JPH059458A - Wet friction material - Google Patents

Abstract

PURPOSE:To provide the title material which contains aramide fiber and has a high coefficient of friction even at a high sliding speed and under a high load. CONSTITUTION:The title material comprises 5-40wt.% binder phase consisting of a thermosetting resin and a filler component contg. aramide fiber covered with a film of the thermosetting resin, and contains pores. The material has a higher porosity, a smaller difference between the coefficient of dynamic friction and that of static friction, and a higher abrasion resistance than those of conventinally available wet friction materials, while maintaining strengths.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction material suitable for so-called wet brake or clutch fading or lining, which is used in the presence of a lubricating oil having a cooling effect.

[0002]

2. Description of the Related Art Generally, wet friction materials can be roughly classified into organic friction materials and inorganic friction materials. Of these, a typical organic friction material is a friction material having a resin and fibers as a matrix.

The fibers contained in the friction material include
Examples include phenolic fiber, glass fiber, carbon fiber, and aramid fiber. Of these, aramid fibers are used in friction materials because they have high strength and high elastic modulus.

A typical friction material containing an aramid fiber and a resin is disclosed in JP-A-59-22137.
4, JP-A-60-206838 and JP-A-63-67436.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Conventional friction materials containing aramid fiber and resin, represented by JP-A-74, JP-A-60-206838 and JP-A-63-67436, differ depending on the manufacturing method. In the case of production, in the step of forming a paper-shaped molded body, the step of cutting this molded body or the step of laminating it in a spiral state after cutting, etc. To fall,
In addition, there is a problem that the manufacturing process is complicated.

Further, when the friction material is molded by a mold or the like, the entangled mesh-shaped aramid fibers are likely to be in the form of fibrils, which causes pills to form, especially during dry mixing, and the mold in the next step. Making it difficult to transfer money to.
Therefore, it is necessary to limit the amount of aramid fiber contained in the friction material, and even if a large amount of aramid fiber is contained, there is a problem that the high strength characteristic of the aramid fiber itself cannot be derived. .

Further, it is preferable that the friction material has a higher porosity in order to improve the coefficient of friction at a high sliding speed, but in the above-mentioned conventional friction material, the effective strength of the aramid fiber can be extracted. Since it is not present, there is a problem that it is difficult to achieve high porosity.

The present invention has solved the above-mentioned problems. Specifically, by containing aramid fibers coated with a resin, high strength and high porosity can be achieved.
An object of the present invention is to provide a wet friction material having a high friction coefficient even under use conditions of high sliding speed and high load.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied how to increase the strength and porosity of a friction material containing a resin and fibers, and firstly, the friction material. Although the aramid fiber is preferable as the fiber to be included in the above, the cut surface of the aramid fiber becomes a hook shape, and during mixing, a pill-like lump is formed by the entanglement of the hook-like portion, and the pill-like lump is rubbed. It was found that the strength of the material was reduced.

Secondly, when the aramid fiber is coated with a resin film, no hook-like formation occurs on the cut surface, and therefore no pill-like lumps occur, and when a friction material is produced using this, the strength is remarkably increased. It has been found that the practical strength can be obtained even if the porosity is increased due to the improvement and the high strength.

The present invention has been completed based on the above-mentioned first and second findings.

That is, the wet friction material of the present invention comprises 5 to
A friction material comprising a filler containing 40% by weight of a thermosetting resin as a binder phase and the remainder containing aramid fibers, wherein the aramid fibers are covered with a film of the thermosetting resin, and the friction material has pores. Are formed.

Specific examples of the thermosetting resin in the present invention include phenol resin, polyimide resin, epoxy resin, furan resin, xylene resin, ketone resin, urea resin, melamine resin, aniline resin, sulfonamide resin, and alkyd. Resin can be mentioned as a typical example.

Of these, the thermosetting resin as the binder phase is preferably a polyimide resin or a phenol resin, and the thermosetting resin as a coating for coating the aramid fiber is, for example, the whole aramid fiber coated with the coating. %, Specifically, about 1% by weight is effective, and this coating is preferably an epoxy resin, especially when the binder phase is composed of a polyimide resin and the coating covering the aramid fiber is composed of an epoxy resin, the strength is Is remarkable, and is preferable.

The shape of the aramid fiber in the present invention varies depending on the use and shape used as the friction material, but the diameter of the aramid fiber is 9 to 15 μm in view of the ease of transfer into the mold during the manufacturing process, particularly the press molding and the strength of the friction material. Length 0.
The content of the aramid fiber is preferably 25% by weight or less, preferably 1 to 10 mm.
% By weight.

The filler in the present invention is specifically,
For example, alumina, silica, mullite, silicon carbide, calcium fluoride, molybdenum disulfide, tungsten disulfide, ceramics such as barium sulfate, natural rubber, NB
R (acrylonitrile / butadiene rubber), SBR (styrene / butadiene rubber), acrylic rubber, urethane rubber, silicone rubber, rubber such as fluorine rubber, carbon,
Inorganic fiber made of glass, metal, ceramics, resin,
Mention may be made of metal or organic fibers, graphite, expanded graphite, amorphous carbon, carbon materials such as coke, metals such as copper, tin, iron, lead, brass or alloys thereof, cashew dust and minerals. .

If the number of pores present in the wet friction material of the present invention is too large, the strength will decrease, and if it is too small, the oil impregnation and elasticity will be poor.
Volume% is preferable, and 30 to 50 volume% is particularly preferable. It is also preferable that the pores are dispersed as uniformly as possible.

In the wet friction material of the present invention, when the binder phase is less than 5% by weight, the filler is relatively increased to more than 95% by weight and the strength is significantly reduced. When it exceeds more than 60%, the filler is relatively 60.
When the content is less than wt%, the elasticity becomes poor, and when friction occurs, the plastic flow of the binder phase increases and the friction coefficient decreases. Therefore, the binder phase in the wet friction material of the present invention is defined as 5 to 40% by weight.

The wet friction material of the present invention can be manufactured by a conventional friction material manufacturing method. In particular, regarding the formation of pores in the present invention, it can be produced by applying a method for producing a porous product such as an oil-impregnated bearing or a filter, and specifically, a thermosetting resin and a filler. It is to add a pore-forming substance that is volatilized during heating and firing to the starting material. Further, the porosity can be controlled by adjusting the amount and type of the pore-forming substance and the volatilization treatment, as in the conventional case.

Examples of the pore-forming substance include stearic acid, sulfanilic acid, sulfamic acid, ammonium sulfamate, naphthol, nitrophenol, paraffin, paraformaldehyde, palmitic acid, phenol and maleic anhydride.

[0021]

In the wet friction material of the present invention, the coating of the thermosetting resin coating the aramid fiber has an intermediary function of firmly binding the aramid fiber and the binder phase of the thermosetting resin together with another filler. It is also possible to combine with.
In particular, in the case of a coating of epoxy resin, since it has a high affinity between the aramid fiber and the coating, it also acts to strengthen the bond between the aramid fiber and the coating. Even if the porosity of the friction material itself is increased by increasing the strength of the material, it is possible to maintain the practical strength.

[0022]

Example 1 Average diameters of aramid fiber, aramid fiber, potassium titanate fiber, glass fiber and carbon fiber coated with an epoxy resin film are 5 to 25 μm,
An average length of 0.1 to 1.0 mm and NBR, barium sulfate, expanded graphite, cashew dust, silica, and a polyimide resin were used and blended as shown in Table 1 (% by weight). After mixing the respective compounded samples in Table 1 with a V-type mixer, the outer diameter was 335 mm, the inner diameter was 283 mm, and the depth was 5 mm.
It was filled in the mold of No. 1 and press-molded. The obtained molded body is heated from room temperature to 250 ° C. and kept at 250 ° C. for 1 hour,
Firing was performed.

The bending strength and the porosity of the products 1 to 5 of the present invention and the comparative products 1 and 2 thus obtained were measured, and the sliding speed was 48 m.
/ Sec and absorbed energy of 10 kgfm / cm ^2, the dynamic friction coefficient, the static friction coefficient and the wear rate were measured during a durability test of 10,000 cycles at a high sliding speed. The results are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, the wet friction material of the present invention has a higher flexural strength in comparison with a comparative friction material containing no aramid fiber, which is not coated with a coating and has a small content, despite its high porosity. Are substantially equal to each other, the difference between the dynamic friction coefficient and the static friction coefficient is small, and the wear resistance is improved.

From this, the wet friction material of the present invention is
It is a useful material that can be put into practical use in a range of applications of conventional friction materials to areas of high load or high sliding speed.

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Claims (5)

[Claims] 1. A friction material comprising a filler containing 5 to 40% by weight of a thermosetting resin as a binder phase and the balance comprising aramid fibers, wherein the aramid fibers are coated with a film of a thermosetting resin, and A wet friction material, wherein pores are formed in the friction material. 2. A wet friction material comprising the aramid fiber in an amount of 1 to 10% by weight based on the total weight. 3. The aramid fiber has a diameter of 9 to 15 μm,
The wet friction material according to claim 1, wherein the wet friction material has a length of 0.2 to 1.0 mm. 4. The binder phase comprises a polyimide resin,
The wet friction material according to claim 1, wherein the coating film of the thermosetting resin is made of an epoxy resin. 5. The wet friction material according to claim 1, wherein the pores are 30 to 50% by volume of the whole.