TECHNOLOGY | MELT FILTRATION
ties. For instance, even food packaging made entirely from bottle flake is not allowed to contain any contaminants. Additionally, tapes or yarn that are stretched must not exhibit any defects that could cause them to tear and disrupt production. The company adds that purity of the recycled
Above: The 60 micron screen size now available on Ettlinger’s ECO series makes these filters ideal for when 100% PET bottle flake is used in thermo- form sheets, packaging tape or staple fibre plants
melt filters will make it easier to treat recycled material for the film, packaging tape and fibre industry and help plastics recyclers remove challenging contaminants like paints, silicones, barrier materials, cross-linked fractions and gels from the melt. In particular, the new filter screens will enable cost-efficient conversion of post-con- sumer PET bottle flake and fines, which generally occur in large amounts, into recycled material with good usage properties. Recycled PET from post-consumer bottle flake is highly sought-after in the industry as a raw material for thermoforming packaging, fibres or packaging tapes, adds Ettlinger. With increased environmental awareness, such products are also widely accepted – and in considerable demand – among consumers. Depending on the application, the recycled materials often have to meet high requirements in terms of appearance and/or mechanical proper-
material is central to its usability. Therefore, the efficiency of the melt filtration process is far more critical than usual. The screen changers and screens normally employed for this purpose have limita- tions, whereas Ettlinger says that its self-cleaning ECO filter systems permit compliance with even the toughest specifications. The core component of the ECO filter is a rotating, cylindrical steel screen with millions of conical holes drilled by laser. When melt flows through this screen from the outside to the inside, any contaminants are retained on the surface and continuously removed by a scraper. The breakthrough as far as PET recycling is concerned is the recent market launch of a microperforation with a filtration fineness of 60 microns. Woven steel mesh screens are made of fine
metal wires. A square mesh is the simplest and most commonly encountered type. The side length of the openings corresponds to the screen’s nominal mesh size. However, in practice, a square mesh allows much larger particles (factor 1.41) to pass owing to the diagonal. Furthermore, the individual wires are only linked together loosely. As the filter cake grows and the pressure rises, some meshes may be enlarged, so that particles bigger than the nominal mesh size slip through. Contami- nants contained in the PET bottle flake, such as aluminium or paper as well as ‘black specks’ – black, degraded plastic particles that occur during
Constant
Melt fi ltration Continuously
Pressure and process constant Stand C310
Unique technologies, innovative solutions, comprehensive technical support, high expertise in all kinds of plastics applications. In others words: typical Gneuss.
Stand 9A38
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PHOTO: ETTLINGER
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