GB2444841A

GB2444841A - Lubricating composition

Info

Publication number: GB2444841A
Application number: GB0724085A
Authority: GB
Inventors: David A Hutchison; Robert T Dittmeier
Original assignee: Afton Chemical Corp
Current assignee: Afton Chemical Corp
Priority date: 2006-12-11
Filing date: 2007-12-10
Publication date: 2008-06-18
Anticipated expiration: 2027-12-10
Also published as: US20080139427A1; FR2910021A1; JP2008144164A; DE102007049964A1; GB2444841B; GB0724085D0

Abstract

A lubricant composition with improved stability to oxidation, especially of silver parts of diesel engines, comprises a major amount of a base oil; and a minor amount of a synergistic additive composition comprising: (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula R<1>-NH-R<2>, wherein R<1> and R<2> are each selected from at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

Description

LUBRICATING COMPOSITION

DESCRIPTION OF THE DISCLOSURE

Field of the Disclosure

The present disclosure is directed to additive and lubricant compositions and methods for use thereof. More particularly, this invention is directed to an additive composition comprising a synergistic combination comprising (I) a triazole compound, and (ii) a nitrogen-containing compound.

Background of the Disclosure

Diesel engines are used in a variety of applications and lubricant compositions for use in diesel engines are well known. Among the various types of diesel engines are the medium speed diesel engines, which are used in applications where thousands of horsepower (e.g., 2000 to 10,000 horsepower) are needed. This includes propulsion engines of deep-draft, sea-going vessels, workboats operating in the inland and coastal waterways, and stationary or continuous electrical power generation for manifold applications including rail locomotives, offshore drilling platforms, and industrial facilities and buildings.

Typically, these engines run at a speed of about 100 to about 1,200 rpm. This imanding enironment results in oxidation of the oil, which can result in corrosion of the metals present in the engine.

Medium speed diesel engines are unique among diesel engines generally because these engines frequently have silver parts, such as silver bearings. Thus, apart from providing stability against oxidation and protection against the formation of sludge and carbonaceous deposits, lubricating compositions intended for use in medium speed diesel engines must be formulated with specialized silver protecting agents in order that silver bearings in the engine are not attacked either by the additives in the oil or by the decomposition products

I

S

produced during extended engine operation. Such agents, often referred to as silver lubricity agents, protect against extreme pressure, wear and corrosion.

A typical engine lubricating composition might comprise extreme pressure agents and antiwear agents. The most commonly used extreme pressure and antiwear agents are sulfur-containing compounds, such as zinc dialkyldithiophosphates (ZDDP). However, it is well known that some sulfur-containing compounds cannot be used in engines having silver parts given their known propensity to damage the silver parts. This recognized tendency is explained, for example, in U.S. Patent No. 4,428,850. Thus, it is desirable to find an additive composition that can provide oxidation protection and in some cases can be essentially free of these potentially damaging compounds containing active sulfur.

SUMMARY OF THE DISCLOSURE

in accordance with the disclosure, there is provided an additive composition comprising (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; (ii) a nitrogen-containing compound represented by the formula: R1R2 wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

In an aspect, there is provided a lubricant composition comprising a major amount of a base oil; and a minor amount of a synergistic additive composition comprising (I) a triazole compound substituted with an aryl moiety, with Sb the proviso that the triazole compound is not an alkyl bis-3-aminn-1;2;4-trizole; and (ii) a nitrogen-containing compound represented by the formula: R1 R2 wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hyd rocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

In another aspect, there is also provided a lubricant composition comprising an additive composition comprising (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-I,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula: R1R2 wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

Moreover, there is provided a method of improving oxidation protection of a lubricant composition, said method comprising: providing to a machine a lubricant composition comprising a major amount of a base oil; and a minor amount of a additive composition comprising (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula:

H

N R2

wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

Further, there is provided a method for operating a machine comprising adding a lubricating composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula:

H

N R1 R2

Additionally, there is provided a method of lubricating at least one moving part of a machine, said method comprising contacting at least one moving part with a lubricant composition comprising a major amount of a base oil and a minor amount of a synergistic additive composition comprising: (i) a triazole compound substituted with an aryl moiety, with the proviso that the tnazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula: R1R2

S

wherein P.1 and P.2 are each ndependent!y se!ected from thA group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

Also provided is the use of a synergistic additive composition of the invention to improve the oxidation protection of a lubricant composition.

Additional objects and advantages of the disclosure will be set forth in part in the description which follows, and/or can be learned by practice of the disclosure. The objects and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not

restrictive of the disclosure, as claimed.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure generally relates to a lubricant composition comprising a major amount of a base oil and a minor amount of an additive composition comprising (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula:

H

N R1 R2

As used herein, the term "major amount" is understood to mean an amount greater than or equal to 50 wt. %, for example from about 80 to about 98 wt.% relative to the total weight of the composition. Moreover, as used herein, the term "minor amount" is understood to mean an amount less than 50 wt. % relative to the total weight of the composition.

As used herein, aromatic" or "aryl", unless expressly stated otherwise, refers to the typical substituted or unsubstituted non-aliphatic hydrocarbyl or heterocyclic moieties of this class, e.g., a polyunsaturated, typically aromatic, hydrocarbyl cyclical, or heterocyclic, substituent, which can have a single ring or multiple rings (up to three rings) that are fused together or linked covalently.

Typical hydrocarbyl aromatic moieties include phenyl, naphthyl, biphenylenyl, phenanthrenyl, phenalenyl, and the like. Such moieties are optionally substituted with one or more substituted or unsubstituted hydrocarbyl substituents. In one embodiment, the substituents on the substituted hydrocarbyl substituents are themselves unsubstituted. Typically, the hydrocarbyl substituents are unsubstituted. Aryl moieties can also be optionally substituted with one or more substituents such as hydroxy, optionally substituted lower alkyl, optionally ----substitutedloweralko,-aminoamide ester moieties-and carbonyl moieties-(eg.,------aldehyde or ketonic moieties). Also included are aryl moieties substituted by other aryl moieties, such as biphenyl. Heterocyclic aryl or aromatic moieties refers to unsaturated cyclical moieties containing carbon atoms in the ring and additionally one or more hetero atoms, which are typically oxygen, nitrogen, sulfur and/or phosphorus, such as pyridyl, thienyl, furyl, thiazolyl, pyranyl, pyrrolyl, pyrazolyl, imidazolyl, pyrazinyl, thiazolyl, etc. Such moieties are optionally substituted with one or more substituents such as hydroxy, optionally substituted lower alkyl, optionally substituted lower alkoxy, amino, amide, ester moieties and carbonyl moieties (e.g.. aldehyde or ketonic moieties). In one embodiment. an aryl moiety comprises from 3 to 30, for example from 6 to 30, carbon atoms.

As used herein, "alkaryl", unless expressly stated otherwise, refers to an alkyl moiety substituted by the typical substituted or unsubstituted non-aliphatic hydrocarbyl or heterocyclic moieties described above. Typical aryl moieties include phenyl, naphthyl, benzyl, and the like. Such moieties are optionally substituted with one or more substituents such as hydroxy, optionally substituted alkyl, optionally substituted alkoxy, amino, amide, ester moieties and carbonyl moieties (e.g., aldehyde or ketonic moieties).

As used herein, the terms "hydrocarbon", "hydrocarbyl" or "hydrocarbon based" mean that the moiety being described has predominantly hydrocarbon character within the context of this invention. These include moieties that are purely hydrocarbon in nature, that is, they contain only carbon and hydrogen. They can also include moieties containing substituents or atoms which do not alter the predominantly hydrocarbon character of the moiety. Such substituents can include halo-, alkoxy-, nitro-, etc. These moieties also can contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and --------include; for example,-sulfur-nitrogen; -oxygen and phosphorus-Therefore-wh lie remaining predominantly hydrocarbon in character within the context of this invention, these moieties can contain atoms other than carbon present in a chain or ring otherwise composed of carbon atoms.

In one embodiment, an alkyl group is a linear or branched alkyl group containing from 1 to 32 carbon atoms, for example from 1 to 24 carbon atoms. A lower alkyl group typically refers to a said alkyl group which contains from 1 to 12 carbon atoms, for example from 1 to 6 carbon atoms. An alkyl group can be substituted by one or more substituents, for example one, two or three substituents, which are the same or different and are selected from halogen. hydroxy, alkoxy, In one embodiment, a cycloalkyl group is cyclic form of a said alkyl group which comprises from 3 to 32 carbon atoms, preferably from 3 to 12, for example 5 or 6, carbon atoms. A cycloalkyl group can comprise one or more ring systems.

In one embodiment, an alkoxy group is a group -OR, wherein R is an alkyl group as defined above. An optionally substituted lower alkoxy group is a group -OR wherein R is an alkyl group which contains from I to 12 carbon atoms, for example 1 to 6 carbon atoms, and is unsubstituted or substituted by one or more substituents, for example one, two or three substituents, which are the same or different and are selected from halogen, hydroxy, alkoxy, amino and thio In one embodiment, a halogen is typically fluorine, chlorine, bromine or iodine and is preferably fluorine, chlorine or bromine, such as fluorine or chlorine.

In one embodiment, an amino group is a group -NRR' wherein R and R' are the same or different and represent hydrogen or an alkyl group containing ------fromiio32tarbonatoms, forexample-from-1-to-24-carbon-atoms.-------In one embodiment, a thio group is a group -SR wherein R represents hydrogen or an alkyl group containing from I to 32 carbon atoms, for example from 1 to 24 carbon atoms.

In one embodiment, a sulfono group is a group -SO2R wherein R represents hydrogen or an alkyl group containing from I to 32 carbon atoms, for example from I to 24 carbon atoms.

In nn cmhnrIimcnf n midn nrniin i rirniin -C((ViNRR' whrin R

-

and R' are the same or different and represent hydrogen or an alkyl group containing from I to 32 carbon atoms, for example from 1 to 24 carbon atoms.

In one embodiment, a phosphoro group is a group -P(O)RR' wherein R and R' are the same or different and represent hydrogen or an alkyl group containing from 1 to 32 carbon atoms, for example from I to 24 carbon atoms.

In one embodiment, an ester group is a group -C(O)OR wherein R represents hydrogen or an alkyl group containing from 1 to 32 carbon atoms, for example from 1 to 24 carbon atoms.

In one embodiment, a carbonyl group is a group -C(O)R wherein R represents hydrogen or an alkyl group containing from 1 to 32 carbon atoms, for example from I to 24 carbon atoms.

In one embodiment, an alkenyl group is a linear or branched alkylene group containing from 1 to 32 carbon atoms, for example from 1 to 24 carbon atoms. Typically, an alkenyl group or moiety is saturated except for one double bond. An alkenyl group can be substituted by one or more substituents, for one, two or three substituents, which are the same or different and are selected from halogen, hydroxy, alkoxy amino andthio substituents.

In one embodiment, a cycloalkenyl group is cyclic form of a said alkenyl group which comprises from 3 to 32 carbon atoms, preferably from 3 to 12, for example 5 or 6, carbon atoms. A cycloalkenyl group can comprise one or more ring systems.

In one embodiment, a cyclic moiety is typically a non-aromatic saturated or unsaturated hydrocarbon ring, having from 3 to 12 carbon atoms. A cyclic moiety can also be a non-aromatic, saturated or unsaturated hydrocarbon ring having from 3 to 12 carbon atoms in which one or more, for example one, two or three, of the carbon atoms are replaced by a heteroatom selected from N, 0 and S. Typically, the cyclic moiety is unsaturated or has one double bond. The cyclic moiety can comprise one or more ring systems and can also comprise bridging carbon atoms. When the cyclic moiety comprises one or more ring systems, said systems can be linked by covalent bonds or can be fused. In one embodiment, the cyclic moiety comprises two fused rings. A cyclic moiety can be substituted with one or more substituents, for example one, two or three substituents, which are the same or different and are selected from hydroxy, alkoxy, amino, amide, ester, oxo, halogen, nitro, thio, phosphoro or sulfono substituents.

In a preferred embodiment, the term "hydrocarbyl group" or "hydrocarbyl" 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 a molecule and having a predominantly hydrocarbon character.

Examples of hydrocarbyl groups include: (1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)or aromatic su bstituents and aromatic-, aliphatic-, and alicyclic-su bstituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through -----. -----another portion-of the molecule (e.g., two substituents together form an-alicyclic ---radical); (2) substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of the description herein, do not alter the predominantly hydrocarbon substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy); (3) hetero-substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this description, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Hetero-atoms include sulfur, oxygen, nitrogen, and encompass substituents such as pyridyl, furyl, thienyl, and imidazolyl.

In general, no more than two, or as a further example, 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 substituent in the hydrocarbyl group. In one embodiment, a hydrocarbyl group comprises from I to 32 carbon atoms, for example I to 24 carbon atoms. In one embodiment, a hetero-substituent comprises from I to 32 carbon atoms, for example 1 to 24 carbon atoms, wherein one, two or three of the carbon atoms is replaced by heteroatoms which are the same or different and are selected from sulfur, oxygen and nitrogen.

In one embodiment, the substituents on an alkyl, alkenyl, alkoxy, cyclic and hydrocarbyl moiety are unsubstituted.

As used herein, the term "synergy" and its grammatical variations refer to the interaction of elements that, when combined, produce a total effect greater than the sum of the individual elements.

A triazole compound suitable for use in the compositions of the present disclosure can be any triazole substituted with an aryl moiety, with the exception of an alkyl bis-3-amino-I,2,4-triazole. In some embodiments the triazole compound is a I,2,3-triazole compound. In other embodiments the triazole --------compound is al2,4-triazole-compound: As usedherein-the triazole compound-is -. -----substituted with an aryl moiety. However, the triazole itself can be further substituted by a substituent such as an alkyl moiety comprising from about 1 to about 24 carbon atoms. Thus, in one embodiment, a triazole substituted with an aryl moiety refers to a triazole ring substituted with an aryl group wherein the triazole ring is further optionally substituted with an alkyl group comprising from about 1 to about 24 carbon atoms. The aryl moiety can be linked to the triazole via a covalent bond, or can be fused to the triazole.

II

For example, the triazo!e compound can be substituted with a substituted or unsubstituted aryl moiety comprising a single ring or multiple rings, for example covalently linked rings. Non-limiting examples of substituted aryl moieties comprising covalently linked rings include biphenyl, 1,1'-binaphthyl, p,p'-bitolyl, biphenylenyl, and the like. As another example, the aryl moiety can comprise multiple fused rings. Non-limiting examples of aryl moieties comprising multiple fused rings include naphthyl, anthryl, pyrenyl, phenanthrenyl, phenalenyl, and the like. As a further example, the aryl moiety can comprise a single ring covalently linked to the triazole. Non-limiting examples of aryl moieties comprising a single ring covalently linked to the triazole include phenyl and the like. As another example, the aryl moiety can comprise a single ring fused to the triazole. A non-limiting example of such a compound includes benzotriazole. An example of a commercially available triazole compound suitable for use herein is a benzotriazole, which is an offwhite solid having a melting point ranging from 95-99 C, a flashpoint of 170 C, and a water solubility of 25 gIL at 20 C. The triazole compound can be combined/reacted/mixed with other additives in order to increase its solubility in a composition.

-In an embodiment, theiriazole compound can be represented by formula (I) below: (L1)R4 (I) wherein R3 is selected from the group consisting of hydrogen and at least one alkyl moiety comprising from about 1 to about 24 carbon atoms, and wherein R4 is selected from the group consisting of hydrogen, at least one alkyl moiety comprising from about 1 to about 24 carbon atoms, and a substituted hydrocrbyI moiety. In another embodiment, R3 and R4 of the triazole compound represented by formula (I) can each independently comprise from about 1 to about 16 carbon atoms. In one embodiment, when R4 is an alkyl moiety it is an unsubstituted alkyl moiety.

The triazole compound can be present in the lubricant and additive compositions in any effective amount, which can be readily determined by one of ordinary skill in the art. Moreover, the triazole compound can be present in any synergistic effective amount. In an embodiment, the lubricating composition of the present disclosure can comprise from about 0.01 wt.% to about 10 wt.%, and for example from about 0.05 wt.% to about 0.5 wt.%, of the triazole compound, relative to the total weight of the lubricating composition. In another embodiment, the additive composition of the present disclosure can comprise from about 0.01 wt.% to about 3 wt.% of the triazole compound, relative to the total weight of the additive composition.

The disclosed compositions can also comprise a nitrogen-containing compound. There is no particular restriction on the type of nitrogen-containing compound that can be used in the disclosed compositions of the present -disclosure. Generally, a nitrogen-containing compound suitable for use herein can be represented by formula (II) below:

H

N R1 R2 (II)

wherein R1 and R2 can each be independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido,

S

phosphoro, and su!fono. For exarnp!e, R1 and R2 of the nitrogen-containing compound can both comprise an aryl moiety comprising from about 6 to about 30 carbon atoms. Non-limiting examples of aryl moieties include alkphenyl of phenyl, benzyl, naphthyl, and alkaryl. As another example, R1 and R2 can each independently comprise alkaryl, such as alkphenyl or alknaphthyl, wherein the alkyl moiety comprises from about 4 to about 30, and for example from about 4 to about 12, carbon atoms. As still another example, R1 and R2 can each independently comprise a substituted or unsubstituted aryl moiety. Non-limiting examples of substituents for the aryl moiety can include an alkyl moiety comprising from about I to about 20 carbon atoms, hydroxyl, carboxyl, and nitro moieties. As another example, R1 and R2 can each independently be an alkyl substituted benzyl, phenyl, or naphthyl.

Other non-limiting examples of nitrogen-containing compounds that are suitable include: phenylamine; diphenylamine; triphenylamine; various alkylated phenylamines, diphenylamines and triphenylamines; N,N'-bis(4-aminophenyl)- alkylamine; 3-hydroxydiphenylamine; N-phenyl-1,2-phenylenediamine; N-phenyl-I,4-phenylenediamine; dibutyldiphenylamine; dioctyldiphenylamine; dinonyldiphenylamine; phenyl-alpha-naphthylamine; phenyl-beta-naphtylamine; -diheptyldiphenylamine; and p-oriented styrenated diphenylamine. Additional non-limiting examples of suitable nitrogen-containing compounds and their methods of preparation include those in U.S. Patent No. 6,218,576, which descriptions are incorporated herein by reference.

The nitrogen-containing compounds used herein can comprise a structure other than that shown above in formula (Il) which shows but one nitrogen atom in the molecule. Thus, the nitrogen-containing compound can comprise a different structure provided that at least one nitrogen has at least one aryl moiety

S

attached thereto. e.g., as in the case of various diamines having a secondary nitrogen atom as well as an aryl attached to one of the nitrogens.

The nitrogen-containing compounds used herein can have antioxidant properties in the disclosed compositions when used alone but can also demonstrate synergistic properties in the presence of a triazole compound described herein. For example, the oxidation protection afforded by the triazole compound and/or the nitrogen-containing compound alone can be significantly enhanced if these materials are present in the disclosed lubricant compositions, thereby demonstrating synergism. The synergy can allow a lower treat rate of the additive composition needed to achieve a desired level of achieving oxidation protection than would otherwise be required if either the triazole compound or nitrogen-containing compound were to be used alone. Additionally, the nitrogen-containing compounds used herein should be soluble in a final lubricant composition.

The amount of the nitrogen-containing compound in the disclosed compositions can vary depending upon specific requirements and applications. In an aspect, the nitrogen-containing compound can be present in a synergistic -------effective-amount.-In an embodiment,-the lubricating composition of the present---disclosure can comprise from about 0.01 wt.% to about 10 wt.%, and for example from about 0.3 wt.% to about 3 wt.%, of the nitrogen-containing compound, relative to the total weight of the lubricating composition. In another embodiment, the additive compositions of the present disclosure can comprise from about 0.07 wt.% to about 33 wt.% of the nitrogen-containing compound, relative to the total weight of the additive composition.

The compositions disclosed herein can optionally contain additives, such as dispersants, ash-containing detergents, ashless-detergents, overbased deteraents. pour point depressing agents, viscosity index modifiers. ash-containing friction modifiers, ashtess friction modifiers, nitrogen-containing friction modifiers, nitrogen-free friction modifiers, esterified friction modifiers, extreme pressure agents, rust inhibitors, antioxidants, corrosion inhibitors, anti-foam agents, titanium compounds, titanium complexes, organic soluble molybdenum compounds, organic soluble molybdenum complexes, boron-containing compounds, boron-containing complexes, tungsten-containing compounds, tungsten-containing complexes, and combinations thereof. In an aspect, the compositions can comprise various levels of at least one titanium-containing compound depending on the needs and requirements of the application. In another aspect, the compositions can comprise various levels of at least one molybdenum-containing compound depending on the needs and requirements of the application.

In an embodiment, the lubricant compositions of the present application can be essentially free, such as devoid, of compounds containing free active sulfur. As used herein, the phrase "active sulfur" is defined as sulfur containing compounds which would substantially react with machine parts to form metal sulfides at normal engine running temperatures ranging from about 100 C to ---below about 400 C: -Active sulfur sdistinguished-from non-active sulfur, which-does not substantially react at temperatures under 400 C, but which may sufficiently react to form metal sulfides at temperatures above 400 C so as to

C

protect engine parts under extreme pressure conditions, or where boundary conditions exist. One of ordinary skill in the art would readily understand that temperatures significantly above 400 can occur at various positions in engines that typically operate at lower temperatures, such asbelow 400 C, due to these boundary regions and extreme pressure regions. Such boundary regions and extreme pressure regions can occur, for example, when a particular engine part, such as a bearing, is placed under load. Non-active sulfur compounds can be employed that will react to protect engine parts as these higher temperatures, while not substantially reacting at the generally lower engine operating temperatures.

Accordingly, one of ordinary skill in the art understands that compounds containing active sulfur, such as zinc dialkyldithiophosphate (ZDDP), can exert a measurable deleterious effect upon some machines, such as medium speed diesel engines or machines that contain silver parts, while non-active sulfur compounds can still be employed to protect engine parts in these machines. For at least this reason, it may be desirable to omit active sulfur compounds from formulations intended for use in such machines. One skilled in the art would know how to determine the effect of sulfur containing compounds on machine parts, such as, for example, by measuring the amount of silver dissolved in the lubricant and/or the amount of deposits on the silver parts. The term "essentially free" is defined for purposes of this application to be concentrations having substantially no measurable deleterious effect.

In some embodiments, the lubricant compositions of the present application are substantially free, such as devoid, of compounds containing ---phosphorus: lnother embodiments; the compositions-of the present application -can be substantially free of compounds containing boron. It can be desirable to omit phosphorus and/or boron containing compounds from formulations of the present application so that these elements can be used as markers to indicate lubricant contamination. For example, railroad engine oils are generally formulated to be free of phosphorus and boron. While in use, the oils are periodically checked for phosphorus and/or boron, the presence of which can indicate that the oil has been contaminated with e.g., ZOOP or, in the case of boron, boron containing coolants, during engine operation. In this manner, the phosphorus and/or boron act

I

as markers to indicate contamination of the lubricant. By the phrase substantially free is meant that the composition comprises only trace amounts of phosphorus and/or boron, so that concentrations of these elements will have substantially no effect on the ability of phosphorus and boron to be used as markers.

Base oils suitable for use in formulating the disclosed compositions can be selected from any of the synthetic or mineral oils or mixtures thereof.

Mineral oils include animal oils and vegetable oils (e.g., castor oil, lard oil) as well as other 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. Oils derived from coal or shale are also suitable. Further, oils derived from a gas-to-liquid process are also suitable.

The base oil can be present in a major amount, wherein "major amount" is understood to mean greater than or equal to 50%, for example from about 80 to about 98 percent by weight of the lubricant composition.

The base oil can have any desired viscosity that is suitable for the intended purpose. Examples of suitable engine oil kinematic viscosities can range from about 2 to about 150 cSt and, as a further example, from about 5 to about 15 cSt at 100 C. Thus, for example, base oils can be rated to have viscosity ranges of about SAE 15 to about SAE 250, and as a further example, from about SAE 20W to about SAE 50. Suitable automotive oils also include multi-grade oils such as 15W-40, 20W-50, 75W-140, 80W-90, 85W-140, 85W-90, and the like.

Non-limiting examples of synthetic oils include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene isobutylene copolymers, etc.); polyalphaolefins such as poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc. and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, di-nonylbenzenes, di-(2-ethylhexyl)benzenes etc.); polyphenyls (e.g.. biphenvls. terphenyl. alkvlated polyphenyls, etc.); alkylated diphenyl ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl moieties have been modified by esterification, etherification, etc., constitute another class of known synthetic oils that can be used. Such oils 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 C fatty acid esters, or the C13 Oxo acid diester of tetraethylene glycol.

Another class of synthetic oils that can be used includes 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,alkyi malonic acids, alkenylmalonic---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 phthalate, 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.

Esters useful as synthetic oils also include those made from C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylol propane, pentaerythritol, diperitaerythritol, tripentaerythritol, etc. Hence, the base oil used which can be used to make the compositions as described herein can be selected from any of the base oils in Groups I-V as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. Such base oil groups are as follows: Group I contain less than 90% saturates and/or greater than 0. 03% sulfur and have a viscosity index greater than or equal to 80 and less than 120; Group II contain greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and have a viscosity index greater than or equal to 80 and less than 120; Group Ill contain greater than or equal to 90% saturates and less than or equal to 0.03% sulfur and have a viscosity index greater than or equal to 120; Group IV are polyalphaolefiris (PAO); and Group V include all other basestocks not included in Group I, II, III or IV.

The test methods used in defining the above groups are ASTM 02007 for saturates; ASTM 02270 for viscosity index; and one of ASTM D2622, 4294,4927and3l2O-for-sulfur. --------Group IV basestocks, i.e. polyalphaolefins (PAO) include hydrogenated oligomers of an alpha-olefin, the most important methods of oligomerisation being free radical processes, Ziegler catalysis, and cationic, Friedel-Crafts catalysis.

The polyalphaolefins typically have viscosities in the range of 2 to cSt at 100 C., for example 4 to 8 cSt at 100 C. They can, for example, be oligomers of branched or straight chain alpha-olefins having from about 2 to about carbon atoms, non-limiting examples include polypropenes, polyisobutenes,

I

nI..1..hiifn nnIv.j..hpypnp nnIv...1..ngfnpq int1 nnlv-1-rlp.c'pnp lnc.IuitIp.d ri -----homopolymers, interpolymers and mixtures.

Regarding the balance of the basestock referred to above, a "Group I basestock" also includes a Group I basestock with which basestock(s) from one or more other groups can be admixed, provided that the resulting admixture has characteristics falling within those specified above for Group I basestocks.

Exemplary basestocks include Group I basestocks and mixtures of Group II basestocks with Group I bright stock.

Basestocks suitable for use herein can be made using a variety of different processes including but not limited to distillation, solvent refining, hydrogen processing, oligomerisation, esterification, and re-refining.

The base oil can be an oil derived from Fischer-Tropsch synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons can be made from synthesis gas containing H2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing in order to be useful as the base oil. For example, the hydrocarbons can be hydroisomerized using processes disclosed in U.S. Pat. No. 6,103,099 or 6,180,575; hydrocracked and hydroisomerizeci using processes disclosed in U.S. Pat. No. 4,943,672 or 6,096,940; dewaxed using processes disclosed in U.S. Pat. No. 5,882,505; or hydroisomerized and dewaxed using processes disclosed in U.S. Pat. No. 6,013,171; 6,080,301; or 6,165,949.

Unrefined, refined and rerefined oils, either mineral or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the base oils. Unrefined oils are those obtained directly from a mineral 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. Rerefined 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 rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives, contaminants, and oil breakdown products.

According to various embodiments, there is a method of improving oxidation protection in a lubricant composition. As used herein, the term "improving oxidation protection" is understood to mean enhancing the oxidation protection that a composition can provide to a machine, e.g., reducing the amount of infrared carbonyl absorption and/or reducing the kinematic viscosity of a composition used in a machine, as compared to a composition that is devoid of the combination disclosed herein. The method of improving oxidation can comprise providing to a machine a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising (I) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II): R1R2 (II) wherein R1 and R2 are each independently selected from the group consisting of 2t least one aryl moiety comprising from about 6 to about 30 atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

According to various embodiments, there is also disclosed a method of lubricating at least one moving part of a machine, said method comprising contacting the at least one moving part with a lubricant composition comprising a major amount of a base oil and a minor amount of the disclosed synergistic additive composition.

In other embodiments, there is also disclosed a method for operating a machine comprising adding a lubricant composition comprising a major amount of a base oil and a minor amount of the disclosed synergistic additive composition.

The machine in the disclosed methods can be selected from the group consisting of spark ignition and compression-ignition internal combustion engines, including diesel engines, marine engines, rotary engines, turbine engines, locomotive engines, propulsion engines, aviation piston engines, stationary power -----generation engines, continuous power generation engines; and engines comprising----silver parts. Moreover, the at least one moving part can be chosen from a gear, piston, bearing, rod, spring, camshaft, crankshaft, rotors, and the like.

The lubricant composition can be any composition that would be effective in lubricating a machine. In an aspect, the composition is selected from the group consisting of medium speed diesel engine oils, passenger car motor oils, and heavy duty diesel engine oils. In an embodiment, the composition is a medium speed diesel engine oil.

S

EXAMPLES

The following examples are illustrative of the invention and its advantageous properties. In these examples as well as elsewhere in this application, all parts and percentages are by weight unless otherwise indicated. It is intended that these examples are being presented for the purpose of illustration only and are not intended to limit the scope of the invention disclosed herein.

Lubricant compositions that were essentially free of compounds containing active sulfur, boron and phosphorus were tested for their ability to protect against oxidation. The following examples show the synergism that exists when a triazole compound and a nitrogen-containing compound, such as an aryl amine, are formulated into lubricant composition, such as an engine oil. The examples also show that this synergism is unique when compared to antioxidant compounds alone or in combination.

EXAMPLE I

In this example, the base lubricant composition was as follows: TABLE 1 -Base Composition --COMPONENT Wt.% Functionalized polymer 2-5 Dialkyl thiadiazole 0.01-1 Sulfurized olefin (antiwear) 0.01-1 Low base detergent 1-4 High base detergent 1-5 Dispersant 1-10 Base oil 40/60 blend Balance As shown in Table 2 below, blends 2 to 8 comprised at least one additional component in addition to the above base composition. A triazole compound was a benzotriazole manufactured by Afton Chemical Corporation wherein 25 wt.% benzotriazole was dissolved in a primary t-alkyl amine (Primene

S

IM-T vaIihIp frnm Pnhm inr -1i PhiIrjpInhj PA\ nr1 snIvnt niufrI minril -...-.--.-.---..-. . .--.-, ---.1***' -..---.. ..---.-oil so that it would be soluble in the base composition of Table 1. The aryl amine compound was a dialkyl diphenylamine. In order to rule out the possibility of the primary t-alkyl amine contributing to the oxidative stability of the compositions, the primary t-alkyl amine was also tested with the triazole compound (5), the aryl amine compound (6), and a combination of the two (8).

TABLE 2 -Lubricant Compositions ___________ 1(Base) 2 3 4 5 6 7 8 N-containing compound (wt.%) ------0.30 --0.30 0.30 0.30 Primary t- alkyl amine(wt.%) ----1.125 --1.125 1.125 --1.125 Triazole compound (wt.%) --0.375 ----0.375 -0.375 0.375 The oxidation stability of these eight lubricant compositions was measured by the Ethyl Oxidation Test. Oxygen was bubbled through a test tube containing suspended iron, copper and lead coupons and one of the lubricant compositions from Table 2 at 300 F. An air condenser retained most of the volatiles, and the lubricant composition was sampled and analyzed every 24 hours.

The used lubricant compositions were evaluated for oxidation control by methods well known in the art for measuring kinematic viscosity increase and infrared carbonyl absorptions of the oil oxidation products.

The greater the carbonyl absorption, the less oxidation protection that particular lubricant composition imparts to the machine. The greater the increase in viscosity, the less stable a particular lubricant composition is to oxidation. The results are provided in Tables 3 and 4 below.

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TARI F -Vi.crnsity lnrrpsp Percent Increase of _________________ Kinematic Viscosity at 100 C Lubricant Composition 48 Hrs 72 Hrs 96 Hrs Base Blend 4.2 24.5 56.2 2 5 30.3 71.4 3 7.1 30.5 68.6 4 -5.1 9.2 41.7 11.4 37.8 83.3 6 -1.6 16.8 44.4 7 -1.4 -1.8 -3.9 8 -1.2 -2.7 -4.1 I TABLE 4 -Infrared Carbonyl Absorption FuR Carbonyl Absorption ________________ abs/cm @ 1710 cm1 Lubricant I Composition 48 Hrs 72 Hrs 96 Hrs Base Blend 108 149 178 2 87 119 154 3 94 134 160 4 72 132 166 104 154 177 6 78 131 153 7 -5 -3 -1 8 7 10 13 -----As shown-in Tables 3 and 4, the base blend comprising the triazole compound (2), primary t-alkyl amine (3), or nitrogen-containing compound (4) showed some early, small oxidation protection. The nitrogen-containing compound (4) performed the best out of the three lubricant compositions with a 33% reduction in carbonyl absorption at 48 test hours, 11% reduction at 72 hours and a 7% reduction at 96 hours. Viscosity increases for the triazole compound (2) or primary t-alkyl amine (3) were comparable to the base blend. The nitrogen-containing compound (4) showed low viscosity increases at 48 and 72 hours, but a large viscosity increase at 96 hours. Lubricant composition (6) was comparable to the nitrogen-containing compound alone (4) in both carbonyl absorptions and viscosity increases. Lubricant composition (5) showed virtually no effect on oxidation, with carbonyl absorption equal to the base blend and viscosity increases larger than the base blend. Thus, the triazole compound (2) and primary t-alkyl amine (3) alone or in combination had little effect in oxidation protection of an active sulfur-free base blend as shown by carbonyl absorption or viscosity increases. With or without the primary t-alkyl amine, the nitrogen-containing compound (4) alone provided some oxidation protection.

The nitrogen-containing compound in combination with the triazole compound (7) showed significant synergism by both carbonyl absorption and viscosity increases. The negative carbonyl absorption values through 96 test hours in Table 4 indicate no detectable oxidation taking place. A small amount of oxidation was evidenced by the small viscosity decrease through 96 hours as shown in Table 3. The ternary combination of nitrogen-containing compound, triazole compound, and primary t-alkyl amine (8) showed small amounts of oxidation products by carbonyl absorption and slightly larger viscosity decreases indicating that the primary t-alkyl amine has a slight pro-oxidation tendency. Thus, ---the synergistic effect is attributable to the combination of the nitrogen-containing ---compound with the triazole compound (7). The primary t-alkyl amine does not play any role in the observed effect on oxidation.

EXAMPLE 2

The base composition of Table 1 was again used, but with varying amounts of a triazole compound and a nitrogen-containing compound as shown in

Table 5 below.

TABLE 5-Lubricant Composit ions ________________ 9 10 11 12 13 14 N-containing compound (wt.%) ------0.30 0.30 0.30 Triazole Compound (wt.%) 0.375 0.100 0.050 0.375 0.100 0.050 The oxidation stability of these compositions was also measured by the Ethyl Oxidation Test. The compositions were evaluated for oxidation control by methods for measuring kinematic viscosity increase and infrared carbonyl absorptions of oxidation products as described above. The results are as shown in Tables 6 and 7 below.

TABLE 6-Viscosity Increase Percent Increase of ____________ _________________ Kinematic Viscosity at 100 C Lubricant Composition 48 Hrs 72 Hrs 96 Hrs 9 5 30.3 71.4 8.3 35.7 84.7 11 3.7 27.4 63.4 12 -1.4 -1.8 -3.9 13 -1.8 -8.4 -0.8 14 I -1.8 -8.7 6.6 TABLE 7 -Infrared Carbonyl Absorption FuR Carbonyl Absorption ________________ abs/cm c 1710 cm1 ___________________ Lubricant Composition 48 Hrs 72 Hrs 96 Hrs 9 87 119 154 96 139 164 11 88 131 145 12 -5 -3 -1 13 6 14 86 14 -8 18 86 The triazo!e compound in Tab!e 2 was tested at 0.375 wL%, traditionally a rather high concentration for benzotriazole. As shown in Table 5, the triazole compound alone and with a nitrogen-containing compound was tested at 0.10 wt.% and 0.05 wt.% benzotriazole to determine if lower triazole amounts affected the results discussed above. As shown in Tables 6 and 7, the tnazote compound in the base blend alone used at lower concentrations, e.g., 0.10 wt.% (10) and 0.05 wt.% (11), still yielded viscosity increases comparable to the base blend. The carbonyl absorptions were comparable for all three triazole concentrations and only about 20% less than the base blend.

The triazole compound used at the two lower concentration with a nitrogen-containing compound, 0.10 wt.% (13) and 0.05 wt.% (14), showed over 90% lower carbonyl absorption at 48 and 72 test hours, and a 50% lower carbonyl absorption at 96 hours. The viscosity decreases of over 8% at 72 hours for both lower concentrations of the triazole compound showed that some oxidation was occurring. Yet even at 96 test hours, the lowest triazole concentration, 0.05 wt.% (14), showed a viscosity increase of only 6.6%, an 88% decrease over the base blend and an 84% decrease over the nitrogen-containing compound alone in the base blend (4). ThUs, significant oxidation protection as measured by carbonyl -absorption and viscosity change was achieved with a nitrogen-containing compound an a triazole compound even at 0.05 wt.%.

It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," include plural referents unless expressly and unequivocally limited to one referent. Thus, for example, reference to "an antioxidant" includes two or more different antioxidants. As used herein, the term "include" and its grammatical variants are intended to be non-limiting, such

I

that recitation of items in a list is not to the exc!usion of other!ike items that can be substituted or added to the listed items For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or can be presently unforeseen can arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they can be amended are intended to embrace all sUch alternatives, modifications variations, improvements, and substantjal -equivalents.

Claims

ri AIR 1. A synergistic additive composition comprising: (i) a triazole

compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1.2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II): R1R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.
2. The synergistic additive composition of claim 1, wherein R1 and R2 are each an aryl moiety comprising from about 6 to about 30 carbon atoms.
3. The synergistic additive composition of claim I or claim 2, wherein the aryl moiety is selected from the group consisting of phenyl, benzyl, naphthyl, and alkaryl.
4. The synergistic additive composition of claim 3, wherein the alkaryl is selected from the group consisting of alkphenyl and alknaphthyl, wherein the alkyl moiety comprises from about 4 to about 30 carbon atoms.
5. The synergistic additive composition of claim 4, wherein the alkyl moiety of the alkaryl comprises from about 4 to about 12 carbon atoms.
6. The synergistic additive composition of any one of the preceding claims, wherein the triazole compound is substituted with a substituted or unsubstituted aryl moiety comprising multiple rings.
7. The synergistic additive composition of any one of c!aims 1 to 5, wherein the tnazole compound is substituted with a substituted or unsubstituted aryl moiety comprising a single ring.
8. The synergistic additive composition of any one of claims I to 5, wherein the triazole compound is represented by the formula (I):

N N

N (I)

wherein R3 is selected from the group consisting of hydrogen and at least one alkyl moiety comprising from about 1 to about 24 carbon atoms, and wherein R4 is selected from the group consisting of hydrogen, at least one alkyl moiety comprising from about I to about 24 carbon atoms, and a
9. The synergistic additive composition of any one of claims I to 5, wherein the triazole compound is a benzotriazole.
10. The synergistic additive composition of any one of the preceding claims, wherein the triazole compound is present in an amount ranging from about 0.01 wt.% to about 3 wt.%, relative to the total weight of the additive composition.
11. The synergistic additive composition of any one of the preceding claims, wherein the nitrogen-containing compound is present in an amount ranging from about 0.07 wt.% to about 33 wt.%, relative to the total weight of the additive composition.
12. The synergistic additive composition of any one of the preceding claims, further comprising at least one additive selected from the group consisting of dispersants, ash-containing detergents, ashless-detergents, overbased detergents, pour point depressing agents; viscosity ir.d ox improving agents, ash-containing friction modifier, ashless friction modifier, nitrogen-containing friction modifier, nitrogen-free friction modifier, esterified friction modifier, extreme pressure agents, rust inhibitors, supplemental antioxidants, corrosion inhibitors, anti-foam agents, titanium compounds, titanium complexes, organic soluble molybdenum compounds, organic soluble molybdenum complexes, boron-containing compounds, boron-containing complexes, tungsten-containing compounds, and tungsten-containing complexes.
13. The synergistic additive composition of any one of the preceding claims, further comprising at least one molybdenum compound
14. The synergistic additive composition of any one of the preceding claims, further comprising at least one titanium compound.
15. A lubricant composition comprising: a major amount of a base oil; and a minor amount of a synergistic additive composition comprising: (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II):

H

N

R1 R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.
16. The lubricant composition of claim 15, wherein the lubricant composition is essentially free of compounds containing boron or phosphorus.
17. The lubricant composition of claim 15 or claim 16, wherein the lubricant composition is essentially free of zinc dialkyldithiophosphate.
18. The lubricant composition of any one of claims 15 to 17, wherein the triazole compound is present in an amount ranging from about 0.05 wt.% to about 0.5 wt.%, relative to the total weight of the composition.
19. The lubricant composition of any one of claims 15 to 18, wherein the nitrogen-containing compound is present in an amount ranging from about 0.01 wt.% to about 10 wt.%, relative to the total weight of the composition.
20. The lubricant composition of any one of claims 15 to 19, wherein the nitrogen-containing compound is present in an amount ranging from about 0.3 wL% to about 3 wt.%, relative to the total weight of the composition.
21. The lubricant composition of any one of claims 15 to 20, wherein the triazole compound is present at 0.05 wt.% and the nitrogen-containing compound is present at 0.3 wt.%, relative to the total weight of the composition.
22. The lubricant composition of any one of claims 15 to 22 wherein the synergistic additive composition is as defined in any one of claims 1 to 11.
23. The lubricant composition of any one of claims 15 to 22, further comprising at -least one additive selected from the group consisting of dispersants, ash-containing detergents, ashless-detergents, overbased detergents, pour point depressing agents, viscosity index improving agents, ash-containing friction modifier, ashless friction modifier, nitrogen-containing friction modifier, nitrogen-free friction modifier, esterified friction modifier, extreme pressure agents, rust inhibitors, supplemental antioxidants, corrosion inhibitors, anti-foam agents, titanium compounds, titanium complexes, organic soluble molybdenum compounds, organic soluble molybdenum complexes, boron-containing compounds, boron-containing complexes, tungsten-containing compounds, and tungsten-containing complexes.
24. The lubricant composition of any one of daims 15 to 23, wherein the!ubricant composition is selected from the group consisting of medium speed diesel engine oils, passenger car motor oils, and heavy duty diesel engine oils.
25. The lubricant composition of any one of claims 15 to 24, further comprising at least one molybdenum compound
26. The lubricant composition of any one of claims 15 to 25, further comprising at least one titanium compound.
27. A lubricant composition comprising: a major amount of a base oil; and a minor amount of an additive composition comprising: (I) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino-1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II):

H

R1R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen,. hydroxy,hydrocarbyl, substituted hydrocarbyl,. amino, amido, phosphoro, and sulfono.
28.A lubricant composition according to claim 27 wherein the additive composition is as defined in any one of claims I to 14.
29. A method of improving oxidation protection of a lubricant composition, said method comprising: providing to a machine a lubricant composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising: (i trinI rnmnnipnd uihstitiitprj with n rvl moiety with the __*_..J - proviso that the triazole compound is not an alkyl bis-3-amino-I,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II):

H

N

R' R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.
30. The method of claim 29, wherein the machine is selected from the group consisting of spark ignition and compression-ignition internal combustion engines.
31. The method of claim 30, wherein the engine is selected from the group consisting of diesel engines, marine engines, rotary engines, turbine engines, locomotive engines, propulsion engines, aviation piston engines, stationary power generation engines, continuous power generation engines, and engines comprising silver parts.
32. A method for operating a machine comprising: -adding to the machine a lubricating composition comprising a major amount of a base oil; and a minor amount of an additive composition comprising: (i) a triazole compound substituted with an aryl moiety, with the proviso that the triazole compound is not an alkyl bis-3-amino- 1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II): R1R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.
33. The method of claim 32, wherein the machine is selected from the group consisting of spark ignition and compression-ignition internal combustion engines.
34. The method of claim 33, wherein the engine is selected from the group consisting of diesel engines, marine engines, rotary engines, turbine engines, locomotive engines, propulsion engines, aviation piston engines, stationary power generation engines, continuous power generation engines, and engines comprising silver parts.
35. A method of lubricating at least one moving part of a machine, said method comprising: contacting the at least one moving part with a lubricant composition comprising a major amount of a base oil; and a minor amount of a synergistic additive composition comprising: (i) a triazole compound substituted with an aryl moiety, with the proviso that the tnazole compound is not an alkyl bis-3-amino- 1,2,4-triazole; and (ii) a nitrogen-containing compound represented by the formula (II): R1R2 (II) wherein R1 and R2 are each independently selected from the group consisting of at least one aryl moiety comprising from about 6 to about 30 carbon atoms, hydrogen, halogen, hydroxy, hydrocarbyl, substituted hydrocarbyl, amino, amido, phosphoro, and sulfono.

I
36. The method of claim 35, wherein the machine is selected from the group consisting of spark ignition and compression-ignition internal combustion engines
37. The method of claim 36, wherein the at least one moving part is selected from the group consisting of gears, pistons, bearings, rods, springs, camshafts, crankshafts, and rotors.
38. The method of any one of claims 29 to 37 wherein the synergistic additive composition is as defined in any one of claims I to 14.
39. Use of a synergistic additive composition according to any one of claims 1 to 14 to improve the oxidation protection of a lubricant composition.
40. A synergistic additive composition according to claim I and substantially as hereinbefore described.
41. A lubricant composition according to claim 15 and substantially as hereinbefore described.
42. A lubricant composition according to claim 27 and substantially as hereinbefore described.
43. A method according to claim 29, claim 32 or claim 35 and substantially as hereinbefore described.

---44. -Use according to claim 39 and substantially as hereinbefore described.