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02 | 2008

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Processing REItruder

Processing REItruder corotating twin-screw extruder Extrusion Lines of Biodegradable Article contributed by Frank Steinbrecher, Processing Engineer Reifenhäuser Extrusion GmbH & Co. KG Troisdorf, Germany 3-layer Filmtec blown film line The focus of Reifenhäuser, a leading manufacturer of high-performance extrusion lines, is on consistent research and further development of line concepts. The resulting innovations maintain the company’s competitive edge worldwide. Especially the use of new raw materials and the involved changes in processing requirements call constantly for new technical solutions. For this reason, biodegradable raw materials (biopolymers), form essential parts of Reifenhäuser’s future strategy. Not least because Reifenhäuser has recognized the importance of the biopolymer market very early already, the company became one of the first members of the European Bioplastics Association. Reifenhäuser is the only extruder manufacturer in this association supporting its ideology as a machine building company. Today, biopolymers are increasingly used in thermoforming sheet and blown film extrusion. In thermoforming sheet extrusion, Reifenhäuser is laying emphasis on a further development of singlescrew extruders and corotating twin-screw extruders for processing biopolymers. The first successes could be presented by the Troisdorf, Germany based company to the expert visitors during its inhouse exhibition held concurrently with ‘K 2007’. PLA was successfully processed by NatureWorks on a 5-layer thermoforming sheet line using a single-screw extruder and a pre-drying stage. A ‘REItruder’ corotating twin-screw extruder without pre-drying operation could also be recommended for the mentioned application. Excellent results were achieved on the pilot line installed in the Reifenhäuser Technology Centre. Trials conducted with thermoform- 26 bioplastics MAGAZINE [02/08] Vol. 3

Thermoforming sheet line Processing for Processing Raw Materials ing PLA sheets by end customers and manufacturers of automatic vaccum forming units were successful without excemption. PLA polymer which has shorter drying times and lower processing temperatures shows the highest resemblance with PET in extrusion processes. Since the presentation of this development project, if not already before, the market has recognized that PLA, in addition to PP, PS and PET is a polymer suitable to be processed into polished sheets on Reifenhäuser extrusion lines. The constantly rising oil price and the resulting price situation of raw materials, such as PP, PS and PET, make PLA an alternative polymer for the production of thermoforming sheets in the future. For this reason, Reifenhäuser expands its proven standard program by targeted further developments in screw geometry, flow channel optimisation and in many other areas - perfectly matched to biopolymers. A further interesting application can be found in the blown film area. Reifenhäuser was able to achieve almost identical performance rates with starch-based polymers and with polyolefins processed on a standard 3-layer blown film line. High throughputs and good mechanical properties of the extruded film can be obtained with a two-third reduction of energy consumption. Special properties of the film are an excellent barrier behaviour, in particular against oxygen and gases, and its biodegradability according to DIN 13432. The international expert public could witness the excellent film quality during the Open House in Troisdorf. The 3-layer blown film line of the Filmtec 3-1700- IBC-RHS type is ideal for the production of laminating film, deep freeze packaging film, stand-up pouches, stretch film and stretch wrapping film. It is also suitable for the production of bio-packagings without the need for modification. Newly developed low-temperature screws and three REItorque single-screw extruders are special features of the versatile line concept. REIcoflow gauge control system ensuring the most exacting tolerances and REIcofly turner bars providing highquality films are part of the standard line equipment. For achieving optimum results in the complex winding process of biopolymers an SFA II tandem winder highly recommended. At Reifenhäuser, processing of biopolymers does not end with the compounding of the raw material, mostly available as pellets, but the company’s Extrusion Center offers solutions for the very production of the finished compound. Especially the twin-screw extruder with corotating screws of modular design is ideally suitable to meet the requirements of the sensitive natural materials. Segmented screws and barrels developed and designed by the Technology Centre for specific raw material formulations, enable the processing of materials sensitive to shear stress and heat. Multi-venting and lateral feeding possibilities extend the application range for bio-fabrics, starch and liquids. The commonly used under-water pelletizing or dieface pelletizing is replaced by Reifenhäuser more and more by direct extrusion. Since there is no need for an intermediate compounding step, up to 30 % of the total production costs can be saved by direct operation. Upon request, blown and cast film lines are available to customers and interested parties for trials in the Reifenhäuser Technology Center. It is also possible to use pelletizing lines, depending on the application. www.reifenhauser.com bioplastics MAGAZINE [02/08] Vol. 3 27

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