KraussMaffei is making what it calls the most advanced industrial-scale recompounding line in the world available for customer trials at its R&D center in Hannover, Germany. High-profile features of the system include a proprietary cutter-compactor unit, a two-stage extrusion process comprising dual twin-screw extruders, and integration of the various pieces of equipment into one turnkey module that requires little more than connection to power, water, and compressed air supplies to begin operation.
|The EdelweissCompounding line installed in the KraussMaffei R&D center is completely integrated into a turnkey module. Image courtesy KraussMaffei.|
The system is based on KraussMaffei’s EdelweissCompounding technology that achieves quality recompound at throughput rates of several metric tons per hour. The well-established process has been further optimized and extended by the machine engineering company, said KraussMaffei.
Unlike conventional systems that combine single- and twin-screw extruders, the new EdelweissCompounding line is composed of two ZE 65 BluePower twin-screw extruders with a maximum output rate of 2,000 kg/h. The benefits of using two twin-screw extruders include high degassing capacity, efficient odor removal, an ideal dispersive and dispersing mixing effect, and gentle melt treatment with almost no limits in terms of throughput rate, according to KraussMaffei.
In the first stage of the process, a twin-screw extruder degasses the starting material and removes any residual malodorous substances, which is especially important when recycling post-consumer waste. Odor minimization can be intensified by using water, nitrogen, or even carbon dioxide during the degassing stage. This capability is facilitated by a range of metering and degassing options in the KraussMaffei twin-screw extruders. “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.
The melt is then conveyed to the second twin-screw extruder, where the actual compounding takes place. “Filling, reinforcing, pigmenting and incorporation of additives — the twin-screw extruder is designed for any given process task. This is why our extruders are equipped with all auxiliary units for metering pellets, powder, fibers, and liquids,” added Poepel. The extruders come with gravimetric metering systems for various media as well as appropriate downstream equipment, such as BKG filters, pumps, and pelletizing units from Nordson Corp.
A cut above
The cutter-compactor unit integrated in the Edelweiss line was recently added to the KraussMaffei portfolio. It plays a critical role in preparing light or fluffy material, such as fibre and film scrap with a high moisture content, for further processing. In the cutter-compactor, the material fraction is dehumidified, compacted, and homogenized before it is transferred into the ZE 65 BluePower extruder.
The cutter-compactor unit operates offline and the resulting agglomerate material is discharged onto a belt weigher. “This enables gravimetric metering with an accuracy of 99.8%,” said Poepel, an improvement over volumetric metering, which is typically used in this process. The technology allows post-consumer LDPE, HDPE, PP, and PS fractions to be easily processed into high-quality recompounds that can be used instead of virgin resin in both injection molding and extrusion applications.
The EdelweissCompounding line installed in the R&D center is completely integrated into a turnkey module. As a result, potential owners can see for themselves the benefits of this type of architecture, which enables easy installation without any preparation and provides set-up flexibility within existing factory space. At installation, the line only needs to be connected to the local power, water, and compressed air supply to start immediate production. In the event of relocation, the module can be transported as is without disassembly.
Potential customers are invited to conduct industrial-scale trials on the EdelweissCompounding line at KraussMaffei's R&D center. A well-equipped analytical laboratory and injection molding machine for the production of first product samples from the compounds also are on site.