Synthesis of block copolymers based on 1,3-diene and ethylene

Description

[0001] The field of the present invention is that of methods for synthesizing block polymers, known as multiblock polymers, based on 1,3-diene and ethylene which contain at least three blocks. More particularly, the field of the invention is that of block polymers which comprise at least a first copolymer block based on ethylene and a 1,3-diene and two other polyethylene blocks, each polyethylene block being attached to a separate end of the first block which happens to be a central block within the block polymer.

[0002] EP 2599809 A1 describes the synthesis of multiblock polymers based on ethylene and 1,3-butadiene. They are synthesized by a first ethylene polymerization step, followed by a 1,3-butadiene polymerization step. Multiblock polymers are also synthesized by repeating several times the sequence composed of the polymerization of a first ethylene monomer charge and the polymerization of a second 1,3-butadiene monomer charge. The block polymers are described as consisting of high-cis polybutadiene blocks and polyethylene blocks characterized respectively by a glass transition temperature of a high-cis polybutadiene and a melting temperature of polyethylene. They are synthesized in the presence of a catalyst system that comprises three components, namely a rare earth metallocene, a borate and an alkylaluminium hydride.Due to the process used, the formation of each additional block after the synthesis of a first block requires the addition of a new monomer charge to the polymerization medium. Thus, the synthesis of a triblock polymer requires the use of three monomer charges, the synthesis of a pentablock five monomer charges, etc. However, those skilled in the art know that the addition of a monomer charge to a polymerization medium during the polymerization reaction is generally accompanied by a deactivation of a portion of the active sites that participate in the polymerization reaction, which has the effect of forming polymer species other than the targeted block polymer. The yield of targeted block polymer is thus reduced.

[0003] The Applicants have discovered a much more efficient process for synthesizing multiblock polymers based on ethylene and 1,3-diene, since it makes it possible to reduce the number of monomer charges and thus increase the yield of the desired multiblock polymer.

[0004] Thus, a first subject of the invention is a process for preparing a multiblock polymer which comprises the random copolymerization of a monomer mixture containing ethylene and a 1,3-diene, then the subsequent polymerization of ethylene in the presence of a catalytic system based at least on a metallocene of formula (Ia) or (Ib) and an organomagnesium compound of formula (IIa) or (IIb) {P(Cp 1< )(Cp 2< )Y} (Ia) Cp 3< Cp 4< Y (Ib) Y denoting a group comprising a rare earth atom, 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 groups Cp 1< and Cp 2< , and comprising a silicon or carbon atom, Cp 3< and Cp 4< , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, RB< -(Mg-RA< ) m -Mg-RA< (IIa) X-Mg-RA< -Mg-X (IIb) RA< being a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, RB< comprising a benzene nucleus substituted by the magnesium atom,one of the carbon atoms of the benzene ring ortho to magnesium being substituted by a methyl, an ethyl, an isopropyl or forming a cycle with the carbon atom which is its nearest neighbor and which is meta to magnesium, the other carbon atom of the benzene ring ortho to magnesium being substituted by a methyl, an ethyl or an isopropyl, X being a halogen atom, m being a number greater than or equal to 1, preferably equal to 1. ,

[0005] A second subject of the invention is a multiblock polymer, in particular a triblock polymer, capable of being obtained by the process according to the invention. Its essential characteristic is that it comprises within the polymer chain a divalent group which results from the process used for its manufacture. It has the advantage of being less polluted by polymer species resulting from the partial deactivation of the active sites of the polymerization. Description

[0006] 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).

[0007] The expression "based on" used to define the constituents of a catalytic system or composition means the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other.

[0008] Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a polymer are expressed as a molar percentage relative to the total number of monomer units constituting the polymer.

[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. 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.

[0010] As is known, an ethylene unit is understood to mean a unit which has the motif -(CH 2 -CH 2 )-. Also as is known, a 1,3-diene can be inserted into a growing polymer chain by a 1,4 or 2,1 insertion or even a 3,4 insertion in the case of a substituted diene such as isoprene to give rise respectively to the formation of 1,3-diene units of 1,4 configuration, 1,3-diene units of 1,2 configuration or 3,4 configuration.

[0011] The process according to the invention comprises the random copolymerization of a monomer mixture containing ethylene and a 1,3-diene, and then the subsequent polymerization of ethylene.

[0012] 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 two Cp 3< and Cp 4< groups or to a ligand molecule consisting of two Cp 1< and Cp 2< groups linked together by a P bridge. These Cp 1< , Cp 2< , Cp 3< and Cp 4< groups, 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. It is recalled that rare earths are metals and designate the elements scandium, yttrium and lanthanides whose atomic number varies from 57 to 71.

[0013] According to a first variant of the invention, the metallocene used as a basic constituent in the catalytic system corresponds to the formula (Ia) {P(Cp 1< )(Cp 2< )Y} (Ia) in which Y denotes a group comprising a rare earth atom, Cp 1< and Cp 2< , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P is a group bridging the two groups Cp 1< and Cp 2< , and comprising a silicon or carbon atom.

[0014] According to a second variant of the invention, the metallocene used as a basic constituent in the catalytic system in accordance with the invention corresponds to the formula (Ib) Cp 3< Cp 4< Y (Ib) in which Y denotes a group comprising an atom of a rare earth, Cp 3< and Cp 4< , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted.

[0015] 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 SiMe 3 . The choice of radicals is also guided by the accessibility of the corresponding molecules that are substituted cyclopentadienyl, fluorenyl and indene, because the latter are commercially available or easily synthesized.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Preferably, the metallocene is of formula (Ia).

[0020] Preferably, 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 C 13 H 8 . The catalytic system according to this preferred embodiment has the particularity of leading to copolymers based on butadiene and ethylene which comprise, in addition to ethylene monomer units and butadiene units, cyclic units of 1,2-cyclohexanediyl unit of the following formula:

[0021] Advantageously, Cp 1< and Cp 2< are identical and each represent an unsubstituted fluorenyl group of formula C 13 H 8 , represented by the symbol Flu.

[0022] Preferably, the symbol Y represents the group Met-G, with Met denoting the rare earth atom and G denoting a group comprising the borohydride unit BH 4 or denoting a halogen atom selected from the group consisting of chlorine, fluorine, bromine and iodine. Advantageously, G denotes a chlorine atom or the group of formula (III): (BH 4 ) (1+y)- L y -N x (III) in which L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, x, whether an integer or not, is equal to or greater than 0, y, an integer, is equal to or greater than 0. Very advantageously, G denotes the group of formula (III).

[0023] Any ether that has the power to complex the alkali metal is suitable as an ether, especially diethyl ether and tetrahydrofuran.

[0024] The metallocene metal, the rare earth, is preferably a lanthanide with an atomic number ranging from 57 to 71, more preferably neodymium, Nd.

[0025] The bridge P connecting the groups Cp 1< and Cp 2< preferably corresponds 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.

[0026] 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 for example described 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.

[0027] According to a particularly preferred embodiment, the metallocene is of formula (III-1), (III-2), (!!!-3), (!!!-4) or (!!!-5): [Me 2 Si(Flu) 2 Nd(µ-BH 4 ) 2 Li(THF)] (III-1) [{Me 2 SiFlu 2 Nd(µ-BH 4 ) 2 Li(THF)} 2 ] (III-2) [Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)] (III-3) [{Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)} 2 ] (III-4) [Me 2 SiFlu 2 Nd(µ-BH 4 )] (III-5) in which Flu represents the group C 13 H 8 .

[0028] Another basic constituent of the catalytic system is the co-catalyst, an organomagnesium compound of formula (IIa) or formula (IIb). RB< -(Mg-R A< ) m -Mg-R B< (IIa) X-Mg-R A< -Mg-X (IIb) RA< being a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, RB< comprising a benzene ring substituted by the magnesium atom, one of the carbon atoms of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl, an isopropyl or forming a cycle with the carbon atom which is its closest neighbor and which is meta to the magnesium, the other carbon atom of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl or an isopropyl, X being a halogen atom, m being a number greater than or equal to 1, preferably equal to 1.

[0029] The co-catalysts of formula (IIa) and (IIb) both have the particularity of comprising two magnesium-carbon bonds involving distinct magnesium atoms. In formula (IIa), two magnesium atoms each share a first bond with a first carbon atom belonging to RB< and a second bond with a second carbon atom belonging to RA< . The first carbon atom constitutes the benzene ring of RB< . The second carbon atom constitutes the aliphatic hydrocarbon chain RA< which may contain within its chain one or more heteroatoms chosen from oxygen and sulfur or one or more arylene groups. In the preferred case where m is equal to 1, each magnesium atom therefore shares a first bond with a first carbon atom of RB< and a second bond with a second carbon atom of RA< .In formula (IIb), each magnesium atom therefore shares a first bond with a halogen atom and a second bond with a carbon atom of RA< .

[0030] In formula (IIa), RB< has the characteristic of comprising a benzene ring substituted by the magnesium atom. The two carbon atoms of the benzene ring of RB< ortho to the magnesium carry a substituent, identical or different. Alternatively, one of the two carbon atoms of the benzene ring of RB< ortho to the magnesium may carry a substituent, the other carbon atom of the benzene ring of RB< ortho to the magnesium may form a ring. The substituent is a methyl, an ethyl or an isopropyl. In the case where one of the 2 carbon atoms of the benzene ring of RB< ortho to the magnesium is substituted by an isopropyl, preferably the second carbon atom of the benzene ring of RB< ortho to the magnesium is not substituted by an isopropyl. Preferably, the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by methyl or ethyl.More preferably, the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by a methyl.

[0031] The organomagnesium compound of formula (IIa) preferably corresponds to formula (IIa-m) in which R 1 and R 5 , identical or different, represent a methyl or an ethyl, preferably a methyl, R 2 , R 3 and R 4 , identical or different, represent a hydrogen atom or an alkyl and RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, m is greater than or equal to 1. Preferably, R 1 and R 5 represent a methyl. Preferably, R 2 and R 4 represent a hydrogen atom.

[0032] The organomagnesium compound of formula (IIa-m) is of formula (Ila-1) in the case where m is equal to 1.

[0033] According to a preferred variant, R 1 , R 3 and R 5 are identical in the formula (Ila-m), in particular in the formula (Ila-1). According to a more preferred variant, R 2 and R 4 represent a hydrogen and R 1 , R 3 and R 5 are identical. In a more preferred variant, R 2 and R 4 represent a hydrogen and R 1 , R 3 and R 5 represent a methyl.

[0034] In formulas (IIa) and (IIa-m), in particular in formula (IIa-1), and in formula (IIb), RA< is a divalent aliphatic hydrocarbon chain which may contain within its chain one or more heteroatoms chosen from oxygen and sulfur or one or more arylene groups. Preferably, RA< is a branched or linear alkanediyl, a cycloalkanediyl or a xylenediyl radical. More preferably, RA< is an alkanediyl.

[0035] Preferably, RA< contains 3 to 10 carbon atoms, especially 3 to 8 carbon atoms.

[0036] Even more preferably, RA< is an alkanediyl having 3 to 10 carbon atoms. Advantageously, RA< is an alkanediyl having 3 to 8 carbon atoms. Very advantageously, RA< is a linear alkanediyl. 1,3-propanediyl, 1,4-butanediyl, 1,5-pentanediyl, 1,6-hexanediyl, 1,7-heptanediyl, 1,8-octanediyl are particularly suitable as RA< groups.

[0037] According to any of the embodiments of the invention, m is preferably equal to 1 in formula (IIa), in particular in formula (IIa-m).

[0038] The organomagnesium compound of formula (IIa) may be prepared by a process, which comprises reacting a first organomagnesium of formula X'Mg-R A< -MgX' with a second organomagnesium of formula RB< -Mg-X', X' representing a halogen atom, preferably bromine or chlorine, RB< and RA< being as defined above. X' is more preferably a bromine atom. The stoichiometry used in the reaction determines the value of m in formula (IIa) and in formula (IIa-m). For example, a molar ratio of 0.5 between the quantity of the first organomagnesium and the quantity of the second organomagnesium is favorable to the formation of an organomagnesium compound of formula (IIa) in which m is equal to 1, whereas a molar ratio greater than 0.5 will be more favorable to the formation of an organomagnesium compound of formula (IV) in which m is greater than 1.

[0039] To carry out the reaction of the first organomagnesium compound with the second organomagnesium compound, a solution of the second organomagnesium compound is typically added to a solution of the first organomagnesium compound. The solutions of the first organomagnesium compound and the second organomagnesium compound are generally solutions in an ether, such as diethyl ether, dibutyl ether, tetrahydrofuran, methyltetrahydrofuran or the mixture of two or more of these ethers. Preferably, the respective concentrations of the solutions of the first organomagnesium compound and the second organomagnesium compound are 0.01 to 3 mol / L and 0.02 to 5 mol / L, respectively. More preferably, the respective concentrations of the first organomagnesium compound and the second organomagnesium compound are 0.1 to 2 mol / L and 0.2 to 4 mol / L, respectively.

[0040] The first organomagnesium compound and the second organomagnesium compound may be prepared in advance by a Grignard reaction from magnesium metal and a suitable precursor. For the first organomagnesium compound and the second organomagnesium compound, the respective precursors are of formula X'-RA< -X' and RB< -X', RA< , RB< and X' being as defined previously. The Grignard reaction is typically carried out by adding the precursor to magnesium metal which is generally in the form of chips. Preferably, iodine (I 2 ) typically in the form of beads is introduced into the reactor before the addition of the precursor in order to activate the Grignard reaction in a known manner.

[0041] Alternatively, the organomagnesium compound of formula (IIa) may be prepared by reacting an organometallic compound of formula MR A< -M and the organomagnesium compound of formula RB< -Mg-X', M representing a lithium, sodium or potassium atom, X', RB< and RA< being as defined above. Preferably, M represents a lithium atom, in which case the organometallic compound of formula MR A< -M is an organolithium.

[0042] The reaction of the organolithium and the organomagnesium is typically carried out in an ether such as diethyl ether, dibutyl ether, tetrahydrofuran, methyltetrahydrofuran. The reaction is also typically carried out at a temperature ranging from 0°C to 60°C. The contacting is preferably carried out at a temperature between 0°C and 23°C. The contacting of the organometallic compound of formula MR A< -M with the organomagnesium of formula RB< -Mg-X' is preferably carried out by adding a solution of the organometallic compound MR A< -M to a solution of the organomagnesium RB< -Mg-X'. The solution of the organometallic compound MR A< -M is generally a solution in a hydrocarbon solvent, preferably n-hexane, cyclohexane or methylcyclohexane, the solution of the organomagnesium compound RB< -Mg-X' is generally a solution in an ether, preferably diethyl ether or dibutyl ether.Preferably, the respective concentrations of the solutions of the organometallic compound and the organomagnesium MR A< -M and RB< -Mg-X' are respectively from 0.01 to 1 mol / L and from 1 to 5 mol / L. More preferably, the respective concentrations of the solutions of the organometallic compound and the organomagnesium MR A< -M and RB< -Mg-X' are respectively from 0.05 to 0.2 mol / L and from 2 to 3 mol / L.

[0043] Like any synthesis carried out in the presence of organometallic compounds, the syntheses described for the synthesis of organomagnesiums take place under anhydrous conditions under an inert atmosphere, in stirred reactors. Typically, solvents and solutions are used under anhydrous nitrogen or argon.

[0044] Once the organomagnesium compound of formula (IIa) is formed, it is generally recovered in solution after filtration carried out under an inert and anhydrous atmosphere. It can be stored before use in its solution in airtight containers, for example capped bottles, at a temperature between -25°C and 23°C.

[0045] Like any organomagnesium compound, the organomagnesium compound of formula (IIa) may be in the form of a monomeric entity (RB< -(Mg-R A< ) m -Mg-R B< ) 1 or in the form of a polymeric entity (RB< -(Mg-R A< ) m -Mg-R B< ) p , p being an integer greater than 1, in particular dimer (RB< -(Mg-R A< ) m -Mg-R B< ) 2 , m being as defined previously. Furthermore, whether in the form of a monomeric or polymeric entity, it 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.

[0046] Compounds of formula (IIb) are well-known compounds as Grignard reagents. However, they are not known to be used as co-catalysts in a catalytic system suitable for the preparation of polyolefins. Grignard reagents of formula (IIb) are described, for example, in the book "Advanced Organic Chemistry" by J. March, 4th Edition, 1992, pages 622-623 or in the book "Handbook of Grignard Reagents", Edition Gary S. Silverman, Philip E. Rakita, 1996, pages 502-503. They can be synthesized by contacting magnesium metal with a dihalogenated compound of formula XR C< -X, RC< being as defined according to the invention. For their synthesis, reference may be made, for example, to the collection of volumes of "Organic Synthesis".

[0047] Like any organomagnesium compound, the organomagnesium compound of formula (IIb) can be in the form of a monomeric entity (X-Mg-R A< -Mg-X) 1 or in the form of a polymeric entity (X-Mg-R A< -Mg-X) p , p being an integer greater than 1, in particular dimer (X-Mg-R A< -Mg-X) 2 . Furthermore, whether in the form of a monomeric or polymeric entity, it can 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. In formula (IIb), X is preferably a bromine or chlorine atom, more preferably a bromine atom.

[0048] The catalytic system can be prepared in a traditional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223. For example, the co-catalyst, in this case the organomagnesium compound of formula (IIa) or formula (IIb), and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20 to 80°C for a period of between 5 and 60 minutes. The quantities of co-catalyst and metallocene reacted are such that the ratio between the number of moles of Mg in the co-catalyst 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. The catalyst system is usually 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.

[0049] Alternatively, the catalytic system may be prepared by a process analogous to that described in patent application WO 2017093654 A1 or in patent application WO 2018020122 A1. According to this alternative, the catalytic system further contains a pre-formation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, in which case the catalytic system is based at least on the metallocene, the co-catalyst and the pre-formation monomer. For example, the organomagnesium compound and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80°C for 10 to 20 minutes to obtain a first reaction product, then with this first reaction product, the preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene is reacted at a temperature of 40 to 90°C for 1 hour to 12 hours.The conjugated diene as preformation monomer is preferably a 1,3-diene such as 1,3-butadiene, isoprene or a 1,3-diene of formula CH 2 =CR-CH=CH 2 , the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms, in particular myrcene or β-farnesene. The catalytic system thus obtained can be used immediately in the process for synthesizing the polymer according to the invention or be stored under an inert atmosphere, in particular at a temperature ranging from -20°C to room temperature (23°C), before its use in the synthesis of polymers.

[0050] Like any synthesis carried out in the presence of organometallic compounds, the synthesis of metallocene, the synthesis of organomagnesium and the synthesis of the catalytic system take place under anhydrous conditions under an inert atmosphere. Typically, the reactions are carried out from solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0051] The catalytic system can be in the form of a solution when it is in the presence of a hydrocarbon solvent. The hydrocarbon solvent can be aliphatic such as methylcyclohexane or aromatic such as toluene. The hydrocarbon solvent is preferably aliphatic, 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 comprises the catalytic system and the hydrocarbon solvent. The catalytic system preferably comprises a hydrocarbon solvent. When the catalytic system is in solution, its concentration is 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.

[0052] The catalytic system is generally introduced into the reactor containing the polymerization solvent and the monomers. To achieve the desired macrostructure of the multiblock polymer, the person skilled in the art adapts the polymerization conditions, in particular the molar ratio of the organomagnesium to the Nd metal constituting the metallocene. The molar ratio can reach the value of 200, knowing that a molar ratio of less than 20 is more favorable for obtaining polymers with high molar masses.

[0053] The skilled person also adapts the polymerization conditions and the concentrations of each of the reactants (constituents of the catalytic system, monomers) according to the equipment (tools, reactors) used to carry out the polymerization. Preferably, the monomer mixture containing ethylene and a 1,3-diene contains more than 50 mol% of ethylene. As is known to the skilled person, the polymerization as well as the handling of the monomers, the catalytic system and the polymerization solvent(s) are carried out under anhydrous conditions and under an inert atmosphere. The polymerization solvents are typically hydrocarbon, aliphatic or aromatic solvents.

[0054] The polymerization is preferably carried out in solution, continuously or discontinuously, in a reactor which is advantageously stirred. The polymerization solvent may be a hydrocarbon solvent, aromatic or aliphatic. Examples of polymerization solvents include toluene and methylcyclohexane. Advantageously, the polymerization is carried out in solution in a hydrocarbon solvent.

[0055] The preparation of the multiblock polymer, also called block polymer, involves the formation of a first block, called the central block of formula AR A< -A which is followed by the formation of the other blocks, called successive blocks. The monomer units constituting the successive blocks are incorporated into the growing polymer chain from each of the chain ends of the central block. The formation of the central block requires a first monomer charge, in this case a monomer mixture containing ethylene and a 1,3-diene. The formation of the successive blocks is carried out by a polymerization reaction which propagates from the distinct ends of the previous block. The formation of two blocks of the same microstructure from the distinct ends of the previous block therefore requires a single monomer charge.Thus, in the synthesis of a triblock polymer, two monomer charges are used: a first monomer charge of a mixture containing ethylene and a 1,3-diene for the synthesis of the central block, a second monomer charge of ethylene for the synthesis of the terminal blocks, in this case polyethylene.

[0056] By the polymerization of successive monomer charges which are respectively a mixture containing ethylene and a 1,3-diene and ethylene, the process according to the invention leads to the preparation of multiblock polymers of formula B-(A 1< -B 1< ) n -AR A< -A-(B 1< -A 1< ) n -B in which A and A 1< each represent a block which is a random copolymer comprising 1,3-diene units and ethylene units, B and B 1< each represent a block which is a polyethylene, n is an integer equal to or greater than 0, RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups. The presence in the polymer chain of the divalent radical comes from the co-catalyst used in the preparation of the multiblock polymer.

[0057] According to the invention, the central block is a so-called statistical copolymer, which means that the monomer units constituting the central block are distributed statistically in the central block, due to a statistical incorporation of the monomers into the growing polymer chain.

[0058] In the preparation of the central block, the polymerization temperature generally varies in a range from 30 to 160°C, preferably from 30 to 120°C. During the preparation of the central block, the temperature of the reaction medium is advantageously kept constant during the copolymerization and the total pressure of the reactor is also advantageously kept constant. The preparation of the central block is completed by cutting off the monomer supply, in particular by dropping the reactor pressure, preferably to approximately 3 bars.

[0059] The subsequent polymerization of ethylene is continued by applying ethylene pressure in the reactor, the ethylene pressure being kept constant until the desired ethylene consumption to reach the desired number-average molar mass of the polyethylene blocks. The ethylene polymerization temperature is preferably carried out at a temperature identical to that of the preparation of the central block. The polymerization temperature for the preparation of the polyethylene blocks generally varies in a range from 30 to 160°C, preferably from 30 to 120°C. The pressure for the preparation of the polyethylene blocks generally varies in a range from 1 bar to 150 bar and preferably from 1 bar to 10 bar. The synthesis of the polyethylene blocks is completed when the polyethylene blocks reach the desired number-average molar mass.

[0060] In the case of the preparation of a triblock polymer, the polymerization is stopped. In the case of the preparation of a multiblock polymer which comprises more than three blocks, such as a pentablock, the polymerization is continued by the subsequent polymerizations of monomer charges. For the successive blocks containing both ethylene units and units of a 1,3-diene, the monomer charges consist of a mixture containing ethylene and a 1,3-diene and the polymerization is carried out under temperature and pressure conditions similar to those of the preparation of the central block. For the successive polyethylene blocks, the monomer charges consist of ethylene and are polymerized under pressure and temperature conditions already described for the synthesis of the polyethylene blocks. At the end of the synthesis of the multiblock polymer, the polymerization is stopped.

[0061] The polymerization can be stopped by cooling the polymerization medium or by adding an alcohol, preferably an alcohol containing 1 to 3 carbon atoms, for example ethanol. The multiblock polymer, in particular triblock, 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.

[0062] In the process according to the invention, the 1,3-diene of the mixture containing ethylene and a 1,3-diene may be a 1,3-diene containing 4 to 20 carbon atoms. The 1,3-diene is preferably 1,3-butadiene, isoprene or a mixture of 1,3-dienes, one of which is 1,3-butadiene. The 1,3-diene is more preferably 1,3-butadiene according to any one of the embodiments of the invention.

[0063] According to a particularly preferred embodiment of the invention, the monomer mixture containing ethylene and a 1,3-diene is a mixture of ethylene and a 1,3-diene, which amounts to saying that ethylene and 1,3-diene are the only monomers in the monomer mixture. Advantageously, the monomer mixture containing ethylene and a 1,3-diene is a mixture of ethylene and a 1,3-diene and contains more than 50 mol% of ethylene.

[0064] According to another particularly preferred embodiment of the invention, the process leads to the synthesis of a triblock polymer of formula BAB in which A, called the central block, is a random copolymer comprising 1,3-diene units and ethylene units, and B, called the terminal block, is a polyethylene. Advantageously, the central block A is a random copolymer comprising 1,3-diene units and more than 50 mol% of ethylene units. Very advantageously, the central block A is a random copolymer of ethylene and 1,3-diene which contains more than 50 mol% of ethylene units. In the present application, the level of ethylene units in the central block, namely the number of moles of ethylene units in the central block, is expressed as a molar percentage relative to the number of moles of monomer units constituting the central block.

[0065] Preferably, the process results in the synthesis of a block polymer which is an elastomer.

[0066] The polymer in accordance with the invention, another subject of the invention, can be prepared by a particular embodiment of the process in accordance with the invention in which RA< is other than an ethylene unit, a unit of a 1,3-diene, a chain of ethylene units, a chain of units of a 1,3-diene, a chain of units consisting of one or more ethylene units and one or more units of a 1,3-diene.The polymer in accordance with the invention is a multiblock polymer of formula (IV) B-(A 1< -B 1< ) n -AR A< -A-(B 1< -A 1< ) n -B (IV) in which A and A 1< each represent a block which is a random copolymer comprising units of a 1,3-diene and ethylene units, B and B 1< each represent a block which is a polyethylene, n is an integer equal to or greater than 0, RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups and RA< is other than an ethylene unit, a unit of a 1,3-diene, a chain of ethylene units, a chain of units of a 1,3-diene, a chain of units consisting of one or more ethylene unit and one or more units of a 1,3-diene.

[0067] Preferably, the polymer in accordance with the invention is an elastomer.

[0068] According to a particularly preferred embodiment of the invention, the multiblock polymer is a polymer of formula (IV) in which n is equal to 0, in which case the polymer is a triblock, preferably elastomer.

[0069] According to another embodiment of the invention which can be combined with the other embodiments relating to the polymer according to the invention, the multiblock polymer contains 1,2-cyclohexanediyl unit units.

[0070] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes. Example :

[0071] High temperature size exclusion chromatography (HT SEC).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 Agitent Technologies) and 3 detectors (differential refractometer and viscometer, and light scattering). 200 µL of a sample solution at a concentration of 3 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 L -1< ). OmniSEC software was used for data acquisition and analysis. The number-average molar masses (Mn) of the synthesized ethylene-butadiene copolymers are calculated using a universal calibration curve calibrated from standard polystyrenes (Peak molar masses Mp: 672 to 12,000,000 g mol -1< ) ​​from Polymer Standard Service (Mainz) using the refractometer and viscometer detectors.

[0072] Nuclear magnetic resonance (NMR). High-resolution 1< H NMR spectroscopy of the copolymers was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe. Acquisitions were made at 363 K. A mixture of tetrachloroethylene (TCE) and deuterated benzene (C 6 D 6 ) (2 / 1 v / v) was used as solvent. Samples were analyzed at a concentration of 17 g L -1< . Chemical shifts are given in ppm, relative to the proton signal of deuterated benzene set at 7.16 ppm. The number of acquisitions is set at 512.

[0073] Differential scanning calorimetry (DSC).The analyses are carried out on a DSC 3 +< device (Mettler Toledo) using a dynamic method comprising 9 temperature levels: Level 1: 20 to 180 °C (10 °C min -1< ), Level 2: isothermal 180 °C (5 min), Level 3: 180 to -80 °C (-10 °C min -1< ), Level 4: isothermal -80 °C (5 min), Level 5: -80 to 180 °C (10 °C min -1< ), Level 6: isothermal 180 °C (5 min), Level 7: 180 to -80 °C (10 °C min -1< ), Level 8: isothermal -80 °C (5 min), Level 9: -80 to 180 °C (10 °C min -1< ). The first two rises allow the thermal history of the sample to be erased. The glass transition and melting temperature measurements are made on the 9th level. The 7th level is also kept to obtain information on the crystallization of the sample. The crystallinity rate is determined relative to a 100% crystalline polyethylene (Δ f H = 293 J g -1; B. Wunderlich, Thermal analysis, Academic Press, 1990, 281). Preparation of the co-catalyst, 1,5-di(magnesium bromide)-pentanediyl (DBMP):

[0074] 1.25 g (50 mmol, 10 equivalents) of magnesium are inerted in a 50 mL flask equipped with a magnetic olive and topped with a 10 mL dropping funnel. A 10 mg iodine bead is introduced onto the magnesium. 11 mL of sodium / benzophenone distilled MeTHF are introduced into the flask with stirring and 9 mL are introduced into the dropping funnel. 0.68 mL of degassed and dried 1,5-dibromopentane (5 mmol, 1 equivalent) over activated molecular sieve are introduced into the dropping funnel. The haloalkane solution is poured dropwise onto the magnesium for 1 h. Stirring is maintained for 12 h at 20 °C. This solution is concentrated under vacuum and then diluted in 10 mL of toluene. The concentration of pentanediyl group is estimated at 0.45 mol L -1< .

[0075] 1< H NMR (C 6 D 6 - 400 MHz - 298 K) δ: ppm = 2.06 (quin, J = 7.6 Hz, “b”), 1.80 (quin, J = 7.4 Hz, “c”), -0.05 (t, J = 7.7 Hz, “a”); quin for quintuplet.

[0076] Preparation of a triblock polymer according to the invention, with a central block of random copolymer of ethylene and 1,3-butadiene and polyethylene end blocks: 200 mL of toluene (Biosolve) purified on a SPS800 MBraun system are introduced into a 250 mL inerted flask equipped with a magnetic olive. 0.6 mL (0.25 mmol) of a solution of 1,5-di(magnesium bromide)pentanediyl (DBMP 0.45 mol L -1< ) ​​prepared are introduced into the flask with stirring. 16 mg (25 µmol of neodymium) of {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 are then introduced into the flask.

[0077] Preparation of the central block (Step 1): The catalytic solution is then transferred using a cannula into a 250 mL reactor under an inert atmosphere at 70 °C. The argon overpressure in the reactor is reduced to 0.5 bar and then the reactor is pressurized to 4 bar with an ethylene / butadiene mixture of 80 / 20 molar ratio while stirring at 1000 rpm. The pressure is kept constant in the reactor using a tank containing the ethylene / butadiene mixture. After a pressure drop in the tank equivalent to approximately 13 g of monomers, the feed is stopped and the reactor is isolated until the pressure in the reactor reaches 2.8 bar to obtain 15 g of copolymer.

[0078] Preparation of the terminal blocks (Step 2): The reactor is again pressurized to 4 bars using a tank containing only ethylene, then approximately 3 g of monomers are consumed by pressure drop in the tank.

[0079] The reactor is degassed and the temperature is brought back to 20 °C. The polymer solution is precipitated in methanol with stirring in the presence of approximately 20 mg of 2,2'-Methylenebis(6-tert-butyl-4-methylphenol) as an antioxidant. The resulting polymer is dried under vacuum at 70 °C for 4 h. 18.5 g of dry triblock polymer are recovered. The characteristics of the triblock polymer are as follows: Glass transition temperature Tg: -35°C corresponding to the statistical copolymer block of ethylene and 1,3-butadiene; Melting temperature Tf: 122°C corresponding to the polyethylene blocks; Crystallinity rate: 8.9% by mass; Mn SEC-HT: 62600 g / mol.

[0080] The ethylene unit rate, the 1,3-butadiene unit rate in the 1,2-configuration (1,2-unit), in the 1,4-configuration (1,4-unit) and the 1,2-cyclohexanediyl unit rate expressed as a molar percentage relative to all the monomer units of the polymer are respectively 81.9%, 6.7%, 4.0% and 7.4%.

Claims

1. Process for preparing a multiblock polymer, which comprises the statistical copolymerization of a monomer mixture containing ethylene and a 1,3-diene, followed by the subsequent polymerization of ethylene in the presence of a catalytic system based on at least one metallocene of formula (Ia) or (Ib) and an organomagnesium reagent of formula (Ila) or (IIb)         {P(Cp1)(Cp2)Y}     (Ia)         Cp3Cp4Y     (Ib) Y denoting a group including a rare-earth metal atom, Cp1 and Cp2, which are 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, Cp3 and Cp4, which are identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted,         RB-(Mg-RA)m-Mg-RB     (IIa)         X-Mg-RA-Mg-X     (IIb) RA being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups, RB comprising a benzene nucleus substituted with the magnesium atom, one of the carbon atoms of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl, an isopropyl or forming a ring with the carbon atom which is its closest neighbour and which is meta to the magnesium, the other carbon atom of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl or an isopropyl, X being a halogen atom, m being a number greater than or equal to 1 and preferably equal to 1.

2. Process according to Claim 1, in which the symbol Y represents the group Met-G, with Met denoting the rare-earth metal atom and G denotes a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine or a group comprising the borohydride unit BH4; preferably, G denotes a chlorine atom or the group of formula (III)         (BH4)(1+y)-Ly-Nx     (III) in which L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, preferably diethyl ether or tetrahydrofuran, x, which may or may not be an integer, is greater than or equal to 0, y, which is an integer, is greater than or equal to 0.

3. Process according to Claim 1 or 2, in which the rare-earth metal is a lanthanide, the atomic number of which ranges from 57 to 71, preferably neodymium.

4. Process according to any one of Claims 1 to 3, in which the bridge P corresponds to the formula ZR1R2, Z representing a silicon or carbon atom and R1 and which may be identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl.

5. Process according to any one of Claims 1 to 4, in which the metallocene is of formula (III-1), (III-2), (!!!-3), (!!!-4) or (III-5):         [Me2Si(Flu)2Nd(µ-BH4)2Li(THF)]     (III-1)         [{Me2SiFlu2Nd(µ-BH4)2Li(THF)}2]     (!!!-2)         [Me2SiFlu2Nd(µ-BH4)(THF)]     (III-3)         [{Me2SiFlu2Nd(µ-BH4)(THF)}2]     (!!!-4)         [Me2SiFlu2Nd(µ-BH4)]     (!!!-5) Flu representing the C13H8 group.

6. Process according to any one of Claims 1 to 5, in which, if one of the two carbon atoms of the benzene nucleus of RB ortho to the magnesium is substituted with an isopropyl, the second carbon atom of the benzene nucleus of RB ortho to the magnesium is not substituted with an isopropyl.

7. Process according to any one of Claims 1 to 6, in which the carbon atoms of the benzene nucleus of RB ortho to the magnesium are substituted with a methyl or an ethyl, preferably a methyl.

8. Process according to any one of Claims 1 to 7, in which the organomagnesium reagent of formula (Ila) is of formula (Ila-m), R1 and R5, which are identical or different, represent a methyl or an ethyl, preferably a methyl, R2, R3 and R4, which are identical or different, being a hydrogen atom or an alkyl, RA being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups, m being a number greater than or equal to 1 and preferably equal to 1.

9. Process according to any one of Claims 1 to 8, in which RA is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical, preferably an alkanediyl.

10. Process according to any one of Claims 1 to 9, in which RA contains 3 to 10 carbon atoms, preferentially 3 to 8 carbon atoms.

11. Process according to any one of Claims 1 to 10, in which X is a bromine or chlorine atom, preferably a bromine atom.

12. Process according to any one of Claims 1 to 11, in which the 1,3-diene is 1,3-butadiene, isoprene or a mixture of 1,3-dienes one of which is 1,3-butadiene, preferably 1,3-butadiene.

13. Process according to any one of Claims 1 to 12, in which the monomer mixture containing ethylene and a 1,3-diene is a mixture of ethylene and a 1,3-diene which advantageously contains more than 50 mol% of ethylene.

14. Process according to any one of Claims 1 to 13, in which the block polymer is a triblock polymer of formula B-A-B in which A, referred to as the central block, is a statistical copolymer comprising 1,3-diene units and ethylene units, and B, referred to as the terminal block, is a polyethylene.

15. Multiblock polymer of formula (IV)         B-(A1-B1)n-A-RA-A-(B1-A1)n-B     (IV) in which A and A1 each represent a block which is a statistical copolymer comprising units of a 1,3-diene and ethylene units, B and B1 each represent a block which is polyethylene, n is an integer greater than or equal to 0, RA is an aliphatic hydrocarbon-based divalent chain, interrupted or not with one or more oxygen or sulfur atoms or one or more arylene groups, and RA is other than an ethylene unit, a 1,3-diene unit, a chain of ethylene units, a chain of 1,3-diene units, a chain of units consisting of one or more ethylene units and one or more 1,3-diene units.