Multi-phase diluted rubber composition based on composite blends

Abstract

The invention discloses a multi-phase diluted rubber composition based on a composite blend. A method of forming a vulcanizable rubber composition includes a series of non-productive mixing steps. In a first non-productive mixing step, the composite blend is mixed with a first elastomer to produce a first mixture. The composite blend includes a second elastomer, which may be the same as or different from the first elastomer, and carbon black. In a second non-productive mixing step, a third elastomer different from the first elastomer is mixed with the first mixture or a mixture produced from the first mixture to produce a second mixture. In a productive mixing step, a curing agent is mixed with the second mixture or a mixture resulting from the second mixture to produce a vulcanizable rubber composition that includes a first elastomer, a second elastomer, and a third elastomer, carbon black from the composite blend, and an additional amount of reinforcing filler.

Description

Technical Field

[0001] A method for forming a rubber composition suitable for forming a component of a pneumatic tire, such as a tire tread, is described herein. The method has particular application in forming a multiphase rubber composition in which one or more fillers are differentially distributed between the phases of the rubber composition. Background Art

[0002] The rubber composition that is suitable for tire generally comprises an elastomer mixture together with reinforcing filler (such as carbon black and silicon dioxide).In order to form rubber composition, in the first non-productive stage, elastomer is combined, usually together with some compositions (such as filler) of rubber composition.Can introduce other composition and mix it with elastomer in one or more other non-productive stages.In the productive stage subsequently, curing agent (such as sulphur) is added in the mixture.Introduce elastomer to produce uncured rubber composition or masterbatch in the first non-productive stage, it comprises uniform polymer matrix, and wherein other compositions are evenly dispersed.

[0003] In some cases, the elastomer includes a mixture of polydiene rubbers, such as a mixture of polybutadiene rubber and styrene-butadiene rubber, or a mixture of two different styrene-butadiene rubbers. For example, U.S. Publication No. 20120077902A1 describes a tread composition comprising two specific styrene-butadiene rubbers and a specific cis-1,4 polybutadiene. U.S. Publication No. 20210032442A1 describes a tread composition comprising a specific solution-polymerized styrene-butadiene rubber, natural rubber, or synthetic polyisoprene, and optionally a specific cis-1,4 polybutadiene. U.S. Publication No. 20200071506A1 describes a tread comprising specific first and second functionalized solution-polymerized styrene-butadiene rubbers and optionally a polyisoprene having a cis-1,4 content greater than 95%.

[0004] Recently, preformed elastomer composite blends (sometimes referred to as "masterbatches") for tire compositions have been developed. These typically contain natural rubber latex (usually high purity) and carbon black, as described, for example, in U.S. Publication Nos. 20120172492A1 and 20190040225A1. The composite blend is formed by combining a liquid latex with an aqueous dispersion of carbon black, resulting in a well-dispersed, coagulated mixture. The mixture can be dried to remove water, thereby forming a solid, which can be in the form of sheets, fibers, or particles. This composite blend can be diluted with additional natural rubber and compounded with a curing agent and other additives to produce a composition suitable for forming a tire tread, for example, as described in U.S. application Ser. No. 18 / 127,763, filed on March 29, 2023, entitled “RUBBER COMPOSITION INCORPORATING A PREFORMED NATURAL RUBBER-CARBON BLACK COMPOSITE MATERIAL.”

[0005] There remains a need for rubber compositions that can utilize such composite blends to provide rubber compositions that can provide improved or different properties, such as improvements in heat build-up, tear performance, abrasion, and wear. Summary of the Invention

[0006] According to one embodiment, the method for forming a vulcanizable rubber composition comprises: in a first non-productive mixing step, a composite blend is mixed with a first elastomer to generate a first mixture. The composite blend includes a second elastomer and carbon black. The second elastomer is the same as or different from the first elastomer. In a second non-productive mixing step, a third elastomer that is different from the first elastomer is mixed with the first mixture or the mixture generated by the first mixture to generate a second mixture. In a productive mixing step, a curing agent is mixed with the second mixture or the mixture generated by the second mixture to generate a vulcanizable rubber composition, wherein the vulcanizable rubber composition includes the first elastomer, the second elastomer and the third elastomer, carbon black from the composite blend, and an additional amount of reinforcing filler.

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

[0008] The first elastomer may be or include a first one of natural rubber and a polydiene elastomer, and the third elastomer may be or include a second one of natural rubber and a polydiene elastomer. The first elastomer may be or include natural rubber, and the third elastomer may be or include a polydiene elastomer.

[0009] The polydiene elastomer may include styrene-butadiene rubber. The styrene-butadiene rubber may be or include emulsion polymerized styrene-butadiene rubber.

[0010] The weight ratio of the first elastomer to the third elastomer in the vulcanizable rubber composition can be at least 1:10, or at least 1:5, or at least 1:2, or at least 1:1.5 or at least 1:1, or at most 10:1, or at most 5:1, or at most 3:1, or at most 2:1 or at most 1.5:1.

[0011] The first and third elastomers may be present in the vulcanizable rubber composition in a total amount of at least 20 phr, or at least 30 phr, or at most 70 phr, or at most 60 phr, or at most 50 phr, or at most 40 phr.

[0012] The second elastomer may be or include natural rubber.

[0013] The composite blend may include carbon black in an amount of at least 40 phr per 100 phr of the second elastomer.

[0014] The reinforcing filler may comprise carbon black in an amount of at least 10 phr, or at least 20 phr, per 100 phr of the second elastomer.The reinforcing filler may also comprise silica in an amount of at least 5 phr.

[0015] The vulcanizable rubber composition may further include at least one of a processing aid, a cure activator, and a cure accelerator.

[0016] A tire tread may be formed from the vulcanizable rubber composition formed by the above method.

[0017] According to another embodiment, can vulcanizable rubber composition comprise 100phr elastomer, described elastomer comprises at least 5phr the first elastomer, at least 20phr the second elastomer (providing with the form of carbon black composite blend) and at least 5phr the 3rd elastomer, the 3rd elastomer is different from the first elastomer on its chemical constitution.Except the carbon black in the composite blend, can vulcanizable rubber composition also comprise at least 5phr granular filler.Described granular filler is selected from carbon black, silicon dioxide and combination thereof.Can vulcanizable rubber composition also comprise curing activator, curing accelerator and based on the curing agent of sulphur.

[0018] In one aspect, the vulcanizable rubber composition comprises a plurality of phases, including: a first phase comprising a first elastomer, a second phase comprising a second elastomer, and a third phase comprising a third elastomer, wherein a carbon black concentration in the third phase is lower than a carbon black concentration in the first phase.

[0019] The vulcanizable rubber composition may further include a processing aid selected from the group consisting of resins, liquid processing aids, waxes, and combinations thereof.

[0020] A tire tread may be formed from the vulcanizable rubber composition. A pneumatic tire may include the tread.

[0021] According to another embodiment, a method for forming a vulcanizable rubber composition comprises: in a first non-productive mixing step, mixing a composite blend, natural rubber, and carbon black together to produce a first mixture, wherein the composite blend comprises natural rubber and carbon black. In a second non-productive mixing step, styrene-butadiene rubber is mixed with the first mixture or a mixture derived from the first mixture to produce a second mixture comprising 100 phr of an elastomer, wherein the elastomer comprises at least 45 phr of natural rubber and at least 10 phr of styrene-butadiene rubber, the second mixture further comprising at least 40 phr of carbon black and at least 5 phr of silica. In a productive mixing step, a curing agent is mixed with the second mixture or a mixture derived from the second mixture to produce a vulcanizable rubber composition.

[0022] Specifically, the present invention discloses the following embodiments:

[0023] Option 1. A method for forming a vulcanizable rubber composition, comprising:

[0024] mixing the composite blend with a first elastomer in a first non-productive mixing step to produce a first mixture, the composite blend comprising a second elastomer and carbon black, the second elastomer being the same as or different from the first elastomer;

[0025] mixing, in a second non-productive mixing step, a third elastomer different from the first elastomer with the first mixture, or with a mixture resulting from the first mixture, to produce a second mixture; and

[0026] In a productive mixing step, a curative is mixed with the second mixture, or with a mixture resulting from the second mixture, to produce a vulcanizable rubber composition comprising the first, second, and third elastomers, carbon black from the composite blend, and an additional amount of reinforcing filler.

[0027] Option 2. The method of Option 1, wherein the first elastomer comprises a first one of natural rubber and a polydiene elastomer, and the third elastomer comprises a second one of natural rubber and a polydiene elastomer.

[0028] Option 3. The method of Option 2, wherein the first elastomer comprises natural rubber and the third elastomer comprises a polydiene elastomer.

[0029] Option 4. The method of Option 2, wherein the polydiene elastomer comprises styrene-butadiene rubber.

[0030] Option 5. The method according to Option 4, wherein the styrene-butadiene rubber comprises emulsion-polymerized styrene-butadiene rubber.

[0031] Option 6. The method of Option 1, wherein the weight ratio of the first elastomer to the third elastomer in the vulcanizable rubber composition is at least 1:10, or at least 1:5, or at least 1:2, or at least 1:1.5, or at least 1:1, or at most 10:1, or at most 5:1, or at most 3:1, or at most 2:1, or at most 1.5:1.

[0032] Option 7. The method of Option 1, wherein the first elastomer and the third elastomer are present in the vulcanizable rubber composition in a total amount of at least 20 phr, or at least 30 phr, or at most 70 phr, or at most 60 phr, or at most 50 phr, or at most 40 phr.

[0033] Option 8. The method of Option 1, wherein the second elastomer comprises natural rubber.

[0034] Item 9. The method of item 1, wherein the composite blend comprises carbon black in an amount of at least 40 phr per 100 phr of the second elastomer.

[0035] Option 10. The method of Option 1, wherein the reinforcing filler comprises carbon black in an amount of at least 10 phr, or at least 20 phr, per 100 phr of the second elastomer.

[0036] Item 11. The method of Item 10, wherein the reinforcing filler further comprises silica in an amount of at least 5 phr.

[0037] Option 12. The method according to Option 1, wherein the vulcanizable rubber composition further comprises at least one of a processing aid, a cure activator, and a cure accelerator.

[0038] Aspect 13. A tire tread formed from a vulcanizable rubber composition formed by the method according to aspect 1.

[0039] Aspect 14. A tire comprising the tread according to aspect 13.

[0040] 15. A vulcanizable rubber composition comprising:

[0041] 100 phr of an elastomer, said elastomer comprising:

[0042] at least 5 phr of a first elastomer,

[0043] at least 20 phr of a second elastomer provided in a composite blend with carbon black, and

[0044] at least 5 phr of a third elastomer, said third elastomer differing in its chemical composition from said first elastomer;

[0045] at least 5 phr of a particulate filler other than carbon black in the composite blend, the particulate filler being selected from the group consisting of carbon black, silica, and combinations thereof;

[0046] Curing activator;

[0047] curing accelerators; and

[0048] Sulfur based curing agent.

[0049] Option 16. A vulcanizable rubber composition according to Option 15, wherein the vulcanizable rubber composition comprises a plurality of phases, including a first phase comprising a first elastomer, a second phase comprising a second elastomer, and a third phase comprising a third elastomer, wherein the carbon black concentration in the third phase is lower than the carbon black concentration in the first phase.

[0050] Option 17. The vulcanizable rubber composition according to Option 15, further comprising a processing aid selected from the group consisting of resins, liquid processing aids, waxes, and combinations thereof.

[0051] Aspect 18. A tire tread formed from the vulcanizable rubber composition according to aspect 15.

[0052] Aspect 19. A pneumatic tire comprising the tread according to aspect 18.

[0053] 20. A method of forming a vulcanizable rubber composition, comprising:

[0054] In a first non-productive mixing step, a compounded blend, natural rubber, and carbon black are mixed together to form a first mixture, the compounded blend comprising natural rubber and carbon black;

[0055] mixing, in a second non-productive mixing step, styrene-butadiene rubber with the first mixture, or with a mixture derived from the first mixture, to produce a second mixture comprising 100 phr of an elastomer comprising at least 45 phr of natural rubber and at least 10 phr of styrene-butadiene rubber, at least 40 phr of carbon black, and at least 5 phr of silica; and

[0056] In a productive mixing step, a curative is mixed with the second mixture, or with a mixture formed from the second mixture, to form a vulcanizable rubber composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a flow chart illustrating a method of preparing a vulcanizable rubber composition and articles formed therefrom. DETAILED DESCRIPTION

[0058] A method of forming a rubber composition is described that includes introducing an elastomer at different stages of the mixing process to form a multiphase vulcanizable rubber composition.

[0059] The rubber composition formed in this method is a mixture of elastomers and additives suitable for forming a cured article (e.g., a tire or a component thereof, such as a tire tread). The elastomers include a first elastomer (e.g., a polyisoprene, such as a natural rubber and / or synthetic rubber), a second elastomer (e.g., a polyisoprene, such as a natural rubber and / or synthetic rubber), and a third elastomer different from the first elastomer (e.g., a polydiene, such as styrene-butadiene rubber (SBR)). In one embodiment, the first elastomer is natural rubber and the third elastomer is styrene-butadiene rubber.

[0060] The second elastomer, for example, polyisoprene, such as natural rubber, is provided in the form of a composite blend. The composite blend provides at least a first portion of the carbon black in the rubber composition, and separately provides an optional second portion of the carbon black.

[0061] Other additives that may be incorporated into the vulcanizable rubber composition include one or more of other reinforcing fillers (eg, silica), liquid processing aids, resins, cure activators, cure accelerators, sulfur-based curing agents, antidegradants, and combinations thereof.

[0062] As an example, the vulcanizable rubber composition is derived from:

[0063] A) 100 phr of an elastomer, said elastomer comprising:

[0064] (i) at least 5 phr of a first elastomer,

[0065] (ii) at least 20 phr of a second elastomer in a composite blend with carbon black, and

[0066] (iii) at least 5 phr of a third elastomer having a chemical composition different from that of the first elastomer;

[0067] B) at least 5 phr of a particulate filler other than the carbon black in the composite material, the particulate filler being selected from the group consisting of:

[0068] (i) carbon black,

[0069] (ii) silicon dioxide, and

[0070] its combination;

[0071] C) Optionally, one or more processing aids, which may be selected from:

[0072] (i) resin,

[0073] (ii) liquid processing aids,

[0074] (iii) wax, and

[0075] its combination;

[0076] D) a curing activator, which may be selected from:

[0077] (i) zinc oxide,

[0078] (ii) fatty acids, and

[0079] its combination;

[0080] E) curing accelerator;

[0081] F) a sulfur-based curing agent; and

[0082] G) Optionally one or more additional components, such as antiozonants, antioxidants, cure retarders, peptizers, and the like.

[0083] In one embodiment, the method for preparing a vulcanizable rubber composition includes a sequence of at least two non-productive mixing stages (NP) (i.e., a mixing stage that occurs before a sulfur-based curing agent is added to the mixture), followed by a productive mixing stage (PR) (wherein a sulfur-based curing agent is added to the mixture). The non-productive mixing stage can include at least a first non-productive mixing stage (NP1) and a subsequent second non-productive mixing stage (NP2). Before or after NP2, additional non-productive mixing stages can optionally be performed. In the first non-productive mixing stage, the composite blend is mixed with a first elastomer and optionally additional reinforcing fillers (e.g., carbon black), the first elastomer being one of polyisoprene and polydiene elastomer. In the second non-productive mixing stage, the mixture formed in NP1 (or in an intermediate NP stage) is mixed with a third elastomer that is different from the first elastomer and that can be another of polyisoprene and polydiene rubber.

[0084] In the resulting vulcanizable rubber composition, carbon black is unevenly distributed in three (or more) elastomers, resulting in the formation of a multiphase mixture, which produces favorable properties in the product formed therefrom (such as the tire tread of a pneumatic tire). Specifically, the vulcanizable rubber composition may include three phases: a first phase, in which carbon black is dispersed in the first elastomer with a first carbon black: elastomer weight ratio (CB:E ratio); a second phase, in which carbon black is dispersed in the second elastomer with a second CB:E ratio; and a third phase, in which carbon black is dispersed in the third elastomer with a third CB:E ratio. Typically, the second phase has the highest CB:E ratio, while the third phase has the lowest CB:E ratio, particularly when little or no carbon black is added in NP2. It is to be understood that the three phases are partially intermixed, but are sufficiently distinguished so as to provide unique physical properties for the rubber composition and the product formed therefrom, and then provide a good comprehensive property of tear resistance, abrasion, and tire heat generation.

[0085] definition

[0086] Unless otherwise indicated, the terms "rubber" and "elastomer" are used interchangeably. The terms "rubber composition" or "compounded rubber" are used interchangeably to refer to "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 indicated, the terms "cured" and "vulcanized" are used interchangeably.

[0087] As used herein, the term "tread" means that portion of a tire that comes into contact with the road when normally inflated and loaded, and optionally also refers to any subtread, unless otherwise indicated.

[0088] As used herein, the term "phr" means parts per hundred parts of rubber by weight. Generally speaking, using this convention, a rubber composition includes 100 parts by weight of rubber / elastomer. The claimed composition may include other rubbers / elastomers in addition to the rubbers / elastomers explicitly mentioned in the claims, as long as the phr value of the claimed rubber / elastomer meets the claimed phr range and the amount of all rubbers / elastomers in the composition results in a total of 100 parts of rubber. The term "phf" means parts per hundred parts by weight of filler in the rubber composition.

[0089] Unless otherwise stated, properties were determined using the following methods:

[0090] The molecular weights, e.g., Mn (number average molecular weight), Mw (weight average molecular weight), and Mz (z-average molecular weight), of elastomers, rubber compositions, and resins 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.

[0091] The glass transition temperature (Tg) of an elastomer or an elastomeric composition is the glass transition temperature(s) of the respective elastomer or elastomeric composition in its uncured state or, in the case of an elastomeric composition, possibly in the cured state.

[0092] The Tg value of the elastomer is measured as the peak midpoint by differential scanning calorimetry (DSC) at a heating rate of 10°C / min in accordance with ASTM D3418-21, "Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry" (hereinafter referred to as ASTM D3418).

[0093] The glass transition temperature (Tg) of the resin was measured as the peak midpoint at a heating rate of 10°C / min by differential scanning calorimetry (DSC) in accordance with ASTM D6604-00 (2017), “Standard Practice for Glass Transition Temperatures of Hydrocarbon Resins by Differential Scanning Calorimetry” (hereinafter referred to as ASTM D6604).

[0094] The glass transition temperature (Tg) of the oil was measured as the peak midpoint by differential scanning calorimetry (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”.

[0095] The softening point of the resin (sometimes referred to as the ring and ball softening point) was measured 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 referred to as ASTM E28).

[0096] The Mooney viscosity (ML 1+4) was measured as MU at 100° C. according to ASTM D1646-19a, “Standard Test Methods for Rubber—Viscosity, Stress Relaxation, and Pre-Vulcanization Characteristics (Mooney Viscometer)” (hereinafter referred to as ASTM D1646).

[0097] The term "alkyl" refers to straight chain, branched chain and cyclic alkyl groups. The term "aryl" refers to a group including at least one aromatic ring and includes alkylaryl groups.

[0098] The cis, trans, and vinyl content (%) of a polymer refers to the molar ratio of 1,4-cis, 1,4-trans, and 1,2-vinylbutadiene units in the polymer, which generally sum to 100% unless otherwise stated. These percentages can be determined by 1H-NMR spectroscopy in accordance with ISO 21561-1:2015. Styrene content refers to the weight percent of bound styrene in a polymer (e.g., styrene-butadiene polymer) and can be determined by FT-IR.

[0099] Exemplary Methods

[0100] The vulcanizable rubber composition may be prepared by combining the vulcanizable elastomer, filler (e.g., carbon black) and other rubber compounding ingredients (excluding the curative) with at least one mechanical mixer in a sequence of mixing stages, generally referred to as a "non-productive" mixing stage, under high shear rubber mixing conditions to elevated temperatures, followed by a final "productive" mixing stage in which a sulfur-based curative and cure accelerator are 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.

[0101] Figure 1 An exemplary method for forming a vulcanizable rubber composition is shown. The method starts at S100.

[0102] At S102, in a first non-productive mixing stage (NP1), the first elastomer is combined with a composite blend (comprising the second elastomer) and optionally a first portion of additives (excluding curing agent(s)) and mixed in a suitable mixing device for a period of time (e.g., at least one minute) to form a first mixture.

[0103] At S104 , after the first non-productive mixing stage, the first mixture may be dropped or otherwise cooled from the mixing device.

[0104] At S106, in a second non-productive mixing stage (NP2), the third elastomer to be incorporated into the rubber composition is combined with the first mixture from S102 or S104 or an intermediate mixture derived therefrom and optionally with a second portion of the additives (excluding the curing agent(s)) and mixed in a suitable mixing device for a period of time, e.g., at least one minute. The output of this step is a second mixture comprising the first, second, and third elastomers and at least a portion of the additives (excluding the curing agent(s)).

[0105] At S108 , after the second non-productive mixing stage, the mixture may be drained from the mixing device or otherwise cooled.

[0106] Optionally, one or more additional non-productive mixing stages may be performed prior to the productive mixing stage.

[0107] At S110, in a productive mixing phase, a curing agent is combined with the mixture output at S106 or S108 (or a subsequent non-productive mixing phase, if performed) and mixed for an appropriate time, such as at least one minute. The output of this step is a vulcanizable rubber composition comprising the first, second, and third elastomers, additives, and a curing agent.

[0108] At S112 , the vulcanizable rubber composition formed at S110 may be extruded, molded, and / or otherwise shaped to form a green rubber component, such as a tire tread or portion thereof.

[0109] At S114 , the green rubber component (optionally along with other components of an article (eg, tire)) may be cured, for example, by heating.

[0110] The method ends at S116.

[0111] It is to be understood that fewer, additional, and / or different steps than those described above may be performed in the method.

[0112] In NP1 (S102), the first elastomer can be mixed with the composite blend, additional carbon black, silica, and a portion or all of the additives (excluding the curing agent) to form a first mixture. The mixing can be performed for about 1-2 minutes to a temperature of 130° C. to 200° C., for example, about 150° C. to about 165° C. This step can be performed in the absence of a third elastomer, or in the presence of a small amount of the third elastomer (for example, no more than 10% by weight, or no more than 5% by weight of the third elastomer).

[0113] After the first mixture is cooled (S104), it is combined with the third elastomer (S106) and any additives that have not yet been added and mixed to form a second mixture. Mixing can be performed for about 2 minutes to a temperature of 130°C to 200°C, for example, from about 150°C to about 165°C. In one embodiment, the incorporation of carbon black (and optionally silica) is performed before the second mixing step, that is, before the addition of all or a major amount (at least 90% by weight, or at least 95% by weight) of the third elastomer. As a result, more carbon black remains dispersed in the first and second elastomers than in the third elastomer.

[0114] After cooling the second mixture (S108), one or more additional non-productive mixing steps (referred to as NP3, etc.) may be performed to generate a third mixture derived from the second mixture, etc. In one embodiment, the third mixing step is performed without adding other ingredients. Mixing in NP3, etc. may be performed for about 2 minutes to a temperature of 130° C. to 200° C., for example, about 150° C. to about 165° C., and then a cooling step is performed.

[0115] In the productive mixing stage (S110), the second mixture (or the third mixture derived therefrom as described above, etc.) is combined with a curing agent. The productive mixing step can be carried out at a temperature lower than the vulcanization (curing) temperature and / or in a short time to avoid undesirable pre-curing of the rubber composition, for example, no more than 120°C, for example, at least 60°C, for example, at a temperature of 110-115°C for 2 minutes. Mixing can be carried out by kneading the ingredients together, for example, in a Banbury mixer or on a milled roll.

[0116] Between each mixing stage, the rubber composition may be cooled to a temperature below about 40° C. For example, after each mixing step, the rubber composition may be discharged from the mixer, sheeted from an open mill or onto a roller die, and allowed to cool to below 40° C. after each mixing step.

[0117] When the curing agent (and any curing accelerator and other ingredients not previously added to the mixture) added in the productive mixing step is fully mixed into the rubber composition, the rubber composition can be molded or otherwise formed into the shape of a green component of a tire, such as a tire tread (S112).

[0118] At S114, the temperature of the green component can be increased to effect curing. Curing of the pneumatic tire or a portion thereof can be carried out at a temperature of 120°C to 200°C, such as at least 140°C, or up to 180°C, or about 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 a tire can be constructed, shaped, molded, and cured by various methods known and readily apparent to those skilled in the art.

[0119] The rubber composition will now be described in more detail.

[0120] A. Elastomer

[0121] For ease of description, the first elastomer will be described in terms of polyisoprene rubber, and the third elastomer will be described in terms of polydiene rubber, and vice versa.

[0122] The weight ratio of the first elastomer to the third elastomer in the vulcanizable rubber composition can be at least 1:10, or at least 1:5, or at least 1:2, or at least 1:1.5, or at least 1:1, or at most 10:1, or at most 5:1, or at most 3:1, or at most 2:1, or at most 1.5: 1. In general, the first elastomer and the third elastomer can be present in the vulcanizable rubber composition in an amount of at least 20 phr, or at least 30 phr, or at most 70 phr, or at most 60 phr, or at most 50 phr, or at most 40 phr.

[0123] (i) First elastic body

[0124] The first elastomer comprises natural and / or synthetic polyisoprene, such as natural rubber, or consists thereof. The first elastomer can be present in the rubber composition in an amount of at least 5 phr, or at least 10 phr, or at least 15 phr, or at most 70 phr, or at most 60 phr, or at most 40 phr, or at most 30 phr, for example, 22 ± 5 phr.

[0125] As used herein, the term "natural rubber" refers to naturally occurring rubber, such as rubber that can be harvested from sources such as Hevea rubber trees and non-Hevea sources (e.g., guayule shrubs and dandelions, such as TKS). In other words, the term "natural rubber" should be understood to exclude synthetic polyisoprene.

[0126] Synthetic polyisoprene refers to polymers made from isoprene monomers and should not be construed to include naturally occurring rubber. However, the term polyisoprene should be understood to include polyisoprene made from isoprene monomers from natural sources.

[0127] The natural rubber is primarily cis-polyisoprene. The cis-1,4-polyisoprene content of the natural rubber may be at least 90%, or at least 95%. In one embodiment, the natural rubber is a natural cis-1,4-polyisoprene rubber having a cis-1,4-content of at least 96% and a Tg in the range of -60°C to -110°C, as determined according to ASTM D3418.

[0128] Several forms of natural rubber are commercially available. Natural rubber can meet the purity specifications of ISO TSR grade 20 or ISO TSR grade 10. ISO TSR 20 natural rubber has a maximum ash content of 1% by weight, as determined in accordance with ISO 247:1990; a maximum volatile matter content of 0.8% by weight, as determined in accordance with ISO 248:1991; a maximum nitrogen content of 0.6% by weight, as determined in accordance with ISO 1656:1996; a minimum initial Wallace plasticity of 30, as determined in accordance with ISO 2007:1991; and a minimum plasticity retention index of 40, as determined in accordance with ISO 2930:1995. For TSR 10, the maximum ash content is 0.75% by weight, the maximum nitrogen content is 0.6% by weight, the maximum volatiles content is 0.8% by weight, the minimum plasticity is 30, and the minimum plasticity retention index is 50. In other embodiments, the natural rubber may be ribbed smoked sheet (RSS) rubber.

[0129] (ii) Second elastomer (composite blend)

[0130] The composite blend includes a mixture of a second elastomer and a particulate filler (e.g., carbon black). Ingredients other than the second elastomer and the particulate filler in the composite blend may be present in an amount of no more than 20 phr, or no more than 10 phr, or no more than 5 phr. The composite blend may be free of a cure accelerator, a cure activator, and a curing agent.

[0131] The weight ratio of the second elastomer to the carbon black in the composite blend can be at least 0.5: 1, or at least 1: 1, or at least 1.5: 1, or at least 1.7: 1, or at most 10: 1, or at most 5: 1, or at most 4: 1; or at most 3: 1, or at most 2.5: 1, or at most 2: 1. In other words, the carbon black can be at least 10 phr, or at least 20 phr, or at least 30 phr, or at least 40 phr, or at least 50 phr, or at most 90 phr, or at most 70 phr, or at most 60 phr, relative to 100 phr of the elastomer(s) in the composite blend.

[0132] In one embodiment, the second elastomer consists of or comprises natural rubber.

[0133] The carbon black in the composite blend can be any ASTM grade commonly used to form rubber compositions as described further below. Exemplary ASTM grades include N134, N220, and N234.

[0134] The composite blend may have a storage viscosity (ML(1+4)@100°C) of at least 140, or at least 150, or at most 200, or at most 190.

[0135] The composite blend is formed by a wet mixing process in which a fluid elastomer latex (e.g., natural rubber) is combined with an aqueous slurry of a particulate filler (e.g., carbon black and / or silica). The composite blend can be formed by the methods described in one or more of U.S. Patent No. 6,048,923A and U.S. Publication Nos. 20020086917A1 and 20190048150A1. These references generally disclose a wet mixing process in which separate streams of carbon black slurry and elastomer latex are combined in a mixing zone under conditions in which the elastomer latex coagulates without the addition of a coagulant. In one embodiment, the slurry is fed to the mixing zone as a continuous, high-speed injection fluid jet, while the natural rubber latex fluid is fed at a relatively low speed, for example, as described in U.S. Publication No. 20190048150A1. The high velocity, flow rate and particle concentration of the filler slurry are sufficient to cause mixing and high shear of the latex fluid, flow turbulence of the mixture in at least the upstream portion of the mixing zone, and substantially complete coagulation of the elastomeric latex before the end of discharge.

[0136] The coagulated mixture can be dehydrated to a water content of about 15% to 25%. After dehydration, the resulting dehydrated coagulum can be dried, for example, by thermal drying. The dehydrated coagulum can be mechanically comminuted while drying. For example, the dehydrated coagulum can be mechanically processed using one or more of a continuous mixer, an internal mixer, a twin-screw extruder, a single-screw extruder, or a roller mill. Further drying can be performed to reduce the water content to less than about 1% by weight, or less than 0.5% by weight, or less than 0.2% by weight. The resulting dried composite blend can be granulated or otherwise comminuted into smaller fragments for easier handling.

[0137] Exemplary composite blends may be used as E 2 C TM DX9730、E 2 C TM FX9390、E 2 C TM DX9660, E2C TM EX9620, E29620, etc. are commercially available from Cabot Corporation.

[0138] Methods for preparing such engineered elastomeric composites (E2Cs) and their properties are further described in, for example, Ting Wang et al., “CEC and its application in off-the-road tires,” Rubber World, 277(6), pp. 33-38 (2003).

[0139] (iii) The third elastic body

[0140] In an exemplary embodiment, the third elastomer is composed of or includes a synthetic conjugated diene-based elastomer (referred to herein as a polydiene or polydiene elastomer). The third elastomer can be present in the rubber composition in an amount of at least 5 phr, or at least 10 phr, or at least 15 phr, or at most 70 phr, or at most 60 phr, or at most 40 phr, or at most 30 phr, for example, 18 ± 5 phr.

[0141] The polydiene elastomer comprises at least one polydiene elastomer, each of which is at least partially derived from butadiene. For example, at least 20% or at least 30% of the units in the polydiene rubber(s) are formed from butadiene. In one embodiment, the polydiene rubber is a copolymer of butadiene and another monomer, for example, a vinyl aromatic monomer such as one or more of styrene, α-methylstyrene, divinylbenzene, and vinylpyridine.

[0142] Exemplary polydiene elastomers include styrene-butadiene rubber (SBR) and polybutadiene (PBD). The styrene-butadiene rubber may be emulsion-polymerized styrene-butadiene rubber (ESBR) and / or solution-polymerized styrene-butadiene rubber (SSBR).

[0143] In one embodiment, (one or more) polydiene elastomers include ESBR or consist of ESBR. ESBR can have a bound styrene content of 5 to 50 wt %, for example 20 to 30 wt %. In emulsion polymerization, styrene and 1,3-butadiene are copolymerized into an aqueous emulsion. Emulsion polymerization methods are described in, for example, U.S. Patent No. 5,583,173A and U.S. Publication Nos. 20050288393A1, 20060266454A1, 20080216935A1, and 20140171557A1.

[0144] An exemplary ESBR is available as PLIOFLEX 1502 TM Available from Goodyear Tire & Rubber Company. It has a styrene content of 23.5% by weight, a Tg of -50°C, and is prepared by tin-catalyzed aqueous emulsion polymerization of styrene and 1,3-butadiene monomers.

[0145] ESBR can be oil-extended to facilitate processing. One oil-extended ESBR is BUNA from Dow TM SB 1723-Schkopau, which is made by cold polymerization using mixed rosin acid / fatty acid soaps. It is plasticized with 37.5 parts of mineral oil per 100 parts of rubber and has a Mooney viscosity ML1+4@100°C of 49. Another example of oil-extended ESBR has a bound styrene content of 40% styrene, a Tg of -33°C, and is extended with 37.5 phr of RAE oil and can be used as 1789 ESBR was obtained from Synthos.

[0146] In one embodiment, (one or more) polydiene elastomers include SSBR or consist of SSBR. The bound styrene content of SSBR can be 5 to 50 weight %, for example, 9 to 36 weight %, or 26 to 31 weight %. 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 using an organolithium compound as an initiator in a hydrocarbon solvent. Alternatively, SSBR is tin coupled. Methods for preparing SSBR are described, for example, in U.S. Patent Nos. 4,843,120A and 6,103,842A; and U.S. Publication Nos. 20020099148A1; US20120077902 A1 and 20140135437A1.

[0147] An exemplary SSBR can be used as 6430 was obtained from Dow.

[0148] SSBR can be oil extended. Oil extended SSBR can have a bound styrene content of 25 to 45 wt %, based on the weight of the rubber, a vinyl 1,2 content of 10 to 60 wt %, and a Tg of -40°C to -5°C. An example of an oil extended SSBR has 40 wt % bound styrene, 14 wt % vinyl, a Tg of -34°C, and is extended with 37.5 phr TDAE oil and is available as SE SLR6430 TM SSBR is available from Dow Schkopau. Another example of an oil-extended SSBR has 34 wt% bound styrene, 38 wt% vinyl, a Tg of -25°C, and is extended with 37.5 phr SRAE oil, which is available as Tufdene TM E680 was obtained from Asahi Chemical.

[0149] In one embodiment, the first elastomer and / or the third elastomer can be hydrogenated and / or functionalized. Hydrogenation reduces the percentage of double bonds in the elastomer. The hydrogenation of the polydiene elastomer can be partial or complete. Partial means that less than all double bonds present in the (one or more) polydiene segments of the elastomer are hydrogenated, for example, hydrogenated with 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 the (one or more) polydiene segments of the elastomer are saturated by hydrogenation. In some embodiments, up to 100% of the double bonds present in the (one or more) polydiene segments of the elastomer are saturated by hydrogenation.

[0150] Various functional groups, such as alkoxysilane groups, primary amine groups, thiol groups and combinations thereof, can be incorporated into the functionalized SBR. For example, functionalized SBR can be obtained by copolymerizing styrene and butadiene with primary amine groups and / or thiol groups and alkoxysilyl groups bonded to the polymer chain. In one embodiment, the alkoxysilyl group is an ethoxysilyl group. For example, styrene-butadiene rubber is produced by the following steps: in a hydrocarbon solvent, styrene and butadiene are polymerized by anionic polymerization using an organic alkali metal and / or an organic alkaline earth metal as an initiator, and when the polymerization is substantially complete, a terminator compound having a primary amine group protected with a blocking group and / or a thiol group and an alkoxysilyl group protected with a blocking group is added to react with the active polymer chain end, and then, for example, deprotected by hydrolysis or other appropriate procedures.

[0151] Methods for preparing functionalized styrene-butadiene rubbers are disclosed, for example, in U.S. Publication Nos. 20040249020A1; 20040254301A1; and 20080287601A1. Chain-functionalized amino-functionalized SBRs are described, for example, in U.S. Publication No. 20040122194A1.

[0152] An SBR functionalized with alkoxysilane and amino groups has a bound styrene content of 27%, a 1,2-vinyl content of 57%, and a Tg of -27°C, available from JSR as HPR 355H. A tin-coupled SBR functionalized with alkoxysilane and thiol groups has a Tg of about -25°C, available as SLR 4602 is available from Trinseo. An SSBR functionalized with alkoxysilane and thiol groups having a bound styrene content of 15 wt%, a 1,2-vinyl content of 30 wt% and a Tg of about -60°C is available as SPRINTAN TM SLR 3402 is available from Trinseo. A hydroxyl functionalized SBR is available as Tufdene 3330TM An epoxy functionalized SBR is available from Asahi as Tufdene E50 TM Available from Asahi. Amino / siloxy functionalized SBR is available as SLR4601 TM Obtained from Trinseo and as T5560 TM Obtained from JSR.

[0153] In one embodiment, (one or more) elastomers can be both functionalized and hydrogenated. The elastomer to be hydrogenated can be functionalized at the end, as described, for example, in U.S. Publication Nos. 20230312780A1; 20230312784A1; 20230312792A1; and 20230312798A1. Functionalization can also be performed in the middle of the end. In another embodiment, the elastomer is functionalized with an alkoxysilane group and optionally at least one functional group selected from primary amines and thiols. For example, a (co)polymer chain of a conjugated diene or a conjugated diene and an aromatic vinyl compound can be terminated with a terminator compound having a protected primary amino group and an alkoxysilyl group, as described, for example, in U.S. Publication No. 20040254301A1. Another SBR functionalized with an alkoxysilane group and a thiol is described in U.S. Publication No. 20080287601A1.

[0154] Suitable styrene-butadiene rubbers functionalized with alkoxysilane groups and primary amine groups are commercially available, for example HPR340 from Japan Synthetic Rubber (JSR).

[0155] Suitable styrene-butadiene rubbers functionalized with alkoxysilane groups and thiol groups are commercially available, for example Sprintan SLR 3402 from Trinseo.

[0156] Polybutadiene rubber, which can be used as the third elastomer, can be prepared, for example, by organic solution polymerization of 1,3-butadiene. The PBD can be characterized, for example, by having a cis-1,4 microstructure content of at least 90% ("high cis" content), or at least 95% or at least 96% cis-1,4 microstructure. The glass transition temperature (Tg) of the PBD, as measured according to ASTM D3418, can range from -95 to -112°C. The PBD can have a Mooney viscosity of 45-65 M.U., as measured according to ASTM D1646.

[0157] Suitable polybutadiene rubbers are commercially available, for example from Goodyear Tire & Rubber Company. 1207, 1208, 1223 and

[0158] 1280. These high cis-1,4-polybutadiene rubbers can be synthesized using nickel or neodymium catalyst systems, such as catalyst systems comprising 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 and 5,451,646. For example, nickel-catalyzed 1207 has a cis 1,4-content of at least 96%, a Mooney viscosity of 55, a Tg of -100°C to -104°C, and is neodymium catalyzed. 1223 has a cis 1,4-content of at least 96%, a Mooney viscosity of 55, and a Tg of about -104°C.

[0159] Where used, PBD may be present 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 50 phr, or at most 40 phr, or at most 35 phr.In other embodiments, PBD is omitted.

[0160] (iv) Other elastomers

[0161] Other vulcanizable elastomers may be present in the rubber composition (e.g., in a total of up to 20 phr, or up to 10 phr, or up to 5 phr, or up to 2 phr, or up to 1 phr). Examples of such other elastomers include halogenated butyl rubbers, such as bromobutyl rubber and chlorinated butyl rubber, nitrile rubber, polynorbornene copolymers, ethylene-propylene-diene rubber, chloroprene rubber, acrylate rubber, fluororubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, rubber), butyl rubber, terpolymers formed from ethylene monomer, propylene monomer and / or ethylene propylene diene monomer (EPDM), isoprene-based block copolymers, styrenic block copolymers, styrene-ethylene / butylene-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 elastomers, 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, acrylic resins, polyurethanes, poly(acrylates), ethylene-acrylic acid copolymers, polyetheretherketones, 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 prepared from propylene, ethylene, C4-C10 alpha-olefin monomers, polypropylene polymers, maleated polyolefins, polyester copolymers, copolyester polymers, ethylene-acrylic acid copolymers and / or polyvinyl acetate. Such polymers optionally include modification and / or functionalization at the polymer chain termini or at pendant positions within the polymer with one or more selected from the group consisting of hydroxyl groups, ethoxy groups, epoxy groups, siloxane groups, amine groups, aminesiloxane groups, carboxyl groups, phthalocyanine groups, and silane-sulfide groups.

[0162] B. Granular filler

[0163] In addition to the granular filler provided by the composite blend, when forming the rubber composition, one or more granular reinforcing fillers of an additional amount (e.g., at least 5 phr, or at least 10 phr, or at least 20 phr, or at least 40 phr, or at most 100 phr, or at most 60 phr) are also used. The example of such granular filler includes carbon black and silica. A sufficient amount of additional filler can be added so that the total granular filler provided to the rubber composition is at least 40 phr, or at least 50 phr, or at least 60 phr, or at most 120 phr, or at most 100 phr, or at most 80 phr of granular filler.

[0164] (i) carbon black

[0165] Carbon black can be present in the rubber combination with at least 10 phr, or at least 15 phr, or at least 20 phr, or at least 30 phr, or at least 40 phr, or at least 50 phr, or at least 60 phr, or at most 90 phr, or at most 80 phr, or at most 75 phr, or at most 70 phr in a total amount. The carbon black present in the composite blend can be at least 1:3, or at least 1:2, or at least 1:1.5, or at most 3:1, or at most 2:1, or at most 1.5:1, or at most 1.2:1.

[0166] Exemplary carbon blacks have a specific surface area of at least 8, or at least 20, or at least 100, or at least 120, or at most 200 m 2 / kg, or up to 132m 2 / kg, as measured according to 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 is contactable with the rubber. Exemplary carbon blacks include furnace black, channel blacks, and lamp blacks. Specific examples of available carbon blacks include super abrasion-resistant furnace black (SAF), high abrasion-resistant furnace black (HAF), fast-pressed furnace black (FEF), fine-grained furnace black (FF), medium abrasion-resistant furnace black (ISAF), semi-reinforced furnace black (SRF), medium processing channel blacks, hard processing channel blacks, and conductive channel black. Other carbon blacks that can be used include acetylene black. In certain embodiments, the rubber composition includes a mixture of two or more carbon blacks.

[0167] Exemplary carbon blacks useful herein as the additional carbon black include carbon blacks 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 by ASTM D1765-21, “Standard Classification System for Carbon Blacks Used in Rubber Products.” These carbon blacks have iodine absorption (as determined according to ASTM D1510-21) ranging from 9 to 145 g / kg and an iodine absorption (as determined according to ASTM D1510-21) ranging from 34 to 150 cm 3 DBP absorption value of / 100g (as determined according to ASTM D2414). For example, grade N121 is a pelletized carbon black with an iodine absorption of about 121 g / kg and a CATB specific surface area of about 121 m 2 / kg, DBP absorption is about 132m 2 / kg, ash content is less than 0.5% by weight. N220 grade is granular carbon black, its iodine absorption is 116-126g / kg, CATB specific surface area is 106-116m 2 / kg, DBP absorption is 109-119m 2 / kg, and the ash content is less than 0.5% by weight.

[0168] (ii) Silicon dioxide

[0169] In some embodiments, the rubber composition may include at least 2 phr of silica, or at least 4 phr, or at least 5 phr, or up to 110 phr, or up to 60 phr, or up to 40 phr, or up to 15 phr, or up to 12 phr of silica. The silica may be at least 1 phr, or at least 5 phr, or at least 8 phr, or up to 40 phr, or up to 20 phr, or up to 12 phr of the reinforcing filler. In other embodiments, the rubber composition does not contain silica.

[0170] When used with carbon black, silica can minimize carbon black loading while reducing hysteresis and improving tear resistance.

[0171] Silica can be amorphous silica (e.g., precipitated silica) and / or crystalline silica. As used herein, the term "silica" refers to silicon dioxide, SiO2 (which may contain small amounts of impurities, typically less than 1% by weight, resulting from the process by which the silica is formed). The term "precipitated silica" refers to synthetic amorphous silica, typically obtained by precipitating silicates with an acidifying agent.

[0172] Silica can be prepared by various methods. Precipitated silica can be prepared by digesting amorphous silica (e.g., present in rice husks or other biowaste) with sodium hydroxide to form sodium silicate and precipitating silica from the sodium silicate by reaction with an acidifying agent (e.g., sulfuric acid or carbon dioxide). The resulting silica precipitate is washed and filtered. Methods for preparing precipitated silica are disclosed, for example, in U.S. Patent No. 5,587,416A and U.S. Publication Nos. 20020081247A1; 20050032965A1; and 20110178227A1. Precipitated silica can also be formed from silica gel, as described, for example, in U.S. Patent No. 5,708,069. Silica gel can be obtained, for example, by hydrophobizing silica hydrogel with, for example, organomercaptosilanes and alkylsilanes and drying the product.

[0173] The surface area of silica can be measured using various methods. One method uses nitrogen adsorption according to ASTM D1993-18, "Standard Test Method for Precipitated Silica - Surface Area by Multipoint BET Nitrogen Adsorption," referred to herein as nitrogen surface area. Another method uses ASTM D6845-20, "Standard Test Method for Silica, Precipitated, Hydrated—CTAB (Cetyltrimethylammonium Bromide) Surface Area," referred to herein as CTAB surface area. CTAB molecules are relatively large; therefore, they do not adsorb to micropores or surface roughness. Therefore, the CTAB surface area only reflects the silica surface that can interact with rubber molecules.

[0174] In exemplary embodiments, the silica has a 2 / g, or at least 160m 2 / g, or at least 200m 2 / g, or at least 220m 2 / g, or up to 350m 2 / g, or up to 300m 2 / g of CTAB surface area.

[0175] Exemplary high surface area silicas are available as Zeosil TM Premium SW is available from Solvay. This silica has a mass of approximately 250 m 2 Other precipitated silicas include Hi-Sil from PPG Industries TM 532.Hi-Sil TM 532 EP and Hi-Sil TM EZ 160G; Hubersil from JMHuber Company TM 4155; Zeosil from Solvay TM , named 115GR, 125GR, 165GR, 175GR, 185GR, 195GR, 1085GR, 1165MP, 1115MP, HRS1200MP, Premium MP, Premium 200MP and 195HR; Ultrasil from Evonik TM , named VN2, VN3, VN3 GR, 5000GR, 7000GR, 9000GR; Zeopol from Evonik TM , named 8755LS and 8745; Newsil from Wuxi Quechen Silicon Chemical Co., Ltd TM , named 115GR and 2000MP; and Tokusil from Maruo Calcium Co., Ltd. TM 315.

[0176] Prior to incorporating the pretreated silica into the rubber composition, the silica may have been surface treated, for example, with an organosilane coupling agent and / or a polyalkylene oxide (e.g., polyethylene glycol), to enhance dispersibility and / or adhesion to the elastomer. In another embodiment, the silica may be treated with a coupling agent and / or polyalkylene oxide in situ in the rubber composition, for example, prior to adding a curing agent.

[0177] Coupling agents typically include a first portion reactive with hydroxyl groups (e.g., silanol groups) present on the surface of precipitated silica, and a second portion capable of reacting with a diene-based elastomer. These two portions are linked by a linking group (e.g., a hydrocarbon group and / or a sulfidic bridge), chemically bonding the precipitated silica to the elastomer. Organosilanes are commonly used coupling agents.

[0178] Other particulate reinforcing fillers that may additionally or alternatively be incorporated into the rubber composition include alumina, aluminum hydroxide, clay (reinforcing grade), magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, and combinations thereof.

[0179] C. Processing aids

[0180] The rubber composition may include processing aids such as liquid plasticizers, waxes, resins, and mixtures thereof.

[0181] 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 hydrocarbon resins, which are typically solid at room temperature. Typically, liquid plasticizers have a Tg below 0°C, typically 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.

[0182] The present invention also can be used for the preparation of the present invention.Suitable liquid plasticizer comprises oil (for example oil and plant origin oil) and other non-oil liquid plasticizer, for example ether plasticizer, ester plasticizer, phosphate / salt plasticizer and sulfonate / salt plasticizer.Liquid plasticizer can be added in one or more stages (for example NP1, NP2) process, or as the filler oil of one of elastomer.The oil based on oil can comprise aromatic oil, naphthenic oil, low polycyclic aromatic (PCA) oil (for example MES, TDAE and SRAE) and composition thereof.Vegetable oil can comprise the oil gathered in the crops from vegetables, nuts, seed and composition thereof, for example triglyceride.

[0183] The liquid plasticizer may be used in the rubber composition at 0 to 30 phr, or at least 0.5 phr, or at least 1 phr, or at least 2 phr, or at most 10 phr, or at most 5 phr.

[0184] Suitable waxes include paraffin waxes and microcrystalline waxes, which may be of the type described in The Vanderbilt Rubber Handbook (1978), pp. 346 and 347. Such waxes may be used as antiozonants.

[0185] Where used, the wax(es) may be present at 0.1 phr or more, such as at least 0.2 phr, or at least 0.5 phr, or at most 5 phr, or at most 3 phr, or at most 2 phr.

[0186] The resin may be used in an amount of 0-10 phr, or at least 0.1 phr, or at least 0.5 phr, or up to 5 phr. When the rubber composition includes one or more resins, the resin(s) may be selected from hydrocarbon traction resins, natural resins (e.g., rosin), tackifying resins (e.g., non-reactive phenolic resins), stiffness resins (e.g., reactive phenolic resins), and combinations thereof.

[0187] Examples of hydrocarbon traction resins that can be used include those having a glass transition temperature, Tg, greater than 20° C., or at least 30° C., or at most 50° C., as determined according to ASTM D6604. The softening point of the traction resin can be at least 30° C., or at least 70° C., or at most 100° C., as determined according to ASTM E28. The Tg is typically lower than its softening point, and the lower the Tg, the lower the softening point. The hydrocarbon traction resin can be selected from terpene-phenol resins, terpene resins, terpene-styrene resins, styrene / α-methylstyrene resins, coumarone-indene resins, polydicyclopentadiene (DCPD) resins, DCPD / C9 resins, hydrogenated DCPD resins (H2DCPD), H2DCPD / C9 resins, C5 resins, C9 resins, H2C5 resins, H2C9 resins, C5 / C9 resins, rosin-derived 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 from which the resin is formed before any functionalization). Such resins can be partially or fully hydrogenated and / or functionalized. Exemplary hydrocarbon-based traction resins are described in U.S. Publication No. 20210032442A1. Resins are also described in U.S. Publication No. 20210355301A1.

[0188] Resins can also be obtained from naturally occurring rosins and derivatives thereof, 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 rosin components may be different. Such resins can be dimerized, polymerized, or disproportionated. Such resins can be in the form of esters of abietic acid and a polyol (e.g., pentaerythritol or glycol). In one embodiment, the rubber composition includes 1-4 phr of rosin.

[0189] D. Curing activator

[0190] Cure activators are additives used to support vulcanization. Cure activators include both (i) inorganic cure activators and (ii) organic cure activators. Zinc oxide is the most widely used inorganic cure activator and can be present in an amount of at least 1 phr, such as at least 2 phr, or at most 7 phr or at most 5 phr.

[0191] Organic curing activators include fatty acids (e.g., stearic acid, palmitic acid, lauric acid, and mixtures thereof), calcium and zinc salts of unsaturated fatty acids, amides of unsaturated fatty acids, and thiourea compounds (e.g., thiourea and dialkylthioureas, 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, ethylenethiourea, N,N'-diisopropylthiourea, N,N'-dicyclohexylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1,1-diphenyl-2-thiourea, 2,5-dithiourea, guanylthiourea, 1-(1-naphthyl)-2-thiourea, 1-phenyl-2-thiourea, p-tolylthiourea, and o-tolylthiourea.

[0192] In one embodiment, a mixture of fatty acids, primarily stearic acid, is used as the organic activator.

[0193] The total amount of organic curing activator(s) may be at least 0.1 phr, such as at least 0.5 phr, or at least 1 phr, or at least 2 phr, or at most 6 phr, or at most 5 phr, or at most 3 phr.

[0194] E. curing accelerator

[0195] Curing accelerator, similar activator, serves as the catalyst of vulcanizing agent.Accelerator is used for controlling the required time and / or temperature of vulcanization, is also used for improving the character (such as by crosslinking) of vulcanized rubber, can be used alone or in combination.The total amount of (one or more) curing accelerator can be 0.1 to 10phr, or at least 0.3phr, or at least 0.5phr, or at the most 3phr.

[0196] In one embodiment, a single accelerator system, i.e. a primary accelerator, can be used. The primary accelerator can be used in an amount of 0.3 to 5phr, or 2phr at the most. In another embodiment, a combination of two or more accelerators can be used. Auxiliary accelerators are used conventionally in a smaller amount to activate and improve the character of the vulcanizate. Such accelerator combinations are known to produce a synergistic effect on the final properties of sulphur-vulcanized rubber, and are more or less superior to the effect produced by using any accelerator alone usually. In addition, a delayed action accelerator can be used, which is less affected by the normal processing temperature, but produces satisfactory solidification under conventional vulcanization temperatures.

[0197] Representative examples of accelerators include amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates. In one embodiment, the primary accelerator is a sulfenamide, such as N-cyclohexylbenzothiazole-2-sulfenamide (CBS) or N-tert-butyl-2-benzothiazole-sulfenamide (TBBS). If a secondary accelerator is used, it can be a guanidine, such as N,N'-diphenylguanidine (DPG), a dithiocarbamate, or a thiuram compound, although secondary sulfenamide accelerators can be used. Examples of thiazole curing accelerators include 2-mercaptobenzothiazole, 2,2'-dithiobis(benzothiazole) (MBTS).

[0198] Curing accelerators with fast curing initiation times (typically less than 3 minutes) are referred to as super accelerators. Exemplary super accelerators that can be used alone or in combination with other accelerators include 1,6-bis(N,N'-dibenzylthiocarbamoyldisulfide)hexane (BDBZTH), tetrabenzylthiuram disulfide (TBzTD), tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetraisobutylthiuram disulfide (TiBTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dibutyldithiocarbamate (ZDBC), zinc dibenzyldithiocarbamate (ZBED), zinc dibenzyldithiocarbamate (ZBEC), and mixtures thereof.

[0199] In some embodiments, the free radical initiator is sometimes referred to as a redox initiator, including a combination of chelated iron salts, sodium formaldehyde sulfoxylate and an organic hydroperoxide. Representative organic hydroperoxides include cumene hydroperoxide, p-menthane hydroperoxide and tert-butyl hydroperoxide. The free radical initiator can be used in combination with a sulfur-based vulcanizing agent, or as a substitute for a sulfur-based vulcanizing agent. In the case of use, the amount of the free radical initiator can be 0.1 to 4 phr, or 0.5 to 2 phr. In other embodiments, the rubber composition does not contain a free radical initiator.

[0200] Cure inhibitors are used to control the vulcanization process, typically delaying or inhibiting vulcanization until the desired time and / or temperature is reached. Exemplary cure inhibitors include cyclohexylthiophthalimide. If used, the amount of the cure inhibitor can be 0.1 to 3 phr, or 0.5 to 2 phr. In one embodiment, no cure inhibitor is used.

[0201] If used, the amount of cure retarder can be from 0.05 to 2 phr, or at least 0.1 phr, or up to 1 phr, or up to 0.5 phr.In one embodiment, no cure retarder is used.

[0202] The rubber composition can include 0.1 to 15 phr of an organosilane coupling agent, such as at least 1 phr, or up to 5 phr. The amount of the organosilane coupling agent can be based on the amount of silica in the composition, such as 1-10 phr.

[0203] Examples of the organosilane coupling agent include those containing groups such as alkylalkoxy groups, mercapto groups, blocked mercapto groups, sulfide-containing groups (e.g., monosulfide-based alkoxy-containing groups, disulfide-based alkoxy-containing groups, tetrasulfide-based alkoxy-containing groups), amino groups, vinyl groups, epoxy groups, and combinations thereof.

[0204] Examples of alkylalkoxysilanes suitable for use include octyltriethoxysilane, octyltrimethoxysilane, trimethylethoxysilane, cyclohexyltriethoxysilane, octadecyltrimethoxysilane, methyloctyldimethoxysilane, and mixtures thereof.

[0205] Examples of bis(trialkoxysilylorgano)polysulfides suitable for use include 3,3'-bis(triethoxysilylpropyl)disulfide, 3,3'-bis(trimethoxysilylpropyl)disulfide, 3,3'-bis(tributoxysilylpropyl)disulfide, 3,3'-bis(tri-tert-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(propyldiethoxysilylpropyl)disulfide, 12,12'-bis(triethoxysilylpropyl)disulfide, 12,12'-bis(tri-tert-but ... -Bis(triisopropoxysilylpropyl)disulfide, 3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropyl-benzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide and mixtures thereof. Bis(3-triethoxysilylpropyl)tetrasulfide can be used as Obtained from Evonik Corporation, bis(3-triethoxysilylpropyl) disulfide has an average of 2.15 linked sulfur atoms in the polysulfide bridge and can be used as Available from Evonik Corporation. An example of a suitable blocked mercaptosilane is NXTTM Silane (3-octanoylthio-1-propyltriethoxysilane), commercially available from Momentive Performance Materials Inc., Albany, NY.

[0206] F. Sulfur-based curing agents

[0207] The vulcanization (curing) of the rubber composition is carried out in the presence of a curing agent (vulcanizing agent), for example, a sulfur-based curing agent. Examples of suitable sulfur-based curing agents include elemental sulfur (free sulfur), insoluble polymeric sulfur, soluble sulfur, and sulfur-donating curing agents, such as amine disulfide, polymeric polysulfide, or sulfur olefin adducts, and mixtures thereof.

[0208] The sulfur-based curing agent can be used in an amount of at least 0.1 phr, such as at least 0.2 phr, or at least 0.4 phr, or at least 0.5 phr, or at most 2 phr, or at most 1.5 phr, or at most 1 phr (calculated as pure sulfur). The amount of sulfur-based curing agent can be minimized by using a sulfur-donating accelerator.

[0209] G. Antioxidants, antidegradants, antiozonants and other additives

[0210] Various compounds may be incorporated into the rubber composition to help reduce oxidation, ozone degradation, and other forms of degradation. These compounds may be present in the rubber composition in an amount of 1 phr or more, such as at least 2 phr, or at least 2.5 phr, or at most 6 phr, or at most 5 phr. In other embodiments, they may not be present.

[0211] Exemplary antidegradants suitable for use in the rubber composition include amine-based antioxidants such as p-phenylenediamines (PPD), including alkyl-aryl p-phenylenediamines such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), p-phenylenediamines such as N,N'-diphenyl-1,4-phenylenediamine (DPPD), and trimethyldihydroquinoline (TMQ) antidegradants, and the like, such as those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344-347.

[0212] In addition to the above ingredients, the rubber composition may also include other rubber compounding ingredients, such as peptizers, for example, pentachlorothiophenol, dibenzamide diphenyl disulfide, or mixtures thereof. If used, typical amounts of peptizers may range from 0.1 phr to 1 phr.

[0213] In one embodiment, the components of the rubber composition other than the first, second and third elastomers, carbon black, silica, activators, accelerators, cure retarders, plasticizers, antiozonants, and sulfur-based curatives are present in an amount not exceeding 20 phr of the rubber composition, or not exceeding 10 phr of the rubber composition, or not exceeding 5 phr of the rubber composition.

[0214] In one embodiment, a tire is provided having a tread formed at least in part from an exemplary rubber composition. Other portions 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 may be a pneumatic tire for a road vehicle (e.g., a bus, truck, or automobile), or a tire for an off-road vehicle, aircraft, or the like.

[0215] The rubber composition is not limited to being used in tires, but can also be applied to rubber tubes, rubber gloves, surgical instruments, and the like.

[0216] Exemplary compositions

[0217] Table 1 shows exemplary rubber compositions according to aspects of the exemplary embodiment.

[0218] Table 1: Exemplary rubber compositions (phr)

[0219]

[0220]

[0221] Tire tread properties

[0222] Use of the rubber composition in a tire (e.g., a tire tread) can result in a tire having improved or desirable tread properties. These improved or desirable properties can include improved mileage while retaining other properties, such as

[0223] Without intending to limit the scope of the exemplary embodiments, the following examples illustrate the preparation of exemplary rubber compositions and their properties.

[0224] Example

[0225] Rubber compositions were prepared using the formulations shown in Table 2. Each composition was mixed in four stages, all but the last of which were non-productive stages (NP), which were then the productive stage (PR). In the first stage, the mixture was drained when it reached approximately 165°C, the second stage at approximately 160°C, the third stage at approximately 155°C, and the final productive stage at approximately 110°C. The formulations were mixed in a laboratory mixer. Curing of the compositions was performed at a temperature of 135°C for 140 minutes.

[0226] Example A uses a mixture of natural rubber (NR) and ESBR as an elastomer, and the ratio of NR:ESBR is 15:85. Example B, C and D all use a composite blend corresponding to 60phr natural rubber and 33phr carbon black. In Example B, the composite blend is diluted with another 21.82phr of natural rubber, then diluted with 18.18phr of ESBR, providing a NR:ESBR ratio of 81.82:18.18. In Example C, the composite blend is only diluted with natural rubber, and in Example D, the composite blend is only diluted with ESBR, obtaining a NR:ESBR ratio of 60:40. The amount of carbon black used in composition A is 60phr, and for Example B to D, the amount of carbon black (excluding the carbon black used as a coupling agent carrier) is similar, being 66phr. However, due to sequential mixing, the distribution of the granular filler (particularly carbon black) in the elastomer is different, producing a multiphase mixture. For example, in Example B, the composite material is mixed with the natural rubber and carbon black in NP1 to produce two natural rubber phases with different weight ratios of carbon black: elastomer (the CB:E ratio in the natural rubber phase produced by the composite blend is higher than the CB:E ratio in the natural rubber added in NP1). Subsequently, ESBR is added to NP2 to produce three phases, all with different CB:E ratios, with the ESBR phase having the lowest CB:E ratio (lowest carbon black ratio) and the natural rubber from the composite blend having the highest CB:E ratio. NP3 is an additional mixing step that does not incorporate additional components and can be omitted.

[0227] Table 2: Rubber composition (expressed in phr)

[0228]

[0229]

[0230] 1 Tin-catalyzed, emulsion-polymerized styrene butadiene copolymer, 23.5% bound styrene, containing some antioxidants. It contains a mixed acid emulsifier and is hydrochloric acid coagulated. From Goodyear Tire & Rubber Company 1502.

[0231] 2 As E2C TM DX9730 is a compounded blend obtained from Cabot consisting of natural rubber and 55 phr carbon black, ie, 93 phr of the compounded blend is equivalent to 60 phr natural rubber and 33 phr carbon black.

[0232] 3 Ribbed Smoked Chips (RSS).

[0233] 3 Technically graded rubber (TSR).

[0234] 5 Carbon black ASTM D 1765 grade N220, obtained from Tokai Carbon.

[0235] 6 Precipitated silica, with a nitrogen (BET) surface area of approximately 250 m 2 / g range, Premium SW, from Solvay.

[0236] 7 Petroleum-based hydrocarbon resins and mixtures of alkylated and aromatic hydrocarbon resins.

[0237] 8 Modified gum rosin tackifying resin, softening point 97°C, available from Resinall Corp. as R-224.

[0238] 9 paraffin.

[0239] 10 N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD).

[0240] 11 As S6, CO2 were obtained from Flow Polymers, Polymer Solutions Group.

[0241] 12 A mixture of fatty acids, mainly stearic acid.

[0242] 13 TBBS (n-tert-butyl-benzothiazolesulfenamide).

[0243] 14 N,N'-diphenylguanidine (DPG).

[0244] 15 N-(cyclohexylthio)phthalimide (optional)

[0245] 16 Bis-[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), as Obtained from Evonik, supported on 50% carbon black, ASTM grade N347, from Tokai Carbon.

[0246] Properties of rubber compositions

[0247] Physical tests were performed on samples of the rubber composition. The results are shown in Table 3.

[0248] Table 3: Physical properties of rubber compositions

[0249]

[0250] Storage modulus G' and G" were measured by a Rubber Process Analyzer (RPA) at 100°C and 1 Hz using a dynamic cure cycle. Tan δ is the ratio of G" to G'. RPA Tan δ at 10% strain is an indicator of the degree of tire heat buildup (lower is better).

[0251] After curing at 135°C for 140 minutes, tensile properties (tensile elongation (TE) at 100% modulus, tensile strength, elongation at break, Instron tear, and rebound at 100°C) were measured using an automated testing system from Instron Corporation. TE and tensile strength tests were performed at 23°C at a tensile speed of 50 cm / min using dumbbell-shaped specimens. Instron tear was measured at 95°C at a tensile speed of 50.8 cm / min (higher values are better). Rebound was measured at 100°C using a Zwick rebound test, which is an indicator of rolling resistance and contributes to tire heat buildup.

[0252] Abrasion (an indicator of tread wear) is measured as the Grosch abrasion rate in mg / km of rubber worn away. A test rubber sample is placed under a constant load (70 Newtons) at a given slip angle while traveling a given distance on a rotating abrasive disc. At a given slip angle, lower abrasion values (mg / km) indicate higher expected mileage.

[0253] The modulus of toughness is the area under the stress-strain curve.

[0254] After curing at 135°C for 140 minutes and aging at 90°C for 7 days, Strebler tear was measured at 100°C. The test was conducted at a tensile speed of 50 cm / min. This is a peel test that measures interfacial adhesion by pulling one rubber composition away from another at right angles to the untorn test specimen. The two ends of the rubber composition are pulled apart at a 180° angle. Higher values are indicative of the toughness of the composition.

[0255] As can be seen from the data, the vulcanizable rubber composition sample of Example B (in which the composite blend is diluted with natural rubber and ESBR) generally performs better than the sample of Comparative Example A, and also performs better than the samples containing either all NR or all ESBR as the diluent elastomer (Examples C and D). In particular, the RPA Tanδ, Instron tear, and abrasion results at 10% strain demonstrate that Example B of the present invention has a good combination of properties. The rebound properties of Examples B, C, and D are comparable.

[0256] Each of the above-mentioned documents is incorporated herein by reference. Except in the examples or otherwise clearly indicated, all quantities of the amount of material, reaction conditions, molecular weight, carbon number, etc. specified in this specification are to be understood as being modified by the word "about". Unless otherwise stated, each chemical or composition mentioned herein should be interpreted as a commercial grade material, which may include isomers, by-products, derivatives, and other such materials that are generally understood to be present in the commercial grade. However, unless otherwise stated, the amount of each chemical component does not include any solvent, diluent oil, or other carrier material that may be generally present in the commercial material. It is to be understood that the upper and lower limits, scopes, and ratio limits described herein can be independently combined. Similarly, the scope and amount of each key element of the present invention can be used together with the scope or amount of any other key element.

[0257] It is to be understood that the above disclosed variants and other features and functions or their alternatives can be combined into many other different systems or applications. Those skilled in the art may subsequently make various currently unforeseen or unanticipated substitutions, modifications, variations or improvements thereto, which are also intended to be encompassed by the appended claims.

Claims

1. A method of forming a vulcanizable rubber composition comprising: mixing the composite blend with a first elastomer in a first non-productive mixing step to produce a first mixture, the composite blend comprising a second elastomer and carbon black, the second elastomer being the same as or different from the first elastomer; in a second non-productive mixing step, mixing a third elastomer different from the first elastomer with the first mixture, or with a mixture resulting from the first mixture, to produce a second mixture; as well as In a productive mixing step, a curative is mixed with the second mixture, or with a mixture resulting from the second mixture, to produce a vulcanizable rubber composition comprising the first, second, and third elastomers, carbon black from the composite blend, and an additional amount of reinforcing filler. 2 . The method of claim 1 , wherein the first elastomer comprises a first one of natural rubber and a polydiene elastomer, and the third elastomer comprises a second one of natural rubber and a polydiene elastomer. 3 . The method of claim 2 , wherein the first elastomer comprises natural rubber and the third elastomer comprises a polydiene elastomer. The method according to claim 2 , wherein the polydiene elastomer comprises styrene-butadiene rubber.

5. The method of claim 4, wherein the styrene-butadiene rubber comprises emulsion-polymerized styrene-butadiene rubber.

6. The method of claim 1 , wherein the weight ratio of the first elastomer to the third elastomer in the vulcanizable rubber composition is at least 1:10, or at least 1:5, or at least 1:2, or at least 1:1.5, or at least 1:1, or at most 10:1, or at most 5:1, or at most 3:1, or at most 2:1, or at most 1.5:

1.

7. The method of claim 1 , wherein the first and third elastomers are present in the vulcanizable rubber composition in a total amount of at least 20 phr, or at least 30 phr, or at most 70 phr, or at most 60 phr, or at most 50 phr, or at most 40 phr.

8. A tire tread formed from a vulcanizable rubber composition formed by the method of claim 1.

9. Tire comprising a tread according to claim 8.

10. A vulcanizable rubber composition comprising: 100 phr of an elastomer, the elastomer comprising: at least 5 phr of a first elastomer, at least 20 phr of a second elastomer provided in a composite blend with carbon black, and at least 5 phr of a third elastomer, said third elastomer differing in its chemical composition from said first elastomer; at least 5 phr of a particulate filler other than carbon black in the composite blend, the particulate filler being selected from the group consisting of carbon black, silica, and combinations thereof; Curing activator; curing accelerators; and Sulfur based curing agent.

Images