MODULAR CONCEPT ALSO AVAILABLE AS A RETROFITTING SOLUTION FOR EXISTING EXTRUSION LINES
The crystallization and drying concepts form the basic building block of the IR-CLEAN concept. If in the drying process, a differentiation is already made between the various residual humidifies required, the output may also be delimited in the Food Grade Process depending on the application. The IR- CLEAN® as a basic unit consists of an Infrared System alone and achieves, with a residence time of clearly below one hour, the limit values required by the FDA in one process step*. The residual humidity of < 300 ppm achieved at the same time is also completely sufficient for multi-screw or single screw extruders including degassing. If any lower limit values are required as for instance partly by the European EFSA, the system may be extended with a Finisher mounted downstream towards the IR CLEAN+ System. This extension consists of an additional drying hopper with a dry air system which primarily helps extending the residence time under high temperatures. This helps to reduce the residual quantities for contaminants with high boiling points such as benzophenone, and delivers as a side effect drying values of < 50ppm. This post-conditioning procedure can still be kept very short with a total residence time of 1.5 hours. Analogously to the IRD drying system, the entire energy consumption is reduced by up to 30% as compared to conventional systems. The reason for this is the fact that the material that has already been pre-dried and perfectly preheated by the IRD will be forwarded to the second drying or decontamination step, which allows minimizing the quantity of air and the heating capacity in the subsequently dryer / finisher substantially.
Both IR-CLEAN® variants achieve the values relevant for the FDA / EFSA already without taking into account the extrusion process, so that its retro fitting in existing singly-screw, twin-screw or multi-screw systems is possible without any problems. Apart from the conveyor technology, filtration units and demisters, the package developed by KREYENBORG also includes a comprehensive control package for the complete process monitoring including the documentation of the process parameters.
RESULTS OF THE CHALLENGE TESTS
The original material used for the Challenge Tests was a commercial PET bottle flake that was deliberately contaminated with defined model contaminants (surrogates). These prepared flakes were subjected to a commercial washing process (15 min. at 75 °C with 1% of caustic soda) and were then rinsed with cold water and mechanically pre-dried. This washing process forms part of the recycling process to be observed, but is also already ensured by the Supplier of PET Flakes.
The washed flakes were treated in the IR-CLEAN process, then analysed and finally subjected to a migration evaluation. The results show a cleaning efficiency of the IR-CLEAN process, depending on the surrogate, of 96 to 99%. A Letter of Non-Objection by the US Food+Drug Administration FDA was issued on the basis of these values, which confirms the harmlessness of the use of packing material with a 100% R-PET share under the criteria C-G (see table) already with the basic module IR- CLEAN®.
The results may also be used for the limit values determined by the European Authority for Food Safety EFSA. For the evaluation, however, the EFSA presumes a use of the packing material of 365 days at 25 °C, which is for example equivalent to a PET bottle of mineral water. On the other hand, the EFSA evaluation also makes a differentiation regarding the consumer and makes a distinction between admissible limit values for babies, toddlers and adults.
With regard to the later application, however, specifically the enhanced approach was selected, according to which thermoformed trays from PET Sheet Production are usually subject to other conditions of use than PET Bottles. Based on a typical use or the storage of a food package for e.g. meat products of max. 30 days at 6%, up to 100% of PET recycling material may be used from the IR CLEAN+ process for all scenarios.