Edited by Lynanne Feilen
Plastics in Converting
In the custom film extrusion business, you’ve got to be versatile. You’ve got to handle many different materials, produce a wide range of web widths and thicknesses, corona treat to high and low dyne levels, and deliver orders both big and small. And, you’ve got to do it all quickly and efficiently to stay competitive. At least that’s the way the plant manager at Atlantis Plastics, Mankato, Minn., sees it.
Atlantis produces blown and cast film roll stock for applications such as packaging, masking, agricultural, lamination, graphics and consumer products. Atlantis can produce film widths from 12 in. to nearly 10 times that. Film thickness is anywhere from 0.020 in. down to 0.00045 in. Materials run the gamut from low, medium and high-density polyethylene to linear low-density PE to polypropylene and ethylene vinyl acetate. “The list of what we don’t do is real short,” says Trapp. With as much flexibility as Atlantis is required to show its customers, the company demands a lot of flexibility from its corona treaters.
Trapp expects the new treaters from Corotec Corp. will increase production by 20 percent on applications requiring high treatment levels. The system was specifically designed to provide almost instant width and treatment level changeovers.
You’d expect the need for versatility to present a challenge to a film producer. Changes in the extruder and die setup, adjustments in the tower, winder and other downstream operations, all need to be made quickly and efficiently. But also consider how these changes might affect the setup and operation of the corona treater. Naturally, if the job requires a higher or lower treatment level, the energy input settings need to be adjusted. And a wider or narrower web width, or thicker or thinner film, necessitates adjustment, too. As line speeds increase, the time the film is in the treater decreases, and you need to compensate with higher power levels. “We treat to higher levels than a lot of companies to begin with,” Trapp says. “Often, we’re way above the 38 to 44-dyne range that most people think is normal, because our customers do a lot of bonding and lamination, which require those high levels. Then, we’re just as likely to run the next job at under 38 dynes, ..exactly the opposite end of the spectrum. We sometimes run extremely thin gauges, too, at very high speeds. So, we need our treater to be flexible.” To answer the flexibility challenge, some treater suppliers recommend installing multiple treating stations on a single blown-film line. Then, they can be brought on-line as necessary to provide the different energy levels, widths, etc. To Trapp, though, it’s very simple: “When you are a custom film producer, doing multiple orders per day, it can’t take you hours to change over your treater. It’s got to be quick.”
Complex system is simpler
Initially, Trapp says, Atlantis wanted a system that would allow it to install or remove electrodes, as required, to control treatment density or to alter the width of the treatment area. And, they wanted to be able to flip electrodes around so that they could treat the underside of the web. What Corotec developed for Atlantis, however; was more complex, and, at the same time, simpler. The system installed at Atlantis is a double-sided treater with eight separate electrodes-four on each side of the web. Any of the electrodes can be energized independently of the others to alter the treatment density or treatment area. To make they system as user friendly as possible, all changes and adjustments to the location and number of operating electrodes can be made with a flip of a switch at a central, floor-level control panel. “Almost anything you might want to do, you can do with this one treating station,” Trapp says. “In terms of capability and flexibility, I’m not aware of another system out there like this one. We are the prototype.” Generally, there’s not one thing that increases output, says Trapp. “Usually, there’s a whole range of factors. But in this case, we’re doing one thing that will increase productivity by 20 percent on high-treat film.”