Tire for vehicle wheels

Abstract

The present invention relates to a tire for vehicle wheels, comprising at least one structural component comprising a vulcanized elastomer compound, said vulcanized elastomer compound being obtained by vulcanization of a vulcanizable elastomer compound, said vulcanizable elastomer compound being made by mixing an elastomer composition comprising (i) at least one diene elastomer polymer and (ii) a reinforcing filler, said reinforcing filler comprising: (a) acicular shaped silicate fibers having nanometric size; and (b) a high dispersibility carbon black having a surface area (NSA) greater than 100 m 2 / g and an OAN (Oil Absorption Number) greater than 100 ml / 100 g; and (c) optionally a conventional silica.

Description

TECHNICAL FIELD

[0001] The present invention relates to a tyre for vehicle wheels. More particularly, the present invention relates to a tyre for vehicle wheels comprising at least one structural component comprising a vulcanized elastomeric compound obtained by vulcanizing a vulcanizable elastomeric compound made by mixing an elastomeric composition comprising: (i) at least one diene elastomeric polymer; and (ii) a reinforcing filler comprising (a) needle-shaped silicate fibres having nanometric dimensions and (b) a highly dispersed carbon black and (c) optionally a conventional silica. BACKGROUND

[0002] In the rubber industry, and in particular in the tyre industry, it is known to add reinforcing fillers to elastomeric compositions in order to improve the mechanical properties and the wear resistance of the elastomeric material obtained by vulcanization.

[0003] Carbon black is a reinforcing filler particularly used due to its high reinforcing efficiency. However, carbon black represents a non-renewable raw material which mainly comes from the incomplete combustion process of fossil fuels, (mainly naphtha, methane gas and other hydrocarbons). Moreover, carbon black can also have an impact on the environment as it can become a potential pollutant if not disposed of properly. Carbon black also increases the hysteresis and thus the rolling resistance and the fuel consumption of the tyre. Therefore, the replacement or reduction of the use of carbon black is not only an objective of interest for tyre manufacturers, but also of the society in general.

[0004] Other reinforcing materials currently used are so-called "white" fillers, such as talc, kaolin, bentonite, titanium dioxide, silica, silicate fibres (such as sepiolite and more recently modified sepiolite), which can partially or totally replace carbon black in the elastomeric material and confer a lower hysteresis to the elastomeric material while maintaining sufficient reinforcement.

[0005] Among the white fillers, silicate fibres, especially sepiolite and modified sepiolite, have proven to be particularly promising in terms of hysteresis and mechanical properties of the elastomeric material into which they are incorporated instead of or in addition to traditional fillers and have proven to give a reduced rolling resistance, better stiffness and wear resistance to the tyre.

[0006] At an industrial level, the method to incorporate these nanofibres into the elastomeric material is either in a traditional batch mixer (e.g. open mill) or in an internal mixer of tangential rotor type (e.g. BANBURY®) or in a continuous mixer (e.g. two-roll mill or BANBURY® continuous mixer) or in a combination of these methods. ) or in internal mixers of the internal mixing type with intermeshing rotors, directly mixed into the solid elastomeric matrix, but the incorporation of these nanofibres into the elastomeric material appears to be difficult due to the high degree of powder of these fibres.

[0007] In fact, once dried from the residual water of the extraction process from the raw mineral or any subsequent derivatisation reactions, these fibres assume a consistency of a powder with a low apparent density, for example, in the case of organically modified sepiolite (Pangel B5 by Tolsa) of about 210 g / l, while in the case of unmodified sepiolite (Pangel S9 by Tolsa) this apparent density is further reduced to 60 g / l.

[0008] Due to the high degree of powder, these fibres are easily dispersed in the air and difficult to handle and add to the other components in the mixing machine, thus creating problems of dosing, dispersibility, pollution of the work environment, potential toxicity to the operators and possible damage to the machine itself.

[0009] To avoid these drawbacks that normally arise when using powdery compounds in industrial plants, one can resort to incorporating them into solid masterbatch compositions (MB) that capture the powders in a compact matrix, thus making them more manageable and easy to manage.

[0010] For example, patent application WO2018 / 116125 in the name of the same applicant describes a process for the preparation of a solid masterbatch elastomeric composition comprising nanometric size fibres of silicate in acicular morphology dispersed in at least one diene elastomer and a tyre for vehicle wheels comprising such a composition as a substitute for carbon black.

[0011] A possible alternative consists in preparing the silica aggregates in the form of non-powdery microbeads that, when incorporated into the elastomeric material, allow the silica to be sufficiently disaggregated and dispersed in the matrix.

[0012] For example, patent application WO2019 / 106562 in the name of the same applicant describes a process for the preparation of a composition in the form of microbeads comprising nanometric size fibres of silicate in acicular morphology and silica and a tyre for vehicle wheels comprising such a composition as a substitute for carbon black.

[0013] In vehicles provided with tyres in which the carbon black is partially replaced with fibres of silicate in acicular morphology, an accumulation of static electricity occurs due to the fact that, unlike carbon black, the silicate fibres are not electrically conductive and therefore do not allow the static charge generated by the rolling of the wheels and by the consequent movement of the vehicle to be discharged to the ground.

[0014] To overcome this drawback, which also occurs when other non-conductive materials (for example, silica-based reinforcing fillers) are used instead of carbon black, the tyre manufacturers have to implement additional processes and / or components. For example, tyres have been manufactured including electrically conductive strips made of a compound including carbon black or other electrically conductive materials and immersed in the tread structure and / or in the sidewalls, in order to provide the vehicle with proper grounding.

[0015] EP 658452 in the name of the same Applicant describes an embodiment of such tyres. The production of such electrically conductive strips involves greater complexity. From a production point of view, the production of such strips requires the use of additional steps and more complex equipment in the extrusion of the compound that will form the tyre's tread. From a structural point of view, the presence of such strips, which constitute a chemical-physical separation element within the elastomeric material, requires the use of specific compounds to avoid triggering early wear phenomena, reducing the mileage of the tyre. SUMMARY

[0016] The Applicant set itself the aim of solving the problem of electrical conductivity associated with the incorporation of nanometric size acicular morphology silicate fibres in elastomeric compositions for tyres.

[0017] The Applicant was therefore faced with the dilemma of either the typical electrical conductivity problems of replacing the traditional carbon black reinforcing filler with a white filler, or the environmental impact and the problems of hysteresis and increased rolling resistance typically associated with the use of traditional carbon black reinforcing fillers.

[0018] The Applicant found that, by using a highly dispersed carbon black as reinforcing filler in an elastomeric composition for tyres and combining it with nanometric size acicular morphology silicate fibres in the form of a solid masterbatch elastomeric composition, in addition to solving the problem of electrical conductivity, an unexpected reduction in hysteresis and Payne effect was also observed.

[0019] The Payne effect is a phenomenon that manifests itself as a reduction in dynamic modulus, which is more pronounced when the deformations to which the elastomeric material is subjected are greater. In fact, at the moment when the tyre is subjected to the greatest stresses, i.e. when the elastomeric material should exhibit the best mechanical properties, the reinforcing effect of the filler is instead lacking. The reason for this phenomenon, which is typical of reinforcing fillers, in particular of silica, is that under dynamic conditions, i.e. when the elastomeric material filled and vulcanized with silica is stressed in the tyre in use, the dispersed filler can partially fail, with consequent negative effects on the mechanical properties.

[0020] The smaller hysteresis values reduce the heat dissipation under dynamic conditions. In tyres, this translates into a reduction in rolling resistance and, in general, into lower fuel consumption, lower production of polluting emissions and lower transport costs.

[0021] It is known that a reduction in the diameter of carbon black particles, with a consequent increase in the surface area, leads to an increase in hysteresis, and this result is all the more surprising.

[0022] Without wishing to be bound to any specific explanation, the Applicant assumes that this surprising result is due to the interaction between the acicular structure of the silicate fibres and the highly dispersed structure of the carbon black.

[0023] Continuing the experiments, the Applicant has also observed that, by using, in the elastomeric composition for tyres, the highly dispersed carbon black in combination with the nanometric size acicular silicate fibres in the form of microbeads, in addition to solving the problem of conductivity, the static mechanical properties are surprisingly improved, in particular the load at different elongations and breakages and the load at the maximum torque value.

[0024] The first aspect of the present application is therefore a tyre for vehicle wheels, comprising at least one structural component comprising a vulcanised elastomeric compound obtained by vulcanisation of a vulcanisable elastomeric compound made by mixing an elastomeric composition comprising: (i) at least one diene elastomeric polymer; and (ii) a reinforcing filler comprising (a) acicular silicate fibres having a nanometric size, (b) a highly dispersed carbon black and (c) optionally a conventional silica.

[0025] In its second aspect, the present application relates to an elastomeric composition comprising, for each 100 phr of diene elastomeric polymer:

[0026] (i) from 5 to 50 phr, preferably from 10 to 40 phr, of acicular silicate fibres having a nanometric size,

[0027] (ii) from 10 to 60 phr of a highly dispersed carbon black,

[0028] (iii) optionally, from 5 to 60 phr of a conventional silica,

[0029] (iv) from 0.1 to 12 phr of at least one vulcanising agent, and

[0030] (v) from 0.1 to 15 phr of a coupling agent.

[0031] Advantageously, the nanometric size, acicular morphology silicate fibres are added to the elastomer composition in the form of (al) a solid masterbatch elastomer composition comprising nanometric size, acicular morphology silicate fibres dispersed in at least one diene elastomer, as described in WO2018 / 116125; and / or (a2) a microbead comprising nanometric size, acicular morphology silicate fibres and silica, as described in WO2019 / 106562.

[0032] Definitions

[0033] The term "elastomer composition" means a composition comprising at least one diene elastomer polymer and one or more additives, which by mixing and possibly heating, provides an elastomer compound suitable for use in tyres and parts thereof.

[0034] The components of the elastomer composition are generally not introduced into the mixing machine simultaneously but are typically added sequentially in order. In particular, the vulcanization additives, such as vulcanizing agents and possibly accelerators and retarders, are generally added in a downstream step with respect to the incorporation and processing of all the other components.

[0035] In the final vulcanizable elastomer compound, the components of the elastomer composition can change or are no longer individually traceable, because they interact with the other components by heat and / or mechanical treatment, resulting in being completely or partially modified. The term "elastomer composition" herein refers to the set of all components used to prepare the elastomer compound, regardless of whether they are actually present simultaneously, introduced sequentially or are subsequently traceable in the elastomer compound or in the final tyre.

[0036] The term "elastomer polymer" means a natural or synthetic polymer which, after vulcanization, can be repeatedly stretched at room temperature to at least twice its original length and substantially immediately returns to approximately its original length with the aid of a force after removal of the stretching load (definition according to the Standard Terminology Relating to Rubber, ASTM D1566-11).

[0037] The term "diene elastomer polymer" means an elastomer polymer derived from the polymerization of one or more different monomers, at least one of which is a conjugated diene (conjugated diene olefin).

[0038] The term "elastomer compound" means a compound obtainable by mixing and possibly heating at least one elastomer polymer with at least one additive commonly used in the preparation of tyre compounds.

[0039] The term "vulcanizable elastomer compound" means an elastomer compound, which is ready for vulcanization, obtainable in the elastomer compound by incorporating all the additives, including those for vulcanization.

[0040] The term "vulcanized elastomer compound" means a material that can be obtained by vulcanization of a vulcanizable elastomer compound.

[0041] The term "green" means a material, compound, composition, part or tire that has not yet been vulcanized.

[0042] The term "vulcanization" means the cross-linking reaction in natural or synthetic rubber caused by typical sulfur-based cross-linking agents.

[0043] The term "vulcanizing agent" means a product capable of transforming natural or synthetic rubber into an elastic and resistant material by forming a three-dimensional network of intermolecular and intramolecular bonds. Typical vulcanizing agents are sulfur-based compounds such as elemental sulfur, polymeric sulfur, sulfur donors such as bis[(trialkoxysilyl)propyl]polysulfides, thiurams, dithio- dimorpholines and caprolactam-disulfides.

[0044] The term "vulcanization accelerator" means a product capable of further promoting vulcanization so that it takes place in a shorter time and possibly at lower temperatures. An example of an accelerator is the stearic acid-zinc oxide system.

[0045] The term "vulcanization activator" means a product capable of further promoting vulcanization so that it takes place in a shorter time and possibly at lower temperatures. An example of an accelerator is the stearic acid-zinc oxide system.

[0046] The term "vulcanization retarder" means a product capable of delaying the start of the vulcanization reaction and / or inhibiting undesired side reactions, for example N-(cyclohexylthio)phthalimide (CTP).

[0047] The term "vulcanization package" means a vulcanizing agent and one or more vulcanization additives selected from the group consisting of vulcanization activators, accelerators and retarders.

[0048] The term "reinforcing filler" generally means a reinforcing material typically used in the art to improve the mechanical properties of the rubber of the tire, preferably selected from the group consisting of carbon black, conventional silica, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

[0049] The term "conventional silica" means a silica precipitated with a strong acid, typically from sand, preferably amorphous silica, fumed silica, wet silica, anhydrous silica or mixtures thereof, having a surface area BET (measured according to the ISO 5794 / 1 standard) between 50 m 2 / g and 500 m 2 / g, preferably between 70 m 2 / g and 200 m 2 / g.

[0050] The term "mixing step (1)" designates a step of the process for the preparation of the elastomer compound wherein one or more additives, other than the vulcanizing agent supplied in step (2), are incorporated by mixing and possibly heating. Mixing step (1) is also referred to as "non-productive step". In the preparation of the compound, several "non-productive" mixing steps, which can be denoted by 1a, 1b, etc., can be present.

[0051] The term "mixing step (2)" designates the next step of the process for the preparation of the elastomer compound wherein the vulcanizing agent and possibly other additives of the curative package are introduced into the elastomer compound obtained from step (1) and mixed in the material at a controlled temperature, typically at a compound temperature lower than 120°C, so as to provide a vulcanizable elastomer compound. Mixing step (2) is also referred to as "productive step".

[0052] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used with reference to a direction substantially parallel to the equatorial plane of the tyre and a direction substantially perpendicular to the equatorial plane of the tyre, respectively (i.e. to a direction substantially perpendicular and a direction substantially parallel to the rotation axis of the tyre, respectively).

[0053] The terms "circumferential" and "circumferentially" are used with reference to a direction of annular extension of the tyre (i.e. to the rolling direction of the tyre, which corresponds to a direction lying on a plane coincident or substantially parallel to the equatorial plane of the tyre).

[0054] "Substantially axial direction" means a direction inclined by an angle comprised between about 70° and about 90° with respect to the equatorial plane of the tyre.

[0055] "Substantially circumferential direction" means a direction extending by an angle comprised between about 0° and about 10° with respect to the equatorial plane of the tyre.

[0056] For the purposes of the present description and of the following claims, the term "phr" (acronym of parts per hundred of rubber) means parts by weight of a given component of the elastomer compound per 100 parts by weight of elastomer polymer, without taking into account any extension oil.

[0057] All percentages are expressed as weight percentages, unless otherwise stated.

[0058] The present application is characterized by one or more of the following preferred aspects, taken alone or in combination.

[0059] Vulcanizable elastomer composition

[0060] The vulcanizable elastomer composition for manufacturing structural components of tyres according to the present application comprises at least, for each 100 phr of diene elastomer polymer:

[0061] (i) from 5 phr to 50 phr, preferably from 10 phr to 40 phr, of needle-shaped silicate fibres having nanometric dimensions,

[0062] (ii) from 10 phr to 60 phr of carbon black with high dispersibility,

[0063] (iii) optionally, from 5 phr to 60 phr of conventional silica,

[0064] (iv) from 0.1 phr to 12 phr of at least one vulcanizing agent, and

[0065] (v) from 0.1 phr to 15 phr of a coupling agent.

[0066] The vulcanizable elastomer composition for tyre components according to the present application is characterized by the adoption, alone or in combination, of one or more of the following preferred aspects.

[0067] Diene elastomer polymer

[0068] The diene elastomer polymer used in the present application can be selected from the diene elastomer polymers typically used in vulcanizable elastomer materials particularly suitable for the production of tyres, i.e. from elastomer polymers or copolymers possessing unsaturated chains, having a glass transition temperature (Tg) generally lower than 20°C, preferably in the range from 0°C to -110°C. These polymers or copolymers can be of natural origin or obtained by solution, emulsion or gas-phase polymerization of one or more conjugated dienes, optionally mixed with at least one comonomer selected from monovinylarenes and / or polar comonomers.

[0069] The conjugated dienes generally contain from 4 to 12, preferably from 4 to 8 carbon atoms and can be selected, for example, from the group comprising 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene or mixtures thereof. 1,3-Butadiene and isoprene are particularly preferred.

[0070] Monovinyl aromatic hydrocarbons which can optionally be used as comonomers generally contain 8 to 20, preferably 8 to 12 carbon atoms and can be selected, for example, from styrene; 1 -vinyl naphthalene; 2-vinyl naphthalene; various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene, such as, for example, a-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, or mixtures. Styrene is particularly preferred.

[0071] Polar comonomers which can optionally be used can be selected, for example, from vinylpyridine, vinylquinoline, acrylic acid and alkyl acrylate, nitrile or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile or mixtures thereof.

[0072] Preferably, the diene elastomeric polymers which can be used in the present application can be selected, for example, from cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (especially polybutadiene having a high 1,4-cis content), isoprene / isobutylene copolymers, optionally halogenated, 1,3-butadiene / acrylonitrile copolymers, styrene / 1,3-butadiene copolymers, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers, or mixtures thereof.

[0073] Diene elastomeric polymers which have been functionalized by reaction with a suitable terminating or coupling agent can also be used. In particular, diene elastomeric polymers which have been obtained by anionic polymerization in the presence of an organometallic initiator, in particular an organolithium initiator, can be functionalized by reaction of the residual organometallic group derived from the initiator with a suitable terminating or coupling agent, such as, for example, an imine, a carbodiimide, an alkyltin halide, a substituted benzophenone, an alkoxysilane or an aryloxysilane.

[0074] Silicate fibres of nanometric size with acicular morphology

[0075] The needle-shaped silicate fibres of nanometric size are selected from the group consisting of magnesium and / or aluminium and / or calcium silicate fibres and mixtures thereof.

[0076] Preferably, the fibres of silicate with a needle-like habit of nanometric size are selected from 2:1 phyllosilicates, characterized by an "inverted ribbons" structure, as described in "Bergaya, F., Jaber, M. and Lambert, J.-F. (2011) Clays and Clay Minerals, in Rubber-Clay Nanocomposites: Science, Technology, and Applications (ed M. Galimberti), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002 / 9781 18092866, Chapter 1".

[0077] Preferably, the fibres of silicate with a needle-like habit of nanometric size are selected from sepiolite fibres, modified sepiolite fibres, palygorskite fibres (also known as attapulgite), wollastonite fibres, imogolite fibres and mixtures thereof, more preferably they are sepiolite fibres, modified sepiolite or mixtures thereof.

[0078] Fibres of silicate with a needle-like habit are different from thin-layered silicates (such as bentonite, dickite, vermiculite or hydrotalcite), at least in terms of average aspect ratio. More specifically, considering that the particle has three dimensions a, b, c, with a > b > c, a particle can be defined as thin-layered when (3 x a / b) < b / c, while it can be defined as needle-like when (2 x a / b) > b / c.

[0079] The term "fibres with a needle-like habit" means fibres whose size (length) is much greater than the diameter or maximum cross-sectional dimension. In particular, this means that the ratio between the maximum dimension (length) and the diameter or maximum cross-sectional dimension of the fibres (aspect ratio) is at least 2:1, preferably at least 3:1, more preferably at least 5:1 or at least 10:1.

[0080] Preferably, the fibres have an aspect ratio of no more than 1000:1, more preferably no more than 100:1.

[0081] Preferably, the ratio is evaluated by microscopic observation, preferably on at least 100 fibres.

[0082] Preferably, at least 70%, 80%, 90% of the fibres have the above aspect ratio.

[0083] The expression "nanometric size" means that the diameter or maximum cross-sectional dimension of the fibres is less than 500 nm.

[0084] Preferably, the diameter or maximum cross-sectional dimension of the fibres is between 1 nm and 100 nm, more preferably between 5 nm and 50 nm, even more preferably between 15 nm and 20 nm.

[0085] Preferably, the length of the fibres is less than 10 microns, more preferably between 0.1 microns and 10 microns, even more preferably between 0.1 microns and 5 microns.

[0086] Generally, the sepiolite is acicular with an aspect ratio between 3:1 and 1000:1, more commonly between 5:1 and 100:1.

[0087] Generally, the wollastonite is acicular with an aspect ratio between 3:1 and 20:1, more commonly between 10:1 and 20:1.

[0088] Generally, the imogolite is acicular with an aspect ratio between 5:1 and 100:1, more commonly between 5:1 and 50:1.

[0089] An example of a silicate fibre that can be used according to the present application is sepiolite marketed by the Tolsa group (http: / / www.tolsa.com / ) under the name Pangel S9 or Pansil 100.

[0090] In the present context, the term "nanometric size acicular morphology silicate fibres" also refers to modified fibres, i.e. fibres that can be obtained from nanometric size acicular morphology silicate fibres by partial acid degradation, partial removal of magnesium, derivatisation (for example salification with organic compounds or silanisation) or surface deposition (for example amorphous silica).

[0091] The nanometric size acicular morphology silicate fibres can be obtained from nanometric size acicular morphology silicate fibres selected from the group consisting of sepiolite fibres, calcium aluminate fibres (also known as attapulgite), wollastonite fibres and mixtures thereof, more preferably modified sepiolite fibres or mixtures thereof.

[0092] In the present text, "modified silicate fibres with nanometric size acicular morphology" means fibres modified, for example, by acid treatment, in which the magnesium is partially removed up to a final content comprised between 3.8% and 12%, which substantially retains the acicular morphology and the original crystal structure described and exemplified in the patent applications WO2016 / 174629A1 (in particular from page 9 to page 15 and from page 30 to page 34) and WO2018 / 078500A1 (in particular from page 8 to page 14 and from page 32 to page 34) in the name of the present applicant, incorporated herein by reference.

[0093] These acid-modified fibers can be optionally further derivatized, for example by adding to the acid-treated suspension of fibers at least one silanizing agent. Preferably, the silanizing agent is selected from mono- or di-functional silanes having one or two or three hydrolysable groups, such as bis-(triethoxysilyl-propyl) disulfide (TESPD), bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), 3-thia-octanoyl-1-propyl-triethoxysilane (NXT), Me2Si(OEt)2, Me2PhSiCl, Ph2SiCl2, more preferably from TESPD and TESPT.

[0094] Further examples of suitable modified fibers are: silicate fibers having a needle-like morphology of nanometric size, which comprise amorphous silica deposited on the surface, as described and exemplified in the patent application WO2016 / 174628A1 in the name of the present applicant, incorporated herein by reference, in particular from page 7 to page 12 and from page 22 to page 23; or sepiolite fibers organically modified by reaction with a quaternary ammonium salt (talloyl benzyl dimethyl ammonium chloride) (sold by Tolsa under the name Pangel B5).

[0095] Finally, the term "silicate fibers having a needle-like morphology of nanometric size" also refers to possible mixtures of one or more of said fibers and / or one or more of said modified fibers.

[0096] Preferably, said "silicate fibers having a needle-like morphology of nanometric size" are sepiolite fibers or modified sepiolite fibers, for example but not only sepiolite fibers or modified sepiolite fibers for treatment with acid, such as described in the cited documents WO2016 / 174629A1 and WO2018 / 078500A1, derivatized by reaction with a quaternary ammonium salt (for example Pangel B5 of Tolsa) or by deposition on the surface of nascent silica according to the process reported in document WO2016 / 174628A1.

[0097] Solid masterbatch elastomer composition

[0098] The term solid masterbatch elastomeric composition or masterbatch (MB) means a concentrated solid composition having an elastomeric matrix, which comprises silicate fibers having a needle-like morphology of nanometric size.

[0099] Preferably, the solid masterbatch elastomeric composition useful for the purposes of the present application consists essentially of an elastomeric matrix and said silicate fibers having a needle-like morphology of nanometric size.

[0100] The elastomeric matrix comprises at least one diene elastomer, said diene elastomer typically comprising a mixture of two or more diene elastomers.

[0101] Preferably, said at least one diene elastomer present in the elastomeric matrix is selected from the group consisting of natural rubber (NR), butyl rubber (BR), styrene-butadiene rubber (SBR) and mixtures thereof.

[0102] In particular, the solid masterbatch elastomeric composition consists of:

[0103] • 100 phr of at least one diene elastomer, and

[0104] • at least 50 phr, 60 phr, 70 phr, 80 phr or 90 phr of silicate fibres in acicular morphology having nanometric size.

[0105] Preferably, the solid masterbatch elastomeric composition consists of:

[0106] • 100 phr of at least one diene elastomer, and

[0107] • from 50 phr to 200 phr, more preferably from 60 phr to 150 phr of silicate fibres in acicular morphology having nanometric size.

[0108] Advantageously, the solid masterbatch elastomeric composition consists of

[0109] • 100 phr of at least one diene elastomer, and

[0110] • 100 phr of silicate fibres in acicular morphology having nanometric size.

[0111] Preferably, the fibres are sepiolite fibres or modified sepiolite fibres or mixtures thereof.

[0112] Preferably, the solid masterbatch elastomeric composition is characterized by a good uniformity of the distribution of the fibres in the elastomeric matrix, which has already been able to be detected visually from the colour uniformity of the lumps.

[0113] The solid masterbatch elastomeric composition according to the present application allows the easy incorporation of silicate fibres in acicular morphology having nanometric size into the elastomeric compositions for tyres.

[0114] Preparation of solid masterbatch elastomer composition

[0115] The process for the preparation of the solid masterbatch elastomeric composition useful in the present application is a preferred discontinuous process, also known as the batch process described in WO2018 / 116125.

[0116] The discontinuous process means a process wherein the components of the composition are periodically fed to a suitable apparatus in predetermined amounts (batch) and left in contact for a predetermined time in order to obtain the elastomeric composition. Once obtained, the elastomeric composition is completely discharged from the apparatus in the form of a single solution.

[0117] A suitable apparatus for the preparation of the solid masterbatch elastomeric composition is for example the IKA Master Plant MP10 or the Silverson 700X mixer.

[0118] Alternatively, the masterbatch elastomeric composition can be prepared with a continuous process, wherein the conditions specified in the present description are met.

[0119] The process provides for providing an elastomeric latex comprising at least one diene elastomer and an aqueous phase.

[0120] The elastomeric latex can be a latex of natural or synthetic origin, preferably it is a latex of natural origin (natural rubber or NR), obtained for example from tropical plants of the Euforbiaceae family, such as the rubber tree and the rubber tree of Guyana.

[0121] Preferably, the elastomeric content of the elastomeric latex is between 10% and 60%, preferably at least 15%, at least 30%, at least 40% w / w.

[0122] Optionally, the latex can be diluted with water before being left in contact with the fibres. Preferably, if diluted by adding water, the elastomeric content of the latex after dilution is between 10% and 60% w / w.

[0123] Generally, in the possible dilution of the latex, the optimal volume ratio of precipitation is taken into account, which is intended to give the final aqueous suspension.

[0124] Preferably, the pH of the elastomeric latex is between 9 and 12, more preferably between 9 and 11.

[0125] Preferably, the elastomeric latex comprises a basic substance, more preferably ammonia, which maintains the pH of the latex in the range from 9 to 12 and keeps it stable. In fact, commercial natural rubber elastomeric latexes are also named HA grade latexes with high ammonia content or MA grade with intermediate content, according to the ammonia content.

[0126] The elastomeric latex comprises at least one diene elastomer, which generally comprises a mixture of two or more diene elastomers.

[0127] Preferably, the at least one diene elastomer present in the latex is selected from natural rubber (NR), styrene-butadiene rubber (SBR) and mixtures thereof.

[0128] Commercial examples of suitable elastomer latices are Von Bundit MA latex (60% elastomer, pH 8-11) and Von Bundit HA (60% elastomer, pH 9-12) and Centex FA latex (60% elastomer, pH 9-12).

[0129] In the present process, the weight ratio between the fibres and the latex elastomer has been shown to be important for obtaining a uniform and quantified coagulum. Preferably, the weight ratio between the fibres and the latex elastomer is at least 0.6:1, at least 0.7:1, at least 0.8:1 or at least 0.9:1.

[0130] Preferably, the weight ratio between the fibres and the latex elastomer is in the range of 0.5:1 to 1.5:1, 0.7:1 to 1.3:1, 0.9:1 to 1.1:1, more preferably about 1:1.

[0131] Preferably, in the process fibres are supplied and then said fibres are present in the solid masterbatch elastomer composition in an amount of at least 50 phr, at least 55 phr, at least 60 phr, at least 70 phr, more preferably at least 80 phr, at least 90 phr or at least 100 phr per 100 parts by weight of diene elastomer.

[0132] Preferably, in the process fibres are supplied and then said fibres are present in the solid masterbatch elastomer in an amount of between 50 phr and 200 phr, preferably between 60 phr and 150 phr, more preferably between 80 phr and 120 phr per 100 parts by weight of diene elastomer.

[0133] The amount of fibres indicated above to be supplied for the preparation of the present solid masterbatch composition is understood to refer to the weight of the dried fibres, i.e. with a residual moisture content lower than 10%, preferably lower than 5%.

[0134] Preferably, in the process wet fibres are used, said wet fibres comprising a high content of residual water (typically between 50% and 95%) from the previous aqueous phase treatment. The residual water content can be easily determined by TGA and taken into account when calculating the effective weight of the fibres needed for the above mentioned weight ratio between the fibres and the elastomer.

[0135] In the present process, the fibres are placed in contact with the elastomer latex to form an aqueous suspension.

[0136] In one embodiment, the fibres can be added to the latex without solvent, provided that the correct volume ratio of the final suspension is respected by possible prior dilution of the latex or re-addition of the aqueous phase after the addition of the fibres.

[0137] Preferably, the coagulation medium in the process is substantially aqueous.

[0138] Preferably, the fibres are previously suspended in water by means of the use of suitable mixing techniques, such as ultrasonic treatment (ultrasound), mechanical stirring, magnetic stirring, impeller stirring or other suitable means to obtain a homogeneous aqueous suspension (A).

[0139] Preferably, the mixing to obtain the suspension (A) lasts from 5 minutes to 60 minutes, preferably from 10 minutes to 30 minutes. In the case of mechanical stirring, the speed is preferably maintained between 200 rpm and 1000 rpm.

[0140] Preferably, for the preparation of the suspension (A), deionized water or distilled water is used.

[0141] Preferably, the aqueous suspension (A) comprises said fibres in an amount of between 10 g / l and 100 g / l, more preferably between 30 g / l and 60 g / l, with respect to water.

[0142] The elastomer latex can be used as such or suitably diluted with water to obtain a diluted suspension (B), preferably until the elastomer content is between 5% and 60%, preferably between 15% and 60% (w / v).

[0143] Preferably, the fibres are added in the form of an aqueous suspension (A).

[0144] In this treatment, the aqueous suspension (A) can be added to the elastomer latex or suspension (B) (direct addition), or alternatively, the elastomer latex or suspension (B) can be added to the suspension (A) (reverse addition) to obtain an aqueous suspension.

[0145] The direct or reverse addition is generally performed in a period of time ranging from a few minutes to 30 minutes, depending on the scale of the reaction.

[0146] Preferably, the fibres are left in contact with the latex under stirring and mixing is carried out throughout the process of coagulation of the latex and precipitation of the masterbatch elastomer composition.

[0147] Preferably, the precipitation is carried out under stirring.

[0148] Preferably, the precipitation occurs in a period of time of approximately 5 minutes and 30 minutes.

[0149] Preferably, the coagulation of the latex is carried out at a temperature of 10° to 50°C, more preferably at a temperature of 20° to 30°C.

[0150] Preferably, the volume ratio of the aqueous suspension (C) obtained by placing the fibres in contact with the elastomer latex, expressed as the volume of the aqueous suspension with respect to the weight of the fibres, is between 15:1 ml / g and 25:1 ml / g, more preferably between 20:1 ml / g and 25:1 ml / g. This volume ratio can be obtained by suitably selecting the volume of the latex or of the possible suspension of the suspension (B) or of the fibres (A), or can be obtained by adding more water to the suspension prepared by placing the suspension (A) in contact with the latex or with the suspension (B) or, in this case, by removing the water from them by evaporation.

[0151] Preferably, the pH of the suspension obtained by placing the fibres in contact with the elastomer latex is in the range from 7.5 to 11.

[0152] Preferably, the pH range is obtained by mixing a commercial latex having a pH generally between 8 and 12 with the optional suspension (A) of fibres, any other water and, if necessary, by correcting the pH by adding a base or an acid.

[0153] Preferably, the coagulation and precipitation of the elastomeric composition do not require the addition of any conventional initiators, such as the addition of an acid or a salt.

[0154] Preferably, the precipitated masterbatch composition is separated from the aqueous phase by spontaneous decanting or by centrifugation, followed by removal of the aqueous phase by suction or filtration.

[0155] Preferably, the precipitated masterbatch composition is filtered and, preferably, washed until neutral.

[0156] Finally, preferably, the composition is dried, for example in an oven, optionally under vacuum, until the weight is constant.

[0157] Microbeads comprising nanometric size acicular morphology silicate fibres and silica

[0158] The term "microbeads" means particles that are substantially spherical and have an average diameter of less than 500 microns. The average diameter of the microbeads can be determined by particle size determination analysis by laser diffraction or dynamic light scattering (DLS) according to ISO 13320.

[0159] The microbeads are characterized by an average diameter preferably of at least 60 microns, 70 microns or 80 microns. The microbeads are characterized by an average diameter preferably between 60 microns and 400 microns, more preferably between 70 microns and 300 microns.

[0160] Advantageously, the microbeads comprise fine powders, i.e. particles having an average diameter of less than 50 microns, in an amount of less than 15%, preferably less than 10%, measured according to the ISO 13320 method.

[0161] The microbeads comprise (A) silica and (B) acicular-shaped silicate fibres in a weight ratio A / B preferably comprised between 0.7:1 and 10:1, 0.7:1 and 5:1, more preferably between 0.8:1 and 3:1, even more preferably between 0.9:1 and 2.5:1 or 0.9:1 and 1.1 :1.

[0162] Advantageously, the microbeads comprise (A) silica and (B) acicular-shaped silicate fibres of nanometric size in a weight ratio A / B equal to about 1 :1.

[0163] The silica (A) and the acicular-shaped silicate fibres of nanometric size add up to at least 90%, preferably at least 95% by weight of the dried microbeads. The 100% by weight of the components can include salts (such as sodium sulfate, sodium chloride, magnesium sulfate or magnesium chloride) and traces of residual solvents.

[0164] The silica (A) comprised in the microbeads is selected from fumed silica, precipitated silica and mixtures thereof. Preferably, one or more precipitated amorphous silicates are used in the microbeads according to the present application.

[0165] Preferably, precipitated amorphous silica is used in case of a BET surface area (measured according to ISO standard 5794 / 1 ) between 50 m 2 / g and 500 m 2 / g, preferably between 70 m 2 / g and 200 m 2 / g.

[0166] Commercial examples of silica (A) are Zeosil 1165MP silica from Rhodia, ULTRASIL 7000 from Evonik and Ebrosil H-155AT from IQESIL.

[0167] Preferably, the content of acicular-shaped silicate fibres (B) of nanometric size in the microbeads is at least 5% by weight, preferably at least 10%, at least 20%, at least 30% or at least 40% with respect to the weight of the microbeads.

[0168] Preferably, the content of acicular-shaped silicate fibres (B) of nanometric size in the microbeads is between 5% and 65% by weight, preferably between 10% and 60% or between 30% and 55% with respect to the weight of the microbeads.

[0169] After drying, the total residual water content of the microbeads is lower than 8% by weight, typically between 4.5% and 7.5% by weight with respect to the weight of the microbeads.

[0170] In a preferred embodiment, the microbeads comprise silica (A) and nanometric size, acicular morphology silicate fibres (B), wherein the fibres are sepiolite fibres or modified sepiolite fibres, and wherein the weight ratio A / B is between 0.9:1 and 1.1:1, preferably about 1:1.

[0171] In a preferred embodiment, the microbeads comprise silica (A) and sepiolite fibres or modified sepiolite fibres (B), wherein the weight ratio A / B is between 0.9:1 and 1:1, preferably about 1:1, and wherein the silica (A) and the fibres (B) together make up at least 90% by weight of the dried microbeads.

[0172] In a preferred embodiment, the microbeads comprise silica (A) and sepiolite fibres or modified sepiolite fibres (B), wherein the weight ratio A / B is between 0.9:1 and 1:1, preferably about 1:1, and the average diameter of the microbeads is at least 70 microns.

[0173] In a preferred embodiment, the microbeads comprise silica (A) and sepiolite fibres or modified sepiolite fibres (B), wherein the weight ratio A / B is between 0.9:1 and 1.1:1, preferably about 1:1, and the average diameter of the microbeads is at least 80 microns, and wherein the silica (A) and the fibres (B) together make up at least 90% by weight of the dried microbeads.

[0174] Preparation of microbeads

[0175] The method for preparing microbeads comprising nanometric size, acicular morphology silicate fibres and silica is characterised by one or more of the parameters, alone or in combination, as described in WO2019 / 106562.

[0176] The method comprises providing an aqueous suspension comprising the silica (A) and the fibres (B), the weight ratio A / B of the silica and the fibres being between 0.5:1 and 15:1, and the total amount A+B being equal to at least 5% by weight with respect to the weight of the suspension.

[0177] Preferably, the aqueous suspension comprises silica (A) and fibres (B), the weight ratio A / B of the silica and the fibres being between 0.7:1 and 10:1, 0.7:1 and 5:1, more preferably between 0.8:1 and 3:1, even more preferably between 0.9:1 and 2.5:1 or 0.9:1 and 1.1:1.

[0178] Preferably, the total amount A+B is at least 10% by weight with respect to the weight of the aqueous suspension to be dried.

[0179] Preferably, the total amount of silica (A) and fibres (B) is between 5% and 40% or between 10% and 30% by weight with respect to the weight of the aqueous suspension to be dried.

[0180] Preferably, the fibres (B) are commercial or modified meerschaum fibres (for example Pangel B5 by Tolsa) or modified meerschaum fibres as described for example in patent applications WO2016 / 174629, WO2016 / 174628 or WO2018 / 078500A1.

[0181] Optionally, the aqueous suspension to be dried can contain residues of previous reactions, in amounts generally not higher than 3% by weight with respect to the suspension.

[0182] Preferably, the aqueous suspension to be dried has a pH value between 5 and 9.

[0183] Preferably, the liquid phase of the suspension consists mainly of water (i.e. at least 80%, 90% or 95% by weight with respect to the weight of the liquid phase), more preferably the liquid phase consists only of water.

[0184] Optionally, the aqueous suspension can include ethanol, propanol, isopropanol or butanol, in amounts preferably less than 10% by weight with respect to the weight of the liquid phase.

[0185] The aqueous suspension to be dried can be prepared according to any possible operating mode, provided that the final composition complies with the above preferences and is suitable for atomization.

[0186] In one embodiment, the aqueous suspension to be dried can be prepared directly by adding both silica (A) and fibres (B) in powder form to the aqueous phase under stirring, according to known techniques.

[0187] In one embodiment, the aqueous suspension to be dried can be prepared by mixing two different aqueous suspensions, one including silica (A) and the other including fibres (B).

[0188] These suspensions in turn can be prepared according to known techniques, following different modes and concentrations.

[0189] For example, the suspensions can be prepared by suspending powders, for example of silica (A), fibres (B) or mixtures thereof, in an aqueous medium.

[0190] The powders can be commercial or prepared on the spot, for example by filtration and subsequent drying of the corresponding filter cake or mixtures thereof.

[0191] Typically, the preparation of the powders of silica (A) and fibres (B) includes the separation of the solids from the reaction medium by filtration, followed by washing if necessary.

[0192] The filtration can be performed using any suitable technique, for example using a filter press, a band filter or a rotary filter.

[0193] In a preferred embodiment, in order to minimize the degree of powder, it is preferred to use directly the wet filter cake of silica (A), of fibers (B) or of both.

[0194] In this case, the aqueous suspension comprising the silica (A) and the fibers (B) is prepared starting from a wet filter cake of silica (A) and fibers (B).

[0195] In this case, the residual water content contained in the filter cake can be sufficient to provide the correct viscosity to the aqueous suspension after suitable dispersion, i.e. already suitable for atomization. Alternatively, it is possible to proceed with the usual adjustments of the water quantity in order to make the final aqueous suspension suitable for atomization.

[0196] In one embodiment, the wet filter cake of silica (A) and fibers (B) is dispersed separately and the two aqueous suspensions are combined together to obtain an aqueous suspension suitable for atomization to be dried.

[0197] In one embodiment, the wet filter cake of silica (A) and fibers (B) is pre-mixed and dispersed together to obtain an aqueous suspension suitable for atomization to be dried.

[0198] The residual water content of the wet filter cake of silica (A) is typically between 70% and 95% by weight with respect to the total weight of the filter cake itself.

[0199] The residual water content of the wet filter cake of fibers (B) is typically between 70% and 95% by weight with respect to the total weight of the filter cake itself.

[0200] The residual water content of the filter cake can be evaluated, for example, by means of thermogravimetric analysis.

[0201] The use of wet fibers, for example extracted from the aqueous phase minerals or modified from previous operations, can also allow to avoid the drying step, which is undoubtedly advantageous in terms of time and costs.

[0202] The person skilled in the art, depending on the residual water content in the filter cake of silica (A), fibers (B) or mixtures thereof, can add a suitable quantity of water during or after the dispersion step in order to obtain a final aqueous suspension suitable for atomization drying.

[0203] The dispersion of the filter cake can be performed according to known techniques, for example by mixing in a ball mill or colloid mill or using a mechanical stirrer.

[0204] Optionally, the viscosity of the suspension to be dried can be further reduced by the addition of an aluminium compound, preferably during the dispersion, as described in document FR 2 536 380.

[0205] Alternatively, the suspension to be dried can be prepared by mixing the silica (A) and the fibres (B) without continuing the separation of the solids by, for example, filtration. For example, under the possible adjustment of the pH, a modified fibre can be produced from an aqueous suspension of silica (A) according to known techniques by acid precipitation of the silicate and / or by the preparation or derivatisation of an aqueous suspension of fibres (B) of silicate (for example by derivatisation with an organic reagent or by acid depletion or by deposition of amorphous silica).

[0206] Optionally, the person skilled in the art will be able to adjust the water volume of the final suspension by partial evaporation or filtration or by dilution, or to make other possible modifications to the medium in order to change, for example, its rheology or pH, etc., in order to adapt the resulting suspension to drying by atomisation.

[0207] In a preferred embodiment, the process comprises the preparation of an aqueous suspension by dispersion of a wet cake comprising precipitated amorphous silica (A) and sepiolite fibres or modified sepiolite fibres (B) of said silica (A) and said fibres (B) in a weight ratio A / B of between 0.9:1 and 1.1 :1 and with a total amount A+B of at least equal to 10% by weight relative to the weight of the suspension. The final aqueous suspension is then subjected to atomisation or spray drying in order to obtain microbeads.

[0208] The spray drying can be carried out using conventional spray equipment, for example using a spray dryer with a turbine, a spray dryer with a nozzle, a single-fluid or double-fluid dryer, or preferably a dryer with a pressure nozzle.

[0209] The hot air temperature from the spray dryer varies greatly, generally from 100° to 700°C, from 110° to 650°C or from 120° to 600°C.

[0210] The atomisation speed of the suspension to be dried depends on the type, size, evaporation capacity of the equipment, the temperature of the hot air, the solid content of the suspension to be dried and the spray pressure.

[0211] The spray pressure can vary greatly, generally from 10 bar to 80 bar, from 15 bar to 60 bar or from 20 bar to 40 bar.

[0212] Preferably, the atomisation nozzle of the atomiser has an orifice with a diameter of between 1 mm and 3 mm.

[0213] The person skilled in the art is able to vary the operating conditions of the dryer in the best way in order to obtain microbeads of a certain diameter and particle size distribution starting from the aqueous suspension suitable for atomization described herein.

[0214] Carbon black

[0215] The high-dispersibility carbon black reinforcing filler used in the present application has a surface area greater than 100 m2 / g measured by the NSA method and a surface area greater than 100 ml / 100 g measured by the OAN method. 2 / g, preferably greater than 110 m2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method.

[0216] According to a preferred embodiment, the high-dispersibility carbon black that can be used in the present application has a surface area greater than 105 m2 / g, preferably greater than 110 m2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g measured by the NSA method. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, preferably greater than 110 m2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method. 2 / g, more preferably greater than 115 m2 / g, even more preferably greater than 120 m2 / g. Preferably, the carbon black has a surface area less than 300 m2 / g, preferably less than 250 m2 / g, more preferably less than 200 m2 / g measured by the NSA method.

[0217] According to a preferred embodiment, the high-dispersibility carbon black that can be used in the present application has a surface area greater than 105 ml / 100 g, preferably greater than 110 ml / 100 g, more preferably greater than 115 ml / 100 g, even more preferably greater than 120 ml / 100 g measured by the OAN method. Preferably, the carbon black has a surface area less than 300 ml / 100 g, preferably less than 250 ml / 100 g, more preferably less than 200 ml / 100 g measured by the OAN method.

[0218] The surface area of the carbon black NSA (nitrogen surface area) is determined according to ISO 18852:2005.

[0219] The surface area of the carbon black OAN (oil absorption number) is determined according to ISO 4656:2012.

[0220] According to a preferred embodiment, the carbon black is present in the elastomeric composition in an amount greater than about 15 phr, more preferably greater than about 20 phr. It is preferred that the carbon black reinforcing filler is present in the elastomeric composition in an amount less than about 55 phr, more preferably less than about 50 phr.

[0221] Vulcanizing agent

[0222] The elastomeric composition can be vulcanized according to known techniques, in particular using sulfur-based vulcanization systems commonly used for diene elastomeric polymers. To this end, sulfur-based vulcanizing agents are incorporated in the elastomeric compound obtained from the elastomeric composition after one or more thermal mechanical processing steps, together with vulcanization accelerators. In the final processing step, the temperature is generally kept below 120°C and preferably below 100°C, in order to avoid the occurrence of undesirable pre-crosslinking phenomena.

[0223] Preferably, the vulcanizing agents comprise sulfur-based vulcanization systems comprising sulfur or sulfur-containing molecules (sulfur donors) and vulcanization accelerators and / or activators known in the art.

[0224] Particularly effective activators are zinc compounds, in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing from 8 to 18 carbon atoms, such as, for example, zinc stearate (which is preferably formed in situ in the elastomeric composition from ZnO and fatty acids).

[0225] Common accelerators can be selected from dithiocarbamic acids, guanidines, thioureas, thiazoles, sulfenamides, thiurams, amines, xanthates or mixtures thereof.

[0226] According to a preferred embodiment, the vulcanizable elastomeric composition comprises vulcanizing agents in an amount equal to or greater than about 1 phr, preferably equal to or greater than about 2 phr.

[0227] Preferably, the amount of vulcanizing agents is lower than or equal to about 7.5 phr, preferably lower than or equal to about 7.

[0228] Advantageously, the amount of sulfur is comprised between about 2 phr and about 6.5 phr.

[0229] Coupling agent

[0230] The vulcanizable elastomeric composition according to the present application can optionally further comprise at least one silane coupling agent capable of interacting with silicate fibers, and optionally conventional silica present as reinforcing filler, and incorporate them onto the diene elastomeric polymer during the vulcanization process.

[0231] Preferably, the vulcanizable elastomeric composition comprises at least one coupling agent.

[0232] Preferably, the silane coupling agents that can be used in the present application are selected from silane coupling agents having at least one hydrolysable silane group, which can be identified, for example, by the following general formula (I):

[0233] (R)3Si-C n H 2n -X (I)

[0234] wherein the R groups, which can be identical or different, are selected from alkyl, alkoxy or aryloxy groups or from halogen atoms, with the proviso that at least one of the R groups is alkoxy or aryloxy or halogen; n is an integer between 1 and 6, inclusive; X is selected from nitroso, mercapto, amino, epoxy, vinyl, imido, chloro, -(S) m C n H 2n groups in -Si-(R)3or -S-COR, wherein m and n are integers between 1 and 6, inclusive, and the groups R are as defined above.

[0235] Among silane coupling agents, particularly preferred silane coupling agents are bis(3-triethoxysilylpropyl) tetrasulfide and bis(3-triethoxysilylpropyl) disulfide. The coupling agents can be used as such or as a suitable mixture with an inert filler (e.g. carbon black) in order to facilitate their incorporation into the elastomeric composition.

[0236] Preferably, the silane coupling agent is present in the vulcanizable elastomeric composition in an amount comprised between 0.1 phr and about 20 phr, preferably between about 0.5 phr and about 10 phr.

[0237] Other additives

[0238] The elastomeric composition can comprise other commonly used additives, which are selected according to the specific application for which the composition is intended. For example, the material can be blended with antioxidants, antidegradants, plasticizers, tackifiers, antiozonants, modified resins or mixtures thereof.

[0239] In particular, in order to improve processability, the vulcanizable elastomeric composition can be blended with a plasticizer, typically selected from mineral oil, vegetable oil, synthetic oil or mixtures thereof, such as, for example, aromatic oil, naphthenic oil, phthalate, soybean oil or mixtures thereof. The amount of plasticizer is typically comprised between 0 phr and about 70 phr, preferably between about 5 phr and about 30 phr.

[0240] Preparation of elastomer composition

[0241] Preferably, the vulcanizable elastomeric composition for manufacturing structural components of a tire according to the present application comprises at least, for each 100 phr of diene elastomeric polymer:

[0242] (i) from 5 phr to 50 phr, preferably from 10 phr to 40 phr, of needle-shaped morphology silicate fibers having nanometric size,

[0243] (ii) 10 to 60 phr of a high-dispersibility carbon black reinforcing filler,

[0244] (iii) optionally, 5 to 60 phr of a conventional silica,

[0245] (iv) 0.1 to 12 phr of at least one vulcanizing agent, and

[0246] (v) 0.1 to 15 phr of a coupling agent.

[0247] The vulcanizable elastomer composition for tire components according to the present application is characterized by one or more of the following preferred aspects, taken individually or in mutual combination.

[0248] The elastomer composition can be prepared by mixing the desired amount of diene elastomer polymer with the needle-shaped morphology silicate fibers of nanometric size, the high-dispersibility carbon black, and the conventional silica, if present, the vulcanizing agent, and the coupling agent, if present, and any other additives that can be present according to techniques known in the art.

[0249] For example, the mixing can be performed using at least one batch mixer and / or at least one continuous mixer.

[0250] The needle-shaped morphology silicate fibers of nanometric size can be fed to the at least one batch mixer and / or at least one continuous mixer according to any method known to the person skilled in the art and suitable for this purpose.

[0251] Advantageously, the needle-shaped morphology silicate fibers of nanometric size are fed in the form of (al) a solid masterbatch elastomer composition comprising the needle-shaped morphology silicate fibers of nanometric size dispersed in at least one diene elastomer, prepared as described above and in WO2018 / 116125, and (a2) microbeads comprising the needle-shaped morphology silicate fibers of nanometric size and silica, prepared as described above and in WO2019 / 106562.

[0252] The solid masterbatch elastomer composition can be fed in the form of a bale or sheet material. The microbeads can be incorporated with equipment and according to conventional methods, without the need for special modifications to the equipment.

[0253] For example, the mixing can be performed using an open mixer of the "open mill" type or an internal mixer with tangential rotors or with intermeshing rotors (Intermix) or in a Ko-Kneader TM type or a continuous mixer of the twin-screw or multi-screw type.

[0254] In the context of the present description and of the appended claims, the term "batch mixer (or mixing device)" means a mixing device configured to periodically feed, in predetermined quantities, the various ingredients of a material to be prepared and to mix them for a predetermined time, in order to obtain a batch of said material.

[0255] At the end of the mixing step, the obtained batch of material is completely discharged from the mixing device in the form of a single solution.

[0256] In the context of the present description and of the appended claims, the term "continuous mixer (or mixing device)" means a mixing device configured to continuously feed, generally by means of controlled dosing distributors, the ingredients of a material to be prepared to mix the ingredients in order to produce the material and to discharge it in the form of a continuous flow, with the exception of cases of stoppage of the mixing device due to maintenance or change of material formulation.

[0257] In the terminology of the field of mixers of elastomeric compounds, the continuous mixing device is sometimes referred to as "mixing extruder", which is considered herein as equivalent to "continuous mixer".

[0258] The continuous mixer is then provided with mixing sections, in particular of its active elements, such as screws or satellites of the mixer, capable of applying high shear stresses to the material being mixed, and with conveying sections, alternating with the mixing sections, capable of applying a thrust to the material being processed in order to feed it from one longitudinal end of the internal chamber to the other. The continuous mixer is also provided with possible redistribution sections.

[0259] Other examples of continuous mixing devices are twin-screw or multi-screw mixers, such as ring mixers, co-penetrating and co-rotating or planetary mixing devices.

[0260] Both batch mixers and continuous mixers are capable of imparting sufficient energy to the material produced with said mixers to mix and homogeneously disperse the various components, even in the case of cold- fed ingredients, and, in the case of materials comprising elastomeric components, to chew the elastomeric compound, increasing its temperature in order to make it processable and plastic, to facilitate the incorporation and / or distribution of the ingredients within the elastomeric polymer matrix.

[0261] The elastomeric compound thus obtained can then be stored or directly sent to the subsequent production steps of the tyre according to the present application.

[0262] Tire

[0263] According to an embodiment, the tyre for vehicle wheels according to the present application comprises:

[0264] - a carcass structure comprising at least one carcass ply having opposite lateral edges associated with respective bead structures;

[0265] - optionally, a belt structure applied in radially outer position with respect to the carcass structure;

[0266] - a tread band applied in radially outer position with respect to the carcass structure and the belt structure, if present, and

[0267] - optionally, an underlayer and / or a wear strip and / or a sidewall and / or a sidewall insert and / or a mini sidewall and / or an underliner and / or a rubberized layer and / or a bead filler and / or a bead filler and / or a sheet.

[0268] According to one embodiment, the structural component for a tyre according to the present application is a wear strip and / or a sidewall and / or an internal component of the tyre.

[0269] Preferably, the internal component of the tyre is selected from the group consisting of a carcass structure rubber layer, a belt structure rubber layer, an underlayer, a sidewall insert, a mini sidewall, a bead filler, a bead filler, an underliner and a sheet.

[0270] The carcass structure is intended to impart the properties of structural integrity and strength required for the tyre, while the belt structure is also intended to transmit to the carcass structure the lateral and longitudinal stresses to which the tyre is subjected in operation as a result of contact with the road surface, in order to provide the required performance in terms of grip, driving stability, controllability, directionality, road grip and comfort. The belt structure can comprise an additional layer commonly referred to as "zero-degree belt". The zero-degree reinforcing layer, if present, is instead intended to limit the radial elongation of the belt structure.

[0271] The tyre according to the present application can be applied on vehicles having two, three or four wheels. The tyre according to the present application can be for summer or winter use or for all seasons.

[0272] The tyre according to the present application can be a tyre for passenger cars, including motor cars such as, for example, high-performance tyres, and tyres for light transport vehicles, for example vans, campers, pick-ups, whose total mass when loaded is generally equal to or less than 3500 Kg. Therefore, tyres for heavy transport vehicles are excluded.

[0273] The tyre according to the present application can be a tyre for motorcycles, such as, for example, motorcycles belonging to the following categories: scooter, road endurance, custom, supersport, superbike and sport touring. The term "tyre for motorcycle wheels" means a tyre having a high camber ratio, generally greater than 0.200, which is able to reach high angles of inclination (roll angle) during the cornering of a motorcycle.

[0274] A tyre according to the application can be manufactured according to a method comprising:

[0275] - building components of a green tyre on at least one forming drum;

[0276] - shaping, moulding and vulcanizing the tyre;

[0277] wherein at least one of the components of the green tyre is built:

[0278] - manufacturing at least one green component comprising the vulcanizable elastomeric composition as described above. BRIEF DESCRIPTION OF DRAWINGS

[0279] Figure 1 is a representation of a tyre for an automobile comprising one or more components according to the application. DETAILED DESCRIPTION

[0280] The following description of certain examples of the application is merely exemplary in nature and is in no way intended to limit the application.

[0281] Figure 1 A radial half-section of a tyre for a vehicle wheel is shown.

[0282] In the Figure 1 In the figures, "a" indicates the axial direction, "r" indicates the radial direction, in particular r-r indicates the profile of the equatorial plane. For simplicity, Figure 1 Only a portion of the tyre is shown, the remaining portion not shown being identical and arranged symmetrically with respect to the equatorial plane "r-r".

[0283] A tyre 100 for a four-wheeled vehicle comprises at least one carcass structure comprising at least one carcass layer 101 having opposite end flaps respectively engaged with corresponding annular anchoring structures 102, called bead cores, and possibly associated with a bead filler 104.

[0284] The carcass layer 101 is optionally made of an elastomeric composition.

[0285] The tyre region comprising the bead core 102 and the filler 104 forms a bead structure 103, which is intended for anchoring the tyre to the corresponding mounting rim (not shown).

[0286] The carcass structure is generally of the radial type, i.e. the reinforcing elements of at least one carcass layer 101 are located 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, for example of rayon, nylon, polyester (for example polyethylene naphthalate, PEN). Each bead structure is associated to the carcass structure by folding back, around an annular anchoring structure 102, the opposite lateral edges of at least one carcass layer 101, to form so-called carcass flaps 101a as shown in Figure 1

[0287] In one embodiment, the coupling between the carcass structure and the bead structure can be provided by a second carcass layer (not shown in the drawings) applied in axially outer position with respect to the first carcass layer. Figure 1

[0288] Optionally, a wear strip 105 made of an elastomeric composition according to the present application is arranged in axially outer position of each bead structure 103.

[0289] The carcass structure is associated to a belt structure 106 comprising one or more belt layers 106a, 106b, radially superposed with respect to each other and to the carcass layers, generally having textile and / or metal reinforcing cords incorporated into a layer of vulcanized elastomeric material.

[0290] Such reinforcing cords can have a direction of development of the cross with respect to the circumference of the tyre 100. The "circumferential" direction means the direction substantially facing the direction of rotation of the tyre.

[0291] At least one zero-degree reinforcing layer 106c, generally known as "0° belt", can be applied in radially outer position of the belt layers 106a, 106b, generally incorporating a plurality of elongated reinforcing elements, usually metal or textile cords, oriented substantially along the circumferential direction, so as to form an angle of a few degrees (for example an angle comprised between about 0° and 6°) with respect to the direction parallel to the equatorial plane of the tyre, and coated with a layer of vulcanized elastomeric material.

[0292] A tread band 109 of vulcanized elastomeric material is applied in radially outer position of the belt structure 106.

[0293] Furthermore, respective sidewalls 108 of vulcanized elastomeric material are applied in axially outer position on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of the tread band 109 at the respective bead structure 103.

[0294] In radially outer position, the tread band 109 has a rolling surface 109a intended to come into contact with the ground. Generally, circumferential grooves are formed on this surface 109a, which are crossed by transversal notches (not shown in the drawings) which are intended to facilitate the expulsion of water and / or mud from the rolling surface 109a. Figure 1 ​​are connected so as to define a plurality of blocks of various shapes and sizes distributed on the rolling surface 109a, for simplicity, in the Figure 1 The surface is shown as smooth in the

[0295] A lower layer 111 of vulcanized elastomeric material can be arranged between the belt structure 106 and the tread band 109.

[0296] A strip (generally referred to as "mini-sidewall") of elastomeric composition 110 of vulcanized elastomeric material can be optionally provided in the joint area between the sidewall 108 and the tread band 109, generally obtained by co-extrusion with the tread band 109 and which allows to improve the mechanical interaction between the tread band 109 and the sidewall 108. Preferably, the end portion of the sidewall 108 directly covers the lateral edge of the tread band 109.

[0297] In the case of a tubeless tire, it is also possible to provide, at a radially inner position with respect to the carcass layer 101, a layer of rubber 112, generally referred to as "liner", which provides the necessary impermeability to the pneumatic air of the tire.

[0298] The stiffness of the sidewall 108 of the tire can be increased by providing the bead structure 103 with a reinforcing layer 120, generally referred to as "bead filler" or additional strip-like insert.

[0299] The bead filler 120 is a reinforcing layer that is wound around the respective bead core 102 and bead filler 104 so as to at least partially enclose said bead core and bead filler, arranged between the at least one carcass layer 101 and the bead structure 103. Typically, the bead filler is in contact with said at least one carcass layer 101 and with said bead structure 103.

[0300] The bead filler 120 generally comprises a plurality of textile cords incorporated into a layer of vulcanized elastomeric material.

[0301] The bead structure 103 of the tire can comprise a further protective layer, generally referred to as the term "bead filler" 121 or protective strip, whose function is to increase the stiffness and integrity of the bead structure 103.

[0302] The bead filler 121 generally comprises a plurality of cords incorporated into a rubber layer of vulcanized elastomeric material. Such cords are generally made of textile material (e.g. aramid or rayon) or metallic material (e.g. steel cords).

[0303] A layer or sheet of elastomeric material (generally referred to as "breaker") 113 can be arranged between the belt structure 106 and the tread band 109. Figure 1The layer can have a uniform thickness. Alternatively, the layer can have a varying thickness in the axial direction. For example, the layer can have a greater thickness proximate to its axial outer edges relative to the central (crown) region.

[0304] Advantageously, the layer or sheet can extend over a surface substantially corresponding to the extended surface of said belt structure.

[0305] In a preferred embodiment, a layer or sheet of elastomeric material as described above can be placed between said belt structure and said tread band, said additional layer or sheet preferably extending over a surface substantially corresponding to the extended surface of said belt structure.

[0306] The vulcanizable elastomeric composition according to the application can advantageously be incorporated into one or more of the tire components selected from the group consisting of the wear strip and / or sidewall and / or internal component of a tire.

[0307] Preferably, the internal component of a tire is selected from the group consisting of a carcass structure rubber layer, a belt structure rubber layer, an underlayer, a sidewall insert, a mini sidewall, a bead filler, a chafer, a liner and a sheet.

[0308] According to an embodiment not shown, the tire can be a tire for a motorcycle wheel, typically a tire having a straight section with a high tread camber angle.

[0309] Example 1

[0310] Preparation of solid masterbatch elastomer composition (MB1) comprising nanometric size acicular morphology silicate fibres (Pangel B5) Example 2

[0311] In a reactor, 30 kg of organically modified sepiolite fibers (commercial Pangel B5) were suspended in 500 kg of deionized water and stirred at 800 rpm for 40 minutes to obtain a homogeneous suspension (A).

[0312] 50 kg of Von Bundit HA latex (60% w / v solids content, equivalent to 30 kg of solids, pH 9 to 11, density 0.95 g / cm 3 ) were diluted with 150 kg of water and stirred at 400 rpm for 10 minutes to obtain suspension (B).

[0313] Suspension (B) 160 kg was added to suspension (A) (reverse addition) in 10 minutes, maintaining the stirring at 350 rpm. The stirring speed was then increased to 200 rpm and the remaining 40 kg of suspension (B) were added in a further 5 minutes. The suspension (C) thus obtained was maintained under stirring at 200 rpm for a further 5 minutes, during which a further 40 kg of water were added.

[0314] The coagulum was filtered, washed with about 1000 kg of water and dried in an oven at 95 °C for 16 hours, thus obtaining 59 kg of composition MB1 (yield 98%), wherein the fiber content is equal to 101.3 phr determined by thermogravimetric analysis (TGA).

[0315] The weight loss curve was determined using a Mettler-Toledo TGA / DSC1 Star-e system apparatus in the temperature range from 150 °C to 800 °C. The temperature program adopted for the measurement involves a step with inert gas (from 25 °C to 150 °C and hold at 150 °C in nitrogen flow) and an oxidation step (from 150 °C to 800 °C in dry air flow).

[0316] In the following table 1 are shown the quantities of reagents used, the theoretical and experimental values related to MB1 :

[0317] Table 1

[0318]

[0319] Note: latex quantity: 50 kg; latex solid content: 30 kg;

[0320] 1 : commercial Pangel B5;

[0321] 2: quantity of water to suspend the fibers;

[0322] 3: total volume of the final suspension obtained by mixing the suspension of fibers with the latex;

[0323] 4: ratio between the total volume of suspension 3 and the weight of fibers;

[0324] 5: ratio between the weight of fibers and the weight of solids contained in the latex;

[0325] 6: theoretical fiber content in MB1 ;

[0326] 7: actual fiber content in MB1 determined by TGA

[0327] Preparation of microbeads from a mixture of an organic modified suspension of sepiolite fibres B2 and a suspension of precipitated silica A2

[0328] Example 3 Preparation of elastomer composition for tires

[0329] 1260 kg of organically modified sepiolite fibers (Pangel B5 by Tolsa) were added to about 13400 kg of deionized water under stirring to obtain a suspension B2 of sepiolite fibers modified at 8.6% by weight of solids.

[0330] Under stirring, 5762 kg of water suspension of precipitated silica A2 in a weight ratio of 20% (equal to 1152 kg of silica) was added to the suspension B2 in order to have a weight ratio A / B between silica and modified sepiolite fibers of about 1 :1. The silica used corresponds to the commercial grade Ebrosil H-155 AT.

[0331] The resulting suspension was dried by spray drying, providing microbeads M2 of silica and modified sepiolite fibers in a weight ratio of 1 :1.

[0332] The spray drying was carried out with a pressure nozzle. The dryer hot air temperature was between 400°C and 500°C, the spray pressure was about 20 bar, the atomizing spray nozzle of the atomizer had a hole with a diameter of 2 mm.

[0333] INV1

[0334] INV2

[0335] The comparative vulcanizable elastomer compound (C1) comprises a conventional carbon black having a surface area of less than 100 m 2 / g (NSA) or 100 ml / 100 g (OAN). The comparative vulcanizable elastomer compounds (C2-C3) comprise nanometric size acicular shaped silicate fibers in the form of a solid masterbatch elastomer composition (MB1) according to example 1, to replace a portion of the traditional carbon black. The vulcanizable elastomer compounds (INV1-INV4) of the present application comprise a reinforcing filler comprising a high dispersibility carbon black having a surface area of more than 100 m 2 / g (NSA) and 100 ml / 100 g (OAN), which completely replaces the conventional carbon black in the comparative compounds (C2-C3). The vulcanizable elastomer compound (INV4) of the present application comprises nanometric size acicular shaped silicate fibers in the form of microbeads M2 according to example 2 instead of the solid masterbatch elastomer composition (MB1) according to example 1.

[0336] The following table 2 shows the phr elastomer component of the vulcanizable elastomer compounds C1-C3 and INV1-INV4.

[0337] Table 2

[0338] C1 C2 C3 INV3 INV4 NR BR MB1 70 55 55 55 55 55 70 CB1 30 30 30 30 30 30 30 CB2 - 30 30 30 30 30 - M2 - - - - - - 20 CB3 52 37 - - - - - CB4 - - 37 - - - - CB5 - - - 37 - - 37 Silica - - - - 37 - - TESPT - - - - 37 - ZnO 10 10 - - - - - Stearic acid 5 5 5 5 5 5 5 Zinc stearate 3.5 3.5 3.5 3.5 3.5 3.5 3.5 6PPD 1 1 1 1 1 1 1 TBBS 80 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Sulfur 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Example 4 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Performance evaluation of elastomer composites 4 4 4 4 4 4 4

[0339] NR: coagulated natural rubber obtained by coagulating and stabilizing with ammonia (60% by weight - sold by Von Bundit Co. Ltd) the natural rubber latex HA obtained by centrifugation;

[0340] BR: polybutadiene (Europrene Europe);

[0341] MB1: Solid masterbatch elastomer composition of Example 1;

[0342] M2: Microbeads from Example 2;

[0343] CB1: Surface area is 91m² 2 Carbon black, N375, 114 ml / 100 g (NSA) and 114 ml / 100 g (OAN), Cabot Corporation;

[0344] CB2: Surface area is 115m² 2 Carbon black at 95 ml / 100 g (NSA) and 95 ml / 100 g (OAN), Raven 1300, BirlaCarbon;

[0345] CB3: Surface area is 158m² 2 Carbon black at 134 ml / 100 g (NSA) and 134 ml / 100 g (OAN), Propel X14, Cabot Corporation;

[0346] CB4: Surface area is 118m² 2 Carbon black, N234, 126 ml / 100 g (NSA) and 126 ml / 100 g (OAN), Cabot Corporation;

[0347] CB5: Surface area is 149m² 2 Carbon black at 126 ml / 100 g (NSA) and 126 ml / 100 g (OAN), BC2115, Birla Carbon.

[0348] Silica: Ultrasil VN3 GR (BET specific surface area 180m²) 2 / g), Evonik

[0349] TESPT: Bis[3-(triethoxysilyl)propyl]tetrasulfide, Evonik ZnO: Zinc oxide; Zincol Ossidi;

[0350] Stearic acid: stearate, Undesa;

[0351] Zinc stearate: Struktol A 50, Struktol Corporation

[0352] 6PPD: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, Solutia Eastman;

[0353] TBBS: N-tert-butyl-2-benzothiazole sulfonamide, Lanxess Deutschland GmbH

[0354] Sulfur: Sulfur, Redball Superfine, International Sulphur Corp.

[0355] All components of the elastomer composition, except sulfur and vulcanization accelerator (TBBS), were mixed in an internal mixer (Brabender) for about 6 minutes (first step).

[0356] When the temperature reached 135 °C, the material was mixed for one more minute and then discharged. The non-vulcanizable elastomer compound (green compound) was left to rest for one day, then sulfur and accelerator (TBBS) were added and mixed in the same mixer for 9 minutes at about 60 °C (second step), thus obtaining a vulcanizable elastomer compound. Finally, the vulcanizable elastomer compound was vulcanized at 170 °C for 10 minutes.

[0357] Shear

[0358] Figure 1

[0359] The following evaluations were performed on the elastomer compound made as described in Example 3.

[0360] The green compound was subjected to MDR (Moving Die Rheometer) measurements according to the ISO 6502 standard to verify the crosslinking kinetics of the green compound using an Alpha Technologies rheometer of the MDR2000 type. The test was performed at 170 °C with an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ± 0.5° for 20 minutes, thus measuring the time required to increase two rheometric units (TS2) and the time required to reach 30% (T30), 60% (T60) and 90% (T90) of the final torque value (Mf), respectively. The maximum torque value MH and the minimum torque value ML were measured.

[0361] The green compound was evaluated for dynamic Payne effect mechanical properties using an Alpha Technologies RPA oscillating chamber rheometer (Rubber Process Analyzer), where the geometry of the chamber is as described in ASTM D6601-19, applying the following method. Payne effect

[0362] Approximately cylindrical test samples with a volume in the range of 4.6 cm 3 to 5 cm 3 were obtained by punching a sheet of green compound of the feature to be explained with a thickness of at least 5 mm. Subsequently, the chamber of the R.P.A. 2000 was initially preheated to 170 °C.

[0363] ​The sample is loaded between the chambers of the rheometer and the chambers are closed. Between the sample of green compound and each chamber of the rheometer two films are interposed to protect the chambers themselves: in contact with the compound is a cast film of nylon 6.6 about 25 microns thick and in contact with the rheometer chamber is a polyester film about 23 microns thick. The sample is then vulcanized for a fixed time of 10 minutes at a temperature of 170°C, while recording the vulcanization curve, i.e. so that the sample is subjected to a sinusoidal deformation of 7% amplitude and 1.67 Hz frequency throughout the vulcanization period.

[0364] The temperature of the rheometer chamber is then brought to 70°C. After a total of 10 minutes from setting the temperature of the chamber at 70°C, at constant temperature of 70°C, by applying a sinusoidal torsional stress to the sample at a fixed frequency of 100 Hz and with an amplitude gradually increasing from 0.3% to 10%, 10 stabilization cycles and 10 measurement cycles are carried out for each condition.

[0365] The temperature of the rheometer chamber is always kept at 70°C, then a dynamic measurement is carried out by applying a sinusoidal torsional stress to the sample at a fixed frequency of 100 Hz and with an amplitude of 9%, 10 stabilization cycles and 20 measurement cycles are carried out.

[0366] In this way, the following parameters are measured as average values recorded in 20 measurement cycles:

[0367] - dynamic shear modulus G' at a strain amplitude of 9%,

[0368] - variation d_G' of the dynamic shear modulus between a sample deformation amplitude of 0.4% and a sample deformation amplitude of 10%;

[0369] - torsional tan delta, i.e. the ratio between the viscous elastic modulus G" and the dynamic elastic modulus G' at a deformation amplitude of 9% (hereinafter TanD(9%)).

[0370] the difference between the modulus (G') at 10% and at 0.5% is evaluated in absolute value Static mechanical properties while the percentage variation of the modulus at 10% and at 0.4% with respect to the modulus G' at 9% is evaluated in relative value Dynamic mechanical properties .

[0371] The vulcanized elastomeric compound is evaluated for Surface resistivity at 23°C on 5 dumbbell straight axis test specimens according to the ISO 37-2011 standard. In this way the following parameters are measured:

[0372] - load at 50% elongation (Ca0.5),

[0373] - load at 100% elongation (Cal),

[0374] - the breaking load (CR), and

[0375] - the elongation at break (AR).

[0376] In the following mode, the vulcanized elastomeric compounds were evaluated in tensile compression mode using an Instron model 1341 dynamic device ​ .

[0377] Test pieces of vulcanized elastomeric compounds (170°C for 10 minutes) in the form of cylinders (length = 25 mm; diameter = 18 mm) were compressed preloaded to a longitudinal deformation of 25% with respect to the initial length and kept at a predetermined temperature (23°C and 70°C) throughout the test.

[0378] After a waiting time of 2 minutes and a mechanical pre-treatment of 125 cycles of deformation amplitude of 5% with respect to the length under pre-load and frequency of 10 Hz, the sample was subjected to a dynamic sinusoidal strain with an amplitude of ± 3.5% with respect to the length under pre-load and a frequency of 10 Hz.

[0379] In this way the following parameters were measured:

[0380] - the dynamic elastic modulus E’,

[0381] - tan delta, i.e. the ratio between the viscous dynamic modulus E” and the dynamic elastic modulus E’.

[0382] The values of the ​ of the vulcanized elastomeric compounds were determined according to the experimental procedure described in the UNI 4288-72 standard.

[0383] The following table 3 shows the results obtained from the characterizations carried out.

[0384] Table 3

[0385]

[0386]

[0387] The data in table 3 demonstrate the following:

[0388] • the presence in the compound C1 (15 phr) of a portion of the conventional carbon black CB1 replaced by nanometric size fibres of silicate of acicular morphology (in the form of a solid masterbatch elastomeric composition MB1 consisting of 15 phr of natural rubber and 15 phr of nanometric size organic modified meerschaum fibres (commercial Pangel B5) causes a significant increase in the surface resistivity in the compound C2 and a significant worsening of the Payne effect (d_G'(0.4-10));

[0389] • the substitution of the conventional carbon black CB2 with a surface area less than 100 ml / 100g (OAN) in the compound C3 in place of the conventional carbon black CB1 with a surface area less than 100 ml / 100g (NSA) in the compound C2 did not bring substantial benefits; 2 • the substitution of the conventional carbon black CB1 with a surface area less than 100 ml / 100g (NSA) in the compound C2 with a high dispersibility carbon black CB3-CB5 with a surface area greater than 100 ml / 100g (NSA) and 100 ml / 100g (OAN) in the compound C2 did not bring substantial benefits;

[0390] • the substitution of the conventional carbon black CB1 with a surface area less than 100 ml / 100g (NSA) in the compound C2 with a high dispersibility carbon black CB3-CB5 with a surface area greater than 100 ml / 100g (NSA) and 100 ml / 100g (OAN) in the compound C2 did not bring substantial benefits; 2 • the substitution of the conventional carbon black CB1 with a surface area less than 100 ml / 100g (NSA) in the compound C2 with a high dispersibility carbon black CB3-CB5 with a surface area greater than 100 ml / 100g (NSA) and 100 ml / 100g (OAN) in the compound C2 did not bring substantial benefits;

[0391] • the use of silicate fibres with a needle-like morphology of nanometric size, different elongation and load at break, which represent an improvement in the static mechanical properties in general;

[0392] • the substitution of the solid masterbatch elastomeric composition MB1 of the compound of the application INV1 with the microbeads M2 of the compound of the application INV4 leads to a significant improvement in the static mechanical properties;

[0393] • the vulcanization kinetic properties are comparable for all the compounds of the application INV1-INV3, while the compound of the application INV4 is slightly slower but with a significant increase in the maximum torque value MH.

Claims

1. A tire for vehicle wheels, comprising at least one structural component comprising a vulcanized elastomer compound, obtained by vulcanization of a vulcanizable elastomer compound, said vulcanizable elastomer compound being obtained by mixing an elastomer composition comprising (i) at least one diene elastomer polymer and (ii) a reinforcing filler, said reinforcing filler comprising: (a) silicate fibres in acicular morphology having nanometric dimensions; and (b) a high dispersibility carbon black having a nitrogen surface area (NSA) determined according to ISO 18852:2005 of more than 100 m 2 / g and an oil absorption number (OAN) determined according to ISO 4656:2012 of more than 100 ml / 100 g.

2. Tyre for vehicle wheels according to claim 1, wherein, The elastomer composition comprises, for each 100 phr of diene elastomer polymer: (i) 5 phr to 50 phr of silicate fibres in acicular morphology having nanometric dimensions, (ii) from 10 phr to 60 phr of a high dispersibility carbon black having a nitrogen surface area (NSA) greater than 100 m 2 / g, an oil adsorption number (OAN) greater than 100 ml / 100 g, (iv) 0.1 phr to 12 phr of at least one vulcanizing agent, and (v) 0.1 phr to 15 phr of a coupling agent.

3. Tyre for vehicle wheels according to claim 1 or 2, wherein, The silicate fibres in acicular morphology having nanometric dimensions are selected from the group consisting of magnesium silicate fibres, aluminium silicate fibres, calcium silicate fibres and mixtures thereof.

4. Tyre for vehicle wheels according to claim 1 or 2, wherein, The silicate fibres in acicular morphology having nanometric dimensions are selected from the group consisting of sepiolite fibres, modified sepiolite fibres, palygorskite fibres, wollastonite fibres, imogolite fibres and mixtures thereof.

5. Tyre for vehicle wheels according to claim 1 or 2, wherein, The silicate fibres in acicular morphology having nanometric dimensions are added to the elastomer composition in the form of (al) a solid masterbatch elastomer composition comprising silicate fibres in acicular morphology having nanometric dimensions dispersed in at least one diene elastomer; and / or (a2) microbeads comprising silica and silicate fibres in acicular morphology having nanometric dimensions.

6. Tyre for vehicle wheels according to claim 5, wherein, The solid masterbatch elastomer composition comprises at least one diene elastomer selected from the group consisting of natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR) and mixtures thereof.

7. Tyre for vehicle wheels according to claim 5, wherein, The solid masterbatch elastomer composition comprises, for each 100 phr of the at least one diene elastomer, 50 phr to 200 phr of the silicate fibres in acicular morphology having nanometric dimensions.

8. Tyre for vehicle wheels according to claim 5, wherein, The microbeads have an average diameter in the range of 60 micrometers to 500 micrometers, measured according to ISO 13320 method.

9. Tyre for vehicle wheels according to claim 5, wherein, The microbeads comprise (A) silica and (B) silicate fibres in acicular morphology having nanometric dimensions, wherein the A / B weight ratio is between 0.7:1 and 10:

1.

10. A tyre for vehicle wheels according to claim 1, wherein, The reinforcing filler further comprises (c) a conventional silica.

11. Tyre for vehicle wheels according to claim 2, wherein, The elastomer composition comprises, for each 100 phr of diene elastomer polymer: (iii) 5 phr to 60 phr of a conventional silica.

12. Tyre for vehicle wheels according to claim 2, wherein, The elastomer composition comprises, for each 100 phr of diene elastomer polymer: (i) 10 phr to 40 phr of silicate fibres in acicular morphology having nanometric dimensions.

13. Tyre for vehicle wheels according to claim 8, wherein, The microbeads have an average diameter in the range of 70 micrometers to 300 micrometers, measured according to ISO 13320 method.

14. Tyre for vehicle wheels according to claim 9, wherein, The A / B weight ratio is between 0.7:1 and 5:

1.

15. Tyre for vehicle wheels according to claim 14, wherein, The A / B weight ratio is between 0.8:1 and 3:

1.

16. Tyre for vehicle wheels according to claim 15, wherein, The A / B weight ratio is between 0.9:1 and 2.5:

1.

17. An elastomer composition comprising, for each 100 phr of diene elastomer polymer: (i) 5 phr to 50 phr of silicate fibres in acicular morphology having nanometric dimensions, (ii) from 10 phr to 60 phr of a high dispersibility carbon black having a nitrogen surface area (NSA) determined according to ISO 18852:2005 of more than 100 m 2 / g and an oil absorption number (OAN) determined according to ISO 4656:2012 of more than 100 ml / 100 g, (iv) 0.1 phr to 12 phr of at least one vulcanizing agent, and (v) 0.1 phr to 15 phr of a coupling agent.

18. The elastomeric composition of claim 17, wherein, The elastomer composition comprises, for each 100 phr of diene elastomer polymer: (i) from 10 phr to 40 phr of a silicate fibres of needle-like morphology having nanometric dimensions.

19. The elastomeric composition of claim 17, wherein, The elastomer composition further comprises, for each 100 phr of diene elastomer polymer: (iii) from 5 phr to 60 phr of a conventional silica.

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