ABSTRACT
Today, even tighter emission controls and better emission monitoring techniques are required from resin manufacturers by the latest regulations of the EPA under the Clean Air Act. Accordingly, the devolatilization step has become a high priority for all major polymer production lines. The single-screw extruder has proved to be a competitive solution. For single-screw extruders, the melt surface renewal occurs at the rotating melt pool and at the barrel surface exposed to the gas space. The characteristic degassing number value allows one to compare single- and twin-screw extruders after adjusting for the additional surface renewal in the twin-screw extruder’s trailing side of the flights. Single-screw extruders are located next to the polymerization reactor, where polymer melt can be delivered at a constant rate to the feed section. The use of water as a stripping agent not only contributes to reducing the partial pressure, it also delivers an additional devolatilization effect compared with the described surface process.
