KR20210069703A - Methods for Synthesis of Ethylene and Myrcene Copolymers - Google Patents

Abstract

The present invention relates to a method for preparing an ethylene and myrcene copolymer comprising ethylene units and myrcene units, wherein the ethylene units in the copolymer are 50 mol% and 95 mol% of the ethylene units and myrcene units of the copolymer. %, wherein the myrcene units in the 1,2 and 3,4 positional configurations in the copolymer represent at least 50 mole % of the myrcene units of the copolymer, the method comprising at least one metallocene and It involves the polymerization of ethylene and myrcene in a reactor in the presence of a catalyst system based on one organomagnesium compound, during which ethylene and myrcene are continuously fed into the reactor.

Description

Methods for Synthesis of Ethylene and Myrcene Copolymers

The field of the present invention is to prepare conjugated diene/ethylene copolymers which are rich in ethylene units and which can be used as elastomers in rubber compositions for tires.

The most widely used diene elastomers for tire manufacture are polybutadiene, polyisoprene, especially natural rubber, and copolymers of 1,3-butadiene and styrene. What these elastomers have in common is a high molar proportion of diene units in the elastomer, usually much greater than 50%, which can make them susceptible to oxidation, especially under the action of ozone.

Applicants, on the contrary, have disclosed elastomers having relatively few diene units, in particular for the purpose of reducing their sensitivity to oxidation events. These elastomers are disclosed, for example, in WO 2007054223 document. These are copolymers of 1,3-butadiene and ethylene containing at least 50 mol % of ethylene units. These elastomers are described as diene elastomers rich in ethylene.

Ethylene-rich copolymers of 1,3-butadiene and ethylene are crystalline and undergo an increase in their crystallinity with ethylene content. The presence of crystalline moieties in the copolymer can be problematic when the copolymer is used in rubber compositions. Because dissolution of the crystalline portion of the copolymer results in a decrease in its stiffness, rubber compositions containing such copolymers and used for tires, when brought to a temperature equal to or exceeding the melting point of the crystalline portion, also It will experience a decrease in stiffness, which may be the case during repeated phases of braking and acceleration of the tire. The dependence of stiffness on temperature can, therefore, lead to uncontrollable fluctuations in the performance quality of the tire. It is advantageous to have diene polymers rich in possible ethylene units, in which case the crystallinity is reduced and in fact even eliminated.

In document WO 2007054224, the Applicant discloses ethylene-rich diene copolymers exhibiting reduced crystallinity. These copolymers are copolymers of 1,3-butadiene and ethylene, further containing a saturated 6-membered cyclic hydrocarbon motif. Nevertheless, these copolymers incorporated into the rubber composition may impart excessively high stiffness to the rubber composition. The high stiffness of the rubber composition is due to the equally high stiffness of the elastomer. The high stiffness of the rubber composition can also be problematic as it may render the rubber composition unsuitable for certain applications.

To prepare these ethylene/1,3-butadiene copolymers, which are ethylene-rich and contain saturated 6-membered cyclic hydrocarbon units, the applicant proposes a catalyst system based on an organomagnesium compound with a metallocene of the formula (I). has been developed and is disclosed, for example, in document WO 2007054224.

P(Cp ¹ Cp ² )Nd(BH ₄ ) _(1+y) -L _y -N _x (I)

Cp ¹ and Cp ² are the same or different, and are selected from the group consisting of a substituted fluorenyl group and an unsubstituted fluorenyl group of _{formula C 13} H ₈ , P is a group connecting ^{two Cp 1} and Cp ^{2 groups} , ^{represents a group ZR 3} R ⁴ , Z represents silicon or a carbon atom, R ³ and R ⁴ are the same or different and each represents an alkyl group comprising 1 to 20 carbon atoms, preferably methyl, and y is is an integer of 0 or more, x is an integer of 0 or more or is not an integer, L represents an alkali metal selected from the group consisting of lithium, sodium and potassium, N represents an ether molecule, preferably diethylether or tetrahydrofuran indicates.

As we all know, the capacity of a unit for making a given polymer is related to the productivity of the production unit. One way to increase the productivity of a production unit comprising polymerization in the presence of a metallocene based catalyst system is to increase the catalytic activity. This advantage of catalytic activity is, therefore, constantly sought to make the polymer synthesis process more productive for the purpose of increasing the production capacity and minimizing the production cost of the polymerization unit.

While pursuing the purpose of synthesizing an ethylene-rich diene elastomer, the applicant can solve the problems mentioned in connection with the synthesis of a polymer having an improved compromise between its crystallinity, its ethylene content and its glass transition temperature. A new method has been found for preparing

Accordingly, the present invention provides a method for preparing an ethylene and myrcene copolymer comprising ethylene units and myrcene units, the method comprising:

the ethylene units of the copolymer represent between 50 mol% and 95 mol% of the ethylene units and myrcene units of the copolymer;

In the copolymer, the myrcene units in the 1,2, and 3,4 position represent 50 mol% or more of the myrcene units of the copolymer;

The process comprises the polymerization of ethylene and myrcene in a reactor in the presence of a catalyst system based on at least one metallocene of formula (I) and an organomagnesium compound of formula (II), during which the ethylene and myrcene are continuously added to the reactor.

P(Cp ¹ Cp ² )Nd(BH ₄ ) _(1+y) -L _y -N _x (I)

MgR ¹ R ² (II)

Cp ¹ and Cp ² are the same or different and are selected from the group consisting of a substituted fluorenyl group and an unsubstituted fluorenyl group of _{formula C 13} H _{8 ,}

P is a group linking ^{two Cp 1} and Cp ^{2 groups, represents a ZR 3} R ⁴ group, Z represents a silicon or a carbon atom, R ³ and R ⁴ are the same or different, each having 1 to 20 carbon atoms an alkyl group comprising, preferably methyl;

y is an integer greater than or equal to 0,

x is an integer greater than or equal to 0 or is not an integer,

L represents an alkali metal selected from the group consisting of lithium, sodium and potassium,

N represents an ether molecule, preferably diethylether or tetrahydrofuran,

R ¹ and R ² are the same or different and represent a carbon group.

As used herein, the interval of any value denoted by the term “between a and b” represents a range of values from greater than a to less than b (ie, excluding a and b), whereas the interval of any value denoted by the term “a to b” is The interval of values of is meant a range of values extending from a to b (ie, including absolute limits a and b).

The term “based” as used to define the components of a catalyst system or composition is understood to mean a mixture of these components, or a product in which some or all of these components have reacted with each other.

Unless otherwise specified, the content of units resulting from the incorporation of a monomer into the copolymer is expressed as a molar percentage of all monomer units in the copolymer. The content of ethylene units in the copolymer expressed as "x mol% of ethylene units and myrcene units in the copolymer" is calculated as the ratio between the number of moles of ethylene units in the copolymer and the total number of monomer units in the copolymer, the ratio being 100 , and the total number of monomer units in the copolymer is the sum of moles of ethylene units and moles of myrcene units present in the copolymer.

The compounds referred to herein may be of fossil or biological origin. In the latter case, they can be partially or wholly generated from biomass or obtained from renewable starting materials derived from biomass. Monomers are particularly relevant.

The myrcene is a substituted 1,3-diene, and myrcene is represented by the 1,2-position arrangement represented by Formula (1), the 3,4-position arrangement represented by Formula (2), and the following Formula (3) It can occur in trans form. The units resulting from the polymerization of myrcene are known as myrcene units.

As is also well known, ethylene units are units of the -(CH ₂ -CH ₂ )- motif.

The process according to the invention makes it possible to prepare ethylene and myrcene copolymers, which means that the monomer units of the copolymer are units resulting from the polymerization of ethylene and myrcene, ie ethylene units and myrcene units. Thus, the copolymer contains ethylene units and myrcene units.

The ethylene and myrcene copolymers contain between 50 and 95 mole % ethylene units. That is, the ethylene units of the copolymer represent between 50 mol% and 95 mol% of the ethylene units and myrcene units of the copolymer. Another essential feature is that it also contains at least 50 mole % of myrcene units, which are myrcene units in the 1,2 and 3,4 positional configurations. That is, the myrcene units of the copolymer represent at least 50 mole % of the myrcene units of the copolymer, regardless of whether they are in the 1, 2 or 3, 4 position configuration. Preferably, the myrcene units of the copolymer of the 1,2 and 3,4 positional configurations are at least 55 mol% of the myrcene units of the copolymer. The remaining portion of 100 mol% of myrcene units in the copolymer is completely or partially formed of myrcene units in the 1,4-position configuration. According to any one of the aspects of the present invention, preferably at least half of the myrcene units in the 1,4-position configuration are in the trans-1,4-position configuration, more preferably all myrcene units in the 1,4-position configuration is the trans-1,4-position configuration.

According to a preferred embodiment of the present invention, the ethylene units of the copolymer represent at least 60 mol% of the ethylene units and myrcene units of the copolymer. More preferably, the ethylene units of the copolymer represent 60 mol% to 90 mol% of the ethylene units and myrcene units of the copolymer.

According to a more preferred aspect of the present invention, the ethylene units of the copolymer represent 70 mol% or more of the ethylene units and myrcene units of the copolymer. More preferably, the ethylene units of the copolymer represent 70 mol% to 90 mol% of the ethylene units and myrcene units of the copolymer.

Preferably, the copolymer has a glass transition temperature of less than -35°C, in particular between -70°C and -35°C.

More preferably, the copolymers prepared according to any one of the embodiments of the invention, in particular those described according to any one of claims 1 to 12, are elastomers.

The catalyst system used in the requirements of the present invention is a catalyst system based on at least one metallocene of formula (I) and an organomagnesium compound of formula (II).

P(Cp ¹ Cp ² )Nd(BH ₄ ) _(1+y) -L _y -N _x (I)

MgR ¹ R ² (II)

Cp ¹ and Cp ² are the same or different and are selected from the group consisting of a substituted fluorenyl group and an unsubstituted fluorenyl group of _{formula C 13} H _{8 ,}

P is a group linking ^{two Cp 1} and Cp ^{2 groups, represents a ZR 3} R ⁴ group, Z represents a silicon or a carbon atom, R ³ and R ⁴ are the same or different, each having 1 to 20 carbon atoms an alkyl group comprising, preferably methyl;

y is an integer greater than or equal to 0,

x is an integer greater than or equal to 0 or is not an integer,

L represents an alkali metal selected from the group consisting of lithium, sodium and potassium,

N represents an ether molecule, preferably diethylether or tetrahydrofuran,

R ¹ and R ² are the same or different and represent a carbon group.

As the substituted fluorenyl group, mention may be made of those substituted by an alkyl radical having 1 to 6 carbon atoms or an aryl radical having 6 to 12 carbon atoms. The choice of radical is also guided by the accessibility of the molecule corresponding to the substituted fluorene, since the substituted fluorene is either commercially available or can be readily synthesized.

More specifically, as the substituted fluorenyl group, a 2,7-di(tert-butyl)fluorenyl group and a 3,6-di(tert-butyl)fluorenyl group can be mentioned. Positions 2, 3, 6 and 7 each represent the position of a carbon atom of the ring shown in the following formula, and position 9 corresponds to the carbon atom to which the linkage P is attached.

The catalyst system is generally introduced into a reactor containing polymerization solvent and monomers.

The catalyst system can be conventionally prepared by a process similar to that disclosed in patent application WO 2007054224. For example, the organomagnesium compound and the metallocene may be reacted in a hydrocarbon solvent at a temperature generally in the range of 20 to 80° C. for a time between 5 minutes and 60 minutes. The catalyst system is generally prepared in an aliphatic hydrocarbon solvent such as methylcyclohexane, or an aromatic hydrocarbon solvent such as toluene. In general, the catalyst system, after synthesis, is used in this form in the process for the synthesis of the copolymer according to the invention.

Alternatively, the catalyst system may be prepared by a process analogous to that disclosed in patent application WO 2017093654 A1 or patent application WO 2018020122 A1. According to this alternative, the catalyst system further contains a preforming monomer selected from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, wherein the catalyst system comprises at least a metallocene, an organomagnesium compound and a preforming monomer is based on For example, the organomagnesium compound and the metallocene are generally reacted at a temperature of 20°C to 80°C in a hydrocarbon solvent for 10 to 20 minutes to obtain a first reaction product, and then conjugated with a conjugated diene, ethylene or ethylene. A pre-forming monomer selected from the mixture of dienes is reacted with the first reaction product at a temperature ranging from 40° C. to 90° C. for 1 hour to 12 hours. Thus, the catalyst system obtained can be used immediately in the process according to the invention or stored under an inert atmosphere before its use in the process according to the invention.

The metallocene used to prepare the catalyst system may be in the form of a crystalline or amorphous powder, or may be in the form of a single crystal. The metallocene may be provided in the form of a monomer or a dimer, and these forms depend on a method for preparing the metallocene, and are disclosed in, for example, patent application WO 2007054224. Metallocenes are usually prepared in a manner similar to that disclosed in patent application WO 2007054224, in particular under inert and anhydrous conditions, in a suitable solvent such as an ether, for example diethyl ether or tetrahydrofuran, or any other solvent known to the person skilled in the art. In , it can be prepared by reaction of an alkali metal salt of a ligand with a rare earth metal borohydride. After the reaction, the metallocene is separated from the reaction by-products by techniques known to those skilled in the art, such as filtration or precipitation from a second solvent. Eventually, the metallocene is dried and isolated in solid form.

As with all syntheses carried out in the presence of organometallic compounds, the syntheses of the metallocenes and their catalyst systems take place under anhydrous conditions under an inert atmosphere. In general, the reaction is carried out starting from anhydrous solvents and compounds under dry nitrogen or argon.

Preferably, the metallocene is of the formula (Ia), (Ib), (Ic), (Id) or (Ie), wherein the symbol Flu represents a fluorenyl group of the _{formula C 13} H _{8 .}

[{Me ₂ SiFlu ₂ Nd(μ-BH ₄ ) ₂ Li(THF)} ₂ ] (Ia)

[Me ₂ SiFlu ₂ Nd(μ-BH ₄ ) ₂ Li(THF)] (Ib)

[Me ₂ SiFlu ₂ Nd(μ-BH ₄ )(THF)] (Ic)

[{Me ₂ SiFlu ₂ Nd(μ-BH ₄ )(THF)} ₂ ] (Id)

[Me ₂ SiFlu ₂ Nd(μ-BH ₄ )] (Ie)

The organomagnesium compound used in the requirements of the present invention has the formula MgR ₁ R ₂ , wherein R ¹ and R ² are the same or different and represent a carbon group. A carbon group means a group containing one or more carbon atoms. Preferably, R ¹ and R ² contain 2 to 10 carbon atoms. More preferably, R ¹ and R ² each represent alkyl. The organomagnesium compound is advantageously a dialkylmagnesium compound, more advantageously butylethylmagnesium or butyloctylmagnesium, even more advantageously butyloctylmagnesium.

According to any one of the aspects of the present invention, the molar ratio of the organomagnesium compound to the metal Nd constituting the metallocene is preferably within a range extending from 1 to 100, and more preferably from 1 to less than 10. A range of values from 1 to less than 10 is particularly advantageous for obtaining high molar mass copolymers.

A person skilled in the art also adjusts the polymerization conditions and the concentration of each reactant (components of the catalyst system, monomers) according to the equipment (equipment, reactor) used to carry out the polymerization and various chemical reactions. As is known to those skilled in the art, the copolymerization and handling of the monomers of the catalyst system and polymerization solvent(s) takes place under anhydrous conditions and under an inert atmosphere. The polymerization solvent is generally an aliphatic or aromatic hydrocarbon solvent.

The polymerization is preferably carried out in solution continuously or in batch mode. The polymerization solvent may be an aromatic or aliphatic hydrocarbon solvent. As examples of the polymerization solvent, toluene and methylcyclohexane may be mentioned. Advantageously, the polymerization is carried out in solution in a hydrocarbon solvent.

Copolymerization, ie polymerization of ethylene and myrcene, is carried out in the selective presence of an inert gas, generally under anhydrous conditions and in the absence of oxygen. The polymerization temperature generally varies within the range from 30°C to 150°C, preferably from 30°C to 120°C. These temperature ranges are applicable to any one of the aspects of the invention, in particular those described according to any one of claims 1 to 12. Preferably, the copolymerization is carried out at constant ethylene pressure.

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 polymer can be recovered according to conventional techniques known to the person skilled in the art, such as, for example, by precipitation, by evaporation of the solvent under reduced pressure, or by steam stripping.

Another essential feature of the process according to the invention is that it comprises the continuous addition of ethylene and myrcene to the reactor during polymerization. That is, the reactor is a fed reactor. Since the binding of myrcene and ethylene to the growing polymer chain is generally random, this successive addition helps to control the degree of binding of the monomer in the growing polymer chain, particularly by controlling the composition of the monomer in the polymerization medium. This can compensate for the consumption of each monomer in the reactor during polymerization. This addition allows better control over the composition of the copolymer throughout its synthesis. It is thus possible to prepare copolymers whose composition along the chain is controlled throughout their synthesis, and to obtain copolymers with low crystallinity even when the molar concentration of ethylene units is very high. In particular, it is also possible to prepare copolymers whose composition is almost constant from one end of the chain to the other.

The ethylene and myrcene, which are continuously added to the reactor, may be mixed before being introduced into the reactor, and thus, thereafter may be continuously introduced into the reactor to form a monomer mixture. Alternatively, the ethylene and myrcene are introduced into the reactor separately, ie they are not in contact with each other before they are introduced into the reactor. When the ethylene and myrcene are continuously added to the reactor in the form of a monomer mixture, the molar ratio between ethylene of the monomer mixture and myrcene of the monomer mixture is preferably 1/9 to 19/1, more preferably 1/ It may be in the range of 1 to 9/1. Thus, the added mixture preferably has an ethylene/myrcene molar composition in the range from 10/90 to 95/5, more preferably from 50/50 to 90/10. When the ethylene and myrcene are separately and continuously added to the reactor, the flow rates of the ethylene and myrcene are more preferably in a molar ratio between ethylene added to the reactor and myrcene added to the reactor from 1/9 to 19/1, more preferably from 1/9 to 19/1. usually in the range of 1/1 to 9/1.

The apparatus for carrying out the process may comprise one or more means for measuring, on the one hand, the myrcene concentration of the reaction medium and, on the other hand, the ethylene pressure of the reactor or the ethylene concentration of the reaction medium. As a non-limiting example, the measuring means may be performed using a method of the absorbance type in the infrared range, or an absorbance type method in the ultraviolet/visible range, or using gas chromatography.

According to certain embodiments of the present invention, a system for managing the addition of monomers can be coupled to the reactor to ensure that the concentrations of ethylene and myrcene in the reactor are constant, thus ensuring a random polymer free from composition gradients.

In one mode of operation, the ethylene concentration of the reaction medium is kept constant by controlling the pressure in the reactor with continuous ethylene additions. Specifically, the ethylene consumption is compensated by maintaining a constant ethylene pressure in the reactor and continuously injecting ethylene at a variable flow rate. Likewise, in this mode of operation, the consumption of myrcene is compensated by the addition of myrcene to the reactor.

In one variant, the ethylene and myrcene are injected according to a predetermined flow ratio. Thus, the injection of the monomer is controlled by the ethylene pressure in the reactor and the myrcene concentration in the reaction medium and the flow rate known by the various tools available to the person skilled in the art (experimental, digital simulation) and is suitable for the catalyst system used.

According to this variant, the myrcene is advantageously injected in liquid form. According to this variant, the ethylene is advantageously injected in gaseous form. The reactor generally includes means for measuring the pressure inside the reactor and is connected to an automatic controller for controlling the pressure in the reactor to control the ethylene injection flow rate. The ethylene and myrcene injection flow rates, which are controlled by opening the valve and measured respectively by the flow rate measuring means, are further controlled by the controller of the feed flow rate ratio of ethylene and myrcene so as to comply with a preset flow rate ratio.

In the second variant, a mixture of ethylene and myrcene is injected. The reactor comprises means for measuring the concentrations of ethylene and myrcene in the reaction medium. This measuring means is connected to an automatic controller which controls the injection flow rate of the ethylene and myrcene mixture through a valve. According to this second variant, the mixture of ethylene and myrcene is advantageously injected in liquid form.

The process is advantageously a semi-continuous process, in which ethylene and myrcene are continuously added to the reactor during polymerization. The polymerization reaction medium is advantageously stirred. Said reactor advantageously comprises at least one stirring means, for example with several blades. The temperature of the reaction medium is advantageously kept constant during the polymerization. The total pressure in the reactor is advantageously kept constant.

Copolymers can be used in rubber compositions, especially when they are elastomers.

The rubber composition comprises a crosslinking system.

The crosslinking system may be based on sulfur, a sulfur donor, peroxide, bismaleimide or mixtures thereof. The crosslinking system is preferably a vulcanization system, ie a system based on sulfur (or sulfur donor) and a primary vulcanization accelerator. Various known secondary vulcanization accelerators or vulcanization activators such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or other known vulcanization retarders may be added to this base vulcanization system.

Preferably, the rubber composition comprises a reinforcing filler. The rubber composition may include any type of "reinforcing" filler known for its ability to reinforce rubber compositions that can be used in the manufacture of tires, for example organic fillers such as carbon black, reinforcing inorganic fillers such as silica, It is combined in a known manner with a coupling agent, or a mixture of these two types of fillers. These reinforcing fillers generally consist of nanoparticles, the average size (by weight) of which is less than 1 micrometer, usually less than 500 nm, mainly between 20 nm and 200 nm, particularly more preferably between 20 nm and 150 nm. The content of the reinforcing filler is adjusted by the person skilled in the art depending on the use of the rubber composition.

The rubber composition may further contain other additives known to be used in rubber compositions for tires, such as plasticizers, anti-ozonants or antioxidants.

The rubber composition is generally prepared in a suitable mixer using two successive manufacturing steps well known to those skilled in the art: the first step of thermodynamic working or kneading at elevated temperatures, with a maximum temperature between 130° C. and 200° C. A "non-productive" stage), followed by a second stage of mechanical operation ("productive" stage) to temperatures as low as generally below 110 °C, for example between 40 °C and 100 °C, a crosslinking system is introduced during the finishing stage.

The rubber composition, which may be either in a raw state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization), can be used in semi-finished tires.

The tire comprises a rubber composition as defined according to any one of the variants described above.

The above-mentioned features and also others of the present invention will be more clearly understood upon reading the following description of various embodiments of the present invention, which are provided by way of non-limiting example.

embodiment of the present invention

All reactants except metallocene [Me ₂ SiFlu ₂ Nd(μ-BH ₄ ) ₂ Li(THF)] and [Me ₂ SiCpFluNd(μ-BH ₄ ) ₂ Li(THF)] are obtained commercially, which are patent pending It is prepared according to the methods disclosed in WO 2007054224 and WO 2007054223.

Butyloctylmagnesium BOMAG (20% in heptane, C=0.88 mol.L ^-1 ) is from Chemtura and stored in Schlenk tubes under an inert atmosphere. N35 grade ethylene comes from Air Liquide and is used without prior purification. Myrcene (purity≥95%) is obtained from Sigma-Aldrich.

1) Determination of the microstructure of the polymer:

Spectral characterization and microstructure determination of ethylene/myrcene copolymers are performed by nuclear magnetic resonance (NMR) spectroscopy.

-Spectrometer: For these measurements, a Bruker Avance III HD 400MHz spectrometer equipped with a Bruker cryo-BBFO z-grad 5mm probe is used.

-Experiment: A ¹ H experiment is recorded using a high-frequency pulse with an inclination angle of 30°, and the number of repetitions is 128 with a recirculation delay of 5 s. Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple-Bond Correlation (HMBC) ¹ H- ¹³ C NMR correlation experiments are recorded with 128 repetitions and 128 increments. Experiments are carried out at 25°C.

- Sample preparation: Dissolve 25 mg of sample in 1 mL of _{deuterated chloroform (CDCl 3 ).}

-Sample Calibration: ^{The axes of 1} H and ¹³ C chemical shifts are corrected for protonated impurities _{in the solvent (CHCl 3} ) at δ1H=7.2 ppm and δ13C=77 ppm.

-Spectral assignment: Signals in the intercalated form of myrcene A, B and C (scheme 1) were observed in the different spectra recorded. According to S. Georges et al. (S. Georges, M. Bria, P. Zinck and M. Visseaux, Polymer, 55 (2014), 3869-3878), -CH=group No. The signal of the 8'' characteristic is -CH=group No. 3 ^{showed the same 1} H and ¹³ C chemical shifts.

Chemical shifts of the signal features of motifs A, B and C are shown in Table 1. The motifs A, B, and C correspond to units of the 3,4-position sequence, the 1,2-position sequence, and the trans-1,4-position sequence, respectively.

Scheme 1:

R ₁ and R ₂ represent the point of attachment of the unit to the polymer chain.

Quantification was performed from integration of ^{1D 1} H NMR spectra using Topspin software.

The integrated signals for quantification of different motifs are as follows:

- ethylene: signal at 1.2 ppm corresponding to 4 protons

- Total myrcene: signal due to group No. 1 (1.59 ppm) corresponding to 6 protons

- Form A: Group No. corresponding to two protons. Signal due to 7 (4.67 ppm)

- Form B: Group No. corresponding to one proton. Signal due to 8' (5.54 ppm)

Quantification of the microstructure is carried out in mole percentages (mol %) as follows:

Mole % of motif = ¹ H integral of motif*100/Σ ( ¹ H integral of each motif).

2) Determination of the glass transition temperature of the polymer:

Glass transition temperature is measured using a differential calorimeter (differential scanning calorimeter) according to standard ASTM D3418 (1999).

3) Determination of the crystallinity of the polymer:

The standard ISO 11357-3:2011 is used to determine the temperature and enthalpy of fusion and crystallization of polymers used by differential scanning calorimetry (DSC). The standard enthalpy of polyethylene is 277.1 J/g (according to Polymer Handbook, 4th Edition, J. Brandrup, E. H. Immergut and E. A. Grulke, 1999).

4) Synthesis of polymers:

4.1 - Control Synthesis: Example 1

The polymer is synthesized according to the following method:

To a 500 mL glass reactor containing 300 mL of toluene, the cocatalyst, butyloctylmagnesium (BOMAG) and then metallocene [Me ₂ SiCpFluNd(μ-BH ₄ ) ₂ Li(THF)] are added. The alkylation time is 10 minutes and the reaction temperature is 20°C. The amounts of each component of the catalyst system are shown in Table 2. Then, monomers are added according to each ratio shown in Table 2, and ethylene (Eth) and 1,3-butadiene (Bde) are in the form of a gas mixture. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling the reactor, degassing and adding 10 mL of ethanol. A sulphating agent is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. Weighing can determine the average catalytic activity of the catalyst system, expressed in kilograms (kg/mol.h) of polymer synthesized per mole of neodymium metal and per hour.

4.2 - Examples not according to the invention: Example 2

The polymer is synthesized according to the following method:

To a 500 mL glass reactor containing 300 mL of methylcyclohexane is added the cocatalyst, butyloctylmagnesium (BOMAG) and then metallocene [Me ₂ Si(Flu) ₂ Nd(μ-BH ₄ ) ₂ Li(THF)] . The alkylation time is 10 minutes and the reaction temperature is 20°C. The amounts of each component of the catalyst system are shown in Table 2. Then, monomers are added according to the respective ratios shown in Table 2, and ethylene (Eth) and 1,3-butadiene (Bde) are in the form of a gas mixture. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling the reactor, degassing and adding 10 mL of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. Weighing can determine the average catalytic activity of the catalyst system, expressed in kilograms (kg/mol.h) of polymer synthesized per mole of neodymium metal and per hour.

4.3 - Examples not according to the invention: Example 3

The polymer is synthesized according to the following method:

To a 500 mL glass reactor containing 300 mL of methylcyclohexane is added the cocatalyst, butyloctylmagnesium (BOMAG) and then metallocene [Me ₂ Si(Flu) ₂ Nd(μ-BH4) ₂ Li(THF)]. The alkylation time is 10 minutes and the reaction temperature is 20°C. The amounts of each component of the catalyst system are shown in Table 2. Next, before injection of ethylene gas, myrcene (10.3 mL, Table 2) was added to the reactor. The polymerization is carried out at 80° C. and a constant ethylene pressure of 4 bar. The polymerization reaction is stopped by cooling the reactor, degassing and adding 10 mL of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. Weighing can determine the average catalytic activity of the catalyst system, expressed in kilograms (kg/mol.h) of polymer synthesized per mole of neodymium metal and per hour.

4.4 - Examples not according to the invention: Example 4

The polymer is synthesized according to the following method:

Butyloctylmagnesium (BOMAG) was added to a reactor containing methylcyclohexane, ethylene and butadiene in the proportions shown in Table 3 at 80° C. to neutralize impurities in the reactor, followed by addition of the catalyst system (see Table 3). At this time, the reaction temperature is adjusted to 80° C., and the polymerization reaction is started. The polymerization reaction takes place at a constant pressure of 8 bar. Ethylene and butadiene in the ratios defined in Table 3 are fed to the reactor throughout the polymerization. The polymerization reaction is stopped by cooling the reactor, degassing and adding 10 mL of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. Weighing can determine the average catalytic activity of the catalyst system, expressed in kilograms (kg/mol.h) of polymer synthesized per mole of neodymium metal and per hour. The catalyst system is a preformed catalyst system. from metallocene in the contents shown in Table 3, [Me ₂ SiFlu) ₂ Nd(μ-BH ₄ ) ₂ Li(THF)], co-catalyst, butyloctylmagnesium (BOMAG) and 1,3-butadiene as a preforming monomer Prepare methylcyclohexane. It is prepared according to the preparation method according to paragraph II.1 of the patent application WO 2017093654 A1.

4.5 - Examples according to the invention: Examples 5 to 6

The polymer is synthesized according to the following method:

To a reactor containing methylcyclohexane, ethylene and myrcene in the proportions indicated in Table 3 at 80° C., butyloctylmagnesium (BOMAG) was added to neutralize impurities in the reactor, followed by addition of the catalyst system (see Table 3). At this time, the reaction temperature is adjusted to 80° C., and the polymerization reaction is started. The polymerization reaction takes place at a constant pressure of 8 bar. Ethylene and myrcene in the proportions defined in Table 3 are fed to the reactor throughout the polymerization. The polymerization reaction is stopped by cooling the reactor, degassing and adding 10 mL of ethanol. An antioxidant is added to the polymer solution. The copolymer is recovered by drying in an oven under vacuum to constant weight. Weighing can determine the average catalytic activity of the catalyst system, expressed in kilograms (kg/mol.h) of polymer synthesized per mole of neodymium metal and per hour. The catalyst system is a preformed catalyst system. Metallocene in the contents shown in Table 3, [Me ₂ Si(Flu) ₂ Nd(μ-BH ₄ ) ₂ Li(THF)], co-catalyst, butyloctylmagnesium (BOMAG) and 1,3- as a preforming monomer Methylcyclohexane is prepared from butadiene. It is prepared according to the preparation method according to paragraph II.1 of the patent application WO 2017093654 A1.

5) Results:

The properties of the polymers are shown in Tables 4 and 5.

In Example 1 (control), the diene copolymer synthesized by polymerization of ethylene and 1,3-butadiene in the presence of ethylene _{-rich and metallocene [Me 2} SiCpFluNd(μ-BH ₄ ) _{2 Li(THF)] was} It exhibits high crystallinity (31%) which may not be suitable for some applications.

In Example 2 (not according to the invention), the ethylene-rich diene copolymer synthesized in the presence of a _{metallocene [Me 2} Si(Flu) ₂ Nd(μ-BH ₄ ) _{2 Li(THF)] was cyclic} Indicates a motif. It contains an ethylene content similar to the control, but is not crystalline.

In Examples 5 and 6 (according to the present invention), the ethylene-rich diene copolymer is a copolymer of ethylene and myrcene synthesized according to the method according to the present invention. Although their crystallinity is much lower than that of the control, their ethylene content is much higher than that of the control.

The copolymer of Example 5 also has the same ethylene content as the copolymer of Example 3, which is a copolymer of ethylene and myrcene, but is synthesized according to a process not according to the invention (no addition of both myrcene and ethylene throughout the polymerization). pay attention to the point However, the copolymer of Example 5 has a lower crystallinity than the copolymer of Example 3. The process according to the invention thus makes it possible to synthesize ethylene and myrcene copolymers having both a very high ethylene content and a degree of crystallinity, while maintaining a given relatively low ethylene content of the copolymer.

It is also noted that in Examples 5 and 6, the catalytic activity is much higher than in Example 4. Surprisingly, the use of myrcene instead of 1,3-butadiene as the ethylene comonomer can greatly enhance the catalytic activity of the catalyst system.

Claims (12)

A method for preparing an ethylene and myrcene copolymer comprising ethylene units and myrcene units, the method comprising:
The ethylene unit in the copolymer represents between 50 mol% and 95 mol% of the ethylene unit and myrcene unit of the copolymer,
In the copolymer, the myrcene units in the 1,2, and 3,4 position represent 50 mol% or more of the myrcene units of the copolymer;
The process comprises the polymerization of ethylene and myrcene in a reactor in the presence of a catalyst system based on at least one metallocene of formula (I) and an organomagnesium compound of formula (II), wherein during the polymerization ethylene and myrcene are continuously added to the reactor as a method.
P(Cp ¹ Cp ² )Nd(BH ₄ ) _(1+y) -L _y -N _x (I)
MgR ¹ R ² (II)
Cp ¹ and Cp ² are the same or different and are selected from the group consisting of a substituted fluorenyl group and an unsubstituted fluorenyl group of _{formula C 13} H _{8 ,}
P is a group linking ^{two Cp 1} and Cp ^{2 groups, represents a ZR 3} R ⁴ group, Z represents a silicon or a carbon atom, R ³ and R ⁴ are the same or different, each having 1 to 20 carbon atoms an alkyl group comprising, preferably methyl;
y is an integer greater than or equal to 0,
x is an integer greater than or equal to 0 or is not an integer,
L represents an alkali metal selected from the group consisting of lithium, sodium and potassium,
N represents an ether molecule, preferably diethyl ether or tetrahydrofuran,
R ¹ and R ² are the same or different and represent a carbon group. The method of claim 1 , wherein the metallocene is of formula (Ia), (Ib), (Ic), (Id) or (Ie).
[{Me ₂ SiFlu ₂ Nd(μ-BH ₄ ) ₂ Li(THF)} ₂ ] (Ia)
[Me ₂ SiFlu ₂ Nd(μ-BH ₄ ) ₂ Li(THF)] (Ib)
[Me ₂ SiFlu ₂ Nd(μ-BH ₄ )(THF)] (Ic)
[{Me ₂ SiFlu ₂ Nd(μ-BH ₄ )(THF)} ₂ ] (Id)
[Me ₂ SiFlu ₂ Nd(μ-BH ₄ )] (Ie)
The symbol Flu represents a fluorenyl group of _{formula C 13} H _{8 .} 3. The method of any one of claims _{1 and 2} , wherein R 1 and R 2 contain 2 to 10 carbon atoms. 4. The method according to any one of claims 1 to 3, wherein R ₁ and R ₂ each represent alkyl. Process according to any one of claims 1 to 4, wherein the organomagnesium compound is a dialkylmagnesium compound, preferably butylethylmagnesium or butyloctylmagnesium, more preferably butyloctylmagnesium. 6. The method according to any one of claims 1 to 5, wherein the ethylene and myrcene are added continuously to the reactor in the form of a monomer mixture, the added mixture is preferably 10/90 to 95/5, more preferably has an ethylene/myrcene molar composition ranging from 50/50 to 90/10. 6. The method of any one of claims 1 to 5, wherein the ethylene and myrcene are added individually and continuously to the reactor, and the flow rates of ethylene and myrcene are between the ethylene added to the reactor and myrcene added to the reactor. wherein the molar ratio ranges from 1/9 to 19/1, more preferably from 1/1 to 9/1. 8. The process according to any one of claims 1 to 7, wherein the polymerization of ethylene and myrcene is carried out at constant ethylene pressure. 9. The method according to any one of claims 1 to 8, wherein the method is a semi-continuous process. 10 . The process according to claim 1 , wherein the catalyst system is also based on a preforming monomer selected from conjugated dienes, ethylene, or mixtures of ethylene and conjugated dienes. 11. The copolymer according to any one of claims 1 to 10, wherein the ethylene units in the copolymer are from 60 mol% to 90 mol%, preferably from 70 mol% to 90 mol% of the ethylene units and myrcene units of the copolymer. representing the method. 12. The process according to any one of claims 1 to 11, wherein the polymerization is carried out in solution, preferably in a hydrocarbon solvent.