JPH06184329A - Production of friction material - Google Patents

Abstract

PURPOSE:To produce a high-performance friction material which is excellent in abrasion resistance, hardly attacks a mating material, and has a stable coefficient of friction. CONSTITUTION:A friction material is produced by mixing 5-30vol.% fibrous reinforcement, 20-45vol.% inorg. filler, 10-25vol.% org. filler, and 10-35vol.% thermosetting resin and thermally molding the resulting mixture. At least 40vol.% of the inorg. filler is composite particles obtd. by coating the surfaces of magnesia particles with alumina. The composite particles enable the production of a friction material excellent in friction characteristics, such as abrasion resistance, attack to a mating material, and stability of friction coefficient. Since magnesia particles which has a relatively low hardness and mild abrasive properties is coated with a hard fine powder of alumina, the attack to a mating material is inhibited while retaining the friction characteristics of alumina.

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 friction material, and more particularly to a method for producing a friction material which is useful as a friction material for vehicles such as automobiles and which has excellent wear resistance and low attacking property against a mating material.

[0002]

2. Description of the Related Art Disc brake pads and brake linings are typical wear materials used in vehicles such as automobiles and industrial machines. Since the disc brake pad is small and has good performance, it is often used in passenger cars and small trucks, and the brake lining is often used in large vehicles.

Conventional wear materials are generally made of fiber materials (asbestos, organic fibers, inorganic fibers, metal fibers), inorganic fillers, organic fillers, and resin materials, and 10 to 20 kinds of these materials are used. It is manufactured by mixing and molding.

[0004]

In the above conventional wear materials, asbestos is usually used as the fiber material, which poses a health problem.

Further, in the conventional wear material, the abrasion wear of the sliding surface is reduced, the aggression to the mating material (rotor, drum, etc.) is reduced, cracks are generated on the surface of the wear material due to frictional heat, and the strength thereof is deteriorated. There are various requirements that should be improved, such as

The present invention has been made in view of the above-mentioned conventional circumstances, and provides a method for producing a high-performance wear material which is more excellent in wear resistance, has a low attack on the mating material, and has a stable friction coefficient. The purpose is to do.

[0007]

According to the method for producing a friction material of the present invention, the reinforcing fiber is 5 to 30% by volume, and the inorganic filler is 20 to.
A method for producing a friction material by thermoforming a molding raw material obtained by mixing 45% by volume, 10 to 25% by volume of an organic filler and 10 to 35% by volume of a thermosetting resin, the method comprising: It is characterized in that 40% by volume or more of them are composite particles in which a coating layer of alumina is formed on the surface of magnesia particles.

The present invention will be described in detail below.

In the present invention, the reinforcing fiber group is blended in order to maintain the strength as an abrasion material, and various organic fibers, inorganic fibers and metallic fibers can be used. Aramid fiber, acrylic fiber, cellulose fiber, vinyl fiber, phenol fiber as the organic fiber, alumina, zirconia, ceramic fibers such as potassium titanate, glass fiber, carbon fiber as the inorganic fiber, steel as the metal fiber Fibers, copper and copper alloy fibers and the like are used. In addition, it is important to use a fiber other than asbestos as the reinforcing fiber.

In the present invention, these fibers can be used singly or in combination of two or more, and within the range of 5 to 30% by volume, the required strength and other properties can be obtained. Accordingly, the blending amount, fiber diameter, fiber length, etc. are determined.

If the proportion of the reinforcing fibers is less than 5% by volume, the strength of the resulting wear material is insufficient, and if it exceeds 30% by volume, the proportion of other fillers is relatively reduced and sufficient friction characteristics are obtained. I can't get it.

The inorganic filler has an effect on the friction coefficient, fade, abrasion wear of the friction material, and the aggression property of the mating material (disk rotor, drum). Generally, graphite, molybdenum disulfide, antimony trioxide, Particles of barium sulfide, ferrite, garnet, lime, alumina, zirconia, etc. are used. In the present invention, 40% by volume or more of such inorganic filler is coated with alumina on the surface of magnesia particles. The composite particles are formed by forming layers. Such composite particles are
For example, it is manufactured as follows. As the base magnesia particles, single crystal or polycrystal magnesia particles having high digestion resistance are used. Specific examples thereof include fused magnesia or clinker, but fused magnesia particles are preferably used. It should be noted that magnesia has a cleavage property and becomes a cube, but it is preferable to use particles whose edges are dropped by attrition or the like. The magnesia particles used preferably have an average particle size of 10 to 100 μm.

Alumina fine particles are coated on the surface of such magnesia particles by using an appropriate organic binder such as polyvinyl alcohol. The average particle diameter of the alumina fine particles used is preferably 0.1 to 0.5 μm, and the coating amount thereof is preferably such that the coating amount of alumina with respect to magnesia is 3 to 30% by volume. If this ratio is less than 3% by volume,
The effect of using the composite particles according to the present invention is not sufficiently obtained, and if it exceeds 30% by volume, the amount of alumina becomes too large, and the aggressiveness of the mating material due to alumina, etc., is not preferable.

In the present invention, the friction material is manufactured by using 40% by volume or more of the inorganic filler as such composite particles. The use ratio of the composite particles is appropriately determined according to the frictional characteristics required of the obtained friction material, but is particularly about 50% by volume of the inorganic filler, which is 20 to 20% of the total components of the friction material. It is preferably 30% by volume.

In the present invention, 20 to 45% by volume of the inorganic filler containing the above composite particles is blended. If the proportion of the inorganic filler is less than 20% by volume, sufficient frictional characteristics cannot be obtained, and if it exceeds 45% by volume, the proportions of other components relatively decrease, and sufficient frictional characteristics and strength cannot be obtained.

The organic filler has the same effect as the inorganic filler and also functions as a friction modifier.
As the organic filler, cashew dust, rubber powder, pulp, cellulosic powder and the like can be used, and these organic fillers are mixed in a ratio of 10 to 25% by volume. If the proportion of the organic filler is less than 10% by volume, sufficient frictional characteristics cannot be obtained, and if it exceeds 25% by volume, the proportions of other components relatively decrease and sufficient frictional characteristics and strength cannot be obtained. .

The thermosetting resin is used as a binder for molding and solidification, and in the present invention, it is preferable to use a phenol resin which is particularly excellent in heat resistance. The thermosetting resin is blended in a proportion of 10 to 35% by volume, but if this proportion is less than 10% by volume, sufficient moldability cannot be obtained, and if it exceeds 35% by volume, the proportion of other components is relatively high. And the sufficient frictional characteristics and strength cannot be obtained.

In the present invention, the reinforcing fiber, the inorganic filler containing the specific composite particles, the organic filler and the thermosetting resin are uniformly mixed in a predetermined ratio by a mixer or the like,
After temporary molding at a pressure of about 50-150 kg / cm ² ,
150 to 500 kg / cm ² , 10 at 130 to 200 ° C
A friction material having a desired shape can be produced by heat-molding for about 30 minutes, and then firing at 200-300 ° C. for about 20-60 minutes.

[0019]

As described above, since the friction material is a material formed by mixing 10 to 20 kinds of materials, the friction characteristics and performance are exhibited by the synergistic effect of the added material. Therefore, sufficient characteristics of the friction material cannot be obtained only by adding and blending a new single material.

By the way, since alumina is a material having a high hardness, it has been widely used as an additive for friction materials. This is added to increase the friction coefficient, and its amount, particle size, and particle shape are various. When a large amount of such alumina is added, the friction coefficient of the obtained friction material becomes high, but on the other hand, the property of attacking the mating material also becomes large, so that the friction material itself also decreases due to the abrasion phenomenon due to the abrasion of the surface. In addition, the coefficient of friction becomes unstable. In particular, alumina having a large particle size has a large attacking property against the mating material, and the above problems are likely to occur. Therefore, it is necessary to use alumina with a small particle size, but in this case, it becomes almost impossible to uniformly disperse the particles.

As the inorganic filler as the material of the friction material, conventionally, not only alumina but also various materials are mixed and used in consideration of the particle size, but it is possible to uniformly mix various kinds of fine particles. The current situation is that it is difficult and a sufficient addition effect is not obtained.

The present inventors have conducted various tests using magnesia in order to solve such a problem.
We have found a good filler that maintains the coefficient of friction, yet has abrasion resistance and attack resistance.

That is, by using the composite particles in which the alumina coating layer is formed on the surface of the magnesia particles, a friction material having extremely good friction characteristics such as wear resistance, attack resistance, and stability of friction coefficient can be manufactured. It has become possible. This is because if such alumina-coated magnesia particles, the magnesia particles as a material having a relatively small hardness and relaxing the abrasivity are coated with a fine powder of hard alumina, while maintaining the friction characteristics of alumina, This is because the aggressiveness against the opponent material is suppressed.

[0024]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

The composite particles A, B and C used in the examples are
Are shown in Table 1 below by magnesia (manufactured by Mitsubishi Materials Corp.) having an average particle size of 50 μm and alumina (manufactured by Showa Denko KK) having an average particle size of 0.3 μm by a pelletizer using polyvinyl alcohol as a binder. It is attached so as to have a coating amount.

[0026]

[Table 1]

Examples 1 to 4 and Comparative Example 1 Each material was uniformly mixed with a mixer according to the formulation shown in Table ² , pre-formed at a pressure of 50 kg / cm ² , and then hot-pressed to 30
A disk pad was manufactured by thermoforming at 0 kg / cm ² and 160 ° C. for 20 minutes and then baking at 250 ° C. for 30 minutes. All the materials used here are commercially available materials that are usually available.

The obtained disc pad was subjected to a full size friction test by a brake dynamo tester (in accordance with JASO method), and the results are shown in Table 2. From Table 2, it is clear that according to the present invention, a high performance friction material can be obtained.

[0029]

[Table 2]

[0030]

As described in detail above, according to the method for producing a friction material of the present invention, composite particles obtained by coating the surface of magnesia particles having a relatively low hardness with alumina having a high hardness are used as the inorganic filler. As a result, it is possible to manufacture a high-performance friction material that has a large friction coefficient, low aggression to the mating material, and less frictional wear of the friction material itself, and that exhibits stable friction characteristics.

Claims (1)

[Claims] 1. A molding raw material obtained by mixing 5 to 30% by volume of reinforcing fiber, 20 to 45% by volume of inorganic filler, 10 to 25% by volume of organic filler, and 10 to 35% by volume of thermosetting resin. A method for producing a friction material by heat molding, wherein 40% by volume or more of the inorganic filler is a composite particle in which a coating layer of alumina is formed on the surface of magnesia particle. Manufacturing method.