Technological watch

If a circular economy is to be realised, it will be necessary to consistently recycle post-consumer thermoformed PET trays back into PET trays. Currently, extensive use is made of post-consumer PET bottle flake is used in the manufacture of PET trays but this supply of feedstock will continue to decrease. As part of the circular economy, PET bottle flake is increasingly recycled into new bottles.

MRS extruder screw with multi rotation sectionThe recycling of regrind from post-consumer PET trays to new sheet for PET trays presents challenges for the recycling process:

• Unlike PET bottle flake, the intrinsic viscosity of the regrind from PET trays is too low to permit direct recycling on a conventional sheet extrusion line.
• The sources of post-consumer PET trays is not as controlled as with PET bottle flake and there is a wide range of different types of trays in circulation, therefore the quality and property of the regrind varies considerably.
• It is unavoidable, that tray regrind will be cross-contaminated with other polymers, as it is difficult to completely exclude other polymers, especially due to co-extruded or laminated layers.
• For food contact applications, efficient decontamination of the polymer (e.g. EFSA, FDA) for monofilm structures is extremely important.
• The material must be efficiently purified but at the same time, the processing should be as gentle as possible if the material is to be processed in a continuous closed loop and if the product quality is to be guaranteed.

For this demanding process of tray-to-tray recycling, Gneuss has developed the innovative MRSjump Extruder with which it is possible to process post-consumer PET regrind from thermoformed trays directly to sheet for thermoforming trays in one step.

According ro company, the new MRSjump Extruder combines the high decontamination performance of the MRS degassing extruder, which has been well established over the past decades, with a viscosity boost:

• Gneuss Tray-to-Tray Recycling Sheet Line with MRSjump ExtruderThe MRSjump extrusion process does not necessitate any pre- or post-treatment of the input material, such as crystallisation or pre-drying of the recycled material or an IV boost in a solid state polycondensation (SSP).
• The high degassing efficiency of the MRSjump Extruder makes it possible to comply with EFSA and FDA limits without time- and cost-intensive upstream or downstream material treatment.
• The simple set-up of the MRSjump direct extrusion process avoids the combination of different material treatments prior or subsequent to extrusion and resulting interface problems.
• Thanks to the short process chain, the melt remains within a narrow, defined residence time spectrum. The thermal and mechanical stress on the material is kept low. This results in excellent mechanical and optical sheet properties.
• The compact design of the MRSjump Extrusion System means that it has a small footprint and compared with other concepts available on the market, it can easily be retrofitted to an existing sheet line within the same spare requirements as an existing conventional extruder.
• The MRSjump Extruder can processes a wide range of input materials, from regrind from mono- and multi-layer trays to material combinations which would stick together in a conventional thermal pre-treatment process (e.g. sheet regrind from PET/PE, GAG, certain copolymers).
• In combination with the Gneuss Rotary Filtration Technology, a high melt purity is guaranteed.
• Quality assurance is also provided by optional systems for measuring melt viscosity and optical properties (colour and transparency measurement).

Thus, recycling and decontamination are for the first time made possible with the MRSjump Extruder, within one single extrusion step without upstream or downstream material treatment steps.