JPH0723465B2 - Friction material and heat treatment method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat treatment method for a special friction material, and particularly to a friction material suitable for improving the fade resistance of an automobile brake pad, and a heat treatment for the friction material. Regarding the method.

(Prior Art) Conventionally, a brake pad for an automobile uses a friction material in which a metal fiber, a glass fiber, a ceramic fiber or the like is used as a base material and a filler and a binder are mixed with the base material.

The heat treatment method for this friction material is 400 to 100 in a non-oxidizing atmosphere.
Heat treatment is performed under the heat treatment condition of 0 ° C. to partially carbonize the binder of the thermosetting resin, preferably the phenol resin, and to obtain a thermally stable carbonaceous substance with a small amount of decomposition products generated at high temperature. The formation of the friction material eliminates the cause of the reduction of the friction coefficient of the friction material and prevents the phenomenon of the reduction of the braking force (fade phenomenon) due to the deterioration of the friction material at high temperature and high load.

(See Japanese Patent Application Laid-Open No. 59-113038) By this heat treatment method, generation of squeal during braking at low speed is reduced and friction characteristics at high temperature are improved.

(Problems to be solved by the invention) However, when a resin mold disc brake pad using a phenol resin as a binder is heat-treated in a non-oxidizing atmosphere, the phenol resin as a binder deteriorates due to heat, so that the strength of the friction material is reduced. There was a problem of lowering.

In order to solve such a problem, an object of the present invention is to provide a friction material having excellent mechanical strength and fade resistance.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides naphthol (5-10
(0% by volume) and phenol (0 to 95% by volume) are subjected to a copolymerization reaction with formaldehyde using an acid and an alkaline shaft medium to cause condensation, and a naphthol-phenol copolymer resin having heat resistance is used as a binder to make steel. Fibers, aluminum fibers, copper fibers, brass fibers, zinc fibers, nickel fibers, chrome fibers, etc. are used as the base material, and conventionally used as friction materials, such as metal fibers and inorganic fibers. Graphite, barium sulfate, etc. are used as the base material. The friction material mixed with the filler is heat treated in a non-oxidizing atmosphere using an inert gas such as nitrogen, helium, argon and carbon dioxide under the set conditions of the treatment temperature of 25 ° C or higher and lower than 1250 ° C. This friction material has a fade resistance due to partial carbonization of the thermosetting resin, and since this resin has heat resistance as compared with general phenolic resins, it is a friction material in which mechanical strength is less likely to decrease due to heat. It is characterized by that.

(Function) By using such a heat-resistant resin, naphthol resin, as a binder, strength reduction due to heat deterioration is prevented and the friction coefficient at high temperature and high load is stabilized.

(Example) A heat treatment method for a friction material according to the present invention will be described. The copolymer resin of naphthol and phenol, which is a binder, is a copolymer resin of naphthol and phenol in a molar ratio of 11: 1, and is subjected to a copolymerization reaction with formaldehyde using an ammonia catalyst which is an alkali to cause condensation. A copolymer resin of naphthol and phenol is obtained.

Using this resin as a binder, steel fibers as a base material, graphite and other fillers are compounded according to the volume ratio (%) shown in Table 1, and this is uniformly kneaded.

Next, the above-mentioned composite material is filled in a mold, and the temperature is 150 ° C and the pressure is 500.
Compress and mold at kg / cm ² . After the resulting molded article is subjected to after-curing at 200 ° C for 4 hours under predetermined conditions, the optimum treatment temperature is 250 ° C or higher and lower than 1250 ° C, more preferably 350 ° C or higher and lower than 800 ° C in a nitrogen atmosphere. The treatment time is 15 minutes or more, more preferably 30 minutes or more and 2 hours or less.

The reason for selecting the heat treatment temperature and the treatment time that are the above setting conditions is that when the treatment temperature exceeds 1250 ° C, rapid decomposition occurs, so the gas generated inside the friction material cannot escape to the outside, causing swelling and cracking. This is because the naphthol resin, which is a binder, decomposes only slightly at 250 ° C. or below even if a heat treatment is performed for a long time at 250 ° C. or less, and it becomes impossible to improve the fade resistance.

In the above examples, in order to confirm the effect of retaining the strength of the friction material, as a specific example, the characteristics of a friction pad subjected to a heat treatment at a heat treatment temperature of 400 ° C. for a treatment time of 1 hour in a nitrogen atmosphere were examined. There is a difference in strength reduction after high temperature heat treatment as shown in Table 2 between the case where the heat-resistant resin naphthol resin is used as the binder and the case where the general phenol resin is used as the binder.

As is clear from Table-2, by performing high temperature heat treatment, the bending strength after heat treatment is significantly reduced in the case of a friction pad using a general phenol resin as a binder, but it is a heat resistant resin. It can be seen that in the case of the friction pad using naphthol, the reduction is half that in the case of the general phenol resin.

Further, in order to confirm the effect of improving the fade resistance, as a specific example thereof, the characteristics of a disc brake pad subjected to a heat treatment at a heat treatment temperature of 400 ° C. for a treatment time of 1 hour were examined.

The heat treated disc brakes, JASOC406 friction coefficient obtained while continuous braking provided credentials every 35 seconds ^-82 in curve shown in FIG. 1, A is naphthol-based resin of the above heat treatment conditions products of the present invention B is a conventional example of the ordinary heat-treated product using a general phenol resin, which is a comparative example in which heat treatment was performed at 200 ° C. for 4 hours in the air.

Curve A shows the initial friction (the number of braking times n is within 10 times)
The friction coefficient was stable at 0.43, showing a remarkable difference compared to the curve B, and the fade resistance by the heat resistant resin in the specific example of the curve A was sufficiently demonstrated.

(Effects of the Invention) As is apparent from the above description, the present invention uses a naphthol-based resin, which is a heat-resistant resin, as a binder of a friction material, and heat-treats a friction pad at high temperature in a non-oxidizing atmosphere to provide friction. It is possible to improve the fade resistance by reducing the strength reduction of the pad and by carbonizing the thermally decomposed material of the binder at high temperature in advance by heat treatment.

In addition to stabilizing the friction coefficient of the friction material at high temperature,
It is possible to suppress the ignition phenomenon due to the pyrolysis gas generated at the time of braking without lowering the coefficient of friction against sudden braking at high speed. Further, it has a secondary effect of preventing squeal during braking.

[Brief description of drawings]

FIG. 1 is a characteristic curve showing the relationship of the friction coefficient with respect to the braking rotational speed of the friction material in this example and the conventional example.

Claims (7)

[Claims] Claims: 1. A naphthol-phenol copolymer resin is used as a binder, a reinforcing fiber is used as a base material, and a friction material material containing graphite, metal powder, an inorganic filler, etc. is thermoformed by a hot press method. In the production of the friction material, the friction material is maintained at a temperature of more than 250 ° C. and less than 1250 ° C. in a non-oxidizing atmosphere. 2. A hot-pressing method is used to thermoform a friction material containing naphthol-phenol copolymer resin as a binder, reinforcing fibers as a base material, and graphite, metal powder, inorganic filler and the like. In the production of the friction material, the friction material is heat-treated at a temperature of more than 250 ° C. and less than 1250 ° C. in a non-oxidizing atmosphere. 3. The friction material according to claim 1, wherein the copolymer resin of naphthol and phenol is synthesized using an acid as a catalyst. 4. The friction material according to claim 1, wherein the copolymer resin of naphthol and phenol is synthesized by using an alkali as a catalyst. 5. The reinforcing fiber is steel fiber, aluminum fiber,
The friction material according to claim 1, which is a metal fiber such as copper fiber, brass fiber, zinc fiber, nickel fiber, or chromium fiber. 6. The friction material according to claim 1, wherein the reinforcing fibers are inorganic fibers such as glass fibers and ceramic fibers. 7. The heat treatment method for a friction material according to claim 2, wherein the non-oxidizing atmosphere is nitrogen, argon, carbon dioxide, helium or the like.