CS216920B2 - Friction material - Google Patents

Abstract

The invention concerns a composition for a friction material, e.g. for a brake lining or clutch facing, of the type containing a fibrous reinforcement, a binder and various additives. The friction material contains no asbestos, but has properties comparable with asbestos-based materials. The composition contains a thermoset binder, which may be based on a phenol-formaldehyde resin, or a heat and chemical resistant rubber, the binder making up 15 to 40% by volume of the material. The fibrous reinforcement is a mixture of an inorganic fibre selected from metal fibres, e.g. steel glass fibre, mineral wools manufactured from slags or naturally occuring rocks such as basalt, silica fibres and ceramic fibres of the alumino silicate type; with at least one organic fibrous material such as wood pulp, jute, sisal, cotton. 70 to 4% by volume of the material consists of the fibrous reinforcement, preferably 50 to 10% by volume. The inorganic fibrous material is the main reinforcement of the friction material, the organic fibrous material providing integrity and strength during manufacture.

Description

The invention relates to a friction material, in particular for brake linings, based on a thermosetting binder, fiber reinforcement, fillers and additives.

Fiber reinforcement usually consists of asbestos. Various proposals have already been made regarding the substitution of asbestos with other materials, but without a perfect result due to the austere working temperatures and pressures that the materials must withstand during their re-action without failure or deterioration of the frictional properties.

According to the invention, the thermosetting binder constitutes 15 to 40% by volume of the material and consists of a phenol-formaldehyde resin or a rubber resistant to heat and chemicals, in particular nitrile rubber, or a mixture of at least half of the resin. % of the material and consists of organic fibrous material and inorganic fibrous material selected from metal fibers, glass fibers, slag wool made from slag or naturally occurring stones, quartz fibers and aluminosilicate type ceramic fibers, the amount of organic fibrous material being 3 to 20% by volume of friction material and the amount of inorganic fibrous material is in the range of 40 to 30% by volume of friction material, filler and additive consisting of organic particulate filler in traces up to 34.5% by volume and inorganic particulate 13 to 33.5% by volume of filler and friction and wear modifiers.

If the inorganic fibrous material is in the form of metal fibers, for example steel fibers, the amount thereof will preferably be in the lower part of the preferred range, for example 3 to 15 vol%, while the inorganic fibrous material. in the form of glass fibers, the amount thereof will preferably be in the upper part of the preferred range, for example 9 to 40 vol%.

The organic fibrous material consists of short sections of fibers and may consist of cellulosic fibers from sources such as pulp, jute, sisal or short cotton from the second gin. The function of the fiber material is to impart a green strength to the material in production, and for this purpose the organic fibers must be loose fibers when using natural materials. Therefore, pulp is a suitable organic fiber material, while wood flour is not, since wood fibers are tightly held by resin and wood flour acts only as a filler.

The inorganic fibrous material is also in the form of short fiber sections and forms the head reinforcement of the friction material. Where to use it. As inorganic reinforcement of slag wool, it is preferred that it contains a minimum amount of small. non-lime mineral agglomerates, commonly referred to as grains. When large quantities of glass fibers in a particular composition are to be used, it is preferable to use ground glass fibers or chopped sliver, i.e. glass in the form of continuous bundles of fine glass fibers, bound together by coatings of sizes commonly used by the glass fiber industry and then chopped to short strands composed of a large number of fine parallel fibers. The preferred length of the chopped strand is 3 to 13 mm. However, shorter fibers may be used if desired. It is also desirable to use glasses whose individual fibers are coated with a binder applied in the manufacturing process to improve the bond between the glass and the heat curable binder.

The preferred metal filament is a steel filament, which may be of soft steel, and is conveniently in the form of short sections of fine steel filaments, for example having a diameter of the order of 0.125 mm and a length of 1 to 5 mm.

In the friction material, the binder, preferably an organic binder, for example a thermosetting resin such as phenol-formaldehyde resin or natural or synthetic rubber, is resistant to heat and chemicals such as nitrile rubber.

Other fillers and additives in the friction material can be taken from a variety of classes of such materials, and the nature of the amount of each such material is selected so as not to achieve the desired combination of cost and properties. If necessary 'may be used or added inorganic particulate fillers such as barytes, whiting, and tripoli, reinforcing fillers such as ¹ mica, friction modifiers and · wear including lubricants such as graphite or molybdenum disulphide, antimony trisulphide, metals such as · copper, zinc, brass or · Aluminum in the form of wires, turning chips or particles. Friction compounds or particles composed of cured and ground thermosetting resins or rubbers may also be added.

Compositions of the invention having a total fiber content of less than about 40 vol% are particularly suitable for use in a method of producing friction materials, which consists in

(a) thoroughly mix all the components of the composition with each other, wherein the uncured liquid resin binder serves to bond the composite material together, or an adhesive uncured rubber binder serves the same purpose;

b) the composition is formed into a sheet,

(c) the sheet shall be shaped if necessary (as in the production of curved drum brake linings); and

d) the material is cured.

In this method, the sheet is required to have adequate strength before drying, and it has been found by the invention that the required strength is provided by organic fibers mixed with inorganic fibers. The process is particularly suitable for producing brake linings.

In another embodiment, particularly for compositions having a total fiber content of above about 30 vol%, it is desirable to produce a friction material according to the invention by a slurry technique wherein the fibers, binder and other components are dispersed in water by means of a beater. · To make a slurry. " The slurry is then shaped into a sheet by depositing on a wire mesh or felt and the water is sucked off. The sheets are then dried, cut into desired shapes and cured under heat and pressure. This technique is particularly suitable for the production of clutch linings.

The invention will now be explained in more detail with reference to several exemplary embodiments.

Examples 1 to 3

Annular clutch liners with an outside diameter of 152.4 mm and an inside diameter of 127 millimeters were made by the above technique using slurries of friction materials of the compositions shown in Table I, all amounts being by volume.

TABLE I Example No. 1.2 3 Phenol formaldehyde binder

resin 25 26 26 fiber materials glass fibers (3mm to 6mm) 40 25 - Aluminosilicate thread] * - - 30 cellulose (wood pulp) 20 May 10 5 Fillers etc. friction fold - 17 17 float chalk 12 14 14 antimony sulphide - 5 5 brass 3 3 3

* The flour is commercially available from morganite and has a fiber length of 6 mm when used in the example.

The linings thus produced had a tear strength of 10,000-12,000 rpm at ambient temperature and 7,000-7,500 rpm at 200 ^° C.

The formed clutch linings showed less wear values and higher coefficients of friction than similar materials containing asbestos when running against a cast iron support surface on a small friction and wear test machine.

The coefficients of friction, as determined, were in the range of 0.3 to 0.4 in a 203.2 mm x 146.05 mm coil spring connector against a cast iron flywheel and a pressure plate.

Example 4

The annular clutch lining with an outside diameter of 203.2 mm was produced by a technique using a slurry of the above composition of the composition given in Table II.

TABLE II Bulk component parts of latex nitrile rubber20 phenol-formaldehyde resin20 ground glass fibers (190 μ nominal length and 9 to 13 μ diameter) 30 pulp10 kaolin10 sulfur1 bentonite2 ground crumb rubber6

The clutch linings thus produced had a tear strength of 11,000 to 11,500 rpm at ambient temperature and 6,750 to 8,000 rpm at 200 ° C (tear strength was measured by rotating the clutch lining around its axis at increasing speed until centrifugal force) and the transverse tensile strength was 75,842 to 82,737 kN / m 2, the transverse tensile strength was measured by placing the lining pattern on two supports spaced apart by

25.4 m and then the load required between the supports was measured; to crush the lining.

Example 5

An annular clutch lining with an outer diameter of 152.4 mm was produced by a technique using a slurry of a material of the composition given in Table III.

TABLE III

Example. 6

The annular clutch lining with an outside diameter of 203.2 mm was manufactured using a slurry of a material of the composition given in Table IV.

TABLE IV Bulk component parts phenol-formaldehyde resin26 ground glass fiber (nominal length 190 μ, diameter · 9 to 12 μ] 30 wood pulp10 friction-component17 antimony sulfide2 brass3 float chalk9 sulfur3

The linings thus formed had a tear strength of 11,000 to 11,500 rpm at ambient temperature and 9,250 to 9,750 rpm at 200 ° C and a transverse breaking strength of 82,737 kN / m 2.

The foregoing examples all illustrate the use of friction materials of the invention in clutch linings. The following examples illustrate the use of these materials for brake linings.

Examples 7 to 16

Compositions according to the compositions given in Tables V and VI were blended and rolled into a sheet shape, formed into a curved shape of a suitable brake lining, cured, thereby obtaining brake lining samples. Curing was carried out in an oven at 238 ° C for a period of 90 minutes.

In any case, the properties of the material in terms of wear and tear were determined on a system of 354 mm x 69.85 mm hydraulic block layers on a dynamometer, and were found to be comparable to conventional brake linings. containing saline.

In the tables below, all quantities are given in parts by volume.

volumetric

component parts nitrile rubber latex 3.25 phenol formaldehyde resin 15 Dec glass fiber strands chopped to a length of 3 mm 304 -texj 25 wood pulp 10 float chalk 21.25 brass 3

TABLE In Example 7 8 9 10 11, a binder liquid phenolic resin

oil modified acacia walnut 25 25 27 Mar: 24 27 Mar: uncured nitrile rubber powder 0 0 0 12 0 dry phenolic resin 5 10 4 0 7 inorganic fiber steel (stapl 3 and 6 mm) 0 0 3 3 0 glass (stapl 3 to 13 mm) 9 0 0 0 3 organic jute fiber 9 9 9 9 9 9 cotton 0 6 0 0 0 wood flour fillers 5 5 5- 5 5 float chalk 20 May 20 May 20 May 20 May 20 May crumb rubber (hardened) 2.5 5 5 5 5 graphite 2.5 0 2.5 0 2 pulverized cured resin particles and dust 22nd 20 May 24.5 22nd 22nd coefficient of friction at 48 km / h and 70 ° C 0.37 0.36 0.39 0.36 0.37

TABLE VI

example no. 12 13 14 15 Dec 16 binder liquid phenolic resin modified with oil and gum nut 23.5 25.5 23.5 25 15 Dec uncured nitrile rubber powder 0 0 4 0 15 Dec dry phenolic resin 9.0 0 0 0 0 inorganic fiber steel (stapl 3 to 6 mm) 8.5 8.5 8.5 13.5 0 glass (stapl 3 to 13 mm) 0 0 0 0 25 organic fiber jute 11.5 11.5 11.5 4,5 5 fillers float chalk 19 Dec 26 24 19 Dec 14 crumb rubber (hardened) 5 5 5 4,5 3 graphite 2.5 2.5 2.5 14.5 10 pulverized cured resin particles and dust 21 21 21 19 Dec 13 coefficient of friction at 48 km / h and 70 ° C 0.40 0.39 0.42 0.43 0.32

Subject

Claims (6)

A friction material, in particular for brake linings, n, and a base of a thermosetting binder, fiber reinforcement, fillers and additives, characterized in that the thermosetting binder constitutes 15 to 40% by volume of the material and consists of phenol-formaldehyde resin or rubber resistant to abrasion heat and chemicals, in particular nitrile rubber, or a mixture of at least half that of resin, the fiber reinforcement constituting 10 to 60% by volume of the material and consisting of an organic fibrous material and an inorganic fibrous material selected from metal fibers, glass fiber, slag wool made from slag or naturally occurring stones, quartz fibers and aluminosilicate type ceramic fibers, the amount of organic fibrous material constituting 3 to 20% vol friction material and the amount of inorganic fibrous material in the range 40 to 30% vol. % of the filler material, filler and additive consist of an organic particulate filler of up to 34.5% by volume and an inorganic particulate filler and friction and wear modifiers of 13 to 33.5% by volume. 2. The friction material of claim 1 wherein the fiber reinforcement comprises a mixture of at least one inorganic fiber material with at least one organic material. 3. Friction material according to claim 2, characterized in that the inorganic fiber material is in the form of steel fibers in the range of 3 to 15% by volume of the friction material. 4. The friction material of claim 2 wherein the inorganic fibrous material is pulp, jute, sisal, or cotton. 5. The friction material of claim 1 wherein the filler is at least one inorganic particulate filler. 6. The friction material of claim 1 wherein the friction or wear modifier is graphite, molybdenum disulfide, antimony sulfide, copper, zinc, brass or lead.