Catalytic systems made of a complex of rare earths for stereospecific polymerisation of conjugated dienes

[0001] The invention relates to a multi-component catalyst system, usable for stereospecific polymerization of 1,4-cis conjugated dienes. More specifically, the invention relates to a catalytic system containing a rare earth complex, as well as a method for preparing said catalyst system and the use of this catalyst system for obtaining diene elastomers with a high content of cis-1,4 conjugate system.

[0002] Boisson et al. Macromol. Chem. Phys. 1999 200 1163-1166 and Monteil et al. Polymer Int. 2004 53 576-581 describe the use of multi-component catalyst systems for the polymerization of butadiene, containing:

tris (amide) neodymium salt of formula Nd [N (TMS) 2] 3, or tris [N, Nbis (trimethylsilyl) amide] of neodymium, aluminum aluminum with formula Al (i-Bu)₃, aluminum alkyl halide, of formula AlEt₂Cl.

[0003] These catalysts are obtained in situ and used for the polymerization of butadiene and for the copolymerization of butadiene and styrene. The molar mass distribution of synthesized polybutadienes is large and multimodal, which translates into poor polymerization control. In addition, such molar mass distribution can be disadvantageous for some applications of diene elastomers obtained, such as especially for motor vehicle tires.

With the same in mind, patent application WO2003033545 describes multi-component catalyst systems for the polymerization of conjugated dienes, some of which are based on the tris (amide) neodymium salt, for example with the formula Nd [N (TMS) 2] 3, and cocatalyst. In embodiments of the invention, the active substance formed by the reaction of the neodymium salt and cocatalyst is of the cationic type because the cocatalyst systematically contains aluminoxane (modified methylaluminoxane MMAO or isobutylaluminoxane - IBAO). Optionally, an aluminum alkyl halide or boride (B (C6F5) 3) is added to the catalyst system shown.

[0005] US 3,297,667 also describes multi-component catalyst systems based on (i) a rare earth compound, (ii) a two-boron organic ligand (iii) (iv) alkylaluminium halide.

[0006] The catalytic system is obtained by reacting (i) with (ii) which results in the formation of one type of isolated chelated rare earth metal. It is then placed in the presence of halide and aluminum alkyl. Based on the compound (i), the method of preparing the catalyst systems of this document mainly gives cerium chloride. However, rare earth chlorides may have insufficient reactivity for some organic (ii) ligands present in the reaction medium due to the poor solubility of the chloride in such medium.

[0007] In addition, US Patent No. 7,300,903 B2 describes an olefin polymerization process resulting in a catalytic system based on:

an isolated compound, based on a transition metal, corresponding to formula (I) below, for which a complete definition is referred to in the patent text,

<img file="PL2424902T3_D0001.tif" />

wherein M is a metal belonging to groups 3 to 11 of the periodic table of the elements, at least one compound selected from:

an organometallic compound, an organoaluminium compound containing an oxygen atom, and a compound capable of reacting with a transition metal-based compound to form an ion pair.

[0008] According to this patent, in formula I, preferably the M metal described in the examples mainly belongs to group 4. This applies to titanium, zirconium or optionally hafnium. All examples of this patent document regarding ethylene-butadiene copolymerization tests were carried out based on titanium or zirconium based catalyst systems. Depending on the experimental conditions and the nature of the catalytic system, these tests allow in particular to obtain copolymers in which the butadiene contents are very low and reach a maximum of 6.6% mol (examples 150 to 157). Although no homopolymerization test for butadiene has been described, the low performance of the catalyst systems of this patent document for the insertion of this monomer suggests that these systems are not suitable for stereospecific polymerization of 1,4-cis butadiene.

[0009] When using motor vehicles for tires, and more specifically in tread, it is important to have diene elastomers with a certain microstructure, mainly polybutadiene having an increased content of the cis-1,4 conjugate system. In addition, the controlled molar mass distribution in a narrow range allows the best adaptation of the elastomer macrostructural properties depending on the desired properties when used in tread. In addition, there is a continuing need for catalytic systems and polymerization methods that allow obtaining, in a reproducible manner, diene elastomers with specific microstructure and macrostructure characteristics, and mainly diene elastomers with an increased content of the cis-1,4 conjugate system and controlled molar mass distribution.

During the research, the inventors discovered a new multi-component catalyst system having sufficient catalytic activity for stereospecific polymerization of conjugated dienes, enabling the preparation of diene elastomers such as polybutadiene or polyisoprene, having an increased content of the cis-1,4 conjugate system, significantly higher than 90%. This new catalytic system is based on a combination of at least three components, namely a rare earth complex, an alkylating agent and an aromatic ring based compound having at least two heteroatoms. This catalytic system also provides the advantage of controlling or significantly reducing the polydispersity index compared to a system containing only a rare earth complex and an alkylating agent. Polydispersity index (Mw / Mn) - Mw means average molar mass by weight, and Mn average molar mass by number - you can control or reduce, depending on the nature of the reagents used and the experimental conditions implemented.

[0011] Consequently, the first object of the invention is a catalyst system based on at least:

(i) the rare earth complex Ln (A) 3 (B) no formula (II) in which Ln is a rare earth metal from the lanthanide family, or yttrium or scandium, A is a ligand selected from the amide family, the family of alcoholates, the family alkyl, aryl or benzyl, borohydride family, and organophosphate family, B is a Lewis base and in is a number from 0 to 3, B in depends on the type of Ln and A used in the corresponding rare earth complex, (ii) an alkylating agent, (iii) a compound based on an aromatic ring and having at least two heteroatoms selected from the elements O, N, S, P, and the corresponding formula (III):

<img file="PL2424902T3_D0002.tif" />

wherein

- R groups are identical or different from each other and each means:

- hydrogen atom,

- an aliphatic, cycloaliphatic or aromatic alkyl radical containing optionally one or more heteroatoms (N, O, P, S, Si) or one or more halogen atoms,

- halogen atom,

- a group based on one or more heteroatoms (N, O, P, S, Si);

- x and y are integers between 0 and 6;

- D is a group having a chemical function in which one of the atoms has a non-binding doublet;

- L is the atom from column 1 of the periodic table;

the aromatic ring substituents are arranged, without distinction, in ortho, meta or para position relative to each other, (iv) optionally, a halogen donor, and (v) optionally, a conjugated preforming die (fr .: preformation).

[0012] Of course, by the expression "based" used to define components of the catalyst system, is meant a mixture of these components and / or the reaction product of these components.

[0013] Another object of the invention is a method for preparing a multi-component catalyst system as defined above.

The invention also relates to a method for preparing a diene elastomer, such as polybutadiene or polyisoprene, with a high content of the cis-1,4 conjugate system and a controlled molar mass distribution, with a significantly reduced polydispersity index.

[0015] Furthermore, one of the constituent elements of the multi-component catalyst system according to the invention is the rare earth complex of formula (II) Ln (A) 3 (B) n, wherein Ln, A, B and n are as described above.

[0016] Ln is a rare earth metal from the lanthanide or yttrium or scandium family. More specifically, Ln is selected from elements like yttrium, neodymium, gadolinium or samarium. Preferably, Ln is yttrium or gadolinium. Even more preferably, Ln is yttrium.

[0017] In definition B, Lewis base means mainly ethers, amines, phosphates and thioethers. For example, as the amine, the family of trialkylamines and aromatic amines such as pyridine or piperazine and its derivatives can be cited. As the phosphate, for example, tri-n-butyl phosphate can be cited. As a thioether, a family of dialkyl sulfides such as dimethyl sulfide can be cited. As the ether, for example, diethyl ether, 1,2-diethoxyethane, 1,2-di-n-propoxyethane, 1,2-di-n-butoxyethane, tetrahydrofuran, dioxane, tetrahydropyran can be cited. More specifically, B is an ether, preferably tetrahydrofuran (THF).

[0018] A is a ligand which can be selected from various types of ligands cited above.

[0019] When A is selected from the amide family, they mainly include dialkylamides, N, N-bis (dialkylsilyl) amides and N, N-bis (trialkylsilyl) amides, alkyl groups having 1 to 10 carbon atoms.

[0020] When A is selected from dialkylamides, B is preferably THF and n is preferably 1. A is then preferably diisopropylamide and dimethylamide. When A is selected from N, N-bis (trialkylsilyl) amides, n is preferably equal to 0. A is then preferably N, N-bis (trimethylsilyl) amide of formula -N [Si (CH3) 3] 2. When A is selected from N, N-bis (dialkylsilyl) amides, B is preferably THF and n is preferably equal to 2 or 3. A is then preferably N, N-bis (dimethylsilyl) amide of formula N [SiH (CH3) 2] 2.

[0021] When A is selected from the borohydride family, A is preferably tetrahydroboride, B is preferably THF and n is preferably equal to 2 or 3.

[0022] When A is selected from the alkoxide family, they include alcohol or polyol alkoxides derived from aliphatic or cyclic hydrocarbons, mainly aliphatic, linear or branched hydrocarbons having 1 to 10 linear chain carbon atoms, more preferably 4 to 8 carbon atoms. Mention may be made, for example, of neo-pentoxide.

[0023] When A is selected from the alkyl family, they include a (trialkylsilyl) alkyl family. Within this family, A is preferably (trimethylsilyl) methyl with the formula -CH2-Si (CH3) 3 or bis (trimethylsilyl) methyl with the formula -CH- [Si (CH3) 3] 2; When A is selected from the aryl or benzyl family, the aromatic ring is preferably substituted with only 5 hydrogen atoms or with 4 hydrogen atoms and one substituent having a tertiary amine function or ether function. More preferably, the group A is dimethylaminobenzyl of the formula -CH2C6H4 [N (CH3) 2].

[0024] When A is selected from the organophosphate family, they include organophosphates of phosphoric acid diesters of the general formula (R'O) (R "O) PO (OH), in which R 'and R", identical or different, represent an alkyl radical , aryl or alkylaryl. Of these identical or different phosphoric acid diesters, identical or different, are nbutyl, isobutyl, pentyl, amyl, isopentyl, 2,2-dimethylhexyl, 1-ethylhexyl, 2-ethylhexyl, tolyl radical; among the organophosphate family, A is most preferably bis (2-ethylhexyl) phosphate. Preferably, according to the invention in formula (II) of the rare earth complex, ligand A is selected from the amide family.

[0025] It should be remembered that according to the invention, according to which ligand A is an amide, Ln is preferably yttrium or gadolinium in formula (II). Even more preferably, according to the invention, the rare earth complex of formula (II) is tris [N, Nbis (trimethylsilyl) amide] yttrium or tris [N, N-bis (trimethylsilyl) amide] gadolinium, and most preferably tris [N, N- bis (trimethylsilyl) amide] yttrium.

[0026] According to the invention, the rare earth complex may be a rare earth mixture complex or else a mixture of several complexes of one or more rare earth elements.

[0027] Another component of the multi-component catalyst system according to the invention is the alkylating agent. As alkylating agents that can be used, there may be mentioned aluminum aluminum compounds, among which the use of a compound selected from:

- trialkylaluminum, an alkyl radical having C1-C10, for example triisobutylaluminum or trioctyluminum;

- dialkylaluminum hydrides, an alkyl radical having C1-C10, for example diisobutylaluminum hydride.

[0028] It should be remembered that this alkylating agent is preferably formed from triisobutylaluminum or diisobutylaluminum hydride, more preferably from triisobutylaluminum.

[0029] Another component of the multi-component catalyst system according to the invention is a compound based on an aromatic ring and having at least two heteroatoms selected from the elements O, N, S, P, corresponding to formula (III):

<img file="PL2424902T3_D0003.tif" />

in which

- R are identical or different from each other and each of them can mean:

- hydrogen atom,

- a C 1 -C 20 aliphatic alkyl, C 5 -C 20 cycloaliphatic or C 6 C 20 aromatic radical, optionally containing one or more heteroatoms (N, O, P, S, Si), preferably nitrogen or oxygen, or one or more halogen atoms, preferably chlorine .

- a halogen atom, preferably selected from chlorine or bromine,

- a group based on one or more heteroatoms (N, O, P, S, Si), preferably selected from the function of alkoxy, a secondary amine or a tertiary amine.

- x and y, identical or different, represent integers between 0 and 6, preferably x is between 0 and 3 and y is between 0 and 3, more preferably x = y = 0;

- D is a group having a chemical function in which one of the atoms has a non-binding doublet, such as the functions of alcohol, amine, ether, imine, phosphine, thioether, thiol;

- L is an atom from column 1 of the periodic table, such as hydrogen, lithium, sodium or potassium, preferably hydrogen;

[0030] The (CH2) x -D and (CH2) yOL substituents of the aromatic ring are preferably in ortho or meta position with respect to each other, even more preferably in ortho position.

Preferably according to the invention in formula (III) D is an imine group. The compound of formula (III) is therefore more preferably selected from those represented by formula (IV):

<img file="PL2424902T3_D0004.tif" />

wherein R, L, x and y are as defined above and R¹ and R², identical or different, each represent a hydrogen atom or a C1-C20 aliphatic alkyl radical. cycloaliphatic C5-C20 or aromatic C6-C20, [0032] Even more preferably, of these compounds x = y = 0 and L is hydrogen and the compound of formula (III) is selected from the phenoxyimine family.

[0033] In the phenoxyimin family, those in which the hydroxyl substituent and the imino substituent are present in an ortho position with respect to each other are preferred. These preferred compounds can be represented by formula (V):

<img file="PL2424902T3_D0005.tif" />

[0034] R¹ and R² are as defined above and R³ to R.⁶ have the same definition as

R above.

[0035] Among the compounds of formula V, more specifically cited are those for which R1 is a C6-C20 aromatic radical, substituted or not. Examples of these compounds are N-phenyl-3,5-di-tert-butylsalicylaldimine represented by formula (VI).

<img file="PL2424902T3_D0006.tif" />

and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine of formula (VII):

<img file="PL2424902T3_D0007.tif" />

[0036] According to another embodiment of the invention, the multi-component catalyst system may comprise an optional component which is a halogen donor agent. Of these agents, alkylaluminium halides, such as, for example, diethylaluminum chloride, diethylaluminium bromide, ethylaluminium dichloride or ethylaluminium chloride, may be cited. Diethylaluminium chloride is more preferred.

[0037] According to a further embodiment of the invention, the catalyst system according to the invention may also comprise a coupled preforming diene. As conjugated diene for preforming, suitable for forming the catalytic system of the invention, 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-di (C1 to C5 alcohol) ) -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, or any other conjugated dienes having 4 to 8 carbon atoms, with 1,3-butadiene as preferred for use.

[0038] Another embodiment of the invention consists of a combination of these two embodiments.

[0039] Preferably, in the catalyst system of the invention, the molar ratio (aromatic / rare earth based metal) may be between 0 and 3 (exclusion limits), more preferably 0.5 to 2 (limits included).

[0040] Even more preferably, in the catalyst system of the invention, the molar ratio (alkylating agent / rare earth metal) may be from 2 to 40 (limits included), even more preferably 2 to 10.

[0041] Also preferably, the catalyst system according to the invention comprises a halogen donor with a molar ratio (halogen donor / rare earth metal) that can have a value of 1 to 3, more preferably 2.5 to 3.

[0042] Also preferably, the catalyst system of the invention comprises a conjugated die preform, with a molar ratio (conjugated die preform / rare earth metal) that can have a value of 10 to 70, more preferably 20 to 60.

[0043] Another object of the invention is to obtain the catalyst system described above.

[0044] According to the first mode of preparation of the catalyst system of the invention, the components of the catalyst system are added directly to the polymerization solvent containing the monomer (s) to be polymerized to obtain a catalyst formed in situ.

[0045] According to a second mode of preparation of the catalyst system according to the invention, the components of the catalyst system are premixed before contacting them with a solvent containing the monomer (s) to be polymerized, by introducing components of the catalyst system into an inert hydrocarbon solvent, for a time between 0 and 120 minutes at a temperature between 10 ° C and 80 ° C, optionally higher than the ambient temperature, generally from 18 ° C to 60 ° C, to obtain a pre-mixed catalyst. The pre-mixed catalyst thus obtained is then contacted with a solvent containing the monomer (s) to be polymerized.

[0046] According to the third mode of preparation of the catalyst system of the invention, after initiating contact of the catalyst system components in an inert hydrocarbon solvent, a small amount of conjugated diene is added to the preforming to obtain the preformed catalyst. The preforming reaction is carried out for a time comprised between 0 and 120 minutes at a temperature between 10 ° C and 80 ° C, optionally higher than the ambient temperature, generally between 18 ° C and 30 ° C. The preformed catalyst thus obtained is then contacted with a solvent containing the monomer or monomers to be polymerized.

[0047] To this end, it should be noted that the components of the catalyst system are preferably mixed prior to contact with a solvent containing the monomer or monomers to be polymerized, i.e. prior to the polymerization reaction. The ingredients, according to the order of addition and their nature, may react with each other or not.

[0048] The preparation of the catalyst system according to the invention is carried out in a low molecular weight aliphatic or alicyclic solvent, such as, for example, cyclohexane, methylcyclohexane, n-heptane, or a mixture of such solvents, preferably in n-heptane, or else in an aromatic solvent such like toluene. It should be remembered that non-aromatic solvents are particularly preferred.

[0049] According to the first order of adding the components of the catalyst system of the invention, they are added as follows: in a first step, the alkylating agent is added to the solvent; in the second stage, the rare earth complex of formula (II) is then added; then, in the third stage, the halogen donor agent is added where appropriate; and in a fourth step the compound of formula (III) and the conjugated diene for preforming are added.

[0050] According to a second order of addition, the components of the catalyst system of the invention are added as follows: in a first step, the rare earth complex of formula (II) is added to the solvent; in the second step a compound of formula (III) is added; then, in the third stage, the alkylating agent and, where appropriate, in the subsequent stages, the conjugated diene for preforming, and finally the halogen donor agent.

[0051] Another object of the invention is a method for preparing diene elastomers with a high content of cis-1,4 conjugate system and controlled molar mass distribution, with a significantly reduced polydispersity index (Mw / Mn).

[0052] This method of the invention involves reacting the catalyst system described above with the monomer (s) having to polymerize to obtain a diene elastomer that can be entirely a homopolymer, or a copolymer, obtained by homopolymerization or copolymerization of at least one conjugated monomer diene having 4 to 12 carbon atoms, optionally with a vinylaromatic compound.

As conjugated diene monomer, 1,3-butadiene, isoprene, 2,3-di (C1 to C5 alkyl) -1,3-butadiene, such as, for example, 2,3-dimethyl-1,3 are suitable -butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, aryl-1,3-butadiene, 1 , 3-pentadiene, 2,4-hexadiene.

[0054] Suitable vinylaromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, commercial mixture of "vinyl-toluene", para-tert-butylstyrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene, vinylnaphthalene.

[0055] The polymerization is preferably carried out in the presence of an inert hydrocarbon solvent, which may be, for example, an aliphatic or alicyclic hydrocarbon such as pentane, hexane, heptane, isooctane, isobutane, cyclohexane, methylcyclohexane or an aromatic hydrocarbon such as benzene, toluene, xylene.

[0056] Polymerization can be carried out continuously or discontinuously. In general, the polymerizations are carried out at a temperature comprised between 20 ° C and 150 ° C, and preferably close to 30 ° C to 110 ° C.

Preferably, and compared to a method for preparing a non-aromatic catalyst system having at least two heteroatoms of formula (III), the method of the invention allows obtaining, with improved catalytic activity, a diene elastomer having an increased content of the cis-1 conjugate system , 4 and controlled molar mass distribution, with a significantly reduced polydispersity index, as shown in the examples below. This elastomer may consist of, for example, polyisoprene (IR) or polybutadiene (BR).

[0058] The above-mentioned features of the invention, as well as others, will be better understood upon reading the following description of several embodiments of the invention, presented as illustrations.

Examples of organic and organometallic syntheses [0059] All organometallic syntheses were carried out under an inert argon atmosphere, using Schlenk techniques or a glove box. All solvents used during these syntheses were anhydrous and stored in an inert atmosphere. Pentane and THF were distilled freshly on sodium / benzophenone. All reagents were from Sigma-Aldrich, Strem and Fluka.

Synthesis of rare earth tris [N, N-bis (trimethylsilyl) amide] complexes [0060] The rare earth tris [N, N-bis (trimethylsilyl) amide] complexes were synthesized according to the method described by Bradley et al. (Bradley, DC, Ghotra, JS, and Hart, FA, J. Chem. Soc., Dalton Trans. 1973, 1021). and modified by Boisson et al. (Boisson, C., Barbotin, F., and Spitz, R., Macromol. Chem. Phys. 1999, 200, 1163). Synthesis of N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine. [0061]

<img file="PL2424902T3_D0008.tif" />

[0062] N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine was synthesized according to the procedure described by Cameron et al. (Cameron, PA, Gibson, VC, Redshaw, C., Segal, JA, Solan, GA, White, AJP, and Williams, DJJ, Chemical Society,

Dalton Transactions 2001, 1472).

Examples of polymerization [0063] All preparations of the catalytic systems were obtained under an inert atmosphere of argon, using Schlenk techniques or a glove box. All solvents used during these reactions were anhydrous and stored under an inert atmosphere. Toluene and heptane were dried twice on a molecular sieve. All reagents were from Sigma-Aldrich, Strem and Fluka. Triisobutylaluminum, diethylaluminum chloride and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine solutions were prepared in heptane based on pure reagents in concentrations of 0.740, 0.027 and 0.100 mol.^-1.

[0064] The molar masses of THF soluble polymers were determined by THF size exclusion chromatography. Samples were injected with a Waters 717 injector on a series of columns placed in a 45 ° C thermostatic chamber. Detection was carried out using a Waters 410 refractometer, and the molar masses of polybutadienes were expressed in polystyrene equivalents (using certified polystyrene standards Polymer Laboratories). The microstructure was determined using an FT-IR spectrometer Nicolet 460 FT-IR (measured at ambient temperature, on 32 scans from 500 to 3800 cm^-1) according to the method described by Morero et al. (Morero, D., Santambrogio, A., Porri, L., and Ciampelli, F., Chim. Ind. (Milano) 1959, 41).

[0065] Polymerizations were carried out in a 250 ml disposable glass vat (Schott flacon) reactor equipped with a stainless steel mixing blade. Temperature control was ensured by a constant-temperature water bath connected to a double polycarbonate jacket. This reactor had all the necessary inputs and outputs for traditional operations: (i) conditioning the reactor at 80 ° C by means of argon vacuum cycles, (ii) introducing solutions with a cannula under an argon atmosphere, and (iii) supplying gas monomers.

Comparative Example 1 [0066] Solution consisting of (in the order of addition) 150 ml heptane, triisobutylaluminum (1.9 ml - 1.4 mmol), tris [N, N-bis (trimethylsilyl) amide] gadolinium (19.2 mg - 0.03 mmol) and diethylaluminum chloride (2.2 ml - 0.06 mmol) was prepared at 23 ° C and stirred for 5 minutes. This solution was then injected under an argon atmosphere into a 250 ml glass reactor. Then the reactor was degassed and butadiene (10 ml - 115 mmol) was introduced. The reactor was heated to 70 ° C and then the solution was stirred for 30 minutes. The reaction was stopped by degassing the reactor followed by cooling. The polymer was obtained by precipitation in a solution of ethanol (200 ml) and 2,6-di-tert-butyl-4-methylphenol (5 mg). The polymer (2.5 g) was isolated after drying.

Example 2 A solution consisting of (in the order of addition) 150 ml heptane, triisobutylaluminum (1.9 ml - 1.4 mmol), tris [N, N-bis (trimethylsilyl) amide] gadolinium (19.2 mg - 0.03 mmol) diethylaluminium chloride (2.2 ml - 0.06 mmol) and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine (0.3 ml - 0.03 mmol) was prepared at 23 ° C and stirred for 5 minutes. This solution was then injected under an argon atmosphere into a 250 ml glass reactor. The reactor was then degassed and butadiene (10 mL 115 mmol) charged. The reactor was heated to 70 ° C and then the solution was stirred for 30 minutes. The reaction was stopped by degassing the reactor followed by cooling. The polymer was obtained by precipitation in a solution of ethanol (200 ml) and 2,6-di-tert-butyl-4-methylphenol (5 mg). The polymer (3.5 g) was isolated after drying.

Comparative Example 3 [0068] A solution consisting of (in the order of addition) 150 ml heptane, triisobutylaluminum (3.2 ml - 2.40 mmol), tris [N, N-bis (trimethylsilyl) amide] yttrium (34.2 mg - 0.06 mmol) and diethylaluminum chloride (4.4 ml - 0.12 mmol) was prepared at 23 ° C and stirred for 5 minutes. This solution was then injected under an argon atmosphere into a 250 ml glass reactor. The reactor was then degassed and butadiene (10 mL 115 mmol) charged. The reactor was heated to 70 ° C and then the solution was stirred for 240 minutes. The reaction was stopped by degassing the reactor followed by cooling. The polymer is obtained by precipitation in a solution of ethanol (200 ml) and 2,6-di-tert-butyl-4-methylphenol (5 mg). The polymer (2.5 g) was isolated after drying.

Example 4 [0069] A solution consisting of (in order of addition) 150 ml heptane, triisobutylaluminum (3.2 ml - 2.40 mmol), tris [N, N-bis (trimethylsilyl) amide] yttrium (34.2 mg - 0.06 mmol) diethylaluminium chloride (4.4 ml - 0.12 mmol) and N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine (0.6 ml - 0.06 mmol) was prepared at 23 ° C and stirred for 5 minutes. This solution was then injected under an argon atmosphere into a 250 ml glass reactor. The reactor was then degassed and butadiene (10 mL 115 mmol) charged. The reactor was heated to 70 ° C and then the solution was stirred for 60 minutes. The reaction was stopped by degassing the reactor followed by cooling. The polymer is obtained by precipitation in a solution of ethanol (200 ml) and 2,6-di-tert-butyl-4-methylphenol (5 mg). The polymer (3.3 g) was isolated after drying.

Summary table of results

<td>Example</td><td>Ln (concentration in mmol. L^-1)</td><td>Conversion in% (time in minutes)</td><td>Activity in g.mol^-1.godz.^-1</td><td>Me in g.mol^-1</td><td>IP</td>

<td> 1</td><td>Gd (0.2)</td><td> 37 (30)</td><td> 43</td><td> 192000</td><td> 4,0</td>

<td> 2</td><td>Gd (0.2)</td><td> 56 (30)</td><td> 65</td><td> 185000*</td><td> 2,8*</td>

<td> 3</td><td>Y (0.4)</td><td> 39 (240)</td><td> 3</td><td> 80000</td><td> 12,1</td>

<td> 4</td><td>Y (0.4)</td><td> 53 (60)</td><td> 15</td><td> 117000</td><td> 4,9</td>

<td>* Distribution</td><td colspan="3">molar masses is bimodal; shows</td><td>data from the main page</td><td>parts (64%</td>

air); the second part (36% air) with an Mn of 11000 g.mol-1 and an IP of 1.74.

Summary table of microstructure Example Microstructure (%)

1,4-cis 1,4-trans 1,2

<td> 1</td><td> 98,8</td><td> 1,2</td><td> 0</td>

<td> 2</td><td> 98,7</td><td> 1,3</td><td> 0</td>

<td> 3</td><td> 95,1</td><td> 4,1</td><td> 0,8</td>

<td> 4</td><td> 91,3</td><td> 6,4</td><td> 2,3</td>

[0070] The addition of the addition of N- (2,6-diisopropyl) phenyl-3,5-di-tert-butylsalicylaldimine during the preparation of the gadolinium or yttrium tris [N, Nbis (trimethylsilyl) amide] or yttrium catalyst system increases the catalytic activity. The stereospecificity of the catalyst was not penalized because the levels of 1,4-cis conjugate systems remained elevated (&gt; 90% for yttrium and&gt; 98% for gadolinium).

Dorota Rzążewska

Patent Attorney