EP2569403A1

EP2569403A1 - Tartaric acid derivatives in hths fluids

Info

Publication number: EP2569403A1
Application number: EP11720362A
Authority: EP
Inventors: Mark C. Davies
Original assignee: Lubrizol Corp
Current assignee: Lubrizol Corp
Priority date: 2010-05-12
Filing date: 2011-05-06
Publication date: 2013-03-20
Also published as: WO2011143051A1; US20150376539A1; CN102918139B; CN102918139A; BR112012028621A2; CA2798388A1; US20130210690A1

Abstract

The present invention provides high-HTHS value lubricating compositions that have improved fuel economy performance. The present invention also provides methods of operating an internal combustion engine utilizing such compositions. The lubricating compositions of the invention utilize butane dioic imide compounds, such as tartrimides, and may also be low sulfur, low ash and low phosphorus, providing lower wear and friction and improved fuel economy.

Description

TITLE

Tartaric Acid Derivatives in HTHS Fluids BACKGROUND OF THE INVENTION

[0001] The present invention relates to a low sulfur, low ash, low phosphorus lubricant composition and method for lubricating an internal combustion engine, providing improved fuel economy and retention of fuel economy and wear and friction reduction, specifically in high temperature high shear (HTHS) fluids, or rather fluids with high HTHS values.

[0002] Fuel economy is of great importance, and lubricants which can foster improved fuel economy by, for instance, reducing friction within an engine, are of significant value. The present invention provides a low sulfur, low ash, low phosphorus lubricant compositions for use with high HTHS value oils, which can lead to improved fuel economy in an internal combustion engine. This improvement is effected by providing an additive package in with a high HTHS value fluid in which the friction modifier component is exclusively or predominantly a derivative of a hydroxyl-carboxylic acid, and more specifically a tartrimide or a tartramide or combinations thereof.

[0003] It is known in the art that fuel economy of vehicles and the HTHS values of the lubricant composition used in the vehicle are related. Vehicles using lubricant compositions having lower HTHS values exhibit improved fuel economy. For every SAE Viscosity Grade, a minimum HTHS of the lubricant composition is specified in the SAE J300 Engine Oil Viscosity Classification. Lubricant compositions with higher HTHS values typically provide worse fuel economy performance and are also less sensitive to conventional friction modifiers and other additives often used to improve fuel economy performance.

[0004] There is need for high-HTHS value lubricating compositions that have improved fuel economy performance.

SUMMARY OF THE INVENTION

[0005] The present invention provides high-HTHS value lubricating compositions that have improved fuel economy performance. The present invention also provides methods of operating an internal combustion engine utilizing such compositions.

[0006] The present invention includes a lubricant composition comprising a derivative of a hydroxyl-carboxylic acid, and more specifically an alkoxy or hydroxy substituted succinimide, which may also be referred to as an alkoxy or hydroxy substituted butane dioic imide. In some embodiments the additives is a tartrimide or a tartramide or combinations thereof. In some embodiments the lubricant composition comprises (a) an oil of lubricating viscosity and (b) an alkoxy or hydroxy substituted butane dioic imide friction modifier wherein the friction modifier is represented by formula I;

wherein R¹ is hydrocarbyl group containing from 8 to 30 or 24 carbon atoms; R² is -H or a hydrocarbyl group; Y is -H, -OH or -OR² with the proviso that when Y is -OR² the two R² groups may be linked to form a ring. In some embodi- ments the additive is an alkyl tartrimide.

[0007] The present invention further includes compositions that are low- sulfur, low-phosphorus and low-ash, suitable for use in an internal combustion engine, and/or where the oil of lubricating viscosity is a high temperature high shear fluid. In some embodiments the lubricant composition has a sulfated ash value of up to about 1.0 percent by weight, a phosphorus content of up to about 0.08 percent by weight and a sulfur content of up to about 0.4 percent by weight.

[0008] The invention further provides a method of lubricating an engine comprising the steps of: supplying to the engine one or more of the lubricant compositions described herein. In some embodiments the engine is present in an automobile wherein the automobile meets Euro 4 and Euro 5 standards. DETAILED DESCRIPTION OF THE INVENTION

[0009] Various preferred features and embodiments will be described below by way of non-limiting illustration.

[0010] HTHS values are viscosity measurements and represent a fluid's resistance to flow under conditions resembling highly-loaded journal bearings in internal combustion engines. The HTHS value of an oil and/or lubricating composition directly correlates to the oil film thickness in a bearing. HTHS values of a fluid may be obtained by using ASTM D4683 at 150°C. The lubricating compositions of this invention may have a HTHS value of at least 2.9 cP or at least 3.5 cP. In some embodiments the lubricating compositions have the present invention have a HTHS value of at least 3.5 cP but have fuel economy performance equivalent to a lubricating composition that has a HTHS value of about 2.9 and which does not contain the additives described herein.

[0011] The present invention provides a composition as described above. Often the composition has total sulfur content in one aspect below 0.4 percent by weight, in another aspect below 0.3 percent by weight, in yet another aspect 0.2 percent by weight or less and in yet another aspect 0.1 percent by weight or less. Often the major source of sulfur in the composition of the invention is derived from conventional diluent oil. A typical range for the total sulfur content is 0.01 to 0.3 or 0.1 percent by weight.

[0012] Often the composition has a total phosphorus content of less than or equal to 800 ppm, in another aspect equal to or less than 500 ppm, in yet another aspect equal to or less than 300 ppm, in yet another aspect equal to or less than 200 ppm and in yet another aspect equal to or less than 100 ppm of the composi- tion. A typical range for the total phosphorus content is 100 to 800 or 500 ppm.

[0013] Often the composition has a total sulfated ash content as determined by ASTM D-874 of below 1.0 percent by weight, in one aspect equal to or less than 0.7 percent by weight, in yet another aspect equal to or less than 0.4 percent by weight, in yet another aspect equal to or less than 0.3 percent by weight and in yet another aspect equal to or less than 0.05 percent by weight of the composition. A typical range for the total sulfate ash content is 0.005 to 0.7 or 0.8 percent by weight. Oil of Lubricating Viscosity

[0014] The lubricating compositions of the present invention include an oil of lubricating viscosity. Suitable oils are described below. In some embodiments the specific HTHS values and ranges described above apply to the oil and/or oils used in the compositions. These HTHS values may also be applied to the overall composition, even if one or more of the oils present does not have such HTHS values when considered alone.

[0015] The oil of lubricating viscosity may include one or more base oils and generally makes up a major amount of the overall composition (i.e. an amount greater than about 50 percent by weight). Generally, the oil component is present in an amount greater than about 60 percent, or greater than about 70 percent, or greater than about 80 percent by weight of the lubricating oil composition. The base oil sulfur content is typically less than 0.2 percent by weight.

[0016] In some embodiment the compositions of the invention include a low- sulfur, low-phosphorus, low-ash lubricating oil component which may result in a low-sulfur, low-phosphorus, low-ash lubricating composition.

[0017] The low-sulfur, low-phosphorus, low-ash lubricating oil composition may have a viscosity of up to about 16.3 mm²/s at 100°C, and in one embodiment 5 to 16.3 mm²/s (cSt) at 100°C, and in one embodiment 6 to 13 mm²/s (cSt) at 100°C. In one embodiment, the lubricating oil composition has an SAE Viscosity Grade of 0W, OW-20, 0W-30, OW-40, OW-50, OW-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40 or 10W-50, 15W, 15W-40 or 15W-50.

[0018] The low-sulfur, low-phosphorus, low-ash lubricating oil composition may have a high-temperature/high-shear viscosity at 150°C as measured by the procedure in ASTM D4683 of up to 4 mm²/s (cSt), and in one embodiment up to 3.7 mm²/s (cSt), and in one embodiment 2 to 4 mm²/s (cSt), and in one embodiment 2.2 to 3.7 mm²/s (cSt), and in one embodiment 2.7 to 3.5 mm²/s (cSt).

[0019] The base oil used in any of the compositions described above may be a natural oil, a synthetic oil or a mixture thereof. In some embodiments it is also provided that the sulfur content of the oils used do not exceed the above- indicated sulfur concentration limits required for the inventive low-sulfur, low- phosphorus, low-ash lubricating oil composition. The natural oils that are useful include animal oils and vegetable oils (e.g., castor oil, lard oil) as well as mineral lubricating oils such as liquid petroleum oils and solvent treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed par- affinic-naphthenic types. Oils derived from coal or shale are also useful. Synthetic lubricating oils include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene isobut- ylene copolymers, etc.); poly(l-hexenes), poly-(l-octenes), poly(l-decenes), etc. and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecyl- benzenes, dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.); alkylated diphenyl ethers and the derivatives, analogs and homologs thereof and the like.

[0020] Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc., constitute another class of known synthetic lubricating oils that can be used. These are exemplified by the oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having an average molecular weight of about 1000, diphenyl ether of polyethylene glycol having a molecular weight of about 500-1000, diethyl ether of polypropylene glycol having a molecular weight of about 1000-1500, etc.) or mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3-8 fatty acid esters, or the carboxylic acid diester of tetraethylene glycol.

[0021] Another suitable class of synthetic lubricating oils that can be used comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc.) Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phtha- late, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.

[0022] Esters useful as synthetic oils also include those made from C5 to C 12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylol propane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc.

[0023] The oil can be a poly-alpha-olefin (PAO). Typically, the PAOs are derived from monomers having from 4 to 30, or from 4 to 20, or from 6 to 16 carbon atoms. Examples of useful PAOs include those derived from octene, decene, mixtures thereof, and the like. These PAOs may have a viscosity from 2 to 15, or from 3 to 12, or from 4 to 8 mm²/s (cSt), at 100°C. Examples of useful PAOs include 4 mm²/s (cSt) at 100°C poly-alpha-olefins, 6 mm²/s (cSt) at 100°C poly-alpha-olefins, and mixtures thereof. Mixtures of mineral oil with one or more of the foregoing PAOs may be used.

[0024] Unrefined, refined and re-refined oils, either natural or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the lubricants of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from primary distillation or ester oil obtained directly from an esterification process and used without further treatment would be an unrefined oil. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Many such purification techniques are known to those skilled in the art such as solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Re-refined oils are obtained by processes similar to those used to obtain refined oils applied to refined oils which have been already used in service. Such re-refined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products. [0025] Additionally, oils prepared by a Fischer-Tropsch gas to liquid synthetic procedure are known and can be used.

Friction Modifier

[0026] The additives of the present invention may be classified as friction modifiers and provide improved fuel economy performance in the HTHS lubricant compositions in which they are used. The additives may be derivatives of tartaric acid and more specifically are tartrimides. The additives may also be descried as alkoxy and/or hydroxy substituted succinimides or even as alkoxy and/or hydroxy substituted butane dioic imides. The compositions of the present invention may also include tartrimides, tartrates, tartrate esters, ester- amides and other derivatives of tartaric acid, in combination with the tartrimides described herein.

[0027] The additive of the present is a friction modifier represented by formula I;

wherein R¹ is hydrocarbyl group containing from 8 to 30 or 24 carbon atoms; R² is -H or a hydrocarbyl group; Y is -H, -OH or -OR² with the proviso that when Y is -OR² the two R² groups may be linked to form a ring.

[0028] In some embodiments the additive is derived from a material represented by formula II and an amine containing from 8 to 30 or 24 carbon atoms;

wherein R² is a hydrocarbyl group; Y is -H, -OH or -OR² with the proviso that when Y is -OR² the two R² groups may be linked to form a ring.

In some embodiments the amine comprises a linear amine containing from 16 to 20 carbon atoms. In some embodiments the additive is oleyl tartrimide.

[0029] The tartrimide additives may be derived by the reaction of tartaric acid and one or more amines, for example, one or more amines having the formula R'R²NH wherein R¹ and R² each independently represent H, a hydrocarbon-based radical of 1 to 150 carbon atoms provided that the sum of carbon atoms in R¹ and R² is at least 8, or -R³OR⁴ in which R³ is a divalent alkylene radical of 2 to 6 carbon atoms and R⁴ is a hydrocarbyl radical of 5 to 150 carbon atoms. In one embodiment each R¹ and R² may contain from 2, 8 , or 12 to 100, 50, 26 or 18 carbon atoms. In one embodiment the amine includes oleyl amine.

[0030] Examples of the additives of the present invention are prepared conveniently by reacting tartaric acid with one or more of the corresponding amine. The tartaric acid used for preparing the tartrimides can be the commercially available type (obtained from Sargent Welch), and it is likely to exist in one or more isomeric forms such as -tartaric acid, /-tartaric acid, J-tartaric acid or meso-tartaric acid, often depending on the source (natural) or method of synthesis (e.g. from maleic acid). These derivatives can also be prepared from functional equivalents to the diacid readily apparent to those skilled in the art, such as esters, acid chlorides, anhydrides, etc.

[0031] The additives of the present invention can be solids, semi-solids, or oils depending on the particular amine used in preparing the tartrimide, or tartramides. For use as additives in oleaginous compositions including lubri- eating and fuel compositions the tartrimides will have to be soluble and/or stably dispersible in such oleaginous compositions. Thus, for example, compositions intended for use in oils are oil-soluble and/or stably dispersible in an oil in which they are to be used. The term "oil-soluble" as used in this specification and appended claims does not necessarily mean that all the compositions in question are miscible or soluble in all proportions in all oils. Rather, it is intended to mean that the composition is soluble in an oil (mineral, synthetic, etc.) in which it is intended to function to an extent which permits the solution to exhibit one or more of the desired properties. Similarly, it is not necessary that such "solutions" be true solutions in the strict physical or chemical sense. They may instead be micro-emulsions or colloidal dispersions which, for the purpose of this invention, exhibit properties sufficiently close to those of true solutions to be, for practical purposes, interchangeable with them within the context of this invention.

[0032] As previously indicated, the additives of this invention are useful as additives for lubricants, in which they function primarily as rust and corrosion inhibitors, friction modifiers, antiwear agents and demulsifiers. They can be employed in a variety of lubricants based on diverse oils of lubricating viscosity, including natural and synthetic lubricating oils and mixtures thereof. These lubricants include crankcase lubricating oils for spark-ignited and compression- ignited internal combustion engines, including automobile and truck engines, two-cycle engines, aviation piston engines, marine and railroad diesel engines, and the like. They can also be used in gas engines, stationary power engines and turbines, and the like. Automatic transmission fluids, transaxle lubricants, gear lubricants, metal-working lubricants, hydraulic fluids and other lubricating oil and grease compositions can also benefit from the incorporation therein of the compositions of the present invention.

[0033] Other friction modifiers maybe present in the lubricants of the present invention and can include glycerol monooleates, oleyl amides, diethanol fatty amines and mixtures thereof. A useful list of friction modifiers is included in U.S. Pat. No. 4,792,410. In some embodiments the lubricating compositions of the present invention contain the tartaric acid derivatives described above in combination with a secondary friction modifier comprising glycerol monooleates, oleyl amides, diethanol fatty amines and/or mixtures thereof.

[0034] Fatty acid esters of glycerol can be prepared by a variety of methods well known in the art. Many of these esters, such as glycerol monooleate and glycerol monotallowate, are manufactured on a commercial scale. The esters useful for this invention are oil-soluble and are preferably prepared from Cg to C₂₂ fatty acids or mixtures thereof such as are found in natural products. The fatty acid may be saturated or unsaturated. Certain compounds found in acids from natural sources may include licanic acid which contains one keto group. Useful Cs to C22 fatty acids are those of the formula R-COOH wherein R is alkyl or alkenyl.

[0035] The fatty acid monoester of glycerol is useful. Mixtures of mono and diesters may be used. Mixtures of mono- and diester can contain at least about 40% of the monoester. Mixtures of mono- and diesters of glycerol containing from about 40% to about 60% by weight of the monoester can be used. For example, commercial glycerol monooleate containing a mixture of from 45% to 55% by weight monoester and from 55% to 45% diester can be used.

[0036] Useful fatty acids are oleic, stearic, isostearic, palmitic, myristic, palmitoleic, linoleic, lauric, linolenic, and eleostearic, and the acids from the natural products tallow, palm oil, olive oil, peanut oil, sunflower oil, soybean oil, rape seed oil or canola oil.

[0037] Fatty acid amides have been discussed in detail in U.S. Pat. No. 4,280,916. Suitable amides are C8-C24 aliphatic monocarboxylic amides and are well known. Reacting the fatty acid base compound with ammonia produces the fatty amide. The fatty acids and amides derived therefrom may be either saturated or unsaturated. Important fatty acids include lauric C₁₂, palmitic C₁₆ and stearic C₁₈. Other important unsaturated fatty acids include oleic, linoleic and linolenic acids, all of which are C₁₈. In one embodiment, the fatty amides of the instant invention are those derived from the C₁₈ monounsaturated fatty acids.

[0038] The fatty amines and the diethoxylated long chain amines such as N,N-bis- (2-hydroxyethyl)-tallowamine themselves are generally useful as components of this invention. Both types of amines are commercially available. Fatty amines and ethoxy- lated fatty amines are described in greater detail in U.S. Patent 4,741,848.

[0039] The lubricating compositions of the present invention may include the friction modifier additive described above at 0.05 to 5 percent by weight. In some embodiments the additive is present in the composition from 0.05, 0.1, 0.25, or 0.4 to 5.0, 2.0, 1.25, or 1.0 percent by weight. In some embodiments the friction modifier additive described herein is not borated. Miscellaneous

[0040] Antioxidants (that is, oxidation inhibitors), including hindered phenolic antioxidants such as 2,6,-di-t-butylphenol, and hindered phenolic esters such as the type represented by the following formula:

t-alkyl

and in a specific embodiment,

wherein R³ is a straight chain or branched chain alkyl group containing 2 to 10 carbon atoms, in one embodiment 2 to 4, and in another embodiment 4 carbon atoms. In one embodiment, R³ is an n-butyl group. In another embodiment R³ can be 8 carbons, as found in Irganox L-135™ from Ciba. The preparation of these antioxidants can be found in Patent 6,559, 105.

[0041] Further antioxidants can include secondary aromatic amine antioxidants such as dialkyl (e.g., dinonyl) diphenylamine, sulfurized phenolic antioxidants, oil-soluble copper compounds, phosphorus-containing antioxidants, molybdenum compounds such as the Mo dithiocarbamates, organic sulfides, disulfides, and polysulfides (such as sulfurized Diels Alder adduct of butadiene and butyl acrylate). An extensive list of antioxidants is found in U.S. Patent 6,251 ,840.

[0042] The EP/antiwear agent used in connection with the present invention is typically in the form of a zinc dialkyldithiophosphate. Although there are an extremely large number of different types of antiwear agents which might be utilized in connection with such functional fluids, the present inventors have found that zinc dialkyldithiophosphate type antiwear agents work particularly well in connection with the other components to obtain the desired characteristics. In one embodiment, at least 50% of the alkyl groups (derived from the alcohol) in the dialkyldithiophosphate are secondary groups, that is, from secon- dary alcohols. In another embodiment, at least 20%, 35% or even 50% of the alkyl groups are derived from C3-C4 alcohols, is some embodiments isopropyl alcohol.

[0043] Ashless detergents and dispersants depending on their constitution may upon combustion yield a non-volatile material such as boric oxide or phosphorus pentoxide. However, ashless detergents and dispersants do not ordinarily contain metal and therefore do not yield a metal-containing ash on combustion. Many types of ashless dispersants are known in the art. Such materials are commonly referred to as "ashless" even though they may associate with a metal ion from another source in situ.

[0044] "Carboxylic dispersants" are reaction products of carboxylic acylat- ing agents (acids, anhydrides, esters, etc.) containing at least 34 and preferably at least 54 carbon atoms which are reacted with nitrogen containing compounds (such as amines), organic hydroxy compounds (such as aliphatic compounds including monohydric and polyhydric alcohols, or aromatic compounds includ- ing phenols and naphthols), and/or basic inorganic materials. These reaction products include imide, amide, and ester reaction products of carboxylic ester dispersants.

[0045] The carboxylic acylating agents include fatty acids, isoaliphatic acids (e.g. 8-methyl-octadecanoic acid), dimer acids, addition dicarboxylic acids 4+2 and 2+2 addition 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). In one embodiment, the carboxylic acylating agent is a fatty acid. Fatty acids generally contain from 8 up to 30, or from 12 up to 30 or 24 carbon atoms. Carboxylic acylating agents are taught in U.S. Patents No. 2,444,328, 3,219,666, 4,234,435 and 6,077,909. [0046] The amine may be a mono- or polyamine. The monoamines generally have at least one hydrocarbyl group containing from 1 to 30 or 24 carbon atoms, or from 1 to 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 hydroxyhy- drocarbyl amines (Ethomeens™ and Propomeens™). The poly amines include alkoxylated diamines (Ethoduomeens™), fatty diamines (Duomeens™), alkyle- nepolyamines (ethylenepolyamines), hydroxy-containing polyamines, poly- oxyalkylene 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).

[0047] The polyamines from which the dispersant is derived include principally alkylene amines conforming, for the most part, to the formula

A— N-(alkylene-N),— H A A

wherein t is an integer typically less than 10, A is hydrogen or a hydrocarbyl group typically having up to 30 carbon atoms, and the alkylene group is typically an alkylene group having less than 8 carbon atoms. The alkylene amines include principally methylene amines, ethylene amines, hexylene amines, heptylene amines, octylene amines, other polymethylene amines. They are exemplified specifically by: ethylene diamine, diethylene triamine, triethylene tetramine, propylene diamine, decamethylene diamine, octamethylene diamine, di(heptamethylene) triamine, tripropylene tetramine, tetraethylene pentamine, trimethylene diamine, pentaethylene hexamine, di(trimethylene) triamine. Higher homologues such as are obtained by condensing two or more of the above-illustrated alkylene amines likewise are useful. Tetraethylene pentamines is particularly useful.

[0048] The ethylene amines, also referred to as polyethylene polyamines, are especially useful. They are described in some detail under the heading "Ethyl- ene Amines" in Encyclopedia of Chemical Technology, Kirk and Othmer, Vol. 5, pp. 898-905, Interscience Publishers, New York (1950).

[0049] Hydroxyalkyl-substituted alkylene amines, i.e., alkylene amines having one or more hydroxyalkyl substituents on the nitrogen atoms, likewise are useful. Examples of such amines include N-(2-hydroxyethyl)ethylene diamine, N,N^'-bis(2-hydroxyethyl)-ethylene diamine, 1 -(2 -hydroxy ethyl) - piperazine, monohydroxypropyl)-piperazine, di-hydroxypropyl-substituted tetra- ethylene pentamine, N-(3-hydroxypropyl)-tetra-methylene diamine, and 2- heptadecyl-1 -(2 -hydroxy ethyl)-imidazoline.

[0050] Higher homologues, such as are obtained by condensation of the above-illustrated alkylene amines or hydroxy alkyl-substituted alkylene amines through amino radicals or through hydroxy radicals, are likewise useful. Condensed polyamines are formed by 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 are described in U.S. Patent 5,230,714 and 5,296,154 (Steckel).

[0051] Examples of these "carboxylic dispersants" are described in British Patent 1 ,306,529 and in many U.S. Patents including the following: 3,219,666, 3,316,177, 3,340,281 , 3,351 ,552, 3,381 ,022, 3,433,744, 3,444, 170, 3,467,668, 3,501 ,405, 3,542,680, 3,576,743, 3,632,51 1 , 4,234,435, 6,077,909 and 6, 165,235.

[0052] Succinimide dispersants are a species of carboxylic dispersants. They are the reaction product of a hydrocarbyl substituted succinic acylating agent with an organic hydroxy compound or, an amine containing at least one hydro- gen attached to a nitrogen atom, or a mixture of said hydroxy compound and amine. The term "succinic acylating agent" refers to a hydrocarbon-substituted succinic acid or succinic acid-producing compound (which term also encompasses the acid itself). Such materials typically include hydrocarbyl-substituted succinic acids, anhydrides, esters (including half esters) and halides.

[0053] Succinic based dispersants have a wide variety of chemical structures including typically structures such as

[0054] In the above structure, each R is independently a hydrocarbyl group, such as a polyolefin-derived group having an Mn of 500 or 700 to 10,000. Typically the hydrocarbyl group is an alkyl group, frequently a polyisobutylene group derived from PIB having a molecular weight of 500 or 700 to 5000, or alternatively 1500 or 2000 to 5000. Alternatively expressed, the R¹ groups can contain 40 to 500 carbon atoms, for instance at least 50, e.g., 50 to 300 carbon atoms, such as aliphatic carbon atoms. The R² are alkylene groups, commonly ethylene (C₂H₄) groups. Such molecules are commonly derived from reaction of an alkenyl acylating agent with a polyamine, and a wide variety of linkages between the two moieties is possible beside the simple imide structure shown above, including a variety of amides and quaternary ammonium salts. Suc- cinimide dispersants are more fully described in U.S. Patents 4,234,435, 3, 172,892 and 6, 165,235.

[0055] The polyalkenes from which the substituent groups are derived are typically homopolymers and interpolymers of polymerizable olefin monomers of 2 to 16 carbon atoms; usually 2 to 6 carbon atoms. The amines which are reacted with the succinic acylating agents to form the carboxylic dispersant composition can be monoamines or polyamines as described above.

[0056] The succinimide dispersant is referred to as such since it normally contains nitrogen largely in the form of imide functionality, although it may be in the form of amine salts, amides, imidazolines as well as mixtures thereof. To prepare the succinimide dispersant, one or more of the succinic acid-producing compounds and one or more of the amines are heated, typically with removal of water, optionally in the presence of a normally liquid, substantially inert organic liquid solvent/diluent at an elevated temperature, generally in the range of 80°C up to the decomposition point of the mixture or the product; typically 100°C to 300°C. [0057] Additional details and examples of the procedures for preparing the succinimide dispersants of the present invention are included in, for example, U.S. Pat. Nos. 3, 172,892, 3,219,666, 3,272,746, 4,234,435, 6,440,905 and 6, 165,235.

[0058] "Amine dispersants" are reaction products of relatively high molecular weight aliphatic halides and amines, preferably polyalkylene polyamines. Examples thereof are described, for example, in the following U.S. Patents: 3,275,554, 3,438,757, 3,454,555, and 3,565,804.

[0059] "Mannich dispersants" are the reaction products of alkyl phenols in which the alkyl group contains at least 30 carbon atoms with aldehydes (especially formaldehyde) and amines (especially polyalkylene polyamines). The materials described in the following U.S. Patents are illustrative: 3,036,003, 3,236,770, 3,414,347, 3,448,047, 3,461 , 172, 3,539,633, 3,586,629, 3,591 ,598, 3,634,515, 3,725,480, 3,726,882, and 3,980,569.

[0060] 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, phosphorus compounds or the like. Exemplary materials of this kind are described in the following U.S. Patents: 3,200,107, 3,282,955, 3,367,943, 3,513,093, 3,639,242, 3,649,659, 3,442,808, 3,455,832, 3,579,450, 3,600,372, 3,702,757, and 3,708,422.

[0061] 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. Examples of polymer dispersants thereof are disclosed in the following U.S. Patents: 3,329,658, 3449,250, 3,519,656, 3,666,730, 3,687,849, and 3,702,300.

[0062] The composition can also contain one or more detergents, which are normally salts, and specifically overbased salts. Overbased salts, or overbased materials, are single phase, homogeneous Newtonian systems characterized by a metal content in excess of that which would be present 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 (such as mineral oil, naphtha, toluene, xylene) for said acidic organic material, a stoichiometric excess of a metal base, and a promoter.

[0063] In some embodiments the lubricating compositions of the present invention include the tartaric acid derivatives described above in combination with one or more detergents, and in some embodiments in combination with an overbased salt detergent.

[0064] The acidic organic compounds useful in making the overbased compositions of the present invention include carboxylic acids, sulfonic acids, phosphorus-containing acids, phenols or mixtures thereof. Preferably, the acidic organic compounds are carboxylic acids or sulfonic acids with sulfonic or thiosulfonic groups (such as hydrocarbyl-substituted benzenesulfonic acids), and hydrocarbyl-substituted salicylic acids. Another type of compound useful in making the overbased composition of the present invention is salixarates. A description of the salixarates useful for of the present invention can be found in publication WO 04/04850.

[0065] The metal compounds useful in making the overbased salts are generally any Group 1 or Group 2 metal compounds (CAS version of the Periodic Table of the Elements). The Group 1 metals of the metal compound include Group la alkali metals (e.g., sodium, potassium, lithium) as well as Group lb metals such as copper. The Group 1 metals are preferably sodium, potassium, lithium and copper, preferably sodium or potassium, and more preferably sodium. The Group 2 metals of the metal base include the Group 2a alkaline earth metals (e.g., magnesium, calcium, strontium, barium) as well as the Group 2b metals such as zinc or cadmium. Preferably the Group 2 metals are magne- sium, calcium, barium, or zinc, preferably magnesium or calcium, more preferably calcium. [0066] The amount of excess metal in the detergent 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 the acidic 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 metal ratio for a sulfonate detergent is calculated based on the ratio of metal to the sulfonate functionality, ignoring the presence of any other incidental acidic groups that may be present in the detergent molecule. The metal ratio of the sulfonate detergents used in the present invention will typically be at least 3, at least 10 or even at least 16. In some embodiments the metal ratio may be from 3, 8, 10, 15 or 16 up to 35 or 30 or 25 or 20.

[0067] Examples of the overbased detergent of the present invention include, but are not limited to calcium sulfonates, calcium phenates, calcium salicylates, calcium salixarates and mixtures thereof. In some embodiments the overbased detergent is a sulfonate, or more specifically a calcium sulfonate, such as a alkylbenzenesulfonate detergent, wherein the sulfonate is derived from predominantly linear alcohols or other compounds. That is, the alkyl group of the sulfonate is derived from predominantly linear alcohols or other compounds. That is not to say the alkyl group may not contain a branch point, as often a linear group will attach at the number 2 position on the chain, leaving a methyl substituent group. In other words the alkyl group referred to here may be linear in the sense that it is a linear alkyl group attached to the benzene or toluene ring at any location along the linear alkyl chain, such as the 2, 3 or 4 position, and this connection point, albeit not at the 1 position, does not result in the group bring non-linear.

[0068] The amount of the overbased material, that is, the detergent, if present, is in one embodiment 0.05 to 3 percent by weight of the composition, or 0.1 to 3 percent, or 0.1 to 1.5 percent, or 0.15 to 1.5 percent by weight.

[0069] Anti-foam agents used to reduce or prevent the formation of stable foam include silicones or organic polymers. Examples of these and additional anti-foam compositions are described in "Foam Control Agents", by Henry T. Kerner (Noyes Data Corporation, 1976), pages 125-162. [0070] The compositions of the present invention are employed in practice as lubricants by supplying the lubricant to an internal combustion engine (such as a stationary gas-powered internal combustion engine) in such a way that during the course of operation of the engine the lubricant is delivered to the critical parts of the engine, thereby lubricating the engine.

[0071] 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. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non- hydrocarbon substituents in the hydrocarbyl group.

[0072] 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.

EXAMPLES

[0073] The invention will be further illustrated by the following examples, which set forth particularly advantageous embodiments. While the examples are provided to illustrate the present invention, they are not intended to limit it.

[0074] Five example lubricants (Examples 1 to 5) are prepared using a formulation designed to meet ACEA C3-08 specifications. Each example was formulated to have a HTHS value of at or above 3.5 cP and a kinematic viscosity at lOOC of about 1 1.7 cSt. All of the lubricants use Yubase Group III base oils in combination with Nexbase PAO Group IV base oil in a ratio of about 85 : 15 by ratio. All five lubricants include the same additive package, which designed to provide a lubricant that meets the specifications listed above. The additive package (including the viscosity modifier) is present in each example at 28 percent by weight of the overall composition. Each example, except for a baseline, is then treated with 0.5% or 0.25%> by weight of a unique friction modifier additive. The balance of each of the examples is the base oil mixture described above. The formulations of the examples are summarized in the table below.

Table I - Example Formulations

[0075] The samples are evaluated using the HFRR test, which is a standard industry test for wear. The test employs apparatus as described in ASTM D- 6079. The test measures the coefficient of friction provided by the lubricant under the testing conditions, while ramping the temperature from 40 to 160 C. The results of the testing are summarized in the table below: Table II - HFRR Results

[0076] The results show that the compositions of the present invention provide unexpected improvement in the wear performance of the lubricating compositions compared to the same compositions without the friction modifier additive as well as the same compositions that contain different friction modifier additives. The inventive example has a smaller average wear scar and a lower average coefficient of friction than any of the other examples.

[0077] The examples are also evaluated using the MTM (mini-traction machine) test, which is used to measure traction and friction over a range of loads and speeds. The test is completed with 36 Newtons of load, a speed of 3000 to 10 mm/s, 50% slide to roll ratio, under isothermal conditions at 40, 60, 80, 100, 120 and 140 C. Lower results indicate better performance. The tables below summarize the results with Table III-3 providing the results at low speed. Table III-l - MTM Results at 2000 mm/s

Table III-2 - MTM Results at 200 mm/s

Table III-3 - MTM Results at 20 mm/s

[0078] The results show that at low speeds (boundary lubrication conditions) and high temperatures (specifically 120C and HOC) the compositions described herein provide a significant reduction in traction coefficient compared to both the baseline and the fully formulated compositions that use different friction modifiers.

[0079] Each of the documents referred to above is incorporated herein by reference. 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." 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. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression "consisting essentially of permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration.

Claims

What is claimed is: 1. A lubricant composition comprising

(a) an oil of lubricating viscosity;

(b) an alkoxy or hydroxy substituted butane dioic imide friction modifier wherein the friction modifier is represented by formula I;

wherein R¹ is hydrocarbyl group containing from 8 to 30 carbon atoms; R² is -H or a hydrocarbyl group; Y is -H, -OH or -OR² with the proviso that when Y is - OR² the two R² groups may be linked to form a ring.

2. The lubricant composition of claim 1 wherein the composition is a low- sulfur, low-phosphorus and low-ash lubricant suitable for use in an internal combustion engine; and wherein the oil of lubricating viscosity is a high temperature high shear fluid.

3. The lubricant composition of claim 1 wherein the lubricant composition is a high temperature high shear fluid having a dynamic viscosity of at least 3.5 cP.

4. The composition of claim 1 wherein component (b) is derived from a material represented by formula II and an amine containing from 8 to 30 carbon atoms;

5. The composition of claim 4 wherein the amine comprises a linear amine containing from 16 to 20 carbon atoms.

6. The composition of claim 1 further comprising an additional friction modifier other than component (b), an overbased detergent, or combinations thereof.

7. The composition of claim 1 wherein component (b) comprises oleyl tartrimide.

8. A method of lubricating an engine comprising the steps of:

I. supplying to the engine a lubricant composition comprising: (a) an oil of lubricating viscosity; (b) an alkoxy or hydroxy substituted butane dioic imide friction modifier wherein the friction modifier is represented by formula

wherein R¹ is hydrocarbyl group containing from 8 to 24 carbon atoms; R² is a hydrocarbyl group; Y is -H, -OH or -OR² with the proviso that when Y is -OR² the two R² groups may be linked to form a ring.

9. The method of claim 8 wherein the engine is present in an automobile wherein the automobile meets Euro 4 and Euro 5 standards.

10. The method of claim 8 wherein the lubricant composition is a low-sulfur, low-phosphorus and low-ash lubricant suitable for use in an internal combustion engine; and wherein the oil of lubricating viscosity is a high temperature high shear fluid.

1 1. The method of claim 8 wherein the lubricant composition is a high temperature high shear fluid having a dynamic viscosity of at least 3.5 cP.

12. The method of claim 8 wherein component (b) is derived from a material represented by formula II and an amine containing from 8 to 30 carbon atoms;

13. The method of claim 12 wherein the amine comprises a linear amine containing from 16 to 20 carbon atoms.

14. The method of claim 8 wherein the lubricant composition further comprises an additional friction modifier other than component (b), an overbased detergent, or combinations thereof.

15. The method of claim 8 wherein component (b) comprises oleyl tartrim- ide.