Polypropylene resin foamed sheet for thermoforming and process for producing the same
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United States of America Patent
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Feb 15, 1994
Issued Date -
N/A
app pub date -
Mar 20, 1991
filing date -
Oct 16, 1987
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A polypropylene resin foamed sheet for thermoforming having compounded therein an inorganic fine powder is disclosed. The sheet contains 10 to 50% by weight of the inorganic fine powder, has a density of 0.2 to 1.2 g/cm and a thickness of 0.2 to 3 mm and having a percent shrinkage of 5 to 30% in each of the longitudinal and crosswise directions on heating at 190.degree. C. for 30 minutes, with the ratio of a residual rate in the longitudinal direction to that in the crosswise direction being from 1:0.7 to 1:1.1. The sheet is produced by extruding and foaming a compounded resin from a ring die of an extruder, and taking off the extruded tubular foamed sheet along a cylindrical drum whose diameter is 2.0 to 3.0 times that of said ring die.
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