TECHNOLOGY | POST-INDUSTRIAL RECYCLING


IMAGE: COPERION


Within the ZSK Mc18 twin screw extruder, shredded production waste is processed such that it can be added back into the multi-layer film production process with high-end product quality


closed-loop approach.” Coperion’s ZSK and STS technologies are also being used for the recycling of post-industrial waste. The company says that production waste from industrial plastics manufacturing is becoming increasingly valuable in times of rising raw materi- als prices and increased environmental pollution. Before recyclate can be processed, the waste plastic must first be shredded. This is then deliv- ered via conveying lines and feeders, together with other recipe components, to the compounding process.


In compounding, the melt is devolatilised and conveyed towards the discharge. Usually, material is fed continuously to the screw via feeders and hoppers from above. However, with the general trend towards rising throughputs the fact that single-screw extruders are fed volumetrically limits their processing capacity. There is also an addi- tional problem encountered in processing waste plastics – single screw extruders exhibit relatively low dispersion and devolatilisation output. De- pending on the available raw material, this can lead to inadequate compound quality, says Coperion. Coperion is offering a twin-screw extruder solution for compounding through two different series that are suited for recycling of post-industrial waste: the high-end ZSK type and the STS series. For both series, feeding of additives, filler and reinforcing materials into the process section takes place using feeders. The extruders can process high percentages of calcium carbonate, talc, glass or natural fibres, due to the extrud- ers’ high torque and optimally adjusted process parameters. Homogenisation and devolatilisa- tion take place with significantly higher intensity than with the single-screw extruder. This also has a positive effect with


26 PLASTICS RECYCLING WORLD | May/June 2021


regard to odours that may be present in the secondary raw material, which are effectively removed. “When recycling plastics, it is necessary to adapt the process parameters and recipes to the various raw materials,” says Jochen Schofer, Business Segment Manager, Recycling & Direct Extrusion. “With their flexibility and high torques, ZSK twin-screw


extruders are optimally suited for processing even the most difficult raw materials to good product quality – and they do it at throughputs that are economical. By using the side devolatilisation unit ZS-EG, not only are unwanted gases removed but operational safety of the entire vacuum system is increased. This applies even for highly volatile viscosities.” Next Generation Recyclingmaschinen (NGR) has developed the NXT:GRAN shredder-feeder- extruder machinery combination as the next generation of S:GRAN recycling machines. The new NXT:GRAN series design provides up to 40% higher throughput rate, simplified control and operation, and has updated safety concepts. NGR says that the technology is ideal for plastic waste generated in the product manufacturing process, such as pipes, films, fibres or blow moulded parts. S:GRAN has been in operation for over two decades. Equipped with a large shredder, feeder and extruder, it repelletises internal scrap for re-use in the primary production process. While in the 1990s a few processors relied on internal recycling to minimise costs, now within the circular economy, recycling equipment is essential to maximise the value in production scrap. As a result, demands placed on in-house recycling are increasing in terms of higher production output, lower energy consumption and higher levels of safety. The simple operation of the S:GRAN has been improved in the new NXT:GRAN model, as


Below: NGR has developed the NXT:GRAN shredder-feeder-extruder machinery combination


www.plasticsrecyclingworld.com


IMAGE: NGR


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