PETpla.net Insider 03 / 2016

TRADE SHOW PREVIEW 51 PET planet insider Vol. 17 No. 03/16 www.petpla.net Starlinger Hall W1 Booth B41 High-tenacity polyester fibre recycling Meeting a growing demand Based on an article by Elfriede Hell, General Manager Starlinger recycling technology rPET produced both from fibre/fabric scrap and post-consumer PET bottle collection is cur- rently being used at a rate of 14,4% in polyester fibre production, mostly for polyester staple fibre. China is by far the greatest user of rPET in fibres, processing almost 80% of the 7 mil- lion tons produced worldwide in 2015. This is why Starlinger will be spotlighting polyester fibre recycling as one of its highlights at Chinaplas. High-tenacity polyester fibres fea- ture low water absorption and mini- mal shrinkage in comparison to other industrial fibres. They are used for threads and ropes, safety belts, etc. Tenacity is the general measure of the specific strength of a fibre or yarn, also called strength-to-weight ratio. The challenges in recycling include different levels of humidity and that the material comes in bales, lumps or fabric. Due to the high strength of the material it is very tough and requires shredding in a single-shaft cutter. In addition, requirements for colour values allow no oxidative or thermal degradation. The reuse rate lies usu- ally around up to 30%, in the same application it can reach up to 100%. Selecting the correct recycling equipment The input material and intended use of the regranulate are important factors for choosing the right recycling equipment. High-tenacity PES fibre recycling applications demand special machine features such as pre-shred- ding, drying before extrusion, high-vac- uum degassing and fine melt filtration. Also, solid stating for IV increase in the produced pellets may be necessary to achieve the characteristics required for reuse. Starlinger’s recycling lines for PES fibre recycling – the recoStar dynamic and recoStar universal recycling lines – have been installed for a number of high-tenacity fibre recycling applications worldwide. In the Smart feeder, a rotating disc at the bottom cuts the input material and creates friction. This frictional process heats and dries the mixed material, densi- fies it and brings it close to the melting point before it is fed into the extruder. Six extruder sizes from 150 – 2,600kg/h (output with degassing) are available. The recoStar universal recycling line is suited for processing hard-to-grind materials such as bales, fibres, fabrics and start-up lumps. In the Active shred- der arranged parallel to the extruder a hydraulic pusher presses the material against a water-cooled rotating shaft and thus provides efficient crushing. In com- bination with the software and the dosing screw, this kind of material preparation allows the processing of materials with different bulk densities without having to change process parameters. Five extruder sizes from 150-1,300kg/h (output with degassing) are available. It is claimed that both lines feature high-vacuum degassing for PES recy- cling to ensure the effective removal of volatile contaminants such as additives and finishing agents. Concerning filtration, reuse and the required filtration fineness at the production line are determining fac- tors; standard filter fineness is 50μm, fine filtration (25μm) with cascade filter system is also possible. The type of pelletiser is mostly a question of which pellets shape of the rPET is preferred – both (auto- matic) strand pelletising or underwater pelletising are possible. Special features are inline viscosity and colour measure- ment. Optionally, crystallisation and solid- stating of PET pellets and flakes can be included. www.recycling.starlinger.com PES yarn bobbins Starlinger’s recoStar dynamic recycling line for fibre and fabric scrap with increased humidity