Method for producing closed-cell rigid polyurethane foams having low thermal conductivity

A process for the production of a rigid polyurethane foam comprising reacting

• a) a polyol component comprising
• 1) from about 40 to about 80% by weight, based on the total weight of polyol component a), of a polyethylene oxide/propylene oxide polyether based on sucrose or sorbitol having a number average molecular weight of from about 300 to about 800,
• 2) from about 3 to about 40% by weight, based on the total weight of polyol component a), of a polyethylene oxide/polypropylene oxide polyether based on an aromatic amine having a number average molecular weight of from about 300 to about 800,
• 3) from about 3 to about 40% by weight, based on the total weight of polyol component a), of a polyethylene oxide/propylene oxide polyether based on an aliphatic amine having a number average molecular weight of from about 200 to about 800,
• 4) from about 3 to about 40% by weight, based on the total weight of polyol component a), of a linear polyethylene oxide/propylene oxide polyether having a number average molecular weight of from about 500 to about 1500, optionally,
• 5) a compound containing at least two isocyanate-reactive hydrogen atoms having a number average molecular weight of from about 150 to about 12,500 which is not a polyether within 1), 2), 3) or 4),
• 6) a catalyst,
• 7) water,
• 8) an alkane, cycloalkane, hydrochlorofluorocarbon or hydrofluorocarbon foaming agent, and optionally,
• 9) a processing aid and/or additive with
• b) a polyisocyanate or modified polyisocyanate having an NCO content of from about 20 to about 48% by weight.