Rubber Compounds

Abstract

The present invention relates to a rubber compound having at least two glass transition temperatures Tg, denoted Tg1 and Tg2, based on at least two rubber compositions denoted C1 and C2, wherein rubber composition C1 comprises at least one elastomer E1 and has a glass transition temperature Tg1, composition C2 comprises at least one elastomer E2 and a reinforcing filler, elastomer E2 being different from elastomer E1 and having a glass transition temperature Tg2, The glass transition temperature Tg1 of the composition C1 is −50° C. or higher, The rubber compound satisfies the mathematical relationship Tg1-Tg2≧23°C, The rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -80°C to 60°C at a frequency of 10 Hz and a constant stress of 0.7 MPa, and showing one or more peaks, wherein all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less; and Elastomer E1 relates to the rubber compound which is the most abundant in the rubber compound. The invention also relates to a tread comprising at least the compound described above, and to a tire comprising at least one of the compounds described above or the tread described above.

Description

[Technical Field]

[0001] The field of the invention is that of reinforced rubber compounds used in particular in the construction of vehicle tires, and more particularly in the manufacture of treads. [Background technology]

[0002] One of the necessary requirements of a tire is to provide optimal grip on the road, especially on wet ground. One way to give a tire increased grip on wet ground is to use a rubber composition in its tread that can have high hysteresis. At the same time, however, the tire tread must minimize its contribution to the rolling resistance of the tire, i.e., have the lowest possible hysteresis. Therefore, the rubber composition of the tread must meet two conflicting requirements: it must have the maximum possible hysteresis to meet the grip requirement, and it must also have the lowest possible hysteresis to meet the rolling resistance requirement. The improvement in rolling resistance is made possible by the use of new rubber compositions reinforced with inorganic fillers, especially highly dispersed special silicas, which compete with conventional tire-grade carbon black in terms of reinforcement, but at the same time provide these compositions with lower hysteresis, representing lower rolling resistance. However, the use of high levels of inorganic reinforcing fillers in rubber compositions has the disadvantage that they adversely affect the wet grip properties of the rubber compositions incorporating them. Thus, meeting both grip and rolling resistance requirements, especially on wet ground, remains a concern for tire manufacturers. Aiming to find the best compromise in terms of performance, tire manufacturers are increasingly developing composite rubber compositions, often incorporating elastomers of several different chemistries, thereby forming rubber compounds. An example of a composite composition is described in patent document EP 3372638, in particular in Example 4, where the composite composition comprises two different elastomers whose glass transition temperatures differ by no more than 20°C, and which composition shows an improvement in terms of the rolling resistance / wear compromise. Thus, there is still a need for rubber compounds that have improved rolling resistance while maintaining good wet grip, or that simultaneously improve this property. Summary of the Invention [Problem to be solved by the invention]

[0003] One object of the present invention is therefore to propose new rubber compounds, in particular for treads, which in particular overcome the above-mentioned drawbacks and exhibit improved hysteresis properties while at the same time maintaining or improving their wet grip performance. [Means for solving the problem]

[0004] This object has been achieved by the Applicant's surprising discovery that rubber compounds having a specific loss factor profile exhibit better rolling resistance while simultaneously maintaining good wet grip properties or exhibiting improved properties, said loss factor profile being based on a specific combination of at least two rubber compositions C1 and C2 having different glass transition temperatures, the difference between these glass transition temperatures being 23°C or more, measured at a frequency of 10 Hz and a constant stress of 0.7 MPa over a temperature range from -80°C to 60°C, with the elastomer of composition C1 being the most prevalent in the mixture.

[0005] A first subject of the present invention is a rubber composition having at least two Tg's, Tg1 and Tg2, based on at least two rubber compositions C1 and C2, wherein the rubber composition C1 comprises at least one elastomer E1 and has a glass transition temperature Tg1, and the composition C2 comprises at least one elastomer E2 and a reinforcing filler, the elastomer E2 being different from the elastomer E1 and having a glass transition temperature Tg2, The glass transition temperature Tg1 of the composition C1 is -50°C or higher, The rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 23°C, the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -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, the profile being such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less; and Elastomer E1 is the most abundant in rubber compounds The present invention relates to a rubber compound characterized by the above.

[0006] Advantageously, the rubber compound satisfies the mathematical relationship Tg1-Tg2≧25°C, preferably Tg1-Tg2≧28°C, and even more advantageously Tg1-Tg2≧30°C. Suitably, the rubber compound may satisfy the mathematical relationship 25°C < Tg1 - Tg2 < 40°C, preferably 28°C < Tg1 - Tg2 < 35°C, more advantageously 28°C < Tg1 - Tg2 < 34°C. Suitably, 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, and more advantageously less than or equal to -57°C. Suitably, the glass transition temperature Tg2 of the composition C2 is within the range of -90°C to -43°C, and preferably within the range of -85°C to -50°C. Preferably, the elastomer E2 of the rubber composition C2 is a diene elastomer, and more preferably, the elastomer E2 of the composition C2 is a functionalized diene elastomer. Advantageously, the glass transition temperature TgE2 of the elastomer E2 is in the range of -110°C to -23°C, preferably -100°C to -28°C, and more advantageously -95°C to -30°C.

[0007] Preferably, the elastomer E2 of the rubber composition C2 is a diene elastomer, preferably functionalized and selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, isobutene / isoprene copolymers, butadiene / styrene copolymers, butadiene / isoprene copolymers, isoprene / styrene copolymers and butadiene / styrene / isoprene copolymers. Advantageously, the elastomer E2 is preferably functionalized and selected from polybutadiene and styrene / butadiene copolymers. Even more advantageously, the elastomer E2 is preferably functionalized and is a styrene / butadiene copolymer. Advantageously, the functionalized diene elastomer E2 of the rubber composition C2 comprises at least one chemical functional group capable of interacting with the reinforcing filler, the chemical functional group comprising at least one heteroatom selected from the group consisting of nitrogen, sulfur, oxygen, phosphorus, tin and silicon. Advantageously, the reinforcing filler of composition C2 comprises predominantly at least one inorganic reinforcing filler, more advantageously predominantly at least one silica. Preferably, the reinforcing filler of composition C2 comprises mainly a reinforcing inorganic filler, advantageously silica, and elastomer E2 may be a functionalized diene elastomer comprising at least one chemical functional group capable of interacting with the reinforcing inorganic filler, the chemical functional group comprising at least one heteroatom selected from the group consisting of nitrogen, sulfur, oxygen and phosphorus. Preferably, the chemical functional group capable of interacting with the reinforcing filler may be a polar functional group comprising at least one oxygen atom.

[0008] Preferably, the glass transition temperature Tg1 of the rubber composition C1 may be in the range of -48°C to -15°C, more advantageously in the range of -48°C to -15°C. Suitably, the glass transition temperature Tg1 of the rubber composition C1 may be −48° C. or higher, preferably −40° C. or higher. Suitably, 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.

[0009] Preferably, the elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer, and butadiene / styrene / isoprene copolymer. Advantageously, the elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer, and butadiene / styrene / isoprene copolymer. More advantageously, the elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of polybutadiene and butadiene / styrene copolymer. Even more advantageously, the elastomer E1 of the rubber composition C1 is a styrene / butadiene copolymer.

[0010] Preferably, the glass transition temperature TgE1 of the elastomer E1 may be in the range of -50°C to 0°C, more advantageously -40°C to 0°C, more advantageously -30°C to 0°C. Advantageously, the content of elastomer E1 in the compound may range from 50 phr to 70 phr, preferably from 55 phr to 70 phr, and more advantageously from 55 phr to 65 phr. Suitably, composition C1 may further comprise a reinforcing filler. Suitably, the rubber compound may include at least one plasticizer.

[0011] Advantageously, the formulations defined above and preferred embodiments thereof can be obtained by a manufacturing process comprising the following steps: preparing the rubber composition C1 by introducing into an internal mixer the elastomer E1 and, where appropriate, other components of the rubber composition C1, such as plasticizers, and carrying out a thermomechanical treatment at a maximum temperature of 200°C to obtain the rubber composition C1; preparing a rubber composition C2 by introducing into an internal mixer the elastomer E2 of the rubber composition C2, the reinforcing filler and, where appropriate, other components such as plasticizers or coupling agents for the reinforcing filler, and carrying out a thermomechanical treatment at a maximum temperature of 200°C to obtain the rubber composition C2; introducing the rubber compositions C1 and C2 obtained in the previous steps into an internal mixer and carrying out a thermomechanical treatment at a maximum temperature of 180°C in order to obtain a combined composition; recovering the combined composition from the previous step and cooling it to a temperature of 110°C or less; and Combining the cooled compositions, including the crosslinking system, and kneading everything at a maximum temperature of less than 110°C, advantageously less than 80°C, and recovering the rubber compound. DETAILED DESCRIPTION OF THE INVENTION

[0012] Another subject of the invention relates to a tread comprising at least one compound as defined above. Another subject of the invention relates to a tire comprising at least one compound as defined above or at least one tread as defined above.

[0013] A first subject of the present invention is a rubber composition having at least two glass transition temperatures Tg, designated Tg1 and Tg2, based on at least two rubber compositions C1 and C2, the rubber composition C1 comprising at least one elastomer E1 and having a glass transition temperature Tg1, the composition C2 comprising at least one elastomer E2 and a reinforcing filler, the elastomer E2 being different from the elastomer E1 and having a glass transition temperature Tg2, The glass transition temperature Tg1 of the composition C1 is -50°C or higher, The rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 23°C, the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -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, the profile being such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less; and Elastomer E1 is the most abundant in rubber compounds The present invention relates to a rubber compound characterized by the above.

[0014] The expression "rubber compound based on at least" should be understood to mean a combination of at least two rubber compositions. The rubber compound may therefore be fully or partially crosslinked or may be uncrosslinked. The expression "rubber composition based on" should be understood to mean a composition comprising a mixture and / or a product of in situ reactions of the various components used, some of which can and / or are intended to at least partially react with one another during the various stages of the preparation of the composition, thus allowing the composition to be in a fully or partially crosslinked or non-crosslinked state. In the present invention, the expression "parts by weight per 100 parts by weight of elastomer" (or phr) is to be understood to mean parts by weight per 100 parts by weight of elastomer in the rubber compound. In this specification, all percentages (%) given are percentages (%) by weight unless expressly indicated otherwise. Furthermore, any interval of values ​​represented by the expression "between a and b" denotes a range of values ​​from greater than a to less than b (i.e., excluding the boundary values ​​a and b), while any interval of values ​​represented by the expression "from a to b" means a range of values ​​from a to b (i.e., including the strict boundary values ​​a and b). When referring to a "most prevalent" compound, it is understood in the present invention to mean that the compound is the most prevalent among compounds of the same type in the rubber compound, i.e., it is the compound that is the most prevalent by mass among compounds of the same type. Thus, for example, the most prevalent elastomer is the elastomer that represents the largest mass relative to the total mass of elastomers in the compound. Similarly, the "most prevalent" filler is the one that represents the most prevalent filler in the compound. For example, in a system containing only one elastomer, the latter is the most prevalent in the sense of the present invention, while in a system containing two elastomers, the most prevalent elastomer is the one that represents more than half the mass of all elastomers. In contrast, a "less prevalent" compound is one that does not represent the largest mass proportion among compounds of the same type. Preferably, the term "most prevalent" is understood to mean that the compound is present in more than 50%, preferably more than 60%, 70%, 80%, or 90%, and more advantageously, the "most prevalent" compound is present in 100%.

[0015] The carbon-containing compounds described in the detailed description may be of fossil origin or bio-based. In the latter case, they may be partially or completely derived from biomass or obtained from renewable starting materials derived from biomass. Polymers, plasticizers, fillers, etc. are particularly relevant.

[0016] The glass transition temperatures, denoted Tg1 and Tg2, of the compounds of the invention are determined according to standard NF EN ISO 11357-2:05-2014 for rubber compounds. The glass transition temperatures of the elastomers, designated TgE1 and TgE2, are measured according to standard ASTM D3418:2008. The loss factor, also known as tan δ, is a physical quantity well known to pneumatic tire manufacturers. The loss factor is the rate of energy dissipated during cyclic stress. The loss factor profile represents the variation of 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 in accordance with standard ASTM D 5992-96 at a frequency of 10 Hz and a constant stress of 0.7 MPa over the temperature range from -80°C to 60°C.

[0017] Components of rubber compositions C1 and C2 The rubber compositions C1 and C2 forming the rubber compound according to the invention each comprise, as at least one elastomer, an elastomer E1 and an elastomer E2, respectively, where the elastomer E1 is different from the elastomer E2. "Elastomer" means a polymer that is flexible, deformable, and exhibits rubber-like elasticity according to the IUPAC definition of an elastomer. Advantageously, E1 of the rubber composition C1 and / or the elastomer E2 of the rubber composition C2 are diene elastomers. "Diene" elastomers (or, without distinction, rubbers) are to be understood as known elastomers, whether natural or synthetic, usually composed at least in part (i.e., homopolymers or copolymers) of diene monomer units (monomers having two conjugated or non-conjugated carbon-carbon double bonds). "Elastomeric matrix" is understood to mean all of the elastomers that form the rubber compound of the invention. Diene elastomers are divided into two categories: "substantially unsaturated" or "substantially saturated". The term "substantially unsaturated" is usually understood to mean a diene elastomer obtained at least in part from conjugated diene monomers having a content of units of diene origin (conjugated diene) of more than 15% (mol %), which means that butyl rubber or copolymers of dienes and α-olefins of the EPDM type do not fall within the scope of the above definition and can in particular be described as "substantially saturated" diene elastomers (low or very low content of units of diene origin, always less than 15 mol %). The diene elastomers that can be used in the rubber compounds according to the invention are more particularly intended to mean: any homopolymer of conjugated or non-conjugated diene monomers having 4 to 18 carbon atoms; Any copolymer of a conjugated or non-conjugated diene monomer having from 4 to 18 carbon atoms and at least one other monomer.

[0018] The other monomer may be an olefin or a conjugated or non-conjugated diene. Suitable conjugated dienes include those containing from 4 to 12 carbon atoms, particularly 1,3-dienes, especially 1,3-butadiene and isoprene. Suitable non-conjugated dienes include those containing 6 to 12 carbon atoms, particularly 1,4-hexadiene, ethylidene norbornene or dicyclopentadiene.

[0019] Suitable olefins include vinyl aromatic compounds containing from 8 to 20 carbon atoms and aliphatic α-monoolefins containing from 3 to 12 carbon atoms. Suitable vinyl aromatic compounds include, for example, styrene, ortho-, meta- or para-methylstyrene, the "vinyl toluene" commercial mixture or para-(tert-butyl)styrene.

[0020] 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 one another or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms; Copolymers of isobutene and isoprene (butyl rubber) and also halogenated versions, especially chlorinated or brominated versions, of copolymers of this type.

[0021] Reinforcing fillers Rubber composition C2 contains one or more reinforcing fillers. In one embodiment of the present invention, the rubber composition C1 may also optionally comprise one or more reinforcing fillers. Any type of "reinforcing" filler known for its ability to reinforce rubber compositions that are particularly useful in the manufacture of pneumatic tires may be used, for example, organic fillers such as carbon black, inorganic fillers such as silica, or a mixture of these two types of fillers. Any carbon black is suitable, especially carbon black conventionally used in pneumatic or non-pneumatic tires or their treads. More specifically, among the latter, mention may be made of reinforcing carbon black 200 series, such as N234 black. These carbon blacks can be used in the form in which they are commercially available or in any other form, for example, as a carrier for some rubber additives. Carbon black may also be present, for example, in a diene elastomer (see, for example, International Publications WO 97 / 36724-A2 and WO 99 / 16600-A1).

[0022] Examples of organic fillers other than carbon black include functionalized polyvinyl organic fillers described in International Publication WO2006 / 069792-A1, WO2006 / 069793-A1, WO2008 / 003434-A1, and WO2008 / 003435-A1. The term "reinforcing inorganic filler" is to be understood in this specification to mean any inorganic or mineral filler, regardless of its color and its origin (natural or synthetic), also called "white", "transparent" or "non-black" filler, in contrast to carbon black, which can be used alone to reinforce rubber compositions without any other means than as intermediate coupling agents intended for the manufacture of pneumatic or non-pneumatic tires. In a known manner, some reinforcing inorganic fillers can be characterized in particular by the presence of hydroxyl (-OH) groups on their surface. Mineral fillers of the siliceous type, advantageously silica (SiO2), or of the alum type, in particular alumina (Al2O3), are particularly suitable as reinforcing inorganic fillers.

[0023] The silica used may be any reinforcing silica known to those skilled in the art, in particular 450m 2 / g or less, preferably 30 to 400m 2 / g, especially 60-300m 2 The silica may be any precipitated or fumed silica exhibiting both a BET specific surface area and a CTAB specific surface area in the range of 0.15 / g. Any type of precipitated silica may be used, in particular highly dispersed precipitated silica (referred to as "HDS" for "highly dispersed" or "highly dispersed silica"). These precipitated silicas may be highly dispersed or not and are well known to those skilled in the art. For example, mention may be made of the silicas described in International Publications WO 03 / 016215-A1 and WO 03 / 016387-A1. Among commercially available HDS silicas, the Ultrasil® 5000GR and Ultrasil® 7000GR silicas from Evonik, or the Zeosil® 1085GR, Zeosil® 1115MP, Zeosil® 1165MP, Zeosil® Premium 200MP, and Zeosil® HRS 1200 MP silicas from Solvay may be used in particular. As non-HDS silicas, the following commercially available silicas can be used: Ultrasil® VN2GR and Ultrasil® VN3GR silicas from Evonik, Zeosil® 175GR silica from Solvay or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210 and Hi-Sil HDP 320G silicas from PPG.

[0024] The physical state in which the reinforcing inorganic filler is provided is immaterial, whether it is in the form of powder, micropearls, granules, beads or any other suitable compacted form. Of course, reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular the silicas mentioned above. Those skilled in the art will understand that other natural reinforcing fillers may be used in place of the inorganic fillers described above, provided that the other natural reinforcing fillers are covered with an inorganic layer such as silica or contain functional sites, particularly hydroxyl sites, on their surface that require the use of a coupling agent to form a bond between the reinforcing filler and the elastomeric matrix. Those skilled in the art will know how to adjust the total content of reinforcing fillers depending on the intended use of the compound of the present invention, in particular depending on the type of pneumatic tire in question, for example a tire for a passenger car or a utility vehicle such as a van or large vehicle.

[0025] As used herein, BET specific surface area is measured 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 specifically, according to the method derived from standard NF ISO 5794-1, supplement E, June 2010 [multipoint (5-point) volumetric method - gas: nitrogen - degassed under vacuum: 160°C for 1 hour - relative pressure p / p range: 0.05 to 0.17]. For inorganic fillers such as silica, for example, CTAB specific surface area values ​​were measured according to standard NF ISO 5794-1, supplement G, June 2010. This method is based on the adsorption of CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) on the "external" surface of the reinforcing filler. For carbon black, STSA specific surface area is determined according to standard ASTM D6556-2016.

[0026] Coupling agents for reinforcing fillers: As is well known, at least difunctional coupling agents (or bonding agents) can be used to bond the reinforcing filler, with the aim of achieving a satisfactory linkage of chemical and / or physical properties between the inorganic filler (the surface of its particles) and the diene elastomer. In particular, at least difunctional organosilanes or polyorganosiloxanes are used. The term "difunctional" is understood to 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 the diene elastomer. For example, such a difunctional compound can have a first functional group containing a silicon atom, which can interact with the hydroxyl groups of the inorganic reinforcing filler, and a second functional group containing a sulfur atom, which can interact with the elastomer, preferably the diene elastomer. Advantageously, the organosilane is selected from the group consisting of organosilane polysulfides (symmetrical or asymmetrical), such as bis(3-triethoxysilylpropyl)tetrasulfide, abbreviated as TESPT, sold by Evonik under the name Si69, or bis(3-triethoxysilylpropyl)disulfide, abbreviated as TESPD, sold by Evonik under the name Si75, polyorganosiloxanes, such as S-(3-(triethoxysilyl)propyl)octanethioate, sold by Momentive under the name NXT Silane, mercaptosilanes, protected mercaptosilanes, etc. More advantageously, the organosilane is an organosilane polysulfide. Of course, mixtures of the above coupling agents may also be used.

[0027] coating agent The rubber composition forming the compound of the present invention may also contain an agent for coating the inorganic filler, which improves the processability of the reinforcing inorganic filler in the uncured state when used in the composition of the present invention. These coating agents are well known (see, for example, International Publications WO 2006 / 125533-A1, WO 2007 / 017060-A1 and WO 2007 / 003408-A1), and may include, for example, hydrolyzable silanes such as hydroxysilanes (see, for example, International Publication WO 2009 / 062733-A2), alkylalkoxysilanes, polyols (e.g., diols or triols), polyethers (e.g., polyethylene glycol), primary, secondary or tertiary amines, hydroxylated or hydrolyzable polyorganosiloxanes (e.g., α,ω-dihydroxypolyorganosilanes (see, for example, Patent Document EP 0784072-A1)).

[0028] plasticizer The rubber composition forming the compound of the present invention may contain at least one plasticizer. As known to those skilled in the art of rubber compositions for pneumatic or non-pneumatic tires, the plasticizer is preferably selected from hydrocarbon resins having a high glass transition temperature (Tg), low Tg hydrocarbon resins, plasticizing oils, and mixtures thereof. Preferably, the plasticizer is selected from high Tg hydrocarbon resins, plasticizing oils, and mixtures thereof. As is known, plasticizers in rubber compositions make it possible to adjust the viscosity of the rubber composition and, therefore, the glass transition temperature of the rubber composition with respect to its optimum use. High Tg hydrocarbon resins are by definition solid at room temperature and pressure (20°C, 1 atmosphere), while plasticizing oils are liquid at room temperature and pressure, and low Tg hydrocarbon resins are viscous at room temperature and pressure.

[0029] Hydrocarbon resins, also known as hydrocarbon plasticizing resins, are polymers well known to those skilled in the art that are essentially carbon- and hydrogen-based but can contain other types of atoms, such as oxygen, and can be used, among other things, as plasticizers. They are inherently at least partially miscible (i.e., compatible) with the rubber compositions for which they are intended to function as true diluents. They are described, for example, in the book entitled "Hydrocarbon Resins" (R. Mildenberg, M. Zander, and G. Collin, New York, VCH, 1997, ISBN 3-527-28617-9). Chapter 5 of this book is devoted to their applications, particularly in the field of pneumatic tire rubber (5.5 "Rubber Tires and Mechanical Goods"). As is known, these hydrocarbon resins can also be called thermoplastic resins, in the sense that they soften upon heating and can therefore be molded. The softening point of hydrocarbon resins is measured according to ISO 4625 (the "ring and ball" method). The Tg is measured according to the standard ASTM D3418 (2008). The macrostructure (Mw, Mn, and PI) of hydrocarbon resins was measured by size exclusion chromatography (SEC); solvent: tetrahydrofuran; temperature: 35°C; concentration: 1 g / L; flow rate: 1 ml / min; solution filtration through a 0.45 μm porosity filter before injection; Moore calibration using polystyrene standards; a series of three Waters columns (Styragel HR4E, HR1, and HR0.5) arranged in series; differential refractometry detection (Waters 2410) and its associated operating software (Waters Empower). Hydrocarbon resins may be aliphatic, aromatic, or aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers. They may be natural or synthetic, and may or may not be petroleum-based (in the latter case, they are also known as petroleum resins). As is known, high-Tg hydrocarbon resins are thermoplastic hydrocarbon resins, and their Tg is greater than 20°C.

[0030] Preferably, the plasticizer may optionally comprise a hydrocarbon resin, which is solid at ambient temperature and pressure and is referred to as a high Tg resin. Preferably, the high Tg hydrocarbon plasticizing resin exhibits at least one of the following properties: · Tg above 30 °C; a number average molecular weight (Mn) of 300 to 2000 g / mol, more advantageously 400 to 1500 g / mol; A polydispersity index (PI) of less than 3, more advantageously less than 2 (note: PI=Mw / Mn, Mw being the weight average molecular weight). More advantageously, the high Tg hydrocarbon plasticized resin exhibits all of the above advantageous properties.

[0031] The plasticizer may optionally comprise a hydrocarbon resin that is viscous at 20°C, so-called "low Tg" resins, ie, that by definition have a Tg within the range of -40°C to 20°C. Preferably, the low Tg hydrocarbon plasticizing resin exhibits at least one of the following properties: a Tg of -40°C to 0°C, more preferably -30°C to 0°C, even more preferably -20°C to 0°C; a number average molecular weight (Mn) of less than 800 g / mol, preferably less than 600 g / mol, and more advantageously less than 400 g / mol; a softening point in the range of 0°C to 50°C, advantageously 0°C to 40°C, more advantageously 10°C to 40°C, preferably 10°C to 30°C; A polydispersity index (PI) of less than 3, more advantageously less than 2 (note: PI=Mw / Mn, Mw being the weight average molecular weight). More advantageously, the low Tg hydrocarbon resin exhibits all of the above advantageous properties.

[0032] Plasticizers can also include extender oils (or plasticizing oils), which are liquid at 20°C and are called "low Tg" plasticizers, i.e., which by definition have a Tg below -20°C, preferably below -40°C. Any extender oil, whether aromatic or non-aromatic, known for its plasticizing properties with elastomers can be used. At room temperature (20°C), these oils are somewhat viscous and liquid (note: i.e., substances that have the ability to ultimately assume the shape of their container), especially unlike high Tg hydrocarbon resins, which are inherently solid at room temperature. Particularly suitable are plasticizing oils selected from the group consisting of naphthenic oils (low or high viscosity, in particular hydrogenated or non-hydrogenated), paraffinic oils, MES (Minor Extraction Solvates) oils, TDAE (Treated Distillate Aromatic Extract) oils, RAE (Residual Aromatic Extract) oils, TRAE (Treated Residual Aromatic Extract) oils and SRAE (Safety Residual Aromatic Extract) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures of these compounds. The high Tg hydrocarbon resins, low Tg hydrocarbon resins, and advantageous plasticizing oils described above are well known to those skilled in the art and are commercially available.

[0033] Other additives The rubber compositions forming the rubber compounds according to the present invention may also contain all or some of the useful additives and processing aids known to those skilled in the art and commonly used in rubber compositions for pneumatic or non-pneumatic tires, especially treads, such as fillers (reinforced or non-reinforced / other than those mentioned above), pigments, protectants such as anti-ozone waxes, chemical antiozonants or antioxidants, anti-fatigue agents or reinforcing resins (such as those described in International Publication WO 02 / 10269).

[0034] Crosslinked system The rubber composition forming the compound according to the invention may comprise at least one crosslinking system, which may be of any type known to those skilled in the art of rubber compositions for pneumatic or non-pneumatic tires, and which may in particular be based on sulfur and / or peroxide and / or bismaleimide. Advantageously, the crosslinking system is sulfur-based, and is therefore called a vulcanization system. The sulfur can be provided in any form, in particular in the form of molecular sulfur or in the form of a sulfur donor. Advantageously, at least one vulcanization accelerator is also present, and optionally, and equally advantageously, known vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds such as stearates, and salts of transition metals, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retarders can be used. Sulphur is used in an advantageous content ranging from 0.5 phr to 12 phr, more advantageously from 0.7 phr to 10 phr. Vulcanisation accelerators are used in an advantageous content ranging from 0.5 phr to 10 phr, more advantageously from 0.5 phr to 5.0 phr. As accelerators, any compound capable of acting as an accelerator of the vulcanization of diene elastomers in the presence of sulfur can be used, in particular accelerators of the thiazole type and also their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate type.

[0035] Rubber composition C1 The rubber compound according to the present invention comprises at least one rubber composition, designated C1, which has a given glass transition temperature, designated Tg1. This rubber composition C1 comprises at least one elastomer E1 as defined above. Preferably, the elastomer E1 is a diene elastomer, and even more advantageously, a non-functionalized diene elastomer. Even more preferably, the elastomer E1 of the rubber composition C1 is selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer, and butadiene / styrene / isoprene copolymer. Advantageously, the elastomer E1 of the rubber composition C1 is selected from the group consisting of synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer, and butadiene / styrene / isoprene copolymer. Even more advantageously, the elastomer E1 of the rubber composition C1 is selected from the group consisting of polybutadiene and butadiene / styrene copolymer. Even more advantageously, the elastomer E1 of the rubber composition C1 is a styrene / butadiene copolymer. Advantageously, this elastomer E1 is a non-functionalized diene elastomer. For the purposes of the present invention, "non-functionalized diene elastomer" is understood to mean a diene elastomer, whether natural or synthetic, that does not have chemical functional groups capable of interacting with reinforcing fillers. Advantageously, the non-functionalized diene elastomer may be substantially composed of carbon and hydrogen atoms. It may be free of heteroatoms or may contain heteroatoms resulting from impurity amounts due to the synthesis method. Advantageously, 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 advantageously, the glass transition temperature TgE1 is in the range of −50° C. to 0° C., more advantageously −40° C. to 0° C., more advantageously −30° C. to 0° C. Advantageously, the rubber composition C1 may further comprise at least one reinforcing filler. The reinforcing filler may be any of the types of reinforcing fillers described above. Advantageously, the reinforcing filler is selected from the group consisting of carbon black, inorganic reinforcing fillers and mixtures thereof. Advantageously, the reinforcing filler is selected from the group consisting of carbon black, silica and mixtures thereof. The rubber composition C1 may also contain at least one plasticizer as described above or any other additive as described above.

[0036] Rubber composition C2 The rubber compound according to the present invention comprises at least one rubber composition, designated C2, which has a given glass transition temperature, designated Tg2. This rubber composition C2 comprises at least one elastomer E2 as defined above. Preferably, the elastomer E2 is a diene elastomer, and even more advantageously a functionalized diene elastomer.

[0037] For the purposes of the present invention, "functionalized diene elastomer" is understood to mean a diene elastomer, whether natural or synthetic, having chemical functional groups capable of interacting with reinforcing fillers. The chemical functional groups capable of interacting with reinforcing fillers may be heteroatoms or groups of atoms containing at least one heteroatom selected from nitrogen, sulfur, oxygen, phosphorus, tin and silicon.

[0038] Advantageously, the elastomer E2 is a diene elastomer, preferably functionalized, selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene / styrene copolymers, butadiene / isoprene copolymers, isobutene / isoprene copolymers, isoprene / styrene copolymers and butadiene / styrene / isoprene copolymers. Advantageously, the elastomer E2 is a diene elastomer, preferably functionalized, selected from the group consisting of polybutadiene and styrene / butadiene copolymers. Even more advantageously, the elastomer E2 is a styrene / butadiene copolymer, preferably functionalized.

[0039] Advantageously, the glass transition temperature TgE2 of the elastomer E2, preferably of a diene elastomer which is in particular functionalized, is in the range of from −110° C. to −23° C., preferably from −100° C. to −28° C., more advantageously from −95° C. to −30° C.

[0040] The functionalization of diene elastomers E2 is known and can be carried out during the synthesis of the diene elastomer or after its synthesis by grafting chemical functional groups onto the monomers of the diene elastomer. The functionalized diene elastomer E2 comprises at least one chemical functional group capable of interacting with the reinforcing filler, the chemical functional group comprising at least one heteroatom selected from the group consisting of nitrogen, sulfur, oxygen, phosphorus, tin, and silicon. Among these functional groups, mention may be made, by way of example, of cyclic or acyclic primary, secondary, or tertiary amines, isocyanates, imines, cyanos, thiols, carboxylates, epoxides, or primary, secondary, or tertiary phosphines. This interaction between the reinforcing filler and the functionalized diene elastomer E2 can be achieved, for example, by covalent, hydrogen, ionic, and / or electrostatic bonds between the functional group(s) of the diene elastomer and the chemical functional groups present on the surface of the reinforcing filler. Advantageously, the chemical functional groups capable of interacting with the reinforcing fillers of the diene elastomer E2 are polar functional groups containing at least one oxygen atom. Advantageously, the polar functional group can be selected from the group consisting of silanol, alkoxysilane, amine-containing alkoxysilane, epoxide, ether, ester, carboxylic acid and hydroxyl. Such functionalized elastomers are known per se and are described in particular in the following patent documents: FR 2740778, US 6013718, WO 2008 / 141702, FR 2765882, WO 01 / 92402, WO 2004 / 09686, EP 1127909, US 6503973, WO 2009 / 000750 and WO 2009 / 000752. The functionalized diene elastomer is preferably a diene elastomer that contains polar functional groups that are silanols. Advantageously, the silanols are located at the chain ends or in the middle of the backbone of the functionalized diene elastomer. Advantageously, the functionalized diene elastomer may be a diene elastomer (especially SBR) in which the silanol functional group is located at the chain end, that is, a silanol functional group or a group of formula -(SiR1R2-O-) at one end of its main chain. m H, wherein m is an integer ranging from 3 to 8, preferably 3, and R1 and R2, which may be the same or different, are alkyl radicals having 1 to 10 carbon atoms, preferably alkyl radicals having 1 to 4 carbon atoms.

[0041] This type of elastomer is obtained according to the method described in patent document EP 0 778 311, and more particularly according to a method which consists in functionalizing, after a step of anionic polymerization, a living elastomer with a functionalizing agent of the cyclic polysiloxane type. Mention may be made, as cyclic polysiloxane, of the type corresponding to formula (V): [ka] In the formula, m is an integer ranging from 3 to 8, preferably 3, and R1 and R2, which may be the same or different, are alkyl radicals having 1 to 10 carbon atoms, preferably alkyl radicals having 1 to 4 carbon atoms. Among these compounds, hexamethylcyclotrisiloxane can be mentioned.

[0042] The functionalized diene elastomer E2 can be a diene elastomer (especially SBR) containing a polar functional group which is an alkoxysilane optionally containing another functional group, in particular an amine functional group. Advantageously, the alkoxysilane optionally containing another functional group, preferably containing an amine group, is located at the end or in the middle of the main chain of the functionalized diene elastomer, and more advantageously, the alkoxysilane group optionally containing an amine group is located in the middle of the main chain of the functionalized diene elastomer. The functionalized diene elastomer E2 thus comprises in its structure at least one alkoxysilane group and at least one other functional group, the silicon atom of the alkoxysilane group being bonded to the elastomer chain(s), the alkoxysilane group optionally being partially or completely hydrolyzed to a silanol.

[0043] In certain variations, the alkoxysilane groups are located primarily at one end of the elastomer backbone. In other variations, the alkoxysilane groups are located primarily in the main elastomer chain, so that the diene elastomer is said to be mid-chain bonded or functionalized, although the groups are not located exactly in the middle of the elastomer chain, as opposed to in a "chain end" position. The silicon atoms of the functional groups are attached to two branches of the diene elastomer main chain.

[0044] The alkoxysilane groups contain C1-C10 alkoxy radicals, optionally partially or fully hydrolyzed to hydroxyl, or C1-C8, preferably C1-C4 alkoxy radicals, more advantageously methoxy and ethoxy.

[0045] The other functional group is preferably carried by the silicon of the alkoxysilane group either directly or via a spacer group defined as an atom or a group of atoms, which is advantageously a saturated or unsaturated, cyclic or acyclic, straight-chain or branched, divalent C1-C18 aliphatic hydrocarbon radical or a divalent C6-C18 aromatic hydrocarbon radical.

[0046] The other functional group is preferably a functional group containing at least one heteroatom selected from N, S, O or P. Among these functional groups, mention may be made, by way of example, of cyclic or acyclic primary, secondary or tertiary amines, isocyanates, imines, cyanos, thiols, carboxylates, epoxides or primary, secondary or tertiary phosphines.

[0047] Thus, secondary or tertiary amine functional groups include amines substituted with C1-C10 alkyl, preferably C1-C4 alkyl, radicals, more preferably methyl or ethyl radicals, or cyclic amines forming a heterocycle containing a nitrogen atom and at least one carbon atom, preferably 2 to 6 carbon atoms. Examples include methylamino, dimethylamino, ethylamino, diethylamino, propylamino, dipropylamino, butylamino, dibutylamino, pentylamino, dipentylamino, hexylamino, dihexylamino, or hexamethyleneamino groups, preferably diethylamino and dimethylamino groups. Examples of imine functional groups include ketimines. Examples include (1,3-dimethylbutylidene)amino, (ethylidene)amino, (1-methylpropylidene)amino, (4-N,N-dimethylaminobenzylidene)amino, (cyclohexylidene)amino, dihydroimidazole, and imidazole groups. Thus, carboxylate functional groups of acrylates or methacrylates are also suitable. Such functional groups are preferably methacrylates. Epoxide functional groups include epoxy or glycidyloxy groups. Secondary or tertiary phosphine functional groups include phosphines substituted with C1-C10 alkyl, preferably C1-C4 alkyl, radicals, more preferably methyl or ethyl radicals, or diphenylphosphine. Suitable groups include, for example, methylphosphino, dimethylphosphino, ethylphosphino, diethylphosphino, ethylmethylphosphino, and diphenylphosphino groups.

[0048] The other functional group is preferably a tertiary amine, more preferably a diethylamino or dimethylamino group. The alkoxysilane group can be represented by the formula: ( * -) a Si(OR') b R c X During the ceremony, · * - is a bond to the elastomer chain; the radical R is a substituted or unsubstituted C1-C10, or C1-C8, alkyl radical, preferably a C1-C4 alkyl radical, more advantageously methyl and ethyl; alkoxyl radical(s) of formula -OR', which may optionally be partially or completely hydrolyzed to hydroxyl, R' being a substituted or unsubstituted C1-C10, or C1-C8, alkyl radical, preferably a C1-C4 alkyl radical, more advantageously methyl and ethyl; X is a group containing another functional group; a is 1 or 2, b is 1 or 2, and c is 0 or 1, provided that a+b+c=3.

[0049] This type of elastomer is primarily obtained by functionalizing living elastomers resulting from anionic polymerization with compounds containing alkoxysilane groups, in particular those selected from trialkoxysilane and dialkoxyalkylsilane compounds, substituted with groups containing other functional groups attached to the silicon atom directly or via spacer groups (functional groups and spacer groups are defined above). It should be noted that, when an elastomer is modified by reacting a functionalizing agent with the living elastomer resulting from the anionic polymerization step, a mixture of modified elastomers is obtained, the composition of which depends on the modification reaction conditions and, in particular, the ratio of reactive sites of the functionalizing agent to the number of living elastomer chains. This mixture may contain end-chain functionalized, bonded, star-branched, and / or non-functionalized materials. These non-functional diene elastomers are commercially available from suppliers such as Nippon Zeon, JSR, Bayer, or can be synthesized by known methods.

[0050] The rubber composition C2 further comprises at least one reinforcing filler, which may be any of the types of reinforcing fillers described above. Advantageously, the reinforcing filler of the composition C2 comprises predominantly at least one inorganic reinforcing filler, more advantageously at least one silica. Advantageously, when the reinforcing filler comprises mainly a reinforcing inorganic filler, advantageously silica, the functionalized diene elastomer E2 may comprise at least one chemical functional group capable of interacting with the reinforcing filler, the chemical functional group comprising at least one heteroatom selected from the group consisting of nitrogen, sulfur, oxygen and phosphorus.

[0051] Rubber composition C2 may also contain at least one plasticizer as described above or any other additive as described above.

[0052] Rubber compound according to the present invention and its manufacturing process As mentioned above, the rubber compound according to the invention has at least two glass transition temperatures Tg1 and Tg2, which are obtained from a specific combination of at least two rubber compositions C1 and C2, chosen so that: The glass transition temperature Tg1 of the composition C1 is -50°C or higher, The rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 23°C, the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -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, the profile being such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less; and · Elastomer E1 is the most abundant in rubber compounds.

[0053] Surprisingly, this particular combination of rubber compositions makes it possible to obtain a rubber compound that simultaneously exhibits good hysteresis characteristics and good grip on wet ground. Without being bound by theory, if the rubber compound exhibits a glass transition temperature difference of less than 23°C, the hysteresis characteristics will be reduced and the rubber compound will not exhibit good rolling resistance. If the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), and this loss factor profile, measured over a temperature range of -80°C to 60°C at a frequency of 10 Hz and a constant stress of 0.7 MPa, shows one or more peaks, and this profile is such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width greater than 23°C, the rubber compound will have an insufficient dynamic friction coefficient, thereby reducing wet grip properties. Advantageously, the rubber compound satisfies the mathematical relationship Tg1-Tg2≧25°C, preferably Tg1-Tg2≧28°C, and even more advantageously Tg1-Tg2≧30°C. Suitably, the rubber compound satisfies the mathematical relationship 25°C < Tg1 - Tg2 < 40°C, preferably 28°C < Tg1 - Tg2 < 35°C, more advantageously 28°C < Tg1 - Tg2 < 34°C. Advantageously, 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. Advantageously, the glass transition temperature Tg1 of the rubber composition C1 is in the range of -48°C to -15°C, preferably in the range of -40°C to -15°C. Advantageously, composition C2 has a glass transition temperature Tg2 of less than or equal to -43°C, preferably less than or equal to -50°C and more advantageously less than or equal to -57°C. Advantageously, the glass transition temperature Tg2 of composition C2 is in the range of -90°C to -43°C, preferably in the range of -85°C to -50°C.

[0054] Advantageously, the rubber compound according to the invention is based on at least one rubber composition C1 having a glass transition temperature Tg1 and comprising a non-functionalized diene elastomer E1, the glass transition temperature Tg1 being in the range of -48°C to -15°C, and a rubber composition C2 having a glass transition temperature Tg2 and comprising a functionalized diene elastomer E2, the glass transition temperature Tg2 being in the range of -85°C to -50°C. The rubber compound satisfies the mathematical relationship Tg1-Tg2 ≥ 28°C, preferably Tg1-Tg2 ≥ 30°C, and the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -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, the profile being such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less, and the elastomer E1 is the most prevalent in the rubber compound.

[0055] Advantageously, the rubber compound according to the invention is based on at least one rubber composition C1 having a glass transition temperature Tg1 and comprising a non-functionalized diene elastomer E1, the glass transition temperature Tg1 being in the range of from -40°C to -15°C, and a rubber composition C2 having a glass transition temperature Tg2 and comprising a functionalized diene elastomer E2, the glass transition temperature Tg2 being in the range of from -90°C to -43°C. The rubber compound satisfies the mathematical relationship Tg1-Tg2≧28°C, preferably Tg1-Tg2≧30°C, and the rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -80°C to 60°C at a frequency of 10Hz and a constant stress of 0.7MPa and showing one or more peaks, and the profile is such that all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less, and the elastomer E1 is the most abundant in the rubber compound.

[0056] Advantageously, the content of elastomer E1, preferably in particular non-functionalized diene elastomer, in the rubber compound of the invention is in the range of from 50 phr to 70 phr, preferably from 55 phr to 70 phr, more advantageously from 55 phr to 65 phr. Advantageously, the content of elastomer E2, preferably diene elastomer, in particular functionalized, in the rubber compound of the invention is less than or equal to 40 phr, more preferably between 30 phr and 50 phr, preferably between 30 phr and 45 phr, and even more advantageously between 35 phr and 45 phr. Preferably, the content of elastomer E1, preferably in particular a non-functionalized diene elastomer, in the rubber compound of the present invention is in the range of 50 phr to 70 phr, and the content of elastomer E2, preferably in particular a functionalized diene elastomer, in the rubber compound of the present invention is in the range of 30 phr to 50 phr. Preferably, the content of elastomer E1, preferably in particular a non-functionalized diene elastomer, in the rubber compound of the present invention is in the range of 55 phr to 70 phr, and the content of elastomer E2, preferably in particular a functionalized diene elastomer, in the rubber compound of the present invention is in the range of 30 phr to 45 phr.

[0057] Preferably, the content of reinforcing filler in the rubber compound of the present invention is in the range of 20 phr to 100 phr, more advantageously 30 phr to 90 phr, and even more advantageously 40 phr to 90 phr, with optimum values ​​varying, as is known, depending on the particular target application. When the reinforcing filler is a reinforcing inorganic filler such as silica, the use of a coupling agent may be advantageous. Advantageously, the content of the coupling agent in the rubber compound of the present invention is preferably 20 phr or less, and it will be understood that it is generally desirable to use as little coupling agent as possible. Typically, the content of the coupling agent is 0.5% to 15% by mass, based on the amount of the reinforcing inorganic filler. The content is advantageously within the range of 0.5 phr to 20 phr. This content can be easily adjusted by those skilled in the art according to the content of the reinforcing inorganic filler used in the composition of the present invention. In a preferred embodiment, the reinforcing filler is predominantly an inorganic reinforcing filler (preferably silica) in the rubber compound according to the invention, i.e., the reinforcing filler comprises more than 50% by weight (>50% by weight) of an inorganic reinforcing filler such as silica, based on the total weight of reinforcing fillers in the rubber compound. Optionally, in this embodiment, the reinforcing filler can also comprise carbon black. In this option, carbon black is used in a content of 20 phr or less, more advantageously 10 phr or less, in the rubber compound (e.g., the carbon black content can be in the range of 0.5 phr to 20 phr, in particular 1 phr to 10 phr, in the rubber compound). Within the indicated ranges, the coloring properties (black pigmentation) and UV stabilization properties of carbon black are beneficial, and furthermore, do not adversely affect the typical performance properties provided by reinforcing inorganic fillers.

[0058] Method for producing rubber compound The rubber compound of the present invention can be obtained by conventional methods for preparing rubber compounds, such as dry mixing of the various components.

[0059] In one embodiment, the rubber compound according to the present invention is prepared in a suitable mixer using two sequential preparation steps well known to those skilled in the art: The first ("non-productive") stage of thermomechanical processing or compounding can be carried out in a single thermomechanical step, during which the elastomer E2 of the rubber composition having a glass transition temperature Tg2, the reinforcing filler, and the optional coupling agent for the reinforcing filler are introduced, in that order, into a suitable mixer, such as a standard internal mixer (for example, a "Banbury" type). During the thermomechanical compounding, these components are maintained at a temperature in the range of 140°C to 200°C for 1 to 2 minutes, after which the elastomer E1 of the rubber composition having a glass transition temperature Tg1 and all the necessary components, except for the crosslinking system, are also introduced into the internal mixer. These components are subjected to thermomechanical compounding for 2 to 10 minutes up to a maximum temperature (called the "drop temperature") in the range of 110°C to 200°C, preferably 130°C to 185°C. The second stage of mechanical processing (the "productive" stage) is carried out in an external mixer, such as an open mill, after cooling the mixture obtained during the non-productive first stage to a lower temperature, usually below 120°C, for example in the range of 40°C to 100°C, followed by mixing for 5 to 15 minutes to incorporate the crosslinking system, in order to obtain the rubber compound of the invention.

[0060] In another preferred embodiment of the present invention, the rubber compound of the present invention is prepared in the form of two rubber compositions, which are then combined to obtain the rubber compound according to the present invention. More specifically, in this embodiment, the formulation as defined above and preferred embodiments thereof can be obtained by a manufacturing process comprising the following steps: preparing the rubber composition C1 by introducing into an internal mixer the elastomer E1 and, where appropriate, other components of the rubber composition C1, such as plasticizers, and carrying out a thermomechanical treatment at a maximum temperature of 200°C to obtain the rubber composition C1; preparing a rubber composition C2 by introducing into an internal mixer the elastomer E2 of the rubber composition C2, the reinforcing filler and, where appropriate, other components such as plasticizers or coupling agents for the reinforcing filler, and carrying out a thermomechanical treatment at a maximum temperature of 200°C to obtain the rubber composition C2; introducing the rubber compositions C1 and C2 obtained in the previous steps into an internal mixer and carrying out a thermomechanical treatment at a maximum temperature of 180°C in order to obtain a combined composition; recovering the combined composition from the previous step and cooling it to a temperature of 110°C or less; or Incorporating the crosslinking system into the cooled composition combination and kneading everything at a maximum temperature of less than 110°C, advantageously less than 80°C, and recovering the rubber compound.

[0061] More specifically, a first rubber composition, designated composition C1, is prepared by mixing the elastomer E1 and other optional components of composition C1, excluding the vulcanization system, such as plasticizers, antiozonants, etc., in a suitable mixer, such as a standard internal mixer (e.g., "Banbury" type). Thermomechanical processing is carried out for 2 to 10 minutes up to a maximum temperature (called the "drop temperature") in the range of 110°C to 200°C, preferably 130°C to 185°C. In this way, rubber composition C1 is recovered. A second rubber composition, designated composition C2, is then prepared by mixing elastomer E2, the reinforcing filler, and other optional components, excluding the vulcanization system, such as plasticizers, coupling agents for the reinforcing filler, antiozonants, etc., in a suitable mixer, such as a standard internal mixer (e.g., "Banbury" type). Thermomechanical processing is carried out for 2 to 10 minutes up to a maximum temperature (called the "drop temperature") in the range of 140°C to 200°C, preferably 140°C to 185°C. In this way, rubber composition C2 is recovered. The two rubber compositions C1 and C2 from the previous step are introduced into a standard internal mixer (for example, of the "Banbury" type) and thermomechanical processing is carried out for 2 to 10 minutes up to a maximum temperature (called the "drop temperature") ranging from 110°C to 180°C, preferably from 130°C to 180°C. The mixture from the previous step is then cooled in an external mixer, such as an open roll mill, to a temperature below 110°C, followed by mixing for 5 to 15 minutes to incorporate the crosslinking system and recover the rubber compound according to the invention.

[0062] Regardless of the method for preparing the rubber compound, the final rubber compound thus obtained is subsequently calendered, for example in the form of sheets or slabs, in particular for laboratory characterization, or extruded in the form of semi-finished rubber products (or profiles), which can be used, for example, as treads for pneumatic or non-pneumatic tires, in particular for passenger cars.

[0063] The rubber compound may be in an uncured state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization) and may be a semi-finished product that can be used in pneumatic or non-pneumatic tires. Crosslinking of the rubber compound can be carried out in a manner known to those skilled in the art, for example under pressure at a temperature in the range of 130°C to 200°C.

[0064] Other Subject Matter of the Invention Another subject of the invention is a tread comprising at least one rubber compound as defined above. The rubber compound according to the invention can constitute the whole of the tread or part of the tread.

[0065] Another subject of the invention relates to a pneumatic or non-pneumatic tire comprising at least one rubber compound as defined above or comprising at least one tread as defined above. A "pneumatic tire" is understood to mean a tire that, in cooperation with a support member, for example a rim, forms a cavity that can be pressurized to a pressure higher than atmospheric pressure. In contrast, a "non-pneumatic tire" cannot be pressurized. A non-pneumatic tire is therefore a torus made of at least one polymer material and intended to perform the function of a tire, but which is not exposed to tire pressure. A non-pneumatic tire can be a solid or hollow body. A hollow non-pneumatic tire may contain air, but at atmospheric pressure, i.e., it does not have the pneumatic stiffness provided by an inflation gas at a pressure higher than atmospheric pressure. The pneumatic tire according to the invention is intended to be fitted to any type of vehicle, such as a passenger car, a motorcycle, a heavy vehicle, an agricultural vehicle, a construction plant vehicle, or an aircraft, or more generally for any rotating equipment. The non-pneumatic tire is in particular intended to be fitted to a passenger car or a motorcycle. Preferably, the pneumatic tire according to the invention is intended to be fitted to a passenger car. Advantageously, the pneumatic or non-pneumatic tire comprises at least one tread comprising at least one rubber compound as defined above.

[0066] Measurement method Determination of the glass transition temperature of elastomers The glass transition temperatures (Tg) of the elastomers before their use are determined using a differential scanning calorimeter according to standard ASTM D3418:2008. Determination of the glass transition temperature of the compound The glass transition temperature of the formulations is measured according to the standard NF EN ISO11357-2:05-2014 using a Mettler Toledo DSC3+ instrument and a 40 μl aluminum crucible. Scanning measurements are performed under helium at a flow rate of 40 ml / min as follows: ·Cool the sample from +25°C to -150°C with a gradient of +50°C / min; ·Isothermal hold at -150°C for 5 min; ·Heating from -150°C to +200°C with a gradient of 20°C / min; · Isothermal hold at +200°C for 5 minutes; ·Cooling from +200°C to -150°C at a gradient of 20°C / min; ·Isothermal hold at -150°C for 5 min; Heating from -150°C to +200°C at a gradient of 20°C / min.

[0067] μ max Determination of coefficients The measurements of the dynamic friction coefficient were carried out according to the same method as L. Busse, A. Le Gal, and M. Kuppel (Modeling of Dry and Wet Friction of Silica-Filled Elastomers on Self-Affine Road Surfaces, Elastomer Friction, 2010, 51, p. 8). Test specimens were prepared by crosslinking square rubber supports (50 mm x 50 mm) with a thickness of 6 mm after molding. After closing the mold, the latter was placed in a press with platens heated to a temperature of 150 °C under a pressure of 1.6 MPa (16 bar) for the time required for crosslinking of the material (usually a few tens of minutes). The surfaces used to carry out these measurements were cores taken from real road surfaces made from bituminous concrete of the BBTM type (standard NF P98-137). To prevent the phenomenon of dewetting between the ground and the material and the appearance of secondary grip forces, the ground + specimen system is immersed in a 5% aqueous solution of surfactant (Sinnozon - CAS number: 25155-30-0). The temperature of the solution is controlled using a thermostatic chamber. The specimen is subjected to a translational sliding movement parallel to the plane of the ground. The sliding speed SV is set to 1.2 m / s. The applied normal stress σ n is 400 kPa (i.e. 4 bar). These conditions are denoted below by "wet ground conditions". The tangential stress σ, relative to the movement of the specimen along the ground, t is measured. Normal stress σ n Tangential stress σ t The ratio of these gives the coefficient of kinetic friction μ. The coefficient of kinetic friction values ​​were measured during a temperature sweep of the aqueous solution from 3°C to 44°C, and the tangential stress σ t is obtained at steady state after stabilization of the value of In the examples, the maximum value of the dynamic friction coefficient (μ max (denoted as "") is shown. Unless otherwise indicated, results are given on a basis of 100. To calculate, an arbitrary value of 100 is assigned to the comparative formulation, and then the maximum dynamic coefficient of friction of the various tested samples is compared. The value based on 100 for the sample being tested is calculated using the formula: (μ of test sample) max Value / μ of comparative formulation max The calculation is: μ max Conversely, a result above 100 indicates a decrease in the μ coefficient and therefore a decrease in wet grip performance. max This indicates an increase in coefficient and therefore an increase in wet grip performance.

[0068] Measurement of dynamic properties after curing Dynamic property tan(δ) max is measured with a viscosity analyzer (Metravib A4000) according to standard ASTM D 5992-96. Samples of vulcanized compounds (2 mm thick and 78.5 mm long) are subjected to a simple alternating sinusoidal shear stress at a temperature of 40°C and a frequency of 10 Hz. 2 The response of two cylindrical specimens with cross sections of 100% to 100% is recorded. A peak-to-peak strain amplitude sweep is performed from 1% to 100% (forward cycle) and then from 100% to 1% (return cycle). The available result is the loss factor tan(δ). For the return cycle, tan(δ) 40℃でのmax The maximum observed value of tan(δ) is expressed as max ) is shown.

[0069] The results are expressed in terms of performance relative to 100, i.e., the tan δ of the various test formulations. 40℃でのmax For purposes of calculating and subsequent comparison, a value of 100 is arbitrarily assigned to the comparative formulation. The value relative to 100 is calculated using the formula: (tan δ of the comparative formulation) 40℃でのmax Value / tanδ of sample 40℃でのmax The value is calculated as follows: (value) x 100. Thus, a lower value represents a decrease in hysteresis characteristics, while a higher value represents an improvement in hysteresis characteristics.

[0070] Measurement of loss factor profile measured according to ASTM D 5992-96 Each is 2mm thick and 78.5mm cross section 2 The response of two 1 cm diameter cylindrical pellet specimens is recorded. The specimens are subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz during a temperature sweep from -80 °C to +100 °C at a gradient of +1.5 °C / min under a constant stress of 0.7 MPa. Data are acquired at a frequency of 0.12 Hz, which can be adapted to obtain the desired accuracy.

[0071] For tan δ peaks present at temperatures above the glass transition temperature Tg1, the half-width of each of these peaks is measured. This half-width is defined as follows: Consider a given maximum at temperature T0 with an associated value of tan δ, Y. Then, record all temperatures associated with a value of tan δ equal to Y / 2. Among these values, the half-width of the peak then corresponds to the difference in °C between the two nearest temperatures adjacent to the maximum temperature T0.

[0072] Example 1-Component: The ingredients used in the examples are as follows: Elastomer (1A): Non-functionalized styrene / butadiene copolymer having a Tg of −28° C., measured according to standard ASTM D3418:2008; styrene content of 41% by weight, relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 14% by weight, relative to the total weight of the copolymer, trans-1,4-butadiene content of 27% by weight, relative to the total weight of the copolymer. Elastomer (1B): styrene / butadiene copolymer having silanol functional groups at the end of the elastomer chain and having a Tg of −24° C., measured according to standard ASTM D3418:2008; styrene content of 25% by weight relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 43% by weight relative to the total weight of the copolymer, trans-1,4-butadiene content of 16% by weight relative to the total weight of the copolymer. Elastomer (1C): Styrene / butadiene copolymer having a Tg of −65° C., measured according to standard ASTM D3418:2008; styrene content of 16% by weight relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 20% by weight relative to the total weight of the copolymer, trans-1,4-butadiene content of 39% by weight relative to the total weight of the copolymer. Elastomer (1D): styrene / butadiene copolymer with an aminoalkoxysilane functional group in the middle of the chain, having a Tg of −65° C., measured according to standard ASTM D3418:2008; styrene content of 16% by weight relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 20% by weight relative to the total weight of the copolymer, trans-1,4-butadiene content of 39% by weight relative to the total weight of the copolymer. Elastomer (1F): styrene / butadiene copolymer with an aminoalkoxysilane functional group in the middle of the chain and a Tg of −48° C., measured according to standard ASTM D3418:2008; styrene content of 27% by weight relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 17.5% by weight relative to the total weight of the copolymer, trans-1,4-butadiene content of 33.5% by weight relative to the total weight of the copolymer. Elastomer (1G): Non-functionalized styrene / butadiene copolymer having a Tg of −48° C., measured according to standard ASTM D3418:2008; styrene content of 27% by weight, relative to the total weight of the copolymer, vinyl-1,2-butadiene content of 17.5% by weight, relative to the total weight of the copolymer, trans-1,4-butadiene content of 33.5% by weight, relative to the total weight of the copolymer. Carbon Black (2): ASTM Grade N234 carbon black sold by Cabot Corporation. Silica (3): Zeosil 1165MP silica sold by Solvay. Silica (4): Bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) silane sold by Evonik under the reference Si69. DPG(5): Diphenylguanidine by Flexsys, Perkacit DPG. Plasticizer (6): DCPD resin sold by Exxon Mobil under the reference PR-383, having a softening point of 100°C and a glass transition temperature of 51°C. Ozone Resistant Wax (7): Varazon 4959 Ozone Resistant Wax by Sasol Wax. Antioxidant (8): N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine sold under the reference Santoflex 6-PPD by Flexsys. ZnO(9): Zinc oxide (industrial grade) sold by Umicore. Stearic acid (10): Pristerene 4031 stearin sold by Uniqema.

[0073] 2. Test 1: Effect of the location of reinforcing fillers in the rubber compound The examples shown in Table 1 are intended to compare various rubber properties of a rubber compound MI1 according to the invention with a series of comparative rubber compounds MT1 and MT2: rubber compound MI1 differs from the other compounds in the distribution of the reinforcing filler within the elastomer matrix.

[0074] Table 1 shows the formulations of these compounds, the ratios being expressed in phr, that is, parts by weight per 100 parts by weight of the elastomer of the compound. [Table 1]

[0075] Comparative formulation MT1 is obtained in the following way: All components in Table 2 were reacted in one or more steps at 414 cm 3 The mixture is introduced into a Polylab internal mixer, filled to 70% by volume, and the initial container temperature is 90°C. Thermomechanical processing is carried out for 6 minutes until a maximum drop temperature of 165°C is reached. The composition thus obtained, designated composition C1, is recovered. All components in Table 3 were reacted in one or more steps with another 414 cm 3 The mixture is introduced into a Polylab internal mixer, filled to 70% by volume, and the initial container temperature is brought to 90°C. Thermomechanical processing is carried out for 6 minutes until a maximum drop temperature of 165°C is reached. The composition thus obtained, designated composition C2, is recovered.

[0076] Next, the previously obtained composition C1 and the above composition C2 were mixed at 414 cm 3 Polylab internal mixer, filled to 70% by volume, and thermomechanical processing is carried out for 5 minutes until a maximum drop temperature of 150°C is reached.

[0077] The mixture from the previous step is then introduced into an external mixer, such as an open mill, so that the mixture cools to a temperature of 40°C. A crosslinking system (1.8 phr of sulfur and 2.2 phr of CBS (N-cyclohexyl-2-benzothiazole sulfenamide, sold by Flexsys under the reference Santocure CBS)) is then introduced and mixed for 20 minutes. The mixture thus obtained is then calendered in the form of a slab in order to carry out measurements of the physical or mechanical properties. Unless otherwise indicated, the rubber properties of the rubber compounds are measured after curing at 170°C for 20 minutes. [Table 2] [Table 3]

[0078] Comparative formulation MT2 and inventive formulation MI1 were prepared according to the process described for comparative formulation MT1, with compositions C1 and C2 in Tables 4 and 5 for comparative formulation MT2 and compositions C1 and C2 in Tables 6 and 7 for inventive formulation MI1, respectively. [Table 4] [Table 5] [Table 6] [Table 7] The rubber properties measured after curing of compounds MT1, MT2 and MI1 are shown in Table 8. [Table 8]

[0079] Comparative compound MT1 has two glass transition temperatures Tg1 and Tg2, one with a high Tg glass transition temperature (composition C1) and one with a low Tg glass transition temperature (composition C2), indicating the presence of two different rubber compositions. The same is true for the second comparative compound MT2 and compound MI1 of the invention.

[0080] Despite having the same amount of reinforcing filler (58.80 phr), the inventive formulation MI1 differs from the control formulations MT1 and MT2 by a different profile of loss factor measured according to ASTM D 5992-96 at a frequency of 10 Hz and a constant stress of 0.7 MPa over the temperature range of -80°C to 60°C.

[0081] The half-width of the loss factor for the compound MI1 according to the invention (21.5°C) is narrower than that of MT1 and MT2 (24.5°C and 34.0°C, respectively). This narrow half-width indicates that the reinforcing filler of the compound has a preferential affinity for the composition with the lowest Tg and is therefore distributed mainly in the composition with the lowest Tg. The half-height width of the loss factor for comparative formulation MT1 is 24.4° C., indicating a uniform distribution of the reinforcing filler between the two compositions of formulation MT1. The half-width of the loss factor for the comparative compound MT2 was 34.0°C, indicating a non-uniform distribution of the reinforcing filler between the two compositions of compound MT2, with the reinforcing filler being distributed mainly in the rubber composition with the highest Tg.

[0082] Compared to formulation MT1, which has a uniform distribution of reinforcing filler in the two compositions, formulation MT2 has comparable hysteresis (tanδ 40℃でのmax ) characteristic, coefficient μ max Therefore, if the hysteresis properties are comparable to the MT1 formulation and the reinforcing filler is located primarily in the rubber composition with the highest Tg, a decrease in wet grip performance is observed.

[0083] Surprisingly, when the reinforcing filler is located primarily in the rubber composition with the lowest Tg (see compound MI1 according to the invention), an improvement in the hysteresis properties and the coefficient μ max A decrease in ρ and therefore an improvement in wet grip performance is observed compared to the control formulation MT1.

[0084] 3. Test 2: Effect of differences in glass transition temperatures of the components forming the rubber compound The examples shown in Table 9 are intended to compare various rubber properties of a rubber compound MI1 according to the invention with two comparative compounds MT3 and MT4.

[0085] Compounds MT3 and MT4 were made so that the rubber compositions from which they were formed had a difference in glass transition temperatures of less than 23°C. In addition, the rubber composition having a higher Tg and constituting compound MT3 has the same composition as the rubber composition having a higher Tg and constituting compound ML1 of the present invention. Furthermore, the rubber composition having a lower Tg and constituting compound MT4 has the same composition as the rubber composition having a lower Tg and constituting compound ML1 of the present invention.

[0086] Table 9 shows the formulations of the test rubber compounds, with the ratios expressed in phr, that is, parts by weight per 100 parts by weight of elastomer in the compound. [Table 9]

[0087] The MT3 and MT4 formulations are prepared by the same process as described in Test 1, using the compositions in Tables 6 (Composition 1-MI1) and 10 for formulation MT3 and the compositions in Tables 11 and 7 (Composition 2-MI1) for formulation MT4, respectively. [Table 10] [Table 11]

[0088] The rubber properties measured after curing of these compounds are shown in Tables 12 and 13. [Table 12]

[0089] Comparative compound MT3 has two glass transition temperatures, Tg1 and Tg2, indicating the presence of two different rubber compositions in the compound.

[0090] When the composition of compound MT3 is modified so that the rubber composition having a lower Tg (composition C2) differs in glass transition temperature from the composition having a higher Tg (composition C1) by 23°C or more to obtain compound MI1 according to the present invention, it is clear that the hysteresis properties of rubber compound MI1 are significantly improved compared to compound MT3. Surprisingly, this improvement in the hysteresis properties of the formulation MI1 according to the invention is due to the coefficient μ max , and therefore not achieved at the expense of wet grip performance. [Table 13] ( *) Compound MT4 has a single glass transition temperature value; this glass transition temperature is measured according to standard NF EN ISO 11357-2:05-2014 and is equal to -51°C. However, according to theoretical calculations, rubber compound MT4 should have two distinct glass transition temperatures. The calculated theoretical glass transition temperature for composition C1-MT4 is -40°C, and for composition C2-MT4 the calculated theoretical glass transition temperature is -49°C, thus resulting in a Tg1 計算 -Tg2 計算 =-9℃.

[0091] When the composition of compound MT4 is modified so that the rubber composition having a higher Tg has a difference of 23°C or more in glass transition temperature with the composition having a lower Tg to obtain compound MI1 according to the present invention, the coefficient μ max It is observed that the wet grip performance is significantly improved. Surprisingly, the improvement in wet grip performance is not achieved at the expense of hysteresis properties, which remain comparable to the comparative formulation MT4.

[0092] 4. Test 3: Comparison with Prior Art The example shown in Table 14 aims to compare various rubber properties of a rubber compound MI1 according to the invention with a comparative compound MT5, which represents Example 4 of patent document EP 3 372 638 A1. The composition of formulation MT5 is shown in Table 14, with proportions expressed in phr. [Table 14]

[0093] Formulation MT5 is prepared according to the same procedure as described in Test 1 using the compositions in Tables 15 and 16, respectively. [Table 15] [Table 16]

[0094] The rubber properties measured after curing of these compounds are shown in Table 17. [Table 17]

[0095] The formulation MI1 according to the invention has a significantly improved coefficient μ compared to the formulation MT5, which is representative of the prior art. max Surprisingly, this significant improvement is not achieved at the expense of hysteresis properties, since the two formulations have the same tan δ 40℃でのmax This is because it has a value of

Claims

1. A method for producing a rubber compound having at least two glass transition temperatures Tg designated Tg1 and Tg2 and based on at least two rubber compositions designated C1 and C2, comprising: Preparing the rubber composition C1, which comprises at least one diene elastomer E1 and has the glass transition temperature Tg1; and preparing the composition C2, which contains at least one diene elastomer E2 different from the diene elastomer E1 and a reinforcing filler in an amount ranging from 20 phr to 100 phr in the rubber compound, and has the glass transition temperature Tg2; The glass transition temperature Tg1 of the composition C1 is −50° C. or higher, The rubber compound satisfies the mathematical relationship 25°C≦Tg1−Tg2≦40°C, The rubber compound has a loss factor profile showing the change in tan δ as a function of temperature (°C), the loss factor profile being measured over a temperature range of -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, wherein all tan δ peaks present at temperatures above the glass transition temperature Tg1 have a half-width of 23°C or less; and The elastomer E1 is the most abundant in the rubber compound. The method for producing the rubber compound is characterized in that

2. The method for producing a rubber compound according to claim 1, wherein the rubber compound satisfies the mathematical relationship 28°C < Tg1 - Tg2 < 35°C.

3. The method for producing a rubber compound according to claim 1 or 2, wherein the glass transition temperature Tg1 of the rubber composition C1 is −48° C. or higher.

4. The method for producing a rubber compound according to any one of claims 1 to 3, wherein the glass transition temperature Tg1 of the rubber composition C1 is within a range of -48°C to -15°C.

5. The method for producing a rubber compound according to any one of claims 1 to 4, wherein the glass transition temperature Tg2 of the composition C2 is -43°C or lower.

6. The method for producing a rubber compound according to any one of claims 1 to 5, wherein the glass transition temperature Tg2 of the composition C2 is within a range of -90°C to -43°C.

7. The method for producing a rubber compound according to any one of claims 1 to 6, wherein the diene elastomer E1 of the rubber composition C1 is a diene elastomer selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer and butadiene / styrene / isoprene copolymer.

8. The method for producing a rubber compound according to any one of claims 1 to 7, wherein the composition C1 further comprises a reinforcing filler.

9. The method for producing a rubber compound according to any one of claims 1 to 8, wherein the diene elastomer E2 of the rubber composition C2 is a functionalized diene elastomer.

10. The method for producing a rubber compound according to any one of claims 1 to 9, wherein the diene elastomer E2 of the rubber composition C2 is selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene / styrene copolymer, isobutene / isoprene copolymer, butadiene / isoprene copolymer, isoprene / styrene copolymer and butadiene / styrene / isoprene copolymer.

11. The method for producing a rubber compound according to any one of claims 1 to 10, wherein said reinforcing filler of composition C2 mainly comprises at least one inorganic reinforcing filler.

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