Method and apparatus for forming thermoplastic foams

Details Method and apparatus for forming thermoplastic foams Method and apparatus for forming thermoplastic foams

1977-12-20

1979-03-27

Anderson, Philip

Plastic and nonmetallic article shaping or treating: processes

Pore forming in situ

By gas forming or expanding

264555, 425376R, 425817C, B29D 2700

Patent

active

041465636

ABSTRACT:
An improved method and apparatus for the preparation of a thermoplastic foam having an enlarged cross-sectional area of a given geometric configuration. A heat-plastified foamable gel of a thermoplastic resin containing a blowing agent is extruded through an orifice of a die into a shaping channel. As the gel expands into a foam generally filling the channel and advances in the longitudinal direction, the foam is supported on a cushion of gas in the area of the channel, relatively near the die orifice, where the surface of the foam is sticky. A sufficient restraining force is applied to the foam in the area, where the foam surface is generally non-sticky, to exert a force in the direction opposite to the normal longitudinal advancement of the foam thereby forcing the foam to expand to a cross-sectional area greater than that of a foam allowed to expand freely. The expanded foam is then cooled to a generally self-supporting condition.

REFERENCES:
patent: 3193406 (1965-07-01), Mittelman
patent: 3335207 (1967-08-01), Richie
patent: 3812230 (1974-05-01), Takahashi
patent: 3835209 (1974-09-01), Karabedian
patent: 3887693 (1975-06-01), Sato et al.
patent: 3922328 (1975-11-01), Johnson
patent: 3954929 (1976-05-01), Hoenke
patent: 3966381 (1976-06-01), Suh
patent: 4049760 (1977-09-01), Lozach

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