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Liquid Courage: Coating Technology for Print Protection

(February 2008) posted on Wed Feb 13, 2008

Liquid lamination offers graphics producers the ability to protect prints at a competitive cost and minimize waste and labor in finishing. Read on to find out more about the technology and the applications for which it is suited.

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By Ben P. Rosenfield

UV coatings have quickly gained popularity in recent years as printers explore production and finishing options that are more environmentally friendly. UV coatings for printed graphics are made without the use of VOCs. They’re composed entirely of convertible solids, meaning they become plastic with nothing evaporating in the process. Water-based coatings, which are often composed of 70% water and 30% resins, take longer to set because the water content must be allowed to evaporate completely before the substrates can be rolled or stacked. Tatum says the evaporation factor adds to the cost of using water-based coatings.

“To get the same type of coverage rate [as UV], you have to put a lot more on; hence, you’re spending more money,” Tatum explains. “The benefit of UV is it works with a reverse-roll coater, a three-roll coating system. It lays down the coating in a very, very thin layer, from about 6-20 microns.”

Water-based coatings have benefited recently from advances in formulation technologies. Just a few years ago, you could find 2-3 lb/gal of VOCs in a water-based coating. Today, some coatings are made with less than a pound per gallon. Tatum explains that high VOC content was one of the main contributors to yellowing. He credits the use of non-stearated resins for the reduction in solvent content in aqueous coatings.

Despite the gains made by waterbased and UV-curable coatings, solventbased formulations still have a place in liquid lamination. David Conrad, equipment product manager for Neschen Americas, says solvent coatings remain prevalent in the sign industry. Flexible displays benefit from solvent coatings, which are designed to resist becoming brittle or cracking with age. He says applications on rigid media are best suited to UV coatings. That’s because UV coatings typically don’t exhibit the same elongation properties found in other types of coatings. And for that reason, as Tatum puts it, UV coatings don’t fit the bill for protecting fleet graphics and vehicle wraps (Figure 2).

“At the very minimum, you should have about 150% elongation to qualify for a proper fleet type of product, because it needs to go around rivets, around intricate curves, and so on, without causing the coating to break,” Tatum explains. “Once the coating breaks, then your ink is toast.”


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