B - Operations – Transporting – 29 – D
Patent
B - Operations, Transporting
29
D
18/639, 18/672,
B29D 27/00 (1980.01)
Patent
CA 1082415
Abstract of the Disclosure 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 a 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 particles 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.
280761
American Hoechst Corporation
Bereskin & Parr
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