ISSUE 02/2000
Materials / Recycling			BACK to contents

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PET recycling technology

Erema GmbH of Ansfelden, Austria, have developed a new “bottle to bottle” PET recycling system which it is claimed will economically produce PET pellets to FDA food contact standards.

The recycled product has already been tested and certified as food contact compatible by the Fraunhofer Institute, testing to FDA guidelines. The manufacturer expects to obtain full “FDA Approval” during the year 2000.

High IV without solid state crystallisation

A wide variety of PET materials such as bottle flakes, X-ray and packaging film, thermo-forming sheets and fibres can be re-cycled at relatively low cost thanks to the energy efficiency and compact design of the plant. A feature of the process is that it operates without the solid state condensation step which is traditionally used to increase the inherent viscosity of the recycled resin to that of virgin PET. A crystallisation drier together with a modified Erema vacuum cutter /drier/extruder combination increases the viscosity in an energy efficient way without chemical additives or reactors. Recycled pellets with an IV as high as 0.81 are obtainable.

No need for external crystallisation and predrying

Recycled pellets can be further processed into preforms directly on conventional injection moulding machines without the need for external crystallisation and predrying. Bottle flakes can also be processed directly into thermo-forming sheet “in-line” without repelletisation. Multi-layer films are produced using 2 or 3 extruders feeding downstream installations added directly to the Erema system. The “in-line” production of film benefits from the food grade quality of the recycled material as the coating traditionally applied to film made from recycled material is not required.

The Plant

The Plant technology meets the stringent conditions laid down by the food industry and the reqirements for PET reclaim in what is claimed to be an extremely efficient, compact and energy saving process with low overall investment cost.
Bottle flakes from the washing and drying plant are fed to the Erema crystallisation drier via a conveyor belt or screw conveyor. The material is preheated, died and crystallised in one continuous process. As it moves to the intermediate storage silo and from there to the combined vacuum cutter/drier/extruder via a vacuum lock the material is kept thermally insulated. A suitable holding period in a very high temperature/high vacuum environment effectively removes contamination in the form of volatile matter from the PET flakes. It also minimises residual moisture and increases viscosity to virgin material levels. The actual degree of contamination is measured and monitored by way of suitable sensors in the vacuum cutter/drier.
When recycling spun fibres an upstream grinder and intermediate silo are used. The vacuum cutter/drier effectively removes any residual spinning oil.

Extrusion and filtration

PET flake with increased viscosity is now fed directly to the extruder. In the extruder the PET material is plasticised, homogenised, degassed and finally passed through a fine filter with an integrated automatic self-cleaning system. In the filter residual solid contamination down to a very small particle size is separated from the PET melt before pelletisation. The optional in-line crystallisation pelletiser produces clean, food grade, semi- crystallised strand pellets which can be reused directly to manufacture PET preforms.
There are already over 100 Erema PET recycling systems in operation around the world and the new system can be supplied in installations outputting from 120 kg/hr up to 1800 kg/hr.

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