| abstract |
The invention relates to a process for the preparation of rigid polyurethane or polyisocyanurate foams by reacting an isocyanate with a polyol in the presence of urethane and / or isocyanurate catalysts, water, optionally further blowing agents, optionally flame retardants and optionally further additives (such as fillers, Emulsifiers, purely organic stabilizers and surfactants, viscosity depressants, dyes, antioxidants, UV stabilizers, antistatic agents) using foam stabilizers of the general formula (I) R-Si (CH 3 ) 2 -O - (--Si (CH 3 ) 2 - O-] n - [- Si (CH3) RO] m -Si (CH 3) 2 -R, wherein R = - (CH 2) x -O- (CH 2 -CHR'-O) y -R means. |