PETpla.net Insider 07+08 / 2021

MATERIALS / RECYCLING PETplanet Insider Vol. 22 No. 07+08/21 www.petpla.net 23 Modular concept even as a retrofit solution for existing PET systems Crystallisation and drying are the key elements of the IR-Clean concept. While various required residual humidity rates are already distinguished in the drying process, delimitation of the performance is to be regarded as a possible feature depending on the specific application in the food grade process as well. The IR-Clean as a basic component con- sists of a continuously working infra- red system alone and - by reducing the residence time to significantly less than one hour - achieves the values imposed by the FDA within one single process step. The residual humidity levels of <300 ppm achieved simul- taneously are perfectly adequate for multi-screw extruders or single screw extruders including a degassing facil- ity. If lower limit values are required, as they can for instance partly be imposed by the European EFSA, it will be possible to extend the system by installing a downstream finisher, thus creating an IR-Clean+ system. This equipment allows an even greater reduction of the residual quantities of contaminants with high boiling points such as benzophenone and achiev- ing drying values of <50 ppm as a side effect. These features even allow the strict limits specified by the EFSA for bottle-to-bottle applications to be achieved. Depending on the portion of recycled material, this recondition- ing process can still be kept very short, not exceeding a total residence time of between <1.5 to <2.5 hours. Exactly like in IRD Drying Systems, the overall energy use can be reduced by up to 30% as compared to con- ventional systems. This is due to the fact that the material pre-dried and perfectly pre-heated in the IRD is transferred into the second drying or decontamination step, whereby the air volume and the heating capacity in the after-drying system / finisher can be considerably minimised. Both IR-Clean variants achieve the required values imposed by the FDA / EFSA already during the solid phase, i.e. independently of the plasticising or extrusion processes. Consequently, retrofitting of existing extruders (single screw, twin screw or multi-screw systems) is possible without any problems. What is more, possibilities do not just open up in the extrusion sector, but in PET preform applications as well. Meanwhile, the latest developments in the area of plasticising units of injection mould- ing machines even permit the direct admixture of rPET flakes to the virgin material. As a pre-drying process of several hours is also indispensable in any case, a combination of the IR- Clean basic unit with existing preform systems is the ideally suited solution. Apart from conveying and transport technology, filtration units and demist- ers, the package developed by Krey- enborg includes a comprehensive set of control systems that allow complete process monitoring, including the doc- umentation of process parameters. Results of the challenge test In the first step, commercial PET bottle flakes were used, which were contaminated with pre-defined model contaminants deliberately. The flake material so prepared was exposed to a customary washing process (15 min at 75 °C with 1% of sodium hydrox- ide), then flushed with cold water and pre-dried mechanically. This wash- ing process is part of the recycling process to be contemplated, but is already performed by the supplier of the PET flakes. The washed flake material was treated in the IR-Clean process, then analysed and submitted to a migra- tion evaluation procedure. The results have shown a cleaning efficiency of the IR-Clean process of 96-99% depending on the surrogate. On the basis of these values, a Letter of Non- Objection was issued by the US Food and Drug Administration FDA, which certifies the safety and soundness of the use of packaging material with a 100% rPET portion under the criteria C-G using the IR-Clean. The results may also be used within the bounds of the limit values determined by the European Authority for Food Safety, EFSA. To make its assessment, how- ever, the EFSA specifies 365 days at 25 °C for use of a packaging material, which corresponds for instance to a PET bottle for mineral water. In addi- tion, EFSA’s evaluation makes distinc- tions with respect to consumers and admissible values for babies, toddlers and adults. According to the company, the IR- Clean is an efficient and cost-effective concept which can be retro-fitted to existing PET systems. www.kreyenborg.com