Erema spent two years intensively researching, testing, and further developing the twin-screw extruder concept presented at K 2022. Working together closely with customers, they have developed a series production solution that is particularly adept at recycling production waste consisting of demanding multi-layer films. The technology also opens up new perspectives for thin-walled post-consumer regrind material.
Producing high-quality recycled pellets using complex input materials such as multilayer film consisting of PE-PA or PE-EVOH is a major challenge for the recycling process. This is where the new TwinPro comes in, with its key feature of highly efficient homogenisation.
The first stage of homogenisation takes place in the preconditioning unit (PCU), which shreds, heats, dries, compacts and buffers the input material. Optimised material preparation right at the start of the recycling process lays the foundation for consistently high-quality end products. Thanks to patented Counter Current technology, the extruder, which is directly coupled at a tangent to the PCU, is continuously filled with heated and pre-compacted material. Even with low bulk density material like film waste, the PCU is able to deliver full throughput. The PCU covers an exceptionally wide bandwidth of input materials, with bulk densities of 30 to 800 grams per litre reliably processed in a single work step, without the need for separate agglomeration, weighing or a stuffing unit.
This is followed by intensive homogenisation in the twin-screw extruder, which is essential for multilayer films so that the different polymer types are mixed in the best possible way. This produces recycled pellets with the improved mechanical properties needed for reuse in multi-layer films.
Originally developed for complex film waste, the TwinPro now opens up new capabilities for using twin-screw extruders in the recycling of 3D packaging. The trend towards thinner wall thickness for plastic packaging increases the demands on extrusion technology. One particular application is PP flakes that have been sorted and hot-washed from very thin-walled packaging such as yoghurt tubs. This is also a challenging application due to very low bulk density and possible moisture fluctuations of the input material. However, the TwinPro can easily process this type of thin-walled packaging that often causes problems in the material feed on conventional twin-screw systems because of its low weight and high volume. What is more, the PCU reliably removes residual moisture from the washing process and also deodorises the material.
