Thermal annealing of plastic pieces

Abstract

Methods of thermal annealing of plastic pieces immediately after hot melt forming are disclosed to accelerate the time required to achieve dimensional stability. The present methods include the essential steps of: (A) forming molten plastic into molded plastic pieces and rapidly cooling to below the melting point of the plastic in a mold to form shaped cooled plastic pieces; (B) immediately thereafter, heating the plastic pieces to a temperature of about 150° to 170° F. (65.5° to 80° C.) to form heated plastic pieces; and, thereafter, (C) cooling the heated plastic pieces to room temperature to form thermally annealed plastic pieces. Tn its product aspect, the present invention resides in physically aged thermoplastic pieces having reduced rates of age shrinkage.

Dependencies are inferred from the claim text.