WO1998039399A1

WO1998039399A1 - Ashless friction modifier with viscosity index improving credit and lubricating oil composition containing same

Info

Publication number: WO1998039399A1
Application number: PCT/US1998/002584
Authority: WO
Inventors: Cyril A. Migdal; John R. Baranski; Edward B. Fox; Thomas H. Peter
Original assignee: Uniroyal Chemical Company, Inc.
Priority date: 1997-03-06
Filing date: 1998-02-12
Publication date: 1998-09-11

Abstract

An ashless additive for a lubricating oil composition is provided which comprises a polyolefin derived from the reaction of an ethylene-alphaolefin copolymer possessing a number average molecular weight of from about 250 to about 15,000 and an unsaturated carboxylic acid and/or anhydride thereof, the resulting carboxyl-modified polyolefin being further reacted with an aminobenzothiazole.

Description

ASHLESS FRICTION MODIFIER WITH VISCOSITY INDEX IMPROVING CREDIT AND LUBRICATING OIL COMPOSITION CONTAINING SAME

BACKGROUND OF THE INVENTION

This invention relates to an ashless friction modifier for lubricating oils and, more particularly, to such a modifier derived from the reaction of a carboxyl- modified ethylene-alphaolefin copolymer and an a inobenzothiazole.

Various carboxyl-modified ethylene-alphaolefin copolymers, e.g., ethylene-propylene copolymers (EP) and ethylene-propylene-diene monomer terpolymers (EPDM) , have been developed for use as ashless additives for lubricating oils where they improve one or more functional properties of the oils such as viscosity index, oxidative stability and anti-wear properties. EPA 353,935 describes oil-soluble lubricating oil additives derived from the reaction of ethylene-alphaolefin copolymers of from 300 to 10,000 number average molecular weight possessing terminal vinylidene unsaturation and an unsaturated carboxylic acid or anhydride thereof. The carboxylate-modified ethylene-alphaolefin copolymers are useful as additives to lubricating oils and can also be reacted with a nucleophilic reagent, such as amines, alcohols, amino alcohols and reactive metal compounds, to form products which are also useful as lubricating oil additives, e.g., as dispersants. Other carboxyl-modified olefinic copolymers useful as lubricating oil additives are disclosed in, among others, U.S. Patent

Nos. 3,687,905, 4,089,794, 4,160,739, 4,169,063, 4,171,273, 4,505,834, 4,735,736 and 5,356,999. SUMMARY OF THE INVENTION

In accordance with this invention, an ashless additive for a lubricating oil composition is provided which comprises a polyolefin derived from the reaction of an ethylene-alphaolefin copolymer possessing a number average molecular weight of from about 250 to about 15,000 and an unsaturated carboxylic acid and/or anhydride thereof, the resulting carboxyl-modified polyolefin being further reacted with an aminobenzothiazole. When incorporated in lubricating oils in the usual amounts, the additives of this invention impart beneficial friction modifying properties and VI improving credit to the oils.

DESCRIPTION, OF THE PREFERRED EMBODIMENTS

The substrate ethylene-alphaolefin copolymers to be modified by carboxyl groups and thereafter derivatized with an aminobenzothiazole in accordance with the present invention comprise copolymers of ethylene and one or more alphaolefins of the formula H₂C=CHR wherein R is a hydrocarbon radical of from 1 to about 10 carbon atoms. The copolymer-forming monomers can optionally include a nonconjugated polyene to form a terpolymer. Preferred alphaolefins include propylene, 1-butene, 1-pentene, 1- pentene, 1-hexene, 3-methyl pentene, 1-heptene, 1-octene and 1-decene.

The optional nonconjugated polyenes nonconjugated include aliphatic dienes such as 1, 4-hexadiene, 1,5- hexadiene, 1,4-pentadiene, 2-methyl-l,4-pentadiene, 3- methyl-l,4-hexadiene, 4-methyl-l, 3-hexadiene, 1, 9-decadiene, exo and endo-dicyclypentadiene and the like; exo- and endo- alkenylnorbornenes such as 5-propenyl-, 5- (buten-2-yl) - and 5-(2-methylbuten-[2' ]-yl) norbornene, and the like; alkylalkenylnorbornenes such as 5-methyl-6- propenylnorbornene, and the like; alkylidenenorbornenes such as 5-methylene, 5-ethylidene, and 5-isopropylidene-2- norbornene, vinylnorbornene, cyclohexenylnorbornene, and the like; alkylnorbornadienes such as methyl-, ethyl- and propylnorbornadiene, and the like; and cyclodienes such as 1,5-cyclooctadiene, 1, 4-cyclooctadiene, and the like.

The ethylene content of the substrate copolymers is generally from about 30 to about 70, preferably from about 35 to about 65, and most preferably from about 40 to about 60, weight percent. When present, the nonconjugated polyene generally ranges from 1 to about 25, preferably from about 2 to about 20, and most preferably from about 4 to about 17 weight percent. The balance of the copolymers (for a total of 100 weight percent) is made up of alphaolefin (s) other than ethylene.

The substrate copolymers can be prepared in accordance with known procedures employing Ziegler-Natta catalysts or metallocene catalysts. Where Ziegler-Natta catalysts are employed, e.g., as disclosed in U.S. Patent Nos. 3,522,180, 3,551,336 an 3,598,738, the contents of which are incorporated by reference herein, the resulting copolymers will possess terminal saturation. However, when metallocene catalysts are employed, e.g., as disclosed in U.S. Patent No. 4,668,834, the contents of which are incorporated by reference herein, the resulting copolymers will possess terminal vinylidene unsaturation. Both types of copolymers are useful for preparing the ashless derivatives of this invention.

The substrate copolymers generally possess a number average molecular weight (Mn) of from about 250 to about 15,000, preferably from about 1,000 to about 12,000, and most preferably from about 3,000 to about 10,000. Such copolymers generally possess an intrinsic viscosity (as measured in tetralin at 135°C.) of from about 0.025 to about 0.55 dl/g, preferably from about 0.075 to about 0.45 dl/g, and most preferably from about 0.2 to about 0.4 dl/g.

The substrate copolymers are further reacted with unsaturated carboxylic acids or anhydrides of the aliphatic or aromatic type, which generally contain three or more carbon atoms and one or more carboxylic acid or anhydride groups per molecule. Exemplary carboxylic acids include maleic acid, mesaconic acid, chloromaleic acid, itaconic acid, citraconic acid, glutaric acid, adipic acid, sebacic acid, pi elic acid, orthophthalic acid, isophthalic acid, terephthalic acid, acrylic acid and ethacrylic acid. Also suitable are anhydrides of the above acids, for example, the anhydrides derived from maleic, succinic, orthophthalic or other mono or di-carboxylic acids. Also suitable, in certain instances, are higher molecular weight organic compounds containing carboxylic or dicarboxylic acid groups or the corresponding anhydrides thereof, for example, 5- (2 , 5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexane-l, 2- dicarboxylic anhydride, glycerol acetate bistrimellitate dianhydride, 3 , 3' ,4, '-benzophenone tetracarboxylic dianhydride or pyromellitic dianhydride, among others.

The substrate ethylene-alphaolefin copolymer is preferably reacted with the carboxylic acid or anhydride in the presence of a free radical initiator. Suitable free radical initiators include organic peroxides with a half life of approximately to 2 hours at a temperature of 70° to 160°C. Some examples of such peroxides are di-t-butyl peroxide, dicumyl peroxide and benzoyl peroxide. Also suitable are peroxyesters such as t-butyl perbenzoate, t- butyl peroxypivalate, 2 ,5-dimethylhexyl-2,5-di (perbenzoate) , and so forth. It is also within the scope of the invention to carry out the reaction by means of free radicals generated by thermal or radiation sources such as ultraviolet light. The carboxyl-modified olefin copolymers can be prepared in any suitable reaction vessel, such as a resin kettle or pressure reactor, which is charged with the copolymer and the carboxylic acid and/or anhydride together with a suitable free radical initiator. The temperature of the reaction is normally within the range of from about 70°C. to about 160°C. The reaction can be carried out in the presence of an inert solvent such as cyclohexane, n- hexane, n-heptane, benzene or xylene. Suitable inert solvents are employed if dilution or a lower viscosity of the mixture is desired. The dilution of the olefin copolymer is optional in that it is already in liquid form. However, for a more controlled reaction rate, dilution may be desirable. Furthermore, the use of lower temperatures than the ab,ove-mentioned range is also optional depending on the requirements of the reaction medium. After being charged with the reactants and optionally the inert solvent, the reactor is sealed, flushed with nitrogen, and the temperature of the reactor is raised to the desired value. The contents of the reactor are continuously stirred as the reaction proceeds to completion. Typically, the reaction is completed in about three half-lives of the initiator. The relative amount of ethylene-alphaolefin copolymer, carboxylic acid and/or anhydride and free radical initiator which can be used in carrying out the reaction to form the carboxyl-modified copolymer depend on factors such as the type and molecular weight of the olefin polymer, the type of carboxylic compound, the type of free radical initiator, the temperature of the reaction, the amount of carboxyl functionality desired in the reaction product and the purity of the reagents. The determination of the reaction conditions in light of these factors would be considered an obvious expedient to one of skill in the art in view of the general parameters outlined above and illustrated in the working examples hereinafter set forth. In general, the amounts of ethylene-alphaolefin copolymer and carboxylic acid/anhydride will be such as to provide a carboxylate-modified ethylene-alphaolefin polymer possessing a functionality of at least about 0.5, preferably at least about 0.8 and more preferably at least about 0.9.

The foregoing carboxyl-modified olefin polyolefin is reacted with an aminobenzothiazole of the general formula:

in which R is hydrogen or a branched or straight chain radical having from 4 to about 24 carbon atoms that can be alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl, aminoalkyl or halogen such as fluoro, chloro or bromo. Specific aminobenzothiazoles that can be used herein include 2-aminobenzothiazole, 4-amino-2 , 1, 3-benzothiadiazole, 2-amino- 6-ethoxybenzothiazole,2-amino-6-fluorobenzothiazole, and the like.

Optionally, a minor amount of the aminobenzothiazole, e.g., up to about 30 mole percent and preferably not more than about 20 mole percent thereof, can be replaced with one or more other amines such as aminopropylmorpholine, aminoethylmorpholine, N',N'- dimethylaminoproplyamine, N' ,N'-dimethylethylamine and N- methylaminopropylpiperazine. The selected carboxyl-modified ethylene- alphaolefin copolymer, aminobenzothiazole and other amine(s) , if utilized, can be readily reacted in an oil solution at from about 100° to about 250°C and preferably from about 125° to about 175°C for from about 1 to about 10 hours and preferably from about 2 to about 6 hours. Reaction ratios of carboxyl-modified ethylene-alpha olefin copolymer to equivalents of aminobenzothiazole and optional additional amine(s) can vary considerably. For example, when the ethylene-alphaolefin has been modified with a dicarboxylic acid or anhydride such as maleic anhydride, from about 0.5 to about 1.0 and preferably from about 0.1 to about 0.6, moles of dicarboxylic acid moiety content per equivalent of amine(s) can be utilized. When the modifying acid is a onocarboxylic acid such as acrylic acid, from about 0.05 to about 1.0, and preferably from about 0.1 to about 0.6, moles of monocarboxylic acid moiety content per equivalent of amine(s) can be used. The reaction can be conducted in a polar or non-polar solvent and is preferably conducted in the presence of a mineral or synthetic lubricating oil.

The ashless additives of this invention can be utilized in lubricating oil compositions in amounts which impart significant friction modifying and VI index improving credit characteristics to the oils. Concentrations of additive of from about 0.001 to about 10 weight percent based on the total weight of the lubricating oil composition can be used. Preferably, the concentration is from about 0.1 to about 3 weight percent. In general, mineral oils, both paraffinic, naphthenic and mixtures thereof, can be employed as the lubricant vehicles, and can be of any suitable lubricating viscosity range, as for example, from about 2 cSt at 100°C to about 1,000 cSt at 100°C and preferably from about 2 to about 100 cSt at 100°C. These oils can have viscosity indices preferably ranging to about 180. The average molecular weights of these oils can range from about 250 to about 800. Where synthetic oils are employed, they can include, but are not limited to, polyisobutylenes, polybutenes, hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylolpropane esters, neopentyl and pentaerythritol esters, di(2-ethylhexyl) sebacate, di(2- ethylhexyl) adipate, dibutyl phthalate, fluorocarbons, silicate esters, silanes, esters of phosphorus-containing acids, liquid ureas, ferocene derivatives, hydrogenated synthetic oils, chain-type polyphenyls, siloxanes and silicones (polysiloxanes) , alkyl-substituted diphenyl ethers typified by a butyl-substituted bis(p-phenoxy phenyl) ether, and phenoxy phenylethers.

The lubricating oil compositions herein can also contain one or more other additives such as detergents, corrosion inhibitors, oxidation inhibitors, dispersants, pour point dispersants, anti-foaming agents, anti-wear agents, other friction and/or VI modifiers, and the like, at the usual levels in accordance with well known practice. The following examples are illustrative of the invention.

EXAMPLE 1 This example illustrates the preparation of a maleic anhydride-modified ethylene-propylene-diene monomer terpolymer.

Trilene® CP-4038 (50 kg) (Uniroyal Chemical Company, Inc.), an ethylene-propylene-copoly er containing approximately 43 ethylene copolymer containing approximately 43 ethylene and approximately 57 propylene and, a number average molecular weight of about 4000, a kinematic viscosity of about 2000 cSt at 100°C, and acetone (0.75 kg) were charged to a reactor, the reactor was purged with nitrogen and then heated to 160°C. Maleic anhydride (3.75 kg), di-t-butyl peroxide (0.75 kg) and acetone (6.0 kg) were continuously added to the reactor over 2 hours. Excess acetone was distilled off, the reactor was held at temperature for an additional hour and excess maleic anhydride was distilled over 2 hours. The resulting ethylene-propylene-copolymer contained approximately 0.02 mole percent grafted maleic anhydride.

EXAMPLE 2

This example illustrates the preparation of an ashless lubricant additive according to the invention employing the carboxyl-modified ethylene-propylene-copolymer intermediate of Example 1. Carboxyl-modified ethylene-propylene-copolymer of

Example 1 (40 g) was charged into a 500 ml 3-neck reactor together with a solvent-extracted neutral oil (250 g) . The reactor was equipped with a mechanical stirrer, thermometer, thermocouple and nitrogen inlet. The temperature was raised to 90°C and thereafter 2-amino-6-ethoxybenzothiazole (6.4 g) was charged to the reactor. The temperature was increased to 160°C and held there for 3 hours. The product was filtered through celite. The product (an approximately 16% concentrate) possessed a kinematic viscosity (100°C) of about 22.5 centistokes.

EXAMPLE 3 This example illustrates the preparation of another ashless lubricant additive according to the invention.

Carboxyl-modified ethylene-propylene-copolymer of Example 1 (30 g) was charged into the same reactor setup as employed in Example 2. The temperature was raised to 90°C and thereafter 2-amino-t-fluorobenzothiazole (4.2 g) was charged to the reactor. The temperature was increased to

160°C and held there for 3 hours. The product was filtered through celite. The product (an approximately 15% concentrate) possessed a kinematic viscosity (100°C) of about 18.5 centistokes. EXAMPLE 4 This example illustrates the friction modifying properties of the additive of Example 2 in a fully formulated lubricating oil compared with those of the same oil containing no friction modifier (control) or unmodified (i.e., nongrafted) Trilene® CP-4038 terpolymer.

The friction modifying properties were measured by a Cameron-Plint TE77 High Frequency Friction Machine employing the test procedure hereinafter described. 10 mL of an oil sample containing additive (or no additive in the case of the control) is placed in the test chamber so as to cover a flat stationary Hardened ground NSOH BOl Gauge Plate (RC 60/0.4 micron) . A reciprocating specimen, a 16 mm long nitride steel dowel pin (6 mm diameter, 60 Re) , is placed on top of the s,teel plate under 50 Newton load, allowed to heat up to 35°C from room temperature over 10 minutes and maintained at 35°C for 5 minutes. Then, with the 50 Newton load in place the reciprocation frequency of 5 Hertz is begun with a 15 millimeter amplitude stroke length. The temperature is then ramped up to 50°C over 10 minutes and maintained at 50°C for 5 minutes. The load is then increased to 100 Newtons and the temperature is ramped up to 165°C over 1 hour. Friction Coefficient data is collected between 60-160°C. The flat specimen is cleaned between runs with hexane and #500 emery cloth. A new dowel pin or surface of the dowel pin is used each time. A reference oil is run alternately between experimental oils. The same flat specimen is used until the reference oil no longer provides reproducible results. The motor oil formulation tested was an SAE 10W-30 grade oil containing dispersant, detergent, antioxidant, rust inhibitor, pour point depressant, OCP VI Improver, and anti-wear additive. Friction modifier was added as a top treat to this formulation. The measured friction coefficient values are set forth in the following Table. A decrease in friction coefficient indicates an increase in friction reduction at the operating temperatures indicated.

Table

Friction

Weiqht % Coefficient

Additive 60°C 100°C 160°C

Additive of Example 2 1 0.117 0.120 0.095 Unmodified Trilene® CP-4038 1 0.124 0.127 0.125 No Additive 0 0.120 0.126 0.130 Additive of Example 2 2 0.125 0.125 .0725

Claims

WHAT IS CLAIMED IS:

1. An ashless additive for a lubricating oil composition which comprises a polyolefin derived from the reaction of an ethylene-alphaolefin copolymer possessing a number average molecular weight of from about 250 to about 15,000 and an unsaturated carboxylic acid and/or anhydride thereof, the resulting carboxyl-modified polyolefin being further reacted with an aminobenzothiazole.

2. The additive of Claim 1 which is derived from an ethylene-propylene copolymer or ethylene-propylene-diene terpolymer.

3. The additive of Claim 2 wherein the number average molecular weight of the copolymer or terpolymer is from about 1,000 to about 12,000.

4. The additive of Claim 1 wherein the unsaturated carboxylic anhydride is maleic anhydride.

5. The additive of Claim 1 wherein the aminobenzothiazole possesses the general formula

in which R is hydrogen or a branched or straight chain radical having from 4 to about 24 carbon atoms selected from the group consisting of alkyl, alkenyl, alkoxyl, aralkyl, alkaryl, hydroxyalkyl and aminoalkyl, or halogen.

6. The additive of Claim 5 wherein the aminobenzothiazole is selected from the group consisting of 2-aminobenzothiazole,2-amino-6-ethoxybenzothiazole, and 2- amino-6-fluorobenzothiazole.

7. The additive of Claim 1 wherein the carboxyl- modified polyolefin is further reacted with an aminobenzothiazole and at least one other a ine.

8. The additive of Claim 7 wherein the other amine is selected from the group consisting of aminopropylmorpholine, aminoethyl orpholine, N',N'- dimethylaminoproplyamine, N' ,N'-dimethylethylamine and N- methylaminopropylpiperzine.

9. A lubricating oil composition comprising a lubricating oil and friction modifying effective amount of an ashless additive which is a polyolefin derived from the reaction of an ethylene-alphaolefin copolymer possessing a number average molecular weight of from about 250 to about 15,000 and an unsaturated carboxylic acid and/or anhydride thereof, the resulting cafboxyl-modified polyolefin being further reacted with an aminobenzothiazole.

10. The lubricating oil composition of Claim 9 wherein the additive from an ethylene-propylene copolymer or ethylene-propylene-diene terpolymer.

11. The lubricating oil composition of Claim 10 wherein the number average molecular weight of the copolymer or terpolymer is from about 1,000 to about 12,000.

12. The lubricating oil composition of Claim 9 wherein the unsaturated carboxylic anhydride is maleic anhydride.

13. The lubricating oil composition of Claim 9 wherein the aminobenzothiazole possesses the general formula

14. The additive of Claim 13 wherein the aminobenzothiazole is selected from the group consisting of 2-aminobenzothiazole,2-amino-6-ethoxybenzothiazole, and 2- amino-6-fluorobenzothiazole.

15. The lubricating oil composition of Claim 9 wherein the carboxyl-modified polyolefin is further reacted with an aminobenzothiazole and at least one other amine.

16. The lubricating oil composition of Claim 15 wherein the other amine is selected from the group consisting of aminopropylmorpholine, aminoethylmorpholine,

N' ,N'-dimethylaminoproplyamine, N' ,N ' -dimethylethylamine and N-methylaminopropylpiperzine.

17. A method for modifying the friction properties of a lubricating oil which comprises adding to the oil a friction modifying effective amount of an ashless additive which is a polyolefin derived from the reaction of an ethylene-alphaolefin copolymer possessing a number average molecular weight of from about 250 to about 15,000 and an unsaturated carboxylic acid and/or anhydride thereof, the resulting carboxyl-modified polyolefin being further reacted with an aminobenzothiazole.

18. The method of Claim 17 wherein the additive is derived from an ethylene-propylene copolymer or ethylene- propylene-diene terpolymer.

19. The method of Claim 18 wherein the number average molecular weight of the copolymer or terpolymer is from about 1,000 to about 12,000.

20. The method of Claim 17 wherein the unsaturated carboxylic anhydride is maleic anhydride.

21. The method of Claim 17 wherein the aminobenzothiazole possesses the general formula

22. The additive of Claim 21 wherein the aminobenzothiazole is selected from the group consisting of 2-aminobenzothiazole,2-amino-6-ethoxybenzothiazole, and 2- amino-6-fluorobenzothiazole.

23. The method of Claim 17 wherein the carboxyl- modified polyolefin is further reacted with an aminobenzothiazole and at least one other amine.

24. The method of Claim 23 wherein the other amine is selected from the group consisting of aminopropylmorpholine, aminoethylmorpholine, N',N'- dimethylaminoproplyamine, N' ,N'-dimethylethylamine and N- methyla inopropylpiperzine.