Production of oriented thermoplastic films by blown-film extrusion.

摘要

A process for producing an oriented blown film of a thermoplastic resin by blown film extrusion, comprising blowing air into an extruded bubble (e) of the resin extruded from a ring die (d) to expand the bubble and cooling the expanded bubble with air from a cooling air ring (24), wherein blown film extrusion is carried out under such conditions that the ratio of (b) the final diameter of the expanded bubble to (a) the diameter of the bubble at the crystallizing temperature of the thermoplastic resin ((b)/(a)) ranges from 1.5 to 10. The process provides an oriented blown film excellent in strength, appearance, and heat shrinkage characteristics.