Patent ID: 8758501

Claim:
A process for preparing a nanoparticulate UV protectant, comprising a) subjecting a nanoparticulate titanium dioxide to hydrothermal treatment, wherein the titanium dioxide has been prepared by a process that includes peptising said titanium dioxide, and wherein the hydrothermal treatment is carried out in a closed container at a temperature of 140° C. to 220° C., and b) subsequently applying a silicon dioxide coating onto said nanoparticulate titanium dioxide by a sol-gel process, in which a water-glass solution is added to a suspension of the titanium dioxide, wherein the application of the silicon dioxide coating is carried out at a pH kept constant in the range of pH=2 to pH=11, or the application of the silicon dioxide coating is carried out without pH regulation after prior pH adjustment of the suspension of the titanium dioxide to a value of pH=7 to pH=11, and the pH is subsequently lowered to a pH=5 to pH=8, and wherein the resultant coating is matured for 1 h to 8 h at a temperature of 50° C. to 110° C.