| 摘要 |
A method is described for the preparation of rigid foams, having urethane and/or isocyanurate groups and being extensively open celled, by reacting polyisocyanates with compounds having at least two groups capable of reacting with isocyanates and the equivalent weight per reactive group of which is about 9 to 800, in the presence of catalysts, surface active substances, as well as, optionally, physical blowing agents, flame retardants and other known auxiliary materials and finishing agents, wherein the reaction is carried out in the presence of liquid, higher molecular weight, unsaturated hydrocarbons, which are free of groups capable of reacting with isocyanates, in amounts of 0.01 to 3.0% by weight, based on the reaction formulation. Particularly preferred hydrocarbons are polybutadiene and polyoctenylene with an average molecular weight of 800 to 10,000 g/mole. The rigid foams, because of their open cell nature, exhibit high dimensional stability.
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