GB1008652A - Titanium dioxide pigment - Google Patents

Abstract

Titanium dioxide pigment is produced by coating titanium dioxide which may contain zinc or antimony oxides, alumina, silica or sodium or potassium sulphate, phosphate or borate with aluminium oxide, silicon dioxide and zirconium dioxide, and heating the resulting coated pigment to a temperature of at least 625 DEG C., and preferably 700-800 DEG C. The preferred percentages of coatings referred to the weight of the final coated pigment are as follows: aluminium oxide 0.5-5%, silicon dioxide 0.05-5%, zirconium dioxide 0.3-3%. It is preferable to coat the pigmentry titanium dioxide first with aluminium oxide and then zirconium dioxide before coating with the silicon dioxide. A further coating of aluminium oxide subsequent to the aluminium oxide, silicon dioxide and zirconium oxide coatings may be applied and this may be followed by a further coating of silicon dioxide. In the example pigmentary titanium dioxide is coated with zirconium dioxide, aluminium oxide, and silicon dioxide by slurrying the pigmentary titanium oxide in water, adding thereto a solution of zirconium and aluminium sulphates followed by an aqueous solution of sodium silicate. Portions of the resulting pigment were heated to 800 DEG C. and 740 DEG C. respectively. A further portion was not heated for comparison purposes only. The three pigments thus obtained were incorporated in paper which was subsequently impregnated with melamine formaldehyde resin and these papers then formed facings for a phenol formaldehyde bonded paper board. The thus prepared laminates were exposed to the light from an ultraviolet lamp to demonstrate the superior light stability of the pigments according to the invention.ALSO:Titanium dioxide pigment is produced by coating titanium dioxide with aluminium oxide, silicon dioxide and zirconium dioxide, and heating the resulting coated pigment to a temperature of at least 625 DEG C., and preferably 700-800 DEG C. The preferred percentages of coatings referred to the weight of the final coated pigment are as follows: aluminium oxide 0.5-5%, silicon dioxide 0.05-5%, zirconium dioxide 0.3-3%. It is preferable to coat the pigmentary titanium dioxide first with aluminium oxide and then zirconium dioxide before coating with the silicon dioxide. A further coating of aluminium oxide subsequent to the aluminium oxide, silicon dioxide and zirconium oxide coatings may be applied and this may be followed by a further coating of silicon dioxide. In the example pigmentary titanium dioxide is coated with zirconium dioxide, aluminium oxide, and silicon dioxide by slurrying the pigmentary titanium oxide in water, adding thereto a solution of zirconium and aluminium sulphates followed by an aqueous solution of sodium silicate. Portions of the resulting pigment were heated to 800 DEG C and 740 DEG C. respectively. A further portion was not heated for comparison purposes only. The three pigments thus obtained were incorporated in paper which was subsequently impregnated with melamine formaldehyde resin and these papers then formed facings for a phenol formaldehyde bonded paper board. The thus prepared laminates were exposed to the light from an ultraviolet lamp to demonstrate the superior light stability of the pigments according to the invention.ALSO:Pigmented resinous materials are made by mixing a titanium dioxide pigment coated with aluminium oxide, silicon dioxide and zirconium dioxide and heated to at least 625 DEG C. and optionally super coated with a further layer of aluminium oxide and if desired a further coating of silicon dioxide with a thermo setting synthetic resin in the manufacture of which is used a reducing agent for example, a urea formaldehyde, melamine formaldehyde, or phenol formaldehyde resin, and curing the resin. The pigment may be incorporated into a supporting material and the material may subsequently be impregnated with the resin. The pigment may be incorporated into a paper in the final beating stage; one or more of the sheets containing the pigment may then be impregnated with a urea formaldehyde or melamine formaldehyde or phenol formaldehyde resin, the sheets thus produced being then subjected to a temperature of 120-150 DEG C. and a pressure of 2000-2700 lbs per sq. inch whereby the resin is cured. In the example papers containing two pigments according to the invention and one used for comparisons only are impregnated with melamine formaldehyde resin and form the facings of a laminate comprising brown unpigmented craft paper bonded with a phenolic resin. The boards thus produced are irradiated with artificial light of a spectral composition identical to sunlight and the pigments according to the invention show superior light stability.