Waterborne UV coatings - combining superior product quality with minimal environmental impact

David Engberg, Product Manager BU TMP and NEO AMEA, Perstorp Group

With the increased focus on sustainable solutions in recent years, we see a growing demand for more sustainable building blocks and water based systems, as opposed to solvent based. UV curing is a resource efficient technology developed some decades ago. By combining the benefits of the fast curing, high quality UV curing with technology for water based systems; it is possible to get the better of two sustainable worlds.

Increased technical focus on sustainable development

The unprecedented development of the pandemic during 2020, drastically changing the way we live and do business, have also had an effect on the focus on sustainable offerings within the chemical industry. New commitments are made on top political levels on several continents, businesses are forced to review their strategies and sustainability commitments are scrutinized down to the details. And it is in the details solutions can be found to how technologies can help fulfil the needs for people and businesses in a sustainable way. How technologies can be used and combined in new ways, for example the combination of UV technology and water based systems.

Environmental push of UV curing technology

UV curing technology was developed already in the 1960s using chemicals with unsaturations to cure with exposure to UV light or Electron Beams (EB). Jointly referred to as radiation curing, the big advantage was instant curing and excellent coating properties. During the 80s the technology developed and started to be used on a commercial scale. As the awareness of solvents’ effect on the environment increased, so did the popularity of radiation curing as a way of reducing the amounts of solvents used. This trend has not slowed down and the increase in adoption and type of applications has continued since, and so has the demand both in terms of performance and sustainability.

Moving away from solvents

Although UV curing in itself is already a very sustainable technology, certain applications still require the use of solvents or monomers (with risk of migration) to lower the viscosity for a satisfying result when applying the coating or ink. Recently, the idea emerged to combine UV technology with another sustainable technology: water based systems. These systems are generally either of a water soluble type (either through ionic dissociation or miscible compatibility with water) or of the PUD (polyurethane dispersion) type where droplets of a non-miscible phase are dispersed in water through the use of a dispersing agent.

Beyond wood coating

Initially the waterborne UV coatings have mainly been adopted by the wood coating industry. Here it was easy to see the advantages of combining benefits from high production rate (compared to non-UV) and high chemical resistance with low VOC. Essential properties in coatings for flooring and furniture. However, lately other applications have started to discover the potential of water based UV as well. Water based UV digital printing (inkjet inks) can benefit from the advantages of both water based (low viscosity and low VOC) as well as UV curing inks (fast cure, good resolution and chemical resistance). Development is moving forward quickly and it is likely that many more applications will soon evaluate the possibilities of using water based UV curing.

Water based UV coatings everywhere?

We are all aware that our planet is facing certain challenges ahead. With a growing population and increased living standards, consumption and therefore resource management becomes more critical than ever. UV curing will not be an answer to all of these challenges but it can be one piece of the puzzle as an energy and resource efficient technology. Traditional solvent borne technologies require high-energy systems for drying, along with the release of VOC. UV curing can be done with the use of low energy LED lights for inks and coatings that are solvent free or, as we learned in this article, using only water as solvent. Choosing more sustainable technologies and alternatives enables you to not only protect your kitchen floor or book shelf with a high-performing coating, but also protect and recognize the limited resources of our planet.

The Perstorp perspective

Perstorp is one of the leading suppliers of polyol building blocks for UV/EB curing. These polyols are often key components in creating resins for high-performing UV curable inks and coatings. Several of these polyols are now also available as bio-attributed grades which enable even more sustainable solutions with significant reductions in the carbon footprint throughout the value chain.

Focusing in on waterborne technologies like UV PUD, Perstorp does not only have polyols building blocks that can be part of the backbone of the structure, but also a range of dispersing agents. Perstorp Bis-MPA™ and Ymer™ for example allow for stable and easy to formulate water dispersions. With a long history and broad portfolio, we at Perstorp are more than happy to share our experience and understanding of the building blocks themselves but also on resin synthesis as well as formulation and evaluation.