In for a Treat

Surface treating equipment suppliers are looking in-depth at tough-to-treat substrates, newer ink preferences, and more do-it-all technologies.

by Susan Friedman

A teeming variety of substrates, particularly films, combined with interest in UV-/water-based inks and omnipresent efficiency emphasis all add up to reveal steadily more sides of surface treating.

Corona treaters remain popular for reasons that likely extend from familiarity to versatility to economics—but gas flame treaters aren't without an established niche. "Despite some of the known advances of flame treaters, I believe corona treaters will remain in the forefront," states Marc Nolan, sales manager at Sherman Treaters, Ontario, Canada. "People have reservations with the concept of a naked flame in the middle of their facility. In extrusion coating, it is common to see flame as a pretreater and corona in a post-treating role."

"Gas flame treating systems are the least costly to buy, but may not be the least costly to run," advises Chuck Schueler, sales manager of surface treatment products at Tantec, Schaumburg, IL. It may also distort or burn thinner films—a non-issue with corona's cold-treatment method, he says.

Following film's footsteps

A more active facet of surface treating technology can be found in suppliers' efforts to educate package printers about treating the multiple—and growing—personalities of films.

Printers face a slightly different surface treatment scenario for films than extruders—an important notion as more and more printers shift away from purchasing pretreated films. "Films are more difficult to treat off-line than during extrusion," explains Jeff Opad, VP of sales and marketing at Pillar Technologies, Hartland, WI.

During extrusion, a material's instability makes it more receptive to surface treatment. By the time a material reaches the printer, treatment may have decayed, or additives may have migrated to the surface, making the material less receptive to treatment and necessitating higher power levels during treatment to achieve the required surface energy, Opad explains. Pretreated material, however, isn't completely out of the picture. Opad adds that bump treating is very common, in which printers buy a 38 dyne substrate and then bump it up to a 42 or 45 dyne for ink needs.

Much emphasis currently hovers over consistent, damage-free treatment of the thinnest of ever-thinning films. Ron Seaman, VP sales at Corotec, Farmington, CT, suggests employing a live shaft, or driven treater roll, to lessen damaging tension on the substrate. In dead shaft applications, lighter-weight treatment rolls reduce pull on thinner films.

Augie Ray, director of corporate communications at Enercon Industries, Menomonee Falls, WI, offers such thin film strategies as a fuller wrap, in which two idler rolls help force more film around the treater roll, eliminating air underneath to minimize wrinkling and undesirable backside treatment. An entry nip roll can provide similar aid, but the treater roll must be driven.

Purchase drivers

Ink preferences, productivity concerns and space constraints can signal the need to re-evaluate surface-treating capabilities. Corotec's Seaman relates corona treating system upgrades are primarily driven by the current movement away from solvent inks. Water-based and UV inks hold increased surface energy, he explains, which in turn increases the energy level needed on substrates. As a result, printers need larger treaters that can provide more wattage per square foot per minute.

Upgraded systems with microprocessor-based, closed-loop generators can automatically maintain and monitor voltage and power levels, states Tantec's Schueler. Closed-loop systems can detect and respond to power levels that go below a certain limit, and can detect and remedy an arcing situation.

To address space scarcities, Pillar's Opad highlights higher frequency and wider ranged power supplies, which reduce station size by utilizing smaller electrodes. In addition, open-style treater stations take up less space than closed stations, so suppliers are adding metal side shields, shock elimination mechanisms and other features to maximize open systems' safety and environmental perks. Jan Westerheim, president of Solo Systems, Rowlett, TX, adds that single-side treaters on movable carts make a minimal footprint and enable occasional treating.

Bare, covered or both

Package printers familiar with corona treating's bare roll/conductive substrate, covered roll/nonconductive substrate distinction will find that the choice can be a bit more multifaceted. "For printing, coating and laminating, 95 percent of the time, the bare roll is going to be the best solution because it will accept conductive and nonconductive substrates," states Enercon's Ray. Covered rolls are a necessity in lane-treating of bags and pouches, he notes. Tantec's Schueler also favors bare rolls with ceramic electrodes, complemented by features that allow storage of treatment parameters for a wide materials range.

Though bare roll systems may provide attractive substrate versatility, suppliers make several cautionary points. "You're not scot-free with bare rolls," observes Solo System's Westerheim. "The ceramic electrodes can be a wear item." Nolan adds, "Bare roll treaters do not deliver the same aggressive corona as a covered roll treater, compromising achievable dyne levels."

A common argument against bare rolls is the inefficiency of their fixed-width electrodes, as compared to the adjustable-width electrodes common to covered roll systems, states Ray. He says the argument is "technically correct," but suppliers are "vastly overplaying the cost savings." Ray calculates that in bare-roll, narrow-web applications 5˝ to 20˝, printers who waste 50 percent of treating power to treat a narrower web will pay an average of 6 cents an hour more. In wide-web applications 30˝ to 120˝, the 'wasted' cost to treat a lesser-width web will average 27 cents an hour.

If a covered roll system most closely matches substrate requirements, printers must choose among the cost and performance implications of several coating materials. According to Seaman, a ceramic coating is the longest lasting, but is typically three to five times more expensive than epoxy or silicone rolls. Silicone's drawbacks emerge with heavy paperboard, which can dig into this coating and cause grooves. Meanwhile, epoxy can come up short in space efficiency. He explains that in a typical 5 kilowatt application, ceramic rolls will require 250 sq. in. per kilowatt, while epoxy rolls will require 500 sq. in. per kilowatt, doubling the diameter of the roll required.

Westerheim notes that ceramic, though a "sturdy, deluxe covering," can get hot. As a result, some films may not stand up to it. Epoxy stays cooler, she notes.

The versatility of universal treating can eliminate the bare roll vs. covered roll dilemma, says Opad. Some convertible treater designs feature a rotary selector switch that enables treatment of conductive or nonconductive materials without roll changes, while other universal treater rolls allow operators to switch between covered roll, bare roll, and dual dielectric systems by changing electrode cartridge.