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Title:
POLYALKYLENE SUCCINIMIDE COMPOSITION USEFUL IN INTERNAL COMBUSTION ENGINES
Document Type and Number:
WIPO Patent Application WO/1999/016852
Kind Code:
A1
Abstract:
A lubricating oil composition for internal combustion engines is preferably composed of a major portion of a base oil; 0.5 % to 15 % of a cyclic carbonate-treated polyalkylene succinimide additive; 0.5 % to 15 % of a borated polyalkylene succinimide additive; 0.5 % to 20 % of a metal-containing detergent; and 0.1 % to 3 % of a zinc dialkyldithiophosphate, other additives such as a molybdenum compound, an oxidation inhibitor and a viscosity index improver can be added. The molecular weight of the polyalkylenes from which the carbonated polyalkylene succinimide is derived is preferably at least 300 greater than the molecular weight of the polyalkylenes from which the borated polyalkylene succinimide is derived.

Inventors:
Nakazato, Morikuni (2197-1, Ikesinden Hamaoka-cho Ogasa-gun Shizuoka, JP)
Hirano, Satoshi (105-1, Omaezaki Omaezaki-cho Haibara-gun Shizuoka, JP)
Willis Jr., William W. (3557 Ponderosa Trail Pinole, CA, 94564, US)
Freerks, Robert L. (110 Hale Court Martinez, CA, 94553, US)
Application Number:
PCT/US1998/020715
Publication Date:
April 08, 1999
Filing Date:
September 30, 1998
Export Citation:
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Assignee:
CHEVRON CHEMICAL COMPANY LLC (555 Market Street San Francisco, CA, 94105, US)
ORONITE JAPAN LIMITED (Landmark Plaza 7F 6-7, Shiba-koen 1-chome Minato-ku Tokyo 105, JP)
International Classes:
C08F8/00; C10M133/56; C10M141/10; C10M163/00; (IPC1-7): C10M141/12; C10M133/56
Foreign References:
EP0648830A21995-04-19
EP0776963A11997-06-04
Attorney, Agent or Firm:
Lee, Steven G. K. (Chevron Corporation Law Dept. P.O. Box 7141 San Francisco, CA, 94120-7141, US)
Nash, David Allan (Haseltine Lake & Co. Imperial House 15-19 Kingsway London WC2B 6UD, GB)
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Claims:
What is claimed is :
1. A lubricating oil composition for internal combustion engines which comprises : (a) a major amount of a base oil of lubricating viscosity ; (b) 0. 5% to 15% of a carbonatetreated polyalkylene succinimide additive prepared by treating a first polyalkylene succinimide with a cyclic carbonate or a linear monoor polycarbonate under reactive conditions ; (c) 0. 5% to 15% of a borated polyalkylene succinimide additive prepared by treating a second polyalkylene succinimide with a boron compound under reactive conditions ; (d) 0. 5% to 20% of a metalcontaining detergent ; and (e) 0. 1 % to 3% of a zinc dialkyldithiophosphate.
2. A lubricating oil composition according to Claim 1 wherein the number average molecular weight of the polyalkylenes from which the carbonate treated polyalkylene succinimide additive is derived is at least 300 greater than the number average molecular weight of the polyalkylenes from which the borontreated polyalkylene succinimide additive is derived.
3. A lubricating oil composition according to Claim 1 or 2 further comprising from 0. 02% to 5% of a molybdenum compound, wherein the molybdenum compound is present in an amount of 10 to 2, 500 ppm in terms of molybdenum element.
4. A lubricating oil composition according to Claim 1, 2, or 3 further comprising at least one of the following : (a) from 1 % to 20% of a viscosity index improver and (b) from 0. 1% to 5% of an oxidation inhibitor selected from the group consisting of phenol compounds and amine compounds.
5. A lubricating oil composition according to any of the above claims wherein the carbonatetreated polyalkylene succinimide additive is a reaction product of a high molecular weight alkenylor alkylsubstituted succinic anhydride and a polyalkylene polyamine having an average of 4 to 10 nitrogen atoms per mole and is posttreated with a cyclic carbonate.
6. A lubricating oil composition according to any of the above claims wherein the polyalkylene of the carbonatetreated polyalkylene succinimide additive is derived from a polybutene having a molecular weight of from 1, 000 to 2, 700, preferably from 1, 900 to 2, 700.
7. A lubricating oil composition according to any of the above claims wherein the polyalkylene of the borated polyalkylene succinimide additive is derived from a polybutene having a molecular weight of 1, 000 to 2, 700.
8. A lubricating oil composition according to any of the above claims wherein the carbonatetreated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are contained in a total amount of 10% to 15%, and wherein the carbonatetreated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are contained in a weight ratio of 2 : 8 to 8 : 2.
9. A polyalkylene succinimide composition comprising : (a) from 10% to 50% of borontreated polyalkylene succinimide prepared by treating a first polyalkylene succinimide with a boron compound under reactive conditions ; and (b) from 50% to 90% of carbonatetreated polyalkylene succinimide prepared by treating a second polyalkylene succinimide with a cyclic carbonate or a linear monoor polycarbonate under reactive conditions ; wherein the number average molecular weight of the polyalkylenes from which the carbonatetreated polyalkylene succinimide is derived is at least 300 greater than the number average molecular weight of the polyalkylenes from which the borontreated polyalkylene succinimide is derived.
10. A polyalkylene succinimide composition according to Claim 9 wherein the difference between the number average molecular weights of the polyalkylenes is from 800 to 1, 000.
11. A polyalkylene succinimide composition according to Claim 10 wherein the first polyalkylene succinimide is a polybutene succinimide derived from polybutenes having a number average molecular weight of from 1, 200 to 1, 400, and wherein the second polyalkylene succinimide is a polybutene succinimide derived from polybutenes having a number average molecular weight of from 2, 000 to 2, 400.
12. A polyalkylene succinimide composition according to Claim 9, 10, or 11 wherein the second polybutene succinimide is prepared by reacting a mixture under reactive conditions, wherein the mixture comprises : (a) a polybutene succinic acid derivative ; (b) an unsaturated acidic reagent copolymer of an unsaturated acidic reagent and an olefin ; and (c) a polyamine.
13. A method for improving the soot dispersancy of a lubricating oil in internal combustion engine applications, said method comprising lubricating said engine with a lubricating oil comprising an effective amount of the polyalkylene succinimide composition according to Claim 9, 10, 11, or 12.
14. A lubricating oil composition comprising a major amount of a base oil of lubricating viscosity and of the polyalkylene succinimide composition according to Claim 9, 10, 11, or 12.
15. A concentrate comprising from 1 % to 20% of a compatible organic liquid diluent and from 5% to 80% of the polyalkylene succinimide composition according to Claim 9, 10, 11, or 12.
Description:
POLYALKYLENE SUCCINIMIDE COMPOSITION USEFUL IN INTERNAL COMBUSTION ENGINES The present invention relates to novel compositions comprising mixtures of post-treated derivatives of polyalkylene succinimides. In a further aspect, the invention relates to methods of preparing these compositions and their uses as dispersants in lubricating oils. In another aspect, the invention relates to concentrates and lubricating oil compositions.

BACKGROUND OF THE INVENTION Lubricating oil compositions for internal combustion engines generally contain a variety of additives to reduce or control deposits, wear, corrosion, etc. The present invention is concerned with compositions useful as dispersants in lubricating oil compositions.

In lubricating oils, dispersants function to control sludge, carbon, and varnish produced primarily by the incomplete combustion of the fuel, or impurities in the fuel, or impurities in the base oil used in the lubricating oil composition.

Dispersants also control viscosity increase due to the presence of soot in diesel engine lubricating oils.

One of the most effective classes of lubricating oil dispersants is polyalkylene succinimides. In some cases, the succinimides have also been found to provide fluid-modifying properties, or a so-called viscosity index credit, in lubricating oil compositions. That produces a reduction in the amount of viscosity index improver which would be otherwise have to be used.

Polyalkylene succinimides are generally prepared by the reaction of the corresponding polyalkylene succinic anhydride with a polyalkyl polyamine.

Polyalkylene succinic anhydrides are generally prepared by a number of well- known processes. For example, there is a well-known thermal process (see, e. g., U. S. Patent No. 3, 361, 673), an equally well-known chlorination process (see, e. g., U. S. Patent No. 3, 172, 892), a combination of the thermal and chlorination processes (see, e. g., U. S. Patent No. 3, 912, 764), and free radical processes (see, e. g., U. S. Patent Nos. 5, 286, 799 and 5, 319, 030). Such compositions include one-to-one monomeric adducts (see, e. g., U. S. Patent

Nos. 3, 219, 666 and 3, 381, 022), as well as"multiply adducted"products, adducts having alkenyl-derived substituents adducted with at least 1. 3 succinic groups per alkenyl-derived substituent (see, e. g., U. S. Patent No. 4, 234, 435).

U. S. Patent Nos. 3, 361, 673 and 3, 018, 250 describe the reaction of an alkenyl- or alkyl-substituted succinic anhydride with a polyamine to form alkenyl or alkyl succinimide lubricating oil dispersants and/or detergent additives.

U. S. Patent No. 4, 612, 132 teaches that alkenyl or alkyl succinimides may be modified by reaction with a cyclic or linear carbonate or chloroformate such that one or more of the nitrogens of the polyamine moiety is substituted with a hydrocarbyl oxycarbonyl, a hydroxyhydrocarbyl oxycarbonyl, or a hydroxy poly (oxyalkylene) oxycarbonyl. These modified succinimides are described as exhibiting improved dispersancy and/or detergency in lubricating oils.

U. S. Patent No. 4, 747, 965 discloses modified succinimides similar to those disclosed in U. S. Patent No. 4, 612, 132, except that the modified succinimides are described as being derived from succinimides having an average of greater than 1. 0 succinic groups per long chain alkenyl substituent.

An article by S. T. Roby, R. E. Kornbrekke, and J. A. Supp"Deposit Formulation in Gasoline Engines, Part 2, Dispersant Effects on Sequence VE Deposits"JOURNAL OF THE SOCIETY OF TRIBOLOGISTS AND LUBRICATION ENGINEERS, Vol. 50, 12, 989-995 (December 1994) teaches that the length of the dispersant alkyl side chain influences deposit control performance, and that, at the same nitrogen level, the low molecular weight (side chain 1, 000 daltons) dispersants that were tested were poorer in controlling deposits than the tested high molecular weight (side chain 2, 000 daltons) succinimide dispersants. This teaching is also consistent with the prior observation comparing 950 Mn side chain succinimides with 2, 200 Mn side chain succinimides.

U. S. Patent No. 4, 234, 435 teaches a preferred polyalkene-derived substituent group with a Mn in the range of 1, 500 to 3, 200. For polybutenes, an especially preferred Mn range is 1, 700 to 2, 400.

A variety of post-treatments for improving various properties of alkenyl succinimides are known to the art, a number of which are described in U. S.

Patent No. 5, 241, 003.

Example 2 of U. S. Patent No. 5, 266, 186 discloses the preparation of dispersants by reacting certain polyisobutenyl-succinic anhydride adducts (see footnote 2 of Table 2) with ethylenediamine, followed by reaction with a maleic anhydride/alpha-olefin copolymer. The patent teaches that, by functioning as an iron sulfide dispersant, the product is useful to inhibit sludge deposits in refinery processing equipment caused by the heat treatment of hydrocarbon feed stocks.

U. S. Patent No. 5, 112, 507 discloses a polymeric ladder type polymeric succinimide dispersant in which each side of the ladder is a long chain alkyl or alkenyl, generally having at least about 30 carbon atoms, preferably at least about 50 carbon atoms. The dispersant is described as having improved hydrolytic stability and shear stress stability, produced by the reaction of certain maleic anhydride-olefin copolymers with certain polyamines. The patent further teaches that the polymer may be post-treated with a variety of post-treatments, and describes procedures for post-treating the polymer with cyclic carbonates, linear mono-or polycarbonates ; boron compounds (e. g., boric acid), and fluorophosphoric acid and ammonia salts thereof.

U. S. Patent Nos. 5, 334, 321 and 5, 356, 552 disclose certain cyclic carbonate post-treated alkenyl or alkylsuccinimides having improved fluorocarbon elastomer compatibility, which are preferably prepared by the reaction of the corresponding substituted succinic anhydride with a polyamine having at least four nitrogen atoms per mole. Both of these patents disclose the possibility of borating certain cyclic carbonate post-treated alkenyl or alkylsuccinimides.

U. S. Patent Nos. 5, 334, 321 discloses that higher molecular weight alkenyl or alkylsuccinimides give better detergency than the corresponding lower molecular weight alkenyl or alkylsuccinimides.

Mixtures of borated and carbonated polyalkylene succinimides have been derived from the same molecular weight polyalkylenes. The mixtures show inferior soot dispersancy to the individual borated and carbonated polyalkylene succinimides used alone.

U. S. Patent No. 5, 716, 912 discloses polyalkylene succinimides 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, then treating those succinimides with cyclic carbonates, linear mono-or polycarbonates, or a boron compound.

SUMMARY OF THE INVENTION The present invention provides a lubricating oil composition with improved detergency.

In one embodiment, the lubricating oil composition of the present invention comprises : (a) a major amount of a base oil of lubricating viscosity ; (b) from 0. 5% to 15% of a carbonate-treated polyalkylene succinimide additive prepared by treating a first polyalkylene succinimide with a cyclic carbonate or a linear mono-or poly-carbonate under reactive conditions ; (c) from 0. 5% to 15% of a borated polyalkylene succinimide additive prepared by treating a second polyalkylene succinimide with a boron compound under reactive conditions ; (d) from 0. 5% to 20% of a metal-containing detergent ; and (e) from 0. 1 % to 3% of a zinc dialkyldithiophosphate.

Preferably, the number average molecular weight of the polyalkylenes from which the carbonate-treated polyalkylene succinimide additive is derived is at least 300 greater than the number average molecular weight of the polyalkylenes from which the boron-treated polyalkylene succinimide additive is derived.

The lubricating oil composition preferably further contains from 0. 02% to 5% of a molybdenum compound. The content of the molybdenum compound in the lubricating oil composition preferably is in an amount of 10 to 2, 500 ppm in terms of molybdenum element.

The lubricating oil composition preferably further contains at least one of the following : from 1 % to 20% of a viscosity index improver and from 0. 1 % to 5%

of an oxidation inhibitor selected from the group consisting of phenol compounds and amine compounds.

Preferably, the carbonate-treated polyalkylene succinimide additive is a reaction product of a high molecular weight alkenyl-or alkyl-substituted succinic anhydride and a polyalkylene polyamine having an average of 4 to 10 nitrogen atoms per mole and is post-treated with a cyclic carbonate.

Preferably, the polyalkylene group of the carbonate-treated polyalkylene succinimide additive is derived from a polybutene having a molecular weight of from 1, 000 to 2, 700, more preferably from 1, 900 to 2, 700.

Preferably, the polyalkylene group of the borated polyalkylene succinimide additive is derived from a polybutene having a molecular weight of from 1, 000 to 2, 700.

Preferably, the carbonate-treated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are contained in a total amount of 1 % to 15%, and the carbonate-treated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are contained in a weight ratio of 2 : 8 to 8 : 2.

In a further aspect, the present invention also provides a polyalkylene succinimide composition that improves the soot dispersancy properties of a lubricating oil composition. This polyalkylene succinimide composition comprises borated and carbonated polyalkylene succinimides derived from different molecular weight polyalkylenes.

The polyalkylene succinimide composition comprises from 10% to 50% of a boron-treated polyalkylene succinimide and from 50% to 90% of a carbonate- treated polyalkylene succinimide. This polyalkylene succinimide composition produces superior soot dispersancy to either the boron-treated polyalkylene succinimide or the carbonate-treated polyalkylene succinimide when used alone.

The boron-treated polyalkylene succinimide is derived from polyalkylenes having a lower molecular weight than the polyalkylenes from which the

carbonate-treated polyalkylene succinimide is derived. This difference in molecular weight is at least 300, preferably from 800 to 1, 000.

Preferably, the boron-treated polyalkylene succinimide is a polybutene succinimide derived from polybutenes having a molecular weight of from 1, 200 to 1, 400 and the carbonate-treated polyalkylene succinimide is a polybutene succinimide derived from polybutenes having a molecular weight of from 2, 000 to 2, 400. Preferably, the carbonate-treated polybutene succinimide 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.

The soot dispersancy of a lubricating oil in internal combustion engine applications can be improved by adding to that lubricating oil an effective amount of the polyalkylene succinimide composition of the present invention.

The invention provides a lubricating oil composition comprises a major amount of a base oil of lubricating viscosity and the polyalkylene succinimide composition of the present invention.

The invention also provides a concentrate comprising the polyalkylene succinimide composition of the present invention, an organic diluent, and preferably at least one other additive. The organic diluent constitutes from 1 % to 20% of the concentrate, and the polyalkylene succinimide composition constitutes from 5% to 80% of the concentrate.

DETAILED DESCRIPTION OF THE INVENTION The present invention involves a lubricating oil composition comprising a major portion of a base oil, specific amounts of a cyclic carbonate-treated polyalkylene succinimide additive, a borated polyalkylene succinimide additive, a metal-containing detergent, and a zinc dialkyldithiophosphate. In a further aspect, the present invention involves a polyalkylene succinimide composition that comprises a mixture of borated and carbonated polyalkylene succinimides derived from different number average molecular weight polyalkylenes.

DEFINITIONS As used herein the following terms have the following meanings unless expressly stated to the contrary : 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, however, 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.

Polyalkylene succinimides are disclosed in numerous references and are well known in the art. Certain fundamental types of succinimides and related materials encompassed by the term of art"succinimide"are taught in U. S.

Patent Nos. 2, 992, 708 ; 3, 018, 291 ; 3, 024, 237 ; 3, 100, 673 ; 3, 219, 666 ; 3, 172, 892 ; and 3, 272, 746, the disclosures of which are hereby incorporated by reference in their entirety for all purposes.

The term"polyalkylene succinic acid derivative"refers to a structure having the formula : wherein R is a polyalkylene, and L and M are independently selected from the group consisting of-OH,-Cl,-O-, lower alkyl or taken together are-O-to form a polyalkylene succinic 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 alcools, form amides, 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,-O-hydrocarbyl,-OM+ where M+ represents one equivalent of a metal, ammonium or amine cation,-NH2,-Cl, -Br, and taken together X and X'can be-O-so as to form an anhydride.

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, dimethyl, 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 molecular weights are number average molecular weights (Mn).

Unless otherwise specified, all percentages are in weight percent and are based on the amount of active and inactive components, including any process oil or diluent oil used to form that component.

BASE OIL OF LUBRICATING VISCOSITY The base oil of lubricating viscosity used in such compositions may be mineral oils or synthetic oils of viscosity suitable for use in the crankcase of an internal combustion engine. The base oil preferably has a dynamic viscosity of 2 to 50 mm2/s at 100°C and may be derived from synthetic or natural sources. Mineral oils for use as the base oil in this invention include paraffinic, naphthenic, and other oils that are ordinarily used in lubricating oil compositions. Synthetic oils include both hydrocarbon synthetic oils and synthetic esters. Useful synthetic hydrocarbon oils include liquid polymers of alpha olefins having the proper viscosity. Especially useful are the hydrogenated liquid oligomers of C6 to C12 alpha olefins such as 1-decene trimer. Likewise, alkyl benzenes of proper viscosity, such as didodecyl benzene, can be used. Useful synthetic esters include the esters of monocarboxylic acids and polycarboxylic acids, as well as monohydroxy alkanols and polyols. Typical examples are didodecyl adipate, pentaerythritol tetracaproate, di-2-ethylhexyl adipate, dilaurylsebacate, and the like. Complex esters prepared from mixtures of mono-and dicarboxylic acids and mono-and dihydroxy alkanols can also be used. Blends of mineral oils with synthetic oils are also useful.

POLYALKYLENE SUCCINIMIDE The polyalkylene succinimides of the lubricating oil composition of the present invention comprises from 0. 5% to 15% of a carbonate-treated polyalkylene succinimide derived from a higher molecular weight polyalkylene and from 0. 5% to 15% of a boron-treated polyalkylene succinimide derived from a lower molecular weight polyalkylene. The combination of the two succinimides produces superior detergency and soot dispersancy to either the boron-treated polyalkylene succinimide or the carbonate-treated polyalkylene succinimide when used alone. The advantages of the boron-treated polyalkylene succinimide in TBN contribution and prevention of bearing corrosion are also preserved.

The individual polyalkylene succinimides of the present invention can be prepared by conventional processes, such as disclosed in U. S. Patent No.

2, 992, 708 ; 3, 018, 250 ; 3, 018, 291 ; 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, the disclosures of which are all hereby incorporated by reference in their entirety for all purposes.

Carbonate-Treated Polyalkylene Succinimide The cyclic carbonate-treated polyalkylene succinimide additive is an ashless dispersant and can be prepared by reaction of a high molecular weight alkenyl- or alkyl-substituted succinic anhydride and a polyalkylene polyamine having an average of 4 to 10 nitrogen atoms (preferably 5 to 7 nitrogen atoms) per mole and is post-treated with a cyclic carbonate. The polyalkylene of the cyclic carbonate-treated polyalkylene succinimide additive is derived from polyalkylenes having a molecular weight of at least 1, 000. Preferably, the carbonate-treated polyalkylene succinimide is a polybutene succinimide derived from polybutenes having a molecular weight of from 1, 000 to 2, 700, more preferably 1, 900 to 2, 700, and most preferably 2, 000 to 2, 400.

The polyalkylene of the cyclic carbonate-treated polyalkylene succinimide additive 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.

Boron-Treated Polyalkylene Succinimide The borated polyalkylene succinimide additive is an ashless dispersant and can be prepared by reaction of a high molecular weight alkenyl-or alkyl- substituted succinic anhydride and a polyalkylene polyamine having an average of 4 to 10 nitrogen atoms (preferably 5 to 7 nitrogen atoms) per mole and is post-treated with a boric acid or boric acid compound. The polyalkylene of the boron-treated polyalkylene succinimide additive is derived from polyalkylenes having a molecular weight of at least 1, 000. Preferably, the boron-treated polyalkylene succinimide is derived from polybutenes having a molecular weight of from 1, 000 to 2, 700, more preferably 1, 200 to 1, 400, most preferably about 1, 300. The boron content in the borated polyalkylene succinimide additive preferably is in the range of 0. 1% to 5%, more preferably 0. 2% to 2%.

In the lubricating oil composition of the invention, the cyclic carbonate-treated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are preferably contained in a weight ratio of 2 : 8 to 8 : 2. The cyclic carbonate-treated polyalkylene succinimide additive and the borated polyalkylene succinimide additive are preferably contained in the lubricating oil composition in a total amount of from 1 % to 15%.

The lubricating oil composition of the invention can further contain other ashless dispersants such as other succinic imide dispersants, succinic acid ester dispersants, and benzylamine dispersants.

POLYALKYLENE SUCCINIMIDE COMPOSITION The polyalkylene succinimide composition of the present invention comprises from 10% to 50% of a boron-treated polyalkylene succinimide derived from a lower molecular weight polyalkylene and from 50% to 90% of a carbonate- treated polyalkylene succinimide derived from a higher molecular weight polyalkylene. Preferably, the polyalkylene succinimide composition of the present invention comprises from 20% to 40% of the boron-treated polyalkylene succinimide and from 60% to 80% of the carbonate-treated polyalkylene succinimide. This polyalkylene succinimide composition produces superior soot dispersancy to either the boron-treated polyalkylene succinimide or the carbonate-treated polyalkylene succinimide when used alone. The advantages of the boron-treated polyalkylene succinimide in TBN contribution and prevention of bearing corrosion are also preserved.

The individual polyalkylene succinimides used in the polyalkylene succinimide composition of the present invention can be prepared by conventional processes, such as disclosed in U. S. Patent No. 2, 992, 708 ; 3, 018, 250 ; 3, 018, 291 ; 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, the disclosures of which are all hereby incorporated by reference in their entirety for all purposes.

The polyalkylene succinimide composition can be prepared by physically mixing the boron-treated polyalkylene succinimide and the carbonate-treated polyalkylene succinimide. The polyalkylene succinimide composition might

have a slightly different composition than the initial mixture, because the components may interact.

METAL DETERGENT The lubricating oil composition of the invention further contains from 0. 5% to 20% of a metal-containing detergent. Representatives of the metal-containing detergents are metal phenates and metal sulfonates.

The metal phenate is an alkali metal salt or an alkaline earth metal salt of a sulfide of an alkylphenol having an alkyl group of approximately 8 to 30 carbon atoms. The metal sulfonate is an alkali metal salt or an alkaline earth metal salt of a sulfonate of a mineral oil having a molecular weight of approximately 400 to 6, 000 or an aromatic compound having an alkyl group. Examples of the alkali metal salts and alkaline earth metal salts also include lithium salts, sodium salts, calcium salts, magnesium salts, and barium salts. The metal phenate and the metal sulfonate can be employed singly or in combination.

Other metal-containing detergents such as an alkaline earth metal salicylate, an alkaline earth metal phosphonate, and an alkaline earth metal naphthenate can be employed in combination with the metal phenate and/or the metal sulfonate.

The metal-containing detergent can be a neutral type or an overbased type having a total base number (TBN) of 150 to 300, or more.

ZINC DIALKYLDITHIOPHOSPHATE The lubricating oil composition of the invention further contains from 0. 1 % to 3% of a zinc dialkyldithiophosphate (i. e., ZnDTP). The zinc dialkyldithiophosphate preferably is zinc dialkyldithiophosphate containing an alkyl group of 3 to 18 carbon atoms. Preferably the alkyl group of the zinc dialkyldithiophosphate is derived from a secondary alcohol of 3 to 18 carbon atoms or a mixture of the secondary alcohol and a primary alcool.

OTHER ADDITIVE COMPONENTS The following additive components are examples of other components that can be favorably employed in the present invention. These examples of additives are provided to illustrate the present invention, but they are not intended to limit it : (1) Oxidation inhibitors The lubricating oil composition preferably may contain an oxidation inhibitor in an amount of 0. 02% to 5%, more preferably 0. 1% to 3%.

(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-butylphenol), 4, 4'-butylene bis (3-methyl-6-tert- butylphenol), 4, 4'-isopropylene bis (2, 6-di-tert-butylphenol), 2, 2'-methylene bis (4-methyl-6-nonylphenol), 2, 2'-isobutylene bis (4, 6-dimethylphenol), 2, 2'-methylene bis (4-methyl- 6-cyclohexylphenol), 2, 6-di-tert-butyl-4-methylphenol, 2, 6-di-tert-butyl-4-ethylphenol, 2, 4-dimethyl-6-tert-butylphenol, 2, 6-di-tert-1-dimethylamino-p-cresol, 2, 6-di-tert-4- (N. N' dimethylaminomethylphenol), 4, 4'-thiobis (2-methyl-6-tert- butylphenol), 2, 2'-thiobis (4-methyl-6-tert-butylphenol), and bis (3-methyl-4-hydroxy-5-tert-butylbenzyl)-sulfide.

(b) Diphenyl amine type oxidation inhibitor : alkylated diphenyl amine, phenyl-a-naphthylamine, and alkylated- a-naphthylamine.

(c) Other types : metal dithiocarbamate (e. g., zinc dithiocarbamate) and methylene bis (dibutyldithiocarbamate).

(2) Rust inhibitors (Anti-rust agents) (a) Nonionic polyoxyethylene surface active agents : polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl 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, dicarboxilic acids, metal soaps, fatty acid amine salts, metal

salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and phosphoric ester.

(3) Demulsifiers : addition product of alkylphenol and ethylene oxide, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan ester.

(4) Friction modifiers : fatty alcool, fatty acid, amine, borated ester, and other esters.

(5) Multifunctional additives : Examples of the molybdenum compounds include a sulfur-containing oxymolybdenum succinic imide complex compound (described in Japanese (examined) Patent Publication No. H3-22438), sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum organo phosphoro dithioate, oxymolybdenum monoglyceride, oxymolybdenum diethylate amide, amine-molybdenum complex compound, and sulfur-containing molybdenym complex compound. The lubricating oil composition preferably contains a molybdenum compound in an amount of 0. 02% to 5%, more preferably 0. 1 to 3%. The content of the molybdenum compound in the lubricating oil composition preferably is in an amount of 10 to 2, 500 ppm in terms of molybdenum element.

(6) Viscosity index improvers : polymethacrylate type polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polyisobutylene, and dispersant type viscosity index improvers. The lubricating oil composition of the invention preferably may contain a viscosity index improver in an amount of 1 % to 20%.

(7) Pour point depressants : polymethyl methacrylate.

(8) Foam Inhibitors : alkyl methacrylate polymers and dimethyl silicone polymers.

LUBRICATING OIL COMPOSITION The lubricating oil composition of the present invention is useful for imparting improved detergency properties to an engine lubricating oil composition. Such a lubricating oil composition comprises a major portion of a base oil, a cyclic carbonate-treated polyalkylene succinimide additive, a borated polyalkylene succinimide additive, a metal-containing detergent, and a zinc dialkyldithiophosphate.

A further aspect of the present invention involves a polyalkylene succinimide composition that comprises a mixture of borated and carbonated polyalkylene succinimides derived from different number average molecular weight polyalkylenes.

The polyalkylene succinimide compositions of the present invention are useful for imparting improved soot dispersancy properties to an engine lubricating oil composition. Such a lubricating oil composition comprises a major part of base oil of lubricating viscosity and an effective amount of the polyalkylene succinimide composition of the present invention. Adding an effective amount of the polyalkylene succinimide compositions of the present invention to a lubricating oil composition improves the soot dispersancy properties of that lubricating oil composition in automotive applications.

In one embodiment, an engine lubricating oil composition would contain (a) a major amount of a base oil of lubricating viscosity ; (b) from 0. 5% to 15% of a carbonate-treated polyalkylene succinimide additive prepared by treating a first polyalkylene succinimide with a cyclic carbonate or a linear mono-or poly-carbonate under reactive conditions ; (c) from 0. 5% to 15% of a borated polyalkylene succinimide additive prepared by treating a second polyalkylene succinimide with a boron compound under reactive conditions ; (d) from 0. 5% to 20% of a metal-containing detergent ; and (e) from 0. 1 % to 3% of a zinc dialkyldithiophosphate.

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. For example, the polyalkylene succinimide composition can be blended with the other components before, during, and/or after the boron-treated polyalkylene succinimide and carbonate-treated polyalkylene succinimide are blended together.

ADDITIVE CONCENTRATES Additive concentrates are also included within the scope of this invention. The concentrates of this invention comprise an organic diluent and the compounds or compound mixtures of the present invention, preferably with at least one of the additives disclosed above. The concentrates contain sufficient organic diluent to make them easy to handle during shipping and storage.

From 1 % to 20% of the concentrate is organic diluent. From 5% to 80% of concentrate is the polyalkylene succinimide composition of the present invention. The remainder of the concentrate may comprise one or more of other additives discussed above.

These percentages are based on the amount of active and inactive components, including any process oil or diluent oil used to form that component. The percent numbers for organic diluent would be greater if only the active components are considered.

Suitable organic diluents which can be used include for example, solvent refined 100N, i. e., Cit-Con 100N, and hydrotreated 100N, i. e., Chevron 100N, and the like. The organic diluent preferably has a viscosity of about from 1 to 20 cSt at 100°C.

The components of the additive concentrate can be blended in any order and can be blended as combinations of components. For example, the polyalkylene succinimide composition can be blended with the other components before, during, and/or after the boron-treated polyalkylene succinimide and carbonate- treated polyalkylene succinimide are blended together.

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 novel dispersants of the present invention. Unlike the percentages used in other sections of this specification, the following percentages are based on the amount of active component, with neither process oil nor diluent oil. (All process oils and diluent oils included are included in the figures for base oil of lubricating viscosity.) These examples are provided to illustrate the present invention, but they are not intended to limit it.

1) Polyalkylene succinimide composition 35% Metal detergent 25% Primary alkyl zinc dithiophosphate 10% Base oil of lubricating viscosity 30% 2) Polyalkylene succinimide composition 40% Metal detergent 20% Secondary alkyl zinc dithiophosphate 5% Dithiocarbamate type oxidation inhibitor 5% Base oil of lubricating viscosity 30% 3) Polyalkylene succinimide composition 35% Metal detergent 20% Secondary alkyl zinc dithiophosphate 5% Phenol type oxidation inhibitor 5% Base oil of lubricating viscosity 35% 4) Polyalkylene succinimide composition 30% Metal detergent 20% Secondary alkyl zinc dithiophosphate 5% Dithiocarbamate type anti-wear agent 5% Base oil of lubricating viscosity 40%

5) Polyalkylene succinimide composition 30% Metal detergent 20% Secondary alkyl zinc dithiophosphate 5% Molybdenum-containing anti-wear agent 5% Base oil of lubricating viscosity 40% 6) Polyalkylene succinimide composition 30% Metal detergent 20% Other additives 10% Primary alkyl zinc dithiophosphate Secondary alkyl zinc dithiophosphate Alkylated diphenylamine-type oxidation inhibitor Dithiocarbamate type anti-wear agent Base oil of lubricating viscosity 40% EXAMPLES The invention will be further illustrated by the following examples, which set forth particularly advantageous embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

EXAMPLES SHOWING IMPROVED SOOT DISPERSANCY Four polybutene succinimides were prepared and post-treated by conventional means. The following percentages are based on the amount of active and inactive components, including any process oil or diluent oil used to form the polybutene succinimides.

POLYBUTENE SUCCINIMIDE A BORATED DISPERSANT DERIVED FROM 1, 300 MN POLYBUTENE The first polybutene succinimide was derived from 1, 300 Mn polybutenes. This succinimide was formed by reacting a polybutene-substituted succinic acid derivative with a heavy polyamine (containing an average of approximately 6. 5 nitrogen atoms per mole), then post-treating the resulting polybutene succinimide with boric acid.

POLYBUTENE SUCCINIMIDE B FIRST CARBONATED DISPERSANT DERIVED FROM 2, 200 MN POLYBUTENE The second polybutene succinimide was derived from 2, 200 Mn polybutenes.

This was formed by reacting a polybutene-substituted succinic acid derivative with a heavy polyamine (containing an average of approximately 6. 5 nitrogen atoms per mole), then post-treating the resulting polybutene succinimide with ethylene carbonate at a ratio of 2 moles of ethylene carbonate to 1 mole of basic nitrogen of the polybutene succinimide.

POLYBUTENE SUCCINIMIDE C SECOND CARBONATED DISPERSANT DERIVED FROM 2, 200 MN POLYBUTENE The third polybutene succinimide was derived from 2, 200 Mn polybutenes. This was formed by reacting a mixture of a polybutene succinic acid derivative, an unsaturated acidic reagent copolymer of an unsaturated acidic reagent and an olefin, and a heavy polyamine (containing an average of approximately 6. 5 nitrogen atoms per mole), then post-treating the resulting polybutene succinimide with ethylene carbonate at a ratio of 2 moles of ethylene carbonate to 1 mole of basic nitrogen of the polybutene succinimide.

POLYBUTENE SUCCINIMIDE D CARBONATED DISPERSANT DERIVED FROM 1, 300 MN POLYBUTENE A comparative carbonated polybutene succinimide was derived from 1, 300 Mn polybutenes. This was formed by reacting a polybutene-substituted succinic acid derivative with a mixture of 80% heavy polyamine (containing an average of approximately 6. 5 nitrogen atoms per mole) and 20% diethylene triamine, then post-treating the resulting polybutene succinimide with ethylene carbonate at a ratio of 2 moles of ethylene carbonate to 1 mole of basic nitrogen of the polybutene succinimide.

RUN SERIES I Polybutene Succinimides A, B and D were each blended separately into a SAE 15W-40 Screening Formulation (X) containing an effective amount of metallic detergent, zinc dithiophosphate, and a molybdenum based oxidation inhibitor.

A non-dispersant viscosity index modifier was chosen to eliminate any effects of viscosity index modifier on the test results.

These compositions were then tested in the ASTM D-5967-96 (Mack T-8) engine oil test. This test evaluates an oil's ability to control viscosity increase due to soot loading in the oil. In general, a lower viscosity increase indicates superior performance. This test is a required performance test for the heavy- duty engine oil performance category, API CG-4. The results are shown in the table below : Run 1 2 3 4 Screening Formulation X X X X Polybutene Succinimide A 10% Polybutene Succinimide B 8% Polybutene Succinimide B 11. 5% Polybutene Succinimide D 10% Viscosity Increase at 3. 8% soot 9. 5 cSt 9. 25 cSt 6. 9 cSt 8. 3 cSt Analysis of this data yields a comparison between the various components.

Comparison of the results of Run 1 (borated dispersant from 1, 300 Mn polybutene) versus Run 4 (carbonated dispersant from 1, 300 Mn polybutene) shows the benefit to carbonate treatment in reducing viscosity increase.

Comparison of the two results of the carbonated dispersant from 2, 200 Mn polybutene (Runs 2 and 3) verifies that the test result improves with increased treat level. The carbonated dispersant from 2, 200 Mn polybutene is superior to the borated dispersant from 1, 300 Mn polybutene, even at a 20% lower dosage. Because the result of Run 4 (carbonated dispersant from 1, 300 Mn polybutene) was intermediate to Runs 2 and 3 (carbonated dispersant from 2, 200 Mn polybutene), no comparison between these polybutene succinimides is possible from this data.

RUN SERIES II Polybutene Succinimides B and C were each blended separately into a Second Screening Formulation (Y) and tested in the ASTM D-5967-96 test as above, and the results tabulated below : Run 5 6 Screening Formulation Polybutene Succinimide B 8% Polybutene Succinimide C 8% Viscosity Increase at 3. 8% soot 8. 81 cSt 4. 94 cSt Comparison of these results shows Polybutene Succinimide C to be superior to Polybutene Succinimide B in controlling viscosity increase. Comparing the two tables, we can infer that Polybutene Succinimide C is also superior to Polybutene Succinimide A in controlling viscosity increase.

RUN SERIES III Polybutene Succinimides A and B together (Run 7) and B alone (Run 8) were blended separately into a Commercial Formulation (Z) and again run in the ASTM D-5967-96 test as above. As previously discussed in U. S. Patent No.

5, 334, 321, boration preserves the TBN contribution of the dispersant, so it was desired to keep some Polybutene Succinimide A in the final formulation : Run 7 8 Screening Formulation Z Polybutene Succinimide A 3. 5% Polybutene Succinimide B 6. 5% 10% Viscosity Increase at 3. 8% soot 5. 85 cSt 9. 5 cSt Surprisingly, the mixture of borated succinimide derived from 1, 300 Mn polybutenes and carbonated succinimide derived from 2, 200 Mn polybutenes gave a lower viscosity increase than the carbonated succinimide alone, despite the fact that the carbonated succinimide has been shown to be superior to borated succinimide in controlling viscosity increase.

This Run Series shows the synergy of using a blend of the borated polybutene succinimide derived from 1, 300 Mn polybutenes and the ethylene carbonated polybutene succinimide derived from 2, 200 Mn polybutenes. That blend provided better soot dispersancy than achieved by using either component alone.

RUN SERIES IV Polybutene Succinimides A and C together were blended into the same Commercial Formulation (Z) as in Run Series III with the following results, when compared to Run 6 of Run Series II (Formulation Y) : Run 9 6 Screening Formulation Z Y Polybutene Succinimide A 3% Polybutene Succinimide C 5% 8% Viscosity Increase at 3. 8% soot 4. 39 cSt 4. 94 cSt Comparing the results of Runs 9 and 6 shows again that the mixture of borated 1, 300 Mn polybutene succinimide and 2, 200 Mn carbonated polybutene succinimide gives superior performance to either dispersant alone. While this comparison was effected in differing formulations, comparison of the Polybutene Succinimide B results from Run Series II and III shows that Formulation Z is more severe in terms of viscosity increase than Formulation Y.

Only 8% of the Polybutene Succinimide B in Formulation Y gave a lower viscosity increase than 10% of the same polybutene succinimide in Formulation Z.

Run Series III and IV differ in how the ethylene carbonated polybutene succinimide was formed prior to post-treatment with ethylene carbonate. In Run Series Hi, that ethylene carbonated polybutene succinimide was formed by reacting polybutene-substituted succinic acid with a heavy polyamine. In Run Series IV, that ethylene carbonated polybutene succinimide was formed by reacting a mixture of a polybutene succinic acid derivative, an unsaturated acidic reagent copolymer of an unsaturated acidic reagent and an olefin, and a heavy polyamine. The above tables show that the second type of carbonated polybutene succinimide provided better soot dispersancy than the first type of carbonated polybutene succinimide.

RUN SERIES V The bearing weight loss of blends of borated polybutene succinimides and carbonated polybutene succinimides of different molecular weight in a standard lubricating oil formulation (Z) were compared to the bearing weight loss of standard lubricating oil formulations having only carbonated polybutene succinimides. The CRC L-38 test is a standard industry test that measures the corrosiveness of oil in terms of bearing weight loss. For the API CG-4 oil performance category, the limit is 43. 7 milligrams maximum weight loss. The results are shown in the table below : Run 7 10 11 12 Screening Formulation Z Z Z Z Polybutene Succinimide A 3. 5% 3. 5% Polybutene Succinimide B 6. 5% 8% Polybutene Succinimide C 6. 5% 8% Bearing Weight Loss 18. 5 24 40. 5 70. 5 Note : As dispersant level increases, the L-38 bearing weight loss increases, thus a fail at 8% would be expected to be a more severe fail at 10%.

Run Series V shows the benefit to the mixed dispersant approach in passivating L-38 bearing weight loss.

RUN SER) ES V ! The ASTM D-5967-96 viscosity increase performance of a blend of borated polybutene succinimides and carbonated polybutene succinimides of the same molecular weight in a modified formulation (X') was compared to the viscosity increase performance of only borated or carbonated polybutene succinimides in Formulation X. The results are shown in the table below : Run 13 1 4 Formulation X'X X Component A 3. 5% 10% Component D 6. 5% 10% Viscosity Increase at 3. 8% soot 10. 76 9. 5 8. 3

This comparative example shows that blends of borated polybutene succinimides and carbonated polybutene succinimides of the same molecular weights gave worse results than formulations having only borated or carbonated polybutene succinimides. In this example the Formulation X' differed from Formulation X in that it contained a second oxidation inhibitor.

This change is not expected to impact the severity of the formulation in terms of viscosity increase.

EXAMPLES SHOWING IMPROVED DETERGENCY Lubricating oil compositions of the invention (Run No. 14 to No. 17) and lubricating oil compositions for comparison (Run No. 18 to No. 21) were prepared according to the formulations set forth as shown below. The lubricating oil compositions were adjusted to give a 10W-30 oil (SAE viscosity grade) by the addition of viscosity index improver. Additionally, an effective amount of oxidation inhibitor, zinc dithiophosphate, and a dispersant viscosity index improver were added to the lubricating oil composition, including as other additives small amounts of anti-rust agent, friction modifier, anti-wear agent, metal-deactivating agent, demulsifier, anti-foaming agent, and pour point depressant. Base oil of 150 neutral oil was used.

POLYBUTENE SUCCINIMIDE E DISPERSANT DERIVED FROM 900 MN POLYBUTENE The first polybutene succinimide of this series was derived from 900 Mn polybutenes. This succinimide (nitrogen content : 1. 4%) was formed by reacting a polybutene-substituted succinic acid derivative with a polyamine.

POLYBUTENE SUCCINIMIDE F BORATED DISPERSANT DERIVED FROM 1, 300 MN POLYBUTENE The second polybutene succinimide of this series (nitrogen content : 1. 5 %, boron content : 0. 5%) was prepared using polybutene of a number-average molecular weight of approximately 1, 300 and treating the resulting succinimide with boric acid, according to Example No. 8 of U. S. Patent No. 5, 356, 552.

POLYBUTENE SUCCINIMIDE G CARBONATED DISPERSANT DERIVED FROM 2, 200 MN POLYBUTENE The third polybutene succinimide of this series (nitrogen content : 0. 7%) was prepared using polybutene of a number-average molecular weight of approximately 2, 200 and treating the resulting succinimide with ethylene carbonate, according to Example No. 17 of United States Patent 5, 356, 552.

The test procedures were : 1) Hot Tube Test (KES 07-803) for evaluating detergency at high temperatures.

In a heater block, a glass tube having an inner diameter of 2 mm is vertically set. The test oil composition and air are introduced into the glass tube from its lower end at rates of 0. 31 cc/hr. and 10 cc/min., respectively, at 290°C (temperature of the heater) for 16 hours. Thereafter, the deposit produced on the glass tube is visually evaluated to mark the lacquer formation on the basis of 10 points. A higher value means that the lacquer is less and the detergency is better.

2) Gasoline engine test-Rocker cover sludge test (JASO M331-91) for evaluating detergency at medium or low temperatures.

A gasoline engine (6-cylindered engine of V-type and 2 L displacement volume) is operated for 300 hours at a cycle run between low speed run and high speed run according to the test method defined by Japan Automobile Standard Organization (JASO M331-91). Thereafter, the sludge deposited on the rocker cover was evaluated to mark the amount of deposit on the basis of 10 points. A higher value means a less amount of deposit.

The results of these test runs are set forth in the following table :

Run Numbera Additives 14 15 16 17 18 19 20 21 Polybutene------2. 5 2. 5 Succimide E Polybutene 1. 5 1. 5 2. 5 2. 5-4. 5-2. 0 Succimide F Polybutene 3. 0 3. 0 2. 0 2. 0 4. 5-2. 0- Succinimide G Hot Tube Test (10 = 6. 0 7. 5 7. 0 8. 0 5. 0 7. 0 5. 5 6. 5 Best) Rocker Cover Sludge 9. 3 9. 3 9. 2 9. 2 9. 4 8. 3 8. 2 7. 9 (10 = Best) aFurther components of the lubricating oil composition : -Calcium phenate sulfide (TBN 250 mg KOH/g) : 1. 8%.

-Calcium sulfonate (TBN 20 mg KOH/g) : 1. 7%.

-ZnDTP (phosphorus content 7. 2% prepared using a secondary alcohol of 3 to 8 carbon atoms) : 1. 3%.

-4, 4'-methylenebis (2, 6-di-t-butylphenol) : 0. 5%.

-Alkylated diphenylamine : 0. 5%.

-Sulfur-containing oxymolybdenum-succinimide complex compound (Mo content 5. 4%) : 0. 2% for Rules Nos. 15 and 17 only.

-Ethylene-propylene copolymer viscosity index improver : 6. 5%.

-Others : 0. 4 %.

-150 Neutral base oil : 82. 8%.

The test results set forth in the above table make it clear that the lubricating oil compositions containing the combination of the cyclic carbonate-treated

polyalkylene succinimide additive and the borated polyalkylene succinimide additive show high detergency at low and medium temperatures (which is required when the lubricating oil composition is used for gasoline engines) and high detergency at a high temperature (which is required when the lubricating oil composition is used for diesel engines). The addition of a molybdenum- containing compound further improves detergency at a high temperature.

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.