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US 4,052,222 AGranted
Treatment of pigment
AssigneeTioxide Group Limited
InventorPeter Barry Howard
Life of this patent
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Abstract
A process for the treatment of titanium dioxide pigment in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound of silicon, an acidic compound of aluminium and an alkaline compound of aluminium, thereby producing a coated pigment.
Claims17
A process for the treatment of titanium dioxide pigment comprising
- a. forming an aqueous dispersion of pigmentary titanium dioxide containing a first water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO.sub.2,
- b. adding to the dispersion
- a first acidic water-soluble compound of aluminum in an amount of from 1.5 to 2.5% by weight expressed as Al.sub.2 O.sub.3,
- an acidic water-soluble compound of zirconium in an amount of from 0.5 to 1.5% by weight expressed as ZrO.sub.2, and
- an acidic water-soluble compound of titanium in an amount of from 1.0 to 2.0% by weight expressed as TiO.sub.2,
- c. changing the pH of the dispersion to a value in the range 7.5 to 8.5, and then
- d. adding to the dispersion a second water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO.sub.2, then
- a second acidic water-soluble compound of aluminum in an amount of from 1 to 2% by weight expressed as Al.sub.2 O.sub.3, and then
- an alkaline water-soluble compound of aluminum in an amount of from 0 to 1.5% by weight expressed as Al.sub.2 O.sub.3, all the percentages by weight being based on the weight of TiO.sub.2 in the pigment and recovering the so treated pigment.
6 more elements
Dependencies are inferred from the claim text.