GB654669A - Improvements in or relating to adhesives for securing non-metallic friction materialto the metallic backings of friction elements - Google Patents

Abstract

Non-metallic friction facings are secured to metallic backings or brake shoes by a dry, flexible film containing, in cured condition, 100 parts by weight of a butadiene-acrylonitrile type copolymer and 75-500 parts of a phenolic resin, the copolymer containing 10-75 per cent of nitrile and the remainder butadiene. Instead of butadiene, derivatives such as isoprene, 1 - methyl - 1,3 - butadiene, 2,3 - dimethyl butadiene and chloroprene, may be used. Suitable nitriles are acrylonitrile, methacrylonitrile, ethacrylonitrile, propyl- and chloro-acrylonitriles. The copolymers are preferably those having a high sol content. Drying of the copolymers before milling is preferably avoided. For the phenolic resin specified phenols are phenol, o-, m- and p-cresols, xylenols, resorcinol, naphthols, o-ethyl phenol, carvacrol and salicylic acid. Suitable aldehydes are formaldehyde, acetaldehyde, propionaldehyde and benzaldehyde. The resins may be modified by oils and alkyd resins. If hexamethylene tetramine is incorporated, the resin should be heat-treated, but not beyond the fusible stage, before milling. Compounding may be effected on any mill with the addition of curing agents, e.g. sulphur, preferably together with accelerators such as benzothiazyl disulphide, thiuram polysulphides, mercaptothiazoles, guanidines, aldehyde-amines, zinc oxide and litharge, for the copolymer and hexamethylene tetramine for the phenolic resin. The composition may be calendered or cast from solution into films which are sandwiched between the friction facing and the backing and cured at a temperature between about 325 DEG and 400 DEG F. Specification 519,730 is referred to.