| 摘要 |
PURPOSE: To obtain a foam sheet substantially containing no residual foaming agent and having substantially good dimensional stability at room temp. by introducing atmospheric gas into a molten thermoplastic resin as a foaming agent and extruding this thermoplastic resin into a form of a foam sheet material. CONSTITUTION: An atmospheric gas such as carbon dioxide, nitrogen or air and, pref., a non-volatile blend agent are mixed and the gas or the gas- containing mixture is introduced into a molten thermoplastic polystyrene resin containing a forming agent (e.g. sodium bicarbonate and citric acid) and this thermoplastic resin is extruded to be formed into a foam. The blend agent is a substance non-volatile at extrusion temp., that is, a high mol.wt. ester low-volatile at high temp.. The mol.wt. thereof is pref. 350-450 and, for example, di-isodecyl adipate, ditridecyl adipate and trioctyl trimellitate are designated. The use amt. of the non-volatile substance is pref. 3 wt.% or less and the use amt. of the atmospheric gas is pref. below 3 wt.%. |
