Patent ID: 8293807

Claim:
A process for producing rigid polyurethane foams, comprising: reacting a) at least one polyisocyanate with b) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence of c) blowing agents and a foam stabilizer, wherein the reaction is conducted in the presence of a catalyst, the compounds having at least two hydrogens which are reactive toward isocyanate groups, comprise: 10 to 25% by weight of at least one graft polyol b1); 25 to 65% by weight of a sucrose-initiated polyether alcohol b2); and 10 to 40% by weight of a polyether alcohol b3) obtained by alkoxylation of a vicinal toluene diamine or ethylene diamine; wherein the at least one graft polyol b1), comprises: acrylonitrile and styrene in a weight ratio of acrylonitrile:styrene of from greater than 1:1 to 4:1; a carrier polyether alcohol b1i) having: a functionality of from 2 to 4, a hydroxyl number in the range from 100 to 250 mg KOH/g, and a polyether chain comprising propylene oxide and up to 20% by weight, based on the polyether alcohol b1i), of ethylene oxide, and at least one compound b1ii) which has at least one olefinic double bond and is miscible with the carrier polyether alcohol b1i).