Patent GB-701637-A (GB)
Title: Improvements in and relating to lubricating greases
Filed: 1950-09-15
Abstract: A lubricating grease comprises a lubricating oil base, a metal soap of a hydroxy fatty acid in which the hydroxy group or groups is or are at least 9 carbon atoms removed from the carboxyl group in an amount sufficient to thicken the oil to a grease consistency, and a metal salt of an organic monocarboxylic acid having a hydroxy, mercapto, amino, keto, thioketo, nitro or sulpho group less than 9 carbon atoms removed from the carboxyl group (the "stabilizing additive").  The metal soap (gelling agent) may be a lithium, sodium, potassium, calcium or aluminium soap, preferably of a mono-hydroxy fatty acid wherein the hydroxyl group is more than 9 carbon atoms removed from the carboxyl group. Mixtures of these soaps may be employed.  The preferred gelling agents are the soaps, especially the lithium soaps, of 12-hydroxy-stearic acid or of the corresponding acids derived from hydrogenated castor oil.  Other soaps may be mixed with the hydroxy fatty acid soap; thus sodium stearate or oleate or a calcium soap may be mixed with the lithium soap of a hydroxy fatty acid.  The soaps may be preferably formed in the presence of at least a portion of the lubricating oil base of the grease.  The stabilizing additive may be a metal salt of an alkane monocarboxylic acid, a cycloalkane monocarboxylic acid or a monocyclic aromatic carboxylic acid having a hydroxy, mercapto, amino, keto, thioketo, nitro or sulpho group less than 9 carbon atoms removed from the carboxyl group.  Preferably the substituted monocarboxylic acid contains from 3 to 18 carbon atoms in the molecule.  Specified additives are as set forth in Specification 701,636, and they may be present in amounts from 0.01 to 1.0 per cent. by weight based on the whole composition. The preferred proportions are 4 to 12 (preferably 4 to 9) mol. per cent. of the total soap plus salt content.  The soap plus salt content of the grease may be 3 to 40 (preferably 6 to 15) per cent. by weight of the grease.  The lubricating oil base of the grease may be any of the lubricants specified in Specification 701,636.  Other additives such as anti-bleeding agents (glycol, glycerine) and antioxidants (p-phenylene diamine) may be present.  The grease may be made by known processes, provided that destruction of the stabilizing additives by heating above 230 DEG C. is prevented. Preferably the grease is made by the quench method described in Specification 701,636.  In example I the results of comparative tests are reported on greases having a total lithium soap plus salt content of 6 per cent. prepared from a turbine oil, hydrogenated castor oil and organic acids in amounts to yield 0.1 or 0.25 per cent. by weight of the grease as follows: lactic acid (0.1 per cent.), a-hydroxy stearic acid (0.25 per cent.), b -hydroxy propionic acid (0.1 per cent.), g -hydroxy valeric acid (0.1 per cent.), d -hydroxy valeric acid (0.1 per cent.), 6-aminocaproic acid (0.25 per cent.), 4-ketovaleric acid (0.1 per cent.), o-hydroxy benzoic acid (0.25 per cent.), m-hydroxy benzoic acid (0.25 per cent.), mandelic acid (0.25 per cent.), o-nitrobenzoic acid (0.25 per cent.), o-aminobenzoic acid (0.25 per cent.) and petroleum hydroxy naphthenic acids (0.25 per cent.). Example III describes a grease stabilized by the addition of sodium alphamercapto stearate.