Tire for a vehicle comprising a grafted polymer in the lower region

Abstract

The invention relates to a tire for a vehicle comprising two beads intended to come into contact with a mounting rim, two sidewalls extending the beads radially outward and joining in a crown comprising a tread, at least one carcass reinforcement extending from the beads through the sidewalls and the crown, the carcass reinforcement being anchored in the two beads, characterized in that the beads comprise a rubber composition C based on at least one grafted isoprene elastomer, the rubber composition C also comprising a crosslinking system and a reinforcing filler.

Description

[0001] Vehicle bandage comprising a polymer grafted in the lower zone

[0002] Technical field of the invention

[0003] The present invention relates to the field of vehicle tires, whether these tires are pneumatic or non-pneumatic.

[0004] Previous art

[0005] Pneumatic tires for vehicles usually comprise ■ two beads intended to come into contact with a mounting rim, each bead comprising at least one annular reinforcing structure called a 'bead' and a filling, the filling being located radially outside the annular reinforcing structure two sidewalls extending radially outwards from the beads and joining in a crown comprising a tread at least one carcass reinforcement extending from the beads through the sidewalls to the crown, and comprising a plurality of carcass reinforcement elements.

[0006] In a particular arrangement, each bead may also include a lateral band positioned axially outside the frame structure and the padding. Such a structure is well known to those skilled in the art and is, for example, described in documents FR 2 940 187 and FR 2 940 188.

[0007] The rubber compositions used in the beading of pneumatic tires must exhibit high rigidity. To this end, these compositions include relatively high reinforcing filler content as well as reinforcing resins.

[0008] Reinforcing resins commonly used to increase the rigidity of compositions are based on a methylene acceptor / donor system. The terms "methylene acceptor" and "methylene donor" are well known to those skilled in the art and widely used to describe compounds capable of reacting together to generate, through condensation, a three-dimensional reinforcing resin that overlaps and interpenetrates with the reinforcing filler / elastomer network on the one hand, and with the elastomer / sulfur network on the other (if the crosslinking agent is sulfur). Typically, the methylene acceptor is a phenolic resin. A hardening agent, also commonly called a "methylene donor," is associated with the methylene acceptor described above and is capable of crosslinking or hardening it.The resin cross-linking occurs during the curing of the rubber matrix, through the formation of methylene bridges between the carbons in the ortho and para positions of the resin's phenolic rings and the methylene donor, thus creating a three-dimensional resin network. Commonly used methylene donors are hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM or H3M), or hexaethoxymethylmelamine.

[0009] However, combining a phenolic resin, a methylene acceptor, with HMT or IH3M, a methylene donor, produces formaldehyde during the crosslinking of the rubber compound. It is desirable to reduce, or even eventually eliminate, formaldehyde from rubber compounds due to their potential environmental impact.

[0010] These resins also have the disadvantage of prolonging the curing time required for the rubber compositions. However, it is important to be able to control the curing kinetics of the different rubber compositions so that no part of the bandage is overcooked or undercooked.

[0011] Continuing her research, the applicant discovered that the use of a grafted elastomer made it possible to avoid the use of reinforcing resins while maintaining, or even increasing, the rigidities of the rubber compositions of the beads, while improving the cooking kinetics.

[0012] Detailed description of the invention

[0013] The invention relates to a vehicle tire comprising two beads for contact with a mounting rim, two sidewalls extending radially outwards from the beads and joining at a crown comprising a tread, at least one carcass reinforcement extending from the beads through the sidewalls and the crown, said carcass reinforcement being anchored in the two beads, characterized in that the beads comprise a rubber composition C comprising at least one grafted isoprenoid elastomer, the graft being at least one compound selected from methacrylic acid, acrylic acid, alkyl acrylates, alkyl methacrylates and their polymers, in which the alkyl group comprises from 1 to 6 carbon atoms, the isoprenoid elastomer trunk representing from 45% to 75% by weight of the grafted isoprenoid elastomer, the graft representing from 25% to 55% by weight of the grafted polyamide elastomer,The C rubber composition also includes a crosslinking system and a reinforcing filler.

[0014] The carbon-containing compounds mentioned in the description can be of fossil origin or bio-based. In the latter case, they may be partially or entirely derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers, plasticizers, fillers, etc.

[0015] The term "radial" refers to a radius of the tire. In this sense, a point P1 is said to be "radially inside" a point P2 (or "radially inside" point P2) if it is closer to the tire's axis of rotation than point P2. Conversely, a point P3 is said to be "radially outside" a point P4 (or "radially outside" point P4) if it is farther from the tire's axis of rotation than point P4. We say that we are moving "radially inward (or outward)" when moving in the direction of smaller (or larger) radii. This meaning of the term also applies when discussing radial distances.

[0016] By "radial cut" or "radial section" we mean here a cut or section along a plane which contains the axis of rotation of the tire.

[0017] An "axial" direction is a direction parallel to the tire's axis of rotation. A point P5 is said to be "axially inside" a point P6 (or "axially inside" point P6) if it is closer to the tire's median plane than point P6. Conversely, a point P7 is said to be "axially outside" a point P8 (or "axially outside" point P8) if it is farther from the tire's median plane than point P8. The tire's "median plane" is the plane that is perpendicular to the tire's axis of rotation and equidistant from the annular reinforcement structures of each bead.

[0018] A "circumferential" direction is a direction that is perpendicular to both a radius of the tire and the axial direction.

[0019] Two reinforcing elements are said to be "parallel" in this document when the angle formed between the two elements is less than or equal to 5°.

[0020] The term "part by weight per hundred parts by weight of elastomer" (or pc) is used in the context of this invention to mean the part, by mass, per hundred parts by mass of elastomer or rubber, the two terms being synonymous. Unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0021] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from greater than a to less than b (that is, excluding the bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (that is, including the strict bounds a and b). In this context, when an interval of values ​​is described by the expression "from a to b," the interval represented by the expression "between a and b" is also, and preferably, being described.

[0022] The expression "composition based on" means a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacturing the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0023] The vehicle tire according to the invention comprises two beads intended to come into contact with a mounting rim, two sidewalls extending the beads radially outwards and joining in a top comprising a tread, at least one carcass reinforcement extending from the beads through the sidewalls to the top, said carcass reinforcement being anchored in the two beads.

[0024] Rubber composition

[0025] The beads comprise a C rubber composition comprising at least one grafted isoprene elastomer, the graft being at least one compound selected from methacrylic acid, acrylic acid, alkyl acrylates, alkyl methacrylates and their polymers, in which the alkyl group comprises from 1 to 6 carbon atoms, the isoprene elastomer trunk representing from 45% to 75% by weight of the grafted isoprene elastomer, the graft representing from 25% to 55% by weight of the grafted isoprene elastomer.

[0026] A grafted isoprene elastomer is a grafted isoprene elastomer, the graft being based on an unsaturated compound selected from methacrylic acid, acrylic acid, alkyl acrylates, and alkyl methacrylates, in which the alkyl group comprises from 1 to 6 carbon atoms, and polymers of these compounds. The alkyl group is preferably a methyl, ethyl, propyl, or butyl group. Preferably, the grafted isoprene elastomer is a methyl methacrylate grafted isoprene elastomer or a polymethyl methacrylate grafted isoprene elastomer, and preferably is a polyisoprene grafted with a polymethyl methacrylate, the isoprene elastomer trunk representing 45% to 75% by weight of the grafted isoprene elastomer, the graft representing 25% to 55% by weight of the grafted isoprene elastomer.

[0027] The grafted isoprene elastomer can be obtained by grafting or other types of polymerization of the elastomer with the unsaturated compound. For example, when the grafted isoprene polymer is a natural rubber, the grafted rubber can be a product obtained by grafting copolymerization of the natural rubber with this ester in monomeric form, the grafting copolymerization being carried out, for example, between an emulsion or dispersion of the natural rubber and the unsaturated compound, for example an alkyl ester, the alkyl ester content in the grafted rubber ranging, for example, from 5% to 60% by weight of the grafted elastomer.

[0028] Such grafted elastomers are marketed for example under the name "Megapoly MG-30" and "Megapoly MG-49", comprising respectively 30% and 49% by weight of poly(methyl methacrylate).

[0029] By "isoprene elastomer" is meant a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR) which can be plasticized or peptized, synthetic polyisoprenes (IR), the various isoprene copolymers, in particular isoprene-styrene copolymers (SIR), isoprene-butadiene copolymers (BIR) or isoprene-butadiene-styrene copolymers (SBIR), and mixtures of these elastomers.

[0030] Preferably, the isoprene elastomer is chosen from the group consisting of synthetic polyisoprenes, natural rubber and their mixtures, preferably from the group consisting of natural rubber.

[0031] Preferably, the rubber composition C comprises at least 50 parts per unit of at least one grafted isoprene elastomer, preferably at least 60 parts per unit of at least one grafted isoprene elastomer.

[0032] Preferably, the rubber composition C also comprises 0 to 50 parts per million of at least one ungrafted diene elastomer, preferably 0 to 40 parts per million, preferably 0 to 30 parts per million, preferably 0 to 20 parts per million of at least one ungrafted diene elastomer. Preferably, the reinforcing filler content in the rubber composition C is at most 50 parts per million, preferably at most 40 parts per million.

[0033] Preferably, the C rubber composition does not comprise any elastomer other than the grafted isoprene elastomer and any non-grafted isoprene elastomer, or contains less than 20 parts per annum, preferably less than 10 parts per annum, preferably still less than 5 parts per annum.

[0034] Reinforcing load

[0035] Preferably, the reinforcing filler of the rubber composition C is chosen from carbon black, an inorganic reinforcing filler, and their mixture.

[0036] The term "reinforcing inorganic filler" here refers to any inorganic or mineral filler, regardless of its color or origin (natural or synthetic), also called "white" filler, "light" filler, or even "non-black" filler (as opposed to carbon black), capable of reinforcing, on its own and without any intermediate coupling agent, a rubber composition intended for the manufacture of tires; in other words, capable of replacing, in its reinforcing function, a conventional tire-grade carbon black. Such a filler is generally characterized, as is known, by the presence of hydroxyl groups (-OH) on its surface.

[0037] Suitable inorganic reinforcing fillers include siliceous mineral fillers, preferably silica (SiO₂). The silica used may be any reinforcing silica known to those skilled in the art, particularly any precipitated or fumed silica with a BET surface area and a CTAB specific surface area both below 450 m². 2 / g, preferably from 30 to 400 m 2 / g, especially between 60 and 300 m 2 / g. Examples of highly dispersible precipitated silicas (known as "HDS") include "Ultrasil" 7000 and "Ultrasil" 7005 from Degussa, "Zeosil" 1165MP, 1135MP and 1115MP from Rhodia, "Hi-Sil" EZ150G from PPG, "Zeopol" 8715, 8745 and 8755 from Huber, and high specific surface area silicas as described in application WO 03 / 16387.

[0038] The BET specific surface area of ​​silica is determined using a known method by gas adsorption with the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" Vol. 60, page 309, February 1938, more specifically according to the French standard NF ISO 9277 of December 1996 (multipoint volumetric method (5 points) - gas: nitrogen - degassing: 1 hour at 160°C - relative pressure range w / in: 0.05 to 0.17). The CTAB specific surface area of ​​silica is determined according to the French standard NF T 45007 of November 1987 (method B).

[0039] As a reinforcing inorganic filler, we will also mention mineral fillers of the aluminous type, in particular alumina (Al2O3) or aluminum (oxide)hydroxides, or even reinforcing titanium oxides.

[0040] Those skilled in the art will understand that, as an equivalent to the inorganic reinforcing filler described in this paragraph, a reinforcing filler of another nature, particularly an organic one such as carbon black, could be used, provided that this reinforcing filler is coated with an inorganic layer such as silica, or has functional sites on its surface, particularly hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer. For example, carbon blacks for tires, such as those described in patent documents WO 96 / 37547 and WO 99 / 28380, could be cited.

[0041] Preferably, the inorganic reinforcing filler content is within a range of 35 to 65 parts per cubic centimeter, more preferably from 35 to 50 parts per cubic centimeter; these value ranges allow for a tire with improved endurance and rigidity properties.

[0042] Advantageously, the reinforcing inorganic filler consists mainly of silica. Even more preferably, the reinforcing inorganic filler is (or consists of) silica.

[0043] To couple the reinforcing inorganic filler to the diene elastomer, a coupling agent (or bonding agent) is used, in a well-known manner. This agent must be at least bifunctional and ensure sufficient chemical and / or physical connection between the inorganic filler (the surface of its particles) and the diene elastomer. Organosilanes or polyorganosiloxanes, at least bifunctional, are particularly commonly used.

[0044] Examples of coupling agents can be found by a person skilled in the art in the following documents: WO 02 / 083782, WO 02 / 30939, WO 02 / 31041, WO 2007 / 061550, WO 2006 / 125532, WO 2006 / 125533, WO 2006 / 125534, US 6 849 754, WO 99 / 09036, WO 2006 / 023815, WO 2007 / 098080, WO 2010 / 072685 and WO 2008 / 055986.

[0045] The coupling agent content preferably represents 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler, preferably 4% to 12%, and preferably 6% to 10% by weight relative to the amount of reinforcing inorganic filler. Typically, the coupling agent content is less than 20%, preferably within the range of 6% to 17%, and preferably 8% to 15%. This percentage can easily be adjusted by a person skilled in the art according to the amount of inorganic filler used in the composition.

[0046] The rubber composition C of the tire according to the invention may also contain, in addition to coupling agents, coupling activators, inorganic filler covering agents or more generally processing aids capable, in a known manner, through an improvement in the dispersion of the filler in the rubber matrix and a reduction in the viscosity of the compositions, of improving their processing ability in the raw state, these agents being for example hydrolyzable silanes such as alkylalkoxysilanes (in particular alkyltriethoxysilanes), polyols, polyethers (for example polyethylene glycols), primary, secondary or tertiary amines (for example trialcanol-amines), hydroxylated or hydrolyzable POS, for example α,δ-dihydroxy-polyorganosiloxanes (in particular α,δ-dihydroxy-polydimethylsiloxanes), fatty acids such as stearic acid.

[0047] The blacks usable within the scope of the present invention can be any black conventionally used in tires or their treads (so-called tire-grade blacks). Among these, special mention should be made of reinforcing carbon blacks of the 100, 200, and 300 series, or blacks of the 500, 600, or 700 series (ASTM grades), such as NI 15, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772. These carbon blacks can be used in isolation, as commercially available, or in any other form, for example, as a carrier for certain rubber additives used. Carbon blacks could for example already be incorporated into the diene elastomer, in particular isoprene in the form of a masterbatch (see for example applications WO 97 / 36724 or WO 99 / 16600).The specific surface area BET of carbon blacks is measured according to standard D6556-10 [multipoint method (minimum 5 points) — gas ■ nitrogen — relative pressure range P / PO ■ 0.1 to 0.3].

[0048] Preferably, the reinforcing filler of rubber compound C comprises predominantly carbon black. Preferably, carbon black constitutes at least 50% by weight relative to the weight of the reinforcing filler. Crosslinking system

[0049] Rubber composition C includes a crosslinking system which can be any type of system known to those skilled in the art in the field of rubber compositions for vehicle tires.

[0050] Preferably, the crosslinking system is sulfur-based; this is then referred to as a vulcanization system. The sulfur can be supplied in any form, including molecular sulfur or a sulfur-donating agent. At least one vulcanization accelerator is also preferably present, and optionally, various known vulcanization activators such as zinc oxide, stearic acid, or equivalent compounds such as stearic acid salts and transition metal salts, guanidine derivatives (particularly diphenylguanidine), or known vulcanization retarders may be used.

[0051] Sulfur is used at a preferential rate of between 2.5 and 10 parts per million (ppm), particularly between 3 and 8 ppm. The vulcanization accelerator is used at a preferential rate in the range of 0.4 to 4 ppm, preferably from 0.5 to 3.5 ppm.

[0052] Any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, including thiazole-type accelerators and their derivatives, sulfenamide-type accelerators, thiurams, dithiocarbamates, dithiophosphates, thioureas and xanthates. Examples of such accelerators include the following compounds: ■ 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide ("CBS"), N,N-dicyclohexyl-2-benzothiazyl sulfenamide ("DCBS"), N-ter-butyl-2-benzothiazyl sulfenamide ("TBBS"), N-ter-butyl-2-benzothiazyl sulfenimide ("TBSI"), tetrabenzylthiuram disulfide ("TBZTD"), zinc dibenzyldithiocarbamate ("ZBEC") and mixtures of these compounds.

[0053] Various additives

[0054] The rubber composition C included in the tire according to the invention may also include all or some of the usual additives commonly used in elastomer compositions for tire manufacturing, such as plasticizers or extending oils, whether aromatic or non-aromatic, pigments, protective agents such as ozone-suppressing waxes, chemical antiozonants, antioxidants, anti-fatigue agents, reinforcing resins such as bismaleimides, acceptors (e.g., novolac phenolic resin), or methylene donors (e.g., HMT or H3M). The rubber composition C may also include cobalt salts, particularly when a layer of rubber composition C is in contact with a metallic reinforcing element.

[0055] Preferably, the C rubber composition comprises less than 5 parts per cubic centimeter of reinforcing resin, preferably less than 3 parts per cubic centimeter of reinforcing resin, and preferably no reinforcing resin at all. This is because the composition is sufficiently rigid to allow for a reduction, or even elimination, of the reinforcing resin.

[0056] Reinforcing resin means a resin known to those skilled in the art to stiffen rubber compositions, stiffness measured for example by Young's Modulus, according to ASTM 412-98a, or the complex dynamic shear modulus G* according to ASTM D 5992-96.

[0057] Composition manufacturing

[0058] Rubber compound C is manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first working or thermomechanical mixing phase (the so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which all the necessary constituents, including the elastomeric matrix, fillers, and any other miscellaneous additives, with the exception of the crosslinking system, are introduced into a suitable mixer such as a standard internal mixer (e.g., of the Banbury type). The incorporation of the filler into the elastomer can be carried out in one or more stages by thermomechanical mixing.In the case where the filler is already incorporated in whole or in part into the elastomer in the form of a masterbatch as described for example in applications WO 97 / 36724 or WO 99 / 16600, it is the masterbatch which is directly mixed and where appropriate the other elastomers or fillers present in the composition which are not in the form of a masterbatch, as well as any other miscellaneous additives other than the crosslinking system, are incorporated.

[0059] The non-productive phase is carried out at high temperature, up to a maximum temperature between 130°C and 170°C, for a duration generally between 2 and 10 minutes. A second mechanical working phase (the so-called "productive" phase) is carried out in an external mixer such as a roller mixer, after the mixture obtained during the first non-productive phase has been cooled to a lower temperature, typically below 110°C, for example between 40°C and 100°C. The crosslinking system is then incorporated, and the mixture is then blended for a few minutes, for example between 1 and 30 minutes.

[0060] The final composition thus obtained is then calendered, for example in the form of a sheet or plate, particularly for characterization in the laboratory, or extruded in the form of a semi-finished (or profile) of rubber usable, for example, as an inner layer in a tire.

[0061] The composition can be either in its raw state (before crosslinking or vulcanization), or in its cooked state (after crosslinking or vulcanization), and can be a semi-finished product that can be used in a tire.

[0062] The crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example at a temperature between 130°C and 200°C, preferably under pressure, for a sufficient time which can vary for example between 5 and 90 min.

[0063] Description of the figures

[0064] [Fig 1] Figure 1 schematically represents, in radial section, the lower area of ​​a tire including a sidewall. The lower area is understood to be the area of ​​the tire including the tire bead. The tire has two beads 20 intended to come into contact with a mounting rim (not shown), each bead 20 having an annular reinforcing structure, in this case a bead 70. Two sidewalls 30 extend the beads 20 radially outwards and join at a crown 25 comprising a crown reinforcement formed of a first layer of reinforcements 80 and a second layer of reinforcements 90, and radially surmounted by a tread 40. Each layer of reinforcements comprises wire reinforcements embedded in a matrix formed of a rubber compound.The reinforcements of each layer of reinforcements are substantially parallel to each other; the reinforcements of the two layers are crossed from one layer to the other at an angle of approximately 20°, as is well known to those skilled in the art for so-called radial tires.

[0065] The tire also includes a carcass reinforcement 60 which extends from the beads 20 through the sidewalls 30 to the top 25. This carcass reinforcement 60 here includes wire reinforcements oriented substantially radially, that is to say making an angle with the circumferential direction greater than or equal to 65° and less than or equal to 90°. The carcass reinforcement 60 comprises a plurality of carcass reinforcement elements and is anchored in the two beads 20 by a turning around the bead 70, so as to form in each bead a forward strand 61 and a return strand 62. The return strand extends radially outwards to an end 63 located at a radial distance DRR from the radially innermost point 71 of the annular reinforcement structure of the bead, the radial distance DRR being preferably greater than or equal to 15% of the radial height H of the tire.

[0066] Each bead has a rod padding 110, the padding extending radially outwards from the rod 70 in contact with said frame armature 60 and, for a good part, between the forward strand 61 and the return strand 62 of the frame armature 60.

[0067] The bead packing 110 extends radially outward from the innermost radial point 71 of the annular bead reinforcement structure, up to a radial distance DRB from said point, the radial distance DRB preferably being greater than or equal to 20% of the radial height H of the tire. Preferably, DRB is less than H / 2.

[0068] The inner surface of the tire is covered with an inner rubber compound 50.

[0069] A lateral band 120 placed axially outside the carcass reinforcement and the padding, extends radially outside from a radially inner end 121 located at a radial distance DRI from the radially innermost point 71 of the annular reinforcement structure 70 of the bead, DRI being preferably less than or equal to 20% of the radial height H of the tire, to a radially outer end 122, the radial distance DRL between the radially outer end 122 of the lateral band and the radially inner end 121 of the lateral band being preferably greater than or equal to 25% of the radial height H of the tire.

[0070] Examples

[0071] Measurement methods

[0072] G*

[0073] The complex shear modulus G* is a well-known dynamic property for those skilled in the art, measured on a Metravib VA4000 or DMA+450 viscoelastic analyzer using specimens containing a baked compound extracted from tires. The specimen's response to a sinusoidal alternating simple shear load at a frequency of 10 Hz is recorded under specified temperature conditions (here, 23°C) according to ASTM D 1349-99. A strain amplitude sweep is performed from 0.1% C'C to 100% c _ c (outward cycle), then 100% c _ c at 0.1% c _ c (return cycle), c _c stands for peak-to-peak. The specimen has a cylindrical cross-section as described in ASTM D5992-96 (2011 re-approved version, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. The complex dynamic shear modulus G* is defined as the square root of the sum of the squares of G' and G”², where G' represents the elastic modulus and G”² represents the viscous modulus. The complex shear modulus G* is measured at 7% of deformation on both the forward and reverse cycles. The results table presents the value measured on the forward cycle as well as the ratio G* reverse to G* forward. This ratio highlights the composition's resilience to deformation.

[0074] Tan(d) max at 23°C

[0075] The dynamic loss tan(d) is a well-known dynamic property for those skilled in the art and is measured on the same Metravib VA4000 or DMA+450 type viscoanalyzer using test specimens containing a baked composition extracted from tires. The response of I test specimens subjected to a sinusoidal alternating simple shear load at a frequency of 10 Hz is recorded under specified temperature conditions (here 23°C) according to ASTM DI 349-99. A strain amplitude sweep is performed from 0.1% cc to 100% cc (forward cycle), then from 100% cc to 0.1% cc (reverse cycle), cc meaning peak-to-peak. The test specimen has a cylindrical cross-section as described in ASTM D 5992-96 (version reapproved in 2011, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33].The tangent tan(d) of the phase angle d between the force exerted on the sample and its displacement represents a dynamic loss and is equal to the ratio G” / G’. The maximum value tan(d)MAx of the tangent tan(d) of the phase angle d observed during the deformation feedback cycle is recorded.

[0076] Rheometry

[0077] Measurements are performed at a given temperature (e.g., 150°C) using an oscillating chamber rheometer, according to DIN 53529 - Part 3 (June 1983). The evolution of the rheometric torque, ACouple, over time describes the progression of the composition's stiffening as a result of the vulcanization reaction. Measurements are processed according to DIN 53529 - Part 2 (March 1983). T0 is the induction time (expressed in minutes), i.e., the time required for the crosslinking reaction to begin; ta (e.g., t95) is the time required to achieve a conversion of a% (e.g., 95%), i.e., a% (e.g., 95%) of the difference between the minimum and maximum torques. The lower the value of ta, the faster the composition will have crosslinked, i.e., the faster the curing process will have been.

[0078] The results are expressed as a base of 100 based on the control composition by performing the following calculation ■ value (base 100) = measured value / measured value for the control *100.

[0079] Preparation of compositions

[0080] The following tests are conducted as follows: ■ The elastomer, the reinforcing filler, and the various other ingredients, with the exception of the vulcanization system, are successively introduced into an internal mixer (final fill level approximately 70% by volume), whose initial tank temperature is approximately 60°C. A thermomechanical process (non-productive phase) is then carried out in a single step, lasting approximately 3 to 4 minutes in total, until a maximum "drop" temperature of 165°C is reached.

[0081] The mixture thus obtained is collected, cooled, and then sulfur and an accelerator (sulfenamide) are incorporated on a mixer (homo-finisher) at 30 °C, mixing everything (productive phase) for an appropriate time (for example between 5 and 12 min).

[0082] The compositions thus obtained are then calendered into plates (2 to 3 mm thick) or thin sheets of rubber and then subjected to a baking step at 150°C for 25 min before measuring their physical or mechanical properties.

[0083] Example

[0084] Tests were carried out with different rubber compositions shown in Table 1.

[0085] It is observed that the compositions according to the invention exhibit stiffnesses, expressed by descriptor G*, similar to, or even significantly higher than, that of the control, while the crosslinking kinetics, expressed by descriptor t95, are faster. Compositions comprising high levels of grafted elastomer and low levels of carbon black not only exhibit improved stiffnesses, but also very good curing kinetics, while also having improved hysteresis properties, expressed by the value of tan(d). [Table 1]

[0086] (1) Natural rubber

[0087] (2) "Megapoly MG _ 49” from Akrochem (3) grade ASTM N326 (Cabot company)

[0088] (4) Paraffin Oil

[0089] (5) Novolac formophenolic resin (“Peracit 4536K” from the Perstorp company)

[0090] (6) N-(1,3-Dimethylbutyl)'N'-phenyl-p-phenylenediamine (Santoflex 6) _ Flexsys' PPD")

[0091] (7) (13) Cobalt naphthenate, Fluka Company Product No. 60830 (8) Stearine, "Pristerene 4931" by Uniqema

[0092] (9) Zinc oxide, industrial grade — Umicore

[0093] (10) Hexamethylenetetramine (from the Degussa company)

[0094] (11) Hexa(methoxymethyl)melamine

[0095] (12) N-tert'butylbenzothiazole-2-sulfenamide

Claims

DEMANDS [Claim 1] A vehicle tire comprising two beads for contact with a mounting rim, two sidewalls extending radially outwards from the beads and joining at a crown comprising a tread, at least one carcass reinforcement extending from the beads through the sidewalls and the crown, said carcass reinforcement being anchored in the two beads, characterized in that the beads comprise a rubber composition C comprising at least one grafted isoprenoid elastomer, the graft being at least one compound selected from methacrylic acid, acrylic acid, alkyl acrylates, alkyl methacrylates and their polymers, wherein the alkyl group comprises from 1 to 6 carbon atoms, the isoprenoid elastomer trunk representing from 45% to 75% by weight of I grafted isoprene elastomer, the graft representing 25% to 55% by weight of I grafted isoprene elastomer, the rubber composition C also comprising a crosslinking system and a reinforcing filler. [Claim 2] Vehicle bandage according to the preceding claim in which the rubber composition C comprises at least 50 parts of at least one grafted isoprene elastomer, preferably at least 60 parts of at least one grafted isoprene elastomer. [Claim 3] Bandage according to any one of the preceding claims wherein the rubber composition C also comprises from 0 to 50 pc of at least one ungrafted diene elastomer, preferably from 0 to 40 pc, preferably from 0 to 30 pc, preferably from 0 to 20 pc of at least one ungrafted diene elastomer. [Claim 4] Bandage according to any one of the preceding claims wherein the reinforcing filler of the rubber composition C is selected from carbon black, an inorganic reinforcing filler, and their mixture. [Claim 5] Bandage according to the preceding claim in which the reinforcing filler of the rubber composition C comprises predominantly carbon black, preferably is made of carbon black. [Claim 6] Bandage according to any one of the preceding claims wherein the reinforcing filler content in the rubber composition C is at most equal to 50 pc, preferably at most equal to 40 pc. [Claim 7] Bandage according to any one of the preceding claims wherein the rubber composition C comprises less than 5 pc of reinforcing resin, preferably comprises less than 3 pc of reinforcing resin and preferably does not comprise any reinforcing resin. [Claim 8] Vehicle tire according to the preceding claim wherein each bead comprises at least one ring-shaped reinforcing structure called bead, an inner layer extending radially outwards from said bead and in contact with said carcass reinforcement, called bead padding and optionally an inner layer located axially outside the carcass reinforcement and the bead padding called side strip, wherein the bead padding and / or the side strip if present is made of rubber composition C.

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