surface pressure) 150 psi, sliding surface speed = 22 m / s (absorbed energy per unit area E = 2.0 × 10 ³ J / c)
m ² ) and measure the average friction coefficient, the instantaneous friction coefficient at the initial stage of braking (until the time when the brake pressure reaches the set value), and the wear amount.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. (Example 1) A pitch-based carbon fiber (“DIAREAD” K321 manufactured by Mitsubishi Chemical) cut into a length of 30 mm was dry-opened to obtain a 202 g / m ² carbon fiber sheet which was two-dimensionally randomly oriented. This sheet was impregnated with a phenol resin diluted with ethanol and then dried to give a basis weight of 332.
A sheet impregnated with g / m ² of phenol resin was prepared. This sheet was laminated in a mold and pressure-molded at 280 ° C. to obtain a molded body having Vf≈48%. 20 this molded body
A densification step of performing primary calcination at 00 ° C., then performing the above-mentioned densification treatment by CVD (CVD volume% ≈22%), subsequently impregnating pitch, and calcining at 1000 ° C. in an inert atmosphere. Was repeated multiple times and the final heat treatment at 1600 ° C. was performed to obtain a C / C composite material having a bulk density of 1.68, Vf of 40% and a Rockwell hardness of 90 to 100 HRP.

When a brake performance test was conducted on this C / C composite material, the results were that the average coefficient of friction was 0.19, the instantaneous coefficient of friction was 0.30, the amount of wear was 1.0 × 10 ^-4 mm / cycle / face.

(Example 2) Pitch-based carbon fiber ("DIAREAD" K321 manufactured by Mitsubishi Chemical Co., Ltd.) cut into 30 mm length was wet-opened and two-dimensionally randomly oriented 487 g / m ²
A carbon fiber sheet of This sheet was impregnated with a phenol resin diluted with ethanol and then dried to prepare a sheet impregnated with a phenol resin having a basis weight of 910 g / m ² . This sheet was laminated in a mold and pressure-molded at 280 ° C. to obtain a molded body having Vf≈46%. After primary firing of this molded body at 2000 ° C., the above-mentioned densification treatment by CVD (CVD volume% ≈20%) is performed, then pitch is impregnated, and firing is performed at 1000 ° C. in an inert atmosphere to carbonize. The densification step described above was repeated a plurality of times and a final heat treatment at 1600 ° C. was performed to obtain a C / C composite material having a bulk density of 1.71, Vf of 43%, and Rockwell hardness of 93 to 105 HRP.

When a brake performance test was conducted on this C / C composite material, the results of average friction coefficient 0.22, instantaneous friction coefficient 0.35, wear amount 2.0 × 10 ⁻⁴ mm / cycle / face were obtained.

(Comparative Example 1) A molded body similar to that of Example 1 was subjected to primary firing under the same conditions, and then subjected to a densification treatment only with the pitch and finally heat-treated under the same conditions as in Example 1 to obtain a bulk density of 1. 72,
Vf≈40%, Rockwell hardness 100 ~ 110HRP
C / C composite material was obtained. A brake performance test of this C / C composite material was performed, and it was found that the hardness and Vf were the same as in Example 1, and the bulk density was rather high, but the average friction coefficient was 0.25 and the instantaneous friction coefficient was 0.39. The result was 3.3 × 10 ⁻⁴ mm / turn / side, which was significantly inferior to that of Example 1.

(Comparative Example 2) A molded body similar to that of Example 1 was subjected to primary firing under the same conditions, then subjected to CVD and densification treatment under the same conditions, and finally heat treated at 2000 ° C to obtain bulk density ≈ 1.72, Vf≈40%, Rockwell hardness 100-
A 110 HRP C / C composite was obtained. A brake performance test of this C / C composite material showed that the bulk density and Vf were the same as in Example 1, but the average friction coefficient was 0.28, the instantaneous friction coefficient was 0.44, and the wear amount was 3.4 × 10 ^{−. The result was 4} mm / turn / side, which was significantly inferior to that of Example 1.

(Comparative Example 3) A tow prepreg was prepared by impregnating a PAN-based carbon fiber ("Torayca" T300 manufactured by Toray Co., Ltd.) with a phenol resin and then drying it and cutting it to a length of 30 mm.
Fill into the mold, press-mold at 280 ° C, Vf≈40
% Molded body was obtained. After the molded body was primarily fired at 2000 ° C., it was densified by the above-mentioned CVD (CVD volume%
≈20%), followed by impregnation with pitch, firing at 1000 ° C. in an inert atmosphere and carbonization, repeated a plurality of times to perform a final heat treatment at 1600 ° C., and bulk density ≈1.68. , Vf≈40%, Rockwell hardness 100 ~
A 110 HRP C / C composite was obtained.

When a brake performance test of this C / C composite material was carried out, the Vf and hardness were the same as in Example 1, but the average friction coefficient was 0.22, the instantaneous friction coefficient was 0.37, and the wear amount was 6.8 ×. The result was 10 ⁻⁴ mm / turn / side, which was significantly inferior to that of Example 1.

[0024]

According to the present invention, a carbon fiber-carbon composite material having excellent friction and sliding characteristics and suitable for a brake sliding material can be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view of a test method for a brake material used in the present invention.

[Explanation of symbols]

 1 rotor disk 2 stator disk

Front Page Continuation (72) Inventor Akihiko Ashiya 1 Kyushu Town, Sakaide City, Kagawa Prefecture Mitsubishi Chemical Co., Ltd. Sakaide Plant

Claims (3)

[Claims] 1. A sheet in which short fibrous pitch-based carbon fibers composed of a plurality of single fibers are opened to fabricate a sheet in which the fibers are two-dimensionally randomly oriented, impregnated with resin or pitch, and then laminated to form 2200. Manufacture of a carbon fiber reinforced carbon composite material in which primary calcination is performed at a temperature of ℃ or less, CVD treatment is performed, pitch impregnation and calcination at a final heat treatment temperature are repeatedly performed, and then final heat treatment is performed at a temperature lower than the primary calcination temperature. Method. 2. A short fibrous pitch-based carbon fiber composed of a plurality of single fibers is opened to prepare a sheet in which the fibers are two-dimensionally randomly oriented, impregnated with a resin or pitch, and then laminated to form 2200. Manufacture of a carbon fiber reinforced carbon composite material in which primary calcination is performed at a temperature of ℃ or below, CVD treatment is performed, resin impregnation and calcination at a final heat treatment temperature are repeatedly performed, and then final heat treatment is performed at a temperature lower than the primary calcination temperature. Method. 3. The method for producing a carbon fiber reinforced carbon composite material according to claim 1, wherein the final heat treatment temperature is lower than the primary firing temperature by at least 100 ° C. or more.