Composition for elastomeric rubber containing tetrazole compatibilizer and tire containing the same

Abstract

The present invention relates to compositions for elastomeric rubber compounds for tires, comprising monotetrazolyl compatibilizers characterized by a precise activation temperature, tire components containing them, and tires for vehicle wheels. Advantageously, the monotetrazolyl compatibilizers of the present invention allow the fracture properties of the rubber compound to be improved while maintaining high filler compatibility.

Description

[0001] The present invention relates to compositions for elastomeric compounds for tires comprising a tetrazole compatibilizer characterized by a precise activation temperature, tire components comprising them and tires for vehicle wheels. Existing technology

[0002] In the rubber industry, and more particularly in the tire industry, it is known to add reinforcing fillers to elastomeric compositions in order to improve their mechanical properties.

[0003] Carbon black is the most commonly used filler due to its high reinforcing capacity. Carbon black imparts strong hysteresis to the product, i.e. it increases heat dissipation under dynamic conditions.

[0004] Alternatively, so-called "white" reinforcing fillers are used, such as chalk, talc, kaolin, bentonite, titanium dioxide and especially silica, which can partially or completely replace the carbon black in the elastomeric composition and impart lower rolling resistance, good wet grip and at the same time sufficient reinforcement to the tire.

[0005] Thus, the elastomeric composition comprising white fillers, in particular silica, can be advantageously used in tires having different properties, such as high performance tires HP, summer tires, all-season or winter tires.

[0006] For such uses, silicas having different characteristics are commercially available or can be prepared according to known methods.

[0007] However, in order for the elastomeric compound to have the desired properties, it is important that the reinforcing filler is uniformly distributed in the elastomer and that it remains uniformly distributed over time, avoiding the formation of agglomerates as much as possible.

[0008] The distribution and dispersion of fillers in a matrix depends on both their chemical properties and the mechanical energy used to mix them. In particular, the more similar their chemical properties are, that is, the more compatible they are, and the greater the mechanical stress applied, the better the distribution and dispersion will be. Typically, in tire rubber compounds, agents called compatibilizers or coupling agents are used to improve the dispersion and compatibility between "white" fillers or inorganic fillers with surface hydroxyl groups (such as silicates, carbonates, or amorphous silica) and rubber.

[0009] The most commonly used coupling agents are polysulfide silane coupling agents, such as bis(3-triethoxysilyl-propyl)tetrasulfide (TESPT) and bis(3-triethoxysilyl-propyl)disulfide (TESPD).

[0010] These agents have a silane head that reacts with the surface hydroxyl groups of the filler, and a polysulfide unit that decomposes upon heating to produce mercapto groups that react with the elastomer, but not always with optimal results.

[0011] In fact, it is known that the thermal decomposition of these polysulfide systems is difficult to control, since it can already occur at low temperatures before the sulfurization step (see, for example, Chapter 3, paragraph 3.17 of the book "Silane Coupling, Compounding Precipitated Silica in Elastomers", Hewitt, Ciullo, William Andrew Publishing, 2007). In addition, the free radical species thus generated are highly reactive and poorly selective, leading to the formation of a mixture of monosulfides and disulfides.

[0012] In order to evenly distribute these polysulfide compatibilizers, the internal temperature in the mixer must be carefully controlled to avoid reaction with the elastomer before satisfactory distribution of the silica and the compatibilizer itself occurs.

[0013] Typically, this mixing step - referred to as the non-productive step (i) or first step - is carried out at a temperature not exceeding 140°C.

[0014] However, despite the use of compatibilizers and energetic mixing, the Applicant has observed that it is not always possible to achieve and, above all, maintain an optimal dispersion of the reinforcing filler in the elastomeric matrix.

[0015] In fact, the disulfide bonds of the compatibilizer with the elastomer are not stable enough since they may break over time and under certain conditions, thus allowing migration and reaggregation of the filler.

[0016] Good dispersion of reinforcing fillers is an important requirement for obtaining compositions suitable for use in tires. In fact, inhomogeneous dispersions forming numerous and / or bulky aggregates have a negative impact on the properties of the material itself, leading to, for example, excessive hysteresis or poor fracture behavior.

[0017] Furthermore, in the case of elastomeric compounds with different polarities, filler migration and accumulation may occur primarily in more similar steps and, as a result, problems associated with compound inhomogeneities arise, such as high aggregate wear and uncontrolled hysteresis of the compound, as well as potential crack initiation.

[0018] In a tire, all this translates into high energy dissipation and excessive sensitivity to mechanical stresses up to rupture.

[0019] On the other hand, it is desirable to be able to distribute the filler in a homogeneous manner in the elastomeric material, so that this homogeneity can then ideally be maintained throughout the mixing process and during all subsequent steps of use of the material.

[0020] On a process level, it would also be advantageous to be able to prolong mixing until the desired distribution is achieved without having to strictly control the temperature, and to subsequently be able to stably fix the well-dispersed filler to the matrix, for example during vulcanization. SUMMARY OF THE INVENTION

[0022] The Applicant has carried out research to improve the affinity of the filler to the elastomeric material in the compound and, above all, to stabilize the dispersion of the filler obtained at the end of mixing.

[0023] To this end, the applicant's research has focused on compatibilizers that are capable of interacting with the selected reinforcing fillers on the one hand and of covalently bonding to the elastomeric component of the rubber compound in a controlled and stable manner on the other. According to the literature, for example, according to JK Stille, AT Chen, Macromolecules, 378, 5, (1972), it is known that upon heating or irradiation with ultraviolet light, 2,5-disubstituted tetrazoles decompose and generate nitrogen, forming highly reactive intermediate species (nitrile imines) that are capable of reacting with double bonds (A=B), such as vinyl groups, as shown in the following Scheme 1:

[0024] Solution 1

[0025]

[0026] This reaction, known as a 1,3-dipolar cyclization, leads to the formation of stable substituted pyrazolines that are easily identified because they are fluorescent when exposed to ultraviolet radiation.

[0027] The temperature at which the 2,5-disubstituted tetrazoles decompose, also referred to herein as the activation temperature Ta, depends on the nature of the groups present in the 2,5-position of the tetrazolyl, as discussed, for example, in Table 1 in the article J. Appl. Polym. Science, Vol. 28, pp. 3671-3679 (1983), in Table 2 in the article Macromolecules, Vol. 5, No. 4, (1972), pp. 377-384, and as investigated by the applicant in the present experimental part (Tables 1 and 2).

[0028] Document JP2009007511A relates to an elastomer composition for tires, which comprises silica, a conventional silane coupling agent and a 5-position monosubstituted tetrazole derivative of the following formula:

[0029]

[0030] Said compositions exhibit an improved affinity of the silica for the rubber and an increased vulcanization rate. This document makes no mention of the possible thermal decomposition of those monosubstituted tetrazoles, nor does it suggest the use of 2,5-disubstituted tetrazoles.

[0031] In this regard, the applicant has experimentally demonstrated that tetrazoles substituted only in 5, such as those shown herein, decompose at very high temperatures, well above 220° C., which is of little practical significance (e.g. Figure 2 TGA analysis).

[0032] JP2017039824A describes an elastomeric composition containing, in addition to a silane coupling agent, a compound having three or more nitrogen atoms in the ring (e.g., tetrazole) and a sulfur atom outside the ring, which exhibits improved reactivity between the silane coupling agent and the rubber. However, the description makes no mention of possible thermal activation of the compound at certain temperatures.

[0033] The applicant has experimentally confirmed that 5-mercapto-substituted tetrazoles, such as Figure 2 As shown in the thermogram of , these do not significantly decompose and release nitrogen when heated, but rather degrade slowly.

[0034] Document JPS 62263239 A describes elastomeric compositions comprising natural or synthetic diene rubber, reinforcing fillers, in particular carbon black, and tetrazole compounds substituted by phenyl groups which themselves are optionally substituted by carboxyl groups, C1-C4 alkyl groups, hydroxyl groups, halogen groups or alkoxy groups.

[0035] Document JPS62215640A discloses an elastomeric composition for tires comprising a diene rubber, a reinforcing filler (in particular carbon black) and a tetrazole compound of formula II, III or IV:

[0036]

[0037] in

[0038] R1 and R2 represent H, alkyl or aryl,

[0039] R3 represents H, alkylaryl, halogen or -NXY, wherein X and Y represent H, alkyl or aryl,

[0040] R4 represents H, alkyl, aryl or halogen, and

[0041] R5 represents H or an alkyl group.

[0042] In his research, the applicant has discovered that certain 2,5-disubstituted monotetrazoles prove to be excellent compatibilizers for reinforcing fillers for elastomers and that their activation at a very precise and particularly variable temperature allows the mixing process to be extended to achieve the desired dispersion and only later to proceed to the stable anchoring of the filler on the elastomer.

[0043] Advantageously, if the substituents on the tetrazole are chosen so as to, for example, increase its activation temperature Ta, the mixing step with the elastomer can be carried out without having to strictly control time and temperature for fear of premature reaction, which in the case of conventional polysulfide-based compatibilizers may already occur, for example, at around 140°C.

[0044] Furthermore, it has been found that by using the monotetrazole compatibilizers according to the invention, it is possible to stably anchor the fillers to the matrix and at least maintain or even improve the mechanical properties of the final compound into which they are incorporated.

[0045] Therefore, a first aspect of the present invention is an elastomeric composition for a tire compound, comprising at least:

[0046] - 100 phr of at least one diene elastomeric polymer,

[0047] - at least 1 phr of at least one reinforcing filler,

[0048] - at least 0.1 phr of at least one monotetrazolyl compatibilizer of the formula

[0049]

[0050] in

[0051] A is absent or represents an at least divalent organic group (linker) optionally containing one or more heteroatoms, which is covalently bonded to the 2-position or 5-position of the tetrazole;

[0052] R is a group covalently bonded to the 5-position or 2-position of the tetrazole, selected from a linear or branched C1-C 10 Alkyl; C6-C 20 Aryl; C3-C 10 Cycloalkyl; a saturated, unsaturated or aromatic monocyclic or bicyclic 5-membered or 6-membered optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S, or O; R is optionally substituted by at least one electron-withdrawing group X or electron-donating group Y, or R is a group B,

[0053] B represents a group having a high affinity for the reinforcing filler, wherein the group is selected from C1-C5 alkoxy, C1-C5 alkyl and / or C6-C 10 Aryl-substituted silane, (HO)2B- group, saturated, unsaturated or aromatic monocyclic or bicyclic, 5-membered or 6-membered, optionally benzo-condensed heterocyclic radical containing at least one heteroatom selected from N, S and O, or aromatic polycyclic hydrocarbon,

[0054] n is an integer from 1 to 3,

[0055] provided that the groups A, B, and R do not include any 2,5-disubstituted tetrazole; and

[0056] - 0 to 20 phr of a vulcanizing agent.

[0057] Another aspect of the invention is an elastomeric compound for tires obtained by mixing and vulcanizing the elastomeric composition according to the invention.

[0058] Another aspect of the present invention is a method for preparing an elastomeric compound according to the present invention, said method comprising:

[0059] - mixing, in one or more steps, all the components of the composition according to the invention, keeping the temperature at a value T1 below the activation temperature Ta of the at least one monotetrazole compatibilizer (I), so as to obtain a compound (1) comprising said monotetrazole compatibilizer (I) and unreacted tetrazole,

[0060] - heating the compound (1) to a temperature T2 equal to or higher than the activation temperature Ta of the monotetrazolyl compatibilizer (I), so as to obtain a compound (2), in which the at least one monotetrazolyl compatibilizer (I) has reacted at least partially by tetrazole decomposition and subsequent addition onto the diene elastomeric polymer, and

[0061] - Optionally vulcanizing the compound.

[0062] Another aspect of the present invention is a tire component for vehicle wheels, comprising or preferably consisting of an elastomeric compound according to the invention.

[0063] Another aspect of the invention is a tyre for vehicle wheels comprising at least one component of a tyre according to the invention.

[0064] The monotetrazolyl compatibilizers (I) of the present invention, when incorporated and vulcanized in elastomeric compounds for tires, impart improved and dynamic and static mechanical properties at least comparable to those found with classical polysulfide compatibilizers.

[0065] Advantageously, by varying the type of substituents on the tetrazole ring, the activation temperature Ta of the monotetrazole compatibilizer (I) can be appropriately adjusted, and process advantages that cannot be achieved using conventional polysulfide compatibilizers can be obtained.

[0066] definition

[0067] The term "monotetrazole compatibilizer" refers to a compound containing a single 2,5-disubstituted tetrazole, i.e., a single tetrazole capable of releasing nitrogen and forming a nitrile imine as described above upon reaching a precise temperature. In the compatibilizer (I) of the present invention, it is possible (although not preferred) to have other tetrazoles that are substituted in other ways and are thermally stable at the activation temperature Ta of the single 2,5-disubstituted tetrazole.

[0068] The term "electron donor group X" refers to an atom or group of atoms that helps increase the electron density on nearby atoms, such as the groups -CH3, -OH, -OR, -NH2.

[0069] The term "electron withdrawing group X" refers to an atom or group of atoms that helps to reduce the electron density on nearby atoms, for example, groups -NO2, -CN, -COOH and halogens.

[0070] The term "groups having a high affinity for reinforcing fillers" B means functional groups capable of interacting with reinforcing fillers, in particular with surface hydroxyl groups of silica or with amorphous carbon of carbon black, forming covalent or ionic bonds, or even through weaker interactions of the van der Waals type, such as dipole-dipole bonds, for example hydrogen bonds.

[0071] The term "polysulfide compatibilizer" refers to a compound containing polysulfide units S n and a compound comprising at least one group having a high affinity for fillers, in particular silica and silicates, wherein n is a number equal to 2 or greater, representing the number of sulfur atoms present in the polysulfide unit. Upon heating, the polysulfide unit decomposes, generating mercapto radicals capable of reacting with the double bonds of the elastomer.

[0072] The term "activation temperature Ta" of the monotetrazolyl compatibilizer (I) refers to the temperature at which the 2,5-disubstituted tetrazole decomposes with loss of nitrogen and forms an intermediate nitrile imine.

[0073] The term “elastomeric composition for tire compounds” means a composition comprising at least one diene elastomeric polymer and one or more additives, which, upon mixing and possible heating, provides an elastomeric compound suitable for use in tires and components thereof.

[0074] The components of the elastomeric composition are not usually introduced into the mixer simultaneously, but are usually added sequentially. In particular, the vulcanization additives, such as the vulcanizing agent and possibly accelerators and flame retardants, are usually added in a step downstream with respect to the incorporation and processing of all the other components.

[0075] In the final vulcanizable elastomeric compound, the individual components of the elastomeric composition may be completely or partially altered or no longer individually traceable as modified due to the interaction with the other components as a result of thermal and / or mechanical processing. The term "elastomeric composition" herein is meant to include the group of all the components used in the preparation of the elastomeric compound, whether or not they are actually present simultaneously, introduced sequentially in the elastomeric compound or in the final tire or are then traceable.

[0076] The term "elastomeric compound" means a compound obtainable by mixing at least one elastomeric polymer with at least one of the additives usually used in the preparation of tire compounds, possibly with heating.

[0077] The term “unvulcanizable elastomeric compound” means a compound obtainable by mixing at least one elastomeric polymer with at least one additive conventionally used in the preparation of tire compounds (except vulcanizing agents), possibly with heating.

[0078] The term "vulcanizable elastomeric compound" denotes an elastomeric compound ready for vulcanization obtainable by incorporating all additives, including vulcanizing additives, into a non-vulcanizable elastomeric compound.

[0079] The term "vulcanized elastomeric compound" means a material obtainable by vulcanization of a vulcanizable elastomeric compound.

[0080] The term "green" refers to a material, compound, composition, component or tire that has not yet been cured.

[0081] The term "vulcanization" refers to a cross-linking reaction in natural or synthetic rubber induced, for example, by sulfur-based vulcanizing agents.

[0082] The term "vulcanizing agent" denotes a product capable of transforming natural or synthetic rubber into an elastic and resistant material due to the formation of a three-dimensional network of inter- and intramolecular bonds.

[0083] The term "vulcanization accelerator" refers to compounds capable of reducing the duration and / or operating temperature of the vulcanization process, such as TBBS, generally, sulfenamides, thiazoles, dithiophosphates, dithiocarbamates, guanidines and sulfur donors such as thiurams.

[0084] The term "vulcanization activator" refers to a product that further accelerates vulcanization, causing it to occur in a shorter time and possibly at a lower temperature. An example of an activator is a stearic acid-zinc oxide system.

[0085] The term "vulcanization retarder" refers to a product that is capable of delaying the onset of the vulcanization reaction and / or inhibiting undesirable secondary reactions, such as N-(cyclohexylthio)phthalimide (CTP).

[0086] The term "cure package" refers to a group of a vulcanizing agent and one or more vulcanizing agents selected from the group consisting of vulcanization activators, accelerators, and retarders.

[0087] The term "elastomeric polymer" means a natural or synthetic polymer which, after vulcanization, can be repeatedly stretched to at least twice its original length at room temperature and which forces its way back to about its original length substantially immediately after removal of the tensile load (as defined in ASTM D1566-11 Standard Terminology Relating to Rubber).

[0088] The term "diene elastomeric polymer" denotes an elastomeric polymer derived from the polymerization of one or more monomers, at least one of which is a conjugated diene.

[0089] The term "reinforcing filler" or filler refers to a compound that is incorporated into an elastomeric compound and is capable of improving the static and dynamic mechanical properties of the vulcanized elastomeric component.

[0090] The term "mixing step (i)" denotes the step of the process for preparing an elastomeric compound in which, in addition to the vulcanizing agent fed in step (ii), one or more additives may be incorporated by mixing and possibly heating. Mixing step (i) is also referred to as a "non-productive step". In the preparation of a compound, there may be several "non-productive" mixing steps, which may be designated as (ia), (ib), etc.

[0091] The term "mixing step (ii)" denotes the next step of the process for preparing the elastomeric compound, wherein the vulcanizing agent and possibly other additives in a vulcanizing package are introduced into the elastomeric compound obtained from step (i) by mixing at a controlled temperature below the vulcanization temperature, generally at a mixing temperature below 120°C, so as to provide a vulcanizable elastomeric compound. Mixing step (ii) is also referred to as "productive step".

[0092] The terms "high performance tyre", commonly referred to as "HP" and "UHP" ("High Performance" and "Ultra High Performance"), refer in particular, but not exclusively, to those tyres belonging to the "T", "U", "H", "V", "ZR", "W", "Y" categories, for example, according to the ETRTO classification suitable for maximum speeds exceeding 190 km / h and up to more than 300 km / h, for which operating properties at high temperatures are critical and constitute one of the most important factors in their design and construction.

[0093] For the purposes of this specification and the following claims, the term "phr" (acronym for parts per hundred parts of rubber) means the parts by weight of a given elastomeric compound component per 100 parts by weight of elastomeric polymer, disregarding any plasticizing extender oil.

[0094] Unless otherwise indicated, all percentages are by weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Refer to the attached figure:

[0097] - Figure 1 schematically shows a half-section view of a tire for a vehicle wheel according to the present invention;

[0098] - Figure 2 A graph showing thermogravimetric analysis (TGA) of tetrazoles described in prior documents JP2009007511A and JP2017039824A is shown;

[0099] - Figure 3shows a graph of thermogravimetric analysis (TGA) of 2,5-disubstituted tetrazoles 1.1 and 1.3;

[0100] - Figure 4 IR spectra of Polyvest oligobutadiene (4A) and its reaction product with tetrazole 1.1 (4B) are shown;

[0101] - Figure 5 1H-NMR spectra of Polyvest oligobutadiene before (5A) and after (5B) cycloaddition reaction with 2,5-disubstituted tetrazole 1.1 are shown;

[0102] - Figure 6 A graph showing a thermogravimetric analysis (TGA) of a sample comprising a mixture of Polyvest oligobutadiene and 2,5-disubstituted tetrazole 1,3;

[0103] - Figure 7 (7A-7E) shows the thermogravimetric analysis (TGA) graphs of the monotetrazolyl compatibilizers 3.1-3.5;

[0104] - Figure 8 The trends of the S′ pairs (relative to a silica content of 8%) are shown comparing the first-stage compounds (TESPT, APTES) and the present invention (monotetrazole 3.1);

[0105] - Figure 9 The trends of the S′ pairs (relative to a silica content of 8%) are shown comparing the final compounds (TESPT, APTES) and the invention (monotetrazole 3.1);

[0106] - Figure 10 The trends of the S' pairs (relative to a silica content of 5%) are shown comparing the final compounds (TESPT, APTES) and the compounds according to the invention (monotetrazole 3.1, monotetrazole 3.4). Detailed Description of the Invention

[0108] The elastomeric composition for a tire compound according to the present invention is characterized by one or more of the following preferred aspects, alone or in combination with one another.

[0109] The elastomeric composition according to the invention comprises 100 phr of at least one diene elastomeric polymer.

[0110] The elastomeric composition according to the invention may comprise a total of 100 phr of a mixture of two or more diene elastomeric polymers.

[0111] The diene elastomeric polymer may be chosen from those usually used in sulfur-vulcanizable elastomeric compositions, which are particularly suitable for the production of tires, i.e. from solid elastomeric polymers or copolymers having unsaturated chains and a glass transition temperature (Tg) generally below 20° C., preferably within the range from 0° C. to −110° C.

[0112] 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 a content of not more than 60% by weight of at least one comonomer chosen from monoolefins, monovinylarenes and / or polar comonomers.

[0113] The conjugated diene generally contains 4 to 12, preferably 4 to 8, carbon atoms and can be selected from, for example, 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.

[0114] The monoolefin may be selected from ethylene and α-olefins generally containing from 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof.

[0115] The monovinyl aromatic hydrocarbons which may optionally be used as comonomers generally contain 8 to 20, preferably 8 to 12, carbon atoms and may be selected, for example, from: styrene; 1-vinylnaphthalene; 2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkaryl or aralkyl derivatives of styrene, such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene and mixtures thereof. Styrene is particularly preferred.

[0116] Polar comonomers which may be used optionally may be selected, for example, from vinylpyridine, vinylquinoline, acrylic acid and alkylacrylates, acrylonitrile or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

[0117] Preferably, the diene elastomeric polymer may be chosen, for example, from: cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (in particular polybutadiene with a high 1,4-cis content), optionally halogenated isoprene / isobutylene 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.

[0118] The elastomeric composition may optionally comprise at least one polymer of one or more monoolefins with an olefin comonomer or a derivative thereof. The monoolefin may be chosen from: ethylene and α-olefins typically containing from 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof. The following are preferred: copolymers selected from ethylene and α-olefins, optionally with dienes; isobutylene homopolymers or copolymers thereof with minor amounts of dienes, which are optionally at least partially halogenated. The dienes that may be present typically contain from 4 to 20 carbon atoms and are preferably chosen from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, vinyl norbornene or mixtures thereof. Among them, the following are particularly preferred: ethylene / propylene (EPR) copolymers or ethylene / propylene / diene (EPDM) copolymers; polyisobutylene; butyl rubber; halogenated butyl rubber, in particular chlorobutyl rubber or bromobutyl rubber; and mixtures thereof.

[0119] The elastomeric composition for a tire according to the invention comprises at least one reinforcing filler.

[0120] The composition of the present invention may comprise two or more reinforcing fillers in admixture.

[0121] The composition of the invention may comprise at least 1.5 phr, 2 phr, 5 phr or at least 10 phr of at least one reinforcing filler or a mixture thereof.

[0122] The composition of the present invention may comprise from 1 phr to 150 phr, from 1 phr to 120 phr, from 5 phr to 120 phr or from 10 phr to 90 phr of at least one reinforcing filler or mixtures thereof.

[0123] Preferably, the reinforcing filler is selected from optionally modified carbon black, silica, silicates, lamellar or fibrous, chalk, talc, kaolin, bentonite, titanium dioxide or mixtures thereof, preferably from carbon black, silica, silicates or mixtures thereof.

[0124] In one embodiment, the reinforcing filler comprises carbon black.

[0125] Preferably, the carbon black is selected from carbon black having a surface area of ​​not less than 20 m 2 / g, preferably greater than 50m 2 / g of carbon black (determined by STSA - Statistical Thickness Surface Area according to ISO 18852:2005).

[0126] The carbon black may be, for example, N234, N326, N330, N375 or N550, N660 sold by the Birla Group (India) or by Cabot Corporation.

[0127] Once distributed in the elastomer, the monotetrazolyl compatibilizer of the present invention can stably bind carbon black and improve the hysteresis behavior of the rubber compound.

[0128] In one embodiment, the reinforcing filler comprises modified carbon black.

[0129] Carbon black can be modified, for example, by reaction with a modifying agent such as serinol pyrrole, as described, for example, in WO2016050887A1, or by oxidation (oxidized carbon black), as shown in application PCT / IB2019 / 060596.

[0130] In one embodiment, the reinforcing filler comprises conventional silica, such as silica from sand precipitated with strong acid, preferably amorphous, or silica from rice hulls, as described, for example, in WO2019229692A1.

[0131] Commercial examples of suitable silicas are Zeosil 1165MP, Zeosil 1115MP, Zeosil 185GR, Efficium from Solvay, Newsil HD90 and Newsil HD200 from Wuxi, K160 and K195 from Wilmar, H160AT and H180AT from IQE, Zeopol 8755 and 8745 from Huber, Perkasil TF100 from Grace, Hi-Sil EZ 120G, EZ 160G, EZ 200G from PPG, Ultrasil 7000GR and Ultrasil 9100GR from Evonik.

[0132] In one embodiment, the reinforcing filler comprises silica mixed with carbon black.

[0133] In one embodiment, the reinforcing filler comprises modified silica.

[0134] Silica can be modified, for example, by reaction with silsesquioxanes (as in WO2018078480A1), by reaction with pyrrole (as in WO2016050887A1), or by reaction with silanizing agents such as bis(triethoxysilylpropyl)tetrasulfide (TESPT), 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltriethoxysilane, triethoxy(octyl)silane, triethoxy(ethyl)silane, triethoxy-3- -(2-imidazolin-1-yl)propylsilane, triethoxy-p-tolylsilane, triethoxy(1-phenylvinyl)silane, triethoxy-2-thienylsilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(triethoxysilyl)propyl isocyanate, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, isobutyltriethoxysilane, n-octadecyltriethoxysilane, (3-chloropropyl)triethoxysilane, triethoxysilane and 3-(triethoxysilyl)propionitrile.

[0135] Commercial examples of suitable silanizing agents are Si69, Dynasilan AMEO and Dynasilan GLYEO from Evonik.

[0136] The modified silica may be sulfided silanized silica.

[0137] Sulfurized silanized silica is silica prepared by reacting silica (e.g., fumed silica, precipitated amorphous silica, wet-process silica (hydrated silicic acid), anhydrous silica (anhydrous silicic acid), or mixtures thereof) or a metal silicate (e.g., aluminum silicate, sodium silicate, potassium silicate, lithium silicate, or mixtures thereof) with at least one sulfurized silanizing agent.

[0138] The term "sulfidosilylating agent" denotes an organic derivative of silicon containing mercapto, sulfide, disulfide or polysulfide groups, which is capable of reacting with the OH groups of silica.

[0139] A commercial example of a suitable sulfurized silanized silica is Agilon 400 silica from PPG.

[0140] In one embodiment, the reinforcing filler comprises modified silica mixed with carbon black.

[0141] In one embodiment, the reinforcing filler comprises a silicate.

[0142] In one embodiment, the silicate is silicate fibers. These fibers are typically nanometer-sized and have a needle-like morphology.

[0143] The silicate fibers are preferably selected from the group consisting of sepiolite fibers, palygorskite fibers (also known as attapulgite), wollastonite fibers, imogolite fibers, and mixtures thereof.

[0144] In one embodiment, the reinforcing filler comprises silicate fibers mixed with carbon black.

[0145] In one embodiment, the silicate fibers are modified silicate fibers.

[0146] In one embodiment, the modified silicate fibers may be fibers modified, for example, by acid treatment and partial removal of magnesium, such as those described and exemplified in patent application WO 2016 / 174629 A1.

[0147] In one embodiment, the modified silicate fibers may be fibers modified, for example, by depositing amorphous silica on the surface, such as those described and exemplified in patent application WO 2016 / 174628 A1.

[0148] In one embodiment, the modified silicate fibers may be fibers that have been organically modified, for example, by reaction with a quaternary ammonium salt, such as sepiolite fibers modified by reaction with tallowoylbenzyldimethylammonium chloride sold by Tolsa under the name Pangel B5.

[0149] In one embodiment, the modified silicate fiber can be a fiber modified by reaction with a silanizing agent selected from, for example, monofunctional or difunctional silanes having one or two or three hydrolyzable groups, such as bis(3-triethoxysilyl-propyl) disulfide (TESPD), bis(3-triethoxysilyl-propyl) tetrasulfide (TESPT), 3-thio-octanoyl-1-propyl-triethoxysilane (NXT), Me2Si(OEt)2, Me2PhSiCl, Ph2SiCl2.

[0150] In one embodiment, the reinforcing filler comprises modified silicate fibers mixed with carbon black.

[0151] In one embodiment, the silicate is a layered silicate, such as bentonite, halloysite, laponite, saponite, vermiculite, or hydrotalcite.

[0152] In one embodiment, the silicate is a modified layered silicate similar to that already described for modified silicate fibers.

[0153] The elastomeric composition for tire compounds of the present invention comprises at least one monotetrazole compatibilizer of formula (I).

[0154] Preferably, the elastomeric composition of the present invention comprises at least 0.5 phr or at least 1 phr or at least 2 phr or at least 3 phr, more preferably at least 5 phr or at least 8 phr of at least one monotetrazole compatibilizer of formula (I).

[0155] The elastomeric composition for tire compounds of the present invention preferably comprises no more than 30 phr, more preferably no more than 20 phr, even more preferably no more than 10 phr of at least one monotetrazole compatibilizer of formula (I).

[0156] The elastomeric composition for tire compounds of the present invention preferably comprises 0.5 to 30 phr, more preferably 1 to 20 phr, even more preferably 2 to 20 phr or 2 to 10 phr of at least one monotetrazole compatibilizer of formula (I).

[0157] The elastomeric composition for tire compounds of the present invention may contain two or more compatibilizers of formula (I) in a mixture, preferably in a total amount of 0.5 to 30 phr, more preferably 1 to 20 phr, even more preferably 2 to 10 phr.

[0158] In the elastomeric composition of the present invention, the monotetrazole compatibilizer of formula (I) is preferably used in an amount proportional to the reinforcing filler incorporated therein.

[0159] The elastomeric composition for tire rubber of the present invention comprises at least one monotetrazole compatibilizer of formula (I) and at least one reinforcing filler, preferably in a weight ratio of 0.01:1 to 0.3:1, more preferably 0.02:1 to 0.15:1 relative to the reinforcing filler.

[0160] Preferably, in the monotetrazole compatibilizer of formula (I)

[0161]

[0162] A is present and is an at least divalent organic group (linker) which has the function of linking at least one group B to the tetrazole and possibly adjusting the physical properties and / or activation temperature of the tetrazole.

[0163] The term "at least divalent organic group (linker)" means an organic group capable of covalently binding tetrazole and at least one group B.

[0164] The linking groups A for the purposes of the present invention must preferably be sufficiently stable under the normal conditions of processing, vulcanization and use of the elastomeric compounds.

[0165] Preferably, the group A is divalent, ie it is bound to only one group B (n=1).

[0166] Group A is an organic group preferably selected from the group consisting of: C1-C10 Alkylene; C6-C 10 Arylene; a monocyclic or bicyclic, 5-membered or 6-membered saturated, unsaturated or aromatic optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S and O; C1-C5 alkylene-C6-C 10 Arylene-; C6-C 10 -Arylene-C1-C5 alkylene; C1-C5 alkylene-C6-C 10 Arylene-C1-C5 alkylene; C1-C5 alkylene-heterocyclylene-; heterocyclylene-C1-C5 alkylene; C1-C5 alkylene-heterocyclylene-C1-C5 alkylene; C6-C 10 Arylene-C6-C 10 Arylene; Heterocyclylene-Heterocyclylene; C6-C 10 Arylene-C1-C5 alkylene-C6-C 10 Arylene; Heterocyclylene-C1-C5 alkylene-heterocyclylene, wherein the heterocyclylene is as defined above and the alkylene optionally contains one or more heteroatoms selected from B, N, S, O, P and Si or a functionalized group selected from -NR3-CO-, -CO-NR3-, -NH-CO-NH-, -COO-, -O-CO-, -CO-, -C=N(R3)-, -CO-N(R3)-CO-, -C=N(OH)-, -O-CO-N(R3)-, -N(R3)-COO-, -SO-, -SO2-, -SO2-, -SO2O-, -CS-, -CS-O-, -COS-, -CS-S-, wherein R3 represents hydrogen or C1-C5 alkyl.

[0167] The alkylene group, the arylene group and the heterocyclic group refer to at least divalent groups obtained by removing at least one hydrogen atom from an alkyl group, an aryl group and a heterocyclic group, respectively.

[0168] C1-C5 alkylene and C1-C 10 Alkylene may be a saturated or unsaturated, linear or branched hydrocarbon group, which optionally contains one or more heteroatoms selected from B, N, S, O, P and Si in the chain or attached to an atom in the chain.

[0169] Alkylene can be, for example, -CH2-, -CH<, -(CH2) 2-10 -, -CH2-O-CH2-, -O-CH2-CH2-; -(O-CH2-CH-R)-, -(CH2)3-NH-C(O)-, -(CH2)3-NH-C(O)-NH-.

[0170] C6-C 20 or C6-C 10Arylene includes carbocyclic, monocyclic, and polycyclic aromatic ring systems in which the individual carbocyclic rings are fused or linked to each other by single bonds.

[0171] C6-C 20 or C6-C 10 The arylene group may be, for example, a phenylene group, a biphenylene group, a naphthylene group, a fluorenylene group, a phenanthrenylene group, a p-alkoxyphenylene group, or a m-chlorophenyl group.

[0172] Preferably, the arylene group is a phenylene group.

[0173] Heterocyclylene includes heteroarylene and its dihydro and tetrahydro derivatives. The attachment site of the heterocyclylene may be a carbon atom or a heteroatom.

[0174] The heterocyclylene group can be derived from a heterocycle such as pyrrole, dihydropyrrole, pyrrolidine, furan, dihydrofuran, tetrahydrofuran, benzofuran, isobenzofuran, dihydrobenzofuran, thiophene, dihydrothiophene, tetrahydrothiophene, benzothiophene, thiazolazole, dihydrothiazole, dihydrothiazole, benzotriazole, tetrazole, dihydrotetrazole, isothiazole, dihydroisothiazole, imidazole, benzimidazole, dihydroimidazole, dihydrobenzimidazole, oxazole, dihydrooxazole, benzoxazole, dihydrobenzoxazole, oxazole

[00145] In some embodiments, the present invention includes but is not limited to benzophenone, isoxazole, dihydroisoxazole, isoxazoline, oxadiazole, pyrazole, benzopyrazole, dihydropyrazole, pyridine, dihydropyridine, piperidine, piperazine, pyrazine, pyridazine, gamma-pyran, tetrahydropyran, dihydropyran, 1,4-dioxane, benzo-1,4-dioxane, morpholine, thiomorpholine, pyrazine, dihydropyrazine, pyrazoline, quinoline, isoquinoline, dihydroquinoline, tetrahydroisoquinoline, indole, indolinoid, dihydroindole, quinazoline, quinoxaline, and the like.

[0175] Preferably, the heterocyclylene group is derived from a heterocycle selected from thiophene and pyrrole.

[0176] Alkylene, arylene and heterocyclylene groups may be optionally replaced by straight or branched C1-C 10 Alkylene, more preferably -(CH2) 2-10 Group, oxy-alkylene-O-C1-C 20 Group, amino-alkylene N(C1-C 20 )2、C(O)C1-C 20 Acyl or corresponding ester and amide substitutions.

[0177] Preferably, the molecular weight of group A is below 1000 g / mol, more preferably below 500 g / mol, even more preferably below 300 g / mol.

[0178] In one embodiment, group A is absent and n is equal to 1.

[0179] In one embodiment, group A is present and represents a divalent organic group, and n is equal to 1.

[0180] In the monotetrazole compatibilizer of formula (I), preferably R is C1-C6 alkyl, C6-C 10 Aryl, C1-C5-aryl C6-C 10 Alkyl, C6-C 10 Aryl-C1-C5 alkyl, C3-C7 cycloalkyl, heterocyclyl defined as group A heterocyclylene, i.e. monocyclic or bicyclic 5- or 6-membered ring containing at least one heteroatom selected from N, S and O, saturated, unsaturated or aromatic, optionally benzo-condensed heterocyclyl.

[0181] R can be, for example, phenyl, 4-hydroxyphenyl, 4-carboxyphenyl, 3,5-dimethylphenyl, 3,5-dimethoxyphenyl, 4-octyloxyphenyl, 4-phenyl-1,2,4-triazolidine-3,5-dione, 1-hexyl, 2-thienyl, 5-amino-2-thienyl, diphenyl, pyrrolyl, 1-4 C1-C1-C1-D ... 20 Alkyl, C1-C 20 Oligo-2,5-thienyl of alkoxy-substituted thiophene, benzo-fused polycyclic aromatic compounds, such as naphthalene, fluorenyl or anthracene, which are optionally replaced by C1-C 20 Alkyl or C1-C 20 Alkoxy substitution.

[0182] Preferably, R is selected from phenyl or thiophene.

[0183] R can be selected from more lipophilic groups, such as 4-hexyl-phenyl, naphthyl, fluorenyl, etc., to increase the solubility of the monotetrazolyl compatibilizer (I) in the elastomer matrix.

[0184] R may be a group B selected from the group defined below. In this case, the compatibilizer (I) of the invention may have additional groups B capable of interacting with the same filler or, in the case of different groups B, with fillers of different nature, such as silica and carbon black.

[0185] In one embodiment, R is different from B.

[0186] R can be selected to appropriately change the activation temperature Ta of the tetrazole.

[0187] The group R may be substituted with at least one electron-withdrawing group X.

[0188] Generally, if R is substituted by an electron-withdrawing group X, the tetrazole is more stable and Ta increases.

[0189] The electron withdrawing group X can be selected from, for example, halogen, substituted carbonyl (-CO-alkyl or -CO-aryl), carboxyl, ester, cyano, nitro, haloalkyl, sulfonyl (SO2-alkyl or SO2-aryl), trihalomethyl.

[0190] It is preferably selected from esters, cyano groups and haloalkyl groups.

[0191] It may be advantageous to choose an electron withdrawing group X that is traceable by suitable analytical techniques such as NMR, even when the monotetrazolyl compatibilizer (I) containing the electron withdrawing group X is diluted in the elastomeric compound. For example, a fluorinated group, such as -CF3.

[0192] The group R may be substituted by at least one electron donor group Y. Generally, if R is substituted by an electron donor group Y, the tetrazole is less stable and Ta decreases.

[0193] The electron donor group Y may be selected, for example, from hydroxyl, C1-C 10 Alkoxy, benzyloxy, C1-C 10 Alkyl, amino, C1-C 10 Alkyl monosubstituted amino, C1-C 10 Alkyl disubstituted amino, primary amide (-NH-COR), hydrazone (CH=N-NR2), etc.

[0194] The monotetrazolyl compatibilizer of formula (I) may contain more than one group having a high affinity for the filler, in particular from 1 (for R different from B and n=1) to 4 groups (for R=B and n=3).

[0195] In one embodiment, the monotetrazolyl compatibilizer of formula (I) comprises only one group B (formula I, n equals 1 and R is different from B).

[0196] The group B having a high affinity for the reinforcing filler is a group which may contain one or more heteroatoms and / or have polar substituents, such as hydroxyl, amine, mercapto, amide, if the reinforcing filler is polar or generally has an affinity for those substituents, such as silica.

[0197] In the case where the reinforcing filler is lipophilic, such as carbon black, the group B having a high affinity for the reinforcing filler may be a group that is lipophilic or not very polar.

[0198] The group B having a high affinity for the reinforcing filler is preferably chosen from C1-C5-trialkoxysilyl, (HO)2B-, a saturated, unsaturated or aromatic monocyclic or bicyclic 5- or 6-membered ring, optionally a benzocondensate, a heterocyclic radical containing at least one heteroatom chosen from N, S and O, said group B being optionally substituted.

[0199] The group B having a high affinity for the reinforcing filler may be a group containing silicon, for example, a C1-C5 alkoxy group, a C1-C5 alkyl group and / or a C6-C 10 Aryl substituted silane, or boronic acid derivative group, or aromatic or heterocyclic polycyclic hydrocarbon group.

[0200] Examples of silicon-containing groups B are triethoxysilylalkyl, triethoxysilylaryl, diethoxyalkylsilylalkyl, diethoxyalkylsilylaryl, ethoxydialkylsilylalkyl, ethoxyalkylsilylaryl, silylarylalkyl or silylaryl.

[0201] If the reinforcing filler comprises silicon dioxide or possibly modified silicates or mixtures thereof, the group B is preferably a group of the formula -Si(OR1)3, wherein R1 are identical or different from one another and are C1-C5 alkyl, more preferably C2-C3 alkyl or a group of the formula -B-(OH)2.

[0202] If the reinforcing filler comprises carbon black, possibly modified, or a mixture thereof, group B may be an aromatic polycyclic hydrocarbon selected from naphthalene, phenanthrene, anthracene, pyrene, benzopyrene, fluorene and their benzocondensed derivatives, or a heterocyclic residue, for example a derivative of serinolpyrrole, as described in patent application WO2016050887A1.

[0203] In the monotetrazolyl compatibilizer (I), there may be 1 to 3 groups B or, in the case where the group R is equal to B, there may be 1 to 4 groups B as defined above.

[0204] Preferably, in the monotetrazole of formula (I), n is 1 or 2, more preferably n is 1.

[0205] The multiple B groups, if present, can be identical to one another and interact with the same filler or different from one another, thereby exhibiting affinity for fillers of different natures (eg, silica and carbon black).

[0206] In one embodiment, the monotetrazolyl compatibilizer of formula (I) is a reagent of formula (IA):

[0207]

[0208] wherein B, A, R and n have the meanings indicated previously for the reagents of formula (I).

[0209] In one embodiment, the monotetrazolyl compatibilizing agent is a reagent of formula (IA) wherein A is present and is a divalent organic group (linker), n is equal to 1 and R is different from B.

[0210] In one embodiment, the monotetrazolyl compatibilizer of formula (I) is a reagent of formula (IB)

[0211]

[0212] wherein A, B, R and n have the meanings indicated previously for the reagents of formula (I).

[0213] In one embodiment, the monotetrazolyl compatibilizer (I) is a reagent of formula (IA) or (IB), wherein

[0214] A is a divalent organic group (linking group) of the formula -A1-A2-, wherein A1 may be absent or selected from C2-C 10 -NH-C(O)-alkylene, C2-C 10 -NH-C(O)-NH-alkylene, and wherein A2 may be absent or selected from C6-C 10 Aryl and monocyclic or bicyclic, saturated, unsaturated or aromatic, optionally benzo-condensed heterocyclic groups having a 5- or 6-membered ring containing at least one heteroatom selected from N, S and O.

[0215] In a preferred embodiment, the monotetrazolyl compatibilizer (I) is a reagent of formula (IA) or (IB), wherein

[0216] A is a divalent organic group (linker) of the formula -A1-A2-, wherein A1 may be absent or selected from -(CH2) (2-4) -NH-C(O)- and -(CH2) (2-4) -NH-C(O)-NH-, and A2 may be absent or selected from phenyl and thiophene; and / or R is selected from C4-C6 alkyl, benzyl, phenyl, thiophene, which is optionally substituted with at least one electron-withdrawing group X or electron-donating group Y; and / or

[0217] B is selected from naphthyl, pyrenyl, (HO)2B- or -Si(OR1)3, wherein R1 are the same as or different from each other, are C1-C3 alkyl, and n is equal to 1.

[0218] Specific examples of reagents of formula (IA) are as follows:

[0219]

[0220] By appropriate choice of the organic group A, the group R, its possible at least one substituent, an electron-withdrawing group X or an electron-donating group Y, and the group B, the activation temperature Ta of the monotetrazolyl compatibilizer (I), its affinity for specific reinforcing fillers and its solubility in the chosen elastomer matrix can be adjusted in particular.

[0221] Preferably, the molecular weight of the monotetrazolyl compatibilizer (I) is lower than 1500 g / mol, more preferably lower than 1000 g / mol, even more preferably lower than 600 g / mol.

[0222] Preferably, the activation temperature Ta of the monotetrazole compatibilizer (I) is not lower than 100°C, more preferably not lower than 120°C, even more preferably not lower than 140°C.

[0223] Depending on the activation temperature of the tetrazole, which can be adjusted by appropriate choice of the substituents R and possibly A, the reaction with the elastomer can be carried out before, during or after vulcanization.

[0224] Monotetrazolyl compatibilizers (I) having an activation temperature Ta below 100° C. are not preferred because they can react with the elastomer from the premixing step of the components before vulcanization, even before a homogeneous dispersion is achieved. Early reactions can lead to concentrations of the compatibilizer and, therefore, of the reinforcing filler in specific areas that are detrimental to the properties of the material and will also lead to an increase in the viscosity of the green compound, making it less processable in the subsequent extrusion and / or calendering steps.

[0225] In one embodiment, the monotetrazole compatibilizer (I) preferably has an activation temperature Ta of not higher than 220° C., more preferably not higher than 210° C., even more preferably not higher than 200° C. In one embodiment, the activation temperature Ta of the monotetrazole compatibilizer (I) is from 140° C. to 220° C., preferably from 140° C. to 190° C., so as not to activate prematurely and to react only when subjected to conventional vulcanization conditions (temperature indicatively from 140° C. to 180° C.).

[0226] In the case of comprising several compatibilizers of different nature, for example silica together with carbon black, it may be advantageous to use in combination at least two compatibilizers of formula (I) having different groups B, which have specific affinities for the different reinforcing fillers in question.

[0227] The monotetrazolyl compatibilizers of formula (I) can be prepared according to one or more conventional synthetic schemes, such as the following general schemes 2 and 3 (exemplified herein for n=1):

[0228] Option 2

[0229]

[0230] Option 3

[0231]

[0232] The elastomer composition for a tire compound according to the present invention may contain a vulcanizing agent.

[0233] Preferably, the composition comprises at least 0.1 phr, at least 0.2 phr, at least 0.5 phr, at least 0.8 phr or at least 1 phr of at least one vulcanizing agent.

[0234] Preferably, the composition comprises 0.1 to 10 phr, 0.2 to 10 phr, 1 to 10 phr or 1.5 to 5 phr of at least one vulcanizing agent.

[0235] The at least one vulcanizing agent is preferably selected from sulfur or, alternatively, sulfur-containing molecules (sulfur donors), such as bis[(trialkoxysilyl)propyl]polysulfides, thiurams, dimorpholine dithioates and caprolactam-disulfides, and mixtures thereof.

[0236] In one embodiment, the vulcanizing agent is selected from the polytetrazolyl crosslinking agents of formula (II) described in patent application IT102019000025804 in the name of the present applicant

[0237]

[0238] in

[0239] A represents an organic group (linker), which may include one or more heteroatoms, identical or different from each other, covalently bonded to n tetrazolies,

[0240] wherein n is an integer from 2 to 10, and each of the n tetrazoles is bound to A at the 2-position or the 5-position and is substituted by an R group at the 5-position or the 2-position, respectively, wherein the R group is independently selected from C3-C 10 Straight chain or branched alkyl, C6-C 20 Aryl, C3-C 10 Cycloalkyl, monocyclic or bicyclic, saturated, unsaturated or aromatic, and having a 5-membered ring or 6-membered ring containing at least one heteroatom selected from N, S, O, which may be a benzo-condensed heterocyclic group, R may in turn be substituted by at least one electron-withdrawing group X or one electron-donating group Y, and the polytetrazolyl crosslinker (C) has a molecular weight of less than 10,000 g / mol.

[0241] Preferably, the vulcanizing agent is sulphur, preferably selected from soluble sulphur (crystalline sulphur), insoluble sulphur (polymeric sulphur), (iii) oil-dispersed sulphur and mixtures thereof.

[0242] A commercial example of a vulcanizing agent suitable for use in the elastomeric composition of the present invention is Redball Superfine sulfur from International Sulphur Inc.

[0243] In the elastomeric composition of the present invention, the vulcanizing agent may be used together with auxiliary agents known to those skilled in the art such as vulcanization activators, accelerators and / or retarders.

[0244] The elastomeric composition according to the invention may optionally comprise at least one vulcanization activator.

[0245] Suitable vulcanization activators for the elastomeric composition of the invention are zinc derivatives, in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms, preferably formed in situ in the elastomeric composition by reaction of ZnO with fatty acids, and Bi2O3, PbO, Pb3O4, PbO2 or mixtures thereof. For example, zinc stearate is used, preferably formed in situ in the elastomeric composition from ZnO and fatty acids, or magnesium stearate is used, formed from MgO, or mixtures thereof.

[0246] The vulcanization activator may be present in the elastomeric composition of the present invention in an amount preferably ranging from 0.2 phr to 15 phr, more preferably from 1 phr to 5 phr.

[0247] A preferred activator is derived from the reaction of zinc oxide and stearic acid.

[0248] An example of an activator is the product Aktiplast ST sold by Rheinchemie.

[0249] The elastomeric composition according to the invention may further comprise at least one vulcanization accelerator.

[0250] Commonly used vulcanization accelerators may, for example, be selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates or mixtures thereof.

[0251] Preferably, the accelerator is selected from the group consisting of mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS) and mixtures thereof.

[0252] A commercial example of an accelerator suitable for use in the elastomeric composition of the present invention is N-cyclohexyl-2-benzothiazolyl-sulfenamide (CBS or CZ), and N-tert-butyl 2-benzothiazolylsulfenamide, sold by Lanxess NZ / EGC.

[0253] Vulcanization accelerators may be used in the elastomeric composition of the present invention in amounts preferably ranging from 0.05 phr to 10 phr, preferably from 0.1 phr to 7 phr, more preferably from 0.5 phr to 5 phr.

[0254] The elastomeric composition according to the invention may optionally comprise at least one vulcanization retarder.

[0255] The vulcanization retarder suitable for use in the elastomeric composition of the present invention is preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.

[0256] A commercial example of a suitable retarder is N-cyclohexylthiophthalimide VULKALENT G from Lanxess.

[0257] Vulcanization retarders may be present in the elastomeric composition of the present invention in an amount preferably ranging from 0.05 phr to 2 phr.

[0258] The elastomeric composition of the invention may comprise in admixture one or more vulcanization retarders as defined above.

[0259] The elastomeric composition according to the present invention may optionally 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.

[0260] 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.

[0261] Preferably, the coupling agent is a silane coupling agent selected from those having at least one hydrolyzable silane group, which can be represented, for example, by the following general formula (III):

[0262] (R′)3Si-C n H 2n -X(III)

[0263] wherein the groups R′ are identical or different from each other and 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 aryloxy group; n is an integer from 1 to 6; X is a group selected from the following: nitroso, mercapto, amino, epoxide, vinyl, imide, chlorine, -(S) m C n H 2n -Si-(R')3 and -S-COR', wherein m and n are integers from 1 to 6, and the group R' is as defined above.

[0264] Particularly preferred silane coupling agents are bis(3-triethoxy-silyl-propyl)tetrasulfide and bis(3-triethoxysilyl-propyl)disulfide, also known as polysulfide compatibilizers. The coupling agents can be added as such or in a mixture with an inert filler, such as carbon black, to facilitate their incorporation into the elastomeric composition.

[0265] An example of a silane coupling agent is TESPT: bis(3-triethoxysilylpropyl)tetrasulfide Si69 sold by Evonik.

[0266] The elastomeric composition according to the present invention may further comprise one or more additional ingredients commonly used in the art, such as plasticizing oil, resin, antioxidant and / or antiozonant (anti-aging agent), wax, adhesive and the like.

[0267] For example, in order to further improve the processability of the rubber compound, the elastomeric composition according to the present invention may further comprise at least one plasticizing oil.

[0268] The amount of plasticizer is preferably from 1 phr to 80 phr, preferably from 10 phr to 70 phr, more preferably from 30 phr to 50 phr.

[0269] The term "plasticizing oil" refers to a process oil derived from petroleum, or a mineral oil or a vegetable oil or a synthetic oil or a combination thereof.

[0270] The plasticizing oil may be a process oil derived from petroleum selected from the group consisting of paraffins (saturated hydrocarbons), cycloparaffins, aromatic polycyclics, and mixtures thereof.

[0271] Examples of suitable process oils derived from petroleum are aromatic oils, paraffinic oils, naphthenic oils, such as those known in the industry as MES (solvated mild extracts), DAE (distillate aromatic extracts), TDAE (treated distillate aromatic extracts), TRAE (treated residual aromatic extracts), RAE (residual aromatic extracts).

[0272] The plasticizing oil may be an oil of natural or synthetic origin derived from the esterification of glycerol with fatty acids, including triglycerides, diglycerides, monoglycerides, or mixtures thereof.

[0273] Examples of suitable vegetable oils are sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil and cottonseed oil.

[0274] The plasticizing oil may be a synthetic oil selected from alkyl or aryl esters of phthalic acid or phosphoric acid.

[0275] The elastomeric composition according to the present invention may further comprise at least one resin.

[0276] If used in the composition, the resin is a non-reactive resin which is preferably selected from hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.

[0277] The amount of resin may range from 0 phr to 80 phr, preferably from 10 phr to 40 phr.

[0278] The elastomeric composition according to the invention may optionally comprise at least one wax.

[0279] The wax may be, for example, a petroleum wax or a mixture of paraffin waxes.

[0280] Commercial examples of suitable waxes are Repsol n-paraffin mixtures and 654 microcrystalline wax.

[0281] The wax may be present in the elastomeric composition of the invention in a total amount generally ranging from 0.1 phr to 20 phr, preferably from 0.5 phr to 10 phr, more preferably from 1 phr to 5 phr.

[0282] The elastomeric composition according to the invention may optionally comprise at least one antioxidant.

[0283] The antioxidant 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′-dimethylphenyl-p-phenylenediamine (DTPD), N,N′-di-β-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 N-1,3-dimethylbutyl-N-phenyl-p-phenylenediamine (6-PPD).

[0284] Commercial examples of suitable antioxidants are 6PPD from Solutia / Eastman or Santoflex produced by Flexsys.

[0285] Antioxidants may be present in the elastomeric composition in a total amount of preferably from 0.1 phr to 20 phr, preferably from 0.5 phr to 10 phr.

[0286] Another aspect of the invention is an elastomeric compound for tires obtained by mixing and vulcanizing the elastomeric composition according to the invention.

[0287] As shown in this experimental section, the elastomeric compounds according to the invention, when vulcanized, have dynamic properties comparable to those of similar compounds containing conventional compatibilizers and better static properties.

[0288] Another aspect of the invention is a process for preparing the elastomeric compound according to the invention.

[0289] The process for preparing the elastomeric compound according to the present invention preferably comprises:

[0290] - mixing, in one or more steps, all the components of the composition of the invention, maintaining the temperature at a value T1 at least 10° C. below the activation temperature Ta of the at least one monotetrazole compatibilizer (I), to obtain a compound (1) comprising the monotetrazole compatibilizer (I) and unreacted tetrazole, and

[0291] - heating the compound (1) to a temperature T2 at least 10° C. higher than the activation temperature Ta of the monotetrazole compatibilizer (I), so as to obtain a compound (2), wherein the at least one monotetrazole compatibilizer (I) reacts at least partially by tetrazole decomposition and subsequent addition onto the diene elastomeric polymer, and

[0292] - Optionally vulcanizing the compound.

[0293] During the first mixing step at temperature T1, the reinforcing filler and the monotetrazolyl compatibilizer (I) are dispersed in the elastomer matrix. Under these conditions, the tetrazolyl ring in the compatibilizer of formula (I) generally remains substantially stable and does not undergo significant decomposition, while generally one or more B groups in the compatibilizer of formula (I) react or interact with the filler.

[0294] During a subsequent heating step at temperature T2 (preferably a step coinciding with the vulcanization step of the tire), the tetrazole rings of the compatibilizer (I) decompose and react with the elastomer, thus anchoring the filler to the matrix.

[0295] Depending on the activation temperature Ta of the monotetrazolyl compatibilizer (I) (which can be adjusted by appropriate choice of the substituents R and possibly A) and the vulcanization temperature, different process variants are possible, and the reaction with the elastomer can take place before, during or after vulcanization.

[0296] In one embodiment, the method preferably comprises heating the rubber compound (1) to a temperature T2 equal to or higher than the activation temperature Ta of the monotetrazole compatibilizer (I) during the tire vulcanization step to obtain a vulcanized rubber compound (2). This step can be carried out in a conventional vulcanization mold. In this embodiment, the monotetrazole compatibilizer (I) is selected so as to have a Ta similar to the temperature used in the vulcanization, for example about 160°C.

[0297] In this embodiment, the mixing step can be performed before vulcanization without strict temperature control, for example by operating at a T below 160°C, and then the filler is fully dispersed in the matrix only subsequently, for example during vulcanization.

[0298] In another embodiment in which the activation temperature Ta of the monotetrazole compatibilizer (I) is lower than the vulcanization temperature T, the monotetrazole compatibilizer (I) can be deliberately reacted prematurely where it is desired to increase the viscosity of the material prior to vulcanization, such as in the preparation of a liner or subliner.

[0299] In another embodiment in which the activation temperature Ta of the monotetrazole compatibilizer (I) is higher than the vulcanization temperature T, the vulcanization of the rubber compound (1) is carried out without activation of the monotetrazole compatibilizer (I) to obtain a vulcanized rubber compound containing unreacted monotetrazole compatibilizer (I).

[0300] When the temperature of the tire in use reaches the activation temperature Ta of the monotetrazolyl compatibilizer (I), this compound, suitable for incorporation into a tire component, for example into a sidewall insert, can undergo consolidation to obtain a compound (2) that is hardened by the anchoring of the agent and the filler. In this application, the elastomeric composition preferably also contains a compatibilizer of the conventional silane type.

[0301] In another embodiment, by incorporating at least two compatibilizers of formula (I) having different Ta in the elastomeric compound, it is possible to activate one during the vulcanization step and subsequently activate the other only when the temperature in the tire under operating conditions reaches the higher Ta of the second agent.

[0302] Other process variations may involve using compatibilizers of formula (I) having different Ta and affinities for different fillers.

[0303] By appropriately choosing the substituents R and B of the compatibilizer (I), the person skilled in the art can plan in which production or use step of the tire one or the other filler is anchored, with possible process and performance advantages in the tire.

[0304] The elastomeric compound of the present invention may be prepared according to a process generally comprising one or more mixing steps in at least one suitable mixer, in particular at least one mixing step (i) (non-productive) and a mixing step (ii) (productive) as defined above.

[0305] Each mixing step may include several intermediate processing steps or sub-steps characterized by momentary interruptions in mixing to allow the addition of one or more ingredients, but generally without intermediate discharge of the compound.

[0306] For example, an open mixer of the "open mill" type or one with tangential rotors can be used. Or a closed mixer with interpenetrating rotors (Intermix) or in a Ko-Kneader TM type The mixing is carried out in a continuous mixer of the twin-screw or multi-screw type.

[0307] The temperatures during the mixing step and the substeps can also be set as a function of the activation temperature Ta of the monotetrazolyl compatibilizer (I) and the process step in which activation is required.

[0308] As previously mentioned, the elastomeric composition preferably comprises, in addition to the monotetrazolyl compatibilizer (I), a vulcanizing agent.

[0309] The monotetrazolyl compatibilizer (I) may be incorporated in one or more of steps (i) or (ii), while the vulcanizing agent is usually added only in the productive step (ii).

[0310] Typically, after one or more thermomechanical processing steps, a vulcanizing agent is incorporated into the material, preferably together with a vulcanization accelerator and / or a retarder. In the final treatment step, the productive step (ii), the temperature is generally kept below 120° C., preferably below 100° C., to prevent any undesirable pre-vulcanization. Thereafter, the vulcanizable rubber compound is incorporated into one or more components of the tire and vulcanized according to known techniques.

[0311] Depending on the desired application, the cured compound may contain unreacted monotetrazole compatibilizer (I) or already bound to the elastomer after decomposition of the tetrazole ring.

[0312] Another aspect of the present invention is a tire component for a vehicle wheel, comprising or preferably consisting of an elastomeric compound according to the present invention, said tire component being preferably selected from the group consisting of a tread cap, a base layer, an anti-wear layer, a sidewall, a sidewall insert, a mini sidewall, a liner, a base liner, a rubber layer, a filler strip, a bead reinforcement layer (cover), a bead protection layer (chafer), a sheet, preferably selected from the group consisting of a tread, a base layer, a rubber layer and a sidewall insert.

[0313] The tire component may comprise, or preferably may consist of, a non-vulcanized elastomeric compound according to the invention (green component) or a vulcanized elastomeric compound according to the invention.

[0314] Another aspect of the invention is a tyre for vehicle wheels comprising at least one component of a tyre according to the invention.

[0315] The tire for vehicle wheels of the invention may comprise at least one tire component consisting of an unvulcanized elastomeric compound according to the invention (green tire) or of a vulcanized elastomeric compound according to the invention (vulcanized tire).

[0316] Preferably, said components are selected from the group consisting of a tread, a base layer, a rubber layer and a sidewall insert.

[0317] In one embodiment, a tire for vehicles according to the present invention comprises at least:

[0318] - a carcass structure comprising at least a carcass ply having opposite lateral edges associated with respective bead structures;

[0319] - a possible pair of sidewalls, each sidewall optionally comprising a sidewall insert applied respectively on the side surface of the carcass structure in an axially external position;

[0320] - for the carcass structure, a possible belt structure applied in a radially external position;

[0321] - a crown applied in a radially external position to said carcass structure or to the belt structure, if present,

[0322] - a possible layer of elastomeric material applied in a radially inner position with respect to said crown, called sublayer,

[0323] At least one of the components, preferably the rubber coating of the crown or at least one carcass ply or the sidewall insert, comprises an elastomeric compound according to the invention, or preferably consists thereof.

[0324] In one embodiment, the tire according to the invention is a car tire, preferably a high performance car tire.

[0325] In one embodiment, the tyre according to the invention is a tyre for motorcycles, wherein at least one component comprises or preferably consists of an elastomeric compound according to the invention.

[0326] In a preferred embodiment, the tyre according to the invention is a tyre for motorcycle wheels, preferably a tyre for sports or racing motorcycles.

[0327] The tyre according to the invention may be a tyre for a two-wheeled, three-wheeled or four-wheeled vehicle.

[0328] The tire according to the invention can be used for summer or winter use or for all seasons.

[0329] In one embodiment, the tyre according to the invention is a tyre for bicycle wheels.

[0330] A tyre for a bicycle wheel generally comprises a carcass structure rotating around a pair of bead cores at the beads, and a crown arranged in a radially outer position with respect to the carcass structure. Preferably, at least the crown and / or the rubber layer comprises an elastomeric compound according to the invention.

[0331] The tire according to the present invention can be produced according to the following method, which comprises:

[0332] - building components of a green tire on at least one building drum;

[0333] - Shaping, molding and vulcanizing tires;

[0334] wherein at least one of the components for constructing a green tire comprises:

[0335] - producing at least one green part comprising or preferably consisting of the vulcanizable elastomeric compound according to the invention.

[0336] Description of the tire according to the invention

[0337] exist Figure 1 A tyre for vehicle wheels according to the invention is shown in radial half section in FIG. 1 , comprising at least one component comprising an elastomeric compound according to the invention.

[0338] exist Figure 1 In the diagram, "a" indicates the axial direction, and "X" indicates the radial direction, and in particular, XX indicates the profile of the equatorial plane. For simplicity, Figure 1 Only a portion of the tire is shown, the remaining portions not shown being identical and arranged symmetrically with respect to the equatorial plane "XX".

[0339] The tyre (100) for a four-wheeled vehicle comprises at least one carcass structure comprising at least one carcass layer (101) having respectively opposite end flaps which engage with corresponding annular anchoring structures (102), called bead cores, which are optionally associated with filler strips (104).

[0340] The tyre region comprising the bead core (102) and the filler strip (104) forms a bead structure (103) intended for anchoring the tyre to a corresponding mounting rim (not shown).

[0341] The carcass structure is generally of radial type, i.e. the reinforcing elements of at least one carcass layer (101) are situated in a plane comprising the axis of rotation of the tyre and substantially perpendicular to the equatorial plane of the tyre. Said reinforcing elements are generally composed of textile cords. Each bead structure is associated with the carcass structure by folding back the opposite lateral edges of at least one carcass layer (101) around annular anchoring structures (102) so as to form a Figure 1 The so-called carcass wing (101a) is shown.

[0342] In one embodiment, a second carcass layer ( Figure 1 ) provide a connection between the carcass structure and the bead structure.

[0343] A wear strip (105), possibly made of an elastomeric material, is arranged in an outer position of each bead structure (103).

[0344] The carcass structure is associated with a belt structure (106) comprising one or more belt layers (106a), (106b) placed radially superposed relative to each other and relative to the carcass layer, typically having textile and / or metal reinforcement cords incorporated within a layer of elastomeric material.

[0345] Such reinforcing cords may have a cross orientation relative to the circumferential development direction of the tire (100). "Circumferential" direction refers to the direction generally facing the direction of rotation of the tire.

[0346] At least one zero-degree reinforcement layer (106c), often called a "0° belt", can be applied in a radially outermost position to the belt layers (106a), (106b), which usually incorporate a plurality of elongated reinforcing elements, usually metal or textile cords, oriented in a substantially circumferential direction so as to form an angle of several degrees (for example, an angle between about 0° and 6°) relative to a direction parallel to the equatorial plane of the tire and are coated with an elastomeric material.

[0347] A tread crown (109) comprising an elastomeric compound according to the invention is applied in a position radially outside the belt structure (106).

[0348] Furthermore, respective sidewalls (108) of elastomeric material are applied in axially outer positions on the side surfaces of the carcass structure, each sidewall extending from one of the side edges of the tread (109) at a respective bead structure (103).

[0349] In the radially outer position, the crown (109) has a rolling surface (109a) intended to be in contact with the ground. Figure 1 Circumferential grooves connected to define a plurality of blocks of various shapes and sizes distributed on the rolling surface (109a) are usually made on this surface (109a) and, for simplicity, the surface (109a) is Figure 1 Indicated as smooth.

[0350] A base layer (111) comprising an elastomeric compound according to the invention may be arranged between the belt structure (106) and the tread crown (109).

[0351] Optionally, strips of elastomeric material (110) may be provided in the connection zone between the sidewalls (108) and the crown (109), generally called "micro-sidewalls", which are generally obtained by coextrusion with the crown (109) and which allow an improvement in the mechanical interaction between the crown (109) and the sidewalls (108). Preferably, the ends of the sidewalls (108) directly overlap the lateral edges of the crown (109).

[0352] In the case of a tubeless tyre, a rubber layer (112), generally called a "liner", may also be provided in a radially inner position relative to the carcass layer (101), this rubber layer (112) providing the necessary impermeability to the tyre inflation.

[0353] The rigidity of the tire sidewall (108) may be improved by providing the bead structure (103) with a reinforcement layer (120) commonly known as flipper or additional strip insert.

[0354] The bead cover (120) is a reinforcement layer that is wound around the corresponding bead core (102) and the filler strip (104) so ​​as to at least partially surround the bead core and the filler strip, and the reinforcement layer is arranged between at least one carcass layer (101) and the bead structure (103). Typically, the bead cover is in contact with the at least one carcass layer (101) and the bead structure (103).

[0355] The flyer cover (120) generally comprises a plurality of textile cords incorporated within a layer of elastomeric material.

[0356] The reinforcing annular structure or bead (103) of the tyre may comprise an additional protective layer, generally referred to by the term "chafer" (121) or protective strip, and having the function of increasing the rigidity and integrity of the bead structure (103).

[0357] The chafer (121) typically comprises a plurality of cords incorporated within a rubber layer of an elastomeric material. Such cords are typically made of a textile material (such as aramid or rayon) or a metallic material (such as steel cord).

[0358] A layer or sheet of elastomeric material may be arranged between the belt structure and the carcass structure. This layer may have a uniform thickness. Alternatively, this layer may have a variable thickness in the axial direction. For example, this layer may have a greater thickness near its axially outer edges relative to the central (crown) region.

[0359] Advantageously, the layer or sheet may extend over a surface substantially corresponding to the surface over which said belt structure extends.

[0360] In a preferred embodiment, a layer of elastomeric material, called underlayer, may be placed between said belt structure and said crown, said underlayer preferably extending over a surface substantially corresponding to the surface of extension of said belt structure.

[0361] The elastomeric compound according to the invention may advantageously be incorporated into one or more of the tire components mentioned above, preferably into the tread, into the sidewall inserts, into the sheets and into the rubber compound.

[0362] According to an embodiment not shown, the tyre may be a tyre for motorcycle wheels, which is generally a tyre having a rectilinear portion characterized by a high tread camber.

[0363] Building of the tyre (100) as described above can be performed by assembling respective semi-finished products suitable for forming tyre components on a forming drum (not shown) by at least one assembling device.

[0364] At least some of the components intended to form the tire carcass structure can be constructed and / or assembled on the forming drum. More specifically, the forming drum is intended to first receive a possible liner and then the carcass structure. Thereafter, unillustrated means coaxially engage one of the annular anchoring structures surrounding each end flap, position the outer sleeve comprising the belt structure and the crown in a coaxially centered position around the cylindrical carcass sleeve, and shape the carcass sleeve into an annular configuration by radially expanding the carcass structure so as to be applied against the radially inner surface of the outer sleeve.

[0365] After the green tire has been constructed, it is generally subjected to molding and vulcanization processes in order to establish the structural stability of the tire through the vulcanization of the elastomeric composition, as well as to impart the desired tread pattern on the crown and any distinguishing graphic symbols on the sidewalls.

[0366] Experimental part

[0367] Analytical methods

[0368] Thermogravimetric analysis (TGA)

[0369] The thermal behavior of the 2,5-disubstituted tetrazoles described herein was investigated, in particular their activation temperatures, Ta, were determined by thermogravimetric analysis using the Mettler Toledo STARE system model under the following conditions:

[0370] Method 1) About 5 mg of pure monotetrazole reagent was placed in a TGA crucible and heated from 30°C to 500°C with a gradient of 5°C / min under N2 flow (see Figure 7C , 7E);

[0371] Method 2) Under nitrogen flow, about 10 mg of pure monotetrazole reagent was placed in a TGA crucible and a thermal program of 30°C to 1000°C was used, with a heating gradient from 30°C to 150°C at 10°C / min, a constant temperature of 150°C for 10 minutes, and heating from 150°C to 1000°C at 10°C / min (see Figure 7A 、 7B , 7D).

[0372] The first weight loss step is usually consistent with the loss of a nitrogen molecule from the tetrazole.The temperature at which nitrogen gas begins to be released from the tetrazole is considered the activation temperature, Ta.

[0373] The reactivity of the monotetrazoles with reactive double bonds was evaluated again by heating in a thermogravimeter under the following conditions: about 1 mg of the monotetrazole compatibilizer (I) (or selected comparative reagent) was dispersed in about 10 mg of the butadiene oligomer Polyvest 130 and the mixture was placed in a TGA crucible using a thermal program from 30° C. to 140° C. (10° C. / min gradient), followed by a hold at 140° C. for 30 minutes, cooling to 30° C. (-10° C. / min gradient), heating from 30° C. to 90° C. (5° C. / min), cooling to 30° C., heating to 170° C. (5° C. / min) and a hold at 170° C. for 30 minutes. This method simulates the thermal history of the elastomeric compound.

[0374] NMR

[0375] NMR spectra were obtained using a Bruker 400 instrument. Samples were prepared by dissolving 5-10 mg of monotetrazole in 0.6 mL of deuterated solvent (chloroform or DMSO).

[0376] IR

[0377] IR spectra were obtained using a Perkin-Elmer Spectrum 100 (FT-IR) instrument. The sample was loaded directly onto the crystal and pressed with a metal tip. The spectra were recorded in ATR (attenuated total reflectance) mode.

[0378] Measurement of dynamic and mechanical rheological properties (RPA) of elastomeric compounds

[0379] The rheological properties were evaluated using a Monsanto RPA2000 rheometer according to the following method: cylindrical specimens weighing 4.5 g to 5.5 g were prepared by punching the first step elastomeric compound - the compound containing reinforcing filler and monotetrazole compatibilizer (I) but without vulcanizing agent and co-vulcanizing agent, and the final green compound (including all components including vulcanizing agent and co-vulcanizing agent).

[0380] The first and last step green compound samples were heated in a rheometer at 190°C for 30 minutes.

[0381] The test was performed at an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ±0.5°.

[0382] exist Figure 8-10 The S' values ​​measured for comparative and inventive first and last step compounds are reported in .

[0383] The dynamic properties of the samples of the final compounds were measured, namely the dynamic shear modulus G′, the viscous dynamic shear modulus G″% at 70° C. and a frequency of 10 Hz (in the deformation range between 0.1% and 100% for samples that have not been subjected to thermal cycles above 130° C., and in the deformation range between 0.1% and 10% for samples that have been subjected to at least one thermal cycle above 130° C.) and the results are reported in Tables 4 and 5.

[0384] Measurement of static mechanical properties

[0385] The elastomeric materials prepared in the aforementioned examples were vulcanized to obtain samples on which static mechanical property evaluations were performed.

[0386] Tensile tests were performed on straight-axis dumbbell-shaped specimens.

[0387] Unless otherwise stated, vulcanization was carried out in a mold in a hydraulic press at 190° C. and a pressure of 200 bar for about 30 minutes.

[0388] According to ISO 37:2005, measured at 23°C Static mechanical properties .

[0389] In particular, the load, breaking load CR, and breaking elongation AR% at different elongation levels (50%, 100%, and 300%, respectively referred to as CA0.5, CA1, and CA3) were measured, and the results are shown in Table 6.

[0390] Example 1

[0391] Study on the Thermal Stability of 2,5-Disubstituted Monotetrazoles

[0392] In order to understand the influence of the substituents present at the 2- and 5-positions of the tetrazole on the activation temperature Ta, 2,5-disubstituted monotetrazoles 1.1-1.23 of the formula (I) shown in Table 1 below were prepared:

[0393] Table 1

[0394]

[0395]

[0396]

[0397] These monotetrazoles were synthesized and then studied by thermogravimetric analysis in order to investigate the influence of the substituents present in the 2- and 5-positions on the activation temperature Ta of the tetrazoles.

[0398] Synthesis of 2,5-Disubstituted Monotetrazoles

[0399] As described in Chem. Commun. (2016), 52, 9426, tetrazole reagents having an aryl group at the 2-position and an optionally substituted aryl group at the 5-position are prepared according to the following general synthetic scheme 2.1, whereby derivatives in which the aromatic group in 5 is a phenyl group are exemplified herein, but are similarly applicable to derivatives in which the group is another aromatic system:

[0400] Solution 2.1

[0401]

[0402] As reported in the literature, the synthesis involves two steps:

[0403] Aromatic aldehyde (1 equivalent) was dissolved in ethanol. Tosylhydrazine (2 equivalents) was added and stirred at reflux for 4 hours. Water was then added and the resulting precipitate was recovered by filtration. The product thus obtained was used in the second step without further purification.

[0404] -The solid obtained in step 1 (1 equivalent) was dissolved in pyridine to obtain solution A. Simultaneously, solution B was prepared by adding a solution of NaNO2 (1 equivalent) in water (xml) to a cooled solution of aniline (1 equivalent), concentrated HCl and water / ethanol (1:1). Solution B, cooled with an ice bath, was slowly added dropwise to solution A and stirred at room temperature overnight at the end of the addition. Subsequently, the reaction mixture was neutralized with dilute HCl and the formed precipitate was recovered by filtration. Depending on the type of tetrazole, the crude reaction product was purified by column chromatography or crystallized from a suitable solvent.

[0405] Monotetrazoles 1.11, 1.15 and 1.16 were prepared by alkylation according to general Scheme 3, and more specifically according to Schemes 4-6 below.

[0406] Synthesis of Monotetrazole 1.11

[0407] Monotetrazole 1.11 was prepared according to the following Scheme 4:

[0408] Option 4

[0409]

[0410] Step 1

[0411] Benzonitrile (1 eq) was suspended in H2O, ZnBr2 (1 eq) and sodium azide (1.1 eq) were added, and the mixture was heated under reflux with stirring for 48 h.

[0412] The reaction was quenched with HCl (37%) and extracted with ethyl acetate. The organic phase was dried and the solvent was evaporated under reduced pressure. The solid obtained was treated with 0.25M NaOH solution and stirred for 30 minutes. The zinc oxide thus formed was filtered by washing with 1N NaOH. The aqueous solution thus obtained was treated with concentrated HCl to an acidic pH. The precipitated tetrazole was recovered, filtered and washed with 3M HCl, and finally dried in an oven. Tetrazole was recovered as a white powder (yield 76%).

[0413] Step 2

[0414] The glassware was ignited under a stream of N2. 5-Phenyl-tetrazole (1 eq) was dissolved in anhydrous dimethylformamide, K2CO3 (1.2 eq) was added, and after 15 min 1-bromohexane (1 eq) was added and the mixture was stirred magnetically at ambient temperature for 24 h.

[0415] The reaction mixture was extracted with dichloromethane. The organic phase was dried and evaporated under reduced pressure. The crude product was purified by column chromatography to obtain 2-hexyl-5-phenyl-tetrazole as a colorless oil (yield 90%).

[0416] Synthesis of Monotetrazole 1.15

[0417] Monotetrazole 1.15 was prepared according to the following Scheme 5:

[0418] Option 5

[0419]

[0420] Step 1

[0421] Benzonitrile (1 eq) was suspended in H2O, ZnBr2 (1 eq) and sodium azide (1.1 eq) were added, and the mixture was heated under reflux with stirring for 48 h.

[0422] The reaction was quenched with HCl (37%) and extracted with ethyl acetate. The organic phase was dried and the solvent was evaporated under reduced pressure. The solid obtained was treated with 0.25M NaOH solution and stirred for 30 minutes. The zinc oxide thus formed was filtered by washing with 1N NaOH. The aqueous solution thus obtained was treated with concentrated HCl to an acidic pH. The precipitated tetrazole was recovered, filtered, washed with 3M HCl, and finally dried in an oven. Tetrazole was recovered as a white powder (yield 76%).

[0423] Step 2

[0424] The glassware was ignited under a stream of N2. 5-Phenyl-tetrazole (1 eq) was dissolved in anhydrous dimethylformamide, K2CO3 (1.2 eq) was added, and after 15 min benzyl bromide (1 eq) was added and the mixture was stirred magnetically at ambient temperature for 24 h.

[0425] The reaction mixture was extracted with dichloromethane. The organic phase was dried and evaporated under reduced pressure. The crude product was purified by column chromatography to obtain 2-benzyl-5-phenyl-tetrazole as a white solid (yield 90%).

[0426] Synthesis of Monotetrazole 1.16

[0427] Monotetrazole 1.16 was prepared according to the following Scheme 6:

[0428] Option 6

[0429]

[0430] Step 1

[0431] 2-Thiophenecarbonitrile (1 eq) was suspended in H2O, ZnBr2 (1 eq) and sodium azide (1.1 eq) were added, and the mixture was heated under reflux with stirring for 48 h.

[0432] The reaction was quenched with HCl (37%) and extracted with ethyl acetate. The organic phase was dried and the solvent was evaporated under reduced pressure. The solid obtained was treated with 0.25M NaOH solution and stirred for 30 minutes. The zinc oxide thus formed was filtered by washing with 1N NaOH. The aqueous solution thus obtained was treated with concentrated HCl to an acidic pH. The precipitated tetrazole was recovered, filtered, washed with 3M HCl, and finally dried in an oven. Tetrazole was recovered as a white powder (yield 74%).

[0433] Step 2

[0434] The glassware was ignited under a stream of N2. 5-Thienyl-tetrazolyl (1 eq) was dissolved in anhydrous dimethylformamide, K2CO3 (1.2 eq) was added, and after 15 min, benzyl bromide (1 eq) was added and the mixture was stirred magnetically at ambient temperature for 24 h.

[0435] The reaction mixture was extracted with dichloromethane. The organic phase was dried and evaporated under reduced pressure. The crude reaction product was purified by column chromatography to give 2-benzyl-5-(thiophen-2-yl)-tetrazolyl as a white solid (yield 85%).

[0436] Characterization of Monotetrazolyl Compatibilizers 1.1-1.23

[0437] Thermogravimetric analysis

[0438] Thermogravimetric analysis of the 2,5-disubstituted monotetrazoles shown in Table 1 was performed according to the above method.

[0439] Figure 3The plots obtained from the TGA of monotetrazoles 1.1 and 1.3 are shown. As can be seen, monotetrazole 1.1 shows a net jump around 210°C as the tetrazole ring decomposes and releases nitrogen. In contrast, monotetrazole 1.3 undergoes a more gradual decomposition starting at approximately 150°C.

[0440] As shown in Table 1, the activation temperature Ta of these derivatives ranges from 150 to 250°C and is affected by the nature of the substituents present in the 2- and 5-positions.

[0441] In particular, it was observed that electron-withdrawing groups, such as carboxyl or triazolidinedione (monotetrazoles 1.1 and 1.2), if present in the para position of the phenyl group bonded to a carbon of the tetrazole ring, stabilize the tetrazole by increasing the activation temperature Ta, whereas electron-donating groups, which may be substituted with amino groups, such as thiophene (monotetrazoles 1.3 and 1.5), have the opposite effect when bonded to a carbon of the tetrazole ring.

[0442] From the values ​​of activation temperature Ta reported in Table 1 , it appears as if tetrazoles with an activation T encompassed within a wide temperature range of technological interest are synthetically accessible.

[0443] By appropriately combining the substituents on the tetrazole, the activation temperature Ta of the system can thus be adapted to the desired application.

[0444] Example 2

[0445] Cycloaddition experiments with unsaturated polymers

[0446] To verify the reactivity of 2,5-disubstituted monotetrazolyl compounds toward polymer double bonds, the following Scheme 7 shows the case of a terminal vinyl group:

[0447] Option 7

[0448]

[0449] Cycloaddition experiments were performed using some of the monotetrazoles of Table 1 with the oligomers described in Examples 2a, 2b, and 2c below.

[0450] For these preliminary cycloaddition experiments, which can be used to evaluate the reactivity of 2,5-disubstituted tetrazoles towards reactive double bonds of elastomers, the liquid polybutadiene Polyvest 130S was chosen because it is a liquid and mixes easily even without the use of solvents.

[0451] Example 2a:

[0452] In a glass test tube, the selected tetrazole derivative and Polyvest 130S oligomer (tetrazole / polymer molar ratio of 1:100, tetrazole / polymer vinyl ratio of 1:1) were mixed without solvent and the mixture was heated to the tetrazole activation temperature Ta for 15-30 minutes.

[0453] The formation of pyrazoline by cycloaddition was highlighted by the fluorescence of the sample under UV light (365 nm) and confirmed by IR and NMR spectra measured at the end of the reaction on the oligomer modified with tetrazole and after precipitation in ethanol. The oligomer was subsequently suspended in ethanol and centrifuged (this process was repeated 3 times) to remove unreacted tetrazole and by-products.

[0454] Figure 4 The results of the analysis of Polyvest 130S ( Figure 4 A) and the reaction product between monotetrazolyl 1.1 and Polyvest 130S ( Figure 4 B) IR spectrum.

[0455] Figure 5 shows that before the cycloaddition reaction with monotetrazolyl 1.1 ( Figure 5 A) and after ( Figure 5 B), 1H-NMR spectrum of Polyvest.

[0456] The 1H-NMR spectrum after the reaction ( Figure 5 In B), new signals can be seen compared to those of Polyvest, which can be attributed to the formation of pyrazoline, in particular the signal around 9.5 ppm (carboxyl protons), the signal between 8.5 and 8.0 ppm (phenyl protons), and the signal around 4 ppm (pyrazoline ring protons).

[0457] According to the tests and analysis performed in this example, it was shown that the tetrazole had decomposed and the nitrile imine had reacted with the double bond of the Polyvest to provide the corresponding pyrazoline, thereby functionalizing the oligomer.

[0458] Example 2b:

[0459] The selected monotetrazole and Polyvest 130S oligomer were mixed in a vial and heated to 70°C to make the oligomer more fluid and better disperse the tetrazole. A portion of the mixture was then placed in a crucible in a thermogravimeter.

[0460] The mixture was heated in a TGA to a temperature at least 20°C higher than the tetrazole activation temperature Ta, with a heating gradient from 70°C to the final T in 5 minutes and then held at this temperature for at least another 5 minutes. Monotetrazole 1.3 was observed to decompose only when the activation T was reached and exceeded.

[0461] Example 2c:

[0462] Another way of heating the Polyvest 130S-monotetrazole 1.3 mixture in a TGA was also tested, which reproduced the thermal steps to which the elastomeric compound is typically subjected under normal tire production conditions, said thermal steps comprising, in sequence: a first heating to 140°C for 30 minutes, corresponding to the initial mixing step in the absence of the monotetrazole, cooling to 40°C, heating to 90°C for 30 minutes, corresponding to the mixing production step with the incorporation of the monotetrazole, a second cooling to 30°C, and a final heating to simulate reaction conditions, wherein T is increased to at least 20°C above the activation temperature Ta of the monotetrazole. As indicated by the only weight loss detectable by TGA, the monotetrazole 1.3 was observed to remain unchanged throughout the thermal processing cycle of the compound, activating only when the activation T was reached and exceeded.

[0463] Figure 6 The thermogram shows a rapid decrease in weight of the sample comprising monotetrazole 1.3 at temperatures above its activation temperature Ta of 150°C.

[0464] Example 3

[0465] Synthesis of 2,5-disubstituted monotetrazoles

[0466] Other 2,5-disubstituted monotetrazoles of formula (I) were synthesized and characterized and are reported in Table 2 below along with some comparative compounds:

[0467] Table 2

[0468]

[0469]

[0470] *Activation temperature of the elastomeric compound (according to the study reported on page 191 of the article "Effects of time and temperature on reaction of TESPT silane coupling agent during mixing with silica filler and tyrerubber" by LAEM Reuvekamp et al., Vol. 75, pp. 187-198, testing TESPT bis(3-triethoxysilyl-propyl)tetrasulfide and APTES (3-aminopropyl)triethoxysilane as a comparison).

[0471] Monotetrazoles 3.1, 3.2 and 3.4 appear to be suitable compatibilizers for silica and silicate fibers, whereas monotetrazoles 3.3 and 3.5 are suitable compatibilizers for carbon black due to the high affinity of pyrene and naphthalene nuclei for this filler.

[0472] Synthesis of Monotetrazole 3.1

[0473] Monotetrazole 3.1 was prepared according to the following Scheme 8:

[0474] Option 8

[0475]

[0476] Step 1

[0477] Ignite the glassware under N2 flow. Dissolve tetrazole 1.1 (1 equivalent) in anhydrous THF and stir magnetically. Add two drops of DMF, then add oxalyl chloride (2 equivalents) and heat under reflux for 2 hours.

[0478] The solvent was evaporated under reduced pressure to afford an orange solid (99% yield).

[0479] Step 2

[0480] The glassware was ignited under a stream of N2. The product obtained in the first step (1 equivalent) was dissolved in anhydrous dichloromethane (CH2Cl2) and stirred magnetically. Pyridine (1 equivalent) was added, followed by APTES (0.95 equivalent) and stirred at room temperature for 24 hours.

[0481] The solvent was evaporated under reduced pressure and washed with dichloromethane to obtain a dark brown solid (83% yield).

[0482] 1H-NMR (400MHz, DMSO): δ8.50 (s, 1H), 8.14 (dd, J = 8.3, 1.0 Hz, 1H), 7.93 (d, J = 3.6 Hz, 1H), 7.78 (d, J = 3.6 Hz, 1H), 7.74-7.67 (m, 1H), 7.67-7.61 (m, 1H).

[0483] According to thermogravimetric analysis (see Figure 7A From the thermogram in FIG. 2 , it can be observed that decomposition and weight loss occur at a temperature of approximately 190° C. due to the release of nitrogen. The activation temperature Ta thus measured is as shown in Table 2 above.

[0484] Synthesis of Monotetrazole 3.2

[0485] Monotetrazole 3.2 was prepared according to the following Scheme 9:

[0486] Option 9

[0487]

[0488] The glassware was ignited under a stream of N2. Tetrazole 1.5 (1 equivalent) was dissolved in anhydrous dioxane and stirred magnetically. Isocyanate (1 equivalent) was added and stirred under reflux for about 3 hours.

[0489] The solvent was evaporated under reduced pressure to obtain a dark brown oil (94% yield).

[0490] According to thermogravimetric analysis (see Figure 7B From the thermogram in FIG, it can be observed that at a temperature of about 150° C., there is decomposition and weight loss due to the release of nitrogen.

[0491] The activation temperature Ta thus measured is shown in Table 2 above.

[0492] Synthesis of Monotetrazole 3.3

[0493] Monotetrazole 3.3 was prepared according to the following scheme 10:

[0494] Option 10:

[0495]

[0496] Ignite the glassware under N2 flow. Pyrenebutyric acid (1 equivalent) is dissolved in anhydrous tetrahydrofuran (THF) and cooled to 0 ° C. Diphenylphosphoryl azide (DPPA 1.1 equivalents) is added and triethylamine (TEA, 1.1 equivalents) is added after about 10 minutes. It is stirred under reflux for 3 hours. Tetrazole 1.5 (1 equivalent) is dissolved in anhydrous THF and added dropwise to the previous solution. It is stirred under reflux for 3 hours. The solvent is evaporated under reduced pressure. The crude product obtained is extracted with dichloromethane, first with aqueous NaHCO3, then with water, and then with HCl (1M). The organic phase is dried and evaporated under reduced pressure.

[0497] The solid obtained by Soxhlet extraction was extracted into ethyl acetate to give a white solid (55% yield).

[0498] 1 H NMR (400MHz, DMSO) δ10.02 (s, 1H), 8.39 (d, J = 9.3Hz, 1H), 8.31-8.22 (m, 4H), 8.1 5(d,J=2.8Hz,2H),8.13-8.09(m,2H),8.07(t,J=7.6Hz,1H),8.01(d,J=7.8Hz,1H ),7.72-7.65(m,2H),7.63(d,J=1.3Hz,1H),7.60(d,J=4.0Hz,1H),6.68(t,J=5. 6Hz, 1H), 6.57 (d, J = 4.0Hz, 1H), 3.43-3.36 (m, 2H), 2.01 (dt, J = 14.5, 7.2Hz, 2H).

[0499] According to thermogravimetric analysis (see Figure 7C ), it can be observed that at a temperature of about 180° C., decomposition and weight loss occur due to the release of nitrogen. The activation temperature Ta thus measured is shown in the previous Table 2.

[0500] Synthesis of Monotetrazole 3.4

[0501] Monotetrazole 3.4 was prepared according to the following scheme 11:

[0502] Plan 11

[0503]

[0504] Step 1

[0505] 5-Formyl-2-thienylboronic acid (1 equivalent) was dissolved in ethanol, toluenesulfonylhydrazide (1 equivalent) was added and stirred under reflux for 4 hours.

[0506] Water was then added and the precipitate formed was recovered by filtration. The product thus obtained was used in the second step without further purification.

[0507] Step 2

[0508] - The solid obtained in step 1 (1 eq) was dissolved in pyridine to give solution A. In parallel, solution B was prepared by adding an aqueous solution of NaNO2 (1 eq) to a cooled solution of aniline (1 eq), concentrated HCl and water / ethanol (1:1).

[0509] Solution B, cooled with an ice bath, was slowly added dropwise to solution A and stirred overnight at room temperature at the end of the addition. Subsequently, the reaction mixture was neutralized with dilute HCl and the formed precipitate was recovered by filtration. The crude reaction product was washed with dichloromethane to obtain a light orange solid.

[0510] 1 H NMR (400MHz, DMSO) δ8.50 (s, 1H), 8.14 (dd, J = 8.3, 1.0 Hz, 1H), 7.93 (d, J = 3.6 Hz, 1H), 7.78 (d, J = 3.6 Hz, 1H), 7.74-7.67 (m, 1H), 7.67-7.61 (m, 1H).

[0511] According to thermogravimetric analysis (see Figure 7D From the thermogram in FIG. 2 ), it can be observed that at a temperature of about 140-150° C., decomposition and weight loss occur due to the release of nitrogen. The activation temperature Ta thus measured is shown in the previous Table 2.

[0512] Synthesis of Monotetrazole 3.5

[0513] Monotetrazole 3.5 was prepared according to the following scheme 12:

[0514] Plan 12

[0515]

[0516] Step 1

[0517] Naphthalene-2-carbonitrile (1 eq) was suspended in H2O, and ZnBr2 (1 eq) and sodium azide (1.1 eq) were added. The mixture was heated under reflux with stirring for 48 h.

[0518] The reaction was quenched with HCl (37%) and extracted with ethyl acetate. The organic phase was dried and the solvent was evaporated under reduced pressure. The solid obtained was treated with 0.25M NaOH solution and stirred for 30 minutes. The zinc oxide thus formed was filtered by washing with 1N NaOH. The aqueous solution thus obtained was treated with concentrated HCl to an acidic pH. The precipitated tetrazole was recovered, filtered and washed with 3M HCl, and finally dried in an oven. 5-naphthyl-tetrazole (41% yield) was obtained as a white powder.

[0519] Step 2

[0520] The glassware was ignited under a stream of N2. 5-Naphthyl-tetrazolyl (1 eq) was dissolved in anhydrous acetonitrile, K2CO3 (10 eq) was added and after 15 min, benzyl bromide (1 eq) was magnetically stirred at room temperature for 24 h.

[0521] The reaction mixture was extracted with dichloromethane. The organic phase was dried and evaporated under reduced pressure. The crude reaction product was purified by column chromatography to obtain 2-benzyl-5-(naphthalen-2-yl)-2H-tetrazole as a white solid (yield 38%).

[0522] 1 H NMR (400MHz, CDCl3) δ: 8,68(s,1H),8,21(d,1H),7,94(d,2H),7,53(m,2H),7,46(d,2H),7,42-7,37(dd,4H),5,85(s,2H).

[0523] According to thermogravimetric analysis (see Figure 7E From the thermogram in FIG. 2 ), it can be observed that at a temperature of about 230° C., decomposition and weight loss occur due to the release of nitrogen. The activation temperature Ta thus measured is shown in the previous Table 2.

[0524] Example 4

[0525] Evaluation of the ability of monotetrazolyl compatibilizers to bond to oligomer double bonds

[0526] The 2,5-disubstituted monotetrazole compatibilizers 3.1-3.5 were dispersed in Polyvest 130 in an amount equal to about 0.5% by weight of the oligomer, and the dispersion was introduced into a test tube and heated to the activation temperature determined by TGA for about 30 minutes.

[0527] In each case, a material with significant fluorescence under UV light was obtained, indicating the formation of pyrazoline and, therefore, bonding of the compatibilizer to the oligomer.

[0528] Example 5

[0529] Preparation of elastomeric compounds containing silica

[0530] Elastomeric compounds were prepared containing equivalent amounts of a conventional silane compatibilizer, TESPT (having two siloxane groups per molecule and a sulfide for anchoring to the elastomer via sulfur bridges, Comparative Examples 5.1 and 5.5), APTES (a conventional silane compatibilizer having only one siloxane group and one NH2 group, Comparative Examples 5.2 and 5.6), or a monotetrazole compatibilizer according to the invention (3.1 with siloxane groups or 3.4 with boric acid groups, Examples 5.3, 5.4, and 5.7). The amounts of the various components, expressed in phr and weight percentage, and the procedure for their addition to the compound are shown in Table 3 below:

[0531] Table 3: Elastomer composition

[0532] step Ingredient phr (% pp) Ex.5.1 Ex.5.2 Ex.5.3 Ex.5.4 Ex.5.5 Ex.5.6 Ex.5.7 contrast contrast invention invention contrast contrast invention 1.0 SBR (equal to 100phr) 137 137 137 137 137 137 137 1.1 Silicon dioxide 60 60 60 60 60 60 60 1.1 Monotetrazole 3.1 (Ta 190℃) -- -- 5.2* -- -- -- 8.5** 1.1 Monotetrazole 3.4 (Ta 140℃) -- -- -- 3* -- -- -- 1.1 TESPT 3 -- -- -- 4.8 -- -- 1.1 APTES 2.5* 3.9** 1.1 6PPD 2.5 2.5 2.5 2.5 2.5 2.5 2.5 1.2 stearic acid 1 1 1 1 1 1 1 1.2 ZnO (80%) 2 2 2 2 2 2 2 2.0 CBS 3 3 3 3 3 3 3 2.0 Sulfur (67%) 1 1 1 1 1 1 1

[0533] in:

[0534] (*) Equivalent amount of Example 5.1 relative to TESPT;

[0535] (**) Equivalent amount relative to TESPT of Example 5.5;

[0536] Relative to the weight of the filler (silicon dioxide), TESPT is 5% by weight in Example 5.1 and 8% by weight in Example 5.5;

[0537] Steps 1.0-1.2: non-productive steps or steps (i);

[0538] Step 2.0: Preparation step or step (ii);

[0539] SBR: Styrene-butadiene copolymer from solution, extended with 37.5 phr TDAE oil per 100 phr dry elastomeric polymer, supplier TRINSEO

[0540] Silica: ZEOSIL 1165MP, supplier: Solvay Rhodia Operations

[0541] Silane: TESPT supplier JINGZHOU JIANGHAN FINE CHEM

[0542] APTES: Dynasilan AMEO supplier Evonik

[0543] Stearic acid: Supplier TEMIX OLEO SRL

[0544] 6PPD: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, supplier: Eastman ZnO(80): 80% zinc oxide, 20% polymer binder and dispersant, supplier: Lanxess Add

[0545] CBS: N-cyclohexyl-2-benzothiazolylsulfenamide, cyclohexylamine content <1%, supplier Duslo

[0546] Sulfur: Crystex OT33 amorphous sulfur, insoluble in CS2 and toluene, treated with 33% hydrotreated heavy naphthenic distillate (petroleum), supplier: Eastman.

[0547] Mixing was performed in several steps using an in-house Brabender laboratory tangential rotor mixer (60 mL mixing chamber).

[0548] In the first step (1-0), 50% of the elastomer was introduced and chewed at 140° C. (set temperature) for 30 seconds.

[0549] In the following step (1.1), the monotetrazolyl compatibilizer (I), TESPT silane or APTES, silica and the remaining elastomer are added. Mixing is continued at 140°C for 2 minutes.

[0550] Subsequently, in step 1.2, antioxidant, ZnO and stearic acid were introduced. Mixing was continued again at 140°C for about 2 minutes until the reaction between stearic acid and zinc was complete, after which a batch, referred to as the first batch, was discharged and its rheological properties were tested.

[0551] After 12-24 hours, in step (ii) using the same mixer, the vulcanizing agent (sulfur) and the accelerator CBS were introduced and mixing was continued at 90°C for about 3 minutes, at which time the final compound was discharged and its dynamic and rheological properties were tested again.

[0552] Dynamic rheological and mechanical properties

[0553] The dynamic mechanical and rheological properties of the comparative and inventive first and last step compounds were analyzed according to the aforementioned methods.

[0554] Figure 8-10 The trend of the rheogram S' (dNm) / time (min) curve is shown.

[0555] In particular, Figure 8 The curves of S' measured on samples of the first-stage compounds of comparative examples 5.5 (TESPT) and 5.6 (APTES) and inventive example 5.7 (monotetrazole 3.1) at 8 wt. % relative to silica heated to 190° C. are shown.

[0556] The effect of the compatibilizer alone on the consolidation of the compound can be assessed based on the S′ curve measured in the absence of a sulfur vulcanization system.

[0557] As expected, TESPT silane releases sulfur which crosslinks the rubber, as evidenced by an increase in S'.

[0558] APTES silane generally acts as a catalyst for the vulcanization package but does not crosslink and in fact the value of S' does not change once the test T is reached.

[0559] With regard to the monotetrazoles 3.1 according to the invention, the very low S' onset values ​​demonstrate the high compatibility of the silica in the compound and the suppression of the interactions between the silica particles usually obtained, while achieving excellent dispersion.

[0560] Figure 9 The curves of the torque S' of samples heated to 190° C. of the final compounds of comparative examples 5.5 (TESPT) and 5.6 (APTES) and of the invention 5.7 (monotetrazole 3.1) with 8% by weight of silica are shown.

[0561] Table 4 below shows the elastic modulus G′ and viscosity G″ values ​​measured for the comparative samples of Examples 5.5 and 5.6 and Example 5.7 of the present invention:

[0562] Table 4

[0563]

[0564]

[0565] 8% relative to silica

[0566] According to the data reported in Table 4 and Figure 9 From the curves of FIG. 3 , it is observed that the samples containing the monotetrazole 3.1 according to the invention have a reduced modulus of the final green compound relative to the control compound.

[0567] This behavior can be attributed to good compatibility and filler dispersion.

[0568] Figure 9 The vulcanization curves of demonstrate the kinetic profile of the compounds according to the invention comprising monotetrazole 3.1, which is comparable to that of the reference compounds.

[0569] Comparing the moduli before and after vulcanization, it can be seen that the deformation modulus of the sample containing the two reference compounds (about 700 kPa) increases to 9% after vulcanization, which is more pronounced than that of the sample according to the invention (about 300 kPa).

[0570] This result may be due to the fact that the reference rubber with different mechanisms can increase the crosslinking of the elastomer, which is different from the tetrazole of the present invention. In fact, it is known to those skilled in the art that TESPT silane can serve as a sulfur donor and contribute to the disulfide bridges forming the lattice. It is also known [see, for example, Journal of Applied Polymer Science, Vol. 123, 2805-2811 (2012)] that APTES silane can contribute to the formation of the sulfur lattice because it serves as a vulcanization accelerator. Regarding the monotetrazole 3.1 of the present invention, the reactivity of the silane is independent of the sulfur crosslinking reaction, so its contribution to the mechanical reinforcement of the vulcanized material is relatively low.

[0571] Figure 10 The curves of the torque S' of samples heated to 190° C. are shown for the final compounds of comparative examples 5.1 (TESPT) and 5.2 (APTES) and according to the invention 5.3 (monotetrazole 3.1) and 5.2 (monotetrazole 3.4) relative to 5 wt % of silica.

[0572] Table 5 below shows the elastic modulus G′ and viscosity G″ values ​​measured for the comparative samples of Examples 5.1 and 5.2 and Examples 5.3 and 5.4 of the present invention:

[0573] Table 5

[0574]

[0575]

[0576] Relative to silica, 5%

[0577] From the values ​​reported in Table 5 it can be observed that Figure 9 Compared to the samples with the added compatibilizer (Examples 5.5-5.7), the G' values ​​of the green samples of the compounds containing APTES (Example 5.2) and monotetrazole 3.4 (Example 5.4) are higher than those of the samples containing TESPT (Example 5.1) at a more reduced amount of compatibilizer. This behavior is likely due to the greater polarity of APTES and monotetrazole 3.4 compared to TESPT, which would ensure a higher interaction with the filler and thus increase the mechanical reinforcement.

[0578] according to Figure 10 Comparable kinetic profiles were again observed for all samples.

[0579] The values ​​of the moduli G′ and G″ of the vulcanized rubber shown in Table 5 are consistent with the value of G′ of the raw rubber, and it is demonstrated that the difference is mainly due to the dispersion state.

[0580] In conclusion, when the amount of compatibilizer increases and its polarity decreases, the monotetrazoles of the present invention show the classical rheological influence of the compatibilizer on the compound, thereby modifying the surface of the conventional filler, ie reducing the G' modulus.

[0581] Indeed, the effect on the mechanical properties of the rubber compound caused by the surface modification is particularly pronounced in the case of higher amounts of compatibilizer, as shown in Examples 5.5 and 5.1, which contain TESPT in amounts equal to 8% and 5% of silica, respectively (Table 4 vs. Table 5).

[0582] In summary, the compatibilizer according to the invention allows for the exclusive expansion of the filler without affecting the crosslinking, consistent with its dynamic and rheological properties, unlike conventional compatibilizers, in which both functions coexist and in which the almost uncontrollable triggering of sulfur crosslinking can occur early in the event of suboptimal filler dispersion. On the other hand, the use of the monotetrazole reagents according to the invention allows for an ideal dispersion of the filler without interfering with the crosslinking, obviating the need for strict control of the mixing temperature, with undeniable advantages both in terms of improved mechanical properties of the material and in terms of process quality.

[0583] Static mechanical properties

[0584] The static mechanical properties of samples of the examples according to the invention and of the comparative compounds vulcanized at 190° C. for 30 minutes were evaluated. The results of these tests are shown in Table 6 below:

[0585] Table 6

[0586] Ex.5.1 Ex.5.2 Ex.5.3 Ex.5.4 Ex.5.5 Ex.5.6 Ex.5.7 Compatibilizer TESPT* APTES* 3.1* 3.4* TESPT** APTES** 3.1** contrast contrast invention invention contrast contrast invention Ca0.5 2.0 1.5 1.4 1.5 1.7 1.5 1.0 Ca1 3.5 1.9 1.4 1.9 3.1 2.0 2.7 Ca3 7.6 5.0 5.4 5.3 13.3 5.8 4.6 CR 15.8 14.4 18.5 18.9 17.5 14.7 13.8 AR% 347 612 659 699 368 547 589

[0587] Where Ca is in MPa; *5% relative to silica; **8% relative to silica

[0588] The exact strain load values ​​of 50%, 100%, and 300% classify the samples containing TESPT as more rigid to traction due to its ability to aid sulfur vulcanization.

[0589] On the other hand, the elongation at break is much lower than that obtainable with all other compatibilizers. Considering that it is usually difficult to obtain a good compromise between mechanical reinforcement (e.g., denoted as Ca3) and elongation at break, the compatibilizers of greatest interest in this study are the monotetrazoles 3.1 and 3.4 according to the invention.

[0590] In summary, it can be seen from the tests carried out and from the results of the above tests that the monotetrazole compatibilizer (I) according to the invention, incorporated into tire rubber compounds, has a significant compatibilizing effect compared to the commercially available silanes APTES and TESPT, especially at higher concentrations, as evidenced by the G′ values ​​of the raw rubber and the vulcanized rubber, which is particularly beneficial to the fracture properties of the vulcanized rubber.

[0591] These results make it possible to use the compatibilizers of the invention as an alternative to traditional compatibilizers in rubber compounds for tires, however with the undoubted advantage of simplifying the manufacturing process associated with the possibility of triggering the reaction of the compatibilizer with the elastomer to a precisely predetermined temperature, for example only during vulcanization, and thus making it possible to process the rubber compound for a longer time without having to carry out strict temperature control.

[0592] The final compounds of the present invention exhibit optimal properties since they combine considerable mechanical reinforcement with excellent fracture properties.

Claims

1. An elastomer composition for tire rubber, comprising at least - 100 phr of at least one diene elastomeric polymer, - at least 1 phr of at least one reinforcing filler; - at least 0.1 phr of at least one monotetrazolyl compatibilizer of the formula (I) in A is absent or represents an at least divalent organic linker group, optionally comprising one or more heteroatoms, covalently bonded to the 2-position or 5-position of the tetrazole; R is a group covalently bonded to the 5-position or 2-position of the tetrazole, selected from a linear or branched C1-C 10 Alkyl; C6-C 20 Aryl; C3-C 10 Cycloalkyl; a saturated, unsaturated or aromatic monocyclic or bicyclic 5-membered or 6-membered optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S, or O; R is optionally substituted by at least one electron-withdrawing group X or electron-donating group Y, or R is a group B, B represents a group having a high affinity for the reinforcing filler, selected from C1-C5 alkoxy, C1-C5 alkyl and / or C6-C 10 an aryl-substituted silane, a -B(HO)2 group, a saturated, unsaturated or aromatic monocyclic or bicyclic, 5-membered or 6-membered optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S and O, or an aromatic polycyclic hydrocarbon, n is an integer from 1 to 3, provided that the groups A, B, and R do not include any 2,5-disubstituted tetrazole; and - 0 to 20 phr of a vulcanizing agent.

2. The composition according to claim 1, wherein n is equal to 1 and A represents a divalent organic group.

3. The composition according to claim 1 or 2, wherein: the diene elastomeric polymer is chosen from natural or synthetic cis-1,4-polyisoprene, 3,4-polyisoprene, polybutadiene, optionally halogenated isoprene / isobutylene 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; and / or - the reinforcing filler is selected from optionally modified carbon black, silica, silicates, chalk, talc, kaolin, bentonite, titanium dioxide and mixtures thereof; and / or The at least one vulcanizing agent is selected from the group consisting of sulfur, sulfur-containing molecules or sulfur donors bis[(trialkoxysilyl)propyl]polysulfide, thiuram, dimorpholine disulfide, caprolactam-disulfide, polytetrazolyl crosslinkers and mixtures thereof.

4. The composition according to claim 1 or 2, comprising - 1 phr to 150 phr or 1 phr to 120 phr or 5 phr to 120 phr of at least one reinforcing filler; and / or - 0.1 to 10 phr, 0.2 to 10 phr, 1 to 10 phr or 1.5 to 5 phr of at least one vulcanizing agent; and / or - 0.5 to 30 phr, 1 to 20 phr or 2 to 10 phr of at least one monotetrazole compatibilizer of formula (I).

5. The composition according to claim 1 or 2, comprising at least one monotetrazole compatibilizer of formula (I) and at least one reinforcing filler in a weight ratio relative to the reinforcing filler of 0.01:1 to 0.3:1 or 0.02:1 to 0.15:

1.

6. The composition according to claim 1 or 2, wherein the molecular weight of the group A is lower than 1000 g / mol, or lower than 500 g / mol, or lower than 300 g / mol.

7. The composition according to claim 1 or 2, wherein the group A is present and is selected from C1-C 10 Alkylene; C6-C 10 Arylene; a monocyclic or bicyclic, 5-membered or 6-membered, saturated, unsaturated or aromatic, optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S and O; C1-C5 alkylene-C6-C 10 Arylene-; C6-C 10 -Arylene-C1-C5 alkylene; C1-C5 alkylene-C6-C 10 Arylene-C1-C5 alkylene; C1-C5 alkylene-heterocyclylene-; heterocyclylene-C1-C5 alkylene; C1-C5 alkylene-heterocyclylene-C1-C5 alkylene; C6-C 10 Arylene-C6-C 10 Arylene; Heterocyclylene-Heterocyclylene; C6-C 10 Arylene-C1-C5 alkylene-C6-C 10 Arylene; Heterocyclylene-C1-C5 alkylene-heterocyclylene, wherein the heterocyclylene is a monocyclic or bicyclic, 5-membered or 6-membered, saturated, unsaturated or aromatic, optionally benzo-condensed heterocyclylene containing at least one heteroatom selected from N, S and O and the alkylene optionally contains one or more heteroatoms selected from B, N, S, O, P and Si or a functionalized group selected from -NR3-CO-, -CO-NR3-, -NH-CO-NH-, -COO-, -O-CO-, -CO-, -C=N(R3)-, -CO-N(R3)-CO-, -C=N(OH)-, -O-CO-N(R3)-, -N(R3)-COO-, -SO-, -SO2-, -SO2O-, -CS-, -CS-O-, -COS-, -CS-S-, wherein R3 represents hydrogen or C1-C5 alkyl.

8. The composition according to claim 1 or 2, wherein the group R is selected from C1-C6 alkyl, C6-C 10 Aryl, C1-C5 alkyl-C6-C 10 Aryl, C6-C 10 Aryl-C1-C5 alkyl, C3-C7 cycloalkyl, monocyclic or bicyclic, 5-membered or 6-membered, saturated, unsaturated or aromatic, optionally benzo-condensed heterocyclic group containing at least one heteroatom selected from N, S and O.

9. composition according to claim 1 and 2, wherein said R group is replaced by at least one electron withdrawing group X or is replaced by at least one electron donating group Y.

10. composition according to claim 9, wherein the electron withdrawing group X is selected from halogen, carbonyl, carboxyl, ester, cyano, nitro, haloalkyl and sulfonyl, and the electron donating group Y is selected from hydroxyl, C1-C 10 Alkoxy, benzyloxy, C1-C 10 Alkyl, amino, C1-C 10 Alkyl monosubstituted amino, C1-C 10 Alkyl disubstituted amino, primary amide (-NH-COR), hydrazone (-CH=N-NR2).

11. The composition according to claim 1 or 2, wherein the B group is a group of formula -Si(OR1)3, wherein R1 are the same as or different from each other and are C1-C5 alkyl, or are polycyclic aromatic hydrocarbons selected from naphthalene, phenanthrene, anthracene, pyrene, benzopyrene, fluorene and benzo condensed derivatives thereof.

12. The composition of claim 1 or 2, wherein the monotetrazole compatibilizer is a reagent of formula (IA): (I-A) or a reagent of formula (IB) (I-B) wherein A is present and is a divalent organic linker group, n is equal to 1 and R is different from B.

13. The composition of claim 12, wherein the monotetrazole compatibilizer is a reagent of formula (IA), wherein: A is a divalent organic linker group of formula -A1-A2-, wherein A1 is absent or selected from -(CH2) (2-4) -NH-C(O)- and -(CH2) (2-4) -NH-C(O)-NH-, and wherein A2 is absent or selected from phenyl and thiophene; R is selected from C4-C6 alkyl, benzyl, phenyl and thiophene, which is optionally substituted with at least one electron-withdrawing group X or electron-donating group Y, B is selected from -Si(OR1)3, wherein R1 is C1-C3 alkyl, -B(HO)2, naphthyl or pyrenyl.

14. The composition according to claim 1 or 2, wherein the molecular weight of the monotetrazole compatibilizer (I) is lower than 1500 g / mol, or lower than 1000 g / mol, or lower than 600 g / mol.

15. The composition according to claim 1 or 2, wherein the activation temperature Ta of the monotetrazole compatibilizer (I) is not less than 100°C, or not less than 120°C, or not less than 140°C and not higher than 220°C, or not higher than 210°C, or not higher than 200°C.

16. An elastomeric compound for tires obtained by mixing and vulcanizing the elastomeric composition according to any one of claims 1 to 15.

17. A method for preparing the elastomeric compound according to claim 16, comprising: - mixing, in one or more steps, all the components of the composition according to any one of claims 1 to 15, maintaining the temperature at a value T1 below the activation temperature Ta of the at least one monotetrazole compatibilizer (I), so as to obtain a compound (1) comprising the monotetrazole compatibilizer (I) and unreacted tetrazole, - heating the rubber (1) to a temperature T2 equal to or higher than the activation temperature Ta of the monotetrazole compatibilizer (I), to obtain a rubber (2), wherein the at least one monotetrazole compatibilizer (I) reacts at least partially by tetrazole decomposition and subsequent addition onto the diene elastomeric polymer, and - Vulcanize the compound.

18. The method according to claim 17, wherein the temperature T1 is at least 10°C lower than the activation temperature Ta of the at least one monotetrazolyl compatibilizer (I), and wherein the temperature T2 is at least 10°C higher than the activation temperature Ta of the at least one monotetrazolyl compatibilizer (I).

19. The method according to claim 17 , wherein the step of heating the rubber compound ( 1 ) at a temperature T2 equal to or higher than the activation temperature Ta of the monotetrazolyl compatibilizer (I) coincides with the step of vulcanizing the rubber compound.

20. A method for preparing the elastomeric compound according to claim 16, comprising: - mixing, in one or more steps, all the components of the composition according to any one of claims 1 to 15, maintaining the temperature at a value T1 below the activation temperature Ta of the at least one monotetrazole compatibilizer (I), so as to obtain a compound (1) comprising the monotetrazole compatibilizer (I) and unreacted tetrazole, and - vulcanizing the compound at a temperature below the activation temperature Ta of said at least one monotetrazole compatibilizer to obtain a vulcanized compound comprising said monotetrazole compatibilizer (I) and unreacted tetrazole.

21. A tire component for a vehicle wheel, said tire component comprising or consisting of the elastomeric compound according to claim 16.

22. The tire component for a vehicle wheel according to claim 21, wherein the component is selected from the group consisting of a tread cap, a base layer, a wear layer, a sidewall, a sidewall insert, a micro sidewall, a liner, a base liner, a rubber layer, a filler strip, a bead reinforcement layer (cover), a bead protection layer (wire bead cover) and a sheet.

23. Tyre for vehicle wheels comprising at least one tyre component according to claim 21 or 22.

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