PET Sheet Extrusion Line Requires No Pre-Drying

An Italian company, RPC Cobeplast, recently purchased a three-layer sheet extrusion line capable of processing undried PET materials. The Berstorff line is built around a co-rotating twinscrew ZE 90A x 34 D UT extruder equipped with vacuum degassing. The line is designed to produce sheet ranging from 100 microns to 1.8 mm in thickness. Raw materials, such as shredded internal scrap, are fed via a material handling system and gravimetric blender directly into the extruder, without pre-drying. A filter system in the extruder removes contamination. A back pulsing system minimizes the amounts of material required for back-purging. A single-screw machine co-extrudes virgin PET for the outer layers and the three melt streams are fed to the wide slot die and then into a horizontal three-roll polishing unit. The sheet undergoes edge trimming, thickness gauging, silicone treatment and lamination before being wound. Up to four web slit widths can be produced at one time on the line, which has a capacity of 1200 kg/h. Elimination of drying saves significant energy costs, and the in-line post-treatment reduces the likelihood of variation and contamination.

Berstorff 859-283-0200