event preview | PET At AMI’s Plastics Recycling T echnology conference on 20-21 June, NGR


will present its LSP process for improving recycled PET to food-contact standards. In this article, NGR explains the benefits of LSP


next generation of PET recycling


Rethinking the


Main image: NGR’s P:REACT unit


Introducing new technology in the field of plastics-recy- cling has always been the aim of Next Generation Recyclingmaschinen from Austria. The Liquid State Polycondensation process for PET recycling combines the benefits of increasing Intrinsic Viscosity (IV), excellent decontamination properties and low energy consumption. PET is a material broadly used in food-packaging, such


as for soft-drink-bottles or PET trays. In this field the global annual consumption reaches some 20 million tonnes. The PET fibre business is approximately double the size. Reasons enough to rethink the general approach of recycling the material and starting to take full advan- tage of PET’s properties by designing a new process. As with all polymers, PET consists of polymer chains. The length of the chains determine the strength


Figure 1: PET process comparison SSP (Solid State


State of PET Environment


Typical Temperature IV – Lift – Speed


Source: NGR 24


Polycondensation) Solid/crystaline


Inert gas or vacuum (200-240) ˚C


(0,01-0,02) dl/g (rPellet) (0,05-0,06) dl/g (flake) per hour


PLASTICS RECYCLING WORLD | June 2017


LSP (Liquid State Polycondensation)


Liquid (melt) Vacuum


(270-280) ˚C (0,01) dl/g


per minute


of the material and the viscosity (measured as IV value). Each step in processing the material (fibre spinning, film extrusion, injection moulding, etc), leads to “breaking” some of the chains apart, thereby causing the material strength to be reduced and the viscosity of the material to be lowered so it becomes easier flowing.


Improving PET properties Due to the petrochemical manufacturing of PET – so called polycondensation – the polymer chains can be restored in length again. The traditional method of achieving this is Solid State Polycondensation (SSP). Crystalline pellets or PET bottle flakes are here heated to about 200 to 240°C and kept at this temperature for several hours, allowing an increase of the IV by approximately 0.01 to 0.02 dl/g per hour (0.05 to 0.06 dl/g in the case of flakes). Liquid State Polycondensa- tion (LSP), on the other hand, takes advantage of the material being at a higher temperature range (270 to 280°C) and therefore an increased reaction speed of the polycondensation. The LSP process can increase the IV value by 0.01 to 0.02 dl/g within minutes and keeps the desired IV within a narrow range of +/- 0.015 dl/g. The backbone of NGR’s LSP process is the P:REACT.


In this reactor the surface/volume ratio of the molten PET is increased by forming strands, and furthermore a


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