Extrusion die for extrusion blow molding equipment

Abstract

Disclosed are resin stream modulation or shut-off control apparatus for use in a multi-layer extrusion die head for forming a multi-layer plastic resin parison tube suitable for blow-molding. The tube can be formed into articles such as containers. By use of the apparatus, the tube, and accordingly articles therefrom can have layers which vary in thickness or can have portions wherein layers are omitted, e.g., portions which become flash. In an apparatus herein, there is a resin channel having an exit orifice defining a merge area where a first resin stream merges with at least one second resin stream. A die member adjacent to the exit orifice can define the resin channel. Movable means and the die element are caused to intermittently abut or contact one another at the merge area to control, i.e., modulate or shut-off, the flow of the first resin. There is preferably no contact downstream of the merge area. In another embodiment a volumetric increase in the flow of the first resin controls or prevents its flow. Methods are directed to utilizing the apparatus and for forming a container having a scrap layer substantially devoid of one or more selected resins. The multi-layer extrusion blow-molded article or container has a layer which includes scrap from parison sections which are substantially devoid of the selected resin(s).