Coextrusion line targets processor resin savings

Two Italian processing equipment makers, Luigi Bandera and SICA, have come up with a complete coextrusion line to produce polypropylene (PP) discharge conduits that promise efficiencies compared to monolayer pipe.The pipes are said to provide extraordinary sturdiness and impact resistance even at low temperatures. Pipes extruded on this system show good resistance to chemical attacks at high working temperatures as well as good soundproofing properties. This three-layer extrusion line is made up of two TR5030L/D single-screw extruders for the outer and inner pipe layers. These units are equipped with gravimetric feeders for up to six components. For the center layer, which is approximately 1.2 mm, the line uses a 2C70-42L/D corotating twin-screw extruder where the screws and barrels are treated by a special wear-resistant coating from Xaloy as the intermediate layer includes the bulk of the additives, some of which can be abrasive. Why a corotating twin screw? Mirko Zisa, Bandera sales manager, says processors have the advantage of doing their own inline compounding with this unit to save on buying costly compounds. During a recent demonstration of the line, up to 40% barium sulphate (which acts as a sound damper) was being compounded into the melt for the center layer, which Zisa says is more homogenously dispersed thanks to the corotating mixing and kneading effect. “The processor also saves up to 20% on energy consumption by using the twin screw over a single screw for this operation,” he says. The line produces pipes in diameters from 50?110 mm in thickness up to 2 mm with an output of 400 kg/hr. Line speed is up to 18 m/min. The twin-screw has a diameter of 70 mm with an L/D of 42:1, while the two single-screw units have screw diameters of 50 mm each with an L/D of 30:1. The line includes a gear pump, a continuous two-path screen changer for the center layer, a vacuum-sizing tank for calibration, and cooling tanks.SICA provides most of the post-extrusion elements including an automatic Everbell3 160 inline belling machine that can produce more than 900 sockets/hr with gasket insertion. Haul-off and cutting on-the-fly for minimum lengths of 200 mm are fully automatic. Pipe stacking and packaging are handled by the Multipack 4000 series. A robot recognizes different lengths coming from the belling machine and arranges these accordingly in tiers separated by saddles to prevent crushing. Costruzioni Meccaniche Luigi Bandera SpA, Busto Arsizio, Italy; +39 0331 398111; www.lbandera.com; SICA SpA, Alfonsine, Italy; +39 054 488711; www.sica-italy.com