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WO2024223826A1 - Pneumatique pour roue de véhicule présentant une résistance à l'usure et une adhérence supérieures - Google Patents

Pneumatique pour roue de véhicule présentant une résistance à l'usure et une adhérence supérieures Download PDF

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Publication number
WO2024223826A1
WO2024223826A1 PCT/EP2024/061544 EP2024061544W WO2024223826A1 WO 2024223826 A1 WO2024223826 A1 WO 2024223826A1 EP 2024061544 W EP2024061544 W EP 2024061544W WO 2024223826 A1 WO2024223826 A1 WO 2024223826A1
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WO
WIPO (PCT)
Prior art keywords
phr
polymer
conjugated diene
mol
tyre
Prior art date
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Pending
Application number
PCT/EP2024/061544
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English (en)
Inventor
Davide Dall'abaco
Lucia Rita RUBINO
Yuta HASHIZUME
Takaaki USHIO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pirelli and C SpA
Pirelli Tyre SpA
Original Assignee
Pirelli SpA
Pirelli Tyre SpA
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Filing date
Publication date
Priority claimed from EP23170341.4A external-priority patent/EP4455203A1/fr
Application filed by Pirelli SpA, Pirelli Tyre SpA filed Critical Pirelli SpA
Publication of WO2024223826A1 publication Critical patent/WO2024223826A1/fr
Priority to MX2025012490A priority Critical patent/MX2025012490A/es
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F236/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
    • C08F236/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
    • C08F236/04—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated
    • C08F236/10—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated with vinyl-aromatic monomers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B60C1/0016—Compositions of the tread
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C08C19/22—Incorporating nitrogen atoms into the molecule
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C08C19/24—Incorporating phosphorus atoms into the molecule
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F236/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
    • C08F236/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
    • C08F236/04—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated
    • C08F236/06—Butadiene

Definitions

  • the present invention relates to a tyre for vehicle wheels, in particular, a tyre for cars. Particularly, the present invention relates to a tyre characterized by a reduced wear for winter or all-seasons or summer applications, said tyre comprising a tyre component comprising a cross-linked elastomeric compound obtained from a cross-linkable elastomeric composition comprising a particular conjugated diene polymer.
  • US2022314696A1 discloses a rubber composition that comprises a random styrene- butadiene polymer functionalized with amino alkoxysilane groups and has a glass transition temperature (Tg) lower than -70 °C.
  • Tg glass transition temperature
  • JP3438317B2 discloses a tread rubber composition that contains a styrene-butadiene polymer having a Tg between -50 °C to -10 °C and silica, providing an improvement of the wet grip performance of the tyre.
  • the polymers described above do not contain polymer chains with two segments having different microstructures and characterized by different Tg, rather they are conventional random styrene-butadiene modified copolymers. According to the Applicant, there is still room for improvement of the physical properties of the known rubber compositions in terms of wear resistance and grip.
  • a tyre with a tyre component comprising a cross- linked elastomeric compound obtained by cross-linking a cross-linkable elastomeric composition comprising a particular conjugated diene polymer (I) as defined below – said polymer appropriately selected with a lower Tg for winter / all-seasons applications and a higher Tg for the summer ones – shows reduced wear and maintains or even improves grip performance in either applications.
  • the increased abrasion resistance, without modification of other important properties of the final tyre is predictive of performance retention over time and a longer tyre life.
  • the present invention relates to a vehicle wheel tyre comprising at least a tyre component comprising a cross-linked elastomeric compound obtained by cross-linking a cross-linkable elastomeric composition, wherein said cross-linkable elastomeric composition comprises at least a conjugated diene polymer (I) comprising bound aromatic vinyl units (X) and bound conjugated diene units (Y), said conjugated diene polymer (I) comprising at least a first polymer segment and at least a second polymer segment.
  • said cross-linkable elastomeric composition comprises at least a conjugated diene polymer (I) comprising bound aromatic vinyl units (X) and bound conjugated diene units (Y), said conjugated diene polymer (I) comprising at least a first polymer segment and at least a second polymer segment.
  • the present invention relates to a vehicle wheel tyre comprising at least a tyre component comprising a cross-linked elastomeric compound obtained by cross-linking a cross-linkable elastomeric composition
  • said cross-linkable elastomeric composition comprises at least a conjugated diene polymer (I) comprising bound aromatic vinyl units and bound conjugated diene units, said conjugated diene polymer (I) comprising at least a first polymer segment and at least a second polymer segment, wherein the conjugated diene polymer (I) has only one DSC glass transition temperature (Tg DSC ), measured according to the method of ISO 22768:2006 at a heating rate of 10 °C/min, and wherein: i) the conjugated diene polymer (I) has a calculated glass transition temperature (Tg CALC) from -75.0 °C to -30.0 °C, preferably from -72.0 °C to -45.0 °C, and the difference between the
  • the conjugated diene polymer (I) has only one DSC glass transition temperature (Tg DSC), measured according to the method of ISO 22768:2006 at a heating rate of 10 °C/min.
  • the conjugated diene polymer (I) has a calculated glass transition temperature (Tg CALC), determined according to Gordon-Taylor equation, from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C.
  • the conjugated diene polymer (I) has only one DSC glass transition temperature (Tg DSC), measured according to the method of ISO 22768:2006 at a heating rate of 10 °C/min and has a calculated glass transition temperature (Tg CALC ), determined according to Gordon-Taylor equation, preferably from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C.
  • Tg DSC DSC glass transition temperature
  • Tg CALC calculated glass transition temperature
  • the difference between the extrapolated Tg end temperature (Tg DSC end) and the extrapolated Tg onset temperature (Tg DSC onset) of the Tg DSC curve of the conjugated diene polymer (I), measured according to the method of ISO 22768:2006 at a heating rate of 10 °C/min is at least 12.0 °C and at most 35.0 °C, preferably at least 15.0 °C and at most 35.0 °C, more preferably at least 15.0 °C and at most 30.0 °C.
  • the conjugated diene polymer (I) has only one Tg DSC, has a Tg CALC preferably from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C and the difference between the extrapolated Tg DSC end and Tg DSC onset temperatures is at least 12.0 °C and at most 35.0 °C, preferably at least 15.0 °C and at most 35.0 °C, more preferably at least 15.0 °C and at most 30.0 °C.
  • the calculated glass transition temperature of the first polymer segment (Tg CALC1) is lower than the calculated glass transition temperature of the second polymer segment (Tg CALC2), said calculated glass transition temperatures being determined according to the Gordon-Taylor equation.
  • the conjugated diene polymer (I) has only one DSC glass transition temperature (Tg DSC ), has a calculated glass transition temperature (Tg CALC ), preferably from -75.0 °C to -30.0 °C, even more preferably from -72.0 °C to -45.0 °C and /or the Tg CALC1 is lower than the Tg CALC2.
  • the difference X2 – X1 (wt%) between the amount of bound aromatic vinyl monomer unit in the second polymer segment X2 (wt%) and the amount of bound aromatic vinyl monomer unit in the first polymer segment X1 (wt%) is higher than 5 wt%.
  • the conjugated diene polymer (I) has only one Tg DSC , optionally has a Tg CALC preferably from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C, has a Tg CALC1 lower than Tg CALC2 and the difference X2 – X1 (wt%) is higher than 5 wt%.
  • the conjugated diene polymer (I) has only one Tg DSC, has a Tg CALC preferably from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C and the difference between the extrapolated Tg DSC end and Tg DSC onset temperatures is at least 12.0 °C and at most 35.0 °C, preferably at least 15.0 °C and at most 35.0 °C, more preferably at least 15.0 °C and at most 30.0 °C.
  • elastomeric composition refers to a composition, comprising at least one diene elastomer polymer and one or more additives, which by mixing provides an elastomeric compound suitable for use in tyre components.
  • the components of the elastomeric composition are generally not all introduced simultaneously into the mixer but typically added sequentially.
  • vulcanizing additives such as the vulcanizing agent and optionally accelerators and retarders, are usually added at a stage downstream from the incorporation and processing of all other components.
  • the individual components of the elastomeric composition do not always remain unaltered or individually traceable, as they may have been transformed, in whole or in part, by interaction with other components, heat and/or mechanical processing.
  • the term “elastomeric composition” herein is intended to include the totality of all components that are added in the preparation of the elastomeric compound, irrespective of whether they are all actually present simultaneously, whether they are introduced sequentially, or whether they are subsequently traceable in the final elastomeric compound or tyre.
  • cross-linkable elastomeric composition refers to an elastomeric composition comprising at least an elastomeric diene polymer(s), a reinforcing filler and a vulcanizing agent.
  • elastomeric compound means the mixture obtainable by mixing and preferably heating, at specific pressure and temperature conditions, at least one elastomeric diene polymer with at least one of the additives commonly used in the preparation of compounds for tyres.
  • vulcanized or cross-linked elastomeric compound means the material obtainable by cross-linking or sulphur-curing an elastomeric compound.
  • conjugated diene polymer refers to a polymer or copolymer derived from the polymerisation of one or more monomers, at least one of which is a conjugated diene (conjugated diolefin).
  • elastomeric polymer means a natural or synthetic polymer which, after vulcanization, can be repeatedly stretched at room temperature to at least twice its original length and after removal of the tensile load returns substantially immediately and forcefully to its approximate original length (as defined in ASTM D1566-11 Standard terminology relating to Rubber).
  • vulcanization refers to the cross-linking reaction in a natural or synthetic rubber induced for example by a sulphur-based vulcanizing agent.
  • raw or green refers to a material, compound, component or tyre that has not yet been vulcanized.
  • vulcanizing agent refers to a cross-linking agent capable of transforming natural or synthetic rubber into an elastic and resistant material through the formation of a three- dimensional network of inter- and intra-molecular cross-links.
  • vulcanization accelerator refers to a chemical agent capable of decreasing the duration of the vulcanization process and/or operating temperature, such as TBBS, sulphenamides in general, thiazoles, dithiophosphates, dithiocarbamates, guanidines, as well as sulphur donors such as thiurams.
  • vulcanizing activator refers to a chemical agent that can further facilitate curing, causing it to take place at a shorter time and optionally lower temperature.
  • An example of an activator is the stearic acid-zinc oxide system.
  • vulcanizing retardant refers to a chemical agent capable of delaying the start of the curing reaction and/or suppressing undesirable secondary reactions, e.g. N- (cyclohexylthio) phthalimide (CTP).
  • curing system refers to a system of chemical agents comprising at least one vulcanizing agent and optionally an accelerator agent, a retardant agent and/or a vulcanisation activating agent
  • reinforcing filler refers to a reinforcing material typically used in the industry to improve the mechanical properties of tyre tyres, chosen preferably from carbon black, conventional silica, such as sand silica precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibres and mixtures thereof.
  • white filler refers to a conventional reinforcing material used in the industry chosen from conventional silica and silicates, such as sepiolite, paligorskite also known as attapulgite, montmorillonite, halloysite and the like, optionally modified by acid treatment and/or derivatisation. Typically, white fillers have surface hydroxyl groups.
  • the term “mixing phase 1" refers to the step (step 1) in the elastomer compound preparation process in which one or more additives may be incorporated by mixing and optionally heating, at specific pressure and temperature conditions, except for the vulcanizer which is fed in phase 2.
  • the mixing phase 1 is also called the “non-production phase”.
  • mixing phase 2 refers to the next step (step 2) in the elastomeric compound preparation process in which the vulcanizing agent and, optionally, the other additives of the vulcanization package are introduced into the elastomeric compound obtained from phase 1, and mixed into the material, at a controlled temperature, generally at a compound temperature of less than 120 °C, so as to provide the vulcanizable elastomeric compound.
  • the mixing phase 2 is also referred to as the “production phase”.
  • Each mixing phase may comprise several intermediate phases or sub-phases of processing, characterised by the momentary interruption of mixing to allow the addition of one or more ingredients but without intermediate dumping of the compound.
  • modification or “functionalisation” refers to a chain-end modification reaction between one end of a single polymer chain and one or more modifying agents.
  • coupling or “branching” reaction corresponds to a chain end reaction between two and, respectively, more than two single polymer chain ends and one or more coupling agents. The chain-end modification reaction between more than two single polymer chain ends and a coupling agent results in polymers comprising three or more arms at the coupling point.
  • coupling functions and modifying functions may be present in the same agent that thus acts as coupling as well as modifying agent, the coupling functions providing the branching and the modifying functions modifying the properties of the polymer, for instance by making it more compatible with the filler and thus allowing a better distribution thereof in the compound.
  • modification rate refers to the weight content ratio, expressed in %, of the modified conjugated diene polymer component having a modifying functional group in the polymer relative to the total amount of the conjugated diene polymer mixture.
  • degree of branching refers to the number of polymer arms/chains at the coupling point.
  • a “random” (or statistical) polymer includes two or more types of monomers that are polymerised in a non-regular or non-coherent manner, i.e. the sequence of monomers within the polymer chain follows a statistical rule.
  • a “block copolymer”, as defined herein, essentially consists of two types of monomers that are polymerised in a regular or coherent manner, thus forming two or more homopolymer subunits that are connected by covalent bonds.
  • segment or polymer segment refers to a portion of the conjugated diene polymer (I) respectively including conjugated diene monomer units and aromatic vinyl monomer units, herein named second polymer segment with a higher Tg, or preferably including conjugated diene monomer units only, herein named first polymer segment, with a lower Tg.
  • first polymer segment refers to the polymer segment with a lower Tg than the second polymer segment.
  • second polymer segment herein refers to the polymer segment with a higher Tg than the first polymer segment.
  • polymer segment ratio in the conjugated diene polymer (I) means the average weight fraction of each polymer segment relative to the entire conjugated diene polymer (I).
  • bound conjugated diene herein refers to the conjugated diene unit which is incorporated into the conjugated diene polymer (I) by polymerization.
  • amount of bound aromatic vinyl unit herein refers to the wt% of bound aromatic vinyl units with respect to a segment weight or the conjugated diene polymer (I) weight.
  • amount of vinyl unit herein refers to the value of the molar fraction (mol%) of 1, 2--vinyl units with respect to the bound conjugated diene monomer units comprised in the conjugated diene polymer (I) or in a segment thereof.
  • microstructure herein refers to the composition of a conjugated diene polymer composed of aromatic vinyl units and conjugated diene units.
  • consisting essentially of means that additional specific components may be present, i.e. those that do not materially influence the essential characteristics of the polymer compound or elastomer composition in question.
  • the tyre according to the invention and the cross-linkable elastomeric composition used to prepare one or more of the tyre components may have one or more of the following preferred characteristics, taken in isolation or in any desired combination with each other. Numerical ranges described as preferable ranges may be replaced with numerical ranges obtained by arbitrarily combining each value described as the upper limit and each value described as the lower limit, even when the combination is not specifically mentioned.
  • the tyre of the invention comprises a tyre component comprising a cross-linked elastomeric compound obtained by cross-linking a cross-linkable elastomeric composition as described below.
  • said tyre component consists essentially of, more preferably consists of a cross-linked elastomeric compound obtained by cross-linking the following cross-linkable elastomeric composition.
  • the present cross-linkable elastomeric composition comprises at least: 100 phr of one or more elastomeric polymer(s), of which at least 20 phr of at least a conjugated diene polymer (I) as defined below, at least 10 phr of a reinforcing filler, and at least 0.1 phr of a vulcanizing agent.
  • the cross-linkable elastomeric composition comprises 100 phr of one or more elastomeric polymer(s), of which preferably at least 30 phr or 40 phr, more preferably at least 50 phr or 60 phr or 70 phr, even more preferably at least 80 phr or 90 phr of one or more conjugated diene polymer(s) (I).
  • the cross-linkable elastomeric composition comprises 100 phr of conjugated diene polymer(s) (I) as the only elastomeric polymer(s).
  • the cross-linkable elastomeric composition may comprise one or more than one conjugated diene polymer(s) (I) in admixture.
  • Conjugated diene polymers (I) suitable for the tyre of the present invention and the manufacture thereof are disclosed for instance in the patent application JP2023-072838 in the name of Asahi, herein incorporated by reference.
  • the present conjugated diene polymer (I) comprises bound conjugated diene units and bound aromatic vinyl units.
  • the total amount of bound aromatic vinyl unit Xall (wt%) in the conjugated diene polymer (I) is the value of the weight fraction of the bound aromatic vinyl unit relative to the total weight of the conjugated diene polymer (I).
  • the total amount of vinyl unit Yall (mol%) of the bound conjugated diene in the present conjugated diene polymer (I) is the value of the mole fraction (mol%) of the 1,2-vinyl units of the bound conjugated diene in the conjugated diene polymer (I).
  • Xall (wt%) and Yall (m beginnerl %) satisfy the Gordon-Taylor equation thus providing a calculated Tg CALC having a value preferably from -75.0 °C to -30.0 °C, even more preferably from -72.0 °C to -45.0 °C.
  • conjugated diene monomer units include, but are not limited to, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3- hexadiene, 1,3-heptadiene and mixtures thereof. Among them, 1,3-butadiene and isoprene are preferred.
  • aromatic vinyl monomer units include, but are not limited to, styrene, p- methylstyrene, ⁇ -methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene and mixtures thereof.
  • the conjugated diene polymer (I) comprises at least a first polymer segment and at least a second polymer segment, in which the first polymer segment preferably does not comprise any aromatic vinyl monomer unit while the second polymer segment comprises an aromatic vinyl monomer unit
  • Polymer segments other than the first polymer segment and second polymer segment need not be comprised but may be present, for instance after first and second segment synthesis, a third segment may be included in order to raise the reactivity between the conjugated diene polymer and coupling agent.
  • the first polymer segment and the second polymer segment may each comprise a plurality of polymer segments, but, preferably, they comprise a single polymer segment.
  • the polymer segments may be directly bound to each other or may be bound via a coupling agent.
  • the % ratio of the sum of the weights of the first and second polymer segments to the total weight of the conjugated diene polymer (I) is preferably higher than 70 %, more preferably higher than 80 % and even more preferably higher than 90 %.
  • the weight of the copolymer comprising styrene as bound aromatic vinyl monomer unit and butadiene as bound conjugated diene monomer unit is at least 70 wt% of the weight of the entire conjugated diene polymer (I), more preferably at least 80 wt%, even more preferably at least 90 wt%.
  • the first and second polymer segments preferably have a predetermined weight ratio – namely a predetermined ratio of the weight of the first polymer segment (r1) and of the weight of the second polymer segment (r2) respectively - to the total weight of the conjugated diene polymer (I).
  • the weight ratio (r1) of the first polymer segment to the total weight of the conjugated diene polymer (I) is at least 30 wt%, more preferably at least 40 wt%, even more preferably at least 50 wt%.
  • the weight ratio (r1) of the first polymer segment to the total weight of the conjugated diene polymer (I) is at most 80 wt%, more preferably at most 75 wt%, even more preferably at most 70 wt%.
  • the weight ratio (r1) of the first polymer segment to the total weight of the conjugated diene polymer (I) is at least 30 wt% and at most 80 wt%, more preferably at least 40 wt% and at most 75 wt%, still more preferably at least 50 wt% and at most 70 wt%.
  • the weight ratio (r2) of the second polymer segment to the total weight of the conjugated diene polymer (I) is at least 20 wt%, more preferably at least 25 wt%, even more preferably at least 30 wt%.
  • the weight ratio (r2) of the second polymer segment to the total weight of the conjugated diene polymer (I) is at most 60 wt%, more preferably at most 55 wt%, even more preferably at most 50 wt%.
  • the weight ratio (r2) of the second polymer segment to the total weight of the conjugated diene polymer (I) is at least 20 wt% and at most 60 wt%, more preferably at least 25 wt% and at most 55 wt%, still more preferably at least 30 wt% and at most 50 wt%.
  • the polymer segments in the conjugated diene polymer (I) differ from each other in their microstructure. Each polymer segment may differ, for example, in the amount of bound aromatic vinyl unit and the amount of vinyl unit of the bound conjugated diene.
  • the amount of vinyl unit Y1 (mol%) in the bound conjugated diene is higher than 10 mol%, more preferably at least 12 mol%, still more preferably at least 15 mol%.
  • the amount of vinyl unit Y1 (mol%) is at most 50 mol%, more preferably at most 45 mol% and still more preferably at most 40 mol%.
  • the amount of vinyl unit Y1 (mol%) in the bound conjugated diene is from 10 mol% to 50 mol%, more preferably from 12 mol% to 45 mol%, even more preferably from 15 mol% to 40 mol%.
  • the amount of vinyl unit Y1 is within the above ranges, the flexibility of the conjugated diene polymer (I) is improved in the low temperature range and the vulcanized compound thereof tends to be superior in wear resistance.
  • the amount of the aromatic vinyl monomer unit X2 (wt%) is at least 10 wt% and at most 40 wt%, more preferably at least 20 wt% and at most 30 wt%.
  • the amount of vinyl unit Y2 (mol%) is at least 25 mol% and at most 65 mol%, more preferably at least 40 mol% and at most 60 mol%.
  • the amount of aromatic vinyl units X2 and Y2 are within the above ranges, there is an improvement in wet grip as long as the stiffness of the compound is kept under control.
  • the difference X2 – X1 (wt%) between the amount of bound aromatic vinyl monomer unit in the second polymer segment X2 (wt%) and the amount of bound aromatic vinyl monomer unit in the first polymer segment X1 (wt%) is higher than 5 wt%, more preferably is at least 10 wt%.
  • said difference is at most 35 wt%, more preferably at most 30%.
  • said difference is higher than 5 wt% to 35 wt%, more preferably from 10 wt% to 30 wt%.
  • the polymer segments have few or no blocks comprising four or more aromatic vinyl monomer units chained together, herein referred as “bound aromatic vinyl monomer unit block”.
  • the content of these blocks in the conjugated diene polymer (I) is at most 1.0 wt%, more preferably at most 0.1 wt%, more preferably is 0 wt% of the total weight of the conjugated diene polymer (I).
  • the content of bound aromatic vinyl monomer unit blocks can be measured by analysing the amount of polystyrene insoluble in methanol according to the Kolthoff method (I. M. Kolthoff, et al., J. Polym. Sci. 1, 429 (1964)). With fewer or no bound aromatic vinyl monomer unit blocks, the conjugated diene polymer (I) more likely has a single glass transition temperature (Tg DSC).
  • the amount of vinyl unit in the bound butadiene can be calculated by the method of Hampton (R.R. Hampton, Analytical Chemistry, 21, 923 (1949)).
  • the total amount of bound aromatic vinyl monomer units Xall (wt%) and the total amount of vinyl unit Yall (m beginnerl %) in the conjugated diene polymer (I) satisfy the Gordon- Taylor equation thus providing a calculated Tg having a value preferably from -75.0 °C to - 30.0 °C, even more preferably from -72.0 °C to -45.0 °C.
  • the total amount of aromatic vinyl unit Xall and of vinyl unit Yall in the conjugated diene polymer (I) can be determined, for instance, by NMR according to the method of ISO 21561- 1:20015 as described in the experimental section below.
  • the conjugated diene polymer (I) preferably has a single glass transition temperature measured by differential scanning calorimetry (DSC) (Tg DSC ) according to ISO 22768:2006.
  • the Tg DSC of the conjugated diene polymer (I) measured value is preferably at least ⁇ 75.0 °C, more preferably at least ⁇ 70.0 °C and preferably at most -35.0 °C, more preferably at most -40.0 °C.
  • the Tg DSC of the conjugated diene-based polymer (I) is measured according to the method reported in the experimental part in accordance with ISO 22768:2006. More specifically, a DSC curve is recorded by performing differential scanning calorimetry (DSC) while increasing the temperature within a predetermined temperature range, and the inflection point of the DSC curve is taken to be the glass transition temperature.
  • the Tg DSC of the conjugated diene polymer (I) is from -75.0 °C to -35.0 °C, more preferably from -70.0 °C to -40.0 °C.
  • the Tg DSC of the conjugated diene polymer (I) is preferably from -70.0 °C to -40.0 °C, more preferably from -65.0 °C to -55.0 °C for winter or all-seasons applications.
  • the Tg DSC of the conjugated diene polymer (I) is from -55.0 °C to -35.0 °C, more preferably from -55.0 °C to -40.0 °C for summer tyres.
  • the vulcanized compound of the conjugated diene polymer (I) tends to have overall optimized performance balance (namely wet grip, wear and RR i.e. fuel economy) for each specific application (winter, all-seasons or summer). From the DSC thermogram of the conjugated diene polymer (I), Tg DSC onset temperature and Tg DSC end temperature can be extrapolated as described in the present experimental part and as illustrated in Figure 4.
  • the extrapolated Tg DSC onset temperature of the conjugated diene polymer (I) is preferably at least -90.0 °C, more preferably at least -85.0 °C and preferably at most -60.0 °C, more preferably at most -65.0 °C.
  • the extrapolated Tg DSC end temperature of the conjugated diene-based polymer (I) is preferably at least -70.0 °C, more preferably at least -65.0 °C and preferably at most -40.0 °C, more preferably at most -45.0 °C.
  • the difference of the extrapolated Tg DSC end temperature and the extrapolated Tg DSC onset temperature is at least 12.0 °C, more preferably at least 13.0 ⁇ C.
  • the difference of the extrapolated Tg DSC end temperature and the extrapolated Tg DSC onset temperature is at least 12.0 °C and at most 35.0 °C, more preferably at least 15.0 °C and at most 35.0 °C, even more preferably at least 15.0 ⁇ C and at most 30.0 °C.
  • the conjugated diene polymer (I), comprising two or more polymer segments undergoes glass transition in a plurality of temperature ranges, as the polymer segments have different glass transition temperatures.
  • the conjugated diene polymer (I) preferably comprises segments comprising vinyl units and aromatic vinyl units with higher Tg (i.e.
  • Tg CALC1 the calculated glass transition temperature of the first polymer segment
  • Tg CALC2 the calculated glass transition temperature of the second polymer segment
  • the polymer segment whose Tg CALC is lower by 5 °C or more with respect to the average Tg CALC of the conjugated diene polymer (I) is herein referred as the "first polymer segment” and the calculated Tg as Tg CALC1 , while if higher by 5 °C or more is herein referred as the "second polymer segment” and the calculated Tg as Tg CALC2.
  • the differences of the amount of aromatic vinyl units and of vinyl units between the first and second polymer segment respectively can be both increased.
  • both said differences increase too much, the two polymer segments become less compatible and the tensile strength of the vulcanized product tends to deteriorate.
  • it is effective to increase the difference in the amount of bound aromatic vinyl monomer units of the two polymer segments (X2 higher than X1) while keeping the amount of vinyl unit in the bound conjugated diene of the two polymer segments (Y2 and Y1), within appropriate ranges, as recited above.
  • the glass transition temperature of the conjugated diene polymer (I) depends on its microstructure and can be estimated from the total amount of bound aromatic vinyl units Xall (wt%) of the conjugated diene polymer (I) and the total amount of vinyl unit Yall (mol%) in the bound conjugated diene of the conjugated diene polymer (I) according to the Gordon- Taylor equation (Gordon, M.; Taylor, J. S.; J. Appl.
  • a conjugated diene polymer comprises styrene and one of the i's is a styrene component
  • the thermal expansion coefficient of polystyrene J. Brandrup et al, Polymer Handbook, Group 3, (US), John Wiley & Sons, Inc.1966, VI-75
  • ⁇ i 3.6 ⁇ 10 -4 K -1
  • Tgi measured by DSC is 105.3 °C
  • ⁇ i 1.02 g/cm 3 from the measured density.
  • the calculated glass transition temperature (Tg CALC) which depends on the microstructure of the conjugated diene polymer (I), preferably falls within the range from -75.0 °C to -30.0 °C, more preferably from -72.0 °C to -45.0 °C by satisfying equation (1) /(1A).
  • the Tg CALC is at least -75.0 °C, more preferably at least -72.0 °C, even more preferably at least -70.0 °C, still more preferably at least -68.0 °C and preferably at most -30.0 °C, more preferably at most -45.0 °C, still more preferably at most -50.0 °C.
  • the best performance of the present conjugated diene polymer (I) are achieved when the amount of bound aromatic vinyl unit Xall (wt%) and the amount of vinyl unit in the bound conjugated diene Yall (mol%) satisfies the above-mentioned equation (1) /(1A) thus preferably providing a Tg CALC of at least -75.0 °C and at most -30.0 °C.
  • the glass transition temperature of the conjugated diene polymer (I) can be controlled within the numerical range described above by adjusting the microstructure of the polymer.
  • butadiene-styrene polymer it can be controlled by adjusting the total amount of bound styrene Xall (wt%) and the total amount of vinyl unit in the bound butadiene Yall (mol%) according to formula (1A).
  • Tg CALC Tg CALC
  • the calculated Tg CALC temperature of the conjugated diene polymer (I) according to equation (1) / (1A) may differ from the observed Tg measured by DSC depending on the polymer microstructure and /or the specific settings of DSC measurements, in particular cooling and heating rates.
  • the discrepancy between the glass transition temperature inferred from equation (1) / (1A) and the actual glass transition temperature by DSC tends to be more pronounced when the difference in the Tg CALC values between the polymer segments (Tg CALC2 – Tg CALC1) is 33 or more, or when the mass ratio r1 of the first polymer segment described above is in the range from 40 to 60.
  • the conjugated diene polymer (I) comprises segments with higher content of aromatic vinyl units and higher Tg, herein named the second polymer segment, and segments with lower content of aromatic vinyl units and lower Tg, herein named the first polymer.
  • the same equation (1) / (1A) is applicable to calculate the Tg CALC of a segment n by using the respective Xn and Yn content in that segment.
  • the estimated Tg of the polymer segments have the same trend, namely the calculated glass transition temperature of the first polymer segment (Tg CALC1) is lower than the calculated glass transition temperature of the second polymer segment (Tg CALC2 ).
  • the value of equation (1)/(1A) when applied to the first polymer segment provides a Tg CALC1 value lower than the value obtained when applied to the conjugated diene-based polymer (I) i.e. the first polymer segment has a Tg CALC1 lower than the Tg CALC of the whole conjugated diene polymer (I).
  • Tg CALC1 is calculated by inserting in equation (1A) the amount of bound styrene in the first polymer segment (X1, which is preferably zero) and the amount of vinyl unit in the bound butadiene (Y1) of the first polymer segment instead of Xall and Yall.
  • the value obtained from equation (1)/(1A) when applied to the second polymer segment provides a Tg CALC2 value higher than the value obtained when applied to the conjugated diene-based polymer (I) i.e.
  • the second polymer segment has a Tg CALC2 higher than the Tg CALC of the whole conjugated diene polymer (I). If the conjugated diene polymer is a butadiene-styrene polymer or a butadiene homopolymer, Tg CALC2 is calculated by inserting in equation (1A) the amount of bound styrene in the second polymer segment (X2) and the amount of vinyl unit in the bound butadiene (Y2) instead of Xall and Yall.
  • the amount of bound aromatic vinyl unit of the second polymer segment X2 (wt%) and the amount of vinyl unit in the bound conjugated diene of the second polymer segment Y2 (mol%) provides a Tg CALC2 higher than -45.0 °C and lower than -5.0 °C.
  • the Tg CALC2 of the second polymer segment is at least -44.0 °C, more preferably at least -43.0 °C and at most -10.0 °C, more preferably at most -15.0 °C.
  • the values of Tg CALC1 and Tg CALC2 can be tailored by adjusting the amount of aromatic vinyl unit and the amount of vinyl unit in the first polymer segment and in the second polymer segment, i.e.
  • the difference between Tg CALC2 and Tg CALC1 is at least 10.0 °C, more preferably at least 20.0 °C, even more preferably at least 35°C.
  • said difference is at most 70.0 °C, more preferably at most 60.0 °C, even more preferably at most 55.0 °C.
  • the difference between Tg CALC2 and Tg CALC1 is from 10.0 °C to 70.0 °C, more preferably from 20.0 °C to 60 °C, even more preferably from 35.0 °C to 55.0 °C.
  • the weight average molecular weight (Mw) of the conjugated diene polymer (I) measured by gel permeation chromatography (GPC) is preferably at least 270,000 g/mol, more preferably at least 300,000, and even more preferably at least 400,000 g/mol and/or preferably at most 1,350,000 g/mol, more preferably at most 900,000 g/mol, even more preferably at most 700,000 g/mol.
  • the weight average molecular weight (Mw) of the conjugated diene polymer (I) is from 300,000 g/mol to 1,350,000 g/mol, preferably from 400,000 g/mol to 1,000,000 g/mol, more preferably from 400,000 g/mol to 700,000 g/mol.
  • the number average molecular weight (Mn) of the conjugated diene polymer (I) measured by GPC is preferably at least 170,000 g/mol, more preferably at least 190,000 g/mol and even more preferably at least 230,000 g/mol and/or at most 800,000 g/mol, more preferably at most 500,000 g/mol, and even more preferably at most 450,000 g/mol.
  • the weight average molecular weight (Mw) and number average molecular weight (Mn) of the conjugated diene polymer (I) can be controlled within the above numerical range by adjusting the amount of the polymerization initiator to the amount of the monomers used, and type and amount of the coupling agent used.
  • the molecular weight distribution of the conjugated diene polymer (I) is represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (polydispersity index Mw/Mn).
  • the conjugated diene polymer (I) preferably has a polydispersity index Mw/Mn of at least 1.2 and at most 2.5.
  • the polydispersity index Mw/Mn of the conjugated diene- based polymer (I) is at least 1.3, more preferably at least 1.4 and/or at most 2.4, more preferably at most 2.2, even more preferably at most 2.0.
  • the conjugated diene polymer (I) preferably comprises a nitrogen containing modifying group and preferably has a modification rate of at least 60%.
  • the modification rate represents the weight ratio of the modified conjugated diene-based polymer (I) containing the nitrogen containing modifying group relative to the total amount of the mixture of the modified and unmodified conjugated diene-based polymer.
  • the modification rate can be measured by chromatography, which can separate modified and non-modified components.
  • the modification rate can be controlled by adjusting the amount of modifying agent added and the reaction method.
  • the conjugated diene polymer (I) preferably has a modification rate of at least 60%, more preferably at least 65%, even more preferably at least 70%.
  • the pair of polymer segments may be directly bound to each other or may be bound via a coupling agent.
  • the obtained degree of branching depends on the type of coupling agent used.
  • the degree of branching of the conjugated diene polymer (I) is greater than 2.
  • the conjugated diene polymer (I) can be manufactured according to conventional polymerization techniques, for instance by a method in which two or more continuous reactors are used, and that includes a first polymerization process (PR1) in which a conjugated diene, a polymerization initiator and a polar substance are added to the continuous reactor to continuously prepare the first polymer segment, and a second polymerization process (PR2) in which an aromatic vinyl monomer and a polar substance are added to the above-mentioned continuous reactor to form a second polymer segment at the end of the above-mentioned first polymer segment.
  • PR1 first polymerization process
  • PR2 second polymerization process
  • the method may further comprise a coupling process with a coupling agent such as a trifunctional or higher reactive agent and/or a process for modifying with a modifier having a nitrogen atom-containing group (preferably with a coupling agent having a nitrogen atom-containing group) at the active terminal of the conjugated diene-based polymer obtained through the polymerization process described above.
  • a coupling agent such as a trifunctional or higher reactive agent
  • a process for modifying with a modifier having a nitrogen atom-containing group preferably with a coupling agent having a nitrogen atom-containing group
  • PR3 the coupling process
  • the weight ratio of the conjugated diene that is added in the above-mentioned first polymerization process (PR1) relative to the total amount of the conjugated diene and aromatic vinyl monomer that are added is from 50 wt% to 80 wt%.
  • the weight ratio of the amount of the aromatic vinyl monomer that is added is from 0.35 to 0.70 relative to the amount of conjugated diene that is added.
  • the polar substance is added in an amount that is greater than the amount of polar substance that is added in the above- mentioned first polymerization process (PR1).
  • the above-mentioned coupling agent is an amino alkoxysilane. At least an organic monolithium compound can be used as the polymerization initiator.
  • suitable polymerisation initiators are n-BuLi, sec-BuLi, tert-BuLi, Li- (CH2)(Me)2Si-N-(C4 H9)2 , Li-(CH2)(Me)2 Si-N-(C2 H5)2 and the like.
  • the amount of the organic monolithium compound used as the polymerization initiator depends on the desired molecular weight of the conjugated diene-based polymer as known in the art.
  • the organomonolithium agent is preferably an alkyl lithium agent with a substituted amino group, namely an amino group having no active hydrogen or having active hydrogen protected.
  • alkyllithium agent bearing an amino group having no active hydrogen are 3-dimethyl aminopropyl lithium, 3-diethyl aminopropyl lithium, 4-(methyl propylamino)butyl lithium and 4-hexamethylene iminobutyl lithium.
  • an alkyl lithium agent having an amino group with a protected active hydrogen are 3-bis trimethyl silyl aminopropyl lithium and 4-trimethyl silyl methyl aminobutyl lithium.
  • a polar substance may be added in the polymerization process.
  • the aromatic vinyl agent can be randomly copolymerized with the conjugated diene agent due to the polar substance.
  • Non limiting examples of polar substances are ethers, tertiary amine agents; alkali metal alkoxide agents, phosphine agents and their admixtures.
  • the polymerization temperature in the polymerization process is preferably a temperature at which living anionic polymerization proceeds, and from the standpoint of productivity it is preferably at least 0 °C and at most 120 °C, more preferably at least 50 °C and at most 100 °C.
  • the conjugated diene based polymer (I) can be prepared as described in JP2023-072838 or in WO2018128285A1.
  • the coupling agent may have any structure as long as it is a reactive agent with a functionality of 3 or more, but a reactive agent with a functionality of 3 or more having a silicon atom is preferable.
  • Examples of preferred coupling agents with a functionality of 3 or more are halogenated silane agents, epoxidised silane agents, vinylated silane agents, alkoxysilane agents and alkoxysilane agents containing nitrogen- containing groups.
  • modifying agents comprising nitrogen atoms include, but are not limited to, isocyanate agents, isothiocyanate agents, isocyanuric acid derivatives, carbonyl agents comprising nitrogen atom group, vinyl agents comprising nitrogen atom group and epoxy agents comprising nitrogen atom group.
  • the nitrogen atom-comprising functional group is an amine having no active hydrogen such as a tertiary amine.
  • Examples of coupling agents that are modifying agents too are epoxy agents having a nitrogen atom-comprising group such as hydrocarbon agents comprising an epoxy group bonded to an amino group, furthermore optionally having an epoxy group bonded to an ether group.
  • a modifying agent is an alkoxysilane agent having a nitrogen atom- comprising group, such as for instance, tris(3-trimethoxysilylpropyl)amine, tris(3- triethoxysilylpropyl)amine, tris(3-tripropoxysilylpropyl)amine, bis(3-trimethoxysilylpropyl)-[3- (2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tetrakis(3-trimethoxysilylpropyl)- 1,3-propanediamine (also referred to as "N,N,N’,N’-tetrakis(3-trimethoxysilylpropyl)-1,3- propanediamine”), tris(3-trimethoxysilylpropyl)-[3-(1-methoxy-2-trimethylsilyl-1-sila-2- azacyclopentane)prop
  • Suitable coupling and/or modifying agents are disclosed for instance in the patent application JP2023-072838.
  • an extender oil a liquid rubber and/or a resin is further added to the produced conjugated diene-based polymer (I).
  • the conjugated diene polymer (I) exhibits excellent wear resistance and tensile properties, and when incorporated into a rubber composition provides for enhanced grip performance.
  • the complement to the conjugated diene polymer(s) (I) up to 100 phr can be one or more conventional elastomeric polymer(s), as described below.
  • the distribution of vinyl units and aromatic vinyl units is either random or anyway not corresponding to the one stated above for the present conjugated diene polymer (I).
  • the conventional elastomeric polymer(s) may be selected from those commonly used in sulphur-vulcanizable elastomeric compositions, which are particularly suitable for producing tyres, i.e.
  • Tg glass transition temperature
  • These polymers or copolymers may be of natural origin or may be obtained by solution polymerization, emulsion polymerization or gas-phase polymerization of one or more conjugated dienes, optionally mixed with at least one comonomer, preferably selected from monoolefins, monovinylarenes and/or polar comonomers, typically in an amount not exceeding 60% by weight.
  • the conjugated dienes generally comprise from 4 to 12, preferably from 4 to 8 carbon atoms and may be selected, for example, from the group comprising: 1,3-butadiene, isoprene, 2,3- dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl- 1,3-butadiene and mixtures thereof.1,3-butadiene and isoprene are particularly preferred.
  • the monoolefins can be selected from ethylene and ⁇ -olefins generally containing from 3 to 12 carbon atoms, such as for example propylene, 1-butene, 1-pentene, 1-hexene, 1- octene or mixtures thereof.
  • Monovinylarenes which may optionally be used as comonomers, generally contain from 8 to 20, preferably from 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, for example, ⁇ -methylstyrene, 3-methylstyrene, 4- propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolyl- styrene, 4- (4-phenylbutyl)styrene, and mixtures thereof.
  • Styrene is particularly preferred.
  • Polar comonomers that may optionally be used, can be selected, for example, from among acrylic acid and alkylacrylic acid esters, acrylonitriles, or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.
  • the elastomeric polymer may be selected, for example, from cis-1,4- polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (in particular polybutadiene with a high content of 1,4-cis), isoprene/isobutene copolymers, halogenated isoprene/isobutene copolymers, 1,3- butadiene/acrylonitrile copolymers, styrene/1,3-butadiene copolymers, styrene/isoprene/1,3-butadiene copolymers, styrene/1,3-butadiene/acrylonitrile copolymers, and mixtures thereof.
  • cis-1,4- polyisoprene natural or synthetic, preferably natural rubber
  • 3,4-polyisoprene polybutadiene (in particular polybutadiene with a high content
  • the cross-linkable elastomeric composition may optionally comprise at least one polymer of one or more monoolefins with an olefinic comonomer or derivatives thereof.
  • the monoolefins can be selected from: ethylene and ⁇ -olefins generally containing from 3 to 12 carbon atoms, such as for example propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or mixtures thereof.
  • the diene optionally present generally contains from 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, vinylnorbornene or mixtures thereof.
  • EPR ethylene/propylene
  • EPDM ethylene/propylene/diene copolymers
  • polyisobutene butyl rubber
  • halobutyl rubbers in particular chlorobutyl or bromobutyl rubbers
  • mixtures thereof are particularly preferred: ethylene/propylene (EPR) copolymers or ethylene/propylene/diene (EPDM) copolymers; polyisobutene; butyl rubber; halobutyl rubbers, in particular chlorobutyl or bromobutyl rubbers; and mixtures thereof.
  • the distribution of vinyl units and aromatic vinyl units is either random or it does not provide first and second polymers segments as the present ones of the conjugated diene polymer (I).
  • the above-mentioned polymers can optionally be functionalised along the main chain or at the ends thereof.
  • the functional group may be introduced into the elastomeric polymer by processes known in the art such as, for example, during the production of the elastomeric polymer by copolymerisation with at least one corresponding functionalised monomer containing at least one ethylene unsaturation; or by subsequent modification of the elastomeric polymer by grafting at least one functionalised monomer in the presence of a free radical initiator (for example, an organic peroxide).
  • a free radical initiator for example, an organic peroxide
  • the cross-linkable elastomeric composition of the present invention preferably comprises at least 10 phr or 20 phr or 30 phr or 40 phr, more preferably at least 40 phr or 50 phr, even more preferably at least 60 phr or 70 phr of at least a reinforcing filler.
  • the present composition may comprise from 1 phr to 150 phr, from 5 phr to 120 phr or from 10 phr to 90 phr of at least one reinforcing filler.
  • the reinforcing filler is selected from carbon black, white fillers, silicate fibres, derivatives and mixtures thereof.
  • said reinforcing filler is a white filler selected from among hydroxides, oxides and hydrated oxides, salts and hydrated salts of metals, silicates fibres, derivatives thereof and mixtures thereof.
  • said white filler is silica.
  • silica Commercial examples of suitable silica are Zeosil 1165 MP, Zeosil 1115 MP, Zeosil 185 GR, Efficium from Solvay, Newsil HD90 and Newsil HD200 from Wuxi, K160 and K195 from Wilmar, H160AT and H180 AT from IQE, Zeopol 8755 and 8745 from Huber, Perkasil TF100 from Grace, Hi-Sil EZ 120 G, EZ 160G, EZ 200G from PPG, Ultrasil 7000 GR and Ultrasil 9100 GR from Evonik.
  • said reinforcing filler comprises silica mixed with carbon black.
  • said reinforcing filler comprises a modified silica.
  • Silica may be modified for instance by reaction with silsequioxanes (as in WO2018078480A1), with pyrroles (as in WO2016050887A1) or with silanizing agents.
  • suitable silanizing agents are Si69, Dynasilan AMEO and Dynasilan GLYEO from Evonik.
  • the modified silica may be a sulphurised silanized silica.
  • Sulphurised silanized silica is a silica prepared by reaction of a silica or of a metal silicate, with at least one sulphurised silanizing agent.
  • a commercial example of suitable sulphurised silanized silica is Agilon 400 silica from PPG.
  • said reinforcing filler comprises a modified silica mixed with carbon black.
  • said reinforcing filler comprises silicates, such as lamellar silicates (e.g. bentonites, halloysite, laponite, saponite, vermiculite or hydrotalcite) or silicate fibres (e.g. sepiolite fibres, paligorskite fibres also known as attapulgite, wollastonite fibres, imogolite fibres) optionally modified, or their admixtures.
  • said reinforcing filler comprises silicate fibres mixed with carbon black.
  • said silicate fibres are modified silicate fibres, such as those described in WO2016174629A1, in WO2016174628A1, those organically modified by reaction, for example, with quaternary ammonium salts or with a silanizing agent.
  • said reinforcing filler is carbon black, preferably selected from those having a surface area not smaller than 20 m 2 /g, preferably larger than 50 m 2 /g (as determined by STSA - statistical thickness surface area according to ISO 18852:2005).
  • Carbon black may be for example N110, N115, N121, N134, N220, N234, N326, N330, N375 or N550, N660 marketed by Birla Group (India) or by Cabot Corporation, Vulcan® 1391 supplied by Cabot Corporation or Birla CarbonTM 2115 supplied by Birla Group.
  • the cross-linkable elastomeric composition of the present invention comprises at least 0.1 phr of a vulcanizing agent
  • the cross-linkable elastomeric composition comprises at least 0.2 phr, 0.5 phr, 0.8 phr or 1 phr of at least one vulcanizing agent.
  • the composition comprises from 0.1 to 10 phr, from 0.2 to 10 phr, from 1 to 10 phr or from 1.5 to 5 phr of at least one vulcanizing agent.
  • the at least one vulcanizing agent is preferably selected from sulphur, sulphurised agents (sulphur donors), such as, for example, bis[(trialkoxysilyl)propyl]polysulphides, caprolactam-disulphide or peroxides and mixtures thereof.
  • the vulcanizing agent is sulphur, preferably selected from soluble sulphur (crystalline sulphur), insoluble sulphur (polymer sulphur), oil-dispersed sulphur and mixtures thereof.
  • a vulcanizing agent suitable for use in the cross-linkable elastomeric composition is the soluble sulphur of Zolfindustria (Italy).
  • the vulcanizing agent may be used together with adjuvants such as vulcanization activators, accelerators and/or retardants known to those skilled in the art.
  • the cross-linkable elastomeric composition may optionally comprise at least one vulcanization activator.
  • Vulcanization activators suitable for use in the present cross-linkable elastomeric composition are zinc agents, in particular ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing from 8 to 18 carbon atoms, which are preferably formed in situ in the cross-linkable elastomeric composition by reaction of ZnO and of the fatty acid or mixtures thereof.
  • zinc stearate is used, preferably zinc stearate formed in situ in the cross-linkable elastomeric composition, from ZnO and fatty acid, or magnesium stearate, formed from MgO, or mixtures thereof.
  • the vulcanization activator may be present in the cross-linkable elastomeric composition in amounts preferably from 0.2 phr to 15 phr, more preferably from 1 phr to 5 phr.
  • Preferred activating agents derive from the reaction of zinc oxide and stearic acid.
  • An example of activator is the product Aktiplast ST marketed by Rheinchemie.
  • the cross-linkable elastomeric composition may further comprise at least one vulcanization accelerator.
  • Vulcanization accelerators that are commonly used may be, for example, selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulphenamides, sulphenimides, thiurams, amines, xanthates, or mixtures thereof.
  • the accelerator agent is selected from mercaptobenzothiazole (MBT), N- cyclohexyl-2-benzothiazol-sulphenamide (CBS), N-tert-butyl-2-benzothiazol-sulphenamide (TBBS) and mixtures thereof.
  • accelerators suitable for use in the present cross-linkable elastomeric composition are N-cyclohexyl-2-benzothiazyl-sulphenamide Vulkacit® (CBS or CZ), and N-terbutyl 2-benzothiazil sulphenamide, Vulkacit® NZ/EGC marketed by Lanxess.
  • Vulcanization accelerators may be used in the present cross-linkable elastomeric composition in an amount preferably from 0.05 phr to 10 phr, preferably from 0.1 phr to 7 phr, more preferably from 0.5 phr to 5 phr.
  • the cross-linkable elastomeric composition may optionally comprise at least one vulcanization retardant agent.
  • the vulcanization retardant agent suitable for use in the present cross-linkable elastomeric composition is preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine N-cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.
  • a commercial example of a suitable retardant agent is N-cyclohexylthiophthalimide VULKALENT G of Lanxess.
  • the vulcanization retardant agent may be present in the present cross-linkable elastomeric composition in an amount of preferably from 0.05 phr to 2 phr.
  • the present cross-linkable elastomeric composition may comprise one or more vulcanization retardant agents as defined above in a mixture.
  • the cross-linkable elastomeric composition may further comprise at least 0.05 phr, preferably at least 0.1 phr or 0.5 phr, more preferably at least 1 phr or 2 phr of at least one silane coupling agent.
  • the cross-linkable elastomeric composition comprises from 0.1 phr to 20.0 phr or from 0.5 phr to 10.0 phr, even more preferably from 1.0 phr to 5.0 phr of at least one silane coupling agent.
  • said coupling agent is a silane coupling agent selected from those having at least one hydrolysable silane group which may be identified, for example, by the following general formula: (R’)3Si-CnH2n-X wherein the groups R’, equal or different from each other, are selected from: alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the groups R’ is an alkoxy or an aryloxy group; n is an integer of from 1 to 6; X is a group selected from: nitrous, mercapto, amino, epoxide, vinyl, imide, chloro, -(S) m C n H 2n -Si-(R’) 3 and -S-COR’ group, wherein m and n are integers from 1 to 6 and R’ groups are as defined above.
  • silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulphide and bis(3-triethoxysilylpropyl)disulphide. Said coupling agents may be added as such or in mixture with an inert filler (such as carbon black) so as to facilitate their incorporation into the cross-linkable elastomeric composition.
  • An example of the silane coupling agent is TESPT bis(3-triethoxysilylpropyl)tetrasulphide Si69 marketed by Evonik.
  • the cross-linkable elastomeric composition may further comprise one or more additional ingredients, commonly used in the field, such as for instance plasticizing oils, resins, antioxidant and/or anti-ozone agents (anti-aging agents), waxes, adhesives and the like.
  • the cross-linkable elastomeric composition according to the present invention in order to improve the workability of the compound, may further comprise at least one plasticizer, preferably a plasticizing oil.
  • the amount of plasticizer is preferably in the range from 5 to 50 phr, preferably from 10 to 40 phr.
  • plasticizing oil means a process oil derived from petroleum, a mineral oil, a vegetable oil, a synthetic oil or combinations thereof.
  • the plasticizing oil may be a process oil derived from petroleum selected from paraffines (saturated hydrocarbons), naphthenes, aromatic polycyclic and mixtures thereof.
  • suitable process oils derived from petroleum are aromatic, paraffinic, naphthenic oils such as MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract) known in the industry.
  • the plasticizing oil may be an oil of natural or synthetic origin derived from the esterification of glycerol with fatty acids, comprising glycerine triglycerides, diglycerides, monoglycerides or mixtures thereof.
  • suitable vegetable oils are sunflower, soybean, linseed, rapeseed, castor and cotton oil.
  • the plasticizing oil may be a synthetic oil selected from among the alkyl or aryl esters of phthalic acid or phosphoric acid.
  • the cross-linkable elastomeric composition may further comprise at least one resin.
  • the resin is a non-reactive resin, preferably selected from among hydrocarbon resins, phenolic resins, natural resins and mixtures thereof.
  • the amount of resin is preferably in the range from 5 to 30 phr, more preferably from 10 to 20 phr.
  • the cross-linkable elastomeric composition may optionally comprise one or more liquid polymer(s). Liquid polymers are preferably selected from among functionalized or not functionalized liquid BR, liquid SBR or liquid IR, with Mw preferably lower than 20,000 g/mol. The amount of liquid polymers is preferably in the range from 5 to 30 phr, more preferably from 10 to 20 phr.
  • the cross-linkable elastomeric composition may optionally comprise at least one wax.
  • the wax may be for example a petroleum wax or a mixture of paraffins.
  • suitable waxes are the Repsol N-paraffin mixture and the Antilux® 654 microcrystalline wax from Rhein Chemie.
  • the wax may be present in the cross-linkable elastomeric composition in an overall amount generally from 0.1 phr to 20 phr, preferably from 0.5 phr to 10 phr, more preferably from 1 phr to 5 phr.
  • the cross-linkable elastomeric composition may optionally comprise at least one antioxidant agent.
  • the antioxidant agent is preferably selected from N-isopropyl-N'-phenyl-p- phenylenediamine (IPPD), N-(-1,3-dimethyl-butyl)-n'-phenyl-p-phenylenediamine (6PPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine (77PD), N,N'-bis-(1-ethyl-3-methyl- pentyl)-p-phenylenediamine (DOPD), N,N'-bis-(1,4-dimethyl-pentyl)-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N,N'- di-beta-naphthyl-p-phenylenediamine (DNPD), N,N'-bis(1
  • a commercial example of a suitable antioxidant agent is 6PPD from Solutia or Santoflex produced by Eastman.
  • the antioxidant agent may be present in the cross-linkable elastomeric composition in an overall amount preferably from 0.1 phr to 20 phr, more preferably from 0.5 phr to 10 phr.
  • a preferred cross-linkable elastomeric composition for winter or all- seasons use comprises: - 100 phr of one or more elastomeric polymer(s), of which at least 50 phr of a conjugated diene polymer (I), the conjugated diene polymer (I) having a Tg DSC from -70.0 °C to -40.0 °C, preferably from -65.0 °C to -55.0 °C, - at least 50 phr, preferably from 80 to 130 phr, of at least a reinforcing filler, preferably silica, - at least 10 phr, preferably from 15 a 25 phr of a plasticizer, preferably of an oil, - optionally at least 20 phr, preferably from 30 to 40 phr, of a resin, - optionally at least 10 phr, preferably from 15 to 25 phr, of a liquid polymer, - at least 0.2
  • a preferred cross-linkable elastomeric composition for summer use comprises: - 100 phr of one or more elastomeric polymer(s), of which at least 50 phr of a conjugated diene polymer (I), the conjugated diene polymer (I) having a Tg DSC from -50.0 °C to -35.0 °C, preferably from -50.0 °C to -40.0 °C, - at least 50 phr, preferably from 70 to 110 phr, of a reinforcing filler, preferably silica, - at least 10 phr, preferably from 15 a 20 phr, of a plasticizer, preferably oil, - optionally at least 10 phr, preferably from 15 to 25 phr, of a resin, - optionally at least 5 phr, preferably from 10 to 20 phr of a liquid polymer, - at least 0.5 phr, preferably from
  • the cross-linkable elastomeric composition described above is then cross-linked to provide the present cross-linked elastomeric compound.
  • the present cross-linked elastomeric compound is characterised by a particular hysteresis pattern.
  • Figure 3B - where the hysteresis results in a narrow high peak centred around the Tg temperature of the compound with a steep decrease after the peak as T increases and consequent low Tan D values in the region from -30 °C to +30 °C - the compounds for the tyre of the invention (Ex.3, Ex.4, Figure 2B and Ex. 5, Ex.
  • the present cross-linked elastomeric compound may be prepared by a conventional process comprising, for instance, a first non-productive step and a second productive step, followed by cross-linking.
  • the process typically comprises: - in the first non-productive step, mixing the elastomeric diene polymer(s) including the present conjugated diene polymer (I), a reinforcing filler and optionally an antioxidant, a compatibilizing agent, an anti-ozone and/or a wax and other optional ingredients but the vulcanizing agent, at a temperature between 110 and 190 °C, to give a first elastomeric compound, - in the second productive step, adding to the first elastomeric compound a curing system comprising at least a vulcanizing agent and optionally at least an accelerator agent, a retardant agent, a vulcanisation activating agent - and mixing the components at a temperature preferably lower than 120 °C, to give a cross-linkable elastomeric compound, and -
  • the process according to the invention typically comprises one or more thermomechanical mixing steps in at least one suitable mixer, in particular at least a first mixing step (step 1 - non-productive) and a second mixing step (step 2 - productive) as defined above.
  • Each mixing step may comprise several intermediate processing steps or sub-steps, characterised by the momentary interruption of the mixing to allow the addition of one or more ingredients but without intermediate dumping of the compound.
  • the mixing may be performed, for example, using an open mixer of the "open-mill” type or an internal mixer of the type with tangential rotors (Banbury®) or with interpenetrating rotors (Intermix), or in continuous mixers of the Ko-KneaderTM type (Buss®) or of the twin-screw or multi-screw type.
  • the temperature is generally controlled to avoid undesired pre- vulcanisation phenomena.
  • the cross-linkable elastomeric compound is incorporated into one or more components of the green tyre and subjected to vulcanisation, according to known techniques. Any of the usual vulcanisation processes may be used in the present process, such as heating in a press or mould, heating with superheated steam or hot air.
  • the tyre component comprising, preferably consisting essentially of, or more preferably consisting of the above cross-linked elastomeric compound is preferably selected from tread band, under-layer, anti-abrasive strip, sidewall, sidewall insert, mini-sidewall, liner, under-liner, rubber layers, bead filler, bead reinforcing layers (flipper), bead protection layers (chafer) and sheet.
  • the tyre component is a tread band.
  • the tyre for vehicle wheels of the invention comprises at least one of the components comprising a cross-linked elastomeric compound obtained by cross-linking the cross- linkable elastomeric composition described above.
  • said component is at least the tread band.
  • a tyre for vehicles comprises at least - a carcass structure comprising at least a carcass ply having opposite lateral edges associated to respective bead structure; - optionally a pair of sidewalls applied to the lateral surfaces of the carcass structure, respectively, in an axially outer position; - optionally a belt structure applied in radially outer position with respect to the carcass structure; - a tread band applied in a radially outer position to said carcass structure or, if present, a belt structure, - optionally a layer of elastomeric material, referred to as under-layer, applied in a radially inner position with respect to said tread band, wherein at least one component, preferably the tread band, comprises, or preferably consists essentially of, or more preferably consists of the present cross-linked elastomeric compound.
  • the tyre component of the tyre according to the invention is the tread band.
  • the tyre according to the invention can be prepared by a process comprising: (a) producing a raw tyre comprising a raw tread band applied at a radially outer position of the tyre; (b) subjecting said raw tyre to moulding and vulcanization so as to obtain a finished tyre; in which said raw tread band comprises or preferably consists essentially of the cross- linkable elastomeric composition described above.
  • the tyre according to the invention may be for summer use.
  • the tyre according to the invention may be for winter and for all-seasons use, depending on structural features and on the selection of the conjugated diene polymer (I) with a suitable Tg in the present cross-linkable elastomeric composition.
  • the vehicle tyre of the invention is a winter tyre or snow tyre.
  • the tyre according to the invention is a tyre for a passenger car, with normal or high performance or for off-road vehicles, preferably a tyre for passengers, conceived for vehicles for personal use, such as sedans, coupes, crossovers, SUVs, minivans and small pickups.
  • the tyre according to the invention is a tyre for motorcycles, wherein at least one component comprises, or preferably consists essentially of, or more preferably consists of the present cross-linked elastomeric compound.
  • the tyre according to the invention may be a tyre for two, three or four-wheeled vehicles.
  • the tyre according to the invention is a tyre for bicycle wheels.
  • a tyre for bicycle wheels typically comprises a carcass structure turned 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.
  • at least the tread band comprises the present cross-linked elastomeric compound.
  • the tyre for vehicles wheels may be built, formed, molded and vulcanized with various methods known to the skilled in the art.
  • the tyre according to the present invention may be manufactured according to a process, which comprises: - building components of a green tyre on at least one forming drum; - shaping, moulding and vulcanising the tyre; wherein building at least one of the components of a green tyre comprises: - manufacturing at least one green component, preferably the tread band, comprising, or preferably consisting essentially of, or more preferably consisting of the present cross- linkable elastomeric compound.
  • a tyre for vehicle wheels according to the invention comprising at least one component comprising the present elastomeric compound, is illustrated in radial half-section in Figure 1.
  • Figure 1 indicates an axial direction and “X” indicates a radial direction, in particular X-X indicates the outline of the equatorial plane.
  • Figure 1 shows only a portion of the tyre, the remaining portion not shown being identical and arranged symmetrically with respect to the equatorial plane “X-X”.
  • the tyre (100) for four-wheeled vehicles comprises at least one carcass structure, comprising at least one carcass layer (101) having respectively opposite end flaps engaged with respective annular anchoring structures (102), referred to as bead cores, optionally associated to a bead filler (104).
  • the tyre area comprising the bead core (102) and the filler (104) forms a bead structure (103) intended for anchoring the tyre onto a corresponding mounting rim, not shown.
  • the carcass structure is usually of radial type, i.e.
  • the reinforcing elements of the at least one carcass layer (101) lie on planes comprising the rotational axis of the tyre and substantially perpendicular to the equatorial plane of the tyre.
  • Said reinforcing elements generally consist of textile cords, such as rayon, nylon, polyester (for example polyethylene naphthalate, PEN).
  • Each bead structure is associated to the carcass structure by folding back of the opposite lateral edges of the at least one carcass layer (101) around the annular anchoring structure (102) so as to form the so-called carcass flaps (101a) as shown in Figure 1.
  • the coupling between the carcass structure and the bead structure can be provided by a second carcass layer, not shown in Figure 1, applied in an axially outer position with respect to the first carcass layer.
  • An anti-abrasive strip (105) optionally made with elastomeric material is arranged in an outer position of each bead structure (103).
  • the carcass structure is associated to a belt structure (106) comprising one or more belt layers (106a), (106b) placed in radial superposition with respect to one another and with respect to the carcass layer, having typically textile and/or metallic reinforcing cords incorporated within a layer of elastomeric material.
  • Such reinforcing cords may have crossed orientation with respect to a direction of circumferential development of the tyre (100).
  • circumferential direction it is meant a direction generally facing in the direction of rotation of the tyre.
  • At least one zero-degree reinforcing layer (106c) commonly known as a “0° belt”, (106b) may be applied in a radially outermost position to the belt layers (106a), which generally incorporates a plurality of elongated reinforcing elements, typically metallic or textile cords, oriented in a substantially circumferential direction, thus forming an angle of a few degrees (such as an angle of between about 0° and 6°) with respect to a direction parallel to the equatorial plane of the tyre, and coated with an elastomeric material.
  • a tread band (109) comprising the present cross-linked elastomeric compound is applied in a position radially outer to the belt structure (106). Moreover, respective sidewalls (108) of elastomeric material are applied in an axially outer position on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of tread (109) at the respective bead structure (103). In a radially outer position, the tread band (109) has a rolling surface (109a) intended to come in contact with the ground. Circumferential grooves, which are connected by transverse notches (not shown in Figure 1) so as to define a plurality of blocks of various shapes and sizes distributed over the rolling surface (109a), are generally made on this surface (109a), which in Figure 1 is represented smooth for simplicity.
  • An under-layer (111) of elastomeric material may be arranged between the belt structure (106) and the tread band (109).
  • a strip consisting of elastomeric material (110), commonly known as “mini-sidewall”, can optionally be provided in the connecting zone between the sidewalls (108) and the tread band (109), this mini-sidewall being generally obtained by co-extrusion with the tread band (109) and allowing an improvement of the mechanical interaction between the tread band (109) and the sidewalls (108).
  • the end portion of the sidewall (108) directly covers the lateral edge of the tread band (109).
  • the rigidity of the tyre sidewall (108) may be improved by providing the bead structure (103) with a reinforcing layer (120) generally known as “flipper” or additional strip-like insert.
  • the flipper (120) is a reinforcing layer which is wrapped around the respective bead core (102) and the bead filler (104) so as to at least partially surround them, said reinforcing layer being arranged between the at least one carcass layer (101) and the bead structure (103).
  • the flipper is in contact with said at least one carcass layer (101) and said bead structure (103).
  • the flipper (120) typically comprises a plurality of textile cords incorporated within a layer of elastomeric material.
  • the reinforcing annular structure or bead (103) of the tyre may comprise a further protective layer which is generally known by the term of “chafer” (121) or protective strip and which has the function of increasing the rigidity and integrity of the bead structure (103).
  • the chafer (121) usually comprises a plurality of cords incorporated within a rubber layer of elastomeric material.
  • Such cords are generally made of textile materials (such as aramid or rayon) or metal materials (such as steel cords).
  • a layer or sheet of elastomeric material can be arranged between the belt structure and the carcass structure (not shown).
  • the layer may have a uniform thickness.
  • the layer may have a variable thickness in the axial direction.
  • the layer may have a greater thickness close to its axially outer edges with respect to the central (crown) zone.
  • the layer or sheet may extend on a surface substantially corresponding to the extension surface of said belt structure.
  • a layer of elastomeric material referred to as under-layer (111) may be placed between said belt structure and said tread band, said under-layer preferably extending on a surface substantially corresponding to the extension surface of said belt structure.
  • the present cross-linked elastomeric compound may advantageously be incorporated in addition to the tread band in one or more of the other above tyre components.
  • the building of the tyre (100) as described above, may be carried out by assembling respective semi-finished products consisting of the respective green compounds, semi- finished products adapted to form the components of the tyre, on a forming drum, not shown, by at least one assembling device. At least a part of the components intended to form the carcass structure of the tyre may be built and/or assembled on the forming drum. More particularly, the forming drum is intended to first receive the possible liner, and then the carcass structure.
  • devices non shown coaxially engage one of the annular anchoring structures around each of the end flaps, position an outer sleeve comprising the belt structure and the tread band in a coaxially centred position around the cylindrical carcass sleeve and shape the carcass sleeve according to a toroidal configuration through a radial expansion of the carcass structure, so as to cause the application thereof against a radially inner surface of the outer sleeve.
  • a moulding and vulcanisation treatment is generally carried out in order to determine the structural stabilisation of the tyre through cross-linking of the elastomeric compositions, as well as to impart a desired tread pattern on the tread band and to impart any distinguishing graphic signs at sidewalls
  • the Applicant has found that by virtue of the characteristics of the cross-linkable elastomer composition described herein, it is possible to provide a tyre with an increased wear resistance that provides better driving performance either on snow/wet winter conditions or on wet/dry summer roads.
  • Figure 1 schematically shows a semi-sectional view of a tyre for vehicle wheels according to the present invention
  • Figure 2 shows the graphs of E’ vs temperature (Figure 2A) and Tan D vs temperature (Figure 2B) of the compounds of Example 1 (reference), of Example 3 and Example 4 (invention), comprising diene polymers A, P1 and P2 respectively, with a Tg DSC lower than -58.0 °C
  • Figure 3 shows the graphs of E’ vs temperature ( Figure 3A) and Tan D vs temperature (Figure 3B) of the compounds of Example 2 (reference), of Example 5 and Example 6 (invention), comprising diene polymers B, P3 and P4 respectively, with a Tg DSC higher than -58.0 °C.
  • Figure 4 illustrates the extrapolation of the Tg DSC onset and end temperatures from the DSC thermogram of an exemplary polymer.
  • EXPERIMENTAL PART Unless otherwise stated, in the present Experimental Part the components of the composition are expressed in phr (parts per hundred of rubber).
  • Test methods Properties of the polymers Weight average molecular weight (Mw) and number average molecular weight (Mn) The Mw and Mn of the polymers were measured by Gel Permeation Chromatography (GPC) technique, with a system composed by a Waters HPLC equipment, Wyatt Multi Angle Light Scattering (MALS) and refractive index (RI) detectors.
  • GPC Gel Permeation Chromatography
  • the chromatographic columns bank was made of three Shodex columns, 8.0 mm ID x 300 mm L (KF802.5+KF805+KF806). Thanks to the combined use of MALS and RI detectors there was no need for columns calibration.
  • Polymer sample (10 mg) was dissolved in tetrahydrofuran (10 ml). The resulting solution was filtered using a 0.45 ⁇ m PTFE filter in a HPLC amber vial and was then analysed for the determination of weight average molecular weight (Mw) and number average molecular weight (Mn). The analysis was performed according to the following conditions: mobile phase tetrahydrofuran (THF), eluent flow 1ml/min, temperature 30 °C.
  • THF mobile phase tetrahydrofuran
  • Glass transition temperature of the reference polymers by DSC was determined by differential scanning calorimetry (DSC) using a DSC Mettler Toledo instrument under the following conditions.
  • DSC differential scanning calorimetry
  • a test sample of weight between 5 mg and 20 mg was weighed and put without any treatment into a pan, the pan was sealed with cover and placed in the cell of the instrument set at 50 °C.
  • the nitrogen gas flow was set at 80 ml/min.
  • the sample was cooled to -120 °C at a cooling rate of 10 °C/min and then maintained at this temperature for 5 minutes.
  • To determine the glass transition temperature the thermogram was recorded during the last heating step from -120 °C to +50 °C at a heating rate of 10 °C/min.
  • the glass transition temperature was measured at the inflection point of the DSC curve (i.e. at the minimum value of the first derivative of the DSC thermogram line) (see Fig.4).
  • Glass transition temperature of the inventive polymers P1 – P4 by DSC Tg DSC
  • the extender oil was first extracted and only after the sample was subjected to measurement of the glass transition temperature in accordance with ISO 22768:2006 under the following conditions.
  • the DSC thermogram was recorded with a "DSC 3200S" differential scanning calorimeter manufactured by MacScience, under a helium flow of 50 ml/minute by increasing the temperature from -120 °C to +40 °C at a heating rate of 10 °C/ min.
  • the extrapolated glass transition onset temperature (Tg DSC onset) was determined as the temperature at the intersection of the straight line, obtained by extending the base line on the lower temperature side to the higher temperature side, and the tangent line drawn at the point where the gradient of the curve of the step-wise change portion of the glass transition reaches a maximum.
  • the extrapolated glass transition end temperature (Tg DSC end) was determined as the temperature at the intersection of the straight line, obtained by extending the base line on the higher temperature side to the lower temperature side, and the tangent line drawn at the point where the gradient of the curve of the step-wise change portion of the glass transition becomes maximum.
  • An example of a graphical extrapolation of Tg DSC and of Tg DSC onset /end temperatures is illustrated in Figure 4.
  • Tg CALC Calculated glass transition temperature
  • Amount of bound styrene in the first polymer segment (X1) A sample of 100 mg of the polymer solution at the discharge portion of the polymerization process 1 for synthetizing the first polymer segment was diluted to 100 ml with chloroform and dissolved to obtain a measurement sample. The amount of bound styrene in the first polymer segment (X1) (wt%) with respect to 100% by weight of the first polymer segment was measured from the UV absorption of the phenyl group of styrene (at wavelength of about 254 nm, spectrophotometer "UV-2450" manufactured by Shimazu Corporation).
  • Amount of bound styrene in the second polymer segment (X2) The segment ratio (r 1 ) of the first polymer segment and the segment ratio (r 2 ) of the second polymer segment were calculated by the method described below, and the bound styrene amount (X2) in the second polymer segment was calculated from equation (2): with the bound styrene amount Xall in the conjugated diene polymer (I) and the bound styrene amount X 1 in the first polymer segment, which were calculated from the previous measurement.
  • Amount of vinyl unit in the first polymer segment (Y1) The content of vinyl units of the first polymer segment was determined in the same manner as for the content of the conjugated diene-based polymer (I) above, except that the sample was changed from the conjugated diene-based polymer (I) to the first polymer segment.
  • Ratio of first polymer segment (r1) The ratio of the polymeric segments in the first polymerization process (PR1) to the total amount of conjugated diene and aromatic vinyl compounds added per hour in polymerizing the conjugated diene polymer (I) was calculated from the solid amount of conjugated diene polymer (I) per hour after the first polymerization process (PR1).
  • the solid content in the conjugated diene polymer solution was determined from the amount of non-volatile components in the polymer solution flowing through the aforementioned first polymerization process (PR1) outlet during unit time. The entire volume of the polymer solution flowing through the discharge outlet of the first polymerization process (PR1) was collected for 3 minutes, and the polymerization terminator was immediately added.
  • the second polymeric segment ratio in the second polymerization process (PR2) to form the second polymeric segment was calculated from the solid amount of conjugated diene polymer per hour after the second polymerization process (PR2) relative to the total amount of conjugated diene compounds and aromatic vinyl compounds added per hour in polymerizing the conjugated diene polymer, and calculated from the difference between the solid amount of conjugated diene polymer per hour after the first polymerization process (PR1).
  • the amount of solids in the conjugated diene-based polymer solution was obtained from the amount of non-volatile components in the polymer solution flowing through the outlet of the second polymerization process (PR2) per unit time.
  • the total amount of the polymer solution flowing through the second polymerization process (PR2) outlet was collected for 3 minutes, and the polymerization terminator was immediately added. After that, it was transferred to a heat-resistant dish or the like, dried in an oven at 140 °C for at least 30 minutes, and the weight M2 of the solid residue was measured.
  • the second polymer segment ratio r 2 was obtained by the equation (5) from the solid weight M1 and the solid weight M2 obtained in the first polymerization process (PR1).
  • the modification rate was measured by exploiting the characteristic adsorption of the modified polymer component to a GPC column packed with silica gel.
  • the amount adsorbed by the silica column was measured from the difference between the chromatogram of the sample solution - containing a sample of the modified polymer and a low-molecular-weight internal standard polystyrene - measured on the polystyrene-based column and the chromatogram of the same sample solution measured on the silica column.
  • - Preparation of the sample solution 10 mg of the sample and 5 mg of standard polystyrene were dissolved in 20 ml of THF (tetrahydrofuran) thus providing the sample solution.
  • Mooney viscosity and relaxation The Mooney stress-relaxation rate (MSR) was determined according to standard ISO 289 with an Alpha Technologies MV2000 viscometer. At the end of the viscosity test at 100 °C, the rotation of the disc was stopped within 0.1 s, reset the zero torque point to the static zero for a stationary rotor and recorded the torque at least every 0.2 s. The relaxation data were collected starting 1.6 s and continuing up to 5.0 s after the rotor was stopped, giving normally a total of 18 data points.
  • cross-linkable elastomeric compounds were subjected to the following evaluations: Mooney viscosity and relaxation (same test described above) MDR rheometric analysis: tests were carried out according to standard ISO 6502 with an MDR2000 Alpha Technologies rheometer, at 170 °C for 20 minutes, at an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ⁇ 0.5°, measuring the time required to reach 90% (T90) of the final torque. The maximum torque MH was also measured.
  • Density density was measured in accordance with ISO2781 method A with an automatic Densitron - Alpha Technologies. Static mechanical properties were measured at 23 °C in accordance with standard ISO 37:2005. Specifically, tensile stress at 300% of elongation (T300%), tensile stress at break TB and elongation at break EB were measured on samples of the elastomeric compounds, vulcanized at 170 °C for 10 minutes. Tensile tests were performed on ring-type specimens having a straight axis.
  • the dynamic mechanical properties were expressed in terms of dynamic modulus of elasticity (E’), of tan delta (Tan D dissipation factor or hysteresis) and of loss compliance D’’ (wet grip indicator).
  • E dynamic modulus of elasticity
  • D loss compliance
  • the value of Tan D was calculated as the ratio between the viscous modulus (E’’) and elastic modulus (E’).
  • Dynamic test by RPA (Rubber Process Analyzer) This test was used to measures dynamic parameters of a cured compound and curing kinetic, Payne Effect ( ⁇ G’) by Strain Sweep, G’ and Tan delta at 9% of strain.
  • the procedure included the following steps and conditions: ⁇ vulcanizing the sample for 10 minutes at 170 °C in dynamic conditions, ⁇ waiting for 10 minutes, to ensure that the material recovered after vulcanization and reached the temperature of 70 °C, ⁇ Strain Sweeping from 0.3% to 10% at 10Hz and 70 °C, ⁇ Mechanical preconditioning of 100 cycles at 70 °C, 10Hz and 9% of strain, ⁇ Dynamic Characterization at 70 °C, 10Hz at 9% and 3% of strain.
  • Glass transition temperature (Tg) by Temperature Sweep This technique was used for determining the glass transition temperature Tg (in tensile mode) of elastomeric compounds subjected to a sinusoidal oscillation at fixed amplitude (strain) and fixed frequency at increasing temperature.
  • the results were reported as curves of storage modulus (E') and Tan D (ratio E”/E’) versus temperature (see Figure 2 and Figure 3). The temperature at the peak of the Tan delta curve was the glass transition temperature (Tg) of the compound.
  • Abrasion resistance (LAT 100 under dry conditions) Resistance to abrasion was determined according to ISO 23233:2009 by using a driven, vertical abrasive disc (LAT 100: Laboratory Abrasion Tester 100).
  • the test specimen was a solid wheel made of the vulcanized compound under test, which was run under load on a rotating abrasive disc at a slip angle to the direction of rotation. Loss in weight by abrasion was determined from the slip caused by setting different slip angles and rotational speeds between the wheel-shaped rubber test piece and the abrasive disc, rotating in planes at right angles to each other and pressed against each other with a specified load.
  • the test result was reported as an abrasion resistance index (ARI).
  • the abrasion resistance index is defined as the abrasion loss in weight per unit running distance normalized on the reference compound (Ex. 1 or Ex. 2 compounds) and was calculated according to the following equations (7) and (8): (7) (8) wherein A was the loss in weight per unit running distance in mg/km, wt i was the initial weight of the sample in mg, wtf was the final weight in mg, s was the running distance in km, A inv. and A ref. the loss in weight per unit running distance in mg/km for the inventive and reference compound respectively. The lower was the AR index, the better was the resistance to abrasion of the compound in comparison with the reference compound.
  • Conjugated diene polymers (I) for the compositions of the tyre of the invention were used for the compositions and compounds of the tyres of the invention.
  • polymers P1-P4 suitable for manufacturing the tyre of the invention are herein named as ”inventive polymers”.
  • the inventive polymers P1 and P2 had a Tg DSC suitable for winter / all-seasons applications while polymers P3 and P4 had a Tg DSC suitable for summer use.
  • the inventive polymers P1-P4 contained 5 phr of oil.
  • n-butyllithium was added for inactivating residual impurities at a rate of 0.104 mmol/min, and after mixing was continuously supplied to the bottom of the reactor 1.
  • 2,2- bis(2-oxolanyl)propane as a polar substance at a rate of 0.145 mmol/min and n-butyllithium as a polymerization initiator at a rate of 0.239 mmol/min were supplied to the bottom of reactor 1 and vigorously mixed, and the internal temperature of the reactor was kept at 78 °C .
  • the polymer solution was continuously supplied from the top of reactor 1 to the bottom of the reactor 2 and stirred while 1,3-butadiene at a rate of 8.3 g/min, styrene at 2.9 g/min, normal hexane at 33.6 g/min and 2,2-bis(2-oxophenol)propane as the polar substance at 0.222 mmol/min were added to reactor 2, and the reaction was continued at 78 ⁇ C.
  • Coupler A 1-methyl-4-[3-(trimethoxysilyl)propyl]piperazine
  • coupling agent B tetrakis(3-trimethoxysilyl propyl)-1,3-propane diamine
  • an antioxidant BHT was continuously added to the coupling-reacted polymer solution at 0.055 g/min (n-hexane solution) at 0.2 g per 100 g of the polymer, and coupling was performed up to completion.
  • 5.0 g of SRAE oil JOMO Process NC140 manufactured by JX Nikko Nisseki Energy Co., Ltd.
  • the solvent was removed by steam stripping to obtain the conjugated diene-based polymer P1.
  • the molecular weight, Mooney viscosity and modification rate were identified.
  • the conjugated diene polymer P2 was obtained following the same procedure described above for the manufacture of polymer P1 with the following differences: 1,3-Butadiene is added to the first reactor at 21.4 g/min, n-hexane at 170.3 g/min, 2,2-bis(2- oxolanyl)propane as polar substance at 0.054 mmol/ min, then 1,3-butadiene at 9.2 g/min, styrene at 3.5 g/min, n-hexane at 36.8 g/min and 2,2-bis(2-oxolanyl)propane at 0.394 mmol/min were added in the second reactor. Other conditions were the same as in Example 1.
  • the conjugated diene polymer P3 was obtained following the same procedure described above for the manufacture of polymer P1 with the following differences: 1,3-Butadiene is added to the first reactor at 19.3 g/min, n-hexane at 161.5 g/min, 2,2-bis(2- oxolanyl)propane as polar substance at 0.145 mmol/ min, then 1,3-butadiene at 8.3 g/min, styrene at 2.9 g/min, n-hexane at 33.6 g/min and 2,2-bis(2-oxolanyl)propane at 0.222 mmol/min were added in the second reactor. Other conditions were the same as in Example 1.
  • the conjugated diene polymer P4 was obtained following the same procedure described above for the manufacture of polymer P1 with the following differences: 1,3-Butadiene is added to the first reactor at 15.4 g/min, n-hexane at 166.0 g/min, 2,2-bis(2- oxolanyl)propane as polar substance at 0.072 mmol/ min, then 1,3-butadiene at 12.6 g/min, styrene at 5.3 g/min, n-hexane at 48.2 g/min and 2,2-bis(2-oxolanyl)propane at 0.340 mmol/min were added in the second reactor. Other conditions were the same as in Example 1.
  • compositions and compounds (Examples 1-6) Reference compositions and the corresponding compounds were prepared by using the polymers A (S-SBR, SLR 3402, Example 1) and B (S-SBR, HPR 621, Example 2). Compositions and compounds for the tyre of the invention were manufactured with the inventive polymers P1 (Example 3), P2 (Example 4), P3 (Example 5) and P4 (Example 6). The recipes of the compositions are shown in the following Table 3: Table 3 (all amounts in phr) Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ref. Ref. Inv. Inv. Inv. Inv. Inv. Inv.
  • the above compositions were compounded in a standard two-step compound process by kneading in an internal lab mixer (Banbury rotor type) with a total chamber volume of 1100 cm3.
  • the first mixing step (step 1) was performed at an initial temperature of 40 °C.
  • the rotor speed of the internal mixer was set in order to reach a temperature between 145 °C – 160 °C and kept at that temperature for 4 min. so that the silanization reaction could complete.
  • Total mixing time for the first step was 2’30”. After dumping the compound, the mixture was cooled down and stored before adding the curing system in the second mixing step.
  • the second mixing step (step 2) was carried out on the compound from the first mixing step for a total time of 2’15”, at an initial temperature of 50 °C, in the same equipment, after addition of sulphur as vulcanizing agent, TBBS and TBZTD as accelerators.
  • Compounds properties Table 4 and Table 5 below set out the results of the static, rheometric and dynamic mechanical properties for cross-linked samples of the polymer compositions according to Examples 1 to 6: Table 4 Ex.1 Ex.3 Ex.4 Ex.2 Ex.5 Ex.6 Ref. Inv. Inv. Ref. Inv. Inv.
  • Tan D (9%) at 70 °C of the inventive compounds was in line with the values of the reference compounds, predicting a similar tyre rolling resistance; - E’, Tan D at -10 °C / 0 °C (snow/wet performance): regarding these dynamic properties the behaviour at low temperatures (snow, wet grip) of the inventive compounds of Ex.3 and Ex.4 was better than the reference compounds of Ex.1 since they show similar or even lower stiffness (E’) and a significant increase of the hysteresis (Tan D). This combination of a lower stiffness with higher hysteresis was predictive of a better grip in winter applications.
  • the viscoelastic properties i.e.
  • the viscoelastic properties i.e.
  • wet grip indicators (D’’ and LAT100 wet) were used to predict wet performance depending on specific test conditions.
  • wet grip indicator D’’ (Tan D/E*) at 0 °C 100Hz was higher for the inventive compounds of Ex.3 and Ex.4 comprising polymers P3 and P4 compared to reference compound of Ex.1.
  • the main advantageous properties of the elastomeric compounds prepared from the above elastomeric compositions were a smoother increase of stiffness (E’) as temperature decreases, a broader hysteresis curve over the temperature range -30 °C / +30 °C with increased grip indicator (D”), a proper level of mechanical properties (T300%, TB, EB, Energy at break) and an optimum filler dispersion (reduced Payne effect and hardness).

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Chemical & Material Sciences (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Tires In General (AREA)

Abstract

La présente invention concerne un pneumatique de type hiver, toutes-saisons ou été, caractérisé par une usure réduite et une adhérence améliorée. Ledit pneumatique comprend un composant de pneu contenant un composé élastomère réticulé obtenu à partir d'une composition élastomère réticulable comprenant un polymère de diène conjugué particulier (I).
PCT/EP2024/061544 2023-04-27 2024-04-26 Pneumatique pour roue de véhicule présentant une résistance à l'usure et une adhérence supérieures Pending WO2024223826A1 (fr)

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EP23170341.4A EP4455203A1 (fr) 2023-04-27 2023-04-27 Pneumatique pour roue de véhicule présentant une résistance à l'usure et une adhérence supérieures
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PCT/EP2024/061518 Pending WO2024223808A1 (fr) 2023-04-27 2024-04-26 Pneumatique pour roue de véhicule présentant une résistance à l'usure et une adhérence supérieures

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