GB644447A - Improvements relating to the manufacture of mouldable friction compounds - Google Patents

Abstract

A friction element for brakes and clutches is made by mixing a frictional filler with a 65-80 per cent solution of an oil-modified thermosetting resin in benzol, alcohol or toluol and with a 12-20 per cent solution of synthetic rubber in a petroleum solvent, extruding the plastic mixture, evaporating the solvents at a temperature too low to set the resin, and moulding the shaped mixture under heat and pressure. The ratio of thermosetting resin to rubber is between 7 : 1 and 1 : 1. Synthetic rubbers mentioned are copolymers of butadiene and styrene or of isoprene and isobutylene. The thermosetting resin mentioned is a phenolformaldehyde resin modified with blown linseed, castor, chinawood, or oiticica oil or mixtures thereof. Three compositions are described. In addition to the two binders they include short asbestos fibre, graphite or a friction powder from cashew liquid, barytes, sulphur, zinc oxide and hexamethylene tetramine, and, in one case, Gilsonite. Preferably the dry ingredients are mixed first, and the synthetic rubber cement added in a dough mixer, followed by the resin solution, or the rubber cement and resin solution are mixed and the dry ingredients added. The product is extruded, air-dried and solvents evaporated in an oven at relatively low temperatures, e.g. 150 DEG F. It is then compacted between unheated press platens or cold rolls, and then moulded with heat and pressure insufficient for complete curing. For brake linings, the partially cured slabs are cut, ground, warmed to make them flexible, and clamped in baking forms which retain them in the desired shape during final curing.