| 摘要 |
PURPOSE: To obtain a shrunk highly expanded styrene resin foam which can restore the bulk factor in a short time with carbon dioxide gas and is suitable for tight adhesion packaging by expanding foamable styrene resin particles to a specified bulk factor and cooling the expanded foam to shrink in the air. CONSTITUTION: This foam is obtained by heating foamable styrene resin particles to expand 100- to 600-fold and cooling the expanded foam to shrink in the air. It spontaneously restores only 10-80% of the original bulk factor in the air, while it can restore 95-100% of the original bulk factor with carbon dioxide. A styrene resin having a foaming agent incorporated therein by the suspension impregnation or extrusion method is dewatered, dried, aged in a cool dark place and then foamed. The amount of the foaming agent is preferably 1-6 pts.wt. based on 100 pts.wt. styrene resin. As the styrene resin, a styrene homopolymer or a styrene/acrylonitrile copolymer is preferably used. As the foaming agent, a readily volatile foaming agent comprising, e.g. an aliphatic hydrocarbon or a halogenated hydrocarbon is preferably used. |
