Process for the preparation of polyurethane rigid foams

摘要

Production of rigid polyurethane (PUR) foam involves reacting (a) organic and/or modified organic di- and/or polyisocyanates with (b) special polyester-polyols (IA) and/or polyether-ester-polyols (IB) and optionally (c) chain extender and/or cross-linking agent in the presence of (d) blowing agent, (e) catalyst and optionally (f) other ancillaries and/or additives. (IA) and (IB) can be prepared by polycondensation of dicarboxylic acids with polyols using polyalkylene terephthalate (II) and, if necessary, reaction with lower alkylene oxide and optionally other higher molecular compounds with NOTLESS 2 reactive hydrogen atoms. The novelty is that the preparation of (IA) and/or (IB) is carried out by polycondensation in stages, with addition of (1) (II) to the starting materials at the beginning and/or during the first stage and (2) catalyst during other stage(s).