Method of lubricating a transmission

Abstract

The disclosed technology relates generally to lubricating compositions (lubricants) and finds particular application in connection with an additive for a lubricating composition and to a lubricating method.

Description

TITLEMethod of Lubricating a TransmissionBACKGROUND

[0001] The disclosed technology relates generally to lubricating compositions (lubricants) and finds particular application in connection with an additive for a lubricating composition and to a lubricating method.

[0002] Driveline power transmitting devices (such as transmissions) present highly challenging technological problems and solutions for satisfying the multiple and often conflicting lubricating requirements, while providing durability and cleanliness.

[0003] Branched sulfonates give excellent frictional performance in automotive oils. However, a lubricant solution that can reduce reliance on branched sulfonates while delivering similar frictional performance would be technically and commercially beneficial.SUMMARY

[0004] The use of dialkylaryl sulfonate chemistry in combination with monoalkyl branched sulfonates was found to be surprisingly beneficial in maintaining static friction levels with reduced requirement for monoalkyl branched sulfonate.

[0005] One aspect of the technology is therefore directed to lubricant comprising an oil of lubricating viscosity, and a detergent concentrate including a mixture of monoalkyl branched sulfonate and dialkylaryl sulfonate. The detergent concentrate mixture can include from about 20 to 75 wt% monoalkyl branched sulfonate and about 25 to 80 wt% dialkylaryl sulfonate.

[0006] Another aspect of the technology encompasses a method of lubricating a driveline power transmitting device by supplying to the driveline power transmitting device a lubricant as described, and operating the driveline power transmitting device. The driveline power transmitting device can be, for example, a transmission.DETAILED DESCRIPTION

[0007] Various preferred features and embodiments will be described below by way of non-limiting illustration. One aspect of the invention is a lubricant containing (a) an oil of lubricating viscosity, and (b) a detergent concentrate containing a mixture of monoalkyl branched sulfonate and dialkylaryl sulfonate.Oil of Lubricating Viscosity

[0008] 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 GroupsI-V of the American Petroleum Institute (API) Base Oil Interchangeability Guidelines(2011), namelyBase Oil Category Sulfur (%) Saturates (%) Viscosity IndexGroup I >0.03 and / or <90 80 to less than 120Group II <0.03 and >90 80 to less than 120Group III <0.03 and >90 >120Group IV All polyalphaolefins (PAOs)Group V All others not included in Groups I, II, III or IV

[0009] 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.

[0010] In one embodiment the oil of lubricating viscosity has a kinematic viscosity at 100 °C by ASTM D445 of 6 to 17.5, or 6.5 to 17, or 7 to 16.5, or 7.5 to 16 mm2 / s.The monoalkyl branched sulfonate

[0011] The lubricant also includes monoalkyl branched sulfonate in a detergent concentrate. The monoalkyl branched sulfonate will be in the detergent concentrate at a level of from about 20% to about 75%, or about 25% to about 70%, or about 30% to about 65% by weight of the detergent concentrate.

[0012] Monoalkyl branched sulfonates are those with one alkyl side chain attached to the sulfonate, as shown in formula IFormula Iwhere R can be a branched alkyl group or branched alkylaryl group of 12 to 36 carbon atoms, or 14 to 32 carbon atoms, or 16 to 28 carbon atoms.

[0013] The R group can be a branched alkylaryl group such that the monoalkyl branched sulfonate is a monoalkylaryl branched sulfonate. For example, R may be an alkyl substituted benzene and the monoalkylaryl branched sulfonate an alkyl-substituted benzenesulfonate. Similarly, R may be an alkyl substituted toluene and the monoalkylaryl branched sulfonate an alkyl-substituted alkyl-substituted toluenesulfonate.The dialkylaryl sulfonate

[0014] The lubricant also includes dialkylaryl sulfonate in a detergent concentrate. The dialkylaryl sulfonate will be in the detergent concentrate at a level of total sulfonic acid substrate from about 25% to about 80%, or about 30% to about 75%, or about 35% to about 70% by weight of the detergent concentrate.

[0015] In one embodiment the dialkylaryl sulfonate may be a predominantly linear alkylbenzenesulfonate. In some embodiments the linear alkyl (or hydrocarbyl) 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. In other embodiments, the alkyl (or hydrocarbyl) group may be branched, that is, formed from a branched olefin such as propylene or 1-butene or isobutene.

[0016] The dialkylaryl sulfonate can be a dialkylbenzene sulfonate having a structure of formula IIwhere Rl, R2, and R3 are, independently, hydrogen or independent hydrocarbyl groups of 1 to 30 carbon atoms, or 2 to 28 carbon atoms, or 3 to 26 carbon atoms, and wherein at least one of Rl, R2, and R3 are H.

[0017] In some embodiments, Rl and R3 can form a ring, that is, Rl + R3 can = Cx, where X ranges from 12 to 28, or from 20 to 26. In such a case, R2 can be hydrogen.The Detergent Concentrate

[0018] In some embodiments, the detergent concentrate can include other detergents beside the monoalkyl branched sulfonate and dialkylaryl sulfonate detergents. In some embodiments, the detergent concentrate will consist essentially of the monoalkyl branched sulfonate and dialkylaryl sulfonate detergents, where either detergent may encompass some structurally similar byproduct detergent, which may be present at up to 15%, or up to 12.5%, or up to 10%, or even up to 7.5%, or even up to 5%.

[0019] The detergent concentrate can be employed in the lubricant at amounts of from about 0.5 to about 5 wt.%, or even from about 1 to about 4.75 wt.%, or from about 1.25 to about 4.5 wt.%, or from about 1.5 to about 4 wt.% or even from about 2 to about 4 wt.% of the lubricant.

[0020] By one approach, the sulfonates can be metal containing detergents, such as neutral or overbased detergents.

[0021] Neutral sulfonate detergent substrates may be salted with an alkali or alkaline earth metal such as, but not limited to, calcium, magnesium, potassium, sodium, lithium, barium, or mixtures thereof. In some embodiments, the sulfonate detergents can be free of barium. The total metal in neutral sulfonate detergent, such as calcium, can range from about 2% to 4%, and in some instances about 3%. Often, the metal is magnesium or calcium.

[0022] Overbased detergents are known in the art. Overbased materials, otherwise referred to as overbased or superbased salts, are generally single phase, homogeneous systems characterized by a metal content in excess of that which would be present for neutralization according to the stoichiometry of the metal and the particular acidic organic compound reacted with the metal. The overbased materials are prepared by reacting an acidic material (typically an inorganic acid or lower carboxylic acid, preferably carbon dioxide) with a mixture comprising an acidic organic compound, a reaction medium comprising at least one inert, organic solvent (mineral oil, naphtha, toluene, xylene, etc.) for said acidic organic material, a stoichiometric excess of a metal base, and a promoter such as a calcium chloride, acetic acid, phenol or alcohol. The acidic organic material will normally have a sufficient number of carbon atoms to provide a degree of solubility in oil. The amount of excess metal is commonly expressed in terms of metal ratio. The term “metal ratio” is the ratio of the total equivalents of the metal to the equivalents of theacidic organic compound. A neutral metal salt has a metal ratio of one. A salt having 4.5 times as much metal as present in a normal salt will have metal excess of 3.5 equivalents, or a ratio of 4.5. The term “metal ratio is also explained in standard textbook entitled “Chemistry and Technology of Lubricants”, Third Edition, Edited by R. M. Mortier, M.F. Fox, and S. T. Orszulik, Copyright 1997.

[0023] In one embodiment the invention provides a lubricating composition further comprising an overbased metal -containing detergent. The metal of the metal-containing detergent may be zinc, sodium, calcium, barium, or magnesium. Typically the metal of the metal-containing detergent may be sodium, calcium, or magnesium.

[0024] Overbased sulphonates typically have a total base number of 250 to 600, or 300 to 500.Other Additives

[0025] Other materials may be present in the lubricant in their conventional amounts including, for example, viscosity modifiers, friction modifiers, antioxidants, dispersants, antiwear / antiscuffing agents, metal deactivators, extreme pressure agents, foam inhibitors, demulsifiers, pour point depressants, corrosion inhibitors, seal swelling agents, and the like, which may be used singly or in combination.

[0026] A lubricant, as used herein, refers to lubricant having sufficient levels of additive to lubricate a driveline power transmitting device, such as a transmission. In this regard, the lubricant can be distinguished from other lubricants, such as engine oil lubricants, based on levels of sulfur and phosphorus. In some embodiments, the lubricant can be sulfur free. The lubricant can have a total sulfur level of about 250 ppm to about 25,000 ppm based on the weight of the lubricant. In some embodiments, the total sulfur level can be from about 500 ppm to about 20,000 ppm, or even about 750 ppm to about 15,000 ppm or about 1000 to about 10,000 ppm.

[0027] The lubricant can also have a total phosphorus level of about 0.01 to about 1 wt.%, or 0.03 to about 0.75 wt.%, or even about 0.05 to about 0.5 wt.%.

[0028] The lubricant can also have a total boron level of about 1 to about 500 ppm, or from about 5 to about 450 ppm, or even from about 10 to about 400 ppm, or from about 25 to about 350 ppm, or even from about 50 to about 300 ppm.

[0029] The lubricant may have a kinematic viscosity at 100 °C by ASTM D445 of between 6 and 25 cSt. The lubricant may have a kinematic viscosity at 100 °C by ASTMby ASTM D445 of between 6 and 18 cSt. The lubricant may have a kinematic viscosity at 100 °C by ASTM D445 of between 6 and 16 cSt. The lubricant may have a kinematic viscosity at 100 °C by ASTM D445 of between 6 and 14 cSt.

[0030] The disclosed technology in general provides a method of maintaining static friction while reducing the level of monoalkyl branched sulfonate in the lubricant by providing to an automotive or off-highway vehicle lubricant system the lubricant as described, and operating the automotive or off-highway vehicle.

[0031] The technology also provides a method of lubricating a driveline system by supply the system with the lubricant, and then operating the system.

[0032] The lubricant can be employed in off-highway vehicles, such as, for example, farm tractors and construction vehicles. Such vehicles often have a common sump that lubricates not only the transmission but also the gears, axles, and hydraulics in the vehicle. In one embodiment, the technology includes a method of lubricating an off-highway vehicle comprising supplying to the vehicle a lubricant having an oil of lubricating viscosity, and a detergent mixture comprising from about 20 to 75 wt% monoalkyl branched sulfonate, and about 25 to 80 wt% dialkylaryl sulfonate.

[0033] The off-highway vehicle lubricated typically has a wet-brake, a transmission, a hydraulic, a final drive, a power take-off system. These parts are typically lubricated by a single lubricant supplied from a common sump.

[0034] The lubricant should be able to meet the other aspects expected of it in normal operation of the driveline power transmitting device.

[0035] 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.

[0036] 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 nonhydrocarbon 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.

[0037] 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 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.

[0038] The invention herein may be better understood with reference to the following examples.EXAMPLES

[0039] While exploring the relationship between detergent components and Driveline frictional performance, several detergents were benchmarked against existing branchedand natural sulfonates running a screener test for the coefficient of friction, which encompassed running 750 ml of test fluid in a SAE #2 test machine with SAE standard sized hardware at a linear speed of 15 m / s, oil temperature of 82°C, specific energy of 0.238 J / mm2and cycle frequency of 20 seconds. The test runs 75 cycles after 800 break in cycles at 1.05 MPa. The 75 total cycles are run at the stated conditions, with 15 cycles performed at five different lining pressures from 0.35 to 1.75 MPa at 0.35 Mpa increments. The average coefficient of friction over the tested pressures can be seen in Table 1. Interestingly, the fluids containing dialkylaryl sulfonate (DAB sulfonate) showed passable friction results against the baseline sample 1.Table 1

[0040] Each of the sulfonates were blended into a prototype formulation targeting 1% overall soap and 3000 ppm Ca (Table 2). Unless otherwise noted, all samples used the same formulation, as shown in Table 2 below, apart from detergent identity.Table 2

[0041] In the screener test, none of the dialkylbenzene sulfonates showed any differentiation over branched sulfonates when used in combination with a linear alkylbenzene sulfonate.

[0042] Linear sulfonates are known to hurt static friction in the screener test, so linear sulfonate content in the next round of friction testing was reduced. Formulations were prepared using the prototype formulation of Table 2, and subjected to the screener. The results (Tables 3 and 4) indicated that indeed high linear content does have a detrimental effect on static friction and this effect is exacerbated when linear content exceeds 50%.Table 3Table 4

[0043] Due to the acceptable coefficient of friction of the all dialkylaryl sulfonate sample 10 in the screener test in Table 1, mixtures with monalkyl branched sulfonate based detergents were also explored to see if frictional performance could be further improved (Table 5).Table 5

[0044] The results highlight the frictional performance of the combination of the dialkylaryl sulfonates with the branched monoalkyl sulfonates as the branched content can be reduced by 50% with no significant reduction in friction performance over the all branched formulation.

[0045] Each of the documents referred to above is incorporated herein by reference, including any prior applications, whether or not specifically listed above, from which priority is claimed. 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, reactionconditions, 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.

[0046] 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. 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.

[0047] 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

What is claimed is:

1. A lubricant composition comprising: a. oil of lubricating viscosity, and b. a detergent concentrate mixture comprising from about 20 to 75 wt% monoalkyl branched sulfonate, and about 25 to 80 wt% dialkylaryl sulfonate.

2. The lubricant composition of claim 1 where the monoalkyl group has 12 to 36 carbon atoms.

3. The lubricant composition of claim 2 where the 12 to 36 carbon atoms are branched.

4. The lubricant composition of claim 1 where the monoalkyl branched sulfonate comprises alkyl substituted benzenesulfonate or an alkyl -substituted toluenesulfonate.

5. The lubricant composition of claim 1 wherein the dialkylaryl sulfonate comprises dialkyl benzene sulfonate.

6. The lubricant composition of claim 5 where the dialkylaryl sulfonate is a dialkylbenzene sulfonate having the structure -where Rl, R2, R3 are, independently, hydrogen or independent hydrocarbyl groups of 1 to 30 carbon atoms, wherein at least one of Rl, R2, and R3 are H.

7. The lubricant composition of claim 6 where Rl + R3 = Cx, where X ranges from 12 to 28 and R2 is hydrogen.

8. The lubricant composition of claim 6 where Rl + R3 = Cx, where X ranges from 20 to 26.

9. The lubricant composition of claim 1 wherein the monoalkyl sulfonate detergent is a metal containing detergent comprising at least one of calcium, magnesium, potassium, sodium, lithium, barium, or mixtures thereof.

10. The lubricant composition of claim 1 wherein the dialkylaryl sulfonate detergent is a metal containing detergent comprising at least one of calcium, magnesium, potassium, sodium, lithium, barium, or mixtures thereof.

11. The lubricant composition of any previous claim where the metal containing detergent is overbased.

12. The lubricant composition of claim 1 where the metal containing detergent is neutral .

13. The lubricant composition of claim 11 or 12 where the total calcium of the detergent ranges from about 2000 to 4000 ppm.

14. The lubricant composition of claim 1, wherein the metal comprises one or more alkali metals, one or more alkaline earth metals, or mixtures thereof.

15. The lubricant composition of claim 14 wherein the alkaline earth metal is selected from magnesium and calcium.

16. A method for lubricating a driveline system by supplying thereto the lubricant composition of any of claims 1 through 15.

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