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PLA Recycling Mechanical

PLA Recycling Mechanical PLA recycling by Steve Dejonghe Looplife Polymers Hulshout, Belgium When PLA was firstly introduced, the main proposal was a shift from fossil resources to renewable ones. But the remarkable versatility of the material also opened new recycling perspectives, further enhancing its environmental profile. Several complementary end-of-life options are therefore possible (ranging from composting to chemical recycling), the most appropriate recycling channel being ultimately determined by the nature of PLA waste. While growing steadily, bioplastics currently account for a marginal share of the global plastic production. Despite the emergence of small PLA post-consumer streams, field experience reveals the difficulties to properly identify recycling channels and shows the challenges to connect streams and potential recycling units. Mid-2000’s, Galactic, a leading actor of the green chemistry, started the first PLA recycling projects in Belgium. Partnering with international key stakeholders, the company was able to build an extensive know-how while acquiring a concrete market experience over the last few years. But to allow further industrial development, Galactic decided end of 2012 to transfer its PLA recycling projects to third parties. The mechanical recycling department has been recently acquired by Devetex, a company active since 1995 in the recycling of off-spec material issued from the textile industry (namely PA66 and PP). As post-consumer streams grew, a dedicated line was also installed in 2005 to handle soiled carpet waste. All know-how and experience acquired by Galactic and Devetex are now combined in one company, LoopLife Polymers, located in Hulshout (Belgium). LoopLife Polymers intends to support market demand for rPLA by proposing a tangible industrial recycling solution for various compatible waste streams, either post-industrial or post-consumer. For this purpose, the company continues to develop national and international partnerships and is setting a first demo-plant for PLA post-consumer streams (e.g. PLA cups). The philosophy is to turn less established waste streams into useful raw material. LoopLife Polymers and NatureWorks are collaborating to map out regular streams of post-industrial and postconsumer waste which can be considered for mechanical recycling. An effective system to valorize waste is an essential part of the biopolymer value chain optimization. For compatible waste streams, mechanical recycling remains a highly interesting option. With an adequate control of the process, thermal degradation is kept to a minimum and the resulting r-PLA still shows adequate mechanical and thermal properties for a wide range of applications. It also combines the advantages of being both bio-based and recycled, with expected benefits in Life Cycle Assessment studies. Furthermore, LoopLife’s recycling process is optimized to lessen environmental impacts. LoopLife Polymers can therefore be a partner; • as an output channel for various PLA waste streams (either Post-industrial, Post-consumer or closed-loop events), with no volume restrictions of compatible streams • as a supplier of several high-quality r-PLA grades with constant specifications Such grades are especially interesting for cost-sensitive applications where prime PLA cannot be considered, helping therefore to broaden the use of PLA. These r-PLA grades are well suited for less-demanding, non-food applications. At term, tailor-made grades could be developed to meet specific customer’s requests. 48 bioplastics MAGAZINE [03/13] Vol. 8

PLA Recycling Supporting ecological advantages A division of Starlinger & Co GmbH (Vienna, Austria), world market leader in the field of machinery and complete lines for woven plastic packaging production, Starlinger recycling technology provides machinery solutions for the recycling and refining of a wide scope of plastics such as PE, PP, PLA, PA, PS, BOPP and PET. Starlinger recycling technology has focused on production waste: although companies emphasize the concept of zero-waste, production waste cannot be avoided completely. Mechanical recycling is the answer as use of rPLA can be up to 100 %. Decisive for the quality of the end product: Input material and recycling process PLA is now used in many applications, such as film for packaging, containers for juices, filaments for fabric, etc. New technologies allow the recycling of PLA in a way that high-quality re-granulate becomes a cost-saving alternative to virgin resin. To ensure the production of high value regranulate – which is the requirement for improving cost efficiency and stability of the production process – an analysis of the input material and the right choice of equipment is paramount. Starlinger recycling technology offers two suitable systems for the recycling of PLA production scrap: recoSTAR basic and recoSTAR universal. Technology principles The recostar basic uses an agglomerator for cutting the material by means of knives on a rotating disc at the bottom, suitable for film and pre-cut material. This frictional process heats and dries the mixed material, densifies it and brings it close to the melting point before it is fed into the extruder. Six extruder sizes from 150 – 2,200 kg/h are available. Equipped with a heavy-duty single-shaft cutter arranged parallel to the extruder, the recostar universal enables also the processing of film and additionally of hard-togrind materials such as containers, fibres and start-up lumps. The hydraulic pusher in the single shaft cutter presses the material against a water-cooled rotating shaft and thus provides efficient crushing. The new feeding system into the extruder accounts for increased operational reliability, simplified operation, and lower energy consumption and higher output at the same time. Five extruder sizes from 150 – 1,300kg/h are available. Vacuum treatment, fine filtration and pelletising It’s all in the melt: To ensure high-quality regranulate although PLA is hygroscopic, both recycling systems can be equipped with an extruder vacuum unit in order to extract volatile contaminants and reduce viscosity loss in the melt. A variety of melt filtration systems ensure clean, high-grade melt: melt filters with and without backflushing, and power backflush filters are the most common. The choice of filter type and size depends on the type and amount of contaminants (e.g. paper) and required fineness (50 µm positively tested). Customers can choose water ring pelletizing, manual and automatic strand pelletising or underwater pelletising. MT bioplastics MAGAZINE [03/13] Vol. 8 49

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