| 摘要 |
The parent patent the prodn. of closed cell polystyrene foams in which the cells contain >=1 blowing agent of formula R1-CF2-R2 (I) in which R1 is (m)ethyl, chloromethyl, fluoromethyl, chlorofluoromethyl, difluoromethyl, or trifluoromethyl gp. and R2 is H, Cl, F, CF3 or methyl gp., such that the cpds. contains not more than 3C atoms and if the cpd. contains only 2F atoms, it must contain 3C atoms. In this addn. improved closed cell polystyrene foams can prepd. using a blowing agent of formula R-CF2-R2 (II) in which R is a dichloromethyl gp. and R2 is H, Cl, F, CF3 or methyl. Pref. a mixt. of blowing agents (II) and (I) is injected into a molten stream of the styrene polymer is an extruder and the molten gel is then passed through a cooled mixer and extruded into a rectangular bar. |
