Formation method null of preform and the hollow formation item which are the not yet by crystal or playback polyethylene

摘要

PURPOSE: To eliminate the need for crystallized molding material and contrive to reduce material cost by a method wherein uncrystallized polyethylene terephthalate is employed as molding material, which is fed to an injection device so as to be turned into semi-molten state and, after being deaerated, thermally melted and injected. ;CONSTITUTION: At molding operation, uncrystallized polyethylene terephthalate as molding material without being dried is fed directly from a hopper 3 into a heating cylinder 1 by properly utilizing a feeding device. Next, the molding material in the heating cylinder 1 is melted under the condition being transferred ahead and metered. At this time, the molding material in semi-molten state is fed under compression to a compression zone 8. The compressed molding material in semi-molten state is extruded to the rear part of a forward screw 6a so as to be expanded at its rear part, resulting in separating water content and volatiles content from the molding material. The deaeration molding material is heated up to the temperature higher than its melting temperature and, at the same time, compressed so as to be injected in a mold under fully kneaded condition in order to obtain the desired molded article.;COPYRIGHT: (C)1994,JPO