Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
  • B60C1/0016—Compositions of the tread
• • 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
  • C08C19/26—Incorporating metal atoms into the molecule
• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L13/00—Compositions of rubbers containing carboxyl groups
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
  • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

• the present invention relates to a crosslinkable or crosslinked rubber composition having improved hysteretic properties in the crosslinked state which can be used to form a tire tread, a process for preparing such a crosslinkable composition, such a tread and a tire with reduced rolling resistance.
• the French patent document FR-A-2 740 778 may be cited in the name of the applicant, which discloses the incorporation into rubber compositions comprising, as reinforcing filler, silica in the majority (for example comprising a blend of silica and carbon black), of diene polymers carrying at the chain end a silanol function or a polysiloxane block having a silanol end.
• a functionalizing agent consisting of a cyclic polysiloxane, such as hexamethylcyclotrisiloxane, is used.
• the functionalized polymers obtained can be separated from the reaction medium, leading to their formation by steam extraction of the solvent, without their macrostructure and, consequently, their physical properties changing.
• EP-A-877 047 discloses the incorporation of such polymers having a silanol function in rubber compositions comprising, as reinforcing filler, carbon black having silica fixed to its surface . It has been established that these polymers confer rubber properties, in particular hysteretic and of reinforcement in the crosslinked state, which are improved compared to those of control compositions based on nonfunctionalized diene polymers, and which are at least analogous to those of compositions based on diene polymers comprising an alkoxysilane function.
• Functionalization along the chain can be carried out by direct metallation, in the presence of N, N, N ', N'-tetramethylethylenediamine (TMED), by means of butyl lithium or metallic sodium (as described in the documents of US patent US-A-3,978
• Such a method has the disadvantage of generally leading to cuts in the chain of the modified polymer.
• a major drawback of the use of one or the other of these two reagents is that it leads to significant changes in macrostructure for the modified polymer.
• This functionalization along the chain can also be implemented by means of carbon monoxide, either by hydroformylation followed by oxidation of the aldehyde formed (as described in the American patent document US-A-4 912 145), or by direct hydrocarboxylation of the polymer (as described in the article "A. Nait Ajjou, H. Alper, Macromolecules 29, 1784 (1996)”).
• the catalysts used for these reactions are based on rhodium or palladium.
• a drawback of this functionalization with carbon monoxide lies, on the one hand, in the drastic nature of the operating conditions and, on the other hand, in the frequent formation of a gel in the reaction medium.
• This document presents a rubber composition filled with carbon black comprising from 25 to 55 phr of polyisoprene and from 45 to 75 phr (phr: parts by weight per hundred parts of elastomeric matrix) of a diene polymer belonging to the group formed with homopolymers of conjugated dienes and copolymers of conjugated dienes with mono-olefins, such as EPDM terpolymers (of ethylene, of propylene and of a diene), part of at least one of these polymers comprising COOH functions grafted along the chain by reaction with a metal salt of unsaturated carboxylic acid, for example zinc dimethacrylate.
• a diene polymer belonging to the group formed with homopolymers of conjugated dienes and copolymers of conjugated dienes with mono-olefins, such as EPDM terpolymers (of ethylene, of propylene and of a diene), part of at least one of these polymers comprising COOH functions graf
• the composition thus obtained is supposed to have a sufficiently high rigidity for its use in an internal reinforcement gum of tire sidewalls, so as to allow the tire to run flat under satisfactory conditions.
• the Applicant has unexpectedly discovered that a crosslinkable or crosslinked rubber composition obtained by the association with an inorganic reinforcing filler of at least one diene elastomer having a molar level of units derived from conjugated dienes greater than 30% and comprising carboxylic acid functions along its chain, exhibits reduced hysteretic losses at small and large deformations, analogous to those presented by known compositions based on polymers comprising active functional groups for coupling to silica (such as the abovementioned alkoxysilane or silanol groups), while having processing properties in the non-crosslinked state which are improved compared to those of these known compositions loaded with silica and which are comparable to those of compositions loaded with silica based on non-functionalized polymers.
• composition according to the invention usable for constituting a tire tread.
• diene elastomers such as butyl rubbers, nitrile rubbers or copolymers of dienes and of alpha-olefins of the EPDM type, for example, cannot be used in the compositions according to the invention, because of their reduced rate in patterns of diene origin which makes the corresponding compositions unsuitable for constituting tire treads.
• said diene elastomer of the composition according to the invention is a "highly unsaturated" diene elastomer, that is to say a diene elastomer having a level of units of diene origin (conjugated dienes) which is greater than 50%.
• diene elastomer capable of being used in the compositions in accordance with the invention, it is possible to use: - a homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms, or
• the diene elastomer used in the compositions according to the invention can be prepared by the anionic route or by any other route, provided that it has the abovementioned characteristics.
• conjugated dienes suitable in particular are 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C1-C5 alkyl) -1,3-butadienes 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, an aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene.
• vinyl-aromatic compounds suitable are styrene, ortho-, meta-, para-methylstyrene, the commercial "vinyl-toluene" mixture, para-tertiobutylstyrene, methoxystyrenes, chlorostyrenes, vinyl mesitylene, divinylbenzene, vinylnaphthalene.
• the copolymers can contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinyl-aromatic units.
• the elastomers can have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the quantities of modifying and / or randomizing agent used.
• the elastomers can be, for example, block, statistical, sequence, microsequenced, and be prepared in dispersion or in solution. They can be coupled and / or stars or functionalized with a coupling and / or star-forming or functionalizing agent.
• polybutadienes are suitable and in particular those having a content of -1,2 units between 4% and 80% or those having a cis-1,4 content greater than 80%, synthetic polyisoprenes, copolymers of butadiene-styrene and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content of -1,2 bonds of the butadiene part of between 4% and 65%, a content of trans-1,4 bonds of between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a glass transition temperature (Tg) of -40 ° C to -80 ° C, isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of between -25 ° C and -50 ° C.
• Tg
• butadiene-styrene-isoprene copolymers especially those having a styrene content of between 5% and 50% by weight and more particularly between 10% and 40%, an isoprene content of between 15% and 60% are suitable.
• the diene elastomer of the composition in accordance with the invention is chosen from the group of highly unsaturated diene elastomers constituted by polybutadians (BR), synthetic polyisoprenes (LR), butadiene-styrene copolymers ( SBR), butadiene-isoprene copolymers (BIR), isoprene-styrene copolymers (SLR), butadiene-styrene-isoprene copolymers (SBIR) or a mixture of two or more of these compounds.
• BR polybutadians
• LR synthetic polyisoprenes
• SBR butadiene-styrene copolymers
• BIR butadiene-isoprene copolymers
• SLR isoprene-styrene copolymers
• SBIR butadiene-styrene-isoprene copolymers
• the diene elastomer belongs to the family consisting of polybutadians, butadiene-styrene copolymers and butadiene-styrene-isoprene copolymers.
• the diene elastomer used is a butadiene-styrene copolymer prepared in solution having a styrene content included between 20% and 30% by weight, a content of vinyl bonds of the butadiene part of between 15% and 65%, a content of trans-1,4 bonds between 15% and 75% and a Tg of between -20 ° C and -55 ° C
• the diene elastomer used is a butadiene-styrene copolymer prepared as an emulsion, and it preferably has a total amount of emulsifier which is less than 3.5 phr (phr: parts by weight per hundred parts of elastomer).
• diene elastomers which are obtained from any anionic initiator, whether it is mono-functional or poly-functional, or non-anionic, are considered in the invention.
• an anionic initiator containing an alkali metal such as lithium, or an alkaline earth metal such as barium.
• organolithium initiators suitable in particular are those comprising one or more carbon-lithium bonds.
• organolithium initiators suitable in particular are those comprising one or more carbon-lithium bonds.
• aliphatic organolithians such as ethyllithium, n-butyllithium (nBuLi), isobutyllithium, polymethylene dilithium such as 1-4 dilithiobutane.
• Lithium amides can also be used, which are obtained from an acyclic or cyclic secondary amine, such as pyrrolidine or hexamethyleneimine.
• diene elastomers which are initiated by transition metal compounds, such as titanium compounds for example, or by rare earths, such as neodymium.
• the polymerization is, as known to those skilled in the art, preferably carried out in the presence of an inert solvent which can be, for example, an aliphatic or alicyclic hydrocarbon such as pentane, hexane, iso-octane, cyclohexane, methylcyclohexane, cyclopentane, or an aromatic hydrocarbon such as benzene, toluene or xylene.
• an inert solvent can be, for example, an aliphatic or alicyclic hydrocarbon such as pentane, hexane, iso-octane, cyclohexane, methylcyclohexane, cyclopentane, or an aromatic hydrocarbon such as benzene, toluene or xylene.
• This polymerization can be carried out continuously or discontinuously. It is generally carried out at a temperature between 20 ° C and 120 ° C, preferably between 30 ° C and 100
• the functionalization of the diene elastomers thus obtained by COOH functions along the chain can be advantageously carried out by implementing the process which is described in French patent application No. 99 05746 in the name of the applicant, which relates to a generally the functionalization of all polymers comprising at least one double bond, for example polymers obtained from monomers such as isoprene, butadiene, isobutylene, a vinyl aromatic compound or terpolymers of ethylene, propylene and d 'a diene.
• This process essentially consists of:
• diisobutyl aluminum hydride is used.
• This first step is advantageously carried out in an inert hydrocarbon solvent, such that the number of moles of agent derived from aluminum per 1000 g of starting polymer is between 0.05 and 5 moles, and preferably between 0.05 and 0.5 mole.
• this first step is carried out at a temperature between 20 ° C and 100 ° C and, even more preferably, between 50 ° C and 70 ° C.
• anhydrides are preferably used as electrophilic agent, in particular carbon dioxide, for obtaining a polymer having carboxylic acid functions along the chain. It is also possible to use a cyclic anhydride, such as succinic anhydride.
• This second step is advantageously carried out in such a way that the molar ratio of the number of moles of electrophilic agent to the number of moles of agent derived from aluminum is equal to or greater than 3.
• this second step Preferably, use is made of this second step at a temperature between 20 °
• a metal complexing agent is preferably added, which also has the effect of making the reaction medium more fluid.
• This complexing agent preferably consists of a metal chelate capable of releasing at least one proton during the complexing reaction.
• acetylacetone is used for said chelate.
• Benzoyl acetone or 8-hydroxyquinoline can also be used.
• the molar ratio of the number of moles of this complexing agent to the number of moles of agent derived from aluminum is then equal to or greater than 3.
• a strong protonic acid is added to the reaction medium to perfect said stopping, for example hydrochloric acid.
• the molar ratio of the number of moles of strong protonic acid to the number of moles of agent derived from aluminum is then equal to or greater than 3.
• carboxylic acid functionalization of a diene elastomer such as a styrene-butadiene copolymer prepared in emulsion
• a diene elastomer such as a styrene-butadiene copolymer prepared in emulsion
• an unsaturated aliphatic mono-carboxylic or di-carboxylic acid for example the acrylic acid, maleic acid or fumaric acid, or a carbocyclic carboxylic acid, such as cinnamic acid.
• compositions of the invention can contain a single diene elastomer such as that mentioned above or a mixture of several of these diene elastomers.
• the diene elastomer (s) according to the invention with COOH functions along the chain can be used alone in the composition in accordance with the invention, or be used in blending with any other elastomer conventionally used in tires, such as natural rubber or a blend based on natural rubber and a synthetic elastomer, or yet another diene elastomer optionally coupled and / or star or also partially or fully functionalized other than with COOH functions along the chain. It will be noted that the improvement in the properties of the rubber composition according to the invention will be all the higher, the proportion of said conventional elastomer (s) in the composition according to the invention will be reduced.
• this or these conventional elastomers may if necessary be present in the composition according to the invention in an amount ranging from 1 to 70 parts by weight per 100 parts by weight of diene elastomer (s) according to the invention with COOH functions along the chain.
• the term "reinforcing inorganic filler” means, 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 present in the composition of the invention in an amount equal to or greater than 40 phr (phr: parts by weight per hundred parts of diene elastomer (s)).
• this reinforcing organic filler is present in the majority in the reinforcing filler of the composition of the invention, in such a way that its mass fraction in said reinforcing filler is greater than 50%.
• said reinforcing inorganic filler is, in whole or at least mainly, silica (Si ⁇ 2).
• the silica used can be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET surface as well as a CTAB specific surface, both less than 450 m 2 / g, even if the highly dispersible precipitated silicas are preferred.
• the BET specific surface is determined in a known manner, according to the Brunauer-Emmet-Teller method described in "The Journal of the American Chemical
• 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.
• preferential highly dispersible silicas mention may be made of Perkasil KS 430 silica from Akzo, BV 3380 silica from Degussa, Zeosil 1165 MP and 1115 MP silica from Rhodia, Hi- silica Sil 2000 from the company PPG, the Zeopol 8741 or 8745 silicas from the Huber company, treated precipitated silicas such as for example the silicas "doped" with aluminum described in application EP-A-0 735 088.
• reinforcing inorganic filler is also understood to mean mixtures of different fillers reinforcing inorganics, 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 NI 15, N134, N234, N339, N347, N375 mention may be made of blacks NI 15, N134, N234, N339, N347, N375.
• black / silica blends or blacks partially or entirely covered with silica are suitable for constituting the reinforcing filler.
• reinforcing inorganic fillers comprising carbon blacks modified by silica
• the fillers which are marketed by the company CABOT under the name "CRX 2000”, and which are described in the patent document international WO-A-96/37547.
• reinforcing inorganic filler it is also possible to use, without limitation,
• - aluminas (of formula Al 2 O 3 ), such as aluminas with high dispersibility which are described in European patent document EP-A-810 258, or also
• the mass fraction of this carbon black in said reinforcing filler is preferably chosen to be less than or equal to 30%.
• the rubber composition according to the invention also conventionally comprises a reinforcing inorganic filler / elastomer matrix (also called coupling agent) bonding agent, which has the function of ensuring a sufficient bonding (or coupling), of a nature chemical and / or physical, between said inorganic charge and the matrix, while facilitating the dispersion of this morganic charge within said matrix.
• a reinforcing inorganic filler / elastomer matrix also called coupling agent
• Coupled agent is understood to mean more precisely an agent capable of establishing a sufficient connection, of 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 ("X" function) capable of physically and / or chemically bonding to the elastomer, for example by means of 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.
• 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 known as "symmetrical” or “asymmetrical” according to their particular structure, are used, as described for example in patents US Pat. No. 3,842,111, US Pat. 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 C r C ls alkylene groups or C 6 -C 12 arylene groups, more particularly C r C 10 , especially C r C 4 alkylene, in particular propylene) ;
• the radicals R 1 substituted or unsubstituted, identical or different from each other, represent an alkyl group in - g, cycloalkyl in C 5 -C 18 or aryl in C 6 -C lg (preferably alkyl groups in -Cg, cyclohexyl or phenyl, in particular C 1 -C 4 alkyl groups, more particularly methyl and / or ethyl).
• radicals R 2 substituted or unsubstituted, identical or different, represent an alkoxyl group - g cycloalkoxy or C 5 -C ls (preferably alkoxyl groups-C6 cycloalkoxy or C 5 -C 3, more preferably alkoxyl groups in -, in particular methoxyl and / or ethoxyl).
• n is a fractional number, preferably included in a field from 2 to 5.
• polysulfurized alkoxysilanes are more particularly of bis (disulfides, disulfide or tetrasulfide) of bis (alkoxyl (C 1 -C 4) alkyl (C 1 - C 4) silylalkyl (C 1 -C 4 alkyl)), such as, for example, the bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulphides.
• TESPD bis (3-triethoxysilylpropyl) tefrasulfide, in short TESPT, of formula [(C 2 H 5 O) 3 Si (CH 2 ) 3 S 2 ] 2 or bis disulfide (triethoxysilylpro ⁇ yle) is used in particular , abbreviated as TESPD, of formula [(C 2 H 5 O) 3 Si (CH 2 ) 3 S] 2 .
• 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 polysulfides), or also by the company Witco under the Silquest Al 589.
• the TESPT is sold, for example, by the company Degussa under the name Si69 (or X50S when it is supported at 50% by weight on carbon black), or by the company Osi Specialties under the name Silquest A1289 (in both cases, commercial mixture of polysulphides with an average value for n which is close to 4).
• compositions in accordance with the invention also comprise, in addition to the diene elastomer (s) containing carboxylic acid functions along the chain and said reinforcing inorganic filler, plasticizers, pigments, antioxidants, anti-ozone waxes, a system of crosslinking based on either sulfur and / or peroxide and / or bismaleimides, crosslinking activators comprising zinc monoxide and stearic acid, extension oils, one or more silica covering agents such as as alkoxysilanes, polyols, or amines.
• compositions can be such that the diene elastomer containing carboxylic acid functions is extended to a paraffinic, aromatic or naphthenic oil, with an amount of extension oil between 0 and 50 phr.
• the invention also relates to a process for the preparation of a crosslinkable rubber composition in accordance with the invention.
• thermo-mechanical working time of the constituents of said composition with the exception of the crosslinking system and at a maximum temperature of between 130 ° C. and 200 ° C., followed by a second mechanical working time implemented at a temperature lower than that of said first time and during which said crosslinking system is incorporated, said first time comprising:
• the Applicant has also unexpectedly discovered that the incorporation of magnesium monoxide during the first thermomechanical working step makes it possible to further minimize the hysteretic losses at low and strong deformations of the composition according to the invention at crosslinked state corresponding to the above definition, while conferring on this composition according to the invention processing properties in the noncrosslinked state which are analogous to those of compositions based on non-functional elastomers.
• a subject of the invention is also a tire tread which is such that it comprises a crosslinkable or crosslinked rubber composition such as that mentioned above, or which is such that it consists of this composition.
• a tire according to the invention is such that it includes this tread.
• the viscosities indicated are inherent viscosities measured at a concentration of lg / 1 in toluene at 25 ° C.
• a chromatograph sold under the name “WATERS” and under the model “150C” is used for the above-mentioned separation.
• the elution solvent is tetrahydrofuran
• the flow rate is 1 ml / min
• the system temperature is 35 ° C
• the analysis time is 30 min.
• a set of two “WATERS” columns is used, the type of which is “STYRAGEL HT6E”.
• the volume injected with the polymer sample solution is 100 ⁇ l.
• the detector is a "WATERS” differential refractometer whose model is “R401”. Chromatographic data processing software is also used, the trade name of which is "WATERS MILLENIUM”.
• b) In order to calculate the rate of COOH functions (in meq / kg of polymer) and the number of corresponding functional units per polymer chain, an assay method was used according to the 1 H NMR technique, after esterification with a excess of diazomethane, reagent known to react with COOH functions. More specifically, this method consists in obtaining, using diazomethane, methyl ester functions from the COOH functions which have been fixed on the elastomer, with a view to indirectly and quantitatively accessing the rates of COOH functions by 1 H NMR
• the diazomethane is prepared beforehand as follows. It is obtained by the action of alcoholic potash on N-methyl-N-nitroso-paratoluene sulfonamide, in the presence of diethyl ether and at the temperature of melting ice. The ethereal phase containing the reagent is then recovered by simple distillation.
• the esterification reaction is then carried out in the following manner.
• the elastomer thus treated is then dried in an oven at 50 ° C., under vacuum and under a nitrogen atmosphere.
• a 1 H NMR analysis is then carried out in the following manner.
• a sample of the polymer thus esterified is dissolved in carbon sulphide.
• a spectrometer marketed under the name BRUKER AC200 is used for the analysis of the 1 H NMR signal.
• the characteristic signal of the three methyl protons of COOCH 3 allows quantitative access to the initial rate of COOH functions of the functional polymer.
• compositions of the invention are evaluated as follows:
• a styrene / butadiene copolymer is first prepared by injecting 167 g of styrene, 476 g of butadiene and 2000 ppm of tefrahydrofuran (THF) into a 10-liter reactor containing 6.4 liters of deaerated heptane.
• the impurities are neutralized using n-BuLi, then 0.0038 mol of n-BuLi is added as well as 0.0011 mol of sodium tertiobutylate used as a randomizing agent.
• the polymerization is carried out at 55 ° C.
• 0.006 mol of methanol is injected into the reactor.
• the polymer solution is stirred for 15 minutes at 55 ° C.
• the polymer is antioxidized by the addition of 0.8 phr of 2,2'-methylene bis (4-methyl-6-tertiobutylphenol) and 0.2 phr of N- (1,3-dimethylbutyl) -N'-p-phenylenediamine, then recovered by stripping with steam and dried on a cylinder tool at 100 ° C.
• the S-SBR A thus obtained has the following characteristics:
• the polymer is antioxidized by the addition of 0.8 phr of 2,2 '-methylene bis (4-methyl-6-tert-butylphenol) and 0.2 phr of N- (1,3-dimethylbutyl) -N'-p-phenylenediamine, then recovered by stripping with steam and dried on a cylinder tool at 100 ° C.
• the measurement of the level of functionalized chains is carried out by N NMR, after purification of the polymer sample by a series of three coagulations in methanol, redissolved in toluene. This rate of functionalized chains is expressed by means of this technique in milliequivalents per kilogram of polymer (meq / kg).
• the NMR * H spectrum is characterized by ranges at 0 and -0.1 ppm corresponding to the group -Si (CH 3 ) 2 -OH.
• S-SBR B X H NMR analysis provides a rate of functions of 4.5 meq / kg, which, given the molecular weight Mn of the polymer is about 70% of functionalised chains.
• the aforementioned SEC technique was also used to determine the molecular weight distributions relating to samples of these polymers.
• the percentages of styrene, 1,4-cis chains, 1,4-trans chains and 1,2 chains of this starting copolymer are respectively 25%, 28%, 32% and 40%.
• this starting solution contains 0.2 phr of the antioxidant Nl, 3-dimethylbutyl- N'-phenyl-p-phenylenediamine and 0.2 phr of the antioxidant 2,2 '-methylene bis (4-methyl-6-t-butylphenol).
• Nl 3-dimethylbutyl- N'-phenyl-p-phenylenediamine
• 2,2 '-methylene bis (4-methyl-6-t-butylphenol 2,2 '-methylene bis (4-methyl-6-t-butylphenol
• the functionalization is then carried out in the same reactor, at 65 ° C. and for 6 hours, by means of a pressurization of 6 bars with carbon dioxide.
• This functionalization is carried out under identical operating conditions, for the preparation of the elastomers S-SBR C, S-SBR D and S-SBR E.
• the reaction is then stopped, first with acetylacetone according to an acetylacetone / aluminum molar ratio of 12, then with hydrochloric acid according to a hydrochloric acid / aluminum molar ratio of 7.5.
• an antioxidant consisting of 2,2 '-methylene-bis (4-methyl-6-t-butylphenol
• a second stripping is then carried out in an acid medium in order to be able to completely eliminate the residual isovaleric acid, which is a by-product of the carboxylation of the isobutyl radicals contained in HDiBA.
• the elastomer thus treated is drained on a cylinder tool at 100 ° C, which is dried under vacuum at 60 ° C (inert nitrogen atmosphere) for 18 hours.
• a first method consisted in determining the carboxylic acid functions by acidimetry and in calculating, on the one hand, the rate of these COOH functions per kg of polymer and, on the other hand, the number of units per chain on the basis of '' an Mn (determined by osmometry) of 180,000 g / mole.
• This acidimetry assay was carried out by dissolving a sample of the elastomer thus prepared in a mixture of toluene and orthodichlorobenzene.
• the COOH functions are neutralized in the presence of pyridine, with a solution of tetrabutylammonium hydroxide in isopropanol. Equivalence is detected by potentiometry.
• the polymerizations are carried out at 5 ° C. with stirring, in 250 ml Steinie bottles, according to methods known to those skilled in the art.
• the water used is deionized and bubbled under a stream of nitrogen to remove all traces of dissolved oxygen.
• an emulsifying solution consisting of 5.45 g of n-dodecylamine, 1.59 g of acetic acid and 543.5 ml of water is introduced. This emulsifying solution is heated to 60 ° C and stirred until the n-dodecylamine is completely dissolved.
• the polymerization is stopped after 6 hours and 30 minutes by the addition of 0.025 g of hydroquinone.
• 10 g of NaCl are added per 100 g of elastomer and the whole is stirred for a few minutes.
• 150 ml of toluene as well as 1 pce of an antioxidant mixture comprising 80% of the product of designation "AO2246" and 20% of N- (1,3- dimethylbutyl) -N'-phenyl-p-phenylenediamine (commonly known as "6PPD").
• the solution is again stirred.
• the latter is finally stripped and the polymer is dried between 30 and 50 ° C. 15 g of a polymer are obtained, the characteristics of which are indicated below.
• the polymerization is stopped after 18 hours by the addition of 0.025 g of hydroquinone.
• the polymer is recovered in the same way as in said paragraph D /.
• the E-SBR G thus obtained has a total amount of emulsifier which is less than 3 phr (the treatment of the polymer obtained by solubilization and by stripping having the effect of reducing the final amount of emulsifier in the E-SBR G).
• the polymerizations are carried out at 5 ° C. with stirring, in a 10 l stainless steel reactor, according to methods known to those skilled in the art.
• the water used is deionized and bubbled under a stream of nitrogen to remove all traces of dissolved oxygen.
• an emulsifying solution consisting of 37.19 g of n-dodecylamine, 10.95 g of acetic acid and 540 ml of water is introduced. This emulsifying solution is heated to 60 ° C. and stirred until the n-dodecylamine is completely dissolved.
• the reactor is cooled to 12 ° C. and 1164 g of butadiene and 1006 g of styrene are added thereto.
• the temperature of the reactor is lowered to 5 ° C.
• 2.55 g of paramenthane hydroxide are added as well as 10.52 g of mercaptan diluted in 68 g of styrene.
• the polymerization is stopped by adding 128 ml of a 40 g / l solution of hydroquinone.
• the polymerization is carried out as in paragraph F /, except that 5.78 g of methacrylic acid are added to the emulsifying solution.
• the polymer is dried in an oven under nitrogen at 30 ° C. and is used in this form for rubber tests (see paragraph 11 / below).
• the characteristics of the dry polymer are indicated in the table below.
• the Mooney ML viscosity (l + 4) of the oil-extended polymer is 48.
• the E-SBR I thus obtained has a total amount of emulsifier which is less than 3 phr (the treatment of the polymer obtained by solubilization and by stripping having the effect of reducing the final amount of emulsifier in the E-SBR G).
• Rubber compositions comprising a reinforcing inorganic filler and the aforementioned elastomers:
• the five elastomers of paragraph I (S-SBR A, S-SBR B, S-SBR C, S-SBR D and S-SBR E) were used for the preparation of rubber compositions A, B, C, D and E of the tourism tread type.
• compositions A, B, C, D and E has the following formulation (expressed in phr: parts by weight per hundred parts of elastomer):
• Aromatic oil (ENERFLEX 65) 40
• thermo-mechanical work is carried out for 4 to 5 minutes, up to a maximum drop temperature of approximately 160 ° C.
• the elastomer block is then recovered and cooled.
• thermomechanical working step is carried out in the same mixer for a period of 3 to 4 minutes, with the addition of the antioxidant and zinc monoxide, up to a maximum drop temperature of 160 ° C. about.
• the first aforementioned time of thermo-mechanical work is thus achieved, it being specified that the average speed of the pallets during this first time is 45 rpm.
• compositions B, C, D and E are higher than that relating to composition A and, on the other hand, that the hysteretic properties (at low and strong deformations) are greatly improved compared to those presented by said composition A.
• compositions C, D and E according to the invention have Mooney “mixture” values which are much lower than that of composition B based on an elastomer functionalized by reaction with rhexamethylcyclotrisiloxane. These Mooney values testify to a workability for the compositions of the invention which is improved compared to that of a composition based on a known functional elastomer.
• compositions C, D and E are close to that of composition A based on a non-functional elastomer S-SBR A, in particular with regard to said compositions C and D (the Mooney value of the composition E according to the invention being between those of compositions A and B).
• the elastomers S-SBR C, S-SBR D and S-SBR E which comprise COOH functions along the chain and, more particularly, S-SBR D, confer on compositions loaded with the silica practically the same rubber properties in the crosslinked state as those imparted by a known functional elastomer to such a composition, and in addition with an ability to be used close to that imparted by a non-functional elastomer.
• the non-functional S-SBR A of paragraph I was used for the preparation of a rubber composition A ′ of the passenger tread type, which differs from the above composition A in that it comprises in addition to a carboxylic acid.
• composition D has the following formulation (expressed in phr: parts by weight per hundred parts of elastomer): Elastomer 100
• Aromatic oil (ENERFLEX 65) 40
• the carboxylic acid used for composition A ′ is oleic acid, and it is incorporated into S-SBR A before the addition of the other additives, so as to carry out a first joint chewing of S- SBR A and oleic acid.
• the level of oleic acid which is added to S-SBR A is 0.62 phr, which corresponds to a stoichiometry of 4 units which are fixed on the chain of the elastomer, by analogy with the S-SBR D of the invention (composition A ′ has the formulation indicated above for compositions A and D, with in addition 0.62 phr of oleic acid).
• compositions are produced, in a first time of thermo-mechanical work, by two stages separated by a cooling phase, then, in a second time of finish, by mechanical work.
• thermo-mechanical work is carried out for 4 to 5 minutes, up to a maximum drop temperature of approximately 160 ° C.
• the elastomer block is then recovered and cooled.
• thermomechanical working step is carried out in the same mixer for a period of 3 to 4 minutes, with the addition of the antioxidant and zinc monoxide, up to a maximum drop temperature of 160 ° C. about.
• thermo-mechanical working time is thus achieved, it being specified that the average speed of the pallets during this first time is 45 rpm.
• compositions thus obtained are then calendered, either in the form of plates
• Crosslinking is carried out at 150 ° C for 40 min.
• composition A Concerning the properties in the crosslinked state, it will be noted, on the one hand, that the ratio MA300 / MA100 relating to composition A 'is very close to that of composition A and, on the other hand, that the hysteretic properties of composition A ′ is not significantly improved compared to those presented by composition A.
• compositions B ′ and D ′ are produced, in a first time of thermomechanical work, by two stages separated by a cooling phase, then, in a second time of finishing, by mechanical work.
• thermo-mechanical work is carried out for 4 to 5 minutes, up to a maximum drop temperature of approximately 160 ° C.
• the elastomer block is then recovered and cooled.
• thermomechanical working step is carried out in the same mixer for a period of 3 to 4 minutes, with the addition of the antioxidant and zinc monoxide, up to a maximum drop temperature of 160 ° C. about.
• the first aforementioned thermo-mechanical working time is thus achieved, it being specified that the average speed of the pallets during this first time is 85 rpm (unlike the examples in paragraph II. A /).
• the mixture thus obtained is recovered, it is cooled and then, in an external mixer (homo-finisher), the sulfur and the sulfenamide are added at 30 ° C., mixing everything again for a period of 3 to 4 minutes (mechanical work ).
• compositions thus obtained are then calendered, either in the form of plates (of a thickness ranging from 2 to 3 mm) or thin sheets of rubber, for the measurement of their physical or mechanical properties, or in the form of directly usable profiles , after cutting and / or assembling to the desired dimensions, for example as semi-finished products for tires, in particular for treads.
• Crosslinking is carried out at 150 ° C for 40 min. It will be noted that the introduction of all of the zinc monoxide (ZnO) is conventionally carried out during the second thermomechanical working step, in order to obtain crosslinkable compositions B ′ and D ′.
• ZnO zinc monoxide
• said S-SBR D was also used for the preparation of a composition D "of the touring tread type, this composition D" being distinguished only from the composition D 'mentioned above, in that the introduction of all of the zinc monoxide is carried out during the first thermomechanical working step, and not in the usual way during the second thermomechanical working step (this composition D "also has the same ingredients and the same wording as in paragraphs II. A / and II. B / above).
• compositions D 'and D "according to the invention Attempts have been made to compare the properties of compositions D 'and D "according to the invention with one another, on the one hand, and with those of composition B', on the other hand.
• the ratio MA300 / MA100 relating to the preferred composition D "according to the invention is greater than that of the other composition D ′ according to the invention and , on the other hand, that the hysteretic properties to small deformations of composition D "are improved compared to those presented by composition D 'and also compared to those presented by composition B' (based on an elastomer functionalized by reaction with hexamethylcyclotrisiloxane).
• composition D according to the invention has a Mooney" mixture "value which is much lower than that of composition B '. This value of
• the S-SBR D elastomer which comprises COOH functions along the chain gives composition D ′′, which is loaded with silica and is obtained by introduction of ZnO during the first working step thermo-mechanical, hysteretic properties with low deformations which are improved compared to those imparted by a known functional elastomer to such a composition, and furthermore exhibits an identical or even improved processability compared to that presented by the composition D ′, which is also based on the elastomer S-SBR D while being loaded with silica but is obtained by usual introduction of ZnO during the second thermomechanical working step.
• composition D "allows to obtain hysteretic properties with small and strong deformations improved compared to those of composition D 'but also compared to composition B' for small deformations .
• composition D ′′ has, in the uncrosslinked state, a Mooney viscosity value of the mixture clearly lower than that of the composition B ′ and substantially close to that of the composition A based on 'A non-functional S-SBR.
• This composition D "' therefore has a workability which is clearly improved compared to that of the compositions based on conventional functional elastomers.
• the composition D ′′ according to the invention has hysteretic properties with low deformations which are improved compared to those of a composition based on a usual functional elastomer while considerably improving the hysteretic properties with strong deformation (losses at 60 ° C.) compared to those of the composition D 'without MgO.
• This composition D' also has a processability which is close to that of the" control "composition A based on 'a non-functional elastomer.
• compositions D "" of the tread type "tourism" based on said S-SBR D were compared with those of compositions A, B ', D'and D "' tested in the paragraphs precedents.
• MgO magnesium oxide
• composition D "" according to the invention makes it possible to obtain properties in the non-crosslinked and crosslinked state which are similar to those of the other composition D "" according to the invention.
• composition D "" makes it possible to obtain hysteretic properties (tg ⁇ max at 23 ° C) greatly improved compared to those of compositions A, B 'and D', with a marked improvement in the ability to the implementation relative to that of composition B 'based on a known functional elastomer.
• compositions D “and D” “according to the invention exhibit hysteretic properties with strong deformations which are improved compared to those of compositions A or D '.
• composition F being based on the non-functional E-SBR F of paragraph I. D / above and composition G being based on E-SBR G comprising acrylic acid functions along the chain (see paragraph I. E / above).
• compositions F and G are produced, in a first time of thermo-mechanical work, by two stages separated by a cooling phase, then, in a second time of finishing, by mechanical work.
• thermo-mechanical work is carried out for 4 to 5 minutes, up to a maximum drop temperature of approximately 160 ° C.
• the elastomer block is then recovered and cooled.
• thermomechanical working step is carried out in the same mixer for a period of 3 to 4 minutes, with the addition of the antioxidant and zinc monoxide, up to a maximum drop temperature of 160 ° C. about.
• the first aforementioned thermo-mechanical working time is thus achieved, it being specified that the average speed of the pallets during this first time is 85 rpm.
• composition G is greater than that of composition F (based on non-functional E-SBR F) and, on the other hand, that the hysteretic properties (losses at 60 ° C and tan ( ⁇ ) max at 23 ° C) are improved compared to those presented by composition F. It also appears that this composition G has a Mooney viscosity of mixture which is analogous to that of composition F, that is to say an ability to process which is close to that of said composition F.
• the elastomer E-SBR G which has acrylic acid functions along the chain, makes it possible to obtain compositions having rubber properties in the crosslinked state which are improved compared to those of "control" compositions based on an elastomer prepared as a non-functional emulsion, and also having an ability to be used which is close to that of such "control" compositions.
• compositions F, G and G 'of the “touring” tread type have been compared with one another, the compositions F and G having been defined in the preceding paragraph and the new composition G' also being based on the elastomer E-SBR G with acrylic acid functions along the chain and differentiating only from composition G by the fact that all of the ZnO is introduced into the internal mixer during the first working step thermo-mechanical and at a temperature of 120 ° C.
• Table 8 The results are given in table 8.
• composition G ′ exhibits low deformation hysteretic properties which are improved compared to those of composition G.
• composition G ′ according to the invention has a Mooney viscosity of mixture which is substantially identical to that of composition F (based on an elastomer prepared in non-functional emulsion).
• this composition G ′ exhibits hysteretic properties with low deformations which are improved compared to those obtained with the compositions F and G, and in addition a workability which is close to that of the said composition. "Witness" F.
• composition H being based on the non-functional E-SBR H and extended to the oil of paragraph I F / above and composition I being based on E-SBR I comprising methacrylic acid functions along the chain (see paragraph I.
• compositions H and I The formulation used for each of these compositions H and I is the following (in pce): Elastomer extended to oil 127.5
• compositions H, I is produced in the manner which has been described in paragraph IL F / above (in particular with conventional introduction of ZnO during the second thermomechanical working step).
• composition I according to the invention based on an elastomer with acid functions methacrylic along the chain
• control composition H based on an elastomer prepared as a non-functional emulsion
• the E-SBR I elastomer makes it possible to obtain compositions having rubber properties in the crosslinked state which are improved compared to those of “control” compositions based on an elastomer prepared in emulsion. non-functional, and also having an ability to use which is close to that of such “control” compositions.
• composition F 60 ° C and tan ( ⁇ ) max at 23 ° C) of composition F according to the invention are improved compared to those of composition H. It also turns out that this composition V makes it possible to obtain hysteretic properties at small deformations which are improved compared to those of composition I.
• composition F has a Mooney viscosity of mixture which is substantially identical to that of said “control” composition H based on an elastomer prepared as a non-functional emulsion.
• the composition F exhibits hysteretic properties with low deformations which are improved compared to those obtained with the compositions H and I, and it furthermore exhibits a workability which is close to that of the said “witness” composition H.

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