UV absorber for waterborne coatings

It is important to know that for waterborne coatings, functional additives such as light stabilizers are meant to exist in film forming resin only. This is due to the fact that water, just like solvent in a solvent-based coating, is only a vehicle.UV absorber for waterborne coatings

It must evaporate in film forming processes to achieve all the properties for which the coating system is designed. Although most commercially available light stabilizer (i.e. Eversorb 80) can be incorporated into film forming resin with relative ease, this does not necessarily mean that functional additives such as a light stabilizer can be easily introduced into a waterborne coating system without running into some kind of problems.

 When Eversorb 80 was introduced into an acrylic based waterborne coating system as it is, it caused a stable emulsion system to collapse as seen in Figure1.  illustrates the same phenomenon in a PU base waterborne coating system.

 Figure1: Eversorb 80, which was added into waterborne acrylic and PU coatings caused resins falling out of the emulsions

To short circuit the potential problem in formulating waterborne coatings with light stabilizers as shown in Figure1.. Everlight Chemical Industrial Corporation (ECIC) has developed a series of proprietary, user-friendly light stabilizer products to address such a potential problem. Figure2 shows the same PU-based waterborne coating remains stable simply by stirring AQ-1 into the system. If coating did collapse, we would be able to collect PU resin on the filter paper as seen in Figure1.              

 Figure2: Added critical high concentration of Eversorb AQ1 into same PU waterborne coatings

Four different AQ series products have been introduced to the coating industry since late 2006. Both AQ-1 & AQ-2 have been identical light stabilizer compositions with a slight twist to suit for different types of coating systems. Because of their compositions, they offer a complete but balances protection from UV light.

On the other hand, AQ-3 & AQ-4 offer basic protection to the coatings if only minimal light fastness is required. AQ-3 is recommended when primary concern is extensive exposure to the sunlight. AQ-4 is suggested if the primary concern is for a long term stability of the coating even the coating is only exposed to ambient light.

Depending on the protection level required; a recommended use level can be anywhere between 0.5% and 3% based on solid content. This translates into the actual between 0.25% and 1.5% when the solid content is 50% - a cost effective way to offer UV light protection to the coatings. Before and after exposure of delta E and 60° gloss measurements (as shown in  Figure3 & Figure4, respectively) confirm that with the addition of AQ-1, coatings would receive different degrees of protection according to its use level. Evidently, a higher use level provides a better protection.