TECHNOLOGY | MELT FILTRATION
Above: Ettlinger’s ECO melt filters are being used in PET bottle-to- bottle recycling
existing screen changer, the re-pelletising line is now capable of processing up to 1,000 kg/h. This was proven in an acceptance test. A higher cost efficiency also results from the reduced melt loss in the filter from formerly 1.5% down to 0.6%.” During the pilot runs, the system remained stable for more than eight weeks and there was a reduced level of operator assistance needed. Ettlinger says: “Consistent quality acceptance of the converter, using the final pellets in bottle productions process, confirmed the ECO filtration efficiency. In comparable projects chemical analyses proved only slight degradation of the rPET well below the set limit values, as an advantage of the short residence times in the ECO melt filter.” The ECO melt filter has a rotating cylindrical
steel screen with millions of laser-drilled conical holes through which the melt is forced from the outside to the inside. This leaves impurities on the
surface, from where they are continuously removed by a scraper. Uwe Kellner, Managing Director at Ettlinger, says: “In general, the PET world has much higher demands on the efficiency of melt filtration than other areas of plastics recycling. Where conven- tional screen changers and screens reach their limits, our self-cleaning ECO filter systems offer considerable reserves to meet even the toughest specifications. The breakthrough came with the recent market launch of a micro perforation with a previously unattained filter fineness of 60 µm. This means that we now also meet the particularly high requirements of PET recycling.” Conventional steel mesh filters are also available with a filter fineness of 60 µm, and even lower, but Ettlinger says that during operation impurities such as aluminium foil or paper, along with black specks in the rPET bottle flakes, can find their way into the recycled material, causing yield losses. Kellner says: “Compared to steel mesh screens, the rigid screens of the ECO melt filters with their laser-drilled micro perforation, in combination with permanently cleaning the surface, enable much better separation performance. At 60 µm filter fineness, the remaining impurities, smaller than 60 µm, are almost no longer visible to the human eye or will not be noticed - an important aspect in clear PET bottle production.” According to Ettlinger, rPET produced in this way and used for fibre or tape applications is considerably less prone to breakage due to the significant reduction of black specks and other particles. This ultimately increases the efficiency of the line, which in turn leads to considerable cost
rPET FLAKE DECONTAMINATION
FOR DIRECT FOOD CONTACT
IR-CLEAN System ®
✓ FDA & EFSA approved
✓ Easy retroffiting for existing lines ✓ Decontamination & drying in one step ✓ Continuous processing
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IMAGE: MAAG
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