UNIDIRECTIONALLY HEAT-SHRINKABLE TUBULAR FILM AND MANUFACTURE THEREOF

摘要

PURPOSE:To manufacture a packaging heat-shrinkable tube which freely fits to a container to be packed by a method wherein the longitudinal direction of an amorphous polyester tube which is simultaneously biaxially oriented is relaxed by the specified value. CONSTITUTION:Firstly, an amorphous polyester tube is heated up to a temperature within its orientation temperature range and simultaneously biaxially oriented. Secondly, the air is charged under pressure into the resultant biaxially oriented tube so as to treat to longitudinally relax the tube within the range: (longitudinal draw radio -1)/(longitudinal draw ratio)X(1-0.75)X100% while the change in the width direction (outer diameter) of said tube is controlled under heated condition. The obtained heat-shrinkable tube exactly fits onto the irregular surface of a bottle and consequently gives very favorable external appearance to the bottle.