WO2013158473A1

WO2013158473A1 - Lubricant compositions containing ionic liquids

Info

Publication number: WO2013158473A1
Application number: PCT/US2013/036281
Authority: WO
Inventors: Cheng Chen; Allison Elaine Falender; Brian Lee Papke
Original assignee: Shell Oil Company; Shell Internationale Research Maatschappij B.V.
Priority date: 2012-04-16
Filing date: 2013-04-12
Publication date: 2013-10-24

Abstract

An internal combustion engine lubricant composition comprising: an engine lubricant composition comprising: a base oil and an ionic liquid which comprises: one or more cations selected from the group of quaternary amine cations, 2-hydroxyethyl trimethyl ammonium, imidazolium cations, piperidinium cations, and pyridinium cations, and one or more anions selected from the group of succinimide, thiophenolate, sulfonimidate, and anions that may be represented by the formula: wherein Y is any alkyl, or an alkoxylated, or aromatic functional group. Also provided is a method for minimizing deposit formation in internal combustion engines. A method for removing engine deposits is also provided.

Description

Lubricant Compositions Containing Ionic Liquids

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S.

Provisional Application No. 61/624,666, filed on 16 April 2012, which is incorporated herein by reference.

BACKGROUND

[0002] The instant disclosure relates to a lubricant composition containing ionic liquids and methods of using such compositions.

[0003] Auto manufacturers and governments continue to request improved fuel economy performance and robustness of motor oils, including improvements in high temperature oxidation, reducing high temperature piston deposit

formation, reducing engine sludge formation, and improving wear. Reductions in piston deposit formation and engine sludge are also important in extending engine life.

Generally, detergents and dispersants are added to engine lubricating oil compositions to minimize piston deposit and engine sludge formation. Such detergents and dispersants typically contain hydrophobic hydrocarbon tails and polar heads. Normally the treat rate of dispersants is 3-6%.

Addition of detergents and dispersants, as is currently practiced, may reduce or remove sludge formation. However, such additives generally significantly increase the kinematic viscosity of the lubricant composition, thereby reducing fuel economy. Further, addition of detergents and/or dispersants should have no adverse effect on fluoroelastomer

compatibility when the engine lubricating oil composition is to be used in an engine with seal material that comprises a fluorinated polymer. Especially crankcase lubricants should be compatible with fluoroelastomers .

[0004] The disclosure provides a lubricant composition containing specific ionic liquid additives which provide a reduction in engine deposits and sludge (hereafter referred to as 'deposits') without a significant increase in kinematic viscosity. Furthermore, specific ionic liquid additives have been found that show an unexpected high compatibility with fluoroelastomers . In particular, specific ionic liquid additives have been found that show a surprisingly high compatibility with fluoroelastomers in the VW PV3334

specification test.

SUMMARY

[0005] The instant disclosure provides lubricant

compositions, methods for minimizing deposit buildup in engines and methods for removing deposits from engines.

[0006] In one embodiment, the instant disclosure provides an engine lubricant composition comprising: a base oil and an ionic liquid which comprises:

- one or more cations selected from the group of quaternary amine cations, 2-hydroxyethyl trimethyl ammonium, imidazolium cations, piperidinium cations, and pyridinium cations, and

- one or more anions selected from the group of succinimide, thiophenolate, sulfonimidate, and anions that may be

represented by the formula:

0

o ¹¹

0-C - Y

wherein Y is any alkyl, or an alkoxylated, or aromatic

functional group.

[0007] In one embodiment, the instant disclosure provides a method for minimizing the formation of engine deposits comprising: preparing a lubricant composition according to the present invention; and lubricating an engine with the lubricant composition.

[0008] In one embodiment, the instant disclosure provides a method for removing engine deposits comprising: preparing a lubricant composition according to the present invention; and lubricating an engine having a deposit of sludge therein with the lubricant composition. DETAILED DESCRIPTION

[0009] The instant disclosure provides lubricant

compositions, methods of using the compositions to minimize the formation of engine deposits and methods of using the compositions to remove engine deposits.

[0010] In one embodiment, the disclosure provides a lubricant composition containing specific ionic liquid additives which provide a reduction in deposits without a significant

increase in kinematic viscosity. Specific ionic liquid additives have been found that show an unexpected high compatibility with fluoroelastomers . In particular, specific ionic liquid additives have been found that show a

surprisingly high compatibility with fluoroelastomers in the VW PV3334 specification test.

[0011] Passing the VW PV334 fluoroelastomer compatibility test is hard with most lubricant compositions. It is

especially difficult to design lubricant compositions that contain one or more nitrogen containing additives and which pass the VW PV334 fluoroelastomer compatibility test as well.

A relatively large number of nitrogen containing additives, however, are able to provide good dispersant and/or

surfactant and/or detergency properties to a lubricant composition . [0012] For years many formulators in the field have been limited in the introduction of additives to lubricant

compositions because of the challenges with passing the VW PV334 fluoroelastomer compatibility test. One article

discussing lubricant formulations and the importance as well as the difficulty to find lubricants that pass the VW PV334 fluoroelastomer compatibility test is "Lubricant formulation effects on oil seal degradation" by R.E. Davies et.al., SAE transactions, 1995, vol. 104, no. 4, pp. 855-863, published by Society of Automotive Engineers, New York (ISSN 0096- 736X) .

[0013] Surprisingly, it was now found to be possible to develop a lubricant composition containing specific ionic liquid additives which provide a reduction in deposits without a significant increase in kinematic viscosity, and which also show an unexpected high compatibility with

fluoroelastomers . Specific ionic liquid additives have been found that show a surprisingly high compatibility with fluoroelastomers in the VW PV3334 specification test.

[0014] Lubricant compositions according to the present invention are highly suitable as crankcase lubricants. The instant disclosure thus also relates to a crankcase lubricant composition, a method of using the composition to minimize the formation of deposits in a crankcase and a method of using the composition to remove deposits in a crankcase.

[0015] The engine lubricant compositions according to the disclosure comprise a base oil and an ionic liquid which comprises a cation and an anion.

[0016] Cations useful in the inventive compositions are quaternary amine cations that may be represented by the formula:

wherein R_lr R₂, R₃ and R₄ are independently selected from the group consisting of alkyls and alkoxyl functional groups. As used herein, independently selected means that each of Ri, R₂, R₃ and R₄ may be any alkyl or alkoxyl functional group without regard to what alkyl or alkoxyl group the remaining R groups are. Any two or more of Ri, R₂, R3 and R₄ may be the same alkyl or alkoxyl functional group. Preferably each Ri, R₂, R₃ or R₄ is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms.

[0017] In one embodiment, one or two of Ri, R₂, R₃ and R₄ is/are alkyl or alkoxyl functional group(s) having in the range of from 21 to 50 carbon atoms, whereby each of the other groups is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms.

[0018] In one embodiment, two or more of Ri, R₂, R₃ and R4 are the same alkyl or alkoxyl functional group, and each R_lr R₂, R₃ or R₄ is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms. In a preferred embodiment, three or more of Ri, R₂, R₃ and R₄ are the same alkyl functional group, and each R_lr R₂, R₃ or R₄ is an alkyl or alkoxyl functional group having in the range of from 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms.

[0019] In one particular embodiment of the inventive

lubricant composition, the cation of the ionic liquid is tetrabutylammonium and may be represented by the formula:

[0020] In one particular embodiment of the inventive

lubricant composition, the cation of the ionic liquid is tetrahexylammonium and may be represented by the formula:

[0021] In one particular embodiment of the inventive

lubricant composition, the cation of the ionic liquid is

2-hydroxyethyl trimethyl ammonium and may be represented by the formula:

[0022] Other cations useful in the inventive compositions are imidazolium cations that may be represented by the formula:

wherein R_x and R₂ may be the same or different alkyl and alkoxylated functional groups. Preferably each R_x and R₂ is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more

preferably 1 to 3 carbon atoms.

[0023] In one particular embodiment of the inventive

lubricant composition, the cation of the ionic liquid is l-ethyl-3-methylimidazolium and may be represented by the formula :

[0024] Other cations useful in the inventive compositions are piperidinium cations that may be represented by the formula:

l 2 wherein Ri and R₂ may be the same or different alkyl and alkoxylated functional groups. Preferably, each Ri and R₂ is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more

preferably 1 to 3 carbon atoms.

[0025] Further cations useful in the inventive compositions are pyridinium cations that may be represented by the

formula :

wherein R_x may be an alkyl or an alkoxylated functional group. Preferably, Ri is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more preferably 1 to 3 carbon atoms.

[0026] Anions useful in the inventive compositions are anions that may be represented by the formula:

wherein Y is any alkyl, or an alkoxylated, or aromatic functional group. Preferably Y is an alkyl or alkoxyl

functional group having in the range of from 1 to 50 carbon atoms, more preferably 1 to 30 carbon atoms, even more preferably 1 to 20 carbon atoms, still more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms. Also preferred are anions in which Y is a benzene group. Also preferred are anions in which Y is a benzene group with one, two or three alkyl groups attached to it in the meta, ortho and/or para position, said alkyl groups having in the range of from 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms, whereby the functional group Y has in total up to 50 carbon atoms.

[0027] In one particular embodiment of the inventive

lubricant composition, the anion of the ionic liquid is lactate and may be represented by the formula:

In this case, the lactate in the ionic liquid preferably is L- ( + ) -lactate .

[0028] In one particular embodiment of the inventive lubricant composition, the anion of the ionic liquid is benzoate and may be represented by the formula:

[0029] In one particular embodiment of the inventive lubricant composition, the anion of the ionic liquid succinimide and ma be represented by the formula:

[0030] In one particular embodiment of the inventive lubricant composition, the anion of the ionic liquid is thiophenolate and ma be represented by the formula:

[0031] Other anions useful in the inventive compositions are thiophenolates that may be represented by any of the

followin formulas:

wherein Ri may be an alkyl or an alkoxylated functional group. Preferably Ri is an alkyl or alkoxyl functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more preferably 1 to 3 carbon atoms. Preferably Ri is an alkyl functional group having in the range of from 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms.

[0032] Further anions useful in the inventive compositions are thiophenolates that may be represented by any of the following formulas:

wherein R_x and ]¾ may be the same or different alkyl and alkoxylated functional groups. Preferably each R_x and R₂ is an alkyl or an alkoxylated functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more preferably 1 to 3 carbon atoms. Preferably each R_x and R₂ is an alkyl functional group having in the range of from 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms.

[0033] Other anions useful in the inventive compositions are thiophenolates that may be represented by the following formula :

wherein Ri, R₂, and R₃ may be the same or different alkyl and alkoxylated functional groups. Preferably each Ri, R₂, and R₃ is an alkyl or an alkoxylated functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more preferably 1 to 3 carbon atoms. Preferably each Ri, R₂, and R₃ is an alkyl functional group having in the range of from 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms. [0034] Other anions useful in the inventive compositions are sulfonimidates that may be represented by the formula:

I I

o o

wherein R_x and R₂ may be the same or different alkyl and halogenated functional groups. Preferably each R_x and R₂ may be an alkyl or a halogenated functional group having in the range of from 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, even more preferably 1 to 7 carbon atoms, still more preferably 1 to 3 carbon atoms. Preferably each Ri and R₂ is a halogenated functional group having in the range of from 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms. In case Ri and/or R₂ are halogenated functional groups, each Ri and R₂ may have 1 to 3 halogen atoms, and preferably has 3 halogen atoms. Most preferably the halogen atoms, if present, are all fluoride atoms.

[0035] In one particular embodiment of the inventive

lubricant composition, the anion of the ionic liquid is bis- trifluoromethane sulfonimidate and may be represented by the formula :

[0036] Specific combinations of the cations and anions listed above are proven to be highly advantageous. [0037] In one particular embodiment of the inventive

lubricant composition, the ionic liquid is tetrabutylammonium benzoate .

[0038] In another particular embodiment of the inventive lubricant composition, the ionic liquid is tetrahexylammonium benzoate .

[0039] In a further particular embodiment of the inventive lubricant composition, the ionic liquid is l-ethyl-3- methylimidazolium L- (+) -lactate .

[0040] In still another particular embodiment of the

inventive lubricant composition, the ionic liquid is

tetrabutylammonium bis-trifluoromethane sulfonimidate .

[0041] In a further particular embodiment of the inventive lubricant composition, the ionic liquid is tetrabutylammonium thiophenolate, whereby the thiophenolate can be represented by the following formula:

[0042] In one particular embodiment of the inventive

lubricant composition, the ionic liquid is 2-hydroxyethyl trimethyl ammonium L- (+) -lactate .

[0043] In another particular embodiment of the inventive lubricant composition, the ionic liquid is tetrabutylammonium succinimide .

[0044] The ionic liquids and precursors thereof are

commercially available. Examples of manufacturers are BASF, EMD Chemicals, Evonik, and Iolitec. [0045] Some embodiments of the inventive lubricant composition comprise from 0.01 to 5 percent by weight of the ionic liquid based on the total weight of the base oil and the ionic liquid. All ranges and subranges from 0.01 to 5 percent by weight are included herein and disclosed herein. For example, the weight percent of the ionic liquid may have a lower limit of 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4 or 4.5 weight percent and an upper limit of 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 weight percent. The weight percent of the ionic liquid in the inventive lubricant composition may range from 0.01 to 5 weight percent.

[0046] In known lubricant compositions, an ionic liquid is typically present in an amount of about 3 weight percent. It has now been found that the advantages of the present

invention are even achieved when as little as 0.1 weight percent of the ionic liquid is present in the inventive lubricant composition.

[0047] The advantages of the present invention are achieved when 5 weight percent or more of the ionic liquid is present in the inventive lubricant composition. Preferably less than 5 weight percent of the ionic liquid is present. More

preferably less than 3 weight percent of the ionic liquid is present in the inventive lubricant composition.

[0048] Preferably the weight percent of the ionic liquid in the inventive lubricant composition is in the range of from 0.05 to 5 percent, more preferably 0.05 to 1, even more preferably 0.05 to 0.5, still more preferably 0.05 to 0.25 percent, and most preferably in the range of from 0.05 to 0.15 percent.

[0049] Any base oil useful in motor engines may be used in various embodiments of the inventive lubricant composition. Such base oils typically include oils selected from the group consisting of natural base oils, synthetic base stocks, and mixtures and/or blends thereof.

[0050] Typically, base oils are a base stock or blend of base stocks which is a lubricant component that is produced by a single manufacturer to the same specifications (independent of feed source or manufacturer's location); that meets the same manufacturer's specification; and that is identified by a unique formula, product identification number, or both. Base stocks may be manufactured using a variety of different processes including but not limited to distillation, solvent refining, hydrogen processing, oligomerization,

esterification, and rerefining.

[0051] The base oil used in various embodiments of the disclosure may comprise mixtures of one or more natural oils and/or one or more synthetic oils. Natural lubricating oils may include animal oils, vegetable oils (e.g., rapeseed oils, castor oils), petroleum oils, mineral oils, and oils derived from coal or shale. Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed

paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

[0052] Synthetic oils include hydrocarbon oils such as olefin oligomers (PAOs), dibasic acid esters, polyol esters, and dewaxed waxy raffinate. Hydrocarbon synthetic oils useful in the disclosure may include, for example, oils prepared from the polymerization of ethylene, i.e., polyalphaolefin or PAO, or from hydrocarbon synthesis procedures using carbon

monoxide and hydrogen gases such as in a Fisher-Tropsch process. Fischer-Tropsch derived base oils useful in the disclosure, may include, for example, the Fischer-Tropsch derived base oils disclosed in EP-A-776959, EP-A-668342, WO- 97/21788, WO-00/15736, WO-00/14188, WO-00/14187, WO-00/14183, WO-00/14179, WO-00/08115, WO-99/41332, EP-1029029, WO- 01/18156 and WO-01/57166.

[0053] Synthetic oils may include hydrocarbon oils and halo- substituted hydrocarbon oils such as polymerized and inter- polymerized olefins, alkylbenzenes , polyphenyls, alkylated diphenyl ethers, alkylated diphenyl sulfides, as well as their derivatives, analogues and homologues thereof, and the like. Synthetic lubricating oils also include alkylene oxide polymers, interpolymers , copolymers and derivatives thereof wherein the terminal hydroxyl groups have been modified by, for example, esterification and/or etherification . Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic acids with a variety of alcohols.

Esters useful as synthetic oils also include those made from C5 to C12 monocarboxylic acids and polyols and polyol ethers. Tri-alkyl phosphate ester oils are also suitable for use as base oils.

[0054] Silicon-based oils (such as the polyalkyl-, polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils and silicate oils) comprise another useful class of synthetic base oils. Other synthetic base oils include, for example, liquid esters of phosphorus-containing acids, polymeric tetrahydrofurans , and polyalphaolefins .

[0055] Oils used as the base oil may be selected or blended depending on the desired end use and the additives in the finished oil to give the desired grade of engine oil, e.g. a lubricating oil composition having an SAE Viscosity Grade of OW, OW-20, OW-30, 0W40, OW-50, OW-60, 5W, 5W-20, 5W-30, 5W40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W40, 10W-50, 15W, 15W- 20, 15W-30, or 15W40.

[0056] Suitable base oils include those in all API categories I, II, III, IV and V as defined in API Publication 1509, 14th Edition, Addendum I, December 1998, which is herein

incorporated for all purposes.

[0057] The base oil may be derived from unrefined, refined, rerefined oils, or mixtures thereof. Unrefined oils are obtained directly from a natural source or synthetic source (e.g., coal, shale, or tar sand bitumen) without further purification or treatment. Examples of unrefined oils include a shale oil obtained directly from a retorting operation, a petroleum oil obtained directly from distillation, or an ester oil obtained directly from an esterification process, each of which may then be used without further treatment. Refined oils are similar to the unrefined oils except that refined oils have been treated in one or more purification steps to improve one or more properties. Suitable

purification techniques include distillation, hydrocracking, hydrotreating, dewaxing, solvent extraction, acid or base extraction, filtration, and percolation, all of which are known to those skilled in the art. Rerefined oils are

obtained by treating used oils in processes similar to those used to obtain the refined oils. These rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques for removal of spent additives and oil breakdown products.

[0058] Base oil derived from the hydroisomerization of wax may also be used, either alone or in combination with the aforesaid natural and/or synthetic base oil. Such wax

isomerate oil is produced by the hydroisomerization of natural or synthetic waxes or mixtures thereof over a hydroisomerization catalyst.

[0059] The total amount of phosphorus in the base oil used in some embodiments of the inventive composition may range from 0.04 to 0.1 wt%, or in the alternative, from 0.04 to 0.09 wt%, or in the alternative, from 0.045 to 0.09 wt%, based on total weight of the inventive lubricant composition.

[0060] In some embodiments of the inventive composition, a major amount of base oil of lubricating viscosity is used. A major amount of base oil herein means that the inventive composition comprises 40 wt% or more of base oil. All ranges and subranges from equal to or greater than 40 wt% are included and disclosed herein. For example, the inventive composition may comprise base oil from a lower limit of 40, 50, 60, 70, 80, 90, 95, 97 or 98 wt% to an upper limit of 45, 55, 65, 75, 85, 95, 97, or 99 wt%. The base oil may be present in the inventive composition in a range from 40 to 98 wt%, or in the alternative, from 50 to 97 wt%, or in the alternative from 70 to 99 wt%.

[0061] In some embodiments of the inventive lubricant

composition, the base oil is present in amounts greater than or equal to 40 percent by weight (wt%) . All ranges and subranges of equal to or greater than 40 wt% are disclosed herein and included herein. For example, the base oil may comprise from greater than or equal to 40, 50, 55, 60, 70,

75, 80, or 90 wt% based on the total weight of the lubricant composition .

[0062] Some embodiments of the inventive lubricant

composition exhibit a cold-cranking simulator viscosity within 5% of the cold-cranking simulator viscosity of the base oil in the absence of the ionic liquid. All ranges and subranges within 5% are disclosed herein and included herein. For example, the cold-cranking simulator viscosity of the inventive lubricant composition may be within 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5% or 1% of the cold-cranking simulator viscosity of the base oil in the absence of the ionic liquid.

[0063] Some embodiments of the inventive lubricant

composition exhibit a phosphorous volatility within 10% of the phosphorous volatility of the base oil in the absence of the ionic liquid. All ranges and subranges within 10% are disclosed herein and included herein. For example, the inventive lubricant composition may have a phosphorous volatility within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of the phosphorous volatility of the base oil in the absence of the ionic liquid.

[ 0064 ] Some embodiments of the inventive lubricant

composition exhibit a kinematic viscosity at 100°C within 10% of the kinematic viscosity at 100°C of the base oil in the absence of the ionic liquid. All ranges and subranges within 10% are included herein and disclosed herein. For example, the inventive lubricant composition may have a kinematic viscosity at 100°C within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1% of the kinematic viscosity at 100°C of the base oil in the absence of the ionic liquid.

[ 0065 ] Some embodiments of the inventive lubricant

composition may further comprise additional additives, including one or more selected from the group consisting of anti-oxidants , anti-wear additives, detergents, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, defoaming agents and seal fix or seal compatibility agents. Representative examples of such additives are disclosed in U.S. Patent No. 7,550,415, the disclosure of which is incorporated herein by reference.

[ 0066] In an alternative embodiment, the instant disclosure further provides a method for minimizing deposit formation in internal combustion engines comprising: preparing a lubricant composition in accordance with any of the foregoing

embodiments; and lubricating an internal combustion engine with the lubricant composition.

[ 0067 ] In another alternative embodiment, the instant

disclosure further provides a method for removing engine deposits in internal combustion engines comprising: preparing a lubricant composition in accordance with any of the

foregoing embodiments; and lubricating an internal combustion engine having deposits therein with the lubricant

composition.

[0068] The inventive lubricant composition may be used in a variety of engines, including but not limited to, internal combustion passenger motor cars, turbine aircraft, diesel engines, and more specifically in those engines in which high temperature deposits tend to be generated.

[0069] Lubricant compositions according to the present invention are highly suitable as crankcase lubricants. One advantage of lubricant compositions according to the present invention is that the piston and the combustion chamber in the crankcase have fewer deposits and are clean. Lubricant compositions according to the present invention can also be used to minimize the formation of deposits in a crankcase which may enable improved engine efficiency and fuel economy. In a method according to the present invention, lubricant compositions according to the present invention are used to remove deposits in a crankcase.

Test Methods

Kinematic viscosity (Kvis)

[0070] Kinematic viscosity (Kvis) was measured in accordance with ASTM D445.

Phosphorus volatility

[0071] Phosphorous volatility was measured in accordance with ASTM D7320.

CCS viscosity

[0072] Cold-cranking simulator viscosity was measured in accordance with ASTM D5293. Elastomer compatability

[0073] Elastomer compatibility was measured in accordance with ASTM D7216. Compatibility with fluoroelastomers was measured in accordance with VW PV3334. Specific test

parameters and passing limits were defined in accordance with the VW 504.00/507.00 specification.

Sequence IIIG BNOx deposit screener test

[0074] A laboratory deposit test which correlates with both weight piston deposit (WPD) merit weighting and ring land deposits (RLD) (herein called the Sequence IIIG BNOx deposit screener test) was developed. The principles behind this test are as follows:

(A) Bulk lubricant oxidation is simulated by passing a dry air/NC>2 gas mixture through a porous gas frit into the hot lubricant mixture. Preferred conditions are 50-400 cc air/NC>2 per minute, with an optimum of 200 cc air/NC>2 per minute. Preferred O2 concentrations are 50-800 ppm NO2, with an optimum condition of 400 ppm O2. Preferred bulk lubricant volume is 100-400 ml, with a preferred volume of 300-350 ml.

(B) Lubricant oxidation is accelerated and made more realistic by pre-blending the test lubricant with a used lubricant taken from a test vehicle. The identity of the vehicle lubricant is not critical, but the same aged vehicle lubricant should be used in all testing so that reliable comparison between the different lubricants may be made.

Vehicle aging should simulate approximately 5000 miles of taxi cab service aging. Preferred blend ratios are 25-75% used taxi oil in the final blend, with an optimum ratio of 50%.

(C) A pre-aging step where the oil blend of test lubricant + aged taxi oil is heated and sparged with air/NC>2. Preferred pre-aging times are 4 to 48 hours, with an optimum time of 15 hours. Preferred pre-aging bulk lubricant

temperatures are 120 - 170 °C, with an optimum temperature of 155 °C.

(D) A deposit-generating step where a heated metal surface is submerged in the pre-aged oil and then withdrawn, allowing a thin lubricant film to remain on the surface. This thin lubricant film is exposed to hot simulated engine exhaust gases for a period of time at high temperatures. The metal surface is then re-submerged in the hot pre-aged oil, and the process repeated. Preferred temperatures for the hot metal surface are 200 - 400 °C, with an optimum temperature of 320 °C . An unlimited variety of metal surfaces may be used, but the preferred metal is a metal similar to combustion engine piston alloys (high silicon aluminum alloys) . Preferred exposure times for the hot metal surface in the hot simulated exhaust gas mixture are 10 - 180 seconds, with an optimum time of 50 - 60 seconds. The hot simulated exhaust gases are those resulting from sparging the hot lubricant with the air/NC>2 mixture. During the deposit-generating step, the bulk lubricant sample continues to be heated and sparged with the air/NC>2 gas mixture. Total time for the deposit- generating step is critical to obtaining acceptable

correlations with Sequence IIIG piston deposits; preferred times for the deposit-generating step are 4 - 12 hours, with an optimum time of 6 - 8 hours.

(E) A merit rating step where the deposit-covered metal surface is visually rated using the same rating scheme developed for the Sequence IIIG engine test. This scale is from 0 to 10, with ' 0 ' being extremely dirty and ^y10' being perfectly clean. In addition, deposit weight is measured by a careful comparison with the initial weight of the clean metal test specimen. All weighing and rating steps are conducted after the metal surface is first cleaned with a suitable hydrocarbon solvent, preferably heptane or toluene. Sequence VG Coupon Sludge Clean-up screener test

[0075] A bench screener test was developed in order to demonstrate deposit control specifically in relation to the ability of a lubricant to "clean-up" real engine sludge rather than just "keep clean."

[0076] A modified Sequence VG "dirty-up" test was conducted as per ASTM D6593, using a new VG engine and a "dirty-up" standard oil which was an API SF specification oil with the following modifications:

[0077] Intermediate sludge ratings of the right side of the engine were carried out every 24 hours on the valve deck, cam cover and cam-baffle.

[0078] Photographs were taken of each of these components every 2 hours .

[0079] The test was run until one of the components had accumulated enough sludge and varnish to achieve a merit rating of approximately 7. The time taken to reach this rating (i.e., ~7) was approximately 216 to 288 hours.

[0080] A cam-baffle was obtained from a VG engine after running the dirty-up phase of the modified Sequence VG test as described above.

[0081] 1 cm x 1 cm samples were cut from the cam-baffle, using a lever-press to avoid contamination with cutting fluid .

[0082] Cam-baffle samples were dipped in lubricating oil compositions to be tested and allowed to drain before initial cleanliness ratings for sludge and varnish were made and photographs were taken for each sample.

[0083] Cam-baffle samples were then suspended in the

lubricating oil compositions to be tested (lOOg) . The lubricating oil compositions were then stirred and maintained at 80°C for a period of up to 14 days.

[0084] A pass/fail criteria was used to evaluate cleaning ability. Coupon visual appearance had to be significantly improved to merit a 'clean' rating.

Examples

[0085] The following examples illustrate the present disclosure but are not intended to limit the scope of the disclosure.

[0086] Comparative Example 1 is a fully formulated lubricant API "SN" quality 5W30 engine oil containing a Group III base oil .

[0087] Inventive Example 1 included the composition of Comparative Example 1 plus 0.1 wt% of tetrabutylammonium benzoate .

[0088] Inventive Example 2 included the composition of Comparative Example 1 plus 0.1 wt% of tetrahexylammonium Benzoate .

[0089] Table 1 provides the results of BNOx deposit testing on a wide variety of ionic liquid components blended as top- treats into conventional API "SN" quality fully formulated engine lubricants. Deposit performance is compared to the same oil without addition of the ionic liquid component. For comparison purposes, HEAVIER indicates the ionic liquid addition had a significant detrimental effect on piston deposit cleanliness, NEUTRAL indicates no substantive change in piston deposits, and FEWER indicates a significant cleanliness benefit was observed. This table demonstrates that the deposit cleanliness benefit obtained from the ionic liquid used in Inventive Example 1 is a unique benefit not provided by all ionic liquids, nor by ionic liquids which contain similar cations or anions. Table 1

[0090] Table 2 displays the results of Coupon clean-up testing using test specimens obtained using a modified

Sequence VG test (ASTM 6593) . The Coupon clean-up testing was performed on a variety of ionic liquid components blended as top-treats into conventional API "SN" quality fully

formulated engine lubricants. This test is indicative of the ability of a composition to clean pre-existing engine

deposits. As shown in Table 2, Inventive Example 1 is able to remove pre-existing deposits from test coupons before or by the end of the testing period. This table demonstrates that the benefit of removing pre-existing deposits obtained from the ionic liquid used in Inventive Example 1 is a unique benefit not provided by all ionic liquids.

Table 2

[0091] Table 3 displays the results of BNOx Deposit testing which correlates with Sequence IIIG test (ASTM 7320) . As shown by the data in Table 3, Inventive Example 1 provided a significant improvement, i.e. reduction, in piston deposits, as illustrated by the higher deposit merit ratings (0-10 scale) .

Table 3

[0092] Table 4 includes the Kvis for each of the Examples, taken at 40 °C and 100 °C . As evident from this data, the inclusion of the ionic liquid in Inventive Example 1 does not substantially raise the viscosity of the inventive lubricant compositions .

Table 4

[0093] Table 5 includes the phosphorous volatility for each of the Examples. As evident from this data, the inclusion of the ionic liquid in Inventive Example 1 does not

substantially change the phosphorous volatility of the inventive lubricant compositions.

Table 5

[0094] Table 6 includes the CCS (Cold-Cranking Simulator) viscosity @ -30°C for each of the Examples. As evident from this data, the inclusion of the ionic liquid in Inventive Example 1 does not substantially change the CCS viscosity of the inventive lubricant compositions.

Table 6

[0095] Tables 7 and 8 include the elastomer compatibility results for each of the Examples.

[0096] Table 7 shows the elastomer compatibility results for each of the Examples measured in accordance with ASTM D7216. Table 7

[0097] Table 8 provides the results of fluoroelastomer compatibility testing in accordance with VW PV3334 on a variety of ionic liquid components blended as top-treats conventional API "SN" quality fully formulated engine

lubricants .

Table 8

[0098] As evident from the data in Table 7 and Table 8, the inclusion of the ionic liquid in Inventive Example 1 does not substantially affect elastomer compatibility, and not even the fluoroelastomer compatibility as measured in accordance with VW PV3334 (504.00/507.00), of the inventive lubricant compositions.

[0099] The present disclosure may be embodied in other forms without departing from the scope and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the disclosure.

Claims

C L A I M S

1. An engine lubricant composition comprising: a base oil and an ionic liquid which comprises:

represented by the formula:

wherein Y is any alkyl, or an alkoxylated, or aromatic

functional group.

2. The lubricant composition according to claim 1, wherein the one or more cations are selected from the group of tetrabutylammonium, 2-hydroxyethyl trimethyl ammonium, and l-ethyl-3-methylimidazolium.

3. The lubricant composition according to claim 1 or 2, wherein the anion is selected from the group of succinimide, thiophenolate that be represented by the following formula:

benzoate, and lactate.

4. The lubricant composition according to claim 1, wherein the ionic liquid is tetrabutylammonium benzoate.

5. The lubricant composition according to claim 1, wherein the ionic liquid is l-ethyl-3-methylimidazolium L- ( + ) -lactate .

6. The lubricant composition according to claim 1, wherein the ionic liquid is tetrabutylammonium bis- trifluoromethane sulfonimidate

7. The lubricant composition according to claim 1, wherein the ionic liquid is tetrabutylammonium thiophenolate, whereby the thiophenolate can be represented by the following formula :

8. The lubricant composition according to claim 1, wherein the ionic liquid is 2-hydroxyethyl trimethyl ammonium L- ( + ) -lactate .

9. The lubricant composition according to claim 1, wherein the ionic liquid is tetrabutylammonium succinimide.

10. The lubricant composition according to any one of the preceding claims, wherein the lubricant composition comprises from 0.01 to 5 percent by weight of the ionic liquid based on the total weight of the base oil and the ionic liquid.

11. The lubricant composition according to any one of the preceding claims, wherein the base oil is selected from the group consisting of natural base stocks, synthetic base stocks, and combinations thereof.

12. The lubricant composition according to any one of the preceding claims, wherein the lubricant composition exhibits a cold-cranking simulator viscosity within 5% of the cold- cranking simulator viscosity of the base oil in the absence of the ionic liquid.

13. The lubricant composition according to any one of the preceding claims, wherein the lubricant composition exhibits a phosphorous volatility within 10% of the phosphorous volatility of the base oil in the absence of the ionic liquid .

14. The lubricant composition according to any one of the preceding claims, wherein the lubricant composition exhibits a kinematic viscosity at 100°C within 10% of the kinematic viscosity at 100°C of the base oil in the absence of the ionic liquid.

15. The lubricant composition according to any one of the preceding claims, wherein the lubricant composition shows to be compatible with fluoroelastomers in a test in accordance with VW PV3334, especially in a test in accordance with VW

PV3334 in which the parameters and passing limits are defined in accordance with the VW 504.00/507.00 specification.

16. A method for minimizing the formation of engine deposits comprising: preparing a lubricant composition according to any one of the preceding claims; and lubricating an engine with the lubricant composition.

17. A method for minimizing the formation of engine deposits comprising: preparing a lubricant composition according to any one of the preceding claims; and lubricating a crankcase with the lubricant composition.

18. A method for removing engine deposits comprising:

preparing a lubricant composition according to any one of the preceding claims; and lubricating an engine having a deposit of sludge therein with the lubricant composition.

19. A method for removing engine deposits comprising:

preparing a lubricant composition according to any one of the preceding claims; and lubricating a crankcase having a deposit of sludge therein with the lubricant composition.