JPH03247628A - Non-asbestos friction material - Google Patents

Abstract

PURPOSE:To provide the subject friction material containing a particular polyacrylonitrile-based carbon fiber as a part of reinforcing fiber, a binder such as phenolic resin and a friction-modifier such as barium sulfate, having excellent frictional characteristics and suitable for vehicle, etc. CONSTITUTION:The objective friction material is produced by using preferably 0.5-70vol.% (based on the total friction material) of a particular polyacrylonitrile- based carbon fiber having a specific gravity of 1.60-1.74 as a part of reinforcing fiber of a friction material containing a reinforcing fiber other than asbestos (e.g. aramid fiber), a binder such as phenolic resin and a friction-modifier such as barium sulfate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a non-asbestos friction material used as brake pads, brake linings, clutch facings, etc. of vehicles, industrial machines, etc. ,
The present invention relates to a high-performance non-asbestos friction material that has excellent strength and frictional properties and causes little damage to the surface.

[Conventional technology] Conventionally, friction materials mainly composed of asbestos have often been used, but it has been pointed out that asbestos dust, which cannot be avoided, is toxic to the human body. As a result, its use is being regulated;
Another reason is that friction materials with higher performance are becoming necessary as the performance of vehicles increases, so there is a need for friction materials that have higher performance than asbestos-based materials and do not use asbestos. Demand is increasing.

Recently, many proposals have been made for friction materials that do not use asbestos, and most of them use organic fibers such as aramid fibers, glass fibers, carbon fibers, or inorganic fibers such as metal fibers as base materials. are using.

[Problems to be Solved by the Invention] However, conventional friction materials using the above-mentioned aramid fibers, glass fibers, carbon fibers, or metal fibers as main reinforcing fibers have had various problems.

In other words, using a brake pad for a vehicle as an example, if the brake is used continuously on a friction material using aramid fibers, the surface temperature of the friction material will rise and the aramid fibers will thermally decompose. There is a problem in that the strength and coefficient of friction decrease, and friction materials using glass fibers have a problem in that the glass fibers fall off at high temperatures, increasing the amount of wear. In addition, although friction materials using metal fibers such as steel fibers and copper fibers have excellent wear resistance and strength, as the temperature increases, the friction coefficient, that is, the degree of effectiveness, becomes abnormally high, and the weight increases. It is also dangerous because it may cause a fire at high temperatures due to the increased heat conductivity and the possibility of ignition.Furthermore, the above-mentioned friction materials using glass fibers and metal fibers may damage the other side such as the rotor or drum. There was also a risk that it would be damaged or ground.

On the other hand, if so-called carbon fiber is used as a reinforcing fiber, it can be used as a friction material that has excellent heat resistance due to its high reinforcing effect and lubricity, and is less likely to damage or grind the other side of the rotor or drum. However, if this carbon fiber is used in a large enough amount to actually achieve these effects, there is a problem that the coefficient of friction will abnormally decrease due to the lubricating effect. Friction materials that use a lot of fibers have not been put to practical use, other than being used as C/C composites in high-speed brakes for aircraft, racing cars, etc., and they need to be used frequently, especially at low speeds. It was considered that it could not be applied to certain automobiles, etc., because it not only had a very low coefficient of friction at low speeds, but also suffered from a lot of wear.

Of course, friction materials using materials other than those mentioned above have been provided, but many of them lack sufficient high-temperature properties, such as wear resistance at high temperatures of 400° C. or higher, or have unstable friction behavior.

The present invention solves the problems of conventional non-asbestos friction materials as described above, and can withstand 40%
The purpose of this invention is to provide a non-asbestos-based friction material that exhibits excellent wear resistance and stable friction performance even at high temperatures of 0° C. or higher, has less surface damage, and has high strength.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs a friction material containing reinforcing fibers other than asbestos, a binder such as a phenolic resin, and a friction modifier such as barium sulfate. The reinforcing fibers include polyacrylonitrile special carbon fibers as part of the reinforcing fibers.

The present invention will be explained in detail below.

Reinforcing fibers other than asbestos used in the present invention include:
For example, organic fibers such as aramid fibers, acrylic fibers, phenolic fibers, PVA fibers and cellulose fibers, inorganic fibers such as glass fibers, ceramic fibers and carbon fibers, and metal fibers such as steel fibers, copper fibers and bronze fibers. A mixture containing one or more types of fibers is used,
These are the same as those used in conventional friction materials.

A feature of the present invention is that a special carbon fiber based on polyacrylonitrile (hereinafter abbreviated as PAN) is included as a part of the reinforcing fiber.

Here, the rPANPAN-based special carbon fiber used in the present invention, the spun PAN, was heated at 2°0 to 20°C in air as a pretreatment.
Oxidized acrylic fiber obtained by baking at 300℃ to make it flame resistant,
Furthermore, it is fired and carbonized at 800 to 1,000°C in an inert gas atmosphere to adjust the specific gravity to 1.60 to 1.74.

In this PAN-based carbon fiber, the specific gravity indicates the carbonization rate, and in the present invention, this PAN-based special carbon fiber is
Preferably 0.5 to 70 based on the total amount as friction material
Contains % by volume.

Incidentally, a typical PAN-based carbon fiber is obtained by firing the above-mentioned acrylic oxide fiber at a high temperature of 1,000 to 1,500°C, and has a specific gravity of 1.75 to 1.80.

On the other hand, as a binder, for example, a thermosetting resin such as phenol resin is used, and as a friction modifier, for example, cashew dust, barium sulfate, calcium carbonate, etc. are used, and these are commonly used in ordinary friction materials. This is what has been done.

[Operations and Effects of the Invention] The non-asbestos friction material of the present invention described above contains PAN-based special carbon fibers as reinforcing fibers in the friction material components. When used as reinforcing fibers, the coefficient of friction does not decrease much compared to ordinary high-density PAN-based carbon fibers, so it can be used in large quantities to achieve excellent reinforcing effects. The developed friction material is excellent and exhibits properties equal to or better than asbestos-based and other non-asbestos-based friction materials.

[Example] The present invention will be explained in more detail below using examples.

Example As a PAN-based special carbon fiber, Toho Rayon Telmex (trade name) with a specific gravity of 1.65 was uniformly mixed with other components using a mixer in the proportions shown in Table 1, and then gold Temperature 150℃, pressure 300Kg/c in mold
Compression molding was performed for 9 minutes at m2 to obtain friction materials of Examples A to F (numbers in the table indicate volume %).

On the other hand, instead of the PAN-based special carbon fiber of Examples A to F above, normal PAN-based carbon fiber (specific gravity 1.79) was used,
Friction materials having the same component ratios were compression molded in the same manner as above to obtain friction materials of Comparative Examples a to f shown in Table 2.

Furthermore, in a manner corresponding to Examples A to D and Comparative Examples a to d, materials using asbestos, aramid fibers, and bronze fibers were compression molded in the same manner as above to obtain Comparative Examples g to d shown in Table 3. A friction material of j was obtained.

(Margins below this page) Table 1 Table 2 Table 3 The friction materials of Examples A to F of the present invention and Comparative Examples a to J were tested according to the JASO C406r passenger car brake system dynamometer test method. A friction test was conducted using the performance test method. After the test, a sample was cut out from the friction material and subjected to a shear test as specified in JASO C444-78 "Methods for testing physical properties of brake linings and pads."

In the friction performance tests of Examples and Comparative Examples, the surface temperature of the friction material during the fade test was 100°C, 200°C, and 300°C.
, the friction coefficient at 400°C and 450°C, the wear amount of the friction material after the test, the facing condition, and the results of the shear test are shown in Table 4-
6.

In addition, as a PAN-based special carbon fiber, in addition to the above-mentioned one with a specific gravity of 1.65, friction materials with a specific gravity of 1.68, 1.70, and 1.72 were used to obtain friction materials and tests were conducted in the same manner. Almost the same results as in Tables 4 to 6 below were obtained.

(Margins below this page) Table 4 Table 5 Table 6 As described above, the present invention is excellent as a non-asbestos friction material used as brake pads, brake linings, clutch facings, etc. of vehicles, industrial machinery, etc. There is.

Claims (1)

[Scope of Claims] 1. A friction material containing reinforcing fibers other than asbestos, a binder such as a phenolic resin, and a friction modifier such as barium sulfate,
A non-asbestos friction material characterized by containing polyacrylonitrile special carbon fiber as a part of the reinforcing fibers. 2. The non-asbestos friction material according to claim 1, wherein the 2-polyacrylonitrile special carbon fiber has a specific gravity of 1.60 to 1.74. 3. The non-asbestos friction material according to claim 1, wherein the amount of the 3-polyacrylonitrile special carbon fiber is 0.5 to 70% by volume based on the total amount of the friction material.