Besides high efficiency, UV stabilizers have to meet some other basic, but most important requirements. To grant such high efficiency, perfect compatibility, that is excellent solubility in the film-forming binder, is a definite must. This requires high permanence and low volatility as well, especially with stoving enamels. These properties must be present along with no negative side effects such as color contribution, interaction with other paint elements or influence on crosslinking.
For obvious reasons, UV stabilizers must be water-repellant. Precipitation, condensation, humidity or other water conditions would easily extract the stabilizers from the film. But such necessarily hydrophobic UV stabilizers are often rather tricky to incorporate into aqueous systems.The traditional method of waterborne paint manufacture offers three stages where these additives could be incorporated: (1) addition to the millbase; (2) addition with the let-down; and (3) addition as an aqueous preparation.