Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • 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
  • B60C1/0025—Compositions of the sidewalls
• • 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
  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/006—Additives being defined by their surface area
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/06—Polymer mixtures characterised by other features having improved processability or containing aids for moulding methods
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2312/00—Crosslinking

Definitions

• the field of the present invention is that of rubber compositions reinforced with carbon black and comprising a highly saturated diene elastomer, the rubber compositions being particularly intended for use in a tire, more particularly in a tire sidewall.
• a tire usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads.
• a sidewall is an elastomeric layer placed outside the carcass reinforcement relative to the internal cavity of the tire, between the crown and the bead so as to completely or partially cover the area of the carcass reinforcement extending from the top to the bead.
• the various constituent components of the crown, of the carcass reinforcement, of the beads and of the sidewalls are assembled to form a tire.
• the assembly step is followed by a step of shaping the bandage to give the toroidal shape to the assembly before the press cooking step.
• the sidewalls are exposed both to the action of ozone and to deformation cycles such as bending during the rolling of the tire.
• the deformation cycles combined with the action of ozone can cause cracks or cracks to appear in the sidewall, preventing the use of the tire independently of the wear of the tread. Consequently, rubber compositions are sought which are very cohesive in order to constitute, for example, tire sidewalls by their capacity to undergo large deformations without breaking, even in the presence of a crack initiator.
• copolymers having a lower sensitivity to oxidation such as for example highly saturated diene elastomers, elastomers comprising ethylene units at a molar rate greater than 50 mol% of the monomer units of the elastomer.
• Mention may be made, for example, of the copolymers of ethylene and of 1,3-diene which contain more than 50 mol% of ethylene, in particular the copolymers of ethylene and of 1,3-butadiene.
• the Applicant has discovered a rubber composition comprising a copolymer of ethylene and of 1,3-diene with a molar content of ethylene greater than 50% which exhibits an improved compromise between the properties of cohesion and resistance to ozone.
• a first subject of the invention is a rubber composition based at least on natural rubber, a copolymer of ethylene and a 1,3-diene, a carbon black and a system of crosslinking, the level of natural rubber in the rubber composition being greater than 50 phr, the ethylene units in the copolymer representing more than 50 mol% of the monomer units of the copolymer.
• a second object of the invention is a tire which comprises a rubber composition according to the invention, preferably in a portion or all of a sidewall of the tire.
• any range of values designated by the expression “between a and b” represents the range of values greater than “a” and less than “b” (that is, limits a and b excluded) while any range of values designated by the expression “from a to b” means the range of values ranging from “a” to "b” (that is to say including the strict limits a and b).
• the abbreviation “pce” means parts by weight per hundred parts of elastomer (of the total elastomers if several elastomers are present).
• composition based on
• a composition comprising the mixture and / or the in situ reaction product of the various constituents used, some of these basic constituents (for example the elastomer, the filler or the constituents of the vulcanization system or other additive conventionally used in a rubber composition intended for the manufacture of tires) being capable of, or intended to react with each other, at least in part, during the various phases of manufacture of the composition intended for the manufacture of tires.
• the expression "all of the monomer units of the elastomer” or “all of the monomer units of the elastomer” means all of the repeating constituent patterns of the elastomer which result from the insertion of the monomers in the elastomer chain by polymerization. Unless otherwise indicated, the contents of a monomer unit or repeating unit in the highly saturated diene elastomer are data in molar percentage calculated on the basis of all the monomer units of the elastomer.
• the compounds mentioned in the description can be of fossil origin or bio-based. In the latter case, they can be, partially or totally, from biomass or obtained from renewable raw materials from biomass. Are concerned in particular elastomers, plasticizers, fillers ...
• the copolymer of ethylene and 1,3-diene which is useful for the purposes of the invention is a preferably statistical elastomer, which comprises ethylene units resulting from the polymerization of ethylene.
• ethylene unit refers to the motif - (CH 2 - CH 2 ) - resulting from the insertion of ethylene into the elastomer chain.
• the ethylene units represent more than 50 mol% of the monomer units of the copolymer.
• the ethylene units in the copolymer represent more than 60%, advantageously more than 70% by mole of the monomer units of the copolymer.
• the highly saturated diene elastomer preferably comprises at most 90% by mole of ethylene unit.
• the copolymer useful for the needs of the invention also designated below under the name of highly saturated diene elastomer, also comprises 1,3-diene units resulting from the polymerization of a 1,3-diene.
• 1,3-diene unit refers to the units resulting from the insertion of 1,3-diene by a 1,4 addition, a 1,2 addition or a 3,4 addition into the isoprene case.
• the 1,3-diene units are those for example of a 1,3-diene or of a mixture of 1,3-dienes, the 1,3-diene (s) having 4 to 12 carbon atoms, such as any particularly 1,3-butadiene and isoprene.
• the 1,3-diene is 1,3-butadiene.
• the copolymer of ethylene and a 1,3-diene contains units of formula (I).
• the presence of a 6-membered saturated cyclic unit, 1,2-cyclohexanediyl, of formula (I) as a monomer unit in the copolymer can result from a series of very specific insertions of ethylene and 1,3-butadiene in the polymer chain during its growth.
• the copolymer of ethylene and a 1,3-diene contains units of formula (II).
• the copolymer of ethylene and a 1,3-diene contains units of formula (I) and of formula (II).
• the highly saturated diene elastomer is devoid of units of formula (I).
• the copolymer of ethylene and a 1,3-diene preferably contains units of formula (II).
• the highly saturated diene elastomer comprises units of formula (I) or units of formula (II) or alternatively units of formula (I) and units of formula (II)
• the molar percentages of the units of formula (I) ) and units of formula (II) in the highly saturated diene elastomer, respectively o and p preferably satisfy the following equation (eq. 1), more preferably the equation (eq. 2), o and p being calculated on the basis of all the monomer units of the highly saturated diene elastomer.
• the highly saturated diene elastomer is preferably a random copolymer.
• the highly saturated diene elastomer in particular according to the first embodiment, according to the second embodiment, according to the third embodiment and according to the fourth embodiment, can be obtained according to various synthetic methods known to man. of the profession, in particular as a function of the targeted microstructure of the highly saturated diene elastomer. Generally, it can be prepared by copolymerization of at least one 1,3-diene, preferably 1,3-butadiene, and ethylene and according to known synthesis methods, in particular in the presence of a catalytic system comprising a metallocene complex.
• the highly saturated diene elastomer can also be prepared by a process using a catalytic system of the type preformed like those described in documents WO 2017093654 A1, WO 2018020122 A1 and WO 2018020123 A1.
• the highly saturated diene elastomer can consist of a mixture of ethylene and 1,3-diene copolymers which differ from each other by their microstructures or by their macrostructures.
• the highly saturated diene elastomer is preferably an ethylene copolymer and 1,3-butadiene, more preferably a copolymer of ethylene and random 1,3-butadiene.
• the essential characteristic of the rubber composition according to the invention is to comprise more than 50 phr of natural rubber.
• the level of natural rubber in the rubber composition is greater than 55 phr and less than or equal to 80 phr. More preferably, it varies in a range from 60 to 80 phr.
• the level of copolymer of ethylene and of a 1,3-diene useful for the needs of the invention, in particular of copolymer of ethylene and of 1,3-butadiene in the rubber composition preferably varies in a range ranging from 20 to 40 pce.
• the rubber composition comprises from 20 to 40 phr of ethylene and 1,3-diene copolymer, in particular of ethylene and 1,3-butadiene copolymer, and from 60 to 80 phr of natural rubber.
• the essential characteristic of the rubber composition useful for the needs of the invention is to include a carbon black as a reinforcing filler.
• a reinforcing filler typically consists of nanoparticles whose average size (by mass) is less than a micrometer, generally less than 500 nm, most often between 20 and 200 nm, in particular and more preferably between 20 and 150 nm.
• the level of carbon black in the rubber composition is within a range ranging from 25 phr to 65 phr. Below 25 phr, the level of reinforcement may prove to be insufficient for certain applications of the rubber composition in the tire. Above 65 phr, the rubber composition may become too rigid for certain applications of the rubber composition in the tire.
• the level of carbon black is advantageously in a range from 25 phr to 65 phr.
• carbon blacks all carbon blacks are suitable, in particular the blacks conventionally used in tires or their treads (so-called pneumatic grade blacks).
• pneumatic grade blacks there may be mentioned more particularly the reinforcing carbon blacks of the 100, 200, 300 series, or the blacks of the 500, 600 or 700 series (ASTM grades), such as, for example, the blacks N115, N134, N234, N326, N330. , N339, N347, N375, N550, N683, N772).
• the carbon black is preferably a carbon black of the 300 series or a carbon black having a BET specific surface ranging from 70 m 2 / g to 100 m 2 / g ⁇
• the BET specific surface can be measured according to standard ASTM D6556-09 [multipoint method (5 points) - gas: nitrogen - relative pressure range R / R0: 0.05 to 0.30].
• the crosslinking system can be based either on sulfur, or on sulfur and / or peroxide and / or bismaleimide donors.
• the crosslinking system is preferably a vulcanization system, that is to say a system based on sulfur (or of a sulfur donor agent) and on a vulcanization accelerator.
• Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and thiourea types can be used as vulcanization accelerator. xanthates.
• sulfenamide compounds N-cyclohexyl-2-benzothiazyl sulfenamide (“CBS”), N, N-dicyclohexyl-2-benzothiazyl sulfenamide (“DCBS”), N- ter-butyl-2-benzothiazyl sulfenamide (“TBBS”) and mixtures of these compounds.
• CBS N-cyclohexyl-2-benzothiazyl sulfenamide
• DCBS N-dicyclohexyl-2-benzothiazyl sulfenamide
• TBBS N- ter-butyl-2-benzothiazyl sulfenamide
• Sulfur is used at a preferential rate of between 0.3 phr and 10 phr, more preferably between 0.3 and 5 phr.
• the primary vulcanization accelerator is used at a preferential rate of between 0.5 and 10 phr, more preferably of between 0.5 and 5 phr.
• Crosslinking if necessary vulcanization, is carried out in known manner at a temperature generally between 130 ° C and 200 ° C, for a sufficient time which can vary for example between 5 and 90 min depending in particular on the baking temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.
• the rubber composition useful for the needs of the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended to be used in a tire, such as, for example, processing agents, plasticizers, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants.
• plasticizers are suitable all plasticizers conventionally used in tires.
• oils which are preferably non-aromatic or very weakly aromatic, chosen from the group consisting of naphthenic oils, paraffinic oils, MES oils, TDAE oils, vegetable oils, ether plasticizers, ester plasticizers.
• the rubber composition When the rubber composition constitutes a part or all of the sidewalls of a tire, it preferably comprises a plasticizer, the content of which in the rubber composition is adjusted to give adequate rigidity for use on the sidewall.
• the amount of plasticizer then varies from 20 phr to 60 phr for a carbon black content comprised in a range ranging from 25 phr to 65 phr.
• the amount of plasticizer varies from 20 to 50 phr.
• the rubber composition can be manufactured in suitable mixers, using two successive preparation phases according to a general procedure well known to those skilled in the art: a first working phase or thermo-mechanical kneading (sometimes referred to as a "non-phase”). productive ”) at high temperature, up to a maximum temperature between 110 ° C and 190 ° C, preferably between 130 ° C and 180 ° C, followed by a second phase of mechanical work (sometimes referred to as" productive phase ”) at a lower temperature, typically less than 110 ° C., for example between 40 ° C. and 100 ° C., the finishing phase during which the sulfur or the sulfur donor and the vulcanization accelerator are incorporated.
• a first working phase or thermo-mechanical kneading (sometimes referred to as a "non-phase”).
• productive at high temperature, up to a maximum temperature between 110 ° C and 190 ° C, preferably between 130 ° C and 180 ° C
• a second phase of mechanical work sometimes referred
• the first (non-productive) phase is carried out in a single thermomechanical step during which is introduced, into a suitable mixer such as a usual internal mixer, all the necessary constituents, the possible setting agents. in complementary and other miscellaneous additives, with the exception of sulfur and the vulcanization accelerator.
• the total duration of the kneading, in this non-productive phase is preferably between 1 and 15 min.
• the sulfur and the vulcanization accelerator are then incorporated at low temperature, generally in an external mixer such as a cylinder mixer; the whole is then mixed (productive phase) for a few minutes, for example between 2 and 15 min.
• the final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for characterization in the laboratory, or else extruded, to form for example a rubber profile used for the manufacture of semi-finished products. finishes such as a tire sidewall.
• the tire another object of the invention, comprises a rubber composition in accordance with the invention.
• the tire has a sidewall, a portion or all of which is made of a rubber composition according to the invention, which composition preferably comprises a plasticizer.
• the rubber composition comprising a plasticizer constitutes the sidewalls of the tire.
• the amount of plasticizer varies from 20 phr to 60 phr, advantageously from 20 phr to 50 phr .
• the carbon black has a BET specific surface ranging from 70 m 2 / g to 100 m 2 / g.
• the rubber composition and the tire in accordance with the invention can be in the raw state (that is to say before crosslinking) or in the cooked state (that is to say after crosslinking).
• the microstructure of the elastomers is determined by 1 H NMR analysis, supplemented by 13 C NMR analysis when the resolution of the 1 H NMR spectra does not allow the allocation and quantification of all the species.
• the measurements are carried out using a BRUKER 500 MHz NMR spectrometer at frequencies of 500.43 MHz for the observation of the proton and 125.83 MHz for the observation of the carbon.
• an HRMAS 4mm z-grad probe is used for non-soluble elastomers but having the capacity to swell in a solvent. Spectra are acquired at rotational speeds from 4000Hz to 5000Hz.
• a liquid NMR probe is used to observe the proton and the carbon in decoupled mode from the proton.
• insoluble samples are done in rotors filled with the analyzed material and a deuterated solvent allowing the swelling, in general deuterated chloroform (CDCI3).
• the solvent used must always be deuterated and its chemical nature can be adapted by a person skilled in the art.
• the quantities of material used are adjusted so as to obtain spectra with sufficient sensitivity and resolution.
• soluble samples are dissolved in a deuterated solvent (about 25 mg of elastomer in lmL), generally deuterated chloroform (CDCI3).
• a deuterated solvent about 25 mg of elastomer in lmL
• CDCI3 deuterated chloroform
• the solvent or solvent mixture used must always be deuterated and its chemical nature can be adapted by a person skilled in the art. In both cases (soluble sample or swollen sample):
• a single pulse sequence of 30 ° is used.
• the spectral window is adjusted to observe all of the resonance lines belonging to the molecules analyzed.
• the number of accumulations is adjusted in order to obtain a signal to noise ratio sufficient for the quantification of each pattern.
• the recycling time between each pulse is adapted to obtain a quantitative measurement.
• a 30 ° single pulse sequence is used with a proton decoupling only during acquisition to avoid the “Nuclear Overhauser” (NOE) effects and remain quantitative.
• the spectral window is adjusted to observe all of the resonance lines belonging to the molecules analyzed.
• the number of accumulations is adjusted in order to obtain a signal to noise ratio sufficient for the quantification of each pattern.
• the recycling time between each pulse is adapted to obtain a quantitative measurement.
• the force and the tear deformation are measured on a test specimen stretched at 500 mm / min to cause rupture of the test specimen.
• the tensile test piece consists of a rubber plate of parallelepiped shape, for example of thickness between 1 and 2 mm, length between 130 and 170 mm and width between 10 and 15 mm, the two lateral edges being each covered lengthwise with a cylindrical rubber bead (diameter 5 mm) allowing anchoring in the jaws of the traction machine.
• 3 very fine cuts of length between 15 and 20 mm are made using a razor blade, half-width and aligned lengthwise of the test piece, one at each end and one in the center of the latter, before the start of the test.
• the force (N / mm) to be exerted to obtain the rupture is determined and the elongation at break and the rupture stress are measured.
• the test was conducted in air, at a temperature of 100 ° C. The higher the values of strain and breaking force or of energy at break, the better the resistance to crack propagation of the rubber composition although having crack initiators, which translates a good cohesion of the rubber composition. The results are given in base 100 relative to a control.
• the elongation at break (AR%) and rupture stress (CR) tests are based on standard NF ISO 37 of December 2005 on a H2 type dumbbell test piece and are measured at a tensile speed of 500 mm / min.
• the elongation at break is expressed in% of elongation.
• the breaking stress is expressed in MPa. All these tensile measurements are carried out at 60 ° C. The results are given in base 100 relative to a control.
• Ozone resistance was assessed using the trapezium test where cracking is determined after the sample has been extended under static conditions. Stressed samples are more likely to crack.
• the samples have a dog bone shape and have been cut with a die and loaded into a V-shaped support.
• the V-shaped support allows deformations of the sample to be obtained from 10% to 150%.
• the V-shaped support with the samples is placed in an ozone chamber.
• the conditions of the ozone chamber were fixed at 50 parts per hundred million ozone (ppcm) and at a temperature of 38 ° C for 144h.
• the results of the trapeze tests indicate the elongation at which the first cracks appeared. The higher the elongation for which the cracks appear, the more the material is resistant to cracking under ozone.
• compositions thus obtained are then calendered either in the form of plates (thickness 2 to 3 mm) or of thin sheets of rubber for measuring their physical or mechanical properties, or extruded to form, for example, a profile for a tire.
• the four rubber compositions contain a highly saturated diene elastomer with a molar level of ethylene greater than 50% and natural rubber.
• the rubber compositions C1 and C2 are not in accordance with the invention, since the content of natural rubber is 40 phr and 50 phr respectively.
• the rubber compositions C3 and C4 are in accordance with the invention, the content of natural rubber being greater than 50 phr.
• the highly saturated diene elastomer is prepared according to the following procedure: 30 mg of metallocene [ ⁇ Me SiFlu Nd (p-BH 4 ) Li (THF) ⁇ , the symbol Flu representing the fluorenyl group of formula C I3 H 8 ] are introduced into a first Steinie bottle in a glove box.
• a catalytic solution After 10 minutes of temperature contact ambient is obtained a catalytic solution.
• the catalytic solution is then introduced into the polymerization reactor.
• the temperature in the reactor is then increased to 80 ° C.
• the reaction starts by injecting a gaseous mixture of ethylene and 1,3-butadiene (80/20 mol%) into the reactor.
• the polymerization reaction takes place at a pressure of 8 bars.
• the proportions of metallocene and co-catalyst are respectively 0.00007 mol / L and 0.0004 mol / L.
• the polymerization reaction is stopped by cooling, degassing of the reactor and addition of ethanol.
• An antioxidant is added to the polymer solution.
• the copolymer is recovered by drying in a vacuum oven.
• results are shown in Table 1. With the exception of the score assigned to quantify the severity of the ozone attack, the results are indicated as a performance index relative to a control.
• the value of the control, composition C2 being arbitrarily fixed at 100, a value greater than 100 indicates improved performance.
• composition F1 to F3 The good cohesion properties obtained with the compositions comprising a highly saturated diene elastomer and enriched with natural rubber (composition F1 to F3) make it possible to envisage their use as a sidewall for a tire, as the results of Table 2 show in comparison with a control rubber composition (composition T) conventionally used in tire sidewalls.

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• Compositions Of Macromolecular Compounds (AREA)
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• 2018
  • 2018-10-09 FR FR1859357A patent/FR3086949B1/fr not_active Expired - Fee Related
• 2019
  • 2019-10-03 WO PCT/FR2019/052340 patent/WO2020074806A1/fr not_active Ceased
  • 2019-10-03 JP JP2021518735A patent/JP7531484B2/ja active Active
  • 2019-10-03 CN CN201980064825.0A patent/CN112789315B/zh active Active
  • 2019-10-03 EP EP19801947.3A patent/EP3864083B1/fr active Active
  • 2019-10-03 US US17/282,614 patent/US20210340359A1/en not_active Abandoned

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