US20080182768A1

US20080182768A1 - Lubricant composition for bio-diesel fuel engine applications

Info

Publication number: US20080182768A1
Application number: US11/960,949
Authority: US
Inventors: Cathy C. Devlin; Charles A. Passut
Original assignee: Afton Chemical Corp
Current assignee: Afton Chemical Corp
Priority date: 2007-01-31
Filing date: 2007-12-20
Publication date: 2008-07-31
Also published as: JP2008189919A; FR2915206A1; GB0801603D0; FR2915206B1; DE102008005330A1; GB2446277A; GB2446277B

Abstract

A diesel engine operating on a fuel containing from about 5 to about 100 wt. % bio-diesel components and being lubricated with a lubricating oil composition including a major amount of oil of lubricating viscosity, and a minor amount of at least one highly grafted, multi-functional olefin copolymer. The olefin copolymer is made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 1,000 in the present of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of at least 0.5 wt. %, and reacting the acylated olefin copolymer with an amine to provide the highly grafted, multi-functional olefin copolymer. As used, the highly grafted, multi-functional olefin copolymer is effective to reduce a viscosity increase in the lubricating oil composition for the engine.

Description

RELATED APPLICATION

This application claims priority to provisional application No. 60/887,539, filed Jan. 31, 2007.

TECHNICAL FIELD

The disclosure relates to bio-diesel fuel engine lubrication and to improved lubricant compositions for bio-diesel fuel engine applications that provide improved properties.

BACKGROUND AND SUMMARY

Emission requirements for all vehicles have become increasingly more stringent. For instance, diesel engine design changes required to meet emission requirements have led to increased levels of soot in engine lubricants. An increased level of soot may cause increased wear when oils are not properly formulated due to an increase in oil viscosity and/or inability of the oil to disperse particles that may cause engine wear. In particular, with the arrival of new exhaust gas recirculation or recycle (hereinafter “EGR”) cooled engines including cooled EGR engines, a problem has developed in the ability of the conventional lubricating oils to handle the resulting increased soot loading. Increases in the soot loading may also result from the use of lower grade fuels such as bio-diesel fuels that are more bio-degradable but often include more soot producing and oil thickening components.
Certain diesel engines with cooled EGR may exhibit undesirable oil thickening because of the way soot and blowby generated in the engine contaminate the engine oil. Increasing the treat rate of standard dispersants in the lubricating oils may not adequately solve the problems caused by an increased use of bio-diesel fuels in the engines. Accordingly, there continues to be a need for lubricant formulations that are more compatible with newer heavy duty diesel fuels, particularly, fuels containing increased levels of bio-fuel components.
In accordance with a first exemplary embodiment, the disclosure provides a diesel engine operating on a fuel containing from about 5 to about 100 percent by weight bio-diesel fuel. The engine is lubricated with a major amount of oil of lubricating viscosity, and a minor amount of at least one highly grafted, multi-functional olefin copolymer made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 1,000 in the present of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of at least 0.5 wt. %, and reacting the acylated olefin copolymer with an amine to provide the highly grafted, multi-functional olefin copolymer. In the engine, the highly grafted, multi-functional olefin copolymer is effective to reduce a viscosity increase in the lubricating oil composition for the engine to less than or equal to a viscosity increase in a lubrication oil composition for an engine operating on a fuel devoid of the bio-diesel components.
In another exemplary embodiment, the disclosure provides method for reducing a viscosity increase in a lubricating oil composition for a diesel engine operating on a fuel containing from about 5 to about 100 wt. % bio-diesel. The engine is lubricated with a lubricant composition containing a major amount of oil of lubricating viscosity, and a minor amount of at least one highly grafted, multi-functional olefin copolymer made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 1,000 in the present of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of at least 0.5 wt. %, and reacting the acylated olefin copolymer with an amine to provide the highly grafted, multi-functional olefin copolymer. The engine is operated to provide a viscosity increase as determined by a T-11 engine test in the lubricating oil composition that is less than a viscosity increase in the lubricating oil for an engine operating on a diesel fuel devoid of bio-diesel components.
Accordingly, a primary advantage of the exemplary embodiments may be an increased in oil change intervals due to a lower viscosity increase in the lubricating oil for an engine operating on a fuel containing bio-diesel components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical comparison of viscosity versus soot loading for lubricants in engines operating on a diesel fuel containing bio-diesel components and a diesel fuel devoid of biodiesel components.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As described in more detail below, a lubricating oil for a diesel engine operating on a fuel containing bio-diesel components may be synergistically improved by the addition of a particular highly grafted, multi-functional olefin copolymer. More particularly, a lubricating oil containing a conventional dispersant/inhibitor (DI) package may be significantly improved for use in certain engines operating on bio-diesel fuels by incorporating the highly grafted olefin copolymer as a dispersant/viscosity index improver. Such lubricating oil compositions, as described more fully herein, may be particularly useful for lubricating internal combustion engines (e.g., heavy duty diesel engines, and light duty diesel engines, including diesel engines equipped with exhaust gas recirculator (EGR) systems). Lubricant compositions containing the highly grafted, multi-functional olefin copolymer may have improved soot dispersing (deagglomeration), deposit control, and boundary film formation performance, as well as improved viscosity performance thereby improving the wear protection for the engine.
In one embodiment, the highly grafted, multi-functional olefin copolymer product may be added to lubricating compositions in an amount sufficient to reduce the amount of oil thickening of the lubricating oil due to soot content, especially in exhaust gas recirculation (EGR) equipped diesel engines.
As described more fully in U.S. Pat. No. 7,253,231, the highly grafted, multi-functional olefin copolymer is provided as the reaction product of a previously dehydrated copolymer substrate that is derived from a polymer of ethylene and one or more C₃to C₂₃alpha-olefins. The copolymer is acylated with an acylating agent and is further reacted with an amine to provide the multi-functional product. The foregoing multi-functional product may be used in lubrication compositions to provide one or more functions including as a viscosity index (VI) modifier, dispersant, film formation improver, deposit controller, as well as other functions.
The polymer substrate starting material for multi-functional olefin copolymer is derived from copolymers of ethylene and one or more C₃to C₂₃alpha-olefins. Copolymers of ethylene and propylene are suitably used to make the copolymer. “Copolymers” herein may include without limitation blends or reacted products of ethylene and one or more C₃to C₂₃alpha-olefins, and additionally optionally other dienes or polyenes. Thus, “copolymers” herein also includes terpolymers, and other higher forms. Other alpha-olefins suitable in place of propylene to form the copolymer or to be used in combination with ethylene and propylene to form a terpolymer include 1-butene, 1-pentene, 1-hexene, 1-octene and styrene; .alpha,ω-diolefins such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene; branched chain alpha-olefins such as 4-methylbutene-1,5-methylpentene-1 and 6-methylheptene-1; and mixtures thereof.
Methods for making the copolymers described above are described, e.g., in U.S. Pat. Nos. 4,863,623, 5,075,383, and 6,107,257, which descriptions are incorporated herein by reference. The polymer substrate also may be commercially obtained having the properties indicated herein.
More complex polymer substrates, often designated as interpolymers, also may be used as the olefin polymer starting material, which may be prepared using a third component. The third component generally used to prepare an interpolymer substrate is a polyene monomer selected from nonconjugated dienes and trienes. The-non-conjugated diene component is one having from 5 to 14 carbon atoms in the chain. For example, the diene monomer may be characterized by the presence of a vinyl group in its structure and can include cyclic and bicyclo compounds. Representative dienes include 1,4-hexadiene, 1,4-cyclohexadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, vinylnorbornene, 5-methylene-2-norborene, 1,5-heptadiene, and 1,6-octadiene. A mixture of more than one diene may be used in the preparation of the interpolymer. A suitable nonconjugated diene for preparing a terpolymer or interpolymer substrate is 1,4-hexadiene.
The triene component may have at least two nonconjugated double bonds, and up to about 30 carbon atoms in the chain. Typical trienes that may be used to prepare the interpolymer of the disclosure are 1-isopropylidene-3α,4,7,7α-tetrahydroindene, 1-isopropylidenedicyclopentadiene, dihydro-isodicyclopentadiene, and 2-(2-methylene-4-methyl-3-pentenyl) [2.2.1]bicyclo-5-heptene.
Ethylene-propylene or higher alpha-olefin copolymers may consist of from about 15 to 80 mole percent ethylene and from about 85 to 20 mole percent C₃to C₂₃alpha-olefin with the mole ratios in one embodiment being from about 35 to 75 mole percent ethylene and from about 65 to 25 mole percent of a C₃to C₂₃alpha-olefin, with the proportions in another embodiment being from 50 to 70 mole percent ethylene and 50 to 30 mole percent C₃to C₂₃alpha-olefin, and the proportions in yet another embodiment being from 55 to 65 mole percent ethylene and 45 to 35 mole percent C₃to C₂₃alpha-olefin.
Terpolymer variations of the foregoing polymers may contain from about 0 to 10 mole percent of a nonconjugated diene or triene. Other termonomer levels are less than 1 mole percent.
The starting polymer that is acylated is desirably an oil-soluble, linear or branched polymer having a number average molecular weight from about 1,000 to 500,000, and for example a number average molecular weight of 50,000 to 250,000, as determined by gel permeation chromatography and universal calibration standardization.
The term “polymer” is used generically to encompass ethylene copolymers, terpolymers or interpolymers. Such materials may contain amounts of other olefinic monomers so long as the basic characteristics of the polymers are not materially changed.
The polymerization reaction used to form an ethylene olefin copolymer may be conducted in the presence of a conventional Ziegler-Natta or metallocene catalyst system. The polymerization medium is not specific and may include solution, slurry, or gas phase processes, as known to those skilled in the art. When solution polymerization is employed, the solvent may be any suitable inert hydrocarbon solvent that is liquid under reaction conditions for polymerization of alpha-olefins; examples of satisfactory hydrocarbon solvents include straight chain paraffins having from 5 to 8 carbon atoms, with hexane being preferred. Aromatic hydrocarbons, for example, aromatic hydrocarbon having a single benzene nucleus, such as benzene, toluene and the like; and saturated cyclic hydrocarbons having boiling point ranges approximating those of the straight chain paraffinic hydrocarbons and aromatic hydrocarbons described above are particularly suitable. The solvent selected may be a mixture of one or more of the foregoing hydrocarbons. When slurry polymerization is employed, the liquid phase for polymerization is preferably liquid propylene. It is desirable that the polymerization medium be free of substances that will interfere with the catalyst components.
The polymer described above, i.e., the olefin polymer component, may be conveniently obtained in the form of ground or pelletized polymer. The olefin polymer may also be supplied as either a pre-mixed bale or a pre-mixed friable chopped agglomerate form.
In one embodiment, ground polymer bales or other forms of the olefin copolymer are fed to an extruder e.g., a single or twin screw extruder, or a Banbury or other mixer having the capability of heating and effecting the desired level of mechanical work (agitation) on the polymer substrate for the dehydration step. A nitrogen blanket can be maintained at the feed section of the extruder to minimize the introduction of air.
The olefin copolymer is initially heated before being admixed with any other reactants in the extruder or other mixer with venting to eliminate moisture content in the feed material. The dried olefin copolymer is in one embodiment then fed into another extruder section or separate extruder in series for conducting the grafting reaction.
A graft monomer is next grafted onto the polymer backbone of the polymer olefin copolymer to form an acylated ethylene-alphaolefin polymer.
Suitable graft monomers include ethylenically unsaturated carboxylic acid materials, such as unsaturated dicarboxylic acid anhydrides and their corresponding acids. Examples of these graft monomers are set forth, for example, in U.S. Pat. No. 5,837,773, which descriptions are incorporated herein by reference. Carboxylic reactants which are suitable for grafting onto the ethylene-alphaolefin interpolymers contain at least one ethylenic bond and at least one carboxylic acid or its anhydride groups or a polar group which is convertible into said carboxyl groups by oxidation or hydrolysis. The carboxylic reactants are selected from the group consisting of acrylic, methacrylic, cinnamic, crotonic, maleic, fumaric and itaconic reactants or a mixture of two or more of these. In the case of unsaturated ethylene copolymers or terpolymers, itaconic acid or its anhydride is useful due to its reduced tendency to form a cross-linked structure during the free-radical grafting process.
The ethylenically unsaturated carboxylic acid materials typically may provide one or two carboxylic groups per mole of reactant to the grafted copolymer. That is, methyl methacrylate may provide one carboxylic group per molecule to the grafted copolymer while maleic anhydride may provide two carboxylic groups per molecule to the grafted copolymer.
The grafting reaction to form the acylated olefin copolymers is generally carried out with the aid of a free-radical initiator either in bulk or in solution. The grafting may be carried out in the presence of a free-radical initiator dissolved in oil. The use of a free-radical initiator dissolved in oil results in a more homogeneous distribution of acylated groups over the olefin copolymer molecules.
The free-radical initiators which may be used to graft the ethylenically unsaturated carboxylic acid material to the polymer backbone include peroxides, hydroperoxides, peresters, and also azo compounds and preferably those which have a boiling point greater than 100° C. and decompose thermally within the grafting temperature range to provide free radicals. Representatives of these free-radical initiators are azobutyronitrile, dicumyl peroxide, 2,5-dimethylhexane-2,5-bis-tertiarybutyl peroxide and 2,5-dimethylhex-3-yne-2,5-bis-tertiary-butyl peroxide. The initiator may be used in an amount ranging from about 0.005% to about 1% by weight based on the weight of the reaction mixture.
To perform the grafting reaction as a solvent-free or essentially solvent-free bulk process, the graft monomer and olefin copolymer are in one embodiment fed to an extruder, e.g., a single or twin screw extruder e.g. Werner & Pfleiderer's ZSK series, or a Banbury or other mixer, having the capability of heating and effecting the desired level of mechanical work (agitation) on the reactants for the grafting step. In one embodiment, grafting is conducted in an extruder, and particularly a twin screw extruder. A nitrogen blanket is maintained at the feed section of the extruder to minimize the introduction of air.
Grafting may also be conducted in an extruder, such as a twin-screw extruder. A nitrogen blanket is maintained at the feed section of the extruder to minimize the introduction of air. In another embodiment, the olefinic carboxylic acylating agent may be injected at one injection point, or is alternatively injected at two injection points in a zone of the extruder without significant mixing e.g. a transport zone. Such injection may result in an improved efficiency of the grafting and leads to a lower gel content.
Suitable extruders are generally known available for conducting grafting, and the prior dehydration procedure. The dehydration of the polymer substrate and subsequent grafting procedures may be performed in separate extruders set up in series. Alternatively, a single extruder having multiple treatment or reaction zones may be used to sequentially conduct the separate operations within one piece of equipment. Illustrations of suitable extruders are set forth, e.g., in U.S. Pat. No. 3,862,265 and U.S. Pat. No. 5,837,773, which descriptions are incorporated herein by reference.
In forming the acylated olefin copolymers, the olefin copolymer generally is fed to plastic processing equipment such as an extruder, intensive mixer or masticator, heated to a temperature of at least 60°, for example, 150° to 240° C., and the ethylenically unsaturated carboxylic acid reagent and free-radical initiator are separately co-fed to the molten copolymer to effect grafting. The reaction is carried out optionally with mixing conditions to effect grafting of the olefin copolymers. If molecular weight reduction and grafting are performed simultaneously, illustrative mixing conditions are described in U.S. Pat. No. 5,075,383, which are incorporated herein by reference. The processing equipment is generally purged with nitrogen to prevent oxidation of the copolymer and to aid in venting unreacted reagents and byproducts of the grafting reaction. The residence time in the processing equipment is controlled to provide for the desired degree of acylation and to allow for purification of the acylated copolymer via venting. Mineral or synthetic lubricating oil may optionally be added to the processing equipment after the venting stage to dissolve the acylated copolymer.
The grafting reaction may also be carried out in solvent-free or essentially solvent free environment. Accordingly, the grafting reaction may be performed in the absence of hydrocarbon solvents. The avoidance of hydrocarbon solvents during the grafting reaction, such as alkanes (e.g., hexane), eliminates or significantly reduces the risk and problem of undesired side reactions of such solvents during the grafting reaction which can form undesired grafted alkyl succinic anhydride by-products and impurities. Also, reduced amounts of transient unfunctionalized polymer (ungrafted polymer) are present after grafting in solventless grafting reactions, which results in a more active product. Therefore, the resulting copolymer intermediate is a more active product. A reduction is achieved in levels of undesirable grafted solvent (i.e., grafted hexyl succinic anhydride) and transient unfunctionalized (nongrafted) copolymer.
Hydrocarbon solvents that may be omitted according to certain embodiments of the present disclosure include solvents that generally are more volatile than the reactants of the grafting reaction described herein, for example, solvents having a boiling point less than about 150° C. under standard atmospheric pressure conditions (i.e., approximately 14.7 lb./in²absolute). The solvents that may be omitted include, for example, open-chain aliphatic compounds such as C₉or lower alkanes, alkenes and alkynes (e.g., C₅to C₈alkanes such as hexane); aromatic hydrocarbons (e.g., compounds having a benzene nucleus such as benzene and toluene); alicyclic hydrocarbons such as saturated cyclic hydrocarbons (e.g., cyclohexane); ketones; or any combinations of these. In one embodiment, it is desirable to omit all solvents having boiling points approximating or lower than that of nonane under standard atmospheric conditions. Some conventional grafting reactions have been performed in the presence of considerable amounts of hydrocarbon solvent, such as approximately 15% to 60% hexane content. By comparison, in one embodiment of the present disclosure, the total amount of these types of such solvents in the grafting reaction mass does not exceed 0.5 wt. % content thereof.
The grafted copolymer intermediate exits from the die face of the extruder either immediately after grafting, or after shearing and vacuum stripping (discussed below in more detail) if performed in different sections of the same extruder or a separate extruder arranged in series with the extruder in which grafting is conducted.
The resulting copolymer intermediate comprises an acylated olefin copolymer characterized by having carboxylic acid acylating functionality randomly within its structure. The amount of carboxylic acid acylating agent (e.g., maleic anhydride) that is grafted onto the prescribed copolymer backbone (i.e., the copolymer substrate) is important. This parameter is referred to herein as the degree of grafting (DOG), further described as the mass percentage of acylating agent on the acylated copolymer. The DOG generally is in the range of 0.5 to 3.0 wt. %, particularly in the range of 1.5 to 2.5 wt. %, and more particularly in the range of 1.7 to 2.3 wt. %, of carboxylic acid acylating agent grafted on the copolymer backbone.
The DOG value of a particular additive reaction product may be determined either by infrared peak ratio analysis of acid or anhydride moiety versus copolymer alkyl functionality or by titration (Total Acid/Anhydride Number) (TAN) of the additive reaction product. The TAN value in turn can be used to estimate the degree of grafting (DOG).
The carboxylic reactant is grafted onto the prescribed copolymer backbone to provide 0.15 to 0.75 carboxylic groups per 1000 number average molecular weight units (Mn) of the copolymer backbone, desirably 0.2 to 0.5 carboxylic groups per 1000 number average molecular weight. For example, a copolymer substrate with M_nof 20,000 is grafted with 3 to 15 carboxylic groups per copolymer chain or 1.5 to 7.5 moles of maleic anhydride per mole of copolymer. A copolymer with M_nof 100,000 is grafted with 15 to 75 carboxylic groups per copolymer chain or 7.5 to 37.5 moles of maleic anhydride per copolymer chain. The minimum level of functionality is the level needed to achieve the minimum satisfactory dispersancy performance.
The molecular weight of the acylated olefin copolymer, i.e., the copolymer intermediate, may be reduced by mechanical, thermal, or chemical means, or a combination thereof. Techniques for degrading or reducing the molecular weight of such copolymers are generally known in the art. The number average molecular weight is reduced to suitable level for use in single grade or multigrade lubricating oils.
In one embodiment, the initial copolymer intermediate has an initial number average molecular weight ranging from about 1,000 to about 500,000 upon completion of the grafting reaction. In one embodiment, to prepare an additive intended for use in multigrade oils, the copolymer intermediate's number average molecular weight is reduced down to a range of about 1,000 to about 80,000.
Alternatively, grafting and reduction of the high molecular weight olefin copolymer may be done simultaneously. In another alternative, the high molecular weight olefin copolymer may be first reduced to the prescribed molecular weight before grafting. When the olefin copolymer's average molecular weight is reduced before grafting, its number average molecular weight is sufficiently reduced to a value below about 80,000, e.g., in the range of about 1,000 to 80,000.
Reduction of the molecular weight of the copolymer intermediate, or the olefin copolymer feed material during or prior to grafting, to a prescribed lower molecular weight typically is conducted in the absence of a solvent or in the presence of a base oil, using either mechanical, thermal, or chemical means, or combination of these means. Generally, the copolymer intermediate, or olefin copolymer, is heated to a molten condition at a temperature in the range of about 250° C. to about 350° C. and it is then subjected to mechanical shear, thermally or chemical induced cleavage or combination of said means, until the copolymer intermediate (or olefin copolymer) is reduced to the prescribed molecular weight. The shearing may be effected within an extruder section, such as described, e.g., in U.S. Pat. No. 5,837,773, which descriptions are incorporated herein by reference. Alternatively, mechanical shearing may be conducted by forcing the molten copolymer intermediate (or olefin copolymer) through fine orifices under pressure or by other mechanical means.
Upon completion of the grafting reaction, unreacted carboxylic reactant and free radical initiator usually are removed and separated from the copolymer intermediate before further functionalization is performed on the copolymer intermediate. The unreacted components may be eliminated from the reaction mass by vacuum stripping, e.g., the reaction mass may be heated to temperature of about 150° C. to about 450° C. under agitation with a vacuum applied for a period sufficient to remove the volatile unreacted graft monomer and free radical initiator ingredients. Vacuum stripping may be performed in an extruder section equipped with venting means.
The copolymer intermediate may be pelletized before further processing in accordance with embodiments of the disclosure herein. Pelletization of the copolymer intermediate helps to isolate the intermediate product and reduce contamination thereof until further processing is conducted thereon at a desired time.
The copolymer intermediate may be formed into pellets by a variety of process methods commonly practiced in the art of plastics processing. Such techniques include underwater pelletization, ribbon or strand pelletization or conveyor belt cooling. When the strength of the copolymer is inadequate to form into strands, the preferred method is underwater pelletization. Temperatures during pelletization should not exceed 30° C. Optionally, a surfactant can be added to the cooling water during pelletization to prevent pellet agglomeration.
The mixture of water and quenched copolymer pellets is conveyed to a dryer such as a centrifugal drier for removal of water. Pellets may be collected in a box or plastic bag at any volume for storage and shipment. Under some conditions of storage and/or shipment at ambient conditions, pellets may tend to agglomerate and stick together. The pellets may be ground by mechanical methods to provide high surface area solid pieces for easy and quick dissolution into oil.
The pelletized copolymer intermediate may be supplied as an unground or ground form of the pellets. The pelletized acylated copolymer intermediate is dissolved in solvent neutral oil. The pellets generally are dissolved in the solvent at an introduction level of from about 5 wt. % to about 25 wt. %, particularly about 10 wt. % to about 15 wt. %, and more particularly about 12 wt. % to about 13 wt. %, based on the resulting solution (solute and solvent) viscosity.
The pelletized copolymer intermediate can be dissolved in the solvent neutral at temperature of, for example, about 135° C. to about 165° C. with mechanical stirring under a nitrogen blanket. The dissolving mixture may be sparged with inert gas during the dissolution for about 4 to 16 hours. Such treatment may be performed in a continuous stirred process vessel of suitable capacity.
The inert sparging gas may be nitrogen. The dissolution and sparging, if used, may be prior to the subsequent amination procedure. One or more spargers are located within the vessel at locations submerged beneath the surface of the solution, preferably near the bottom of the solution, and bubble inert gas through the solution. Nitrogen sparging removes moisture from the dissolved copolymer intermediate and solvent oil. Importantly, the removal of moisture from the copolymer intermediate may act to convert any polymeric dicarboxylic diacids present back to the desired copolymeric dicarboxylic anhydride form.
For instance, where maleic anhydride is used as the grafting monomer, some portion of the pelletized copolymer intermediate may inadvertently transform to a copolymeric succinic diacid form. In general, this change is more apt to occur as a function of a longer shelf life. The conducting of nitrogen sparging during dissolution of the copolymer intermediate and prior to amination has the benefit of converting the copolymeric succinic diacid back into the desired active polymeric succinic anhydride form before the copolymer intermediate is further reacted and functionalized (e.g., aminated). Consequently, a more highly functionalized and active aminated product may be obtained in subsequent processing. The conversion of polymeric succinic diacid back into the active polymeric succinic anhydride form can be monitored by measuring the viscosity of the solution. The solution viscosity decreases significantly from an initial higher value down to a steady-state value upon conversion of all or essentially all of the polymeric succinic diacid back into the desired polymeric succinic anhydride form.
The neutral oil may be selected from Group I base stock, Group II base stock, Group III base stock, Group IV or poly-alpha-olefins (PAO), or base oil blends thereof.
The base stock or base stock blend preferably has a saturate content of at least 65%, more preferably at least 75%; a sulfur content of less than 1%, preferably less than 0.6%, by weight; and a viscosity index of at least 85, preferably at least 100. Such base stocks may be defined as follows:

- (i) Group I: base stocks containing less than 90% saturates and/or greater than 0.03% sulfur and having a viscosity index greater than or equal to 80 and less than 120 using test methods specified in Table 1 of the American Petroleum Institute (API) publication “Engine Oil Licensing and Certification Sheet” Industry Services Department, 14.sup.th Ed., December 1996, Addendum I, December 1998;
- (ii) Group II: base stocks containing greater than or equal to 90% saturates and/or greater than 0.03% sulfur and having a viscosity index greater than or equal to 80 and less than 120 using test methods specified in Table 1 referenced above;
- (iii) Group III: base stocks which are less than or equal to 0.03 wt % sulfur, greater than or equal to 90% saturates, and greater than or equal to 120 using test methods specified in Table 1 referenced above.
- (iv) Group IV: base stocks which comprise PAO's.

For these definitions, saturates level may be determined by ASTM D 2007, the viscosity index maybe determined by ASTM D 2270; and sulfur content by any one of ASTM D 2622, ASTM D 4294, ASTM D 4927, or ASTM D 3120.
The dissolved pelletized copolymer intermediate possessing carboxylic acid acylating functions subsequently reacted with an amine compound. The amine may be selected from compounds such as described, e.g., in U.S. Pat. Nos. 4,863,623, 5,075,383, and 6,107,257, which descriptions are incorporated herein by reference.
In one embodiment, the amine compound may be selected from the group consisting of:

- (a) an N-arylphenylenediamine represented by the formula:

- in which Ar is aromatic and R¹is —H, —NH₂, —(—NH-Aryl)_n-H, —(—NH-Alkyl)_n—H, —NH-arylalkyl, a branched or straight chain radical having from 4 to 24 carbon atoms that can be alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl or aminoalkyl, R²is (—NH₂, —(NH(CH₂)_n—)_m—NH₂, —(CH₂)_n—NH₂, -aryl-NH₂, in which n and m each has a value from 1 to 10, and R³is hydrogen, alkyl, alkenyl, alkoxyl, aralkyl, alkaryl having from 4 to 24 carbon atoms,
- (b) an aminocarbazole represented by the formula:

- in which R and R¹represent hydrogen or an alkyl, alkenyl, or alkoxyl radical having from 1 to 14 carbon atoms,
- (c) an aminoindole represented by the formula:

- in which R represents hydrogen or an alkyl radical having from 1 to 14 carbon atoms,
- (d) an amino-indazolinone represented by the formula:

- in which R is hydrogen or an alkyl radical having from 1 to 14 carbon atoms,
- (e) an aminomercaptotriazole represented by the formula:

- in which R can be absent or can be C₁-C₁₀linear or branched hydrocarbon selected from the group consisting of alkyl, aryl, alkaryl, or arylalkyl.
- (f) an aminopyrimidine represented by the formula:

- in which R represents hydrogen or an alkyl or alkoxyl radical having from 1 to 14 carbon atoms.

In one embodiment, the amine compound may be, e.g., an N-arylphenylenediamine represented by the general formula:
in which R¹is hydrogen, —NH-aryl, —NH-arylalkyl, —NH-alkyl, or a branched or straight chain radical having from 4 to 24 carbon atoms that can be alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl or aminoalkyl; R²is —NH₂, CH₂—(CH₂)_n—NH₂, CH₂-aryl-NH₂, in which n has a value from 1 to 10 and R.sup.3 is hydrogen, alkyl, alkenyl, alkoxyl, aralkyl, alkaryl having from 4 to 24 carbon atoms.
Particularly useful amines in the present disclosure are the N-arylphenylenediamines, more specifically the N-phenylphenylenediamines, for example, N-phenyl-1,4-phenylenediamine, N-phenyl-1,3-phenylendiamine, and N-phenyl-1,2-phenylenediamine.
Illustrations of other useful amines include those described in U.S. Pat. Nos. 4,863,623 and 6,107,257, which are incorporated herein by reference.
It is desirable that the amines contain only one primary amine group so as to avoid coupling and/or gelling of the olefin copolymers.
The reaction between the copolymer having grafted thereon carboxylic acid acylating function and the prescribed amine compound may be conducted by heating a solution of the copolymer substrate under inert conditions and then adding the amine compound to the heated solution generally with mixing to effect the reaction. It is convenient to employ an oil solution of the copolymer substrate heated to 120° to 175° C., while maintaining the solution under a nitrogen blanket. The amine compound may be added to this solution and the reaction is effected under the noted conditions.
The amine compound may be dissolved with a surfactant and added to a mineral or synthetic lubricating oil or solvent solution containing the acylated olefin copolymer. The solution of amine and olefin copolymer may be heated with agitation under an inert gas purge at a temperature in the range of 120° to 200° C. as described in U.S. Pat. No. 5,384,371, the disclosure of which is herein incorporated by reference. The reactions may be carried out conveniently in a stirred reactor under nitrogen purge.
In one aspect, a polymeric succinic anhydride oil solution is reacted with N-phenyl-1,4-phenylenediamines, along with ethoxylated lauryl alcohol in a reactor carried out at 165° C.
Surfactants which may be used in carrying out the reaction of the acylated olefin copolymer with the polyamine(s) include but are not limited to those characterized as having (a) solubility characteristics compatible with mineral or synthetic lubricating oil, (b) boiling point and vapor pressure characteristics so as not to alter the flash point of the oil and (c) polarity suitable for solubilizing the polyamine(s).
A suitable class of such surfactants includes the reaction products of aliphatic and aromatic hydroxy compounds with ethylene oxide, propylene oxide or mixtures thereof. Such surfactants are commonly known as aliphatic or phenolic alkoxylates. Useful surfactants can include those surfactants that contain a functional group, e.g., —OH, capable of reacting with the acylated olefin copolymer. Ethoxylated lauryl alcohol (C₁₂H₂₅(OCH₂CH₂)_nOH) is also useful herein. Ethoxylated lauryl alcohol is identified under CAS no. 9002-92-0. The ethoxylated lauryl alcohol is a processing aid and viscosity stabilizer for the final multifunctional viscosity modifier product. The ethoxylated lauryl alcohol facilitates the amine charge into the reaction mixture. It is a reaction agent ensuring that no acylated functionality is left unreacted. Any unreacted acylated functionality may cause undesirable viscosity drift in finished lubrication formulations. The surfactant also modifies the viscoelastic response in the multifunctional viscosity modifier product allowing improved handling at low temperature (70 to 90° C.).
The quantity of surfactant used depends in part on its ability to solubilize the amine. Typically, concentrations of 5 to 40 wt. % amine are employed. The surfactant may also be added separately, instead of or in addition to the concentrates discussed above, such that the total amount of surfactant in the finished additive is 10 wt. % or less.
The highly grafted, multi-functional olefin copolymers of the present disclosure may be incorporated into lubricating oil in any convenient way. Thus, the highly grafted, multi-functional olefin copolymers may be added directly to the lubricating oil by dispersing or dissolving the same in the lubricating oil at the desired level of concentration. Such blending into the lubricating oil may occur at room temperature or elevated temperatures. Alternatively, the highly grafted, multi-functional olefin copolymers can be blended with a suitable oil-soluble solvent/diluent (such as benzene, xylene, toluene, lubricating base oils and petroleum distillates) to form a concentrate, and then blending the concentrate with a lubricating oil to obtain the final formulation. Such additive concentrates will typically contain (on an active ingredient (A.I.) basis) from about 3 to about 45 wt. %, and preferably from about 10 to about 35 wt. %, highly grafted, multi-functional olefin copolymer additive, and typically from about 20 to 90 wt %, preferably from about 40 to 60 wt %, base oil based on the concentrate weight.
Several of the amine reactants have the tendency to form highly colored oxidation products, comprising members of the class of staining amine antioxidants. Unreacted amine which is left in the oil solution after the amination reaction may give rise to undesirable and/or unstable color in the oil solution. The acylated olefin copolymer also may be color stabilized after the amination reaction, such as by reacting the acylated olefin copolymer with a C₇to C₁₂alkyl aldehyde (e.g., nonyl aldehyde). For example, the reaction may proceed when the alkyl aldehyde agent is added in an amount of about 0.2 to about 0.6 wt. % under similar temperature and pressure conditions as used in the amination reaction for about 2 to about 6 hours.
To increase the purity of the aminated, color stabilized acylated olefin copolymer product, it may be filtered by either bag or cartridge filtration or both in series.
As indicated above, the copolymer intermediate may be prepared in the absence of solvent. Also, the copolymer intermediate may be received in pelletized or bale form as a starting material for performing the additional functionalization(s), viz. amination and color stabilization, on the grafted copolymer intermediate. The copolymer intermediate need not be received directly from the die face of an extruder or similar grafting reaction vessel, but instead the copolymer intermediate has been vacuum stripped of unreacted reactants and pelletized before these further functionalizations are performed on it. Therefore, the pelletized copolymer intermediate contains less contaminants than a product that has been grafted in the presence of a solvent (which can lead to side reaction products) and/or aminated immediately after the grafting reaction as part of a continuous process flow arrangement (which leaves unreacted components as impurities in the reaction mass).
In addition, the use of inert gas sparging on the copolymer intermediate dissolved in neutral oil prior to amination has the benefit of converting polymeric succinic diacid present back into the desired active polymeric succinic anhydride form before the copolymer intermediate is further reacted and functionalized (e.g, aminated).
Also, since unreacted graft monomer, e.g., maleic anhydride is effectively removed after the grafting step during vacuum stripping that precedes pelletizing and dissolution, amination proceeds more efficiently. That is, the presence of unreacted graft monomers are undesirable during the amination step as they may compete with the grafted copolymer (polymer intermediate) in reactions with the amine, reducing the level of functionalization achieved.
Therefore, the multi-functional reaction end product of embodiments of the present disclosure may contain fewer impurities (i.e., unreacted reactants, side reaction products and by-products) and may be more active for a given amount thereof. In one embodiment, the additive reaction product may contain less than 0.1 wt. % total impurities comprising unreacted reactants, side reaction products and reaction by-products. The remainder may be composed of active grafted, multifunctionalized olefin copolymer either entirely, or substantially in combination with some minor amount of beneficial or inert additive introduced during processing, such as an antioxidant or colorant, which does not significantly reduce or impair the activity of the product compound.
The highly grafted, multi-functional olefin copolymer product compounds of the present disclosure optionally may be post-treated so as to impart additional properties necessary or desired for a specific lubricant application. Post-treatment techniques are well known in the art and include boronation, phosphorylation, glycolation, ethylene-carbonation, and maleination.
Lubricating oil formulations for diesel engines as described herein may conventionally contain additional additives that will supply the characteristics that are required in the formulations. Among these types of additives are included additional viscosity index improvers, antioxidants, corrosion inhibitors, detergents, dispersants, pour point depressants, antiwear agents, antifoaming agents, demulsifiers and friction modifiers. These additives are provided in what is commonly called a dispersant/inhibitor (DI) package.
One component of the DI package is a metal-containing or ash-forming detergent that functions as both a detergent to reduce or remove deposits and as an acid neutralizer or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with a long hydrophobic tail. The polar head comprises a metal salt of an acidic organic compound. The salts may contain a substantially stoichiometric amount of the metal in which case they are usually described as normal or neutral salts, and would typically have a total base number or TBN (as can be measured by ASTM D2896) of from 0 to 80. A large amount of a metal base may be incorporated by reacting excess metal compound (e.g., an oxide or hydroxide) with an acidic gas (e.g., carbon dioxide). The resulting overbased detergent comprises neutralized detergent as the outer layer of a metal base (e.g. carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically will have a TBN of from 250 to 450 or more.
Detergents that may be used include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e.g., barium, sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, which may both be present in detergents used in a lubricant, and mixtures of calcium and/or magnesium with sodium. Particularly convenient metal detergents are neutral and overbased calcium sulfonates having TBN of from 20 to 450, neutral and overbased calcium phenates and sulfurized phenates having TBN of from 50 to 450 and neutral and overbased magnesium or calcium salicylates having a TBN of from 20 to 450. Combinations of detergents, whether overbased or neutral or both, may be used. In one preferred lubricating oil composition.
Detergents generally useful in the formulation of lubricating oil compositions also include “hybrid” detergents formed with mixed surfactant systems, e.g., phenate/salicylates, sulfonate/phenates, sulfonate/salicylates, sulfonates/phenates/salicylates, as described, for example, in U.S. Pat. Nos. 6,153,565, 6,281,179, 6,429,178 and 6,429,179.
It is not unusual to add a detergent or other additive, to a lubricating oil, or additive concentrate, in a diluent, such that only a portion of the added weight represents an active ingredient (A.I.). For example, detergent may be added together with an equal weight of diluent in which case the “additive” is 50% A.I. detergent. As used herein, the term weight percent (wt. %), when applied to a detergent or other additive refers to the weight of active ingredient. Detergents conventionally comprise from about 0.5 to about 5 wt. %, preferably from about 0.8 to about 3.8 wt. %, most preferably from about 1.2 to about 3 wt. % of a lubricating oil composition formulated for use in a heavy duty diesel engine.
Dispersants maintain in suspension materials resulting from oxidation during use that are insoluble in oil, thus preventing sludge flocculation and precipitation, or deposition on metal parts. Dispersants useful in the context of the disclosure include the range of nitrogen-containing, ashless (metal-free) dispersants known to be effective to reduce formation of deposits upon use in gasoline and diesel engines, when added to lubricating oils. The ashless, dispersants comprise an oil soluble polymeric long chain backbone having functional groups capable of associating with particles to be dispersed. Typically, such dispersants have amine, amine-alcohol or amide polar moieties attached to the polymer backbone, often via a bridging group. The ashless dispersant may be, for example, selected from oil soluble salts, esters, amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having polyamine moieties attached directly thereto; and Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine.
Generally, each mono- or dicarboxylic acid-producing moiety will react with a nucleophilic group (amine or amide) and the number of functional groups in the polyalkenyl-substituted carboxylic acylating agent will determine the number of nucleophilic groups in the finished dispersant.
The polyalkenyl moiety of the dispersant described herein has a number average molecular weight of at least about 1800, preferably between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100 to 2500, and most preferably from about 2200 to about 2400. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety as the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.
The polyalkenyl moiety from which dispersants may be derived has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (M.sub.w) to number average molecular weight (M_n). Specifically, polymers from which the dispersants may be derived have a M_w/M_nof from about 1.5 to about 2.0, preferably from about 1.5 to about 1.9, most preferably from about 1.6 to about 1.8.
Suitable hydrocarbons or polymers employed in the formation of the dispersants of the disclosure include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C₃to C₂₈alpha-olefin wherein the polymer contains carbon-to-carbon unsaturation, preferably a high degree of terminal ethenylidene unsaturation. Useful alpha-olefin monomers and comonomers include, for example, propylene, butene-1, hexene-1, octene-1,4-methylpentene-1, decene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures of propylene and butene-1, and the like). Exemplary of such polymers are propylene homopolymers, butene-1 homopolymers, ethylene-propylene copolymers, ethylene-butene-1 copolymers, propylene-butene copolymers and the like, wherein the polymer contains at least some terminal and/or internal unsaturation. Preferred polymers are unsaturated copolymers of ethylene and propylene and ethylene and butene-1. The interpolymers of disclosure may contain a minor amount, e.g. 0.5 to 5 mole % of a C₄to C₁₈non-conjugated diolefin comonomer. However, it is preferred that the polymers comprise only alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers and interpolymers of ethylene and alpha-olefin comonomers. The molar ethylene content of the polymers may be in the range of 0 to 80%, and more preferably 0 to 60%. When propylene and/or butene-1 are employed as comonomer(s) with ethylene, the ethylene content of such copolymers is most preferably between 15 and 50%, although higher or lower ethylene contents may be present.
Polyisobutylene polymers that may be employed as the polymer backbone to make the dispersants described above are generally based on a hydrocarbon chain of from about 1800 to 3000. Methods for making polyisobutylene are known. Polyisobutylene may be functionalized by halogenation (e.g. chlorination), the thermal “ene” reaction, or by free radical grafting using a catalyst (e.g. peroxide).
The hydrocarbon or polymer backbone can be functionalized, e.g., with carboxylic acid producing moieties (preferably acid or anhydride moieties) selectively at sites of carbon-to-carbon unsaturation on the polymer or hydrocarbon chains, or randomly along chains using any of the three processes mentioned above or combinations thereof, in any sequence.
Processes for reacting polymeric hydrocarbons with unsaturated carboxylic acids, anhydrides or esters and the preparation of derivatives from such compounds are disclosed in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,215,707; 3,231,587; 3,272,746; 3,275,554; 3,381,022; 3,442,808; 3,565,804; 3,912,764; 4,110,349; 4,234,435; 5,777,025; 5,891,953; as well as EP 0 382 450 B1; and CA-1,335,895.
The functionalized oil-soluble polymeric hydrocarbon backbone is then derivatized with a nitrogen-containing nucleophilic reactant, such as an amine, amino-alcohol, amide, or mixture thereof, to form a corresponding derivative. Amine compounds are preferred. Useful amine compounds for derivatizing functionalized polymers comprise at least one amine and can comprise one or more additional amine or other reactive or polar groups. These amines may be hydrocarbyl amines or may be predominantly hydrocarbyl amines in which the hydrocarbyl group includes other groups, e.g., hydroxy groups, alkoxy groups, amide groups, nitrites, imidazoline groups, and the like. Particularly useful amine compounds include mono- and polyamines, e.g., polyalkene and polyoxyalkylene polyamines of about 2 to 60, such as 2 to 40 (e.g., 3 to 20) total carbon atoms having about 1 to 12, such as 3 to 12, preferably 3 to 9, most preferably form about 6 to about 7 nitrogen atoms per molecule. Mixtures of amine compounds may advantageously be used, such as those prepared by reaction of alkylene dihalide with ammonia. Preferred amines are aliphatic saturated amines, including, for example, 1,2-diaminoethane; 1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines such as diethylene triamine; triethylene tetramine; tetraethylene pentamine; and polypropyleneamines such as 1,2-propylene diamine; and di-(1,2-propylene)triamine. Example of suitable amines can be found in U.S. Pat. Nos. 4,938,881; 4,927,551; 5,230,714; 5,241,003; 5,565,128; 5,756,431; 5,792,730; and 5,854,186.
Other useful amine compounds include: alicyclic diamines such as 1,4-di(aminomethyl)cyclohexane and heterocyclic nitrogen compounds such as imidazolines. Another useful class of amines is the polyamido and related amido-amines as disclosed in U.S. Pat. Nos. 4,857,217; 4,956,107; 4,963,275; and 5,229,022. Also usable is tris(hydroxymethyl)amino methane (TAM) as described in U.S. Pat. Nos. 4,102,798; 4,113,639; 4,116,876; and UK 989,409. Dendrimers, star-like amines, and comb-structured amines may also be used. Similarly, one may use condensed amines, as described in U.S. Pat. No. 5,053,152. The functionalized polymer is reacted with the amine compound using conventional techniques as described, for example, in U.S. Pat. Nos. 4,234,435 and 5,229,022, as well as in EP-A-208,560.
A preferred dispersant composition is one comprising at least one polyalkenyl succinimide, which is the reaction product of a polyalkenyl substituted succinic anhydride (e.g., PIBSA) and a polyamine (PAM) that has a coupling ratio of from about 0.65 to about 1.25, preferably from about 0.8 to about 1.1, most preferably from about 0.9 to about 1. In the context of this disclosure, “coupling ratio” may be defined as a ratio of the number of succinyl groups in the PIBSA to the number of primary amine groups in the polyamine reactant.
Another class of high molecular weight ashless dispersants comprises Mannich base condensation products. Generally, these products are prepared by condensing about one mole of a long chain alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5 moles of carbonyl compound(s) (e.g., formaldehyde and paraformaldehyde) and about 0.5 to 2 moles of polyalkylene polyamine, as disclosed, for example, in U.S. Pat. No. 3,442,808. Such Mannich base condensation products may include a polymer product of a metallocene catalyzed polymerization as a substituent on the benzene group, or may be reacted with a compound containing such a polymer substituted on a succinic anhydride in a manner similar to that described in U.S. Pat. No. 3,442,808. Examples of functionalized and/or derivatized olefin polymers synthesized using metallocene catalyst systems are described in the publications identified supra.
Preferred dispersants include those in which greater than about 50 wt. % of the nitrogen is non-basic. The normally basic nitrogen of nitrogen-containing dispersants can be rendered non-basic by reacting the nitrogen-containing dispersant with a so-called “capping agent”. Conventionally, nitrogen-containing dispersants have been capped to reduce the adverse effect such dispersants have on the nitrile seals used in engines. Numerous capping agents and methods are known. The reaction of a nitrogen-containing dispersant and tautomeric acetoacetate (e.g., ethyl acetoacetate (EAA)) is described, for example, in U.S. Pat. Nos. 4,839,071; 4,839,072 and 4,579,675. The reaction of a nitrogen-containing dispersant and formalin and/or formic acid is described, for example, in U.S. Pat. No. 3,185,704. Capping of nitrogen-containing dispersants with epoxides is described, for example, in U.S. Pat. Nos. 3,267,704; 3,373,021 and 3,373,111. The reaction product of a nitrogen-containing dispersant and other known capping agents are described in U.S. Pat. Nos. 3,366,569 (acrylonitrile); 4,636,322 and 4,663,064 (glycolic acid); 4,612,132; 5,334,321; 5,356,552; 5,716,912; 5,849,676; 5,861,363 carbonates, e.g., ethylene carbonate) 4,686,054 (maleic anhydride or succinic anhydride); 3,254,025; 3,087,963 (boron). The foregoing list is not exhaustive and other methods of capping nitrogen-containing dispersants are known to those skilled in the art.
For the purpose of reducing rate at which the kinematic viscosity of lubricating oil increases in the presence of soot and acids generated upon use of heavy duty diesel engines provided with EGR systems that operate in a condensing mode, nitrogen-containing dispersants in which greater than about 50 wt. % of the nitrogen is rendered non-basic by reaction with formalin, formic acid, epoxides and tautomeric acetoacetate (e.g., ethyl acetoacetate), are preferred.
Additional additives may be incorporated into the compositions of the disclosure to enable particular performance requirements to be met. Examples of additives which may be included in the lubricating oil compositions of the present disclosure are metal rust inhibitors, viscosity index improvers (other than polymer i, iii and/or iii), corrosion inhibitors, oxidation inhibitors, friction modifiers, anti-foaming agents, anti-wear agents and pour point depressants (other than polymer iii). Some are discussed in further detail below.
Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and antioxidant agents. The metal may be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or copper. The zinc salts are most commonly used in lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2 wt. %, based upon the total weight of the lubricating oil composition.
The preferred zinc dihydrocarbyl dithiophosphates are oil soluble salts of dihydrocarbyl 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, preferably 2 to 12, carbon atoms and including radicals such as alkyl, alkenyl, aryl, arylalkyl, 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, amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, butenyl. In order to obtain oil solubility, the total number of carbon atoms (i.e. R and R′) in the dithiophosphoric acid will generally be about 5 or greater. The zinc dihydrocarbyl dithiophosphate can therefore comprise zinc dialkyl dithiophosphates. The disclosed embodiments are particularly useful when used with lubricant compositions containing phosphorus levels of from about 0.02 to about 0.12 wt. %, preferably from about 0.03 to about 0.10 wt. %. More preferably, the phosphorous level of the lubricating oil composition will be less than about 0.08 wt. %, such as from about 0.05 to about 0.08 wt. %.
Oxidation inhibitors or antioxidants reduce the tendency of mineral oils to deteriorate in service. Oxidative deterioration can be evidenced by sludge in the lubricant, varnish-like deposits on the metal surfaces, and by viscosity growth. Such oxidation inhibitors include hindered phenols, alkaline earth metal salts of alkylphenolthioesters having preferably C₅to C₁₂alkyl side chains, calcium nonylphenol sulfide, oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons or esters, phosphorous esters, metal thiocarbamates, oil soluble copper compounds as described in U.S. Pat. No. 4,867,890, and molybdenum-containing compounds.
Aromatic amines having at least two aromatic groups attached directly to the nitrogen constitute another class of compounds that is frequently used for antioxidancy. While these materials may be used in small amounts, preferred embodiments of the present disclosure are free of these compounds. They are preferably used in only small amounts, i.e., up to 0.4 wt. %, or more preferably avoided altogether other than such amount as may result as an impurity from another component of the composition.
Typical oil soluble aromatic amines having at least two aromatic groups attached directly to one amine nitrogen contain from 6 to 16 carbon atoms. The amines may contain more than two aromatic groups. Compounds having a total of at least three aromatic groups in which two aromatic groups are linked by a covalent bond or by an atom or group (e.g., an oxygen or sulfur atom, or a—CO—, —SO₂— or alkylene group) and two are directly attached to one amine nitrogen also considered aromatic amines having at least two aromatic groups attached directly to the nitrogen. The aromatic rings are typically substituted by one or more substituents selected from alkyl, cycloalkyl, alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups. The amount of any such oil soluble aromatic amines having at least two aromatic groups attached directly to one amine nitrogen should preferably not exceed 0.4 wt. % active ingredient.
Representative examples of suitable viscosity modifiers are polyisobutylene, copolymers of ethylene and propylene, polymethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, interpolymers of styrene and acrylic esters, and partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadiene, as well as the partially hydrogenated homopolymers of butadiene and isoprene.
Friction modifiers and fuel economy agents that are compatible with the other ingredients of the final oil may also be included. Examples of such materials include glyceryl monoesters of higher fatty acids, for example, glyceryl mono-oleate; esters of long chain polycarboxylic acids with diols, for example, the butane diol ester of a dimerized unsaturated fatty acid; oxazoline compounds; and alkoxylated alkyl-substituted mono-amines, diamines and alkyl ether amines, for example, ethoxylated tallow amine and ethoxylated tallow ether amine.
Other known friction modifiers comprise oil-soluble metallic compounds such as organo-molybdenum compounds, organo-titanium compounds and organo-tungsten compounds. Such organo-metallic friction modifiers may also provide antioxidant and antiwear credits to a lubricating oil composition. As an example of such oil soluble organo-metallic compounds, there may be mentioned the carboxylates, dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates, sulfides, and the like, and mixtures thereof. Particularly preferred organo-metallic compounds include molybdenum dithiocarbamates, dialkyldithiophosphates, alkyl xanthates, and alkylthioxanthates. Other organo-metallic compounds may include the oil soluble titanium and tungsten carboxylates.
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. These do mean, however, that they are, for instance, soluble or stably dispersible in oil to an extent sufficient to exert their intended effect in the environment in which the oil is employed. Moreover, the additional incorporation of other additives may also permit incorporation of higher levels of a particular additive, if desired.
Pour point depressants, otherwise known as lube oil flow improvers (LOFI), lower the minimum temperature at which the fluid will flow or can be poured. Such additives are well known. Typical of those additives that improve the low temperature fluidity of the fluid are C₈to C₁₈dialkyl fumarate/vinyl acetate copolymers, and polymethacrylates. Foam control may be provided by an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.
Some of the above-mentioned additives can provide a multiplicity of effects; thus for example, a single additive may act as a dispersant-oxidation inhibitor. This approach is well known and need not be further elaborated herein.
When lubricating compositions contain one or more of the above-mentioned additives comprising the DI package, each additive is typically blended into the base oil in an amount that enables the additive to provide its desired function. Representative effective amounts of such additives, when used in crankcase lubricants, are listed below. All the values listed are stated as mass percent active ingredient.


	Mass %	Mass %
Additive	(Broad)	(Typical)

Metal Detergents	0.1 to 15.0	0.29 to 9.0
Dispersants	0.1 to 10.0	1.0 to 6.0
Corrosion Inhibitor	0 to 5.0	0 to 1.5
Metal Dihydrocarbyl Dithiophosphate	0.1 to 6.0	0.1 to 4.0
Antioxidant	0 to 5.0	0.01 to 2.0
Pour Point Depressant	0.01 to 5.0	0.01 to 1.5
Antifoaming Agent	0 to 5.0	0.001 to 0.15
Supplemental Antiwear Agents	0 to 1.0	0 to 0.5
Friction Modifiers	0 to 5.0	0 to 1.5
Viscosity Modifier	0.01 to 10.0	0.25 to 3.0
Basestock	Balance	Balance

In the preparation of lubricating oil formulations it is common practice to introduce the additives in the form of 10 to 80 wt. % active ingredient concentrates in hydrocarbon oil, e.g. mineral lubricating oil, or other suitable solvent.
Usually these concentrates may be diluted with 3 to 100, e.g., 5 to 40, parts by weight of lubricating oil per part by weight of the additive package in forming finished lubricants, e.g. crankcase motor oils. The purpose of concentrates, of course, is to make the handling of the various materials less difficult and awkward as well as to facilitate solution or dispersion in the final blend. Thus, the highly grafted, multi-functional olefin copolymer would usually be employed in the form of a 10 to 50 wt. % concentrate, for example, in a lubricating oil fraction. In one embodiment, the amount of concentrate in a finished lubricating oil is from about 0.05 weight percent to about 8 weight percent of the total lubricating oil.
The highly grafted, multi-functional olefin copolymers of the present disclosure will generally be used in admixture with a lube oil base stock, comprising an oil of lubricating viscosity, including natural lubricating oils, synthetic lubricating oils and mixtures thereof.
Natural oils include animal oils and vegetable oils (e.g., castor, lard oil), liquid petroleum oils and hydrorefined, solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale are also useful base oils. The synthetic lubricating oils used in this disclosure include one of any number of commonly used synthetic hydrocarbon oils, which include, but are not limited to, poly-alpha-olefins, alkylated aromatics, alkylene oxide polymers, copolymers, terpolymer, interpolymers and derivatives thereof here the terminal hydroxyl groups have been modified by esterification, etherification, etc, esters of dicarboxylic acids, and silicon-based oils.
The highly grafted, multi-functional olefin copolymer products of the present disclosure find their primary utility in lubricating oil compositions which employ a base oil in which the additives are dissolved or dispersed in amount sufficient to provide the desired functionality. Such base oils may be natural, synthetic or mixtures thereof. Base oils suitable for use in preparing the lubricating oil compositions for use in diesel engines operating on bio-diesel fuels include those conventionally employed as crankcase lubricating oils for spark-ignited and compression-ignited internal combustion engines, such as automobile and truck engines, marine and railroad diesel engines, and the like. The internal combustion engines which may be advantageously lubricated with crankcase lubricating oils containing the highly grafted olefin copolymer additive set forth herein include diesel fuel powered engines, particularly diesel engines operating on bio-diesel components. The diesel engines that may be particularly affected include heavy duty diesel engines, including those equipped with exhaust gas recirculation (EGR) systems.
Among other advantages, these additives have been observed in performance tests, such as described in the examples below, to provide improved soot dispersing and/or viscosity stabilizing performance on diesel engines operated on bio-diesel fuels as compared to the same engines using the same lubricants operated on non-biodiesel fuels. Bio-diesel fuels are typically fatty acid ethyl or methyl esters derived animal fats and from edible or non-edible vegetable oils such as, but not limited to, canola, sunflower, rapeseed, soyabean, linseed, and palm oils.
The cooled lubricated EGR engines within the scope of the present disclosure include heavy and light duty diesel engines that or operated on a variety of bio-diesel fuels. The engines may include EGR engines cooled by the circulation or heat exchange of water, water/hydrocarbon blends or mixtures, water/glycol mixtures, and/or air or gas.
The lubricating oil composition of the present disclosure was tested on a diesel engine operating on an ultra-low sulfur diesel PC-10 fuel devoid of bio-diesel components and an engine operating on a similar diesel fuel containing 20 wt. % bio-diesel components. The engine tests were extended T-11 engine tests. As shown in FIG. 1, curve A represents a viscosity soot curve for a lubricant used in the engine operating on bio-diesel fuel. Curve B represents the results for the engine operating on a fuel devoid of bio-diesel components. As shown in FIG. 1, the lubricant composition of the disclosure provided a synergistic decrease in viscosity increase at a higher soot loading when the engine was operated on a bio-diesel fuel as compared to the engine operating on a fuel devoid of bio-diesel components. The result was totally unexpected in view of the increased tendency of bio-diesel fuels to contribute to the soot loading of the lubricants.
The present disclosure is further directed to a method of extending lubricant drain intervals in a vehicle is contemplated. The method includes adding to and operating in the crankcase of the vehicle the lubricating oil composition described above.
The disclosures of all patents, articles and other materials described herein are hereby incorporated, in their entirety, into this specification by reference. Compositions described as “comprising” a plurality of defined components are to be construed as including compositions formed by admixing the defined plurality of defined components The principles, preferred embodiments and modes of operation of the present disclosure have been described in the foregoing specification. What applicants submit, however, is not to be construed as limited to the particular embodiments disclosed, since the disclosed embodiments are regarded as illustrative rather than limiting. Changes may be made by those skilled in the art without departing from the spirit of the disclosed embodiments.

Claims

1. A diesel engine operating on a fuel containing from about 5 to about 100 wt. % bio-diesel components and being lubricated with a lubricating oil composition comprising a major amount of oil of lubricating viscosity, and a minor amount of at least one highly grafted, multi-functional olefin copolymer made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 1,000 in the presence of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of at least 0.5 wt. %, and reacting the acylated olefin copolymer with an amine to provide the highly grafted, multi-functional olefin copolymer, wherein the highly grafted, multi-functional olefin copolymer is effective to reduce a viscosity increase in the lubricating oil composition for the engine to less than or equal to a viscosity increase in a lubrication oil composition for an engine operating on a fuel devoid of the bio-diesel components.

2. The diesel engine of claim 1, wherein the oil of lubricating viscosity has a saturates content of at least 75 wt. %, and the olefin copolymer comprises a copolymer of ethylene and one or more C₃-C₂₃alpha olefins.

3. The diesel engine of claim 1, wherein the lubricating oil composition further comprises a dispersant/inhibitor package.

4. The diesel engine of claim 3, wherein the dispersant/inhibitor package comprises a dispersant, a metal-containing detergent, an antiwear agent, an antioxidant, and a friction modifier.

5. The diesel engine of claim 4, wherein the detergent is selected from the group consisting of neutral and overbased calcium sulfonate, overbased magnesium sulfonate, calcium phenate, calcium salicylate, magnesium salicylate, magnesium phenate, and mixtures thereof.

6. The diesel engine of claim 4, wherein the dispersant comprises one or more polyalkenyl succinimide dispersants.

7. The diesel engine of claim 4, wherein the friction modifier is selected from the group consisting of non-metal containing organic friction modifiers, organometallic friction modifiers, and mixtures thereof.

8. The diesel engine of claim 7, wherein the organometallic friction modifier is selected from the group consisting of oil soluble organo-titanium, oil soluble organo-molybdenum compounds, and oil soluble organo-tungsten compounds.

9. The diesel engine of claim 7, wherein the non-metal containing friction modifier is selected from the group consisting of glycerol monooleate, and nitrogen containing friction modifiers.

10. The diesel engine of claim 1, wherein the acylated olefin copolymer has a degree of grafting (DOG) ranging from about 1.5 to about 2.5 wt. %.

11. The diesel engine of claim 1, wherein the diesel engine is equipped with an exhaust gas recirculation system.

12. A method for reducing a viscosity increase in a lubricating oil composition for a diesel engine operating on a fuel containing from about 5 to about 100 wt. % bio-diesel, comprising:

lubricating the engine with a lubricant composition comprising a major amount of oil of lubricating viscosity, and a minor amount of at least one highly grafted, multi-functional olefin copolymer made by reacting an acylating agent with an olefin copolymer having a number average molecular weight greater than about 1,000 in the present of a free radical initiator to provide an acylated olefin copolymer having a degree of grafting (DOG) of the acylating agent on the olefin copolymer of at least 0.5 wt. %, and reacting the acylated olefin copolymer with an amine to provide the highly grafted, multi-functional olefin copolymer, and

operating the engine to provide a viscosity increase as determined by a T-11 engine test in the lubricating oil composition that is less than a viscosity increase in the lubricating oil for an engine operating on a diesel fuel devoid of bio-diesel components.

13. The method of claim 12, wherein the diesel engine comprises a diesel engine having an exhaust gas recirculation system.

14. The method of claim 12, wherein the lubricant composition has a saturates content of at least 75 wt. %, and the olefin copolymer comprises a copolymer of ethylene and one or more C₃-C₂₃alpha olefins.

15. The method of claim 14, wherein the lubricant composition further comprises a dispersant/inhibitor package.

16. The method of claim 15, wherein the dispersant/inhibitor package comprises a dispersant, a metal-containing detergent, an antiwear agent, an antioxidant, and a friction modifier.

17. The method of claim 16, wherein the detergent is selected from the group consisting of neutral and overbased calcium sulfonate, overbased magnesium sulfonate, calcium phenate, calcium salicylate, magnesium salicylate, magnesium phenate, and mixtures thereof.

18. The method of claim 16, wherein the dispersant comprises one or more polyalkenyl succinimide dispersants.

19. The method of claim 16, wherein the friction modifier is selected from the group consisting of non-metal containing organic friction modifiers, organometallic friction modifiers, and mixtures thereof.

20. The method of claim 19, wherein the organometallic friction modifier is selected from the group consisting of oil soluble organo-titanium, oil soluble organo-molybdenum compounds, and oil soluble organo-tungsten compounds.

21. The method of claim 19, wherein the non-metal containing friction modifier is selected from the group consisting of glycerol monooleate, and nitrogen-containing friction modifiers.

22. The method of claim 12, wherein the acylated olefin copolymer has a degree of grafting (DOG) ranging from about 1.5 to about 2.5 wt. %.