Treatment of pigment
AssigneeTioxide Group Limited
InventorPeter Barry Howard
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Abstract
A process for the treatment of titanium dioxide pigment which involves adding to a pigment slurry a compound of phosphorus, of aluminium, of zirconium, of titanium and of silicon, adjusting the pH of the slurry to a value of from 3.5 to 4.5, followed by adding to the slurry a compound of phosphorus of an alkaline reacting compound of aluminium prior to the addition of mineral acid to adjust the pH of the slurry to a value of 6.5 to 8.
Claims20
A process for the treatment of titanium dioxide pigment which comprises forming an aqueous dispersion of pigmentary titanium dioxide containing a water-soluble compound of phosphorus in an amount of from 0.2 to 1.0% by weight expressed as P.sub.2 O.sub.5, adding to the dispersion so formed an acidic water-soluble compound of aluminium in an amount of from 2.5 to 3.5% by weight expressed as Al.sub.2 O.sub.3, a water-soluble acidic compound of zirconium in an amount of from 0.5 to 1.5% by weight expressed as ZrO.sub.2, an acidic water-soluble compound of titanium in an amount of from 1.5 to 3% by weight expressed as TiO.sub.2 and a water-soluble compound of silicon in an amount of from 0.2 to 2.0% by weight expressed as SiO.sub.2, adjusting the pH of the dispersion to a value of from 3.5 to 4.5 and then adding to the dispersion a water-soluble compound of phosphorus in an amount of from 0.2 to 1.0% by weight expressed as P.sub.2 O.sub.5 and an alkaline reacting water-soluble compound of aluminium in an amount of from 0.5 to 1.5% by weight expressed as Al.sub.2 O.sub.3, with all the percentages by weight being based on the weight of TiO.sub.2 in the pigment, and adding to the dispersion a mineral acid to adjust the pH to a value of 6.5 to 8 and recovering the treated pigment.
Dependencies are inferred from the claim text.