COEXTRUSION APPARATUS, COEXTRUSION METHODS, MULTIPLE LAYER FILMS AND PACKAGING MADE THEREFROM

摘要

Apparatus and method for fabricating films, especially films containing vinylidene chloride copolymer, enable the process to be performed on a continuous basis over an extended period of time greater than a few days, typically for at least 2 weeks between shut downs for cleaning the equipment of polymer degradation products. The apparatus comprises a coextrusion feedblock (20) in combination with an annular extrusion die (10) having a crosshead mandrel (11), and means (22) for conveying the exit stream (24) from the feedblock (20) to the die (10). The particular apparatus combination especially reduces the rate of carbon buildup in the extrusion apparatus during extrusion of VDC copolymer, such that the extrusion process can be operated for a longer time between shutdowns for cleaning and maintenance of the die. In general, the method is able to produce tubular films having more layers than an annular extrusion die (10) has annular orifices (31).