GB1035903A - Polyurethane foams - Google Patents

Abstract

A process for the production of polyurethane foams comprising forming a mixture of a poly-alkylene glycol, a blowing agent, a polyisocyanate and a catalyst, the latter encapsulated in micro-capsules, and subsequently initiating the foam-forming reaction by rupturing the micro-capsules so that the catalyst comes into contact with the reactants. The catalyst may consist of two or more ingredients encapsulated singly or in unreactive combinations. An activator and/or a co-catalyst may be incorporated in the catalyst, e.g. stannous octoate or another oil-soluble salt of tin may be used with an amine catalyst, e.g. triethylene diamine. The capsules may be ruptured by submitting to ultrasonic waves or by dielectric heating, e.g. by use of a medium of low melting point, e.g. 30-40 DEG C. and high dielectric constant. In an example an aqueous solution of triethylene diamine was encapsulated in a chlorinated hydrocarbon capsule of 1 to 2a . Stannous octaoate was also encapsulated and 3.5 parts of the amine solution and 0.3 parts of the tin compound were added to 100 parts of polypropylene glycol and 40 parts of tolylene diisocyanate containing 0.7 parts of a silicon oil, and subjected to dielectric heating.