KR20160090872A - The use of polyalkylene glycol esters in lubricating oil compositions - Google Patents

Abstract

The invention as claimed in the present invention relates to the use of polyalkylene glycol esters prepared by reacting polytetrahydrofuran with at least one C ₉ -C ₂₇ acid in a lubricating oil composition.

Description

The use of polyalkylene glycol esters in lubricating oil compositions is disclosed in < RTI ID = 0.0 > U. < / RTI >

The invention as claimed in the present invention relates to the use of polyalkylene glycol esters prepared by reacting polytetrahydrofuran with at least one C ₉ -C ₂₇ acid in a lubricating oil composition.

Lubricant compositions are used in a variety of applications such as industrial applications, transportation means and engines. Industrial applications are made up of applications such as hydraulic oil, air compressor oil, gas compressor oil, gear oil, bearing and circulating system oil, refrigeration compressor oil and steam and gas turbine oil.

Typical lubricant compositions include a base stock, a cosolvent, and additives. The base stock is selected according to the viscosity desired in the application sketched in each case. The different viscosities, i. E. The combination of low and high viscosity base stocks, are often used to adjust the required final viscosity. The co-solvent is generally used to dissolve the polar additive in a less polar or non-polar base stock.

The most common additives are antioxidants, detergents, anti-wear additives, metal deactivators, corrosion inhibitors, friction modifiers, extreme pressure additives, defoamers, anti-foaming agents, viscosity index improvers and anti-fogging agents. These additives are used to impart additional advantageous properties to the lubricant composition, including longer stability and additional protection.

However, after a certain working time, the lubricating oil composition should be replaced for various reasons such as lubricity loss and / or product degradation. Depending on the affinity of the machine (engine, gear box, compressor ...), engineering design and lubricating components attached to the surface, certain residues of the lubricating oil composition (hold-up) Gears and so on. When replaced with unused and possibly different lubricant compositions, the lubricant used and the new lubricant are mixed with each other. Thus, in order to avoid any complexity during operation, compatibility between old lubricant and new lubricant is very important.

Depending on its chemical nature, the various components of the lubricating oil composition may be non-compatible with one another, i.e. mixtures of these components cause oil gelling, phase separation, solidification or foaming. Oil gelling causes a dramatic increase in viscosity, which can eventually lead to engine problems, and even if the damage is severe, the engine may need to be replaced. Thus, when providing a novel compound for use in a lubricating oil composition, it must always ensure that such compound is compatible with the compounds commonly used in lubricating oil compositions.

In addition to compatibility with other lubricants, another area to consider is energy efficiency. Efficiency can be increased if losses are minimized. Losses can be classified as loss without load and loss with load, the sum of which is total loss. Within many parameters that can be influenced by geometry, materials, etc., lubricant viscosity has a major effect on loss-free loss, or spilling: loss with load can be affected by low friction coefficient have. Thus, at a given viscosity, the energy efficiency is highly variable with the friction coefficient measured for the lubricant.

The coefficient of friction can be measured by various methods such as Mini-Traction-Machine (MTM), SRV, 2 disc test rig, and the like. The benefit of MTM is that it can see the coefficient of friction as an effect of the slide roll ratio. The slide rotation rate describes the difference in speed of the ball and disk used in the MTM.

EP 0 193 870 A2 discloses a cooling mill lubricant for steel sheets containing polyalkylene glycol esters prepared from polyethylene glycol and linear fatty acids.

DE 195 1 493 C1 describes compositions comprising at least one base oil which is a thickener and a polyether.

Japanese Patent Application Publication Nos. 2005-232434 and 2008-7741 disclose bearing lubricants comprising polyalkylene glycol esters derived from linear or branched saturated aliphatic monocarboxylic acids and polyalkylene glycols .

US 5,744,432 discloses polyesters which are the reaction products of one or more carboxylic acids and polyalkylene glycols. These polyesters are used in aqueous-based stamping lubricants.

It is therefore an object of the invention claimed in the present invention to provide a compound which exhibits a low coefficient of friction and is compatible with base stocks, such as mineral oils and polyalphaolefins, which are commonly used in lubricating oil compositions for the production of lubricating oil compositions.

Surprisingly, polyalkylene glycol esters prepared by reacting polytetrahydrofuran with one or more C ₉ -C ₂₇ acids exhibit low coefficient of friction and are generally used in base oils such as mineral oils and polyalphaolefins, Is compatible with low viscosity polyalphaolefins and can thus be used in formulation of lubricating oil compositions.

Thus, in one embodiment, the claimed invention relates to the use of a polyalkylene glycol ester of formula (I) as a lubricant:

[Wherein,

k is an integer ranging from 2 or more to 30 or less,

R ¹ and R ² are the same or different and are each a C 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, Unsubstituted, branched alkyl radicals.

The term "lubricant" means a component capable of reducing friction between surfaces in the sense of the claimed invention.

As used herein, "branched" refers to a chain of atoms having one or more side chains attached thereto. Branching occurs by substitution by a covalently bonded alkyl radical, for example by replacement of a hydrogen atom.

"Alkyl radical" refers to a moiety consisting of carbon atoms and hydrogen atoms alone, without any type of unsaturation, e. G., Double bonds and / or triple bonds.

In other words, the branched alkyl radical has at least one branched carbon atom, more preferably one or two or three branched carbon atoms, even more preferably one or two branched carbon atoms, most preferably one Containing a branched carbon atom. Within the scope of the present invention, a "branched carbon atom" means a carbon atom (3 ° carbon atom) of an alkyl radical bonded to three additional carbon atoms and a carbon atom (4 ° carbon Atom).

The polyalkylene glycol esters of the formula (I) claimed in the present invention are useful and they are mineral oils and / or polyalphaolefins in a weight ratio of 10:90, 50:50 and 90:10, preferably low viscosity polyalpha When mixed with an olefin, the polyalkylene glycol ester of formula (I) claimed in the present invention is allowed to stand for 24 hours at room temperature for two or more weight ratios in three weight ratios of 10:90, 50:50 and 90:10 But does not exhibit phase separation.

Preferably the polyalkylene glycol is ≥ 30 mm ² / s to ≤ 300 mm is the kinematic viscosity measured in accordance with ASTM D 445 eseo 40 ℃ ² / s, more preferably ≥ 30 mm ² / s of formula (I) Lt; ² > / s.

Preferably, the polyalkylene glycol esters of formula (I) have a kinematic viscosity measured according to ASTM D 445 of > 5 mm ² / s to 100 mm ² / s to 100 mm ² / s, more preferably 7 mm ² / s Lt; ² > / s.

Preferably the polyalkylene glycol esters of formula (I) have pour points in the range of > -40 DEG C to < 0 DEG C, more preferably > -30 DEG C to < 0 DEG C, according to DIN ISO 3016.

Preferably, the polyalkylene glycol esters of formula (I) have a weight average molecular weight Mw of 500 to 4500 g / mol, more preferably in the range of 500 to 4000 g / mol, measured according to DIN 55672-1, More preferably from 600 to 3500 g / mol, even more preferably from 700 to 3500 g / mol.

Preferably, the polyalkylene glycol esters of formula (I) have a number average molecular weight, Mn, determined according to DIN 55672-1 of 400 to 4000 g / mol, more preferably 500 to 3500 g / mol, most preferably 500 To 3000 g / mol, even more preferably from 500 to 2500 g / mol.

Preferably, the polyalkylene glycol esters of formula (I) have a polydispersity of from 1.1 to 2.0, more preferably from 1.1 to 1.9 and most preferably from 1.1 to 1.8 as measured according to DIN 55672-1.

Preferably, the polyalkylene glycol esters of formula (I) have a total acid number of not less than 0.01 to not more than 2.5 mg KOH / g, more preferably not less than 0.01 to not more than 2.4 mg KOH / g measured according to ASTM D664, Is in the range of 0.05 or more to 2.2 mg KOH / g or less.

Preferably, the polyalkylene glycol esters of formula (I) have a hydroxyl value in the range of 0.1 to 20 mg KOH / g, measured according to DIN 53240.

Preferably, k is an integer ranging from 3 or more to 25 or less, more preferably k is an integer ranging from 3 or more to 20 or less, most preferably 5 or more to 20 or less, still more preferably 6 or more to 16 Lt; / RTI >

Preferably R ¹ and R ² are the same or different and represent an unsubstituted, branched alkyl radical having 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 carbon atoms, respectively. More preferably, R ¹ and R ² are the same or different and represent an unsubstituted, branched alkyl radical having 15, 16, 17, 18, 19 or 20 carbon atoms, respectively.

Preferably R ¹ and R ² are the same and each represents an unsubstituted, branched alkyl radical having 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 carbon atoms. More preferably, R ¹ and R ² are the same and represent an unsubstituted, branched alkyl radical having 15, 16, 17, 18, 19 or 20 carbon atoms, respectively.

Preferably R ¹ and R ² are the same or different and more preferably identical and represent a residue selected from the group consisting of:

[Wherein n is an integer ranging from 8 or more to 23 or less]

[Wherein m is an integer ranging from 7 or more to 22 or less]

Wherein o is an integer ranging from 1 or more to 6 or less, p is an integer ranging from 2 or more to 19 or less, and (o + p) is an integer ranging from 8 or more to 21 or less]

And

Wherein Q is an integer ranging from 1 or more to 6 or less, R is an integer ranging from 2 or more to 19 or less, and (Q + R) is an integer ranging from 8 or more to 20 or less.

In another preferred embodiment, the claimed invention relates to the use of a polyalkylene glycol ester of formula (I) as a lubricant:

[Wherein,

k is an integer ranging from 3 or more to 25 or less,

R ¹ and R ² are the same and each represents a residue selected from the group consisting of:

(Wherein n is an integer ranging from 10 or more to 18 or less).

In another preferred embodiment, the invention claimed herein relates to the use of a polyalkylene glycol ester of formula (I) as a lubricant:

[Wherein,

k is an integer ranging from 3 or more to 20 or less,

R ¹ and R ² Are the same and each represent a residue selected from the group consisting of:

(Wherein n is an integer ranging from 11 or more to 16 or less).

Polyalkylene glycol esters of formula (I) is optionally obtained by reacting one or more poly-tetrahydrofuran block copolymer and at least one C ₉ -C ₂₇ acid in the presence of at least one catalyst. Preferably, the polyalkylene glycol esters of formula (I) are obtained by reacting one or more C ₉ -C ₂₇ acids with one or more polytetrahydrofuran block polymers in the presence of one or more catalysts.

Preferably, the at least one C ₉ -C ₂₇ acid is selected from the group consisting of 4,7-dimethyl-nonanoic acid, 4,8-dimethyl-decanoic acid, 8-methyl-undecanoic acid, iso-dodecanoic acid, Dodecanedioic acid, 4,10-dimethyl-undecanoic acid, iso-tridecanoic acid, 4,10-dimethyl-undecanoic acid, iso-tetradecanoic acid, Dimethyl-tetradecanoic acid, 4,12-dimethyl-tetradecanoic acid, isohexadecanoic acid, 4,11-dimethyl-pentadecanoic acid, 4,13-dimethyl-pentadecanoic acid, isoheptadecanoic acid, Heptadecanoic acid, iso-octadecanoic acid, iso-octadecanoic acid, iso-eicosanoic acid, iso-dodecanoic acid, iso-tetracosonic acid, iso-pentanoic acid and iso-hexanoic acid.

Preferably the at least one catalyst is selected from the group consisting of magnesium carbonate, zinc carbonate, zinc borate, tin (II) acetate, tin (II) octanoate, tin (II) lactate, zinc acetate, aluminum acetate, tin ), Tin (II) methanesulfonate, tin (II) p-toluenesulfonate, dibutyltin dilaurate (DBTL) ), antimony oxide (Sb ₂ 0 _3), butyl titanate, isopropyl titanate, acetic acid, methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 1-butane sulfonic acid, trifluoromethane sulfonic acid, benzenesulfonic acid, p- toluenesulfonic Sulfonic acid, phosphoric acid, triethylamine, pyridine, dimethylaminopyridine, histidine, imidazole, 1,8-diazabicyclo [2.2.1] Is selected from the group consisting of bicyclo [5.4.0] unde-7-ene (DBU) and 1,5-diazabicyclo (4.3,0) More preferably, the at least one catalyst is tin (II) octanoate or p-toluenesulfonic acid.

In another embodiment, the claimed invention relates to a process for the preparation of a lubricating oil composition, comprising reacting a polyalkylene glycol ester of the defined formula (I) or of a polyalkylene glycol ester of the above defined formula (I) To the use of the mixture.

In another embodiment, the claimed invention relates to a lubricating oil composition comprising a polyalkylene glycol ester of one of the above defined formula (I) or a mixture of polyalkylene glycol esters of formula (I) defined above . Preferably, the lubricating oil composition is present in the lubricating oil composition in an amount of 1 to 10 wt.%, Or 1 to 40 wt.%, Or 20 to 100 wt.%, More preferably 1 wt. Or more to 5 wt% or less or 1 wt% or more to 35 wt% or less or 25 wt% or more to 100 wt% or less, most preferably 1 wt% or more to 2 wt% or less or 2 wt% or more to 30 wt% Or from 30% to 100% by weight of one or more polyalkylene glycol esters of the above defined formula (I).

Preferably, the lubricating oil composition according to the invention claimed in the present invention has a coefficient of friction of 0.003 to 0.030 at 25% slide rotation ratio (SRR) measured using a miniature retractor (MTM) device at 70 DEG C and 1 GPa, More preferably in the range of 0.003 to 0.020.

In another embodiment, the claimed invention relates to an industrial oil comprising one or more polyalkylene glycol esters of formula (I) as defined above.

A lubricating oil composition comprising one or more polyalkylene glycol esters of formula (I) as defined above or a mixture of polyalkylene glycol esters of formula (I) defined above may be used in a variety of applications such as small, medium and large engine oils, The present invention relates to a lubricating oil composition for use in a lubricating oil composition for industrial engines, marine engine oils, automobile engine oils, crankshaft oils, compressor oils, refrigerant oils, hydrocarbon compressor oils, cryogenic lubricants and fats, high temperature lubricants and fats, wire rope lubricants, Transmission fluid, transmission fluid, transmission fluid, transmission fluid for passenger vehicles, transmission fluid for trucks, transmission oil for industrial use, industrial gear oil, lubricating oil for automotive industry, lubricating oil for aircraft, turbine oil for aircraft, transmission oil, gas turbine oil, spindle oil, Insulation oil, equipment oil, brake Oils for heating and cooling work, oils for liquids and coolants, oils for liquids, oils for liquids, refining oils, oils for metalworking fluids, lubricating oils for transmissions , Oil for semisynthetic metalworking fluids, synthetic metalworking fluids, soil-boring drilling detergents, hydraulic oils, biodegradable lubricants or lubricating greases or waxes, chain saw oils, mold release fluids, guns, pistols and rifles, Lubricants and food grade approved lubricants.

The lubricating oil composition may comprise base stock, cosolvent and various other additives in varying proportions.

Preferably, the lubricating oil composition also comprises a mineral oil (I, II or III group oil), poly alpha olefin (IV group oil), polymerized and interpolymerized olefins, alkyl naphthalene, alkylene oxide polymers, silicone oils, phosphate esters And a carboxylic acid ester (V group oil). Preferably the lubricating oil comprises from 50% to 99% by weight or from 80% by weight to 99% by weight or from 90% by weight to 99% by weight based on the total amount of the lubricating oil composition.

The definition of base stock in the present invention is the same as that disclosed in the American Petroleum Institute ("API Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998) Do. The literature categorizes the base stock as follows:

a) Group I base stocks contain less than 90% saturates and / or greater than 0.03% sulfur and have a viscosity index of 80 or greater and less than 120 using the test methods specified in the following table.

b) Group II base stocks contain 90% or more of saturates and 0.03% or less of sulfur and have a viscosity index of 80 or more and less than 120 using the test method specified in the following table.

c) Group III base stocks have a viscosity index of 120 or more, containing 90% or more of lead and 0.03% or less of sulfur and using the test method specified in the following table.

Analysis method for base stock

Group IV base stocks contain polyalphaolefins. Synthetic low viscosity fluids suitable for the present invention include synthetic oils from hydrocracking or hydroisomerization of Fischer Tropsch high boiling fractions, including polyalphaolefins (PAO) and waxes. This is a stock consisting of a filler with a low impurity level consistent with its synthetic origin. Hydrogenated Fischer-Tropsch wax is a very highly water-soluble, water-insoluble, oil-in-water emulsion containing a saturated component of an iso-paraffinic feature (resulting mainly from the isomerization of n-paraffin in Fischer-Tropsch wax) yielding a high viscosity index and a good combination of low pour point. Suitable base stock. Hydrogenation of Fischer-Tropsch waxes is described in U.S. Patent Nos. 5,362,378; 5,565,086; 5,246,566 and 5,135,638 and in EP 710710, EP 321302 and EP 321304.

Polyalphaolefins suitable for the present invention as low viscosity or high viscosity fluids, depending on their specific properties, include, but are not limited to, alpha olefins comprising C ₂ to about C ₃₂ alpha olefins and C ₈ to about C ₁₆ alpha olefins such as Preferably a known PAO material comprising a relatively low molecular weight hydrogenated polymer or oligomer such as 1-octene, 1-decene, 1-dodecene, and the like. Preferred polyalphaolefins are poly-1-octene, poly-1-decene and poly-1-dodecene, although dimers of higher olefins in the C ₁₄ to C ₁₈ range provide a low viscosity base stock.

Low viscosity PAO fluids suitable for the present invention can be prepared by reacting a polymerization catalyst such as a Friedel-Craft catalyst such as aluminum trichloride, boron trifluoride or boron trifluoride with water, an alcohol such as ethanol, propanol or butanol, By polymerization of alpha olefins in the presence of a carboxylic acid or a complex of an ester such as ethyl acetate or ethyl propionate. For example, the methods disclosed by U.S. Patent 3,149,178 or 3,382,291 may be used in this application. Other details of the PAO synthesis are found in the following US patents: 3,742,082 (Brennan); 3,769,363 (Brennan); 3,876,720 (Heilman); 4,239,930 (Allphin); 4,367,352 (Watts); 4,413,156 (Watts); 4,434, 308 (Larkin); 4,910,355 (Shubkin); 4,956,122 (Watts); And 5,068,487 (Theriot).

Group V base stocks contain any base stock not listed by groups I through IV. Examples of Group V base stocks include alkyl naphthalene, alkylene oxide polymers, silicone oils, phosphate esters and carboxylic acid esters.

Synthetic lubricating oils include, but are not limited to, hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins such as polybutylene, polypropylene, propylene-isobutylene copolymer, chlorinated polybutylene, poly 1-octene), poly (1-decene)); Alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di (2-ethylhexyl) benzene); Polyphenyls (e.g., biphenyl, terphenyl, alkylated polyphenols); And alkylated diphenyl ethers and alkylated diphenyl sulfides and derivatives, analogs and analogs thereof.

Additional carboxylic acid esters suitable for the present invention are esters of monovalent and polyvalent acids with monoalkanols (simple esters) or mixtures of mono and polyalkanols (complex esters), and monocarboxylic acids (simple esters) Polyol esters of a mixture of polycarboxylic acids (complex esters). Esters of the monobasic / polybasic type include, for example, monocarboxylic acids such as heptanoic acid and dicarboxylic acids such as phthalic acid, succinic acid, alkylsuccinic acid, alkenylsuccinic acid, maleic acid, azelaic acid, suberic acid, Such as fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acid, alkenylmalonic acid and the like and various alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol or its mixture with polyalkanol ≪ / RTI > Specific examples of these types of esters include nonyl heptanoate, dibutyl adipate, di (2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl Azelate, dioctyl phthalate, didecyl phthalate, diescosyl sebacate, dibutyl-TMP-adipate, and the like.

Also suitable in the present invention are esters such as one or more polyhydric alcohols, preferably disoriented polyols such as neopentyl polyols such as neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, Propane, trimethylolbutane, pentaerythritol and dipentaerythritol and monocarboxylic acids having 4 or more carbon atoms, generally C ₅ to C ₃₀ acids such as saturated straight chain fatty acids such as caprylic acid, capric acid, lauric acid, Acid, palmitic acid, stearic acid, arachic acid and behenic acid, or a corresponding branched chain fatty acid or unsaturated fatty acid such as oleic acid or a mixture thereof, polycarboxylic acid.

Alkylene oxide polymers and copolymers and derivatives thereof wherein the terminal hydroxyl groups are modified by esterification, etherification, etc. constitute another class of known synthetic lubricating oils. These include polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol ether having a molecular weight of 1000 or a molecular weight of 1000-1500 Diphenyl ether of poly-ethylene glycol); And mono- and polycarboxylic acid esters thereof, for example acetic acid esters, mixed C ₃ -C ₈ fatty acid esters and C ₁₃ oxo acid diesters of tetraethylene glycol.

Silicon-based oils such as polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxy silicone oils and silicate oils include another useful class of synthetic lubricants; The oil may be selected from the group consisting of tetraethyl silicate, tetraisopropyl silicate, tetra- (2-ethylhexyl) silicate, tetra- (4-methyl-2-ethylhexyl) silicate, tetra- - (4-methyl-2-ethylhexyl) disiloxane, poly (methyl) siloxane and poly (methylphenyl) siloxane. Other synthetic lubricating oils include liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decyl phosphonic acid) and polymeric tetrahydrofuran.

The lubricating oil composition of the present invention optionally also comprises one or more other performance additives. Other performance additives include, but are not limited to, dispersants, metal deactivators, detergents, viscosity modifiers, extreme pressure agents (typically boron- and / or sulfur- and / or phosphorus-containing), antarctics, antioxidants Or molybdenum compounds), corrosion inhibitors, foam inhibitors, demulsifiers, pour point depressants, seal swell agents, friction modifiers, and mixtures thereof.

The total combined amount of other performance additives (excluding viscosity modifier) present on a non-oil basis is from 0% to 25%, or from 0.01% to 20%, or from 0.1% to 15% %, Or 0.5 wt% to 10 wt%, or 1 to 5 wt%.

Although one or more other performance additives may be present, it is common for the other performance additives to be present in different amounts relative to one another.

In one embodiment, the lubricating composition also comprises at least one viscosity modifier.

If present, the viscosity modifier may be present in an amount of from 0.5 wt% to 70 wt%, 1 wt% to 60 wt%, or 5 wt% to 50 wt%, or 10 wt% to 50 wt% of the lubricating composition.

The viscosity modifier may be selected from the group consisting of (a) polymethacrylates, (b) (II) vinyl aromatic monomers and (ii) esterified copolymers of unsaturated carboxylic acids, anhydrides or derivatives thereof, (c) (II) alpha-olefins; (E) an ethylene-propylene copolymer, (f) a polyisobutene, (g) an ethylene-propylene copolymer, A hydrogenated styrene-isoprene polymer, (h) a hydrogenated isoprene polymer, or (II) a mixture thereof.

In one embodiment, the viscosity modifier comprises (a) polymethacrylate, (b) (II) a vinyl aromatic monomer; And (ii) an esterified copolymer of an unsaturated carboxylic acid, anhydride or derivative thereof, (c) (II) an alpha-olefin; And (ii) an esterified interpolymer of an unsaturated carboxylic acid, anhydride or derivative thereof, or (d) a mixture thereof.

Extreme pressure agents include compounds containing boron and / or sulfur and / or phosphorus.

The extreme pressure agent may be present in the lubricating composition from 0% to 20%, or from 0.05% to 10%, or from 0.1% to 8% by weight of the lubricating composition.

In one embodiment, the extreme pressure agent is a sulfur-containing compound. In one embodiment, the sulfur-containing compound may be a sulfurized olefin, polysulfide or a mixture thereof. Examples of the sulfurized olefin include sulfided olefins derived from propylene, isobutylene, and pentene; Organic sulfides and / or polysulfides such as benzyl disulfide; Bis- (chlorobenzyl) disulfide; Dibutyl tetrasulfide; Di-tert-butyl polysulfide; And sulfurized methyl esters of oleic acid, alkylated phenol sulfides, dipentene sulfides, terphenyl sulfides, Diels-Alder adducts, sulfated N'N-dialkyldithiocarbamates; Or mixtures thereof.

In one embodiment, the olefin sulphide comprises a sulphurised olefin derived from propylene, isobutylene, pentene, or mixtures thereof.

In one embodiment, the extreme pressure sulfur-containing compound comprises a dimercaptothiadiazole or derivative or a mixture thereof. Examples of dimercaptothiadiazoles include compounds such as 2,5-dimercapto-1,3,4-thiadiazole or hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole Sol or oligomers thereof. Oligomers of hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazoles typically have a sulfur-containing group between 2,5-dimercapto-1,3,4-thiadiazole units, Sulfur bonds to form derivatives or oligomers of at least two of the thiadiazole units. Suitable 2,5-dimercapto-1,3,4-thiadiazole derived compounds are, for example, 2,5-bis (tert-nonyldithio) -1,3,4-thiadiazole or 2-tert -Nonyldithio-5-mercapto-1,3,4-thiadiazole. The number of carbon atoms on the hydrocarbyl substituent of the hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole is typically from 1 to 30, or from 2 to 20, or from 3 to 16 .

In one embodiment, dimercaptothiadiazole may be a thiadiazole-functionalizing dispersant. A detailed description of the thiadiazole-functionalized dispersant is in paragraphs [0028] to [0052] of WO 2008/014315.

The thiadiazole-functionalizing dispersant may be prepared by a process comprising heating, reacting, or complexing the thiadiazole compound with a dispersant substrate. The thiadiazole compound may be covalently bonded to a dispersant, chlorinated, complexed, or otherwise solubilized, or a mixture thereof.

The relative amounts of dispersant substrate and thiadiazole used to prepare the thiadiazole-functionalized dispersant may vary. In one embodiment, the thiadiazole compound is present in 0.1 to 10 parts by weight based on 100 parts by weight of the dispersant substrate. In different embodiments, the thiadiazole compound is present in excess of 0.1 to 9, or more than 0.1 and less than 5, or less than 0.2 to 5, based on 100 parts by weight of the dispersant substrate. The relative amount of thiadiazole compound to dispersant substrate may also be (0.1-10): 100 or (> 0.1-9): 100, (e.g., (> 0.5-9) , Or (from 0.2 to less than 5): 100.

In one embodiment, the dispersant substrate is present in 0.1 to 10 parts by weight based on 1 part by weight of the thiadiazole compound. In a different embodiment, the dispersant substrate is present from greater than 0.1 to 9, or from greater than 0.1 to less than 5, or from about 0.2 to less than 5, based on 1 part by weight of the thiadiazole compound. The relative amount of dispersant substrate to thiadiazole compound may also be (0.1-10): 1, or (> 0.1-9): 1, such as (> 0.5-9) , Or (less than 0.2 to 5): 1.

The thiadiazole-functionalizing dispersant may be a succinimide dispersant (e.g., N-substituted long chain alkenyl succinimides, typically polyisobutylene succinimides), Mannich dispersants, ester-containing dispersants, fatty hydrocarbyl A condensation product of a monocarboxylic acylating agent with an amine or ammonia, an alkylaminophenol dispersant, a hydrocarbyl-amine dispersant, a polyether dispersant, a polyether amine dispersant, a viscosity modifier containing a dispersant functional group Polymeric viscosity index modifiers (VMs)), or mixtures thereof. In one embodiment, the dispersant matrix comprises a succinimide dispersant, an ester-containing dispersant, or a Mannich dispersant.

In one embodiment, the extreme pressure agent comprises a boron-containing compound. Boron-containing compounds include borate esters (which may in some cases also be represented as borated epoxides), borated alcohols, borated dispersants, borated phosphates, or mixtures thereof. In one embodiment, the boron-containing compound may be a borate ester or a borated alcohol.

The borate ester can be prepared by the reaction of a boron compound and at least one compound selected from an epoxy compound, a halohydrin compound, an epihalohydrin compound, an alcohol and a mixture thereof. Alcohols include divalent alcohols, trihydric alcohols or higher alcohols, and in one embodiment the hydroxyl groups are adjacent (ie, in proximity) to the carbon atoms.

Suitable boron compounds for preparing borate esters include various forms selected from the group consisting of boric acid (e.g., metaboric acid, orthoboric acid and tetraboric acid), boric oxide, boron trioxide and alkyl borates. Borate esters can also be prepared from boron halides.

In one embodiment, suitable borate ester compounds include tripropyl borate, tributyl borate, tripentyl borate, trihexyl borate, triheptyl borate, trioctyl borate, trinonyl borate, and tridecyl borate. In one embodiment, the borate ester compound comprises tributyl borate, tri-2-ethylhexyl borate, or mixtures thereof.

In one embodiment, the boron-containing compound is a borated dispersant typically derived from an N-substituted long chain alkenylsuccinimide. In one embodiment, the borated dispersant comprises polyisobutylene succinimide. Borated dispersants are described in U.S. Patent Nos. 3,087,936; And in patent 3,254,025.

In one embodiment, the borated dispersant may be used in combination with a sulfur-containing compound or a borate ester.

In one embodiment, the extreme pressure agent is other than a ball-rate dispersant.

The number average molecular weight of the hydrocarbons (from which the long chain alkenyl groups are derived) may range from 350 to 5000, or from 500 to 3000, or from 550 to 1500. The long-chain alkenyl group may have a number average molecular weight of 550, or 750, or 950 to 1000.

N-substituted long chain alkenyl succinimides are borated using various agents such as boric acid (e.g., metaboric acid, orthoboric acid and tetraboric acid), boric oxide, boron trioxide and alkyl borates. In one embodiment, the borating agent is boric acid, which may be used alone or in combination with other borating agents.

The borated dispersant comprises a boron compound and an N-substituted long-chain alkenyl succinimide and is reacted at a suitable temperature such as 80 to 250 캜, or 90 to 230 캜, or 100 to 210 캜, ≪ / RTI > The molar ratio of the boron compound to the N-substituted long chain alkenyl succinimide may range from 10: 1 to 1: 4, or from 4: 1 to 1: 3; Or the molar ratio of the boron compound to the N-substituted long chain alkenyl succinimide may be 1: 2. Alternatively, the ratio of molar B: mol N (i.e., atoms of B: atoms of N) in the borated dispersant may range from 0.25: 1 to 10: 1 or from 0.33: 1 to 4: 1 or from 0.2: 1 to 1.5: Or 0.25: 1 to 1.3: 1 or 0.8: 1 to 1.2: 1 or about 0.5: 1. An inert liquid may be used in carrying out the reaction. The liquid may comprise toluene, xylene, chlorobenzene, dimethylformamide or mixtures thereof.

In one embodiment, the lubricating composition also comprises a borated phospholipid. The borated phospholipid may be derived from boronization of the phospholipid (e.g. boronation by boric acid may be performed). Phospholipids and lecithin are described in detail in Encyclopedia of Chemical Technology, Kirk and Othmer, 3rd Edition, "Fats and Fatty Oils", Volume 9, pages 795-831 and "Lecithins", Volume 14, pages 250-269.

The phospholipid may be any lipid containing phosphoric acid, such as lecithin or cephalin or derivatives thereof. Examples of phospholipids include phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphotidic acid, and mixtures thereof. Phospholipids may be glycerol phospholipids, glycerol derivatives of the above list of phospholipids. Typically, glycerophospholipids have one or two acyl, alkyl or alkenyl groups at the glycerol moiety. The alkyl or alkenyl groups may contain 8 to 30 or 8 to 25 or 12 to 24 carbon atoms. Examples of suitable alkyl or alkenyl groups include octyl, dodecyl, hexadecyl, octadecyl, dococanyl, octenyl, dodecenyl, hexadecenyl and octadecenyl.

Phospholipids can be synthetically produced or can be derived from natural sources. Synthetic phospholipids can be prepared by methods known in the art. Naturally derived phospholipids are often extracted by processes known in the art. Phospholipids can be derived from animal or vegetable sources. Useful phospholipids are derived from sunflower seeds. Phospholipids typically contain 35% to 60% phosphatidylcholine, 20% to 35% phosphatidylinositol, 1% to 25% phosphatidic acid and 10% to 25% phosphatidylethanolamine wherein the percentages are based on the weight of total phospholipid standards And. The fatty acid content may be from 20% to 30% by weight palmitic acid, from 2% by weight to 10% by weight stearic acid, from 15% by weight to 25% by weight oleic acid and from 40% by weight to 55% by weight linoleic acid.

Friction modifiers include fatty amines, esters such as borated glycerol esters, fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, Diols, carboxylic acids and polyalkylene-polyamines.

In one embodiment, the lubricating composition may contain a phosphorus- or sulfur-containing antarctic agent other than the compound described as an extreme pressure agent of the amine salt of the phosphate ester described above. Examples of anti-aging agents are nonionic compounds (typically compounds having phosphorus atoms with an oxidation state of +3 or +5), metal dialkyldithiophosphates (typically zinc dialkyldithiophosphates), metal mono- Or di-alkyl phosphate (typically zinc phosphate), or mixtures thereof.

Non-ionic compounds include phosphite esters, phosphate esters or mixtures thereof.

In one embodiment, the lubricating composition of the present invention also comprises a dispersing agent. Dispersing agents may be selected from the group consisting of succinimide dispersants (e.g., N-substituted long chain alkenyl succinimides), Mannich dispersants, ester-containing dispersants, condensation products of fatty hydrocarbyl monocarboxylic acylating agents with amines or ammonia, A phenol dispersant, a hydrocarbyl-amine dispersant, a polyether dispersant, or a polyether amine dispersant.

In one embodiment, the succinimide dispersant comprises a polyisobutylene-substituted succinimide, wherein the polyisobutylene from which the dispersant is derived may have a number average molecular weight of 400 to 5000, or 950 to 1600.

Succinimide dispersants and methods for their preparation are described in more detail in U.S. Patent Nos. 4,234,435 and 3,172,892.

Suitable ester-containing dispersants are typically high molecular weight esters. Such materials are described in more detail in U.S. Patent No. 3,381,022.

In one embodiment, the dispersant comprises a borated dispersant. Typically, the borated dispersant comprises a succinimide dispersant comprising polyisobutylene succinimide, wherein the polyisobutylene from which the dispersant is derived may have a number average molecular weight of from 400 to 5000. The borated dispersants are described in more detail in the detailed description of extreme pressure agents.

Dispersant viscosity modifiers (often referred to as DVM) include ethylene-propylene copolymers containing functionalized polyolefins, for example functionalized by the reaction product of maleic anhydride and amine, polymethacrylates functionalized with amines, or An esterified styrene-maleic anhydride copolymer reacted with an amine may also be used in the compositions of the present invention.

Corrosion inhibitors include 1-amino-2-propanol, octylamine octanoate, dodecenylsuccinic acid or anhydride and / or condensation products of fatty acids such as oleic acid and polyamines.

The metal deactivator includes a derivative of benzotriazole (typically tolyltriazole), 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole or 2-alkyldithiobenzothiazole do. Metal deactivators can also be described as corrosion inhibitors.

Foaming inhibitors include copolymers of ethyl acrylate and 2-ethylhexyl acrylate and optionally vinyl acetate.

The demulsifiers include trialkyl phosphates and various polymers and copolymers of ethylene glycol, ethylene oxide, propylene oxide or mixtures thereof.

Pour point depressants include esters of maleic anhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides.

The seal swell agents include ^{Exxon Necton-37 TM (FN 1380} ) and ^{Exxon Mineral Seal Oil TM (FN 3200} ).

Preferably the lubricating oil composition is selected from the group consisting of di-isodecyl adipate, di-propyl adipate, di-isotrydecyl adipate, trimethylpropyl tricaprylate, di-isooctyl adipate, di- Nonyl adipate, and a nonyl adipate. Preferably, the lubricating oil composition contains a cosolvent in an amount of not less than 0.5 wt% to not more than 35 wt%, more preferably not less than 1 wt% to not more than 30 wt% based on the total weight of the lubricating oil composition.

In another embodiment, the invention as claimed in the present invention is directed to a process for preparing a lubricating oil composition which comprises combining the lubricating oil composition with at least one polyalkylene glycol ester of formula (I) as defined above or a polyalkylene glycol ester of formula (I) To a method of reducing the coefficient of friction of a lubricating oil composition in lubrication of a mechanical device.

The friction-modifying properties are measured by measuring the coefficient of friction at an average speed of 4 m / s, 0-25% slide rotation ratio (SRR) using a small retractor (MTM) meter at 70 ° C and 1 GPa loading. The reduction in the coefficient of friction means that in the sense of the invention claimed in the present invention the coefficient of friction of the lubricating oil composition comprising the carboxylic acid ester defined above is lower than the coefficient of friction of the lubricating oil composition not containing the carboxylic acid ester do.

In another embodiment, the invention claimed in the present invention is directed to a process for the preparation of a friction modifying composition of a lubricating oil composition in the lubrication of a mechanical device, which comprises formulating the lubricating oil composition with a polyalkylene glycol ester of one or more of the above- And a method for improving the characteristics.

Improving the friction-modifying properties means, in the sense of the present invention, that the coefficient of friction of the lubricating oil composition comprising the carboxylic acid ester defined above is lower than the coefficient of friction of the lubricating oil composition containing no carboxylic acid ester . The friction-modifying properties are measured by measuring the coefficient of friction at 25% slide rotation ratio (SRR) using a small retractor (MTM) meter at 70 캜 and 1 GPa.

A mechanical device is a mechanism consisting of an apparatus that operates in mechanical theory in the sense of the invention claimed in the present invention.

The mechanical device is preferably selected from the group consisting of bearings, gears, joints and guidance. Preferably, the mechanical apparatus is operated at a temperature in the range of -80 DEG C to 500 DEG C, most preferably in the range of -80 DEG C to 250 DEG C inclusive.

Example

Way

OHZ = hydroxyl, measured according to DIN 53240

Mn = number-average molecular weight, measured according to DIN 55672-1 and referred to the polystyrene calibration standard,

Mw = weight average molecular weight, measured according to DIN 55672-1 and referred to the polystyrene calibration standard,

PD = polydispersity measured according to DIN 55672-1,

SZ = acid value determined according to ASTM D664.

Measurement of physical properties

The kinematic viscosity was measured according to standard international method ASTM D 445.

The viscosity index was measured according to ASTM D2270.

The pour point was measured in accordance with DIN ISO 3016.

Evaluation of Friction Coefficient

The fluid was tested in an MTM (small-retractor) device using the so-called pull test method. In this manner, the coefficient of friction is measured at a constant average rate over the range of slide rotation ratio (SRR) to yield the traction curve. SRR = sliding speed / average running speed = 2 (U1-U2) / (U1 + U2) where U1 and U2 are the ball and disk speed, respectively.

The disks and balls used in the experiments are made of steel (AISI 52100) with a hardness of 750 HV and an Ra of less than 0.02 탆. The diameters were 45,0 mm and 19,0 mm for the disc and ball, respectively. The traction curve was run at a contact pressure of 1,00 GPa, an average speed of 4 m / s and a temperature of 70 ° C. The slide-to-turn ratio (SRR) was varied from 0 to 25% and the coefficient of friction was measured.

Evaluation of oil compatibility

The method was developed internally to measure oil compatibility. The oil and the test material were mixed at a ratio of 10/90, 50/50 and 90/10% w / w, respectively. The mixture was mixed at room temperature by rotating for 12 hours. The appearance of the mixture was again measured after homogenization and after 24 hours. If the phase separation is not observed after 24 hours for two or more of the irradiated ratios, the test substance is considered to be compatible with the oil.

Synthesis of polyalkylene glycol

Example 1

(302.7 g / mol; 454.1 g, 1.5 mol) was mixed with 5,1 mg of KOH / g of an acid Lt; RTI ID = 0.0 > 180 C < / RTI > 25 ml condensate was thus obtained. Then tin (118 g / mol; 3.13 g, granule) is added. The reaction mixture was again heated to 180 < 0 > C and held at this temperature for 48 hours. The acid value of the crude product had an acid value of 0.7 mg KOH / g. The reaction mixture was cooled to 25 DEG C and 2,0 ml of water and powdered sodium hydrogencarbonate (50 g) were added. The mixture was stirred for 12 h and filtered under pressure (filter type Seitz K900). The final product was characterized:

Yield: 0.523 kg (99% of theory)

Acid SZ: 0.7 mg KOH / g = 0.5% isostearic acid; 99.5% turnover;

GPC: Mn: 1121; Mw: 1168; D: 1.04

Example 2

(302.7 g / mol; 843.2 g, 2.78 mol), and when the acid value is 8,9 mg KOH / g, the amount of the polyhydric alcohol Lt; RTI ID = 0.0 > 220 C < / RTI > for 15 h. 50 ml condensate was thus obtained. Tin octanoate (405 g / mol; 4.03 g, 10 mmol) was then added. The reaction mixture was again heated to < RTI ID = 0.0 > 220 C < / RTI > and held at this temperature for 48 h. The acid value of the crude product had an acid value of 3.9 mg KOH / g. The reaction mixture was cooled to 25 [deg.] C and 2.5 ml water and powdered sodium bicarbonate (260 g) were added. The mixture was stirred for 12 h and filtered under pressure (Seitz K150 filter type). The final product was characterized:

Yield 1.5 kg (99% of theory)

Acid SZ: 2.0 mg KOH / g = 2.2% isostearic acid; 97.8% turnover;

GPC: Mn: 1578; Mw: 2104; D: 1.33

Example 3

(302 g / mol; 302.7 g, 2.00 mol) was mixed with a solution of 10.6 mg KOH / g of acid close to 8 g of KOH / g of polystyrene (PTHF 1000; MW 1000 g / h < / RTI > under nitrogen flow. 14 ml of a condensate was thus obtained. Then 0.5 g para-toluenesulfonic acid and tin powder (405 g / mol; 4.03 g, 5 mmol) were added. The reaction mixture was heated to 180 < 0 > C and held at this temperature for 21 h. The acid value of the crude product had an acid value of 0.1 mg KOH / g. The reaction mixture was allowed to cool to 25 C and powdered sodium hydrogencarbonate (50 g) was added. The mixture was stirred for 12 h and filtered under pressure (filter type Seitz 900). The final product was characterized:

Yield: 0.789 kg (99% of theory)

Acid SZ: 0.1 mg KOH / g, 99.9% Turnover

GPC: Mn: 1940; Mw: 3070; D: 1.58

Example 4 (comparative)

Ethyl hexanoic acid (144.2 g / mol; 288.4 g, 2.00 mol) was mixed with polytetrahydrofuran (pTHF 650; MW 650.0 g / mol, Lt; RTI ID = 0.0 > 200 C < / RTI > under nitrogen flow for 18 hours. 17 ml of a condensate was thus obtained. Tin octanoate (405 g / mol; 4.03 g, 5 mmol) was then added. The reaction mixture was heated to 240 < 0 > C and held at this temperature for 6 hours. The acid value of the crude product had an acid value of 1.1 mg KOH / g. The reaction mixture was cooled to 25 < 0 > C and powdered sodium bicarbonate (150 g) was added. The mixture was stirred for 12 h and filtered under pressure (Seitz K150 filter type). The final product was characterized:

Yield: 0.9 kg (98% of theory)

Acid SZ: 0.6 mg KOH / g = 0.5% 2-ethylhexanoic acid; 99.5% turnover;

GPC: Mn: 1380; Mw: 1950; D: 1.41

Example 5 (comparative)

(284.5 g / mol, 1.0 mol) was mixed with stearic acid (4.0 g / mol of KOH / g) Lt; RTI ID = 0.0 > 220 C < / RTI > for 92 h. 17 ml of a condensate was thus obtained. Then tin octanoate (405 g / mol; 1.82 g, 5 mmol) was added. The reaction mixture was heated to 220 < 0 > C and held at this temperature for 48 h. The acid value of the crude product had an acid value of 0.97 mg KOH / g. The reaction mixture was cooled to 90 < 0 > C and 200 ml toluene was added to dissolve the product. Powdered sodium bicarbonate (230 g) was added. The mixture was stirred at 25 < 0 > C for 12 h and filtered under pressure (Seitz K900 filter type). Toluene was removed from the filtrate at 60 [deg.] C / 10 mbar. The final product was characterized.

Yield: 0.553 kg (98% of theory)

Acid SZ: 0.9 mg KOH / g = 1.05% isostearic acid; 99% turnover;

Example 6 (comparative)

Polybutylene oxide (MW 1242.0 g / mol, 621 g, 0.50 mol) was mixed with isostearic acid (284.4 g / mol; 285.7 g, 1.0 mol) and 20 g h < / RTI > under nitrogen flow. Thus, 30.2 ml condensate was obtained. Then tin octanoate (405 g / mol; 1.2 g, 3 mmol) was added. The reaction mixture was again heated to 220 < 0 > C and held at this temperature for 8 h. The acid value of the crude product had a value of 0.1 mg KOH / g. The final product was characterized:

Yield: 0.85 kg (99% of theory)

Acid SZ: 0.1 mg KOH / g = 0% isostearic acid; 99.9% turnover;

result

The oil compatibility and friction data are summarized in Table 1. The data show that the molecules derived from the present invention (Examples 1, 2 and 3), i.e. polyalkylene glycol esters produced by reacting polytetrahydrofuran (p-THF) with isostearic acid ( _C18 ) It exhibits compatibility with low viscosity poly alpha olefins, while demonstrating a low coefficient of friction (less than 0.015 under 25% SRR in MTM experiments).

Table 1

Claims (15)

Use of a polyalkylene glycol ester of formula (I) as a lubricant:

[Wherein,
k is an integer ranging from 2 or more to 30 or less,
R ¹ and R ² are the same or different and are each a C 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, Unsubstituted, branched alkyl radicals. The use according to claim 1, wherein k is an integer ranging from 3 to 25 inclusive. The polyalkylene glycol ester of formula (I) according to claim 1 or 2, wherein the polyalkylene glycol ester of formula (I) has a weight average molecular weight Mw, measured according to DIN 55672-1 (polystyrene calibration standard), in the range of 500 to 4500 g / mol Usage. The polyalkylene glycol ester of claim 1 or 2, wherein the polyalkylene glycol ester of formula (I) has a number average molecular weight Mn, measured according to DIN 55672-1 (polystyrene calibration standard), in the range of 400 to 4000 g / mol Usage. 5. A polyalkylene glycol ester according to any one of claims 1 to 4, wherein the polyalkylene glycol ester of formula (I) has a polydispersity measured according to DIN 55672-1 (polystyrene calibration standard) in the range of 1.1 to 2.0 Usage. 6. Use according to any one of claims 1 to 5, wherein R ¹ and R ² are the same or different and each represents a residue selected from the group consisting of:

[Wherein n is an integer ranging from 8 or more to 23 or less]

[Wherein m is an integer ranging from 7 or more to 22 or less]

Wherein o is an integer ranging from 1 or more to 6 or less, p is an integer ranging from 2 or more to 19 or less, and (o + p) is an integer ranging from 8 or more to 21 or less]
And

Wherein Q is an integer ranging from 1 or more to 6 or less, R is an integer ranging from 2 or more to 19 or less, and (Q + R) is an integer ranging from 8 or more to 20 or less. 7. Use according to any one of claims 1 to 6, wherein R < ¹ > and R < ² > 8. The use according to any one of claims 1 to 7, wherein the polyalkylene glycol ester of formula (I) has a total acid value of from 0.01 to 2.5 mg KOH / g measured according to ASTM D664. 9. Use according to any one of claims 1 to 8, wherein the polyalkylene glycol esters of formula (I) have a hydroxyl value measured according to DIN 53240 of from 0.1 to 20 mg KOH / g. The use according to claim 1, wherein:
k is an integer ranging from 3 or more to 25 or less,
R ¹ and R ² are the same and each represents a residue selected from the group consisting of:

Wherein n is 10, 11, 12, 13, 14, 15, 16, 17 or 18. A lubricating oil composition comprising at least one polyalkylene glycol ester of formula (I) as defined in any of claims 1 to 10. The friction of a lubricating oil composition in the lubrication of mechanical devices, comprising formulating said lubricating oil composition with at least one polyalkylene glycol ester of formula (I) as defined in any of claims 1 to 10. ≪ / RTI > 13. The method of claim 12, wherein the friction coefficient is measured at 0-25% slide rotation ratio (SRR) at an average speed of 4 m / s using a mini-traction machine (MTM) ≪ / RTI > The friction of a lubricating oil composition in the lubrication of mechanical devices, comprising formulating said lubricating oil composition with at least one polyalkylene glycol ester of formula (I) as defined in any of claims 1 to 10. To improve the reforming property. Use of at least one polyalkylene glycol ester of formula (I) as defined in any one of claims 1 to 10 for reducing friction in a lubricating oil composition.