Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By gas forming or expanding
Patent
1990-10-12
1992-06-09
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By gas forming or expanding
264 53, 264321, 425 4C, 425817C, B29C 4788
Patent
active
051204819
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. 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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Brackman Joseph A.
Breindel Raymond M.
Thurlow Jeffery
U.C. Industries, Inc.
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