| abstract |
A thickened lubricating oil composition, particularly a lubricating grease, comprises a lubricating oil, sufficient inorganic gel to thicken the oil and minor proportions of a cationic surface-active agent and a water-soluble inorganic nitrite. The lubricating oil may be a mineral or synthetic lubricating oil or mixtures thereof. Specific synthetic lubricating oils mentioned are oxyalkylene polymers (e.g. propylene oxide polymers, ethylene oxide-propylene oxide copolymers, trimethylene glycol polymers and ethylene glycol-trimethylene glycol polymers), silicone fluids, organic phosphates (e.g. tricresyl, trioctyl, diphenylcresyl or diphenyloctyl phosphate), polymerized olefins, polyvinyl caprylate, octyl caprylate and esters of dicarboxylic acids (e.g. di (2-ethylhexyl) sebacate and di (3-methylhepty) adipate. The inorganic gel may be silica, alumina, magnesia, the oxides of calcium, copper, barium and strontium and mixtures thereof, synthetic zeolites, saponite, hectorite, montmorillonite, bentonite, mixed silicate-silica gels and mixed silicate-hydroxide gels. The inorganic gel may be an aerogel and the inorganic gel may be first treated with the cationic surface-active agent, where this is a quaternary ammonium salt. Thus bentonite may be treated with dimethyldicetyl-ammonium chloride to form the aliphatic ammonium bentonite complex. Nitrates mentioned are those of ammonium, sodium, potassium, lithium, barium, calcium, magnesium, copper, iron, lead, aluminium and zinc. The cationic surface-active agents are discussed under the following headings:-(a) quaternary ammonium salts, (b) amine salts of organic or inorganic acids and (c) miscellaneous organic nitrogen compounds such as oleic acid salt of 2-heptadecylimidazoline, acrolein ammonia condensation products, diallylamine-H2S condensation products and partial fatty acid amides of epichlorhydrin-ammonia condensation products. Among the examples, compositions are described consisting of mineral lubricating oil, sodium nitrate, a partial amide of tall oil fatty acids with an epichlorhydrinammonia condensation product, and either silica gel or a mixed silica-magnesium silicate gel. |