Extrusion International 6-2022

58 Extrusion International 6/2022 PIPE EXTRUSION Without Premixing to the Highly Filled PVC Pipe Direct Dosing of Chalk Supports Sustainable Extrusion Process Flexibility, process stability and minimized wear are only some of the advantages resulting from the production of PVC pipes with high filler content using the solution currently being presented by battenfeld-cincinnati. At its booth at K 2022, the extrusion specialist showcased the twinEX 93-34 parallel twin screw extruder model with a gravimetric dosing unit for processing up to 100 parts of chalk without premixing. H igh proportions of filler chalk make PVC pipes, which are pri- marily used as sewer pipes, not only cheaper, but also reduce the use of fossil resources. At the K 2022, bat- tenfeld-cincinnati presented the ideal solution for manufacturing PVC pipes with a high filler content. A basic PVC formulation and the filler material are fed separately to the production line. The individual components are then put together in a collection hopper and subsequently blended with each other in the cold mixer connected to it. After mixing, the finished formu - lation is passed on to the feed open- ing of the extruder via a vertical dos- ing unit. Both the mixing ratio and the entire material throughput are gravimetrically monitored and con- trolled. All containers along the chalk transport and chalk dosing line are equipped with agitators. Thus, the filler material is kept in motion along the entire route to prevent bridging. A twinEX 93-34 parallel twin screw extruder serves as processing unit for the PVC formulation. The process- ing unit features a specially adapted screw geometry with anti-wear pro- tection to transport and plasticize the blend evenly and homogeneously. The advantage of this solution is its chalk content variability ranging from 30 to 100 parts, which can be easily adjusted at any time and at short no- tice to the formulation required for the specific product. A further benefit of direct gravimetric chalk dosing is the enormous process stability, which ensures a high-quality end product. Finally, the process eliminates the need for premixing of PVC and chalk in a heating/cooling mixer. This pro- cess change involves several benefits. Central heating/cooling mixers can be kept smaller in size, or any mix- ing capacities which become free can be made available to other produc- tion lines. De-mixing during material transport can be prevented, since the filler material is fed to the production line directly after transport. With the combination of an extrud- er and a gravimetric metering unit shown at the fair, solid PVC pipes with filler content can be produced using a mono-layer pipe die. For 3-layer pipes with a filled middle layer and external layers without filler content, batten - feld-cincinnati offers the appropri- ate three-layer pipe dies and conical co-extruders. In this way, pipes up to 400 mm in diameter can be produced economically and resource-efficiently, which of course can also be recycled after the end of their service life. battenfeld-cincinnati www.battenfeld-cincinnati.com TwinEX 93R-34 with inline addition system