UV-curable inks and coatings have offered a number of environmentally friendly benefits for many years for print media and packaging products. One of the primary reasons is that they don’t require an energy-intensive thermal drying process. These formulations cure with exposure to UV light, which requires much less energy than the thermal curing process, especially with LED UV curing systems. UV-curable inks and coatings are also essentially 100% solids, which greatly reduces VOCs released in the nearly instant curing process.

UV-curable inks and coatings continue to gain market share because of their performance and sustainability features across numerous end-uses in the ink and coatings markets. Helping drive this growth are polymeric dispersants, which are a key component for energy-curable systems to deliver value and performance. Dispersants accomplish this by improving one or more technical aspects such as pigment dispersion quality, speed of dispersion, pigment loadings, ink stability, and optimized viscosity. The right dispersant often improves color and appearance properties of the final ink or coating (color strength and optical density, transparency or opacity, gloss or matting efficiency). Improvements in tinctorial strength can result in potential cost savings, if for example, target color strength can be achieved at lower pigment loading.

The Importance of Polymeric Dispersants

Energy-cured systems are solvent free, 100% active formulated from low molecular-weight monomers and oligomers – which generally don’t disperse pigment to the degree needed for high quality inks and coatings. The dispersant must do the heavy lifting, regardless of the type of particle being used.

Solvent-based systems are the standard for color and performance and have a high percentage of resin that’s used to help wet-out the pigment and form the final film when the ink is printed. These resins or binders generally have molecular weights in the tens of thousands, and as such they can help achieve a stable dispersion. When compared to a UV-curable ink, the molecular weights of the components are much lower and offer very little to no help in achieving the required colloidal stability of the pigment dispersion.

The chart below compares the approximate molecular weight of resins used in traditional solvent-based inks and coatings to the monomers and oligomers used in 100%-solid, energy-cured applications. The use of polymeric dispersants in formulation of pigment dispersions for UV-curable inks and coatings achieves equal, and potentially improved, performance.

In inks, highly colored, transparent organic pigments are used to provide color for very thin films, which means a higher percentage of pigment is needed. For instance, the percentage of pigment in an ink film might be 10 times that of a traditional coating. That requires higher pigment loadings, making the impact of dispersant even more important.

In addition to high strength organic pigments, there are other pigments used, like white, silica matting agents and other types of particles where the dispersant is equally important. Here again, the dispersant is used to provide the necessary viscosity reduction to achieve proper flow and final print or coating properties.

An important consideration is to work with a supplier who is an expert at developing dispersants to help you achieve the necessary requirements for your UV-curable inks and coatings. The right supplier also has the ability to help you develop innovative solutions when more pigment or different pigments are needed, or when exploring new applications, like UV-cured 3D printing.

Lubrizol Dispersants for Energy-Curable Systems

At Lubrizol, we have developed and continue to develop new and novel monomer soluble, 100%-active dispersants for energy curable inks and coatings.

Our broad portfolio of well-established dispersants covers all areas of energy-curable UV and EB inks and coatings for all types of pigments; carbon black, transparent organic pigments, TiO2, silica matting agents and advanced ceramics. Marketed under the Solsperse™ Hyperdispersants tradename, these products are suitable for the dispersion and stabilization of pigments and particles used across numerous energy-curable systems of varying molecular weights and polarity: UV Offset, UV Flexo, UV Screen, UV Digital, UV Wood and UV clear/over print varnishes.

As the energy-curable market continues to grow, Lubrizol continues to innovate and develop for this exciting sector. Our portfolio continues to expand to be used in new applications like 3D printing, while also developing dispersants with more bio-based content. We are currently testing and validating developmental products with customers and look forward to bringing these new innovations to market to deliver ever-more advanced performance for UV inks and coatings.

The Important Role of Dispersants in UV-Cured Inks and Coatings