Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2002-06-05
2004-03-30
McAvoy, Ellen M (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S591000, C252S073000
Reexamination Certificate
active
06713439
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a power transmission fluid composition capable of reducing the energy consumption of transmissions, differentials, or other devices in which it is used.
Over the last decade manufacturers of gear systems, especially automobile builders, have sought methods to reduce the energy consumption of these devices and the automobiles in which they are used. Improvements in automobile transmissions such as continuously variable transmissions and 6 speed automatic transmissions have made large strides in reducing energy consumption of cars. In some cases, such as manual transmissions, differentials used in axles and in fixed speed reduction gearing little improvement in the hardware can be made to gain further energy conservation. In these cases manufacturers seek improvements in the lubricant to provide the energy savings. The challenge is to reduce energy dissipated in the gear contact. This energy is lost as heat. Therefore, lowering the energy lost in the gear contact will lower the bulk fluid temperature. If the lubricant is capable of doing this, either through judicious choice of lubricant base stocks, or additives, then it can truly be called an energy conserving power transmission fluid.
It is well known that lowering the viscosity of a lubricant can lower the energy consumed in the device in which it is used. This technique is especially important at lower operating temperatures where lubricant viscosities are elevated. The technique works as long as adequate hydrodynamic films are provided in the device. If viscosity is lowered too far, hydrodynamic films fail and friction increases, thereby increasing energy consumption. Reduction of energy consumption through reducing fluid viscosity is often referred to as reducing “churning losses”. However, we have now found that by appropriate selection of lubricant basestocks energy consumption in gear contact can be reduced, independent of viscosity, thereby permitting the formulation of energy conserving lubricants of higher viscosity.
For the purposes of this invention a power transmission fluid is defined as any lubricant used in contact with gears involved in the transmission of mechanical energy. Commonly these devices would include, but not be limited to, automatic transmissions, manual transmissions, continuously variable transmissions, automated manual transmissions, transfer cases, axles and differentials used in mobile applications. They would also include stationary gearing used in industrial applications as well as industrial transmissions.
We have found that power transmission fluids comprised of base fluids made up of high viscosity polyalphaolefins, certain polyol esters and other lubricant basestocks, containing appropriate performance additive packages for the required applications, can yield significant energy savings when compared to the same composition without the polyol ester.
SUMMARY OF THE INVENTION
This invention relates to an energy conserving power transmission fluid composition comprising:
(a) from 1 to 49 wt. % of a polyalphaolefin base stock having a kinematic viscosity of from 40 mm
2
/s at 100° C. to 500 mm
2
/s at 100° C.;
(b) from 1 to 95 wt. % of a lubricant basestock having a kinematic viscosity of from 2 mm
2
/s at 100° C. to 10 mm
2
/s at 100° C.;
(c) from 1 to 49 wt. % of a polyol ester of a C
5
to C
30
monocarboxylic acid and a polyol of the formula R(OH)
n
where n is at least 2, up to 5, and R is any aliphatic or cycloaliphatic hydrocarbyl group; and
(d) an effective amount of a performance additive package
provided that the composition has a kinematic viscosity of at least 4 mm
2
/s at 100° C.
The stabilization temperature of the compositions of this invention with the polyol ester is at least 2° C. lower than the same composition tested without the polyol ester, when tested by an appropriate method.
DETAILED DESCRIPTION OF THE INVENTION
Polyalphaolefin
Polyalphaolefins (PAO) are oligomers of terminally unsaturated alkenes. The polyalphaolefins of the present invention are characterized by their viscosities. For purposes of this invention, the high viscosity polyalphaolefins are defined as possessing kinematic viscosities at 100° C. of from about 40 to about 500 mm
2
/s. Production of high viscosity polyalphaolefins is well known in the art and is described for example in U.S. Pat. No. 4,041,098.
Polyalphaolefins can be made from any terminally unsaturated olefin or mixtures of terminally unsaturated olefins. The preferred polyalphaolefins are made from 1-octene or 1-decene or mixtures thereof. They can be saturated or unsaturated. The preferred PAO's have kinematic viscosities from about 40 to about 250 mm
2
/s, and the most preferred from about 40 to 100 mm
2
/s. The most preferred PAO's are also saturated by hydrogenation.
The compositions of this invention will contain a minor amount of the high viscosity polyalphaolefin. Typically, amounts will range from 1 to 49% by weight. The exact amount will be determined by the desired kinematic viscosity of the final lubricant.
Lubricant Basestock
Lubricating oils contemplated for use in this invention are either natural lubricating oils, synthetic lubricating oils or derived from mixtures of natural lubricating oils and synthetic lubricating oils. Suitable lubricating oils also include basestocks obtained by isomerization of synthetic wax and slack wax, as well as basestocks produced by hydrocracking (rather than by solvent treatment) the aromatic and polar components of the crude. The lubricating oil will have a kinematic viscosity ranging from about 2 to about 10 mm
2
/s (cSt) at 100° C. Natural lubricating oils include animal oils, vegetable oils (e.g., castor oil and lard oil), petroleum oils, mineral oils, and oils derived from coal or shale. The preferred natural lubricating oil is mineral oil.
The mineral oils useful in this invention include all common mineral oil basestocks. This would include oils that are naphthenic or paraffinic in chemical structure as well as oils that are refined by conventional methodology using acid, alkali, and clay or other agents such as aluminum chloride, or they may be extracted oils produced, e.g., by solvent extraction or treatment with solvents such as phenol, sulfur dioxide, furfural, dichlorodiethyl ether, etc. They may be hydrotreated or hydrofined, dewaxed by chilling or catalytic dewaxing processes, or hydrocracked. The mineral oil may be produced from natural crude sources or be composed of isomerized wax materials or residues of other refining processes.
A particularly useful class of mineral oils are those mineral oils that are severely hydrotreated or hydrocracked. These processes expose the mineral oils to very high hydrogen pressures at elevated temperatures in the presence of hydrogenation catalysts. Typical processing conditions include hydrogen pressures of approximately 3000 pounds per square inch (psi) at temperatures ranging from 300° C. to 450° C. over a hydrogenation-type catalyst. This processing removes sulfur and nitrogen from the lubricating oil and saturates any alkylene or aromatic structures in the feedstock. The result is a base oil with extremely good oxidation resistance and viscosity index. A secondary benefit of these processes is that low molecular weight constituents of the feed stock, such as waxes, can be isomerized from linear to branched structures thereby providing finished base oils with significantly improved low temperature properties. These hydrotreated base oils may then be further de-waxed either catalytically or by conventional means to give them exceptional low temperature fluidity. Commercial examples of lubricating base oils made by one or more of the aforementioned processes are Chevron RLOP, Petro-Canada P65, Petro-Canada P100, Yukong, Ltd., Yubase 4, Imperial Oil Canada MXT, Fortum Nexbase 3060, and Shell XHVI 5.2.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as oligomerized, polymerized, and interpolymerized olefins [e.g., polybutylene
Infineum International Ltd.
McAvoy Ellen M
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