Guidelines for tracer printing in packaging for effective sorting, management after use

CIRCULAR FoodPack aims to facilitate the circular use of plastic packaging, specifically addressing the most sensitive product category: food packaging. One of the main objectives in the project was to design, develop and upscale sortable and fully recyclable flexible packaging materials with post-consumer polyethylene recyclates (PE PCRs). The approach to achieving recyclability focuses on the use of polyethylene (PE)-based monomaterial multilayer laminate structures designed for flexible food packaging applications. According to the European Food Safety Authority (EFSA) requirements, PE PCRs intended for use in flexible food packaging must be produced from food packaging input waste. Therefore, to enable closed-loop recycling of these recyclable food packaging materials after their end-of-life, it is necessary to sort them out of a mixed food- and non-food post-consumer waste streams. This sorting process is achieved through the implementation of Tracer-Based-Sorting (TBS) technology. The TBS technology enables the separation of food packaging items from non-food packaging with a sorting purity of 99% by applying fluorescent tracer particles to flexible packaging. The sorted food packaging items are then recycled, and the resulting PE PCRs are reintegrated into the newly designed flexible food packaging materials. Within the CIRCULAR FoodPack project, this has been successfully achieved by embedding PE PCR layer between two functional barrier layers of the packaging laminate. The tracers are integrated into the laminate structure so that they are easily detectable during the sorting process, do not compromise the intended use of the packaging as food-safe, and can be removed during subsequent recycling processes. This is accomplished by incorporating the tracers into the printing inks, which are later removed through deinking processes also developed in the project. This deliverable includes findings regarding the printability of the newly developed tracers after mixing them with printing inks. Various printing techniques were screened, including gravure, flexo, and inkjet printing. Gravure printing has been identified as the most suitable technology for the application of tracer-containing inks. Considering the location of the tracer-printed layer within the laminate, both surface printing and reverse printing are viable options. However, reverse printing is advantageous due to superior scratch resistance and improved surface finish. Guidelines have been established for tracer printing in flexible packaging, ensuring the effective sorting of food packaging items at the end of their life cycle. These guidelines address the optimal location of tracers within the flexible packaging laminate, the type and concentration of tracer used, particle size, the selection of appropriate ink binders and the suitable printing processes. Note: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101003806.