PETpla.net Insider 07+08 / 2021

MATERIALS / RECYCLING PETplanet Insider Vol. 22 No. 07+08/21 www.petpla.net 22 FDA approval for Kreyenborg infrared rotary drum Recycling and Circular Economy are highly topical issues among both end consumers and legislators today, while plastic package and wrap are regarded critically in the food industry in general and in particular. When using PET post-consumer recycling ware for packages with direct food contact, however, a so-called Super Clean Process authorised by the FDA and / or EFSA is currently required and will be needed all the more in future. With its IR-Clean System, Kreyen- borg offers an attractive alternative for the subsequent use of PET post-con- sumer ware - this system allows direct decontamination without any kind of vacuum technology. On the basis of the experience gained with manifold installed IRD crystallisation and drying systems, the focus in the development of the IR-Clean (R) was in the first instance focused on the requirements and ancillary conditions prevailing in PET sheet extrusion processes. In these applications, a fairly high portion of recycled material originating from in-house and post-consumer flakes in the form of ground PET bottle flakes has always been fed into the pro- cess. PET post-consumer recycling ware, however, is used at 100% on very few occasions. This is due to the given circumstances in film production cycles, where edge trim and skeleton scrap from the thermoforming process are fed into the extrusion process on a regular basis. These are classified as post-industrial ground stock and do not need any Super Clean Process. In establishing standards and collecting systems even for PET trays, it is fore- seeable that these will be available as post-consumer ware in the near future as well and will thus be a useful com- plement to the rPET bottle flakes which are used almost exclusively today. As a result, this so-called tray-to-tray recy- cling process will open up even more potential for the use of rPET and, thus, for the R-Clean system. However, Super Clean Recycling Processes applied for the decon- tamination of PET flakes are in most cases based on the technically com- plex bottle-to-bottle processes, which do not only require food suitability, but also the development of intrinsic vis- cosity (iV) by Solid State Polyconden- sation (SSP). The vacuum technology required for this purpose is relatively expensive and requires intensive maintenance, though, due to the high complexity of the equipment needed. But as PET sheet extrusion requires much lower viscosities as compared to pre-form production processes, the increase of the Intrinsic Viscosity (IV) is in principle unnecessary. Even in preform systems, direct processing of rPET flakes has meanwhile become possible from a technical point of view - but in these cases, the portion of recycled material remains in the lower range of double-digit percentages, so that the impact on viscosity is insignifi- cant here as well. These special aspects of PET sheet extrusion have been taken into account consistently in the develop- ment of the IR-Clean concept, aimed at offering an effective, but at the same time easily and cost-efficiently man- ageable solution to end users, which can also be applied and retrofitted independently of the extruder type. Optimisation of a proven principle The IR-Clean represents an optimisation of the well-proven and already successfully used Infrared Rotary Drum (IRD) in terms of process technology. The standard process of crystallisation and drying of PET post-consumer bottle flakes in the IRD has been modified by a number of development features inside the machine and new process parameters - this has resulted in remarkably good decontamination results, which have been proven in several challenge tests carried out in collaboration with the Fraunhofer Institute IVV, Freising, Germany. The key to the good results lies in the general functional principle of the Infrared Rotary Drum - the small quantity treated in the process and the continuous movement of the material ensure a permanent surface exchange of the recycling material to be treated. At the same time, the material is continually circulated in the helical flights of the rotary drum and is in this way conveyed towards the sur- face by a repetitive movement. Addi- tionally, the helix welded inside the rotary drum guarantees an accurately defined flow of material (first-in / first- out) - which is an important aspect as regards the process monitoring and documentation requirements. This good mixing behaviour inside the rotary drum then combines the IR-Clean with the quick and direct heat input by infrared radiation. High temperatures can be achieved within just a few minutes thanks to the halo- gen radiation used, for the material is heated up directly without resorting to the influx of hot air. These are two of the most important criteria to fulfil for an efficient decontamination process: surface and temperature. Through- out this process, the IR-Clean basic concept can completely do without cooling water or pre-conditioned process air and - above all - without any expensive and high maintenance vacuum systems.