| abstract |
Polyurethane foams having a smooth and homogeneous surface appearance, showing little or no shrinkage, and consequently requiring little or no calendering, and any calendering required need not be carried out immediately after moulding, are obtained by preparing the foam in the presence of 0.1 - 5 % of an organo silicon compound which is: (1) an organopolysiloxane comprising units of the formulae R2SiO and RSiO1.5 having a R/Si ratio ranging from 1.05 to 1.5 and containing at least 1% by weight of hydroxyl groups bonded to silicon atoms, each symbol R, which may be the same or different, representing a monovalent hydrocarbon radical of 1 to 7 carbon atoms, or (2) a compound of the general formula |