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Anilox choice is key to switching from solvent to water-based flexo printing on film

June 2024

Long reserved for paper, carton, and board printing, advances in water-based ink technology are opening new avenues for printing on a wider range of substrates. Today’s water-based formulations are starting to match the performance characteristics of solvent-based alternatives, enabling them to be used with traditionally more challenging materials like multilayer films.

However, as mounting regulations and the drive for more sustainable printing prompts converters to consider switching to water-based inks, it’s essential that they are prepared for the challenges that can emerge.

Water-based inks can trace a history back to 1938, but only in recent years has their performance and flexibility begun to match alternative formulations. The advantages of using water-based inks on paper and board are well understood, and their lower volatile organic compound (VOC) content compared to solvent-based inks has both environmental and health and safety benefits. This makes them ideal for compliance with changing regulations that require printers to minimise their environmental impact.

At the same time, the chemical characteristics of water-based inks have hindered their performance on less absorbent substrates. Specifically, problems with ink adhesion, and challenges with drying on non-absorbent surfaces have led to water-based inks struggling to offer the required scratch and scuff resistance.

Advances in ink formulation are closing this performance gap. Many of today’s water-based inks are perfectly suited for use on non-absorbent substrates, and as a result, a growing number of printers are considering whether switching completely to water-based inks could be right for their business.

Any change of ink systems comes with its own challenges, but transitioning to water-based ink requires an even greater level of forethought and investment. A changeover cannot be carried out overnight, and anilox rollers will require particular attention to ensure optimal performance and avoid damaging critical equipment.

Water-based inks require a completely different anilox engraving to solvent-based inks. For example, a standard anilox designed for printing HD with solvent-based inks would have approximately 500 lines per cm at a 3.5 volume. Similar designs for water-based inks would require a much more open engraving, a coarser line count, and a lower volume to manage the higher pigment level in the ink. This means that switching entirely to water-based inks can require an expensive upfront investment in new rollers.

Getting anilox selection right is also essential to ensuring ease of cleaning after use. These formulations have always been among the most difficult to clean from an anilox as they adhere to the roller’s surface, leaving a high degree of residue stuck to the cell walls. This can happen more quickly than with solvent-based inks.

Any anilox designed for use with water-based inks also must consider how it will tackle the problem of corrosion. Anilox coatings are by nature slightly porous, meaning any liquids can eventually penetrate through the ceramic coating to the metal core. With water-based inks, this can lead to oxidation, causing the core to rust and impact the ceramic coating’s integrity.

Sandon Global provides a solution to this problem through its Enhanced Densification Treatment (EDT). EDT is a process applied prior to laser engraving to provide a preventative barrier to substrate corrosion and oxidation, making the chromium oxide coating completely impervious to liquid. As a result, the core of the anilox is protected against substrate corrosion caused by water-based inks and coatings, promoting more efficient and consistent ink evacuation.

These solutions combine to highlight Sandon Global’s expertise in creating the right anilox for any application – expertise that was critical to the success of a recent trial of water-based inks with Slovenian packaging material manufacturer Stratum Plastika Mesojedec (‘Plastika’). During Plastika’s trial of Sun Chemical’s SunStrato® AquaLam Gen2 water-based inks on OPP and PET substrates, the company found that when used alongside a Sandon Global anilox, the ink was able to match the performance of solvent-based solutions.

Sandon Global’s contribution in adapting the anilox specification, optimising volumes and cell structure to suit the water-based ink is a service offered to all customers. The Sandon team’s expertise in anilox development, combined with the industry’s highest hardness and lowest porosity anilox, results in anilox that can easily support printers transitioning to water-based formulations. With specialist knowledge in corrosion resistance and how to adapt cells to ensure easy cleaning, Sandon Global works with its customers to match solutions to their unique requirements.

Get in touch today to learn how Sandon Global’s expertise in water-based inks can help avoid the technical challenges associated with switching from solvent to water-based printing.

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