Reexpandable shrunken foam bodies of styrene-acrylonitrile type resin,

Abstract

Improved reexpandable shrunken foam bodies of styrene-acrylonitrile type resin possessing an ability to reexpand to the original volume of the highly foamed state when left standing at room temperature under atmospheric pressure and a method for the manufacture of such reexpandable shrunken foam bodies. The aforementioned shrunken foam bodies are obtained by causing a styrene-acrylonitrile type resin to contain a prescribed large amount of a specific foaming agent exhibiting a slow gas permeation speed to the base resin and possessing the boiling point exceeding a fixed lower limit, heating the resin with steam thereby setting it to foam highly, and releasing the foamed resin into the atmosphere to be cooled and shrunk therein. The aforementioned shrunken foam bodies are convenient for the purpose of transportation and storage. They are useful as fillers intended to absorb shocks and insulate heat. The foam bodies, when reexpanded, form useful materials used for in-mold shaped articles designed for absorbing shock and insulating heat.