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
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,
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
- 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
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
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
- Austrian Erema (TE-VS reactor holds flake for about 1 hr and
feeds flake continuously into a single-screw extruder.);
- German OHL;
- 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
- 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
- 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
- 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.