Rubber composition for tire tread

Abstract

The invention discloses a rubber composition for a tire tread. The tire tread is formed from a vulcanizable rubber composition comprising, in parts by weight per hundred parts of elastomer (phr), 100 phr of an elastomer component comprising a polyisoprene rubber and a polydiene rubber in a weight ratio of at least 1: 1; at least 40 phr of a filler component comprising carbon black and silica in a weight ratio of at least 0.8: 1; at least 1 phr of an organosilane coupling agent; at least 1 phr of a hydrocarbon traction resin; a sulfur-based curing agent; and a curing accelerator, the curing accelerator comprising a super accelerator. The tire tread is suitable for use on heavy vehicles, such as trucks and buses.

Description

Technical Field

[0001] Described herein is a component suitable for forming a pneumatic tire, such as a rubber composition for a tire tread. The composition is particularly suitable for providing highway tires having improved rolling resistance while maintaining good tread wear characteristics. Background Art

[0002] Rubber compositions suitable for use in tires generally include a mixture of elastomers and reinforcing fillers such as carbon black and / or silica. For example, for radial medium truck (RMT) tires used in regional transportation and urban applications, lower rolling resistance is desirable, which contributes to lower CO 2 emissions. The tire tread is an important contributor to overall tire performance. The frictional energy dissipated under deformation during rolling depends on factors such as the material properties of the rubber composition used.

[0003] To reduce rolling resistance, rubber compositions including various types of synthetic and natural rubbers have traditionally been used in the manufacture of tire treads. However, lower rolling resistance typically results in a tread wear trade-off.

[0004] Rubber compositions have been developed for improving tread wear without significantly increasing rolling resistance. For example, U.S. Publication No. 20170145195 A1 describes a vulcanizable rubber composition that includes solution-polymerized styrene-butadiene rubber, polybutadiene, silica, coumarone-indene resin, and a hydrocarbon resin derived from styrene and α-methylstyrene. U.S. Publication No. 20210032442 A1 describes a tire tread rubber composition that includes solution-polymerized styrene-butadiene rubber, natural rubber or synthetic polyisoprene; cis-1,4 polybutadiene, processing oil, hydrocarbon resin, and silica.

[0005] However, under wet conditions, such compositions do not perform well. There is still a need for a rubber composition that improves wet traction while also reducing rolling resistance. Summary of the Invention

[0006] According to one embodiment, a tire tread is formed from a vulcanizable rubber composition that includes, in parts by weight per hundred parts of elastomer (phr), 100 phr of an elastomer component, the elastomer component comprising polyisoprene rubber and polydiene rubber in a weight ratio of at least 1:1; at least 40 phr of a filler component, the filler component comprising carbon black and silica in a weight ratio of at least 0.8:1; at least 1 phr of an organosilane coupling agent; at least 1 phr of a hydrocarbon traction resin; a sulfur-based curing agent; and a curing accelerator, the curing accelerator comprising a super accelerator.

[0007] In various aspects, individually or in combination:

[0008] The polyisoprene rubber may include natural rubber, and the polydiene rubber may include polybutadiene rubber. The weight ratio of natural rubber to polybutadiene rubber may be at least 60:40, or at least 65:35, or at most 80:20, or at most 75:25, or at most 70:30. The polybutadiene rubber may have a cis-1,4 content of at least 95%.

[0009] The weight ratio of carbon black to silica may be at least 1:1, or at least 1.1:1, or at least 1.2:1, or at most 2:1, or at most 1.6:1, or at most 1.4:1. The rubber composition may include 15 to 45 phr or 30 to 40 phr of carbon black and 20 to 40 phr or 24 to 35 phr of silica.

[0010] The rubber composition may include at least 2 phr, or at most 7 phr, or at most 5 phr of an organosilane coupling agent.

[0011] The hydrocarbon tackifying resin may be selected from terpene-phenol tackifying resins, α-methylstyrene tackifying resins, aromatic-modified aliphatic petroleum-based hydrocarbon resins, and combinations thereof. The rubber composition may include at least 1.5 phr, or at most 6 phr, or at most 4 phr of the hydrocarbon tackifying resin.

[0012] The rubber composition may include no more than 0.5 phr of a liquid plasticizer.

[0013] The super accelerator may include at least one of the thiuram type, dithiocarbamate, and xanthate / salt functional groups. The super accelerator may be selected from 1,6-bis(N,N'-dibenzylthiocarbamoyl disulfide) hexane, zinc dibenzyl dithiocarbamate, tetrabenzylthiuram disulfide, and combinations thereof. The rubber composition may include at least 0.1 phr, or at least 0.2 phr, or at most 1 phr, or at most 0.7 phr of the super accelerator.

[0014] The accelerator may further include at least one of benzothiazole(s), sulfenamide, and guanidine curing accelerators. The sulfenamide curing accelerator may include benzothiazole sulfenamide curing accelerators.

[0015] The rubber composition may in total include at least 0.5 phr, or at least 0.8 phr, or at most 2 phr, or at most 1.5 phr of at least one of benzothiazole(s), sulfenamide, and guanidine curing accelerators.

[0016] The tire may include a tire tread of any of the above aspects.

[0017] According to another embodiment, a method of forming a tire tread includes forming a rubber composition by blending together: 100 phr of an elastomeric component that includes natural rubber and polybutadiene rubber in a weight ratio of natural rubber to polybutadiene rubber of at least 60:40; at least 40 phr of a filler component that includes carbon black and silica in a weight ratio of carbon black to silica of at least 1:1; at least 1 phr of an organosilane coupling agent; at least 1 phr of a hydrocarbon tackifying resin; a curing package that includes a sulfur-based curing agent, zinc oxide; optional one or more organic activators, and a curing accelerator that includes a super-accelerator. The method further includes curing the rubber composition to form a tire tread.

[0018] According to another embodiment, a vulcanizable rubber composition includes, in parts by weight per hundred parts of elastomer (phr), 100 phr of an elastomeric component that includes natural rubber and polybutadiene rubber in a weight ratio of at least 60:40; at least 40 phr of a filler component that includes carbon black and silica in a weight ratio of 1:1 to 2:1; 1 to 7 phr of an organosilane coupling agent; 1 to 6 phr of a hydrocarbon tackifying resin; 0.5 to 3 phr of wax; and a curing package that includes a sulfur-based curing agent, zinc oxide; an organic activator, and a curing accelerator that includes 0.1 to 1.0 phr of a super-accelerator and 0.5 to 2 phr of a sulfenamide curing accelerator.

[0019] The tire tread can be formed from the vulcanizable rubber composition.

[0020] Disclosed herein is a rubber composition suitable for use in the tread of a radial medium truck (RMT) tire, particularly for high mileage applications such as tires for city buses and regional and long haul transport trucks. The rubber composition provides improvements in tire wear, rolling resistance, and tear properties. The rubber composition benefits from the use of a curing agent system that produces a lower crosslink density and shorter crosslinks.

[0021] The curing agent system includes a super-accelerator that acts as an anti-reversion agent. This helps limit aging and heat buildup in the tire. The super-accelerator is dispersed in a polymer matrix of high natural rubber content, silica and carbon black fillers, and a tackifying resin. The combination of the super-accelerator and the tackifying resin produces improvements in tread wear and rolling resistance while also providing wet traction.

[0022] In addition to the crosslinks formed with the sulfenamide system (in conventional vulcanization (CV) and efficient vulcanization (EV) systems), ultra-accelerators tend to undergo additional reactions to form stable monosulfide crosslinks. This reduces the need for other compounding techniques, such as increasing the sulfur level to achieve the desired cure state, which can make the rubber composition more prone to age hardening. The combination of ultra-accelerators with tackifying resins and low sulfur content provides unique properties, particularly a combination of low rolling resistance and improved wear as demonstrated by aging and cut resistance.

[0023] The present invention discloses the following embodiments:

[0024] 1. A tire tread formed from a vulcanizable rubber composition comprising, expressed in parts by weight per hundred parts of elastomer (phr):

[0025] 100 phr of an elastomer component comprising polyisoprene rubber and polydiene rubber in a weight ratio of at least 1:1;

[0026] At least 40 phr of a filler component comprising carbon black and silica in a weight ratio of at least 0.8:1;

[0027] At least 1 phr of an organosilane coupling agent;

[0028] At least 1 phr of a hydrocarbon tackifying resin;

[0029] A sulfur-based curing agent; and

[0030] A curing accelerator comprising an ultra-accelerator.

[0031] 2. The tire tread according to embodiment 1, wherein the elastomer component comprises natural rubber and polybutadiene rubber.

[0032] 3. The tire tread according to embodiment 2, wherein the weight ratio of natural rubber to polybutadiene rubber is at least 60:40.

[0033] 4. The tire tread according to embodiment 2, wherein the polybutadiene rubber has a cis-1,4 content of at least 95%.

[0034] 5. The tire tread according to embodiment 1, wherein the weight ratio of carbon black to silica is at least 1:1.

[0035] 6. The tire tread according to embodiment 1, wherein the rubber composition comprises 15 to 45 phr of carbon black and 20 to 40 phr of silica.

[0036] 7. The tire tread according to embodiment 1, wherein the rubber composition comprises at least 2 phr of an organosilane coupling agent.

[0037] 8. The tire tread according to embodiment 1, wherein the hydrocarbon tackifying resin is selected from terpene-phenol tackifying resins, α-methylstyrene tackifying resins, aromatic-modified aliphatic petroleum-based hydrocarbon resins, and combinations thereof.

[0038] 9. The tire tread according to embodiment 1, wherein the rubber composition comprises at least 1.5 phr of a hydrocarbon tackifying resin.

[0039] 10. The tire tread according to embodiment 1, wherein the rubber composition comprises no more than 0.5 phr of a liquid plasticizer.

[0040] 11. The tire tread according to embodiment 1, wherein the ultra-accelerator comprises at least one of the thiuram, dithiocarbamate, and xanthate / xanthate salt functional groups.

[0041] 12. The tire tread according to embodiment 11, wherein the ultra-accelerator is selected from 1,6-bis(N,N'-dibenzylthiocarbamoyl disulfide) hexane, zinc dibenzyl dithiocarbamate, tetrabenzylthiuram disulfide, and combinations thereof.

[0042] 13. The tire tread according to embodiment 1, wherein the rubber composition comprises at least 0.1 phr of an ultra-accelerator.

[0043] 14. The tire tread according to embodiment 1, wherein the accelerator further comprises at least one of benzothiazole(s), sulfenamide, and guanidine curing accelerators.

[0044] 15. The tire tread according to embodiment 14, wherein the sulfenamide curing accelerator comprises a benzothiazole sulfenamide curing accelerator.

[0045] 16. The tire tread according to embodiment 14, wherein the rubber composition in total comprises at least 0.5 phr of at least one of benzothiazole(s), sulfenamide, and guanidine curing accelerators.

[0046] 17. A tire comprising the tire tread according to embodiment 1.

[0047] 18. A method of forming a tire tread, which comprises:

[0048] Forming a rubber composition, which comprises blending together the following:

[0049] An elastomer component of 100 phr, said elastomer component comprising natural rubber and polybutadiene rubber, the weight ratio of natural rubber to polybutadiene rubber being at least 60:40;

[0050] A filler component of at least 40 phr, said filler component comprising carbon black and silica, the weight ratio of carbon black to silica being at least 1:1;

[0051] At least 1 phr of an organosilane coupling agent;

[0052] At least 1 phr of a hydrocarbon tackifying resin;

[0053] A curing package, which comprises a sulfur-based curing agent, zinc oxide; optionally one or more organic activators, and a curing accelerator, said curing accelerator comprising a super accelerator; and

[0054] Curing the rubber composition to form a tire tread.

[0055] 19. A vulcanizable rubber composition, which comprises, expressed in parts by weight per hundred parts of elastomer (phr):

[0056] 100 phr of an elastomer component, said elastomer component comprising natural rubber and polybutadiene rubber in a weight ratio of at least 60:40;

[0057] At least 40 phr of a filler component, said filler component comprising carbon black and silica in a weight ratio of 1:1 to 2:1;

[0058] 1 to 7 phr of an organosilane coupling agent;

[0059] 1 to 6 phr of a hydrocarbon tackifying resin;

[0060] 0.5 to 3 phr of wax; and

[0061] A curing package, which comprises a sulfur-based curing agent, zinc oxide; an organic activator, and a curing accelerator, said curing accelerator comprising 0.1 to 1.0 phr of a super accelerator and 0.5 to 2 phr of a sulfenamide curing accelerator.

[0062] 20. A tire tread formed from the vulcanizable rubber composition of embodiment 19. Detailed Description

[0063] Definition

[0064] Unless otherwise specified, the terms "rubber" and "elastomer" are used interchangeably. The terms "rubber composition" or "compounded rubber" are used interchangeably to mean "rubber that has been blended or mixed with various ingredients and materials", and these terms are well known to those skilled in the art of rubber mixing or rubber compounding. Unless otherwise specified, the terms "cure" and "vulcanize" are used interchangeably.

[0065] As used herein, the term "tread" refers to the portion of a tire that contacts the road under normal inflation and load, and optionally any subtread, unless otherwise specified.

[0066] As used herein, the term "phr" refers to parts per hundred parts of rubber by weight. Generally, using this convention, a rubber composition includes 100 parts by weight of rubber / elastomer. The claimed composition may include other rubber / elastomers other than those specifically mentioned in the claims, provided that the phr values of the claimed rubber / elastomers are within the claimed phr ranges and the amounts of all rubber / elastomers in the composition total 100 parts of rubber. The term "phf" refers to parts per hundred parts of filler in the rubber composition.

[0067] Unless otherwise specified, the following methods are used to determine properties:

[0068] The molecular weights of elastomers, rubber compositions, and resins, such as M n (number average molecular weight), M w (weight average molecular weight), and M z (z average molecular weight) are determined herein using gel permeation chromatography (GPC) according to ASTM D5296 - 19, "Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High - Performance Size - Exclusion Chromatography" using polystyrene calibration standards.

[0069] The glass transition temperature (Tg) of an elastomer or an elastomer composition is one or more glass transition temperatures of the respective elastomer or elastomer composition in its uncured state or, in the case of an elastomer composition, possibly in the cured state.

[0070] The Tg value of the elastomer was determined as the peak midpoint by a differential scanning calorimeter (DSC) at a heating rate of 10 °C / min according to ASTM D3418-21, "Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry" (hereinafter ASTM D3418).

[0071] The glass transition temperature Tg of the resin was determined as the peak midpoint by a differential scanning calorimeter (DSC) at a heating rate of 10 °C / min according to ASTM D6604-00(2017), "Standard Practice for Glass Transition Temperatures of Hydrocarbon Resins by Differential Scanning Calorimetry" (hereinafter ASTM D6604).

[0072] The glass transition temperature Tg of the oil was determined as the peak midpoint by a differential scanning calorimeter (DSC) at a heating rate of 10 °C / min according to ASTM E1356-08(2014), "Standard Test Method for Assignment of the Glass TransitiOn Temperatures by Differential Scanning Calorimeter".

[0073] The softening point of the resin was determined according to ASTM E28-18, "Standard Test Methods for Softening Point of Resins Derived from Pine Chemicals and Hydrocarbons, by Ring-and-Ball Apparatus" (hereinafter ASTM E28), which is sometimes referred to as the ring-and-ball softening point.

[0074] The Mooney viscosity (ML 1+4) is measured at 100 °C in M.U. according to ASTM D1646-19a, "Standard Test Methods for Rubber-Viscosity, Stress Relaxation, and Pre-Vulcanization Characteristics (Mooney Viscometer)" (hereinafter ASTM D1646).

[0075] The term "alkyl" refers to straight-chain, branched-chain, and cycloalkyl groups. The term "aryl" refers to a group containing at least one aromatic ring and includes alkylaryl groups.

[0076] Unless otherwise stated, the cis, trans, and vinyl contents (%) of the polymer refer to the molar ratios of the 1,4-cis, 1,4-trans, and 1,2-vinyl butadiene units of the polymer and generally total 100%. These percentages can be determined by 1H-NMR spectroscopy according to ISO 21561-1:2015. The styrene content refers to the weight % of bound styrene in the polymer (such as a styrene-butadiene polymer) and can be determined by FT-IR.

[0077] Rubber composition

[0078] An exemplary tire tread is formed from a vulcanizable rubber composition, expressed in parts by weight per hundred parts of elastomer (phr), the vulcanizable rubber composition comprising:

[0079] 1) 100 phr of an elastomer component, the elastomer component comprising:

[0080] a) Polyisoprene rubber, such as natural rubber (NR); and

[0081] b) Optionally, a polydiene rubber, such as polybutadiene (PBD);

[0082] 2) At least 40 phr of a filler component, which includes:

[0083] a) Carbon black; and

[0084] b) Silica;

[0085] 3) Optionally, at least 1 phr of an organosilane coupling agent;

[0086] 4) At least 1 phr of a hydrocarbon traction resin;

[0087] 5) Optionally, one or more processing aids selected from:

[0088] a) A liquid plasticizer, such as oil,

[0089] b) wax,

[0090] and mixtures thereof;

[0091] 6) A curing package, comprising:

[0092] a) A sulfur-based curing agent;

[0093] b) One or more activators selected from (i) zinc oxide and (ii) one or more organic activators such as fatty acids, alkaline earth metal salts of fatty acids, and combinations thereof;

[0094] c) A curing accelerator, including a super accelerator; and

[0095] d) Optionally, a curing retarder; and

[0096] 7) Optionally, additional rubber compounding materials such as antioxidants, antiozonants, and anti-degradants.

[0097] Examples of these components are described below.

[0098] 1) Elastomer

[0099] One or more vulcanizable elastomers can be used in the rubber composition. These elastomers can be derived from monomers including at least one double bond, such as a C═C bond, or monomers having at least two double bonds, such as diene-based elastomers.

[0100] In one embodiment, the elastomer includes polyisoprene rubber, such as natural rubber (NR), and optionally a polydiene rubber, such as polybutadiene rubber (PBD). Natural rubber can be the major component in the elastomer, for example, more than the other elastomers in the combination, and in some embodiments can be the only elastomer.

[0101] In one embodiment, PBD and NR are the only elastomers used in the rubber composition, or together account for at least 95 phr or at least 98 phr of the elastomers.

[0102] The weight ratio of natural rubber to polybutadiene rubber can be from 60:40 to 100:0, or at least 65:35, or at most 80:20, or at most 75:25, or at most 70:30.

[0103] a) Polyisoprene rubber, such as natural rubber

[0104] Synthetic polyisoprene refers to a polymer made from isoprene monomers and should not be construed to include naturally occurring rubber. However, the term polyisoprene should be construed to include polyisoprene made from isoprene monomers of natural origin.

[0105] As used herein, the term "natural rubber" refers to rubber that occurs naturally and can be harvested from sources such as Hevea rubber trees and non-Hevea sources (such as guayule shrubs and dandelions like TKS). In other words, the term "natural rubber" should be construed to exclude synthetic polyisoprene. Natural rubber is mainly cis-polyisoprene. The cis-1,4-polyisoprene content in natural rubber can be at least 90% or at least 95%. In one embodiment, natural rubber is natural cis-1,4-polyisoprene rubber with a cis-1,4 content of at least 96% and a Tg of -60 °C to -110 °C, such as approximately -65 °C, as determined according to ASTM D3418.

[0106] Several forms of natural rubber are commercially available. The purity of natural rubber can meet the ISO TSR 20 grade specification or the ISO TSR 10 grade specification. ISO TSR 20 natural rubber has a maximum ash content of 1 wt% as determined according to ISO 247:1990, a maximum volatile matter of 0.8 wt% as determined according to ISO 248:1991, a maximum nitrogen content of 0.6 wt% as determined according to ISO 1656:1996, a minimum initial Wallace plasticity of 30 as determined according to ISO 2007:1991, and a minimum plasticity retention index of 40 as determined according to ISO 2930:1995. For TSR 10, a maximum ash of 0.75 wt%, a maximum nitrogen of 0.6 wt%, a maximum volatile of 0.8 wt%, a minimum plasticity of 30, and a minimum plasticity retention of 50 are specified. In other embodiments, natural rubber can be ribbed smoked sheet (RSS) rubber.

[0107] Polyisoprene rubber, such as natural rubber, can be used in a rubber composition in an amount of at least 60 phr, or at least 65 phr, or at most 100 phr, or at most 90 phr, or at most 85 phr, or at most 80 phr, or at most 75 phr, such as 70 ± 5 phr.

[0108] b) Polydiene rubber

[0109] The rubber composition may include a synthetic conjugated diene-based elastomer (referred to herein as poly-diene or poly-diene elastomer). The poly-diene elastomer includes at least one poly-diene elastomer, and each of the poly-diene elastomers is at least partially derived from butadiene. For example, at least 20%, or at least 30%, of the units in one or more poly-diene rubbers are formed from butadiene. In one embodiment, the poly-diene rubber includes polybutadiene rubber, i.e., synthetic polybutadiene, which is a homopolymer of the single monomer butadiene. Cis-1,4-polybutadiene rubber can be particularly used. In another embodiment, the poly-diene rubber is a copolymer of butadiene and another monomer, such as a vinylarene monomer, for example, one or more of styrene, α-methylstyrene, divinylbenzene, and vinylpyridine, such as styrene-butadiene rubber (SBR).

[0110] Suitable polybutadiene rubbers can be prepared, for example, by the organic solution polymerization of 1,3-butadiene. PBD can be conveniently characterized by, for example, having a cis-1,4 microstructure content of at least 90%, or at least 95%, or at least 96% (“high cis” content). The glass transition temperature (Tg) of PBD measured according to ASTM D3418 can be from -95 °C to -112 °C. PBD can have a Mooney viscosity of 43 - 65 M.U. measured according to ASTM D 1646.

[0111] Suitable polybutadiene rubbers are commercially available, such as those from The Goodyear Tire & Rubber Company 1207, 1208, 1223 and 1280 and those from Arlanxeo CB 25. These high cis-1,4-polybutadiene rubbers can be synthesized using nickel or neodymium catalyst systems, such as those including a mixture of (1) an organonickel compound, (2) an organoaluminum compound, and (3) a fluorine-containing compound, as described, for example, in U.S. Patent Nos. 5,698,643 A and 5,451,646 A. For example, nickel-catalyzed 1207 has a cis 1,4-content of at least 96%, a Mooney viscosity of 55, and a Tg of -100 °C to -104 °C, while neodymium-catalyzed 1223 has a cis 1,4-content of at least 96%, a Mooney viscosity of 55, and a Tg of approximately -104 °C.

[0112] PBD can be used in the rubber composition in an amount of at least 10 phr, or at least 15 phr, or at least 20 phr or at most 40 phr, or at most 35 phr, such as 30 ± 5 phr. In some other embodiments, PBD is omitted (and / or may be at least partially replaced by SBR).

[0113] Styrene-butadiene rubber can be an emulsion-polymerized styrene-butadiene rubber (ESBR) and / or a solution-polymerized styrene-butadiene rubber (SSBR) when in use. Exemplary ESBR can have a bound styrene content of 5 to 50 wt%, such as 20 to 30 wt%. In emulsion polymerization, styrene and 1,3-butadiene are copolymerized in the form of an aqueous emulsion. Emulsion polymerization methods are described in, for example, U.S. Patent No. 5,583,173 A and U.S. Publication Nos. 20050288393 A1, 20060266454 A1, 20080216935 A1, and 20140171557 A1. Exemplary SSBR can have a bound styrene content of 5 to 50 wt%, for example 9 to 36 wt%, or 26 to 31 wt%. An ESBR can be obtained as 1789 from Synthos Dwory.

[0114] SSBR can be prepared, for example, by anionic polymerization in an inert organic solvent. For example, SSBR can be synthesized by copolymerizing styrene and 1,3-butadiene monomers in a hydrocarbon solvent using an organolithium compound as an initiator. Alternatively, SSBR is tin-coupled. Methods for preparing SSBR are described in, for example, U.S. Patent Nos. 4,843,120; 5,239,009; and 6,559,240; and U.S. Publication No. 20120077902 A1.

[0115] In one embodiment, one or more elastomers for the rubber composition can be hydrogenated and / or functionalized. Hydrogenation reduces the percentage of double bonds in the elastomer. Hydrogenation of the polydiene elastomer can be partial or complete. Partial means, for example, hydrogenating less than all of the double bonds present in one or more polydiene segments of the elastomer using a hydrogenation catalyst. For example, at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 60%, or at least 80% of the double bonds present in one or more polydiene segments of the elastomer become saturated by hydrogenation. In some embodiments, up to 100% of the double bonds present in one or more polydiene segments of the elastomer become saturated by hydrogenation.

[0116] Various functional groups can be introduced by functionalization, such as alkoxysilyl groups, primary amine groups, thiol groups, and combinations thereof. For example, functionalized SBR can be obtained by copolymerizing styrene and butadiene with primary amino groups and / or thiol groups and alkoxysilyl groups bonded to the polymer chain. In one embodiment, the alkoxysilyl group is ethoxysilyl. For example, styrene-butadiene rubber is prepared by polymerizing styrene and butadiene in a hydrocarbon solvent by anionic polymerization using an organic alkali metal and / or an organic alkaline earth metal as an initiator, adding a terminator compound having a primary amino group protected by a protecting group and / or a thiol group protected by a protecting group and an alkoxysilyl group at the end of the polymerization to react with the active polymer chain end, and then deprotecting, for example, by hydrolysis or other appropriate procedures.

[0117] Methods for preparing functionalized styrene-butadiene rubbers are disclosed, for example, in U.S. Publication Nos. 20040249020 A1; 20040254301 A1; 20080287601 A1; and 20140135437 A1. Chain-functionalized amino-functionalized SBR is described, for example, in U.S. Publication No. 20040122194 A1.

[0118] c) Other elastomers

[0119] Other curable elastomers may be present in minor amounts (e.g., up to 10 phr in total, or up to 5 phr, or up to 2 phr). Examples of such other elastomers include halogenated butyl rubbers such as bromobutyl rubber and chlorobutyl rubber, nitrile rubber, polynorbornene copolymers, ethylene-propylene-diene rubbers, chloroprene rubber, acrylate rubber, fluororubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, butyl rubber, terpolymers formed from ethylene monomers, propylene monomers, and / or ethylene propylene diene monomers (EPDM), isoprene-based block copolymers, styrenic block copolymers, styrene-ethylene / butene-styrene block copolymers (SEBS), styrene-[ethylene-(ethylene / propylene)]-styrene block copolymers (SEEPS), styrene-isoprene-styrene block copolymers (SIS), random styrenic copolymers, hydrogenated styrenic block copolymers, polyisobutylene, ethylene vinyl acetate (EVA) polymers, polyolefins, amorphous polyolefins, semi-crystalline polyolefins, alpha-polyolefins, reactor-ready polyolefins, acrylates, metallocene-catalyzed polyolefin polymers and elastomers, reactor-made thermoplastic polyolefin elastomer, olefin block copolymers, copolyester block copolymers, polyurethane block copolymers, polyamide block copolymers, thermoplastic polyolefins, thermoplastic vulcanizates, ethylene vinyl acetate copolymers, ethylene n-butyl acrylate copolymers, ethylene methyl acrylate copolymers, chloroprene rubber, acrylics, polyurethanes, poly(acrylates), ethylene acrylic acid copolymers, polyetheretherketone, polyamides, atactic polypropylene, polyethylene including atactic polypropylene, ethylene-propylene polymers, propylene-hexene polymers, ethylene-butene polymers, ethylene-octene polymers, propylene-butene polymers, propylene-octene polymers, metallocene-catalyzed polypropylene polymers, metallocene-catalyzed polyethylene polymers, ethylene-propylene-butene terpolymers, copolymers made from propylene, ethylene, C 4 -C 10 α-olefin monomers, polypropylene polymers, maleated polyolefins, polyester copolymers, copolyester polymers, ethylene acrylic acid copolymers, and / or polyvinyl acetate. Such polymers optionally include, at the polymer chain ends or at side chain positions within the polymer, one or more modifications and / or functionalizations selected from hydroxyl, ethoxy, epoxy, siloxane groups, amine groups, aminosiloxane groups, carboxyl groups, phthalocyanine groups, and silane-sulfide groups.

[0120] 2) Filler

[0121] The rubber composition may comprise one or more particulate reinforcing fillers in a total amount of at least 40 phr, or at least 45 phr, or at least 50 phr, or at most 80 phr, or at most 70 phr, or at most 65 phr, or at most 60 phr.

[0122] In one embodiment, only two reinforcing fillers are used in the rubber composition: carbon black (CB) and silica. In other embodiments, additional fillers may be used.

[0123] The weight ratio of carbon black to silica may be at least 0.8:1, or at least 1:1, or at least 1.1:1, or at least 1.2:1, for example at most 2:1, or at most 1.8:1, or at most 1.6:1, or at most 1.4:1.

[0124] a) Silica

[0125] The term "silica" is used herein to refer to silicon dioxide SiO 2 (which may contain small amounts of impurities, typically less than 1 wt%, from the method of forming the silica). The silica may be precipitated silica formed by digesting amorphous silica with sodium hydroxide to form sodium silicate and precipitating silica from the sodium silicate by reaction with an acidifying agent such as sulfuric acid or carbon dioxide. The resulting precipitate is washed and filtered. Other methods for preparing precipitated silica are described, for example, in U.S. Patent Nos. 5,587,416 A, 5,708,069 A, 5,789,514 A, 5,800,608 A, and 5,882,617 A; and U.S. Publication Nos. 20020081247 A1; 20050032965 A1; and 20110178227 A1.

[0126] The silica may be present in the rubber composition in an amount of at least 15 phr, or at least 20 phr, or at least 25 phr, or at most 35 phr, or at most 30 phr. Expressed as total filler, the silica may be present in the rubber composition in an amount of at least 30 phf, or at least 45 phf, or at most 75 phf, or at most 60 phf, or at most 55 phf, or at most 50 phf, or at most 48 phf.

[0127] The silica may have a surface area of at least 120 m 2 / g, or at least 140 m 2 / g, or at most 400 m 2 / g, or at most 300 m 2CTAB surface area per g. The CTAB surface area is measured according to ASTM D6845 - 20, "Standard Test Method for Silica, Precipitated, Hydrated - CTAB (Cetyltrimethylammonium Bromide) Surface Area". This test method covers the measurement of the specific surface area of precipitated silica, excluding the area contained in micropores that are too small to accommodate cetyltrimethylammonium bromide (CTAB) molecules.

[0128] The surface area of silica can also be measured by nitrogen adsorption according to ASTM D1993 - 18, "Standard Test Method for Precipitated Silica - Surface Area by Multipoint BET Nitrogen Adsorption", which is referred to herein as the nitrogen surface area. The nitrogen surface area can be slightly higher than the CTAB surface area.

[0129] Exemplary precipitated silica that can be used includes Hi - Sil TM 532, Hi - Sil TM 532EP and Hi - Sil TM EZ 160G; Hubersil TM 4155 from J.M.Huber Company; Zeosil labeled 115GR, 125GR, 165GR, 175GR, 185GR, 195GR, 1085GR, 1165MP, 1115MP, HRS1200MP, Premium MP, Premium 200MP, Premium SW, and 195HR from Solvay TM ; Ultrasil labeled VN2, VN3, VN3GR, 5000GR, 7000GR, 9000GR from Evonik TM ; Zeopol labeled 8755LS and 8745 from Evonik TM ; Newsil labeled 115GR and 2000MP from Wuxi Quechen Silicon Chemical Co., Ltd TM ; and Tokusil TM 315 from Maruo Calcium Co., Ltd.

[0130] b) Carbon black

[0131] Carbon black can be present in the rubber composition in an amount of at least 10 phr, or at least 20 phr, or at least 25 phr, or at least 30 phr, or at most 50 phr, or at most 45 phr, or at most 40 phr. Expressed as total filler, carbon black can be present in the rubber composition in an amount of at least 10 phf, or at least 25 phf, or at least 40 phf, or at least 50 phf, or at most 70 phf, or at most 60 phf, or at most 55 phf, or at most 50 phf, or at most 48 phf.

[0132] When in use, carbon black can be present in an amount of at most 10 phr, or at most 5 phr, or at least 0.5 phr, and can have a specific surface area of at least 8, or at least 20, or at least 100, or at least 120, or at most 132 m 2 / kg as determined by ASTM D6556-21, "Standard Test Method for Carbon Black-Total and External Surface Area by Nitrogen Adsorption". The specific (external) surface area based on the statistical thickness method (STSA) is defined as the specific surface area that the rubber can reach.

[0133] Exemplary carbon blacks useful herein include those having ASTM designations N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990, and N991 as specified in ASTM D1765-21, "Standard Classification System for Carbon Blacks Used in Rubber Products". These carbon blacks have an iodine absorption of 9 to 145 g / kg as determined by ASTM D1510-21 and a DBP absorption value of 34 to 150 cm 3 / 100 g as determined by ASTM D2414. For example, the N121 grade has an iodine absorption of approximately 121 g / kg, a CATB specific surface area of approximately 121 m 2 / kg, and a specific surface area of approximately 132 m 2Granular carbon black with DBP absorption of 116 - 126 g / kg and ash content of less than 0.5 wt%. The N220 grade has an iodine absorption of 116 - 126 g / kg, a CATB specific surface area of 106 - 116 m 2 / kg, and a DBP absorption of 109 - 119 m 2 / kg and granular carbon black with an ash content of less than 0.5 wt%.

[0134] c) Other fillers

[0135] In addition to silica and carbon black, reinforcing fillers can be used, for example, in an amount of up to 30 phr, or up to 20 phr, or up to 10 phr, or up to 1 phr, or no reinforcing filler may be present. Examples of such additional reinforcing fillers include alumina, aluminum hydroxide, clay (reinforcing grade), magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, reinforcing zinc oxide, and combinations thereof.

[0136] In some embodiments, one or more non - reinforcing fillers can be used in the rubber composition. Examples of such fillers include clay (non - reinforcing grade), graphite, magnesium dioxide, starch, boron nitride (non - reinforcing grade), silicon nitride, aluminum nitride (non - reinforcing grade), calcium silicate, silicon carbide, rubber powder, and combinations thereof. The term "non - reinforcing filler" is used to refer to particulate materials having a nitrogen absorption specific surface area (N2SA) of 20 m 2 / g or less, for example 10 m 2 / g or less as determined by ASTM D6556 - 21. In certain embodiments, the non - reinforcing filler can be particulate materials having a particle size greater than 1000 nm.

[0137] The total amount of non - reinforcing filler can be 0 to 10 phr, or up to 5 phr, or up to 1 phr.

[0138] In one embodiment, the components in the rubber composition other than polybutadiene, natural rubber, carbon black, and silica (such as other elastomers, other reinforcing fillers, non - reinforcing fillers, organosilane coupling aids, resins, processing aids, antioxidants, antiozonants, anti - degradants, and curing packages) are present in an amount not exceeding 40 phr, or not exceeding 30 phr, or not exceeding 25 phr of the rubber composition.

[0139] 3. Organosilane coupling agent

[0140] Organosilane coupling agents help to make silica more hydrophobic, which aids in the dispersion of silica in the elastomer and the formation of covalent bonds between the elastomer and silica.

[0141] The amount of organosilane coupling agent can be based on the amount of silica in the composition, such as 2 to 15 parts per hundred parts of silica.

[0142] The organosilane coupling agent can be at least 1 phr, or at least 2 phr, or at least 3 phr, or at most 10 phr, or at most 7 phr, or at most 5 phr.

[0143] Examples of organosilane coupling agents include those containing groups such as alkyl, alkoxy, mercapto, blocked mercapto, sulfide-containing groups (e.g., groups containing alkoxy based on monosulfide, alkoxy based on disulfide, alkoxy based on tetrasulfide), amino, vinyl, epoxy, and combinations thereof.

[0144] In one embodiment, the organosilane coupling agent is an alkylalkoxysilane having the general formula (R 1 ) p Si(OR 2 ) 4-p , where each R 2 is independently a monovalent organic group, p is an integer from 1 to 3, such as 1, and at least one R 1 is an alkyl group. Each R 1 can independently be C 1 to C 20 aliphatic (or C 6 to C 15 aliphatic, or C 8 to C 14 aliphatic), C 5 to C 20 alicyclic, or C 6 to C 20 aromatic group. Each R 2 can independently be C 1 to C 6 aliphatic group.

[0145] Exemplary mercapto silanes have the general formula HS-R 3 -Si(R 4 )(R 5 ) 2 , where R 3 is a divalent organic group, R 4 is a halogen atom or an alkoxy group, and each R 5 is independently a halogen, an alkoxy group, or a monovalent organic group. The halogen is chlorine, bromine, fluorine, or iodine. The alkoxy group can have 1 - 3 carbon atoms.

[0146] Exemplary blocked mercapto silanes have the general formula B-S-R 6 -Si-X 3, which has a silyl group capable of reacting with silica in the silica-silane reaction and a blocking group B that replaces the mercapto hydrogen atom to block the reaction of the sulfur atom with the polymer. In the foregoing general formula, B is a blocking group in the form of an unsaturated heteroatom or a carbon directly bonded to sulfur via a single bond, R 6 is C 1 to C 6 a straight-chain or branched-chain alkylene group, and each X is independently selected from C 1 to C 4 alkyl groups and C 1 to C 4 alkoxy groups.

[0147] Examples of suitable alkylalkoxysilanes include octyltriethoxysilane, octyltrimethoxysilane, trimethylethoxysilane, cyclohexyltriethoxysilane, isobutyltriethoxysilane, ethyltrimethoxysilane, cyclohexyltributoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, propyltriethoxysilane, hexyltriethoxysilane, heptyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, tetradecyltriethoxysilane, octadecyltriethoxysilane, methyloctyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, heptyltrimethoxysilane, nonyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, octadecyltrimethoxysilane, methyloctyldimethoxysilane, and mixtures thereof.

[0148] Examples of suitable bis(trialkoxysilylorgano) polysulfides include bis(trialkoxysilylorgano) disulfides and bis(trialkoxysilylorgano) tetrasulfides.

[0149] Examples of bis(trialkoxysilylorgano) disulfides include 3,3'-bis(triethoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl) disulfide, 3,3'-bis(tributoxysilylpropyl) disulfide, 3,3'-bis(tritert-butoxysilylpropyl) disulfide, 3,3'-bis(trihexyloxysilylpropyl) disulfide, 2,2'-bis(dimethylmethoxysilylethyl) disulfide, 3,3'-bis(diphenylcyclohexyloxysilylpropyl) disulfide, 3,3'-bis(ethyl-di-sec-butoxysilylpropyl) disulfide, 3,3'-bis(propyl diethoxysilylpropyl) disulfide, 12,12'-bis(triisopropoxysilylpropyl) disulfide, 3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide, and mixtures thereof.

[0150] Examples of bis(trialkoxysilyl organic group) tetrasulfide silica coupling agents include bis(3-triethoxysilylpropyl) tetrasulfide, bis(2-triethoxysilylethyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl-benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, and mixtures thereof.

[0151] Exemplary bis-(3-triethoxysilylpropyl) polysulfides can have an average of 2 to 2.6 or 3.5 to 4 linked sulfur atoms in the polysulfide bridge. Examples include bis(3-triethoxysilylpropyl) tetrasulfide (TESPT) available as from Evonik Corporation and bis-(3-triethoxysilylpropyl) disulfide having an average of 2.15 linked sulfur atoms in the polysulfide bridge available as from Evonik Corporation.

[0152] Non-limiting examples of suitable mercapto silanes include 1-mercaptomethyltriethoxysilane, 2-mercaptoethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 2-mercaptoethyltripropoxysilane, 18-mercaptooctadecyldiethoxysilane chloride, and mixtures thereof.

[0153] Examples of the closed mercapto silanes include 2-triethoxysilyl-1-ethyl thioacetate, 2-trimethoxysilyl-1-ethyl thioacetate, 2-(methyldimethoxysilyl)-1-ethyl thioacetate, 3-trimethoxysilyl-1-propyl thioacetate, triethoxysilylmethyl-thioacetate, trimethoxysilylmethyl thioacetate, triisopropoxysilylmethyl thioacetate, methyldiethoxysilylmethyl thioacetate, methyldimethoxysilylmethyl thioacetate, methyldiisopropoxysilylmethyl thioacetate, dimethylethoxysilylmethyl thioacetate, dimethylmethoxysilylmethyl thioacetate, dimethylisopropoxysilylmethyl thioacetate, 2-triisopropoxysilyl-1-ethyl thioacetate, 2-(methyldiethoxysilyl)-1-ethyl thioacetate, 2-(methyldiisopropoxysilyl)-1-ethyl thioacetate, 2-(dimethylethoxysilyl-1-ethyl thioacetate, 2-(dimethylmethoxysilyl)-1-ethyl thioacetate, 2-(dimethylisopropoxysilyl)-1-ethyl thioacetate, 3-triethoxysilyl-1-propyl thioacetate, 3-triisopropoxysilyl-1-propyl thioacetate, 3-methyldiethoxysilyl-1-propyl-thioacetate, 3-methyldimethoxysilyl-1-propyl thioacetate, 3-methyldiisopropoxysilyl-1-propyl thioacetate, 1-(2-triethoxysilyl-1-ethyl)-4-thioacetyl cyclohexane, 1-(2-triethoxysilyl-1-ethyl)-3-thioacetyl cyclohexane, 2-triethoxysilyl-5-thioacetyl norbornene, 2-triethoxysilyl-4-thioacetyl norbornene, 2-(2-triethoxysilyl-1-ethyl)-5-thioacetyl norbornene, 2-(2-triethoxy-silyl-1-ethyl)-4-thioacetyl norbornene, 1-(1-oxo-2-thia-5-triethoxysilylphenyl) benzoic acid, 6-triethoxysilyl-1-hexyl thioacetate, 1-triethoxysilyl-5-hexyl thioacetate, 8-triethoxysilyl-1-octyl thioacetate, 1-triethoxysilyl-7-octyl thioacetate, 6-triethoxysilyl-1-hexyl thioacetate, 1-triethoxysilyl-5-octyl thioacetate, 8-trimethoxysilyl-1-octyl thioacetate, 1-trimethoxysilyl-7-octyl thioacetate, 10-triethoxysilyl-1-decyl thioacetate, 1-triethoxysilyl-9-decyl thioacetate, 1-triethoxysilyl-2-butyl thioacetate, 1-triethoxysilyl-3-butyl thioacetate,1-triethoxysilyl-3-methyl-2-butyl thioacetate, 1-triethoxysilyl-3-methyl-3-butyl thioacetate, 3-trimethoxysilyl-1-propyl thiooctanoate, 3-triethoxysilyl-1-propyl-1-propyl thiopalmitate, 3-triethoxysilyl-1-propyl thiooctanoate, 3-triethoxysilyl-1-propyl thiobenzoate, 3-triethoxysilyl-1-propyl thio-2-ethylhexanoate, 3-methyldiacetoxysilyl-1-propyl thioacetate, 3-triacetoxysilyl-1-propyl thioacetate, 2-methyldiacetoxysilyl-1-ethyl thioacetate, 2-triacetoxysilyl-1-ethyl thioacetate, 1-methyldiacetoxysilyl-1-ethyl thioacetate, 1-triacetoxysilyl-1-ethyl-thioacetate, tris-(3-triethoxysilyl-1-propyl) trithiophosphate, bis-(3-triethoxysilyl-1-propyl) methyl dithiophosphonate, bis-(3-triethoxysilyl-1-propyl) ethyl dithiophosphonate, 3-triethoxysilyl-1-propyl dimethyl thiophosphinate, 3-triethoxysilyl-1-propyl diethyl thiophosphinate, tris-(3-triethoxysilyl-1-propyl) tetrathiophosphate, bis-(3-triethoxysilyl-1-propyl) methyl trithiophosphonate, bis-(3-triethoxysilyl-1-propyl) ethyl trithiophosphonate, 3-triethoxysilyl-1-propyl dimethyl dithiophosphinate, 3-triethoxysilyl-1-propyl diethyl dithiophosphinate, tris-(3-methyldimethoxysilyl-1-propyl) trithiophosphate, bis-(3-methyldimethoxysilyl-1-propyl) methyl dithiophosphonate, bis-(3-methyldimethoxysilyl-1-propyl)-ethyl dithiophosphonate, 3-methyldimethoxysilyl-1-propyl dimethyl thiophosphinate, 3-methyldimethoxysilyl-1-propyl diethyl thiophosphinate, 3-triethoxysilyl-1-propyl methyl thiosulfate, 3-triethoxysilyl-1-propyl methanesulfonate, 3-triethoxysilyl-1-propyl ethanesulfonate, 3-triethoxysilyl-1-propyl benzenesulfonate, 3-triethoxysilyl-1-propyl toluenesulfonate, 3-triethoxysilyl-1-propyl naphthalenesulfonate, 3-triethoxysilyl-1-propyl xylenesulfonate, triethoxysilylmethyl methyl thiosulfate, triethoxysilylmethyl methanesulfonate, triethoxysilylmethyl ethanesulfonate, triethoxysilylmethyl benzenesulfonate,Triethoxysilylmethyl toluene thiosulfonate, triethoxysilylmethyl naphthalene thiosulfonate, triethoxysilylmethyl xylene thiosulfonate, etc. Mixtures of various blocked mercapto silanes can be used.

[0154] An example of a suitable blocked mercapto silane is NXT available from Momentive Performance Materials Inc., Albany, N.Y. TM Silane (3 - octanoylthio - 1 - propyltriethoxysilane).

[0155] In one embodiment, the organosilane is loaded on a carrier such as carbon black. For example, bis - [3 - (triethoxysilyl)propyl] tetrasulfide (TESPT) can be obtained by loading on ASTM grade N330 carbon black.

[0156] In another embodiment, the organosilane coupling agent is added to the rubber composition in the form of pretreated silica. The pretreated silica can be silica that has been surface - pretreated with an organosilane before being added to the rubber composition. Using pretreated silica allows the two components (i.e., silica and silica coupling agent) to be added as one component, which generally tends to make rubber compounding easier and also reduces the amount of organosilane coupling agent required.

[0157] In another embodiment, the organosilane coupling agent is added to the rubber composition alone.

[0158] 4. Resin

[0159] Exemplary rubber compositions include at least one hydrocarbon traction resin. The hydrocarbon traction resin can be present in the rubber composition in a total amount of at least 1 phr, or at least 1.5 phr, or at most 8 phr, or at most 4 phr, or at most 3 phr.

[0160] One or more hydrocarbon traction resins can have a glass transition temperature Tg measured according to ASTM D6604 greater than 20 °C, or at least 30 °C, or at most 50 °C. The traction resin can have a softening point measured according to ASTM E28 of at least 30 °C, or at least 70 °C, or at most 100 °C. Tg is generally lower than its softening point, and the lower Tg is, the lower the softening point is. The traction resin helps to improve the wet traction of the tire, which can be estimated by the tanδ value at 0 °C.

[0161] In one embodiment, the resin is partially or fully hydrogenated.

[0162] In one embodiment, the hydrocarbon traction resin is functionalized.

[0163] In one embodiment, the hydrocarbon tackifying resin is an optionally functionalized and / or hydrogenated hydrocarbon resin or a blend of such resins.

[0164] The hydrocarbon tackifying resin may be selected from terpene-phenol resins, terpene resins, terpene-styrene resins, α-methylstyrene resins, styrene / α-methylstyrene resins, coumarone-indene resins, poly(dicyclopentadiene) (DCPD) resins, DCPD / C9 resins, hydrogenated DCPD resins (H2DCPD), H2DCPD / C9 resins, C5 resins, C9 resins, H2C5 resins, H2C9 resins, C5 / C9 resins, and copolymers and mixtures thereof (H2 indicates that the resin is hydrogenated, and C5 and C9 indicate the number of carbon atoms in the monomers prior to any functionalization in forming the resin).

[0165] Exemplary coumarone-indene resins have a backbone (main chain) containing units derived from coumarone and indene monomers. Monomers other than coumarone and indene that may be incorporated into the backbone may include, for example, methylcoumarone, styrene, α-methylstyrene, methylindene, vinyltoluene, cyclopentadiene, dicyclopentadiene, and diolefins such as isoprene and piperylene. Coumarone-indene resins may have a softening point measured by the ring and ball method (ASTM E28) of 10 °C to 160 °C, or at least 30 °C, or at most 100 °C.

[0166] Petroleum-based resins suitable as tackifying resins include aromatic and non-aromatic resins. Examples of aromatic resins include aromatic homopolymer resins and aromatic copolymer resins. Aromatic copolymer resins refer to hydrocarbon resins comprising a combination of one or more aromatic monomers with one or more other (non-aromatic) monomers, where the majority by weight of all monomers is typically aromatic. Aromatic resins may have an Mw of at least 1000 g / mol, and / or at most 4000 g / mol.

[0167] Several types of petroleum-derived resins are available. Some resins have low unsaturation and high aromatic content, while some are highly unsaturated, and still others contain no aromatic structure at all. The differences in the resins are mainly due to the olefins in the raw materials from which the resins are derived. Exemplary olefins include C5, C9, and dicyclopentadiene (DCPD) and combinations thereof. C5 resins are derived from aliphatic monomers containing an average of five carbon atoms, such as one or more of the following: cyclopentene, 1,3-pentadiene (e.g., cis or trans), 2-methyl-2-butene, cyclopentadiene, dicyclopentadiene, diolefins such as isoprene and piperylene. C9 resins are derived from aromatic olefins containing an average of 9 carbon atoms, such as one or more of vinyltoluene, methylstyrenes such as α-methylstyrene, indene, and methylindene. Resins may also be formed from mixtures of the above C5 and C9 monomers and are thus referred to as C5 / C9 copolymer resins. This type of petroleum resin may be obtained with a softening point of 10 °C to 120 °C, or at least 30 °C, or at least 70 °C, or at most 100 °C.

[0168] Dicyclopentadiene is a highly reactive thermoplastic resin that forms through the Diels - Alder addition reaction of two cyclopentadiene molecules, resulting in two stereoisomers: endo - DCPD and exo - DCPD. DCPD readily copolymerizes with many vinyl monomers and resins, including alkyd resins, unsaturated esters, phenolic resins, and epoxy resins. It also acts as a reactive diluent, cross - linker, and curing agent.

[0169] Examples of alkylphenol resins include alkylphenol - acetylene resins such as p - tert - butylphenol - acetylene resins, and alkylphenol - formaldehyde resins (such as those with low degrees of polymerization). Vinyl aromatic resins can include one or more of the following monomers: α - methylstyrene, styrene, o - methylstyrene, m - methylstyrene, p - methylstyrene, vinyltoluene, p - (tert - butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene, etc. Examples of vinyl aromatic copolymer resins include vinyl aromatic / terpene copolymer resins (such as limonene / styrene copolymer resins), vinyl aromatic / C5 fraction resins (such as C5 fraction / styrene copolymer resins), vinyl aromatic / aliphatic copolymer resins (such as CPD / styrene copolymer resins, and DCPD / styrene copolymer resins).

[0170] In the case of aromatic resins based on one or more of the above - mentioned vinyl aromatic monomers (such as styrene, α - methylstyrene), at least 80 wt%, or at least 85 wt%, or at least 90 wt%, or at least 95 wt%, or up to 100 wt% of the monomers in the aromatic resin can be aromatic monomers.

[0171] Terpene resins include polymers of at least one of α - pinene, β - pinene, limonene (such as L - limonene, D - limonene, dipentene as a racemic mixture of the L - isomer and D - isomer), β - phellandrene, δ - 3 - carene, δ - 2 - carene, and combinations thereof. Terpene - phenol resins can be obtained by copolymerizing phenolic monomers with terpenes such as limonene, pinene, and δ - 3 - carene.

[0172] In one embodiment, the hydrocarbon resin includes a combination of aromatic and aliphatic / alicyclic hydrocarbons. In such cases, the total amount of any aliphatic and / or alicyclic resin used in combination with the aromatic resin can be no more than 3 phr, or less than 2 phr, or more than 20 wt%, or no more than 15 wt%, or no more than 10 wt% of the total amount of the hydrocarbon resin.

[0173] C9 modified resins are resins (such as C5 resins) that have been modified or functionalized with one or more aromatic monomers, which aromatic monomers may be selected from indene, methylindene, vinyltoluene, styrene, and methylstyrene (such as α-methylstyrene). Hydrogenated DCPD-C9 copolymer resins are thermoplastic resins obtained from the copolymerization and hydrogenation of C5 aliphatic olefins and C9 aromatic olefins generated during the thermal cracking of naphtha.

[0174] Exemplary styrene / α-methylstyrene resins are relatively short-chain copolymers of styrene and α-methylstyrene having a styrene / α-methylstyrene molar ratio of from 0.05 to 1.50. Such resins can be prepared by cationic copolymerization of styrene and α-methylstyrene in a hydrocarbon solvent.

[0175] Exemplary α-methylstyrene (AMS) tackifying resins are available as SYLVATRAXX TM 4401 and SYLVATRAXX TM 4412 from Kraton Corp. Exemplary HDCPD / C9 resins are available as OPPERA TM PR 383 from ExxonMobil. The resin has an aromatic hydrogen content of about 10 mol%, an aliphatic hydrogen content of about 89 mol%; a softening point (ring and ball method) of about 103 °C; a Tg of 55 °C; an Mn of 480 g / mol; and an Mw of 770 g / mol. Other suitable OPPERA TM resins include PR100A, PR100N, PR120, PR140, OPPERA TM PR373 and PR395. An exemplary terpene-phenol tackifying resin, 4,6,6-trimethylbicyclo[3.1.1]hept-3-en-1-ol is available as YS POLSTER T160 TM from Yasuhara Chemical.

[0176] Additional hydrocarbon-based tackifying resins are described in U.S. Publication No. 20210032442 A1.

[0177] Resins can also be derived from naturally occurring rosin and its derivatives, including, for example, gum rosin, wood rosin, and tall oil rosin. Gum rosin, wood rosin, and tall oil rosin have similar compositions, although the amounts of the components of the rosin may vary. Such resins can be dimerized, polymerized, or disproportionated. Such resins can be in the form of esters of rosin acids and polyols such as pentaerythritol or (eth)ylene glycol.

[0178] Other exemplary resins that can be used in the rubber composition in addition to the traction resin include tackifying resins such as non-reactive phenolic resins, and rigid resins such as reactive phenolic resins and resorcinol or resorcinol and hexamethylenetetramine, which can be used in an amount of 1 to 10 phr, wherein if the tackifying resin is used, it is at least 1 phr, and if the rigid resin is used, it is at least 3 phr. Other resins include benzoxazine resins as described in U.S. Publication No. 20220195153A1 to Papakonstantopoulos et al., which can be used in an amount of, for example, 2 phr to 10 phr.

[0179] 5. Processing aid

[0180] Processing aids, particularly waxes and liquid plasticizers such as oils, can be used in a total amount of 1 to 10 phr, or at least 1.5 phr, or at most 5 phr, or at most 4 phr, or at most 3 phr, or at most 2 phr. In one embodiment, the traction resin replaces the oil, and the oil is present only in a small amount, such as 1 phr or less, or is completely omitted.

[0181] a) Wax

[0182] Suitable waxes include paraffin wax and microcrystalline wax, which can be of the types described on pages 346 and 347 of The Vanderbilt Rubber Handbook (1978). Such waxes can act as anti-ozonants.

[0183] One or more waxes can be present in an amount of 0.1 phr or more, such as at least 0.3 phr, or at least 0.5 phr, or at most 5 phr, or at most 3 phr, or at most 2.5 phr.

[0184] b) Liquid plasticizer (including oil and non - oil)

[0185] The term liquid plasticizer is used to refer to a plasticizer component that is liquid at room temperature (i.e., liquid at 25 °C and above). In contrast to liquid plasticizers, hydrocarbon resins are usually solid at room temperature. Generally, liquid plasticizers will have a Tg below 0 °C, usually well below 0 °C, such as below -30 °C, or below -40 °C, or below -50 °C, such as a Tg of 0 °C to -100 °C.

[0186] When present, the rubber composition can include at least 1 phr, or at most 5 phr, or at most 3 phr, or at most 2 phr of liquid plasticizer. In other embodiments, the rubber composition includes no more than 0.5 phr, or no more than 0.1 phr of liquid plasticizer. In one embodiment, the rubber composition does not contain liquid plasticizer.

[0187] Suitable liquid plasticizers include oils (e.g., petroleum oils and oils of plant origin) and non-oil liquid plasticizers such as ether plasticizers, ester plasticizers, phosphate ester plasticizers, and sulfonate ester plasticizers. The liquid plasticizer can be added during the compounding process or later as an extender oil, which is used to fill the rubber. The Tg of one or more of the oils used can be from -40°C to -100°C.

[0188] Suitable oils can include aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and low polycyclic aromatic (PCA) oils such as MES, TDAE, SRAE, and heavy naphthenic oils. Suitable low PCA oils include those having a polycyclic aromatic hydrocarbon content of less than 3 wt% as determined by the IP346 method. The procedure for the IP346 method can be found in Standard Methods for Analysis & Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd edition, published by the Institute of Petroleum, United Kingdom. Some representative examples of vegetable oils that can be used include soybean oil, sunflower oil, canola (rapeseed) oil, corn oil, coconut oil, cottonseed oil, olive oil, palm oil, peanut oil, and safflower oil. Soybean oil and corn oil are generally preferred vegetable oils.

[0189] 6. Curing package

[0190] The curing package includes a) a vulcanizing (curing) agent, and b) optionally at least one of the following: a curing accelerator, a curing activator, and a curing inhibitor. The curing package can be used in the rubber composition at 0.5 to 20 phr, or at least 5 phr, or at most 10 phr.

[0191] a) Vulcanizing (curing) agent

[0192] Vulcanization of the rubber composition is carried out in the presence of a vulcanizing agent such as a sulfur-based vulcanizing agent.

[0193] Examples of suitable sulfur-based vulcanizing agents include elemental sulfur (free sulfur), insoluble polymeric sulfur, soluble sulfur, and sulfur-donating vulcanizing agents such as disulfide amines, polymeric polysulfides, or sulfur olefin adducts and mixtures thereof.

[0194] The sulfur vulcanizing agent can be used in an amount of at least 0.1 phr, such as at least 0.4 phr, or at least 0.7 phr, or at least 1 phr, or at most 7 phr, or at most 2 phr, or at most 1.2 phr, based on the weight of sulfur.

[0195] b) Curing accelerator, including ultra - accelerator

[0196] Curing accelerators and activators act as catalysts for the vulcanizing agent. Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanized rubber. The total amount of one or more curing accelerators can be 0.1 to 5 phr, or at least 0.5 phr, or at least 1 phr, or at least 1.2 phr, or at least 1.5 phr, or at most 4 phr, or at most 3 phr, or at most 2 phr, or at most 1.7 phr.

[0197] Exemplary accelerators include primary accelerators, optional secondary accelerators, and super accelerators. Primary accelerators can be used in an amount of 0.5 to 4 phr. When combined with a secondary accelerator, the primary accelerator is typically used in a larger amount (e.g., 0.5 to 3 phr) and the secondary accelerator is typically used in a smaller amount (e.g., 0.05 to 0.50 phr) in order to activate and improve the properties of the vulcanized rubber. Historically, combinations of such accelerators have been known to produce a synergistic effect on the final properties of sulfur-vulcanized rubber and are generally somewhat better than those produced by using either accelerator alone. Additionally, delayed-action accelerators can be used, which are less affected by normal processing temperatures but produce satisfactory curing at ordinary vulcanization temperatures.

[0198] Representative examples of accelerators include amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates / salts. In one embodiment, the primary accelerator is a sulfenamide. If a secondary accelerator is used, the secondary accelerator can be a guanidine compound, although a secondary sulfenamide accelerator can be used.

[0199] Examples of thiazole curing accelerators include 2-mercaptobenzothiazole, 2,2′-dithiobis(benzothiazole) (MBTS). Guanidine curing accelerators include diphenylguanidine (DPG). Examples of sulfenamide curing accelerators include benzothiazole sulfenamides such as N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and N-tert-butyl-2-benzothiazole sulfenamide (TBBS).

[0200] Curing accelerators having a rapid vulcanization initiation time (referred to as "t0") of less than 3 minutes are called super accelerators. Super accelerators can contain thiuram, dithiocarbamate, and / or xanthate / salt functional groups. These accelerators start the curing process faster than other accelerators, producing a shorter crosslinking that is desirable for this application. They can be used in place of conventional secondary accelerators. They also act as an anti-reversion aid, protecting the polymer matrix of the formed tire tread, especially when it gets hot. This helps reduce chunking and spalling, where small pieces of the tire break off.

[0201] Exemplary super accelerators include 1,6-bis(N,N′-dibenzylthiocarbamoyldisulfanyl)hexane (BDBZTH), tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetra-isobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyldithiocarbamate (ZDBC), zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, tellurium diethyldithiocarbamate (TDEC), zinc dibenzyldithiocarbamate (ZBED), zinc diisononyldithiocarbamate, zinc pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate (ZBEC), zinc isopropylxanthate (ZIX), zinc butylxanthate (ZBX), sodium ethylxanthate (SEX), sodium isobutylxanthate (SIBX), sodium isopropylxanthate (SIPX), sodium n-butylxanthate (SNBX), sodium amylxanthate (SAX), potassium ethylxanthate (PEX), potassium amylxanthate (PAX), zinc 2-ethylhexyl dithiophosphate (ZDT / S), and mixtures thereof.

[0202] A super accelerator that also provides improved abrasion resistance and more stable curing for the tire tread is 1,6-bis(N,N′-dibenzylthiocarbamoyldisulfanyl)hexane (BDBZTH). Other available super accelerators are zinc dibenzyldithiocarbamate (ZBED) and tetrabenzylthiuram disulfide (TBzTD).

[0203] The rubber composition may include at least 0.1 phr, or at least 0.2 phr, or at most 1 phr, or at most 0.5 phr of the super accelerator.

[0204] Combinations of super accelerators such as BDBZTH with one or more slower-acting accelerators such as sulfenamides and / or guanidine curing accelerators may also be used. The weight ratio of one or more other accelerators (such as sulfenamides, guanidines, and / or benzothiazole(s) accelerators) to one or more super accelerators may be at least 3:1 or at least 3.5:1 or at least 4:1, or at most 6:1, or at most 5:1.

[0205] c) Curing activator

[0206] Curing activators are additives used to support vulcanization. Curing activators include inorganic and organic curing activators. Zinc oxide is the most widely used inorganic curing activator and may be present in an amount of 1 phr to 6 phr, such as at least 2 phr, or at most 5 phr.

[0207] The organic curing activators include fatty acids such as stearic acid, palmitic acid, lauric acid, calcium and zinc salts of unsaturated fatty acids, amides of unsaturated fatty acids, and thiourea compounds such as thiourea and dihydrocarbylthioureas such as dialkylthioureas and diarylthioureas, and mixtures thereof. Specific thiourea compounds include N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea (DEU), N,N'-dimethylthiourea, N,N'-dibutylthiourea, ethylene thiourea, N,N'-diisopropylthiourea, N,N'-dicyclohexylthiourea, 1,3-bis(o-tolyl)thiourea, 1,3-bis(p-tolyl)thiourea, 1,1-diphenyl-2-thiourea, 2,5-bisthiourea, amidinothiourea, 1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, and o-tolylthiourea.

[0208] The total amount of one or more organic curing activators can be from 0.1 to 5 phr, such as at least 0.5 phr, or at least 1 phr, or at most 4 phr.

[0209] d) Curing retarder

[0210] Curing retarders are used to control the vulcanization process and generally retard or inhibit vulcanization until the desired time and / or temperature is reached. An exemplary curing retarder is N-(cyclohexylthio)phthalimide.

[0211] If used, the amount of the curing retarder can be from 0.1 to 2 phr, or at least 0.2 phr, or at most 1 phr, or at most 0.5 phr.

[0212] 7. Antioxidant, anti - degradation agent and anti - ozone agent

[0213] Various compounds can be incorporated into the rubber composition and they help to reduce oxidation, ozone degradation and other forms of degradation. These compounds can be present in the rubber composition in a total amount of 1 phr or more, such as at least 2 phr, or at least 3 phr, or at most 6 phr, or at most 5 phr. In some other embodiments, they may be absent.

[0214] Exemplary antioxidants suitable for rubber compositions include amine-based antioxidants such as p-phenylenediamine (PPD), including diaryl p-phenylenediamines such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), p-phenylenediamine and others, such as those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344 - 346. Such antioxidants can also act as antiozonants and can be used at 0.1 to 6 phr, such as at least 0.3 phr, or at least 1 phr, or at least 2 phr. In some embodiments, at least a portion of the antioxidant is provided in one or more elastomers.

[0215] In use, the anti-degradants can include amine-based anti-degradants and phenolic-containing anti-degradants and can be used at 1 to 5 phr. Phenolic-containing anti-degradants include polymeric hindered phenol antioxidants and the like, such as those included in The Vanderbilt Rubber Handbook (1978), pages 344 - 347. Examples include trimethyl-dihydroquinoline (TMQ) anti-degradants, which are based on polymeric aniline-acetone condensation products. Such anti-degradants can be used at 0.1 to 6 phr, such as at least 0.3 phr, or at least 0.5 phr.

[0216] In addition to the above components, the rubber composition can include other rubber compounding ingredients such as peptizers, such as pentachlorothiophenol, dibenzoylaminodiphenyl disulfide or mixtures thereof. If used, the typical amount of peptizer can be 0.1 phr to 1 phr.

[0217] Preparation of rubber composition

[0218] A rubber composition can be prepared by mixing a vulcanizable elastomer, silica, carbon black, and other rubber compounding ingredients excluding a curing agent to an elevated temperature in at least one continuous mixing stage (commonly referred to as one or more "non-productive" mixing stages) using at least one mechanical mixer under high shear rubber mixing conditions, followed by a final "productive" mixing stage where a sulfur-based curing package (such as a sulfur-based curing agent and a curing accelerator) is added to the mixture and mixed at a lower mixing temperature to avoid unnecessary pre-curing of the rubber mixture during the productive mixing stage. The ingredients can be mixed for 2 minutes at a temperature of 130°C to 200°C, for example, approximately 145°C, in one or more non-productive mixing stages. Once the curing package (or at least the curing agent) is added, the subsequent productive mixing step can be carried out at a temperature below the vulcanization (curing) temperature and / or for a short duration to avoid unwanted pre-curing of the rubber composition, for example, not exceeding 120°C, such as at least 40°C, or at least 60°C, for example, for 2 minutes at a temperature of 110 - 115°C. Mixing can be carried out, for example, by kneading the ingredients in a Banbury mixer or on a milled roll. Between each mixing stage, the rubber composition can be cooled to a temperature below 40°C. For example, the rubber composition can be discharged from the mixer after each mixing step, sheeted out from a calender, and cooled to a temperature below 40°C after each mixing step.

[0219] When the curing package is thoroughly mixed, the rubber composition can be molded or otherwise formed into the shape of a green component of a tire, such as a tire tread. The temperature of the green component can be raised to effect curing. Curing of a pneumatic tire or its components can be carried out at a temperature of 120°C to 200°C, for example, at least 140°C, or at most 180°C, or approximately 150°C, for at least 10 minutes. Any conventional vulcanization method can be used, such as heating in a press or mold, or heating with superheated steam or hot air. Such tires can be constructed, shaped, molded, and cured by various known methods, and will be apparent to those skilled in the art.

[0220] The use of silica filler may optionally require a separate re-mill stage to add a portion or all of such filler separately. This stage is typically carried out at temperatures similar to, although usually slightly lower than, those employed in other productive mixing stages, for example, rising from 90°C to 150°C.

[0221] In one embodiment, a tire is provided that has a tread formed at least in part from an exemplary rubber composition. Other components of the tire, such as the tire sidewall, may additionally or alternatively be formed at least in part from a rubber composition as described herein. The tire can be a pneumatic tire for a road vehicle (such as a bus or truck) or an automobile, or a tire for an off-road vehicle, an aircraft, etc. The tread depth of the tire tread can be at least 20 mm, such as at least 22 mm, such as up to 28 mm, or up to 27 mm, which is suitable for a truck.

[0222] The rubber composition is not limited to being used in tires, but can be applied to rubber gloves, surgical instruments, etc.

[0223] Exemplary composition

[0224] Table 1 shows an exemplary rubber composition according to various aspects of an exemplary embodiment.

[0225] Table 1: Exemplary rubber compositions

[0226]

[0227]

[0228] As an example, in a polymer matrix with a high natural rubber content filled with silica and carbon black, in the case of adding a traction resin for compound properties, a rubber composition is formed with a curing package targeted at a lower and shorter crosslink density (for better TW / RR balance and tear) and an anti-reversion agent (for better stability / aging and heat buildup). More specifically, the natural rubber / synthetic rubber weight ratio is from 100 / 0 to 60 / 40, the CTAB surface area of the silica is 150 to 200 m 2 / g, and the weight ratio of silica to elastomer is from 20 / 100 to 40 / 100. The traction resin can be a hydrocarbon traction resin and / or a functionalized hydrocarbon resin, or a blend thereof. The resin can be selected from one or more of terpene-phenol resins, terpene-styrene resins, and / or DCPD, DCPD / C9, H2DCPD, H2DCPD / C9, C5, C9, H2C5, H2C9, C5 / C9 resins, and mixtures thereof.

[0229] Tire tread properties

[0230] Using the rubber composition in a tire, such as a tire tread, can result in a tire having improved or desirable tread properties. These improved or desirable properties can include reduced rolling resistance, reduced tread wear, good wet handling, and improved abrasion resistance.

[0231] Without intending to limit the scope of the exemplary embodiments, the following examples illustrate the preparation and properties of exemplary rubber compositions.

[0232] Examples

[0233] Prepare rubber compositions (Examples A - E) using the formulations shown in Table 2. Formulations for Examples A and E are prepared for the tire treads of buses, such as electric buses used in urban areas. Formulations for Examples B, C, and D are prepared for the tire treads of long - haul trucks, where the vehicles are mainly used for highway driving.

[0234] Mix the formulations in a laboratory mixer. Use the treads formed from the rubber compositions to construct prototype tires to demonstrate the benefits in terms of physical properties and tire performance compared to three reference formulations (REF.1, a formulation for buses, and REF.2 and 3, formulations for long - haul trucks).

[0235] Table 2: Rubber composition (phr)

[0236]

[0237] 1 REF.1 and 2 use technically - classified rubber or block rubber (TSR), and REF.3 and Examples A - E use ribbed smoked sheet (RSS).

[0238] 2 All examples use high - cis - 1,4 - polybutadiene rubber with a cis - 1,4 content of at least 96% prepared by catalyzing 1,3 - butadiene monomer. For REF.1, PBD as 1207 is obtained from The Goodyear Tire & Rubber Company (nickel - catalyzed), having an initial Tg of approximately - 109 °C and a Mooney viscosity of 55; for REF.2, PBD as 1208 is obtained from The Goodyear Tire & Rubber Company (nickel - catalyzed), having an initial Tg of - 109 °C and a Mooney viscosity of approximately 46; for Ex.A - D, PBD as 1223 is obtained from The Goodyear Tire & Rubber Company (neodymium - catalyzed), having an initial Tg of approximately - 110 °C and a Mooney viscosity of 55; and REF.3 and Ex.E use CB 25 (neodymium - catalyzed) from Arlanxeo, having a Mooney viscosity of approximately 44.

[0239] 3REF.1 uses an emulsion polymerization type copolymer of butadiene and styrene (ESBR) that does not contain nitrosamines and nitrosamine-forming components. ESBR is manufactured by cold emulsion polymerization at 10 °C or below, emulsified by a mixture of soaps of organic acids, and stabilized with a non-coloring antioxidant, which is used as 1502 obtained from The Goodyear Tire & Rubber Company; REF.3 uses a solution-polymerized styrene-butadiene rubber with a styrene content of 18% and a 1,2-vinyl content of 10%, Tg = -78 °C, having a total of 2.9% of the repeating units derived from styrene (in the form of blocks containing five or more styrene repeating units), as 18B10 obtained from The Goodyear Tire & Rubber Company.

[0240] 4 ASTM grade N121 carbon black. Note: All carbon black additionally includes approximately 3.5 phr of carbon black for loading an organosilane coupling agent.

[0241] 5 Silica with a BET nitrogen surface area of approximately 165 m 2 / g and a CTAB surface area of approximately 160 m 2 / g, as Zeosil TM 1165 obtained from Solvay.

[0242] 6 A mixture of bis-[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) and ASTM grade N330 carbon black in approximately equal weights by weight, i.e., approximately 3.5 phr of a silane coupling agent, obtained as Si69 from Evonik Industries.

[0243] 7 Naphthenic oil

[0244] 8 REF.1 and 2 do not use a traction resin; Ex.A uses a terpene-phenol traction resin, 4,6,6-trimethylbicyclo[3.1.1]hept-3-enol, as YS POLSTER T160 TM obtained from Yasuhara Chemical; Ex.B, C, and D use an α-methylstyrene (AMS) traction resin as SYLVATRAXX TM 4401 obtained from Kraton Corp; and Ex.E uses an aromatic-modified aliphatic petroleum-based hydrocarbon resin with a softening point of approximately 90 °C, which is used as OPPERA TMPR373 is obtained from Exxonmobil.

[0245] 9 A mixture of calcium soaps and amides of unsaturated fatty acids, as WB 16 is obtained from Struktol and is used as a curing activator and also as a demolding aid (reducing adhesion on the mixer, etc.).

[0246] 10 A fatty acid mixture, mainly stearic acid.

[0247] 11 Paraffin

[0248] 12 Diaryl - p - phenylenediamine antioxidant

[0249] 13 Trimethyl - dihydroquinoline (TMQ) anti - degradation agent, based on the polymeric aniline - acetone condensation product.

[0250] 14 N - (1,3 - dimethylbutyl) - N′ - phenyl - p - phenylenediamine (6PBD)

[0251] 15 Elemental sulfur

[0252] 16 For REF.1 and Ex.A - C, it is N - cyclohexylbenzothiazole - 2 - sulfenamide (CBS), and for Ex.D, it is N - tert - butylbenzothiazole sulfenamide (TBBS).

[0253] 17 Ex.A uses 1,6 - bis - N,N - (dibenzylthiocarbamoyl) disulfide (BDBZTH), Ex.B and C use zinc dibenzyldithiocarbamate (ZBED), and Ex.D and E use tetrabenzylthiuram disulfide (TBzTD) TM obtained from Performance Additives, Italy.

[0254] It can be noted that none of the exemplary compositions A - E use any processing oil. In these compositions, the traction resin also serves as a processing oil while avoiding the undesirable properties caused by oil in the cured rubber composition.

[0255] Properties of rubber composition

[0256] The cured rubber compositions were tested. The results are shown in Table 3.

[0257] Table 3: Results of tests conducted on cured rubber compositions

[0258] Tests Rer.1 Ref.2 Ref.3 Ex.A Ex.B Ex.C Ex.D Ex.E <![CDATA[Stiffness below 1% A > 2.279 2.051 2.195 2.996 2.755 2.628 2.183 2.525 <![CDATA[Stiffness below 15% A > 1.264 1.057 1.208 1.604 1.515 1.486 1.267 1.356 <![CDATA[Stiffness at 50% A > 0.874 0.738 0.875 1.062 1.014 1.010 0.900 0.925 <![CDATA[Lag B > 0.149 0.194 0.172 0.159 0.155 0.148 0.159 0.166 <![CDATA[Rebound at 100 °C [%] C > 65.4 61.1 63 66 66.0 66.8 67.0 64.7 Rebound at 0°C [%] C > 33 37.0 40.4 37 36.5 38.2 39.2 35.8 <![CDATA[Loss modulus, G″ D > 4.49 2.58 2.35 3.92 3.23 3.30 2.42 3.630 <![CDATA[Shore A hardness E > 67 66.7 66.5 74 71 70.2 67.7 69.6 <![CDATA[Modulus at 300% loop [MPa] F > 14.5 13.8 14.5 15.3 15.7 15.4 15.0 14.5 <![CDATA[Elongation at break [%] F > 741 465 443 470 452 453 459 546 <![CDATA[Tensile strength [MPa] F > 21.7 21.8 21 22.6 22.3 21.9 22 20.8 <![CDATA[Tear strength [N / mm] F > 24.9 23.6 19 23 20.9 22.6 21 24.5 <![CDATA[Abrasion, moderate severity G > 709 505 482 <![CDATA[Abrasion, high severity G > 1512 998 1035

[0259] A Based on ASTM D5289, using the RPA 2000 from Alpha Technologies TM The rubber processing analyzer was used to determine the stiffness as G’ at 1%, 15%, and 50% at 191 °C and 1.67 Hz.

[0260] B Hysteresis was measured using the RPA 2000 TM The rubber processing analyzer was used to measure tanδ (the ratio of the loss modulus G″ to the storage modulus G′) at 10% strain (the lower the better).

[0261] C Based on ASTM D1054, the rebound of the cured samples was measured at 0 °C and 100 °C using a Zwick rebound tester. The rebound at 0 °C is an indicator of the wet braking ability of the tire, and generally the lower the value, the better. The rebound at 100 °C is an indicator of the rolling resistance, and generally the higher the value, the better.

[0262] D The loss modulus G″ was measured at -30 °C at a frequency of 7.8 Hz and a deformation of 6% using a Metravib dynamic mechanical analyzer.

[0263] E The Shore A hardness was measured at 23 °C.

[0264] F The tensile properties (ring modulus at 300%, elongation at break, tensile strength, and tear strength (average load / width at 23 °C)) were measured using an automatic test system instrument from Instron Corporation.

[0265] G Abrasion, indicating tread wear, was determined as the Grosch abrasion rate in mg / km of the worn rubber. When testing a rubber sample across a given distance on a rotating grinding disc, the test rubber sample was placed at a slip angle (medium or high) under a constant load (Newtons). A lower abrasion value at a given slip angle indicates a higher expected mileage, especially for high slip angles.

[0266] From the results, it can be seen that the cured Ex.E composition has a higher stiffness and a higher rebound at 100 °C, a lower rebound at 0 °C, and a higher loss modulus than the comparative REF.2, all of which indicate that the composition is more suitable for use in the tread of bus tires than the reference material.

[0267] It can also be seen that the cured Ex.D composition has better resilience properties than REF.1, indicating that the composition is more suitable than the reference for use in the tread of tires for long-haul truck applications. For medium and high slip angles, the Grosch abrasion is also better for Example D than REF.1.

[0268] The tires are formed of the treads of some rubber compositions and are assembled onto vehicles as follows:

[0269] Tire 1, REF.1 tread on a long-haul truck

[0270] Tire 2, REF.2 tread on an urban bus

[0271] Tire 3, REF.3 tread on a long-haul truck

[0272] Tire 4, Ex.A tread on an urban bus

[0273] Tire 5, Ex.C tread on a long-haul truck

[0274] Tire 6, Ex D tread on a long-haul truck

[0275] Tire 7, Ex.E tread on an urban bus

[0276] The following tests are conducted on the tires operating on a simulated road to provide the following comparative values:

[0277] The rolling resistance is determined as a function of the wheel load.

[0278] The wetland performance is evaluated using the wet grip index.

[0279] The durability is evaluated by the time when visible damage appears.

[0280] The results are shown in Table 4.

[0281] Table 4: Results of tests conducted on tires

[0282]

[0283] The results show that both Tire 4 with Ex.A tread and Tire 7 with Ex.E tread have lower (better) rolling resistance indices and higher (better) wet grip indices than Tire 2 with REF.2 tread on an urban bus. Both Tire 5 with Ex.C tread and Tire 6 with Ex.D tread have lower (better) rolling resistance indices in the simulated road test than Tire 3 with REF.3 tread.

[0284] The various documents mentioned above are incorporated herein by reference. Except in the examples or where otherwise explicitly indicated, all numerical quantities specified in this specification, such as amounts of materials, reaction conditions, molecular weights, numbers of carbon atoms, etc., should be understood to be modified by the word "about". Unless otherwise stated, each chemical or composition mentioned herein should be construed as a commercial grade material, which may contain isomers, by-products, derivatives, and other such materials that are commonly understood to be present in commercial grade materials. However, unless otherwise stated, the amounts of each chemical component stated do not include any solvents or diluent oils that may conventionally be present in commercial materials. It is to be understood that the upper and lower limits, ranges, and ratio limits set forth herein may be combined independently. Similarly, the ranges and amounts of the various elements of the present invention may be used in conjunction with the ranges or amounts of any other element.

[0285] It is recognized that variations or alternatives of the features and functions disclosed above and others may be combined into many other different systems or applications. Those skilled in the art may subsequently make various substitutions, modifications, variations, or improvements that are presently unforeseen or unexpected, and these are also intended to be covered by the following claims.

Claims

1. A tire tread formed from a vulcanizable rubber composition comprising, expressed in parts by weight per hundred parts of elastomer (phr): 100 phr of an elastomeric component comprising polyisoprene rubber and polydiene rubber in a weight ratio of at least 1:1; at least 40 phr of a filler component, the filler component comprising carbon black and silica in a weight ratio of at least 0.8:1; At least 1 phr of an organosilane coupling agent; at least 1 phr of a hydrocarbon drawing resin; Sulfur-based curing agents; and A curing accelerator, wherein the curing accelerator comprises a super accelerator.

2. The tire tread of claim 1, wherein the elastomeric component comprises natural rubber and polybutadiene rubber.

3. The tire tread of claim 2, wherein the weight ratio of natural rubber to polybutadiene rubber is at least 60:

40.

4. The tire tread of claim 2, wherein the polybutadiene rubber has a cis-1,4 content of at least 95%.

5. The tire tread of claim 1, wherein the weight ratio of carbon black to silica is at least 1:

1.

6. The tire tread of claim 1, wherein the rubber composition comprises 15 to 45 phr of carbon black and 20 to 40 phr of silica.

7. A tire comprising the tire tread of claim 1.

8. A method of forming a tire tread, comprising: A rubber composition is formed which comprises blending together: 100 phr of an elastomer component, the elastomer component comprising natural rubber and polybutadiene rubber, the weight ratio of natural rubber to polybutadiene rubber being at least 60:40; at least 40 phr of a filler component, the filler component comprising carbon black and silica, the weight ratio of carbon black to silica being at least 1:1; At least 1 phr of an organosilane coupling agent; at least 1 phr of a hydrocarbon drawing resin; A cure package comprising a sulfur-based curative, zinc oxide; optionally one or more organic activators, and a cure accelerator comprising an ultra accelerator; and curing the rubber composition to form a tire tread.

9. A vulcanizable rubber composition comprising, expressed in parts by weight per hundred parts of elastomer (phr): 100 phr of an elastomeric component, the elastomeric component comprising natural rubber and polybutadiene rubber in a weight ratio of at least 60:40; at least 40 phr of a filler component, the filler component comprising carbon black and silica in a weight ratio of 1:1 to 2:1; 1 to 7 phr of an organosilane coupling agent; 1 to 6 phr of a hydrocarbon drawing resin; 0.5 to 3 phr of wax; and A curing package comprising a sulfur-based curing agent, zinc oxide; an organic activator, and a curing accelerator comprising 0.1 to 1.0 phr of a super accelerator and 0.5 to 2 phr of a sulfenamide curing accelerator.

10. A tire tread formed from the vulcanizable rubber composition of claim 9.

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