GB768192A - Process for the production of foamed substances based on isocyanate-modified polyesters by using compounds which split off formaldehyde - Google Patents

Abstract

Polyurethane foams are produced by reacting a polyester and a polyisocyanate in the presence as blowing agent of a formaldehyde generator. Water may be present and also carboxyl groups in the polyester as auxiliary blowing agents and the foaming may be enhanced by heating the polyester. Specified formaldehyde generators are dimethylol thiourea, dimethyl ethylene urea, hexamethylol melamine, o- and p-cresol dialcohol, methylol compounds of carboxylic acid amides, sulphonamides and ketones, paraformaldehyde and N,N1 - dimethylolimidazol - 2 - thione. The residues of the formaldehyde generators become bound into the resin structure. In examples: (1) 80 parts of a polyester from 5 mol. phthalic acid, 1 mol. adipic acid, and 8 mol. hexanetriol, 20 parts of a polyester from 1.5 mol. adipic acid, 1 mol. 1.3 butylene glycol and 1 mol. hexanetriol, 10 parts siliceous chalk, 6 parts dimethlol thiourea and 1 part of an esteramine from adipic acid and diethyl ethanolamine are mixed with heating to 50 DEG C. and the mixture reacted, after cooling, with 45 parts of tolylene diisocyanate to give a hard foam; (2) as in (1) but using 6 parts N,N1-dimethylol - imidazol - 2 - thione as formaldehyde generator; (3) as in (1) but using 6 parts dimethylol-p-cresol; (4) 100 parts of a carboxy polyester from 5 mol. adipic acid, 1 mol. phthalic acid and 8 mol. hexanetriol, 10 parts silica filler, 8 parts dimethylol thiourea and 0.5 parts hexahydrodimethylaniline are mixed with heating to 50 DEG C. and reacted with 50 parts tolylene diisocyanate; (5) as in (4) but with the addition of 1 part water and using 6 parts dimethylol thiourea, 1 part of the esteramine of Example 1 and 60 parts tolylene diisocyanate. In all the examples hard foams were produced.