Patent Description:
Market demands are driving lubricating fluids towards lower viscosities in an effort to minimize energy losses due to mechanical operations. At lower viscosities it becomes increasingly difficult to achieve the performance requisite of driveline and industrial lubricants. For example, the removal of viscosity modifier to achieve lower viscosity fluids can be detrimental to thermal stability as well as traction performance. New solutions are needed to address these problems.

<CIT> discloses a process, comprising: a) selecting an API Group II base stock with selected viscosity index and pour point; b) blending a base oil with the base stock, and c) adding to the base oil: i) a liquid ethylene propylene copolymer viscosity modifier, and ii) an additive package, to make a driveline fluid that has a defined viscosity index and shear stability. Also disclosed in <CIT> is a driveline fluid composition having the high viscosity index and excellent shear stability, comprising: a) a base oil comprising from <NUM> wt% to <NUM> wt% API Group II base stock; b) a liquid ethylene propylene copolymer viscosity modifier; and c) an additive package.

The disclosed technology, therefore, solves the problem of providing an improved combination of clean operation with minimized viscosity increase along with reductions in traction and friction and improved efficiency performance by combining two types of viscosity modifiers along with optional esters.

One aspect of the technology disclosed herein is directed to a lubricant composition containing a) a hydrocarbon lubricating base stock, and b) a viscosity modifier composition.

The viscosity modifier composition itself will contain i) at least one olefin polymer having a number average molecular weight ("Mn") as measured by Gel Permeation Chromatography ("GPC") with a polystyrene standard of <NUM> to <NUM>,<NUM>, and ii) at least one grafted olefin polymer having an Mn as measured by GPC with a polystyrene standard of <NUM> to <NUM>,<NUM>, comprising carboxylic acid functionality or a reactive equivalent thereof grafted onto the polymer backbone, wherein the carboxylic acid functionality or reactive equivalent thereof is further reacted with an amine.

The lubricant composition can additionally contain a carboxylic acid ester. The carboxylic acid ester can be, for example, a carboxylic acid mono-ester, a dicarboxylic acid di-ester, or a combination thereof.

The technology also provides a method of lubricating a driveline device or an industrial gear with a composition as described, and operating the driveline device or industrial gear.

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

One component of the disclosed technology is a hydrocarbon lubricating base stock. Such oils include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined and re-refined oils and mixtures thereof.

Unrefined oils are those obtained directly from a natural or synthetic source generally without (or with little) further purification treatment. 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. Purification techniques are known in the art and include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation and the like. Re-refined oils are also known as reclaimed or reprocessed oils, and are obtained by processes similar to those used to obtain refined oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

Natural oils useful in making the inventive lubricants include mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types and oils derived from coal or shale or mixtures thereof.

Synthetic hydrocarbon lubricating oils suitable for use include Group IV oils or polyalpha olefins (PAO). Group IV oils include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene-isobutylene polymers); poly(<NUM>-hexenes), poly(<NUM>-octenes), poly(<NUM>-decenes), and mixtures thereof.

Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines (<NUM>). The base oil groups suitable for use include Group II and Group II+, Group III and Group III+,and Group IV oils. Group II and Group III oils have a sulfur content ≤<NUM> wt %, and ≥<NUM> wt % saturates. Group II oils have a viscosity index <NUM> to less than <NUM>, while Group III oils have a viscosity index ≥<NUM>. Group II+ base oil refers to a API Group II base oil having a viscosity index greater than or equal to <NUM> and less than <NUM>, as described in <NPL>, as well as in <CIT>, column <NUM> line <NUM>. Group III+ base oil are characterized by having significantly lower cycloparaffinic content and higher isoparaffinic oil relative to the corresponding Group III base oils, resulting in an increase in VI in the III+ oil relative to the III oil by <NUM> to <NUM> units. Group III+ base oils encompass wax isomerates, such as gas-to-liquid ("GTL") oils which include oils produced by Fischer-Tropsch reactions as well as other GTL oils. Group IV oils include all polyalphaolefins (PAOs).

The hydrocarbon lubricating base stock may be an API Group IV oil, or mixtures thereof, i.e., a polyalphaolefin. The polyalphaolefin may be prepared by metallocene catalyzed processes or from a non-metallocene process.

The hydrocarbon lubricating base stock may comprise an API Group II oil, or mixtures thereof. The hydrocarbon lubricating base stock may comprise an API Group II+ oil, or mixtures thereof. The hydrocarbon lubricating base stock can also be a Group III oil, or mixtures thereof. The hydrocarbon lubricating base stock may comprise an API Group III+ oil, or mixtures thereof. The hydrocarbon lubricating base stock can also be a Group IV oil, or mixtures thereof. The hydrocarbon lubricating base stock may comprise a mixture of at least two of an API Group II oil, Group II+ oil, API Group III oil, Group III+ oil, and API Group IV oil.

The hydrocarbon lubricating base stock, or base oil, will overall have a kinematic viscosity at <NUM> of <NUM> to <NUM> cSt or, in some embodiments <NUM> to <NUM> or <NUM> to <NUM> or <NUM> or <NUM> cSt, as measured by ASTM D445. Kinematic viscosities for the base oil at <NUM> or from about <NUM> to <NUM> or from <NUM> to <NUM> cSt are also suitable.

The amount of the hydrocarbon lubricating base stock present is typically the balance remaining after subtracting from <NUM> wt % the sum of the amount of the performance additives in the composition. Illustrative amounts may include <NUM> to <NUM> percent by weight, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> percent.

The technology also includes a viscosity modifier composition combining i) an olefin polymer, and ii) a grafted olefin polymer. As used herein, the term "a," or "an," as in "a" viscosity modifier, or "an" olefin polymer, is not limited to just one of the stated elements, but is used to mean "at least one," which includes one or more of the stated elements, as well as two or more, three or more and so on.

The olefin polymer may be prepared from ethylene and propylene or it may be prepared from ethylene and a higher olefin within the range of C<NUM>-C<NUM> alpha-monoolefins. In certain embodiments, the olefin polymer may be prepared from isobutylene or isoprene.

More complex polymer substrates, often designated as interpolymers, may be prepared using a third component. The third component generally used to prepare an interpolymer substrate may be a polyene monomer selected from conjugated or non-conjugated dienes and trienes. The non-conjugated diene component may be one having from about <NUM> to about <NUM> carbon atoms. The diene monomer may be characterized by the presence of a vinyl group in its structure and can include cyclic and bicyclo compounds. Representative dienes include <NUM>,<NUM>-hexadiene, <NUM>,<NUM>-cyclohexadiene, dicyclopentadiene, <NUM>-ethylidene-<NUM>-norbornene, <NUM>-methylene-<NUM>-norbornene, <NUM>,<NUM>-heptadiene, and <NUM>,<NUM>-octadiene. A mixture of more than one diene can be used in the preparation of the interpolymer.

A triene component may also be present, which will have at least two non-conjugated double bonds and up to about <NUM> carbon atoms. Typical trienes include <NUM>-isopropylidene-3a,<NUM>,<NUM>,7a-tetrahydroindene, <NUM>-isopropylidenedicyclopentadiene, and <NUM>-(<NUM>-methylene-<NUM>-methyl-<NUM>-pentenyl)-[<NUM>. <NUM>] bicyclo-<NUM>-heptene.

Suitable backbone polymers of the olefin polymer variety include ethylene propylene polymers, ethylene-propylene-alpha olefin terpolymers, ethylene-alpha olefin polymers, ethylene propylene polymers further containing a non-conjugated diene, and isobutylene/conjugated diene polymers.

Ethylene-propylene or higher alpha monoolefin polymers may consist of <NUM> to <NUM> mole % ethylene and <NUM> to <NUM> mole % propylene or higher monoolefin, in some embodiments, the mole ratios being <NUM> to <NUM> mole % ethylene and <NUM> to <NUM> mole % of at least one C<NUM> to C<NUM> alpha monoolefin, for example, <NUM> to <NUM> mole % ethylene and <NUM> to <NUM> mole % propylene. In another embodiment, the ethylene-propylene or higher alpha monoolefin polymers may consist of <NUM> to <NUM> mole % propylene and <NUM> to <NUM> mole % ethylene or higher monoolefin, in some embodiments, the mole ratios being <NUM> to <NUM> mole % propylene and <NUM> to <NUM> mole % of at least one C<NUM> to C<NUM> alpha monoolefin, for example, <NUM> to <NUM> mole % propylene and <NUM> to <NUM> mole % ethylene, or <NUM> to <NUM> mole % propylene and <NUM> to <NUM> mole % ethylene. Terpolymer variations of the foregoing polymers may contain up to <NUM> mole % of a non-conjugated diene or triene.

In these embodiments, the polymer substrate, such as the ethylene polymer or terpolymer, can be substantially linear and oil-soluble, and is, in an embodiment, a liquid. Also, in certain embodiments the polymer can be in forms other than substantially linear, that is, it can be a branched polymer or a star polymer. The polymer can also be a random polymer or a block polymer, including di-blocks and higher blocks, including tapered blocks and a variety of other structures. These types of polymer structures are known in the art and their preparation is within the abilities of the person skilled in the art.

The term polymer is used generically to encompass ethylene and/or higher alpha monoolefin polymers, copolymers, terpolymers or interpolymers. These materials may contain minor amounts of other olefinic monomers so long as their basic characteristics are not materially changed.

The olefin polymer of the disclosed technology may have a number average molecular weight (by gel permeation chromatography, polystyrene standard), which can typically be about <NUM> to about <NUM>,<NUM>, or about <NUM> to about <NUM>, or about <NUM> to about <NUM>, or about <NUM> to about <NUM>, or about <NUM> to about <NUM>, or about <NUM> to about <NUM> or <NUM>, or even about <NUM> to about <NUM>, or about <NUM> to about <NUM>. In some cases the number average molecular weight can be from about <NUM> to <NUM>, or from about <NUM> or <NUM> to about <NUM>.

Another component is a grafted copolymer that is a condensation reaction product of an olefin polymer having carboxylic acid (or equivalent) functionality grafted thereon, the grafted olefin reacted with a monoamine or a polyamine which may have a single primary amino group. If the olefin polymer is an ethylene/propylene copolymer, then said polyamine is not a poly(ethylene amine).

The polymer substrate will be an olefin polymer such as that described above. The olefin polymer substrate employed in the derivatized graft copolymer will contain grafted carboxylic acid functionality or a reactive equivalent of carboxylic acid functionality (e.g., anhydride or ester). The reactive carboxylic acid functionality will typically be present as a pendant group attached by, for instance, a grafting process.

An ethylenically unsaturated carboxylic acid material is typically radically grafted onto the polymer backbone. These materials which are attached to the polymer typically contain at least one ethylenic bond (prior to reaction) and at least one, such as two, carboxylic acid (or its anhydride) groups or a polar group which is convertible into said carboxyl groups by oxidation or hydrolysis. Maleic anhydride or a derivative thereof is suitable. It grafts onto the olefin polymer, (e.g., ethylene copolymer or terpolymer) to give two carboxylic acid functionalities. Examples of additional unsaturated carboxylic materials include maleic anhydride, itaconic anhydride, or the corresponding dicarboxylic acids, such as maleic acid, fumaric acid and their esters, as well as cinnamic acid and esters thereof.

The ethylenically unsaturated carboxylic acid material may be radically grafted onto the polymer (such as the ethylene/propylene copolymer). The free-radical induced grafting of ethylenically unsaturated carboxylic acid materials may also be conducted in solvents, such as hexane or mineral oil. It may be carried out at an elevated temperature in the range of <NUM> to <NUM> , e.g., <NUM> to <NUM>, or <NUM> to <NUM>, e.g., above <NUM>.

The free-radical initiators which may be used include peroxides, hydroperoxides, and azo compounds, typically those which have a boiling point greater than about <NUM> and which decompose thermally within the grafting temperature range to provide free radicals. Representative of these free-radical initiators include azobisisobutyronitrile and <NUM>,<NUM>-dimethyl-hex-<NUM>-yne-<NUM>,<NUM>-bis-tertiary-butyl peroxide. The initiator may be used in an amount of <NUM>% to <NUM>% by weight based on the weight of the reaction mixture solution. The grafting may be carried out in an inert atmosphere, such as under nitrogen blanketing. The resulting polymer intermediate is characterized by having carboxylic acid acylating functions within its structure.

In an alternative embodiment, the unsaturated carboxylic acid material, such as maleic anhydride, can be first condensed with a monoamine or polyamine, typically having a single primary amino group (described below) and the condensation product itself then grafted onto the polymer backbone in analogous fashion to that described above.

The amount of the reactive carboxylic acid on the polymer chain, and in particular the amount of grafted carboxylic acid on the chain is typically <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, or <NUM> to <NUM> weight percent, based on the weight of the polymer backbone, or in some embodiments <NUM> to <NUM> weight percent. In some embodiments the amount of the reactive carboxylic acid on the polymer chain, and in particular the amount of grafted carboxylic acid on the chain can be from about <NUM> to about <NUM>, or in other embodiments from about <NUM> to <NUM>, or from about <NUM> to <NUM> weight percent or <NUM> to <NUM> weight percent. These numbers represent the amount of carboxyl-containing species with particular reference to maleic anhydride as the graft material. The amounts may be adjusted to account for carboxyl-containing species having higher or lower molecular weights or greater or lesser amounts of acid functionality per molecule, as will be apparent to the person skilled in the art. The grafting may be of an extent to provide an acid functionalized polymer having a total acid number (TAN per ASTM D664) of <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or about <NUM> to about <NUM> or <NUM> mgKOH/g.

The acid-containing polymer is reacted with a monoamine or a polyamine typically having a single primary amino group. If the olefin polymer is an ethylene/propylene copolymer, then said polyamine is not a poly(ethyleneamine). The reaction may consist of condensation to form an imide, amide, or half-amide or amide-ester (assuming a portion of alcohol is also reacted) or an amine salt. A primary amino group will typically condense to form an amide or, in the case of maleic anhydride, an imide. It is noted that in certain embodiments the amine will have a single primary amino group, that is, it will not have two or more primary amino groups (except perhaps a very small an inconsequential amount of additional primary amino groups within the entire amine component, e.g., less than <NUM>% or <NUM>% or <NUM>% or <NUM>%, or <NUM> to <NUM>%, especially <NUM>% or less, such as <NUM> to <NUM>%, of amine groups being primary). This feature will minimize the amount of crosslinking that might otherwise occur. Poly(ethyleneamine)s may generally, and in an oversimplified manner, be depicted as H<NUM>N-(C<NUM>H<NUM>-NH-)n-C<NUM>H<NUM>-NH<NUM>, where n may be, for instance, <NUM> through <NUM>. These typically have on average about <NUM> primary amino groups, so their use is typically undesirable for functionalization of ethylene/propylene copolymers, so that any undesirable crosslinking may be minimized or avoided. In those embodiments in which the polyamine is not a poly(ethyleneamine), the amine component employed to make the condensation product will be free of or substantially free of poly(ethyleneamine), such as less than <NUM> percent by weight of the amine component is poly(ethyleneamine), or less than <NUM> percent, or <NUM> to <NUM> percent by weight.

Suitable primary amines may include aromatic amines, such as amines wherein a carbon atom of the aromatic ring structure is attached directly to the amino nitrogen. The amines may be monoamines or polyamines. The aromatic ring will typically be a mononuclear aromatic ring (i.e., one derived from benzene) but can include fused aromatic rings, such as those derived from naphthalene. Examples of aromatic amines include aniline, N-alkylanilines such as N-methylaniline, and N-butylaniline, di-(para-methylphenyl)amine, naphthylamine, <NUM>-aminodiphenylamine, N,N-dimethylphenylenediamine, <NUM>-(<NUM>-nitrophenylazo)aniline (disperse orange <NUM>), sulfamethazine, <NUM>-phenoxyaniline, <NUM>-nitroaniline, <NUM>-aminoacetanilide, <NUM>-amino-<NUM>-hydroxy-benzoic acid phenyl ester (phenyl amino salicylate), N-(<NUM>-amino-<NUM>-methoxy-<NUM>-methyl-phenyl)-benzamide (fast violet B), N-(<NUM>-amino-<NUM>,<NUM>-dimethoxy-phenyl)-benzamide (fast blue RR), N-(<NUM>-amino-<NUM>,<NUM>-diethoxy-phenyl)-benzamide (fast blue BB), N-(<NUM>-amino-phenyl)-benzamide and <NUM>-phenylazoaniline. Other examples include para-ethoxyaniline, para-dodecylaniline, cyclohexyl-substituted naphthylamine, and thienyl-substituted aniline. Examples of other suitable aromatic amines include amino-substituted aromatic compounds and amines in which an amine nitrogen is a part of an aromatic ring, such as <NUM>-aminoquinoline, <NUM>-aminoquinoline, and <NUM>-aminoquinoline. Also included are aromatic amines such as <NUM>-aminobenzimidazole, which contains one secondary amino group attached directly to the aromatic ring and a primary amino group attached to the imidazole ring. Other amines include N-(<NUM>-anilinophenyl)-<NUM>-aminobutanamide (i.e., φ-NH-φ-NH-COCH<NUM>CH(CH<NUM>)NH<NUM>). Additional aromatic amines include aminocarbazoles, aminoindoles, aminopyrroles, aminoindazolinones, aminoperimidines, mercaptotriazoles, aminophenothiazines, aminopyridines, aminopyrazines, aminopyrimidines, pyridines, pyrazines, pyrimidines, aminothiadiazoles, aminothiothiadiazoles, and aminobenzotriaozles. Other suitable amines include <NUM>-amino-N-(<NUM>-anilinophenyl)-N-isopropyl butanamide, and N-(<NUM>-anilinophenyl)-<NUM>-{(<NUM>-aminopropyl)-(cocoalkyl)amino} butanamide. Other aromatic amines which can be used include various aromatic amine dye intermediates containing multiple aromatic rings linked by, for example, amide structures. Examples include materials of the general structure φ-CONH-φ-NH<NUM> where the phenyl groups may be substituted. Suitable aromatic amines include those in which the amine nitrogen is a substituent on an aromatic carboxylic compound, that is, the nitrogen is not sp<NUM> hybridized within an aromatic ring.

The amine may also be non-aromatic, or in other words, an amine in which an amino nitrogen is not attached directly to a carbon atom of an aromatic ring, or in which an amine nitrogen is not a part of an aromatic ring, or in which an amine nitrogen is not a substituent on an aromatic carboxylic compound. In some instances such non-aromatic amines may be considered to be aliphatic, or cycloaliphatic. Such amines may be straight, or branched or functionalized with some functional group. The non-aromatic amines can include monoamines having, e.g., <NUM> to <NUM> carbon atoms, such as methylamine, ethylamine, and propylamine, as well as various higher amines. Diamines or polyamines can also be used, and typically will have only a single primary amino group. Examples include dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, dimethylaminoethylamine, diethylaminoethylamine, dibutylaminoethylamine, <NUM>-(<NUM>-aminoethyl)piperidine, <NUM>-(<NUM>-aminoethyl)pyrrolidone, N,N-dimethylethylamine; <NUM>-(dimethylamino)-<NUM>-propylamine; O-(<NUM>-aminopropyl)-O'-(<NUM>-methoxyethyl)polypropylene glycol; N,N-dimethyldipropylenetriamine, aminoethylmorpholine, <NUM>-morpholinopropylamine; aminoethylethyleneurea and aminopropylmorpholine.

In certain embodiments non-aromatic amines can be used alone or in combination with each other or in combination with aromatic amines. The amount of aromatic amine may, in some embodiments, be a minor amount compared with the amount of the non-aromatic amines, or in some instance, the composition may be substantially free or free of aromatic amine.

In certain embodiments the grafted olefin polymer may have a nitrogen content, calculated using ASTM D5291, of <NUM> to <NUM> percent by weight, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> percent by weight.

The olefin polymer and the grafted olefin polymer can be added to the lubricant composition in amounts to achieve the desired viscosity grade.

In general, the amount of the olefin polymer may be <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> percent by weight, or <NUM> to <NUM> percent by weight of the lubricant composition or may be <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> percent by weight, or <NUM> to <NUM> percent by weight of the lubricant composition.

In general, the amount of the grafted olefin polymer may be <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM> percent by weight, or <NUM> to <NUM> percent by weight of the lubricant composition.

In an embodiment, the lubricant composition may contain from <NUM> to <NUM> percent by weight olefin polymer and <NUM> to <NUM> percent by weight grafted olefin polymer. In an embodiment, the lubricant composition may contain from <NUM> to <NUM> percent by weight olefin polymer and <NUM> to <NUM> percent by weight grafted olefin polymer. In an embodiment, the lubricant composition may contain from <NUM> to <NUM> percent by weight olefin polymer and <NUM> to <NUM> percent by weight grafted olefin polymer. In an embodiment, the lubricant composition may contain from <NUM> to <NUM> percent by weight olefin polymer and <NUM> to <NUM> percent by weight grafted olefin polymer. In an embodiment, the lubricant composition may contain from <NUM> to <NUM> percent by weight olefin polymer and <NUM> to <NUM> percent by weight grafted olefin polymer.

In any event, the olefin polymer and the grafted olefin polymer can be in the composition at a ratio of between about <NUM>/<NUM> wt% to about <NUM>/<NUM> wt%. In some embodiments, the olefin polymer and the grafted olefin polymer can be in the composition at a ratio of between about <NUM>/<NUM> wt% to about <NUM>/<NUM> wt%. In some embodiments, the olefin polymer and the grafted olefin polymer can be in the composition at a ratio of between about <NUM>/<NUM> wt% to about <NUM>/<NUM> wt%.

The lubricating composition may optionally include at least one carboxylic acid ester, either in the form of a carboxylic acid mono-ester or mixtures thereof, dicarboxylic acid di-ester or mixtures thereof, or a combination of carboxylic acid mono-ester or mixtures thereof and dicarboxylic acid di-ester and mixtures thereof.

The carboxylic acid-mono-ester is a molecule having a formula RC(O)OR', where RC(O)O- represents the carboxylic acid moiety and R' represents a hydrocarbyl group.

The R group of the carboxylic acid moiety, RC(O)O-, of the carboxylic acid mono-ester can be a C<NUM> to C<NUM> linear or branched hydrocarbyl group. In some embodiments, the R group of the carboxylic acid moiety of the carboxylic acid mono-ester can be a C<NUM> to C<NUM>, or a C<NUM> to C<NUM> linear or branched hydrocarbyl group. The hydrocarbyl group can, in some embodiments, include heteroatoms, but in many instances the hydrocarbyl group will be an alkyl group. Thus, in some embodiments, the R group of the carboxylic acid moiety of the carboxylic acid mono-ester can be a C<NUM> to C<NUM>, C<NUM> to C<NUM>, or a C<NUM> to C<NUM> or even a Cs to C<NUM> linear or branched alkyl group.

Carboxylic acid from which the RC(O)O- moiety may be derived include, but are not limited to, for example, lauric acid, tallow acid, oleic acid, palmitic acid, and the like. Thus, the carboxylic acid mono-ester may be, for example, a lauric acid mono-ester, tallow acid mono-ester, oleic acid mono-ester, palmitic acid mono ester, and combinations thereof.

The hydrocarbyl group, R', of the carboxylic acid mono-ester can be C<NUM> to C<NUM> linear or branched alkyl moiety. Alkyl moieties envisaged include, but are not limited to, for example, a hexyl moiety, ethylhexyl moiety, methylpentyl moiety, ethylpentyl moiety, dimethylhexyl moiety, ethylmethylhexyl moiety and the like.

In an embodiment, the carboxylic acid mono-ester may be, for example, <NUM>-ethylhexyl tallate, <NUM>-ethylhexyl oleate, <NUM>-ethylhexyl laurate, <NUM>-ethylhexyl palmitate, and combinations thereof.

The carboxylic acid mono-ester may be present in the lubricant composition at from about <NUM> or <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM>, or about <NUM> to about <NUM> wt. %, or even from about <NUM> to about <NUM> wt. % or about <NUM> to <NUM> wt.

The dicarboxylic acid di-ester is a molecule having a formula R'O(O)CRC(O)OR', where -O(O)CRC(O)O- represents the dicarboxylic acid moiety and each R' represents a hydrocarbyl group.

The R group of the dicarboxylic acid moiety, -O(O)CRC(O)O-, of the dicarboxylic acid di-ester can be a C<NUM> to C<NUM> or C<NUM> to C<NUM> linear or branched hydrocarbyl group. The hydrocarbyl group can, in some embodiments, include heteroatoms, but in many instances the hydrocarbyl group will be an alkyl group. Thus, in some embodiments, the R group of the carboxylic acid moiety of the carboxylic acid mono-ester can be a C<NUM> to C<NUM>, or a C<NUM> to C<NUM> linear or branched alkyl group.

Dicarboxylic acid from which the -O(O)CRC(O)O- moiety may be derived include, but are not limited to, for example, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Thus, the dicarboxylic acid di-ester may be, for example, a glutaric acid di-ester, adipic acid di-ester, azelaic acid di-ester, sebacic acid di-ester, and combinations thereof.

The hydrocarbyl groups, R', of the dicarboxylic acid di-ester can be C<NUM> to C<NUM> linear or branched alkyl moieties. Alkyl moieties envisaged include, but are not limited to, for example, a hexyl moiety, ethylhexyl moiety, methylpentyl moiety, ethylpentyl moiety, dimethylhexyl moiety, ethylmethylhexyl moiety and the like.

In an embodiment, the dicarboxylic acid di-ester may be, for example, di-<NUM>-ethylhexyl azelate, di-isotridecyl adipate, di-isooctyl adipate, and combinations thereof.

The dicarboxylic acid di-ester may be present in the lubricant composition at from about <NUM> or <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM>, or about <NUM> to about <NUM> wt. %, or even from about <NUM> to about <NUM> wt. or about <NUM> to <NUM> wt.

The total amount of carboxylic acid mono-ester and dicarboxylic acid di-ester may be from <NUM> or <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM>, or about <NUM> to about <NUM> wt. %, or even from about <NUM> to about <NUM> wt. or about <NUM> to <NUM> wt. %, or <NUM> to <NUM> wt.

The ratio of carboxylic acid mono-ester to dicarboxylic acid di-ester may be from <NUM> wt. %:<NUM> wt. % to <NUM> wt. %:<NUM> wt. %, or <NUM> wt. %:<NUM> wt. % to <NUM> wt. %:<NUM> wt. %, or even <NUM> wt. %:<NUM> wt. % to <NUM> wt. %:<NUM> wt. In embodiments, the ratio of carboxylic acid mono-ester to dicarboxylic acid di-ester may be from <NUM> wt. %:<NUM> wt. % to <NUM> wt. %:<NUM> wt. %, or even <NUM> wt. %:<NUM> wt. % to <NUM> wt. %:<NUM> wt. %, or some cases even <NUM> wt. %:<NUM> wt.

The lubricant composition can be employed in either driveline applications or in industrial gear applications. As a driveline lubricant, the lubricant composition can contain other additives typically used in driveline applications, including, for example, detergents, dispersants, extreme pressure agents, friction modifiers, antiwear agents, corrosion inhibitors, viscosity modifiers, anti-oxidants, oil-soluble titanium compounds, metal alkylthiophosphate, organo-sulfides, including polysulfides, such as sulfurized olefins, thiadiazoles and thiadiazole adducts such as post treated dispersants.

The organo-sulfide can be present in a range of <NUM> wt % to <NUM> wt %, <NUM> wt % to <NUM> wt %, <NUM> wt % to <NUM> wt %, <NUM> wt % to <NUM> wt %, <NUM> wt % to <NUM> wt %, or <NUM> wt % to <NUM> wt % of the lubricating composition.

The organosulfide may alternatively be a polysulfide. In one embodiment at least about <NUM> wt % of the polysulfide molecules are a mixture of tri- or tetra-sulfides. In other embodiments at least about <NUM> wt %, or at least about <NUM> wt % of the polysulfide molecules are a mixture of tri- or tetra-sulfides. The polysulfides include sulfurized organic polysulfides from oils, fatty acids or ester, olefins or polyolefins.

Oils which may be sulfurized include natural or synthetic oils such as mineral oils, lard oil, carboxylate esters derived from aliphatic alcohols and fatty acids or aliphatic carboxylic acids (e.g., myristyl oleate and oleyl oleate), and synthetic unsaturated esters or glycerides.

Fatty acids include those that contain <NUM> to <NUM>, or <NUM> to <NUM> carbon atoms. Examples of fatty acids include oleic, linoleic, linolenic, and tall oil. Sulfurized fatty acid esters prepared from mixed unsaturated fatty acid esters such as are obtained from animal fats and vegetable oils, including tall oil, linseed oil, soybean oil, rapeseed oil, and fish oil.

The polysulfide may also be derived from an olefin derived from a wide range of alkenes, typically having one or more double bonds. The olefins in one embodiment contain <NUM> to <NUM> carbon atoms. In other embodiments, olefins contain <NUM> to <NUM>, or <NUM> to <NUM> carbon atoms. In one embodiment the sulfurized olefin includes an olefin derived from propylene, isobutylene, pentene, or mixtures thereof. In one embodiment the polysulfide comprises a polyolefin derived from polymerizing, by known techniques, an olefin as described above. In one embodiment the polysulfide includes dibutyl tetrasulfide, sulfurized methyl ester of oleic acid, sulfurized alkylphenol, sulfurized dipentene, sulfurized dicyclopentadiene, sulfurized terpene, and sulfurized Diels-Alder adducts; phosphosulfurized hydrocarbons.

Examples of a thiadiazole include <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole, or oligomers thereof, a hydrocarbyl-substituted <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole, a hydrocarbylthio-substituted <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole, or oligomers thereof. The oligomers of hydrocarbyl-substituted <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole typically form by forming a sulfur-sulfur bond between <NUM>,<NUM>-dimercapto-<NUM>,<NUM>,<NUM>-thiadiazole units to form oligomers of two or more of said thiadiazole units. Further examples of thiadiazole compounds are found in <CIT>, paragraphs <NUM> through <NUM>.

In an embodiment, the lubricant composition can have a total sulfur level from all additives (i.e., not including base oil) of about <NUM> or <NUM> to about <NUM> wt. %, or from about <NUM> or <NUM> to about <NUM> wt. % or from about <NUM> or <NUM> to about <NUM> wt. In another embodiment, the lubricant composition can have a total sulfur level from all additives (i.e., not including base oil) of about <NUM> to about <NUM> wt%, or from about <NUM> to about <NUM> wt.

In an embodiment, the lubricant composition can be substantially free, or free of sulfurized olefin.

Lubricant compositions for automotive gears, axles, and bearings can be distinguished from other lubricant compositions, such as those for engine oils, by the presence of non-metal phosphorous containing compounds. The lubricant composition described herein will contain just such a non-metal phosphorous containing compound. Such compounds can include, for example, phosphorous amine salts, sulfur containing phosphorous amine salts, phosphites, phosphonates, sulfur containing phosphites, sulfur containing phosphonates, and non-metal dithiophosphates. Such compounds can bring to the lubricant composition, alone or in combination, a total phosphorus level of about <NUM> to about <NUM> wt. %, or <NUM> to about <NUM> wt. %, or even about <NUM> to about <NUM> wt. %, or about <NUM> to about <NUM> wt. %, or about <NUM> to about <NUM> wt. %, or about <NUM> to about <NUM> wt.

The phosphorous amine salt can be an amine salt of one or more of the following: phosphorus acid esters, dialkyldithiophosphoric acid esters, phosphites, phosphonates, and mixtures thereof. The amine salt of the phosphorus acid ester may comprise any of a variety of chemical structures. In particular, a variety of structures are possible when the phosphorus acid ester compound contains one or more sulfur atoms, that is, when the phosphorus-containing acid is a thiophosphorus acid ester, including mono- or dithiophosphorus acid esters. A phosphorus acid ester may be prepared by reacting a phosphorus compound such as phosphorus pentoxide with an alcohol. Suitable alcohols include those containing up to <NUM> or to <NUM>, or to <NUM> carbon atoms, including primary or secondary alcohols such as isopropyl, butyl, amyl, s-amyl, <NUM>-ethylhexyl, hexyl, cyclohexyl, octyl, decyl and oleyl alcohols, as well as any of a variety of commercial alcohol mixtures having, e.g., <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM> carbon atoms. Polyols such as diols may also be used. The amines which may be suitable for use as the amine salt include primary amines, secondary amines, tertiary amines, and mixtures thereof, including amines with at least one hydrocarbyl group, or, in certain embodiments, two or three hydrocarbyl groups having, e.g., <NUM> to <NUM> or <NUM> to <NUM> or <NUM> to <NUM> or <NUM> to <NUM> carbon atoms.

In one embodiment, the phosphorous amine salts can include, for example, a substantially sulfur-free alkyl phosphate amine salt having at least <NUM> mole percent of the phosphorus atoms in an alkyl pyrophosphate structure (sometimes referred to as the POP structure), as opposed to an orthophosphate (or monomeric phosphate) structure, as shown, for example, in the following formula R<NUM>O(O<NUM>)POP(O<NUM>)OR<NUM>•(R<NUM><NUM>)NH+, or variants thereof, where, each R<NUM> is independently an alkyl group of <NUM> to <NUM> carbon atoms, and each R<NUM> is independently hydrogen or a hydrocarbyl group or an ester-containing group, or an ether-containing group, provided that at least one R<NUM> group is a hydrocarbyl group or an ester-containing group or an ether-containing group (that is, not NH<NUM>).

Further phosphorous amine salts can be the amine salt of a phosphate hydrocarbon ester prepared by reaction between phosphorus pentoxide with an alcohol (having <NUM> to <NUM> carbon atoms), followed by a reaction with a primary (e.g., <NUM>-ethylhexylamine), secondary (e.g., dimethylamine), or tertiary (e.g., dimethyloleylamine) amine to form an amine salt of a phosphate hydrocarbon ester.

In one embodiment, sulfur containing amine phosphate salts may be prepared by reacting an alkylthiophosphate with an epoxide or a polyhydric alcohol, such as glycerol. This reaction product may be used alone, or further reacted with a phosphorus acid, anhydride, or lower ester. The epoxide is generally an aliphatic epoxide or a styrene oxide. Examples of useful epoxides include ethylene oxide, propylene oxide, butene oxide, octene oxide, dodecene oxide, styrene oxide, etc. Ethylene oxide and propylene oxide are preferred. The glycols may be aliphatic glycols having from <NUM> to about <NUM>, or from <NUM> to about <NUM>, or from <NUM> or <NUM> carbon atoms. Glycols include ethylene glycol, propylene glycol, and the like. The alkylthiophosphate, glycols, epoxides, inorganic phosphorus reagents and methods of reacting the same are described in <CIT> and <CIT>.

In some embodiments the non-metal phosphorus-containing compound can be a phosphite or a phosphonate. Suitable phosphites or phosphonates include those having at least one hydrocarbyl group with <NUM> or <NUM> or more, or <NUM> or more, or <NUM> or more, carbon atoms. The phosphite may be a mono-hydrocarbyl substituted phosphite, a di-hydrocarbyl substituted phosphite, or a tri-hydrocarbyl substituted phosphite. The phosphonate may be a mono-hydrocarbyl substituted phosphonate, a di-hydrocarbyl substituted phosphonate, or a tri-hydrocarbyl substituted phosphonate.

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

The phosphite or phosphonate may be represented by the formulae:
<CHM>
<CHM>
wherein at least one R may be a hydrocarbyl group containing at least <NUM> carbon atoms and the other R groups may be hydrogen. In one embodiment, two of the R groups are hydrocarbyl groups, and the third is hydrogen. In one embodiment every R group is a hydrocarbyl group, i.e., the phosphite is a tri-hydrocarbyl substituted phosphite. The hydrocarbyl groups may be alkyl, cycloalkyl, aryl, acyclic or mixtures thereof.

In the art, a phosphonate (i.e., formula XI with R = hydrocarbyl) may also be referred to as a phosphite ester. Where one of the R groups in formula XII is an H group, the compound would generally be considered a phosphite, but such a compound can often exist in between the tautomers of formula XI and XII, and thus, could also be referred to as a phosphonate or phosphite ester. For ease of reference, the term phosphite, as used herein, will be considered to encompass both phosphites and phosphonates.

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

In one embodiment, the other phosphorus-containing compound can be a C<NUM>-<NUM> hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R may independently be hydrogen or a hydrocarbyl group having <NUM> to <NUM>, or <NUM> to <NUM> carbon atoms, typically <NUM> carbon atoms. Typically the C<NUM>-<NUM> hydrocarbyl phosphite comprises dibutyl phosphite.

In one embodiment, the phosphorus-containing compound can be a C<NUM>-<NUM> hydrocarbyl phosphite, or mixtures thereof, i.e., wherein each R may independently be hydrogen or a hydrocarbyl group having <NUM> to <NUM>, or <NUM> to <NUM> carbon atoms, typically <NUM> to <NUM> carbon atoms. Typically the C<NUM>-<NUM> hydrocarbyl phosphite comprises a C<NUM>-<NUM> hydrocarbyl phosphite. Examples of alkyl groups for R<NUM>, R<NUM> and R<NUM> include octyl, <NUM>-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonadecyl, eicosyl or mixtures thereof.

In some embodiments, the other phosphorus containing compound can include both a C<NUM>-<NUM> and a C<NUM> to C<NUM> hydrocarbyl phosphite.

In one embodiment, the phosphite ester comprises the reaction product of (a) a monomeric phosphoric acid or an ester thereof with (b) at least two alkylene diols; a first alkylene diol (i) having two hydroxy groups in a <NUM>,<NUM> or <NUM>,<NUM> or <NUM>,<NUM> relationship; and a second alkylene diol(ii) being an alkyl-substitute <NUM>,<NUM>-propylene glycol.

Sulfur containing phosphites can include, for example, a material represented by the formula [R<NUM>O(OR<NUM>)(S)PSC<NUM>H<NUM>(C)(O)OR<NUM>O]nP(OR<NUM>)<NUM>-n(O)H, wherein R<NUM> and R<NUM> are each independently hydrocarbyl groups of <NUM> to <NUM> carbon atoms, or <NUM> to <NUM> carbon atoms, or wherein R<NUM> and R<NUM> together with the adjacent O and P atoms form a ring containing <NUM> to <NUM> carbon atoms; R<NUM> is an alkylene group of <NUM> to <NUM> carbon atoms or <NUM> to <NUM> carbon atoms; R<NUM> is hydrogen or a hydrocarbyl group of <NUM> to about <NUM> carbon atoms; and n is <NUM> or <NUM>.

In one embodiment, the other phosphorus containing compound can be a phosphorus containing amide. Phosphorus containing amides can be prepared by reaction of dithiophosphoric acid with an unsaturated amide. Examples of unsaturated amides include acrylamide, N,N'-methylene bisacrylamide, methacrylamide, crotonamide and the like. The reaction product of the phosphorus acid and the unsaturated amide may be further reacted with a linking or a coupling compound, such as formaldehyde or paraformaldehyde. The phosphorus containing amides are known in the art and are disclosed in <CIT>, <CIT> and <CIT> which are incorporated by reference for their disclosures of phosphorus amides and their preparation.

The phosphorus containing compound can also be a dithiophosphate ester can be formed by reaction of a dithiophosphoric acid represented by (RO)<NUM>PSSH with an unsaturated compound. In one embodiment, the unsaturated compounds is an unsaturated carboxylic acid or ester. Examples of unsaturated carboxylic acids or anhydrides include acrylic acids or esters, methacrylate acid or esters, itaconic acid or ester, fumaric acid or esters, and maleic acid, anhydride, or esters.

Other materials may be present in the lubricant composition in their conventional amounts including, for example, viscosity modifiers, dispersants, pour point additives, extreme pressure agents, antifoams, copper anticorrosion agents (such as dimercaptothiadiazole compounds), iron anticorrosion agents, friction modifiers, dyes, fragrances, optional detergents and antioxidants, and color stabilizers, for example.

The final lubricant composition can have a kinematic viscosity at <NUM> by ASTM D445 of <NUM> to <NUM>, or <NUM> to <NUM>, or even <NUM> or <NUM> to <NUM>, or <NUM> to <NUM><NUM>/s. In one embodiment the final lubricant composition can have a kinematic viscosity at <NUM> by ASTM D445 of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM><NUM>/s. In some embodiments, the lubricant composition can have a kinematic viscosity at <NUM> by ASTM D445 of <NUM> to <NUM>, or <NUM> to <NUM>, or <NUM> to <NUM><NUM>/s. The final lubricant composition can have a kinematic viscosity at <NUM> by ASTM D445 of <NUM> to <NUM>, or <NUM> to <NUM>, or even <NUM> to <NUM>, or <NUM> to <NUM>, or even <NUM> to <NUM><NUM>/s. In some embodiments, the final lubricant composition can have a kinematic viscosity to meet SAE Viscosity grade as shown in the following table:.

As a lubricant for industrial gears, the lubricant composition can contain other additives typically used in industrial gear applications, including, for example, foam inhibitors, demulsifiers, pour point depressants, antioxidants, dispersants, metal deactivators (such as a copper deactivator), antiwear agents, extreme pressure agents, viscosity modifiers, or some mixture thereof. The additives may each be present in the range from <NUM>, <NUM>, <NUM> or even <NUM> ppm up to <NUM>, <NUM>, <NUM>, <NUM> or even <NUM> percent by weight, or from <NUM> ppm to <NUM> percent by weight, from <NUM> ppm to <NUM> percent by weight, or from <NUM> ppm to <NUM> percent by weight, where the percent by weight values are with regards to the overall lubricant composition. In other embodiments the other industrial additives, as a total additive package, can be present from <NUM> to <NUM>, or from <NUM> to <NUM> percent by weight of the overall lubricant composition. However, it is noted that some additives, including viscosity modifying polymers, which may alternatively be considered as part of the base fluid, may be present in higher amounts including up to <NUM>, <NUM>, or even <NUM>% by weight when considered separate from the base fluid. The additives may be used alone or as mixtures thereof.

In some embodiments the industrial lubricant additive packages, or the resulting industrial lubricant compositions, include a demulsifier, a corrosion inhibitor, a friction modifier, or combination of two or more thereof. In some embodiments the corrosion inhibitor includes a tolyltriazole. In still other embodiments the industrial additive packages, or the resulting industrial lubricant compositions, include one or more sulfurized olefins or polysulfides; one or more phosphorus amine salts; one or more thiophosphate esters, one or more thiadiazoles, tolyltriazoles, polyethers, and/or alkenyl amines; one or more ester polymers; one or more carboxylic esters; one or more succinimide dispersants, or any combination thereof.

The disclosed technology provides a method of lubricating a driveline device, such as an automotive gear, axle or transmission, comprising supplying thereto a lubricating composition as described herein, that is, either a lubricating composition having (a) a hydrocarbon lubricating base stock, and (b) a viscosity modifier composition comprising a combination of i) an olefin polymer, and ii) a grafted olefin copolymer, and optionally c) a carboxylic acid ester, and operating the driveline device. In an embodiment, the lubricant composition disclosed herein can be employed to improve the traction coefficient of the lubricated gear at temperatures below <NUM>.

The automotive gear may comprise a gear as in a gearbox of a vehicle (e.g., a manual transmission or automated manual transmission) or in an axle or differential, or in other driveline power transmitting driveline devices. The automotive gear may also include bearings. Lubricated gears may include hypoid gears, such as those for example in a rear drive axle. The axle may be from a traditional petroleum powered vehicle, may be from an electrically driven vehicle, or a hybrid thereof. The electrically driven axle can combine an electric motor, power electronics and transmission in a unit directly powering the vehicle's axle.

The disclosed technology also provides a method of lubricating an industrial gear comprising supplying thereto a lubricating composition as described herein, that is, either a lubricating composition having (a) a hydrocarbon lubricating base stock, and (b) a viscosity modifier composition comprising a combination of i) an olefin polymer, and ii) a grafted olefin copolymer, and optionally c) a carboxylic acid ester, and operating the driveline device. In an embodiment, the lubricant composition disclosed herein can be employed to improve the traction coefficient of the lubricated gear at temperatures below <NUM>.

The amount of each chemical component described is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, that is, on an active chemical basis, unless otherwise indicated. However, unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, byproducts, derivatives, and other such materials which are normally understood to be present in the commercial grade.

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. The present invention encompasses the composition prepared by admixing the components described above.

As used herein, the term "about" means that a value of a given quantity is within ±<NUM>% of the stated value. In other embodiments, the value is within ±<NUM>% of the stated value. In other embodiments, the value is within ±<NUM>% of the stated value. In other embodiments, the value is within ±<NUM>% of the stated value. In other embodiments, the value is within ±<NUM>% of the stated value. In other embodiments, the value is within ±<NUM>% of the stated value.

The invention herein is useful for fully formulated gear oils or industrial gear oils, which may be better understood with reference to the following examples.

Copolymer A is an olefin copolymer of ethylene and propylene (<NUM>:<NUM>) with an Mn of <NUM> as measured by Gel Permeation Chromatography ("GPC") with a polystyrene standard.

Functionalized Copolymer B was made by reacting olefin copolymer A with 2wt% methacrylic acid in the presence of a peroxide initiator. The grafted olefin from this reaction was then further reacted with n-aminopropylmorpholine. The product was diluted with PAO-<NUM> synthetic oil to <NUM>% actives.

A series of fully formulated automotive gear oils were prepared according to the formulations in Table <NUM> below.

These fully formulated lubricating oils were subjected to oxidation testing via the CEC L-<NUM> DKA Oxidation method. In this test, a sample of fluid was heated to <NUM> in a glass tube for <NUM> hours with <NUM>/hour of air purging the fluid. At the end of test, the kinematic viscosity of the fluid is measured at both <NUM> and <NUM> and the tube is rated for deposits. The Aspect is a visual rating of <NUM>, <NUM> or <NUM> that is indicative of the cleanliness of the tube that contained the fluid. The lower the number, the cleaner the tube. The results in table <NUM> below show that when only unfunctionalized olefin copolymer A is present, the viscosity control is good, however the cleanliness rating is higher than desirable. By creating a mixture of functionalized and unfunctionalized copolymer with just 20wt% of functionalized olefin copolymer, the cleanliness improves without drastically impacting the viscosity performance. If <NUM>% of the viscosity modifier is functionalized olefin copolymer B, the cleanliness ratio is good, but the viscosity at the end of test has increased significantly.

Given that the viscosity modifier mixture containing 80wt% copolymer A and 20wt% copolymer B (Sample <NUM>) showed both good cleanliness and good viscosity control after oxidation, additional mixtures were made containing <NUM> and <NUM> weight percent of the copolymer A mixed with <NUM> and <NUM> wt% respectively of the copolymer B.

Samples <NUM>-<NUM> were also evaluated via the CEC L-<NUM> DKA Oxidation method. The results shown in Table <NUM> indicate that 10wt% of copolymer B is not enough to improve the cleanliness Aspect rating to a <NUM> from a <NUM>.

Given the promising results in the DKA oxidation test, the <NUM>/<NUM> mixture of viscosity modifiers was tested in the L-<NUM>-<NUM> (ASTM D5704) extended <NUM> hour test with three different additive packages.

Table <NUM> shows the varnish and sludge ratings in the L-<NUM>-<NUM> extended <NUM> hr test for each fluid, all of which would be accepted within the industry.

While cleanliness is an important performance attribute, fluid efficiency is another key performance parameter. One way of investigating fluid efficiency is to measure the traction coefficient of the fluid. Traction is the internal resistance of a fluid and has a dominant effect in the mixed and boundary lubrication regimes. The copolymers described here were then evaluated using a standard mini-traction machine (MTM) with a frictional force of <NUM> GPa pressure applied. Each fluid was run at <NUM> temperatures using a slide to roll ratio from <NUM> to <NUM>. Samples <NUM>-<NUM> all contained the same additive package, commercially available from the Lubrizol Corporation as Anglamol® <NUM>. Sample <NUM> contained only copolymer A, sample <NUM> contained only copolymer B, while sample <NUM> contained the <NUM>/<NUM> mixture of copolymer A/copolymer B without a pour point depressant and sample <NUM> contained the <NUM>/<NUM> mixture of copolymer A/copolymer B with a pour point depressant. Selected traction coefficient data for these fluids can be found in Table <NUM>.

The traction coefficient data indicates that copolymer A and copolymer B have similar performance when used alone. However, when used in combination, the traction coefficient was lowered demonstrating a synergy when the copolymers are used in combination.

Further improvements in traction coefficient were observed by adding a mixture of esters to Samples <NUM> -<NUM>. Samples <NUM>-<NUM> all contain a <NUM>:<NUM> mixture of a mono ester and a diester. Sample <NUM> contained only copolymer A, sample <NUM> contained only copolymer B and Sample <NUM> contained the <NUM>/<NUM> mixture of copolymer A/copolymer B.

Traction coefficients for Samples <NUM> - <NUM> that contained the ester mixture were all lower than samples <NUM>-<NUM> that did not contain the ester mixture. Again, a synergistic improvement in the traction coefficient was observed for the <NUM>/<NUM> copolymer mixture compared to either of the copolymers alone.

The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word "about. " It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.

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.

Claim 1:
A lubricant composition comprising:
a) a hydrocarbon lubricating base stock,
b) a viscosity modifier composition comprising a ratio of between <NUM>/<NUM> to <NUM>/<NUM> wt% of polymer i)/ii) of:
i) at least one olefin copolymer having a number average molecular weight ("Mn") as measured by Gel Permeation Chromatography ("GPC") with a polystyrene standard of <NUM> to <NUM>,<NUM>,
ii) at least one grafted olefin copolymer having an Mn as measured by GPC with a polystyrene standard of <NUM> to <NUM>,<NUM>, comprising carboxylic acid functionality or a reactive equivalent thereof grafted onto the polymer backbone, wherein the carboxylic acid functionality or reactive equivalent thereof is further substituted with an amine.