| 摘要 |
1519518 Mould release of polyurethanes DOW CORNING CORP 17 Sept 1975 [19 May 1975] 38186/75 Headings C3R and C3T Polyurethanes, which release freely from the moulds used in their preparation, are prepared by reacting a composition comprising (A) a curable urethane polymer containing free isocyanate groups and (B) 0À5 to 5% based on the weight of (A) plus (B) of a siloxane-polyoxyalkylene copolymer selected from wherein each X has an average value of 3 to 45, each Y has an average value of 8 to 198, Me is a methyl radical and -(OR)xis the residue of a polyoxyalkylene polymer or copolymer wherein R is composed of ethylene radicals or mixtures of propylene or butylene radicals with ethylene radicals, the amount of propylene or butylene radicals relative to the ethylene radicals being such that the ratio of carbon atoms to oxygen atoms in the total -(OR)- block ranges from 2À0 : 1 to 2-9 : 1. In specific Examples, siloxane-polyoxyalkylene copolymers are prepared by reacting hydroxyl end blocked polydimethylsiloxanes with ethylene oxide based polyethers in the presence of dodecylbenzenesulphonic acid and the copolymers are incorporated into a reaction mixture comprising a polyether-based polyurethane prepolymer, 1,4-butane diol, triethylenediamine as catalyst and a small amount of water. The resulting elastomers are easily demoulded. |
