Owens-corning Fiberglass Technology, Inc.

U.c. Industries, Inc.

Joseph A Brackman

Raymond Marshall Breindel

Robert L Sadinski

An extrusion system utilizes single or tandem extruders and a mixer-cooler to extrude a foamable extrudate through a die in a sealable chamber. The foamable extrudate is shaped and calibrated within the chamber. The die is mounted on the end of a gel tube projecting through a gland seal in a fixed bulkhead forming the upstream end of the chamber. The gel tube and mixer-cooler are mounted on a movable carriage, movement of which may be used to adjust the die with respect to shaping and calibrating equipment inside the chamber. The mixer-cooler achieves a selected narrow range of uniform viscosity of the melt at the die depending on the size of the product and density. The chamber is preferably a vacuum chamber producing low density foams. The product exits the chamber to atmosphere on a continuous basis through a submerged orifice in a water baffle immersion seal. The mixer-cooler enables a large size low density product to be produced with uniform cellular structure without cell collapse or density gradients, as the product is subjected to the pressure and temperature transformations passing from the chamber to atmosphere through the water. The seal includes the submerged orifice with a free wheeling guiding system upstream of the orifice. Immediately ahead of the guiding system, the parameters of the foam extrudate are sensed to control the configuration of the orifice on a continuous basis. Before the extrudate passes into the water baffle seal it moves over a floating dancer roll, the position of which controls a haul-off such as a vacuum belt at the tail end of the system. This avoids pushing on the extrudate.

Foam extrusion apparatus

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. In one embodiment, the region of less than atmospheric pressure is formed by an elongated chamber with the blowable resin mixture passing through a die at one end of such chamber and such foam body passing through a pool of water at the opposite end of the chamber. The process results in the formation of extruded expanded thermoplastic resins such as polystyrene resins characterized as having relatively small average cell sizes such as from about 0.2 to about 0.5 mm., improved and higher compressive strengths, and higher cell volumes.

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Uniontown, OH, United States of America

Joseph A Brackman