JPH0555735B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a friction material for brakes mainly used in automobiles, railway vehicles, airplanes, industrial machines, etc. [Conventional technology] Conventionally, this type of friction material has mainly used asbestos as the fiber base material, but recently, asbestos-free friction materials have been promoted to improve the working environment and prevent asbestos pollution. . Inorganic fibers such as glass fiber, alumina fiber, rock wool, and potassium titanate fiber, metal fibers such as steel fiber, copper fiber, and brass fiber, hemp, cotton, rayon, phenol fiber, and aromatic fibers can be used as fiber base materials to replace asbestos. Fiber base materials containing organic fibers such as polyamide fibers alone or in appropriate combinations are being considered. For example, friction compositions using steel fibers, graphite, and mixtures of graphite and rubber were published in JP-A-61
It is disclosed in Publication No. 168684. Also, JP-A-62-
Publication No. 106980 discloses a friction material comprising metal fibers (metal powder), aramid fibers (aramid bulbs), a lubricant such as graphite or molybdenum disulfide, a binder, and a filler. [Problems to be Solved by the Invention] However, in this type of friction material whose main components are metal fibers such as steel fibers and graphite, graphite, which is used as a wear resistance improver of the friction material, becomes resistant to friction during high-temperature braking. There is a problem in that it adheres to the disc rotor, which is a material, and reduces the coefficient of friction. [Means for Solving the Problems] An object of the present invention is to solve the above problems and provide a friction material for brakes that has a high coefficient of friction and excellent wear resistance. The present inventors have continued their intensive research in order to solve the above problems. As a result, they discovered that the degree of crystallinity of graphite has a significant effect on its adhesion to a mating material, leading to the completion of the present invention. That is, the present invention provides a brake friction material comprising a fiber base material containing at least metal fibers, a filler, and a thermosetting resin, which comprises crystal particles (La,
The friction material for brakes is characterized by containing graphite having Lc) of 80 to 90 nm. The metal fibers used in the present invention are steel fibers, shiny fibers, and titanium fibers. Fiber base materials other than metal fibers include glass fiber, silica fiber,
Inorganic fibers such as alumina fiber, rock wool, potassium titanate fiber, linen, cotton, rayon,
One or more types of organic fibers such as phenol fibers and aromatic polyamide fibers can be used. The fiber diameter of the fiber base material is preferably 5 μm to 100 μm, and the fiber length is preferably 0.1 mm to 3 mm. The graphite used in the present invention has crystal particles (La, Lc) of 80
~90nm, and the layer spacing (C/2) is
0.3357nm is preferred. The expression "degree of graphitization" is used to indicate how close the crystal structure of graphite is to an ideal graphite crystal, and the degree of graphitization is generally defined as the degree of graphitization of crystal particles (La, Lc).
and interlayer distance (C/2). Generally, the crystal particles of natural graphite are 100 nm or more and have a high degree of graphitization, so it has good wear resistance, but it has a low coefficient of friction after heat history, which is not preferable. The blending amount of graphite having crystal grains of 80 to 90 nm is preferably 5 to 20% by weight based on the total friction material. In the present invention, a friction modifier such as cashew dust, rubber dust, barium sulfate, diatomaceous earth, alumina, dolomite, calcium carbonate, etc. can be included as a filler other than graphite having crystal particles of 80 to 90 nm. Next, the thermosetting resin used in the present invention is one or more of phenolic resin, melamine resin, epoxy resin, polyester resin, phenol-modified melamine resin, and oil, rubber, melamine, epoxy, or polyvinyl butyral-modified phenolic resin. A mixture is used. The blending amount of these thermosetting resins is preferably 5 to 15% by weight in the total friction material. Next, the method for manufacturing the asbestos-free friction material for brakes of the present invention is a conventionally used method, and is as follows. A mixed raw material is produced by thoroughly and uniformly mixing predetermined amounts of the fiber base material, filler, and powdered thermosetting resin using a Banbury mixer, a Henschel mixer, a kneader, a V-type blender, or the like. This mixed raw material is filled into a mold and pressed to perform preforming. This preform is heated and pressurized to harden and bond with a thermosetting resin, and then further heat treated to produce a friction material. [Operations and Effects of the Invention] According to the friction material for brakes of the present invention, crystal particles of 80 to
Containing 90nm graphite, it has good wear resistance and strong peeling strength between crystal particles, which suppresses adhesion of graphite to the mating material and prevents a decrease in the coefficient of friction during high-temperature braking. If the crystal grain size is less than 80 nm, the wear resistance will not be sufficient, and if the crystal grain size exceeds 100 nm, the friction coefficient after thermal history will be low. [Example] Examples of the present invention will be shown below, but the present invention is not limited thereto. Examples 1 and 2 and Comparative Examples 1 and 2 The compositions shown in Table 1 were uniformly mixed using a V-type blender to obtain mixed raw materials. This mixed raw material was preformed for 20 seconds in a molding machine adjusted to a surface pressure of 300 kg/cm ² at room temperature to obtain a preformed product. Rear pressure 300Kg/
The mixture was heated and pressurized for 7 minutes using a molding machine adjusted to a cm ² mold temperature of 150°C. Thereafter, it was heat-treated in a heating furnace at 250°C for 2 hours and 30 minutes, and after being allowed to cool, it was polished to a predetermined size to obtain a friction material. Friction materials obtained using the formulations shown in Table 1 were subjected to a wear resistance test and a fade resistance test using a brake dynamometer tester. The test results are shown in Table 2. The abrasion resistance test method is JASO-C427-83 [Brake model: PD51s, rotor: 18mm ventilated type, inertia (load): 4.0Kg・f・
m・S ² , initial braking speed: 50Km/h, deceleration: 0.3G]
It is. The third efficacy test method is JASO-C406-82
[Brake model: PD51s, rotor: 18mm ventilated type, inertia (load): 5.0Kg・
f·m·s ² , the effectiveness after the second fade].

【table】

【table】

[Table] As shown in Table 2, the brake friction materials of Examples 1 and 2 had lower wear rates than the friction materials of Comparative Examples 1 and 2, and there was no decrease in the third effect friction coefficient. It can be seen that it is an excellent friction material with good balance.

Claims (1)

[Claims] 1. A brake friction material comprising a fiber base material containing at least metal fibers, a filler, and a thermosetting resin, the brake material comprising graphite having crystal particles (La, Lc) of 80 to 90 nm. Friction material for use.