CS259402B1 - Asbestos-free friction material - Google Patents

Abstract

The solution relates to an asbestos-free friction material consisting of 15 to 35% by weight of glass continuous or staple fibers or yarns, 0.7 to 10% of butyl-diene styrene or butadiene acrylonitrile rubber, 8 to 25% of phenol-formaldehyde resin, 0 to 15% of metal particles and 10 to 73% of fillers, such as graphite, carbon black, barite, metal sulfides and crosslinking agents, wherein these fillers are dispersed in unequal amounts in the rubber and phenotypic, urea or melamine resin. Glass fibers can be partially replaced by fibers of oxidized polyacrylonitrile, carbon fibers, natural or synthetic fibers in an amount of up to 15%.

Description

239402 3

BACKGROUND OF THE INVENTION The present invention relates to asbestos-free friction materials for producing brake linings, clutches and other friction mechanisms.

Until recently, friction materials have been manufactured by various friction-compositing processes of various compositions, the common feature of the vast majority of these materials being the presence of asbestos as the main component used in the form of fibers of different lengths or after pretreatment of fibers into yarns or fabrics or nonwovens.

The main drawback of these types of friction materials is the risk of severe illnesses caused by fine asbestos fibers, such as respiratory disorders and heart disease induced by them, sometimes accompanied by tumors of the lungs or other organs. This risk is manifested in the extraction and processing of asbestos, but also in the manufacture, processing, assembly, handling and operation of the blower materials. Recently, many manufacturers have been trying to replace asbestos fiber with other reinforcing fibers. The simple substitution of asbestos fiber with other natural or synthetic fibers is associated with technological difficulties, because these fiber substitutes significantly differentiate the properties of asbestos in terms of diameter and fiber length, the flexibility, fragility and workability of existing technologies. Significant difficulties are encountered in the manufacture of a molding composition and composite materials reinforced with these substitute fibers, the majority of which are present in the existing crushing, length-reducing, forming closed aggregates that do not penetrate other components of the mixture, these mixtures being further they are difficult to shape the filament memory of these filaments due to their flexibility and rigidity. Thus, it can be said that for most of the established products, the original asbestos friction material technology can be used to process substitute fibers either with great difficulty or is negligible. As a consequence of these technological difficulties, the product values are reduced, resulting in a decrease in mechanical values such as tensile strength, resistance to elevated temperature, wear and cold wear.

Usually, it is not possible to achieve the bulk density of the reinforcing fiber customary for asbestos, which, due to the lower modulus of strength of most of these replacement asbestos fibers, leads to a decrease in the strength values of the friction materials. At the same time, the price of most substitute fibers is higher than the price of asbestos fibers, so that the economic losses resulting from the lower utilization of the reinforcing effect due to processing difficulties increase further.

These disadvantages are eliminated in the asbestos-free friction material, consisting of 15 to 35% by weight of glass continuous or staple fibers, 12 to 30% of binder consisting of 0.7 to 10% butadiene styrene butadiene acrylonitrile rubber and 6 to 25% phenol formaldehyde, urea chimlamine resins, 0 to 15% metal particles and 10 to 73% fillers, such as graphite, sucrose, barite, metal sulfides, mica dust, and crosslinking agents; unequal amounts of rubber in the rubber and the resin used. Glass reinforcing fibers can be replaced by up to 15% by weight of fibers of oxidized polyacrylonitrile, carbon fibers or natural or synthetic fibers. In the asbestos-free friction materials of the previous composition, most of the previously mentioned drawbacks are avoided. Glass fiber has been working for many years without any proven effects on the development of lung fibrosis and the development of tumor diseases. The described material contains a high proportion of reinforcing fibers, up to 40 percent, and in this respect is equal to the usual composition of asbestos material. The tensile strength values of the materials thus obtained are as high as 130 MPa, while the impact strength values are higher than the conventional asbestos compositions.

The appropriate viscosity and adhesion of the two binder components allows good dispersion of a large proportion of binders, some of which have a high specific gravity (barite, coVy, sulfide, and the like) without significant separation efforts, as is the case with a variety of materials and compositions. also for a number of asbestos materials.

As an example of the actual embodiment of the friction material according to the invention, mention may be made of the following:

1500 grams of powdery solids are mixed into 600 grams of aqueous resol, followed by addition of 1500 grams of butadiene acrylonitrile rubber solution in trichlorethylene (12%). The two liquid phases are formed by stirring an emulsion, further 700 g of powdered components are mixed in. This emulsion is impregnated under pressure with a 6-ply 0.85ktex glass silk which, after drying, forms an infinite strand of glass fiber composition 27% butadiene acrylonitrile rubber 5 % phenolic resin 14% brass dust 9% barite 32.5% carbon black 3.5% graphite 4% rubber chemicals 1% antimony sulphide 4% More than 1,800 g of powdered components are dispersed in the resin component; a proportion of up to 400 g is dispersed in the rubber. It forms an annulus preform in the case of coiling and presses the connecting liner from it.

Claims (2)

EXAMPLE 2 Emulsion impregnation according to Example 1 incorporates graphite-filled yarn of bulk glass silk and viscose yarn. After excitation, a strand of composition was obtained in a glass fiber ratio of 20% viscose yarn with graphite 4% butadiene acrylonitrile rubber 5.2% phenolic resin 14.6 ° / o brass dust 9.3% barite 33.8% 3.6 ° / o graphite 4.4% rubber chemicals 1.0% antimony sulphide 4.1 ° / os by similar distribution of powdery components in rubber and resin as in Example 1. Example 3 To 1000 g of butadiene styrene rubber solution in trichlorethylene 1000 g of powdered components are mixed (10 ° / o). The homogeneous solution is mixed with 1000 g of aqueous resol, in which an additional 850 g of fillers are pre-mixed. 400 g of staple glass fibers are mixed into the resulting emulsion. After drying, a butadiene-styrene rubber fiber mass is obtained of 3.3% phenolic resin 16.6% glass fiber 18.3% copper powder 4.9% / o limestone ground 21.1% barite flotated 21.1% graphite 3 , 2% lead sulphide 5.2% alumina 5.6% rubber chemicals 0.7% In this case, the rubber component contains 1000 g of powdered components, whereas only 850 g of fillers are mixed in the resin component. From this mass, the friction linings of the brakes or clutches are produced by pressing. The advantage of this solution is the possibility to change the composition of both liquid phases on a wider scale and thus influence the functional properties of the product. Another advantage is the sustained microheterogeneity of the coating, which positively affects the regenerative effects of the friction material. Due to the beneficial physical-mechanical properties of the thus produced friction materials, by using components, for example thermally insulating fillers, this material can be used to produce high-temperature insulating elements similar to dynamic forces, or other applications. object 1. Asbestos-free friction material, characterized in that it comprises 15 to 35% by weight of glass continuous fibrous fibers 12 to 30% of a binder consisting of 0.7 to 16% by weight of butadiene acrylonitrile or butadiene styrene rubber 6 to 25% of phenol formaldehyde, urea melamine resin. up to 15% of metal particles, such as brass, copper, zinc dust or chips 10 to 73% of fillers, such as graphite, silage, bait, metal sulphides, mica dust, crosslinking particles, these fillers and metal particles being dispersed in unequal amounts of rubber and resin used. 2. The asbestos-free friction material according to claim 1, wherein the reinforcing glass fibers are replaced by carbon fibers, natural fibers or synthetic fibers in a total amount of up to 15% by weight.