Patent ID: 8546484

Claim:
A UV-shielding silicone coating composition comprising (A) a dispersion in a dispersing medium of composite zinc oxide nanoparticles which are zinc oxide nanoparticles surface-coated with at least one member selected from the group consisting of oxides and hydroxides of Al, Zr and Sn, said surface-coated zinc oxide nanoparticles are further surface-treated with at least one member selected from hydrolysable silanes and partial hydrolytic condensates thereof, said hydrolysable silane having the general formula (2): (R 4 ) x (R 5 ) y Si(X) 4-x-y (2) wherein R 4 and R 5 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, said zinc oxide nanoparticles from which the composite zinc oxide nanoparticles in dispersion A have been prepared by heating and vaporizing a zinc source in direct current arc plasma, oxidizing the zinc vapor, and cooling, said dispersion having a photocatalytic degradability (PD) 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 the following formula: 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 silicone resin is obtained from (co)hydrolytic condensation of at least one member selected from alkoxysilanes having formula (1) and partial hydrolytic condensates thereof, said alkoxysilane having the general formula (1): (R 1 ) m (R 2 ) n Si(OR 3 ) 4-m-n (1) wherein R 1 and R 2 are each independently hydrogen or a substituted or unsubstituted monovalent hydrocarbon group, wherein R 1 and R 2 are optionally bonded together, R 3 is a C 1 -C 3 alkyl group, and m and n are independently 0 or 1 and m+n is 0, 1 or 2, in the presence of a dispersion in a dispersing medium of composite zinc oxide nanoparticles which are zinc oxide nanoparticles surface-coated with at least one member selected from the group consisting of oxides and hydroxides of Al, Zr, and Sn, (C) a curing catalyst, and (D) a solvent, the solids content of composite zinc oxide nanoparticle dispersion (A) being 1 to 50% by weight based on the solids content of silicone resin (B).