GB683504A - Improvements in the production of polyurethanes - Google Patents

Abstract

Polymethanes are prepared by forming an acid dispersion of a bis-chloroformate, preferably dissolved in an inert solvent, water and a diamine, and then adding alkali to bring the pH above 7, thereby causing poly condensation of the reactants, the polymer precipitating as a finely divided solid. The initial pH is preferably between 3 and 5 and the final pH preferably above 10. The Specification lists a large number of diamines (including diamines with secondary amine groups) and bis-chloroformates as suitable reactants. The reactants are preferably present in equimolecular proportions but this is not essential for high polymers. Specified solvents for the bischloroformate are benzene, toluene, xylene, chlorinated hydrocarbons, octanes, naphthenes and petroleum fractions. Dispersing agents, a list of which is given, may be used, in particular N-butyl-N-lauroyl-b -amino ethane sodium sulphonate. Suitable acids and alkalis for creating the required pH conditions are also listed. The reaction is preferably performed at low temperatures, i.e. 30 DEG to -20 DEG C., antifreeze agents being used if necessary. Mixtures of diamines and/or bischloroformates may be reacted to give mixed polymethanes. A pigment may be incorporated in the reaction mixture, e.g. titanium dioxide and Franconia Blue. In examples: (1) to (4) and (7) to (9) tetramethylene diamine and 1,4-butane - diol - bis - chloroformate were reacted under various conditions; (5) tetramethylene diamine, ethylene diamine and 1,4-butanediol-bis - chloroformate were co - condensed; (6) ethylene diamine and 1,4-butane-diol-bis-chloroformate were reacted. Several of the polymers were drawn into fibres, the fibres being capable of cold-drawing. Specification 615,884 is referred to.