Sulfate-base rutile tio2 pigment and method for producing same

Claim 1

IN A PROCESS FOR PRODUCING A SULFATE-BASE RUTILE TIO2 PIGMENT WHEREIN A TIO2 HYDROLYSATE PRODUCED BY A SULFATE PROCESS IS DRIED, CALCINED AND MILLED THE IMPROVEMENT WHICH COMPRISES: FEEDING THE SULFATE-BASE TIO2 CALCINER DISCHARGE TO A DRY MILL, DRY MILLING SAID TIO2 CALCINER DISCHARGE WITH SUFFICIENT INTENSITY SUCH THAT THE DRY MILLED CALCINER DISCHARGE COMPRISES DISCRETE PARTICLES HAVING A WEIGHT MEAN SIZE NO GREATER THAN ABOUT 0.33 MICRON AND A STANDARD DEVIATION OF DISTRIBUTION NO GREATER THAN ABOUT 0.17 MICRON, SLURRYING SAID MILLED CALCINER DISCHARGE IN AN AQUEOUS MEDIUM WITH SOLUBLE SALTS OF METALS SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ALUMINUM, SILICON AND MIXTURES THEREOF IN AN AMOUNT NOT LESS THAN 1% AS THE HYDROUS METAL OXIDE ON A TIO2 WEIGHT BASIS, ADJUSTING THE PH OF SAID AQUEOUS SLURRY TO FORM AND PRECIPIATE THE CORRESPONDING HYDROUS METAL OXIDES ON SAID DRY MILLED CALCINER DISCHARGE AND INTENSELY DRY MILLING THE HYDROUS METAL OXIDE COATED CALCINER DISCHARGE.