Deinking of Post-Consumer Waste Flakes – a Novel Approach for the Objective Assessment of Ink Removal on Inhomogeneous Film Fractions

The deinking of plastic packaging waste offers the potential of decreasing contamination and thus increasing the overall quality of recycled plastics, enabling their use in more demanding applications. The removal of printing inks from the usually heavily printed flexible polyethylene (PE) plastic films yields transparent flakes that generally allow the recycling into materials with better mechanical properties as well as lower odor and optical defects. However, for flexible PE packaging waste, the deinking is not yet implemented on an industrial scale and there is currently no objective methodology to evaluate the deinking effect on those inhomogeneous flakes. In this study, a novel approach for the objective assessment of the ink removal on flexible post-consumer waste (PCW) is proposed. Via an image-based analysis, the transparency of the flakes is transformed into the 8-bit grey scale, and the calculation of statistical characteristics from these grey value distributions allows to quantifiably compare the deinking efficiency of several experiments. Using this analysis method allows to investigate the general behavior of contaminated PCW materials in deinking and to identify the most effective parameters for ink removal.