KR0162242B1 - Non-asbestos friction material - Google Patents

Abstract

A non-asbestos friction material composed of a reinforcing fiber other than asbestos, a binder such as phenol resin, and a friction modifier such as barium sulfate, and a part of the reinforcing fiber is a polyacrylonitrile-based special carbon fiber.

Description

Non-asbestos Friction Material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-asbestos friction material used as brake pads, brake linings, clutch facings and the like in vehicles and industrial machinery.

More specifically, the present invention relates to a high performance non-asbestos friction material which is excellent in strength and friction characteristics and has little damage such as a brake drum or a brake disc rotor.

Conventional friction materials used asbestos as a main component.

However, the demand for non-asbestos friction materials having higher performance than asbestos systems is increasing for two reasons.

One is that the inevitable dust generated from asbestos is found to be harmful to the human body, and as a result the use of asbestos is regulated.

Another is that as vehicles have high performance, friction materials having higher performance than asbestos systems are needed.

Therefore, in recent years, many proposals have been made for non-asbestos friction materials, and many of them use organic fibers such as aramid fibers, inorganic fibers such as glass fibers, carbon fiber metal fibers and the like as basic components.

However, the conventional friction material which uses aramid fiber, glass fiber, carbon fiber, or metal fiber as a main reinforcing fiber has various problems.

These problems arise when the friction material or the like is used for brake pads of a vehicle or the like.

In a friction material using aramid fibers, the surface temperature of the friction material increases due to the continuous use of the brake, which causes thermal decomposition of the aramid fibers, resulting in a decrease in strength and coefficient of friction.

In the friction material using glass fiber, the glass fiber falls off at high temperature, and the amount of wear increases.

Friction materials using metal fibers such as steel fibers, copper fibers and the like, although excellent in wear resistance, also have various problems.

That is, as the temperature rises more, their coefficient of friction (i.e. their effect) becomes unusually high, their volume increases and their thermal conductivity becomes high, thus they can cause ignition at high temperatures.

Moreover, the friction material using glass fiber or metal fiber may damage or polish a brake drum, a brake disc rotor, etc.

On the other hand, when carbon fiber is used as the reinforcing fiber, it is expected to obtain a friction material having low heat resistance and low polishing or damage of the brake drum or brake disc rotor due to the lubricity and high reinforcing effect of the carbon fiber.

However, when a large amount of carbon fiber is used to substantially obtain the above-mentioned effect, a strange reduction in the coefficient of friction occurs due to the high lubricating effect.

Such friction materials using a large amount of carbon fiber are only applied to high-speed driving brakes such as aircraft, racing cars, etc. as C / C composites; Because of their high wear at low speeds and their very low coefficient of friction, they are often operated at low speeds and are not available for automobiles and the like.

In addition, friction materials using materials other than those mentioned above have been proposed.

However, many of them have not only high temperature characteristics but also wear resistance at high temperatures of 400 ° C. or higher, and are unstable in friction.

The present invention has been made to solve the above problems of the conventional non-asbestos friction material, and has stable friction characteristics and excellent wear resistance at high temperatures of 400 ° C. or higher as well as normal use temperature, and low damage to the brake drum or brake disc rotor, and high It is to provide a non-asbestos friction material having strength.

In order to achieve the above object, the present invention is a friction material composed of reinforcing fibers other than asbestos, a binder such as phenol resin, and a friction modifier such as barium sulfate, wherein a part of the reinforcing fibers is polyacrylonitrile-based. The non-asbestos friction material including the special carbon fiber and the specific gravity of the polyacrylonitrile-based special carbohydrate fiber is 1.60 to 1.74.

Hereinafter, the present invention will be described in detail.

In the present invention, as reinforcing fibers other than asbestos, for example, organic fibers (for example, aramid fibers, acrylic fibers, phenol fibers, polyvinyl alcohol fibers, cellulose fibers), inorganic fibers (for example, glass fibers, ceramic fibers, carbon fibers) and One fiber selected from metal fibers (eg steel fibers, copper fibers, bronze fibers) or mixtures thereof is used.

These fibers are the same as those used as middle fiber.

The present invention is characterized in that some of the reinforcing fibers are polyacrylonitrile (hereinafter referred to as PAN) -based carbon fibers.

PAN-based special carbon fiber used in the present invention, after spinning the PAN, pre-treated (burning at 200 to 300 ℃ in air) to obtain the oxidized PAN fiber to prevent the flame, 800 to 1000 It means a fiber having a specific gravity of carbon fiber group 1.6 to 1.74 obtained by carbonizing the fiber under inert gas at 占 폚.

In the PAN-based special carbon fiber, specific gravity indicates the carbonization rate of the fiber, and in the present invention, the PAN-based special carbon fiber is preferably used in an amount of 0.5 to 70% by volume based on the total amount of the friction material. Do.

PAN-based conventional carbon fibers are obtained by carbonizing the oxidized PAN fibers at a high temperature of 1000 to 1500 占 폚 and have a specific gravity of 1.75 to 1.80.

As the binder, for example, a thermosetting resin such as a phenol resin is used, and as the friction modifier, for example, cashew dust, barium sulfate, calcium carbonate and the like are used.

These are widely used as conventional friction materials.

As described above, the non-asbestos friction material of the present invention is composed of PAN-based special carbon fibers as part of the reinforcing fibers.

When used for a friction material as a reinforcing fiber, this PAN-based special carbon fiber cannot significantly reduce the friction coefficient of the friction material as compared with carbon fibers having a high specific gravity.

Therefore, it can be used in large quantities and can exhibit the outstanding effect (for example, a reinforcing effect), and the friction material obtained can exhibit the characteristic at least the same as that of an asbestos friction material and other non-asbestos friction materials.

Hereinafter, an Example demonstrates this invention in detail.

EXAMPLE

Tome Rayon Co., Ltd. Termex (Samsung, PAN special carbon fiber) having a specific gravity of 1.65 was uniformly mixed with other ingredients using a mixer in the ratio shown in Table 1.

The resulting mixture was compression molded in a mold for 9 minutes at a temperature of 150 ° C. and a pressure of 300 kg / cm 2 to obtain the friction materials of Examples A to F (numbers in Table 1 indicate volume%).

Instead of using the PAN-based special fibers used in each of Examples A to F, the same operation as described above, except that PAN-based ordinary carbon fibers having a specific gravity of 1.79, was used. A friction material was obtained.

In addition, asbestos, same aramid fiber, same copper fiber, instead of PAN-based special carbon fiber or PAN-based conventional carbon fiber, arid fiber and bronze fiber, which are used in each of Examples A to D and Comparative Examples a to d, A friction material of g to j was obtained in the comparison shown in Table 3 by the same operation as above except using the same aramid fiber and the same bronze fiber.

The friction material of Examples A to F and the friction material of Comparative Examples a to J according to the present invention were subjected to a friction test by a JASO C406 passenger car brake device dynamometer test method.

Furthermore, the sample was cut out from each friction material after the said test, and the shear test prescribed | regulated by the physical property test method of JASO C444-78 friction material was done.

The results of the two tests in Tables 4 to 6, namely (a) friction of the fade test when each friction material exhibited surface temperatures of 100 ° C, 200 ° C, 300 ° C, 400 ° C and 450 ° C. Coefficients, (b) the amount of wear of each friction material after the test, (c) the condition of the brake drum or brake disc rotor after the test, and (d) the shear strength of each friction material after the test.

Using three different PAN-based special carbon fibers having specific gravity of 1.68, 1.70, and 1.72, friction materials were prepared in the same manner as above, and the same tests were carried out, and almost the same results as in Tables 4 to 6 were obtained.

As described above, the non-asbestos friction material of the present invention can be preferably used as brake pads, brake linings and clutch facings in vehicles, industrial machines and the like.

Claims (2)

In a friction material composed of a reinforcing fiber other than asbestos, a binder such as phenolic resin, and a friction modifier such as barium sulfate, a part of the reinforcing fiber includes polyacrylonitrile-based special carbon fiber, Non-asbestos friction material, characterized in that the specific gravity of the nitrile-based special carbon fiber 1.60 ~ 1.74. The non-asbestos friction material according to claim 1, wherein the polyacrylonitrile-based special carbon fiber is 0.5 to 70% by volume based on the total amount of the friction material.