Self-supporting tire for a vehicle wheel

Abstract

The invention relates to a self-supporting tire for vehicle wheels having a sidewall reinforcing insert (113) with reduced stiffness. These tires have good mileage, improved comfort and significantly reduced rolling resistance under run-flat conditions compared to known self-supporting tires having a sidewall reinforcing insert with a higher modulus.

Description

Technical Field

[0001] The present invention relates to a self-supporting tire for a vehicle wheel. In recent years, tire manufacturers have sought to eliminate the need for bulky spare tires in vehicles while ensuring that the vehicle can continue its journey in the event of severe or complete loss of pressure in one or more tires.

[0002] The spare wheel is now usually replaced by a reduced-section wheel or a repair / inflation kit, which however usually requires stopping the vehicle and performing the operation under critical conditions.

[0003] A self-supporting tire is one that is capable of supporting the vehicle load under a substantial or complete loss of pressure, allowing the driver to travel the distance to a garage without having to stop for roadside assistance or to change / re-inflate the tire in potentially dangerous situations.

[0004] When the inflation pressure is significantly lower than the operating pressure, or even zero (this is called "run-flat" mode), the tire must be able to travel a certain distance at a certain speed, for example 80 km at 80 km / h.

[0005] This performance, known as "EM" (Extended Mobility) performance, is required by law or by vehicle manufacturers to enable manufacturers to demonstrate that a tire is suitable for runflat operation.

[0006] When the inflation pressure is close to the operating pressure (in this case referred to as "normal driving" mode), the highest possible performance of the tire is desired, such as, inter alia, maneuverability, low weight, low rolling resistance and adequate comfort.

[0007] Therefore, the structure of the self-supporting tire must have sufficient strength to prevent the sidewall structure and inner surface from collapsing when the tire is used in a deflated condition. On the other hand, when the tire is in a normally inflated working condition, it must have good comfort and low rolling resistance.

[0008] Several techniques have been used to achieve this support effect without compromising normal driving conditions.

[0009] Thus, for example, in order to impart self-supporting characteristics to the tyre, i.e. the above-mentioned ability to travel short / medium distances at a reduced or essentially zero inflation pressure (e.g. after a puncture), it is known to integrate one or more sidewall reinforcing inserts of elastomeric material into the sidewall structure of the tyre, in an axially outer position relative to the layer of airtight elastomeric material and in an axially inner position relative to each sidewall, said one or more sidewall reinforcing inserts of elastomeric material typically having a lens-shaped and / or essentially semicircular profile.

[0010] These sidewall reinforcement inserts of elastomeric material have the purpose of adequately supporting the vehicle load when the normal inflation pressure of the tire is reduced, for example after a puncture.

[0011] Thus, the self-supporting tire for a vehicle wheel, thus configured, comprises:

[0012] - a carcass structure comprising at least one carcass ply having opposite lateral edges associated with respective annular anchoring structures;

[0013] - a belt structure applied in a radially external position to the carcass structure;

[0014] - a tread band applied in a radially outer position to the belt structure;

[0015] - a pair of sidewall structures each comprising a sidewall extending in an axially outer position of the carcass structure and extending radially between one of the annular anchoring structures and an axially outer portion of the tread band;

[0016] - a layer of airtight elastomeric material, called liner, applied in a radially inner position of the carcass structure; and

[0017] - At least one pair of sidewall structure reinforcing inserts incorporated in the sidewall structure of the tyre, at a position axially external to the layer of air-impermeable elastomeric material and at an axially internal position of each sidewall. Background Art

[0018] In the field of self-supporting tires, various embodiments have been proposed that aim to impart the characteristics necessary for self-supporting capabilities without unduly compromising ride comfort and consumption at normal inflation pressure. These solutions are inherently diverse in terms of the physico-chemical characteristics of the elastomeric material used to make the sidewall reinforcing inserts, the number of sidewall inserts envisaged, and their positioning relative to the carcass ply or plies.

[0019] According to a method proposed in the prior art, the self-supporting capability is ensured by reinforcing the sidewall structure with at least one specific rubber insert located axially outside the layer of airtight elastomeric material and axially inside each sidewall.

[0020] Typically, sidewall reinforcement inserts work by supporting the flat tire.

[0021] According to the prior art, inserts should be made of a material with a high modulus to ensure lift, low hysteresis to minimize rolling resistance, and good elongation at break, primarily to allow for easy mounting and removal of the tire from the rim. To determine the optimal compromise, compound development typically starts with a high modulus that does not meet the high rolling resistance requirements and results in poor comfort. The thickness of the insert is then gradually reduced to lower rolling resistance until the minimum value is determined that guarantees the required run-flat distance. However, this result is unsatisfactory, given the still-high rolling resistance values.

[0022] In fact, the prior art teaches conferring high modulus to reinforcing inserts in different ways, for example by using elastomeric compounds loaded with high amounts of reinforcing material and / or comprising elastomers with high modulus and / or by increasing the crosslinking density using high amounts of vulcanizing agents or additional crosslinking systems.

[0023] For example, document WO2009080144A1 describes a self-supporting tire with a sidewall reinforcement insert comprising a crosslinked elastomeric material obtained by crosslinking an elastomeric composition loaded with 20-35 phr of a specific diatomaceous earth and 10-35 phr of at least one other reinforcement. The exemplary compound comprises at least 50 phr of filler, i.e. at least 30.4% by weight, and is characterized by a relatively high modulus value E', which is greater than 6 MPa.

[0024] Document US2020056014A discloses an elastomeric composition for a sidewall reinforcing insert for a self-supporting tire, comprising a low molecular weight polymer and a vulcanization accelerator. As for the reinforcing filler, in the experimental section, it only shows a composition containing 60 phr of carbon black, equivalent to 31% by weight.

[0025] JP2010215831A describes an elastomeric composition for sidewall reinforcement inserts in self-supporting tires, comprising two silicas of different surface areas (generally indicated in a total amount of 10 to 150 phr) and preferably also carbon black (paragraph 28). The total amount of filler, including silica and carbon black, is 40 to 170 phr (paragraph 30). Table 1 in the experimental section shows a composition (Comparative Example 2) containing 35 phr of carbon black (a composition with poor driving performance, especially poor run-flat performance), while all other compositions contain 50 phr of total filler. This document does not disclose the modulus values ​​of the compositions described therein.

[0026] JP2014019725A describes an elastomeric composition similar to previous elastomeric compositions for sidewall reinforcement inserts in self-supporting tires, which also includes a specific functionalized polymer. One of the purported advantages of using syndiotactic polybutadiene is increased stiffness, thereby improving run-flat performance (paragraph 296). The compositions exemplified in the table (pp. 63-67) include a total of at least 54 phr of filler, including 50 phr of carbon black and 4 to 155 phr of silica. The document does not disclose dynamic modulus values ​​for the compositions described therein.

[0027] Document EP2700513A1 addresses the problem of heat accumulation in the beads of self-supporting tires, potentially causing serious damage when driving on a flat tire, and improves their service life by creating indentations or protrusions closer to the tire bead. Regarding the sidewall reinforcement layer, the document states that the material's complex elastic modulus (E*) must be quite high, more precisely ranging from 6 MPa to 12 MPa (Claim 5). The specification does not disclose any specific elastomeric composition.

[0028] Document WO2019086785A1 describes a self-supporting tire comprising a sidewall reinforcing insert, wherein the insert is formed from a material having a high modulus, in particular a complex shear dynamic modulus G* generally at least equal to 1.0 MPa (claim 1), preferably at least equal to 1.9 MPa (claim 3), and in an example equal to 3.15 MPa, with a Tan Delta of 0.09, a typical value for very stiff and relatively consumable materials. This specification does not disclose any elastomeric composition in detail.

[0029] Document US5526862 describes a self-supporting tire for motorcycles, the carcass of which incorporates, on each sidewall, an elastic support insert comprising a substantially rigid contrast core made of an elastomeric material having a high dynamic compression modulus E' greater than 6 MPa, preferably ranging from 8 MPa to 16 MPa. This document does not disclose any specific elastomeric composition.

[0030] Document EP1242256A1 describes a self-supporting tire in which each sidewall is reinforced with at least one wedge-shaped insert comprising alternating regions of flexible and more rigid material. The more rigid material limits lateral expansion of the insert, providing good ride comfort during normal inflation and good sidewall reinforcement during run-flat conditions. This document does not disclose any detailed elastomer compositions, nor does it report modulus or hysteresis values ​​for the composites comprising the sidewall-reinforcing inserts.

[0031] Document WO2019243713A1 describes an elastomeric composition for a sidewall reinforcement insert in a self-supporting tire, comprising at least 50 phr of a butadiene elastomer (preferably functionalized), generally 5 to 30 phr of carbon black, and 2 to 30 phr of an inorganic filler. The composition exemplified in Table 1 contains 30 to 60 phr of total filler (carbon black, silica, gypsum, and / or kaolin) and a significant amount of polybutadiene (65 phr), which predicts a high complex dynamic shear modulus G*.

[0032] Documents WO02096677A1 and WO02096672A2 describe a self-supporting tire in which each side includes a support system consisting of two adjacent inserts made of elastomeric material. The first insert, closer to the outer sidewall, consists of an elastomer vulcanized with a sulfur system, while the second insert is made more rigid by crosslinking the elastomer with a peroxide catalyst and a metal salt of a carboxylic acid, such as zinc (meth)acrylate. The compositions shown in Table 1 all have a high content of polybutadiene, which contributes to stiffness, especially when carbon black is present in low amounts (Ex. 4 and 5: 20 phr) or absent (Ex. 6), and they have a higher content of the crosslinking system (zinc acrylate ranging from 45 to 100 phr). Due to the crosslinking, these composites have a very high stiffness, as evidenced by hardness values ​​ShA greater than 90 for the second insert, a tensile modulus greater than 10 MPa for an elongation of 10% (Table 2) and high values ​​of the shear modulus G' in the range of 10 MPa to 50 MPa, as shown in the examples and claims (claim 9).

[0033] In summary, in the prior art, it seems uniform that in this type of tire, the sidewall reinforcing insert must be of considerable stiffness in order to guarantee sufficient self-supporting capacity. However, this need contrasts with the need to minimize rolling resistance and ensure sufficient ride comfort. Summary of the Invention

[0034] In view of the prior art, the Applicant has conducted research to improve the performance of self-supporting tires, in particular to further reduce rolling resistance and therefore fuel consumption, thereby improving comfort while maintaining performance in run-flat conditions.

[0035] In this respect, the Applicant has realized that during driving in normal inflation conditions, which represents almost the entire time of use, the presence of sidewall reinforcement inserts with a high elastic modulus exerts strong stresses and leads to an increase in rolling resistance and an undesirable reduction in ride comfort.

[0036] The Applicant has discovered that it is possible to reconcile the need to give the tyre an even greater reduction in rolling resistance while allowing the self-supporting characteristics required by the minimum mileage required by the car manufacturers and better performance and comfort during normal driving.

[0037] Surprisingly, and contrary to what the prior art teaches, this result has been achieved by reducing the stiffness of the sidewall reinforcement inserts (primarily by reducing their reinforcing filler content, preferably also by replacing at least a portion of the conventional silica with a special white filler, and possibly by selecting an elastomeric component with less stiffness) and, possibly, by increasing the thickness of the inserts to compensate for the reduction in self-supporting capacity. In this way, an overall result of unexpectedly improved rolling resistance and run-flat distance has been achieved, compared to prior art self-supporting tires featuring stiffer, high-modulus inserts. In fact, according to the present invention, the reduction in the modulus of the insert material has resulted in maintaining the run-flat distance (which is otherwise associated with a significant and unexpected increase in rolling resistance) or minimizing its quite acceptable reduction.

[0038] Therefore, the object of the present invention is a self-supporting tyre for vehicle wheels comprising - a carcass structure having opposite side edges associated with respective annular anchoring structures;

[0039] - a belt structure applied in a radially external position to the carcass structure;

[0040] - a tread band applied in a radially outer position to the belt structure;

[0041] - a pair of sidewall structures each comprising a sidewall extending in an axially outer position of the carcass structure and extending radially between one of the annular anchoring structures and an axially outer portion of the tread band; and

[0042] - at least one pair of sidewall reinforcing inserts, each of said inserts being embedded in the corresponding sidewall structure, at an axially inner position of each sidewall,

[0043] Characterized in that at least one of the sidewall reinforcement inserts comprises, preferably consists of, an elastomeric compound having a shear modulus value G' less than 1.25 MPa measured at 70°C, 10 Hz, 9% strain according to the method disclosed in this description.

[0044] Preferably, both said sidewall reinforcement inserts comprise, preferably consist of, said elastomeric compound.

[0045] Preferably, the elastomeric compound of the insert is prepared by mixing and vulcanizing an elastomeric composition comprising at least:

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

[0047] - at least one reinforcing filler composition in a total amount of less than 30% by weight of the total weight, and

[0048] - at least 0.1 phr of at least one vulcanizing agent.

[0049] definition

[0050] In this specification and the claims that follow, the following definitions apply.

[0051] The term “elastomeric composition” means a composition comprising at least one diene elastomeric polymer and one or more additives which, upon mixing and possible heating, provides an elastomeric compound suitable for use in tires and components thereof.

[0052] The components of the elastomeric composition are not usually introduced into the mixer simultaneously but are typically added sequentially. In particular, vulcanization additives, such as vulcanizing agents and possible accelerators and retarders, are usually added in a downstream step relative to the incorporation and processing of all other components.

[0053] In the final vulcanizable or even vulcanized elastomeric compound, the individual components of the elastomeric composition may change or no longer be individually traceable, as they interact with other components as a result of thermal and / or mechanical treatments and thus become fully or partially modified.

[0054] The term "elastomeric compound" denotes a compound obtainable by mixing and possibly heating at least one elastomeric polymer with at least one of the additives usually used in the preparation of tyre compounds.

[0055] The term "vulcanizable elastomeric compound" denotes an elastomeric compound that is ready for vulcanization, obtainable by incorporating all additives, including those that are vulcanizable.

[0056] The term "vulcanized elastomeric compound" refers to a material obtainable by vulcanization of a vulcanizable elastomeric compound.

[0057] The term "green" refers to a material, compound, composition, component or tire that has not yet been cured.

[0058] The term "vulcanization" refers to the cross-linking reaction in natural or synthetic rubber caused by sulfur-based and / or peroxide-based vulcanizing agents.

[0059] The term "vulcanizing agent" refers to a product that is capable of converting natural or synthetic rubber into an elastic and resistant material by forming a three-dimensional network of intermolecular and intramolecular bonds. Typically, vulcanizing agents are sulfur-based compounds such as elemental sulfur, polymeric sulfur, sulfur-containing agents (sulphurized agents) (such as bis[(trialkoxysilyl)propyl]polysulfide, thiuram, dimorpholine dithioate, and caprolactam-disulfide. Alternatively, vulcanizing agents are peroxides that contain O-O bonds and that generate reactive free radicals when heated.

[0060] The term "vulcanization accelerator" refers to compounds capable of reducing the duration and / or operating temperature of the vulcanization process, such as TBBS, sulfenamides, thiazoles, dithiophosphoric acids, dithiocarbamic acids, guanidines and sulfur donors such as thiuram.

[0061] The term "vulcanization activator" denotes a product that further accelerates vulcanization, so that vulcanization occurs in a shorter time and possibly at a lower temperature. An example of an activator is a stearic acid-zinc oxide system. In the case of peroxide vulcanizing agents, examples of activators are polymethacrylic acids, such as ethylene glycol dimethacrylate.

[0062] The term "vulcanization retarder" refers to a product capable of delaying the onset of the vulcanization reaction and / or inhibiting undesirable side reactions, such as N-(cyclohexylthio)phthalimide (CTP).

[0063] The term "vulcanization package" refers to a vulcanizing agent and one or more vulcanization additives selected from the group consisting of vulcanization activators, accelerators and retarders.

[0064] The term "elastomeric polymer" or "elastomer" or "rubber" refers to a natural or synthetic polymer that, after vulcanization, can be repeatedly stretched to at least twice its original length at room temperature and positively recovers essentially immediately to approximately its original length after the tensile load is removed (as defined in ASTM D1566-11 Standard Terminology Relating to Rubber).

[0065] The term "diene elastomeric polymer" means an elastomeric polymer derived from the polymerization of one or more monomers, at least one of which is a conjugated diene.

[0066] The term "reinforcing filler" refers to reinforcing materials typically used in this field to improve the mechanical properties of tire rubber, preferably chosen from carbon black, conventional silica, silica from sand, for example precipitated with strong acids, preferably amorphous silica, diatomaceous earth, calcium carbonate, titanium dioxide, talc, aluminum oxide, aluminosilicates, kaolin, silicate fibers, derivatives thereof, and mixtures thereof.

[0067] The term "white filler" refers to conventional reinforcing materials used in this field, selected from conventional silicas and silicates, such as sepiolite, palygorskite also known as attapulgite, montmorillonite, alloisite and the like, which may be modified by acid treatment and / or derivatization. Typically, white fillers have surface hydroxyl groups that may be partially derivatized.

[0068] The term "mixing step (1) or first step" denotes the step of the process for the preparation of an elastomeric compound in which one or more additives other than the vulcanizing agent and the vulcanizing package fed in step (2) are incorporated by mixing and possibly heating. The mixing step (1) is also known as a "non-productive step". In the preparation of a compound, there may be several "non-productive" mixing steps, which may be designated 1a, 1b, etc.

[0069] The term "mixing step (2) or second step" denotes the next step of the process for the preparation of the elastomeric compound, in which the vulcanizing agent and possibly other additives in a vulcanizing package are introduced into the elastomeric compound obtained from step (1) and mixed into the material at a controlled temperature, generally at a compound temperature below 120° C., so as to provide a vulcanizable elastomeric compound. Mixing step (2) is also known as a "productive step". In the preparation of the compound, there may be several "productive" mixing steps, which may be designated 2a, 2b, etc.

[0070] The term "dynamic shear modulus" or "sliding modulus" G' refers to the ratio between the shear stress applied to a sample of a vulcanized elastomeric compound and the resulting deformation. Details of the experimental measurement method are reported in this description.

[0071] The term "dynamic elastic compression or extension modulus E'" refers to the ratio between the uniaxial compressive or tensile stress applied to a sample of a vulcanized elastomeric compound and the resulting deformation. Details of the experimental measurement method are reported in this description.

[0072] The terms "axial extension" or "thickness" of a sidewall reinforcement insert (Li, insert width) refer to the extension of such element measured perpendicular to a plane (Ti) tangential to the outer surface of the reinforcement insert.

[0073] The term “equatorial plane” of the tire means the plane perpendicular to the tire's axis of rotation and dividing the tire into two symmetrically identical parts.

[0074] The terms “radial” and “axial” and the expressions “radially inward / outward” and “axially inward / outward” are used with reference to directions perpendicular to and parallel to the tire's axis of rotation, respectively.

[0075] The terms "circumferential" and "circumferentially" are used with reference to the direction of the annular extension of the tyre, ie its rolling direction, which corresponds to a direction lying in a plane coinciding with or substantially parallel to the equatorial plane of the tyre.

[0076] The term "cord" or "reinforcement cord" refers to an element consisting of one or more thread-like elements (hereinafter also referred to as "threads") incorporated in a matrix of elastomeric material. Depending on the circumstances and the specific application, the thread-like elements may be made of textile and / or metallic material.

[0077] “Reinforcing elements oriented in a substantially circumferential direction” means that they form an angle of a few degrees (for example an angle between about 0° and 6°) with the equatorial plane of the tire.

[0078] The term "phr" (acronym for "parts per hundred parts of rubber") means parts by weight per 100 parts by weight of the total elastomeric base. Any additives (such as any elastomeric resins or extender oils) are not taken into account when calculating 100 parts of the total elastomeric base.

[0079] Unless otherwise indicated, all percentages are expressed as weight percent. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 A self-supporting tyre for a vehicle wheel according to the invention is schematically shown in a half-section. DETAILED DESCRIPTION

[0081] The present invention may have one or more of the following preferred features, which may be combined arbitrarily according to application requirements.

[0082] The elastomeric composition of the invention comprises at least 100 phr of at least one diene elastomeric polymer.

[0083] The diene elastomeric polymer may be chosen from the diene elastomeric polymers commonly used in sulfur-vulcanizable elastomeric compositions, particularly suitable for the production of tires, i.e. from solid elastomeric polymers or copolymers possessing unsaturated chains and having a glass transition temperature (Tg) generally lower than 20° C., preferably ranging from 40° C. to −110° C.

[0084] These polymers or copolymers may be of natural origin or may be obtained by solution polymerization, emulsion polymerization or gas phase polymerization of one or more conjugated dienes, optionally mixed with an amount not exceeding 60% by weight of at least one comonomer chosen from monoolefins, monovinylarenes and / or polar comonomers.

[0085] The conjugated diene generally contains 4 to 12, preferably 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 and mixtures thereof.

[0086] The monoolefins may be selected from ethylene and α-olefins generally containing from 3 to 12 carbon atoms, such as, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof.

[0087] The monovinyl aromatic hydrocarbons which may optionally be used as comonomers generally contain 8 to 20, preferably 8 to 12, carbon atoms and may be selected, for example, from styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, various alkyl, cycloalkyl, aryl, alkaryl or aralkyl derivatives of styrene, such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4-(4-phenylbutyl)styrene, and mixtures thereof. Styrene is particularly preferred.

[0088] Polar comonomers that may optionally be used may be chosen, for example, from: esters of acrylic acid and alkylacrylic acid, acrylonitrile or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

[0089] The diene elastomeric polymer may be chosen, for example, from cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (especially polybutadiene with a high 1,4-cis content), optionally halogenated isoprene / isobutylene copolymers, 1,3-butadiene / acrylonitrile copolymers, styrene / 1,3-butadiene copolymers, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers, and mixtures thereof.

[0090] The elastomeric composition may comprise at least one polymer of one or more monoolefins and an olefinic comonomer or a derivative thereof. The monoolefin may be selected, for example, from ethylene and α-olefins typically containing from 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof. Of these copolymers, ethylene / propylene (ERR) or ethylene / propylene / diene (EPDM) copolymers are preferred.

[0091] The above polymers may optionally be functionalized along the backbone or at their termini.

[0092] Functional groups can be introduced into the elastomeric polymer by methods known in the art, such as, for example, during the production of the elastomeric polymer by copolymerization with at least one corresponding functionalized monomer containing at least one ethylenic unsaturation; or by grafting at least one functionalized monomer in the presence of a free radical initiator (e.g., an organic peroxide) to subsequently modify the elastomeric polymer.

[0093] Alternatively, the functionalization can be carried out by reaction with a suitable terminator or coupling agent. In particular, the diene elastomeric polymer obtained by anionic polymerization in the presence of an organometallic initiator, in particular an organolithium initiator, can be functionalized by reacting the residual organometallic groups derived from the initiator with a suitable terminator or coupling agent, such as, for example, amines, amides, imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes, aryloxysilanes, alkylthiols, alkyldimercaptosilanes, carboxyalkylthiols, carboxyalkylmercaptosilanes and thioglycols.

[0094] Useful examples of terminators or coupling agents are known in the art and are described in, for example, patents EP2408626, EP2271682, EP3049447A1, EP2283046A1, EP2895515A1, EP451604, US4742124, WO2015086039A1 and WO2017211876A1.

[0095] Preferably, the at least one functionalized elastomeric polymer is obtained from polybutadiene (especially polybutadiene with a high 1,4-cis content), styrene / 1,3-butadiene copolymers, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers and mixtures thereof.

[0096] The elastomeric composition may comprise two or more elastomeric polymers as defined above in a mixture.

[0097] Preferably, the elastomeric composition comprises polybutadiene in an amount of less than 50 phr, more preferably less than 30 phr, even more preferably less than 20 phr. Preferably, the elastomeric composition does not comprise polybutadiene. Preferably, the elastomeric composition comprises:

[0098] - 70 to 100 phr of synthetic or natural polyisoprene or mixtures thereof,

[0099] - 0 to 30 phr polybutadiene.

[0100] More preferably, the elastomeric composition comprises:

[0101] - 80 to 100 phr of synthetic or natural polyisoprene or mixtures thereof,

[0102] - 0 to 20 phr of polybutadiene.

[0103] The term "polyisoprene" refers to isoprene polymers and copolymers.

[0104] The term "polybutadiene" refers to butadiene polymers and copolymers.

[0105] The elastomeric composition of the insert comprises at least one reinforcing filler in a total amount preferably less than 27% by weight, more preferably less than 25% or 20% by weight of the total weight of the composition.

[0106] Preferably, the reinforcing fillers are present in a total amount ranging from 5% to 30% by weight, more preferably from 5% to 26% or from 10% to 20% by weight relative to the total weight of the composition.

[0107] Preferably, the reinforcing filler is selected from carbon black, white fillers, silicate fibers, derivatives thereof, and mixtures thereof.

[0108] In one embodiment, the reinforcing filler comprises carbon black.

[0109] Preferably, the carbon black is selected from carbon black having a surface area of ​​not less than 20 m 2 / g, preferably about 40m 2 / g-50m 2 / g (determined by STSA-Statistical Thickness Surface Area according to ISO 18852:2005).

[0110] The carbon black may be, for example, N234, N326, N330, N375 or N550, N660, preferably N550 or N660, commercially available from Birla Group (India) or Cabot Corporation.

[0111] In one embodiment, the reinforcing filler is a white filler selected from the group consisting of metal hydroxides, oxides and hydrated oxides, salts and hydrated salts, silicate fibers, derivatives thereof, and mixtures thereof.

[0112] In one embodiment, the reinforcing filler may include silica, for example, selected from fumed silica, precipitated amorphous silica, wet-process silica (hydrated silicic acid), anhydrous silica (anhydrous silicic acid), or mixtures thereof.

[0113] The silicon dioxide that can be used in the present invention may have a 10m 2 / g to 300m 2 / g, preferably 30m 2 / g to 250m 2 / g, more preferably 40m 2 / g to 190m2 BET surface area of ​​1,2-dimethyl-1,2-dioxane (measured according to ISO standard 5794 / 1).

[0114] Commercial examples of suitable silicas are Zeosil 1165MP, Zeosil 1115MP, Zeosil 185GR, Efficium from Solvay, Newsil HD90 and Newsil HD200 from Wuxi, K160 and K195 from Wilmar, H160AT and H180AT from IQE, Zeopol 8755 and 8745 from Huber, Perkasil TF100 from Grace, Hi-Sil EZ 120G, EZ 160G, EZ 200G from PPG, Ultrasil 7000GR and Ultrasil 9100GR from Evonik. Another example of a suitable silica is the rice hull silica described in WO2019229692A1.

[0115] In one embodiment, the reinforcing filler comprises silica mixed with carbon black.

[0116] In one embodiment, the reinforcing filler comprises modified silica.

[0117] Silica can be modified, for example, by reaction with silsesquioxanes (as in WO2018078480A1), by reaction with pyrrole (as in WO2016050887A1) or by reaction with a silanizing agent such as bis(triethoxysilylpropyl)tetrasulfide (TESPT), 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltriethoxysilane, triethoxy(octyl)silane, triethoxy(ethyl)silane, triethoxy-3-( 2-Imidazolin-1-yl)propylsilane, triethoxy-p-tolylsilane, triethoxy(1-phenylvinyl)silane, triethoxy-2-thienylsilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(triethoxysilyl)propyl isocyanate, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, isobutyltriethoxysilane, n-octadecyltriethoxysilane, (3-chloropropyl)triethoxysilane, triethoxysilane, and 3-(triethoxysilyl)propionitrile.

[0118] Commercial examples of suitable silanizing agents are Si69, Dynasilan AMEO and Dynasilan GLYEO from Evonik.

[0119] The modified silica may be sulfided silanized silica.

[0120] Sulfurized silylated silica is silica prepared by reacting silica (e.g., fumed silica, precipitated amorphous silica, wet-process silica (hydrated silicic acid), anhydrous silica (anhydrous silicic acid), or mixtures thereof) or a metal silicate (e.g., aluminum silicate, sodium silicate, potassium silicate, lithium silicate, or mixtures thereof) with at least one sulfurized silanizing agent.

[0121] The term "sulfiding silanizing agent" denotes an organic derivative of silicon containing mercapto, sulfide, disulfide or polysulfide groups, which is capable of reacting with the OH groups of silicon dioxide.

[0122] A commercial example of a suitable sulfurized silanized silica is Agilon 400 silica available from PPG.

[0123] In one embodiment, the reinforcing filler comprises modified silica mixed with carbon black.

[0124] In one embodiment, the reinforcing filler comprises a silicate.

[0125] In one embodiment, the silicate is a layered silicate, such as bentonite, halloysite, hectorite, saponite, vermiculite, or hydrotalcite.

[0126] In one embodiment, the silicate is a modified layered silicate, similar to the description below for modified silicate fibers.

[0127] In one embodiment, the silicate is silicate fibers. These fibers are typically nanometer-sized and exhibit a needle-like morphology.

[0128] The silicate fibers are preferably selected from the group consisting of sepiolite fibers, palygorskite fibers (also known as attapulgite), wollastonite fibers, imogolite fibers, and mixtures thereof.

[0129] In one embodiment, the reinforcing filler comprises silicate fibers mixed with carbon black.

[0130] In one embodiment, the silicate fibers are modified silicate fibers.

[0131] In one embodiment, the modified silicate fibers may be fibers modified, for example by acid treatment, and partial removal of magnesium, such as those described and exemplified in patent application WO 2016 / 174629 A1.

[0132] In one embodiment, the modified silicate fibers may be fibers modified, for example, by depositing amorphous silica on the surface, such as those described and exemplified in patent application WO 2016 / 174628 A1.

[0133] In one embodiment, the modified silicate fiber may be a fiber that has been organically modified, for example, by reaction with a quaternary ammonium salt, such as sepiolite fiber modified by reaction with tallowoylbenzyldimethylammonium chloride sold by Tolsa under the name Pangel B5.

[0134] In one embodiment, the modified silicate fiber can be a fiber modified by reaction with a silanizing agent, wherein the silanizing agent is selected from, for example, mono- or difunctional silanes having one or two or three hydrolyzable groups, such as bis-(3-triethoxysilyl-propyl) disulfide (TESPD), bis(3-triethoxysilyl-propyl) tetrasulfide (TESPT), 3-sulfo-octanoyl-1-propyl-triethoxysilane (NXT), Me2Si(OEt)2, Me2PhSiCl, Ph2SiCl2.

[0135] In one embodiment, the reinforcing filler comprises modified silicate fibers mixed with carbon black.

[0136] In a preferred embodiment, the reinforcing filler comprises sepiolite fibers.

[0137] In a preferred embodiment, the reinforcing filler comprises a white filler prepared as described in WO2019106562A1.

[0138] Particularly preferred are the reinforcing filler M2 prepared according to Example 1 of patent application WO2019106562A1 in the name of the present applicant, the reinforcing filler M4A prepared according to Example 2, and the reinforcing filler M6 prepared according to Example 3. These white fillers will be referred to hereinafter as: SilSep1 (reinforcing filler M2 prepared according to Example 1 of patent application WO2019 / 106562A1), SilSep2 (reinforcing filler M6 prepared according to Example 3 of patent application WO2019 / 106562A1), and SilSep3 (reinforcing filler M4A prepared according to Example 2 of patent application WO2019 / 106562A1).

[0139] In a preferred embodiment, the reinforcing filler comprises carbon black, silica and sepiolite fibers.

[0140] In a more preferred embodiment, the reinforcing filler comprises carbon black in a range of 0 phr to 10 phr, silica in a range of 5 phr to 20 phr, and sepiolite fiber in a range of 5 phr to 20 phr.

[0141] In an even more preferred embodiment, the reinforcing filler comprises carbon black in a range of 0 to 6 phr and a total amount of SilSep1 and / or SilSep2 and / or SilSep3 in a range of 10 to 20 phr.

[0142] The Applicant has observed that the balance between rolling resistance and run-flat is particularly favourable if part or all of the conventional silica in the elastomeric composition is replaced by SilSep1 and / or SilSep2 (see summary table 8 and the associated comments).

[0143] The elastomeric composition for a tire compound according to the present invention may comprise from 0.1 to 10 phr of a vulcanizing agent.

[0144] Preferably, the composition comprises at least 0.2 phr, 0.5 phr, 0.8 phr or 1 phr of at least one vulcanizing agent.

[0145] Preferably, the composition comprises 0.1 phr to 10 phr, 0.2 phr to 10 phr, 1 phr to 10 phr or 1.5 phr to 5 phr of at least one vulcanizing agent.

[0146] At least one vulcanizing agent is preferably selected from sulfur, or alternatively sulfur-containing agents (sulfur donors), such as, for example, bis[(trialkoxysilyl)propyl]polysulfides, thiurams, dimorpholine dithioates and caprolactam-disulfides and mixtures thereof. Alternatively, the vulcanizing agent is a peroxide containing an O-O bond and can generate reactive free radicals by heating.

[0147] Preferably, the vulcanizing agent is sulphur, preferably selected from soluble sulphur (crystalline sulphur), insoluble sulphur (polymeric sulphur), (iii) oil-dispersible sulphur and mixtures thereof.

[0148] Commercial examples of vulcanizing agents suitable for use in the elastomeric compositions of the present invention are Redball Superfine sulfur, Crystex TM OT 33AS Sulfur and Eastmann Crystex TM HS OT20 Sulfur.

[0149] In the elastomer composition of the present invention, the vulcanizing agent may be used together with auxiliary agents known to those skilled in the art, such as vulcanization activators, accelerators and / or retarders.

[0150] The elastomeric composition may optionally include at least one vulcanization activator.

[0151] Suitable vulcanization activators for use in the elastomeric composition of the invention are zinc compounds, in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms (preferably formed in situ in the elastomeric composition by reaction of ZnO with fatty acids), or mixtures thereof. For example, zinc stearate (preferably formed in situ in the elastomeric composition by reaction of ZnO with fatty acids) or magnesium stearate formed from MgO, or mixtures thereof, are used.

[0152] The vulcanization activator may be present in the elastomeric composition of the present invention in an amount preferably ranging from 0.2 phr to 15 phr, more preferably from 1 phr to 5 phr.

[0153] The preferred activator is derived from the reaction of zinc oxide and stearic acid.

[0154] An example of an activator is the product Aktiplast ST sold commercially by RheinChemie.

[0155] The elastomeric composition may further comprise at least one vulcanization accelerator.

[0156] Commonly used vulcanization accelerators may be selected, for example, from dithiocarbamic acids, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates, or mixtures thereof.

[0157] Preferably, the accelerator is selected from the group consisting of mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS) and mixtures thereof.

[0158] A commercial example of an accelerator suitable for use in the elastomeric composition of the present invention is N-cyclohexyl-2-benzothiazole-sulfenamide commercially available from Lanxess. (CBS or CZ) and N-tert-butyl 2-benzothiazole-sulfenamide NZ / EGC.

[0159] Vulcanization accelerators may be used in the elastomeric composition of the present invention in amounts ranging preferably from 0.05 phr to 10 phr, preferably from 0.1 phr to 7 phr, more preferably from 0.5 phr to 5 phr.

[0160] The elastomeric composition may optionally include at least one vulcanization retarder.

[0161] Vulcanization retarders suitable for use in the elastomeric composition of the present invention are preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.

[0162] A commercial example of a suitable retarder is N-cyclohexylthiophthalimide VULKALENT G from Lanxess.

[0163] The vulcanization retarders may preferably be present in the elastomeric composition of the present invention in an amount ranging from 0.05 to 2 phr.

[0164] The elastomeric composition of the present invention may comprise one or more vulcanization retarders as defined above in the form of a mixture.

[0165] Depending on the elastomeric composition, a person skilled in the art can adjust the composition of the vulcanization package and the crosslinking conditions in order to impart to the vulcanized elastomeric compound a degree of crosslinking commensurate with not exceeding the shear modulus value G′ set according to the invention.

[0166] The elastomeric composition may further comprise at least 0.05 phr, preferably at least 0.1 phr or 0.5 phr or 0.7 phr, more preferably at least 1 phr or 2 phr of at least one silane coupling agent capable of interacting with silica-based reinforcing fillers so as to bind them to the elastomeric polymer during vulcanization.

[0167] Preferably, the silane coupling agent is present in an amount of at least 7% by weight, more preferably at least 9% by weight, relative to the weight of the white filler.

[0168] Preferably, the elastomeric composition comprises from 0.1 phr to 20.0 phr or from 0.5 phr to 10.0 phr, even more preferably from 1.0 phr to 5.0 phr of at least one silane coupling agent.

[0169] Preferably, the coupling agent is a silane coupling agent selected from silane coupling agents having at least one hydrolyzable silane group, which can be identified, for example, by the following general formula (III):

[0170] (R')3Si-C n H 2n -X(III)

[0171] wherein the R' groups are identical or different from each other and are selected from alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the R' groups is an alkoxy or aryloxy group; n is an integer from 1 to 6; X is selected from nitroso, mercapto, amino, epoxy, vinyl, imide, chlorine, -(S) m C n H 2n -Si-(R')3 and -S-COR', wherein m and n are integers from 1 to 6, and the group R' is as defined above.

[0172] Particularly preferred silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide, 3-thio-octanoyl-1-propyl-triethoxysilane (NXT) and bis(3-triethoxysilylpropyl)disulfide. The coupling agents can be added as such or in a mixture with an inert filler (e.g., carbon black) to facilitate their incorporation into the elastomer composition.

[0173] An example of a silane coupling agent is TESPT: bis(3-triethoxysilylpropyl)tetrasulfide Si69 commercially available from Evonik.

[0174] The elastomeric composition may further comprise one or more additional ingredients commonly used in the art, such as, for example, plasticizing oils, resins, antioxidants and / or antiozonants (anti-aging agents), waxes, adhesives, and the like.

[0175] For example, in order to further improve the processability of the compound, the elastomeric composition according to the present invention may further comprise at least one plasticizing oil.

[0176] The amount of plasticizer used is preferably in the range of 0.5 to 10 phr, preferably in the range of 1 to 7 phr.

[0177] The term "plasticizing oil" refers to a process oil derived from petroleum or mineral oil or vegetable oil or synthetic oil or a combination thereof.

[0178] The plasticizing oil may be a petroleum-derived process oil selected from the group consisting of paraffins (saturated hydrocarbons), cycloparaffins, aromatic polycyclics, and mixtures thereof.

[0179] Examples of suitable process oils derived from petroleum are aromatic oils, paraffinic oils, cycloparaffinic oils, such as those known in the industry as MES (mild extraction solvate), DAE (distillate aromatic extract), TDAE (treated distillate aromatic extract), TRAE (treated residual aromatic extract), RAE (residual aromatic extract).

[0180] The plasticizing oil may be an oil of natural or synthetic origin derived by esterifying glycerol with fatty acids and includes triglycerides, diglycerides, monoglycerides of glycerol, or mixtures thereof.

[0181] Examples of suitable vegetable oils are sunflower oil, soybean oil, linseed oil, rapeseed oil, castor oil and cottonseed oil.

[0182] The plasticizing oil may be a synthetic oil selected from the group consisting of alkyl or aryl esters of phthalic acid or phosphoric acid.

[0183] The elastomeric composition according to the present invention may further comprise at least one resin.

[0184] The resin is a non-reactive resin, preferably selected from hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.

[0185] The amount of resin used is preferably in the range of 0.5 to 10 phr, more preferably in the range of 1 to 5 phr.

[0186] The elastomeric composition may optionally include at least one wax.

[0187] The wax may be, for example, a petroleum wax or a paraffin mixture.

[0188] Commercial examples of suitable waxes are Repsol N-paraffin mixtures and Microcrystalline wax.

[0189] Waxes may generally be present in the elastomeric composition of the present invention in a total amount ranging from 0.1 phr to 5 phr, preferably from 0.5 phr to 3 phr.

[0190] The elastomeric composition may optionally include at least one antioxidant.

[0191] The antioxidant is preferably selected from N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethyl-butyl)-n'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine (77PD), N,N'-bis-(1-ethyl-3-methyl-pentyl)-p-phenylenediamine (DOPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine (DPPD), PD), N,N'-dimethylphenyl-p-phenylenediamine (DTPD), N,N'-di-β-naphthyl-p-phenylenediamine (DNPD), N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine (44PD), N-phenyl-N-cyclohexyl-p-phenylenediamine, N-phenyl-N'-1-methylheptyl-p-phenylenediamine and the like, and mixtures thereof, preferably it is N-1,3-dimethylbutyl-N-phenyl-p-phenylenediamine (6-PPD).

[0192] Commercial examples of suitable antioxidants are 6PPD available from Solutia / Eastman or Santoflex manufactured by Flexsys.

[0193] The antioxidant may be present in the elastomeric composition in a total amount preferably of from 0.1 phr to 6 phr, more preferably of from 0.5 phr to 4 phr.

[0194] The cured elastomeric compounds of the present invention may be characterized by the following dynamic and static mechanical properties.

[0195] The vulcanized elastomeric compound has a shear modulus value G' measured at 70°C, 10 Hz, 9% deformation according to the RPA method reported in this specification, which is preferably less than 1.20 MPa, more preferably less than 1.10 MPa, even more preferably less than 1.05 MPa, even more preferably less than 0.95 MPa.

[0196] The vulcanized elastomeric compound has a shear modulus value G′ preferably between 0.50 MPa and 1.25 MPa, more preferably between 0.70 MPa and 1.10 MPa.

[0197] The vulcanized elastomeric compound has a shear modulus value G' preferably higher than 0.50 MPa, more preferably higher than 0.70 MPa.

[0198] The vulcanized elastomeric compound has a dynamic compression modulus value E′ measured at 23° C. and 10 Hz according to the method reported in this description, preferably less than 7.50 MPa, more preferably less than 6.00 MPa, even more preferably less than 5.00 MPa.

[0199] The vulcanized elastomeric compound has a dynamic compression modulus value E' preferably in the range of 3.00 MPa to 8.00 MPa, more preferably in the range of 3.50 MPa to 7.50 MPa, even more preferably in the range of 4.00 MPa to 6.00 MPa.

[0200] The vulcanized elastomeric compound has a Tan Delta value measured at 70° C., 10 Hz according to the RPA method reported in this specification, which is preferably not higher than 0.080, more preferably not higher than 0.072, even more preferably not higher than 0.060.

[0201] The vulcanized elastomeric compound has a Tan Delta value measured at 70° C., 10 Hz according to the RPA method reported in this specification, said Tan Delta value preferably ranging from 0.030 to 0.080, more preferably from 0.035 to 0.072, even more preferably from 0.040 to 0.070.

[0202] The vulcanized elastomeric compound has an elongation at break value AR (%) measured according to the UNI 6065:2001 method, preferably higher than 150%, more preferably higher than 200%, even more preferably higher than 230%.

[0203] The vulcanized elastomeric compound has a tensile strength value CR (%) measured according to the UNI 6065:2001 method of preferably at least 5.0 MPa, preferably at least 7.0 MPa, more preferably at least 8.0 MPa.

[0204] The vulcanized elastomeric compound has a tensile strength value CR (%) measured according to the UNI 6065:2001 method, preferably ranging from 6.0 MPa to 25.0 MPa, preferably from 7.0 MPa to 20.0 MPa.

[0205] In the self-supporting tire of the present invention, the above-described elastomeric composition is used to form the sidewall reinforcing insert.

[0206] Sidewall reinforcement insert refers to a coating disposed inside the sidewall portion of a self-supporting tire.

[0207] The sidewall reinforcement insert may be made partially, substantially (eg more than 70% by weight) or preferably completely from the cured elastomeric compound of the present invention.

[0208] In one embodiment, the sidewall reinforcement insert is composed entirely of the elastomeric composite of the present invention.

[0209] In one embodiment, the self-supporting tire of the present invention comprises a single pair of sidewall reinforcement inserts, one of said sidewall reinforcement inserts being arranged on each sidewall.

[0210] In one embodiment, the self-supporting tire of the present invention comprises two pairs of sidewall reinforcement inserts, each pair being arranged in a sidewall.

[0211] In one embodiment, the sidewall reinforcement insert can have a layered structure (sandwich structure) consisting of a layer of the elastomeric composite of the present invention, an internal reinforcement layer (e.g. a textile chafer) and another layer of the elastomeric composite of the present invention, in symmetrical variants in which the composite layers have the same thickness, as well as in asymmetrical variants.

[0212] In one embodiment, the sidewall reinforcement insert may have a layered structure consisting of a layer of the elastomeric compound of the invention, an internal reinforcement layer (e.g. another carcass ply) and another layer of the elastomeric compound of the invention, wherein the other carcass ply is folded around the axially outermost reinforcement insert.

[0213] Sidewall reinforcement inserts can have different shapes and thicknesses.

[0214] Typically, the sidewall reinforcement insert may have a half-moon shape with thickness tapering towards both ends.

[0215] The sidewall reinforcing insert of the tyre according to the invention may have a maximum axial extension Li measured perpendicular to a plane Ti tangential to the external surface of the sidewall reinforcing insert, for example from a minimum of 3 mm to a maximum of 14 mm, preferably from 5 mm to 12 mm, more preferably from 7 mm to 10 mm.

[0216] As known to those skilled in the art, generally the thickness of the sidewall reinforcing insert varies according to the type of tire and in particular it depends on the section height of the tire, the number of carcass plies, the hardness of the carcass, ie the standard or extra load for which the tire is designed.

[0217] For example, in the case of a conventional self-supporting tire with a nominal section height of 80 mm, the thickness of the sidewall reinforcing insert is generally within the range of 3 to 5 mm, in the case of a nominal section height of 100 mm, the thickness is from 5 to 7 mm, and in the case of a nominal section height of 130 mm, the thickness is from 7 to 10 mm. In the tire of the present invention, in particular when the elastomeric composition comprises a particularly small amount of reinforcing fillers and / or a high-modulus elastomeric polymer, the maximum axial extension of the sidewall reinforcing insert can be increased, for example, by 1.5 or 2 mm, for a total thickness of a maximum of 14 mm, preferably not exceeding 11 mm, more preferably not exceeding 10 mm.

[0218] In this way, even in the case of compounds with particularly low modulus, the self-supporting properties required of the tire can be achieved with a much lower rolling resistance.

[0219] Preferably, in the self-supporting tyre of the invention, the reinforcing inserts of the two sidewall structures have the same thickness.

[0220] Preferably, in the self-supporting tyre of the invention, the reinforcing inserts of the two sidewall structures have the same thickness and the same shape.

[0221] For each sidewall of the tire, a sidewall reinforcement insert extends radially from the bead portion to the shoulder portion.

[0222] In one embodiment, for each sidewall of the tire, a sidewall reinforcement insert extends radially from the tread end to the bead portion.

[0223] In one embodiment of the tyre of the present invention, the sidewall reinforcement insert is arranged at an axially inner position of the carcass structure.

[0224] In one embodiment of the tyre of the present invention, the sidewall reinforcement insert is arranged at an axially outer position of the carcass structure.

[0225] Examples of reinforcement inserts are Figure 1 Element (113) shown in cross section.

[0226] Preferred embodiments of the self-supporting tire of the present invention include:

[0227] - a carcass structure having opposite side edges associated with respective annular anchoring structures;

[0228] - a belt structure applied in a radially external position to the carcass structure;

[0229] - a tread band applied in a radially outer position to the belt structure;

[0230] - a pair of sidewall structures each comprising a sidewall extending in an axially outer position of the carcass structure and extending radially between one of the annular anchoring structures and an axially outer portion of the tread band;

[0231] a layer of airtight elastomeric material, called liner, situated in the radially innermost position of the tyre and extending at least as far as the tread band; and

[0232] - at least one pair of sidewall reinforcing inserts, each of which is incorporated in the corresponding sidewall structure, at a position axially inside each sidewall and axially outside the layer of airtight elastomeric material, characterized in that said sidewall reinforcing inserts have a shear modulus value G' lower than 1.25 MPa measured at 70°C, 10 Hz and 9% deformation according to the method reported in this specification.

[0233] In a preferred embodiment, the liner extends from one bead structure to the other. Where applicable, all preferences described above for the tire of the invention also generally characterize, in particular, the tire of the invention comprising the liner. Another component of the self-supporting tire of the invention that may advantageously include the elastomeric compound of the invention is the underlying liner.

[0234] Lower lining (see Figure 1 The element 112a) shown in FIG. 1 is a layer of elastomeric material which is preferably arranged in a radially outer position of the liner for the entire extension of the liner, ie between the liner and the carcass structure.

[0235] In one embodiment of the tire of the invention, the underlayer and the liner extend only over the tread portion.

[0236] In one embodiment of the tire of the invention, the underlayer and the liner extend from one bead structure to the other.

[0237] Typically, the underliner consists of an elastomeric compound with a high reinforcing filler content and a high viscosity in order to protect the liner from any movement of the carcass cords during tire conformation during the tire building process.

[0238] The Applicant has found that in the self-supporting tire of the present invention, the underliner, if present, may advantageously comprise or more preferably consist of the elastomeric compound of the present invention, which has low filler and reduced viscosity, with further unexpected advantages in rolling resistance and mileage under run-flat conditions.

[0239] Therefore, in a preferred embodiment, the self-supporting tire of the present invention comprises:

[0240] - a carcass structure having opposite side edges associated with respective annular anchoring structures;

[0241] - a belt structure applied in a radially external position to the carcass structure;

[0242] - a tread band applied in a radially outer position to the belt structure;

[0243] - a pair of sidewall structures each comprising a sidewall extending in an axially outer position of the carcass structure and extending radially between one of the annular anchoring structures and an axially outer portion of the tread band;

[0244] - a layer of air-impermeable elastomeric material, called liner and situated in the radially innermost position of the tyre and extending at least at the tread band;

[0245] - at least one pair of sidewall reinforcement inserts, each of said sidewall reinforcement inserts being embedded in the corresponding sidewall structure, at an axially inner position of each sidewall, and

[0246] a layer of elastomeric material, called lower liner and situated radially on the outside of said liner, radially on the inside of said carcass structure, axially on the inside of said sidewall reinforcing insert and preferably not extending beyond the extension of the liner,

[0247] Characterized in that the sidewall reinforcement insert and the underlying liner preferably comprise an elastomeric compound having a shear modulus value G' less than 1.25 MPa measured at 70°C, 10 Hz, 9% strain according to the method disclosed herein.

[0248] Preferably, the elastomeric composite of the lower lining is also prepared by mixing and vulcanizing an elastomeric composition comprising at least:

[0249] - 100 phr of at least one diene elastomeric polymer,

[0250] - less than 30% by weight of the total weight of at least one reinforcing filler composition, and

[0251] - at least 0.1 phr of at least one vulcanizing agent.

[0252] Where applicable, all the preferences described above for the tire of the invention also generally characterize, in particular, the tire of the invention comprising said liner and subliner.

[0253] In the self-supporting tire according to the invention, on the radially innermost surface of the liner, further tire components may optionally be applied, such as, for example, a sound insulation system, sealants or sensors.

[0254] The self-supporting tire of the present invention is suitable for four-wheel vehicles for road use, as a tire suitable for medium- and high-powered passenger vehicles (maximum chord size 195-245 mm).

[0255] The applicant believes that the invention is also applicable to tires for small cars or high performance tires (HP High Performance - UHP Ultra High Performance) with a maximum chord size of, for example, from 145 mm to 355 mm.

[0256] These tires are preferably mounted on rims having a mounting diameter equal to or greater than 13 inches, preferably no greater than 24 inches, and more preferably between 16 inches and 23 inches.

[0257] In general, the tires according to the present invention may be tires for passenger vehicles, including automotive tires (such as high performance tires as defined below) and tires for light transport vehicles (e.g. vans, campers, pickup trucks, typically having a total mass when fully loaded equal to or less than 3500 kg). Therefore, tires for heavy transport vehicles are excluded.

[0258] The tire of the present invention can also be used for vehicles other than the above-mentioned automobiles, such as high-performance road and sports motorcycles, i.e. motorcycles capable of reaching speeds even higher than 270 km / h. Such motorcycles belong to the categories generally identified by the following classifications: supersport, hypersport, sport touring, as well as motorcycles in the lower speed classes: scooters, street enduros and custom.

[0259] The term "tyre for motorcycle wheels" refers to a tyre having a high curvature ratio (generally greater than 0.200) capable of achieving large inclination angles (roll angles) of the plane of symmetry of the motorcycle with respect to the vertical during cornering.

[0260] Self-supporting tires may be HP (High Performance) or UHP (Ultra High Performance) tires, intended for use in vehicles primarily used for the transport of people, such as sedans, minivans, family cars, SUVs (Sports Utility Vehicles) and / or CUVs (Crossover Utility Vehicles), typically tires that allow high-speed travel.

[0261] High-performance and ultra-high-performance tires are, in particular, tires that allow speeds of at least 160 km / h, above 200 km / h, and up to over 300 km / h to be reached. Examples of such tires are tires belonging to the "T", "U", "H", "V", "Z", "W", and "Y" categories according to the ETRTO (European Tyre and Rim Technical Organisation) standard, in particular tires for four-wheeled, high-powered vehicles. Typically, tires belonging to these categories have a cross-sectional width equal to or greater than 185 mm, preferably not greater than 325 mm, and more preferably between 195 mm and 325 mm. These tires are preferably mounted on rims having a mounting diameter equal to or greater than 15 inches, preferably not greater than 24 inches, and more preferably between 17 inches and 22 inches. SUVs and CUVs are vehicles with a raised profile, usually four-wheel drive, and typically with a displacement greater than or equal to 1800 cc, more preferably between 2000 cc and 6200 cc. Preferably, these vehicles have a mass greater than 1,400 kg, more preferably between 1500 kg and 3000 kg.

[0262] The tire of the present invention can be used as a summer or winter or "all-season" (a tire that can be used in all seasons) tire.

[0263] Description of the tire according to the invention

[0264] Reference is not to scale Figure 1 Further characteristics and advantages of the self-supporting tyre according to the invention will become apparent from the following description of a preferred embodiment thereof, given below by way of non-limiting example.

[0265] Figure 1 is a radial half-section view of a portion of a preferred embodiment of a self-supporting tire according to the invention.

[0266] exist Figure 1 , reference numeral (100) denotes a self-supporting tire for a vehicle wheel according to a preferred embodiment of the present invention.

[0267] exist Figure 1 In the embodiment shown, the tire (100) is of the type used for motor vehicles.

[0268] exist Figure 1 In , "a" represents the axial direction, "X" represents the radial direction, and in particular XX represents the profile of the equatorial plane. For simplicity, Figure 1 Only a portion of the tire is shown, the remaining portions not shown being identical and arranged symmetrically with respect to the equatorial plane "XX".

[0269] A tyre (100) for a four-wheeled vehicle comprises at least one carcass structure including at least one carcass layer (101) having respective opposite end flaps engaged with respective annular anchoring structures (102) called bead cores, which may be coupled to a bead filler (104).

[0270] The tyre region comprising the bead core (102) and the filler (104) forms a bead structure (103) intended for anchoring the tyre to a corresponding mounting rim, not shown.

[0271] 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 including the axis of rotation of the tire and substantially perpendicular to the equatorial plane of the tire. Said reinforcing elements are generally composed of textile cords. Each bead structure is formed by folding back the opposite lateral edges of at least one carcass layer (101) around an annular anchoring structure (102) so as to Figure 1 The so-called carcass flaps (101a) shown are connected to the carcass structure.

[0272] In one embodiment, the coupling between the carcass structure and the bead structure may be provided by a second carcass layer ( Figure 1 Not shown) provided.

[0273] A wear strip (105), possibly made of an elastomeric material, is arranged at an outboard position of each bead structure (103).

[0274] The carcass structure is associated with a belt structure (106) comprising one or more belt layers (106a), (106b) radially superimposed relative to each other and relative to the carcass layer, the belt layers typically having textile and / or metal reinforcing cords incorporated into a layer of elastomeric material.

[0275] Such reinforcing cords may have a cross orientation relative to the circumferential development direction of the tire (100).A "circumferential" direction is a direction generally facing the direction of rotation of the tire.

[0276] At least one zero-degree reinforcement layer (106c), often referred to as a "0° belt", can be applied in the radially outermost position of the belt layers (106a), (106b), which typically incorporates a plurality of elongated reinforcing elements, which are typically metal or textile cords and are oriented in a substantially circumferential direction so as to form an angle of several degrees (e.g., an angle between about 0° and 6°) with a direction parallel to the equatorial plane of the tire and are coated with an elastomeric material.

[0277] The tire (100) may also include another belt layer (not shown), which is placed between the carcass structure (101) and the radially innermost belt layer of the above-mentioned belt layers (106a), (106b) and includes a plurality of reinforcing cords, which have an inclined orientation with an angle equal to 90° relative to the circumferential direction of the tire (100) or the equatorial plane XX of the tire (100).

[0278] A tread band (109) is applied in a radially outer position to the belt structure (106).

[0279] Furthermore, respective sidewalls (108) of elastomeric material are applied in an axially outer position on the lateral surface of the carcass structure, each sidewall extending from one of the lateral edges of the tread (109) at a respective bead structure (103).

[0280] A rubber layer (112), often called a "liner", may be present radially inside the carcass layer (101), said rubber layer providing the necessary impermeability to inflation to the tire.

[0281] A layer of elastomeric material, ie, a lower lining (112a), may also be provided radially outside the lining (112).According to a preferred embodiment of the present invention, the lower lining (112a) is made of the elastomeric composite of the present invention.

[0282] The sidewall (108) of the tire (100) also includes a pair of corresponding sidewall reinforcement inserts (113) made from the elastomeric compound of the present invention.

[0283] A sidewall reinforcement insert (113) is incorporated into the sidewall structure in a position axially outside the underlying liner (112a) and axially inside the carcass layer (101).

[0284] exist Figure 1 In the embodiment shown, the sidewall reinforcement insert (113) has a plane T perpendicular to a plane tangential to the outer surface of the sidewall reinforcement insert (113). i The maximum axial extension Li measured in the direction of

[0285] In a radially outer position, the tread band (109) has a rolling surface (109a) intended to come into contact with the ground. This surface (109a) is usually provided with circumferential grooves, formed by transverse notches ( Figure 1 (not shown) connecting the circumferential grooves to define a plurality of blocks of different shapes and sizes distributed on the rolling surface (109a), which for simplicity is shown in FIG. Figure 1 Shown as smooth.

[0286] Strips of elastomeric material (110), generally called "mini-sidewalls", may optionally be provided in the connection zone between the sidewall (108) and the tread band (109), said mini-sidewalls generally being obtained by co-extrusion with the tread band (109) and allowing an improvement in the mechanical interaction between the tread band (109) and the sidewall (108). Preferably, the end portions of the sidewall (108) directly overlap the lateral edges of the tread band (109).

[0287] The stiffness of the tire sidewall (108) can be increased by providing the bead structure (103) with a reinforcement layer (120), which is often referred to as a flipper or additional strip-like insert.

[0288] The bead cover (120) is a reinforcement layer wound around the corresponding bead core (102) and bead filler (104) to at least partially surround the bead core and bead filler, and the reinforcement layer is arranged between at least one carcass layer (101) and the bead structure (103). Generally, the bead cover is in contact with the at least one carcass layer (101) and the bead structure (103).

[0289] The flyer cover (120) generally comprises a plurality of textile cords incorporated within a layer of elastomeric material.

[0290] The reinforcing annular structure or bead (103) of the tire may comprise an additional protective layer, generally known by the term "chafer" (121) or protective strip and having the function of increasing the rigidity and integrity of the bead structure (103).

[0291] The chafer (121) generally comprises a plurality of cords incorporated into a rubber layer of an elastomeric material. Such cords are generally made of textile material or metal material.

[0292] A layer or sheet of elastomeric material (not shown) may be arranged between the belt structure and the carcass structure.

[0293] Optionally, in the self-supporting tire of the invention, the elastomeric compound of the invention may also be advantageously incorporated into the underlying liner (112a) and the reinforcing insert (113), if present.

[0294] The building of the tyre (100) as described above can be carried out by assembling respective semi-finished products suitable for forming the components of the tyre on a forming drum, not shown, by at least one assembling device.

[0295] At least a portion of the components intended to form the carcass structure of the tire can be built and / or assembled on a forming drum. More specifically, the forming drum is suitable for first receiving any liner and subliner, sidewall reinforcement inserts, and subsequently the carcass structure. Thereafter, unillustrated means coaxially engage one of the annular anchoring structures around each of the end flaps, position the outer sleeve comprising the belt structure and the tread band in a coaxially centered position around the cylindrical carcass sleeve, and, by radial expansion of the carcass structure, shape the carcass sleeve into an annular configuration so as to bear against the radially inner surface of the outer sleeve.

[0296] After the green tire has been constructed, it is generally subjected to molding and vulcanization processes in order to establish the structural stability of the tire by crosslinking the elastomeric composition, as well as to impart the desired tread pattern on the tread band and any distinctive graphic markings on the sidewalls.

[0297] The following examples are now provided for illustration and non-limiting purposes only.

[0298] Example

[0299] Evaluation Method

[0300] The static mechanical properties according to the UNI 6065:2001 standard (CA1 load at 100% elongation, CR tensile strength, AR% elongation at break) were measured at 23°C on samples of elastomeric material vulcanized at 170°C for 10 minutes.

[0301] The compressive dynamic mechanical properties E' and Tan delta were measured using an Instron model 1341 dynamic apparatus in the tension-compression mode described herein. A specimen of the cross-linked material (170°C, 10 minutes) was preloaded in compression to a longitudinal strain of 25% relative to the initial length and maintained at a predetermined temperature of 23°C throughout the test, subjected to a dynamic sinusoidal strain with an amplitude of ±3.5% relative to the length under preload and a frequency of 10 Hz. The specimen of the cross-linked material had a cylindrical shape (length = 25 mm; diameter = 14 mm). The dynamic mechanical properties are expressed in terms of dynamic elastic modulus (E') and Tan delta (loss factor). The Tan delta value is calculated as the ratio between the viscous dynamic modulus (E") and the dynamic elastic modulus (E').

[0302] Dynamic mechanical properties of dynamic shear modulus G' and Tan delta were evaluated using an Alpha Technologies RPA2000 oscillating chamber rheometer (Rubber Process Analyzer) with the chamber geometry as per ASTM D6601-19. Figure 1 As described in , the following method is applied:

[0303] 1) Obtaining a volume of 4.6 cm by punching a sheet of the raw vulcanizable elastomeric composition to be characterized having a thickness of at least 5 mm 3 Up to 5cm 3 Approximately cylindrical test samples within the range;

[0304] 2) The chamber of the RPA equipment is initially preheated to 170°C;

[0305] 3) Load the sample between the chambers of the RPA apparatus and close the chambers. Two films were inserted between the sample of the raw vulcanizable elastomeric composition and each chamber of the RPA apparatus to protect the chambers themselves: a nylon 6.6 cast film of approximately 25 microns in contact with the composite and a polyester film of approximately 23 microns in contact with the chambers of the RPA apparatus;

[0306] 4) The sample is then vulcanized at a temperature of 170° C. for a fixed time of 10 minutes while recording the vulcanization curve, i.e., the sample is subjected to a sinusoidal deformation with an amplitude of 7% and a frequency of 1.67 Hz during the entire vulcanization period;

[0307] 5) The temperature of the chamber of the RPA apparatus was then adjusted to 70° C. After the chamber temperature was set to 70° C. and maintained for 10 minutes, a series of dynamic measurements were performed at a constant temperature of 70° C. by applying a sinusoidal torsional stress to the sample at a fixed frequency of 10 Hz and an amplitude gradually increasing from 0.3% to 10%, with 10 stabilization cycles and 10 measurement cycles for each condition.

[0308] 6) Dynamic measurement is again carried out at 70°C by applying a sinusoidal torsional stress to the sample at a fixed frequency of 10 Hz and an amplitude of 9%, for 10 stabilization cycles and 20 measurement cycles: the results are expressed as the average value measured in 20 measurement cycles, which is the dynamic shear modulus G' and Tan Delta (the ratio between the viscous modulus G" and G', Tan Delta = G" / G').

[0309] Rolling resistance (RR) evaluation

[0310] The rolling resistance (RR) of the tire samples thus produced was measured in accordance with Annex 6 of UNECE reg. 117 Rev. 4 - ISO 28580:2018 (Section 4b (Torque method)) - Notification No. 2011-237 (Korea). The rolling resistance coefficient is expressed in N / kN.

[0311] The tires thus tested are then assigned a relative rolling resistance index, which is equal to the ratio of the rolling resistance measured for the tire in question to that of a reference tire. The lower the value of this index, the lower the rolling resistance of the tested tire, and therefore the better its performance.

[0312] Tables 3 to 7 report the results of the tests performed. In these tables, a decrease in the RR result (e.g., from 100 to 92) indicates an improvement in performance, while an increase in the value (e.g., from 100 to 104) indicates a deterioration.

[0313] Evaluation of driving distance under deflated conditions (run-flat test)

[0314] A BMW 5 Series car was equipped with four tires, depending on whether the tire set considered (see Example 2 below, sample tire preparations P1-P12) was a reference tire or an invention tire.

[0315] Each tire set was subjected to a run-flat test by fully defusing the left rear tire and driving on a mixed course at a driving speed not exceeding 80 km / h until obvious damage to the tire occurred.

[0316] The test was repeated twice for each tire group, and the results were averaged.

[0317] To compare the performance of tires, an "RF" distance index of 100 is assigned to the reference tire of each set of tires being compared.

[0318] A relative "RF" index is then assigned to the other tires of the same group, corresponding to the ratio between the distance measured under run-flat conditions for the test tire and the distance of the reference tire set to 100, said distances having been measured in close comparison.

[0319] The results are reported in Tables 3-7 and Summary Table 8.

[0320] In these tables, a maintained or moderately decreased value (e.g., from 100 to 75) in the run-flat result indicates comparable or even slightly deteriorated but perfectly acceptable performance. An increase in the value (e.g., from 100 to 120) indicates improved performance, i.e., longer range, while a significant decrease in the value (e.g., less than 65) indicates unacceptable performance.

[0321] Example 1: Preparation of an Elastomeric Composite for a Sidewall Reinforcement Insert

[0322] The reference composition reported in Table 1 below and the composition of the tire according to the invention were prepared as elastomeric compositions for the sidewall reinforcing inserts:

[0323] Table 1: Elastomer composition (phr)

[0324]

[0325]

[0326] Where Ref. = Reference, Inv. = Invention, and

[0327] IR: synthetic polyisoprene (SKI-3Nizhnekamskneftekhim); NR: natural rubber (StandardThai Rubber STR20-Thaiteck Rubber); BR: polybutadiene (Europrene -PolymersEurope); N550: carbon black (N550 Birla Carbon); silica: ZEOSIL 1115HP (Solvay); SilSep1: white filler in the form of M2 microbeads prepared according to Example 1 of patent application WO2019106562A1; SilSep2: white filler in the form of M6 microbeads prepared according to Example 3 of patent application WO2019106562A1; stearic acid: STEARINA N (SOGIS); zinc oxide: ZnO-80 (RheinChemie); TESPT 50% on CB: a mixture of bis(triethoxysilylpropyl)tetrasulfide (TESPT 50%) supported on carbon black (50%), produced by Evonik Industries AG, Germany; TMQ (anti-aging agent): polymerized NAUGARD Q (CHEMTURA CORPORATION); 6-PPD (antioxidant): N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (Santoflex™ 6PPD-Eastman); TBBS (accelerator): N-tert-butyl-2-benzothiazolesulfenamide ( NZ / EGC-Lanxess); isobutyl TUADS (isobutylthiuram disulfide) accelerator produced by RT Vanderbilt; sulfur (vulcanizing agent): insoluble 67%, Solfotecnica. Starting from the elastomer compositions shown in Table 1, the corresponding elastomer compounds were prepared according to the following process.

[0328] The mixing of the components was carried out in two steps using an internal mixer (Banbury, Intermix or Brabender).

[0329] In a first step (1), all the ingredients except the vulcanizing agent and the accelerator are introduced. Mixing is continued for a maximum of 5 minutes, reaching a temperature of about 145°C. Subsequently, in a second test (2), again carried out using an internal mixer, the vulcanizing agent and the accelerator are added and mixing is continued for about 4 minutes while maintaining the temperature below 100°C. The compound is then unloaded. After cooling and at least 12 hours after preparation, some samples of the compound are vulcanized in a press at 170°C for 10 minutes to provide samples that can be used for mechanical characterization.

[0330] Characterization of the complex

[0331] The main static and dynamic properties of the above elastomer composite measured by the above method are shown in Table 2 below

[0332] Table 2

[0333]

[0334] Example 2: Production of self-supporting tires

[0335] In order to evaluate the performance of tires with sidewall reinforcing inserts according to the invention relative to reference and comparative tires in terms of rolling resistance and maximum mileage in deflated condition, groups of eight tires were prepared for each of the tires P1 to P12 having the characteristics shown in Tables 3 to 7.

[0336] Each tire includes two sidewall reinforcement inserts, one inner and one outer, located at an axially inner position of each sidewall. Figure 1 As shown, the two inserts have the same composition, the same thickness and the same shape.

[0337] In each group, the tires were compared under identical operating conditions, modified only in the elastomeric composition of the reinforcing insert and / or its thickness, all other characteristics of the insert and of the tire being identical.

[0338] Preparation of sample tires

[0339] The first set of sample tires includes self-supporting tires of size 245 / 45R18 100Y XL produced by the applicant, and the self-supporting tires are configured as follows:

[0340] - a self-supporting tire comprising a sidewall reinforcement insert consisting of the composition Ref. 1, having a maximum thickness (Li) of 7 mm (tire P1 , reference);

[0341] - a self-supporting tire comprising a sidewall reinforcing insert of composition Ref. 2, having the same thickness (tire P2 / comparison);

[0342] A self-supporting tire comprising a sidewall reinforcement insert of reduced thickness made of composition Ref. 2 (tire P3 / comparative).

[0343] The main characteristics of the first group of self-supporting tires evaluated according to the above method, as well as their rolling resistance and maximum mileage performance under deflated conditions are shown in Table 3 below:

[0344] Table 3

[0345] tire P1 P2 P3 IRF composition Ref.1 Ref.2 Ref.2 Relative IRF thickness 100 100 86 Relative RR 100 100 97 Relative RF 100 157 45

[0346] in

[0347] IRF composition = elastomeric composition of the sidewall reinforcement insert; relative IRF thickness = thickness reparameterized by setting the thickness of the sidewall reinforcement insert of tire P1 to 100; RR = relative rolling resistance reparameterized by setting the RR of tire P1 to 100; RF = run-flat, relative maximum mileage under deflated conditions, i.e., in run-flat running, relative maximum mileage reparameterized by setting the run-flat mileage of tire P1 to 100.

[0348] The second set of sample tires includes self-supporting tires of size 245 / 45R18 100Y XL produced by the applicant, and the self-supporting tires are configured as follows:

[0349] - a self-supporting tire comprising a sidewall reinforcing insert consisting of the composition Ref. 1, having a maximum thickness Li of 7 mm (tire P4, reference);

[0350] A self-supporting tire comprising a sidewall reinforcement insert of composition Ref. 3, having the same thickness (tire P5 / comparison).

[0351] The main characteristics of the second group of self-supporting tires evaluated according to the above method, as well as their rolling resistance and maximum mileage performance under deflated conditions are shown in Table 4 below:

[0352] Table 4

[0353] tire P4 P5 IRF composition Ref.1 Ref.3 Relative IRF thickness 100 100 Relative RR 100 97 Relative RF 100 47

[0354] The third set of sample tires includes self-supporting tires of size 225 / 45R17 94Y XL RF produced by the applicant, and the self-supporting tires are configured as follows:

[0355] - a self-supporting tire comprising a sidewall reinforcement insert consisting of the composition Ref. 1, having a maximum thickness Li of 7 mm (tire P6, reference);

[0356] - A self-supporting tire comprising a sidewall reinforcing insert of the same thickness consisting of the composition Inv. 1 (tire P7, invention).

[0357] The main characteristics of the third group of self-supporting tires evaluated according to the above method, as well as their rolling resistance and maximum mileage performance under deflated conditions are shown in Table 5 below:

[0358] Table 5

[0359] tire P6 P7 IRF composition Ref.1 Inv.1 Relative IRF thickness 100 100 Relative RR 100 97 Relative RF 100 84

[0360] The fourth set of sample tires includes self-supporting tires of size 225 / 45R19 RF produced by the applicant, and the self-supporting tires are configured as follows:

[0361] - a self-supporting tire comprising a sidewall reinforcement insert consisting of the composition Ref. 1, having a maximum thickness Li of 7 mm (tire P8, reference);

[0362] - A self-supporting tire comprising a sidewall reinforcing insert of the same thickness consisting of composition Inv. 3 (tire P9, invention).

[0363] The main characteristics of the fourth group of self-supporting tires evaluated according to the above method, as well as their rolling resistance and maximum mileage performance under deflated conditions are shown in Table 6 below:

[0364] Table 6

[0365] tire P8 P9 IRF composition Ref.1 Inv.3 Relative IRF thickness 100 100 Relative RR 100 95 Relative RF 100 78

[0366] The fifth set of sample tires includes self-supporting tires of size 245 / 45R18 100Y XL produced by the present applicant, and the self-supporting tires are configured as follows:

[0367] - a self-supporting tire comprising a sidewall reinforcement insert consisting of the composition Ref. 1, having a maximum thickness Li of 7 mm (tire P10, reference);

[0368] - Self-supporting tires comprising sidewall reinforcing inserts of the same thickness consisting of composition Inv. 6 (tire P11, invention);

[0369] - A self-supporting tire comprising a sidewall reinforcing insert of increased thickness consisting of composition Inv. 6 (tire P12, invention).

[0370] The main characteristics of the fifth set of self-supporting tires evaluated according to the above method, as well as their rolling resistance and maximum mileage performance under deflated conditions are shown in Table 7 below:

[0371] Table 7

[0372] tire P10 P11 P12 IRF composition Ref.1 Inv.6 Inv.6 Relative IRF thickness 100 100 127 Relative RR 100 92 94 Relative RF 100 13 90

[0373] All of the above tires are produced by assembling all green tire components and subsequently shaping and vulcanizing.

[0374] Table 8 below summarizes the structural characteristics of the self-supporting tire:

[0375] Table 8

[0376]

[0377] As can be seen from Table 3-7 and Summary Table 8:

[0378] By comparing the compositions Ref.1 and Ref.2, it is observed that by replacing the conventional silica in the compound with more reinforcing fillers (SilSep1, SiiSep2), similar stiffness (E' and CA1 at 23°C increase, while G' remains essentially constant) and reduced hysteresis are achieved (see Table 2). Considering the corresponding data on the tires (P1, P2, P3 in Table 3), it is noted that by replacing the conventional silica in the composition of the reinforcing insert with more reinforcing fillers, at the same thickness (tires P1 compared to P2), there is a significant improvement in run-flat range (index from 100 to 157), but not in rolling resistance (constant index of 100). On the other hand, if, in addition to replacing the silica, the thickness of the sidewall reinforcing insert is reduced by 14% (tires P1 compared to P3), a significant reduction in rolling resistance is advantageously achieved, but this is at the expense of run-flat range, whose index drops from 100 to 45. The fluctuating trends in rolling resistance compared to run-flat distance demonstrate how difficult it is to find the right compromise between these properties.

[0379] Comparing compositions Ref.1 and Ref.3, it is observed that by modifying the filler (i.e., replacing carbon black and silica with the more reinforcing filler SilSep1) and reducing its total amount in the compound, a reduction in stiffness, in terms of shear modulus G', and a reduction in hysteresis are achieved (see G', Tan D at 70°C in Table 2). Considering the corresponding data on the tire (P4 and P5 in Table 4), it is noted that by modifying and reducing the total filler content in the sidewall reinforcing insert composition, the rolling resistance is significantly reduced (from 100 to 97) at the same thickness, however, at the expense of the run-flat distance, which drops from 100 to 47. It is conceivable that the reduced hysteresis is responsible for the improvement in rolling resistance, while the deterioration in run-flat distance may be due to the reduction in G'. These results discourage research activities directed towards reducing the total filler content and G' values, and in particular towards using SilSep2 fillers as the sole or main reinforcement.

[0380] By comparing compositions Ref. 1 and Inv. 1, it is observed that by reducing the total filler content in the compound, using polyisoprene as the main polymer and adjusting the vulcanization system, the stiffness, in terms of E' and G', is significantly reduced, as well as the hysteresis (see E' at 23°C, G' at 70°C and Tan D in Table 2). Considering the corresponding data on the tire (P6 and P7 in Table 5), it is noted that by reducing the total filler content in the sidewall reinforcing insert composition, the rolling resistance is significantly reduced (from 100 to 97), with the run-flat distance dropping from 100 to 84, which is acceptable, at the same thickness.

[0381] - By comparing compositions Inv. 1 and Inv. 2, it is observed that by replacing silica with carbon black, similar results are obtained (Table 2).

[0382] Comparing compositions Ref. 1 and Inv. 3, it is observed that by modifying the filler (i.e., replacing part of the silica with the more reinforcing filler SilSep 2), reducing its total content in the compound, using polyisoprene as the main polymer, and adjusting the vulcanization system, stiffness is significantly reduced in terms of E' at 23°C and G' at 70°C, as well as hysteresis (see E' at 23°C, G' at 70°C, and Tan D in Table 2). Considering the corresponding data on the tire (P8 and P9 in Table 6), it is noted that by modifying and reducing the total filler content in the sidewall reinforcing insert composition, rolling resistance is significantly reduced (from 100 to 95), and the run-flat distance drops from 100 to 78, at the same thickness, which is acceptable.

[0383] - By comparing compositions Inv.3 and Inv.4, it is observed that by modifying the filler, i.e. completely replacing silica with the more reinforcing filler SilSep2 and significantly reducing its total amount in the compound, a further reduction in the modulus E' at 23°C and G' at 70°C is achieved, and most importantly, a significant reduction in the hysteresis, while hardly changing the tensile properties (Table 2).

[0384] - By comparing compositions Inv. 4 and Inv. 5, it is observed that by modifying the vulcanization system, the hardness and hysteresis properties can be advantageously adjusted, thereby increasing the hardness in traction (Table 2).

[0385] - By comparing compositions Inv.5 and Inv.6, it is observed that by modifying the filler from SilSep2 to SilSep1 and further reducing its amount, the hardness and hysteresis properties can be further improved.

[0386] - By comparing the compositions Ref.1 and Inv.6, it is observed that by modifying the filler, i.e. replacing silica with the more reinforcing filler SilSep1, significantly reducing its total amount in the compound, using polyisoprene as the main polymer and adjusting the vulcanization system, a significantly reduced stiffness is obtained in terms of E' and G' at 23°C, as well as a significantly reduced hysteresis (see E' at 23°C, G' at 70°C and Tan D in Table 2). Considering the corresponding data on the tires (P10, P11, P12 in Table 7), it is noted that by modifying and reducing the total filler in the composition of the sidewall reinforcing insert, at the same thickness, there is a very significant reduction in rolling resistance (from 100 to 92), but at the expense of the distance under run-flat conditions, which drops from 100 to 13 (tires P10 compared to P11); however, if, in addition to replacing the silica with a more reinforcing filler and reducing the total filler, the thickness of the sidewall reinforcing insert is increased by 27% (tires P10 compared to P12), it is recovered under run-flat conditions (from 13 to 90) with minimal penalty in rolling resistance (from 92 to 94), resulting in a very favorable overall result.

[0387] From these data it can be seen that the self-supporting tires according to the invention (P7, P8 and P12) are able to meet the minimum required distance under run-flat conditions.

[0388] In summary, from the above tests it was found that by reducing the stiffness of the sidewall reinforcing insert of the self-supporting tire and possibly compensating for the reduction in self-supporting capacity by increasing the thickness of the insert, an overall favorable result can be achieved, in that it provides acceptable mileage under run-flat conditions, but with unexpected improvements in rolling resistance and comfort compared to prior art self-supporting tires characterized by stiff inserts with a higher modulus.

Claims

1. A self-supporting tire for a vehicle wheel, the self-supporting tire comprising: - a carcass structure (101) having opposite side edges associated with respective annular anchoring structures (102); - a belt structure (106) applied in a radially outer position to said carcass structure (101); - a tread band (109) applied in a radially outer position to the belt structure (106); - a pair of sidewall structures, each of said sidewall structures comprising a sidewall (108) extending at an axially outer position of said carcass structure (101) and extending radially between one of said annular anchoring structures (102) and an axially outer portion of said tread band (109); and - at least one pair of sidewall reinforcement inserts (113), each of said sidewall reinforcement inserts being embedded in the corresponding sidewall structure at an axially inner position of each of said sidewalls (108), Characterized in that both sidewall reinforcement inserts (113) comprise an elastomeric compound having a shear modulus value G' measured according to the RPA method at 70°C, 10 Hz, 9% strain of less than 1.25 MPa, and wherein the elastomeric composite of the sidewall reinforcement insert is prepared by mixing and vulcanizing an elastomeric composition comprising at least: - 100 phr of at least one diene elastomeric polymer, - at least one reinforcing filler in a total amount ranging from 5% to 30% by weight relative to the total weight of the elastomeric composition, wherein the at least one reinforcing filler is chosen from white fillers, silicate fibers, derivatives thereof, and mixtures thereof, and - at least 0.1 phr of at least one vulcanizing agent.

2. The tire according to claim 1, wherein Both of the sidewall reinforcement inserts (113) are composed of the elastomeric composite.

3. The tire according to claim 1 or 2, wherein: The elastomeric composition comprises polybutadiene in an amount less than 50 phr.

4. The tire according to claim 1 or 2, wherein: The elastomeric composition comprises polybutadiene in an amount less than 20 phr.

5. The tire according to claim 1 or 2, wherein: The elastomeric composition does not include polybutadiene.

6. The tire according to claim 1 or 2, wherein: The elastomeric composition comprises at least one reinforcing filler in a total amount by weight less than 27% of the total weight of the elastomeric composition.

7. The tire according to claim 1 or 2, wherein: The elastomeric composition comprises at least one reinforcing filler in a total amount less than 25% by weight of the total weight of the elastomeric composition.

8. The tire according to claim 5, wherein: The elastomeric composition comprises at least one reinforcing filler in a total amount less than 20% by weight of the total weight of the elastomeric composition.

9. The tire according to claim 6, wherein: The reinforcing fillers include sepiolite and silica fibers.

10. The tire according to claim 6, wherein The shear modulus value G' is less than 1.20 MPa.

11. The tire according to claim 8, wherein The shear modulus value G' is less than 0.95 MPa.

12. The tire according to claim 6, wherein Said elastomeric compound of said sidewall reinforcement insert has a dynamic compressive elastic modulus value E', measured at 23°C, 10 Hz, of less than 7.50 MPa.

13. The tire according to claim 6, wherein: The elastomeric compound of the sidewall reinforcement insert has a Tan Delta value of no greater than 0.080 measured according to the PRA method at 70° C., 10 Hz.

14. The tire according to claim 6, wherein The elastomeric compound of the sidewall reinforcement insert has an elongation at break AR (%) value greater than 150%, measured according to the ISO 37 UNI 6065 method.

15. The tire according to claim 6, wherein The elastomeric compound of the vulcanized sidewall reinforcement insert has a breaking load value CR of at least 5.0 MPa, measured according to the ISO 37 UNI 6065 method.

16. The tire according to claim 1 or 2, wherein: The sidewall reinforcement insert (113) has a maximum axial extension (Li) of 3 mm to 14 mm measured in a direction perpendicular to a plane (Ti) tangential to the outer surface of the sidewall reinforcement insert.

17. The tire according to claim 1 or 2, wherein: The sidewall reinforcement inserts (113) have the same thickness.

18. Tyre according to claim 1 or 2, further comprising a layer of airtight elastomeric material, called liner (112), at the radially innermost position of the tyre and extending at least at the tread band.

19. Tire according to claim 18, further comprising a layer of elastomeric material, called underliner (112a), situated radially outside said liner (112), radially inside said carcass structure (101), and axially inside said sidewall reinforcing insert (113), said underliner (112a) also comprising said elastomeric compound.

Images