RUBBER COMPOUND WITH RAPID VULCANIZATION ACCELERATOR

Description

[0001] Rubber mixture comprising a rapid vulcanization accelerator The field of the present invention is that of reinforced rubber mixtures, in particular used in the manufacture of vehicle tires, more particularly used for the manufacture of treads.

[0002] One of the requirements for a tire is to ensure optimal grip on the road, especially on wet surfaces. One way to give the tire high wet grip is to use a rubber compound in its tread, which compound has a high hysteretic potential. But at the same time, the tire tread must also minimize its contribution to the tire's rolling resistance, i.e., be as hysteretic as possible.

[0003] Thus, the rubber composition, in particular of the tread, must satisfy two contradictory requirements, namely to have a maximum hysteresis potential to satisfy the grip requirement and to have as low a hysteresis as possible to satisfy the rolling resistance requirement.

[0004] The improvement in rolling resistance has been made possible by the use of new rubber compositions reinforced with inorganic fillers, in particular specific silicas of the highly dispersible type, capable of competing from a reinforcing point of view with a conventional tire-grade carbon black, while providing these compositions with lower hysteresis, synonymous with lower rolling resistance.

[0005] However, the use of a high level of inorganic reinforcing fillers in rubber compositions has the disadvantage of penalizing the wet grip properties of the rubber compositions in which they are incorporated.

[0006] Meeting both the requirement for grip, particularly on wet ground, and rolling resistance therefore remains a constant concern for tire manufacturers.

[0007] Thus, JPH0827313A describes a diene elastomeric composition for a pneumatic tire exhibiting a good balance between wet grip and low rolling resistance without adversely affecting the wear resistance of the tire.

[0008] With a view to seeking the best performance compromise, in particular between rolling resistance and wet grip, tire manufacturers are developing increasingly complex rubber compositions, often incorporating several elastomers of different chemical nature, thus forming a rubber compound and creating different phases. Examples of complex rubber compounds are described in document FR20 / 05862 belonging to the applicant. In this document, these complex rubber compounds are defined by two glass transition temperatures noted Tg1 and Tg2 with Tg1 -Tg2 ≥ 23°C, and by a specific loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa specific; these complex rubber compounds exhibit an improvement in the rolling resistance / wet grip compromise.

[0009] Continuing its research, the Applicant sought to further improve this resistance compromise for some of its complex rubber mixtures.

[0010] She surprisingly discovered that a rubber compound having a particular loss factor profile, the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa, and being based on a combination of at least one specific vulcanization system and at least two rubber compositions C1 and C2 having different glass transition temperatures and the difference in these glass transition temperatures being greater than or equal to 23°C and in which the elastomer of composition C1 being the majority in the compound, the elastomer of composition C2 being an isoprene diene elastomer and the vulcanization system comprising a specific ultra-accelerator, exhibited better rolling resistance while retaining good wet grip properties, or even improved road grip properties.

[0011] Thus, a first subject of the invention relates to a rubber mixture having at least two glass transition temperatures Tg, Tg1 and Tg2, based on at least one sulfur vulcanization system and at least two rubber compositions C1 and C2, the rubber composition C1 comprising at least one elastomer E1, and having the glass transition temperature Tg1, the composition C2 comprising at least one elastomer E2, different from the elastomer E1 and a reinforcing filler, and the composition C2 having the glass transition temperature Tg2, characterized in that: the glass transition temperature Tg1 of composition C1 is greater than or equal to -50°C; the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 23°C; the rubber mixture has a loss factor profile showing the evolution of tan δ as a function of temperature in °C, the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa and showing one or more peaks, this profile being such that all the tan δ peaks present at a temperature above the glass transition temperature Tg1 have a width at half-maximum less than or equal to 23°C; the elastomer E1 is the majority in the rubber mixture; the elastomer E2 is an isoprene diene elastomer;and the sulfur vulcanization system comprises at least one vulcanization accelerator A selected from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof.;

[0012] Preferably, the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 25°C, preferably Tg1 -Tg2 ≥ 28°C.

[0013] Advantageously, the rubber compound can satisfy the mathematical relationship 25°C ≤Tg1 -Tg2 ≤ 40°C.

[0014] Advantageously, the glass transition temperature Tg2 of composition C2 may be less than or equal to -43°C, preferably less than or equal to -50°C.

[0015] Advantageously, the glass transition temperature Tg2 of composition C2 is within a range from -90°C to -43°C, preferably from -85°C to -50°C.

[0016] Advantageously, the elastomer E2 of the rubber composition C2 is an isoprene diene elastomer chosen from the group consisting of natural rubber and synthetic polyisoprene, more preferably still natural rubber.

[0017] Advantageously, the glass transition temperature TgE2 of the elastomer E2 may be within a range from -110°C to -23°C, preferably from -100°C to -28°C, more preferably from -95°C to -30°C.

[0018] Preferably, the reinforcing filler of composition C2 may mainly comprise at least one inorganic reinforcing filler, more preferably may mainly comprise at least one silica.

[0019] Advantageously, the reinforcing filler of composition C2 may comprise mainly a reinforcing inorganic filler, preferably mainly a silica, and the isoprene diene elastomer E2 may be natural rubber.

[0020] Advantageously, the glass transition temperature Tg1 of the rubber composition C1 may be within a range from -48°C to -15°C, more preferably may be within a range from -40°C to -15°C.

[0021] Advantageously, the glass transition temperature Tg1 of the rubber composition C1 may be greater than or equal to -48°C, preferably greater than or equal to -40°C.

[0022] Advantageously, the elastomer E1 of the rubber composition C1 may be a diene elastomer. Preferably, the elastomer E1 of the rubber composition C1 is a non-functionalized diene elastomer.

[0023] Advantageously, the elastomer E1 of the rubber composition C1 is a diene elastomer chosen from the group consisting of polybutadienes, copolymers of butadiene and styrene, copolymers of butadiene and isoprene, copolymers of isoprene and styrene, copolymers of butadiene-styrene-isoprene and mixtures thereof. Preferably, the elastomer E1 of the rubber composition C1 is a diene elastomer chosen from the group consisting of polybutadienes, copolymers of butadiene and styrene and mixtures thereof. Even more preferably, the elastomer E1 of the composition C1 is a copolymer of styrene and butadiene, in particular non-functionalized.

[0024] Advantageously, the glass transition temperature TgE1 of the elastomer E1 may be within a range from -50°C to 0°C, more preferably from -40°C to 0°C, more preferably from -30°C to 0°C.

[0025] Advantageously, the level of elastomer E1 in the rubber mixture may be within a range of 50 pce to 70 pce, preferably 55 pce to 70 pce, more preferably 55 pce to 65 pce.

[0026] Advantageously, composition C1 may further comprise a reinforcing filler.

[0027] Advantageously, the rubber mixture may comprise at least one plasticizer.

[0028] Advantageously, the rubber mixture as defined above and its preferred embodiments can be obtained according to a manufacturing process which comprises the following steps: preparing the rubber composition C1 in an internal mixer by introducing the elastomer E1 of the rubber composition C1 and, if necessary, other ingredients such as a plasticizer and carrying out thermomechanical work up to a maximum temperature of 200°C to obtain the rubber composition C1; preparing the rubber composition C2 in an internal mixer by introducing the elastomer E2, isoprene diene elastomer, of the rubber composition C2, the reinforcing filler, if necessary, other ingredients such as a plasticizer or a coupling agent for the reinforcing filler, and carrying out thermomechanical work up to a maximum temperature of 200°C to obtain the rubber composition C2; introducing the rubber compositions C1 and C2 obtained in the preceding steps into an internal mixer and carrying out thermomechanical work up to a maximum temperature of 180°C to obtain a combination of compositions;recovering the combination of compositions from the previous step and cooling it to a temperature less than or equal to 110°C; incorporating into the cooled combination of compositions the sulfur vulcanization system; the vulcanization system at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures, and kneading this assembly to a maximum temperature less than 110°C, preferably less than 80°C, and recovering the rubber mixture.;

[0029] Another object of the present invention relates to a pneumatic or non-pneumatic tire tread comprising at least one rubber mixture defined above.

[0030] Another subject of the present invention relates to a pneumatic or non-pneumatic tire comprising at least one rubber mixture defined above or comprising at least one tread defined above.

[0031] By "rubber mixture based on at least" is meant a combination of at least two rubber compositions. The rubber mixture may thus be in a fully or partially crosslinked state or in a non-crosslinked state.

[0032] By "rubber composition based on", we mean 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 manufacture of the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0033] By the expression "part by weight per hundred parts by weight of elastomer" (or pce), it is meant, for the purposes of the present invention, the part, by mass per hundred parts by mass of elastomers in the rubber mixture.

[0034] In this document, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

[0035] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (i.e., excluding the limits a and b) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (i.e., including the strict limits a and b).

[0036] When a “majority” compound is referred to, within the meaning of the present invention, this compound is the majority among the compounds of the same type in the rubber mixture, i.e. it is the one that represents the largest quantity by mass among the compounds of the same type. Thus, for example, a majority elastomer is the elastomer representing the largest mass relative to the total mass of the elastomers in the mixture. In the same way, a so-called majority filler is the one representing the largest mass among the fillers in the mixture. For example, in a system comprising a single elastomer, this is the majority within the meaning of the present invention; and in a system comprising two elastomers, the majority elastomer represents more than half of the mass of the elastomers. On the contrary, a “minority” compound is a compound that does not represent the largest mass fraction among the compounds of the same type.Preferably by majority, we mean present at more than 50%, preferably more than 60%, 70%, 80%, 90%, and more preferably the “majority” compound represents 100%.

[0037] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Obviously, the compounds mentioned may also come from the recycling of materials already in use, that is to say, they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes in particular polymers, plasticizers, fillers, etc.

[0038] The glass transition temperatures, noted Tg1 and Tg2, of the rubber mixture of the invention are measured according to the standard NF EN ISO 11357-2:05-2014 on the rubber mixture.

[0039] The glass transition temperatures of elastomers, denoted TgE1 and TgE2, are measured according to the ASTM D3418:2008 standard on elastomers.

[0040] The loss factor, also called tan δ (also written tan delta), is a physical quantity well known to tire manufacturers. The loss factor represents the fraction of energy dissipated during cyclic loading.

[0041] The loss factor profile represents the change in the loss factor, tan δ, as a function of temperature when a constant stress is applied at a given frequency. In the context of the present invention, the loss factor profile is measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa according to ASTM D 5992-96. Ingredients of rubber compositions C1 and C2

[0042] The rubber compositions C1 and C2 forming the rubber mixture according to the invention each comprise at least one elastomer, respectively elastomer E1 and diene elastomer E2; the elastomer E1 being different from the diene elastomer E2; that is to say that the elastomer E1 does not have the same chemical nature as the diene elastomer E2.

[0043] By "elastomer" is meant a polymer which is flexible, deformable, exhibiting rubber-like elasticity according to the IUPAC definition of elastomers. Preferably, the elastomers E1 and E2 which can be used in the context of the present invention are random elastomers.

[0044] Preferably, the elastomer E1 of the rubber composition C1 is a diene elastomer.

[0045] By "diene elastomer or indistinctly rubber", whether natural or synthetic, must be understood in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not).

[0046] By “elastomeric matrix” is meant all of the elastomers forming the rubber mixture of the invention.

[0047] Diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated". "Essentially unsaturated" generally means a diene elastomer derived at least in part from conjugated diene monomers, having a content of units or motifs of diene origin (conjugated dienes) which is greater than 15% (mol %); thus, diene elastomers such as butyl rubbers or copolymers of dienes and alpha-olefins such as EPDM do not fall within the previous definition and can be described in particular as "essentially saturated" diene elastomers (low or very low content of motifs of diene origin, always less than 15%).

[0048] More particularly, the term diene elastomer capable of being used in the rubber mixtures in accordance with the invention means: any homopolymer of a diene monomer, conjugated or not, having from 4 to 18 carbon atoms; any copolymer of a diene, conjugated or not, having from 4 to 18 carbon atoms and at least one other monomer.

[0049] The other monomer can be an olefin or a diene, conjugated or not.

[0050] Suitable conjugated dienes are conjugated dienes having 4 to 12 carbon atoms, in particular 1,3-dienes, such as 1,3-butadiene and isoprene.

[0051] Suitable non-conjugated dienes are non-conjugated dienes with 6 to 12 carbon atoms, such as 1,4-hexadiene, ethylidene norbornene, dicyclopentadiene.

[0052] Suitable olefins are vinylaromatic compounds with 8 to 20 carbon atoms and aliphatic α-monoolefins with 3 to 12 carbon atoms.

[0053] Suitable vinyl aromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture "vinyl-toluene", para-tert-butylstyrene.

[0054] More specifically, the diene elastomer is: any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more vinylaromatic compounds having from 8 to 20 carbon atoms; a copolymer of isobutene and isoprene (butyl rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer. Reinforcing charge

[0055] The C2 rubber composition comprises one or more reinforcing fillers.

[0056] According to one embodiment of the invention, the rubber composition C1 may optionally also comprise one or more reinforcing fillers. In this embodiment, the level of the reinforcing filler in the composition C1 is lower than the level of the reinforcing filler in the composition C2.

[0057] Any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition that can be used in particular for the manufacture of pneumatic tires, can be used, for example an organic filler such as carbon black, an inorganic filler such as silica or a mixture of these two types of fillers.

[0058] Suitable carbon blacks are all carbon blacks, in particular those conventionally used in pneumatic or non-pneumatic tires or their treads. Among the latter, reinforcing carbon blacks of the 200 series, such as N234, will be mentioned in particular. These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a carrier for certain of the rubber additives used. The carbon blacks could, for example, already be incorporated into the diene elastomer (see, for example, applications WO97 / 36724-A2 or WO99 / 16600-A1).

[0059] Examples of organic fillers other than carbon blacks include functionalized polyvinyl organic fillers as described in applications WO2006 / 069792-A1, WO2006 / 069793-A1, WO2008 / 003434-A1 and WO2008 / 003435-A1.

[0060] By "reinforcing inorganic filler" is meant here any inorganic or mineral filler, whatever its color and origin (natural or synthetic), also called "white" filler, "clear" filler or even "non-black" filler 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 pneumatic or non-pneumatic tires. As is known, certain reinforcing inorganic fillers may be characterized in particular by the presence of hydroxyl groups (-OH) on their surface.

[0061] Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, preferably silica (SiO 2 ) or of the aluminous type, in particular alumina (Al 2 O 3 ).

[0062] The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or pyrogenic silica having a BET specific surface area and a CTAB specific surface area both less than 450 m 2 / g, preferably within a range from 30 to 400 m 2 / g, in particular from 60 to 300 m 2 / g. Any type of precipitated silica may be used, in particular highly dispersible precipitated silicas (known as "HDS" for "highly dispersible" or "highly dispersible silica"). These precipitated silicas, whether highly dispersible or not, are well known to those skilled in the art. Examples include the silicas described in applications WO03 / 016215-A1 and WO03 / 016387-A1.Among the commercial HDS silicas, we can notably use the silicas “Ultrasil ®< 5000GR”, “Ultrasil ®< 7000GR” from the company Evonik, the silicas “Zeosil ®< 1085GR”, “Zeosil ®< 1115 MP”, “Zeosil ®< 1165MP”, “Zeosil ®< Premium 200MP”, “Zeosil ®< HRS 1200 MP” from the company Solvay. As non-HDS silica, the following commercial silicas can be used: silicas “Ultrasil ®< VN2GR”, “Ultrasil ®< VN3GR” from Evonik, silica “Zeosil ®< 175GR” from Solvay, silicas “Hi-Sil EZ120G(-D)”, “Hi-Sil EZ160G(-D)”, “Hi-Sil EZ200G(-D)”, “Hi-Sil 243LD”, “Hi-Sil 210”, “Hi-Sil HDP 320G” from PPG.

[0063] The physical state in which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules, or even beads or any other suitable densified form. Of course, the term reinforcing inorganic filler also means mixtures of different reinforcing inorganic fillers, in particular silicas as described above.

[0064] Those skilled in the art will understand that, as a replacement for the reinforcing inorganic filler described above, a reinforcing filler of another nature could be used, provided that this reinforcing filler of another nature is covered with an inorganic layer such as silica, or else comprises functional sites on its surface, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between this reinforcing filler and the elastomeric matrix.

[0065] A person skilled in the art will be able to adapt the total reinforcing filler rate according to the relevant use of the rubber mixture of the invention, in particular according to the type of pneumatic tires concerned, for example a pneumatic tire for a motorcycle, for a passenger vehicle or even for a utility vehicle such as a van or heavy goods vehicle.

[0066] In this presentation, the BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the NF ISO 5794-1 standard, annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / po: 0.05 to 0.17]. For inorganic fillers such as silica, for example, CTAB specific surface area values ​​were determined according to NF ISO 5794-1, Annex G of June 2010. The process is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler. For carbon blacks, the STSA specific surface area is determined according to ASTM D6556-2016.

[0067] Coupling agents for the reinforcing filler: In a known manner, to couple the reinforcing filler, it is possible to use an at least bifunctional coupling agent (or bonding agent) intended to ensure a sufficient connection, of a chemical and / or physical nature, between the inorganic filler (surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. By "bifunctional", we mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the elastomer, preferably diene.For example, such a bifunctional compound may comprise a first functional group comprising a silicon atom, said first functional group being capable of interacting with the hydroxyl groups of an inorganic reinforcing filler and a second functional group comprising a sulfur atom, said second functional group being capable of interacting with the elastomer, preferably diene.

[0068] Preferably, the organosilanes are chosen from the group consisting of polysulfurized organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, marketed under the name “Si69” by the company Evonik or bis-(triethoxysilylpropyl) disulfide, abbreviated to TESPD, marketed under the name “Si75” by the company Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate marketed by the company Momentive under the name “NXT Silane”. More preferably, the organosilane is a polysulfurized organosilane.

[0069] Of course, mixtures of the coupling agents described above could also be used. Debt collectors

[0070] The rubber compositions forming the rubber mixture of the invention may also contain agents for covering the reinforcing inorganic filler when a reinforcing inorganic filler is used in a composition of the mixture of the invention, making it possible to improve their processability in the raw state. These coating agents are well known (see for example patent applications WO2006 / 125533-A1, WO2007 / 017060-A1 and WO2007 / 003408-A1), examples of which are hydrolyzable silanes such as hydroxysilanes (see for example WO2009 / 062733-A2), alkylalkoxysilanes, polyols (for example diols or triols), polyethers (for example polyethylene glycols), primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes (for example α,ω-dihydroxy-poly-organosilanes (see for example EP0784072-A1). Plasticizers

[0071] The rubber compositions forming the rubber blend of the invention may comprise at least one plasticizer.

[0072] In a manner known to those skilled in the art of rubber compositions for pneumatic or non-pneumatic tires, this plasticizer is preferably chosen from high glass transition temperature (Tg) hydrocarbon resins, low Tg hydrocarbon resins, plasticizing oils, and mixtures thereof. Preferably, the plasticizer is chosen from high Tg hydrocarbon resins, plasticizing oils, and mixtures thereof.

[0073] As is known, plasticizers in rubber compositions make it possible to modify the viscosity of a rubber composition, to adjust the glass transition temperature of the rubber composition relative to its optimum use.

[0074] A high Tg hydrocarbon resin is by definition a solid at room temperature and pressure (20°C, 1 atm), while a plasticizing oil is liquid at room temperature and pressure and a low Tg hydrocarbon resin is viscous at room temperature and pressure.

[0075] Hydrocarbon resins, also called hydrocarbon plasticizing resins, are polymers well known to those skilled in the art, essentially based on carbon and hydrogen but which may contain other types of atoms, for example oxygen, which can be used in particular as plasticizing agents. They are by nature at least partially miscible (i.e., compatible) at the rates used with the rubber compositions for which they are intended, so as to act as true diluting agents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted to their applications, in particular in rubber manufacturing for pneumatic tires (5.5. "Rubber Tires and Mechanical Goods").As is known, these hydrocarbon resins can also be described as thermoplastic resins in that they soften upon heating and can thus be molded. The softening point of hydrocarbon resins is measured according to ISO 4625 (“Ring and Ball” method). The Tg is measured according to ASTM D3418 (2008). The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by size exclusion chromatography (SEC): tetrahydrofuran solvent; temperature 35°C; concentration 1 g / l; flow rate 1 ml / min; solution filtered through a 0.45 µm porosity filter before injection; Moore calibration with polystyrene standards; set of 3 “WATERS” columns in series (“STYRAGEL” HR4E, HR1 and HR0.5); detection by differential refractometer (“WATERS 2410”) and its associated operating software (“WATERS EMPOWER”).Hydrocarbon resins can be aliphatic, aromatic, or aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers. They can be natural or synthetic, petroleum-based or not (if so, also known as petroleum resins). High Tg hydrocarbon resins are known to be thermoplastic hydrocarbon resins with a Tg greater than 20°C.

[0076] Preferably, the plasticizer may optionally comprise a hydrocarbon resin, a solid at room temperature and pressure, called a high Tg resin. Preferably, the high Tg hydrocarbon plasticizing resin has at least one of the following characteristics: a Tg greater than 30°C; a number-average molecular mass (Mn) between 300 and 2000 g / mol, more preferably between 400 and 1500 g / mol; a polymolecularity index (Ip) less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw weight-average molecular mass).

[0077] More preferably, this high Tg hydrocarbon plasticizing resin has all of the above preferred characteristics.

[0078] The plasticizer may optionally include a hydrocarbon resin that is viscous at 20°C, known as “low Tg”, i.e. by definition has a Tg in the range from -40°C to 20°C.

[0079] Preferably, the low Tg hydrocarbon plasticizing resin has at least any one of the following characteristics: a Tg of between -40°C and 0°C, more preferably between -30°C and 0°C and even more preferably between -20°C and 0°C; a number-average molecular mass (Mn) of less than 800 g / mol, preferably less than 600 g / mol and more preferably less than 400 g / mol; a softening point in a range from 0 to 50°C, preferably from 0 to 40°C, more preferably from 10 to 40°C, preferably from 10 to 30°C; a polydispersity index (Ip) of less than 3, more preferably less than 2 (reminder: Ip = Mw / Mn with Mw weight-average molecular mass).

[0080] More preferably, this low Tg hydrocarbon resin has all of the above preferred characteristics.

[0081] The plasticizer may also contain an extender oil (or plasticizing oil) that is liquid at 20°C, known as "low Tg", i.e. by definition has a Tg lower than -20°C, preferably lower than -40°C. Any extender oil, whether aromatic or non-aromatic, known for its plasticizing properties with respect to elastomers, can be used. At room temperature (20°C), these oils, which are more or less viscous, are liquids (i.e., as a reminder, substances that have the capacity to eventually take the shape of their container), in contrast in particular to high Tg hydrocarbon resins which are by nature solid at room temperature.Particularly suitable are plasticizing oils chosen from the group consisting of naphthenic oils (low or high viscosity, in particular hydrogenated or not), paraffinic oils, MES oils (Medium Extracted Solvates), TDAE oils (Treated Distillate Aromatic Extracts), RAE oils (Residual Aromatic Extract oils), TRAE oils (Treated Residual Aromatic Extract) and SRAE oils (Safety Residual Aromatic Extract oils), mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds.

[0082] The above high Tg hydrocarbon resins, low Tg hydrocarbon resins, and preferred plasticizing oils are well known to those skilled in the art and commercially available. Other additives

[0083] The rubber compositions forming the rubber mixture in accordance with the invention may also comprise all or part of the usual additives and processing agents, known to those skilled in the art and usually used in rubber compositions for pneumatic or non-pneumatic tires, in particular for treads, such as, for example, fillers (reinforcing or non-reinforcing / other than those mentioned above), pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents, reinforcing resins (as described, for example, in application WO 02 / 10269). Sulfur vulcanization system

[0084] The rubber mixture according to the invention comprises at least one sulfur vulcanization system, this vulcanization system comprises at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures.

[0085] Sulfur may be in the form of molecular sulfur and / or sulfur donor agent. Examples of sulfur donor agents include polymeric sulfur or caprolactam disulfide.

[0086] Advantageously, the sulfur content in the rubber mixture of the invention is within a range from 0.5 to 12 pce, more preferably from 0.5 to 10 pce.

[0087] Generally speaking, vulcanization accelerators can be classified into two categories, depending on whether they allow a more or less rapid triggering of vulcanization. This triggering of vulcanization can be represented by the so-called "t0" value of the accelerator. A distinction is thus made between vulcanization accelerators having a vulcanization triggering time "t0" strictly less than 3.0 minutes, preferably less than or equal to 2.5 minutes, also called ultra-vulcanization accelerator, and vulcanization accelerators having a vulcanization triggering time "t0" greater than or equal to 3.0 minutes. The term ultra-accelerator is therefore known to designate vulcanization accelerators having a "t0" shorter than a conventional vulcanization accelerator, i.e. here a "t0" strictly less than 3.0 minutes.

[0088] The value of "t0" for a given accelerator must be measured in a given rubber composition, at a given vulcanization temperature. In order to compare so-called slow or fast accelerators according to their value of "t0", the reference composition is given here as a composition comprising 100 phr of NR, 47 phr of carbon black N326, 0.9 phr of stearic acid, 7.5 phr of ZnO, 4.5 phr of sulfur, and the accelerator whose "t0" is to be determined, at a molar rate of 2.3 mmol per 100 parts by weight of elastomer. The method for measuring "t0" is in accordance with standard DIN-53529, at 150°C. For the purposes of the present application, "t0" means the t0 as defined and measured above.

[0089] For example, table no. 1 below gives the “t0” of certain vulcanization accelerators measured with the proposed measurement method. [Table 1] CBS (1)< TBzTD (2)< molar mass (g / mol) 264,41 544,42 "t0" in min 3,0 1,5 (1) N-cyclohexyl-2-benzothiazol-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C”, (2) Tetrabenzylthiuram disulfide (TBzTD) marketed by Harwick under the reference “Ekaland TBZTD C”. This vulcanization accelerator is classified as an ultra-vulcanization accelerator.

[0090] The vulcanization (ultra-)accelerator A that can be used in the context of the mixtures of the present invention is chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures. Those skilled in the art understand that these accelerators of the thiuram, dithiocarbamate, dithiophosphate, xanthate type and their mixtures are accelerators of the thiuram, dithiocarbamate, dithiophosphate, xanthate type and their mixtures, and has a vulcanization onset time, called "t0", strictly less than 3.0 minutes, preferably less than or equal to 2.5 minutes.

[0091] Particularly advantageously, the vulcanization (ultra-)accelerator A may be selected from the group consisting of tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyldithiocarbamate (ZDBC), zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, tellurium diethyldithiocarbamate (TDEC), zinc diisononyldithiocarbamate, zinc pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), zinc isopropylxanthate (ZIX), zinc butyl xanthate (ZBX), sodium ethyl xanthate (SEX), sodium iso-butyl xanthate, (SIBX), sodium iso-propyl xanthate (SIPX), sodium n-butyl xanthate (SNBX), sodium amyl xanthate (SAX),potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX), zinc 2-ethylhexylphosphorodithioate (ZDT / S), and mixtures of these compounds.,

[0092] More preferably, the vulcanization (ultra-)accelerator A may be selected from the group consisting of tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyl dithiocarbamate (ZDBC), zinc diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, zinc diisononyl dithiocarbamate, zinc pentamethylene dithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), and mixtures of these compounds.

[0093] Even more preferably, the vulcanization (ultra-)accelerator A may be chosen from the group consisting of tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), zinc dibutyl dithiocarbamate (ZDBC), zinc dibenzyldithiocarbamate (ZBEC), and mixtures of these compounds.

[0094] The level of vulcanization (ultra-)accelerator A, in the rubber mixture of the invention, may preferably be within a range from 0.5 to 10 pce, preferably from 1.0 to 4.5 pce, even more preferably from 1.0 to 3 pce.

[0095] Preferably, the ratio of the sulfur content expressed in pce to the content of vulcanization (ultra-)accelerator A expressed in pce is within a range from 0.05 to 24, preferably from 0.16 to 10.

[0096] To this basic vulcanization system may be added, incorporated during the first non-productive phase and / or during the productive phase as described later, various known secondary accelerators or vulcanization activators such as metal oxides (typically zinc oxide), stearic acid derivatives (typically stearic acid) or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), well known to those skilled in the art.

[0097] The vulcanization system usable for the rubber mixture of the invention may comprise a level of metal oxide (preferably zinc oxide) of less than 12 phr. Preferably, the level of metal oxide (preferably zinc oxide) is in a range from 0.5 to 10 phr, preferably from 1.0 to 7 phr. The level of stearic acid derivative (i.e. stearic acid or a stearic acid salt, preferably stearic acid) is preferably less than 10 phr. Preferably, the level of stearic acid derivative (i.e. stearic acid or a stearic acid salt, preferably stearic acid) is in a range from 0.5 to 10 phr, more preferably from 1.0 to 5 phr.

[0098] In the present invention, the term "stearic acid derivative" means stearic acid or a stearic acid salt, both of which are well known to those skilled in the art. As an example of a stearic acid salt that can be used in the context of the present invention, mention may in particular be made of zinc or cadmium stearate.

[0099] Preferably, in addition to the sulfur of the vulcanization (ultra-)accelerator A, the vulcanization system may comprise zinc oxide, the ratio of the zinc oxide content expressed in pce to the content of vulcanization (ultra-)accelerator A expressed in pce is within a range from 0.05 to 20, more preferably from 0.22 to 7.

[0100] Also described herein is a rubber mixture according to the invention, in which the vulcanization system comprises sulfur at a level in a range from 0.5 to 10 phr, a vulcanization (ultra-)accelerator A as defined above, including these preferred forms, at a level in a range from 1 to 4.5 phr (more preferably from 1 to 3 phr), and zinc oxide, at a level where the ratio of the zinc oxide level expressed in phr to the level of vulcanization (ultra-)accelerator A expressed in phr is in a range from 0.05 to 20, more preferably from 0.22 to 7.

[0101] Advantageously, the rubber mixture according to the invention does not comprise a vulcanization accelerator, called in the remainder of the description vulcanization accelerator B, having a "t0" greater than or equal to 3.0 minutes or comprising less than 0.5 pce, preferably comprising less than 0.1 pce.

[0102] Very preferably, the rubber mixture does not include vulcanization accelerator B.

[0103] Vulcanization accelerator B, i.e. having a “t0” greater than or equal to 3.0 minutes, may for example be chosen from the group consisting of thiazole type accelerators and their derivatives, sulfenamide type accelerators, thiourea accelerators and their mixtures. For example, the vulcanization accelerator having a "t0" greater than or equal to 3.0 minutes may be selected from the group comprising or consisting of 2-mercaptobenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiazyl sulfenamide (DCBS), N-tert-butyl-2-benzothiazyl sulfenamide (TBBS), N-tert-butyl-2-benzothiazyl sulfenimide (TBSI), morpholine disulfide, N-morpholino-2-benzothiazyl sulfenamide (MBS), dibutylthiourea (DBTU), and mixtures of these compounds.

[0104] According to this embodiment, the sulfur vulcanization system for the rubber mixture of the invention comprises at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures, more preferably from the group consisting of thiurams, dithiocarbamates and their mixtures and at least one vulcanization accelerator B at a rate less than or equal to 0.5 pce, more preferably less than 0.1 pce; the vulcanization accelerator B being chosen from the group consisting of thiazoles, sulfenamides, thioureas and their mixtures. Rubber composition C1

[0105] The rubber mixture according to the invention comprises at least one rubber composition, denoted C1, having a defined glass transition temperature denoted Tg1.

[0106] This rubber composition C1 comprises at least one elastomer E1 as defined above; it being understood that the elastomer E1 is of a different chemical nature from the diene elastomer E2. Preferably, the elastomer E1 is a diene elastomer, more preferably still, is a non-functionalized diene elastomer.

[0107] More preferably still, the elastomer E1 of the rubber composition C1 is chosen from the group consisting of polybutadienes, copolymers of butadiene and styrene, copolymers of butadiene and isoprene, copolymers of isoprene and styrene and copolymers of butadiene-styrene-isoprene. Preferably, the elastomer E1 of the rubber composition C1 is chosen from the group consisting of polybutadienes and copolymers of butadiene and styrene. More preferably, the elastomer E1 of the rubber composition C1 is a copolymer of styrene and butadiene.

[0108] Preferably, this elastomer E1 is a non-functionalized diene elastomer. For the purposes of the present invention, the term "a non-functionalized diene elastomer" means a diene elastomer, whether natural or synthetic, which does not carry a chemical function capable of interacting with a reinforcing filler. Preferably, the non-functionalized diene elastomer may consist essentially of carbon and hydrogen atoms. It may not comprise heteroatoms or may only comprise them in quantities which are impurities and which result from its synthesis process.

[0109] Preferably, the diene elastomer E1, preferably a styrene-butadiene copolymer, is non-functionalized and has a glass transition temperature TgE1 greater than or equal to -50°C. More preferably, the glass transition temperature TgE1 is within a range from -50°C to 0°C, more preferably from -40°C to 0°C, more preferably from -30°C to 0°C.

[0110] In one embodiment, the rubber composition C1 may further comprise at least one reinforcing filler. The reinforcing filler may be any type of reinforcing filler as described above. Preferably, the reinforcing filler is chosen from the group consisting of a carbon black, an inorganic reinforcing filler and mixtures thereof. Even more preferably, the reinforcing filler is chosen from the group consisting of a carbon black, a silica and mixtures thereof. In this embodiment, the level of the reinforcing filler in the composition C1 is lower than the level of the reinforcing filler in the composition C2.

[0111] The rubber composition C1 may also comprise at least one plasticizer as described above or any other additive described above. C2 rubber composition

[0112] The rubber mixture according to the invention comprises at least one rubber composition, denoted C2, having a defined glass transition temperature denoted Tg2.

[0113] This rubber composition C2 comprises at least one diene elastomer E2 which is an isoprene elastomer.

[0114] The term "isoprene elastomer" is understood to mean, in a known manner, a homopolymer or copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), various isoprene copolymers and mixtures of these elastomers. Among the isoprene copolymers, mention will be made in particular of isobutene-isoprene (butyl rubber - IIR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) copolymers.

[0115] The isoprene diene elastomer E2 is preferably natural rubber or a synthetic cis-1,4 polyisoprene. Among these synthetic polyisoprenes, polyisoprenes having a rate (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used.

[0116] Advantageously, the glass transition temperature TgE2 of the elastomer E2, preferably diene in particular functionalized, is within a range from -110°C to -23°C, preferably from -100°C to -28°C, more preferably from -95°C to -30°C.

[0117] The rubber composition C2 further comprises at least one reinforcing filler. The reinforcing filler may be any type of reinforcing filler as described above. Preferably, the reinforcing filler of the composition C2 mainly comprises at least one inorganic reinforcing filler, more preferably mainly comprises at least one silica.

[0118] The rubber composition C2 may also comprise at least one plasticizer as described above or any other additive described above. Rubber mixture according to the invention and its manufacturing process

[0119] As seen previously, the rubber mixture in accordance with the invention has at least two glass temperatures Tg1 and Tg2 and results from the specific combination of a sulfur vulcanization system and at least two rubber compositions C1 and C2 selected in such a way that: the glass transition temperature Tg1 of composition C1 is greater than or equal to -50°C, the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 23°C, the rubber mixture has a loss factor profile showing the evolution of tan δ as a function of temperature in °C, the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa and showing one or more peaks, this profile being such that all the tan δ (tan delta) peaks present at a temperature above the glass transition temperature Tg1 have a width at half-maximum less than or equal to 23°C; and the elastomer E1 is the majority in the rubber mixture, the elastomer E2 is an isoprene diene elastomer;and the sulfur vulcanization system comprises at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof. ;

[0120] Surprisingly, this specific combination of rubber compositions whose vulcanization system includes at least one vulcanization accelerator A selected from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof makes it possible to obtain a rubber mixture simultaneously exhibiting improved hysteresis properties and good wet grip. Without being bound by any theory, if the rubber mixture has a difference in glass transition temperatures of less than 23°C, then the hysteresis properties are deteriorated and the rubber mixture does not exhibit good rolling resistance.If the rubber compound has a loss factor profile showing the evolution of tan δ as a function of temperature in °C, the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa and showing one or more peaks, this profile being such that all the tan δ (tan delta) peaks present at a temperature above the glass transition temperature Tg1, have a width at half-height greater than 23°C, then the rubber compound has a poor dynamic friction coefficient, therefore deteriorated wet grip properties. The presence of the specific vulcanization system as mentioned above makes it possible to improve these properties when the elastomer E2 is an isoprene diene elastomer, preferably natural rubber.

[0121] Preferably, the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 25°C, preferably Tg1 -Tg2 ≥ 28°C.

[0122] Advantageously, the rubber mixture satisfies the mathematical relationship 25°C ≤Tg1 - Tg2 ≤ 40°C.

[0123] Preferably, the glass transition temperature Tg1 of the rubber composition C1 is greater than or equal to -48°C, preferably greater than or equal to -40°C.

[0124] Preferably, the glass transition temperature Tg1 of the rubber composition C1 is within a range from -48°C to -15°C, preferably within a range from -40°C to -15°C.

[0125] Preferably, the glass transition temperature Tg2 of composition C2 is less than or equal to -43°C, preferably less than or equal to -50°C.

[0126] Preferably, the glass transition temperature Tg2 of composition C2 is within a range from -90°C to -43°C, preferably from -85°C to -50°C.

[0127] Preferably, the rubber mixture according to the invention is based on at least one sulfur vulcanization system and at least one rubber composition C1 with a glass transition temperature Tg1 and comprising a non-functionalized diene elastomer E1, more preferably still a copolymer of styrene and butadiene, and the glass transition temperature Tg1 being in a range from -48°C to -15°C and a rubber composition C2 with a glass transition temperature Tg2 and comprising an isoprene diene elastomer E2, preferably natural rubber, and the glass transition temperature Tg2 being in a range from -90°C to -43°C; the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 28°C, the rubber mixture having a loss factor profile showing the evolution of tan δ as a function of temperature in °C,the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa and having one or more peaks, this profile being such that all the tan δ peaks present at a temperature above the glass transition temperature Tg1 have a width at half-height less than or equal to 23°C, the elastomer E1 being the majority in the rubber mixture and the sulfur vulcanization system comprising at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof, more preferably at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates and mixtures thereof.,

[0128] Preferably, the rubber mixture according to the invention is based on at least one sulfur vulcanization system and at least one rubber composition C1 with a glass transition temperature Tg1 and comprising a non-functionalized diene elastomer E1, more preferably still a copolymer of styrene and butadiene, and the glass transition temperature Tg1 being in a range from -40°C to -15°C and a rubber composition C2 with a glass transition temperature Tg2 and comprising an isoprene diene elastomer E2, preferably natural rubber, and the glass transition temperature Tg2 being in a range from -85°C to -50°C, the rubber mixture satisfies the mathematical relationship Tg1 -Tg2 ≥ 28°C, the rubber mixture having a loss factor profile showing the evolution of tan δ as a function of temperature in °C,the loss factor profile being measured over a temperature range from -80°C to 60°C at a frequency of 10 Hz and at a constant stress of 0.7 MPa and having one or more peaks, this profile being such that all the tan δ peaks present at a temperature above the glass transition temperature Tg1 have a width at half-height less than or equal to 23°C, the elastomer E1 being the majority in the rubber mixture and the sulfur vulcanization system comprising at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof, more preferably at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates and mixtures thereof.,

[0129] Preferably, the level of the elastomer E1, preferably diene, in particular non-functionalized, more preferably still a copolymer of styrene and butadiene, in the rubber mixture of the invention is within a range from 50 phr to 70 phr, preferably from 55 phr to 70 phr, more preferably from 55 phr to 65 phr.

[0130] Preferably, the level of the isoprene diene elastomer E2, preferably natural rubber, in the rubber mixture of the invention is less than or equal to 40 phr, more preferably is within a range of 30 phr to 50 phr, preferably 30 phr to 45 phr, more preferably 35 phr to 45 phr.

[0131] Advantageously, the content of the elastomer E1, preferably diene, in particular non-functionalized, more preferably still a copolymer of styrene and butadiene, in the rubber mixture of the invention is comprised in a range going from 50 pce to 70 pce and the content of the isoprene diene elastomer E2, preferably natural rubber, in the rubber mixture of the invention is comprised in a range going from 30 pce to 50 pce. Advantageously, the content of the elastomer E1, preferably diene, in particular non-functionalized, more preferably still a copolymer of styrene and butadiene, in the rubber mixture of the invention is comprised in a range going from 55 pce to 70 pce and the content of the isoprene diene elastomer E2, preferably natural rubber, in the rubber mixture of the invention is comprised in a range going from 30 pce to 45 pce.

[0132] Preferably, the level of reinforcing filler in the rubber mixture of the invention is within a range from 20 to 100 phr, more preferably from 30 to 90 phr, and even more preferably from 40 to 90 phr; the optimum being, in a known manner, different depending on the particular applications targeted.

[0133] When the reinforcing filler is a reinforcing inorganic filler such as silica for example, it may be advantageous to use a coupling agent. Preferably, the content of coupling agent in the rubber mixture of the invention is advantageously less than or equal to 20 phr, it being understood that it is generally desirable to use as little as possible. Typically the level of coupling agent represents from 0.5% to 15% by weight relative to the amount of reinforcing inorganic filler. Its level is preferably within a range from 0.5 to 20 phr. This level is easily adjusted by a person skilled in the art according to the level of reinforcing inorganic filler used in the composition of the invention.

[0134] According to a preferred embodiment, the reinforcing filler is predominantly an inorganic reinforcing filler (preferably silica) in the rubber mixture according to the invention, that is to say that the reinforcing filler comprises more than 50% (>50%) by weight of an inorganic reinforcing filler such as silica relative to the total weight of the reinforcing filler in the rubber mixture. Optionally according to this embodiment, the reinforcing filler may also comprise carbon black. According to this option, the carbon black is used at a level less than or equal to 20 phr in the rubber mixture, more preferably less than or equal to 10 phr (for example the level of carbon black may be within a range from 0.5 to 20 phr, in particular from 1 to 10 phr in the rubber mixture).Within the indicated ranges, the coloring (black pigmenting agent) and anti-UV properties of carbon blacks are benefited from, without otherwise penalizing the typical performance provided by the reinforcing inorganic filler. Rubber compound manufacturing process

[0135] The rubber mixture of the invention can be obtained by the usual processes for manufacturing rubber mixtures such as dry mixing of the different ingredients.

[0136] According to one embodiment, the rubber mixture in accordance with the invention is manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first thermomechanical working or mixing phase (so-called "non-productive" phase), which can be carried out in a single thermomechanical step during which the isoprene diene elastomer E2 of the rubber composition with a glass transition temperature Tg2, the reinforcing filler and possibly the coupling agent of the reinforcing filler are introduced into a suitable mixer such as a conventional internal mixer (for example of the "Banbury" type), in the following sequential order. After thermomechanical mixing during which these ingredients are maintained at a temperature in a range from 140°C to 200°C for one to two minutes, the elastomer E1 of the rubber composition with a glass transition temperature Tg1, as well as all the necessary constituents, with the exception of the vulcanization system, are introduced into the internal mixer.These ingredients undergo thermomechanical mixing for 2 to 10 minutes up to a maximum temperature in a range from 110°C to 200°C, preferably from 130°C to 185°C (and called "falling temperature"); a second phase of mechanical work (so-called "productive" phase) is carried out in an external mixer such as a cylinder mixer, after cooling the mixture obtained during the first non-productive phase to a lower temperature, typically below 120°C, for example in a range from 40°C to 100°C.The vulcanization system is then incorporated, comprising at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures, more preferably at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates and their mixtures, by mixing for 5 to 15 min, to obtain the rubber mixture of the invention.

[0137] According to another preferred embodiment of the invention, the rubber mixture of the invention is prepared in the form of two rubber compositions, and then the rubber compositions are combined so as to obtain the rubber mixture according to the invention.

[0138] More specifically, according to this embodiment, the rubber mixture as defined above and its preferred embodiments can be obtained according to the manufacturing method comprising the following steps: preparing the rubber composition C1 in an internal mixer by introducing the elastomer E1 of the rubber composition C1 and, if necessary, other ingredients such as a plasticizer and carrying out thermomechanical work up to a maximum temperature of 200°C to obtain the rubber composition C1; preparing the rubber composition C2 in an internal mixer by introducing the isoprene diene elastomer E2 of the rubber composition C2, the reinforcing filler, if necessary, other ingredients such as a plasticizer or a coupling agent for the reinforcing filler, and carrying out thermomechanical work up to a maximum temperature of 200°C to obtain the rubber composition C2; introducing the rubber compositions C1 and C2 obtained in the preceding steps into an internal mixer and carrying out thermomechanical work up to a maximum temperature of 180°C to obtain a combination of compositions;recovering the combination of compositions from the previous step and cooling it to a temperature less than or equal to 110°C; incorporating into the cooled combination of compositions the vulcanization system comprising at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and their mixtures, more preferably at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates and their mixtures, and kneading the whole to a maximum temperature less than 110°C, preferably less than 80°C, and recovering the rubber mixture.;

[0139] More precisely, the first rubber composition, called composition C1, is prepared by mixing in a suitable mixer such as a conventional internal mixer (for example of the “Banbury” type) the elastomer E1 and the other possible constituents of composition C1 such as the plasticizer(s), antiozonant(s), etc., with the exception of the vulcanization system. Thermomechanical work is carried out for 2 to 10 minutes up to a maximum temperature in a range from 110°C to 200°C, preferably from 130°C to 185°C (called the “falling temperature”). The rubber composition C1 is thus recovered.

[0140] The second rubber composition, called composition C2, is then prepared by mixing in a suitable mixer such as a conventional internal mixer (for example of the “Banbury” type) the isoprene diene elastomer E2, the reinforcing filler and the other possible constituents such as the plasticizer(s) and the reinforcing filler coupling agent, the antiozonants, etc., with the exception of the vulcanization system. Thermomechanical work is carried out for a period of 2 to 10 minutes up to a maximum temperature in a range from 140°C to 200°C, preferably from 140°C to 185°C (and called the “falling temperature”). The rubber composition C2 is thus recovered.

[0141] The two rubber compositions C1 and C2 from the previous steps are introduced into a standard internal mixer (for example of the “Banbury” type) and thermomechanical work is carried out for 2 to 10 minutes up to a maximum temperature in a range from 110°C to 180°C, preferably from 130°C to 180°C (and called “falling temperature”).

[0142] The mixture from the previous step is then cooled on an external mixer such as a roller mixer to a temperature less than or equal to 110°C. The vulcanization system is then incorporated, comprising at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof, more preferably at least one vulcanization accelerator A chosen from the group consisting of thiurams, dithiocarbamates and mixtures thereof, by mixing for 5 to 15 min, and the rubber mixture according to the invention is recovered.

[0143] Whatever the method of preparation of the rubber mixture, the final rubber mixture thus obtained is then calendered, for example, in the form of a sheet or plate, in particular for characterization in the laboratory, or extruded in the form of a semi-finished (or profiled) rubber usable, for example, as a tread for a pneumatic or non-pneumatic tire, in particular for a passenger vehicle.

[0144] The rubber compound can be either in the raw state (before vulcanization) or in the cured state (after vulcanization), can be a semi-finished product which can be used in a pneumatic or non-pneumatic tire.

[0145] The vulcanization of the rubber mixture can be carried out in a manner known to those skilled in the art, for example at a temperature in a range from 130°C to 200°C, under pressure. Other objects of the invention

[0146] Another subject of the present invention is a pneumatic or non-pneumatic tire tread comprising at least one rubber mixture defined above. The rubber mixture according to the invention may constitute the entire tread or a part of the tread.

[0147] Another object of the present invention relates to a pneumatic tire or non-pneumatic tire comprising at least one rubber mixture defined above or at least one tread defined above.

[0148] The term "pneumatic tire" means a tire intended to form a cavity by cooperating with a support element, for example a rim, this cavity being capable of being pressurized to a pressure higher than atmospheric pressure. In contrast, a "non-pneumatic tire" is not capable of being pressurized. Thus, a non-pneumatic tire is a toric body made of at least one polymeric material, intended to perform the function of a tire but without being subjected to inflation pressure. A non-pneumatic tire may be solid or hollow. A hollow non-pneumatic tire may contain air, but at atmospheric pressure, that is to say, it does not have pneumatic rigidity provided by an inflation gas at a pressure higher than atmospheric pressure.

[0149] The pneumatic tires according to the invention are intended to equip in particular vehicles of all types such as passenger vehicles, two-wheeled vehicles, heavy goods vehicles, agricultural vehicles, civil engineering vehicles or aircraft or, more generally, on any rolling device. The non-pneumatic tires are intended to equip in particular passenger vehicles or two-wheeled vehicles. Preferably, the pneumatic tires according to the invention are intended to equip passenger vehicles.

[0150] Preferably, the pneumatic tire or the non-pneumatic tire comprises at least one tread comprising at least one rubber mixture defined above. MEASUREMENT METHODS Determination of the glass transition temperature of elastomers

[0151] The glass transition temperatures (Tg) of elastomers, before use, are determined using a differential scanning calorimeter according to ASTM D3418:2008. Determination of the glass transition temperature of the rubber mixture

[0152] The glass transition temperature of the rubber compound is measured according to NF EN ISO 11357-2:05-2014 using a Mettler Toledo DSC3+ device and 40 µl aluminum crucibles.

[0153] The scanning measurements are carried out as follows under helium at a flow rate of 40 ml / min: Sample heated from +25°C to -150°C with a ramp of 50°C / min; Isotherm at -150°C for 5 min; Heating from -150°C to +200°C with a ramp of 20°C / min Isotherm at +200°C for 5 min; Cooling from +200°C to -150°C with a ramp of 20°C / min Isotherm at -150°C for 5 min; Heating from -150°C to +200°C with a ramp of 20°C / min Determination of the coefficient µ max

[0154] The dynamic friction coefficient measurements were carried out using a method identical to that described by L. Busse, A. Le Gal, and M. Küppel (Modelling of Dry and Wet Friction of Silica Filled Elastomers on Self-Affine Road Surfaces, Elastomere Friction, 2010, 51, p. 8). The specimens are produced by molding and then vulcanizing a 6 mm thick square rubber support (50mmx50mm). After closing the mold, it is placed in a press with heated plates at a temperature of 150°C, and for the time necessary for the vulcanization of the material (typically several tens of minutes), at a pressure of 16 bars. The soil used to carry out these measurements is a core sample taken from a real road surface made of BBTM type bituminous concrete (NF P 98-137 standard).To avoid dewetting phenomena and the appearance of parasitic adhesion forces between the soil and the material, the soil + specimen system is immersed in a 5% aqueous solution of a surfactant (Sinnozon - CAS number: 25155-30-0). The temperature of the aqueous solution is regulated using a thermostatic bath. The specimen is subjected to a sliding movement in translation parallel to the ground plane. The sliding speed Vg is set at 1.2 m / s. The applied normal stress σ n is 400 kPa (i.e. 4 bar). These conditions are described below as "wet soil conditions". The tangential stress σ t opposite to the movement of the specimen on the soil is continuously measured. The ratio between the tangential stress σ t and the normal stress σ n gives the dynamic friction coefficient µ.The dynamic friction coefficient values ​​are measured during a temperature sweep of the aqueous solution, ranging from 3°C to 44°C, and are obtained in steady state after stabilization of the value of the tangential stress σ t .

[0155] In the examples, the maximum value of the dynamic friction coefficient (noted µ max ) measured during this scan is indicated.

[0156] Unless otherwise stated, results are given in base 100. The arbitrary value 100 is assigned to the comparative mixture to calculate and then compare the maximum dynamic friction coefficient of the different samples tested. The value in base 100 for the sample to be tested is calculated according to the operation: (value of µ max of the sample to be tested / value of µ max of the comparative mixture) × 100. In this way, a result below 100 will indicate a decrease in the coefficient µ max and therefore a decrease in wet grip performance. Conversely, a result above 100 will indicate an increase in the coefficient µ max and therefore an increase in wet grip performance. Measurement of dynamic properties after cooking.

[0157] The dynamic properties tan(δ) are measured on a viscoanalyzer (Metravib V A4000), according to the ASTM D 5992 - 96 standard. The response of a sample of the vulcanized mixture (2 cylindrical specimens of 2 mm thickness and 78.5 mm 2< of section) is recorded, subjected to a sinusoidal stress in alternating simple shear, at the frequency of 10 Hz and at a temperature of 23°C. A peak-to-peak strain amplitude sweep is carried out from 1 to 100% (forward cycle), then from 100% to 1% (return cycle). The results used are the loss factor (tan δ). For the return cycle, the maximum value of tan δ observed at 23°C (tanδmax) is indicated, noted tan δ max at 23°C.

[0158] For tan δ max at 23°C, the results are expressed in performance base 100, that is to say, the value 100 is arbitrarily assigned to the comparative mixture, to then calculate and compare the tan δ max at 23°C of the different mixtures tested. The value in base 100 is calculated according to the operation: (value of tan δ max at 23°C of the comparative mixture / value of tan δ max at 23°C of the sample) * 100. In this way, a lower value represents a decrease in the hysteresis properties while a higher value represents an improvement in the hysteresis properties, therefore an improvement in rolling resistance.

[0159] It is recalled, in a manner well known to those skilled in the art, that the value of tan δ at 0°C is representative of the wet grip potential. For this, the same sample is also subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, during a temperature sweep of -80°C to +100°C, under a fixed stress of 0.7 MPa. The value tan δ at 0°C is recorded (tan δ at 0°C). The higher the tan δ at 0°C, the better the grip. The results are expressed in performance base 100, that is to say that the value 100 is arbitrarily assigned to the comparative mixture, to then calculate and compare the tan δ at 0°C of the different mixtures tested. The value in base 100 is calculated according to the operation: (value of tan δ at 0°C of the comparative mixture / value of tan δ at 0°C of the sample) * 100. Loss factor profile measurement measured according to ASTM D 5992-96

[0160] The response of a specimen consisting of two cylindrical pellets, each 2 mm thick, 78.5 mm 2< in cross-section and one centimeter in diameter, is recorded. The specimen is subjected to a sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, during a temperature sweep from -80°C to + 100°C with a ramp of +1.5°C / min under a constant stress of 0.7 MPa. Data acquisition is carried out at a frequency of 0.12 Hz which can be adapted to obtain the desired precision.

[0161] We then determine, for the tan δ peaks present at a temperature above the glass transition temperature Tg1, the width of the peak at mid-height of each of these peaks.

[0162] This width at half-height is defined as follows: let a given maximum be at a temperature T0 and have an associated value of tan δ Y. We then note all the temperatures associated with values ​​of tan δ equal to Y / 2. Among these values, the width of the peak at half-height then corresponds to the difference in °C between the two closest temperatures framing T0 the temperature of the maximum. EXAMPLES 1- Ingredients :

[0163] The ingredients used in the examples are: Elastomer (1A): Styrene-butadiene copolymer, non-functionalized, having a Tg of -28°C measured according to ASTM D3418:2008, a styrene content of 41% by weight relative to the total weight of the copolymer, a 1,2-vinyl butadiene content of 14% by weight relative to the total weight of the copolymer, a 1,4-trans butadiene content of 27% by weight relative to the total weight of the copolymer. Elastomer (1B): Styrene-butadiene copolymer carrying an amino-alkoxysilane function in the middle of the chain and having a Tg of -65°C measured according to standard ASTM D3418:2008, a styrene content of 16% by weight relative to the total weight of the copolymer, a 1,2-vinyl butadiene content of 20% by weight relative to the total weight of the copolymer, a 1,4-trans butadiene content of 39% by weight relative to the total weight of the copolymer. Elastomer (1C): Natural rubber having a Tg of -70°C. Silica (2): “Zeosil 1165MP” silica marketed by Solvay.Silane (3): Bis[3-(triethoxysilyl)propyl] tetrasulfide silane (TESPT) marketed by Evonik under the reference “Si69”. DPG (4): Diphenylguanidine “Perkacit DPG” from Flexsys. Plasticizer (5): DCPD resin with a softening point of 100°C and a glass transition temperature of 51°C marketed under the reference “PR-383” by Exxon Mobil. ZnO (6): Zinc oxide (industrial grade) marketed by Umicore. Stearic acid (7): Stearin “Pristerene 4031” marketed by Uniquema. Anti-ozone wax (8): Anti-ozone wax “VARAZON 4959” from the company Sasol Wax Anti-oxidant (9): N-1,3-dimethylbutyl-N-phenyl-para-phenylenediamine marketed by Flexys under the reference “Santoflex 6-PPD. . 2. Test 1:

[0164] The purpose of this test is to show the improvement in rubber properties of the mixtures according to the invention (rubber mixture MI1 and MI2) compared to control rubber mixtures (rubber mixture MT1 to MT4) depending on the sulfur vulcanization system and the formulation of the mixtures.

[0165] Comparative rubber compound MT1 is a complex rubber compound based on two compositions and including a sulfur vulcanization system with a conventional vulcanization accelerator.

[0166] The MT2 comparative rubber compound differs from the MT1 rubber compound in its sulfur vulcanization system which includes an ultra-vulcanization accelerator instead of the conventional accelerator.

[0167] Comparative rubber compound MT3 differs from rubber compound MT1 by the nature of the elastomer used in composition C2 of Tg2.

[0168] The MT4 comparative rubber compound differs from the MT3 rubber compound by the nature of the vulcanization accelerator used.

[0169] The rubber mixture according to the invention MI1 is distinguished from the comparative mixture MT2 by the nature of the elastomer used in composition C2 of Tg2.

[0170] The rubber mixture according to the invention MI2 differs from the rubber mixture according to the invention MI1 by the use of a vulcanization ultra-accelerator of a different chemical nature.

[0171] The formulation of the comparative mixtures MT1 to MT4 and those of the invention MI1 and MI2 are presented in table n°2 and n°3; the proportions are expressed in pce, that is to say in parts by weight per 100 parts by weight of the elastomers of the mixture. [Table 2] MT1 MT2 Elastomer (1A) 60,0 60,0 Elastomer (1B) 40,0 40,0 Silica (3) 55,0 55,0 Silane (4) 5,5 5,5 DPG (5) 1,2 1,2 Plasticizer (6) 18,4 18,4 ZnO (9) 5,0 5,0 Stearic acid (10) 2,0 2,0 Anti-ozone wax (7) 2,0 2,0 Antioxidant (8) 1,0 1,0 Sulfur 0,5 0,5 CBS 2,0 (-) TBzTD (-) 5,0 [Table3] MT3 MT4 MI1 MI2 Elastomer (1A) 60,0 60,0 60,0 60,0 Diene elastomer (1C) 40,0 40,0 40,0 40,0 Silica (2) 55,0 55,0 55,0 55,0 Silane (3) 5,5 5,5 5,5 5,5 DPG (4) 1,2 1,2 1,2 1,2 Plasticizer (5) 18,4 18,4 18,4 18,4 ZnO (6) 5,0 5,0 5,0 5,0 Stearic acid (7) 2,0 2,0 2,0 2,0 Anti-ozone wax (8) 2,0 2,0 2,0 2,0 Antioxidant (9) 1,0 1,0 1,0 1,0 Sulfur 0,5 0,5 0,5 0,5 CBS 2,0 (-) (-) (-) MBTS (-) 2,0 (-) (-) ZBEC (-) (-) (-) 2,0 TBzTD (-) (-) 2,0 (-)

[0172] The comparative mixture MT1 is obtained as follows: Step A: All the ingredients in Table 4 are introduced in one or more batches into a 414 cm 3 internal mixer, filled to 70% by volume and with an initial tank temperature of 90°C. Thermomechanical work is carried out for 6 minutes until a maximum drop temperature of 165°C is reached. The composition thus obtained, called composition C1, is recovered. Step B: All the ingredients in Table 5 are introduced in one or more batches into another 414 cm 3 internal mixer, filled to 70% by volume and with an initial tank temperature of 90°C. Thermomechanical work is carried out for 6 minutes until a maximum drop temperature of 165°C is reached. The composition thus obtained, called composition C2, is recovered.Step C: The previously obtained composition C1 and the previous composition C2 are then introduced into a 414 cm 3 internal “Polylab” mixer, filled to 70% by volume, and thermomechanical work is carried out for a period of 5 min until a maximum drop temperature of 150°C is reached. Step D: The mixture from the previous step is then introduced into an external mixer, such as a cylinder mixer, so as to cool this mixture to a temperature of 40°C. The vulcanization system (0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C” is then incorporated and mixed for 20 min. The mixture thus obtained is then calendered in the form of plates to carry out measurements of its physical or mechanical properties.

[0173] Unless otherwise stated, the rubber properties of the rubber compound are measured after curing at 170°C for 20 min. [Table 4] Elastomer (1A) 60,0 Silica (2) 15,3 Silane (3) 2,2 DPG (4) 0,6 Composition 1 Plasticizer (5) 11,0 ZnO (6) 2,5 Stearic acid (7) 1,00 Anti-ozone wax (8) 1,0 Antioxidant (9) 0,5 [Table 5] Elastomer (1B) 40,0 Silica (2) 39,7 Silane (3) 3,3 DPG (4) 0,6 Composition 2 Plasticizer (5) 7,4 ZnO (6) 2,5 Stearic acid (7) 1,0 Anti-ozone wax (8) 1,0 Antioxidant (9) 0,5

[0174] The MT2 mixture is obtained by reproducing steps A to C of the process described for the comparative mixture MT1 above with the compositions C1 and C2 of the respective tables No. 4 and No. 5. Step D described previously is also reproduced except that the vulcanization system of the MT1 mixture (0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C” is replaced by the following vulcanization system: 0.5 pce of sulfur and 2.0 pce of tetrabenzylthiuram disulfide (TBzTD) marketed by the company Harwick under the reference “Ekaland TBZTD C”.

[0175] The comparative mixture MT3 is obtained by reproducing steps A to C of the process described for the comparative mixture MT1 with the compositions C1 and C3 of the respective tables No. 4 and No. 6. Step D described previously is also reproduced with the vulcanization system of the mixture MT1 (i.e. 0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C”). [Table 6] Elastomer (1C) 40,0 Silica (3) 39,7 Silane (4) 3,3 DPG (5) 0,6 Composition 3 Plasticizer (6) 7,4 Anti-ozone wax (7) 1,0 Antioxidant (8) 0,5 ZnO (9) 2,5 Stearic acid (10) 1,0

[0176] The MT4 mixture is obtained by reproducing steps A to C of the process described for the comparative mixture MT1 above with the compositions C1 and C3 of the respective tables No. 4 and No. 6. Step D described previously is also reproduced except that the vulcanization system of the MT1 mixture (0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C” is replaced by the following vulcanization system: 0.5 pce of sulfur and 2.0 pce of 2-mercaptobenzothiazyl disulfide (MBTS) marketed by the company Quimica under the reference “Rubator MBTS”.

[0177] The mixture MI1 according to the invention is obtained by reproducing steps A to C of the process described for the comparative mixture MT1 above with the compositions C1 and C3 of the respective tables No. 4 and No. 6. Step D described previously is also reproduced except that the vulcanization system of the mixture MT1 (0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C” is replaced by the following vulcanization system: 0.5 pce of sulfur and 2.0 pce of tetrabenzylthiuram disulfide (TBzTD) marketed by the company Harwick under the reference “Ekaland TBZTD C”.

[0178] The mixture MI2 according to the invention is obtained by reproducing steps A to C of the process described for the comparative mixture MT1 above with the compositions C1 and C3 of the respective tables No. 4 and No. 6. Step D described previously is also reproduced except that the vulcanization system of the mixture MT1 (0.5 pce of sulfur and 2.0 pce of N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS) marketed by Quimica under the reference “Rubenamid-C” is replaced by the following vulcanization system: 0.5 pce of sulfur and 2.0 pce of zinc dibenzyldithiocabamate (ZBEC) marketed by the company Performance additives under the reference “Perkacit ZBEC C”.

[0179] The rubber properties of the MT1 to MT4 and MI1 and MI2 mixtures, measured after curing, are presented in tables 7 and 8. [Table 7] MT1 MT2 Glass transition temperature of the mixture (measured in °C) Tg1 -19°C -18°C Tg2 -49°C -47°C Loss Factor Profile Peak width at mid-height 17,3°C 16,6°C Tan δ max at 23°C (base 100) 100 100 Tan δ at 0°C (base 100) 100 94 [Table 8] MT3 MT4 MI1 MI2 Glass transition temperature of the mixture (measured in °C) Tg1 -18°C -17°C -17°C -18°C Tg2 -55°C -55°C -55°C -55°C Loss Factor Profile Peak width at mid-height 23,0°C 22,9°C 22,6°C 21,8°C Tan δ max at 23°C (base 100) 100 94 107 107 Tan δ at 0°C (base 100) 100 61 113 168

[0180] When comparing the comparative mixture MT1 and the comparative mixture MT2, it is found that the use of an ultra-vulcanization accelerator from the thiuram family instead of a usual vulcanization accelerator from the sulfenamide family does not lead to improvements in wet grip properties (Tan δ at 0°C) and rolling resistance (Tan δ max at 23°C).

[0181] Surprisingly, this effect is not observed for the mixture according to the invention (comparison of the mixture MI1 according to the invention with the comparative mixture MT3). Contrary to what was observed for the comparative mixtures MT1 and MT2, the use of this same ultra-vulcanization accelerator in a rubber mixture whose lower Tg phase comprises an isoprene elastomer and a reinforcing filler (see the mixture according to the invention MI1) allows a simultaneous improvement in the wet grip properties and an improvement in the rolling resistance (improvement of the Tan δ max descriptor at 23°C) compared to a rubber mixture whose lower Tg phase comprises an isoprene elastomer and a reinforcing filler and whose vulcanization system is based on a conventional vulcanization accelerator (see comparative mixture MT3).The simultaneous improvement of wet grip and rolling resistance properties is also observed with the use of another ultra-accelerator from the dithiocarbamate family (mixture according to the invention MI2) but not with another vulcanization accelerator (comparative mixture MT4).

Claims

1. Rubber compound having at least two glass transition temperatures Tg, denoted Tg1 and Tg2 and based on at least one sulfur vulcanization system and at least two rubber compositions, denoted C1 and C2, the rubber composition C1 comprising at least one elastomer E1 and having the glass transition temperature Tg1, the composition C2 comprising at least one elastomer E2, different from the elastomer E1, and a reinforcing filler, and the composition C2 having the glass transition temperature Tg2, characterized in that: - the glass transition temperature Tg1 of the composition C1 is above or equal to -50°C; - the rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 23°C; - the rubber compound has a loss factor profile exhibiting the change in tan δ as a function of the temperature in °C, the loss factor profile being measured over a temperature range extending from -80°C to 60°C at a frequency of 10 Hz and a constant stress of 0.7 MPa and exhibiting one or more peaks, this profile being such that all the tan δ peaks present at a temperature above the glass transition temperature Tg1 have a width at half height below or equal to 23°C; - the elastomer E1 is predominant in the rubber compound, - the elastomer E2 is an isoprene diene elastomer; - and the sulfur vulcanization system comprises at least one vulcanization accelerator A selected from the group consisting of thiurams, dithiocarbamates, dithiophosphates, xanthates and mixtures thereof and wherein e glass transition temperature Tg1 and Tg2 are measured according to the standard NF EN ISO11357-2:05-2014.

2. Rubber compound according to Claim 1, in which the rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 25°C, preferably Tg1-Tg2 ≥ 28°C.

3. Rubber compound according to either one of the preceding claims, in which the glass transition temperature Tg1 of the rubber composition C1 is above or equal to -48°C, preferably above or equal to -40°C.

4. Rubber compound according to any one of the preceding claims, in which the glass transition temperature Tg2 of the composition C2 is below or equal to -43°C, preferably below or equal to -50°C.

5. Rubber compound according to any one of the preceding claims, in which the elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of polybutadienes, butadiene / styrene copolymers, butadiene / isoprene copolymers, isoprene / styrene copolymers and butadiene / styrene / isoprene copolymers and mixtures thereof; more preferably the elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of polybutadienes, butadiene / styrene copolymers and mixtures thereof.

6. Rubber compound according to any one of the preceding claims, in which the content of the elastomer E1 in the rubber compound may be within a range extending from 50 phr to 70 phr, preferably from 55 phr to 70 phr, more preferentially from 55 phr to 65 phr.

7. Rubber compound according to any one of the preceding claims, in which the isoprene diene elastomer E2 of the rubber composition C2 is selected from the group consisting of natural rubber and synthetic polyisoprene; preferably, the isoprene diene elastomer E2 of the rubber composition C2 is natural rubber.

8. Rubber compound according to any one of the preceding claims, in which the reinforcing filler of the composition C2 predominantly comprises at least one inorganic reinforcing filler, more preferentially predominantly comprises at least one silica.

9. Rubber compound according to any one of the preceding claims, in which the vulcanization accelerator A is selected from the group consisting of tetrabenzylthiuram disulfide (TBzTD), tetramethyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD), tetraisobutyl thiuram disulfide (TiBTD), dipentamethylene thiuram tetrasulfide (DPTT), zinc dibutyl dithiocarbamate (ZDBC), zinc diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, copper dimethyl dithiocarbamate, tellurium diethyl dithiocarbamate (TDEC), zinc diisononyl dithiocarbamate, zinc pentamethylene dithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), zinc isopropyl xanthate (ZIX), zinc butyl xanthate (ZBX), sodium ethyl xanthate (SEX), sodium isobutyl xanthate (SIBX), sodium isopropyl xanthate (SIPX), sodium n-butyl xanthate (SNBX), sodium amyl xanthate (SAX), potassium ethyl xanthate (PEX), potassium amyl xanthate (PAX), zinc 2-ethylhexylphosphorodithioate (ZDT / S), and the mixtures of these compounds.

10. Rubber compound according to any one of the preceding claims, in which the vulcanization accelerator A is selected from the group consisting of tetrabenzyl thiuram disulfide (TBzTD), tetramethyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD), tetraisobutyl thiuram disulfide (TiBTD), dipentamethylene thiuram tetrasulfide (DPTT), zinc dibutyl dithiocarbamate (ZDBC), zinc diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, zinc diisononyl dithiocarbamate, zinc pentamethylene dithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), and mixtures of these compounds.

11. Rubber compound according to any one of the preceding claims, in which the content of vulcanization accelerator A is within a range extending from 0.5 to 10 phr, more preferentially 1.0 to 4.5 phr, more preferentially extending from 1.0 to 3 phr.

12. Rubber compound according to any one of the preceding claims, in which the sulfur vulcanization system comprises zinc oxide, the ratio of the zinc oxide content, expressed in phr, to the vulcanization accelerator A content, expressed in phr, is within a range extending from 0.05 to 20, even more preferentially extending from 0.22 to 7.

13. Rubber compound according to any one of the preceding claims, in which the ratio of the content of sulfur, expressed in phr, to the content of vulcanization accelerator A, expressed in phr, is within a range extending from 0.05 to 24, even more preferentially extending from 0.16 to 10.

14. Pneumatic or non-pneumatic tyre tread comprising at least one compound defined according to any one of Claims 1 to 13.

15. Pneumatic or non-pneumatic tyre comprising at least one compound defined according to any one of Claims 1 to 13 or a tread according to Claim 14.