TREATMENT OF PIGMENT

摘要

1479989 Treating TiO 2 TIOXIDE GROUP Ltd 27 May 1976 [17 July 1975] 30049/75 Heading ON TiO 2 pigment is treated by forming an aqueous dispersion of the pigment containing a water-soluble P compound in amounts of 0À2- 1-0% by weight expressed as P 2 O 5 , adding to the dispersion acidic water-soluble compounds of Al, Ti and Zr in amounts to provide 2À5- 3-5% Al 2 O 3 , 0À5-1À5% ZrO 2 and 1À5-3% TiO 2 and thereafter a water-soluble Si compound in an amount to provide 0À2-2À0% SiO 2 , adjusting pH to 3À5-4À5 and adding a water-soluble P compound in amounts to provide 0À2-1À0% P 2 O 5 and then an alkaline reacting water-soluble Al compound in amounts of 0À5-1À5% Al 2 O 3 (all percentages by weight being based on the weight of TiO 2 in the pigment) and adding to the dispersion a mineral acid to adjust pH to 6À5-8 and recovering the treated pigment. The starting pigment is preferably a calcined "sulphate process" titanium dioxide containing at least 95% rutile. The starting pigment may contain 0À1-0À5% Al 2 O 3 . The aqueous dispersion containing the watersoluble P compound is preferably wet milled in the presence of an alkali prior to further treatment. The Al, Ti and Zr compounds are preferably added to the dispersion in the form of a mixed aqueous solution, e.g. a mixed sulphate solution of pH 0À7-1À2. The treated pigment after recovery may be milled in a fluid energy mill, preferably in the presence of an amine (e.g. an alkanolamine) or polyol.