machinery feature | Screenchangers
Ettlinger’s ERF series of melt filters is
suitable for heavily
contaminated plastics
polymer is maintained at constant pressure, ensuring uniform processing downstream. One key to the efficiency is the design of the steel strainer tubes, which are available with micro-holes ranging from 120 to 750 microns. The holes are conical in shape, permitting passage of molten polymer while preventing blockage by contaminant. This design and the symmetrically positioned knives in the drum contribute to the long working life of the tube before it needs to be replaced. Once cleaned, the tube can be reused.
High efficiency In similar fashion, Ettlinger showcased an enhanced range of high-efficiency melt filters. Its ERF series, which is suitable for heavily contami-
nated plastics, can now handle higher throughputs, while the Eco models are optimised for filtering PET and PE in film and foil lines – as well as low-viscosity thermoplastics and polyamide. The patented, continuously operating ERF and ECO
melt filters can be incorporated into almost any extrusion line. At the heart of both types is a rotating filter drum with conical perforations, through which the contaminated melt flows from the outside to the inside. A scraper continuously removes contaminants from the surface of the drum and feeds them to an exit screw. This enables the filter to be used continuously and fully automatically over long periods without having to replace the screen. The advantages of this include constant melt pressure, low melt losses, good mixing and homogenis- ing of the melts, and short contaminant residence times
Hitech’s BPC
screenchanger operates at processing
pressures of 5,000psi
on the filter surface. ERF filters, for through- puts up to 6,000kg/h, are
suitable for separating contaminants such as paper, aluminium, wood, silicones and high-viscosity plastics from heavily contaminated polyolefins and polysty- renes. Improvements to the flow channels lead to lower
differential pressures, which can increase throughput rates boost productivity by up to 15%. ERF melt filters are mainly used in the extrusion of PP, HDPE, LDPE, PS and some engineering thermoplastics such as packaging films, yoghurt cups (web scrap), and pipes, and are processed into
granulates, sheets, films or profiles. Eco melt filters, designed for maximum throughputs
of 1,800kg/h (Eco 200) and more than 3,000kg/h (Eco 250), are optimised to support sophisticated extrusion processes such as the manufacture of films, sheets and other semi-finished products. They are ideal for filtering polyolefins, PET and PA as well as recycled materials containing up to 1.5% contaminants. Around two-thirds of the Eco melt filters installed to
date are used to process PET – with 80% of these used in the manufacture of thermoforming sheets and packaging tapes made from bottle regrind. The remaining third are used in the processing of polyole- fins. A major application here is in the manufacture of construction sheeting and thermoforming sheets made of virgin material, where they help to reduce the number of surface specks.
Taking the pressure High-Technology Corp (Hitech) says that its new Model BPC screenchanger can filter under extreme conditions – such as high processing and differential pressure – without distorting or tearing the screen media. It is designed to operate at processing pressures up
to 5,000psi and differential pressures as high as 1,500psi. The device uses proprietary flow-channels and breaker plate geometry to form a balanced polymer seal that promotes consistent screen displacement, says the company. Good results have been achieved in applications including co-extruded cast film lines running polymers with high concentrations of calcium carbonate, using ultra-fine (55 micron) filtration with multi-screen media.
14 FILM & SHEET EXTRUSION | December 2016
www.filmandsheet.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58