Abstract: A process for preparing an extruded thermoplastic resin elongate foam body comprising an alkenyl-substituted aromatic resin characterized as having a density of between about 0.9 to about 3.5 pounds per cubic foot is described. The process comprises the steps of (A) heat plastifying the thermoplastic resin; (B) adding at least one fluid blowing agent comprising at least one of 1-chloro-1,1-difluoroethane, 1,1,1,2-tetrafluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane; (C) uniformly mixing the blowing agent in the resin under a pressure sufficient to prevent blowing of the resin thereby forming a blowable resin mixture; (D) extruding the mixture into a region of reduced pressure which is less than atmospheric pressure wherein the blowable resin mixture expands into a foam body; and (E) cooling the foam body.

Abstract: A foam extrusion system and method employs a horizontal vacuum chamber with a bulkhead and extrusion die at one end of the chamber, the extrusion die being inside the chamber when the bulkhead is closed. A liquid baffle, preferably water, is provided at the opposite end of the chamber through which the extrudate passes from the chamber to atmosphere. The baffle comprises a pond of liquid having a higher level in the chamber and a lower level outside the chamber. The higher level of the pond is formed between a dam plate and a seal plate, the latter forming the opposite end of the chamber. The seal plate includes a size adjustable window through which the extrudate passes, the extrudate being guided by a conveyor to extend inclined downwardly into the pond and to exit through the seal plate and pond with a large radius upwardly curved section.