MATERIALS / RECYCLING PETplanet Insider Vol. 26 No. 10/25 www.petpla.net 24 decontamination, SSP (Solid State polycondensation) and granulation for use in bottles for direct food contact applications. The ‘super-clean’ rPET process is the conventional recycling process, which has been enhanced with an integrated decontamination step (as specified by FSSAI or any other regulatory body) to remove absorbed contaminants through a combination of surface treatment, high heat, and/or high vacuum in a controlled environment so that the output can be used for direct food contact applications. It has multiple levels of decontamination: Pre-drying, plasticising, filtration, pelletising, crystallising, cooling, bagging. The decontamination process happens in the extruder and in SSP. The SSP process is conducted in an inert gas atmosphere. Melt-in recycling Virgin PET (vPET) production operation enhanced with the ability of incorporating PET flakes in the molten form. It is decontaminated through a combination of high heat and high vacuum Paste-in recycling Virgin PET production operation enhanced with the ability of incorporating PET flakes in the paste form, via partial glycolysis. It is equipped with an integrated system of removing absorbed contaminants via chemical distillation, vacuum degassing etc. Chemical recycling or advanced recycling In the long term, demand for rPET resin cannot be met by mechanical recycling alone. Interest in nonmechanical PET recycling is growing worldwide, including in India. This also includes chemical recycling. This is a chemical reaction process in which PET flakes are completely depolymerised into purified ethylene glycol and terephthalic acid (or dimethyl terephthalate) or bis(2-hydroxyethyl terephthalate). According to the guidelines of ISO 15270, the purified, depolymerised monomer can be used to produce virginquality polymers. The manufacturer of FCM-rPET, which uses chemical recycling processes, submits an application and the relevant documentation to the food authority (in accordance with Form 1 of the FSSAI in its guidelines for the approval of recycled PET as a food contact material FCMrPET). Enzymatic recycling Enzymatic recycling is a rapidly emerging technology worldwide with great futuristic potential in India. It enables the recycling of polyester waste, most of which has not been recycled to date. All this waste could be recycled on a large scale tomorrow, so the potential of these waste materials in India is enormous. It offers the opportunity to use far more economical raw materials, as this process can utilise all types of polyester textile waste as well as those PET bottles (like coloured or multi-layered bottles), which are difficult to recycle. The development of bio-recycling technologies to redesign the life cycle of PET plastics and polyester textiles faces the challenge of transitioning from end-of-life to end-of-cycle models. First, it is important to understand the basic principle of enzymatic recycling. Depolymerisation technologies break down plastics such as PET into monomers (PTA and MEG) so that they can be reprocessed into new plastics (PET resin). This process breaks down molecular chains and decomposes plastics into monomers, which can be used to produce new high-quality plastics (PET) after purification. The enzymatic depolymerisation process is promising because it uses enzymes as catalysts to break down polymers. One of the technology providers has successfully established a link between polymer science and enzymology. The process enables the enzymatic recycling of PET and produces monomers similar to those found in virgin material. It will have a high purity and consistent rPET quality, allowing direct contact with food. Process Enzymes are currently used in many everyday applications (detergents, biofuels, food, textiles and paper), but their use for degradation and thus enabling the recycling of plastics and textiles for industrial purposes has not been considered in the past. These enzymes have been developed to optimise polymer degradation activity. Their activity, including their thermostability, is necessary for efficient and competitive use in industrial recycling processes. These optimised enzymes are used in enzymatic recycling (for both PET packaging and textiles) and increase the composting efficiency of biodegradable plastics (PLA).
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