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
1999-03-30
2001-01-16
Medley, Margaret (Department: 1714)
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...
C508S563000
Reexamination Certificate
active
06174842
ABSTRACT:
TECHNICAL FIELD
This invention relates to lubricating oil compositions, their method of preparation, and use. More specifically this invention relates to lubricating oil compositions that contain a molybdenum compound, a diarylamine and an alkaline-earth metal phenate, wherein the molybdenum compound is substantially free of reactive sulfur. The use of the molybdenum compound in combination with the diarylamine and the phenate, within certain concentration ranges, provides a lubricating oil with improved oxidation control, reduced tappet wear and decreased piston, ring and valve deposits.
BACKGROUND OF THE INVENTION
Lubricating oils for internal combustion engines of automobiles or trucks are subjected to a demanding environment during use. This environment results in the oil suffering oxidation which is catalyzed by the presence of impurities in the oil such as iron compounds and is also promoted by the elevated temperatures of the oil during use. This oxidation of lubricating oils during use is typically controlled to some extent by the use of antioxidant additives which may extend the useful life of the oil, particularly by reducing or preventing unacceptable viscosity increases.
We have now discovered that a combination of about 50 to 1000, preferably 50 to 500, more preferably 50 to 250, parts per million (ppm) of molybdenum, based on the total weight of the finished lubricating oil composition, from an oil-soluble molybdenum compound which is substantially free of reactive sulfur; from 1,000 to 20,000, preferably 1,000 to 10,000, ppm of an oil-soluble diarylamine; and from 2,000 to 40,000 ppm of an alkaline-earth metal phenate, is highly effective in inhibiting oxidation in lubricant compositions and providing the lubricating oil with excellent sliding friction characteristics that reduces tappet wear and valve and piston deposits in gasoline, diesel and natural gas (NG) engines.
Lubricant compositions containing various molybdenum compounds and antioxidants, such as aromatic amines, have been used in lubricating oils for some time. Such prior compositions include active sulfur or phosphorus as part of the molybdenum compound, use additional metallic additives or various amine additives which are different from those used in this invention, and/or have concentrations of components that are different than those disclosed by this invention.
Engines have been designed and built specifically for natural gas (NG). These engines are used primarily in stationary applications and are operated under relatively constant operating conditions. Most recently there have been applications of compressed natural gas (CNG) in motor vehicles, especially buses and fleet trucks, due to the economic and environmental benefits associated with NG.
While the basic designs for stationary NG engines and conventional fueled engines (diesel and gasoline) are similar, the differences in operating conditions and maintenance practices have resulted in two distinct lubricant product groups. Stationary NG engine lubricants are usually high viscosity monograde formulations with a low ash content. Conventional fueled engines for vehicles typically use multigrade oils with much higher ash content. The needs of NG engines in transportation applications have not been adequately met by the lubricants presently available and a need exists to design lubricant products that simultaneously fulfill the performance criteria of NG engines in non-stationary applications, gasoline engines and diesel engines. Gasoline and diesel vehicular lubricants are often qualified based on dynamometer tests in a relatively short period of time based upon substantial field experience. However, with the use of an alternative fuel, such as NG, the possibility exists that the performance of accepted oil additives for conventionally fueled engines will be very different in the NG setting. None of the prior art lubricant compositions are directed to solving the special lubricant problems associated with NG engines.
DESCRIPTION OF THE RELATED ART
The prior art discloses the use of molybdenum complexes in lubricating oils, as described in U.S. Pat. No. 3,285,942 to Price et al.; U.S. Pat. No. 4,394,279 to de Vries et al.; U.S. Pat. No. 4,832,857 to Hunt et al.; and U.S. Pat. No. 4,846,983 to Ward. Additional references disclosing lubricating compositions containing molybdenum include U.S. Pat. Nos. 4,889,647; 4,812,246; 5,137,647; 5,143,633; and WO95/07963 to Shaub. However, the prior art has failed to suggest a three-component mixture of molybdenum compounds substantially-free of reactive sulfur, diarylamines and alkaline-earth metal phenates to provide high temperature antioxidant properties and low deposit characteristics to a lubricating oil.
WO95/07962 to Richie et al. and WO95/07966 to Atherton disclose crankcase lubricant compositions for use in automobile or truck engines that contain molybdenum, and amine antioxidants. In addition to the requirement for use of additional elements, these publications recite very broad ranges for concentrations of the molybdenum and the amine. Also, many of the molybdenum compounds of these references contain reactive sulfur, phosphorus, and other elements and the amines disclosed include compounds such as primary amines that are not within the scope of this invention.
U.S. Pat. No. 5,605,880 and WO95/27022 to Arai et al. disclose a lubricating oil composition comprising a specified base oil, an alkyldiphenylamine and/or phenyl-&agr;-naphthylamine and an oxymolybdenum sulfide dithiocarbamate and/or an oxymolybdenum sulfide organophosphorodithioates. This reference does not suggest the use of molybdenum compounds substantially free of reactive sulfur in combination with a diarylamine and an alkaline-earth metal phenate to produce an oil additive that creates a lubricating composition that has low friction characteristics, high heat-resistance, a high stability to oxidation, proper viscosity properties, and low deposit formation.
U.S. Pat. No. 5,650,381 to Gatto et al. discloses a lubricating oil composition which contains a molybdenum compound which is substantially free of reactive sulfur, and a secondary diarylamine. U.S. Pat. No. 5,840,672, also to Gatto discloses an antioxidant system that utilizes molybdenum as a component, however, no mention nor suggestion is made that a molybdenum compound substantially-free of reactive sulfur be used with a diarylamine and an alkaline-earth metal phenate.
U.S. Pat. No. 5,726,133 to Blahey et al. discloses a low ash natural gas engine oil and an additive system which is a mixture of detergents. The additive mixture is disclosed as comprising a mixture of detergents comprising at least one first alkali or alkaline earth metal salt or mixture thereof of low Total Base Number (TBN) of about 250 and less, and at least one second alkali or alkaline earth metal salt or mixture thereof which is more neutral than the first low TBN salt. This reference fails to teach molybdenum compounds substantially-free of reactive sulfur for inclusion in the NG engine oil.
SUMMARY OF THE INVENTION
In one aspect, this invention is directed to a lubricating composition comprising (a) a major amount of an oil of lubricating viscosity, (b) at least one oil-soluble molybdenum compound substantially free of reactive sulfur which provides about 50 to 1000 parts per million (ppm) of molybdenum to the lubricating composition; (c) about 1000 to 20,000 ppm of at least one oil-soluble diarylamine; and (d) about 2,000 to 40,000 ppm of at least one alkaline-earth metal phenate detergent.
In another aspect, the present invention is directed to a method for improving the antioxidancy and friction properties of a lubricant by incorporating in the lubricant a molybdenum compound that is substantially free of reactive sulfur, a diarylamine and an alkaline-earth metal phenate in the above described concentrations. This three-component system provides a lubricating oil with highly beneficial properties that are not obtained with combinations of any two of these components alone.
In still another aspe
Gatto Vincent James
Kuo Cheng
Perozzi Edmund F.
Ethyl Corporation
Hamilton Thomas
Medley Margaret
Moore James T.
Rainear Dennis H.
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