GB976328A - Improvements in or relating to the production of metal oxide sols - Google Patents

Abstract

Sols of non-actinide polyvalent metal oxides are prepared by mixing a solution in a polar solvent of a salt of the metal with an ion-exchange material in such proportions that the specific conductivity of the mixture is maintained in the range 0.001 to 10 mhos/cm., agitating the mixture until the bulk of the solubilizing ions are removed by the ion-exchange material, and thereafter separating the ion-exchange material from the resulting polyvalent metal oxide sol. The term "non-actinide-metal oxides" is defined and the term "solubilizing ion" refers to the anion of a single salt or the cation of a salt in which the metal is part of a complex anion, i.e. the solubilizing ion is the the ion which does not contain the polyvalent metal. The polar solvents are water, alcohols, acetone or dimethyl formamide, and the temperature range used is 0 DEG to 150 DEG C. Both weak and strong ion-exchange resins are used which may be in solid and liquid form, the latter being as described in Specification 968,202. When the ion-exchange material is an anion exchanger and the polyvalent metal is one whose salts are hydrolysable, the pH is maintained at 3 to 7 and when a cation exchanger is used a pH of 7 to 11 is used. When non-hydrolysable polyvalent metal salts are used conductivity measurements control the process. The specific conductivity is controlled by controlling the ratio of salt solution and ion-exchange material used. Alternatively, the sols may be prepared by subjecting the polyvalent metal salt solution to electrodialysis using at least one selectively semi-permeable membrane, the specific conductivity being maintained in the range 0.001 to 10 mhos./cm. Mixed oxide sols may be prepared by using mixtures of polyvalent metal salt solutions. The product sols have particle sizes of 1 to 100 mm and the mixed sols, e.g. those containing ferric oxide, on drying at 200-250 DEG C. exhibit ferromagnetic permeabilities. The sol may be subsequently transferred to a non-polar medium by contacting with a solution in an organic non-polar solvent of an organic transfer agent, agitating the mixture and removing the organic phase which comprises an organo sol. Specified transfer agents are di-2-ethylhexylphosphate or oleate, quaternary amine salts and hydrocarbons. The hydrocarbon may be polymerized to form a solid having polyvalent metal oxide particles dispersed therein. The examples describe the preparation of aqueous and organo sols of lead oxide, chromium, alumina and calcium hydroxide; aqueous sols of nickel oxide-ferric oxide, tungstic oxide, barium oxide-ferric oxide and gadalinium oxide. Specifications 450,308, 450,309, 557,414 and 924,999 also are referred to.ALSO:Styrene monomer containing the ammonium salt of di-2-ethyl-hexyl phosphoric acid is shaken with an aqueous chromia sol, thus transferring chromia particles to the styrene phase. After separating off the water the styrene is polymerized in the presence of benzoyl peroxide at 50 DEG C. to produce an opaque green polystyrene plastic material. Vinyl acetate and vinyl alcohol may be used instead of styrene.ALSO:Non-actinide polyvalent metal oxide sols are transferred from aqueous to organic non-polar mediums, e.g. hydrocarbons. In all examples, chromium, calcium, barium and magnesium sols are incorporated into kerosene. Gasoline may also be used.ALSO:Sols of non-actinide polyvalent metal oxides are prepared by subjecting a polyvalent metal salt solution to electrodialysis using at least one selectively semipermeable membrane, the specific conductivity of the solution being maintained in the range 0.001-10 mhos/cm. In Example 8, aluminium chloride is passed through an electrodialysis cell between pairs of permselective anion and cation membranes. Direct current was passed and the specific conductivity maintained in the above range. The aluminium sol produced had a particle size of 7.0 mm . The sol may be subsequently transferred to a non-polar medium by contacting with a solution in an organic non-polar solvent of an organic transfer agent, agitating and removing the organic phase. Specification 924,999 is referred to.