Patent ID: 8148440

Claim:
A process for preparing rigid urethane-modified polyisocyanurate foam comprising the step of reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive component comprising at least 30 wt % of polyester polyols in the presence of a blowing agent, selected from the group consisting of, an alkane, an alkene, a cycloalkane, or combinations thereof, wherein the blowing agent consists of carbon and hydrogen atoms, a urethane catalyst, and a metal salt trimerisation catalyst characterized in that the process is carried out in the presence of a carboxylic acid that is functionalised with at least one OH, SH, NH 2 , NHR, NO 2 or halogen functional group and R is an alkyl, cycloalkyl or aryl group, wherein the urethane catalyst is used in an amount ranging from 0.1 to 3.5% by weight based on the isocyanate-reactive component and the metal salt trimerisation catalyst is used in an amount ranging from 0.4 to 4.5% by weight based on the isocyanate-reactive component.