GB885405A - Improvements in or relating to polyurethane resins - Google Patents

Abstract

Films and coatings on glass or glass fibre/polyester resin laminates are formed from a polyurethane product obtained by reacting (a) a polyurethane adduct derived from the reaction of (1) a water-free hydroxyl-terminated linear-polyester having an acid number of no greater than 5 with (2) an excess of a water-free organic diisocyanate having two reactive NCO groups, with (b) a cross-linking agent consisting of a tetrahydroxy polyol containing a tertiary nitrogen atom, said adduct and said cross-linking agent being combined in such stoichiometric proportions as to produce an approximate 1:1 ratio of hydroxy groups to NCO groups. After adding the cross-linking agent the mixture may be applied to the surface where drying and curing take place. As a primer there may first be applied to the surface a coating of a solution of an amine-hardenable epoxy resin. In examples the polyurethane compositions are prepared in toluene from glycol/adipic acid or glycol/sebacic acid polyesters; diisocyanato-diphenylmethane or tolylene or naphthalene diisocyanates; and N, N, N1, N1-tetrakis (2-hydroxypropylene)-ethylene diamine.ALSO:A process of forming a substantially bubble-free polyurethane product comprises reacting (a) a polyurethane adduct derived from the reaction of (1) a water-free hydroxyl-terminated linear polyester having an acid number of no greater than 5 with (2) an excess of a water-free organic diisocyanate having two reactive NCO groups, with (b) a cross-linking agent consisting of a tertrahydroxy polyol containing a tertiary nitrogen atom, said adduct and said cross-linking agent being combined in such stoichiometric proportions as to produce an approximate 1:1 ratio of hydroxy groups to NCO groups. After adding the cross-linking agent the mixture may be applied to form a film on a mould surface, where it cures rapidly. The amount of NCO groups in the product from reaction (1) is determined by refluxing with excess dibutylamine and back-titrating with hydrochloric acid. In Examples (1) an alkyd of acid no. 4.0 from the reaction of glycol and adipic acid in the presence of aluminium is reacted in toluene with excess tolylene diisocyanate and to the resulting mixture is added N, N, N1, N1-tetrakis (2-hydroxypropyl) ethylene diamine in ethyl acetate. Films of the mixture were dried at room temperature or at 100 DEG C. until cured; (2) a polyester from glycol and sebacic acid is reacted similarly; (3) a product from an adipic acid/glycol polyester, naphthalene diisocyanate and N, N, N1, N1-tetrakis (2-hydroxy-propylene) ethylene diamine, with acetyl chloride as inhibitor, is used to coat a glass fibre/polyester laminate; (4) in a process similar to (3) the adduct is prepared from polyethylene sebacate, p, p1 - diisocyanato - diphenylmethan and toluylene diisocyanate.