Functional copolymers of ethylene and 1, 3-butadiene and their use in engine lubricating compositions

Abstract

The invention relates to a copolymer of ethylene and 1, 3-butadiene, containing from more than 90 mol% to less than 97 mol% of ethylene units and bearing a single monomeric unit of methacrylate at one chain end thereof. Such copolymers are useful as thickeners in engine lubricating oil compositions.

Description

Technical Field

[0001] The field of the invention is copolymers of ethylene and 1,3-butadiene intended for use as additives in engine oils in order to improve the properties of the engine oils. Background Art

[0002] Engine oils are lubricating compositions containing mineral base oils used in engines to minimize energy losses caused by friction in the engine under low-temperature conditions and to maintain a continuous lubricating film on the engine's lubricated components under high-temperature conditions. It is important that the viscosity of the lubricating composition decreases as little as possible during operation under high-temperature conditions to avoid disrupting the lubricating film. To provide these two functions under both low and high-temperature conditions, it is desirable to have a lubricating composition with minimal viscosity change with temperature. Lubricating compositions with a high viscosity index are sought, as a high viscosity index ensures a smaller drop in viscosity as the temperature rises.

[0003] Mineral base oils are the main components of lubricating compositions (e.g., engine oils). The viscosity of mineral base oils decreases with increasing temperature and increases with decreasing temperature. Therefore, the viscosity of lubricating compositions primarily containing mineral base oils also changes with temperature.

[0004] In order to reduce the effect of temperature on the viscosity of lubricating compositions, it is known to add additives to mineral base oils. These additives, known as viscosity modifiers or viscosity index improvers, have the effect of selectively thickening the lubricating composition as the temperature rises, in order to partially compensate for the viscosity drop noted at high temperatures. They typically increase the high-temperature viscosity to offset the reduction in the viscosity of the mineral base oil without significantly increasing its viscosity at low temperatures. Viscosity index improvers are typically polymers. The two major classes of polymers sold as viscosity index improvers are polymers with ester functionality (e.g., poly(meth)acrylates), and hydrocarbon-based polymers (e.g., polyisobutylene, copolymers of ethylene and propylene) (also known as OCPs), hydrogenated copolymers of dienes and styrene, and hydrogenated polydienes. However, there is still a need to further improve the viscosity index of lubricating compositions (e.g., engine oils) containing mineral base oils.

[0005] Applicants have discovered novel functional copolymers of ethylene and 1,3-butadiene that, when used as additives in lubricating compositions containing a base oil, are capable of improving the viscosity index of the lubricating composition. Summary of the Invention

[0006] A first subject of the present invention is therefore a copolymer of ethylene and 1,3-butadiene containing from more than 90 mol% to less than 97 mol% of ethylene units and carrying a single monomer unit of methacrylate at one end of its chain.

[0007] A second subject of the present invention is a lubricating composition comprising a mineral base oil and the copolymer of ethylene and 1,3-butadiene according to the invention. DETAILED DESCRIPTION

[0008] Any numerical interval represented by the expression "between a and b" represents a numerical range greater than a and less than b (i.e., excluding the limits a and b), while any numerical interval represented by the expression "a to b" represents a numerical range from a to b (i.e., including the strict limits a and b).

[0009] The compounds mentioned in this specification may be of fossil origin or bio-based. In the latter case, they may be derived partly or completely from biomass, or from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of used materials, i.e., they may be derived partly or completely from a recycling process, or from the raw materials themselves generated by the recycling process.

[0010] In the present invention, the molar content (expressed as mole percentage) of a unit in the copolymer of ethylene and 1,3-butadiene according to the present invention is calculated based on the total number of moles of ethylene, butadiene, and 1,2-cyclohexane units present in the copolymer. The number of moles of 1,2-cyclohexane units in the copolymer may be equal to or different from 0.

[0011] The essential feature of the copolymer according to the present invention is that it is a copolymer of ethylene and 1,3-butadiene, meaning that the monomer units of the copolymer are those resulting from the copolymerization of ethylene and 1,3-butadiene. Therefore, the copolymer contains ethylene units and butadiene units. As is well known, ethylene units are monomer units with the structure -(CH2-CH2)-. As is well known, butadiene units are monomer units with the structure -CH2-CH(CH=CH2)-, known as 1,2 units, or with the structure -CH2-CH=CH-CH2-, known as 1,4 units, depending on whether the 1,3-butadiene monomer is incorporated into the polymer chain via 1,2-addition or 1,4-addition during polymerization.

[0012] In the copolymer according to the invention, the molar content of ethylene units is greater than 90% and less than 97%. Preferably, the molar content of ethylene units in the copolymer is from 92% to 95%. Preferably, the copolymer contains 1,2 units.

[0013] According to a preferred embodiment of the present invention, the copolymer also contains 1,2-cyclohexane units. The presence of these saturated 6-membered hydrocarbon rings in the copolymer is due to the very specific insertion of ethylene and 1,3-butadiene during their copolymerization, as described in document WO 2007054224. The 1,2-cyclohexane units correspond to formula (I)

[0014]

[0015] 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%.

[0016] According to a preferred embodiment of the present invention, the molar content of 1,2-cyclohexane units in the copolymer is greater than 1% and less than 4%.

[0017] According to a particularly preferred embodiment of the present invention, the molar content of 1,2-cyclohexane units in the copolymer is greater than or equal to 2% and less than 4%.

[0018] Preferably, the molar content of butadiene units in the copolymer is greater than 1%, preferably greater than or equal to 2%.According to any embodiment of the present invention, the molar content of butadiene units in the copolymer is preferably less than 5%.

[0019] Preferably, more than 30 mol% of the butadiene units in the copolymer are 1,2 units. When the copolymer contains 1,4-units, preferably more than 50 mol%, more preferably more than 80 mol% of the 1,4-units are in the trans configuration. According to any embodiment of the present invention, the copolymer preferably contains 1,2-units and 1,4-units.

[0020] The copolymer according to the present invention is a functional copolymer because it also has a fundamental characteristic of having a functional group at one of its chain ends. The functional group is composed of a methacrylate monomer unit. Typically, the methylene group (CH2) of the -CH2-CHMe-COO- unit of the methacrylate monomer unit forms a covalent bond with a carbon atom of the ethylene / 1,3-butadiene copolymer chain.

[0021] Preferably, the methacrylate is an alkyl methacrylate, in which case the functional group is of the formula -CH2-CHME-COOR, with R being an alkyl group. As alkyl methacrylates, mention may be made in particular of alkyl methacrylates in which the alkyl group contains from 1 to 20 carbon atoms, more particularly of alkyl methacrylates in which the alkyl group contains from 1 to 8 carbon atoms. The alkyl methacrylate is advantageously methyl methacrylate.

[0022] Preferably, the copolymers according to the invention are statistical copolymers.

[0023] It is also preferred that the copolymer according to the present invention has a crystallinity greater than 30% and less than 45%. More preferably, the crystallinity of the copolymer is greater than 35%. Even more preferably, the crystallinity of the copolymer is less than 43%.

[0024] Preferably, the number average molar mass (Mn) of the copolymer is greater than 8000 g / mol, preferably greater than 10000 g / mol.

[0025] Preferably, the number average molar mass of the copolymer is less than 200,000 g / mol, preferably less than 150,000 g / mol, more preferably less than 130,000 g / mol, even more preferably less than 100,000 g / mol.

[0026] According to a particularly preferred embodiment of the present invention, the copolymer according to the invention has a number-average molar mass of more than 8,000 g / mol and less than 130,000 g / mol.

[0027] According to an especially more preferred embodiment of the present invention, the number-average molar mass of the copolymer is greater than 10,000 g / mol and less than 100,000 g / mol.

[0028] Dispersion coefficient of copolymer (equal to Mw / Mn (Mw is the weight average molar mass)) is preferably greater than 1 and less than 5, preferably less than 4, more preferably less than 3. Mn, Mw and The values ​​of were measured by size exclusion chromatography calibrated with polystyrene.

[0029] The melting temperature of the copolymer is preferably greater than or equal to 97°C, more preferably a melting temperature greater than 97°C.

[0030] The copolymers according to the present invention can be prepared by copolymerizing ethylene and 1,3-diene in the presence of a catalyst system, followed by functionalization of the copolymer chain ends. The catalyst system comprises a metallocene of formula (II) and an organomagnesium compound.

[0031] P(Cp 1 Cp 2 )Nd(BH4) (1+y) -L y -N x (II)

[0032] Cp 1 and Cp 2 , the same or different, selected from formula C 13 The substituted fluorenyl and unsubstituted fluorenyl of H8,

[0033] P is a bridge between two Cp 1 and Cp 2 Group and represents ZR 1 R 2 The group of the group, Z represents silicon or carbon atom, R 1 and R 2 are the same or different, each representing an alkyl group containing 1 to 20 carbon atoms, preferably a methyl group,

[0034] y is an integer greater than or equal to 0,

[0035] x is an integer or non-integer greater than or equal to 0,

[0036] L represents an alkali metal selected from lithium, sodium and potassium,

[0037] N represents an ether molecule, preferably diethyl ether or tetrahydrofuran.

[0038] In formula (II), the neodymium atom is connected to two groups Cp linked together by a bridge P 1 and Cp 2 Preferably, the symbol P represented by the term bridge corresponds to the formula ZR 1 R 2 , Z represents silicon atom, R 1 and R 2 are the same or different and represent an alkyl group containing 1 to 20 carbon atoms. More preferably, the bridge P has the formula SiR 1 R 2 , R 1 and R 2 Same as and as previously defined. Even more preferably, P corresponds to the formula SiMe2.

[0039] As substituted fluorenyl groups, those substituted with an alkyl group having 1 to 6 carbon atoms or with an aryl group having 6 to 12 carbon atoms may be mentioned. The choice of group also depends on the availability of the corresponding molecule (i.e., substituted fluorene), since substituted fluorenes are commercially available or easily synthesized.

[0040] As substituted fluorenyl groups, 2,7-di(tert-butyl)fluorenyl and 3,6-di(tert-butyl)fluorenyl may be mentioned more particularly. Positions 2, 3, 6 and 7 represent the positions of the carbon atoms of the ring as shown in the figure below, and position 9 corresponds to the carbon atom to which the bridge P is attached.

[0041]

[0042] Optimized Cp 1 and CP 2 Advantageously, in formula (II), Cp 1 and Cp 2 Each represents a fluorenyl group. The fluorenyl group has the formula C 13 H8. Preferably, the metallocene has the formula (IIa), (IIb), (IIc), (IId) or (IIe), wherein the symbol Flu represents a metallocene of formula C 13 The fluorenyl group of H8.

[0043] [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2] (IIa)

[0044] [Me2SiFlu2Nd(μ-BH4)2Li(THF)] (IIb)

[0045] [Me2SiFlu2Nd(μ-BH4)(THF)] (IIc)

[0046] [{Me2SiFlu2Nd(μ-BH4)(THF)}2] (IId)

[0047] [Me2SiFlu2Nd(μ-BH4)] (IIe)

[0048] The organomagnesium compound used as a cocatalyst in the catalytic system is a compound having at least one C-Mg bond. As organomagnesium compounds, mention may be made of diorganomagnesium compounds, in particular dialkylmagnesium compounds, and organomagnesium halides, in particular alkylmagnesium halides. The diorganomagnesium compound generally has the formula MgR 3 R 4 , where the same or different R 3 and R 4 The term "carbonyl group" is understood to mean a group containing one or more carbon atoms. 3 and R 4 Contains 2 to 10 carbon atoms. More preferably, R 3 and R 4 The organomagnesium reagent is advantageously a dialkylmagnesium compound, more preferably butylethylmagnesium or butyloctylmagnesium, even more preferably butyloctylmagnesium.

[0049] The catalytic system can be conventionally prepared by methods similar to those described in patent application WO 2007054224. For example, the organomagnesium reagent and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20° C. to 80° C., for a time period between 5 and 60 minutes. The catalytic system is typically prepared in an aliphatic hydrocarbon solvent (e.g., methylcyclohexane) or an aromatic hydrocarbon solvent (e.g., toluene).

[0050] The metallocene that is used to prepare the catalyst system can be the form of crystallization or non-crystalline powder, or the form of single crystal.Metallocene can be monomer or dimer form, and these forms depend on the method for preparing metallocene, for example described in patent application WO2007054224.Metallocene can be by the conventional preparation of the method described in patent application WO 2007054224 that is similar to, particularly by under inertness and anhydrous condition, in suitable solvent such as ether, for example ether or tetrahydrofuran (THF), or any other solvent well known to persons skilled in the art, make alkali metal salt of part and rare earth metal borohydride reaction.After the reaction, by technology well known to persons skilled in the art (for example filtering or precipitating from the second solvent), metallocene is separated from byproduct of reaction.Finally dry and isolate the metallocene of solid form.

[0051] Those skilled in the art adjust the molar ratio of the organomagnesium compound to the Nd metal constituting the metallocene according to the desired molar mass of the copolymer. The molar ratio can reach a value of 100, and a molar ratio of less than 10 is known to be more conducive to obtaining a polymer with a high molar mass.

[0052] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of the metallocene and the catalyst system is carried out under anhydrous conditions and an inert atmosphere. Typically, the reaction starts with an anhydrous solvent and compound and is carried out under anhydrous nitrogen or argon atmosphere. In particular, the solvent is usually purified in a known manner, for example by distillation, treatment on an alumina column, bubbling with an inert gas such as nitrogen or argon, or treatment with an organometallic compound such as an organolithium compound, an organomagnesium compound, or an organoaluminum compound.

[0053] The catalytic system is typically introduced into a reactor containing the polymerization solvent and monomers.

[0054] The catalyst system can be conventionally prepared by methods similar to those described in patent application WO 2007054224. For example, an organomagnesium reagent and a metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20° C. to 80° C., for a time period between 5 and 60 minutes. The catalyst system is typically prepared in an aliphatic hydrocarbon solvent (e.g., methylcyclohexane) or an aromatic hydrocarbon solvent (e.g., toluene). Typically, after its synthesis, the catalyst system is used as is in the method for synthesizing the copolymers of the present invention.

[0055] Alternatively, the catalytic system can be prepared by a method similar to that described in patent application WO 2017093654 A1 or patent application WO2018020122 A1. According to this alternative, the catalytic system further comprises a preformed monomer selected 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 a metallocene, an organomagnesium reagent, and a preformed monomer. For example, the organomagnesium reagent and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20°C to 80°C for 10 to 20 minutes to obtain a first reaction product, and then a preformed monomer selected from a mixture of conjugated diene, ethylene, or ethylene and a conjugated diene is reacted with the first reaction product at a temperature of 40°C to 90°C for 1 to 12 hours. The catalytic system thus obtained can be used in the method for synthesizing the copolymer according to the present invention immediately after its synthesis, or can be stored under an inert atmosphere, particularly at a temperature within the range of -20°C to ambient temperature (23°C), before being used in the method for synthesizing the copolymer according to the present invention.

[0056] Those skilled in the art also adjust the polymerization conditions and the concentration of each reactant (components of the catalyst system, monomers) according to the equipment (device, reactor) used to carry out the polymerization and various chemical reactions. As known to those skilled in the art, the copolymerization and processing of monomers, catalyst systems and polymerization solvents are carried out under anhydrous conditions and an inert atmosphere.

[0057] The polymerization reaction is preferably carried out in a solution in a continuous, semi-continuous or batch manner. The polymerization solvent can be an aromatic or aliphatic hydrocarbon solvent. Examples of polymerization solvents that may be mentioned include toluene and methylcyclohexane. The monomers can be introduced into a reactor containing the polymerization solvent and the catalyst system, or conversely, the catalyst system can be introduced into a reactor containing the polymerization solvent and the monomers. The monomers and the catalyst system can be introduced simultaneously into the reactor containing the polymerization solvent, especially in the case of continuous polymerization. The polymerization is usually carried out under anhydrous and oxygen-free conditions, and an inert gas can be optionally added. The polymerization temperature usually varies in the range of 25°C to 120°C, preferably 30°C to 100°C. The skilled person in the art adjusts the polymerization conditions, such as the polymerization temperature, the concentration of each reactant or the pressure in the polymerization reactor, according to the composition of the monomer mixture, the polymerization reactor and the desired microstructure and macrostructure of the copolymer chain.

[0058] The polymerization is preferably carried out under a constant pressure of the monomers. Each monomer or one of the monomers can be added continuously to the polymerization reactor, in which case the polymerization reactor is a feed reactor. This embodiment is particularly suitable for the synthesis of statistical copolymers.

[0059] When the desired monomer conversion is achieved, the copolymer chain end functionalization reaction is carried out. The functionalization reaction comprises combining a functionalizing agent (methacrylate) with the polymerization product, preferably with stirring, to introduce a single methacrylate monomer unit at one end of the copolymer chain without any subsequent polymerization of the methacrylate.

[0060] Prior to adding the methacrylate, the reactor is preferably degassed and inerted. Degassing the reactor allows for the removal of gaseous residual monomers and also facilitates the addition of the methacrylate to the reactor. Inerting the reactor, for example with nitrogen, prevents deactivation of carbon-metal bonds present in the reaction medium, which are essential for the functionalization of the copolymer. The methacrylate can be added neat or diluted in a hydrocarbon solvent, preferably an aliphatic hydrocarbon solvent such as methylcyclohexane. The methacrylate is contacted with the reaction product from step a) for a time sufficient to functionalize the copolymer chain ends. The functionalization reaction can typically be monitored by chromatographic analysis to monitor methacrylate consumption. The functionalization reaction is preferably conducted at a temperature range of 23-120°C with stirring for 1 to 60 minutes. The functionalization reaction is preferably conducted with an excess of methacrylate relative to the molar amounts of neodymium and magnesium. To achieve nearly quantitative functionalization, the molar ratio of methacrylate to neodymium and magnesium is preferably greater than 2, particularly greater than 5, and more particularly between 10 and 50.

[0061] Once the chain ends have been modified, the reactive sites still present in the reaction medium are deactivated. The chain terminator is usually brought into contact with the reaction product from step b), which is usually in its reaction medium, for example by adding the terminator to the reaction medium at the end of the functionalization reaction, or vice versa. The terminator is usually in stoichiometric excess relative to the molar amounts of neodymium and magnesium. The terminator is usually a protic compound, i.e. a compound containing relatively acidic protons. As terminators, water, carboxylic acids, in particular C2-C 18 Fatty acids (such as acetic acid or stearic acid), aliphatic or aromatic alcohols (such as methanol, ethanol or isopropanol), or phenolic antioxidants.

[0062] The functional copolymer can be recovered according to 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.

[0063] The functional copolymers are advantageously used as additives to lubricating compositions.

[0064] Functional copolymers are usually added to mineral base oils to form lubricating compositions, which is another theme of the present invention. As suitable mineral base oils, Class I base oils, Class II base oils and Class III base oils, and mixtures thereof, can be mentioned. As is well known, Class I to Class III are defined according to the American Petroleum Institute (API) in its "API N ° 1509 Engine Oil Licensing and Certification System, Appendix E, 14th Edition" published in December 1996. Mineral base oils are usually obtained by atmospheric and vacuum distillation of crude oil, and optionally refining operations can be carried out subsequently. Preferably, the mineral base oil is a Class I base oil.

[0065] The amount of functional copolymer added to the mineral base oil is adjusted by a person skilled in the art according to the nature of the mineral base oil, according to the characteristics of the functional copolymer, such as its ethylene unit content, its crystallinity, its 1,2-cyclohexane unit content or its number-average molar mass, and, of course, according to the intended use of the lubricating composition. The weight content of the functional copolymer or the mixture of functional copolymers in the lubricating composition may be 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. The functional copolymer as a component of the lubricating composition may be a mixture of copolymers as defined above, said copolymers differing from one another in their crystallinity, microstructure, and macrostructure.

[0066] The lubricating composition may also contain other additives usually used in engine oils, such as detergents and dispersants, antioxidants, compounds having an anti-rust, foam, ice formation effect.

[0067] Like engine oils containing conventionally used viscosity modifiers (e.g., copolymers of ethylene and propylene), the lubricating compositions according to the present invention exhibit temperature-dependent selective thickening properties. Compared to lubricating compositions containing ethylene and propylene copolymers, which are commonly used as base oil thickening additives and typically contain up to 50 mol% ethylene units, the lubricating compositions according to the present invention can prove more effective in terms of temperature selectivity. The lubricating compositions are also more effective than those containing polymethacrylates. Indeed, by blending mineral base oils with the functional copolymers according to the present invention, rather than with copolymers of ethylene and propylene or polymethacrylates, viscosity indices at least as high or even higher can be achieved.

[0068] Preferably, the lubricating composition according to the invention is an engine oil.

[0069] In summary, the present invention is advantageously implemented according to any one of the following embodiments 1 to 21:

[0070] 1. A copolymer of ethylene and 1,3-butadiene containing from more than 90 mol% to less than 97 mol% of ethylene units and having a single monomer unit of methacrylate at one end of its chain.

[0071] 2. The copolymer according to embodiment 1, wherein the molar content of ethylene units in the copolymer is from 92% to 95%.

[0072] 3. The copolymer according to embodiment 1 or 2, wherein the methacrylate is an alkyl methacrylate.

[0073] 4. The copolymer of any one of embodiments 1 to 3, wherein the methacrylate is methyl methacrylate.

[0074] 5. The copolymer of any one of embodiments 1 to 4, having a crystallinity greater than 30% and less than 45%.

[0075] 6. The copolymer of any one of embodiments 1 to 5, having a crystallinity greater than 35%.

[0076] 7. The copolymer according to any one of embodiments 1 to 6, which is a statistical copolymer.

[0077] 8. The copolymer according to any one of embodiments 1 to 7, which contains 1,2-cyclohexane units, ie, cyclic units of formula (I)

[0078]

[0079] 9. The copolymer according to any one of embodiments 1 to 8, wherein the molar content of 1,2-cyclohexane units is greater than 1%, preferably greater than or equal to 2%.

[0080] 10. The copolymer according to any one of embodiments 1 to 9, wherein the molar content of 1,2-cyclohexane units is less than 4%.

[0081] 11. The copolymer according to any one of embodiments 1 to 10, wherein the molar content of butadiene units is greater than 1%, preferably greater than or equal to 2%.

[0082] 12. The copolymer according to any one of embodiments 1 to 11, wherein the molar content of butadiene units is less than 5%.

[0083] 13. The copolymer according to any one of embodiments 1 to 12, having a number average molar mass of greater than 8000 g / mol, preferably greater than 10000 g / mol.

[0084] 14. The copolymer according to any one of embodiments 1 to 13, having 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, even more preferably less than 100,000 g / mol.

[0085] 15. The copolymer according to any one of embodiments 1 to 14, having a number average molar mass of greater than 8,000 g / mol and less than 130,000 g / mol.

[0086] 16. The copolymer according to any one of embodiments 1 to 15, having a number average molar mass of greater than 10,000 g / mol and less than 100,000 g / mol.

[0087] 17. The copolymer of any one of embodiments 1 to 16, having a melting temperature greater than or equal to 97°C.

[0088] 18. A lubricating composition comprising a mineral base oil and the copolymer of ethylene and 1,3-butadiene according to any one of embodiments 1 to 17.

[0089] 19. The lubricating composition of embodiment 18, wherein the mineral base oil is a Group I oil, a Group II oil, or a Group III oil.

[0090] 20. The lubricating composition of embodiment 18 or 19, which is an engine oil.

[0091] 21. The lubricating composition according to any one of embodiments 18 to 20, wherein the weight content of the copolymer of ethylene and 1,3-butadiene varies in the range of 0.01 wt% to 5 wt% of the lubricating composition.

[0092] A better understanding of the above-mentioned and other characteristics of the present invention will be obtained on reading the following description of embodiments of the invention, which are given by way of illustration and not by way of limitation.

[0093] Example

[0094] Determination of polymer microstructure:

[0095] High-resolution NMR spectra of the polymers were performed on a Bruker 600 Avance III HD spectrometer equipped with a CP2.1 BBO 600S3 probe for protons, operating at 600 MHz. Acquisition was performed at 368 K. o-Dichlorobenzene (o-DCB) was used as solvent. In the proton NMR ( 1 In the H NMR analysis, samples were analyzed at a concentration of approximately 1 wt%. Chemical shifts were determined relative to the proton signal of o-dichlorobenzene, which was set at 7.2 ppm. 2D analysis was performed using the following sequence: HSQC: pulse program; hsqcetgpsi2 "HSQC with gradient"; SW1: 180 ppm ( 13 C); SW2: 12ppm( 1 H); d1: 10s; 90° "hard" pulse 1 HP1=13μs and 16W, 13 C P2 = 26 μs and 84 W; gradient: SMSQ10.100.

[0096] The determination of copolymer microstructure is defined in the literature according to Llauro et al., Macromolecules, 2001, 34, 6304-6311.

[0097] Determination of polymer macrostructure:

[0098] Size exclusion chromatography is used. It should be recalled that SEC allows the separation of macromolecules in solution according to their size by passing them through a column filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest macromolecules eluting first. SEC is not an absolute method, but it allows us to understand the molar mass distribution of polymers. Various number-average molar masses (Mn) and weight-average molar masses (Mw) can be determined according to commercial standards, and the dispersion coefficient ( ) can be calculated using a "mole" calibration.

[0099] Preparation of polymer: The polymer samples were not specifically treated prior to analysis. They were simply dissolved in 1,2,4-trichlorobenzene containing 300 ppm BHT (2,6-di-tert-butyl-p-cresol), at a concentration of approximately 1 g / l. The solution was stirred at 160°C for 2 hours before injection. The chromatography apparatus used was equipped with an in-line filtration system.

[0100] SEC analysis: High temperature size exclusion chromatography or HT-SEC was used. The apparatus used was a GPC-IR spectrometer from Polymer Char equipped with an IR-6 infrared detector. The vibration bands of CH2 and CH3 groups were detected by the IR detector. A set of three "Mixed BN-LS" commercial reference columns from Polymer Char was used. The elution solvent was 1,2,4-trichlorobenzene containing 300 ppm of BHT. The flow rate was 1 ml / min, the system temperature was 160°C, and the analysis time was 90 minutes (min).

[0101] The volume of the polymer sample solution injected was 200 μl. The software that utilized the chromatographic data was the GPC-one system from PolymerChar.

[0102] The average molar mass was determined from a calibration curve generated using the PSS Ready Cal-Kit commercial polystyrene standards.

[0103] Determination of glass transition temperature, crystallinity and melting point of polymers:

[0104] The crystallinity and melting point were determined by differential scanning calorimetry (DSC). The analysis was performed on a Netzsch DSC214 Polyma DSC device calibrated with indium. The temperature range of the device extends from -150°C to 700°C. A computer integrated with the DSC controls the device using Netzsch's Proteus software. The sample (approximately 10 mg) was weighed and sealed in a 40 μl aluminum crucible. Prior to the measurement, the crucible was pierced with a fine needle. The sample was analyzed at 40 ml / min under helium according to a dynamic method comprising 7 temperature steps:

[0105] Step 1: Cool from 25°C to -150°C at 50°C / min; Step 2: Isothermal at -150°C for 5 min; Step 3: Heat from -150°C to 200°C at 20°C / min; Step 4: Isothermal at 200°C for 5 min; Step 5: Cool from 200°C to -150°C at 20°C / min; Step 6: Isothermal at -150°C for 5 min; Step 7: Heat from -150°C to 200°C at 20°C / min.

[0106] The first four steps erase the thermal history of the sample. The glass transition temperature (Tg) and melting temperature (Tm) are measured in step 7. Step 7 is also retained to obtain information about the crystallization of the sample and determine the degree of crystallinity.

[0107] The Tg and Tm values ​​are determined by data reprocessing using Proteus software from Netzsch. The Tg value is measured using the tangent method as described in standard ASTM-3418 and corresponds to the well-known midpoint. The melting temperature (Tm) corresponds to the tip of the melting peak. Crystallinity is determined by measuring the temperature and enthalpy of melting and crystallization of the polymer used by differential scanning calorimetry (DSC) using standard ISO 11357-3:2011. The reference enthalpy of polyethylene is 293 J / g (source: B. Wunderlich, Thermal Analysis, Academic Press, 1990, 281).

[0108] Determination of viscosity of lubricating composition:

[0109] The viscosity index results are expressed relative to a control with a base value of 100. Unless otherwise stated, the control consisted of the same base oil used in the lubricating composition. The viscosity index is measured according to standard ASTM D2270.

[0110] Preparation of copolymers of ethylene and 1,3-butadiene (Poly 1 and Poly 2)

[0111] The copolymers were prepared using a semi-continuous, or "fed-batch," process. Ethylene and 1,3-butadiene were introduced into an 80-liter reactor containing 60 liters of methylcyclohexane and heated to 100°C according to the weight ratios given in Table 1 until a pressure of 6 bar was reached in the reactor, which was maintained at 100°C. A 0.88 mol / l solution of butyloctyl magnesium (BOMAG) in methylcyclohexane was injected into the reactor, followed by the catalyst system (2.66 mmol equivalent of Nd, i.e., 1.7 g of catalyst system). The reaction temperature was adjusted to 100°C, the pressure in the reactor was increased to 8 bar, and the polymerization reaction began. The polymerization reaction was carried out at a constant pressure of 8 bar. Ethylene and 1,3-butadiene were fed into the reactor according to the given weight ratios throughout the polymerization reaction. The synthesis conditions for each polymer are shown in Table 1, specifically the weight ratios of ethylene and 1,3-butadiene and the amount of BOMAG solution.

[0112] The catalyst system is a preformed catalyst. It is prepared in methylcyclohexane from 0.0065 mol / l of the metallocene [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)], the cocatalyst butyloctyl magnesium (BOMAG) (BOMAG / Nd molar ratio equal to 2.2), and the preformed monomer 1,3-butadiene (1,3-butadiene / Nd molar ratio equal to 90). The medium is heated at 80°C for 5 hours. It was prepared according to the preparation method described in Section II.1 of patent application WO 2017093654 A1.

[0113] All reactants are commercially available except for the metallocene of formula [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2] which can be prepared according to the method described in document WO 2007054224. Butyloctylmagnesium BOMAG (20 wt% in heptane, C=0.88 mol.l -1 ) was sourced from Lanxess and stored in metal cylinders under an inert atmosphere. N35 grade ethylene was obtained from AirLiquide and used without prior purification. 1,3-Butadiene was purified over an alumina blanket. Methylcyclohexane solvent from BioSolve was dried and purified over an alumina column in an mBraun solvent purifier and used under an inert atmosphere. All reactions were performed under an inert atmosphere.

[0114] The conversion of the polymerization reaction was measured by solid content and when the weight of the polymer reached 6 kg, the injection of monomer into the reactor was stopped. The steps were then carried out according to step 1 or according to step 2.

[0115] Step 1: To synthesize the non-functional polymer Poly2, the polymerization reaction was terminated by injecting 122 ml of a 1 mol / l ethanol solution in methylcyclohexane. 226 ml of Irganox 1520L (an antioxidant) at a concentration of 218 g / l in methylcyclohexane was injected into the reactor. The contents of the reactor were transferred to another reactor, designated the "stripping reactor," where the solvent was removed by steam distillation while maintaining a temperature of 100°C. The copolymer was recovered and then dried in a 60°C oven under vacuum and a nitrogen flush for 48 hours.

[0116] Step 2: To synthesize the functional polymer Poly 1, 677.1 ml of methyl methacrylate was injected. The copolymer was contacted with methyl methacrylate at 80°C for 15 minutes. After 15 minutes, 216 ml of a 1 mol / l ethanol solution in methylcyclohexane was injected. 220 ml of Irganox 1520L (antioxidant) was injected into the reactor at a concentration of 218 g / l in methylcyclohexane. The contents of the reactor were transferred to another reactor, designated the "stripping reactor," where the solvent was removed by steam distillation while maintaining a temperature of 100°C. The copolymer was recovered and then dried in a 60°C oven under vacuum and nitrogen flushing for 48 hours.

[0117] The weighed mass of the copolymer makes it possible to determine the average catalytic activity of the catalytic system, expressed as kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h).

[0118] The macrostructural characteristics of the polymers are shown in Table 1, and the microstructural characteristics, as well as the melting temperature and crystallinity, are shown in Table 2. The unit content is expressed as a mole percentage, calculated relative to the total number of moles of ethylene units, butadiene units, and 1,2-cyclohexane units (denoted as "rings" in Table 2). The two copolymers, Poly1 and Poly2, are statistical copolymers: they have a single Tg measured at -53°C.

[0119] Table 1

[0120]

[0121] Table 2

[0122]

[0123] Preparation of lubricating composition:

[0124] The lubricating composition is prepared according to the following steps:

[0125] 0.5 g or 1.5 g of polymer were introduced into a 250 ml steinie bottle containing 200 g of base oil to prepare a composition containing 0.25% or 0.75% polymer, respectively. The steinie bottle was capped and stirred in a thermostatically controlled bath at 90° C. for 12 hours. The viscosity of the resulting mixture was measured at 100° C. The polymers were polymers Poly1 and Poly2 and an OCP polymer sold by Lubrizol under product number 7077, a copolymer of ethylene and propylene containing about 50 mol% ethylene (having a crystallinity of 2.3% and an Mn of 79,200 g / mol), and a polymethacrylate sold by Lubrizol under product number 7775 (Mn of 16,700 g / mol). In some compositions, a mixture of additives for gearbox oils sold by Lubrizol under the name Anglamol 6043 was also added.

[0126] The formulations of the lubricating compositions are shown in Tables 3, 4 and 5, and the contents are expressed as weight percentages relative to the amount of the lubricating compositions.

[0127] Base oil Core TM Exxon 100 is a Group I mineral base oil sold by Exxon, commonly used as a base oil in engine oils. Its viscosity index is 96.

[0128] Base oil Core TM 600 is a Group I mineral base oil sold by Exxon, commonly used as a base oil in engine oils. Its viscosity index is 96.

[0129] Base oil Core TM 50 is a Group II mineral base oil sold by Exxon and is commonly used as a base oil in engine oils.

[0130] Compositions C2, C3, and C8 to C10 all contain a functional copolymer according to the present invention and a mineral base oil and are lubricating compositions according to the present invention. Compositions T1, T2, and T3 are their respective control compositions. Compositions C1 and C5 to C7, which contain a mineral base oil and a commercial viscosity modifier not according to the present invention, are reference lubricating compositions.

[0131] Composition C4 is a lubricating composition not according to the invention since the viscosity modifier is a non-functional copolymer of ethylene and 1,3-butadiene.

[0132] The viscosity index values ​​of the lubricating compositions are shown in Tables 3 to 5.

[0133] Table 3

[0134]

[0135] Table 4

[0136]

[0137] Table 5

[0138] Lubricating composition T3 C9 C10 base oil 50 50 50 polymer - 0.25% Poly1 0.75% Poly1 Anglamol 6043 15％ 15％ 15％ Viscosity Index 100 125 125

[0139] It is observed that the viscosity index of the lubricating composition according to the present invention is greater than that of its corresponding control composition. It should also be noted that the functional copolymers according to the present invention prove to be more effective than commercial polymers, even when they are used at lower levels. Finally, a comparison with composition C4 shows that the functional copolymer according to the present invention (Poly 1) proves to be more effective as a viscosity improver than its non-functional homolog (Poly 2), even though Poly 1 has a slightly lower number average molar mass.

Claims

1. A copolymer of ethylene and 1,3-butadiene containing from more than 90 mol% to less than 97 mol% of ethylene units and having a single monomer unit of methacrylate at one end of its chain.

2. The copolymer according to claim 1, wherein the methacrylate is an alkyl methacrylate.

3. The copolymer according to claim 1 or 2, wherein the methacrylate is methyl methacrylate. 4 . The copolymer according to claim 1 , having a crystallinity of greater than 30% and less than 45%.

5. The copolymer according to any one of claims 1 to 4, having a crystallinity greater than 35%.

6. The copolymer according to any one of claims 1 to 5, which is a statistical copolymer.

7. The copolymer according to any one of claims 1 to 6, comprising 1,2-cyclohexane units, i.e., cyclic units of formula (I), preferably in a molar content greater than 1%, more preferably in a molar content greater than or equal to 2%.

8. The copolymer according to any one of claims 1 to 7, having a number average molar mass of greater than 8000 g / mol, preferably greater than 10000 g / mol.

9. The copolymer according to any one of claims 1 to 8, having 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, even more preferably less than 100,000 g / mol.

10. A lubricating composition comprising a mineral base oil and the copolymer of ethylene and 1,3-butadiene according to any one of claims 1 to 9.

11. The lubricating composition of claim 10, wherein the mineral base oil is a Group I oil, a Group II oil, or a Group III oil.

12. The lubricating composition according to any one of claims 10 and 11, which is an engine oil.

13. The lubricating composition according to any one of claims 10 to 12, wherein the weight content of the copolymer of ethylene and 1,3-butadiene varies within the range of 0.01% to 5% by weight of the lubricating composition.

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