Compensating Material Quality Differences
By using more recycled material, the process needs to handle an additional component with much impact on the final product. „The quality of the recyclate containing dirt particles fluctuates significantly. Thus, we cannot guarantee that the quality of the final product is always the same. We needed to enable ourselves to react flexibly to varying levels of contamination, „says Sven Pastrik, Manager of Extrusion at RKW in Echte.
As a first step, continuous screen changers were implemented. These filters allow operators to change screens without interrupting production and adjust screen fineness for different production batches based on quality requirements. "As a result, we have significantly fewer machine downtimes, and the productivity of our plants has increased significantly," reports Sven Pastrik. "We can compensate quality differences in the material very well and process high proportions of recyclate, for example, in our FFS bag production."
The use of recyclate in RKW ProVent plastic bags, commonly used in the construction and chemical industry for packaging powdery goods, is becoming more prevalent and continues to increase. "Here, it is essential that the protective and barrier properties are guaranteed and that no dust, dirt, or moisture can penetrate," explains Thomas Steffen. "We inspect our films with optical systems before further processing. But for us, finding defects is not a strategy; the goal is to prevent them altogether. We knew that the proportion of recycled material would keep increasing and that we would have to redefine the filtration process when designing a new 5-layer line."
The goal was a system in which high-quality films could be produced in a continuous, automated process. "We needed a plant concept with fast setup and changeover times. We don't want to deal with screen changes and thus line downtimes often and for a long time, but rather ensure an extrusion process that is as uninterrupted as possible."
RKW had a positive experience with Nordson® BKG® screen changers, leading them to approach the filter manufacturer again. Their new five-layer plant is now equipped with continuous BKG screen changers and has been running successfully since 2021. "We are very satisfied with the performance of the system. Thanks to continuous filtration, we produce high-quality films with high recycled content in an uninterrupted process and can cover a wide application window," explains Sven Pastrik.
At RKW and Nordson, they were certain that the development must go further. "The use of recyclates will continue to increase in the future," explains Stefan Wöstmann. "The EU's Green Deal and national packaging laws are massively increasing the pressure and forcing system - and component manufacturers - to act."