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Flexo Ink



Developments in water based and UV curable inks mean greater potential for converters.



Published July 12, 2005
Related Searches: UV curing Anilox rolls UV flexo Flexography
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The printing ink business today pulls in revenues of about $12 billion worldwide. Of that number, flexographic inks account for approximately $1.8 billion, or 15 percent. In the United States, flexography is more popular than it is in the rest of the world, and US printers consume about $1 billion of the total flexo ink market. That’s more than half of the global flexo ink consumption, and about 20 percent of the total US printing ink market.

Flexo inks are employed in the printing of wide web packaging products, of newspapers, and of corrugated products. In the narrow web segment, flexography dominates in North America, and is roaring along in Europe and other parts of the world.

While the consumption of water based flexo inks are growing at a modest 3 to 4 percent, according to industry sources, the growth of ultraviolet curable flexo inks is a marvel to behold. Mike Buystedt, vice president of Akzo Nobel Inks, Plymouth, MN, estimates the annual growth of UV flexo inks at 15 percent. “UV inks are taking share away from conventional water based inks,” he says.

Still, the market for water based flexo inks is huge, and in the narrow web industry they are dominant. Solvent based inks, once the standard and still employed in some industries, have virtually disappeared from the inventories of label and other narrow web printers.

The days of 120 line screen reproduction are basically over, according to prepress experts, and the popular 133 line screen images are finding a great deal more competition from those set at 150, 175 or even 200. This shift means quite a bit both to ink manufacturers and press operators. Higher screen counts mean higher anilox counts, and that in turn translates to ink that had better perform like a magician on the substrate.

“Our fellow suppliers are all pushing each other toward a stopping point,” says Mike Waddell, sales and marketing for Monarch Color Corp., Charlotte, NC. “The people in the plate industry are pushing 175 and 200 line screens. The anilox people are pushing the line count, so that 1,000 line is now common. Some even giggle about a 1,400 line anilox roll. I don’t know how much finer we can go with anilox rolls and expect any kind of an ink film thickness.”

Ink manufacturers have been busy in their laboratories tinkering with formulas for their water based products. “Strength” is the operative word today.

“Flexo inks now have higher strength for film printing,” says Buystedt. “They have been at higher strength for porous materials over the past five or six years, and now they’re stronger for films, so you can run a 1,000 line anilox roll. The time to dry is reduced, and you use less ink.”

Strength means a greater amount of pigment in the product. “When inks are stronger, you can put less ink onto the substrate, and you can turn down the dryers a bit because you don’t use as much energy to dry the water. You reduce the amount of ink consumption because you’re using less ink.” The added pigment raises the cost of the stronger inks by about 10 percent, he adds.

“You have to have ink thickness to get density and opacity with a transparent ink,” says Waddell, “and most of our inks are made out of transparent materials — they are a little translucent. So you have to have thickness to get desired densities. Once you get an ink loaded with so much pigment, the challenge is how you get it to transfer to the substrate. Our new challenge is to look for better resin materials. We try to get as high a pigment load as we can, but you’re looking at a product that’s 48 to 50 percent liquid, a combination of water and amines; the other percent is made up of resin and pigment, defoamers, wax surfactants and things of that nature. When you take one ingredient out of the recipe you make room for something else.

“The great challenge we’re faced with now is that everyone is trying to look for that super ultra process ink that’s thin and strong.”

Changes in substrates are having an impact on ink application, adherence and drying times. “It has always been a challenge to get water based inks to adhere to nonpaper substrates,” notes Waddell. “Years ago when a customer would call with a question about a vinyl or a type of polyester, we’d ask the dyne level. Usually the magic number was around 40-42 dynes in order for the ink to stick. “Today we’re seeing new coatings — alkaline versus acid based coatings, so now we also have know what the coating is. If you have an alkaline coating, it’s difficult for an alkaline based water ink to stick to it. You need to know the pH of the material along with the dyne level.”

Waddell recommends the application of a UV primer early in the print process, in order to overcome the adherence issue. “If there’s a way to put a primer down, a UV primer, you can get good results from that, because water based ink will adhere to a UV coating. The next time a person buys a press, they should get a UV curing unit in the first station. Traditionally they have one at the end for the coating. but if you have one in the beginning you can put down an opaque white, or if you’re using a nonpaper you can put down a primer. I think that’s an absolute necessity these days. It means you can do many more things with that press.”

“As aniloxes are going to higher line counts, the strength of the inks must improve,” says John Samony Sr., president of Braden Sutphin’s Flexographic Division, Colmar, PA. “They want the ability to hold dots, hold performance on press with higher speeds on different types of substrates, and we see four-color process quality being forced higher.

“Printers say, ‘Give me the strongest ink you can, and let me cut it back if I have to’,” says Samony. “Our chemists are looking at many new products to run faster, smoother and cleaner.”

Flexo inks differ in composition for use with film and paper substrates. These days, film inks are more user friendly, according to Buystedt. “They’re easier to maintain on press, and they print cleaner than they used to, without sacrificing performance characteristics.”

Inks for films and nonporous materials use different resin technologies, and present their own challenges on press. “The amines flash out of the system faster during drying,” he adds, “meaning that the operator has to pay more attention on press. These inks have a tendency to dry on press, requiring more press-side maintenance.”

The converter has to have the right drying package, he adds. “Speeds of 450 feet per minute are obtainable on a narrow web press using water base film ink, and even faster with paper because the ink is being absorbed into the stock more quickly.”


UV ink and viscosity
More converters are joining the ranks of those printing with ultraviolet curable flexo inks, which accounts for the strong growth in that product segment.

“The growth is fueled by people who have been using other print processes and who are now looking into flexo,” says Samony. “They want to know whether UV is the better application. The solvent people, instead of going to water based flexo, are looking to see if UV is the answer.”

Buystedt pegs Akzo Nobel’s sales of UV curable inks at between 15 and 20 percent of total sales. “In dollar percentage it can grow faster because it’s not as large,” he says.

The hottest trend among UV curable flexo inks today is lower viscosity. Since the process was introduced, UV flexo inks have been thick, pasty substances that often raised choruses of chagrin from their users. That has changed.

“Over the past two years there has been quite a bit of development of low viscosity UV inks,” says Waddell. “Customers were complaining about the viscosity being too high, and they were having problems with the anilox rolls backing away, or the ink not adhering. Our inks today are very close to water based ink in viscosity. We’re putting our UV process inks into opaque black jugs, and the press operator will be able to pour them just like the water based inks.

“With a lower viscosity you can run a higher line anilox roll. With the thicker inks you’ll be using 400s, 600s or 700s to do screens, but with the lower viscosity you can use 800s to 1,000s, and some are pushing 1,200 with very good results,” says Waddell.

Akzo Nobel’s newest UV flexo ink, known as Flexocure HD, features lower viscosity and higher strength, says Buystedt. “The printer uses less ink, so he gets increased mileage, and uses less watt density to cure because there’s less ink thickness.”


Converter challenges
Printers have a long list of ink problems, and they are quick to bring them to the attention of the ink suppliers. These challenges include poor adhesion, bleeding, color variation, dirty printing, excessive ink consumption, fill-in of reverses and type, foaming, halos, hazing, fogging, kick-out, mottling, piling, pinholing, plate swelling, screening, tracking, and striations, to name a few.

“Adhesion is the big one,” says Buystedt. “We can modify the ink to help it dry faster, and use a primer coat. Another problem is light sensitivity, and that’s because they didn’t use the right specific pigment in the ink.

“People sometimes don’t understand that all inks aren’t the same, that they’re made from different pigments. Some last for years, others fade within a month. Our description of every ink is specified on the Blue Wool scale (blue wool is used to measure light fastness, and is a common global scale), and we put that rating on the ink. If it has Blue Wool of two or three it will fade faster outside. If it has a rating of seven or eight it will last two to three years, typically.” Most converters don’t know the Blue Wool scale, he adds, “but we try to educate them.”

Another pair of challenges, in Samony’s view, are price and repeatability, the consistency of the product. “What the converter wants is the same ink all the time, but a more universal look. The more material a converter can push out the better, and he doesn’t want to have to fight the ink — he wants it to be trouble-free. But it’s still a chemistry,” he adds.

Everybody’s into a price situation today,” he says. “They want the best and lowest price. If the converter wants the ink company to provide a quality product at a declining price, something’s going to give. I believe that many converters consider ink to be a commodity product. That’s just not true.

“They call and say, ‘I have new material, and I want to run this ink on it, can you help me? But I don’t want to spend any more on the ink’,” Samony says. “In a price war, quality suffers.”



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