PET flakes can now be processed into granules using ZSK twin-screw extruders from Coperion, Stuttgart, without pre-drying, condensed in an SSP reactor and further processed into bottles of the same new quality.
Recycling PET produced using this process has received FDA approval for direct food contact. Coperion systems for this bottle-to-bottle recycling process achieve throughput rates from 2 to 8 tons/hour.
According to Coperion, recycling companies can save up to 30% energy compared to other PET recycling methods, in addition to operating costs and logistics costs.
Before PET can be reprocessed, it must first be crushed, flaked and cleaned. Previous techniques then required PET flakes to be pre-dried, crystallized, or agglomerated. With special technology from Coperion, shredded PET can be fed directly to ZSK twin screw extruder and assembled there.
The shredded chips are injected into the ZSK extruder via SWB belt scales or Coperion K-Tron gravity feeders. New materials, mixtures or new materials can also be added. In the process part of ZSK, melting, intense degassing and complete homogenization occur before conveying the material flow through a gear pump and filter with automatic screen changer to an underwater strand or pelletizer to produce pellets.
Then the granules are condensed in the SSP reactor. Its quality is in line with that of new goods and has passed FDA food grade certification (No Objection Letter). In the next step, for example, the granules can be processed into bottles again.
According to Coperion, the quality of the final product is very high in the bottle-to-bottle conversion process. The material is handled carefully. The stability time of the ZSK extruder is short and the dispersion is good. The high torque of the ZSK extruder allows PET to be processed at lower temperatures and with virtually no viscosity loss. The self-cleaning twin screw extruder allows for quick changes in recipe and color. Thanks to ZSK’s vacuum options, volatile components such as monomers, oligomers and water are removed from the molten and removed from the exhaust gas flow in appropriate separators before the vacuum pump.
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