RIGID PU-PIR FOAM WITH IMPROVED ADHESION IN COMPOSITE ELEMENTS

摘要

The present invention relates to a process for producing a rigid polyurethane-polyisocyanurate foam via foaming of a polyol composition comprising at least one ester polyether polyol, obtainable via reaction of at least one dicarboxylic acid equivalent with at least one polyhydric alcohol, and alkoxylation of the resultant reaction product with at least one epoxide, with an isocyanate component in the presence of a specific blowing agent mixture. The blowing agent component comprises formic acid in a molar proportion of from = 5 mol% to = 40 mol%, physical blowing agents in a molar proportion of from = 50 mol% to = 85 mol% and water in a molar proportion of from = 5 mol% to = 45 mol%. The invention further relates to a rigid polyurethane-polyisocyanurate foam obtainable by the process according to the invention, use thereof in the production of upper-layer-rigid-foam sandwich elements, and the resultant sandwich elements.