Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Nitrogen and heavy metal – or nitrogen and aluminum – in the...
Reexamination Certificate
1997-09-17
2001-01-09
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Nitrogen and heavy metal, or nitrogen and aluminum, in the...
C508S363000, C508S370000, C508S379000, C508S443000, C508S496000, C508S499000
Reexamination Certificate
active
06172013
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to lubricating oil compositions having enhanced friction coefficients and improved wear properties. More particularly this invention relates to synergistically enhancing the friction coefficient and wear properties of lubricating compositions by molybdenum and particular ester additives.
BACKGROUND OF THE INVENTION
Lubricating compositions in use today are prepared from a wide variety of natural and synthetic base stocks to which have been mixed various additive packages and solvents depending upon the intended field of application. The various additives employed in the additives packages can include one or more additives selected from viscosity index improvers, corrosion inhibitors, oxidation inhibitors, dispersants, lube oil flow improvers, detergents and rust inhibitors, pour point depressants, anti-foaming agents, anti-wear agents, seal swellants, friction modifiers, extreme pressure agents, color stabilizers, demulsifiers, wetting agents, water loss improving agents, bactericides, drill bit lubricants, thickeners or gellants, anti-emulsifying agents, metal deactivators, and additive solubilizers. These additives are added to base stocks such as mineral oils, highly refined mineral oils, poly alpha olefins, polyalkylene glycols, phosphate esters, silicone oils, diesters and polyol esters.
There has been considerable effort expended to develop lubricating oil compositions which will reduce friction and wear in engines, particularly automobile engines, since such reduced friction and wear improves the fuel efficiency of the engine. As a result of these efforts, various friction-modifiers and new reduction additives have been added to lubricating compositions.
A number of oil soluble molybdenum (Mo) compounds have been disclosed as useful in providing desirable lubricating oil properties such as antiwear, antioxidant and friction reduction properties. Among the disclosures of molybdenum compounds for such purposes there may be mentioned U.S. Pat. Nos. 4,164,473; 4,176,073; 4,176,074; 4,192,757; 4,248,720; 4,201,683; 4,289,635; 4,479,883 and Japanese Paten Publication No. 56000896. As an example of such molybdenum compounds, there may be mentioned, molybdenum dithiocarbamate (MoDTC) which has been recognized as providing benefits in all three of the aforesaid areas. Good antiwear and antioxidant benefits as well as some friction modification properties are obtained at molybdenum concentrations of 100 ppm. For good friction modification properties, molybdenum concentration of about 500 ppm are employed.
For improved lubricating oil package stability in engine oils, especially for fully synthetic oils, and also for improved sludge handling, piston cleanliness and antioxidant benefits, small amount of generally from about 5 to about 15 wt % of ester base oils have been employed.
It has previously been disclosed in U.S. Pat. No. 4,479,883 that lubricating oil compositions of somewhat improved friction reducing properties are obtained when a hydroxy substituted soluble ester of a saturated or unsaturated polycarboxylic acid having from 24 to 90 carbon atoms between the carboxylic acid groups and a metal dithiocarbamate such as a molybdenum dithiocarbamate (MoDTC) are both employed in a lubricating oil composition.
However, when an additive of a high hydroxyl ester comprising trimethylolpropane and a C
8
-C
10
acid having about one hydroxyl group per molecule of trimethylolpropane left unconverted is employed as an ester in combination with a MoDTC and added to a lubricating oil composition the end friction coefficient and wear volume properties were not improved, but were found to be generally less favorable than a composition of the lubricating oil and the high hydroxyl ester of trimethylolpropane and a C
8
-C
10
acid.
There continues to be a need for additives that can be added to lubricating base composition to provide significantly enhanced and improved properties in regard to friction coefficients and wear properties.
SUMMARY OF THE INVENTION
Lubricating compositions of significantly enhanced friction coefficient and wear properties are provided in accordance with this invention by providing a lubricating composition comprising a major amount of oil of lubricating viscosity and a minor amount of an additive comprising molybdenum and a dialkyl ester of an aliphatic or aromatic dicarboxylic acid. It has been discovered that the combination of molybdenum and the aforesaid dicarboxylic acid diesters produce an unexpected, significantly synergistically enhanced effect with respect to reduced engine friction and wear.
The molybdenum additive will generally comprise from about 0.005 wt % to about 0.2 wt %, preferably from about 0.01 to about 0.1 wt % and the diester additive will generally comprise from about 3 wt % to about 20 wt %, preferably from about 5 to about 12 wt % of the total lubricating oil composition.
DETAILED DESCRIPTION OF THE INVENTION
The lubricating compositions of this invention can comprise any suitable oil having a lubricating viscosity and can be used in formulations for various lubricants, such as, crankcase engine oils (i.e., passenger car motor oils, heavy duty diesel motor oils, and passenger car diesel oils), two-cycle engine oils, catapult oil, hydraulic fluids, drilling fluids, aircraft and other turbine oils, greases, compressor oils, functional fluids and other industrial and engine lubrication applications. The lubricating oils contemplated for use with the present invention include animal, vegetable, mineral or synthetic hydrocarbon oils of lubricating viscosity and mixtures thereof. The synthetic hydrocarbon oils include long chain alkanes such as cetanes and olefin polymers such as oligomers of hexene, octene, decene, and dodecene, etc. The other synthetic oils include (1) fully esterified ester oils, with no free hydroxyls, such as pentaerythritol esters of monocarboxylic acids having 2 to 20 carbon atoms, trimethylol propane esters of monocarboxylic acids having 2 to 20 carbon atoms, (2) polyacetals and (3) siloxane fluids. Especially useful among the synthetic esters are those made from polycarboxylic acids and monohydric alcohols. More preferred are the ester fluids made by fully esterifying pentaerythritol, or mixtures thereof with di- and tripentaerythritol, with an aliphatic monocarboxylic acid containing from 1 to 20 carbon atoms, or mixtures of such acids.
The oils of lubricating viscosity suitable for use in the composition of this invention are natural oils, hydrocarbon-based oils and synthetic oils, preferably the natural oils being at least one oil selected from rapeseed oils, canola oils and sunflower oils; said hydrocarbon-based oils are at least one oil selected from mineral oils and highly refined mineral oils; and said synthetic oils are at least one oil selected from poly alpha olefine, polyalkylene glycols, polyisobutylenes, phosphate esters, silicone oils, polyol esters, and other synthetic esters.
In some of the lubricant formulations set forth above a solvent be employed depending upon the specific application. Solvents that can be used include the hydrocarbon solvents, such as toluene, benzene, xylene, and the like.
Crankcase Lubricating Oils
The compositions can be used in the formulation of crankcase lubricating oils (i.e., passenger car motor oils, heavy duty diesel motor oils, and passenger car diesel oils) for spark-ignited and compression-ignited engines. The additives listed below are typically used in such amounts so as to provide their normal attendant functions. Typical amounts for individual components are also set forth below. All the values listed are stated as mass percent active ingredient.
MASS %
MASS %
ADDITIVE
(Broad)
(Preferred)
Ashless Dispersant
0.1-20
1-8
Metal detergents
0.1-15
0.2-9
Corrosion Inhibitor
0-5
0-1.5
Metal dihydrocarbyl
0.1-6
0.1-4
dithiophosphate
Supplemental anti-oxidant
0-5
0.01-1.5
Pour Point Depressant
0.01-5
0.01-1.5
Anti-Foaming Agent
0-5
0.
Holt David G. L.
Leta Daniel P.
Exxon Chemical Patents Inc
Johnson Jerry D.
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