GB2328217A - Lubricating oil compositions suitable for use in low speed diesel engines - Google Patents

Abstract

The wear of a low-speed marine diesel engine is reduced by contacting the internal surfaces of that engine with a lubricating oil composition comprising a major amount of a base oil of lubricating viscosity, from 0.5% to 2.5% of a polyalkylene succinimide, and up to 6% of a highly overbased detergent, such as an alkyl aromatic sulfonate.

Description

LUBRICATING OIL COMPOSITION SUITABLE FOR USE IN LOW-SPEED DIESEL ENGINES The present invention relates to lubricating oil compositions suitable for use in low-speed diesel engines operating on heavy fuel containing a high sulfur level (greater than 1% by weight).

BACKGROUND OF THE INVENTION Wear in large bore marine diesel engines is expensive to the operators. Oil degradation due to oxidation and poor thermal stability may cause excessive piston deposit formation, which in turn may cause excessive engine liner and ring wear. Highly overbased sulfonate detergents are known to have particularly poor oxidative and thermal stability=Therefore, it is desirable to find a method of improving the oxidative and thermal stability of highly overbased sulfonate detergents.

Polyalkylene succinimide compounds have been used in marine engines as dispersants, but they were not known to have antiwear properties.

European Patent Application No. 0 271 363 discloses compositions containing metal salts (preferably copper or zinc salts) of polyalkenyl substituted monounsaturated mono- or dicarboxylic acids which may be used as a compatibilizing material for mixtures of high molecular weight dispersants, high total base number detergents, and various antiwear or antioxidant materials.

European Patent Application No. 0 330 522 discloses a lubricating oil additive mixture comprising a dispersant (ashless dispersant and/or polymeric viscosity index improver dispersant) and a demulsifier additive (reaction product of an alkylene oxide and adduct obtained by reacting a bis-epoxide with a polyhydric alcohol). Additionally, the additive can contain a glycol ester or hydroxyamide derivative of a C2-go carboxylic acid.

European Patent Application No. 0 662 508 discloses a lubritcating oil composition suitable for use in low or medium speed diesel engines. ThätYubricating oil composition comprises a fuel oil with a residual oil content, a hydrocarbylsubstituted phenate concentrate having a BN of greater than 300, and at least one of a hydrocarbyl-substituted salicylate and a hydrocarbyl-substituted sulfonate.

Preferably, the hydrocarbyl-substituted phenate concentrate is modified by incorporation of a carboxylic acid.

SUMMARY OF THE INVENTION The present invention provides a method of reducing the wear of a low- speed marine diesel engine and for improving the anti-wear performance of a lubricating oil composition suitable for use in that type of engine.

While polyalkylene succinimide compounds have been used in marine engines as dispersants, we have discovered that from 0.5% to 2.5% of a polyalkylene succinimide compound is useful as an additive for improving the anti-wear performance. The internal surfaces of the engine contacting with a lubricating oil compositiorrunmprising a major amount of a base oil of lubricating viscosity; and from 0.5% to 2.5% of a polyalkylene succinimide.

The lubricating oil composition can further comprise up to 6% of a highly overbased detergent. That highly overbased detergent can be an alkyl or alkenyl phenate, an alkyl or alkenyl phenate-carboxylate, an alkyl or alkenyl aromatic sulfonate, or a mixture thereof. Preferably, the highly overbased detergent is an alkyl aromatic sulfonate.

DETAILED DESCRIPTION OF THE INVENTION In its broadest aspect, the present invention involves a method of reducing the wear of a low- speed marine diesel engine.

Prior to discussing the invention in further detail, the following terms will be defined: DEFINITIONS As used herein, the following terms have the following meanings, unless expressly stated to the contrary: The term "Base Number" or BN" refers to the amount of base equivalent to milligrams of KOH in one gram of sample. Thus, higher BN numbers reflect more alkaline products, and therefore a greater alkalinity reserve. The BN of a sample can be determined by ASTM Test No. D2896 or any other equivalent procedure.

The term "overbased detergent" refers to a composition comprising a diluent (e.g., lubricating oil) and a detergent complex wherein additional alkalinity is provided by a stoichiometric excess of a metal base, based on the amount required to react with the acidic moiety of the detergent. Enough diluent should be incorporated in the overbased detergent to ensure easy handling at safe operating temperatures.

The term "highly overbased detergent" refers to an overbased detergent having a BN of from 225 to 350, or more.

The term "succinimide" is understood in the art to include many of the amide, imide, etc. species that are also formed by the reaction of a succinic anhydride with an amine. The predominant product, howevei,is succinimide and this term has been generally accepted as meaning the product of a reaction of an alkenyl- or alkyl-substituted succinic acid or anhydride with a polyamine. Alkenyl or alkyl succinimides are disclosed in numerous references and are well known in the art.

The term "PIBSA" means polyisobutenyl succinic anhydride.

The term "alkenyl or alkylsuccinic acid derivative" refers to a structure having the formula

wherein L and M are independently selected from the group consisting of -OH, -Cl, -0-, lower alkyl or taken together are -0- to form an alkenyl or alkylsuccinic anhydride group.

The term "unsaturated acidic reagent" refers to maleic or fumaric reactants of the general formula:

wherein X and X' are the same or different, provided that at least one of X and X' is a group that is capable of reacting to esterify alcohols, form am ides, or amine salts with ammonia or amines, form metal salts with reactive metals or basically reacting metal compounds and otherwise function as acylating agents. Typically, X and/or X' is -OH, --OO-hydrocarbyi, "--OM+ where M+ represents one equivalent of a metal, ammonium or amine cation, --NH2, ----Cl, -Br, and taken together X and X' can be -0-so as to form an anhydfide. Preferably, X and X' are such that both carboxylic functions can enter into acylation reactions. Maleic anhydride is a preferred unsaturated acidic reactant. Other suitable unsaturated acidic reactants include electron-deficient olefins such as monophenyl maleic anhydride; monomethyl, diethyl, monochloro, monobromo, monofluoro, dichloro and difluoro maleic anhydride, N-phenyl maleimide and other substituted maleimides; isomaleimides; fumaric acid, maleic acid, alkyl hydrogen maleates and fumarates, dialkyl fumarates and maleates, fumaronilic acids and maleanic acids; and maleonitrile, and fumaronitrile.

Unless otherwise specified, all percentages are in weight percent and all molecular weights are number average molecular weights (Mn).

BASE OIL OF LUBRICATING VISCOSITY As regards the base oil of lubricating viscosity, this may be any oil suitable for the lubrication of a low-speed diesel engine, particularly a marine diesel engine. The base oil may suitable be an animal, a vegetable or a mineral oil. Suitably the base oil is a petroleum-derived lubricating oil, such as a naphthenic base, paraffin base, or mixed base oil. Alternatively, the base oil may be a synthetic lubricating oil.

Suitable synthetic lubricating oils include synthetic ester lubricating oils, which oils include diesters such as di-octyl adipate, di-octyl sebacate and tri-decyl adipate, or polymeric hydrocarbon lubricating oils, for example liquid polyisobutene and poly alpha olefins. Commonly, a mineral oil is employed. The base oil may be suitable for the lubrication of a low-speed marine diesel engine without adjustment of its viscosity. If viscosity adjustment is required it may be achieved by the addition of, for example, bright stock. The base oil will generally comprise greater than 70%, typically greater than 80% of the composition.

POLYALKYLENE SUCCINIMIDE From 0.5% to 2.5% of a polyalkylene succinimide compound is used as an additive for improving the anti-wear performance of a lubricating oil composition suitable for use in low speed diesel engines The polyalkylene succinimides can be prepared by conventional processes, such rs disclosed in U.S. Patent No. 2,992,708; 3,018,250; 3,018,1; 3,024,237; 3,100,673; 3,172,892; 3,219,666; 3,272,746; 3,361,673; 3,381,022; 3,912,764; 4,234,435; 4,612,132; 4,747,965; 5,112,507; 5,241,003; 5,266,186; 5,286,799; 5,319,030; 5,334,321; 5,356,552; 5,716,912. Preferably, the polyalkylene succinimide is derived from polybutenes having a number average molecular weight of at least 1800, more preferably from 2000 to 2400.

Preferably, it is prepared by reacting, under reactive conditions, a mixture of a polybutene succinic acid derivative, an unsaturated acidic reagent copolymer of an unsaturated acidic reagent and an olefin, and a polyamine, such as taught in U.S.

Patent No. 5,716,912.

The polyalkylene succinimide can be prepared by contacting the desired alkyl or alkenyl succinic acid derivative with an unsaturated acidic reagent copolymer and polyamine under reactive conditions:

wherein R is a polyalkyl or polyalkylene having a molecular weight of at least 1000; R1 is hydrogen, alkyl having from 6 to 40 carbon atoms, cycloalkyl, aryl, alkylaryl, vinyl, alkoxy, or alkylcarboxy; Z is a polyalkylene polyamine linking radical; n is a whole integer of from 1 to 3; Int. is an initiating radical; and Ter. is a terminating group.

L and M are independently selected from the group consisting of -OH, -Cl, -O-, lower alkyl, or taken together are -0- to form an alkenyl or alkylsuccinic anhydride group.

Typically the above process is conducted by contacting from 1.5 to 10 equivalents of alkenyl or alkylsuccinic acid derivative (Aer mole of unsaturated acidic reagent copolymer (B) and from 0.4 to 1.0 equivalents of amine (C) per equivalent of alkenyl or alkylsuccinic acid derivative (A) plus unsaturated acidic reagent copolymer (B). In one preferred embodiment, there are from 0.4 to 0.6 equivalents of amine (C) per equivalent of alkenyl or alkylsuccinic acid derivative (A) plus unsaturated acidic reagent copolymer (B) to produce a bissuccinimide. In conducting this reaction, it is convenient to first add the alkenyl or alkylsuccinic acid derivative and the unsaturated acidic reagent copolymer together and then add the polyamine. It may be desirable to conduct the reaction in an inert organic solvent.

Optimum solvents will vary with the particular copolymer and can be determined from literature sources or routine experimentation. For example, in the case of maleic anhydride poly a-olefin copolymers,100N diluent oil, and mixtures of Og aromatic solvents are acceptable solvents.

When less than 1.5 equivalents of alkenyl or alkylsuccinic acid derivative (A) per mole of unsaturated acidic reagent copolymer (B) are used then the polymer sometimes contains gels, which is undesirable.

Typically, the reaction is conducted at temperatures in the range of about from 140 to 1800C, preferably 1500 to 17000 for about from one to ten hours, preferably four to six hours. Typically the reaction is conducted at about atmospheric pressure; however, higher or lower pressures can also be used depending on the reaction temperature desired and the boiling point of the reactants or solvent.

Water, present in the system or generated by the reaction of the amine with the succinic or maleic anhydride moieties of (A) and (B) alkyl succinimide, is preferably removed from the reaction system during the course of the reaction via azeotroping or distillation. After reaction completion, the system can be stripped at elevated temperatures (typically 100"C to 2500C) and reduced pressures to remove any volatile components which may be present in the product.

THE ALKENYL OR ALKYLSUCCINIC ACID DERIVATIVES - REACTANT (A) Alkyl and alkenylsuccinic acid derivatives having a calculated succinic ratio of about from 1:1 to 2.5:1, and preferably about from 1:1 to 1.5:1, may be used in the present process. More preferably, the alkyl or alkenyl succinic acid derivatives have a succination ratio of about from 1:1 to 1.2:1. Most preferably, alkyl or alkenylsuccinic anhydrides are used. Accordingly preferably alkenyl succinic anhydride is usedprepared by the thermal process, both because the calculate succination ratio of material prepared by this process is typically 1.0 to 1.2, and because the produce is essentially chlorine-free because chlorine is not used in the synthesis.

The thermal reaction of a polyolefin with maleic an hydroxide is well known and is described, for example, in U.S. Patent No. 3,361,673. The less desirable is the chlorination process characterized by the reaction of a chlorinated polyolefin, with maleic anhydride, which is also well known and is described, for example, in U.S.

Patent No. 3,172,189. Various modifications of the thermal process and chlorination process are also well known, some of which are described in U.S.

Patent Nos. 4,388,471; 4,450,281; 3,018,250 and 3,024,195. Free radical procedures for preparing alkenyl succinic anhydrides are, for example, described in U.S. Patent Nos. 5,286,799 and 5,319,030.

In accordance with the invention, the alkenyl or alkyl succinic anhydride reactant is derived from a polyolefin having a Mn from 1000 to 5000 and a Mw/Mn ratio of 1:1 to 5:1. In a preferred embodiment, the alkenyl or alkyl group of the succinimide has a Mn value from 1800 to 3000. Most preferred are alkenyl or alkyl substituents having a Mn of from 2000 to 2400.

Suitable polyolefin polymers for reaction with maleic anhydride include polymers comprising a major amount of C2 to Cs monoolefin, e.g., ethylene, propylene, butylene, iso-butylene, and pentene. The polymers can be homopolymers, such as polyisobutylene, as well as copolymers of two or more such olefins, such as copolymers of ethylene and propylene, butylene, and isobutylene, etc. Other copolymers include those in which a minor amount of the copolymer monomers (e.g., 1 to 20 mole percent), is a C4 to C8 nonconjugated diolefin, e.g., a copolymer of isobutylene and butadiene or a copolymer of ethylene, propylene and 1,4hexadiene, etc.

A particularly preferred class of olefin polymers for reaction with maleic an hydroxide comprises the polybutenes, which are prepared by polymerization of one or more of 1 -butene, 2-butene and isobutene. Preferably, the polybutenes have a number average molecular weight of from 2000 to 2400. Especially desirable are polybutenes containing a substantial proportion of units derived from isobutene.

The polybutene may contain minor amounts of butadiene, which may or may not be incorporated in the polymer. These polybutenes are readily available commercial materials well known to those skilled in the art. Exarf les of procedures illustrating the preparation of such material can be found, for example, in U.S. Patents Nos. 3,215,707; 3,231,587; 3,515,669; 3,579,450; 3,912,764 and 4,605,808.

The alkenyl or alkylsuccinic anhydride may also be prepared using the so-called highly reactive or high methyl vinylidene polyalkylene, most commonly polyisobutene, such as described in U.S. Patent Nos. 4,152,499; 5,071,919; 5,137,980; 5,286,823; 5,254,649; published International Applications Numbers WO 93 24539-A1; WO 9310063-A1; and published European Patent Applications Numbers 0355895-A; 0565285A; and 0587381A. Other polyalkenes can also be used including, for example, polyalkenes prepared using metallocene catalysts such as for example described in published German patent application DE 4313088A1.

THE UNSATURATED ACIDIC REAGENT COPOLYMER - REACTANT (B) The unsaturated acidic reagent copolymers used in the present invention can be random copolymers or altemating copolymers, and can be prepared by known procedures. Further, in most instances, examples of each class are readily commercially available. Such copolymers may be prepared by the free radical reaction of an unsaturated acidic reagent with the corresponding monomer of the other unit of the copolymer. Thus, in the present case, the monomer will correspond to R in formula (I) plus a vinyl group, i.e., R1-CH=CH2. Hence, where R1 is phenyl the monomer will be styrene. Accordingly, the unsaturated acidic reagent copolymer can be prepared by the free radical reaction of an unsaturated acidic reagent, preferably maleic anhydride, with the corresponding C8 to C48 1olefin, C8 to C28 polyalkylene, ethylene, styrene, 1,3-butadiene, C3+ vinyl alkyl ether, or C4+ vinyl alkanoate.

Preferably, alpha olefins from C12 to C28 are used because these materials are commercially readily available, and because they offer a desirable balance of the length of the molecular weight tail, and the solubility of the copolymer in non-polar solvents. Mixtures of olefins, e.g. C14, C16. and C,8 are especially desirable.

The degree of polymerization of the copolymers can vary over a wide range. In general copolymers of high molecular weight can be produced at low temperatures and copolymers of low molecular weight can be produced at high temperatures.

Preferably, lovv molecular weight copolymers, i.e., low molecular weight (20004800 for example) are used because higher molecular weight copolymers (greater than 10,000 for example) can sometimes produce polymers that contain gels.

The copolymerizalion is conducted in the presence of a suitable free radical initiator; typically a peroxide type initiator, e.g. di(t-butyl) peroxide dicumyl peroxide or azo type initiator, e.g., isobutylnitrile type initiators. Procedures for preparing poly a-olefin copolymers are, for example1 described in U.S. Patent Nos. 3,560,455 and 4,240,916. Both patents also describe a variety of initiators.

Some examples of maleic anhydride 1-olefin copolymers are: Poly(styreneomaleic anhydride) resins: These materials are known as SMA resins. There are two molecular weight versions. The low molecular weight resin is called SMA resin and is available from ARCO Chemical with styrene to maleic anhydride ratios of 1:1, 2:1, and 3:1. The high molecular weight resin is produced by Monsanto (Lytron, ARCO (Dylark9, or American Cyanamide (Cypress9.

Other names for SMA copolymers are Styrolmol, Maron MS, and Provimal ST resins. In some cases partially esterified resins are also available.

Poly(ethylene-co-maleic anhydride) resins: These materials are manufactured by Monsanto under the trade name EMAe. They are also called Malethamer and Vinac resins.

Poly(alpha olefin-co-maleic anhydride) resins are available from Chevron Chemical as PA-18 (octadecene-1-co-maleic anhydride), or can be prepared as in Preparation 1. Alternately mixtures of alpha olefins can be used. These materials have been described in U. S. Pat. Nos. 3,461,108; 3,560,455; 3,560,456; 3,560,457; 3,580,893; 3,706,704; 3,729,450; and 3,729,451. Partially esterified olefin co maleic anhydride resins can also be used. Some examples of these types of resins are called Ketjeniubee resins available from AKZO Co.

Poly(isobutene-co-maleic anhydride) resins are available'under the name ISOBAMe from Curaray Co. Ltd. They are also available from Humphrey chemical Co. under the code K-66.

Poly(butadiene-so-maleic anhydride) resins are available under the name Maldenee from Borg-Warner Corp.

Poly(methylvinylether-co-maleic anhydride) resins are available under the name Gantrey An from GAF Corporation. Other names are called Visco Frey.

Poly(vinylacetate-co-maleic anhydride) resins are available under the names Lytron 897, 898, and 899 from Monsanto. They are also available under the name Pouimalya resins in Europe.

Excellent results can be obtained using a copolymer prepared by the free radical polymerization of maleic anhydride and C12 to C18 1 -olefins or olefin mixtures thereof.

THE POLYAMINE - REACTANT (C) The polyamine reactant should have at least three amine nitrogen atoms per mole, and preferably 4 to 12 amine nitrogens per molecule. Most preferred are polyamines having from about 6 to about 10 nitrogen atoms per molecule. The number of amine nitrogen atoms per molecule of polyamine is calculated as follows: Average number of nitrogen atoms in = %NxM, molecule of polyamine 14 x 100 wherein % N = percent nitrogen in polyamine or polyamine mixture Mpa = number average molecular weight of the polyamine or polyamine mixture Preferred polyalkylene polyamines also contain from about 4 to about 20 carbon atoms, there being preferably from two to three carbon atoms per alkylene unit.

The polyamine preferably has a carbon-to-nitrogen ratio of from 1:1 to 10:1.

Examples of suitable polyamines that can be used to form the compounds in this invention include the following: tetraethylene pentamine, pentaethylene hexamine, Dow E-1 00 heavy polyamine (Mn = 303, available from Dow Chemical Company, Midland, Ml.), and Union Carbide HPA-X heavy polyamine (Mn = 275, available from Union Carbide Corporation, Danbury, CT.). Such amines encompass isomers, such as branched-chain polyamines, and the previously mentioned substituted polyamines, including hydrocarbyl-substituted polyamines. HPA-X heavy polyamine ("HPA-X") contains an average of approximately 6.5 amine nitrogen atoms per molecule. Such heavy polyamines generally afford excellent results.

The polyamine reactant may be a single compound but typically will be a mixture of compounds reflecting commercial polyamines. Typically the commercial polyamine will be a mixture in which one or several compounds predominate with the average composition indicated. For example, tetraethylene pentamine prepared by the polymerization of aziridine or the reaction of dichloroethylene and ammonia will have both lower and higher amine members, e.g., triethylene tetramine ("TETA"), substituted piperazines and pentaethylene hexamine, but the composition will be largely tetraethylene pentamine and the empirical formula of the total amine composition will closely approximate that of tetraethylene pentamine.

Other examples of suitable polyamines include admixtures of amines of various sizes, provided that the overall mixture contains at least 4 nitrogen atoms per molecule. Included within these suitable polyamines are mixtures of diethylene triamine ("DETA") and heavy polyamine. A preferred polyamine admixture reactant is a mixture containing 20% by weight DETA and 80% by weight HPA-X; as determined by the method described above, this preferred polyamine reactant contains an average of about 5.2 nitrogen atoms per mole.

Methods of preparation of polyamines and their reactions are detailed in Sidgewick's THE ORGANIC CHEMISTRY OF NITROGEN, Clarendon Press, Oxford, 1966; Noller's CHEMISTRY OF ORGANIC COMPOUNDS, Saunders, Philadelphia, 2nd Ed., 1957; and Kirk-Othmer's ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, 2nd Ed., especially Volumes 2, pp. 99-116.

POST-TREATMENTS The dispersancy of the present polymers is generally further improved by reaction with a cyclic carbonate. The resulting modified polymer has one or more nitrogens of the polyanrii-io moiety subsfflutedwith a hydroxy hydrocarbyl oxycarbonyl, a hydroxy poly(oxyalkylene) oxycarbonyl, a hydroxyalkylene, hydroxyalkylenepoly (oxyalkylene), or mixture thereof.

The cyclic carbonate post-treatment is conducted under conditions sufficient to cause reaction of the cyclic carbonate with secondary amino group of the polyamino substituents. Typically, the reaction is conducted at temperatures of about from 0 to 250"C preferably about from 100" to 200"C. Generally, best results are obtained at temperatures of about from 150C to 1800C.

The reaction may be conducted neat, wherein both the polymer and the cyclic carbonate are combined in the proper ratio, either alone or in the presence of a catalyst (such as an acidic, basic or Lewis acid catalyst). Depending on the viscosity of the polymer reactant, it may be desirable to conduct the reaction using an inert organic solvent or diluent, for example, toluene or xylene. Examples of suitable catalysts include, for example, phosphoric acid, boron trifluoride, alkyl or aryl sulfonic acid, alkali or alkaline carbonate. Generally, the same solvents or diluents as described above with respect to the preparation for the co-polymer (A) or polymer (I) can also be used in the cyclic carbonate post-treatment.

The reaction of polyamino alkenyl or alkyl succinimides with cyclic carbonates is known in the art and is described in U.S. Patent No. 4,612,132. Generally, the procedures described to post-treat polyamino alkenyl or alkyl succinimides with cyclic carbonates can also be applied to post-treat the present polymers.

A particularly preferred cyclic carbonate is 1,3-dioxolan-2-one (ethylene carbonate) because it affords excellent results and also because it is readily commercially available.

The molar charge of cyclic carbonate employed in the post-treatment reaction is preferably based upon the theoretical number of basic nitrogens contained in the polyamino substituent of the succinimide. Thus, when one equivalent of tetraethylene pentamine ("TEPA") is reacted with one equivalent of succinic anhydride and one equivalent of copolymer, the resulting bissuccinimide will theoretically contain three basic nitrogens. Accordingly, a molar charge of two would require that two moles of cyclic carbonate be added for each basic nitrogen or in this case six moles of cyclic carbonate for each mole equivalent of polyalkylene succinimide or succinimide prepared from TEPA. Mole ratios of the cyclic carbonate to the basic amine nitrogen of the polyamino alkenyl succinimide employed in the process in this invention are typicy in the range of from about 1:1 to about 4:1; although preferably from about 2:1 to about 3:1.

As described in U.S. Patent No. 4,612,132, cyclic carbonates may react with the primary and secondary amines of a polyamino alkenyl or alkyl succinimide to form two types of compounds. In the first instance, strong bases, including unhindered amines such as primary amines and some secondary amines, react with an equivalent of cyclic carbonate to produce a carbamic ester. In the second instance, hindered bases, such as hindered secondary amines, may react with an equivalent of the same cyclic carbonate to form a hydroxyalkyleneamine linkage. (Unlike the carbamate products, the hydroxyalkyleneamine products retain their basicity.) Accordingly, the reaction of a cyclic carbonate may yield a mixture of products.

When the molar charge of the cyclic carbonate to the basic nitrogen of the succinimide is about 1 or less, a large portion of the primary and secondary amines of the succinimide will be converted to hydroxy hydrocarbyl carbamic esters with some hydroxyhydrocarbylamine derivatives also being formed. As the mole ratio is raised above 1, increased amounts of poly(oxyalkylene) polymers of the carbamic esters and the hydroxyhydrocarbylamine derivatives are produced.

Both the polymers and post-treated polymers in this invention can also be reacted with boric acid or a similar boron compound to form borated dispersants having utility within the scope in this invention. In addition to boric acid (boron acid), examples of suitable boron compounds include boron oxides, boron halides and esters of boric acid. Generally from about 0.1 equivalents to 10 equivalents of boron compound to the modified succinimide may be employed.

In addition to the carbonate and boric acids post-treatments both the compounds may be post-treated, or further post-treatment, with a variety of post-treatments designed to improve or impart different properties. Such post-treatments include those summarized in columns 27-29 of U.S. Patent No. 5,241,003. Such treatments include, treatment with: Inorganic phosphorous acids or anhydrates (e.g., U.S. Patent Nos.

3,403,102 and 4,648,980); Organic phosphorous compounds (e.g., U.S. Patent No. 3,502,677); Phosphorous pentasulfides; Boron compounds as already noted above (e.g., U.S. Patents Nos.

3,178,663 and 4,652,387); Carboxylic acid, polycarboxylic acids, anhydrides and/or acid halides (e.g., U.S. Patent Nos. 3,708,52aJand 4,948,386); Epoxides polyepoxiates or thioexpoxides (e.g., U.S. Patent Nos. 3,859,318 and 5,026,495); Aldehyde or ketone (e.g., U.S. Patent No. 3,458,530); Carbon disulfide (e.g., U.S. Patent No. 3,256,185); Glycidol (e.g., U.S. Patent No. 4,617,137); Urea, thourea or guanidine (e.g., U.S. Patent Nos. 3,312,619; 3,865,813; and British Patent GB 1,065,595); Organic sulfonic acid (e.g., U.S. Patent No. 3,189,544 and British Patent GB 2,140,811); Alkenyl cyanide (e.g., U.S. Patent Nos. 3,278,550 and 3,366,569); Diketene (e.g., U.S. Patent No. 3,546,243); A diisocyanate (e.g., U.S. Patent No. 3,573,205); Alkane sultone (e.g., U.S. Patent No. 3,749,695); 1,3-Dicarbonyl I ,3-Dicarbonyl Compound (e.g., U.S. Patent No. 4,579,675); Sulfate of alkoxylated alcohol or phenol (e.g., U.S. Patent No. 3,954,639); o Cyclic lactone (e.g., U.S. Patent Nos. 4,617,138; 4,645,515; 4,668,246; 4,963,275; and 4,971,711); Cyclic carbonate or thiocarbonate linear monocarbonate or polycarbonate, or chloroformate (e.g., U.S. Patent Nos. 4,612,132; 4,647,390; 4,648,886; 4,670,170); Nitrogen-containing carboxylic acid (e.g., U.S. Patent 4,971,598 and British Patent GB 2,140,811); Hydroxy-protected chlorodicarbonyloxy compound (e.g., U.S. Patent No.

4,614,522); Lactam, thiolactam, thiolactone or ditholactone (e.g., U.S. Patent Nos.

4,614,603 and 4,666,460); Cyclic carbonate or thiocarbonate, linear monocarbonate or plycarbonate, or chloroformate (e.g., U.S. Patent Nos. 4,612,132; 4,647,390; 4,646,860; and 4,670,170); Nitrogen-containing carboxylic acid (e.g., U.S. Patent No. 4,971,598 and British Patent GB 2,440,811); Hydroxy-protected chlorodicarbonyloxy compound (e.g., U.S. Patent No.

4,614,522); Lactam, thiolactam, thiolactone or dithiolactone (e.g., U.S. Patent Nos.

4,614,603, and 4,666,460); Cyclic carbamate, cyclic thiocarbamate or cyclic dithiocarbamate (e.g., U.S.

Patent Nos. 4,663,062 and 4,666,459); tdydroxyaliphatic carboxylic acid (e.g., U.S. Patent Nos. 4,482;464; 4,521,318; 4,713,189); Oxidizing agent (e.g., U.S. Patent No. 4,379,064); Combination of phosphorous pentasulfide and a polyalkylene polyamine (e.g., U.S. Patent No. 3,185,647); Combination of carboxylic acid or an aldehyde or ketone and sulfur or sulfur chloride (e.g., U.S. Patent Nos. 3,390,086; 3,470,098); Combination of a hydrazine and carbon disulfide (e.g. U.S. Patent No.

3,519,564); Combination of an aldehyde and a phenol (e.g., U.S. Patent Nos.

3,649,229; 5,030,249; 5,039,307); Combination of an aldehyde and an O-diester of dithiophosphoric acid (e.g., U.S. Patent No. 3,865,740); Combination of a hydroxyaliphatic carboxylic acid and a boric acid (e.g., U.S. Patent No. 4,554,086); Combination of a hydroxyaliphatic carboxylic acid, then formaldehyde and a phenol (e.g., U.S. Patent No. 4,636,322); Combination of a hydroxyaliphatic carboxylic acid and then an aliphatic dicarboxylic acid (e.g., U.S. Patent No. 4,663,064); Combination of formaldehyde and a phenol and then glycolic acid (e.g., U.S.

Patent No. 4,699,724); Combination of a hydroxyaliphatic carboxylic acid or oxalic acid and then a diisocyanate (e.g. U.S. Patent No. 4,713,191); Combination of inorganic acid or anhydride of phosphorus or a partial or total sulfur analog thereof and a boron compound (e.g., U.S. Patent No.

4,857,214); Combination of an organic diacid then an unsaturated fatty acid and then a nitrosoaromatic amine optionally followed by a boron compound and then a glycolating agent (e.g., U.S. Patent No. 4,973,412); Combination of an aldehyde and a triazole (e.g., U.S. Patent No.

4,963,278); Combination of an aldehyde and a triazole then a boron compound (e.g., U.S. Patent No.4,981,492); Combination of cyclic lactone and a boron compound (e.g., U.S. Patent No.

4,963,275 and 4,971,711).

HIGHLY OVERBASED DETERGENT.

The polyalkylene succinimide is used in combinatiwrwith up to 6% of a highly overbased detergent. That detergent can be a phenate, a phenate-stearate, a sulfonate, or a mixture thereof.

In one embodiment, the lubricating oil composition contains a highly overbased alkyl or alkenyl phenate (sulfurized or unsulfurized). Preferably, the highly overbased hydrocarbyl phenate is a sulfurized alkylphenate.

The preparation of overbased phenates, in general, is described, for example, in U.S. Patent Nos. 2,680,096; 3,178,368; 3,367,867; 3,801,507; and the like.

Typically, overbased phenates have been prepared by combining, under elevated temperatures, an alkylphenol, a neutral or overbased hydrocarbyl or hydrocarbaryl sulfonate, a high molecular weight alcohol, lubricating oil, a Group II metal oxide, hydroxide or C1 to Ce alkoxide, sulfur, and a polyol promoter, typically an alkylene glycol, to the heated mixture. The water of reaction is removed and carbon dioxide added. Uncombined carbon dioxide is removed and the reaction vessel is then further heated under vacuum to remove the alkylene glycol, water, and the high molecular weight alcohol. The product is overbased by incorporation therein of hydrated lime and carbon dioxide. Typically an alkylene glycol is used to promote both the neutralization and sulfurization, and also to facilitate overbasing.

U.S. Patent No. 5,677,270 discloses that sulfurized alkylphenates can be advantageously prepared without the use 6f a polyol or alkanol sulfurization promoter by conducting the sulfurization neutralization in the presence of a lower molecular weight alkanoic acid, i.e., formic acid, acetic acid, or propionic acid, or a mixture of lower alkanoic acids.

The alkyl or alkenyl phenate can be treated with long-chain carboxylic acid (such as stearic acid), anhydride or salt thereof to produce an alkyl or alkenyl phenatecarboxylate. This treatment been disclosed in U.S. Patents 5,069,804; 5,162,085; 5,716,914; 5,714,443; and 5,728,657 In another embodiment, the lubricating oil composition contains a highly overbased alkyl or alkenyl aromatic sulfonate. Preferably, the overbased alkyl or alkenyl aromatic sulfonate is an alkyl or alkenyl benzene sulfonate or an alkyl or alkenyl toluene sulfonate.

The preparation of overbased aromatic sulfonates is well known in the art and is described, for example, in U.S. Patent No. 4,797,217. That patent teaches a process for making overbased lithium sulfonates (BN of at least 250) using lithium hydroxide monohydrate.

OTHER ADDITIVE COMPONENTS The following additive components are examples of some components that can be favorably employed in combination with the polyalkylene succinimide in the compositions of the present invention. These examples of additives are provided to illustrate the present invention, but they are not intended to limit it: 1. Other metal detergents: sulfurized or unsulfurized metal salts of multi hydroxy alkyl or alkenyl aromatic compounds, alkyl or alkenyl hydroxy aromatic sulfonates, sulfurized or unsulfurized alkyl or alkenyl salicylates, sulfurized or unsulfurized alkyl or alkenyl naphthenates, metal salts of alkanoic acids, metal salts of an alkyl or alkenyl multiacid, and chemical and physical mixtures thereof.

2. Oxidation inhibitors (a) Phenol type oxidation inhibitors: 4,4'-methylene bis (2,6-di-tert butylphenol), 4, 4'-bis(2, 6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert butylphenol), 2,2'-methylene bis(4-methyl-6-tert-butyl-phenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropyl idenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl- 6-nonylphenol), 2,2'-isobutylidene-bis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2 6-di-tert-butyl- 4-methyl-phenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butyl phenol, 2,6-di-tert-4-(N.N' dimethylaminomethylphenol), 4,4'-thiobis(2 methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)-sulfide, and bis (3,5-di-tert butyl-4-hydroxybenzyl).

(b) Diphenylamine type oxidation inhibitor: alkylated diphenylamine, phenyl a-naphthylamine, and alkylated-a-naphthylamine.

(c) Other types: metal dithiocarbamate (e.g., zinc dithiocarbamate), and methylenebis (dibutyl-dithiocarbamate).

3. Rust inhibitors (Anti-rust agents) (a) Nonionic polyoxyethylene surface active agents: polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and polyethylene glycol monooleate.

(b) Other compounds: stearic acid and other fatty acids, dicarboxylic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and phosphoric ester.

4. Demulsifiers: addition product of alkylphenol and ethyleneoxide, poloxyethylene alkyl ether, and polyoxyethylene sorbitan ester.

5. Extreme pressure agents (EP agents): zinc dialkyldithiophosphate (primary alkyl type & secondary alkyl type), sulfurized oils, diphenyl sulfide, methyl trichlorostearate, chlorinated naphthalene, fluoroalkylpolysiloxane, and lead naphthenate.

6. Friction modifiers: fatty alcohol, fatty acid, amine, borated ester, and other esters.

7. Multifunctional additives: sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum organo phosphoro dithioate, oxymolybdenum monoglyceride, amine-molybdenum complex compound, and sulfur containing molybdenum complex compound.

8. Pour point depressants: polymethyl methacrylate.

9. Foam Inhibitors: alkyl methacrylate polymers and dimethyl silicone polymers.

MARINE LUBRICATING OIL COMPOSITION The present invention comprises a lubricating oil composition suitable for use in low-speed diesel engines operating on heavy fuel containing a high sulfur level.

That lubricating ail composition comprises: (a) a major amount of a base oil of lubricating viscosity; (b) from 0.5% to 2.5% of the polyalkylene succinimide described above, and (c) up to 6% of the highly overbased detergents described above.

That lubricating oil composition can also comprise other additives described above.

The wear of a low-speed diesel engines operating on heavy fuel containing a high sulfur level can be reduced by contacting the surfaces of those engines with the above lubricating oil composition.

In a further embodiment, an engine lubricating oil composition is produced by blending a mixture of the above components. The lubricating oil composition produced by that method might have a slightly different composition than the initial mixture, because the components may interact. The components can be blended in any order and can be blended as combinations of components.

ADDITIVE CONCENTRATES Additive concentrates are also included within the scope in this invention. The concentrates in this invention comprise the polyalkylene succinimide, preferably with at least one other additive, as disclosed above. The concentrates contain sufficient organic diluent to make them easy to handle during shipping and storage.

From 20% to 80% of the concentrate is organic diluent. Suitable organic diluents that can be used include mineral oil or synthetic oils, as described above in the section entitled "Base Oil of Lubricating Viscosity." EXAMPLES OF ADDITIVE PACKAGES Below are representative examples of additive packages that can be used in a variety of applications. These representative examples employ the polyalkylene succinimide and the highly overbased detergents of the present invention. Those compounds may be used either with or without other metal-containing detergents, depending upon the desired BN of the final product. The following percentages are based on the amount of active component, with neither process oil nor diluent oil.

These examples are provided to illustrate the present invention, but they are not intended to limit it.

1) Highly overbased detergent 60% Polyalkylene succinimide 5% Primary alkyl zinc dithiophosphate 5% Diluent oil 30% 2) Highly overbased detergent 60% Polyalkylene succinimide 5% Phenol type oxidation inhibitor 10% Diluent oil 25% 3) Highly overbased detergent 50% Polyalkylene succinimide 5% Alkylated diphenylamine-type oxidation inhibitor 15% Diluent oil 30% 4) Highly overbased detergent 50% Polyalkylene succinimide 5% Phenol-type oxidation inhibitor 5% Alkylated diphenylamine-type oxidation inhibitor 5% Diluent oil 25% EXAMPLES The invention will be further illustrated by following examples, which set forth particularly advantageous method embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

The antiwear effect of polyalkylene succinimides on engine oils containing overbased metal detergents was determined for five different formulations. In each formulation, tne same base oil of lubricating viscosity was used petroleum-derived SAE 50 lubricating oil Group I solvent refined 500 and 600 neutral and 150 bright stock base oils) and the same polyalkylene succinimide was used (Polyalkylene succinimide prepared by the reaction between PIBSA and a combination of Heavy Polyamine and DETA). In each formulation, the Falex Pin Wear was measured.

In the first formulation, 16.99% of a highly overbased alky! aromatic sulfonate was used. Without the addition of polyalkylene succinimide, the Falex Pin Wear was 49 mg. With the addition of 2.30% polyalkylene succinimide, the Falex Pin Wear was reduced to 5 mg.

In the second formulation, 18.00% of a 80/20 BN ratio of highly overbased alkylphenate-stearate and highly overbased alkyl aromatic sulfonate was used.

Without the addition of polyalkylene succinimide, the Falex Pin Wear was 100mg.

With the addition of 0.77% polyalkylene succinimide, the Falex Pin Wear was reduced to 46 mg. With the addition of 1.53% polyalkylene succinimide, the Falex Pin Wear was reduced to 30 mg. With the addition of 2.30% polyalkylene succinimide, the Falex Pin Wear was reduced to 30 mg.

In the third formulation, 27.6% of a highly overbased alkylphenate was used.

Without the addition of polyalkylene succinimide, the Falex Pin Wear was 79 mg.

With the addition of 2.00% polyalkylene succinimide, the Falex Pin Wear was reduced to 14 mg.

In the fourth formulation, 17.1% of a highly overbased alkyl aromatic sulfonate was from a different production batch. Without the addition of polyalkylene succinimide, the Falex Pin Wear was 69 mg. With the addition of 2.00% polyalkylene succinimide, the Falex Pin Wear was reduced to 39 mg.

In the fifth formulation, 22.3% of a 50/50 BN ratio of highly overbased alkylphenate and highly overbased alkyl aromatic sulfonate was used. Without the addition of polyalkylene succinimide, the Falex Pin Wear was 79 mg. With the addition of 2.00% polyalkylene succinimide, the Falex Pin Wear was reduced to 6 mg.

Thus, the use of a polyalkylene succinimide compound as an additive significantly increases the anti-wear performance of a lubricating oil compositiop.

While the present invention has been described with reference to specific embodiments, this application is intended to cover those various changes and substitutions that may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

Claims (4)

What is claimed is:

1. The use of from 0.5% to 2.5% of a polyalkylene succinimide compound as an additive for improving the anti-wear performance of a lubricating oil composition suitable for use in low- speed marine diesel engines.

2. A method of reducing the wear of a low- speed marine diesel engine, said method comprising contacting the internal surfaces of said engine with a lubricating oil composition comprising: (a) a major amount of a base oil of lubricating viscosity; and (b) from 0.5% to 2.5% of a polyalkylene succinimide.

3. A method of reducing the wear of a low- speed marine diesel engine according to Claim 2 wherein said lubricating oil composition further comprises: (c) up to 6% of a highly overbased detergent selected from the group consisting of: (1) alkyl or alkenyl phenate, (2) alkyl or alkenyl phenate-carboxylate (3) alkyl or alkenyl aromatic sulfonate, and (4) mixtures thereof.

4. A method of reducing the wear of a low- speed marine diesel engine according to Claim 3 wherein said highly overbased detergent is an alkyl aromatic sulfonate.