At KraussMaffei’s Hannover R&D centre, interested customers have for some months now been able to view and test what the company calls the ‘most advanced industrial-scale recompounding system worldwide’.
Featuring a two-stage extrusion process with two ZE 65 BluePower twin-screw extruders designed for a maximum output rate of 2,000 kg/h, complete with all the necessary downstream equipment, and a newly developed proprietary cutter-compactor unit, the demonstration line has been completely integrated into a turnkey module.
When delivered, the line only needs to be connected to the local power, water and compressed air supply, said the company. For customers, this means it can be installed in any hall, with no special preparation required. Plus, the entire module is easily moved to a different location if necessary, where it can simply be plugged in, hooked up and switched on for production.
Where previously the recompounding lines consisted of a single-screw and a twin-screw extruder, the use of two twin-screw extruders is ‘a real novelty’, said KraussMaffei. The benefits of this solution are multiple, including high degassing capacities, efficient odour removal, ideal dispersive and dispersing mixing effect and gentle melt treatment. Moreover, there are almost no limits in terms of throughput rate.
In the first stage, the ZE65 BluePower twin-screw extruder degasses the starting material to remove odour, which can be particularly noxious when recycling post-consumer waste. Odour minimization can be intensified by using water, nitrogen or even carbon dioxide as entrainer for degassing.
“In addition, the first twin-screw extruder ensures optimum homogenization of the input material that is often characterized by rather inhomogeneous quality,” said Carl-Philip Poepel, director of product management Extrusion Technology at KraussMaffei.
Via a melt pipe, the melt is conveyed into the second twin-screw extruder where the actual compounding process takes place.
“Filling, reinforcing, pigmenting and incorporation of additives – the twin-screw extruder is designed for any given process task,” he added.
The extruders are fully equipped with gravimetric metering systems for various media, as well as with the appropriate downstream equipment such as fine filters, pumps and pelletizing unit from BKG-Systems from the Nordson Corporation.
The cutter-compactor unit, a recent addition to KraussMaffei’s portfolio, serves to prepare lighter material fractions - fibre and film scrap with high input moisture contents of up to 10% - for processing. In the unit, these materials are first dehumidified, compacted and homogenized before being transferred into the ZE 65 BluePower extruder. Rigid fractions with an apparent density of over 0.3 kg/l are simply fed directly into the first twin-screw extruder.
The new cutter-compactor unit is operated offline and the agglomerate material produced is discharged onto a belt weigher.
“This enables gravimetric metering with an accuracy of 99.8 %,” says Poepel, as the metering variations 
that tend to occur with light fractions when using a volumetric metering system are eliminated.
And he issued an invitation to any customers who wish to carry out industrial-scale trials on the EdelweissCompounding line at the R&D centre: they are welcome, he stressed.
A well-equipped analytical laboratory and an injection moulding machine for the production of first product samples from the compounds produced on the EdelweissCompounding line are also available on site.