Adhesive Technologies

Zone coating, pattern adhesive coating, UV curable adhesives. Cold foil transfer. Thin film liners. Home-grown pressure sensitive laminates. Higher speeds, greater widths. These are the topics that are causing a great deal of excitement among adhesives suppliers, press makers and a handful of converters who are willing to step out on a limb to pursue new technology. Most narrow web converters are not experts in adhesives, and relatively few deal directly with adhesive application. They have to be somewhat knowledgeable about adhesives, however, because they have to cut through them on the die stations, and strip them away with the matrix. They have to know the basic properties that the adhesives offer, so that they can sell the proper pressure sensitive product to a customer.

Adhesives come in three basic types — hot melt rubber based, solvent based, and emulsion or water based. Recently UV curable adhesives have been gaining more attention.

“Adhesives have been going the same way inks have gone,” says Ray Mackura, technical support manager in the product identification division of Avery Dennison, Fasson Roll. “The trend is to move away from solvent based adhesives and toward emulsion or water based. For some it is an economical move, but there are more often environmental concerns.” Hot melt, he says, is still a major player, and is “typically more economical. Some of the technology that we have come up with allows them to be converted on a wider web, greater than 10 inches.” Avery Dennison’s new C2500 adhesive contains polymers unavailable until recently, and allows higher speeds, a sharper diecut, and converts cleaner, Mackura adds.

“The demands are for higher speeds, and more versatility in the patterns,” says Ernie Gregory, narrow web industry manager for Nordson Corp., Duluth, Ga., which manufactures adhesive application equipment. “The converters want to be able to do multiple projects with one piece of equipment, UV curing both hot melts and liquids, heat sealable products, tapes in line, and applications of pressure sensitive products to release liners on press.”

The interest in applying adhesives — and silicone liner coating — at the converter level has begun to grow. “We see two areas of interest,” says Steve Lapins, technical director of Northwest Coatings, Oak Creek, Wis. “First there is in-line converting of label stock, and second is using UV curable pressure sensitive adhesives for specialized construction, using existing label stocks. The second type is the one that’s easier to implement, and we’re seeing more interest and activity in that kind of use.”

Pattern adhesive coating and cold foil transfer, particularly the latter, are starting to gain a foothold in the narrow web flexo industry. Pattern coating is the application of an adhesive (and silicone liner) only to that portion of the web which will be diecut, thereby leaving the matrix uncoated and recyclable.

Facing the risks
“The concept of cold foil transfer has become a huge opportunity,” says David Meshirer, president of Beacon Adhesives, Mt. Vernon, N.Y. “Some people have done well using our products, but others are fearful. It’s very new to them and they consider it a risk. Many say that they have enough of a challenge keeping registration without adding the dynamics of applying adhesives.

“It’s so easy,” he adds. “We’ve printed them on the backs of labels with no problem. The difficulty we faced in the past is that very few people are set up to test the technology. They have million-dollar presses and they run them 18 hours a day, and they’re not happy when we come in and say ‘Let’s pour this adhesive in your press and see how it behaves’. They want to see a proven product.”

Beacon recently took deliver of its own flexo press, an Allied Gear machine that has the ability to run unsupported film, and equipped with Honle “cool” UV lamps. By using the press for research and development, the company hopes to be able to go to a converter with a complete process of pattern adhesive coating.

“What we’re finding is that it works 90 percent of the way,” Meshirer says. “We’re going after the other 10 percent now, using different anilox rolls, different speeds.”

With pattern printing, the printer lays down a lot more adhesive than ink. Consistency of the adhesive thickness is important, as is the type of anilox roll used. “Our adhesives are printing up to 500 feet per minute,” notes Meshirer, “more than sufficient for most printers. And we’ve learned that printers can lay down higher viscosities than with conventional inks, though we’re testing to see how they behave at higher line speeds.”

A new system unveiled
Andrew Wilkey is the managing director of DAS Systems Ltd., based in Wales. Over the past several years he has developed (and patented) a system of adhesive and silicone application on-press that is attracting the attention of both press manufacturers and converters alike. The DAS process involves two webs — a face stock and a thin film liner — unwinding at one end of the press. The face stock is printed with ink, and then receives an adhesive coating on the back. The adhesive coating is applied in a pattern, according to the design of the label, though the glue is purposely applied through a wider window to a portion of the stock that will become the matrix.

Farther down the press, the film liner is pattern coated with the silicone, which is applied only to the area that will be beneath the actual label. Following these applications, the two webs are nipped and passed through a UV curing station.

Conventional PS laminates produce a matrix that contains adhesive and silicone throughout. These add to the cost of the product and create an unrecyclable product. “With our system,” Wilkey says, “we stick the waste area to the backing material; we don’t coat it with silicone but with adhesive. That strengthens the carrier. We can marry a 50-micron face stock to a 20-micron back, to form a carrier now 70 microns thick.”

Comco International, the press manufacturer based in Milford, Ohio, is at work today developing a press that incorporates the DAS system. The company will unveil its new product, which is based on a 16” seven-color Comco ProGlide press, at Labelexpo Europe in October.

“We didn’t have to re-engineer,” says Chris Faust, marketing manager for Comco. “We’ve made some relatively minor additions of components to run multiple webs.”

The adhesive locks to the liner, Faust says, making it much stronger. “When you go to peel the label, the silicone is in the shape of the diecut label, and the label comes off clean and crisp, but the matrix stays married to the liner, and you can recycle that liner.”

“If you can keep the weight of silicone below 1 percent of the total weight of the carrier, you can recycle it,” adds Wilkey. “We’ve had our products tested by recyclers and the adhesive doesn’t present a problem.”

DAS is working on other partnerships in the Western Hemisphere. CL&D Graphics, a label converter in Oconomowoc, Wis., is installing one of the systems on a Comco press, and will be licensing the technology in the United States.

“In theory, if you look at the cost of film and adhesive and silicone, and put that package together,” says President Brian Dowling, “you can manufacture a film label for the same cost as a paper label.” Dowling views the challenges as more of a chemical problem than a manufacturing problem. “We’re looking at the technical advances that the adhesives people can bring to the party — that’s the undecided area at this point."