RIGID PACKAGING | INNOVATION
systems as the PET bottles they are attached to, before being separated in a float-sink tank so they can be further processed. German technology group Gneuss said that if treated with its Super Clean Process, the regrind can be reprocessed back into bottle caps, thus closing the recycling loop. The Gneuss OMNImax recycling system used in this process has undergone multiple tests and been awarded several food contact approvals and Letters of No Objection. The technology does not require any upstream or downstream process steps, which is of particular importance for PE as it must be treated at low temperatures and requires long residence times due to the slow diffusion processes involved.
Bottle caps
Gneuss says the OMNImax system purifies the polymer by subjecting it to highly efficient degas- sing using an MRSpure extruder and a robust vacuum system to remove volatile contaminants. The Multi Rotation System (MRS) is preceded by a melt extruder, which separates the plasticising and degassing/deodorising/decontamination steps so the process parameters can be optimised individu- ally. Downstream of the melt extruder the RSFge- nius filtration system removes hard contaminants by ultra-fine filtration, while its fully automatic, consist- ent operation cleans the contaminated screens before they re-enter the melt channel. Typical filtration finenesses in HDPE recycling are 125-300 µm. For HDPE milk bottle recycling, the material can be fed into the extruder via a 3C rotary feeder. Gneuss says a key feature of this system is its
flexibility as it automatically compensates for variations in the waste being processed in terms of moisture, contamination, viscosity, and bulk density. By adjusting the process parameters, material of consistently high quality can be produced and batch changes made quicker due to the short residence time so downtime can be reduced. This makes the OMNImax recycling system very cost-effective, the company says, especially in applications where food contact or odour reduction is required. Last year, sorting technology provider Tomra
partnered with Greenpath Enterprises, to install and optimise a flake sorting production line specifically to identify and separate polyolefin caps from beverage bottles. PE and PP have such close density characteristics that they can be difficult to separate, which is one reason mixed polyolefins are usually downcycled into more forgiving applica- tions that allow for higher levels of contamination. Discussions eventually led to Greenpath
adopting Tomra’s Innosort Flake sorter. “Develop- ing a mechanical sorting process to close the loop
www.plasticsrecyclingworld.com
for food-grade cap-to-cap recycling is ground- breaking,” explained Joe Castro, president of Greenpath Enterprises. “It’s a game changer to create a system to consistently separate mixed polyolefins by polymer and colour with high purity. Tomra’s technology is allowing us to purify at a higher level that opens up the whole circular opportunity with going cap to cap.”
PP identification Earlier this year Tomra introduced three new applications made possible by GAINnext, the company’s deep learning-based sorting add-on for its AUTOSORT units which makes it possible to quickly and efficiently separate food-grade from non-food-grade PET, PP and HDPE for the first time. By combining its traditional NIR, visual spectrometry or other sensors with deep learning technology, Tomra says it has developed a highly accurate solution capable of achieving a degree of purity upwards of 95%. (For more on Tomra’s technology, see feature on Sorting p13.) Partners in Project OMNI, a collaborative
research project in France, reported results demonstrating efficient decontamination of food-grade PP waste sorted by AI and computer vision. TotalEnergies, Recycleye and Valorplast took part in the project which they said has led to an alternative approach from digital and physical marking solutions for identifying PP packaging which require system-wide packaging changes. (For more on Recycleye’s technology, see feature on Sorting on p13 in this issue.) In a demonstration unit, Recycleye built and
trained an AI model based on wastes collected from five locations across France supplied and characterised by Valorplast. The AI and robotic sorting achieved a successful pick rate of 50% of the food-grade material, with >95% purity. This sorting activity produced material used for further
September 2024 | PLASTICS RECYCLING WORLD 31
Above: Food-grade sorting is now possible for PP, PET and HDPE, says Tomra
IMAGE: TOMRA
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