Classifications

• • 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
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
  • C08F297/04—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes
  • C08F297/046—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type polymerising vinyl aromatic monomers and conjugated dienes polymerising vinyl aromatic monomers and isoprene, optionally with other conjugated dienes
• • 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
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S152/00—Resilient tires and wheels
  • Y10S152/905—Tread composition

Definitions

• the present invention relates to a process for the preparation of a block copolymer which can be used in a rubber composition crosslinkable with sulfur and of hysteresis reduced in the crosslinked state, such a block copolymer and such a rubber composition which can be used in a strip of tire casing bearing.
• the invention also relates to such a tread and to a tire covering incorporating it, which has a reduced rolling resistance. Reducing the hysteresis of mixtures is a permanent objective of the tire industry in order to limit fuel consumption and thus preserve the environment.
• Block copolymers are generally made of materials with segregated phases. Mention may for example be made of polyisoprene-polystyrene diblock copolymers, the synthesis of which is widely described in the literature. These diblock copolymers are known to exhibit advantageous impact resistance properties.
• Block copolymers comprising polyisoprene and polybutadiene blocks (IR and BR for short, respectively) are also described in the literature.
• thermoplastic materials For example, during the hydrogenation of a BR-IR-BR triblock copolymer, the butadiene fraction forms a crystalline polyethylene, while the isoprene fraction leads to a rubber material of ethylene / butylene type.
• Diblock copolymers IR-SBR polyisoprene - copolymer of styrene and butadiene
• the number average molecular mass of the IR block is preferably between 70,000 and 150,000 g / mol, and that of the SBR block is preferably between 220,000 and 240,000 g / mol.
• the ratio of the number average molecular weight of the IR block to that of the SBR block must be greater than 33% and can be up to 300%.
• the rubber compositions described in this document may have a variable structure, which is of the lamellar type when said ratio is close to 33%, and of the sphere type when said ratio is close to 300%.
• IR-BR block copolymers have also been envisaged as compatibilizing agents for polyisoprene and polybutadiene blends. As such, we can cite the article by D. J. Zanzig, F. L. Magnus, W. L. Hsu, A. F. Halasa,
• the diblock copolymers used have IR blocks of number average molecular mass equal to 104,000 g / mol, or equal to 133,000 g / mol.
• the relatively high molecular mass of the IR blocks and of the BR blocks also leads to a strong segregation of the phases relating to these two blocks.
• a catalytic system comprising at least one hydrocarbon solvent, a compound A of a metal from the IDA group, a compound B of an alkaline earth metal and a polymeric initiator C comprising a bond C -Which consists of a monolithic polyisoprene obtained anionically, makes it possible to prepare, by copolymerization of one or more monomers comprising a conjugated diene other than isoprene, a functional or non-two-block copolymer which is such that:
• one of said blocks consists of a polyisoprene (IR) formed from said polymeric initiator C, such that - the other block consists of a diene elastomer whose molar ratio of units derived from conjugated dienes is higher at 15% and which has a content of 1,4-trans sequences equal to or greater than 70%, and such that
• the number-average molecular mass M n ⁇ of the IR block is between 2,500 and 20,000 g / mol
• the number-average molecular mass M n2 of the other block made up of said diene elastomer being between 65,000 and 350,000 g / mol
• the copolymer thus obtained being usable in a rubber composition crosslinkable with sulfur and making it possible to optimize significantly for this composition, in the crosslinked state, the results of reduction of hysteresis and, in the uncrosslinked state, the results of aptitude for implementation.
• hystereses relating to “control” diene elastomers whose molar level of units derived from conjugated dienes is greater than 15% such as a copolymer of styrene and butadiene (SBR), a copolymer with two blocks according to the invention, such as an IR-SBR copolymer, is characterized by a hysteresis which is more reduced than that which relates to this “control” elastomer.
• SBR styrene and butadiene
• the ratio of said number average molecular weights M n ⁇ / M n2 is substantially between 5 and 20%.
• any homopolymer obtained is understood by polymerization of a conjugated diene monomer other than isoprene having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more dienes conjugated together or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms carbon.
• 1, 3-butadiene, 2, 3-di (C1 to C5 alkyl) 1, 3-butadiene such as for example 2, 3 dimethyl-1, 3-butadiene, 2, 3-diethyl-l, 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.
• vinyl aromatic compounds suitable in particular are styrene, ortho-, para-, or meta-methylstyrene, the commercial mixture "vinyl toluene", para-tertiobutylstyrene, methoxystyrenes, vinyl mesitylene.
• organometallic compounds which can be used the following organometallic compounds: organoalumines, halogenated or not such as triethyl aluminum, tri-isobutyl- aluminum, diethyl aluminum chloride, ethyl aluminum dichloride, ethyl aluminum sesquichloride, methyl aluminum sesquichloride; dialkyl aluminum hydrides, such as diethyl aluminum hydride, diisobutyl aluminum hydride, etc.
• organoalumines halogenated or not such as triethyl aluminum, tri-isobutyl- aluminum, diethyl aluminum chloride, ethyl aluminum dichloride, ethyl aluminum sesquichloride, methyl aluminum sesquichloride
• dialkyl aluminum hydrides such as diethyl aluminum hydride, diisobutyl aluminum hydride, etc.
• a trialkyl aluminum is used, the number of carbon atoms ranging from 1 to 12, advantageously trioctyl aluminum.
• hydrides H 2 Ba and H 2 Sr salts of mono or polyfunctional organic acids of formulas (R-COO) 2 Ba or Sr , R ⁇ - (COO) 2 Ba or Sr, in which R and R t are organic radicals, the first monovalent and the second divalent, the corresponding thioacids, the mono or polyfunctional alcoholates and the corresponding thiolates; mono or polyfunctional phenates and the corresponding thiophenates; the salts of alcoholic acids and phenolic acids of barium or strontium and the corresponding thio-products; barium or strontium ⁇ -diketonates such as the reaction products of barium or strontium with acetylacetone, dibenzoylmethane,stenoyltrifluoro-acetone, benzoyltrifluoro-acetone, benzoyl-acetone; organic derivatives of barium or strontium
• this catalytic system consists of a cocatalyst, resulting from the reaction product in said hydrocarbon solvent of said compound A and of said compound B, and by said initiator C.
• the preparation process according to the invention consists in implementing the following steps: - in a first step, said co-catalyst is prepared by reacting, in said inert hydrocarbon solvent, the two metal compounds A and B. Then the mixture obtained is preferably heated to a temperature between 20 ° C and 120 ° C, even more preferably between 30 ° C and 50 ° C and for a sufficient time to allow the reaction of two compounds A and B. This duration is generally between 1 and 60 minutes, preferably between 20 and 40 minutes; then
• said cocatalyst in a second step, said cocatalyst is brought into contact with the polymerization medium comprising said monomer or monomers to be copolymerized (which are for example in solution in a polymerization solvent, in the case of copolymerization in solution), excluding said polymeric initiator C; then - in a third step, said initiator C is added to the polymerization medium thus obtained, so as to react the mixture obtained in said second step, and the polymerization reaction is subsequently stopped to obtain said polymers, for obtain a functional or non-functional copolymer, which is then recovered as known per se.
• the polymerization medium comprising said monomer or monomers to be copolymerized (which are for example in solution in a polymerization solvent, in the case of copolymerization in solution), excluding said polymeric initiator C; then - in a third step, said initiator C is added to the polymerization medium thus obtained, so as to react the mixture obtained in said second step, and the polymer
• the preparation process according to the invention then consists in implementing the following steps:
• a second step consists in adding said polymeric initiator C to the premix obtained in the first step and formed by compounds A and B, optionally after adding an alkyl lithian compound to improve the activity of the catalytic system.
• this alkyl lithian compound is butyl lithium.
• a third step consists in adding the catalytic system thus obtained to the polymerization medium comprising said monomer or monomers to be copolymerized (which are for example in solution in a polymerization solvent, in the case of a copolymerization in solution) and to subsequently stop polymerization, to obtain a functional or non-functional copolymer according to the invention.
• the temperature conditions are the same as those of said first example.
• said catalytic system consists of a premix of said compounds A and C in said hydrocarbon solvent and by said compound B.
• this premix containing the compounds A and C is added to the polymerization medium comprising said monomer or monomers to be copolymerized (which are for example in solution in a polymerization solvent, in the case of a copolymerization in solution), then all of said compound B is added and the polymerization is subsequently stopped, in order to obtain a functional or non-functional copolymer according to the invention.
• an amount of reagents A and B is used such that the molar ratio A / B is between 0.5 and 5, and preferably between 2.5 and 4.
• an amount of the two reactants B and C is used such that the molar ratio C / B is between 0.2 and 4, and preferably between 1.5 and 4.
• the polymerization solvent is preferably a hydrocarbon solvent, preferably cyclohexane, and the polymerization temperature is between 20 ° C and 150 ° C, and preferably between 60 ° C and 110 ° C.
• the concentration of alkaline earth metal in the catalytic system according to the invention is between 0.01 and 0.5 mol.1 "1 , preferably between 0.03 and 0.25 mol. l "1 .
• the polymerization according to the invention can be continuous, discontinuous and that it can also be carried out in bulk.
• the polyisoprene (IR) block of the copolymer according to the invention has a rate of vinyl sequences (3.4 and 1.2) which is substantially between 1 and 20%.
• styrene and butadiene are used as monomers to be copolymerized with the polyisoprene present in said lithiated initiator C, for obtaining a copolymer with two IR-SBR blocks (polyisoprene / styrene-butadiene).
• the block of the copolymer according to the invention which is formed from said diene elastomer other than a polyisoprene, for example an SBR block, has an interactive function with a reinforcing filler.
• This function can be interactive with a reinforcing inorganic filler, such as silica, and it can for example comprise a silanol group or a mono, di or tri-alkoxysilane group.
• This function can also be interactive with carbon black, and it can for example comprise a C-Sn bond.
• this function can be obtained as known per se by reaction with an organohalo-tin type functionalizing agent which can correspond to the general formula R 3 SnCl, or with an organodihalo-tin type coupling agent which can correspond to the general formula R 2 SnCl, or with a starter agent of organotrihalo-tin type which can correspond to the general formula RSnCl 3 , or of tetrahalo-tin type which can correspond to the formula SnCl 4 (where R is an alkyl, cycloalkyl or aryl radical).
• Said interactive function with carbon black can also comprise an amino group.
• a rubber composition according to the invention which is adapted to have improved processability in the non-crosslinked state and reduced hysteresis in the crosslinked state, is such that its elastomeric matrix comprises a block copolymer according to the invention as defined above, the block of said copolymer formed from said diene elastomer other than a polyisoprene being functionalized, coupled or star for the connection with said reinforcing filler.
• This reinforcing filler comprises, for example, a predominantly reinforcing inorganic filler (that is to say according to a mass fraction greater than 50%).
• the term "reinforcing inorganic filler” is understood, in a known manner, an inorganic or mineral filler, whatever its color and its origin (natural or synthetic), also called “white” filler or sometimes “clear” filler "in contrast to carbon black, this inorganic filler being capable of reinforcing on its own, without other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words capable of replacing, in its reinforcing function, a conventional charge of pneumatic grade carbon black.
• the reinforcing inorganic filler is, in whole or at least mainly, silica (Si ⁇ 2).
• the silica used can be any reinforcing silica known to a person skilled in the art, in particular any precipitated or pyrogenic silica having a surface
• the BET specific surface is determined in a known manner, according to the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society” Vol. 60, page 309, February 1938 and corresponding to the AFNOR-NFT- standard
• CTAB specific surface is the external surface determined according to the same standard AFNOR-NFT-45007 of November 1987.
• highly dispersible silica is understood to mean any silica having a very high ability to disaggregate and to disperse in an elastomer matrix, observable in known manner by electron or optical microscopy, on fine sections.
• preferred highly dispersible silicas mention may be made of Perkasil KS 430 silica from Akzo, BN 3380 silica from Degussa, Zeosil 1165 MP and 1115 MP silica from Rhodia, Hi-Sil 2000 silica from PPG, Zeopol 8741 or 8745 silica from Huber company, treated precipitated silicas such as for example the silicas "doped" with aluminum described in patent document EP-A-735088.
• reinforcing inorganic filler is also understood to mean mixtures of various reinforcing inorganic fillers, in particular highly dispersible silicas as described above.
• the reinforcing filler of a rubber composition according to the invention may contain, as a blend (mixture), in addition to the abovementioned reinforcing inorganic filler (s), carbon black on a minor basis (that is to say according to a mass fraction of less than 50%).
• carbon blacks all carbon blacks are suitable, in particular blacks of the HAF, ISAF, SAF type, conventionally used in tires and particularly in tire treads.
• blacks ⁇ 115, NI 34, N234, N339, N347, N375.
• black / silica blends or blacks partially or entirely covered with silica are suitable for constituting the reinforcing filler.
• carbon blacks modified by silica such as, without limitation, the fillers which are marketed by the company CABOT under the name "CRX 2000", and which are described in the document of international patent WO-A-96/37547.
• said reinforcing filler mainly comprises carbon black.
• said reinforcing filler comprises a blend of 50% of reinforcing inorganic filler and of 50% carbon black.
• a coupling agent inorganic filler / elastomer
• bond which has the function of ensuring the bond or "coupling” between the inorganic filler and the elastomer, while facilitating the dispersion of this inorganic filler within the elastomer matrix.
• coupling agent is meant more precisely an agent capable of establishing a sufficient connection, of a chemical and / or physical nature, between the filler considered and the elastomer, while facilitating the dispersion of this filler within the elastomer matrix;
• a coupling agent at least bifunctional, has for example as simplified general formula "Y-T-X", in which:
• Y represents a functional group (“Y” function) which is capable of physically and / or chemically binding to the inorganic charge, such a bond being able to be established, for example, between a silicon atom of the coupling agent and surface hydroxyl groups (OH) of the inorganic filler (for example surface silanols when it is silica);
• - X represents a functional group (function "X") capable of physically and or chemically bonding to the elastomer, for example via a sulfur atom;
• - T represents a group making it possible to connect Y and X.
• Coupling agents should in particular not be confused with simple agents for recovery of the charge considered which, in known manner, may include the function Y active with respect to the charge but are devoid of the function X active vis -to the elastomer.
• any coupling agent known for, or capable of ensuring effectively, in diene rubber compositions which can be used for the manufacture of tires, the binding or coupling between a reinforcing white filler such as silica and a diene elastomer can be used in fact.
• organosilanes in particular polysulphurized alkoxysilanes or mercaptosilanes, or alternatively polyorganosiloxanes carrying the abovementioned X and Y functions.
• Silica / elastomer coupling agents in particular, have been described in a large number of documents, the best known being bifunctional alkoxysilanes such as polysulphurized alkoxysilanes.
• Polysulphurized alkoxysilanes are used in particular, as described for example in patents US-A-3,842,111, US-A-3,873,489, US-A-3 978 103, US-A-3 997 581, US-A-4 002 594, US- A-4 072 701, US-A-4 129 585, or in more recent patents US-A-5 580 919, US -A-5 583 245, US-A-5 650 457, US-A-5 663 358, US-A-5 663 395, US-A-5 663 396, US-A-5 674 932, US-A -5,675,014, US-A-5,684,171, US-A-5,684,172, US-A-5,696,197, US-A-5,708,053, US- A-5,892,085, EP-A-1 043 357 which detail such known compounds.
• - n is an integer from 2 to 8 (preferably from 2 to 5);
• - A is a divalent hydrocarbon radical (preferably alkylene groups in C ⁇ -C 18 or arylene groups in C 6 -C ⁇ 2 , more particularly alkylene in Ci -Ci o, in particular in CpC 4 in particular propylene);
• R2 R2 R2 wherein: - the R radicals, substituted or unsubstituted, identical or different, represent alkyl, C ⁇ -C ⁇ 8 cycloalkyl, C 5 -C ⁇ 8 or C 6 -C ⁇ 8 (preferably C ⁇ -C 6 alkyl, cyclohexyl or phenyl groups, in particular C ⁇ -C 4 alkyl groups, more particularly methyl and / or ethyl).
• R radicals substituted or unsubstituted, identical or different, represent an alkoxyl group C ⁇ -C ⁇ 8 cycloalkoxy or C 5 -C ⁇ 8 (preferably alkoxyl groups, C] -C 8 cycloalkoxy or C 5 -C 8 , more preferably C ⁇ -C alkoxyl groups, in particular methoxyl and / or ethoxyl).
• n is a fractional number, preferably included in a domain from 2 to 5.
• polysulphides in particular disulphides, trisulphides or tetrasulphides
• bis- (alkoxyl (C ⁇ -C 4 ) -alkyl (C ⁇ - C 4 ) silylalkyl (C ⁇ -C 4 ) for example bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulphides.
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (triethoxysilylpropyl) disulfide
• the TESPD is marketed for example by the company Degussa under the names Si266 or Si75 (in the second case, in the form of a mixture of disulfide (at 75% by weight) and of polysulfides), or also by the company Witco under the name Silquest Al 589.
• TESPT is marketed for example by the company Degussa under the name Si69 (or X50S when supported at 50% by weight on carbon black), or by the company Osi Specialties under the name Silquest Al 289 (in both cases, commercial mixture of polysulphides with an average value for n which is close to 4). Mention will also be made of monoalkoxysilanes tetrasulphides, such as monoethoxydimethylsilylpropyl tetrasulphide (abbreviated as MESPT), which are the subject of international patent application PCT / EP02 / 03774 in the name of the applicants.
• MESPT monoethoxydimethylsilylpropyl tetrasulphide
• compositions according to the invention contain, in addition to said elastomer matrix, said reinforcing filler and optionally one or more reinforcing inorganic filler / elastomer binding agents, all or part of the other constituents and additives usually used in rubber mixtures, such as plasticizers , pigments, antioxidants, anti-ozonizing waxes, a crosslinking system based on either sulfur and / or peroxide and / or bismaleimides, crosslinking accelerators, extension oils, one or more inorganic load recovery agents reinforcing, such as alkoxysilanes, polyols, amines, etc.
• a tire tread according to the invention which can be used to reduce the rolling resistance of a tire incorporating it, is such that it comprises a crosslinked rubber composition as defined above.
• a tire casing according to the invention is such that it includes such a tread.
• the SEC technique size exclusion chromatography was used to determine the number-average molecular weights of the copolymers obtained. 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 “15 OC” is used for the above-mentioned separation.
• a set of two “WATERS” columns is used, the type of which is “STYRAGEL HT6E”.
• 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 Ds.
• Low power, wide proton band decoupling is used to eliminate scalar couplings l H- 13 C during acquisition , 3 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.
• compositions of the invention are evaluated as follows:
• PH (%) 100 x (Wo-W ⁇ ) / W ⁇ , with Wo: energy supplied and Wi: energy restored;
• G * dynamic shear properties
• the hysteresis is expressed by the measurement of tan delta, at 7% deformation according to standard ASTM D2231-71 (re-approved in 1977);
• the descriptor of hysteresis is the value of tan delta, which is measured in sinusoidal compression at 10 Hz and at temperatures of 0 ° C, 20 ° C and 50 ° C.
• Rubber composition A according to the invention based on a copolymer A according to the invention with two SBR-IR blocks, in comparison with a “control” composition B based on an SBR copolymer B.
• Cyclohexane (154 ml), butadiene and styrene are introduced into a 0.25 1 bottle kept under nitrogen, according to the respective mass ratios 1 / 0.108 / 0J00. 0.49 ml of said co-catalyst (ie 50 ⁇ mol of barium equivalent) is added, then 117 ⁇ mol of said lithiated polyisoprene.
• the polymerization is carried out at 80 ° C., and the level of monomer converted is 65% after 30 min. This rate is determined by weighing a dried extract at 110 ° C, under reduced pressure of 200 mmHg. The copolymerization is stopped with an excess of methanol relative to the lithium.
• the inherent viscosity measured for the SBR-IR copolymer obtained is 1.61 dl / g and its Monney ML viscosity (l + 4) at 100 ° C is 51.
• This SBR-IR copolymer is subjected to an antioxidant treatment by the addition of 0.4 parts per hundred parts of elastomers (phr) of 4,4'-methylene-bis-2,6-tert-butylphenol.
• This copolymer is recovered by the conventional stripping operation with water vapor, then it is dried in an oven at 50 ° C. under a stream of nitrogen.
• the number-average molecular mass of the copolymer A (SBR-IR) obtained, determined by the SEC technique, is 108,000 g / mol.
• microstructure of this copolymer A is determined by the 13 C NMR technique.
• the rate of BR 1,4-trans is 77%, the rate of BR 1,4-cis is 19% and the rate of BR 1,2 is 4% (each of these three rates relates to butadiene units ).
• the rate of styrene is 30% (by mass).
• IR 3,4 motifs The rate of IR 3,4 motifs is 8%, the rate of 1,4-trans IR motifs is 24% and the rate of 1,4-cis IR motifs is 68% (each of these three rates relates polyisoprene block).
• This “control” B SBR is prepared by a copolymerization of styrene and butadiene implemented according to paragraph 1J) above, except that the copolymerization is initiated by means of n-butyl lithium as lithiated initiator, in place of the above-mentioned lithiated polyisoprene (the co-catalyst used being the same as above).
• the SBR B obtained is subjected to the above-mentioned antioxidant treatment and to the same stripping and drying operations.
• the inherent viscosity measured for this SBR B is 1.52 dl / g and its Mooney viscosity
• the microstructure of this “control” copolymer B is determined by the near infrared spectroscopy technique.
• the rate of BR 1,4-trans is 83%
• the rate of BR 1,4-cis is 14%
• the rate of BR 1,2 is 3% (each of these three rates relates to butadiene units ).
• the rate of styrene is 30% (by mass). 2) Composition of rubber A according to the invention based on said copolymer A SBR-IR, in comparison with a composition B "control" based on copolymer SBR B
• each composition A, B devoid of reinforcing filler
• copolymer A or B 100
• composition A, B is prepared in an internal mixer by thermomechanical work in one step which lasts 5 min. for a pallet speed of 50 revolutions / min., until the same maximum drop temperature of 100 ° C is obtained, while the incorporation of the crosslinking system is carried out on a “homo-finisher” at 30 ° C.
• Cross-linking is carried out at 165 ° C for 25 min.
• composition A according to the invention base of said copolymer A with SBR-IR blocks, is lowered compared to those obtained with the “control” composition B, based on the “control” SBR B copolymer.
• Rubber composition A ' accordinging to the invention based on said copolymer A (SBR-IR), in comparison with a "control" composition B' based on said SBR copolymer B.
• compositions A ′ and B ′ were tested here, which each comprise 65 phr of carbon black of series 300 as reinforcing filler, unlike the uncharged compositions of Example 1.
• the formulation of each composition A ′, B ' is as follows (in pce): copolymer A or B 100
• composition A ', B' is prepared in an internal mixer by thermo-mechanical work in one step which lasts 5 min. for a pallet speed of 80 revolutions / min., until the same maximum drop temperature of 160 ° C is obtained, while the incorporation of the crosslinking system is carried out on a “homo-finisher” at 30 ° C.
• Crosslinking is carried out at 150 ° C for 20 min.
• composition A ' As regards the properties in the crosslinked state of these compositions loaded with carbon black, it is deduced therefrom that the hysteretic properties (at low and strong deformations) of composition A 'according to the invention, based on said copolymer A with SBR- blocks IR and carbon black, are improved compared to those of the “control” composition B 'based on said SBR B copolymer and the same carbon black.
• Rubber composition C according to the invention based on a copolymer C functionalized according to the invention with two SBR-IR blocks, in comparison with a “control” composition D based on a functionalized SBR D.
• This functionalized copolymer C is prepared by copolymerization of styrene and butadiene implemented according to the process described in paragraph 1J) of Example 1 above
• SBR-IR block copolymer C thus functionalized is subjected to the antioxidant treatment and to the stripping and drying operations mentioned above in Example 1.
• copolymer C is 1.51 dl g and the Mooney ML viscosity (l + 4) at 100 ° C is approximately 50.
• microstructure of this copolymer C is determined by the NMR technique C.
• the rate of BR 1,4-trans is 78%, the rate of BR 1,4-cis is 17% and the rate of BR 1,2 is 5% (each of these three rates relates to butadiene units ).
• the rate of styrene is 31% (by mass).
• IR 3,4 units The percentage of IR 3,4 units is 5%, the percentage of I 1,4-trans units is 23% and the percentage of IR 1,4-cis units is 72% (each of these three rates relates polyisoprene block).
• This “control” functionalized SBR D is prepared by copolymerization of styrene and butadiene implemented according to the process described in paragraph 1J) of Example 1 above, except that the copolymerization is initiated by means of n-butyl. lithium as a lithiated initiator, in place of the lithiated polyisoprene (the co-catalyst used being the same as above), and the reaction is stopped with 2 equivalents of 4,4′-bis (N, N-diethylamino) benzophenone compared to lithium.
• the SBR D thus functionalized is subjected to the above-mentioned antioxidant treatment and to the same stripping and drying operations.
• the inherent viscosity measured is 1.43 dl / g.
• the number-average molecular mass of this SBR D obtained, determined by SEC, is 100,000 g / mol.
• the microstructure of this copolymer D is determined by the 13 C NMR technique.
• the rate of BR 1,4-trans is 83%, the rate of BR 1,4-cis is 14% and the rate of BR 1,2 is 3%.
• the rate of styrene is 31% (by mass).
• the functionalization rate, evaluated by N NMR, is 66%.
• each composition C, D is as follows (in pce): Copolymer C or D 100
• composition C, D is prepared in an internal mixer by thermomechanical work in one step which lasts 5 min. for a pallet speed of 80 revolutions / min., until the same maximum drop temperature of 160 ° C is obtained, while the incorporation of the crosslinking system is carried out on a “homo finisher” at 30 ° C.
• Cross-linking is carried out at 150 ° C for 20 min.
• composition C As regards the properties in the crosslinked state of these compositions C and D charged with carbon black, it is deduced therefrom that the hysteretic properties (at low and strong deformations) of composition C according to the invention, based on said functionalized copolymer C to SBR-IR blocks, are improved compared to those of the “control” composition D based on said control copolymer D also functionalized.
• Rubber composition E according to the invention based on a star E copolymer according to the invention with two SBR-IR blocks, in comparison with a “control” composition F based on a star SBR F.
• the polyisoprene is continuously prepared in a 32.5 liter capacity reactor, which is equipped with a turbine type agitator. Cyclohexane and isoprene are introduced continuously into this reactor on the one hand according to the respective mass ratios of 100/20 and, on the other hand, a solution of 12500 ⁇ mol of active sec-butyllithium (s-BuLi ) per 100 g of isoprene.
• s-BuLi active sec-butyllithium
• the flow rates of the different solutions are adjusted so that the average residence time is 40 min.
• the reactor temperature is maintained at 70 ° C.
• the conversion to monomers is 100%.
• the level of residual butyllithium is determined on a sample, by means of an adduct which is obtained by means of benzophenone and which is assayed by the technique of gas chromatography using a chromatograph of denomination " HP
• the number-average molecular mass of the living polyisoprene thus obtained is 8400 g / mol.
• This tonometry technique is implemented using an osmometer sold under the name "Gonotec” and of the model "Osmomat 090".
• the glass transition temperature Tg of this polyisoprene is -64 ° C., and the rate of linkages 3.4 is 8%.
• This lithiated polyisoprene is stored under nitrogen at a temperature of 10 ° C. No change in the titer is observed, during storage for several weeks under nitrogen pressure at this temperature.
• Cyclohexane, butadiene and styrene are introduced into a 32.5 1 reactor at respective mass flow rates of 100/12/8.
• 600 micromoles are injected for 100 g of monomers of the living polyisoprene solution described in paragraph 1. 1. 1).
• the different flow rates are adjusted so that the average residence time in the reactor is 40 min.
• the temperature is maintained at 95 ° C.
• the conversion rate which is measured on a sample taken at the outlet of the reactor, is 65%, and the inherent viscosity, which is measured at 0J g / dl in toluene, is 1.63 dl / g.
• the copolymer thus treated is separated from its solution by a stripping operation with steam, then it is dried on a roller tool at 100 ° C for 20 min, to obtain the star copolymer E with SBR-IR blocks according to the invention.
• the inherent viscosity of this copolymer E is 1.87 dl / g, and its viscosity ML (l + 4) at 100 ° C is 55.
• the number average molecular weight of the copolymer, determined by SEC, is 80,000 g / mol.
• microstructure of this copolymer E is determined by the 13 C NMR technique.
• the SBR block of this copolymer E contains 31% of styrene (by mass) and, for its butadiene part, 77% of 1,4 trans units.
• the mass fraction of the polyisoprene block in this copolymer E is 7%.
• This polyisoprene block comprises 8% of 3,4 units, 24% of 1,4 trans units and 68% of 1,4 cis units.
• This SBR F star is prepared by copolymerization of styrene and butadiene using the method described in the preceding paragraph 1. 1. 2), except that the amount of barium ethyldiglycolate is 525 micromoles per 100 g of monomers ( the Al / Ba ratio still being 3.5) and that the 600 micromoles per 100 g of living polyisoprene monomers are replaced by 1100 ⁇ mol / 100 g of active n-BuLi monomers, for the initiation of this copolymerization.
• the conversion rate at the outlet of the reactor is 68%, and the inherent viscosity of the SBR obtained, before addition of 210 micromoles per 100 g of tris- (nonylphenyl) phosphite monomers, is 1.44 dl / g.
• the SBR is subjected to the aforementioned antioxidant treatment and to the said stripping and drying operations.
• the inherent viscosity of the copolymer F thus obtained is 1.79 dl / g, and its viscosity ML is 55.
• the number average molecular weight of the copolymer, determined by SEC, is 71,000 g / mol.
• this copolymer F is identical to that mentioned above for the SBR block of said copolymer E.
• composition E is as follows (in pce):
• composition E, F is prepared in an internal mixer by thermomechanical work in one step which lasts 5 min. for a pallet speed of 80 revolutions / min., until the same maximum drop temperature of 160 ° C is obtained, while the incorporation of the crosslinking system is carried out on a “homo-finisher” at 30 ° C.
• Crosslinking is carried out at 150 ° C for 20 min. The results are reported in the following table 4
• composition E As regards the properties in the crosslinked state of these compositions E and F charged with carbon black, it is deduced therefrom that the hysteretic properties (at low and strong deformations) of composition E according to the invention, based on said star copolymer E to SBR-IR and carbon black blocks are improved compared to those of the “control” composition F based on said star copolymer SBR F and the same carbon black.
• Rubber composition G according to the invention based on a linear copolymer G according to the invention with two SBR-IR blocks, in comparison with a “control” composition H based on a linear SBR H.
• This linear copolymer G is prepared by using the method described in paragraph 1. 1. 2) of Example 4 for said copolymer E, except that:
• the amount of barium ethyldiglycolate is here 230 micromoles per 100 g of monomers (the Al Ba ratio always being 3.5);
• Example 4 The added amount of living polyisoprene (prepared according to the protocol described in 1JJ) of Example 4 is here 480 micromoles per 100 g of monomers;
• the conversion rate at the outlet of the reactor is 60%, the number-average molecular mass of the block copolymer G (linear SBR-IR) obtained is 99,000 g / mol and its inherent viscosity is 1.93 dl / g.
• the copolymer obtained is subjected to the abovementioned antioxidant treatment and to the said stripping and drying operations.
• the viscosity ML (l + 4) at 100 ° C. of the copolymer G thus obtained is 56.
• This linear copolymer H is prepared by using the method described in paragraph 1. 1) of this example 5 for said copolymer G, except that: the amount of barium ethyldiglycolate is here 365 micromoles per 100 g of monomers (the Al / Ba ratio always being 3.5);
• the living polyisoprene is here replaced by an amount of n-butyllithium of 770 micromoles per 100 g of monomers;
• the conversion rate at the reactor outlet is 68%, and the inherent viscosity of the linear SBR-IR block copolymer H obtained is 1.83 dl / g.
• the number average molecular weight of this copolymer H is 83,000 g / mol.
• the copolymer obtained is subjected to the abovementioned antioxidant treatment and to said stripping and drying operations.
• the viscosity ML (l + 4) at 100 ° C. of the copolymer H thus obtained is 55.
• the microstructure of this copolymer H (measured by 13 C NMR) is identical to that mentioned above for the SBR block of said copolymer E of the example 4.
• composition G H is as follows (in pce):
• composition G, H is prepared in an internal mixer by thermomechanical work in one step which lasts 5 min. for a pallet speed of 80 revolutions / min., until the same maximum drop temperature of 160 ° C is obtained, while the incorporation of the crosslinking system is carried out on a “homo-finisher” at 30 ° C.
• Crosslinking is carried out at 150 ° C for 20 min.
• composition G As regards the properties in the crosslinked state of these compositions G and H charged with carbon black, it is deduced therefrom that the hysteretic properties (at low and strong deformations) of composition G according to the invention, based on said linear copolymer G with SBR-IR and carbon black blocks are improved compared to those of the “control” H composition based on said linear SBR H copolymer and the same carbon black.

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