Scratch resistant clearcoats containing suface reactive microparticles and method therefore

A method for forming a scratch resistant coating comprising

• I) applying to a substrate a pigmented basecoat composition;
• II) forming a basecoat film of the coating composition applied in I);
• III) applying to the basecoat film a clearcoat coating composition, wherein the clearcoat coating composition comprises
• (A) a film forming binder system containing a crosslinkable resin and optionally a crosslinking agent reactive with the crosslinkable resin;
• (B) colloidal silica microparticles, ranging in size from about 1 to 1000 nanometers prior to incorporation into the clearcoat composition, wherein the microparticles are reacted with a divalent coupling agent to form composite particles of the inorganic particles and coupling agent, said coupling agent comprising a polyvalent backbone which is selected from the group consisting of silicone and phosphorus radicals, alkyl groups having a carbon chain length of from 1 to 12 carbon atoms, compounds selected from the group consisting of acrylic, polyester, polyether, urethane, urea, polyamide, epoxy, and alkyd oligomers and polymers, and mixtures thereof;
• the first functionality reactive with the inorganic particles is selected from the group consisting of hydroxy, phenoxy, hydroxy ether, silane and aminoplast functionalities;
• and
• the second functionality reactive with the crosslinkable resin is selected from the group consisting of carbamate, isocyanate, carboxyl, epoxy, amine, urea, amide, silane and aminoplast backbone;
• (C) a solvent system for the crosslinkable resin, optional crosslinking agent, and microparticles, wherein the crosslinkable resin is present in an amount from about 10 to about 80% by weight and the inorganic microparticles are present in an amount from 0.1 to 60.0% by weight based on the sum of the weights of the crosslinkable resin, the optional crosslinking agent, and the inorganic microparticles;
• and
• IV) baking the basecoat and clearcoat either separately or together to form a cured film on the substrate.