Process for preparing a stable suspension of a divalent metal salt in an oily medium

Abstract

Abstract A stable suspension of a divalent metal salt or mixtures of said salts in an oil, on which said salt is insoluble or substantially insoluble, is prepared by taking a solution of the salt which is immiscible or not completely miscible with the oil, and emulsifying said solution to a stable emulsion in the oil in the presence of a number of molar equivalents of an emulsifier, which is smaller than the number of molar equivalents of the salt, and subsequently removing solvent for the salt from the emulsion to produce a stable suspension. The average particle size of the dispersed divalent metal salt is not more than 2m and the invention is particularly useful with mineral and synthetic lubricating oils used in diesel engines, which may additionally contain fatty oils and the usual additives. Metal salts used are generally calcium, barium, magnesium zinc, cadmium and lead and the acid radical is generally derived from organic acids, e.g. formates, acetates and propionates, but nitrites may also be used. The solution used is generally an aqueous solution, but lower aliphatic alcohols such as methanol and ethanol are also useful. Emulsifiers exemplified are esters of polyhydric alcohols, glycerol mono-oleate, glycerol mono-stearate, glycerol monoricinoleate, diethylene glycol mono-laurate, diethylene glycol mono-oleate, diethylene glycol mono-stearate and sorbitol mono- and polyoleates, polyoxyethylene sorbitol esters of oleic acid or other fatty acids or resin acids, oil-soluble polyvalent metal salts particularly alkaline earth metal salts derived from fatty acids, naphthenic acids or organic sulphonic acids such as petroleum sulphonic acids. Mixtures of emulsifying agents may be employed, for example, a mixture of a polyvalent metal petroleum sulphonate with a polyvalent metal salt of an alkylated aromatic carboxylic acid or hydroxy carboxylic acid or with a polyvalent metal phenolate derived from an alkyl phenol. In addition resin acids, lanolin, oxidized vegetable oils and lecithin or mixtures of the same may be used as emulsifying agents. The soap type emulsifiers are used in quantities of 0.05-0.5 per cent by weight of the metal while the non-ionic emulsifiers are used in quantities of 1 to 5 per cent by weight of the emulsion. In an example, a water-in-oil emulsion is prepared from aqueous calcium acetate solution and mineral lubricating oil, using a mixture of basic calcium petroleum sulphonate and basic calcium salts of C14-C18 alkyl salicylic acids as emulsifying agents. The water is evaporated from the emulsion to produce the final suspension. Specification 755,799, 778,822 and 786,596 are referred to.

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