Zinc oxide dispersions
AssigneeTioxide Specialties Limited
InventorsCarole Allyson Maria Tapley, Philip Laurence Lyth, Iain Michael Harper
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Abstract
A stabilised aqueous dispersion of particulate zinc oxide comprises water, a stabilising agent and zinc oxide, the particles of which are coated with dense amorphous silica. Useful stabilising agents include cellulose ethers which contain quaternary ammonium groups and polyalkylene glycols. The dispersions have excellent stability at high concentrations of zinc oxide and are useful for preparing sunscreen formulations, cosmetics and veterinary products.
Claims28
A stabilised aqueous dispersion of particulate zinc oxide comprising water, a stabilising agent and zinc oxide, the particles of which are coated with dense amorphous silica which has been deposited on the surface of the zinc oxide particles by mixing an alkali metal silicate and an acid in the presence of zinc oxide particles in an aqueous suspension, the aqueous suspension being maintained at a pH of at least 8 during the mixing of said silicate and said acid.
A method for the preparation of a stabilised aqueous dispersion comprising mixing water, a stabilising agent and zinc oxide the particles of which are coated with dense amorphous silica which has been deposited on the zinc oxide particles by mixing an alkali metal silicate and an acid in the presence of zinc oxide particles in an aqueous suspension, the aqueous suspension being maintained at a pH of at least 8 during mixing of said silicate and said acid.
Dependencies are inferred from the claim text.