PET recycling: Decontamination and IV control in one step

The recycling of post-consumer PET bottle flake is well-established with the focus increasingly shifting toward using other sources of PET waste for recycling, such as post-industrial fibre waste and to other post-consumer sources of PET, such as thermoformed pots, tubs and trays.

There is, however, an important difference in recycling these materials. With PET bottle flake, a certain IV drop extrusion is acceptable, the IV of fibre waste or thermoformed pots, tubs and trays is at a level that any further IV drop would result in unacceptable mechanical properties.

Typically, the solution involves installation of a complicated and/or energy-intensive liquid phase or solid state IV boosting processes downstream of the extruder.

The Gneuss MRS extruder for PET offers unparalleled decontamination performance and has food contact approval for post-consumer waste without the need for additional thermal treatment of the material. Furthermore, the new MRSjump version of this extruder provides a drastically increased surface exchange rate under vacuum so that partial polycondensation takes place within the extruder, and it is thus possible to retain the input IV.

Additionally, the intense devolatilisation and long residence time of the polymer under vacuum can be controlled to provide a consistent output IV despite the inevitable variations in the residual moisture level of the input material.

The new Gneuss MRSjump offers both decontamination performance to food contact levels and the ability to maintain and control the IV of the PET in a single extrusion processing step. There is no need to treat the material prior to extrusion and no need for an additional melt or solid phase IV boosting process in addition to extrusion.

The result is lower energy consumption, better material quality, greater flexibility, smaller machine footprint, lower complexity, less operator attention and the possibility of using types of raw material which were previously uneconomic to recycle.