JPH0467049B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a cork friction material that substantially improves the wear resistance and increases the amount of oil impregnated without impairing the frictional properties of cork. Regarding.

[Conventional technology]

Natural cork, which has an excellent coefficient of friction, is used as a friction material for clutches of industrial sewing machines, clutch facings of motors, brake shoes, etc. Conventionally, in order to form this cork friction plate, the manufacturing method generally used is to crush natural cork bark and compressively bond the bark with an adhesive.

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 service life due to abnormal wear caused by a partially engaged clutch.

Therefore, as a method to solve this problem, oil is impregnated into the intergranular spaces of a cork friction material made by integrally molding cork particles via an adhesive, thereby improving the wear resistance.

[Problem that the invention seeks to solve]

However, since the cork friction plate uses an adhesive such as phenol resin, epoxy resin, or vinyl acetate resin to compress and bond the cork particles, there are very few gaps between the cork particles and the adhesive. Even if oil is impregnated by vacuum or pressure impregnation at room temperature or heating, the amount of oil impregnated is extremely small, less than 10%, and the desired improvement in wear resistance cannot be obtained much. Because it impregnates almost only the surface portion of the friction material, when it is used, the surface oil is removed in a short period of time, leaving only a small amount of internal oil remaining, resulting in a significant drop in wear resistance.

Therefore, 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 cork particles, and then a phenolic adhesive etc. is mixed in, stirred and put into a mold. A method of obtaining cork friction material as a fixed and integrated material was considered. 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. There is a high risk of cork friction material being destroyed under harsh conditions such as clutch facing and brake shoeing, where strong forces are applied, and stirring of cork particles, oil, and adhesive takes time and is not uniform. It had disadvantages such as difficult stirring and 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.

[Means for solving problems]

The present invention relates to a cork friction material obtained by integrally molding cork particles having an appropriate size, substantially 10 to 80 mesh, with an adhesive, and a cork friction material that is obtained by molding cork particles having an appropriate size, substantially 10 to 80 mesh, into one body using an oil (including but not limited to vegetable oil or mineral oil). A cork friction material impregnated with cork particles, which is obtained by mixing cork particles, an adhesive, and a water-absorbing resin, and then agglomerating and molding them together via an adhesive to obtain a cork friction material.
Further, the cork friction material is impregnated with oil by immersing it in heated oil and adding vacuum to evaporate the desired amount of water contained in the water-absorbing resin, replacing water with oil. It is characterized by

At this time, the water to be included in the water-absorbing resin is either impregnated in advance into the water-absorbing resin when mixing each before molding, or is it impregnated into the water-absorbing resin in the formed cork friction material afterwards. Either of these methods can be selected, and the desired method can be selected depending on the process.

[Effect]

The present invention mixes a water-absorbing resin into a cork friction material that has very few voids that can be impregnated with oil, and makes it possible to impregnate a large amount of oil using the water-absorbing resin. A water-absorbing resin that has absorbed a large amount of water is present in the material, and this water is evaporated under heating and vacuum to form voids in the areas occupied by the water, and oil is substituted and impregnated into the voids. It is something. In this replacement, the vacuum process is used to perform the important function of boiling the water in the water-absorbing resin at a low temperature and evaporating it in a short time, and forcibly impregnating it with oil. By heating the oil to 60°C to 100°C at the same time as vacuuming and immersing the cork friction material in the oil, it is possible to impregnate a large amount of oil in a shorter time, which was not possible with conventional methods. It is possible to easily obtain a cork friction material (specifically, a cork friction material impregnated with oil at a weight ratio of 25 to 30% to cork particles) suitable for use in required clutch facings, brake shoes, etc. I can do it.

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 optimal weight ratio is 25 to 30%, but according to the present invention, the amount of water absorbent resin mixed in This value can be easily obtained by controlling the amount of water absorbed.

〔Example〕

Next, the present invention will be explained with reference to Examples.

Cork particles with a size of about 20 to 70 mesh are used, and a water-absorbing resin (trade name, Sumikagel SP-520 manufactured by Sumitomo Chemical Co., Ltd.) and adhesive are added to the cork particles.
Stir for ~10 minutes, put the desired amount into a mold, heat and compress, and then take out from the mold to obtain a cork friction material in the desired shape. At this time, the water-absorbing resin present between the cork particles has its characteristics (weight ratio 25 ~
(Has 200 times the water absorption capacity), it absorbs a large amount of water, and the absorbed water secures sufficient space within the cork friction material. This was immersed in turbine oil #200 heated to 75°C to 85°C and vacuum impregnated at 3 mmHg for 40 minutes to obtain a cork friction material with an oil weight ratio of 42.0% by weight.

With this method, it is possible to impregnate oil up to a maximum of 55% by weight by adjusting the amount of water-absorbing resin mixed, the amount of water to be absorbed, the vacuum impregnation time, etc. However, impregnation in an amount greater than this cannot be practically produced because the water-absorbing resin cannot retain the oil and the oil flows out.

In carrying out the present invention, it is also possible to apply the cork friction material to the metal substrate of clutches, brakes, etc. in advance and then impregnate it with oil, which increases the adhesive strength between the cork and the metal substrate. Clutch facings and brake shoes with excellent friction characteristics can be easily obtained.

Furthermore, in the cork friction material of the present invention, the water-absorbing resin creates a strong bond between the cork and the adhesive without imposing any burden, so even if it is impregnated with oil, the adhesive strength will not be impaired at all. Nor.

〔Effect of the invention〕

As described above, according to the present invention, by the action of the impregnated oil that replaces the water in the water-absorbing resin, the friction characteristics are significantly improved without impairing the friction coefficient, and the life of the cork friction material is maintained for a long time. In addition, the distribution of oil is almost uniform, so cork friction material obtained by machining by cutting from a block can have the same effect, and is an excellent product that cannot be obtained with conventional methods. It is a cork friction material.

Claims (1)

[Claims] 1. In a cork friction material formed by integrally molding cork particles with an adhesive; after mixing cork particles, an adhesive, and a water-absorbing resin, the cork friction material is molded with an adhesive. A cork friction material that is integrally molded and whose water-absorbing resin contains a desired amount of water is immersed in heated oil, and vacuum is added to evaporate the water and replace the water with oil. A method for producing a cork friction material, characterized by impregnating it with oil. 2. The cork friction material according to claim 1, wherein the oil is impregnated in an amount of 15 to 50% by weight based on the weight of cork.