CN115175977A

CN115175977A - Lubricant composition for limiting friction

Info

Publication number: CN115175977A
Application number: CN202080086505.8A
Authority: CN
Inventors: 米凯尔·德博尔; 卡特琳·沙兰
Original assignee: Total Energy Technology
Current assignee: Total Energy Technology
Priority date: 2019-12-13
Filing date: 2020-12-11
Publication date: 2022-10-11
Also published as: FR3104609A1; KR20220115603A; FR3104609B1; JP2023505728A; US20230013280A1; EP4073211A1; WO2021116368A1

Abstract

The present invention relates to a lubricant composition comprising, relative to the total weight of the lubricant composition: at least one base oil; 0.005 wt% to 10 wt% of at least one polymeric organic friction modifier; and 0.005 to 10 weight percent of at least one ester that is the product of an esterification reaction between a saturated or unsaturated, linear, cyclic, or branched, mono-or poly-carboxylic acid having 1 to 10 carbon atoms or between a linear, cyclic, or branched polyol and a saturated or unsaturated, linear, cyclic, or branched, mono-or monocarboxylic acid having 1 to 10 carbon atoms, the polymeric organic friction modifier being the reaction product of: a) At least one hydrophobic polymer subunit comprising a hydrophobic polymer selected from the group consisting of polyolefins, polyacrylic acid, and polystyrene; b) At least one hydrophilic polymer subunit comprising a hydrophilic polymer selected from the group consisting of polyethers, polyesters, and polyamides; c) Optionally at least one backbone moiety capable of linking the polymer subunits together; and d) optionally a chain terminating group.

Description

Lubricant composition for limiting friction

Technical Field

The present invention relates to novel lubricant compositions, in particular for reducing friction between mechanical parts, preferably between two parts of an engine, such as a vehicle engine. For example, the lubricant composition according to the invention can be used for lubricating an internal combustion engine, in particular a vehicle engine, in particular a motor vehicle engine.

Background

The purpose of lubricants is to reduce the friction and wear of mechanical parts, especially in vehicle engines, more particularly in motor vehicles.

To reduce these friction phenomena, it is known to add friction modifiers to the lubricant.

Among friction modifiers, organomolybdenum compounds represent a class of compounds, the friction reducing properties of which have been widely described. However, it is known to those skilled in the art that the use of organomolybdenum compounds (in particular organomolybdenum compounds comprising dithiocarbamate groups) can exacerbate wear of mechanical components. Other solutions have then been proposed to reduce the friction between the two mechanical parts.

Of these alternatives, polymeric organic friction modifiers are sometimes used today. Polymeric organic friction modifiers include the reaction product of an optionally functionalized polyolefin, a polyether, a polyol, and a carboxylic acid end group. WO2011/107739 describes polymeric organic friction modifiers.

Polymeric friction modifiers of this type are capable of achieving a coefficient of friction between mechanical components that is sometimes too high for the envisaged application.

Disclosure of Invention

Therefore, it is of particular interest to provide lubricant compositions to reduce friction between machine components.

It is an object of the present invention to provide a lubricant composition for reducing friction between machine components.

Further objects will become apparent from the following description of the invention.

These objects are achieved by the invention which provides a lubricant composition comprising, based on the total weight of the lubricant composition:

-at least one base oil;

-0.005 to 10 wt% of at least one polymeric organic friction modifier; and

-from 0.005% to 10% by weight of at least one ester which is the product of an esterification reaction between a saturated or unsaturated, linear, cyclic or branched monoalcohol having from 1 to 10 carbon atoms and a polycarboxylic acid or between a linear, cyclic or branched polyalcohol and a saturated or unsaturated, linear, cyclic or branched monocarboxylic acid having from 1 to 10 carbon atoms,

the polymeric organic friction modifier is the reaction product of:

a) At least one hydrophobic polymer subunit comprising a hydrophobic polymer selected from the group consisting of polyolefins, polyacrylic acid, and polystyrene;

b) At least one hydrophilic polymer subunit comprising a hydrophilic polymer selected from the group consisting of polyethers, polyesters, and polyamides;

c) Optionally at least one backbone moiety capable of linking the polymeric subunits together; and

d) Optionally a chain terminating group.

Detailed Description

More specifically, the inventors have surprisingly found that the combination of a polymeric organic friction modifier of the above type with an ester preferably selected from the group consisting of glycerol esters, citric acid esters, tartaric acid esters and mixtures thereof significantly improves the coefficient of friction between the mechanical parts.

Indeed, the inventors have found that esters more particularly selected from the group consisting of glycerol esters, citric acid esters, tartaric acid esters and mixtures thereof can surprisingly enhance the effect of polymeric organic friction modifiers.

Preferably, the polymeric organic friction modifier has a weight average molecular weight of from 1000 to 30000 daltons, preferably from 1500 to 25000 daltons, advantageously from 2000 to 20000 daltons. Weight average molecular weight can be measured by size exclusion chromatography.

According to one embodiment of the invention, the polymeric organic friction modifier is as defined in application WO 2011/107739.

Preferably, the hydrophobic polymeric subunits of the polymeric organic friction modifier comprise a hydrophobic polymer derived from a polymer of a monoolefin comprising from 2 to 6 carbon atoms, preferably selected from the group consisting of ethylene, propylene, butylene and isobutylene, more preferably isobutylene, and the polymer of the monoolefin contains a chain of from 15 to 500, preferably from 50 to 200 carbon atoms.

The hydrophilic polymer subunits of the polymeric organic friction modifier comprise a hydrophilic polymer selected from polyethers, polyamides, and polyesters, preferably from polyethers.

The hydrophilic polymer subunits are preferably linear or branched.

The polyester is for example selected from the group consisting of polyethylene terephthalate, polylactide and polycaprolactone.

The polyether is for example selected from polyglycerols and polyalkylene glycols.

According to a particularly preferred embodiment, the hydrophilic polymer subunits comprise a hydrophilic polymer which is a polymer of a water-soluble alkylene glycol. Preferably, the hydrophilic polymer subunits comprise a hydrophilic polymer which is polyethylene glycol (PEG), preferably PEG having a molecular weight of from 300 daltons to 5000 daltons, advantageously from 400 daltons to 1000 daltons, especially from 400 daltons to 800 daltons.

For example, the hydrophilic polymer subunits comprise a material selected from the group consisting of PEG ₄₀₀ 、PEG ₆₀₀ And PEG ₁₀₀₀ The hydrophilic polymer of (1).

According to another embodiment, the hydrophilic polymer subunits comprise poly (ethylene-propylene glycol) or poly (ethylene-butylene glycol) copolymers.

Alternatively, the hydrophilic polymer subunits comprise a hydrophilic polymer selected from polyethers and polyamides derived from diols and diamines, respectively, containing at least one functional group selected from acid groups such as carboxylic acid groups, sulfonyl groups such as sulfonyl styrene groups, amine groups such as Tetraethylenepentamine (TEPA) or Polyethyleneimine (PEI), and hydroxyl groups such as glycosyl monomers or copolymers.

According to one embodiment, some of the hydrophobic polymer subunits and hydrophilic polymer subunits may be linked to form block copolymer units. The hydrophobic polymer subunits and the hydrophilic polymer subunits capable of forming block copolymer units include functional groups that enable them to bind to each other.

Preferably, the hydrophobic polymer subunits comprise at least one diacid or anhydride group which is incorporated into the hydrophobic polymer subunits by reaction with an unsaturated diacid or anhydride, such as maleic anhydride. Hydrophobic polymer subunits having at least one diacid or anhydride group can be reacted by esterification with hydroxyl-terminated hydrophilic polymer subunits, such as polyalkylene glycols.

Alternatively, the hydrophobic polymer subunits comprise at least one epoxide group which is incorporated into the hydrophobic polymer subunits by epoxidation with a peracid, such as perbenzoic acid or peracetic acid. Hydrophobic polymer subunits having at least one epoxy group are capable of reacting with hydrophilic hydroxyl and/or acid-terminated polymer subunits.

In yet another embodiment, the hydrophobic polymer subunits have at least one unsaturated terminus created by an esterification reaction between at least one hydroxyl group of a hydrophilic polymer subunit and an unsaturated monocarboxylic acid, such as a vinyl acid, particularly acrylic or methacrylic acid. The hydrophobic polymer subunits have at least one unsaturated terminus and are capable of free radical copolymerization with the hydrophobic polyolefin polymer subunits.

Preferably, the hydrophobic polymer subunits comprise polyisobutylene succinic anhydride (PIBSA) having a molecular weight of from 300 daltons to 5000 daltons, preferably from 500 daltons to 1500 daltons, especially from 800 daltons to 1200 daltons. The polyisobutylene succinic anhydride is derived from the maleation of polyisobutylene, particularly from the reaction between polyisobutylene having unsaturated end groups and maleic anhydride.

The block copolymer units as described above are directly linked to each other.

Alternatively, the block copolymer units as described above are linked through the at least one backbone moiety.

The backbone moieties are selected from polyols and polycarboxylic acids, preferably from polyols.

The polyol is selected from the group consisting of diols; a triol; a tetrol; dimers or trimers of diols, triols or tetrols, and chain-extended polymers of diols, triols or tetrols.

Preferably, the polyol is selected from the group consisting of glycerol, neopentyl glycol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, dipentaerythritol, tripentaerythritol and sorbitol.

Advantageously, the polyol is glycerol.

The polycarboxylic acid is selected from the group consisting of dicarboxylic acids and tricarboxylic acids. Preferably, the polycarboxylic acid is a dicarboxylic acid, preferably a linear dicarboxylic acid, more preferably a dicarboxylic acid with a chain length of 2 to 10 carbon atoms.

Advantageously, the polycarboxylic acid is chosen from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and maleic acid.

Advantageously, the polycarboxylic acid is adipic acid.

Alternatively, the backbone moiety is selected from low molecular weight Alkenyl Succinic Anhydrides (ASA), preferably from C ₁₈ Alkenyl succinic anhydrides.

The choice of backbone moieties that can link the block copolymer units together depends on whether the units are linked between two hydrophobic polymer subunits, between two hydrophilic polymer subunits, or between a hydrophobic polymer subunit and a hydrophilic polymer subunit.

The backbone segments included in the polymeric organic friction modifier have the same or different properties.

The number of block copolymer units contained in the polymeric organic friction modifier is from 1 to 20, preferably from 1 to 15, preferably from 1 to 10, advantageously from 1 to 7.

When the reaction product used to produce the polymeric organic friction modifier is terminated with a reactive group (e.g., a hydroxyl group of PEG), in some cases it may be desirable or useful to introduce a chain terminating group at the end of the reaction product.

Preferably, the chain terminating group is selected from fatty carboxylic acids, preferably from linear or branched, saturated or unsaturated C ₁₂ -C ₂₂ The acid, more preferably chosen from lauric acid, erucic acid, isostearic acid, palmitic acid, oleic acid and linoleic acid, is advantageously chosen from palmitic acid, oleic acid and linoleic acid.

Preferably, the polymeric organic friction modifiers used in the present invention have an acid number below 20, preferably below 15.

The reaction of the polymeric organic friction modifiers used in the present invention is a single or multi-step process.

According to one embodiment, the polymeric organic friction modifier used in the present invention is the reaction product of a functionalized polyolefin, a polyether, a polyol, and a carboxylic acid end group.

The lubricant composition according to the present invention comprises from 0.005 to 10 wt. -%, preferably from 0.05 to 5 wt. -%, more preferably from 0.1 to 3 wt. -%, more preferably from 0.2 to 2 wt. -% of the polymeric organic friction modifier as defined above, based on the total weight of the lubricant composition.

The lubricant composition according to the present invention comprises from 0.005 to 10 wt. -%, preferably from 0.05 to 5 wt. -%, preferably from 0.1 to 3 wt. -%, more preferably from 0.2 to 2 wt. -% of at least one ester selected from the group consisting of glycerol esters, citric acid esters, tartaric acid esters and mixtures thereof, based on the total weight of the lubricant composition.

The esters used according to the invention may be mono-, di-or triesters. It may be a mixture of mono-, di-and/or tri-esters. Preferably, the ester used according to the invention comprises at least one triester.

Preferably, the ester is selected from the group consisting of glycerides, citrates and mixtures thereof.

According to one embodiment of the invention, the glycerol ester is an ester of glycerol with a carboxylic acid having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms. Preferably, the carboxylic acid is a monocarboxylic acid. In one embodiment of the invention, the glyceride is selected from the group consisting of glyceryl heptanoate and mixtures thereof.

The carboxylic acids used to prepare the glycerides are saturated or unsaturated linear, cyclic or branched carboxylic acids, optionally substituted with hydroxyl and/or epoxy groups.

Preferably, the carboxylic acids used to prepare the glycerides are linear and saturated and have a hydrocarbon chain consisting of carbon and hydrogen atoms. In other words, according to a particular embodiment, the carboxylic acid used to prepare the glyceride does not contain any heteroatoms other than the acid functional group.

In one embodiment, the glycerides are obtained from raw materials of renewable origin. Carboxylic acids which can be used to form glycerides are, for example, carboxylic acids derived from vegetable oils, fats of animal or vegetable origin, such as butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, azelaic acid, capric acid, crotonic acid, isocrotonic acid, sorbic acid, isovaleric acid, used alone or in mixtures. In another embodiment, the glycerides are obtained from fossil derived raw materials. These are known as synthetic carboxylic acids. Synthetic carboxylic acids such as butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid may also be used alone or in mixtures.

The glycerides used in the present invention may be obtained by methods well known to the skilled person, for example by reacting a carboxylic acid with glycerol. These chemical reactions, which are well known to those skilled in the art, may take place with or without a catalyst, with or without a solvent.

According to one embodiment, the glycerol ester used in the lubricant composition according to the invention is triheptanoin.

According to one embodiment, the tartaric acid ester is an ester of tartaric acid with an alcohol having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms. Preferably, the alcohol used to prepare the tartrate ester is a monohydric alcohol.

In one embodiment of the invention, the tartrate ester is selected from triesters of tartaric acid.

According to one embodiment, the citric acid ester is an ester of citric acid with an alcohol having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms. Preferably, the alcohol used to prepare the citrate ester is a monohydric alcohol.

In one embodiment of the invention, the citric acid ester is selected from citric acid triesters.

The alcohol used to prepare the citrate or tartrate ester is a saturated or unsaturated, linear, cyclic or branched alcohol, optionally substituted with acid and/or epoxy groups.

Preferably, the alcohol used to prepare the citrate or tartrate ester is linear and saturated and has a hydrocarbon chain consisting of carbon and hydrogen atoms. In other words, according to a particular embodiment, the alcohol used for preparing the citrate or tartrate does not comprise any heteroatoms other than hydroxyl functions.

The citric or tartaric acid esters used in the present invention can be obtained by methods well known to those skilled in the art, for example by reacting citric or tartaric acid with one or more alcohols. These chemical reactions, well known to those skilled in the art, may occur with or without a catalyst, with or without a solvent.

In one embodiment, the citric acid ester is selected from triethyl citrate, tributyl citrate and mixtures thereof.

According to one embodiment of the invention, the ester of the lubricant composition is selected from:

triesters of glycerol with monocarboxylic acids having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms; and

-triesters of citric acid with monohydric alcohols having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms; and

mixtures thereof.

According to one embodiment of the invention, the ester of the lubricant composition is selected from the group consisting of triheptanoin, triethyl citrate, tributyl citrate and mixtures thereof.

The lubricant composition according to the invention comprises one or more base oils, preferably in an amount of at least 50 wt. -%, more preferably at least 60 wt. -% or even at least 70 wt. -%, based on the total weight of the lubricant.

The base oil may be selected from mineral, synthetic or natural, animal or vegetable lubricating base oils known to those skilled in the art.

The base oil used in the lubricant composition according to the invention may be an oil of mineral or synthetic origin belonging to groups I to V according to the categories defined in the API classification (or their equivalents classified according to ATIEL) (table 1) or a mixture thereof.

[ Table 1]

The mineral base oils according to the present invention include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, dealkalization, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

Mixtures of synthetic and mineral oils may also be used.

There is generally no limitation on the use of different lubricating base oils to prepare lubricant compositions according to the present invention, except that they must have properties suitable for their use, in particular viscosity, viscosity index, sulphur content, oxidation resistance.

The base oil of the lubricant composition according to the invention may also be selected from synthetic oils, such as esters of certain carboxylic acids and alcohols, and from polyalphaolefins. Polyalphaolefins used as base oils are, for example, obtained from monomers having 4 to 32 carbon atoms, for example from octene or decene, and have a viscosity at 100 ℃ of 1.5 to 15 mm according to ASTM D445 ² .s ^-1 . They generally have an average molecular weight of from 250 to 3000 according to ASTM D5296.

According to a particular embodiment, the lubricant composition according to the invention comprises 60% to 99.5% by weight of base oil, preferably 70% to 99.5% by weight of base oil, relative to the total weight of the composition.

Many additional additives may be used in such lubricant compositions according to the present invention.

Preferred additional additives for use in the lubricant composition according to the present invention are selected from detergent additives, antiwear additives other than phosphorus and sulfur removing additives, friction modifiers other than the polymeric organic friction modifiers described above, extreme pressure additives, dispersants, pour point depressants, anti-foaming agents, thickeners, and mixtures thereof.

Amine phosphates are antiwear additives that can be used in lubricant compositions according to the present invention. However, the phosphorus provided by these additives can be a poison for automotive catalytic systems because these additives can generate ash. These effects can be minimized by partial replacement of the amine phosphate with non-phosphorus additives (e.g., polysulfides, especially sulfur-containing olefins).

Advantageously, the lubricant composition according to the present invention may comprise from 0.01 to 6 wt. -%, preferably from 0.05 to 4 wt. -%, more preferably from 0.1 to 2 wt. -% of antiwear and extreme pressure additives, based on the total weight of the lubricant composition.

Preferably, the lubricant composition according to the invention comprises, based on the total weight of the lubricant composition:

-at least 50 wt%, preferably at least 60 wt%, more preferably 70 wt% of one or more base oils;

-from 0.005 to 10 wt.%, preferably from 0.05 to 5 wt.%, preferably from 0.1 to 3 wt.%, more preferably from 0.2 to 2 wt.% of one or more polymeric organic friction modifiers;

-from 0.005 to 10 wt%, preferably from 0.05 to 5 wt%, preferably from 0.1 to 3 wt%, more preferably from 0.2 to 2 wt% of one or more esters selected from glycerides, citrates, tartrates and mixtures thereof;

-optionally 0.005 wt% to 30 wt%, preferably 0.1 wt% to 25 wt%, more preferably 1 wt% to 20 wt% of one or more functional additives other than polymeric organic friction modifiers and glycerides, citrates and tartrates, preferably selected from detergent additives, antiwear additives other than phosphorus and sulfur additives, friction modifying additives, extreme pressure additives, dispersants, pour point depressants, anti-foaming agents, thickeners, and mixtures thereof.

Advantageously, the lubricant composition according to the invention may comprise at least one additional friction modifier additive different from the polymeric organic friction modifier defined above. The additional friction modifier additive may be selected from metallic element providing compounds and ashless compounds. Among the compounds providing the metallic element, transition metal complexes can be mentioned, such as Sb, sn, fe, cu, zn, mo, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms.

Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive.

Antioxidant additives generally retard the degradation of the lubricant composition in use. This degradation may result in the formation of deposits, the presence of sludge, or an increase in the viscosity of the lubricant composition.

The antioxidant additive acts as a free radical inhibitor or hydroperoxide breaker. Common antioxidant additives include phenolic antioxidant additives, amine antioxidant additives, and phosphorus and sulfur antioxidant additives. Some of these antioxidant additives (e.g., phosphorus sulfur antioxidant additives) can form ash. The phenolic antioxidant additives may be ashless and may also be in the form of neutral or basic metal salts. The antioxidant additive may be chosen in particular from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols containing thioether bridges, diphenylamines, hindered amines, and antioxidants ₁ -C ₁₂ Alkyl-substituted diphenylamines, N' -dialkylaryldiamines, and mixtures thereof.

Preferably, according to the invention, the sterically hindered phenol is chosen from compounds comprising a phenol group in which at least one carbon ortho to the carbon bearing the alcohol function is substituted by at least one C ₁ -C ₁₀ Alkyl, preferably C ₁ -C ₆ Alkyl, preferably C ₄ Alkyl radicals, preferably byTert-butyl substitution.

Amino compounds are another class of antioxidant additives that can be used in combination with possible phenolic antioxidant additives. Examples of amino compounds are aromatic amines, e.g. of the formula NR ⁷ R ⁸ R ⁹ Wherein R is ⁷ Represents an aliphatic or aromatic radical (optionally substituted), R ⁸ Represents an aromatic radical (optionally substituted), R ⁹ Represents a hydrogen atom, an alkyl group, an aryl group; or formula R ¹⁰ S(O) _z R ¹¹ Wherein R is ¹⁰ Represents alkylene or alkenylene, R ¹¹ Represents an alkyl group, an alkenyl group or an aryl group, and z represents 0, 1 or 2.

Sulfurized alkylphenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

Another class of antioxidant additives are copper compounds, such as copper thio-or dithiophosphates, copper carboxylates, copper dithiocarbamates, copper sulfonates, copper phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts may also be used.

The lubricant composition according to the invention may comprise any type of antioxidant additive known to the person skilled in the art.

Advantageously, the lubricant composition comprises at least one ashless antioxidant additive.

Also advantageously, the lubricant composition according to the invention comprises from 0.5 to 2% by weight of at least one antioxidant additive, based on the total mass of the composition.

The lubricant composition according to the present invention may further comprise at least one detergent additive.

Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving oxidation and combustion byproducts.

Detergent additives for use in lubricant compositions according to the present invention are generally known to those skilled in the art. The detergent additive can be an anionic compound comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali metal or alkaline earth metal.

The detergent additive is preferably selected from alkali or alkaline earth metal carboxylates, sulfonates, salicylates, naphthenates and phenates. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts generally contain a stoichiometric amount or an excess (i.e., an amount greater than the stoichiometric amount) of the metal. These are overbased detergent additives; the excess metal to give the detergent an overbased character is typically present in the form of an oil-insoluble metal salt, for example a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate.

Advantageously, the lubricant composition according to the invention may comprise from 2 to 4% by weight of detergent additive, relative to the total weight of the lubricant composition.

Also advantageously, the lubricant composition according to the invention may also comprise at least one pour point depressant additive.

Pour point depressant additives generally improve the condensation performance of lubricant compositions according to the present invention by slowing the formation of paraffin wax crystals.

Examples of pour point depressant additives are polyalkylmethacrylates, polyacrylates, polyaramides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

Advantageously, the lubricant composition according to the invention may also comprise at least one dispersant.

The dispersant may be selected from mannich bases, succinimides and derivatives thereof.

Advantageously, the lubricant composition according to the invention may comprise from 0.2 to 10 wt. -% of dispersant, based on the total weight of the lubricant composition.

The lubricant compositions of the present invention may also comprise at least one additional polymer that can improve the viscosity index. Examples of additional viscosity index improving polymers are polymeric esters of styrene, butadiene and isoprene, hydrogenated or non-hydrogenated homo-or copolymers, polymethacrylates (PMA).

The invention also relates to the use of a lubricant composition as defined above for lubricating metal parts, in particular for lubricating engines, in particular internal combustion engines, such as vehicle engines.

Advantageously, the lubricant composition according to the invention is capable of reducing friction, in particular between two parts of two mechanical parts (such as an engine, in particular an internal combustion engine, for example a vehicle engine).

The present invention therefore relates to the use of a lubricant composition according to the invention for reducing wear of a machine part, such as an engine part, in particular a vehicle engine.

The invention also relates to a method of lubricating a mechanical component, in particular in an engine such as an internal combustion engine, comprising at least one step of contacting the component with a lubricating composition according to the invention.

The invention will now be described by means of non-limiting examples.

Example 1: lubricant composition

The compositions in table 2 (LC: lubricant composition according to the invention; CC: comparative composition) were prepared by mixing the ester and/or polymeric friction modifier into a composition comprising a base oil, a viscosity index improver and an additive package at 60 ℃ to give the ratios shown in table 2. The percentages indicated are based on 100 wt.% of the lubricant composition comprising the ester and/or the polymeric friction modifier.

TABLE 2 Lubricant compositions according to the invention and comparative compositions

* The organic friction modifier according to the invention is the reaction product of:

a) A hydrophobic polymer subunit comprising a hydrophobic polymer selected from the group consisting of polyolefins, polyacrylic acid, and polystyrene;

b) A hydrophilic polymer subunit comprising a hydrophilic polymer selected from the group consisting of polyethers, polyesters, and polyamides;

d) Optionally a chain terminating group.

* Comprising a detergent, a dispersant, an antioxidant and an antiwear agent

The compositions in Table 3 (LC: lubricant composition according to the invention; CC: comparative composition) were prepared by mixing the ester and/or polymeric friction modifier into a composition comprising base oil, viscosity index improver and additive package at 60 ℃ to give the ratios shown in Table 3. The percentages indicated are based on 100 wt.% of the lubricant composition comprising the ester and/or the polymeric friction modifier.

TABLE 3 Lubricant compositions according to the invention and comparative compositions

Lubricant composition	LC7 (wt%)	CC3 (weight%)	CC4 (weight%)
				Citric acid triethyl ester	1	-	-
The organic friction modifier of the invention	0.5	-	0.5
				Additive package 2	10.7	10.9	10.8
Viscosity index improver (acrylic acid polymer)	5.8	5.9	5.9
				Group III and group IV base oils	82	83.2	82.8

* Comprising a detergent, a dispersant, an antioxidant and an antiwear agent.

Example 2: results of tribology tests

The tribology test was performed under the following conditions:

[ Table 4] tribology test conditions

The coefficient of friction of the tested lubricant compositions was determined at 100 ℃ using an MTM (Mini traction machine) apparatus on a hardened steel plane using hardened steel balls of 2cm diameter.

The MTM device may be a PCS Instruments set. The device allows the steel ball and steel plane to move relative to each other to determine the coefficient of friction for a given lubricant composition while varying various characteristics such as speed, load and temperature.

The hardened steel plane is AISI 52100 with a mirror finish (Ra less than 0.01 μm) and the ball is also AISI 52100 made of hardened steel.

The applied load was 30N (0.96 GPa) and the rotation speed was 0.007 to 3m/s.

About 50ml of the lubricant composition tested was introduced into the apparatus. The ball is in face-to-face engagement with the flats, the ball and flats being independently actuated to produce a mixed rolling/sliding contact.

The friction coefficient is measured and recorded by means of a force sensor.

The test lasted 121 minutes (alternating between slip and strerbek periods). The speed was initially kept constant at 0.1m/s and increased from 3m/s to 0.007m/s for one minute at each interval defined in the table, and then returned to 0.1m/s at the end of the defined period.

Thus, the coefficient of friction is measured as a function of the defined speed.

Table 5 gives the results for the compositions in table 2, expressed as coefficient of friction versus sliding speed.

[ Table 5]

	Speed of 0.01m/s	Speed of 0.1m/s
			Coefficient of friction CC1	0.068	0.070
Coefficient of friction CC2	0.133	0.112
			Coefficient of friction LC1	0.040	0.040
Coefficient of friction LC2	0.022	0.021
			Coefficient of friction LC3	0.050	0.061
Coefficient of friction LC4	0.048	0.047
			Coefficient of friction LC5	0.040	0.041

Table 6 gives the results for the compositions in table 3, expressed as coefficient of friction as a function of sliding speed.

[ Table 6]

	Speed of 0.01mm/s	Speed of 0.1mm/s
			Coefficient of friction LC7	0.073	0.065
Coefficient of friction CC3	0.131	0.115
			Coefficient of friction CC4	0.142	0.122

The test result shows that:

the value of the friction coefficient does not significantly depend on the content of polymeric friction modifier and/or ester;

when the ester is used alone, the ester has no significant effect on the coefficient of friction in the absence of a polymeric friction modifier;

there is a synergy between the esters defined in the present invention and the polymeric friction modifiers in the lubricant composition to significantly reduce the coefficient of friction and thus limit the friction between the mechanical parts.

Claims

1. A lubricant composition comprising, based on the total weight of the lubricant composition:

-at least one base oil;

-0.005 to 10 wt% of at least one polymeric organic friction modifier; and

the polymeric organic friction modifier is the reaction product of:

d) Optionally a chain terminating group.

2. The composition of claim 1, wherein the polymeric organic friction modifier has a weight average molecular weight of 1000 to 30000 daltons.

3. The composition of any of claims 1 or 2, wherein the organic friction modifier is a reaction product of a functionalized polyolefin, a polyether, a polyol, and a carboxylic acid end group.

4. The composition according to any one of claims 1 to 3, wherein the ester is selected from:

triesters of glycerol with monocarboxylic acids having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms; and

-triesters of citric acid with monohydric alcohols having from 1 to 10 carbon atoms, preferably from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms; and

-mixtures thereof.

5. Composition according to any one of claims 1 to 4, wherein the ester is selected from triheptanoin, triethyl citrate, tributyl citrate and mixtures thereof.

6. The composition of any one of claims 1 to 5, comprising, based on the total weight of the lubricant composition:

-0.005 to 10 wt. -%, preferably 0.05 to 5 wt. -%, preferably 0.1 to 3 wt. -%, more preferably 0.2 to 2 wt. -% of one or more polymeric organic friction modifiers;

-optionally 0.005 to 30 wt. -%, preferably 0.1 to 25 wt. -%, more preferably 1 to 20 wt. -% of one or more functional additives other than polymeric organic friction modifiers and glycerides, citrates and tartrates, preferably selected from detergent additives, antiwear additives other than phosphorus and sulfur removing additives, friction modifying additives, extreme pressure additives, dispersants, pour point depressants, antifoaming agents, thickeners and mixtures thereof.

7. Use of a composition according to any one of claims 1 to 6 for reducing friction between two mechanical parts, preferably between two parts of an engine, such as a vehicle engine.

8. Use according to claim 7 for reducing wear of components, in particular engine components.

9. A method for lubricating a mechanical component, in particular in an engine, especially in an internal combustion engine, comprising at least one step of contacting the component with a lubricating composition according to any of claims 1 to 6.