Solvent-Free Defoamers Developed Specifically for 100% UV-Cured Systems: BYK-1788 & BYK-1799

Compared to traditional solvent-based systems, solvent-free and UV-cured paint systems are gaining increasing importance in many applications thanks to their superior environmental compatibility, economical formulation and application properties. UV-cured paint system technology is one of the technologies with above-average annual growth rates worldwide. In addition to wood, furniture and general industrial paints, these systems are increasingly used in the printing ink industry as well. However, environmentally responsible solvent-free formulations and the processing difficulties that typically arise, or high application viscosity in solvent-free 100% UV-cured paint systems, make foam removal difficult. Particularly if the formulation contains matting agents or pigments, or if application takes place under very difficult conditions, the use of a high-efficiency defoamer is essential. With these technical requirements in mind, two new solvent-free defoamers have been developed specifically for solvent-free 100% UV-cured paint systems: BYK-1788 and BYK-1799. BYK-1788 is a solvent- and silicone-free polymer defoamer with balanced defoaming properties and good compatibility with the system. For this reason, it is particularly suitable for paint systems requiring high levels of gloss and transparency. By contrast, BYK-1799 is a solvent-free defoamer based on organically modified polydimethylsiloxane with extremely powerful defoaming properties and is an excellent choice for use in matte or pigmented solvent-free UV-cured systems. It removes both macro and micro foam and, thanks to its highly efficient defoaming properties, is a product well-suited to common application methods such as roller application.

Defoaming Properties for Solvent-Free UV-Cured Clear Coat Systems

BYK-1788 and BYK-1799 were tested in comparison with other products in the portfolio for defoaming power in various 100% UV-cured systems. Figure 1 summarizes the application technology results for a urethane acrylate-based solvent-free 100% UV-cured clear coat system. In each case, 0.2% defoamer based on total formulation was added. After samples were left to stand for one day, they were foamed using a solvent at a rotation speed of 2 m/s for one minute and immediately poured onto a Plexiglas panel fixed at a 65° angle and cured with UV light after waiting two minutes. As summarized in Figure 1, BYK-1788 has the most balanced ratio in terms of efficiency and compatibility compared to all other defoamers tested, thus providing excellent defoaming capability for clear coat systems without adversely affecting transparency or causing cratering. Due to BYK-1799's strong defoaming properties, its use at the stated amount (0.2%) was found to have a negative effect on the system's transparency and cause cratering. The main reason for this result is the application rate. Particularly when using BYK-1799, it is clearly evident that defoamer compatibility depends on the selected amount. As a result, BYK-1799, as shown in Figure 2, can be used in clear coat systems at lower amounts (0.05%) without showing negative side effects on leveling or transparency. Figure 1. Evaluation of the defoaming properties of defoamers tested (5=excellent – 1=inadequate), cratering tendency (5=no cratering tendency and 1=significant cratering) and effect on transparency of a urethane acrylate-based UV-cured clear coat system (5=no turbidity, 1=high turbidity)

Defoaming Properties for Matte Solvent-Free 100% UV-Cured Paint Systems

In addition to UV-cured clear coat systems, BYK-1788 and BYK-1799 were also comprehensively tested for matte solvent-free 100% UV-cured paint systems. As an example, the application results shown in Figures 3 and 4 were recorded for an unsaturated polyester-based matte solvent-free 100% UV-cured paint system. To test the defoamers, each was added at 0.3% based on total formulation and mixed. After samples were left to stand for one day, they were foamed using a solvent at a rotation speed of 2 m/s for one minute and immediately poured onto a Plexiglas panel fixed at approximately 65° and cured with UV light after waiting two minutes. BYK-1799 demonstrated very strong defoaming properties by removing macro and micro foam without adversely affecting paint leveling or showing cratering tendency, and proved its effectiveness in this test. For the silicone-free polymeric defoamer BYK-1788, it can be concluded that it has quite balanced compatibility in matte systems and does not adversely affect leveling or cause cratering; however, it was observed to be insufficient for effectively removing foam in matte systems. Figure 2. Defoaming properties of BYK-1799 at 0.05% based on total formulation (right) compared to a system without defoamer (left) for a 100% UV-cured clear coat system applied using a Moltopren roller Figure 3. Evaluation of the defoamers tested in terms of macro and micro foam (5=excellent – 1=inadequate), effect on leveling (5=no effect – 1=very high negative effect) and cratering tendency (5=no cratering tendency – 1=significant cratering tendency) for an unsaturated polyester-based matted UV-cured paint system Figure 4. Photo protocol of variable efficiencies of defoamers tested for an unsaturated polyester-based matted UV-cured paint system. Macro and micro foam evaluation; 5=excellent – 1=inadequate   Figure 5. Inclusion of BYK-1788 and BYK-1799 in the defoamer portfolio for solvent-free 100% UV-cured paint systems as a function of defoamer compatibility and resulting defoaming properties (fig. shows a representative selection of defoamers).

Summary

BYK-1788 and BYK-1799 were developed due to the growing importance of solvent-free 100% UV-cured paint systems and the fact that effective defoaming properties are an important criterion in these systems. The distinguishing feature of both defoamers is that they meet the needs of both solvent-free 100% UV-cured clear coat systems requiring maximum gloss and transparency, and matte or pigmented 100% UV-cured paint systems where maximum defoaming properties are very important. (see Figure 5). The more system-compatible polymeric structure of BYK-1788 and the relatively incompatible polydimethylsiloxane structure in BYK-1799 make these two defoamers the most ideal defoamers in the available portfolio for use in solvent-free UV-cured paint systems. Author: Marcel Krohnen - Global Head of Final Wood and Furniture Coatings - BYK Additives & Instruments Compiled by: Özge Şahin - Technical Sales Manager Paints, Inks, Adhesives - IMCD Turkey