EP2336278A1

EP2336278A1 - Use of a lubricating composition

Info

Publication number: EP2336278A1
Application number: EP09179202A
Authority: EP
Inventors: Don-Hak Bae; Robert Jude Sutherland; Mark Clift Southby
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2009-12-15
Filing date: 2009-12-15
Publication date: 2011-06-22

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 long-term friction reduction properties and/or extending drain interval, preferably in internal combustion engines.

Description

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. Furthermore, WO 2009/053414 discloses the use of poly(hydroxycarboxylic acid) amide salts derivatives in order to improve friction reduction and anti-wear properties in an internal combustion engine.
It is known in the field of lubricants that many components (or compositions containing them) that are useful for friction reduction quickly lose their activity to lower the friction in aged oils. See for example "Consortium to Develop a New Sequence VID Fuel Efficiency Test for Engine Oils", final report dated 15 October 2008, available via www.astmtmc.cmu.edu, disclosing that the typical lifetime of friction modifiers is about 2000 to 3000 miles of engine use.
It has now surprisingly been found according to the present invention that poly(hydroxycarboxylic acid) amide salts derivatives also exhibit surprisingly advantageous long-term friction reduction properties and thereby allow an extended drain interval.
Accordingly, the present invention provides the 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⁺]_m pX^q- (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 long-term friction reduction properties and/or extending drain interval, preferably in internal combustion engines.

According to the present invention with "long-term" friction reduction is meant, longer than the typical lifetime of friction modifiers (which is about 2000 to 3000 miles of engine use), e.g. longer than 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10,000, 12,000 or even longer than 15,000 miles of service in an operating engine.
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 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 C_1-4 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 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 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 C_1-4 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)
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)₂CH₂- and -NH(CH₂)₃-. Preferably, R⁺ may be represented by formula (V)
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 ^-, O^2-, O₂ ^2-, BeF₃ ^-, F^-, Na^-, [Al(H₂O)₂(OH)₄]^-, SiO₃ ^2- , SiF₆ ^2-, H₂PO₄ ^-, P^3-, PO₄ ^3-, HPO₄ ^2-, Cl^-, ClO₃ ^-, ClO₄ ^-, ClO^-, KO^-, SbOH₆ ^-, SnCl₆ ^2-, [SnTe4]^4-, CrO₄ ^2-, Cr₂O₇ ^2-, MnO₄ ^-, NiCl₆ ^2-, Cu(CO₃)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, 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 "insert" 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 C_1-4 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 -250°C, 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 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 (-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 , 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-1,3-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(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 .
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-1,3-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 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
paraffinic/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, more 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 °C, 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, anti-wear additives, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, defoaming agents and seal fix or seal compatibility agents. For examples of suitable and preferred additives reference is made to page 15, line 9 - page 17, line 5 and page 19, line 3 - page 23, line 4 of WO 2007/128740 , the teaching of which is incorporated by specific reference.
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 further additives that are usually present in lubricating compositions, for example as herein before described, with mineral and/or synthetic base oil.
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 friction reduction 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 SAE 5W-30 engine oils according to the so-called SAE J300 Specifications (as revised in January 2009). SAE stands for Society of Automotive Engineers.
The "Base oil" was a API group III base oil, according to the definitions of American Petroleum Institute (API) in API 1509.
The additive package (the same for both compositions) was a conventional additive package containing detergents, PIB succinimide dispersant, zinc dithiophosphate anti-wear additive, pour point depressant, viscosity index improver, 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

Component [wt. %] Example 1 Comp. Ex. 1

Base oil 88.65 90.65

Additive package 9.35 9.35

"CH-5" additive 2.0 -

TOTAL 100 100

HFFR Friction Screener Test

In order to demonstrate the improved long-term friction properties of the present invention, friction coefficient measurements were made using the HFFR (High Frequency Friction Rig) friction screener test according to ASTM D 6079 whilst using a HFFR friction screener having a ball-on-plate geometry (ball: 52100 3/16" hardened steel (58-66 Rockwell C, Ra < 0.05 microns); disk: 52100 polished steel (190-210 Hv30; Ra < 0.02 microns). The following settings were used in the HFFR Friction Screener Test:

- Temperature: 60-140°C (10°C increments);

- Load: 3.92 N (400 g);

- Speed: 20 Hz;

- Stroke length: 1 mm;

- Test time: 10 min at each temperature.
Before measurement in the HFFR-test, the above engine oils were aged in a taxi fleet in New York City, NY, USA. The engine oils were sampled every few thousand miles for about 10,000 (Comparative Example 1) to 15,000 (Example 1) test miles. The taxi drivers were unaware of the engine oils being tested in their taxis and so went about their normal daily routines. The measured friction coefficients of the sampled engine oils at 100°C, 120°C and 140°C are indicated in Table 2 below.

Discussion

As can be learned from Table 2, the long-term friction coefficients for Example 1 were significantly improved when compared with Comparative Example 1; the data in Table 2 shows that the present invention allows to significantly extend the lifetime (and thereby the drain interval) of the engine oil, whilst maintaining desirable friction coefficient values.
The data in Table 2 show that the friction reduction properties of Example 1 continue to function even after 5000, 7000, 10,000 and even up to or beyond 15,0000 miles of service in an operating engine. This is surprising as traditional friction reduction agents stop functioning after a few thousand (typically 2000-3000) miles of service in operating service; see in this respect the "Consortium to Develop a New Sequence VID Fuel Efficiency Test for Engine Oils", final report, as mentioned above.
The findings according to the present invention are even more remarkable in the sense that ageing of engine oils under taxi service is deemed more severe than under "normal" passenger car service.
The person skilled in the art will understand the positive influence the present invention may have on emissions and fuel economy in view of the desirable friction coefficient values.

Claims

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*]_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;
for the improvement of long-term friction reduction properties and/or extending drain interval, preferably in internal combustion engines.
Use according to claim 1, wherein the long-term friction reduction properties are determined using the HFFR test according to ASTM D 6709.
Use according to claim 1 or 2, wherein the drain interval is extended beyond 3,000 miles, preferably beyond 5,000 miles, more preferably beyond 10,000 miles, even more preferably beyond 15,000 miles.