Лако-красочные материалы — производство

When producing titanium dioxide of maximum purity, the hydrate is heated (cal­cined) without any further additions. This gives a fairly coarse grade of TiO2 with a rutile content that depends on the heating temperature. However, to produce specific pigment grades, the hydrate must be treated with alkali metal compounds and phos­phoric acid as mineralizers (<1%) prior to calcination (r). Anatase pigments contain more phosphoric acid than rutile pigments. To produce rutile pigments, rutile nuclei (<10%) must be added; ZnO, Al2O3, and/or Sb2O3 (<3%) are sometimes also added to stabilize the crystal structure.

Nuclei are produced by converting the purified titanium oxide hydrate to sodium titanate, which is washed free of sulfate and then treated with hydrochloric acid to produce the rutile nuclei. Rutile nuclei can also be prepared by precipitation from titanium tetrachloride solutions with sodium hydroxide solution.