WO2010149712A1

WO2010149712A1 - Lubricating composition

Info

Publication number: WO2010149712A1
Application number: PCT/EP2010/058933
Authority: WO
Inventors: Dennis Borisovich Kruchinin; Cara Siobhan Tredget; Mark Philip Wakem
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2009-06-25
Filing date: 2010-06-23
Publication date: 2010-12-29

Abstract

The present Invention provides a lubricating composition comprising: a base oil; a poly (hydroxycarboxylic acid) amide salt derivative having formula (III) : [Y-CO [O-A-CO]_n-Z-R⁺]_m pX^q- (III) wherein Y is hydrogen or an optionally substituted hydrocarbyl group, A is a divalent optionally substituted hydrocarbyl group, n is from 1 to 100, preferably from 1 to 10, m is from 1 to 4, q is from 1 to 4 and p is an integer such that pq = m, Z is an optionally substituted divalent bridging group which is attached to the carbonyl group through a nitrogen atom, R⁺ is an ammonium group and X^q- is an anion; and an optionally alkylated triaryl phosphate ester.

Description

LUBRICATING COMPOSITION

The present invention relates to a lubricating composition for particular use in internal combustion engines. More specifically, the present invention relates to lubricating compositions for use in aviation piston engines.

An example of a lubricating composition for use in aviation piston engines has been disclosed in US 6 191 078.

EP 2 055 729 discloses the use of a lubricating composition containing a base oil and one or more poly (hydroxycarboxylic acid) amide salt derivatives for improving anti-wear and friction reduction properties, in particular in an internal combustion engine. There is no reference in EP 2 055 729 to the improvement of the dispersion of lead salts.

A problem of known lubricating compositions, especially when intended for use in an aviation piston engines, is that they have limited ability of dispersion of lead salts such as PbO, Pb₂Br₂O₃, PbBr₂ and Pb₃O₄ that arise from combustion of leaded fuel (such as leaded

Aviation Gasoline, also called "AvGas") . The build-up of these lead salts results in undesirable engine deposits.

It is an object of the present invention to avoid or at least minimize the above problem. It is another object of the present invention to provide alternative lubricating compositions, especially- for use in an aviation piston engines.

One or more of the above or other objects can be obtained by the present invention by providing a lubricating composition comprising: a base oil; a poly (hydroxycarboxylic acid) amide salt derivative having formula (III) :

[Y-CO[O-A-CO] _n-Z-R⁺] _m pX^q~ (III) wherein Y is hydrogen or an optionally substituted hydrocarbyl group, A is a divalent optionally substituted hydrocarbyl group, n is from 1 to 100, preferably from 1 to 10, m is from 1 to 4, q is from 1 to 4 and p is an integer such that pq - m, Z is an optionally substituted divalent bridging group which is attached to the carbonyl group through a nitrogen atom, R⁺ is an ammonium group and X^q~ is an anion; and an optionally alkylated triaryl phosphate ester. It has now surprisingly been found according to the present invention that the lubricating compositions according to the present invention may exhibit improved lead dispersion properties.

In this respect it is noted that WO 2007/128740 discloses a lubricating composition containing poly (hydroxycarboxylic acid) amide salts derivatives in order to reduce deposits in an internal combustion engine. However, WO 2007/128740 is not concerned with aviation piston engines and does not disclose the use of an optionally alkylated triaryl phosphate ester.

In formula (III) according to the present invention, R⁺ may be a primary, secondary, tertiary or quaternary ammonium group. R⁺ is preferably a quaternary ammonium group.

In formula (III) , A is preferably a divalent straight chain or branched hydrocarbyl group as hereafter described for formulae (I) and (II). That is to say, in formula (III), A is preferably an optionally substituted aromatic, aliphatic or cycloaliphatic straight chain or branched divalent hydrocarbyl group. More preferably, A is an arylene, alkylene or alkenylene group, in particular an arylene, alkylene or alkenylene group containing in the range of from 4 to 25 carbon atoms, more preferably in the range of from 12 to 20 carbon atoms.

Preferably, in said compound of formula (III) , there are at least 4 carbon atoms, more preferably in the range of from 8 to 14 carbon atoms connected directly between the carbonyl group and the oxygen atom derived from the hydroxyl group.

In the compound of formula (III) , the optional substituents in the group A are preferably selected from hydroxy, halo or alkoxy groups, especially Ci_~4 alkoxy groups .

In formula (III) , Y is preferably an optionally substituted hydrocarbyl group as hereinafter described for formula (I) .

That is to say, the optionally substituted hydrocarbyl group Y in formula (III) is preferably aryl, alkyl or alkenyl containing up to 50 carbon atoms, more preferably in the range of from 7 to 25 carbon atoms. For example, the optionally substituted hydrocarbyl group Y may be conveniently selected from heptyl, octyl, undecyl, lauryl, heptadecyl, heptadenyl, heptadecadienyl, stearyl, oleyl and linoleyl.

Other examples of said optionally substituted hydrocarbyl group Y in formula (III) herein include C₄-₈ cycloalkyls such as cyclohexyl; polycycloalkyls such as polycyclic terpenyl groups which are derived from naturally occurring acids such as abietic acid; aryls such as phenyl; aralkyls such as benzyl; and polyaryls such as naphthyl, biphenyl, stibenyl and phenylmethylphenyl .

In the present invention, the optionally substituted hydrocarbyl group Y in formula (III) may contain one or more functional groups such as carbonyl, carboxyl, nitro, hydroxy, halo, alkoxy, amino, preferably tertiary amino (no N-H linkages), oxy, cyano, sulphonyl and sulphoxyl. The majority of the atoms, other than hydrogen, in substituted hydrocarbyl groups are generally carbon, with the heteroatoms (e.g., oxygen, nitrogen and sulphur) generally representing only a minority, about 33% or less, of the total non-hydrogen atoms present.

Those skilled in the art will appreciate that functional groups such as hydroxy, halo, alkoxy, nitro and cyano in a substituted hydrocarbyl group Y will displace one of the hydrogen atoms of the hydrocarbyl, whilst functional groups such as carbonyl, carboxyl, tertiary amino (-N-) , oxy, sulphonyl and sulphoxyl in a substituted hydrocarbyl group will displace a -CH- or -CH₂- moiety of the hydrocarbyl. More preferably, the hydrocarbyl group Y in formula

(III) is unsubstituted or substituted by a group selected from hydroxy, halo or alkoxy group, even more preferably Ci_₄ alkoxy.

Most preferably, the optionally substituted hydrocarbyl group Y in formula (III) is a stearyl group, 12-hydroxystearyl group, an oleyl group or a 12- hydroxyoieyl group, and that derived from naturally occurring oil such as tall oil fatty acid.

In formula (III) , Z is preferably an optionally substituted divalent bridging group represented by formula (IV)

-N-B- (IV)

R¹ wherein R¹ is hydrogen or a hydrocarbyl group and B is an optionally substituted alkylene group.

Examples of hydrocarbyl groups that may represent R¹ include methyl, ethyl, n-propyl, n-butyl and octadecyl. Examples of optionally substituted alkylene groups that may represent B include ethylene, trimethylene, tetramethylene and hexamethylene. Examples of preferred Z moieties in formula (III) include -NHCH₂CH₂-, -NHCH₂C(CH₃J₂CH₂- and -NH (CH₂) 3-. Preferably, R⁺ may be represented by formula (V)

R³

/

~ ^•++NI -R² { V} \

R⁴ wherein R², R³ and R⁴ may be selected from hydrogen and alkyl groups such as methyl.

The anion X^q~ of the compound of formula (III) can be any anion (or mixture of anions) suitable to balance the positive charge of the poly (hydroxycarboxylic acid) amide cation. In a first preferred embodiment, the anion X^q~ of the compound of formula (III) is a sulphur-containing anion. More preferably said anion is selected from sulphate and sulphonate anions.

In a second preferred embodiment, the anion X^q" is a non-sulphur-containing anion such as a non-sulphur- containing organic anion or a non-sulphur-containing inorganic anion.

Non-limiting examples of suitable anions are OH^", CH^", NH₃ ^", HCO₃ ^", HCOO^", CH₃COO^", H^", BO₃ ^3", CO₃ ^2", C₂H₃O₂ ^", HCO^2", C₂O₄ ^2", HC₂O₄ ^", NO₃ ^", NO₂ ^", N^3", NH₂ ^", 0^2", O₂ ^2", BeF₃ ^", F^", Na^", [Al(H₂O)₂(OH)₄]^", SiO₃ ^2", SiF₆ ^2", H₂PO₄ ^", P³% PO₄ ^3-, HPO₄ ^2", Cl^", ClO₃ ^", ClO₄ ^", ClO^", KO^", SbOH₆ ^", SnCl₆ ^2", [SnTe4]^4", CrO₄ ^2", Cr₂O₇ ^2", MnO₄ ^", NiCl₆ ^2", [Cu(COs)₂(OH)₂]⁴-, AsO₄ ^3", Br^"", BrO₃ ^", IO₃-, I^", CN^", OCN^", etc. Suitable anions may also include anions derived from compounds containing a carboxylic acid group (e.g. a carboxylate anion) , anions derived from compounds containing a hydroxyl group (e.g. an alkoxide, phenoxide or enolate anion) , nitrogen based anions such as nitrate and nitrite, phosphorus based anions such as phosphates and phosphonates, or mixtures thereof. Non-limiting examples of suitable anions derived from compounds containing a carboxylic acid group include acetate, oleate, salicylate anions, and mixtures thereof.

Non-limiting examples of suitable anions derived from compounds containing a hydroxyl group include phenate anions, and mixtures thereof. Preferably, the anion X^q~ is selected from the group consisting of OH, a phenate group, a salicylate group, an oleate group and an acetate group. Most preferably the anion X^q~ is OH.

The one or more poly (hydroxycarboxylic acid) amide salt derivatives may be obtained by reaction of an amine and a poly (hydroxycarboxylic acid) of formula (I)

Y-CO[O-A-CO]_n-OH (I) wherein Y is hydrogen or optionally substituted hydrocarbyl group, A is a divalent optionally substituted hydrocarbyl group and n is from 1 to 100, preferably from 1 to 10, with an acid or a quaternizing agent.

As used herein, the term "hydrocarbyl" represents a radical formed by removal of one or more hydrogen atoms from a carbon atom of a hydrocarbon (not necessarily the same carbon atoms in case more hydrogen atoms are removed) .

Hydrocarbyl groups may be aromatic, aliphatic, acyclic or cyclic groups. Preferably, hydrocarbyl groups are aryl_r cycloalkyl, alkyl or alkenyl, in which case they may be straight-chain or branched-chain groups.

Representative hydrocarbyl groups include phenyl, naphthyl, methyl, ethyl, butyl, pentyl, raethylpentyl, hexenyl, dimethylhexyl, octenyl, cyclooctenyl, methylcyclooctenyl, dimethylcyclooctyl, ethylhexyl, octyl, isooctyl, dodecyl, hexadecenyl, eicosyl, hexacosyl, triacontyl and phenylethyl.

In the present invention, the phrase "optionally substituted hydrocarbyl" is used to describe hydrocarbyl groups optionally containing one or more "inert" heteroatom-containing functional groups. By "inert" is meant that the functional groups do not interfere to any substantial degree with the function of the compound. The optionally substituted hydrocarbyl group Y in formula (I) herein is preferably aryl, alkyl or alkenyl containing up to 50 carbon atoms, more preferably in the range of from 7 to 25 carbon atoms. For example, the optionally substituted hydrocarbyl group Y may be conveniently selected from heptyl, octyl, undecyl, lauryl, heptadecyl, heptadenyl, heptadecadienyl, stearyl, oleyl and linoleyl.

Other examples of said optionally substituted hydrocarbyl group Y in formula (I) herein include C4-₈ cycloalkyls such as cyclohexyl; polycycloalkyls such as polycyclic terpenyl groups which are derived from naturally occurring acids such as abietic acid; aryls such as phenyl; aralkyls such as benzyl; and polyaryls such as naphthyl, biphenyl, stibenyl and phenylmethylphenyl .

In the present invention, the optionally substituted hydrocarbyl group Y may contain one or more functional groups such as carbonyl, carboxyl, nitro, hydroxy, halo, alkoxy, tertiary amino (no N-H linkages) , oxy, cyano, sulphonyl and sulphoxyl. The majority of the atoms, other than hydrogen, in substituted hydrocarbyl groups are generally carbon, with the heteroatoms (e.g., oxygen, nitrogen and sulphur} generally representing only a minority, about 33% or less, of the total non-hydrogen atoms present.

Those skilled in the art will appreciate that functional groups such as hydroxy, halo, alkoxy, nitro and cyano in a substituted hydrocarbyl group Y will displace one of the hydrogen atoms of the hydrocarbyl, whilst functional groups such as carbonyl, carboxyl, tertiary amino (-N-) , oxy, sulphonyl and sulphoxyl in a substituted hydrocarbyl group will displace a -CH- or -CHa- moiety of the hydrocarbyl.

The hydrocarbyl group Y in formula (I) is more preferably unsubstituted or substituted by a group selected from hydroxy, halo or alkoxy group, even more preferably C₁-₄ alkoxy.

Most preferably, the optionally substituted hydrocarbyl group Y in formula (I) is a stearyl group, 12-hydroxystearyl group, an oleyl group, a 12- hydroxyoleyl group or a group derived from naturally occurring oil such as tall oil fatty acid.

In a preferred embodiment of the present invention, the one or more poly (hydroxycarboxylic acid) amide salt derivatives are sulphur-containing poly (hydroxycarboxylic acid) amide salt derivatives.

More preferably, said one or more poly (hydroxycarboxylic acid) amide salt derivatives have a sulphur content in the range of from 0.1 to 2.0 wt.%, even more preferably in the range of from 0.6 to 1.2 wt.% sulphur, as measured by ICP-AES, based on the total weight of said poly (hydroxycarboxylic acid) amide salt derivatives.

The preparation of poly (hydroxycarboxylic acid) and its amide or other derivatives is known and is described, for instance, in EP 0 164 817, WO 95/17473, WO 96/07689, US 5 536 445, GB 2 001 083, GB 1 342 746, GB 1 373 660, US 5 000 792 and US 4 349 389.

The preparation of the poly (hydroxycarboxylic acid) s of formula (I) may be made by the interesterification of one or more hydroxycarboxylic acids of formula (II)

HO-A-COOH (II) wherein A is a divalent optionally substituted hydrocarbyl group, optionally in the presence of a catalyst according to well known methods. Such methods are described, for example, in US 3 996 059, GB 1 373 660 and GB 1 342 746.

The chain terminator in said interesterification may be a non-hydroxycarboxylic acid. The hydroxyl group in the hydroxycarboxylic acid and the carboxylic acid group in the hydroxycarboxylic acid or the non-hydroxycarboxylic acid may be primary, secondary or tertiary in character.

The interesterification of the hydroxycarboxylic acid and the non-hydroxycarboxylic acid chain terminator may be effected by heating the starting materials, optionally in a suitable hydrocarbon solvent such as toluene or xylene, and azeotroping off the formed water. The reaction may be carried out at a temperature up to -250⁰C, conveniently at the reflux temperature of the solvent.

Where the hydroxyl group in the hydroxycarboxylic acid is secondary or tertiary, the temperature employed should not be so high as to lead to dehydration of the acid molecule.

Catalysts for the interesterification, such as p-toluenesulphonic acid, zinc acetate, zirconium naphthenate or tetrabutyl titanate, may be included, with the objective of either increasing the rate of reaction at a given temperature or of reducing the temperature required for a given rate of reaction.

In the compounds of formulae (I) and (II), A is preferably an optionally substituted aromatic, aliphatic or cycloaliphatic straight chain or branched divalent hydrocarbyl group. Preferably, A is an arylene, alkylene or alkenylene group, in particular an arylene, alkylene or alkenylene group containing in the range of from 4 to 25 carbon atoms, more preferably in the range of from 12 to 20 carbon atoms. Preferably, in said compounds of formulae (I) and (II), there are at least 4 carbon atoms, more preferably in the range of from 8 to 14 carbon atoms connected directly between the carbonyl group and the oxygen atom derived from the hydroxyl group.

In the compounds of formulae {I) and (II) , the optional substituents in the group A are preferably selected from hydroxy, halo or alkoxy groups, more preferably C₁-₄ alkoxy groups. The hydroxyl group in the hydroxycarboxylic acids of formula (II) is preferably a secondary hydroxyl group.

Examples of suitable hydroxycarboxylic acids are 9-hydroxystearic acid, 10-hydroxystearic acid, 12-hydroxystearic acid, 12-hydroxy-9-oleic acid (ricinoleic acid) , 6-hydroxycaρroic acid, preferably 12- hydroxystearic acid. Commercial 12-hydroxystearic acid (hydrogenated castor oil fatty acid) normally contains up to 15% wt of stearic acid and other non-hydroxycarboxylic acids as impurities and can conveniently be used without further admixture to produce a polymer of molecular weight about 1000-2000.

Where the non-hydroxycarboxylic acid is introduced separately to the reaction, the proportion which is required in order to produce a polymer or oligomer of a given molecular weight can be determined either by simple experiment or by calculation by the person skilled in the art.

The group (-O-A-CO-) in the compounds of formulae (I) and (II) is preferably a 12-oxystearyl group, 12- oxyoleyl group or a 6-oxycaproyl group.

Preferred poly (hydroxycarboxylic acid)s of formula (I) for reaction with amine include poly (hydroxystearic acid) and poly (hydroxyoleic acid).

The amines which react with poly (hydroxycarboxylic acid) s of formula (I) to form poly (hydroxycarboxylic acid) amide intermediates may include those defined in WO 97/41092.

For example, various amines and their preparations are described in US 3 275 554, OS 3 438 757, US 3 454 555, US 3 565 804, US 3 755 433 and US 3 822 209.

The amine reactant is preferably a diamine, a triamine or a polyamine.

Preferred amine reactants are diamines selected from ethylenediamine, N,N-dimethyl-l, 3-proρanediaitιine, triamines and polyamines selected from dietheylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and tris (2-aminoethyl) amine. The aπiidation between the amine reactant and the

{poly (hydroxycarboxylic acid} of formula (I) may be carried out according to methods known to those skilled in the art, by heating the poly (hydroxycarboxylic acid) with the amine reactant, optionally in a suitable hydrocarbon solvent such as toluene or xylene, and azeotroping off the formed water. Said reaction may be carried out in the presence of a catalyst such as p-toluenesulphonic acid, zinc acetate, zirconium naphthenate or tetrabutyl titanate. The poly (hydroxycarboxylic acid) amide intermediate formed from reaction of the amine and the poly (hydroxycarboxylic acid) of formula (I) may be reacted with an acid or a quaternizing agent to form a salt derivative, according to well-known methods. Acids that may be used to form the salt derivative may be selected from organic or inorganic acids. Said acids are preferably sulphur-containing organic or inorganic acids. Preferably, said acids are selected from sulphuric acid, methanesulphonic acid and benzenesulphonic acid. Quaternizing agents that may be used to form the salt derivative may be selected from dimethylsulphuric acid, a dialkyl sulphate having from 1 to 4 carbon atoms, an alkyl halide such as methyl chloride, methyl bromide, aryl halide such as benzyl chloride.

In a preferred embodiment, the quaternizing agent is a sulphur-containing quaternizing agent, in particular dimethylsulphuric acid or an dialkyl sulphate having from 1 to 4 carbon atoms. The quaternizing agent is preferably dimethyl sulphate.

Quaternization is a well-known method in the art. For example, quaternization using dimethyl sulphate is described in US 3 996 059, US 4 349 389 and GB 1 373 660.

There are no particular limitations regarding the optionally alkylated triaryl phosphate ester used in the lubricating composition according to the present invention and various commercial available compounds may be used.

Examples of commercially available optionally alkylated triaryl phosphate esters are those available from Chemtura under the trade designations Reolube OMTI, Durad 310M, Durad 110, Durad 150B, Reolube TXP, Durad 220B, Durad 620B, Durad HOB, Fryquel 150 and Fryquel 220, those available from Rhein Chemie under the trade designations Additin RC 3661, Additin RC 3760 and Additin RC 3680 and those commercially available from Supresta under the trade designations Syn-O-Ad 8475, Syn-O-Ad 8484, Syn-O-Ad 8485, Syn-O-Ad 8478, Syn-O-Ad 8477, Syn-O- Ad 8499 and Syn-O-Ad 9578. Also mixtures of phosphate esters containing optionally alkylated triaryl phosphate esters may be used.

Preferably the optionally alkylated triaryl phosphate ester is an alkylated triaryl phosphate ester, more preferably the aryl moieties thereof are all monoalkylated.

Further it is preferred that the alkyl moieties of the alkylated triaryl phosphate ester are alkyl groups having from 1 to 8 carbon atoms (such as methyl, ethyl, propyl, butyl, t-butyl, pentyl, hexyl, heptyl, octyl, etc.), preferably the alkyl groups are t-butyl groups.

Typically, the composition comprises from 0.1 to 3.0 wt. % of the optionally alkylated triaryl phosphate ester, based on the total weight of the lubricating composition. Preferably, the composition comprises from 0.1 to 2.0 wt.%, preferably from 0.5 to 1.9 wt.%, more preferably above 1.3 wt.% and even more preferably above 1.5 wt.% of the optionally alkylated triaryl phosphate ester, based on the total weight of the lubricating composition.

According to preferred embodiment of the present invention, the poly (hydroxycarboxylic acid) amide salt derivative is present in the lubricating composition of the present invention in an amount in the range of from 0.1 to 10.0 wt.%, more preferably in an amount in the range of from 0.1 to 5.0 wt.%, based on the total weight of the lubricating composition. According to an especially preferred embodiment of the present invention, the composition comprises less than 2.5 wt.%, preferably less than 2.0 wt.%, more preferably less than 1.5 wt.%, even more preferably less than 1.2 wt.% of the one or more poly (hydroxycarboxylic acid) amide salt derivative, based on the total weight of the lubricant composition. Poly (hydroxycarboxylic acid} amide salt derivatives that are preferred in the present invention are those which each have a TBN {total base number} value of less than 10 mg KOH/g, as measured by ASTM D 4739. More preferably, the poly (hydroxycarboxylic acid) amide salt derivatives each have a TBN value of less than 5 mg KOH/g, most preferably 2 rag KOH/g or less, as measured by ASTM D 4739.

Examples of poly (hydroxycarboxylic acid) amide salt derivatives that are available commercially include that available from Lubrizol under the trade designation "SOLSPERSE 17000" {a reaction product of poly{12- hydroxystearic acid) with N,N-dimethyl-l, 3-propanediamine and dimethyl sulphate) and those available under the trade designations "CH-5" and "CH-7" from Shanghai Sanzheng Polymer Company.

There are no particular limitations regarding the base oil used in the lubricating composition according to the present invention, and various conventional mineral oils, synthetic oils as well as naturally derived esters such as vegetable oils may be conveniently used.

The base oil used in the present invention may conveniently comprise mixtures of one or more mineral oils and/or one or more synthetic oils; thus, according to the present invention, the term "base oil" may refer to a mixture containing more than one base oil. Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

Suitable base oils for use in the lubricating oil composition of the present invention are Group I-III mineral base oils, Group IV poly-alpha olefins (PAOs) , Fischer-Tropsch derived base oils, Group V synthetic oils and mixtures thereof.

By "Group I", "Group II", "Group III", "Group IV" and "Group V" base oils in the present invention are meant lubricating oil base oils according to the definitions of American Petroleum Institute (API) for category III and IV. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.

Fischer-Tropsch derived base oils are known in the art. By the term "Fischer-Tropsch derived" is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil in the lubricating composition of the present invention are those as for example disclosed in EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO 00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166. Synthetic oils include hydrocarbon oils such as olefin oligomers (including polyalphaolefin base oils; PAOs) , dibasic acid esters, polyol esters, polyalkylene glycols (PAGs), alkyl naphthalenes and dewaxed waxy isomerates. Synthetic hydrocarbon base oils sold by the Shell Group under the designation "Shell XHVI" (trade mark) may be conveniently used.

Poly-alpha olefin base oils (PAOs) and their manufacture are well known in the art. Preferred poly- alpha olefin base oils that may be used in the lubricating compositions of the present invention may be derived from linear Oz to C₃₂, preferably Cg to Ci₆, alpha olefins. Particularly preferred feedstocks for said poly- alpha olefins are 1-octene, 1-decene, - 1-dodecene and 1- tetradecene. The total amount of base oil incorporated in the lubricating composition of the present invention is preferably present in an amount in the range of from 60 to 99 wt. %, more preferably in an amount in the range of from 65 to 98 wt.% and most preferably in an amount in the range of from 70 to 95 wt.%, with respect to the total weight of the lubricating composition.

Preferably, the finished lubricating composition has a kinematic viscosity in the range of from 2 to 80 mm²/s at 100 ⁰C, more preferably in the range of from 3 to 70 ram²/s, most preferably in the range of from 4 to 50 mmVs.

The lubricating composition of the present invention may further comprise additional additives such as anti- wear additives, anti-oxidants, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, defoaming agents and seal fix or seal compatibility agents.

As the person skilled in the art is familiar with the above and other additives, these are not further discussed here in detail. Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526. The lubricating compositions of the present invention may be conveniently prepared by admixing the poly (hydroxycarboxylic acid) amide salt derivative, triaryl phosphate ester and, optionally, any further additives that are usually present in lubricating compositions, for example as herein before described, with mineral and/or synthetic base oil.

According to an especially preferred embodiment the composition has an ash content of below 0.011 wt.% according to ASTM D 482. Also it is preferred according to the present invention that the composition comprises less than 20.0 wt.% additives (i.e. components other than base oil), based on the total weight of the lubricating composition. In this case, the lubricating composition contains at least 80.0 wt.% base oil. Further it is preferred that the lubricating composition comprises a Fischer-Tropsch derived base oil.

When the compositions according to the present invention are to be used as aviation piston engine oils, the compositions typically have low S and P contents

(meeting the standards of SAE J 1899 and SAE J1966) which contents are dependent on the actual viscosity grade. Preferably, the S content is below 1.2 wt.%, more preferably below 1.0 wt.%, even more preferably below 0.6 wt.% (according to ASTM D 129), based on the total weight of the composition.

Preferably the lubricating composition according to the present invention meets all the specifications of a SAE J1899 (Grades 30, 40, 50, 60 or Multigrade, preferably Grade 50 or Multigrade) formulation (as revised in August 2005; SAE stands for Society of Automotive Engineers) . More in particular, the lubricating composition preferably has a pour point of not higher than -18°C (according to ASTM D97) and a flash point of not lower than 243°C (according to ASTM D92) .

Although there is no particular limitation regarding the base oil used in the above SAE 1899 (Grades 30, 40, 50, 60 or Multigrade) and other compositions according to the present invention, there is a preference for a combination of a mineral derived Group I base oil and a Fischer-Tropsch derived base oil or a combination of a PAO base oil and a Fischer-Tropsch derived base oil; in addition further base oils may be present (although the above combinations are preferred) . In the case of the combination of a mineral derived

Group I base oil and a Fischer-Tropsch derived base oil, the Group I base oil is preferably present in an amount of from 35 to 85 wt.%, more preferably from 50 to 75 wt.% and even more preferably from 50 to 70 wt.%, based on the total weight of the lubricating composition. In this case, the Fischer-Tropsch derived base oil is preferably present in an amount of from 10 to 60 wt.%, more preferably from 20 to 50 wt.% and even more preferably from 20 to 45 wt.%, based on the total weight of the lubricating composition.

In the case of a combination of a PAO base oil and a Fischer-Tropsch derived base oil, the PAO base oil is preferably present in an amount of from 35 to 85 wt.%, more preferably from 40 to 60 wt.% and even more preferably from 45 to 55 wt.%, based on the total weight of the lubricating composition. In this case the Fischer- Tropsch derived base oil is preferably present in an amount of from 20 to 70 wt.%, more preferably from 30 to 70 wt.% and even more preferably from 40 to 65 wt.%, based on the total weight of the lubricating composition.

In another aspect, the present invention provides the use of a poly (hydroxycarboxylic acid) amide salt derivative as defined in the present invention, in particular a lubricating composition containing it, for improving the dispersion of lead salts in an internal combustion engine, preferably an aviation piston engine fuelled by leaded fuel.

The person skilled in the art will readily understand that the lubricating composition according to the present invention may also be suitably used for other uses than in an internal combustion engine, especially where the reduction of deposits plays a role.

The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way. Examples Lubricating Compositions

Various lubricating compositions were formulated. Table 1 indicates the composition of the lubricating compositions that were tested; the amounts of the components are given in wt.%, based on the total weight of the compositions. All tested compositions were so-called low ash compositions, i.e. containing an ash content of below 0.011 wt.% according to ASTM D 482.

"Base oil 1" was a commercially available Group I base oil having a kinematic viscosity at 100⁰C (ASTM D445) of approx. 31.6 cSt (IHm²S^"1). Base oil 1 is commercially available from e.g. Shell Nederland

Raffinaderij B. V. under the trade designation "HVI 650".

"Base oil 2" was a commercially available Group I base oil having a kinematic viscosity at 100⁰C (ASTM D445} of approx. 8.5 cSt (ItSm²S^"1). Base oil 2 is commercially available from e.g. Shell UK Oil Products Limited under the trade designation "HVI 115".

"Base oil 3" was a Fischer-Tropsch derived base oil ("GTL 8") having a kinematic viscosity at 100⁰C (ASTM D445) of approx. 8 cSt (IRm²S^""1) . This GTL base oil may be conveniently manufactured similar to the process as described in e.g. WO 02/070631, the teaching of which is hereby incorporated by reference.

As the poly (hydroxycarboxylic acid) amide salt derivative a product commercially available from Shanghai Sanzheng Polymer Company under the trade designation "ens'' was used. "CH-5" product has a TBN value of approximately 2.0 mg KOH/g, as measured by ASTM D 4739. Furthermore, "CH-5" product has a sulphur content of approximately 0.86 wt.%, as measured by ICP-AES. As the optionally alkylated triaryl phosphate ester, a product commercially available from Supresta (Akzo Nobel; Amersfoort, The Netherlands) under the trade designation "Syn-O-Ad 8485" was used. Syn-O-Ad 8485 contains a mixture of triaryl esters including up to 60 wt.% trialkylated triaryl phosphate esters. The compositions of Examples 1-3 and Comparative Examples 1-11 were obtained by mixing the base oils with the other components (if any) using conventional lubricant blending procedures .

Table 1

Lead Dispersion Test

In order to demonstrate the lead dispersion properties of the present invention, measurements were performed according to the following bench test. A mixture of lead salts was used to mimic typical lead species found in aged piston engine oils. To this end a mixture of 112 mg PbO, 350 mg PbBr₂ and 300 mg Pb₃O₄ (all commercially available, e.g. from Aldrich Chemical Company, United Kingdom) was added to 30 ml of the compositions of Examples 1-3 and Comparative Examples I'll in a 50 ml test tube.

In a separate set of experiments, 340 mg PbO was added to 30 ml of the compositions of Examples 1-3 and Comparative Examples 1-11 in a 50 ml test tube. The leaded compositions were stirred using a magnetic stirrer bar and heated (60⁰C) during 9 hours to obtain homogenized suspensions containing lead concentrations of about 2000 ppm Pb. The homogenized leaded compositions were subsequently stored undisturbed at room temperature during 20 days (apart from Example 5 which was stored for 21 days) .

A 1 ml sample of each leaded composition was taken from the upper part of each composition. Each sample was diluted ten-fold using a commercially available SAE Grade 50 oil, composed of Group I mineral base oil. The diluted samples were analysed for total lead content by X-ray fluorescence (XRF) spectroscopy.

The total lead content of the samples was determined using a PANalytical Axios Petro 4 kW WD-XRF instrument {available from PANalytical, Almelo, The Netherlands) ; as a reference the SAE Grade 50 oil as such was used.

The following settings were used: sample cell: liquid sample cell using 2.5 μm Mylar film - collimator mask: 150 μm - analysing crystal: LiF 220

- power: 60 kV, 66 rriA (4kW) .

The measured total lead contents (in ppm) suspended in the compositions are indicated in Table 2 below, both for the samples containing the lead salt mixture and the samples containing PbO. Table 2

SAE J1899 (Grade 50 & Multigrade) Formulations

In addition to the formulations as indicated in Table 1 above, compositions meeting the SAE J1899 (Grade 50 & Multigrade} specification (as revised in August 2005) for use in aviation piston engines were formulated.

Table 3 indicates the composition of the lubricating compositions that were tested {Examples 4-8 and Comparative Examples 12-14); the amounts of the components are given in wt.%, based on the total weight of the compositions .

For "Base oil 3", "CH-5" and "Syn-O-Ad 8485" reference is made to the information as given above.

"Base oil 4" was a Fischer-Tropsch derived base oil ("GTL 5") having a kinematic viscosity at 100⁰C (ASTM D445) of approx. 5 cSt; this GTL base oil may be conveniently manufactured similar to the process as described in e.g. above-mentioned WO 02/070631.

"Base oil 5" was a commercially available PAO base oil (Group IV) having a kinematic viscosity at 100⁰C (ASTM D445) of approx. 6 cSt (TtIm²S^"1) . Base oil 5 is commercially available from e.g. Chevron Phillips Chemical Company LP (The Woodlands, TX, USA) under the trade designation "Synfluid® PAO 6 cSt". "Base oil 6" was a commercially available Group I base oil having a kinematic viscosity at 100 ^σC (ASTM D445) of approx. 7.05 cSt (JTUn²S^"1). Base oil 6 is commercially available from e.g. Shell Canada Products, (Brockville, Ontario, Canada) under the trade designation "HVI 95".

"Base oil 1" was a commercially available Group I base oil having a kinematic viscosity at 100⁰C (ASTM D445) of approx. 32.9 cSt (ITIm²S^"1) . Base oil 7 is commercially available from e.g. Shell Canada Products (Brockville, Ontario, Canada) under the trade designation "HVI 650".

The "Additive package 1" (the same for Examples 4, 5 and Comparative Examples 12 and 13) contained a conventional combination of additives including a phenolic anti-oxidant , a viscosity modifier, a pour point depressant, a triazole-type corrosion inhibitor, a glycerol mono-oleate type friction modifier and an antifoam agent.

The "Additive package 2" (the same for Examples 6-8 and Comparative Example 14) contained a conventional combination of additives including a phenolic antioxidant and an aminic antioxidant, a viscosity modifier, a pour point depressant, a succinimide dispersant, a triazole-type corrosion inhibitor, a glycerol mono-oleate type friction modifier and an antifoam agent. For Examples 6-8 and Comparative Example 14 the amount of additive package is different as the amount of VI improver was adapted (the other additives were used in the same treat rate) with changes in the base oils (in order to meet the SAE J1899 (Grade Multigrade) specifications) .

Table 3

K)

Whilst using the same lead dispersion test procedure as described above (apart from the fact that the samples were stored for 12 days instead of 20/21 days) , the measured total lead contents (in ppm) suspended in the compositions were obtained as indicated in Table 4 below, again both for the samples containing the lead salt mixture and the samples containing PbO. Table 4

Discussion

As is clearly shown in Tables 2 and 4, the lead dispersion properties for the compositions according to the present invention were significantly improved when compared with the Comparative Examples (a high measured lead content indicates a good lead dispersion) .

From Table 2 it can be learned that especially desired lead dispersion values were obtained according to the present invention when a Group I mineral derived base oil was used.

From Comparative Examples 1, 2 and 3 it is evident that the poly (hydroxycarboxylic acid) amide salt derivative ("CH-5") as such is able to suspend lead salts effectively without the use of an alkylated triaryl phosphate (NB: this has not been acknowledged yet in the prior art) . However, from Example 2 (containing the alkylated triaryl phosphate ester) and Comparative Example 2 (not containing the alkylated triaryl phosphate ester) it can be learned, that there is a preference for presence of the alkylated triaryl phosphate ester, as an improved PbO dispersion can be obtained. In this respect it is noted that Example 2 shows a clear synergy with respect to lead dispersion when compared with Comparative Example 8 (containing the same base oil and same amount of alkylated triaryl phosphate ester but not the poly (hydroxycarboxylic acid) amide salt derivative "CH- 5") and Comparative Example 2. It can clearly be seen from Table 2 that the total lead content for PbO for Example 1 (containing both the CH-5 product and the alkylated triaryl phosphate ester) is significantly higher than for Comp. Ex. 1 {not containing the alkylated triaryl phosphate ester) . Although the total lead content for PbO, PbBr₂ and Pb₃O^ was better for Comp. Ex. 1 than for Example 1, it is to be noted that in both cases the value was above a desirable 200 ppm, indicating satisfying lead dispersion properties. Example 3 (containing a Fischer-Tropsch derived base oil) shows - when compared with Comparative Examples 9-11 - that a surprising advantage of the present invention is that desirable lead dispersion properties can also be obtained when using a non-polar base oil type such as PAO, XHVI and in particular Fischer-Tropsch derived base oils. This is surprising as non-polar base oils are usually quite ineffective at dispersing and suspending polar salts (such as lead salts) within the fluid.

The results in Table 4 show that desirable lead dispersion properties are obtained in SAE 1899 (Grade 50 & Multigrade) lubricating compositions as well. Also, Table 4 shows that these desirable properties can be obtained whilst using a combination of a mineral derived base oil and a Fischer-Tropsch derived base oil, a combination of a mineral derived base oil and a PAO base oil or a combination of a PAO base oil and a Fischer-Tropsch derived base oil. By comparing e.g. Comparative Example 14 and Example 6 it can be clearly seen that significant improvement in lead dispersion can be obtained according to the present invention.

Claims

L A I M S

1. A lubricating composition comprising:

- a base oil;

- a poly {hydroxycarboxylic acid) amide salt derivative having formula (III) :

[Y-CO [O-A-CO]_π~Z-R⁺]_m pX^q" (III) wherein Y is hydrogen or an optionally substituted hydrocarbyl group, A is a divalent optionally substituted hydrocarbyl group, n is from 1 to 100, preferably from 1 to 10, m is from 1 to 4, q is from 1 to 4 and p is an integer such that pq = m, Z is an optionally substituted divalent bridging group which is attached to the carbonyl group through a nitrogen atom, R⁺ is an ammonium group and X^q~ is an anion; and

- an optionally alkylated triaryl phosphate ester.

2. Lubricating composition according to claim 1, wherein the alkyl moieties of the alkylated triaryl phosphate ester are alkyl groups having from 1 to 8 carbon atoms, preferably t-butyl groups.

3. Lubricating composition according to claim 1 or 2, wherein composition comprises from 0.10 to 2.0 wt.% of the optionally alkylated triaryl phosphate ester, based on the total weight of the lubricating composition.

4. Lubricating composition according to any of the preceding claims 1 to 3, wherein the poly (hydroxycarboxylic acid) amide salt derivative has a TBN (total base number) value of less than 10 mg KOH/g.

5. Lubricating composition according to any of the preceding claims 1 to 4, wherein the composition comprises less than 2.5 wt.%, preferably less than 2.0 wt.%, more preferably less than 1.5 wt.%, even more preferably less than 1.2 wt.% of the poly {hydroxycarboxylic acid) amide salt derivative, based on the total weight of the lubricating composition.

6. Lubricating composition according to any of the preceding claims 1 to 5, wherein the composition has an ash content of below 0.011 wt.% according to ASTM D 482.

7. Lubricating composition according to any of the preceding claims 1 to 6, wherein the composition comprises less than 5.0 wt.% additives, based on the total weight of the lubricating composition.

8. Lubricating composition according to any of the preceding claims 1 to 7, wherein the composition comprises a Fischer-Tropsch derived base oil.

9. Lubricating composition according to any of the preceding claims 1 to 8, wherein the composition comprises a Group I mineral derived base oil.

10. Lubricating composition according to any of the preceding claims 1 to 9, wherein the composition comprises a PAO base oil.

11. Lubricating composition according to any of the preceding claims 1 to 10, meeting the specifications of a SAE J1899 formulation.

12. Use of a lubricating composition according to any of the preceding claims for improving the dispersion of lead salts in an internal combustion engine, preferably an aviation piston engine fuelled by leaded fuel.