Feed Enhancement Technology for Twin-Screw Extruder Compounding of Low Bulk Density Material

摘要

Effectively feeding low bulk density material into a co-rotating twin-screw extruder has always been a challenge. However with the introduction of even finer particle size fillers (sub-micron in some cases) as well as new generations of polymer reactor resins, the issue has become even more problematic. Additionally as bulk density decreases, the materials tend to fluidize more easily. Fluidization lowers the “effective” bulk density even further and exacerbates feeding issues. Typical unit operations within the compounding process where material is more susceptible to fluidization are: transfer from storage vessel to feeders, from feeder to twin-screw extruder and within the feed zone conveying section of the twin-screw extruder. While there are methods to minimize the potential for fluidization such as dense phase conveying from storage to feeder, minimization of the feeder height above the extruder feed opening, incorporating a vent into the feed hopper, extending the length of the conveying zone in the extruder feed section, the process eventually reaches a feed volume limitation, which more often than not is well below an economically viable production rate. This paper will review a new Feed Enhancement Technology (FET) that provides significant improvement for the introduction of fine particle / low bulk density materials into the extruder.