Patent GB-874113-A (GB)
Title: Improvements in or relating to lubricating compositions
IPC: C10M169/00
Filed: 1958-11-10
Abstract: A lubricating composition (see Group III) may comprise (1) one or more esters of tricarboxylic acids all of the carboxyl groups of which are located on non-adjacent carbon atoms, at least two of the carboxyl groups being esterified with aliphatic monohydric alcohols containing 6-14 carbon atoms, together with (2) an antioxidant. Tricarboxylic acids which may be used in the preparation of ingredient (1) include hexane-1,3,6-tricarboxylic acid, isocamphoric acid, a -santoronic acid, 2-methyl - pentane - 1,3,5 - tricarboxylic acid, g -methyl -g -carboxy-pimelic acid, heptane-2,4,6-tricarboxylic acid and 5-methyl-octane-2,5,7-tricarboxylic acid.  Esters for use as ingredient (1) may also be prepared by hydrogenating trimers of esters of methacrylic acid and thereafter, if necessary, introducing the desired alcohol residues by trans-esterification. Thus, methyl methacrylate may be trimerized, then hydrogenated and finally trans-esterified to replace 2 or 3 of the methyl groups by higher alkyl groups.  The antioxidant (2) may be phenthiazine or 4-tert.butyl-2-phenyl phenol.ALSO:A lubricating composition comprises (1) one or more esters of tricarboxylic acids all of the carboxyl groups of which are located on non-adjacent carbon atoms, at least two of the carboxyl groups being esterified with aliphatic monohydric alcohols containing 6-14 carbon atoms, together with (2) one or more materials chosen from antioxidants, corrosion inhibitors, viscosity index improvers, high pressure additives, detergents, anti-foam agents, thickeners, and additional lubricating and/or hydraulic oils. Tricarboxylic acids which may be used in the preparation of ingredient (1) include hexane-1,3,6-tricarboxylic acid, isocamphoric acid, a -santoronic acid, 2-methyl-pentane1,3,5-tricarboxylic acid, g -methyl-g -carboxypimelic acid and heptane-2,4,6-tricarboxylic acid. Esters for use as ingredient (1) may also be prepared by hydrogenating trimers of esters of methacrylic acid and thereafter, if necessary, introducing the desired alcohol residues by trans-esterification.  Thus, methyl methacrylate may be trimerized, then hydrogenated, and finally trans-esterified to replace 2 or 3 of the methyl groups by higher alkyl groups.  The triester ingredient (1) may contain hetero-atoms, such as nitrogen, sulphur or oxygen, in the alcohol residues or elsewhere in the molecule.  Specified ingredients (2) are phenthiazine (antioxidant), barium petroleum sulphonate (corrosion inhibitor), polymethacrylates (viscosity index improvers), tricresyl phosphate (high pressure additive), silicone oil (anti-foam agent), zinc didodecyl phenyl stearate (detergent) and copper phthalocyanin (thickener).  In examples, lubricating oils consist of (a) tri-n-hexyl ester of 5-methyloctane-2,5,7-tricarboxylic acid, 4-tert.butyl-2-phenyl phenol and zinc dixylyl stearate, with or without di-2-ethylhexyl sebacate, (b) tri-n-heptyl ester of 5-methyl-octane-2,5,7-tricarboxylic acid, phenthiazine and barium dinonyl naphthalene sulphonate or (c) tri-n-hexyl ester of 5-methyl-octane-2,5,7-tricarboxylic acid, phenthiazine, polyoctyl methacrylate, silicone oil and tricresyl phosphate.  In further examples, a grease consists of tri-n-hexyl ester of 5-methyl-octane-2,5,7-tricarboxylic acid, dilauryl selenide and copper phthalocyanin, while a hydraulic oil consists of tri-n-octyl ester of 5-methyl-octane-2,5,7-carboxylic acid, decyl methacrylate/methyl methacrylate copolymer, tricresyl phosphate, zinc didodecyl phenyl stearate, 4-tert.butyl-2-phenyl phenol and silicone oil.