Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/30—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule
  • C08C19/42—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups
  • C08C19/44—Addition of a reagent which reacts with a hetero atom or a group containing hetero atoms of the macromolecule reacting with metals or metal-containing groups of polymers containing metal atoms exclusively at one or both ends of the skeleton
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F36/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
  • C08F36/02—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
  • C08F36/04—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated

Definitions

• the present invention relates to linear or branched diene elastomers having a mass content of cyclic vinyl units, such as vinylcycloalkane units, which is equal to or greater than 15%, processes for the anionic preparation of these diene elastomers and catalytic systems for the implementation of these processes.
• the anionic polymerization reactions are usually initiated by an organolithian, in the presence of a hydrocarbon solvent and one or more conjugated diene monomers.
• the elastomers produced by these reactions have on average a mass rate of vinyl chains which is reduced, being generally between 8% and 15%.
• Tg glass transition temperature
• These batch polymerization processes are carried out at a temperature between 30 and 100 ° C., and they consist in particular in using catalytic systems comprising: a polar agent comprising one or more hetero atoms, such as tetrahydrofuran (THF) or tetramethylethylenediamine (TMEDA), an organolithium initiator, such as n-butyllithium, and an alkali metal salt of an aliphatic or alicyclic alcohol, such as tert-amylate or sodium mentholate.
• a polar agent comprising one or more hetero atoms, such as tetrahydrofuran (THF) or tetramethylethylenediamine (TMEDA)
• THF tetrahydrofuran
• TEDA tetramethylethylenediamine
• organolithium initiator such as n-butyllithium
• an alkali metal salt of an aliphatic or alicyclic alcohol such as tert-amylate
• document US-A-5 620 939 discloses, in its examples, molar ratios [(salt / initiator), (salt / polar agent), (polar agent / initiator)] which are equal to [1; 0.33; 3], [2; 0.66; 3], [3; 1; 3], [0.5; 0.17; 3], [1; 0.5; 2] and [1; 0.2; 5].
• Document US-A-6 140 434 discloses, in its examples, the following values for said molar ratios: [0.25; 0.03; 8], [0.25; 0.05; 5], [0.25; 0.08; 3], [0.25; 0.25; 1], [0.25; 0.5; 0.5], [0.15; 0.05; 3], [0.5; 0.17; 3], [1; 0.33; 3] and [0.25; 0.13; 2].
• the polymerization is carried out continuously, at a temperature between -20 ° C and 150 ° C, and the polybutadienes obtained have a mass rate of cycles greater than 40% but a number average molecular mass not exceeding 2,000 g / mol.
• Quack, LJ Fetters, Polymer, Vol 22, pp.382- 386 also describe continuous cyclization processes in the polymerization medium, consisting of use catalytic systems comprising an organolithium-containing initiator, such as n-butyllithium, and a polar agent consisting of TMEDA (reference may be made to page 383, right column of the last document cited, for a description of the cyclization mechanism).
• the polymerizations are carried out at temperatures between 30 and 90 ° C., and the polybutadienes obtained have a mass content of vinylcyclopentane cycles of at least 18% but a number-average molecular mass not exceeding 5,000 g / mol.
• a major drawback of these cyclization processes therefore lies in the very reduced value of the number-average molecular mass of the diene elastomers obtained.
• the object of the present invention is to remedy this drawback, and it has been achieved in that the applicant has surprisingly discovered that the anionic polymerization of one or more monomers comprising at least one conjugated diene monomer, comprising the reaction, in an ahphatic or alicyclic inert hydrocarbon solvent, of the monomer (s) with a catalytic system comprising an organolithium initiator and a polar agent comprising several hetero atoms, the reaction being carried out:
• the molar ratio (salt / initiator) belongs to a range ranging from 0.01 to 2
• the molar ratio (salt / polar agent) belongs to a range ranging from 0.001 to 0.5.
• cyclic vinyl units are of vinylcycloalkane type, and they correspond to the following generic formula:
• organolithium initiator which can be used in this catalytic system according to the invention, mention may be made of monolithic compounds comprising an ahphatic or alicyclic hydrocarbon group having from 1 to 10 carbon atoms, such as n-butyllithium (n-BuLi for short). below), sec-butyllithium, tert-butyllithium, n-propyllithium, amyllithium, cyclohexyllithium, or phenylethyllithium.
• n-butyllithium n-BuLi for short
• sec-butyllithium sec-butyllithium
• tert-butyllithium n-propyllithium
• amyllithium cyclohexyllithium
• phenylethyllithium phenylethyllithium
• the amount of initiator which is used to form the catalytic system is preferably between 0.002 and 0.01 mol per kg of monomer (s).
• polar agent comprising several hetero atoms (oxygen or nitrogen atoms) which can be used in this catalytic system according to the invention
• multidentate polar agents such as diethers and diamines, for example tetramethylethylenediamine (TMEDA), dimethoxyethane (DME), diethylcarbitol (DEC), triethylene glycoldimethyl ether (or “triglyme”), tetraethylene glycoldimethyl ether (or “tetraglyme”), or dipiperidinoethane.
• TEDA tetramethylethylenediamine
• DME dimethoxyethane
• DEC diethylcarbitol
• triglyme triethylene glycoldimethyl ether
• tetraethylene glycoldimethyl ether or "tetraglyme”
• dipiperidinoethane dipiperidinoethane.
• This polar agent is used to form the catalytic system according to the invention
• the polar agents comprising a single hetero atom such as monoamines and monoethers, for example tetrahydrofuran (THF) are not suitable for implementing the methods according to the invention, fact that they do not make it possible to obtain the aforementioned mass rate of cyclic vinyl units in the diene elastomer.
• said process (2) which comprises the anionic polymerization in a continuous reactor stirred with at least one diene monomer conjugated by the reaction, in an ahphatic or alicyclic inert hydrocarbon solvent, of the monomer (s) with a catalytic system comprising said organolithium initiator and said polar agent comprising several hetero atoms so that said relation (i) is verified, advantageously makes it possible to obtain linear elastomers of masses Mn equal to or greater than 60,000 g / mol, or even equal to or greater than 100 000 g / mol in the case of the incorporation of said salt into the catalytic system so that this system also satisfies the conditions (ii) and (iii) above.
• This continuous process (2) according to the invention including the use of said salt constitutes a preferred embodiment of the present invention, because it makes it possible to obtain diene elastomers having both very high molecular weights compared to l 'known state of the art and a mass content of cyclic vinyl units equal to or greater than 20%. It will also be noted that the methods (1) and (2) according to the invention advantageously make it possible to control the distribution of the molecular masses of the diene elastomers obtained, which have a relatively reduced polymolecularity index Ip (less than 3).
• the linear diene elastomers obtained have a molecular mass Mn ranging from 10,000 to 30,000 g / mol and a mass content of cyclic vinyl units equal to or greater than 35%.
• discontinuous process (1) which is characterized by a value of molar ratio (polar agent / initiator) greater than 8, this ratio is advantageously equal to or greater than 10 and, even more advantageously, equal to or greater than 15. It is possible, for example, to limit the value of this molar ratio to 100.
• the molar ratio (polar agent / initiator) is advantageously equal to or greater than 5 and , even more advantageously, this molar ratio is equal to or greater than 10. It is possible, for example, to limit the value of this molar ratio to 100.
• the catalytic systems according to the invention are such that the molar ratio (polar agent / initiator) is equal to or greater than 15, which represents very high quantities of polar agent in these catalytic systems compared to the quantities used in known catalytic systems.
• the molar ratio polar agent / initiator
• alkali metal salt of an ahphatic or alicyclic alcohol which can be used in these processes according to the invention, use is preferably made of a salt in which the alcohol contains from 3 to 12 carbon atoms and, even more preferably, from 3 to 8 carbon atoms.
• a sodium or potassium salt of an ahphatic alcohol is used, such as sodium tert-butoxide, sodium tert-amylate or sodium isopentylate, or else an alicyclic alcohol, such as a dialkylated sodium cyclohexanolate, for example sodium mentholate.
• the catalytic system used in said process (2) continuously including said salt is such that the molar ratio (salt / polar agent) belongs to a range from 0.001 to 0.1.
• the catalytic system used in this process (2) continuously is such that the molar ratio (salt / initiator) belongs to a range ranging from 0.01 to 0.6.
• this ratio belongs to a range ranging from 0.01 to 0.2 and, according to a second embodiment, this ratio belongs to a range ranging from 0.3 to 0.6.
• a catalytic system according to the invention which can be used to prepare by said process (2) continuously a linear diene elastomer having a mass content of cyclic vinyl units equal to or greater than 15 % and a mass Mn ranging from 10,000 to 300,000 g / mol, comprises an organolithic initiator, a polar agent comprising several hetero atoms and an alkali metal salt of an ahphatic or alicyclic alcohol, and it satisfies the conditions following: (i ') the molar ratio (polar agent / initiator) is greater than 8,
• the molar ratio (salt / initiator) belongs to a range ranging from 0.01 to 2
• the molar ratio (salt / polar agent) belongs to a range ranging from 0.001 to 0.5.
• this catalytic system is such that the molar ratio (salt / initiator) belongs to a range ranging from 0.01 to 0.2 or 0.3 to 2 and that the molar ratio (salt / agent) polar) belongs to a range from 0.001 to 0.1.
• these linear elastomers of low molecular mass can advantageously be obtained with a reduced amount of organolithium initiator in the catalytic system according to the invention, which contributes to reducing the cost obtaining these low mass elastomers.
• the mass content of vinyl units in the diene elastomers obtained by the methods according to the invention is between 40% and 65%.
• inert hydrocarbon solvent which can be used in the processes according to the invention, mention may be made of aliphatic or ahcyclic solvents such as pentane, hexane, the commercial mixture of hexane / methylcyclopentane, heptane, methylcyclohexane, or cyclohexane.
• aromatic solvents such as toluene
• the diene elastomer according to the invention preferably comprises a mass fraction of units derived from conjugated dienes which is greater than 30%, and it can be any homopolymer or copolymer obtained by polymerization:
• conjugated diene monomers suitable in particular, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C1-C5 alkyl) -1,3-butadienes such as 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, an aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene.
• 1,3-butadiene 2-methyl-1,3-butadiene
• 2,3-di (C1-C5 alkyl) -1,3-butadienes such as 2, 3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isoprop
• vinyl aromatic compounds examples include styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyltoluene", para-tertiobutylstyrene, divinylbenzene. It will be noted that styrene is used on a preferential basis.
• 1,3-butadiene and / or isoprene is used in the process according to the invention as the conjugated diene monomer (s) and styrene as the vinyl aromatic monomer, for the 'obtaining copolymers of butadiene / isoprene (BIR), styrene / butadiene (SBR), styrene / isoprene (SIR), or butadiene / styrene / isoprene (SBIR).
• BIR butadiene / isoprene
• SBR styrene / butadiene
• SIR styrene / isoprene
• SBIR butadiene / styrene / isoprene
• the butadiene-1, 3 and the styrene are co-polymerized to obtain an SBR having at least 70% by weight of butadiene and at most 30% by weight of styrene and, preferably, at least 90% butadiene and at most 10% styrene.
• the diene elastomers obtained by the methods according to the invention can then be branched (ie coupled or stars) or not.
• a branched diene elastomer according to the present invention which also comes from at least one conjugated diene and capable of being obtained by reaction of said linear diene elastomer according to the invention with a branching agent (ie coupling or star-forming), contains cyclic vinyl units at a mass rate equal to or greater than 15% and it has a number-average molecular mass ranging from 30,000 to 350,000 g / mol, advantageously ranging from 150,000 to 350,000 g / mol.
• a branching agent ie coupling or star-forming
• said mass content of cyclic vinyl units is equal to or greater than 20%.
• the SEC technique size exclusion chromatography was used to determine the molecular weights and the polymolecularity indices of the elastomers. According to this technique, the macromolecules are physically separated according to their respective sizes in the swollen state, in columns filled with a porous stationary phase.
• a chromatograph sold under the name “WATERS” and under the model “150C” is used for the above-mentioned separation. We use a set of two columns
• the carbon 13 nuclear magnetic resonance technique ( 13 C NMR) was also used to determine microstructure characteristics relating to the elastomers obtained. The details of this characterization are explained below.
• the 13 C NMR analyzes are carried out on a “Bruker AM250” spectrometer. The nominal frequency of carbon 13 is 62.9 MHz. To be quantitative, the spectra are recorded without the “Nuclear Overhauser” (NOE) effect. The spectral width is 240 ppm.
• the angle pulse used is a 90 ° pulse whose duration is 5 ⁇ s. Decoupling a low power and a wide proton band is used to remove the scalar couplings ⁇ - 13 C during acquisition 13 C. The sequence repetition time is 4 seconds. The number of transients accumulated to increase the signal / noise ratio is 8192.
• the spectra are calibrated on the CDC1 3 band at 77 ppm.
• Butadiene 1 4-Cis - (C) Butadiene 1, 4-Trans - (T) Butadiene 1, 2 - (V)
• the cis / trans ratio of the diene part is determined in the ahphatic region of the spectrum, from attributes well known to those skilled in the art (see documents (1) to (5) above).
• the polymerization is carried out continuously in a perfectly stirred reactor of 0.8 1.
• Cyclohexane, butadiene, styrene and tetramethylethylenediamine (TMEDA) are introduced into this reactor, in mass quantities of 100 / 12.2 / 2 , 1 / 0.057, respectively (the amount of tetramethylethylenediamine in the reaction medium being approximately 500 ppm).
• 200 ⁇ mol of n-BuLi per 100 g of monomers are introduced at the line entry, in order to neutralize the protic impurities provided by the various constituents present in this line entry.
• 700 ⁇ mol of n-BuLi are introduced per 100 g of monomers.
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min, and the temperature is maintained at 80 ° C.
• the molar ratio (TMEDA / n-BuLi) is here substantially equal to 4.9.
• the conversion rate, measured on a sample taken at the reactor outlet, is
• the SBR obtained is subjected to an antioxidant treatment, using 0.2 phr of 2,2'-methylene bis (4-methyl-6-tertiobutylphenol) and of 0.2 phr of N- (1,3-dimethylbutyl) -N'- phenyl-p-phenylenediamine (phr: parts by weight per hundred parts of elastomer).
• the number-average molecular mass Mn of the linear SBR obtained, evaluated by the above-mentioned SEC technique, is 130,000 g / mol.
• the polymolecularity index Ip is 1.80.
• the microstructure of this SBR according to the invention is such that it has, for the butadiene part, a mass content of vinyl units of 53% and a mass content of vinyl encyclopentane units of 10 %.
• the Tg before oil extension of this SBR according to the invention is -31 ° C.
• This SBR according to the invention is continuously prepared under conditions identical to those of Example 1, except that a solution of sodium tertioamylate is introduced into the reactor, in addition to the above ingredients. 0.2 sodium / active lithium ratio.
• the molar ratio (TMEDA / n-BuLi) is here substantially equal to 4.9.
• the conversion rate, measured on a sample taken from the reactor, is 97%, and the inherent viscosity of the SBR obtained, measured at 0.1 g / dl in toluene, is 1.80 dl / g.
• the linear SBR obtained has a mass Mn of 120,000 g / mol and an Ip index of 2.47.
• the mass content of styrenic sequences is 15%.
• the mass content of vinyl sequences is 53% and the mass content of vinylcyclopentane units is 23%.
• the Tg before oil extension of this SBR according to the invention is -14 ° C.
• This SBR is continuously prepared in a perfectly stirred 14 L reactor.
• Cyclohexane, butadiene, styrene and tetramethylethylenediamine are introduced into this reactor, in mass quantities of 100 / 13.6 / 0.7 / 0.17, respectively (the quantity of tetramethylethylenediamine in the reaction medium being about 1500 ppm).
• 300 ⁇ mol of n-BuLi per 100 g of monomers are introduced at the line entry, in order to neutralize the protic impurities provided by the various constituents present in this line entry.
• 500 ⁇ mol of n-BuLi are introduced per 100 g of monomers, so that the molar ratio (TMEDA / n-Buli) is approximately 20.5.
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min, and the temperature is maintained at 80 ° C.
• the conversion rate measured on a sample taken at the outlet of the reactor, is 84% and the inherent viscosity of the linear SBR obtained, measured at 0.1 g / dl in toluene, is 2.21 dl / g.
• the molecular mass Mn of this linear SBR is 135,000 g / mol.
• a starter agent consisting of tris- (2,4-di-tert-butylphenyl) phosphite is introduced, then this star SBR is subjected to an antioxidant treatment, using 0, 2 phr of 2,2'-methylene bis (4-methyl-6-tertiobutylphenol) and 0.2 phr of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine.
• the molecular mass Mn of this star SBR is 180,000 g / mol, and the index Ip is
• This star SBR has a mass content of styrenic sequences of 5%.
• it has a mass content of vinyl units of 60% and a mass content of vinylcyclopentane units of 9%.
• the Tg before oil extension of this SBR according to the invention is -34 ° C.
• COMPARATIVE EXAMPLE 3bis Preparation of a high molecular weight “control” star SBR, free of vinylcyclopentane motifs.
• This SBR is continuously prepared in a perfectly stirred 14 L reactor.
• Toluene, butadiene, styrene, tetrahydrofuran and dimethoxyethane are introduced into this reactor in mass quantities of 100 / 10.15 / 4.15 / 0.68 / 0.25 respectively.
• 200 ⁇ mol of n-BuLi per 100 g of monomers are introduced at the line entry, in order to neutralize the protic impurities provided by the various constituents present in this line entry.
• 150 ⁇ mol of n-BuLi are introduced per 100 g of monomers.
• the molar ratio (polar agents / n-BuLi) is approximately 569.
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min, and the temperature is maintained at 60 ° C.
• the conversion rate, measured on a sample taken at the outlet of the reactor, is 87% and the inherent viscosity of the linear SBR obtained, measured at 0.1 g / dl in toluene, is 2.61 dl / g.
• a staring agent consisting of propylene glycol carbonate is introduced, then this star SBR is subjected to an antioxidant treatment, using 0.2 phr of 2,2′-methylene bis (4-methyl-6-tertiobutylphenol) and 0.2 phr of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine.
• This “control” star SBR has a mass content of styrenic sequences of 25%. For the butadiene part, it has a mass content of vinyl units of 58% and the vinylcyclopentane units are not detected.
• the Tg before oil extension of this “control” SBR is -24 ° C.
• This SBR according to the invention is continuously prepared under conditions identical to those described in Example 3, except that there is introduced into the reactor, in addition to the above ingredients, a solution of sodium tertioamylate according to an active sodium / lithium ratio of 0.04, and which is introduced at the inlet of the reactor 660 ⁇ mol of n-BuLi per 100 g of monomers.
• the molar ratio sodium / tetramethylethylenediamine
• the conversion rate measured on a sample taken at the outlet of the reactor, is 90%, and the inherent viscosity of the linear SBR obtained, measured at 0.1 g / dl in toluene, is 2.30 dl g.
• This linear SBR has a molecular weight Mn of 150,000 g / mol.
• the molar ratio (TMEDA / n-BuLi) is approximately 15.5. We proceed to the staring of this SBR as indicated in Example 3.
• This star SBR has a mass Mn of 260,000 g / mol and an Ip index of 2.56.
• the mass content of this star SBR according to the invention in styrenic sequences is 6%.
• the mass content of vinyl sequences is 57% and the mass content of vinylcyclopentane units is 22%.
• the Tg before oil extension of this SBR according to the invention is -25 ° C.
• This polybutadiene (BR) according to the invention is continuously prepared under conditions identical to those described in Example 4, except that a quantity of butadiene equal to 14.3 parts per hundred parts is introduced into the reactor. of cyclohexane, which does not introduce styrene into this reactor and which is introduced at the inlet of the reactor 600 ⁇ mol of n-BuLi per 100 g of monomers.
• the molar ratio (TMEDA / n-BuLi) is approximately 17.1.
• the conversion rate measured on a sample taken at the outlet of the reactor, is 92%, and the inherent viscosity of the linear BR obtained, measured at 0.1 g / dl in toluene, is 1.86 dl / g.
• the molecular mass Mn of this linear BR is 130,000 g / mol.
• the aforementioned star-forming agent is introduced as above at the outlet of the reactor, before subjecting the star BR obtained to the same antioxidant treatment.
• This BR star has a mass Mn equal to 181,000 g / mol and an index Ip equal to 2.89.
• This star BR according to the invention has a mass content of vinyl sequences of 56% and a mass content of vinylcyclopentane units of 20%.
• the Tg before oil extension of this BR according to the invention is -29 ° C.
• This example also shows that by incorporating an alkali metal salt of an ahphatic or alicyclic alcohol in the catalytic system, one obtains following the polymerization (carried out continuously with a molar ratio (polar agent / initiator) greater than 15 ) a mass content of cyclic vinyl units equal to 20% for a linear polybutadiene of molecular mass Mn greater than 100,000 g / mol.
• the polymer is prepared continuously in a perfectly stirred reactor of 0.8 1. Cyclohexane, butadiene, styrene, tetramethylethylenediamine are introduced into this reactor in mass quantities of 100 / 13.15 / 1.13 / 0 , 29 respectively. 200 ⁇ mol of n-BuLi per 100 g of monomers are introduced at the line entry, in order to neutralize the protic impurities provided by the various constituents present in this line entry. At the inlet of the reactor, 1200 ⁇ mol of n-BuLi are introduced per 100 g of monomers.
• the molar ratio (TMEDA / n-BuLi) is approximately 14.6.
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min, and the temperature is maintained at 80 ° C.
• the conversion rate measured on a sample taken at the outlet of the reactor, is 92% and the inherent viscosity of the linear SBR obtained, measured at 0.1 g / dl in toluene, is 1.35 dl / g.
• the molecular mass Mn of this linear SBR is 75,000 g / mol.
• a staring agent consisting of methyltrichlorosilane (400 ⁇ mol per 100 g of monomers) is introduced, then this star SBR is subjected to an antioxidant treatment, using 0.2 phr of 2, 2'-methylene bis (4-methyl-6-tert-butylphenol) and 0.2 phr of N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine.
• This star SBR has a mass content of vinyl units of 51% and a mass content of vinylcyclopentane units of 18%.
• the Tg before oil extension of this SBR according to the invention is -28 ° C.
• This example shows that it is not necessary to incorporate a salt of an alkali metal of an ahphatic or alicyclic alcohol in the catalytic system, to obtain following the polymerization (carried out continuously with a molar ratio (polar agent / initiator) greater than 10) a mass content of cyclic vinyl units greater than 15% for a linear elastomer of molecular weight Mn of between 50,000 and 100,000 g / mol.
• the polymerization is carried out continuously in a perfectly stirred reactor of 0.8 1.
• Cyclohexane, butadiene, styrene and tetramethylethylenediamine are introduced into this reactor, in mass quantities of 100 / 12.30 / 2/0, 35, respectively (the amount of tetramethylethylenediamine in the reaction medium being approximately 3000 ppm).
• 200 ⁇ mol of n-BuLi per 100 g of monomers are introduced at the line entry, in order to neutralize the protic impurities provided by the various constituents present in this line entry.
• 1500 ⁇ mol of n-BuLi are introduced per 100 g of monomers, so that the molar ratio (tetramethylethylenediamine / n-Buli) is approximately 14.1.
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min, and the temperature is maintained at 80 ° C.
• the conversion rate, measured on a sample taken at the outlet of the reactor, is of
• the SBR obtained is subjected to the antioxidant treatment mentioned in the above examples.
• the mass Mn of the SBR obtained is 50,000 g / mol.
• This SBR according to the invention has a mass content of styrenic sequences of 16% and, for the butadiene part, a mass content of vinyl units of 57% and a mass content of vinylcyclopentane units of 17%.
• the Tg before oil extension of this SBR according to the invention is -19 ° C.
• This example also shows that it is not necessary to incorporate a salt of an alkali metal of an ahphatic or alicyclic alcohol in the catalytic system, to obtain following the polymerization (carried out continuously with a molar ratio (agent polar / initiator) greater than 10) a mass content of cyclic vinyl units greater than 15% for a linear elastomer of molecular mass Mn equal to 50,000 g / mol.
• This SBR according to the invention is continuously prepared under conditions identical to those described in Example 6, except that there is introduced into the reactor, in addition to the above ingredients, a solution of sodium tertioamylate according to an active sodium / lithium ratio of 0.4.
• the molar ratio (sodium / tetramethylethylenediamine) is 0.05.
• the conversion rate, measured on a sample taken from the reactor, is 99%, and the inherent viscosity of the SBR obtained, measured at 0.1 g / dl in toluene, is 0.43 dl / g.
• the molar ratio (TMEDA / n-BuLi) is approximately 14.1.
• This linear SBR according to the invention has an Mn equal to 6000 g / mol.
• the mass content of styrenic sequences is 16% and, for the butadiene part, the mass content of vinyl sequences is 43% and the mass content of vinylcyclopentane units is 40%.
• the Tg of this SBR according to the invention is -12 ° C.

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