Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2002-03-05
2004-02-10
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S192000, C508S199000, C508S371000, C508S421000, C508S569000
Reexamination Certificate
active
06689723
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the preparation and use of an additive for lubrication oils in which the additive includes at least one dihydrocarbyl polysulfide compound. The present invention also relates to finished lubrication oils having the dihydrocarbyl polysulfide additive and a base stock. In particular, the present invention relates to the use of a mixture of a dihydrocarbyl sulfide and dihydrocarbyl polysulfides having a desired ratio to provide a finished lubrication oil having certain desired performance attributes. This invention further relates to lubricating compositions, concentrates and greases containing the combination of a dihydrocarbyl polysulfide and a phosphorus or boron compound.
BACKGROUND OF THE INVENTION
Polysulfides have been used in lubrication compositions to provide extreme pressure protection. The polysulfides have certain disadvantages including copper corrosion, oxidation stability, thermal instability and seal compatibility problems. Additionally, the use of a polysulfide compound to improve one performance parameter, e.g., wear resistance, may introduce a deleterious performance characteristic, i.e., gear tooth breakage in severe application or attack of elastomeric seals. It is desirable to find a polysulfide which, when used alone or in combination with other additives, provides good extreme pressure properties to lubricants without adverse effects.
Different types of base stocks have different performance characteristics. Ester base stocks, for example, the neopentyl polyol esters such as the pentaerythritol esters of monobasic carboxylic acids, have excellent high performance properties as indicated by their common use in gas turbine lubricants. They also provide excellent anti-wear characteristics when conventional anti-wear additives are present and they do not have any adverse effect on the performance of rust inhibitors. On the other hand, esters have relatively poor hydrolytic stability, undergoing hydrolysis readily in the presence of water at even moderate temperatures. They are, therefore, less well suited for use in wet applications such as papermaking machinery.
Hydrolytic stability can be improved by the use of hydrocarbon base stocks. The use of alkyl aromatics in combination with the other hydrocarbon base stocks such as hydrogenated polyalphaolefin (PAO) synthetic hydrocarbons and the improved hydrolytic stability of these combinations is described, for example, in U.S. Pat. No. 5,602,086, corresponding to EP 496 486. Traditional formulations containing PAOs, however, present other performance problems. Although the hydrolytic stability of hydrocarbon base stocks, including PAOs is superior to that of the esters, it is frequently difficult to obtain a good balance of the surface-related properties such as anti-wear and anti-rust because, as noted above, these surface-related properties are dependent upon the extent to which the additives present in the base stock compete for sites on the metal surfaces which they are intended to protect and high quality hydrocarbon base stocks such as PAOs do not favorably interact with the additives used for this purpose. It is therefore a continuing problem to produce a good combination of surface-related properties including anti-wear performance and anti-rust performance in synthetic oils based on hydrocarbon base stocks such as PAOs.
A need exists for a polysulfide additive that provides improved performance characteristics for a finished lubricant composition comprising the polysulfide additive. A need exists for a polysulfide additive that improves at least one performance characteristic of a finished lubricant while reducing at least one of the deleterious effects caused by the use of a polysulfide additive in a finished lubricant.
SUMMARY OF THE INVENTION
The present invention relates to lubricating oil compositions, including dihydrocarbyl polysulfides, which are especially adapted for use in mechanical systems where gears are subjected to great stress and extremely high pressures such as those found in automotive rear axles or off highway transmissions and gear boxes. The present invention relates to lubricants and functional fluids, having a dihydrocarbyl polysulfide, that are useful particularly in environments characterized by high pressure and rubbing surfaces.
One embodiment according to the present invention includes a lubricating composition comprising a major amount of an oil of lubricating viscosity, at least one dihydrocarbyl polysulfide comprising less than about 88% dihydrocarbyl trisulfide; and a phosphorous compound or a boron compound, or mixtures of phosphorous compounds and boron compounds. The oil of lubricating viscosity is generally in a major amount when the oil is about 70 wt. % or greater of the total lubrication composition, preferably when the oil is about 90 wt. % or greater of the total lubrication composition.
Another embodiment according to the present invention further includes the polysulfide having at least about 7.5 wt. % dihydrocarbyl tetrasulfide or higher polysulfides.
One embodiment of the present invention includes a complex mixture of organic sulfides forming an additive that includes a monosulfide having the formula R—S—R
1
, where R and R
1
may independently be a hydrocarbyl group as described below and a polysulfide having the formula R
2
—S
X
—R
3
, wherein R
2
and R
3
may independently be a hydrocarbyl group as described below and X is equal to or greater than about 2. The ratio of R—S—R
1
to polysulfides, wherein X is equal to or greater than about 4, ranges from about 0.087 to about 0.112.
Another embodiment of the present invention is a lubricant oil composition containing the polysulfide additive and an oil or base stock of lubricating viscosity in which the base stock may be a mineral oil or a synthetic base stock.
Another embodiment according to the present invention includes a lubricating composition including a major amount of an oil of lubricating viscosity, at least one dihydrocarbyl polysulfide having less than about 88% dihydrocarbyl trisulfide, less than about 5.5 wt. % dihydrocarbyl disulfide; at least about 7.5 wt. % dihydrocarbyl tetrasulfide or higher polysulfides; and a phosphorous compound or a boron compound, or mixtures thereof.
Another embodiment according to the present invention includes a concentrate comprising from 0.1% to 49.9% by weight of a substantially inert, organic diluent and at least one dihydrocarbyl polysulfide comprising less than about 88% dihydrocarbyl trisulfide, less than about 5.5 wt. % dihydrocarbyl disulfide, at least about 7.5 wt. % dihydrocarbyl tetrasulfide or higher polysulfides and at least one phosphorus or boron compound or mixtures thereof.
Another embodiment according to the present invention includes a grease composition comprising at least one oil of lubricating viscosity, at least one thickening agent, and at least one dihydrocarbyl polysulfide comprising less than about 88% dihydrocarbyl trisulfide, less than about 5.5 wt. % dihydrocarbyl disulfide, and at least about 7.5 wt. % dihydrocarbyl tetrasulfide or higher polysulfides; and at least one phosphorus or boron compound, or mixtures thereof.
Another embodiment of the present invention includes the polysulfide additive, a mineral oil, alkyl phosphate/phosphite ester, a detergent or dispersant, borated alkylsuccinimide, primary amine, heterocyclic copper passivator, and a defoamant.
DETAILED DESCRIPTION OF THE INVENTION
The invention described herein includes polysulfide additives that provide improved performance characteristics, such as extreme pressure protection, when used in lubricating compositions; greases; and concentrates, and methods for the use thereof.
The term “hydrocarbyl” includes hydrocarbon, as well as substantially hydrocarbon groups. “Substantially hydrocarbon” describes groups which contain heteroatom substituents that do not substantially alter the predominantly hydrocarbon nature of the substituent. Non-limiting examples of hydrocarbyl groups include the following: (1
Coolbaugh Thomas Smith
Kanga Percy Rohinton
Sullivan William T.
ExxonMobil Chemical Patents Inc.
McAvoy Ellen M.
Moreno Louis N.
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