WO2023117456A1

WO2023117456A1 - Lubricant composition

Info

Publication number: WO2023117456A1
Application number: PCT/EP2022/084954
Authority: WO
Inventors: Robert NGO; Julien Thuilliez; Thibaut SOUCHARD
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2021-12-21
Filing date: 2022-12-08
Publication date: 2023-06-29
Also published as: FR3130838A1; FR3130838B1

Abstract

The invention relates to a lubricant composition which contains a mineral base oil and a copolymer of ethylene and 1,3-butadiene which contains more than 90% to less than 97% by mole of ethylene units and which has a crystallinity rate of more than 30% and less than 45%. It can be used as engine oil.

Description

Lubricant composition

The field of the present invention is that of lubricating compositions containing a mineral base oil and intended for use as engine oils to improve the performance of engines.

Motor oils, lubricating compositions containing mineral base oils, are used in an engine to minimize the energy losses caused by friction in the engine when cold and to maintain a continuous film of lubricant on the lubricated elements of the engine when hot. It is important that the viscosity of the lubricating composition decreases as little as possible during hot operation to avoid the breakdown of the lubricating film. To perform both of these functions when cold and when hot, it is desirable to have a lubricating composition which has the lowest variation in viscosity with temperature. As a high viscosity index guarantees a lesser drop in viscosity when the temperature increases, lubricating compositions having a high viscosity index are therefore sought after.

Mineral base oils represent a major constituent of lubricating compositions such as motor oils. The viscosity of a mineral base oil decreases with an increase in temperature and increases with a decrease in temperature. It follows that the viscosity of a lubricating composition mainly containing a mineral base oil also sees its viscosity vary with temperature.

To lessen this influence of temperature on the viscosity of a lubricating composition, it is known to add additives to a mineral base oil. These so-called viscosity index improver additives (in English “viscosity improver” or “viscosity index improver”) have a role of selective thickening of the lubricating composition when the temperature increases to partially remedy the drop in viscosity noted when hot. They generally increase viscosity at high temperature to counter the decrease in viscosity of mineral base oil without significantly increasing it at low temperature. Viscosity index improvers are generally polymers. The two main families of polymers marketed as viscosity index improvers are polymers with an ester function such as poly(meth)acrylates and hydrocarbon polymers such as polyisobutylenes, copolymers of ethylene and propylene also called OCP, copolymers of hydrogenated diene and styrene, as well as hydrogenated polydienes. Nevertheless, there is still a need to further improve the viscosity index of lubricating compositions containing a mineral base oil such as motor oils.

The Applicant has discovered a new lubricating composition which has an improved viscosity index. Thus, a first object of the invention is a lubricating composition which comprises a mineral base oil and a copolymer of ethylene and 1,3-butadiene which contains more than 90% to less than 97% by mole of ethylene units. and which has a degree of crystallinity greater than 30% and less than 45%.

detailed description

Any interval of values denoted by the expression "between a and b" represents the range of values greater than "a" and less than "b" (i.e. limits "a" and "b" excluded) while that any interval of values denoted by the expression "from a to b" means the range of values going from "a" to "b" (i.e. including the strict limits "a" and "b ").

The compounds mentioned in the description can be of fossil origin or biosourced. In the latter case, they can be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. In the same way, the compounds mentioned can also come from the recycling of materials already used, that is to say they can be, partially or totally, from a recycling process, or obtained from materials raw materials themselves from a recycling process.

In the present invention, the molar rates (expressed in molar percentage) in one unit in the copolymer of ethylene and 1,3-butadiene useful for the purposes of the invention are calculated with respect to the total number of moles of ethylene units , butadiene and 1,2-cyclohexane which are present in the copolymer. The number of moles of 1,2-cyclohexane units in the copolymer can be equal to 0 or different from 0.

The copolymer entering into the lubricating composition in accordance with the invention has the characteristic of being a copolymer of ethylene and 1,3-butadiene, which implies that the monomer units of the copolymer are those resulting from the copolymerization of ethylene and 1,3-butadiene. The copolymer therefore contains ethylene units and butadiene units. In the copolymer useful for the purposes of the invention, the molar content in ethylene units is greater than 90% and less than 97%. In a known manner, an ethylene unit is a monomer unit with the unit -(CH2-CH2)-. Preferably, the molar rate of ethylene units in the copolymer is from 92% to 95%.

The copolymer contains butadiene units. In a known manner, a butadiene unit is a monomer unit with the -CH2-CH(CH=CH2)- or -CH2-CH=CH-CH2- unit depending on whether the 1,3-butadiene monomer is inserted into the polymer chain at the during the polymerization reaction by a 2,1 or 1,4 addition. Preferably, the copolymer contains units of formula -CH2-CH(CH=CH2)-, referred to as the 1,2 unit.

According to a preferred embodiment of the invention, the copolymer also contains 1,2-cyclohexane units. The presence of these 6-membered saturated hydrocarbon cyclic units in the copolymer results from a very specific insertion of ethylene and 1,3- butadiene during their copolymerization, as described for example in document WO 2007054224. A 1,2-cyclohexane unit corresponds to formula (I).

Preferably, the molar content of 1,2-cyclohexane units in the copolymer is greater than 1%, preferably greater than or equal to 2%. Preferably, the molar content of 1,2-cyclohexane units in the copolymer is less than 4%.

According to a preferred embodiment of the invention, the molar content of 1,2-cyclohexane units in the copolymer is greater than 1% and less than 4%.

According to a particularly preferred embodiment of the invention, the molar content of 1,2-cyclohexane units in the copolymer is greater than or equal to 2% and less than 4%.

Preferably, the molar content of butadiene units in the copolymer is greater than 1%, preferably greater than or equal to 2%. According to any one of the embodiments of the invention, the molar content of butadiene units in the copolymer is preferably less than 5%.

Preferably, more than 30% by mole of the butadiene units in the copolymer are 1,2 units of formula -CH2-CH(CH=CH2)-. When the copolymer contains 1,4 units of formula -CH2-CH=CH-CH2- , preferably more than 50%, more preferably more than 80% by mole of the 1,4e units are of trans configuration. According to any one of the embodiments of the invention, the copolymer preferably contains 1,2 units of formula -CH2-CH(CH=CH2)- and 1,4 units of formula -CH2-CH=CH- CH2-.

According to one embodiment of the invention, the copolymer in accordance with the invention is a random copolymer.

The copolymer useful for the purposes of the invention also has the characteristic of having a degree of crystallinity greater than 30% and less than 45%. Preferably, the degree of crystallinity of the copolymer is greater than 35%. Preferably, the degree of crystallinity of the copolymer is less than 43%.

Preferably, the copolymer has a number-average molar mass, Mn, greater than 8000 g/mol, preferentially greater than 10000 g/mol.

Preferably, the copolymer has a number-average molar mass of less than 200,000 g/mol, preferably less than or equal to 150,000 g/mol, plus preferably less than or equal to 130,000 g/mol, even more preferably less than or equal to 100,000 g/mol.

According to a particularly preferred embodiment of the invention, the copolymer in accordance with the invention has a number-average molar mass greater than 8000 g/mol and less than 130,000 g/mol.

According to a particularly more preferred embodiment of the invention, the copolymer has a number-average molar mass greater than 10,000 g/mol and less than 100,000 g/mol.

The copolymer preferably has a dispersity £), equal to Mw/Mn (Mw being the weight-average molar mass) greater than 1 and less than 5, preferably less than 4, more preferably less than 3. The values of Mn, Mw and £) are measured by size exclusion chromatography analysis with polystyrene calibration.

The copolymer preferably has a melting temperature greater than or equal to 97°C, more preferably a melting temperature greater than 97°C.

The copolymer in accordance with the invention can be prepared by copolymerization of ethylene and 1,3-diene in the presence of a catalytic system. The catalytic system comprises a metallocene of formula (II) and an organomagnesium P(Cp ¹ Cp ² )Nd(BH ₄ )(i _+y )-Ly-N _x (II)

Cp ¹ and Cp ² , identical or different, being chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C13H8,

P being a group bridging the two Cp ¹ and Cp ² groups and representing a ZR ¹ R ² group, Z representing a silicon or carbon atom, R ¹ and R ² , identical or different, each representing an alkyl group comprising 1 to 20 carbon atoms, preferably a methyl, y, whole number, being equal to or greater than 0, x, whole number or not, being equal to or greater than 0,

L representing an alkali metal chosen from the group consisting of lithium, sodium and potassium,

N representing a molecule of an ether, preferably diethyl ether or tetrahydrofuran.

In formula (II), the neodymium atom is linked to a molecule of ligand consisting of the two groups Cp ¹ and Cp ² linked together by the bridge P. Preferably, the symbol P, designated by the term bridge, has the formula ZR ¹ R ² , Z representing a silicon atom, R ¹ and R ² , which are identical or different, representing an alkyl group comprising from 1 to 20 carbon atoms. More preferably, the bridge P has the formula SiR ¹ R ² , R ¹ and R ² , being identical and as defined above. Even more preferably, P has the formula SiMe™. As substituted fluorenyl groups, mention may be made of those substituted by alkyl radicals having 1 to 6 carbon atoms or by aryl radicals having 6 to 12 carbon atoms. The choice of the radicals is also oriented by the accessibility to the corresponding molecules which are the substituted fluorenes, because the latter are commercially available or easily synthesized.

As substituted fluorenyl groups, mention may more particularly be made of the 2,7-ditertiobutyl-fluorenyl and 3,6-ditertiobutyl-fluorenyl groups. Positions 2, 3, 6 and 7 respectively designate the position of the carbon atoms of the cycles as shown in the diagram below, position 9 corresponding to the carbon atom to which the bridge P is attached.

Preferably, Cp ¹ and Cp ² are identical. Advantageously, in formula (II), Cp ¹ and Cp ² each represent the fluorenyl group. The fluorenyl group has the formula C13H8. Preferably, the metallocene is of formula (Ha), (IIb), (Ile), (I Id) or (Ile) in which the symbol Flu presents the fluorenyl group of formula C13H8.

[{Me ₂ SiFlu ₂ Nd(p-BH4)2Li(THF)}2] (Ha) [Me ₂ SiFlu2Nd(p-BH ₄ )2Li(THF)] (llb) [Me ₂ SiFlu ₂ Nd(p-BH ₄ )(THF)] (Ile) [{Me ₂ SiFlu2Nd(p-BH ₄ )(THF)} ₂ ] (Hd) [Me ₂ SiFlu ₂ Nd(p-BH ₄ )] (Ile)

The organomagnesium used in the catalytic system as cocatalyst is a compound which has at least one C—Mg bond. As organomagnesium compounds, mention may be made of diorganomagnesiums, in particular dialkylmagnesiums and organomagnesium halides, in particular alkylmagnesium halides. A diorganomagnesium is typically of formula MgR ³ R ⁴ in which R ³ and R ⁴ , identical or different, represent a carbon group. By carbon group is meant a group which contains one or more carbon atoms. Preferably, R ³ and R ⁴ contain 2 to 10 carbon atoms. More preferably, R ³ and R ⁴ each represent an alkyl.

The organomagnesium is advantageously a dialkylmagnesium, better still butylethylmagnesium or butyloctylmagnesium, even better still butyloctylmagnesium.

The catalytic system can be prepared conventionally by a process similar to that described in patent application WO 2007054224. For example, the organomagnesium and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20 to 80°C for a period of between 5 and 60 minutes. The catalytic system is generally prepared in a hydrocarbon solvent, aliphatic like methylcyclohexane or aromatic like toluene.

The metallocene used to prepare the catalytic system can be in the form of crystallized powder or not, or even in the form of monocrystals. The metallocene can be in a monomer or dimer form, these forms depending on the mode of preparation of the metallocene, as for example described in patent application WO 2007054224. The metallocene can be prepared in a traditional way by a process similar to that described in patent application WO 2007054224, in particular by reaction under inert and anhydrous conditions of the salt of an alkali metal of the ligand with a rare earth borohydride in a suitable solvent, such as an ether, such as diethyl ether or tetrahydrofuran or any another solvent known to those skilled in the art. After reaction, the metallocene is separated from the reaction by-products by techniques known to those skilled in the art, such as filtration or precipitation in a second solvent. The metallocene is finally dried and isolated in solid form.

A person skilled in the art adapts the molar ratio of the organomagnesium to the Nd metal constituting the metallocene according to the molar mass of the desired copolymer. The molar ratio can reach the value of 100, knowing that a molar ratio of less than 10 is more favorable for obtaining polymers of high molar masses.

Like any synthesis carried out in the presence of an organometallic compound, the synthesis of the metallocene and that of the catalytic system take place under anhydrous conditions under an inert atmosphere. Typically, the reactions are carried out from solvents and anhydrous compounds under anhydrous nitrogen or argon. In particular, the solvents are generally purified, for example in a known manner by distillation, by treatment on alumina columns, by bubbling of an inert gas such as nitrogen or argon or by treatment with an organometallic compound such as an organolithium, an organomagnesium or an organoaluminum.

The catalytic system is generally introduced into the reactor containing the polymerization solvent and the monomers.

The catalytic system can be prepared conventionally by a process similar to that described in patent application WO 2007054224. For example, the organomagnesium and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20 to 80° C. for a period of between 5 and 60 minutes. The catalytic system is generally prepared in a hydrocarbon solvent, aliphatic like methylcyclohexane or aromatic like toluene. Generally after its synthesis, the catalytic system is used as it is in the process for synthesizing the copolymer in accordance with the invention. Alternatively, the catalytic system can be prepared by a process similar to that described in patent application WO 2017093654 Al or in patent application WO 2018020122 Al. According to this alternative, the catalytic system also contains a preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, in which case the catalytic system is based at least on the metallocene, the organomagnesium and the preformation monomer. For example, the organomagnesium and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80° C. for 10 to 20 minutes to obtain a first reaction product, then with this first reaction product, reacted at a temperature ranging from 40 to 90° C. for 1 h to 12 h the preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene. The catalytic system thus obtained can be used immediately after its synthesis in the process for synthesizing the copolymer in accordance with the invention or be stored under an inert atmosphere, in particular at a temperature ranging from -20° C. to room temperature (23° C. C), before its use in the process for synthesizing the copolymer in accordance with the invention.

A person skilled in the art also adapts the polymerization conditions and the concentrations of each of the reagents (constituents of the catalytic system, monomers) according to the equipment (tools, reactors) used to carry out the polymerization and the various chemical reactions. As is known to those skilled in the art, the copolymerization as well as the handling of the monomers, of the catalytic system and of the polymerization solvent(s) take place under anhydrous conditions and under an inert atmosphere.

The polymerization is preferably carried out in solution, in a continuous, semi-continuous or discontinuous process. The polymerization solvent can be a hydrocarbon, aromatic or aliphatic solvent. By way of example of polymerization solvent, mention may be made of toluene and methylcyclohexane. The monomers can be introduced into the reactor containing the polymerization solvent and the catalytic system or conversely the catalytic system can be introduced into the reactor containing the polymerization solvent and the monomers. The monomers and the catalytic system can be introduced simultaneously into the reactor containing the polymerization solvent, in particular in the case of continuous polymerization. The polymerization is typically carried out under anhydrous conditions and in the absence of oxygen, in the optional presence of an inert gas. The polymerization temperature generally varies within a range ranging from 25 to 120°C, preferably 30 to 100°C.

During the polymerization of ethylene and 1,3-butadiene in a polymerization reactor, a continuous addition of ethylene and 1,3-butadiene can be carried out in the polymerization reactor, in which case the polymerization reactor is a powered reactor. This embodiment is particularly suitable for the synthesis of random copolymers. The polymerization can be stopped by cooling the polymerization medium or by adding an alcohol, preferably an alcohol containing 1 to 3 carbon atoms, for example ethanol. The copolymer can be recovered using conventional techniques known to those skilled in the art, for example by precipitation, by evaporation of the solvent under reduced pressure or by steam stripping.

The copolymer useful for the purposes of the invention which constitutes the lubricating composition can be a mixture of copolymers as defined previously which differ from each other by their degree of crystallinity, their microstructure, their macrostructure. The copolymer is typically added to a mineral base oil to form a lubricating composition according to the invention. Suitable mineral base oils include Group I base oils, Group II base oils and Group III base oils, and mixtures thereof. Groups I to III are defined in a known manner according to the "American Petroleum Institute" (API) in its publication "API N°1509 Engine Oil Licensing and Certification System, Appendix E, 14th Edition" of December 1996. Base oils Minerals are typically obtained by atmospheric and vacuum distillation of crude oil, possibly followed by refining operations.

The rate of the copolymer added to the mineral base oil is adjusted by those skilled in the art according to the nature of the mineral base oil, according to the characteristics of the copolymer such as its content of ethylene units, its degree of crystallinity, its in cyclohexane units, its number-average molar mass, and of course according to the use of the lubricating composition. The mass content of the copolymer in the lubricating composition or of the mixture of copolymers useful for the purposes of the invention in the lubricating composition can range up to 5% by weight of the lubricating composition, for example from 0.01 to 5% by weight of the lubricating composition, preferably from 0.05 to 2% by weight of the lubricating composition. Preferably, the mineral base oil is a Group I base oil.

The mixture formed by the base oil and the copolymer constitutes a lubricating composition which may also contain other additives traditionally used in a motor oil such as detergents and dispersants, antioxidants, compounds having an action against the formation rust, moss, frost.

The lubricating composition in accordance with the invention has properties of selective thickening as a function of temperature like motor oils containing traditionally used viscosity improvers such as copolymers of ethylene and propylene. The lubricating compositions according to the invention can prove to be even more efficient with regard to their temperature selectivity than the lubricating compositions containing copolymers of ethylene and propylene generally containing at most 50% by mole of ethylene units, typically used as base oil thickener additives. Indeed, a viscosity index at least as high, or even higher, is obtained by mixing a mineral base oil with a copolymer useful for the needs of the invention rather than with a copolymer of ethylene and propylene. This increase in performance is attributed both to the high molar content of ethylene unit in the copolymer useful for the purposes of the invention and to its degree of crystallinity.

Preferably, the lubricating composition in accordance with the invention is a motor oil.

In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 32:

Mode 1: Lubricating composition which comprises a mineral base oil and a copolymer of ethylene and 1,3-butadiene which contains more than 90% to less than 97% by mole of ethylene units and which has a higher degree of crystallinity 30% and less than 45%.

Mode 2: Lubricating composition according to mode 1 in which the degree of crystallinity of the copolymer of ethylene and 1,3-butadiene is greater than 35%.

Mode 3: Lubricating composition according to mode 1 or 2 in which the degree of crystallinity of the copolymer of ethylene and 1,3-butadiene is less than 43%.

Mode 4: Lubricating composition according to any one of modes 1 to 3 in which the copolymer of ethylene and 1,3-butadiene contains from 92% to 95% by mole of ethylene units.

Mode 5: Lubricating composition according to any one of modes 1 to 4 in which the copolymer of ethylene and 1,3-butadiene contains 1,2 units of formula -CH ₂ -CH(CH=CH ₂ )-.

Mode 6: Lubricating composition according to any one of modes 1 to 5 in which the copolymer of ethylene and 1,3-butadiene contains 1,2-cyclohexane units, cyclic units of formula (I).

CH - CH

/ \ (D

Mode 7: Lubricating composition according to mode 6 in which the copolymer of ethylene and 1,3-butadiene contains 1,2-cyclohexane units at a molar rate greater than 1%.

Mode 8: Lubricating composition according to mode 7 in which the copolymer of ethylene and 1,3-butadiene contains 1,2-cyclohexane units at a molar rate greater than or equal to 2%. Mode 9: Lubricating composition according to any one of modes 6 to 8 in which the molar content of 1,2-cyclohexane units in the copolymer is less than 4%.

Mode 10: Lubricating composition according to any one of modes 6 to 9 in which the molar rate of 1,2-cyclohexane units in the copolymer is greater than or equal to 2% and less than 4%

Mode 11: Lubricating composition according to any one of modes 1 to 10 in which the copolymer contains more than 1% by mole of butadiene units.

Mode 12: Lubricating composition according to any one of modes 1 to 11 in which the copolymer contains at least 2% by mole of butadiene units.

Mode 13: Lubricating composition according to any one of modes 1 to 12 in which the copolymer contains less than 5% by mole of butadiene units.

Mode 14: Lubricating composition according to any one of modes 1 to 13 in which more than 30% by mole of the butadiene units in the copolymer are 1,2 units of formula -CH ₂ -CH(CH=CH ₂ )-.

Mode 15: Lubricating composition according to any one of modes 1 to 14 in which the copolymer contains 1,4 units of formula -CH ₂ -CH=CH-CH ₂ - and more than 50% of 1,4 units of formula -CH ₂ -CH=CH-CH ₂ - are of trans configuration.

Mode 16: Lubricating composition according to any one of modes 1 to 15 in which the copolymer contains 1,4 units of formula -CH ₂ -CH=CH-CH ₂ - and more than 80% of 1,4 units of formula -CH ₂ -CH=CH-CH ₂ - are of trans configuration.

Mode 17: Lubricating composition according to any one of modes 1 to 16 in which the copolymer has a number-average molar mass greater than 8000 g/mol.

Mode 18: Lubricating composition according to any one of modes 1 to 17 in which the copolymer has a number-average molar mass greater than 10,000 g/mol.

Mode 19: Lubricating composition according to any one of modes 1 to 18 in which the copolymer has a number-average molar mass of less than 200,000 g/mol.

Mode 20: Lubricating composition according to any one of modes 1 to 19 in which the copolymer has a number-average molar mass of less than 150,000 g/mol.

Mode 21: Lubricating composition according to any one of modes 1 to 20 in which the copolymer has a number-average molar mass of less than 130,000 g/mol.

Mode 22: Lubricating composition according to any one of modes 1 to 21 in which the copolymer has a number-average molar mass of less than 100,000 g/mol. Mode 23: Lubricating composition according to any one of modes 1 to 22 in which the copolymer has a dispersity £) greater than 1 and less than 5.

Mode 24: Lubricating composition according to any one of modes 1 to 23 in which the dispersity of the copolymer is greater than 1 and less than 4.

Mode 25: Lubricating composition according to any one of modes 1 to 24 in which the dispersity of the copolymer is greater than 1 and less than 3.

Mode 26: Lubricating composition according to any one of Modes 1 to 25 in which the copolymer has a melting point greater than or equal to 97°C.

Mode 27: Lubricating composition according to any one of modes 1 to 26 in which the copolymer is a random copolymer.

Mode 28: A lubricating composition according to any of Modes 1 to 27 wherein the mineral base oil is a Group I oil, a Group II oil or a Group III oil.

Mode 29: A lubricating composition according to any one of Modes 1 to 28 wherein the mineral base oil is a Group I oil.

Mode 30: A lubricating composition according to any one of Modes 1 to 29 wherein the composition is motor oil.

Mode 31: Lubricating composition according to any one of modes 1 to 30 in which the mass content of the copolymer of ethylene and 1,3-butadiene varies within a range ranging from 0.01 to 5% by weight of the lubricating composition.

Mode 32: Lubricating composition according to any one of modes 1 to 31 in which the mass content of the copolymer of ethylene and 1,3-butadiene varies within a range ranging from 0.05 to 2% by weight of the lubricating composition.

The aforementioned characteristics of the present invention, as well as others, will be better understood on reading the following description of embodiments of the invention, given by way of non-limiting illustration.

Examples

Determination of the microstructure of polymers:

The high resolution NMR spectroscopy of the polymers was carried out on a Bruker 600 Avance III HD spectrometer operating at 600 MHz equipped with a CP2.1 BBO 600S3 probe for the proton. Acquisitions are made at 368 K. Orthodichlorobenzene (o-DCB) is used as solvent. The samples were analyzed at a concentration of approximately 1% by mass for proton NMR ( ¹ H NMR) analyses. The chemical shifts are determined relative to the proton signal of ortho-dichlorobenzene set at 7.2 ppm. A 2D analysis was performed using the following sequence: HSQC: Pulse program; hsqcetgpsi2 “HSQC with gradients”; SW1: 180 ppm ( ¹³ C) SW2: 12 ppm ( ¹ H); d1: 10 sec;

Pulse 90° “hard” ¹ H PI = 13 ps and 16 W and ¹³ C P2 = 26 ps and 84 W; gradient:

SMSQ10.100.

The determination of the microstructure of copolymers is defined in the literature, according to the article by Llauro et al., Macromolecules 2001, 34, 6304-6311.

Determination of the macrostructure of polymers:

Size Exclusion Chromatography is used. It is recalled that SEC makes it possible to separate the macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first. Without being an absolute method, the SEC makes it possible to apprehend the distribution of the molar masses of a polymer. From commercial standard products, the various number-average (Mn) and weight-average (Mw) molar masses can be determined and the dispersity (£) = Mw/Mn) calculated via a so-called MOORE calibration.

ere There is no particular treatment of the polymer sample before analysis. This is simply dissolved in 1,2,4-trichlorobenzene containing 300 ppm of BHT (“butylated hydroxytoluene” or butylated hydroxytoluene), at a concentration of approximately 1 g/l. The solution is stirred for 2 hours at 160° C. before injection, the chromatograph apparatus used is equipped with an in-line filtration system.

High temperature steric exclusion chromatography is used.

SEC-HT. The equipment used is a “GPC-IR” chromatograph equipped with an “IR-6” infrared detector from “Polymer Char”. The detection is carried out by the IR detector on the bands of vibrations of the groups CH? and CH3. A set of 3 commercial reference columns “Mixed BN-LS” from “Polymer Char” is used. The eluting solvent is 1,2,4-trichlorobenzene containing 300 ppm BHT. The flow rate is 1mL/min, the system temperature is 160°C and the analysis time is 90 minutes (min).

The injected volume of the polymer sample solution is 200 µl. The chromatographic data processing software is the “GPC-one” system from “Polymer Char”.

The average molar masses are determined from a calibration curve produced from “PSS READY CAL-KIT” commercial polystyrene standards.

Determination of the degree of crystallinity of polymers and their melting point:

The degree of crystallinity and the melting point are determined by differential scanning calorimetry (DSC). The analyzes are carried out on a “NETZSCH DSC 214 Polyma” DSC device calibrated with indium. This device has a temperature range of -150 to 700°C. A computer integrated into the DSC controls the device using Proteus software from Netzsch. The sample (about 10 mg) is weighed and sealed in a 40 pL aluminum crucible. The crucible is pierced with a fine needle just before the measurement. The samples are analyzed under helium at 40 mL/min using a dynamic method comprising 7 temperature levels:

Level 1: cooling from 25°C to -150°C at 50°C/min; Level 2: isothermal at -150°C for 5 min; Level 3: heating from -150°C to 200°C at 20°C/min; Level 4: isothermal at 200°C for 5 min; Level 5: cooling from 200°C to -150°C at 20°C/min; Level 6: isothermal at -150°C for 5 minutes; Level 7: heating from -150°C to 200°C at 20°C/min.

The first four stages make it possible to erase the thermal past of the sample. Measurements of the melting temperature (Tf) are made on the ^7th stage. The ^7th stage is also kept to obtain information on the crystallization of the sample and to determine the crystallinity rate.

The values of Tf are determined by applying the data reprocessing of the “Proteus” software from “Netzsch”. The degree of crystallinity is determined using the ISO 11357-3: 2011 standard for measuring the temperature and the enthalpy of melting and crystallization of the polymers used by differential scanning calorimetry (DSC). The reference enthalpy of polyethylene is 293 J/g (source: B. Wunderlich, Thermal analysis, Academie Press, 1990, 281).

Determination of the viscosity of lubricating compositions:

The viscosity index results are presented in base 100 relative to a control. The control consists of the same base oil that is used in the lubricating compositions. The viscosity index is measured according to the ASTM D2270 standard.

Preparation of ethylene and 1,3-butadiene copolymers:

The copolymers are prepared according to a semi-continuous process, that is to say a so-called “fed batch” process. In an 80 L reactor containing methylcyclohexane (60 L) and heated to 100°C, ethylene and 1,3-butadiene are introduced according to a mass ratio given in table 1 until a pressure of 6 bars is reached. in the reactor maintained at 100°C. A solution of butyloctylmagnesium (BOMAG) at 0.88 mol/L in methylcyclohexane is injected into the reactor, then the catalytic system (2.66 mmol equivalent of Nd, ie 1.7 g of catalytic system). The reaction temperature is regulated at a temperature of 100° C., the pressure in the reactor increases to 8 bars and the polymerization reaction starts. The polymerization reaction takes place at a constant pressure of 8 bar. The reactor is fed throughout the polymerization reaction with ethylene and 1,3-butadiene according to the given mass ratio of ethylene and 1,3-butadiene. The conditions for each of the syntheses of the polymers are shown in Table 1, in particular the mass ratio of ethylene and 1,3-butadiene and the amount of BOMAG solution.

The catalyst system is a preformed catalyst system. It is prepared in methylcyclohexane from a metallocene, [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] at 0.0065 mol/L, of a co-catalyst, butyloctylmagnesium (BOMAG) whose molar ratio BOMAG/Nd is equal to 2.2, and of a preformation monomer, 1,3-butadiene whose molar ratio 1,3- butadiene/Nd is equal to 90. The medium is heated to 80° C. over a period of 5 hours. It is prepared according to a preparation method in accordance with paragraph 11.1 of patent application WO 2017093654 Al.

All the reagents are obtained commercially except for the metallocene of formula [{MezSiFluzNdfp-BI-hLifTHF)}?] which can be prepared according to the procedure described in document WO 2007054224. BOMAG butyloctylmagnesium (20% by mass in heptane, C = 0.88 mol L ^-1 ) comes from Lanxess and is stored in a metal carboy under an inert atmosphere. Ethylene, of N35 quality, comes from Air Liquide and is used without prior purification. The 1,3-butadiene is purified on alumina guards. The methylcyclohexane solvent from BioSolve is dried and purified on an alumina column in a solvent fountain from mBraun and used in an inert atmosphere. All reactions are carried out in an inert atmosphere.

The conversion of the polymerization reaction is measured by dry extract, and when the mass of 6 kg of polymer is reached, the injection of the monomers into the reactor is stopped. 152 mL of 1 mol/L ethanol are injected to stop the polymerization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g/L are injected into the reactor. The contents of the reactor are transferred to another reactor called a "stripping reactor" to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered, then dried for 48 hours in an oven at 60° C. under vacuum and flushing with nitrogen.

The weighed mass of copolymer makes it possible to determine the average catalytic activity of the catalytic system expressed in kilogram of polymer synthesized per mole of neodymium metal and per hour (kg/mol.h).

The macrostructural characteristics of the polymers are shown in Table 1, those of the microstructure as well as the melting point and the degree of crystallinity in Table 2. The rate of units is expressed as a molar percentage calculated with respect to the total number of moles of ethylene, butadiene and 1,2-cyclohexane units.

Table 1

Table 2:

Preparation of lubricating compositions containing a base oil 100:

Six lubricating compositions are prepared according to the following procedure:

To a 250 mL steinie bottle containing 200 g of CORE™ 100 Group I mineral base oil is charged 1 g of polymer. The steinie bottle is capped and stirred in a bath thermostated at 90° C. for 12 hours. The viscosity of the resulting mixture is measured at 100°C. The polymers are the Poly 1, Poly 2, Poly 3, Poly 4 and Poly 5 polymers as well as an OCP polymer marketed by the company Lubrizol under the reference "7077", a copolymer of ethylene and propylene at approximately 50% molar d ethylene and a crystallinity rate of 2.3%.

Compositions C2 to C6 each contain a 100 base oil and a copolymer of ethylene and 1,3-butadiene. Composition C5 is not in accordance with the invention, since the copolymer has a degree of crystallinity of 46%. Compositions C2 to C4 and C6 are in accordance with the invention. Composition C1, which also contains base oil 100, is a reference composition, since it contains an OCP copolymer, a copolymer of ethylene and propylene “7077” from the company Lubrizol, an additive commonly used in motor oils. "CORE™ 100" base oil is a Group I mineral base oil marketed by the Exxon Company and is commonly used as a base oil in motor oils. Its viscosity index is 96.

The values of the viscosity indices are presented in table 3. Table 3

It is observed that the lubricating compositions in accordance with the invention have a viscosity index higher than that of the base oil 100 and are therefore effective as engine oil. Furthermore, it is noted that the viscosity indices of the compositions C3, C4 and C6 are higher than the viscosity index of the reference composition C1. Surprisingly, the lubricating compositions C3, C4 and C6 which contain a copolymer of ethylene and 1,3-butadiene whose degree of crystallinity is less than 43% even prove to perform better than the lubricating composition C1 containing an OCP copolymer.

Claims

1. A lubricating composition which comprises a mineral base oil and a copolymer of ethylene and 1,3-butadiene which contains more than 90% to less than 97% by mole of ethylene units and which has a degree of crystallinity greater than 30% and less than 45%.

2. Lubricating composition according to claim 1 wherein the degree of crystallinity of the copolymer of ethylene and 1,3-butadiene is greater than 35%.

3. Lubricating composition according to claim 1 or 2 wherein the degree of crystallinity of the copolymer of ethylene and 1,3-butadiene is less than 43%.

4. A lubricating composition according to any one of claims 1 to 3 wherein the copolymer of ethylene and 1,3-butadiene contains from 92% to 95% by mole of ethylene units.

5. Lubricating composition according to any one of claims 1 to 4 in which the copolymer of ethylene and 1,3-butadiene contains 1,2 units of formula -CH2-CH(CH=CH2)-

6. Lubricating composition according to any one of claims 1 to 5 wherein the copolymer of ethylene and 1,3-butadiene contains 1,2-cyclohexane units, cyclic units of formula (I), preferably at a rate molar greater than 1%, more preferably at a molar rate greater than or equal to 2%.

CH - CH

/ \ (D

7. Lubricating composition according to claim 6, in which the molar ratio of 1,2-cyclohexane units in the copolymer is less than 4%.

8. Lubricating composition according to any one of claims 1 to 7, in which the copolymer contains more than 1% by mole of butadiene units, preferably at least 2% by mole of butadiene units.

9. A lubricating composition according to any one of claims 1 to 8 wherein the copolymer contains less than 5 mol% of butadiene units.

10. Lubricating composition according to any one of claims 1 to 9, in which the copolymer has a number-average molar mass greater than 8000 g/mol, preferably greater than 10,000 g/mol.

11. Lubricating composition according to any one of claims 1 to 10, in which the copolymer has a number-average molar mass of less than 200,000 g/mol, preferably less than 150,000 g/mol, more preferably less than 130,000 g/mol. mol, even more preferably less than 100,000 g/mol.

12. A lubricating composition according to any one of claims 1 to 11 wherein the copolymer is a random copolymer.

13. A lubricating composition according to any one of claims 1 to 12 wherein the mineral base oil is a Group I oil, a Group II oil or a Group III oil.

14. A lubricating composition according to any one of claims 1 to 13, which composition is motor oil.

15. A lubricating composition according to any one of claims 1 to 14 wherein the mass content of the copolymer of ethylene and 1,3-butadiene varies within a range ranging from 0.01 to 5% by weight of the lubricating composition.