| abstract |
After subjecting a calcined titanium dioxide pigment to a wet treatment, a non-ionic surfactant, e.g. 0.1-0.4%, is added to the pigment before drying. The calcined pigment is obtained by the sulphate process or by the vapour phase oxidation or hydrolysis of a titanium tetrahalide. The wet treatment comprises wetting the pigment with a liquid, e.g. water, to form a dispersion, slurry or paste. The surfactant may be a water-soluble condensation product of ethylene oxide with an alkylated phenol or a long chain fatty alcohol. In an example, a titanium dioxide pigment was produced by precipitation from a sulphate solution using nitrile inducing nuclei and the precipitate was washed, calcined, milled and dispersed in an aqueous slurry with 0.5% sodium silicate, hydro-separated to remove aggregates, dewatered, treated with 0.2% a surfactant, filtered, dried and milled. |