WO2007001445A2

WO2007001445A2 - Multifunctional lubricant additive package

Info

Publication number: WO2007001445A2
Application number: PCT/US2005/039766
Authority: WO
Inventors: Hongmei Wen; Clark V. Cooper
Original assignee: United Technologies Corporation
Priority date: 2004-11-04
Filing date: 2005-11-04
Publication date: 2007-01-04
Also published as: US20090137436A1; JP2008519127A; WO2006137928A3; EP1828358A2; EP1814968A2; WO2007001445A3; WO2007001443A3; WO2007001443A2; EP1814969A2; US20090082236A1; US20080312116A1; WO2007001444A2; US20090011964A1; JP2008519124A; JP5362990B2; JP2008519125A; JP2008519126A; EP1828357A2; WO2007001444A3; WO2006137928A2

Abstract

The present invention provides a multifunctional lubricant additive package or composition for improving load-carrying capacity, scuffing (scoring) resistance, and other performance characteristics of a lubricant. The composition includes a molybdenum compound, a secondary zinc dithiophosphate compound, an aryl or alkyl phosphite compound, and a compound having an alkylthiocarbamoyl group. The present invention further provides a method for improving the performance characteristics of a lubricant. The method includes mixing a lubricant base stock or a fully-formulated lubricant with the above-described multifunctional lubricant additive composition.

Description

MULTIFUNCTIONAL LUBRICANT ADDITIVE PACKAGE

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional

Application No. 60/625,416 filed November 4, 2004, and is related to the following co-pending and commonly-owned applications which were filed herewith and are hereby incorporated by reference in full: "Lubricant Additive Packages for Improving Load-Carrying Capacity and Surface Fatigue Life" (Attorney Docket No. 0002290WOU, EH-11605), U.S. Serial No. ;

"Lubricants Containing Multifunctional Additive Packages Therein for Improving Load-Carrying Capacity, Increasing Surface Fatigue Life and Reducing Friction" (Attorney Docket No. 0002294WOU, EH-11697), U.S. Serial No. ; and "Multifunctional Lubricant Additive Package for a Rough Mechanical Component Surface" (Attorney Docket No. 0002295WOU, EH-11698), U.S. Serial No. .

GOVERNMENT RIGHTS IN THE INVENTION

The invention was made by or under contract with the National Institute of Standards and Technology of the United States Government under contract number: 70NANB0H3048.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multifunctional lubricant additive composition or package for improving the performance characteristics of a lubricant. More particularly, the present invention relates to a multifunctional lubricant additive composition or package for providing a lubricant with superior performance characteristics such as improved load-carrying ability, anti-scuffing (anti-scoring) capacity, friction reduction, and improved surface- fatigue life.

2. Description of Related Art

Mechanical systems such as manual or automatic transmissions; single and multi-speed aviation transmissions, including but not limited to those used to propel rotorcraft and those used to alter the rotational speed of the sections within gas turbine engines; push-belt type continuous variable transmissions; and traction drive continuous variable transmissions, have large surface areas of contact portions or zones. These contact portions or zones, such as drive rolling surfaces, and gear and ball-and roller bearings, are known to be susceptible to high surface pressures. In addition, internal combustion engines and other propulsion devices, especially those that are common for high-performance and racing applications, are subject to taxing demands in the form of inertial loading, high sliding and/or rolling speeds, and marginal lubrication. Moreover, the need for reducing friction, resistance, and fatigue within larger contact zones of mechanical systems is increased by many recently developed transmission systems that are designed to be miniaturized or weight-reduced to maximize transmission throughput capacity.

To address these severe application demands, lubricants, especially those containing specific additives, play a critical role in protecting and minimizing the wear and scuffing (scoring) of surfaces. The lubricants generally reduce principal damage accumulation mechanisms of lubricated components caused by surface fatigue and overloading. Examples of known lubricants are discussed in the following publications, which are hereby incorporated in full by reference: Phillips, W. D., Ashless phosphorus-containing lubricating oil additives: Lubricant Additives Chemistry and Application 45-111 (L.R. Rudick, Marcel Dekker, Inc. 2003); and Kenbeck, D. and T.F. Buenemann, Organic Modifiers: Lubricant Additives Chemistry and Application 203-222 (L.R. Rudick, Marcel Dekker, Inc. 2003).

Recently developed system-optimization approaches for increasing overall power throughput of mechanical systems, underscore the need for new and better performing lubricant additives. By reducing friction, wear, pressure, and improving scoring (scuffing) resistance, these additives prolong surface fatigue life for lubricated contacts within transmission systems and propulsive devices.

The present invention provides lubricant additives for improving the performance characteristics, such as load carrying capacity of mechanical systems. Combining the additive composition provided by this invention with lubricant stocks, and optionally other additives, results in a fully formulated lubricant with many performance advantages such as reduction in friction, wear and scuffing (scoring).

SUMMARY OF THE INVENTION

The present invention provides a lubricant additive comprising elements or components that are intended to enhance the performance characteristics of a lubricant base stock or fully formulated lubricant, including anti-wear (AW), extreme pressure (EP), friction modifying (FM) and surface fatigue life (SFL) modifying compositions. In a preferred embodiment, this invention provides a multifunctional lubricant additive composition for improving the performance characteristics of a natural or synthetic lubricant for use in transmission fluid products that meet both civil and military specifications.

In another embodiment, the present invention provides a multifunctional composition for use in improving performance of metals and alloys of power transmission components, including gears, bearings, splines, shafts, and springs.

In another embodiment, this invention provides a multifunctional lubricant additive composition for improving the performance characteristics of engines and related propulsive devices used to power automobiles, both stock (production) and specialty (e.g. racing and other high performance) varieties, and heavy on- and off-road equipment, such as farm implements and construction equipment.

In another embodiment the present invention provides a multifunctional lubricant additive composition capable of being combined with lubricant stocks and other additives to produce a fully formulated lubricant that beneficially reduces friction and scuffing (scoring), and increases resistance to surface degradation, including but not limited to, fatigue including micro and and macro pitting and wear.

In yet another embodiment, the present invention provides a multifunctional lubricant additive composition for improving the performance characteristics of a lubricant, which includes one or more of the following components: (a) a molybdenum compound represented by the general formula:

- MoO_mS₄— (I)

wherein X¹ is an oxygen or sulfur atom and R³ and R⁴ are each independently a C_nH_2n+i alkyl group, wherein n is an integer of about 2 < n < 10, and m is an integer of about 0 < m < 4;

(b) a secondary zinc dithiophosphate compound represented by the general formula:

wherein R³, R⁴, R⁵, and R⁶ are each a C_hH₂h+i secondary alkyl group represented by the formula:

R'

CH

R^e wherein h is an integer of about 3 < h < 11 , wherein R⁷ and R⁸ are each a CiH₂i+i alkyl group, and i is an integer of about 1 < i < 5;

(c) an aryl or alkyl phosphite compound represented by the general formula:

wherein R⁹, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each a C_jH_2j+i alkyl group, and j is an integer of about 1 < j < 20, wherein the alkyl groups exhibit tertitary structures, and;

(d) a compound having at least one alkylthiocarbamoyl group represented by the general formula:

wherein R¹⁵, R¹⁶, R¹⁷, and R¹⁸ are each a C_kH_2k+i alkyl group, k is an integer of about 1 < k < 30, and R¹⁵, R¹⁶, R¹⁷, and R¹⁸ optionally form a ring structure with the nitrogen atom to which they are bonded; wherein (A) is a chain of sulfur atoms, S_n, or S-(CH₂)_m-S, n is an integer of about 1 < n < 10, and m is an integer of about 1 < m < 6; wherein the total amount of compounds (a) to (d) is equal to or less than about 15% by mole, based on the total amount of lubricant.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure shows the relationship between the average traction (friction) coefficient and average load stage for various lubricants. The vertical arrows 11 , 21 , 31 indicate the average scuffing (scoring) failure load stage (load carrying capacity) of Hatco HXL-7944 Oil 10, Exxon-Mobil Jet Oil Il 20; and Formulation #4 30, respectively. A higher scuffing (scoring) failure load stage indicates greater load-carrying capacity of the lubricant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a multifunctional lubricant additive composition for improving the performance characteristics of a lubricant base stock or fully formulated lubricant. Preferably the composition includes the following components set forth below: (I) about 0.1 % to about 6% by mole concentration of a molybdenum compound (a), based on the total amount of lubricant; (II) about 0.1% to about 6% by mole concentration of a secondary zinc dialkyl dithiophosphate compound (b), based on the total amount of lubricant; (III) about 0.1 % to about 6% by mole concentration of an aryl or alkyl phosphite compound (c), based on the total amount of lubricant; and (IV) about 0.1 % to about 6% by mole concentration of an alkylthiocarbamoyl compound (d), based on the total amount of lubricant, wherein the total concentration of the four additives in the composition will not exceed about 15% by mole based on the total amount of the lubricant.

The multifunctional lubricant additive composition is prepared from the following components:

(a) a molybdenum compound represented by the general formula:

- MoO_mS₄— (I)

wherein X¹ is an oxygen or sulfur atom and R³ and R⁴ are each independently a C_nH₂n+i alkyl group, wherein n is an integer of about 2 < n < 10, preferably about 4 ≤ n < 6, and m is an integer of about 0 ≤ m < 4.

(b) a secondary zinc dithiophosphate compound (or zinc dialkyl dithiophosphate compound) represented by the general formula:

wherein R³, R⁴, R⁵, and R⁶ are each a C_hH₂h+i secondary alkyl group represented by the formula: R'

CH

R⁰

wherein h is an integer of about 3 < h ≤ 11 , preferably about 4 < h < 6; wherein R⁷ and R⁸ are each CiH₂i₊i alkyl groups, and i is an integer of about 1 < i < 5, preferably about 1 < I < 3;

(c) an aryl or alkyl phosphite compound represented by the general formula:

wherein R⁹, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each a C₁H₂J_+I alkyl group, and j is an integer of about 1 ≤ j ≤ 20, preferably about 4 ≤ j ≤ 8, wherein the alkyl groups exhibit tertiary structures, and;

wherein R¹⁵, R¹⁶, R¹⁷, and R¹⁸ are each a CkH₂ι_<+i alkyl group, and k is an integer of about 1 < k < 30, preferably about 4 < k < 8, and R¹⁵, R¹⁶, R¹⁷, and R¹⁸ optionally form a ring structure with the nitrogen atom to which they are bonded; wherein (A) is a chain of sulfur atoms, S_n, or S-(CH₂)m-S, and n is an integer of about 1 < n < 10, preferably about 1 < n < 6, and m is an integer of about 1 < m ≤ 6, preferably about 1 < m < 3; wherein the total amount of compounds (a) to (d) is equal to or less than about 15% by mole, based on the total amount of lubricant.

Compound (a) of the multifunctional lubricant additive composition is present in an amount from about 0.1 % to about 6% by mole, based on the total amount of lubricant. In a preferred embodiment, compound (a) is present in an amount from about 0.1 % to about 3% by mole, based on the total amount of lubricant.

Compound (b) of the multifunctional lubricant additive composition is present in an amount from about 0.1% to about 6% by mole, based on the total amount of lubricant. In a preferred embodiment, compound (b) is present in an amount from about 0.1 % to about 3% by mole, based on the total amount of lubricant.

Compound (c) of the multifunctional lubricant additive composition is present in an amount from about 0.1% to about 6% by mole, based on the total amount of lubricant. In a preferred embodiment, compound (c) is present in an amount from about 0.1 % to about 3% by mole, based on the total amount of lubricant.

Compound (d) of the multifunctional lubricant additive composition is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant. In a preferred embodiment, compound (d) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

Lubricants that the present invention can improve include but are not limited to gear oil, bearing oil, sliding surface lubrication oil, chain lubricating oil, and engine oil. In a preferred embodiment, various types of lubricants, greases, especially synthetic polyol ester (POE) based lubricants, can be used as lubricant bases.

The present invention is useful as an additive composition for natural and synthetic aviation (aerospace) and automotive lubricants. Moreover, a combination of the multifunctional additive composition with the above- described lubricants improves transmission power throughput and system power density.

Specific uses also include turbine engine and transmission oils designed to meet government civil (FAA) and military (DoD) specification and requirements. Additional uses of the multifunctional additive composition include the demonstrated ability to improve scuffing (scoring) performance of metals and alloys that are commonly used for power transmission components, including but not limited to gears, bearings, splines, shafts, and springs. As such, these improvements decrease the incidence of component and system failure and rejection during customer acceptance test protocols (ATPs). The additive composition also improves pitting (surface) fatigue life and reduces the rate of component and system degradation due to wear and other phenomena.

In another embodiment, the present invention provides a method of improving the performance characteristics of a lubricant. The method comprises the step of: mixing a lubricant with a multifunctional lubricant additive composition that includes at least one of the compounds (a) to (d) of the above-described multifunctional lubricant additive composition thereby producing a fully formulated lubricant. For this embodiment, the molar concentration of compounds (a) to (d) may be varied to achieve a desired effect, provided however, that the total amount of the four additives is about 15% or less by mole based on the total amount of lubricant.

The following formulations and experimental results illustrate some non- limiting embodiments of the multifunctional additive compositions of this invention.

Formulation #4

In this embodiment, a multifunctional additive package was added to Hatco HXL-7994 oil to create Formulation #4. Hatco HXL-7994 oil was specially prepared by Hatco to replicate Exxon-Mobil Jet Oil II, but without Exxon-Mobil Jet Oil ll's anti-wear additive tricresyl phosphate (TCP). Hatco HXL-7994 oil contains an anti-oxidant package and a yellow metal corrosion inhibitor and uses a 5 cSt polyol ester base stock, HXL-1570, having the typical properties noted in Table A below. TABLE A. Properties of HXL-1570

Formulation #4 contained the following additives:

This multifunctional additive package of Formulation #4 increased the load-carrying capacity of the Hatco HXL-7994 oil by about 3.94 times, which is superior to conventional oils such as Exxon-Mobil Jet Oil Il (a standard version of MIL-PRF-23699, a 5 cSt gas turbine engine oil), which typically has excellent lubricant performance as compared to other brands and versions of MIL-PRF-23699 oil. As can be seen in the figure, the Hatco HXL-7994 oil 10 had an average scuffing (scoring) failure load stage of about 5.7 (arrow 11 ), the Exxon-Mobil Jet Oil Il 20 had an average scuffing (scoring) failure load stage of about 19.2 (arrow 21 ), and Formulation #4 30 had an average scuffing (scoring) failure load stage of about 22.5 (arrow 31 ), which indicates that Formulation #4 has a load carrying capacity about 3.94 times greater than that of the Hatco HXL-7994 oil.

Experimental Results

The experimental results for Formulation #4 of this invention and the two reference oils (Hatco HXL-7994 oil and Exxon-Mobil Jet Oil II) were obtained using a generally accepted modified variation of the Wedeven Associates, Inc. WAM Load Capacity Test Method ("WAM Test"). The WAM Test is designed to evaluate the loading capacity of lubricants and load bearing surfaces by evaluating the wear, tear, and scuffing (scoring) thereof over a large temperature range.

Table B below shows a summary of the WAM Test conditions that were utilized to test various lubricants of this invention.

TABLE B.

Ball: AISI 9310; Ra: 10-12 //in Rolling Velocity: 158 in/sec Disc: AISI 9310; Ra: 6 //in Sliding Velocity: 345 in/sec Ball Velocity: 234 in/sec Entraining Velocity: 158 in/sec Disc Velocity: 234 in/sec Velocity Vector Angle (Z): 95° Disc Hardness: 62.5 - 63.5 HRC Temperature: Ambient (-22⁰C) Bali Hardness: 62.5 - 63.5 HRC

For a detailed description of the WAM Test, see WAM High Speed Load Capacity Test Method, SAE Aerospace AIR4978, Revision B, 2002, and U.S. Patent No. 5,679,883 to Wedeven, both of which are hereby incorporated in full by reference.

High load-carrying oils frequently result in test suspension at load stage 30 without a scuffing (scoring) event. To differentiate candidate formulations that reach test suspension, tests can be run with a modified test protocol. The modified test protocol operates at a lower entraining velocity than the standard test protocol, which reduces the EHD film thickness and increases the test severity by causing greater asperity interaction. The test essentially operates at a reduced film thickness to surface roughness (h/σ) ratio.

The modified test protocol was developed for high load-carrying oils used for aviation gearboxes. These oils include the DOD-PRF-85734 oils for the U.S. Navy and the Def Stan 91-100 oils for the U.K. Ministry of Defense. With the modified test protocol, the highest load-carrying oils currently used in military aircraft experience scuffing (scoring) failures at load stages that range from approximately 19 to 28.

AISI 9310 specimen preparation:

Formulation #4, the Hatco HXL-7944 oil, and the Exxon-Mobil Jet Oil Il were comparatively evaluated for scuffing (scoring) resistance using a load capacity test method developed for the US Navy. The test method used ball and disc specimens. The ball specimens were 13/16-inch diameter, and the disc specimens were 4 inches in diameter and Vz inch thick. Material composition, hardness and surface finish were closely controlled. The specimens were fabricated from AISI 9310 steel, a surface-carburizing alloy that is very common for gear applications. AISI 9310 balls, or "Hard Ground" balls were heat-treated and ground in a ball manufacturing process. The balls were fabricated through the hard grinding stage. The surface finish following this operational stage was between about 10-12 microinch Ra.

The composition, hardness and surface finish of the specimens are given below:

Scuffing (Scoring) Results:

The scuffing (scoring) results of Formulation #4, the Hatco HXL-7944 oil, and the reference oil Exxon-Mobil Jet Oil II) are summarized in Table C and shown in the figure.

Table C.

Jet Oil II

Exxon-Mobil

UTLCC3 UTLCC3-9a 9-10a/3 5 24 Jet Oil II

Exxon-Mobil

UTLCC4 UTLCC3-9b 9-I0a/3 4 25 Jet Oil II

Exxon-Mobil

UTLCC5 UTLCC5-9a 9-10a/3 3 7 15 19.2 Jet Oil II

The load carrying capacity is indicated by an average scuffing (scoring) failure stage (load stage). Increased performance is observed with higher load stages. As shown in Table C, our experimental results show that the average scuffing (scoring) failure stage of Formulation # 4 is about 22.5. This scuffing (scoring) load is 3.94 times greater than that of the Hatco HXL-7944 oil, which delivered an average scuffing (scoring) failure stage of 5.7. The load carrying capacity of Formulation #4 is also superior to that of Exxon-Mobil Jet Oil II, which delivered an average scuffing (scoring) failure stage of 19.2.

While the embodiments described above are directed to lubricants of the polyol ester (POE) type, a skilled artisan would recognize that the compositions apply equally to other lubricant stock compositions including, but not limited to, lubricants comprising grease, mineral (hydrocarbon-based), polyalkylene glycol (PAG), aromatic naphthalene (AN), alkyl benzenes (AB) and polyalphaolefin (PAO) types.

It should therefore be understood that the foregoing description is only illustrative of the present invention. A skilled artisan, without departing from the present invention, can devise various alternatives and modifications.

Accordingly, the present invention is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A multifunctional lubricant additive composition comprising:

(a) a molybdenum compound of the general formula:

- MoO_mS₄— (I)

wherein X¹ is an oxygen or sulfur atom and R³ and R⁴ are each independently a CnH_2n+i alkyl group, wherein n is an integer of about 2 < n < 10, and m is an integer of about 0 < m < 4;

(b) a secondary zinc dithiophosphate compound of the general formula:

wherein R³, R⁴, R⁵, and R⁶ are each a C_hHb_h+i secondary alkyl groups of the formula: R'

CH

R⁰

wherein h is an integer of about 3 < h < 11 , wherein R⁷ and R⁸ are each a CjH2i+i alkyl group, and i is an integer of about 1 < i < 5;

(c) an aryl or alkyl phosphite compound of the general formula:

wherein R⁹, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each a C_jH_2j+1 alkyl group, and j is an integer of about 1 < j < 20, wherein the alkyl groups exhibit tertiary structures, and;

(d) a compound having at least one alkylthiocarbamoyl group of the general formula:

wherein R¹⁵, R¹⁶, R¹⁷, and R¹⁸ are each C_kH_2k+i alkyl groups, and k is an integer of about 1 < k < 30, and R¹⁵, R¹⁶, R¹⁷, and R¹⁸ optionally form a ring structure with the nitrogen atom to which they are bonded; wherein (A) is a chain of sulfur atoms, S_n, or S-(CH₂)_m-S, and n is an integer of about 1 < n < 10, and m is an integer of about 1 < m < 6; wherein the total amount of compounds (a) to (d) is about 15% or less by mole, based on the total amount of lubricant.

2. A composition according to claim 1 , wherein compound (a) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

3. A composition according to claim 1 , wherein compound (a) is present in an amount from about 0.1% to about 3% by mole based on the total amount of lubricant.

4. A composition according to claim 1 , wherein compound (b) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

5. A composition according to claim 1 , wherein compound (b) is present in an amount from about 0.1% to about 3% by mole based on the total amount of lubricant.

6. A composition according to claim 1 , wherein compound (c) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

7. A composition according to claim 1 , wherein compound (c) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

8. A composition according to claim 1 , wherein compound (d) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

9. A composition according to claim 1 , wherein compound (d) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

10. A composition according to claim 1 , wherein the lubricant is selected from a group consisting of: gear oil, bearing oil, sliding surface lubrication oil, chain lubricating oil, and engine oil.

11. A method of improving the performance characteristics of a lubricant, comprising the step of: mixing a lubricant with a multifunctional lubricant additive composition comprising:

a) a compound represented by the general formula:

wherein X¹ is an oxygen or sulfur atom and R³ and R⁴ are each a C_nH_2n+i alkyl group, wherein n is an integer of about 2 < n < 10, and m is an integer of about 0 < m < 4;

(b) a compound represented by the general formula:

wherein R³, R⁴, R⁵, and R⁶ are each a C_hH_2h+i secondary alkyl group represented by the formula:

^R7\

CH

wherein h is an integer of about 3 < h < 11 ; wherein R⁷ and R⁸ are each a CjH_2J+I alkyl group, and i is an integer of about 1 < i < 5;

(c) a compound represented by the general formula:

(d) a compound represented by the general formula:

R 15 'R 17

(IV)

N (A) -C N

R 16_/ R 18

wherein R¹⁵, R¹⁶, R¹⁷, and R¹⁸ are each a C_kH₂ι_<+i alkyl group, and k is an integer of about 1 < k < 30, and R¹⁵, R¹⁶, R¹⁷, and R¹⁸ optionally form a ring structure with the nitrogen atom to which they are bonded; wherein (A) is a chain of sulfur atoms, S_n, or S-(CH₂)m-S, and n is an integer of about 1 < n < 10, and m is an integer of about 1 ≤ m ≤ 6; wherein the total amount of compounds (a) to (d) is equal to or less than about 15% by mole, based on the total amount of lubricant.

12. A method according to claim 11 , wherein compound (a) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

13. A method according to claim 11 , wherein compound (a) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

14. A method according to claim 11 , wherein compound (b) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

15. A method according to claim 11 , wherein compound (b) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

16. A method according to claim 11 , wherein compound (c) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

17. A method according to claim 11 , wherein compound (c) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

18. A method according to claim 11 , wherein compound (d) is present in an amount from about 0.1 % to about 6% by mole based on the total amount of lubricant.

19. A method according to claim 11 , wherein compound (d) is present in an amount from about 0.1 % to about 3% by mole based on the total amount of lubricant.

20. A method according to claim 11 , wherein the lubricant is selected from a group consisting of: gear oil, bearing oil, sliding surface lubrication oil, chain lubricating oil, and engine oil.

21. A multi-functional lubricant comprising:

a base lubricant; and at least one additive selected from the group consisting of: a molybdenum compound, a secondary zinc dithiophosphate compound, an aryl or alkyl phosphite compound, and a compound having at least one alkylthiocarbamoyl group, wherein

(a) the molybdenum compound has the general formula:

- MoO_mS₄— (I)

wherein X¹ is an oxygen or sulfur atom and R³ and R⁴ are each independently a C_nH₂n₊i alkyl group, wherein n is an integer of about 2 < n < 10, and m is an integer of about 0 ≤ m ≤ 4; (b) the secondary zinc dithiophosphate compound has the general formula:

wherein R³, R⁴, R⁵, and R⁶ are each a C_hH_2h+i secondary alkyl groups of the formula:

R⁷.

wherein h is an integer of about 3 ≤ h < 11 , wherein R⁷ and R⁸ are each a QH_2J+I alkyl group, and i is an integer of about 1 < i < 5;

(c) the aryl or alkyl phosphite compound has the general formula:

wherein R⁹, R¹⁰, R¹¹, R¹², R¹³, and R¹⁴ are each a CjH₂j+i alkyl group, and j is an integer of about 1 < j < 20, wherein the alkyl groups exhibit tertiary structures, and;

(d) the compound having at least one alkylthiocarbamoyl group has the general formula:

R 15 'R 17

(IV)

N (A) -C -N

R 16, \R 18

wherein R¹⁵, R¹⁶, R¹⁷, and R¹⁸ are each C_kH₂ι_<+i alkyl groups, and k is an integer of about 1 < k < 30, and R¹⁵, R¹⁶, R¹⁷, and R¹⁸ optionally form a ring structure with the nitrogen atom to which they are bonded; wherein (A) is a chain of sulfur atoms, S_n, or S-(CH2)_m-S, and n is an integer of about 1 < n < 10, and m is an integer of about 1 < m < 6; wherein the total amount of compounds (a) to (d) is about 15% or less by mole, based on the total amount of lubricant.

22. The multifunctional lubricant additive composition of claim 1 , wherein the molar ratio of constituent compounds (a), (b), (c) and (d) is about 1 :1 :1 :1.

23. The multifunctional lubricant additive composition of claim 1 , wherein the molar ratio of constituent compounds (a) and (b) is about 1 :1.

24. The multifunctional lubricant additive composition of claim 1 , wherein the molar ratio of constituent compounds (a), (b), (c) and (d) is about 10:10:5:1.