Simulation of the Decontamination Efficiency of PET Recycling Processes based on Solid-state Polycondensation

摘要

The recollection rates for postconsumer poly(ethylene terephthalate) (PET) bottles and the recycling capacities are increasing year by year. The postconsumer PET bottles were recycled either to fibres or to new packaging applications. For packaging applications, the so-called super-clean recycling technologies are applied to decontaminate the postconsumer PET pellets. Most of these processes are based on solid-state polycondensation processes. Because experimental determination of the cleaning efficiency is a time-consuming and expensive procedure, it would be useful to predict the cleaning efficiencies, e.g. for process development and optimization. Within this study, the decontamination kinetics of a PET super-clean recycling process based on solid-state polycondensation was determined. From the decontamination kinetics, the diffusion coefficients were calculated. By use of the diffusion coefficients, the decontamination kinetics was simulated using migration modelling approaches for spherical pellets. The result of this study shows that the decontamination of PET pellets in solid-state polycondensation processes follows Fickian laws. The diffusion coefficients of the investigated migrants are not influenced by vacuum or inert gas process conditions. The diffusion equations used in commercially available software packages for migration calculation can be used for the simulation of the decontamination efficiencies of PET recycling processes.