Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Solid hydrocarbon polymer
Reexamination Certificate
2000-07-24
2001-11-06
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Solid hydrocarbon polymer
C585S010000, C585S012000, C585S018000
Reexamination Certificate
active
06313077
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions of automotive engine oils using synthetic poly alpha olefins derived from 1-dodecene or 1-tetradecene, to improve engine oil performance, as demonstrated by the severe Volkswagen T-4, Volkswagen TDI, and Sequence IIIE tests.
BACKGROUND OF THE INVENTION
Today's automobiles tend to have smaller, more demanding engines operating at higher temperatures. Thus, the engine oil has to function in an increasingly severe environment while meeting fuel economy demands. Besides changes in the additive package, increasingly synthetic base oils are being used instead of conventional mineral oils. Of the synthetic oils, poly alpha olefins (PAO) are among the most popular.
PAO is manufactured by the oligomerization of linear alpha olefins followed by hydrogenation to remove unsaturated bonds and fractionation to obtain the desired product slate. 1-decene is the most commonly used alpha olefin in the manufacture of PAO, but 1-dodecene and 1-tetradecene can also be used. PAO's are commonly categorized by the numbers denoting the approximate viscosity in centistokes of the PAO at 100° C. It is known that PAO 2, PAO 2.5, PAO 4, PAO 5, PAO 6, PAO 7, PAO 8, PAO 9 and PAO 10 and combinations thereof can be used in engine oils. The most common of these are PAO 4, PAO 6 and PAO 8.
Conventionally, base oils of lubricating viscosity used in motor oil compositions may be mineral oil or synthetic oils of viscosity suitable for use in the crankcase of an internal combustion engine. Crankcase base oils ordinarily have a viscosity of about 1300 cSt at 0° F. (−18° C.) to 24 cSt at 210° F. (99° C.). The base oils may be derived from synthetic or natural sources. Mineral oil for use as the base oil in this invention includes paraffinic, naphthenic and other oils that are ordinarily used in lubricating oil compositions. Synthetic oils include both hydrocarbon synthetic oils and synthetic esters.
Although the common 1-decene based PAO 4, 6 and 8 offer better performance than mineral oil based engine oils, they encounter difficulties when subjected to the severe PV 1449, CEC L-78-T-96 and Sequence IIIE tests. The PV 1449 and Sequence IIIE tests evaluate fully formulated engine oils with respect to high temperature oxidative stability and piston deposits. The CEC L-78-T-96 test evaluates fully formulated engine oils with respect to piston cleanliness and piston ring sticking. The PV 1449 and CEC L-78-T-96 tests will be referred to hereinafter as the Volkswagen T-4 and TDI engine tests, respectively.
It has been found to be difficult to blend an engine oil of the desired 0W30 viscosity grade based on PAO 4 and 6 that successfully completes the TDI test. Repeatedly, it was found that too low oil pressure caused the engine to fail from 2 to 8 hours before the end of the test. In the T-4 test, it was found that the increase in engine oil viscosity resulting in engine failure during the test was related to oil oxidation stability and volatility. To pass the T-4 test, it was found that the PAO 4/6 based engine oil requires large quantities of expensive anti-oxidants. The other way to obtain PAO 4/6 based oil which passes the T-4 test is to use an expensive fully synthetic oil.
The Volkswagen T-4 and TDI tests have recently become an important measure of engine lubrication oil quality under very severe conditions. The Sequence IIIE test is analogous to a T-4 test but is specifically developed for U.S. built engines. The T-4 and Sequence IIIE tests are for gasoline engines and the TDI test is for diesel engines. They replicate the severe engine conditions put on motor lubrication oil by sustained, very high speed driving, as on the German Autobahn. What is needed is a PAO based oil which is able to successfully complete severe engine tests such as the Volkswagen T-4 and TDI tests and the Sequence IIIE test without having to use large quantities of anti-oxidants or a fully synthetic oil.
Surprisingly, it has been found that lubrication oils based on a feed consisting of 1-dodecene or 1-tetradecene, and that have approximate viscosities at 100° C. of from 3.5 to 8.5 centistokes, successfully pass the T-4 and TDI tests with PAO based oil weight percentages much lower than previously achieved. This represents a major development in the search for an economical lubrication oil that is well suited for modern driving conditions.
SUMMARY OF THE INVENTION
In its broadest aspect the present invention relates to a base oil composition suitable for use in an engine oil which comprises a mixture of trimer and higher oligomers derived from an alpha olefin feed consisting essentially of either 1-dodecene or 1-tetradecene wherein said oligomer mixture contains less than 2 weight percent of combined monomer and dimer. When used in this specification the phrase” consisting essentially of either 1-dodecene or 1-tetradecene” refers to a feed which contains at least 85% by weight of 1-dodecene or 1-tetradecene. In the preferred embodiment of the invention the base oil composition will consist essentially of only the trimer and higher oligomers of either 1-dodecene or 1-tetradecene. The term “oligomer mixture” as used herein is intended to mean a mixture of the different oligomers of either dodecene or tetradecene. It is not intended to mean a mixture of oligomers derived from alpha olefins other than dodecene or tetradecene.
The present invention also relates to the use of PAO oil as a base oil, or as a component of a base oil, in an engine oil for the purpose of improving the high temperature stability wherein the PAO oil comprises a mixture of trimer and higher oligomers derived from an olefin feed consisting of either 1-dodecene or 1-tetradecene wherein said oligomer mixture contains less than 2 weight percent of combined monomer and dimer.
In another embodiment, the present invention relates to the use of the PAO derived from 1-dodecene or 1-tetradecene as a base oil, or a component of a base oil, in an engine oil comprised of said base oil, in addition to dispersants, detergents, oxidation inhibitors, foam inhibitors, anti-wear agents and at least one viscosity index improver, for the purpose of improving the high temperature stability of the engine oil to at least the point at which the engine oil is able to pass the VW T-4, VW TDI, or Sequence IIIE tests. Preferably, the base oil comprises between 15 to 85 weight percent of the engine oil and at least 15 weight percent of the base oil consists of the PAO derived from 1-dodecene or 1-tetradecene.
The PAO derived from 1-dodecene or 1-tetradecene, as used in the present invention, preferably will have a viscosity at 100° C. of between about 3.5 centistokes to about 9.5 centistokes. Particularly preferred for use in manufacturing base oils of the present invention are those PAO's having a viscosity at 100° C. of approximately 5 centistokes, approximately 6 centistokes, or approximately 7 centistokes, i.e, PAO 5, PAO 6, or PAO 7. Especially preferred for use in the present invention are PAO 5 and PAO 7. The viscosity of the PAO will depend upon the relative percentage of the various oligomers present in the product. In general, the higher the percentage of higher molecular weight oligomers, the higher the viscosity of the PAO. Thus for example, in the case of dodecene, PAO 5 would have a higher percentage of trimer present than PAO 6 or PAO 7. PAO 7 would have a higher percentage of tetramer or higher oligomers than PAO 5 or PAO 6. The different viscosity PAO's are readily separated by distillation to yield the desired oligomer cut.
As used in this disclosure the words “comprises” or “comprising” is intended as an open-ended transition meaning the inclusion of the named elements, but not necessarily excluding other unnamed elements. The phrase “consists essentially of” or “consisting essentially of” is intended to mean the exclusion of other elements of any essential significance to the composition. When specifically referring to the feed composition the phrase “consisting essentially of either 1-
Duchesne Perla
Raddatz Jurgen H.
Stunnenberg Frank
McAvoy Ellen M.
Phillips Petroleum Company
Scott Reece A.
LandOfFree
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