By Industrial Print Magazine Staff
The Water-Based Printing Inks Global Market Report 2021: COVID 19 Impact and Recovery to 2030 published by The Business and Research Company states that the global water-based printing inks market is expected to grow from $10.84B in 2020 to $11.36B in 2021 at a compound annual growth rate (CAGR) of 4.8 percent. The market is expected to reach $13.36B in 2025 at a CAGR of four percent.
Above: Label examples from Avery Dennison that benefit from primers when printed with water-based ink.
One driver in the growth of water-based printing inks is the companies involved in this market shifting to manufacturing environmentally friendly inks, as customer demand dictates, with water-based printing inks fitting under this category. For packaging and labeling printers in particular, offering water-based inks is ideal, as they are considered more suitable for interacting with packaging that touches food or anything that a person might ingest.
However, water-based inks do present challenges, most notably time to dry inhibits the speed of some production-level printing presses and causes obstacles in terms of material compatibility. Using a primer can overcome this by ensuring ink adhesion to the substrate at hand while providing a visually appealing image that stands up through production to real-world handling.
Addressing Water-Based Inkjet
Water-based inkjet printing is popular for a number of reasons, especially in the labels and packaging space. For one, water-based inks present fewer environmental concerns when it comes to issues with chemicals migrating from the package to the product inside it.
“Although slow in adoption versus other digital platforms, water-based inkjet printing continues to grow in popularity due to its sustainability and regulatory aspects and increased speed performance versus other print methods for short-run, fast-turn jobs,” notes Catherine Heckman, business director, Ashland Laminating Adhesives & Coatings.
André Salié, project development, ACTEGA, agrees that as the market looks for more sustainable options, water-based inkjet seems like an alluring choice. “Today the market is focused on solutions that offer sustainability, less environmental impact, and increased recyclability. Water-based products meet these demands as well as enable easier handling, transportation, and fewer concerns around migration.”
Traditionally, inkjet printing for labels as well as packaging are completed with UV-curable ink technology. However, UV presents a few challenges in this space and for these applications.
“For more non-absorbent materials, you will find UV chemistry to be the popular choice because this offers fast and reliable curing and good adhesion on these substrates. However, working with UV chemistry also means more complex rules regrading transportation and its handling around the machine and during the process, as well as more concerns regarding migration of substances, especially in food packaging. But it is proven technology, based on decades of experience and know how,” explains Salié.
Phil Jackman, global product manager – digital, Sun Chemical, notes that the term “packaging” encompasses many different end-product applications and substrates and because of this “generally package printing is produced on wider and faster printing machines than label presses, often for food-based items and potentially on thin substrates for flexible packaging.”
Based on this statement, he believes water-based inkjet printing is growing in popularity for three reasons. “High-productivity printing machines tend to be more sensitive to the cost of the print and the cost of the ink and water-based inkjet has the potential to be at a lower price point than UV. Water-based inkjet inks dry to a thinner film than the 100 percent solids content of UV and thus are more suited to thin substrates. There is a need for food packaging compliance, and this is sometimes better delivered with aqueous ink technology.”
“While the share of products in a waterborne fluid from petrochemical sources is much lower, it is easy to see why water-based—as a renewable resource—products are in increasingly high demand. Especially since, combined with the hardware technology now available, printers can achieve the same productivity, high-quality results, and final products as those using UV, while still fulfilling the regulatory aspects of production,” adds Salié.
The Need for Primers
Water-based inkjet printing in the labels and packaging space does not require primers, however they are advantageous.
Heckman argues that primers are necessary. “Water-based inkjet inks are not compatible with any pre-primed surface due to their chemical make-up, thus requiring specially formulated primers that accept the inks. The primer’s main purpose is ink adhesion with no bleed or smudging and provides fast drying results.”
Paul Lender, business development manager, digital technology, Avery Dennison Label & Packaging Material North America, agrees that in most water-based systems special primers and media are required. “A water-based inkjet drop is around 80 percent water and that has to be managed so coatings and primers supply that function. The primer helps hold the colorant and/or pigment in place while evaporation occurs.”
“For the utmost reliability and performance, primers are very beneficial. The main purpose of primers is to create an inkjet receptive, homogenous layer, which provides consistent dot gain and image quality on a range of substrates,” explains Jackman.
Primers help to simplify the process, says Salié. “Primers can be used to increase the adhesion of the ink to the substrate. They also support the drying process of water-based inks and can increase productivity, because you do not have to change your entire ink set, just the primer.”
“Compared to printing with UV inkjet ink—which can be pinned—the image quality of water-based inkjet ink is determined by the rate at which ink drops stop coalescing with each other on the substrate. At one extreme there are very absorbent paper-based boards, and at the other, impermeable films,” notes Jackman.
Of course the manner in which the primer reacts during the course of yielding optimum image quality to each substrate varies. “A primer on a very absorbent media will be tasked with holding the pigments up at the surface so that color strength is not lost within the fibers. A primer on a film must control drop spread and arrest the neighboring colors from bleeding into each other,” explains Jackman.
Another example, when lamination after printing is required, primers can help to improve the overall resistance of the laminated printed surface, notes Salié.
Specific Feature Sets
Features like ink fixation, curing, and water resistance should be addressed when developing a primer for water-based inkjet printing in labels and packaging.
Ink adhesion and by association image quality is first and foremost the most important feature when manufacturing a primer, according to Jackman. Primer function varies by application and substrate, but as aforementioned, all applications and substrates “require ink fixation in terms of drop spread to achieve optimum and reliable image quality.”
Demands that are application-specific, suggests Jackman, include overcoating susceptibility, lamination suitability, and water/solvent resistance.
“Water resistance, in particular, is an important requirement in flexible packaging and labels. To get a good wet-rub or wet-knitter test with water-based inks is not easy and a primer helps a lot. With all of these benefits and the ability to easily change the properties of the substrate, primers can help to widen the substrate portfolio of a printer,” shares Salié.
Lender adds light fastness or fade resistance, as well as dry times as additional considerations when working with water-based inkjet.
Media compatibility is important, as we previously discussed. A primer’s main function is to assist in creating an optimal image on the media, and it must work well with the media in question to achieve this.
In an ideal scenario, one primer would work for both paper and film substrates used in packaging and labels. “The primers’ function is to provide a homogenous print layer thereby mitigating the variances of as many different media as possible. If a single primer can enable good printing onto all the required substrates, then this is ideal,” admits Jackman.
“Papers are typically easier to apply coatings to. Paper fibers are anchor points. Papers can also use less coating because the fibers can help manage all that water,” explains Lender.
Heckman says special attention should be made to films. “Media compatibility is mostly important using film substrates. Today’s technology dictates the film must be topcoated for primer adhesion and has been proven that corona-treated films are not a sufficient surface treatment. Paper’s porous surface accepts water-based inkjet primers.”
While compatibility between primer and substrate is key, there is a challenge—compatibility with the inks and possibly overprint varnishes later on, admits Salié. “A primer is designed based on required performance and resistances. To achieve this, the formulation will be tuned to a particular application. If you change something in this recipe you may win new capabilities, but lose others.”
Primers are of course beneficial, but only once on the substrate. Both inline and offline options are available.
Jackman believes inline is preferred, if the press architecture allows for it. “This is primarily due to the repeatability of the process and the fact that primer will arrive in a freshly dried condition to the subsequent inkjet print station. This removes any aging effects that are sometimes seen on older coated materials.”
Adversely, Heckman suggests offline. “This is due to the high deposition of the coat weight needed for ink adhesion, significant oven capacity is required for drying of the primer. Most coaters do not have the needed equipment to adequately dry and must toll out the process.”
“It depends on the individual production process—which primer application makes technically more sense or is economically better? Having an offline process will not block production if you have to stop printing for a primer changeover, instead, you can prepare your material and print it right away. On the other hand, it technically may be necessary to have the primer inline if you want to achieve a very extra bond between substrate, primer, and ink, and probably other finishing steps afterwards,” explains Salié.
Primers are useful in water-based inkjet scenarios especially in the packaging and labels segment. In all instances they enhance ink adhesion, ensuring a high-quality image printed on any substrate. IPM
Jun2021, Industrial Print Magazine
primers, adhesion, water-based inkjet