JPS62195027A - Production of frictional material - Google Patents

Abstract

PURPOSE:To obtain a frictional material capable of exhibiting a stable friction coefficient even on braking with high frictional heat, by heat-treating a raw material mixture containing a thermosetting resin for a binder in a nonoxidizing atmosphere, adding a small amount of a thermosetting resin to the resultant granules and hot-molding the resultant mixture under pressure. CONSTITUTION:A raw material mixture containing a thermosetting resin for a binder is heat-treated in a nonoxidizing atmosphere to give a granular mixture. A small amount of a thermosetting resin is then added and mixed with the resultant mixture and hot-molded under pressure. EFFECT:Improved abrasion resistance and adhesive property to back plates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a friction material, particularly a method for manufacturing a friction material used for automobile brakes, clutches, etc.

[Prior art]

Conventionally, the method for manufacturing friction materials involves weighing and mixing raw materials such as a base material made of fibers, a filler as a friction and wear modifier, and a binder made of a mixture.
After preforming with a mold, main molding is performed using pressure and heat to obtain a molded product, and heat treatment is performed to completely harden the uncured binder remaining in the molded product to reduce friction. Methods of manufacturing materials are known.

By the way, the heat generation temperature of the friction material during braking is 400°C.
In contrast, the heating temperature in the main molding process in the prior art described above is 130 to 200°C, and the heating temperature in the heat treatment process for the molded product obtained by this main molding is 150 to 300°C. . For this reason, in friction materials manufactured by conventional methods, the phenolic resin decomposes and generates gas due to high temperatures during braking, and the gas is interposed in a film between the friction material and the disk, causing the friction material to As a result of lowering the coefficient of friction of

Therefore, it is possible to reduce the amount of phenolic resin mixed to reduce the amount of cracked gas generated and suppress the decrease in the coefficient of friction, but this reduces the bonding force of the phenolic resin that binds the base material and filler. However, there is a problem that the amount of wear of the friction material increases. On the other hand, as another solution,
There is a technique disclosed in Japanese Patent No. 97113038. That is, this technique involves performing a heat treatment process of the molded product at high temperature in a non-oxidizing atmosphere to partially carbonize the mixture, preferably a phenolic resin binder, and attaching it to the backing metal via an adhesive at high temperature. However, the friction material treated at high temperature in a non-oxidizing atmosphere has a problem in that its adhesive strength with the backing metal decreases.

[Problem that the invention seeks to solve]

The present invention was made in view of the above-mentioned drawbacks of the prior art, and the problem to be solved by the present invention is to provide a stable coefficient of friction even during braking when the friction material becomes hot due to frictional heat. At the same time, the objective is to improve wear resistance and adhesion to the backing metal.

[Means for solving problems]

The features of the means of the present invention configured to solve the above-mentioned problems include: heat-treating a mixture of raw materials in a non-oxidizing atmosphere; and after heat-treating the mixture of raw materials in a non-oxidizing atmosphere;
This is due to the fact that it is pressurized and heated.

Next, the present invention will be explained in detail.

First, the raw materials for the friction material mainly consist of a base material made of fiber material, a filler point as an abrasion and friction modifier, and a binder.

Here, the fiber materials include inorganic fiber materials such as steel and ceramics, and organic fiber materials such as aromatic polyamide. For example, steel fiber materials are formed to have a wire diameter of several tens of microns and a length of 2 to 8 fl. ing. Next, barium sulfate, for example, is used as the filler.

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, ut &f 7 , z / -nt@B@ are used.

' According to the method of the present invention, the above-mentioned raw materials are first mixed using, for example, a Henschel mixer to obtain a mixture.

The mixture is then exposed to a non-oxidizing atmosphere, such as nitrogen (N2
), heat treatment in an inert gas atmosphere such as argon (Ar), helium (He), etc. This heat treatment consists of a curing treatment in which the mixture is cured at a relatively low temperature, and a high temperature discharge treatment in which decomposition products such as gas are discharged from the mixture.

First, in the curing process, the mixture is heated in a constant temperature bath set at a temperature higher than the curing temperature of the mixture, for example 160°C, for a predetermined period of time, and the mixture is cured to adjust the mixing ratio of the base material, filler, and mixture. Accordingly, a homogeneously containing granular mixture is produced. Thereafter, the mixture is heated at a temperature higher than the decomposition temperature, for example, 400° C., for a predetermined period of time, for example, 60 minutes, to discharge decomposition products such as gas from the mixture. The reason why this heat treatment is performed in a non-oxidizing atmosphere is that if raw materials for the friction material are subjected to high heat treatment in the presence of oxygen (in the atmosphere), each raw material will be oxidized and its properties will deteriorate. Therefore, among the heat treatments, the hardening treatment performed at a relatively low temperature may be performed in the atmosphere.

The granular mixture produced as described above is again charged into the Henschel mixer, and a small amount, for example 4
% of the mixture by weight and mix to obtain the final mixture.

Then, by filling the final mixture into a mold or the like, pressurizing and heating it, a friction material having a predetermined shape can be formed.

Although the friction material molded as described above is attached to the back metal via an adhesive, the adhesive may be molded integrally with the metal in the mold.

According to the manufacturing method of the present invention described above, firstly, the mixture of raw materials is heat-treated at a high temperature higher than the decomposition temperature, so that even if the friction material reaches a high temperature, the mixture can be used to bond the base material and filler. Gas etc. will not be generated from the Second, each raw material is produced into a granular mixture with a uniform blending ratio, and the surface area is smaller than when each raw material is mixed in its original form. A small amount of the mixture added to bind the two is sufficient.

Thus, according to the present invention, due to the above-mentioned reasons 1 and 2, the friction material is heated to a high temperature of 40°0 to 70° due to the frictional heat during braking.
It is possible to produce a friction material that can maintain a stable coefficient of friction even under severe conditions of temperatures as low as 00°C.

In addition, since a small amount of the mixture for binding the granular final mixture is mixed into the friction material without undergoing high-temperature heat treatment, the friction material has excellent wear resistance and adhesion. can be manufactured.

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

Example Each raw material shown in Table 1 was mixed using a Henschel mixer at 2,000 ml.
Mix for 2 minutes at 0 rpm. The resulting mixture was subjected to a first heat treatment at 160° C. above the curing temperature of the phenolic resin.
By heating for 30 minutes in a constant temperature bath at 0.degree. C. to thermoset the phenol resin in the mixture, a granular mixture containing each raw material uniformly according to the mixing ratio is produced. Next, as a second heat treatment, the granular mixture was heated at 400'C, which is higher than the decomposition temperature of the phenolic resin, for 60 hours in a nitrogen atmosphere.
Heating is performed for a minute to decompose and discharge the gasified components in the phenol resin.

Next, 4% by weight of phenolic resin is further added to the heat-treated granular mixture as described above and mixed in a Henschel mixer to obtain a final mixture. Then, a predetermined amount of the final mixture is weighed and molded into a mold. and pressure 500 k+r/c
a. A friction material was manufactured by pressurizing and heat forming at a temperature of 155°C.

Table Also, the performance of the friction material manufactured by filling a mold and pressurizing and heat forming at a pressure of 500 kg/c + J and a temperature of 155°C and the friction material manufactured by the example method was determined according to JASO standard C-40.
Comparative evaluation was performed according to 6.

The comparison results are shown in Table 2, and the friction material manufactured by the method of the example was able to obtain a stable coefficient of friction even in the severe test.

Claims (1)

[Claims] In a method for producing a friction material containing a thermosetting resin for a binder as a raw material, a mixture of the raw materials is heat-treated in a non-oxidizing atmosphere, and a small amount of a thermosetting resin is added and mixed to the resulting granular mixture, and then A method for manufacturing a friction material, characterized by pressurization and heat molding.