Particulate material
AssigneeTioxide Group Limited
InventorAlan G. Cowie
Life of this patent
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Abstract
There is an increasing demand for products which are effective in the absorbancy of UV light but still remain transparent to visible light. Titanium dioxide has been proposed for this use. A new form of titanium dioxide has been developed which is very effective in use and which is acicular in shape and having a ratio of the largest dimension to the shortest within the range 8:1 to 2:1 and wherein the largest dimension is from 0.01 to 0.15 micron and in which the particles have a coating of a hydrous oxide of aluminium and of silicon in a weight ratio of at least 1.5 and not greater than 4.5 expressed as the oxides. The materials are eminently suitable for use in cosmetics and other skin care products.
Claims17
Particulate material comprising non-calcined titanium dioxide the particles of which are acicular in shape and which have a ratio of the longest dimension to the shortest dimension within the range of 8:1 to 2:1 and wherein the largest dimension is within the range 0.01 to 0.15 micron and said particles having a coating comprising an oxide or hydrous oxide of aluminum and an oxide or hydrous oxide of silicon in a weight ratio of Al.sub.2 O.sub.3 :SiO.sub.2 of at least 1.5 and not greater than 4.5 and said material being substantially transparent to visible light and substantially absorbant to UV light.
A method for the manufacture of a particulate material which comprises forming an aqueous dispersion of titanium dioxide the particles of which are acicular in shape and which have a ratio of the longest dimension to the shortest dimension within the range 8:1 to 2:1 and wherein the largest dimension is within the range 0.01 to 0.15 micron and which has not undergone any intervening calcination process, mixing the dispersion with a hydrolysable compound of aluminum and a hydrolysable compound of silicon to deposit on said particles a coating of a hydrous oxide of aluminum and a hydrous oxide of silicon in a weight ration of Al.sub.2 O.sub.3 :SiO.sub.2 of at least 1.5 and not greater than 4.5 and drying the resultant product at a temperature substantially below calcination temperature.
Dependencies are inferred from the claim text.