JPH0987613A - Filler for friction material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a filler, having the particle surface with excellent hydrophilicity, uniformly and readily dispersible in a wet type friction material due to fine particles and having effects on development of a stable high friction coefficient, and useful for a wet brake, etc., by finely pulverizing a cashew dust. SOLUTION: This filler for frictional materials is obtained by finely pulverizing (A) a cured material consisting essentially of a cashew polymer (e.g. cashew dust particles, obtained by pulverizing the cashew dust in the air and having about 200μm average particle diameter) in (B) water, e.g. in an amount of 200 pts. based on 100 pts. in an attritor at rotational speed of 200 r.p.m. rotational speed for 10min. The resultant fine particles have <=20μm average particle diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filler used for friction materials such as wet clutches and wet brakes.

[0002]

Wet friction materials used in automatic transmissions are
It is generally manufactured by the following steps. That is, fibers, fillers, friction modifiers are dispersed in water, paper is made to make paper, the paper cut into a predetermined shape is impregnated with a binder, dried and cured, and then an adhesive is applied. The paper is attached to the core metal.

The fibers include natural pulp fibers such as cotton,
Organic synthetic fibers such as aramid and inorganic fibers such as glass are used, and clay, silica, graphite, cashew dust, etc. are used as the filler. A phenol resin or a modified phenol resin is used as the binder.

Among the fillers, cashew dust is more flexible than other fillers and is therefore used in wet friction materials in the hope of increasing the friction coefficient.

[0005]

However, since cashew dust produced by a general manufacturing method is impact-crushed in air, even fine particles are coarse particles having a particle size of about 100 to 150 μm and the surface is hydrophobic. Low dispersibility in water used during papermaking. Further, when the material is cut into a predetermined shape after molding, the particle diameter of the cashew dust is coarse, so that the cashew dust falls off from the cut surface or sticks out, so that the desired shape cannot be obtained. Further, since cashew dust is projected and present on the surface after molding, there is a problem that the friction material and the mating material cannot contact each other uniformly.

An object of the present invention is to provide a cashew dust which is fine particles and easily dispersed in water, and a method for producing the same. By using the cashew dust, a friction material having a smooth surface and a uniform contact with a mating material is provided. Is to get.

[0007]

The present inventors have further pulverized crushed cashew dust particles in water so that the average particle diameter is 20 μm or less, and crushed in water to obtain cashew dust. It was possible to obtain the cashew dust which imparted hydrophilicity to the surface of and was easily dispersed in water.
Then, the present inventors have found that it is extremely effective to use the cashew dust as a filler for wet friction materials, and have completed the present invention.

[0008]

Function: Cashew dust crushed in air has a hydrophobic surface and is hard to be wet with water. As a result, they tend to float in water, and even when paper is made, cashew dust is unevenly distributed on the surface of the paper and is not uniformly dispersed inside. However, cashew dust finely pulverized in water does not cause the above phenomenon, is uniformly dispersed in water, and is fine particles. Therefore, when papermaking, it is uniformly dispersed on paper.

The improvement in the dispersibility of cashew dust finely pulverized in water in water is considered to be due to the introduction of hydrophilic groups such as hydroxyl groups on the surface of cashew dust due to the occurrence of a mechanochemical reaction in the pulverization process. To be done.

The friction material in which the cashew dust fine particles are uniformly dispersed has a large contact area with the mating material, has a high friction coefficient, and even if it wears, the cashew dust is uniformly dispersed inside, so that the surface properties are Does not change, and the coefficient of friction changes little over time.

[0011]

EXAMPLES Examples of the present invention will be shown below and described in more detail.

(1) Underwater crushing production method of cashew dust Cashew dust particles crushed in air (average particle size 20)
(0 μm) 100 parts and 200 parts of water are mixed, and this is 200 with an attritor (MA-C10 type, Mitsui Miike Seisakusho).
r. p. The particles were pulverized for 10 minutes to obtain fine particles having an average particle diameter of 13 μm.

(2) Manufacture of Friction Material Using the cashew dust obtained by the treatment of (1) above, a wet friction material was manufactured according to a conventional method with the composition shown in Table 1. For comparison, a wet friction material was manufactured using conventional cashew dust having a coarse particle size.

[0014]

[Table 1]

The friction material was punched out into a predetermined shape, immersed in a phenol resin tank adjusted to a solid content of 35% with methanol, and then heated at 80 ° C. for 1.0 hour and further at 150 ° C. for 2. hours.
It was dried and cured for 0 hours.

This friction material was adhered to a core metal to compare the performance. In the comparative example at the time of paper making, cashew dust floated on water, and high-speed stirring was performed with a stirring mixer, but part of cashew dust remained floating on water. In the example, it was easily dispersed.

(3) Evaluation The friction performance between the friction material according to the example of the present invention and the friction material according to the comparative example was tested by an inertia absorption friction tester. The results are shown in FIGS. 1 to 6.

From these results, it is clear that the friction material using the friction material filler of the present invention has a larger coefficient of friction than the conventional one and has very little change over time.

[0019]

The cashew dust described in detail above is uniformly and easily dispersed in the wet friction material and has a fine particle size, so that the contact area between the friction material and the mating material is increased, and the stability is stable. It has the effect of developing a high friction coefficient.
The fact that this contributes to the improvement of the reliability of the friction material is very large and is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of test cycles and μ _S in an example. Here, μ _S is the maximum friction coefficient when the completely engaged clutch is forcibly rotated.

FIG. 2 is a diagram showing the relationship between the number of test cycles and μ _{S in} a comparative example.

FIG. 3 is a diagram showing the relationship between the number of test cycles and μ _D in the example. Here, μ _D is a dynamic friction coefficient in the process of starting the engagement of the clutch and lowering the rotation speed.

FIG. 4 is a diagram showing the relationship between the number of test cycles and μ _{D in} a comparative example.

FIG. 5 is a diagram showing the relationship between the number of test cycles and μ _O in the example. Here, μ _O is the maximum coefficient of friction immediately before the engagement of the clutch is completed.

FIG. 6 is a diagram showing the relationship between the number of test cycles and μ _{O in} a comparative example.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadao Katahira 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Within Tohoku Kako Co., Ltd. (72) Inventor Mikio Nishimura 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo No. Tohoku Kako Co., Ltd.

Claims (2)

[Claims] 1. A method for producing a filler for a friction material, which comprises finely pulverizing a cured product containing cashew polymer as a main component in water. 2. A filler for a friction material produced by the method as set forth in claim 1.