| 摘要 |
<p>PURPOSE:To prepare a styrenic resin foam excellent in long-term heat insulating properties by using such a pressure and temp. condition that the melting amount of an evaporation type foaming agent is specific with respect to the addition amount thereof and the mean melting speed of the foaming agent per 1g of a styrenic resin is within a specific range. CONSTITUTION:When an evaporation type foaming agent prepared by mixing HFC-134a with an easy permeable foaming agent having a valve equal to or more than that of air in the gas permeability to a polystyrene membrane is added to perform extrusion foaming, in such a case that the addition amount of HFC-134a is set to (l/rho)X1.7X10<-5>-(1/rho)X5.3X10<-5>mol per 1g of a styrene resin, the melting amount of the evaporation type foaming agent calculated by integrating formula (a) is 95% or more of the addition amount thereof. When mean melting speed is 1.0X10<-7>-7.0X10<-7> mol./g.sec, an objective polystyrenic resin foam is obtained. When the melting amount is below 95% of the addition amount, the liberation phenomenon of the foaming agent is generated and appearance and physical properties lower. When the melting speed is 1.0X10<-7>mol/g.sec or less, a stagnation time is too long and productivity lowers. When the melting speed is 7.0X10<-7> mol/g.sec or more, an extrusion system becomes unstable.</p> |
