PET Recycling: Decontamination and IV Control in One Extrusion Step

Currently, the recycling of post-consumer PET Bottle Flake is well established and it has become a sought after secondary meantime. Increasingly, the focus is 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.

The important difference in recycling these materials is that whereas 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 only answer is to install 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 any additional thermal treatment of the material). In addition to this, 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 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 in spite of the inevitable variations in the residual moisture level of the input material.

The new Gneuss MRSjump therefore offers both decontamination performance to food contact levels and the ability to maintain and control the IV of the PET in one 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:

• 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.