| 摘要 |
The present invention relates to a process for the production of semi-rigid foams containing urethane groups which exhibit very good flow properties during the production process. These semi-rigid foams are produced by reacting a reaction mixture of: 1) polyisocyanates, 2) organic compounds containing at least two isocyanate-reactive hydrogen atoms and having a molecular weight in the range from 400 to 10,000, and 3) water and/or organic blowing agents. In particular, the polyisocyanates comprise a mixture of: a) 55 to 87% by weight, based on 100% by weight of the mixture, of 4,4'-diphenylmethane diisocyanate, b) 8 to 40% by weight, based on 100% by weight of the mixture, of 2,4'-diphenylmethane diisocyanate, c) 0.1 to 4% by weight, based on 100% by weight of the mixture, of 2,2'-diphenylmethane diisocyanate, and d) 5 to 35% by weight, based on 100% by weight of the mixture, of polyphenyl polymethylene polyisocyanates. |
