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PET Recycle -- Enhance the Value of PET Flake

It is well known that post consumer PET bottles are mainly recycled into textiles (or garments), carpets and sheets. The bottle grade PET has high quality and high performance among the various PET grade, and that presents an opportunity to utilized this high performance in recycled PET products. That leads to enhancing the value of PET flakes.

Kenplas has newly developed an economical & cost effective "Bottle to Bottle" (hereafter called B2B) method for recycling PET bottle flake into bottle grade PET resin, under 3R policy (Reduce, Re-user, Recycle).

Challenges to PET Recycling
  • During the life cycle of a PET bottle, material characteristics change due to thermal influences, resulting in a reduction of viscosity (from IV 0,82 to IV < 0,76 dl/g), which in turn leads to a deterioration of the stability and pressure-resistance of the bottle.
  • The diffusion of filled product (i. e. components of the filled liquid) into the PET material also presents a challenge, especially where the consumer has made alternative use of the bottle (e.g for aggressive substances like acids, fertilizers, household detergents etc).
Aim of PET Recycling
  • The material characteristics return to those required for bottle production (IV= or > 0,82 dl/g).
  • Aromatic substances and chemicals are effectively removed.
  • No chemical additives should be used.
  • Gas chromatography analyses show that the sensory characteristics of recyclate are even better than those of virgin product. The acetaldehyde and ethylene glycol contents for example are far lower than the required values as a result of solid stating under vacuum.
Procedure of PET Recycling
  • the PET bottle flakes are continuously fed into a modified two shaft extruder without preliminary drying. Utilising a specific worm configuration as well as a certain arrangement of differentiated degassing zones, the ground material is carefully dried and the melt efficiently degassed. Comparison of different extrusion systems during production showed that the modified two shaft extruder guarantees the most unique treatment of all the different post-consumer flakes on the market. Additionally, a down-stream melt filter ensures that non-meltable solids are separated from the melt to avoid unnecessary losses in quality. A slight increase of yellowing with minimal degradation is however unavoidable.
  • After pelletizing the resulting amorphous PET chips are fed into a discontinuous solid state process (SSP) and are set at the parameters necessary for conformity with foodstuffs. In a vacuum-tight Stehning tumble dryer the reaction runs in two main phases - crystallization and condensation/decontamination. The process parameters necessary for the reaction, i.e. pressure, temperature and holding time, are stored and varied fully automatically according to the process phase.
Reference of PET Recycling Equipment on the World
  • Stehning process;
  • Austrian Erema (TE-VS reactor holds flake for about 1 hr and feeds flake continuously into a single-screw extruder.);
  • German OHL;
  • Schmalbach-Lubeca Supercycle;
  • URRC technology(United Resource Recovery Corporation);
    • The process is a combination of conventional mechanical methods and chemical recycling.
    • The prime material supplied to the plant consists of PET beverage bottles, sorted by colour. The bottles are supplied in the form of compressed bales, each containing between 3,000 and 5,000 bottles. Each bale is given an electronic identity in order to facilitate traceability in the material stream as well as automatic material storage and control.
    • The bales are loaded onto a conveyor belt and unstrapped to free the bottles, which are fed to one of two shredders. The material is shredded, in a dry state, down to a unified granule size. The resultant material is a mixture of PET, labels and closures, which must be separated.
    • The plastic and paper labels are removed from the stream by an air blowing process. Any labels adhering to the PET with glue are subsequently removed by intensive washing. In the next stage polyolefins (closures) and PET are separated using the difference in their densities.
    • The cleaned and sorted PET granulate is now coated with caustic soda as it passes through a special high temperature rotating drum some 26 metres long and 3 metres in diameter. In order to avoid the breakdown of the PET polymer chain ?which occurs when wet material is subjected to high temperatures ?the materials have to be dried as they enter the drum.
    • The PET and the caustic soda are heated and undergo a solid-phase reaction in which the outer surface of the PET granules is stripped off, and ethylene glycol and terephthalic acid are produced as by-products. Any contamination adhering to the surface, such as label glue or remnants is removed with the outer PET layer. The last remnants are removed from the material at the end of this process stage by a combination of controlled temperature and air blowing.
    • The total process lasts a number of hours, at the end of which the result is a solid phase mixture of a salt and cleaned PET granules.
    • The PET and the salt are now separated by mechanical filtration, following which any salt remnants are removed by washing. Finally any minute metallic particles are removed by a metal separator.
    • To ensure consistent quality levels the material is sampled for QC checks at regular intervals. This includes checking that the PET specification conforms to the processing and food contact standards.
Notice on PET Bottle Collection

In order to ensure a successful recycling process, please always remove the lids of the bottles and rinse them out thoroughly. Extraneous material inhibits the re-use ability of these goods.

 Please remember the following procedure when putting out your Pet Bottles and Plastic Bottles for collection.

1.Remove the label.
2.Remove the cap.
3.Rinse the bottle.
4.Empty the bottle of water.

 Please remember to follow the procedure when putting your bottles out for collection. Extraneous material hinders the recycling process.

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