| abstract |
The object of the invention is a process for coating a titanium dioxide pigment according to which a dispersion of titanium dioxide in water is formed, optionally in the presence of a dispersing agent, such as a water soluble silicate and/or an aminoalcohol, whereafter to the titanium dioxide pigment dispersion (1) an acidic hydrolysable titanium compound in an amount of 0.1 to 1.5% by weight calculated as TiO 2 , (2) a water soluble phosphate in an amount of 0.1 to 1.0% by weight calculated as P 2 O 5 , (3) an acidic hydrolysable zirconium salt in an amount of 0.1 to 1.4% by weight calculated as ZrO 2 , is added, the slurry is made alkaline with a base, and (4) a water soluble hydrolysable alkaline aluminium compound is added in an amount of 0.5 to 5.5% by weight calculated as Al 2 O 3 , whereby all the percentages by weight are calculated from the weight of the TiO 2 -pigment and the alkaline slurry formed is neutralized with an acid and the coated titanium dioxide pigment is recovered. The produced pigment has excellent gloss and weather resistance properties. |