JPS63130642A - Wet friction material composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which is inexpensive and excellent in compression set, heat resistance and abrasion resistance and can give, e.g., a brake of a long-term reliability, by using a highly saturated acrylonitrile/ butadiene rubber as a binder for a composite material containing a filler. CONSTITUTION:In the production of a friction material composition containing a filler, a reinforcement, general additives for a friction material and general additives for a rubber, a highly saturated acrylonitrile/butadiene rubber is used as a binder, and a peroxide (e.g., dicumyl peroxide) is used as a curing agent. Said acrylonitrile/butadiene rubber is suitably one of a degree of saturation of about 95-100%, and its amount of use is preferably 20-35wt%, based on the composition. By adding a resin material as a cocuring agent (e.g., polybutadiene or triallyl isocyanate), the heat resistance, compression set, etc., can be further improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to wet friction applied to wet brakes and wet clutches that require durability and high reliability under high loads, such as industrial machinery and heavy construction machinery. It concerns a new composition of materials.

Prior Art and its Problems This type of wet friction material composition using an elastomer as a binder has been used as a high-load friction material in place of a sintered alloy. The greatest advantage of sintered alloy friction materials is that they have high heat resistance due to their composition, but on the other hand,
Because it is made of metal, it has poor ability to follow the undulations and irregularities of the mating surface when engaged, and it generates hot spots, so-called heat spots, resulting in mechanical fatigue failure and instability of the friction material. IiI! This leads to A behavior. Also,
Another disadvantage of being made of metal is its weight, which is not compatible with the recent trend toward smaller and lighter weights, and the direction of progress is to simultaneously seek higher friction coefficients and smaller and lighter weights. .

As one of the answers to this question, fluororubber has attracted a lot of attention due to its heat resistance and oil resistance, but it is also used in engine oil, transmission oil, etc. where wet friction materials are used.
It had a serious defect in that it could be susceptible to chemical attack and deterioration due to certain amine-based strong basic additives contained in ATF, gear oil, etc. In addition, the high cost is also a factor inhibiting the spread of fluororubber wet friction materials.

On the other hand, there is also a wet friction material that is made by copolymerizing carboxylated acrylonitrile butadiene rubber and epoxy resin to form a binder resin. Although this material is inexpensive, the molding process is complicated, and under conditions of use where high temperatures persist for long periods of time, it hardens and deteriorates significantly, resulting in the lack of flexibility, which is an advantage of rubber-based friction materials. It has the disadvantage of being lost. It is well known that the cause of this is the double bond in carboxylated acrylonitrile butadiene rubber. Various anti-aging agents have been used to prevent the progress of hardening and deterioration, but these additives are easily consumed by heating during the molding process and cannot provide a fundamental solution.

Means and Effects for Solving the Problems The present invention uses highly saturated acrylonitrile butadiene rubber as a binder for wet friction materials in place of various conventional rubbers and the above-mentioned copolymer of carboxylated acrylonitrile butadiene rubber and epoxy resin. By using this, we can solve problems and contribute to the improvement and advancement of high-load brake and clutch systems for industrial machinery, heavy construction machinery, etc.

In other words, the present invention has heat resistance comparable to that of fluororubber while maintaining sufficient elasticity, has wear resistance comparable to that of sintered alloys without being attacked by lubricating oil, and has a carboxylated acrylonitrile butadiene rubber. The objective is to provide a wet friction material composition that maintains a higher coefficient of friction for a longer period of time than friction materials based on copolymers of epoxy resin and epoxy resin, and is also less expensive than fluororubber and sintered alloys. be.

In the wet friction material composition of the present invention, in addition to the binder, organic or inorganic fibrous or powder fillers, reinforcing agents, friction modifiers such as graphite, Teflon fine particles, molybdenum disulfide, cachet resin, barium sulfate, etc. Conventionally known formulations for wet friction materials and rubbers such as curing accelerators, curing agents, dispersants, and anti-aging agents can be used.

The present invention is characterized in that highly saturated acrylonitrile butadiene rubber in which the 2m bonds inherent in acrylonitrile butadiene rubber are saturated is used as the binder of the wet elastic friction material. The saturation of double bonds is usually achieved by hydrogenation to a degree of saturation of 90 to 100%.

As a result, compared to the case where the above-mentioned copolymer of acrylonitrile butadiene rubber and epoxy resin is used as a binder resin, the chemical reactivity is fundamentally low and it is difficult to cure and deteriorate, and the characteristics of acrylonitrile butadiene rubber are This made it possible to construct a composite material that also has oil resistance. Furthermore, it is sufficiently cheaper than fluororubber.

Furthermore, the present invention provides a wet friction material composition with further improved heat resistance, chemical resistance, and abrasion resistance by blending highly saturated acrylonitrile butadiene rubber with a resin material as a co-curing agent.

Although there is still insufficient theoretical elucidation as to how materials such as rubber, which inherently have poor heat resistance, can be imparted with high performance and long-term reliability to friction materials used under high loads. , can be thought of as follows.

Rigid friction materials such as sintered alloys come into contact with the opposing surfaces that are rotating relative to each other, and when the engagement is completed, the non-parallel parts that exist on the mutual surfaces have a low followability due to their high elastic modulus numbers. This generates a local high surface pressure, and as a result, generates a large amount of heat locally while absorbing the engagement energy in that limited area. The localized high heat generated at this time is carried away from the retaining tip by the high heat transfer coefficient and large heat capacity due to metal bending, absorption by oil evaporation, and diffusion by oil flow. On the other hand, this retention energy absorption mechanism is aggressive toward the opposing surface, and as the load increases, it easily causes heat spots and distortion of the opposing surface, and is also damaged. On the other hand, when a rubber-based friction material completes engagement with a relatively rotating mating surface, its flexibility makes it easy to deform along the unevenness of the mating surface, and in fact, a sufficient contact area is secured. . Therefore, the absorbed energy per unit area is small, and no local high surface pressure is generated and no local high temperature is generated.

With this engagement energy absorption mechanism, the present invention significantly reduces heat spots and distortion of the friction material on the mating surface. As a result, even when used for a long time, the initial state is kept good and the amount of wear is extremely small. In addition, because it is difficult to generate localized high surface pressure, the oil film does not break on the engagement surfaces, and the generation of high heat is suppressed, and even with materials with poor heat resistance such as rubber, friction materials Not only can it be used satisfactorily, but it is also considered to be advantageous.

The invention of claim 1 provides a friction material composition using a highly saturated acrylonitrile butadiene rubber alone as a binder, preferably having a saturation degree of 95.
% to lOO% of highly saturated acrylonitrile butadiene rubber is used. In this case, the rubber undergoes peroxide vulcanization (curing).

In a friction material composition containing a filler, a reinforcing agent, a general compounding agent as a friction material, and a general compounding agent as a rubber, the proportion of highly saturated acrylonitrile butadiene rubber is 15 to 50.
% by weight, the composition will provide useful performance as a wet friction material, but preferably the highly saturated acrylonitrile butadiene rubber should be contained in the blend in an amount of 20 to 35% by weight. Peroxides used as curing agents include dicumyl peroxide, ditertiary-butyl peroxide, benzoyl peroxide, and lauroyl peroxide.

These peroxides are blended in an amount of 4 to 12 parts per 100 parts of highly saturated acrylonitrile butadiene rubber.

The invention of claim 2 is based on highly saturated acrylonitrile (・
In addition to peroxide as a curing agent, a resin material as a co-curing agent is blended with lylbutadiene rubber.It is a general compounding agent for fillers, reinforcing agents, friction materials, and general compounding agents for rubber. In friction material compositions containing highly saturated acrylonitrile butadiene rubber and co-curing agent, the ratio of highly saturated acrylonitrile butadiene rubber and co-curing agent is usually 15 to 50% by weight of the total, and the ratio of highly saturated acrylonitrile-butadiene rubber to co-curing agent is 10% by weight. :0~
l:9, preferably 9:1 to 4:6.

As mentioned above, peroxide is blended as a curing agent for highly saturated acrylonitrile butadiene rubber, and the resin materials used as co-curing agents are triallyl isocyanate, diallyl phthalate, polybutadiene, trimethylpropane trimecrylate, and magnesium dimethacrylate. , zinc dimethacrylate, ethylene dimethacrylate, P-
Quinonedioxime, P,P'-dibenzoylquinonedioxime, unsaturated polyester, N,N'-m-phenylene.

One or more types of lenbismaleimide are blended.

Thereby, the resin material participates in the curing of the rubber as a co-curing agent and forms a copolymer with the rubber. Therefore, the heat resistance, compression set properties, etc. are further improved than when highly saturated acrylonitrile butadiene rubber is used alone, and it is possible to obtain more stable long-term reliability as a wet friction material.

In the present invention, "curing" means so-called "crosslinking".

Although the addition of epoxy resins and phenolic resins does not contribute to the hardening of rubber, they contribute to improving the holding power of fillers, especially carbon fibers, in composite materials, reducing wear, improving the coefficient of friction, and reducing changes over time. It has the effect of reducing

Examples In the table on the next page, ■ is a conventional formulation example using a copolymer of carboxylated acrylonitrile butadiene rubber) and epoxy resin, and ■ is an example of the example described in claim 1. Yes, ■, ■, ■ are examples of claim 2.

Here, Z-ball is an example of a highly saturated acrylonitrile butadiene rubber and peroximone is an example of a peroxide as a rubber curing agent.

[Table 1: Formulation example] [Table 2: Wet clutch test conditions] Facing Ku Amami 335
mm single side facing I product 25
0.2 cm2 Number of friction surfaces
8 population oil temperature
80℃ cycle time
20 sec inertia+
1.02kg0m, 5ec2engine gauge speed
2000 rpm surface pressure 14.6 kg/cm21 official oil engine oil #30
Equivalent [Table 3: Cadder composition ■ ■ ■ ■ ■ Coefficient of dynamic friction: Initial 0.115 0.115 0.
115 0.120 0.1201 After 0.000 cycles 0.105 Q, Llo 0.110
Q, 115 0.11750,000+after cycle 0.085 0.100 0.105 0.
110 0.113 Volumetric wear rate 1.43X 1
0-' 4.67X 10-84.48X 10= 2
．． 19 x 10-'' 1.05 x 10-8 Wet clutch durability tests were conducted for each formulation in Table 1 under the conditions in Table 2, and the results shown in Table 3 were obtained.

From these results, it was found that compared to conventional rubber-based wet friction (formulation ■), the friction material composition of the present invention using highly saturated acrylonitrile butadiene rubber alone or a resin material as a co-curing agent ■、■、■.

It is clear that (2) shows little change over time and little wear.

Effects of the Invention By using the wet friction material composition of the present invention, wet clutches and wet brakes are guaranteed to have stable performance over a long period of time, and can be maintenance-free.

Claims (2)

[Claims] (1) A wet friction material composition characterized in that highly saturated acrylonitrile butadiene rubber is used as a binder for a composite material containing a filler. (2) A wet friction material composition characterized in that highly saturated acrylonitrile butadiene rubber is used as a binder of a composite material containing a filler, and a resin material is blended as a co-curing agent.