Tyre for vehicle wheels

DESCRIPTION

The present invention relates to a tyre for vehicle wheels.

The invention also relates to a hybrid reinforcing cord to be used in tyres for vehicle wheels.

The tyre of the invention is, preferably, a tyre for sports vehicle wheels, in particular high and ultra-high performance vehicles.

Tyres for high and ultra-high performance vehicles, commonly defined as "HP" or "UHP" tyres, are in particular those that allow speeds of over 190 km/h, up to more than 300 km/h, to be reached. Examples of such tyres are those carrying speed codes "T", "U", "H", "V", "Z","W", "Y", according to the E.T.R.T.O. (European Tyre and Rim Technical Organisation) standard and racing tyres, in particular for high-power four-wheeled vehicles. Typically, tyres that carry the aforementioned speed codes have a section width equal to or greater than 185 mm, preferably comprised between 195 mm and 385 mm, more preferably comprised between 195 mm and 355 mm. Such tyres are preferably mounted on rims having fitting diameters equal to or greater than 13 inches, preferably not greater than 24 inches, more preferably comprised between 16 inches and 23 inches.

However, the tyre of the invention can be used in vehicles other than the aforementioned automobiles, for example in sports motorcycles intended to offer high performance in terms of power, comfort and mileage, like for example motorcycles of the "Sport Touring" type, i.e. motorcycles designed to be used on different types of terrains and with different road surface conditions.

Typically, motorcycles of the Sport Touring type are motorcycles with large piston displacement (for example 800 cm ³ or more) and/or high power (for example 100-120 horsepower or more). The tyre of the invention comprises hybrid reinforcing cords as defined in the rest of this description.

PRIOR ART

US 7222481 B2, EP 3196343 Al, US 4343343 Al, EP 329590 Al describe tyres having reinforcing cords comprising a core made of a textile material and, around the core, a winding of textile filaments.

WO 2020/128943 A2, to the Applicant, describes a reinforcing cord comprising two yarns twisted to one another with a predetermined twisting pitch. Each of said two yarns comprises a monofilament textile wire embedded in the filaments of the yarn.

SUMMARY OF THE INVENTION

Throughout the present description and in the following claims, when reference is made to certain values of angles, these are deemed to be absolute values, i.e. both positive values and negative values with respect to a plane or direction of reference, unless specified otherwise.

Moreover, when reference is made to any range of values comprised between a minimum value and a maximum value, the aforementioned minimum and maximum values are deemed to be included in the aforementioned range, unless expressly stated to the contrary.

Moreover, all of the ranges include any combination of the described minimum and maximum values and include any intermediate range, even if not specifically expressly described.

Even if not expressly indicated, any numerical value is deemed to be preceded by the term "about" to also indicate any numerical value that differs slightly from that described, for example to take into account the dimensional tolerances typical of the field of reference.

Hereinafter, the following definitions apply.

The term "motorcycle tyre" is used to indicate a tyre having a high curvature ratio (typically greater than 0.20) and capable of reaching high camber angles during cornering.

The term "curvature ratio" is used to indicate the ratio between the distance comprised between the radially highest point of the tread band and the maximum width of radial section (also called "maximum cord") of the tyre, and the same maximum width of the tyre, in a cross section thereof.

The term "maximum width of radial section", or "maximum cord", is used to indicate the maximum width of the profile of the tyre, i.e. the dimension of the segment having the two axially outermost points of the profile of the tread band as extremities.

The term "equatorial plane" of the tyre is used to indicate a plane perpendicular to the rotational axis of the tyre and that divides the tyre into two symmetrically equal parts.

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

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

The term "substantially axial direction" is used to indicate a direction inclined, with respect to the equatorial plane of the tyre, by an angle comprised between 70° and 90°.

The term "substantially circumferential direction" is used to indicate a direction oriented, with respect to the equatorial plane of the tyre, at an angle comprised between 0° and 10°.

The term "elastomeric material" or "elastomer" is used to indicate a material comprising a vulcanizable natural or synthetic polymer and a reinforcing filler, wherein such a material, at room temperature and after having been subjected to vulcanization, can have deformations caused by a force and is capable of quickly and energetically recovering the substantially original shape and size after the elimination of the deforming force (according to the definitions of standard ASTM D1566-11 Standard Terminology Relating To Rubber).

The term "reinforcing cord", or more simply "cord" is used to indicate an elongated element consisting of one or more elongated elements (also called "wires" or "yarns") possibly coated with, or incorporated in, a matrix of elastomeric material.

Hereinafter, the term "wire" will be used to refer to a single elongated element consisting of a single textile filament (in this case the term "monofilament textile wire" will also be used), whereas the term "yarn" will be used to refer to an elongated element made through aggregation of a plurality of textile filaments (in this case the term "multifilament textile yarn" will also be used).

Each filament can also be called "fiber".

The yarns can have one or more "ends", where the term "end" is used to indicate a bundle of filaments twisted together. For example, a single end or at least two ends twisted together can be foreseen.

The yarns can be identified with a symbol that represents the textile material, the linear density of the fiber used and the number of ends that form the yarn. For example, a yarn with ends made of PET (polyethylene terephthalate) identified with PET 1672 indicates a yarn comprising fibers made of PET with linear density 1670 dtex, formed of two ends twisted together.

Two yarns are deemed "twisted" to one another or with one another when each of the two yarns is wound on the other yarn, i.e. when each of the two yarns extends around the other yarn along a non- rectilinear trajectory, in particular along a helical trajectory or a spiral trajectory. This definition does not include the case in which one of the two yarns (first yarn) is wound around the other yarn (second yarn) but not vice-versa. In this case, the reinforcing cord is not obtained by twisting together the two yarns but rather by winding the first yarn around the second yarn. In such a reinforcing cord the first yarn extends around the second yarn along a non-rectilinear trajectory, in particular a helical trajectory or a spiral trajectory, whereas the second yarn always extends in a radially inner position with respect to the first yarn along a substantially rectilinear trajectory.

In a yarn, a monofilament textile wire is deemed "incorporated" in the filaments of the yarn when the monofilament textile wire is arranged or embedded between the filaments of the yarn. This definition does not include the case in which the monofilament textile wire defines a central core around which the filaments of the yarn are wound helically or in a spiral.

The expression "hybrid reinforcing cord" is used to indicate a textile reinforcing cord comprising two non-identical yarns twisted together.

In the case of yarns, the "diameter" of a yarn is the diameter of an ideal circumference that circumscribes all the filaments that define the yarn.

The term "linear density" or "count" of a cord or of a wire/yarn is used to indicate the weight of the cord or of the wire/yarn per unit length. The linear density can be measured in dtex (grams per 10 km of length).

In this description, two materials are deemed different also when one is a recycled material and the other is a corresponding non- recycled material. Therefore, for example, a recycled PET is a material different from a non-recycled PET.

The term "recycled material" is used to indicate a plastic material obtained from refuse or industrial waste products made of a corresponding material of plastic origin (typically, even if not necessarily, of fossil origin) and subjected to suitable mechanical and/or chemical and/or thermal treatments to be able to then give rise to reusable products.

The term "non-recycled material" is used to indicate a plastic material of fossil origin.

The term "biologically-based material" is used to indicate a material that is not of fossil origin and that is not obtained from refuse or industrial waste products, but that is obtained from renewable sources, like for example farming and forestry products that are cultivated and/or used by people for purposes different from human or animal nutrition.

Hereinafter, when reference is made to a percentage of product made of recycled or biologically-based material, we refer to the weight of such a product with respect to the weight of the yarn that incorporates such a product. Therefore, for example, a 65% recycled or biologically-based yarn indicates a yarn in which 65% of the total weight of the yarn is produced from recycled or biologically-based material and the remaining 35% of the total weight of the yarn is produced from material of fossil origin.

The terms "left-handed" and "right-handed" are used to indicate the twisting direction of a reinforcing cord, or of the yarns, when the reinforcing cord is oriented vertically and the inclination of the various turns and/or of the portions of cord/wire/yarn/end that connect the various turns of the spiral defined by the cord/wire/yarn/end is observed. The twisting direction is left-handed when the aforementioned turns and/or portions are inclined like in an S, whereas the twisting direction is right-handed when the aforementioned turns and/or portions are inclined like in a Z. The left-handed twisting direction is therefore also briefly indicated with "S" and the right- handed direction with "Z".

The term "number of twists" is used to indicate the number of twists applied to a cord/yarn/wire per unit length of cord/yarn/wire. The number of twists is indicated with TPI (twists per inch) and therefore indicates the number of twists in an inch of cord/yarn/wire. In the case of wires and/or yarns that must be twisted, the twist is applied before the cord is made.

The term "breaking load" of a cord/yarn/wire is used to indicate the load at which the cord/yarn/wire breaks, evaluated in accordance with the BISFA (Bureau International pour la Standardisation des Fibres Artificielles) standard relative to the material subjected to testing according to the definition given below.

For the purposes of the present invention, for the measurement of the linear density and for determining the tensile properties (like for example the breaking load), reference is made to flat wires, with no twists applied in the testing phase, according to the tests regulated by the BISFA standard. In particular:

- for Polyester (PET), reference is made to BISFA - Testing methods for polyester yarns - 2004 edition:

• Determination of the linear density - Chapter 6 - Procedure A;

• Determination of the tensile properties - Chapter 7 - Procedure A;

• Preparation of laboratory samples: Preparation of samples under relaxation - paragraph 7.4.1.1 => preparation of samples on collapsible reel; • Preparation of laboratory samples and performance of testing: Manual test - paragraph 7.5.2.1 => c);

• Start procedure => e) pretension at the start of procedure;

• Tractions carried out with Zwick - Roell Z010 dynamometer.

- for Nylon (NY), reference is made to BISFA - Testing methods for polyamide yarns - 2004 edition:

• Determination of the linear density - Chapter 6 - Procedure A;

• Determination of the tensile properties - Chapter 7 - Procedure A;

• Preparation of laboratory samples: Preparation of samples under relaxation - paragraph 7.4.1.1 => preparation of samples on collapsible reel;

• Preparation of laboratory samples and performance of testing: Manual test - paragraph 7.5.2.1 => c);

• Start procedure => e) pretension at the start of procedure;

• Tractions carried out with Zwick - Roell Z010 dynamometer.

The term "radial carcass structure" is used to indicate a carcass structure comprising a plurality of reinforcing cords, each of which being oriented, in a crown portion of the tyre, along a substantially axial direction. Such reinforcing cords can be incorporated in a single carcass ply or in a plurality (preferably two) of carcass plies radially juxtaposed over one another.

The term "crossed belt structure" is used to indicate a belt structure comprising a first belt layer including reinforcing cords substantially parallel to one another and inclined, with respect to the equatorial plane of the tyre, by a predetermined angle and at least one second belt layer arranged in a radially outer position with respect to the first belt layer and including reinforcing cords substantially parallel to one another but oriented, with respect to the equatorial plane of the tyre, with opposite inclination to that of the cords of the first belt layer.

The term "zero degrees reinforcing layer" is used to indicate a reinforcing layer comprising at least one reinforcing cord wound on the belt structure (in the case of tyres for automobiles) or on the carcass structure (in the case of tyres for motorcycles) according to a substantially circumferential winding direction. In motorcycle tyres, the zero degrees reinforcing layer can itself define the "belt structure" of such tyres or can be replaced by two juxtaposed reinforcing layers that define a crossed belt structure.

The term "structural component" of a tyre is used to indicate any ply or layer of the tyre containing reinforcing cords, like for example a carcass ply of automobile or motorcycle tyres, or a belt layer of automobile tyres, or a zero-degrees reinforcing layer (or a crossed belt structure) of a motorcycle tyre, or a stiffening layer associated with a carcass ply of automobile tyres at or close to a respective turned end edge of the carcass ply and indicated below as "flipper" and "chafer".

The term "thread count" of a structural component of the tyre is used to indicate the number of reinforcing cords per unit length provided in such a component. The thread count can be measured in cords/dm (number of cords per decimeter).

Hereinafter, when the adhesion capability of a textile reinforcing cord, and more generally of elongated elements, to the elastomeric material is discussed, it is deemed to refer to the adhesion capability given to the textile reinforcing cord solely by its shape or structure, thus without considering surface coating treatments through adhesive compositions. In the field of tyre production it is indeed known to use adhesive compositions, for example Resorcinol-Formaldehyde- Latex (RFL) composition, in order to promote the adhesion between the elongated elements and the elastomeric material and thus ensure the performance properties of the tyre during use. Such RFL-based adhesive compositions are applied to the polymeric elongated elements, generally by immersion in an aqueous RFL-based solution, i.e. a rubber latex emulsion in an aqueous solution of resorcinol and formaldehyde (or pre-condensed resin obtained from reaction between resorcin and formaldehyde). Some materials, such as rayon and aliphatic polyamides, already acquire optimal properties for adhesion to the elastomeric material through a single immersion in an RFL-based bath (dipping, one-step process) whereas others, such as polyesters or aromatic polyamides, bond with greater difficulty to the elastomeric material and therefore take advantage of special physical or chemical activating pretreatments. For example, elongated elements made of polyester or aromatic polyamides are subjected to a surface pre-activation through pre-treatment with a first activating bath (pre-dipping, two-step process) or through pre-treatments with ionizing rays, with plasma or with solvents.

Tyres for sports automobiles and for motorcycles are required to have a high capability to adhere to the ground, so as to be able to effectively discharge to the ground the high drive torque which they are subjected to and, therefore, to achieve a high thrust and an effective braking force. Such tyres must also be light and provide an adequate response to the stresses which they are subjected to during travel in a straight line and during cornering.

Sports vehicle tyres typically comprise a radial carcass structure, a crossed belt structure arranged in a radially outer position with respect to the carcass structure, a zero degrees reinforcing layer arranged in a radially outer position with respect to the crossed belt structure and a tread band arranged in a radially outer position with respect to the zero degrees reinforcing layer.

In tyres for sports motorcycles, the belt structure may or may not be crossed. In the second case the belt structure defines a zerodegrees reinforcing layer.

The carcass structure is intended to provide the tyre with the desired characteristics of integrity and structural strength, whereas the crossed belt structure, in addition to contribute to provide the aforementioned characteristics of integrity and structural strength, is intended to transfer to the carcass structure the lateral and longitudinal stresses which the tyre is subjected to during travel upon contact with the road surface, so as to provide the tyre with the desired performance characteristics (i.e. grip, driving stability, controllability, directionality, road holding). The zero-degrees reinforcing layer, on the other hand, is intended to limit the radial deformation of the belt structure (in automobile tyres) or of the carcass structure (in motorcycle tyres).

In order to achieve the aforementioned structural and performance characteristics, one or more reinforcing layers are provided in the carcass structure and in the belt structure of automobile tyres and in the carcass structure of motorcycle tyres (in the carcass structure the reinforcing layer corresponds to one or more "carcass plies"), each reinforcing layer comprising a plurality of reinforcing cords suitably inclined with respect to the circumferential or rolling direction, whereas in the zero degrees reinforcing layer reinforcing cords oriented substantially parallel to the circumferential or rolling direction are provided.

At least some of the aforementioned reinforcing cords are textile reinforcing cords.

With the aim of making textile reinforcing cords having mechanical characteristics suitable for being used in the carcass structure of its automobile or motorcycle tyres and in the belt structure of its automobile tyres, the Applicant has thought to twistg together two yarns each comprising a plurality of filaments and a monofilament textile wire embedded in said filaments, as described in WO 2020/128943 A2.

The Applicant has indeed observed that due to the presence of at least two monofilament textile wires, such a type of reinforcing cord has a high stiffness, particularly in the cases in which the diameter of the monofilament textile wires is greater than 0.22 mm. Such a high stiffness makes it possible not only to achieve a high resistance to impacts, but also to be able to foresee thread counts lower than those typically provided in the case of use of conventional textile reinforcing cords comprising only multi-filament textile yarns, with a consequent reduction in weight of the tyre.

However, the Applicant has found that a high stiffness can penalize the behavior under fatigue of the reinforcing cords, and therefore their duration or useful life.

The Applicant has found that by twisting at least one multifilament textile yarn with a yarn comprising both a plurality of filaments and a monofilament textile wire, it is possible to make hybrid reinforcing cords that offer an excellent compromise between stiffness and fatigue resistance and that are particularly suitable for being used in the carcass structure of automobile and motorcycle tyres.

Indeed, the reinforcing cords of the carcass structures are stressed mainly to bending and must therefore maintain an adequate flexibility so as not to compromise the behavior under fatigue. It is therefore necessary for them not to be excessively stiff. By suitably selecting the diameter of the monofilament textile wire it is possible to obtain the desired degree of stiffness.

Since filaments are more suitable than the monofilament textile wire for adhering to the surrounding elastomeric material, the Applicant has also thought of embedding the monofilament textile wire in the filaments of the respective yarn.

Therefore, the present invention relates, in a first aspect thereof, to a tyre for vehicle wheels.

Preferably, the tyre comprises at least one structural component including a plurality of hybrid reinforcing cords.

Preferably, at least some of said hybrid reinforcing cords comprise at least two yarns twisted together.

Preferably, each of said at least two yarns comprises a plurality of filaments.

Preferably, a single yarn of said at least two yarns further comprises a single monofilament textile wire.

Preferably, in any cross section of said single yarn said monofilament textile wire is at least partially embedded in the filaments of said single yarn.

In a second aspect thereof, the invention relates to a hybrid reinforcing cord.

Preferably, the hybrid reinforcing cord comprises at least two yarns twisted together.

Preferably, each of said at least two yarns comprises a plurality of filaments.

Preferably, a single yarn of said at least two yarns further comprises a single monofilament textile wire.

Preferably, in any cross section of said single yarn said monofilament textile wire is at least partially embedded in the filaments of said single yarn.

The Applicant believes that it is possible to use hybrid reinforcing cords of the type described above in the carcass structures of its automobile or motorcycle tyres in place of the textile reinforcing cords currently used.

The Applicant also believes that the hybrid reinforcing cords described above are suitable for being used also or only in other structural components of the tyre, like for example in the structural components of automobile tyres that are described below and are indicated as "flipper" and "chafer".

In at least one of the aforementioned aspects, the present invention can have at least one of the preferred characteristics described below.

Preferably, in any cross section of said single yarn the monofilament textile wire is completely embedded in the filaments of the yarn, so as to maximize the adhesion of the hybrid reinforcing cord to the surrounding elastomeric material.

In some preferred embodiments, said monofilament textile wire has a diameter lower than, or equal to, 0.22 mm, more preferably lower than, or equal to, 0.21 mm, even more preferably lower than, or equal to, 0.20 mm.

Such a reinforcing cord has a preferred application in the carcass structure of a motorcycle tyre.

In other embodiments, the monofilament textile wire has a diameter greater than, or equal to, 0.22 mm, preferably greater than, or equal to, 0.25 mm, more preferably greater than, or equal to, 0.30 mm.

Such a reinforcing cord has a preferred application in the carcass structure and/or in the flippers and chafers of an automobile tyre. In this case, not only it is possible to provide the reinforcing cord with an adequate stiffness in light of the stresses that it is intended to withstand, but it is also possible to provide lower thread counts than those typically provided in the case of use of conventional textile reinforcing cords comprising only multifilament textile yarns, with a consequent reduction of weight.

Preferably, the monofilament textile wire is made of an at least partially recycled or biologically-based material, so as to satisfy the ever-increasing request to use materials of non-fossil origin in place of the conventional materials of fossil origin, so as to protect the environment.

Preferably, the filaments of said single yarn are made of an at least partially recycled or biologically-based material.

Preferably, the filaments of at least one second yarn of said at least two yarns are made of an at least partially recycled or biologically- based material.

The hybrid reinforcing cords can be made totally of recycled material, or totally of biologically-based material, or partially of recycled material and partially of biologically-based material, or partially of recycled material and partially of material of fossil origin, or partially of biologically-based material and partially of material of fossil origin, or using recycled material, biologically-based material, and material of fossil origin. In all these cases, the provision in the hybrid reinforcing cords of filaments and/or of a monofilament textile wire made of a recycled and/or biologically-based material makes it possible to achieve the desired benefits in terms of environmental sustainability. Such benefits are the greater the greater the percentage of recycled or biologically-based material used.

The choice of the material of the monofilament textile wire and of the filaments of the various yarns can be made depending on the availability offered by the market and/or the relative cost at the time of selection.

Preferably, the monofilament textile wire is made of at least partially recycled or biologically-based PET or nylon.

Preferably, the filaments of said single yarn are made of at least partially recycled or biologically-based PET or nylon.

More preferably, the material of the aforementioned filaments is identical to that of the monofilament textile wire.

Preferably, the filaments of said at least one second yarn are made of at least partially recycled or biologically-based PET or nylon.

The Applicant has verified that monofilament textile wires and yarns made of the aforementioned materials are available on the market.

Preferably, the material of all of the filaments of the hybrid reinforcing cord is identical to that of the monofilament textile wire.

Preferably, said hybrid reinforcing cords consist of said single yarn and of a single second yarn.

Preferably, said at least one structural component is a carcass ply.

In some embodiments of an automobile tyre, said at least one structural component is a stiffening layer associated with a carcass ply at or close to a respective turned end edge of the carcass ply, like for example a flipper and/or a chafer.

In further embodiments, the hybrid reinforcing cords of the invention are used both in the carcass ply and in the aforementioned stiffening layer.

Preferably, said single yarn is twisted on itself with a predetermined first twisting pitch. The Applicant has found that such a provision contributes to optimize the behavior under fatigue of the reinforcing cord.

Preferably, said first twisting pitch is equal to the twisting pitch of said at least two yarns.

Preferably, said at least one second yarn is twisted on itself with a second twisting pitch.

Preferably, said second twisting pitch is equal to the twisting pitch of said at least two yarns.

In some embodiments, the monofilament textile wire is twisted on itself with a respective twisting pitch that, preferably, is equal to the twisting pitch of the yarns. In this way, the embedding of the monofilament textile wire in the filaments of the yarn is maximized, to the benefit of the adhesion of the reinforcing cord to the surrounding elastomeric material.

In some embodiments, in said at least one second yarn said at least one second monofilament textile wire is twisted on itself with a respective twisting pitch that, preferably, is equal to the twisting pitch of the yarns.

Preferably, the hybrid reinforcing cord is twisted on itself with a respective twisting pitch that can be equal to, or different from, the twisting pitch of the yarns and/or of the monofilament textile wire.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Further characteristics and advantages of the tyre of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings. In such drawings:

- figure 1 is a schematic partial half-cross section view of a portion of an automobile tyre according to an embodiment of the present invention;

- figure 2 shows a radial cross section view of a motorcycle tyre according to an embodiment of the present invention;

- figure 3 is a schematic side view of a segment of an example of hybrid reinforcing cord in accordance with the present invention, such a hybrid reinforcing cord being used in the tyres of figures 1 and 2;

- figure 4 is an enlarged schematic view of a cross section of an embodiment of the hybrid reinforcing cord of figure 3, such a cross section being taken on the section plane S-S indicated in figure 3. Figure 1 shows only a part of an example embodiment of a tyre 100 for automobiles or four-wheeled vehicles in accordance with the present invention, the remaining part, which is not shown, being substantially identical and being arranged symmetrically with respect to the equatorial plane M-M of the tyre.

Preferably, the tyre 100 is an HP or UHP tyre for sports and/or high and ultra-high performance automobiles.

In particular, the tyre 100 carries one of the following speed codes: . "T", "U", "H", "V", "Z","W", "Y", according to the E.T.R.T.O. standard.

In Figure 1, "a" indicates an axial direction, "c" indicates a radial direction, "M-M" indicates the equatorial plane of the tyre 100 and "R-R" indicates the rotation axis of the tyre 100.

The tyre 100 comprises a carcass structure 101 of the radial type, which in turn comprises at least one carcass ply 111.

Hereinafter, for the sake of simplicity of presentation, reference will be made to an embodiment of the tyre 100 comprising a single carcass ply 111 (mono-ply tyre). However, it is understood that what is described with reference to the carcass ply 111 is also valid for each carcass ply of tyres comprising more than one carcass ply, unless indicated to the contrary. Indeed, embodiments of the tyre 100 of the invention in which the carcass structure 101 comprises for example two carcass plies 111 (two-ply tyre) are foreseen.

The carcass ply 111 comprises a plurality of reinforcing cords 10' coated with, or incorporated in, a layer of cross-linked elastomeric material. In the case in which the tyre 100 is a two-ply tyre, the reinforcing cords of a first carcass ply can be substantially parallel to those of the other carcass ply or inclined with respect to those of the other carcass ply by an angle lower than 40°.

Preferably, the carcass ply 111 has a thread count greater than, or equal to, 70 cords/dm and lower than, or equal to, 95 cords/dm, more preferably comprised between 75 cords/dm and 90 cords/dm. For example, in a preferred embodiment of the tyre 100 of the invention, the aforementioned thread count is equal to 85 cords/dm.

Preferably, the carcass ply 111 has a thickness comprised between 0.7 mm and 1.5 mm, more preferably between 0.9 mm and 1.3 mm. For example, in the aforementioned preferred embodiment of the tyre 100 of the invention, the aforementioned thickness is equal to 1.1 mm.

The carcass ply 111 has axially opposite end edges engaged with respective annular anchoring structures 102, called bead cores, possibly associated with an elastomeric filler 104. The area of the tyre

100 comprising the bead core 102 and the possible elastomeric filler 104 forms an annular reinforcing structure 103 called "bead structure" and intended to allow the anchoring of the tyre 100 on a corresponding mounting rim, not shown.

Each annular reinforcing structure 103 is associated with the carcass structure 101 by folding back (or turning) of the opposite end edges of the at least one carcass ply 111 around the bead core 102 and the possible elastomeric filler 104, so as to form the so-called turns 101a of the carcass structure 101.

In an embodiment, the coupling between carcass structure

101 and annular reinforcing structure 103 can be made through a layer (not shown in figure 1) applied in a radially outer position with respect to the carcass ply 111.

An anti-abrasion strip 105 is arranged at each annular reinforcing structure 103 so as to wind around the annular reinforcing structure 103 along the axially inner, axially outer and radially inner areas of the annular reinforcing structure 103, thus being arranged between the latter and the rim of the wheel when the tyre 100 is mounted on the rim. Such an anti-abrasion strip 105 may however not be provided.

The tyre 100 comprises, in a radially outer position with respect to the carcass structure 101, a crossed belt structure 106 comprising at least two belt layers 106a, 106b arranged in radial juxtaposition with respect to one another.

The belt layers 106a, 106b comprise a plurality of reinforcing cords 10a, 10b, respectively. Such reinforcing cords 10a, 10b have an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle comprised between 15° and 45°, preferably between 20° and 40°. For example, such an angle is equal to 30°.

The tyre 100 can also comprise a further belt layer (not shown) arranged between the carcass structure 101 and the radially innermost belt layer of the aforementioned belt layers 106a, 106b and comprising a plurality of reinforcing cords having an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle equal to 90°.

The tyre 100 can also comprise a further belt layer (not shown) arranged in a radially outer position with respect to the radially outermost belt layer of the aforementioned belt layers 106a, 106b and comprising a plurality of reinforcing cords having an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle comprised between 20° and 70°.

The reinforcing cords 10a, 10b of a belt layer 106a, 106b are parallel to each other and have a crossed orientation with respect to the reinforcing cords of the other belt layer 106b, 106a.

In ultra-high performance tyres, the belt structure 106 can be a turned crossed belt structure. Such a belt structure is made by arranging at least one belt layer on a support element and by turning the opposite side end edges of said at least one belt layer. Preferably, a first belt layer is initially deposited on the support element, then the support element is radially expanded, then a second belt layer is deposited on the first belt layer and finally the opposite axial end edges of the first belt layer are turned over the second belt layer to at least partially cover the second belt layer, which is the radially outermost one. In some cases, it is possible to arrange a third belt layer on the second belt layer. Advantageously, the turning of the axially opposite end edges of a belt layer over another belt layer arranged on a radially outer position with respect to the first one provide the tyre with a greater reactivity and responsiveness when cornering.

The tyre 100 comprises, in a radially outer position with respect to the crossed belt structure 106, at least one zero degrees reinforcing layer 106c, commonly known as "zero degrees belt". It comprises reinforcing cords 10c oriented in a substantially circumferential direction. Such reinforcing cords 10c thus form an angle of a few degrees (typically lower than 10°, for example comprised between 0° and 6°) with respect to the equatorial plane M-M of the tyre 100.

The reinforcing cords 10a, 10b, 10c are coated with an elastomeric material or incorporated in a matrix of cross-linked elastomeric material.

A tread band 109 made of elastomeric material is applied in a radially outer position with respect to the zero degrees reinforcing layer 106c.

Respective sidewalls 108 made of elastomeric material are also applied on the side surfaces of the carcass structure 101, in an axially outer position with respect to the carcass structure 101 itself. Each sidewall 108 extends from one of the side edges of the tread band 109 up to the respective annular reinforcing structure 103.

The anti-abrasion strip 105, if provided, extends at least up to the respective sidewall 108.

In some specific embodiments, like the one shown and described herein, the stiffness and integrity of the annular reinforcing structure 103 and of the sidewall 108 can be improved by providing a stiffening layer 108, generally known as "flipper" or additional strip-like insert.

The flipper 120 is wound around a respective bead core 102 and around the elastomeric filler 104 so as to at least partially wrap around the annular reinforcing structure 103. In particular, the flipper 120 winds around the annular reinforcing structure 103 along the axially inner, axially outer and radially inner areas of the annular reinforcing structure 103.

The flipper 120 is arranged between the turned end edge of the carcass ply 111 and the respective annular reinforcing structure 103. Usually, the flipper 120 is in contact with the carcass ply 111 and the annular reinforcing structure 103.

In some specific embodiments, like the one shown and described herein, the annular reinforcing structure 103 can also comprise a further stiffening layer 121 that is generally known by the term "chafer", or protective strip, and which has the function of increasing the stiffness and integrity of the annular reinforcing structure 103.

The chafer 121 is associated with a respective turned end edge of the carcass ply 111 in an axially outer position with respect to the respective annular reinforcing structure 103 and extends radially towards the sidewall 108 and the tread band 109.

The flipper 120 and the chafer 121 comprise reinforcing cords lOd (in figure 1 those of the flipper 1 are not visible) coated with an elastomeric material or incorporated in a matrix of cross linked elastomeric material.

The tread band 109 has, in a radially outer position thereof, a rolling surface 109a intended to come into contact with the ground. Circumferential grooves (not shown in figure 1) are formed on the rolling surface 109a, said grooves being connected by transversal notches (not shown in figure 1) so as to define on the rolling surface 109a a plurality of blocks of various shapes and sizes (not shown in figure 1).

An under-layer 107 is arranged between the crossed belt structure 106 and the tread band 109.

In some specific embodiments, like the one shown and described herein, a strip 110 consisting of elastomeric material, commonly known as "mini-sidewall", can optionally be provided in the connection area between the sidewall 108 and the tread band 109. The mini-sidewall 110 is generally obtained through co-extrusion with the tread band 109 and allow an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108.

Preferably, an end portion of the sidewall 108 directly covers the side edge of the tread band 109.

In the case of tubeless tyres, like the one shown and described herein, a layer of rubber 112, generally known as "liner", is provided in a radially inner position with respect to the carcass ply 111 to provide the necessary impermeability to the inflation air of the tyre 100.

At least some of the reinforcing cords 10' (preferably all the reinforcing cords 10' of the carcass layer 111) and/or of the reinforcing cords lOd of the flipper 120 and/or of the chafer 121 are hybrid reinforcing cords 10 in accordance with the present invention, of the type shown in figures 3 and 4 and described below.

On the other hand, the reinforcing cords 10a, 10b and 10c are, preferably, reinforcing cord of the known type, comprising for example only multifilament textile yarns and/or metallic wires and/or a combination thereof. The cords 10a and 10b can also be of the type described in WO 2020/128943 A2.

Figure 2 shows an embodiment of a motorcycle tyre according to the present invention. Such a tyre is indicated with 1. In particular, it is a tyre intended to be used on the rear wheel of a Sport Touring motorcycle.

The tyre 1 comprises a radial carcass structure 2 having a central crown portion 16 including at least one carcass ply 3, described hereinafter in greater detail.

The carcass structure 2 is preferably coated on the inner walls thereof by a sealing layer 11, or so-called "liner", essentially consisting of an airtight layer of elastomeric material, adapted to provide the tyre itself, once inflated, with the hermetic seal.

The carcass ply 3 has its axially opposite side edges 3a turned around respective annular reinforcing structures 4, or bead cores.

A tapered elastomeric filler 5 is applied on the outer perimeter edge of the bead cores 4. The filler 5 occupies the space defined between the carcass ply 3 and the corresponding turned side edge 3a of the carcass ply 3.

In an alternative embodiment, that is not shown, the carcass ply has the opposite side edges thereof associated without turning with particular annular reinforcing structures provided with two metallic annular inserts. In this case, a filler made of elastomeric material can be arranged in an axially outer position with respect to the first annular insert. The second annular insert, on the other hand, is arranged in an axially outer position with respect to the end of the carcass ply. Finally, is possible to provide a further filler in an axially outer position with respect to said second annular insert, and not necessarily in contact with it. This further filler ends the building of the annular reinforcing structure.

The area of the tyre comprising the bead core 4 and the filler 5 forms the so-called "bead", globally indicated in figure 2 with 15, which is intended for anchoring the tyre 1 on a corresponding mounting rim, not shown.

A belt structure 6, also described hereinafter in greater detail, is provided in a radially outer position with respect to the aforementioned carcass structure 2.

A tread band 8 is provided in a radially outer position with respect to the belt structure 6. The tyre 1 makes contact with the ground by the tread band 8.

The tyre 1 can also comprise a pair of sidewalls 2a applied laterally to the carcass structure 2 on axially opposite sides to the equatorial plane M-M thereof. The sidewalls 2a extend from the tread band 8 to the bead 15 of the tyre 1.

The carcass ply 3 is preferably made of elastomeric material and comprises a plurality of reinforcing cords 10" arranged parallel to one another and perpendicular to the equatorial plane M-M.

Preferably, the belt structure 6 comprises reinforcing cords lOe which are arranged substantially parallel and side-by-side in the axial direction on the crown portion 16 of the carcass structure 2, to form a plurality of turns. Such turns are substantially oriented according to the rolling direction of the tyre 1 (in particular with an angle comprised between 0° and 5° with respect to the equatorial plane M-M), such a direction usually being called "zero degrees" or "circumferential". The aforementioned turns preferably extend over the entire crown portion 16 of the carcass structure 2.

Preferably, the belt structure 6 comprises windings of a single reinforcing cord lOe, or of a band of rubber-coated fabric comprising reinforcing cords lOe, preferably up to five, arranged side-by-side, wound in a spiral on the crown portion 16 of the carcass structure 2 from one end to the other end of the crown portion 16.

Alternatively, the belt structure 6 can comprise at least two radially juxtaposed layers, each consisting of an elastomeric material reinforced with reinforcing cords arranged parallel to one another. The layers are arranged so that the reinforcing cords of the first belt layer are oriented obliquely with respect to the equatorial plane of the tyre, whereas the reinforcing cords of the second layer also have an oblique orientation, but such an orientation is symmetrically crossed with respect to that of the reinforcing cords of the first layer, to form the so- called "crossed belt".

Preferably, the belt structure 6 comprises a support layer 9 substantially consisting of a sheet of elastomeric material arranged between the layer of reinforcing cords lOe and the carcass ply 3 and on which the aforementioned turns are wound. The layer 9 preferably extends on a surface having an axial extension substantially corresponding to the surface on which the aforementioned turns extend. Alternatively, the layer 9 can extend over a surface smaller than the surface of extension of the turns, for example only on opposite side portions of the belt structure 6.

In a further embodiment that is not shown, an additional layer of elastomeric material is arranged between the belt structure 6 and the tread band 8. Such a layer preferably extends over a surface corresponding to the surface of extension of the belt structure 6. Alternatively, the aforementioned additional layer can extend over a surface smaller than the surface of extension of the belt structure 6, for example only on opposite side portions of the belt structure 6.

The tread band 8 has a tread pattern defined by a plurality of grooves (some of which are indicated in figure 2 with 17) formed on the outer surface of the tread band 8 through a molding operation carried out concurrently with the vulcanization of the tyre 1.

At least some of the reinforcing cords 10" (preferably all the reinforcing cords 10") are hybrid reinforcing cords 10 in accordance with the present invention, of the type shown in figures 3 and 4 and described below.

On the other hand, the reinforcing cords lOe are, preferably, reinforcing cords of the known type, comprising only multifilament textile yarns.

With reference to figures 3 and 4, the hybrid reinforcing cord 10 comprises two yarns 20a, 20b twisted to one another with a predetermined twisting pitch P.

The twisting pitch P is preferably comprised between about 1 mm and about 20 mm, more preferably between about 2 mm and about 15 mm, for example equal to about 12.5 mm.

The two yarns 20a, 20b are different from one another. In particular, the yarn 20a comprises a single monofilament textile wire 21a embedded in the filaments 22a of a multifilament textile yarn 23a, whereas the yarn 20b comprises a plurality of filaments 22b of a multifilament textile yarn 23b and no monofilament textile wire. The yarn 20a could however comprise many multifilament textile yarns. The yarn 20b could comprise many multifilament textile yarns as well.

In any cross section of the reinforcing cord 10, the monofilament textile wire 21a is embedded in the filaments 22a of the yarn 20a, i.e. the filaments 22a are arranged around the monofilament textile wire 21a so as to completely surround the monofilament textile wire 21a, which is thus not visible from the outside since it is entirely covered by the filaments 22a of the yarn 20a.

Although it is particularly preferred an embodiment, like that of figure 4, in which the monofilament textile wire 21a is, in any cross section of the reinforcing cord 10, completely embedded in the filaments 22a of the yarn 20a, other embodiments which are deemed equally preferred are those in which, in any cross section of the reinforcing cord 10, the monofilament textile wire 21a is only partially embedded in the filaments 22a of the yarn 20a, and in particular those in which at least 50% of the outer surface of the monofilament textile wire 21a is embedded in the filaments 22a of the yarn 20a.

The monofilament textile wire 21a extends along a longitudinal direction A, shown in figure 3.

The mutual arrangement of the monofilament textile wire 21a and of the filaments 22a of the yarn 20a along the longitudinal direction A can be such that the monofilament textile wire 21a extends substantially parallel to the filaments 22a, or such that the filaments 22a are wound in a helix on the monofilament textile wire 21a with a predetermined winding pitch that, preferably, is equal to the twisting pitch P.

In this last case, the twisting direction of the two yarns 20a, 20b is preferably the same as the winding pitch of the filaments 22a on the monofilament textile wire 21a, but it is possible to foresee opposite directions.

The yarns 20a, 20b may or may not be twisted on themselves with respective twisting pitches that, preferably, are equal to the twisting pitch P.

The direction of twisting of the yarns 20a, 20b on themselves can be the same as or opposite to the direction of twisting of the two yarns 20a, 20b to each other.

The monofilament textile wire 21a may or may not be twisted on itself with a twisting pitch that, preferably, is equal to the twisting pitch P.

The twisting direction of the monofilament textile wire 21a on itself can be the same as or opposite to that of twisting of the two yarns 20b, 20b to each other.

The filaments 22a, 22b of the yarns 20a, 20b are made of recycled or biologically-based material, in particular recycled or biologically-based PET or nylon. For example, it is possible to use one or more of the following materials: 100% recycled PET, 30% biologically- based PET, nylon 4.10 (70% biologically-based), nylon 6.10 (100% biologically-based), nylon 56 (45% biologically-based).

The monofilament textile wire 21a is made of recycled or biologically-based material, in particular recycled or biologically-based PET or nylon. For example, it is possible to use one or more of the following materials: 100% recycled PET, nylon 6.10 (60% biologically- based), nylon 1010 (up to 99% biologically-based).

Irrespective of the specific type of textile material used for the filaments 22a, 22b, such a material is made suitably adhesive on the surface so as to offer adequate adhesion to the surrounding elastomeric material. Typically, the adhesion treatment can be carried out by coating with an adhesive substance or through a chemical or physical treatment.

For example, the adhesion treatment is carried out through immersion of the reinforcing cord 10 in a solution comprising the adhesive substance after having twisted together the two yarns 20a, 20b.

Preferably, the yarns 20a, 20b have a linear density comprised between about 400 dTex and about 4000 dTex, preferably between about 800 dTex and about 2500 dTex, also depending on the structural component of the tyre 100 of figure 1 or of the tyre 1 of figure 2 in which the reinforcing cords 10 are arranged.

The monofilament textile wire 21a has a diameter greater than 0.22 mm, preferably greater than, or equal to, 0.25 mm, more preferably greater than, or equal to, 0.30 mm, for example equal to 0.30 mm or 0.40 mm when the reinforcing cord 10 is used in the carcass structure 101 and/or in the flippers 120 and/or in the chafers 121 of the tyre 100 of figure 1, whereas it has a diameter lower than, or equal to, 0.22 mm, preferably lower than, or equal to, 0.21 mm, even more preferably lower than, or equal to, 0.20 mm when the reinforcing cord 10 is used in the carcass structure 3 of the tyre 1 of figure 2.

In specific embodiments of the tyre 100 of figure 1, only the reinforcing cords 10', and not also the reinforcing cords lOd, or vice- versa, are hybrid reinforcing cords 10 of the type described above.

When the reinforcing cords lOd are hybrid reinforcing cords 10 of the type described above, such hybrid reinforcing cords 10 can be used only in the flipper 120 (if the flipper 120 is provided and when the chafer 121 is not provided or is provided and comprises conventional reinforcing cords), only in the chafer 121 (if the chafer 121 is provided and when the flipper 120 is not provided or is provided and comprises conventional reinforcing cords), or both in the flipper 120 and in the chafer 121 (if both are provided).

Some preferred embodiments of hybrid reinforcing cords 10 in accordance with the present invention which can be used in the carcass structure of automobile tyres are described in the following paragraph "COMPARATIVE TESTS".

A preferred embodiment of a hybrid reinforcing cord 10 in accordance with the present invention which can be used in the carcass structures of motorcycle tyres comprises two yarns 20a, 20b twisted together, in which the yarn 20a comprises a plurality of filaments 22a made of 100% recycled PET with linear density equal to 3340 dtex and a monofilament textile wire 21a made of 100% recycled PET and having a diameter equal to 0.197 mm, whereas the yarn 20b comprises a plurality of filaments 22b made of 100% recycled PET with linear density equal to 3340 dtex.

COMPARATIVE TESTS

The Applicant has subjected hybrid reinforcing cords 10 in accordance with the present invention to comparative tests in order to evaluate their resistance to fatigue and, consequently, their duration or useful life.

Each of the aforementioned reinforcing cords 10 comprised two yarns twisted together, wherein a yarn comprised filaments made of 100% recycled PET with linear density equal to 1680 dtex and a monofilament textile wire made of 100% recycled PET and having a diameter equal to 0.30 mm, whereas the other yarn comprised filaments made of 100% recycled PET with linear density equal to 1680 dtex. Such reinforcing cords are indicated with INV.

The reinforcing cords INV were made by imparting to the two yarns 310 twists in the right-handed direction and to the reinforcing cord INV 180 twists in the left-handed direction.

A test piece was made comprising a strip of elastomeric material, on which a layer of elastomeric material comprising the reinforcing cords INV was juxtaposed. Such a layer had a thickness equal to 2 mm. The test piece had a total thickness equal to 3.1 mm, a length equal to 360 mm and a width equal to 25 mm.

The test piece was vulcanized at 151 °C for 30 minutes and conditioned at room temperature for 16 hours.

The test piece was subjected to bending/compression cycles in a testing machine of the De Mattia type according to the standard ISO 132.

The aforementioned cycles were carried out for 4-8-16-24-48 hours keeping the temperature under control so that it did not exceed 70°. At the end of the test the test piece was conditioned at room temperature for 16 hours. Thereafter, the reinforcing cords INV were extracted from the test piece and subjected to traction tests.

A test piece that differed from the one described above only in the it comprises a plurality of textile reinforcing cords of the type described in WO 2020/128943 A2 (reference test piece) was also subjected to an analogous test. Such textile reinforcing cords are indicated with REF and, in the opinion of the Applicant, have excellent fatigue resistance and therefore a high useful life and are used in the carcass structure of automobile tyres of the Applicant.

Each of the reinforcing cords REF comprised two multifilament textile yarns twisted together, each of the two yarns comprising filaments made of PET of fossil origin and a monofilament textile wire made of PET of fossil origin having a diameter equal to 0.30 mm. Such reinforcing cords REF were also made by imparting to the two yarns 310 twists in the right-handed direction and to the reinforcing cord REF 180 twists in the left-handed direction.

At the end of the test the reinforcing cords REF were extracted from the aforementioned test piece and also subjected to traction tests.

The resistance to fatigue of each of the aforementioned reinforcing cords REF was determined as the difference between the breaking load of the cords subjected to the test described above and that of analogous cords not subjected to the aforementioned bending/compression cycles on the De Mattia machine.

The Applicant also measured the degradation of the reinforcing cords REF, understood as the ratio between the resistance to fatigue determined as described above and the breaking load of the cords not subjected to the aforementioned bending/compression cycles.

The result of the traction tests is given in Table 1 herein below.

Table 1

The comparative tests therefore confirmed that the reinforcing cords INV, when stressed under fatigue, have an even greater useful life (or a lesser degradation) than that of the reinforcing cords REF made in accordance with what is described in WO 2020/128943 A2.

The reinforcing cords INV of the invention can therefore actually replace the latter in the cases in which it is deemed preferable for the reinforcing cords not to be excessively stiff, so as to withstand to bending stresses, like for example in the case of use in the carcass structures of automobile and motorcycle tyres.

Of course, those skilled in the art can make further modifications and variants to the present invention described above in order to satisfy specific and contingent application requirements, these variants and modifications in any case being within the scope of protection defined by the following claims.