Direct extrusion | machinery feature
removing any final contaminants in the recycled PET. The filtration features four filters ensuring that screen cleaning can be carried out without interrupting production or impacting on product quality. BSG, which is a member of the Kreyenborg Group, is
supplying the control system for the direct extrusion process. This works along with the Leistritz control system for the extruder and integrates the control of the downstream film production. Static mixers can be used to further homogenize the
The down- stream
equipment, or the ‘cold
portion’ of the line is supplied by Kuhne
The complete line While each line is custom-made for a specific applica- tion, Leistritz and Kuhne explained a typical set-up as used for the demonstration line that was running at the Direct Extrusion Day. Handling PET flakes with their low bulk density
requires special handling and feeding equipment. Leistritz works with companies such as Main Tech and Doteco to supply the systems for conveying the PET flake from big bags to the extruder, providing dust filtration, metal separation and gravimetric blending. At the heart of the line is a Leistritz ZSE Maxx twin-
screw extruder fitted with vacuum-hardened screws and barrel liners for handling the PET. The company says that the extra volume and torque of the ZSE Maxx is particularly suited to processing PET, delivering high throughput levels. Degassing is carried out using a vacuum system. The
extrusion line can handle initial PET moisture levels up to around 4,000 ppm, and Leistritz is working on developments to increase this significantly. Because the twin-screw extruder does not create sufficient pressure for the film die, it is fitted with a spe- cial gear pump. Furthermore, melt filters are used for
melt before it enters the feedblock. The flat die includes variable internal deckling, allowing users to adjust the width of the extrudate or reduce the edge bead while the process is still running. The downstream equipment or the ‘cold portion’ of the line is provided by Kuhne, which has extensive experience in this field. It can offer a variety of options for producing multi-layer films, for example including PE and PET. In addition to coextrusion, laminating can be carried out inline or offline.
Early successes Leistritz entered the market for direct extrusion of cast films several years ago and has various systems in operation at customers processing a mixture of PET including 100% reclaim and in-house scrap. It is also supplying lines for BOPET, BOPP and BOPA, where using twin-screws can be used for multiple layers and for adapting formulations in-line. Direct extrusion is not limited to film and sheet, and the company has also supplied twin-screw extruders for the production of pipes using filled PP.
Click on the links for more information: ❙
www.leistritz.com ❙
www.kuhne-group.com ❙
www.maintechworld.it ❙
www.doteco.com ❙
www.bsg.de
AMI Strategy Seminars
These one-day seminars are given by an AMI director and provide invaluable insights into market trends and industry strategies. They are held in small groups and provide ample opportunities for questions and discussions.
The Plastics Industry Strategy Seminar – 29 March 2012, Singapore Click here to download the programme and booking form
The Plastics Industry Strategy Seminar – 25 June 2012, Chicago, IL, USA Click here to download the programme and booking form
The Plastics Industry Strategy Seminar – 5 November 2012, Philadelphia, PA, USA Click here to download the programme and booking form
www2.amiplastics.com/Seminars
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