Extrusion International 4-2017

36 Extrusion International 4/2017 RECYCLING Innovative technologies for polymer processing and recycling Quick and cost-efficient reprocessing of PET industrial and post-consumer waste The Gneuss Processing Unit (GPU) has been available for sev- eral years now and has proven itself on the reprocessing of bulky PET waste such as post-consumer bottle flake and in- dustrial waste from fibre and film manufacture. This Gneuss Processing Unit consists of the Gneuss MRS extruder with its unmatched devolatilisation and decontamination perfor- mance together with the highly-efficient Gneuss Rotary Disc melt filtration systems and the Gneuss Online Viscometer for intelligent dynamic viscosity control, monitoring and logging. Additionally to MRS design optimization since the last year, Gneuss has developed the new JUMP system. This is installed directly downstreamof the Gneuss ProcessingUnit and thanks to its ingenious process ensures an accurate and controllable IV boost of the PET in the melt phase. The Jump system is a compact, quick and efficient alternative to conventional SSP (solid state) systems and enables direct reintroduction of the polymer into the production process without the need to re- melt the PET. With the Gneuss industrial waste concept, industrial waste is first fed through a shredder or a knife mill until the size is re- duced so that it can be fed into the extruder. This can mean either compaction of the size reduced waste or a crammer feeder fitted directly to the extruder. The first important processing stage: melt decontamination takes place in the extruder. With its enormous devolatilisa- tion capacity, the MRS extruder can process PET waste with high residual moisture levels and/or contamination (such as spin finish oils) without the need for any pre-treatment of the waste. In the Multi Rotation (MRS) section of the extrud- er a huge polymer surface area and extremely rapid surface exchange rate under vacuum ensure that all these volatile contaminants are reliably extracted. Solid contamination is extracted with the fully-automatic and process-constant Gne- uss Rotary Melt Filtration System. With filtration fineness’s of down to 20 µm and below, a pure and particle – free polymer melt is guaranteed. During the second important stage of the process, the purified and homogenised polymer is fed by means of a melt pump into the JUMP. Here, too a large surface area of the poly- mer melt and optimum residence time of the polymer under vacuum are decisive factors. Subsequently, the purified and homogenised polymer is fed by means of a melt pump into the JUMP, where the second important stage of the process takes place. Here, too a large surface area of the polymer melt and optimum residence time of the polymer under vacuum are decisive factors. The polymer melt is kept under vacuum as it passes over slowly rotating elements. Through control of the residence time and the speed of the rotating elements, controlled polycondensation takes place whereby controlled IV boosting takes place of typically 0,02 to maximum 0,3 dl/g. The design of the Jump system avoids the ingress of oxygen so that the yellowing effect encountered during the recy- cling of PET is reduced to an absolute minimum. After the PET melt has passed through a stilling chamber in the JUMP system, the polymer is pumped directly into the production process (for example direct extrusion spinning, strapping) or to a pelletis- ing (chip cutting) system. With the complete system consisting of the Gneuss Processing Unit with the MRS Extruder and a JUMP system, indus- trial waste can be quickly and effi- ciently reprocessed in one processing step to a high quality polymer melt which can be directly processed to a finished product. Fig. 1: JUMP Polyreactor with Gneuss Processing Unit GPU