Patent GB-634720-A (GB)
Title: An organic lubricating oil composition
Filed: 1947-01-14
Abstract: Organic lubricating oil compositions comprise a mineral lubricating oil, a non-drying fatty oil, a liquid wax, a synthetic lubricating oil or a mixture of such substances and a wear-reducing amount, less than 0.1 per cent by weight, e.g. 0.01-0.05 per cent, of a sulphurized product of an unsaturated fatty acid having at least 8 carbon atoms in the molecule (see Group IV (b)), and, as a corrosion inhibitor, 0.01 to 0.5 per cent by weight of a dicarboxylic acid, a thio-equivalent thereof, a monocarboxylic acid containing a -NO2, -NO, -CN, or aromatic sulphonyl group not more than 3 carbon atoms removed from the carboxylic radical, or a hydroximic acid or mixture of such acids, the acids being in each case insoluble in water and soluble in the organic lubricating oil composition.  The corrosion inhibitor may be a relatively high molecular weight dicarboxylic acid with two carboxylic radicals separated by not more than four and preferably by not more than two or three carbon atoms, e.g. an alkyl succinic acid having at least 16, and preferably 20 or more, atoms in the molecule, or alkylated glutaric or adipic acids.  The sulphurized product of an unsaturated fatty acid may be a sulphurized product of oleic acid and may be prepared by reacting more than one and preferably less than two gram atoms of sulphur with one gram molecule of the acid, at about 150 DEG  to about 300 DEG  C. (see Group IV (b)).  The composition may contain in addition to the constituents described a minor proportion of an antioxidant such as a poly-alkyl arylhydroxy compound, e.g. di-tertiary-butyl para-cresol.  The oxygen in the acid radicals of the corrosion inhibitor of the dicarboxylic acid type may be replaced in whole or in part by sulphur to give such thio equivalents as thiolic (-COSH), thionic (-CSOH) or thionthiolic (-CSSH) acids.  When the corrosion inhibitor is a monocarboxylic acid containing a -NO2, -NO, -CN, or aromatic sulphonyl group, the acid should preferably contain a minimum of 12 to 16 carbon atoms in the molecule in addition to any introduced in the added radical, e.g. the acid may be alpha or beta nitro, nitroso, cyano or phenylsulphonyl stearic acid.  One or both of the acidic groups may be attached to an aromatic nucleus as in alpha (orthocarboxyl aryloxy) carboxylic acids such as <FORM:0634720/III/1> In corrosion inhibitors of the dicarboxylic acid type the two acidic groups may be joined through an oxygen, sulphide, disulphide or nitrogen linkage, for example in accordance with the general formula <FORM:0634720/III/2> wherein X represents an oxygen, sulphur or nitrogen atom, u and y = 0 or 1, z is a small integer such as 1 or 2, and each R is an organic radical, such as a fatty acid radical.  The corrosion inhibitor may also contain ether, amino, sulphide, and disulphide radicals elsewhere in the molecule.  The preferred corrosion inhibitors are saturated dicarbocylic acids containing only carbon, hydrogen and oxygen.  The sulphurized unsaturated fatty acid may be hypogaeic, elaidic, erucic, brassidic, linoleic or linolenic acid.  The unsaturated fatty acids may be sulphurized with sulphur, sulphur mono-chloride, or a phosphorus polysulphide, Tables are given showing the wear, rusting, resistance to displacement by water, oxidation stability and demulsibility of oxidation-inhibited turbine oils containing varying proportions of a saturated alkyl succinic acid and of sulphurized oleic acid, alpha-mercapto stearic acid, and sulphurized sperm oil. The compounded lubricating oils of the invention, when prepared with turbine oil "base stocks" and containing suitable oxidation inhibitors, are said to be especially applicable for use in steam turbines.  A list of suitable anti-oxidants is given.  These include 2,4,6-trimethyl phenol, pentamethyl phenol, pentaethyl phenol, and di - tertiary - butyl para - cresol.  U.S.A. Specification 2,133,734 is referred to.  The Specification as open to inspection under Sect. 91 refers also to monocarboxylic acids containing a hydrosulphide radical such as alpha or beta mercapto stearic acid.  This subject-matter does not appear in the Specification as accepted.ALSO:Sulphurized fatty acids having at least 8 carbon atoms in the molecule and used as wear-reducing agents in lubricating oils (see Group III), are prepared by reacting more than one and less than two gram-atoms of sulphur with one gram molecule of the acid at about 150-300 DEG  C.  Examples of fatty acids which may be sulphurized are oleic, hypogaeic, elaidic, erucic, brassidic, linoleic or linolenic acid.  In the example, oleic acid is sulphurized by heating the acid for about 3 1/2 -4 hours at about 150 DEG  to 180 DEG  C. with about 14.6 per cent by weight of sulphur.  The product is then purified by heating to about 140-160 DEG  C. with 20 to 30 per cent by weight of an acid-activated adsorbtive clay, the clay being then removed by filtration.