Patent ID: 6827888
Filing Date: 2004-12-07
Classification: B29C

Abstract:
A method of producing polystyrene foam, comprising:heating a polystyrene resin to a melt temperature therefor; selecting at least one blowing agent consisting of at least one ambient gas; combining the heated polystyrene resin with the at least one blowing agent to create a mixture; extruding polystyrene foam sheet from the mixture, the polystyrene foam having a density of between about 0.05 g/cc and about 0.15 g/cc and an average cell diameter of about 0.05 mm to about 1 mm, the polystyrene foam sheet having a thickness of between about 0.75 mm and about 6 mm; wherein the extruding comprises guiding the mixture through an annular exiting channel to an exit with a cross-sectional area larger than at least one point within the exiting channel, and reducing friction within at least a portion of the exiting channel; and wherein the exiting channel comprises a first portion from an entrance to a point having a smallest cross-sectional area and a second portion from the point having the smallest cross-sectional area to the exit, and wherein the reducing comprises controlling a temperature of second portion.