JPS594455B2 - Friction material with excellent wear resistance and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a friction material made of carbon fiber as a base material and a phenolic resin as a binder. This is what we provide.

The friction material of the present invention is used for automobile brakes, clutches, etc.
It is one of the top 10 organic friction materials used in brake shoes, slide plates, etc. of railway vehicles, and various industrial machines.

Conventional organic friction materials generally consist of asbestos as a base material, phenolic resin as a binder, and various friction modifiers added.

However, although asbestos has various excellent properties, in 1972, at a medical symposium sponsored by the International Agency for Research on Cancer, the carcinogenicity of asbestos became an issue, and as a result, regulations regarding the handling of asbestos became worldwide. has been strengthened.

On the other hand, since asbestos is a natural product, it is becoming increasingly difficult to use it as desired from the standpoint of resource conservation. As mentioned above, the use of asbestos involves so-called environmental and resource issues, and there is an urgent need to develop various asbestos substitute materials in the future without the use of asbestos. For this reason, among organic friction materials, glass fibers, steel fibers, various ceramic fibers, carbon fibers, and the like are being considered as substitutes for asbestos.

30 The purpose of developing the carbon fiber organic friction material of the present invention is not only to meet the above-mentioned asbestos regulations, but also to improve the drawbacks that asbestos-based organic friction materials have conventionally had and to provide excellent performance. The objective is to provide a friction material with improved properties.

35 Several prior art techniques are already known regarding the application of carbon fibers to friction materials.

For example, Special Publication No. 38-26574, Special Publication No. 48-15
No. 127, JP-A No. 48-33272 (U.S. Patent No. 40)
19912), JP-A-52-132269, JP-A-51-133351, JP-A-48-14801, JP-A-49-128049, etc. Special Public Service 1973-26
No. 574 discloses a brake lining made of a system of carbon fibers and a resin binder, but does not disclose anything about its manufacturing method or characteristics. Special Public Service 1973
No. 5127 discloses a carbon fiber, filler and binder composition for a reinforced synthetic brake shoe.

JP-A No. 48-33272 discloses a fiber-reinforced friction material composed of carbon fiber and an inorganic binder such as molten glass or clay. JP-A-52-132269 points out that carbon fiber-based organic friction materials generally have a low coefficient of friction, and discloses that as a measure to improve this, the carbon fibers used include inorganic fine powder in advance. . JP-A-51-1
No. 33351 discloses that polyoxyphenylmethane phenoxysiloxane is effective as a binder in carbon fiber-based organic friction materials. Japanese Unexamined Patent Publication 1973-148
No. 01 discloses that a friction material for use in oil is obtained by making paper from pulp, asbestos, carbon fiber, etc., impregnating it with resin, and then molding it.0 JP-A-49-128049 discloses that a friction material for use in oil is obtained by making paper from pulp, asbestos, carbon fiber, etc., impregnating it with resin, and then molding it. It is disclosed that a composite material composition with excellent sliding properties can be obtained by adding carbon fiber to a resin-based composite material. Although each of the above-mentioned prior art techniques has developed the application of carbon fibers to friction materials, it is difficult to say that they have yet reached a technology that fully utilizes the excellent characteristics of carbon fibers.

The present inventors have discovered the excellent friction and wear properties of carbon fiber,
The present invention was arrived at as a result of intensive studies aimed at fully exhibiting heat resistance, mechanical properties, etc. as a friction material.

In other words, conventional friction materials generally have a combination weight of various materials →
Although it is manufactured through the process of mixing (dry mixing) → preheating, preforming → hot press molding → post-curing, the main point of the present invention is a friction material composed of carbon fiber, phenolic resin, and friction modifier. Introducing a new pre-heat treatment process during the production of
A mixture having the above composition is obtained by mechanically pressurizing and shearing kneading at a temperature of 100 mL, and then the mixture is hot-press molded to obtain a friction material that fully exhibits the various properties of carbon fibers.

Even if the carbon fibers used in the present invention are long fibers, it is an essential requirement to cut the length of the carbon fibers to an average fiber length of 0.4wn or less through a mechanical pressure-shear kneading process. Become. If the average fiber length is 0.4 m or more, the effect of pressurized shear kneading will be insufficient, and the dispersion state of carbon fibers in the molded product will be poor, and the porosity will be 15% or more, resulting in a dense molded product. Therefore, the excellent friction, wear characteristics, and mechanical properties that are the characteristics of the present invention described below are no longer exhibited.

The molded product obtained by the present invention exhibits surprisingly superior friction and wear characteristics compared to molded products obtained by conventional molding methods, that is, molded products obtained by molding methods that do not include a mechanical pressure-shearing and kneading process. did.

In other words, the wear resistance is in the low temperature range (100 to 200
℃), but also in the high temperature range (250 to 350℃)
The abrasion rate was extremely low, and it showed an unexpectedly excellent abrasion resistance even for carbon fiber-based molded products and asbestos-based friction materials obtained by conventional molding methods.

In addition, with regard to the friction coefficient, conventional asbestos-based friction materials exhibit a remarkable decrease in the friction coefficient in the high temperature range (250 to 350 C) (so-called fade phenomenon), whereas the molded product obtained by the present invention does not exhibit this phenomenon. This was not observed at all, and the coefficient of friction remained stable even in the high temperature range. On the other hand, regarding mechanical properties, the molded products showed superior bending strength and impact strength values compared to molded products obtained by conventional molding methods.
As described above, a carbon fiber-based molded product can be obtained using a conventional molding method by introducing a new pre-treatment process, that is, a mechanical pressure shearing and kneading process, into the molding process, which is the key point of the present invention, for carbon fiber-based organic friction materials. It has become possible to exhibit significantly improved friction, wear characteristics, and mechanical properties compared to asbestos-based friction materials.

Composite materials obtained by conventional molding methods without a pre-heat treatment step, ie, a mechanical pressure-shear kneading step, do not have the friction and wear characteristics of the present invention. Although the theoretical explanation for this difference in effects is still unclear,
In the pre-heat treatment step, the carbon fibers are cut due to pressure shear kneading, and at the same time, the molten binder resin, filler and fibers are thoroughly kneaded and the affinity with the resin is significantly improved.
This is thought to be because a dense molded product is obtained as a result.

As described above, the present invention has excellent properties as a friction material, and the introduction of the preheat treatment step according to the present invention greatly contributes to improving the working environment.

The preheat treatment, that is, the mechanical pressurized shear kneading is carried out using a Banbury type mixer, a continuous mixer, a roll, a kneader, a screw type extruder, or the like.

The temperature during kneading is preferably 70 to 140°C, and external heating or frictional heat generated by kneading may be used. If the temperature is below 70°C, the phenolic resin will not melt sufficiently, and if it is above 140°C, the curing of the phenolic resin will progress, which is disadvantageous.

The composition of the friction material of the present invention is as follows: carbon fiber, phenolic resin, and friction modifier each contain 5 to 60% by weight of carbon fiber;
Preferably 20-50% by weight, 10-50% by weight of phenolic resin
O-carbon fibers of which 30% by weight, preferably 15 to 25% by weight and the remainder are friction modifiers, may be made from polyacrylonitrile, rayon, pitch, etc., but pitch is preferred from the viewpoint of industrial economy. Carbon fiber used as a raw material is preferable.

The length of the carbon fibers used is not particularly limited, but from the viewpoint of ease of mixing, carbon fibers of 150 Tt1n or less are preferred. As the phenolic resin, commercially available phenolic resins for friction materials, that is, straight resins, and modified resins such as Kashi-modified, epoxy-modified, and elastomer-modified resins are used. 〇Friction modifiers are conventionally known ones, such as barium sulfate. , cashew dust resin, rubber dust, metal powders such as copper and iron, and fiber materials such as pulp, synthetic fibers, and inorganic fibers.

In the present invention, one or more of these is added, but the type is not particularly limited. The present invention will be explained in more detail below using Examples and Comparative Examples.

Example 1 Pitch carbon fiber (Kureha Carbon Fiber C-106t8, manufactured by Taiyo Kaken Co., Ltd.) with an average fiber length of 6 m, 30% by weight, phenolic resin (BP-7008, manufactured by Gunei Chemical Co., Ltd.)
20% by weight and 50% by weight of barium sulfate were mixed for 30 seconds using a pen shell mixer.

The mixture was kneaded under pressure and shear using a Konidader 1 (PR-46 [F], a continuous kneader manufactured by Busu Co., Ltd.), at which time the temperature of the kneaded material was controlled at about 100°C. It was observed that the length of the carbon fibers in the obtained kneaded material was about 0.5 TWL as shown in the photograph shown in FIG. 1, and the average fiber length was about 0.25 m. The first
The photograph shows the carbon fibers recovered by heat-treating the kneaded material in air at 450° C. for 30 minutes to burn out the phenol resin, and the recovered material was observed under a microscope and photographed.

Then, the kneaded material was heated at 160°C and 20°C using a mold.
0kg/Cr! It was molded by compression molding for 15 minutes under the conditions of i.

Further, the molded product was post-cured at 180° C. for 15 hours.
The porosity of the obtained molded article was calculated by measuring the bulk density and was found to be 8.9 (F6).The porosity was calculated as follows.

The obtained molded product was then subjected to the following physical property evaluation.

Two test pieces of 25 Trm square and 5 wn thick were cut out from the molded plate, and their friction and wear characteristics were evaluated by a constant speed friction test in accordance with JISD-4411.

The results are shown in Table 1. Also, the width is 12.5 mm from the molded plate.
A test piece with a length of 100 tfrm and a thickness of 3.5Wr1rL was cut out and subjected to a bending test and an impact test. The bending test was conducted according to ASTM. D-970, impact test ASTM.
It was conducted in accordance with D-256.

The results are shown in Table 2. Example 2 40% by weight of pitch-based carbon fiber (Kureha Carbon Fiber M-107t [F], manufactured by Taiyo Kaken Co., Ltd.) with an average fiber length of 0.77 m, phenol resin (Kashiyu-ichi modified resin manufactured by Kashiyu-ichi Co., Ltd.) ) and 40% by weight of barium sulfate were respectively charged into a second cylinder and kneaded by pressurization and shearing.

At this time, the temperature of the kneaded material was controlled at 115°C.The length of the fibers in the obtained kneaded material was 0, the average fiber length.
It was observed that the temperature was about 2 Tm. The kneaded material was then compression molded using a mold for 15 minutes at 160° C. and 200 Kf/i.

Further, the molded product was post-cured at 180° C. for 15 hours.
The porosity of the molded product was found to be 7.1% by measuring the bulk density. The obtained molded product was subjected to a friction test, a bending test, and an impact test in the same manner as in Example 1.

The results are shown in Tables 1 and 2, respectively. Comparative Example 1 Pitch carbon fiber with an average fiber length of 0.7 m (Kureha Carbon Fiber M-107t [F], manufactured by Taiyo Kaken Co., Ltd.) 40% by weight, phenol Resin (Kashiyu-ichi modified resin manufactured by Kashiyu-ichi Co., Ltd.) 20% by weight, barium sulfate 40% by weight
were mixed for 30 seconds using a pen shell mixer.

The length of the carbon fibers in the mixture is the starting fiber length 0
．． It was found that it was approximately 7Trr1n and was not particularly cleaved. The mixture was then molded in the same manner as in Example 1 using a mold.

The porosity of the obtained molded product was 17%. The results of the friction test and mechanical property evaluation of the molded product are shown in Tables 1 and 2, respectively.

Comparative Example 2 Pitch-based carbon fiber (Kureha Carbon Fiber M-101 [F], manufactured by Taiyo Kaken Co., Ltd.) with an average fiber length of 0.1 WWL, 40% by weight, phenol resin (Kashiyu-ichi modified resin manufactured by Kashiyu-ichi Co., Ltd.) ) and 40% by weight of barium sulfate were mixed for 30 seconds using a pen shell mixer.

The length of the carbon fibers in the mixture remains the same as the starting fibers and is 0.
．． The mixture was then molded in the same manner as in Example 1 using a mold. The porosity of the molded article obtained was 9.2%. The evaluation results of the friction test and mechanical properties of the molded product are shown in Tables 1 and 2, respectively.〇Even if the fiber length is 0.4wr1n or less and the porosity of the molded product is 15% or less, it will not work as in the present invention unless pressure-sheared and mixed in the preheat treatment. As described above, the friction material of the present invention exhibits a stable friction coefficient and excellent wear resistance in a high temperature region,
It is clear that it has even better mechanical properties.

[Brief explanation of the drawing]

FIG. 1 is a micrograph of carbon fibers recovered by pressurizing and shearing a mixture of carbon fibers, phenolic resin, and barium sulfate, then burning off the phenolic resin, and the white short fibers indicate carbon fibers.

Claims (1)

[Claims] 1. Carbon fibers in a composite material obtained by mixing carbon fibers, a phenolic resin, and a friction modifier by pressure-shear kneading as a preheat treatment, and then hot-pressing the mixture. Average fiber length is 0.4mm or less and porosity is 1
Friction material of 5% or less. 2. The friction material according to claim 1, wherein the composition of carbon fiber, phenolic resin, and friction modifier is 5 to 60% by weight of carbon fiber, 10 to 30% by weight of phenolic resin, and the balance is friction modifier. . 3. When manufacturing a friction material composed of carbon fiber, phenolic resin, and friction modifier, 70 to 14
1. A method for producing a friction material, which comprises obtaining a mixture by pressure-shearing and kneading at 0° C., and then molding the mixture under heat. 4. The friction material according to claim 3, wherein the composition of carbon fiber, phenolic resin, and friction modifier is 5 to 60% by weight of carbon fiber, 10 to 30% by weight of phenolic resin, and the balance is friction modifier. manufacturing method.