New Sol-Gel Technologies for the protection of High-End Metallic Effect Pigments

 
Sol-Gel encapsulation is a well-established technology for the passivation of metallic effect pigments especially for water-borne coatings. In recent years the demand for chrome-like and dark-chrome effects in the coatings market has grown. Due to their outstanding properties pigments produced by physical vapour deposition (PVD) are able to fulfil these needs. On the other hand a trend to environmentally more benign aqueous lacquers is seen. Generally this poses a problem for the effect pigment manufacturers as the very thin PVD pigments have to be passivated reliably without sacrificing their excellent optics. We show how this challenge can be mastered with modifications to the "classical" sol-gel route. Three main levers were identified: a) the metal-silica interface b) the properties of the silica layer itself, and c) the interactions between surface and coating matrix. Thereby a flexible toolbox is available which allows the stabilization of high-end metallic pigments even under demanding conditions.