Stabilisers & Manufacturing # 2004 Milan
Due to its excellent material characteristics and its outstanding price / performance ratio, until today PVC-U is the worldwide most used material for pipes made from plastics. As the market is very competitive manufacturers of PVC-U pipes have been exposed to increasing pressure on prices and costs for years. At the same time higher and higher demands are made on the quality of their products. Further developments not only in polymer and compound formulation but also in extrusion machinery are the logical consequence. Counter-rotating twin screw extruders are used to plasticise PVC-dryblends and transform them into pipes. Here the distinct increases of gearbox torque was the basis for the increase of extruder output at constant screw diameter. Longer processing units in combination with new screw geometries gently transfer the motor energy into the polymer. This results into homogeneous melt qualities and high output rates at low investment costs. At the same time new surface treatments were developed to protect screws and barrel. New die concepts help to achieve higher throughputs in PVC-U pipe extrusion. Beside the traditional PVC die heads double spider dies offer a wide application range for a more flexible production. Moreover control systems enable the pipe producers to minimize material consumption. Finally teamwork between material producers, machine suppliers and pipe manufacturers can optimise the lines profitability to meet the future demands in pipe extrusion.