Catalytic system for the stereospecific polymerization of dienes and their use in the synthesis process of diene polymers

Abstract

The invention relates to a catalytic system comprising the metallic components of formulas R1R2Mg and Ca(AR'y)2(L)x, in which: - each of R1 and R2 represents, independently of each other, a C1-C10 aliphatic radical, substituted or unsubstituted, or a C6-C20 aromatic radical, substituted or unsubstituted; - A denotes a nitrogen atom (N) or an oxygen atom (O); - y is 2 when A is N and y is 1 when A is O; - each R' represents, independently of each other, a C1-C10 aliphatic radical, substituted or unsubstituted, a C6-C20 aromatic radical, substituted or unsubstituted, a silyl radical, substituted or unsubstituted, a C1-C10 aliphatic radical substituted by at least one silyl radical, substituted or unsubstituted, or a C6-C20 aromatic radical substituted by at least one silyl radical. substituted or not, - L represents a ligand, - x is a number from 0 to 4.The use of this catalytic system for the anionic polymerization of conjugated dienes allows the obtaining of diene polymers with high trans content.

Description

Title of the invention: Catalytic system for the stereospecific polymerization of dienes and their use in the synthesis process of diene polymers. Technical field

[0001] The present invention relates to a catalytic system for the stereospecific polymerization of conjugated dienes favoring 1,4-trans insertion of monomers. More particularly, the invention relates to a polymetallic catalytic system for the stereospecific polymerization of conjugated dienes favoring 1,4-trans insertion of monomers. The invention also relates to a process for synthesizing diene polymers with a high 1,4-trans linkage rate using a polymetallic catalytic system for monomer polymerization. Previous technique

[0002] The use of polymetallic catalytic systems for the stereospecific polymerization of diene monomers to manufacture diene polymers with high 1,4-trans chaining ratio has been described in the past.

[0003] The Applicant has proposed, in EP 1 018 521 Al, a process for the synthesis of diene polymers having a 1,4-trans linkage ratio greater than 70% by weight using a trimetallic lithium catalytic system for the initiation of the polymerization of 1,3-diene monomers. The catalytic system used comprised an organolithium polymerization initiator and two metallic co-catalysts, one being a compound of a metal from group 13 of the periodic table of elements, in particular aluminum, and the other being a compound of an alkaline earth metal, in particular strontium or barium.

[0004] The Applicant also proposed in WO2022008838A1 a process for synthesizing diene polymers exhibiting a higher 1,4-trans linkage ratio than that obtained with an alkyllithium derivative alone, using a bimetallic lithium catalytic system. The catalytic system used comprised an organolithium polymerization initiator, in particular an alkyllithium, and a calcium-based complex, in particular calcium bis(trimethylsilyl)amide. The conversion is high, even at near-ambient temperatures. Similarly, the Applicant proposed in WO2022008833A1 another process for synthesizing diene polymers exhibiting a higher 1,4-trans linkage ratio than that obtained with an alkyllithium derivative alone, using a bimetallic lithium catalytic system comprising other alkaline earth metal-based components.

[0005] These catalytic systems use alkyllithium derivatives as initiators, which are conventional initiators of the anionic polymerization of dienes. However, with the ever-increasing global demand for lithium, driven primarily by growing use in the battery sector, the lithium market is evolving, and a lithium-free approach to anionic polymerization is becoming relevant.

[0006] Focused on the use of alkaline earth metal derivatives as anionic initiators, the literature also reports anionic polymerization processes of lithium-free 1,3-diene monomers.

[0007] Thus, it has already been considered to combine rare-earth organic compounds and magnesium organic compounds for the polymerization of 1,3-diene monomers capable of generating stereospecificity of the 1,4-cis or 1,4-trans configurations, and in particular of the 1,4-trans configuration. For example, the Applicant proposed, in WO2022258907A1, a process for the synthesis of diene polymers exhibiting a high degree of 1,4-trans chaining and a low degree of 1,2- chaining using a preformed catalytic system comprising a neodymium tris(organophosphate) and a dialkylmagnesium, in particular n-butylethylmagnesium or n-butyloctylmagnesium.

[0008] Other alkaline earth metals besides magnesium have also been considered for the anionic polymerization of lithium-free 1,3-diene monomers. For example, Lindsell et al. described a Grignard-type initiator (Ph3CCaCl(THF)2) and (Ph3CCaBr(THF)4) capable of initiating butadiene polymerization in THF at low temperature (-10°C), giving polybutadiene with relatively high dispersities on the order of 2.

[0009] Although catalytic systems used in stereospecific polymerizations of conjugated dienes have already been described in the past, there remains a need for other methods of synthesizing diene polymers exhibiting a high 1,4-trans chaining ratio with control of molar masses, which does not require the use of an organolithium compound as a polymerization initiator.

[0010] The technical problem addressed by the present invention is to provide a method for synthesizing diene polymers, without lithium-based compounds, exhibiting greater stereospecificity towards the trans-1,4 insertion of conjugated diene monomers than that observed with an alkyllithium derivative alone, while ensuring control over polymer dispersity. Description of the invention

[0011] The invention solves this problem by proposing a catalytic system, combining an organic magnesium compound with an organic calcium compound, for the polymerization of conjugated dienes exhibiting stereospecificity with respect to of the trans-1,4 insertion and ensuring satisfactory polymerization kinetics with low dispersity of molar masses.

[0012] The use of the catalytic system according to the invention in a process for synthesizing a diene polymer makes it possible to avoid the use of lithium, the resources and market of which are uncertain, while offering the possibility of obtaining diene polymers exhibiting a low dispersity D of at most 1.6 and a 1,4-trans chaining ratio higher than those obtained with a conventional initiation system based on a single alkyllithium, which is known to be on the order of 50 to 55% in hydrocarbon medium. Indeed, the use of the catalytic system according to the invention makes it possible to achieve 1,4-trans chaining ratios of at least 65% by weight relative to the diene portion of the polymer.

[0013] In a first aspect, the invention relates to such a catalytic system.

[0014] In another aspect, the invention relates to a method for synthesizing a diene polymer using such a catalytic system. Summary of the invention

[0015] The invention, described in more detail below, relates to at least one of the embodiments listed in the following points:

[0016] 1. Catalytic system consisting of the following metallic components:

[0017] (a) an organic calcium compound of formula Ca(AR'y)2(L)x, in which

[0018] - A denotes a nitrogen atom N or an oxygen atom O, - y depends on the valence of A, y is 2 when A is N and y is 1 when A is O, - each R' represents, independently of each other, an aliphatic radical in C1-C10, substituted or unsubstituted, an aromatic radical in C6-C20, substituted or unsubstituted, a silyl radical, substituted or unsubstituted, - L represents a ligand, - x is a number ranging from 0 to 4,

[0019] (b) an organic magnesium compound of formula R*R2Mg, in which each of R1 and Represents, independently of each other, an aliphatic radical in Ci-Cio, substituted or not, or an aromatic radical in C6-C20, substituted or not.

[0020] 2. Catalytic system according to the preceding embodiment characterized in that the radical aliphatic in Ci-Cio, in the definition of R' is an alkyl radical in Ci-Cio.

[0021] 3. Catalytic system according to any one of the preceding embodiments characterized in that the aromatic radical in the definition of R' is a C6-C20 aryl radical.

[0022] 4. Catalytic system according to any one of the preceding embodiments characterized in that the silyl radical in the definition of R' is a substituted silyl radical.

[0023] 5. Catalytic system according to any one of the preceding embodiments characterized in that the silyl radical in the definition of R' is a silyl radical substituted by at least one alkyl radical in Ci-C5, cycloalkyl in C3-C6, aryl in C6-Ci0 or aralkyl in C7-C12.

[0024] 6. Catalytic system according to any one of the preceding embodiments in where A is a nitrogen atom and y has a value of 2.

[0025] 7. Catalytic system according to any one of the preceding embodiments characterized in that R' is a silyl radical substituted by three Cr C5 alkyl radicals.

[0026] 8. Catalytic system according to any one of the preceding embodiments characterized in that R' is a trimethylsilyl, triethylsilyl or tripropylsilyl radical, preferably trimethylsilyl.

[0027] 9. Catalytic system according to any one of the preceding embodiments characterized in that the ligand L is chosen from ethers, amines, phosphates, thioethers, pyridines, bipyridines, phenantrolines, imidazoles and amides.

[0028] 10. Catalytic system according to the preceding embodiment characterized in that the ligand L is an ether or an amine.

[0029] 11. Catalytic system according to the preceding embodiment characterized in that the ligand L is 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran or tetramethylethylenediamine.

[0030] 12. Catalytic system according to any one of the preceding embodiments in which x equals 2.

[0031] 13. Catalytic system according to any one of the preceding embodiments characterized in that the ligand L is tetrahydrofuran and x is 2.

[0032] 14. Catalytic system according to any one of the preceding embodiments characterized in that the organic compound of calcium is Ca(N(SiMe3)2)2(THF)2.

[0033] 15. Catalytic system according to the preceding embodiment in which the radical aliphatic, in the definition of R'R2Mg is an alkyl radical in Ci-Cio, substituted or not.

[0034] 16. Catalytic system according to the preceding embodiment in which the radical aliphatic, in the definition of R1 and R2 is an alkyl radical in Ci-Cio chosen from among a methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl radical.

[0035] 17. Catalytic system according to any one of the preceding embodiments in which the organic magnesium compound of formula R1 R2Mg is n-dibutylmagnesium, s-dibutylmagnesium or butylmagnesium.

[0036] 18. Catalytic system according to any one of the preceding embodiments characterized in that the molar ratio of Ca(AR'y)2 (L)x to R'R2Mg (or of Ca to Mg) is at least 0.2.

[0037] 19. Catalytic system according to any one of the preceding embodiments in in which the molar ratio of Ca(AR'y)2(L)x to R*R2Mg (or of Ca to Mg) is less than or equal to 4.0.

[0038] 20. Catalytic system according to any one of the preceding embodiments in in which the molar ratio of Ca(AR'y)2(L)x to R*R2Mg (or of Ca to Mg) is less than or equal to 2.0.

[0039] 21. Catalytic system according to any one of the preceding embodiments in in which the molar ratio of Ca(AR'y)2 (L)x to R'R2Mg (or of Ca to Mg) varies in a range from 0.2 to 2.0, preferably from 0.5 to 1.5.

[0040] 22. A process for synthesizing a diene polymer comprising a step of anionic polymerization of at least one diene monomer in the presence of a catalytic system according to any one of the preceding embodiments.

[0041] 23. A process according to the preceding embodiment, characterized in that the monomer dienic is a 1,3-diene monomer having 4 to 8 carbon atoms.

[0042] 24. A process according to the preceding embodiment, characterized in that the monomer dienic acid is butadiene or isoprene.

[0043] 25. A method according to any one of the preceding embodiments 22 to 24 characterized in that the diene monomer is copolymerized with at least one other monomer.

[0044] 26. A process according to the preceding embodiment, characterized in that the monomer dienic is copolymerized with at least one other monomer selected from among the 1,3-diene monomers having 4 to 8 carbon atoms.

[0045] 27. A process according to embodiment 25 or 26 characterized in that the diene monomer is copolymerized with at least one other monomer selected from vinylaromatic compounds, preferably styrene. Definition

[0046] The terms “radical”, “group” and “grouping”, in the singular or plural, are equivalent and interchangeable.

[0047] The expression "in Cx-Cy" for a hydrocarbon radical means that said radical comprises x to y carbon atoms.

[0048] In this description, unless expressly stated otherwise, all percentages (%) given are percentages (%) by weight. The percentages (%) relating to the 1,2-, 1,4-trans, and 1,4-cis butadiene units in the diene polymer are percentages by weight relative to the diene portion of the polymer. Thus, a 1,4-trans chaining ratio of more than 65% in a diene polymer corresponds to a 1,4-trans diene unit rate of more than 65% by weight relative to the weight of the diene portion of the polymer.

[0049] In this description, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from more than a to less than b (i.e., bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict bounds a and b).

[0050] The carbon-containing compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. These include, in particular, polymers, monomers, plasticizers, fillers, etc.

[0051] Thus, for example, butadiene can advantageously be obtained directly from biomass in a known manner or from a bio-based precursor, for example, bio-based ethanol. Isoprene can advantageously be obtained directly from biomass in a known manner or from a bio-based precursor, for example, from bio-based isobutene. Detailed description of the invention

[0052] The invention relates to a catalytic system consisting of the following metallic components: (1) an organic calcium compound of formula Ca(AR'y)2(L)x, in which

[0053] - A denotes a nitrogen atom N or an oxygen atom O, - y depends on the valence of A, y is 2 when A is N or 1 when A is O, - Each R' represents, independently of each other, an aliphatic radical in the form of Ci-Cio, substituted or unsubstituted, an aromatic radical in the form of C6-C20, substituted or unsubstituted, a silyl radical, substituted or unsubstituted, an aliphatic radical in the form of CrCio, substituted by at least one silyl radical, substituted or unsubstituted, an aromatic radical in the form of C6-C20, substituted by at least one silyl radical, substituted or unsubstituted, - L represents a ligand, - x is a number ranging from 0 to 4,

[0054] (2) an organic magnesium compound of formula R*R2Mg, in which each of R1 and Represents, independently of each other, an aliphatic radical in Ci-Cio, substituted or not, or an aromatic radical in C6-C20, substituted or not.

[0055] In the formula Ca(AR'y)2(L)x, the (AR'y) radicals of Ca have a lipophilic character so that the catalytic system is soluble in an organic medium. In the absence of this lipophilic character of the radicals, the Ca(AR'y)2(L)x component of the catalytic system would be poorly soluble in the organic medium in which it is generally The diene monomers are polymerized in solution. The lack of solubility of the catalytic system in such an organic medium can lead to a decrease in catalytic activity and in particular a decrease in the stereospecificity of the catalytic system towards the 1,4-trans insertions of the conjugated diene monomers during the synthesis of diene polymers.

[0056] In the formula Ca(AR'y)2(L)x, R' can be an aliphatic radical in the Ci-Cio group, preferably in C5-C10, substituted or unsubstituted. Examples of aliphatic radicals representing R include alkyl groups in the CrCio group, preferably in C5-C10, alkenyl groups in the CrC10 group, preferably in C5-C10, and alkynyl groups in the C1-C10 group, preferably in C5-C10, cyclic or non-cyclic.

[0057] In the formula Ca(AR'y)2(L)x, R' can be a C6-C20 aromatic radical, substituted or unsubstituted. Examples of aromatic radicals representing R include C6-C20 aryl groups.

[0058] In the formula Ca(AR'y)2(L)x, R' may be a substituted or unsubstituted silyl radical. The substituted silyl radical may be mono-, di-, or trisubstituted. The substituents of the silyl group may independently be chosen from C1-C5 alkyl radicals, C6-Ci0 aryl radicals (e.g., phenyl or naphthyl), or C7-Ci2 aryl radicals. Examples of monosubstituted silyl groups include Ci-C5 alkylsilyls (e.g., methylsilyl) and arylsilyls (e.g., phenylsilyl). Examples of disubstituted silyl groups include di-Ci-C5 alkylsilyls (e.g., dimethylsilyl) and di-arylsilyls (e.g., diphenylsilyl). Examples of trisubstituted silyl groups include tri-Ci-C5-alkylesilyls (e.g., trimethylsilyl, triethylsilyl, tripropylsilyl), tri-arylsilyls (e.g., triphenylsilyl, trinaphthylsilyl, tritoylsilyl), and silyls substituted with alkyl and aryl radicals (e.g., dimethylphenylsilyl, methyldiphenylsilyl).

[0059] In the formula Ca(AR'y)2(L)x, R' can be a C1-C10 aliphatic radical substituted by at least one silyl radical, substituted or unsubstituted. Examples of aliphatic radicals include C1-C10 alkyl groups, C2-C10 alkenyl groups, and C2-C10 alkynyl groups, whether cyclic or non-cyclic. The silyl radical is as described above. In particular, when the aliphatic radical is a non-cyclic C1-C4 alkyl radical and the silyl radical is a trisubstituted silyl radical, R' can be selected from (tri-C1-C5-alkylsilyl)alkyl radicals such as (trimethylsilyl)methylene, (trimethylsilyl)ethylene, l-(trimethylsilyl)propylene...

[0060] In the formula Ca(AR'y)2(L)x, R' can be a C6-C2o aromatic radical, substituted or unsubstituted. The aromatic radical and the silyl radical are as described above.

[0061] The aliphatic or aromatic radical defining R' can be substituted, for example, by one or more substituents chosen in particular from among the C6 aryl groups -Cio and silyl groups, substituted or unsubstituted, as defined above. The aromatic radical defining R and the aromatic radical defining R' may further or alternatively be substituted by one or more substituents independently chosen from the alkyl groups in Ci-Cio, alkenyl groups in C2-Ci0, alkynyl groups in C2-Cio and aralkyl groups in C7-Ci2.

[0062] According to certain particular embodiments of the invention, R' is a silyl radical substituted by three alkyl radicals in C1-C5.

[0063] According to certain particular embodiments of the invention, R' is a trimethylsilyl, triethylsilyl or tripropylsilyl radical, preferably trimethylsilyl.

[0064] The ligand L is generally a hindered ligand selected from among the Lewis bases and results from the synthesis of the alkaline earth complex. The ligand L can be selected from ethers, amines, phosphates, thioethers, pyridines, bipyridines, phenantrolines, imidazoles, and amides. Examples of ethers include diethyl ether, 1,2-diethoxyethane, 1,2-di-n-propoxyethane, 1,2-di-n-butoxyethane, tetrahydrofuran, dioxane, and tetrahydropyran. Examples of amines include tertiary amines such as trialkylamines, in particular tetramethylethylenediamine (TMEDA), and aromatic amines such as pyridine or piperazine and its derivatives. An example of a phosphate includes tri-n-butylphosphate. Examples of thioethers include compounds in the dialkyl sulfide family, such as dimethyl sulfide.

[0065] x may be an integer or not. Those skilled in the art will understand that the number x, corresponding to the number of L present in the alkaline earth complex, depends on the method of preparing the complex. This number varies from 0 to 4.

[0066] In the formula Ca (AR'y)2(L)x, A is preferably a nitrogen atom.

[0067] The catalytic system according to the invention also contains an organic magnesium compound of formula R*R2Mg.

[0068] In the formula R*R2Mg, R1 and R2 can be identical or different.

[0069] In the formula R*R2Mg, at least one of R1 and R2 may be an aliphatic radical in C1-C10, substituted or unsubstituted. Examples of aliphatic radicals include C1-C10 alkyl groups, C2-C10 alkenyl groups, and C2-C10 alkynyl groups, whether cyclic or non-cyclic. Specifically, when either R1 or R2 is an aliphatic radical, it is a non-cyclic C1-C10 alkyl radical chosen from among the methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl radicals.

[0070] In the formula R*R2Mg, at least one of R1 and R2 may be a C6-C2O aromatic radical, substituted or unsubstituted. Examples of aromatic radicals include C6-C2O aryl groups.

[0071] By substituted aliphatic radical or substituted aromatic radical, we mean a radical substituted by one or more hydrocarbon groups having from 1 to 10 carbon atoms.

[0072] According to preferred embodiments of the invention, in the formula R'R2Mg, R1 and R2 each denote a non-cyclic Ci-Cio alkyl radical, preferably a Ci-C8 alkyl radical, substituted or unsubstituted.

[0073] According to these embodiments, the organic magnesium compound of formula R1 R2Mg is very preferably n-dibutylmagnesium, s-dibutylmagnesium or butylmagnesium.

[0074] Those skilled in the art will understand that the embodiments of the invention mentioned above are combinable with each other in all their particular and preferred aspects, provided they are compatible. Thus, according to certain particularly advantageous embodiments, the catalytic system has at least one of the following characteristics and preferably all of them: - A represents a nitrogen atom and y has a value of 2, - each R' represents a silyl radical substituted by three alkyl radicals in C1-C5, preferably R' is trimethylsilyl, triethylsilyl or tripropylsilyl, - the ligand L is tetrahydrofuran, - x equals 2 and - R1 and R2 each denote a non-cyclic CrC8 alkyl radical, preferably s-butyl, n-butyl or octyl.

[0075] According to certain particularly advantageous embodiments, the catalytic system according to the invention consists of Ca(N(SiMe3)2)2(THF)2 and s-dibutylmagnesium or of Ca(N(SiMe3)2)2(THF)2 and n-dibutylmagnesium or of Ca(N(SiMe3)2)2(THF)2 and butyloctylmagnesium.

[0076] Furthermore, those skilled in the art will understand that the Ca(AR'y)2(L)x component may not be found in a unit form in the catalytic system, but rather in an agglomerated form forming a crystalline lattice. Thus, at the scale of this lattice, it is possible that it may share certain molecules, whether Ca, (AR'y) or L, with one or more other lattice units.

[0077] In the catalytic system according to the invention, the molar ratio of Ca(AR'y)2(L)x to R1 R2Mg (or of Ca to Mg) is greater than 0 since each of the co-catalysts is always present in the system. Although it is conceivable to use a catalytic system according to the invention with a molar ratio of Ca(AR'y)2(L)x to R*R2Mg greater than 4.0, the molar ratio of Ca(AR'y)2(L)x to R*R2Mg is preferably less than or equal to 4.0. Indeed, beyond this value of 4.0, the level of component consumption Ca(AR'y)2(L)x is much higher than that required to achieve the intended objectives. Preferably, the molar ratio of Ca(AR'y)2(L)x to R*R2Mg is less than or equal to 2.0, as this achieves a satisfactory 1,4-trans chaining rate of over 65%, and unnecessary overconsumption of the Ca(AR'y)2(L)x component would impair the productivity of polymer synthesis.

[0078] According to certain particular embodiments of the invention, the molar ratio of Ca(AR'y)2(L)x to R'R2Mg is preferably at least 0.2 when the catalytic system is used for the polymerization of conjugated dienes. According to these particular embodiments of the invention, the molar ratio of Ca(AR'y)2(L)x to R'R2Mg varies in a range from 0.2 to 2.0, preferably from 0.5 to 1.5. Within these value ranges, when the catalytic system is used for the polymerization of conjugated dienes, in particular 1,3-dienes such as 1,3-butadiene, a 1,4-trans chaining rate of at least 65% can be observed, in particular varying between 65% and 75%.

[0079] The catalytic system according to the invention does not contain any lithium-based compound.

[0080] The R*R2Mg compounds can be manufactured in a known manner.

[0081] The Ca(AR'y)2(L)x compounds can be obtained for example in the following manner.

[0082] For the synthesis of Ca(NR'2)2(L)x, where R' denotes a substituted silyl radical, reference can be made to the synthesis method described in Krieck, S., Schüler, P., Peschel, J., & Westerhausen, M. (2018). Straightforward One-Pot Syntheses of Silylamides of Magnesium and Calcium via an In Situ Grignard Metalation Method. Synthesis, 57(05), 1115-1122. One reaction route involves the reaction at room temperature of benzylpotassium with alkaline earth metal iodide in an organic solvent such as THF, leading to the formation of alkaline earth metal dibenzyl. The benzylpotassium is first obtained by metallation of toluene in the presence of a superbase. Alkaline earth metal dibenzyl is reacted with bis(trimethylsilyl)amine (or HMDS) and produces calcium bis(trimethylsilyl)amide (Ca(HMDS)2) which is soluble in an organic solvent such as toluene.

[0083] The catalytic system according to the invention can advantageously be used in a process for synthesizing diene polymers, which process is also the subject of the present invention. Indeed, it turns out that the catalytic system described above, used in such a process, allows anionic polymerization of 1,3-diene, in particular of 1,3-butadiene, without an organolithium initiator, with a high conversion rate of up to 100% and with low molar mass dispersion, the dispersity not exceeding 1.6. Furthermore, the catalytic system according to the invention promotes the trans insertion of conjugated diene monomers, thus allowing the production of 1,3-butadiene polymers with 1,4-trans linkage rates greater than or equal to 65% and with a low 1,2- linkage rate, on the order of 10-11%.

[0084] The invention therefore also relates to a method for synthesizing a diene polymer comprising an anionic polymerization step of at least one diene monomer in the presence of a catalytic system as described above.

[0085] As a diene monomer according to the invention, a conjugated diene having 4 to 12 carbon atoms, preferably a 1,3-diene, may be mentioned in particular.

[0086] Suitable conjugated dienes include, in particular, 1,3-butadiene, isoprene, 2,3-di(alkyl in C1 to C5)-1,3-butadiene such as, for example, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, etc...

[0087] According to certain embodiments of the invention, the diene monomer is a 1,3-diene, in particular 1,3-butadiene or isoprene, preferably 1,3-butadiene.

[0088] According to certain embodiments of the invention, the polymerization step of the process is a homopolymerization step of a 1,3-diene monomer in the presence of a catalytic system as described above.

[0089] According to certain embodiments of the invention, the polymerization step of the process is a copolymerization step of at least one conjugated diene monomer, in particular 1,3-diene, in the presence of a catalytic system as described above. The diene monomer is then copolymerized with at least one other monomer.

[0090] As another suitable monomer, in particular a conjugated diene monomer having 4 to 8 carbon atoms as defined above, different from the first diene monomer.

[0091] As another suitable monomer, a vinylaromatic compound is also suitable. Examples of vinylaromatic monomers include vinylaromatic monomers having 8 to 20 carbon atoms, such as styrene, ortho-, meta-, para-methylstyrene, 2,4,6-trimethylstyrene, divinylbenzene and vinylnaphthalene, preferably the vinylaromatic monomer is styrene.

[0092] According to certain embodiments of the invention, the polymerization step of the process is a polymerization step of 1,3-butadiene in the presence of a catalytic system as described above.

[0093] According to some embodiments of the invention, the polymerization step of the process is a copolymerization step of 1,3-butadiene and styrene in the presence of a catalytic system as described above.

[0094] The polymerization step can be carried out in a known manner, continuously or discontinuously, generally and in a known manner at a temperature ranging from 15°C to 120°C.

[0095] The polymerization step can be carried out in an organic solvent conventionally used for the polymerization of diene monomers. According to the invention, an organic solvent is understood to be an inert hydrocarbon solvent which may be, for example, an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, cyclohexane, methylcyclohexane, or an aromatic hydrocarbon such as benzene, toluene, xylene, or mixtures of these solvents. It should be noted that non-aromatic solvents are particularly preferred.

[0096] The catalytic system used in the process of synthesizing a diene polymer according to the invention is as described above in all its embodiments.

[0097] In the context of the invention, the species used to control molar masses is dialkylmagnesium, which generates a propagation chain per magnesium atom. Those skilled in the art will therefore understand that the proportion of magnesium per 100 g of monomers depends on the target molar mass of the polymer. Generally, the amount of dialkylmagnesium varies within a range of values ​​from 100 pmol to 100,000 pmol.

[0098] The catalytic system according to the invention can be prepared by adding the components of the catalytic system directly to the polymerization solvent containing the monomer(s) to be polymerized (in situ preparation). The components of the catalytic system can be added simultaneously or sequentially. In the latter case, the calcium-based co-catalyst can be added first. The magnesium organic compound is then added.

[0099] Alternatively, the calcium-based co-catalyst can first be mixed with the monomers to be polymerized. The organic magnesium compound is then added to carry out the polymerization reaction.

[0100] Alternatively, the catalytic system according to the invention can be prepared by premixing the components of the catalytic system before contacting them with the solvent containing the monomer(s) to be polymerized. The components of the catalytic system are then introduced into an inert hydrocarbon solvent for a time of between 0 and 120 minutes, at a temperature ranging from 10°C to 120°C, advantageously above ambient temperature, so as to obtain a premixed catalyst. The premixed catalyst thus obtained is then contacted with the solvent containing the monomer(s) to be polymerized.

[0101] According to this latter alternative, the preparation of the catalytic system is typically carried out in a low molecular weight hydrocarbon solvent, such as, for example, cyclohexane, methylcyclohexane, n-heptane, or a A mixture of these solvents, preferably in n-heptane, or alternatively in an aromatic solvent such as toluene, is used. It should be noted that non-aromatic solvents are particularly preferred. The components of the catalytic system can be added as follows: In a first step, the calcium-based cocatalyst is added to the solvent. In a second step, the magnesium-based organic compound is added. Alternatively, the components of the catalytic system can be added as follows: In a first step, the magnesium-based organic compound is added to the solvent. In a second step, the calcium-based cocatalyst is added.

[0102] Following the polymerization step, the process for synthesizing a diene polymer according to the invention can be continued in a manner known per se. Thus, in certain embodiments, the polymerization can be stopped, possibly after a post-polymerization modification step of the diene polymer.

[0103] The process then proceeds in a manner known per se by separating and recovering the prepared diene polymer. Unreacted monomers and / or the solvent can be removed using methods known to those skilled in the art.

[0104] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the present invention, given by way of illustration and not limitation. Examples Measurements and tests used

[0105] Determination of the microstructure of polymers:

[0106] The microstructure of the elastomers is characterized by NMR. Liquid-state ¹H NMR (400.2 MHz) and ¹³C NMR (inverted-gate decoupling, 100.6 MHz, OD = 10 s, 4096 scans) spectra were recorded at 298 K on a Bruker Avance 400 spectrometer in CDC13. Nuclear Overhauser effect (NOE) suppression allows quantification of the microstructure using the following integrations: 43.5 ppm or 34 ppm for 1,2 units (Ii>2), 32.8 ppm for 1,4-trans units (Ii,4trans), and 27.5 ppm for 1,4-cis units (Ii>4cis). The 1,4-trans and 1,2 unit levels are determined as follows: It 2 11 11 1.4trans(%) = ;---------- ------xl 00 1.2(%) =------:— —— xlOO G1.4trans + ïl.4cis) / + C2 (li,4trans ll,4cis) ' 2 * Ij 2

[0107] The rate of 1,4-cis units follows from this.

[0108] Determination of the macrostructure of polymers:

[0109] The SEC (“Size Exclusion Chromatography”) technique allows the separation of the macromolecules in solution, separated by size, pass through columns filled with a gel porous. Macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0110] While not an absolute method, SEC allows for the determination of the molar mass distribution of a polymer. From commercial standard products, the various number-average (Mn) and weight-average (Mw) molar masses can be determined, and the polydispersity index (D = Mw / Mn), also called "dispersity," can be calculated.

[0111] No special treatment of the polymer sample prior to analysis is required. It is simply solubilized in a tetrahydrofuran solution. The elution solvent is tetrahydrofuran. The apparatus used is an Ultimate 3000 system equipped with a Wyatt Technology dRI differential refractive index detector. The polymers were separated on three TOSOH HXL G2000, G3000, and G4000 gel columns (300 x 7.8 mm) (exclusion limits from 1,000 Da to 400,000 Da) at a flow rate of 1 mL / min. The column temperature was maintained at 40°C. The molar masses of polybutadiene were determined using polystyrene standards and applying a correction factor of 0.6 determined separately.

[0112] The flow rate is 0.7 ml / min, the system temperature is 35°C, and the analysis time is 90 min. A set of four WATERS columns in series is used, with the trade names "STYRAGEL HMW7", "STYRAGEL HMW6E", and two "STYRAGEL HT6E". The injected volume of the polymer sample solution is 100 µl. The detector is a "WATERS 2410" differential refractometer, and the chromatographic data processing software is the "WATERS EMPOWER" system. The calculated average molar masses are relative to a calibration curve prepared using commercially available "PSS READY CAL-KIT" polystyrene standards. Conversion#:

[0113] The conversion of the polymerization is determined by proton NMR analysis (400 MHz, 25°C, CDC13) by comparing the integrations of the monomer (Im = CHbut = 6.25–6.45 ppm) and the polymer (Ip = CHI>2 + CHi^trans + CHlt4_cis = 5.3–5.7 ppm). Denoting a as the rate of 1.4 and b as the rate of 1.2, the conversion is then expressed as follows: Conversion(%) = 1 / (2a+b) -------------xlOO (Ini / 2 + Ip / (2a+b))

[0114] Synthesis of bis(trimethylsilyl calcium amide)

[0115] The synthesis of the calcium amine salt was carried out according to a procedure described in AM Johns, SC Chmely, and TP Hanusa, “Solution Interaction of Potassium and Calcium Bis(trimethylsilyl)amides; Preparation of Ca[N(SiMe3)2]2 from Dibenzylcalcium,” Inorg. Chem., vol. 48, no. 4, pp. 1380-1384, 2009.

[0116] Metallic calcium (1 g, 25 mmol, eq) is dispersed in dry THF under an inert atmosphere (25 mL). The following are added to this dispersion under an inert atmosphere: hexamethyldisilazane 'HMDS' is added all at once (5.2 mL, 25 mmol, eq), followed by bromoethane in three additions (3 x 1 mL, 3 x 3.5 mmol, 3 x 0.54 eq = 1.6 eq) with a 1h30 interval between additions. The reaction is allowed to proceed until the metallic calcium has completely reacted. Once the calcium has been completely consumed, the reaction mixture is dried under vacuum at 30°C. The crude product is extracted with 25 mL of dry pentane all at once and then filtered under an inert atmosphere to separate it from insoluble compounds such as calcium dibromide. The filtrate is collected and dried under vacuum at 30°C. The white solid obtained is the calcium complex [(THF)2Ca{N(SiMe3)2}2].

[0117] *H NMR (400 MHz, C6D6, 25 °C): ô 3.54 ppm (t, 8H, THF), ô 1.21 ppm (t, 8H, THF), ô 0.37 ppm (s, 36H, N(SiMe3)2). 13C NMR (400 MHz, C6D6, 25 °C): δ 69.7, 24.9 (THF), 5.87 ppm (N(SiMe3)2).

[0118] Butadiene polymerizations using the catalytic system comprising sec-dibutyl magnesium and bis(trimethylsilyl methylamide) calcium

[0119] Anionic polymerization under argon in a high-pressure glass reactor equipped with a magnetic stirrer and fitted with PTFE shut-off valves pre-dried with a flame under vacuum was carried out as follows:

[0120] [Ca(HMDS)2(THF)2] was weighed and then added under argon flow to a schlenk previously flame-dried under vacuum. Cyclohexane was introduced under vacuum through connected glass tubes, followed by s-Bu2Mg in a hexane solution via a syringe under argon flow. Finally, butadiene (22.8 mmol; 1.23 g) was introduced under vacuum through connected glass tubes to initiate polymerization. After a reaction time indicated in the table, degassed methanol was added to stop the reaction, and any remaining butadiene and cyclohexane were removed under vacuum.

[0121] As an example for [Ca] / [Mg] = 0.75 with a target Mn of 9800 g / mol, 53 mg of [(THF)2Ca(HMDS)2] (105 pmol) were introduced into the glass reactor followed by 9 mL of cyclohexane. 200 pL of s-Bu2Mg (140 pmol) solution in hexane (0.7 M) were then added via syringe under argon flow followed by 2 mL of liquid butadiene (22.8 mmol; 1.23 g) to carry out the polymerization, and then heated to 60°C. The calcium / magnesium complex with a ratio of [Ca] / [Mg] = 0.75 in a cyclohexane solution (5-10 mL) was analyzed by ¹H and ¹³C NMR in deuterated benzene. A sample of the complex solution was first dried in a Young's tube under vacuum to eliminate all volatile compounds before adding the deuterated solvent under vacuum.

[0122] The conversions were determined by 'H NMR (integration of butadiene relative to polybutadiene) with a sample taken during polymerization.

[0123] [Tables 1] [Mg] time T (°C) Conv. (%) Âfn,th(gm or1) A?n,exp(g*Ïil ol1) D 1.2 (%) 1.4-trans (%) 1.4-cis (%) 0.5 24h 40 68 6 600 4 600 1.1 11 75 14 24h 60 99 9 700 5 700 1.2 10 73 17 0.75 24h 40 78 7,600 5,200 1.1 10 75 15 24h 60 100 9,800 7,000 1.1 10 74 16 1 24h 40 80 7,800 6,900 1.1 11 75 14 24h 60 98 9 600 7 300 1.2 10 73 17 1.25 24h 40 80 7 800 7 300 1.1 11 75 14 24h 60 99 9 700 8 300 1.1 10 73 17 1.5 24h 40 84 8 200 8 000 1.2 10 74 16 24h 60 99 9 700 9 200 1.2 10 73 17 0.75 * 4d 60 100 8 800 8 100 1.1 10 74 16 4d 60 100 26,000 23 300 1.2 8 75 17 6d 60 97 105 000 103 400 1.4 7 68 25

[0124] * In a closed reactor, without taking any sample during polymerization.

[0125] Mn>th represents the theoretical Mn targeted knowing that there is a propagation chain per atom of Mg. Mn represents the experimental Mn measured according to the method described above.

[0126] It is observed that the use of catalytic systems according to the invention based on s-butylmagnesium / bis(trimethylsilyl)calcium amide produces polybutadiene with a very high conversion rate. The polybutadiene produced exhibits low dispersibility, varying in the range of 1.0 to 1.2, and a 1,4-trans chaining content of more than 70% by weight, with a 1,2-chaining content not exceeding 11% by weight.

Claims

Demands

1. A catalytic system consisting of the following metallic components: (1) an organic calcium compound of formula Ca(AR'y)2(L)x, in which - A denotes a nitrogen atom N or an oxygen atom O, - y is 2 when A is N and y is 1 when A is O, - each R' represents, independently of each other, a Ci-Cæ aliphatic radical, substituted or unsubstituted, a C6-C2O aromatic radical, substituted or unsubstituted, a silyl radical, substituted or unsubstituted, a Ci-CiO aliphatic radical substituted by at least one silyl radical, substituted or unsubstituted, a C6-C2O aromatic radical substituted by at least one silyl radical, substituted or unsubstituted, - L represents a ligand, - x is a number from 0 to 4, (2) an organic magnesium compound of formula R*R2Mg, in which each of R1 and Represents, independently of each other, an aliphatic radical in C1-C10, substituted or not, or an aromatic radical in C6-C20, substituted or not.

2. Catalytic system according to claim 1 characterized in that A represents a nitrogen atom and y is equal to 2.

3. Catalytic system according to claim 1 or 2 characterized in that the silyl radical in the definition of R' is a silyl radical substituted by at least one alkyl radical in Ci-C5, cycloalkyls in C3-C6, aryls in C6-Ci0 or aralkyls in C7-Ci2.

4. Catalytic system according to any one of the preceding claims characterized in that R' is a silyl radical substituted by three Ci-C5 alkyl radicals, preferably R' is trimethylsilyl, triethylsilyl or tripropylsilyl.

5. Catalytic system according to any one of the preceding claims characterized in that the ligand L is selected from ethers, preferably 1,2-dimethoxyethane or tetrahydrofuran (THF), and amines, preferably tetramethylethylenediamine (TMEDA).

6. Catalytic system according to any one of the preceding claims characterized in that the ligand L is tetrahydrofuran and x is 2.

7. Catalytic system according to any one of the preceding claims characterized in that the organic calcium compound is Ca(N(SiMe3)2)2(THF)2.

8. Catalytic system according to any one of the preceding claims, wherein the aliphatic radical, in the definition of RiR2Mg, is a Ci-Cio alkyl radical, substituted or unsubstituted, preferably a CrC8 alkyl radical, substituted or unsubstituted.

9. Catalytic system according to any one of the preceding claims, characterized in that the organic magnesium compound of formula R*R2Mg is n-dibutylmagnesium, s-dibutylmagnesium or butylmagnesium.

10. Catalytic system according to any one of the preceding claims characterized in that the molar ratio of Ca(AR'y)2 (L)x to R*R2Mg (or of Ca to Mg) is at least 0.

2.

11. Catalytic system according to any one of the preceding claims characterized in that the molar ratio of Ca(AR'y)2 (L)x to R'R2Mg (or of Ca to R'R2Mg) is at most 2.

0.

12. Catalytic system according to any one of the preceding claims characterized in that the molar ratio of Ca(AR'y)2 (L)x to R'R2Mg (or of Ca to Mg) varies in a range from 0.2 to 2.0, preferably from 0.5 to 1.

5.

13. A method for synthesizing a diene polymer comprising an anionic polymerization step of at least one diene monomer in the presence of a catalytic system as defined in any one of the preceding claims.

14. A process according to the preceding claim characterized in that the diene monomer is butadiene or isoprene.

15. A process according to claim 13 or 14 characterized in that the diene monomer is copolymerized with at least one other monomer selected from vinylaromatic compounds, preferably styrene.