Patent ID: 8895636

Claim:
A process for producing rigid polyurethane foams by reaction of A) at least one polyisocyanate, B) at least one polyetherester polyol obtainable by esterification of b1) 10 to 70 mol % of a dicarboxylic acid composition comprising b11) 100 mol %, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof, b2) 2 to 30 mol % of one or more fatty acids or fatty acid derivatives, b3) 10 to 70 mol % of one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof, b4) 2 to 50 mol % of a polyether polyol having a functionality of greater than 2 and not more than 4, and an OH value in the range of 300 to 1250, prepared by ethoxylating a polyol having a functionality of above 2, all based on the total amount of components b1) to b4), wherein said components b1) to b4) sum to 100 mol %, C) optionally one or more further polyester polyols other than those of component B), D) at least one polyetherol polyol selected from the group consisting of polyoxyethylene polyols, E) optionally one or more flame retardants, F) one or more blowing agents, G) one or more catalysts, and H) optionally one or more further auxiliaries or admixture agents, wherein the mass ratio of total components B) and optionally C) to component D) is at least 7.