Vacuum extrusion system and method

An extrusion line comprising an extruder, a horizontal vacuum chamber, an extrusion die inside the chamber forming an extrudate, an interior vacuum chamber pond at one level and an exterior atmospheric pond at another lower level, a submerged hood extending from said chamber into said atmospheric pond operative to direct the extrudate to said atmospheric pond before exiting to atmosphere, and a controlled orifice in said hood closely accommodating the extrudate as it moves from the vacuum chamber pond to the atmospheric pond.

A vacuum extrusion line comprising an extruder, a vacuum chamber, an extrusion die within the chamber forming an extrudate, a pond of liquid through which said extrudate passes having a portion at one level in said chamber and another portion at a lower level outside said chamber, and means to circulate liquid from the portion of the pond within the chamber to the portion outside the chamber independently of the movement of the extrudate, and control means continuously to regulate the amount of water circulated, said control means being responsive to the one level of the pond within the chamber.

A continuous extrusion line comprising an extruder, a bulkhead, an extrusion die mounted inside the bulkhead, a pond forming dam, a structural beam extending from the dam to the bulkhead for supporting shaping and sizing apparatus, a vacuum chamber comprising a fixed section surrounding said dam, and a telescoping section of said vacuum chamber around said beam adapted to move away from and toward the bulkhead to open and close the chamber.

A method of preparing foam plastic comprising the steps of extruding a foamable plastic melt into a vacuum chamber, passing the foaming extrudate into a body of liquid which has a higher level portion within and a lower level portion outside such chamber to exit the chamber through such body of liquid, controlling the higher level of that portion of the body of liquid within such chamber by continuously circulating liquid from that portion of the body of liquid within such chamber, and controlling the amount of liquid continuously circulated in response to the higher liquid level within the chamber.

A method of extruding plastic foam comprising the steps of extruding a foamable plastic melt into an elongated vacuum chamber at one end thereof and to exit such chamber through an exit orifice at the other end, such exit orifice being submerged in a body of liquid having a higher level portion inside said chamber and a lower level portion outside said chamber, and continuously circulating such liquid from said higher level portion inside the chamber to said lower level portion outside the chamber to maintain the higher level of liquid inside said chamber, with the amount of liquid being circulated controlled by the higher level within the chamber.

A foam extrusion method comprising the steps of using a horizontally extending vacuum chamber with an extrusion die at one end of said chamber forming a foam extrudate, passing the extrudate through water baffle means at the opposite end of said chamber operative to enable said chamber to be maintained under vacuum as the extrudate exits to atmosphere, and forming said vacuum chamber with a fixed and telescoping chamber section.

A continuous extrusion line comprising an extruder, a vacuum chamber including an upstream bulkhead, an extrusion die for forming an extrudate on the interior of said upstream bulkhead, a downstream bulkhead, a structural beam extending between said bulkheads along the line, and at least two vacuum chamber sections surrounding said beam, one of said sections being movable parallel to the beam to open and close the vacuum chamber.