Method for extruding foamable polymer material

Abstract

A method for preparing a thermosetting foam, such as polyisocyanurate or polyurethane foam, includes introducing polyol and isocyanate to a screw of an extruder and mixing in the extruder screw. Catalyst is then added and mixed with the already formed mixture in the extruder screw. This mixture is extruded onto a conveyor and foamed on the conveyor. Finely divided carbon black, dispersing agent and/or surfactant may be mixed with polyol before introducing to the screw of the extruder or carbon black may be dispersed in polyol in the extruder and a polyol premix made before the remainder of the polyol is added. Foam cell size is decreased when extruder speed is increased. The foaming agent, which is preferably HCFC or water, may be mixed with one of the components, preferably the polyol, before introducing to the screw of the extruder. The mixture is cooled before extruding onto a conveyor to delay the foaming step until the mixture is outside the extruder. A carbon black dispersion may also be made, for future use. The process described may be used for making foam boards or bunstock.