EP0444830A1

EP0444830A1 - Succinimide composition

Info

Publication number: EP0444830A1
Application number: EP91301434A
Authority: EP
Inventors: Roger Scattergood; David Kenvyn Walters; John F. Sieberth
Original assignee: Afton Chemical Ltd
Current assignee: Afton Chemical Ltd
Priority date: 1990-02-26
Filing date: 1991-02-22
Publication date: 1991-09-04

Abstract

Lubricants and lubricating oils are provided which contain an oil-soluble copper-containing antioxidant and an oil-soluble dispersant prepared by a process which comprises (i) reacting at least one polyamine with at least one acyclic hydrocarbyl substituted succinic acylating agent in which the substituent contains an average of at least about 40 carbon atoms, and (ii) reacting the product so formed with a vicinal dicarboxylic acylating agent having 4 to about 30 carbon atoms in the molecule, the process being characterized in that in step (i) the acylating agent is reacted with the polyamine in a mole ratio of from 1.05 to about 2.85 moles of acylating agent per mole of polyamine, and in that in step (ii) the mole ratio of the vicinal dicarboxylic acylating agent is from 0.10 to 2.50 moles per mole of said polyamine with the proviso that the total mole ratio of the acylating agents in (i) and (ii) per mole of said polyamine is at least 2.40. Such compositions exhibit enhanced compatibility toward fluoroelastomers while at the same time possess enhanced oxidative and thermal stability.

Description

Technical Field

This invention relates to succinimide compositions. More particularly, this invention relates to lubricants and lubricating oil additive concentrates of enhanced performance capabilities.

Background

A continuing problem in the art of lubrication is to provide lubricant compositions which satisfy the demands imposed upon them by the original equipment manufacturers. One such requirement is that the lubricant not contribute to premature deterioration of seals, clutch face plates or other parts made from fluoroelastomers. Unfortunately, and as is well known, succinimide dispersants commonly used in oils tend to exhibit a strong adverse effect upon fluoroelastomers, by causing them to lose their flexibility and tensile strength, to become embrittled, and in severe cases, to disintegrate. It has been postulated that the co-presence of zinc-containing additives such as zinc dialkyldithiophosphates tends to increase the severity of this problem. Contemporary test methods for evaluating fluoroelastomer compatibility of lubricant compositions are the Volkswagen P.VW 3334 Seal Test and the CCMC Viton Seal Test (CEL L-39-T-87 Oil/Elastomer Compatibility Test). An effective, practical way of overcoming this adverse property of succinimide dispersants would be a welcome contribution to the art.
In providing lubricant compositions suitable for commercial use, it is also necessary that the lubricant possess enhanced stability against oxidative and/or thermal degradation during storage and use. Heretofore, oil-soluble copper containing antioxidants have been described for use as lubricant additives. See in this connection U.S. Patent Nos. 4,122,033 and 4,486,326, Published European Patent Application No. 24146, and published U.K. Patent Application No. 2 056 482. U.S. 4,122,033 recommends that the copper antioxidants be utilized in combination with an aliphatic amine in order to achieve an improved effect.
Unfortunately, oil-soluble organic copper compounds can themselves be thermally or oxidatively degraded under service conditions whereby the lubricant can be deprived of its soluble copper content due to sludge formation.

The Invention

This invention provides compositions capable of exhibiting enhanced compatibility toward fluoroelastomers while at the same time possessing enhanced oxidative and thermal stability.
In accordance with one of its embodiments, this invention provides a lubricant composition which comprises:
(a) a major amount of lubricating oil; (b) a minor but effective amount of at least one oil-soluble copper-containing antioxidant; and (c) a minor but effective amount of at least one oil-soluble dispersant prepared by a process which comprises (i) reacting at least one polyamine with at least one acyclic hydrocarbyl substituted succinic acylating agent in which the substituent contains an average of at least about 40 carbon atoms, and (ii) reacting the product so formed with a vicinal dicarboxylic acylating agent having 4 to about 30 carbon atoms in the molecule, the process being characterized in that in step (i) the acylating agent is reacted with the polyamine in a mole ratio of from 1.05 to about 2.85 moles of acylating agent per mole of polyamine, and in that in step (ii) the mole ratio of the vicinal dicarboxylic acylating agent is from 0.10 to 2.50 moles per mole of said polyamine with the proviso that the total mole ratio of the acylating agents in (i) and (ii) per mole of said polyamine is at least 2.40:1. Preferably, the total mole ratio of acylating agents in (i) and (ii) per mole of said polyamine is in the range of 2.70:1 to 5.00:1, and most preferably is at least 3.05:1.
In another of its embodiments, this invention provides lubricant additive concentrates comprising components (b) and (c) above.
Pursuant to still further embodiments of this invention there are provided lubricating oil additive concentrates and lubricating oil compositions as just described which additionally contain a zinc-containing additive complement, especially one or a mixture of zinc dihydrocarbyldithiophosphates, such as one or a combination of zinc dialkyldithiophosphates, one or a combination of zinc diaryldithiophosphates, or a combination of one or more zinc dialkyldithiophosphates with one or more zinc diaryldithiophosphates.
A feature of this invention is that the lubricant compositions exhibit enhanced compatibility toward fluoroelastomers and enhanced oxidative and thermal stability as compared to corresponding lubricants devoid of component (b) or component (c), or both of components (b) and (c). This invention thus provides, inter alia, new and highly effective compositions which exhibit good dispersancy while at the same time exhibiting good compatibility with fluoroelastomers and good stability during storage and service conditions. The additive components utilized enhance the stability of the lubricants during service conditions by preventing or at least inhibiting loss of soluble copper content by way of sludge formation.
In a preferred embodiment of this invention the reactants used in forming component (c) above are employed in relative proportions such that the molar ratio of acylating agent(s) in (i) : acylating agent(s) in (ii) is above 1:1, more preferably above 1.4:1, and most preferably in the range of 1.45:1 to 2.70:1.
Preferred lubricants and functional fluids provided for use and used pursuant to this invention include those which pass either (a) the Volkswagen P.VW 3334 Seal Test, or (b) the CCMC Viton Seal Test, CEC L-39-T-87 Oil/Elastomer Compatibility Test, or most preferably, both such tests. The Volkswagen P.VW 3334 Seal Test involves keeping a test specimen of fluoroelastomer (VITON AK6) in an oil blend at 150°C for 96 hours and then comparing both the change in elongation to break and the tensile strength of the test specimen to the corresponding properties of a fresh specimen of the same fluoroelastomer. The exposed test specimen is also examined for the presence of cracks. In these tests, a lubricant passes the test if the exposed test specimen exhibits a change in elongation to break (as compared to an untested specimen) of no more than -25% and a tensile strength (as compared to an untested specimen) of no more than -20%, and possesses no cracks. The CCMC Viton Seal Test is similar to the VW Test except that it is a 7-day test rather than a 4-day test, the elastomer is VITON RE I, and the pass/fail points are -50% tensile strength and -60% elongation.
These and other embodiments and features of this invention will be apparent from the ensuing description and appended claims.

Copper-Containing Antioxidants

Any of a wide variety of oil-soluble organic copper compounds can be used in the practice of this invention. The copper compounds may be utilized either singly or in various combinations or mixtures. By oil-soluble is meant that the compound is soluble under normal blending conditions in the oil or additive concentrate.
One preferred type of copper-containing antioxidant are the oil-soluble copper salts of synthetic or natural carboxylic acids, that is, oil-soluble copper carboxylate compounds. The copper carboxylate compound may be added in the cuprous or cupric form, and can comprise a copper monocarboxylate or polycarboxylate, such as for example the dicarboxylates, tricarboxylates, etc. The carboxylate moiety of such compounds can thus be derived from a monocarboxylic acid or a polycarboxylic acid. The monocarboxylic acids may be represented by the formula RCOOH and the polycarboxylic acids may be represented by the formula R'(COOH)_n wherein R and R' are hydrocarbyl groups containing a sufficient number of carbon atoms to render the copper carboxylate oil-soluble and n is an integer averaging at least 2, preferably 2 to 4, and most preferably 2 to 3. Thus the hydrocarbyl groups R and R' will usually contain 5 to 40 carbon atoms, typically from 12 to 24 carbon atoms, and in most cases from 14 to 20 carbon atoms.
Exemplary R groups are alkyls of from 5 to 34 carbon atoms, preferably 11 to 23 carbon atoms, and can be branched or straight chained, e.g., heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, 2-methylhexyl, 3,5-diethyloctyl; and alkenyls of from 6 to 36 carbon atoms, such as octenyl, dodecenyl, eicosenyl, and the like. When R is aryl, the aryl group will generally contain from 6 to 20 carbon atoms, e.g., phenyl, naphthyl and the like. When R is alkaryl, each above aryl group can be substituted by alkyl groups, which can be branched or straight chained, and the total carbon atoms in such alkaryl groups will generally contain from 7 to 34, preferably 11 to 23, carbon atoms. Illustrative of such alkaryl groups are -Ar(CH₃), -Ar(C₂H₅), -Ar(C₉H₁₉), -Ar(C₄H₉)₂, -Ar(CH₃)₂, -Ar(C₁₀H₂₁), and the like, wherein "Ar" is a phenyl ring. When R is aralkyl, the alkyl group, which can be branced or straight chained, can contain from 1 to 28 carbon atoms, and can be substituted by from 1 to 3 (e.g., 1 or 2) aryl groups, such as those described above (e.g., phenyl). Examples of such aralkyl groups are ArCH₂-, ArC₂H₄-, ArC₈H₁₆-, ArC₉H₁₈-, CH₃CH(Ar)C₆H₁₂-, and the like. When R is cycloalkyl, the cycloalkyl group will generally contain from 3 to 18 carbon atoms, e.g., cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, cyclododecyl and the like.
Exemplary of R' groups are straight chain alkylene of from 2 to 33 carbon atoms, e.g., -(CH₂)_x-, wherein x is from 2 to 33, such as -C₃H₆-, -C₈H₁₆-, -C₁₀H₂₀-, -C₁₂H₂₄-, -C₁₄H₂₈-, and the like. When R' is alkenylene, the R' group will generally contain from 4 to 33 carbon atoms, e.g., -CH=C₂H₃-, -CH₂CH=CHC₄H₈- and the like. When R' is arylene, the arylene group will generally contain from 6 to 20 carbon atoms, e.g., phenylene, naphthylene, and the like. The arylene groups may be alkyl substituted by from 1 to 14 carbon atoms. Exemplary of such alkarylene groups are -Ar(CH₃)-, -Ar(C₂H₅)-, -Ar(CH₃)₂-, -Ar(CH₃)₃-, and the like, wherein "Ar" is a benzene ring. When R' is aralkylene, the alkylene groups as described above, can be substituted by one or more (e.g., 1-3) aryl groups, e.g., phenyl, tolyl, etc.
Examples of suitable carboxylic acids include C₁₀ to C₁₈ fatty acids such as dodecanoic, myristic, lauric, stearic and palmitic acids, unsaturated acids such as oleic and linoleic acids, and branched carboxylic acids such as naphthenic acids of molecular weight from 200 to 500, neodecanoic or 2-ethylhexanoic acid, cyclohexane carboxylic acid, phenylacetic acid, benzoic acid, alkyl or alkenyl substituted dicarboxylic acids such as polyalkene substituted succinic acids, e.g. octadecenyl succinic acids, dodecenyl succinic acids and polyisobutenyl succinic acids, and such polycarboxylic acids as phthalic acid, isophthalic acid, terephthalic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, penta-, hexa-, hepta-, and octadecanedioic acids, and the like.
Another type of oil-soluble organic copper compounds suitable for use in the practice of this invention are the copper dithiocarbamates of the general formula (RR'NCSS)_nCu, where n is 1 or 2 and R and R' are the same or different and are hydrogen atoms or, more preferably, hydrocarbyl groups, preferably containing 1 to 18, and most preferably 2 to 12 carbon atoms such as alkyl, alkenyl, aryl, aralkyl, alkaryl and cycloalkyl radicals. Thus the hydrocarbyl groups of the dithiocarbamates include ethyl, propyl, butyl, isobutyl, sec-butyl, amyl, hexyl, 4-methylpentyl, octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, tolyl, butylphenyl, benzyl, phenethyl, methylcyclopentyl, propenyl, butenyl, dodecenyl, heptynyl, and cyclopropylcarbinyl, among others.
Still another group of oil-soluble organic copper compounds which may be used in the practice of this invention are the oil-soluble copper dihydrocarbyl thiophosphates and the oil-soluble copper hydrocarbyl dithiophosphates wherein the hydrocarbyl groups preferably contain from 1 to 18, and more preferably from 2 to 12 carbon atoms.
Other types of oil-soluble organic copper compounds which can be used in the practice of this invention include, but are not limited to, copper mercaptides, copper disulfides, copper thioxanthates, copper sulphonates, copper phenates, copper acetylacetonates, copper acetoacetic acid ester complexes, copper complexes of oil-soluble hydrocarbon substituted mono- or bis-oxazolines, and copper complexes of oil-soluble hydrocarbon substituted lactone oxazolines. The copper antioxidants are non-overbased compounds, i.e., they are not reacted with carbon dioxide under conditions that would form a carbonate-containing copper compound or complex. Thus the total base number (ASTM D2896) of the copper antioxidants is less than 50 and preferably less than 20.
Illustrative oil-soluble copper compounds which may be used in accordance with this invention include cuprous diphenyl dithiophosphate, cuprous di-sechexyl dithiophosphate, cuprous di-isooctyldithiophosphate, cupric naphthenate, cupric oleate, cupric dithiocarbamate, cupric diethyldithiocarbamate, cupric dibutyldithiocarbamate, cupric dioctyldithiocarbamate, lactone oxazoline complexed with copper thiocyanate, bis-oxazoline complexed with copper thiocyanate, bis-oxazoline complexed with copper acetate, copper acetylacetonate, copper octylacetoacetate, and the like.
The copper-containing antioxidant is employed in the lubricating oil compositions in amounts in the range of 40 to 500, and preferably in the range of 60 to 300, and most preferably, in the range of 100 to 200 parts by weight of copper, per million parts by weight of the lubricant.

Succinimide Dispersants

As noted above, the succinimide dispersants are prepared by reacting a polyamine with an acyclic hydrocarbyl-substituted succinic acid acylating agent and then reacting the product so formed with a suitable vicinal dicarboxylic acylating agent. As also noted above, the reactants are suitably proportioned such that the final succinimide dispersant exhibits enhanced compatibility toward fluoroelastomers.
Acyclic hydrocarbyl-substituted succinic acid acylating agents and methods for their preparation are well known to those skilled in the art and are extensively reported in the patent literature. See for example the following U.S. Patents:

The disclosures of the foregoing patents are incorporated herein by reference as regards acyclic hydrocarbyl substituted succinic acylating agents and methods for their production. As indicated in such prior patents, the acyclic hydrocarbyl substituted succinic acylating agents include the hydrocarbylsubstituted succinic acids, the hydrocarbyl-substituted succinic anhydrides, the hydrocarbyl-substituted succinic acid halides (especially the acid fluorides and acid chlorides), and the esters of the hydrocarbyl-substituted succinic acids and lower alcohols (e.g., those containing up to 7 carbon atoms), etc., that is, hydrocarbyl-substituted compounds which can function as carboxylic acylating agents. Of these compounds, the hydrocarbyl-substituted succinic acids and the hydrocarbyl-substituted succinic anhydrides and mixtures of such acids and anhydrides are generally preferred, the hydrocarbyl-substituted succinic anhydrides being particularly preferred.
Preferably, the hydrocarbyl substituent of the succinic acylating agent used in step (i) is an alkyl or, more preferably, an alkenyl group containing 50 and more preferably 70 or more carbon atoms. Particularly preferred acylating agents for use in (i) have alkenyl substituents with a number average molecular weight (as determined by gel permeation chromatography) of at least 980 (and more preferably in the range of 1,200 to 5,000), especially where the alkenyl substituents are formed from polyolefins made from C₃ or C₄ olefins (e.g., isobutylene, 1-butene, and mixtures of butenes containing the same as the predominant components). Polyisobutenylsuccinic acids, polyisobutenyl succinic anhydrides, and mixtures of polyisobutenylsuccinic acids and polyisobutenylsuccinic anhydrides are most especially preferred for use in the practice of step (i) above.
Suitable polyamines for use in step (i) above are described in many of the above cited U.S. Patents and thus the disclosure of such patents relating to polyamines used in the preparation of hydrocarbyl-substituted succinimides are incorporated herein by reference as if fully set forth herein. For best results, the polyamines should contain at least two primary amino groups in the molecule.
The preferred polyamines used in the practice of this invention are the alkylene polyamines represented by the formula

H₂N(CH₂)_n(NH(CH₂)_n)_mNH₂

wherein n is 2 to 10 (preferably 2 to 4, more preferably 2 to 3, and most preferably 2) and m is 0 to 10, (preferably 1 to 6). Illustrative are ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, spermine, pentaethylene hexamine, propylene diamine (1,3-propanediamine), butylene diamine (1,4-butanediamine), hexamethylene diamine (1,6-hexanediamine), decamethylene diamine (1,10-decanediamine), and the like. Preferred for use is tetraethylene pentamine or a mixture of ethylene polyamines which approximates tetraethylene pentamine such as "DOW E-100" (a commercial mixture available from Dow Chemical Company, Midland, Michigan).
As used herein the term succinimide is meant to encompass the completed reaction product from steps (i) and (ii) and is intended to encompass compounds wherein the product may have amide, amidine, and/or salt linkages in addition to the imide linkage of the type that results from the reaction of a primary amino group and an anhydride moiety.
The acylating agent utilized in step (ii) above is (1) one or a mixture of vicinal dicarboxylic acids containing from 4 to 30 (preferably 4 to 10) carbon atoms in the molecule and characterized in that the two carboxyl groups are separated from each other by two aliphatic carbon atoms, or (2) one or a mixture of anhydrides, acid halides, or esters of such dicarboxylic acids, or (3) any combination of (1) and (2). Among suitable acylating agents for use in step (ii) are:

(a) one or a mixture of vicinal dicarboxylic acids of the formula
wherein each of R₁ and R₂ is, independently, a hydrogen atom, an alkyl or alkenyl group, or a hydroxyl group; or
(b) the anhydride, acid halide, or ester of such vicinal dicarboxylic acid(s) of (a); or
(c) a combination of at least one component from (a) and at least one component from (b); or
(d) one or a mixture of vicinal dicarboxylic acids of the formula
wherein each of R₁ and R₂ is, independently, a hydrogen atom, or an alkyl or alkenyl group; or
(e) the anhydride, acid halide, or ester of such vicinal dicarboxylic acid(s) of (d) or;
(f) a combination of at least one component from (d) and at least one component from (e); or
(g) any combination of at least one component from (a), (b), and/or (c), and at least one component from (d), (e), and/or (f).

Such acylating agent thus encompasses such compounds as maleic anhydride, maleic acid, fumaric acid, malic acid, thiomalic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, chloromaleic acid, ethylmaleic anhydride, dimethylmaleic anhydride, ethylmaleic acid, dimethylmaleic acid, hexylmaleic acid, succinic acid, succinic anhydride, butylsuccinic anhydride, octenylsuccinic anhydride, hexenylsuccinic anhydride, octadecenylsuccinic anhydride, eicosenylsuccinic anhydride, docosenylsuccinic anhydride, etc., and the corresponding acid halides, or esters which are preferably esters of lower alcohols.
As noted above, the succinimide dispersants utilized pursuant to this invention are prepared by a process which comprises (i) reacting at least one polyamine with at least one oil soluble acyclic hydrocarbyl substituted succinic acylating agent in which such acyclic hydrocarbyl substituent contains an average of at least 40 carbon atoms, such reaction being conducted using proportions such that the acylating agent is reacted with the polyamine in a mole ratio of from 1.05 to 2.85 moles per mole of polyamine, and (ii) reacting the product so formed with (a) at least one vicinal dicarboxylic acid acylating agent containing 4 to 30 carbon atoms in the molecule and in which the two carboxyl groups are separated from each other by two aliphatic carbon atoms, or (b) an anhydride, acid halide, or ester of at least one such dicarboxylic acid acylating agent, or (c) a combination of (a) and (b), using in the reaction of (ii) proportions such that the mole ratio of such acylating agent is from 0.10 to 2.50 moles per mole of said polyamine with the proviso that the total mole ratio of the acylating agents in (i) and (ii) per mole of said polyamine is at least 2.40, and preferably in the range of 2.40 to 5.00, most preferably in the range of 3.05 to 4.50.
The reactions involved in steps (i) and (ii) are conducted at conventional temperatures in the range of about 80°C to 200°C, more preferably 140°C to 180°C. These reactions may be conducted in the presence or absence of an ancillary diluent or liquid reaction medium, such as a mineral lubricating oil solvent. If the reaction is conducted in the absence of an ancillary solvent of this type, such is usually added to the reaction product on completion of the reaction. In this way, the final product is in the form of a convenient solution in lubricating oil and thus is compatible with a lubricating oil base stock. Suitable solvent oils are the same as the oils used as a lubricating oil base stock and these generally include lubricating oils having a viscosity (ASTM D 445) of 2 to 40, preferably 3 to 12 mm²/sec at 100°C, with the primarily paraffinic mineral oils such as Solvent 100 Neutral being particularly preferred. Other types of lubricating oil base stocks can be used, such as synthetic lubricants including polyesters, hydrogenated and unhydrogenated poly-α-olefins, and the like. Blends of mineral oil and synthetic lubricating oils are also suitable for various applications in accordance with this invention.

Additive Concentrates

The additive concentrates of this invention will generally contain a suitable diluent or solvent such as a natural or synthetic lubricating oil of appropriate viscosity, together with the above-described oil-soluble copper-containing antioxidant and the above-described succinimide dispersant. Ordinarily the concentrate will contain the copper-containing antioxidant or mixture of copper-containing antioxidants and the succinimide or mixture of succinimide dispersants in relative amounts such that there is 0.0001 to 0.5, preferably from 0.0004 to 0.1, and most preferably from 0.001 to 0.01 part by weight of copper per part by weight of the succinimide dispersant(s). However, departures from these ranges are permissible and are within the scope of this invention whenever such departures are deemed necessary or appropriate under any given set of circumstances.
Preferred additive concentrates of this invention will additionally contain customary proportions of one or more additional components of the type described hereinafter.

Lubricant Base Stocks

The dispersant-antioxidant combinations utilized according to the invention can be incorporated in a wide variety of lubricants. They can be used in lubricating oil compositions, such as automotive crankcase lubricating oils, automatic transmission fluids, gear oils, etc. in effective amounts to provide succinimide dispersant concentrations in finished formulations generally within the range of 0.5 to 10 weight percent, for example, 1 to 9 weight percent, preferably 2 to 8 weight percent, of the total composition. The dispersants can be admixed separately with the lubricating oils as solution concentrates in a suitable oil. These solutions may contain as much as 50 weight percent or more of the active ingredient additive compound dissolved in mineral oil, preferably a mineral oil having an ASTM D-445 viscosity of 2 to 40, preferably 3 to 12 centistokes at 100°C. The lubricating oil includes not only hydrocarbon oils of lubricating viscosity derived from petroleum but also include synthetic lubricating oils such as hydrogenated and unhydrogenated polyolefin oils such as decene trimer; alkyl esters of dicarboxylic acids, complex esters of dicarboxylic acid, polyglycol and alcohol; alkyl esters of carbonic or phosphoric acids; polysilicones; fluorohydrocarbon oils; and mixtures of mineral lubricating oils and synthetic oils in any proportions, etc. Natural oils, including vegetable oils such as rapeseed oil can also be used either alone or in combination with other lubricant types. The term lubricating oil for this disclosure includes all the foregoing. The succinimide dispersant may be conveniently dispersed as a concentrate of 10 to 80 weight percent of mineral oil, e.g., Solvent 100 Neutral oil with or without other additives being present, and such concentrates are a further embodiment of this invention.

Additional Components

Finished lubricating oil compositions and additive concentrates of this invention are prepared containing the oil-soluble copper-containing antioxidant and a succinimide dispersant produced as described above, together with conventional amounts of one or more other additives to provide their normal attendant functions. Thus use may be made of such conventional additives as viscosity index improvers, dispersant viscosity index improvers, rust inhibitors, metal detergent additives, antiwear additives, extreme pressure additives, and the like. If desired, additional antioxidants such as phenolic antioxidants, amine antioxidants, etc., can be utilized in the compositions of this invention. Reference may be had to the various U.S. Patents referred to hereinabove for exemplary disclosures of various conventionally used additives for lubricating oils.
A particularly preferred ancillary additive used in the lubricant and lubricant additive compositions is a grafted copolymer dispersant VI improver of the type described in U.S. Pat. No. 4,519,929, all disclosure of which is incorporated herein by reference.
Among the well-known additional additives that can be used in forming finished lubricants or finished additive concentrates of this invention are such substances as the zinc dialkyl (C₃-C₈) dithiophosphate wear inhibitors, generally present in amounts of about 0.5 to 5 weight percent. Useful detergents include the oil-soluble normal basic or over-based metal, e.g., calcium, magnesium, barium, etc., salts of petroleum naphthenic acids, petroleum sulfonic acids, alkyl benzene sulfonic acids, oil-soluble fatty acids, alkyl salicylic acids, sulfurized or unsulfurized alkyl phenates, and hydrolyzed or unhydrolyzed phosphosulfurized polyolefins. Gasoline engine crankcase lubricants typically contain, for example, from 0.5 to 5 weight percent of one or more detergent additives. Diesel engine crankcase oils may contain substantially higher level of detergent additives. Preferred detergents are the calcium and magnesium normal or overbased phenates, sulfurized phenates or sulfonates.
Oxidation inhibitors include hindered phenols (e.g., 2,6-di-tert-butyl-para-cresol, 2,6-di-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), and mixed methylene bridged polyalkyl phenols), amines (e.g. octylated diphenylamine and nonylated diphenylamine), sulfurized phenols and alkyl phenothiazines usually present in amounts of from 0.001 to 1 weight percent.
Pour point depressants which may be present in amounts of from 0.01 to 1 weight percent include wax alkylated aromatic hydrocarbons, olefin polymers and copolymers, acrylate and methacrylate polymers and copolymers.
Viscosity index improvers, the concentrations of which may vary from 0.2 to 15 weight percent, (preferably from 0.5 to 5 weight percent) depending on the viscosity grade required, include hydrocarbon polymers grafted with, for example, nitrogen-containing monomers, olefin polymers such as polybutene, ethylene-propylene copolymers, hydrogenated polymers and copolymers and terpolymers of styrene with isoprene and/or butadiene, polymers of alkyl acrylates or alkyl methacrylates, copolymers of alkyl methacrylates with N-vinyl pyrrolidone or dimethylamino-alkyl methacrylate, post-grafted polymers of ethylene-propylene with an active monomer such as maleic anhydride which may be further reacted with an alcohol or an alkylene polyamine, styrene/maleic anhydride polymers post-treated with alcohols and amines, etc.
Antiwear activity can be provided by about 0.01 to 2 weight percent of the aforementioned metal dihydrocarbyl dithiophosphates and the corresponding precursor esters, phosphosulfurized pinenes, sulfurized olefins and hydrocarbons, sulfurized fatty esters and alkyl polysulfides. Preferred are the zinc dihydrocarbyl dithiophosphates which are salts of dihydrocarbyl esters of dithiophosphoric acids.
Other additives include effective amounts of friction modifiers or fuel economy additives such as the alkyl phosphonates as disclosed in U.S. 4,356,097, aliphatic hydrocarbyl substituted succinimides as disclosed in EPO 0020037, dimer acid esters, as disclosed in U.S. 4,105,571, oleamide, etc., which are present in the oil in amounts of 0.1 to 5 weight percent. Glycerol oleates are another example of fuel economy additives and these are usually present in very small amounts, such as 0.05 to 0.2 weight percent based on the weight of the formulated oil.
The practice and the benefits achievable by the practice of this invention are illustrated in the following specific examples which are not to be construed as limitations on this invention. Examples 1-14 illustrate the preparation of typical, but preferred, succinimide dispersants utilized in the practice of this invention.

EXAMPLE 1

In a first stage reaction, polyisobutenylsuccinic anhydride (PIBSA) formed from polyisobutylene (number average molecular weight = 1300) and tetraethylene pentamine (TEPA) in a mole ratio of 1.8:1 are reacted at 165-170°C for 4 hours. In a second stage reaction, maleic anhydride (MA) is added to the first stage reaction product in amount equivalent to 1.25 moles per mole of TEPA used in the first stage and the resultant mixture is heated at 165-170°C for 1.5 hours. The succinimide is thus formed using a total mole ratio of anhydrides to TEPA of 3.05:1. The mole ratio of PIBSA:MA in this synthesis is 1.44:1. To provide a handleable concentrate, the reaction product is suitably diluted with 100 solvent neutral mineral oil such that the nitrogen content of the blend is about 1.8%.

EXAMPLE 2

The procedure of Example 1 is repeated except that in the first stage the PIBSA and TEPA are reacted in a mole ratio of 2.05:1 and in the second stage the MA is used in amount equivalent to a mole ratio of 1:1 relative to the TEPA used in the first stage. Thus the total mole ratio of anhydrides to polyamine is again 3.05:1. The mole ratio of PIBSA:MA in this synthesis is 2.05:1.

EXAMPLE 3

The same general procedure as in Example 1 is employed except that the PIBSA:TEPA mole ratio in the first stage is 2.3:1 and that in the second stage the MA is used in amount equivalent to a mole ratio of 1:1 relative to the TEPA used in the first stage. The total mole ratio of anhydrides to polyamine is thus 3.3:1, and the mole ratio of PIBSA:MA is 2.3:1.

EXAMPLE 4

The procedure of Example 1 is repeated except that in the first stage the PIBSA and TEPA are reacted in a mole ratio of 2.05:1 and in the second stage the MA is used in amount equivalent to a mole ratio of 2:1 relative to the TEPA used in the first stage. Thus the total mole ratio of anhydrides to polyamine is 4.05:1, and the PIBSA:MA mole ratio is 1.03:1.

EXAMPLE 5

The procedure of Example 3 is repeated except that in the first stage the PIBSA:TEPA mole ratio is 1.5:1. Thus the total mole ratio of acylating agents to polyamine is 2.5:1.

EXAMPLE 6

In a first stage reaction, PIBSA formed from polyisobutylene (number average molecular weight = 1300) and TEPA in a mole ratio of 2.05:1 are reacted at 165-170°C for 4 hours. In a second stage reaction, maleic acid is added to the first stage reaction product in amount equivalent to one mole per mole of TEPA used in the first stage and the resultant mixture is heated at 165-170°C for 1.5 hours. The succinimide is thus formed using a total mole ratio of acylating agents to TEPA of 3.05:1, and the mole ratio of PIBSA to maleic acid is 2.05:1. As in Example 1, the reaction product is suitably diluted with mineral oil base stock to provide a handleable concentrate.

EXAMPLE 7

The procedure of Example 6 is repeated except that fumaric acid is used in the second stage in amount equivalent to a mole ratio of 1:1 relative to the TEPA used in the first stage. Thus the total mole ratio of acylating agents to polyamine is 3.05:1, and the mole ratio of PIBSA to fumaric acid is 2.05:1.

EXAMPLE 8

The procedure of Example 7 is repeated using an equivalent amount of malic acid in lieu of fumaric acid in the second stage. The total mole ratio of acylating agents to polyamine is 3.05:1, and the mole ratio of PIBSA to malic acid is 2.05:1.

EXAMPLE 9

The procedure of Example 8 is repeated using in the second stage an equivalent amount of succinic acid in lieu of malic acid. The total mole ratio of of acylating agents to polyamine is 3.05:1, and the mole ratio of PIBSA to succinic acid is 2.05:1.

EXAMPLE 10

Example 9 is repeated except that 2 moles of succinic acid per mole of TEPA are employed in the second stage such that the total mole ratio of acylating agents to polyamine is 4.05:1, and the mole ratio of PIBSA to succinic acid is 1.03:1.

EXAMPLE 11

In the first stage, PIBSA formed from polyisobutylene (number average molecular weight = 1300) and TEPA in a mole ratio of 2.3:1 are reacted at 165-170°C for 4 hours. In the second stage, succinic anhydride is added to the first stage reaction product in amount equivalent to one mole per mole of TEPA used in the first stage and the resultant mixture is heated at 165-170°C for 1.5 hours. The succinimide is thus formed using a total mole ratio of acylating agents to TEPA of 3.3:1, and the mole ratio of PIBSA to succinic anhydride is 2.3:1.

EXAMPLE 12

The first stage reaction involves reaction of PIBSA and TEPA in a mole ratio of 2.05:1. The reaction is conducted at 165-170°C for 4 hours. In the second stage, an alkenyl succinic anhydride in which the alkenyl group contains an average of between 20 and 24 carbon atoms is employed in an amount equivalent to one mole per mole of TEPA used in the first stage, and the reaction is conducted at 165-170°C for 1.5 hours. The resultant succinimide is thus formed using a total mole ratio of acylating agents to TEPA of 3.05:1. The mole ratio of PIBSA to alkenyl succinic anhydride is 2.05:1. For ease of handling, the result product is diluted with mineral oil.

EXAMPLE 13

Using the procedure of Example 12, PIBSA is reacted with TEPA in the first stage in a mole ratio of 2.3:1. In the second stage, maleic anhydride is reacted using 0.75 mole per mole of TEPA used in the first stage. The product thus is formed with a total mole ratio of acylating agents to TEPA of 3.05:1. The mole ratio of PIBSA to MA is 3.07:1.

EXAMPLE 14

The procedure of Example 13 is repeated substituting an equivalent amount of fumaric acid for the maleic anhydride in the second stage. The total mole ratio of acylating agent to TEPA is thus 3.05:1. The mole ratio of PIBSA to fumaric acid is 3.07.1.
Examples 15 and 16 illustrate the formation of additive concentrates of this invention.

EXAMPLE 15

With separate portions of the respective dispersants of Examples 1-14, diluted with mineral oil or a synthetic lubricating oil such as diester oil or hydrogenated poly-α-olefin lubricating oil, are individually admixed various copper-containing antioxidants in amounts such that the weight ratio of elemental copper to succinimide dispersant is in one instance 0.0005:1, in another instance 0.001:1, in still another instance 0.002:1, in yet another instance 0.005:1, and in a further instance 0.01:1, and in a still further instance 0.05:1 The respective copper compounds employed in this manner are as follows:
Copper naphthenate
Copper oleate
Copper di-2-ethylhexyldithiophosphate
Copper dibutyldithiocarbamate
Copper diisooctyldithiophosphate
Copper acetylacetonate
Copper octylacetoacetate
Copper palmitate
Copper azelate
Copper octadecanedioate

EXAMPLE 16

To individual portions of the respective additive concentrates of Example 15 are added the following components such that the finished concentrates contain 5.5, 17.6, and 27.5% of overbased sulfonates; 1.7, 10.2, and 21.25% of zinc dialkyl dithiophosphate; and/or 0.002, 0.006, and 0.02% of antifoam agent.
Examples 17 and 18 illustrate the formation of lubricating oil compositions of this invention.

EXAMPLE 17

The additive concentrates of Example 15 are blended with mineral lubricating oil base stocks and synthetic lubricating oil base stocks such as diester oils and hydrogenated poly-α-olefin lubricants in amounts such that the copper content of the finished lubricant is in one instance 40 ppm, in another instance 80 ppm, in still another instance 100 ppm, in yet another instance 140 ppm, in a further instance 160 ppm, in yet a further instance 200 ppm, and in a still further instance 300 ppm. Viscosity index improver is included in the base oils in amounts between 0.5 and 5% to achieve desired viscosity specifications.

EXAMPLE 18

The procedure of Example 17 is repeated using the finished additive concentrates of Example 16.
Finished gasoline engine crankcase lubricating oils containing the substituted succinimide dispersants of Examples 1-3 were formulated. Each such oil contained 7.0% of an additive concentrate comprising, in addition to the succinimide dispersant, conventional amounts of overbased sulfonates, zinc dialkyl dithiophosphate, phenolic antioxidant, viscosity index improver, rust inhibitor, and antifoam agent to provide an SAE 15W/40 crankcase lubricating oil. The amount of succinimide dispersant in the concentrates was such as to provide a nitrogen content in the concentrate of 1.8%. Each finished lubricating oil composition was blended to a nitrogen content of 0.13%.
The resultant finished lubricating oils were subjected to the ASTM Sequence VE Engine Test procedure and the Volkswagen P.VW 3334 Seal Test. For comparative purposes, a corresponding lubricating oil containing a conventional commercial succinimide dispersant (at a level of 1.8% nitrogen) in the same finished formulation was subjected to the same tests. The results of this series of tests are summarized in Table 1.
In order to determine the compatibility of various succinimide dispersants with fluoroelastomers, a series of finished crankcase lubricating oils for use in internal combustion engines containing various substituted succinimide dispersants were formulated. The results are summarized in Table 2, wherein "Elongation Change, %" refers to the change in elongation to break compared to a fresh seal, and "Tensile Strength Change, %" refers to tensile strength as compared to a fresh seal. Except for Test No. 3 wherein a diesel engine crankcase formulation was employed, each such oil contained, in addition to the succinimide dispersant, conventional amounts of overbased sulfonates, zinc dialkyl dithiophosphate, phenolic antioxidant, viscosity index improver, rust inhibitor, and antifoam agent to provide an SAE 15W/40 crankcase lubricant oil. Each such lubricant contained an amount of the succinimide dispersant to provide a nitrogen content of 0.13%. The resultant finished lubricating oils were subjected to the Volkswagen P.VW 3334 Seal Test.
It will be noted from the data in Table 2 that all of the formulations containing the succinimides utilized in accordance with this invention (Examples 1-4 and 6-11) exhibited superior fluoroelastomer compatibility as compared to the commercial succinimide dispersant. Moreover, the lubricants of tests 1-8 and 10 satisfied the requirements of the stringent Volkswagen Seal Test.

Claims

A lubricating oil additive concentrate which comprises
a) at least one oil-soluble copper-containing antioxidant; and

b) at least one oil-soluble dispersant obtainable from a process which comprises (i) reacting at least one polyamine with at least one acyclic hydrocarbyl substituted succinic acylating agent in which the substituent contains an average of at least 40 carbon atoms, and (ii) reacting the product so formed with a vicinal dicarboxylic acylating agent having 4 to 30 carbon atoms in the molecule, the process being characterized in that in step (i) the acylating agent is reacted with the polyamine in a mole ratio of from 1.05 to 2.85 moles of acylating agent per mole of polyamine, and in that in step (ii) the mole ratio of the vicinal dicarboxylic acylating agent is from 0.10 to 2.50 moles per mole of said polyamine with the proviso that the total mole ratio of the acylating agents in (i) and (ii) per mole of said polyamine is at least 2.40.
A concentrate according to claim 1 wherein the hydrocarbyl substituted succinic acylating agent used in (i) is predominantly or entirely alkenyl-substituted succinic anhydride obtainable from polyolefins which are made from C₃ or C₄ olefins and which have a number average molecular weight in the range of 700 to 5,000.
A concentrate according to claim 1 or 2 wherein the hydrocarbyl substituted succinic acylating agent used in (i) is predominantly or entirely polyisobutenylsuccinic acid and/or polyisobutenylsuccinic anhydride, obtainable from polyisobutene having a number average molecular weight in the range of 900 to 5,000.
A concentrate according to claim 1, 2 or 3 wherein the polyamine used is predominantly or entirely alkylene polyamine of formula

H₂N(CH₂)_n(NH(CH₂)_n)_mNH₂

wherein each n is, independently, 2, 3 or 4 and m is from 0 to 10.
A concentrate according to claim 4 wherein the polyamine used is tetraethylene pentamine, triethylene tetramine or a combination of ethylene polyamines which approximates tetraethylene pentamine or triethylene tetramine.
A concentrate according to any one of the preceding claims wherein the reactants are employed in relative proportions such that the molar ratio of acylating agent in (i) : acylating agent in (ii) is at least 1.4:1.
A concentrate according to any one of the preceding claims wherein the vicinal dicarboxylic acylating agent employed is predominantly or entirely maleic anhydride, maleic acid, fumaric acid, malic acid, succinic acid, or succinic anhydride.
A concentrate according to any one of the preceding claims wherein the mole ratio in step (i) of acylating agent to polyamine is 2.00 to 2.85 moles of acylating agent per mole of polyamine.
A concentrate according to any one of the preceding claims wherein the copper-containing antioxidant is present in an amount such that there is 0.0001 to 0.5 part by weight of copper per part by weight of said oil-soluble dispersant.
A concentrate according to any one of the preceding claims wherein the total mole ratio of acylating agents in (i) and (ii) is at least 3.05 moles per mole of said polyamine.
A concentrate according to any one of the preceding claims wherein said concentrate, when blended in a lubricating oil base stock, provides a lubricating oil composition which satisfies the requirements of the Volkswagen P.VW 3334 Seal Test as defined in the specification.
A lubricant composition which comprises a major amount of lubricating oil and a minor but effective amount

claims.
A lubricant composition according to claim 12 wherein the copper-containing antioxidant is present in an amount of from 40 to 500 ppm by weight of copper.
A lubricant composition according to claim 12 wherein the copper-containing antioxidant comprises at least one oil-soluble copper carboxylate compound present in an amount of from 100-300 ppm by weight of copper.