JP2014031414A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction material which does not necessitate application of a mold releasing agent and has a low probability of generating defective products and stabilized quality.SOLUTION: The friction material contains an organic material containing silicone rubber powder. A temporarily-molded friction material is disposed in a thermo-molding metal die 10, heated and pressurized, and heat-treated while being pressurized to be pressed between metal dies to produce the friction material 12. When the friction material, to which the silicone rubber powder is not added, is produced, the liquid mold releasing agent is applied to the front end face 18 of an upper die 14 and the internal low surface 20 of a lower die 16 to form films respectively thereon.

Description

  The present invention relates to a friction material, and more particularly to a friction material used for a vehicle brake.

  When the friction material is blended and the friction material is thermoformed using a mold, the molded product is prevented from sticking to the mold by various methods.

  Patent Document 1 discloses a brake pad in which a friction agent is applied to the inner wall surface of a mold and molded with a film containing a solid lubricant interposed therebetween, and the friction material side surface is provided with a film. ing. Further, Patent Document 2 discloses a mixed material for manufacturing a brake friction material, which is a mixed material used for manufacturing a brake friction material and can prevent adhesion to a mold by adding a fatty acid.

Japanese Patent Laid-Open No. 11-22767 JP 2002-226607 A

  In manufacturing the friction material disclosed in Patent Document 1, a process of applying a mold release agent to a mold for thermoforming and a process of cleaning the mold to remove the applied mold release agent are necessary. Yes, work efficiency is poor. In addition, many release agents contain moisture, and when the release agent is applied to the mold, excess moisture may adversely affect the molded product, resulting in low physical properties of the resulting friction material, The ability to produce a product within the established standard limits is low. In addition, the friction material disclosed in Patent Document 2 uses a mixed material containing a fatty acid to maintain releasability so that it can be easily taken from the mold. There is a problem that the physical properties of the friction material are not stable.

Therefore, the present invention has been made to solve the above-mentioned problems, and the object is as follows.
An object of the present invention is to provide a friction material that does not require application of a release agent, has a low probability of occurrence of defective products, and has stable quality.

  In order to achieve the above object, the friction material of the present invention has the following configuration. That is, the present invention is a friction material containing an organic material, wherein the organic material contains silicone rubber powder. According to this configuration, by adding the silicone rubber powder, it becomes possible to suppress the friction material from sticking to the mold during thermoforming, and it becomes unnecessary to apply a release agent. Further, the friction material is not affected by the release agent, and stable physical properties can be obtained for the friction material. Furthermore, work efficiency is improved by eliminating the need for a step of applying a release agent.

  Moreover, in this invention, it is preferable that content of the said silicone rubber powder is 0.5 wt%-3.0 wt% with respect to the said friction material. According to this, sufficient releasability can be obtained while ensuring the hardness of the friction material.

  Moreover, in this invention, it is preferable to contain cashew dust in the said organic material. According to this, the friction coefficient at the time of low surface pressure can be stabilized.

  According to the friction material of the present invention, it is not necessary to apply a release agent, and the probability that a defective product is generated is low, and the quality is stable.

It is explanatory drawing which shows the friction material which concerns on embodiment of this invention, and shows an example of the shape of the thermoforming metal mold | die used in order to manufacture a friction material.

  Hereinafter, embodiments of the present invention will be described in detail.

  The feature of the friction material according to the present embodiment is that it contains silicone rubber powder. Since silicone rubber powder has heat resistance, it is not easily affected by heat during thermoforming, and silicone rubber powder is blended into the friction material material to improve mold releasability between the mold and the friction material. Furthermore, the friction material obtained by blending and rubber-molding silicone rubber powder can be used without any problem as a brake friction material even if it contains silicone rubber powder. In addition, the silicone rubber powder improves the mold releasability without applying a mold release agent to the mold, thus stabilizing the quality of the resulting friction material and reducing the probability of defective products. The desired friction material can be obtained.

  The raw materials for the various friction materials including the silicone rubber powder may be mixed uniformly, and it is not necessary to arrange a large amount of the silicone rubber powder near the surface of the friction material in contact with the mold. For this reason, a friction material can be easily manufactured without using a special mixing method or molding method. Furthermore, since it is not necessary to apply or spray the mold release agent on the mold, these steps are not required, the work efficiency is improved, and the productivity is increased.

  The silicone rubber powder used is solid (granular) at room temperature, and is solid (granular) during and after thermoforming. At the time of thermoforming, the binding material, which is a friction material raw material, is melted by heat and has fluidity, and each material is coated with the binding material. A friction material is formed by applying pressure to bring the coated materials into contact with each other and then cooling and curing. At this time, since the silicone rubber powder does not hinder the fluidity of the molten binder, the binder spreads uniformly over the entire friction material. As a result, the unevenness of the binding material in the friction material is eliminated, and a friction material having a desired quality is easily obtained. Furthermore, the physical properties of the friction material obtained for each production unit are stabilized.

  In order to improve the releasability between the mold and the friction material, a liquid release agent is not used, and a liquid release agent is not blended to produce a friction material. Furthermore, a friction material is not manufactured by blending a mold release agent that becomes liquid during thermoforming. In addition, a release agent diluted and dispersed with a solvent such as water or a liquid dispersion medium is not used. These are different from the friction material containing the silicone rubber powder described above.

  When molding a friction material, if a liquid mold release agent or a mold release agent dispersed in a liquid is applied and sprayed on the mold, the temperature of the thermoforming mold is lowered, and the physical properties of the resulting friction material are poor. Become stable. By not using a liquid release agent or a release agent dispersed in a dispersion medium, extra water (moisture) does not touch the friction material and the temperature of the thermoforming mold can be stabilized. The physical properties of the obtained friction material can be stabilized.

  When a liquid mold release agent diluted with water or a mold release agent dispersed in a liquid is mixed with the friction material material and thermoformed, the fluidity of the binding material such as a resin in which the liquid is melted is inhibited. Furthermore, the release agent that melts into a liquid during thermoforming also inhibits the fluidity of the binder. When these mold release agents are blended with the friction material material and thermoformed, liquid materials may collect in the friction material during thermoforming. The liquid material is a liquid release agent, a molten release agent, a solvent, or a dispersion medium, and these liquid materials impede the fluidity of the binder in which the liquid material has been melted. When the fluidity of the binding material is hindered, unevenness of the binding material in the friction material is generated, and a portion where the friction material is not partially bonded is formed, so that the friction material is hardly formed. For this reason, the mold release agent to be used must be solid at the time of thermoforming, as well as solid at room temperature.

  In addition, if fatty acid is included in the friction material material to maintain the releasability during the thermoforming of the friction material, the fatty acid is easily affected by the heat during thermoforming and melts. The physical properties are not stable. Therefore, the friction material is molded without adding a fatty acid.

  The type of friction material that improves the releasability by addition of the silicone rubber powder is not particularly limited, and the silicone rubber powder can be added to various types of friction material materials. The obtained friction material has a small variation within a predetermined standard and a stable quality. Although the friction material material is not particularly limited, the friction material material includes a binder, a fiber base material, an inorganic material, and a metal material in addition to an organic material such as silicone rubber powder.

  The fiber base material is a material that becomes a skeleton of the friction material, and can use metal fibers, inorganic fibers such as rock wool, and organic fibers such as aramid fibers. These 1 type can be used individually or in combination of 2 or more types. Combining the fiber materials, the hardness of the entire fiber base material is adjusted and is not too soft and not too hard.

  The content of the silicone rubber powder is 0.5 wt% to 3.0 wt% with respect to the friction material. When the content of the silicone rubber powder is less than 0.5 wt%, sufficient releasability cannot be obtained, and when it exceeds 3 wt%, the hardness of the friction material decreases.

  As the binder, a thermosetting resin such as phenol resin can be used. When the resin is used, the resin is dissolved by heat at the time of thermoforming and has fluidity, and each raw material is coated. The resin coated on each material adheres by point contact by pressure and hardens.

In addition to silicone rubber powder, cashew dust is preferably used as the organic material. By using cashew dust, the friction coefficient of the friction material at the time of low surface pressure can be stabilized.
As the inorganic material, triiron tetroxide, calcium hydroxide, barium sulfate, calcium carbonate, alumina or the like can be used. As the metal material, an appropriate amount of metal powder such as aluminum may be blended.

  Hereinafter, the present embodiment will be described with reference to examples, but the present invention is not limited to these examples.

The raw materials having the blending ratios shown in Table 1 were stirred, mixed, temporarily formed, and the friction material thus formed was placed in a thermoforming mold 10 as shown in FIG. The friction material 12 was manufactured by applying heat treatment while pressing the thermoforming mold 10 under conditions of a thermoforming temperature of 160 ° C. to 170 ° C., a molding pressure of 20 MPa to 30 MPa, and a time of 5 min to 10 min. After the friction material 12 was manufactured, the friction material 12 was manufactured several tens of times using the same thermoforming mold 10 again.
The friction material of the comparative example to which silicone rubber powder is not added is coated with a liquid release agent on the tip surface 18 of the upper mold 14 and the inner bottom surface 20 of the lower mold 16 for each molding. Formed. The friction material temporarily formed in the lower die 16 was placed and press-molded. After press molding, the upper die 14 was taken out and extruded in the direction of the arrow in FIG. 1 to remove the friction material 12 from the die. In Examples 1 and 2 in which silicone rubber powder was added at 0.5 wt% and 3.0 wt%, the friction material 12 was removed from the mold without applying a release agent to the mold.

  A Rockwell hardness test was performed on the evaluation of the friction material prepared from the raw materials having the blending ratios shown in Table 1. Based on JIS D 4421, it measured by S scale and calculated | required Rockwell hardness (HRS). About mold release property, it investigated smoothly whether it can remove from a metal mold | die smoothly and there is no sticking. Tables 2 and 3 show the results of Rockwell hardness and demoldability of each friction material.

In addition, Cpk shown in Table 2 is a process capability index, and is an index for evaluating the ability to produce a product within a defined standard limit defined by JIS Z 8101 and is related to the occurrence rate of defective products. If the process capability index is high, the ability to produce a product within the standard limits is high, and the incidence of defective products is low. Here, using the measured values for 25 times, the average value of Rockwell hardness is μ, the standard deviation is σ, the standard value is 80 ± 20, the upper limit standard value (USL) is 100, and the lower limit standard value (LSL) Cpk was calculated with 60 as the value. In the two-sided standard, Cpk is
Cpk = (1-K) Cp
It is. here,
Cp = (USL−LSL) / 6σ
K = | (USL + LSL) −2μ | / (USL−LSL)
It is. Further, in the demoldability investigation shown in Table 3, it was investigated whether the friction material sticks to the mold and whether the friction material can be smoothly demolded from the mold.

From the results shown in Table 2, the friction materials manufactured in Examples 1 and 2 have a higher average value of Rockwell hardness than that of the comparative example, a higher process capability index, and a process control capable of producing a product that satisfies the quality standards. The ability is high.
From the results shown in Table 3, the friction materials produced in Examples 1 and 2 did not cause the friction material to stick to the mold, and did not take much time for demolding, thus improving the work efficiency. On the other hand, in the comparative example, although a release agent was applied for each molding, sticking occurred at the 12th time.
From the above, the addition of silicone rubber powder has improved the releasability and suppressed the sticking of the friction material at the time of thermoforming, so that a friction material having stable physical properties could be obtained.

10 Thermoforming mold 12 Friction material 14 Upper mold 16 Lower mold 18 Tip surface 20 Inner bottom surface

Claims (3)

  A friction material containing an organic material, wherein the organic material contains silicone rubber powder.   2. The friction material according to claim 1, wherein a content of the silicone rubber powder is 0.5 wt% to 3.0 wt% with respect to the friction material.   The friction material according to claim 1 or 2, wherein the organic material contains cashew dust.