Protective Coats

Coatings are somewhat unsung heroes in the package-printing world. They provide many important functions, yet most people don’t even know they’re there. These people don’t care either—except that if the coatings weren’t there, they might not like the label or package as much, might even complain about it, or worse yet, might not buy the product.

Whoa, Nellie! “Houston, We’ve got a problem.” “Iceberg dead ahead!” Now, we’ve got somebody’s heart pumpin’.

Coatings to the rescue

No, coatings can’t help much when it comes to world calamities, but if the heart that’s “pumpin’” happens to be a product manager, now we’re playing in the right ballpark.

Coatings are available in several general forms including solvent-based, aqueous, and UV/EB. Each has its own strengths and weaknesses, and can provide an adequate or even best-suited solution for any particular packaging application.

However, energy-curable (UV and EB) coatings, being relative newcomers to the field, are making their presence felt—UV in particular. Generally, UV coatings provide enhanced gloss and resistance characteristics versus their competing cousins, along with other desirable product and processing features.

“UV coatings have the distinct advantage of providing a high-gloss finish when compared to water-based coatings,” says John Signet, marketing manager for Water Ink Technologies. “It’s the high gloss that is important to many of the consumer products companies.”

Deanna Whelan, marketing manager for XSYS Print Solutions, notes that in addition to the desirable high-gloss finish, additional effects can be achieved with UV coatings, such as matte finishes and tactile properties that provide a look and feel not achievable with other coating technologies. Other enhanced properties she mentions include: optical brighteners for backlight capabilities; glitter and pearlescent enhancements; and different levels of COF (coefficient of friction) to optimize application and storage of packaged products.

The functional attributes that coatings provide include wear and exposure resistance to various environmental factors. Again, UV and EB coatings offer a number of advantages, “generally providing enhanced product resistance versus non-crosslinked systems,” says Mike Sajdak, research chemist for INX International.

“Certain UV formulations offer exceptional flexibility and resistance to detergents, alcohol, and grease,” adds Bob Waddington, general manager, UVitec Printing Ink. He also points out that UV coatings can be formulated to provide excellent bonding to difficult substrates.

A noteworthy advantage that UV systems have versus solvent-based coatings is their lack of VOCs. “It’s a 100 percent solids system, which is environmentally-friendly and easy to use on press,” says Mike Kucharski, market manager, graphic arts for Cytec.

Sajdak believes that this environmental advantage is a big selling point. Ink and coating systems that have VOCs must contend with Air Quality Management Districts (AQMD) that target and regulate VOC emissions.

Ease of use in the pressroom shows up in a number of ways. “With UV, you get an instantaneous cure so you can diecut, score, and fold and finish printed material right away,” says Waddington. “UV coatings can also stay open in the fountain and do not require the addition of pH adjusters or other additives as the jobs run.”

It’s not all gravy

Not surprisingly, there are various extenuating factors that need to be considered when using UV/EB coatings. These include cost, odor and migration, operator handling, and press speeds.

“UV/EB coatings can be more expensive than water-based coatings,” says Whelan. This is especially true if low-odor or low-migration UV coatings are selected since they are relatively special items.

To get a true picture, however, “you have to look at the total costs/benefits,” says Kucharski. “So many printers only look at the initial investment for the UV lamps and equipment.”

The reason for considering low-odor UV coatings is that odor is one of the issues with the use of UV components. “Products coated with UV can have a strong odor, which is why many consumer product companies still do not take advantage of UV coatings,” says Signet. The availability of low-odor UV formulations opens the door for use in some applications.

Handling of UV inks and coatings can also cause some problems because of the potential for skin sensitivity. “Many of the UV coatings on the market today can cause press operators to have adverse skin reactions,” notes Signet. “Users should check with their UV supplier for verification that their UV products do not contain aggressive skin sensitizers.”

In the equation for productivity, press speed is one of those higher-order factors that gets a lot of attention. In some applications, the UV curing process—the curing equipment and the UV formulations—can slow down a press. “Converters sometimes are not able to run their press as fast as they would like, which can limit productivity,” says Signet.

So, while UV and EB coatings can provide a good number of advantages and will continue to see expanded application in package printing, their use must be considered with all factors thrown into the mix. The following is a sampling of coating products.

Low odor UV coating
GlossCoat ULO is a low-odor, water- and rub-resistant, free-radical UV coating suitable for retort pouches or other retail, cosmetic, or pharmaceutical packaging applications requiring low extractables and low migration. —Water Ink Technologies, www.waterinktech.com

Fade resistance
A new screen UV-curable coating system, 22459-77, can withstand fade by absorbing the UV rays in sunlight before they hit the printed ink. It can be used on flatbed or rotary screen equipment.—UVitec Printing Ink, www.uvitec.com

Tactile varnish
SensiCure Tactile Screen Varnish is a one-component varnish for tactile text printing. It can create special effects like embossed or raised images suitable for specialty applications. —XSYS Print Solutions, www.xsys-printsolutions.com

Finishing varnish
The Uviscreen UV Series has a range of cost-effective print varnishes, including flexible “cut-and-crease” varnish, matt varnish, spot varnish for OPP laminates, and a foil-blockable varnish.—Sun Chemical, www.sunchemical.com

Coatings for IML
Northwest Coatings, now part of Ashland Inc., offers gloss coatings for in-mold label applications using paper or synthetic/film substrates. The coatings provide heat, abrasion, and static resistance.—Northwest Coatings/Ashland, www.ashland.com

Aqueous flexo coatings
HYDROTM SKID-RESISTANT aqueous flexo coating is designed to protect PE-coated cartons from alkali-based ingredients in ice cream and companion products during refrigeration storage.—Color Resolutions, www.colorresolutions.com

Envirocure
Envirocure® coatings offer a wide range of finishes including matte, imprintable, glow-in-the-dark, pearled, and tactile/textured. —Environmental Inks and Coatings, www.envinks.com

Matte texture coatings
RAD-KOTE matte texture coatings are UV-curable specialty coatings available in flexo and screen formulations. They feature low odor and are water, detergent, solvent, and abrasion resistant.—Rad-Cure Corp., www.radcure.com

Non-skid UV coating
Craigcoat 1077NSA is a non-skid, high-gloss, UV coating for multi-wall and paper bags. It has no VOCs, cures fast, and is odorless. —Craig Adhesives and Coatings, www.craigadhesives.com