The Dow Chemical Company

Richard O Kirk

Hoang T Pham

Chad A Strait

Ray A Herring

Kathryn S Jones

Forest Busby

Paul D Haemhouts

A process for reducing polymer surging, lowering pressure and temperature fluctuations, and reducing polymer degradation while providing good overall throughput rate when plasticating and extruding low bulk density polycarbonate materials. The process involves a two-stage extrusion screw having a feed section with a constant channel depth of at least about 12 percent of the screw diameter and a transition section having a compression ratio of at least about 3:1. Thermoplastic low bulk density polycarbonate materials are extruded through a die in the shape of sheets, profiles, or films.

Method for extruding polycarbonate of low bulk density

A corotating multiple-screw extruder comprising first and second intermeshing screws of more than one flight. The first screw comprises first and second segments paired with first and second segments of the second screw, respectively. On the first segment of the first screw, the height of the first flight is less than the height of the second flight and on the second segment of the second screw, the height of the first flight is less than the height of the second flight and screws for use in such extruder.

High efficiency extruder

A multiple-screw extruder in which paired co-rating screws, or segments thereof, contain unequal numbers of flights; and a screw for use in such extruder.

Multiple-screw extruder

An extruder screw having a plurality of plasticating sections sufficient for plasticating polymeric materials of different bulk density.

Single screw method and apparatus

Single screw extruder method and apparatus

A polycarbonate pellet having a size between 200 and 1,500 microns, not inclusive, is produced by extruding molten polycarbonate through a die and cutting such extrudate with a die face cutter.

Growing community of inventors

Lake Jackson, TX, United States of America

Richard O Kirk