Extrusion International 1-2024

29 Extrusion International 1/2024 RECYCLING – CASE STUDY New Filtration Compounder for Higher Product Quality and Reduced Energy Consumption in PCR and Polymer Recycling For recycling of post-consumer recyclate (PCR) or any highly contaminated polymer, Coperion has developed the innovative ZSK FilCo filtration compounder that allows filtration and compounding in a single production step. W ith the new ZSK FilCo sys- tem, waste plastic is fed into a ZSK twin screw extruder, where it is melted, homogenized and devolatilized. The melt is then fed through a filter to remove all con - taminants before it is fed back into the same ZSK extruder to be com- pounded with reinforcing materi- als or fillers. Compared to the two-step production lines that have been the norm until now, Coperion’s new ZSK FilCo is distinguished by a markedly more streamlined equipment set-up. Energy con- sumption and emissions for the extrusion process are reduced by more than 50%. Moreover, the ZSK FilCo is able to achieve a significantly higher product quality. Recompounds can be produced much faster and Coperion K-Tron gravimetric feeders ensure the high- accuracy incorporation of additives for an optimal result. Filtration and Compounding in Single Production System In conventional recycling plants, PCR and contami- nated polymers must first be melted using a single or twin screw extruder, then filtered and pelletized there - after. For plastics upcycling purposes the filtered recom - pounds are then fed into a separate twin screw extruder where they are again melted and compounded with the aid of additives, reinforcing materials and fillers before finally being pelletized. In this production set-up, en - ergy for melting must be introduced twice. Along with high energy consumption, the recyclate is subjected to high thermal stress which in turn results in increased degradation, shortening of polymer chains and thus a reduction in product quality. The newZSK FilComakes it possible tomelt, filter, com - pound and pelletize recyclate in a single production sys- tem. Waste plastic is fed into the ZSK extruder in the form of regrind, fiber pellets, film flakes or agglom - erate and is melted, homogenized, and devolatilized there, together with all its components (all polymers, PE, PP, PA, PS, PC/ABS, etc.). Next the melt is fed through an integrated filter that removes all contaminants. Reintro - duction into the ZSK extruder process section follows, where reinforcing materials such as glass, wood, and car- bon fibers, or fillers such as talc, CaCO3 or ground PEX are added, after which the recompound is pelletized. The ZSK FilCo’s space requirement is comparatively low. All product streams are added gravimetrically to the process with no fluctuations. The recyclate needs to be melted only once. The ZSK FilCo thus consistently achieves a higher product quality thanmulti-part systems that have been typically used for this recycling process. Moreover, energy consumption and emissions for the extrusion process are markedly reduced with the new solution. Thanks to the twin screw extruder’s high me- chanical energy input, the melting process is more en- ergy efficient than with a single screw extruder. In ad - dition, the second melting process for compounding is completely eliminated in the ZSK FilCo solution and pel- letizing of the intermediate compounds is also omitted. The new ZSK FilCo filtration compounder markedly simplifies recycling of post-consumer recyclate (PCR) and any highly contaminated polymer: Filtration and compounding can now take place in one single production system (Photo: Coperion, Stuttgart Germany)