This is an indispensable function during start-up for diffi cult products that are sensitive to temperature fl uctuation. In underwater pelletizing, an optimized volume fl ow per die hole must be ensured right from the start. Most of the upstream equipment responds rather slowly, e.g., ramping up of the extruder. The polymer diverter permits a controlled start-up of these upstream components until the required throughput has been attained and allows a visual control of the compounding process by the operator. The option of diverting the melt is often used for online material or color changes.
The polymer diverter valve consists of a heated housing with an integrated bolt that can be moved hydraulically. This bolt allows the melt flow to be diverted from the start-up position to production position, e.g., toward the die plate, within one second. In many cases, the inlet channel of the polymer diverter valve is adapted directly to the extruder outlet, screen changer or to the melt pump, eliminating the need for an additional intermediate adapter. The integration of a nose cone on the die plate at the outlet of the polymer diverter valve reduces the length of the fl ow channel and the volume of melt dead area before the die plate. This reduction of dead area prevents excessive melt fl ow through the die plate after extrusion has stopped so the system can be restarted with a generally clean die plate. This helps prevent the risk of polymer wrapping and increased agglomerate formation during start-up.
A mobile support stand simplifi es the removal or backing away of the polymer diverter valve pulling from the extruder screw.