The first compounding plant for biodegradable plastics in Portugal underlines the expertise of Coperion GmbH, formerly Werner & Pfleiderer, in biodegradable material processing systems. The extrusion line is being operated by the Portuguese compounding company Cabopol, S. A. based in Porto de Mós and went into trial operation in January 2010. Cabopol is the first manufacturer of biodegradable polymers on the Iberian Peninsula.
The processing system includes materials handling for all raw materials – that is storage, conveying, weighing and dosing – as well as compounding with downstream pelletizing and drying. Biodegradable compounds based on compostable polyesters with and without starch are being manufactured. The materials supply system stands out for a high flexibility, allowing the addition of several different components. The processing extruder, a ZSK Megacompounder Plus, has a ZS-B twin screw side feeder and a venting unit. The die discharges into a water bath for strand cooling followed by suction drying of the strand surface prior to strand pelletizing. All the peripherals are integrated into the EpcNT plant control system. A modem allows remote software updates and monitoring of the compounding plant.
Cabopol procured a ZSK 26 Megacompounder laboratory extruder especially for this project and during the optimisation of the screw geometry and process technology was able to make use of know-how from Coperion. It is the formulations including starch that represent a particular challenge: The melting zone in the compounding extruder has to not only melt the polymer, but also plastify the non-melting starch by adding liquid.
Three story framework
The plant was installed in a three storey steel framework. The upper level is used for the management of pellets and powders. It houses the intermediate materials storage system with day bins, four big bag emptying stations (one of which is Atex rated for the starch), a sack station as well as the central aspiration system. On the mezzanine level there are gravimetric dosing stations for solid material, and pumping stations for liquids are located on the ground level along with the ZSK Megacompounder Plus compounding extruder.
The biodegradable compounds are sold by Cabopol under the Biomind brand. Their most important markets are non-durable products for household, industrial and agricultural applications. Examples of these are disposable nappies and cutlery, rubbish bags, food packaging, shopping bags, drinking straws and agricultural films.