Diene coupling copolymer rich in ethylene units and preparation method thereof

Abstract

The invention relates to a copolymer of a 1, 3-diene and an olefin, said copolymer comprising more than 50 mol% of ethylene units, said olefin being ethylene or a mixture of ethylene and an alpha-monoolefin, said copolymer being a coupled copolymer, the chains of which are connected to each other by a group comprising at least two units of formula 1 (-(CH2-CH (CH3)-CO-O)-), each copolymer chain is attached to a different unit of Formula 1 by a covalent bond between a carbon atom of a copolymer chain monomer unit and a carbon atom of a methylene group of a unit of Formula 1.

Description

Field of the Invention

[0001] The field of the invention is that of polymers rich in ethylene units and containing 1,3-diene units. Background of the Invention

[0002] For example, diene polymers rich in ethylene units are known from patent applications WO 2007054223 and WO 2007054224. Such copolymers are intended, for example, for tire treads. Compared with diene polymers conventionally used in rubber compositions, which are polybutadiene, polyisoprene, and copolymers of butadiene and styrene, the high molar content of ethylene units in these copolymers, which is greater than 50%, makes these copolymers less sensitive to oxidation phenomena.

[0003] It has been found that these copolymers containing 1,3-diene units and more than 50 mol% of ethylene units tend to flow under their own weight. This cold flow is not controlled and can cause difficulties in using these copolymers, especially during their storage in the form of balls or in storage tanks. To overcome this problem, it has been proposed in patent application WO 2021 / 123592 to branch the copolymers during their growth in the polymerization reaction. There is still a need to provide other methods capable of preparing new copolymers rich in ethylene units, which contain 1,3-diene units and have a lower tendency to flow. Summary of the Invention

[0004] In the continuing effort to overcome these storage fluidity problems, the applicant company has developed new coupled copolymers by using a coupling agent containing at least two methacrylate functional groups in the preparation method.

[0005] Thus, a first subject of the invention is a copolymer of 1,3-diene and an olefin, the olefin being ethylene or a mixture of ethylene and an α-monoolefin, the copolymer containing more than 50 mol% of ethylene units and being a coupled copolymer, the chains of the copolymer being linked to one another by a group containing at least two units of formula 1

[0006] -(CH 2 -CH(CH 3 )-CO-O)- of formula 1,

[0007] Each copolymer chain is bonded to a different unit of formula 1 by a covalent bond between a carbon atom of a copolymer chain monomer unit and a carbon atom of the methylene group of the unit of formula 1.

[0008] A second subject of the invention is a method for preparing a coupled copolymer of 1,3-diene and an olefin, the copolymer containing more than 50 mol% of ethylene units, the method comprising successive stages a), b) and c),

[0009] - Stage a) is the polymerization of a monomer mixture comprising a 1,3-diene and an olefin in the presence of a catalytic system based at least on a metallocene of formula (Ia) and an organomagnesium compound (cocatalyst),

[0010] {P(Cp 1 )(Cp 2 )Nd(BH 4 ) (1+y) -L y -N x} (Ia)

[0011] Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted,

[0012] P is a group bridging the two Cp 1 and Cp 2 groups and containing a silicon atom or a carbon atom,

[0013] Nd represents a neodymium atom,

[0014] L represents an alkali metal selected from lithium, sodium and potassium,

[0015] N represents an ether molecule,

[0016] x is an integer or non-integer equal to or greater than 0,

[0017] y is an integer equal to or greater than 0,

[0018] The olefin is ethylene or a mixture of ethylene and an α-monoolefin,

[0019] - Stage b) is the reaction of a coupling agent (a compound comprising at least two methacrylate functional groups of formula CH 2 =C(CH 3 )CO-O-) with the polymerization reaction product of stage a),

[0020] - Stage c) is a chain termination reaction.

[0021] A third subject of the present invention is a polymer composition comprising a copolymer having 2 branches and a copolymer having 3 branches according to the present invention or obtainable by a process according to the present invention. Detailed description

[0022] Any numerical interval expressed by the statement "between a and b" represents a numerical range greater than "a" and less than "b" (i.e., the extreme values a and b are not included), while any numerical interval expressed by the statement "a to b" means a numerical range extending from "a" up to "b" (i.e., the strict extreme values a and b are included).

[0023] The compounds mentioned in the specification can be compounds of fossil origin or biobased compounds. In the case of biobased compounds, they can be partially or completely derived from biomass, or obtained from renewable raw materials derived from biomass. In the same way, the mentioned compounds can also be derived from the recycling of pre-used materials, i.e., they can be partially or completely derived from recycling processes, or partially or completely obtained through starting materials that themselves are derived from recycling processes.

[0024] The expression "based on" used to define the components of the catalytic system is understood to mean a mixture of these components, or the reaction product of some or all of these components with each other.

[0025] The basic characteristic of the copolymer according to the present invention is that it is a copolymer of a 1,3-diene and an olefin. The olefin is ethylene or a mixture of ethylene and an α-monoolefin. The constituent units of the copolymer are those resulting from the polymerization of the 1,3-diene and the olefin. In the case where the olefin is ethylene, the constituent units are those resulting from the polymerization of the 1,3-diene and ethylene, and the copolymer is a copolymer of ethylene and a 1,3-diene. In the case where the olefin is a mixture of ethylene and an α-monoolefin, the constituent units are those resulting from the polymerization of the 1,3-diene, ethylene, and the α-monoolefin, and the copolymer is a copolymer of ethylene, a 1,3-diene, and an α-monoolefin. Preferably, the α-monoolefin is styrene.

[0026] The basic characteristic of the copolymer also lies in that it contains more than 50 mol% of ethylene units. The copolymer preferably contains more than 60 mol% of ethylene units, more preferably contains more than 65 mol% of ethylene units. The copolymer preferably contains less than 90 mol% of ethylene units, more preferably contains at most 85 mol% of ethylene units, and even more preferably contains at most 80 mol% of ethylene units. The content of ethylene units in the copolymer is expressed relative to all the units resulting from the polymerization of the 1,3-diene and the olefin.

[0027] The 1,3-diene is a single compound (i.e., a single (one) 1,3-diene), or a mixture of 1,3-dienes with different chemical structures. In particular, 1,3-dienes having 4 to 20 carbon atoms are suitable as the 1,3-diene.

[0028] Preferably, the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene or a mixture thereof (e.g., a mixture of at least two of them). The mixture of at least two of them is advantageously a mixture containing 1,3-butadiene.

[0029] According to a specific embodiment of the present invention, the 1,3-diene is a mixture of 1,3-dienes containing 1,3-butadiene.

[0030] According to another particularly preferred embodiment of the present invention, the copolymer according to the present invention contains 1,3-butadiene units and cyclic units (1,2-cyclohexane units). The 1,2-cyclohexane units have the formula (I). In addition to the conventional ethylene units and 1,3-butadiene units (-(CH 2 -CH 2 )-, -(CH 2 -CH=CH-CH 2 )- and -(CH 2 -CH(C=CH 2 ))-), the cyclic units are generated by the specific insertion of ethylene monomers and 1,3-butadiene monomers into the polymer chain. The mechanism for obtaining such a microstructure is described, for example, in the literature Macromolecules, 2009, 42, 3774-3779.

[0031]

[0032] When the copolymer according to the present invention contains 1,2-cyclohexane units, it preferably contains at most 15 mol% of 1,2-cyclohexane units, the percentage being expressed relative to all the units produced by the polymerization of 1,3-diene and olefin. Such a copolymer can be prepared by the method according to the present invention according to such a pattern, wherein the metallocene of the catalyst system has two substituted or unsubstituted fluorenyl groups as ligands.

[0033] Preferably, the copolymer according to the present invention is a copolymer of ethylene and 1,3-diene. In this case, the constituent monomer units of the copolymer are those produced by the copolymerization of ethylene and 1,3-diene. Very preferably, the copolymer according to the present invention is a copolymer of ethylene and 1,3-butadiene, or a copolymer of ethylene, 1,3-butadiene and myrcene, or a copolymer of ethylene, 1,3-butadiene and β-farnesene.

[0034] According to any one of the embodiments of the present invention, the copolymer according to the present invention is preferably a statistical copolymer. In other words, the constituent monomer units of the copolymer chains (or branches) of the statistical copolymer according to the present invention are statistically distributed in the copolymer chains. Such a copolymer can be prepared according to the method of the present invention according to such a pattern, wherein the polymerization reaction is carried out in a reactor under a constant monomer pressure, and a continuous addition of each monomer or one of the monomers is carried out in the reactor. Advantageously, the copolymer according to the present invention is a statistical copolymer of ethylene and 1,3-butadiene, or a statistical copolymer of ethylene, 1,3-butadiene and myrcene, or a statistical copolymer of ethylene, 1,3-butadiene and β-farnesene.

[0035] Another characteristic of the copolymer according to the present invention is also that it is coupled. The copolymer chains constituting the copolymer according to the present invention are connected to each other by a group containing at least two units of formula 1

[0036] -(CH 2 -CH(CH 3 )-CO-O)-Formula 1,

[0037] Each copolymer chain is bonded to a different unit of formula 1 by a covalent bond between the carbon atom of the copolymer chain monomer unit and the carbon atom of the methylene group of the unit of formula 1. In other words, the group connecting the copolymer chains to each other can be represented by the following formula: Z’-[O-CO-CH(CH 3 )-CH 2 -] v -, Z’ is a group with a valence v, and v is an integer of at least equal to 2, preferably in the range of 2 to 3.

[0038] Preferably, the copolymer according to the present invention is a coupled copolymer with 2 branches or 3 branches.

[0039] According to a preferred embodiment of the present invention, the coupled copolymer is a coupled copolymer with 2 branches, and the two constituent copolymer chains of the coupled copolymer are connected together by a group containing two units of formula 1. The coupled copolymer with 2 branches preferably corresponds to formula 2

[0040] [P-CH 2 -CH(CH 3 )-CO-O] 2 -Z 1 Formula 2

[0041] P represents a copolymer chain,

[0042] Z 1 represents a divalent hydrocarbon group or a divalent hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups, and the divalent group can be substituted by one or more CH 2=C(CH 3 )CO-O- substituted by a methacrylate functional group.

[0043] According to the first variant form, the coupled copolymer having 2 branches corresponds to formula 2

[0044] [P-CH 2 -CH(CH 3 )-CO-O] 2 -Z 1 Formula 2

[0045] P represents a copolymer chain,

[0046] Z 1 represents a divalent hydrocarbon group or a divalent hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups.

[0047] A hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups is understood to mean a hydrocarbon chain interrupted by one or more oxygen atoms or sulfur atoms to form an ether bond or a thioether bond, respectively.

[0048] Advantageously, Z 1 is an acyclic group. Z 1 can be a linear group or a branched group. The number of carbon atoms in Z 1 itself is not limited. Z 1 can contain up to 20 carbon atoms. Preferably, Z 1 is an alkanediyl group or an alkanediyl group containing one or more ether functional groups. Preferably, the alkanediyl group of Z 1 contains 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms. Particularly suitable as the alkanediyl group of Z 1 are 1,2-ethanediyl, 1,1-ethanediyl, 1,3-propanediyl, 1,2-propanediyl, 1,4-butanediyl, 1,3-butanediyl, 1,5-pentanediyl, 2,2-dimethyl-1,3-propanediyl, 1,6-hexanediyl, 2,5-hexanediyl, 1,4-cyclohexanediyl and 1,4-cyclohexanediyldimethylene groups. Also suitable are divalent groups interrupted by one or more oxygen atoms to form an ether bond, preferably alkanediyl groups, such as the formula -(CH 2 -CH 2 -O) n -CH 2 -CH 2 - or -(CH 2 -CH 2 -CH 2 -O) n -CH 2 -CH 2 -CH 2a divalent group, where n is an integer greater than or equal to 1, particularly in the range of 1 to 10, more particularly in the range of 1 to 2.

[0049] According to the second variant form, the coupled copolymer having 2 branches has the formula 2, where Z 1 the divalent hydrocarbon group is further substituted by one or more methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-, preferably substituted by one methacrylate functional group of the formula CH 2 =C(CH 3 )CO-O-. According to the second variant form, Z 1 is preferably an alkanediyl substituted by a methacrylate functional group.

[0050] Advantageously, in formula 2, Z 1 is an alkanediyl or an alkanediyl substituted by a methacrylate functional group.

[0051] According to another preferred embodiment of the present invention, the coupled copolymer is a coupled copolymer having 3 branches, and the three constituent copolymer chains of the coupled copolymer are linked together by a group containing three units of formula 1. Preferably, the coupled copolymer having 3 branches corresponds to formula 3

[0052] [P-CH 2 -CH(CH 3 )-CO-O] 3 -Z 2 Formula 3

[0053] P represents a copolymer chain,

[0054] Z 2 represents a trivalent hydrocarbon group or a trivalent hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups.

[0055] Advantageously, Z 2 is an acyclic group. Z 2 can be a linear group or a branched group. The number of carbon atoms in Z 2 itself is not limited. Z 2 can contain up to 20 carbon atoms. Preferably, Z 2 is an alkanetriyl or an alkanetriyl containing one or more ether functional groups. An alkanetriyl is generally a saturated trivalent aliphatic hydrocarbon group. Preferably, the alkanetriyl of Z 2 contains 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms.

[0056] Particularly suitable as Z 2The alkanetriyl groups are propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, 2-ethylpropane-1,2,3-triyl, propane-1,1,1-triyl trimethylene and 1,2,5-pentanetriyl groups.

[0057] Also suitable are trivalent groups comprising an alkylene oxide chain (such as an ethylene oxide chain or a propylene oxide chain) or a polyalkylene oxide chain (such as a polyethylene oxide chain or a polypropylene oxide chain), preferably alkanetriyl groups.

[0058] Mention may be made of propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, 2-ethylpropane-1,2,3-triyl or propane-1,1,1-triyl trimethylene groups comprising one or more alkylene oxide chains or polyalkylene oxide chains (especially ethylene oxide chains or polyethylene oxide chains).

[0059] For example, suitable are propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl or 2-ethylpropane-1,2,3-triyl groups comprising three ethylene oxide chains or polyethylene oxide chains at the 1, 2, 3 positions, or propane-1,1,1-triyl trimethylene groups comprising three ethylene oxide chains or polyethylene oxide chains at the 1, 1, 1 positions. Diagrams of these groups are shown below, where n, m and p are integers greater than or equal to 1, especially in the range from 1 to 10, more especially in the range from 1 to 2.

[0060]

[0061] For example, also suitable are alkanetriyl groups comprising ω-alkoxy poly(alkylene oxide) groups (such as ω-methoxy poly(ethylene oxide) groups). Mention may be made, for example, of 2-(ω-methoxy poly(ethylene oxide))propane-1,2,3-triyl and 1-(methoxy poly(alkylene oxide))methane-1,1,1-triyl trimethylene groups.

[0062] Advantageously, in formula (3), Z 2 represents alkanetriyl.

[0063] According to any one of the embodiments, the copolymer according to the invention is preferably an elastomer and is intended for use in rubber compositions. In particular, the coupled copolymers having 2 branches and the coupled copolymers having 3 branches are preferably elastomers.

[0064] Particularly preferred are the coupled copolymers having three branches according to the invention, because compared with non-coupled copolymers, polymers having a single branch or coupled copolymers having two branches (the branches of the non-coupled copolymers and the coupled copolymers having two branches are substantially the same in composition and length as the branches of the coupled copolymers having three branches), the coupled copolymers having three branches exhibit a favorable compromise between their macroscopic structure and their rheological (in particular viscosity) properties.

[0065] Particularly preferred are polymer compositions (mixtures comprising a coupled copolymer having two branches and a coupled copolymer having three branches according to the invention), because compared with non-coupled copolymers or coupled copolymers having two branches (the branches of the non-coupled copolymers and the coupled copolymers having two branches are substantially the same in composition and length as the branches of the coupled copolymers having three branches), the polymer compositions also exhibit improved rheological properties.

[0066] Also very particularly preferred are mixtures comprising a coupled copolymer having two branches and a coupled copolymer having three branches according to the invention, both being elastomers.

[0067] The copolymers according to the invention can be prepared by a process (which is another subject of the invention) comprising successive stages a), b) and c),

[0068] - Stage a) consists in polymerizing a monomer mixture comprising a 1,3-diene and an olefin in the presence of a catalytic system based at least on a metallocene of formula (Ia) and an organomagnesium compound,

[0069] {P(Cp 1 )(Cp 2 )Nd(BH 4 ) (1+y) -L y -N x} (Ia)

[0070] Cp 1 and Cp 2 are identical or different and are selected from fluorenyl, cyclopentadienyl and indenyl, these groups being substituted or unsubstituted,

[0071] P is a group bridging the two Cp 1 and Cp 2 groups and containing a silicon or carbon atom,

[0072] Nd represents a neodymium atom,

[0073] L represents an alkali metal selected from lithium, sodium and potassium,

[0074] N represents an ether molecule,

[0075] x is an integer or non-integer equal to or greater than 0,

[0076] y is an integer equal to or greater than 0,

[0077] The olefin is ethylene or a mixture of ethylene and an α-monoolefin,

[0078] - Step b) is the reaction of a coupling agent (a compound containing at least two methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-) with the polymerization reaction product of step a),

[0079] - Step c) is a chain termination reaction.

[0080] Step a) of the process according to the invention is the polymerization of a monomer mixture of a 1,3-diene and an olefin, which enables the preparation of copolymer chains of a 1,3-diene and an olefin, the growing chains being intended to react with a coupling agent in the next step (step b)).

[0081] The 1,3-diene of the monomer mixture in step a) is a single compound (i.e., a single (one) 1,3-diene) or a mixture of 1,3-dienes with different chemical structures. Particularly suitable as the 1,3-diene are 1,3-dienes having 4 to 20 carbon atoms, such as 1,3-butadiene, isoprene, myrcene, β-farnesene and mixtures thereof. The 1,3-diene is preferably 1,3-butadiene, isoprene, myrcene, β-farnesene or a mixture thereof, especially a mixture of at least two of them. More preferably, the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene, the mixture preferably being a mixture of 1,3-butadiene and myrcene, or a mixture of 1,3-butadiene and β-farnesene.

[0082] According to a first variant of the invention, the olefin of the monomer mixture in step a) is ethylene. According to this variant, the monomer mixture is a mixture of a 1,3-diene and ethylene, and the polymerization reaction product of step a) is such a polymer chain, the constituent units of which are produced by the insertion of ethylene and 1,3-diene into the growing chain. The copolymer prepared by this first variant is a copolymer of ethylene and a 1,3-diene.

[0083] According to a second variant form of the present invention, the monomer mixture in stage a) is a mixture of 1,3-diene and olefins, and the olefins themselves are a mixture of ethylene and α-monoolefins. According to this variant form, the polymerization reaction product in stage a) is such a polymer chain, and the constituent units of the polymer chain are generated by the insertion of ethylene, α-monoolefins, and 1,3-diene into the growing chain. The α-monoolefin is preferably styrene or styrene in which the benzene ring is substituted by an alkyl group, and more preferably styrene. The copolymer prepared by the preferred embodiment of the second variant form is a copolymer of ethylene, 1,3-diene, and styrene.

[0084] Preferably, the monomer mixture in stage a) contains more than 50 mol% of ethylene, and the percentage is expressed relative to the total molar number of the monomers in the monomer mixture in stage a). When the monomer mixture contains an α-monoolefin (such as styrene), it preferably contains less than 40 mol% of the α-monoolefin, and the percentage is expressed relative to the total molar number of the monomers in the monomer mixture in stage a).

[0085] The copolymerization of the monomer mixture can be carried out using a catalytic system composed of a metallocene and an organomagnesium compound according to Patent Applications WO 2007054223 A2 and WO 2007054224 A2.

[0086] In the present patent application, a metallocene is understood to mean an organometallic complex in which the metal (in this case, a neodymium atom) is bonded to a molecule called a ligand and composed of Cp 1 and Cp 2 two groups, and the Cp 1 and Cp 2 two groups are connected together by a bridge P. These Cp 1 and Cp 2 groups are the same or different and are selected from fluorenyl, cyclopentadienyl, and indenyl, and these groups can be substituted or unsubstituted.

[0087] According to the present invention, the metallocene used as a basic component in the catalytic system corresponds to formula (Ia)

[0088] {P(Cp 1 )(Cp 2 )Nd(BH 4 ) (1+y) -L y -N x} (Ia)

[0089] P is a group that bridges the Cp 1 and Cp 2 two groups and contains a silicon atom or a carbon atom.

[0090] Cp 1 and Cp2 identical or different and selected from fluorenyl, cyclopentadienyl and indenyl, these groups being substituted or unsubstituted,

[0091] Nd represents a neodymium atom,

[0092] L represents an alkali metal selected from lithium, sodium and potassium,

[0093] N represents an ether molecule,

[0094] x is an integer or non-integer equal to or greater than 0,

[0095] y is an integer equal to or greater than 0.

[0096] Any ether having the ability to coordinate with an alkali metal (in particular diethyl ether, methyltetrahydrofuran and tetrahydrofuran) is suitable as the ether.

[0097] As substituted cyclopentadienyl, fluorenyl and indenyl, mention may be made of those substituted by an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms or a trialkylsilyl group (such as the SiMe 3 group). The choice of the group also depends on the availability of the corresponding molecule (substituted cyclopentadiene, fluorene and indene), since these molecules are commercially available or can be easily synthesized.

[0098] As substituted fluorenyl, mention may be made of those substituted at the 2, 7, 3 or 6 positions, in particular 2,7-di(tert-butyl)fluorenyl or 3,6-di(tert-butyl)fluorenyl. The 2, 3, 6 and 7 positions respectively represent the positions of the carbon atoms of the ring as shown in the following figure, and the 9 position corresponds to the carbon atom connected to the bridge P.

[0099]

[0100] As substituted cyclopentadienyl, mention may be made of those substituted at the 2 (or 5) position which is equally effective as the 3 (or 4) position, in particular those substituted at the 2 position, more particularly tetramethylcyclopentadienyl. As shown in the following figure, the 2 (or 5) position represents the position of the carbon atom adjacent to the carbon atom connected to the bridge P. It will be recalled that substitution at the 2 or 5 position also represents substitution at the α position relative to the bridge.

[0101]

[0102] As substituted indenyl, mention may be particularly made of those substituted at the 2 position, more particularly 2-methylindenyl or 2-phenylindenyl. As shown in the following figure, the 2 position represents the position of the carbon atom adjacent to the carbon atom connected to the bridge P.

[0103]

[0104] Preferably, Cp 1 and Cp 2 are the same or different and are a cyclopentadienyl group substituted at the α-position relative to the bridge, a substituted fluorenyl group, a substituted indenyl group, or a fluorenyl group of formula C 13 H 8 or an indenyl group of formula C 9 H 7 . More preferably, Cp 1 and Cp 2 are the same or different and are selected from substituted fluorenyl groups and unsubstituted fluorenyl groups of formula C 13 H 8 . Advantageously, Cp 1 and Cp 2 are the same and each represents an unsubstituted fluorenyl group of formula C 13 H 8 represented by the symbol Flu.

[0105] Preferably, the bridge P connecting the groups Cp 1 and Cp 2 has the formula ZR 1 R 2 , where Z represents a silicon atom or a carbon atom, and R 1 and R 2 are the same or different and each represents an alkyl group containing 1 to 20 carbon atoms, preferably methyl. In the formula ZR 1 R 2 , Z advantageously represents a silicon atom Si.

[0106] Even better, the metallocene has the formula (I-1), (I-2), (I-3), (I-4), or (I-5):

[0107] [Me 2 Si(Flu) 2 Nd(μ-BH 4 ) 2 Li(THF)] (I-1)

[0108] [{Me 2 SiFlu 2 Nd(μ-BH 4 ) 2 Li(THF)} 2 (I-2)

[0109] [Me 2 SiFlu 2 Nd(μ-BH 4 )(THF)] (I-3)

[0110] [{Me 2 SiFlu 2 Nd(μ-BH4 )(THF)} 2 (I-4)

[0111] [Me 2 SiFlu 2 Nd(μ-BH 4 )] (I-5)

[0112] where Flu represents C 13 H 8 group.

[0113] The metallocene used in the synthesis of the catalyst system can be in the form of a crystalline powder or an amorphous powder, or in the form of single crystals. The metallocene can be provided in monomeric or dimeric form, and these forms depend on the method of preparing the metallocene, as described, for example, in patent applications WO 2007054224 A2 or WO 2007054223 A2. The metallocene can be conventionally prepared by a method similar to the methods described in patent applications WO 2007054224 A2 or WO 2007054223 A2, in particular by the reaction of a salt of an alkali metal of a ligand with a borohydride of the rare earth metal neodymium 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) under inert and anhydrous conditions. After the reaction, the metallocene is separated from the reaction by-products by techniques known to those skilled in the art (such as filtration or precipitation in a second solvent). Finally, the metallocene is dried and separated in solid form.

[0114] The organomagnesium compound (another essential component of the catalyst system) is a cocatalyst for the catalyst system. Generally, the organomagnesium compound can be a diorganomagnesium compound or a halide of an organomagnesium compound. Preferably, the organomagnesium compound has the formula (IIa), (IIb), (IIc) or (IId), where R 3 , R 4 , R 5 and R B are the same or different and represent carbon-containing groups, R A represents a divalent carbon-containing group, X is a halogen atom, and m is a number greater than or equal to 1, preferably equal to 1.

[0115] MgR 3 R 4 (IIa)

[0116] XMgR 5 (IIb)

[0117] R B -(Mg-R A ) m -Mg-R B(IIc)

[0118] X-Mg-R A -Mg-X (IId).

[0119] R A may be a divalent aliphatic hydrocarbon chain, which is interrupted or not interrupted by one or more oxygen atoms or sulfur atoms or one or more arylene groups.

[0120] The carbon-containing group is understood to mean a group containing one or more carbon atoms. The carbon-containing group may be a hydrocarbon group (hydrocarbon group) or a hetero-hydrocarbon group (i.e., a group containing one or more heteroatoms in addition to carbon atoms and hydrogen atoms). The compounds described as transfer agents in patent application WO2016092227 A1 may be suitable as organomagnesium compounds having hetero-hydrocarbon groups. The carbon-containing groups represented by the symbols R 3 、R 4 、R 5 、R B and R A are preferably hydrocarbon groups.

[0121] Preferably, R A contains 3 to 10 carbon atoms, especially 3 to 8 carbon atoms.

[0122] Preferably, R A is a divalent hydrocarbon chain. Preferably, R A is a linear or branched alkanediyl, cycloalkanediyl or xylene diyl group. More preferably, R A is an alkanediyl. Even more preferably, R A is an alkanediyl having 3 to 10 carbon atoms. Advantageously, R A is an alkanediyl having 3 to 8 carbon atoms. Very advantageously, R A is a linear alkanediyl. Very particularly suitable as the R A group are 1,3-propanediyl, 1,4-butanediyl, 1,5-pentanediyl, 1,6-hexanediyl, 1,7-heptanediyl and 1,8-nonanediyl.

[0123] The carbon-containing groups represented by R 3 、R 4 、R 5 and R B may be aliphatic or aromatic. They may contain one or more heteroatoms, such as oxygen atoms, nitrogen atoms, silicon atoms or sulfur atoms. Preferably, they are alkyl groups, phenyl groups or aryl groups. They may contain 1 to 20 carbon atoms.

[0124] The carbon-containing groups represented by R 3 、R 4 、R 5 and R BThe alkyl group represented may contain 2 to 10 carbon atoms and is particularly ethyl, butyl or octyl.

[0125] The aryl group represented by R 3 , R 4 , R 5 and R B may contain 7 to 20 carbon atoms and is particularly phenyl substituted by one or more alkyl groups (such as methyl, ethyl or isopropyl).

[0126] R 3 , R 4 and R 5 are preferably an alkyl group containing 2 to 10 carbon atoms, phenyl or an aryl group containing 7 to 20 carbon atoms.

[0127] According to a specific embodiment of the present invention, R 3 contains a benzene nucleus substituted by a magnesium atom, and one carbon atom adjacent to the magnesium in the benzene nucleus is substituted by methyl, ethyl or isopropyl, or forms a ring with the carbon atom closest to it and located in the meta position of the magnesium, and the other carbon atom adjacent to the magnesium in the benzene nucleus is substituted by methyl, ethyl or isopropyl, and R 4 is an alkyl group. According to this specific embodiment, R 3 is advantageously 1,3-dimethylphenyl, 1,3-diethylphenyl, mesityl or 1,3,5-triethylphenyl, and R 4 is advantageously ethyl, butyl or octyl.

[0128] According to another specific embodiment of the present invention, both R 3 and R 4 are alkyl groups containing 2 to 10 carbon atoms, particularly ethyl, butyl or octyl.

[0129] Preferably, R 5 is an alkyl group containing 2 to 10 carbon atoms, particularly ethyl, butyl or octyl.

[0130] Advantageously, R B contains a benzene nucleus substituted by a magnesium atom, and one carbon atom adjacent to the magnesium in the benzene nucleus is substituted by methyl, ethyl or isopropyl, or forms a ring with the carbon atom closest to it and located in the meta position of the magnesium, and the other carbon atom adjacent to the magnesium in the benzene nucleus is substituted by methyl, ethyl or isopropyl. Even better, R B is 1,3-dimethylphenyl, 1,3-diethylphenyl, mesityl or 1,3,5-triethylphenyl.

[0131] Suitable organomagnesium compounds are, for example, butylethylmagnesium, butyloctylmagnesium, ethylmagnesium chloride, butylmagnesium chloride, ethylmagnesium bromide, butylmagnesium bromide, octylmagnesium chloride, octylmagnesium bromide, 1,3 - dimethylphenylbutylmagnesium, 1,3 - diethylphenylethylmagnesium, butylmesitylmagnesium, ethylmesitylmagnesium, 1,3 - diethylphenylbutylmagnesium, 1,3 - diethylphenylethylmagnesium, 1,3 - diisopropylphenylbutylmagnesium, 1,3 - diisopropylphenylethylmagnesium, 1,3,5 - triethylphenylbutylmagnesium, 1,3,5 - triethylphenylethylmagnesium, 1,3,5 - triisopropylphenylbutylmagnesium, 1,3,5 - triisopropylphenylethylmagnesium, 1,3 - propanediylbis(magnesium bromide), 1,3 - propanediylbis(magnesium chloride), 1,5 - pentanediylbis(magnesium bromide), 1,5 - pentanediylbis(magnesium chloride), 1,8 - octanediyl(magnesium bromide) and 1,8 - octanediylbis(magnesium chloride).

[0132] The organomagnesium compound of formula (IIc) can be prepared by a method comprising the reaction of a first organomagnesium compound of formula X’Mg - R A -MgX’ with a second organomagnesium compound of formula R B -Mg - X’, where X’ represents a halogen atom, preferably a bromine atom or a chlorine atom, and R B and R A are as defined above. X’ is more preferably a bromine atom. The stoichiometry used in the reaction determines the value of m in formula (IIc). For example, a molar ratio of 0.5 of the amount of the first organomagnesium compound to the amount of the second organomagnesium compound favors the formation of the organomagnesium compound of formula (IIc) with m equal to 1, while a molar ratio greater than 0.5 will more favor the formation of the organomagnesium compound of formula (IIc) with m greater than 1.

[0133] To carry out the reaction of the first organomagnesium compound with the second organomagnesium compound, a solution of the second organomagnesium compound is usually added to a solution of the first organomagnesium compound. The solutions of the first organomagnesium compound and the second organomagnesium compound are usually solutions in an ether (such as diethyl ether, dibutyl ether, tetrahydrofuran, methyltetrahydrofuran) or a mixture of two or more of these ethers. Preferably, the respective concentrations of the solution of the first organomagnesium compound and the solution of the second organomagnesium compound are 0.01 mol / l to 3 mol / l and 0.02 mol / l to 5 mol / l, respectively. More preferably, the respective concentrations of the first organomagnesium compound and the second organomagnesium compound are 0.1 mol / l to 2 mol / l and 0.2 mol / l to 4 mol / l, respectively.

[0134] The first organomagnesium compound and the second organomagnesium compound can be pre-prepared in a reactor by a Grignard reaction starting from magnesium metal and a suitable precursor. For the first organomagnesium compound and the second organomagnesium compound, the respective precursors have the formula X'-R A -X' and R B -X', R A 、R B and X' are as defined above. The Grignard reaction is usually carried out by adding the precursor to magnesium metal, which is usually provided in the form of turnings. Preferably, iodine (I 2 ) in the form of beads is introduced into the reactor before adding the precursor, thereby activating the Grignard reaction in a known manner.

[0135] Alternatively, the organomagnesium compound of formula (IIc) can be prepared by the reaction of an organomagnesium compound of formula M-R A -M with an organomagnesium compound of formula R B -Mg-X', where M represents a lithium atom, a sodium atom or a potassium atom, and X', R B and R A are as defined above. Preferably, M represents a lithium atom, in which case the organometallic compound of formula M-R A -M is an organolithium compound.

[0136] The reaction of the organolithium compound with the organomagnesium compound is usually carried out in an ether (such as diethyl ether, dibutyl ether, tetrahydrofuran or methyltetrahydrofuran), methylcyclohexane, toluene or a mixture thereof. The reaction is also usually carried out at a temperature in the range of 0 °C to 60 °C. The contacting operation is preferably carried out at a temperature between 0 °C and 23 °C. The operation of contacting the organometallic compound of formula M-R A -M with the organomagnesium compound of formula R B -Mg-X' is preferably carried out by adding a solution of the organometallic compound M-R A -M to a solution of the organomagnesium compound R B -Mg-X'. The solution of the organometallic compound M-R A -M is usually a solution in a hydrocarbon solvent (preferably n-hexane, cyclohexane or methylcyclohexane), and the solution of the organomagnesium compound R B -Mg-X' is usually a solution in an ether (preferably diethyl ether or dibutyl ether). Preferably, the respective concentrations of the solution of the organometallic compound M-R A -M and the solution of the organomagnesium compound R B -Mg-X' are 0.01 mol / l to 1 mol / l and 0.02 mol / l to 5 mol / l, respectively. More preferably, the solution of the organometallic compound M-R A -M and the solution of the organomagnesium compound R BThe respective concentrations of the solution of -Mg-X’ are 0.05 mol / l to 0.5 mol / l and 0.2 mol / l to 3 mol / l respectively.

[0137] As with any synthesis carried out in the presence of an organometallic compound, the synthesis described for the synthesis of the organomagnesium compound is carried out in an anhydrous condition in an inert atmosphere in a stirred reactor. Generally, a solvent and a solution are used under anhydrous nitrogen or argon.

[0138] After the formation of the organomagnesium compound of formula (IIc), it is generally recovered in solution after filtration under an inert anhydrous atmosphere. Before use, its solution can be stored in a sealed container (such as a capped bottle) at a temperature between -25 °C and 23 °C.

[0139] The compound of formula (IId) (which is a Grignard reagent) is described, for example, in the work “Advanced Organic Chemistry” by J. March (4th edition, 1992, pages 622 - 623) or in the work “Handbook of Grignard Reagents” edited by Gary S. Silverman and Philip E. Rakita (1996, pages 502 - 503). They can be synthesized by contacting magnesium metal with a dihalide of formula X-R A -X, where R A is as defined according to the present invention. For its synthesis, reference can be made to, for example, the volumes of “Organic Synthesis”.

[0140] The compounds of formula (IIa) and (IId) (which are also Grignard reagents) are well-known; some of them are even commercial products. For their synthesis, reference can also be made to, for example, the volumes of “Organic Synthesis”.

[0141] Like any organomagnesium compound, the organomagnesium compound constituting the catalytic system (especially the organomagnesium compound of formula (IIa), (IIb), (IIc) or (IId)) can be provided in the form of monomeric entities or polymeric entities. As an example, the organomagnesium compound (IIc) can be in the form of monomeric entities (R B -(Mg-R A ) m -Mg-R B ) 1 or in the form of polymeric entities (R B -(Mg-R A ) m -Mg-R B ) p (especially the dimer (R B-(Mg-R A ) m -Mg-R B ) 2 ) is provided in the form, where p is an integer greater than 1 and m is as defined above. In the same manner, also by way of example, the organomagnesium compound of formula (IId) can be provided in the form of a monomeric entity (X-Mg-R A -Mg-X) 1 or a polymeric entity (X-Mg-R A -Mg-X) p (especially a dimer (X-Mg-R A -Mg-X) 2 ), where p is an integer greater than 1.

[0142] Furthermore, regardless of whether it is in the form of a monomeric entity or a polymeric entity, the organomagnesium compound can also be provided in the form of an entity coordinated with one or more molecules of a solvent (preferably an ether, such as diethyl ether, tetrahydrofuran or methyltetrahydrofuran).

[0143] In formulas (IIb) and (IId), X is preferably a bromine atom or a chlorine atom, more preferably a bromine atom.

[0144] According to any one of the embodiments of the present invention, the organomagnesium compound preferably has the formula (IIa).

[0145] The amounts of the cocatalyst and the metallocene reacted are such that the ratio of the number of moles of Mg of the cocatalyst to the number of moles of the rare earth metal (neodymium) of the metallocene preferably ranges from 0.5 to 200, more preferably from 1 to less than 20. The numerical range from 1 to less than 20 is particularly advantageous for obtaining polymers with high molar mass.

[0146] According to the first embodiment, the catalytic system can be conventionally prepared by a method similar to the methods described in patent applications WO 2007054224 A2 or WO2007054223 A2. For example, the cocatalyst (in this case an organomagnesium compound) and the metallocene are usually reacted in a hydrocarbon solvent at a temperature between 20 °C and 80 °C for a time between 5 minutes and 60 minutes. The catalytic system is usually prepared in an aliphatic hydrocarbon solvent (such as methylcyclohexane) or an aromatic hydrocarbon solvent (such as toluene), preferably in an aliphatic hydrocarbon solvent (such as methylcyclohexane). Usually, after synthesis, the catalytic system is used in this form for stage a).

[0147] According to the second embodiment, the catalytic system can be prepared by a method similar to the method described in patent application WO 2017093654 A1 or patent application WO 2018020122 A1: it is called the preformed type. For example, an organomagnesium compound and a metallocene are usually reacted in a hydrocarbon solvent at a temperature of 20 °C to 80 °C for 10 minutes to 20 minutes to obtain a first reaction product, and then the preformed monomer is reacted with this first reaction product at a temperature in the range of 40 °C to 90 °C for 1 h to 12 h. The preformed monomer is preferably used according to a (preformed monomer / metal of metallocene) molar ratio in the range of 5 to 1000, preferably 10 to 500. Before its use in polymerization, the catalytic system of the preformed type can be stored under an inert atmosphere, especially at a temperature in the range of -20 °C to ambient temperature (23 °C). According to this second embodiment, the catalytic system of the preformed type has a preformed monomer as a basic component, and the preformed monomer is selected from 1,3-dienes, ethylene and mixtures thereof. In other words, in addition to the metallocene and the cocatalyst, the "preformed" catalytic system also contains a preformed monomer. As the preformed monomer, the 1,3-diene can be 1,3-butadiene, isoprene or a 1,3-diene of the formula CH 2 =CR 6 -CH=CH 2 , the symbol R 6 represents a hydrocarbon group having 3 to 20 carbon atoms, especially myrcene or β-farnesene. The preformed monomer is preferably 1,3-butadiene.

[0148] The catalytic system is usually provided in a solvent, and the solvent is preferably the solvent for preparing the catalytic system. Then, the concentration of the rare earth metal (i.e., neodymium) of the metallocene is preferably in the range of 0.0001 mol / l to 0.2 mol / l, more preferably 0.001 mol / l to 0.03 mol / l.

[0149] Like any synthesis carried out in the presence of an organometallic compound, the synthesis of the metallocene, the synthesis of the organomagnesium compound and the synthesis of the catalytic system are carried out under anhydrous conditions in an inert atmosphere. Usually, the reaction starts with an anhydrous solvent and compounds under anhydrous nitrogen or argon.

[0150] The polymerization of the monomer mixture is preferably carried out continuously or discontinuously in solution in a reactor. The polymerization solvent is usually a hydrocarbon solvent, preferably an aliphatic hydrocarbon solvent. Methylcyclohexane is very particularly suitable as an example of an aliphatic hydrocarbon solvent. The monomer mixture can be introduced into a reactor containing the polymerization solvent and the catalyst system, or conversely, the catalyst system can be introduced into a reactor containing the polymerization solvent and the monomer mixture. The monomer mixture and the catalyst system can be introduced simultaneously into a reactor containing the polymerization solvent, especially in the case of continuous polymerization. The polymerization is generally carried out under anhydrous conditions, in the absence of oxygen, in the presence of an optional inert gas. The polymerization temperature generally varies in the range of 40 °C to 150 °C, preferably 40 °C to 120 °C. Those skilled in the art adjust the polymerization conditions (such as polymerization temperature, concentration of each reactant, or pressure of the reactor) according to the composition of the monomer mixture, the polymerization reactor, and the desired microstructure and macrostructure of the copolymer chain.

[0151] The polymerization is preferably carried out at a constant monomer pressure. The continuous addition of each monomer or one of the monomers is carried out in the polymerization reactor, in which case the polymerization reactor is a feed reactor. This embodiment is very particularly suitable for the statistical introduction of monomers. Preferably, the polymerization in stage a) is a statistical polymerization, which is reflected by the statistical introduction of the monomers of the monomer mixture used in stage a).

[0152] After reaching the desired monomer conversion in the polymerization reaction of stage a), stage b) is carried out.

[0153] Stage b) of the process according to the invention combines the reaction product of stage a) and a coupling agent (a compound containing at least two methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-). Stage b) is a coupling reaction of the copolymer chains, in which one end reacts with the coupling agent without subsequent polymerization of the methacrylate functional groups. After deactivating the reaction sites by a termination reaction of the polymer chains (stage c), a coupling copolymer of 1,3-diene and olefin is obtained, and the chains of the copolymer are connected to each other by groups containing at least two units of formula 1

[0154] -(CH 2 -CH(CH 3 )-CO-O)-Formula 1,

[0155] Each copolymer chain is bonded to a different unit of formula 1 by a covalent bond between the carbon atom of the terminal monomer unit of the copolymer chain and the carbon atom of the methylene group of the unit of formula 1. The terminal monomer unit is usually the compositional monomer unit at the end of the copolymer chain, which is obtained at the end of stage a) and reacts with the coupling agent.

[0156] The methacrylates required for use in the present invention as coupling agents can be dimethacrylates or trimethacrylates. They can be commercial products. These methacrylates are preferably commercially available products. When the methacrylate is packaged in the presence of a stabilizer, as is the case with most commercial methacrylates, it is generally used after removing the stabilizer (which can be carried out in a known manner by distillation or by treatment on an alumina column).

[0157] According to a first preferred embodiment of the present invention, the coupling agent is a dimethacrylate, and the compound contains two methacrylate functional groups preferably having the formula 3

[0158] [CH 2 =C(CH 3 )-CO-O] 2 -Z 3 Formula 3

[0159] Z 3 represents a divalent hydrocarbon group or a divalent hydrocarbon group substituted by one or more functional groups selected from ether functional groups and thioether functional groups.

[0160] Advantageously, Z 3 is an acyclic group. Z 3 can be a linear group or a branched group. The number of carbon atoms in Z 3 itself is not limited. Z 3 can contain up to 20 carbon atoms. Preferably, Z 3 is an alkanediyl or an alkanediyl substituted by one or more ether functional groups, more preferably an alkanediyl. Preferably, the alkanediyl of Z 3 contains 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms. Particularly suitable as the alkanediyl group of Z 3 are 1,2-ethanediyl, 1,1-ethanediyl, 1,3-propanediyl, 1,2-propanediyl, 1,4-butanediyl, 1,3-butanediyl, 1,5-pentanediyl, 2,2-dimethyl-1,3-propanediyl, 1,6-hexanediyl, 2,5-hexanediyl, 1,4-cyclohexanediyl and 1,4-cyclohexanediyldimethylene groups. Also suitable are divalent hydrocarbon groups interrupted by one or more oxygen atoms to form ether bonds, preferably alkanediyl groups, such as the formula -(CH 2 -CH 2 -O) n -CH 2 -CH 2 - and -(CH 2 -CH 2 -CH 2 -O) n -CH 2 -CH 2-CH 2 a divalent group, where n is an integer greater than or equal to 1, especially in the range of 1 to 10, more especially in the range of 1 to 2. To illustrate dimethacrylates containing polyoxyalkylene chains, mention may be made of triethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, neopentyl glycol polyoxypropylene dimethacrylate or bisphenol A ethoxylated dimethacrylate.

[0161] For reasons of commercial availability, the coupling agent is advantageously diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, thio - 2,1 - ethanediyl dimethacrylate, ethylene dimethacrylate, 1,2 - propanediol dimethacrylate, 1,3 - propanediol dimethacrylate, 1,3 - butanediol dimethacrylate, 1,4 - butanediol dimethacrylate, neopentyl glycol dimethacrylate, 1,4 - cyclohexanediol dimethacrylate or cyclohexane - 1,4 - dimethanol dimethacrylate, more advantageously diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene dimethacrylate, 1,2 - propanediol dimethacrylate, 1,3 - propanediol dimethacrylate, 1,3 - butanediol dimethacrylate, 1,4 - butanediol dimethacrylate or neopentyl glycol dimethacrylate, still more advantageously ethylene dimethacrylate, 1,2 - propanediol dimethacrylate, 1,3 - propanediol dimethacrylate, 1,3 - butanediol dimethacrylate, 1,4 - butanediol dimethacrylate or neopentyl glycol dimethacrylate.

[0162] According to a second preferred embodiment of the present invention, the coupling agent is a trimethacrylate, and the compound contains three methacrylate functional groups preferably having the formula 4

[0163] [CH 2 =C(CH 3 )-CO - O] 3 -Z 4 Formula 4

[0164] Z 4 represents a trivalent hydrocarbon group or a trivalent hydrocarbon group substituted by one or more functional groups selected from ether functional groups and thioether functional groups.

[0165] Advantageously, Z 4 is an acyclic group. Z 4 can be a linear group or a branched group. The number of carbon atoms in Z 4 itself is not limited. Z 4 can contain up to 20 carbon atoms. Preferably, Z 4 is an alkanetriyl or an alkanetriyl substituted by one or more ether functional groups, more preferably an alkanetriyl. An alkanetriyl is generally a saturated trivalent aliphatic hydrocarbon group. Preferably, Z4 The alkanetriyl contains 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms.

[0166] Particularly suitable as Z 4 Alkanetriyl groups are propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, 2-ethylpropane-1,2,3-triyl, propane-1,1,1-triyltrimethylene, and 1,2,5-pentanetriyl groups.

[0167] Also suitable are trivalent groups containing an oxyalkylene chain (such as an ethylene oxide chain or a propylene oxide chain) or a polyoxyalkylene chain (such as a polyethylene oxide chain or a polypropylene oxide chain), preferably alkanetriyl groups.

[0168] Mention may be made of propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, 2-ethylpropane-1,2,3-triyl, or propane-1,1,1-triyltrimethylene groups containing one or more oxyalkylene chains or polyoxyalkylene chains (especially ethylene oxide chains or polyethylene oxide chains).

[0169] For example, suitable are propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, or 2-ethylpropane-1,2,3-triyl groups containing three ethylene oxide chains or polyethylene oxide chains at the 1, 2, and 3 positions, or propane-1,1,1-triyltrimethylene groups containing three ethylene oxide chains or polyethylene oxide chains at the 1, 1, and 1 positions. Diagrams of these groups are shown below, where n, m, and p are integers greater than or equal to 1, especially in the range of 1 to 10, more especially in the range of 1 to 2.

[0170]

[0171] For example, also suitable are alkanetriyl groups containing ω-alkoxy poly(oxyalkylene) groups (such as ω-methoxy poly(ethylene oxide) groups). Mention may be made, for example, of 2-(ω-methoxy poly(ethylene oxide))propane-1,2,3-triyl and 1-(methoxy poly(oxyalkylene))methane-1,1,1-triyltrimethylene groups.

[0172] For reasons of commercial availability, the coupling agent is advantageously glycerol trimethacrylate (also known by the name propane-1,2,3-triyl tris(2-methylacrylate)), 1,1,1-trimethylolpropane trimethacrylate, or 1,2,5-pentanetriyl trimethacrylate.

[0173] Preferably, stage b) is carried out in an aliphatic hydrocarbon solvent (such as methylcyclohexane). Advantageously, it is carried out in the reaction medium produced by stage a). It is generally carried out by adding the coupling agent to the reaction product of stage a) in its reaction medium under stirring.

[0174] Before adding the coupling agent, the reactor is preferably degassed and inerted. Degassing of the reactor removes gaseous residual monomers and also facilitates the addition of the coupling agent to the reactor. Alternatively, the coupling agent can be injected into the reactor by overpressure. Inerting of the reactor (e.g., using nitrogen) prevents the deactivation of the carbon-metal bonds required for the coupling reaction of the copolymer chains present in the reaction medium. A pure coupling agent or a coupling agent diluted in a hydrocarbon solvent (preferably an aliphatic hydrocarbon solvent (such as methylcyclohexane) or an aromatic hydrocarbon solvent (such as toluene)) can be added. The time required for the coupling reaction by contacting the coupling agent with the reaction product of stage a) is provided. The coupling reaction can generally be monitored by chromatography to monitor the consumption of the coupling agent. The coupling reaction is preferably carried out under stirring at a temperature in the range of 23 °C to 120 °C for 1 minute to 60 minutes. The coupling reaction is preferably carried out with one molar equivalent of methacrylate functional groups relative to the number of carbon-magnesium bonds of the cocatalyst per mole of the catalyst system. However, the ratio of the number of molar equivalents of methacrylate functional groups to the number of carbon-magnesium bonds per mole of cocatalyst can vary depending on the desired content of the coupled polymer in the polymer obtained at the end of stage c), the desired number of branches in the coupled copolymer, and, in the case of producing a mixture of coupled copolymers with different numbers of branches, according to their respective proportions. A ratio close to 1, typically in the range of 0.85 to 1.05, promotes the highest degree of coupling. Advantageously, stage b) (the coupling reaction) is carried out with a ratio of the number of molar equivalents of methacrylate functional groups to the number of carbon-magnesium bonds per mole of cocatalyst that varies from 0.85 to 1.5. Generally, in a diorganomagnesium compound (such as butyloctylmagnesium (BOMAG)), there are two carbon-magnesium bonds per mole of the magnesium compound. One mole of a compound having two methacrylate functional groups is equivalent to two molar equivalents of methacrylate functional groups; more generally, one mole of a compound having n methacrylate functional groups is equivalent to n molar equivalents of methacrylate functional groups, where n is an integer greater than or equal to 2.

[0175] After modifying the chain ends, stage b) is followed by stage c).

[0176] Stage c) (the chain termination reaction) is generally a reaction capable of deactivating the active sites still present in the reaction medium produced in stage b). In stage c), a chain terminator is brought into contact with the reaction product of stage b), usually in its reaction medium, for example, by adding the terminator to the reaction medium at the end of stage b) or by pouring the reaction medium obtained at the end of stage b) into a solution containing the terminator. The terminator is usually in stoichiometric excess. The terminator is generally a protonic compound (a compound containing relatively acidic protons). As terminators, water, carboxylic acids (especially C 2 -C18 fatty acids, such as acetic acid or stearic acid), aliphatic alcohols or aromatic alcohols (such as methanol, ethanol or isopropanol) or phenolic antioxidants.

[0177] After reacting with the protonic compound, the method gives a coupled copolymer according to the invention. The copolymer prepared according to the method of the invention can be separated from the reaction medium of stage c) by methods known to those skilled in the art (such as by evaporation of the solvent under reduced pressure or by steam stripping).

[0178] The method using a coupling agent having two methacrylate functional groups preferably prepares a coupled copolymer having 2 branches, while the method using a coupling agent having three methacrylate functional groups preferably prepares a coupled copolymer having 3 branches, or prepares a mixture comprising a coupled copolymer having 2 branches and a coupled copolymer having 3 branches.

[0179] The advantage of the method according to the invention is that a coupled copolymer is prepared without polymerization of the methacrylate functional groups, which is reflected by the fact that no polymethacrylate is formed either in block polymer form or in homopolymer form. Thus, a coupled copolymer according to the invention that is not contaminated with polymethacrylate is obtained, whether in block copolymer form or in homopolymer form.

[0180] In summary, the present invention can be implemented according to any one of the following embodiments 1 to 52:

[0181] Embodiment 1: A copolymer of a 1,3-diene and an olefin, the olefin being ethylene or a mixture of ethylene and an α-monoolefin, the copolymer comprising more than 50 mol% of ethylene units and being a coupled copolymer, the chains of the copolymer being linked to each other by a group comprising at least two units of formula 1

[0182] -(CH 2 -CH(CH 3 )-CO-O)-Formula 1,

[0183] Each copolymer chain is bonded to a different unit of formula 1 by a covalent bond between a carbon atom of a copolymer chain monomer unit and a carbon atom of the methylene group of the unit of formula 1.

[0184] Embodiment 2: The copolymer according to Embodiment 1, the copolymer being a coupled copolymer having 2 branches or having 3 branches.

[0185] Embodiment 3: The copolymer according to Embodiment 1 or 2, the copolymer corresponding to formula 2

[0186] [P-CH 2 -CH(CH3 )-CO-O] 2 -Z 1 Formula 2

[0187] P represents a copolymer chain,

[0188] Z 1 represents a divalent hydrocarbon group or a divalent hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups.

[0189] Embodiment 4: The copolymer according to Embodiment 3, wherein Z 1 is an alkanediyl group or an alkanediyl group containing one or more ether functional groups.

[0190] Embodiment 5: The copolymer according to Embodiment 3 or 4, wherein Z 1 is an alkanediyl group.

[0191] Embodiment 6: The copolymer according to Embodiment 4 or 5, wherein Z 1 the alkanediyl group of which contains 1 to 10 carbon atoms.

[0192] Embodiment 7: The copolymer according to any one of Embodiments 4 to 6, wherein Z 1 the alkanediyl group of which is 1,2-ethanediyl, 1,1-ethanediyl, 1,3-propanediyl, 1,2-propanediyl, 1,4-butanediyl, 1,3-butanediyl, 1,5-pentanediyl, 2,2-dimethyl-1,3-propanediyl, 1,6-hexanediyl, 2,5-hexanediyl, 1,4-cyclohexanediyl or 1,4-cyclohexanediyldimethylene group.

[0193] Embodiment 8: The copolymer according to any one of Embodiments 3 to 7, wherein Z 1 the divalent hydrocarbon group of which is additionally substituted by one or more methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-.

[0194] Embodiment 9: The copolymer according to Embodiment 8, wherein Z 1 is an alkanediyl group substituted by a methacrylate functional group.

[0195] Embodiment 10: The copolymer according to Embodiment 1 or 2, the copolymer corresponding to Formula 3

[0196] [P-CH 2 -CH(CH 3 )-CO-O] 3 -Z 2 Formula 3

[0197] P represents a copolymer chain,

[0198] Z 2 represents a trivalent hydrocarbyl group or a trivalent hydrocarbyl group containing one or more functional groups selected from ether functional groups and thioether functional groups.

[0199] Embodiment 11: The copolymer according to Embodiment 10, wherein Z 2 is an alkanetriyl group or an alkanetriyl group containing one or more ether functional groups.

[0200] Embodiment 12: The copolymer according to Embodiment 11, wherein Z 2 the alkanetriyl group of which contains 3 to 10 carbon atoms.

[0201] Embodiment 13: The copolymer according to any one of Embodiments 10 to 12, wherein Z 2 is an alkanetriyl group.

[0202] Embodiment 14: The copolymer according to any one of Embodiments 10 to 13, wherein Z 2 the alkanetriyl group of which is a propane-1,2,3-triyl, 2-methylpropane-1,2,3-triyl, 2-ethylpropane-1,2,3-triyl, propane-1,1,1-triyltrimethylene or 1,2,5-pentanetriyl group.

[0203] Embodiment 15: The copolymer according to any one of Embodiments 1 to 14, wherein the copolymer contains more than 60 mol% of ethylene units.

[0204] Embodiment 16: The copolymer according to any one of Embodiments 1 to 15, wherein the copolymer contains more than 65 mol% of ethylene units.

[0205] Embodiment 17: The copolymer according to any one of Embodiments 1 to 16, wherein the copolymer contains less than 90 mol% of ethylene units.

[0206] Embodiment 18: The copolymer according to any one of Embodiments 1 to 17, wherein the copolymer contains at most 85 mol% of ethylene units.

[0207] Embodiment 19: The copolymer according to any one of Embodiments 1 to 18, wherein the copolymer contains at most 80 mol% of ethylene units.

[0208] Embodiment 20: The copolymer according to any one of Embodiments 1 to 19, wherein the α-olefin is styrene.

[0209] Embodiment 21: The copolymer according to any one of Embodiments 1 to 20, wherein the copolymer is a copolymer of ethylene and a 1,3-diene.

[0210] Embodiment 22: The copolymer according to any one of Embodiments 1 to 21, wherein the copolymer is a statistical copolymer.

[0211] Embodiment 23: The copolymer according to any one of Embodiments 1 to 22, wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene, or a mixture thereof.

[0212] Embodiment 24: The copolymer according to any one of Embodiments 1 to 23, wherein the 1,3-diene is 1,3-butadiene.

[0213] Embodiment 25: The copolymer according to any one of Embodiments 1 to 24, wherein the 1,3-diene is a mixture of 1,3-dienes containing 1,3-butadiene.

[0214] Embodiment 26: The copolymer according to any one of Embodiments 1 to 25, wherein the copolymer contains 1,3-butadiene units and 1,2-cyclohexane units.

[0215] Embodiment 27: The copolymer according to any one of Embodiments 1 to 26, wherein the copolymer contains at most 15 mol% of 1,2-cyclohexane units.

[0216] Embodiment 28: The copolymer according to any one of Embodiments 1 to 27, wherein the copolymer is a copolymer of ethylene and 1,3-butadiene.

[0217] Embodiment 29: The copolymer according to any one of Embodiments 1 to 28, wherein the copolymer is a copolymer of ethylene, 1,3-butadiene, and myrcene.

[0218] Embodiment 30: The copolymer according to any one of Embodiments 1 to 29, wherein the copolymer is a copolymer of ethylene, 1,3-butadiene, and β-farnesene.

[0219] Embodiment 31: The copolymer according to any one of Embodiments 1 to 30, wherein the copolymer is an elastomer.

[0220] Embodiment 32: A method for preparing a coupled copolymer of a 1,3-diene and an olefin, the copolymer containing more than 50 mol% of ethylene units, the method comprising consecutive stages a), b), and c),

[0221] - Stage a) is to polymerize a monomer mixture containing a 1,3-diene and an olefin in the presence of a catalytic system based at least on a metallocene of formula (Ia) and an organomagnesium compound (cocatalyst),

[0222] {P(Cp 1 )(Cp2 )Nd(BH 4 ) (1+y)- L y -N x}(Ia)

[0223] Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted,

[0224] P is a bridging Cp 1 and Cp 2 two groups and contains a silicon atom or a carbon atom group,

[0225] Nd represents a neodymium atom,

[0226] L represents an alkali metal selected from lithium, sodium and potassium,

[0227] N represents an ether molecule,

[0228] x is an integer or non-integer equal to or greater than 0,

[0229] y is an integer equal to or greater than 0,

[0230] The olefin is ethylene or a mixture of ethylene and an α-monoolefin,

[0231] -Stage b) is the reaction of a coupling agent (a compound containing at least two methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-) with the polymerization reaction product of stage a),

[0232] -Stage c) is a chain termination reaction.

[0233] Embodiment 33: The method according to embodiment 32, wherein the coupling agent is a dimethacrylate or a trimethacrylate.

[0234] Embodiment 34: The method according to embodiment 32 or 33, wherein the coupling agent is a coupling agent of formula 3 or formula 4

[0235] [CH 2 =C(CH 3 )-CO-O] 2 -Z 3 Formula 3

[0236] [CH 2 =C(CH 3 )-CO-O] 3 -Z 4 Formula 4

[0237] Z3 represents a divalent hydrocarbon group or a divalent hydrocarbon group substituted by one or more functional groups selected from ether functional groups and thioether functional groups,

[0238] Z 4 represents a trivalent hydrocarbon group or a trivalent hydrocarbon group substituted by one or more functional groups selected from ether functional groups and thioether functional groups.

[0239] Embodiment 35: The method according to embodiment 34, wherein Z 3 is an alkanediyl or an alkanediyl substituted by one or more ether functional groups, preferably an alkanediyl.

[0240] Embodiment 36: The method according to embodiment 34 or 35, wherein Z 3 of the alkanediyl contains 1 to 10 carbon atoms.

[0241] Embodiment 37: The method according to any one of embodiments 32 to 34, wherein the coupling agent is diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, 1,2-propanediol dimethacrylate, 1,3-propanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate or neopentyl glycol dimethacrylate.

[0242] Embodiment 38: The method according to embodiment 34, wherein Z 4 is an alkanetriyl or an alkanetriyl substituted by one or more ether functional groups.

[0243] Embodiment 39: The method according to embodiment 34 or 38, wherein Z 4 of the alkanetriyl contains 3 to 10 carbon atoms.

[0244] Embodiment 40: The method according to any one of embodiments 32 to 34, wherein the coupling agent is glycerol trimethacrylate, 1,1,1-trimethylolpropane trimethacrylate or 1,2,5-pentanetriyl trimethacrylate.

[0245] Embodiment 41: The method according to any one of embodiments 32 to 40, wherein stage b) is carried out at a ratio of the number of molar equivalents of methacrylate functional groups varying from 0.85 to 1.5 to the number of carbon-magnesium bonds per mole of cocatalyst.

[0246] Embodiment 42: The method according to any one of embodiments 32 to 41, wherein stage b) is carried out in an aliphatic hydrocarbon solvent.

[0247] Embodiment 43: The method according to any one of embodiments 32 to 42, wherein the olefin is ethylene.

[0248] Embodiment 44: The method according to any one of Embodiments 32 to 43, wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene, or a mixture thereof.

[0249] Embodiment 45: The method according to any one of Embodiments 32 to 44, wherein the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes containing 1,3-butadiene, and the mixture is preferably a mixture of 1,3-butadiene and myrcene or a mixture of 1,3-butadiene and β-farnesene.

[0250] Embodiment 46: The method according to any one of Embodiments 32 to 45, wherein R 1 and R 2 each represent a methyl group.

[0251] Embodiment 47: The method according to any one of Embodiments 32 to 46, wherein Z represents a silicon atom.

[0252] Embodiment 48: The method according to any one of Embodiments 32 to 47, wherein the metallocene has the formula (I-1), (I-2), (I-3), (I-4), or (I-5):

[0253] [Me 2 Si(Flu) 2 Nd(μ-BH 4 ) 2 Li(THF)] (I-1)

[0254] [{Me 2 SiFlu 2 Nd(μ-BH 4 ) 2 Li(THF)} 2 (I-2)

[0255] [Me 2 SiFlu 2 Nd(μ-BH 4 )(THF)] (I-3)

[0256] [{Me 2 SiFlu 2 Nd(μ-BH 4 )(THF)} 2 (I-4)

[0257] [Me 2 SiFlu 2 Nd(μ-BH 4 )] (I-5)

[0258] wherein Flu represents C 13 H 8 group.

[0259] Embodiment 49: The method according to any one of Embodiments 32 to 48, wherein the organomagnesium compound has the formula (IIa), wherein R 3 and R 4 are the same or different and represent carbon-containing groups

[0260] MgR 3 R 4 (IIa).

[0261] Embodiment 50: The method according to any one of Embodiments 32 to 49, wherein R 3 and R 4 are alkyl groups.

[0262] Embodiment 51: The method according to any one of Embodiments 32 to 50, wherein R 3 and R 4 are alkyl groups containing 2 to 10 carbon atoms.

[0263] Embodiment 52: A polymer composition comprising a copolymer having 2 branches and a copolymer having 3 branches, the copolymer being defined as in any one of Embodiments 1 to 31 or obtainable by a method defined as in any one of Embodiments 32 to 51.

[0264] The above and other features of the present invention will be more clearly understood by reading the following description of the embodiments of the present invention given as an illustration.

[0265] Examples

[0266] Size Exclusion Chromatography (SEC):

[0267] a) Measurement principle:

[0268] Size exclusion chromatography or SEC can separate macromolecules in solution according to the size of the macromolecules passing through a column filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, and the macromolecules with the largest volume are eluted first.

[0269] Combined with a triple detector (3D) (refractometer, viscometer and 90° light scattering detector), SEC can obtain the distribution of the absolute molar mass of the polymer. The number-average absolute molar mass (Mn) and weight-average absolute molar mass (Mw) and dispersity of each can also be calculated

[0270] b) Preparation of the polymer:

[0271] Each sample was dissolved in tetrahydrofuran at a concentration of approximately 1 g / l. Then, before injection, the solution was filtered through a 0.45 μm porosity filter.

[0272] c) 3D SEC analysis:

[0273] To determine the number-average molar mass (Mn) of the polymer and, where appropriate, the weight-average molar mass (Mw) and polydispersity index (Ip or expressed as ), the following method was used.

[0274] The number-average molar mass (Mn), weight-average molar mass (Mw) and polydispersity index of the polymer (hereinafter referred to as the sample) were determined in an absolute manner by triple detection size exclusion chromatography (SEC). The advantage of triple detection size exclusion chromatography is that it directly measures the average molar mass without calibration.

[0275] The value of the refractive index increment dn / dc of the sample solution was measured online using the peak area detected by a refractometer (RI) of a liquid chromatography device. To apply this method, it must be verified that 100% of the sample mass was injected and eluted through the column. The area of the RI peak depends on the concentration of the sample, the constant of the RI detector and the value of dn / dc.

[0276] To determine the average molar mass, a pre-prepared and filtered 1 g / l tetrahydrofuran solution was used and injected into the chromatographic line. The device used was a Wyatt chromatographic line. The elution solvent was tetrahydrofuran containing 250 ppm of BHT (2,6-bis(tert-butyl)-4-methylphenol), with a flow rate of 1 ml.min -1 , the system temperature was 35 °C, and the analysis time was 60 min. The columns used were a set of three Agilent columns with the trade name PL Gel Mixed B LS. The injection volume of the sample solution was 100 μl. The detection system consisted of a Wyatt differential viscometer with the trade name Viscostar II, a Wyatt differential refractometer with the trade name Optilab T-Rex with a wavelength of 658 nm, and a Wyatt multi-angle static light scattering detector with the trade name Dawn Heleos 8+ with a wavelength of 658 nm.

[0277] To calculate the number-average molar mass and polydispersity index, the value of the refractive index increment dn / dc of the sample solution obtained above was integrated. The software used to evaluate the chromatographic data was the Astra system from Wyatt.

[0278] Nuclear Magnetic Resonance (NMR):

[0279] By 1H, 13 C, and 29 Si NMR spectroscopy was used to characterize the copolymer. NMR spectra were recorded on a Bruker Avance III HD 500 MHz spectrometer equipped with a BBFO z - axis 5 mm “broadband” cryoprobe. Quantitative 1 H NMR experiments were performed using a simple 30° pulse sequence and a repetition time of 5 s between each acquisition. 64 to 256 accumulations were carried out. Quantitative 13 C NMR experiments were performed using a simple 30° pulse sequence with proton decoupling and a repetition time of 10 s between each acquisition. 1024 to 10240 accumulations were carried out. Relative to the solvent (CDCl 3 ) calibration of the proton chemical shift axis was made at δ 1H = 7.20 ppm for the protonated impurity. 1 Relative to the solvent (CDCl 3 ) calibration of the 13C C chemical shift axis was made at δ 13 = 77 ppm for the signal.

[0280] Determination of the glass transition temperature of polymers:

[0281] The glass transition temperature (Tg) was measured by differential scanning calorimetry according to standard ASTM D3418 (1999).

[0282] Crystallinity of polymers:

[0283] The temperature, melting enthalpy, and crystallinity of the polymers used were determined by differential scanning calorimetry (DSC) using standard ISO 11357 - 3:2011. The reference enthalpy for polyethylene is 277.1 J / g (according to Polymer Handbook, 4th Edition, J. Brandrup, E. H. Immergut, and E. A. Grulke, 1999).

[0284] Viscosity:

[0285] The dry polymer was redissolved in toluene at 0.1 g / dl. Viscosity measurements were made using an Ostwald viscometer immersed in a water bath at 25 °C. A closed - circulation heating bath was used to control the temperature of the bath.

[0286] The viscosity of the polymer was measured relative to the solvent in the solution in relative terms. Measuring the viscosity of toluene in the Ostwald viscometer gave t 0 (the elution time between point A and point B, expressed in hundredths of a second).

[0287] The viscosity measurement of the polymer in solution can be obtained by conducting it in toluene at 0.1 g / dl (C) in an Ostwald viscometer to obtain t 1 (the elution time between point A and point B, expressed in hundredths of a second).

[0288] Subsequently, the viscosity of the polymer (expressed in dl / g) is calculated according to the following formula:

[0289] Viscosity = 1 / C × (t 1 - t 0 ) / t 0 .

[0290] Preparation of copolymers:

[0291] The metallocene [{Me 2 SiFlu 2 Nd(μ - BH 4 ) 2 Li(THF)}] 2 is prepared according to the procedure described in patent application WO 2007054224.

[0292] Butyloctylmagnesium BOMAG (20% heptane, 0.88 mol·l -1 ) is from Chemtura and is stored in a Schlenk tube under an inert atmosphere.

[0293] Ethylene (grade N35) is from Air Liquide and can be used without prior purification.

[0294] 1,3 - Butadiene is purified through an alumina guard bed.

[0295] The coupling agent is trimethylolpropane trimethacrylate sold by Sigma - Aldrich. The trimethacrylate is used after purification on an alumina guard bed and after purging with nitrogen.

[0296] The methylcyclohexane (MCH) solvent from BioSolve is dried and purified on an alumina column in a solvent purifier from mBraun used under an inert atmosphere.

[0297] All reactions are carried out under an inert atmosphere.

[0298] All polymerization and coupling reactions are carried out in a reactor equipped with a disposable glass container (Schott flask) with 500 ml and having a stainless - steel stirring blade. The temperature is controlled by a thermostatically controlled oil bath connected to a polycarbonate heating jacket. The reactor has all the inlets or outlets required for handling operations.

[0299] The cocatalyst and then the metallocene were added to a 500 ml glass reactor containing MCH. The amount of metallocene introduced was 40 mg, and the amount of active BOMAG was 154 μmol. The activation duration was 10 minutes and the reaction temperature was 80 °C.

[0300] Polymerization was carried out in a 500 ml glass reactor containing 300 ml of polymerization solvent (methylcyclohexane) and the catalyst system at 80 °C and an absolute initial pressure of 4 bar. 1,3-Butadiene and ethylene were introduced in the form of a gas mixture containing 20 mol% of 1,3-butadiene.

[0301] At the desired conversion (i.e., after consumption of approximately 10 g of polymer monomer), step A (for synthesizing an uncoupled control copolymer) or step B (for synthesizing a coupled copolymer according to the invention) was carried out.

[0302] Step A: Synthesis of an uncoupled control copolymer (Example 1)

[0303] The polymerization reaction was stopped by adding ethanol in an amount in excess of the molar amounts of magnesium and neodymium. The copolymer was recovered by precipitation in methanol and then dried at 60 °C under vacuum under a nitrogen stream.

[0304] Step B: Synthesis of a coupled copolymer according to the invention (Examples 2 to 5)

[0305] The coupling agent was introduced by overpressure under an inert atmosphere according to the molar contents shown in Table 1 (which are expressed as the number of carbon-magnesium bonds of the cocatalyst (active BOMAG) per mole of catalyst system (coupling agent / C-Mg molar ratio)).

[0306] The reaction medium was stirred at 80 °C for 60 minutes and then degassed and cooled. After degassing and cooling the reactor, ethanol was introduced into the reaction medium in an amount in excess of the molar amounts of magnesium and neodymium. Subsequently, the reaction medium was precipitated in methanol and then the recovered polymer was dried at 60 °C under vacuum under a nitrogen stream of constant weight. Subsequently, it was analyzed by SEC (THF) and NMR.

[0307] Tables 1 and 2 show the copolymerization and coupling reaction conditions specific to each example and the characteristics of the synthesized copolymers. The number-average molar mass and weight-average molar mass were determined using the 3D SEC method, and the microstructure of the polymer was determined by NMR. The content of ethylene units, the content of 1,3-butadiene units in the 1,2-configuration (1,2-units), the content of 1,3-butadiene units in the 1,4-configuration (1,4-units), and the content of 1,2-cyclohexane units (ring units) are expressed as mole percentages relative to all monomer units of the copolymer.

[0308] 3D SEC analysis can determine the intrinsic viscosity values at each number-average molar mass in the overall distribution of the polymer. From the Mark-Houvink-Sakurada relationship that relates the intrinsic viscosity to the number-average molar mass according to the equation ln(viscosity) = ln(K) + αln(Mn), the coefficient α of the polymer population with an average molar mass can be calculated.

[0309] It is known to those skilled in the art that the structure of the polymer is associated with the coefficient α. If this coefficient decreases, this indicates that the polymer viscosity changes little with its molar mass and that the polymer is structured (i.e., star-branched). The results are shown in Table 3.

[0310] Table 1

[0311]

[0312] Table 2

[0313]

[0314] Table 3

[0315]

[0316] The viscosity values measured using an Ostwald viscometer and shown in Table 2 indicate that the polymer synthesized according to Step B (reacted with a trimethacrylate coupling agent) has a higher viscosity than the non-coupled control (Example 1), and indicates that the reaction with the coupling agent forms a coupled polymer. The increase in the number-average molar mass and weight-average molar mass shown in Table 2 confirms the formation of coupled chains, especially coupled chains with 2 branches and coupled chains with 3 branches, as the average molar mass increased by about 2 to 3 times. The observed increase in viscosity reflects the change in the rheological properties of the polymer compared to the control (non-coupled polymer). The coupled polymer has a lower tendency to flow.

[0317] The results in Table 3 (which are derived from the Mark-Houvink-Sakurada relationship) indicate that the reaction with the trimethacrylate coupling agent produces a mixture containing a coupled polymer with 2 branches (structural coefficient greater than 0.6) and a coupled polymer with 3 branches (a star-branched polymer with a structural coefficient less than 0.6).

[0318] It is also noted that a molar ratio of the number of methacrylate functional groups to the number of moles of magnesium (i.e., the molar ratio of the number of moles of the trimethacrylate coupling agent to the number of carbon-magnesium bonds per mole of cocatalyst equal to 0.3) closer to 1 is more favorable for producing a coupled polymer with 3 branches (star-branched polymer).

[0319] Finally, as shown in Table 2, the results of DSC analysis showed that each copolymer exhibited a single Tg and a relatively low δT value (since it was 6 °C or 7 °C). These combined data demonstrated that a statistical elastomer was obtained.

Claims

1. A copolymer of a 1,3-diene and an olefin, wherein the olefin is ethylene or a mixture of ethylene and an α-monoolefin, the copolymer contains more than 50 mol% of ethylene units and is a coupled copolymer, and the chains of the copolymer are connected to each other through a group containing at least two units of formula 1 -(CH 2 -CH(CH 3 )-CO-O)-Formula 1 Each copolymer chain is bonded to a different unit of formula 1 through a covalent bond between a carbon atom of a copolymer chain monomer unit and a carbon atom of the methylene group of the unit of formula 1.

2. The copolymer according to claim 1, which is a coupled copolymer having 2 branches or having 3 branches.

3. The copolymer according to claim 1 or 2, which corresponds to formula 2 [P-CH 2 -CH(CH 3 )-CO-O] 2 -Z 1 Formula 2 P represents a copolymer chain. Z 1 represents a divalent hydrocarbon group or a divalent hydrocarbon group containing one or more functional groups selected from ether functional groups and thioether functional groups, and the divalent group may be substituted by one or more methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O-.

4. The copolymer according to claim 1 or 2, which corresponds to formula 3 [P-CH 2 -CH(CH 3 )-CO-O] 3 -Z 2 Formula 3 P represents a copolymer chain. Z 2 represents a trivalent hydrocarbyl group or a trivalent hydrocarbyl group containing one or more functional groups selected from ether functional groups and thioether functional groups.

5. The copolymer according to claim 3 or 4 wherein Z 1 is an alkanediyl or an alkanediyl substituted by a methacrylate functional group, and Z 2 is an alkanetriyl.

6. The copolymer according to any one of claims 1 to 5, which is a copolymer of ethylene and a 1,3-diene.

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

8. The copolymer according to any one of claims 1 to 7 wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene or a mixture thereof.

9. The copolymer according to any one of claims 1 to 8, which contains 1,3-butadiene units and 1,2-cyclohexane units of formula (I) 10. The copolymer according to any one of claims 1 to 9, which is an elastomer.

11. A method for preparing a coupled copolymer of a 1,3-diene and an olefin, the copolymer containing more than 50 mol% of ethylene units, the method comprising successive stages a), b) and c) - Stage a) is the polymerization of a monomer mixture containing a 1,3-diene and an olefin in the presence of a catalytic system based at least on a metallocene of formula (Ia) and an organomagnesium compound cocatalyst {P(Cp 1 )(Cp 2 )Nd(BH 4 ) (1+y)- L y -N x} (Ia) Cp 1 and Cp 2 are the same as or different from each other and are selected from fluorenyl, cyclopentadienyl and indenyl, and these groups are substituted or unsubstituted, P is a bridging Cp 1 and Cp 2 two groups and a group containing a silicon atom or a carbon atom Nd represents a neodymium atom L represents an alkali metal selected from lithium, sodium and potassium N represents an ether molecule x is an integer or non-integer equal to or greater than 0 y is an integer equal to or greater than 0 the olefin is ethylene or a mixture of ethylene and an α-monoolefin - Stage b) is the reaction of a coupling agent with the polymerization reaction product of stage a), said coupling agent being a compound comprising at least two methacrylate functional groups of the formula CH 2 =C(CH 3 )CO-O- - Stage c) is a chain termination reaction.

12. The method according to claim 11 wherein the coupling agent is a dimethacrylate or a trimethacrylate.

13. The method according to claim 11 or 12 wherein the coupling agent is a coupling agent of formula 3 or formula 4 [CH 2 =C(CH 3 )-CO-O] 2 -Z 3 Formula 3 [CH 2 =C(CH 3 )-CO-O] 3 -Z 4 Formula 4 Z 3 represents a divalent hydrocarbon group or a divalent hydrocarbon group substituted by one or more functional groups selected from an ether functional group and a thioether functional group Z 4 represents a trivalent hydrocarbon group or a trivalent hydrocarbon group substituted by one or more functional groups selected from ether functional groups and thioether functional groups.

14. The method according to any one of claims 11 to 13 wherein stage b) is carried out in an aliphatic hydrocarbon solvent.

15. A polymer composition, which contains a copolymer having 2 branches and a copolymer having 3 branches, the copolymer being defined as in any one of claims 1 to 10 or obtainable by a method defined as in any one of claims 11 to 14.

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