Process for making lightweight polyester articles

Details Process for making lightweight polyester articles Process for making lightweight polyester articles

1989-03-31

1991-01-01

Thurlow, Jeffery

Plastic and nonmetallic article shaping or treating: processes

Pore forming in situ

By mechanically introducing gas into material

264 85, 264553, 264171, 264211, 26421121, 264321, 264322, 425 4C, B29C 5102, B29C 6720

Patent

active

049816314

ABSTRACT:
This invention relates to a process for making a lightweight article which involves the steps of: (1) feeding a thermoplastic resin composition into an extruder, wherein the thermoplastic resin composition contains (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin; (2) mixing an inert gas into the thermoplastic resin composition in the extruder while the thermoplastic resin composition is in the molten state; (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25; and (4) thermoforming the cellular sheet in a heated mold to produce the lightweight article. Dual-ovenable trays and other types of food containers can be made utilizing the process of this invention. It is advantageous to utilize the process of this invention in making such articles because they are lightweight and can be made utilizing less polymeric materials.

REFERENCES:
patent: 3374300 (1968-03-01), Azuma
patent: 3651181 (1972-03-01), Ramaika
patent: 4405400 (1983-09-01), Petersen-Hoj
patent: 4426065 (1984-01-01), Komatsuzaki et al.
patent: 4466933 (1984-08-01), Huggard

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