JPH0451322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cork friction material that significantly improves wear resistance and increases the amount of oil impregnated without substantially impairing the frictional properties of cork.

Conventionally, particles of crushed cork, which has the excellent properties of natural products, especially the excellent coefficient of friction, have been compressed and bonded via adhesive and used to make friction plates for clutches such as industrial sewing machines and clutch facings for motors. It was widely used in brake shoes, etc. However, cork has low physical strength, and has disadvantages such as making noise when the clutch or brake is activated, producing a strange odor due to frictional heat, and shortening the life of the clutch due to abnormal wear caused by the clutch being partially engaged.

To solve this problem, a cork friction material made by integrally molding cork particles with an adhesive was impregnated with oil into the intergranular voids to improve wear resistance. Because cork particles were compressed and bonded using adhesives such as phenolic resin, urea resin, and vinyl acetate resin,
There are very few voids between cork particles and the adhesive,
Even if this is impregnated with oil by vacuum or pressure impregnation at room temperature or heating, the amount of oil impregnated is 10%.
% or less, the desired improvement in wear resistance cannot be obtained much, and most of the oil impregnation is concentrated on the surface of the friction material, and during long-term use, the oil on the surface is removed and only a small amount of oil remains. There was a drawback that no residue remained and the wear resistance was significantly reduced.

For this reason, as a method to increase the amount of oil impregnated, cork particles and oil are mixed and stirred in advance to make the oil adhere to the coil particles, and then phenol adhesive etc. is mixed in, stirred, and fixed in a mold. A method was devised to obtain a cork friction material in one piece. However, although the amount of oil impregnated in this material is certainly higher than that of the cork friction material mentioned above, the adhesive force is significantly reduced because the oil that prevents the adhesive from adhering is attached to the entire outer surface of the cork particles. Under harsh conditions such as clutch facing and brake shoeing, where strong forces are applied, the cork friction material is destroyed, and stirring the cork particles, oil, and adhesive takes time and makes it difficult to mix uniformly. However, there were other drawbacks such as problems with strength.

The present invention eliminates these drawbacks and provides a cork friction material that is easy to work with, has a large amount of oil impregnated, and has oil impregnated not only on the surface but also in the center.

The present invention is a cork friction material obtained by integrally molding cork particles having an appropriate size, substantially 10 to 80 mesh, using an adhesive using a conventional method, and an oil (not limited to vegetable oil or mineral oil, etc.). ), the adhesive is a urethane adhesive.
The use of a urethane adhesive as a binder in the cork friction material of the present invention means that when the cork friction material using the urethane adhesive is immersed in an oil bath or impregnated under vacuum or pressure, oil will be absorbed between the cork particles. Of course, there are gaps between the adhesive and the adhesive.
Since the urethane adhesive itself can be impregnated with a large amount of oil, which was not possible with conventional methods, the weight ratio to cork particles is 25 to 30%, which is suitable for use in clutch facings, brake shoes, etc. Cork friction material impregnated with oil can be easily obtained. In addition, the amount of oil impregnated is suitably 15 to 50% by weight depending on the purpose and application of the cork friction material, and the most suitable is 25 to 30% by weight, but according to the present invention, this value can be easily adjusted. You can get things.

In addition, if the cork friction material is affixed to the metal substrate of clutches, brakes, etc. in advance and then impregnated with oil, it can be used as a clutch facing that has adhesive strength between the cork and the metal substrate and has excellent friction properties. It is also possible to easily obtain a brake shoe.

Furthermore, since the cork friction material of the present invention gives priority to the bonding between the cork and the adhesive, even if it is impregnated with oil, the adhesive strength will not be impaired in the slightest.

Furthermore, in order to accomplish the purpose of the present invention, fine particles of a material having fine voids such as foamed urethane, the fine voids of which are impregnated with oil, are dispersed and included in the urethane adhesive. If a cork friction material is formed using the above methods, the oil will be uniformly impregnated into the adhesive, and the adhesive strength will be sufficient, making it possible to obtain a member that meets the ideal conditions for a cork friction material, which has been traditionally desired. It will be done.
Of course, it is possible to first disperse fine particles such as urethane foam to form a cork friction material, and then impregnate the minute voids of the fine particles with oil, and the same effect can be obtained.

Next, the present invention will be explained with reference to Examples. Cork particles of 30 to 70 mesh were used, urethane adhesive was added to this, stirred for 5 to 10 minutes, and the desired amount was put into a mold and compressed to harden the adhesive. Thereafter, the cork friction material is removed from a mold to obtain a cork friction material having a desired shape.

The obtained cork friction material was heated under 3 mmHg for 1 hour.
By vacuum impregnating turbine oil #200, a cork friction material with a weight ratio of oil to cork particles of 28.8% by weight was obtained, and it was impregnated with turbine oil #200 for 2 hours under 3 mmHg.
By vacuum impregnation, a cork friction material with a weight ratio of oil to cork particles of 34.2% by weight was obtained.

Therefore, by adjusting the vacuum impregnation time and pressure, the amount of oil impregnated can be adjusted to 0%, 5%, 15%, 20%, 25%, 30%,
When we made 35%, 45%, and 60% cork friction materials and measured the friction coefficient and amount of friction, we obtained good values as shown in the graphs in Tables 1 and 2.

Note that if the amount of oil impregnated is 60% or more, it cannot be retained inside the cork friction material and the oil will flow out, so it is virtually impossible to manufacture it.

Looking at the friction coefficient in Table 1, the decrease in the coefficient due to oil is very small, without impairing the friction characteristics, and in Table 2
As shown in the figure, the amount of wear due to the addition of oil is significantly reduced compared to the one with 15% impregnation, and its effect is clearly visible.

As described above, according to the present invention, due to the action of the oil impregnated between the cork particles and the adhesive, the wear characteristics can be significantly improved without impairing the friction coefficient, and the life of the cork friction material can be maintained for a long time. In addition, the oil distribution is almost uniform, so cork friction material obtained by cutting from a block can have the same effect, making it an excellent cork material that cannot be obtained with conventional methods. It is a friction material.

Claims (1)

[Scope of Claims] 1. A cork friction material formed by integrally molding cork particles with an adhesive and impregnated with oil, wherein the adhesive is a urethane adhesive,
A cork friction material characterized by a weight ratio of oil to cork of 15 to 50%. 2. The cork friction material according to claim 1, characterized in that, in the urethane adhesive, fine particles of urethane foam or the like impregnated with oil are dispersed in the urethane adhesive. .