MATERIALS | WATERPROOF MEMBRANES


Above: KraussMaffei says that its ZE Bluepower compounding machines can be used in a process to make roofing sheet via direct extrusion


process conditions regarding coating or impregna- tion, said Butz. There was also faster film formation (during the drying stage), making energy savings and higher line outputs possible.


Sheet production Hilmar Heithorst, division manager for sheet and foam extrusion lines at KraussMaffei, told del- egates of a new concept for medium capacity production of roofing sheet. He said that direct extrusion – using its ZE Blue-


power range of compounding machines – converts raw materials into finished sheet in a single step. “Intermediate compounding or pelletising – fol- lowed by sheet extrusion – requires extra capital


equipment, production and logistic expenditure, and results in additional heat history for the polymer,” he said. “Direct extrusion, using a co-rotating twin screw extruder, can melt the polymer, incorporate fillers and additives, degas, and extrude in a single step.” He said there are limits to direct extrusion, which


are imposed by physical and chemical barriers – such as liquid diffusion and temperature. In trials with the ZE BP 65 (with an L/D ratio above 40), he said that one point of entry for the plasticiser is enough. “Filler content is the key to control temperature, and acts like a stabiliser,” he said. In addition, a gear pump helps to reduce melt


temperature, while processing length can be increased, in order to add extra time for diffusion.


� PET EXTRUSION LINES


BG PLAST IMPIANTI s.r.l. Via Venezia 232 21050 Marnate - Italy Phone: +39 0331 365 865


info@gbplast.it


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