Nanosized particles of molybdenum sulfide and derivatives, method for its preparation and uses thereof as lubricant additive

A lubricant composition is disclosed that comprises: (a) a lubricant and (b) at least one molybdenum-containing compound in the form of surface-capped nanosized particles of the general formula: (Z)n(X—R)m wherein Z is an inorganic moiety comprising molybdenum and sulfur in the form of particles having dimensions in the range of from about 1 to about 100 nm; (X—R) is a surface-capping reagent wherein R is a C4 to C20 straight or branched-chain alkyl or alkylated cycloalkyl radical or radicals and X is a functional group capable of specific sorption and/or chemical interaction with molybdenum/sulfur moiety; n is the number of molecules of Z in the particles; m is an integer representing the amount of surface-capping reagents relative to a single particle; and the ratio of m to n is in the range of from about 1:1 to about 10:1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to organo molybdenum derivatives and their use as multifunctional friction modifier, antiwear, extreme pressure, antioxidant additives for lubricants.

2. Description of Related Art

Regulatory agencies today are seeking to improve the fuel economy of cars on the road through legislation (CAFE requirements) putting this responsibility on the car manufacturers who, in turn, transfer some of this responsibility to the lubricant oil manufacturers via engine oil specifications. It can be seen that as these fuel economy requirements become more stringent, friction modifier additives become more important to incorporate into lubricant compositions. It is an object of this invention to provide a friction modifier additive that imparts a reduction in the coefficient of friction to a lubricant composition.

In addition, zinc dialkyldithiophosphates (ZDDP) have been used in formulated oils as anti-wear and antioxidant additives for more than 50 years. However, zinc dialkyldithiophosphates give rise to ash, which contributes to particulate matter in automotive exhaust emissions. Regulatory agencies are seeking to reduce emissions of zinc into the environment. In addition, the phosphorus is also suspected of limiting the service life of catalytic converters, used on cars to reduce pollution. It is important to limit the particulate matter and pollution formed during engine use for toxicological and environmental reasons, but it is also important to maintain, undiminished, the anti-wear and antioxidant properties of the lubricating oil. In view of the aforementioned shortcomings of the known zinc and phosphorus-containing additives, it is a further object of this invention to provide anti-wear and antioxidant additives that contain neither zinc nor phosphorus.

In developing lubricating oils, there have been many attempts to provide additives that impart anti-frictional or oiliness properties to lubricating oils and molybdenum compounds are known to be useful as friction modifiers, anti-wear, extreme pressure, and antioxidants in lubrication oil compositions.

Thiocarbamate additives for lubricating oils, particularly molybdenum-containing thiocarbamates have been disclosed in the patent literature. For example, U.S. Pat. Nos. 4,395,343; 4,402,840; 4,285,822; 4,265,773; 4,272,387; 4,369,119; 4,259,195; 4,259,194; and 4,283,295, all to DeVries and King, disclose a variety of molybdenum, sulfur, and nitrogen containing compounds, including dithiocarbamates, that are useful as antioxidants for lubricants.

U.S. Pat. No. 3,509,051 discloses various molybdenum dialkyldithiocarbamates, derived from secondary amines, which are said to be useful as antioxidant and antiwear compounds for lubricating oils.

Complexes of molybdenum oxides and nitrogen-containing moieties, including dialkyldithiocarbamates, which are said to have utility as additives for lubricants, are disclosed in U.S. Pat. No. 3,419,589 to Larson et al and U.S. Pat. No. 4,164,473 to Coupland et al.

U.S. Pat. No. 3,541,014 to LeSuer discloses molybdenum complexes of Group II metal-containing compounds, e.g., overbased Group II metal sulfonates that are said to improve extreme pressure properties and antiwear properties in lubricant compositions.

A molybdenum dihydrocarbyldithiocarbamate compound said to be useful as an additive for lubricants is disclosed in U.S. Pat. No. 4,098,705 to Sakurai et al.

U.S. Pat. No. 4,266,945 discloses the preparation of molybdenum-containing compositions by the reaction of an acid of molybdenum or salt thereof, phenol or aldehyde condensation product therewith, and a primary or secondary amine. The preferred amines are diamines such as tallow-substituted trimethylene diamine and their formaldehyde condensation products. An optional but preferred ingredient in the reaction mixture is at least one oil-soluble dispersant. The molybdenum-containing compositions are said to be useful as additives in lubricants and fuels, especially in lubricants when combined with compounds containing active sulfur.

Sulfur and phosphorus-containing molybdenum compositions said to be useful for improving fuel economy for internal combustion engines are disclosed in U.S. Pat. No. 4,289,635 to Schroeck.

U.S. Pat. No. 4,315,826 discloses multipurpose lubricant additives that are prepared by reaction of carbon disulfide with thiomolybdenum derivatives of polyalkenylsuccinimides having basic nitrogen functions. The subject additives function as dispersants and are said to possess excellent anti-frictional properties and to impart anti-wear and anti-oxidant properties to a lubricant.

U.S. Pat. No. 4,474,673 discloses the preparation of anti-friction additives for lubricating oil by reacting a sulfurized organic compound having an active hydrogen or potentially active hydrogen with a molybdenum halide.

U.S. Pat. No. 4,479,883 discloses a lubricating oil composition that contains a relatively low level of phosphorus and is said to have particularly improved friction reducing properties that comprises an ester of a polycarboxylic acid with a glycol or glycerol and a selected metal dithiocarbamate.

U.S. Pat. No. 4,501,678 discloses a lubricant containing molybdenum dialkyldithiocarbamates said to be useful for improving fatigue life of gears.

U.S. Pat. No. 4,765,918 discloses the preparation of a lubricating oil additive by reacting a triglyceride with a basic nitrogen compound to form a reaction product, reacting said reaction product with an acidic molybdenum compound to form an intermediate reaction product, and reacting said intermediate reaction product with a sulfur compound to produce a lubricating oil additive.

U.S. Pat. No. 4,889,647 discloses molybdenum complexes prepared by reacting (a) a fatty oil, (b) diethanolamine, and (c) a molybdenum source. The molybdenum complexes are said to impart antifriction and antiwear properties to lubricating compositions and to decrease fuel consumption in internal combustion engines using them.

U.S. Pat. No. 4,995,996 discloses a lubricating composition comprising a major amount of an oil of lubricating viscosity and a minor amount of an additive having the formula Mo2L4wherein L is a ligand selected from xanthates and mixtures thereof and, in particular, xanthates having a sufficient number of carbon atoms to render the additive soluble in the oil. In general, the xanthate ligand, L, will have from about 2 to 30 carbon atoms.

U.S. Pat. No. 5,498,809 discloses oil soluble copolymers derived from ethylene and 1-butene that have a number average molecular weight between about 1,500 and 7,500, at least about 30 percent of all polymer chains terminated with ethylvinylidene groups, and ethylene-derived content of not greater than about 50 weight percent, and which form solutions in mineral oil free of polymer aggregates, as determined by light scattering measurements. Lubricating oil additives, particularly dispersants, produced by the functionalization and derivatization of these copolymers are said to have enhanced performance (e.g., improved dispersancy and pour point) in lubricating oil compositions, attributable in part to the combination of properties characterizing the copolymers.

The preparation of nanosized surface-capped inorganic sulfides via intermediate reverse microemulsion formation is described in the following references:

Boakye et al.J. Coll. Interface Sci.163(1):120-129 (1994) describe the synthesis of molybdenum sulfide nanosized particles in the range of 10-80 nm without surface-capping reagents.

Deng et al.,Chem. Lett.(6):483-484 (1997) describe a novel synthetic approach to CdS nanoparticles capped with an electric neutral surface capping agent of 2,2-bipyridine in sodium(bis-2-ethylhexyl) sulfosuccinate (AOT) reverse micelle.

Huang et al.,Langmuir13(2):172-175 (1997) describe copper nanoparticles capped with poly-(N-vinylpyrrolidone) and prepared by the reduction of Copper II acetate in water and 2-ethoxyethanol using hydrazine under reflux.

Meldrum et al.J. Chem. Soc. Faraday Trans.91 (4):673-680 (1995) describe the formation of thin particulate films from silver nanoparticles, generated by the sodium borohydride reduction of aqueous silver nitrate within sodium(bis-2-ethylhexyl) sulfosuccinate reverse micelles in 2,2,4-trimethylpentane and capped with octadecanethiol.

Motte et al.,J. Phys III7(3):517-527 (1997) describe reverse micelles that have been used to synthesize 5.6 nm silver sulfide particles. These nanoparticles are coated with dodecanethiol, extracted from reverse micelles, and then dissolved in heptane.

Motte et al.,J. Phys. Chem.,99(44):16425-16429 (1995) describe utilization of dodecanethiol for surface capping of various metal sulfide nanosized particles.

Steigerwald et al.J. Amer. Chem. Soc.110(10):3046-3050 (1988) describe a synthesis of nanometer-sized clusters of CdSe using organometallic reagents in inverse micellar solution and chemical modification of the surface of these cluster compounds to form a PhSe layer on the CdSe surface.

Yanagida et al.Bull. Chem. Soc. Jpn.68(3):752-758 (1995) describe size-controlling CdS nanocrystallites that were prepared by using thiophenol or hexanethiol as a capping reagent by controlling the ratio of Cd++to bis(trimethylsilyl) sulfide as a source of the sulfide ion in reversed micelles.

Unfortunately, a problem remains in that many molybdenum compounds exhibit poor solubility in lubricant oils. No disclosures are known to the present inventors that teach or even suggest nanosize particles comprising a molybdenum/sulfur moiety whose surface is modified with an appropriate ligand that prevents the coagulation of the nanoparticles and provides their solubility and stability in hydrocarbons or similar solvents, which further improves anti-wear properties, antioxidant properties, extreme pressure properties, and friction modifying properties in lubricating oil compositions.

SUMMARY OF THE INVENTION

The additives of the present invention are complex reaction products prepared in a series of reactions. The additives are molybdenum sulfide nanosized particles [MoSx] whose surfaces are modified with one or more appropriate ligands to prevent the coagulation of the nanoparticles and provide solubility and stability therefor in hydrocarbons or similar solvents.

More specifically, the present invention is directed to a lubricant composition comprising:A) a lubricant, andB) at least one molybdenum-containing compound in the form of surface-capped nanosized particles of the general formula
(Z)n(X—R)m
wherein:Z is an inorganic moiety comprising molybdenum and sulfur in the form of particles having dimensions in the range of from about 1 to about 100 nm;(X—R) is a surface-capping reagent where R is a C4to C20straight or branched-chain alkyl or alkylated cycloalkyl radical or radicals and X is a functional group capable of specific sorption and/or chemical interaction with the molybdenum/sulfur moiety;n is the number of molecules of Z in the particles;m is an integer representing the amount of surface-capping reagents relative to a single particle; andthe ratio of m to n is in the range of from about 1:1 to about 10:1.

In another aspect, the present invention is directed to a process for preparing a molybdenum-containing compound in the form of surface-capped nanosized particles of the general formula
(Z)n(X—R)m
wherein:Z is an inorganic moiety comprising molybdenum and sulfur in the form of particles having dimensions in the range of from about 1 to about 100 nm;(X—R) is a surface-capping reagent wherein R is a C4to C20straight or branched-chain alkyl or alkylated cycloalkyl radical or radicals and X is a functional group capable of specific sorption and/or chemical interaction with the molybdenum/sulfur moiety;n is the number of molecules of Z in the particles;m is an integer representing the amount of surface-capping reagents relative to a single particle; andthe ratio of m to n is in the range of from about 1:1 to about 10:1; wherein the process comprises the steps of:A) creating a reversed microemulsion comprising a hydrocarbon-soluble surfactant solution in an organic solvent or solvent mixture and an aqueous solution of a water-soluble inorganic molybdenum (VI) compound;B) is necessary to create a molybdenum/sulfur moiety, converting the water-soluble inorganic molybdenum (VI) compound into a thio-derivative by reaction with hydrogen sulfide;C) adding a surfactant that chemically interacts with and/or adsorbs on the molybdenum/sulfur moiety;D) removing water and the organic solvent(s) from the microemulsion and extracting the molybdenum/sulfur moiety-containing products thereof in the form of surface-capped nanosized particles with a suitable organic solvent; andE) removing said suitable organic solvent.

The present invention is also directed to the use of the surface-capped nanosize molybdenum sulfide derivative particles as friction modifying, antiwear, extreme pressure, and antioxidant additives for lubricating oils.

The present invention is also directed to lubricating oil compositions comprising a lubricating oil and a functional-property-improving amount of the surface-capped nanosize molybdenum/sulfur moiety-containing particles described above.

Preferably, the present invention is directed to a composition comprising:A) a lubricant;B) surface-capped nanosize molybdenum/sulfur moiety-containing particles; and, optionally,C) one or more auxiliary additives selected from the group consisting of dispersants, detergents, rust inhibitors, antioxidants, metal deactivators, anti-wear agents, antifoamants, friction modifiers, seal swell agents, demulsifiers, VI improvers, and pour point depressants.

EXAMPLES

Preparation of Surface-Capped Molybdenum Sulfide Nanoparticles Using Various Surface-Capping Agents

Organic Amine Modification

Cetyltrimethylammonium bromide (0.652 g) was dissolved in 45 mL of chloroform and 100 μL of a saturated aqueous solution of (NH4)6Mo7O24.2H2O was added with stirring. The opaque solution was heated, then 20 mL of isooctane and 20 mL of chloroform were added, and 10 drops of concentrated aqueous HCl solution, resulting in a clear solution. Excess H2S was bubbled in until a weak yellow color was obtained, then 11 mL of a solution obtained by dissolving 0.577 g of isopropyloctadecylamine in 50 mL of chloroform (Mo:N˜1:5) was added. Three days later, all solvents were evaporated from the resulting dark solution containing small sediment, the residue was stirred with 30 mL tetrahydrofuran (THF), undissolved cetyltrimethylammonium bromide (CTAB) containing some MoS3was filtered off, and the resulted dark clear solution was evaporated.

CTAB (0.757 g) was dissolved in 100 mL of chloroform and diluted with 100 mL of hexane. One hundred mL of saturated aqueous solution of (NH4)6Mo7O24.2H2O was added with stirring, followed by 12 μL of concentrated aqueous HCl solution, which resulted in a clear solution. H2S was bubbled in over a one hour period until the color became gray-brown, then 30 μL of sec.-butylamine was added, whereupon the solution became a deep brown. Twenty-four hours later, all the solvents were evaporated from the dark solution, the residue was stirred with 15 mL of tetrahydrofuran (THF), undissolved CTAB containing some MoS3was filtered off, and the resulting dark clear solution was evaporated to yield 0.1279 g of a dark substance.

Alkenyl succinimide (ASI, 1.7 mL) (the reaction product of Indapol H-1500 (polyisobutylene) with maleic anhydride, which is then reacted with triethylenetetraamine (TETA), (Uniroyal Chemical Company) solution (0.2185 g ASI in 5 mL chloroform) was dissolved in 100 mL of a 0.01M solution of CTAB in chloroform-hexane solution (1:1 v/v) with stirring. After 10 minutes, 0.05 mL of a saturated aqueous solution of (NH4)6Mo7O24was added to produce an opaque microemulsion (ASI:Mo=1,6:1.1 by moles). Addition of approximately 8.5 μL of concentrated aqueous HCl resulted in a clear solution, into which excess H2S was bubbled. The color of the solution changed from green to brown and, after 24 hours, a brown precipitate formed. Organic solvents were evaporated under vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. The resulting residual brown substance (0.0523 g) was nanosized molybdenum sulfide particles modified with ASI in a modifier to Mo ratio of approximately 1:1.

Alkenyl succinimide solution (0.85 mL of 0.2185 g ASI in 5 mL chloroform) was dissolved in 100 mL 0.01M solution of CTAB in a chloroform-hexane solution (1:1 v/v) with stirring. After 10 minutes, 0.05 mL of a saturated aqueous solution of (NH4)6Mo7O24was added to produce an opaque microemulsion (ASI:Me=0.56:1.1 by moles). Addition of approximately 7 μL of concentrated aqueous HCl resulted in a clear solution, into which excess H2S was bubbled. The solution turned opaque and its color changed from greenish to brown. After 24 hours the solution was still opaque and brown and no precipitate had formed. The organic solvents were evaporated under vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. The residual brown substance (0.04 g) was nanosized molybdenum sulfide particles modified with ASI in a modifier to Mo ratio of approximately 1:2.

A saturated aqueous solution of (NH4)6Mo7O24(0.05 mL) was added to 100 mL 0.01M CTAB solution in a chloroform-hexane mixture (1:1 v/v). After 5 minutes, 1.7 mL of alkenyl succinimide solution (0.2185 g of ASI in 5 mL chloroform) was added to produce a colorless opaque microemulsion (ASI:Me=1.6:1.1 by moles). The addition of approximately 6 μL of concentrated aqueous HCl resulted in a clear solution, into which excess H2S was bubbled. The solution slowly turned brown. After 24 hours, the organic solvents were evaporated under vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. The residual brown substance (0.094 g) was nanosized molybdenum sulfide particles modified with ASI in a modifier to Mo ratio of approximately 1:1.

Example 5 was repeated except that the ASI solution was added to the CTAB solution first, and then the saturated aqueous solution of (NH4)6Mo7O24was added. Hydrogen sulfide was bubbled in over a period of approximately 2.5 hours. Product isolation resulted in 0.1052 g of nanosized molybdenum sulfide particles modified with ASI in a modifier to Mo ratio of approximately 1:1.

Carboxylic Acid Modification

Seven μL of saturated aqueous ammonium molybdate solution was added with stirring to 7 mL of 0.01 mol/L CTAB solution in a 1:1 v/v isooctane-chloroform mixture, then the mixture was stabilized by addition of concentrated aqueous HCl (1 drop). After 30 minutes, H2S was bubbled into the slightly blue solution turning it yellow, and 0.19 mL of a solution containing 0.0282 g behenic acid in 5 mL of chloroform was added. Excess H2S was further bubbled in. After 24 hours, a light brown sediment formed The residue, after removing all solvents, dissolved in chloroform and benzene (except for CTAB, in the latter case).

Two mL of behenic acid solution (0.2165 g of behenic acid in 10 mL of chloroform) was dissolved in 100 mL of 0.01M solution of CTAB in chloroform-hexane solution (1:1 v/v) with stirring. After 10 minutes, 0.05 mL of a saturated aqueous solution of (NH4)6Mo7O24was added, producing an opaque microemulsion (C22acid:Mo=1;1.3 by moles). Addition of approximately 5.5 μL of concentrated aqueous HCl resulted in a clear solution, into which excess H2S was bubbled for 2.5 hours. The color of the solution changed from green to brown. After 24 hours, the organic solvents were evaporated in vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. A residual brown substance (0.037 g) resulted, representing nanosized molybdenum sulfide particles modified with behenic acid in a modifier to Mo ratio of approximately 1:1.3.

Dialkyldithiophosphoric Acid Derivatives Modification

Fifty mL of aqueous saturated ammonium molybdate solution was added to 10 mL of 0.01 mol/L CTAB solution in isooctane-chloroform in a 1:1 v/v mixture under reflux, followed by 75 μL of concentrated aqueous HCl . Then 0.07 μL of a solution containing 0.1 g di-2-ethylhexyl-dithiophosphoric acid in 2 mL chloroform was added (10 molar % relative to Mo) and excess H2S bubbled in. Twenty-four hours later, a sediment was formed that was isolated by filtration. The dark-brown solid thus obtained dissolves in chloroform, THF, and slightly in benzene, CCl4and sec. —C4H9NH2.

Dialkyldithiocarbamic Acid Derivatives Modification

Tetra(hexadecyl)thiuram disulfide (THDTS) solution. (1.5 mL of 0.204 g THDTS in 5 mL of chloroform) was dissolved in 100 mL of a 0.01M solution of CTAB in chloroform-hexane solution (1:1 v/v) with stirring. After 10 minutes, 0.05 mL of a saturated aqueous solution of (NH4)6Mo7O24was added to produce an opaque microemulsion (THDTS:Mo=1:1 by moles). Addition of approximately 5 μL of concentrated aqueous HCl resulted in a clear solution, and excess H2S (about 300 mL) was bubbled in. The solution's color changed from light-brown to dark green-brown. After 24 hours, no visible precipitate had formed in the solution. The organic solvents were evaporated under vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. The residual brown substance (0.0673 g) was nanosized molybdenum sulfide particles modified with THDTS in a modifier to Mo ratio of approximately 1:1. The whole sample completely dissolves in 3 mL benzene.

Sodium di(hexadecyl)dithiocarbamate (NaHDTC) solution (1.5 mL of 0.204 g NaHDTC in 5 mL chloroform) eras dissolved in 100 mL of a 0.01M solution of CTAB in chloroform-hexane solution (1:1 v/v) with stirring. After 10 minutes, 0.05 mL of a saturated aqueous solution of (NH4)6Mo7O24was added to produce a light-yellow solution (NaHDTC:Mo=1:1 by moles). Addition of approximately 2.5 μL of concentrated aqueous HCl resulted in a clear solution, and excess H2S (about 300 mL) was bubbled in. The solution's, color changed to yellow-brown. After 24 hours, no visible precipitate had formed in the solution. The organic solvents were evaporated under vacuum, the residue was stirred with 15 mL of freshly distilled THF, the undissolved matter was filtered off, and the THF was evaporated. The residual brown substance (0.043 g) was nanosized molybdenum sulfide particles modified with NaHDTC in a modifier to Mo ratio of approximately 1:1. The whole sample completely dissolves in 5 mL benzene.

Preparation of Additives and of Lubricant Compositions

Lubricant Composition A

The sample obtained in Example 1 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition H

The sample obtained in Example 2 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition C

The sample obtained in Example 3 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition D

The sample obtained in Example 4 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition E

The sample obtained in Example 5 was dissolved in 0.07 g ASI on heating to about 60° C. An additional 0.06 g ASI was added to improve solubility, although some solid particulate material remained, which was later filtered off Then 1.6 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing less than about 10 wt % of the additive package.

Lubricant Composition F

The sample obtained in Example 6 was dissolved in 0.132 g ASI on heating to about 60° C. and 4.486 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition G

The sample obtained in Example 7 was dissolved in 0.16 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt % of the additive package.

Lubricant Composition H

The sample obtained in Example 7 was dissolved in 0.149 g ASI on heating to about 60° C., and 4.7 mL T46 oil was added on heating to about 60° C. Some solid particulate material was later filtered off. The warm solution was clear, but cooling to ambient temperature resulted in sediment formation. This sample was not tested.

Lubricant Composition I

The sample obtained in Example 8 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition J

The sample obtained in Example 9 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package,

Lubricant Composition K

The sample obtained in Example 10 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark-brown composition containing about 5 wt. % of the additive package.

Lubricant Composition L

The sample obtained in Example 11 was dissolved in 0.2 g ASI on heating to about 60° C., and 5 mL of T46 oil was added. The solution was filtered to produce a dark brown composition containing about 5 wt % of the additive package.

SRV Tribometer Determination of Friction Coefficient and Antiscuffing Properties

Friction coefficient measurements were performed using SRV vibration tribometer (Optimol Instruments GmbH, Germany) for the ball-area pair (friction point) at 50 MHz, stepwise loading from 20 to 1000 N. Friction coefficient versus load value was measured, as well as load-carrying ability of the lubricant tested. Better results are assumed to be those demonstrating a lower value of friction coefficient and a higher value of scuffing load.

Lubricant compositions containing the surface-capped nanosized molybdenum sulfide particles were prepared on the basis of Turbine Oil T46 and included different amounts of the molybdenum-containing additives. Tribological properties of the lubricant compositions of this invention are compared with those of a composition containing 1 wt. % of molybdenum oxosulfo-(diisooctyldithiocarbamate) complex (Composition M), see Zaimovskaya T. A. et al.Izv. AN SSSR Ser. Khim., No.5:2151 (1991).

The test results are presented in Table 2.

Cetyltrimethylammonium bromide (CTAB) (0.757 g, 0.02 mol) was dissolved in 100 mL in CHCl3, stirred for a period of 15 minutes, and then the mixture was diluted with 100 mL hexane (solution A). Alkenyl succinimide (0.2188 g) was dissolved in 2 mL of CHCl3(solution B). Freshly re-crystallized salt (NH4)6Mo7O24was dissolved in distilled water to give a saturated solution (room temperature, approx. 40% by weight) (solution C). A quantity of 1.327 mL of solution B (approx. 2.2×10−4mol) was added with stirring to solution A. Ten minutes later, 100 μL of solution C (approx. 2.8×10−5mol of salt, 1.93×10−4mol Mo) was added using a microsyringe. Finally, 0.2 mL of hydrochloric acid (36% by weight, 2×10−3mol) was added. The solution thus obtained was clear and colorless. An excess of H2S was bubbled through the resultant solution over a period of 2.5 hours, Sixteen hours later (the next day) all volatile matter was removed under reduced pressure and the solid residue was dried under reduced pressure (0.1 mm Hg). Ten mL of freshly distilled tetrahydrofuran (THF) was added to the residue and the mixture was filtered through a porous glass filter (precipitate left on filter (CTAB) was white). The resultant dark-brown solution was evaporated to dryness under reduced pressure (temperature less than 60° C.) and dried to give 0.1505 g of a dark-brown substance. Alkenyl succinimide (0.301 g) was added to the residue and the entire mixture was heated to 60° C. and thoroughly mixed manually using a glass rod. This product was tested in the Cameron-Plint machine after being formulated into an engine oil.

Cetyltrimethylammonium bromide (CTAB) (1.1355 g, 0.03 mol) was dissolved in 150 mL CHCl3, stirred for a period of 15 minutes and the mixture was diluted with 150 mL of hexane (solution AA). Alkenyl succinimide (0.4370 g) was dissolved in 4 mL of CHCl3(solution BB). Freshly re-crystallized salt, (NH4)6Mo7O24, was dissolved in distilled water to give a saturated solution (room temperature, approx. 40% by weight) (solution C). A quantity of 1.99 mL of solution BB (approx. 3×10−4mol) was added with stirring to solution AA and 150 μL of solution C (approx. 4.2×10−5 mol of salt, 2.94×10−4mol Mo) was added using a microsyringe. Finally, 0.3 mL of hydrochloric acid (36% by weight, 3×10−3mol) was added. The solution thus obtained was clear and colorless. An excess of H2S was bubbled through the resultant solution over a period of 5 hours, at the end of which, the solution had become opaque. Sixteen hours later (the next day) all volatile matter was removed under reduced pressure and the solid residue was dried under reduced pressure (0.1 mm Hg). Fifteen mL of freshly distilled tetrahydrofuran (THF) was added to the residue and the mixture was filtered through a porous glass filter (the precipitate left on the filter (CTAB) was brown). The resultant dark-brown solution was evaporated to dryness under reduced pressure (temperature less than 60° C.) and dried to give 0.2526 g of a dark-brown substance. Alkenyl succinimide (0.505 g) was added to the residue and the entire mixture was heated to 60° C. and thoroughly mixed manually using a glass rod. This product was tested in the Cameron-Plint machine after being formulated into an engine oil.

Cameron-Flint TE77 High Frequency Friction Machine Friction Coefficient

Testing

The anti-friction properties of the oil solubilized molybdenum nano-particles in a fully formulated lubricating oil were determined in the Cameron Plint TE77 Friction Test. The fully formulated lubricating oils tested contained 1.5 wt. % of the additive. The additives were tested for effectiveness in a motor oil at increasing temperature points and compared to are identical formulation without the friction modifier. In Table 3, the numerical value of the tee: results (Coefficient of Friction) decreases with an increase in effectiveness. In other words, the lower the Friction Coefficient value the better the additive is at reducing friction.

The test procedure for determining the friction coefficient with the Cameron-Plint TE77 High Frequency Friction Machine is as follows. Ten mL of an oil sample containing additive is placed in the test chamber so as to cover a flat stationary hardened ground NSOH B01 Gauge Plate (RC 60/0.4 micron). A reciprocating specimen, a 16 mm long nitrided steel dowel pin (6 mm diameter, 60 Rc), is placed on top of the steel plate under 50 Newton load, allowed to heat up to 35° C. from room temperature over 10 minutes and maintained at 35° C. for 5 minutes. Then, with the 50 Newton load in place, the reciprocation frequency of 5 Hertz is begun with a 15 millimeter amplitude stroke length. The temperature is then ramped up to 50° C. over 10 minutes and maintained at 50° C. for 5 minutes. The load is then increased to 100 Newtons and the temperature is ramped up to 165° C. over 1 hour. Friction Coefficient data are collected between 60-160° C. The flat specimen is cleaned between runs with hexanes and #500 emery cloth. A new dowel pin or surface of the dowel pin is used each time. A reference oil is run alternately between experimental oils: The same flat specimen is used until the reference oil no longer provides reproducible results.

The motor oil formulation tested is a SAE 10W-30 grade containing dispersant, detergent, antioxidant, rust inhibitor, pour point depressant, OCP VI Improver, and anti-wear additive. Friction modifier was added as a top treat to this formula.

TABLE 3Cameron-Plint High Frequency Friction Machine Friction ResultsMoC of FC of FC of FC of FC of FC of FWt. %(ppm)(μ) @(μ) @(μ) @(μ) @(μ) @(μ) @Additive(in oil)(in oil)60° C.80° C.100° C.120° C.140° C.160° C.Ex. 241.53110.1150.1140.1110.0900.0550.048Ex. 251.52600.1150.1130.1100.1150.1050.064No FM10.0—0.1250.1270.1300.1330.1300.125CFM21.0—0.1150.1180.1150.1150.1210.121MoDTC30.533090.1100.1130.1000.0850.0650.5251The reference oil is a fully formulated 10W-30 gasoline crank case motor oil containing no friction modifier.2CFM is an ashless commercially available friction modifier based upon a mixture of fatty acid amides, glycerol esters, and glycerol.3MoDTC is a commercially available molybdenum dithiocarbamate.Additive from Example 24 contained 2.07 wt. % Mo, therefore the oil with the additive from Example 24 contained 311 ppm Mo.Additive from Example 25 contained 1.73 wt. % Mo, therefore the oil with the additive from Example 25 contained 260 ppm Mo.Additive MoDTC contained 5.83 wt. % Mo, therefore the oil with the additive MoDTC contained 309 ppm Mo.

In view of the many changes and modifications that can be made without departing from principles underlying the invention, reference should be made to the appended claims for an understanding of the scope of the protection to be afforded the invention.