METHOD OF DRAWING THERMOPLASTIC SYNTHETIC RESIN FILM OVER A POLYANGULAR MANDREL

摘要

A method of drawing a tubular thermoplastic resin film comprising transporting said tubular film onto a mandrel which has a polyangular conical shape, causing the uniform occurrence of necking initiation points around the circumference of said film by drawing said film around said mandrel, and continuing to draw said film by the action of fluid pressure exerted within said film after said film has passed over said mandrel.