WO2009156393A1

WO2009156393A1 - Use of a lubricating composition comprising a poly(hydroxycarboxylic acid) amide

Info

Publication number: WO2009156393A1
Application number: PCT/EP2009/057807
Authority: WO
Inventors: Jane Elizabeth Frank; Mark Clift Southby
Original assignee: Shell Internationale Research Maatschappij B.V.
Priority date: 2008-06-24
Filing date: 2009-06-23
Publication date: 2009-12-30
Also published as: RU2499036C2; JP2011525563A; BRPI0914271A2; EP2300580A1; RU2011102385A; CN102105572A

Abstract

The present invention provides the use of a lubricating composition comprising a base oil and one or more poly (hydroxycarboxylic acid) amide salt derivatives for the improvement of piston cleanliness, preferably in internal combustion engines, in particular tested according to one or more of TU5 (CEC L- 88 -TO 2) and ASTM D6984. Preferably, one or more of the poly (hydroxycarboxylic acid) amide salt derivatives have a TBN (total base number) value of less than 10 mg.KOH/g,

Description

_ i _

USE OF A LUBRICATING COMPOSITION COMPRISING A POLY(HYDROXYCARBOXYLIC ACID) AMIDE

The present invention relates to the use of a lubricating oil for particular use in internal combustion engines .

WO 2007/128740 discloses the use of poly (hydroxycarboxylic acid) amide salts derivatives in order to reduce deposits in an internal combustion engine .

It has now surprisingly been found according to the present invention that poly (hydroxycarboxylic acid) amide salts derivatives not only suppress internal combustion engine fouling, exhibit advantageous cleaning performance in the reduction of deposits such as sludge and varnish, show surprisingly advantageous friction reduction and anti-wear properties but also exhibit improved piston cleanliness.

Accordingly, the present invention provides a lubricating composition comprising: a base oil; and one or more poly (hydroxycarboxylic acid) amide salt derivatives having formula (III) :

[Y-CO [0-A-CO]_n-Z-R⁺] _m pX^g- (III)

wherein Y is hydrogen or 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; for the improvement of piston cleanliness, preferably in internal combustion engines, in particular tested according to one or more of TU5 (CEC L-88-T02) and ASTM D6984. In this respect it is noted that on the one hand sludge and varnish deposits and on the other hand piston deposits are chemically different and formed through different processes.

As described in the above-mentioned WO 2007/128740 (see in particular page 2, lines 12-23) sludge and varnish deposits form through complex interactions of lubricating oil composition components with contaminants under differing engine conditions. Under low temperature operating conditions, such as short automotive trips, a lubricating oil composition may not get hot enough for contaminants such as water and fuel components to evaporate. At high temperatures a lubricating oil composition can oxidise, producing reactive groups and thickening. These conditions promote reactions with unburnt and partially burnt fuel, water, soot, acids, blow-by gases and other contaminants to form sludges and varnish.

In contrast, piston deposits (which are specifically avoided according to the present invention) are hard carbon deposits resulting from the carbonisation of the lubricating oil and fuel on hot surfaces. These deposits have a lower carbon content than soot and usually contain oily material and ash. They are commonly found on the piston top lands and crowns and in piston ring grooves. In formula (III) of 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 hydroxy1 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 hereinbefore 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 naphtliyl, 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 σarbonyl, 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 sulph.ox.yi 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- hydroxyoleyl 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) R I¹ 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(CH₃)SCH₂- and -NH (CH₂) ₃-. Preferably, R⁺ may be represented by formula (V)

R³ / -⁺N~R² (V)

\

R⁴

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

Preferably, 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.

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]₁₁-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, 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, methylpentyl , 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 C_4-8 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 -CH₂- 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-^ 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 hydroxy1 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 hyάroxycarboxylic 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 interesterifiσation, 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 C_1-4 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-hydroxycaproic 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 (-0-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, US 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-propanediamine, triamines and polyamines selected from dietheylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and tris (2-aminoethyl) amine.

The amidation 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 (hydroxycarboxylie 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. According to preferred embodiment of the present invention, the one or more poly (hydroxycarboxylic acid) amide salt derivatives are 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.% and most preferably in an amount in the range of from 0.2 to 4.0 wt. %, based on the total weight of the lubricating 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 mg.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. The one or more anti -wear additives in the lubricating composition of the present invention are preferably present in an amount in the range of from 0.01 to 10.0 wt. %, based on the total weight of the lubricating composition. Preferably, the one or more anti-wear additives present in the lubricating composition may comprise zinc dithiophosphates. The or each zinc dithiophosphate may be selected from zinc dialkyl-, diaryl- or alkylaryl- dithiophosphates . For preferred zinc dithiophosphates reference is made to page 15, line 19 - page 16, line 17 of WO 2007/128740, the teaching of which is incorporated by specific reference.

The lubricating composition according to the present invention preferably comprises in the range of from 0.01 to 10.0 wt .% of zinc dithiophosphates, based on total weight of the lubricating composition.

Additional or alternative anti-wear additives may be conveniently used in the lubricating composition of the present invention.

In a preferred embodiment of the present invention, the lubricating composition further comprises one or more detergents, in particular one or more salicylate, phenate or sulphonate detergents. Said detergents are preferably selected from alkali metal or alkaline earth metal salicylate, phenate or sulphonate detergents. Calcium and magnesium salicylates, phenates and sulphonates are particularly preferred.

Said detergents are preferably used in amounts in the range of 0.05 to 12.5 wt.%, more preferably from 1.0 to 9.0 wt.% and most preferably in the range of from 2.0 to 5.0 wt.%, based on the total weight of the lubricating composition.

There are no particular limitations regarding the base oil used in the present invention, and various conventional known mineral oils and synthetic 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.

Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed paraffiniσ/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

Naphthenic base oils have low viscosity index (VI) (generally 40-80) and a low pour point. Such base oils are produced from feedstocks rich in naphthenes and low in wax content and are used mainly for lubricants in which colour and colour stability are important, and VI and oxidation stability are of secondary importance.

Paraffinic base oils have higher VI (generally >95) and a high pour point. Said base oils are produced from feedstocks rich in paraffins, and are used for lubricants in which VI and oxidation stability are important.

Fischer-Tropsch derived base oils may be conveniently used as the base oil in the lubricating composition of the present invention, for example, the Fischer-Tropsch derived base oils 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 processes enable molecules to be built from simpler substances or to have their structures modified to give the precise properties required.

Synthetic oils include hydrocarbon oils such as olefin oligomers (PAOs), dibasic acid esters, polyol esters, and dewaxed waxy raffinate. Synthetic hydrocarbon base oils sold by the Shell Group under the designation "XHVI" (trade mark) may be conveniently used.

Preferably, the base oil is constituted from mineral oils and/or synthetic oils which contain more than 80 wt. % of saturates, preferably more than 90 wt.%, as measured according to ASTM D2007.

It is further preferred that the base oil contains less than 1.0 wt.%, preferably less than 0.1 wt.% of sulphur, calculated as elemental sulphur and measured according to ASTM D2622, ASTM D4294, ASTM D4927 or ASTM D3120.

Preferably, the viscosity index of the base oil is more than 80, mox^~e preferably more than 120, as measured according to ASTM D2270.

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 92 wt. %, more preferably in an amount in the range of from 75 to 90 wt . % and most preferably in an amount in the range of from 75 to 88 wt.%, with respect to the total weight of the lubricating composition.

Preferably, the 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 mm²/s, most preferably in the range of from 4 to 50 mm²/s.

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

Antioxidants that may be conveniently used include those selected from the group of aminic antioxidants and/or phenolic antioxidants. In a preferred embodiment, said antioxidants are present in an amount in the range of from 0.1 to 5.0 wt.%, more preferably in an amount in the range of from 0.3 to 3.0 wt . % , and most preferably in an amount of in the range of from 0.5 to 1.5 wt.%, based on the total weight of the lubricating composition.

For examples of suitable or preferred aminic and phenolic antioxidants, reference is made to page 19, line 18 - page 21, line 32 of WO 2007/128740, the teaching of which is hereby incorporated by specific reference. The lubricating compositions of the present invention may additionally contain an ash-free dispersant which is preferably admixed in an amount in the range of from 5 to 15 wt.%, based on the total weight of the lubricating composition. Examples of ash- free dispersants which may be used include the polyalkenyl succinimides and polyalkenyl succininic acid esters disclosed in Japanese Laid-Open Patent Application Nos. JP 53-050291 A, JP 56-120679 A, JP 53-056610 A and JP 58-171488 A. Preferred dispersants include borated succinimides.

Examples of viscosity index improvers which may conveniently be used in the lubricating composition of the present invention include the styrene-butadiene copolymers, styrene-isoprene stellate copolymers and the polymethacrylate copolymer and ethylene-propylene copolymers. Dispersant -viscosity index improvers may be used in the lubricating composition of the present invention. Such viscosity index improvers may be conveniently employed in an amount in the range of from 1 to 20 wt.%, based on the total weight of the lubricating composition.

Polymethacrylates may be conveniently employed in the lubricating compositions of the present invention as effective pour point depressants.

Furthermore, compounds such as alkenyl succinic acid or ester moieties thereof, benzotriazole-based compounds and thiodiazole-based compounds may be conveniently used in the lubricating composition of the present invention as corrosion inhibitors.

Compounds such as polysiloxanes, dimethyl polycyclohexane and polyacrylates may be conveniently used in the lubricating composition of the present invention as defoaming agents. Compounds which may be conveniently used in the lubricating composition of the present invention as seal fix or seal compatibility agents include, for example, commercially available aromatic esters.

The lubricating compositions of the present invention may be conveniently prepared by admixing the one or more poly (hydroxycarboxylic acid) amide salt derivatives and, optionally, one or more anti-wear additives, one or more detergents and further additives that are usually present in lubricating compositions, for example as herein before described, with mineral and/or synthetic base oil .

In another aspect the present invention provides a method of improving piston cleanliness properties, in particular tested according to one or more of TU5 (CEC L- 88-T02) and ASTM D6984, and preferably in an internal combustion engine, which method comprises lubricating (preferably said internal combustion engine) with the lubricating composition according to the present invention. The person skilled in the art will readily understand that the lubricating composition may also be suitably used for other uses than in an internal combustion engine, where piston cleanliness properties play 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 Oil Compositions

Table 1 indicates the composition of the lubricating oil compositions that were tested; the amounts of the components are given in wt . % .

All tested compositions were formulated as 15W-40 engine oils according to the so-called SAE J300

Specifications (as revised in May 2004) . SAE stands for Society of Automotive Engineers.

The "Base oil" was a API group I base oil, according to the definitions of American Petroleum Institute (API) . The additive package (the same for both compositions) was a conventional additive package containing sulphonate and phenate detergents having TBNs in the range of from 30 to 350 mg.KOH/g, PIB succinimide dispersant, zinc dithiophosphate anti-wear additive, pour point depressant, anti-foam agent and diluent oil.

The poly (hydroxycarboxylic acid) amide salt derivative according to the present invention that was used in testing was a product available commercially from Shanghai Sanzheng Polymer Company under the trade designations "CH-5" .

"CH-5" product has a TBN value of approximately 1.9 mg.KOH, as measured by ASTM D 4739. Furthermore, "CH- 5" product has a sulphur content of approximately 0.95 wt . % as measured by ICP-AES. Table 1

TU5 (CEC L-88-T02) Test

In order to demonstrate the improved piston cleanliness properties of the present invention, measurements were made according to the Peugeot TU5 test . The Peugeot TU5 test evaluates high-temperature deposits, ring sticking and oil thickening in a modern engine with controlled ignition. This test simulates high-speed, European highway driving.

For this test, a Peugeot TU5 JP+L4 , 1.5 litre, inline, 4-cylinder engine with a modified oil sump, mounted on a test stand with a dynamometer, is used.

The test runs six 12 -hour, 2 -phase cycles for a total test duration of 72 hours. Phase 1 (11 hours 50 minutes) is at wide-open throttle, 5,600 rpm, 150⁰C oil and coolant temperatures. Phase 2 is at idle for 10 minutes .

The pistons are rated for lacquer, carbon, and ring sticking. The measured piston cleanliness values (merits) are indicated in Table 2 below. Sequence HIF Test (ASTM D6984)

In order to demonstrate the improved piston cleanliness properties of the present invention, measurements were made according to the Sequence IIIF test.

The Sequence IIIF test measures oil thickening and piston deposits under high-temperature conditions and provides information about valve train wear. The test simulates high-speed service under relatively high ambient conditions.

A 1996/1997 231 CID (3,800 cc) Series II General Motors V- 6 fuel- injected gasoline engine was used.

In the test, using unleaded gasoline, the engine runs a 10-minute initial oil-leveling procedure followed by a 15--minute slow ramp up to speed and load conditions, It then operates at 100 bhp, 3,600 rpm, and 155 ⁰C oil temperature for 80 hours, interrupted at 10 -hour intervals for oil level checks. At the end of test, all six pistons are inspected for deposits and varnish, camshaft and lifters are measured for wear, oil screen plugging is evaluated, kinematic viscosity increase (percent) at 4O⁰C is compared to a new oil baseline every 10 hours and wear metals (Cu, Pb, and Fe) are evaluated.

The measured piston cleanliness values (merits) are indicated in Table 2 below. Table 2

Discussion

As can be learned from Table 2 the piston cleanliness for Example 1 was significantly improved when compared with Comparative Example 1.

The above shows that lubricating compositions containing poly (hydroxycarboxylic acid) amide salts derivatives not only suppress internal combustion engine fouling, exhibit advantageous cleaning performance in the reduction of deposits such as sludge and varnish (as shown already in WO 2007/128740) , but also exhibit improved piston cleanliness, in particular according to TU5 (CEC L-88-T02) and ASTM D6984.

Claims

C L A I M S

1. Use of a lubricating composition comprising: a base oil; and one or more poly (hydroxycarboxylic acid) amide salt derivatives having formula (III) :

[Y-CO[O-A-CO]_n-Z-R⁺]_ni pX^q" (III)

wherein Y is hydrogen or an optionally substituted hydrocarbyl group, A is a divalent optionally substituted bydrocarbyl 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; for the improvement of piston cleanliness, preferably in internal combustion engines, in particular tested according to one or more of TU5 (CEC L-88-T02) and ASTM D6984.

2. Use according to claim 1, wherein one or more of the poly (hydroxycarboxylic acid) amide salt derivatives have a TBN (total base number) value of less than 10 mg.KOH/g.

3. A method of improving piston cleanliness properties, in particular tested according to one or more of TU5 (CEC L-88-T02) and ASTM D6984, preferably in an internal combustion engine, which method comprises lubricating with a lubricating composition as defined in claim 1 or 2.