Davis-Standard (Pawcatuck, Connecticut / USA; www.davis-standard.com) and plastic melt filtration systems specialist Gneuss (Bad Oeynhausen / Germany; www.gneuss.de) have collaborated on a non-dried PET sheet system that is claimed to combine high output with cost-saving technology. The development combines Davis-Standard machine engineering with a “multi rotation” system (MRS) from Gneuss, resulting in processing rates of 900 kg/h for PET thermoformed sheet.

A blender combines the PET, post-consumer or industrial flake with virgin pellet flake from hoppers in one step, eliminating the crystallising and drying processes. Once blended, the resin is vacuum conveyed to the feed throat of the MRS extruder for processing. The MRS extruder is comparable to the vent section of a single or twin screw extruder where degassing of the melt stream occurs under precise vacuum control. However, the degassing section of the MRS is much larger, 25 times that of a twin screw and 50 times that of a single screw, making it possible to remove moisture and volatiles in the melt stream more efficiently, even at moderate vacuum levels.

The companies say the melt has low shear and thermal stress and excellent pressure build-up, which can eliminate the need for a gear pump in some applications, low energy consumption and compact design. The result is high quality sheet and a process that saves time and money. When processing post consumer waste, the degassing section provides high decontamination of the material. FDA approval for processing PET bottle flakes is pending.