ketone functionalization process of polyethylenes and copolymers containing ethylene units and 1,3-diene units.

Abstract

The invention relates to a process for the selective preparation of a polymer bearing a ketone function at the chain end which comprises the steps a) to c) which are a) the polymerization reaction of ethylene or of a monomer mixture containing ethylene and a 1,3-diene in the presence of a neodymocene borohydride, b) the reaction of a zinc dihalide with the reaction product of step a), c) the reaction of an acid halide with the reaction product of step b).

Description

Title of the invention: process for ketone functionalization of polyethylenes and copolymers containing ethylene units and 1,3-diene units.

[0001] The field of the present invention is that of processes for the selective functionalization of polyethylenes and copolymers containing ethylene units and 1,3-diene units.

[0002] Highly saturated polymers such as polyethylenes and diene copolymers rich in ethylene units are essentially hydrocarbon-based and have little affinity with polar materials, which has the consequence of restricting the field of application of these highly saturated hydrocarbon-based polymers. In order to improve this affinity, the introduction of a single or several ketone functions has been described in the case of polyethylenes. For example, the synthesis of a copolymer of ethylene and carbon monoxide is widely described, but the synthesis method does not apply to copolymers of ethylene and an α-olefin such as a 1,3-diene or a mixture of a 1,3-diene and a vinylaromatic compound. Furthermore, the synthesis method does not selectively lead to the introduction of a ketone function at the chain end. The introduction of a single ketone function at the chain end of a polyethylene is also described.For example, Polymer Science, Ser. B, Vol. 46, Nos. 9-10, 2004, 308-311 describes the reaction of nitrous oxide and a polyethylene that carries a vinyl group at the chain end. The introduction of the ketone function at the chain end of the polyethylene results from the oxidation reaction of the double bond of the vinyl group by nitrous oxide. Therefore, it appears that the synthesis method is not applicable to the selective functionalization at the chain end of copolymers of ethylene and a 1,3-diene that contain double bonds also outside the chain ends.

[0003] The Applicants have described, for example, in documents WO 2007054223 and WO 2007054224, catalytic systems containing a neodymium metallocene and an organomagnesium compound for the synthesis of copolymers of ethylene and 1,3-butadiene. The organomagnesium compound is used in the catalytic system as a co-catalyst to activate the metallocene for polymerization. The catalytic systems are useful in the synthesis of both polyethylene and copolymers of ethylene and 1,3-diene.

[0004] The Applicants, continuing their efforts, have developed a new process which allows the functionalization of polymers such as polyethylenes and copolymers containing ethylene units and 1,3-diene units, with a very high selectivity towards ketone functionalization. The high selectivity towards ketone functionalization is made possible by the synthesis of a polymer intermediate that contains a bond between a constituent carbon of the polymer and a zinc atom.

[0005] Thus, a first subject of the invention is a process which is a process for preparing a polymer carrying a ketone function, preferably at the chain end, which process comprises the following steps a), b) and c), (a) the polymerization reaction of ethylene or of a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system based on at least: of a metallocene of formula (la) of an organomagnesium {P(Cp1)(Cp2)Nd(BH4)(1+y).Ly-Nx} (la) Cp1 and Cp2, identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, Being a group bridging the two groups Cp1 and Cp2, 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, whole number or not, being equal to or greater than 0, y, an integer, being equal to or greater than 0, b) reacting a zinc dihalide with the reaction product of step a), c) reacting an acid halide with the reaction product of step b).

[0006] Another object of the invention is a process for preparing a polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a chain of the polymer and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX the term "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, X being a halogen atom, which process comprises steps a) and b) of the process, first subject of the invention, the polymer being obtained at the end of step b).

[0007] The invention also relates to a polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a chain of the polymer and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX, the deno mination "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, X being a halogen atom. Detailed description

[0008] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​greater than "a" and less than "b" (i.e., excluding the limits a and b) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0009] 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. In the same way, the compounds mentioned may also come from the recycling of materials already used, 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.

[0010] By the expression "based on" used to define the constituents of the catalytic system or catalytic composition, we mean the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other.

[0011] Step a) is a polymerization reaction of ethylene or of a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system.

[0012] An essential constituent of the catalytic system useful for the purposes of the invention is a metallocene.

[0013] In the present application, the term 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 groups Cp1 and Cp2 linked together by a P bridge. These groups Cp1 and Cp2, identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, these groups possibly being substituted or unsubstituted.

[0014] 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 trialkylsilyl radicals such as SiMe3. The choice of radicals is also guided by the accessibility to the corresponding molecules that are substituted cyclopentadienyl, fluorenyl and indene groups, because the latter are commercially available or easily synthesized.

[0015] 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.

[0016] 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. P

[0017] 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.

[0018] Preferably, Cp1 and Cp2, identical or different, each represent a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

[0019] More preferably, Cp1 and Cp2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula CnH8. Advantageously, Cp1 and Cp2 are identical and each represent an unsubstituted fluorenyl group of formula CnH8, represented by the symbol Flu.

[0020] Any ether which has the power to complex the alkali metal, in particular diethyl ether and tetrahydrofuran, is suitable as an ether.

[0021] The bridge P connecting the groups Cp1 and Cp2 preferably corresponds to the formula ZR'R2, in which Z represents a silicon or carbon atom, R1 and R2, identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl. In the formula ZR'R2, Z advantageously represents a silicon atom, Si.

[0022] The metallocene useful for the synthesis of the catalytic system useful for the purposes of the invention may be in the form of crystallized or non-crystalized 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.

[0023] According to a particularly preferred embodiment, the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (III-1) [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (III-2) [Me2SiFlu2Nd(p-BH4)(THF)] (III-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (III-4) [Me2SiFlu2Nd(p-BH4)] (III-5) in which Flu represents the Ci3H8 group.

[0024] Another essential constituent of the catalytic system useful for the purposes of the invention is an organomagnesium, co-catalyst of the catalytic system. In a known manner, organomagnesium is understood to mean an organometallic compound which contains a bond between a magnesium atom and a carbon atom. Organomagnesiums include Grignard reagents and diorganomagnesiums. Also in a known manner As is well known, Grignard reagents are organometallic compounds in which the magnesium atom is bonded to a carbon atom and a halogen atom and diorganomagnesium compounds are organometallic compounds in which the magnesium atom is bonded respectively to two carbon atoms belonging to a distinct carbon chain. The diorganomagnesium compounds useful for the purposes of the invention are typically of formula R2Mg in which the symbols R, identical or different, represent a carbon group. A carbon chain is understood to mean a chain which contains at least one carbon atom, such as an alkyl group.

[0025] According to one embodiment of the invention, the organomagnesium is a Grignard reagent, preferably a halide of an alkylmagnesium typically of formula RMgX, R representing an alkyl, X a halogen atom, preferably a chlorine atom or a bromine atom, more preferably a chlorine atom. The organomagnesium is even more preferably a chloride of an alkylmagnesium.

[0026] According to another embodiment of the invention, the organomagnesium compound is a diorganomagnesium compound, preferably a dialkylmagnesium compound. The dialkylmagnesium compound is preferably of formula MgR3R4 in which the alkyl represented by the symbol R3 is different from the alkyl represented by the symbol R4.

[0027] Preferably, the alkyls of the halide of an alkylmagnesium and of the diorgano-magnesium contain 2 to 10 carbon atoms. Advantageously, the alkyl of the halide of an alkylmagnesium is butyl. Advantageously, R3 is butyl and R4 is ethyl or octyl.

[0028] The catalytic system useful for the purposes of the invention can be prepared in a traditional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223, the co-catalyst being the organomagnesium compound useful for the purposes of the invention. For example, in a hydrocarbon solvent, the organomagnesium compound is 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 the organomagnesium and metallocene reacted to form the catalytic system are such that the ratio between the number of moles of Mg in the organomagnesium and the number of moles of rare earth metal in the metallocene preferably ranges from 1 to 200, more preferably from 1 to less than 20. The range of values ​​from 1 to less than 20 is particularly more favorable for obtaining polymers with high molar masses.

[0029] The catalytic system is generally in the form of a solution, i.e. in a solvent, in particular in a hydrocarbon solvent. The hydrocarbon solvent may be aliphatic such as methylcyclohexane or aromatic such as toluene. The hydrocarbon solvent is preferably aliphatic, so more preferably methylcyclohexane. Generally, the catalytic system is stored in the form of a solution in the hydrocarbon solvent before being used in polymerization. We can then speak of a catalytic solution which includes the catalytic system and the hydrocarbon solvent. The concentration of the catalytic solution is typically defined by the metallocene metal content in the solution. The metallocene metal concentration has a value preferably ranging from 0.0001 to 0.2 mol L *, more preferably from 0.001 to 0.03 mol L *.

[0030] Like any synthesis carried out in the presence of an organometallic compound, the synthesis of the catalytic system takes place under anhydrous conditions under an inert atmosphere. Typically, the reactions are carried out from anhydrous solvents and compounds under anhydrous nitrogen or argon.

[0031] The polymerization reaction 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, a 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. The 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-famesene] 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.

[0032] 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, in particular into the case of continuous polymerization. The polymerization is typically carried out under anhydrous conditions and in the absence of oxygen, in the possible presence of an inert gas, in a generally stirred reactor. The polymerization temperature generally varies in a range from 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. The polymerization is preferably carried out at constant pressure in monomers, in particular at constant ethylene pressure.

[0033] 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 in the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the synthesis of random copolymer.

[0034] According to one embodiment of the invention, the polymer chains prepared at the end of step a) are polyethylene chains.

[0035] According to another embodiment of the invention, the polymer chains prepared at the end of step a) are copolymer chains of ethylene and a 1,3-diene, preferably random copolymer chains of ethylene and a 1,3-diene, the 1,3-diene preferably being 1,3-butadiene, isoprene, myrcene, [3-farnesene or their mixtures such as a mixture of at least two of them, more preferably 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0036] According to yet another embodiment of the invention, the polymer chains prepared at the end of step a) are copolymer chains of ethylene and 1,3-butadiene, preferably random copolymer chains of ethylene and 1,3-butadiene.

[0037] According to any one of the embodiments of the invention, the polymer chains prepared at the end of step a) are chains which preferably contain more than 50 mol% of ethylene.

[0038] 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 Cp1 and Cp2 are each an unsubstituted fluorenyl group of formula C13H8, the polymer chains prepared contain, in addition to the ethylene monomer units and the butadiene units, cyclic units, 1,2-cyclohexane units of the following formula: CHS—CH2 / \ CHS( CH2 \ / CK CH / \ / V \

[0039] 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 contains 1,2-cyclohexane units, it preferably contains at most 15 mol%, the percentage being expressed relative to all the repeating units constituting the polymer.

[0040] Step b) is a reaction between the reaction product of step a) and a zinc dihalide, typically added to the reaction medium resulting from step a). The zinc dihalide is generally added in the form of a solution such as a solution in ether. Before adding the zinc dihalide, the reactor is preferably degassed and inerted. Degassing the reactor removes residual gaseous monomers and also facilitates the addition of the zinc dihalide to the reactor. Alternatively, the zinc dihalide may be injected by overpressure into the reactor. Inerting the reactor, for example with nitrogen, makes it possible not to deactivate the carbon-metal bonds present in the reaction medium and necessary for the reaction of the zinc dihalide with the polymer chains formed during the polymerization reaction.During the addition of the zinc dihalide as well as after, the reactor is preferentially stirred to promote the dispersion of the zinc dihalide in the reaction medium obtained at the end of step a), the reaction medium generally being maintained at the temperature of step a). The reaction time of step b) is typically 5 to 45 minutes.

[0041] Preferably, the ratio between the number of moles of zinc dihalide and the number of moles of carbon-magnesium bond per mole of the organomagnesium is greater than 0.45 and preferably less than 1, more preferably less than 0.55. For example, in a halide of an alkylmagnesium such as n-butylmagnesium chloride, there is one carbon-magnesium bond per mole of the halide; in dialkylmagnesiums such as butyloctylmagnesium (BOMAG) there are two carbon-magnesium bonds per mole of the dialkylmagnesium. Within these preferred ranges of the ratio between the number of moles of zinc dihalide and the number of moles of carbon-magnesium bond per mole of the organomagnesium, both the rates of functions in ketone function and the rates of selectivity with respect to the functionalization reaction are high. The ratio between the number of moles of zinc dihalide and the number of moles of magnesium carbon bond per mole of the organomagnesium can also be greater than 1, without the selectivity of the reaction being modified, but a value greater than 1 represents an additional cost of the process linked to the use of a larger quantity of zinc dihalide.

[0042] The zinc dihalide is preferably zinc dichloride, zinc dibromide or a mixture of zinc dichloride and zinc dibromide, more preferably zinc dichloride or zinc dibromide.

[0043] Step b) is followed by step c) which is a modification reaction with an acid halide to introduce a ketone function into the polymer. As is well known, acid halides, also called acyl halides, are halogenated derivatives of carboxylic acids in which the OH group of the carboxylic acid function COOH is substituted by a halogen atom. Acid halides are therefore compounds which contain one or more COX1 groups, X1 denoting a halogen atom.

[0044] The acid halide can be added pure or diluted in a hydrocarbon solvent, preferably aliphatic such as methyl hexane or aromatic such as toluene. The acid halide is left in contact with the polymer chains for the time necessary for the reaction between the acid halide and the polymer chains produced in the previous step, which is step b). As with any reaction involving organometallic species, step c) is typically carried out under an inert atmosphere, for example nitrogen, so as not to deactivate the carbon-metal bonds present in the reaction medium and necessary for the reaction between the polymer chains and the acid halide. The reaction between the acid halide and the polymer chains can typically be followed by chromatographic analysis to monitor the consumption of the acid halide.Preferably, it is carried out at a temperature ranging from 23 to 120°C, preferably from 70°C to 90°C, for 1 to 120 minutes, preferably from 10 to 40 minutes, with stirring. The modification reaction is preferably carried out with one molar equivalent of COX1 group relative to the total number of carbon-magnesium bonds per mole of co-catalyst and carbon-zinc bonds per mole of zinc compound. The ratio between the number of molar equivalents of COX1 group and the total number of carbon-magnesium bonds per mole of co-catalyst and carbon-zinc bonds per mole of zinc compound can however vary within a wide range, for example from 0.1 to 10, depending on the desired level of polymer carrying a ketone function in the prepared polymer. A ratio close to 1, typically ranging from 0.85 to 1.05, favors the highest levels of ketone function.

[0045] The acid halide may contain one or more COX1 groups, X1 denoting a halogen atom. The acid halide may be an aliphatic or aromatic compound. An aromatic acid halide is preferred from the point of view of characterizing the modified polymer, in particular by highlighting the aromatic ring in the modified polymer by nuclear magnetic resonance analysis. Preferably, the acid halide is of formula Ar-(COX')n, Ar representing an aromatic ring, preferably a benzene ring, n an integer equal to 1, 2 or 3, X1 a halogen atom. The aromatic ring, in particular benzene, may carry one or more substituents other than the COX1 groups.Suitable for this purpose are 4-methoxybenzoyl chloride, p-toluoyl chloride, 4-iodobenzoyl chloride, 4-bromobenzoyl chloride, 4-nitrobenzoyl chloride, 4-methoxy benzoyl chloride, 4-(methoxymethyl)benzoyl chloride, 3-methoxy-benzoyl bromide, 4-(dimethylamino)benzoyl chloride, 4-[(dimethylamino)methyl]benzoyl chloride, 4-[2-(dimethylamino)ethyl]benzoyl chloride, trimesoyl chloride, 5-methoxy-1,3-benzenedicarbonyl dichloride, benzoyl bromide, isophthaloyl dichloride, terephthaloyl chloride.

[0046] Acid halides having a single COX1 group provide access to polymers carrying a ketone function at the chain end. Acid halides having two COX1 groups can lead to coupled polymers which result from the coupling between two polymer chains. Acid halides having more than two COX1 groups can lead to star polymers which result from the coupling between at least three polymer chains.

[0047] According to any one of the embodiments of the invention, the acid halide is advantageously an acid chloride, in which case the COX1 group is the COQ group.

[0048] Once the polymer chains have been modified, an additional step can be carried out which makes it possible to deactivate the reactive sites still present in the reaction medium, for example by adding a terminating agent to the reaction medium or by pouring the reaction medium onto a solution containing the terminating agent. The terminating agent is generally in stoichiometric excess. The terminating agent is typically a protic compound, a compound which comprises a relatively acidic proton. Examples of terminating agents which may be mentioned are water, carboxylic acids, in particular C2-Ci8 fatty acids such as acetic acid, stearic acid, aliphatic or aromatic alcohols, such as methanol, ethanol, isopropanol, and phenolic antioxidants.The modified polymer can be separated from the reaction medium according to methods well known to those skilled in the art, for example by an operation of evaporation of the solvent under reduced pressure, by precipitation or by a steam stripping operation.

[0049] The polymer prepared after reaction with the acid halide carries one or more ketone functions. The modification reaction for introducing a ketone function into the polymers prepared according to the ketone functionalization process in accordance with the invention is highly selective. The selectivity rate of the modification reaction reaches 100% or almost 100% in ketone function.

[0050] The high selectivity of the functionalization reaction in ketone function is made possible thanks to the synthesis of the polymers obtained at the end of step b). The polymers obtained at the end of step b), another object of the invention, have the essential characteristic of containing a bond between a carbon atom of the terminal monomer unit constituting a polymer chain and a zinc atom. They are of formula (poly)2Zn or (poly)ZnX, the name "poly" in the formula designating the polymer chain, X being a halogen atom. The polymer chain designated by the name "poly" is typically a polymer chain prepared at the end of step a), in particular a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, more particularly a copolymer chain of ethylene and a 1,3-diene. The copolymer chain designated by the name “poly” is advantageously statistical.The copolymer chain designated by the name “poly” very advantageously contains cyclic units, 1,2-cyclohexane units of the following formula: . CHs—CHg / x ChV: CH? \ / x X

[0051] When the copolymer chain contains 1,2-cyclohexane units, it preferably contains at most 15% by mole, the percentage being expressed relative to all the repeating units constituting the copolymer chain.

[0052] According to any one of the embodiments of the invention in which the copolymer chain designated by the name "poly" is a copolymer chain of ethylene and a 1,3-diene, the 1,3-diene of the copolymer chain designated by the name "poly" is advantageously 1,3-butadiene, isoprene, myrcene, [3-farnesene or their mixtures such as a mixture of at least two of them, more advantageously 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0053] According to any one of the embodiments of the invention, the halogen atom X in the formula (poly)ZnX is advantageously a chlorine atom or a bromine atom, more advantageously a chlorine atom.

[0054] In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 31:

[0055] Method 1: Process for the preparation of a polymer carrying a ketone function, preferably at the chain end, which process comprises the following steps a), b) and c), (a) the polymerization reaction of ethylene or of a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system based on at least: of a metallocene of formula (la) of an organomagnesium {P(Cp9(Cp2)Nd(BH4)(1+y)^ Cp1 and Cp2, identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, Being a group bridging the two groups Cp1 and Cp2, 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, whole number or not, being equal to or greater than 0, y, an integer, being equal to or greater than 0, b) reacting a zinc dihalide with the reaction product of step a), c) reacting an acid halide with the reaction product of step b).

[0056] Mode 2: Process according to mode 1 in which the organomagnesium is a Grignard reagent or a diorganomagnesium.

[0057] Mode 3: Process according to mode 1 or 2 in which the organomagnesium is a halide of an alkylmagnesium.

[0058] Mode 4: Process according to any one of modes 1 to 3 in which the organomagnesium compound is a chloride of an alkylmagnesium.

[0059] Mode 5: Process according to mode 2 in which the organomagnesium is a dialkyl-magnesium.

[0060] Mode 6: Process according to any one of modes 3 to 5 in which the alkyls of the halide of an alkylmagnesium and of the diorganomagnesium contain 2 to 10 carbon atoms.

[0061] Mode 7: Process according to mode 5 or 6 in which the dialkylmagnesium is of formula (Ilia) MgR3R4 (Ilia) in which the alkyl represented by the symbol R3 is different from the alkyl represented by the symbol R4.

[0062] Mode 8: Process according to mode 7 in which R3 is butyl and R4 ethyl or octyl.

[0063] Mode 9: Process according to mode 3, 4 or 6 in which the alkyl of the halide of a alkylmagnesium is butyl.

[0064] Mode 10: Process according to any one of modes 1 to 9 in which the zinc dihalide is zinc dichloride, zinc dibromide or a mixture of zinc dichloride and zinc dibromide.

[0065] Mode 11: Process according to any one of modes 1 to 10 in which Cp1 and Cp2, identical or different, each represent a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

[0066] Mode 12: Process according to any one of modes 1 to 11 in which Cp1 and Cp2 are identical and are selected from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C13H8.

[0067] Mode 13: Process according to any one of modes 1 to 12 in which Cp1 and Cp2 each represent a fluorenyl group.

[0068] Method 14: Process according to any one of methods 1 to 13 in which the bridge P connecting the groups Cp1 and Cp2 corresponds to the formula ZR'R2, in which Z represents a silicon or carbon atom, R1 and R2, identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms.

[0069] Mode 15: Process according to any one of modes 1 to 14 in which R1 and R2 each represent a methyl.

[0070] Mode 16: Method according to any one of modes 1 to 15 in which Z represents a silicon atom.

[0071] Method 17: Process according to any one of methods 1 to 16 in which the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (III-1) [{Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (III-2) [Me2SiFlu2Nd(p-BH4)(THF)] (III-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (III-4) [Me2SiFlu2Nd(p-BH4)] (III-5) in which Flu represents the group Ci3H8.

[0072] Mode 18: Process according to any one of modes 1 to 17 in which the 1,3-diene is 1,3-butadiene, isoprene, myrcene, [3-famesene or mixtures thereof.

[0073] Mode 19: Process according to any one of modes 1 to 18 in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0074] Mode 20: Process according to any one of modes 1 to 19 in which the ratio between the number of moles of zinc dihalide and the number of moles of magnesium carbon bond per mole of the organomagnesium is greater than 0.45.

[0075] Mode 21: Process according to any one of modes 1 to 20 in which the ratio between the number of moles of zinc dihalide and the number of moles of magnesium carbon bond per mole of the organomagnesium is less than 1.

[0076] Mode 22: Process according to any one of modes 1 to 21 in which the ratio between the number of moles of zinc dihalide and the number of moles of magnesium carbon bond per mole of the organomagnesium is less than 0.55.

[0077] Method 23: Process according to any one of methods 1 to 22 in which the acid halide is of formula Ar-(COX')n, Ar representing an aromatic cycle, preferably a benzene cycle, n an integer equal to 1, 2 or 3, X1 a halogen atom.

[0078] Mode 24: Process according to any one of modes 1 to 23 in which the acid halide is an acid chloride.

[0079] Mode 25: Process for preparing a polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a polymer chain and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX, the name "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, X being a halogen atom, which process comprises steps a) and b) defined in any one of modes 1 to 24, the polymer being obtained at the end of step b).

[0080] Mode 26: Polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a polymer chain and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX, the name "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, X being a halogen atom.

[0081] Mode 27: Polymer according to mode 26 in which the halogen atom X in the formula (poly)ZnX is a chlorine atom or a bromine atom.

[0082] Mode 28: Polymer according to mode 27 in which the name “poly” designates a copolymer chain of ethylene and a 1,3-diene.

[0083] Mode 29: Polymer according to mode 28 in which the 1,3-diene is 1,3-butadiene, isoprene, myrcene, [3-famesene or mixtures thereof.

[0084] Mode 30: Polymer according to mode 28 or 29 in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

[0085] Mode 31: Polymer according to any one of modes 26 to 30 in which the copolymer chain containing ethylene units and units of a 1,3-diene contains 1,2-cyclohexane units of the following formula: CHS—CH2: \ CHg'^ k CH- CH / \ A

[0086] 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. Examples

[0087] Ethylene homopolymers and ethylene-butadiene copolymers were prepared 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. The organomagnesium and zinc compounds are commercial products. Unless otherwise indicated, the following are used: butyloctylmagnesium in heptane at 0.88 mol L 1 from Chemtura; butylmagnesium chloride in diethyl ether at 2 mol L 1 from Sigma Aldrich; Sigma Aldrich Paratoluoyl Chloride, 98% Purity; zinc dichloride in diethyl ether at 1 mol L 1 from Sigma Aldrich; zinc dibromide in powder form from Sigma Aldrich and diluted in diethyl ether at 1 mol L *.

[0088] The polymers were characterized using the methods described below. The ethylene, N35 grade, comes from Air Liquide and is used without prior purification. 1,3-Butadiene is purified on alumina guards.

[0089] 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.

[0090] All reactions are carried out under an inert atmosphere.

[0091] 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 (differential refractometer and viscometer, and light scattering). 200 qL of a sample solution at a concentration of 8 mg mL 1 was eluted in 1,2,4-trichlorobenzene using a flow rate of 1 mL min 1 at 150 °C. The mobile phase was stabilized with 2,6-di(tert-butyl)-4-methylphenol (400 mg L1). The software OmniSEC was used for data acquisition and analysis. The number-average (MJ) and mass-average (Mw) molar masses of the synthesized polyethylenes were calculated using a calibration curve obtained from standard polyethylenes (Mw: 338, 507, 770, 1890, 17000, 27300, 43400, 53100, 65700, 78400 g mol ') from Polymer Standards Service (Mainz).

[0092] THF size exclusion chromatography (SEC-THF) for ethylene and 1,3-butadiene copolymers: Size exclusion chromatography analyses were performed using a Viscotek instrument (Malvem Instruments) equipped with 3 columns (SDVB, 5 qm, 300 x 7.5 mm from Polymer Standards Service), a guard column and 3 detectors (refractometer, differential viscometer and light scattering). 1 mL of a solution of the sample with a concentration of 5 mg mL 1 in THF was filtered through a 0.45 qm PTFE membrane. 100 qL 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 (M„) and mass (Mw) molar masses of the synthesized ethylene and butadiene copolymers were calculated using a universal calibration curve obtained from standard polystyrenes (Mw: 1,306 to 2,520,000 g mol′) from Polymer Standards Service (Mainz).

[0093] Nuclear magnetic resonance (NMR): 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 probe for the proton and on a Bruker 400 Avance II spectrometer operating at 400 MHz equipped with a 10 mm PSEX 13C probe for the carbon. Acquisitions were made in a mixture of tetrachloroethylene (TCE) and deuterated benzene (C6D6) (2 / 1 v / v) at 363 K for the ethylene homopolymers, and in deuterated chloroform (CDCl3) at 298 K for the ethylene-butadiene copolymers. Samples were analyzed at a concentration of 1% by mass for the proton and 5% by mass for the 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.

[0094] Comparative Example 1: Synthesis of polyethylene with a diorgano-magnesium compound (butyloctylmagnesium) without prior addition of a zinc dihalide before the functionalization reaction with 4-methoxybenzoyl chloride [example not in accordance with the invention) 196 mL of toluene taken from the solvent fountain (SPS800 MBraun) are introduced into a 250 mL inerted flask equipped with a magnetic olive. 2.27 mL of butyloctylmagnesium in heptane (0.88 mol L1) and 4 mL diethyl ether (38.5 mmol) are introduced introduced into the flask with stirring. 8.3 mg (13 pmol as 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 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 with stirring and the temperature is simultaneously brought to 80°C. Using a tank containing ethylene, the pressure is kept constant in the stirred reactor. When the desired quantity of ethylene has been consumed, i.e. after 26 min, the reactor is degassed and then p-toluoyl chloride in solution in toluene at 0.5 mol L 1 (3.9 mmol) is added to the reactor at 80°C. The reaction medium is stirred for 1 h at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48 h.4.4 g of polyethylene are recovered (activity of 750 kg / mol / h). The number-average molar mass of polyethylene is 1400 g mol *, the dispersity is 1.4 and 55% of the chains are functional. The 55% of the functional chains do not carry a ketone function, but an alcohol function or a function deriving from the dehydration of the alcohol function. The process implemented which is not in accordance with the invention does not lead to the synthesis of a polymer carrying a ketone function.

[0095] Example 2: Synthesis of polyethylene with a diorganomagnesium compound (butyloctyhnagnesium) then addition of a zinc dihalide (zinc dichloride) before the functionalization reaction with paratoluovle chloride (example in accordance with the invention): 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 L1) are introduced into the flask while stirring. 7.7 mg (12 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 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar then the reactor is pressurized to 4 bars of ethylene while stirring and the temperature is simultaneously brought to 80 °C. Using a tank containing ethylene, the pressure is maintained constant in the stirred reactor. When the desired quantity of ethylene has been consumed, i.e. after 15 min, the reactor is degassed and then 1 mmol of zinc dichloride (1 eq / Mg) is added.30 minutes later, p-toluoyl chloride in solution in toluene at 0.5 mol L 1 (2 mmol) is added to the reactor at 80°C. The reaction medium is stirred for 1 h at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48 h. 4.8 g of polyethylene are recovered (activity of 1520 Kg / mol / h). The number-average molar mass of polyethylene . is 2100 g mol *, the dispersity is 1.1 and 48% of the chains are functional. The 48% of the functional chains are functional and carry a ketone, i.e. a selectivity of the functionalization reaction of 100%.

[0096] Example 3: Synthesis of polyethylene with a Grignard reagent (butyl-magnesium chloride) then addition of a zinc dihalide (zinc dichloride) before the functionalization reaction with paratoluovle chloride (example in accordance with the invention): 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 / 10 mL (2 mmol) of butylmagnesium chloride in diethyl ether (2 mol L1) are introduced into the flask while stirring. A quantity of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 corresponding to 16 umolcs in neodymium is then introduced into the flask. The catalytic solution is transferred using a cannula into a 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar then the reactor is pressurized to 4 bars of ethylene while stirring and the temperature is simultaneously brought to 80°C. Using a tank containing ethylene, the pressure is maintained constant in the stirred reactor. When the desired amount of ethylene has been consumed, i.e. after 13 min, the reactor is degassed and then 1 mmol of zinc dichloride (0.5 eq / Mg) is added.10 minutes later, p-toluoyl chloride in solution in toluene at 0.5 mol L 1 (2 mmol) is added to the reactor at 80°C. The reaction medium is stirred for 40 min at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48h. 4.5 g of polyethylene are recovered (activity of 1340 Kg / mol / h). The number-average molar mass of polyethylene is 2100 g mol *, the dispersity is 1.1 and 53% of the chains are functional. The 53% of the functional chains are functional and carry a ketone function, i.e. a selectivity of the functionalization reaction of 100%.

[0097] Example 4: Synthesis of polyethylene with a Grignard reagent (butyl-magnesium chloride) then addition of a zinc dihalide (zinc dichloride) before the functionalization reaction with paratoluoyl chloride (example in accordance with the invention): 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 mL (2 mmol) of butylmagnesium chloride in diethyl ether (2 mol L1) are introduced into the flask while stirring. A quantity of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 corresponding to 12.5 qmol in neodymium is then introduced into the flask. The catalytic solution is transferred using a cannula into a 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar and then the The reactor is pressurized to 4 bars of ethylene with stirring and the temperature is simultaneously brought to 80°C. Using a tank containing ethylene, the pressure is kept constant in the stirred reactor. When the desired amount of ethylene has been consumed, i.e. after 12 min, the reactor is degassed and then 2 mmol of zinc dichloride (1 eq / Mg) are added. 10 minutes later, p-toluoyl chloride in solution in toluene at 0.5 mol L 1 (2 mmol) is added to the reactor at 80°C. The reaction medium is stirred for 40 min at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48 h. 4.5 g of polyethylene are recovered (activity of 1800 Kg / mol / h). The number-average molar mass of polyethylene is 2300 g mol *, the dispersity is 1.1 and 56% of the chains are functional and carry a ketone function, i.e. a selectivity of the functionalization reaction of 100%.

[0098] Example 5: Synthesis of polyethylene with a Grignard reagent (butyl-magnesium chloride) then addition of a zinc dihalide (zinc dichloride) before the functionalization reaction with paratoluoyl chloride (example in accordance with the invention): 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 / 10 mL (2 mmol) of butylmagnesium chloride in diethyl ether (2 mol L1) are introduced into the flask while stirring. A quantity of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 corresponding to 12.5 pmol in neodymium is then introduced into the flask. The catalytic solution is transferred using a cannula into a 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar then the reactor is pressurized to 4 bars of ethylene while stirring and the temperature is simultaneously brought to 80°C. Using a tank containing ethylene, the pressure is maintained constant in the stirred reactor. When the desired quantity of ethylene has been consumed, i.e. after 16 min, the reactor is degassed and then 1 mmol of zinc dichloride (0.5 eq / Mg) is added.20 minutes later, 1,4 dioxane (2.4 mmol) is added to the reactor at 80° followed by p-toluoyl chloride in solution in toluene at 0.5 mol L 1 (2 mmol). The reaction medium is stirred for 40 min at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48 h. 4.2 g of polyethylene are recovered (activity of 1120 Kg / mol / h). The number-average molar mass of polyethylene is 2200 g mol *, the dispersity of 1.2 and 11% of the chains are functional and carry a ketone function, i.e. a selectivity of the functionalization reaction of 100%.

[0099] Example 6: Synthesis of polyethylene with a Grignard reagent (butyl-magnesium chloride) then addition of a zinc dihalide (zinc dibromide) before the functionalization reaction with paratoluoyl chloride (example in accordance with the invention'): 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 mL (2 mmol) of butylmagnesium chloride in diethyl ether (2 mol L1) are introduced into the flask while stirring. A quantity of {(Me2Si(Ci3H8)2)Nd(p-BH4)[(p-BH4)Li(THF)]}2 corresponding to 12.5 pmoles of neodymium is then introduced into the flask. The catalytic solution is transferred using a cannula into a 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar then the reactor is pressurized to 4 bars of ethylene while stirring and the temperature is simultaneously brought to 80°C. Using a tank containing ethylene, the pressure is maintained constant in the stirred reactor. When the desired amount of ethylene has been consumed, i.e. after 15 min, the reactor is degassed and then 1 mmol of zinc dibromide (0.5 eq / Mg) is added.30 minutes later, p-toluoyl chloride in solution in toluene at 0.5 mol / L (2 mmol) is added to the reactor at 80°C. The reaction medium is stirred for 1 hour at 80°C, then the polymer is precipitated in methanol, recovered by filtration and dried in a vacuum oven at 60°C for 48 hours. 4.7 g of polyethylene are recovered (activity of 1670 kg / mol / h). The number-average molar mass of polyethylene is 2600 g mol *, the dispersity is 1.1 and 49% of the chains are functional and carry a ketone function, i.e. a selectivity of the functionalization reaction of 100%.

[0100] The examples show that the process according to the invention allows a functionalization reaction with a high selectivity with respect to the ketone functionalization reaction. This result is obtained thanks to the succession of steps a), b) and c) as defined in the present invention. This high selectivity is attributed to the formation of polymers containing a carbon-zinc bond which is prior to the functionalization reaction with an acid chloride.

Claims

Claims

1. Process for the preparation of a polymer carrying a ketone function, preferably at the chain end, which process comprises the following steps a), b) and c), a) the polymerization reaction of ethylene or of a monomer mixture containing ethylene and a 1,3-diene in the presence of a catalytic system based at least on: a metallocene of formula (la) an organomagnesium compound {P(Cp1)(Cp2)Nd(BH4)(1+y)_Ly-Nx} (la) Cp1 and Cp2, 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 groups Cp1 and Cp2, 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, whole number or not, being equal to or greater than 0, y,integer, being equal to or greater than 0, b) the reaction of a zinc dihalide with the reaction product of step a), c) the reaction of an acid halide with the reaction product of step b).,

2. Process according to claim 1 in which the organomagnesium is a Grignard reagent, preferably a halide of an alkyl-magnesium, more preferably a chloride of an alkylmagnesium.

3. Process according to claim 1 in which the organomagnesium is a diorganomagnesium, preferably a dialkylmagnesium.

4. A process according to claim 2 or 3 wherein the alkyls of the halide of an alkylmagnesium and the diorganomagnesium contain 2 to 10 carbon atoms.

5. Process according to any one of claims 3 to 4 in which the dialkylmagnesium is of formula MgR3R4 in which the alkyl represented by the symbol R3 is different from the alkyl represented by the symbol R4, preferably R3 being butyl and R4 ethyl or octyl.

6. A method according to claim 2 or 4 wherein the alkyl of the halide of an alkylmagnesium is butyl.

7. A method according to any one of claims 1 to 6 wherein the zinc dihalide is zinc dichloride, zinc dibromide or a mixture of zinc dichloride and zinc dibromide.

8. Method according to any one of claims 1 to 7 in which Cp1 and Cp2, identical or different, each represent a fluorenyl group, substituted or not, or a cyclopentadienyl group, substituted or not.

9. A method according to any one of claims 1 to 8 wherein Cp1 and Cp2 are identical and are selected from the group consisting of substituted fluorenyl groups and unsubstituted fluorenyl groups of formula CnH8, preferably each representing an unsubstituted fluorenyl group of formula C13H8.

10. Process according to any one of claims 1 to 9 in which the bridge P connecting the groups Cp1 and Cp2 corresponds to the formula ZR'R2, in which Z represents a silicon or carbon atom, R1 and R2, identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl.

11. A process according to any one of claims 1 to 10 wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, [3-farnesene or mixtures thereof, preferably 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.

12. Process according to any one of claims 1 to 11 in which the ratio between the number of moles of zinc dihalide and the number of moles of carbon magnesium bond per mole of organomagnesium is greater than 0.45 and preferably less than 1.

13. A process for preparing a polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a polymer chain and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX, the term "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, X being a halogen atom, which process comprises steps a) and b) defined in any one of claims 1 to 12, the polymer being obtained at the end of step

14. b). Polymer which contains a bond between a carbon atom of the terminal monomer unit constituting a polymer chain and a zinc atom, which polymer is of formula (poly)2Zn or (poly)ZnX, the term "poly" in the formula designating the polymer chain, the polymer chain being a polyethylene chain or a copolymer chain containing ethylene units and units of a 1,3-diene, preferably 1,3-butadiene, X being a halogen atom.

15. Polymer according to claim 14 in which the name "poly" denotes a copolymer chain of ethylene and a 1,3-diene, the 1,3-diene preferably being 1,3-butadiene, isoprene, myrcene, [3-farnesene or their mixtures, more preferably 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene.