WO2022018000A1

WO2022018000A1 - Lubricating composition with improved anti-corrosion properties for a motor vehicle drive train

Info

Publication number: WO2022018000A1
Application number: PCT/EP2021/070073
Authority: WO
Inventors: Goulven BOUVIER; Hakim EL-BAHI; Sonia YOUNESSE
Original assignee: Totalenergies Marketing Services
Priority date: 2020-07-22
Filing date: 2021-07-19
Publication date: 2022-01-27
Also published as: MX2023000842A; KR20230042288A; JP2023534529A; FR3112791A1; FR3112791B1; US20230295532A1; CN116194559A; EP4185675A1

Abstract

The present invention relates to a lubricating composition comprising at least one base oil, at least one dispersant and at least one phosphite polymer having formula (I) wherein - each of the R1, R2, R3 and R4 can be independently selected from the C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers and Y-OH groups; - Y is selected from among the C2-C40 alkylene, C2-C40 alkyl lactone -R7- N(R8)-R9- groups, wherein R7, R8 and R9 are independently selected from among hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers; - m is an integer from 2 to 100; - n is an integer from 1 to 1000.

Description

Title: Lubricant composition for automobile transmission with improved anti-corrosion properties.

Technical area

The present invention relates to the field of lubricating compositions, in particular for motor vehicles, in particular for lubricating the transmission components of motor vehicles, in particular the gears of the transmissions of heat or electric motors.

State of the art

Motor vehicle transmission components operate under heavy load and high speeds. The oils for these transmissions must therefore be particularly effective in protecting the parts against wear and fatigue, and in particular protecting the gear teeth against the phenomenon of chipping.

Flaking occurs after a long time of aging, preceding visible deterioration. The mechanisms are not well known, but the phenomenon starts with the initiation of cracks at a certain depth under the surface, these cracks propagate, and when cracks normal to the surface are created, scales are detached suddenly.

The prevention of this phenomenon passes by a reduction of the stresses of contact thanks to an appropriate geometry of the parts, and by the reduction of the frictions, by avoiding adhesion. The lubricating composition intervenes in this prevention process, mainly through the physico-chemical reactivity of its additives.

Sulphur, phosphorus or borate anti-wear and extreme pressure additives are generally added to give transmission oils protective properties against chipping. The other additives present in the lubricating composition can also have an impact, positive or negative, on the propagation of cracks inside the parts and therefore on the spalling phenomenon.

During its use, the lubricating composition used in the transmission components may deteriorate.

It is therefore an object of the present invention to provide a lubricating composition for manual or automatic transmission, in particular for gears of thermal or electric motor transmissions, having good anti-corrosion properties, in particular with respect to copper.

Document WO 2010/126760 describes a lubricating composition comprising a base oil and a polymer of phosphorus ester type comprising the product of the condensation reaction of an acid or phosphorus ester with a diol where the two hydroxy functions are separated by a chain. from 4 to 100 carbon atoms.

Document WO 2016/089565 describes a lubricating composition comprising a base oil and a phosphite ester composition comprising the product of the condensation reaction of a phosphorus acid or ester with at least two diols.

These two documents do not relate to the anticorrosion properties and do not specifically describe the phosphite polymer of formula (I) as defined in the present invention.

Summary of the invention

More specifically, the present invention relates to a lubricating composition comprising:

- at least one base oil,

- at least one dispersant,

- at least one phosphite polymer of formula (I):

[Chem 1]

in which,

- each of R1, R2, R3 and R4 can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, methoxy alkyl glycol ethers in Cl-20 and Y-OH;

- Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone, -R7-N(R8)-R9-, in which R7, R8 and R9 are independently of each other chosen from hydrogen, C2-C40 alkyl C1-C20, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers, - m is an integer ranging from 2 to 100,

- n is an integer ranging from 1 to 1000.

According to one embodiment of the invention, the polymer of formula (I) has a weight-average molecular mass of less than 30,000 g/mol.

According to one embodiment of the invention, the phosphite polymer represents from 0.01 to 10% by weight of the total weight of the lubricating composition.

According to one embodiment of the invention, the dispersant is a borated dispersant preferably chosen from borated and optionally phosphated succinimides, preferably borated and optionally phosphated polyisobutylene succinimides.

According to one embodiment of the invention, the lubricating composition comprises from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of the lubricating composition.

According to one embodiment of the invention, the lubricating composition further comprises at least one anti-wear additive chosen from phosphorus anti-wear, sulfur anti-wear, phospho-sulfur anti-wear, phosphorus anti-wear -amine, sulphur-amine anti-wear agents, and their mixture, preferably in a proportion ranging from 0.01 to 5% by weight, relative to the total weight of the lubricating composition.

According to one embodiment of the invention, the lubricating composition comprises from 5 to 4000 ppm by weight of sulfur, preferably from 7 to 1000 ppm by weight of sulfur, more preferably from 10 to 800 ppm by weight of sulfur, by relative to the total weight of the lubricating composition.

According to one embodiment of the invention, the lubricating composition comprises: from 70 to 99% by weight of one or more base oil(s), and from 0.01 to 10% by weight of phosphite polymer, from 0 0.01 to 5% by weight of dispersant(s), preferably including at least one boron dispersant, optionally from 0.01 to 5% by weight of anti-wear additive(s) chosen from phosphorus anti-wear, anti- sulfur wear agents, phospho-sulfur anti-wear agents, phospho-amine anti-wear agents, sulfur-amine anti-wear agents, and their mixture, optionally from 1 to 30% by weight of one or more functional additives, of preferably selected from viscosity index improver additives, antioxidant additives, antifoam additives, non-boronated dispersants, detergents, viscosity modifier additives, and mixtures thereof, relative to the total weight of the lubricating composition.

The invention also relates to the use of a phosphite polymer in combination with a dispersant, to improve the anticorrosion properties of a lubricating composition comprising at least one base oil, said phosphite polymer corresponding to the formula (I):

[Chem 1]

in which,

- each of R ¹ , R ² , R ³ and R ⁴ can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, methoxy C1-20 and Y-OH alkyl glycol ethers;

- Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone, -R ⁷ - N(R ⁸ )-R ⁹ -, in which R ⁷ , R ⁸ and R ⁹ are independently of each other chosen from hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers,

- m is an integer ranging from 2 to 100,

- n is an integer ranging from 1 to 1000.

The invention also relates to the use of the lubricating composition according to the invention, for lubricating at least one mechanical part of a motor vehicle, preferably present in a transmission member of a motor vehicle, preferably a gear a motor vehicle. The lubricating composition according to the invention has the advantage of having very good properties for reducing the phenomenon of flaking, in particular when it is used under heavy load and high speeds.

The lubricating composition according to the invention typically exhibits good durability.

The lubricating composition according to the invention also has improved copper corrosion resistance properties. Copper will notably be present in the transmission systems of electric vehicles.

In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the Terminals are included unless otherwise stated.

Unless otherwise indicated, the quantities in a product are expressed by weight, relative to the total weight of the product.

detailed description

The present invention relates to a lubricating composition comprising:

- at least one base oil,

- at least one phosphite polymer corresponding to the formula (I),

- at least one dispersant, preferably a borated dispersant,

- optionally at least one anti-wear additive.

Phosphite polymer

The lubricating composition according to the invention comprises at least one phosphite polymer corresponding to formula (I):

[Chem 1]

in which,

- each of R ¹ , R ² , R ³ and R ⁴ can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, methoxy C1-20 alkyl glycol ethers and Y-OH (serving as terminal group);

- Y is chosen from C2-C40 alkylene, C2-C40 alkyl lactone, -R ⁷ -N(R ⁸ )-R ⁹ -, in which R ⁷ , R ⁸ and R ⁹ are independently of each other chosen from hydrogen, C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, C1-20 methoxy alkyl glycol ethers,

- m is an integer ranging from 2 to 100,

- n is an integer ranging from 1 to 1000.

Within the meaning of the present invention, the term “alkyl” is understood to mean a linear or branched noncyclic hydrocarbon-based chain, saturated, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the alkyls consist of carbon and hydrogen atoms.

Within the meaning of the present invention, the term "alkenyl" is understood to mean a linear or branched non-cyclic hydrocarbon-based, unsaturated chain, optionally comprising one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. Preferably, the alkenyls consist of carbon and hydrogen atoms.

For the purposes of the present invention, the term "cycloalkyl" means a saturated monocyclic or polycyclic group optionally having one or more alkyl or alkenyl substituents, said ring(s) may themselves be substituted by one or more heteroatoms, such as atoms of oxygen, nitrogen or sulfur. Preferably, the cycloalkyls consist of carbon and hydrogen atoms.

For the purposes of the present invention, the term "cycloalkenyl" means a monocyclic or polycyclic unsaturated group optionally having one or more alkyl or alkenyl substituents, said ring(s) may themselves be substituted by one or more heteroatoms, such as atoms of oxygen, nitrogen or sulfur. Preferably, the cycloalkenyls consist of carbon and hydrogen atoms.

Within the meaning of the present invention, a “Ci-Cj” group is a group comprising from i to j carbon atoms. According to a preferred embodiment, the group Y is chosen from alkylene comprising from 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms.

According to one embodiment, m ranges from 4 to 100.

According to one embodiment, the phosphite polymer of formula (I) has a weight-average molecular mass of less than 30,000 g/mol, preferably ranging from 3,000 to 20,000 g/mol. The weight average molecular mass can be measured by size exclusion chromatography.

According to one embodiment, the phosphite polymer of formula (I) has a number-average molecular mass of less than 10,000 g/mol, preferably ranging from 1,000 to 5,000 g/mol. The number average molecular weight can be measured by size exclusion chromatography.

According to one embodiment, the phosphite polymer of formula (I) has a polydispersity index ranging from 1 to 5, preferably ranging from 2 to 4.

Preferably, the phosphite polymer of formula (I) contains less than 2% by weight, preferably less than 1% by weight, or even less than 0.7% by weight of (alkyl)phenol group, relative to the total weight of the phosphite polymer of formula (I).

Preferably, the phosphite polymer of formula (I) is completely free of aromatic groups other than (alkyl)phenol groups.

Typically, the phosphite polymer is in liquid form.

According to one embodiment, the phosphite polymer has a phosphorus content ranging from 0.5 to 20% by weight, preferably from 1 to 10% by weight, relative to the total weight of the phosphite polymer.

The phosphite polymer used in the invention can be obtained according to the process described in the document WO2011102861. In particular, the polymer can be obtained according to the process described in paragraphs 27 to 32 of this document.

The synthesis of the polymers of formula (I) generally involves a transesterification in which the triphenyl phosphite (or any other suitable alkyl or aryl phosphite) can be reacted with a saturated or unsaturated alcohol or an ether. polyethylene or polypropylene glycol and a diol or a polymer diol H(OY) _m OH where Y and m are as defined previously with an appropriate basic catalyst at a temperature between 20°C and 250°C, and preferably at a temperature between 50°C and 185°C. Non-limiting examples of saturated or unsaturated alcohols include decyl, isodecyl, lauryl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, stearyl, isostearyl , oleic, monohydroxylated glycol ethers.

Preferably, the lubricating composition according to the invention comprises from 0.01 to 10% by weight of phosphite polymer(s), relative to the total weight of the lubricating composition.

Base oil(s)

The lubricating composition according to the invention comprises one or more base oils, preferably in a content of at least 70% by weight, preferably ranging from 70 to 99% by weight, more preferably from 80 to 98% by weight , preferably from 85 to 95% by weight, relative to the total weight of the lubricating composition.

These base oils can be chosen from the base oils conventionally used in the field of lubricating oils, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

The base oils of the lubricating compositions considered according to the invention may in particular be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in Table 1 below or mixtures thereof.

[Table 1]

Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, de-alpha removal, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing .

Blends of synthetic and mineral oils, which may be biosourced, can also be used.

There is generally no limitation as to the use of different base oils to produce the compositions used according to the invention, except that they must have properties, in particular in terms of viscosity, viscosity index, or resistance to oxidation, suitable for use for propulsion systems of an electric or hybrid vehicle.

The base oils of the compositions used according to the invention can also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, polyalphaolefins (PAO), and polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

The PAOs used as base oils are for example obtained from monomers comprising from 4 to 32 carbon atoms, for example from octene or decene. The weight average molecular weight of PAO can vary quite widely. Preferably, the weight-average molecular mass of the PAO is less than 600 Da. The weight-average molecular mass of the PAO can also range from 100 to 600 Da, from 150 to 600 Da, or even from 200 to 600 Da. Advantageously, the base oil or oils of the lubricating composition according to the invention can be chosen from group II or III base oils.

According to an alternative embodiment, the oil or base oils of the composition implemented according to the invention are chosen from polyalphaolefins (PAO), polyalkylene glycol (PAG) and esters of carboxylic acids and alcohols.

dispersant

The lubricating composition according to the invention comprises at least one dispersant. Typically, the dispersant will make it possible to ensure the maintenance in suspension and the evacuation of the insoluble solid contaminants constituted by the secondary products of oxidation which are formed when the lubricating composition is in service.

According to one embodiment, the dispersant may be chosen from succinimide dispersants, succinic ester dispersants, succinic ester-amide dispersants, Mannich base dispersants, and mixtures thereof, said dispersants possibly being in the borated form and/or phosphorus.

Thus, the lubricating composition according to the invention comprises at least one boron dispersant and/or at least one non-boron dispersant, preferably at least one boron dispersant.

By “non-boronated dispersant”, within the meaning of the present invention, is meant a dispersant additive free of boron atoms, said dispersant possibly comprising one or more phosphorus atoms.

According to one embodiment, the non-boronated dispersant is chosen from succinimide compounds, such as polyisobutylene succinimide (PIB SI).

By “boronated dispersant”, within the meaning of the present invention, is meant a dispersant additive comprising at least one boron atom, said dispersant possibly comprising one or more phosphorus atoms, one will then speak of a boronated and phosphorus dispersant.

According to one embodiment, the borated dispersant is chosen from borated succinimide compounds, such as borated polyisobutylene succinimide (PIBSI), or from phospho-boronated compounds, such as borated and phosphated polyisobutylene succinimide (PIBSI). According to one embodiment, the boron compound is chosen from the reaction products of a PIB SA and of a borated polyalkylene amine (PIB SA/borated P AM), the reaction products of a PIB SA and of a borated and phosphated polyalkylene amine (PIB SA/P AM borated and phosphated).

According to the embodiment implementing a dispersant (boronated and/or non-boronated) bearing a polyisobutylene (PIB) chain, the PIB chain preferably has a molar mass ranging from 750 to 3000 g/mol.

According to one embodiment, the boron dispersant has a boron content ranging from 0.1 to 10% by weight, preferably from 0.2 to 5% by weight, more preferably from 0.25 to 3% by weight, based on the total weight of the borated dispersant.

According to one embodiment, in the case where the boron dispersant is chosen from phospho-boron compounds, then the boron content preferably ranges from 0.1 to 10% by weight, preferably from 0.2 to 5% by weight. weight, more preferably 0.25 to 3% by weight, and the phosphorus content is preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight, more preferably 0 2 to 1.5% by weight, based on the total weight of the boron dispersant.

According to a particular embodiment, the boron dispersant does not include phosphorus.

According to one embodiment, the lubricating composition comprises from 0.01 to 5% by weight of borated and/or non-boronated dispersant(s), preferably from 0.1 to 4% by weight of borated and/or non-boronated dispersant(s), relative to the total weight of the lubricating composition.

The inventors thus discovered that the combination of a dispersant, preferably boron, and the phosphite polymer of formula (I) made it possible to improve the anticorrosion properties of the lubricating composition.

Anti-wear additive

The anti-wear additives optionally used in the lubricating composition according to the invention are chosen from phosphorus anti-wear, sulfur anti-wear, phospho-sulphur anti-wear, and mixtures thereof.

It should be noted that the anti-wear additive optionally added to the lubricating composition according to the invention will typically be different from the phosphite polymer of formula (I). Within the meaning of the present invention, a "phosphorus anti-wear" will designate an anti-wear comprising at least one phosphorus atom and not comprising sulfur, said phosphorus anti-wear may optionally comprise one or more nitrogen atoms (in addition carbon and hydrogen atoms). In this case, it can then be referred to as "phosphorus-amine anti-wear".

Within the meaning of the present invention, a "sulfur anti-wear" will designate an anti-wear comprising at least one sulfur atom and not comprising phosphorus, said phosphorus anti-wear may optionally comprise one or more nitrogen atoms (in addition carbon and hydrogen atoms). In this case, it can then be referred to as “sulphur-amine anti-wear”.

Within the meaning of the present invention, a "phosphor-sulfur anti-wear" will designate an anti-wear comprising at least one phosphorus atom and at least one sulfur atom, said phospho-sulphur anti-wear may optionally comprise one or more atoms nitrogen (in addition to carbon and hydrogen atoms). In this case, it can then be referred to as “sulphur-amine anti-wear”.

Mention may be made, among phosphorus anti-wear additives, of phosphates, phosphites and phosphonates. These terms denote both phosphoric, phosphorous and phosphonic acids, their mono, di and triesters, for example alkyl phosphates, alkyl phosphonates, and their salts, for example amines.

The phospho-sulfur anti-wear additives optionally used in the present invention may be (mono or di) thiophosphates and thiophosphites, these terms including thiophosphoric and thiophosphorous acids, the esters of these acids, their salts, dithiophosphites and dithiophosphates.

Mention may be made, as examples of phospho-sulfur anti-wear additives, of monobutylthiophosphate, monooctylthiophosphate, monolaurylthiophosphate, dibutylthiophosphate, dilaurylthiophosphate, tributylthiophosphate, trioctylthiophosphate, triphenylthiophosphate, monooctylthiophosphite, trilaurylthiophosphate, monolaurylthiophosphite, monobutylthiophosphite, dibutylthiophosphite, dilaurylthiophosphite, tributylthiophosphite, trioctylthiophosphate, , triphenylthiophosphite, trilaurylthiophosphite and their salts. Examples of salts of esters of thiophosphoric acid and of thiophosphorous acid are those obtained by reaction with a nitrogen compound such as ammonia or an amine or zinc oxide or zinc chloride.

According to a particular embodiment, the anti-wear additive(s) used in the invention are chosen from phospho-sulfur anti-wear, sulfur-amine anti-wear, and mixtures thereof.

By way of example, the lubricating composition according to the invention may comprise from 0.01 to 5% by weight of anti-wear additive(s), preferably from 0.05 to 3% by weight of additive(s). ) anti-wear, relative to the total weight of the lubricating composition.

The quantity of anti-wear additives may be adapted in order to obtain a phosphorus content ranging from 5 to 9150 ppm by weight in the lubricating composition. Preferably, the phosphorus content in the lubricating composition according to the invention ranges from 5 to 4500 ppm by weight, relative to the total weight of the lubricating composition.

The inventors have discovered that the combination of the phosphite polymer of formula (I), a boron dispersant and a phosphorus, sulfur or phosphosulfur anti-wear additive makes it possible to further improve the anti-corrosion properties of the lubricating composition.

Complementary additives

The lubricating composition according to the invention may also further comprise all types of functional additives, distinct from the phosphite polymer and anti-wear additives defined in the context of the present invention, suitable for use in a lubricant for motor vehicles, in particular for manual or automatic transmission of motor vehicles.

Such additives, known to those skilled in the art in the field of motor vehicle lubrication, can be chosen from detergents, antioxidants, pour point depressants, anti-foaming agents, viscosity, and mixtures thereof.

Advantageously, the composition according to the invention comprises at least one functional additive chosen from detergents, antioxidants, pour point depressants, antifoaming agents, viscosity index improvers, and mixtures thereof. Typically, when they are present, these additional functional additives represent (in total) from 1 to 30% by weight, preferably from 1.5 to 25% by weight, preferably from 2 to 20% by weight, of the weight total of the lubricating composition.

These additives can be introduced separately and/or in the form of a mixture similar to those already available for sale for formulations of commercial lubricants for vehicle engines, with a performance level as defined by T ACEA (Association European Automobile Manufacturers) and/or TAPI (American Petroleum Institute), well known to those skilled in the art.

The lubricating composition according to the invention may comprise at least one antioxidant additive.

The antioxidant additive generally makes it possible to delay the degradation of the composition in service. This degradation can in particular result in the formation of deposits, in the presence of sludge or in an increase in the viscosity of the composition.

Antioxidant additives act in particular as free radical inhibitors or destroyers of hydroperoxides. Among the antioxidant additives commonly employed, mention may be made of antioxidant additives of the phenolic type, antioxidant additives of the amine type, phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, can be ash generators. Phenolic antioxidant additives can be ash-free or in the form of neutral or basic metal salts. The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one CI 2 alkyl group, N,N '-dialkyl-aryl-diamines and mixtures thereof.

Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one carbon vicinal to the carbon bearing the alcohol function is substituted by at least one Ci-Cio alkyl group, preferably an alkyl group C _I -C _O , preferably a C4 alkyl group, preferably by the tert-butyl group.

Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. From Examples of amino compounds are aromatic amines, for example aromatic amines of formula NR ¹⁰ R ^U R ¹² in which R ¹⁰ represents an aliphatic group or an optionally substituted aromatic group, R ¹¹ represents an optionally substituted aromatic group, R ¹² represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R ¹³ S(0) _z R ¹⁴ in which R ¹³ represents an alkylene group or an alkenylene group, R ¹⁴ represents an alkyl group, an alkenyl or an aryl group and z represents 0, 1 or 2

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

Another class of antioxidant additives is that of copper compounds, for example copper thio- or dithio-phosphates, salts of copper and carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.

The lubricating composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

Advantageously, the lubricating composition according to the invention comprises at least one ash-free antioxidant additive.

The lubricating composition according to the invention may comprise from 0.5 to 2% by weight of at least one antioxidant additive, relative to the total weight of the composition.

The lubricating composition according to the invention may also comprise at least one detergent additive.

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

The detergent additives which can be used in the lubricating composition according to the invention are generally known to those skilled in the art. Detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali or alkaline earth metal. The detergent additives are preferably chosen from alkali metal or alkaline-earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline-earth metals are preferably calcium, magnesium, sodium or barium.

These metallic salts generally comprise the metal in a stoichiometric quantity or else in excess, therefore in a quantity greater than the narrow stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of an oil-insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferentially a carbonate .

The lubricating composition suitable for the invention may for example comprise from 0.5 to 4% by weight of detergent additive, relative to the total weight of the composition.

Also, the lubricating composition according to the invention may comprise at least one non-boronated dispersing agent.

The non-boronated dispersing agent can be chosen from Mannich bases or compounds of succinimide type, such as polyisobutylene succinimide (PIBSI).

The lubricating composition according to the invention may, for example, comprise from 0.2 to 10% by weight of non-boronated dispersing agent(s), relative to the total weight of the composition.

The lubricating composition according to the invention may also comprise at least one antifoaming agent.

The antifoaming agent can be chosen from silicones.

The lubricating composition according to the invention may comprise from 0.01 to 2% by mass or from 0.01 to 5% by mass, preferably from 0.1 to 1.5% by mass or from 0.1 to 2% by mass of agent antifoam, relative to the total weight of the composition.

The lubricating composition according to the invention may also comprise at least one pour point depressant additive (also called “PPD” agents for “Pour Point Depressant” in English). By slowing down the formation of paraffin crystals, pour point depressants generally improve the cold behavior of the composition. As an example of pour point depressant additives, mention may be made of polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

The lubricating composition according to the invention may also comprise at least one viscosity index improver (VI improver). Examples of IV improvers include polymethacrylates, polyisobutenes or fatty acid esters. When they are present, these additives can represent from 1 to 25% by weight, of the total weight of the lubricating composition.

In terms of formulation of such a lubricating composition, the phosphite polymer, the dispersant and, where appropriate, the anti-wear additive can be added to an oil or mixture of base oils, then the other optional additional additives added.

Alternatively, the phosphite polymer, the dispersant and, where appropriate, the anti-wear additive can be added to a pre-existing conventional lubricant formulation, comprising in particular one or more base oils, and optionally additional additives.

Alternatively, the phosphite polymer, the dispersant and, where appropriate, the anti-wear additive defined in the present invention can be combined with one or more additional additives when they are present, and the "package" of additives thus formed added to an oil or mixture of base oils.

Advantageously, the lubricating composition according to the invention has a kinematic viscosity, measured at 40° C. according to the ASTM D445 standard, ranging from 5 to 300 mm ² /s, in particular from 10 to 25 mm ² /s.

Advantageously, the lubricating composition according to the invention has a kinematic viscosity, measured at 100° C. according to the ASTM D445 standard, ranging from 1 to 20 mm ² /s, in particular from 2 to 15 mm ² /s. According to a particular embodiment, the lubricating composition according to the invention comprises, or even consists of:

- a base oil or mixture of base oils;

- a phosphite polymer corresponding to the formula (I);

- a borated or non-boronated dispersant chosen from the PIBs SI optionally borated and/or phosphated;

- optionally a phospho-sulphur and/or sulphur-amine anti-wear additive;

- optionally one or more additional additives chosen from viscosity index modifiers, detergents, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.

According to a particular embodiment, the lubricating composition according to the invention comprises, or even consists of:

- a base oil or mixture of base oils;

- a phosphite polymer corresponding to the formula (I);

- a borated dispersant chosen from borated PIBSI and borated and phosphated PIBSI;

- optionally a phospho-sulphur and/or sulphur-amine anti-wear additive;

- optionally one or more additional additives chosen from viscosity index modifiers, detergents, antioxidants, pour point depressants, antifoaming agents and mixtures thereof.

- at least 70% by weight, preferably 70 to 99% by weight of base oil(s);

- from 0.05% to 10% by weight, in particular from 0.1% to 7% by weight, and more particularly from 1% to 5% by weight, of phosphite polymer(s) corresponding to formula (I) ;

- from 0.01 to 5% by weight of borated and/or non-borated dispersant(s) chosen from the optionally borated and/or phosphated PIBSIs;

- from 0.05 to 10% by weight, in particular from 0.1% to 7% by weight, and more particularly from 1% to 5% by weight, of phospho-sulfur anti-wear additive(s) and/ or sulfur-amine;

- optionally from 1 to 20% by weight, preferably from 1.5 to 10% by weight, and more particularly from 2 to 5% by weight, of one or more functional additives, preferably selected from viscosity index modifiers, detergents, antioxidants, pour point depressants, anti-foaming agents and mixtures thereof.

- at least 70% by weight, preferably 70 to 99% by weight of base oil(s);

- from 0.01 to 5% by weight of borated dispersant(s) chosen from borated PIBSIs and borated and phosphated PIBSIs;

- optionally from 1 to 20% by weight, preferably from 1.5 to 10% by weight, and more particularly from 2 to 5% by weight, of one or more functional additives, preferably chosen from index modifiers viscosifiers, detergents, antioxidants, pour point depressants, antifoaming agents and mixtures thereof.

According to one embodiment, the lubricating composition according to the invention comprises from 5 to 4000 ppm by weight of sulfur, preferably from 7 to 1000 ppm by weight of sulfur, more preferably from 10 to 800 ppm by weight of sulfur, by relative to the total weight of the lubricating composition.

According to one embodiment, the lubricating composition according to the invention comprises from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of the lubricating composition.

According to one embodiment, the boron content of the lubricating composition ranges from 5 to 500 ppm, preferably from 10 to 300 ppm by weight, relative to the total weight of the lubricating composition.

The present invention also relates to the use of the phosphite polymer as defined above in combination with a boronated and/or non-boronated dispersant in a lubricating composition comprising at least one base oil, in order to improve the anti-corrosion properties of the lubricating composition, in particular the corrosion resistance of copper.

The present invention also relates to the use of the lubricating composition according to the invention for lubricating the transmissions of motor vehicles, in particular the gears of the transmissions. Transmissions can be manual or automatic transmissions.

Preferably, the lubricating composition according to the invention is used to reduce the wear of a mechanical part of a motor vehicle transmission, in particular of a motor vehicle gear. Thus, according to this embodiment, the lubricating composition according to the invention makes it possible to reduce the wear of the gears of the transmissions.

Preferably, the lubricating composition according to the invention is used to reduce the spalling of a mechanical part of a motor vehicle transmission, in particular of a motor vehicle gear.

According to an advantageous embodiment, the lubricating composition according to the invention is used to both reduce wear and reduce spalling of a mechanical part of a motor vehicle transmission, in particular of a vehicle gear. automobiles.

The invention also relates, according to another of its aspects, to a method for lubricating at least one part of a transmission of a motor vehicle, in particular a gear of a motor vehicle, comprising at least one step bringing at least said part into contact with a lubricating composition as described above.

The invention also relates, according to another of its aspects, to a process for improving the resistance to copper corrosion of a lubricating composition, said process comprising a step of mixing at least one phosphite polymer of formula (I ) and at least one boronated and/or non-boronated dispersant as defined in the present invention, with at least one base oil, preferably, said polymer and said dispersant are further mixed with an anti-wear additive such as defined in the present invention. All of the characteristics and preferences described for the lubricating composition according to the invention as well as for its uses also apply to these processes.

According to the invention, the particular, advantageous or preferred characteristics of the composition according to the invention make it possible to define uses according to the invention which are also particular, advantageous or preferred.

The invention will now be described by means of the following examples, given of course by way of non-limiting illustration of the invention.

Examples

Example 1: Preparation of the lubricating compositions

The lubricating compositions were prepared by mixing the ingredients at a temperature of approximately 40° C., according to methods well known to those skilled in the art. The lubricating compositions which were prepared and tested are detailed in Table 2 below. The percentages are percentages by weight, relative to the total weight of the lubricating composition.

The elemental contents of phosphorus, boron, sulfur were calculated according to the element contents in the ingredients and are also indicated in table 2 in ppm by weight. Finally, the kinematic viscosities at 40°C and at 100°C were determined by the ASTM D445 method and are indicated in Table 2.

[Table 2]

In the compositions of Table 2:

- the base oils are group III base oils,

- the phosphite polymer corresponds to formula (I) and comprises 4.50% by weight of phosphorus and zero sulphur, it has a weight-average molecular mass of approximately 10,000 g/mol and a number-average molecular mass of approximately 3000 g/mol, it can be obtained for example according to the method described in example 2 of document WO 2011/102861,

- the phosphorus anti-wear is of the dibutyl phosphite type (not corresponding to formula (I)) and comprises 15.80% by weight of phosphorus and zero sulfur, - the phospho-sulfur anti-wear is of the phosphorothionate type and comprises 9.30% by weight phosphorus and 19.80% by weight sulfur,

- the borated dispersant is a borated PIBSI comprising 0.40% by weight of boron and zero phosphorus,

- the phospho-boron dispersant is a borated and phosphated PIBSI comprising 1% by weight of boron and 0.75% by weight of phosphorus,

- the non-boronated dispersant is an amino dispersant comprising 3.20% by weight of nitrogen and zero boron and zero phosphorus,

- G antioxidant is an alkylated diphenylamine antioxidant,

- G anti-corrosion is a tolytriazine, - the detergent is an overbased calcium sulfonate detergent.

Example 2: Studies of the performances of the lubricating compositions The corrosion resistance of the lubricating compositions described in Table 2 was tested by the CEC L-48-00 method with the addition of a copper strip.

Copper corrosion is evaluated after 168 hours of testing at 150°C, by determining the amount of copper in the lubricating composition at the end of the test, which is indicated in Table 3.

The mass of the copper strip is measured before and after the 168h test at 150°C. The difference (Amasse) is shown in Table 3.

[Table 3]

The results of Table 3 show a very low copper content in the lubricating composition at the end of the test and a low loss of mass of the copper strip, which shows that the lubricating compositions according to the invention have good anti-corrosion properties vis -to-copper.

Claims

1. Lubricant composition comprising:

- at least one base oil,

- at least one dispersant,

- at least one phosphite polymer of formula (I): [Chem 1]

in which,

- each of R ¹ , R ² , R ³ and R ⁴ can be chosen independently of each other from C1-C20 alkyl, C3-C22 alkenyl, C6-C40 cycloalkyl, C7-C40 cycloalkenyl, methoxy C1-20 alkyl glycol ethers and Y-OH;

- m is an integer ranging from 2 to 100,

- n is an integer ranging from 1 to 1000.

2. Lubricating composition according to claim 1, in which the polymer of formula (I) has a weight-average molecular mass of less than 30,000 g/mol.

3. Lubricating composition according to any one of the preceding claims, in which the phosphite polymer represents from 0.01 to 10% by weight of the total weight of the lubricating composition.

4. Lubricating composition according to any one of the preceding claims, in which the dispersant is a borated dispersant preferably chosen from borated and optionally phosphated succinimides, preferably borated and optionally phosphated polyisobutylene succinimides.

5. Lubricating composition according to any one of the preceding claims, comprising from 5 to 9150 ppm by weight of phosphorus, preferably from 5 to 4500 ppm by weight of phosphorus, relative to the total weight of the lubricating composition.

6. Lubricating composition according to any one of the preceding claims, further comprising at least one anti-wear additive chosen from phosphorus anti-wear, sulfur anti-wear, phospho-sulfur anti-wear, phosphorus anti-wear - amine, sulphur-amine anti-wear, and their mixture, preferably in a proportion ranging from 0.01 to 5% by weight, relative to the total weight of the lubricating composition.

7. Lubricating composition according to one of the preceding claims, comprising from 5 to 4000 ppm by weight of sulfur, preferably from 7 to 1000 ppm by weight of sulfur, more preferably from 10 to 800 ppm by weight of sulfur, relative to the total weight of the lubricating composition.

8. Lubricating composition according to any one of the preceding claims, comprising: from 70 to 99% by weight of one or more base oils, and from 0.01 to 10% by weight of phosphite polymer, from 0 0.01 to 5% by weight of dispersant(s), preferably including at least one boron dispersant, optionally from 0.01 to 5% by weight of anti-wear additive(s) chosen from phosphorus anti-wear, anti-wear - sulfur wear, phospho-sulfur anti-wear, phospho-amine anti-wear, sulfur-amine anti-wear, and a mixture thereof, optionally from 1 to 30% by weight of one or more functional additives, preferably selected from viscosity index improver additives, antioxidant additives, antifoam additives, non-boronated dispersants, detergents, viscosity modifier additives, and mixtures thereof, based on the total weight of the lubricating composition.

9. Use of a phosphite polymer in combination with a dispersant, to improve the anticorrosion properties of a lubricating composition comprising at least one base oil, said phosphite polymer corresponding to formula (I):

[Chem 1]

in which,

- m is an integer ranging from 2 to 100,

- n is an integer ranging from 1 to 1000.

10. Use of the composition according to any one of claims 1 to 8, for lubricating at least one mechanical part of a motor vehicle, preferably present in a transmission member of a motor vehicle, preferably a gear of a motor vehicle.