Patent ID: 8889756

Claim:
A process for producing a rigid polyurethane foam, the process comprising reacting (a) at least one organic polyisocyanate with (b) at least one compound comprising at least two hydrogen atoms which are reactive an toward isocyanate group in the presence of (c) at least one blowing agent, (d) at least one catalyst and, (e) optionally, at least one selected from a group consisting of an auxiliary and an additive, wherein (b) comprises a mixture, having an average hydroxyl number of from 400 to 550 mg KOH/g, and comprising: from 20 to 70 parts by weight of (b1) at least one high-functionality polyether alcohol, prepared from hydroxyl-comprising high-functionality starter molecules, and having a functionality of from 3.7 to 5.2 and a hydroxyl number of from 370 to 500 mg KOH/g; from 5 to 30 parts by weight of (b2) at least one polyether alcohol based on at least one aromatic amine and having functionalities of from 3 to 4 and a hydroxyl number of from 260 to 500 mg KOH/g; from 5 to 20 parts by weight of (b3) at least one OH-comprising fatty acid ester; and from 1 to 20 parts by weight of (b4) at least one selected from the group consisting of a low molecular weight chain extender and a crosslinker, having a functionality of from 2 to 3 and a molecular weight Mw of <400 g/mol; and where (b1) and (b2) are the only types of polyether alcohols used in said process.