TUBULAR MULTILAYER FILMS, METHOD AND APPARATUS FOR PREPARING THE SAME.

摘要

A method for coextruding a multilayer tubular film having a barrier material comprises (a) extruding a core extrudate of barrier material with a core extruder; (b) providing a preencapsulation die adjacent the outlet of the core extruder, the prencapsulation die capable of producing a non-uniform layer thickness; (c) extruding a preencapsular extrudate of preencapsular material and directing said preencapsular extrudate to the preencapsulation die; (d) joining the core extrudate and the preencapsular extrudate in the preencapsulation die in a coaxial relationship wherein the preencapsular extrudate is disposed radially outwardly of the core extrudate to form a preencapsulated core extrudate having a non-uniform layer thickness; (e) extruding an inner layer extrudate and an outer layer extrudate; (f) feeding the preencapsulated ore extrudate through a distribution manifold to a coextrusion die, the distribution manifold designed to overlap opposing longitudinally extending edges; and (g) forming a multilayer blown film having the inner layer extrudate disposed radially inwardly of the preencapsulated core extrudate and the outer layer extrudate disposed radially outwardly of the preencapsulated core extrudate. In preferred embodiments the inner layer extrudate and the outer layer extrudate are joined to the preencapsulated core extrudate before, or alternatively while, the preencapsulated core extrudate is fed through the coextrusion die.