JPH051277A - Frictional material - Google Patents

Abstract

PURPOSE:To provide a nonsteel frictional material excellent in abrasion resistance by compounding a specific graphite as a friction-controlling agent into the material. CONSTITUTION:A frictional material is prepd. by compounding a fibrous base material, a binder, and a friction-controlling agent comprising graphite contg. at least 85wt.% fixed carbon and at least 5wt.% ash in an amt. of graphite of about 1-20wt.% based on the material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used for brakes and clutch facings of automobiles, industrial vehicles and the like.

[0002]

2. Description of the Related Art In recent years, due to the pollution problem of asbestos, friction materials containing no asbestos in the base fiber have been put into practical use. As an example, there is a so-called semi-metallic friction material using steel fiber as a substitute fiber for asbestos. Graphite as a lubricant is blended with these friction materials as a friction modifier to stabilize the coefficient of friction and wear resistance. For example, Japanese Patent Application Laid-Open No. 2-117985 discloses a friction material containing copper-based fibers and steel fibers in a specific ratio and compounding a solid lubricant graphite and a metal sulfide as components of a friction modifier. However, this semi-metallic friction material has a problem that it becomes heavy and rusts or damages the mating material.

Therefore, a non-asbestos-based friction material containing no steel fiber has been proposed to solve the above-mentioned problems of the semi-metallic friction material. JP-A-2-298
In Japanese Patent No. 575, the fiber base material does not contain asbestos and iron-based fibers, and the friction modifier contains graphite of 5 to 20% by volume as an inorganic lubricant.
Added friction materials are disclosed. Japanese Patent Laid-Open No. 1-2726
Japanese Patent Publication No. 84 discloses a friction material in which long columnar granulated graphite is mixed with a friction modifier.

[0004]

However, the above-mentioned non-steel type friction material is added with graphite showing lubricity in order to maintain wear resistance, but the obtained friction material does not always have wear resistance. It does not reach a satisfactory state. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-steel friction material that is more excellent in wear resistance.

[0005]

The friction material of the present invention comprises a fibrous base material, a binder, and a friction modifier, wherein the friction modifier has a fixed carbon content of 85% by weight or more and an ash content of at least 50% by weight. It is characterized by containing 5% by weight or more of graphite.
This friction material is formed by mixing a friction modifier and a binder on a fiber base material and molding the mixture. Then, the friction modifier is bound and integrated with the fiber base material by the entanglement binder to develop friction characteristics.

It is generally said that graphite having a higher proportion of fixed carbon content and lower ash content has a graffiti structure and a higher lubricating effect. On the other hand, the main component of ash is silicon oxide,
Alumina, iron oxide, etc. usually impair lubricity. However, it has been found that it is not always a good idea to add a small amount of ash to graphite to add its effect to a friction material as a lubricant and to exert its effect.

That is, it was found that the wear resistance of the friction material was improved by using graphite having a relatively high ash content.
It has been clarified that the wear resistance of the friction material can be maintained by using graphite containing 5% by weight or more of ash in graphite and 85% by weight or more of fixed carbon in order to maintain lubricity. became. Therefore, when graphite satisfying this requirement is used, the friction material retains its lubricity and is firmly bonded by the binder, so that the wear resistance is improved.

The fixed carbon content and ash content referred to here are JI
It is a value obtained by measurement according to SM8511.
When the amount of ash in the graphite is increased, the binding force with the binding resin is increased and the lubricity is enhanced, but if the ash is too large, the fixed carbon content becomes insufficient, which is not preferable. Fixed carbon amount is 85
It is necessary that the content be at least wt% in order to exert lubricity.

That is, in order for graphite to exhibit a lubricating effect in the friction material and to be a friction material having wear resistance, it is necessary that graphite is firmly held on the friction surface. If graphite is not firmly adhered and held by the binder resin, it is thought that the graphite will fall off from the friction material during use and the abrasion resistance will decrease. Further, if the particle size of graphite is within a specific range, the lubricity is improved. Particularly, those having a particle size in the range of 50 to 150 μm are more preferable because the bondability with the resin is enhanced and the lubricity is improved. The amount of graphite added is in the range of 1 to 20% by weight in the friction material.

As the fiber substrate, copper fibers, glass fibers, silica fibers, alumina fibers, potassium titanate fibers, ceramic fibers such as rock wool, and organic fibers such as nylon, rayon, phenol fibers and aramid fibers can be used. In addition to graphite, friction modifiers are cashew dust, rubber dust, barium sulfate, diatomaceous earth, alumina, dolomite,
Calcium carbonate etc. can be used.

As the binder, phenol resin, melamine resin, epoxy resin, modified phenol resin and the like can be used. In this friction material, a predetermined amount of a mixture of a fiber base material, a friction modifier and a binder is mixed sufficiently uniformly with a Banbury mixer, a Hensell mixer, a kneader or a V-type blender. This mixture is filled in a mold and pressed to perform preforming. This preform is heated and pressed to harden the binder, and then heat-treated to obtain an ordinary method.

[0012]

In the friction material of the present invention, since the graphite contained in the friction modifier has a fixed carbon content and an ash content in a specific range, it is firmly held in the friction material by the binder. Therefore, even if the friction material receives friction, the graphite does not fall off, so that the lubricating action is maintained, the wear resistance is improved, and the life can be extended.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples. Table 1 shows the composition of the graphite used in Examples and Comparative Examples (fixed carbon content, ash content, and volatile content). This is JIS M-851
It is a value measured according to 1. (Example 1) A friction material was prepared by molding a mixture of a fiber base material having the composition shown in Table 2, a friction modifier and a binder. That is, as the fiber base material, 10% by weight of aramid fiber, 6% by weight of copper fiber, 8% by weight of potassium titanate fiber, 6% by weight of rock wool, 8% by weight of graphite A as a friction modifier, 10% by weight of cashew dust, and silica 3 Wt%, talc 8 wt

[0014]

[Table 1] This product is manufactured by Nippon Graphite Co., Ltd. %, 31% by weight of barium sulfate, and 10% by weight of a phenolic resin as a binder were mixed uniformly in a V-blender.

This mixture was pressed to preform and then
400kg / cm at 160 ℃ in mold ²Pressure for 10 minutes
Thermoform and heat treat at 250 ° C for 120 minutes
It was used as an abrasive. (Example 2) As shown in Table 2, the types of graphite of Example 1 were changed.
Instead, use graphite B, which has a relatively low fixed carbon content and a high ash content.
The same composition and the same molding conditions as in Example 1 were used except for the use.
An abrasive was prepared. (Comparative Examples 1 and 2) In this case also, as shown in Table 2, other than graphite
Is a friction material manufactured under the same composition and molding conditions as in Example 1.
It was In Comparative Example 1, graphite has an ash content of 3% as shown in Table 1.
And less graphite C was used. In Comparative Example 2, graphite is shown in Table 1.
As shown in, the ash content is as high as 20% and the fixed carbon content is 77.5.
% Graphite D was used.

The wear rate of the friction material is JASO-C427-
According to No. 83, each friction material was processed into a predetermined shape. Caliper type: PD51s, rotor: 18m
m ventilated type, inertia: I = 3.5kg
fmS ² , 50 → 0 km / h × 0.3 G, and the friction material temperature is 100 ° C. and 200 ° C. The wear rate at 300 ° C. was examined. The results are shown in Table 2.

[0017]

[Table 2] As shown in Table 2, in Examples, the wear rate is lower at any temperature than in Comparative Examples. In Comparative Example 1, the ash content of graphite is less than 5%, and the wear rate is larger than that of the Examples even when the fixed carbon content estimated to be a graffiti structure is as large as 96%. In other words, it is considered that the friction surface has come off. On the other hand, in Comparative Example 2, the ash content of graphite is as high as 20%, but the fixed carbon content is 77.5%, which is significantly less than the 85% of the range of the present invention, so that it does not exhibit a sufficient lubricating action, and the friction material has wear resistance Low. Therefore, it is understood that when the solid carbon content in the graphite is 85% or more and the ash content is 5% or more, the friction material has improved wear resistance and durability.

[0018]

In the friction material of the present invention, the graphite contained in the friction modifier contains 85% or more of fixed carbon and a relatively large amount of ash. Therefore, the wear resistance is improved as compared with the conventional case where graphite having a low ash content is used. It is presumed that this is based on the fact that the binder is firmly held in the friction agent via the ash. The reason why the amount of ash is 5% or more is unknown, but the binding force with the resin is higher than in the case of a high concentration of fixed carbon and the ash is retained in the fiber base material. Therefore, the lubricity of the friction material is maintained and the wear resistance can be improved.

Claims (1)

Claim: What is claimed is: 1. A friction material comprising a fiber base material, a binder and a friction modifier, wherein the friction modifier has a fixed carbon content of 85% by weight or more and an ash content of 5% by weight or more. A friction material characterized by containing.