Modern Vacuum Technology for Melt Degassing During Extrusion
However, there is one constant in all of the extruders: for the extraction of vapors and gases from the molten material in the screw sections, PolyComp relies exclusively on PLASTEX degassing systems from Busch Vacuum Solutions. Equipped with MINK claw vacuum pumps, these systems are exceptionally reliable and easy to maintain.
Fig. 1: One of a total of seven PLASTEX degassing systems at PolyComp. They are installed one floor above the extruders.
About PolyCompPolyComp was founded as a management buy-out in 2000, and its headquarters are based in Norderstedt on the outskirts of Hamburg, Germany. In 2013, PolyComp was taken over by the Hamburg-based Feddersen Group, which focuses on the global trade of chemical and technical products.
PolyComp's core business includes the compounding of polyolefins (PP/PE), as well as EVA, PA, PBT, PC, ABS, EVOH, POM and PMMA. These compounds are mixed with various additives ranging from carbon or natural fibers, simple fillers to glass beads, color additives or waxes.
Film CompoundsOne of PolyComp's specialties are film compounds, which require extremely low quantities of gel. The production process involves an extrusion stage using specific screw configurations and the application of a screen changer with a high degree of filtration precision. The company uses a total of eight single or twin screw extruders. The molten material is degassed in six of the extruders. Up to 2009, the company used liquid ring vacuum pumps for this process.
Our SolutionSearching for an environmentally friendly solution in 2009, the company came into contact with Busch, which offered a PASTEX degassing system (fig. 1) that required no operating fluids. The system consists mainly of a MINK claw vacuum pump (fig. 2) and an upstream standing filter and fine filter. The filters are used to separate out condensates and solids. MINK claw vacuum pumps do not require any operating fluids such as water or oil. This means that the pumped vapors and gases do not come into contact with any operating fluids, with which they could mix or react. However, even the most careful separator technology cannot always prevent residual monomers from getting into the pumps' interiors and cracking there. For this reason, the MINK claw vacuum pump is equipped with a flushing device. This enables a precisely dosed quantity of flushing liquid to be fed into the vacuum pump after defined intervals, helping to dissolve any cracks. Maintenance manager Stefan Stolp defined the quantity of flushing liquid and flushing intervals for each of the materials extruded. The flushing process can take place during periods of downtime or even while production is running.
Fig. 2: MINK claw vacuum pumps form the heart of PLASTEX degassing systems. Thanks to their contact-free operating principle, they do not require any operating fluids such as water or oil.
Engineer Simone Patermann has identified another benefit of using PLASTEX degassing systems. As head of the production, she always has her eye on energy consumption, not least because PolyComp is certified under ISO 50001 for energy management systems.
In 2018, PolyComp launched a new extrusion line, whose heart is a twin screw extruder with an output of up to 1,500 kilograms per hour. The two side dispensing units (fig. 3) allow different types of powder-based fillers to be added at the same time and compounded with a high output capacity. One side dispensing unit can be connected to a PLASTEX degassing system. This reduces the volume of the fillers and enables the bulk density to be tripled compared to a side dispensing unit without degassing. This significantly increases the total output rate.
Fig. 3: The two side dispensing units on the twin screw extruder. A PLASTEX degassing system helps to reduce the volume when adding filler material. Source: PolyComp