Patent GB-1023590-A (GB)
Title: Titanium dioxide pigments and compositions therefrom
Inventor: KYLE THOMAS IAN
IPC: C09C1/36
Filed: 1963-05-21
Abstract: Aqueous emulsion paints are formed by mixing together a film-forming polymer and an aqueous dispersion of aluminium phosphate coated titanium dioxide pigment particles the preparation of which is described (see Division C1) or by mixing the particles, water, a polymerizable film-forming monomer or monomers, and surface-active agents capable of "flushing" the pigment into the monomer (A) and thereafter polymerizing the monomer. Polymers of vinyl esters of aliphatic monocarboxylic acids having from 2 to 8 carbon atoms, e.g. vinyl acetate, of acrylic or methacrylic esters of aliphatic monocarboxylic acids containing 1 to 10 carbon atoms, e.g. methyl-, ethyl-, propyl- or butyl acrylates or methacrylates; of acrylonitrile; of vinylidene chloride; of styrene or butadiene or copolymers thereof or copolymers of styrene or butadiene and diesters of maleic or fumaric acids may be used.  Thickening agents such as cellulose ethers and/or polyacrylate salts; inorganic extenders; tinting pigments; preservatives such as phenol or mercury derivatives; corrosion inhibitors such as sodium benzoate or nitrite and/or film-forming aids such as cellulose acetate or butyl carbitol acetate may be added.ALSO:An aluminium phosphate is precipitated on to titanium dioxide particles by adding a water-soluble compound of aluminium, e.g. salts of mineral or organic acids such as the sulphate, chloride, nitrate or acetate, to an aqueous dispersion of said particles, thereafter adding a phosphoric acid or water soluble compound thereof, e.g. ortho- or pyro-phosphoric acid or their alkali metal salts, say sodium dihydrogen ortho-phosphate, disodium hydrogen ortho-phosphate or tri-sodium ortho-phosphate, and adjusting the pH of the dispersion to at least 6 by addition of an alkali, e.g. alkali metal or ammonium hydroxides or carbonates, or in part sufficient alkali metal silicate to also precipitate 0.1 to 2.0% silica on the particles.  Other water-soluble compounds may be added before or after adding the aluminium compound, e.g. salts of titanium, cerium, zirconium or tin, such as sulphates or chlorides, to precipitate hydrous oxides.  The particles, obtained by the "sulphate" process and calcined to at least 600 DEG  C. or by the vapour phase oxidation of a titanium tetrahalide may be anatase or at least 90% rutile and may be previously milled, hydroclassified, and dispersed with say 0.2 to 1% agent, e.g. sodium silicate, hydroxide and/or phosphate, polyphosphate, or organic compound. The treated particles may be recovered, e.g. by filtration, washing, drying and final milling, and incorporated into aqueous emulsion points by adding say a mixture containing emulsified film-forming polymer to a dispersion in water containing an inorganic dispersing agent such as sodium silicate, phosphate or polyphosphate or an organic compound such as the aminohydroxycompounds.  Polymers of vinyl esters of aliphatic monocarboxylic acids having from 2 to 8 carbon atoms, e.g. vinyl acetate; of acrylic or methacrylic esters of aliphatic monocarboxylic acids containing 1 to 10 carbon atoms, e.g. methyl-, ethyl-, propyl- or butyl acrylates or methacrylates; of acrylonitrile; of vinylidene chloride; of styrene or butadiene or copolymers thereof or copolymers of styrene or butadiene and diesters of maleic or fumaric acids may be used.  Thickening agents such as cellulose ethers and/or polyacrylate salts; inorganic extenders; tinting pigments; preservatives such as phenol or mercury derivatives; corrosion inhibitors such as sodium benzoate or nitrite and/or film-forming aids such as cellulose acetate or butyl carbitol acetate may also be added. Aqueous emulsion paints may also be formed by mixing treated particles, water and a polymerizable film-forming monomer or monomers and a surface-active agent capable of "flushing" the pigment into the monomer(s) and thereafter polymerizing the monomer.  The treated titanium dioxide pigments have reduced reactivity with the paint media.