Classifications

• • 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
  • C08K13/00—Use of mixtures of ingredients not covered by one single of the preceding main groups, each of these compounds being essential
  • C08K13/02—Organic and inorganic ingredients
• • 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
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/548—Silicon-containing compounds containing sulfur
• • 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
  • B60C9/00—Reinforcements or ply arrangement of pneumatic tyres
• • 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
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L21/00—Compositions of unspecified rubbers
• • 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
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2296—Oxides; Hydroxides of metals of zinc
• • 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
• • 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
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T152/00—Resilient tires and wheels
  • Y10T152/10—Tires, resilient
  • Y10T152/10495—Pneumatic tire or inner tube
  • Y10T152/10765—Characterized by belt or breaker structure
  • Y10T152/1081—Breaker or belt characterized by the chemical composition or physical properties of elastomer or the like

Definitions

• the present invention relates to tires and reinforcements for the reinforcement of the top of these tires, also called “belts”.
• compositions of diene elastomers reinforced with an inorganic filler such as silica used to constitute all or part of the rubbery matrix of such reinforcements as well as to the binding agents used for the coupling of these reinforcing inorganic fillers and diene elastomers.
• a tire with a radial carcass reinforcement in a known manner, comprises a tread, two inextensible beads, two sidewalls connecting the beads to the tread and a belt disposed circumferentially between the carcass reinforcement and the tread, this belt consisting of various plies (or “layers") of rubber reinforced or not by reinforcing elements (“reinforcements”) such as cables or monofilaments, of the metallic or textile type.
• a tire belt generally consists of at least two superimposed belt plies, sometimes called “working” plies or “crossed” plies, the reinforcements of which are arranged practically parallel to each other inside a ply, but crossed from one ply to the other, that is to say inclined, symmetrically or not, with respect to the median circumferential plane, by an angle which is generally between 10 ° and 45 ° depending on the type of tire considered.
• Each of these two crossed plies consists of a rubber matrix, sometimes called "calendering gum", coating the reinforcements.
• the crossed plies can be completed by various other plies or layers of auxiliary rubber, of variable widths depending on the case, with or without reinforcements; by way of example, there are simple rubber cushions, so-called “protective” plies responsible for protecting the rest of the belt from external attacks, perforations, or even so-called “hooping" plies comprising reinforcements oriented substantially according to the circumferential direction (so-called “zero degree” plies), whether radially external or internal with respect to the crossed plies.
• the third requirement is particularly strong for envelopes heavy Weight- tires designed to be retreaded one • or more times when the treads they comprise reach a critical degree of wear after prolonged travel.
• the elastomeric compositions of tire belts are generally based on isoprene elastomer, most often natural rubber, and carbon black as the majority reinforcing filler. They may contain, in small proportion, a reinforcing inorganic filler such as silica intended to improve the adhesive properties of rubber with regard to metallic or textile reinforcements.
• Application EP-A-0 722 977 (or US-A-5 871 957) has proposed replacing all of the carbon black with silica, combined with a coupling agent of the silane-polysulfide type, with a view to lower the hysteresis of the tires and thus reduce the rolling resistance of the tires.
• inorganic filler particles In known manner, for reasons of reciprocal affinities, inorganic filler particles have an unfortunate tendency, in an elastomeric matrix in the raw state, to agglomerate with one another. These interactions, in addition to the fact that they can limit the dispersion of the filler and therefore the reinforcing properties, tend to increase the consistency, the viscosity of the compositions during thermo-mechanical mixing operations, and therefore to make their processability more difficult. only in the presence of carbon black, as soon as the inorganic charge rate is relatively high. This increase in hardness is also detrimental to industrial calendering operations in the raw state of the compositions for the preparation of the metallic or textile fabrics targeted, or even incompatible in certain cases with such operations.
• the invention thus offers to the crown reinforcement reinforcements of the tires, as well as to these tires themselves, an overall compromise of new and particularly advantageous properties.
• a first subject of the invention relates to a tire belt comprising at least one elastomeric composition based on at least one isoprene elastomer, an inorganic reinforcing filler and a silane-polysulfide, characterized in that said silane-polysulfide responds to formula (I):
• the symbols R and R identical or different, each represent a monovalent hydrocarbon group chosen from alkyl, linear or branched, having from 1 to 6 carbon atoms and the phenyl radical;
• the symbols R which may be identical or different, each represent hydrogen or a monovalent hydrocarbon group chosen from alkyl, linear or branched, having from 1 to 4 carbon atoms and alkoxyalkyls, linear or branched, having from 2 to 8 atoms of carbon ;
• the symbols Z which may be identical or different, are divalent linking groups containing from 1 to 18 carbon atoms;
• x is an integer or fractional number equal to or greater than 2.
• the invention also relates to any tire comprising such a belt.
• the tires of the invention are particularly intended to equip motor vehicles of the touring type, SUV ("Sport Utility Vehicles"), two wheels (in particular motorcycles), airplanes, such as industrial vehicles chosen from vans, "Heavy goods vehicles” - ie metro, bus, road transport equipment ' (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering machinery -, other transport or handling vehicles.
• SUV Sport Utility Vehicles
• two wheels in particular motorcycles
• airplanes such as industrial vehicles chosen from vans, "Heavy goods vehicles” - ie metro, bus, road transport equipment ' (trucks, tractors, trailers), off-road vehicles such as agricultural or civil engineering machinery -, other transport or handling vehicles.
• the invention also relates to the use of a belt according to the invention for the manufacture of new tires or for retreading used tires, very particularly in the case of truck tires.
• the belts according to the invention are prepared by a process which constitutes another object of the present invention; said method comprises the following steps:
• a reinforcing inorganic filler into an isoprene elastomer; a silane-polysulphide as coupling agent, • thermomechanically knead everything, in one or more batches, until reaching a maximum temperature between 110 ° C and 190 ° C;
• silane-polysulphide corresponds to formula (I) above.
• the invention also relates, per se, to the use of a silane-polysulphide of formula (I) mentioned above for the manufacture of a tire belt comprising at least one isoprene composition based on a reinforcing inorganic filler.
• the rubber compositions are characterized before and after curing, as indicated below.
• the Mooney plasticity measurement is carried out according to the following principle: the composition in the raw state (Le., Before baking) is molded in a cylindrical enclosure heated to 100 ° C. After one minute of preheating, the rotor turns within the test tube at 2 revolutions / minute and the useful torque is measured to maintain this movement after 4 minutes of rotation.
• the measurements are carried out at 150 ° C. with an oscillating chamber rheometer, according to standard DIN 53529 - part 3 (June 1983).
• the evolution of the rheometric torque as a function of time describes the evolution of the stiffening of the composition as a result of the vulcanization reaction.
• the measurements are processed according to DIN 53529 - part 2 (March 1983): tj is the induction time, that is to say the time necessary for the start of the vulcanization reaction; t ⁇ (for example t 95 ) is the time necessary to reach a conversion of ⁇ %, that is to say ⁇ % (for example 95%) of the difference between the minimum and maximum couples.
• the conversion speed constant denoted K (expressed in min "1 ), of order 1, calculated between 30% and 80% conversion, is also measured, which makes it possible to assess the vulcanization kinetics.
• the dynamic properties are measured on a viscoanalyzer (Metravib NA4000), according to standard ASTM D5992-96.
• the response of a sample of vulcanized composition (4 mm thick cylindrical test piece and 400 mm 2 section) is recorded, subjected to a sinusoidal stress in alternating single shear, at the frequency of 10 Hz, at a temperature of 100 ° C.
• a deformation amplitude sweep is carried out from 0.1 to 50% (outward cycle), then from 50% to 1% (return cycle); for the return cycle, the maximum value of the loss factor, recorded tan ( ⁇ ) max , is recorded.
• the resistance to fatigue and to the propagation of notches (with initial initiation), expressed in number of cycles or in relative units (ur), is measured in a known manner on a test tube comprising a notch of 1 mm and subjected to repeated pulling of low frequency up to an elongation of 20%>, using a Monsanto device (type "MFTR"), until rupture of the test piece, according to French standard ⁇ F T46-021.
• MFTR Monsanto device
• the essential characteristic of the tire belts of the invention is to incorporate, into all or part of their rubbery matrix, at least one elastomeric composition based on at least each of the following constituents: (i) one (at least one) isoprene elastomer; (ii) one (at least one) inorganic filler as reinforcing filler, (iii) one (at least one) specific silane-polysulfide of formula (I) as coupling agent (inorganic filler / isoprene elastomer).
• composition based on
• a composition comprising the mixture and / or the in situ reaction product of the various constituents used, some of these base constituents being capable of, or intended to react between them, at least in part, during the different stages of manufacturing rubber compositions, belts and tires, in particular during their vulcanization.
• iene elastomer or rubber
• elastomer an elastomer derived at least in part (Le., A homopolymer or a copolymer) from diene monomers, that is to say from monomers carrying two carbon double bonds -carbon, conjugated or not.
• essentially unsaturated diene elastomer is meant here a diene elastomer derived at least in part from conjugated diene monomers, having a proportion of units or units of diene origin (conjugated dienes) which is greater than 15%> (%> molar ); in the category of “essentially unsaturated” diene elastomers, the expression “highly unsaturated” diene elastomer is understood in particular to mean a diene elastomer having a rate of units of diene origin (conjugated dienes) which is greater than 50%.
• isoprene elastomer in a known manner, a isoprene homopolymer or copolymer, in other words a diene elastomer chosen from the group consisting of natural rubber (NR ), synthetic polyisoprenes (IR), the various isoprene copolymers and mixtures of these elastomers.
• NR natural rubber
• IR synthetic polyisoprenes
• isoprene copolymers mention will be made in particular of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene copolymers (SBIR).
• This isoprene elastomer is preferably natural rubber or a synthetic polyisoprene of the cis-1,4 type.
• polyisoprenes are preferably used having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%).
• the compositions of the invention may contain diene elastomers other than isoprene, preferably in the minority (Le., For less than 50% by weight, or less than 50 pce); in such a case, the isoprene elastomer more preferably represents 75 to 100% by weight of the total diene elastomer, ie 75 to 100 phr (parts by weight per hundred parts of elastomer).
• diene elastomers other than isoprenics
• any highly unsaturated diene elastomer chosen in particular from the group consisting of polybutadienes (BR), in particular the cis-1,4 or 1,2-syndiotactic polybutadienes and those having a content of 1,2 units between 4% and 80%>
• butadiene copolymers in particular styrene-butadiene copolymers (SBR), and in particular those having a styrene content between 5 and 50% ) by weight and more particularly between 20%) and 40%> by weight, a content of -1,2 bonds of the butadiene part of between 4% and 65% o, a content of trans-1,4 bonds of between 30 %> and 80%
• SBIR styrene-butadiene copolymers- isoprene
• the belt of the invention when intended for a passenger-type tire, if such a cut is used, it is preferably a mixture of SBR and BR which is used in cutting with natural rubber up to 'up to 25%) by weight (i.e. a maximum of 25 pce).
• the belt of the invention is particularly intended for a truck tire, whether it is a new or used tire (in the case of retreading).
• the isoprene elastomer is preferably used alone, that is to say without cutting with another diene or polymer elastomer; more preferably still, this isoprene elastomer is exclusively natural rubber.
• the term “reinforcing inorganic filler” is understood, in 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 white or inorganic filler used as reinforcing filler can constitute all or only part of the total reinforcing filler, in the latter case associated for example with carbon black.
• the reinforcing inorganic filler constitutes the majority, that is to say more than 50% of the total reinforcing filler, more preferably more than 80% of this total reinforcing filler.
• any type of reinforcing inorganic filler known for its capacity to reinforce a rubber composition which can be used for the manufacture of tires, in particular intended for the belt or their tread, can be used.
• mineral fillers of the siliceous type in particular silica (Si ⁇ 2), or of the aluminous type, in particular of alumina (AI2O3) or aluminum (oxide-) hydroxides, are suitable.
• 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, preferably from 30 to 400 m 2 / g.
• Precipitated silicas of the highly dispersible type can be used in particular, in particular when the invention is implemented for the manufacture of tires having a low rolling resistance.
• the reinforcing alumina preferably used is an alumina having a BET surface of 30 to 400 m 2 / g, more preferably between 60 and 250 m 2 / g, an average particle size at most equal to 500 nm, more preferably at most equal to 200 nm, as described in application EP-A-810 258 (or US 5,900,449).
• a preferred embodiment of the invention consists in using a reinforcing inorganic filler, in particular a silica, having a high BET specific surface area , greater than 130 m 2 / g, more preferably within a range of 150 to 250 m 2 / g, due to the high reinforcing power recognized for such loads.
• reinforcing inorganic filler is also understood to mean mixtures of various reinforcing inorganic fillers, in particular of highly dispersible silicas and / or aluminas as described above.
• the reinforcing inorganic filler can also be used in blending with carbon black, preferably in a minority proportion (Le., For less than 50%>).
• carbon black preferably in a minority proportion (Le., For less than 50%>).
• all carbon blacks are suitable, in particular those of the HAF, ISAF, SAF type, conventionally used in tires (so-called "pneumatic grade” blacks), and in particular in the belts of these tires, such as, for example, blacks of 300 series carbon (N326, N330, N339, N347, N375, etc.).
• a carbon black in combination with the reinforcing inorganic filler, a carbon black at a rate of between 2 and 20 phr, more preferably comprised within a range of 5 to 15 phr.
• a carbon black at a rate of between 2 and 20 phr, more preferably comprised within a range of 5 to 15 phr.
• the rate of reinforcing inorganic filler is between 30 and 150 phr, more preferably between 40 and 120 phr, the optimum being different depending on the intended applications.
• the level of reinforcement expected on a tire for a passenger vehicle is in known manner lower than that required on a truck tire capable of supporting heavy loads while driving at high speed in a sustained manner.
• the level of reinforcing inorganic filler is preferably greater than 50 phr, more preferably greater than 55 phr, understood for example, advantageously, between 60 and 100 phr.
• CTAB is the external surface determined according to French standard NF T 45-007 of November 1987 (method B).
• a reinforcing organic filler in particular a carbon black, could be used, covered at least in part with an inorganic layer. , for example silica, requiring the use of a coupling agent to establish the bond with the diene elastomer.
• coupling agent is meant, in known manner, an agent capable of establishing a sufficient bond, of chemical and / or physical nature, between the inorganic filler and the diene elastomer; such a coupling agent, at least bifunctional, has for example as simplified general formula "Y-A-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 the 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 diene elastomer, for example via a sulfur atom; - A represents a divalent group making it possible to connect Y and X.
• Coupling agents should in particular not be confused with simple agents for recovery of the inorganic charge which, in known manner, may comprise the "Y" function active with respect to the inorganic charge but are devoid of the function "X" activates with respect to the diene elastomer.
• Coupling agents in particular (silica / diene elastomer), have been described in a very large number of documents, the best known being bifunctional organosilanes carrying alkoxyl functions (that is to say, by definition, "alkoxysilanes ”) as” Y “functions and, as” X “functions, functions capable of reacting with the diene elastomer such as for example polysulfide functions (see for example US-A-3,842,111, US- A-3 873 489, US-A-3 997 581; the aforementioned applications EP-A-722 977, EP-A-735 088, EP-A-810 258, or international applications WO 96/37547, WO 97 / 42256, WO 98/42778, WO 99/28391, WO 00/05300, WO 00/05301, WO 01/55252, WO 01/55253, WO 02/10269).
• the bis- (trialkoxylsilylpropyl) polysulfides must be mentioned in particular, bis 3-triethoxysilylpropyl disulfide (abbreviated “TESPD”) and bis 3-triethoxysilylpropyl tetrasulfide (abbreviated "TESPT ").
• TESPD bis 3-triethoxysilylpropyl disulfide
• TESPT bis 3-triethoxysilylpropyl tetrasulfide
• TESPT of formula [(C 2 H 5 O) 3 Si (CH 2 ) 3 S] 25 is sold in particular by the company Degussa under the name Si69 (or X50S when it is supported at 50%) by weight on carbon black), in the form of a commercial mixture of polysulphides S x with an average value for x which is close to 4.
• TESPT in particular, is considered today as the product providing the best compromise in terms of safety in roasting, hysteresis and reinforcing power, for rubber compositions reinforced with a reinforcing inorganic filler such as silica.
• a reinforcing inorganic filler such as silica.
• it is the benchmark coupling agent for those skilled in the art for tires loaded with silica with low rolling resistance, sometimes qualified as “Green Tires” for the energy savings offered (or “energy- saving Green Tires "), including for the belts of these tires (see EP-A-722 977 above).
• silane-polysulfide used in the belts of tires in accordance with the invention corresponds to the general formula (I):
• R and R identical or different, each represent a monovalent hydrocarbon group chosen from alkyl, linear or branched, having from 1 to 6 carbon atoms and the phenyl radical
• R 3 identical or different, each represent hydrogen or a monovalent hydrocarbon group chosen from alkyl, linear or branched, having from 1 to 4 carbon atoms and alkoxyalkyls, linear or branched, having from 2 to 8 atoms of carbon
• the symbols Z which may be identical or different, are divalent linking groups containing from 1 to 18 carbon atoms
• x is an integer or fractional number equal to or greater than 2.
• X a polysulfide functional group (S x ) capable of forming a stable bond with the diene elastomer
• Y a polysulfide functional group
• the Z groups comprising from 1 to 18 carbon atoms represent in particular an alkylene chain, a saturated cycloalkylene group, an arylene group, or a divalent group consisting of a combination of at least two of these groups. They are preferably chosen from C 1 -C 6 alkenes and C 6 -C 2 arylenes; they can be substituted or interrupted by one or more heteroatoms, chosen in particular from S, O and N.
• R 1 and R 2 are chosen from methyl, ethyl, n-propyl and isopropyl; the symbol R is chosen from hydrogen, methyl, ethyl, n-propyl and isopropyl; the symbols Z are chosen from C 1 -C 8 alkylene.
• the symbols R 1 and R 2 are chosen from methyl and ethyl; the symbol R 3 is chosen from hydrogen, methyl and ethyl; the symbols Z are chosen from C ⁇ -C 4 alkylene, in particular methylene, ethylene or propylene, more particularly propylene - (CH 2 ) 3 -.
• polysulphides corresponding to formula (I) mention will be made in particular of bis-monoalkoxydimethylsilylpropyl polysulphides and mixtures of these polysulphides, in particular those of particular formulas (II), (III) or (IV) below. after:
• the number x is then an integer, including preferably in a range of 2 to 8.
• this number x is generally a fractional number the average value of which can vary according to the mode of synthesis adopted and the specific conditions of this synthesis.
• the polysulphide synthesized is in fact made up of a distribution of polysulphides centered on an average value (in moles) of " x "preferably ranging from 2 to 8, more preferentially from 2 to 6, even more preferably included in a range from 2 to 4.
• a silane-tetrasulfide is used.
• tetrasulfide is meant in the present application the tetrasulfide S 4 proper as well as any mixture of polysulfides S x whose average number of atoms of S (denoted "x"), per silane molecule, is between 3 and 5 , especially in a range from 3.5 to 4.5.
• MESPT mono-ethoxy-dimethylsilylpropyl tetrasulfide
• the monoethoxydimethylsilyl-propyl disulfide (abbreviated "MESPD”) of general formula (III) can be used, monoethoxylated homolog of the above-mentioned TESPD, having the structural formula (VII) (x neighbor of 2):
• Silane-polysulfide compounds corresponding to the formulas (I) to (VIII) above have been described in the prior art, for example in applications EP-A-680 997 (or US-A-5650457), WO 02 / 30939, WO 02/31041, EP-A-1 043 357 (or CA-A-2 303 559), FR-A-2 823 215 (or WO 02/83782) where they are exemplified in rubber compositions type SBR usable for the manufacture of treads for passenger car tires.
• the optimal level of coupling agent in moles / m 2 of inorganic filler is calculated from the weight ratio [coupling agent / inorganic filler], the BET surface area of the filler and the molar mass of the coupling agent (denoted M below), according to the known relationship:
• the amount of polysulphide coupling agent used in the compositions is between 10 -7 and 10 " 5 moles per m 2 of reinforcing inorganic filler. More preferably still, this amount is between 5.10" 7 and 5.10 " 6 moles per m 2 of inorganic filler.
• the silane-polysulphide content is preferably between 2 and 20 phr. Below the minimum indicated the effect is likely to be insufficient, while beyond the maximum recommended there is generally no longer any improvement, while the costs of the composition increase; for these various reasons, this content is more preferably still between 2 and 10 phr.
• silane-polysulfide of formula (I) could be grafted beforehand on the inorganic filler (for example via its alkoxysilyl function, in particular ethoxysilyl), the filler thus "precoupled” can then be linked to the diene elastomer via the free polysulfide function.
• the rubber matrices compliant belts to the invention also comprise all or some of the conventional used in rubber compositions • additives for the manufacture of tire belts, such as extender oils, plasticizers, agents to protection such as anti-ozone waxes, anti-ozone chemicals, antioxidants, anti-fatigue agents, coupling activators as described for example in applications WO00 / 05300, WO00 / 05301, WO01 / 55252, WO01 / 55253, acceptors and donors of methylene, bismaleimides or other reinforcing resins as described for example in WO02 / 10269, a crosslinking system based either on sulfur or on sulfur and / or peroxide donors, vulcanization accelerators, activators or vulcanization retardants, systems for promoting adhesion of rubber to metal such as for example metal salts or complexes (for example of cobalt, bo re, phosphorus).
• additives for the manufacture of tire belts such as extender oils, plasticizers,
• the isoprenic matrices can also contain, in addition to the silane-polysulphides described above, agents for recovery of the reinforcing inorganic filler, comprising for example the only function Y, or more generally agents for aid in the implementation which are likely to known, thanks to an improvement in the dispersion of the inorganic filler in the rubber matrix and to a lowering of the viscosity of the compositions, of improving their processability, these agents being for example alkylalkoxy-silanes, in particular alkyltriethoxy-silanes, like for example the 1-octyl-triethoxysilane marketed by the company Degussa-H ⁇ s under the name Dynasylan Octeo or the 1- hexa-decyl-triethoxysilane marketed by Degussa-H ⁇ ls under the name Si216, polyols, polyethers (for example polyethylene glycols ), primary, secondary or tertiary amines
• trialcanol-amines s hydroxylated or hydrolyzable polyorganosiloxanes, for example, ⁇ -dihydroxy-polyorganosiloxanes (in particular ⁇ , ⁇ -dihydroxy-polydimethylsilpxanes).
• the isoprenic compositions described above are intended to form all or part of the rubbery matrix of the belt of a tire, in particular of a truck tire. They can, for example, be used as a calendering rubber for a cable web of cabled fabric, whether it is a "crossed" web, a web of protection or of a hooping ply (at zero degree), or intended to form a simple cushion, strip or strip of rubber, devoid of reinforcements, disposed radially above or below the various plies of the aforementioned belt, or even interposed between them, for example to constitute an under-layer of the tread, or else placed at the lateral ends of these belt plies, 'in the "shoulder" zones of the pneumatic, for example to constitute decoupling gums.
• the appended figure schematically represents a radial section of a truck tire 1 with a radial carcass reinforcement which may or may not conform to the invention, in this general representation.
• This tire 1 has a crown 2, two sidewalls 3, two beads 4, a radial carcass reinforcement 7 extending from one bead to the other.
• the crown 2, surmounted by a tread (not shown in this very schematic figure, for simplification) is in known manner reinforced by a belt 6 consisting of at least two "crossed" crown plies, covered with at least one protective top ply, all of these plies being reinforced with metallic carbon steel cables.
• the carcass reinforcement 7 is wound around the two rods 5 in each bead 4, the reversal 8 of this reinforcement 7 being for example placed towards the outside of the tire 1 which is here shown mounted on its rim 9.
• the reinforcement of carcass 7 consists of at least one ply reinforced by so-called "radial" metal cables, that is to say that these cables are arranged practically parallel to one another and extend from one bead to the other so as to form an angle between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is located midway between the two beads 4 and passes through the middle of the belt 6) .
• the tire according to the invention of the above example has the essential characteristic of having at its apex 2 a belt 6 according to the invention, the isoprene composition based on inorganic filler and on silane-polysulphide of formula (I ) constituting the calendering gum of the belt plies 6 (two crossed plies and a protective ply, in this example).
• the gum for calendering the woven fabric that it is in the form of a ply of a certain width, close the width of the crossed plies, narrower strips or even a unitary wire sheathed in rubber, or also based on a reinforcing inorganic filler and silane-polysulfide of formula (I).
• the rubber composition based on the isoprene elastomer, the reinforcing inorganic filler and the silane-polysulfide of formula (I) present in the vulcanized state (Le., After firing), a secant module in extension (E10) which is greater than 5 MPa, more preferably between 9 and 20 MPa. It is in the areas of modules indicated above that the best endurance compromise has been recorded.
• the rubber compositions are produced in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first working phase or thermo-mechanical kneading (sometimes called a "non-productive" phase) at high temperature, up to a maximum temperature (denoted T max ) of 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 ") at a lower temperature, typically below 110 ° C., for example between 40 ° C. and 100 ° C. 5 finishing phase during which the crosslinking or vulcanization system is incorporated.
• a first working phase or thermo-mechanical kneading sometimes called a "non-productive" phase
• T max maximum temperature
• productive second phase of mechanical work
• the process for manufacturing the compositions according to the invention is characterized in that at least the reinforcing inorganic filler and the silane-polysulfide of formula (I) are incorporated by kneading with the isoprene elastomer during the first phase, called non- productive, that is to say that one introduces into the mixer and that one thermomechanically kneads, in one or more stages, at least these different basic constituents until reaching a maximum temperature of between 110 ° C. and 190 ° C, preferably between 130 ° C and 180 ° C.
• the first (non-productive) phase is carried out in a single thermomechanical step during which all the necessary basic constituents are introduced into a suitable mixer such as a conventional internal mixer. (isoprene elastomer, reinforcing inorganic filler and silane-polysulphide), then in a second step, for example after one to two minutes of mixing, any additional covering or implementing agents and other various additives, with the exception of vulcanization system; when the apparent density of the reinforcing inorganic filler is low (general case of silicas), it may be advantageous to split its introduction into two or more parts.
• a suitable mixer such as a conventional internal mixer.
• thermomechanical working step can be added to this internal mixer, after the mixture has fallen and intermediate cooling (cooling temperature preferably less than 100 ° C.), with the aim of subjecting the compositions to a complementary thermomechanical treatment, in particular to improve still the dispersion, in the elastomeric matrix, of the reinforcing inorganic filler and of its coupling agent.
• the total duration of the kneading, in this non-productive phase is preferably between 2 and 10 minutes.
• the vulcanization system is 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 5 and 15 minutes.
• the process according to the invention for preparing a tire belt according to the invention, comprising an isoprene elastomer composition based on a reinforcing inorganic filler and a silane-polysulphide coupling agent, comprises the following steps:
• silane-polysulfide corresponds to the above formula (I).
• the vulcanization or curing is carried out in known manner at a temperature of reference between 130 ° C and 200 ° C under pressure for a sufficient time which may vary for example between 5 and 90 minutes depending on the curing temperature , the vulcanization system adopted, the vulcanization kinetics and the size of the tire considered.
• the crosslinking system proper is preferably based on sulfur and a primary vulcanization accelerator, in particular a sulfenamide type accelerator.
• a primary vulcanization accelerator in particular a sulfenamide type accelerator.
• various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (especially diphenylguanidine), vulcanization retarders, etc. .
• Sulfur is used at a preferential rate of between 1 and 10 phr, more preferably of between 2 and 8 phr, in particular when the invention is applied to a tire of the Truck type.
• the primary vulcanization accelerator is used at a preferential rate of between 0.5 and 5 phr, more preferably of between 0.5 and 2 phr.
• an isoprene elastomer (or mixture of diene elastomers) is introduced into an internal mixer, filled to 70% and whose initial tank temperature is approximately 60 ° C. , if applicable), the reinforcing filler, the coupling agent, then, after one to two minutes of kneading, the various other ingredients with the exception of the vulcanization system.
• Thermomechanical work (non-productive phase) is then carried out in one or two stages (total duration of mixing equal for example to about 7 min), until a maximum "fall" temperature of around 165-170 ° C is reached. .
• the mixture thus obtained is recovered, cooled, then the vulcanization system (sulfur and primary sulfenamide accelerator) is added on an external mixer (homo-finisher) at 30 ° C, mixing everything (productive phase) for example for 3 10 min.
• compositions thus obtained are then either extradited in the form of plates (thickness of 2: to 3 mm) for the measurement of their physical or mechanical properties, or calendered to produce a wired metallic fabric forming a “working” belt ply of a truck tire.
• the purpose of this test is to demonstrate the improved performance of an isoprene composition based on a reinforcing inorganic filler (silica) and of a silane-polysulfide of formula (I), compared on the one hand with a first control composition using carbon black (without coupling agent) as reinforcing filler, on the other hand to a second control composition using silica as reinforcing filler and a conventional silane-polysulfide as coupling agent.
• compositions based on natural rubber are prepared for this.
• composition noted C-1 carbon black (control 1); composition denoted C-2: silica + TESPT (control 2); - composition denoted C-3: silica + MESPT (invention).
• compositions are intended to constitute the "calendering rubber” of working plies of a truck tire belt.
• Composition C-1 is the control composition based on carbon black
• composition C-2 is a composition based on silica according to the prior art (EP-A-722 977 cited above); only composition C-3 is in accordance with the invention.
• Their rate represents less than 10% by weight relative to the amount of reinforcing inorganic filler, less than 1% as regards the composition according to the invention.
• TESPT the standard coupling agent for silica-based compositions
• TESPT sold by the company Degussa under the name "Si69" is used in this test (x mean equal to 3.75 according to the supplier's technical sheet).
• the above MESPT was prepared as follows (see FR-A-2 823 215 above).
• the H 2 S (23 g, or 0.676 mole) is introduced by bubbling using a dip tube, ie for 45 to 60 minutes.
• the solution changes from an orange color with yellow-orange particles to a dark brown color without particles.
• the mixture Under a stream of argon, the mixture is heated at 60 ° C for 1 hour so as to complete the conversion to anhydrous Na 2 S 4 .
• the reaction medium changes from a dark brown color to a red-brown color with brown particles.
• the reaction medium is then cooled using refrigeration means (to 10-15 ° C) to reach a temperature close to 20 ° C.
• a mass of 244 g of ⁇ -chloropropylethoxydimethylsilane (1.352 moles, equivalent to 2 moles for one mole of H 2 S) is added using a peristaltic pump (10 ml / min) over 30 minutes.
• the reaction medium is then heated to 75 ⁇ 2 ° C for 4 h. During the test, the NaCl precipitates.
• a mass of 280 g of bis-monoethoxydimethylsilylpropyl tetrasulfide (0.669 mole) is then obtained in the form of an yellow-orange oil.
• a control by 1 H NMR, 29 Si NMR and 13 C NMR makes it possible to verify that the structure obtained is indeed in accordance with formula (VI).
• the average number x of sulfur atoms per MESPT molecule, determined in known manner (elementary analysis by X-ray fluorescence and GPC) is equal to 3.9 (therefore practically equal to 4).
• Tables 1 and 2 give the formulation of the three compositions (Table 1 - rate of the various products expressed in pce), their properties before and after cooking (60 min at 140 ° C).
• the vulcanization system consists of sulfur and sulfenamide.
• composition C-1 a significant rise (close to 45%) in hysteresis compared to composition C-1, synonymous with an increase in the temperature of the belt in operation, therefore a priori detrimental to its endurance; it should be noted that this rise nevertheless remains much lower than that which would have been observed at an equivalent rate of carbon black;
• compositions C-1 and C-2 are little modified between compositions C-1 and C-2.
• the replacement of carbon black by silica does not make it possible to obtain a compromise of satisfactory properties in terms of rigidity-hysteresis-processability.
• compositions C-3 and C-2 show on the other hand that the replacement of the conventional coupling agent (TESPT) by the silane-polysulfide of formula (I) (MESPT), in accordance with the invention, unexpectedly leads to a person skilled in the art: - maintaining the stiffness values (MA 10) at a satisfactory level, clearly superior to the control solution with carbon black (composition Cl), while offering
• composition C-2 a hysteresis (see tan ( ⁇ ) max ) significantly reduced compared to composition C-2, favorable to the rolling resistance and to the overall endurance of the tire and its belt; - Finally, a significant reduction in Mooney plasticity compared to composition C-2, synonymous with improved processability, in particular during calendering operations.
• Reduced baking times are particularly advantageous for belts intended for complete retreading of tires, whether it be "cold” retreading (use of a prebaked belt) or conventional "hot” retreading (use of a belt in the raw state).
• a reduced cooking time in addition to the fact that it reduces production costs, limits the overcooking (or postcooking) imposed on the rest of the envelope (" carcass ") of the used tire, already vulcanized; at the same curing time, the belts can also be cooked at a lower temperature, which is another means of preserving the" carcass "from the problem of overcooking mentioned above.

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