MELT FILTERS | PROCESSING
As more processors look to handle recycled feedstocks, effective melt filtration will become increasingly important in maintaining product
quality.Peter Mapleston reports
Melt filters take on recycling challenge
Melt filters are a key component in many plastics extrusion systems but especially in those where recycled polymers are being processed. Melt filtration systems can handle recycled
materials from a wide range of sources, with much of the more recent development work among filtration system suppliers concentrated on improv- ing the quality of melts containing post-consumer recyclate (PCR). “To achieve high quality pellets at the end of the
recycling process, the right filtration technology should be chosen based on the input materials,” said Robert Obermayr, head of the Powerfil business unit at Erema. The Austrian plastics recycling systems maker established its Powerfil operation three years ago. It says it wanted to offer melt filters to the industry that it had already proven as individual components in its systems. Its SW RTF partial surface backflush filter system and Laserfilter are compatible with Erema
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extrusion systems and those of other suppliers. The company says that cyclical filtration using
wire mesh filters in a piston screen changer is typically appropriate for contamination levels of up to around 0.05%, while continuous filtration using a laser filter is able to process contamination levels of 3-5 %. For its wire mesh filters, Erema uses piston screen changer systems with back flushing. Each piston carries two filter cavities in which the wire mesh screen packages are inserted. “Because the filter is made out of woven wires it provides high porosity, which means that it has a high proportion of open area per unit of surface area,” said Obermayr Erema wire mesh filter systems start with one piston and two screens and go up to six pistons and twelve screens. “With the six-piston screen changer the melt
pressure difference during backflushing is extreme- ly low,” said Obermayr.
� January/February 2021 | PIPE & PROFILE EXTRUSION 11
Main image: Developments in melt filters aim to enable more heavily contaminated material to be processed with higher yield, reduced downtime, and improved process
consistency
IMAGE: GNEUSS
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