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
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/17—Amines; Quaternary ammonium compounds
  • C08K5/18—Amines; Quaternary ammonium compounds with aromatically bound amino groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D30/00—Producing pneumatic or solid tyres or parts thereof
  • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
  • B29D30/08—Building tyres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D30/00—Producing pneumatic or solid tyres or parts thereof
  • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
  • B29D30/38—Textile inserts, e.g. cord or canvas layers, for tyres; Treatment of inserts prior to building the tyre
  • B29D30/40—Chemical pretreatment of textile inserts before building the tyre
• • 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
  • B60C9/18—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers
  • B60C9/20—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel
  • B60C9/2003—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords
  • B60C9/2006—Structure or arrangement of belts or breakers, crown-reinforcing or cushioning layers built-up from rubberised plies each having all cords arranged substantially parallel characterised by the materials of the belt cords consisting of steel cord plies only
• • 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
  • B60C2001/0066—Compositions of the belt layers
• • 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 reinforcement of the top of these tires, also called “belts”.
• It relates more particularly to the diene elastomer compositions used to form all or part of the rubber matrix of such reinforcements, as well as to the antioxidant agents used for the anti-aging protection of such compositions.
• a tire with a radial carcass reinforcement comprises, in known manner, a tread, two inextensible beads, two flanks connecting the beads to the tread and a belt circumferentially disposed between the carcass reinforcement and the tread. tread, this belt consisting of various plies (or “layers") of rubber reinforced or not by reinforcing elements (or “reinforcements”) such as cords or monofilaments, metal or textile type.
• the tire belt generally consists of at least two superimposed layers or web plies, sometimes referred to as "working” webs or “crossed” webs, the reinforcements of which are arranged substantially parallel to each other inside a web. layer, but crossed from one layer to another, that is to say inclined, symmetrically or otherwise, with respect to the median circumferential plane, of an angle which is generally between 10 ° and 45 ° depending on the type considered.
• Each of these two crossed layers consists of a rubber matrix generally isoprenic based, sometimes called “calendering rubber", coating the reinforcements.
• the crossed layers may be supplemented by various other layers or layers of auxiliary rubber, of varying widths depending on the case, with or without reinforcements; examples of simple rubber cushions are so-called “protective” layers intended to protect the rest of the belt from external aggressions, perforations, or so-called “hooping” layers comprising reinforcements oriented substantially according to the circumferential direction (so-called “zero degree” layers), whether they are radially external or internal with respect to the crossed layers.
• the third condition requires, in particular, rubber compositions forming tire belts, that they have a very high resistance to crack propagation and thermo-oxidation, which is attained notably by the use of antioxidant agents which provide a high degree of stability. effective anti-aging protection.
• PPD p-phenylenediamine derivatives
• I-PPD N-isopropyl-N'-phenyl-p-phenylenediamine
• 6-PPD N-isopropyl-N'-phenyl-p-phenylenediamine
• a first subject of the invention relates to a tire belt comprising a rubber composition based on at least one isoprene elastomer, a reinforcing filler, a crosslinking system and an antioxidant agent, characterized in that said agent antioxidant comprises a 4,4'-bis (alkylamino) -triphenylamine corresponding to formula (I):
• R 1 and R 2 each represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms.
• the invention thus provides tire crown reinforcements, as well as these tires themselves, with an overall compromise of new and particularly advantageous properties.
• the invention also relates to any tire comprising a belt according to the invention, in particular that this tire is of the radial or non-radial type.
• the tires of the invention are particularly intended for equipping tourism-type motor vehicles, SUVs ("Sport Utility Vehicles"), two wheels (in particular motorcycles), planes, such as industrial vehicles chosen from light trucks, "heavy vehicles”. - that is, metros, buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles such as agricultural or civil engineering vehicles -, 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 the retreading of used tires, particularly in the case of heavy-duty tires.
• the belts according to the invention are prepared by a method which constitutes another object of the present invention, said method comprising the following steps:
• a reinforcing filler a reinforcing filler; an antioxidant, by thermomechanically kneading the whole, in one or more times, until a maximum temperature of between 0 ° C and 190 ° C; o cool the assembly to a temperature below 100 ° C; o then incorporate a crosslinking system; kneading the whole up to a maximum temperature below 110 ° C .; calender or extrude the composition thus obtained in the form of a layer of rubber; o incorporate this layer, after possible addition of textile or metal reinforcements, in the tire belt,
• antioxidant agent comprises a 4,4'-bis (alkylamino) triphenylamine of formula (I) above. . .
• the invention also relates, in itself, to the use of a compound of formula (I) above for the anti-aging protection of a tire belt.
• the rubber compositions are characterized before and after firing, as indicated below.
• the Mooney plasticity measurement is carried out according to the following principle: the raw composition (i.e., before firing) is molded in a cylindrical chamber heated to 100 ° C. After one minute of preheating, the rotor rotates 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 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): t, is the induction time, that is to say the time required for the beginning of the vulcanization reaction; t a (for example tg,,) is the time necessary to reach a conversion of ⁇ %, that is to say ⁇ % (for example 99%) of the difference between the minimum and maximum couples.
• the conversion rate constant denoted by K (expressed in min -1 ), of order 1, calculated between 30% and 80% conversion, which makes it possible to evaluate the kinetics of vulcanization, is also measured. .
• the fatigue and nick propagation resistance (with initial primer), expressed in number of cycles or in relative units (ur), is measured in a known manner on a test specimen with a 1 mm notch and subjected to repeated tractions. from low frequency to an elongation of 20%, using a Monsanto device ("MFTR" type), until the test piece is broken, according to the French standard NF T46-021.
• MFTR Monsanto device
• thermo-oxidative aging 26 days, the sample of the composition tested being placed in a ventilated oven maintained at a temperature of 80 ° C. and at an ambient humidity of 40%.
• the tire belts of the invention have the essential feature of incorporating, in 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) reinforcing filler; (iii) a crosslinking system; and (iv) a (at least one) compound of formula (I) as an antioxidant.
• composition based on means a composition comprising the mixture and / or the reaction product in situ of the various constituents used, some of these basic constituents being capable of or intended to react. between them, less in part, during the various phases of manufacture of rubber compositions, belts and tires, in particular during their vulcanization.
• elastomer or rubber, both considered synonymous
• diene monomers that is to say monomers carrying two carbon-carbon double bonds (conjugated or otherwise).
• isoprenic elastomer is understood to mean a homopolymer or copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR) and synthetic polyisoprenes. (IR), the various isoprene copolymers and the mixtures of these elastomers.
• isoprene copolymers mention will in particular be made of copolymers of isobutene-isoprene (butyl rubber - HR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR).
• isobutene-isoprene butyl rubber - HR
• isoprene-styrene SIR
• BIR isoprene-butadiene
• SBIR isoprene-butadiene-styrene
• the isoprene elastomer is preferably natural rubber or synthetic polyisoprene of the cis-1,4 type.
• synthetic polyisoprenes polyisoprenes having a content (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used.
• the compositions of the invention may contain diene elastomers other than isoprenic, preferably minor (i.e., less than 50 phr).
• the isoprene elastomer is more preferably 75 to 100% by weight of the total of diene elastomers, ie 75 to 100 phr (parts by weight per hundred parts of elastomer).
• any diene elastomer of the unsaturated type chosen in particular from the group consisting of polybutadienes (BR), in particular cis-1,4 or 1,2-syndiotactic polybutadienes, and those having a 1,2-unit content of between 4% and 80%, and butadiene copolymers, especially styrene-butadiene copolymers (SBR), and in particular those having a styrene content of between 5 and 50% by weight and more particularly between 20% and 40% by weight, a 1,2-butadiene content of the butadiene part of between 4% and 65%, a . .
• BR polybutadienes
• SBR styrene-butadiene copolymers
• trans-1,4 bond content of between 30% and 80%, styrene-butadiene-isoprene copolymers (SBIR), and mixtures of these different elastomers (BR, SBR and SBIR).
• SBIR styrene-butadiene-isoprene copolymers
• BR, SBR and SBIR mixtures of these different elastomers
• the belt of the invention when intended for a tire of the tourism type, if such a cutting is used, it is preferentially a mixture of SBR and BR that is used in cutting with the natural rubber, preferably up to less than 25% by weight (ie less than 25 phr) of SBR and BR mixture.
• the belt of the invention is particularly intended for a truck tire, whether it is a new or used tire (in the case of a 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.
• reinforcing filler known for its capacity to reinforce a rubber composition that can be used for manufacturing tires, for example an organic filler such as carbon black, or a reinforcing inorganic filler such as silica to which must be associated with a coupling agent.
• Carbon blacks are suitable for all carbon blacks, in particular blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks).
• the reinforcing carbon blacks of the 100, 200 or 300 series for example blacks Nl 15, Nl 34, Nt34, N326, N330, N339, N347 or N375, or more particularly , depending on the intended applications, blacks of higher series (for example N660, N683, N772).
• the carbon blacks could for example already be incorporated into the isoprene elastomer in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).
• any inorganic or mineral filler (regardless of its color and origin (natural or synthetic), also called “white” filler, “clear” filler or “non-blackfiller” as opposed to carbon black, capable of reinforcing on its own, without any 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 carbon black of pneumatic grade, such a charge is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.
• -OH hydroxyl groups
• Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, in particular silica (SiC 2), or aluminous type, in particular alumina (Al 2 O 3).
• the silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m 2 / g, preferably from 30 to 400 m 2 / g.
• HD highly dispersible precipitated silicas
• Ultrasil 7000 and Ultrasil 7005 silicas from Degussa
• Zeissil 1165MP, 1135MP and 1135MP silicas from Rhodia
• Hi-SiI silica EZ150G. from PPG
• the Zeopol 8715, 8745 and 8755 silicas of the Huber Company the high surface area silicas as described in the application WO 03/16837.
• the reinforcing inorganic filler used in particular if it is silica, preferably has a BET surface area of between 45 and 400. m 2 / g, more preferably between 60 and 300 m 2 / g.
• the total reinforcing filler content (carbon black, reinforcing inorganic filler or mixture of the two types of filler) is between 20 and 200 phr, more preferably between 30 and 150 phr, the optimum being in a different known manner. according to the particular applications concerned.
• an at least bifunctional coupling agent is used in known manner to ensure a sufficient chemical and / or physical connection between the inorganic filler ( surface of its particles) and the diene elastomer, in particular organosilanes or bifunctional polyorganosiloxanes.
• polysulfurized silanes called “symmetrical” or “asymmetrical” silanes according to their particular structure, are used, as described for example in the applications WO03 / 002648 and WO03 / 002649.
• n is an integer of 2 to 8 (preferably 2 to 5);
• - A is a divalent hydrocarbon radical (preferably alkylene groups Ci-Ci 8 or arylene groups C 2 -C 6, particularly alkylene Ci-Ci 0, in particular Ci-C 4, in particular propylene );
• Z is one of the following formulas:
• R.1 radicals substituted or unsubstituted, identical or different, represent an alkyl group -C g cycloalkyl, C 5 -C 8 aryl or C 6 -C 8 (preferably alkyl C 1 -C 6 alkyl, cyclohexyl or phenyl, especially C 1 -C 4 alkyl groups, more particularly methyl and / or ethyl).
• R.2 radicals substituted or unsubstituted, identical or different, represent an alkoxy group or Ci-Ci 8 cycloalkoxy, C 5 -C 8 (preferably a group selected from alkoxyls C 8 and C 5 -C 8 cycloalkoxyls, more preferably still a group selected from C 1 -C 4 alkoxyls, in particular methoxyl and ethoxyl).
• the average value of "n" is a fractional number preferably between 2 and 5, more preferably close to 4.
• silane polysulfides are more particularly the bis (mono, trisulfide or tetrasulfide) of bis (alkoxyl (Ci-C 4) alkyl (Ci-C 4) alkyl silyl (Cj-C 4 )), such as polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl).
• TESPT bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis (3-triethoxysilylpropyl) tetrasulfide
• TESPD bis-disulfide ( triethoxysilylpropyl)
• polysulfides in particular disulfides, trisulphides or tetrasulfides
• bis- (monoalkoxyl (Ci-C 4 ) -dialkyl (Ci-C 4 ) silylpropyl) more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide. as described in patent application WO 02/083782.
• the content of coupling agent is preferably between 4 and 12 phr, more preferably between 3 and 8 phr.
• the coupling agent could be grafted beforehand on the diene elastomer or on the reinforcing inorganic filler. However, it is preferred, particularly for reasons of better implementation of the compositions in the green state, to use the coupling agent is grafted on the reinforcing inorganic filler, or in the free state (Le., Ungrafted).
• the tire belts of the invention have the essential characteristic of comprising, as an antioxidant, a 4,4'-bis (alkylamino) -triphenylamine corresponding to formula (I):
• R 1 and R 2 each represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms.
• R 1 and R 2 which are identical or different, each represent an alkyl having from 2 to 8 carbon atoms, preferably chosen from the group consisting of ethyl, propyl (ie, n-propyl, iso-propyl), butyl ( ie, n-butyl, sec-butyl and tert-butyl), pentyl, hexyl, heptyl and octyl, or a cycloalkyl group having 5 to 8 carbon atoms (cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl), more preferably a cyclohexyl group .
• R 3 , R 4 , R 5 and R 6 which are identical or different, each represent an alkyl group whose number of carbon atoms is in accordance with the preferred definitions given above for R 1 and R 2 .
• branched radicals R 1 and R 2 By way of more preferred examples of branched radicals R 1 and R 2 , mention may be made in particular of isopropyl (a), 1,3-dimethylbutyl (b) and 1,4-dimethylpentyl (c) of the formulas below. below:
• the tire belt of the invention uses as antioxidant one of the following compounds:
• the level of antioxidant of formulas (I), (II) or (III) is preferably between 1 and 10 phr. Below the minimum indicated, the endurance may be insufficient while beyond the maximum recommended, there is a risk of degradation of the mechanical properties due to a parasitic plasticizing effect.
• this level of antioxidant is more preferably between 2 and 8 phr, in particular between 2 and 6 phr.
• the rubber matrices of the belts according to the invention may also comprise all or part of the usual additives used in rubber compositions intended for the manufacture of tire belts, such as, for example, extension oils, plasticizers, anti-aging protection other than those mentioned above, such as anti-ozone, other anti-ozonants chemical or anti-oxidants, anti-fatigue agents, acceptors and donors of methylene, bismaleimides or other reinforcing resins, a crosslinking system based sulfur, or sulfur and / or peroxide donors, vulcanization accelerators, vulcanization activators or retarders, rubber-to-metal adhesion promoter systems such as example salts or metal complexes (for example cobalt, boron, phosphorus, or even lanthanide salts as described in WO 2005/133666 cited above).
• additives used in rubber compositions intended for the manufacture of tire belts such as, for example, extension oils, plasticizers, anti-aging protection other than those mentioned above, such as anti-ozone
• the isoprenic matrices may also contain, in addition to any coupling agents for reinforcing inorganic fillers, agents for recovering these inorganic fillers, or more generally, agents for assisting the processing which can in known manner, thanks to a improving the dispersion of the filler in the rubber matrix and lowering the viscosity of the compositions, to improve their processability.
• the isoprenic compositions previously described are intended to form all or part of the rubber matrix of the belt of a tire, in particular of a truck tire for heavy vehicles or tourism.
• calendering gums with a layer or a cabled fabric web ply, whether it is a "crossed" layer, a protective layer or a hooping layer (with zero degrees), or intended to form a simple cushion, strip or strip of rubber, lacking reinforcements, arranged radially above or below the different belt layers mentioned above, or even inserted between the latter, for example to form an underlayer of the tread, or placed (e) at the lateral ends of these belt layers, in the "shoulder" areas of the tire, for example to form decoupling gums.
• FIG. 1 schematically represents a radial section of a heavy-vehicle tire 1 with a radial carcass reinforcement that may or may not conform to the invention, in this general representation.
• This tire 1 comprises an apex 2, two flanks 3, two beads 4, a radial carcass reinforcement 7 extending from one bead to the other.
• the top 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" top layers, covered with at least one protective top layer, all of these layers being reinforced by carbon steel wire cords.
• the carcass reinforcement 7 is wound around the two rods 5 in each bead 4, the upturn 8 of this armature 7 being for example disposed towards the outside of the tire 1 which is shown here mounted on its rim 9.
• the armature of carcass 7 consists of at least one ply or layer reinforced by so-called "radial" metal cables, that is to say that these cables are arranged substantially parallel to each other and extend from a bead to the other so as to form an angle of 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 feature of having in its top 2 a belt 6 according to the invention, the isoprene composition based on the compound of formula (I) constituting the calendering rubber belt layers 6 (two crossed layers and one protective layer, in this example).
• the calendering gum of the woven fabric that it is in the form of a layer of a certain width, the width of the crossed layers, narrower strips or even a unit wire wrapped in rubber, is also based on an isoprene composition comprising the compound of formula (I).
• the rubber composition based on the isoprene elastomer, the reinforcing filler and the antioxidant of formula (I) has, in the vulcanized state (ie, after firing). a secant modulus in extension (ElO) which is greater than 5 MPa, more preferably between 7 and 20 MPa. It is in the module areas indicated above that the best endurance tradeoff has been recorded.
• ElO secant modulus in extension
• the rubber compositions are manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature. 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 mechanical working phase (sometimes referred to as a "productive” phase). ”) at a lower temperature, typically less than 110 ° C, for example between 40 ° C and 100 ° C, finishing phase during which is incorporated the crosslinking system or vulcanization.
• a first phase of work or thermomechanical mixing (sometimes referred to as a "non-productive" phase) at a high temperature. temperature, up to a maximum temperature (denoted T max ) of between 110 ° C. and 190 ° C., preferably between 130 ° C. and 180 ° C.
• T max
• the method of manufacturing the tire belts according to the invention is characterized in that at least the reinforcing filler and the compound of formula (I) are incorporated by kneading with the isoprene elastomer during the so-called non-productive first phase. , that is to say that is introduced into the mixer and that is kneaded thermomechanically, in one or more steps, at least these different basic constituents until 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, in a suitable mixer such as a conventional internal mixer, all the necessary basic constituents are first introduced.
• the vulcanization system is then incorporated at low temperature, generally in an external mixer such as a roll mill; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 minutes.
• the final composition thus obtained is then calendered, for example in the form of plates (thickness of 2 to 3 mm) or thin rubber sheets for the measurement of its physical or mechanical properties, in particular for a characterization in the laboratory, or extruded to form a rubber profile directly usable, after cutting or assembly to the target dimensions, and after adding the desired metal or textile reinforcements, as a belt layer.
• the method according to the invention for preparing a tire belt according to the invention comprising a rubber composition based on at least one isoprene elastomer, a reinforcing filler, a crosslinking system and an antioxidant , comprises the following steps:
• said antioxidant agent comprises a 4,4'-bis (alkylamino) triphenylamine corresponding to the formula (I) above.
• the vulcanization or cooking is carried out in a known manner at a temperature preferably between 130 ° C. and 200 ° C., under pressure, for a sufficient time which may vary, for example, between 5 and 90 min depending, in particular, on the cooking temperature, of the vulcanization system adopted, the kinetics of vulcanization and the size of the tire in question.
• the actual crosslinking system 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 between 2 and 8 phr, especially when the invention is applied to a truck-type tire.
• the primary vulcanization accelerator is used at a preferential rate of between 0.5 and 5 phr, more preferably between 0.5 and 2 phr.
• accelerator any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, especially thiazole type accelerators and their derivatives, thiuram type accelerators, zinc dithiocarbamates.
• accelerators are more preferably selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS”), N-cyclohexyl-2-benzothiazyl sulfenamide (abbreviated “CBS”), N, N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated “DCBS”), N-tert-butyl-2-benzothiazylsulfenamide (abbreviated “TBBS”), N-tert-butyl-2-benzothiazylsulfenimide (abbreviated “TBSI”), zinc dibenzyldithiocarbamate (in abbreviated "ZBEC”) and mixtures of these compounds.
• MBTS 2-mercaptobenzothiazyl disulfide
• CBS N-cyclohexyl-2-benzothiazyl sulfenamide
• DCBS N-dicyclohex
• the invention relates to belts and tires previously described both in the said state “raw” (ie, before cooking) in the state said "cooked” or vulcanized (ie, after crosslinking or vulcanization) .
• the isoprene elastomer, the reinforcing filler (carbon black) is introduced into an internal mixer, filled to 70% and whose initial tank temperature is approximately 60 ° C. ), then, after one to two minutes of mixing, the various other ingredients, including the compound of formula (III), at the exception of the vulcanization system.
• Thermomechanical work (non-productive phase) is then carried out in one or two stages (total mixing time, for example, equal to about 7 minutes), until a maximum "falling" temperature of about 165 ° -170 ° C. is reached.
• the mixture thus obtained is recovered, cooled and then the vulcanization system (sulfur and primary sulfenamide accelerator) is added to an external mixer (homo-finisher) at 30 ° C., mixing the whole (productive phase), for example during 3 to 10 min.
• vulcanization system sulfur and primary sulfenamide accelerator
• compositions thus obtained are then either extruded in the form of plates (thickness of 2 to 3 mm) for the measurement of their physical or mechanical properties, or calendered for producing a metallic cabled fabric forming a belt layer ("layer" of work ”) of a truck tire.
• compositions based on natural rubber are prepared:
• composition noted C-I control
• composition noted C-2 in accordance with the invention.
• compositions of rigorously identical formulations apart from the nature and the weight concentration of antioxidant, are intended to constitute the "calendering gum" of working layers of a heavy-duty tire belt.
• Tables 1 and 2 give the formulation of the two compositions (Table 1 - rate of the different products expressed in phr), their properties before and after cooking (60 min.
• the vulcanization system consists of sulfur and sulfenamide.
• the two antioxidants are used at a substantially isomolar level, that is to say that, regardless of the composition tested, the same number of moles of active functions (secondary amines) are used. ); this explains the difference in weight of product (expressed in phr).
• the second molecule has a much larger steric hindrance and therefore a lower ability to diffuse, which for the skilled person is a priori unfavorable to effective anti-fatigue protection.

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