JP3383991B2 - Carbon fiber reinforced carbon composite and sliding material using it - 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 fiber reinforced carbon composite material (hereinafter referred to as C / C composite material) having excellent wear resistance, and a sliding material using the same.

[0002]

2. Description of the Related Art Conventionally, metal disc rotors have been used as sliding materials for brakes for aircraft and vehicles and clutches for vehicles. However, in recent years, C / C composite materials have been used for sliding materials such as disc rotors of brakes for the purpose of reducing the weight of vehicles and improving the characteristics such as heat resistance. A general method for producing a C / C composite material is to impregnate or mix a long fiber or short fiber carbon fiber bundle with a resin or pitch, and heat-mold under pressure, and then heat this under an inert atmosphere at 600 to 2500 ° C. Bake at. Repeatedly impregnated with pitch or resin and fired as necessary, or by precipitating carbon in the pores by a gas phase reaction, or by using both of them, a densification treatment is performed,
The final C / C composite is obtained.

[0003]

However, the C / C composite material is inferior in wear resistance particularly under high load conditions such as high energy level and high pressure, and if it is repeatedly used under high load conditions, it will be short-term. There is a problem that the wear progresses in the meantime and the replacement is required. Therefore, it is an object of the present invention to provide a C / C composite material having excellent wear resistance even under a high load condition and to expand the use of the C / C composite material as a sliding material.

[0004]

Means for Solving the Problems In solving the above-mentioned problems, the inventors have found that if the fibers and the matrix are firmly bonded to each other and breakage at the micro level is less likely to occur,
As a result of repeated studies, considering that the wear resistance is improved, C / of a final porosity of 10 vol% or less obtained by a specific method
It was found that the intended purpose was achieved by the C composite material, and the present invention was completed. That is, the present invention relates to a C / C composite material having excellent wear resistance even under a high load condition and a sliding material using the same. Hereinafter, the details of the present invention will be described.
As the carbon fiber used in the present invention, any of pitch-based, PAN-based, rayon-based carbon fiber and the like can be used. However, if the sizing agent is attached to the carbon fiber bundle,
The impregnating property of the matrix raw material into the fiber is deteriorated, and the adhesive property between the fiber and the matrix is reduced. Therefore, in the present invention, the carbon fiber bundle to which the sizing agent is not attached is used. If sizing agent is attached, solvent wash,
The sizing agent is previously removed by a method such as thermal decomposition treatment. The form of the carbon fiber is usually a tow, strand, roving, yarn or the like composed of a bundle of 2000 to 8000 single fibers, and a short fiber-like one obtained by cutting these is used. In the present invention, it is usually 0.
A short fiber bundle of 3 to 100 mm, preferably about 5 to 50 mm is used.

Next, these short fiber bundles are defibrated to produce a two-dimensional random sheet. At that time, if necessary, Si
Inorganic fibers such as C, Al ₂ O ₃ and carbon black, and inorganic substances may be added. As a method of manufacturing the sheet,
For example, after defibrating with a wet method using a method of dry defibration using a random webber, which is common in the production of non-woven fabrics, a beater used for beating treatment of pulp or pulper used for defibration treatment, etc. There is a method of paper making and drying.
The carbon fiber sheet thus obtained is impregnated to prepare a prepreg as described by the inventors of the present invention in Japanese Patent Laid-Open No. 3-140211, and the prepreg is appropriately laminated according to the purpose and molded, Bake in an inert atmosphere. On this occasion,
When the firing temperature exceeds 2000 ° C., the adhesiveness between the fiber and the matrix decreases due to the shrinkage of the fiber in the radial direction, the development of crystallinity on the fiber surface and the like. Therefore, the firing temperature is 2
000 ° C or less, more preferably 1600 to 2000 ° C
And

The fired compact has a large number of pores,
As it is, it cannot be practically used due to its characteristics. Therefore, in order to reduce the pores, the densification treatment of impregnating the pitch and firing is repeated a plurality of times. A preferable pitch is a softening point of 70 to 100 ° C., more preferably 80 to
90 ° C., toluene insoluble content 10 to 30%, more preferably 13 to 20%, quinoline insoluble content 1% or less, fixed carbon 40% or more, further preferably 50% or more. In order to improve the wear resistance, the densification treatment is repeated until the final porosity becomes 10% or less. The porosity is measured by a conventional method, and specifically, a mercury porosimeter is used. When the firing temperature exceeds 2000 ° C., the crystallinity of the impregnated matrix develops and the shrinkage accompanies the decrease in adhesiveness between the fiber and the matrix. On the contrary, when the temperature is low, the oxidation resistance becomes poor. Therefore, the firing temperature is 20 in all cases.
It should not exceed 00 ° C, and more preferably the maximum temperature therein should be in the range of 1600 to 2000 ° C.
Thus, finally, a C / C composite material having excellent wear resistance can be manufactured. If this is used as a sliding material, it can be used as a C / C sliding material having excellent durability.

[0007]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. (Production Example 1) 40 filaments cut into 30 mm length
The pitch-based carbon fiber bundle of No. 00 having no sizing agent attached thereto was defibrated with a random webber to obtain a two-dimensional randomly oriented sheet having a basis weight of 200 g / m ² . Next, the sheet was impregnated with a phenol resin diluted with ethanol and then dried to prepare a sheet impregnated with 130 g / m ² of the phenol resin per unit area. This sheet is laminated in a mold and pressure-molded at 250 ° C. to obtain Vf (fiber volume ratio).
A molded body of -50% was obtained. This molded body is heated to 200 in a heating furnace.
After firing to 0 ° C, impregnate pitch and heat in a heating furnace to 100
Baked at 0 ° C. After repeating this impregnation-firing operation four times, firing was performed at 2000 ° C., impregnation was performed again, and then firing was performed at 2000 ° C. to obtain a porosity of 8
% Of the invention C / C composite was obtained. Using this C / C composite material, the rotation speed is 7,000 rpm and the surface pressure is 12 kg / cm ^2.
The inertia friction test was repeated 20 times under the conditions of. Then, the change in the thickness of the test piece before and after the test was measured, and the wear amount per test was calculated from the change, to obtain the wear rate. This C /
Table 1 shows the wear rate of the C composite material.

(Comparative Example 1) A pitch type carbon fiber bundle having 4000 filaments cut to a length of 30 mm and having a 1% polyvinyl alcohol sizing agent attached thereto was used, and in the same manner as in Example 1, C having a porosity of 8% was used. / C composite material was obtained, and its wear rate was measured. The wear rate of this C / C composite material is shown in Table 1. (Comparative Example 2) Molded in the same manner as in Example 1 to obtain 2000
After firing at ℃, it was heated to 550 ℃ by a high-frequency heating device, dichloroethylene vapor was introduced into the reaction vessel using nitrogen gas as a carrier gas, and the pores were filled with pyrolytic carbon. Then impregnate the pitch and 1000 in a heating furnace
Baked at ° C. After repeating this impregnation-calcination operation again, calcination was performed at 2000 ° C. to obtain C having a porosity of 12%.
A / C composite material was obtained. Then, the wear rate was measured in the same manner as in Example 1. The wear rate of this C / C composite material is shown in Table 1. (Comparative Example 3) A C / C composite material having a porosity of 8% was obtained in the same manner as in Example 1 except that the firing temperature immediately after molding was 2400 ° C, and the wear rate was measured. The wear rate of this C / C composite material is shown in Table 1.

[0009]

According to the present invention, a C / C composite material having excellent wear resistance even under high load conditions can be easily obtained.

[0010]

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-140211 (JP, A) JP-A-1-275468 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 35/83

Claims (2)

(57) [Claims] 1. A short fiber carbon fiber bundle consisting of a plurality of single fibers, to which a sizing agent is not attached, is defibrated and impregnated with resin or pitch to form a prepreg, and the prepreg is laminated and molded. A carbon fiber reinforced carbon composite material having a final porosity of 10 vol% or less, which is obtained by repeating pitch impregnation and firing at 2000 ° C. or less after firing at 2000 ° C. or less. 2. A sliding material using the carbon fiber reinforced carbon composite material according to claim 1.