Elastomer compound for tire tread band and related tire

Abstract

The present invention relates to an elastomer compound for tyres for vehicle wheels, in particular for the tread band of tyres, preferably for big enduro motorcycle tyres. By using special diene-based elastomeric polymers, preferably mixed with liquid polymers, the elastomeric compound incorporated in the tread band gives the tyre a high mileage and good handling, especially in wet conditions.

Description

[Technical Field]

[0001] The present invention relates to an elastomeric compound for a tire for a vehicle wheel, in particular for the tread band of a tire. [Background technology]

[0002] Typically, the elastomer compounds used to manufacture the tread bands of vehicle wheel tyres contain a mixture of polybutadiene rubber (BR) and styrene butadiene rubber (SBR), as well as plasticizers such as process oils and resins.

[0003] Polybutadiene rubbers (BR), especially those containing a large amount of cis-double bonds, such as EUROPRENE® NEOCIS BR 60 from Versalis, are highly valued for their mechanical properties, including high resistance to abrasion.

[0004] Solution-polymerized styrene-butadiene SBR rubbers (S-SBR), such as TUFDENE E680 from Ashai, are commonly used to improve handling performance, especially in wet conditions, while emulsion-polymerized SBR rubbers (E-SBR), such as SBR 1739 from Synthos, have a higher weight average molecular weight Mw than standard solution-polymerized styrene-butadiene rubbers (S-SBR) due to their higher tear strength.

[0005] To provide tires with high tear and abrasion resistance and long running life, tread band compounds can preferably use blends of emulsion-polymerized styrene-butadiene copolymers (E-SBR) with polybutadiene (BR), often with a high cis content, but at the expense of wet road performance. On the other hand, replacing part of the E-SBR and polybutadiene rubber with conventional solution-polymerized styrene-butadiene rubbers (S-SBR), such as Asahi's Tufdene E680 and Tufdene 3830, can improve handling in wet conditions, but at the expense of reduced mechanical resistance. This performance is generally more important and is fundamental in certain demanding applications, such as enduro motorcycle driving.

[0006] In other words, based on current knowledge in this field, it appears that it is very difficult to achieve a balance between the conflicting demands of long distances and wet driving using the aforementioned polymers, and in practice one must settle for the best possible compromise.

[0007] Paragraph 0060 of document US20180362740A1 describes an elastomer composition containing butadiene rubber (BR150B from Ube Industries), emulsion-polymerized styrene-butadiene rubber (E-SBR SBR1723 from JSR Corporation) and non-functionalized solution-polymerized styrene-butadiene rubber (S-SBR Tufdene 3830 from Asahi Kasei Corporation). Summary of the Invention [Problem to be solved by the invention]

[0008] The applicant has set out the problem of how to further improve the road performance of current tires, particularly on wet roads, without compromising tear resistance and therefore mileage. [Means for solving the problem]

[0009] In this regard, the applicant has conducted several studies and found that it is possible to achieve this challenging result by modifying conventional tread band compounds by partially replacing high-cis polybutadiene (BR) and emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) with a specific type of solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a new generation of very high molecular weight, multi-branching agents. When incorporated into elastomer tread compositions in precise amounts, this class of solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with high molecular weight, multi-branching agents imparts higher mechanical strength to the elastomer compound compared to typical blends of emulsion-polymerized solid styrene-butadiene copolymer and polybutadiene (E-SBR / BR) for tread bands, while at the same time, unexpectedly, demonstrating better wet performance, given the polymer's high molecular weight and the predictable increase in compound stiffness that accompanies it.

[0010] Furthermore, in preferred embodiments, the applicant has succeeded in not only maintaining the mechanical strength properties but also improving the wet performance of the material. This additional benefit is obtained by further increasing the molecular weight of the polymer matrix, i.e., by partially replacing the conventional oil / resin plasticizer mixture with a mixture of liquid polymers.

[0011] Accordingly, a first aspect of the present invention is an elastomer composition for a vehicle wheel tire, comprising: At least one liquid polymer 0-30 phr; At least one resin 0-20 phr; 10 to 60 phr of at least one plasticizing oil; 100 phr of a mixture of solid diene-based elastomeric polymers; at least 40 phr of at least one reinforcing filler; at least 1 phr, preferably at least 2 phr, of at least one vulcanizing agent; wherein the total of the liquid polymer, the resin, if present, and the plasticizing oil is 20 to 90 phr; wherein the mixture of polymers comprises: a weight average molecular weight Mw of 300,000 g / mol to 600,000 g / mol, and 10 to 50 phr of at least one solid polybutadiene (BR) having a cis double bond content of at least 95%; Tg of -60℃ to -20℃ Mooney viscosity at 160°C between 30 and 70 MU, and 10 to 70 phr of at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) having a styrene content of between 15% and 50%; a weight average molecular weight Mw greater than 500,000 g / mol, and / or Between 25% and 50% styrene, between 10% and 50% vinyl, and / or Tg between -50°C and -20°C, and / or and, comprising, or preferably consisting of, 10 to 80 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, having a Mooney viscosity at 160°C of 60 to 100 MU; The properties of the solid diene-based elastomeric polymer of said mixture are measured according to the methods given in the experimental part, elastomer composition for vehicle wheel tires.

[0012] A further aspect of the present invention is an elastomeric compound for the tread band of a tire, obtainable by mixing and vulcanizing the elastomeric composition according to the invention.

[0013] A further aspect of the present invention is a tire tread band for a vehicle wheel comprising an elastomeric compound according to the present invention.

[0014] A further aspect of the invention is a tyre for a vehicle wheel comprising a tyre tread band according to the invention.

[0015] definition The term "phr" (parts per hundreds of rubber) means the parts by weight of a given component of a vulcanizable elastomeric composition per 100 parts by weight of a mixture of solid diene-based elastomeric polymers.

[0016] The term "elastomeric composition" means a composition comprising at least one diene-based elastomeric polymer and one or more additives, which upon mixing provide an elastomeric compound suitable for use in a tire component.

[0017] The components of the elastomer composition are generally not all introduced into the mixer at the same time, but are typically added sequentially. In particular, vulcanization additives, such as vulcanizing agents and, in some cases, accelerators and retarders, are usually added downstream relative to the compounding and processing of all other components.

[0018] In the intermediate elastomer compound or the final elastomer compound, the individual components of the elastomer composition may not always remain unchanged or be individually traceable, as they may have been completely or partially altered by interactions with other components, thermal and / or mechanical processing. As used herein, the term "elastomer composition" is meant to include the collection of all components added in the preparation of the elastomer compound, whether those components are all present at the same time, introduced sequentially, or subsequently traceable in the elastomer compound or in the final tire.

[0019] The term "elastomer compound" refers to a compound obtainable by mixing, and optionally heating, at least one diene-based polymer with at least one additive commonly used in the preparation of tire compounds.

[0020] The term "vulcanized elastomeric compound" means a material obtainable by crosslinking or sulfur vulcanization of an elastomeric compound.

[0021] The term "diene-based polymer" refers to a polymer or copolymer obtained by polymerization of one or more monomers, at least one of which is a conjugated diene (conjugated diolefin).

[0022] The term "solid diene-based elastomeric polymer" refers to a natural or synthetic polymer that, after vulcanization, can be repeatedly stretched at room temperature to at least twice its original length and will substantially immediately return to nearly its original length upon application of force after the tensile load is removed (as defined in ASTM D1566-11 Standard terminology relating to Rubber).

[0023] The term "vulcanization" refers to the crosslinking reaction of natural or synthetic rubber caused by, for example, sulfur-based vulcanizing agents.

[0024] The term "green" refers to a material, compound, composition, component or tire that has not yet been vulcanized.

[0025] The term "vulcanizing agent" refers to a cross-linking agent capable of transforming natural or synthetic rubber into an elastic and resistant material through the formation of a three-dimensional network of inter- and intra-molecular bonds.

[0026] The term "vulcanization accelerator" means compounds capable of reducing the duration and / or operating temperature of the vulcanization process, such as sulfur donors such as TBBS, sulfenamides in general, thiazoles, dithiophosphates, dithiocarbamates, guanidines, and thiurams.

[0027] The term "vulcanization activator" refers to a product that further accelerates vulcanization, allowing it to be carried out in a shorter time and sometimes at a lower temperature. An example of an activator is a stearic acid-zinc oxide system.

[0028] The term "vulcanization retarder" means a product capable of delaying the initiation of the vulcanization reaction and / or suppressing undesired secondary reactions, such as N-(cyclohexylthio)phthalimide (CTP).

[0029] The term "reinforcing filler" is meant to refer to reinforcing materials typically used in the field to improve the mechanical properties of tire rubber, and is preferably selected from among carbon black, conventional silica, for example silica from sand precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

[0030] The term "white filler" is intended to refer to conventional reinforcing materials used in this field, selected from among the conventional silicas and silicates such as sepiolite, palygorskite, also known as attapulgite, montmorillonite, alloysite, etc., optionally modified and / or derivatized by acid treatment. Typically, white fillers have hydroxyl groups on their surface.

[0031] The term "mixing step (1)" refers to the step in the process of preparing an elastomeric compound where one or more additives, except for the vulcanizing agent, may be compounded by mixing and, optionally, heating. The vulcanizing agent is provided in step (2). Mixing step (1) is also referred to as a "non-productive step." There may be multiple "non-productive" mixing steps in the preparation of a compound, and these may be designated 1a, 1b, etc.

[0032] The term "mixing step (2)" refers to the next step in the process of preparing an elastomeric compound, in which vulcanizing agents and, optionally, other additives of the vulcanization package are introduced into the elastomeric compound obtained from step (1) and mixed into the material at a controlled temperature, generally a compounding temperature below 120°C, to produce a vulcanizable elastomeric compound. Mixing step (2) is also called the "productive step." Each mixing step may include several intermediate processing steps or substeps, characterized by temporary interruptions in mixing to allow for the addition of one or more components, but without intermediate discharge of the compound. DETAILED DESCRIPTION OF THE INVENTION

[0033] The elastomeric composition according to the invention is characterized by one or more of the following preferred aspects, taken alone or in combination with one another:

[0034] The compositions of the present invention may comprise at least one or more, e.g., two or more, liquid polymers of each class or category of component in the mixture, the total amount of which conforms to the amount preferences specified herein.

[0035] The elastomeric composition according to the present invention may comprise at least one liquid polymer.

[0036] The liquid polymer may be present in an amount of preferably 0 to 28 phr, more preferably 0 to 23 phr.

[0037] The liquid polymer may be present in an amount greater than 3 phr, preferably greater than 4 phr, and / or less than 25 phr, preferably less than 20 phr.

[0038] The composition may preferably comprise at least one liquid polymer selected from liquid polybutadiene, liquid styrene butadiene copolymer, liquid polyisoprene and mixtures thereof.

[0039] The term "liquid polymer" means a diene-based polymer obtained by polymerization of one or more monomers, at least one of which is a conjugated diene, said polymer being a pourable liquid or low-viscosity fluid at a temperature of 23°C.

[0040] Preferably, the liquid polymer has the following parameters: a weight average molecular weight (Mw) of 80,000 g / mol or less, and / or a glass transition temperature (Tg) below 0°C.

[0041] The weight average molecular weight (Mw) can be measured according to techniques known in the art, such as, for example, GPC (gel permeation chromatography) according to the ISO 13885 method.

[0042] The glass transition temperature Tg can be conveniently measured using a differential scanning calorimeter (DSC) according to methods well known to those skilled in the art (ISO 22768 "Rubber, Raw - Determination of the glass transition temperatures by differential scanning calorimetry (DSC)").

[0043] Preferably, the liquid polymer is characterized by an (Mw) of 500 to 80,000 g / mol, more preferably 500 to 50,000 g / mol.

[0044] Preferably, the liquid polymer is characterized by a glass transition temperature (Tg) of between -120°C and 0°C, more preferably between -110°C and -40°C.

[0045] The at least one liquid polymer may be liquid polybutadiene.

[0046] Preferably, the liquid polybutadiene is characterized by a weight average molecular weight of 500 to 30,000 g / mol, preferably 8,000 to 20,000 g / mol, 10,000 to 15,000 g / mol.

[0047] Preferably, the liquid polybutadiene is characterized by a glass transition temperature (Tg) of from -120°C to -50°C, more preferably from -110°C to -90°C.

[0048] Preferably, the liquid polybutadiene has a vinyl content of 0 to 90%, preferably 1 to 50%.

[0049] Optionally, the liquid polybutadiene may be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups or hydroxyl groups or trialkoxysilyl groups.

[0050] Examples of suitable liquid polybutadienes include butadiene-based liquid polymers sold by Evonik under the trade names POLYVEST 110, POLYVEST 130, and POLYVEST MA 75; liquid polymers sold by Kuraray under the trade names LBR 307, LBR 305, and LBR 300; and liquid polymers sold by Cray Valley under the trade names RICON 130, RICON 130MA8, RICON 130MA13, RICON 150, RICON 156, and RICON 157.

[0051] The at least one liquid polymer may be a liquid styrene butadiene copolymer.

[0052] Preferably, the liquid styrene butadiene copolymer is characterized by a weight average molecular weight of 500 to 10,000 g / mol, preferably 2,000 g / mol to 6,000 g / mol.

[0053] Preferably, the liquid styrene butadiene copolymer is characterized by a glass transition temperature (Tg) of from -90°C to -20°C, more preferably from -70°C to -50°C.

[0054] Preferably, the liquid styrene butadiene copolymer has a vinyl content of 0 to 90%, preferably 1 to 50%.

[0055] Optionally, the liquid styrene butadiene copolymer may be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups or hydroxyl groups or trialkoxysilyl groups.

[0056] Examples of suitable liquid styrene butadiene copolymers are available from Cray Valley (Total) under the trade names RICON® 100, RICON® 181, and RICON® 184, and from Kuraray Co., Ltd. under the trade names LSBR820, There is a styrene butadiene-based liquid polymer sold under the trade name LSBR841.

[0057] The at least one liquid polymer may be liquid polyisoprene.

[0058] Preferably, the liquid polyisoprene has a weight average molecular weight of 3,000 to 80,000 g / mol, preferably 20,000 to 60,000 g / mol.

[0059] Preferably, the liquid polyisoprene has a glass transition temperature (Tg) comprised between -80°C and -30°C, preferably between -70°C and -40°C.

[0060] Optionally, the liquid polyisoprene may be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups, hydroxyl groups, or trialkoxysilyl groups.

[0061] Examples of suitable liquid polyisoprene A include liquid polymers based on isoprene (IR) sold by Kuraray under the trade names LIR 30, LIR 50, LIR 403, and LIR 410, and natural polyisoprenes such as DPR 35, DPR 40, DPR 75, and DPR 400 sold by DPR INDUSTRIES.

[0062] Preferably, the at least one liquid polymer is a liquid polybutadiene and / or a liquid styrene butadiene copolymer.

[0063] The elastomeric composition according to the present invention may comprise at least one resin.

[0064] The resin may be present in an amount of preferably 0 to 15 phr, more preferably 3 to 10 phr.

[0065] The resin may be present in an amount greater than 2 phr, preferably greater than 4 phr, and / or less than 17 phr, preferably less than 11 phr.

[0066] The term "resin" is used to mean a polymer that is thermoplastic or has at least partially thermoplastic properties (as in the case of elastomeric / thermoplastic block copolymers).

[0067] The term "thermoplastic" refers to the tendency of a polymer to increase in viscosity, i.e., to undergo plastic deformation, upon increasing temperature and / or sufficiently strong deformation. This thermoplastic property distinguishes the behavior of resins from that of elastomers, as defined below. Furthermore, unlike liquid polymers and diene-based elastomeric polymers, as defined herein, resins are not obtained by polymerization of conjugated dienes.

[0068] The resin of the present composition is a non-crosslinkable polymer (non-reactive resin).

[0069] Preferably, the resin has the following parameters: - weight average molecular weight (Mw) between 200 and 3,000 g / mol, and / or - a glass transition temperature (Tg) above 0°C.

[0070] The weight average molecular weight (Mw) can be measured according to techniques known in the art, such as SEC (size exclusion chromatography) according to ASTM D6579-11 method "Standard Practice for Molecular Weight Averages and Molecular Weight Distribution of Hydrocarbon, Rosin and Terpene Resins by Size-Exclusion Chromatography."

[0071] The glass transition temperature (Tg) and softening temperature (Tm) can be conveniently measured using a differential scanning calorimeter (DSC) according to methods well known to those skilled in the art, such as ASTM D-6604 (Glass Transition Temperatures of Hydrocarbon Resins by Differential Scanning Calorimetry).

[0072] More preferably, the resin is characterized by a weight average molecular weight (Mw) of 500 to 3,000 g / mol, more preferably 500 to 2,000 g / mol.

[0073] More preferably, the resin is characterized by a glass transition temperature (Tg) greater than 20°C.

[0074] The resin may be a solid having a softening temperature (Tm) higher than 0°C, and more preferably has a softening temperature of 10°C to 160°C, or 60°C to 90°C.

[0075] The resin used in the composition is preferably selected from the group comprising hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.

[0076] Preferably, the resin is a hydrocarbon resin.

[0077] Preferably, the resin is a mixture of natural and hydrocarbon resins.

[0078] The hydrocarbon resin may be aliphatic, aromatic or a combination thereof, meaning that the base polymer of the resin may be composed of aliphatic and / or aromatic monomers.

[0079] Hydrocarbon resins may be natural (e.g., vegetable), synthetic, or petroleum-derived. In some cases, but not limiting to the present invention, these resins contain essentially only hydrogen and carbon atoms.

[0080] Preferably, the hydrocarbon resin has a weight average molecular weight of 500 to 3000 g / mol, preferably 700 to 1500 g / mol.

[0081] Preferably, the hydrocarbon resin is selected from homopolymers or copolymers of cyclopentadiene (CPD), dicyclopentadiene (DCPD), homopolymers or copolymers of terpenes, homopolymers or copolymers of C5 fractions and mixtures thereof, preferably DCPD / vinyl aromatic copolymers, DCPD / terpene copolymers, DCPD / C5 fraction copolymers, terpene / vinyl aromatic copolymers, C5 fraction / vinyl aromatic copolymers and combinations thereof.

[0082] Examples of vinyl aromatic monomers include styrene, α-methylstyrene, ortho-, meta-, para-methylstyrene, vinyltoluene, para-tert-butylstyrene, methoxystyrene, chlorostyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene, vinyl aromatic monomers derived from C8-C10 fractions, in particular C9 fractions.

[0083] Preferably, the hydrocarbon resin is selected from resins derived from coumarone indene, styrene indene, styrene alkyl styrene, aliphatic resins.

[0084] A specific example of a commercially available hydrocarbon resin is NOVARES C resin (indene coumarone synthetic resin) manufactured by RUETGERS CHEMICAL GmbH, and NOVARES C10, C30, and C90 are particularly preferred.

[0085] Examples of commercially available styrene-indene hydrocarbon resins include UNILENE A 100 manufactured by Braskem and Novares TL 90 manufactured by Ruetgers.

[0086] Examples of commercially available alkylstyrene hydrocarbon resins include Sylvares SA 85 manufactured by Arzona Chemical Company and Kristalex F 85 manufactured by Eastman Company.

[0087] Examples of commercially available aliphatic hydrocarbon resins include Escorez® 1102 (ExxonMobil), Piccotac 1100 (Eastman), and Quintone A 100 (Zeon Chemicals).

[0088] Alternatively, the resin is a phenolic resin.

[0089] Preferably, the phenolic resin is selected from alkylphenol-formaldehyde resins, rosin-modified alkylphenol resins, alkylphenol-acetylene resins, alkylphenol-modified resins, and terpene phenol resins.

[0090] Examples of commercially available phenolic resins that can be used in the present invention include RESINA SP-1068 (manufactured by SI Group) (octylphenol-formaldehyde resin), DUREZ 32333 (manufactured by Sumitomo Bakelite Co., Ltd.) (phenol-formaldehyde resin), KORESIN (manufactured by BASF) (pt-butylphenol-acetylene resin), and SYLVARES TP115 (manufactured by Arizona Chemicals) (terpene-phenolic resin).

[0091] Alternatively, the resin is a natural terpene-based resin.

[0092] Preferably, the resin is a polyterpene resin selected from homopolymers or copolymers of α-pinene, β-pinene, limonene, vinyl aromatic monomers (styrene) and / or aromatic monomers (phenols).

[0093] Preferably, the resin is a polyterpene resin having a glass transition temperature (Tg) greater than 25°C.

[0094] Preferably, the resin is a polyterpene resin having a softening temperature (Tm) of 50°C to 150°C.

[0095] Preferably, the resin is a polyterpene resin having a weight average molecular weight of 500 to 3000 g / mol.

[0096] Examples of commercially available natural terpene resins that can be used in the present invention include Piccolyte F90 and Piccolyte F105 manufactured by PINOVA, and Dercolyte A 115 and Dercolyte M 115 manufactured by DRT.

[0097] Alternatively, the resin is a rosin-based natural resin.

[0098] The term rosin generally refers to a mixture of isomeric organic acids (rosin acids) characterized by a common structure containing three C6 fused rings, different numbers and positions of double bonds, and a single carboxyl group.

[0099] Examples of rosin-based resins are sold under the trade names HYDROGRAL G and DERTOLINE P 105 by DRT Corporation.

[0100] The elastomeric composition according to the present invention comprises at least one plasticizing oil.

[0101] Preferably, the composition comprises at least 10 phr, at least 15 phr, at least 20 phr and / or up to 60 phr, up to 50 phr, up to 40 phr of at least one plasticizing oil.

[0102] Preferably, the composition comprises from 20 to 50 phr, more preferably from 25 to 45 phr, of at least one plasticizing oil.

[0103] The plasticizing oil may function as a thinner (extender) derived in whole or in part from commercial compositions of solid diene-based elastomeric polymers.

[0104] The term "plasticizing oil" means a processing oil derived from petroleum, mineral, vegetable, synthetic oils, or combinations thereof.

[0105] Plasticizing oils differ from the liquid polymers and diene-based elastomeric polymers defined herein in that they are not derived from the polymerization of conjugated dienes.

[0106] Preferably, the plasticizing oil has the following characteristics: Weight average molecular weight (Mw) of 600 g / mol or less, or 400 to 10,000 g / mol for RAE class, and / or a glass transition temperature (Tg) below -30°C.

[0107] Preferably, the plasticizing oil is a petroleum-derived process oil selected from paraffins (saturated hydrocarbons), naphthenes, polycyclic aromatics, and mixtures thereof.

[0108] Examples of suitable petroleum-derived process oils include aromatic, paraffinic, and naphthenic oils such as Mild Extract Solvated (MES), Distillate Aromatic Extract (DAE), Treated Distillate Aromatic Extract (TDAE), Treated Residual Aromatic Extract (TRAE), and Residual Aromatic Extract (RAE), which are known in the industry.

[0109] The term RAE refers to a complex mixture of mainly polycyclic aromatic hydrocarbons obtained by extracting the distillation residue of crude oil with a solvent (CAS number 64742-10-5).

[0110] Preferably, the plasticizing oil is a petroleum-derived process oil having a low aromatic content, for example selected from TDAE, TRAE, MES, paraffinic oils, or naphthenic oils.

[0111] Examples of suitable plasticizing oils include petroleum-derived oils such as NYTEX 4700 available from Nynas, EXTENSOIL 1471 available from Repsol, and VIVATEC 500 available from H&R; and vegetable oils such as RADIA 6132 available from Oleon, and Agripure AP 18 and Agripure AP 75 available from Cargill.

[0112] Alternatively, the plasticizing oil may be of natural or synthetic origin obtained from the esterification of glycerol with fatty acids, including glycerol triglycerides, diglycerides, monoglycerides, or mixtures thereof.

[0113] Preferably, these oils have a glass transition temperature (Tg) below -70°C.

[0114] Examples of suitable vegetable oils include sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil, and cottonseed oil.

[0115] Alternatively, the plasticizing oil is a synthetic oil selected from alkyl or aryl esters of phthalic or phosphoric acid. Preferably, these esters have a glass transition temperature (Tg) below -70°C.

[0116] These oils can be used alone or in mixtures.

[0117] The elastomer composition according to the invention preferably comprises 25 to 80 phr, more preferably 30 to 60 phr, of a plasticizing mixture, by which is meant all the constituents of the liquid polymer, the resin, if present, and the plasticizing oil.

[0118] The amount of plasticizing mixture corresponds to the sum of the amounts of liquid polymer, resin, if present, and plasticizing oil, as defined above.

[0119] The elastomer composition according to the invention preferably comprises at least 20 phr, 30 phr or 40 phr of the plasticizing mixture.

[0120] Preferably, the composition contains no more than 90 phr, 80 phr or 70 phr of the plasticizing mixture.

[0121] The three components of the plasticizing mixture, i.e., at least one liquid polymer, optionally at least one resin, and at least one plasticizing oil, do not necessarily have to be premixed together to give a separate plasticizing mixture, but may be added individually to the composition in any order or step of the preparation process, as detailed below, or may be accompanied in whole or in part by one or more of the other components, as in the case of plasticizing oils that are already at least partially compounded as thinners into commercially available elastomeric polymers.

[0122] The elastomer composition for a tire according to the present invention comprises: 15 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 350,000 to 550,000 g / mol and a cis double bond content of 95 to 99%; 10 to 60 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -25°C, a Mooney viscosity of 40 to 60 MU, and a styrene content of 20% to 45%; a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol; Styrene content: 30%~45%, vinyl content: 15%~40%, Tg between -45°C and -25°C, and / or and 15 to 75 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, having a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0123] In one embodiment, the mixture of solid diene-based elastomeric polymers of the composition according to the present invention comprises: 15 to 50 phr of at least one solid polybutadiene (BR), 10 to 60 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR), and It comprises, or preferably consists of, 15 to 75 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent.

[0124] In one embodiment, the mixture of solid diene-based elastomeric polymers of the composition according to the present invention comprises: 25-40 phr of at least one solid polybutadiene (BR), 10 to 40 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR), and It comprises, or preferably consists of, 30 to 65 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent.

[0125] In one embodiment, in the elastomer composition of the present invention, the solid polybutadiene (BR) has a weight average molecular weight Mw of 350,000 to 550,000 g / mol and a cis double bond content of 95 to 99%, Emulsion polymerized solid styrene butadiene copolymer (E-SBR) has a Tg of -60°C to -25°C, a Mooney viscosity of 40 to 60 MU, and a styrene content of 20% to 45%. At least one solution-polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, and / or Styrene content between 30% and 45%, vinyl content between 15% and 40%, and / or Tg between -45°C and -25°C, and / or It has a Mooney viscosity of 70 to 90 MU measured at 160°C.

[0126] In a preferred embodiment, the elastomer composition for a tire according to the present invention comprises: 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 300,000 g / mol to 600,000 g / mol and a cis double bond content of at least 95%; Tg of -60℃ to -20℃ a Mooney viscosity (at 160°C) of 30 to 70 MU, and 10 to 70 phr of at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) having a styrene content of 15% to 50%; a weight average molecular weight Mw greater than 800,000 g / mol; Styrene content: 25%~50%, vinyl content: 10%~50%, Tg between -50°C and -20°C, and and 10 to 80 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, having a Mooney viscosity measured at 160°C of 60 to 100 MU.

[0127] In a more preferred embodiment, the elastomer composition for a tire according to the present invention comprises 15 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 350,000 to 550,000 g / mol and a cis double bond content of 95 to 99%; Tg of -60℃ to -25℃ Mooney viscosity of 40-60 MU, and 10 to 60 phr of at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) having a styrene content of 20% to 45%; a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol; Styrene content: 30%~45%, vinyl content: 15%~40%, Tg between -45°C and -25°C, and and 15 to 75 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, having a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0128] Suitable solid diene-based elastomeric polymers for the present compositions are elastomeric polymers or copolymers having a glass transition temperature (Tg) generally below 20°C, preferably in the range of 0°C to -110°C.

[0129] Preferably, the solid diene-based elastomeric polymer of the elastomeric compound of the present invention has a weight average molecular weight (Mw) greater than 80,000 g / mol.

[0130] By solid polybutadiene (BR) is meant a polymer obtained by polymerization of 1,3-butadiene, optionally in the presence of other conjugated diolefins as described below, in which 1,3-dibutadiene is present in an amount of 50% by weight or more, relative to the total weight of monomers.

[0131] Examples of suitable polybutadienes include polybutadienes rich in 1,4-cis double bonds, polybutadienes rich in vinyl units, metallocene polybutadienes, and 1,3-butadiene / acrylonitrile copolymers.

[0132] Examples of suitable commercially available polybutadienes (BR) include polybutadiene (Europrene Neocis® BR40) (Versalis), SKD NHEODIMIO (Nizhnekamskneftechim Export), and BUNA CB 29 MES (Lanxess).

[0133] Preferably, the solid polybutadiene (BR) has a weight average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of 96 to 98%.

[0134] Preferably, the at least one solid polybutadiene (BR) is present in the composition in an amount ranging from 15 to 45 phr, more preferably from 25 to 35 phr.

[0135] Preferably, the solid polybutadiene (BR) has a glass transition temperature (Tg) below -85°C, preferably in the range of -110°C to -90°C.

[0136] One or more solid polybutadienes may be present in the composition in admixture.

[0137] The elastomeric composition comprises two or more solid styrene butadiene copolymers (SBR).

[0138] Generally, the term "solid styrene-butadiene copolymer SBR" refers to a copolymer obtained by polymerization of one or more diolefins conjugated with at least one monovinylarene monomer, and optionally a polar comonomer. Preferably, the conjugated diolefin contains 4 to 12, more preferably 4 to 8, carbon atoms, and is preferably selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, or mixtures thereof. 1,3-butadiene and isoprene are particularly preferred.

[0139] Preferably, the monovinylarene contains 8 to 20, preferably 8 to 12, carbon atoms and is preferably selected from styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene, such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, or mixtures thereof. Styrene is particularly preferred.

[0140] Preferably, the polar comonomer is selected from vinylpyridine, vinylquinoline, acrylic acid and alkyl acrylate esters, nitriles or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile, or mixtures thereof.

[0141] The elastomeric composition of the present invention comprises at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR).

[0142] By emulsion polymerized solid styrene butadiene copolymer (E-SBR) is meant a copolymer obtained by emulsion polymerization of one or more diolefins conjugated with at least one monovinylarene monomer, and optionally a polar comonomer as defined above.

[0143] Examples of suitable emulsion polymerized solid styrene butadiene copolymers (E-SBR) include styrene / 1,3-butadiene (SBR), styrene / isoprene / 1,3-butadiene, and styrene / 1,3-butadiene / acrylonitrile copolymers.

[0144] Examples of suitable commercially available emulsion-polymerized solid styrene butadiene copolymers (E-SBR) include SBR 1723 TDAE from Sibur, BUNA™ SBR 1723 from Synthos, INTOL® 1723 from Versalis (Eni Group), SBR 1739 from LG Chem, SBR 1739 from Versalis, Nipol® SBR 1739 from Nippon Zeon, and BUNA™ SB 1739 Schkopau from Trinseo.

[0145] Preferably, the emulsion polymerized solid styrene butadiene copolymer (E-SBR) has a Tg of -58°C to -28°C, a Mooney viscosity of 43 to 57 MU, and a styrene content of 20% to 43%.

[0146] Preferably, at least the emulsion polymerized solid styrene butadiene copolymer (E-SBR) is present in the composition in an amount ranging from 10 to 60 phr, more preferably from 10 to 50 phr.

[0147] Preferably, the emulsion polymerized solid styrene butadiene copolymer (E-SBR) has a glass transition temperature (Tg) below -10°C, preferably in the range of -60 to 40°C.

[0148] One or more emulsion-polymerized solid styrene butadiene copolymers (E-SBR) may be admixed in the composition.

[0149] The elastomeric composition of the present invention comprises at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) as defined herein.

[0150] Solution-polymerized solid styrene-butadiene copolymer (S-SBR) means a copolymer obtained by solution polymerization of one or more diolefins conjugated with at least one monovinylarene monomer, and optionally a polar comonomer as defined above.

[0151] The solution-polymerized solid styrene-butadiene copolymers (S-SBR) of the present invention are polymers that have been functionalized along the chain, and optionally also at the ends, with a hyperbranched coupling agent.

[0152] In the solution-polymerized solid styrene-butadiene copolymer (S-SBR) of the present invention, functional groups can be introduced into the chain by reaction with a suitable multi-branched coupling agent, or optionally, by reaction with a terminal terminating agent. In particular, diene-based elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (particularly, an organolithium initiator) can be functionalized by reacting the organometallic residue derived from the initiator with a suitable terminating agent and / or coupling agent, such as an amine, amide, imine, carbodiimide, alkyltin halide, substituted benzophenone, alkoxysilane, aryloxysilane, alkyldithiol, alkyldithiolsilane, carboxyalkylthiol, carboxyalkylthiolsilane, thioglycol, etc.

[0153] General examples of terminating or coupling agents known in the art are described, for example, in patents EP2408626, EP2271682, EP3049447A1, EP2283046A1, EP2895515A1, EP451604, US4742124, WO2015086039A1 and WO2017211876A1.

[0154] Particularly suitable examples of hyperbranched coupling agents include the polyorganosiloxanes described in paragraphs 0040 to 0043 of patent application SG10201800553S(A) in the name of JSR Corporation, in particular those of formula (6):

[0155] [ka] and the meaning of the variables reported in the literature.

[0156] A specific example of a preferred multi-branched coupling agent is the product of formula (6.1) below:

[0157] [ka]

[0158] Preferably, the at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent is a functionalized polymer obtained from styrene / 1,3-butadiene, styrene / isoprene / 1,3-butadiene, styrene / 1,3-butadiene / acrylonitrile, and mixtures thereof.

[0159] Suitable functionalized solution polymerized solid styrene butadiene copolymers (S-SBR) are described, for example, in patent application SG10201800553S(A) in the name of JSR Corporation.

[0160] An example of a preferred solution polymerized solid styrene butadiene copolymer functionalized with a hyperbranched coupling agent is HPR 620 from JSR Corporation.

[0161] Preferably, the at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent has a weight average molecular weight Mw of 500,000 to 2,000,000 g / mol, more preferably 800,000 to 1,200,000 g / mol.

[0162] In one embodiment, the solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent is a weight average molecular weight Mw greater than 500,000 g / mol; Styrene content: 25%~50%, vinyl content: 10%~50%, Tg between -50°C and -20°C, and It is characterized by a Mooney viscosity of 60 to 100 MU at 160°C.

[0163] Preferably, at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent is present in the composition in an amount of from 25 to 80 phr, more preferably from 30 to 75 phr.

[0164] Preferably, the at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent has a glass transition temperature (Tg) of less than -10°C, preferably in the range of -50 to 20°C.

[0165] Admixed in the composition may also be one or more solution-polymerized solid styrene butadiene copolymers (S-SBR) functionalized with a hyperbranched coupling agent.

[0166] The solid diene-based elastomeric polymers constituting the mixture can optionally be functionalized by reaction with a suitable conventional terminating or coupling agent (i.e., a non-multibranched coupling agent) (solid diene-based elastomeric polymer a'). In particular, diene-based elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (especially an organolithium initiator) can be functionalized by reacting the organometallic residues derived from the initiator with a suitable terminating or coupling agent, such as an imine, carbodiimide, alkyltin halide, substituted benzophenone, alkoxysilane, or aryloxysilane.

[0167] In one embodiment, the mixture of solid diene-based elastomeric polymers comprises: 20 phr to 45 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 350,000 to 550,000 g / mol and a cis double bond content of at least 95%; 10 to 55 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -25°C, a Mooney viscosity of 40 to 60 MU, and a styrene content of 20% to 43%; and 10-70 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, styrene in an amount of 25% to 50%, vinyl in an amount of 10% to 50%, Tg between -50°C and -20°C, and a Mooney viscosity measured at 160°C of 60 to 100 MU.

[0168] More preferably, the mixture of solid diene-based elastomeric polymers is 25 to 35 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of at least 97%; 10 to 45 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -58°C to -28°C, a Mooney viscosity of 45 to 55 MU, and a styrene content of 22% to 42%; and 30-65 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, styrene in an amount of 30% to 45%, vinyl in an amount of 15% to 40%, Tg between -45°C and -25°C, and a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0169] The elastomeric composition of the present invention comprises at least one reinforcing filler.

[0170] The elastomeric composition according to the invention preferably comprises at least 50 phr, at least 60 phr, at least 70 phr, or at least 80 phr of at least one reinforcing filler.

[0171] Preferably, the composition comprises no more than 150 phr, no more than 140 phr, no more than 130 phr, no more than 120 phr, no more than 110 phr, or no more than 100 phr of at least one reinforcing filler.

[0172] Preferably, the composition comprises 10 to 150 phr, 30 to 120 phr, 50 to 120 phr, 70 to 110 phr, or 80 to 100 phr of at least one reinforcing filler.

[0173] Preferably, the reinforcing filler is selected from carbon black, white filler, or mixtures thereof.

[0174] In one embodiment, the reinforcing filler is a white filler selected from hydroxides, oxides and hydrated oxides, salts and hydrated salts of metals, silica, optionally derivatized and / or modified silicate fibers, or mixtures thereof.

[0175] Preferably, the reinforcing filler is silica.

[0176] Silica present in the composition can interact during mixing with the silane coupling agent added to make the silica compatible and dispersible in the elastomeric polymer.

[0177] In one embodiment, the reinforcing filler comprises or consists of carbon black.

[0178] Preferably, said carbon black is present in the elastomeric composition in an amount ranging from 5 phr to 120 phr, preferably from 10 phr to 110 phr.

[0179] Preferably, the carbon black is present in the elastomeric composition in an amount greater than 35 phr, more preferably greater than 40 phr.

[0180] Preferably, the carbon black reinforcing filler is 20 ml 2 / g or more, preferably 50m 2 / g (determined by the STSA method - statistical thickness surface area according to ISO 18852:2005).

[0181] An example of carbon black is N234 sold by Birla Group (India) or Cabot Corporation.

[0182] In one embodiment, the reinforcing filler comprises a mixture of multiple fillers from those defined above, preferably mixed silica and carbon black.

[0183] The elastomeric composition includes at least one vulcanizing agent.

[0184] Preferably, the composition comprises at least 1.5 phr, 2 phr, 3 phr, or 4 phr of at least one vulcanizing agent.

[0185] Preferably, the composition contains no more than 10 phr or no more than 8 phr of at least one vulcanizing agent.

[0186] Preferably, the composition comprises 1 to 10 phr or 2 to 10 phr of at least one vulcanizing agent.

[0187] Preferably, the vulcanizing agent is selected from sulfur and sulfur-containing molecules that act as sulfur donors.

[0188] Sulfur or its derivatives can be advantageously chosen, for example, from: (i) soluble sulfur (crystalline sulfur); (ii) insoluble sulfur (polymeric sulfur); (iii) sulfur dispersed in oil (e.g., 33% sulfur known under the trade name Crystex Ot33 from Solutia); (iv) Sulfur donor compounds such as caprolactam disulfide (CLD), bis[(trialkoxysilyl)propyl] polysulfides, dithiophosphates; thiurams, dithiodimorphline, caprolactam disulfide, or mixtures thereof.

[0189] Alternatively, the vulcanizing agent may be selected from peroxides such as dialkyl peroxides RO-O-R (where R is an alkyl group), alkyl-aryl peroxides R-O-R' (where R is an alkyl group and R' is an aryl group), diaryl peroxides R'-OO-R' (where R' is an aryl group), diacyl peroxides RC(O)-OO-(O)C-R' (where R and R' are aryl and / or alkyl groups), peroxyketals R-O-(R)C(R')-OO-R' (where R and R' are aryl and / or alkyl groups), peroxyesters RC(O)-OO-R' (where R and R' are aryl and / or alkyl groups), metal oxides such as zinc oxide, quinones, resins and organic bases.

[0190] The vulcanizing agent is preferably used in conjunction with adjuvants such as activators, vulcanization accelerators and / or retarders known to those skilled in the art.

[0191] Particularly effective vulcanization activators are zinc compounds, in particular ZnO, ZnCO3, and zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms.

[0192] For example, zinc stearate, preferably formed in situ in the elastomer composition with ZnO and fatty acid, as well as magnesium stearate formed with MgO, or mixtures thereof, are preferably used.

[0193] The vulcanization activator is preferably used in an amount of 0.5 to 10 phr in the elastomer composition, more preferably 1 to 5 phr in the elastomer composition, and even more preferably 1.5 to 3.5 phr in the elastomer composition.

[0194] An example of an activator is the product Aktiplast ST sold by the company Rheinchemie.

[0195] Preferably, the elastomer composition may further comprise at least one vulcanization accelerator.

[0196] Commonly used vulcanization accelerators can be selected, for example, from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates, or mixtures thereof.

[0197] An example of a vulcanization accelerator is N-cyclohexyl-2-benzothiazylsulfenamide Vulkacit® CZ / C, available from Lanxess.

[0198] The vulcanization accelerator is preferably used in the elastomer composition in an amount of 0.05 phr to 10 phr.

[0199] More preferably, the vulcanization accelerator is used in the elastomer composition in an amount of 0.1 phr to 5 phr.

[0200] More preferably, the vulcanization accelerator is used in the elastomer composition in an amount of 0.5 phr to 3 phr.

[0201] The elastomeric composition may optionally contain one or more vulcanization retarders such as, for example, N-cyclohexylthiophthalimide (VULKALENT G, -Lanxess).

[0202] Preferably, when present, the retarder is used in an amount of from 0.05 phr to 2 phr.

[0203] The elastomer composition according to the present invention may further comprise at least one silane coupling agent, preferably in an amount ranging from 0.5 to 20 phr.

[0204] Preferably, the silane coupling agent is a silane coupling agent selected from those having at least one hydrolyzable silane group, such as a silane coupling agent represented by the following general formula (I): (R')3Si-C n H 2n -X (I) wherein the R' groups, which may be equal to or different from one another, are selected from alkyl, alkoxy, or aryloxy groups, or halogen atoms, provided that at least one of the R' groups is an alkoxy or aryloxy group; n is an integer from 1 to 6, inclusive; and X is selected from the group consisting of nitroso, mercapto, amino, epoxy, vinyl, imide, chloro, -(S) m C n H 2n The silane coupling agents may be identified by a group selected from -Si-(R')3 and -S-COR', where m and n are integers from 1 to 6, inclusive, and the R' group is as defined above. Among the silane coupling agents, bis(3-triethoxysilylpropyl) tetrasulfide and bis(3-triethoxysilylpropyl) disulfide are particularly preferred. The silane coupling agents may be used as such or in a suitable mixture with an inert filler (such as carbon black) to facilitate incorporation into the elastomer composition.

[0205] Preferably, the silane coupling agent is present in the elastomer composition in an amount ranging from 0.5 phr to 10 phr, preferably from 0.5 phr to 7 phr.

[0206] An example of a silane coupling agent is TESPT: bis(3-triethoxysilylpropyl) tetrasulfide Si69, available from Evonik.

[0207] The elastomeric composition may also contain other commonly used additives, such as antioxidants, anti-reversion agents, adhesives, anti-ozonants, especially of the p-phenylenediamine type, antioxidants, waxes, fibers (e.g., Kevlar® pulp), or mixtures thereof, selected according to the particular use intended for the composition.

[0208] In one embodiment, the elastomeric composition of the present invention comprises: 0 to 20 phr of at least one liquid polymer selected from liquid polybutadiene, liquid styrene butadiene copolymers, and mixtures thereof; 0 to 10 phr, preferably at least 1 phr, of at least one resin; 20-40 phr of at least one plasticizing oil; 100 phr of a mixture of solid diene-based elastomeric polymers; 60 to 100 phr of at least one reinforcing filler; and 1 to 4 phr of at least one vulcanizing agent, wherein the mixture of polymers comprises: 20 phr to 40 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of at least 97%; 10 to 50 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57°C to -25°C, a Mooney viscosity value of 45 to 55 MU, and a styrene content of 22% to 42%; and 25 to 70 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, styrene in an amount of 30% to 45%, vinyl in an amount of 15% to 40%, Tg between -45°C and -25°C, and a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0209] In a preferred embodiment, the elastomer composition of the present invention comprises 0 to 12 phr, preferably 1 to 12 phr, of at least one resin; 20-40 phr of at least one plasticizing oil; 100 phr of a mixture of solid diene-based elastomeric polymers; at least 60 phr of at least one reinforcing filler; comprising, or preferably consisting of, at least 1.0 phr, preferably at least 2 phr, of at least one vulcanizing agent; wherein the mixture of polymers comprises: At least one solid polybutadiene (BR) 20 phr to 40 phr having a weight average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of at least 97%; 10 to 50 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57°C to -25°C, a Mooney viscosity value of 45 to 55 MU, and a styrene content of 22% to 42%; and 25-70 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, 30% to 45% styrene, 15% to 40% vinyl, a Tg of -45°C to -25°C, and a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0210] In a more preferred embodiment, the elastomer composition of the present invention comprises 10 to 20 phr of at least one liquid polymer selected from liquid polybutadiene, liquid styrene butadiene copolymers, and mixtures thereof; 3 to 8 phr of at least one resin, 15 to 35 phr of at least one plasticizing oil; 100 phr of a mixture of solid diene-based elastomeric polymers; at least 60 phr of at least one reinforcing filler; and comprising, or preferably consisting of, at least 1 phr, preferably at least 2 phr, of at least one vulcanizing agent; wherein the mixture of polymers comprises: At least one solid polybutadiene (BR) 20 phr to 40 phr having a weight average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of at least 97%; 10 to 30 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57°C to -25°C, a Mooney viscosity value of 45 to 55 MU, and a styrene content of 22% to 42%; and 40-70 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, preferably greater than 900,000 g / mol, styrene in an amount of 30% to 45%, vinyl in an amount of 15% to 40%, Tg between -45°C and -25°C, and a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0211] Preferably, the elastomeric composition of the present invention does not contain omega-9 fatty acid amides, such as those described in paragraph 043 of US2018 / 0362740A1.

[0212] A further aspect of the present invention is an elastomeric compound for the tread band of a tire, obtainable by mixing and vulcanizing the elastomeric composition according to the invention.

[0213] Advantageously, the elastomer compounds according to the invention have the following characteristics, measured according to the methods reported in the experimental part: - Mooney viscosity (1+4 at 100°C) of 60-90 MU, higher than 50.00 MU, typically higher than 60 MU; - 1.100~1.500g / cm 3 density of; - a load at 300% elongation (Ca3) greater than 8.50 MPa, preferably greater than 8.60 MPa, typically between 8.60 and 10.60 MPa; - breaking load greater than 17 MPa, preferably greater than 19 MPa; - elongation at break greater than 500%, preferably greater than 600%; - IRHD hardness at 23 ° C of 60 to 70, preferably 62 to 68; - tear strength at 23°C greater than 45.00 N / mm, preferably greater than 46.00 N / mm, typically between 46 and 55 N / mm; - 75.00mm 3 Less than, preferably 70.00 mm 3 Less than 65.00mm, preferably 3 Resistance to abrasion with material loss of less than a dynamic modulus of elasticity E' at 23°C of less than 10.00 MPa, preferably less than 9.00 MPa, typically between 8.00 and 8.90 MPa; a loss factor (Tan δ) at 23 ° C., calculated as the ratio of the viscous dynamic modulus (E″) to the dynamic modulus (E′), greater than or equal to 0.370, preferably greater than or equal to 0.380 and more preferably greater than or equal to 0.400; The present invention has one or more of the following:

[0214] Preferably, the loss factor is 0.400 to 0.420.

[0215] The elastomer compounds of the present invention can typically be prepared according to a process comprising one or more mixing steps in at least one suitable mixer, in particular at least one mixing step (i) (non-productive) and mixing step (ii) (productive) as defined above.

[0216] Each mixing step may include multiple intermediate processing steps or substeps characterized by temporary interruptions in mixing to allow for the addition of one or more components, but generally without intermediate discharge of the compound.

[0217] Mixing can be carried out using, for example, open mixers of the "open mill" type, internal mixers of the tangential rotor (Banbury®) or interpenetrating rotor (Intermix) type, or continuous mixers of the Ko-Kneader™ type (Buss®) or twin-screw or multi-screw type.

[0218] Typically, after one or more thermomechanical processing steps, vulcanizing agents, preferably together with vulcanization accelerators and / or retarders, are compounded into the material in the final processing step (ii). In this step, temperatures are generally kept below 120°C, preferably below 100°C, to prevent undesirable pre-vulcanization. The vulcanizable compound thus obtained can then be calendered, for example in the form of a sheet, or extruded to form profiled rubber elements, such as tread bands. This is then incorporated into a tire and vulcanized according to known techniques.

[0219] A further aspect of the present invention consists of a tire tread band comprising an elastomeric compound obtained from the elastomeric composition according to the invention.

[0220] Preferably, such a component is a tread band comprising at least 50%, preferably at least 70%, 90%, 95% or 100% of an elastomeric compound according to the invention.

[0221] A further aspect of the invention is a tyre for a vehicle wheel comprising a tread band according to the invention.

[0222] In the tire of the invention, the tread band comprises or is composed of the elastomer compound of the invention.

[0223] The tire according to the present invention may be a two-, three-, or four-wheel vehicle tire, and may be summer, winter, or all-season.

[0224] The tire of the present invention is suitable for four-wheeled vehicles used on roads, and may be, for example, a tire suitable for installation on a medium- to high-displacement vehicle (maximum cord dimension 195 mm to 245 mm) for transporting people.

[0225] The tyre according to the invention may be suitable for electric vehicles.

[0226] The tire according to the invention may be a tire for light utility vehicles or high performance vehicles (HP High Performance - UHP Ultra High Performance) with a maximum cord size of, for example, 145 mm to 355 mm.

[0227] These tires are mounted on rims having a seat diameter of preferably 13 inches or more, preferably 24 inches or less, and more preferably 16 inches to 23 inches.

[0228] The tyre according to the invention may be a passenger tyre, including both automobile tyres, e.g. high performance tyres, and light transport tyres, e.g. vans, campers, pick-ups, etc., which typically have a total mass of up to 3500 kg when fully loaded.

[0229] The tire of the present invention may be an HP (High Performance) or UHP (Ultra High Performance) tire intended for mounting on vehicles primarily used to transport people, such as sedans, minivans, families, SUVs (Sports Utility Vehicles) and / or CUVs (Crossover Utility Vehicles), which are typically tires capable of high speeds.

[0230] High-performance and ultra-high-performance tires are, in particular, tires capable of reaching speeds of at least 160 km / h, more than 200 km / h, and up to 300 km / h or more. Examples of such tires include tires belonging to classes "T," "U," "H," "V," "Z," "W," and "Y" of the ETRTO (European Tire and Rim Technical Organization) standard, particularly tires for four-wheel high-power vehicles. Typically, tires belonging to these classes have a section width of 185 mm or more, preferably 325 mm or less, and more preferably 195 mm to 325 mm. These tires are preferably mounted on rims with a seat diameter of 15 inches or more, preferably 24 inches or less, and more preferably 17 inches to 22 inches. SUVs and CUVs refer to upsized vehicles, typically four-wheel drive, typically with an engine displacement of 1800 cc or more, more preferably 2000 cc to 6200 cc. Preferably, these vehicles have a mass greater than 1400 kg, more preferably between 1500 kg and 3000 kg.

[0231] The tire of the present invention can also be used on vehicles other than the aforementioned automobiles, such as high-performance road bikes and sport bikes, i.e., motorcycles capable of reaching speeds even higher than 270 Km / h, which typically belong to the categories identified by the following classifications: hypersport, supersport, sport touring, and, at lower speed ratings, scooter, street enduro, and custom.

[0232] The term "motorcycle tire" means a tire with a large curvature ratio (typically greater than 0.200) that allows the plane of symmetry of the motorcycle to reach high angles of inclination (roll angles) relative to the vertical when the motorcycle is cornering.

[0233] In a preferred embodiment, the tire of the present invention is a motorcycle tire, more preferably a big enduro type motorcycle tire, whose tread band comprises the elastomer compound of the present invention.

[0234] In this preferred embodiment, the tire of the present invention is intended to be fitted to the front and / or rear wheels of "big enduro" (or "big adventuring" or "dual purpose") type motorcycles, i.e., motorcycles with high displacement, power output, and mass, designed for both paved and off-road riding. These motorcycles generally have a cylinder capacity of 1000 cm3 or less. 3 The output must be 100cv or more, the maximum torque must be 100Nm or more, and the mass must be 180kg or more.

[0235] In this particular application, the tire of the present invention is particularly advantageous because it combines high resistance to tear and abrasion, which is particularly useful in off-road driving, with excellent grip in cold and wet conditions that are more likely to be encountered in road driving than in off-road driving.

[0236] Examples of "big enduro" motorcycles include the BMW® GS 1250 R, the KTM 1290 Super Adventure R, and the Honda CRF1100L Africa Twin.

[0237] In one embodiment, the tire according to the invention comprises at least - a carcass structure including at least a carcass ply having opposite side edges associated with each bead structure; - optionally a pair of sidewalls applied respectively to the lateral surfaces of the carcass structure at axially outer positions; - optionally a belt structure applied in a radially outer position relative to said carcass structure; - a tread band applied in a radially outer position relative to the carcass structure or, if present, the belt structure; - optionally a layer of elastomeric material, called an underlayer, applied in a position radially inward relative to said tread band, At least one component, preferably at least the tread band, comprises or preferably consists of an elastomer compound according to the invention.

[0238] In one embodiment, the tire according to the invention is a tire for bicycle wheels, which typically comprises a carcass structure wrapped around a pair of bead cores at the beads, and a tread band located radially outwardly of the carcass structure, the tread band including, or preferably consisting of, the elastomer compound according to the invention.

[0239] The tire according to the present invention comprises: - building green tire components on at least one forming drum; - can be manufactured according to a process that includes shaping, molding and vulcanizing the tire; Building at least one of the components of a green tire is - manufacturing at least one green part comprising or preferably consisting of an elastomer compound according to the invention, preferably said at least one green part being a tread band.

[0240] The Applicant has discovered that the characteristics of the tread band prepared using the elastomeric compound of the present invention make it possible to achieve a significant improvement in wet running performance while maintaining high mileage, thus producing a tire with an optimal balance of these opposing properties. [Brief explanation of the drawings]

[0241] [Figure 1] 1 is a half-sectional view showing a schematic view of a tire for a vehicle wheel according to the present invention; [Figure 2] 1 is a perspective view of a typical big enduro anobby motorcycle tire according to a preferred embodiment of the present invention; FIG.

[0242] Description of the tire according to the present invention FIG. 1 illustrates a tire according to the invention.

[0243] With respect to Figure 1, "a" indicates the axial direction, and the "xx" trace at the equatorial plane of the tire indicates the radial direction. For simplicity, Figure 1 shows only a portion of the tire; the remaining portion, not shown, is identical and symmetrically disposed about the radial direction "r."

[0244] Reference numeral (100) indicates in FIG. 1 a tire for a vehicle wheel according to the invention formed by a number of structural elements.

[0245] The tire (100) for a four-wheel vehicle includes at least one carcass structure (101) having end flaps on each side engaged with respective annular anchor structures (102) called bead cores, and possibly associated bead fillers (104). The tire area comprising the bead cores (102) and the fillers (104) forms a reinforcing annular structure (103) called a bead, intended to secure the tire to a corresponding mounting rim (not shown).

[0246] The carcass structure is usually of the radial type, i.e., the reinforcing elements of at least one carcass layer (101) lie in a plane substantially perpendicular to the tire's equatorial plane, which contains the tire's axis of rotation. The reinforcing elements may be made of textile cords, such as rayon, nylon, polyester (e.g., polyethylene naphthalate (PEN) or metal cords). Each reinforcing annular structure is attached to the carcass structure by folding back the two side edges of at least one carcass layer (101) around annular anchor structures (102) to form so-called carcass flaps (101a), as shown in Figure 1.

[0247] In one embodiment, the connection between the carcass structure and the reinforcing annular structure may be provided by a second carcass layer (not shown in FIG. 1) applied at an axially outer position relative to the first carcass layer.

[0248] An anti-wear strip (105) is disposed at an outer position of each reinforcing annular structure (103). Preferably, each anti-wear strip (105) is disposed at least axially outer position relative to the reinforcing annular structure (103) extending at least between the sidewall (108) and a radially lower portion of the reinforcing annular structure (103).

[0249] Preferably, the anti-wear strips (105) are arranged to surround the reinforcing annular structure (103) along the axially inner and outer sides and the radially lower region of the reinforcing annular structure (103), and are interposed between the reinforcing annular structure (103) and the wheel rim when the tire (100) is mounted on the rim.

[0250] The carcass structure is associated with a belt structure (106) comprising one or more belt layers (106a), (106b) radially overlapping each other and the carcass layers, typically having metallic reinforcing cords. Such reinforcing cords may be oriented transversely to the circumferential direction of development of the tire (100). "Circumferential" generally means facing the direction of rotation of the tire.

[0251] At least one 0° reinforcing layer (106c), commonly known as a "0° belt", may be applied to the radially outermost position of the belt layers (106a), (106b), and this 0° reinforcing layer generally incorporates a plurality of reinforcing cords, typically textile cords, fibers or metal, optionally interlaced with one another, oriented substantially circumferentially, thus forming an angle of several degrees (e.g., an angle between 0° and 6°) with respect to the equatorial plane of the tire, and coated with an elastomeric material.

[0252] In a radially outer position of the belt structure (106) is applied a tread band (109) comprising a vulcanized elastomeric compound obtained by vulcanization of an elastomeric composition according to the invention.

[0253] Furthermore, respective sidewalls (108) of elastomeric material are further applied to the lateral surfaces of the carcass structure at axially outer positions, each sidewall extending from one of the lateral edges of the tread (109) at a respective reinforcing annular structure (103).

[0254] At its radially outer position, the tread band (109) comprising the elastomeric compound according to the invention has a rolling surface (109a) intended to come into contact with the ground. Depending on the intended use, the rolling surface may be smooth, as shown in Figure 1, or may have circumferential and / or lateral grooves and notches (not shown in Figure 1).

[0255] An underlayer (111) is disposed between the belt structure (106) and the tread band (109).

[0256] A strip (110) of elastomeric material, commonly known as a "mini-sidewall", may optionally be provided in the connecting zone between the sidewall (108) and the tread band (109), this mini-sidewall generally being obtained by co-extrusion with the tread band (109) and allowing an improved mechanical interaction between the tread band (109) and the sidewall (108). Preferably, the end of the sidewall (108) directly covers the lateral edge of the tread band (109).

[0257] Typically, a rubber layer (112), commonly referred to as a "liner," which provides the necessary impermeability to the tire's inflation air, may also be provided radially inward relative to the carcass layer (101).

[0258] The reinforcing annular structure (103) of the tire may be provided with additional protective layers, commonly known as "chafers" (121) or protective strips, whose function is to increase the stiffness and integrity of the bead structure (103).

[0259] The chafer (121) typically comprises a plurality of cords, generally made of a fibrous material (eg, aramid or rayon) or a metallic material (eg, steel cord), embedded in a cross-linked elastomeric material.

[0260] The stiffness of the tire sidewall (108) can be increased by providing the reinforcing annular structure (103) with a reinforcing layer (120), commonly known as a "flipper" or additional strip-like insert.

[0261] The flipper (120) is a reinforcing layer that is wrapped around each anchor annular structure (102) and bead filler (104) to at least partially surround the respective anchor annular structure (102) and bead filler (104), and the reinforcing layer is disposed between the at least one carcass layer (101) and the reinforcing annular structure (103). Typically, the flipper is in contact with the at least one carcass layer (101) and the reinforcing annular structure (103).

[0262] The flipper (120) typically comprises a plurality of metal or textile cords embedded in a cross-linked elastomeric material.

[0263] The construction of the tire (100) described herein can be carried out by assembling each semi-finished product adapted to form a tire component on a forming drum (not shown) by at least one assembly device.

[0264] At least some of the components intended to form the tire carcass structure are built and / or assembled on a forming drum. More specifically, the forming drum is intended to first receive the liner, if present, and then the carcass structure. A device (not shown) then coaxially engages one of the annular anchor structures around each end flap, positions the outer sleeve including the belt structure, underlayer, and tread band in a coaxially central position around the cylindrical carcass sleeve, and shapes the carcass sleeve to a toroidal shape through radial expansion of the carcass structure, applying the carcass sleeve against the radially inner surface of the outer sleeve.

[0265] After the green tire has been constructed, a molding and vulcanization process is generally carried out to stabilize the tire structure by crosslinking the elastomeric composition and to give the tread band the desired tread pattern and the sidewalls the characteristic graphic signature.

[0266] As shown in FIG. 2, the tire 1 according to the present invention is of the knobby type for "big enduro" motorcycles. That is, the tire 1 has a plurality of lateral and circumferential grooves that separate a plurality of spaced apart blocks. The tire 1 has a "camber ratio" defined by the ratio of deflection to the maximum radial cross-sectional width. Preferably, for a big enduro rear tire, the deflection of the tire 1 is about 40 mm to about 60 mm. The camber ratio of the tire 1 is about 0.25 to about 0.35, for example, equal to about 0.26. For a front tire, the deflection is about 35 mm to about 60 mm, and the camber ratio is about 0.30 to about 0.40, for example, equal to 0.38. The blocks and grooves define a tread pattern with a void / full ratio of 0.4 to 0.65, preferably 0.5 to 0.6, for example 0.51 for a 170 / 60 / R17 rear tire and 0.56 for a 150 / 70 / R18 rear tire.

[0267] The following examples are now provided for illustrative and non-limiting purposes only.

[0268] Experimental Part In this experimental part, the composition components are expressed in phr (parts per hundreds of rubber). Unless otherwise specified, all percentages are expressed by weight.

[0269] Analysis method Double bond content: The double bond content in the polymers provided by the supplier was determined by 1H-NMR.

[0270] Weight average molecular weight: The weight average molecular weight of the polymers provided by the supplier was determined according to known techniques, for example GPC (gel permeation chromatography) according to the ISO 13885 method.

[0271] Glass transition temperature (Tg): The glass transition temperature Tg of the elastomeric polymers and vulcanized compounds, determined based on the peak value of Tan δ, was measured by dynamomechanical analysis (DMA).

[0272] Specifically, the samples were analyzed using an EPLEXOR® 150 (GABO) instrument, where a temperature scan was performed from -80°C to +30°C at a heating rate of 2°C / min, and a dynamic tensile deformation of 0.1% was applied at a frequency of 1 Hz. The specimen dimensions were 1 mm thick, 10 mm wide, 46 mm long, and a reference length of 29 mm (representing the free length involved in deformation while two clamps blocked both ends of the specimen).

[0273] Tear strength was measured according to ASTM D624B.

[0274] The abrasion resistance was evaluated according to the DIN 53516 standard.

[0275] The dynamic mechanical properties (MDR) of the compounds were evaluated using a rotorless rheometer at 170 °C for 10 min vulcanization according to ISO 6502-3 (2018).

[0276] Mooney viscosity: ML(1+4) viscosity was measured at 100°C according to the ISO 289-1:2015 standard. For high molecular weight polymers (E-SBR and S-SBR), ML(3+4) viscosity was measured at 160°C, also according to the ISO 289-1:2015 standard.

[0277] Density was measured according to ISO 2781(2018).

[0278] The static mechanical properties (CA1 load at 100% elongation, CA3 load at 300% elongation, CR tear strength, AR% elongation at break%) were measured at 23°C on samples of the elastomeric materials vulcanized at 170°C for 10 min according to the ISO 37:2017 standard.

[0279] Compressive dynamic mechanical properties E' and Tan δ were measured in tension-compression mode using an Instron 1341 dynamic apparatus, as described herein. Test specimens of vulcanized material (170°C for 10 min) with a cylindrical geometry (length = 25 mm; diameter = 14 mm) were preloaded in compression to a longitudinal strain of 25% of the initial length, maintained at a designated temperature of 10°C, 23°C, or 70°C throughout the test, and subjected to a dynamic sinusoidal strain at a frequency of 100 Hz with an amplitude of ±3.5% of the preloaded length. Dynamic mechanical properties are expressed as the dynamic modulus (E') and Tan δ (loss factor). Tan δ was calculated as the ratio of the viscous dynamic modulus (E'') to the dynamic modulus (E').

[0280] The hardness at IRHD hardness (23°C and 70°C) was measured according to the ISO 48:2007 standard on samples of the above elastomeric materials vulcanized at 170°C for 10 minutes.

[0281] Preparation of elastomer compounds Starting from the elastomer compositions shown in Table 1 below, reference elastomer compounds REF1 and REF2 and elastomer compounds INV1 and INV2 according to the invention were prepared.

[0282] [Table 1]

[0283] *Oil extended: Total phr (polymer + oil*) in parentheses. NEOCIS BR 60 is ENI's EUROPRENE® NEOCIS BR 60, a solid polybutadiene prepared in solution, produced using a neodymium organometallic catalyst, has a high cis content (minimum 97%), and a weight average molecular weight of approximately 550,000 g / mol. Sibur's SBR 1723 TDAE is a low-temperature emulsion polymerized solid styrene butadiene copolymer (E-SBR) using a mixture of rosin acid and fatty acid soap as emulsifiers, with a Tg of approximately -50°C, a Mooney viscosity of approximately 48 MU, a styrene content of approximately 23%, and is oil-extended with 37.5 parts treated distillate aromatic extract oil (TDAE) per 100 phr of dry polymer. SBR 1739 is Synthos' Buna® SB1739-Schkopau, a low-temperature emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) using a mixed rosin / fatty acid soap, oil-extended with 37.5 parts oil per 100 phr of dry polymer, and has a Tg of about −40° C. Asahi Kasei's TUFDENE E680 is a solution-polymerized solid styrene-butadiene copolymer, chain-end functionalized with a functionalizing terminator, oil-extended with 37.5 parts TDAE oil per 100 phr of dry polymer, with a styrene content of about 34%, vinyl of about 58% (relative to butadiene), a Tg of about −25° C. (oil-extended polymer), and a Mw of about 1,470,000 g / mol. JSR HPR 620 is a commercially available styrene butadiene copolymer, chain functionalized with a polyorganosiloxane hyperbranched coupling agent, solution polymerized as described in SG10201800553S(A), and oil extended with 25 parts TDAE oil per 100 phr of dry polymer, with a weight average molecular weight of about 1,000,000 g / mol, a styrene content of about 40%, vinyl of about 25%, a Tg of about -33°C, and a Mooney viscosity of about 80 MU [Mooney viscosity ML(3+4) at 160°C]. Evonik's POLYVEST 130 is a stereospecific liquid polybutadiene (PB) with a high content of 1,4-cis double bonds (77% 1,4-cis double bonds, 22% 1,4-trans double bonds, 1% 1,2-vinyl double bonds), a Tg of -99°C, and a weight-average molecular weight of 12,000 g / mol. Cray Valley (Total) RICON® 100 is a low molecular weight (Mn 4500) liquid (25% styrene) butadiene styrene copolymer (PBS) with a Tg of −57° C. Hansen & Rosenthal's VIVATEC 500 is a process oil (treated distilled aromatic extract TDAE). The tetrasulfide is bis[3-(triethoxysilyl)propyl]tetrasulfide JH-S69 from Chem Spec Ltd. Novares' NOVARES TT30 is a hydrocarbon resin made by polymerization of C9 / C10 unsaturated aromatic hydrocarbons. Novares' Novares TT90 is The zinc oxide is RHENOGRAN ZNO from Zincol Ossidi. 6PPD is Eastman N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine SANTOFLEX 6PPD. Rhodia's Zeosil 1165 is a highly dispersible amorphous precipitated silica. N234 is a high surface area carbon black (STSA 112m 2 / g). TBBS is N-tert-butyl-2-benzothiazylsulfenamide from Huatai. SULPHUR is Lanxess' Rhenocure® IS90-20, a 90:10 mixture of insoluble and soluble sulfur with 20% added oil.

[0284] REF1 is the reference elastomer composition for the tread band of a "big enduro" motorcycle tire, and is a composition comprising a mixture of a die-tread polymer and a conventional plasticized mixture.

[0285] REF2 is an elastomer composition for tread bands with improved wet performance, prepared by modifying the reference composition REF1 in accordance with industry knowledge, i.e., by replacing part of the emulsion polymerized solid styrene butadiene copolymer (E-SBR) (SBR1739) and polybutadiene (BR) with a high molecular weight, chain-end functionalized solution polymerized solid styrene butadiene copolymer (S-SBR) such as TUFDENE E680.

[0286] INV1 is an elastomeric composition according to the invention, other constituents being equal, but composition REF1 has been modified by incorporating 54 phr of solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent (HPR620) instead of 44 phr of emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) (SBR1739) and 10 phr of high-cis polybutadiene (BR) (NEOCIS BR 60).

[0287] INV2 is an elastomer composition according to the invention, other constituents being equal, but the INV1 composition has been modified by introducing a resin (NOVARES TT30) and, partially, liquid polymers (POLYVEST 130 and RICON 100) in place of the process oil (VIVATEC 500).

[0288] The elastomer compositions in Table 1 maintained substantially the same total plasticizer content.

[0289] The reference elastomer compound and the compound according to the invention were prepared from the above composition according to the following process.

[0290] Mixing of the components was carried out in two stages using an internal mixer (Banbury, Intermix or Brabender).

[0291] In the first step (1), all ingredients were introduced except for the vulcanizing agents and accelerators. Mixing continued for a maximum of 5 minutes, reaching a temperature of approximately 145°C. Then, in a second test (2), also carried out using an internal mixer, the vulcanizing agents and accelerators were added and mixing continued for 4 minutes, maintaining the temperature below 100°C. The compound was then unloaded. After cooling, and at least 12 hours after preparation, some samples of the compound were vulcanized in a press at 170°C for 10 minutes to obtain test specimens useful for mechanical property evaluation.

[0292] Properties of elastomer compounds The main static and dynamic properties of the compounds prepared from the above compositions were measured by the methods described above and the results are shown in Table 2 below.

[0293] [Table 2]

[0294] As can be seen from the tensile test data, the INV1 compound exhibited a significant increase in Ca3 value (10.03 MPa) compared to the REF1 and REF2 compounds (8.35 MPa and 8.53 MPa) due to the incorporation of a solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent (HPR620) into the composition, predicting particularly high mileage. When a liquid polymer was incorporated into the composition instead of process oil and resin, as in the case of the INV2 compound, the Ca3 load value was comparable to that of the reference compound (8.85 MPa). The static mechanical properties (CA3, CR, AR%) of the latter were even better when a solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent was combined with the liquid polymer, predicting high durability and mileage.

[0295] The IRHD hardness values ​​at 23° C. of the compounds INV1 and INV2 according to the invention are lower than the reference compound, which predicts good performance on wet surfaces.

[0296] The inherent tear and abrasion resistance of high-cis polybutadiene and emulsion-polymerized solid styrene-butadiene copolymers (E-SBR) (REF1) was surprisingly not compromised by the use of solution-polymerized solid styrene-butadiene copolymers (S-SBR) functionalized with a high molecular weight hyperbranched coupling agent (INV1). Furthermore, the properties were not compromised by further replacing process oil and resin with liquid polymers (INV2), as opposed to replacing part of the polybutadiene (BR) and emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) with conventional solution-polymerized solid styrene-butadiene copolymer (S-SBR) (Tufdene E680, REF2).

[0297] These results are highlighted by the respective values ​​for tear and abrasion, which for both INV1 and INV2 were almost identical to those of REF1 and, especially in terms of abrasion, were higher than those of REF2 in both cases.

[0298] Furthermore, considering that a lower ratio of E' to Tan δ (grip index) at 23°C corresponds to better wet grip, the unexpected improvement in grip was highlighted in the inventive materials compared to REF1. Both inventive materials were obtained by introducing a solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent (INV1) instead of part of the polybutadiene (BR) and emulsion-polymerized solid styrene-butadiene copolymer (E-SBR), and by further replacing the process oil and resin with a liquid polymer (INV2).

[0299] The latter material showed a significant improvement in wet grip compared to REF1, as predicted by its lower Grip Index value at 23°C, while maintaining comparable wear and tear properties.

[0300] Experts would have expected that the introduction of solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a high molecular weight Mw hyperbranched coupling agent into the INV1 and INV2 compounds would increase the stiffness of the material and therefore worsen wet performance. However, surprisingly, both the INV1 and even the INV2 compounds showed values ​​of E', Tan δ and Grip Index that predicted excellent behavior in wet conditions.

[0301] From the measurements of the rheological properties (MDR 170°C, 10 min), a substantial maintenance of the vulcanization kinetics was observed between the reference compounds REF1, REF2 and the compounds INV1, INV2 of the invention.

[0302] In conclusion, the compounds according to the invention INV1 and INV2 show an optimum combination of hardness, resistance to tear and abrasion, modulus E' and hysteresis, which predicts long mileage for the tire as well as improved wet performance.

[0303] On the other hand, this result could not be achieved by simply using a conventional solution-polymerized solid styrene-butadiene copolymer (S-SBR), as shown by the reference compound REF2, which, despite having good wet performance, showed significantly reduced mileage and tear resistance.

Claims

1. An elastomer composition for a vehicle wheel tire, comprising: 0 to 30 phr of at least one liquid polymer; 0 to 20 phr of at least one resin; 10 to 60 phr of at least one plasticizing oil; 100 phr of a mixture of solid diene-based elastomeric polymers; at least 40 phr of at least one reinforcing filler; and at least 1 phr of at least one vulcanizing agent; wherein the total of the liquid polymer, the resin, if present, and the plasticizing oil is from 20 to 90 phr; wherein the mixture of polymers comprises: 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 300,000 g / mol to 600,000 g / mol and a cis double bond content of at least 95%; Tg of -60°C to -20°C, a Mooney viscosity at 160°C comprised between 30 and 70 MU, and 10 to 70 phr of at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) having an amount of styrene comprised between 15% and 50%; a weight average molecular weight Mw greater than 500,000 g / mol, and / or the amount of styrene being between 25% and 50%, the amount of vinyl being between 10% and 50%, and / or a Tg of -50°C to -20°C, and / or and 10 to 80 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the SBR having a Mooney viscosity at 160°C of 60 to 100 MU; wherein said multi-branched coupling agent is polyorganosiloxane, and the properties of the solid diene-based elastomeric polymer of said mixture are measured according to the methods shown in the experimental part.

2. said liquid polymer may be present in an amount of from 0 to 28 phr; said resin may be present in an amount of 0 to 15 phr; said plasticizing oil is present in an amount of from 20 to 50 phr; The composition of claim 1, wherein the total of said liquid polymer, said resin, if present, and said plasticizing oil is from 25 to 80 phr.

3. - The liquid polymer may be present in an amount of 0 to 23 phr; said resin may be present in an amount of from 3 to 10 phr; said plasticizing oil is present in an amount of from 25 to 45 phr; The composition of claim 2, wherein the total of said liquid polymer, said resin, if present, and said plasticizing oil is from 30 to 60 phr.

4. the mixture of solid diene-based elastomeric polymers comprising: 15 to 50 phr of at least one solid polybutadiene (BR), 10 to 60 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR), and 10. The composition of claim 1, comprising 15 to 75 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) that is chain-functionalized with a hyperbranched coupling agent.

5. the mixture of solid diene-based elastomeric polymers comprising: 25 to 40 phr of at least one solid polybutadiene (BR), 10 to 40 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR), and The composition of claim 4, comprising 30 to 65 phr of at least one solution-polymerized styrene-butadiene copolymer (S-SBR) that is chain-functionalized with a hyperbranched coupling agent.

6. the solid polybutadiene (BR) has a weight average molecular weight Mw of 350,000 to 550,000 g / mol and a cis double bond content of 95 to 99%, the emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) has a Tg of -60°C to -25°C, a Mooney viscosity of 40 to 60 MU, and a styrene content of 20% to 45%, 10. The composition of claim 1, wherein the solution-polymerized solid styrene butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent has a weight average molecular weight Mw of greater than 800,000 g / mol, styrene in an amount of 30% to 45%, vinyl in an amount of 15% to 40%, Tg of -45°C to -25°C, and / or Mooney viscosity measured at 160°C of 70 to 90 MU.

7. the mixture of solid diene-based elastomeric polymers comprising: 25 to 35 phr of at least one solid polybutadiene (BR) having a weight-average molecular weight Mw of 370,000 to 550,000 g / mol and a cis double bond content of at least 97%, - 10 to 45 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -58°C to -28°C, a Mooney viscosity of 45 to 55 MU, and a styrene content of 22% to 42%, 2. The composition of claim 1, comprising 30 to 65 phr of at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a hyperbranched coupling agent, the polymer having a weight average molecular weight Mw greater than 800,000 g / mol, styrene in an amount of 30% to 45%, vinyl in an amount of 15% to 40%, Tg between -45°C and -25°C, Mooney viscosity measured at 160°C between 70 and 90 MU.

8. 10. The composition of claim 1 comprising at least 50 phr of at least one reinforcing filler.

9. An elastomer compound for tire tread bands, obtainable by mixing and vulcanizing the elastomer composition according to any one of claims 1 to 8.

10. The following characteristics were measured according to the methods shown in the experimental part: - Mooney viscosity higher than 50 MU; - density between 1.100 and 1.500 g / cm3; - load at 300% elongation (Ca3) greater than 8.50 MPa; - a breaking load greater than 17 MPa; - elongation at break greater than 500%; - IRHD hardness at 23°C of 60 to 70 IRHD hardness; - a tear strength at 23°C greater than 45.00 N / mm; - 75.00 mm ３ Resistance to abrasion with material loss of less than a dynamic modulus of elasticity E' at 23°C of less than 10.00 MPa; - a loss factor (Tan δ) at 23°C, calculated as the ratio of the viscous dynamic modulus (E″) to the dynamic modulus (E′), of 0.370 or more.

11. The following characteristics measured according to the method shown in the experimental part: - Mooney viscosity higher than 60 MU; - density between 1.100 and 1.500 g / cm 3 ; - load at 300% elongation (Ca3) greater than 8.60 MPa; - a breaking load greater than 19 MPa; - elongation at break greater than 600%; - IRHD hardness at 23°C of 62 to 68 IRHD hardness; - a tear strength at 23°C greater than 46.00 N / mm; - resistance to abrasion with a material loss of less than 65.00 mm 3 ; a dynamic modulus of elasticity E' at 23°C of less than 9.00 MPa; - a loss factor (Tan δ) at 23°C, calculated as the ratio of the viscous dynamic modulus (E″) to the dynamic modulus (E′), of 0.400 or more.

12. A tread band for a tire for a vehicle wheel, comprising the elastomer compound of claim 10.

13. A tire for a vehicle wheel, comprising a tread band as described in claim 12.

14. 14. A tire according to claim 13 for a motorcycle wheel.

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