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United States Patent 6132077
Douris , ê et al. October 17, 2000

Method of cooling a foam extrusion mixture to an extrudable temperature

Fogarty October 17, 2000

Abstract

A method of cooling a foam extrusion mixture to an extrudable temperature as the foam extrusion mixture passes through an elongate barrel including the steps of drawing heat from a perimeter surface of the barrel, while urging the extrusion mixture through the barrel towards an outlet of the barrel, and also circulating at least some quantities of the extrusion mixture disposed a spaced apart distance from the perimeter surface of the barrel away from the outlet of the barrel and towards the perimeter surface of the barrel by passing at least some of the extrusion mixture through at least one circulation channel defined in the screw flight a spaced apart distance from the perimeter surface of the barrel, and having an asymmetrical, partially tapered inlet area that is smaller than its outlet area, thereby maximizing the quantity and flow velocity of said extrusion mixture which enters said circulation channel and disrupting a flow pattern of the extrusion mixture through the circulation channel in order to achieve substantially uniform cooling and homogenization of the extrusion mixture.