Method for pre-expanding and molding expandable thermoplastic polymer particles

摘要

Expandable thermoplastic polymer beads are introduced into a tank and are agitated therein in a heated moisture-free condition. The beads are pressurized within the tank with a hot gaseous medium to soften them and are then subjected within the tank to a selected degree of vacuum to expand the beads or particles. The vacuum is removed and atmospheric pressure is re-established in the tank. The expanded hot moisture-free particles are introduced into a mold where they are fused into an integral mass, followed by cooling of the fused mass within the mold to form an outer skin on the mass. The fused mass is ejected from the mold.