Open-cell, cross-linked, elastic polyurethane foams prodn. - from pref. polyetherpolyols in presence of urea derivatives, to reduce creaming time and shrinkage

摘要

The parent patent described the prepn. of polyurethane foams with an open-cell, cross-linked and elastic structure, from polyols, esp. polyetherpolyols, of OH value 700-5000, polyisocyanates, water and catalysts, as well as org. blowing agents, emulsifiers or stabilisers and cross-linking agents comprising crystalline (un)satd. (cyclo)aliphatic, heteroaliphatic or arylaliphatic polyhydroxy cpds. which are not or hardly soluble at room temp. in the polyols to be foamed and which have =3 OH groups and melt at 60-160 degrees C, these polyhydroxy cpds. being used in amt. of 0.1-5 OH equiv. wt. per OH equiv. wt. of the polyol to be foamed. 0.5-50 wt.%, based on the water content of the foaming compsn., of cpds. (I) which degrade the association prodts. of water are now added to the foaming compsn. Creaming time, i.e. the time taken for the reactn. mixt. to become creamy at the onset of CO2 formation, is reduced. Presence of (I) stabilises dispersions of the polyhydroxy crosslinking agents in the polyether polyol, i.e. they do not tend to become viscous after a few days and their storage stability is unlimited.