Compositions for elastomeric compounds and tyres for vehicle wheels comprising reversible cross-linking modifying agents

Abstract

The present invention relates to compositions for elastomeric compounds for high- performance tyres, such as motorsport tyres, comprising specific reversible cross- linking modifying agents, tyre components and vehicle wheel tyres comprising them. The present elastomeric compounds, by virtue of their particular hysteretic behaviour, allow the manufacture of tyres characterised by high roadholding and handling in all driving conditions.

Description

[0001] TITLE

[0002] “Compositions for elastomeric compounds and tyres for vehicle wheels comprising reversible cross-linking modifying agents”

[0003] DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to compositions for elastomeric compounds, preferably but not limited to high-performance tyres, in particular for racing tyre treads, comprising particular reversible cross-linking modifying agents, tyre components and vehicle wheel tyres comprising them.

[0006] Prior art

[0007] High-performance tyre technology is constantly evolving, with intense research and development to improve performance, durability and safety.

[0008] Racing tyres come in various sizes and types, suited to specific racing disciplines, and are typically made with specialised elastomeric compounds, designed to provide maximum grip and traction on different racing surfaces (e.g. asphalt, soil, or wet conditions).

[0009] In a racing context, it is desirable for the tyre to provide maximum grip both initially at the start and later in the race to allow the vehicle to accelerate, brake and take comers effectively and quickly, even at the expense of greater wear.

[0010] Tyre grip is influenced by several factors, including road surface conditions, type of compound, operating temperature, inflation pressure and tread pattern.

[0011] Typically, tyre performance and specifically road grip are profoundly affected by temperature: in fact, cold tyres may lack grip, while overheated ones may decrease in performance.

[0012] To maximise grip, the correct choice of tyre and, in particular, of its constituent compounds, based on the track conditions and expected temperatures, therefore becomes crucial.

[0013] Highly dissipative compounds, including materials with high hysteresis, may give the tyre greater grip on the ground. In fact, the energy dissipated under deformation contributes to creating a sort of “dynamic adhesion”, improving the grip. Furthermore, a higher hysteresis of the materials may be advantageous as it is associated with a faster and more controlled response during manoeuvres. However, the Applicant has realised that satisfactory grip cannot be imparted to the materials at all tyre operating temperatures simply by selecting the elastomeric polymers to be used based on their glass transition temperature (Tg) values. In fact, elastomeric compounds with high Tg polymers that typically have maximum grip performance at operating temperatures around 80 °C - 120 °C (hereinafter “hot”), typical of sportier driving, prove to be too rigid and with poor grip at the lower temperatures of the starting step. To overcome this, during races the tyres are normally pre-heated (warm up), which raises the temperature of the compounds to the operating temperature at which they perform best.

[0014] Instead, it would be desirable to have elastomeric compounds that, even at initial temperatures around 50 °C - 70 °C (hereinafter referred to as “cold”), had good grip so as to guarantee satisfactory road grip performance for all phases of the race and at all temperatures. This result does not appear to be achievable using compounds with lower Tg polymers as the improved cold grip is not accompanied by sufficient dissipative behaviour when hot. At the level of the elastomeric material of the tread, it is therefore difficult to reconcile these opposing tendencies and, in practice, one settles for the best possible compromise, i.e. compounds that perform especially when hot and which must be pre-heated at the start of the race. In any case, a strong decrease in hysteresis is generally observed at higher temperatures.

[0015] In order to vary the properties of elastomeric materials for tyres, different modifying agents have been used over time, for example modifying agents capable of binding to diene polymers and then reversibly cross-linking with the formation of hydrogen bonds.

[0016] For example, US9394434 addresses how to reduce compound hysteresis by improving the dispersion of the reinforcing filler. In this regard, the document describes elastomeric compositions characterised by low hysteresis and high stiffness comprising modifying agents of formula

[0017] Q - Sp - A wherein Q comprises a nitrogen dipole, Sp represents a spacer linking A to Q, and A comprises a nitrogenous associative group.

[0018] Specifically, the nitrogenous associative group of A may be any group capable of associating with itself through hydrogen, ionic and / or hydrophobic bonds, for example an oxazoline or a thiazoline, preferably an imidazolinyl, ureyl, bis-ureyl, ureidopyrimidyl and triazolyl group according to formulas (II) - (VI) reported therein. The group Q, which preferably comprises a nitrile oxide, a nitrone or an iminonitrile, is capable of covalently binding to the elastomer, preferably by [3+2] cycloaddition. The document does not discuss or suggest any particular value for the formation constant KA of complexes of associative groups of A nor does it show or teach that modifying agents in which such groups have certain specific values of KA may increase the hysteresis of the corresponding compounds incorporating them.

[0019] The only associative group actually synthesised, the imidazolidinone (Formula XII), in light of its structural similarity to the N-dodecyl-imidazolidinone, the object of selfassociation studies, would have a KA estimated by the literature around 1.1 M-1 (Johnson, DW; Hof, F.; Palmer, LC; Martin, T.; Obst, U.; Rebek, Jr., J. Glycoluril Ribbons Tethered by Complementary Hydrogen Bonds. Chem. Commun. 2003, No. 14, 1638-1639. https: / / doi.org / 10.1039 / B303508E). Another associative group suggested here is ureido-pyrimidone (formula V) which due to structural similarity would have a KA estimated by the literature of about 6 x 107M-1 (Ligthart, GBWL; Ohkawa, H.; Sijbesma, RP; Meijer, EW Complementary Quadruple Hydrogen Bonding in Supramolecular Copolymers. J. Am. Chem. Soc. 2005, 127 (3), 810- 811. https: / / doi.Org / 10.1021 / ja043555t. ).

[0020] Patent application US20220403056A1 addresses the problem of degradation of the mechanical properties of vulcanised compounds which occurs in use as a result of irreversible rupture of the lattices and network of reinforcing fillers. The document describes vulcanised elastomeric compositions comprising hydrogen bonding networks and covalent bonding networks. In these compositions, elastomeric polymers are reacted in solution with a functionalising agent which includes (i) at least one group capable of forming a covalent bond with the elastomeric polymer and (ii) at least one moiety capable of forming a hydrogen bond. As regards this last portion, the document indicates binding constant (k) values greater than 103M’1(par. 25). The experimental part shows that the hysteresis of the materials incorporating the so-called functionalising agents, tested not above 60 °C, decreases or remains constant compared to the controls.

[0021] Document WO2021 / 260635A1 deals with compositions for elastomeric compounds for tyres, including monotetrazole compatibilising agents characterised by precise activation temperatures, tyre components and tyres containing them. This document does not consider the self-assembly of these tetrazoles nor does it provide association constant Ka values. US2006084730A1 describes a Q-A-B agent, wherein Q comprises a nitrogencontaining dipolar group which may give 1 , 3-d ipolar addition on unsaturated carboncarbon bonds; B is an oxazoline, thiazoline, alkoxysilane or alkyltin group and A is a linking atom or group bridging Q and B, used to improve the dispersion of fillers in polymeric compositions. This document does not consider the self-assembly of groups B nor provides association constant Ka values for them, but rather focuses on their reactivity with the reactive surface groups of the charges.

[0022] In conclusion, the above-mentioned documents do not teach how to give elastomeric compounds a high cold and hot grip but rather suggest that the introduction of modifying agents, capable of binding to diene polymers and then reversibly cross-linking with the formation of hydrogen bonds, would lead to a decrease in the hysteresis of the compounds that comprise them.

[0023] Summary of the invention

[0024] The Applicant has surprisingly found that it is possible to ad-hoc increase the hysteresis of a conventional elastomeric tyre compound, without significantly increasing the rigidity and hardness thereof, in order to manufacture tyres characterised by high road grip both when cold and hot, particularly suitable for sports driving, by virtue of the use of particular cross-linking modifying agents in the compound. These cross-linking modifying agents are capable of covalently binding to diene polymers and, once anchored, of interacting with each other and optionally with other components of the compound, forming reversible adducts. The Applicant has found that by appropriately selecting the portion capable of forming the adduct, herein called self-assembling portion, based on the specific value of the association constant (KA) thereof, it is possible to significantly increase the hysteresis of the compound starting from 50-70 °C, in the case of black compounds or even from room temperature for white compounds, and increasingly as the temperature increases, while avoiding excessively stiffening or making the material brittle, especially when cold.

[0025] By virtue of the anchoring reaction of these cross-linking modifying agents to the elastomers, a reaction that may be advantageously carried out during the normal tyre manufacturing process, on the one hand, and to the efficient formation of reversible adducts on the other, an additional cross-linking is obtained which confers greater hysteresis precisely under the most demanding conditions and at the highest temperatures of sports driving, where the formation of the adducts becomes labile, presumably triggering a dynamic dissipative mechanism linked to the breaking under stress and the rapid reformation of the hydrogen bonds. Instead, at the lower temperatures typical of the initial phase of the race, where the additional crosslinking is presumably more stable, it surprisingly does not significantly increase the moduli and hardness of the materials, thus allowing good grip even when cold.

[0026] In conclusion, by virtue of the specific reversible cross-linking modifying agents identified by the Applicant, it is possible to provide elastomeric compounds that are not too hard when cold and with increasing hysteresis as the temperature increases, which, incorporated into the tyre, especially in the tread, provide good grip and roadholding in all conditions.

[0027] Therefore, a first aspect of the present invention is an elastomeric composition comprising at least

[0028] - 100 phr of at least one diene elastomeric polymer,

[0029] - at least 0.1 phr of at least one cross-linking modifying agent of formula (I)

[0030] A - B - C (I) wherein

[0031] A is at least one anchoring group capable of covalently bonding to the elastomeric polymer,

[0032] B, optionally present, is an organic residue that is at least divalent, covalently bonded to groups A and C, preferably having a molecular weight of less than 1000 g / mol,

[0033] C is at least one self-assembling group capable of forming a reversible adduct with itself, characterised by an association constant KA between 5 and 1000 M’1, measured by NMR according to the consecutive dilutions method described herein,

[0034] - at least 1 phr of at least one reinforcing filler, and

[0035] - at least 0.1 phr of at least one vulcanising agent.

[0036] A further aspect of the present invention is a vulcanised elastomeric compound for tyre obtained by mixing and vulcanising the elastomeric composition according to the invention.

[0037] A further aspect of the present invention is a process for preparing the vulcanised elastomeric compound according to the invention, which comprises:

[0038] (i) optionally a functionalisation step of at least one diene elastomeric polymer,

[0039] (ii) at least a first non-productive processing step,

[0040] (iii) at least a second productive processing step, in which - in the first non-productive processing step (ii), at least one diene elastomeric polymer, optionally functionalised in step (i), is mixed with at least one reinforcing filler, preferably at a temperature of between 100 and 200 °C, to give a non- vulcanisable elastomeric compound,

[0041] - in the second productive step (iii), at least one vulcanising agent is added to the non-vulcanisable elastomeric compound and the components are mixed at a temperature preferably below 120 °C to give a vulcanisable elastomeric compound, and

[0042] (iv) a vulcanisation step of the vulcanisable elastomeric compound at a temperature preferably between 140 °C and 200 °C, to give the vulcanised elastomeric compound, characterised in that at least one cross-linking modifying agent of formula (I) as defined above is added in at least one of the steps i) to iii).

[0043] A further aspect of the present invention is a tyre component comprising the elastomeric compound according to the invention.

[0044] A further aspect of the present invention is a tyre for vehicle wheels comprising at least one component of a tyre according to the invention.

[0045] A further aspect of the present invention is represented by the use of an elastomeric compound comprising at least one cross-linking modifying agent of formula (I) as defined above in a tyre for sports applications.

[0046] Definitions

[0047] The term “elastomeric composition for tyre compound” means a composition comprising at least one diene elastomeric polymer and one or more additives, which by mixing and possible heating, provides an elastomeric compound suitable for use in tyre and their components.

[0048] The components of the elastomeric composition are not generally introduced simultaneously into the mixer but typically added in sequence. In particular, the vulcanisation additives, such as the vulcanising agent and optionally the accelerators and retarders, are usually added in a downstream step with respect to the incorporation and processing of all the other components.

[0049] In the final vulcanisable or even more vulcanised elastomeric compound, the individual components of the elastomeric composition may be altered or no longer individually traceable as modified, completely or in part, due to the interaction with the other components, of heat and / or mechanical processing. The term “elastomeric composition” herein is meant to include the set of all the components that are used in the preparation of the elastomeric compound, regardless of whether they are actually present simultaneously, are introduced sequentially or are then traceable in the elastomeric compound or in the final tyre.

[0050] The term “elastomeric compound” indicates the compound obtainable by mixing and optionally heating at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tyre compounds.

[0051] The term "non-vulcanisable elastomeric compound" indicates the compound obtainable by mixing and optionally heating at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tyre compounds, with the exception of the vulcanising agents.

[0052] The term “vulcanisable elastomeric compound” indicates the elastomeric compound ready for vulcanisation, obtainable by incorporation into a non-vulcanisable elastomeric compound of all the additives, including those of vulcanisation.

[0053] The term “vulcanised elastomeric compound” means the material obtainable by vulcanisation of a vulcanisable elastomeric compound.

[0054] The term “green” indicates a material, a compound, a composition, a component or a tyre not yet vulcanised.

[0055] The term “vulcanisation” refers to the cross-linking reaction in a natural or synthetic rubber induced by a typically sulphur-based vulcanising agent, but also others such as peroxides.

[0056] The term “cross-linking modifying agent” refers to a product of formula (I) A - B - C which typically during vulcanisation binds, at least in part, covalently via the anchoring group A to the elastomer, modifying it and which is capable of forming a three-dimensional network comprising reversible inter- and / or intramolecular bonds, such as hydrogen, ionic and / or hydrophobic bonds, via the self-assembling group C.

[0057] The term “anchoring group” refers to a functional group which, through various mechanisms such as cycloaddition reactions, formation of mono- or polysulphide bridges, insertion reaction of a carbene or nitrene into a C-H bond, is capable of reacting with the elastomer forming covalent bonds that are stable under the conditions of use. Conveniently the anchoring group reacts when heated to vulcanisation conditions but other possible activation mechanisms are not excluded. The term “self-assembling group” refers to a functional group which is capable of forming a reversible adduct with itself, through the formation of hydrogen bonds, ionic and / or hydrophobic, preferably hydrogen bonds.

[0058] The term “vulcanising agent” indicates a product capable of transforming natural or synthetic rubber into elastic and resistant material due to the formation of a three- dimensional lattice of stable inter- and / or intra-molecular bonds. Typically, the vulcanising agent is a sulphur-based product such as elemental sulphur, polymeric sulphur, sulphurised agents such as bis[(trialkoxysilyl)propyl]polysulphides, thiurams, dithiodimorpholines and caprolactam-disulphide. Alternatively, the vulcanising agent is a peroxide which contains an 0-0 bond and may generate reactive radicals by heating.

[0059] The term “vulcanisation accelerator” means a product capable of decreasing the duration of the vulcanisation process and / or the operating temperature, such as TBBS, sulphenamides in general, thiazoles, dithiophosphates, dithiocarbamates, guanidines, as well as sulphur donors such as thiurams.

[0060] The term “vulcanisation activator” indicates a product capable of further facilitating the vulcanisation, making it happen in shorter times and optionally at lower temperatures. An example of activator is the stearic acid-zinc oxide system. In the case of peroxide vulcanising agents, an example of activator is given by polymethacrylates such as ethylene glycol dimethacrylate.

[0061] The term “vulcanisation retarder” indicates a product capable of delaying the onset of the vulcanisation reaction and / or suppressing undesired secondary reactions, for example N-(cyclohexylthio)phthalimide (CTP).

[0062] The term “vulcanisation package” is meant to indicate the vulcanising agent and one or more vulcanisation additives selected from among vulcanisation activators, accelerators and retarders.

[0063] The term “elastomeric polymer” indicates a natural or synthetic polymer which, after vulcanisation, may be stretched repeatedly at room temperature to at least twice its original length and after removal of the tensile load substantially immediately returns with force to approximately its original length (according to the definitions of the ASTM D1566-11 Standard terminology relating to Rubber).

[0064] The term “diene elastomeric polymer” indicates an elastomeric polymer derived from the polymerization of one or more monomers, of which at least one is a conjugated diene. The term “reinforcing filler” is meant to refer to a reinforcing material typically used in the sector to improve the mechanical properties of tyre rubbers, preferably selected from among carbon black, conventional silica, such as silica from sand precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibres, derivatives thereof and mixtures thereof.

[0065] The term “white filler” is meant to refer to a conventional reinforcing material used in the sector selected from among conventional silica and silicates, such as sepiolite, paligorskite also known as attapulgite, montmorillonite, alloisite and the like, optionally modified by acid treatment and / or derivatised. Typically, white fillers have surface hydroxyl groups.

[0066] The term “first step” indicates the step of the preparation process of the elastomeric compound in which one or more additives may be incorporated by mixing and optionally heating, except for the vulcanising agent and the vulcanisation package which are fed in the second step. The first step is also called the “non-productive processing step”. In the preparation of a compound there may be several “nonproductive” mixing steps.

[0067] The term “second step” indicates the next step of the preparation process of the elastomeric compound in which the vulcanising agent and, optionally, other additives among which those of the vulcanisation package are introduced into the elastomeric compound obtained from the first step, and mixed in the material, at controlled temperature, generally at a compound temperature lower than 120 °C, so as to give the vulcanisable elastomeric compound. The second step is also called the “productive processing step”. In the preparation of a compound there may be several “productive” steps.

[0068] For the purposes of the present description and the following claims, the term “phr” (acronym for parts per hundreds of rubber) indicates the parts by weight of a given elastomeric compound component per 100 parts by weight of the elastomeric polymer, considered net of any plasticising extension oils.

[0069] Unless otherwise indicated, all the percentages are expressed as percentages by weight.

[0070] Description of the figures

[0071] With reference to the accompanying Figures: - Figure 1 schematically shows a semi-sectional view of a tyre for vehicle wheels according to the present invention;

[0072] - Figure 2 shows the Tan Delta trend with increasing temperature (shear DMA, initial T = 23 °C, final T =120 °C; 10 Hz; 1 % strain) of samples prepared from the elastomeric compositions for black compounds of Ex. 2.1 (Ref.), Ex. 2.3 (Inv.) and Ex. 2.5 (Comp.);

[0073] - Figure 3 shows the Tan Delta trend with increasing temperature (tensile DMA, initial T = 23 °C, final T =150 °C; 10 Hz; 25% pre-strain, 3.5% strain) of samples prepared from the elastomeric compositions for black compounds of Ex. 2.1 (ref.), Ex. 2.2 (Inv.) and Ex. 2.3 (Inv.);

[0074] - Figure 4 shows the Tan Delta trend with increasing temperature (tensile DMA, initial T = 23 °C, final T =150 °C; 10 Hz; 25% pre-strain, 3.5% strain) of samples prepared from the elastomeric compositions for white compounds of Ex. 2.6 (Ref.), Ex. 2.7 (Inv.) and Ex. 2.8 (Inv).

[0075] Detailed description of the invention

[0076] The elastomeric composition for tyre compound according to the present invention is characterised by one or more of the following preferred aspects taken alone or in combination with one another.

[0077] The elastomeric composition according to the invention comprises 100 phr of at least one diene elastomeric polymer.

[0078] The diene elastomeric polymer (A) may be selected from those commonly used in sulphur-vulcanisable elastomeric compositions, which are particularly suitable for producing tyres, i.e. from among solid elastomeric polymers or copolymers with an unsaturated chain having a glass transition temperature (Tg) generally lower than 20 °C, preferably in the range from 0 °C to -110 °C.

[0079] These polymers or copolymers may be of natural origin or may be obtained by solution polymerization, emulsion polymerization or gas-phase polymerization of one or more conjugated dienes, optionally mixed with at least one comonomer, preferably selected from monoolefins, monovinylarenes and / or polar comonomers, typically in an amount not exceeding 60% by weight.

[0080] The conjugated dienes generally contain from 4 to 12, preferably from 4 to 8 carbon atoms and may be selected, for example, from the group comprising: 1 ,3-butadiene, isoprene, 2, 3-dimethyl-1 ,3-butadiene, 1 ,3-pentadiene, 1 ,3-hexadiene, 3-butyl-1 ,3- octadiene, 2-phenyl-1 ,3-butadiene and mixtures thereof. 1 ,3-butadiene and isoprene are particularly preferred.

[0081] The monoolefins may be selected from ethylene and a-olefins generally containing from 3 to 12 carbon atoms, such as for example propylene, 1 -butene, 1 -pentene, 1 - hexene, 1 -octene or mixtures thereof.

[0082] Monovinylarenes, which may optionally be used as comonomers, generally contain from 8 to 20, preferably from 8 to 12 carbon atoms and may be selected, for example, from: styrene; 1 -vinylnaphthalene; 2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene, such as, for example, a- methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4- dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, and mixtures thereof. Styrene is particularly preferred.

[0083] Polar comonomers that may optionally be used may be selected, for example, from acrylic acid and alkylacrylic acid esters, acrylonitriles, or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

[0084] Preferably, the diene elastomeric polymer (A) may be selected, for example, from cis-1 ,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4- polyisoprene, polybutadiene (in particular polybutadiene with a high content of 1 ,4- cis), optionally halogenated isoprene / isobutene copolymers, 1 ,3- butadiene / acrylonitrile copolymers, styrene / 1 ,3-butadiene copolymers, styrene / isoprene / 1 ,3-butadiene copolymers, styrene / 1 ,3-butadiene / acrylonitrile copolymers, and mixtures thereof.

[0085] The elastomeric composition may optionally comprise at least one polymer of one or more monoolefins with an olefinic comonomer or derivatives thereof. The monoolefins may be selected from: ethylene and a-olefins generally containing from 3 to 12 carbon atoms, such as, for example, propylene, 1 -butene, 1 -pentene, 1 - hexene, 1 -octene or mixtures thereof. The following are preferred: copolymers selected from ethylene and an a-olefin, optionally with a diene; isobutene homopolymers or copolymers thereof with small amounts of a diene, which are optionally at least partially halogenated. The diene, optionally present, generally contains from 4 to 20 carbon atoms and is preferably selected from: 1 ,3-butadiene, isoprene, 1 ,4-hexadiene, 1 ,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5- methylene-2-norbornene, vinylnorbornene or mixtures thereof. Among them, the following are particularly preferred: ethylene / propylene (EPR) copolymers or ethylene / propylene / diene (EPDM) copolymers; polyisobutene; butyl rubber; halobutyl rubbers, in particular chlorobutyl or bromobutyl rubbers; and mixtures thereof.

[0086] The above-mentioned polymers can optionally be functionalised along the main chain or at the ends thereof.

[0087] The functional group may be introduced into the elastomeric polymer by processes known in the art such as, for example, during the production of the elastomeric polymer by copolymerisation with at least one corresponding functionalised monomer containing at least one ethylene unsaturation; or by subsequent modification of the elastomeric polymer by grafting at least one functionalised monomer in the presence of a free radical initiator (for example, an organic peroxide).

[0088] Alternatively, the functionalisation may be introduced by reaction with suitable terminating agents or coupling agents. In particular, the diene elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (in particular, an organolithium initiator) may be functionalised by reacting the residual organometallic groups derived from the initiator with suitable terminating agents or coupling agents such as, for example, amines, amides, imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes, aryloxy silanes, alkyldithiols, alkyldithiolsilanes, carboxyalkylthiols, carboxyalkylthiolsilanes, and thioglycols.

[0089] Useful examples of terminating agents or coupling agents are known in the art and described, for example in patents EP2408626, EP2271682, EP3049447A1 , EP2283046A1 , EP2895515A1 , EP451604, US4742124, W02015 / 086039A1 and WO2017 / 211876A1 .

[0090] Preferably, said at least one functionalised elastomeric polymer is obtained from polybutadiene (in particular polybutadiene with a high content of 1 ,4-cis), styrene / 1 ,3-butadiene copolymers, styrene / isoprene / 1 ,3-butadiene copolymers, styrene / 1 ,3-butadiene / acrylonitrile copolymers, and mixtures thereof.

[0091] Advantageously, said at least one functionalised elastomeric polymer (b) is obtained from styrene / 1 ,3-butadiene copolymers. Useful examples of functionalised diene elastomeric polymers are the functionalised styrene butadiene copolymers SPRINTAN™ SLR 3402 and SPRINTAN™ SLR 4602, SPRINTAN™ SLR 4630, manufactured and distributed by Trinseo, PA, USA. The elastomeric composition according to the invention may comprise two or more elastomeric polymers as defined above, in a mixture.

[0092] The elastomeric composition according to the present invention comprises at least one cross-linking modifying agent of formula (I)

[0093] A - B - C (I) preferably in amounts of at least 0.5 phr, more preferably at least 2 phr, even more preferably at least 3 phr.

[0094] The elastomeric composition according to the present invention preferably comprises not more than 20 phr, not more than 15 phr, not more than 10 phr of at least one cross-linking modifying agent of formula (I).

[0095] Preferably, the elastomeric composition according to the present invention comprises from 0.5 to 20 phr, preferably from 1 to 15 phr or from 2 to 10 phr or from 3 to 8 phr of at least one cross-linking modifying agent of formula (I).

[0096] In the cross-linking modifying agent of formula (I), A represents at least one anchoring group capable of covalently binding to one or more elastomeric polymers. Group A may bind to the elastomeric polymers of the compound directly or via components of the vulcanisation package, forming for example mono or polysulphide bridges.

[0097] Preferably, A is a group selected from the activated double bonds, the sulphur groups such as mercapto, di- and polysulphides and thioesters, the reactive phenols having at least one unsubstituted ortho or para position, the precursors of 1 ,3- dipoles, such as the 2,5-disubstituted tetrazoles described for example in patent application WO2021 / 137143A1 , the pyrroles substituted in the positions proximal to nitrogen as described for example in WO2020225595A1 and WO20180876851 A1 , nitrones, azides, sulphonazides, including the groups Q defined in patent US9394434, and the diene groups capable of giving Diels-Alder reactions.

[0098] In one embodiment, group A is an activated double bond.

[0099] By activated double bond it is meant a double bond made reactive by conjugated electron-attracting or donor groups, by electron-rich or electron-poor atoms or by particular steric constraints such as the inclusion of the double bond in tensioned cycles. Examples of activated double bonds are vinyls, unsaturated tensioned cyclic systems and unsaturated alpha-beta bonds, preferred examples are norbornene, methacryl and vinyl ether.

[0100] In one embodiment, group A is a sulphur group.

[0101] Examples of preferred sulphur groups capable of covalently binding to the elastomeric polymer are the -SH, -S-S-, -S-(S)n-S-, -SC(O)R', -SC(S)R' -S-NR"R"' wherein R', R" and R'" independently represent C1-C20 alkyl, C6-C20 aryl, alkyl-Ci- Cio-aryl-Ce-C , aryl-Ce-Cio-alkyl-C-i-C-io, or R" and R'" may optionally be fused in a cycle. Group A may be a 4- to 10-membered cyclic thioether or a 4- to 10-membered cyclic polythioether.

[0102] In a preferred embodiment, group A is selected from azide (-N3) and 1 ,2-dithiolanes. Particularly preferred is the anchoring group A 1 ,2 dithiolane of formula derived from lipoic acid, a natural product available from various plant and animal sources.

[0103] At least one group A is present in the cross-linking modifying agent of formula (I) but two or more groups A, equal or different from each other, may be present.

[0104] In a preferred embodiment, only one group A is present in the cross-linking modifying agent of formula (I).

[0105] Typically these functional groups react with the elastomer under normal vulcanisation conditions, forming covalent bonds.

[0106] During the reaction, the group A of the cross-linking modifying agent may partially interfere with the sulphur-based vulcanising system present in the compound and bind to the elastomer through mono- or polysulphide bridges, thus consuming part of the vulcaniser and, in fact, reducing the extent of the sulphur cross-linking. In these cases, those skilled in the art will be able to suitably modify the sulphur vulcanisation package, varying amounts and components, to compensate for the possible loss in the sulphur cross-linking and restore the normal level thereof.

[0107] Alternatively, by selecting anchoring groups A with greater or lesser reactivity, it is possible to make the anchoring reaction to the polymer occur at different moments in the production process or use of the tyre. In the cross-linking modifying agent of formula (I) there is optionally present a group B, i.e. an at least divalent inert spacer organic residue, covalently linked to groups A and C, which acts as a spacer.

[0108] By inert organic residue B it is meant an organic residue which is sufficiently stable under normal conditions of processing, vulcanisation and use of the elastomeric compound.

[0109] In one embodiment, group B is absent.

[0110] In a preferred embodiment, group B is present and is selected from C1-C20 alkylene, C6-C20 arylene, C1-C10 alkylene-Ce-Cw arylene, C6-C10 arylene-C-i-C-io alkylene, optionally comprising in the chain one or more heteroatoms such as N, 0, S, B, P or Si or one or more functional groups such as for example -COO-, -OCO-, -CONH- , -NHCO-, -OCONH-, -NHCONH-, -CO-, -NH-C(NH)-NH-, -C(S)-S-, -S-C(S)-.

[0111] Alkylene and arylene refer to an at least divalent radical obtained by removing at least one hydrogen atom from an alkyl and aryl group, respectively.

[0112] Preferably, group B is divalent, that is, it is linked to only one anchoring group A and to only one self-assembling group C.

[0113] Examples of preferred divalent B groups are C1-C15 alkylene, -O-CH2-, -O-(CH2)e-, -0-(CH2)IO-, -O-(CH2)11, -O-C(O)-NH-(CH2)6-NH-C(O)-O-, NH-C(O)-NH-, -(CH2)6- NH-C(O)-.

[0114] Preferably, the group B has a molecular weight lower than 500 g / mol, more preferably lower than 300 g / mol, even more preferably lower than 200 g / mol.

[0115] In the cross-linking modifying agent of formula (I), at least one self-assembling group C is present, i.e. a group capable of forming a reversible adduct with itself through the formation of labile intermolecular bonds such as hydrogen bonds, ionic and / or hydrophobic bonds, preferably hydrogen bonds.

[0116] The self-assembling group C preferably comprises at least one donor site and one acceptor site for the hydrogen bond, so that two identical self-assembling groups are self-complementary and capable of associating with each other to form at least two hydrogen bonds.

[0117] Alternatively, if there are several different self-assembling C groups, it may also happen that the association occurs not only between identical groups C but also between different self-assembling groups C, each carrying one or more donor and acceptor sites. The self-assembling groups C may also optionally associate via hydrogen bonds, ionic bonds and / or hydrophobic bonds with the functions present on the reinforcing fillers.

[0118] Preferably, the self-assembling group C in the adduct forms at least 2 and no more than 4 intermolecular hydrogen bonds. In a preferred embodiment, the selfassembling group C in the adduct forms 3 intermolecular hydrogen bonds.

[0119] In addition to these, one or more labile intramolecular bonds may form in the adduct which influence the stability and the value of the association constant KA.

[0120] The self-assembling group C is characterised by a value of the association constant KA between 5 and 1000 M’1, excluding extremes, meaning greater than 5 and less than 1000 M-1, preferably between 5 and 500 M-1, more preferably between 5 and 100 M’1, even more preferably between 10 and 50 M’1.

[0121] Preferably, the association constant KA is less than 800 M’1, more preferably less than 500 M’1, 300 M’1, 200 M’1or 100 M’1.

[0122] Preferably, the association constant KA is higher than 8 M-1, more preferably it is higher than 10 M’1.

[0123] The association constant KA is determined according to the NMR method by consecutive dilutions described herein in the experimental part.

[0124] The following Table 1 shows some examples of self-assembling groups and / or adducts and the related association constant KA values taken from the literature:

[0125] Table 1

[0126] The Applicant found that incorporating modifying agents characterised by low KA values into the compound does not result in a significant increase in hot hysteresis. On the other hand, with modifying agents characterised by high KA values, excessive cold stiffening is observed, while with modifying agents with intermediate KA values, a particularly high hot hysteresis is observed, associated with a low cold modulus, predictive of high grip in extreme performances without excessive rubber rigidity and therefore with good grip even when cold.

[0127] The cross-linking modifying agent (I) may comprise one or more self-assembling groups C, equal or different from each other, preferably it comprises only one selfassembling group C.

[0128] The self-assembling group C may be charged or neutral, preferably it is neutral. Preferably, the self-assembling group C comprises at least one mono- or polycyclic, 5- or 6-membered ring heterocycle, saturated, unsaturated or aromatic, optionally benzocondensate, comprising at least one heteroatom selected from N, P, S and 0. Preferably, the heterocycle is a nitrogenous heterocycle.

[0129] Preferably, the self-assembling group C comprises at least one nitrogenous heterocycle, optionally benzocondensed and optionally substituted, selected from pyridine, bipyridine, terpyridine, pyrazine, pyrimidine, pyridazine, imidazole, pyrrole, pyrazole, indole, 1 ,10-phenanthroline, quinoline, isoquinoline, triazole, tetrazole, triazine, tetrazine, naphthyridine, purine, benzothiazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole, substituted or unsubstituted oxadiazole, and oxosubstituted derivatives thereof, for example pyrimidinone, quinolinone, naphthyridinone. More preferably, the self-assembling group C comprises at least one nitrogenous heterocycle selected from pyrimidine, pyrimidinone, benzimidazole and quinolinone.

[0130] Preferably, the heterocycle is suitably substituted with one or more functional groups capable of forming labile bonds, preferably hydrogen bonds, such as for example hydroxyl, amino, amido, ureido, aminocarbonyl, oxo, carbamate, thiocarbonyl and thiourea.

[0131] An example of a particularly preferred self-assembling group C is the following 2- amido-pyrimidinone: wherein R1 preferably represents linear or branched C1-C20 alkyl, optionally substituted C6-C10 aryl, (Ci-C2o)-0-(Ci-C2o) alkyl-ether-alkyl, (Ci-C2o)-OC(0)-(Ci- C20) alkyl-ester and (CI-C2O)-NC(0)-(CI-C2O) alkyl amide.

[0132] Those skilled in the art, by appropriately selecting the self-assembling group C and its optional substituents, is able to modulate the complexation capacity thereof and therefore to conveniently shift the reaction equilibrium as a function of the operating temperatures for the tyre applications of interest. Furthermore, as shown in the experimental part, by ad hoc modifying the substituent groups of the self-assembling group C it is also possible to intervene on the interactions of the cross-linking modifying agent (I) with the reinforcing filler and therefore on the rigidity of the material.

[0133] Examples of preferred self-assembling groups C are the groups according to the invention listed herein in Table 2.

[0134] Preferably, the self-assembling group C is not one of the groups listed in U.S. patent 9394434 as groups A at formulae (II) to (VI) below: wherein R means a hydrocarbon group, optionally containing heteroatoms, and X means an oxygen or sulphur atom, preferably an oxygen atom.

[0135] Preferably, the self-assembling group C does not include an imidazolidinone group or a ureidopyrimidinone group.

[0136] In a preferred embodiment, in the cross-linking modifying agent of formula (I)

[0137] A - B - C (I) there is only one group A, one self-assembling group C, and group B is present and is divalent.

[0138] In a particularly preferred embodiment, in the cross-linking modifying agent of formula (I)

[0139] A - B - C (I) there is only one group A, only one self-assembling group C and group B is present and is divalent, and

[0140] A is selected from azide and 1 ,2-dithiolanes

[0141] B is an alkylene from 4 to 12, and

[0142] C is selected from pyrimidones, benzoimidazoles and quinolinones.

[0143] The elastomeric composition according to the present invention may comprise at least 0.5 phr of at least one reinforcing filler.

[0144] The present composition may comprise from 1 phr to 150 phr, from 5 phr to 120 phr or from 10 phr to 90 phr of at least one reinforcing filler.

[0145] Preferably, the reinforcing filler is selected from carbon black, white fillers, silicate fibres, derivatives thereof and mixtures thereof.

[0146] In an embodiment, said reinforcing filler is a white filler selected from among hydroxides, oxides and hydrated oxides, salts and hydrated salts of metals, silicates fibres, derivatives thereof and mixtures thereof. Preferably, said white filler is silica. Preferably, said silica may be present in the elastomeric composition in an amount ranging between 1 phr and 100 phr, more preferably between 30 phr and 70 phr.

[0147] Commercial examples of suitable silica are Zeosil 1165 MP, Zeosil 1115 MP, Zeosil 185 GR, Efficium from Solvay, Newsil HD90 and Newsil HD200 from Wuxi, K160 and K195 from Wilmar, H160AT and H 180 AT from IQE, Zeopol 8755 and 8745 from Huber, Perkasil TF100 from Grace, Hi-Sil EZ 120 G, EZ 160G, EZ 200G from PPG, Ultrasil 7000 GR and Ultrasil 9100 GR from Evonik.

[0148] In one embodiment, said reinforcing filler comprises silica mixed with carbon black.

[0149] In one embodiment, said reinforcing filler comprises a modified silica. Silica may be modified for example by reaction with silsequioxanes (as in W02018078480A1 ), by reaction with pyrroles (as in W02016050887A1 ) or by reaction with silanising agents, such as bis(triethoxysilylpropyl)tetrasulphide (TESPT), 3-aminopropyltriethoxysilane (APTES) 3-glycidyloxypropyltriethoxysilane triethoxy(octyl)silane, triethoxy(ethyl)silane, triethoxy-3-(2-imidazolin-1 - yl)propylsilane, triethoxy-p-tolylsilane, triethoxy(1 -phenylethenyl)silane, triethoxy-2- thienylsilane, 1 H, 1 H,2H,2H-perfluorooctyltriethoxysilane, 3-(triethoxysilyl)propyl isocyanate, 1 H,1 H,2H,2H-perfluorodecylthriethoxysilane, isobutyltriethoxysilane, n- octadecyltriethoxysilane, (3-chloropropyl)triethoxysilane, triethoxysilane and 3- (triethoxysilyl)propionitrile.

[0150] Commercial examples of suitable silanising agents are Si69, Dynasilan AMEO and Dynasilan GLYEO from Evonik.

[0151] The modified silica may be a sulphurised silanised silica.

[0152] Sulphurised silanised silica is a silica prepared by reaction of a silica, such as fumed silica, precipitated amorphous silica, wet silica (hydrated silicic acid), anhydrous silica (anhydrous silicic acid), or mixtures thereof, or of a metal silicate, such as aluminium silicate, sodium silicate, potassium silicate, lithium silicate or mixtures thereof, with at least one sulphurised silanising agent.

[0153] The term “sulphurised silanising agent” indicates an organic derivative of silicon containing mercapto, sulphide, disulphide or polysulphide groups, said derivative being capable of reacting with the OH groups of silica.

[0154] A commercial example of suitable sulphurised silanised silica is Agilon 400 silica from PPG.

[0155] In one embodiment, said reinforcing filler comprises a modified silica mixed with carbon black.

[0156] In one embodiment, said reinforcing filler comprises silicates.

[0157] In one embodiment, said silicates are lamellar silicates, such as bentonites, alloysite, laponite, saponite, vermiculite or hydrotalcite.

[0158] In one embodiment, said silicates are modified lamellar silicates analogously to what is described below for modified silicate fibres.

[0159] In one embodiment, said silicates are silicate fibres. These fibres typically have nano dimensions and have needle-like morphology. The silicate fibres are preferably selected from sepiolite fibres, paligorskite fibres (also known as attapulgite), wollastonite fibres, imogolite fibres and mixtures thereof.

[0160] In one embodiment, said reinforcing filler comprises silicate fibres mixed with carbon black.

[0161] In one embodiment, said silicate fibres are modified silicate fibres.

[0162] In one embodiment, the modified silicate fibres can be for example fibres modified by acid treatment with partial removal of magnesium, such as those described and exemplified in patent application WO2016174629A1 .

[0163] In one embodiment, the modified silicate fibres can be for example fibres modified by deposition of amorphous silica on the surface, such as those described and exemplified in patent application WO2016174628A1 .

[0164] In one embodiment, the modified silicate fibres may be fibres organically modified by reaction, for example, with quaternary ammonium salts such as sepiolite fibres modified by reaction with talloyl benzyl dimethyl ammonium chloride marketed by Tolsa under the name Pangel B5.

[0165] In one embodiment, the modified silicate fibres may be fibres modified by reaction with a silanising agent selected for example from mono or bifunctional silanes with one or two or three hydrolysable groups such as bis-(3-triethoxysilyl- propyl)disulphide (TESPD), bis(3-triethoxysilyl-propyl)tetrasulphide (TESPT), 3- thio-octanoyl-1 -propyl-triethoxysilane (NXT), Me2Si(OEt)2, Me2PhSiCI, Ph2SiCl2.

[0166] In one embodiment, said reinforcing filler is carbon black.

[0167] Preferably, said carbon black is present in the elastomeric composition in an amount ranging between 1 phr and 100 phr, preferably between 5 phr and 70 phr.

[0168] Preferably, the carbon black is selected from those having a surface area not smaller than 20 m2 / g, preferably larger than 50 m2 / g (as determined by STSA - statistical thickness surface area according to ISO 18852:2005).

[0169] Carbon black may be for example N110, N115, N121 , N134, N220, N234, N326, N330, N375 or N550, N660 marketed by Birla Group (India) or by Cabot Corporation, Vulcan® 1391 supplied by Cabot Corporation or Birla Carbon™ 2115 supplied by Birla Group.

[0170] The elastomeric composition according to the invention may comprise 0.1 to 10 phr of a vulcanising agent. Preferably, the composition comprises at least 0.2 phr, 0.5 phr, 0.8 phr or 1 phr of at least one vulcanising agent.

[0171] Preferably, the composition comprises from 0.1 to 10 phr, from 0.2 to 10 phr, from 1 to 10 phr or from 1 .5 to 5 phr of at least one vulcanising agent.

[0172] The at least one vulcanising agent is preferably selected from sulphur, sulphurised agents (sulphur donors), such as, for example, bis[(trialkoxysilyl)propyl]polysulphides, caprolactam-disulphide or peroxides and mixtures thereof.

[0173] Preferably, the vulcanising agent is sulphur, preferably selected from soluble sulphur (crystalline sulphur), insoluble sulphur (polymeric sulphur), oil-dispersed sulphur and mixtures thereof.

[0174] Commercial example of a vulcanising agent suitable for use in the elastomeric composition of the invention is the Redball Superfine sulphur by International sulphur Inc.

[0175] In the present elastomeric composition, the vulcanising agent may be used together with adjuvants such as vulcanisation activators, accelerators and / or retarders known to those skilled in the art.

[0176] The elastomeric composition according to the invention may optionally comprise at least one vulcanisation activator.

[0177] The vulcanisation activators suitable for use in the present elastomeric composition are zinc products, in particular ZnO, ZnCOs, zinc salts of saturated or unsaturated fatty acids containing from 8 to 18 carbon atoms, which are preferably formed in situ in the elastomeric composition by reaction of ZnO and of the fatty acid or mixtures thereof. For example, zinc stearate is used, preferably formed in situ in the elastomeric composition, by ZnO and fatty acid, or magnesium stearate, formed by MgO, or mixtures thereof.

[0178] The vulcanisation activators may be present in the elastomeric composition of the invention in amounts preferably from 0.2 phr to 15 phr, more preferably from 1 phr to 5 phr.

[0179] Preferred activators derive from the reaction of zinc oxide and stearic acid.

[0180] An example of activator is the product Aktiplast ST marketed by Rheinchemie.

[0181] The elastomeric composition according to the invention may further comprise at least one vulcanisation accelerator. Vulcanisation accelerators that are commonly used may be for example selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulphenamides, sulphenimides, thiurams, amines, xanthates, or mixtures thereof.

[0182] Preferably, the accelerator is selected from mercaptobenzothiazole (MBT), N- cyclohexyl-2-benzothiazol-sulphenamide (CBS), N-tert-butyl-2-benzothiazol- sulphenamide (TBBS) and mixtures thereof.

[0183] Commercial examples of accelerators suitable for use in the present elastomeric composition are N-cyclohexyl-2-benzothiazyl-sulphenamide Vulkacit® (CBS or CZ), and N-terbutyl 2-benzothiazil sulphenamide, Vulkacit® NZ / EGC marketed by Lanxess.

[0184] Vulcanisation accelerators may be used in the present elastomeric composition in an amount preferably from 0.05 phr to 10 phr, preferably from 0.1 phr to 7 phr, more preferably from 0.5 phr to 5 phr.

[0185] The elastomeric composition according to the invention may optionally comprise at least one vulcanisation retarder.

[0186] The vulcanisation retarder suitable for use in the present elastomeric composition is preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine N- cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.

[0187] A commercial example of a suitable retarder is N-cyclohexylthiophthalimide VULKALENT G of Lanxess.

[0188] The vulcanisation retarder may be present in the present elastomeric composition in an amount of preferably from 0.05 phr to 2 phr.

[0189] The present elastomeric composition may comprise one or more vulcanisation retarders as defined above in a mixture.

[0190] The elastomeric composition according to the invention may further comprise at least 0.05 phr, preferably at least 0.1 phr or 0.5 phr, more preferably at least 1 phr or 2 phr of at least one silane coupling agent.

[0191] Preferably, the elastomeric composition according to the invention comprises from 0.1 phr to 20.0 phr or from 0.5 phr to 10.0 phr, even more preferably from 1 .0 phr to 5.0 phr of at least one silane coupling agent.

[0192] Preferably, said coupling agent is a silane coupling agent selected from those having at least one hydrolysable silane group which may be identified, for example, by the following general formula (VII):

[0193] (R’)3Si-CnH2n-Y (VII) wherein the groups R’, equal or different from each other, are selected from: alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the groups R’ is an alkoxy or an aryloxy group; n is an integer of from 1 to 6; Y is a group selected from: nitrose, mercapto, amino, epoxide, vinyl, imide, chloro, -(S)mCnH2n- Si-(R’)s and -S-COR’, wherein m and n are integers of from 1 to 6 and the groups R’ are as defined above.

[0194] Particularly preferred silane coupling agents are bis(3- triethoxysilylpropyl)tetrasulphide and bis(3-triethoxysilylpropyl)disulphide. Said coupling agents may be added as such or in mixture with an inert filler (such as carbon black) so as to facilitate their incorporation into the elastomeric composition. An example of the silane coupling agent is TESPT: bis(3- triethoxysilylpropyl)tetrasulphide Si69 marketed by Evonik.

[0195] The elastomeric composition according to the invention may further comprise one or more additional ingredients, commonly used in the field, such as for example plasticising oils, resins, antioxidant and / or antiozonant agents (anti-aging agents), waxes, adhesives and the like.

[0196] For example, the elastomeric composition according to the present invention, in order to further improve the workability of the compound, may further comprise at least one plasticising oil.

[0197] The amount of plasticiser is preferably in the range from 5 to 25 phr, preferably from 8 to 20 phr.

[0198] The term “plasticising oil” means a process oil derived from petroleum or a mineral oil or a vegetable oil or a synthetic oil or combinations thereof.

[0199] The plasticising oil may be a process oil derived from petroleum selected from paraffins (saturated hydrocarbons), naphthenes, aromatic polycyclic and mixtures thereof.

[0200] Examples of suitable process oils derived from petroleum are aromatic, paraffinic, naphthenic oils such as MES (Mild Extract Solvated), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract) known in the field.

[0201] The plasticising oil may be an oil of natural or synthetic origin derived from the esterification of glycerol with fatty acids, comprising glycerine triglycerides, diglycerides, monoglycerides or mixtures thereof. Examples of suitable vegetable oils are sunflower, soybean, linseed, rapeseed, castor and cotton oil.

[0202] The plasticising oil may be a synthetic oil selected from among the alkyl or aryl esters of phthalic acid or phosphoric acid.

[0203] The elastomeric composition according to the present invention may further comprise at least one resin.

[0204] The resin is a non-reactive resin, preferably selected from among hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.

[0205] The amount of resin is preferably from 5 to 25 phr, more preferably from 7 to 20 phr. The elastomeric composition according to the invention may optionally comprise at least one wax.

[0206] The wax may be for example a petroleum wax or a mixture of paraffins.

[0207] Commercial examples of suitable waxes are the Repsol N-paraffin mixture and the Antilux® 654 microcrystalline wax from Rhein Chemie.

[0208] The wax may be present in the elastomeric composition of the invention in an overall amount generally from 0.1 phr to 20 phr, preferably from 0.5 phr to 10 phr, more preferably from 1 phr to 5 phr.

[0209] The elastomeric composition according to the invention may optionally comprise at least one antioxidant agent.

[0210] The antioxidant agent is preferably selected from N-isopropyl-N'-phenyl-p- phenylenediamine (IPPD), N-(-1 ,3-dimethyl-butyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1 ,4-dimethyl-pentyl)-p-phenylenediamine (77PD), N,N'-bis-(1 - ethyl-3-methyl-pentyl)-p-phenylenediamine (DOPD), N , N'-bis-( 1 ,4-dimethyl-pentyl)- p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p- phenylenediamine (DTPD), N,N'-di-beta-naphthyl-p-phenylenediamine (DNPD), N,N'-bis(1 -methylheptyl)-p-phenylenediamine, N,N'-Di-sec-butyl-p- phenylenediamine (44PD), N-phenyl-N’-cyclohexyl-p-phenylenediamine, N-phenyl- N'-1 -methylheptyl-p-phenylenediamine and the like, and mixtures thereof, preferably it is N-1 ,3-dimethylbutyl-N-phenyl-p-phenylenediamine (6-PPD).

[0211] A commercial example of a suitable antioxidant agent is 6PPD from Solutia or Santoflex produced by Eastman.

[0212] The antioxidant agent may be present in the elastomeric composition in an overall amount preferably from 0.1 phr to 20 phr, more preferably from 0.5 phr to 10 phr. A further aspect of the present invention is a vulcanised elastomeric compound for tyre obtained by mixing and vulcanising the elastomeric composition according to the invention.

[0213] The elastomeric compound of the invention is characterised by a particular balance of hysteresis with respect to stiffness.

[0214] In fact, compared to conventional elastomeric compounds (e.g. reference compound 1 , Figures 2-4), the compound of the invention has Tan Delta values that are decidedly higher at operating temperatures in a sports driving regime starting from 50-70 °C in the case of black compounds (Figures 2 and 3) or even at room temperature in the case of white compounds.

[0215] Furthermore, the elastomeric compound of the invention has dynamic moduli close to or lower than those of the reference compound, thus showing that the crosslinking modifying agent of the invention does not alter the properties of the compound in which it is inserted, in particular it does not induce significant cold hardening of the compound, thus imparting good roadholding in all conditions and handling.

[0216] A further aspect of the present invention is a process for preparing the vulcanised elastomeric compound according to the invention, which preferably comprises:

[0217] (i) optionally a functionalisation step of at least one diene elastomeric polymer,

[0218] (ii) at least a first non-productive processing step,

[0219] (iii) at least a second productive processing step, in which

[0220] - in the first non-productive processing step (ii), at least one diene elastomeric polymer, optionally functionalised in step (i), is mixed with at least one reinforcing filler, and optionally at least one antioxidant, a vulcanisation activator, a compatibilising agent, an antiozonant and / or a wax at a temperature preferably between 110 and 190 °C, to give a non-vulcanisable elastomeric compound,

[0221] - in the second productive step iii), at least one vulcanising agent and optionally at least one accelerator, a retarder, a compatibilising agent, a vulcanisation activator and / or a peroxide are added to the non-vulcanisable elastomeric compound and the components are mixed at a temperature preferably lower than 120 °C, to give a vulcanisable elastomeric compound, and

[0222] (iv) a vulcanisation step of the vulcanisable elastomeric compound at a temperature preferably between 150 °C and 200 °C, to give the vulcanised elastomeric compound, characterised in that at least one cross-linking modifying agent of formula (I) as defined above is added in at least one of the steps i) to iii).

[0223] In the process according to the present invention, the at least one cross-linking modifying agent of formula (I) may be added in the first step or in the second step depending on its melting point and its reactivity.

[0224] In one embodiment of the present process, the cross-linking modifying agent of formula (I) is added in the first non-productive processing step ii).

[0225] In one embodiment of the present process, the cross-linking modifying agent of formula (I) is added in the second productive step iii).

[0226] In the process according to the present invention, the at least one cross-linking modifying agent of formula (I) may be added in several steps, for example in the first step and in the second step.

[0227] In a preferred embodiment, the at least one cross-linking modifying agent of formula (I) is added in the second step.

[0228] In the present process, the at least one diene elastomeric polymer may optionally be functionalised by reaction with at least one cross-linking modifying agent of formula (I) in an optional functionalisation step i) preceding the non-productive steps ii) and productive steps iii).

[0229] The functionalisation of the at least one diene elastomeric polymer may be carried out in one or more thermomechanical mixing steps in at least one suitable mixer, optionally also comprising at least one step in which the temperature of the compound comprising the at least one diene elastomeric polymer and the at least one cross-linking modifying agent of formula (I) is maintained for a predefined time at a level such as to ensure at least partial functionalisation of the polymer itself, for example for 5 minutes at 170 °C.

[0230] Alternatively, the at least one cross-linking modifying agent of formula (I) may be pre-mixed with at least one diene elastomeric polymer in liquid form, for example in the form of an aqueous emulsion or a solution in organic solvents, followed by the removal of the volatile components of the compound, such as water and / or solvents, to give a mixture comprising at least the diene elastomeric polymer and at least the cross-linking modifying agent (I), optionally at least partially reacted with each other, usable in the first non-productive processing step ii) or directly in the second productive processing step iii). The process according to the invention typically comprises one or more thermomechanical mixing steps in at least one suitable mixer, in particular at least a first non-productive mixing step and at least a second productive mixing step as defined above.

[0231] Each mixing step may comprise several intermediate processing steps or sub-steps, characterised by the momentary interruption of the mixing to allow the addition of one or more ingredients but without intermediate discharge of the compound.

[0232] The mixing may be performed, for example, using an open mixer of the "open-mill" type or an internal mixer of the type with tangential rotors (Banbury®) or with interpenetrating rotors (Intermix), or in continuous mixers of the Ko-Kneader™ type (Buss®) or of the twin-screw or multi-screw type, optionally coupled with singlescrew extruders.

[0233] Generally, but not necessarily, at the end of the first non-productive step ii), the non- vulcanisable elastomeric compound is discharged and after a variable period of time charged back into the same or another suitable mixer, for the subsequent second productive step iii).

[0234] In the second productive step iii), the temperature is generally controlled to avoid undesired pre-vulcanisation phenomena.

[0235] At the end of the second step, the vulcanisable elastomeric compound is incorporated into one or more components of the green tyre, preferably in the tread band, and subjected to vulcanisation, according to known techniques.

[0236] Any of the usual vulcanisation processes may be used in the present process, such as heating in a press or mould, heating with superheated steam or hot air.

[0237] The tyres may be built, formed, moulded and vulcanised with various methods known to those skilled in the art.

[0238] A further aspect of the present invention is a tyre component for vehicle wheels comprising, or preferably consisting of, an elastomeric compound, according to the invention, preferably selected from the tread band, under-layer, anti-abrasive strip, sidewall, sidewall insert, mini-sidewall, liner, under-liner, rubber layers, bead filler, bead reinforcing layers (flipper), bead protection layers (chafer), sheet. Preferably, the tyre component is a tread band.

[0239] The green tyre component is produced with the vulcanisable elastomeric compound and then vulcanised, preferably together with the other components, to give the vulcanised tyre component. A further aspect of the present invention is a tyre for vehicle wheels comprising at least one of the components according to the invention.

[0240] Preferably, said component is a tread band.

[0241] In one embodiment, a tyre for vehicles according to the present invention comprises at least

[0242] - a carcass structure comprising at least a carcass ply having opposite lateral edges associated to respective bead structure;

[0243] - optionally a pair of sidewalls applied to the lateral surfaces of the carcass structure, respectively, in an axially outer position;

[0244] - optionally a belt structure applied in radially outer position with respect to the carcass structure;

[0245] - a tread band applied in a radially outer position to said carcass structure or, if present, a belt structure,

[0246] - optionally a layer of elastomeric material, referred to as under-layer, applied in a radially inner position with respect to said tread band, wherein at least one component, preferably the tread band, comprises, or preferably consists of, the elastomeric compound according to the invention.

[0247] The tyre according to the invention may be for summer, winter use or for all seasons. In one embodiment, the tyre according to the invention is a tyre for a passenger car, with normal or high performance or for off-road vehicles, preferably it is a tyre for high performance vehicles such as sports or racing cars.

[0248] Preferably, the tyre according to the invention is used in those demanding applications where the operating temperature of the tyre is in the range from about 60 °C to about 120 °C, such as in sports competitions.

[0249] In one embodiment, the tyre according to the invention is a tyre for motorcycles, wherein at least one component comprises, or preferably consists of, the elastomeric compound according to the invention. It is preferably a racing motorcycle tyre.

[0250] In one embodiment, the tyre according to the invention is a tyre for bicycle. A tyre for bicycle wheels typically comprises a carcass structure turned around a pair of bead cores at the beads and a tread band arranged in a radially outside position with respect to the carcass structure. Preferably, at least the tread band comprises the elastomeric compound according to the invention. The tyre according to the present invention may be produced according to a process which comprises:

[0251] - building components of a green tyre on at least one forming drum;

[0252] - shaping, moulding and vulcanising the tyre; wherein building at least one of the components of a green tyre comprises:

[0253] - manufacturing at least one green component, preferably the tread band, comprising, or preferably consisting of, the vulcanisable elastomeric compound of the invention.

[0254] Description of a tyre according to the invention

[0255] A tyre for vehicle wheels according to the invention, comprising at least one component comprising the present elastomeric compound, is illustrated in radial half-section in Figure 1 .

[0256] In Figure 1 , “a” indicates an axial direction and “X” indicates a radial direction, in particular X-X indicates the outline of the equatorial plane. For simplicity, Figure 1 shows only a portion of the tyre, the remaining portion not shown being identical and arranged symmetrically with respect to the equatorial plane “X-X”.

[0257] The tyre (100) for four-wheeled vehicles comprises at least one carcass structure, comprising at least one carcass layer (101 ) having respectively opposite end flaps engaged with respective annular anchoring structures (102), referred to as bead cores, optionally associated to a bead filler (104).

[0258] The tyre area comprising the bead core (102) and the filler (104) forms a bead structure (103) intended for anchoring the tyre onto a corresponding mounting rim, not shown.

[0259] The carcass structure is usually of radial type, i.e. the reinforcement elements of the at least one carcass layer (101 ) lie on planes comprising the rotational axis of the tyre and substantially perpendicular to the equatorial plane of the tyre. Said reinforcement elements generally consist of textile cords, such as rayon, nylon, polyester (for example polyethylene naphthalate, PEN). Each bead structure is associated to the carcass structure by folding back of the opposite lateral edges of the at least one carcass layer (101 ) around the annular anchoring structure (102) so as to form the so-called carcass flaps (101 a) as shown in Figure 1 .

[0260] In one embodiment, the coupling between the carcass structure and the bead structure can be provided by a second carcass layer, not shown in Figure 1 , applied in an axially external position with respect to the first carcass layer. An anti-abrasive strip (105) optionally made with elastomeric material is arranged in an outer position of each bead structure (103).

[0261] The carcass structure is associated to a belt structure (106) comprising one or more belt layers (106a), (106b) placed in radial superposition with respect to one another and with respect to the carcass layer, having typically textile and / or metallic reinforcement elements incorporated within a layer of elastomeric material.

[0262] Such reinforcement elements may have crossed orientation with respect to a direction of circumferential development of the tyre (100). By “circumferential” direction it is meant a direction generally facing in the direction of rotation of the tyre. At least one zero-degree reinforcing layer (106c), commonly known as a "0° belt", may be applied in a radially outermost position to the belt layers (106a), (106b), which generally incorporates a plurality of elongated reinforcement elements, typically metallic or textile cords, oriented in a substantially circumferential direction, thus forming an angle of a few degrees (such as an angle of between about 0° and 6°) with respect to a direction parallel to the equatorial plane of the tyre, and coated with an elastomeric material.

[0263] A tread band (109) comprising the elastomeric compound according to the invention is applied in a position radially outer to the belt structure (106).

[0264] Moreover, respective sidewalls (108) of elastomeric material are applied in an axially outer position on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of tread (109) at the respective bead structure (103).

[0265] In a radially outer position, the tread band (109) has a rolling surface (109a) intended to come in contact with the ground. Circumferential grooves, which are connected by transverse notches (not shown in Figure 1 ) so as to define a plurality of blocks of various shapes and sizes distributed over the rolling surface (109a), are generally made on this surface (109a), which for simplicity is represented smooth in Figure 1 . An underlayer (111 ) of elastomeric material may be arranged between the belt structure (106) and the tread band (109).

[0266] A strip consisting of elastomeric material (110), commonly known as “mini-sidewall”, may optionally be provided in the connecting zone between the sidewalls (108) and the tread band (109), this mini-sidewall being generally obtained by co-extrusion with the tread band (109) and allowing an improvement of the mechanical interaction between the tread band (109) and the sidewalls (108). Preferably, the end portion of the sidewall (108) directly covers the lateral edge of the tread band (109). In the case of tubeless tyres, a rubber layer (112), generally known as “liner”, which provides the necessary impermeability to the inflation air of the tyre, may also be provided in a radially inner position with respect to the carcass layer (101 ).

[0267] The rigidity of the tyre sidewall (108) may be improved by providing the bead structure (103) with a reinforcing layer (120) generally known as “flipper” or additional strip-like insert.

[0268] The flipper (120) is a reinforcing layer which is wound around the respective bead core (102) and the bead filler (104) so as to at least partially surround them, said reinforcing layer being arranged between the at least one carcass layer (101 ) and the bead structure (103). Usually, the flipper is in contact with said at least one carcass layer (101 ) and said bead structure (103).

[0269] The flipper (120) typically comprises a plurality of textile cords incorporated within a layer of elastomeric material.

[0270] The reinforcing annular structure or bead (103) of the tyre may comprise a further protective layer which is generally known by the term of “chafer” (121 ) or protective strip and which has the function of increasing the rigidity and integrity of the bead structure (103).

[0271] The chafer (121 ) usually comprises a plurality of cords incorporated within a rubber layer of elastomeric material. Such cords are generally made of textile materials (such as aramide or rayon) or metal materials (such as steel cords).

[0272] A layer or sheet of elastomeric material may be arranged between the belt structure and the carcass structure (not shown). The layer may have a uniform thickness. Alternatively, the layer may have a variable thickness in the axial direction. For example, the layer may have a greater thickness close to its axially outer edges with respect to the central (crown) zone.

[0273] Advantageously, the layer or sheet may extend on a surface substantially corresponding to the extension surface of said belt structure.

[0274] In a preferred embodiment, a layer of elastomeric material, referred to as underlayer (111 ), may be placed between said belt structure and said tread band, said under-layer preferably extending on a surface substantially corresponding to the extension surface of said belt structure.

[0275] The elastomeric compound according to the present invention may advantageously be incorporated in one or more of the above tyre components, preferably in the tread band. The building of the tyre (100) as described above, may be carried out by assembling respective semi-finished products consisting of the respective green compounds, semi-finished products adapted to form the components of the tyre, on a forming drum, not shown, by at least one assembling device.

[0276] At least a part of the components intended to form the carcass structure of the tyre may be built and / or assembled on the forming drum. More particularly, the forming drum is intended to first receive the possible liner, and then the carcass structure. Thereafter, devices non shown coaxially engage one of the annular anchoring structures around each of the end flaps, position an outer sleeve comprising the belt structure and the tread band in a coaxially centred position around the cylindrical carcass sleeve and shape the carcass sleeve according to a toroidal configuration through a radial expansion of the carcass structure, so as to cause the application thereof against a radially inner surface of the outer sleeve.

[0277] After building of green tyre, a moulding and vulcanisation treatment is generally carried out in order to determine the structural stabilisation of the tyre through crosslinking of the elastomeric compositions, as well as to impart a desired tread pattern on the tread band and to impart any distinguishing graphic signs at sidewalls.

[0278] Experimental part

[0279] Methods of analysis

[0280] 1H-NMR analysis

[0281] Nuclear magnetic resonance (NMR) spectroscopy was conducted with a Bruker Avance DPX 400 spectrometer at frequencies of 400.19 MHz for1H and 100.63 MHz for13C. The spectra obtained were calibrated on the residual signal of the solvent used (CDCh: 7.26 ppm1H; 77.16 ppm13C or DMSO-d6: 2.50 ppm1H; 39.52 ppm13C). The data were processed using the MestReNova software (v 11.0) and all chemical shifts 5 are reported in parts per million (ppm) with coupling constants in Hz (multiplicity: s = singlet, d = doublet, dd = doublet of doublets, t = triplet, dt = doublet of triplets, ddd = doublet of doublets of doublets, sep = septuplet, m = multiplet, br = broad signal).

[0282] Determination of the association constant KA

[0283] The method used herein to analyse the complexation equilibrium and determine the association constant KA was the NMR dilution method, as described by Thordarson, P. in chapter Binding Constants and Their Measurement. In Supramolecular Chemistry, in particular in par. 2.6.2, Gale, P. A., Steed, J. W., Eds.; Wiley, 2012. https: / / doi.org / 10.1002 / 9780470661345.smc018; and exemplified by Chu, W.-J.; Yang, Y.; Chen, C.-F. Multiple Hydrogen-Bond-Mediated Molecular Duplexes Based on the Self-Complementary Amidourea Motif. Org. Lett. 2010, 12 (14), 3156- 3159. https: / / doi.org / 10.1021 / ol101068n and, in particular, in the related "Supporting Information" on pages S13-S15.

[0284] The method consists in preparing a sufficiently concentrated solution of the product, if possible greater than 10 mM, measuring the NMR spectrum thereof at 298 °K and then performing a series of consecutive dilutions until reaching the detection limit of the NMR instrument, in some cases below 0.1 mM. The chemical shifts associated with the hydrogens involved in hydrogen bonding show significant variations with changes in concentration. The variation of the chemical shifts (5) of the peaks of interest may be described, for the exemplified cases, by the following equation: wherein

[0285] 5: Experimentally observed chemical shift

[0286] 5 mono: Chemical shift of the product in the monomeric state

[0287] 5 dim: Chemical shift of the product in the dimeric state

[0288] KA: Association constant

[0289] [M]o: Initial concentration of product

[0290] For each concentration there will be a pair of values, 5 and [M]o, which may be plotted on a graph. Through nonlinear regression methods it is possible to calculate the fitting of the curve described by the above equation to the experimentally obtained points, deriving the unknown parameters, i.e. 5dim, bmono and KA, the latter with a possible error estimated around ± 10%.

[0291] Measurement of static mechanical properties

[0292] The static mechanical properties of the compounds were evaluated according to the ISO 37-2011 standard at 23 °C, on 5 Dumbell specimens prepared by vulcanisation (at 170 °C for 10 minutes) of the elastomeric compounds to be examined. In this way the following parameters were measured:

[0293] - load at 50% elongation (Ca0.5),

[0294] - load at 100% elongation (Ca1 ),

[0295] - load at 300% elongation (Ca3), - breaking load (OR), and

[0296] - % elongation at break (AR).

[0297] The IRHD hardness was measured at 23 °C on vulcanised elastomeric compositions according to the ISO 48:2007 standard.

[0298] Analisi RPA (Rubber Process Analyser)

[0299] The dynamic mechanical properties of dynamic shear modulus G’ and Tan Delta and the rheometric properties of the compounds were evaluated using an Alpha Technologies R.P.A. (Rubber Process Analyser) oscillating chamber rheometer with chamber geometry according to the ASTM D6601 -19 standard, Figure 1 , applying the following method.

[0300] An approximately cylindrical test sample with a volume in the range from 4.6 to 5 cm3was obtained by punching a sheet of the green vulcanisable elastomeric composition to be characterised having a thickness of at least 5 mm. Subsequently, the chambers of the R.P.A. 2000 were preliminarily preheated to 170 °C.

[0301] The sample was loaded between the chambers of the rheometer and the chambers were closed. Between the sample of the green vulcanisable elastomeric composition and each chamber of the rheometer, two films were interposed to protect the chamber itself: in contact with the compound, a film of Nylon 6.6 cast about 25 microns thick while in contact with the chamber of the rheometer a polyester film about 23 microns thick. The sample was then vulcanised for a fixed time of 10 minutes at a temperature of 170 °C while recording the vulcanisation curve, i.e. subjecting the sample to a sinusoidal deformation of 7% amplitude and 1 .67 Hz frequency for the entire duration of the vulcanisation.

[0302] The temperature of the rheometer chambers was then brought to 70 °C. After a total time of 10 minutes since the chamber temperature was set at 70 °C, a sequence of dynamic measurements was performed at a constant temperature of 70 °C by sinusoidally stressing the sample in torsion at a fixed frequency of 10 Hz and amplitude progressively increasing from 0.4% to 10%, carrying out 10 stabilisation cycles and 10 measurement cycles for each condition.

[0303] Always keeping the temperature of the rheometer chambers at 70 °C, a dynamic measurement was then carried out by sinusoidally stressing the sample in torsion at the fixed frequency of 10 Hz and amplitude of 9%, with 10 stabilisation cycles and 20 measurement cycles. In this way, the following parameters were measured as an average of what was recorded in the 20 measurement cycles:

[0304] - dynamic shear elastic modulus G’ at a strain amplitude of 9%,

[0305] - torsion Tan Delta, i.e. the ratio between the viscous elastic modulus G” and the dynamic elastic modulus G’, at a deformation amplitude of 9% (hereinafter Tan Delta (9%)).

[0306] Punctual analysis of dynamic properties in compression

[0307] The dynamic mechanical properties in compression of the compounds at predefined punctual temperatures (70 °C, 100 °C and 120 °C) were evaluated using an Instron model 1341 dynamic device in the compression mode according to the following procedure.

[0308] A specimen of vulcanised material (170 °C for 10 minutes) having a cylindrical shape (length = 25 mm; diameter = 18 mm) was compressed preloaded up to a longitudinal deformation of 25% with respect to the initial length and maintained at the predetermined temperature (for example, 70 °C) for the entire duration of the test. After a waiting time of 2 minutes followed by a mechanical pre-conditioning of 125 cycles at 10Hz at 5% deformation amplitude with respect to the length under preload, the specimen was subjected to a dynamic sinusoidal stress having an amplitude of ± 3.5% of the length under pre-load, with a frequency of 10Hz.

[0309] In this way the following parameters were measured:

[0310] - dynamic elastic modulus E’,

[0311] - Tan delta, i.e. the ratio between the viscous dynamic module E” and the dynamic elastic modulus E’.

[0312] Dynamic Mechanical Analysis (DMA)

[0313] The dynamic properties of the compounds as a function of temperature were measured with two different procedures using two different instruments in shear or tensile mode.

[0314] In the first case (shear mode), the Metravib instrument was used, suitable for measuring specimens of two cylinders with a diameter of 10 mm and a thickness of 2 mm glued between three brass cylinders with a diameter of 10 mm and a length of 14 mm.

[0315] In the second case (tensile mode), the Eplexor Gabo instrument was used, suitable for measuring rectangular specimens with dimensions 1 cm x 5mm x 1 mm (length x width x thickness). In the DMA measurement in shear mode (DMA1 ), the method involved the application of a sinusoidal dynamic deformation of an amplitude equal to ±1 % with respect to the length under preload of 0.01 MPa, at a frequency of 10 Hz, and at the same time of a ramp of temperature with constant increase of 3 °C / min from 23 °C to 120 °C.

[0316] In the DMA measurement in tensile mode (DMA2), the sample placed under constant temperature of 23 °C, and 25% pre-load, where the percentage refers to the length of the sample being examined calculated from the distance between the two clamps, a sinusoidal dynamic deformation with an amplitude equal to ±3.5% with respect to the length under pre-load was applied, at a frequency of 10 Hz, until the equilibrium of the dynamic elastic modulus (E’) was reached, such as reaching a constant value (less than 0.05% variation in 5 minutes) of E’. Once the dynamic equilibrium of the material was reached, a temperature ramp with a constant increase of 3 °C / min from 23 °C to 150 °C was applied.

[0317] The dynamic elastic properties were expressed in terms of dynamic elastic modulus (E’) and tan Delta (loss factor).

[0318] Example 1 : preparation and characterisation of cross-linking modifying agents (I) The following Table 2 lists the cross-linking modifying agents of formula (I)

[0319] A - B - C (I) according to the invention or comparative, and the non-cross-linking (IC) and nonmodifying (IN) agents respectively used in the present experimental part with the relative association constants KA:

[0320] Table 2 wherein the association constant KA values were experimentally measured (meas.) (NMR in CDCh at 298 °K) (l-D, l-E, l-M, l-N) or were estimated (est.) on the basis of the values reported in the literature (see Table 1 , l-B, l-H, l-L) or on the basis of the values measured experimentally herein for structurally similar adducts (l-A and l-F vs l-M; l-G vs l-N; l-l, l-J, l-K vs l-E) or in the absence of the group C it was considered equal to zero (l-C).

[0321] Example 1 -A: preparation and characterisation of the cross-linking modifying agent U-Al

[0322] The cross-linking modifying agent according to the invention of formula was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII) according to the following synthesis scheme:

[0323] Scheme 1

[0324] (VIII) (l-A)

[0325] Lipoic acid (1 eq.) was dissolved in anhydrous DMF, under nitrogen atmosphere. The solution was cooled to 0 °C. 4-(dimethylamino)pyridine (0.5 eq.) and N-(3- dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (1.2 eq.) were added, stirred for 10 min, and then the aminopyrimidone (1 eq.) was added. The reaction was stirred at room temperature and under nitrogen atmosphere for 72 hours. The mixture was then poured into a solution of HCI (1 M), under stirring, and a precipitate was formed, which was filtered, washed with ethanol and dried in an oven, to yield the pure agent (l-A).

[0326] 1H NMR (400 MHz, DMSO-d6) 5 11 .97 (s, 1 H), 5.95 (s, 1 H), 3.65 (dq, 1 H), 3.24 -

[0327] 3.08 (m, 2H), 2.47 - 2.41 (m, 3H), 2.41 - 2.32 (m, 2H), 1 .88 (dq, 1 H), 1 .75 - 1 .50

[0328] (m, 2H), 1 .44 - 1 .34 (m, 2H), 1 .20 (t, 3H).

[0329] The amino-pyrimidone (VIII), in which R1 meant CH3 herein, was prepared according to Scheme 2:

[0330] Scheme 2 R

[0331] RA according to the following procedure.

[0332] The corresponding [3-ketoester (1 eq.) was dissolved in ethanol and guanidine carbonate (0.5 eq.) was added, heated under reflux under magnetic stirring for 24 hours. The solvent was evaporated and the solid was filtered, washing with ethyl ether. The product was dried in an oven and used for the next reaction without further purification.

[0333] The group C of the cross-linking modifying agent (l-A) formed the adduct with three intermolecular hydrogen bonds represented here: wherein R2 =

[0334] The estimated association constant KA for the agent (l-A) was about 30 M’1by structural analogy with the adduct formed by the cross-linking modifying agent (I- M). The same preparation procedure from lipoic acid was used for the synthesis of the other amido derivatives (l-E), (l-F), (l-l), (l-J) and (l-K), starting from the corresponding amines commercially available or preparable according to known common methods (see above the preparation of intermediate VIII).

[0335] Example 1 -B: preparation and characterisation of the comparative cross-linking modifying agent (l-B)

[0336] The comparative cross-linking modifying agent of formula was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII, where R1 = methyl) according to the following synthesis scheme:

[0337] Scheme 3

[0338] (VIII) (l-B)

[0339] Lipoic acid (1 eg.) was dissolved in anhydrous DMF, under nitrogen atmosphere. The solution was cooled to 0 °C, diphenyl phosphoryl azide (DPPA, 1.1 eg.) and triethylamine (1.1 eg.) were added, heated to 80 °C for 3 h, and then aminopyrimidone (VIII) (1 eg.) was added. The reaction was stirred at 80 °C and under nitrogen atmosphere for 18 hours. The mixture was then poured into a solution of HCI (1 M), under stirring, and a precipitate was formed, which was filtered, washed with ethanol and dried in an oven, to yield the pure agent (l-B).

[0340] 1H NMR (400 MHz, CDCIs) 5 13.09 (s, 1 H), 11.86 (s, 1 H), 10.18 (s, 1 H), 5.82 (s, 1 H), 3.58 (dg, 1 H), 3.26 (dd, 2H), 3.22 - 3.06 (m, 2H), 2.53 - 2.41 (m, 1 H), 2.23 (s, 3H), 1 .92 (d, 1 H), 1 .80 - 1 .40 (m, 6H).

[0341] The group C of the comparative cross-linking modifying agent (l-B) formed the adduct with four intermolecular hydrogen bonds represented here: wherein R2 =

[0342] An analogous adduct, wherein R2 = C3H7, was characterised by a literature association constant KA around 6- 107M’1(Ligthart, GBWL; Ohkawa, H.; Sijbesma, R.P.; Meijer, E.W.; Complementary Quadruple Hydrogen Bonding in Supramolecular Copolymers', J. Am. Chem. Soc. 2005, 127 (3), 810-811 ).

[0343] The cross-linking modifying agent (l-B) corresponded to the ureido-pyrimidone group-containing molecules shown in patent application US20220403056A1 .

[0344] Example 1 -C: preparation and characterisation of the comparative non-cross-linking agent (l-C)

[0345] The comparative non-cross-linking agent of formula was prepared from lipoic acid and methanol following a procedure similar to that of Example 1 -A.

[0346] The agent (l-C) did not form an adduct with itself (not self-assembling) since the group C was absent (-COOCH3 did not form hydrogen bonds). The association constant KA was therefore considered egual to 0.

[0347] Example 1 -D: preparation and characterisation of the cross-linking modifying agent (EDI

[0348] The comparative cross-linking modifying agent of formula

[0349] (l-D) was prepared from lipoic acid and the corresponding 2-amino-pyridine following a procedure similar to that of Example 1 -A.1H NMR (400 MHz, CDCIs) 5 8.26 (ddd, 1 H), 8.20 (d, 1 H), 8.06 (s, 1 H), 7.73 - 7.67 (m, 1 H), 7.03 (ddd, 1 H), 3.58 (dq, 1 H), 3.23 - 3.06 (m, 2H), 2.51 - 2.37 (m, 3H), 1 .91 (dq, 1 H), 1 .82 - 1 .66 (m, 4H), 1.61 - 1.42 (m, 2H).

[0350] The group C of the cross-linking modifying agent (l-D) formed the adduct with two intermolecular hydrogen bonds represented here: wherein R2 =

[0351] The adduct was characterised by an association constant KA equal to about 3.5 M-1, determined by NMR according to the method described above.

[0352] This constant was in line with the value estimated in the literature around 2 M-1(Steven C. Zimmerman and Thomas J. Murray; New Supramolecular Architectures Using Hydrogen Bonding-, Phil. Trans. R. Soc. Lond. A 1993, 345 (1674), 49-56).

[0353] Example 1-E: preparation and characterisation of the cross-linking modifying agent

[0354] OzEl

[0355] The cross-linking modifying agent according to the invention of formula

[0356] (l-E) was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII where R1 = tert-butyl) as described in Example 1-A.1H NMR (400 MHz, CDCIs) 5 11 .68 (s, 1 H), 7.98 (s, 1 H), 6.12 (s, 1 H), 3.58 (dt, 1 H),

[0357] 3.24 - 3.08 (m, 2H), 2.54 - 2.42 (m, 3H), 1 .93 (dq, 1 H), 1 .83 - 1 .65 (m, 4H), 1 .59 -

[0358] 1.47 (m, 2H), 1.20 (s, 9H).

[0359] The group C of the cross-linking modifying agent (l-E) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A).

[0360] The adduct was characterised by an association constant KA equal to about 26.1 M’1, determined by NMR according to the method described above.

[0361] Example 1 -F: preparation and characterisation of the cross-linking modifying agent

[0362] OzEl

[0363] The cross-linking modifying agent according to the invention of formula was prepared from 11 -bromoundecanoic acid and the corresponding amino- pyrimidone (VIII, where R1 = methyl) according to the following synthesis scheme:

[0364] Scheme 4 step 1

[0365] (VIII) (l-F)

[0366] Step 1 : 11 -Bromoundecanoic acid (1 eq.) was dissolved in a solution of dimethylformamide and water (ratio 9:1 ), sodium azide (1.5 eq.) was added and heated to 80 °C for 22 hours. At the end of the reaction, water was added and extracted with diethyl ether, the organic phase was dried and evaporated to yield the pure intermediate.

[0367] Step 2: 11 -azido-undecanoic acid (1 eq.) was dissolved in anhydrous DMF, under nitrogen atmosphere. The solution was cooled to 0 °C and 4- (dimethylamino)pyridine (0.5 eq.) and N-(3-dimethylaminopropyl)-N’- ethylcarbodiimide hydrochloride (1 .2 eq.) were added. It was stirred for 10 min and then the amino-pyrimidone (1 eq.) was added. The reaction was stirred at room temperature and under nitrogen atmosphere for 72 hours. The mixture was then poured into a solution of HCI (1 M), under stirring, and a precipitate was formed, which was filtered, washed with ethanol and dried in an oven, to yield the pure agent

[0368] 1H NMR (400 MHz, CDCIs) 5 12.00 (s, 1 H), 6.00 (s, 1 H), 3.25 (t, 2H), 2.47 (t, 2H), 2.24, (s, 3H), 1.69 (dt, 2H), 1.64 - 1.55 (m, 2H), 1.41 - 1.24 (m, 12H).

[0369] The group C of the cross-linking modifying agent (l-F) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A).

[0370] The adduct was characterised by an association constant KA estimated to be about 30 M’1by structural analogy with the adduct formed by the cross-linking modifying agent (l-M).

[0371] Example 1 -G: preparation and characterisation of the cross-linking modifying agent

[0372] UzGl

[0373] The cross-linking modifying agent according to the invention of formula was prepared from lipoic acid and the corresponding 2-amino-benzimidazole as described in Example 1 -A.

[0374] 1H NMR (400 MHz, DMSO-d6) 5 12.03 (s, 1 H), 11 .48 (s, 1 H), 7.53 - 7.33 (m, 2H), 7.07 (dd, 2H), 3.64 (dq, 1 H), 3.26 - 3.06 (m, 2H), 2.48 - 2.38 (m, 3H), 1 .88 (dq, 1 H), 1 .77 - 1 .53 (m, 4H), 1.51 - 1 .35 (m, 2H).

[0375] The group C of the cross-linking modifying agent (l-G) formed the adduct with two intermolecular and one intramolecular hydrogen bonds represented here wherein R2 =

[0376] The adduct was characterised by a KA estimated around 18 M’1due to structural analogy with the adduct formed by the non-modifying agent (l-N).

[0377] Example 1 -H: preparation and characterisation of the cross-linking modifying agent (PHI

[0378] The comparative cross-linking modifying agent of formula was prepared from lipoic acid and the corresponding imidazolidinone according to the following synthesis scheme:

[0379] Scheme 5 step 1

[0380] Step 1 : lipoic acid (1 eq.) was dissolved in anhydrous DMF, under nitrogen atmosphere. The solution was cooled to 0 °C and 4-(dimethylamino)pyridine (0.5 eq.) and N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (1.2 eq.) were added. It was stirred for 10 min and then 11 -bromo-undecanol (1 eq.) was added. The reaction was stirred at room temperature and under nitrogen atmosphere for 72 hours. It was then extracted with diethyl ether, dried and the organic phase evaporated to yield the pure intermediate.

[0381] Step 2: 2-imidazolidinone (1 eq.) was dissolved in anhydrous dimethyl formamide, under nitrogen atmosphere. Potassium carbonate (3 eq.) and potassium iodide (0.1 eq.) were added and heated to 80 °C for 1 hour. Subsequently, the intermediate from step 1 was added and heated to 80 °C for 48 h. Once the reaction was complete, the reaction mixture was poured into water and a precipitate was waited for to form, which was then filtered to yield the pure product.

[0382] 1H NMR (400 MHz, CDCIs) 5 4.05 (t, 2H), 3.62 (dd, 1 H), 3.58 - 3.46 (m, 2H), 3.21 - 3.06 (m, 2H), 2.54 - 2.39 (m, 1 H), 2.31 (t, 2H), 1 .90 (td, 1 H), 1 .75 - 1 .53 (m, 8H), 1.51 - 1 .39 (m, 2H), 1 .39 - 1 .21 (m, 16H).

[0383] The group C of the cross-linking modifying agent (l-H) formed the adduct with two intermolecular hydrogen bonds represented here: wherein R2 =

[0384] The adduct was characterised by an association constant KA estimated from the literature to be about 1.1 M’1(Chem. Commun. 2003, No. 14, 1638-1639).

[0385] The cross-linking modifying agent (l-H) corresponded to the molecules containing the imidazolidinone group shown in U.S. patent 9394434.

[0386] Example 1 -1: preparation and characterisation of the cross-linking modifying agent (l-l)

[0387] The cross-linking modifying agent according to the invention of formula was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII, where R1 = isopropyl) as described in Example 1 -A.

[0388] 1H NMR (400 MHz, CDCI3) 5 12.82 - 11 .34 (s, 1 H), 9.70 - 8.28 (s, 1 H), 6.01 (s, 1 H), 3.58 (dg, 1 H), 3.24 - 3.07 (m, 2H), 2.56-2.42 (m, 3H), 2.00 - 1 .86 (m, 1 H), 1 .83 - 1.44 (m, 7H), 1.24 - 1.10 (m, 6H).

[0389] The group C of the cross-linking modifying agent (l-l) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A). The adduct was characterised by an association constant KA estimated to be around about 26 M’1by structural analogy with the adduct formed by the crosslinking modifying agent (l-E).

[0390] Example 1 -J: preparation and characterisation of the cross-linking modifying agent (kJ)

[0391] The cross-linking modifying agent according to the invention of formula was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII, where R1 = propyl) as described in Example 1 -A.

[0392] 1H NMR (400 MHz, DMSO-d6) 5 11 .67 (s, 1 H), 5.89 (s, 1 H), 3.63 (dg, 1 H), 3.24 - 3.08 (m, 2H), 2.47 - 2.41 (m, 3H), 2.41 - 2.32 (m, 2H), 1 .88 (dg, 1 H), 1 .74 - 1 .51 (m, 6H), 1 .44 - 1 .34 (m, 2H), 0.89 (t, 3H).

[0393] The group C of the cross-linking modifying agent (l-J) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A).

[0394] The adduct was characterised by an association constant KA estimated to be around about 26 M-1by structural analogy with the adduct formed by the crosslinking modifying agent (l-E).

[0395] Example 1 -K: preparation and characterisation of the cross-linking modifying agent

[0396] £lzK}

[0397] The cross-linking modifying agent according to the invention of formula was prepared from lipoic acid and the corresponding amino-pyrimidone (VIII, where R1 = paramethoxyphenyl) as described in Example 1 -A.

[0398] 1H NMR (400 MHz, CDCIs) 5 7.96 - 7.67 (m, 2H), 7.02 - 6.88 (m, 2H), 6.52 (s, 1 H), 3.85 (s, 3H), 3.58 (dg, 1 H), 3.24 - 3.07 (m, 2H), 2.53 - 2.40 (m, 2H), 1.97 - 1 .87 (m, 1 H), 1 .83 - 1 .63 (m, 4H), 1.57 - 1 .43 (m, 2H). The group C of the cross-linking modifying agent (l-K) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A).

[0399] The adduct was characterised by an association constant KA estimated to be around about 26 M-1by structural analogy with the adduct formed by the crosslinking modifying agent (l-E).

[0400] Example 1 -L: preparation and characterisation of the cross-linking modifying agent

[0401] (! )

[0402] The cross-linking modifying agent according to the invention of formula was prepared from 11 -bromo-undecanol and the corresponding guinolinone according to the following synthesis scheme:

[0403] Scheme 6 step 1 step 2 step 3

[0404] 7-hydroxy-2-quinolinone

[0405] Step 1 : 11 -Bromo-undecanol (1 eg.) was dissolved in a solution of dimethyl formamide and water (ratio 9:1 ), sodium azide (1.5 eg.) was added and heated at 80 °C for 22 hours. At the end of the reaction, water was added and extracted with diethyl ether, the reaction was dried and the organic phase was evaporated to yield the pure intermediate. Step 2: The intermediate from Step 1 was dissolved in anhydrous dichloromethane under a nitrogen atmosphere. It was cooled with an ice bath and triethylamine (3 eq.), dimethylamino pyridine (0.05 eq.) and subsequently tosyl chloride (1.2 eq.) were added. The reaction was stirred at room temperature for 18 hours. At the end of the reaction, water was added and extracted with diethyl ether, the reaction was dried and the organic phase was evaporated. The crude was purified by silica gel chromatography, eluting with dichloromethane, to yield the pure intermediate.

[0406] Step 3: 7-hydroxy-2-quinolinone (1 eq.) was dissolved in anhydrous dimethyl formamide, under nitrogen atmosphere. Potassium carbonate (3 eq.) and potassium iodide (0.1 eq.) were added and heated to 80 °C for 1 hour. Subsequently, the intermediate from step 2 was added and heated to 80 °C for 48 h. Once the reaction was complete, the reaction mixture was poured into water and a precipitate was waited for to form, which was then filtered to yield the pure product.

[0407] 1H NMR (400 MHz, CDCIs) 5 11 .26 (s, 1 H), 7.72 (d, 1 H), 7.44 (d, 1 H), 6.81 (dd, 1 H), 6.74 (d, 1 H), 6.53 (d, 1 H), 4.04 (t, 2H), 3.26 (t, 2H), 1 .89 - 1 .75 (m, 2H), 1.54 - 1 .42 (m, 2H), 1.44 - 1.19 (m, 14H).

[0408] The group C of the cross-linking modifying agent (l-L) formed an adduct with two intermolecular hydrogen bonds represented here: wherein R3 =

[0409] The adduct was characterised by an association constant estimated from the literature to be about 46 M-1(New Supramolecular Architectures Using Hydrogen Bonding. Phil. Trans. R. Soc. Lond. A 1993, 345 (1674), 49-56. https: / / d0i.0rg / l 0.1098 / rsta.1993.0116.)

[0410] Example 1 -M: preparation and characterisation of the cross-linking modifying agent (EM)

[0411] The cross-linking modifying agent according to the invention of formula was prepared from 5-bromopentanoic acid and the corresponding amino- pyrimidone (VIII with R1 =methyl) similarly to what was described in Example 1 -F.

[0412] 1H NMR (400 MHz, CDCI3) 5 6.01 (s, 1 H), 3.34 (t, 2H), 2.55 (t, 2H), 2.24 (d, 3H),

[0413] 1.87 - 1 .76 (m, 2H), 1 .73 - 1 .62 (m, 2H).

[0414] The group C of the cross-linking modifying agent (l-M) formed an adduct with three intermolecular hydrogen bonds similar to that of agent (l-A) (adduct lll-A).

[0415] The adduct was characterised by an association constant KA equal to about 30 M’

[0416] 1, determined by NMR according to the method described above.

[0417] Example 1-N: preparation and characterisation of the comparative non-modifying agent (l-N)

[0418] The comparative non-modifying agent - because it lacks the anchoring group A - of formula was prepared from stearic acid and the corresponding 2-amino-benzimidazole as described in Example 1-G.

[0419] 1H NMR (400 MHz, CDCIs) 5 7.38 (dd, 2H), 7.25 - 7.21 (m, 2H), 3.03 (t, 2H), 1.91 - 1 .81 (m, 2H), 1 .33 - 1 .21 (m, 28H), 0.88 (t, 3H).

[0420] The group C of the comparative non-modifying agent (l-N) formed an adduct with two intermolecular hydrogen bonds similar to that of the agent (l-G) (adduct lll-G). The adduct was characterised by an association constant KA equal to about 18 M’1, determined by NMR according to the method described above.

[0421] Example 2

[0422] Preparation of the elastomeric compounds

[0423] Reference, comparative or inventive elastomeric compounds were prepared from the compositions reported in the following Tables 3 to 6:

[0424] Table 3: Elastomeric compositions for black compounds wherein

[0425] Ref. = standard reference composition; Inv. = composition according to the invention; Comp. = comparative composition; d = density;

[0426] SBR was a styrene-butadiene (high styrene) elastomeric polymer HP755B oil extended with 37.5 phr of TDAE) from JSR;

[0427] Stearic acid was supplied by S.O.G.I.S. INDUSTRIA CHIMICA S.p.A.;

[0428] Carbon black was Vulcan 1391 from Cabot;

[0429] Alpha-methyl styrene resin was supplied by Eastman;

[0430] TDAE oil was supplied by H&R Olwerke Schindler GmbH; Zn salts of fatty acids were from Eigenmann & Veronelli;

[0431] ZnO was supplied by Lanxess;

[0432] 6PPD was N-(1 ,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine supplied by Eastman Chemical Company;

[0433] Tetraisobutyl thiuram disulphide (Isobutyl TUADS) was supplied by Shandong Yanggu Huatai Chemical Co., ltd;

[0434] Caprolactam disulphide (Rhenogran CLD 80) was supplied by Rhein Chemie;

[0435] CBS (N-cyclohexyl-2-benzothiazolsulphenamide) was supplied by General Quimica; VULKUREN KA 9188 (1 ,6-Bis(N,N-dibenzylthiocarbamoyldithio)hexane) was supplied by LANXESS Deutschland GmbH;

[0436] (l-A), (l-B) and (l-C) were the cross-linking and non-cross-linking modifying agents described above in Example 1 , present in equimolar amounts in compounds 2.3, 2.4 and 2.5.

[0437] Table 4: Elastomeric compositions for white compounds wherein silica was Si 1165 from Solvay;

[0438] TESPT was bis(triethoxysilylpropyl)tetrasulphide from Evonik; and the other ingredients and meanings were as given in the above Tables.

[0439] Table 5: Elastomeric compositions for black compounds

[0440] wherein the ingredients and meanings were as reported in the above Tables (l-A),

[0441] (l-B), (l-D), (l-E), (l-F), (l-G) were the cross-linking modifying agents described above in Example 1 , present in equimolar amounts in compounds 2.10-2.15.

[0442] Table 6: Elastomeric compositions for black compounds wherein the ingredients and meanings were as reported in the above Tables and (I- H), (l-J), (l-l), (l-K) were the cross-linking modifying agents described above in Example 1 , present in equimolar amounts in compounds 2.16-2.19.

[0443] Starting from the elastomeric compositions shown in Tables 3 to 6, the corresponding elastomeric compounds were prepared according to the following process.

[0444] The mixing of the components was carried out in two steps (herein indicated as step 1 and step 2) with a Brabender Plasti-Corder® PL2000 Lab-Station (Brabender GmbH & Co. KG, Duisburg, Germany) equipped with a mixing system with a total capacity of 55 cm3.

[0445] In the first step (1 -0), SBR was introduced. Mixing at 60 rpm was continued for 1 minute at 130 °C. Then (1 -1 ) the alpha-methyl styrenic resin, the stearic acid, the TDAE oil and part of the reinforcing filler (carbon black or silica, in this case with all the silane) were added. Mixing at 60 rpm was continued for 2 minutes at 130 °C. The remaining part of the reinforcing filler (carbon black or silica) was then added (1 -2). Mixing at 60 rpm was continued for 2 minutes, at 130 °C. Then (1 -3) 6PPD, stearic acid, ZnO were added and mixing at 60 rpm was continued for 2 minutes, at 130 °C.

[0446] Subsequently, in the second step (2), carried out using the same mixer, sulphur, CBS, TiBTD, vulkuren, the cross-linking modifying agent were added and mixing at 50 rpm continued for about 2 minutes at 80 °C, when the vulcanisable compounds were discharged and subsequently vulcanised in a press at 170 °C for 10 min.

[0447] Characterisation of the compounds

[0448] Static mechanical properties

[0449] The main static properties of elastomeric compounds vulcanised for 10 minutes at 170 °C prepared from the compositions of Ex. 2.1 - 2.8, measured with the methods described above (Dumbbell), are reported in the following Tables 7 and 8:

[0450] Table 7: Static properties (black compounds from compositions Ex. 2.1 - 2.5) wherein CR was the breaking load, Ca0.5, Ca1 and Ca3 were the load for 50%, 100% and 300% elongation respectively, AR% and Energy were the elongation and energy at break.

[0451] As may be observed from the data reported in Table 7, the static properties varied with a certain linearity going from a content of 4 phr (Ex. 2.2) to 8 phr (Ex. 2.3) (see for example Ca05 which increases by about 10%) and were comparable at equal moles (Ex. 2.3 vs Ex. 2.4). Furthermore, it was noted that the agent (l-C), comprising lipoic acid but lacking the self-assembling group C, did not particularly influence the static properties which remained similar to those of the reference compound (Ex. 2.5 compared to 2.1 ).

[0452] Table 8: Static properties (white compounds from compositions Ex. 2.6 - 2.8)

[0453] The agent (l-A) was also tested in white compounds to verify any effects on the static properties resulting from the interaction of the agent with the silica.

[0454] No major changes were observed with respect to the reference and the static properties were found to be substantially aligned.

[0455] Dynamic mechanical properties

[0456] The dynamic mechanical properties of the elastomeric compounds prepared from the compositions of Examples 2.1 - 2.19 were measured both in punctual temperature conditions at 70, 100 and 120 °C in compression, and in temperature sweep in shear or tensile conditions (DMA1 and DMA2) as described above, and the results are reported in the following Tables 9 and 10 and in Figures 2-4:

[0457] Table 9: Punctual dynamic properties

[0458] (black compounds from compositions of Ex. 2.1 - 2.5)

[0459] (Ex. 2.2 vs Ex. 2.3) the values of both the moduli and the Tan Delta increase proportionally, the latter being especially high at higher temperatures and predictive of good grip together with an acceptable cold modulus (70 °C). As regards the comparative agent (l-B) (ureido-pyrimidone), it was noted that the increase in hysteresis with respect to the reference compound was substantially zero at 70 °C and strongly reduced with respect to the inventive agent (l-A) even at 120 °C at equal moles. Furthermore, the compound of Ex. 2.4 proved to be too stiff at 70 °C, showing the highest E’ value (Ex. 2.4 vs Ex. 2.1 ), attributable to the excessive stability of the complex characterised by the formation of as many as 4 intermolecular hydrogen bonds.

[0460] In the case of the agent (l-C) there was no formation of hydrogen bonds, the properties of the compound of Ex. 2.5 were similar to those of the reference and the hysteresis was not increased. Table 10: Punctual dynamic properties

[0461] (white compounds from compositions of Ex. 2.6 - 2.8

[0462] Even in the case of the white compounds, the data in Table 10 showed a significant increase in hysteresis at all temperatures, proportional to the amount of agent (l-A) present, with completely acceptable cold modulus values, predictive of good road holding.

[0463] In Figure 2 the Tand values of samples of the black compounds of Ex. 2.3 (Inv. I-A), Ex. 2.5 (Comp. I-C) and Ex. 2.1 (Ref., no agent) subjected to dynamic shear test (DMA1 ) with temperature sweep from 23 °C to 120 °C (10 Hz, 1 % strain) were plotted against temperature.

[0464] As may be observed from the graph, in the case of the agent (l-A) at temperatures around 60-70 °C a Tan Delta peak appeared, i.e. a marked heat dissipation associated with the formation-breaking mechanism of hydrogen bonds and a hysteresis that was always much higher than the reference even at higher temperatures, particularly advantageous for sports applications.

[0465] This trend was surprising in light of the above-cited patents US9394434 and US20220403056A1 which taught the use of similar agents, characterised by different KA values, to reduce the hysteresis of elastomeric compounds.

[0466] In the case of the non-cross-linking agent (l-C), however, since there were no hydrogen bonds, the behaviour was completely similar to that of the reference.

[0467] The samples were subjected to a further dynamic test in tensile mode (DMA2) (10 Hz, 25% pre-strain, 3.5% strain) with temperature sweep from 23 °C to 150 °C and the Tan Delta values were plotted against temperature, as shown in Figure 3 for the black compounds of Ex. 2.2 (Inv. I-A, 4 phr), Ex. 2.3 (Inv., I-A 8 phr) and Ex. 2.1 (Ref., no agent) and in Figure 4 for the white compounds of Ex. 2.7 (Inv., I-A, 2 phr), Ex. 2.8 (Inv., I-A, 4 phr) and Ex. 2.6 (Ref., no agent).

[0468] In particular, in the graph of Figure 3, starting from around 70 °C, we observe the Tan Delta peak, associated with the breaking of hydrogen bonds, and subsequently hysteresis that is always much higher and proportional to the amount of agent (I-A) due to the hydrogen bond breaking - formation mechanism.

[0469] To further highlight the increase in hysteresis obtained, quite surprisingly in light of the literature, the following Table 11 reports the percentage variations of Tan Delta at different temperatures, in the above-mentioned DMA2 dynamic test, of the black compounds according to the invention of Ex. 2.2 and Ex. 2.3 compared to the Tan Delta values measured for the reference compound of Ex. 2.1 :

[0470] Table 11 to the invention showed at lower temperatures hysteresis values in line with or slightly lower than the reference, while an increasingly marked increase in the same hysteresis was observed starting from 60-70 °C and up to 150 °C. Similarly, Figure 4 showed the Tan Delta trend with increasing temperature (DMA2 tensile test from 23 °C to 150 °C; 10 Hz; 25% pre-strain, strain 3.5%) of samples prepared from the compositions for white compounds of Ex. 2.7 (Inv), Ex. 2.8 (Inv) - comprising respectively 2 phr and 4 phr of cross-linking modifying agent (IA) - and of Ex. 2.6 (Ref.). Unlike the black compounds, an increase in hysteresis compared to the reference was observed with the white compounds at all temperatures, in particular starting from room temperature. This behaviour was particularly interesting for example for motorcycle applications, especially racing, where high road holding is required at all temperatures. The following Table 12 shows the percentage variations of Tan Delta at different temperatures, in the above mentioned DMA2 dynamic test, of the white compounds according to the invention of Ex. 2.7 (Inv) and Ex. 2.8 (Inv) compared to the Tan Delta values measured for the reference compound of Ex. 2.6 (ref):

[0471] Table 12

[0472] As may be observed from the data reported in Table 12, the white compounds according to the invention showed an increase in hysteresis at all temperatures compared to the reference with very high increases at higher temperatures, predictive of excellent roadholding at all operating temperatures. Table 13: rheological properties (RPA)

[0473] (white elastomeric compounds compositions Ex. 2.6 - Ex. 2.8) comprising the cross-linking modifying agents of formula (I) maintain a processability and in particular a rheometric behaviour completely similar to the reference compound.

[0474] It is also observed in this test that with the same modulus G’ (9%) it is possible to observe an increase in Tan Delta at 70 °C.

[0475] In the following summary Table 14, all the evaluations of the main properties of the black compounds (moduli, hysteresis, statics, hardness) compared to the reference black compound have been collected, expressed as percentage variation.

[0476] Table 14: percentage variation of properties compared to the reference composition

[0477] (black compounds)

[0478] Est.=estimated; Meas.=measured

[0479] From the data reported in Table 14 it appeared that:

[0480] - with the agent lacking the self-assembling group C (agent l-C), the properties of the compound did not vary significantly compared to the reference, thus excluding any effect of lipoic acid per se (see compound of Ex. 2.5 vs Ex. 2.1 ); furthermore, there were no substantial differences in the properties of the final compounds if the anchoring group A was modified in the cross-linking modifying agent (I); see in this regard, the compounds of Ex. 2.12 vs Ex. 2.13 where, with the same selfassembling group C, agent (l-A) contained lipoic acid compared to agent (l-F) which contained azide as the anchoring group;

[0481] - the best properties, i.e. a significant increase in hysteresis at all temperatures with substantially equal modulus and hardness, were associated with cross-linking modifying agents capable of forming complexes with 3 intermolecular hydrogen bonds and / or having a KA, for those exemplified herein (l-G), (l-J), (l-l), (l-E), (l-K), (l-A) and (l-F), from about 18 to 30 M-1; see in particular the performances of the compounds of Ex. 2.14, 2.17, 2.18, 2.11 , 2.19, 2.12 and 2.13;

[0482] - it was possible to finely modulate and balance the properties of interest of the compound by intervening on the structure of the self-assembling group C of the cross-linking modifying agent; for example, by ad hoc modifying the substituent in 6 of the pyrimidone system it was possible to intervene on the interaction with carbon black and therefore on the rigidity; see in this regard, the compounds of Ex. 2.12 (I- A, CH3), EX. 2.17 (l-J, n-propyl), Ex. 2.18 (l-l, iso-propyl) and Ex. 2.11 (l-E, tertbutyl): as the steric hindrance of the substituent increases from methyl to iso-propyl, the cold modulus and IRDH hardness values at 23 °C and 10 °C decrease and therefore the rigidity of the compound at cold with substantially the same increase in hysteresis at hot, better balancing these two properties;

[0483] - the cross-linking modifying agents capable of self-assembling with the formation of only 2 hydrogen bonds, with KA lower than 5 M’1, i.e. the agents (l-D) (2-amino pyridine) and (l-H) (imidazolidinone) (patent US9394434), gave the compounds lower moduli, hysteresis and hardness than the cross-linking modifying agent (l-A) which instead self-assembled with the formation of 3 hydrogen bonds, with KA estimated around 30 M’1(see the values of E’, Tan Delta and IRHD hardness of the compounds in Ex. 2.16, Ex. 2.10 vs Ex. 2.12);

[0484] - the cross-linking modifying agent (l-G) (benzomidazole), which was capable of forming a more stable complex than agents (l-D) and (l-H) characterised by 2 intermolecular hydrogen bonds, 1 intramolecular hydrogen bond and a higher KA (estimated «18), gave the compound advantageous properties entirely comparable to those of the compound containing agent (l-A) (see Ex. 2.14 vs Ex. 2.12), with significant increase in hysteresis at 70 °C and 120°C without excessive stiffening or hardening;

[0485] - the cross-linking modifying agent (l-B) (ureido-pyrimidinone, see patent US9394434 and patent application US20220403056A1 ), which formed very stable complexes with 4 intermolecular hydrogen bonds and an estimated KA of 6 x 107, tended to stiffen the compound too much as evidenced by the increase in cold modulus of over 40% for only a modest increase in hysteresis (see the compound of Ex. 2.15).

Claims

CLAIMS1 . An elastomeric composition comprising at least- 100 phr of at least one diene elastomeric polymer,- at least 0.1 phr of at least one cross-linking modifying agent of formula (I)A - B - C (I) whereinA is at least one anchoring group capable of covalently bonding to the elastomeric polymer,B, optionally present, is an organic residue that is at least divalent, covalently bonded to groups A and C, preferably having a molecular weight of less than 1000 g / mol,C is at least one self-assembling group capable of forming a reversible adduct with itself, characterised by an association constant KA between 5 and 1000 M’1, measured by NMR according to the consecutive dilutions method,- at least 1 phr of at least one reinforcing filler, and- at least 0.1 phr of at least one vulcanising agent.

2. The elastomeric composition according to claim 1 comprising 0.5 to 20 phr, preferably 1 to 15 phr or 2 to 10 phr of said at least one cross-linking modifying agent of formula (I).

3. The composition according to claim 1 or 2, wherein in said at least one crosslinking modifying agent of formula (I) there is only one anchoring group A, only one self-assembling group C and the organic residue B is present and is divalent.

4. The composition according to any one of the preceding claims, wherein the at least one anchoring group A of said at least one cross-linking modifying agent of formula (I) is a group selected from activated double bonds, sulphur groups, reactive phenols, 1 ,3-dipole precursors, pyrroles substituted in positions close to nitrogen, nitrones, azides, sulphonazides and diene groups capable of giving Diels-Alder reactions.

5. The elastomeric composition according to claim 4, wherein said group A is selected from azide (-N3) and 1 ,2-dithiolanes.

6. The composition according to any one of the preceding claims, wherein the group B of said at least one cross-linking modifying agent of formula (I) is present and is selected from C1-C20 alkylene, C6-C20 arylene, C1-C10 alkylene-Ce-Cw arylene, Ce- C10 arylene-Ci-Cw alkylene, optionally comprising in the chain one or moreheteroatoms such as N, 0, S, B, P or Si or one or more functional groups such as for example -COO-, -OCO-, -CONH-, -NHCO-, -OCONH-, -NHCONH-, -CO- -NH- C(NH)-NH- -C(S)-S- and -S-C(S)-.

7. The composition according to any one of the preceding claims, wherein the group B of said at least one cross-linking modifying agent of formula (I) is present and has a molecular weight of less than 500 g / mol, preferably less than 300 g / mol, more preferably less than 200 g / mol.

8. The composition according to any one of the preceding claims, wherein the at least one self-assembling group C of said at least one cross-linking modifying agent of formula (I) has an association constant KA between 5 and 500 M’1, preferably between 5 and 100 M-1, more preferably between 10 and 50 M’1.

9. The composition according to any one of the preceding claims, wherein the at least one self-assembling group C of said at least one cross-linking modifying agent of formula (I) comprises at least one mono- or polycyclic, 5- or 6-membered ring, saturated, unsaturated or aromatic, optionally benzocondensed heterocycle comprising at least one heteroatom selected from N, P, S and O, preferably said heterocycle is a nitrogen-containing heterocycle.

10. The composition according to claim 9, wherein said heterocycle is a nitrogencontaining heterocycle, optionally benzocondensed and optionally substituted, selected from pyridine, bipyridine, terpyridine, pyrazine, pyrimidine, pyridazine, imidazole, pyrrole, pyrazole, indole, 1 ,10-phenanthroline, quinoline, isoquinoline, triazole, tetrazole, triazine, tetrazine, naphthyridine, purine, benzothiazole, oxazole, iso-oxazole, thiazole, isothiazole, thiadiazole, substituted or unsubstituted oxadiazole, and substituted oxo derivatives thereof, preferably said nitrogenous heterocycle is selected from pyrimidine, pyrimidinone, benzimidazole and quinolinone.11 . The composition according to any one of the preceding claims, wherein said at least one self-assembling group C forms with itself an adduct with at least 2 and not more than 4 intermolecular hydrogen bonds, preferably with 3 intermolecular hydrogen bonds.

12. The composition according to any one of the preceding claims, wherein in the cross-linking modifying agent of formula (I)A - B - C (I)only one group A is present, only one self-assembling group C is present and group B is present and it is divalent, andA is selected from azide and 1 ,2-dithiolanesB is an alkylene from 4 to 12, andC is selected from pyrimidones, benzoimidazoles and quinolinones.

13. A vulcanised elastomeric tyre compound obtained by mixing and vulcanising the elastomeric composition according to any one of claims 1 to 12.

14. A process for preparing the vulcanised elastomeric compound according to claim 13, comprising:(i) optionally a functionalisation step of at least one diene elastomeric polymer,(ii) at least a first non-productive processing step,(iii) at least a second productive processing step, in which- in the first non-productive processing step (ii), at least one diene elastomeric polymer, optionally functionalised in step (i), is mixed with at least one reinforcing filler, preferably at a temperature of between 100 and 200 °C, to give a non- vulcanisable elastomeric compound,- in the second productive step (iii), at least one vulcanising agent is added to the non-vulcanisable elastomeric compound and the components are mixed at a temperature preferably below 120 °C to give a vulcanisable elastomeric compound, and(iv) a vulcanisation step of the vulcanisable elastomeric compound at a temperature preferably between 140 °C and 200 °C, to give the vulcanised elastomeric compound, characterised in that at least one cross-linking modifying agent of formula (I) according to any one of claims 1 to 12 is added in at least one of the steps i) to iii).

15. A tyre component for vehicle wheels comprising the elastomeric compound according to claim 13.

16. The tyre component according to claim 15, selected from tread band, underlayer, anti-abrasive strip, sidewall, sidewall insert, mini-sidewall, liner, underliner, rubberising layers, bead filler, bead reinforcing layers (flipper), bead protection layers (chafer) and sheet.

17. A tyre for vehicle wheels comprising at least one tyre component according to claim 15 or 16.

18. The tyre according to claim 17, wherein said tyre component is a tread band.

19. The tyre according to claim 17 or 18 for high performance car or motorbike racing.

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