EB's Bright Future

Numbers show that the usage of EB inks and equipment are on the rise. Now suppliers are working to get them in the spotlight.

"POINTING TO THE significant operations and 'enabling' benefits of the process, suppliers of ultraviolet (UV) and electron beam (EB) technology are bullish on near-term growth prospects," says the RadTech biennial survey North American Market Update. "Survey respondents, including over 80 industry suppliers and end users, project market growth of six to nine percent each year over the next three years ... and report growth of UV- and EB-formulated product usage up over eight percent during the two-year period 2000 and 2001, to just over 77,000 metric tons."

Reaping the advantages

EB equipment first hit the scene in the 1960s, and while the machinery and inks have had many facelifts, the basic foundation has remained essentially untouched. "Today's equipment offers many advantages," says Ed Maguire, VP, global marketing and sales at Energy Sciences Inc. (ESI). "Some of the more impactful benefits include the removal of all inter-station dryers (the actual hardware), the related heat (which can cause waste on heat-sensitive materials), and the excessive chilling costs associated with inter-station drying." Maguire adds that since EB inks are solventless, these systems also eliminate the need for explosion-proofing, incinerators, and licensing fees, along with all additional solvent-related issues (VOCs, retained solvents, etc.).

Bob Waddington, national sales manager at UVitec, believes the advantages are more mechanical and cost related versus actual ink performance. "One EB unit at the end of the press requires less overall energy and less complex interfacing with the press because you have one unit [as compared to multiple units with UV curing].

Wikoff's Director of Research Don Duncan, expands on the the financial side of the process: "The primary advantage of curing at the end of the press is that only one EB cure unit must be bought and maintained. The initial cost of the unit, the cost of nitrogen purging to maintain the oxygen-free cure zone, and the maintenance cost for a moderately complex piece of equipment are minimized by only requiring one."

The EB curing process also offers the distinct advantage of security. Steve D'Angelo, director of marketing, Packaging Division of Flint Ink, explains that the immediate and absolute cure subsequent to printing is, in and of itself, a vital step in the process. "With most types of printing, there is always an element of uncertainty related to complete cure of the print. In flexo or gravure, for example, we have a high confidence in the press' ability to dry the ink, but there is always a chance that they may fail to dry completely and thus still contain some residual liquids. These residuals can cause an unpleasant taste or odor or, even worse, a complete print job failure.

"EB-curable inks are virtually 100 percent cured subsequent to EB exposure, and residuals and extractable levels are virtually nonexistent. This is the security many food packagers required for highly sensitive food products," D'Angelo says.

The ink: A work in progress

New EB ink technology offers flexible packaging converters quick and easy access into energy-curable technology and the associated marketplace with minimal investment. According to Mike McGovern, Sun Chemical's director of sales and marketing for energy curable products, it allows converters to move into solvent-free printing technology, with longer term use leading to the design of significantly lower-cost presses and press equipment.

Last summer, Sun Chemical debuted WetFlex EC™, a flexographic printing process using UniQure™ inks, which is a line of wet-trapping UV and EB inks. It allows colors to trap over each other from one printing station to the next without smearing. McGovern feels this technology will lead to a major change in the way converters do business in the future. "The WetFlex process is still in the developmental stages, but from a print/press performance standpoint, use of the energy curable UniQure line will offer inks that require no diluents, remain stable in the sump and pan, print sharply, and provide tremendous color consistency."

However, some ink suppliers question the idea of wet-trapping effectiveness: "From an ink performance standpoint, there really isn't much to gain by wet trapping," says Waddington. "Some inks can pinhole or lay down poorly if they are exposed to an energy source before they wet out completely. This can usually be remedied by changing the rheology of the ink or switching anilox rollers on a flexo press."

EB's piece of the pie

The largest impact of EB ink is in the folding carton sector, especially in food packaging. The very high degree of cure, instant drying, and very low residual odor potential have allowed EB inks to make a large penetration into food cartons. Duncan says nearly all gable-top juice cartons, and a significant percentage of ice cream cartons, frozen food packages, cereal boxes, and cracker boxes are printed with EB inks.

Flexible packaging has been impacted by EB inks, but to a lesser degree than folding cartons, and mainly in food packaging. Duncan predicts that the use of EB inks and EB coatings to eliminate the need for a lamination structure in flexible pouches will be a major market trend in the next few years.

Of the three areas, tag and label is the least affected by EB inks. Some labels are printed EB now, but Duncan explains this is mainly seen where EB inks' high chemical resistance is needed. "A few printers are running UV flexo, using just enough inter-station UV curing to prevent set-off, and then running the web through an EB unit at the end of the press to punch up the degree of cure," he explains. "This is an effective process to increase cure and reduce residual odorous materials when flexo printing is required, kind of a back door into EB flexo. However, photoinitiators still are required, and their fragments remain in the ink film."

Waddington sees the potential for energy-curable products in the tag and label market: "Narrow web flexo is interested in EB technology because they can cure a very thick film of ink at high speeds," he says. "Folding carton and sheetfed printers are interested in it because they can sufficiently cure with one unit at the end of their press instead of having multiple cure units throughout the press."

Additionally, there has been significant activity around EB coatings as a replacement for an outer layer of a laminated structure of flexible packaging. "Today, there are still some challenges with this initiative; however, they appear to be relatively minor and it is possible that in the future, EB coatings will replace a major portion of the current lamination segment," says D'Angelo.

According to Steve Lapin, VP/technical director of Northwest Coatings, EB adhesives are being used to laminate inline or offline on packages. The primary advantage is that the full bond strength is achieved immediately upon curing.

"UV laminating has been used for more than ten years for the production of laminated labels," begins Lapin. "Labels are typically surface printed followed by application of the adhesive, and then UV cured through the clear overlaminate film. However, EB curing allows improved graphics quality due to the fact that the top film can be reverse printed and the EB can cure the adhesive through the printed label, resulting in graphics that are unobscured by adhesive." He believes this technology could be a very attractive alternative for wide-web laminated label converters.

The EB lamination of folding cartons appears to have several advantages over conventional topcoated cartons. Lapin says the lamination provides superior appearance as well as outstanding moisture barrier properties. Another aspect includes the creation of windows in the carton using the same film layer used for the lamination. Reverse printing of the film may allow superior package appearance with relatively low-cost board stock. In addition to clear films, various metallized and holographic films can also be laminated to board stock with EB adhesives.

The largest potential impact of EB laminating technology is in flexible packaging. EB laminating offers full bond strength immediately upon cure. "This allows inline slitting and immediate shipping of the laminated product. This is in contrast to the two to five-day cure time often needed for two-component adhesive systems," Lapin concludes.

The sky's the limit?

Duncan believes there are three primary limitations of currently installed EB systems on the printing process: they must be web, not a sheetfed, processes; they must be lithographic, not a flexographic, operations; and the curing zones must be nitrogen purged, or oxygen-free. The reasons for these limitations are interrelated, and several companies are working on methods to overcome them.

He continues by explaining that the reasons behind these limitations are also threefold: "Current EB curing units are big, expensive, and not well-suited for inter-station mounting. Since the inks are wet until curing and the EB unit is at the end of the press, the inks must be wet-trapped, ruling out current flexographic processing. And complete curing cannot be achieved if oxygen is present, as oxygen is an effective cure inhibitor."

Currently, several companies are working on energy-curable flexo inks that will wet-trap like litho inks, and many suppliers will make this technology commercially accessible within the near future. Duncan also says there have been attempts to set up sheetfed EB systems using much smaller EB cure units, but there are several real challenges. The largest problem is the difficulty in maintaining an oxygen-free cure zone with the large openings in the EB unit needed to allow room for sheetfed gripper bars.

In recognizing all the advantages an EB flexo ink could deliver, Sun Chemical is tackling the issues this technology has already faced. "Since the WetFlex process is still in the developmental stages, we know that we will run into issues that will need to be addressed," concludes McGovern. "We feel that this chemistry will allow us to accommodate most of the common printing surfaces and will provide the physical properties that energy-curable products are noted for. The main issue at this time is the differing viscosities of energy-curable flexographic inks versus conventional solvent or water-based materials. The UniQure inks' viscosity will demand using peristaltic pumps and may require alterations in doctor blade assemblies."

"There is always development going on in application-specific areas but the next steps in EB technology are really more commercial in nature," Maguire says. "[Depending on the application,] much of the equipment, chemistry, and application developments are complete. Most of the supply chain, i.e. film, ink, coating, and equipment suppliers, are now in the commercialization phase of these completed developments and plan to globalize in the coming months and years.

"Our vision of the future is a press that prints wet-on-wet and cures at the end of the press. It can add high-gloss EB coatings or instantly laminate a film inline and all be instantly cured with one EB at the end, generating a 100 percent solvent-free, completely in-line, high-speed, high-quality print job with none of the headaches of solvent," Maguire concludes.