BORON CONTAINING AUTOMOTIVE GEAR OIL

Description

BACKGROUND OF THE INVENTION

[0001] The disclosed technology relates to an automotive gear oil, which may be used, for example, in manual transmissions and axles. The automotive gear oil is particularly useful as a single lubricant to lubricate both the transmission and the axle.

[0002] Deposits of decomposition products such as carbon, varnish and sludge cause serious problems in gearboxes. The tendency towards decomposition products is particularly strong among synthetic automotive gear oils which have long drain intervals. As such, cleanliness is a mandatory requirement in automotive gear oils, and particularly modern automotive gear oils based on synthetic base oils.

[0003] Most modern automotive gear oils contain dispersants that help maintain the cleanliness of the oil. However, dispersants were not always included in automotive gear oil products. With the tendency towards more synthetics, there is a need to provide improved cleanliness to some of the older automotive gear oil formulations, without losing the performance that the automotive gear oil provided. Unfortunately, it has been found that the addition of dispersant to an automotive gear oil can have a detrimental effect on the frictional characteristics of the oil. As frictional characteristics are a set parameter for a given oil, a solution is needed to balance the need for cleanliness while maintaining proper friction. US 2005/014656 A1 discloses a lubricating composition containing (a) a hydrocarbyl phosphite; (b) the condensation product of at least one fatty acid with a polyamine; (c) a borate ester; (d) a borated dispersant; and (e) an oil of lubricating viscosity.

SUMMARY OF THE INVENTION

[0004] The present technology solves the problem of balancing cleanliness with frictional properties in automotive gear oils by providing an automotive gear oil for lubricating an automotive gear having a. an oil of lubricating viscosity, b. 0.025 to 0.9 wt % of a succinimide dispersant, c. 0.2 to 2.0 wt % of at least one boron-containing compound in an amount sufficient to provide from 75 ppm to 500 ppm of boron to the automotive gear oil, wherein the at least one boron-containing compound is a borate ester of formula I,

wherein each R, independently, is a C3 to C12 alkyl, and d. 0.01 to 0.5 wt. % of a dimercaptothiadiazole or derivative thereof, wherein the derivative of the dimercaptothiadizole (DMTD) is: a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole or 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole and mixtures thereof; b) carboxylic esters of DMTD; c) condensation products of α-halogenated aliphatic monocarboxylic acids with DMTD; d) reaction products of unsaturated cyclic hydrocarbons and unsaturated ketones with DMTD; e) reaction products of an aldehyde and diaryl amine with DMTD; f) amine salts of DMTD; g) dithiocarbamate derivatives of DMTD; h) reaction products of an aldehyde, and an alcohol or aromatic hydroxy compound, and DMTD; i) reaction products of an aldehyde, a mercaptan and DMTD; j) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; or k) products from combining an oil soluble dispersant with DMTD and mixtures thereof.

[0005] It has been found that the presence of the boron-containing compound not only enhances the cleansing ability of any dispersant present, but also suppresses any harmful effects to the oil's frictional characteristics from the dispersant.

[0006] In embodiments, the automotive gear oil can also include at least one phosphorous containing compound present in an amount to deliver 100 to 1500 ppm of phosphorus to the automotive gear oil. In embodiments, the phosphorous containing compound can be at least one of: (1) a C_3-8 hydrocarbyl phosphite, (2) a phosphite ester composition that comprises the reaction product of a monomeric phosphorous acid or an ester thereof with at least two alkylene diols, or (3) mixtures of (1) and (2).

[0007] The automotive gear oil can also include 0.1 wt % to 5 wt % of a poly(meth)acrylate ester polymer viscosity modifier.

[0008] In an embodiment, the automotive gear oil can have a kinematic viscosity at 100°C of from 8 cSt to 24 cSt.

[0009] The disclosed technology also includes a method of lubricating an automotive gear by supplying to the automotive gear the automotive gear oil composition, and operating the automotive gear. The automotive gear can be, for example, in a manual transmission, on an axle, and/or on a differential.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention is disclosed in and by the appended claims.

[0011] Various preferred features and embodiments will be described below by way of non-limiting illustration.

[0012] One aspect of the present technology is an automotive gear oil. The automotive gear oil can be employed to provide lubrication to the gears of automotive vehicles, such as, for example, manual transmissions, axles and differentials. The composition includes, among other things, a. an oil of lubricating viscosity, b. 0.025 to 0.9 wt % of a succinimide dispersant, c. 0.2 to 2.0 wt % of at least one boron-containing compound in an amount sufficient to provide from 75 ppm to 500 ppm of boron to the automotive gear oil, wherein the at least one boron-containing compound is a borate ester of formula I,

wherein each R, independently, is a C3 to C12 alkyl, and d. 0.01 to 0.5 wt. % of a dimercaptothiadiazole or derivative thereof, wherein the derivative of the dimercaptothiadizole (DMTD) is: a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole or 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole and mixtures thereof; b) carboxylic esters of DMTD; c) condensation products of α-halogenated aliphatic monocarboxylic acids with DMTD; d) reaction products of unsaturated cyclic hydrocarbons and unsaturated ketones with DMTD; e) reaction products of an aldehyde and diaryl amine with DMTD; f) amine salts of DMTD; g) dithiocarbamate derivatives of DMTD; h) reaction products of an aldehyde, and an alcohol or aromatic hydroxy compound, and DMTD; i) reaction products of an aldehyde, a mercaptan and DMTD; j) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; or k) products from combining an oil soluble dispersant with DMTD and mixtures thereof.

Oils of Lubricating Viscosity

[0013] Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines (2011). The five base oil groups are as follows: Group I (sulfur content >0.03 wt %, and/or <90 wt % saturates, viscosity index 80 to less than 120); Group II (sulfur content ≤0.03 wt %, and ≥90 wt % saturates, viscosity index 80 to less than 120); Group III (sulfur content ≤0.03 wt %, and ≥90 wt % saturates, viscosity index ≥120); Group IV (all polyalphaolefins (PAOs)); and Group V (all others not included in Groups I, II, III, or IV). The oil of lubricating viscosity may also be a Group II+ base oil, which is an unofficial API category that refers to a Group II base oil having a viscosity index greater than or equal to 110 and less than 120, as described in SAE publication "Design Practice: Passenger Car Automatic Transmissions," fourth Edition, AE-29, 2012, page 12-9, as well as in US 8,216,448, column 1 line 57. The oil of lubricating viscosity may also be a Group III+ base oil, which, again, is an unofficial API category that refers to a Group III base oil having a viscosity index of greater than 130, for example 130 to 133 or even greater than 135, such as 135-145. Gas to liquid ("GTL") oils are sometimes considered Group III+ base oils.

[0014] The oil of lubricating viscosity may be an API Group IV oil, or mixtures thereof, i.e., a polyalphaolefin. The polyalphaolefin may be prepared by metallocene catalyzed processes or from a non-metallocene process. The oil of lubricating viscosity may also comprise an API Group I, Group II, Group III, Group IV, Group V oil or mixtures thereof. Often the oil of lubricating viscosity is an API Group I, Group II, Group II+, Group III, Group IV oil or mixtures thereof. Alternatively the oil of lubricating viscosity is often an API Group II, Group II+, Group III or Group IV oil or mixtures thereof. Alternatively the oil of lubricating viscosity is often an API Group II, Group II+, Group III oil or mixtures thereof.

[0015] The oil of lubricating viscosity, or base oil, will overall have a kinematic viscosity at 100 °C of 2 to 10 cSt or, in some embodiments 2.25 to 9 or 2.5 to 6 or 7 or 8 cSt, as measured by ASTM D445. Kinematic viscosities for the base oil at 100 °C of from about 3.5 to 6 or from 6 to 8 cSt are also suitable.

[0016] The amount of the oil of lubricating viscosity present is typically the balance remaining after subtracting from 100 wt % the sum of the amount of the performance additives in the composition. Illustrative amounts may include 50 to 99 percent by weight, or 60 to 98, or 70 to 95, or 80 to 94, or 85 to 93 percent.

[0017] The lubricating composition may be in the form of a concentrate and/or a fully formulated lubricant. If the lubricating composition of the invention is in the form of a concentrate (which may be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the components of the invention to the oil of lubricating viscosity and/or to diluent oil include the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 by weight.

Dispersant

[0018] The automotive gear oil according to present invention contains 0.025 to 0.9 wt % of a succinimide dispersant. Many types of dispersants are known in the art.

[0019] "Carboxylic dispersants" are reaction products of carboxylic acylating agents (acids, anhydrides, esters) containing at least about 34 and preferably at least about 54 carbon atoms with nitrogen containing compounds (such as amines), organic hydroxy compounds (such as aliphatic compounds including monohydric and polyhydric alcohols, or aromatic compounds including phenols and naphthols), and/or basic inorganic materials. These reaction products include imide, amide, and ester reaction products of carboxylic ester dispersants.

[0020] The carboxylic acylating agents include fatty acids, isoaliphatic acids (e.g. 8-methyl-octadecanoic acid), dimer acids, addition dicarboxylic acids (addition (4+2) and 2+2) products of an unsaturated fatty acid with an unsaturated carboxylic reagent), trimer acids, addition tricarboxylic acids (Empol^® 1040, Hystrene^® 5460 and Unidyme^® 60), and hydrocarbyl substituted carboxylic acylating agents (from olefins and/or polyalkenes). The carboxylic acylating agent may be a fatty acid. Fatty acids generally contain from about 8 up to about 30, or from about 12 up to about 24 carbon atoms. Carboxylic acylating agents are taught in U.S. Patents No. 2,444,328, 3,219,666 and 4,234,435.

[0021] The amine may be a mono- or polyamine. The monoamines generally have at least one hydrocarbyl group containing from 1 to about 24 carbon atoms, or from 1 to about 12 carbon atoms. Examples of monoamines include fatty (C8-30) amines (Armeens), primary ether amines (SURFAM^® amines), tertiary-aliphatic primary amines ("Primenes"), hydroxyamines (primary, secondary or tertiary alkanol amines), ether N-(hydroxyhydrocarbyl) amines, and hydroxyhydrocarbyl amines ("Ethomeens" and "Propomeens). The polyamines include alkoxylated diamines (Ethoduomeens), fatty diamines ("Duomeens"), alkylenepolyamines (ethylenepolyamines), hydroxy-containing polyamines, polyoxyalkylene polyamines (Jeffamines), condensed polyamines (a condensation reaction between at least one hydroxy compound with at least one polyamine reactant containing at least one primary or secondary amino group), and heterocyclic polyamines. Useful amines include those disclosed in U.S. Patent 4,234,435 (Meinhart) and U.S. Patent 5,230,714 (Steckel).

[0022] An example carboxylic dispersant can include, for example, "succinimide dispersants," prepared by the reaction of a hydrocarbyl-substituted succinic acylating agent with an amine such as a polyamine.

[0023] The hydrocarbyl-substituted succinic acylating agents include succinic acids, halides, esters, and anhydrides, preferably, acids, esters or anhydrides, more preferably anhydrides. The hydrocarbyl group generally contains an average of at least about 8, or about 30, or about 35 up to about 350, or to about 200, or to about 100 carbon atoms. In one embodiment, the hydrocarbyl group is derived from a polyalkene, such as, for example, polyisobutylene, generally having a number average molecular weight of from 100 to 5000, or 500 to 4000 or 1000 to 3000.

[0024] The amine which reacts with the succinic acylating agent may be a polyamine. The polyamine may be aliphatic, cycloaliphatic, heterocyclic or aromatic. Examples of the polyamines include alkylene polyamines, hydroxy containing polyamines, arylpolyamines, and heterocyclic polyamines.

[0025] "Amine dispersants" are reaction products of relatively high molecular weight aliphatic halides and amines, preferably polyalkylene polyamines.

[0026] "Mannich dispersants" are the reaction products of alkyl phenols in which the alkyl group contains at least about 30 carbon atoms with aldehydes (especially formaldehyde) and amines (especially polyalkylene polyamines).

[0027] Post-treated dispersants are obtained by reacting carboxylic, amine or Mannich dispersants with reagents such as dimercaptothiadiazoles, urea, thiourea, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boron compounds, or phosphorus compounds.

[0028] Polymeric dispersants are interpolymers of oil-solubilizing monomers such as decyl methacrylate, vinyl decyl ether and high molecular weight olefins with monomers containing polar substituents, e.g., aminoalkyl acrylates or acrylamides and poly-(oxyethylene)-substituted acrylates.

[0029] Dispersants and dispersant chemistry is well-known in the art. The dispersants suitable for use in automotive gear oils are not particularly limited. In the present invention, the level of dispersant may be minimized in view of the use of the boron-containing compounds, as described below.

[0030] Mixtures of the foregoing dispersants can also be used. The dispersant can have a nitrogen content of greater than or equal to about 11,000 ppm by weight of the dispersant, or greater than or equal to about 11,500ppm or greater than or equal to about 12,000 ppm.

[0031] The total amount of dispersant or dispersants, whether post-treated or not (e.g., borated or non-borated) or combinations thereof, in the compositions, may be, for example, 0.025 to 0.9 percent or 0.05 to 0.8 weight percent of the final blended fluid formulation, although in a concentrate, the amounts will be proportionately higher.

Boron-Containing Compound

[0032] The automotive gear oil contains at least one boron-containing compound in an amount sufficient to provide from 75ppm to 500 ppm of boron to the automotive gear oil, or from about 85 to about 450 ppm or about 95 to about 350 ppm boron, or from about 100 to about 400ppm boron to the automotive gear oil.

[0033] The boron containing compound includes a borate ester. The borate ester is a compound represented by formula (I):

wherein each R is independently a C₃ to C₁₂ alkyl. Examples of useful R groups include isopropyl, n-butyl, isobutyl, amyl, 4-methyl-2-pentyl, 2-ethyl-1-hexyl, isooctyl, decyl, dodecyl, and 2-propylheptyl. Others can be found, for example, in WO2017/083548.

[0034] Suitable examples of the borate ester include, for example, tripropyl borate, tributyl borate, tripentyl borate, trihexyl borate, triheptyl borate, trioctyl borate, trinonyl borate and tridecyl borate. Other borate ester examples can include, for example, tri-2-ethylhexyl borate, tris(2-propylheptyl) borate and mixtures thereof. In an embodiment the borate ester can be a C₈ borate ester, or a C₁₀ borate ester. In one embodiment the borate ester can be tris(2-propylheptyl) borate. In some embodiments the borate ester can be tri-2-ethylhexyl borate.

[0035] In one embodiment, the borated ester can be represented by the formula B(OC₅H₁₁)₃ or B(OC₄H₉)₃. In one embodiment, the borated ester can be tri-n-butyl borate.

[0036] The borate ester is employed in the automotive gear oil at 0.2 or 0.3 to 2.0 wt.% based on the weight of the automotive gear oil, or in some cases about 0.35 to 2.0 wt.%, and in one embodiment from about 0.25 to about 1.0 wt.%, and in one embodiment about 0.25 to about 0.75 wt.%.

Other Additives

[0037] The automotive gear oil contains further additives aside from the dispersant and boron-containing compound.

Phosphorus Containing Compound

[0038] The automotive gear oil can additionally contain a phosphorous containing compound. The phosphorus-containing compound may be an acid, salt or ester. In one embodiment the phosphorus-containing compounds are in the form of a mixture of two or three, or two to four (typically two or three) phosphorus-containing compounds.

[0039] In some embodiments the phosphorus-containing compound is a phosphite. Suitable phosphites 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.

[0040] In one embodiment the phosphite is sulphur-free i.e., the phosphite is not a thiophosphite.

[0041] The phosphite 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.

[0042] The R hydrocarbyl groups may be linear or branched, typically linear, and saturated or unsaturated, typically saturated.

[0043] In one embodiment, the 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 45 wt %, or 50 wt % to 100 wt %, or 50 wt % to 90 wt % or 60 wt % to 80 wt % of the total amount of phosphorus from the phosphorus-containing compound.

[0044] 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 automotive gear oil at about 0.05 wt.% to about 1.0 wt.% of the automotive gear oil, or from about 0.1 wt.% to about 0.5 wt.% of the automotive gear oil.

[0045] In some embodiments, the phosphorous containing compound can include both a C_3-8 and a C₁₂ to C₂₄ hydrocarbyl phosphite.

[0046] The lubricant composition optionally further contains an antiwear agent in the form of a hydrocarbyl amine salt of an alkyl(thio)phosphate. The alkyl(thio)phosphate may also be an amine alkylthiophosphate, wherein the alkylthiophosphate is represented by the formula (R'O)₂PSSH, wherein each R' is independently a hydrocarbyl group containing from about 3 to about 30, preferably from about 3 up to about 18, or from about 3 up to about 12, or from up to about 8 carbon atoms. Example R' groups can include isopropyl, isobutyl, n-butyl, sec-butyl, the various amyl, n-hexyl, methylisobutyl carbinyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, behenyl, decyl, dodecyl, and tridecyl groups. Illustrative lower alkylphenyl R' groups include butylphenyl, amylphenyl, heptylphenyl, etc. Examples of mixtures of R' groups include: 1-butyl and 1-octyl; 1-pentyl and 2-ethyl-1-hexyl; isobutyl and n-hexyl; isobutyl and isoamyl; 2-propyl and 2-methyl-4-pentyl; isopropyl and sec-butyl; and isopropyl and isooctyl.

[0047] In one embodiment, the alkylthiophosphate of the amine alkylthiophosphate may be reacted 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 polyhydric alcohols are described above. The glycols may be aliphatic glycols having from 1 to about 12, or from about 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.

[0048] In one embodiment the hydrocarbyl amine salt of an alkyl(thio)phosphate is the reaction product of a C₁₄ to C₁₈ alkylated phosphoric acid with Primene 81R^™ (produced and sold by Rohm & Haas) which is a mixture of C₁₁ to C₁₄ tertiary alkyl primary amines. Other amines which may be used include alkyl alkanol amines, dialkanolamines, trialkanolamines such as triethanolamines as well as borated amines as described hereinbelow.

[0049] The amine salt as used as this component may thus comprise a C₈ to C₂₀ alkylamine salt of a mono- or di-alkyl phosphate ester, or mixtures thereof.

[0050] The amount of the hydrocarbyl amine salt of an alkylphosphoric acid ester in the lubricant can be 0.3 to 2 weight percent, or 0.4 to 1.9, or 0.5 to 1.8, or 0.7 to 1.7 weight percent. The amounts will be proportionally higher in a concentrate. The amount of said amine salt may also be an amount to contribute 0.03 to 0.2 weight percent phosphorus to the lubricant composition, or alternatively 0.08 to 0.17, or 0.11 to 0.17 weight percent.

[0051] The automotive gear oil can also include a substantially sulfur-free alkyl phosphate amine salt having at least 30 mole percent of the phosphorus atoms in an alkyl pyrophosphate structure, as opposed to an orthophosphate (or monomeric phosphate) structure. The percentage of phosphorus atoms in the pyrophosphate structure may be 30 to 100 mole %, or 40 to 90 % or 50 to 80% or 55 to 70 % or 55 to 65%. The remaining amount of the phosphorus atoms may be in an orthophosphate structure or may consist, in part, in unreacted phosphorus acid or other phosphorus species. In one embodiment, up to 60 or up to 50 mole percent of the phosphorus atoms are in mono- or di-alkyl-orthophosphate salt structure.

[0052] The substantially sulfur-free alkyl phosphate amine salt, as present in the pyrophosphate form (sometimes referred to as the POP structure), may be represented in part by the following formulas (I) and/or (II):

or variants thereof, such as:



where, each R¹ is independently an alkyl group of 3 to 12 carbon atoms, such as, for example, 2-butyl, 2-pentyl, 3-pentyl, 3-methyl-2-butyl, 2-hexyl, 3-hexyl, cyclohexyl, 4-methyl-2-pentyl, and other such secondary groups and isomers thereof having 6, 7, 8, 9, 10, 11, or 12 carbon atoms. In some embodiments the alkyl group can have a methyl branch at the α-position of the group, an example being the 4-methyl-2-pentyl (also referred to as 4-methylpent-2-yl) group.

[0053] While the pyrophosphate ester may be isolated, if desired, from the orthoesters, it is also possible, and may be commercially preferable, to use the reaction mixture without separation of the components.

[0054] The structures of formulas (I) and (II) are shown as entirely sulfur-free species, in that the phosphorus atoms are bonded to oxygen, rather than sulfur atoms. However, it is possible that a small molar fraction of the O atoms could be replaced by S atoms, such as 0 to 5 percent or 0.1 to 4 percent or 0.2 to 3 percent or 0.5 to 2 percent.

[0055] The pyrophosphate phosphate ester or mixture of phosphate esters with be reacted with an amine to form an amine salt. The extent of neutralization in practice, that is, the degree of salting of the -OH groups of the phosphorus esters, may be 50% to 100%, or 80% to 99%, or 90% to 98%, or 93% to 97%, or about 95%, which may be determined or calculated on the basis of the amount of amine charged to the phosphate ester mixture.

[0056] The amine may be represented by R²₃N, where 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). Suitable hydrocarbyl amines include primary, secondary or tertiary amines having 1 to 18 carbon atoms, or 3 to 12, or 4 to 10 carbon atoms. Ester containing amines, such as an N-hydrocarbyl-substituted γ- or δ-amino(thio)ester. The amine, of whatever type, will be reacted to neutralize the acidic group(s) on the phosphorus ester component, which will comprise the pyrophosphate ester as described above as well as any orthophosphate esters that may be present.

[0057] The amount of the substantially sulfur-free alkyl phosphate amine salt in the lubricant composition may be 0.1 to 5 percent by weight. This amount refers to the total amount of the phosphate amine salt or salts, of whatever structure, both orthophosphate and pyrophosphate (with the understanding that at least 30 mole percent of the phosphorus atoms are in an alkyl pyrophosphate salt structure). The amounts of the phosphate amine salts in the pyrophosphate structure may be readily calculated therefrom. Alternative amounts of the alkyl phosphate amine salt may be 0.2 to 3 percent, or 0.2 to 1.2 percent, or 0.5 to 2 percent, or or 0.6 to 1.7 percent, or 0.6 to 1.5 percent, or 0.7 to 1.2 percent by weight. The amount may be suitable to provide phosphorus to the lubricant formulation in an amount of 200 to 3000 parts per million by weight (ppm), or 400 to 2000 ppm, or 600 to 1500 ppm, or 700 to 1100 ppm, or 1100 to 1800 ppm.

[0058] The automotive gear oil can also include a material represented by the formula

wherein R¹ and R² are each independently hydrocarbyl groups of 3 to 12 carbon atoms, or 6 to 8 carbon atoms, or are groups represented by

or wherein R¹ and R² together with the adjacent O and P atoms form a ring containing 2 to 6 carbon atoms; R³ is hydrogen or a methyl group, R⁴ is an alkylene group of 2 to 6 carbon atoms, R⁵ is hydrogen or a hydrocarbyl group of 1 to about 12 carbon atoms, and n is 1 or 2. The material represented by the above formula is typically a neutral compound (or mixture of compounds) as the hydrogen atom shown attached to the phosphorus is not considered to be particularly acidic.

[0059] In certain embodiments the material of Formula X may be represented by the formula

that is, Formula X in which R³ is hydrogen, R⁴ is an ethylene group, and n is 2. As in the case of Formula X, one or both of the R¹ or R² groups may groups represented by

In either Formula X or Formula XI, in certain embodiments R¹ and R ² may each independently be C₆ or C₈ alkyl groups, or mixtures thereof, such as 2-ethylhexyl groups or 4-methyl-2-pentyl groups or mixtures thereof.

[0060] The amount of any the phosphorous ester product described above used in the automotive gear oil may be an amount sufficient to provide 0.01 to 0.3 or to 0.1 weight percent phosphorus to the composition or, in other embodiments, 0.02 to 0.07 weight percent or 0.025 to 0.05 weight percent. The actual amount of the product which corresponds to these amounts of phosphorus will, of course, depend upon its phosphorus content. Suitable amounts of the ester product in the automotive gear oil may be 0.01 to 1.0 weight percent, or 0.02 to 0.5 weight percent, or 0.03 to 0.30 weight percent, or even 0.05 to 0.25 weight percent.

[0061] While each of the phosphorus containing compounds described above may be present in the automotive gear oil on its own, the automotive gear oil may also include a mixture of two or more. In some embodiments, the phosphorous containing compound can include a C_3-8 hydrocarbyl phosphite and a phosphite ester product. In some embodiments, the phosphorous containing compound can include each of a C_3-8 hydrocarbyl phosphite, a C₁₂ to C₂₄ hydrocarbyl phosphite, and a phosphite ester product. In either event, the phosphorus containing compound should be present in an amount to deliver 100 to 1500 ppm of phosphorus to the automotive gear oil. In some embodiments, the at least one phosphorus containing compound can be present in an amount to deliver 250 to 1250 ppm of phosphorus, or from 500 to 1000 ppm phosphorus to the automotive gear oil.

[0062] Another component of the automotive gear oil according to present invention is a metal deactivator which is the dimercaptothiadiazole or derivative thereof. Examples of such materials include 2,5-dimercapto-1,3,4-thiadiazole and/or derivatives thereof. Such materials are described in European Patent Publication 0761805. Further examples of a metal deactivator include the thiadiazole compounds, such as those described in US9,816,044, and represented by the formula:

R = t-nonyl, n-octyl

or n-dodecyl or t-dodecyl

[0063] The metal deactivators that are useful herein reduce the corrosion of metals, such as copper. Metal deactivators are also referred to as metal passivators. These metal deactivators are typically nitrogen and/or sulfur containing heterocyclic compounds, such as dimercaptothiadiazoles, triazoles, aminomercaptothiadiazoles, imidazoles, thiazoles, tetrazoles, hydroxyquinolines, oxazolines, imidazolines, thiophenes, indoles, indazoles, quinolines, benzoxazines, dithiols, oxazoles, oxatriazoles, pyridines, piperazines, triazines, and derivatives of any one or more thereof. Examples of suitable compounds are benzotriazole, alkyl-substituted benzotriazole (e.g., tolyltriazole, ethylbenzotriazole, hexylbenzotriazole, octylbenzotriazole), aryl-substituted benzotriazole (e.g., phenol benzotriazoles), and alkylaryl- or arylalkyl-substituted benzotriazole and substituted benzotriazoles where the substituent may be hydroxy, alkoxy, halo (especially chloro), nitro, carboxy and carboxyalkoxy.

[0064] In one embodiment, the metal deactivator is the reaction product of a dispersant with a dimercaptothiadiazole. The dispersants may be generally characterized as the reaction products of carboxylic acids with amines and/or alcohols. These reaction products are commonly used in the lubricant arts as dispersants and are sometimes referred to generically as dispersants despite the fact that they may have other uses in addition to or instead of that as dispersants. The carboxylic dispersants include succinimide dispersants, and ester type dispersants. Succinimide dispersants are generally the reaction of a polyamine with an alkenyl succinic anhydride or acid. Ester type dispersants are the reaction product of an alkenyl succinic anhydride or acid with a polyol compound. The reaction product may then be further treated with an amine such as a polyamine. Examples of useful dispersants are disclosed in U.S. Pat. Nos. 3,219,666 and 4,234,435. Useful dispersants also include the ashless dispersants discussed below. Generally the reaction occurs between the dispersant and the dimercaptothiadiazole by mixing the two and heating to a temperature above about 100 °C. U.S. Pat. Nos. 4,140,643 and 4,136,043 describe compounds made by the reaction of such dispersants with a dimercaptothiadiazole. These patents disclose dispersants, dimercaptothiadiazole, the method for reacting the two and the products obtained from such reaction.

[0065] In one embodiment, the metal deactivator is the reaction product of a phenol with an aldehyde and a dimercaptothiadiazole. The phenol is preferably an alkyl phenol wherein the alkyl group contains at least about 6, preferably from 6 to about 24, more preferably about 6, or about 7, to about 12 carbon atoms. The aldehyde is preferably an aldehyde containing from 1 to about 7 carbon atoms or an aldehyde synthon, such as formaldehyde. Preferably, the aldehyde is formaldehyde or paraformaldehyde. The aldehyde, phenol and dimercaptothiadiazole are typically reacted by mixing them at a temperature up to about 150 °C, preferably about 50 °C to about 130 °C, in molar ratios of about 0.5 to about 2 moles of phenol and about 0.5 to about 2 moles of aldehyde per mole of dimercaptothiadiazole. Preferably, the three reagents are reacted in equal molar amounts.

[0066] In one embodiment, the metal deactivator is a bis(hydrocarbyldithio)thiadiazole. Preferably each hydrocarbyl group is independently an alkyl, aryl or aralkyl group, having from 6 to about 24 carbon atoms. Each hydrocarbyl can be independently t-octyl, nonyl, decyl, dodecyl or ethylhexyl. The metal deactivator can be bis-2,5-tert-octyl-dithio-1,3,4-thiadiazole or a mixture thereof with 2-tert-octylthio-5-mercapto-1,3,4-thiadiazole. These materials are available commercially under the trade name of Amoco 150, which is available from Amoco Chemical Company. These dithiothiadiazole compounds are disclosed as Component (d) in PCT Publication WO 88/03551. In the preferred embodiments the metal deactivator is a dimercaptothiadiazole derivative. Example D-1 is a specific example.

Example D-1

[0067] 2,5-dimercapto-1,3,4-thiadiazole oxidatively coupled with t-nonyl mercaptan; 100% chemical, 36% S, 6.4% N.

[0068] The amount of metal deactivator (dimercaptothiadiazole or derivative thereof) in the automotive gear oil is in the range of 0.01 to 0.5 wt.% by weight of the automotive gear oil. In some embodiments, the amount of the metal deactivator is in the range of about 0.02 to about 0.42 wt.% or about 0.03 to about 0.33 wt,% or about 0.04 to about 0.24 wt.% by weight of the automotive gear oil.

[0069] Another material which may optionally be present is a viscosity modifier. Viscosity modifiers (VM) and dispersant viscosity modifiers (DVM) are well known. Examples of VMs and DVMs may include polymethacrylates, polyacrylates, polyolefins, hydrogenated vinyl aromatic-diene copolymers (e.g., styrene-butadiene, styrene-isoprene), styrene-maleic ester copolymers, and similar polymeric substances including homopolymers, copolymers, and graft copolymers, including polymers having linear, branched, or star-like structures. The DVM may comprise a nitrogen-containing methacrylate polymer or nitrogen-containing olefin polymer, for example, a nitrogen-containing methacrylate polymer derived from methyl methacrylate and dimethylaminopropyl amine. The DVM may alternatively comprise a copolymer with units derived from an α-olefin and units derived from a carboxylic acid or anhydride, such as maleic anhydride, in part esterified with a branched primary alcohol and in part reacted with an amine-containing compound.

[0070] Examples of commercially available VMs, DVMs and their chemical types may include the following: polyisobutylenes (such as Indopol^™ from BP Amoco or Parapol^™ from ExxonMobil); olefin copolymers (such as Lubrizol^® 7060, 7065, and 7067, and Lucant^® HC-2000, HC-1100, and HC-600 from Lubrizol); hydrogenated styrene-diene copolymers (such as Shellvis^™ 40 and 50, from Shell and LZ^® 7308, and 7318 from Lubrizol); styrene/maleate copolymers, which are dispersant copolymers (such as LZ^® 3702 and 3715 from Lubrizol); polymethacrylates, some of which have dispersant properties (such as those in the Viscoplex^™ series from RohMax, the Hitec^™ series of viscosity index improvers from Afton, and LZ^® 7702, LZ^® 7727, LZ^® 7725 and LZ^® 7720C from Lubrizol); olefin-graft-polymethacrylate polymers (such as Viscoplex^™ 2-500 and 2-600 from RohMax); and hydrogenated polyisoprene star polymers (such as Shellvis^™ 200 and 260, from Shell). Viscosity modifiers that may be used are described in U.S. patents 5,157,088, 5,256,752 and 5,395,539. The VMs and/or DVMs may be used in the functional fluid at a concentration of up to 50% or to 20% by weight, depending on the application. Concentrations of 1 to 20%, or 1 to 12%, or 3 to 10%, or alternatively 20 to 40%, or 20 to 30% by weight may be used.

[0071] Other optional materials may include antioxidants, e.g., aromatic amine antioxidants, hindered phenolic antioxidants including ester-containing hindered phenolic antioxidants, and sulfurized olefin antioxidants. In an embodiment, the automotive gear oil may contain a mixture of at least two anti-oxidants. These antioxidants may optionally be present in amounts of 0.01 to 5, or 0.15 to 4.5 or 0.2 to 4, or 0.2 to 2 percent by weight.

[0072] In one embodiment, the automotive gear oil can include an aryl amine antioxidant. The aryl amine antioxidant may be a phenyl-α-naphthylamine (PANA) or a hydrocarbyl substituted diphenylamine, or mixtures thereof. The hydrocarbyl substituted diphenylamine may include mono- or di- C₄ to C₁₆-, or C₆ to C₁₂-, or C₉-alkyl diphenylamine. For example the hydrocarbyl substituted diphenylamine may be octyl diphenylamine, or di-octyl diphenylamine, dinonyl diphenylamine, typically dinonyl diphenylamine.

[0073] When present the aryl amine antioxidant may be present at 0.2 wt % to 1.2 wt %, or 0.3 wt % to 1.0 wt %, or 0.4 wt % to 0.9 wt % or 0.5 wt % to 0.8 wt %, of the automotive gear oil.

[0074] The hindered phenol antioxidant often contains a secondary butyl and/or a tertiary butyl group as a sterically hindering group. The phenol group is often further substituted with a hydrocarbyl group and/or a bridging group linking to a second aromatic group. Examples of suitable hindered phenol antioxidants include 2,6-ditert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol. In one embodiment the hindered phenol antioxidant may be an ester and may include, e.g., Irganox^™ L-135 from Ciba, or butyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate.

[0075] If present, the hindered phenol antioxidant may be present at 0.1 wt % to 1 wt %, or 0.2 wt % to 0.9 wt % or 0.1 wt % to 0.4 wt %, or 0.4 wt % to 1.0 wt %, of the automotive gear oil.

[0076] Antioxidants also include sulfurized olefins such as mono-, or disulfides or mixtures thereof. These materials generally have sulfide linkages having 1 to 10 sulfur atoms, for instance, 1 to 4, or 1 or 2. Materials which can be sulfurized to employ as sulfurized antioxidants in the automotive gear oil can include oils, fatty acids and esters, olefins and polyolefins made thereof, terpenes, or Diels-Alder adducts. Details of methods of preparing some such sulfurized materials can be found in U.S. Pat. Nos. 3,471,404 and 4,191,659.

[0077] The automotive gear oil may also include a calcium-containing detergent. While the calcium-containing detergent is preferably not present, it can be included in an amount to deliver up to 150 ppm or 180 ppm of calcium to the composition, or from 30 ppm to 180 ppm, or 30 ppm to 150 ppm of calcium, or from 60 ppm to 180 ppm, or even from 60 ppm to 150 ppm of calcium.

[0078] In some embodiments, the calcium-containing detergent may be present at 90 ppm or less, or from 1 to 90 ppm, or even from 5 to 80 ppm or 10 to 75 ppm.

[0079] The calcium-containing detergent may be an overbased detergent, a non-overbased detergent, or mixtures thereof. Typically the detergent is overbased.

[0080] The preparation of the calcium-containing detergent is known in the art. Patents describing the preparation of overbased calcium-containing detergents include U.S. patents 2,501,731; 2,616,905; 2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585; 3,365,396; 3,320,162; 3,318,809; 3,488,284; and 3,629,109.

[0081] The calcium-containing detergent may be a non-overbased detergent (may also be referred to as a neutral detergent). The TBN of a non-overbased may be 20 to less than 200, or 30 to 100, or 35 to 50 mg KOH/g. The TBN of a non-overbased calcium-containing detergent may also be 20 to 175, or 30 to 100 mg KOH/g. When a non-overbased calcium-containing detergent is prepared from a strong acid such as a hydrocarbyl-substituted sulphonic acid, the TBN may be lower (for example 0 to 50 mg KOH/g, or 10 to 20 mg KOH/g).

[0082] As used herein the TBN values quoted and associated range of TBN is on "an as is basis," i.e., containing conventional amounts of diluent oil. Conventional amounts of diluent oil typically range from 30 wt % to 60 wt % (often 40 wt % to 55 wt %) of the detergent component.

[0083] The calcium-containing detergent may be an overbased detergent, having, for example, a TBN of greater than 200 mg KOH/g (typically 250 to 600, or 300 to 500 mg KOH/g).

[0084] The overbased calcium-containing detergent may be formed by the reaction of a basic calcium compound and an acidic detergent substrate. The acidic detergent substrate may include an alkyl aromatic sulphonic acid (such as, alkyl naphthalene sulphonic acid, alkyl toluene sulphonic acid or alkyl benzene sulphonic acid), an alkyl salicylic acid, or mixtures thereof.

[0085] The basic calcium compound is used to supply basicity to the detergent. The basic calcium compound is a compound of a hydroxide or oxide of the calcium.

[0086] The oxides and/or hydroxides may be used alone or in combination. The oxides or hydroxides may be hydrated or dehydrated, although hydrated is typical. In one embodiment the basic calcium compound may be calcium hydroxide, which may be used alone or mixtures thereof with other metal basic compounds. Calcium hydroxide is often referred to as lime. In one embodiment the calcium basic compound may be calcium oxide which may be used alone or mixtures thereof with other metal basic compounds.

[0087] In one embodiment the calcium-containing detergent may be a sulphonate, or mixtures thereof. The sulphonate may be prepared from a mono- or di-hydrocarbyl-substituted benzene (or naphthalene, indenyl, indanyl, or bicyclopentadienyl) sulphonic acid, wherein the hydrocarbyl group may contain 6 to 40, or 8 to 35 or 9 to 30 carbon atoms.

[0088] The hydrocarbyl group may be derived from polypropylene or a linear or branched alkyl group containing at least 10 carbon atoms. Examples of a suitable alkyl group include branched and/or linear decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonodecyl, eicosyl, un-eicosyl, do-eicosyl, tri-eicosyl, tetra-eicosyl, penta-eicosyl, hexa-eicosyl or mixtures thereof.

[0089] In one embodiment the hydrocarbyl-substituted sulphonic acid may include polypropene benzenesulphonic acid and/or C₁₆-C₂₄ alkyl benzenesulphonic acid, or mixtures thereof.

[0090] In one embodiment a calcium sulphonate detergent may be a predominantly linear alkylbenzene sulphonate detergent having a metal ratio of at least 8 as is described in paragraphs [0026] to [0037] of US Patent Application 2005065045 (and granted as US 7,407,919). In some embodiments the linear alkyl group may be attached to the benzene ring anywhere along the linear chain of the alkyl group, but often in the 2, 3 or 4 position of the linear chain, and in some instances predominantly in the 2 position.

[0091] When neutral or slightly basic, a calcium sulphonate detergent may have TBN of less than 100, or less than 75, typically 20 to 50 mg KOH/g, or 0 to 20 mg KOH/g.

[0092] When overbased, a calcium sulphonate detergent may have a TBN greater than 200, or 300 to 550, or 350 to 450 mg KOH/g.

[0093] Phenate detergents are typically derived from p-hydrocarbyl phenols or, generally, alkylpheols. Alkylphenols of this type may be coupled with sulfur and overbased, coupled with aldehyde and overbased, or carboxylated to form salicylate detergents. Suitable alkyl salicylates include those alkylated with oligomers of propylene, oligomers of butene, especially tetramers and pentamers of n-butenes, as well as those alkylated with alpha-olefins, isomerized alpha-olefins, and polyolefins like polyisobutylene. In one embodiment, the automotive gear oil comprises less than 0.2 wt %, or less than 0.1 wt %, or even less than 0.05 wt % of a salicylate detergent derived from para-dodecylphenol (PDDP). In one embodiment, the automotive gear oil comprises a salicylate detergent that is not derived from PDDP. In one embodiment, the automotive gear oil can comprise a salicylate detergent prepared from PDDP, such detergent contains less than 1.0 weight percent unreacted PDDP, or less than 0.5 weight percent unreacted PDDP, or is substantially free of PDDP.

[0094] The detergent may be borated or non-borated.

[0095] Chemical structures for sulphonates, and salicylate detergents are known to a person skilled in the art. The standard textbook entitled "Chemistry and Technology of Lubricants", Third Edition, Edited by R. M. Mortier and S. T. Orszulik, Copyright 2010, pages 220 to 223 under the sub-heading 7.2.6 provide general disclosures of said detergents and their structures.

[0096] In one embodiment the calcium-containing detergent may be an overbased calcium sulphonate, an overbased calcium salicylate, or mixtures thereof. Typically the detergent may be an overbased calcium sulphonate.

[0097] In one embodiment the calcium-containing detergent may be in a mixture with a zinc-, barium-, sodium-, or magnesium- containing detergent. The zinc-, barium-, sodium-, or magnesium- containing detergent is also well known in the art and described in the same references describing a calcium-containing detergent. The TBN and metal ratios may however, differ slightly. The zinc-, barium-, sodium-, or magnesium- containing detergent may be a phenate, a sulphur-containing phenate, sulphonate, salixarate or salicylate. Typically a zinc-, barium-, sodium-, or magnesium- containing detergent may be a magnesium phenate, a magnesium sulphur-containing phenate, or a magnesium sulphonate.

[0098] A more detailed description of the expressions "metal ratio", TBN and "soap content" are known to a person skilled in the art and explained in standard textbooks, such as, for example, "Chemistry and Technology of Lubricants", Third Edition, Edited by R. M. Mortier and S. T. Orszulik, Copyright 2010, pages 219 to 220 under the sub-heading 7.2.5. Detergent Classification.

[0099] The automotive gear may also include a friction modifier. In one embodiment the friction modifier may be, for example, long chain fatty acid derivatives of amines, long chain fatty esters, or derivatives of a long chain fatty epoxides; fatty imidazolines; amine salts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyl tartrimides; fatty alkyl tartramides; fatty glycolates; and fatty glycolamides, or combinations thereof. The friction modifier may be present at 0 wt % to 6 or to 5 wt %, or 0.01 wt % to 4 wt %, or 0.05 wt % to 2 wt %, or 0.1 wt % to 2 wt % of the lubricating composition. The amount of friction modifier, if present, also may be 0.05 to 5 percent by weight, or 0.1 to 2 percent, or 0.1 to 1.5 percent by weight, or 0.15 to 1 percent, or 0.15 to 0.6 percent.

[0100] As used herein the term "fatty alkyl" or "fatty" in relation to friction modifiers means a carbon chain having 10 to 22 carbon atoms, typically a straight carbon chain. Alternatively, the fatty alkyl may be a mono branched alkyl group, with branching typically at the β-position. Examples of mono branched alkyl groups include 2-ethylhexyl, 2-propylheptyl or 2-octyldodecyl.

[0101] Examples of suitable friction modifiers include long chain fatty acid derivatives of amines, fatty esters, or fatty epoxides; fatty imidazolines such as condensation products of carboxylic acids and polyalkylene-polyamines; amine salts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyl tartrimides; fatty alkyl tartramides; fatty phosphonates; fatty phosphites; borated phospholipids, borated fatty epoxides; glycerol esters; borated glycerol esters; fatty amines; alkoxylated fatty amines; borated alkoxylated fatty amines; hydroxyl and polyhydroxy fatty amines including tertiary hydroxy fatty amines; hydroxy alkyl amides; metal salts of fatty acids; metal salts of alkyl salicylates; fatty oxazolines; fatty ethoxylated alcohols; condensation products of carboxylic acids and polyalkylene polyamines; or reaction products from fatty carboxylic acids with guanidine, aminoguanidine, urea, or thiourea and salts thereof.

[0102] Friction modifiers may also encompass materials such as sulphurised fatty compounds and olefins, molybdenum dialkyldithiophosphates, molybdenum dithiocarbamates, sunflower oil or soybean oil monoester of a polyol and an aliphatic carboxylic acid.

[0103] In one embodiment the friction modifier may be a long chain fatty acid ester. In another embodiment the long chain fatty acid ester may be a mono-ester and in another embodiment the long chain fatty acid ester may be a triglyceride

[0104] In an embodiment, the automotive gear oil is substantially free of friction modifiers. In some embodiments, the automotive gear oil is completely free of friction modifiers.

[0105] The automotive gear oil may have a kinematic viscosity at 100°C of from 8 cSt to 24 cSt, or for example, from 9 cSt to 21 cSt, or even 10 cSt to 20 cSt.

[0106] One aspect is therefore a method of lubricating an automotive gear by supplying to the automotive gear the automotive gear oil as disclosed herein, and operating the automotive gear. The automotive gear oil will be suitable for lubricating automotive gears, including gears in transmissions, such as manual or dual clutch transmission, gears on axles, and gears on differentials.

[0107] The automotive gear oil may, in particular, be employed in a manual gearbox of a manual transmission, which may be unsynchronized, or may contain a synchronizer mechanism. The gearbox may be self-contained, or may additionally contain any of a transfer gearbox, planetary gear system, differential, limited slip differential or torque vectoring device, which may be lubricated by a manual transmission fluid.

[0108] The automotive gear oil may be used in planetary hub reduction axles, mechanical steering and transfer gear boxes in utility vehicles, synchromesh gear boxes, power take-off gears, limited slip axles, and planetary hub reduction gear boxes.

[0109] In an embodiment, the automotive gear oil can be employed as a single lubricant to lubricate the entire driveline system of an automobile having a manual transmission. That is, in an embodiment, the automotive gear oil may be employed as a "total driveline lubricant," suitable to lubricate all the gears in the automobile, including in the transmission and in the axles and differentials.

[0110] As used herein, the term "condensation product" is intended to encompass esters, amides, imides and other such materials that may be prepared by a condensation reaction of an acid or a reactive equivalent of an acid (e.g., an acid halide, anhydride, or ester) with an alcohol or amine, irrespective of whether a condensation reaction is actually performed to lead directly to the product. Thus, for example, a particular ester may be prepared by a transesterification reaction rather than directly by a condensation reaction. The resulting product is still considered a condensation product.

[0111] 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, byproducts, derivatives, and other such materials which are normally understood to be present in the commercial grade.

[0112] 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.

[0113] It is known that some of the materials described above 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 acidic or anionic 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. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses the composition prepared by admixing the components described above.

[0114] As used herein, the term "about" means that a value of a given quantity is within ±20% of the stated value. In other embodiments, the value is within ±15% of the stated value. In other embodiments, the value is within ±10% of the stated value. In other embodiments, the value is within ±5% of the stated value. In other embodiments, the value is within ±2.5% of the stated value. In other embodiments, the value is within ±1% of the stated value.

[0115] Additionally, as used herein, the term "substantially" means that a value of a given quantity is within ±10% of the stated value. In other embodiments, the value is within ±5% of the stated value. In other embodiments, the value is within ±2.5% of the stated value. In other embodiments, the value is within ±1% of the stated value.

[0116] The invention herein is useful for lubricating an automotive gear, which may be better understood with reference to the following examples.

EXAMPLES

[0117] Automotive gear oils were prepared and tested for dynamic friction, µ-V gradient, and thermal stability (to test cleanliness). The fluids can be seen in table 1 below.

	Baseline Fluid 1	Baseline Fluid 2	Experimental Fluid 1
4 cSt Oil of Lubricating Viscosity	70.49	71.99	70.99
Viscosity Modifier	21	21	21
Extreme Pressure Agent	3.80	3.80	3.80
Corrosion Inhibitor	0.10	0.10	0.10
Borated Dispersant1	0.43	0.31	0.31
Non-Borated Dispersant	0.71	0.18	0.18
Antiwear Agent2	1.32	1.00	1.00
Antifoam	0.01	0.01	0.01
Friction Modifier	0.35	0.3	0.3
Boron Containing Compound3			1.0
Total	100	100	100

1Delivers 133, 95 and 95 ppm Boron to the fluids, respectively 2Delivers 1115, 845 and 845 ppm Phosphorus to the fluids, respectively 3Delivers 270ppm Boron to the fluid

[0118] The formulations were tested in a synchronizer test rig in a "durability test." This is a screening test that is customarily used to evaluate friction and durability characteristic of a clutch synchronizer. The test rig typically does not simulate a full engagement of the synchronizer components, but does measure the friction between the synchronizer ring and the gear cone. The rig comprises a test rig bath in which the components are assembled.

[0119] An Automax^® rig comprises a test rig bath in which the components are assembled. The synchronizer is attached to the test rig key on one side of the chamber and the cone assembled onto a test rig jig on the other side. The test conditions used are shown in the Table below. The fluids are maintained at 80° C. with the synchronizer typically rotating at 1000 rpm. In each test, there is an initial break-in phase of 100 cycles of engagement. Thereafter, multiple cycles of engagement consist of 0.2 seconds of contact followed by 5 seconds of separation, running at 1000 r.p.m. at 80° C. and a load during contact of 981 N (100 kg).

Oil Temperature	(° C.)	80
Speed	(rpm)	1000
Load	(kg)	100
	(N)	980.6
On Time	(sec)	0.2
Off Time	(sec)	5.0
Inertia	(kg cm sec2)	2.67
Calculated Torque	(Nm)	41

[0120] The key features of the synchronizer used in this experiment are summarized in the table below. All other parts are original equipment manufacturer production parts used in standard vehicles:

Phenolic Resin Synchronizer

[0121] 

Gear Cone Angle (degrees)	7.0
Effective radius (mm)	62
Composition	Phenolic Resin

[0122] The data from the test provides several key parameters that allow a comparison of the friction performance of the candidates. Comparisons of the relative durability and shift quality of the different candidates are made based upon a number of parameters including dynamic friction level assessed by the friction value during durability testing, friction durability assessed by the stability, and trends in average friction values during the durability phase.

[0123] Shift quality is assessed by examining the performance test profiles which show the variation of friction with rotational speed. It is desirable to have a flat frictional profile, with a level or slight decrease in friction at low speed providing improved synchronizer engagement and improved shift quality.

[0124] The dynamic coefficient of friction may be presented as a function of cycle number. A quantitative representation of the performance may be obtained by calculating the number of cycles to stability. Ideally, a fluid should show stable friction throughout the duration of the test. Some fluids may vary in friction at the start of the test, before stabilizing to a final value after a number of cycles. Other fluids may not stabilize at all and the friction may be still increasing or decreasing after 10,000 cycles. One method of assessing dynamic friction is to evaluate the mean and standard deviation of the friction values during the 10,000 cycle test.

Dynamic Friction

[0125] 

Cycle	Baseline Fluid 1 µV-AVG	Baseline Fluid 2 µV-AVG	Experimental Fluid 1 µV-AVG
1	0.116	0.112	0.113
200	0.119	0.116	0.115
500	0.12	0.114	0.115
1000	0.118	0.108	0.116
2000	0.114	0.105	0.116
3000	0.113	0.104	0.115
4000	0.112	0.103	0.115
5000	0.112	0.102	0.115
6000	0.111	0.102	0.114
7000	0.111	0.102	0.114
8000	0.111	0.102	0.114
9000	0.111	0.102	0.113
10000	0.11	0.102	0.113

[0126] In order to assess the shift-quality of an individual engagement it is necessary to evaluate the friction versus speed relationship. One parameter that is useful is to assess the curvature of the speed-friction relationship. In order to do this a chord is drawn between the µ values between 50 to 1000 rpm. The area of the difference between the actual µ_d and the chord gives a value that we will refer to as the curvature of the line. A large negative curvature value represents a poor result and a value that is close to zero or positive, indicates a better performance.

	Pre-Test Friction
		Baseline Fluid 1	Baseline Fluid 2	Experimental Fluid 1
	rpm	Initial Measurement	Initial Measurement	Initial Measurement
	50	0.119	0.112	0.116
	75	0.121	0.114	0.117
	100	0.123	0.115	0.118
	125	0.123	0.115	0.118
	200	0.121	0.114	0.117
	300	0.12	0.113	0.117
	500	0.118	0.111	0.115
	750	0.117	0.111	0.114
	1000	0.117	0.112	0.113

	Post-Test Friction
		Baseline Fluid 1	Baseline Fluid 2	Experimental Fluid 1
	rpm	Initial Measurement	Initial Measurement	Initial Measurement
	50	0.131	0.125	0.12
	75	0.129	0.122	0.121
	100	0.126	0.118	0.123
	125	0.126	0.116	0.123
	200	0.121	0.112	0.122
	300	0.119	0.11	0.121
	500	0.116	0.107	0.119
	750	0.113	0.105	0.116
	1000	0.113	0.103	0.114

[0127] As can be seen in the tables, Experimental Fluid 1 shows a stabilized friction over the test cycles.

[0128] The wear performance provided by the lubricant was also be tested. Wear may be determined from the test rig profile described above, by measuring mg weight loss from the synchronizer ring at the end of the testing. The wear readings for the fluids are provided below.

	Baseline Fluid 1 (mg)	Baseline Fluid 2 (mg)	Experimental Fluid 3 (mg)
Wear reading	87.9	41.4	36.4

[0129] 500 ml samples of the fluids were tested for thermal stability by the JIS K2514-1 Indiana Stirring Oxidation Test at 150°C, heated for 96 hours at 1,300 rpm. The results are shown in the table below. The laquer rating scale is as follows: 0 = no deposit, 1 = light deposit, 2 = medium deposit and 3 = heavy deposit.

	Baseline Fluid 1	Baseline Fluid 2	Experimental Fluid 1
Heating Time/hours	Lacquer Rating
0		0	0
24		1	1
48		1	1
96	3	3	2

[0130] 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 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.

[0131] 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 any element or step not specified and "consisting essentially of" permits the inclusion of additional un-recited elements or steps that do not materially affect the essential or basic and novel characteristics of the composition or method under consideration.

[0132] 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

1. An automotive gear oil for lubricating an automotive gear comprising

a. an oil of lubricating viscosity

b. 0.025 to 0.9 wt % of a succinimide dispersant, and

c. 0.2 to 2.0 wt % of at least one boron-containing compound in an amount sufficient to provide from 75 ppm to 500 ppm of boron to the automotive gear oil, wherein the at least one boron-containing compound is a borate ester of formula I,

wherein each R, independently, is a C3 to C12 alkyl, and

d. 0.01 to 0.5 wt. % of a dimercaptothiadiazole or derivative thereof, wherein the derivative of the dimercaptothiadizole (DMTD) is: a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole or 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole and mixtures thereof; b) carboxylic esters of DMTD; c) condensation products of α-halogenated aliphatic monocarboxylic acids with DMTD; d) reaction products of unsaturated cyclic hydrocarbons and unsaturated ketones with DMTD; e) reaction products of an aldehyde and diaryl amine with DMTD; f) amine salts of DMTD; g) dithiocarbamate derivatives of DMTD; h) reaction products of an aldehyde, and an alcohol or aromatic hydroxy compound, and DMTD; i) reaction products of an aldehyde, a mercaptan and DMTD; j) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole; or k) products from combining an oil soluble dispersant with DMTD and mixtures thereof.

2. The automotive gear oil of claim 1 wherein the automotive gear oil has a kinematic viscosity at 100°C of from 8 cSt to 24 cSt.

3. The automotive gear oil of any previous claim further comprising at least one phosphorous containing compound present in an amount to deliver 100 to 1500 ppm of phosphorus to the automotive gear oil.

4. The automotive gear oil of claim 3, where the phosphorous containing compound comprises at least one of: (1) a C_3-8 hydrocarbyl phosphite, (2) a phosphite ester composition that comprises the reaction product of a monomeric phosphorous acid or an ester thereof with at least two alkylene diols, (3) a phosphate ester amine salt, (4) a pyrophosphate amine salt, or (5) mixtures of any of (1) to (4).

5. The automotive gear oil of any previous claim further comprising a viscosity modifier.

6. The automotive gear oil of any previous claim further comprising a friction modifier.

7. The automotive gear oil of any previous claim further comprising a detergent.

8. A method of lubricating an automotive gear comprising supplying to the automotive gear a composition of any previous claim, and operating the automotive gear.

9. The method of claim 8, wherein the automotive gear is in a manual transmission.

10. The method of claim 8 or 9, wherein the automotive gear is on an axle.

11. The method of any one of claims 8 to 10, wherein the automotive gear is on a differential.

Ansprüche

1. Kraftfahrzeuggetriebeöl zum Schmieren eines Kraftfahrzeuggetriebes, umfassend

a. ein Öl mit Schmierviskosität;

b. zu 0,025 bis 0,9 Gew.-% ein Succinimid-Dispergiermittel und

c. zu 0,2 bis 2,0 Gew.-% mindestens eine borhaltige Verbindung in einer Menge, die ausreicht, um 75 ppm bis 500 ppm Bor dem Kraftfahrzeuggetriebeöl bereitzustellen, wobei die mindestens eine borhaltige Verbindung ein Boratester der Formel I ist,

wobei jedes R unabhängig ein C3- bis C12-Alkyl ist, und

d. zu 0,01 bis 0,5 Gew.-% ein Dimercaptothiadiazol oder Derivat davon, wobei das Derivat des Dimercaptothiadiazol (DMTD) Folgendes ist: a) 2-Hydrocarbyldithio-5-mercapto-1,3,4-thiadiazol oder 2,5-Bis-(hydrocarbyldithio)-1,3,4-thiadiazol und Mischungen davon; b) Karbonsäureester von DMTD; c) Kondensationsprodukte von α-halogenierten aliphatischen Monokarbonsäuren mit DMTD; d) Reaktionsprodukte von ungesättigten cyclischen Kohlenwasserstoffen und ungesättigten Ketonen mit DMT; e) Reaktionsprodukte eines Aldehyds und Diarylamin mit DMTD; f) Aminsalze von DMTD; g) Dithiocarbamatderivate von DMTD; h) Reaktionsprodukte eines Aldehyds und eines Alkohols oder aromatischer Hydroxyverbindung und DMTD; i) Reaktionsprodukte eines Aldehyds, eines Mercaptan und DMTD; j) 2-Hydrocarbylthio-5-mercapto-1,3,4-thiadiazol; oder k) Produkte aus dem Kombinieren eines öllöslichen Dispergiermittels mit DMTD und Mischungen davon.

2. Kraftfahrzeuggetriebeöl nach Anspruch 1, wobei das Kraftfahrzeuggetriebeöl eine kinematische Viskosität bei 100 °C von 8 cSt bis 24 cSt aufweist.

3. Kraftfahrzeuggetriebeöl nach einem der vorstehenden Ansprüche, ferner umfassend mindestens eine phosphorhaltige Verbindung, die in einer Menge vorhanden ist, um 100 bis 1500 ppm Phosphor an das Kraftfahrzeuggetriebeöl zu liefern.

4. Kraftfahrzeuggetriebeöl nach Anspruch 3, wobei die phosphorhaltige Verbindung mindestens eines von Folgendem umfasst: (1) ein C_3-8-Hydrocarbylphosphit (2) eine Phosphitesterzusammensetzung, die das Reaktionsprodukt einer monomeren Phosphorsäure oder eines Esters davon mit mindestens zwei Alkylendiolen umfasst, (3) ein Phosphatesteraminsalz, (4) ein Pyrophosphataminsalz oder (5) beliebige Mischungen nach einem von (1) bis (4).

5. Kraftfahrzeuggetriebeöl nach einem der vorstehenden Ansprüche, ferner umfassend einen Viskositätsmodifizierer.

6. Kraftfahrzeuggetriebeöl nach einem der vorstehenden Ansprüche, ferner umfassend einen Reibungsmodifizierer.

7. Kraftfahrzeuggetriebeöl nach einem der vorstehenden Ansprüche, ferner umfassend ein Detergens.

8. Verfahren zum Schmieren eines Kraftfahrzeuggetriebes, umfassend ein Zuführen zu dem Kraftfahrzeuggetriebe einer Zusammensetzung nach einem der vorstehenden Ansprüche und Betreiben des Kraftfahrzeuggetriebes.

9. Verfahren nach Anspruch 8, wobei das Kraftfahrzeuggetriebe in einem Schaltgetriebe ist.

10. Verfahren nach Anspruch 8 oder 9, wobei das Kraftfahrzeuggetriebe auf einer Achse ist.

11. Verfahren nach einem der Ansprüche 8 bis 10, wobei das Kraftfahrzeuggetriebe an einem Differential ist.

Revendications

1. Huile d'engrenage automobile permettant de lubrifier un engrenage automobile comprenant

a. une huile de viscosité lubrifiante

b. 0,025 à 0,9 % en poids d'un dispersant succinimide, et

c. 0,2 à 2,0 % en poids d'au moins un composé contenant du bore en une quantité suffisante pour fournir de 75 ppm à 500 ppm de bore à l'huile d'engrenage automobile, dans laquelle l'au moins un composé contenant du bore est un ester de borate de formule I,

dans laquelle chaque R, indépendamment, représente un alkyle en C3 à C12, et

d. 0,01 à 0,5 % en poids d'un dimercaptothiadiazole ou un dérivé de celui-ci, dans laquelle le dérivé du dimercaptothiadizole (DMTD) est : a) 2-hydrocarbyldithio-5-mercapto-1,3,4-thiadiazole ou 2,5-bis-(hydrocarbyldithio)-1,3,4-thiadiazole et des mélanges de ceux-ci ; b) des esters carboxyliques de DMTD ; c) des produits de condensation d'acides monocarboxyliques aliphatiques α-halogénés avec le DMTD ; d) des produits de réaction d'hydrocarbures cycliques insaturés et de cétones insaturées avec le DMTD ; e) des produits de réaction d'un aldéhyde et d'une diarylamine avec le DMTD ; f) des sels d'amine de DMTD ; g) des dérivés dithiocarbamates de DMTD ; h) des produits de réaction d'un aldéhyde, et d'un alcool ou d'un composé hydroxy aromatique, et de DMTD ; i) des produits de réaction d'un aldéhyde, d'un mercaptan et de DMTD ; j) 2-hydrocarbylthio-5-mercapto-1,3,4-thiadiazole ; ou k) des produits provenant de la combinaison d'un dispersant soluble dans l'huile avec du DMTD et des mélanges de ceux-ci.

2. Huile d'engrenage automobile selon la revendication 1 dans laquelle l'huile d'engrenage automobile a une viscosité cinématique à 100 °C de 8 cSt à 24 cSt.

3. Huile d'engrenage automobile selon l'une quelconque revendication précédente comprenant en outre au moins un composé contenant du phosphore présent en une quantité pour fournir 100 à 1 500 ppm de phosphore à l'huile d'engrenage automobile.

4. Huile d'engrenage automobile selon la revendication 3, dans laquelle le composé contenant du phosphore comprend au moins l'un parmi : (1) un phosphite d'hydrocarbyle en C_3-8, (2) une composition d'ester de phosphite qui comprend le produit de réaction d'un acide phosphoreux monomère ou d'un ester de celui-ci avec au moins deux diols d'alkylène, (3) un sel d'amine d'ester de phosphate, (4) un sel d'amine de pyrophosphate, ou (5) des mélanges de n'importe quel élément (1) à (4).

5. Huile d'engrenage automobile selon une quelconque revendication précédente comprenant en outre un modificateur de viscosité.

6. Huile d'engrenage automobile selon une quelconque revendication précédente comprenant en outre un modificateur de friction.

7. Huile d'engrenage automobile selon une quelconque revendication précédente comprenant en outre un détergent.

8. Procédé de lubrification d'un engrenage automobile consistant à fournir à l'engrenage automobile une composition selon une quelconque revendication précédente, et à faire fonctionner l'engrenage automobile.

9. Procédé selon la revendication 8, dans lequel l'engrenage automobile est dans une transmission manuelle.

10. Procédé selon la revendication 8 ou 9, dans lequel l'engrenage automobile est sur un essieu.

11. Procédé selon l'une quelconque des revendications 8 à 10, dans lequel l'engrenage automobile est sur un différentiel.