EP4013841B1

EP4013841B1 - Composition and method for lubricating automotive gears, axles and bearings

Info

Publication number: EP4013841B1
Application number: EP20761943.8A
Authority: EP
Inventors: Hyungsoo KIM; Patricia Standen; Binbin Guo; Suzanne M. Patterson; Brian B. Filippini
Original assignee: Lubrizol Corp
Current assignee: Lubrizol Corp
Priority date: 2019-08-16
Filing date: 2020-08-12
Publication date: 2023-10-04
Anticipated expiration: 2040-08-12
Also published as: EP4013841A1; CA3150270A1; WO2021034553A1; US20220282178A1; CN114402058A; CN114402058B

Description

BACKGROUND

The disclosed technology relates to a lubricant composition for automotive gears, axles and bearings, the lubricant composition containing an oil of lubricating viscosity and an oil-soluble titanium compound in place of boron compounds, as well as a method of obtaining thermal stability performance in automotive gears, axles and bearings without the boron content that is typical, by lubricating such automotive gears, axles and bearings with a lubricant composition containing an oil-soluble titanium compound.
Driveline power transmitting devices (such as gears or transmissions) present highly challenging technological problems and solutions for satisfying the multiple and often conflicting lubricating requirements, while providing durability and cleanliness.
Lubricants are expected to be able to pass thermal stability tests, e.g. the L-60-1 test (ASTM D5704) (comprising a 50 hr test for axle oils). The lubricant should be able to provide adequate thermal stability as well as viscosity control to pass these tests.
In order to prepare lubricants which are thermally stable, it has become common practice to add boron compounds to the lubricating oil, such as borated dispersants.
It would be beneficial to provide lubricant compositions substantially free of, or even free of, boron compounds for automotive gears, axles and bearings. EP 0 848 052 A2 discloses a boron-free additive composition and its use in the lubrication of motor-vehicle gears.

SUMMARY

It has been found that the use of titanium compounds can replace the typical boron containing materials in lubricant compositions for automotive gears, axles and bearings that contain amine-containing phosphorus antiwear agents, while still providing at least equivalent, if not improved, thermal stability performance. This finding was surprising, as the prevailing understanding has been that boron compounds were required for such stability.
Thus, one aspect of the disclosed technology is related to a lubricant composition for an automotive gear, axle, or bearing, as evidenced by a total sulfur level of the lubricant of about 0.75 to about 5 wt.% based on the weight of the lubricant composition (referred to hereinbelow as an automotive gear oil), containing an oil of lubricating viscosity, an amine-containing phosphorus antiwear agent and an oil-soluble titanium compound (also referred to as "titanium compound" for short), where the automotive gear oil is substantially free, or free, of boron.
The titanium compound is not particularly limited, but it was found that the addition of titanium (IV) alkoxides, such as titanium (IV) 2-ethylhexoxide, to an automotive gear oil showed unexpected thermal stability performance.
The titanium compound is included in the automotive gear oil at levels that deliver greater than 200 ppm of titanium to the lubricant composition.
In addition to an amine-containing phosphorus antiwear agent, the automotive gear oil can also contain other additives, including other, non-amine containing, phosphorus compounds.
Another aspect of the current technology includes a method of lubricating an automotive gear (such as an automotive gear, axle or bearing), with the automotive gear oil as disclosed herein.

DETAILED DESCRIPTION

Various preferred features and embodiments will be described below by way of non-limiting illustration. One aspect of the invention is an automotive gear oil containing an oil of lubricating viscosity, an amine-containing phosphorus antiwear agent, and an oil-soluble titanium compound, and being substantially free, or free, of boron. By substantially free, it is meant that the composition contains less than 50 ppm boron, or less than 30 ppm, or even less than 10 ppm or 5 ppm, or even less than 1 ppm boron.

Oil of Lubricating Viscosity

One component of the disclosed technology is an oil of lubricating viscosity, also referred to as a base oil. The base oil may be selected from any of the base oils in Groups I-V of the American Petroleum Institute (API) Base Oil Interchangeability Guidelines (2011), namely

Base Oil Category	Sulfur (%)	Saturates (%)	Viscosity Index
Group I	>0.03 and/or	<90	80 to less than 120
Group II	≤0.03 and	≥90	80 to less than 120
Group III	≤0.03 and	≥90	≥120
Group IV	All polyalphaolefins (PAOs)
Group V	All others not included in Groups I, II, III or IV

Groups I, II and III are mineral oil base stocks. Other generally recognized categories of base oils may be used, even if not officially identified by the API: Group II+, referring to materials of Group II having a viscosity index of 110-119 and lower volatility than other Group II oils; and Group III+, referring to materials of Group III having a viscosity index greater than or equal to 130. The oil of lubricating viscosity can include natural or synthetic oils and mixtures thereof. Mixtures of mineral oil and synthetic oils, e.g., polyalphaolefin oils and/or polyester oils, may be used.
The oils employed in the composition are not particularly limited and can include a kinematic viscosity at 100 °C by ASTM D445 of 1 to 40, or 1 to 30, or even 1 to 15 or 20, or 1.25 to 10 mm²/s. In some embodiments the oil of lubricating viscosity can have a kinematic viscosity at 100 °C by ASTM D445 of 1.5 to 7.5, or 2 to 7, or 2.5 to 6.5, or 3 to 6 mm²/s. In one embodiment the oil of lubricating viscosity comprises a poly alpha olefin having a kinematic viscosity at 100 °C by ASTM D445 of 1.5 to 7.5 mm²/s or any of the other aforementioned ranges.

Amine-Containing Phosphorus Antiwear Agent

Amine-containing phosphorus antiwear agents can include, for example, amine salts of phosphoric acid esters; dialkyl mono-thio and di-thio phosphoric acid esters; and mono-alkyl or di-alkyl phosphites or phosphonates; and mixtures thereof. The amine salt of the phosphoric acid ester may comprise any of a variety of chemical structures. In particular, a variety of structures are possible when the phosphoric acid ester compound contains one or more sulfur atoms, that is, when the phosphorus-containing acid is a thiophosphoric acid ester, including mono- or dithiophosphoric acid esters. A phosphoric acid ester may be prepared by reacting a phosphorus compound such as phosphorus pentoxide with an alcohol. A dithiophosphoric acid ester may be prepared by reacting phosphorus pentasulfide with an alcohol. Suitable alcohols include those containing up to 30 or to 24, or to 12 carbon atoms, including primary or secondary alcohols such as isopropyl, butyl, amyl, s-amyl, 2-ethylhexyl, hexyl, cyclohexyl, octyl, decyl and oleyl alcohols, as well as any of a variety of commercial alcohol mixtures having, e.g., 8 to 10, 12 to 18, or 18 to 28 carbon atoms. Polyols such as diols may also be used. The amines which may be suitable for use as the amine salt include primary amines, secondary amines, tertiary amines, as well as diamines, and mixtures thereof, including amines with at least one hydrocarbyl group, or, in certain embodiments, two or three hydrocarbyl groups having, e.g., 2 to 30 or 6 to 12, or 8 to 26 or 10 to 20 or 13 to 19 carbon atoms.
In one embodiment, sulfur containing amine phosphate salts may be prepared by reacting an alkylthiophosphate with an epoxide or a polyhydric alcohol, such as glycerol. This reaction product may be used alone, or further reacted with a phosphorus acid, anhydride, or lower ester. The epoxide is generally an aliphatic epoxide or a styrene oxide. Examples of useful epoxides include ethylene oxide, propylene oxide, butene oxide, octene oxide, dodecene oxide, styrene oxide, etc. Ethylene oxide and propylene oxide are preferred. The glycols may be aliphatic glycols having from 2 to about 12, or from 2 to about 6, or from 2 or 3 carbon atoms. Glycols include ethylene glycol, propylene glycol, and the like. The alkylthiophosphate, glycols, epoxides, inorganic phosphorus reagents and methods of reacting the same are described in U.S. Pat. Nos. 3,197,405 and 3,544,465 .
In one embodiment, the amine-containing phosphorus antiwear agent can be substantially sulfur-free. Examples include the amine salt of a phosphate hydrocarbon ester prepared by reaction between phosphorus pentoxide with an alcohol (having 4 to 18 carbon atoms), followed by a reaction with a primary (e.g., 2-ethylhexylamine or oleylaminopropyl amine), secondary (e.g., dimethylamine), or tertiary (e.g., dimethyloleylamine) amine to form an amine salt of a phosphate hydrocarbon ester.
Another example of an amine-phosphate antiwear agent is a substantially sulfur-free alkyl phosphate amine salt having at least 30 mole percent of the phosphorus atoms in an alkyl pyrophosphate structure (sometimes referred to as the POP structure), as opposed to an orthophosphate (or monomeric phosphate) structure, as shown, for example, in the following formula R¹O(O₂)POP(O₂)OR¹•(R² ₃)NH⁺, or variants thereof, where, each R¹ is independently an alkyl group of 3 to 12 carbon atoms, and each R² is independently hydrogen or a hydrocarbyl group or an ester-containing group, or an ether-containing group, provided that at least one R² group is a hydrocarbyl group or an ester-containing group or an ether-containing group (that is, not NH₃).
The amount of the amine-containing phosphorus antiwear agent in the automotive gear oil may be 0.1 to 5 wt.%. Alternative amounts of the amine-containing phosphorus antiwear agent may be 0.2 to 3 wt.%, or 0.2 to 2.5 wt.%, or 0.2 to 2 wt.%, or 1 to 2 wt.%, or 0.3 to 1.9 wt.%, or 0.4 to 1.8 wt.%, or 0.4 to 1.7 wt.%. The amount may be suitable to provide phosphorus to the automotive gear oil in an amount of 200 to 3000 parts per million by weight (ppm), or 250 to 2750, or 300 to 2500, or 350 to 2250, or 400 to 2000 ppm, or 600 to 1500 ppm, or 700 to 1100 ppm, or 1100 to 1800 ppm.

Oil-Soluble Titanium Compound

The oil-soluble titanium compound can also be referred to more generally as a hydrocarbon-soluble titanium compound. By "oil-soluble" or "hydrocarbon soluble" it is meant a material which will dissolve or disperse on a macroscopic or gross scale in an oil or hydrocarbon, as the case may be, typically a mineral oil, such that a practical solution or dispersion can be prepared. In order to prepare a useful lubricant formulation, the titanium compound should not precipitate or settle out over a course of several days or weeks, and preferably months or years. Such materials may exhibit true solubility on a molecular scale or may exist in the form of agglomerations of varying size or scale, provided however that they have dissolved or dispersed on a gross scale.
The nature of the oil-soluble titanium compound can be diverse. Among the titanium compounds that may be used in the lubricating compositions are various Ti (IV) compounds such as titanium (IV) sulfide; titanium (IV) nitrate; titanium (IV) alkoxides such as titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide; titanium (IV) 2-ethylhexoxide; and titanium (IV) (triethanolaminato)isopropoxide; and other titanium compounds or complexes including but not limited to titanium phenates; titanium carboxylates such as titanium (IV) 2-ethyl-1-3-hexanedioate or titanium citrate or titanium oleate. Other forms of titanium that may be employed include titanium phosphates such as titanium dithiophosphates (e.g., dialkyldithiophosphates) and titanium sulfonates (e.g., alkylsulfonates), or, generally, the reaction product of titanium compounds with various acid materials to form salts, especially oil-soluble salts. Titanium compounds can thus be derived from, among others, organic acids, alcohols, and glycols. Titanium compounds may also exist in dimeric or oligomeric form, containing Ti--O--Ti structures. Such titanium compounds are commercially available or can be readily prepared by appropriate synthesis techniques which will be apparent to the person skilled in the art. Titanium compounds may exist at room temperature as a solid or a liquid, depending on the particular compound, and may also be provided in a solution form in an appropriate inert solvent.
In embodiments, the titanium can be supplied as a Ti-modified dispersant, such as a succinimide dispersant. Such materials may be prepared by forming a titanium mixed anhydride between a titanium alkoxide and a hydrocarbyl-substituted succinic anhydride, such as an alkenyl- (or alkyl) succinic anhydride. The resulting titanate-succinate intermediate may be used directly or it may be reacted with any of a number of materials, such as (a) a polyamine-based succinimide/amide dispersant having free, condensable -NH functionality; (b) the components of a polyamine-based succinimide/amide dispersant, i.e., an alkenyl- (or alkyl-)succinic anhydride and a polyamine, (c) a hydroxy-containing polyester dispersant prepared by the reaction of a substituted succinic anhydride with a polyol, aminoalcohol, polyamine, or mixtures thereof. Alternatively, the titanate-succinate intermediate may be reacted with other agents such as alcohols, aminoalcohols, ether alcohols, polyether alcohols or polyols, or fatty acids, and the product thereof either used directly to impart titanium to a lubricant, or else further reacted with the succinic dispersants as described above. As an example, 1 part (by mole) of tetraisopropyl titanate may be reacted with 2 parts (by mole) of a polyisobutene-substituted succinic anhydride at 140-150 °C for 5 to 6 hours to provide a titanium modified dispersant or intermediate. The resulting material (30 g) may be further reacted with a succinimide dispersant from polyisobutene-substituted succinic anhydride and a polyethylenepolyamine mixture (127 g+diluent oil) at 150 °C for 1.5 hours, to produce a titanium-modified succinimide dispersant.
In another embodiment, the titanium can be supplied as a tolyltriazole oligomer salted with and/or chelated to titanium. The surface active properties of the tolyltriazole allow it to act as a delivery system for the titanium, imparting the titanium performance benefits described herein, as well as the copper deactivating performance of tolyltriazole. In one embodiment, this material can be prepared by first combining tolyltriazole (1.5 eq) and formaldehyde (1.57 eq) in an inert solvent followed by addition of diethanolamine (1.5 eq) and then hexadecyl succinic anhydride (1.5 eq) and a catalytic amount of methanesulfonic acid, while heating and removing water of condensation. This intermediate can be reacted with titanium isopropoxide (0.554 eq) at 60 °C, followed by vacuum stripping to provide a red viscous product.
Other forms of titanium can also be provided, such as surface-modified titanium dioxide nanoparticles, as described in greater detail in Q. Xue et al., Wear 213, 29-32, 1997 (Elsevier Science S.A.), which discloses TiO₂ nanoparticles with an average diameter of 5 nm, surface modified with 2-ethylhexoic acid. Such nanoparticles capped by an organic hydrocarbyl chain are said to disperse well in non-polar and weakly polar organic solvents. Their synthesis is described in greater detail by K. G. Severin et al. in Chem. Mater. 6, 8990-898, 1994.
In one embodiment, the titanium is not a part of or affixed to a long-chain polymer, that is, a high molecular weight polymer. Thus, the titanium species may, in these circumstances, have a number average molecular weight of less than 150,000 or less than 100,000 or 30,000 or 20,000 or 10,000 or 5000, or 3000 or 2000, e. g, about 1000 or less than 1000. Non-polymeric species providing the titanium as disclosed above will typically be below the molecular weight range of such polymers. For example, a titanium tetraalkoxide such as titanium isopropoxide may have a number average molecular weight of 1000 or less, or 300 or less, as may be readily calculated. A titanium-modified dispersant may include a hydrocarbyl substituent with a number average molecular weight of 3000 or less or 2000 or less, e.g., about 1000.
The amount of titanium (that is titanium atom as opposed to titanium compound) present in the automotive gear oil is greater than 200 parts per million by weight (ppm), or greater than 250 ppm, or greater than 300 or 325 ppm. In some embodiments, the titanium compound may be present at from about 200 to about 2000 ppm, or from 200 or 250 to about 1500 ppm or even about 300 to about 1250 or even about 325 or 350 to about 900 or 1000 ppm.
These limits may vary with the particular system investigated and may be influenced to some extent by the anion or complexing agent associated with the titanium. Also, the amount of the particular titanium compound to be employed will depend on the relative weight of the anionic or complexing groups associated with the titanium. Titanium isopropoxide, for instance, is typically commercially supplied in a form which contains 16.8% titanium by weight. Thus, if amounts of 20 to 100 ppm of titanium are to be provided, about 119 to about 595 ppm (that is, about 0.01 to about 0.06 wt.%) of titanium isopropoxide would be used, and so on.
In certain embodiments, the titanium compound may be selected from the group consisting of titanium alkoxides, titanium modified dispersants, titanium salts of aromatic carboxylic acids (such as benzoic acid or alkyl-substituted benzoic acids), and titanium salts of sulfur-containing acids (such as those of the formula R--S--R'--CO₂H, where R is a hydrocarbyl group and R' is a hydrocarbylene group).

Other Additives

An automotive gear oil, as used herein, refers to a lubricant composition having sufficient levels of additive to lubricate an automotive gear, such as a gear, bearing or axle. In this regard, automotive gear oils can be distinguished from other lubricants, such as engine oil lubricants, based on levels of sulfur and phosphorus.
The automotive gear oil can have a total sulfur level of about 0.75 to about 5 wt.% based on the weight of the automotive gear oil. In some embodiments, the total sulfur level can be from about 0.8 to about 4 wt.%, or even about 0.9 to about 3.5 wt.% or about 1 to about 3 wt.%. The sulfur can be provided, for example, from organo-sulfides, including polysulfides, such as sulfurized olefins, thiadiazoles and thiadiazole adducts such as post treated dispersants.
Organo-sulfides can be present in in the automotive gear oil in a range of, for example, 0 wt.% to 10 wt.%, 0.01 wt.% to 10 wt.%, 0.1 wt.% to 8 wt.%, 0.25 wt.% to 6 wt.%, 2 wt.% to 5 wt.%, or 3 wt.% to 5 wt.%, 3% to 6% of the automotive gear oil.
Examples of a thiadiazole include 2,5-dimercapto-1,3,4-thiadiazole, or oligomers thereof, a hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole, a hydro-carbylthio-substituted 2,5-dimercapto-1,3,4-thiadiazole, or oligomers thereof. The oligomers of hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole typically form by forming a sulfur-sulfur bond between 2,5-dimercapto-1,3,4-thiadiazole units to form oligomers of two or more of said thiadiazole units. Further examples of thiadiazole compounds are found in WO 2008,094759 , paragraphs 0088 through 0090.
The organosulfide may alternatively be a polysulfide. In one embodiment at least about 50 wt.% of the polysulfide molecules are a mixture of tri- or tetra-sulfides. In other embodiments at least about 55 wt.%, or at least about 60 wt.% of the polysulfide molecules are a mixture of tri- or tetra-sulfides. The polysulfides include sulfurized organic polysulfides from oils, fatty acids or ester, olefins or polyolefins.
Oils which may be sulfurized include natural or synthetic oils such as mineral oils, lard oil, carboxylate esters derived from aliphatic alcohols and fatty acids or aliphatic carboxylic acids (e.g., myristyl oleate and oleyl oleate), and synthetic unsaturated esters or glycerides.
Fatty acids include those that contain 8 to 30, or 12 to 24 carbon atoms. Examples of fatty acids include oleic, linoleic, linolenic, and tall oil. Sulfurized fatty acid esters prepared from mixed unsaturated fatty acid esters such as are obtained from animal fats and vegetable oils, including tall oil, linseed oil, soybean oil, rapeseed oil, and fish oil.
The polysulfide may also be derived from an olefin derived from a wide range of alkenes, typically having one or more double bonds. The olefins in one embodiment contain 3 to 30 carbon atoms. In other embodiments, olefins contain 3 to 16, or 3 to 9 carbon atoms. In one embodiment the sulfurized olefin includes an olefin derived from propylene, isobutylene, pentene, or mixtures thereof. Isobutene, propylene and their dimers, trimers and tetramers, and mixtures thereof are further olefinic compounds. Of these compounds, isobutylene and diisobutylene are particularly desirable because of their availability and the particularly high sulfur containing compositions which can be prepared therefrom. In one embodiment the polysulfide comprises a polyolefin derived from polymerizing, by known techniques, an olefin as described above. In one embodiment the polysulfide includes, dibutyl disulfide, dibutyl tetrasulfide, sulfurized methyl ester of oleic acid, sulfurized alkylphenol, sulfurized dipentene, sulfurized dicyclopentadiene, sulfurized terpene, and sulfurized Diels-Alder adducts; phosphosulfurized hydrocarbons.
The automotive gear oils can also have a total phosphorus level of about 0.03 to about 0.5 wt.%, or 0.03 to about 0.35 wt.%, or even about 0.05 to about 0.3 wt.%, or about 0.08 to about 0.2 wt.%, or about 0.13 to about 0.2 wt.%, or about 0.1 to about 0.25 wt.%. The phosphorus can be brought to the automotive gear oil, for example, from the amine-containing phosphorus antiwear agents discussed above, or other phosphorus containing compounds.
Other phosphorus-containing compounds may be included along with the amine-containing phosphorus antiwear agents. Such other phosphorus containing compounds can include phosphites or phosphonates. Suitable phosphites or phosphonates include those having at least one hydrocarbyl group with 3 or 4 or more, or 8 or more, or 12 or more, carbon atoms. The phosphite may be a mono-hydrocarbyl substituted phosphite, a di-hydrocarbyl substituted phosphite, or a tri-hydrocarbyl substituted phosphite. The phosphonate may be a mono-hydrocarbyl substituted phosphonate, a di-hydrocarbyl substituted phosphonate, or a tri-hydrocarbyl substituted phosphonate.
In one embodiment the phosphite is sulphur-free i.e., the phosphite is not a thi-ophosphite.
The phosphite or phosphonate may be represented by the formulae:

wherein at least one R may be a hydrocarbyl group containing at least 3 carbon atoms and the other R groups may be hydrogen. In one embodiment, two of the R groups are hydrocarbyl groups, and the third is hydrogen. In one embodiment every R group is a hydrocarbyl group, i.e., the phosphite is a tri-hydrocarbyl substituted phosphite. The hydrocarbyl groups may be alkyl, cycloalkyl, aryl, acyclic or mixtures thereof.
In the art, a phosphonate (i.e., formula XI with R = hydrocarbyl) may also be referred to as a phosphite ester. Where one of the R groups in formula XII is an H group, the compound would generally be considered a phosphite, but such a compound can often exist in between the tautomers of formula XI and XII, and thus, could also be referred to as a phosphonate or phosphite ester. For ease of reference, the term phosphite, as used herein, will be considered to encompass both phosphites and phosphonates.
The R hydrocarbyl groups may be linear or branched, typically linear, and saturated or unsaturated, typically saturated.
In one embodiment, the other phosphorus-containing compound can be a C_3-8 hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R may independently be hydrogen or a hydrocarbyl group having 3 to 8, or 4 to 6 carbon atoms, typically 4 carbon atoms. Typically the C_3-8 hydrocarbyl phosphite comprises dibutyl phosphite. The C_3-8 hydrocarbyl phosphite may deliver at least 175 ppm, or at least 200 ppm of the total amount of phosphorus delivered by the phosphorus-containing compounds. The C_3-8 hydrocarbyl phosphite may deliver at least 25wt.%, 35 wt.%, 45 wt.%, or 50 wt.% to 80 wt.%, or 50 wt.% to 75 wt.% or 60 wt.% to 70 wt.% of the total amount of phosphorus to the lubricant composition.
In one embodiment, the phosphorus-containing compound can be a C_12-22 hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R may independently be hydrogen or a hydrocarbyl group having 12 to 24, or 14 to 20 carbon atoms, typically 16 to 18 carbon atoms. Typically the C_12-22 hydrocarbyl phosphite comprises a C_16-18 hydrocarbyl phosphite. Examples of alkyl groups for R³, R⁴ and R⁵ include octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl or mixtures thereof. The C_12-22 hydrocarbyl phosphite may be present in the lubricant composition at about 0.05 wt.% to about 4.0 wt.% of the lubricant composition, or from about 0.05 wt.% to about 3 wt.%, or from about 0.05 wt.% to about 1.5 wt.%, or from about 0.05 wt.% to about 1 wt.%, or from about 0.1 wt.% to about 0.5 wt.% of the lubricant composition.
In some embodiments, the other phosphorus containing compound can include both a C_3-8 and a C₁₂ to C₂₄ hydrocarbyl phosphite.
In one embodiment, the phosphite ester comprises the reaction product of (a) a monomeric phosphoric acid or an ester thereof with (b) at least two alkylene diols; a first alkylene diol (i) having two hydroxy groups in a 1,4 or 1,5 or 1,6 relationship; and a second alkylene diol(ii) being an alkyl-substitute 1,3-propylene glycol.
Sulfur containing phosphites can include, for example, a material represented by the formula [R¹O(OR²)(S)PSC₂H₄(C)(O)OR⁴O]_nP(OR⁵)_2-n(O)H, wherein R¹ and R² are each independently hydrocarbyl groups of 3 to 12 carbon atoms, or 6 to 8 carbon atoms, or wherein R¹ and R² together with the adjacent O and P atoms form a ring containing 2 to 6 carbon atoms; R⁴ is an alkylene group of 2 to 6 carbon atoms or 2 to 4 carbon atoms; R⁵ is hydrogen or a hydrocarbyl group of 1 to about 12 carbon atoms; and n is 1 or 2. The C_12-22 hydrocarbyl phosphite may be present in the lubricant composition at about 0.05 wt.% to about 1.5 wt.% of the lubricant composition, or from about 0.1 wt.% to about 1.0 wt.% of the lubricant composition.
In one embodiment, the other phosphorus containing compound can be a phosphorus containing amide. Phosphorus containing amides can be prepared by reaction of dithiophosphoric acid with an unsaturated amide. Examples of unsaturated amides include acrylamide, N,N'-methylene bisacrylamide, methacrylamide, crotonamide and the like. The reaction product of the phosphorus acid and the unsaturated amide may be further reacted with a linking or a coupling compound, such as formaldehyde or paraformaldehyde. The phosphorus containing amides are known in the art and are disclosed in U.S. Pat. Nos. 4,670,169 , 4,770,807 and 4,876,374 .
Other materials may be present in the automotive gear oil in their conventional amounts including, for example, viscosity modifiers, dispersants, pour point additives, extreme pressure agents, antifoams, copper anticorrosion agents (such as dimercaptothiadiazole compounds), iron anticorrosion agents, friction modifiers, dyes, fragrances, optional detergents and antioxidants, and color stabilizers, for example.
The disclosed technology provides a method of lubricating an automotive gear, comprising supplying thereto an automotive gear oil as described herein, that is, an automotive gear oil having a total sulfur level of 0.75 to 5 wt.% and containing (a) an oil of lubricating viscosity, (b) an oil-soluble titanium compound, and (c) an amine-containing phosphorus antiwear agent, and operating the driveline device.
The automotive gear may comprise a gear as in a gearbox of a vehicle (e.g., a manual transmission) or in an axle or differential, or in other driveline power transmitting driveline devices. The automotive gear may also include bearings. Lubricated gears may include hypoid gears, such as those for example in a rear drive axle.
The amount of each chemical component described is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, that is, on an active chemical basis, unless otherwise indicated. However, unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade.
As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring);
substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);
hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. Heteroatoms include sulfur, oxygen, and nitrogen. In general, no more than two, or no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; alternatively, there may be no non-hydrocarbon substituents in the hydrocarbyl group.

It is known that some of the materials described herein may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other electron rich sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the present invention in its intended use, may not be susceptible of easy description.
The present invention encompasses the composition prepared by admixing the components described above.
The invention herein may be better understood with reference to the following examples.

EXAMPLES

Several Automotive Gear Oils ("AGO") were prepared for testing according to the following formulations (numbers represent wt%).

	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5
Olefin polymer	22	22	22	22	22
Sulfurized olefin	4.57	4.57	4.57	4.57	4.57
Phosphorus amine salt-1*	1.66	1.66	1.66	1.66	1.66
Substituted thiadiazole	0.15	0.15	0.15	0.15	0.15
Alkyl amide	0.13	0.13	0.13	0.13	0.13
Antifoam	0.1	0.1	0.1	0.1	0.1
Borated dispersant	0.78
Non-borated dispersant		0.75	0.75	0.75	0.75
Oil soluble Ti compound			0.12	0.24	0.37
Oil of lubricating viscosity	Sum to 100

*Phosphorus amine salt-1 contains sulfur.

The gear oil samples were evaluated in the L-60-1 Thermal Oxidative Stability of Gear Lubricants Test (based on ASTM Method D5704 ), which is a 50 hour test. SAE J2360 standard for thermal stability requires the lubricant tested under L-60-1 to show a gear sludge rating of 9.4 minimum, gear carbon/varnish rating of 7.5 minimum, viscosity increase of 100% maximum, pentane insoluble of 3.0% maximum and toluene insoluble of 2.0% maximum.

	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5
ppm B	247
ppm Ti			106	202	303
L-60-1 Result
Sludge	9.4	9.5	9.5	9.6	9.6
Carbon/Varnish	8.8	2.4	4.3	8.2	8.1
Viscosity Increase %	17	13	13	21	23
Pentane insoluble	0.3	0.1	0.1	0.6	0.2
Toluene insoluble	0.2	0	0	0.9	0.2

The impact of borated dispersant can be observed by comparing the carbon/varnish ratings for Sample 1 vs. Sample 2. Like Sample 2, Samples 3-5 do not contain borated dispersant. However, these samples contain increasing amounts of oil soluble titanium resulting in improved carbon/varnish ratings.

Additional gear oil samples were prepared in which the sulfur containing phosphorus amine salt was replaced with a substantially sulfur-free phosphorus amine salt. Gear oil samples 6-9 were prepared according to the following formulations (numbers represent wt%):

	Sample 6	Sample 7	Sample 8	Sample 9
Methacrylate copolymer	9	9	9	9
Sulfurized olefin	4.6	4.6	4.6	4.6
Phosphorus amine salt-2*	1.84	1.84	1.84	1.84
Substituted thiadiazole	0.2	0.2	0.2	0.2
Rust inhibitor	0.2	0.2	0.2	0.2
Antifoam	0.04	0.04	0.04	0.04
Borated dispersant	0.78
Non-borated dispersant	0.75	0.75	0.75	0.75
Oil soluble Ti compound			0.3	0.6
Oil of lubricating viscosity	Sum to 100

Phosphorus amine salt-2* is substantially sulfur free.

Gear oil samples 6-9 contain identical concentrations of non-borated dispersant. Only Sample 6 contains borated dispersant. Samples 6 and 7 are Ti-free, and Samples 8 and 9 contain 300 ppm Ti and 600ppm Ti respectively. These four samples were also tested in the L-60-1 Thermal Oxidative Stability of Gear Lubricants Test (based on ASTM Method D5704 ). Samples 6 and 7 are comparative samples that were tested to again demonstrate the importance of the presence of borated dispersant to achieve the desired carbon/varnish rating. Boron-free samples 8 and 9 contain oil soluble Ti which improves the carbon/varnish rating to achieve the desired thermal oxidative stability in this test.

	Sample 6	Sample 7	Sample 8	Sample 9
ppm B	252
ppm Ti			261	516
L-60-1 Result
Sludge	9.5	9.6	9.7	9.5
Carbon/Varnish	9.7	6.4	8.7	9
Viscosity Increase %	13	11	20	29
Pentane insoluble	0.6	0.3	0.1	0.1
Toluene insoluble	0	0.4	0.1	0.1

Gear oil samples 10-13 were prepared without borated dispersant according to the following formulations (numbers represent wt%):

	Sample 10	Sample 11	Sample 12	Sample 13
Methacrylate copolymer	9	9	9	9
Sulfurized olefin	4.6	4.6	4.6	4.6
Phosphorus amine salt-3*	1.41	1.41	1.41	1.41
Substituted thiadiazole	0.2	0.2	0.2	0.2
Rust inhibitor	0.2	0.2	0.2	0.2
Antifoam	0.04	0.04	0.04	0.04
Non-borated dispersant	0.75	0.75	0.75	0.75
Oil soluble Ti compound	0	0.3	0.6	0.9
Oil of lubricating viscosity	Sum to 100

Phosphorus amine salt-3* is substantially sulfur free and at least 30 mole percent of the phosphorus atoms are in an alkyl pyrophosphate structure.

Gear oil samples 10-13 contain identical concentrations of non-borated dispersant. Sample 10 is Ti-free, and Samples 11, 12 and 13 contain 300 ppm Ti, 600ppm Ti and 900ppm Ti respectively. These four samples were also tested in the L-60-1 Thermal Oxidative Stability of Gear Lubricants Test (based on ASTM Method D5704 ). Samples 10 was tested to demonstrate the carbon/varnish performance without the presence of a borated dispersant. Boron-free samples 11, 12 and 13 contain increasing amounts of oil soluble Ti which improves the carbon/varnish rating to achieve the desired thermal oxidative stability in this test.

	Sample 10	Sample 11	Sample 12	Sample 13
ppm B
ppm Ti		319	618	775
L-60-1 Result
Sludge	9.7	9.6	9.7	9.8
Carbon/Varnish	2.7	5.7	9.8	10
Viscosity Increase %	11	17	36	39
Pentane insoluble	0.4	0.1	0.9	0.6
Toluene insoluble	0.4	0	0.4	0.1

Gear oil samples 14 and 15 do not contain borated dispersant. These samples contain a mixture of Phosphorus amine-salt-1 and phosphite. Sample 14 is a comparative sample without an oil soluble Ti compound, while Sample 15 contains 525ppm Ti.

	Sample 14	Sample 15
Methacrylate copolymer	9	9
Sulfurized olefin	4.6	4.6
Phosphorus amine salt-1*	0.82	0.82
Phosphite	0.725	0.725
Substituted thiadiazole	0.2	0.2
Rust inhibitor	0.2	0.2
Antifoam	0.04	0.04
Non-borated dispersant	0.75	0.75
Oil soluble Ti compound	0	0.6

Addition of the oil soluble Ti compound in the absence of boron-containing compounds results in improved Carbon/Varnish ratings in the L-60-1 test.

	Sample 14	Sample 15
ppm B
ppm Ti		525
L-60-1 Result
Sludge	9.6	9.7
Carbon/Varnish	4.1	10
Viscosity Increase %	8	15
Pentane insoluble	0.1	0.1
Toluene insoluble	0.2	0

The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as optionally modified by the word "about." It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.
As used herein, the transitional term "comprising," which is synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional, un-recited elements or method steps. However, in each recitation of "comprising" herein, it is intended that the term also encompass, as alternative embodiments, the phrases "consisting essentially of" and "consisting of," where "consisting of" excludes novel characteristics of the composition or method under consideration. The expression "consisting of" or "consisting essentially of," when applied to an element of a claim, is intended to restrict all species of the type represented by that element, notwithstanding the presence of "comprising" elsewhere in the claim.
While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. In this regard, the scope of the invention is to be limited only by the following claims.

Claims

A lubricant composition comprising an oil of lubricating viscosity, an amine-containing phosphorus antiwear agent, and an oil-soluble titanium compound, wherein the lubricant composition contains less than 50 ppm of boron, wherein the lubricant comprises a total sulfur level of about 0.75 to about 5 wt.%, and wherein the composition comprises greater than 200 ppm titanium.
The lubricant composition of claim 1, wherein the oil-soluble titanium compound comprises at least one of titanium (IV) sulfide; titanium (IV) nitrate; titanium (IV) alkoxides; titanium phenates; titanium carboxylates; titanium phosphates; titanium sulfonates.
The lubricant composition of any previous claim, where the oil-soluble titanium compound comprises titanium (IV) 2-ethylhexoxide.
The lubricant composition of any of claims 1-3 wherein the amine-containing phosphorus antiwear agent as an amine (thio)phosphate salt.
The lubricant composition of any of claims 1 to 4, wherein the lubricant comprises a total phosphorus level of about 0.03-0.5 wt.%.
The lubricant composition of any of claims 1 to 5, further comprising an additional phosphorus-containing agent other than the amine-containing phosphorus antiwear agent.
A method of lubricating a driveline device, comprising supplying to the driveline device the lubricant composition of any previous claim, and operating the driveline device.
The method of claim 7, wherein the driveline device comprises an axle.
The method of claim 7, wherein the driveline device comprises a bearing.
The method of claim 7, wherein the driveline device comprises a gear.