EP4185671A1

EP4185671A1 - Oxidation-stable lubricating composition for a motor vehicle drive train

Info

Publication number: EP4185671A1
Application number: EP21746441.1A
Authority: EP
Inventors: Goulven BOUVIER; Hakim EL-BAHI; Sonia YOUNESSE; Florence Bredon
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2020-07-22
Filing date: 2021-07-19
Publication date: 2023-05-31
Also published as: FR3112792A1; KR20230042293A; MX2023000843A; FR3112792B1; US20230303945A1; CN116264838A; WO2022018001A1; US12098348B2; JP2023534509A

Abstract

The present invention relates to a lubricating composition comprising at least one base oil, at least one borated dispersant, at least two antioxidants selected from amine antioxidants, phenolic antioxidants substituted with one or more linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof, and at least one phosphite polymer having the 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 C2-C40 alkylene, C2-C40 alkyl lactone, -R7- N(R8)-R9- groups, in which R7, R8 and R9 are independently selected from 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: Oxidation-stable automotive transmission lubricating composition.

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 thermal or electric vehicles.

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, in particular under the effect of oxidation.

It is therefore an object of the present invention to provide a lubricating composition for manual or automatic transmission, in particular for gearing of thermal or electric motor transmissions, having good oxidation stability.

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 disclose the composition of 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 borated dispersant,

- at least two antioxidants chosen from amino antioxidants, phenolic antioxidants substituted by one or more linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof, and

- 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 and Y-OH alkyl glycol ethers (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.

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 borated dispersant is chosen from borated and optionally phosphated succinimides, preferably borated 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 comprises:

- at least one amino antioxidant, and

- at least one phenolic antioxidant substituted by one or more linear or branched alkyl groups having from 1 to 30 carbon atoms.

According to one embodiment of the invention, in the lubricating composition:

- the amino antioxidant(s) are chosen from diphenylamines, diphenylamines substituted with at least one C1-C30 alkyl group, N,N'-dialkyl-aryl-diamines, and/or

- the phenolic antioxidant(s) substituted by one or more linear or branched C1-C30 alkyl groups are chosen from triphenylphosphites whose phenyl groups are substituted by at least one linear or branched C1-C30 alkyl group, phenols substituted by two C1-C30 alkyl groups and a C1-C30 ester group, the compounds comprising two phenols each substituted by at least one C1-C30 alkyl group and connected by a thioether bridge optionally having an ester function on each side of said bridge.

According to one embodiment of the invention, the lubricating composition comprises: from 70 to 99% by weight of one or more base oils, and from 0.01 to 10% by weight of phosphite polymer, from 0.01 to 5% by weight of boron dispersant(s) ), from 0.01 to 5% by weight of the mixture of at least one amino antioxidant and at least one phenolic antioxidant substituted with one or more linear or branched C1-C30 alkyl groups; optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improver additives, antioxidant additives, antifoam additives, non-boronated dispersants, detergents, anti-wear additives , the viscosity modifier additives, and their mixture, relative to the total weight of the lubricating composition.

The invention also relates to the use of a phosphite polymer in combination with a boron dispersant and two antioxidants, to improve the stability to oxidation of a lubricating composition comprising at least one base oil, said phosphite polymer satisfying the 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 (serving as a terminal group);

- 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, said two antioxidants being chosen from amino antioxidants, phenolic antioxidants substituted by one or more linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof.

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 of a vehicle automobile.

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 implemented under heavy load and high speed.

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

The lubricating composition according to the invention also has good anti-corrosion properties.

The lubricating composition according to the invention also has very good oxidation stability.

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 borated dispersant,

- at least two antioxidants chosen from amino antioxidants, antioxidants phenolics substituted with linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof.

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, C ₇ -C _{40 cycloalkenyl} , methoxy glycol alkyl ethers, Cl - ₂₀ and Y-OH (serving terminal group);

- Y is selected from the group alkylene, C ₂ -C ₄₀ alkyl lactone C ₂ -C _40, -R ⁷ -N (R ⁸⁾ - R ⁹ - wherein R ^7, R ⁸ and R ⁹ are independently from 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.

Within the meaning of the present invention, the term "cycloalkyl" means a saturated monocyclic or polycyclic group optionally having one or more substituents alkyl or alkenyl, said ring(s) may themselves be substituted by one or more heteroatoms, such as oxygen, nitrogen or sulfur atoms. 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 Y group 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.

Synthesis of the polymers of formula (I) generally involves transesterification in which triphenyl phosphite (or any other suitable alkyl or aryl phosphite) may be reacted with a saturated or unsaturated alcohol or a polyethylene ether or of polypropylene glycol and a diol or a polymer diol H(OY) _m OH where Y and m are as defined above with an appropriate basic catalyst at a temperature between 20°C and 250°C, and preferably at a temperature between 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 may 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 acid esters 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.

Boron dispersant

The lubricating composition according to the invention comprises one or more boron dispersants.

By “boronated dispersant”, within the meaning of the present invention, is meant a dispersant additive comprising at least one boron atom. 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 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 borated compound is chosen from the reaction products of a PIBSA and a borated polyalkylene amine (PIBSA/borated PAM), the reaction products of a PIBSA and a borated polyalkylene amine and phosphate (PIBSA/PAM borated and phosphated). According to the embodiment implementing a dispersant 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 dispersant(s), preferably from 0.1 to 4% by weight of borated dispersant(s), relative to the total weight of the lubricating composition.

Antioxidants

The lubricating composition according to the invention comprises at least two different antioxidants. Said at least two antioxidants are chosen from amino antioxidants, phenolic antioxidants substituted with one or more linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof.

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.

Within the meaning of the present invention, a compound is said to be "phenolic substituted by one or more linear or branched alkyl groups having from 1 to 30 carbon atoms" when it comprises at least one structure of the -O-phenyl type, said phenyl ring being substituted by at least one linear or branched alkyl group having from 1 to 30 carbon atoms. According to one embodiment, the phenolic antioxidants substituted by one or more linear or branched C ₁ _{-C 30} alkyl groups are chosen from triphenylphosphites whose phenyl groups are substituted by at least one linear or branched C ₁ -C alkyl group _30, phenols substituted with two alkyl groups in C ₁ -C ₃₀ ester group and a C ₁ -C _30, compounds comprising two substituted phenols each by at least one alkyl group in C ₁ -C ₃₀ and connected by a bridge thioether optionally having an ester function on each side of said bridge.

Preferably, at least one of the substituents of the phenol groups is chosen from linear or branched C1-C16, preferably C1-C10, more preferably C _I -C 6 _alkyls . According to one embodiment, at least one of the substituents of the phenol groups is a tert-butyl group.

According to one embodiment, the amino antioxidants are chosen from 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 ^{1 1} 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 group or an aryl group and z represents 0, 1 or 2.

Within the meaning of the present invention, an “aromatic” group denotes a group comprising at least one aromatic ring. It may be, for example, a phenyl or naphthyl ring.

Within the meaning of the present invention, an “aliphatic” group designates a group which is not aromatic. It may be, for example, an alkyl, alkenyl, cycloalkyl or cycloalkenyl group.

According to one particular embodiment, the amino antioxidants are chosen from diphenylamines, diphenylamines substituted with at least one C ₁ _{-C 30} alkyl group, N,N'-dialkyl-aryl-diamines, preferably from diphenylamines, diphenylamines substituted with at least one C ₁ -C _{30 alkyl group,.}

Preferably, the amino antioxidant(s) used in the invention comprise from 1 to 10% by weight of nitrogen, preferably from 2 to 7% by weight of nitrogen, relative to the weight of said antioxidant. According to one embodiment of the invention, the lubricating composition comprises at least two antioxidants chosen from triphenylphosphites whose phenyl groups are substituted by at least one linear or branched C1-C30 alkyl group, phenols substituted by two alkyl groups in C1-C30 and a C1-C30 ester group, compounds comprising two phenols each substituted by at least one C1-C30 alkyl group and connected by a thioether bridge optionally having an ester function on each side of said bridge, diphenylamines, diphenylamines substituted with at least one C1-C30 alkyl group, N,N'-dialkyl-aryl-diamines, and mixtures thereof.

According to one embodiment, the lubricating composition comprises:

- at least one amino antioxidant, and

- at least one phenolic antioxidant substituted with one or more linear or branched C1-C30 alkyl groups.

Preferably, the lubricating composition comprises:

- at least one antioxidant chosen from diphenylamines, diphenylamines substituted with at least one C1-C30 alkyl group, N,N'-dialkyl-aryl-diamines, and mixtures thereof, and

- at least one antioxidant chosen from triphenylphosphites whose phenyl groups are substituted by at least one linear or branched C1-C30 alkyl group, phenols substituted by two C1-C30 alkyl groups and a Ci-C30 ester group, compounds comprising two phenols each substituted by at least one C1-C30 alkyl group and connected by a thioether bridge optionally having an ester function on each side of said bridge.

Preferably, the lubricating composition comprises from 0.01 to 5% by weight, or even from 0.1 to 3% by weight, of a mixture of at least two antioxidants chosen from amino antioxidants, phenolic antioxidants substituted by a or more linear or branched alkyl groups having from 1 to 30 carbon atoms, and mixtures thereof, relative to the total weight of the lubricating composition.

The inventors have in fact discovered that the combination of a phosphite polymer of formula (I), of a boron dispersant and of two specific antioxidants made it possible to unexpectedly improve the stability to oxidation 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 antioxidant additives and boron dispersant 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 anti-wear additives, detergents, non-boronated dispersants, antioxidants different from the antioxidants defined in the present invention, pour point depressants, antifoaming agents, viscosity index improvers, and mixtures thereof.

Advantageously, the composition according to the invention comprises at least one functional additive chosen from anti-wear additives, detergents, non-boronated dispersants, antioxidants, pour point depressants, anti-foam agents, improvers of viscosity index, 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 like those already available for sale for the formulations of commercial lubricants for vehicle engines, with a performance level as defined by the ACEA ( Association of European Automobile Manufacturers) and/or the API (American Petroleum Institute), well known to those skilled in the art.

The lubricating composition according to the invention may optionally comprise one or more anti-wear additives. Said anti-wear additives can be chosen from phosphorus anti-wear, sulfur anti-wear, phospho-sulfur anti-wear, and a mixture thereof.

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, 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 nitrogenous 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), 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 lubricating composition according to the invention may comprise at least one antioxidant additive different from the antioxidant additives defined previously in the present invention. Said (different) antioxidant can be chosen from copper compounds, for example copper thio- or dithio-phosphates, salts of copper and of 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 comprise from 0.5 to 2% by weight of at least one antioxidant additive different from the antioxidants defined above in the context of the invention, 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 the succinimide type, such as non-boronated 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). As examples of IV improvers, mention may be made of 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 boron 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 boron dispersant and, where applicable, 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 boron 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 a 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 dispersant chosen from borated SI PIBs and borated and phosphated SI PIBs;

- an amino antioxidant; - a phenolic antioxidant substituted with one or more linear or branched C1-C30 alkyl groups;

- optionally one or more additional additives chosen from anti-wear additives, viscosity index modifiers, detergents, non-boronated dispersants, antioxidants, pour point depressants, anti-foam agents and their mixtures.

- at least 70% by weight, preferably from 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 dispersant(s) chosen from borated PIBSIs and borated and phosphated PIBSIs;

- from 0.01 to 5% by weight of the mixture of at least one amino antioxidant and at least one phenolic antioxidant substituted by one or more linear or branched C1-C30 alkyl groups;

- 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 anti-wear additives , viscosity index modifiers, detergents, non-boronated dispersants, 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. According to one embodiment, the nitrogen content of the lubricating composition ranges from 5 to 5000 ppm, preferably from 10 to 2000 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 boron dispersant and two antioxidants as defined in the present invention, in a lubricating composition comprising at least one base oil, in order to improve the stability to the oxidation of said lubricating composition.

Preferably, the use of the invention is characterized by a change in viscosity at 100° C. of the lubricating composition comprising at least one base oil, said phosphite polymer, said boron dispersant, and said antioxidants, of less than 10% according to the DIN 51659-2 method.

A subject of the present invention is also 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 stability to oxidation of a lubricating composition, said process comprising a step of mixing at least one phosphite polymer of formula (I) as defined in the present invention, of at least one boron dispersant and of at least two antioxidants as defined in the present invention, with at least one base oil, preferably said polymer, said dispersant and said antioxidants are additionally mixed with an anti-wear additive.

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 and amine were calculated according to the elemental 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 phospho-sulfur anti-wear is of the phosphorothionate type and comprises 9.30% by weight of phosphorus and 19.80% by weight of sulfur,

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

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

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

- amino antioxidant 1 is an alkylated diphenylamine antioxidant comprising 4.50% by weight of nitrogen,

- amino antioxidant 2 is a naphthyl-phenyl-alkylamine antioxidant comprising 4.78% by weight of nitrogen,

- the phenolic antioxidant 1 is an antioxidant comprising a phenol group substituted by two C1-C30 alkyl groups and a C1-C30 ester group, this phenolic antioxidant 1 does not contain sulfur, phosphorus or nitrogen,

- the phenolic antioxidant 2 is an antioxidant comprising two phenol groups each substituted by at least one C1-C30 alkyl group and connected by a thioether bridge having an ester function on each side of said bridge, this phenolic antioxidant 2 comprises 4.90% by weight of sulphur, and zero nitrogen and zero phosphorus,

- the phenolic antioxidant 3 is a triphenylphosphite antioxidant whose 3 phenyl groups are substituted by at least one linear or branched C1-C30 alkyl group, this phenolic antioxidant 3 comprises 5% by weight of phosphorus, and zero nitrogen and zero sulphur,

- G anti-corrosion is a tolytriazine,

- the detergent is an overbased calcium sulfonate detergent,

- the additive package contains a pour point improver and a defoamer.

Example 2: Studies of the performances of the lubricating compositions Oxidation stability was evaluated by measuring the change in viscosity at 100°C during a 192h test at 170°C, according to DIN 51659-2. The change in viscosity is expressed in % in Table 3 below.

[Table 3]

The results in Table 3 show that the viscosity does not vary substantially during this test at 170° C. for a long period, which shows the very good oxidation stability of the lubricating compositions according to the invention. In particular, the compositions according to the invention have better oxidation stability than the comparative composition CCI.

Example 3: Studies of the performances of the lubricating compositions

In this example, the oxidation stability was evaluated by measuring the change in viscosity at 100°C during a test of 384h at 170°C, according to DIN 51659-2. The change in viscosity is expressed in % in Table 4 below.

[Table 4]

The results in Table 4 show that the viscosity does not vary substantially during this test at 170° C. for a very long period, which shows the very good oxidation stability of the lubricating compositions according to the invention. In particular, the composition according to the invention has better oxidation stability than the comparative compositions CC1 and CC2.

Claims

1. Lubricant composition comprising:

- at least one base oil,

- at least one borated 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;

- 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.

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 borated dispersant is chosen from borated and optionally phosphated succinimides, preferably borated 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, comprising:

- at least one amino antioxidant, and

7. Lubricating composition according to one of the preceding claims, in which:

- the amino antioxidant(s) are chosen from diphenylamines, diphenylamines substituted with at least one C ₁ _{-C 30} alkyl group, N,N'-dialkyl-aryl-diamines, and/or

- the phenolic antioxidant(s) substituted by one or more linear or branched C ₁ _{-C 30} alkyl groups are chosen from triphenylphosphites whose phenyl groups are substituted by at least one linear or branched C ₁ _{-C 30} alkyl group, phenols substituted with two alkyl groups in C ₁ -C ₃₀ ester group and a C ₁ -C _30, compounds comprising two substituted phenols each by at least one alkyl group in C ₁ -C ₃₀ and linked by a thioether bridge optionally having an ester function on each side of said bridge.

8. Lubricating composition according to any one of the preceding claims, comprising: 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 boron dispersant(s), from 0.01 to 5% by weight of the mixture of at least one amino antioxidant and at least one phenolic antioxidant substituted with one or more linear or branched C1-C30 alkyl groups _; optionally from 1 to 30% by weight of one or more functional additives, preferably chosen from viscosity index improver additives, antioxidant additives, antifoam additives, non-boronated dispersants, detergents, anti- wear, viscosity modifier additives, and their mixture, relative to the total weight of the lubricating composition.

9. Use of a phosphite polymer in combination with a boron dispersant and two antioxidants, to improve the oxidative stability of a lubricating composition comprising at least one base oil, said phosphite polymer having the formula

(I):

[Chem 1] in which,

- each of R ^1, R ^2, R ³ and R ⁴ may be independently selected from each other from alkyl C1-C2 ₀ alkenyl, C3-C22 cycloalkyl, C ₆ -C 4 _0, ₇ cycloalkenyl C -C ₄₀ , methoxy alkyl glycol ethers in Ci - ₂₀ and Y-OH (serving as terminal group);

- Y is selected from the group alkylene, C ₂ -C ₄₀ alkyl lactone C ₂ -C _40, -R ⁷ -N (R ⁸⁾ - R ⁹ - wherein R ^7, R ⁸ and R ⁹ are independently from each other selected from hydrogen, C1-C2 ₀ alkenyl, C3-C22 cycloalkyl, C ₆ -C 4 _0, cycloalkenyl, C4-C7 _0, methoxy glycol alkyl ethers Ci -2 _0,

- m is an integer ranging from 2 to 100,

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. a motor vehicle.