Patent ID: 6297292
Filing Date: 2001-10-02
Classification: B29C,C08J,Y10S

Abstract:
A process for the preparation of expanded polystyrene particles by expanding polystyrene beads containing water as the sole expanding agent characterized by the following stages:A) polystyrene beads, in which from 2 to 20 wt % of water is incorporated, are heated to temperatures above 100.degree. C. to produce pre-expanded particles,B) the pre-expanded particles are dried at temperatures between 20.degree. and 95.degree. C. over a period of from 1 to 10 hours,C) the dried expanded particles are further expanded with steam or a gas mixture containing at least 50 vol % of steam at temperatures of from 100.degree. to 140.degree. C., andD) the stages b and c are repeated as often as is necessary to achieve the desired bulk density.