Process for the preparation of polyurethane rigid foams having a low thermal conductivity and their use

Abstract

The present invention relates to a process for the preparation of polyurethane rigid foams having a low thermal conductivity, comprising reacting: a) organic and/or modified organic polyisocyanates with, b) at least one higher molecular weight compound having at least two reactive hydrogen atoms, and optionally c) lower molecular weight chain extending agents and/or crosslinking agents in the presence of, d) cyclopentane (d1) or mixtures (d2) comprising, d2i) cyclopentane, and/or cyclohexane, d2ii) at least one compound homogeneously miscible with cyclopentane and/or cyclohexane, said compound preferably has a boiling point below 35.degree. C. and is selected from the group consisting of alkanes, cycloalkanes having a maximum of 4 carbon atoms, dialkylethers, cycloalkylene ethers and fluoroalkanes, optionally combined with water as said blowing agent (d), e) catalysts, and optionally f) auxiliaries and/or additives. Polyurethane rigid foams are used in the low temperature appliance industry and as insulating materials in heating and composite elements.

Dependencies are inferred from the claim text.