Melt processing decolouration of plastics
Recycling of plastics in respect to circular economy is getting a more important topic every year, due to economic reasons as well as because of the legislation at European level. One of the most prominent and persistent problems is the separation of contaminants, especially colours from plastics. Here are several approaches in the field – some working with a washing type of process to dissolve inks, others are dissolving the plastic, filtering off the colourants and precipitate the plastic again. Nevertheless, these methods have some drawbacks in regard to the energy consumption to dissolve the materials as well as to regain the solvents and also the complete separation of the solvent from the polymer is a demanding task. Furthermore, these methods typically do not work on all colours in the market. In addition, there are ecological restrictions when using solvent in such processes.
Therefore, the aim of the work is to investigate different approaches to separate organic pigments from plastics, where the main focus in on meltprocessing, as these has a high chance of being applied in the future. The approach aims to use „bleaching agents“, which at least decolour the pigments, and where the generated fragments then can be degassed in the process, to estimate any hazardous potential. This approach will be validated at a recycling machine.