Solvent-based ink currently covers about 90 percent of flexible packaging.
Water-based ink is primarily used in printing paper and paperboard. UV ink is mainly for label printing and EB ink points to specialized production. Today, development of UV LED adds output performance and profits to your print operation.
Flexible packaging materials are printed in an area that needs close scrutiny for the reduction of volatile organic compound (VOC) solvent emissions, lower energy costs and the “circular economy” in packaging. Since many wide web converters already have pollution control equipment, they make the decision to stay with solvent inks for higher speeds. However, is this the best choice for short runs and multiple SKUs?
Improved UV LED inks are coming on stream every day to meet the demand to eliminate solvent inks and at the same time produce extremely high-quality flexographic printing. The ability to use expanded gamut (EG) colors becomes easier because of the stability of the ink on press throughout the run and consistency from one run to another.
Reduction of spot colors and color matching can also lead to a reduction in setup waste. A reduced environmental footprint using food packaging-compliant UV LED inks is possible if converters can overcome the fears associated with radiation curing inks.
Good manufacturing practices must be followed—then the cure can be consistent, repeatable and reliable. Because there are no direct, online methods of determining degree of cure and since there is a variation in types of UV lamps, age of the lamps and ink used, the UV exposure conditions must be monitored and correlated with the cure result for the purpose of verifying the exposure is maintained within predetermined limits.
Any fears of inks not being fully cured are being overcome by new technology that delivers consistent output as a way of better ensuring full cure with migration issues under control.
UV LED lamps will not cause heat expansion of the central impression (CI) drum. Lamps can be easily removed for cleaning and maintenance. Among the wide-ranging benefits:
- Low to zero VOC and hazardous air pollutants (HAP)
- UV-cured resin generates up to 87 percent less carbon dioxide, compared to thermal curing
- No dryers results in an estimated 80 percent total energy reduction in BTU, including natural gas and electrical power
- Lower profile makes the machine operator friendly
- Less material waste is attributable to a shorter web path
- Reduced fire and explosion hazard
- UV LED curing can be turned on and off in an instant. Unlike UV lamps, no warmup or cooldown time is required, increasing production efficiencies
- Heat from hot air drying has always been an issue for heat-sensitive substrates and for thinner films, including PET shrink film
- Heat from hot air drying can lead to substrate shrinkage, causing registration errors that will impact the print quality. UV LED curing will help to take this factor out of the equation
- UV LED lamps are known to last for more than 30,000 print hours. However, mercury vapor UV lamps can lose power on average after 1,000 to 1,500 print hours
- Digital imprint enhancements and personalization are also possible inline and in register to the main press. Generally speaking, it can range from one to four colors
- Embellishments are a growing opportunity for packaging printers/converters. With the ability to produce embellishments on digital devices, inline with analog flexography, this will offer additional opportunities
UV LED low-migration inks offer new business opportunities for food packaging that demand food safety-compliant inks, especially for converters that do not want to install solvent abatement equipment.
The ability to execute fast changeovers and process a wider range of substrates including combinations of paper, film, foil and thinner gauge flexible substrates that are extensible in nature in this ever-changing environment, demands a more flexible approach to how these materials are processed.
Narrow web companies benefit from the fact that most manufacturers, especially those operating in the food and drink sectors, have widely embraced controlled inventory costs. The ability to produce both flexible packaging and shrink sleeves on the same press yields a faster payback if volumes require this flexibility.
For wide web printing, this translates into more frequent runs with reduced profitability. Converters should consider separate approaches to be more profitable for both short and long runs, rather than just stay with the way it has been done in the past.
EG, 6- or 7-color ink sets cut pre-production lead times by removing the need to qualify new inks every time you go to press. You’re eliminating things like washup time on press, and material waste with quicker setups, not to mention the savings in ink waste with multiple washups daily.
With the use of higher viscosity and stronger ink pigments, a thinner ink film can be applied leading to better print quality, faster ink cure and less ink consumption.
A wide range of barrier coatings and overprint varnishes is currently being used for some applications to eliminate multi-layer laminations. It is possible to add downstream stations for special coatings in register to the main press on the front or back of the web.
“Bio-based and Biodegradable,” “Recycling or Reuse,” we do not know where packaging’s “circular economy” is going. With new developments every day, this concept will keep the converter flexible to this changing environment. By using biorenewable-sourced resin content, the ink will decompose over time, or with de-inking properties when surface printed.
There has also been a growing interest in water-based UV curing technology in the last decade. You will be able to move in any direction according to the dictates of the new regulations and developments.
So, ask yourself, “What does flexographic printing have to do with the circular economy?” The entire cycle—from production and consumption to waste management—has to be considered. Some legislators want the producers of packaging and consumer product companies to pay for circular economy costs.
The battle is on to show which materials will best serve all aspects of food protection, preservation and cost, yet meet the demands of the circular economy.
- Mono-layer materials with barrier coatings with functional additives are becoming part of the landscape for sustainable packaging in response to pressure to recycle and reuse plastics
- Multi-layer materials will certainly see some changes
- Plastic recycling faces many challenges, ranging from mixed plastics to hard-to-remove residues, to cost-effective and efficient recycling of mixed plastics (the third being perhaps the biggest challenge facing the recycling industry)
Experts believe that designing plastic packaging with recycling in mind is the only way to meet this challenge. Undoubtedly, the pressure will be on the converter to apply these barrier coatings with functional additives inline with printing. Hand in hand with that demand comes this one: At the same time, reduce the waste generated. All production waste, even at the converter’s plant, will need to be recycled and the costs accounted for.