Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Patent
1986-06-18
1988-05-24
Anderson, Philip
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
264 459, 264 53, 264171, 264DIG5, 264DIG13, 264DIG14, C08J 934, C08J 912, B29C 4706, B29C 6722
Patent
active
047464771
ABSTRACT:
In a method of extruding a plastic product having a foamed core layer and at least one unfoamed skin layer by forcing contiguous flows of a resin through a coextrusion die, one of the flows containing a blowing agent and a nucleating agent for forming the core layer and the second of the flows containing only the blowing agent, for forming the skin layer, the steps of establishing a fluent stream of resin containing the blowing agent, dividing the stream into separate streams which are separately conducted to the coextrusion die to constitute the core-forming and skin-forming flows, respectively, and selectively adding the nucleating agent only to that one of the separate streams which constitutes the core-forming flow. The nucleating agent used can be one which is effectively completely expended when the core layer foams, so that the foamed product is essentially free of active nucleating agent.
REFERENCES:
patent: 3956438 (1976-05-01), Schippers
patent: 4410602 (1983-10-01), Komoda et al.
patent: 4518557 (1985-05-01), Wecker
Kohl Lou
Wecker Sheldon M.
Anderson Philip
James River--Norwalk, Inc.
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