KR910000052B1 - Composition of friction material - Google Patents

Abstract

The friction material composition consists of 3-50 wt.% paraoriented aramid staple fiber, 10-40 wt.% resin as binding agent, and 10-87 wt.% filler, where the fiber and binder are mixed in the volume ratio of 1:1.5 to 1:5. The above resin is chosen from one of phenolformaldehyde, melaine-formaldehyde, epoxy, urea- formaldehyde, and cross-linked alkali resins. The filler is composed of more than one selected from aluminum oxide, aluminum, dolomite, barium sulfate, marble white, clay, talc, mica, sulfur, etc., and at least one solid lubricating agent chosen from graphite, carbon, coal, bitumen, molybdenum disulfide, and boron nitride. The material is useful for lining brake shoes and clutch plates.

Description

Friction material composition

The present invention relates to a friction material composition, and more particularly, by using para-oriented aramid short fibers instead of asbestos as a main material, there is a health and pollution advantage as well as a change in friction coefficient with temperature when used as a friction material. The present invention relates to a friction material composition having low wear resistance, excellent wear resistance, and good mechanical strength and durability.

Generally, brakes and clutches used in automobiles, trucks, buses, and similar power machines such as agricultural machines, industrial vehicles, and industrial machines use friction materials having excellent wear resistance as a rotating member. This inexpensive asbestos was used to produce friction materials excellent in wear durability, friction and strength. For example, asbestos is about 50 to 60% by weight based on the entire mixture of the friction material composition, and other components include a binder, a filler and a lubricant, and are mixed by using a Patterson-Kelly twin shell mixer, which is heated and compressed. After molding, heat treatment and polishing were used to prepare a friction material and attach it to a brake shoe.

However, asbestos, which is used as a main material when manufacturing friction materials by such a conventional method, poses a serious health threat to workers who directly deal with it. When asbestos fibers are inhaled, dust accumulates in the lungs. Not only does it cause lung disease called "Asbestosis" that destroys lung tissue, but there is a risk of causing lung cancer called "Mesotheliona" if inhaled for a long time.

In addition, when a brake of an automobile or the like manufactured using a friction material containing asbestos fibers is operated for a long time, the friction material degrades friction performance at high temperature and is easily worn, thereby causing the health of asbestos fibers in the air. Emissions can also be a source of environmental pollution that pollutes the air.

Therefore, in recent years, studies are actively being conducted to replace asbestos fibers which threaten such strong health, and in response to this, some other fibers are already used as substitutes instead of asbestos fibers.

Accordingly, the present invention replaces para-oriented aramid short fibers instead of asbestos as the main material of the friction material in order to solve the problems of the friction material caused by the use of asbestos. The purpose of the present invention is to provide a new friction material composition that is excellent in performance and does not cause health threats and air pollution problems.

Hereinafter, the present invention will be described in detail.

In the friction material composition, 3 to 50% by weight of para-oriented aramid short fibers and 10 to 40% by weight of a thermosetting resin as a binder and 10 to 87% by weight of a filler are mixed, and thus, para-oriented aramid short fibers and a binder. Is characterized in that the mixture is 1: 1.5 to 1: 5 by weight.

Hereinafter, the present invention will be described in more detail.

The friction material composition according to the present invention is composed of a mixture of para-oriented aramid short fibers, a binder resin, and a filler made of organic and inorganic materials, the para-oriented aramid is an organic polymer, the structural formula

The intrinsic viscosity of the short fiber itself has 1.0 to 8.0. There are two kinds of para-oriented aramid short fibers manufacturing process. First, polymer obtained by condensation polymerization of monomer in solution is dissolved in solution, and then wet spinning to obtain long filament. There is a method of cutting to a certain length to obtain a staple, and grinding the staple to obtain para-oriented aramid short fibers in pulp. Second, after condensation polymerization of each monomer in a solution through a unit There is a method of obtaining staple or pulp type short fibers. The second method is well represented in "Method for producing short fibers of aromatic polyamide" known from Korean Patent Publication No. 84-726.

As described above, the fiber prepared according to the method for preparing para-oriented aramid short fibers may have an intrinsic viscosity of 1.0 to 8.0. The intrinsic viscosity (I. V Inberent Biscosity) is measured as follows. Can be done by expression.

Where? Rel is the relative viscosity and C represents the concentration of 0.5% in 100 ml of solvent expressed in g / l.

Where? Rel is the flow time of dilution solution of the polymer divided by the flow time of the pure solvent in the capillary viscometer, and C is the concentration of the dilution solution used to measure? Rel. And the flow time is measured at 30 degreeC using concentrated sulfuric acid (97%) as a solvent.

Intrinsic viscosity (I. V.) indicates the degree of polymerization of para-oriented aramid short fibers. In order to obtain high strength para-oriented aramid short fibers, high polymerization degree of para-oriented aramid short fibers must be obtained.

The para-oriented aramid short fibers thus obtained have a thickness of 0.1 to 10 µm, a length of 0.5 to 20 mm, and an average density of about 1.4 g / cm 3.

Meanwhile, the para-oriented aramid short fibers refer to staple type short fibers and pulp type short fibers, as also shown in the above manufacturing process.

Using para-oriented aramid short fibers as in the present invention can not only sufficiently prevent the occurrence of health diseases when using conventional asbestos fibers, but also prevent air pollution, and in particular, glass fibers and carbon fibers can be used. As a problem pointed out as a problem, when the fine glass fiber and carbon fiber exposed to the air during work are penetrated into the skin by workers, it can prevent the problem of suffering, and even when applied as a friction material Friction and wear resistance, strength, durability and thermal stability is very excellent.

As described above, para-oriented aramid short fibers show performance as a bond reinforcing material and abrasion resistant material in the composition of the friction material, and may be used in a mixture of about 3 to 50% in the mixture of the total friction material composition. What is necessary is just to mix by 40 weight%. At this time, the mixing ratio of the para-oriented aramid short fibers and the resin is 1: 1.5 to 1: 5 by weight ratio is particularly advantageous to improve the strength, durability and friction performance of the friction material. If the amount of the mixed resin is larger than the above, it is difficult to make the composition fair and the color fading phenomenon occurs.

On the other hand, the resin used in the present invention is suitable for thermosetting resin that can withstand high temperature of 500 ℃ sufficiently, for example, phenol formaldehyde resin, melamine formaldehyde resin, epoxy resin, urea formaldehyde resin and crosslinked alkali Resin is suitable, and among them, phenol formaldehyde resin has excellent performance and is very simple in terms of manufacturing process.

Further, in the present invention, the filler included in the friction material composition is composed of a mixture of organic and inorganic fillers, and the organic or inorganic fillers include aluminum oxide, brass chips, aluminum chips, wollastonite, dolomite, barium sulfate, maable white ( marble white), barite, clay, talc, rubber, cashew dust, mica, sulfur and other common fillers and solid lubricants such as graphite, carbon, coal, bituminous coal, molybdenum disulfide, boron nitride, etc. When used, at least two or more of the general fillers and at least one solid lubricant should be used in combination.

At this time, the filler is an inorganic filler is mixed 30 to 90% by weight of the organic filler 5 to 40% by weight of the organic filler, 1 to 30% by weight of the solid lubricant.

At this time, when the inorganic filler is added at 30% by weight or less of the total filler, the coefficient of friction of the final friction material is lowered, and when 90% by weight or more is added, the mechanical strength is lowered.

In the above fillers, graphite, carbon, coal, bituminous coal, molybdenum disulfide, boron nitride, and the like are particularly preferred to be blended into the friction material composition as a solid lubricant. That is, the compounding of the solid lubricant removes the discoloration of the friction material. At least one or more materials are used depending on the use of the friction material. The filling amount may be selected and used within the range of about 1 to 30% by weight based on the filler. If the amount of the solid lubricant is less than 1% by weight, the effect is almost insignificant. On the other hand, if it is added more than 30% by weight, it is finally manufactured and the friction coefficient of the friction material is lowered. Therefore, it is used as the solid lubricant in the filling mixture. It is preferable to use the above materials within an appropriate range according to the present invention.

When the filler is added to the friction material composition, the filler is preferably about 10 to 87% by weight based on the total mixture. In this case, the particle size (diameter) of the filling mixture is preferably 500 μm or less. Preferably it is 100 micrometers or less, More preferably, it is good to use 50 micrometers or less.

Cashew dust, on the other hand, is a cashew-based friction material that controls friction and abrasion performance. Brass chips are generally 3 mm long and have an average particle thickness of 0.4 mm. It is good to do this, which gives the friction material additional wear performance. Coal is a pulverized bituminous coal and gives the necessary friction performance at 100 ~ 200 ℃, Maable white has a calcium carbonate composition, 325 mesh, that is, the average particle size is preferably about 43㎛, as wollastonite It is recommended to use an average particle size of 325 mesh, which serves to give the friction material proper friction and wear performance.

Such a method for producing a friction material using the friction material composition according to the present invention is carried out by a known method, that is, thermo-setting resins such as para-oriented aramid short fibers and phenol resins, epoxy resins, melamine resins urea resins, inorganic and inorganic Filler and solid lubricant, and if necessary a small amount of metal is uniformly mixed and then pseudo-molded, and put into a predetermined mold to 130 ~ 250 ℃, preferably at a pressure of 50kg / ㎠ or more, preferably 100kg / ㎠ or more Next, the molding is performed at a molding temperature of 150 to 200 ° C. After molding, the sample is taken out of the mold and heat-treated for the purpose of completing the reaction of the thermosetting resin.

As a result, the friction material obtained by using the composition of the present invention has a small change in the friction coefficient with temperature, excellent wear resistance, and has better mechanical strength, durability, and strength than the conventional asbestos fiber friction material. It is very useful for lining, clutch facing, disc pad, etc., and it is effective to prevent health threats and air pollution problems that occurred during the manufacture of friction materials.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

After mixing the sample well in a henshell mixer (henshell mixer), about 150g of the sample is temporarily molded for 15 seconds at a pressure of 70kg / ㎠ at room temperature to have a constant shape. Then, the thermocompressor was thermoformed at 150 kg / cm 2 again for 4 minutes at a temperature of 170 ° C., and heat-treated at 170 ° C. for 6 hours. This will give you the diskpad you want. Grinding this pad and measuring the performance of the friction material according to Ks R 4024 standard are shown in Table 1 below.

TABLE 1

Example 2

The friction material composition as described above is uniformly mixed and preformed at a pressure of 70 kg / cm 2 for 15 seconds at room temperature, and then compression molded again at a temperature of 170 ° C. for 5 minutes in a heat compressor. And the heat treatment at 170 ℃ for 5 hours to complete the curing reaction of the phenol-formaldehyde resin and cold polishing in air performance of the friction material is shown in Table 2 (measured according to the method of Ks R 4024).

TABLE 2

[Comparative Example]

After uniformly mixing the composition of the friction material as described above by molding, heat treatment, polishing by a known method to measure the friction performance as shown in Table 3.

TABLE 3

Example 3

The sample having the composition described above is uniformly mixed in a powerful mixer, and then temporarily molded at a pressure of 70 kg / cm 2 at a temperature of 80 ° C. Then, the preformed mixture was put into a mold and compression molded for 7 minutes at a temperature of 160 ° C. and a pressure of 150 kg / cm 2 in a thermal compressor, and then heat-treated at 200 ° C. for 5 hours in a heat treatment tank to form a phenol-formaldehyde resin. The performance of the friction material obtained by perfecting the curing reaction, slowly cooling in the air and then polishing is shown in Table 4 (measured according to the method of Ks R 4024).

TABLE 4

Claims (4)

In the friction material composition, 3 to 50% by weight of the para-oriented aramid short fibers, 10 to 40% by weight of the binder resin and 10 to 87% by weight of the filler are mixed, wherein the para-oriented aramid short fibers and the binder is 1: Friction material composition, characterized in that the mixture in a weight ratio of 1.5 to 1: 5. The composition of claim 1, wherein the resin is selected from phenol-formaldehyde resins, melamine formaldehyde resins, epoxy resins, urea-formaldehyde resins and crosslinked alkali resins. The composition of claim 1, wherein the filler is a mixture of an organic filler and an inorganic filler. 4. The filler according to claim 3, wherein the filler comprises at least one organic filler selected from aluminum oxide, brass chips, aluminum, wollastonite, dolomite, barium sulfate, marbling white, barite, clay, talc, rubber, cashew dust, mica and sulfur and at least At least one inorganic filler and at least one solid lubricant selected from graphite, carbon, coal, bituminous coal, molybdenum disulfide or boron nitride.