Elastomeric compounds for tire and tread band of relative tire

Abstract

The present invention relates to an elastomeric compound for tyres for vehicle wheels, in particular an elastomeric compound for the tread band of tyres, preferably for large capacity motorcycles. The elastomeric compound incorporated in the tread band confers to the tyre a long mileage and a high manoeuvrability, in particular in wet conditions, by using a special diene elastomeric polymer, preferably in combination with a liquid polymer.

Description

TECHNICAL FIELD

[0001] The present invention relates to an elastomeric compound for a tyre for vehicle wheels, in particular an elastomeric compound for a tread band of a tyre. BACKGROUND

[0002] Typically, the elastomeric compounds used in the manufacture of the tread band of a tyre for vehicle wheels comprise a mixture of polybutadiene rubber (BR) and styrene butadiene rubber (SBR) together with plasticizers such as process oil and resins.

[0003] Polybutadiene rubber (BR), in particular polybutadiene rubber (BR) with high content of cis double bonds, such as BUDIKON® from Versalis, is appreciated for its mechanical properties, in particular for its high abrasion resistance. NEOCIS BR 60, is appreciated for its mechanical properties, in particular for its high abrasion resistance.

[0004] Solution-polymerized styrene butadiene SBR rubber (S-SBR), such as TUFDENE E680 from Ashai, is typically used to improve the handling properties, in particular in wet conditions, while emulsion-polymerized SBR rubber (E-SBR), such as SBR 1739 from Synthos, has a higher weight average molecular weight Mw than standard solution-polymerized styrene butadiene rubber (S-SBR) due to its high tear strength.

[0005] In order to have a tyre with high tear resistance and abrasion resistance and therefore with long road life, it is possible to use in the tread band compound a blend of styrene-butadiene copolymer emulsion (E-SBR) and polybutadiene (BR), which preferably has a high content of cis, but at the expense of the wet road performance. On the other hand, by replacing the emulsion styrene butadiene rubber (E-SBR) and part of the polybutadiene rubber (BR) with a conventional solution-polymerized styrene butadiene rubber (S-SBR) (such as Tufdene E680 or Tufdene 3830 from Asahi) to improve the handling in wet conditions, a decrease in the mechanical resistance properties is observed, which are often important and essential in certain demanding applications, such as in enduro type motorcycles.

[0006] In other words, based on the existing industry knowledge, it seems very difficult to reconcile the opposite requirements of long distance and driving on wet ground by using the above mentioned polymers and, in practice, one has to seek the best compromise.

[0007] Document US20180362740A1 describes in paragraph 0060 an elastomeric composition comprising a butadiene rubber (BR150B from Ube), an emulsion polymerized styrene-butadiene rubber (E-SBRSBR1723 from JSR) and a non-functionalized solution polymerized styrene-butadiene rubber (S-SBRTufdene3830 from Asahi Kasei). SUMMARY

[0008] The Applicant has set itself the problem of how to further improve the road performance of current tyres, especially in the wet, without losing the tear resistance and the resistance and therefore the mileage.

[0009] In this regard, the Applicant has carried out several studies and has found that this difficult result can be obtained by modifying the traditional tread band compound with the partial substitution of the high-cis polybutadiene (BR) and the emulsion polymerized solid styrene-butadiene copolymer (E-SBR) with a special type of solution polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a new generation of very high molecular weight multi-branching agent. This type of solution polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a high molecular weight multi-branching agent, when introduced in the elastomeric tread composition in precise amounts, confers to the elastomeric compound a high mechanical strength, comparable to the typical mixtures of emulsion polymerized solid styrene-butadiene copolymer and polybutadiene used for the tread band (E-SBR / BR), and at the same time, surprisingly considering the high molecular weight of the polymer and the consequent increase in the stiffness of the compound, confers good wet performance.

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

[0011] The first aspect of the present application is therefore an elastomeric composition for a tyre for vehicle wheels, comprising:

[0012] from 0 to 30 phr of at least one liquid polymer,

[0013] from 0 to 20 phr of at least one resin,

[0014] from 10 to 60 phr of at least one plasticizing oil,

[0015] wherein the sum of the plasticizing oil and, if present, the liquid polymer and the resin is from 20 to 90 phr,

[0016] 100 phr of a mixture of solid diene elastomer polymers, wherein the mixture of polymers comprises, preferably consists of:

[0017] 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 300 000 g / mol and 600 000 g / mol and a content of cis double bonds of at least 95 %;

[0018] 10 to 70 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg between -60 °C and -20 °C, a Mooney viscosity at 160 °C between 30 and 70 MU, and a styrene amount between 15 % and 50 %, and

[0019] 10 to 80 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having:

[0020] a weight average molecular weight Mw greater than 500 000 g / mol, and / or

[0021] a styrene amount between 25 % and 50 % and a vinyl amount between 10 % and 50 %, and / or

[0022] a Tg between -50 °C and -20 °C, and / or

[0023] a Mooney viscosity at 160 °C between 60 and 100 MU,

[0024] wherein the properties of the solid diene elastomer polymers of the mixture are measured according to the methods indicated in the experimental part,

[0025] at least 40 phr of at least one reinforcing filler, and

[0026] at least 1.0 phr, preferably at least 2 phr of at least one vulcanizing agent.

[0027] Another aspect of the present invention is an elastomeric compound for a tread band of a tire for vehicle wheels, obtained by mixing and vulcanizing the elastomeric composition according to the present invention.

[0028] Another aspect of the present invention is a tread band for a tire for vehicle wheels, comprising the elastomeric compound according to the present invention.

[0029] Another aspect of the present invention is a tire for vehicle wheels, comprising the tread band for a tire according to the present invention.

[0030] Definitions

[0031] The term "phr" (parts per hundred parts of rubber) means the weight parts of a given component of the vulcanizable elastomer composition in 100 weight parts of the solid diene elastomer polymer mixture.

[0032] The term "elastomer composition" means a composition comprising at least one diene elastomer polymer and one or more additives, provided by mixing, which gives an elastomer compound suitable for use in a tire component.

[0033] The components of the elastomer composition are not generally all introduced into the mixer at the same time, but are typically added sequentially. In particular, the vulcanization additives (such as vulcanizing agents and possibly accelerators and retarders) are generally added in a downstream step with respect to the incorporation and processing of all the other components.

[0034] In the intermediate or final elastomer compound, the individual components of the elastomer composition are not always maintained or traceable individually, as they can be completely or partially transformed due to interactions with other components, heat and / or mechanical processing. The term "elastomer composition" herein refers to the set comprising all the components added in the preparation of the elastomer compound, regardless of whether they are all actually present at the same time, introduced sequentially or then traceable in the elastomer compound or in the final tire. The term "elastomer compound" indicates a compound that can be obtained by mixing at least one diene polymer with at least one additive typically used to prepare tire compounds and possibly heating.

[0035] The term "vulcanized elastomer compound" means a material that can be obtained by crosslinking or vulcanization with sulfur of an elastomer compound.

[0036] The term "diene polymer" indicates a polymer or copolymer derived from the polymerization of one or more monomers, at least one of which is a conjugated diene (conjugated diene hydrocarbon).

[0037] The term "solid diene elastomer polymer" indicates a natural or synthetic polymer that, after vulcanization, can be repeatedly stretched at room temperature to at least twice its original length and immediately upon removal of the stretching load returns to approximately its original length (according to the definition of the ASTM D1566-11 Standard Terminology Relating to Rubber).

[0038] The term "vulcanization" refers to the crosslinking reaction in natural or synthetic rubber initiated, for example, by sulfur-based vulcanizing agents.

[0039] The term "green" indicates a material, compound, composition, component or tire that has not yet been vulcanized.

[0040] The term "vulcanizing agent" indicates a crosslinking agent capable of transforming natural or synthetic rubber into an elastic and resistant material due to the formation of a three-dimensional network of inter- and intra-molecular bonds.

[0041] The term "vulcanization accelerator" indicates a product capable of further accelerating the vulcanization, making it occur in a shorter time and possibly at lower temperatures. An example of accelerator is the stearic acid-zinc oxide system.

[0042] The term "vulcanization activator" indicates a product capable of further accelerating the vulcanization, making it occur in a shorter time and possibly at lower temperatures. An example of accelerator is the stearic acid-zinc oxide system.

[0043] The term "vulcanization retarder" means a product capable of delaying the start of the vulcanization reaction and / or inhibiting unwanted side reactions, such as N-(cyclohexylthio) phthalimide (CTP).

[0044] The term "reinforcing filler" means a reinforcing material typically used in the industry to improve the mechanical properties of the rubber of the tire, preferably selected from carbon black, conventional silica, such as silica from sand precipitated with strong acid (preferably amorphous), diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

[0045] The term "white filler" means a conventional reinforcing material used in the industry, selected from conventional silica and silicates, such as sepiolite, paligorskite (also known as attapulgite), montmorillonite, alloisite, etc., possibly modified by acid treatment and / or derivatization. Typically, the white filler has surface hydroxyl groups.

[0046] The term "mixing step (1)" indicates a step of the preparation process of the elastomeric compound in which one or more additives can be incorporated by mixing and possibly heating, in addition to the vulcanizing agents supplied in step (2). Mixing step (1) is also called "non-productive step". In the preparation of the compound, there can be several "non-productive" mixing steps, which can be indicated with 1a, 1b, etc.

[0047] The term "mixing step (2)" indicates the next step of the preparation process of the elastomeric compound in which the vulcanizing agents and possibly other additives that package the vulcanization are introduced into the elastomeric compound obtained from step (1) and mixed in the material at controlled temperature, usually at a compound temperature lower than 120°C, to provide a vulcanizable elastomeric compound. Mixing step (2) is also called "productive step". Each mixing step can comprise several intermediate processing steps or sub-steps, characterized by a momentary interruption of the mixing to allow the addition of one or more ingredients, but without intermediate discharge of the compound. DETAILED DESCRIPTION

[0049] The elastomer composition according to the application is characterized by one or more of the following preferred aspects, alone or in combination with each other.

[0050] For each class or category of ingredient, the present composition can include at least one or two or more, for example two or more liquid polymers in a mixture, the total amount of which complies with the amount preferences described herein.

[0051] The elastomer composition according to the application can include at least one liquid polymer.

[0052] The liquid polymer can be present in an amount preferably between 0 and 28 phr, more preferably between 0 and 23 phr.

[0053] The liquid polymer can be present in an amount greater than 3 phr, preferably less than 4 phr and / or less than 25 phr, preferably less than 20 phr.

[0054] The present composition can include at least one liquid polymer, which is preferably selected from the group consisting of liquid polybutadiene, liquid styrene butadiene copolymer, liquid polyisoprene and mixtures thereof.

[0055] The term "liquid polymer" means a diene polymer derived from the polymerization of one or more monomers, at least one of which is a conjugated diene, which is a pourable liquid or a low viscosity fluid at a temperature of 23°C.

[0056] Preferably, the liquid polymer is characterized by one or more of the following parameters:

[0057] a weight average molecular weight (Mw) not higher than 80000 g / mol, and / or

[0058] a glass transition temperature (Tg) lower than 0°C.

[0059] The weight average molecular weight (Mw) can be measured by GPC (Gel Permeation Chromatography) according to known techniques in the art, for example according to ISO 13885 method.

[0060] The glass transition temperature Tg can be conveniently measured by Differential Scanning Calorimetry (DSC) using methods well known to the person skilled in the art (ISO 22768 "Rubber, raw - Determination of the glass transition temperature by Differential Scanning Calorimetry (DSC)").

[0061] Preferably, the liquid polymer is characterized by a (Mw) between 500 and 80000 g / mol, more preferably between 500 and 50000 g / mol.

[0062] Preferably, the liquid polymer is characterized by a glass transition temperature (Tg) between -120°C and 0°C, more preferably between -110°C and -40°C.

[0063] The at least one liquid polymer can be a liquid polybutadiene.

[0064] Preferably, the liquid polybutadiene is characterized by a weight average molecular weight between 500 and 30000 g / mol, preferably between 8000 and 20000 g / mol, between 10000 and 15000 g / mol.

[0065] Preferably, the liquid polybutadiene is characterized by a glass transition temperature (Tg) between -120°C and -50°C, more preferably between -110°C and -90°C.

[0066] Preferably, the liquid polybutadiene has a vinyl content between 0 and 90%, preferably between 1 and 50%.

[0067] Possibly, the liquid polybutadiene can be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups or hydroxyl groups or trialkoxy-silyl groups.

[0068] Examples of suitable liquid polybutadienes are liquid polymers based on butadiene sold by Evonik under the trade name POLYVEST 110, POLYVEST 130, POLYVEST MA 75, by Kuraray under the trade name LBR 307, LBR 305, LBR 300, and by Cray Valley under the trade name RICON 130, RICON 130MA8, RICON 130MA 13, RICON 150, RICON 156, RICON 157.

[0069] The at least one liquid polymer can be a liquid styrene butadiene copolymer.

[0070] Preferably, the liquid styrene butadiene copolymer is characterized by a weight average molecular weight between 500 and 10000 g / mol, preferably between 2000 g / mol and 6000 g / mol.

[0071] Preferably, the liquid styrene butadiene copolymer is characterized by a glass transition temperature (Tg) between -90°C and -20°C, more preferably between -70°C and -50°C.

[0072] Preferably, the liquid styrene butadiene copolymer has a vinyl content between 0 and 90%, preferably between 1 and 50%.

[0073] Possibly, the liquid styrene butadiene copolymer can be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups or hydroxyl groups or trialkoxy-silyl groups.

[0074] Examples of suitable liquid styrene-butadiene copolymers are the liquid polymers based on styrene-butadiene sold by Cray Valley (Total) under the trade name CRAYVAC® 100、 181、 184 and by Kuraray as LSBR 820, LSBR 841.

[0075] The at least one liquid polymer can be a liquid polyisoprene.

[0076] Preferably, the liquid polyisoprene has a weight average molecular weight between 3000 and 80000 g / mol, preferably between 20000 and 60000 g / mol.

[0077] Preferably, the liquid polyisoprene has a glass transition temperature (Tg) between -80°C and -30°C, preferably between -70°C and -40°C.

[0078] Possibly, the liquid polyisoprene can be modified with maleic anhydride, esterified or acid carboxyl groups, epoxy groups or hydroxyl groups or trialkoxy-silyl groups.

[0079] Examples of suitable liquid polyisoprene A are the liquid polymers based on isoprene (IR) sold by Kuraray under the trade name LIR 30, LIR 50, LIR 403, LIR 410; among natural polyisoprenes: DPR 35, DPR 40, DPR 75, DPR 400 by DPR Industries.

[0080] Preferably, the at least one liquid polymer is a liquid polybutadiene and / or a liquid styrene butadiene copolymer.

[0081] The elastomer composition according to the application can comprise at least one resin.

[0082] The resin can be present in an amount preferably between 0 and 15 phr, more preferably between 3 and 10 phr.

[0083] The resin can be present in an amount greater than 2 phr, preferably less than 4 phr and / or less than 17 phr, preferably less than 11 phr.

[0084] The term "resin" is used to refer to a polymer having thermoplastic or at least partially thermoplastic properties (as in the case of elastomer / thermoplastic block copolymers).

[0085] Thermoplastic properties are used to indicate the tendency of a polymer to increase its viscosity, i.e. to deform plastically when subjected to a temperature increase and / or to a deformation strong enough. These thermoplastic properties distinguish the behaviour of a resin from the behaviour of an elastomer, as defined hereafter. Moreover, unlike liquid polymers and diene elastomer polymers as defined herein, a resin is not derived from the polymerization of a conjugated diene.

[0086] The resin of the present composition is a non-crosslinkable polymer (non-reactive resin).

[0087] Preferably, the resin is characterized by one or more of the following parameters:

[0088] a weight average molecular weight (Mw) between 200 and 3000 g / mol, and / or

[0089] a glass transition temperature (Tg) higher than 0°C.

[0090] The weight average molecular weight (Mw) can be measured according to known techniques in the art, for example by SEC (Size Exclusion Chromatography) according to the ASTM D6579-11 method “Standard Practice for Molecular Weight Averages and Molecular Weight Distribution of Hydrocarbon, Rosin, and Terpene Resins by Size Exclusion Chromatography”.

[0091] The glass transition temperature (Tg) and the softening temperature (Tm) can be conveniently measured using a Differential Scanning Calorimeter (DSC) according to methods well known by the person skilled in the art, for example the ASTM D-6604 method (Measurement of Glass Transition Temperatures of Hydrocarbon Resins by Differential Scanning Calorimeter).

[0092] More preferably, the resin is characterized by a weight average molecular weight (Mw) between 500 and 3000 g / mol, more preferably between 500 and 2000 g / mol.

[0093] More preferably, the resin is characterized by a glass transition temperature (Tg) higher than 20°C.

[0094] The resin can be a solid having a softening temperature (Tm) higher than 0°C, more preferably a softening temperature between 10 and 160°C or between 60 and 90°C.

[0095] The resin used in the composition is preferably selected from the group comprising hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.

[0096] Preferably, the resin is a hydrocarbon resin.

[0097] Preferably, the resin is a mixture of a natural resin and a hydrocarbon resin.

[0098] The hydrocarbon resin can be aliphatic, aromatic or a combination thereof, meaning that the base polymer of the resin can consist of aliphatic and / or aromatic monomers.

[0099] The hydrocarbon resin can be natural (e.g. plant) or synthetic or derived from petroleum. In some non-limiting cases of the present application, these resins comprise essentially only hydrogen and carbon atoms.

[0100] Preferably, the weight average molecular weight of the hydrocarbon resin is between 500 and 3000 g / mol, preferably between 700 and 1500 g / mol.

[0101] Preferably, the hydrocarbon resin is selected from the group consisting of homopolymers or copolymers of cyclopentadiene (CPD), dicyclopentadiene (DCPD), homopolymers or copolymers of terpenes, homopolymers or copolymers of C5 cuts, and mixtures thereof, preferably DCPD / vinyl aromatic copolymers, DCPD / terpene copolymers, DCPD / C5 cut copolymers, terpene / vinyl aromatic copolymers, C5 cut / vinyl aromatic copolymers, and combinations thereof.

[0102] Examples of vinyl aromatic monomers include styrene, a-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-tert-butylstyrene, methoxystyrene, chlorostyrene, vinylmesitylene, divinylbenzene, vinyl naphthalene, vinyl aromatic monomers derived from C8-C10cuts, in particular from C9.

[0103] Preferably, the hydrocarbon resin is selected from the group consisting of coumarone-indene, styrene-indene, styrene-alkylstyrene derived resins and aliphatic resins.

[0104] A particular example of a commercially available hydrocarbon resin is NOVARES C resin manufactured by RUETGERS CHEMICAL GmbH (indene-coumarone synthetic resin), NOVARES C10, C30 and C90 are particularly preferred.

[0105] Examples of commercially available styrene-indene hydrocarbon resins are UNILENE A 100 manufactured by Braskem and Novares TL 90 manufactured by Ruetgers.

[0106] Examples of commercially available alkyl-styrene hydrocarbon resins are Sylvares SA 85 manufactured by Arzona Chemical, Kristalex F 85 manufactured by Eastman.

[0107] Examples of commercially available aliphatic hydrocarbon resins are: 1102 (manufactured by ExxonMobil), Piccotac 1100 (manufactured by Eastman), Quintone A100 (manufactured by Zeon Chemicals).

[0108] Alternatively, the resin is a phenol-formaldehyde resin.

[0109] Preferably, the phenol-formaldehyde resin is selected from the group consisting of alkylphenol-formaldehyde based resins, rosin modified alkylphenol resins, alkylphenol-acetylenic group resins, alkylphenol modified resins and terpene-phenol based resins.

[0110] Examples of commercially available phenol-formaldehyde resins that can be used in the present application are: RESINA SP-1068 (manufactured by SIGROUP) (octylphenol-formaldehyde resin); DUREZ 32333 (manufactured by Sumitomo Bakelite) (phenol-formaldehyde resin); KORESIN (manufactured by BASF) (pt-butylphenol-acetylene resin); SYLVARES TP 115 (manufactured by Arizona Chemicals) (terpene phenol resin).

[0111] Alternatively, the resin is a natural terpene based resin.

[0112] Preferably, the resin is a polyterpene resin selected from the group consisting of homopolymers or copolymers of a-pinene, b-pinene, limonene and vinyl aromatic monomers (styrene) and / or aromatic monomers (phenol).

[0113] Preferably, the resin is a polyterpene resin having a glass transition temperature (Tg) higher than 25°C.

[0114] Preferably, the resin is a polyterpene resin having a softening temperature (Tm) between 50°C and 150°C.

[0115] Preferably, the resin is a polyterpene resin having a weight average molecular weight between 500 and 3000 g / mol.

[0116] Examples of commercially available natural terpene based resins that can be used in the present application are: Piccolyte F90, Piccolyte F105 manufactured by PINOVA; Dercolyte A 115 and Dercolyte M 115 manufactured by DRT.

[0117] Alternatively, the resin is a rosin based natural resin.

[0118] The term rosin generally indicates a mixture of isomeric organic acids (rosin acids) characterized by a common structure comprising three C6 fused rings, different number and position of double bonds and a single carboxyl group.

[0119] Examples of rosin-based resins are sold by DRT under the trade names HYDROGRAL G and DERTOLINE P 105.

[0120] The elastomer composition according to the application comprises at least one plasticizing oil.

[0121] Preferably, the composition comprises at least 10 phr or at least 15 phr or at least 20 phr and / or not more than 60 phr or 50 phr or 40 phr of at least one plasticizing oil.

[0122] Preferably, the composition comprises 20 to 50 phr, more preferably 25 to 45 phr of at least one plasticizing oil.

[0123] The plasticizing oil can be entirely or partially from a commercial composition of solid diene elastomer polymer in which it is used as a diluent (extender).

[0124] The term "plasticizing oil" means a process oil derived from petroleum or mineral oil or vegetable oil or synthetic oil or a combination thereof.

[0125] Unlike the liquid polymer and the diene elastomer polymer as defined herein, the plasticizing oil is not derived from the polymerization of conjugated dienes.

[0126] Preferably, the plasticizing oil exhibits one or more of the following characteristics:

[0127] a weight average molecular weight (Mw) not higher than 600 g / mol, or, if of RAE type, a weight average molecular weight between 400 and 10000 g / mol, and / or

[0128] a glass transition temperature (Tg) lower than -30°C.

[0129] Preferably, the plasticizing oil is a process oil derived from petroleum selected from paraffins (saturated hydrocarbons), naphthenes, aromatic polycyclics and mixtures thereof.

[0130] Examples of suitable process oils derived from petroleum are aromatic, paraffinic, naphthenic oils, such as MES (solventized mild extract), DAE (distillate aromatic extract), TDAE (treated distillate aromatic extract), TRAE (treated residual aromatic extract), RAE (residual aromatic extract) known in the industry.

[0131] The term RAE means a complex mixture of mainly polycyclic aromatic hydrocarbons (CAS No. 64742-10-5) obtained by extraction of the distillation residue of crude oil with a solvent.

[0132] Preferably, the plasticizing oil is a process oil derived from petroleum having a low aromatic content, chosen for example from TDAE, TRAE, MES, paraffinic oil or naphthenic oil.

[0133] Examples of suitable plasticizing oils are oils derived from petroleum: NYTEX 4700 sold by Nynas, EXTENSOIL 1471 sold by Repsol, VIVATEC 500 sold by H&R; and vegetable oils: RADIA 6132 sold by Oleon, Agripure AP 18 and Agripure AP 75 sold by Cargill.

[0134] Alternatively, the plasticizing oil is an oil of natural or synthetic origin derived from the esterification of glycerol with fatty acids, including glycolipids, diglycerides, monoglycerides or mixtures thereof.

[0135] Preferably, these oils have a glass transition temperature (Tg) lower than -70°C.

[0136] Examples of suitable vegetable oils are sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil and cottonseed oil.

[0137] Alternatively, the plasticizing oil is a synthetic oil chosen from alkyl or aryl esters of phthalic acid or phosphoric acid. Preferably, these esters have a glass transition temperature (Tg) lower than -70°C.

[0138] These oils can be used alone or as a mixture.

[0139] The elastomer composition according to the application preferably comprises from 25 to 80 phr, more preferentially from 30 to 60 phr of plasticizing mixture, by plasticizing mixture we mean the sum of the quantities of liquid polymer, of resin if present and of plasticizing oil as defined above.

[0140] The quantity of plasticizing mixture corresponds to the sum of the quantities of liquid polymer, of resin if present and of plasticizing oil as defined above.

[0141] The elastomer composition according to the application preferably comprises at least 20 phr, 30 phr or 40 phr of plasticizing mixture.

[0142] Preferentially, the composition comprises no more than 90 phr, 80 phr or 70 phr of plasticizing mixture.

[0143] The three components of the plasticized 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 pre-mixed together to obtain a separate plasticized mixture, but in the preparation, they can be added individually to the composition in any order or step of the preparation process, as detailed below, or they can be all or partially associated with one or more other components, for example in the case of plasticizing oils, they have been at least partially incorporated as diluents into commercial elastomeric polymers.

[0144] The elastomeric composition for tires according to the present application comprises a mixture of 100 phr of solid diene elastomeric polymers, said mixture comprising, preferably consisting of:

[0145] 15 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 350000 to 550000 g / mol and a content of cis double bonds of 95 to 99%,

[0146] 10 to 60 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -25°C, a Mooney viscosity between 40 to 60 MU and a % styrene content between 20% to 45%, and

[0147] 15 to 75 phr of at least one solution polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having:

[0148] a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene amount between 30% to 45% and a vinyl amount between 15% to 40%,

[0149] a Tg between -45°C to -25°C, and / or

[0150] a Mooney viscosity measured at 160°C between 70 to 90 MU.

[0151] In one embodiment, the mixture of solid diene elastomeric polymers of the composition according to the present application comprises, preferably consists of:

[0152] 15 to 50 phr of at least one solid polybutadiene (BR),

[0153] 10 to 60 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR), and

[0154] 15 to 75 phr of at least one solution polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent.

[0155] In one embodiment, the mixture of solid diene elastomeric polymers of the composition according to the present application comprises, preferably consists of:

[0156] 25 to 40 phr of at least one solid polybutadiene (BR),

[0157] 10 to 40 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR), and

[0158] 30 to 65 phr of at least one solution polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent.

[0159] In one embodiment, in the elastomeric composition of the present application, the solid polybutadiene (BR) has a weight average molecular weight Mw of 350000 to 550000 g / mol and a content of cis double bonds of 95% to 99%,

[0160] The emulsion polymerized solid styrene butadiene copolymer (E-SBR) has a Tg of -60°C to -25°C, a Mooney viscosity between 40 to 60 MU, and a % styrene content between 20% to 45%, and

[0161] The solution polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent has:

[0162] a weight average molecular weight Mw of more than 800000 g / mol, preferably more than 900000 g / mol, and / or

[0163] a styrene amount between 30% to 45% and a vinyl amount between 15% to 40%, and / or

[0164] a Tg between -45°C to -25°C, and / or

[0165] a Mooney viscosity measured at 160°C between 70 to 90 MU.

[0166] In one preferred embodiment, the elastomeric composition for tires according to the present application comprises 100 phr of a mixture of solid diene elastomeric polymers, which comprises, preferably consists of:

[0167] 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 300000 g / mol to 600000 g / mol and a content of cis double bonds of at least 95%,

[0168] 10 to 70 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -20°C, a Mooney viscosity (at 160°C) between 30 and 70 MU, and a styrene amount between 15% and 50%,

[0169] 10 to 80 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having:

[0170] a weight average molecular weight Mw greater than 800000 g / mol,

[0171] a styrene amount between 25% and 50% and a vinyl amount between 10% and 50%,

[0172] a Tg between -50°C and -20°C, and

[0173] a Mooney viscosity measured at 160°C between 60 and 100 MU.

[0174] In a more preferred embodiment, the elastomeric composition for tires according to the present application comprises 100 phr of a mixture of solid diene elastomeric polymers comprising, preferably consisting of:

[0175] 15 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw of 350000 to 550000 g / mol and a content of cis double bonds of 95% to 99%,

[0176] 10 to 60 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -25°C, a Mooney viscosity between 40 and 60 MU, and a % styrene content between 20% and 45%,

[0177] 15 to 75 phr of at least one solution polymerized styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having:

[0178] a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene amount between 30% and 45% and a vinyl amount between 15% and 40%,

[0179] a Tg between -45°C and -25°C, and

[0180] a Mooney viscosity measured at 160°C between 70 and 90 MU.

[0181] The solid diene elastomeric polymers suitable for the present composition are elastomeric polymers or copolymers generally having a glass transition temperature (Tg) lower than 20°C, preferably in the range of 0°C to -110°C.

[0182] Preferably, the solid diene elastomeric polymers of the present elastomer compound have a weight average molecular weight (Mw) greater than 80000 g / mol.

[0183] By solid polybutadiene (BR) it is meant a polymer derivable from the polymerization of 1,3-butadiene, optionally in the presence of other conjugated dienes as described below, wherein the 1,3-butadiene is present in an amount not lower than 50% by weight with respect to the total weight of monomers.

[0184] Examples of suitable polybutadienes are polybutadienes with a high content of 1,4-cis bonds of double bonds, polybutadienes with a high content of vinyl units, metallocene polybutadienes, 1,3-butadiene / acrylonitrile copolymers.

[0185] Examples of preferred commercial polybutadienes (BR) are polybutadienes (Europrene BR40) - (Versalis), SKD NHEODIMIO (Nizhnekamskneftechim Export), BUNA CB 29 MES (Lanxess).

[0186] Preferably, the solid polybutadiene (BR) has a weight average molecular weight Mw in the range of 370000 to 550000 g / mol and a content of cis double bonds in the range of 96% to 98%.

[0187] Preferably, the at least one solid polybutadiene (BR) is present in the present composition in an amount in the range of 15 to 45 phr, more preferably 25 to 35 phr.

[0188] Preferably, the solid polybutadiene (BR) has a glass transition temperature (Tg) lower than -85°C, preferably in the range of -110°C to -90°C.

[0189] In the present composition, the one or more solid polybutadienes can be present in a mixture.

[0190] The present elastomer composition comprises more than one solid styrene butadiene copolymer (SBR).

[0191] Typically, solid styrene-butadiene copolymers (SBRs) refer to copolymers derived from the polymerization of one or more dienes conjugated with at least one monovinyl aromatic monomer and optionally a polar comonomer. Preferably, the conjugated diene comprises 4 to 12, more preferably 4 to 8 carbon atoms and is preferably selected from: 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.

[0192] Preferably, the monovinyl aromatic hydrocarbon comprises 8 to 20, more 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.

[0193] Preferably, the polar comonomer is selected from vinylpyridine, vinylquinoline, acrylic acid and alkyl acrylates, nitrile or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile or mixtures thereof.

[0194] This elastomer composition includes at least one emulsion-polymerized solid styrene-butadiene copolymer (E-SBR).

[0195] Emulsion-polymerized solid styrene-butadiene copolymers (E-SBR) refer to copolymers as defined above derived from emulsion polymerization of one or more dienes conjugated with at least one monovinyl aromatic monomer and optionally a polar comonomer.

[0196] Examples of suitable emulsion-polymerized solid styrene-butadiene copolymers (E-SBR) are styrene / 1,3-butadiene (SBR), styrene / isoprene / 1,3-butadiene, and styrene / 1,3-butadiene / acrylonitrile copolymers.

[0197] Examples of suitable commercially viable emulsion-polymerized solid styrene-butadiene copolymers (E-SBR) are SBR 1723TDAE from Sibur and BUNA from Synthos. TM SBR 1723, from Versalis (Eni Group) 1723, SBR from LG Chem; 1739, SBR from Versalis; 1739 from ZEON. SBR 1739 and Trinseo BUNA TM SB 1739 Schkopau.

[0198] Preferably, the emulsion polymerized solid styrene-butadiene copolymer (E-SBR) has a Tg of -58°C to -28°C, a Mooney viscosity between 43 to 57 MU, and a % styrene content between 20% to 43%.

[0199] Preferably, the at least emulsion polymerized solid styrene-butadiene copolymer (E-SBR) is present in the present composition in an amount ranging from 10 to 60 phr, more preferably from 10 to 50 phr.

[0200] Preferably, the glass transition temperature (Tg) of the emulsion polymerized solid styrene-butadiene copolymer (E-SBR) is below -10°C, preferably in the range of -60°C to 40°C.

[0201] In the present composition, one or more emulsion polymerized solid styrene-butadiene copolymers (E-SBR) can be present in the mixture.

[0202] The present elastomer composition comprises at least one solution polymerized solid styrene-butadiene copolymer (S-SBR) as defined herein.

[0203] The solution polymerized solid styrene-butadiene copolymer (S-SBR) refers to a copolymer derived from the solution polymerization of one or more dienes, conjugated with at least one monovinylidene aromatic monomer and optionally a polar comonomer as defined above.

[0204] The present solution polymerized solid styrene-butadiene copolymer (S-SBR) is a polymer functionalized on the chain and optionally also at its end with a multi-branching coupling agent.

[0205] In the present solution polymerized solid styrene-butadiene copolymer (S-SBR), the functionalization can be introduced into the chain by reaction with a suitable multi-branching coupling agent and possibly at the end with a terminator. In particular, diene elastomer polymers obtained by anionic polymerization in the presence of organometallic initiators, in particular organolithium initiators, can be functionalized by reacting the residual organometallic groups derived from the initiator with a suitable terminator and / or coupling agent, such as amines, amides, imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes, aryloxysilanes, alkyl dithiols, alkyl dithiol silanes, carboxyalkyl mercaptans, carboxyalkyl mercaptan silanes and thiodiglycols.

[0206] General examples of terminating agents or coupling agents known in the art are described, for example, in patents EP2408626, EP2271682, EP3049447A1, EP2283046A1, EP2895515A1, EP451604, US4742124, WO2015086039A1 and WO2017211876A1.

[0207] An example of a particularly suitable multi-branched coupling agent is the polyorganosiloxane described in patent application SG10201800553S(A) in paragraphs 0040 to 0043 in the name of JSR Corporation, in particular with respect to formula (6)

[0208]

[0209] and the meaning of the variables recited therein.

[0210] A particular example of a preferred multi-branched coupling agent is the product of the following formula (6.1):

[0211]

[0212] Preferably, the at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent is a functionalized polymer obtained from styrene / 1,3-butadiene, styrene / isoprene / 1,3-butadiene, styrene / 1,3-butadiene / acrylonitrile and mixtures thereof.

[0213] 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.

[0214] An example of a preferred solution-polymerized solid styrene-butadiene copolymer functionalized with a multi-branched coupling agent is HPR 620 from JSR.

[0215] Preferably, the at least one solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a multi-armed coupling agent has a weight average molecular weight Mw between 500000 and 2000000 g / mol, more preferably between 800000 and 1200000 g / mol.

[0216] In one embodiment, the solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent is characterized in that:

[0217] a weight average molecular weight Mw greater than 500000 g / mol,

[0218] a styrene amount between 25% and 50% and a vinyl amount between 10% and 50%, a Tg between -50°C and -20°C, and

[0219] a Mooney viscosity between 60 and 100 MU at 160°C.

[0220] Preferably, the at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent is present in the composition in an amount between 25 and 80 phr, more preferably between 30 and 75 phr.

[0221] Preferably, the at least one solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent has a glass transition temperature (Tg) lower than -10°C, preferably in the range of -50°C to 20°C.

[0222] The one or more solution-polymerized solid styrene butadiene copolymers (S-SBR) functionalized with a multi-branched coupling agent in the mixture can be present in the composition.

[0223] The solid diene elastomeric polymers making up the mixture can also optionally be functionalized (solid diene elastomeric polymers a') by reaction with a suitable conventional terminating agent or coupling agent (i.e. not a multi-branched agent). In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator, in particular an organolithium initiator, can be functionalized by reacting the residual organometallic groups derived from the initiator with a suitable terminating agent or coupling agent, such as an imine, a carbodiimide, an alkyltin halide, a substituted benzophenone, an alkoxysilane or an aryloxysilane.

[0224] In one embodiment, the mixture of solid diene elastomeric polymers comprises, preferably consists of:

[0225] 20 phr to 45 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 350 000 and 550 000 g / mol and a cis double bond content of at least 95%,

[0226] 10 to 55 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60°C to -25°C, a Mooney viscosity between 40 and 60 MU and a % styrene content between 20% and 43%,

[0227] 10 to 70 phr of at least one solution polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with multi-branched coupling agent chains having a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene amount between 25% and 50% and a vinyl amount between 10% and 50%, a Tg between -50°C and -20°C and a Mooney viscosity measured at 160°C between 60 and 100 MU.

[0228] More preferably, the mixture of solid diene elastomeric polymers comprises, preferably consists of:

[0229] 25 to 35 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370000 and 550000 g / mol and a cis double bond content of at least 97%,

[0230] 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 between 45 and 55 mu and a % styrene content between 22% and 42%,

[0231] 30 to 65 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with multi-branched coupling agent chains having a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene amount between 30% and 45% and a vinyl amount between 15% and 40%, a Tg between -45°C and -25°C and a Mooney viscosity measured at 160°C between 70 and 90 MU.

[0232] The present elastomeric composition comprises at least one reinforcing filler.

[0233] The elastomeric composition according to the present application 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.

[0234] Preferably, the composition comprises not more than 150 phr, 140 phr, 130 phr, 120 phr, 110 phr or 100 phr of at least one reinforcing filler.

[0235] Preferably, the composition comprises 10 to 150 phr, 30 to 120 phr, 50 to 120 phr, 70 to 110 phr or 80 to 100 phr of at least one reinforcing filler.

[0236] Preferably, the reinforcing filler is selected from carbon black, white filler or a mixture thereof.

[0237] In one embodiment, the reinforcing filler is a white filler selected from hydroxides, oxides and hydrated oxides, metal salts and hydrated metal salts, silica, silicate fibers (optionally derivatized and / or modified) or mixtures thereof.

[0238] Preferably, the reinforcing filler is silica.

[0239] The silica present in the composition can interact during the mixing with the silane coupling agent added in order to make it compatible and dispersible in the elastomeric polymer.

[0240] In one embodiment, the reinforcing filler comprises or consists of carbon black.

[0241] Preferably, the 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.

[0242] Preferably, the carbon black is present in the elastomeric composition in an amount higher than 35 phr, more preferably higher than 40 phr.

[0243] Preferably, the carbon black reinforcing filler is selected from carbon black reinforcing fillers having a surface area not less than 20 m 2 / g, preferably greater than 50 m 2 / g, preferably greater than 50 m

[0244] An example of carbon black is N234 sold by Birla Group (India) or by the company Cabot.

[0245] In one embodiment, the reinforcing filler comprises a mixture of several of those reinforcing fillers defined above, preferably comprising a mixture of silica and carbon black.

[0246] The elastomeric composition comprises at least one vulcanizing agent.

[0247] Preferably, the composition comprises at least 1.5 phr, 2 phr, 3 phr or 4 phr of at least one vulcanizing agent.

[0248] Preferably, the composition comprises not more than 10 phr or 8 phr of at least one vulcanizing agent.

[0249] Preferably, the composition comprises 1-10 phr or 2-10 phr of at least one vulcanizing agent.

[0250] Preferably, the vulcanizing agent is selected from sulfur and sulfur-containing molecules used as sulfur donors.

[0251] The sulfur or its derivatives can advantageously be selected from, for example:

[0252] (i) soluble sulphur (crystalline sulphur);

[0253] (ii) insoluble sulphur (polymeric sulphur);

[0254] (iii) sulphur dispersed in oil (for example 33% sulphur known under the trade name Crystex OT33 by Solutia);

[0255] (iv) sulphur donor compounds, for example caprolactam disulphide (CLD), bis[(trialkoxysilyl)propyl] polysulphides, dithiophosphates; thiurams, dithio- dimorpholines and caprolactam-disulphides or mixtures thereof.

[0256] Alternatively, the vulcanizing agent can be selected from peroxides, for example dialkyl peroxides R-O-O-R, wherein R is an alkyl group, alkyl-aryl peroxides R-O-O-R’, wherein R is an alkyl and aryl R’ group, diaryl peroxides R’-O-O-R’, wherein R’ is an aryl group, diacyl peroxides R-C(O)-O-O-(O)C-R’, wherein R and R’ are aryl and / or alkyl groups, peroxy ketones R-O-O-(R)C(R’)-O-O-R’, wherein R and R’ are aryl and / or alkyl groups, peroxy esters R-C(O)-O-O-R’, wherein R and R’ are aryl and / or alkyl groups, metal oxides, for example zinc oxide, quinones, resins and organic bases.

[0257] The vulcanizing agent is preferably used together with auxiliaries known to the person skilled in the art, for example activators, vulcanization accelerators and / or retarders.

[0258] Particularly effective vulcanization activators are zinc compounds. In particular, use is made of zinc stearate, which is preferably formed in situ in the elastomer composition from ZnO and a fatty acid, and magnesium stearate, which is formed from MgO, or mixtures thereof.

[0259] For example, use is made of zinc stearate, which is preferably formed in situ in the elastomer composition from ZnO and a fatty acid, and magnesium stearate, which is formed from MgO, or mixtures thereof.

[0260] The vulcanization activator is preferably used in the elastomer composition in an amount of from 0.5 phr to 10 phr. More preferably, the vulcanization activator is used in the elastomer composition in an amount of from 1 phr to 5 phr. Even more preferably, the vulcanization activator is used in the elastomer composition in an amount of from 1.5 phr to 3.5 phr.

[0261] An example of an activator is the product Aktiplast ST marketed by Rheinchemie.

[0262] Preferably, the elastomer composition can further comprise at least one vulcanization accelerator.

[0263] Typically used vulcanization accelerators can be chosen, for example, from dithio carbamates, guanidines, thioureas, thiazoles, sulfonamides, sulfenamides, thiurams, amines, xanthates or mixtures thereof.

[0264] An example of a vulcanization accelerator is N-cyclohexyl-2-benzothiazyl-sulfenamide sold by Lanxess under the trade name of CZ / C.

[0265] The vulcanization accelerator is preferably used in the elastomer composition in an amount of 0.05 phr to 10 phr.

[0266] More preferably, the vulcanization accelerator is used in the elastomer composition in an amount of 0.1 phr to 5 phr.

[0267] Even more preferably, the vulcanization accelerator is used in the elastomer composition in an amount of 0.5 phr to 3 phr.

[0268] The present elastomer composition can optionally include one or more vulcanization retarders, such as N-cyclohexylthiophthalimide (VULKALENT G, - Lanxess).

[0269] Preferably, the retarder, if present, is used in an amount of between 0.05 phr and 2 phr.

[0270] The elastomer composition according to the present application can further include at least one silane coupling agent, preferably in an amount in the range of 0.5 to 20 phr.

[0271] Preferably, the silane coupling agent is chosen from those silane coupling agents having at least one hydrolysable silane group, which can be represented, for example, by the following formula (I):

[0272] (R’)3Si-C n H 2n -X (I) wherein the R’ groups, equal to or different from each other, are chosen from: alkyl, alkoxy or aryloxy groups, or from halogen atoms, with the proviso that at least one R’ group is an alkoxy or aryloxy group; n is an integer between 1 and 6, inclusive; X is a group chosen from: nitroso, mercapto, amino, epoxide, vinyl, imide, chloro, -(S) m C n H 2n- Si-(R')3 and -S-COR', with m and n being integers between 1 and 6, inclusive, and the R' groups being as defined above. Among silane coupling agents, bis(3-trimethylsilylpropyl) tetrasulphide and bis(3-trimethylsilylpropyl) disulphide are particularly preferred. The silane coupling agent can be used as such or as a suitable mixture with an inert filler such as carbon black, in order to facilitate its incorporation into the elastomer composition.

[0273] Preferably, the silane coupling agent is present in the elastomer composition in an amount ranging between 0.5 phr and 10 phr, preferably between 0.5 phr and 7 phr.

[0274] Examples of silane coupling agents are TESPT: bis(3-triethoxysilylpropyl) tetrasulphide Si69, sold by Evonik.

[0275] The elastomer composition can comprise other additives commonly used, chosen according to the specific application intended for the composition, such as anti-aging agents, anti-reversion agents, adhesion agents, anti-ozonants, in particular of the p-phenylenediamine type, antioxidants, waxes, fibres (such as pulp) or mixtures thereof.

[0276] In one embodiment, the elastomer composition of the application comprises, preferably consists of:

[0277] 0 to 20 phr of at least one liquid polymer chosen from liquid polybutadienes, liquid styrene butadiene copolymers and mixtures thereof,

[0278] 0 to 10 phr, preferably at least 1 phr, of at least one resin,

[0279] 20 to 40 phr of at least one plasticizing oil,

[0280] 100 phr of a mixture of solid diene elastomer polymers,

[0281] wherein the mixture of polymers comprises:

[0282] 20 phr to 40 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370 000 and 550 000 g / mol and a content of cis double bonds of at least 97%,

[0283] 10 to 50 phr of at least one emulsion-polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57°C to -25°C, a Mooney viscosity value between 45 and 55 MU and a % styrene content between 22% and 42%,

[0284] 25 to 70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent chain having a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene amount between 30% and 45% and a vinyl amount between 15% and 40%, a Tg between -45°C and -25°C, a Mooney viscosity measured at 160°C between 70 and 90 MU,

[0285] 60 to 100 phr of at least one reinforcing filler, and

[0286] 1 to 4 phr of at least one vulcanizing agent.

[0287] In a preferred embodiment, the elastomeric composition of the application comprises, preferably consists of:

[0288] 0 to 12 phr, preferably 1 to 12 phr, of at least one resin,

[0289] 20 to 40 phr of at least one plasticizing oil,

[0290] 100 phr of a mixture of solid diene elastomeric polymers,

[0291] wherein the mixture of polymers comprises, preferably consists of:

[0292] 20 phr to 40 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370000 and 550000 g / mol and a cis double bond content of at least 97%,

[0293] 10 to 50 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57°C to -25°C, a Mooney viscosity value between 45 and 55 MU and a % styrene content between 22% and 42%,

[0294] 25 to 70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent chain having a weight average molecular weight Mw greater than 800000 g / mol, preferably greater than 900000 g / mol, a styrene and a vinyl between 30% and 45% and between 15% and 40%, a Tg between -45°C and -25°C, a Mooney viscosity measured at 160°C between 70 and 90 MU,

[0295] at least 60 phr of at least one reinforcing filler, and

[0296] at least 1.0 phr, preferably at least 2 phr of at least one vulcanizing agent.

[0297] In a more preferred embodiment, the present elastomer composition comprises, preferably consists of the following components:

[0298] 10 to 20 phr of at least one liquid polymer selected from liquid polybutadiene, liquid styrene butadiene copolymer and mixtures thereof,

[0299] 3 to 8 phr of at least one resin, 15 to 35 phr of at least one plasticizing oil,

[0300] 100 phr of a mixture of solid diene elastomer polymers,

[0301] wherein the mixture of polymers comprises, preferably consists of the following components:

[0302] 20 phr to 40 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370 000 and 550 000 g / mol and a content of cis double bonds of at least 97 %;

[0303] 10 to 30 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg in the range of -57 °C to -25 °C, a Mooney viscosity value between 45 and 55 MU and a % styrene content between 22 and 42 %.

[0304] 40 to 70 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having a weight average molecular weight Mw greater than 800 000 g / mol, preferably greater than 900 000 g / mol, a styrene amount between 30 and 45 % and a vinyl amount between 15 and 40 %, a Tg between -45 °C and -25 °C, a Mooney viscosity measured at 160 °C between 70 and 90 MU,

[0305] at least 60 phr of at least one reinforcing filler, and

[0306] at least 1 phr, preferably at least 2 phr of at least one vulcanizing agent.

[0307] Preferably, the elastomer composition of the present application does not comprise omega-9 fatty acid amides, such as those described in US 2018 / 0362740 A1 paragraph 043.

[0308] Another aspect of the present application is an elastomeric compound for the tread band of a tire obtained by mixing and vulcanizing the elastomer composition according to the present application.

[0309] Advantageously, the elastomeric compound according to the present application has one or more of the following characteristics measured according to the methods described in the experimental part:

[0310] - a Mooney viscosity (1 +4 at 100°C) higher than 50.00 MU, typically higher than 60 MU and comprised between 60 and 90 MU;

[0311] - a density comprised between 1.100 and 1.500 g / cm 3 ;

[0312] - a load at 300% elongation (Ca3) higher than 8.50 MPa, preferably higher than 8.60 MPa, typically comprised between 8.60 and 10.60 MPa;

[0313] - a breaking load higher than 17 MPa, preferably 19 MPa;

[0314] - an elongation at break higher than 500%, preferably higher than 600%;

[0315] - an IRHD hardness at 23°C comprised between 60 and 70 IRHD, preferably between 62 and 68 IRHD;

[0316] - a tear strength at 23°C higher than 45.00 N / mm, preferably higher than 46.00 N / mm, typically comprised between 46 and 55 N / mm;

[0317] - a wear resistance with a material loss lower than 75.00 mm 3 , preferably lower than 70.00 mm 3 , more preferably lower than 65.00 mm 3 ;

[0318] - a dynamic elastic modulus E’ at 23°C lower than 10.00 MPa, preferably lower than 9.00 MPa, typically comprised between 8.00 and 8.90 MPa;

[0319] - a loss factor (tan delta) not less than 0.370, preferably not less than 0.380, more preferably not less than 0.400, calculated at 23°C as the ratio between the viscous dynamic modulus (E”) and the dynamic elastic modulus (E’).

[0320] Preferably, the loss factor is comprised between 0.400 and 0.420.

[0321] The present elastomeric compound can be prepared according to a process typically comprising one or more mixing steps, in particular at least one mixing step (i) (non-productive) and mixing step (ii) (productive) as defined above, in at least one suitable mixer.

[0322] Each mixing step can comprise several intermediate processing steps or sub-steps, characterized by a momentary interruption of the mixing to allow the addition of one or more ingredients, but generally without intermediate discharge of the compounds.

[0323] Mixing can be carried out, for example, using an "open-mill" type of open mixer or internal mixer of the type with tangential rotors or with intermixing rotors (Intermix), or in a Ko-Kneader TM type or continuous mixer of the twin-screw or multi-screw type.

[0324] Typically, after one or more thermo-mechanical treatment steps, the vulcanizing agent is incorporated into the material, preferably together with vulcanization accelerators and / or retarders, in a final treatment step, i.e. production step (ii), in which the temperature is generally kept below 120°C and preferably below 100°C, in order to prevent any unwanted pre-vulcanization phenomena. Subsequently, the vulcanizable compound thus obtained can be subsequently calendered or extruded, for example in the form of a sheet, for example to form shaped rubber elements (for example tread bands), which are incorporated into the tire according to known techniques and subjected to vulcanization.

[0325] Another aspect of the present application consists of a tire tread band comprising an elastomeric compound obtained from the elastomeric composition according to the present application.

[0326] Preferably, the component is a tread band comprising at least 50%, preferably at least 70% or 90% or 95% or 100% of the elastomeric compound according to the present application.

[0327] Another aspect of the present application is a tire for vehicle wheels comprising a tread band according to the present application.

[0328] In the tire of the present application, the tread band comprises or consists of the present elastomeric compound.

[0329] The tire according to the present application can be a tire for vehicles having two, three or four wheels and can be used for summer or winter use or for all seasons.

[0330] The tire of the present application is suitable for four-wheeled vehicles for use on roads, for example it can be a tire suitable for equipping vehicles with medium-high engine capacity for the transport of people (maximum chord length measurements of 195 mm to 245 mm).

[0331] The tire according to the present application can be suitable for electric vehicles.

[0332] The tyre according to the application can be a tyre for small commercial vehicles or for high performance vehicles (HP high performance - UHP ultra high performance) having a maximum chord dimension of, for example, 145 mm to 355 mm.

[0333] These tyres are preferably mounted on a rim having a seat diameter equal to or greater than 13 inches, preferably not greater than 24 inches, more preferably between 16 inches and 23 inches.

[0334] The tyre according to the application can be a tyre for passenger vehicles, including car tyres, for example high performance tyres, and tyres for light transport vehicles, for example vans, campers, pick-ups, typically having a total mass equal to or less than 3500 kg under full load.

[0335] The tyre of the application can be a HP (high performance) or UHP (ultra high performance) tyre intended for equipping vehicles mainly used for transporting people, for example saloon cars, small vans, family, SUV (Sport Utility Vehicle) and / or CUV (Cross Utility Vehicle), typically tyres which allow high speed travel.

[0336] High and ultra high performance tyres are in particular those which allow reaching speeds higher than at least 160 km / h, higher than 200 km / h up to more than 300 km / h. Examples of such tyres are in particular those according to the E.T.R.T.O. (European Tyre and Rim Technical Organisation) standards belonging to the categories "T", "U", "H", "V", "Z", "W", "Y" for four-wheel high-power vehicles. Typically, the cross-section width of tyres belonging to these categories is equal to or greater than 185 mm, preferably not greater than 325 mm, more preferably between 195 mm and 325 mm. These tyres are preferably mounted on a rim having a seat diameter equal to or greater than 15 inches, preferably not greater than 24 inches, more preferably between 17 inches and 22 inches. SUV and CUV mean vehicles with a raised distribution, typically four-wheel drive, typically having a displacement greater than or equal to 1800 cc, more preferably between 2000 cc and 6200 cc. Preferably, the mass of these vehicles is greater than 1400 Kg, more preferably between 1500 Kg and 3000 Kg.

[0337] The tyre of the application can also be used in vehicles other than the above-mentioned cars, for example in high performance road and sports motorcycles, i.e. motorcycles capable of reaching speeds even higher than 270 km / h. Such motorcycles are those belonging to the categories typically identified with the following classifications: super sports, super sports touring, sports touring, and for lower speed classes: scooter, street endurance and custom.

[0338] The term "tyre for motorcycle wheels" means a tyre having a high curvature ratio (typically greater than 0.200) which is able to reach high angles of inclination (roll angles) of the motorcycle symmetry plane with respect to the vertical plane during the motorcycle cornering.

[0339] In a preferred embodiment, the tyre of the application is a motorcycle tyre, more preferably of the "big endurance" type, in which the tread band comprises the elastomeric compound of the application.

[0340] In this preferred embodiment, the tyre of the application is intended to be mounted on the front and / or rear wheel of a "big endurance" (or "big adventure" or "dual purpose") type motorcycle, i.e. of large displacement, power and mass, designed to travel both on paved roads and on off-road roads. The cylinder capacity of these motorcycles is generally equal to or greater than 1000 cm 3 , the power is equal to or greater than 100 cv, the maximum torque is equal to or greater than 100 Nm and the mass is equal to or greater than 180 kg.

[0341] In this particular application, the tyre of the application is particularly advantageous as it combines high tear resistance and wear resistance, particularly useful in off-road travel, with excellent grip in cold and wet conditions, which can be encountered in road travel.

[0342] Examples of "big endurance" motorcycles are the BMW GS 1250 R, the KTM 1290 Super Adventure R and the Honda CRF 1100 L Africa Twin.

[0343] In an embodiment, the tyre according to the application comprises at least:

[0344] - a carcass structure comprising at least one carcass layer having opposite side edges associated with respective bead structures;

[0345] - possibly a pair of sidewalls applied to the lateral surfaces of the carcass structure in axially external positions, respectively;

[0346] - possibly a belt structure applied in radially external positions with respect to the carcass structure;

[0347] - a tread band applied to the carcass structure or to the belt structure, if present, in radially external positions,

[0348] - possibly a layer of elastomeric material, known as cushion layer, applied in radially internal positions with respect to the tread band,

[0349] wherein at least one component, preferably at least the tread band, comprises or preferably consists of the elastomeric compound according to the application.

[0350] In one embodiment, the tyre according to the present application is a tyre for a bicycle wheel. The tyre for a bicycle wheel typically comprises a carcass structure turned around a pair of bead cores at the beads, and a tread band comprising and preferably consisting of the elastomeric compound of the present application, arranged in a radially external position with respect to the carcass structure.

[0351] The tyre according to the present application can be manufactured according to a process comprising:

[0352] - building components of the green tyre on at least one forming drum;

[0353] - shaping, moulding and vulcanizing the tyre;

[0354] wherein building at least one component of the green tyre comprises:

[0355] - manufacturing at least one green component comprising or preferably consisting of the elastomeric compound according to the present application. Preferably, the at least one green component is a tread band.

[0356] The Applicant has found that, by virtue of the features of the tread band prepared with the present elastomeric compound, it is possible to manufacture a tyre which achieves a significant improvement in wet running performance, while maintaining high mileage, and an optimal balance of significantly conflicting properties. BRIEF DESCRIPTION OF DRAWINGS

[0357] Figure 1 A half-section view of a tyre for vehicle wheels according to the present application is schematically shown.

[0358] Figure 2 A perspective view of a typical endurance rear knobby motorcycle tyre according to a preferred embodiment of the present application is shown. DETAILED DESCRIPTION

[0359] Figure 1 A tyre according to the present application is exemplified.

[0360] REFERRING TO Figure 1 “a” indicates the axial direction and the “x-x” trace of the equatorial plane of the tyre indicates the radial direction. For simplicity, Figure 1 Only a portion of the tyre is shown, the remaining portion not shown being identical and arranged symmetrically with respect to the radial direction “r”.

[0361] The reference (100) indicates, in Figure 1 , a tyre for motor vehicle wheels according to the present application formed by a plurality of structural elements.

[0362] A tyre (100) for four-wheeled vehicles comprises at least one carcass structure comprising at least one carcass layer (101) having opposite end flaps engaged with respective annular anchoring structures (102), known as bead cores, possibly associated with a bead filler (104). The tyre region comprising the bead core (102) and the filler (104) forms a reinforcing annular structure (103), i.e. a so-called bead, for anchoring the tyre to a respective unshown mounting rim.

[0363] The carcass structure is generally of the radial type, i.e. the reinforcing elements of the at least one carcass layer (101) lie on a plane comprising the rotation axis of the tyre and substantially perpendicular to the equatorial plane of the tyre. Said reinforcing elements can consist of textile cords, for example of rayon, nylon, polyester, for example polyethylene naphthalate (PEN), or metal cords. Each reinforcing annular structure is associated with the carcass structure by folding back the opposite side edges of the at least one carcass layer (101) around the annular anchoring structure (102), thus forming the so-called carcass flaps (101a) as shown in Figure 1

[0364] In one embodiment, the coupling between the carcass structure and the reinforcing annular structure can be provided by applying a second carcass layer (not shown in the drawings) in an axially external position with respect to the first carcass layer. Figure 1

[0365] In an axially external position of each reinforcing annular structure (103) an anti-abrasion strip (105) is arranged. Preferably, each anti-abrasion strip (105) is arranged at least in an axially external position with respect to the reinforcing annular structure (103), extending at least between the sidewall (108) and the portion radially below the reinforcing annular structure (103).

[0366] Preferably, the anti-abrasion strip (105) is arranged so as to surround the reinforcing annular structure (103) along the axially internal and external regions and the radially below region of the reinforcing annular structure (103), so as to be interposed between the reinforcing annular structure and the wheel rim when the tyre (100) is mounted on the rim.

[0367] Said carcass structure is associated with a belt structure (106) comprising one or more belt layers (106a), (106b) placed in radial superposition with respect to each other and with respect to the carcass layer, typically having metal reinforcing cords. Such reinforcing cords can be cross-oriented with respect to the circumferential development direction of the tyre (100). The "circumferential" direction means the direction substantially coinciding with the rotation direction of the tyre.

[0368] ​​At least one zero-degree reinforcing layer (106c) (commonly referred to as "0° band") can be applied in a radially outermost position with respect to the belt layers (106a), (106b), which generally incorporates a plurality of reinforcing cords, typically textile cords, optionally textile or metal cords combined with each other, oriented in a substantially circumferential direction, thus forming an angle of a few degrees (for example an angle between 0° and 6°) with respect to the equatorial plane of the tyre, and coated with an elastomeric material.

[0369] In a radially outer position with respect to the belt structure (106), a tread band (109) is applied, comprising a vulcanized elastomeric compound obtained by vulcanizing an elastomeric composition according to the present application.

[0370] Furthermore, in an axially outer position on the lateral surfaces of the carcass structure, respective sidewalls (108) of elastomeric material are further applied, each extending from one of the lateral edges of the tread (109) at the respective reinforcing annular structure (103).

[0371] In a radially outer position, the tread band (109) comprising the elastomeric compound according to the present application has a rolling surface (109a) intended to come into contact with the ground. Depending on the intended use, the rolling surface is smooth, as shown in Figure 1 , or the rolling surface has circumferential and / or transversal grooves and notches (not shown in Figure 1 ).

[0372] A cushion layer (111) is arranged between the belt structure (106) and the tread band (109).

[0373] A strip (110) of elastomeric material, commonly referred to as "microsidewall", which is generally obtained by co-extrusion with the tread band (109) and allows to improve the mechanical interaction between the tread band (109) and the sidewall (108), can optionally be provided in the junction zone between the sidewall (108) and the tread band (109).

[0374] Preferably, the end portion of the sidewall (108) directly covers the lateral edge of the tread band (109).

[0375] Typically, a rubber layer (112) commonly referred to as "liner", which provides the necessary impermeability to inflation of the tyre, can also be provided in a radially inner position with respect to the carcass layer (101).

[0376] The reinforcing annular structure (103) of the tyre can comprise a further protective layer, commonly referred to as "chafer" (121) or protective strip, and having the function of increasing the rigidity and integrity of the bead structure (103).

[0377] The bead filler (104) is generally composed of a plurality of cords incorporated in a cross-linked elastomeric material, and said plurality of cords is generally made of textile material (for example aramid or rayon) or metal material (for example steel cords).

[0378] The rigidity of the tire side wall (108) can be improved by providing the reinforcing annular structure (103) with a reinforcing layer (120), commonly referred to as "fins" or additional strip-like inserts.

[0379] The fins (120) are reinforcing layers that are wrapped around the respective anchoring annular structures (102) and bead fillers (104) so as to at least partially enclose them, said reinforcing layers being arranged between the at least one carcass layer (101) and the reinforcing annular structure (103). Typically, said fins are in contact with said at least one carcass layer (101) and said reinforcing annular structure (103).

[0380] The fins (120) typically comprise a plurality of metal or textile cords incorporated in a cross-linked elastomeric material.

[0381] The building of the tire (100) as described herein can be carried out by assembling, on a molding drum, not shown, respective semi-finished products suitable for forming the tire components, by means of at least one assembly device.

[0382] At least one portion of the components intended to form the carcass structure of the tire can be built and / or assembled on the molding drum. More particularly, the molding drum is intended to first receive a possible liner, then the carcass structure. Thereafter, a device, not shown, engages coaxially with one of the annular anchoring structures around each end flap, places the outer sleeve comprising the belt structure, the cushion layer and the tread band in a coaxially central position around the cylindrical carcass sleeve, and according to the annular configuration, the carcass sleeve is shaped by radial expansion of the carcass structure, thereby causing it to be applied on the radially inner surface of the outer sleeve.

[0383] After building the green tire, a molding and vulcanization process is generally carried out in order to determine the structural stability of the tire by cross-linking of the elastomeric composition, as well as to impart the desired tread pattern on the tread band and any distinctive graphic logo at the side wall.

[0384] As Figure 2As shown, the tyre 1 according to the application is of the type for "big endurance" motorcycles, having a profile, i.e. it comprises a plurality of transversal and circumferential grooves which delimit a plurality of mutually spaced blocks. The tyre 1 has a "camber ratio" defined by the ratio between the camber and the maximum radial section width. Preferably, in the case of big endurance rear tyres, the camber of the tyre 1 is between about 40 mm and about 60 mm. The camber ratio of the tyre 1 is between about 0.25 and about 0.35, for example equal to about 0.26. In the case of front tyres, the camber 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 which has a void / fill ratio between 0.4 and 0.65, preferably between 0.5 and 0.6, for example equal to 0.51 in the case of a rear tyre measured as 170 / 60 / R17 and equal to 0.56 in the case of a rear tyre measured as 150 / 70 / R18.

[0385] The following examples are now provided for illustrative and non-limiting purposes only.

[0386] Experimental part

[0387] In this experimental part, the components of the compositions are expressed in phr (parts per hundred of rubber). All percentages are expressed as weight percentages, unless otherwise stated.

[0388] Analytical methods

[0389] % content of double bonds: content of double bonds in the polymer as supplied, determined by 1H-NMR.

[0390] Weight average molecular weight: weight average molecular weight of the polymer as supplied, measured by GPC (Gel Permeation Chromatography) according to known techniques, for example according to ISO 13885 method.

[0391] Glass transition temperature (Tg): glass transition temperature Tg of the elastomeric polymer and of the vulcanizing compounds, determined by the peak of tan delta, measured by Dynamic Mechanical Analysis (DMA).

[0392] In detail, the samples were analyzed by means of a 150 (GABO) apparatus by means of a temperature scan from -80°C to +30°C with a temperature increase of 2°C / min, applying a dynamic tensile deformation of 0.1% at a frequency of 1 Hz. The test specimens had the following dimensions: thickness 1 mm, width 10 mm, length 46 mm, reference length 29 mm (expressed as the free length involved in the deformation when the ends of the specimen are blocked by the two clamps).

[0393] Tear strength was measured according to ASTM D624B.

[0394] The abrasion resistance was evaluated according to DIN 53516 standard.

[0395] The kinetic properties of the compounds (MDR) were evaluated according to ISO 6502-3 (2018) using a rotorless rheometer under the conditions of 170°C for 10 minutes of vulcanization.

[0396] The Mooney viscosity: the ML (1+4) viscosity was measured at 100°C according to ISO 289-1 :2015 standard. For higher molecular weight polymers (E-SBR and S-SBR), the ML (3+4) viscosity was measured again at 160°C according to ISO 289-1 :2015 standard.

[0397] The density was measured according to ISO 2781 (2018).

[0398] The static mechanical properties (CA1 load at 100% elongation, CA3 load at 300% elongation, CR tear strength, AR% elongation at break%) were measured on samples of the elastomeric material vulcanized at 170°C for 10 minutes according to ISO 37:2017 standard at 23°C.

[0399] The compression dynamic mechanical properties E’ and tan delta were measured using an Instron model 1341 dynamic device in tensile-compression mode as described herein. A test piece of vulcanized material (170°C for 10 minutes) having a cylindrical shape (length = 25 mm; diameter = 14 mm), preloaded in compression to a longitudinal strain of 25% relative to the initial length and maintained at a predetermined temperature of 10°C, 23°C or 70°C throughout the test duration, was subjected to a dynamic sinusoidal strain having an amplitude of ± 3.5% relative to the length under preloading at a frequency of 100 Hz. The dynamic mechanical properties are expressed in dynamic elastic modulus (E’) and tan delta (loss factor). The tan delta value is calculated as the ratio between the viscous dynamic modulus (E”) and the dynamic elastic modulus (E’).

[0400] The hardness in IRHD degrees (at 23°C and 70°C) was measured on samples of the above elastomeric material vulcanized at 170°C for 10 minutes according to ISO 48:2007 standard.

[0401] Preparation of the elastomeric compounds

[0402] The reference elastomeric compounds REF1 and REF2 and INV1 and INV2 according to the application were prepared starting from the elastomeric compositions shown in the following Table 1:

[0403] Table 1: Elastomeric compositions (phr)

[0404]

[0405]

[0406] wherein:

[0407] * Extender oil; total phr in brackets (polymer + oil);

[0408] NEOCIS BR 60 is a solid polybutadiene from ENI produced with a neodymium organometallic catalyst, having a high cis content (minimum 97%), a weight average molecular weight of about 550000 g / mol; NEOCIS BR 60, a solid polybutadiene prepared in solution, produced with a neodymium organometallic catalyst, having a high cis content (minimum 97%), a weight average molecular weight of about 550000 g / mol;

[0409] SBR 1723 TDAE from Sibur is a solid styrene butadiene copolymer (E-SBR) cold emulsion polymerized using a mixture of rosin acid and fatty acid soaps as emulsifiers, Tg of about -50°C, Mooney viscosity of about 48 MU, styrene content of about 23%, oil extended with 37.5 parts of treated Distilled Aromatic Extracted Oil (TDAE) extender oil per 100 phr of dry polymer;

[0410] SBR 1739 is from Synthos SB 1739-Schkopau, a solid styrene butadiene copolymer (E-SBR) cold emulsion polymerized using a mixed rosin / fatty acid soap, oil extended with 37.5 parts of oil extender oil per 100 phr of dry polymer, Tg of about -40°C;

[0411] TUFDENE E680 from Asahi Kasei is a solid styrene butadiene copolymer solution polymerized functionalized at the chain end with a functionalized terminator, extended with 37.5 parts of TDAE oil per 100 phr of dry polymer, styrene content of about 34%, vinyl of about 58% (with respect to butadiene), Tg equal to about -25°C (extended oil polymer) and Mw of about 1470000 g / mol;

[0412] HPR 620 from JSR is a commercial styrene-butadiene copolymer functionalized with polyorganosiloxane multi-branched coupling agent chains, solution polymerized as described in SG10201800553S(A), extended with 25 parts of TDAE oil per 100 phr of dry polymer, having a weight average molecular weight of about 1000000 g / mol, a styrene content of about 40%, a vinyl of about 25%, a Tg equal to about -33°C and a Mooney viscosity of about 80 MU [Mooney viscosity ML (3+4) at 160°C];

[0413] POLYVEST 130 from Evonik is a stereo-specific liquid polybutadiene (PB) with a high content of 1,4-cis double bonds (77% of 1,4-cis double bonds, 22% of 1,4-trans double bonds, 1% of 1,2-vinyl double bonds), Tg of -99°C, weight average molecular weight of 12000 g / mol;

[0414] Vestenamer 3010 from Cray Valley (Dow) is a high molecular weight (Mn 45000) liquid (25% styrene) butadiene styrene copolymer (PBS), Tg of - 57°C; 100 is a low molecular weight (Mn 4500) liquid (25% styrene) butadiene styrene copolymer (PBS), Tg of -57°C;

[0415] VIVATEC 500 from Hansen & Rosenthal is a process oil (treated distillate aromatic extract, TDAE);

[0416] Tetrasulfide is Bis[3-(trimethylsilyl)propyl]tetrasulfide JH-S69 from ChemSpec Ltd;

[0417] NOVARES TT30 from Novares is a hydrocarbon resin produced by polymerization of C9 / C10 unsaturated aromatic hydrocarbons;

[0418] Novares TT90 from Novares is a hydrocarbon resin produced by polymerization of C9 / C10 unsaturated aromatic hydrocarbons;

[0419] Zinc oxide is RHENOGRAN ZNO from Zincol Ossidi;

[0420] 6PPD is N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine SANTOFLEX 6PPD from Eastman;

[0421] Zeosil 1165 from Rhodia is a highly dispersible amorphous precipitated silica;

[0422] N234 is a high surface area carbon black (STSA 112m 2 / g);

[0423] TBBS is N-tert-butyl-2-benzothiazolesulfenamide from Huatai;

[0424] Sulfur is from Lanxess 90-20 is a mixture of insoluble / soluble sulfur in a ratio of 90:10 plus 20% oil.

[0425] REF1 is a reference elastomer composition for the tread band of a "Grand-Prix" motorcycle tire, a composition comprising a mixture of diene tread polymers and a conventional plasticizing mixture.

[0426] REF2 is an elastomeric composition for tire treads prepared by modifying the reference composition REF1 according to the industrial knowledge to improve wet performance, i.e. by substituting the emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) (SBR1739) and part of the polybutadiene (BR) with a solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a high molecular weight chain end like TUF DENE E680.

[0427] INV1 is an elastomeric composition according to the present application wherein the other components are equal, the composition REF1 is modified by introducing 54 phr of a solution-polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branching coupling agent (HPR620) instead of 44 phr of an emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) (SBR1739) and 10 phr of a high-cis polybutadiene (BR) (NEOCIS BR 60).

[0428] INV2 is an elastomeric composition according to the present application wherein the other components are equal, the composition INV1 is modified by introducing liquid polymers (POLYVEST 130 and RICON 100) instead of the resin (NOVARES TT30) and part of the process oil (VIVATEC 500).

[0429] The elastomeric compositions of Table 1 maintain substantially the same total plasticizer content.

[0430] The reference elastomeric compounds according to the present application are prepared from the above compositions according to the following procedure.

[0431] The mixing of the components is carried out in two steps using an internal mixer (Banbury, Intermix or Brabender).

[0432] In the first step (1), all the ingredients except the vulcanizing agents and accelerators are introduced. The mixing is continued for a time of at most 5 minutes, reaching a temperature of about 145°C. Subsequently, in a second trial (2) carried out again using the internal mixer, the vulcanizing agents and accelerators are added and the mixing is continued for 4 minutes while keeping the temperature below 100°C. The compound is then unloaded. After cooling and at least 12 hours from preparation, some samples of the compound are vulcanized in a press at 170°C for 10 minutes to obtain test specimens useful for the mechanical properties.

[0433] Properties of the elastomeric compounds

[0434] The main static and dynamic properties of the compounds prepared from the above compositions, measured with the above methods, are shown in the following Table 2:

[0435] Table 2

[0436]

[0437]

[0438] From the data relating to the tensile test, it can be seen that the INV1 compound shows a significant increase in the value of Ca3(10.03 MPa) compared to the REF1 and REF2 compounds (8.35 and 8.53 MPa), in particular indicative of high mileage, due to the introduction into the composition of a solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent (HPR620). When a liquid polymer is introduced into the composition instead of a process oil and a resin, as in the case of the INV2 compound, the value of the Ca3load returns to values comparable to the reference (8.85 MPa). The static mechanical properties (CA3, CR, AR%) of the INV2 compound, in which a solution-polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent and a liquid polymer are used in combination, are even better and are indicative of high durability and mileage.

[0439] The compounds INV1 and INV2 according to the present application have IRHD hardness values at 23 °C lower than the reference compounds, indicative of good performance on wet surfaces.

[0440] Surprisingly, contrary to the substitution of part of the polybutadiene (BR) and of the emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) with a traditional solution-polymerized solid styrene-butadiene copolymer (S-SBR) (Tufdene E680, REF2), the specific properties of tear resistance and abrasion resistance, attributable to the high-cis polybutadiene and to the emulsion-polymerized solid styrene-butadiene copolymer (E-SBR) (REF1), are not compromised by the use of a solution-polymerized solid styrene-butadiene copolymer (S-SBR) functionalized with a high-molecular-weight multi-branched coupling agent (INV1), nor by the further substitution of the process oil and of the resin with a liquid polymer (INV2).

[0441] These results are highlighted by the corresponding values of tear and abrasion, which for both INV1 and INV2 are in line with the values of REF1 and in both cases are higher than the values of REF2, especially in terms of abrasion.

[0442] Furthermore, considering that the lower the ratio between E' and tan delta (grip index) the better the wet grip at 23°C, the materials of the present application highlight an unexpected improvement in terms of grip compared to REF1, obtained by introducing a solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a multi-branched coupling agent instead of a partial polybutadiene (BR) and an emulsion polymerized solid styrene butadiene copolymer (E-SBR) (INV1) and further substituting process oil and resin with liquid polymers (INV2).

[0443] The latter material shows a significant improvement in terms of wet grip compared to REF1, predicted by the lower grip index value at 23°C, while maintaining consistent wear and tear properties.

[0444] By introducing a solution polymerized solid styrene butadiene copolymer (S-SBR) functionalized with a high molecular weight Mw multi-branched coupling agent into the INV1 and INV2 compounds, one would expect an increase in the stiffness of the material, therefore a worsening of the wet performance.

[0445] However, surprisingly, both the INV1 and especially the INV2 compounds show E', tan delta and grip index values that are indicative of their excellent behavior when wet.

[0446] From the measurements of rheological properties (MDR 170°C, 10 minutes), it is observed that the vulcanization kinetics is substantially maintained between the reference compounds REF1, REF2 and those of the present application, INV1, INV2.

[0447] In conclusion, the compounds INV1 and INV2 according to the present application show the best combination of hardness, tear resistance and wear resistance, modulus E' and hysteresis, indicative of long mileage of the tire and improved wet performance.

[0448] On the other hand, this result is not achieved by simply using a traditional solution polymerized solid styrene butadiene copolymer (S-SBR) as shown in the reference compound REF2, which, despite having good wet performance, has a significant loss in terms of mileage and tear resistance.

Claims

1. An elastomeric composition for a tire for vehicle wheels 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, wherein the sum of plasticizing oil and, if present, liquid polymer and resin is 20 to 90 phr, 100 phr of a mixture of solid diene elastomeric polymers, wherein the mixture of solid diene elastomeric polymers comprises the following components: 10 to 50 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 300000 and 600000 g / mol and a content of cis double bonds of at least 95%, 10 to 70 phr of at least one emulsion polymerized solid styrene butadiene copolymer (E-SBR) having a Tg of -60 to -20 °C, a Mooney viscosity at 160 °C of between 30 and 70 MU, and a styrene amount of between 15 and 50%, and 10 to 80 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent having: a weight average molecular weight Mw greater than 500000 g / mol, and / or a styrene amount of between 25 and 50% and a vinyl amount of between 10 and 50%, and / or a Tg of between -50 and -20 °C, and / or a Mooney viscosity at 160 °C of between 60 and 100 MU, wherein the properties of the solid diene elastomeric polymers of the mixture are measured according to the methods indicated in the experimental section, at least 40 phr of at least one reinforcing filler, and at least 1 phr of at least one vulcanizing agent.

2. The elastomeric composition according to claim 1, wherein: the liquid polymer can be present in an amount of between 0 and 28 phr; the resin can be present in an amount of between 0 and 15 phr; the plasticizing oil is present in an amount of between 20 and 50 phr; and the sum of plasticizing oil and, if present, liquid polymer and resin is 25 to 80 phr.

3. The elastomeric composition according to claim 2, wherein, the liquid polymer can be present in an amount of between 0 and 23 phr; the resin can be present in an amount of between 3 and 10 phr; the plasticizing oil is present in an amount of between 25 and 45 phr; and the sum of plasticizing oil and, if present, liquid polymer and resin is 30 to 60 phr.

4. The elastomer composition of claim 1, wherein, the mixture of solid diene elastomeric polymers comprises the following components: 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 15 to 75 phr of at least one solution polymerized solid styrene-butadiene copolymer (S-SBR) chain-functionalized with a multi-branched coupling agent.

5. The elastomeric composition of claim 4, wherein, The mixture of solid diene elastomer polymers comprises the following components: 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 30 to 65 phr of at least one solution polymerized solid styrene-butadiene copolymer chain functionalized with a multi-branching coupling agent (S-SBR).

6. The elastomeric composition of claim 5, wherein, The mixture of solid diene elastomer polymers consists of the following components: 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 30 to 65 phr of at least one solution polymerized solid styrene-butadiene copolymer chain functionalized with a multi-branching coupling agent (S-SBR).

7. The elastomer composition according to claim 1, wherein: The solid polybutadiene (BR) has a weight average molecular weight Mw of 350000 to 550000 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 to -25°C, a Mooney viscosity between 40 MU to 60 MU and a % styrene content between 20 to 45%, and The solution polymerized solid styrene butadiene copolymer chain functionalized with a multi-branching coupling agent (S-SBR) has a weight average molecular weight Mw of more than 800000 g / mol, a styrene amount between 30 to 45% and a vinyl amount between 15 to 40%, a Tg between -45 to -25°C and / or a Mooney viscosity measured at 160°C between 70 MU to 90 MU.

8. The elastomer composition of claim 1, wherein, The mixture of solid diene elastomer polymers comprises the following components: 25 to 35 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370000 to 550000 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 to -28°C, a Mooney viscosity between 45 MU to 55 MU and a % styrene content between 22 to 42%, 30 to 65 phr of at least one solution polymerized solid styrene-butadiene copolymer chain functionalized with a multi-branching coupling agent (S-SBR) having a weight average molecular weight Mw of more than 800000 g / mol, a styrene amount between 30 to 45% and a vinyl amount between 15 to 40%, a Tg between -45 to -25°C and a Mooney viscosity measured at 160°C between 70 MU to 90 MU.

9. The elastomeric composition of claim 8, wherein, The mixture of solid diene elastomer polymers consists of the following components: 25 phr to 35 phr of at least one solid polybutadiene (BR) having a weight average molecular weight Mw between 370 000 g / mol and 550 000 g / mol and a content of cis double bonds of at least 97%, 10 phr 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 between 45 MU and 55 MU and a % styrene content between 22% and 42%, 30 phr to 65 phr of at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a multi-branched coupling agent having a weight average molecular weight Mw greater than 800 000 g / mol, a styrene amount between 30% and 45% and a vinyl amount between 15% and 40%, a Tg between -45°C and -25°C and a Mooney viscosity measured at 160°C between 70 MU and 90 MU.

10. The elastomeric composition according to claim 1, comprising at least 50 phr of at least one reinforcing filler.

11. The elastomeric composition of claim 1, wherein, The multi-branched coupling agent of the at least one solution polymerized solid styrene butadiene copolymer (S-SBR) chain functionalized with a multi-branched coupling agent is a polyorganosiloxane.

12. An elastomeric compound for a tread band of a tyre, obtained by mixing and vulcanizing the elastomeric composition according to any one of claims 1 to 11.

13. The elastomeric compound according to claim 12, having one or more of the following characteristics: a Mooney viscosity higher than 50 MU; Density between 1.100 g / cm 3 and 1.500 g / cm 3 ; a load at 300% elongation higher than 8.50 MPa; a breaking load higher than 17 MPa; an elongation at break higher than 500%; an IRHD hardness at 23°C between 60 and 70 degrees IRHD; a tear strength at 23°C higher than 45.00 N / mm; Material loss less than 75.00 mm 3 Wear resistance; a dynamic elastic modulus E’ at 23°C less than 10.00 MPa; a loss factor (tan delta) calculated as the ratio between the viscous dynamic modulus (E”) and the dynamic elastic modulus (E’) at 23°C, not less than 0.370 and measured according to the method indicated in the experimental part.

14. A tread band for a tyre for vehicle wheels, comprising the elastomeric compound according to claim 12.

15. A tyre for vehicle wheels, comprising the tread band according to claim 14.

16. The tyre according to claim 15, for motorcycle wheels.

17. The tyre according to claim 15, for car wheels.

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