PP/PE/PET/BOPP/Foil – Converting from Solvent Ink to Water Based Ink

Water based Inks for Plastics and Foil – How to convert from solvents. Buy UV varnish digital inks flexo inks

A Practical Approach

In the 1980s, everyone was excited about the prospect of using water based inks for flexible packaging films.

We already had success printing water based inks on paper and corrugated board. But the thinking of the day was that water could replace solvent in more areas of printing and the world would be a much better place.

Of course, back then there wasn’t the kind of focused attention on sustainability, recycling and the environment that we see today.  In fact, the term “eco-friendly” was still a new concept.

Today, we have taken the lessons of the past twenty something years and we now have a host of new raw materials. These raw materials allow us to push the envelope further than we ever have. Printers today are using water based inks to print on a wide variety of non-porous substrates.


The Great Solvent Ink

What makes solvent based inks so great – and let’s agree that solvent inks are great because they are so ubiquitous in our industry.

The solvent ink is the “ideal” because it does what we need in a way that’s commercially acceptable:

  • It runs fast
  • the print quality is great
  • it adheres to many substrates and
  • the necessary raw materials are readily available to the world (see infographic below).

But wait a minute.

If we examine the number of positive attributes of water based inks, water seems to easily win. Looking at the info-graphic below there are many more positive things associated with water based inks than there are with solvent inks.

So what’s going on here?

The problem is that the printing world still operates on the solvent ink paradigm. Printing ink success is still skewed toward the attributes of solvent ink – not the water based ink. Put it another way – we value the attributes of the solvent ink more than we do those of water based ink.

SOLVENT OR WATER? THE BENEFITS OF USING WATER BASED INKS Low or no VOC component. Lower odor. Inks utilize sustainable resources. Non-flammable (therefore less regulated environmentally). Longer in-can ink stability than solvent ink. Easier to formulate inks for direct/in-direct food contact. Reduced potential for discharging toxic materials. Improves plant working conditions. Increases life of photopolymer plates (flexography). Less wear on gravure doctor blades, particularly with white (Ti02) ink. Reduced environmental costs. No/Reduced incinerator costs.

Not so fast...

We also have to consider a couple of other important factors that affect ink performance, film treatment and printing cylinders.

Uncoated substrates should be treated to a minimum of 42 dynes/cm to allow adequate ink wetting and adhesion. In most cases the best results are obtained when in-line treaters are used on the printing press.

This is one area where water-based inks are less forgiving than solvent inks, so if you’re having adhesion issues, the first place to look is at the film treatment levels.

When it comes to cylinders, many printers use the same cylinders for solvent and water based inks, but this isn’t recommended.

Typically gravure cylinders and flexographic anilox rolls should have shallower engravings for water based inks. The main reason is that it’s easier to evaporate water from lower volumes of ink, regardless of the type of printing press and its drying capability.

Common gravure engravings currently being used for water based inks range between 175 LPI – 200 LPI, and anilox specifications of 180 LPI to up to 1200 LPI for process printing. Actual cell volumes vary depending on the design and the required color strength.

Final Thoughts

The conversion from solvent to water-based packaging inks is still a work in progress.

In modern printing, the biggest challenge for water based inks is to keep up with the high press speeds (in excess of 300m/min) commonly in place for solvent inks.

Water will never dry as quickly as a solvent, but the benefits of water are clear. In the days ahead most companies are focusing on modifying existing printing equipment to make using water based inks easier.

On the raw material side there is a keen interest in developing faster-drying emulsions and those with better adhesion characteristics.

At Infinity Inks we have striven to make advancements in these areas to help  the transition from solvent inks to water based inks with our Hydroflex line of inks.

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