Patent ID: 7943679

Claim:
A process for producing a rigid polyurethane foam having a molded density of 33 to 38 kg/m 3 and Lambda (10° C.) of less than 21 mW/m.K and a ratio of molded foam density (kg/m 3 ) to Lambda (10° C.) (mW/m.K), measured 24 hours after foam production, from 1.65 to 2.15, obtained by injecting into a closed mold cavity a reaction mixture at a packing factor of 1.03 to 1.9 wherein the mold cavity has a reduced pressure of 300 to 950 mbar and the reaction mixture comprises: A) an organic polyisocyanate; B) a physical blowing agent present in an amount from 10 to 30 weight percent of the polyol composition wherein the blowing agent is a hydrocarbon selected from n-pentane, iso-pentane, cyclopentane, n-butane, cyclohexane or a mixture thereof, C) a polyol composition containing at least one polyol with a functionality of 3 or greater and a hydroxyl number between 300 and 800 D) water present at 0.1 to 2.5 weight percent of the total polyol formulation; E) catalyst and F) auxiliary substances and/or additives.