MXPA99005513A - Lubricating oil compositions containing organic molybdenum complexes - Google Patents

Abstract

A lubricating oil composition is provided comprising a major amount of an oil of lubricating viscosity and a minor amount of, as an additive, at least one compound comprising a trinuclear molybdenum core and bonded thereto ligands capable of rendering the compound oil-soluble or oil-dispersible.

Description

COMPOSITIONS OF LUBRICANT OIL CONTAINING ORGANIC COMPOUNDS OF MOLYBDENUM FIELD OF THE INVENTION The present invention relates to lubricant compositions containing molybdenum compounds, and to methods for manufacturing them. BACKGROUND OF THE INVENTION Molybdenum disulfide is a known lubricating additive. Unfortunately, it has certain known drawbacks, some of which are caused by its insolubility in lubricating oils. Accordingly, some oil-soluble sulfur-containing molybdenum compounds have been proposed and investigated as lubricant additives. Patents of the United States of North America Numbers US-A-2,951,040; 3,419,589; 3,840,463; 4,966,719; 4,995,996, and 4,978,464 are representative of the patent specifications describing both molybdenum and sulfur. The molybdenum compounds for use as lubricant additives described in the art are mainly dinuclear molybdenum compounds, characterized by the oxidation state Mo (V). The present invention relates to the use of trinuclear molybdenum compounds as lubricant additives, that is, characterized by a different oxidation state (Mo (IV)); it is surprisingly found, in accordance with the present invention, that the trinuclear molybdenum compounds have better properties as lubricant additives, compared to the dinuclear molybdenum compounds, as evidenced by the test results mentioned hereinafter, thereby lessening the problem of the demands of a better operation of the lubricant of the original equipment manufacturers (FEO). The person skilled in the art could not predict the behavior of the compounds of Mo (IV) in lubricating oils from the behavior of the dinuclear compounds. More specifically, in view of the difference in the oxidation state, the functioning of these compounds in the oxidation-reduction reactions typical of systems containing lubricant additives would not be known or predictable, given an understanding of the operation of the dinuclear molybdenum compounds in these systems. U.S. Patent No. US-A-4, 846, 983 generally discloses compositions with cores containing metal and oxygen and optionally sulfur, wherein the core contains at least one in general from 1 to 25 metal atoms. , and the metal can be molybdenum. However, it does not describe the synthesis of oxymolybdenum and oxosulfidomolybdene compounds containing trinuclear molybdenum. Moreover, the synthetic conditions described therein are similar to those disclosed in the patents and known in the art for the manufacture of monolleate and dinuclear molybdenum thiocarbamates. The literature describes trinuclear molybdenum compounds, but either in an ionic form, or with ligands with short chain alkyl groups; see, for example, Shibahara, Coord. Chem. Rev. 123, 73-148 (1993). These described compounds, therefore, are not soluble in oil, and have not been described as lubricating oil additives. SUMMARY OF THE INVENTION In a first aspect, the invention is a lubricating oil composition comprising, or which can be made by mixing, a greater amount of an oil of lubricating viscosity, and a smaller amount, as an additive, of at least one compound comprising a trinuclear molybdenum core, and ligands bonded thereto capable of rendering the compound oil soluble or oil dispersible. Preferably, the core contains non-metallic atoms that consist wholly or partly of sulfur, and more preferably consists of trinuclear molybdenum and sulfur. The additive may be in the form of mixtures of these compounds. The lubricating compositions according to the first aspect of the invention have excellent anti-wear, anti-rust, and friction-reducing properties; they can also be compatible with other additives used in the formulation of commercial lubricant compositions, and can be made from readily available starting materials. In a second aspect, the invention is an additive concentrate for mixing with an oil of lubricating viscosity comprising, or made by mixing, an oleaginous vehicle, and from 1 to 200,000 ppm by weight, for example 50 to 150,000, such as from 50 to 100,000 molybdenum of an additive defined in the first aspect of the invention, based on the weight of the concentrate. In a third aspect, the invention is a compound having the formula Mo3SkLnQz, wherein L represents independently selected ligands, n is from 1 to 4, k is at least 4, for example from 4 to 10, such as from 4 to 7 , Q is a neutral electron donor compound, and z is from 0 to 5, wherein the compound has a core having the structure: ÍD In a fourth aspect, the invention is a method for lubricating an internal combustion engine, which comprises operating the engine and lubricating the engine with a lubricating oil composition of the first aspect of the invention. In a fifth aspect, the invention is the use of an additive as defined in the first aspect of the invention, to improve one or more lubricating oil properties, of a lubricating oil composition. In a sixth aspect, the invention is a method for the preparation of a compound comprising a trinuclear thio olibdene core, and linked thereto, ligands capable of rendering the compound oil soluble or oil dispersible, which method comprises reacting a trinuclear molybdenum source, a source of the ligands, and a sulfur source, to react in a liquid medium in order to form said compound. The source of Mo and the source of S may be in the same source. The molybdenum source, for example, may be a compound containing the [Mo3S13] ion, or a trinuclear thiomolybdenum halide.

Detailed Description of the Invention • LUBRICANT COMPOSITION OIL This oil can be selected from vegetable, animal, mineral, or synthetic oils. The oils can have a viscosity from light mineral distillate oils to heavy lubricating oils, such as gas engine oil, mineral lubricating oil, motor vehicle oil, and heavy duty diesel oil. The oils may be unrefined, refined, and re-refined. The oil can be used oil. In general, the viscosity of the oil will be from about 2 centistokes to about 30 centistokes, and especially in the scale from 5 centistokes to 20 centistokes, at 100 ° C.

• COMPOUNDS For example, the compounds may have the formula Mo3SkLn, or mixtures thereof, wherein: L represents a ligand that is independent of other ligands represented by L when n is greater than 1; n is on the scale of 1 to 4; and is at least 4, for example on the scale of 4 to 10, such as from 4 to 7, preferably 4 or 7.

Also, the compounds can have the formula Mo3SkE? Ln or mixtures thereof, wherein L and n are as defined above, k is at least 1, E is oxygen or selenium, x is at least 1, and the sum of kyx is at least 4. The above formulas (Mo3SkLn and Mo3SkE? Ln) may each additionally include a fraction Qz, wherein Q represents a neutral electron donor compound, such as water, amines, alcohols, phosphines, and ethers, and z is on the scale from 0 to 5, and includes non-stoichiometric values. The Mo3Sk cores in the above formulas have a net charge of +4. Consequently, in order to neutralize these nuclei, the total charge among all the ligands, L, in Mo3SkLn, must be -4. Four monoanionic L ligands are preferred. As indicated in the formulas, it is believed that oxygen and / or selenium can be replaced by sulfur in the core. However, in addition to trinuclear molybdenum, the core must contain at least 1, and preferably it must be primarily (i.e., more than 50 percent) sulfur. More preferred is a core consisting of molybdenum and sulfur only. The rest, if any, is oxygen and / or selenium. When the nucleus consists only of trinuclear molybdenum and sulfur, it is represented by the formula Mo3Sk, and with bound ligands, it is represented by the formula Mo3SkLn.

The electron donor compound, Qz, is merely present in the above formulas to fill any empty coordination sites on the trinuclear molybdenum compound. Ligands, including ligands L, can be independently selected from the group of: X- -R Xi? 2 R2 and mixtures thereof, and the pertio derivatives thereof, wherein X, X1, X2, and Y are independently selected from the oxygen and sulfur group, and wherein R, R2, and R are independently selected from the group consisting of H and organ groups that may be the same or different. Preferably, the organ groups are hydrocarbyl groups, such as alkyl groups (for example, wherein the carbon atom attached to the remainder of the ligand is primary, secondary, or tertiary), aryl, substituted aryl, and ether. Most preferably, all ligands are the same. It is important that the organ groups of the ligands have a sufficient number of carbon atoms to make the compounds soluble or dispersible in the oil. The solubility or dispersibility in oil of the compounds can be influenced by the number of carbon atoms in the ligands. Preferably, the selected ligand source has a sufficient number of carbon atoms to make the compound soluble or dispersible in the oil. In the compounds of the present invention, the total number of carbon atoms present among all the organ groups of the ligands of the compounds will normally be at least 21, for example from 21 to 800, such as at least 25, at least 30. , or at least 35. For example, the number of carbon atoms in each alkyl group will generally be between 1 and 100, preferably between 1 and 40, and more preferably between 3 and 20. Preferred ligands include dialkyl dithiophosphate (" ddp "), xanthates, thioxantates, dialkyl phosphate, dialkyl dithiocarbamate (" dtc "), and carboxylate, and of these, dialkyl dithiocarbamate is more preferred. The ultidentate organic ligands containing at least two of the above functionalities are also capable of binding to at least one of the trinuclear nuclei, and serving as ligands. Without wishing to be bound by any theory, it is believed that one or more trinuclear molybdenum cores can be linked or interconnected by means of at least one of these multidentate ligands. These structures fall within the scope of this invention. This includes the case of a multidentate ligand that has multiple connections to a core. Those skilled in the art will appreciate that the formation of the compounds will require the selection of the appropriate ligands that have an adequate charge to balance the charge of the corresponding core. The term "hydrocarbyl" denotes a substituent having carbon atoms directly attached to the remainder of the ligand, and is of a predominantly hydrocarbyl character within the context of this invention. These substituents include the following: (1) hydrocarbon substituents, i.e., aliphatic (eg, alkyl or alkenyl), alicyclic (eg, cycloalkyl or cycloalkenyl) substituents, aromatic substituted aliphatic, aliphatic, and alicyclic, and the like, as well as cyclic substituents wherein the ring is completed through another portion of the ligand (i.e., any two indicated substituents can together form an alicyclic group); (2) Substituted hydrocarbon substituents, ie, those containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbyl character of the substituent. Those skilled in the art will be aware of suitable groups (for example halogen (especially chlorine and fluorine), amino, alkoxy, mercapto, alkylmercapto, nitro, nitroso, sulfoxy, etc.); (3) hetero substituents, ie, substituents which, although being predominantly hydrocarbon in character within the context of this invention, contain atoms other than carbon present in an otherwise chain or ring composed of carbon atoms. Compounds having the formula Mo3SkLnQz have cationic nuclei surrounded by anionic ligands which may be represented by structures (I) and (II), as illustrated above. In general, compounds containing trinuclear molybdenum can be prepared by reaction of a suitable molybdenum source, with a source of ligand, and optionally with a sulfur abstraction substance. This can be done in a suitable liquid medium which can be aqueous or organic. Soluble or oil dispersible trinuclear molybdenum compounds can be prepared, for example, by reaction in the appropriate solvents of (M1) 2Mo3S13n (H20), where n ranges from 0 to 2, and includes non-stoichiometric values, with a suitable ligand source such as a tetraalkylthiuram disulfide. Other soluble or oil dispersible trinuclear molybdenum compounds can be formed by the reaction of (M1) 2Mo3S13n (H20), wherein n ranges from 0 to 2 and includes non-stoichiometric values, a source of ligand such as tetraalkylthiuram disulfide, dithiocarbamate of dialkyl, or dialkyl dithiophosphate, and a sulfur abstraction substance such as cyanide ions, sulfite ions, or substituted phosphines. Alternatively, a trinuclear sulfur-molybdenum halide salt, such as [M '] 2 [Mo3S7A6], may be reacted, wherein A = Cl, Br, or I, with a source of ligand, such as a dialkyl dithiocarbamate or dialkyl dithiophosphate in the appropriate solvents to form a soluble or oil dispersible trinuclear molybdenum compound. In the above formulas, M1 is a counter-ion such as NH4. The trinuclear molybdenum compounds are related by the number of sulfur atoms in the molybdenum core. Within the scale disclosed, the number of sulfur atoms in the core can be altered by the addition of sulfur abstractors, such as cyanide and substituted phosphines, or sulfur donors such as elemental sulfur and organic trisulfides to the compounds of trinuclear molybdenum. In general, trinuclear molybdenum compounds can be modified by well-known techniques, such as chromatography; however, it may not be necessary to purify the compounds. The lubricating oil compositions of the present invention can be prepared by adding to a lubricating viscosity oil, a mixture of a less effective amount of at least one trinuclear molybdenum compound, which can be prepared in amounts as described above, and if necessary, one or more co-additives, such as are described hereinafter. This preparation can be carried out by adding the trinuclear molybdenum compound directly to the oil, or by first mixing the trinuclear molybdenum compound in a suitable carrier fluid to achieve solubility or dispersibility in oil, and adding the mixture to the lubricating oil. Co-additives may be added to the oil by any method known to those skilled in the art, either prior to, in a manner contemporaneous with, or subsequent to, the addition of the trinuclear molybdenum compound. The terms "oil soluble" or "dispersible" used herein, do not necessarily indicate that the compounds or additives are soluble, dissolvable, miscible, or capable of being suspended in the oil in all proportions. However, they do mean that they are, for example, soluble or stably dispersible in oil to a sufficient degree to exert their intended effect in the environment in which the oil is used. Moreover, the further incorporation of other additives may also allow the incorporation of higher levels of a particular additive, if desired. Concentrates of trinuclear and co-additive molybdenum compounds, if required, in a suitable oleaginous carrier fluid, usually hydrocarbon, provide a convenient means of handling them before use. Lubricating viscosity oils, such as those described above, as well as aliphatic, naphthenic and aromatic hydrocarbons, are examples of suitable carriers for the concentrates. These concentrates may contain from 1 to 90, preferably from 1 to 70, and more preferably, from 20 to 70 weight percent of the additives, based on the weight of the concentrate. When a co-additive comprising at least one antioxidant additive is used as defined herein, the concentrate may contain from 1 to 90, such as from 1 to 50 weight percent of the additives, based on the weight of the concentrate. The concentrates may comprise, or may be made by mixing, the carrier fluid and the additives. The lubricating oil compositions made by the combination of a lubricating viscosity oil containing at least one trinuclear molybdenum compound of the types and in the amounts described herein, and optional co-additives, can be used to lubricate components of mechanical engines, particularly an internal combustion engine, by adding lubricating oil thereto. The trinuclear molybdenum compounds of the present invention also possess antioxidant properties when used in a lubricant composition. Tests using the eumeno hydroperoxide model compound in a base supply of mineral oil, revealed that compounds having o3Sk cores are more effective antioxidants than conventional organic antioxidants or commercially available dinuclear molybdenum additive compounds, such as alkylated dithiocarbamate. of dinuclear molybdenum. The lubricant compositions and concentrates of this invention comprise defined components that may or may not remain chemically the same before and after mixing with an oil vehicle. This invention encompasses compositions and concentrates comprising the components defined before mixing, or after mixing, or both, before and after mixing.

CO-ADDITIVES Other known lubricating additives may also be used to mix in the lubricant composition of this invention. These include dispersants, detergents, for example simple or mixed metal detergent systems, melting point depressants, viscosity improvers, antioxidants, surfactants, anti-wear substances, and friction reducing substances. These can be combined in proportions known in the art. For example, additives containing phosphorus and / or sulfur compounds, such as zinc dialkyldithiophosphate (ZDDP), can be prepared and used with the compounds of the present invention. However, the compounds of the present invention may be effective, or may even possess better properties when used in lubricating compositions that are free or substantially free of phosphorus and / or added sulfur, i.e., phosphorus and / or sulfur in addition to (that is, with the exception of) the phosphorus or sulfur contained in the trinuclear molybdenum compounds themselves. A lubricant composition that is substantially free of phosphorus and / or sulfur is one in which the amount of phosphorus and / or sulfur is not greater than what is inherently present in base oils of lubricating viscosity. It is worth noting particularly the use of antioxidants in combination with the trinuclear molybdenum compounds.

Examples of suitable antioxidants are selected from antioxidants containing copper, sulfur-containing antioxidants, aromatic amine-containing antioxidants, and phenolic antioxidants. Examples of suitable copper-containing antioxidants include oil-soluble copper compounds described in European Patent Numbers EP-B-24,146, EP-A-280,579, and EP-A-280,580. Accordingly, for example, the copper can be mixed in the oil as an oil soluble copper salt of a synthetic or natural carboxylic acid. Examples of the carboxylic acids from which suitable copper salts may be derived include carboxylic acids of 2 to 18 carbon atoms (eg, acetic acid, and fatty acids such as stearic acid and palmitic acid), unsaturated acids ( for example, oleic acid), branched carboxylic acids (for example, naphthenic acids of a molecular weight of 200 to 500, neodecanoic acid, and 2-ethylhexanoic acid), and dicarboxylic acids substituted by alkyl or by alkenyl (for example, succinic acids substituted by polyalkenyl, such as octadecenylsuccinic acids, dodecenylsuccinic acids, and polyisobutenylsuccinic acids). In some cases, suitable compounds can be derived from an acid anhydride, for example, from a substituted succinic anhydride. The copper antioxidant can be, for example, a copper dithiocarbamate or copper dithiophosphate. Other antioxidant compounds containing copper and sulfur, for example mercaptides, xanthates, copper thioxanthates, for use in accordance with the invention, as well as sulfonates, phenates (optionally sulfided), and copper acetylacetonates are also suitable. Other copper compounds that can be used according to the invention are the overbased copper compounds. Examples of these compounds, and of the processes for their preparation, are described in Patent Numbers US-A-4, 664, 822 and EP-A-0, 425, 367. The copper compound may be in cuprous form or cupric Examples of suitable aromatic amine-containing antioxidants are aromatic amines having at least one aromatic group directly attached to at least one nitrogen atom of the amine. Secondary aromatic amines, especially those having two aromatic groups attached to the same amine nitrogen atom, are preferred, but the use of other aromatic amines is not excluded. Amines may contain one or more aromatic groups, for example at least two aromatic groups. When there are two aromatic groups, both are preferably linked directly to the same amine nitrogen. Compounds may be used in which two aromatic groups are linked by a covalent bond or by an atom or group (for example, an oxygen or sulfur atom, or a group -CO-, -S02-, a or alkylene). The aromatic rings, which are preferably aromatic hydrocarbon rings, can be unsubstituted or substituted by one or more substituents selected from alkyl, cycloalkyl, alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups. Amines containing alkyl-substituted aromatic hydrocarbon rings are preferred, especially those containing two phenyl groups substituted by alkyl. Preferred N-arylamines to be used according to the invention are naphthylamines, and especially diphenylamines, including diphenylamines substituted by alkyl, wherein the alkyl group may be the same or different, having from 1 to 28 carbon atoms. In this invention, other antioxidants containing nitrogen, for example phenothiazine type compounds, can also be used. Examples of the phenolic antioxidants include: (a) sterically hindered tertiary alkyl substituted monohydric phenols, such as those described in greater detail in U.S. Patent Nos. US-A-2, 944, 086; -3,043,775; and -3,211,652; and (b) methylene bridged tertiary alkyl polyphenols, such as 4,4'-methylenebis (2,6-dibutyl tertiary-phenol), and 2,2'-methylenebis (4,6-di- (1,1, 2-trimethylpropyl) phenol), and mixtures of (a) and (b), such as those described in greater detail in European Patent Number EP-B-0456925.

Examples of the sulfur-containing antioxidants (compounds) are alkaline earth metal salts of alkylphenol thioesters preferably having alkyl side chains of 5 to 12 carbon atoms, nonylphenolic calcium sulfide, oil-soluble phenates without ash, and phenates sulphides, phosphorosulfurized or sulphurized hydrocarbons, phosphorus esters and other compounds containing molybdenum and containing sulfur. Other examples of sulfur-containing antioxidants are metal salts of dihydrocarbyl dithiophosphate or dihydrocarbyl dithiocarbamate compounds, wherein the metal is selected from Zn, Mn, Ni, Al, Group 1 metals and Group 2 metals. Sulfur-containing compounds include those described in European Patent Number EP-A-699, 759, for example sulfides of oils, fats, or polyolefins, wherein a sulfur group having two or more sulfur atoms, is attached and links to each other in a molecular structure. Examples include sulphurated sperm oil, sulfurized pinene oil, sulfurized soy bean oil, sulfurized polyolefin, sulfurized esters, dialkyl disulfide, dialkyl polysulfide, dibenzyl disulfide, dibutyl dibutyl disulfide, polyolefin polysulfide, compound of type of thiadiazole such as thiadiazole of bis-alkyl polysulfide, and sulfurized phenol. Preferred antioxidants are copper containing antioxidants, aromatic amine containing compounds, including diphenylamines and derivatives thereof having a comparable effect herein with diphenylamines, and mixtures thereof. Examples of the copper-containing antioxidants include copper polyisobutylensuccinic anhydride ("copper PIBSA"), and copper oleate; the diphenylamines include all effective diphenylamin derivatives. Accordingly, the lubricant compositions of the present invention may include a minor amount of at least one antioxidant and at least one oil soluble or oil dispersible trinuclear molybdenum compound. The lubricant composition may include a mixture of the trinuclear molybdenum compounds and antioxidants of the types disclosed herein, the lubricating oil and / or other additives disclosed herein being presented by themselves, and / or any intermediates and reaction products, as a result of the mixture. In combination, antioxidants and trinuclear molybdenum compounds are present in a lower effective amount to produce improved lubricant performance, particularly friction reduction, friction reduction, anti-oxidation, and / or anti-wear properties in the oil. The trinuclear molybdenum compounds disclosed herein, in combination with the above antioxidants, produce an improved effect with respect to lubricant performance not evident in the presence of the trinuclear molybdenum compounds or the antioxidants alone. Additionally, the improved effect of the trinuclear molybdenum compounds in the presence of these antioxidants would not be expected by one skilled in the art based on the performance of the dinuclear molybdenum and copper additives, due to the difference in the oxidation state of the molybdenum in the trinuclear molybdenum compounds and in the dinuclear molybdenum compounds. The mixture of antioxidants with the trinuclear molybdenum compounds allows reducing the molybdenum treatment rates for an effective friction reduction. The benefits are exemplified herein with bis-alkyldiphenylamine ("DPA") and copper polyisobutylensuccinic anhydride, with copper polyisobutylensuccinic anhydride demonstrating a stronger improvement. Accordingly, in the present invention, the combination of the trinuclear molybdenum compounds and the antioxidants demonstrates better performance at reduced treatment rates than the dinuclear molybdenum additives, such as Mo202S2 (dtc) 2. The improved performance of the combination of Trinuclear molybdenum compounds with these antioxidants can normally allow the use of the trinuclear molybdenum compounds in concentrations approximately twice as low as without the antioxidants.

According to the present, an effective improvement of the lubricant operation can be achieved, for example reduction of friction (lower coefficients of friction). The lubricant compositions may contain effective minor amounts, such as at least one ppm, preferably from 1 to 2,000 ppm molybdenum from the trinuclear molybdenum compounds, such as from 5 to 1,000, preferably from 20 to 1,000, and more preferably from 5 to 750 ppm, and most preferably from 10 to 300 ppm, all based on the weight of the lubricant composition. The amount of antioxidant additive is a lower effective amount, preferably from about 0.001 to about 10 weight percent, based on the weight of the finished oil, more preferably from about 0.01 to about 2 weight percent of the weight of the finished oil. final oil. Normally, for antioxidants containing copper, the amount is 1 to 1,000 ppm of copper, such as 1 to 200 ppm of copper, and for antioxidants, for example antioxidants containing aromatic amine and sulfur, phenolics, and zinc dialkyldithiophosphate, the preferred amount is up to 2 percent by weight. Within the above ranges, a person skilled in the art can select the particular effective combinations of the quantities to produce the improvement in the lubricating properties, particularly friction reduction and / or against wear, desired for the particular application. The selection within these ranges can be made in order to optimize either improved friction reduction, or anti-wear performance, or both. Therefore, the trinuclear molybdenum compounds allow the use of a better amount of antioxidant, or alternatively, with an equal amount of antioxidant, allow the use of a smaller amount of trinuclear compound, compared to the use of the compounds of dinuclear molybdenum, while still achieving the desired improved lubricant performance, ie wear and / or friction, in the oil, thus making its use potentially more cost-effective than current additives. These benefits can be achieved in the base supply, as well as in fully formulated lubricating oils. Essentially phosphorus and / or sulfur-free oils can also be treated. ADDITIONAL TECHNICAL EFFECTS OF THE INVENTION As is known in the art, lubricating oil compositions, such as those containing dinuclear molybdenum sulfide additives, lose their effectiveness over time when used in an engine. It is believed that one reason for this loss in effectiveness is that the lubricating oil is adversely affected by exposure to the N0X compounds present in the crankcase. Some attempts to remedy this deficiency have focused on the incorporation of sulfur donors and complementary antioxidants, such as dibenzyl disulfide derivatives (DBDS). These attempts have not been completely successful. The additives of the invention are effective in reducing friction at a low concentration, and remain effective even after being used in an engine, are effective at a low concentration, and retain their friction-reducing properties even in the absence of sulfur sources. complementary antioxidants. Accordingly, in a further aspect of the invention, a method for improving the frictional reduction retention properties of a lubricant composition by adding to a larger amount of lubricating viscosity oil, a lesser amount of a lubricant composition, is disclosed. first aspect of the invention. It was found in a surprising manner that these compounds improve the lubricating properties of the compositions when used in concentrations as low as 50 ppm molybdenum, based on the total weight of the composition. This is a very large reduction in concentration, comparing with the conventional dinuclear sulfur and molybdenum additives. These additives are normally used in concentrations that rise from 500 ppm, based on the total weight of the lubricant composition. Additionally, conventional dinuclear additives require complementary sulfur donor compounds in order to be as effective as the compounds of the present invention. It was found that the compounds of the present invention improve the friction reduction and friction retention properties of the lubricant compositions. For example, lubricant compositions containing 150 ppm molybdenum as Mo3S7 (dtc) 4, based on the weight of the lubricant composition, were exposed to treatment with N02. In comparison, it was found that conventional dinuclear molybdenum sulfide lubricating oil additives were less effective than the trinuclear molybdenum compounds of this invention, when the dinuclear compounds were used at a concentration of 150 ppm molybdenum, based on the weight of the the composition, before and after exposure to N02. It is believed that the fuel economy and fuel economy retention properties of a lubricant composition are related to the friction reduction and friction retention properties of the composition. Accordingly, it is believed that lubricant compositions containing trinuclear molybdenum compounds having the formula Mo3S7 (dtc) 4, and mixtures thereof, possess good fuel economy and fuel economy retention properties. As is also known in the art, lubricating oil compositions containing molybdenum sulfide additives lose their friction reducing effectiveness over time when used in an internal combustion engine. Although an improvement in the friction reducing properties is observed when the compound is added to a fresh oil, little, if any, reduction of friction is observed, when Mo202S2 (dtc) 2 is added to a used oil, where presented a loss in the friction reducing properties, depending on the degree of aging and degradation of the oil. The invention provides a composition that can improve and restore the friction reducing effectiveness of lubricating oils. Accordingly, in a still further aspect, the invention is a composition that can improve the friction reduction properties of a used lubricating oil. The friction reduction properties of a used oil can be improved or restored by adding a larger amount of used oil of a lubricating viscosity, of a minor amount of at least one compound as defined in the first aspect of the invention. A smaller amount of at least one trinuclear molybdenum compound can be added to a fresh oil in order to improve its effectiveness, particularly its friction reducing and wear reducing effectiveness. Oils can have a viscosity from lightweight mineral distillate oils to heavy lubricating oils, such as gas engine oil, mineral lubricating oil, motor vehicle oil, and heavy-duty diesel oil. A used lubricating oil is one that has been subjected to operating conditions, such as exposure to high shear forces, exposure to high temperature, exposure to a hostile chemical or physical environment, or to similar conditions. The compounds of the present invention can also be used as additives in the formulation of fresh lubricating oil compositions. As such, they possess superior friction reduction properties compared to the dinuclear molybdenum sulfide additives known in the art. In cases where the compounds of the present invention are added to a used lubricating oil that is known in the art, the resulting friction reduction performance may exceed that of the fresh oil originally formulated. EXAMPLES The invention will be more fully understood by reference to the following examples. The procedures and equipment used for the Falex Block On Ring test were similar to those used in ASTM677-83 (Classification of Resistance to Slip Wear Materials Using the Ring Block Wear Test). As used herein, "AO" means antioxidant, "eh" means "ethylhexyl." SL300 (MR) and SL321 (MR) are commercial dinuclear molybdenum compounds available from Ashai Denka, Japan. MV-LMR is Moly Van-L, a commercial dinuclear molybdenum compound available from Vanderbilt Chemical Company. As used herein "coconut" is an alkyl chain or a mixture of chains of different even numbers of carbon atoms, typically from 8 to 18 carbon atoms, "dtc" means dialkyl dithiocarbamate, "ddp" means dithiophosphate of dialkyl. Example 1; Synthesis of Mo3S4 [(2-ethylhexyl) 2dtc] 4 by Abstraction of Sulfur with Sulfite in Water. (NH4) 2Mo3 S13-2H20 (0.77 grams, 1 millimole) was added to a solution of potassium bis (2-ethylhexyl) dithiocarbamate (2.13 grams, 6 mmol) in water (50 milliliters). In another flask, potassium sulfite (0.95 grams, 6 mmol) was dissolved in water (50 milliliters). The potassium sulfite solution was added dropwise to the dialkyl molybdenum / -dithiocarbamate mixture. The mixture was allowed to react for 24 hours at room temperature, and then extracted with ether, and the ether solution was filtered. The ether extract was distilled off, the product was extracted with methanol (3 x 30 milliliters), to give the product, which was dried in vacuo to give Mo3S4 [(2-ethylhexyl) 2dtc] 4. Example 2: Synthesis of Mo3S4 [(2-ethylhexyl) 2dtc] 4, by Abstraction of Sulfur with Cyanide in Water. (NH4) 2Mo3S13-2H20 (0.77 grams, 1 millimole) was added to a solution of potassium bis (2-ethylhexyl) dithiocarbamate (2.13 grams, 6 mmol) in water (50 milliliters). In another flask, potassium cyanide (0.39 grams, 6 mmol) was dissolved in water (50 milliliters). The potassium cyanide solution was added dropwise to the molybdenum / dialkyl dithiocarbamate mixture. The mixture was allowed to react for 24 hours at room temperature, and then extracted with ether, and the ether solution was filtered. The ether extract was distilled off, the residue was extracted with methanol (3 x 30 milliliters), to give the product, which was dried under vacuum to give Mo3S4 [(2-ethylhexyl) 2dtc] 4. Example 3: Synthesis of Mo3S4 [(2-ethylhexyl) 2ddp] 4, by Abstraction of Sulfur with Phosphine. A solution of acetonitrile (50 milliliters) containing (NH4) 2Mo3 S13-2H20 (0.77 grams, 1.0 millimoles) and PPh3 (1.57 grams, 6.0 millimoles), and bis (2-ethylhexyl) dithiophosphoric acid (2.34 grams, 6.6 millimoles), it was refluxed for 24 hours, and then cooled to room temperature. The acetonitrile was decanted, and the residue was washed twice with metansl (20 milliliters). The residue was dissolved in pentane and filtered; The pentane solution was concentrated by distillation, and filtered again, and the rest of the pentane was removed to give Mo3S4 [(2-ethylhexyl) 2ddp] 4. Example 4: Synthesis of Mo3S4 [(octyl) 2dtc] 4, by Abstraction of Sulfur with Cyanide Using Tioram Disulfide as a Source of Ligand. A solution in methanol (50 milliliters) containing (NH4) 2Mo3 S13-2H20 (0.77 grams, 1.0 mmol) and KCN (0.585 grams, 9.0 mmol), and tetraoctyl thiuram disulfide (2.1 grams, 3.3 mmol), was placed refluxed for 24 hours, and then cooled to room temperature. The methanol was decanted, and the residue was washed twice with ethanol (20 milliliters). The residue was dissolved in pentane and filtered, and the pentane was evaporated to give Mo3S4 [(octyl) 2dtc] 4. Example 5; Synthesis of Mo3S7 [(lauryl) 2ddp] 4. To a solution of potassium dilauryl dithiophosphate (2.2 grams, 4.4 mmol) in methanol (100 milliliters), a solution of [NEt4] 2Mo3S7 was added. Cl6 (0.98 grams, 0.1 mmol) in acetonitrile (50 milliliters). The combined solution was heated to 60 ° C with stirring for 12 hours. The solvents were decanted, and the residue was washed with methanol, followed by acetonitrile. The washed residue was dissolved in pentane and filtered. The pentane was evaporated to give Mo3S7 [(lauryl) 2ddp] 4. Example 6: Synthesis of Mo3S7 [(2-ethylhexyl) 2dtc] 4. A 1: 1 solution of methanol / tetrahydrofuran containing (NH4) 2Mo3 S13-2H20 (3.88 grams, 5.0 mmol), and tetra (2-ethylhexyl) thiouram disulfide (9.5 grams, 15 mmol), was heated to 60 ° C. for 24 hours, and cooled to room temperature. The solution was filtered, and the solvents were evaporated, and the residue was washed with methanol. The residue was dissolved in tetrahydrofuran, the resulting solution was filtered, and the tetrahydrofuran was removed by distillation to give Mo3S7 [(2-ethylhexyl) 2dtc] 4. The compounds of Mo3SkL4 (k = 4-7) are related by the number of sulfur atoms in the molybdenum-sulfur core. The number of sulfur atoms in the core can be altered by the addition of sulfur abstractors, such as substituted cyanide and phosphines, or sulfur donors such as elemental sulfur and organic trisulfides, to the Mo3SkL4 compounds. In Examples 7 to 10, the compounds were evaluated for friction and wear performance using a Falex On-Ring Block tribometer. The data were obtained at a speed of 420 revolutions per minute, a load of 100 kilograms (220 pounds), and a temperature of 100 ° C for 2 hours. The reported data include the volume of block wear mark, measured by profilometry, the end of the test coefficient of friction (Ultimate Coefficient), and the coefficient of friction (Average Coefficient) during the 2 hour test. The end of the test coefficient of friction is obtained at the end of the test, and the average coefficient of friction provides information on the activity of the aggregate material, that is, it is considered that the samples that obtain the same friction coefficients decreased faster , contain more active friction reducing compounds. In Examples 7 to 10, the samples tested consisted of 150 Neutral Solvent (S150N) as a lubricating oil, 1 percent zinc dialkyldithiophosphate, and the compounds of the present invention with 500 ppm molybdenum, based on the total weight of the oil lubricant. The procedures and equipment used in the Examples 7 to 10 are similar to those used in the ASTM test G77-83 (Classification of Resistance of Materials to Slip Wear Using the Block Wear Test on Ring).

Comparative Example 11 For comparison purposes, the Falex Over Ring Block was conducted using only 150 Neutral Solvent (S150N) and 1 percent zinc dialkyldithiophosphate. The results are shown in Table I. TABLE I Examples 12 to 15: In these examples, the compounds of the invention were evaluated to determine their friction and wear performance as described in Examples 7 to 10. In Examples 12 to 15, the samples tested consisted of a fully formulated oil IOW30 combined with the compounds of the present invention having 500 ppm molybdenum, based on the total weight of the lubricating oil.

Comparative Example 16: For comparison purposes, the Falex Overhead Block was driven using a fully formulated IOW30 motor oil. The results are shown in Table II. TABLE II Examples 17-20: Differential scanning calorimetry (DSC) tests were conducted on samples in Solvent 150 Neutral (S150N), with the compounds of the present invention, which had 500 ppm molybdenum, based on the total weight of the lubricating oil. This differential scanning calorimetry test, a sample of the oil is heated at a rate of, eg. 5 ° C / minute, and the elevation in the temperature of the sample is measured in relation to an inert reference. The temperature at which an exothermic reaction occurs or the oxidation establishment temperature is a measure of the oxidative stability of the sample. It is believed that higher differential scanning calorimetry temperatures indicate better oxidative stability, compared to compounds that have lower differential scanning calorimetry temperatures. The results of the tests are shown in Table III. Comparative Example 21: The differential scanning calorimetry test was performed with Solvent 150 Neutral (S150N) for comparison purposes. The results are shown in Table III.

TABLE III Example 22: The compounds of this invention were evaluated for their ability to decompose the hydroperoxides. It is known that hydroperoxides have reactions that degrade the lubricant, consume the additives, and cause increased viscosity, wear, and formation of sludge and deposits. In this test, a compound of a base supply mixture (mixture of 2.25: 1 Solvent 150 Neutral (S150N): Solvent 100 Neutral (S100N) by weight) content zinc dialkyldithiophosphate is reacted with a known amount of hydroperoxide of eumeno (CHP). The eumeno hydroperoxide solution and the compound is reacted at a temperature of 125 ° C for 1 hour, and the product is analyzed by gas chromatography linked with mass spectrometry (GC / MS). The amount of eumeno hydroperoxide consumed indicates the effectiveness of the compound in the neutralizing hydroperoxides, that is, a higher amount indicates a better antioxidation. The concentration of elemental molybdenum in the test solution was constant. In compositions A and B, the base supply contained a primary zinc dialkyldithiophosphate and a trinuclear molybdenum compound. For a comparison, composition C also contained a primary zinc dialkyldithiophosphate and a commercial dinuclear molybdenum lubricant additive, Mo202S2 (dtc) 2, having a mixture of octyl2dtc and coco-dte ligands. In compositions D and E, the base supply contained a secondary zinc dialkyldithiophosphate and a trinuclear molybdenum compound. For a comparison, composition F contained a secondary zinc dialkyldithiophosphate and Mo202S2 (dtc) 2.

TABLE IV Table IV shows that the trinuclear molybdenum compounds of the present invention decompose the cumene hydroperoxide approximately seven times lower than the commercial dinuclear additive on a molecular basis in this test. On a standard molybdenum molar base, the novel trinuclear compounds work four to five times better than the commercial dinuclear molybdenum additive in this test. Example 23: In this example, the compounds of the present invention and a commercial additive were evaluated to determine their friction and wear performance. The tests were run at a concentration of 500 ppm molybdenum in a synthetic base supply free of sulfur with added esters to increase the solubility of the molybdenum compounds in the synthetic lubricating oil. Table V shows the performance results for the trinuclear molybdenum compounds of the present invention against a commercial molybdenum additive. A comparative example using an oil substantially free of sulfur, and not containing added molybdenum compounds, was not possible, because the oil only caused arrest during the test start before the load of 220 pounds was reached (100 kilograms). TABLE V Trinuclear molybdenum dithiocarbamate compounds reduce friction in sulfur-free base supplies more than dinuclear molybdenum dithiocarbamate. Example 24: In this example, the compounds of the invention and the commercial additives were evaluated to determine their friction and wear performance in a Falex Ring Block test procedure. The data was acquired at a speed of 420 revolutions per minute, a load of 220 pounds (100 kilograms), and a temperature of 100 ° C for 120 minutes. The samples were run at a concentration of 500 ppm molybdenum in a motor oil completely formulated without zinc dialkyldithiophosphate (a common additive against wear), and without compounds containing additional phosphorus. Although some of the molybdenum compounds contain phosphorus, molybdenum compounds were added at a lower treatment rate than what is typically used for zinc dialkyldithiophosphate, and contained less phosphorus by weight. The total phosphorus concentration in these oils was < 0.02 percent Tests 1 to 4 show the performance results of the samples of trinuclear molybdenum dithiocarbamates of the present invention, and commercial dinuclear molybdenum dithiocarbamates; These test cases are free of phosphorus. Tests 5 to 7 show the operation of the trinuclear molybdenum compounds of the present invention and a commercial dinuclear additive with dithiophosphate ligands. Samples from tests 5 to 7 are substantially free of phosphorus beyond the content in the ligands. A lubricant composition that is substantially free of phosphorus is one in which the amount of phosphorus is not greater than that which is inherently present in the base oils of lubricating viscosity. For comparison purposes, test 8 shows the operation of the completely formulated motor oil without zinc dialkyldithiophosphate used as the lubricating oil in this test; this test case was free of phosphorus.

TABLE VI In the following Examples 25 to 28, reference will be made to the following drawings, in which: Figure 1 shows the average friction coefficients obtained from the 2-hour Falex On-Block Test of molybdenum compounds, and molybdenum compounds in an oil formulated with or without antioxidants, but without zinc dialkyldithiophosphate. The Y axis is from 0.0 to 0.13. Figure 2 shows the comparative friction traces for a series of oils, with or without antioxidants. Figure 3 shows the friction traces comparing a Mo dinuclear compound with a trinuclear Mo compound, with or without antioxidants. Figure 4 shows the friction traces for 75 ppm of Mo as Mo3S7 [(coconut) 2dtc] 4, in four base oils. Figure 5 shows the friction traces for a dinuclear Mo compound, at a concentration of 75 ppm of Mo, in oils with or without antioxidants, and the comparative friction traces of a trinuclear Mo compound with an antioxidant. Example 25 The mixtures were prepared as follows: The dinuclear molybdenum complex, or the trinuclear molybdenum-containing compound, was placed with the appropriate equivalent of Cu (II) carboxylate (2.0 equivalents for Mo2S (dtc) 2; 0.5, 1.0, and 1.5 equivalents for Mo3S4 (dtc) 2 or Mo3S4 (ddp) 2, in a flask, and tetrahydrofuran ("THF11) was added.

After stirring for 24 hours, tetrahydrofuran was evaporated, and the resulting mixture was dissolved in S150N base oil, which contained zinc dialkyldithiophosphate ("ZDDP").

Alternatively, the examples indicated with an asterisk (*) were prepared by mixing the additives in S150N containing zinc dialkyldithiophosphate at temperatures up to 70 ° C for a sufficient period of time to dissolve the additives. The results of friction and wear are detailed in Table VII below. The compositions formed by the above methods using a starting material containing Mo3 as a class, possess characteristics of ultraviolet and infrared spectra of compounds containing trinuclear molybdenum. Friction and Wear Testing The results of the friction and wear tests using the combination of copper and trinuclear molybdenum compounds in S150N with 1 percent zinc dialkyldithiophosphate are given in Table VII. For comparison purposes, the results for molybdenum are listed in the form of Mo2S4 (coco2dtc) 2 dinuclear, and Mo3S4 (octyl2dtc) 2 or Mo3S4 (2-ethylhexyl2dtc) 2 trinuclear, Mo3S7 (coco2dtc) 2, Mo3S4 (normal octyl2ddp) 2, or Mo3S4 (2-ethylhexyl2ddp) 2, Mo3S7 (lauryl2ddp) 4, Cu (oleate) 2, and copper in combination with certain dinuclear and trinuclear molybdenum compounds. The friction and wear data were acquired using a Falex Ring Block tribometer as described above.

TABLE VII Molybdenum at 500 ppm Mo. The wear and friction results indicated that a trinuclear molybdenum compound in combination with copper carboxylates had a better effect on wear property in S150N with zinc dialkyldithiophosphate. Total wear was 50 percent lower than S150N with zinc dialkyldithiophosphate alone, and up to 75 percent less than trinuclear molybdenum compounds alone in S150N with zinc dialkyldithiophosphate. Trinuclear molybdenum in combination with copper carboxylates also exhibited a tendency towards better friction. The examples given for the dinuclear molybdenum complexes (Mo2) showed that significantly more copper was required to obtain an operation comparable to that of the trinuclear molybdenum compounds used with lower copper concentrations. Accordingly, it is demonstrated that the addition of the trinuclear molybdenum and copper (II) carboxylate compounds to lubricating oils improves the lubricating properties of the oils. EXAMPLE 26 To test the performance of the trinuclear molybdenum compounds having dtc and ddp ligands in combination with antioxidants, the bench-tribometer test was performed using a Falex Block-On-Tribometer. The compounds containing molybdenum were added at a concentration of 500 ppm Mo to an oil that was completely formulated, but without zinc dialkyldithiophosphate or complementary antioxidants. The compounds were also tested in the same formulation without zinc dialkyldithiophosphate to which were added two antioxidants, bis-nonylphenylamine (DPA) at 0.35 weight percent, and copper polyisobutylene succinic anhydride at 0.4 weight percent, yielding approximately 70 ppm coppermade. The formulations were tested in a block-on-ring tribometer (BSA) Falex as described below. The results are specified in Table VIII.

TABLE VIII Figure I shows the average coefficients of friction obtained both with and without antioxidants in a zinc dialkyl dichlorophosphate formulation.

The data demonstrate that trinuclear molybdenum compounds with antioxidants provide better performance, particularly as demonstrated by the average coefficients of friction, compared to the dinuclear molybdenum complexes in the presence of antioxidants. The samples are identified as: a Crankcase base oil without zinc dialkyldithiophosphate. b Base crankcase oil without zinc dialkyldithiophosphate + antioxidants. c Mo202S2 (coco2dtc) 2 d Mo202S2 (coco2dtc) 2 + antioxidants Mo202S2 (2 -eh2dtc) 2 ff Mo202S2 (2-eh2dtc) 2 + antioxidants g Mo3S4 (2 -eh2dt c) 2 h Mo3S4 (2-eh2dtc) 2 + antioxidants i Mo3S7 (coco2dtc) 4 j Mo3S7 (coco2dtc) 4 + Antioxidants k Mo202S2 (2 -eh2ddp) 2 1 Mo202S2 (2-eh2ddp) 2 + antioxidants m Mo2? 2S2 (hexyl2ddp) 2 n Mo202S2 (hexyl2ddp) 2 + antioxidants or Mo202S2 (2 -eh2ddp) 2 p Mo202S2 (2-eh2ddp) 2 + antioxidants q o3S4 (octil2ddp) 4 r Mo3S4 (octil2ddp) 4 + antioxidants s Mo3S7 (lauryl2ddp) 4 t Mo3S7 (lauryl2ddp) 4 + antioxidants Example 27 The friction properties of a set of oils (1 + 6) were determined. All the oils were based on the same formulated oil that contained zinc dialkyldithiophosphate, the "starting oil". Four of the oils (1 to 4) contained Mo in a concentration of 150 ppm by weight, provided by mixing the trinuclear Mo compound, Mo3S4 ((2-ethylhexyl) 2dtc) with the "starting oil", but differed in their respective contents of antioxidants. The two remaining oils (5 and 6) were both free of Mo, but differed in their antioxidant content. The results are shown first in Figure 2 as the traces a, b, c, d, e, and f, showing the characteristics of Oils 1-6, and the identity of the trace corresponding to a particular oil: oils 7 and 8 are described below).

? Whether with or without the specified antioxidants, the coefficients of friction are similar and vary between 0.12 and 0.14 across the entire temperature range tested for the Mo-exempt oils (Traces a and b in Figure 2). At a molybdenum concentration of 150 ppm, an improvement in the coefficients of friction is observed for the combination of Mo3S4 ((2-ethylhexyl) 2dtc) 4 with the antioxidants, used individually or together. (Strokes c, d, e, and f in Figure 2).

For purposes of further comparison, Oils 7 and 8 (see above), based on the "starting oil", were similarly tested and contained a dinuclear Mo compound represented by Mo202S2 (coco2dtc) 2 (MV822 from Vanderbilt Chemical Company ) at a concentration of 150 ppm of Mo. Their friction traces (k and 1, respectively) together with the trace f, are shown in Figure 3. The data demonstrate the best performance of the trinuclear molybdenum compounds with antioxidants, in comparison with the dinuclear molybdenum compounds in a low concentration of 150 ppm molybdenum. Example 28 The procedure of Example 27 was repeated using Mo3S7 (coco2dtc) 4 as the compound of trinuclear Mo, and in a concentration of 75 ppm of Mo, identifying the corresponding oils as Oils 9-12. The Mo dinuclear comparison compound was the same as that used in Example 27, but at a concentration of 75 ppm Mo, the corresponding oils being identified as Oils 13 and 14, respectively. The results are shown first in Figure 4 as the lines g, h, i, and j, showing the characteristics of the Oils 9-14, and the identity of the trace corresponding to a particular oil: The comparative friction traces for the oils containing the compound containing dinuclear are shown in Figure 5 as the traces m and n, along with the trace j. The data show that at 75 ppm of Mo, only minor frictional improvements are seen on molybdenum-free oils without antioxidants or with dialkyldiphenylamine coadition, while the use of copper polyisobutylensuccinic anhydride and the combination of copper polyisobutylensuccinic anhydride and dialkyldiphenylamine produced better coefficients of friction in a concentration of the trinuclear molybdenum compounds corresponding to 75 ppm of Mo. They also demonstrate a better performance for the trinuclear Mo compounds, compared to the Mo dinuclear compounds. In Figures 2 to 5: axis y = coefficient of friction from 0 to 0.14 axis and secondary for temperature + degrees C from 0 to 500 x axis = time from 0 to 2 hours and t is a representative temperature profile.

In the following examples 29 to 33, reference will be made to the accompanying drawings, in which: Figure 6 shows the average coefficient of friction of fresh oils containing dinuclear and trinuclear-sulfur molybdenum compounds, at a concentration of 150 ppm Mo, based on the weight of the oil.

Figure 7 shows the average coefficient of friction at 140 ° C, of oils containing molybdenum-sulfur additive in a concentration of 150 ppm, before and after the treatment with N02. Figure 8 shows the average coefficient of friction a 100 ° C, of oils containing molybdenum-sulfur compounds in a concentration of 500 ppm molybdenum, before and after treatment with N02. Figure 9 shows the average coefficient of friction at 100 ° C of oils containing molybdenum-sulfur compounds in a concentration of 750 ppm molybdenum, before and after treatment with N02. Figure 10 compares the coefficient of friction at 110 ° C of an oil containing a trinuclear-sulfur molybdenum compound, and a dinuclear-sulfur molybdenum compound, when both are subjected to N02 treatment Figure 11 compares the coefficient of friction at 135 ° C of an oil containing a trinuclear-sulfur molybdenum compound, and a dinuclear-sulfur molybdenum compound, when both are subjected to N02 treatment Figure 12 shows the coefficient of friction and wear for lubricating compositions containing molybdenum-sulfur compounds in different concentrations.

Figure 13 shows the wear volume and the dinuclear and trinuclear molybdenum compounds during the test. Figure 14 shows the coefficient of friction of the dinuclear and trinuclear molybdenum compounds during the test. Example 29 In order to evaluate the retention of the friction reducing properties of the compounds of the present invention, the compounds were mixed in a fully formulated oil, their friction properties were determined, then treated with N02 for a period of time fixed, and finally, the friction properties were determined again. Accordingly, the degree of retention of the friction reducing properties is determined by measuring the friction properties of the test oil before (fresh) and after the treatment with N02 (used). A sample with a good retention of the friction reducing properties will exhibit a minimum change in its case, in its friction properties, before and after the treatment with N02. Conditions for Treatment with NO-, 1.15 grams of a sludge precursor (heavy disintegrated naphtha waste at 150 ° C) was added to one sample (130 grams). 1% N02 was bubbled in air through the resulting mixture at 130 ° C for 9 hours, at a rate of 2.67 liters per hour. The friction measurement of oil treated with N02 was determined the next day after treatment with N02. Conditions for Measurement of Friction Limit Limit friction measurements were determined on a high frequency reciprocating rig (ARAF) at three temperatures (60 ° C, 100 ° C and 140 ° C) for 30 minutes at each temperature. The friction was measured using a 6-millimeter steel ball in a reciprocating motion against a flat steel plate under a 4N load, a stroke length of 1 millimeter, and a reciprocating frequency of 20 Hz. The average surface roughness of the centerline for the ball is approximately 0.01 microns. The coefficient of friction was sampled every 5 seconds, and was cited as an average friction during the 30 minute period. Fresh oil, disk, and ball were used at each temperature. Compositions with good friction reducing properties provide values of low coefficient of friction, that is, the lower the coefficient of friction, the better the friction reducing property. The coefficient of friction at 100 ° C and 140 ° C is mentioned, since it is considered that these temperatures are the most suitable in relation to the operation of the molybdenum friction reducing additives in the lubrication of motor contacts. This example demonstrates that lubricant compositions containing compounds having the formula Mo3S7 (dtc) 4 or Mo3S4 (dtc) 4, have superior limit friction properties, compared with lubricant compositions containing dinuclear-sulfur molybdenum additives, even when use dinuclear additives in the presence of complementary sulfur sources, such as DBDS, in low concentrations of molybdenum, such as 150 ppm molybdenum, based on the total weight of the composition. It is also shown that the "S7" compounds have better boundary friction and retention improvement properties than the "S4" compounds; however, the trinuclear molybdenum compounds coordinated with 4 sulfur atoms possess better frictional limit and friction retention properties compared to the dinuclear molybdenum compounds. Figures 6 and 7 show the superiority of the compounds of Mo3S7 (dtc) 4 both in the reduction of friction limit and in the retention of reduction of friction, comparing with three other formulated oils. The compounds represented by Mo20? S dtc2 Sakuralube 155HR are supplied by Ashai Denka, Japan. The four lubricant compositions contained 150 ppm of molybdenum as the indicated molybdenum-sulfur additive. Additionally, the compositions contained 0.09 weight percent phosphorus. The details of the formulation are summarized in Table IX. Figure 6 shows that samples containing Mo3S7 (dtc) exhibit an upper limit friction between 60 ° C and 140 ° C. Figure 7 shows that the average coefficient of friction at 140 ° C remains low, even after exposure to a 1 percent N02 treatment in air, for the sample containing Mo3S7 (dtc) 4. The four oils are oils fully formulated containing known lubricating additives, for example, dispersant, anti-wear substance, detergent, viscosity improvers, and antioxidants, in the proportions known in the art Example 30 This example shows that the trinuclear-sulfur molybdenum compositions have properties of friction reduction and retention of friction reduction, compared to conventional dinuclear molybdenum sulfide additives, when used in concentrations normally used for dinuclear additives, for example, 500 and 750 ppm molybdenum. Figures 8 and 9. Formulation details are given in Table IX.

Table IX Example 31 Resistance to loss of operation due to N02. In order to simulate the loss of the frictional benefits of the molybdenum additives due to the aging of the oil in an engine, several formulated oils containing 500 ppm of Mo were degraded either as MV822 or Mo3S7 ((coconut) 2dtc) 4 by dispersion medium of N02 / air at an elevated temperature. In this example, MV822MR is represented by Mo202S2 (dtc) 2, and is available from Vanderbilt Chemical Company. The 250 milliliter samples of the oils were maintained at 130 ° C with a dispersion of 55 milliliters / minute of 1 percent N02 in air for 18 hours, with a periodic removal of 20 milliliter samples for the friction test. The friction performance of the sampled oils was determined using a Cameron-Plint TE77 tribometer. The test protocol uses a 6-millimeter steel ball in a reciprocating motion against a flat steel plate under a normal load of 5 kilograms, a stroke length of 7 millimeters, and a reciprocating frequency of 22 Hz. During the test, the oil is maintained for approximately 20 minutes at each of four temperatures, 50 ° C, 80 ° C, 110 ° C, and 135 ° C, while the coefficient of friction is measured. The coefficients of friction measured at the end of the temperature periods of 110 ° C and 135 ° C as a function of the hours of treatment with N02, are shown in Figures 10 and 11, respectively. It is considered that these temperatures are significant in relation to the operation of the molybdenum friction reducing additives for the automotive fuel economy. In Figures 10 and 11 it can be seen that the trinuclear molybdenum compound Mo3S7 ((coconut) 2dtc) 4 (open frames) demonstrates a much higher retention of its friction reduction performance under oxidation with N02, than the dinuclear additive of Mo202S2 (dtc) 2 (shaded boxes). Example 32 - Operation in Low Concentrations In order to compare the frictional and wear-reducing performance of trinuclear molybdenum compounds with conventional dinuclear molybdenum additives, friction and wear of a series of oils in different grades was tested on the bench. concentrations less than or equal to 500 ppm Mo in formulated automotive oil. The formulations were tested in a Falex Block Block (BSA) at 100 ° C with a load of 220 pounds (100 kilograms), a speed of 420 revolutions per minute (44 radians / second) (0.77 meters per second), and a duration of the test of 2 hours. The coefficients of friction are reported as the end of the test value. The reported data include the volume of block wear mark, measured by profilometry, and the end of the friction coefficient of the test. The results are shown in Table X.

TABLE X The results are also graphically represented in Figure 12. It can be seen that the trinuclear Mo compound provides superior performance of friction and wear at low concentrations. EXAMPLE 33 In order to further test the retention properties of the trinuclear Mo compounds, and compare them with those of commercially available dinuclear additives, a number of small motor aging tests were performed with periodic sampling and friction performance measurement and wear, using a block-on-falex tribometer. The compounds were tested in a 10 -30 fully formulated oil containing complementary antioxidants, i.e., zinc dialkyldiphenyl phosphate was present, but Cu, diarylamines, and / or phenols were not included. Three formulations containing molybdenum were examined in this formulation according to the following test: The oils were aged in a 12-horsepower, water-cooled 2-cylinder "generator engine" Sling. Incidentally, the operating conditions were established similar to those of the high-temperature oxidation tests of Sequence III-E / III F. The engine is a four-stroke carbureted overhead cam engine, and is attached to an electrical generator of 6.5 kw The engine was operated under continuous state conditions at 3,600 rpm, at a sinking temperature of 150 ° C, at an air / fuel ratio of 16.5 / 1, and the power was set at 4.8 kw. The fuel used was a mixture of 90 percent isooctane and 10 percent toluene. The fuel consumption during the test was approximately 1.36 kilograms per hour. An initial lubricant load of 2,000 grams was used, filler oil being added continuously by means of a low flow peristaltic pump. Samples were removed every 12 hours for friction and wear measurements. The addition of filler oils is then the combination of the consumption rate (approximately 12 grams / hour) and the sample size (150 grams) for an average rate of addition of approximately 25 grams per hour. The fresh sample and a number of the samples removed in a Falex Block Block (BSA) tribometer were tested at an oil temperature of 100 ° C, a load of 220 pounds (100 kilograms), a speed of 420 revolutions per minute (44 radians per second) (0.77 meters per second), for 2 hours. The coefficients of friction are reported both as the end of the test value (final friction coefficient), and the average value (average coefficient of friction), during the two hours. Following the test, the block wear volumes are determined by multiples and profilometry, and are presented as cubic millimeters x 100.

The procedures followed and the equipment used in the Falex Ring Block tests were similar to those of the ASTM G77-83 (Slip Wear Resistance Classification Using the Ring Block Wear Test). The results of the friction and wear test for the three engine aging tests according to the test are shown in Table XI. Table XI Figures 13 and 14 show that the trinuclear Mo compounds provided superior performance retention compared to the commercial Mo dinuclear additive, when tested in equal concentrations (500 ppm Mo).

Even at 50 ppm Mo, the tested trinuclear compound provided a performance retention against wear and a significant degree of friction benefit and performance retention. In the following example 34, and in the Comparative Example , reference should be made to the accompanying drawings, in which Figure 15 shows the results of friction performance measurements (heavy stroke) of an oil containing a commercial dinuclear molybdenum additive over time. The temperature of the oil was varied during the test, illustrating the temperature in the fine line. Figure 16 shows the results of the friction performance measurements (heavy stroke) of an oil containing a compound having the formula Mo3S4 (2-ethylhexyl2dtc) 4. The temperature of the oil was varied during the test; the temperature is illustrated in the thin line. Figure 17 shows the results of measurements of friction (heavy stroke) performance of an oil containing a compound having the formula Mo3S7 ((coconut) 2dtc) 4. The temperature of the oil was varied during the test; the temperature is illustrated in the thin line. Figure 18 shows the friction operation of five lubricant compositions. Before the start of the measurement, four samples of lubricating oil were aged for a period of time under operating conditions. A sample did not age. At the conclusion of the aging, a commercial dinuclear molybdenum compound was added to the oil. The temperatures of each mixture were varied in time (trace T), and the friction performance was measured for the oil that did not age (trace a), the aged for 12 hours (trace b), the aged for 23 hours (trace c), the aged for 36 hours (trace d), and aged for 72 hours (trace e). Example 34 In order to test the effectiveness of friction reduction by the addition of molybdenum-containing compounds to used motor lubricants, a dimeric molybdenum additive (Mo202S2 (dtc) 2), and various tri-meric molybdenum compounds ( Mo3S4 (2-ethylhexyl2dtc) 4 and Mo3S7 ((coconut) 2dtc) 4, at a concentration of 500 ppm molybdenum, to an oil not containing molybdenum, which was aged in a Honda generator engine for 72 hours, under conditions simulating a Sequence IIIE engine test.The aging was conducted on a 12-horsepower, water-cooled, four-stroke carbureted Honda "2-cylinder" generator engine.The engine was attached to a generator 6.5 kW electric motor during the test, the engine was operated under continuous state conditions at 3,600 rpm, at a sinking temperature of 150 ° C, at an air / fuel ratio of 16.5 / 1, and at a fixed power output of 4.8 k.

The friction performance of the aged oil treated with the different molybdenum additives was determined using a Cameron-Plint TE77 tribometer. The test protocol used a 6-millimeter steel ball in a reciprocating motion against a flat steel plate under a normal load of 5 kilograms, a stroke length of 7 millimeters, and a reciprocating frequency of 22 Hz. During the test, the oil is maintained for approximately 20 minutes at each of the four temperatures of 50 ° C, 80 ° C, 110 ° C, and 135 ° C, while the coefficient of friction is measured. From the friction trace of Figure 15, it can be clearly seen that the commercial dinuclear molybdenum additive Mo202S2 (dtc) 2 does not impart the expected low coefficients of friction, generally < 0.06, at temperatures above 100 ° C for a fully effective molybdenum additive, to oil. On the other hand, Figures 16 and 17 show that the nuclear molybdenum compound, Mo3S4 (2-ethylhexyl2dtc) 4 (Figure 16) and Mo3S7 ((coconut) 2dtc) 4 (Figure 17), give very low coefficients of friction between 0.04 and 0.05 at higher test temperatures. Comparative Example 35 The friction reducing properties of commercial dinuclear molybdenum additives were also investigated for a comparison with the compounds of the present invention. Fresh oil of lubricating viscosity was used in an internal combustion engine under operating conditions for different times, to form a used lubricating oil. Then a dinuclear molybdenum additive having the formula Mo202S2 (dtc) 2 was combined with the lubricating oil used at 500 ppm Mo. Then the friction performance of the additive was determined according to the method of Example 34. Figure 18 shows the results of these tests. The different lines show the operation of mixtures of the dinuclear molybdenum additive with aged lubricating oils during progressively longer times. The trace (a) is a fresh oil, the trace (b) is aged for 12 hours, the trace (c) is aged for 23 hours, the trace (d) is aged for 36 hours, and the trace (e) is aged for 72 hours. The trace (T) shows the temperature variation over time during the test run. Figure 18 reveals that although some improvement in friction reduction performance is obtained when the dinuclear molybdenum additive is combined with a fresh oil, this benefit gradually decreases when this additive is combined with lubricating oils that have aged under operating conditions . In these examples, no benefit is obtained when the commercial additive is combined with oils that have aged for 72 hours or more. In comparison, Example 34 shows that a benefit is obtained when the lubricating oils that have been aged for 72 hours are combined with the trinuclear molybdenum compounds of the present invention.

Claims (19)

1. NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered as a novelty, and therefore, property is claimed as contained in the following: CLAIMS 1. A lubricating oil composition, which comprises, or is made by the mixing, a larger amount of a lubricating viscosity oil, and a minor amount, as an additive, of at least one compound comprising a trinuclear molybdenum core, and linked thereto, ligands capable of rendering the compound oil soluble or dispersible in oil.
2. 2. The composition according to claim 1, characterized in that the core contains non-metallic atoms that consist totally or partially of sulfur.
3. 3. The composition as claimed in claim 1 or claim 2, characterized in that the core consists of trinuclear molybdenum and sulfur.
4. 4. The composition as claimed in any of the preceding claims, characterized in that the compound has the formula Mo3SkLn, or mixtures thereof, wherein: L represents a ligand that is independent of other ligands represented by L, when n is greater than 1; n is on the scale of 1 to 4; and k is at least 4, for example in the scale from 4 to 10, such as from 4 to 7.
5. The composition according to claim 1 or claim 2, characterized in that the compound has the formula Mo3SkE ? Ln, or mixtures thereof, wherein L and n are defined as in claim 4, k is at least 1, E is oxygen or selenium, x is at least 1, and the sum of k and x is at least 4.
6. 6. The composition as claimed in claim 4 or claim 5, characterized in that the formula further includes a fraction Qz, where Q represents a neutral electron donor compound, and z is on the scale of 0 to 5, and includes non-stoichiometric values.
7. 7. The composition according to claim claimed in any of the preceding claims, characterized in that the ligands, or ligands L, are represented by one or more of the structures having the formula: -X Ri - - 2 and mixtures thereof, and pertio derivatives thereof, wherein X, X1, X2 and Y are independently selected from the oxygen and sulfur group, and wherein R1, R2, and R are independently selected from the group which consists of H and organ groups that can be the same or different.
8. 8. The composition according to claim 7, characterized in that the organ groups independently represent alkyl, substituted or unsubstituted aryl, or ether groups.
9. 9. The composition according to claim 8, characterized in that the groups are alkyl groups, each having from 1 to 100, for example from 1 to 40, such as from 3 to 20 carbon atoms.
10. 10. The composition as claimed in any of the preceding claims, characterized in that the ligands are, or L independently, a dialkyl dithiophosphate ligand, thioxanthate, dialkyl phosphate, dialkyl dithiocarbamate, xanthate, or carboxylate.
11. 11. The composition as claimed in any of the preceding claims, characterized in that the weight of the molybdenum from the trinuclear molybdenum compound is at least 1, for example 1 to 2,000, such as 5 to 1,000, preferably 20 at 1,000 ppm, based on the weight of the composition.
12. 12. The composition as claimed in any of the preceding claims, characterized in that the total number of carbon atoms in all ligands or in all organ L groups is at least 21, such as 21 to 800.
13. 13 The composition as claimed in any of the preceding claims, characterized in that the lubricating viscosity oil is substantially free of sulfur.
14. 14. The composition as claimed in any of the preceding claims, which also comprises, or is made by mixing, at least one antioxidant additive.
15. 15. The composition as claimed in claim 14, characterized in that the antioxidant is an antioxidant containing copper, a sulfur-containing antioxidant, a phenolic antioxidant, an aromatic amine-containing antioxidant, or mixtures thereof.
16. 16. The composition as claimed in any of the preceding claims, characterized in that it further comprises one or more dispersants, detergents, melting point depressants, viscosity modifiers, surfactants, and anti-wear substances.
17. 17. An additive concentrate for mixing with an oil of lubricating viscosity comprising, or made by blending, an oil vehicle, and from 1 to 200,000 ppm by weight, for example 50 to 150,000, such as 50 to 100,000 , of the molybdenum of an additive as defined in any of claims 1 to 12, based on the weight of the concentrate.
18. 18. An additive concentrate according to claim 17, characterized in that it further comprises, or is made by mixing, at least one antioxidant additive as defined in claim 14 or claim 15, wherein the concentrate contains 1 to 90 weight percent, such as from 1 to 50, of additives, based on the weight of the concentrate.
19. 19. A compound that has the formula Mo3SkLnQz, where L independently represents a dialkyl dithiophosphate ligand, thioxanthate, dialkyl phosphate, dialkyl dithiocarbamate, xanthate, or carboxylate; n is from 1 to 4, k is at least 4, for example from 4 to 10, such as from 4 to 7; Q is a neutral electron donor compound, and z is from 0 to 5, wherein the compound has a core having the structure: \ ^ S ^ / (i) Xt Ji (ii) ^