Extrusion head for multilayer parisons of unstable material combinations.

摘要

A polymer resin extrusion head is provided for molding multilayer tubular articles with resins of unequal viscosities wherein such resins are not combined into a multilayer structure until a point near the outlet of the extrusion head to minimize unstable flows. In some embodiments, the inner layer of the multilayer structure is added last to help minimize unstable flows. In preferred embodiments, unstable flows are minimized by combining all components of the multilayer structure within 4'' of the extrusion head outlet.