JPH11322961A - Friction material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a friction material which does not make screechy sound even when it becomes hot under braking by using a cashew-silicone composite dust as a part of a filler component. SOLUTION: A cashew-silicone composite dust which is a composite of a cured cashew nut shell liquid (referred to as a cashew component) and a silicone rubber or resin component (referred to as a silicone component) is incorporated into a friction material comprising a fibrous substrate, a binder, and a filler. Pref., the compounding ratio of the cashew component to the silicone component is (95/5)-(90/40). Pref., the composite dust is incorporated in an amt. of 1-20 wt.%, is in the form of a powder, and has an average particle size of 50-500 μm. The dust is prepd. e.g. by mixing a cashew nut shell liquid with a silicone component powder and curing and grinding the resultant mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a friction material used for a brake pad of a vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, friction materials used for brake pads for vehicles have a large braking force and good wear resistance, and a small change in the braking force due to a change in temperature, pressure and the like. It is required that the material be stable (such as fade resistance) and have a high material strength without being affected by water or oil.

[0003] As a friction material which relatively satisfies such characteristics, a friction material comprising a fibrous base material, a binder and a filler is generally used. Here, as the filler, an inorganic filler such as barium sulfate and calcium carbonate,
Solid lubricants such as graphite and molybdenum disulfide, abrasive materials such as cashew dust, metal powder and silica, and other additives for friction adjustment are used.

[0004] With the recent trend toward high performance such as high speed and high grade of vehicles, various demands for friction materials have been increasing. One of them is to suppress the generation of unpleasant noise generated during braking, that is, squeal. This squealing occurs when friction materials are pressed against a rotor, a drum, or the like for braking.

As a friction material which suppresses the occurrence of this squeal, at least a part of cashew dust used as an additive of the friction material is made of a cashew rubber comprising a composite of a cured product component of a cashew nut shell liquid and a rubber component. A friction material replaced with composite dust is disclosed in JP-A-8-12770.

[0006]

However, even in the friction material described in the above publication, when the friction material is heated to a high temperature by frictional heat, the generation of squeal is not sufficiently suppressed.
The present invention has been made in view of the above situation, and has as its object to provide a friction material in which generation of squeal is suppressed even when the temperature becomes high due to braking.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have repeatedly studied cashew dust contained in a friction material as an additive. As a result, a silicone rubber component or a silicone resin component and a cashew nut shell liquid were used. It has been found that mixing the composite with the cured component instead of cashew dust results in a friction material with reduced squealing.

That is, the friction material of the present invention is a friction material comprising a fibrous base material, a binder, and a filler, wherein the filler is a cashew nut shell liquid cured product component and a silicone rubber component or a silicone resin. It is characterized by containing cashew / silicone composite dust composed of a composite with components.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The friction material of the present invention contains, as a filler, cashew-silicone composite dust comprising a composite of a cured product of cashew nut shell liquid and a silicone rubber component or a silicone resin component.
By compounding the cashew / silicone composite dust, it is possible to suppress the generation of squeal of the friction material due to the vibration damping action of the composite dust. Further, since the silicone rubber component and the silicone resin component have high heat resistance, the vibration damping action is maintained even if the friction material becomes high temperature due to braking, so that it is possible to suppress the occurrence of squeal.

The cashew / silicone composite dust is a composite comprising a cured product of cashew nut shell liquid (cashew component) and a silicone rubber component (Si rubber component) or a silicone resin component (Si resin component). The compounding ratio with the Si rubber component or the Si resin component is preferably such that the cashew component / Si rubber component (Si resin component) ratio is 95/5 to 90/40.

The cashew / silicone composite dust is compounded to suppress the occurrence of squeal.
The compounding amount is preferably 1 to 20% by weight.
The cashew / silicone composite dust is preferably compounded in a powder form, and has an average particle size of 50 to 500.
μm is preferred. Here, the cashew component is
It is preferably composed of the same components as cashew dust, and is obtained by curing cashew nut shell liquid (cashew oil) with an aldehyde such as furfural or formaldehyde or a curing agent such as hexamethylenetetramine.

It is preferable that the Si rubber component contains linear polydimethylsiloxane as a main raw material and partially contains methylvinylsilane, methylphenylvinylsilane, and phenylsilane. The Si resin component preferably has a molecular skeleton of siloxane and contains a phenyl group and a methyl group as organic groups. Note that among the modified phenol resins used for the binder, the silicone modified phenol resin is a silicone resin component.

The cashew-silicone composite dust can be manufactured in various ways. For example, as one method, there is a method in which a silicone component powder is mixed with a cashew nut shell liquid, cured, and then pulverized into a powder. As the fibrous base material used in the present invention, those used in conventional friction materials can be used. For example,
Inorganic fiber such as rock wool, glass fiber, silicate fiber, alumina fiber, carbon fiber, metal fiber such as steel fiber, stainless steel fiber, titanium fiber, etc.
Organic fibers such as hemp, cotton, and aromatic polyamide fibers can be used.

As the binder, those used for conventional friction materials can be used. For example, phenol resin, epoxy resin, polyimide resin and the like can be mentioned. As the filler, those used in ordinary friction materials other than cashew dust can be used. Examples of the filler include fillers such as barium sulfate and calcium carbonate, solid lubricants such as graphite and molybdenum disulfide, abrasives such as metal powder and silica, and other additives for adjusting friction.

[0015] The friction material of the present invention can be manufactured by the same method as a normal friction material. That is, fibrous base material,
After sufficiently stirring the raw material consisting of the binder and the additive including the cashew-silicone composite dust, preforming is performed, thermoforming is performed in a mold, and heat treatment is further performed to stabilize the curing reaction of the binder. Conventional manufacturing methods can be used.

[0016]

The present invention will be described below with reference to examples. (Adjustment of friction material) Table 1 shows an example of the friction material of the present invention.
The raw materials having the compositions shown in (1) and (2) are sufficiently mixed with a V-type blender so as to be uniform, and charged into a preforming mold.
Preforming was performed by pressing at a pressure of 00 kg / cm ² for 1 minute, and the molded product was put into a thermoforming mold together with a pretreated back metal, and thermoforming was performed at 160 ° C. by applying a pressure of 400 kg / cm ² for 10 minutes. Thereafter, a brake pad subjected to a heat treatment of heating at 250 ° C. for 120 minutes was produced.

[0017]

[Table 1]

Here, as the composite dust blended in the examples, the composite dust in which the cashew component, the Si rubber component and the Si resin component are blended in the ratio shown in Table 2 is used. The composite dust containing the Si rubber component is made by mixing 100 parts of a viscous solution obtained by adding 10 parts of furfural as a curing agent to 100 parts of a cashew polymer heated and polymerized by adding an acid to cashew and silicon rubber. The mixture was mixed in a kneader (kneader) to prepare a mixture in which the silicone rubber component was uniformly dispersed. The mixture was poured into a stainless steel container and placed in a drier kept at 200 ° C. for 24 hours to heat. It was produced by curing and pulverizing it to a predetermined particle size with a pulverizer. Here, the average particle size of the composite dust was 100 to 300 μm.

The composite dust containing the Si resin component is obtained by adding 100 parts of a cashew polymer obtained by adding an acid to cashew and heating and polymerizing, and adding 100 parts of furfural as a curing agent to 100 parts of a viscous solution, A solution in which the three components were mixed by stirring and mixing with the silicone resin was prepared, and the mixed solution was poured into a stainless steel container, placed in a drier kept at 200 ° C. for 24 hours, and heated and cured. It was manufactured by crushing to a predetermined particle size with a crusher. Here, the average particle size of the composite dust was 100 to 300 μm.

[0020]

[Table 2]

As Comparative Examples of the present invention, Comparative Example 1 in which the composite dust was only cashew dust and Comparative Example 2 in which the composite dust of cashew dust and nitrile rubber (NBR) were prepared. The composite dust of Comparative Example 2 was obtained by previously kneading NBR, sulfur (vulcanizing agent), carbon black, and an antioxidant, and further adding and mixing a cashew nut shell liquid polymer and furfural. This is dust that has been polymerized by heating and crushed into powder.

(Evaluation Test) Using the brake pads of Examples and Comparative Examples, a fade performance evaluation test and an investigation of occurrence of squeal were conducted. The results are shown in Table 3. 4. The fade performance evaluation test uses a caliper of PD51-18V.
Under the conditions of the inertia of 0kgfms ^2, JASO-C4
The measurement was performed by measuring the minimum coefficient of friction at the first fade (minimum μ at the time of fade) according to 06-82.

The investigation of the occurrence of squeal was conducted at a vehicle speed of 10 to 50 km.
/ H, brake fluid pressure 2-40 kg / cm ² , temperature 50-
The occurrence of brake squeal at 200 ° C. was examined. The evaluation criteria in the survey results were as follows: ○: no squealing occurred, □: Slightly squeezed, △: Slight squealing, ×: Squealing. .

[0024]

[Table 3]

From Table 3, it can be seen that the embodiment of the present invention suppresses the occurrence of squeal. Also, the minimum μ when faded
It can be seen that the occurrence of squeal is suppressed without impairing the performance as a friction material since the squeal does not decrease.

[0026]

According to the friction material of the present invention, generation of squeal is suppressed by the silicone component of the cashew-silicone composite dust compounded as an additive. Since silicone rubber and silicone resin blended as silicone components have high heat resistance, the vibration damping action is maintained even when the friction material is heated to a high temperature due to frictional heat.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Misawa 1141-1, Okawagahara, Iino, Oji, Fujioka-cho, Nishikamo-gun, Aichi Prefecture Aisin Chemical Co., Ltd. (72) Inventor Hiroshi Kondo 2-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Address Aisin Seiki Co., Ltd. (72) Mikio Nishimura Inventor 7-9-4 Nishigotanda, Shinagawa-ku, Tokyo Tohoku Kako Co., Ltd.

Claims (1)

[Claims] 1. A friction material comprising a fibrous base material, a binder, and a filler, wherein the filler comprises a composite of a cured product component of cashew nut shell liquid and a silicone rubber component or a silicone resin component. A friction material comprising cashew / silicone composite dust.