Patent ID: 8809438

Claim:
A UV-shielding coating composition, comprising: (A) a dispersion in a dispersing medium of composite zinc oxide nanoparticles, wherein the composite zinc oxide nanoparticles are obtained by coating surfaces of zinc oxide nanoparticles with at least one member selected from the group consisting of oxides and hydroxides of Al, Si, Zr and Sn, and further surface treating said coated surfaces of zinc oxide nanoparticles with at least one member selected from the group consisting of a hydrolyzable silane and a partial hydrolytic condensate of a hydrolysable silane, said hydrolysable silane having formula (1): (R 1 ) x (R 2 ) y Si(X′) 4-x-y (1) wherein R 1 and R 2 are each independently hydrogen or a substituted or unsubstituted monovalent hydrocarbon group, X′ is a halogen atom, C 1 -C 3 alkoxy group, C 1 -C 3 acyloxy group or isocyanate group, x is 0 or 1, y is 0, 1 or 2, and x+y is 0, 1, 2 or 3, wherein said zinc oxide nanoparticles, from which the composite zinc oxide nanoparticles in dispersion (A) are derived, have been prepared by heating and vaporizing a zinc source in direct current arc plasma, oxidizing the zinc vapor, and cooling, said dispersion has a photocatalytic degradability of up to 25%, wherein the photocatalytic degradability (PD) is determined by adding the dispersion to a methylene blue solution, irradiating black light to the methylene blue solution for 12 hours, measuring the absorbance of the solution at 653 nm before and after the black light irradiation, and calculating according to: PD(%)=[( A 0− A )/ A 0]×100 wherein A0 is the initial absorbance and A is the absorbance after the black light irradiation, (B) a vinyl copolymer consisting of a copolymer of (b-1) 1 to 50% by weight of an alkoxysilyl-containing vinyl monomer, (b-2) 5 to 40% by weight of a UV-absorbing vinyl monomer, and (b-3) 35 to 90% by weight of a (meth)acrylic monomer selected from the group consisting of a (meth)acrylic acid ester of a monohydric alcohol, a (meth)acrylic acid ester of an alkoxy(poly)alkylene glycol, a mono(meth)acrylic acid ester of a polyol, a poly(meth)acrylic acid ester of a polyol, a (poly)ester of a non-polymerizable polybasic acid with a hydroxyalkyl(meth)acrylate, and an epoxy-containing (meth)acrylate, and (C) an organic solvent, wherein the dispersing medium is at least one member selected from the group consisting of an alcohol, an ester, a ketone, a glycol ether, an aromatic hydrocarbon, and a saturated hydrocarbon, and wherein the solids content of composite zinc oxide nanoparticle dispersion (A) being 1 to 50% by weight based on the solids content of vinyl copolymer (B).