GB833057A - Improvements in and relating to alumina abrasive materials - Google Patents

Abstract

An alumina abrasive material, suitable for use in dentifrice compositions, is prepared by heating gibbsite to 900-1050 DEG C., and maintaining the alumina thus formed within this temperature range for at least an hour. The alumina may be held at this temperature until there is present not more than 20% gamma-alumina, not more than 10% alpha alumina, and between 20% and 90%, preferably 20%-55%, kappa-type alumina, in the product. All these phases are defined with respect to their X-ray diffraction patterns. The product may have a median particle size of 6-10m with 80% of the particles in the range 3-20m and substantially no particles below 3m . The gibbsite may be previously dehydrated by heating it to 500-800 DEG C., the rate of heating to this temperature preferably being below 210 DEG C. per minute. In the preferred manner of preparing the abrasive, the gibbsite is maintained at 1000 DEG C. for not more than 10 hours.ALSO:A dentifrice comprises an alumina abrasive prepared by heating gibbsite to 900 DEG to 1050 DEG C. and maintaining the temperature for at least an hour (see Group III). Preferably at least 80% of the particles should have diameters ranging from 3m to 20 m . Toothpastes contain a thickener such as natural gums, gum karaya, gum arabic, gum tragacanth, seaweed derivatives such as Irish moss and alginates and water-soluble salts of cellulose ethers, such as sodium carboxymethyl cellulose and sodium carboxymethyl hydroxymethyl cellulose. Colloidal magnesium aluminium silicate will improve the texture. A sudsing agent, such as water-soluble alkyl- and alkyl ether sulphates and sulphonates having 8 to 18 carbon atoms in the alkyl group, water-soluble salts of sulphonated monoglycerides of fatty acids having from 10 to 18 carbon atoms, salts of fatty acid amides of taurines, such as sodium-N-methyl-N-polymitoyl tauride, and salts of fatty acid esters of isethionic acid may be added. A humeclant, such as glycerine, sorbitol or other polyhydric alcohol, and flavouring such as oil of winter-green, oil of peppermint, saccharine dextrose and levulose, may be added. Tooth powders consist of the abrasive, 0 to 5% of sudsing agent, and flavouring. Other suitable additives to the dentifrice composition include sarcosinates, fluorine-containing compounds, quaternary ammonia compounds, chlorophyll, sodium dehydroacetates, sodium lauryl sulphate, tyrothrycin, penicillin and hexachlorophene.