Elastomeric compound for tire tread bands and related tires

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 tyres for vehicle wheels, in particular for the tread bands of tyres. [Background technology]

[0002] Typically, the elastomeric compounds used in the manufacture of the tread bands of tyres for vehicle wheels 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 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) for their higher tear strength.

[0005] To give the tire high tear and abrasion resistance and long running life, the tread band compound can preferably use a blend of emulsion polymerized styrene butadiene copolymer (E-SBR) with high cis content and polybutadiene (BR), but at the expense of wet road performance. On the other hand, by replacing part of the emulsion polymerized styrene butadiene rubber (E-SBR) and polybutadiene rubber (BR) with conventional solution polymerized styrene butadiene rubber (S-SBR), for example Asahi's Tufdene E680 and Tufdene 3830, handling in wet conditions can be improved, but a decrease in mechanical resistance performance is observed. This performance is generally more important and is fundamental in certain demanding applications, for example enduro type motorcycle driving.

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

[0007] Paragraph 0060 of document US20180362740A1 describes an elastomer composition comprising a butadiene rubber (BR150B from Ube Industries), an emulsion-polymerized styrene-butadiene rubber (E-SBR SBR1723 from JSR Corporation) and a 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 set out the problem of how to further improve the road performance of current tires, especially on wet road conditions, without compromising the tear resistance and therefore the mileage. [Means for solving the problem]

[0009] In this regard, the Applicant has carried out some research and found that it is possible to obtain this challenging result by modifying conventional tread band compounds by partially replacing high cis polybutadiene (BR) and emulsion polymerized solid styrene butadiene copolymers (E-SBR) with a particular type of solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a new generation, highly molecular weight hyperbranching agent. The class of solution polymerized solid styrene butadiene copolymers (S-SBR) functionalized with high molecular weight hyperbranching agents, when introduced in precise amounts into the elastomer tread composition, imparts higher mechanical strength to the elastomer compound compared to the typical mixture of emulsion polymerized solid styrene butadiene copolymer and polybutadiene for the tread band (E-SBR / BR) and at the same time, unexpectedly, good wet performance, considering the high molecular weight of the polymer and the predictable increase in stiffness of the compound that accompanies it.

[0010] Moreover, in a preferred embodiment, the applicant has succeeded in not only maintaining the mechanical strength properties but also improving the wet performance of the material: this additional benefit was 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] Thus, a first aspect of the present invention is an elastomer composition for a vehicle wheel tyre, comprising: At least one liquid polymer 0-30 phr; At least one resin 0-20 phr; At least one plasticizing oil, 10 to 60 phr; 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 sum of the liquid polymer, the resin, if present, and the plasticizing oil is between 20 and 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: -60℃~-20℃ Mooney viscosity at 160°C between 30 and 70MU, and At least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a styrene content of between 15% and 50%, from 10 to 70 phr; a weight average molecular weight Mw greater than 500,000 g / mol, and / or The amount of styrene is between 25% and 50%, the amount of vinyl is between 10% and 50%, and / or Tg between -50°C and -20°C, and / or and, preferably consisting of, 10-80 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 60-100 MU; The properties of the solid diene-based elastomeric polymer of said mixture are measured according to the methods given in the experimental part, being an elastomeric composition for vehicle wheel tires.

[0012] A further aspect of the 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 vehicle wheels comprising an elastomeric compound according to the 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) refers to 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 elastomeric composition are generally not all introduced into the mixer at the same time, but are typically added sequentially. In particular, the vulcanization additives, such as vulcanizing agents and, optionally, accelerators and retarders, are usually added downstream relative to the compounding and processing of all the other components.

[0018] In the intermediate elastomer compound or in the final elastomer compound, the individual components of the elastomer composition may have been completely or partially altered by interaction with other components, by thermal and / or mechanical processing, and therefore may not always remain unchanged or be individually traceable. 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 they 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 of the additives 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 essentially 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, for example, by 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 intermolecular and intramolecular bonds.

[0026] The term "vulcanization accelerator" refers to 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 products that further accelerate vulcanization, allowing it to be carried out in less time and sometimes at lower temperatures. An example of an activator is the 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 undesirable 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, preferably selected from among carbon black, conventional silica, for example 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 meant to refer to conventional reinforcing materials used in the field, selected from among the conventional silicas and silicates such as sepiolite, palygorskite also known as attapulgite, montmorillonite, alloysite, etc., possibly modified and / or derivatized by acid treatment. Typically, the white filler has hydroxyl groups on the surface.

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

[0032] The term "mixing step (2)" refers to the next step in the process of preparing the elastomeric compound, in which the vulcanizing agents and possibly 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 result in 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 in that the mixing is temporarily interrupted to allow the addition of one or more components, but without intermediate discharge of the compound. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 components in the mixture, the total amount of which conforms to the amount preferences defined 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 -120°C to 0°C, more preferably -110°C to -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 -120°C to -50°C, more preferably -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 under the trade names POLYVEST 110, POLYVEST 130, and POLYVEST MA 75 by Evonik, LBR 307, LBR 305, and LBR 300 by Kuraray, and RICON 130, RICON 130MA8, RICON 130MA13, RICON 150, RICON 156, and RICON 157 by Cray Valley.

[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 of 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 -90°C to -20°C, more preferably -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 copolymers 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 under the trade names LIR 30, LIR 50, LIR 403, and LIR 410 by Kuraray Co., Ltd., and, among natural polyisoprenes, DPR 35, DPR 40, DPR 75, and DPR 400 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 preferably from 0 to 15 phr, more preferably from 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 thermoplastic property is used to refer to the tendency of a polymer to increase in viscosity, i.e., to undergo plastic deformation, when subjected to an increase in temperature and / or a 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 composition is a non-crosslinkable polymer (non-reactive resin).

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

[0070] The weight average molecular weight (Mw) can be measured according to techniques known in the art, such as, for example, 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 method (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 the C9 fraction.

[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 among 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 (SI Group) (octylphenol-formaldehyde resin), DUREZ 32333 (Sumitomo Bakelite) (phenol-formaldehyde resin), KORESIN (BASF) (pt-butylphenol-acetylene resin), and SYLVARES TP115 (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-based 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 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 a commercial composition 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, unlike the liquid polymers and diene-based elastomeric polymers defined herein, 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 for RAE class, 400 to 10,000 g / mol; 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 extraction of 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: NYTEX 4700 available from Nynas, EXTENSOIL 1471 available from Repsol, VIVATEC 500 available from H&R; and vegetable oils: RADIA 6132 available from Oleon, Agripure AP 18 and Agripure AP 75 available from Cargill.

[0112] Alternatively, the plasticizing oil may be of natural or synthetic origin obtained by 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 elastomeric composition according to the invention preferably comprises from 25 to 80 phr, more preferably from 30 to 60 phr, of a plasticizing mixture, by which is meant all the constituents thereof: 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 elastomeric composition according to the invention preferably comprises at least 20 phr, 30 phr or 40 phr of the plasticizing mixture.

[0120] Preferably, the composition comprises 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 in preparation, as detailed below, they may be added to the composition individually, in any order or step of the preparation process, or may be accompanied in whole or in part by one or more of the other components, as is the case with plasticizing oils that are already at least partially compounded as thinners in commercially available elastomeric polymers.

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

[0123] In one embodiment, the mixture of solid diene-based elastomeric polymers of the composition according to the present invention comprises: At least one solid polybutadiene (BR) from 15 to 50 phr, At least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) from 10 to 60 phr, and It comprises, or preferably consists of, 15-75 phr of at least one solution polymerized styrene butadiene copolymer (S-SBR) that is 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: At least one solid polybutadiene (BR) 25-40 phr, At least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) from 10 to 40 phr, and 30-65 phr of at least one solution polymerized styrene butadiene copolymer (S-SBR) that is 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 of greater than 800,000 g / mol, preferably greater than 900,000 g / mol, and / or The amount of styrene is between 30% and 45%, the amount of vinyl is between 15% and 40%, and / or Tg between -45°C and -25°C, and / or It has a Mooney viscosity measured at 160°C of 70 to 90 MU.

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

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

[0128] The solid diene-based elastomeric polymers suitable for the present composition 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) are polybutadiene (Europrene Neocis® BR40)--(Versalis), SKD NHEODIMIO (Nizhnekamskneftechim Export), 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, 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 comprising 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 copolymers of styrene / 1,3-butadiene (SBR), styrene / isoprene / 1,3-butadiene, and styrene / 1,3-butadiene / acrylonitrile.

[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 57MU, 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] By solution polymerized solid styrene-butadiene copolymer (S-SBR) is meant 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 copolymers (S-SBR) of the present invention, functionalization can be introduced into the chain by reaction with a suitable hyperbranched coupling agent, or, in some cases, at the end by reaction with a terminating agent. In particular, diene-based elastomeric polymers obtained by anionic polymerization in the presence of organometallic initiators (in particular organolithium initiators) can be functionalized by reacting the organometallic residues derived from the initiator with suitable terminating and / or coupling agents, such as amines, amides, imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes, aryloxysilanes, alkyldithiols, alkyldithiolsilanes, carboxyalkylthiols, carboxyalkylthiolsilanes, thioglycols, 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 patent application SG10201800553S(A) in the name of JSR Corporation, paragraphs 0040 to 0043, in particular those of formula (6):

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

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

[0157] [ka]

[0158] Preferably, said at least one solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent is a functionalized polymer derived 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 of 25%~50%, vinyl content of 10%~50%, Tg between -50°C and -20°C, and It is characterized by a Mooney viscosity at 160°C of 60 to 100 MU.

[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 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 be one or more solution polymerized solid styrene butadiene copolymers (S-SBR) that are functionalized with a hyperbranched coupling agent.

[0166] The solid diene-based elastomeric polymers constituting the mixture can also be optionally functionalized (solid diene-based elastomeric polymer a') by reaction with suitable conventional terminating or coupling agents (i.e. non-multibranched coupling agents). In particular, diene-based elastomeric polymers obtained by anionic polymerization in the presence of organometallic initiators (in particular organolithium initiators) can be functionalized by reacting the organometallic residues derived from the initiator with suitable terminating or coupling agents, such as imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

[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%; at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) 10-55 phr having a Tg of -60°C to -25°C, a Mooney viscosity of 40-60 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, having a weight average molecular weight Mw of 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 of -50°C to -20°C, Mooney viscosity measured at 160°C of 60 to 100 MU.

[0168] More preferably, the mixture of solid diene based elastomeric polymers comprises 25-35 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%; at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) 10-45 phr having a Tg of -58°C to -28°C, a Mooney viscosity of 45-55 MU, and a styrene content of 22% to 42%; and, preferably consisting of, 30-65 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent, 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 of -45°C to -25°C, 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 at most 150 phr, at most 140 phr, at most 130 phr, at most 120 phr, at most 110 phr, or at most 100 phr of at least one reinforcing filler.

[0172] Preferably, the composition comprises from 10 to 150 phr, from 30 to 120 phr, from 50 to 120 phr, from 70 to 110 phr, or from 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 fillers are white fillers 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] The 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, said 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 mm 2 / g or more, preferably 50m 2 / g (as 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 a plurality of fillers from those defined above, preferably including 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 a derivative thereof 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, for example, caprolactam disulfide (CLD), bis[(trialkoxysilyl)propyl] polysulfides, dithiophosphates; thiurams, dithiodimorpholines, caprolactam disulfide, or mixtures thereof.

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

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

[0191] Particularly useful vulcanization activators are zinc compounds, in particular ZnO, ZnCO3, 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 elastomeric composition with ZnO and fatty acid, as well as magnesium stearate formed with MgO, or mixtures thereof, are used.

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

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

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

[0196] Commonly used vulcanization accelerators may 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 elastomeric 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, for example, 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 or different, are selected from alkyl, alkoxy or aryloxy groups, or halogen atoms, with the proviso 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 nitroso, mercapto, amino, epoxy, vinyl, imido, chloro, -(S) m C n H 2n The silane coupling agents may be characterized by a group selected from -Si-(R')3 and -S-COR', where m and n are integers from 1 to 6, including terminals, 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 elastomeric composition.

[0205] Preferably, said silane coupling agent is present in the elastomeric 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 contain other commonly used additives, such as antiaging agents, antireversion agents, adhesives, antiozonants, 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: 0-20 phr of at least one liquid polymer selected from liquid polybutadiene, liquid styrene butadiene copolymers and mixtures thereof; 0-10 phr, preferably at least 1 phr, of at least one resin; At least one plasticizing oil, 20-40 phr; 100 phr of a mixture of solid diene-based elastomeric polymers; At least one reinforcing filler, 60-100 phr; 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%; 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%, from 10 to 50 phr; and 25-70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent, 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 of -45°C to -25°C, Mooney viscosity measured at 160°C of 70 to 90 MU.

[0209] In a preferred embodiment, the elastomeric composition of the present invention comprises At least one resin, 0 to 12 phr, preferably 1 to 12 phr; At least one plasticizing oil, 20-40 phr; 100 phr of a mixture of solid diene-based elastomeric polymers; At least 60 phr of at least one reinforcing filler; 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%, 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%, from 10 to 50 phr; and, comprising, or preferably consisting of, 25-70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent, 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, a Mooney viscosity measured at 160°C of 70 to 90 MU.

[0210] In a more preferred embodiment, the elastomeric 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; At least one resin, 3 to 8 phr; at least one plasticizing oil, 15 to 35 phr; 100 phr of a mixture of solid diene-based elastomeric polymers; At least 60 phr of at least one reinforcing filler; 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%, 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%, from 10 to 30 phr; and, preferably consisting of, 40-70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent, 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 of -45°C to -25°C, 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 US 2018 / 0362740 A1.

[0212] A further aspect of the 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 elastomeric compounds according to the invention have the following characteristics, measured according to the methods reported in the experimental part: -Mooney viscosity greater than 50.00 MU, typically greater than 60 MU, 60-90 MU (1+4 at 100°C); - 1.100~1.500g / cm 3 density; - 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 IRHD hardness; - a tear strength at 23°C of 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 70.00mm, preferably 3 Less than 65.00mm, more preferably 3 Resistance to abrasion with less than material loss; - 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 between the viscous dynamic modulus (E ″) and 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 elastomeric 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 in that the mixing is temporarily interrupted to allow for the addition of one or more components, but with generally no intermediate discharge of the compound.

[0217] Mixing can be carried out using open mixers, for example 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, in the final processing step, production step (ii), vulcanizing agents are compounded into the material, preferably together with vulcanization accelerators and / or retarders. In production step (ii), the temperature is generally kept below 120°C, preferably below 100°C, to prevent undesirable pre-vulcanization phenomena. The vulcanizable compound thus obtained can then be subsequently calendered, for example in the form of sheets, or extruded to form profiled rubber elements, for example tread bands. It is incorporated into a tire and undergoes vulcanization according to known techniques.

[0219] A further aspect of the 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 according to the invention, the tread band comprises or is composed of the elastomeric compound according to the invention.

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

[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 mounting on medium to high displacement vehicles (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 tyre according to the invention may be a tyre 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, typically having 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 to be fitted to 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 speed driving.

[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 more than 300 km / h. Examples of such tires are tires belonging to the classes "T", "U", "H", "V", "Z", "W" and "Y" of the ETRTO (European Tyre and Rim Technical Organisation) standard, in particular 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, 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, more preferably 17 inches to 22 inches. SUV and CUV refer to raised-mounted vehicles, typically with four-wheel drive and typically with a 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 tyre of the invention can also be used on vehicles other than the aforementioned motor vehicles, such as high performance road and sport bikes, i.e. motorcycles capable of reaching speeds even higher than 270 Km / h, typically belonging 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) with respect to the vertical when the motorcycle is cornering.

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

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

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

[0236] Examples of "big enduro" motorcycles are 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 opposing 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 comprising a layer of elastomeric material, called an underlayer, applied in a radially inner position relative to said tread band, At least one component, preferably at least the tread band, comprises or is preferably made of an elastomeric 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 relative to the carcass structure and including or preferably consisting of an elastomeric compound according to the invention.

[0239] The tire according to the present invention comprises: - building a green tire part on at least one building drum; - the tire can be manufactured according to a process that includes shaping, moulding 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 with the elastomeric compound of the present invention make it possible to achieve a significant improvement in wet running performance while at the same time maintaining high mileage, producing a tire with an optimal balance of opposing properties. [Brief description of the drawings]

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

[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 being identical and symmetrically disposed with respect to the radial direction "r".

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

[0245] The tire (100) for four-wheel vehicles comprises at least one carcass structure with at least one carcass layer (101) having end flaps on each side engaged with respective annular anchor structures (102) called bead cores, possibly associated with bead fillers (104). The tire area with the bead cores (102) and the fillers (104) forms a reinforcing annular structure (103) called a bead, intended to fix 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. Said 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 an annular anchor structure (102) so as to form a so-called carcass flap (101a), as shown in FIG. 1.

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

[0248] An anti-wear strip (105) is disposed at an outer location of each reinforcing annular structure (103). Preferably, each anti-wear strip (105) is disposed at least at an axially outer location 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 its axially inner and outer sides, as well as along its radially lower region, 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 with each other and with the carcass layers, typically having metallic reinforcing cords. Such reinforcing cords may be oriented crosswise with respect to the circumferential 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), this 0° reinforcing layer generally incorporating a plurality of reinforcing cords, typically textile cords, textile or metallic, optionally interlaced with one another, oriented substantially in the circumferential direction and 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] Additionally, respective sidewalls (108) of elastomeric material are further applied to axially outer locations of the lateral surfaces of the carcass structure, 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 an 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 being generally 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 inflating air, may also be provided radially inward from the carcass layer (101).

[0258] The reinforcing annular structure (103) of the tire may be provided with further 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 crosslinked 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 of the anchor annular structures (102) and bead fillers (104) at least partially, said reinforcing layer being 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 in this specification 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 carcass structure of the tire are built and / or assembled on a forming drum. More specifically, the forming drum is intended to receive first the liner, if present, and then the carcass structure. Then, a device (not shown) coaxially engages one of the annular anchor structures around each end flap, places the outer sleeve with the belt structure, the underlayer and the tread band in a coaxial central position around the cylindrical carcass sleeve, and shapes the carcass sleeve according to a toroidal form through radial expansion of the carcass structure, so as to apply the carcass sleeve against the radially inner surface of the outer sleeve.

[0265] After the green tire has been built, a molding and vulcanization process is generally carried out in order 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 invention is of the type for knobby "big enduro" motorcycles. That is to say, the tire 1 comprises a number of lateral and circumferential grooves separating a number of spaced apart blocks. The tire 1 has a "camber ratio" defined by the ratio of the deflection to the maximum radial section width. Preferably, for a big enduro rear tire, the deflection of the tire 1 is between about 40 mm and about 60 mm. The camber ratio of the tire 1 is between about 0.25 and about 0.35, for example equal to about 0.26. For a front tire, the deflection is between about 35 mm and about 60 mm, and the camber ratio is between about 0.30 and about 0.40, for example equal to 0.38. The blocks and grooves define a tread pattern having a void / full ratio of 0.4 to 0.65, preferably 0.5 to 0.6, such as 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 stated, 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 dynamo-mechanical analysis (DMA).

[0272] In detail, the samples were analyzed using an EPLEXOR® 150 (GABO) instrument, with a temperature scan from −80° C. to +30° C. at a heating rate of 2° C. / min, and a dynamic tensile deformation of 0.1% at a frequency of 1 Hz. The dimensions of the specimen were 1 mm thick, 10 mm wide, 46 mm long, and a reference length of 29 mm (representing the free length involved in the deformation while the 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 curing conditions according to ISO 6502-3 (2018).

[0276] Mooney Viscosity: The ML(1+4) viscosity was measured according to the ISO 289-1:2015 standard at 100° C. For the high molecular weight polymers (E-SBR and S-SBR), the 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 instrument as described herein. Test specimens of vulcanized material (170°C for 10 min) with cylindrical geometry (length = 25 mm; diameter = 14 mm) were preloaded in compression to a longitudinal strain of 25% relative to the initial length, maintained at a given temperature of 10°C, 23°C or 70°C for the entire duration of the test, and subjected to a dynamic sinusoidal strain with an amplitude of ±3.5% relative to the preloaded length at a frequency of 100 Hz. The dynamic mechanical properties are expressed as dynamic modulus of elasticity (E') and Tan δ (loss factor). Tan δ values ​​were calculated as the ratio of viscous dynamic modulus of elasticity (E'') to dynamic modulus of elasticity (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, the reference elastomer compounds REF1 and REF2 and the elastomer compounds INV1 and INV2 according to the invention were prepared.

[0282] [Table 1]

[0283] *Oil extended: Total phr (polymer + oil*) is in parentheses. NEOCIS BR 60 is EUROPRENE® NEOCIS BR 60 from ENI, a solid polybutadiene prepared in solution, produced with a neodymium organometallic catalyst, has a high cis content (minimum 97%) and a weight average molecular weight of about 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, has a Tg of about -50°C, a Mooney viscosity of about 48 MU, a styrene content of about 23%, and is extended with 37.5 parts treated distillate aromatic extract (TDAE) per 100 phr of dry polymer. SBR 1739 is a solid styrene butadiene copolymer (E-SBR) from Synthos, Buna® SB1739-Schkopau, low temperature emulsion polymerized using mixed rosin / fatty acid soap, oil extended with 37.5 parts oil per 100 phr dry polymer, with a Tg of about −40° C. Asahi Kasei's TUFDENE E680 is a solid solution polymerized styrene butadiene copolymer, chain end functionalized with a functionalizing terminator, oil extended with 37.5 parts TDAE oil per 100 phr 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 at 160°C ML(3+4)]. POLYVEST 130 from Evonik 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. RICON® 100 from Cray Valley (Total) 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 distillate aromatic extract TDAE). The tetrasulfide is bis[3-(triethoxysilyl)propyl]tetrasulfide JH-S69 from Chem Spec Ltd. Novares' NOVARES TT30 is a hydrocarbon resin produced by polymerization of C9 / C10 unsaturated aromatic hydrocarbons. The Novares TT90 is ZINC OXIDE is a RHENOGRAN ZNO from Zincol Ossidi. 6PPD is Eastman's 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 "big enduro" motorcycle tyres and is a composition comprising a mixture of a diene tread polymer and a conventional plasticised 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 introducing 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 elastomeric 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 was continued for a maximum of 5 minutes, reaching a temperature of about 145°C. Then, in a second test (2), also carried out using an internal mixer, the vulcanizing agents and accelerators were added and mixing was continued for 4 minutes, keeping 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 the evaluation of the mechanical properties.

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

[0293] [Table 2]

[0294] As can be seen from the data on tensile tests, the INV1 compound shows a significant increase in the Ca3 value (10.03 MPa) compared to the REF1 and REF2 compounds (8.35 MPa and 8.53 MPa) due to the introduction 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 is introduced into the composition instead of process oil and resin, as is the case for the INV2 compound, the value of the Ca3 load shows a value comparable to that of the reference compound (8.85 MPa). The static mechanical properties (CA3, CR, AR%) of the latter are even better when a solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a hyperbranched coupling agent is used in combination 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, predicting a good performance on wet surfaces.

[0296] The inherent tear and abrasion resistance attributed to 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 high molecular weight hyperbranched coupling agents (INV1), nor by the further replacement of process oils and resins with liquid polymers (INV2) as opposed to the partial replacement of polybutadiene (BR) and emulsion polymerized solid styrene butadiene copolymers (E-SBR) with conventional solution polymerized solid styrene butadiene copolymers (S-SBR) (Tufdene E680, REF2).

[0297] These results are highlighted by the respective values ​​of 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] Moreover, an unexpected improvement in grip was highlighted in the inventive material compared to REF1, taking into account that a lower ratio of E' to Tan δ (grip index) at 23° C. corresponds to a better wet grip. 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 a portion of the polybutadiene (BR) and emulsion polymerized solid styrene butadiene copolymer (E-SBR), and by further replacing the process oil and resin with liquid polymer (INV2).

[0299] The latter material showed a significant improvement in wet grip compared to REF1, as predicted by the 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 copolymers (S-SBR) functionalized with high molecular weight Mw hyperbranched coupling agents in the INV1 and INV2 compounds would increase the stiffness of the material and therefore worsen its wet performance, but surprisingly, both the INV1 and also the INV2 compound showed values ​​of E', Tan δ and Grip Index predicting good 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 high mileage for the tire as well as improved wet performance.

[0303] On the other hand, this result could not be obtained 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 a significant decrease in 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; at least 1 phr, preferably at least 2 phr, of at least one vulcanizing agent; wherein the total of said liquid polymer, said resin, if present, and said plasticizing oil is from 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 between -60°C and -20°C, a Mooney viscosity at 160° C. comprised between 30 and 70 MU, and at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having an amount of styrene comprised between 15% and 50%, from 10 to 70 phr; 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 polymer having a Mooney viscosity at 160° C. of 60 to 100 MU; An elastomeric composition for vehicle wheel tyres, wherein the properties of the solid diene-based elastomeric polymer of said mixture are measured according to the methods given in the experimental part.

2. said liquid polymer may be present in an amount ranging from 0 to 28 phr, preferably from 0 to 23 phr; said resin may be present in an amount of from 0 to 15 phr, preferably from 1 to 12 phr, more preferably from 3 to 10 phr; said plasticizing oil is present in an amount ranging from 20 to 50 phr, preferably from 25 to 45 phr; A composition according to claim 1, in which the sum of said liquid polymer, said resin, if present, and said plasticizing oil is between 25 and 80 phr, preferably between 30 and 60 phr.

3. The mixture of solid diene-based elastomeric polymers 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 3. The composition according to claim 1 or 2, comprising, or preferably consisting of, 15 to 75 phr of at least one solution polymerized styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent.

4. The mixture of solid diene-based elastomeric polymers comprises: 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 4. The composition of claim 3, comprising, or preferably consisting of, 30 to 65 phr of at least one solution polymerized styrene butadiene copolymer (S-SBR) that is chain functionalized with a hyperbranched coupling agent.

5. 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%; 5. The composition of any one of claims 1 to 4, 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, preferably greater than 900,000 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.

6. The mixture of solid diene-based elastomeric polymers comprises: - 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%, 6. Composition according to any one of claims 1 to 5, comprising, or preferably consisting of, 30 to 65 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a hyperbranched coupling agent, having a weight average molecular weight Mw of more than 800,000 g / mol, preferably more than 900,000 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, Mooney viscosity measured at 160°C of 70 to 90 MU.

7. 7. The composition of any one of claims 1 to 6, comprising at least 50 phr, at least 60 phr, at least 70 phr, or at least 80 phr of at least one reinforcing filler.

8. 8. The composition of any one of claims 1 to 7, wherein the hyper-branched coupling agent of the at least one chain-functionalized solution-polymerized solid styrene-butadiene copolymer (S-SBR) is a polyorganosiloxane.

9. An elastomeric compound for tread bands of tires, obtainable by mixing and vulcanizing the elastomeric 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: - a Mooney viscosity higher than 50MU, preferably higher than 60MU; - 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; - a breaking load greater than 17 MPa, preferably greater than 19 MPa; - elongation at break greater than 500%, preferably greater than 600%; - an IRHD hardness at 23°C of 60 to 70, preferably 62 to 68 IRHD hardness; - a tear strength at 23°C greater than 45.00 N / mm, preferably greater than 46.00 N / mm; - 75.00 mm ３ Less than 70.00 mm, preferably ３ Less than 65.00 mm, more preferably ３ Resistance to abrasion with less than material loss; a dynamic modulus E' at 23°C of less than 10.00 MPa, preferably less than 9.00 MPa; - a loss factor (Tan δ) at 23°C, calculated as the ratio between the viscous dynamic modulus (E″) and the dynamic modulus (E′), equal to or greater than 0.370, preferably equal to or greater than 0.380 and more preferably equal to or greater than 0.

400.

11. A tread band of a tyre for vehicle wheels, comprising or preferably consisting of an elastomeric compound according to claim 9 or 10.

12. A tyre for a vehicle wheel comprising a tread band according to claim 11.

13. Tyre according to claim 12 for a motorcycle wheel, preferably for a "big enduro" type motorcycle wheel.

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