Injection moulding of polyurethane elastomers - using polyol, chain extender, polyisocyanate prepolymer and catalyst

摘要

Injection moulding of liquid mixts. forming polyurethane elastomers is effected by (a) combining a soln. or dispersion contg. a polyether or polyester diol with terminal OH groups, a bifunctional org. chain extender chosen from diamines, amino alcohols, and glycols with a greater reactivity than alkylene glycols or sterically hindered amines, e.g. ethylenediamine and thiodiglycol, and a catalyst, with a prepolymer obtained by reacting a polyether or polyester diol with terminal OH groups, and an org. diisocyanate; this prepolymer having a free CNO:OH ratio of more than 2:1, and the polyurethane components being mixed at a rate sufficient to give a homogeneous liquid mixt. without appreciable polymsn. before injecting into the mould, (b) injecting the mixt. into the mould, (c) allowing the mixt. to polymerise to form a polyurethane elastomer moulding, and (d) demoulding the finished pdt. Gives high quality mouldings.