GB2037317A - Molybdenum complexes of ashless nitrogen dispersants as friction reducing antiwear additives in lubricating oils - Google Patents

Abstract

A lubricating oil comprises an oil- soluble molybdenum complex of an ashless nitrogen dispersant, preferably an oil-soluble acylated nitrogen compound, e.g. the reaction product of a molybdenum compound, such as molybdic oxide, with 0.5 to 1 molar equivalent of polybutenyl succinic anhydride reacted with polyamine. The complex additive improves both the sludge dispersancy and antifriction property of the oil which also contains an oil-soluble active sulphur donor which is one of six specified classes of compounds.

Description

SPECIFICATION Molybdenum complexes of ashless nitrogen dispersants as friction reducing antiwear additives for lubricating oils Background of the invention The present invention concerns oil-soluble molybdenum complexes of ashless nitrogen dispersants, their method of preparation, and the utility of said molybdenum containing dispersants as lubricating oil additives, which markedly improve the sludge dispersancy, friction-reducing properties of lubricating oils employed for crankcase lubrication of internal combustion engines.

There are two principle environments which are encountered by automotive crankcase lubricants, i.e.

cyclical high and low temperatures from stop-and-go driving and continuous high temperatures from extended operation of the automobile over long distances. Each of these environments provokes the presence in the lubricant of varying proportions of foreign particles such as dirt, soot, water and decomposition products resulting from breakdown of the oil. This foreign matter appears responsible for the deposition of a mayonniase-like sludge which circulates with the oil.

During the past decade, ashless sludge dispersants have become increasingly important, primarily in improving the performance of lubricants in keeping the engine clean of deposits and permitting extended crankcase oil drain periods while avoiding the undesirable environmental impact of the earlier used metal-containing additives. One commercial type of ashless dispersant contains nitrogen resulting from the attachment of an amine or polyamine to a long-chain hydrocarbon polymer (the oil solubilizing portion of the molecule), usually polyisobutylene through an acid group, e.g. polyisobutenyl succinic anhydride, by forming amide or imide linkages.

In the operation of an internal combustion engine, there are many "Boundary Lubrication" conditions where two rubbing surfaces must be lubricated, or otherwise protected, so as to prevent wear and to insure continued movement. Moreover, where, as in most cases, friction between the two surfaces will increase the power required to effect movement and where the movement is an integral part of an energy conversion system, it is most desirable to effect the lubrication in a manner which will minimize this friction and/or reduce wear. As is also well known, both wear and friction can be reduced, with various degrees of success, through the addition of a suitable additive or combination thereof, to a natural or synthetic lubricant.

Similarly, continued movement can be insured, again with varying degrees of success, through the addition of one or more appropriate additives.

While there are many known lubricant additives which may be classified as antiwear, antifriction and extreme pressure agents and some may in fact satisfy more than one of these functions as well as provide other useful functions, it is also known that many of these additives act in a different physical or chemical manner and often compete with one another, e.g. they may compete for the surface of the moving metal parts which are subjected to lubrication. Accordingly, extreme care must be exercised in the selection of these additives to insure compatability and effectiveness.

The metal dihydrocarbyl dithiophosphates, e.g. the zinc dialkyl dithiophosphates, are one of the additives which are known to exhibit antioxidant and antiwear properties. While they afford excellent oxidation resistances and exhibit superior antiwear properties, it has heretofore been believed that the same increases or significantly limits their ability to decrease friction between moving surfaces. As a result, compositions containing zinc dialkyl dithiophosphates were not believed to provide the most desirable lubricity and, in turn, it was believed that use of compositions containing the same would lead to significant energy losses in overcoming friction even when antifriction agents are included in the composition.

Known ways to solve the problem of energy losses due to high friction in crankcase lubrication include the use of synthetic ester base oils which are expensive and the use of insoluble molybdenum sulfide and graphite dispersions which have the disadvantage of giving the oil composition a black or hazy appearance.

It would be desirable then to provide oil-soluble molybdenum compounds and thus overcome the disadvantage. Oil-soluble molybdenum additives taught as useful in lubricating oils include the molybdates of organic nitrogen bases obtained from heating an aqueous solution of molybdic acid and an aliphatic amine or heterocyclic nitrogen base (see U.S. 3,144,712).

The practical exploitation of various types of molybdenum compounds and complexes as lubricant additives has been hindered not only by their insolubility and/or corrosiveness but also by low thermal stability.

Summary of the invention It has now been discovered that ashless nitrogen-containing dispersants can be reacted with a source of molybdenum to provide a molybdenum-containing ashelss dispersant of improved thermal stability in lubricating oils and having the property of importing enhanced lubricity to said lubricating oil. This has been accomplished by use of an aqueous-non-aqueous reaction medium.The operational embodiment of the invention thus is a lubricating oil composition comprising a major proportion of mineral oil and a minor but a friction reducing amount of an oil-soluble molybdenum-containing ashless nitrogen lubricating oil dispersant, said dispersant having from 0.5 to 20 wt.% molybdenum based on the weight of said dispersant These materials are prepared from conventional ashless nitrogen dispersants by reaction of said dispersant with an inorganic molybdenum compound in a binary solvent system comprising an aqueous component of the class consisting of water and ammonium hydroxide and a non-aqueous component consisting of the class consisting of tetrahydrofuran (THF) and a hydrocarbon boiling between 70 and 250 C.

The volume ratio of aqueous to non-aqueous component ranges from 1:1000 to 1:1, preferably 1:100 to 1:4, optimally 1:10. In the context of this invention, the aqueous component can be considered a promoter for the molybdation of the nitrogen dispersant. Thus, for the purposes of this discussion, both the water and the ammonium hydroxide could be defined as an essential promoter of molybdation in a non-aqueous reaction medium.

It has now been further discovered that a stable molybdenum complex can be obtained with little if any destruction of the ash less dispersant when complexing is effected at a temperature of 40 C. to 250 C., preferably from 50 to 200 C, in said binary solvent system.

In accordance with the present invention, it is preferred that the lubricity enhancing, i.e. friction reducing, additive is present in the mineral oil in an amount to provide from about 0.01 to 2.0, preferably 0.02-1.0 and optimally 0.05-0.5 weight percent molybdenum in said oil, all weight percent being based on the total weight of the lubricating composition.

In preferred form, the molybdenum complex is that of a nitrogen compound derived from the reaction of one to three moles of a hydrocarbyl substituted dicarboxylic acid material, such as poly(isobutenyl) succinic anhydride wherein said hydrocarbyl substituent e.g. the poly(isobutenyl) group has a (Mn) ranging from about 700 to 5,000, optimally from about 900 to 1600 and preferably 1.3 moles of said dicarboxylic acid material, with about 1 mole of tetraethylene pentamine (includes commercal equivalent); said compound being complexed with from 1 to 2 molar equivalents of molybdic oxide, i.e. MoO3 and containing from 0.5 to 20, preferably .2 to 10, optimally 5, wt.% molybdenum.

DETAILED DESCRIPTION OF THE INVENTION Lubricating oil dispersant Generally, any nitrogen-containing dispersant additives including mineral oil-soluble salts, amides, imides, and esters or mono- and dicarboxylic acids (and where they exist the corresponding acid anhydrides) and various amines of nitrogen-containing materials having amino nitrogen or heterocyclic nitrogen and at least one amido capable of salt, amide or imide formation can be complexed with molybdenum according to this invention. Other nitrogen-containing dispersants which may be used in this invention include those wherein a nitrogen-containing polyamine is attached directly to the long chain aliphatic hydrogen as shown in U.S. Patents 3,275,554 and 3,565,804 where the halogen group on the halogenated hydrocarbon is displaced with various alkylene polyamines.

The nitrogen-containing dispersants described hereinafter are characterized by a long chain hydrocarbon group, or groups of number average molecular weight (Mw) from 700 to 250,000, which may be attached, e.g. to the acid, so the acid contains a total of about 50 to about 400 carbon atoms, said acid being attached to the amine either through salt, imide, amide, or ester groups. Usually, these dispersants are made by condensing a dicarboxylic acid, preferably a succinic acid-producing material, such as alkenyl succinic anhydride, with an amine or polyamine.

The hydrocarbyl substitutent may also be a copolymer of 30 to 80 wt. % ethylene and 20 to 70 wt.% of one or more C3 to C18 alpha-olefin, preferably propylene having a number average molecular weight of 700 to 250,000, preferably 10,000 to 200,000 as determined by vapour pressure osmometry (VPO).

Terpolymers of ethylene, said alpha-olefin and 0.5 to 20 mol.% based on said total polymer, of a non-conjugated diolefin, such as hexadiene, may also be used. The hydrocarbyl substitutent may also be a hydrogenated copolymer of butadiene and styrene or a terpolymer of a butadiene, styrene and isoprene. If the hydrocarbyl group has a molecular weight above 10,000 then the molybdenum containing dispersant also has viscosity-index improving properties. The molybdenum-containing dispersant contains between 0.001 and 25 wt.%, preferably 0.01 to 10 wt.% and more preferably between 0.05 and 5 wt.% oxygen and nitrogen.

The most commonly used dicarboxylic acid is alkenyl succinic anhydride wherein the alkenyl group contains about 50 to about 400 carbon atoms.

Primarily because of its ready availability and low cost, the hydrocarbon portion of the mono- or dicarboxylic acid or other substituted group is preferably derived from a polymer of a C2 to C8 monoolefin, said polymer generally having a molecular weight of about 700 to about 5000. Particularly preferred is polyisobutylene.

Polyalkyleneamines are usually the amines used to make the dispersant. These polyalkyleneamines include those represented by the general formula: H2N(CH2)n- [ NH)ch2ln ] rn-NH(CH2)nNH2 wherein n is 2 or 3, and m is O to 10. Examples of such polyalkyleneamines include diethylene triamine, tetraethylene pentamine, octaethylene nonamine, tetrapropylene pentamine, as well as various cyclic polyalkyleneamines.

Dispersants formed by reacting about equal molar amounts of polyisobutenyl succinic anhydride and a tetraethylene pentamine are described in U.S. Patent 3,202,678. Similar dispersants, but made by reacting a molar amount of alkenyl succinic anhydride with about two molar amounts of polyalkylleneamines, are described in U.S. Patent 3,154,560. Other dispersants, using still other molar ratios of alkenyl succinic anhydride and polyalkylenamines are described in U.S. Patent No. 3,172,892. Still other dispersants of alkenyl succinic anhydride with other amines are described in U.S. Patents 3,024,195 and 3,024,237 (piperazine amines) and 3,219,666. An ester derivative is taught in Belgian Patent 662,875 where N-alkyl morpholinone esters, e.g. N-(2-hydroxyethyl)-2-morpholinone, are formed by reaction with polyisobutenyl succinic anhydride.The prior art also teaches that the alkenyl succinic polyamine type dispersants can be further modified by reacting a fatty acid having up to 22 carbon atoms, e.g. acetic acid, with the reaction product of the alkenyl succinic anhydride and polyamine (see U.S. Patent 3,216,936).

While any of the above type ashless nitrogen dispersants may be complexed according to this invention, particularly preferred are those prepared with alkenyl succinic acid/anhydrides where the alkenyl radicals have a molecular weight of at least about 700 to 5,000 and preferably at least about 1200 and more preferably at least about 1300.

Particularly preferred nitrogen containing dispersants are those derived from amine compounds having the following formulas: (A) alkylene polyamines

wherein x is an integer of about 1 to 10, preferably about 2 to 4, R is hydrogen, a hydrocarbon or substantially a hydrocarbon group containing about 1 to 7, preferably about 1 to 4 carbon atoms and the alkylene radical is a straight or branched chain alkylene radical having up to about 7 preferably about 2 to 4 carbon atoms;; (B) polyoxyalkylene polyamines (i) NH2 alkylene- O-alkylene4wNH2 where m has a value of about 3 to 70 and preferably 10 to 35 and (ii) R L alkylene ( O-alkylene4NH2l3-6 where n has a value of about 1 to 40 with the proviso that the sum of all the n's is from about 3 to about 70 and preferably from about 6 to about 35 and R is a polyvalent saturated hydrocarbon radical of up to ten carbon atoms having a valence of 3 to 6. The alkylene groups in either formula (i) or (ii) may be straight or branched chains containing about 1 to 7 and preferably about 1 to 4 carbon atoms; and (C) primary amines and hydroxy substitutes thereof R - NH2 where R is a monovalent organic group having up to 20, preferably 10 carbon atoms and may contain one or more alcoholic hydroxyl groups and preferably 1 to 6 alcoholic hydroxyl groups.The R group in this formula may be an aliphatic, aromatic, heterocyclic or carbocyclic radical. An alcoholic hydroxyl group being one not attached to a carbon atom forming part of an aromatic nucleus.

The alkylene polyamines of formula (A) above include, for example, methylene amines, ethylene amines, butylene amines, propylene amines, pentylene amines, hexylene amines, heptylene amines, octylene amines, other polymethylene amines, and the cyclic and higher homologs of these amines such as the piperazines, and the amino-alkyl-substituted piperazines.These amines include, for example, ethylene diamine, triethylene tetramine, propylene diamine, di(heptamethylene) triamine, tripropylene tetramine, tetra-ethylene pentamine, trimethylene diamine, pentaethylene hexamine, di(trimethylene) triamine, 2-heptyl-3-(2-aminopropyl)imidazoline, 4-methylimidazoline, 1 ,3-bis-(2-aminoethyl) imidazoline, pyrimidine, 1-(2-aminopropyl) piperazine, 1,4-bis-(2-aminoethyl) piperazine, N,N-dimethylaminopropyl amine, N,Ndioctylethyl amine, N-octyl-N '-methylethylene diamine, and 2-methyl-1-(2-aminobutyl) piperazine. Other higher homologs which may be used can be obtained by condensing two or more of the above-mentioned alkylene amines in a known manner.

The ethylene amines which are particularly useful are described, for example, in the Encyclopedia of Chemical Technology under the heading of "Ethylene Amines" (Kirk and Othmer), Volume 5, pgs. 898-905; Interscience Publishers, New York (1950). These compounds are prepared by the reaction of an alkylene chloride with ammonia. This results in the production of a complex mixture of alkylene amines, including cyclic condensation products such as piperazines. While mixtures of these amines may be used for purposes of this invention, it is obvious that pure alkylene amines may be used with complete satisfaction. A particularly useful alkylene amine comprises a mixture of ethylene amines prepared by the reaction of ethylene chloride and ammonia which may be characterized as having a composition that corresponds to that of tetraethylene pentamine.In addition, the alkylene amines having one or more hydroxyalkyl substitutents on the nitrogen atoms may be used. These hydroxy-alkyl-substituted alkylene amines are preferably compounds wherein the alkyl group is a lower alkyl group, i.e. having less than about 6 carbon atoms and include, for example, N-(2-hydroxyethyl) ethylene diamine, N,N'-bis(2-hydrnxyethyl)ethylene diamine, 1 -(2-hydroxyethyl) piperazine, monohydroxypropylsubstituted diethylene triamine, 1 ,4-bis(2- hydroxy-propyl )-piperazine, dihydroxy-propyl-su bstituted tetraethylene pentamine, N-(3-hydroxy-propyl) tetramethylene diamine, 2-heptadecayl-1 -(2-hydroxyethyl) imidazole, etc.

The polyoxyalkylene polyamines of formula (B) above, which may be complexed according to this invention, e.g polyoxyalkylene diamines and polyoxyalkylene triamines, may have average molecular weights ranging from about 200 to about 4000 and preferably from about 400 to about 2000. The preferred polyoxyalkylene polyamines for purposes of this invention include the polyoxyethylene and polyoxypropylene diamines and the polyoxypropylene triamines having average molecular weights ranging from about 200 to 2000. The polyoxyalkylene polyamines are commercially available and may be obtained, for example, from the Jefferson Chemical Company, Inc. under the trade name "Jeffamines D-230, D-400, D-1000, D-2000, T-403", etc.

The primary and hydroxy substitutes thereof, as defined by formula (C) include aliphatic amines, aromatic amines, heterocyclic or carbocyclic amines as well as the hydroxy substitutes thereof. Specific amines of this type include methylamine, cyclohexylamine, aniline, dodecylamine, 2-amino-1-butanol, 2-amino-2-methyl 1 -propanol, p-()3-hydroxyethyl)-aniline, 2-amino-1 -propanol, 3-amino-1 -propanol, N-(p'-hydrnxy-prnpyl)-N'- (P-aminoethyl)-piperazine, 2-amino-I -butanol, ethanolamine, ss-13-hydroxy-ethoxy)-ethylamine, glucamine, glucosamine, 4-amino-3-hydroxy-3-methyl-1-butene (which can be prepared according to procedures known in the art by reacting isopreneoxide with ammonia), N-(3-amono-prnpyl )-4-(2-hydroxyethyl)-piperidine, 2-amino-6-methyl-6-heptanol, 5-amino-1 -pentanol,N(p- hydroxyethyl ,3-diamino propane, 1 ,3-diamino-2-hydroxypropane,N-(P-hydroxy )-ethylene diamine, and the like. Mixtures of these or similar amines can also be employed.

The amine derived dispersants are obtained by reacting from 1 to 3 moles of the hydroxycarbyl substituted dicarboxylic acid with one mole of the amine. It is also particularly preferred that the nitrogen content of the prepared amine derived dispersant be less than about 2 percent by weight and preferably less than 1.5 percent. The preferred dispersants are those derived from polyisobutenyl succinic anhydride and polyethylene amines, e.g. tetraethylene pentamine and polyoxyethylene amines, e.g. polyoxypropylene diamine and combinations thereof.

To further enhance the dispersancy, the acyl nitrogen dispersant, e.g. the alkenyl succinic polyamine, is readily borated as generally taught in U.S. Patent 3,254,025. This is readily accomplished by treating said acyl nitrogen dispersant with a boron compound selected from the class consisting of boron oxide, boron halides, boron acids and esters of boron acids in an amount to provide from about 0.1 atomic proportion of boron for each mole of said acylated nitrogen composition to about 10 atomic proportions of boron for each atomic proportion of nitrogen of said acylated nitrogen composition. The borated dispersants for complexing with the molybdenum source according to this invention contain from about 0.1 to 2.0, preferably 0.2 to 0.8, wt% boron based on the total weight of said borated acyl nitrogen compound.The boron, which appears to be in the reactant dispersant as dehydrated boric acid polymers (primarily HBO2)3, attaches chemically to the dispersants imides and diimides as amine salts e.g. the metaborate salt of said diimide and appears not displaced in the molybdenumization step.

Borating is readily carried out by adding from about 1 to 3 wt.% (based on the weight of said acylnitrogen compound) of said boron compound, preferably boric acid which is most usually added as a slurry to said acyl nitrogen compound and heating with stirring and at from about 1359C. to 165 C. forfrom 1 to 5 hours followed by nitrogen stripping at said temperature ranges and filtration if desired.

Amination and/or imidation of the carboxylic acid material is usefully carried as a solution reaction with the carboxylic acid material, e.g. polyisobutenylsuccinic anhydride dissolved in a solvent such as mineral oil to which the other reactant is added. The formation of the imide dispersants in high yield can be effected by adding from about 0.3 to 1, preferably about 0.4 to 0.7, molar proportions of alkylene polyamine per molar proportion of dicarboxylic acid material of the nitrogen compound to said solution and heating the mixture at 1 40cC. to 1 65eC. until the appropriate amount of water of reaction is evolved. Typically the solvent mineral oil is adjusted so that it constitutes 50% weight of the final acyl nitrogen compound solution.

Molybdenum source The source of molybdenum is a molybdenum oxygen-or-sulfur-containing compound capable of complexing with the ashless dispersant to provide a thermally stable molybdenum complex containing from about 0.5 to 20, preferably 2 to 10, optimally about 5, wt.% molybdenum based on the total weight of said complex. The sources of molybdenum include molybdic acid, molybdic trioxide (preferred) which is also known as molybdic anhydride and as molybdic oxide, ammonium chiomolybdate, ammonium bismolybdace, molybdenum halides, and ammonium heptamolybdate tetrahydrate.

Method of preparing the complex The organo molybdenum complex is substantially the product of a binary solution reaction of 1 to 2 moles ashless dispersant (either the borated or non-borated) and 1 mole of molybdenum metal derived from the molybdenum source. The reaction is readily carried out by reaction at an elevated temperature of from 40 C.

to 250 C., preferably 50 C. to 200 C., optimally 60 C. to 180"C. to react and stabilize the product complex. The reaction is carried out in a binary solution system wherein water is present (either as water or ammonium hydroxide) along with a non-aqueous component such astetrahydrofuran (THF) or a hydrocarbon boiling between 70 C. and 250 C. and as preferred a second non-aqueous component which is a higher boiling point hydrocarbon as mineral oil. A highly useful reaction system is 1 to 20% water or ammonium hydroxide and mixtures thereof, 20 to 60% mineral oil and the balance xylene, toluene or tetrahydrofuran.

The reaction is carried out over a period of from about 4to 20, preferably 6 to 12, hours in order to suitably stabilize the complex after which the binary solvents are generally removed and the complex dissolved in mineral oil for ease of handling.

Carrying out the organo molybdenum complexing reaction in a binary solvent system wherein one part by weight water or ammonium hydroxide per 1 to 1000 parts by weight of THF or said lower boiling hydrocarbon provides a number of benefits over a reaction without solvent or in a light aromatic solvent such as toluene or a light hydrocarbon oil, e.g. mineral oil including: faster reaction time; completion of reaction to a stabilized molybdenum complex at a lower temperature; and, an additive product solution which when added to lubricating oil provides both enhanced friction reduction and sludge dispersancy.

Sulfur donors The hydrocarbon-soluble molybdenum complexes of ashless dispersants provide not only dispersancy for lubricating oils but enhanced lubricity as well when used in combination with an active sulfur donor which can be defined as a compound which when used in admixture with the dispersant-molybdenum complex reduces the coefficient of friction at least about 10% relative to that provided by the complex alone. The active sulfur donor is present in an amount of from about 0.1 to 10, preferably 0.2 to 2, parts by weight per part by weight of molybdenum complex.

Illustrative of active sulfur donors are metal dihydrocarbyl dithiophosphates and the corresponding precursor esters, phosphosulfurized pinenes, sulfurized olefins and hydrocarbons, sulfurized fatty esters and sulfurized alkyl phenols.

Preferred are the zinc dihydrocarbyl dithiophosphates which are salts of dihydrocarbyl esters of dithiophosphoric acids and may be represented by the following formula:

wherein R and R' may be the same or different hydrocarbyl radicals containing from 1 to 18 and preferably 2 to 12 carbon atoms and including radicals such as alkyl, alkenyl, aryl, aralkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as R and R' groups are alkyl groups of 2 to 8 carbon atoms. Thus, the radicals may, for example, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, amyl n-hexyl, i-hexyl, n-heptyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, butenyl, etc.In order to obtain oil solubility, the total number of carbon atoms in the dithiophosphoric acid will average about 5 or greater.

The zinc dihydrocarbyl dithiophosphates which are useful as the coadditive, i.e. sulfur donor, of the present invention may be prepared in accordance with known techniques by first esterifying a dithiophosphoric acid usually by reaction of an alcohol or phenol with P2S5 and then neutralizing the dithiophosphoric acid ester with a suitable zinc compound such as zinc oxide.

In general, the zinc dihydrocarbyl dithiophosphate will be used in the lubricating composition at a concentration within the range of about 0.01 to about 5 parts by weight per 100 parts of lubricating oil and preferably from about 0.5 to about 1.5. This is adequate for sulfur donation whereby the lubricity enhancement of the lubricating oil composition by the coadditive combination is realized.

As noted earlier, an equally suitable active sulfur donor is the dihydrocarbyl esters of dithiophosphoric acid which may be represented by the formula: S RO - P - SH OR' where R and R' are as previously defined. Particularly useful is the dibutylphenyl dithiophosphate.

The phosphorosulfurized terpenes as represented by pinene, dipentene, allo-ocimene, etc., are another group of dithiophosphate diesters which are active sulfur donors. Of the terpenes, the bicyclic pinene is preferred. The phosphosulfurized terpene is readily obtained by reaction of about one mole of diester of thiophosphoric acid and one mole of pinene at a temperature of at least 100"C., e.g.100 C.to 200 C. The preferred active sulfur donor can be characterized as the bornyl ester of dihydrocarbyl (C2-C20) dithiophosphoric acids (as shown in U.S. 2,689,258).

The sulfurized olefins and hydrocarbons are further esters of thiophosphoric acids which are useful sulfur donors. These esters are achieved by reaction with olefins such as ethylene, propylene, isobutylene, decene, dodecene, octadecene, etc., olefin polymers of molecular weight ranging from 100 to 50,000 such as ethylene, propylene, isobutylene, etc., aromatics such as benzene, naphthalene, toluene xylene, etc., petroleum fractions and condensation products of halogenated aliphatic hydrocarbons with aromatic compounds, e.g. wax-naphthalene (see U.S. 2,804,431).

The sulfurized fatty esters are another subclass of esters which are active sulfur donors. These products are readily obtained from the reaction of P2S5 and aliphatic alcohols usefully having from about 8 to 22 carbons obtained from natural sources including linoleic, behenic, stearic, palmitic, lauric, capric, etc., as well as mixtures obtained from vegetable and animal oils, such as tall oil.

The sulfurized alkyl phenols are generally C4 to C20 alkyl phenl sulfides. These sulfurized akyl phenols are readily produced by sulfurizing an alkyl phenol with a sulfur halide or elemental sulfur.

Other additives for lubricating compositions In addition to the molybdenum complex of the ashless dispersant and active sulfur donor, the lubricating oil composition may contain other well-known lubricating oil additives to provide trouble-free operation of the lubricated equipment, such as ashless dispersants, metallic detergents, supplemental oxidation and corrosion inhibitors, extreme pressure agents, rust inhibitors, pour point depressants, viscosity index improvers, etc.

1. Ashless dispersants As used herein, the terminology "ashless dispersant" in describing both the reactant and the additive is intended to describe the now well-known class of the non-metal-containing oil-soluble polymeric additives or the acyl derivatives of relatively high molecular weight carboxylic acids which are capable of dispersing contaminants and the like in hydrocarbons such as lubricating oils. The carboxylic acids may be mono- or polycarboxylic acids and they are generally characterized by substantially hydrocarbon constitutents containing an average of 50 to 250 aliphatic carbon atoms.

A preferred class of ashless dispersants are the nitrogen-containing dispersant additives which are generally known in the art as sludge dispersants for crankcase motor oils. These dispersants include mineral oil-soluble salts, amides, imides and esters made from high molecular weight mono- and dicarboxylic acids (and where they exist the corresponding acid anhydrides) and various amines of nitrogen-containing materials having amino nitrogen or heterocyclic nitrogen and at least one amido or hydroxy group capable of salt, amide, imide or ester formation. Usually, these dispersants are made by condensing a monocarboxylic acid or a dicarboxylic acid or anhydride, preferably a succinic acid producing material such as alkenyl succinic anhydride, with an amine or alkylene polyamine.Usually, the molar ratio of acid or anhydride to amine is between 1:1 to 5:1, e.g. 1 mole of C50-C100 polyisobutenyl succinic anhydride to 2 moles of tetraethylene pentamine.

Primarily because of its ready availability and low cost, the hydrocarbon portion of the mono-, or dicarboxylic acid or anhydride is preferably derived from a polymer of a C2to C8 monoolefin, said polymer generally having between 50 and 250 carbon atoms. A particularly preferred polymer is polyisobutylene.

Polyalkyleneamines are usually used to make the non-metal-containing dispersant. These polyalkyleneamines include those represented by the general formula: NH2(CH2)n [ NH(CH2)n ] rnNH2 wherein n is 2 to 3 and m is a number from 0 to 10. Specific compounds coming within the formula include diethylenetriamine, tetraethylenepentamine, dipropylenetriamine, octaethylenenonamine, and tetrapropylenepentamine; N,N-di-(2-aminoethyl) ethylenediamine may also be used. Other aliphatic polyamino compounds that may be used are N-amino-alkylpiperazines, e.g. N-(2-aminoethyl) piperazine. Mixtures of alkylene polyamines approximating tetraethylene pentamine are commercially available, e.g. Dow E-100 sold by Dow Chemical Company of Midland, Michigan.

Representative dispersants are formed by reacting about one molar amount of polyisobutenyl succinic anhydride with from about one to about two molar amounts of tetraethylene pentamine or with from about 0.5 to 1 moles of a polyol, e.g. pentaerythritol.

It is possible to modify the ashless dispersants generally by the addition of metals such as boron in order to enhance the dispersancy of the additive. This is readily accomplished by adding boric acid to the reaction mixture after the imidation or esterification is substantially complete and heating the mixture at temperatures of 100 to 1 500C for a few hours.

2. Other additives Detergents useful in conjunction with dispersants, preferably the ashless type, include normal, basic or overbased metal, e.g. calcium, magnesium, etc., salts of petroleum naphthenic acids, petroleum sulfonic acids, alkyl benzene sulfonic acids, oil-soluble fatty acids, alkyl salicyclic acids, alkylene-bis-phenols, and hydrolyzed phosphorosulfurized polyolefins.

Oxidation inhibitors include hindered phenols, e.g. 2,6-ditert. butyl para-cresol, amines, sulfurized phenols and alkyl phenothiazines.

Pour point depressants include wax alkylated aromatic hydrocarbons, olefin polymers and copolymers, acrylate and methacrylate polymers and copolymers.

Viscosity Index Improvers include olefin polymers such as polybutene, ethylene-propylene copolymers, hydrogenated polymers and copolymers and terpolymers of styrene with isoprene and/or butadiene, polymers of alkyl acrylates or alkyl methacrylates, copolymers of alkyl methacrylates with N-vinyl pyrollidone or dimethylaminoalkyl methacrylate, post-grafted polymers of ethylene-propylene with an active monomer such as maleic anhydride which may be further reacted with an alcohol or an alkylene polyamine, styrene/maleic anhydride polymers post-reacted with alcohols and amines, etc.

The hydrocarbons in which the additive combination of the invention is most effective are mineral oils having a viscosity as measured by ASTM D-445 of from about 2 to 40, preferably 5 to 20 centistokes at 99"C.

If the molybdenum-containing acylated nitrogen dispersant is used as an additive concentrate, the concentrate may consist essentially of from about 5 to 80 weight percent of molybdenum containing dispersant, based on the total weight of said concentrate, the remainder being a suitable solvent such as kerosene, mineral oil, synthetic oil and a naphtha or the like. The preferred concentrate contains about 10-60 weight percent of the additive combination in the solvent.

Whether the molybdenized acylated nitrogen dispersant is used alone or in combination with other additives, its concentration may vary appreciably with the particular application. For example, when the said molybdenum containing dispersants are used alone in a fuel such as gasoline, the concentration of the additive ranges from 1 to 1000, preferably 5-50 parts per million, based on the total weight of the gasoline. In a lubricant, however, it is used from about 0.1 to 20 preferably 0.5-5% based on the total weight of the oil.

The invention will be further understood by reference to the following Examples which illustrate a preferred form of the invention and compares the same with different, though similar compositions.

The following Examples illustrate more clearly the compositions of the present invention. However, these illustrations are not to be interpreted as specific limitations on this invention.

Example 1 90.4 of polyisobutenylsuccinic polyamine ashless dispersant (acid to amine molar ratio of 2.1:1) in 50% S1 SON mineral oil (the polyisobutenyl substitutent has a number average molecular weight (Mn) of 900 and the dispersant contains 2.1% nitrogen) and 5.5 of molybdic acid, MoO3H2O, were refluxed 8 hours in 500 ml of tetrahydrofuran and 10 ml of H2O. The temperature was 60"-70"C. The tetrahydrofuran and excess water were then removed using a rotoevaporator. It was then dissolved in hexane and filtered through celite. This was then evaporated on the rotary evaporator to remove the hexane. The resulting greenish viscous material contained 3.49 wt.% molybdenum.

Example 2 90.4 g of the polyisobutenyl succinic polyamine ashless dispersant in 50% mineral oil (same additive as in Ex. 1) and 13.0 g of molybdic acid, MoO3H3O, were refluxed in 500 ml of THF and 10 ml of NHIIOH for 3 hours. The THF was removed by a nitrogen sparge and the product diluted with hexane and filtered. This was rotoevaporated to give a clear, dark green viscous material containing 5.2 wt.% molybdenum.

Example 3 A mixture of 80 g of a 50% mineral oil solution of the dispersant product prepared from polyisobutenyl succinic anhydride (Mn ~ 1000) and a polyethylene amine approximating to tetraethylene pentamine in a charge molar ratio of 1.5:1 and 3.52 g ammonium heptamolybdate tetrahydrate in xylene (50 cm3) and water (5 cm3) was refluxed with stirring for 5 hours. During this time, water and xylene were removed by distillation. The reactants were freed from solid material by filtration and the filtrate stripped of volatile material by rotoevaporation. The product was a dark viscous oil containing 2.1% molybdenum. This represents a conversion, based on molybdenum, of 91% on theory.

Example 4 A mixture of the dispersant product solution of Ex. 3 (80 g), molybdic oxide (3.39 g), xylene (50 cm3) and water (5 cm3) was refluxed with stirring for 3 hours. The product was isolated by filtration and stripping to yield a dark brown oil with a molybdenum content of 2.6%. This represents a conversion of 95% based on molybdenum.

Example 5 (a) A mixture of the dispersant product solution of Ex. (80 g), molybdic oxide (4.24 g), xylene (50 cm3) and water (5 cm3) was refluxed with stirring for 3 hours. The product, isolated by filtration and stripping the filtrate from volatiles, was a dark brown oil with a molybdenum content of 3.39%. This represents a quantitative conversion based on molybdenum charged.

(b) Carrying out the same reaction, i.e. 5(a), for 2 hours rather than 3 yielded a dark brown oil containing 4.98% molybdenum.

Example 6 A mixture of a 50 wt.% mineral oil solution of a dispersant obtained from the reaction of polyisobutenyl succinic anhydride with a tetraethylene pentamine (40 g) (acid to amine molar ratio 2.1:1) molybdic oxide (2.44 g), xylene (50 cm3) and water (5 cm3) were refluxed with stirring for 6.5 hours. The product was isolated in the same manner as previous Examples 3-5 to yield a dark brown oil containing 3.72% molybdenum.

Example 7 40 g of the dispersant solution used and described in Ex. 6, ammonium heptamolybdate tetrahydrate (2.96 g), xylene (50 cm3) and water (5 cm3) was refluxed with stirring for 7.25 hours. The product, isolated in the usual manner, was a dark brown oil containing 3.72% molybdenum (97% conversion based on molybdenum).

Example 8 A mixture of 50 wt.% mineral solution of a borated dispersant derived from the condensation of 1.5 moles of polyisobutenyl succinic anhydride to 1 mole of tetraethylene pentamine and containing 0.35% boron (80 g), molybdic oxide (4.18 g), xylene (50 cm3) and water (5 cm3) was stirred at refluxfor 6.75 hours. The product, isolated in the normal manner, was a dark green oil containing 3.0% molybdenum (90% conversion based on molybdenum).

Example 9 80 g of a borated condensation product of polyisobutenyl succinic anhydride and an alkylene polyamine (acid to amine ratio of 2.1 to 1) dissolved in 50 wt.% mineral oil (commercially available as ECA 5025 from Exxon Chemical Company of Houston, Texas), molybdic oxide (3 g), xylene (50 cm3) and water (5 cm3) were stirred at reflux for 6 hours. The product, a dark green oil, isolated in the normal manner, contained 3.62% molybdenum (82% conversion based on molybdenum).

Example 10 Some of these molybdated dispersants were evaluated, in a formulated oil, for their effect on friction in a Roxana Four-Ball Tester. As a comparative example, in each case, an oil containing the dispersant but without molybdenum was run. The concentration of the molybdenum-containing dispersant was adjusted to provide 0.1% molybdenum in the oil. A total dispersant concentration of 2.5% was maintained in all tests.

The lubricant composition was: Component Wt% Active Ingredient Dispersant 2.5 Magnesium Suifonate 0.4 (overbased) Zinedialkyl dithiophosphate 1.0 Mineral Oil 96.1 The Roxana Four-ball weartesterwith the Brown/GE modification from Roxana Machine Works, St. Louis, MO was used to measure friction properties by the following procedure. The tester was assembled in the normal wear procedure as described in ASTM D2266-67 using four 1/2" bearing steel balls. The tester was brought to 110CC and run at 1200 rpm and 15 kg for a minimum of 45 minutes. If the frictional force has seen on the strip chart recorder is constant for the last 10 minutes, the speed is reduced to 25 rpm. Otherwise, the test is carried on until frictional force as stabilized. The test at 25 rpm is carried out at 110to. and 15 kg for 15 minutes or until frictional force has stabilized.

The compounds of the invention were then evaluated by subjecting the products to a study of their utility as a lubricity enhancing and!or antiwear additive for lubricating oils by using said Testing Procedure; the results are shown in the following Table. It will be seen that the molybdenum-containing dispersants of the invention provide lubricity enhancement to lubricating oils superior to their non-molybdized counterparts when an active sulfur donor is present.

TABLE Comparison of molybdenum containing for friction reduction Molybdate Weight % Dispersant Weight % Coefficient Product of Active of Active of Friction Test # Example # Ingredient* Example # Ingredient Friction (3) Reduction(2) 1200 rpm 50 rpm 1200 rpm (%) 50 rpm 1 - - 3 2.5 .088 .101 2 4 1.4 3 1.1 .046 .058 48 43 3 - - 6 2.5 .082 .101 4 6 1.35 6 1.15 .049 .057 40 44 7 - - 8 2.5 .085 .103 8 8 1.35 8 1.15 .050 .057 41 45 9 - - 9 2.5 .083 .091 10 9 2.1 9 0.4 .048 .068 42 25 (1) 15 kg load (2) Relative to base case *This is calculated on the bassis thAt the molybdenum containing oil product of each Example (1-9) was 50 wt.% molybdate dispersant and 50 wt.% mineral oil

Claims (11)

1. A lubricating oil composition comprising lubricating oil and at least a friction-reducing amount of the combination of: (a) an oil-soluble molybdenum complex of a molybdenum compound and an ashless nitrogen dispersant, said complex having from 0.5 to 20 wt.% molybdenum based on the weight of said dispersant; and (b) an oil-soluble active sulfur donor, said combination providing from about 0.01 to 2.0 weight percent molybdenum and said sulfur donor being present in at least 0.25 weight percent, all of said weight percent being based on the total weight of said composition; wherein said ashless nitrogen dispersant comprises the reaction product of one to three moles of a hydrocarbyl-substituted dicarboxylic acid material, wherein said hydrocarbyl substitutent has a number average molecular weight (Mn) ranging from 700 to 250,000 with about 1 mole of polyalkyleneamine of the general formula:: H2N(cH2)n-(NH(cH2)n)m-NH(cH2)nNH2 wherenis20r3.andmis0tol0; wherein a molar proportion of said ashless nitrogen dispersant is complexed by reacting with from 1 to 2 molar proportions of a molybdenum compound selected from the group consisting of a molybdic oxide, molybdic acid, ammonium thiomolybdate, ammonium bismolybdate, molybdenum halide and ammonium hepcamolybdatetetrahydrate; and wherein said sulfur donor is selected from the group consisting of metal dihydrocarbyl dithiophosphates, dihydrocarbyl esters of dithiophosphoric acid, phosphosulfurized pinenes, sulfurized hydrocarbons, sulfurized fatty esters and sulfurized alkyl phenols.

2. The composition of claim 1, wherein said hydrocarbyl substitutent is a copolymer of ethylene and a C3 to C18 alphaolefin having a Mn of 10,000 to 200,000.

3. The composition of claim 1, wherein said hydrocarbyl substituent has a molecularweight (Mn) of 700 to 5,000.

4. A lubricating oil composition according to claims 1-3, wherein said dispersant is the reaction product of polyisobutenyl succinic anhydride and polyethyleneamine.

5. A lubricating oil composition according to claims 1-4, wherein said dispersant is borated.

6. A lubricating oil composition according to claims 1-5, wherein said molybdenum compound is molybdic oxide, molybdic acid, or ammonium heptamolybdate tetrahydrate.

7. A lubricating oil composition according to claims 1-6, wherein said sulfur donor is zinc dihydrocarbyl dithiophosphate.

8. A lubricating oil composition according to claims 1-7, wherein said molybdenum complex is the reaction product of said molybdenum compound with 0.5 to 1 molar equivalent of polyisobutenyl succinic anhydride reacted with said polyamine, in a binary solvent system comprising an aqueous component of the class consisting of water and ammonium hydroxide and a non-aqueous component of the class consisting of tetrahydrofuran and a hydrocarbon boiling between 70 and 250 C.

9. A lubricating oil composition according to claims 1-8, wherein said lubricating oil is mineral oil, said polyalkyleneamine is tetraethylene pentamine.

10. A lubricating oil composition according to claims 1-9, wherein said lubricating oil is a mineral oil having a viscosity as measured by ASTM- D-445 of from about 2 to 40 centistokes at 99it., said substituted dicarboxylic acid material is poiy(isobutenyl) succinic anhydride wherein said poly(isobutenyl) group has a (Mn) ranging from 900 to 1600, and present in the amount of 1.3 moles per mole of tetraethylene pentamine and said active sulfur donor is zinc dihydrocarbyl dithiophosphate present in an amount of from 0.2 to 2 parts by weight per part by weight of said molybdenum complex which is present in an amount of from 0.02 to 1.0 wt. %, based upon the total weight of said composition.

11. A lubricating oil composition according to claims 1-10, which is a concentrate comprising from 5 to 80 weight percent of the combination of an oil-soluble molybdenum complex of an ashless nitrogen dispersant and from about 0.1 to 10 parts by weight of active sulfur donor per part by weight of said complex and 20 to 95 weight percent of mineral oil.