PETpla.net Insider 03 / 2011

MATERIAL / RECYCLING 12 PET planet insider Vol. 12 No. 03/11 www.petpla.net An innovative approach from Unisensor/Germany The power of sorting by Wolfgang von Schroeter The Powersort sensor system identifies the “good material” in a PET flake flow using high-speed laser spectroscopy, separating it from various contaminants in a single pro- cess step. Unisensor, the makers of Powersort claim that, depending on the type of impurity, separation levels of up to 98% can be achieved with a minimum loss of product. It is common knowledge that PET waste from clean bottles makes clean PET flakes or pellets. But col- lected bottles are by no means all clean. When collecting PET bottles all ingredients – visible or invisible - are collected as well. The visible ele- ments are metal, labels, etiquettes and glue residue, caps screwed and unscrewed, external dirt and concrete material contamination. Non-visible elements include components inte- grated into the PET material like PVC, PC, PA 66, additives and blends. The number of possible impurities and material defects is on a permanent increase – one reason being a longer service life time, another the growing complexity of final applications and the repeated recycling of products. Thus the challenges for the industries involved are not going to go away. Most of these unwelcome ingredients - if not all - need to be removed for food contact approved PET flakes or pellets. The higher the contamination of collected bottles, the more complex the recycling. There is no single universal answer to solve the problem. Many individual proposals, mainly devel- oped over long periods of trial and error, have resulted in the possibility of re-using recycled material. Some of these proposals are suitable for less demanding applications such as for fibre, sheet and strapping. Others require great effort to meet very par- ticular applications, such as for RPET bottles for beverages. Nevertheless and despite numerous costly efforts – the recycling methods known so far were unable to identify and remove all of the unwanted contaminants. An innovative response to the problem recently came from Unisen- sor – Sensorsysteme GmbH, located in Karlsruhe, Germany. They brought to the recycling equipment market their Powersort sensor system which is able to detect and separate from a PET flake product flow invisible com- ponents, such as additives or PA 66, PVC or silicone and any other barrier substances used in food packaging. The first Powersort was sold in 2007. To date, the company has sold units to leading recycling firms in Europe, the US and most recently to Mexico. Powersort uses a measuring proce- dure based on high-speed laser spec- troscopy. It identifies the “good mate- rial” in a PET flake flow on its specific opto-electronic spectrum, separating it in a single process step from various contaminants previously defined. The detection system excites the plastic particles with a powerful laser light, analysing the light spectrum that the individual part then emits. Each mate- rial has its own spectrum, or its own physical fingerprint. The sorting system separates out material whose spectrum differs from the reference spectrum of the “good” material. This means that