Core/Shell Silica Nanoparticle Dispersions to Improve Scratch Resistance of Solvent-borne Coatings

摘要

A solvent-borne nanoparticle dispersion with an inorganic core and an organic shell has been developed, containing silica in the core and covalently bonded dimethyl polysiloxane and adsorbed wetting agent in the shell. This surface modified nano-silica with excellent flocculation stability provides a much stronger increase of scratch resistance and abrasion resistance of clearcoats or high gloss topcoats than unmodified silica particles, without affecting transparency of the clearcoat, or having a negative impact on gloss and haze. Results in various types of two-pack polyurethane and baking systems will be higlighted. The improvement can be detected by using several standardized test methods, and depends on the binder type and crosslinking mechanism as well. Best results can be obtained in the range of 1 to 4% silica nanoparticles on the complete coating formulation. The new technology can be used to improve properties of air drying and baking systems, e.g. car refinishes, plastic coatings, industrial coatings and wood coatings.