Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By gas forming or expanding
Patent
1992-10-13
1994-01-25
Simmons, David A.
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By gas forming or expanding
264 55, 2642094, 2642107, 264565, B29D 700
Patent
active
052813770
ABSTRACT:
A foamed polyolefin sheet is formed by extruding a molten polyolefin resin, which contains a blowing agent, into a low-pressure zone through an annular die provided at an end of the extruder to form a foamed tubular body, bringing the foamed tubular body into contact with a peripheral surface of a cylindrical cooling device to cool the foamed tubular body and then slitting the thus-cooled foamed tubular body and then slitting the thus-cooled foamed tubular body in the direction of extrusion to open same. The cylindrical cooling device is divided into an upstream section and at least one other spaced downstream sections. The internal pressure of the foamed tubular body is increased to from about 5.times.10.sup.-4 to 3.times.10.sup.-2 kg/cm.sup.2 (G) between the die and the upstream section of the cylindrical cooling device and also between at least two adjacent sections of the cylindrical cooling device to apply tension to the foamed tubular body at the inner wall and prevent the formation of corrugations.
REFERENCES:
patent: 2433937 (1948-01-01), Tornberg
patent: 2987765 (1961-06-01), CiChelli
patent: 3311681 (1967-03-01), Cherney et al.
patent: 3619445 (1971-11-01), Carlson, Jr.
patent: 4165356 (1979-08-01), Heider
patent: 4426065 (1984-01-01), Komatsuzaki et al.
patent: 4487731 (1984-12-01), Kobayashi
Ishihara Yoshihisa
Iwano Shoji
Wakabayashi Kouichi
Japan Styrene Paper Corporation
Matney, Jr. William J.
Simmons David A.
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