US 7,238,231 B1Granted

Process for manufacturing zirconia-treated titanium dioxide pigments

AssigneeTronox LLC

InventorsDaniel H. Craig, Jeffrey D. Elliott, Harmon E. Ray

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Abstract

An improved process is described for manufacturing zirconia-treated titanium dioxide pigments, wherein the zirconia treatment is accomplished in the process of fluidizing a titanium dioxide filter or press cake and then drying the same, through the addition to the filter or press cake of one or more alkaline water-soluble zirconium reagents selected from ammonium zirconyl carbonate, the water-soluble ammonium zirconyl carboxylates and mixtures of these. Aqueous solutions of such zirconium reagents, in addition to being effective for imparting a zirconia surface treatment to the titanium dioxide materials, also prove to be effective fluidizing agents for forming high solids dispersions of the zirconia-treated titanium dioxide pigment materials which can be spray dried without substantial dilution and excessive energy requirements.

Claims11

Dependent claims

A process for manufacturing zirconia-treated titanium dioxide, comprising the steps of:

a) forming a mixture comprising a titanium dioxide material in water;
b) wet milling said mixture;
c) after step b), optionally depositing on said wet milled titanium dioxide material one or more inorganic oxides selected from the group consisting of the oxides of aluminum, boron, cerium, phosphorus, silicon, tin, titanium and zirconium;
d) achieving a pH of the mixture resulting from steps b) or c) between about 5 and about 9, whereby the titanium dioxide material is sufficiently flocculated to be recovered by vacuum or pressure filtration;
e) removing said titanium dioxide material from said mixture by vacuum or pressure filtration;
f) washing the titanium dioxide material recovered by filtration;
g) converting the washed titanium dioxide material to a fluid dispersion by addition of one or more alkaline water-soluble zirconium reagents selected from the group consisting of ammonium zirconyl carbonate, the water-soluble ammonium zirconyl carboxylates and mixtures of these;
h) drying the dispersion to yield a dry zirconia surface treated titanium dioxide powder.

5 more elements

Dependencies are inferred from the claim text.