Tyre for bicycle wheel

Abstract

The invention relates to a tyre (100) for bicycle wheels, comprising:-a carcass structure (2) comprising at least one carcass ply (3) having ends (3a) rolled up around respective bead cores (4a, 4b) to form respective opposite beads (5a, 5b),-a tread band (7) arranged in a radially outer position relative to the carcass structure (2), and-a layer (8) of vulcanized elastomeric material superimposed or interposed in said carcass structure (2) in a radially inner or outer position, said layer (8) of vulcanized elastomeric material extending axially from at least one bead (5a) to an opposite bead (5b), characterized in that the layer (8) of vulcanized elastomeric material is arranged in the carcass structure (2). The layer (8) of vulcanized elastomeric material is produced by vulcanization of a vulcanizable elastomer compound comprising micron-sized fibrillated polymer fibers.

Description

Technical Field

[0001] The present invention relates to a tyre for bicycle wheels having improved properties. The tyre of the present invention can be used on wheels of racing bicycles, off-road bicycles and city bicycles. Existing technology

[0002] A tyre for a bicycle wheel generally comprises a carcass structure rotating around a pair of bead cores at the beads and a tread band arranged in a radially outer position with respect to the carcass structure.

[0003] The carcass structure is designed to withstand the inflation pressure and support the weight of the bicycle and its rider. It comprises one or more carcass plies, each containing a plurality of appropriately oriented reinforcing cords. In the case of several carcass plies, they are tilted relative to each other to form a cross structure.

[0004] The bead core, also defined as the annular anchoring structure, ensures that the tire is anchored to the rim.

[0005] The tread belt is designed to ensure the tyre's grip on the asphalt or the ground (or generally on the rolling surface).

[0006] At a radially inner position of the carcass structure, an air chamber may be provided, into which pressurized air is introduced.

[0007] However, there are types of tyres known as "tubeless", i.e., without an inner tube. In these tyres, pressurized air acts directly on the carcass structure, and a layer known as a "liner" is provided, extending between a pair of bead cores and situated radially between the carcass structure and the tread band, or alternatively radially inside the carcass, to achieve airtightness. The carcass structure, the annular anchoring structure, and the rim are shaped in such a way that their mutual anchoring ensures airtightness.

[0008] There is another type of tire, called "tubeless ready," which has no inner tube and in which the liner is replaced by a ply extending from bead to bead between a pair of bead cores (called "bead to bead"). The bead to bead ply is located radially between the tread band and the carcass structure. Airtightness is ensured by a sealant that is interposed between the tire and the bicycle rim and that forms a thin, airtight membrane. The carcass structure, the annular anchoring structure, and the rim are shaped in such a way that their mutual anchoring ensures airtightness.

[0009] In order to prevent debris from penetrating into the carcass structure and thus puncturing any inner tube and / or damaging the carcass structure itself, a protective layer (also called "puncture-proof layer" or breaker) may be provided at a radially internal position of the tread band. This protective layer may be arranged radially on the inside of the carcass structure or radially between the carcass structure and the tread band. Summary of the Invention

[0010] The Applicant has observed that, in order to optimize the performance of a tyre for bicycle wheels, many requirements must be taken into account, which are interconnected and in some cases conflicting with one another.

[0011] In particular, the Applicant has observed that the requirements placed on tyres for bicycle wheels require good puncture resistance, ie good resistance of the tyre to punctures and tears, combined with perfect airtightness, good comfort and handling, low rolling resistance and low weight.

[0012] The problem facing the Applicant is that of producing a tire that best satisfies all the desired characteristics.

[0013] The Applicant has observed that, in tires intended for use without an inner tube (i.e. tubeless or tubeless-ready tires), the use, instead of the lining or "bead-to-bead" ply, of a layer made of an elastomeric compound comprising micron-sized fibrillated polymer fibers, placed in a radially internal position relative to the carcass structure, allows achieving the above-mentioned objectives.

[0014] In particular, the Applicant has observed that a layer made of an elastomeric compound containing micron-sized fibrillated polymer fibers, placed in a radially internal position relative to the carcass structure, allows to obtain good puncture resistance and good airtightness under all conditions of use, while maintaining good driving comfort and handling, and at a weight equal to or even lower than that of conventional tubeless or tubeless-ready tires.

[0015] In fact, the Applicant has observed that the presence of micron-sized fibrillated polymer fibers confers good airtightness to the elastomeric compound of the layer, thus ensuring the airtightness of the tire without requiring the use of halogenated butyl compounds typically used in the liners of tubeless tires.

[0016] Furthermore, the Applicant has observed that the presence of micron-sized fibrillated polymeric fibers confers excellent puncture resistance to the elastomeric compound of the layer.

[0017] Additionally, Applicants have observed that elastomeric compounds containing micron-sized fibrillated polymer fibers exhibit low hysteresis, indicative of reduced rolling resistance.

[0018] Finally, the Applicant observed that tires manufactured with an elastomeric compound comprising micron-sized fibrillated polymer fibers, placed in a radially inner position relative to the carcass structure, have equivalent, if not better, weight, comfort and handling characteristics compared to conventional tubeless or tubeless-ready tires.

[0019] Continuing with the experiments, the Applicant also observed that similar results were obtained by placing a layer made of an elastomeric compound comprising micron-sized fibrillated polymer fibers in a radially external position with respect to the carcass structure or interposed between the carcass plies.

[0020] Thus, in its first aspect, the present invention relates to a tyre for a bicycle wheel comprising:

[0021] - a carcass structure (2) comprising at least one carcass ply (3) having ends (3a) turned up around respective bead cores (4a, 4b) to form respective opposite beads (5a, 5b),

[0022] - a tread band (7) arranged in a radially external position relative to said carcass structure (2), and

[0023] - a layer (8) of vulcanized elastomeric material superimposed to the carcass structure (2) in a radially inner or outer position, or inserted in the carcass structure (2), said layer (8) of vulcanized elastomeric material extending axially from at least one bead (5a) to the opposite bead (5b),

[0024] The layer (8) of vulcanized elastomeric material is produced by vulcanization of a vulcanizable elastomeric compound containing micron-sized fibrillated polymer fibers. DETAILED DESCRIPTION

[0025] Throughout this specification and the following claims, the following definitions apply.

[0026] "Racing bicycle" means a high-performance bicycle used for road or track racing. These bicycles include those that comply with the rules set forth by the International Cycling Union (UCI) - Volume I - General Regulations of Cycling - Chapter 3: Equipment, Section 2. Also included within the scope of the present invention are recumbent bicycles, time trial bicycles, and / or triathlon bicycles. Also included are so-called fitness bicycles (racing bicycles used for recreational purposes).

[0027] "City bike" means a bicycle intended primarily for urban use, for urban travel on roads or predominantly asphalt bike paths (town bikes, city bikes, hiking bikes and touring bikes, as well as electric or pedal-assisted versions). These bikes are usually equipped with accessories designed to improve comfort and safety, such as good front and rear lighting for good visibility, a crankcase (or chain guard) to protect clothing from the chain, a luggage rack or front basket for light luggage, and are usually built with 26" or 28" wheels with intermediate covers, neither smooth like racing bikes nor with chocks like off-road bikes.

[0028] "Off-road bicycle" means a bicycle intended for use on generally uneven or irregular terrain, i.e., surfaces that vary greatly from one another and from asphalt, such as mud, sand, rock, compacted, soft ground, etc. These bicycles include those that meet the rules laid down by the International Cycling Union (UCI) for the various disciplines, and specifically include mountain bikes (MTBs) or all-terrain bikes (ATBs), conventionally divided into cross-country (XC), marathon, trail, all-mountain, enduro, freeride, and downhill categories, as well as fat bikes, cyclocross, and electric or pedal-assist versions.

[0029] By "equatorial plane" of a tire is meant the plane perpendicular to the tire's axis of rotation and which divides the tire into two symmetrically equal parts.

[0030] The terms “radial” and “axial” and the expressions “radially inner / outer” and “axially inner / outer” are used to refer to directions perpendicular to and parallel to the tire's axis of rotation, respectively.

[0031] The terms "circumferential" and "circumferentially" are used to refer to the direction of toroidal development of the tire, ie the direction in which the tire rolls, which corresponds to a direction lying in a plane coinciding with or parallel to the equatorial plane of the tire.

[0032] The term "elastomeric compound" is used to denote a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, this composition also contains additives such as a crosslinking agent and / or a plasticizer. Due to the presence of the crosslinking agent, this compound can be crosslinked (vulcanized) by heating.

[0033] As used herein, the term "elastomeric polymer" or "elastomer" means a vulcanizable natural or synthetic polymer that, after being vulcanized, is readily deformed by a force at room temperature and is capable of rapidly and forcefully recovering substantially its original shape and dimensions after the deforming force is removed (as defined in ASTM D1566-11, Standard Terminology for Rubber).

[0034] The term “cord” or the expression “reinforcement cord” is used to denote an element consisting of one or more thread-like elements (hereinafter also called “cords”), optionally coated with or incorporated into an elastomeric compound matrix.

[0035] The expression “reinforced belt-like element” means an elongated article having a flat cross-sectional profile and comprising one or more reinforcing cords extending parallel to the longitudinal development of the article and incorporated in or at least partially coated with at least one layer of an elastomeric compound matrix.

[0036] "Diameter" of a cord or thread means the thickness of the cord or thread as measured by BISFA E10 (International Bureau for Standardization of Man-Made Fibers, Internationally Recognized Test Methods for Steel Tire Cord, 1995 Edition).

[0037] "Density" or "cord density" of a layer or ply or fabric means the number of reinforcing cords per unit length present in that layer / ply / fabric. Density can be measured in TPI (threads per inch).

[0038] The "linear density" or "thread count" of a cord or thread means the weight of the reinforcing cord per unit length. The linear density can be measured in dtex (grams per 10 km length).

[0039] The expression "high elastic modulus fiber" means a fiber of a material having an elastic modulus or rigidity of not less than 30 GPa, such as aramid fiber and lyocell fiber.

[0040] For aramid fibers (AR), the elastic modulus is evaluated according to: BISFA - Test Methods for Aramid Yarns, 2002 Edition, Determination of Linear Density - Chapter 6, Determination of Tensile Properties - Chapter 7 - Test Procedures - Paragraph 7.5 - Initial Pre-Stretching Procedure.

[0041] For lyocell fibers, the elastic modulus is evaluated according to: BISFA - Test Methods for Viscose, Cupro, Acetate, Triacetate and Lyocell Filament Yarns - 2007 Edition, Determination of Tensile Properties - Chapter 7 - Tensile Test Conditions: Oven Dry Test - Table 7.1 - Test Procedure - Paragraph 7.5 - Oven Dry Test on Relaxed Specimens - Subparagraph 7.5.2.4.

[0042] The term "fitting diameter" of a tire means the diameter of the tire measured at the inside diameter of the bead core used to anchor the tire to the rim, as specified in ETRTO (European Tire and Rim Technical Organization).

[0043] “Axial development of the tread band or a portion thereof” means the development of the radially outermost profile of the tread band or a portion thereof, in a cross section of the tyre, passing through a plane containing the axis of rotation of the tyre.

[0044] “Axial development” of a tire means the development of the radially outermost contour of the tire, in a cross-section of the tire passing through a plane containing the axis of rotation of the tire, such axial development being measured between the ends of the tire beads.

[0045] “Width” of a tyre means the maximum axial extension of the tyre, such width being measured between the axially outermost points of the tyre according to Sg width of ETRTO Standard - Manual Standard 2022 - Cycle and Motorcycle Tyres - M5.

[0046] “Tread camber” of a tire means the camber measured by the camber radius of a portion of the tire's cross-sectional profile.

[0047] By "crown radius" of a portion of the profile of a tire cross section is meant the radius of the circle closest to the circumference of that profile portion.

[0048] By "rolling resistance" is meant the force opposing the rolling of a tire, and more generally, the energy dissipated per unit distance traveled by a rolling tire. The measurement of rolling resistance can be performed, for example, according to the method described in Example 5.

[0049] Tires for bicycle wheels

[0050] A tyre for a bicycle wheel generally comprises a carcass structure rotating around a pair of bead cores and a tread band arranged in a radially outer position with respect to the carcass structure.

[0051] A tyre for a bicycle wheel is characterized by a high transverse camber. The tyre may be designed to be mounted on the wheel of an off-road or urban racing bicycle.

[0052] Preferably, in the crown of a tire for a racing bicycle, the tire has a crown radius of 10 to 18 mm, more preferably 12 to 15 mm, inclusive, and in the side sections, the crown radius is 15 to 30 mm, more preferably 20 to 25 mm. For example, the crown radius may be approximately 13 mm, and the crown radius in the side sections may be approximately 25 mm.

[0053] Preferably, in the crown of a tire for off-road bicycles, the crown radius of the tire is between 15 mm and 50 mm, more preferably between 25 mm and 35 mm, inclusive, while in the side sections the crown radius is between 15 mm and 60 mm, more preferably between 30 mm and 40 mm. For example, the crown radius in the crown may be equal to about 30 mm, and the crown radius in the side sections may be equal to about 35 mm.

[0054] Preferably, in the case of a tire for a racing bicycle wheel, the tire has a weight less than about 400 g, preferably less than or equal to about 350 g.

[0055] Preferably, in the case of a tire for an off-road bicycle wheel, the tire has a weight greater than or equal to about 300 g, more preferably greater than or equal to about 350 g.

[0056] Preferably, in the case of a tyre for a city bicycle wheel, the tyre has a weight greater than approximately 250 g, preferably greater than or equal to approximately 350 g.

[0057] Preferably, in the case of a tire for a wheel of an off-road bicycle or a city bicycle, the tire has a weight less than or equal to about 2 kg, more preferably less than or equal to about 1.5 kg, even more preferably less than or equal to about 750 g, even more preferably less than or equal to about 650 g.

[0058] In a preferred embodiment, in the case of a tire for an off-road bicycle wheel, the tire has a weight of from about 300 g to about 2 kg, more preferably from about 350 g to about 1.5 kg, more preferably from about 350 g to about 750 g, more preferably from about 350 g to about 650 g (inclusive).

[0059] Carcass structure

[0060] Preferably, the carcass structure of the tire of the present invention comprises at least one carcass ply engaged at its axially opposite ends with a pair of annular anchoring structures (commonly referred to as bead cores) and comprising a plurality of reinforcing cords inclined at a first angle of about 30° to about 60° (inclusive) relative to the equatorial plane of the tire.

[0061] Preferably, the reinforcing cords of said at least one carcass ply are made of textile material, in order to limit as much as possible the weight of the tyre.

[0062] The reinforcing cords are preferably made of a textile material selected from nylon, rayon, PET, PEN, lyocell, aramid or combinations thereof in one or more ends, preferably 1 or 2 ends.

[0063] Specific examples of textile materials that can be used for the reinforcing cords are nylon 930 dtex / 1, nylon 470 dtex / 1, nylon 230 dtex / 1, and aramid 470 / 1 fibers, wherein the number 1 after dtex indicates the number of strands.

[0064] In the first embodiment of tire, carcass structure comprises single carcass ply.Hereinafter, this tire is also referred to as "single-ply tire".

[0065] In a second embodiment of the tire, the carcass structure comprises a first carcass ply comprising a first plurality of reinforcing cords inclined at said first angle relative to said equatorial plane, and a second carcass ply arranged in a radially external position to the first carcass ply and comprising a second plurality of reinforcing cords inclined at said first angle relative to said equatorial plane on the side opposite to said first plurality of cords, thereby defining a crossed, preferably two-ply, carcass structure. Such tires are hereinafter also referred to as "two-ply tires".

[0066] In an alternative embodiment, the carcass structure may comprise more than two carcass plies, each carcass ply being arranged to define with an adjacent radially inner carcass ply a cross structure identical to that described above with respect to the first and second carcass plies.

[0067] The reinforcing cords are inclined at an angle of about 30° to about 60°, inclusive, relative to the equatorial plane of the tire.

[0068] Preferably, in the case of a single-ply tire, the aforementioned angle is about 45°, in which case the wings may exhibit an inclination parallel to one another in the crown and inversely inclined relative to the inclination of the reinforcing elements of the first carcass layer (radially innermost) close to the equatorial plane.

[0069] On the other hand, in the case of a two-ply tire, a first carcass ply comprises a plurality of reinforcing cords inclined at an angle preferably ranging from about 30° to about 60° (inclusive) relative to the equatorial plane of the tire, and a second carcass ply, arranged radially external to the first carcass ply, comprises a second plurality of reinforcing cords inclined at the same angle relative to the equatorial plane, on the opposite side relative to the reinforcing cords of the first carcass ply. In the latter case, the reinforcing cords lie on respective planes inclined relative to the axis of rotation, thereby defining a cross carcass structure.

[0070] In the case of tires for wheels for racing or city bicycles, preferably, the single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a tire with two or more carcass plies) has a density greater than or equal to about 20 TPI, more preferably greater than or equal to about 30 TPI, even more preferably greater than or equal to about 60 TPI, even more preferably greater than or equal to about 120 TPI.

[0071] In the case of tires for wheels for racing or city bicycles, preferably, the single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a tire with two or more carcass plies) has a density less than or equal to about 360 TPI, more preferably less than or equal to about 300 TPI, even more preferably less than or equal to about 240 TPI, even more preferably less than or equal to about 200 TPI.

[0072] In the case of tires for off-road bicycle wheels, preferably, the single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a tire with two or more carcass plies) has a density greater than or equal to about 20 TPI, more preferably greater than or equal to about 60 TPI.

[0073] In the case of tires for off-road bicycle wheels, preferably, the single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a tire with two or more carcass plies) has a density of less than or equal to about 150 TPI, more preferably less than or equal to about 120 TPI.

[0074] Preferably, in the case of a two-ply (or more than two carcass plies) tire, the second carcass ply (or at least the additional carcass ply) has substantially the same density as the first carcass ply.

[0075] Preferably, the reinforcing cords of a single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a two-ply or more than two carcass ply tire) have a diameter less than or equal to about 0.55 mm, more preferably less than or equal to about 0.35 mm.

[0076] Preferably, the reinforcing cords of a single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a two-ply or more than two carcass ply tire) have a diameter greater than or equal to about 0.10 mm, more preferably greater than or equal to about 0.12 mm.

[0077] Preferably, the reinforcing cords of a single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a two-ply tire or tires with more than two carcass plies) have a linear density greater than or equal to about 110 dtex, more preferably greater than or equal to about 200 dtex.

[0078] Preferably, the reinforcing cords of a single carcass ply (in the case of a single-ply tire) or each carcass ply (in the case of a two-ply or more than two carcass ply tire) have a linear density of less than or equal to about 1300 dtex, more preferably less than or equal to about 940 dtex.

[0079] Layer comprising fibrillated polymer fibers

[0080] According to the present invention, the tire for bicycle wheels comprises a layer of vulcanized elastomeric material superimposed on a carcass structure in a radially inner or outer position or inserted in the carcass structure, wherein said layer of vulcanized elastomeric material is produced by vulcanization of a vulcanizable elastomeric compound containing micron-sized fibrillated polymer fibers.

[0081] The elastomeric layer according to the invention extends symmetrically with respect to the equatorial plane of the tyre at the carcass structure.

[0082] According to a preferred embodiment, the elastomeric layers according to the invention extend from bead to bead up to 100% of the axial development of the tyre, overlapping in a radially internal position of the carcass structure, such as Figure 2-5 As shown, and covering the carcass wing at the bead core.

[0083] According to an alternative embodiment, the elastomeric layer according to the invention extends from bead to bead to 100% of the axial development of the tire, itself inserted in the carcass structure, such as Figure 6 and7 Specifically, Figure 6 In the embodiment of the present invention, the elastomer layer is interposed between the two turned-up ends of the carcass ply in a radially outer position relative to the bead core, terminating at the bead core. Figure 7 In the embodiment, the layer according to the invention is inserted in the carcass structure in a radially inner position with respect to the bead core, behind the carcass wings surrounding the bead core.

[0084] According to other alternative embodiments, the elastomeric layers according to the invention extend from bead to bead up to 100% of the axial development of the tyre, overlapping in a radially external position of the carcass structure, such as Figure 8 As shown, it terminates at the bead core.

[0085] Preferably, the thickness of the elastomeric layer according to the invention is from 0.1 mm to 0.7 mm, more preferably from 0.2 mm to 0.6 mm, advantageously from 0.3 mm to 0.5 mm.

[0086] The vulcanizable elastomeric compound of the elastomeric layer according to the invention comprises at least one diene elastomeric polymer, as described hereinafter in this description, and one or more types of micron-sized fibrillated polymer fibers, as described hereinafter in this description.

[0087] Preferably, the elastomeric layer according to the present invention comprises micron-sized fibrillated polymer fibers in an amount equal to or greater than 3 phr, preferably equal to or greater than 4 phr, more preferably equal to or greater than 5 phr.

[0088] Preferably, the elastomeric layer according to the present invention comprises micron-sized fibrillated polymer fibers in an amount equal to or lower than 30 phr, preferably equal to or lower than 25 phr, more preferably equal to or lower than 20 phr.

[0089] Advantageously, the elastomeric layer according to the invention comprises micron-sized fibrillated polymer fibers in an amount ranging from 5 to 20 phr, preferably from 5 to 10 phr.

[0090] Micron-sized fibrillated polymer fibers

[0091] Preferably, the micron-sized fibrillated polymer fibers are polymer fibers having a melting point of at least 170°C, preferably at least 190°C.

[0092] The fibrillated polymer fibers that can be used in the present invention are represented, for example, by the following: aramid fibers (e.g. of Pulp or Teijin Aramid pulp), polyester fibers (such as Engineered fibres Technology pulp), acrylic fibers (such as Engineered Fibers Technology's Fibrillated fibers and Sterling fibers pulp), microfibrillated cellulose fibers (e.g. WMFC Q_ECO from WEIDMANNfibre TECHNOLOGY) and vegetable fibers (e.g. ).

[0093] The term "fibrillated polymer fibers" means that the fibers themselves have an irregular and branched shape, with a main trunk from which thinner filaments of the frayed fibers branch out, which gives the fibers a larger surface area and better anchoring and bonding characteristics than non-fibrillated fibers. "Fibrillated polymer fibers" are obtained from non-fibrillated fibers by mechanical, thermal and chemical processes.

[0094] The term "micrometer-sized" with respect to fibers means that the fibers have a diameter or largest cross-sectional dimension less than 100 μm (micrometers) and typically greater than 500 nm (nanometers).

[0095] Aramid fibers are synthetic fibers obtained from aromatic polyamides, i.e., a specific type of nylon obtained by condensing aromatic diamines and aromatic dicarboxylic acids in solution. Aramid fibers and methods for their preparation are known in the literature and are described, for example, in patents US Pat. Nos. 3,006,899, 3,063,966, 3,094,511, 3,287,323, 3,322,728, 3,349,062, 3,354,127, 3,380,969, 3,671,542, and 3,951,914.

[0096] It is a specific aramid fiber obtained by condensing 1,4-phenylenediamine (p-phenylenediamine) monomer and terephthaloyl chloride in solution.

[0097] The pulp is obtained by Proprietary technology enables Materials obtained by fibrillation of fibers. The pulp usually has a total length of 0.5-1 mm and a specific surface area of ​​7-11 m 2 / g and fibers with a main fiber diameter of 10 to 18 microns (μm).

[0098] Polyester fibers are synthetic fibers obtained from polyester, or polymers obtained by condensation of monomers containing at least one carboxyl group (—COOH) and at least one hydroxyl group (—OH).

[0099] It is a fully aromatic polyester with melt-crystalline liquid characteristics, obtained by the condensation of 4-hydroxybenzoic acid and 6-hydroxy-2-carboxynaphthoic acid, produced by Kuraray and Celanese.

[0100] The pulp is made by Materials obtained by fibrillation of fibers, for example from Engineered Fibers Technology. Pulps typically have fibers with a total length of 1 to 6 mm and a fibril diameter of a few micrometers.

[0101] Acrylic fibers are synthetic fibers obtained from polyacrylates, or polymers obtained by polymerization, generally free radical polymerization, of acrylic monomers and in particular acrylonitrile.

[0102] “ The pulp is obtained by fibrillating a specific polyacrylate grade of Engineered Fibres Technology, with main fibres of approximately 20 μm in diameter and up to 7 mm in length, fibrils of approximately 1 μm in diameter and up to 50 mm in length. 2 / g specific surface area.

[0103] Microfibrillated cellulose fibers are natural fibers obtained by fibrillation of cellulose, for example from WEIDMANN fiber TECHNOLOGY, typically having a length of 0.05 to 1 mm and a fibril diameter typically less than 1 μm.

[0104] ECCO Gleittechnik Fibrillated natural fibers are obtained by mechanically treating plant fibers and have a maximum length of 7-8 mm and about 1 m 2 / g specific surface area.

[0105] The fibrillated polymer fibers preferably used in the present invention are composed of a trunk having a length of about 0.05 mm to about 8 mm, preferably about 0.1 mm to about 2 mm, a diameter of 5 to 30 μm, and an aspect ratio greater than 30, from which a plurality of fibrils having a diameter smaller than the trunk diameter branch out. The fibrillated polymer fibers have a length of about 0.5 to about 60 μm. 2 The specific surface area of ​​the fibers is 10 to about 200 times greater than that of the equivalent but non-fibrillated polymer fibers.

[0106] Elastomer compounds

[0107] The vulcanizable elastomeric compound that can be used in the present invention comprises 100 phr of at least one diene elastomeric polymer.

[0108] Preferably, the diene elastomeric polymer that can be used in the present invention can be chosen from those usually used in sulfur-crosslinkable elastomeric compounds, which are particularly suitable for the production of tires and tire components, i.e. from elastomeric polymers or copolymers having unsaturated chains, characterized in that they have a glass transition temperature (Tg) generally below 20° C., preferably between 0° C. and −110° C. These polymers or copolymers can be of natural origin or can be obtained by solution, emulsion or gas phase polymerization of one or more conjugated dienes, optionally mixed with at least one comonomer chosen from monovinylarenes and / or polar comonomers in an amount not exceeding 60% by weight.

[0109] The conjugated diene generally contains 4 to 12, preferably 4 to 8, carbon atoms and can be selected, for example, from the following: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene and mixtures thereof. 1,3-Butadiene and isoprene are particularly preferred.

[0110] The monovinyl aromatic hydrocarbon which may optionally be used as a comonomer generally contains 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, alkylaryl or arylalkyl 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.

[0111] Polar comonomers which may optionally be used may be selected, for example, from vinylpyridine, vinylquinoline, acrylates and alkyl acrylates, nitriles or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

[0112] Preferably, the diene elastomeric polymer that can be used in the present invention can be chosen, for example, from cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (in particular polybutadiene with a high 1,4-cis content), isoprene / isobutylene copolymers, optionally halogenated, 1,3-butadiene / acrylonitrile copolymers, styrene / 1,3-butadiene copolymers, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers and mixtures thereof.

[0113] According to a preferred embodiment, the vulcanizable elastomeric compound comprises at least 10% by weight, preferably from 20% to 100% by weight, of natural rubber relative to the total weight of the at least one diene elastomeric polymer.

[0114] The above-mentioned vulcanizable elastomeric compound may optionally contain at least one elastomeric polymer (a') of one or more monoolefins and olefin comonomers or their derivatives. The monoolefins may be selected from: ethylene and α-olefins generally containing 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and mixtures thereof. The following are preferred: copolymers selected from ethylene and α-olefins, optionally with dienes; isobutylene homopolymers or copolymers thereof with small amounts of dienes, optionally at least partially halogenated. The optional diene generally contains 4 to 20 carbon atoms and is preferably selected from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, vinyl norbornene and mixtures thereof. Among them, the following are particularly preferred: ethylene / propylene (EPR) copolymers or ethylene / propylene / diene (EPDM) copolymers; polyisobutylene; butyl rubber; halogenated butyl rubber, in particular chlorinated butyl rubber or brominated butyl rubber; or mixtures thereof.

[0115] It is also possible to use diene elastomeric polymers or elastomeric polymers functionalized by reaction with suitable end-capping or coupling agents. In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of organometallic initiators, in particular organolithium initiators, can be functionalized by reacting residual organometallic groups originating from the initiator with suitable end-capping or coupling agents, such as imines, carbodiimides, alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

[0116] According to aspects of the present invention, micron-sized fibrillated polymer fibers (e.g. The syrup) is incorporated into the diene elastomeric polymer together with other components to produce a vulcanizable elastomeric compound, with which a layer of vulcanized elastomeric material is formed which is arranged in a radial position inside the carcass structure.

[0117] Preferably, the fibrillated polymer fibers are present in the elastomeric compound in an amount ranging from 0.1 phr to 20 phr, preferably from 0.5 phr to 10 phr, more preferably from 1 phr to 5 phr.

[0118] Preferably, the vulcanizable elastomeric compound comprises a reinforcing filler.

[0119] Preferably, the reinforcing filler is chosen from carbon black, precipitated amorphous silica, amorphous silica of natural origin, preferably unmodified silicate fibers and mixtures thereof.

[0120] Preferably, the reinforcing filler is present in the vulcanizable elastomeric compound in an amount ranging generally from 1 phr to 120 phr, preferably from 20 phr to 90 phr.

[0121] Preferably, the total amount of reinforcing fillers present in the vulcanizable elastomeric compound is at least 20 phr, more preferably at least 30 phr.

[0122] Preferably, the total amount of reinforcing fillers present in the vulcanizable elastomeric compound is from 20 phr to 120 phr, more preferably from 30 phr to 90 phr.

[0123] Preferably, the reinforcing filler is or contains a filler having a thickness of not less than 20 m 2 / g of carbon black with a specific surface area (determined by STSA - Statistical Thickness Surface Area according to ISO 18852:2005).

[0124] Preferably, the carbon black reinforcing filler is present in the vulcanizable elastomeric compound in an amount ranging from 1 phr to 120 phr, preferably from 20 phr to 90 phr.

[0125] Advantageously, the reinforcing filler is or comprises a silica chosen from fumed silica or preferably precipitated silica, the BET specific surface area of ​​which (measured according to ISO 5794 / 1 standard) is 50 m 2 / g to 500m 2 / g, preferably 70m 2 / g to 200m 2 / g.

[0126] The vulcanizable elastomeric compound comprises at least one vulcanizing agent.

[0127] The vulcanizing agent most advantageously used is sulfur, or alternatively, sulfur-containing molecules (sulfur donors), together with accelerators, activators and / or retarders known to those skilled in the art.

[0128] Sulfur or its derivatives may advantageously be chosen, for example, from: (i) soluble sulfur (crystalline sulfur); (ii) insoluble sulfur (polymeric sulfur); (iii) sulfur dispersed in oil (such as 33% sulfur from Eastman, known under the trade name Crystex OT33); (iv) sulfur donors, such as caprolactam disulfide (CLD), bis[(trialkoxysilyl)propyl]polysulfide, dithiophosphates; and mixtures thereof.

[0129] The vulcanizing agent is present in the vulcanizable elastomeric compound in an amount of 0.1 to 15 phr, preferably 0.5 to 10 phr, more preferably 1 to 7 phr.

[0130] Preferably, the vulcanizing agent is used in combination with accelerators and activators known to those skilled in the art.

[0131] Typically used accelerators may be selected from the group consisting of dithiocarbamates, guanidines, thioureas, thiazoles, sulfonamides, thiurams, amines, xanthates and mixtures thereof.

[0132] Preferably, the vulcanization accelerator is present in the vulcanizable elastomeric compound in an amount ranging from 0.1 to 8 phr, preferably from 0.3 to 6 phr.

[0133] Particularly effective activators are zinc compounds, and in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms, such as zinc stearate, which are preferably formed in situ in the vulcanizable elastomeric compound from ZnO and fatty acids, as well as Bi2O3, PbO, Pb3O4, PbO2 or mixtures thereof.

[0134] Preferably, the vulcanization activator is present in the vulcanizable elastomeric compound in an amount ranging from 0.2 to 15 phr, preferably from 0.5 to 10 phr.

[0135] The vulcanizable elastomeric compound may optionally also comprise at least one silane coupling agent capable of interacting with the silica and / or silicate optionally present as reinforcing filler and binding it to the diene elastomeric polymer during vulcanization.

[0136] Preferably, the silane coupling agent that can be used in the present invention is selected from those having at least one hydrolyzable silane group, which can be represented, for example, by the following general formula (I):

[0137] (R)3Si-C n H 2n -X (I)

[0138] wherein the R groups may be the same or different and are selected from: alkyl, alkoxy or aryloxy groups or halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group or a halogen atom; n is an integer from 1 to 6, inclusive; and X is a group 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, inclusive, and the R group is as defined above.

[0139] Among the silane coupling agents, bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide are particularly preferred. The coupling agents can be used as such or as a suitable mixture with an inert filler, such as carbon black, to facilitate their incorporation into the vulcanizable elastomeric compound.

[0140] Preferably, the silane coupling agent is present in the vulcanizable elastomeric compound in an amount of 0.1 phr to 20 phr, preferably 0.5 phr to 10 phr.

[0141] The vulcanizable elastomer compound may contain other commonly used additives selected based on the specific application intended for the compound. For example, the compound may be mixed with antioxidants, anti-aging agents, plasticizers, adhesives, antiozonants, modifying resins, or mixtures thereof.

[0142] Specifically, in order to further improve processability, the vulcanizable elastomeric compound can be mixed with at least one plasticizer, which is generally selected from mineral oils, vegetable oils, synthetic oils, low molecular weight polymers and mixtures thereof, such as aromatic oils, naphthenic oils, phthalates, soybean oil and mixtures thereof. The amount of plasticizer is generally 0 phr to 70 phr, preferably 5 phr to 30 phr.

[0143] The above-mentioned vulcanizable elastomeric compound can be prepared by mixing the polymer components with reinforcing fillers and other optional additives according to techniques known in the industry. Mixing can be done, for example, using an open mixer of the open mill type or a mixer with tangential rotors. Or with an interpenetrating rotor (Intermix) type closed mixer, or in a Ko-Kneader TM type Or it is carried out in a twin-screw or multi-screw continuous mixer.

[0144] tread belt

[0145] The tread band of the tire of the present invention comprises a layer of vulcanized elastomeric compound made with the vulcanizable elastomeric compound described above.

[0146] Preferably, the tread band of the tyre may have a thickness of from about 0.8 to about 8 mm, depending on the type of tyre.

[0147] Preferably, the tread band has a width equal to or less than 50% of the axial development of the tyre, more preferably equal to or less than 45% of the axial development of the tyre.

[0148] Preferably, the tread band has a width equal to or greater than 30% of the axial development of the tyre, more preferably equal to or greater than 35% of the axial development of the tyre.

[0149] Preferably, the tread band has a width of 30% to 50% of the axial development of the tire, more preferably 35% to 50% of the axial development of the tire, even more preferably 30% to 45% of the axial development of the tire, even more preferably 35% to 45% of the axial development of the tire, for example about 40% of the axial development of the tire.

[0150] In tires intended for racing bicycle wheels, the tread band is usually smooth. In tires intended for city bicycle wheels, the tread band comprises grooves and notches that are more or less angled relative to one another, so as to promote good grip on asphalt in all weather conditions of use. In tires intended for off-road bicycle wheels, the tread band comprises a plurality of blocks that are spaced relatively far apart from one another, so as to promote good grip on rough terrain.

[0151] Protective layer or "buffer"

[0152] Advantageously, the protective layer may be arranged in a radially inner position with respect to the carcass structure, or interposed radially between the carcass structure and the tread band.The protective layer is also called a "breaker layer".

[0153] Preferably, said protective layer has a width equal to or less than 50% of the axial development of the tyre.

[0154] Preferably, the protective layer has a width equal to or greater than 20% of the axial development of the tyre, more preferably equal to or greater than 22% of the axial development of the tyre.

[0155] Preferably, said protective layer has a width ranging from 20% to 45% of the axial development of the tire, more preferably from 22% to 40% of the axial development of the tire, even more preferably from 22% to 35% of the axial development of the tire.

[0156] In order to allow sufficient puncture resistance of the tyre while accommodating its weight, the Applicant has observed that it is advantageous if said protective layer has a width equal to, and preferably less than, the axial development of the tread band.

[0157] Preferably, the protective layer has a width equal to or less than 95%, more preferably equal to or less than 90%, even more preferably equal to or less than 85% of the axial development of the tread band.

[0158] Preferably, the protective layer has a width equal to or greater than 50% of the axial development of the tread band, more preferably equal to or greater than 60% of the axial development of the tread band, more preferably equal to or greater than 70% of the axial development of the tread band, even more preferably equal to or greater than 75% of the axial development of the tread band.

[0159] Preferably, the protective layer has a width of 50% to 95% of the axial development of the tread band, more preferably 50% to 90% of the axial development of the tread band, even more preferably 50% to 85% of the axial development of the tread band.

[0160] Preferably, the protective layer is arranged symmetrically with respect to the equatorial plane.

[0161] Reinforced belt elements or "chafers"

[0162] At the annular anchoring structure, also called bead core, a reinforcing belt-like element may be applied in a radially outer position with respect to the carcass structure. The reinforcing belt-like element is also called a "chafer".

[0163] When the tire is mounted on such a rim, this reinforcing belt-like element is interposed radially between the carcass ply and the rim.

[0164] The reinforcing belt-like elements have a limited axial extension, preferably between 2% and 15% of the axial development of the tire. The purpose of the reinforcing belt-like elements is to allow adhesion and friction with the rim and also to avoid possible damage due to wear of the carcass ply after friction with the rim. DETAILED DESCRIPTION

[0165] Other features and advantages of the tire of the present invention will appear more clearly from the following detailed description of some of its preferred embodiments, which is made with reference to the accompanying drawings, in which:

[0166] - Figure 1 is a schematic radial cross-sectional view of a tire for a bicycle wheel as is conventionally known in the art;

[0167] - Figure 2-8 A possible schematic construction diagram of an embodiment of a tyre according to the invention is shown.

[0168] exist Figure 1 In the drawings, reference numeral 100 represents a tire for a bicycle wheel. This tire can be designed to be mounted on the wheel of a racing bicycle or an off-road bicycle (mountain bike or MTB) or an urban bicycle (town bike or city bike).

[0169] Figure 1 The tyre 100 of WO 2007 / 051448 PCT / EP2007 / 000444 comprises a carcass structure 2 comprising a crown portion 2a preferably arranged symmetrically with respect to the equatorial plane XX and an opposite side portion 2b arranged on an axially opposite side to the crown portion 2a.

[0170] In the embodiment shown in the drawings, the carcass structure 2 comprises a single carcass ply 3 (single-ply tyre), but other embodiments are provided (not shown) in which the carcass structure 2 comprises several carcass plies, preferably two (two-ply tyre).

[0171] Unless expressly stated otherwise, the description below with reference to the carcass plies shown in the accompanying drawings applies both to a single carcass ply of a single-ply tire and to each carcass ply of a two-ply tire.

[0172] The carcass ply 3 extends axially from a side 2 b of the carcass structure 2 to an opposite side 2 b.

[0173] The carcass ply 3 is engaged at its respective axially opposite ends 3a with respective annular anchoring structures 4a and 4b, generally called "bead cores".

[0174] Each end portion 3a of the carcass ply 3 is turned up around a respective bead core 4a and 4b.

[0175] The bead cores 4a and 4b are preferably made of textile fibers having a high elastic modulus such as aramid fibers (a general name for aromatic polyamide fibers) or metal wires such as steel.

[0176] A conical elastomeric filler may be applied to the outer peripheral edges of the bead cores 4a and 4b, which occupy the space defined around the bead cores by the carcass wings.

[0177] The area of ​​the tire containing the bead cores 4a and 4b and the optional elastomeric filler forms the so-called "bead". Figure 1 Indicated as a whole by the reference numerals 5a and 5b, they are intended to anchor the tyre on a corresponding mounting rim (not shown) by elastic forced fitting.

[0178] On the turned-up end 3a of the carcass ply 3, a reinforcing strip element ( Figure 1 When the tyre is mounted on such a rim, this reinforcing belt-like element is interposed between the carcass ply 3 and the rim of the wheel.

[0179] refer to Figure 1 In the tire, the two edges of the carcass wings 3a each extend to cover the crown 2a, overlapping to form three carcass layers with a first radially inner carcass layer in the crown 2a.

[0180] In a radially outer position with respect to the carcass structure 2 a tread band 7 is provided, whereby the tyre 100 contacts the road surface.

[0181] The tread band 7 extends axially and in a radially outer position relative to the crown structure 2a over a width that may be smaller than or at least equal to that of the crown structure 2a.

[0182] If the tire 100 is intended for a racing bicycle wheel, it typically has an axial dimension (also referred to herein as "axial extension" or "width") preferably from about 19 mm to about 38 mm, more preferably from about 19 mm to about 32 mm, and even more preferably from about 23 mm to about 28 mm (inclusive). Tires 100 intended for various types of bicycles preferably have an outer diameter (expressed in inches, according to English nomenclature) of from about 24 inches to about 29 inches, more preferably from about 26 inches to about 29 inches (inclusive). Accordingly, the fitting diameter according to ISO or ETRTO specifications is preferably about 559 mm (which corresponds to an outer diameter of 26 inches for mountain bikes (MTBs), or about 571 mm (which corresponds to an outer diameter of 26 inches for road racing bikes), or about 584 mm (which corresponds to an outer diameter of 27.5 inches for mountain bikes), or about 622 mm (which corresponds to an outer diameter of 28 inches for road racing bikes and an outer diameter of 29 inches for mountain bikes), or about 630 mm (which corresponds to a specific outer diameter of 27 inches for road racing bikes).

[0183] For example, Figure 1 The first embodiment of the tire 100 has an outer diameter of 26 inches, the second embodiment has an outer diameter of 28 inches, and the third embodiment has an outer diameter of 29 inches.

[0184] In the case of a tire designed for a wheel of a mountain bike (MTB), the tire 100 has an axial dimension preferably of about 37 mm to about 120 mm (inclusive).

[0185] A tyre 100 intended for a city bicycle wheel generally has an axial dimension of preferably about 32 mm to 62 mm (inclusive).

[0186] The tire 100 for an off-road bicycle or a city bicycle preferably has an outer diameter of about 26 inches to about 29 inches (inclusive). Accordingly, the fitting diameter according to ISO or ETRTO specifications is preferably about 559 mm to about 622 mm.

[0187] For example, Figure 1 The first embodiment of the tire 100 has an outer diameter of 26 inches (mounted diameter equal to 559 mm), the second embodiment has an outer diameter of 28 inches (mounted diameter equal to 584 mm), and the third embodiment has an outer diameter of 29 inches (mounted diameter equal to 622 mm).

[0188] Figure 2-8 Different construction diagrams of a tire according to the invention are shown.

[0189] exist Figure 2, the end portions 3 a of the carcass ply 3 partially overlap each other at the tread 7 and the protective layer 6 .

[0190] exist Figure 2 In the example of , a reinforcing strip element 10 is applied to the turned-up end 3 a of the carcass ply 3 and to the layer 8 , close to the bead core 5 .

[0191] exist Figure 2 In the figure, the layer 8 of elastomeric material containing fibrillated polymer fibers is superimposed on the carcass ply 3 in a radially inner position from the bead core 4a to the opposite bead core 4b, wherein the end portions 8a and 8b are interrupted at wings around the respective bead cores 4a and 4b and the reinforcing strip elements 10.

[0192] Figure 3 The structural diagram and Figure 2 The figure differs from that of FIG. 1 in that the ends 3 a of the carcass ply 3 are axially spaced from each other.

[0193] Figure 4 The structural diagram in Figure 2 The figure in FIG. 1 differs from FIG. 2 in that it does not include the protective layer 6 .

[0194] Figure 5 The structural diagram in Figure 2 The figure in FIG. 1 differs in that it does not contain reinforcing strip elements 10 .

[0195] Figure 6 The structural diagram and Figure 2 The figure differs in that it comprises a layer 8 of elastomeric material containing fibrillated polymer fibers, which layer 8 is inserted between the two ends 3a and 3b of the carcass ply 3 in a radially external position relative to the bead cores 4a and 4b, extending from bead to bead (5a, 5b), wherein the ends 8a and 8b are interrupted at a reinforcing strip element 10 before surrounding the wings of the respective bead cores 4a and 4b.

[0196] Figure 7 The structural diagram and Figure 2 The figure differs in that it comprises a layer 8 of elastomeric material containing fibrillated polymer fibers, which is inserted in the carcass structure 2 in a radially internal position relative to the bead core, extending from bead to bead (5a, 5b), with the end portions 8a and 8b being interrupted at the wings around the respective beads 4a and 4b and the reinforcing strip element 10.

[0197] Figure 8 The structural diagram and Figure 2in that it comprises a layer 8 of elastomeric material containing fibrillated polymer fibers, superimposed on the carcass structure 2 in a radially external position, extending from bead to bead (5a, 5b), with the end portions 8a and 8b being interrupted at a reinforcing strip element 10 before surrounding the wings of the respective bead cores 4a and 4b.

[0198] The present invention will be further described below through a number of examples, which are provided for illustration only and do not limit the present invention in any way.

[0199] Example 1 - Preparation test

[0200] The elastomeric compound used for making the layer of elastomeric material radially internal with respect to the carcass structure was prepared as follows (the amounts of the various components are given in phr).

[0201] Compound R1 represents a reference compound for conventional liners comprising a mixture of natural rubber and halogenated butyl rubber; Compound I2 represents a compound of the present invention comprising micron-sized fibrillated polymer fibers dispersed in natural rubber; and Compound C3 represents a comparative compound comprising natural rubber alone.

[0202] All components except sulfur, retarder (PVI) and accelerator (CBS) were mixed together in an internal mixer (model Pomini PL 1.6) for about 5 minutes (step 1). Once the temperature reached 145 ± 5 ° C, the elastomer compound was unloaded. Then sulfur, retarder and accelerator (CBS) were added and mixed in an open roll mixer (step 2).

[0203] Table 1

[0204] Components R1 I2 C3 natural rubber 30 90 100 Halogenated butyl rubber 70 - - Fibrillated polymer fibers - 16.7 - CB1 13 60 60 CB2 70 - - stearic acid 2 0.8 0.8 zinc oxide 5 6.5 6.5 Oil 7 - - 6PPD 0.5 2 2 CBS 1 1 1 PVI - 0.3 0.3 sulfur 1.8 6 6

[0205]

[0206]

[0207] Example 2 - Preparation of Tire

[0208] Then prepare according to Figure 2 The structure shown is a size 28-622 racing bicycle tire comprising a layer of elastomeric material located radially to the inside relative to the carcass structure, made with the elastomeric compound described in Example 1. For all tires, the thickness of the layer of elastomeric material located radially to the inside relative to the carcass structure is about 0.35 mm.

[0209] The tire PR1 comprises a layer made with compound R1, the tire PI2 comprises a layer made with compound I2 and the tire PC3 comprises a layer made with compound C3.

[0210] In all cases, the carcass structure is provided with a rubberized carcass ply of 0.4 mm total thickness, made of nylon 6.6 with a density of 120 TPI and a linear density of 235 dtex, turned up on an aramid bead core and provided with two rubberized non-abrasive square fabrics at the edges.

[0211] The tire is manufactured with a protective layer 6 (such as Figure 2 As shown, extending over the entire axial direction of the tread band 7), the protective layer is made of a square fabric, including aramid fiber reinforcement cords in the weft direction (initial modulus of 75 GPa, linear density of 220 dtex and density of 55 TPI), and PET in the warp direction (linear density of 330 dtex and density of 80 TPI, oriented at an angle of 45° with respect to the equatorial plane of the tire).

[0212] Example 3 - Properties of Compounds

[0213] The elastomeric materials prepared in the previous examples were vulcanized to obtain test specimens on which analytical characterization and evaluation of dynamic mechanical properties were carried out.

[0214] Unless otherwise stated, vulcanization was carried out in a mold in a hydraulic press at 170° C. and at a pressure of 200 bar for about 10 minutes.

[0215] IRHD hardness : IRHD hardness is measured at 23° C. on a vulcanized elastomeric composition according to ISO 48:2007 standard.

[0216] Static modulus Static mechanical properties were measured on three dumbbell specimens at 23° C. according to ISO 37:2005. Specifically, tensile stress, elongation at break (AR) and load at break (CR) were measured on samples of the vulcanized elastomeric composition at different elongation levels (10%, 50%, 100% and 300%, sequentially designated as CA0.1, CA0.5, CA1 and CA3).

[0217] Dynamic modulus Dynamic mechanical properties were measured using an Instron dynamic device in compression and tension operation using the following method: a cylindrical sample of the vulcanized elastomeric composition (length = 25 mm; diameter = 18 mm) was preloaded under compression to a longitudinal deformation of 25% relative to the initial length and maintained at a predetermined temperature (23° C. or 70° C.) during the test, and the sample was subjected to a dynamic sinusoidal voltage with an amplitude of ±3.5% relative to the preloaded length and a frequency of 10 Hz.

[0218] The dynamic mechanical properties are expressed as dynamic elastic modulus (E'), viscous dynamic modulus (E") and tan delta (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').

[0219] Penetration : The permeability is measured according to ISO 2782:2006 standard at 23° C. on test specimens with a diameter of 120 mm and a nominal thickness of 1 mm, which are conditioned at 23° C. for 16 hours.

[0220] The results are summarized in Table 2 below.

[0221] Table 2

[0222]

[0223] The data in Table 2 show that, compared to the reference compound R1 comprising halogenated butyl rubber, the inventive compound I2 (containing no halogenated butyl rubber but containing fibrillated polymer fibers) exhibits improved mechanical characteristics, excellent dynamic properties, in particular reduced hysteresis at both 23°C and 70°C, and a permeability sufficient to ensure airtightness in bicycle tires. In contrast, the comparative compound C3 (containing no halogenated butyl rubber and without the addition of fibrillated polymer fibers), despite exhibiting good mechanical properties and low hysteresis, exhibits a permeability insufficient to ensure airtightness in bicycle tires.

[0224] Example 4 - Puncture resistance test

[0225] Samples of the vulcanized compounds I2 and C3 from Example 2 with dimensions of approximately 200×200×1 mm were subjected to a puncture test according to the DIN EN 14477 standard (adapted to the test conditions described below).

[0226] This test allows the evaluation of the resistance of a material to perforation by subjecting it to the action of a penetrator (a punch or screwdriver that penetrates the sample at a constant speed). The test is performed with the aid of a dynamometer capable of recording the applied force (measured in N at different penetration depths) and the elastic deformation of the material (measured in mm).

[0227] Therefore, this applied force is an indication of the resistance of the sample to penetration by foreign bodies (the higher the force value, the greater the resistance of the material); and the elastic deformation is an indication of the ability of the material to absorb penetration by foreign bodies (for the same force, the higher the value of the deformation, the more elastic the material).

[0228] The test was performed in a conditioning environment at a controlled temperature of 23 ± 2° C. The samples were conditioned for 48 hours prior to testing.

[0229] The test conditions used are as follows:

[0230] Test speed = 50 mm / min;

[0231] Initial distance between the tip of the penetrator and the tire = 10 mm;

[0232] Applied preload = 0.5N.

[0233] The test was performed on 10 samples and the average values ​​obtained are given in Table 3 below.

[0234] Table 3

[0235]

[0236] The data in Table 3 show that the inventive compound I2 (which contains no halogenated butyl rubber but contains fibrillated polymer fibers) exhibits much greater puncture resistance (tested with a round tip punch) and tear resistance (tested with a knife tip punch) than shown by the comparative compound C3 (which contains neither halogenated butyl rubber nor fibrillated polymer fibers).

[0237] Example 5 - Rolling Resistance Test

[0238] The rolling resistance test was carried out using the tire PI2 according to the invention and the reference tire PR1 according to Example 2.

[0239] In order to carry out the tire rolling resistance test, each wheel (19-inch rim and tire inflated to 6.0bar) is all installed above the rotary drum with a diameter of 2000mm, applying a load of 588.4N (corresponding to 60kg). The drum rotates at a speed of 106 revolutions per minute (which corresponds to 40km / h). After the drum starts to rotate for 20 minutes, the driving torque required for keeping the drum rotating is measured, and the average value (M1) of the collection of the last ten seconds is calculated. Subsequently, the load is reduced to 100N for 2 minutes, and the average driving torque (M2) required for keeping the drum rotating is measured in the last 10 seconds. Subsequently, the load is increased to 588.4N for 3 minutes, and the average driving torque (M3) required for keeping the drum rotating is measured in the last 10 seconds. Finally, the load is reduced to 100N again for 2 minutes, and the average driving torque (M4) required for keeping the drum rotating is measured in the last 10 seconds.

[0240] After calculating the difference between the first and second measured values ​​(M1-M2) and the difference between the third and fourth measured values ​​(M3-M4), the rolling resistance of the tire is calculated as the average of these two values ​​multiplied by the angular velocity of the drum (11.1 rad / s). It is found that the rolling resistance of the tire PI2 according to the invention is about 20% lower than the rolling resistance of the reference tire PR1.

[0241] The present invention has been described with reference to some preferred embodiments. Various modifications may be made to the embodiments described above while remaining within the scope of the invention as defined by the following claims.

Claims

1. A tire (100) for a bicycle wheel, comprising: - a carcass structure (2) comprising at least one carcass ply (3) having ends (3a) turned up around respective bead cores (4a, 4b) to form respective opposite beads (5a, 5b), - a tread band (7) arranged in a radially external position relative to said carcass structure (2), and - a layer (8) of vulcanized elastomeric material superimposed to or inserted in said carcass structure (2) in a radially inner or outer position, said layer (8) of vulcanized elastomeric material extending axially from at least one bead (5a) to the opposite bead (5b), It is characterized by: The layer (8) of vulcanized elastomeric material is produced by vulcanization of a vulcanizable elastomeric compound containing micron-sized fibrillated polymer fibers.

2. The tire (100) according to claim 1, characterized in that The fibrillated polymer fibers are selected from aramid fibers, polyester fibers, acrylic fibers, microfibrillated cellulose fibers and plant fibers.

3. The tire (100) according to claim 1, characterized in that The fibrillated polymer fibers have a diameter of less than 100 μm and a length of about 0.05 mm to about 8 mm.

4. The tire (100) according to claim 1, characterized in that The fibrillated polymer fibers exhibit an aspect ratio of length to diameter greater than 30:

1.

5. The tire (100) according to claim 1, characterized in that The fibrillated polymer fibers exhibited a 0.5 m 2 / g to about 60m 2 / g of surface area.

6. The tire (100) according to claim 1, characterized in that The vulcanizable elastomeric compound comprises: (a) 100 phr of at least one diene elastomeric polymer; (b) 0.1 phr to 20 phr of said fibrillated polymer fibers, and (c) 1 to 120 phr of reinforcing filler.

7. The tire (100) according to claim 1, characterized in that The fibrillated polymer fibers are present in the elastomeric compound in an amount of from 0.5 phr to 10 phr, preferably from 1 phr to 5 phr.

8. The tire (100) according to claim 1, characterized in that Said end portions (3a) extend until overlapping at said tread band (7).

9. The tire (100) according to claim 1, characterized in that The layer (8) of vulcanized elastomeric material is superposed to the carcass structure in a radially inner position and extends from the bead core (4a) to the opposite bead core (4b), with end portions (8a, 8b) turned up around the bead cores (4a, 4b).

10. The tire (100) according to claim 1, characterized in that The layer (8) of vulcanized elastomeric material is superposed to the carcass structure in a radially outer position and extends from the bead core (4a) to the opposing bead core (4b).

11. The tire (100) according to claim 1, characterized in that The layer (8) of vulcanized elastomeric material is inserted into the carcass structure and extends from the bead core (4a) to the opposite bead core (4b), optionally with ends (8a, 8b) turned up around the bead core (4a, 4b).

12. The tire (100) according to claim 11, characterized in that The layer (8) of vulcanized elastomeric material is in a radially outer position relative to the bead core (4a, 4b).

13. The tire (100) according to claim 11, characterized in that The layer (8) of vulcanized elastomeric material is in a radially inner position relative to the bead core (4a, 4b), with the end portions (8a, 8b) turned up around the bead core (4a, 4b).

14. The tire (100) according to claim 1, characterized in that It comprises, at each bead (5a, 5b), a reinforcing strip-like element (10) in a radially external position relative to said carcass structure (2).

15. The tire (100) according to claim 1, characterized in that It comprises a protective layer (6) at said tread band (7).

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