Spotlight on ’Silent Pipe’ at Krauss Maffei

Krauss Maffei Extrusion of Munich, Germany – held a Spotlight Direct Extrusion open day on the 7^th of May, 2009, in which they showcased an example of a direct extrusion system; a complete extrusion line for highly-filled, three-layer wastewater ‘Silent Pipe’, with a soundproofing middle layer thanks to the high mineral filler content. This type of ‘silent pipe’ is in demand for use in apartment blocks, hotels, hospitals and other large populated buildings.

Direct extrusion integrates the two processing stages, compounding and extrusion, so that highly-filled pipe can be produced from a polymer and filler in a single process step. Processors can significantly reduce manufacturing costs by eliminating one production step. The advantages being a reduction in material costs, lower energy consumption, better utilization of production capacity and reduced handling effort. The one step process is gentle on the material, which is now only plasticized once.

The example line shown at the Spotlight Open Day consisted of a KMG81-40 counter rotating twin-screw extruders as main extruder for the middle layer, a KME 45-30 B/R coextruder for the thin inner and outer layers, and a KM-3L RKW 74 3-layer pipehead. The line includes the complete downstream for pipe production – calibration, cooling and haul-off, sawing, chamfering and socketing. The extremely stiff and impact resistant PP block polymer used for the middle layer is fed into the extruder’s main feed master batch – and regrind as required. 70% by weight barium sulphate is fed into the side feed throat. The necessary die counter pressure is provided by a KM-ZSP 90 melt gear pump.