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No dryer, lots of interest in PTi’s dryer-less sheet extruder

One way to reduce the energy, space, and maintenance impact of dryers in the extrusion of materials like polyethylene terephthalate (PET) and polylactic acid (PLA) is to eliminate the need for them altogether. That's the promise of the "dryer-less" twin-screw sheet extrusion technology that Processing Technologies International (PTi; Aurora, IL) showcased during a Sept. 20 open house at its company headquarters in Aurora, IL.

Converting space formerly used for storage, PTi invested $3 million in the setup of the operational production-scale demonstration line that relies on Italian supplier Bandera's patented High-Vacuum Twin-Screw Extruder (HVTSE) with downstream coating, accumulating, and winding technology from PTi. The system was up and running for a contingent of visitors, including attendees of the Society of Plastics Engineers (SPE) 20th annual Thermoforming Conference, who were bussed in from that event being held in nearby Schaumburg, as well as trade media and Linda Chapa LaVia, the democratic state representative for Illinois' 83rd district, which includes Aurora.

A process tour

Tom Limbrunner, PTi's VP of Engineering, walked visitors through the entire line, starting with the two-level material handling system, which starve fed a mix of virgin (40%), thermoforming scrap (40%), and post-consumer resin (20%) via a UnaDyn material handling system, including vacuum loaders. On the second mezzanine, there is a dosing/blending system for up to five components, with a typical setup including three resins plus two additives, although at the open house only resin was being mixed. Two windows on the system allowed visitors to see regrind within the feeder/blender, with a vibratory feeder set behind.

The material handling system starve fed an 85-mm, 52 L/D twin screw corotating extruder from Bandera, which features three vents down its barrel. At the first vent, any initial moisture cooked off, with two more stations for the extraction of volatiles and offgassing. Two pumps, one for each vacuum tank, pull any moisture or sludge off the vents and send it to condensers, which fill tanks that need to be emptied at different intervals, ranging from daily or weekly to monthly.

Prior to the Cloeren flat die, a four-position Kreyenborg screen changer filtered the melt while the line ran, with a static mixer installed before the feedblock. Limbrunner pointed out that at this position a second extruder could be tied into the feedblock to support co-extrusion. Running at around 1200 lb/hr, the system extruded 15-mil-thick sheet in a 57-inch wide web, which was later trimmed to 50 inches with two ribbons of scrap fed to a grinder.

PTi sais the system is capable of processing rates in excess of 2000 lb/hr (900 kg/hr) and running a variety of resins including post-consumer and industrial PET/PLA. In addition to allowing moisture and other volatiles to be removed as part of the extrusion process, in the case of recycled PET, the need for re-crystallization is also eliminated. Cutting those steps can produce energy savings up to 30-35% versus conventional methods, according to PTi.

In the demonstration line, the die fed a PTi Globaline vertical roll stand with a 100-ft accumulator roll, including an antistatic bath with integrated dryer. The cold roll features an integral silicone bath, with blowers and heaters, that allows extruders to coat the web's top, bottom, both, or neither.

Alongside the rollstand stood a three-screen PTi Titan control operator station. The center screen was identical to the control console on the machine, while the left image showed real-time web thickness via a Scantech inline, X-ray thickness gauge.

During the open house, PTi demonstrated a roll changeover, which was accomplished without stopping production thanks to the accumulator system's design. During the roll change, the winder is stopped, and the accumulator rolls split apart, giving the web more room to wind while the new roll is set up. Once the new roll was installed, the operator closed the door and restarted the system. Between the accumulator and the winder, a slitting system allows the web to be cut into desired widths.

Already in the market

PTi officials noted that the company has already sold a system into the market, with installation underway at an unidentified facility in South Carolina. Setup of the demonstration line began towards the end of July, with the line completely operational in early September. PTi officials said the company has already run trials for customers and is looking to book more. The company also plans to have version of the system at its NPE booth next April in Orlando.

PTi President Dana Hanson told PlasticsToday that his company views this technology as being different from Gneuss's patented MRS extruder technology, which allows dryer-less processing of reclaimed PET. Launched at K 2007 and debuting in North America at NPE2009, Gneuss's MRS has also moved into the devolatization of polyolefins. "We're first in this technology," Hanson said, adding that in addition to the line being installed in South Carolina, the company is finalizing another sale into North America.

In the spring of 2010, Bandera and PTi entered into a 10-year exclusive agreement covering North America, where PTi would promote and incorporate Bandera's HVTSE technology into PTi sheet-extrusion lines. These lines would then be manufactured, serviced and supported from PTi's headquarters in Aurora.

Importance for PET, PLA sheet extruders

Allan Griff, PlasticsToday's Extrusion Expert, was on hand for the PTi event, and offered his assessment for where the technology could be headed, pointing out the inescapable reality of cost. "The future of PTi's new development will depend as much on what they charge for it as on what it does," Griff said, adding that in some ways likely more important than the dryer-less aspect of the unit is the integration of blending, twin-screw compounding and sheet-making in a state-of-the-art system. "It won't make the market any bigger, and won't stop some people from buying dryer lines, including from PTi," Griff said, "but it certainly should be considered by anyone planning a PET or PLA sheet operation, or even some compounding where materials are mixed to form pellets."

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