An improved process for making an organosilicon compound surface-treated
titanium dioxide material, comprising (a) forming a mixture of the
titanium dioxide material in water, (b) wet milling the mixture, (c)
adjusting the pH of the slurry resulting from step (b) to between about
5.0 and about 8.5, (d) after step (c), removing the titanium dioxide
material from the mixture by vacuum or pressure filtration, (e) after
step (d), washing the titanium dioxide material so removed, (f) after
step (e), converting the washed titanium dioxide material to a fluid
dispersion having a pH of from 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, with
mixing, and (h) spray drying the dispersion of the washed titanium
dioxide material resulting from step (g) to yield a dry titanium dioxide
pigment powder.