Patent ID: 6607682
Filing Date: 2003-08-19
Classification: B29C,C08J

Abstract:
A process for preparing cellular moldings of a polypropylene resin from pre-expanded particles comprising the steps of imparting an inner pressure to polypropylene resin pre-expanded particles having an expandability of 1.0 to 1.5, filling said pre-expanded particles in a mold capable of being closed but incapable of being hermetically sealed, and heating said particles to fuse together, said expandability being represented by the equation: Expandability=Expansion  ratio  of  polypropylene  resin  pre-expanded  particle  after  steam  heatingExpansion  ratio  of  polypropylene  resin  pre-expanded  particle  before  steam  heatingwherein the expandability is measured by subjecting the pre-expanded particle to the steam heating without imparting an inner pressure thereto, said steam has a temperature equal to the melting point peak temperature of said polypropylene resin measured by differential scanning calorimetry under the conditions that 1 to 10 mg of the pre-expanded particles is heated to 210Â° C. at a rate of 10Â° C./minute, then cooled to 40Â° C. at a rate of 10Â° C./minute and heated again to 210Â° C. at a rate of 10Â° C./minute, and said expansion ratio of polypropylene resin pre-expanded particle after steam heating denotes the value measured after the restoration from shrinking by impregnating the pre-expanded particle with air.