GB754732A - Improvements in elastomeric polymeric polyurethane compositions - Google Patents

Abstract

An elastomeric polymer obtained by reacting a di-isocyanate-modified polyester or polyesteramide with a cross-linking agent, e.g. water capable of introducing urea bridging groups into the structure is filled with a fibrous material in the form of flock. It is stated that the flock may react with the polymer. Preferred proportions are from 2-40 parts of flock per 100 parts by weight of polymer. The flock may be rayon, cotton, nylon, glass or wool flock or flock from purified wood cellulose. The flock considerably increases the tear resistance of the rubber particularly in proportions of 10-30 per cent. The flock may be incorporated by milling with the uncured gum or by mixing with the liquid modified polymer before the reaction with water or other compound to introduce urea groups. In examples the tensile and tear strengths and elongations of compositions based on a glycoladipic acid polyester modified with p,p1-diphenylmethane di-isocyanate and cross-linked with water and containing from 0 to 50 per cent of cotton, rayon and nylon flocks are compared with those of natural rubber similarly filled. A further example is given using glass flock. Graphs are also given showing the relationship between physical properties and flock content for the polyurethane rubber and natural rubber. The products are particularly useful for applications such as sheeting, unsupported or on fabric backings, which is to be stitched.ALSO:The Specification discloses a rubber composition consisting of natural rubber 100 parts, stearic acid 1 part, zinc oxide 5 parts, mercaptobenzothiazole 1 part, sulphur 3 parts, and from 0 to 50 parts of cotton, rayon or nylon flock, all parts by weight. The tensile strength, tear strength and elongation of the cured products are compared with those for polyurethane rubbers filled with flock. Other flocks referred to are glass, wool and alpha cellulose flock from purified wood cellulose.