Plastics Engineering - May 2014 - (Page 19)

looking at filtration systems to get rid of the contamination"-whether it be dirt, metals, paper products, or plastics that get mixed in with the plastic they want to use. The same is true for the recyclers that turn bales of material back into pellets and flakes, even though they take out a lot of contaminants before the pelletizing or flake process, says Monika gneuss, vice president of sales and marketing manager at gneuss inc. in Matthews, North Carolina. "One of the trends is that the contamination rates [of incoming bales of plastic] are going up," she says. "recyclers are using dirtier materials because it is what they can get, and they need to clean it up. So people now realize that screen changers [and filtration systems] are critical elements of process regrind. "We are selling a lot more backflush screen changers," she adds. "it is the biggest investment someone can make, but it gives the end customer more flexibility to use recycled materials and materials that are more contaminat[ed] without it negatively affecting the process." Continuous Filtration John Whaley, business manager for Key Filters products from Parkinson Technologies inc. in Woonsocket, rhode island, USA, also sees companies making the shift toward melt filtration systems that run continuously. "Prior to the last five years, filtration systems were viewed as a necessary evil," says Whaley. "But now companies are starting to view them as a competitive advantage and an asset. They have started to look at the real cost of [temporarily] shutting down their process to change filters and realized that if they upgrade their melt filter to continuous operation, they can spent less money for raw materials and not have to shut down their process [for filter changes]." The patented Nordson Kreyenborg V-type screen changer has an integrated self-cleaning function for recycling applications with medium- to high-viscosity materials for which economic filtration is required. A Maag filtration system opened up to display its "arched" screen filter The market has responded to the greater interest in filtration systems with a slew of new products in the last 3-5 years. Some have rotary and drum filters designed to filter more contaminants from melt. There are also continuous belt ribbon systems that always have a new area of filtration coming in from behind. Others have arched instead of square filters, increasing the filter space four-fold. And even more have double-piston filtration systems with as many as four screen cavities and automatic backflushing features that allow continuous operation. There is also an increasing number of dual-bolt automatic screen changers that allow companies to change filtration screens without any interruption of the production process. "There has been an expansion of product offerings," says Tuttle, whose company makes filters under the Nordson Kreyenborg brand name. "You are seeing two-piston screen changers, multiple screens within a single chamber, extended areas for filtration on screens, technology that is extending the life of screens, and power backflushes." What type of filtration system is best depends on the specific needs of a processor, compounder, or recycler; the type of product they are making; the type and amount of material they are using; and the level of contaminants they need to filter out. "There is everything from simple low-cost solutions where you shut down the process temporarily and change screens, to highly automated systems," says Harald Pohl, product manager of polymer filtration for Maag Pump Systems gmbH in Wettringen, germany. "You need to know the material you are using, its viscosity, the desired throughput, whether you need to filter out fines, and how the size of the screen will impact the pressure," as the efficiency of the process often depends on the melt pressure behind the screen changer. "The finer your filter, the higher your pressure will be," adds Pohl. "You have to size the screen changer for the best performance, best efficiency and the most cost effectiveness." www.plasticsengineering.org | www.4spe.org | MAY 2014 | PlASTiCS ENgiNEEriNg | 19 http://www.plasticsengineering.org http://www.4spe.org

Plastics Engineering - May 2014

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