Coupled polyethylene or ethylene and 1, 3-diene coupled copolymer and preparation method thereof

Abstract

The present invention relates to a coupled polyethylene and a coupled copolymer of ethylene with a 1, 3-diene and optionally a vinyl aromatic compound, said copolymer containing greater than 50 mol% ethylene; the process comprises polymerizing monomers in the presence of a metallocene neodymium borohydride complex and a halide of an organo-magnesium compound, followed by a coupling reaction with a compound having at least two nitrile functional groups, each nitrile functional group preferably replacing a different or the same aromatic group, followed by a hydrolysis reaction.

Description

Technical Field

[0001] The field of the invention is that of polyethylene and copolymers of ethylene with α-olefins, said copolymers being rich in ethylene units. Background Art

[0002] The synthesis of coupled diene polymers is very widely described as the coupling of living polymer chains synthesized by anionic polymerization in the presence of a lithium-based initiator. Due to the nature of the bonds involved in the synthesis of polydiene chains with a high 1,4-cis content in the presence of a Ziegler Natta type catalyst, the synthesis of stereospecific diene polymers by coupling polydiene chains with a high 1,4-cis content is less well described. For example, in WO 2010 / 085631, the synthesis of coupled polybutadiene with a high 1,4-cis content by coupling reaction with compounds containing nitrile functional groups is described. In both anionic and stereospecific polymerization synthesis, the reaction involves σ-alkyl lithium bonds (i.e., η 2 -alkyl-Li) or π-allyl complex (i.e. η 3 -allyl bond).

[0003] The synthesis of diene polymers rich in ethylene units is carried out by polymerization of ethylene with 1,3-dienes in the presence of a catalytic system based on a neodymium hydroboride complex and an organomagnesium reagent. This polymerization differs from the other polymerizations mentioned above in that its polymerization mechanism is carried out by a large number of chain transfer reactions between neodymium atoms and magnesium atoms and involves completely different reaction substances. For example, reference can be made to the articles ACS Catalysis (2016) (6, 1028-1036) and ACS Catalysis (2019) (9, 9298-9309). Summary of the invention

[0004] The applicant has developed a method for preparing ethylene-rich coupled polymers. The method is applicable to polyethylene and ethylene-rich diene copolymers and has the advantage of producing a high degree of coupling in a particular embodiment of the invention.

[0005] A first subject of the invention is a process for preparing a coupled polymer containing more than 50 mol % of ethylene (expressed as a molar percentage relative to all the monomer units of the polymer), the polymer being polyethylene or a copolymer of ethylene with a 1,3-diene and optionally a vinyl aromatic compound, comprising the successive steps a), b) and c):

[0006] - Step a) consists in polymerizing the monomers in the presence of a catalytic system based on at least one metallocene of formula (I) and an alkylmagnesium halide of formula (II)

[0007] {P(Cp 1 )(Cp 2 )Nd(BH4) (1+y)- L y -N x} (I)

[0008] XMgR (II)

[0009] Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted,

[0010] P is the bridge Cp 1 and Cp 2 Two groups and groups containing silicon atoms or carbon atoms,

[0011] Nd represents a neodymium atom,

[0012] L represents an alkali metal selected from lithium, sodium and potassium,

[0013] N represents an ether molecule,

[0014] x can be an integer or non-integer greater than or equal to 0.

[0015] y is an integer greater than or equal to 0,

[0016] X is a halogen atom and R is an alkyl group,

[0017] - step b) is to react the reaction product of step a) with a compound containing at least two nitrile functional groups, each nitrile functional group being preferably a substituent of the same or different aromatic groups,

[0018] - Step c) is a hydrolysis reaction,

[0019] The polymer is polyethylene or a copolymer of ethylene with a 1,3-diene and optionally a vinyl aromatic compound.

[0020] A second subject of the invention is a coupled polymer consisting of polymer chains containing more than 50 mol % of ethylene units, these polymer chains being linked together by groups containing at least two keto functions, each keto function being covalently bonded to a monomer unit of a different polymer chain, the polymer being polyethylene, a copolymer of ethylene with a 1,3-diene and optionally a vinylaromatic compound, obtainable by the process according to the invention.

[0021] illustrate

[0022] Any numerical interval represented by the expression "between a and b" means a numerical range greater than "a" and less than "b" (i.e., excluding the end values ​​a and b), while any numerical interval represented by the expression "a to b" means a numerical range extending from "a" to "b" (i.e., including the strict end values ​​a and b).

[0023] Unless otherwise specified, the content of the unit resulting from the insertion of a monomer into a copolymer is expressed as a mole percentage relative to all units resulting from the polymerization of the monomer.

[0024] The compounds mentioned in this specification may be compounds of fossil origin or may be bio-based compounds. In the case where the compounds are bio-based compounds, they may be partially or completely derived from biomass or may be obtained by renewable raw materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of already used materials, i.e. they may be partially or completely produced by a recycling process or may be obtained by raw materials that themselves are produced from a recycling process.

[0025] The term "based on" used to define the components of the catalytic system means a mixture of these components, or a product of the reaction of some or all of these components with one another.

[0026] Step a) of the process according to the invention is a polymerization reaction allowing the preparation of a growing polymer chain intended to react with a coupling agent (compound containing at least two nitrile functional groups) in the next step (step b)). Step b) is a coupling reaction.

[0027] According to a first alternative, the polymerization is the polymerization of ethylene. According to this alternative, the product of the polymerization in step a) is a polymer chain whose constituent units result from the insertion of ethylene. The polymer prepared by the first alternative is an ethylene homopolymer, i.e. polyethylene.

[0028] According to a second alternative, the polymerization reaction is the polymerization of a monomer mixture of ethylene and 1,3-diene. According to this alternative, the reaction product of the polymerization in step a) is a polymer chain resulting from the insertion of constituent units of ethylene and 1,3-diene. The polymer prepared by the second alternative is a copolymer of ethylene and 1,3-diene.

[0029] According to a third alternative of the invention, the polymerization reaction is the polymerization of a monomer mixture of ethylene, 1,3-diene and a vinyl aromatic compound. According to this alternative, the reaction product of the polymerization in step a) is a polymer chain whose constituent units result from the insertion of ethylene, 1,3-diene and a vinyl aromatic compound. The polymer prepared by the third alternative is a copolymer of ethylene, 1,3-diene and a vinyl aromatic compound.

[0030] The 1,3-dienes of the monomer mixture in step a) for the purposes of the second alternative and the third alternative are either single compounds, i.e. single 1,3-dienes, or mixtures of 1,3-dienes which differ from one another in chemical structure. Suitable 1,3-dienes for use are 1,3-dienes containing 4 to 20 carbon atoms, such as 1,3-butadiene, isoprene, myrcene and β-farnesene, and mixtures thereof. The 1,3-dienes are preferably 1,3-butadiene, isoprene, myrcene, β-farnesene or mixtures thereof, in particular mixtures of at least two thereof.

[0031] The vinyl aromatic compound of the monomer mixture in step a) for the purpose of the third alternative is a single compound, i.e. a single vinyl aromatic compound, or a mixture of vinyl aromatic compounds having chemical structures different from each other. The term "vinyl aromatic compound" means an aromatic compound substituted by a vinyl functional group having the well-known formula (-CH=CH2). The most particularly suitable vinyl aromatic compounds are compounds containing an aromatic group substituted by a vinyl functional group, more particularly compounds containing a phenyl group substituted by a vinyl functional group. The vinyl aromatic compound is preferably styrene or styrene in which the benzene ring is substituted by an alkyl group. The vinyl aromatic compound is more preferably styrene. The copolymer prepared by the preferred embodiment of the third alternative is a copolymer of ethylene, 1,3-diene and styrene.

[0032] Preferably, the monomer mixture to be polymerized in step a) according to the second alternative and the third alternative contains more than 50 mol % of ethylene, this percentage being expressed relative to the total number of moles of monomers in the monomer mixture of step a). When the monomer mixture contains a vinyl aromatic compound such as styrene, it preferably contains less than 40 mol % of vinyl aromatic compound, this percentage being expressed relative to the total number of moles of monomers in the monomer mixture of step a).

[0033] The polymerization of the monomers can be carried out according to patent applications WO 2007 / 054223 A2 and WO 2007 / 054224 A2. The catalytic system (or catalytic composition) used for the polymerization of the monomers consists of a metallocene and an alkylmagnesium halide.

[0034] In the present patent application, the term "metallocene" means an organometallic complex whose metal (in appropriate cases a neodymium atom) is bound to a Cp bond called a ligand and which is linked together by bridges P. 1 and Cp 2 These Cp 1 and Cp 2 The groups are identical or different and are selected from fluorenyl, cyclopentadienyl and indenyl, and these groups may be substituted or unsubstituted.

[0035] According to the present invention, the metallocene used as an essential component in the catalytic system corresponds to the formula (Ia)

[0036] {P(Cp 1 )(Cp 2 )Nd(BH4) (1+y) -L y -N x} (I)

[0037] P is the bridge Cp 1 and Cp 2 Two groups and groups containing silicon atoms or carbon atoms,

[0038] Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted,

[0039] Nd represents a neodymium atom,

[0040] L represents an alkali metal selected from lithium, sodium and potassium,

[0041] N represents an ether molecule,

[0042] x can be an integer or non-integer greater than or equal to 0.

[0043] y is an integer greater than or equal to 0.

[0044] In formula (I), the neodymium atom is connected to a Cp bonded together by a bridge P. 1 and Cp 2 Preferably, the symbol P represented by the term bridge corresponds to the formula ZR 1 R 2 , Z represents a silicon atom or a carbon atom, R 1 and R 2 are the same or different and represent an alkyl group containing 1 to 20 carbon atoms. More preferably, the bridge P is of the formula SiR 1 R 2 , R 1 and R 2 Same and as defined above. Even more preferably, P corresponds to the formula SiMe2.

[0045] In formula (I), any ether capable of complexing an alkali metal (especially diethyl ether, methyltetrahydrofuran and tetrahydrofuran, preferably tetrahydrofuran) is suitable as the ether.

[0046] As substituted cyclopentadienyl, fluorenyl and indenyl, mention may be made of those substituted by a group containing 1 to 6 carbon atoms, or a group containing 6 to 12 carbon atoms, or a trialkylsilyl group such as SiMe3.1 and Cp 2 When substituted, they are preferably substituted by methyl, butyl (especially tert-butyl) or trimethylsilyl. The choice of the radical also depends on the availability of the corresponding molecules, which are substituted cyclopentadienes, fluorenes and indenes, since said molecules are commercially available or can be easily synthesized.

[0047] As substituted fluorenyl groups, those substituted at positions 2, 7, 3 or 6 may be mentioned, in particular 2,7-di(tert-butyl)fluorenyl and 3,6-di(tert-butyl)fluorenyl. As shown in the figure below, positions 2, 3, 6 and 7 represent the positions of the carbon atoms of the ring, respectively, and position 9 corresponds to the carbon atom to which the bridge P is attached.

[0048]

[0049] As substituted cyclopentadienyl, mention may be made of those substituted at position 2 (or 5) as well as at position 3 (or 4), in particular those substituted at position 2, more particularly tetramethylcyclopentadienyl. Position 2 (or 5) denotes the position of the carbon atom adjacent to the carbon atom to which the bridge P is attached, as shown in the figure below. As a reminder, substitution at position 2 or 5 is also referred to as substitution at the alpha position relative to the bridge.

[0050]

[0051] As substituted indenyl groups, mention may in particular be made of those substituted in position 2, more particularly 2-methylindenyl or 2-phenylindenyl. Position 2 denotes the position of the carbon atom adjacent to the carbon atom to which the bridge P is attached, as shown in the figure below.

[0052]

[0053] Preferably, Cp 1 and Cp 2 The same or different, is a cyclopentadiene, a substituted fluorenyl, a substituted indenyl or a substituted indenyl of formula C 13 More preferably, Cp 1 and Cp 2 The same or different, is a substituted fluorenyl or a C 13 H8 is an unsubstituted fluorenyl group. Advantageously, Cp 1 and Cp 2 Formula C 13 The unsubstituted fluorenyl group of H8 is represented by the symbol Flu.

[0054] Even more preferably, the metallocene is of formula (I-1), (I-2), (I-3), (I-4) or (I-5):

[0055] [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)] (I-1)

[0056] [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2] (I-2)

[0057] [Me2SiFlu2Nd(μ-BH4)(THF)] (I-3)

[0058] [{Me2SiFlu2Nd(μ-BH4)(THF)}2] (I-4)

[0059] [Me2SiFlu2Nd(μ-BH4)] (I-5)

[0060] Where Flu represents C 13 H8 group.

[0061] The metallocene used for the synthesis of the catalyst system can be in the form of a crystalline powder or a non-crystalline powder, or in a single crystal form.Metallocene can be in monomeric form or dimer form, and these forms depend on the preparation method of metallocene, as described in for example patent application WO 2007 / 054224 A2 or WO 2007 / 054223 A2.Metallocene can be conventionally prepared by a method similar to the method described in patent application WO 2007 / 054224 A2 or WO 2007 / 054223 A2, particularly by reacting the alkali metal salt of the part with the borohydride of the rare earth metal neodymium in a suitable solvent (for example ether (such as diethyl ether or tetrahydrofuran), or any other solvent known to those skilled in the art) under inertia and anhydrous conditions to prepare.After the reaction, by technology known to those skilled in the art, for example filter or separate out from the second solvent, thereby metallocene is separated from byproduct of reaction.Finally, the metallocene is dried and separated in solid form.

[0062] Alkyl magnesium halide is another basic component of the catalyst system and is a co-catalyst of the catalyst system. It is preferably an alkyl magnesium chloride or an alkyl magnesium bromide, more preferably an alkyl magnesium chloride. The alkyl group can be linear or branched, preferably linear. The alkyl group preferably contains 2 to 10 carbon atoms. Suitable alkyl groups are especially ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl. More preferably, the alkyl group represented by the symbol R in formula (II) is a linear alkyl group containing 2 to 10 carbon atoms. In this respect, ethyl magnesium chloride, n-butyl magnesium chloride, n-pentyl magnesium chloride, ethyl magnesium bromide, n-butyl magnesium bromide, n-pentyl magnesium bromide, n-octyl magnesium chloride and n-octyl magnesium bromide are suitable for use as alkyl magnesium halide. The alkyl group represented by the symbol R in formula (II) is even more preferably ethyl, n-propyl, n-butyl, n-pentyl or n-octyl, more preferably n-butyl.

[0063] The compounds of formula (II) are also well known as Grignard reagents, some of which are even commercial products. For their synthesis, reference may also be made to the compilations of, for example, "Organic Synthesis". As with any organomagnesium compound, the alkylmagnesium halide constituting the catalyst system may be in the form of a monomeric substance or in the form of a polymeric substance. In addition, whether in the form of a monomeric substance or in the form of a polymeric substance, the alkylmagnesium halide may also be in the form of a substance coordinated with one or more molecules of a solvent (preferably an ether, such as diethyl ether, tetrahydrofuran or methyltetrahydrofuran).

[0064] The use of an alkylmagnesium halide of formula (II) in step a) of the process according to the invention makes it possible to synthesize coupled polymers, whether polyethylene or copolymers of ethylene with 1,3-dienes and optionally vinylaromatic compounds, preferably styrene.

[0065] The amount of the cocatalyst and the metallocene in the reaction satisfies that the ratio of the molar number of Mg of the cocatalyst to the molar number of the rare earth metal (neodymium) of the metallocene is preferably 0.5 to 200, more preferably 1 to less than 20. These preferred ranges are applicable to any embodiment of the present invention. The value range of 1 to less than 20 is particularly conducive to obtaining a copolymer with a high molar mass.

[0066] According to one embodiment, the catalytic system can be conventionally prepared by a method similar to that described in patent applications WO 2007 / 054224A2 or WO2007 / 054223 A2. For example, the cocatalyst (in this case an alkyl magnesium halide) and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20° C. to 80° C., for a period of time (between 5 minutes and 60 minutes). The catalytic system is typically prepared in an aliphatic hydrocarbon solvent (such as methylcyclohexane) or an aromatic hydrocarbon solvent (such as toluene). Typically, after synthesis, the catalytic system is used as is in step a).

[0067] According to another embodiment, the catalytic system can be prepared by a method similar to that described in patent application WO 2017 / 093654A1 or patent application WO 2018 / 020122 A1: it is called preformed type. For example, alkyl magnesium halide and metallocene are reacted in a hydrocarbon solvent, usually 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 the first reaction product at a temperature ranging from 40°C to 90°C for 1 hour to 12 hours. The preformed monomer is preferably used in a molar ratio (preformed monomer / metal of metallocene) ranging from 5 to 1000, preferably 10 to 500. Before being used for polymerization, the preformed catalytic system can be stored under an inert atmosphere, especially at a temperature ranging from -20°C to room temperature (23°C). According to this second embodiment, the preformed catalytic system has a preformed monomer selected from 1,3-diene, ethylene and mixtures thereof as its essential component. In other words, in addition to the metallocene and the cocatalyst, the "preformed" catalytic system also comprises a preformed monomer. The 1,3-diene used as the pre-formed monomer may be 1,3-butadiene, isoprene or a 1,3-diene of the formula CH2=CR 1 -CH=CH2 1,3-diene, symbol R 1 denotes a hydrocarbyl group containing from 3 to 20 carbon atoms, in particular myrcene or β-farnesene. The preformed monomer is preferably 1,3-butadiene.

[0068] The catalytic system is usually present in a solvent, which is preferably a solvent for preparing the catalytic system. 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 in the range of 0.001 mol / L to 0.03 mol / L.

[0069] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of the alkylmagnesium halide and the synthesis of the catalyst system are carried out under anhydrous conditions and in an inert atmosphere. Typically, the reaction is started under anhydrous nitrogen or argon using anhydrous solvents and compounds.

[0070] The polymerization of the monomer mixture is preferably carried out continuously or in batches in a solution. The polymerization solvent is generally an aromatic hydrocarbon solvent or an aliphatic hydrocarbon solvent, such as toluene, cyclohexane or methylcyclohexane, or a mixture of two of them, or even a mixture of three. The monomer mixture can be introduced into a reactor comprising a polymerization solvent and a catalyst system, or conversely, the catalyst system can be introduced into a reactor comprising a polymerization solvent and a monomer mixture. The monomer mixture and the catalyst system can be introduced simultaneously into a reactor comprising a polymerization solvent, particularly in the case of continuous polymerization. The polymerization is generally carried out under anhydrous conditions and in the absence of oxygen and optionally in the presence of an inert gas. The range of the polymerization temperature is generally 40°C to 150°C, preferably 40°C to 120°C. Those skilled in the art adjust the polymerization conditions, such as the polymerization temperature, the concentration of each reagent, and the pressure in the reactor according to the monomer mixture composition, the polymerization reactor, and the desired microstructure and macrostructure of the copolymer chain.

[0071] The polymerization is preferably carried out at a constant monomer pressure. The continuous addition of each monomer or of one monomer can be carried out in the polymerization reactor, in which case the polymerization reactor is a feed reactor. This embodiment is most particularly suitable for statistical incorporation of monomers.

[0072] According to a preferred embodiment of the invention, the polymerization in step a) is a statistical polymerization, which reflects a statistical incorporation of the monomers in the monomer mixture used in step a). This embodiment, which allows the preparation of statistical polymer chains in step a), is suitable for the synthesis of coupled statistical polymers.

[0073] According to another preferred embodiment of the invention, the polymerization in step a) comprises a statistical polymerization of a first monomer mixture containing ethylene and a 1,3-diene, followed by the polymerization of a second monomer mixture, the composition of which differs from the first, for example because it does not contain said 1,3-diene or any 1,3-diene. This embodiment, which makes it possible to prepare block polymer chains in step a), is suitable for the synthesis of coupled block polymers.

[0074] Once the desired degree of monomer conversion has been achieved in the polymerization reaction in step a), step b) is carried out.

[0075] Step b) of the process according to the invention brings a coupling agent (a compound containing at least two nitrile functions) into contact with the reaction product of step a).

[0076] Preferably, step b) is also carried out in a hydrocarbon solvent. Advantageously, it is carried out in the reaction medium produced in step a). It is usually carried out in the reaction medium under stirring by adding a compound containing at least two nitrile functional groups to the reaction product of step a).

[0077] Prior to adding the compound containing at least two nitrile functional groups, the reactor is preferably degassed and rendered inert (also referred to as inertization). Degassing the reactor can remove residual gaseous monomers and also facilitates the addition of the compound containing at least two nitrile functional groups to the reactor. Making the reactor inert (e.g., with nitrogen) helps prevent the deactivation of carbon-metal bonds present in the reaction medium and necessary for the polymer coupling reaction. The compound containing at least two nitrile functional groups can be added undiluted or diluted in a hydrocarbon aliphatic or aromatic solvent. The compound containing at least two nitrile functional groups is contacted with the reaction product in step a) for the time required for the coupling reaction, preferably under stirring. The coupling reaction can usually be monitored by chromatographic analysis to track the consumption of the compound containing at least two nitrile functional groups. The coupling reaction is preferably carried out at a temperature ranging from 23° C. to 120° C., preferably from 40° C. to 100° C.

[0078] The coupling reaction (step b) is preferably carried out with one molar equivalent of nitrile functional groups relative to the number of carbon-magnesium bonds per mole of the cocatalyst (organomagnesium halide). However, the ratio between the number of molar equivalents of nitrile functional groups and the number of carbon-magnesium bonds per mole of the cocatalyst can vary depending on the desired level of coupled polymer in the polymer obtained after step c). A ratio close to 1 (usually ranging from 0.95 to 1.05) is conducive to achieving the highest degree of coupling. Typically, in an organomagnesium halide (such as n-butylmagnesium chloride), there is one mole of carbon-magnesium bonds per mole of magnesium reagent; while in a diorganomagnesium reagent (such as butyloctylmagnesium (BOMAG)), there are two moles of carbon-magnesium bonds per mole of magnesium reagent. One mole of a compound containing two nitrile functional groups is equivalent to two molar equivalents of nitrile functional groups; more typically, one mole of a compound containing n nitrile functional groups is equivalent to n molar equivalents of nitrile functional groups, n being an integer greater than or equal to 2.

[0079] The compound containing at least two nitrile functional groups can be an aliphatic compound or an aromatic compound, preferably an aromatic compound. The compound containing at least two nitrile functional groups is generally a compound having a hydrocarbyl chain substituted by at least two nitrile functional groups. The hydrocarbyl chain of the compound containing at least two nitrile functional groups can be linear, annular or branched.

[0080] According to any embodiment of the present invention, the compound containing at least two nitrile functional groups is a compound in which the number of nitrile functional groups is preferably two or three, more preferably two.

[0081] According to a first embodiment of the present invention, the compound containing at least two nitrile functional groups is an alkane substituted by the nitrile functional group (preferably two nitrile functional groups or three nitrile functional groups, more preferably two nitrile functional groups). The length of the hydrocarbyl chain of the alkane substituted by the nitrile functional group has no inherent restriction, and the number of carbon atoms in the hydrocarbyl chain can vary greatly, for example, 1 to 11 carbon atoms. The selection of the alkane substituted by at least two nitrile functional groups can be due to it being commercially available or easily synthesized. 1,2-dicyanoethane or succinonitrile, 1,3-dicyanopropane or glutaronitrile, 1,4-dicyanobutane or adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,2,3-propanetricarbonitrile and 1,3,5-pentanetricarbonitrile are suitable for use, preferably succinonitrile, glutaronitrile and adiponitrile.

[0082] According to the second particularly preferred embodiment, the compound containing at least two nitrile functional groups is such a compound containing at least two nitrile functional groups, and each of the nitrile functional groups is a substituent of an identical or different aromatic group. The compound containing at least two nitrile functional groups is more preferably a benzene substituted by the nitrile functional group (preferably two nitrile functional groups or three nitrile functional groups, more preferably two nitrile functional groups). For example, 1,3-dicyanobenzene, 1,4-dicyanobenzene and 1,3,5-tricyanobenzene are suitable for use, preferably 1,3-dicyanobenzene and 1,4-dicyanobenzene.

[0083] Once the chain ends have been modified, step b) is followed by step c). Step c) is generally a hydrolysis reaction which allows the formation of keto functions in the polymer chain and, where appropriate, deactivates reactive sites still present in the reaction medium. The hydrolysis reaction is generally carried out by adding water to the reaction medium (or vice versa), optionally in the presence of an acid. Typically, the reaction medium resulting from step b) is contacted with an aqueous hydrochloric acid solution. The hydrolysis reaction can be carried out at a temperature ranging from 0°C to 100°C, preferably at room temperature (23°C) or at the reaction temperature of step b), or even at a temperature ranging from room temperature to the reaction temperature of step b).

[0084] After step c), the polymer can be separated from the reaction medium according to methods well known to those skilled in the art, for example by an evaporation of the solvent under reduced pressure or by a steam stripping operation or by precipitation of the polymer. According to a variant of the invention, step c) and the separation of the polymer from the reaction medium can be carried out in the same operation (for example a steam stripping operation), in particular in the presence of an acid.

[0085] The polymer that can be synthesized by the method according to the present invention has the characteristics of being a coupled polymer, which is usually obtained by the coupling reaction of a polymer chain with a coupling agent (in this case, a compound containing at least two nitrile functional groups). In a known manner, a coupled polymer consists of polymer chains that are covalently linked to each other by a group (or "part"). According to the present invention, the group is produced by the coupling reaction and hydrolysis reaction between the polymer chain and the coupling agent that occur in steps b) and c) of the method according to the present invention, respectively. It will be understood by those skilled in the art that the group is not confused with the monomer unit of the polymer. In the present case, the group contains at least two ketone functional groups. Each of the ketone functional groups of the group is covalently bound to the monomer unit of different polymer chains. Therefore, the polymer according to the present invention consists of polymer chains linked together by the group. They contain more than 50 mol % of ethylene units and are copolymers of polyethylene, ethylene, 1,3-diene and optional vinyl aromatic compounds (preferably styrene).

[0086] According to a preferred embodiment of the present invention, the group containing at least two keto functional groups is such a group, that is, wherein the keto functional groups are each a substituent of the same or different aromatic groups (preferably phenyl). The number of keto functional groups in the group is advantageously two or three, very advantageously two.

[0087] Preferably, the copolymer further contains 1,2-cyclohexane ring units. The 1,2-cyclohexane ring units are of formula (IV).

[0088]

[0089] When the copolymer contains 1,2-cyclohexane ring units, it is a copolymer according to a special embodiment of the invention, in which the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes (one of which is 1,3-butadiene), the ring units resulting from the specific insertion of ethylene and 1,3-butadiene monomers in the polymer chain, in addition to the conventional ethylene and 1,3-butadiene units -(CH2-CH2)-, (CH2-CH=CH-CH2)- and (CH2-CH(C=CH2))-. It is obtained in particular by an embodiment of the process according to the invention in which the metallocene of the catalyst system has two substituted or unsubstituted fluorenyl groups as ligands. The mechanism for obtaining this microstructure is described, for example, in Macromolecules 2009 (42, 3774-3779). When the polymer according to the invention contains 1,2-cyclohexane ring units, it preferably contains not more than 15 mol % of 1,2-cyclohexane ring units, this percentage being expressed relative to all units resulting from the polymerization of the monomers in the monomer mixture.

[0090] When the polymer according to the present invention is a polymer having a plurality of monomers, the constituent polymer chains of the polymer may be block chains or statistical chains.

[0091] According to the embodiment of the invention in which the constituent polymer chains of the polymer are statistical chains, the copolymers according to the invention are statistical copolymers and are obtainable according to a particular embodiment of the process according to the invention which comprises in step a) a statistical polymerization of a monomer mixture.

[0092] According to the embodiment of the invention in which the constituent polymer chains of the polymer are block chains, the copolymer according to the invention contains block chains and can be obtained according to a particular embodiment of the process according to the invention which comprises in step a) a statistical polymerization of a first monomer mixture containing ethylene and 1,3-diene, followed by polymerization of a second monomer mixture which differs in composition from the first monomer mixture in that the second monomer mixture, for example, does not contain 1,3-diene.

[0093] The polymers according to the invention, whether copolymers or polyethylenes, may be used in compositions containing one or more ingredients or components other than the polymers according to the invention, such as additives commonly used in polymer compositions, such as antioxidants, plasticizers, pigments or fillers.

[0094] In summary, the present invention is advantageously carried out according to any one of the following embodiments 1 to 22:

[0095] Embodiment 1: Process for preparing a coupled polymer containing more than 50 mol% of ethylene (expressed as a molar percentage relative to all monomer units of the polymer), the polymer being polyethylene or a copolymer of ethylene with a 1,3-diene and optionally a vinyl aromatic compound, the process comprising the consecutive steps a), b) and c):

[0096] - Step a) consists in polymerizing the monomers in the presence of a catalytic system based on at least one metallocene of formula (I) and an organomagnesium halide of formula (II)

[0097] {P(Cp 1 )(Cp 2 )Nd(BH4) (1+y)- L y -N x} (I)

[0098] XMgR (II)

[0099] Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted,

[0100] P is the bridge Cp 1 and Cp 2 Two groups and groups containing silicon atoms or carbon atoms,

[0101] Nd represents a neodymium atom,

[0102] L represents an alkali metal selected from lithium, sodium and potassium,

[0103] N represents an ether molecule,

[0104] x can be an integer or non-integer greater than or equal to 0.

[0105] y is an integer greater than or equal to 0,

[0106] X is a halogen atom and R is an alkyl group,

[0107] - step b) is to react the reaction product of step a) with a compound containing at least two nitrile functional groups, each nitrile functional group being preferably a substituent of the same or different aromatic groups,

[0108] - Step c) is a hydrolysis reaction.

[0109] Embodiment 2: The method according to embodiment 1, wherein the polymerization reaction is polymerization of ethylene.

[0110] Embodiment 3: The method according to embodiment 1, wherein the polymerization reaction is a copolymerization of a monomer mixture of ethylene and 1,3-diene and optionally a vinyl aromatic compound.

[0111] Embodiment 4: The method of Embodiment 3, wherein the vinyl aromatic compound is styrene.

[0112] Embodiment 5: The method according to any one of Embodiment 1 or Embodiments 3 and 4, wherein the 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene or a mixture thereof.

[0113] Embodiment 6: The method according to any one of Embodiments 1 or 3 and 4, wherein the monomer mixture in step a) contains greater than 50 mol% of ethylene, the percentage being expressed relative to the total moles of monomers in the monomer mixture of step a).

[0114] Embodiment 7: The method according to any one of embodiments 1 to 6, wherein Cp 1 and Cp 2 The same or different, is a substituted fluorenyl or a C 13 The unsubstituted fluorenyl group of H8 is preferably an unsubstituted fluorenyl group.

[0115] Embodiment 8: The method according to any one of Embodiments 1 to 7, wherein the metallocene is of formula (I-1), (I-2), (I-3), (I-4) or (I-5):

[0116] [Me2Si(Flu)2Nd(μ-BH4)2Li(THF)] (I-1)

[0117] [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}2] (I-2)

[0118] [Me2SiFlu2Nd(μ-BH4)(THF)] (I-3)

[0119] [{Me2SiFlu2Nd(μ-BH4)(THF)}2] (I-4)

[0120] [Me2SiFlu2Nd(μ-BH4)] (I-5)

[0121] Where Flu represents C 13 H8 group.

[0122] Embodiment 9: The method according to any one of Embodiments 1 to 8, wherein the ratio between the number of molar equivalents of nitrile functional groups and the number of carbon-magnesium bonds per mole of organomagnesium halide ranges from 0.95 to 1.05.

[0123] Embodiment 10: The method according to any one of embodiments 1 to 9, wherein step b) is carried out with one molar equivalent of nitrile functional groups per mole of carbon-magnesium bonds of the organomagnesium halide.

[0124] Embodiment 11: The method according to any one of Embodiments 1 to 10, wherein the alkyl magnesium halide is alkyl magnesium chloride or alkyl magnesium bromide, preferably alkyl magnesium chloride.

[0125] Embodiment 12: The method according to any one of Embodiments 1 to 11, wherein the alkyl group represented by the symbol R in formula (II) is a linear alkyl group containing 2 to 10 carbon atoms.

[0126] Embodiment 13: The method according to any one of Embodiments 1 to 12, wherein the alkyl group represented by the symbol R in formula (II) is ethyl, n-propyl, n-butyl, n-pentyl or n-octyl, more preferably n-butyl.

[0127] Embodiment 14: The method according to any one of Embodiments 1 to 13, wherein the compound containing at least two nitrile functional groups is a hydrocarbon compound substituted with at least two nitrile functional groups.

[0128] Embodiment 15: The method according to any one of Embodiments 1 to 14, wherein the compound containing at least two nitrile functional groups is a compound having two or three nitrile functional groups.

[0129] Embodiment 16: The method according to any one of Embodiments 1 to 15, wherein the compound containing at least two nitrile functional groups is an alkane substituted with the nitrile functional groups.

[0130] Embodiment 17: The method according to any one of Embodiments 1 to 15, wherein the compound containing at least two nitrile functional groups is a compound containing at least two nitrile functional groups as follows: each nitrile functional group is a substituent of the same or different aromatic groups.

[0131] Embodiment 18: The method according to any one of Embodiments 1 to 15 or Embodiment 17, wherein the compound containing at least two nitrile functional groups is benzene substituted with the nitrile functional groups.

[0132] Embodiment 19: A coupled polymer consisting of polymer chains containing more than 50 mol % of ethylene units, these polymer chains are linked together by groups containing at least two ketone functional groups, each ketone functional group being covalently bonded to a monomer unit of a different polymer chain, the polymer being polyethylene, a copolymer of ethylene with 1,3-diene and optionally a vinyl aromatic compound.

[0133] Embodiment 20: The coupled polymer according to Embodiment 19, wherein the group containing at least two keto functional groups is a group wherein the keto functional groups are substituents of the same or different aromatic groups.

[0134] Embodiment 21: The coupled polymer according to Embodiment 20, wherein the aromatic group is a phenyl group.

[0135] Embodiment 22: The coupled polymer according to any one of Embodiments 19 to 21, which is a copolymer of ethylene with a 1,3-diene and optionally a vinyl aromatic compound, and contains 1,2-cyclohexane ring units, and the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes (one of which is 1,3-butadiene). DETAILED DESCRIPTION

[0136] The above mentioned and other characteristics of the invention will be more clearly understood on reading the following description of an embodiment of the invention given by way of non-limiting illustration.

[0137] Example

[0138] Characterization of polymers:

[0139] High Temperature Size Exclusion Chromatography (HT-SEC) is used to characterize polyethylene:

[0140] High temperature size exclusion chromatography (HT-SEC) analysis was performed using a Viscotek machine (Malvern Instruments) equipped with three columns (PLgel Olexis 300 mm x 7 mm ID from Agilent Technologies) and three detectors (differential refractometer, viscometer and light scattering). -1 The concentration of 200 μl of elution in 1,2,4-trichlorobenzene is 8 mg.mL -1 The mobile phase was 2,6-di(tert-butyl)-4-methylphenol (400 mg.L -1 ) was stable. Data acquisition and analysis were performed using OmniSEC software. Standard polyethylene (M) from Polymer Standard Service (Mainz) was used. p : 338, 507, 770, 1890, 17000, 27300, 43400, 53100, 65700, 78400g.mol -1 ) was used to calculate the number average molar mass (M) of the synthesized polyethylene. n ) and weight average molar mass (M w ).

[0141] Size Exclusion Chromatography THF (SEC-THF) was used to characterize ethylene / 1,3-butadiene copolymers:

[0142] Size exclusion chromatography was performed using a Viscotek machine (Malvern Instruments) equipped with three columns (SDVB from Polymer Standard Service, 5 μm, 300 x 7.5 mm), a guard column and three detectors (differential refractometer, viscometer and light scattering). 1 mL of 5 mg.mL THF was filtered through a 0.45 μm PTFE membrane. -1 At 35°C, use 0.8 mL / min -1 100 μL of this solution was eluted in THF at a flow rate of 1.5 %. Data acquisition and analysis were performed using OmniSEC software. Standard polystyrene (M) from Polymer Standard Service (Mainz) was used. p :1306g.mol -1 to 2520000g.mol -1) was used to calculate the number average molar mass (M) of the synthesized ethylene / 1,3-butadiene copolymer. n ) and weight average molar mass (M w ) and its dispersion

[0143] Nuclear Magnetic Resonance (NMR):

[0144] The spectrometer was operated on a Brüker 400Avance III spectrometer equipped with a 5 mm BBFO proton probe and at 400 MHz and a 10 mm PSEX 13 C carbon probe and on a Brüker 400Avance II spectrometer operating at 400MHz, high-resolution NMR spectroscopy of polymers was performed. Ethylene homopolymers were collected at 363K in a mixture of tetrachloroethylene (TCE) and tritiated benzene (C6D6) (2 / 1 v / v), and ethylene / 1,3-butadiene copolymers were collected at 298K in tritiated chloroform (CDCl3). Samples were analyzed at a concentration of 1% by mass for protons and 5% by mass for carbon. Chemical shifts are given in ppm relative to the tritiated benzene proton signal set at 7.16ppm (or relative to the tritiated chloroform at 7.26ppm) and the TCE carbon signal set at 120.65ppm.

[0145] Preparation of polymer:

[0146] The metallocene [{Me2SiFlu2Nd(μ-BH4)2Li(THF)}]2 was prepared according to the procedure described in patent application WO 2007 / 054224.

[0147] Butyloctylmagnesium BOMAG (20% in heptane, 0.88 mol.L -1 ) was obtained from Chemtura and stored in a Schlenk tube under an inert atmosphere.

[0148] Magnesium halides were from Sigma-Aldrich unless otherwise stated.

[0149] N35 grade ethylene was obtained from the company Air Liquide and was used without prior purification.

[0150] Purification of 1,3-butadiene through an alumina protection tube. Purification of toluene through an alumina protection tube.

[0151] In the procedures described, "cannulation" means the transfer is performed using a cannula.

[0152] Synthesis of coupled polyethylene:

[0153] Embodiment 1:

[0154] 198 mL of toluene from the solvent tank (SPS800 MBraun) was placed in a 250 mL inert round bottom flask equipped with an olive-shaped magnet. Under stirring, 2.0 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether (4.0 mmol, 20 mM in a 98 / 2 mol / mol toluene / diethyl ether mixture) was placed in the flask. Then 8.0 mg (12.5 μmol of neodymium) of {(Me2Si(C 13 H8)2)Nd(μ-BH4)[(μ-BH4)Li(THF)]}2. Under an inert atmosphere, the catalytic solution was transferred to a 250 mL reactor by inserting a cannula. The pressure in the reactor was reduced to 0.5 bar, and then the reactor was pressurized to 4 bar with ethylene, while the temperature was raised to 80°C. The pressure in the reactor was kept constant by a tank filled with ethylene. When the required amount of ethylene was consumed (after 17 minutes in this case), the reactor was degassed, 10 mL (5%) of the polymer solution was taken out of the reactor by inserting a cannula, and then the polymer was precipitated from methanol, recovered by filtration and dried. It was named PE1NF.

[0155] 243 mg of 1,3-dicyanobenzene (1.9 mmol, 1 molar equivalent of nitrile functional groups / carbon-magnesium bond) dissolved in 5 mL of toluene was added to the remaining polymer solution in the reactor. After stirring at 80°C for 40 min, 3 mL of 15% aqueous hydrochloric acid was added to deactivate the system, and then the temperature was lowered to 20°C. The polymer solution was poured into methanol under stirring to precipitate the polymer. The precipitated polymer (PE1F) was filtered, washed with methanol, and then vacuum dried at 80°C for characterization.

[0156] 4.44 g of the formula H-(CH2-CH2) was recovered. n -C(O)-(C6H4)-C(O)-(CH2-CH2) n -H polymer PE1F, and 0.22 g of the formula H-(CH2-CH2) was recovered from the sample collected before the coupling reaction. n The proton NMR spectrum of polymer PE1F (TCE / C6D6 2 / 1 v / v, 400 MHz, 363 K) showed that the methylene proton at the α position to the ketone was located at δ = 2.76 ppm (triplet, (CH2-CH2) n -C H 2-C(O)-(C6H4)-C(O)-C H 2-(CH2-CH2) n) and three aromatic proton signals located at δ = 7.26 ppm (triplet, 1H), 7.92 ppm (doublet, 2H), 8.43 ppm (singlet, 1H). The functional group content in polymer PE1F was determined by NMR spectra of C(O)-C H The sum of the integrals of the 2-CH2 and CH3 signals was normalized (to 5) to calculate. Therefore, in PE1F, 88% of the polymer chain ends were modified with ketones. No by-products were identified by NMR. Therefore, in PE1F, 88% of the polymer chains were coupled.

[0157] Synthesis of coupled copolymers of ethylene and 1,3-butadiene:

[0158] Embodiment 2:

[0159] 199 mL of toluene from the solvent tank (SPS800 MBraun) was placed in a 250 mL inert round bottom flask equipped with an olive-shaped magnet. Under stirring, 1.0 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether (2.0 mmol, 10 mM in a toluene / diethyl ether mixture) was placed in the flask. Then 32.0 mg (50 μmol of neodymium) of {(Me2Si(C 13 H8)2)Nd(μ-BH4)[(μ-BH4)Li(THF)]}2. Under an inert atmosphere, the catalytic solution was transferred to a 250 mL reactor by cannula. The pressure in the reactor was reduced to 0.5 bar, and then the reactor was pressurized to 4 bar with an 80 / 20 mol / mol mixture of ethylene / 1,3-butadiene, while the temperature was raised to 80°C. The pressure in the reactor was kept constant by a tank filled with an 80 / 20 mol / mol mixture of ethylene / 1,3-butadiene gas. When the required amount of monomers was consumed (after 33 minutes in this case), the reactor was degassed and the temperature was reduced to 20°C. 10 mL (5%) of the polymer solution was taken out of the reactor by cannula, and the polymer was then precipitated from methanol containing 2,6-di-tert-butyl-4-methylphenol, washed with methanol, and then dried in vacuo at 70°C. It was named EBR1NF.

[0160] 121 mg of 1,3-dicyanobenzene (0.95 mmol, 1 molar equivalent of nitrile functionality / carbon-magnesium bond) dissolved in 5 mL of toluene was added to the remaining polymer solution in the reactor. After stirring at 80°C for 40 minutes, 3 mL of 15% aqueous hydrochloric acid was added to deactivate the system. The polymer solution was poured into methanol under stirring to precipitate the polymer. The precipitated polymer (EBR1F) was filtered, washed with methanol, and then dried for characterization. Thus, 3.76 g of polymer EBR1F was recovered, and 0.21 g of polymer EBR1NF was recovered from the sample collected before the coupling reaction.

[0161] Embodiment 3:

[0162] The synthesis of polymer EBR2 was the same as described in Example EBR1, except that:

[0163] - 1.0 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether was replaced with 0.5 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether (1.0 mmol, 5 mM in a toluene / diethyl ether mixture);

[0164] - The coupling reaction was carried out by adding 5 mL of a 0.095 M solution of adiponitrile in toluene (0.475 mmol, 1 molar equivalent of nitrile functionality per carbon-magnesium bond);

[0165] - Deactivation reaction was carried out after 15 minutes at 80°C.

[0166] 13.86 g of polymer EBR2F was recovered, and 0.67 g of polymer EBR2NF was recovered from the sample collected before the coupling reaction.

[0167] Embodiment 4:

[0168] The synthesis of polymer EBR3 was the same as described in Example EBR1, except that:

[0169] - 1.0 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether was replaced by 0.57 mL of a 0.88 M solution of BOMAG in heptane (0.5 mmol, 2.5 mM in a toluene / heptane mixture);

[0170] - The coupling reaction was carried out by adding 5 mL of a 0.095 M solution of adiponitrile in toluene (0.475 mmol, 1 molar equivalent of nitrile functionality per carbon-magnesium bond);

[0171] - Deactivation reaction was carried out after 15 minutes at 80°C.

[0172] 14.10 g of polymer EBR3F was recovered, and 0.75 g of polymer EBR3NF was recovered from the sample collected before the coupling reaction.

[0173] Embodiment 5:

[0174] 199 mL of toluene from the solvent tank (SPS800 MBraun) was placed in a 250 mL inert round-bottom flask equipped with an olive-shaped magnet. Under stirring, 0.5 mL of a 2.0 M solution of butylmagnesium chloride in diethyl ether (1.0 mmol, 5 mM in a toluene / diethyl ether mixture) was placed in the flask. Then 32.0 mg (50 μmol of neodymium) of {(Me2Si(C13 H8)2)Nd(μ-BH4)[(μ-BH4)Li(THF)]}2. Under an inert atmosphere, the catalytic solution was transferred to a 250 mL reactor by inserting a cannula. The pressure in the reactor was reduced to 0.5 bar, and then the reactor was pressurized to 4 bar with an 80 / 20 mol / mol ethylene / 1,3-butadiene mixture, while the temperature was raised to 80°C. The pressure in the reactor was kept constant by a tank filled with an 80 / 20 mol / mol ethylene / 1,3-butadiene gas mixture.

[0175] After consuming 15 g of the ethylene / 1,3-butadiene mixture, the pressure in the reactor was reduced to 0.5 bar, and then the reactor was pressurized to 4 bar with ethylene, and the temperature was maintained at 80°C. After consuming 1 g of ethylene, the reactor was degassed and the temperature was reduced to 20°C. 10 mL (5%) of the polymer solution was taken out of the reactor by inserting a cannula, and then the polymer was precipitated from methanol containing 2,6-di-tert-butyl-4-methylphenol, washed with methanol, and dried in vacuo at 70°C. It was named EBR-b-PE1NF. The polymer chain before the coupling reaction is a block polymer chain, which consists of statistical polymer blocks of ethylene and 1,3-butadiene and polyethylene blocks.

[0176] 5 mL of a 0.095 M solution of adiponitrile in toluene (0.475 mmol, 1 molar equivalent of nitrile functionality per carbon-magnesium bond) are added to the polymer solution remaining in the reactor and the reaction medium is then stirred at 80° C. for 1 hour.

[0177] After stirring at 80°C for 40 minutes, 3 mL of 15% hydrochloric acid aqueous solution was added to deactivate the system. The polymer solution was poured into methanol under stirring to precipitate the polymer. The precipitated polymer (EBR-b-PE1) was filtered, washed with methanol, and then characterized.

[0178] 15.39 g of polymer EBR-b-PE1F was recovered, and 0.88 g of polymer EBR-b-PE1NF was recovered from the sample collected before the coupling reaction.

[0179] The polymerization conditions are given in Table 1. Table 1 also shows the catalytic activity calculated over the entire polymerization time for each example, in kg.mol -1 .h -1Table 1 also shows the coupling agents used. The characteristics of the synthesized polymers are shown in Table 2. The molar mass was determined using the SEC-THF method and the microstructure of the polymer was determined by NMR. The ethylene unit content, the content of 1,3-butadiene units of 1,2-configuration (1,2-unit), the content of 1,3-butadiene units of 1,4-configuration (1,4-unit) and the content of 1,2-cyclohexane units (cyclic units) are expressed as molar percentages relative to all monomer units of the polymer.

[0180] Examples 1, 2, 3 and 5 are in accordance with the invention. Example 4 is an example out of accordance with the invention because the cocatalyst used is not an alkylmagnesium halide but a dialkylmagnesium reagent, in this case n-butyl-n-octylmagnesium (BOMAG).

[0181] The copolymers in Examples 2 and 3 are statistical copolymers. The copolymer in Example 4 is also a statistical copolymer. The copolymer in Example 5 is a block copolymer because it consists of coupled polymer chains, each of which consists of a statistical polymer block of ethylene and 1,3-butadiene and a polyethylene block.

[0182] Table 1

[0183]

[0184]

[0185] *For the polymerization of ethylene / 1,3-butadiene polymer blocks

[0186] Table 2

[0187]

[0188] **Mp molar mass peak: For EBR2F and EBR-b-PE1F, there is a bimodal distribution.

[0189] Regardless of whether the polymer is polyethylene or an ethylene-rich diene copolymer, it can be observed that the process according to the invention does allow the synthesis of coupled polymers.

[0190] Specifically, in Examples 2, 3 and 5, the coupled polymers EBR1F, EBR2F and EBR-b-PE1F exhibited peak molar masses that were approximately twice the peak molar masses measured for the polymers before the coupling reaction (EBR1NF, EBR2NF and EBR-b-PE1NF, respectively).

[0191] On the other hand, the use of a dialkylmagnesium reagent such as BOMAG (Example 4, EBR3F) as a cocatalyst did not produce coupled polymers.

[0192] Furthermore, the use of coupling agents whose nitrile functions are substituted by benzene also allows the coupling of the chains to be carried out with the best yields. Specifically, in the case of polyethylene, the degree of coupling quantified by NMR is close to 90% (Example 1, PE1F), while in the case of copolymers of ethylene and 1,3-butadiene, a single molar mass peak is determined (Example 2, EBR1F). No by-products are detected, which also reflects the coupling reaction carried out according to a selective method in the case of the use of coupling agents containing at least two nitrile functions, each nitrile function replacing an aromatic group.

Claims

1. A process for preparing a coupled polymer containing more than 50 mol% of ethylene, expressed as a molar percentage relative to all the monomer units of the polymer, the polymer being a polyethylene or a copolymer of ethylene with a 1,3-diene and optionally a vinyl aromatic compound, the process comprising the successive steps a), b) and c): - Step a) consists in polymerizing the monomers in the presence of a catalytic system based on at least one metallocene of formula (I) and an organomagnesium halide of formula (II) {P(Cp 1 )(Cp 2 )Nd(BH4) (1+y)- L y -N x }(I) XMgR(II) Cp 1 and Cp 2 are the same or different and are selected from fluorenyl, cyclopentadienyl and indenyl, which groups are substituted or unsubstituted, P is the bridge Cp 1 and Cp 2 Two groups and groups containing silicon atoms or carbon atoms, Nd represents a neodymium atom, L represents an alkali metal selected from lithium, sodium and potassium, N represents an ether molecule, x can be an integer or non-integer greater than or equal to 0, y is an integer greater than or equal to 0, X is a halogen atom and R is an alkyl group, - step b) is to react the reaction product of step a) with a compound containing at least two nitrile functional groups, each nitrile functional group being preferably a substituent of the same or different aromatic groups, - Step c) is a hydrolysis reaction.

2. The method according to claim 1, wherein: The polymerization reaction is a polymerization of ethylene, a copolymerization of a monomer mixture of ethylene and a 1,3-diene and optionally a vinyl aromatic compound, preferably styrene.

3. The method according to claim 1 or 2, wherein: The 1,3-diene is 1,3-butadiene, isoprene, myrcene, β-farnesene or a mixture thereof.

4. The method according to any one of claims 1 to 3, wherein: Cp 1 and Cp 2 The same or different, is a substituted fluorenyl or a C 13 The unsubstituted fluorenyl group of H8 is preferably an unsubstituted fluorenyl group.

5. The method according to any one of claims 1 to 4, wherein: The alkylmagnesium halide is alkylmagnesium chloride or alkylmagnesium bromide, preferably alkylmagnesium chloride.

6. The method according to any one of claims 1 to 5, wherein: The alkyl group represented by the symbol R in formula (II) is a linear alkyl group containing 2 to 10 carbon atoms.

7. The method according to any one of claims 1 to 6, wherein: The alkyl group represented by the symbol R in formula (II) is ethyl, n-propyl, n-butyl, n-pentyl or n-octyl, more preferably n-butyl.

8. The method according to any one of claims 1 to 7, wherein: The compound containing at least two nitrile functional groups is a hydrocarbyl compound substituted with at least two nitrile functional groups.

9. The method according to any one of claims 1 to 8, wherein: Compounds containing at least two nitrile functional groups are compounds in which the number of nitrile functional groups is two or three.

10. The method according to any one of claims 1 to 9, wherein: Compounds containing at least two nitrile functional groups are alkanes substituted with said nitrile functional groups.

11. The method according to any one of claims 1 to 9, wherein: A compound containing at least two nitrile functions is a compound containing at least two nitrile functions wherein each nitrile function is a substituent of an identical or different aromatic group.

12. The method according to any one of claims 1 to 9 or claim 11, wherein: The compound containing at least two nitrile functional groups is a benzene substituted by said nitrile functional groups.

13. Coupled polymers consisting of polymer chains containing more than 50 mol % of ethylene units, these polymer chains being linked together by groups containing at least two keto functional groups, each keto functional group being covalently bonded to a monomer unit of a different polymer chain, said polymers being polyethylene, copolymers of ethylene with 1,3-diene and optionally vinyl aromatic compounds.

14. The coupled polymer according to claim 13, wherein A radical containing at least two keto functions is a radical in which the keto functions are each a substituent of an identical or different aromatic radical.

15. The coupled polymer according to claim 14, wherein The aromatic group is phenyl.

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