Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By gas forming or expanding
Patent
1975-07-22
1977-06-28
Anderson, Philip
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By gas forming or expanding
264DIG9, 264DIG10, 264DIG13, 425817R, 425DIG39, 432 13, B29D 2700
Patent
active
040326098
ABSTRACT:
An energy saving and material conserving method and apparatus are provided for expanding and molding expandable thermoplastic polymer particles. Especially significant is the ability to produce molded objects of generally uniform density in the higher density range in the order of 4-15 pounds per square inch, or greater, as well as lower density molded objects due to improved control of the particle expansion.
The particles are partially expanded in a vessel in a heated substantially dry atmosphere and agitated in a manner to provide uniform heating thereof. After an initial heating period to soften and partially expand the particles they are subjected to superatmospheric pressure to substantially prevent further expansion and are discharged and conveyed to a mold for further expansion therein. In certain instances, the particles are subjected to superatmospheric pressure within the vessel during a portion of the initial heating period to prevent premature particle expansion and loss of blowing agent within the particles. The temperature of the particles are continuously maintained above the boiling point of the blowing agent within said particles at all times subsequent to the partial expansion of the particles up to the final expansion and fusion of the particles in a mold.
REFERENCES:
patent: 3162704 (1964-12-01), Attanasio et al.
patent: 3207820 (1965-09-01), Scarvelis et al.
patent: 3262686 (1966-07-01), Kraus et al.
patent: 3273873 (1966-09-01), Stanchel
patent: 3309440 (1967-03-01), Kracht
patent: 3446882 (1969-05-01), Landon
patent: 3452124 (1969-06-01), Knapp
patent: 3577360 (1971-05-01), Immel
Anderson Philip
Foster Grant Co., Inc.
Selman Leonard S.
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