Tioxide Group Services Limited

John Robb

Leslie Ainsley Simpson

Paul F Dietz

Guy Decelles

John Temperley

Ian G Dobson

Banford Johnathan

A composite particulate pigmentary material is disclosed which comprises an association of at least two chemically distinct materials in which the particles of one material carry a positive surface charge and the particles of the second material carry a negative surface charge and particles are held in association as a result of these surface charges. Also disclosed is a method for preparing composite particulate pigmentary material comprising forming aqueous dispersions of two particulate materials under conditions in which the surface charges of the particles of the two materials are of different signs and mixing the dispersions. Typical materials useful for preparing the composite include inorganic pigments, fillers and extenders and organic polymeric microspheres. The product is useful as a pigment in, for example, paints, inks, paper and plastics.

Composite pigmentary material

A novel inorganic particulate powder coated with an organic polymer is claimed. The product is obtainable by dispersing in water inorganic particles at a pH higher than their isoelectric point in the presence of a polymeric polybasic acid as a dispersing agent to produce particles having a modified isoelectric point. The pH of the dispersion is then adjusted to a value below 9 but above the modified isoelectric point and an ethylenically unsaturated monomer is polymerized in the presence of the dispersion so as to coat the inorganic particles with polymerized monomer. A method for forming the particles is also claimed. The particles prepared by the method have been shown to be uniformly and discretely coated with an organic polymeric coating and can be used in many applications where it is desired to disperse inorganic particles in organic media such as paints, inks and plastics compositions.

Coated inorganic particles

A process for the production of a suspension of nuclei has been developed in which an aqueous mixture of titanium tetrachloride, aluminium ions and hydroxyl ions is cured at at temperature of from 50.degree. to the boiling point. The pH of the suspension before or after curing has a value of from 6.5 to 10.5. The aqueous mixture is prepared by mixing a solution of titanium tetrachloride with a solution of a base, e.g. sodium hydroxide and aluminium hydroxide. When used to nucleate hydrolysis in the 'sulphate' process a large crystal size anatase pigment is produced.

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Fairfield, United Kingdom

John Robb