Preparation of finely divided solids and suspensions thereof

Abstract

Abstract A suspension of finely divided particles of a water-soluble solid in a water-immiscible liquid which is a non-solvent for the solid is prepared by mixing the liquid with an aqueous solution of the solid, in the presence of 0.5-5 per cent by weight, based on the solid, of an emulsifying agent, to form an emulsion of the water-in-oil type, and then substantially dehydrating the emulsion. The solid may be a corrosion inhibitor for addition to lubricating oils and greases; examples are sodium, potassium and ammonium nitrite, dicyclohexylammonium nitrate, alkali metal, ammonium, and amine chromates, phosphates, and iodates, sodium and potassium arsenite, sodium carbonate and bicarbonate, alkali metal hypochlorites, silicates, chlorates, and perchlorates, borax, and boric acid. Solids suitable as extreme pressure agents in oils and greases are glycolic, lactic, 1 - ethylidene lactic, ethylene lactic, alpha - hydroxy caproic acetonic, leucic, alpha - hydroxy valeric, ascorbic, saccharic succinic, oxalic, maleic, aconitic, glutaconic, citraconic, glyceric, arabonic, gluconic, galactonic, talonic, manonic, citric, tartaric, tartronic, and malic acids, sodium benzoate and acetate, urea, acetamide, thiourea, succinimide, maleimide, glycine, alanine, cysteine, glutamic acid, aspartic acid, and the sulphhydryl analogues of the above hydroxy acids. The aqueous solution may have a solids content of 5-85 per cent by weight. The water-immiscible liquid may be a mineral lubricating oil, residual fuel oil, gas oil, kerosine, diesel oil, stove oil, or a pure hydrocarbon, e.g. hexane. If the emulsification is carried out under pressure, ethylene, propylene, or propane may be used. One part by weight of immiscible liquid may be emulsified with 0.25-4 parts by weight of aqueous solution. The finely divided solid having emulsifying agent deposited on its surface may be obtained in the dry state by filtration or evaporation of the final suspension. Suitable emulsifying agents are (a) alkali metal salts of alkyl esters of sulphodicarboxylic acids, e.g. sodium dibutyl sulphosuccinate, sodium dihexyl sulphosuccinate, and sodium dioctyl sulphosuccinate; (b) alkali metal soaps of hydrocarbon sulphonic acids, e.g. the oil-soluble sodium soaps of petroleum sulphonic acids; (c) alkali metal soaps of monocarboxylic acids of at least 10 carbon atoms, e.g. sodium oleate, sodium stearate, potassium linoleate, lithium linoleate, and soaps of 12 - hydroxy - stearic acid; (d) cationic surface active agents containing one or more amino nitrogen atoms and one or more hydroxy groups as described in Specification 703,169. The mixture may be emulsified in an emulsifying mill and then dehydrated, for example by evaporation while stirring or passing through the emulsifier; evaporation may take place under vacuum. An example describes the dispersion of sodium nitrite in a mineral lubricating oil using as emulsifying agent the partial amide of the condensation product of epichlorhydrin and ammonia, sodium stearate, or sodium petroleum sulphonate. The suspension is added as a corrosion inhibitor to a lubricating grease comprising a mineral oil and 5 per cent of a bentonite clay previously treated with the partial amide of the condensation product of epichlorhydrin and ammonia.

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