Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heterocyclic ring compound; a heterocyclic ring is one...
Patent
1996-11-13
1998-03-24
McAvoy, Ellen M.
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heterocyclic ring compound; a heterocyclic ring is one...
508253, 508254, 508364, 508370, C10M14100
Patent
active
057312737
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to lubricating compositions, including functional fluids. The invention relates in particular to crankcase lubricants for automobiles and trucks.
There is an increasing demand for longer intervals between changes in crankcase oils, and for a reduction in the volume of used oil to be disposed of. For these and other reasons, there is a need to improve the efficiency and useful life of oil-based lubricants, particularly those used as crankcase lubricants in internal combustion engines in automobiles and trucks.
One of the factors which substantially shortens the useful life of lubricating compositions is oxidation of the oil component. Oxidation results in the formation of acids, which tend to corrode engine parts, and in an undesirable increase in viscosity, which renders the composition less useful as a lubricant.
While high quality oils are themselves relatively resistant to oxidation, contaminants, for example iron, which are inevitably present in internal combustion engines, and common lubricant additives, for example magnesium- and/or calcium-containing detergents and alkenyl succinic acid/polyamine or polyester dispersants, have the effect of greatly accelerating the oxidation process, to the extent that oxidation is one of the major contributors to reduced lubricant life. Further, lower quality basestocks have a greater tendency to oxidize than do basestocks of higher quality.
Examples of oxidation inhibitors which have been proposed for use in crankcase lubricants are zinc dihydrocarbyl dithiophosphates which, although primarily used as antiwear agents, also act as antioxidants; aromatic amines, for example, alkylated diphenylamines and phenyl-.alpha.-naphthylamines; hindered phenols; alkaline earth metal salts of sulphurized alkyl phenols in which the alkyl groups preferably contain 5 to 12 carbon atoms, for example, calcium nonylphenyl sulphide and barium octylphenyl sulphide; phosphosulphurized or sulphurized hydrocarbons; and oil-soluble copper compounds.
Some of the above-mentioned oxidation inhibitors have been found to be very effective in use. European Patent Specification No. 24 146 B claims lubricating compositions comprising a major amount of lubricating oil, from 1 to 10 wt % of certain ashless dispersant compounds or from 0.3 to 10 wt % of certain ashless dispersant compounds or from 0.3 to 10 wt % of certain nitrogen- or ester-containing polymeric viscosity index improver dispersants, or mixtures of dispersant(s) and viscosity index improver dispersant(s), 0.01 to 5 wt % of zinc dihydrocarbyl dithiophosphate (ZDDP) and 5 to 500 parts per million by weight of added copper in the form of an oil-soluble copper compound. For particularly severe conditions, where it may be desirable to use a supplementary antioxidant, the amount of the supplementary antioxidant required is small (far less than the amount required in the absence of the copper compound). Supplementary antioxidants mentioned in Specification No. 24 146 B include diphenylamine, alkylated diphenylamines, and phenyl-1-naphthylamine and its alkylated derivatives.
Despite the effectiveness of the copper-containing compositions discussed above, even more highly effective antioxidants for lubricating compositions, particularly lubricating compositions suitable for use as crankcase lubricants, would represent an important contribution to the art.
It has now been found that copper and a phenothiazine, optionally together with an aromatic amine, provide surprisingly good oxidation control as the sole antioxidant system, or in combination with other antioxidants.
The present invention provides the use of copper present in oil-soluble form and at least one oil-soluble phenothiazine as an antioxidant system for a lubricating composition, that is, to inhibit oxidation of the lubricating composition.
The invention also provides a lubricating composition suitable for use as a crankcase lubricant, comprising a major proportion of lubricating oil, 1 to 500 parts per million by mass (ppm) of added copper present in
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Exxon Chemical Patents Inc.
McAvoy Ellen M.
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