New Packaging Solutions Thanks to Rapid Cooling
5Pages

Thanks to watercooling, films can be produced with especially good optical and mechanical properties (figures: Windmöller & Hölscher) New Packaging Solutions Thanks to Rapid Cooling Extrusion. Water-cooling can achieve very high cooling rates for blown film extrusion. The result is soft, elastic films with near-amorphous molecular structures. The resulting low tendency to curl is a clear advantage when asymmetric multilayer film structures are processed further. LENNART EDERLEH TILL BERGMANN INGO PUTSCH trong pressure from competition in the packaging sector continues to push demands on the manufacturers of raw materials and machines to develop more sustainable packaging solutions. Translated from Kunststoffe 5/2014, pp. 26–31 Article as PDF-File at www.kunststoffeinternational.com; Document Number: PE111673 In the flexible packaging sector, pouches are showing the strongest growth. Their advantages of reduced packaging weight together with the resulting lower production and logistic costs are behind its expansion into new applications [1]. Water-Cooled Blown Film Extrusion Blown film extrusion and cast film extrusion are currently the conventional processes for manufacturing films for flexible packaging solutions. Whereas classic blown film extrusion with plastics melt by convective cooling exhibits schows relatively slow cooling rates of 20 to 80 K/m, cast film extrusion can achieve approx. ten times higher values thanks to contact cooling on the chill roll. However, with water-cooled blown film extrusion, even higher cooling rates can be achieved on the order to 1,000 to 3,000 K/m [2]. That means that films © Carl Hanser Verlag, Munich Internet-PDF-Datei. Diese PDF Datei enthält das Recht zur unbeschränkten Intranet- und Internetnutzung, sowie zur Verbreitung über elektronische Verteiler. Eine Verbreitung in gedruckter Form ist mit dieser PDF-Datei nicht gestattet.

Fig. 1. In water-cooled blown film extrusion, the film tube is extruded downward manufactured by this technology exhibit a range of properties that makes them especially interesting for flexible packaging. Due to such rapid cooling, crystallization processes can be inhibited, thereby enabling films to be produced with nearamorphous molecular structure while lending very good surface gloss and high transparency to such films. At the same time, the amorphous structure of the films makes them very soft and puncture resistant. Moreover, they can be processed very well by thermoforming. In...

and dried fruit. Where perishable food stuffs are involved, or longer shelf life is demanded, multi-layer barrier films are used. They are characterized by special functional layers that reduce permeability to water and/or moisture, gases and aromas. Typically speaking, these films have a symmetric structure with 5, 7, 9, or 11 layers, whereby the functional layers of PA and EVOH are arranged symmetrically in the middle of the structure (Fig. 4). Since these materials are incompatible with PE, bonding layers have to be included in order to ensure sufficient inter-layer adhesion. Each of the...

PE Frost line: 120–80 °C PE solidifies + shrinks PA solid PA Frost line: 180–140 °C PA solidifies + shrinks PE molten + elastic Die orifice: > 220 °C Entirely molten Fig. 5. With conventional blown film extrusion, curling often occurs on asymmetric structures cluded in a border layer of a multi-layered film (Fig. 4). This approach eliminates the laminating process, thereby reducing the overall cost of manufacturing the film. In both cases, higher temperatures can reduce sealing time in the FFS equipment and with it the cycle time. The marked difference in the melting temperatures of PA and...

a soft, elastic film characterized by very good weldability. The resulting low tendency to curl is a clear advantage when asymmetric multi-layer composites are processed further. REFERENCES 1 N.N.: Converted Flexible Packaging - Industry Market Research, Market Share, Market Size, Sales, Demand Forecast, Market Leaders, Company Profiles, Industry Trends. Industry Study 3094, The Freedonia Group Inc., Cleveland, OH, USA, November 2013 2 Leopold, T.: Film Production: System Options for Wafer-Thin Protection, Kunststoffe international 102 (2012) 7, pp. 45-48 Fig. 7. Pillow pouches for edible...