Patent ID: 7250080
Filing Date: 2007-07-31
Classification: C01P,C09C

Abstract:
1. An improved process for making an organosilicon compound surface-treated titanium dioxide material, comprising the steps of: (a) forming a mixture comprising a titanium dioxide material in water; (b) wet milling said mixture; (c) adjusting the pH of a slurry resulting from step (b) to between about 5.0 and about 8.5; (d) after step (c), removing said titanium dioxide material from said mixture by vacuum or pressure filtration; (e) after step (d), washing said titanium dioxide material; (f) after step (e), converting said washed titanium dioxide material to a fluid dispersion having a pH value of about 3.5 to less than about 7 via addition of a fluidizing agent comprising a water-soluble monoprotic acid; (g) after, or concurrently with, step (f), adding to the resulting dispersion of titanium dioxide material an organosilicon compound as a organic surface treatment, with mixing; and (h) after step (g), spray drying the dispersion of the washed titanium dioxide material resulting from step (g) to yield a dry titanium dioxide pigment powder.