Di-secondary alkyl hindered phenol antioxidants

FIELD OF INVENTION

[0001] The present invention relates to a novel antioxidant compositions derived from the Mannich product formed from the reaction of (a) an aldehyde, ammonia or an amine and a di-secondary alkyl hindered phenol; and (b) at least one additive selected from the group consisting of hydrocarbyl diphenylamines, sterically hindered phenols other than component (a), metal hydrocarbyl dithio-phosphates, sulphurised olefins and mixtures thereof. The invention further relates to the use of the novel antioxidant compositions in an oil of lubricating viscosity.

BACKGROUND OF THE INVENTION

[0002] It is known to use tertiary alkyl hindered phenols as antioxidants in oils of lubricating viscosity. Particularly common tertiary alkyl hindered phenols used are derivatives of tertiary butyl phenol. During the preparation of tertiary butyl phenols trace amounts of an impurity tris-tert-butyl phenol is formed and retained in the final product. Tris-tert-butyl phenol is known to bio-accumulate and builds up to high concentrations in sediment.

[0003] U.S. Pat. Nos. 3,462,368, 3,778,460, 3,565,029, 3,810,869, 6,096,695 and 6,001,786 disclose the use, in oils of lubricating viscosity, of sulphur containing di-secondary hindered phenol antioxidants. However, sulphur oxides derived from engine lubricants have been shown to contribute in part to particulate emissions and poison the catalysts used in catalytic converters, resulting in a reduction in performance of the catalysts.

[0004] U.S. Pat. No. 3,305,483 discloses the use of an antioxidant formed from the reaction of an amine, an aldehyde and di-tertiary-alkyl substituted phenols or a di-secondary alkyl substituted phenol. The di-secondary alkyl substituted phenol is N-(sec-amyl)-N,N-bis-(3,5-di-sec-butyl-4-hydroxybenzyl)amine.

[0005] U.S. Pat. No. 6,495,496 discloses low molecular weight Mannich base condensates of hydroxy aromatic compounds, an aldehyde and an amine suitable for use as soot dispersants in lubricating oils when used alone or in combination with other high molecular weight dispersants.

[0006] U.S. Pat. No. 4,248,725 discloses an additive imparting dispersant and antioxidant properties for lubricating oils. The additive is the product obtained by reacting a substituted succinimide dispersant having free amine groups in its molecular structure, an aldehyde and an antioxidant compound capable of condensing with an aldehyde. The antioxidant can be substituted mononuclear or polynuclear phenols. The substituted phenol ring has alkyl, cycloalkyl or aralkyl radicals containing fewer than 13 carbon atoms. The amines utilized by the invention include H2N(CH2CHR1NH)xH, where R1 is a substituent with 1 to 6 carbon atoms and x is an integer with a value of at least 1.

[0007] U.S. Pat. No. 3,224,974 discloses the use of di-tertiary hindered phenols or di-secondary hindered phenols as antioxidants for a wide variety of organic materials including gasoline, jet fuel, kerosene, fuel oil, turbine oil and motor oil. The di-tertiary hindered phenols or di-secondary hindered phenols are prepared by the reaction of formaldehyde; and a primary or secondary amine; and di-tertiary hindered phenols or di-secondary 2,6-hindered phenols. The 2,6-hindered phenols contain at position 2 a bridged aryl substituent and alkyl group containing 1 to 3 carbon atoms.

[0008] It would be desirable to have a composition with antioxidant properties and capable of preventing the formation of sulphur oxides from sulphur containing antioxidants and decreasing the bioaccumulation of tris-tert-butyl phenol.

SUMMARY OF THE INVENTION

[0009] The present invention provides a lubricating oil composition comprising:

[0010] a. a Mannich product formed from the reaction of an aldehyde, ammonia or an amine and a di-secondary alkyl hindered phenol;

[0011] b. at least one additive selected from the group consisting of hydrocarbyl diphenylamines, sterically hindered phenols other than component (a), metal hydrocarbyl dithiophosphates, molybdenum dithiocarbamates, sulphurised olefins and mixtures thereof; and

[0012] c. an oil of lubricating viscosity.

[0013] The invention further provides a process to prepare a lubricating oil composition comprising:

[0014] a. reacting, optionally in an organic solvent, a di-secondary alkyl phenol with an aldehyde and ammonia or an amine to form a Mannich product; and

[0015] b. mixing the Mannich product with base oil.

[0016] The invention further provides a method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the composition as described herein.

[0017] The invention further provides a lubricating oil composition with antioxidant properties. The invention further provides a lubricating oil composition capable of decreasing bioaccumulation of tris-tert-butyl phenol. and capable of decreasing the amount of sulphur oxides produced from sulphur containing antioxidants.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The lubricating oil composition of the present invention comprises:

[0019] a. a Mannich product formed by the reaction of an aldehyde, ammonia or an amine and a di-secondary alkyl hindered phenol;

[0020] b. at least one additive selected from the group consisting of hydrocarbyl diphenylamines, sterically hindered phenols other than component (a), metal hydrocarbyl dithiophosphates, molybdenum dithiocarbamates, sulphurised olefins and mixtures thereof; and

[0021] c. an oil of lubricating viscosity.

[0022] As used herein “at least one additive selected from the group consisting of hydrocarbyl diphenylamines, sterically hindered phenols other than component (a), metal hydrocarbyl dithiophosphates, sulphurised olefins and mixtures thereof” is refers to a group characterized as “compounds with antioxidant properties.”

[0023] The weight percent ratio of the Mannich product to compounds with antioxidant properties is typically 99:1 to 1:99, preferably 95:5 to 5:95, more preferably 85:15 to 15:85, even more preferably 70:30 to 30:70, even more preferably 60:40 to 40:60 and most preferably 55:45 to 45:55.

[0024] As used herein the term “Mannich product formed from the reaction of an aldehyde, an amine and a di-secondary alkyl hindered phenol” is referred to as the Mannich product.

[0025] As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

[0026] hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring);

[0027] substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);

[0028] hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

[0029] Amines

[0030] The amines of the invention can contain equal to or less than 4 free >N—H groups, preferably equal to or less than 3 free >N—H groups, more preferably equal to or less than 2 more free >N—H groups and most preferably exactly one free >N—H group, where an >N—H group represents a nitrogen atom bound to at least one hydrogen atom.

[0031] Suitable amines can be represented by R1R2N—H, wherein R1 and R2 are independently hydrogen, hydrocarbyl groups or mixtures thereof. In one embodiment, the hydrocarbyl groups can be alkyl or alkenyl. The alkyl or alkenyl groups contain 1 to 20, preferably 1 to 10, more preferably 1 to 5 and most preferably 1 to 3 carbon atoms. Examples of suitable alkyl or alkenyl groups include methyl, ethyl, propyl, propenyl, isobutyl, isobutenyl, pentyl, pentenyl and mixtures thereof. A preferred alkyl group is methyl and may be used alone or in combination with other groups.

[0032] In one embodiment, the hydrocarbyl group can be —CHR3R4, wherein R3 can be hydrogen or a hydrocarbyl group contains 1 to 3 and preferably 1 to 2 carbon atoms. R4 can be an aromatic ring, preferably with 5 to 12, more preferably 6 to 12 carbon atoms. The aromatic rings can be substituted or unsubstituted, although unsubstituted is preferred. The aromatic rings can optionally contain 0 to 3, preferably 0 to 2 and most preferably 0 to 1 heteroatoms. The heteroatoms can include nitrogen, sulphur and oxygen, although nitrogen is preferred. Unsubstituted aromatic rings can optionally contain a hydrocarbyl group with 1 to 10, preferably 1 to 6 and most preferably 1 to 3 carbon atoms.

[0033] Examples of suitable amine compounds of the invention can be selected from the group consisting of methylamine, ethylamine, propylamine, propenylamine, isobutylamine, isobutenylamine, pentylamine, pentenylamine, benzylamine, naphthylamine, dimethylamine, diethylamine, dipropylamine, dipropenylamine, diisobutylamine, diisobutenylamine, dipentylamine, dipentenylamine, dibenzylamine, dinaphthylamine and mixtures thereof.

[0034] Aldehydes

[0035] The aldehydes of the invention can be represented by the formula R5—C(O)H, wherein R5 is hydrogen or a hydrocarbyl group with 1 to 7, preferably 1 to 5 and most preferably 1 to 3 carbon atoms. Examples of suitable aldehydes include formaldehyde, acetaldehyde, propionaldehyde and mixtures thereof. In one embodiment the aldehyde is formaldehyde, which can be monomeric, polymeric (paraformaldehyde), oligomeric (e.g, the cyclic trimer) or in aqueous solution; preferably the formaldehyde is in aqueous solution (formalin).

[0036] Di-Secondary Alkyl Hindered Phenol

[0037] The di-secondary alkyl hindered phenols of the invention can be represented by the formula:

[0038] wherein R6, R7, R8 and R9 are independently alkyl groups with 1 to 6, preferably 1 to 4 and most preferably 1 to 3 carbon atoms. Examples of suitable di-secondary alkyl hindered phenols include 2,6-(1-methylpropyl)-phenol, 2,6-(1-methylbutyl)-phenol, 2,6-(1-ethylpropyl)-phenol and mixtures thereof. A preferred di-secondary alkyl hindered phenols is 2,6-(1-methylpropyl)-phenol.

[0039] In one embodiment adjacent group R6-R7 and/or R8-R9 can together form be linked through cycloalkyl group. Suitable cycloalkyl groups can contain 3 to 11, preferably 4 to 10 and most preferably 5 to , for example 5 or 6 carbon atoms.

[0040] Organic Solvents

[0041] The reaction to form the Mannich product can be conducted in an organic solvent. Suitable organic solvents include aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons or mixtures thereof. Preferably the organic solvent has a boiling point above 100° C. Aromatic hydrocarbons typically contain alkyl groups with 1 to 20, preferably 1 to 10 and most preferably 1 to 3 carbon atoms. Examples of suitable aromatic solvents include commercial aromatic solvent mixtures sold under the trade names Caromax 26®, Solvesso 150®, toluene, xylene, a base oil, a lubricating oil or mixtures thereof. In one embodiment the aromatic hydrocarbon is toluene.

[0042] Suitable aliphatic hydrocarbons typically contain 6 to 24, preferably 8 to 20 carbon atoms. Examples of suitable aliphatic hydrocarbons include Kerosene or commercial aliphatic solvent mixtures sold under the trade name Isopar® or mixtures thereof.

[0043] The Mannich Product

[0044] The Mannich product can be represented by the formulae:

[0045] wherein R1, R2, R5, R4, R6, R7, R8 and R9 are as described above. Examples of suitable Mannich products can include: 4-[(dimethylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(methylethylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(diethylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(methylpropylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(ethylpropylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(dipropylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(dibenzylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(methylbenzylamino)methyl]-2,6-bis-(1-methylpropyl)phenol or mixtures thereof. Preferably the Mannich products can be 4-[(methylamino)methyl]-2,6-bis-(1-methylpropyl)phenol, 4-[(benzylamino)methyl]-2,6-bis(1-methylpropyl)-phenol or mixtures thereof.

[0046] Oils of Lubricating Viscosity

[0047] The lubricating oil composition of the present invention can be added to an oil of lubricating viscosity. The oil includes natural and synthetic oils, oil derived from hydrocracking, hydrogenation, hydrofinishing, unrefined, refined and re-refined oils, or mixtures thereof.

[0048] Unrefined oils are those obtained directly from a natural or synthetic source generally without (or with little) further purification treatment.

[0049] Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Purification techniques are known in the art and include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation and the like.

[0050] Re-refined oils are also known as reclaimed or reprocessed oils, and are obtained by processes similar to those used to obtain refined oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

[0051] Natural oils useful in making the inventive lubricants include animal oils, vegetable oils (e.g., castor oil, lard oil), mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types and oils derived from coal or shale or mixtures thereof.

[0052] Synthetic lubricating oils are useful and include hydrocarbon oils such as polymerised and interpolymerised olefins (e.g., polybutylenes, polypropylenes, propyleneisobutylene copolymers); poly(1-hexenes), poly(1-octenes), poly(1-decenes), and mixtures thereof; alkyl-benzenes (e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls); alkylated diphenyl ethers and alkylated diphenyl sulphides and the derivatives, analogs and homologs thereof or mixtures thereof.

[0053] Other synthetic lubricating oils include but are not limited to liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester of decane phosphonic acid), and polymeric tetrahydrofurans. Synthetic oils may be produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes.

[0054] Oils of lubricating viscosity can also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. The five base oil groups are as follows: Group I (sulphur content >0.03 wt %, and/or <90 wt % saturates, viscosity index 80-120); Group II (sulphur content ≦0.03 wt %, and ≧90 wt % saturates, viscosity index 80-120); Group III (sulphur content ≦0.03 wt %, and ≧90 wt % saturates, viscosity index ≧120); Group IV (all polyalphaolefins (PAOs)); and Group V (all others not included in Groups I, II, III, or IV). The oil of lubricating viscosity comprises an API Group I, II, III, IV, or V oil or mixtures thereof. Preferably the oil of lubricating viscosity an API Group II, III, IV, or V oil or mixtures thereof

[0055] The oil of lubricating viscosity is typically present at 30 to 99.99, preferably 55 to 98.45, and more preferably 65 to 96.9 and most preferably 75 to 94.5 weight percent of the lubricating oil composition.

[0056] The total combined amount of the Mannich product and compounds with antioxidant properties present in an oil of lubricating viscosity is typically 0.01 to 30, preferably 0.05 to 20, and more preferably 0.1 to 15 and most preferably 0.5 to 10 weight percent of the lubricating oil composition.

[0057] Compounds with Antioxidant Properties

[0058] When present, the hydrocarbyl diphenylamines can be represented by the formula:

[0059] wherein R10 and R11 hydrocarbyl groups, preferably arylalkyl or alkyl groups. The arylalkyl groups contain 6 to 20, preferably 6 to 10 carbons atoms. The alkyl groups can be linear or branched, preferably linear; the alkyl group contains 1 to 24, preferably 2 to 18 and most preferably 4 to 12 carbon atoms; and z is independently 0, 1, 2, or 3, provided that at least one aromatic ring contains a hydrocarbyl group. Preferred alkylated diphenylamines can include octyl diphenylamine, nonyl diphenylamine, bis-octyl diphenylamine, bis-nonyl diphenylamine or mixtures thereof.

[0060] When present, the sterically hindered phenols other than component (a) can be represented by the formula:

[0061] wherein R12 and R13 are independently branched or linear alkyl groups containing 1 to 24, preferably 4 to 18, and most preferably 4 to 12 carbon atoms; and q is hydrogen, hydrocarbyl, a bridging group linking to a second aromatic group or mixtures thereof.

[0062] R12 and R13 can be either straight or branched chain; branched is preferred. Preferably the phenol is butyl substituted containing two t-butyl groups. When the t-butyl groups occupy the 2,6-positions, the phenol is sterically hindered. Examples of suitable hydrocarbyl groups include 2-ethylhexyl, n-butyl, dodecyl or mixtures thereof. Examples of suitable bridging groups include —CH2— (methylene bridge) or —CH2OCH2— (ether bridge).

[0063] When present, the sterically hindered bridged phenols other than component (a) can be represented by the formulae:

[0064] wherein R14, R15, R16, R17, R18, R19 are either straight or branched chain and contain 4 to 18, preferably 4 to 12 carbon atoms. Preferably the phenol is butyl substituted. R20 and R21 are independently hydrogen or hydrocarbyl; preferably R20 and R21are arylalkyl or alkyl groups. The alkyl groups of R20 and R21 can be linear or branched, linear being preferred. R20 and R21 are preferably in the para position. The arylalkyl or alkyl groups typically contain 1 to 15, preferably 1 to 10, and more preferably 1 to 5 carbon atoms. The bridging group Y can include —CH2— (methylene bridge) or —CH2OCH2— (ether bridge).

[0065] Examples of methylene-bridged sterically hindered phenols include 4,4′-methylenebis(6-tert-butyl o-cresol), 4,4′-methylenebis(2-tert-amyl-o-cresol), 2,2-methylenebis(4-methyl-6-tert-butylphenol), 4,4-methylene-bis(2,6-di-tertbutylphenol) or mixtures thereof.

[0066] In one embodiment, the sterically hindered phenols other than component (a) suitable for the invention can be hindered esters represented by the formula:

[0067] wherein R22, R23 and R24 are straight or branched alkyl groups that can be substituted or unsubstituted, containing 2 to 22, preferably 2 to 18, more preferably 4 to 8 carbon atoms. Specific examples include of alkyl groups include 2-ethylhexyl or n-butyl ester, dodecyl, —CH2CH2COOH or mixtures thereof.

[0068] When present, the metal hydrocarbyl dithiophosphates can be represented by the formula:

[0069] wherein R25 and R26 are independently hydrogen, hydrocarbyl groups or mixtures thereof, provided that at least one of R25 and R26 is a hydrocarbyl group, preferably alkyl or cycloalkyl with 1 to 30, preferably 2 to 20 and most preferably 2 to 15 carbon atoms.

[0070] M is a metal, and n is an integer equal to the available valence of M. M is mono- or di- or trivalent, preferably divalent, more preferably a divalent transition metal, and most preferably zinc.

[0071] Examples of suitable zinc hydrocarbyl dithiophosphates can include zinc isopropyl methylamyl dithiophosphate, zinc isopropyl isooctyl dithiophosphate, barium di(nonyl)-dithiophosphate, zinc di(cyclohexyl) dithiophosphate, calcium di(hexyl) dithiophosphate, zinc isobutyl isoamyl dithiophosphate, zinc isopropyl n-butyl dithiophosphate, isobutyl primary amyl dithiophosphate, methylamyl dithiophosphate, isopropyl 2-ethylhexyl dithiophosphate, and mixtures thereof.

[0072] When present, molybdenum dithiocarbamates can be represented by the formula:

[0073] wherein R27 and R28 are independently hydrogen, hydrocarbyl groups, aminoalkyl groups, acylated aminoalkyl groups or mixtures thereof typically containing 3 to 20, preferably 5 to 19 and more preferably 8 to 18 carbon atoms, but both such groups are not hydrogen; m and n are positive integers whose combined total is 4.

[0074] In one embodiment the aminoalkyl groups R27 or R28 can be derived from polyalkylenepolyamines. Suitable examples of polyalkylenepolyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and mixtures thereof.

[0075] In one embodiment aminoalkyl groups R27 or R28 are acylated to form acylated aminoalkyl groups. These groups can be derived from the reaction of an aminoalkyl group with an acylating agent. The acylating agents can include monobasic or polybasic carboxylic acids and reactive equivalents thereof. Equivalents of carboxylic acids include anhydrides, esters, acylated nitrogen, acyl halide, nitriles, and salts. Among these, anhydrides, particularly of diacids, are preferred. Suitable monobasic carboxylic acids and derivatives thereof can include (meth)acrylic acid, cinnamic acid, crotonic acid, 3-phenylpropenoic acid, α,β-decenoic acid, glyoxylic acid and mixtures thereof. (The expression “(meth)acrylic” is intended to encompass both acrylic and methacrylic). Suitable dibasic carboxylic acids and derivatives thereof can include fumaric acid, maleic acid, mesaconic acid, itaconic acid, and citraconic acid. A particularly preferred derivative of a dibasic carboxylic acid is maleic anhydride.

[0076] Suitable examples of molybdenum dithiocarboamates include commercial materials sold under the trade names such as Vanlube 822™ and Moly-van™ A from R. T. Vanderbilt Co., Ltd., and Adeka Sakura-Lube™ S-100, S-165 and S-600 from Asahi Denka Kogyo K. K or mixtures thereof.

[0077] When present, the sulphurised olefin can be mono- or di- or poly-sulphides and contain 1 to 10, preferably 1 to 5 and more preferably 1 to 2 sulphur atoms. The olefin can be represented by the formula:

[0078] wherein R29, R30, R31 and R32 are independently hydrogen, hydrocarbyl or substituted hydrocarbyl. The hydrocarbyl can be substituted, unsubstituted, branched, unbranched or mixtures thereof; and the hydrocarbyl can be arylaliphatic or alicyclic, alkyl, alkenyl or mixtures thereof. Typical hydrocarbyl groups in formula (XI) include —C(R33)3, —COOR33, —CON(R33)2, —COON(R33)2, —COOM, —CN, —X—, —YR33 or Ar, wherein R33 is hydrogen or a hydrocarbyl group containing alkyl, alkenyl, aryl or mixtures thereof; and M is one equivalent of a metal cation, preferably an alkali metal or alkaline earth metal, more preferably sodium, potassium, magnesium, calcium, barium or mixtures thereof; and —X— is a halogen, preferably chloro-, bromo-, iodo- or mixtures thereof; and Y is oxygen or sulphur; and Ar is an aryl or substituted aryl group containing 6 to 12 carbon atoms. The olefin can contain from 3 to 40, preferably 3 to 30 and most preferably 4 to 20 carbon atoms. The olefin can be mono- or di- olefinic, al- though mono-olefinic is preferred. Alternatively, the olefin can be a Diels-Alder adduct of a diene such as 1,3-butadiene and an unsaturated ester such as butyl acrylate.

[0079] Examples of suitable olefins that can be sulphurised include propylene, isobutylene, pentene, hexane, heptene, octane, nonene, decene, undecene, dodecene, undecyl, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, octadecenene, nonodecene, eicosene or mixtures thereof. In one embodiment, hexadecene, heptadecene, octadecene, octadecenene, nonodecene, eicosene or mixtures thereof and their dimers, trimers and tetramers are especially preferred olefins.

[0080] Another class of sulphurised olefins include fatty acids and their esters. The fatty acids are often obtained from vegetable oil or animal oil; and typically contain 4 to 22 carbon atoms. Examples of suitable fatty acids and their esters include triglycerides, oleic acid, linoleic acid, palmitoleic acid or mixtures thereof. Often, the fatty acids are obtained from lard oil, tall oil, peanut oil, soybean oil, cottonseed oil, sunflower seed oil or mixtures thereof. In one embodiment fatty acids and mixed with olefins.

[0081] Optional Additives

[0082] Optionally the lubricating oil composition can include additives selected from the group consisting of metal deactivators, detergents, dispersants, antiwear agents, corrosion inhibitors, antiscuffing agents, extreme pressure agents, foam inhibitors, demulsifiers, friction modifiers, viscosity modifiers, pour point depressants and mixtures thereof. Typically a fully-formulated lubri-cating oil will contain one or more of these additives.

[0083] The total combined amount of the optional additives present can be 0 to 41, preferably 0.5 to 25, more preferably 3 to 20 and most preferably 5 to 15 weight percent of the lubricating oil composition.

[0084] Metal Deactivators

[0085] Metal deactivators can be used to neutralise the catalytic effect of metal for promoting oxidation in lubricating oil. Examples of metal deactivators can include derivatives of benzotriazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercapto thiadiazoles or mixtures thereof.

[0086] Preferably the metal deactivator is a hydrocarbyl substituted benzotriazole compound. The benzotriazole compounds with hydrocarbyl substitutions include at least one of the following ring positions 1- or 2- or 4- or 5- or 6- or 7-benzotriazoles. The hydrocarbyl groups contain 1 to 30, preferably 1 to 15, preferably 1 to 7 carbon atoms, and most preferably the metal deactivator is 5-methylbenzotriazole which may be used alone or in combination.

[0087] Dispersants

[0088] Dispersants are often known as ashless-type dispersants because, prior to mixing in a lubricating oil composition they do not contain ash-forming metals; and they do not normally contribute any ash forming metals when added to a lubricant and polymeric dispersants. Ashless type dispersants are characterised by a polar group attached to a relatively high molecular weight hydrocarbon chain. Typical ashless dispersants include N-substituted long chain alkenyl succinimides. Examples of N-substituted long chain alkenyl succinimides include polyisobutylene succinimide with number average molecular weight in the range 350 to 5000, preferably 500 to 3000. Succinimide dispersants and their preparation are disclosed, for instance in U.S. Pat. No. 4,234,435.

[0089] Another class of ashless dispersant is Mannich bases. Mannich dispersants are the reaction products of alkyl phenols in which the alkyl group contains at least 30 carbon atoms with aldehydes (especially formaldehyde) and amines (especially polyalkylene polyamines).

[0090] Dispersants can also be post-treated conventional method by a reaction with any of a variety of agents. Among these are urea, thiourea, dimercap-tothiadiazoles, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleic anhydride, nitrites, epoxides, boron compounds, and phosphorus compounds.

[0091] Detergents

[0092] Detergents are known and can include neutral or overbased, Newtonian or non-Newtonian, basic salts of alkali, alkaline earth and transition metals with one or more hydrocarbyl sulphonic acid, carboxylic acid, phosphorus acid, mono- and/or di- thiophosphoric acid, alkyl phenol, sulphur coupled alkyl phenol compounds, salixarates, saligenins or mixtures thereof. Commonly used metals include sodium, potassium, calcium, magnesium, lithium or mixtures thereof. Most commonly used metals include sodium, magnesium, calcium or mixtures thereof. Detergents and in particular overbased detergents and their preparation are disclosed in U.S. Pat. No. 3,629,109.

[0093] Antiwear

[0094] The lubricating oil composition may additionally contain an antiwear agent. Useful antiwear agents include phosphoric acid esters or salt thereof; phosphites; and phosphorus-containing carboxylic esters, ethers, and amides, zinc dialkyldithiophosphates, and mixtures thereof.

[0095] Corrosion Inhibitors

[0096] Corrosion inhibitors can include amine salts of carboxylic acids such as octylamine octanoate, condensation products of dodecenyl succinic acid or anhydride and a fatty acid such as oleic acid with a polyamine, e.g. a polyalkylene polyamine such as triethylenetetramine, and half esters of alkenyl succinic acids in which the alkenyl radical contains 8 to 24 carbon atoms with alcohols such as polyglycols.

[0097] Antiscuffing Agents

[0098] The lubricant may also contain an antiscuffing agent. Antiscuffing agents that decrease adhesive wear are often sulphur containing compounds. Typically the sulphur containing compounds include organic sulphides and polysulphides, such as benzyldisulphide, bis-(chlorobenzyl) disulphide, dibutyl tetrasulphide, di-tertiary butyl polysulphide, sulphurised sperm oil, sulphurised methyl ester of oleic acid, sulphurised alkylphenol, sulphurised dipentene, sulphurised terpene, sulphurised Diels-Alder adducts, alkyl sulphenyl N′N-dialkyl dithiocarbamates, the reaction product of polyamines with polybasic acid esters, chlorobutyl esters of 2,3-dibromopropoxyisobutyric acid, acetoxymethyl esters of dialkyl dithiocarbamic acid and acyloxyalkyl ethers of xanthogenic acids or mixtures thereof.

[0099] Extreme Pressure Agents

[0100] Extreme Pressure (EP) agents that are soluble in the oil include sulphur and chlorosulphur-containing EP agents, chlorinated hydrocarbon EP agents, phosphorus EP agents, and mixtures thereof. Examples of such EP agents include chlorinated wax; organic sulphides and polysulphides such as benzyldisulphide, bis-(chlorobenzyl) disulphide, dibutyl tetrasulphide, sulphurised sperm oil, sulphurised methyl ester of oleic acid, sulphurised alkylphenol, sulphurised dipentene, sulphurised terpene, and sulphurised Diels-Alder adducts; phosphosulphurised hydrocarbons such as the reaction product of phosphorus sulphide with turpentine or methyl oleate; phosphorus esters such as the dihydrocarbon and trihydrocarbon phosphites, e.g., dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite, pentylphenyl phosphite; dipentylphenyl phosphite, tridecyl phosphite, distearyl phosphite and polypropylene substituted phenol phosphite; metal thiocarbamates such as zinc dioctyldithiocarbamate and barium heptylphenol diacid; the zinc salts of a phosphorodithioic acid; amine salts of alkyl and dialkylphosphoric acids, including, for example, the amine salt of the reaction product of a dialkyldithiophosphoric acid with propylene oxide; and mixtures thereof.

[0101] Foam Inhibitors

[0102] Foam inhibitors are known and can include organic silicones such as polyacetates, dimethyl silicone, polysiloxanes, polyacrylates or mixtures thereof. Examples of foam inhibitors include poly ethyl acrylate, poly 2-ethylhexylacrylate, poly vinyl acetate or mixtures thereof.

[0103] Demulsifiers

[0104] Demulsifiers are known and include derivatives of propylene oxide, ethylene oxide, polyoxyalkylene alcohols, alkyl amines, amino alcohols, diamines or polyamines reacted sequentially with ethylene oxide or substituted ethylene oxides or mixtures thereof.

[0105] Examples of demulsifiers include trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides, (ethylene oxide-propylene oxide) polymers or mixtures thereof.

[0106] Pour Point Depressants

[0107] Pour point depressants are known and include esters of maleic anhydride-styrene copolymers, polymethacrylates; polyacrylates; polyacrylamides; condensation products of haloparaffin waxes and aromatic compounds; vinyl carboxylate polymers; and terpolymers of dialkylfumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers or mixtures thereof.

[0108] Friction Modifiers

[0109] Friction modifiers are known and can include fatty amines, esters, especially glycerol esters such as glycerol monooleate, borated glycerol esters, fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, sulfurized olefins, fatty imidazolines, condensation products of carboxylic acids and polyalkylene-polyamines, amine salts of alkylphosphoric acids

[0110] Viscosity Modifiers

[0111] Viscosity modifiers are known and are typically polymeric materials including styrene-butadiene rubbers, ethylene-propylene copolymers, polyisobutenes, hydrogenated styrene-isoprene polymers, hydrogenated radical isoprene polymers, polymethacrylate acid esters, polyacrylate acid esters, polyalkyl styrenes, alkenyl aryl conjugated diene copolymers, polyolefins, polyalkyl-methacrylates, esters of maleic anhydride-styrene copolymers or mixtures thereof.

[0112] Process

[0113] A process to prepare the composition of the present invention comprises the steps of:

[0114] a) Reacting di-secondary alkyl phenol with an aldehyde and ammonia or an amine to form a Mannich product; and

[0115] b) mixing the Mannich product with base oil, compounds with antioxidant properties, optionally other additives or mixtures thereof.

[0116] The process optionally includes using a solvent in steps (a) and/or (b).

[0117] The reaction conditions for step (a) are typically 15° C. to 130° C., preferably 20° C. to 120° C. and most preferably 25° C. to 110° C.; and for a period of time in the range 30 seconds to 48 hours, preferably 2 minutes to 24 hours, and most preferably 5 minutes to 16 hours; and at pressures in the range 650 mm of Hg to 2000 mm of Hg (equivalent to 86.45 kPa to 266 kPa), preferably 690 mm of Hg to 1500 mm of Hg (equivalent to 91.77 kPa to 199.5 kPa), and most preferably 715 mm of Hg to 1000 mm of Hg (equivalent to 95.1 kPa to 133

[0118] In one embodiment the process can also include the step of separating the Mannich product from the organic solvent at the end of step (a). The resulting mixture of step (b) can also include adding optional additives selected from of at least one compound from the group consisting of detergents, dispersants, antiwear agents, rust inhibitors, foam inhibitors, demulsifiers, viscosity modifiers, pour point depressants and mixtures thereof. The optional additives can be added sequentially, separately or as a concentrate.

[0119] If the present invention is in the form of a concentrate (which can be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of each of the above-mentioned dispersant, as well as other components, to diluent oil is typically in the range of 99:1 to 10:90 by weight.

[0120] Industrial Application

[0121] The compositions of the present invention are useful as additives in various lubricants such as greases, gear oils, industrial fluids, hydraulic fluids, transmission fluids, turbine oils, circulating oils, fuel oils and engine oils.

[0122] In one embodiment of the invention provides a method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the composition as described herein. The invention is particularly suitable for diesel fuelled engines, gasoline fuelled engines, natural gas fuelled engine or a mixed gasoline/alcohol fuelled engine. The use of the lubricating oil composition can impart antioxidant properties, reduction in amount of sulphur oxides formed from sulphur containing antioxidants and decreases the bioaccumulation of tris-tert-butyl phenol.

[0123] The following examples provide an illustration of the invention. These examples are non exhaustive and are not intended to limit the scope of the invention.

EXAMPLES

Reference Examples R1-R6

Reference Example R1

[0124] A flask is charged at room temperature with approximately 100 g of 2,6-di-sec-butylphenol, 100 ml of toluene and approximately 39 g of 37 wt % aqueous formaldehyde in a nitrogen atmosphere and stirred for 30 minutes. Approximately 18.7 g of methylamine is added to the flask over a period of 30 minutes and continuously stirred for 1 hour. The mixture is then heated to 90° C. and held for 90 minutes. The toluene layer is collected and concentrated under reduced pressure to provide the product. The reaction product is mixed at a 2 wt % in Group 4 PAO-6 base oil, 6 mm2s−1 (cSt) at 100° C.

Reference Example 2

[0125] The experimental procedure is identical to the process of Example 1 except methylamine is replaced with approximately 20 g of benzylamine.

Reference Example 3

[0126] The experimental procedure is identical to the process of Example 1 except methylamine is replaced with approximately 20.5 g of dimethylamine.

Reference Examples R4-R6

[0127] R4 and R5 contain 2 wt % of 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, octyl ester (supplied by Ciba Specialty Chemicals) and bis-nonylated diphenylamine respectively in a Group 4 PAO-6 base oil, 6 mm2s−1 (cSt) at 100° C. R6 is a mixture of 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, octyl ester, and bis-nonylated diphenylamine with weight % ratio of 1:1 in a Group 4 PAO-6 base oil, 6 mm2s−1 (cSt) at 100° C.

Example 1

[0128] The product formed from 1 wt % of Reference Example 1, is mixed with 1 wt % of bis-nonylated diphenylamine in Group 4 PAO-6 base oil, 6 mm2s−1 (cSt) at 100° C.

Example 2

[0129] The product formed from 1 wt % of Reference Example 1, is mixed with 1 wt % of 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, octyl ester, in Group 4 PAO-6 base oil, 6 mm2s−1 (cSt) at 100° C.

[0130] Test 1: KV40 Viscosity Increase

[0131] The percentage change in KV40 viscosity (kinematic viscosity at 40° C.) is determined by calculating the percentage difference in KV40 viscosity of a new sample and the same heat-treated sample. This determined by measuring the time for 40 g of oil to flow under gravity through a calibrated glass capillary viscometer as described in ASTM D445. Lower viscosity increases indicate compositions with better antioxidant properties. Oil containing the antioxidant blends of the invention (Examples 1 and 2) show viscosity increases comparable with conventional antioxidants (Reference Examples).

[0132] Test 2: 300° C. Sand Interface Hot Tube

[0133] 300° C. Hot Tube tests are designed to evaluate the amount of deposits on reactor walls. Approximately 5 ml of sample is placed in a glass tube half filled with sand. The glass tube is encased in an aluminum jacket and inserted into a furnace. The sample is heated to 300° C. and held for 20 hours. The amount of deposit formed is graded visually between 1 and 10, with 1 having little deposition and 10 having high deposition. The results obtained for the sand interface hot tube are:

1ExampleHot Tube RatingR110R210R310R43R52R621321

[0134] The analysis indicates, that although di-secondary hindered phenols used in the invention (R1-R3) by themselves are less effective at hot tube than conventional antioxidants (R4 and R5), surprisingly when used in combination with conventional antioxidants, they are equally effective as a combination of tert-butyl phenols with other conventional antioxidant (for example substituted diphenylamines) in combination other compounds with antioxidant properties (R6). Further, the combination of di-secondary hindered phenols of the invention with other compounds with antioxidant properties decreases bioaccumulation of tris-tert-butyl phenol.

[0135] Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression “consisting essentially of” permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration.

Di-secondary alkyl hindered phenol antioxidants

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