Bicycle tyre

Abstract

The present invention relates to a bicycle tyre comprising a tread comprising a rubber composition based at least on an elastomeric matrix comprising from 50 to 95% by weight of at least one substantially unsaturated diene elastomer, and from 5 to 50% by weight of an ethylene-propylene-diene copolymer (called EPDM), a reinforcing filler comprising silica, from 6 to 20% by weight relative to the total weight of the rubber composition of at least one plasticizing resin having a Tg greater than 20°C, and a crosslinking system.

Description

Technical Field

[0001] This invention relates to bicycle tires, and more particularly to a rubber composition for the tread of which is designed to contact the ground during rolling. Background Technology

[0002] Bicycle tire treads must meet a number of often conflicting technical requirements, including rolling resistance, grip, both dry and wet grip, abrasion resistance, stiffness of the cured composition (related to the ability to keep the handlebars straight after contact with branches or stones or to maintain contact with the ground after a jump), as well as curing characteristics and viscosity of the composition in the uncured state (related to the ease of industrial processing or processability of the composition).

[0003] Ozone is known to have adverse effects on rubber products, typically causing glazing and / or cracking on the surface of these products. In the case of bicycle tires, these cracks can be detrimental to the tire's performance quality, particularly in terms of durability, thus reducing tire lifespan, and also in terms of maintaining inflation pressure.

[0004] To combat these adverse effects, anti-ozone waxes, known to those skilled in the art, are typically used. However, using excessive amounts of anti-ozone wax can cause the rubber composition to whiten (“bloom”), which is undesirable to users. Furthermore, due to the low thickness of the layers that make up the tire, the amount of anti-ozone wax present may be insufficient to counteract the effects of ozone.

[0005] Ethylene-propylene-diene copolymer (EPDM) is known for its ability to resist ozone attack. However, adding EPDM to the rubber composition used in bicycle tire treads can impair other intended tread properties, particularly abrasion resistance and grip.

[0006] Therefore, there is a need for a bicycle tire that exhibits improved ozone resistance without compromising other tire performance qualities, particularly wet grip (which is important for rider safety), rolling resistance (which reflects the energy provided by the rider or, when the bicycle has electric assistance, by the battery), and abrasion resistance. Advantageously, it is worthwhile to maintain good ozone resistance while improving one or more of these other performance qualities.

[0007] Due to the nature of bicycles (weight, wheel size, tire structure and geometry, usage conditions, etc.), bicycle tires are subject to very specific limitations. Therefore, engineers in the bicycle tire field do not consider simply transferring existing solutions from other fields (such as motorcycle tires) to the bicycle tire field.

[0008] In the course of continuing its research, the applicant company unexpectedly discovered that by using a specific rubber composition in the tire tread, it was possible to improve the trade-off between the performance quality of bicycle tires in terms of wear resistance, rolling resistance, and wet grip. Summary of the Invention

[0009] Therefore, one subject of the present invention is a bicycle tire comprising a tread, said tread comprising at least a rubber composition based on the following: - An elastomer matrix comprising 50% to 95% by weight of at least one substantially unsaturated diene elastomer and 5% to 50% by weight of an ethylene-propylene-diene copolymer (referred to as EPDM). - Reinforcing filler containing silica, - At least one plasticizing resin with a Tg greater than 20°C, comprising 6% to 20% by weight relative to the total weight of the rubber composition, and - Crosslinking system.

[0010] In this document, unless otherwise stated, the terms "composition" or "composition according to the invention" refer to the rubber composition of the tread of a bicycle tire according to the invention.

[0011] I- Definition The statement “composition based” should be understood to mean that the composition comprises a mixture of various components used and / or products of in-situ reactions, some of which are capable of reacting with each other at least partially and / or intended to react with each other during various stages of composition manufacturing, and thus the composition may be in a fully or partially crosslinked state or in a non-crosslinked state.

[0012] The term "elastomer matrix" should be understood to mean all elastomers in the composition, including copolymers as described below.

[0013] Unless otherwise stated, the content of units resulting from monomer insertion into the copolymer is expressed as a molar percentage relative to all monomer units in the copolymer.

[0014] Within the meaning of this invention, the expression "parts by weight of 100 parts by weight of elastomer" (or phr) should be understood to mean the mass of 100 parts of elastomer present in the rubber composition under consideration.

[0015] Unless otherwise expressly stated, all percentages (%) indicated herein are weight percentages (%).

[0016] Furthermore, any numerical interval expressed as "between a and b" represents a range of values ​​extending from greater than a to less than b (i.e., excluding the limits a and b), while any numerical interval expressed as "from a to b" means a range of values ​​extending upwards from a to b (i.e., including the strict limits a and b). In this document, when a numerical interval is expressed as "from a to b," it is also preferred to represent the interval expressed as "between a and b."

[0017] When referring to a "major" compound, within the meaning of this invention, it is understood to mean that among compounds of the same type in the composition, this compound is dominant, i.e., it is the compound that accounts for the largest amount by weight among compounds of the same type. Thus, for example, a major elastomer is the elastomer that accounts for the largest weight percentage relative to the total weight of elastomers in the composition. Similarly, a "major" filler is the filler that accounts for the largest weight percentage among the fillers in the composition. For example, in a system containing only one elastomer, said elastomer is dominant within the meaning of this invention, while in a system containing two elastomers, the major elastomer accounts for more than half the weight of the elastomer. Conversely, a "minor" compound is a compound that does not account for the largest weight percentage among compounds of the same type. Preferably, "major" should be understood to mean present in an amount greater than 50%, preferably greater than 60%, 70%, 80%, or 90%, and more preferably, the "major" compound accounts for 100%.

[0018] The compounds mentioned in the specification can be fossil-derived or bio-based. In the latter case, they can be partially or wholly derived from biomass, or from renewable starting materials derived from biomass. Similarly, the mentioned compounds can also be derived from the recycling of previously used materials; that is, they can be partially or wholly derived from the recycling process, or obtained from starting materials themselves generated by the recycling process. Polymers, plasticizers, fillers, etc., are particularly relevant.

[0019] Unless otherwise stated, all glass transition temperature “Tg” values ​​described herein were measured in a known manner by DSC (differential scanning calorimetry) in accordance with standard ASTM D3418 (1999). Detailed Implementation

[0020] II-1 Elastomer Matrix The term “diene” elastomer (or indiscriminately called rubber), whether natural or synthetic, should be understood in the known manner as an elastomer that is at least partially (i.e., a homopolymer or copolymer) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds).

[0021] These diene elastomers can be divided into two categories: "substantially unsaturated" or "substantially saturated". "Substantially unsaturated" is generally understood to mean diene elastomers that are at least partially derived from conjugated diene monomers and have a diene-derived unit (conjugated diene) content greater than 15% (mol%). Therefore, diene elastomers such as butyl rubber or EPDM-type copolymers of diene and α-olefins do not fall under the foregoing definition and can be specifically described as "substantially saturated" diene elastomers (with a low or very low content of diene-derived units, always less than 15%).

[0022] Advantageously, the substantially unsaturated elastomer is one or more diene elastomers at least partially derived from conjugated diene monomers, the diene elastomer having a diene-derived unit content of greater than 30 mol%, preferably greater than 50 mol%.

[0023] Advantageously, the at least one substantially unsaturated elastomer is selected from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymer, isoprene copolymer, and mixtures of these elastomers, preferably selected from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene-styrene copolymer (SBR), and mixtures of these elastomers.

[0024] Suitable conjugated dienes are those with 4 to 12 carbon atoms, especially 1,3-dienes, such as 1,3-butadiene and isoprene.

[0025] According to the present invention, the composition of the bicycle tire is based on an elastomer matrix comprising 50% to 95% by weight of at least one substantially unsaturated diene elastomer and 5% to 50% by weight of an ethylene-propylene-diene copolymer (referred to as EPDM).

[0026] The at least one substantially unsaturated diene elastomer may be selected from polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers, and mixtures thereof. The butadiene copolymer is particularly selected from styrene-butadiene copolymer (SBR).

[0027] Those polybutadienes particularly suitable as polybutadienes are those with a 1,2-unit content (mol%) between 4% and 80% or a cis-1,4-unit content (mol%) greater than 80%. Those butadiene-styrene copolymers particularly suitable as butadiene-styrene copolymers are those with a Tg (glass transition temperature (Tg, determined according to ASTM D3418-99) between 0°C and -90°C, a styrene content between 1 wt% and 60 wt% (more particularly between 10 wt% and 50 wt%), a 1,2-bond content (mol%) between 4% and 75% in the butadiene moiety, and a trans-1,4-bond content (mol%) between 10% and 80%. It should be noted that SBRs can be prepared in an emulsion manner (ESBR) or a solution manner (SSBR).

[0028] The essentially unsaturated diene elastomer can be modified, i.e., coupled and / or star-branched, or functionalized, or coupled and / or star-branched and simultaneously functionalized.

[0029] Therefore, substantially unsaturated diene elastomers can be coupled and / or star-branched, for example, by linking silicon or tin atoms together in the elastomer chains. The substantially unsaturated diene elastomer may simultaneously or alternatively contain at least one functional group. The term "functional group" should be understood to mean a group containing at least one heteroatom selected from Si, N, S, O, and P. Particularly suitable functional groups are those containing at least one functional group such as silanol, alkoxysilane, primary, secondary, or tertiary amine (cyclic or acyclic), thiol, or epoxy functional groups.

[0030] Advantageously, the elastomer matrix comprises a mixture of substantially unsaturated diene elastomers.

[0031] In particular, the at least one substantially unsaturated diene elastomer may comprise natural rubber and a butadiene-styrene copolymer. In this case, the substantially unsaturated diene elastomer in the elastomer matrix advantageously comprises 50% to 95% by weight, preferably 70% to 90% by weight, of a butadiene-styrene copolymer, and 5% to 50% by weight, preferably 10% to 30% by weight, of natural rubber.

[0032] The at least one substantially unsaturated diene elastomer may also additionally comprise polybutadiene. In this case, the substantially unsaturated diene elastomer in the elastomer matrix advantageously comprises 5% to 40% by weight, preferably 10% to 30% by weight, of natural rubber, 20% to 90% by weight, preferably 40% to 80% by weight, of butadiene-styrene copolymer, and 5% to 40% by weight, preferably 10% to 30% by weight, of polybutadiene.

[0033] When the substantially unsaturated diene elastomer comprises a butadiene-styrene copolymer, the latter advantageously has a Tg of less than -20°C, preferably in the range of -40°C to -80°C, and more preferably in the range of -60°C to -70°C.

[0034] The total content of substantially unsaturated diene elastomers in the elastomer matrix of the composition according to the invention is preferably in the range of 55% to 90% by weight, more preferably in the range of 60% to 85% by weight.

[0035] Any EPDM can be used in the context of this invention. However, in the context of this invention, it may be advantageous to use a particular EPDM. The EPDM may be a single EPDM or a mixture of multiple EPDMs.

[0036] In particular, preferably, the EPDM has an ethylene content in the range of 41% to 75% by weight, and more preferably in the range of 50% to 71.5% by weight, relative to the weight of the EPDM.

[0037] Relative to the weight of EPDM, EPDM also advantageously has a propylene content in the range of 13% to 58% by weight, preferably in the range of 17% to 42% by weight.

[0038] Relative to the weight of EPDM, EPDM also advantageously has a diene content in the range of 1% to 12% by weight, preferably in the range of 8% to 11.5% by weight.

[0039] The diene of EPDM can be selected from ethylene norbornene, dicyclopentadiene, and mixtures thereof. Preferably, the diene of EPDM is ethylene norbornene, particularly 5-ethylene-2-norbornene (ENB).

[0040] The ethylene, propylene, and diene content of EPDM can be determined by infrared spectroscopy, with the ethylene and propylene content determined according to ASTM D3900 standard and the diene content according to ASTM D6047 standard.

[0041] The EPDM content in the elastomer matrix of the composition according to the invention is preferably in the range of 10% to 45% by weight, more preferably in the range of 15% to 40% by weight.

[0042] Advantageously, EPDM is introduced into the rubber composition in an uncrosslinked (or unvulcanized) form to improve the co-crosslinking of EPDM with other elastomers (particularly substantially unsaturated diene elastomers) in the rubber composition during the subsequent crosslinking process of the rubber composition for bicycle tire molding.

[0043] Preferably, the elastomer matrix does not contain any elastomer other than at least one substantially unsaturated diene elastomer and EPDM, i.e., the total content of substantially unsaturated diene elastomer and EPDM in the elastomer matrix of the composition according to the invention is 100 by weight.

[0044] II-2 Reinforced Packing The rubber composition of the tread of the bicycle tire according to the invention comprises a reinforcing filler, which is known for its ability to enhance the rubber composition that can be used to manufacture tires. This reinforcing filler typically consists of particles with an average size (by weight) of less than 1 micrometer, typically less than 500 nm, most commonly between 20 nm and 200 nm, and particularly and more preferably between 20 nm and 150 nm.

[0045] According to the present invention, the reinforcing filler comprises silica. It may also additionally comprise another reinforcing filler, particularly carbon black.

[0046] Any type of precipitated silica, particularly highly dispersed precipitated silica (referred to as HDS), can be suitable as silica. These precipitated silicas (whether highly dispersed or not) are well known to those skilled in the art. For example, references can be made to the silica described in applications WO03 / 016215-A1 and WO03 / 016387-A1. Among commercially available HDS silicas, Ultrasil® 5000GR and Ultrasil® 7000GR silica from Evonik or Zeosil® 1085GR, Zeosil® 1115 MP, Zeosil® 1165MP, Zeosil® Premium 200MP, and Zeosil® HRS 1200 MP silica from Solvay can be used in particular. The following commercially available silicas can be used as non-HDS silicas: Ultrasil® VN2GR and Ultrasil® VN3GR silicas from Evonik, Zeosil® 175GR silicas from Solvay, or Hi-Sil EZ120G(-D), Hi-Sil EZ160G(-D), Hi-Sil EZ200G(-D), Hi-Sil 243LD, Hi-Sil 210, and Hi-Sil HDP 320G silicas from PPG.

[0047] To couple silica to a diene elastomer, at least bifunctional coupling agents (or binders) can be used in a known manner, designed to provide a satisfactory chemical and / or physical bond between the inorganic filler (the surface of its particles) and the diene elastomer. In particular, at least bifunctional organosilanes or polyorganosiloxanes are used. The term "bifunctional" should be understood to mean a compound having a first functional group capable of interacting with the inorganic filler and a second functional group capable of interacting with the diene elastomer. For example, such a bifunctional compound may contain a first functional group (containing a silicon atom) and a second functional group (containing a sulfur atom), the first functional group being capable of interacting with the hydroxyl group of the inorganic filler and the second functional group being capable of interacting with the diene elastomer.

[0048] Preferably, the organosilane is selected from organosilane polysulfides (symmetric or asymmetric), such as bis(3-triethoxysilylpropyl)tetrasulfide (abbreviated as TESPT) sold by Evonik under the name Si69, or bis(triethoxysilylpropyl)disulfide (abbreviated as TESPD) sold by Evonik under the name Si75, polyorganosiloxanes, mercaptosilanes, and terminal mercaptosilanes (e.g., S-(3-(triethoxysilyl)propyl)octylthioester sold by Momentive under the name NXT silane). More preferably, the organosilane is an organosilane polysulfide.

[0049] Those skilled in the art can readily adjust the content of the coupling agent. Typically and preferably, the coupling agent content is 0.5% to 15% by weight relative to the amount of silica.

[0050] Advantageously, the content of reinforcing filler in the composition is in the range of 8% to 24% by weight relative to the total weight of the rubber composition, preferably in the range of 15% to 24% by weight, preferably in the range of 16% to 23% by weight, and preferably in the range of 17% to less than 20% by weight.

[0051] Advantageously, the reinforcing filler content in the composition is in the range of 11 to 55 phr, preferably in the range of 20 to less than 50 phr, and more preferably in the range of 15 to 45 phr.

[0052] The reinforcing filler may contain more than 50% to 100% by weight, preferably 75% to 100% by weight, and more preferably 95% to 100% by weight of silica relative to the total weight of the reinforcing filler. In particular, the reinforcing filler may contain 100% by weight of silica. This is particularly advantageous when it is desired to use pigments to color the tread of bicycle tires.

[0053] When a black tread is desired, the reinforcing filler in the composition advantageously comprises 0.5% to 5% by weight, preferably 1% to 3% by weight, of carbon black. In this case, the reinforcing filler comprises 95% to 99.5% by weight, preferably 97% to 99% by weight, of silica.

[0054] The carbon black that can be used in the context of this invention can be any carbon black conventionally used for tires or their treads (“tire-grade” carbon black). More specifically, reference will be made to reinforcing carbon blacks of the 100, 200, and 300 series, or carbon blacks of the 500, 600, or 700 series (ASTM grades), such as N115, N134, N234, N326, N330, N339, N347, N375, N550, N683, and N772 carbon black. These carbon blacks can be used alone (e.g., in commercially available form) or in any other form, such as as a carrier for some rubber additives used. Carbon black can, for example, be introduced into diene elastomers, particularly isoprene elastomers, in the form of masterbatches (see, for example, applications WO 97 / 36724 and WO 99 / 16600).

[0055] II-3. Plasticizing System The plasticizing system of the rubber composition of the tread of the bicycle tire according to the present invention is also based on at least one plasticizing resin having a glass transition temperature greater than 20°C, referred to as "high Tg" (also referred to herein as "plasticizing resin" for simplicity).

[0056] In this patent application, the term "resin" as defined by those skilled in the art means a compound that is solid at room temperature (23°C), as opposed to a liquid plasticizing compound (such as an oil).

[0057] Plasticizing resins are polymers known to those skilled in the art, which are essentially based on carbon and hydrogen, but may also contain other types of atoms. These plasticizing resins can be used, in particular, as plasticizers or tackifiers in polymer matrices. They are typically inherently miscible (i.e., compatible) with the target polymer composition at the level of use, thus acting as a true diluent. They have been described in works such as those by R. Mildenberg, M. Zander, and G. Collin under the name "..." Hydrocarbon Resins The book described in the author's work (New York, VCH, 1997, ISBN 3-527-28617-9) discusses their applications in Chapter 5, particularly in the field of tire rubber (5.5.). Rubber Tires and Mechanical GoodsThey can be aliphatic, cycloaliphatic, aromatic, hydrogenated aromatic, or aliphatic / aromatic, i.e., based on aliphatic and / or aromatic monomers. They can be natural or synthetic, and petroleum-based or not (if petroleum-based, they are also called petroleum resins). Their Tg is preferably greater than 20°C (typically between 30°C and 95°C).

[0058] These plasticized resins can also be described as thermoplastic resins in a known manner, as they soften upon heating and are therefore moldable. They can also be defined by their softening point. The softening point of a plasticized resin is typically about 50°C to 60°C higher than its Tg value. The softening point is measured according to standard ISO 4625 (“Ring and Ball” method). The macrostructure (Mw, Mn, and PI) is determined by size exclusion chromatography (SEC) as shown below.

[0059] As a reminder, SEC analysis, for example, involves separating macromolecules in solution based on their size using a column packed with a porous gel; molecules are separated according to their hydrodynamic volume, with the largest molecules eluting first. The sample to be analyzed is pre-dissolved simply in a suitable solvent, tetrahydrofuran, at a concentration of 1 g / L. The solution is then filtered through a filter with a 0.45 μm porosity before being injected into the instrument. The instrument used is, for example, a Waters Alliance chromatography system, with the following conditions: - Elution solvent: tetrahydrofuran; - Temperature: 35°C; - Concentration: 1 g / L; - Flow rate: 1 mL / min; - Injection volume: 100 µL; - Molar calibration using polystyrene standards: - A set of 3 Waters columns in series (Styragel HR4E, Styragel HR1 and Styragel HR 0.5); - Detection is performed using a differential refractometer (e.g., Waters 2410), which can be equipped with operating software (e.g., Waters Millennium).

[0060] Molar calibration was performed using a series of commercially available polystyrene standards with low polydispersity index (PI) (less than 1.2) and known molar masses, covering the mass range to be analyzed. The weight-average molar mass (Mw), number-average molar mass (Mn), and polydispersity index (PI = Mw / Mn) were derived from the recorded data (weight distribution curves of molar mass).

[0061] Therefore, all molar mass values ​​shown in this patent application are relative to calibration curves generated using polystyrene standards.

[0062] The plasticizing resin may have at least one of the following characteristics, preferably two or three, and more preferably all of the following characteristics: - Tg greater than 25°C (especially between 30°C and 100°C), more preferably greater than 30°C (especially between 30°C and 95°C); - Softening point greater than 50°C (especially between 50°C and 150°C); - The number-average molar mass (Mn) is between 300 and 2000 g / mol, preferably between 400 and 1500 g / mol; - The polydispersity index (PI) is less than 3, preferably less than 2 (as a reminder: PI = Mw / Mn, where Mw is the weight-average molar mass).

[0063] The preferred high-Tg plasticizing resins described above are well known to those skilled in the art and are commercially available, for example, in the following forms: - Polylimonene resin: sold by DRT under the name Dercolyte L120 (Mn = 625 g / mol; Mw = 1010 g / mol; PI = 1.6; Tg = 72℃), or by Arizona Chemical under the name Sylvagum TR7125C (Mn = 630 g / mol; Mw = 950 g / mol; PI = 1.5; Tg = 70℃); - C5 fraction / vinyl aromatic copolymer resins, especially C5 fraction / styrene or C5 fraction / C9 fraction copolymer resins: sold by Neville Chemical under the names Super Nevtac 78, Super Nevtac 85 and Super Nevtac 99, by Goodyear Chemicals under the name Wingtack Extra, by Kolon under the names Hikorez T1095 and Hikorez T1100, or by Exxon under the names Escorez 2101 and Escorez 1273; - Limonene / styrene copolymer resin: sold by DRT under the name Dercolyte TS 105, or by Arizona Chemical under the names ZT115LT and ZT5100.

[0064] The plasticizing resin with a glass transition temperature greater than 20°C can be selected from cyclopentadiene (CPD) homopolymer or copolymer resins, dicyclopentadiene (DCPD) homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5 fraction homopolymer or copolymer resins, C9 fraction homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and mixtures thereof. Preferably, the plasticizing resin is selected from terpene homopolymer or copolymer resins, C5 fraction homopolymer or copolymer resins, and C9 fraction homopolymer or copolymer resins; more preferably, the plasticizing resin is selected from terpene homopolymer or copolymer resins.

[0065] The term "terpene" here combines α-pinene, β-pinene, and limonene monomers in a known manner; limonene monomers are preferred, which are compounds known to exist in three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or dipentene (a racemic mixture of dextrorotatory and levorotatory enantiomers). Suitable as vinyl aromatic monomers are, for example: styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinyltrimethylbenzene, divinylbenzene, vinylnaphthalene, or any derivative derived from the C9 fraction (or more generally derived from C8 to C9). 10 Vinyl aromatic monomers (distillate fraction).

[0066] More specifically, reference may be made to plasticizing resins selected from the following: (D)CPD homopolymer resins, (D)CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D(CPD) copolymer resins, C5 fraction / styrene copolymer resins, C5 fraction / C9 fraction copolymer resins, and mixtures of these resins.

[0067] All of the aforementioned plasticizing resins are well known to those skilled in the art and are commercially available, such as polylimonene resin sold by DRT under the name Dercolyte, C5 fraction / styrene resin or C5 fraction / C9 fraction resin sold by Neville Chemical under the name Super Nevtac, by Kolon under the name Hikorez, or by ExxonMobil under the name Escorez, or mixtures of aromatic and / or aliphatic resins sold by Struktol under the names 40 MS or 40 NS.

[0068] According to the present invention, the content of a plasticizing resin with a glass transition temperature greater than 20°C in the composition according to the present invention is in the range of 6% to 20% by weight, relative to the total weight of the rubber composition of the tread of the bicycle tire according to the present invention. Preferably, this content is in the range of 6.5% to 18% by weight, and more preferably in the range of 7% to 15% by weight, relative to the total weight of the rubber composition.

[0069] In the compositions according to the invention, the content of plasticizing resin with a glass transition temperature greater than 20°C can be in the range of 10 to 40 phr, preferably in the range of 11 to 30 phr.

[0070] Although not essential for carrying out the invention, the plasticizing system of the rubber composition according to the invention may contain a plasticizer that is liquid at 23°C, referred to as "low Tg," i.e., having a Tg of less than -20°C, preferably less than -40°C, by definition. According to the invention, the composition may optionally contain 0 to 30 phr of plasticizer that is liquid at 23°C, or contain 0 to 20% by weight of plasticizer relative to the total weight of the rubber composition of the tread of the bicycle tire according to the invention.

[0071] When a plasticizer that is liquid at 23°C is used, the content of the plasticizer in the composition according to the invention may be in the range of 4 to 20 phr, or in the range of 5% to 15% by weight relative to the total weight of the rubber composition of the tread of the bicycle tire according to the invention.

[0072] Any plasticizer (or oil) that is liquid at 23°C, whether aromatic or non-aromatic, can be used, provided that it is known to have plasticizing properties for diene elastomers. At ambient temperature (23°C), these plasticizers or these oils (which are more or less viscous) are liquid (i.e., as a reminder, these substances have the ability to ultimately take on their container shape), which is particularly different from plasticized resins, which are essentially solid at ambient temperature.

[0073] The following plasticizers that are liquid at 23°C are particularly suitable: liquid diene polymers, polyolefin oils, naphthenic oils, paraffin oils, DAE oils, MES (medium extraction solvates) oils, TDAE (treated distillate aromatic extracts) oils, RAE (residual aromatic extracts) oils, TRAE (treated residual aromatic extracts) oils, SRAE (safe residual aromatic extracts) oils, mineral oils, vegetable oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers, and mixtures thereof.

[0074] Preferably, the plasticizer that is liquid at 23°C is selected from TDAE oil, vegetable oil, and mixtures thereof.

[0075] II-4 Crosslinking System The crosslinking system can be any type of system known to those skilled in the art of tire rubber compositions. It can be, in particular, based on sulfur, and / or peroxides and / or bismaleimides.

[0076] Preferably, the crosslinking system is sulfur-based, and is referred to as a vulcanization system. Advantageously, the vulcanization system comprises molecular sulfur and / or at least one sulfur donor. It is also preferred that at least one vulcanization accelerator is present, and optionally and even more preferably, various known vulcanization activators can be used, such as zinc oxide, stearic acid or equivalent compounds such as stearates and transition metal salts, guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders can be used.

[0077] Sulfur is preferably used in amounts between 0.5 and 12 phr, particularly between 1 and 10 phr. A vulcanization accelerator is preferably used in amounts between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr.

[0078] Any compound that can be used as a vulcanization accelerator for diene elastomers in the presence of sulfur can be used as an accelerator, particularly thiazole-type accelerators and their derivatives, or sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate-type accelerators. Examples of such accelerators include, in particular, 2-mercaptobenzothiazole disulfide (MBTS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), N-(tert-butyl)-2-benzothiazole sulfenamide (TBBS), N-(tert-butyl)-2-benzothiazole sulfenimide (TBSI), tetrabenzylthiuram disulfide (TBZTD), zinc dibenzyl dithiuram (ZBEC), and mixtures of these compounds.

[0079] II-5 Possible Additives The rubber composition of the tire tread according to the invention may optionally contain all or part of the commonly used additives typically used in tire elastomer compositions, such as pigments, protective agents such as anti-ozone waxes, chemical anti-ozone agents or antioxidants, anti-fatigue agents, etc.

[0080] Preparation of II-6 Composition The compositions according to the invention can be manufactured in a suitable mixer using two consecutive preparation stages known to those skilled in the art: - The first thermomechanical processing or kneading stage (“non-production” stage), which can be carried out in a single thermomechanical stage, involves introducing all necessary components (particularly the elastomer matrix, reinforcing fillers, and various other optional additives) into a suitable mixer, such as a standard internal mixer (e.g., a Banbury type mixer), except for the crosslinking system. The introduction of fillers into the elastomer can be accomplished by one or more thermomechanical kneading processes. Where the fillers have already been introduced into the elastomer in whole or in part as masterbatch (as described, for example, in patent applications WO 97 / 36724 or WO 99 / 16600), the masterbatch is kneaded directly, and where appropriate, other elastomers or fillers in non-masterbatch forms present in the composition, along with various other optional additives besides the crosslinking system, are introduced. The non-production stage can be carried out at high temperatures, up to between 110°C and 200°C, preferably between 130°C and 185°C, for a duration typically between 2 and 10 minutes.

[0081] - The second machining stage (“production” stage) can be carried out in an open mixer (e.g., a two-roll mill) after the mixture obtained in the first non-production stage has been cooled to a lower temperature (typically below 120°C, for example, between 40°C and 100°C). The crosslinking system is then introduced and all materials are mixed for a few minutes, for example, between 5 and 15 minutes.

[0082] These phases have been described, for example, in applications EP-A-0 501 227, EP-A-0 735 088, EP-A-0 810 258, WO00 / 05300 and WO 00 / 05301.

[0083] The resulting final composition is then calendered, for example, in the form of sheets or plates, particularly for laboratory characterization, or extruded (or co-extruded with another rubber composition) as a rubber semi-finished product (or molding element), which can be used, for example, as the tread of a bicycle tire. These products can then be used to manufacture tires according to techniques known to those skilled in the art.

[0084] The composition may be in an uncured state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization), or it may be a semi-finished product that can be used in tires.

[0085] Crosslinking of the composition can be carried out in a manner known to those skilled in the art, for example, at a temperature between 130°C and 200°C, under pressure.

[0086] II-7 bicycle tires According to the invention, the tire is intended to equip any type of bicycle without particular limitation, whether or not it has an electric auxiliary motor. Advantageously, the bicycle tire is a tire for road bicycles, all-terrain bicycles, or all-terrain bicycles; preferably, the bicycle tire is a tire for road bicycles. The bicycle tire can be a bicycle tire.

[0087] The term "tire" should be understood to mean either a pneumatic tire or a non-pneumatic tire. Pneumatic tires for bicycles typically consist of a carcass reinforcement layer anchored in two bead rings by turning upwards around two bead wires. The bead rings extend radially from the carcass plies, which themselves extend from the tread. By definition, a pneumatic tire is designed to contain compressed air when mounted on a bicycle wheel. Non-pneumatic tires can be provided in various forms, such as solid or non-solid tires. As an example describing a non-pneumatic tire for bicycles, application FR 3 042 736 A1 may be mentioned. According to the invention, the tire according to the invention is preferably a pneumatic tire.

[0088] The tire according to the invention can be a tubeless tire, i.e., directly mounted on the rim without an inner tube, or an inner tube tire that requires an inner tube. The tire according to the invention can also be a solid or airless non-pneumatic tire.

[0089] The width of the bicycle tire according to the invention can be in the range of 20 to 70 mm, preferably in the range of 25 to 50 mm. For pneumatic tires, the tire width is measured on a tire that is installed and under the manufacturer's recommended pressure.

[0090] The tread thickness of the bicycle tire according to the invention can be in the range of 0.5 to 5 mm, preferably in the range of 1 to 2 mm.

[0091] III- Example III-1 Measurements and Tests Used Mechanical properties (after curing): Tensile test These tensile tests determine elastic stress and fracture characteristics. Unless otherwise specified, these tests are performed according to French Standard NF T 46-002 of September 1988. Processing the tensile records also allows for the plotting of modulus versus elongation. The modulus used here is the nominal (or apparent) secant modulus measured at initial elongation, calculated by conversion to the initial cross-sectional area of ​​the specimen. The nominal secant modulus (or apparent stress, in MPa) is measured at 10%, 100%, and 300% elongation at initial elongation and is designated MSA10, MSA100, and MSA300, respectively.

[0092] The MSA300 / MSA100 reinforcement index, which is usually used to indicate the abrasion resistance of rubber compositions, cannot be used in this case because the crosslinking agent tested broke before reaching 300% elongation.

[0093] Therefore, the MSA100 / MSA10 enhancement index is used instead, which is also a good indicator of wear resistance, especially in the field of bicycle tires.

[0094] The MSA100 / MSA10 performance enhancement results are expressed as a base of 100, with values ​​of 100 assigned to the control. Results greater than 100 indicate that the compositions of the considered embodiments have improved abrasion resistance.

[0095] Dynamic characteristics According to standard ASTM D 5992-96, the dynamic property tan(δ)max was measured on a viscosity analyzer (Metravib VA4000) at a temperature of 23°C. According to standard ASTM D 1349-99, samples of cross-linked compositions (4 mm thickness and 400 mm² cross-sectional area) were recorded. 2 The response of a cylindrical specimen subjected to simple alternating sinusoidal shear stress at a frequency of 10 Hz under defined temperature conditions (e.g., 23 °C) was analyzed. Strain amplitude scans were performed from 0.1% to 50% (outward cycle) and then from 50% to 0.1% (backward cycle). The result used is the loss factor tan(δ). For the backward cycle, the observed maximum value of tan(δ) is indicated, denoted as tan(δ)max at 23 °C.

[0096] It should be noted that, in a manner known to those skilled in the art, the value of tan(δ)max at 23°C represents hysteresis. The tan(δ)max performance results at 23°C are expressed on a base of 100, with values ​​of 100 assigned to controls. A result greater than 100 indicates that the composition of the considered embodiment exhibits lower hysteresis at 23°C, reflecting lower rolling resistance in treads containing the composition.

[0097] In addition, the integral characteristics of tan(δ) values ​​observed from -30°C to 0°C (Int. tan(δ) [-30°C; 0°C]) were measured on a viscosity analyzer (Metravib VA4000) according to standard ASTM D5992-96. Crosslinked composition samples (4 mm thickness, 400 mm² cross-sectional area) were recorded. 2 The response of a cylindrical specimen subjected to simple alternating sinusoidal shear stress at a frequency of 10 Hz under a constant stress of 0.7 MPa during a temperature scan.

[0098] It should be noted that, in a manner known to those skilled in the art, the integral of the tan(δ) value observed from -30°C to 0°C represents wet grip. Int. tan(δ) [-30°C; 0°C] performance results are expressed on a base of 100, with a value of 100 assigned to the control. A result greater than 100 indicates that the composition has better wet grip.

[0099] Preparation of the III-2 Composition In the following examples, the rubber composition was prepared as described in Section II.6 above. Specifically, the "non-production" stage was carried out in a 0.4-liter mixer at an average paddle speed of 50 revolutions per minute for 3.5 minutes until the maximum discharge temperature of 160°C was reached. The "production" stage was carried out in an open mill at 23°C for 5 minutes.

[0100] The crosslinking of the composition was carried out under pressure at a temperature between 130°C and 200°C.

[0101] III-3 Tests on rubber compositions The examples given below are intended to compare the performance trade-offs between the compositions (I1-I4) according to the invention and the control compositions (C1-C3) in terms of abrasion resistance, rolling resistance and wet grip.

[0102] The control composition C1 is a reference composition for use in the tread of road bicycle tires. It comprises: 10 phr of natural rubber, 40 phr of 98% cis-1,4-neodymium polybutadiene (Tg = -110°C), 50 phr of tin-functionalized SBR (with 15% styrene units, 30% 1,2-units in the butadiene moiety, Tg = -64°C), 20 phr of oil (Tudalen 11 from Hansen und Rosenthal ChemPharm), 60 phr of silica (Zeosil 1165MP from Solvay), 4.8 phr of liquid TESPT silane (Si69 from Evonik), 5 phr of 2,4,6-tris(1-phenylethyl)phenol (SPC) as an antioxidant (Kumanox from Kumho), 3 phr of cyclic acetal as an antioxidant (Vulkazon AFS / LG from Lanxess), and 7 phr of anti-ozone wax (from Sasol). Varazon 4959 from Wax, 2 phr of black pigment (Microlen BK 0062 MCN from BASF), 2 phr of diphenylguanidine (PerkacitDPG from Flexsys), 3.5 phr of industrial-grade zinc oxide (Umicore), 2 phr of stearic acid (Pristerene4931 from Uniqema), 2 phr of sulfur, and 2 phr of N-cyclohexyl-2-benzothiazole sulfenamide as a vulcanization accelerator (Santocure CBS from Flexsys).

[0103] Other compositions tested (in phr) and the results obtained are presented in Table 1. In addition to the components shown in Table 1, all tested formulations contained 3 phr of 2,4,6-tris(1-phenylethyl)phenol (SPC) (Kumanox from Kumho), 1.5 phr of cyclic acetal (Vulkazon AFS / LG from Lanxess), 1.5 phr of anti-ozone wax (Varazon 4959 from Sasol Wax), 2 phr of black pigment (Microlen BK 0062 MCN from BASF), 1.5 phr of diphenylguanidine (Perkacit DPG from Flexsys), 3.5 phr of industrial-grade zinc oxide (Umicore), 2 phr of stearic acid (Pristerene 4931 from Uniqema), 3.5 phr of sulfur, and 2 phr of N-cyclohexyl-2-benzothiazole sulfenamide as a vulcanization accelerator (Santocure CBS from Flexsys).

[0104] The differences between the compositions presented in Table 1 and the reference composition C1 are particularly the presence of EPDM (known for improving ozone resistance) and the reduction in the total amount of anti-ozone wax.

[0105] The only difference between the control compositions C2 and C3 and composition I2 and composition I1 is the content of plasticizing resin.

[0106] Compositions I3 and I4 conform to the present invention, and differ from composition I1 in either the silica content (the weight ratio of coupling agent to silica is constant) or the presence of a plasticizer that is liquid at 23°C.

[0107] Results for abrasion resistance, rolling resistance, and wet grip performance are expressed as a percentage relative to 100 of control composition C1. Values ​​greater than 100 indicate improvements in the properties under discussion.

[0108] The performance trade-offs between abrasion resistance, rolling resistance, and wet grip can be considered as the arithmetic mean of the results presented on a base of 100.

[0109] [Table 1] (1) Natural rubber (2) 98% cis-1,4-neodymium polybutadiene; Tg = -110℃ (3) Tin-functionalized solution SBR with 15% styrene units and 30% 1,2-polybutadiene units in the butadiene moiety (Tg = -64℃) (4) EPDM, from Arlanxeo's Keltan 3960, with 56% ethylene units and 11% ENB units. (5) Polylimonene resin, Dercolyte L120 from DRT (Tg = 72℃) (6) Trioctyl phosphate (tris(2-ethylhexyl) phosphate), from Lanxess's Disflamoll TOF (7) Silica, Zeosil 1165MP from Solvay (8) Triethoxysilylpropyltetrasulfide (TESPT) liquid silane, from Evonik's Si69 It has been found that the compositions according to the present invention have ozone resistance comparable to that of the reference compositions.

[0110] Furthermore, the results shown in Table 1 above indicate that all compositions according to the present invention also improve rolling resistance by more than 1.2 times relative to the reference composition C1, without excessively affecting abrasion resistance and wet grip, and may even improve them.

[0111] Control composition C2 did show an improvement in rolling resistance, but it was detrimental to wet grip performance, which could be harmful to rider safety. Control composition C3 did show an improvement in performance trade-offs, but it did not adequately improve rolling resistance.

Claims

1. A bicycle tire comprising a tread, said tread comprising a rubber composition based on at least the following: - An elastomer matrix comprising 50% to 95% by weight of at least one substantially unsaturated diene elastomer, and 5% to 50% by weight of an ethylene-propylene-diene copolymer called EPDM. - Reinforcing filler containing silica, - At least one plasticizing resin with a Tg greater than 20°C, comprising 6% to 20% by weight relative to the total weight of the rubber composition, and - Crosslinking system.

2. The tire according to claim 1, wherein the at least one substantially unsaturated diene elastomer is selected from polybutadiene, natural rubber, synthetic polyisoprene, butadiene copolymers, isoprene copolymers, and mixtures thereof.

3. The tire according to claim 1 or 2, wherein the at least one substantially unsaturated diene elastomer comprises natural rubber and butadiene-styrene copolymer.

4. The tire according to claim 3, wherein the butadiene-styrene copolymer has a Tg of less than -20°C, preferably in the range of -40°C to -80°C, and more preferably in the range of -60°C to -70°C.

5. The tire according to any one of the preceding claims, wherein the ethylene content of the EPDM is in the range of 41% to 75% by weight relative to the weight of the EPDM, preferably in the range of 50% to 71.5% by weight.

6. The tire according to any one of the preceding claims, wherein the propylene content of the EPDM is in the range of 13% to 58% by weight relative to the weight of the EPDM, preferably in the range of 17% to 42% by weight.

7. The tire according to any one of the preceding claims, wherein the diene content of the EPDM is in the range of 1% to 12% by weight relative to the weight of the EPDM, preferably in the range of 8% to 11.5% by weight.

8. The tire according to any one of the preceding claims, wherein the diene of the EPDM is selected from ethylidene norbornene, dicyclopentadiene, and mixtures thereof; preferably, the diene of the EPDM is ethylidene norbornene.

9. The tire according to any one of the preceding claims, wherein the EPDM content in the elastomer matrix is ​​in the range of 10% to 45% by weight, preferably in the range of 15% to 40% by weight.

10. The tire according to any one of the preceding claims, wherein the reinforcing filler comprises more than 50% to 100% by weight, preferably 75% to 100% by weight, of silica relative to the total weight of the reinforcing filler.

11. The tire according to any one of the preceding claims, wherein the content of reinforcing filler in the rubber composition is in the range of 11 to 55 phr, preferably in the range of 20 to less than 50 phr, and more preferably in the range of 15 to 45 phr.

12. The tire according to any one of the preceding claims, wherein the plasticizing resin is selected from cyclopentadiene homopolymer or copolymer resins, dicyclopentadiene homopolymer or copolymer resins, terpene homopolymer or copolymer resins, C5 fraction homopolymer or copolymer resins, C9 fraction homopolymer or copolymer resins, α-methylstyrene homopolymer or copolymer resins, and mixtures thereof; preferably, the plasticizing resin is selected from terpene homopolymer or copolymer resins, C5 fraction homopolymer or copolymer resins, and C9 fraction homopolymer or copolymer resins.

13. The tire according to any one of the preceding claims, wherein the content of plasticizer resin in the rubber composition is in the range of 10 to 40 phr, preferably in the range of 11 to 30 phr.

14. The tire according to any one of the preceding claims, wherein the crosslinking system is based on molecular sulfur and / or at least one sulfur donor.

15. The tire according to any of the preceding claims, wherein the bicycle tire is a tire for a road bicycle, an all-terrain bicycle, or an all-road bicycle; preferably, the bicycle tire is a tire for a road bicycle.

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