Leistritz testing dryer-less PET sheet extrusion

Extrusion machinery supplier Leistritz has set up two of its MAXX twin-screw extrusion systems, and related auxiliary equipment, in its Somerville, NJ lab to process undried PET and directly extrude it in sheet form. Leistritz says the result is a quality product with "dramatically less energy consumption."

In most production environments, PET resin typically is dried separately before being processed on a single-screw extruder. The ZSE-27 and ZSE-50 extruders that are being fed undried PET pellets or regrind have multi-stage vacuum venting to minimize or avoid hydrolysis. The extruders have a gear pump, screen changer, and flexible-lip sheet die attached, which feeds the 3-roll stack that cools and forms the PET sheet.

Leistritz says the ZSE-MAXX series, with increased torque capabilities and a 1:66 OD/ID ratio, is especially well suited to PET processes that are torque-, heat-, and shear-sensitive. The series also has an improved barrel cooling design that benefits PET processing.