U.S. 8,182,602 B2
Sachtleben Pigments has been granted a patent for a method of preparing a well- dispersable, rutile-structured, microcrys- talline titanium dioxide product having a crystal size of less than 60 nm from a TiO2 starting material, the method is comprised of the (A) stages of treating a TiO2 oxide starting material to convert it into TiO2 so that (A1) the starting material is treated with a base to have an alkaline pH value; (A2) a precipitate obtained from stage A1 is treated with hydrochloric acid so that a
final hydrochloric acid content is adjusted to 8 to 35 g/l; (A3) the precipitate obtained from stage A2 is neutralized into slurry to a pH value of 4.0 to 6.0; (A4) the neu- tralized slurry obtained from stage A3 is primed with a pretreatment chemical; (A5) the primed slurry obtained from stage A4 is calcinated; and (B) further treating the TiO2 obtained from stage A to convert it into a TiO2 end product.