| 摘要 |
Polyurethanes are produced by a method comprising reacting a polyol and an organic polyisocyanate in the presence of a catalyst comprising a secondary imidazole and externally heating the system to accelerate the reaction between hydroxyl and isocyanate groups to form urethane groups. The imidazoles specified are 2-propylimidazole; 2-butylimidazole; 2-benzilimidazole; 2-benzyl-4-methylimidazole; 2-butyl-4-methylimidazole; 2,4,5-trimethylimidazole; 2,4,5 - triethylimidazole; 2,4 - dimethylimidazole; 2 - ethylimidazole; imidazole and 2 - methyltetrahydrobenzimidazole. Polyols specified are hydroxy polyesters, polyether polyols, monomeric polyhydric alcohols, hydroxyalkylated amines or alkylene polyamines and castor oil and its derivatives such as ricinoleic acid esters, ricinoleyl alcohol and condensation products of castor oil with glycols or with diglycollic acid or mixtures thereof. Various polyisocyanates are specified and prepolymers obtained by reacting them with polyols or, their dimers or trimers may also be used. The reaction mixture may contain optional ingredients, e.g. benzene, silicones, stannous octoate and, as a blowing agent, water. The process may be used in the production of adhesives, coatings, mouldings and foamed polyurethanes.ALSO:Wire or panels of plywood or metal may be coated by successively dipping in a solution of 2,4-dimethylimidazole and a silicone in diphenylmethane di-isocyanate and in a prepolymer from castor oil and diphenylmethane di-isocyanate and curing at 80-110 DEG C. in curing ovens which may be infra-red heated. |
