Catalytic system comprising a metallocene for the synthesis of polyethylene and ethylene and 1,3-diene copolymer

Abstract

The invention relates to a catalytic system based at least on a borohydrido-neodymocene, a dialkyl magnesium compound and a dialkyl zinc compound. The catalytic system can be used both in the homopolymerization of ethylene and in the copolymerization of ethylene and a 1,3-diene.

Description

[0001] Catalytic system comprising a metallocene for the synthesis of polyethylene and ethylene-1,3-diene copolymer.

[0002] The field of the present invention is that of catalytic systems usable in the preparation of polyethylene and copolymer of ethylene and 1,3-diene.

[0003] The synthesis of polyolefin by polymerization of an olefin such as ethylene or a mixture of ethylene and a 1,3-diene in the presence of a catalytic system comprising a rare earth metallocene is well known. For example, in patent applications WO 2007054223 and WO 2007054224, the Applicants have described catalytic systems containing a neodymium metallocene and an organomagnesium compound.

[0004] The organomagnesium compound, a dialkylmagnesium compound, is used in the catalyst system as a cocatalyst to activate the metallocene for polymerization. The catalyst systems are useful in the synthesis of both polyethylene and ethylene-1,3-diene copolymers.

[0005] Continuing their efforts in the synthesis of polyethylene and copolymers of ethylene and 1,3-diene, the Applicants have developed a new catalytic system which exhibits a catalytic activity much superior to the catalytic system already described, by replacing a part of the dialkylmagnesium co-catalyst with a dialkylzinc compound in the synthesis of polyethylene. The new catalytic system also has the advantage of being able to be used both in the homopolymerization of ethylene and in the copolymerization of ethylene and a 1,3-diene.

[0006] Thus, a first object of the invention is a catalytic system based on at least: a metallocene of formula (Ia), a dialkylmagnesium, a dialkylzinc, {P(Cp 1 )(Cp 2 )Nd(BH4)(i + y)-L y -N x} (there)

[0007] CP 1 and Cp 2 , identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted,

[0008] P being a group bridging the two Cp groups 1 and Cp 2 , and comprising a silicon or carbon atom,

[0009] Nd denoting the neodymium atom,

[0010] L representing an alkali metal chosen from the group consisting of lithium, sodium and potassium,

[0011] N representing a molecule of an ether, x, integer or not, being equal to or greater than 0, y, integer, being equal to or greater than 0.

[0012] The invention also relates to a process for preparing a polymer which comprises the polymerization of ethylene or a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system according to the invention. Detailed description

[0013] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​greater than "a" and less than "b" (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0014] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, that is to say, they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0015] The expression "based on" used to define the constituents of the catalytic system or catalytic composition means the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other.

[0016] In the present application, metallocene is understood to mean an organometallic complex in which the metal, in this case the rare earth atom, is linked to a ligand molecule consisting of two Cp groups 1 and Cp 2 connected to each other by a P bridge. These Cp groups 1 and Cp 2 , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, these groups being able to be substituted or unsubstituted.

[0017] As substituted cyclopentadienyl, fluorenyl and indenyl 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 or by trialkyl radicals such as SiMej. The choice of radicals is also guided by the accessibility of the corresponding molecules, which are substituted cyclopentadienyl, fluorenyl and indene, because the latter are commercially available or easily synthesized.

[0018] As substituted fluorenyl groups, mention may be made of those substituted in position 2,7, 3 or 6, particularly 2,7-ditertiobutyl-fluorenyl, 3,6-ditertiobutyl-fluorenyl. Positions 2, 3, 6 and 7 respectively designate the position of the carbon atoms of the rings as shown in the diagram below, position 9 corresponding to the carbon atom to which the P bridge is attached. As substituted cyclopentadienyl groups, mention may be made of those substituted both in position 2 (or 5) and in position 3 (or 4), particularly those substituted in position 2, more particularly the tetramethylcyclopentadienyl group. Position 2 (or 5) designates the position of the carbon atom which is adjacent to the carbon atom to which the P bridge is attached, as shown in the diagram below.

[0019] As substituted indenyl groups, mention may be made in particular of those substituted in position 2, more particularly 2-methylindenyl, 2-phenylindenyl. Position 2 designates the position of the carbon atom which is adjacent to the carbon atom to which the P bridge is attached, as shown in the diagram below.

[0020] Preferably, Cp 1 and Cp 2, identical or different, each represents a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

[0021] More preferably, Cp 1 and Cp 2 are identical and are selected from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C11H2. Advantageously, Cp 1 and Cp 2 are identical and each represents an unsubstituted fluorenyl group of formula CIÎHS, represented by the symbol Flu.

[0022] Any ether that has the power to complex the alkali metal is suitable as an ether, especially diethyl ether and tetrahydrofuran.

[0023] The P bridge connecting the Cp groups 1 and Cp 2 preferably responds to the formula ZR 1 R 2 , in which Z represents a silicon or carbon atom, R 1 and R 2, identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl. In the formula ZR 1 R 2 , Z advantageously represents a silicon atom, Si.

[0024] The metallocene useful for the synthesis of the catalytic system may be in the form of a crystallized or non-crystalline powder, or in the form of single crystals. The metallocene may be in a monomeric or dimeric form, these forms depending on the method of preparation of the metallocene, as described for example in patent application WO 2007054224 or WO 2007054223. The metallocene may be prepared in a conventional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223, 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 other 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.

[0025] According to a particularly preferred embodiment, the metallocene is of formula (III-1), (111-2), (111-3), (111-4) or (111-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (III-1) [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (111-2) [Me2SiFlu2Nd(p-BH4)(THF)] (111-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (111-4) [Me2SiFlu2Nd(p-BH4)] (111-5) in which Flu represents the CisHs group.

[0026] The catalytic system also has as other essential components an organomagnesium compound and a zinc compound. The organomagnesium compound is a dialkylmagnesium compound and the zinc compound is a dialkylzinc compound. The alkyls of the dialkylmagnesium compound and the dialkylzinc compound are preferably alkyls containing 2 to 10 carbon atoms.

[0027] The organomagnesium compound is a dialkylmagnesium compound which is typically of the formula R2Mg in which the R symbols each represent an alkyl. The alkyls represented by the R symbols can contain 2 to 10 carbon atoms and include ethyl, butyl, octyl.

[0028] Dialkylmagnesium compounds are well-known organometallic reagents, some of which are even commercial products. For their synthesis, one can also refer, for example, to the collection of volumes of "Organic Synthesis". Like any organomagnesium compound, the dialkylmagnesium compound constituting the catalytic system can be in the form of a monomeric entity or in the form of a polymeric entity. For illustration, the dialkylmagnesium compound can be in the form of a monomeric entity (R2Mg)i or in the form of a polymeric entity (R2Mg) p, p being an integer greater than 1, in particular dimer (R2Mg)2, m being as defined previously. Furthermore, whether in the form of a monomeric or polymeric entity, the organomagnesium compound may also be in the form of an entity coordinated to one or more molecules of a solvent, preferably an ether such as diethyl ether, tetrahydrofuran or methyltetrahydrofuran.

[0029] Preferably, the dialkylmagnesium is of formula (Ilia)

[0030] MgR 3 R 4 (Ilia) in which the alkyl represented by the symbol R 3 is different from the alkyl represented by the symbol R 4 , preferably R 3 being butyl and R 4 ethyl or octyl.

[0031] The zinc compound is a dialkylzinc compound typically of formula R2Zn in which the symbols R each represent an alkyl. The alkyls represented by the symbols R can contain 2 to 10 carbon atoms and are preferably ethyl, butyl, octyl. Preferably, the dialkylzinc compound is of formula (IIa) ZnR 5 R 6 (Ha) in which the alkyls represented by the symbols R 5 and R 6 are identical. More preferably, the alkyls represented by the symbols R 5 and R 6 are the same and are ethyl or octyl.

[0032] Preferably, the ratio Nzn / (Nzn +NM8) which is the ratio between the number of moles of Zn of the dialkylzinc compound (Nzn) and the sum of the number of moles of Zn of the dialkylzinc compound and the number of moles of Mg of the dialkylmagnesium compound (NM8) is greater than 0.01 and less than 0.95. More preferably, this ratio is greater than 0.1 and less than 0.85.

[0033] The catalytic system in accordance with the invention may be prepared in a traditional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223, the organomagnesium compound and the zinc compound useful for the purposes of the invention acting as co-catalysts. For example, in a hydrocarbon solvent, the organomagnesium compound and the zinc compound are placed in the presence of the metallocene, typically at a temperature ranging from 20 to 80°C for a period of between 5 and 60 minutes. The quantities of organomagnesium, zinc compound and metallocene reacted to form the catalytic system are such that the ratio (Nzn +NM8) / N which is the ratio between the sum of the number of moles of Mg of the organomagnesium and the number of moles of Zn of the zinc compound and the number of moles of rare earth metal of the metallocene (NNCI) preferably ranges from 1.5 to 200, more preferably from 1.5 to less than 20.The range of values ​​from 1.5 to less than 20 is particularly more favorable for obtaining polymers with high molar masses.

[0034] The catalytic system is generally prepared in a hydrocarbon solvent, aliphatic such as methylcyclohexane or aromatic such as toluene. Generally after its synthesis, the catalytic system is used as is in the process for synthesizing the polymer in accordance with the invention. The catalytic system is typically in the form of a catalytic solution, i.e. in a solvent which is preferably the solvent in which it was prepared, and the metal concentration of the catalytic solution, i.e. in rare earth metallocene, is then within a range preferably ranging from 0.0001 to 0.2 mol L 1 , more preferably from 0.001 to 0.03 mol L 1 .

[0035] As with any synthesis carried out in the presence of organometallic compounds, the synthesis of the catalytic system takes place under anhydrous conditions under an inert atmosphere. Typically, reactions are carried out from solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0036] The catalytic system according to the invention is intended to be used in polymer synthesis processes, in particular in the synthesis of polymers containing ethylene, more particularly in the synthesis of polymers containing more than 50 mol% of ethylene. A first process for preparing a polymer which allows in particular the preparation of polyethylene comprises the polymerization of ethylene in the presence of a catalytic system in accordance with the invention.

[0037] A second process for preparing a polymer which in particular allows the preparation of a copolymer of ethylene and a 1,3-diene, preferably a random copolymer of ethylene and a 1,3-diene, comprises the polymerization of a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system in accordance with the invention.

[0038] The polymerization reaction common to both processes according to the invention is a polymerization reaction of a monomer, the monomer being ethylene or a monomer mixture containing ethylene and a 1,3-diene. The monomer mixture containing ethylene and a 1,3-diene preferably contains more than 50 mol% of ethylene, molar percentage calculated with respect to the total of the monomers constituting the monomer mixture containing ethylene and a 1,3-diene. The monomer mixture containing ethylene and a 1,3-diene is preferably a mixture of ethylene and a 1,3-diene or a mixture of ethylene, a 1,3-diene and an α-monoolefin. α-monoolefin is understood to mean an α-olefin which has a single carbon-carbon double bond, the double bonds in aromatic compounds not being taken into account. For example, styrene is considered an α-monoolefin. α-Monoolefin is preferably styrene.1,3-diene is a single compound, i.e., a single (in English "one") 1,3-diene, or a mixture of 1,3-dienes which differ from each other in their chemical structure. Suitable 1,3-dienes include 1,3-dienes having from 4 to 20 carbon atoms. Preferably, the 1,3-diene is 1,3-butadiene, isoprene, myrcene, |3-farnesene or mixtures thereof such as a mixture of at least two of them. The mixture of at least two of them is advantageously a mixture which contains 1,3-butadiene. The 1,3-diene is preferably 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0039] The polymerization is preferably carried out in solution, continuously or discontinuously. The polymerization solvent may be a hydrocarbon, aromatic or aliphatic solvent. Examples of polymerization solvents include toluene and methylcyclohexane. The monomer may be introduced into the reactor containing the polymerization solvent and the catalytic system or, conversely, the catalytic system may be introduced into the reactor containing the polymerization solvent and the monomer. The monomer and the catalytic system may be introduced simultaneously into the reactor containing the polymerization solvent, particularly 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 of 40 to 150°C, preferably 40 to 120°C.The person skilled in the art adapts the polymerization conditions such as the polymerization temperature, the concentration of each of the reactants, the pressure in the reactor according to the composition of the monomer mixture, the polymerization reactor, the desired microstructure and macrostructure of the polymer chain. The polymerization is preferably carried out at constant pressure in monomers, in particular at constant ethylene pressure.

[0040] During the polymerization of ethylene and 1,3-dienes in a polymerization reactor, a continuous addition of ethylene and 1,3-dienes may be carried out into the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the synthesis of random copolymer.

[0041] According to one embodiment of the invention, the polymer prepared is a polyethylene.

[0042] According to another embodiment of the invention, the polymer prepared is a copolymer of ethylene and a 1,3-diene, preferably a random copolymer of ethylene and a 1,3-diene, the 1,3-diene advantageously being 1,3-butadiene, isoprene, myrcene, p-farnesene or mixtures thereof such as a mixture of at least two of them.

[0043] According to a preferred embodiment of the invention, the polymer prepared is a copolymer of ethylene and 1,3-butadiene, preferably a random copolymer of ethylene and 1,3-butadiene.

[0044] According to a particularly preferred embodiment of the invention in which the monomer is a monomer mixture containing ethylene and 1,3-butadiene and the ligands of the catalytic system represented by Cp 1 and Cp 2are each an unsubstituted fluorenyl group of formula C13H8, the prepared polymer contains in addition to the ethylene monomer units and butadiene units cyclic units, 1,2-cyclohexane units of the following formula:

[0045] The cyclic units result from a particular insertion of the ethylene and 1,3-butadiene monomers into the polymer chain, in addition to the conventional ethylene and 1,3-butadiene units, respectively -(CH2-CH2)-, -(CH2-CH=CH-CH2)- and -(CH2-CH(C=CH2))-. The mechanism for obtaining such a microstructure is for example described in the document Macromolecules 2009, 42, 3774-3779. When the polymer in accordance with the invention contains 1,2-cyclohexane units, it preferably contains at most 15 mol% thereof, the percentage being expressed relative to all the repeating units constituting the polymer.

[0046] 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 or methanol. The polymer can be recovered according to conventional techniques known to those skilled in the art, such as for example by precipitation, by evaporation of the solvent under reduced pressure or by stripping with water vapor. In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 22:

[0047] Mode 1: Catalytic system based on at least: a metallocene of formula (Ia), a dialkylmagnesium, a dialkylzinc, {P(Cp 1 )(Cp 2 )Nd(BH4)(i + y)-Ly-N x} (there)

[0048] CP 1 and Cp 2, identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted,

[0049] P being a group bridging the two Cp groups 1 and Cp 2 , and comprising a silicon or carbon atom,

[0050] Nd denoting the neodymium atom,

[0051] L representing an alkali metal chosen from the group consisting of lithium, sodium and potassium,

[0052] N representing a molecule of an ether, x, integer or not, being equal to or greater than 0, y, integer, being equal to or greater than 0.

[0053] Mode 2: Catalytic system according to mode 1 in which Cp 1 and Cp 2 , identical or different, each represents a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

[0054] Mode 3: Catalytic system according to mode 1 or 2 in which Cp 1 and Cp 2 are identical and are selected from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula CisHs.

[0055] Mode 4: Catalytic system according to any one of modes 1 to 3 in which Cp 1 and Cp 2 each represent a fluorenyl group.

[0056] Mode 5: Catalytic system according to any one of modes 1 to 4 in which the P bridge connecting the Cp groups 1 and Cp 2 responds to the formula ZR 1 R 2 , in which Z represents a silicon or carbon atom, R 1 and R 2 , identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms.

[0057] Mode 6: Catalytic system according to mode 5 in which Z represents a silicon atom.

[0058] Mode 7: Catalytic system according to mode 5 or 6 in which R 1 and R 2 each represent a methyl.

[0059] Mode 8: Catalytic system according to any one of modes 1 to 7 in which the metallocene is of formula (Il 1-1), (Il 1-2), (Il 1-3), (Il 1-4) or (Il 1-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (lll-l) [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (111-2) [Me2SiFlu2Nd(p-BH4)(THF)] (111-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (111-4) [Me2SiFlu2Nd(p-BH4)] (HI-5) in which Flu represents the CisHs group.

[0060] Mode 9: Catalytic system according to any one of modes 1 to 8 in which the alkyls of the dialkylmagnesium and dialkylzinc are alkyls containing 2 to 10 carbon atoms.

[0061] Mode 10: Catalytic system according to any one of modes 1 to 9 in which the dialkylmagnesium is of formula (Ilia) MgR 3 R 4 (Ilia) in which the alkyl represented by the symbol R 3is different from the alkyl represented by the symbol R 4 .

[0062] Mode 11: Catalytic system according to mode 10 in which R 3 is butyl and R 4 ethyl or octyl.

[0063] Mode 12: Catalytic system according to any one of modes 1 to 11 in which the dialkylzinc compound is of formula (IIa) ZnR 5 R 6 (Ha) in which the alkyls represented by the symbols R 5 and R 6 are identical.

[0064] Mode 13: Catalytic system according to mode 12 in which R 5 and R 6 are ethyl or octyl.

[0065] Mode 14: Catalytic system according to any one of modes 1 to 13 in which the ratio between the number of moles of Zn of the dialkylzinc compound and the sum of the number of moles of Zn of the dialkylzinc compound and the number of moles of Mg of the dialkylmagnesium compound is greater than 0.01 and less than 0.95.

[0066] Mode 15: Catalytic system according to any one of modes 1 to 14 in which the ratio between the number of moles of Zn of the dialkylzinc compound and the sum of the number of moles of Zn of the dialkylzinc compound and the number of moles of Mg of the dialkylmagnesium compound is greater than 0.1 and less than 0.85.

[0067] Mode 16: Catalytic system according to any one of modes 1 to 15 in which the ratio between the sum of the number of moles of Mg of the organomagnesium compound and the number of moles of Zn of the zinc compound and the number of moles of rare earth metal of the metallocene (N Nd) ranges from 1.5 to 200.

[0068] Mode 17: Catalytic system according to any one of modes 1 to 16 in which the ratio between the sum of the number of moles of Mg of the organomagnesium compound and the number of moles of Zn of the zinc compound and the number of moles of rare earth metal of the metallocene (NNU) ranges from 1.5 to less than 20.

[0069] Method 18: A process for preparing a polymer which comprises polymerizing ethylene or a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalyst system defined in any one of methods 1 to 17.

[0070] Method 19: Preparation process according to method 18 in which the 1,3-diene is 1,3-butadiene, isoprene, myrcene, p-farnesene or mixtures thereof. Method 20: Preparation process according to method 18 or 19 in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0071] Method 21: Preparation process according to any one of methods 18 to 20 in which the polymer is a polyethylene or a copolymer of ethylene and a 1,3-diene.

[0072] Method 22: Preparation process according to method 21 in which the copolymer of ethylene and a 1,3-diene is a random copolymer of ethylene and a 1,3-diene.

[0073] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of the exemplary embodiments of the invention, given for illustrative and non-limiting purposes.

[0074] Examples

[0075] Ethylene homopolymers and ethylene-butadiene copolymers were synthesized using the metallocene {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 prepared according to the procedure described in patent application WO 2007054224. Unless otherwise indicated, organomagnesium and zinc compounds are commercial products. The following were used: butyloctylmagnesium in solution in heptane at 0.88 mol L 1 from Chemtura; diethylzinc in hexane solution at 1 mol L 1 from Sigma-Aldrich; zinc dibromide in powder form at 99.99% from Sigma-Aldrich; octylmagnesium bromide at 2.0 mol L 1 in Sigma-Aldrich diethyl ether.

[0076] Dioctylzinc is synthesized according to the following procedure:

[0077] 10 mL of a 2.0 mol / L solution of octylmagnesium bromide in diethyl ether (9.61 g, 20 mmol) is added dropwise to 2.25 g of zinc dibromide (10 mmol) in 20 mL of sodium / benzophenone distilled diethyl ether. The reaction mixture is stirred overnight at room temperature and then the solvent is evaporated under vacuum. 20 mL of hexane is added and the solution is filtered through Celite. The solvent is then evaporated under vacuum. The product obtained is distilled under vacuum at 120 °C to obtain a colorless oil (1.61 g, 5.5 mmol, 55% yield). 3.9 mL of toluene is added to obtain a 1.0 mol L solution. 1 .

[0078] The polymers were characterized using the methods described below.

[0079] The ethylene, N35 grade, comes from Air Liquide and is used without prior purification.

[0080] 1,3-Butadiene is purified on alumina guards.

[0081] The toluene solvent from BioSolve is dried and purified on an alumina column in a solvent fountain from mBraun and used under an inert atmosphere.

[0082] All reactions are carried out under an inert atmosphere.

[0083] High-temperature size exclusion chromatography (HT-SEC) for polyethylenes: High-temperature size exclusion chromatography (HT-SEC) analyses were performed using a Viscotek instrument (Malvern Instruments) equipped with 3 columns (PLgel Olexis 300 mm x 7 mm ID from Agilent Technologies) and 3 detectors (refractometer, differential viscometer and light scattering). 200 pL of a sample solution at a concentration of 8 mg mL 1 were eluted in 1,2,4-trichlorobenzene using a flow rate of 1 mL min 1at 150 °C. The mobile phase was stabilized with 2,6-di(tert-butyl)-4-methylphenol (400 mg L -1 ). OmniSEC software was used for data acquisition and analysis. The number-average molar masses (M n ) and in mass (M w ) of synthesized polyethylenes were calculated using a calibration curve obtained from standard polyethylenes (M p 338, 507, 770, 1890, 17000, 27300, 43400, 53100, 65700, 78400 g mol -1 ) from Polymer Standard Service (Mainz).

[0084] THF size exclusion chromatography (SEC-THF) for ethylene and 1,3-butadiene copolymers:

[0085] Size exclusion chromatography analyses were performed using a Viscotek apparatus (Malvern Instruments) equipped with 3 columns (SDVB, 5 μm, 300 x 7.5 mm from Polymer Standards Service), a guard column and 3 detectors (differential refractometer and viscometer, and light scattering). 1 mL of a sample solution with a concentration of 5 mg mL 1 in THF was filtered through a 0.45 μm PTFE membrane. 100 pL of this solution was eluted in THF using a flow rate of 0.8 mL min 1 at a temperature of 35 °C. OmniSEC software was used for data acquisition and analysis. The number-averaged molar masses (M n ) and in mass (M w ) of synthesized ethylene and butadiene copolymers were calculated using a universal calibration curve obtained from standard polystyrenes (M p : 1,306 to 2,520,000 g mol -1 ) from Polymer Standards Service (Mainz).

[0086] Nuclear Magnetic Resonance (NMR):

[0087] High-resolution NMR spectroscopy of the polymers was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO proton probe and on a Bruker 400 Avance II spectrometer operating at 400 MHz equipped with a PSEX probe. 13 C 10 mm for carbon. Acquisitions were made in a mixture of tetrachloroethylene (TCE) and deuterated benzene (CeDe) (2 / 1 v / v) at 363 K for ethylene homopolymers, and in deuterated chloroform (CDCI3) at 298 K for ethylene and butadiene copolymers. Samples were analyzed at a concentration of 1% by mass for the proton and 5% by mass for carbon. Chemical shifts are given in ppm, relative to the proton signal of deuterated benzene set at 7.16 ppm (respectively of deuterated chloroform at 7.26 ppm) and to the carbon signal of TCE set at 120.65 ppm.

[0088] Example 1: Synthesis of polyethylene (example not in accordance with the invention:

[0089] 196 mL of toluene taken from the solvent fountain (SPS800 MBraun) are introduced into a 250 mL inerted flask equipped with a magnetic olive. 1.14 mL of butyloctylmagnesium in heptane (0.88 mol L -1) are introduced into the flask under stirring. 8.0 mg (12.5 pmoles in neodymium) of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 are then introduced into the flask. The catalytic solution is transferred using a cannula into a stirred 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar and then the reactor is pressurized to 4 bar (absolute pressure) of ethylene and the temperature is simultaneously brought to 80 °C. The pressure is kept constant in the reactor using a tank containing ethylene. When the desired quantity of ethylene has been consumed, i.e. after 82 min, the reactor is degassed and then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60 °C for 48 h. 3.6 g of polyethylene is recovered (activity of 200 kg / mol / h) with a number average molar mass of 2800 g mol 1 and a dispersity of 2.1.

[0090] Example 2: Synthesis of polyethylene (example in accordance with the invention:

[0091] 196 mL of toluene taken from the solvent fountain (SPS800 MBraun) are introduced into an inerted 250 mL flask equipped with a magnetic olive. 0.96 mL of diethylzinc in toluene (1 mol L -1 ) then 0.09 mL of butyloctylmagnesium in heptane (0.88 mol L -1) are introduced into the flask under stirring. 8.0 mg (12.5 pmoles in neodymium) of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 are then introduced into the flask. The catalytic solution is transferred using a cannula into a stirred 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar and then the reactor is pressurized to 4 bar of ethylene and the temperature is simultaneously brought to 80 °C. The pressure is kept constant in the reactor using a tank containing ethylene. When the desired amount of ethylene has been consumed, i.e. after 6 min, the reactor is degassed and then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60 °C for 48 h. 4.1 g of polyethylene is recovered (activity of 3700 kg / mol / h) with a number average molar mass of 2300 g mol 1 and a dispersity of 1.1.

[0092] Example 3: Synthesis of copolymer of ethylene and 1,3-butadiene (example in accordance with the invention:

[0093] 199 mL of toluene taken from the solvent fountain (SPS800 MBraun) are introduced into a 250 mL inerted flask equipped with a magnetic olive. A given volume of a 0.88 M butyloctylmagnesium solution in heptane and a given volume of a 0.05 M diethylzinc solution in toluene are introduced into the flask while stirring.

[0094] 32.0 mg (50 pmol as neodymium) of {(Me2Si(Ci3H8)2)Nd(-BH4)[(-BH4)Li(THF)]}2 are then introduced into the flask. The catalytic solution is transferred using a cannula into a 250 mL stirred reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar and then the reactor is pressurized to 4 bar with an ethylene / 1,3-butadiene mixture 80 / 20 mol / mol and the temperature is simultaneously brought to 80 °C. The pressure is kept constant in the reactor using a tank containing a gaseous mixture of ethylene / 1,3-butadiene 80 / 20 mol / mol. When the desired quantity of monomers has been consumed, the reactor is degassed and the temperature is brought back to 20 °C. The polymer is precipitated in methanol containing 2,6-di-tert-butyl-4-methylphenol, washed with methanol and oven dried at 60°C under vacuum for 48 hours.The introduced volumes of organomagnesium and zinc compound (respectively VBOM G and VEtzzn), the polymerization times (Poly duration), the quantities of polymers prepared (Polymer mass), the values ​​of M. n and dispersity of the prepared polymers and the catalytic activity values ​​are reported in Table 1 below.

[0095] Table 1

[0096] The examples show that the catalytic system containing both a dialkylmagnesium and a dialkylzinc compound exhibits a catalytic activity in the polymerization of ethylene which is much higher than that of a catalytic system lacking the zinc compound.

[0097] The catalytic system according to the invention is as versatile as the catalytic system devoid of zinc compound: like the catalytic system devoid of zinc compound, it allows the production of both polyethylenes and copolymers of ethylene and 1,3-diene, in this case 1,3-butadiene. The copolymers of ethylene and 1,3-butadiene of tests 3-1 to 3-3 have the same microstructure as the copolymer of ethylene and 1,3-butadiene of test 3-4, namely 75.9% of ethylene unit, 10.4% of 1,2-cyclohexane unit, 7.7% of butadiene unit in the vinyl form and 6.0% of butadiene unit in the 1,4-trans form, the percentages being molar relative to all the repeating units constituting the copolymer. Furthermore, the molar mass and dispersity values ​​are almost identical.

[0098] In the homopolymerization of ethylene, the catalytic system allows the production of polymers with low dispersity, lower than that of the polymers obtained with the catalytic system without zinc compound.

[0099] In the copolymerization of ethylene and 1,3-butadiene, the addition of the zinc compound has no impact on either the microstructure or the macrostructure, which reflects the versatility of the catalytic system according to the invention both in the homopolymerization of ethylene and the copolymerization of ethylene and 1,3-butadiene.

Claims

Claims 1. Catalytic system based on at least: a metallocene of formula (Ia), a dialkylmagnesium, a dialkylzinc, {P(Cp 1 )(Cp 2 )Nd(BH4)(i + y)-Ly-N x} (there) CP 1 and Cp 2 , identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P being a group bridging the two Cp groups 1 and Cp 2 , and comprising a silicon or carbon atom, Nd denoting the neodymium atom, L representing an alkali metal chosen from the group consisting of lithium, sodium and potassium, N representing a molecule of an ether, x, integer or not, being equal to or greater than 0, y, integer, being equal to or greater than 0.

2. Catalytic system according to claim 1 in which Cp 1 and Cp 2 , identical or different, each represents a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

3. Catalytic system according to claim 1 or 2 in which Cp 1 and Cp 2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula CisHs, preferably each representing a fluorenyl group.

4. Catalytic system according to any one of claims 1 to 3 in which the bridge P connecting the Cp groups 1 and Cp 2 responds to the formula ZR 1 R 2 , in which Z represents a silicon or carbon atom, R 1 and R 2 , identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl.

5. Catalytic system according to any one of claims 1 to 4 being of formula (III-1), (111-2), (111-3), (111-4) or (111-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (lll-l) [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (111-2) [Me2SiFlu2Nd(p-BH4)(THF)] (111-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (111-4) [Me2SiFlu2Nd(p-BH4)] (111-5) in which Flu represents the CisHs group.

6. Catalytic system according to any one of claims 1 to 5 in which the alkyls of the dialkylmagnesium and dialkylzinc are alkyls containing 2 to 10 carbon atoms.

7. Catalytic system according to any one of claims 1 to 6 in which the dialkylmagnesium is of formula (IIIa) MgR 3 R 4 (Ilia) in which the alkyl represented by the symbol R 3 is different from the alkyl represented by the symbol R 4 , preferably R 3being butyl and R 4 ethyl or octyl.

8. Catalytic system according to any one of claims 1 to 7 in which the dialkylzinc compound is of formula (IIa) ZnR 5 R 6 (Ha) in which the alkyls represented by the symbols R 5 and R 6 are identical, preferably ethyl or octyl.

9. Catalytic system according to any one of claims 1 to 8 in which the ratio between the number of moles of Zn of the dialkylzinc compound and the sum of the number of moles of Zn of the dialkylzinc compound and the number of moles of Mg of the dialkylmagnesium compound is greater than 0.01 and less than 0.95, preferably greater than 0.1 and less than 0.

85.

10. Catalytic system according to any one of claims 1 to 9 in which the ratio between the sum of the number of moles of Mg of the organomagnesium compound and the number of moles of Zn of the zinc compound and the number of moles of rare earth metal of the metallocene (NNCI) ranges from 1.5 to 200, preferably from 1.5 to less than 20.

11. A process for preparing a polymer which comprises the polymerization of ethylene or a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system defined in any one of claims 1 to 10.

12. Preparation process according to claim 11 in which the 1,3-diene is 1,3-butadiene, isoprene, myrcene, p-farnesene or mixtures thereof.

13. Preparation process according to claim 11 or 12 in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

14. Preparation process according to claim 11 in which the polymer is a polyethylene.

15. Preparation process according to any one of claims 11 to 13 in which the polymer is a copolymer of ethylene and a 1,3-diene, preferably a random copolymer of ethylene and a 1,3-diene.

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