Double metering extruder screw and method of extrusion
AssigneeUnion Carbide Corporation
InventorsJohn C. Miller, Archibald L. Burnett
Life of this patent
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Abstract
A high output extruder screw which produces throughputs at lower temperatures and lower specific energy input. The screw has a feed section, a first short transition section, a first metering section, a second short transition section and a second metering section wherein the screw diameter increases from the feed section to the second metering section. There is also provided a method for extruding specific ethylene polymers.
Claims11
An extruder screw for extruding low density narrow molecular weight distribution linear ethylene polymers which comprises:
- a screw root and a helical feed flight of constant pitch;
- a feed section wherein said screw root diameter is constant;
- a first short transition section having at least about one-half turn of said helical feed flight and wherein said screw root has an increasing diameter and is larger than the diameter in said feed section;
- a first metering section wherein said screw root has a constant screw root diameter greater than the screw root diameter in said feed and first short transition sections;
- a second short transition section having at least about one-half turn of said helical flight and wherein said screw root diameter is larger than the diameter of the screw root in said first metering section;
- and
- a second metering section wherein said screw has a constant screw root diameter greater than the screw root diameter in said first metering section.
A method for extruding low density narrow molecular weight distribution, linear, ethylene polymers which comprises introducing said granular polymers into an extruder apparatus having an extruder screw having a helical feed flight of constant pitch and including a feed zone comprising a constant screw root diameter;
- thence passing said polymers through a first short transition zone of said screw wherein the screw root diameter increases;
- thence passing said polymers through a first metering zone of said screw having a constant screw root diameter greater than the screw root diameter in said feed zone;
- continuing passage of said polymer into and through a second short transition zone wherein the screw root diameter increases;
- and thence passing said polymer into and through a second metering zone having a constant screw root diameter greater than the screw root diameter in said first metering zone.
Dependencies are inferred from the claim text.