TECHNOLOGY | PET RECYCLING
Right: At K2022 Starlinger unveiled the RecoStar PET Art recycling line for PET bottle-to-bottle applications. Compared to the previous model, it saves around 21% in production costs
phy is that waste material needs to be purified as much as possible before it is remelted, partly because the surface:volume ratio of flakes is much higher than that of granules. For the last four years, Erema has been working
with Polymetrix (previously a Bühler business unit, but now 80% owned by Sanlian Hope), which is expert in SSP technology, complementing Erema’s expertise in pre-treatment, says Heitzinger. Togeth- er they created the Vacunite system four years ago, which uses a processing environment completely free of oxygen to reduce degradation – and hence yellowing – of the PET. Erema has more recently developed EcoGentle technology, which involves the use of a new plasticising screw design to provide more gentle shear and extension, massive energy savings (due in part to reduced processing temperatures), and reduced AA levels. “[Production rates] Up to 6 tonnes/hour are possible with the new technology,” says Heitzinger. Measurements on a Vacurema Basic 2628 T system resulted in up to 12% saving in specific total energy consumption and between 30 and 47% energy saving for the extruder drive on Vacurema Basic plants from size 2021 upwards. Coperion has been in PET recycling for some 30
years, with systems based on its ZSK twin-screw extruders converting bottle flake to sheet, and bottles to fibres. It introduced systems for bottle-to- bottle around five years ago; these have a maxi- mum capacity of around 7 tonnes/hour. Coperion is now thinking about even bigger lines for bottle-to-bottle recycling. Like Erema, Coperion cooperates with Polymetrix on SSP equipment, while washing lines come from Herbold Meckesheim, which is now part of Coperi- on’s Recycling BU following parent company Hillenbrand’s takeover in July. Focus area is on larger capacities, upwards of around 2.5 tonnes/hour. Coperion claims to offer a technology that can handle virgin material and various recyclates (regrind, agglomerates or flakes). Everything can be processed together in the ZSK twin-
Below: Erema introduced the EcoGentle plasticising unit at K2022
screw extruder. One novel (albeit not new) solution that Coperion offers involves partial glycolysis, in which ethyl alcohol is injected into the ZSK extrud- er to reduce IV down to around 0.3; this enables particularly fine filtration of the material – which is useful for highly contaminated waste. After leaving the extruder, the melt can be mixed with virgin PET and the IV fully restored using liquid-state polycon- densation (LSP). Alternatively, it can be further depolymerised back to BHET monomer and further purified, and then repolymerised. “Glycolysis is becoming of more interest as a
way of processing very dirty material, but it does require LSP afterwards,” says Jochen Schofer, Head of Sales, Recycling, at Coperion. Bandera has a long history in equipment for PET sheet and film extrusion, but is a relative newcomer in PET recycling. It claims technology superiority with its twin-screw system over more established rivals’ single-screw systems. Bandera also cooper- ates with Polymetrix on systems with high levels of purification. German company MOPET, part of major recycling group Morssinkhof-Rymoplast, uses a Bandera/Polymetrix system rated at 5 tonnes/hour. NGR reported a “complete success” for its
presence at K2022. “In addition to numerous completed orders, a great deal of global interest in [our] innovative PET recycling process was gener- ated,” it says, noting that an increasing number of brand owners worldwide rely on its LSP technology for the processing of post-consumer PET. Günther Klammer, CTO of NGR, says: “We are finding that LSP is a real game changer in PET improvement and is rapidly gaining popularity due to its better energy efficiency and outstanding
20 PLASTICS RECYCLING WORLD | November/December 2022
www.plasticsrecyclingworld.com
IMAGE: EREMA
IMAGE: PETER MAPLESTON
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