PETpla.net Insider 06 / 2020

MATERIALS / RECYCLING PETplanet Insider Vol. 21 No. 06/20 www.petpla.net 35 market price thereof, the charge for recycled PET has continuously risen over the last three years. Companies now have to pay about 20% more for rPET than for the original material – also because the supply cannot meet the growing demand. High standards of quality Not only do hurdles have to be overcome at the raw materials end; some beverage producers also have reservations. They often fear that the rPET material may discolour or that the level of intrinsic viscosity may drop. Another issue is safety stand- ard and thus the harmlessness of the material. Time and again the question is raised as to whether multiple recy- cling can affect the quality. Although this has not yet been fully researched in practice, one thing is clear: as the polymer chains reform, no compro- mises must be made as regards the material quality as long as the addi- tives can be completely separated off. The European PET Bottle Platform (EPBP) is just one of the institutions that helps to assure high standards of quality with its clear specifications and certifications. Whereas just a few years ago experimentation was rife and the beverage and food industries gained their experience with recycled PET through sheer trial and error, from a technical standpoint there is now nothing preventing the global use of high percentages of recycled PET. More and more beverage pro- ducers and brands are even opting to use bottles made of 100% recy- clate. Where this is not yet the case, voluntary commitments are being publicised; Poland Spring, one of the biggest water brands in the USA, and Evian want to use recycled PET only by 2025. The other brands by Danone Waters, Pepsi and Coca-Cola plan to introduce a worldwide quota of 50% by this date. Their objective? They would like the consumer to interpret the slight graying that can occur when PET bottles are recycled several times over as a hallmark of quality for sustainable packaging. Sound expertise: studying rPET since 2012 The KHS Group has been exam- ining the use of recyclate for some time now – in fact since 2012. KHS’ Bottles and Shapes service program focuses on the practical application thereof on the stretch blow mould- ers and indeed all of the filling and packaging lines engineered by the Dortmund systems supplier. “We run tests to qualify recycled PET so that we can tell our customers in advance which impact the mate- rial will have on the blow moulder and bottle quality,” says Arne Wiese, product manager for Bottles & Shapes at KHS Corpoplast. The aim is to be able to quantify the vari- ous different qualities. In doing so, KHS must work closely with preform manufacturers. They are ultimately often the companies which subject the washed PET flakes or rPET granulate to further thermomechani- cal processing and prepare them for injection moulding. “We’re consult- ing with all of the major plastics processors in Europe on this topic,” Wiese emphasises. KHS is liaising with various engineering companies on preform manufacture. Thanks to this close cooperation, data from the injection moulding process can be used just in time to adapt the stretch blow moulding process. Adaptations needed “With recyclate the colour can vary from batch to batch, for instance,” is how Wiese outlines one of the challenges faced. “Darker material absorbs heat better. The lower heating capacity requires less energy. This makes produc- tion more efficient yet means that adaptations must be made to the blow moulding program on the stretch blow moulder.” It is there- fore essential that the effects are quantified, he continues. Another challenge is the intrinsic viscos- ity (IV). “The longer the recyclate is boiled under vacuum, the longer the polymer chains become. This means that the IV increases and the quality improves. However, this results in additional costs which not everyone is prepared to invest,” Wiese adds. “Here, we have to come up with ways of redistributing the material from uncritical areas – the bottle base in the case of still water – to more critical zones.” Experi- ence shows that manufacturers of premium brands – whose contain- ers have thicker walls – have less cause for adjustment than discount- ers, where all of the lightweighting options have often been exhausted. This is where recyclate can reach its limits. In this context a technology developed by KHS in cooperation with inspection technology manu- facturer Agr International scores points: Unit Mold Control, a digital, automated control system which regulates the blow stations on the InnoPET Blomax individually. It helps to control material distribu- tion more precisely, reduces varia- tions in the wall thickness by up to 30% and lessens any fluctuations in quality during stretch blow moulding. “This is especially relevant when using recycled PET,” explains Frank Haesendonckx, head of Technol- ogy at KHS Corpoplast. “Here, the quality of the material can vary, meaning that the lower the preform weight, the greater the fluctuations in material in the bottle and the more unstable it becomes.” During con- tinuous wall thickness inspection the new system identifies any unwanted material displacement and auto- matically counteracts this, states Haesendonckx. “Unit Mold Control combines weight reduction with bottle stability and is thus one of the many sustainable and effective answers KHS has to the challenges thrown up by the current packaging debate.” According to Bottles & Shapes expert Arne Wiese there are no con- vincing arguments against the use of recycled PET in beverage bottles. The only relevant difference he sees between virgin PET and recycled material is the slightly darker colour. This is a question of sorting, how- ever – and only really visible in water bottles. With other beverages, such as the Beyond Juice bottle developed by KHS which is made entirely of recyclate, the consumer would not even notice the difference once the bottle is filled. As far as the mechanics are concerned, there is nothing to stop companies convert- ing to rPET, providing ideal condi- tions for the creation of a functioning circular economy. www.khs.com