By Cassandra Balentine
Part one of three
Digital print technologies continue to penetrate industrial markets as they continue to advance. One area, flooring, is expected to see increased adoption of the technology. Depending on the material used and the specifics of the job, pre- and post-treatment options may be necessary when digitally printing this application.
The October issue of Industrial Print magazine dives into the growth in this space and touches on the need for pre- and post-treatment in certain scenarios. We expand on pre- and post-treatment considerations in this web series as well as present a case study.
Pre-Treatment Advantages
A pre-treatment or primer might be required to ensure a successful floor print depending on the printed surface’s characteristics.
The role of a primer is to make the ink stay on the same place and on top of the substrate. “This means that there is less ink needed, which is a big savings. There is no limitation in using primers,” offers Mike Horsten, global business manager, InterioJet, Agfa.
Wilson Lee, director of business development, and Tom Gilbertson, VP of application engineering, Enercon Industries, agree, noting that pre-treatments and primers bring lower costs and extreme repeatability. “This means a better overall product.”
Stephen Sanker, manager, digital printing products, Koenig & Bauer US, sees specific benefits to integrating pre-treatments inline, as it helps to eliminate steps and consolidate the production workflow for printing. “In the end we are all focused on reducing costs and workflows that reduce labor requirements,” he shares.
Pre-Treatment Options
A variety of pre-treatment options are available based on the specifics of the job at hand and the surface in question.
Agfa has three different primers available, which are used for different technologies. “So a top coat is different than a mono coat, the way HPL behaves is different than short cycle and you would need a different primer,” says Horsten.
Agfa’s InterioJet primers are tested and approved for Agfa Digital Inks. “This is a huge advantage for the customer,” offers Horsten.
Enercon’s Blown-ion Plasma systems can treat from one half inch up to two inches with a single nozzle. Treatment speeds can be as high as 100 feet per minute (fpm).
Its Blown-arc Plasma systems treats up to seven inches wide with a single system. This is used for slower printing applications.
Enercon’s Flame plasma systems can treat at any width needed and also is able to treat at speeds up to 100 fpm.
Corona treatment increases the surface energy plastic films, foils, and paper to enable wettability and bonding of inks, adhesives, coatings, and laminations, according to Lee and Gilbertson. “Corona is created by discharging high frequency high voltage energy across a metal or insulated electrode mounted above a grounded roll. The air between the electrode and grounded roll is ionized and is visually identifiable as a purple glow. Our corona treaters can treat rolls of product from ten inches wide up to ten meters wide and beyond,” they share.
Deciding which pretreatment to use depends on how you are printing on the product. “If you are printing in a roll-to-roll format, a wide web corona treater would be the best option. If you are printing on smaller object like a plank or a tile, then you need to consider the cycle time for each part. This will allow you to pick the proper plasma solution,” note Lee and Gilbertson.
The Hymmen Digital Printing Technology ensures a high-quality and cost-effective production because all steps in the production process—from pre-treatment over the digital printing to the finishing of the surface are inline and delivered from one hand. The whole process is based on years of intensive development in the Hymmen technology center in close partnership with the lacquer producer Hesse Lignal. It is a technology that has proved reliable quality for years,” says Dr. Anke Pankoke, head of marketing/PR, Hymmen.
She explains that the recipe of the primer and base-lacquer is a highly complex topic. “Every customer is free to choose his own partner of delivery for the production materials—the substrate as well as the lacquer. Hymmen can only stand for the quality of the lacquer that was tested in the Hymmen technology center.”
Typically, application is done with Hymmen’s liquid coating machines that apply primer and base lacquer with roller applicators. “Depending on the quality expectations concerning the outcome more layers can be applied. Another option for SPC or LVT boards is the lamination of a white base foil before printing. But this is less often used.”
Industrial Inkjet Ltd. carries out print sample trials for each customer to determine the optimum pretreatment solution. “This has to take into account their existing manufacturing processes, design requirements—e.g. gloss level, and any other requirements such as IKEA compliance,” shares John Corrall, chairman, Industrial Inkjet Ltd.
Corrall points out that another kind of pretreatment is to print a white layer. “White is usually not printed to help with ink adhesion so much as to allow the colored inks to achieve the required color gamut. Most inkjet inks are transparent and if printed onto a dark surface they can only make the surface darker still. You can’t print a color that is lighter than the original surface. The solution is to print a white layer then the colors are printed on top of it. Now almost any color can be achieved. Note that with LVT tiles the white might be printed after the color. This is because it’s common to print the design onto the back of what will be the top layer of the tile. So the colored image is printed first—with the image reversed so it looks correct when looking thru the vinyl tile—and the white added later to produce an opaque layer.”
Koenig & Bauer’s RotaJET bring capacity, modularity, and inline integration to the table as pretreatment options for digitally printed flooring. In addition, Sanker points out that it has the ability to integrate OPV, flexographic, or gravure units to be incorporated as stations post inkjet printing. “All of these design and production elements translate to high efficiency models for the customer. We are doing this on an industrial scale while matching critical color requirements maintaining the highest color consistency requirements at the same time.”
The pretreatment selection is dependent on the ink formulation and the ink manufacturer’s specification for working in combination with the substrate. “In the case of décor applications, we have special formulations for digital ink and special formulations for pre-treatment, which we commonly refer to as primer because we are laying this material down just prior to printing with inkjet technology.”
Pretreatment and Primers
Preparing a surface for optimal printing is a crucial step when producing digitally printed flooring. There are various options to consider. In part two of this series we move on to post-treatment considerations.
Oct2023, Industrial Print Magazine