GB601346A - Improvements in or relating to lithium base lubricating grease compositions and method of preparing the same - Google Patents

Abstract

Lithium base lubricating greases comprise an oleaginous vehicle and a lithium soap, formed from either a soap-forming hydroxy fatty acid or a glyceride of such fatty acid, or of a blend of such material with a soap-forming fatty acid material not of the hydroxy type. In the latter case the hydroxy fatty acid may comprise at least 35 per cent of the blend or the hydroxy fatty acid glyceride may comprise at least 50 per cent of the blend. The nonhydroxy fatty acid material may be a saturated fatty acid and an oxidation inhibitor may be present. The fatty acids and/or glycerides may be saponified with a basic lithium compound at temperatures below 300 DEG F., the soap dehydrated at 270 DEG F. to 330 DEG F. and the mineral oil then added. In an example, 12 lbs. of hydrogenated castor oil, 12 lbs. of a mildly-refined mineral oil having a viscosity of 57 S.U.S. at 100 DEG F. and 4 lbs. of stearic acid were stirred at 170-200 DEG F. with a solution of 2.40 lbs. of 53.6 per cent lithium hydroxide in 16 lbs. of water until the fatty constituents had been saponified. The product was then dehydrated by heating to 280-300 DEG F., and a further quantity of the same oil added, followed by 0.35 lb. stearic acid and 0.35 lb. of phenyl alpha naphthylamine. Addition of the oil was then continued until the grease had a worked ASTM penetration of 320 at 77 DEG F. It contained 14.6 per cent by weight of soap, had an ASTM dropping point of 357 DEG F., a "Navy Water absorption" of 5, and when worked with a perforated piston in a closed cylinder for 8 hours at 225 DEG F. at the rate of 49 strokes per minute, remained practically unchanged in penetration. These greases when prepared with very low power point mineral oils, are adapted for the lubrication of aircraft control bearings at temperatures ranging down to approximately minus 100 DEG F. They are stated to have the advantages over the conventional lithium base greases that high temperatures are not necessary in their manufacture and that they maintain their structure without separation of oil and soap when subjected to prolonged shearing stresses at temperatures above atmospheric. The oleaginous vehicle may be a mineral lubricating oil, derived from petroleum, a synthetic lubricating oil obtained by cracking and polymerization, as in the Fisher-Tropsch process, or wholly or partly a synthetic oleaginous compound within the lubricating oil viscosity range, e.g. aliphatic dicarboxylic acid esters, such as the alkyl esters of sebacic acid, high molecular weight aliphatic ethers, such as normal hexyl ether, or the alkyl esters of benzoic or phthalic acids. The preferred oleaginous vehicle is a mineral lubricating oil viscosity 40-70 S.U.S. at 100 DEG F., V.I. 30 or more, and having a low pour point.