Rubber formulations comprising two-stage cured statistical copolymer comprising a high-temperature cure monomer

Abstract

Embodiments of the present disclosure are directed to rubber formulations, wherein the formulations include a two-stage cured statistical copolymer. The two-stage cured statistical copolymer includes a polymerized reaction product of a conjugated diene monomer and a monomer capable of crosslinking at a high-temperature. The two-stage cured statistical copolymer undergoes a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking. The two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking.

Description

RUBBER FORMULATIONS COMPRISING TWO-STAGE CURED STATISTICAL COPOLYMER COMPRISING A HIGH-TEMPERATURE CURE MONOMERCROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Patent Application Serial Number 63 / 615,325, filed on December 28, 2023, entitled "Rubber Formulations Comprising Two-Stage Cured Statistical Copolymer Comprising a High-Temperature Cure Monomer," the entire contents of which are incorporated by reference in the present disclosure.TECHNICAL FIELD

[0002] Embodiments of the present disclosure are generally related to statistical copolymers, and are specifically related to rubber formulations comprising two-stage cured statistical copolymers.BACKGROUND

[0003] Run flat tires may travel a fixed distance even in a state in which the internal pressure of the tire has decreased. Specifically, side reinforcing rubbers are provided at the tire sidewall of the run flat tire to provide enhanced stiffness. However, after puncture and resulting excessive deformation, conventional side reinforcing rubbers may not provide the desired stiffness.

[0004] Accordingly, a continual need exists for rubber formulations that provide improved stiffness after a puncture event.SUMMARY

[0005] Embodiments of the present disclosure are directed to rubber formulations including a two-stage cured statistical copolymer, which provides an improved stiffness to the rubber formulation after undergoing an elevated temperature, such as after a puncture event. Specifically, the two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking, thereby providing further stiffness to the tire.

[0006] According to one embodiment, a rubber formulation is provided. The formulations include a two-stage cured statistical copolymer. The two-stage cured statistical copolymer includes a polymerized reaction product of a conjugated diene monomer and a monomer capable of crosslinking at a high-temperature. The two-stage cured statistical copolymer undergoes a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking. The two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking.

[0007] Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, and the claims.DRAWINGS

[0008] FIG. 1 is a plot of S' (y-axis; in deciNewton meters (dNm)) versus time (x-axis; in minutes) of comparative rubber formulations and example rubber formulations, according to one or more embodiments described herein.DETAIEED DESCRIPTION

[0009] Embodiments of the present disclosure are directed to rubber formulations. The rubber formulations may comprise a two-stage cured statistical copolymer. The two-stage cured statistical copolymer may comprise a polymerized reaction product comprising a conjugated diene monomer and a monomer capable of crosslinking at a high-temperature. The two-stage cured statistical copolymer may undergo a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking. The two-stage cured statistical copolymer may undergo a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking.

[0010] The disclosure should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the subject matter to those skilled in the art.

[0011] Definitions

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the disclosure herein is for describing particular embodiments only and is not intended to be limiting.

[0013] Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0014] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components; plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0015] As used in the specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Thus, for example, reference to “a” component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0016] The term “statistical copolymer,” as described herein, refers to a copolymer in which individual monomer units are arranged along the polymer chain following a statistical distribution. Statistical copolymers are copolymers in which the sequential distribution of the monomeric units obeys known statistical laws; for example, the monomer sequence distribution may follow Markovian statistics of zeroth (Bernoullian), first, second, or higher order. Kinetically, theelementary processes leading to the formation of a statistical sequence of monomeric units do not necessarily proceed with equal a priori probability. These processes may lead to various types of sequence distribution comprising those in which the arrangement of monomeric units tends toward alternation, tends toward clustering of like units, or exhibits no ordering tendency at all. In simple binary copolymerization, the nature of this sequence distribution may be indicated by the numerical values of a function either of the reactivity ratios or of the related run number.

[0017] The term “phr,” as described herein, refers to parts by weight of the identified component per 100 parts rubber.

[0018] Number average molecular weight Mnand weight average molecular weight Mw, as described herein, are determined by gel permeation chromatography, as elaborated on in the Examples.

[0019] Glass transition temperature Tg, as described herein, is measured by differential scanning calorimetry, as elaborated on in the Examples.

[0020] Polydispersity, as described herein, refers to the weight average divided by the number average molecular weight (Mw / Mn).

[0021] As used herein, the term “S'” refers to a torque value of a material as measured with a moving die rheometer and is provided in units of Deci Newton Meters (“dNm”), as elaborated on in the Examples. A relatively greater S' corresponds to a relatively greater material stiffness.

[0022] As used herein, the term “sustainable,” refers to a material that comes from biological or recycled sources or is certified using a mass balance approach.

[0023] As discussed hereinabove, run flat tires include side reinforcing rubbers at the tire sidewall to provide enhanced stiffness. However, after puncture and resulting excessive deformation, conventional side reinforcing rubbers may not provide the desired stiffness.

[0024] Disclosed herein are rubber formulations, which mitigate the aforementioned problems. Specifically, the rubber formulations disclosed herein comprise a two-stage cured statistical copolymer, which results in a rubber formulation that has improved stiffness after being subjected to an elevated temperature (e.g., greater than or equal to about 190 °C), such as during a puncture event. Specifically, the two-stage cured statistical copolymer includes a high-temperature curemonomer that undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking, thereby improving the stiffness of the rubber formulation and the tire in which the rubber formulation is included after a puncture event.

[0025] Two-stage Cured Statistical Copolymer

[0026] The two-stage cured statistical copolymers disclosed herein may generally be described as a polymerized reaction product comprising a conjugated diene monomer and a monomer capable of crosslinking at a high-temperature.

[0027] The statistical copolymers disclosed herein comprise a conjugated diene. Without being bound by theory, it is believed that monomer units capable of crosslinking at a high- temperature (e.g., vinylbenzocyclobutane (“VBCB”)) may form crosslinks with other high- temperature cure monomer units and with the carbon-carbon double bonds of the conjugated diene monomer units. This may allow for increased crosslink density, as the high-temperature cure monomer may be able to form more crosslinks when compared to polymers that do not comprise a high-temperature cure monomer. The terms “monomer capable of crosslinking at a high- temperature,” “high-temperature cure monomer,” and “high-temperature cure monomer units” are used interchangeably throughout. The term “high-temperature,” refers to greater than or equal to about 190 °C.

[0028] In embodiments, the conjugated diene monomer may comprise a sustainable conjugated diene monomer. In embodiments, the conjugated diene monomer may be selected from the group consisting of 1,3 -butadiene, isoprene, 1,3 -pentadiene, 1,3 -hexadiene, 2, 3 -dimethyl- 1,3 -butadiene, 2-ethyl- 1,3 -butadiene, 2-methyl-l,3-pentadiene, 3-methyl-l,3-pentadiene, 4-methyl-l,3- pentadiene, 2,4-hexadiene, 1,3 -cyclopentadiene, 1,3 -cyclohexadiene, 1,3-cycloheptadiene, 1,3- cyclooctadiene, and combinations thereof. In embodiments, the conjugated diene monomer may comprise 1,3 -butadiene.

[0029] In embodiments, the statistical copolymer may comprise from about 50 wt.% to about 99.98 wt.% of the conjugated diene monomer, based on the total weight of the statistical copolymer. In embodiments, the statistical copolymer may comprise the conjugated diene monomer in an amount, based on the total weight of the statistical copolymer, greater than or equal to about 50 wt.%, greater than or equal to about 55 wt.%, greater than or equal to about 60 wt.%,or even greater than or equal to about 65 wt.%. In embodiments, the statistical copolymer may comprise the conjugated diene monomer in an amount, based on the total weight of the statistical copolymer, less than or equal to about 99.98 wt.%, less than or equal to about 99 wt.%, less than or equal to about 95 wt.%, less than or equal to about 90 wt.%, less than or equal to about 85 wt.%, or even less than or equal to about 80 wt.%. In embodiments, the statistical copolymer may comprise the conjugated diene monomer in an amount, based on the total weight of the statistical copolymer, from about 50 wt.% to about 99.98 wt.%, from about 50 wt.% to about 99 wt.%, from about 50 wt.% to about 95 wt.%, from about 50 wt.% to about 90 wt.%, from about 50 wt.% to about 85 wt.%, from about 50 wt.% to about 80 wt.%, from about 55 wt.% to about 99.98 wt.%, from about 55 wt.% to about 99 wt.%, from about 55 wt.% to about 90 wt.%, from about 55 wt.% to about 85 wt.%, from about 55 wt.% to about 80 wt.%, from about 60 wt.% to about 99.98 wt.%, from about 60 wt.% to about 99 wt.%, from about 60 wt.% to about 95 wt.%, from about 60 wt.% to about 90 wt.%, from about 60 wt.% to about 85 wt.%, from about 60 wt.% to about 80 wt.%, from about 65 wt.% to about 99.98 wt.%, from about 65 wt.% to about 99 wt.%, from about 65 wt.% to about 95 wt.%, from about 65 wt.% to about 90 wt.%, from about 65 wt.% to about 85 wt.%, or even from about 65 wt.% to about 80 wt.%, or any and all sub-ranges formed from any of these endpoints.

[0030] In embodiments, the statistical copolymer may be a polymerized, crosslinkable reaction product derived from a conjugated diene monomer, a vinyl aromatic monomer, and the monomer capable of crosslinking at high-temperatures (e.g., VBCB). Without being bound by theory, it is believed that the presence of a vinyl aromatic monomer may increase the glass transition temperature of the polymer, when compared to polymer without a vinyl aromatic monomer.

[0031] In embodiments, the vinyl aromatic monomer may comprise a sustainable vinyl aromatic monomer. In embodiments, the vinyl aromatic monomer may be selected from the group consisting of styrene, alpha-methyl styrene, p-methylstyrene, o-methylstyrene, p-butyl styrene, vinylnapthalene, p-tertbutylstyrene, 4-vinylbiphenyl, 2-vinylnapthalene, 9-vinylanthracene, vinyl catechol, and combinations thereof. In embodiments, the conjugated diene monomer may be 1,3- butadiene and the vinyl aromatic monomer may be styrene.

[0032] In embodiments, the statistical copolymer may comprise from about 5 wt.% to about 50 wt.% of vinyl aromatic monomer, when present, based on the total weight of the statistical copolymer. In embodiments, the amount of vinyl aromatic monomer in the statistical copolymermay be, based on a total weight of the statistical copolymer, greater than or equal to about 0 wt.%, greater than or equal to about 5 wt.%, or even greater than or equal to about 10 wt.%. In embodiments, the amount of vinyl aromatic monomer in the statistical copolymer may be, based on a total weight of the statistical copolymer, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, or even less than or equal to about 10 wt.%. In embodiments, the amount of vinyl aromatic monomer in the statistical copolymer may be, based on a total weight of the statistical copolymer, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 40 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 20 wt.%, from about 5 wt.% to about 10 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 30 wt.%, or even from about 10 wt.% to about 20 wt.%, or any and all sub-ranges formed from any of these endpoints.

[0033] In embodiments, the statistical copolymer may have an average molecular weight of incorporated conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units (e.g., VBCB monomer units) from about 10,000 g / mol to about 50,000 g / mol. In embodiments, the statistical copolymer may have an average molecular weight of conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units of greater than or equal to about 10,000 g / mol, greater than or equal to about 15,000 g / mol, greater than or equal to about 20,000 g / mol, or even greater than or equal to about 25,000 g / mol. In embodiments, the statistical copolymer may have an average molecular weight of conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units of less than or equal to about 50,000 g / mol, less than or equal to about 45,000 g / mol, less than or equal to about 40,000 g / mol, or even less than or equal to about 35,000 g / mol. In embodiments, the statistical copolymer may have an average molecular weight of incorporated conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units of from about 10,000 g / mol to about 50,000 g / mol, from about 10,000 g / mol to about 45,000 g / mol, from about 10,000 g / mol to about 40,000 g / mol, from about 10,000 g / mol to about 35,000 g / mol, from about 15,000 g / mol to about 50,000 g / mol, from about 15,000 g / mol to about 45,000 g / mol, from about 15,000 g / mol to about 40,000 g / mol, from about 15,000 g / mol to about 35,000 g / mol, from about 20,000 g / mol to about 50,000 g / mol, from about 20,000 g / mol to about 45,000 g / mol, from about 20,000g / mol to about 40,000 g / mol, from about 20,000 g / mol to about 35,000 g / mol, from about 25,000 g / mol to about 50,000 g / mol, from about 25,000 g / mol to about 45,000 g / mol, from about 25,000 g / mol to about 40,000 g / mol, or even from about 25,000 g / mol to about 35,000 g / mol, or any and all sub-ranges formed from any of these endpoints. Without being bound by theory, it is believed that an average molecular weight of incorporated conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units of less than about 10,000 g / mol may cause a rubber formulation to cure too tightly and may negatively impact the elongation of the cured rubber. It is also believed that an average molecular weight of incorporated conjugated diene monomers, incorporated vinyl aromatic monomers, or combinations thereof between the high-temperature cure monomer units of greater than about 50,000 g / mol may cause a rubber formulation to lack the desired crosslink density.

[0034] The statistical copolymer comprises a high-temperature cure monomer. Without being bound by theory, it is believed that when subjected to a first stage cure at a first temperature less than or equal to about 180 °C, the conjugated diene monomer units within a polymer chain may form crosslinks with the unsaturation in the polymeric backbone of other polymer chains via sulfur crosslinking. These crosslinks may provide the statistical copolymer with desired mechanical properties once the statistical copolymer is cured, such as to function as a sidewall in a tire. When subjected to a subsequent second stage cure at a second temperature greater than or equal to about 190 °C, such as during a puncture event, the high-temperature cure monomer units (e.g., VBCB monomer units) may form further crosslinks with other high-temperature cure monomer units as well as form crosslinks with the unsaturation in the polymeric backbone of other polymer chains, thereby improving the stiffness of the rubber formulation and the tire in which the rubber formulation is included.

[0035] In embodiments, the high-temperature cure monomer units may comprise VBCB. The description herein may be directed to VBCB. However, one skilled in the art would appreciate that the high-temperature cure monomer units may comprise any monomer units that, when subjected to a subsequent second stage cure at an elevated temperature as described herein, form further crosslinks, thereby improving the stiffness of the rubber formulation and the tire in which the rubber formulation is included.

[0036] In embodiments, the statistical copolymer may comprise VBCB in an amount, based on the total weight of the statistical copolymer, greater than or equal to about 0.02 wt.%, greaterthan or equal to about 0.1 wt.%, greater than or equal to about 0.25 wt.%, greater than or equal to about 0.5 wt.%, greater than or equal to about 0.75 wt.%, or even greater than or equal to about 1.0 wt.%. In embodiments the statistical copolymer may comprise VBCB in an amount, based on a total weight of the statistical copolymer, less than or equal to about 2.0 wt.%, less than or equal to about 1.75 wt.%, less than or equal to about 1.5 wt.%, or even less than or equal to about 1.25 wt.%. In embodiments, the statistical copolymer may comprise VBCB in an amount, based on a total weight of the statistical copolymer, from about 0.02 wt.% to about 2.0 wt.%, from about 0.02 wt.% to about 1.75 wt.%, from about 0.02 wt.% to about 1.5 wt.%, from about 0.02 wt.% to about 1.25 wt.%, from about 0.1 wt.% to about 2.0 wt.%, from about 0.1 wt.% to about 1.75 wt.%, from about 0.1 wt.% to about 1.5 wt.%, from about 0.1 wt.% to about 1.25 wt.%, from about 0.25 wt.% to about 2.0 wt.%, from about 0.25 wt.% to about 1.75 wt.%, from about 0.25 wt.% to about 1.5 wt.%, from about 0.25 wt.% to about 1.25 wt.%, from about 0.5 wt.% to about 2.0 wt.%, from about 0.5 wt.% to about 1.75 wt.%, from about 0.5 wt.% to about 1.5 wt.%, from about 0.5 wt.% to about 1.25 wt.%, from about 0.75 wt.% to about 2.0 wt.%, from about 0.75 wt.% to about 1.75 wt.%, from about 0.75 wt.% to about 1.5 wt.%, from about 0.75 wt.% to about 1.25 wt.%, from about 1.0 wt.% to about 2.0 wt.%, from about 1.0 wt.% to about 1.75 wt.%, from about 1.0 wt.% to about 1.5 wt.%, or even from about 1.0 wt.% to about 1.25 wt.%, or any and all sub-ranges formed from any of these endpoints. Without being bound by theory it is believed that a statistical copolymer that comprises less than 0.02 wt.% of VBCB may not have the desired crosslink density and distribution after curing. It is also believed that VBCB in an amount greater than 2.0 wt.%, may negatively impact the tensile properties of the cured rubber formulation, such as, for example, the elongation of the rubber formulation.

[0037] In embodiments, the statistical copolymer may comprise from 1 to 15 VBCB monomer units per polymer chain. In embodiments, the polymer may comprise greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, or even greater than or equal to 7 VBCB monomer units per polymer chain. In embodiments, the polymer may comprise less than or equal to 15, less than or equal to 14, less than or equal to 13, less than or equal to 12, less than or equal to 11, or even less than or equal to 10 VBCB monomer units per polymer chain. In embodiments, the polymer may comprise from 1 to 15, from 1 to 14, from 1 to 13, from 1 to 12, from 1 to 11, from 1 to 10, from 2 to 15, from 2 to 14, from 2 to 13, from 2 to 12, from 2 to 11, from 2 to 10, from 3 to 15, from 3 to 14, from 3 to 13, from 3 to 12, from 3 to 11, from 3 to 10, from 4 to 15, from 4 to 14, from 4 to13, from 4 to 12, from 4 to 11, from 4 to 10, from 5 to 15, from 5 to 14, from 5 to 13, from 5 to 12, from 5 to 11, from 5 to 10, from 6 to 15, from 6 to 14, from 6 to 13, from 6 to 12, from 6 to 11, from 6 to 10, from 7 to 15, from 7 to 14, from 7 to 13, from 7 to 12, from 7 to 11, or even from 7 to 10, or any and all sub-ranges formed from any of these endpoints, VBCB monomer units per chain.

[0038] In embodiments, the statistical copolymer may have at least 1 VBCB monomer unit at an end of the polymer chain. In embodiments, the statistical copolymer may have at least 2, at least 3, or even at least 4 VBCB monomer units at the end of the polymer chain. In embodiments, the statistical copolymer may have from 1 to 4, from 1 to 3, from 1 to 2, from 2 to 4, from 2 to 3, from 3 to 4, or any and all sub-ranges formed from any of these endpoints, VBCB monomer units at the end of the polymer chain.

[0039] In embodiments greater than or equal to about 50% of polymer chains in the statistical copolymer may have from 0.5 to 3 VBCB monomer units on the end of the polymer. In embodiments, greater than or equal to about 55%, greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, or even greater than or equal to about 90% of polymer chains in the statistical copolymer may have from 0.5 to 3 VBCB monomer units on the end of the polymer chain. In embodiments, greater than or equal to about 50% of polymer chains in the statistical copolymer may have from 0.5 to 3, from 0.5 to 2.5, from 0.5 to 2, from 0.5 to 1.5, from 0.5 to 1 from 1 to 3, from 1 to 2.5, from 1 to 2, from 1 to 1.5, from 1.5 to 3, from 1.5 to 2.5, from 1.5 to 2, from 2 to 3, from 2 to 2.5, from 2.5 to 3, or any and all sub-ranges formed from any of these endpoints, VBCB monomer units on the end of the polymer chain. In such embodiments, the remainder of VBCB monomer units may be statistically distributed throughout the polymer chain.

[0040] While not wishing to be bound by theory, a statistical copolymer having a VBCB unit at an end of the polymer chain may result in a rubber formulation with similar mechanical properties (e.g., elongation at break) as compared to a traditionally cured (e.g., sulfur) polymer and improved mechanical properties as compared to a rubber formulation comprising a statistical copolymer with VBCB units randomly distributed therein.

[0041] In embodiments, the statistical copolymer may have a weight average molecular weight Mwgreater than or equal about 100 kg / mol. In embodiments, the statistical copolymer may have a weight average molecular weight Mwof greater than or equal to about 100 kg / mol, greater than or equal to about 200 kg / mol, or even greater than or equal to about 300 kg / mol. In embodiments, the statistical copolymer may have a weight average molecular weight Mwof less than or equal to about 2000 kg / mol, less than or equal to about 1500 kg / mol, less than or equal to about 1000 kg / mol, or even less than or equal to about 500 kg / mol. In embodiments the statistical copolymer may have a weight average molecular weight Mwof from about 100 kg / mol to about 2000 kg / mol, from about 100 kg / mol to about 1500 kg / mol, from about 100 kg / mol to about 1000 kg / mol, from about 100 kg / mol to about 500 kg / mol, from about 200 kg / mol to about 2000 kg / mol, from about 200 kg / mol to about 1500 kg / mol, from about 200 kg / mol to about 1000 kg / mol, from about 200 kg / mol to about 500 kg / mol, from about 300 kg / mol to about 2000 kg / mol, from about 300 kg / mol to about 1500 kg / mol, from about 300 kg / mol to about 1000 kg / mol, or even from about 300 kg / mol to about 500 kg / mol, or any and all sub-ranges formed from any of these endpoints. Without being bound by theory, it is believed that a statistical copolymer having a weight average molecular weight of less than about 100 kg / mol may be more difficult to process than a statistical copolymer having a weight average molecular weight of from about 100 kg / mol to about 2000 kg / mol because of an increased risk of cold flow. It is also believed that a statistical copolymer having a weight average molecular weight of greater than about 2000 kg / mol may be more difficult to process than a statistical copolymer having a weight average molecular weight of from about 100 kg / mol to about 2000 kg / mol because of the increased viscosity of the statistical copolymer.

[0042] In embodiments, the statistical copolymer may have a number average molecular weight Mngreater than or equal about 100 kg / mol. In embodiments, the statistical copolymer may have a number average molecular weight Mnof greater than or equal to about 100 kg / mol, greater than or equal to about 200 kg / mol, or even greater than or equal to about 300 kg / mol. In embodiments, the statistical copolymer may have a number average molecular weight Mnof less than or equal to about 2000 kg / mol, less than or equal to about 1500 kg / mol, less than or equal to about 1000 kg / mol, or even less than or equal to about 500 kg / mol. In embodiments the statistical copolymer may have a number average molecular weight Mnof from about 100 kg / mol to about 2000 kg / mol, from about 100 kg / mol to about 1500 kg / mol, from about 100 kg / mol to about 1000 kg / mol, from about 100 kg / mol to about 500 kg / mol, from about 200 kg / mol to about 2000 kg / mol,from about 200 kg / mol to about 1500 kg / mol, from about 200 kg / mol to about 1000 kg / mol, from about 200 kg / mol to about 500 kg / mol, from about 300 kg / mol to about 2000 kg / mol, from about 300 kg / mol to about 1500 kg / mol, from about 300 kg / mol to about 1000 kg / mol, or even from about 300 kg / mol to about 500 kg / mol, or any and all sub-ranges formed from any of these endpoints. Without being bound by theory, it is believed that a statistical copolymer having a number average molecular weight of less than about 100 kg / mol may be more difficult to process than a statistical copolymer having a number average molecular weight of from about 100 kg / mol to about 2000 kg / mol because of an increased risk of cold flow. It is also believed that a statistical copolymer having a number average molecular weight of greater than about 2000 kg / mol may be more difficult to process than a statistical copolymer having a number average molecular weight of from about 100 kg / mol to about 2000 kg / mol because of the increased viscosity of the statistical copolymer.

[0043] In embodiments, the statistical copolymer may have a polydispersity (Mw / Mn) of less than or equal to about 2.2, less than or equal to about 2.1, less than or equal to about 2.0, less than or equal to about 1.9, or even less than or equal to about 1.8.

[0044] In embodiments, the statistical copolymer may have a glass transition temperature Tgof from about -120 °C to about -20 °C. In embodiments, the statistical copolymer may have a glass transition temperature Tgof greater than or equal to -120 °C, greater than or equal to -110 °C, or even greater than or equal to -100 °C. In embodiments, the statistical copolymer may have a glass transition temperature Tgof less than or equal to -20 °C, less than or equal to -30 °C, less than or equal to -40 °C, or even less than or equal to -50 °C. In embodiments the statistical copolymer may have a glass transition temperature Tgof from about -120 °C to about -20 °C, from about -120 °C to about -30 °C, from about -120 °C to about -40 °C, from about -120 to about -50 °C, from about -110 °C to about -20 °C, from about -110 °C to about -30 °C, from about -110 °C to about -40 °C, from about -110 °C to about -50 °C, from about -100 °C to about -20 °C, from about -100 °C to about -30 °C, from about -100 °C to about -40 °C, or even from about -100 °C to about -50 °C, or any and all sub-ranges formed from any of these endpoints. Without wishing to be bound by theory, a relatively low Tg (e.g., less than or equal to about -20 °C) allows the rubber formulation to be flexible at relatively low temperatures, which may be desirable in tire sidewall applications.

[0045] In embodiments, a rubber component of the rubber formulation may comprise the statistical copolymer in an amount, based on the total weight of the rubber component, greater than or equal to about 20 phr, greater than or equal to about 30 phr, greater than or equal to about 40 phr, or even greater than or equal to about 50 phr. In embodiments, the rubber components may comprise the statistical copolymer in an amount, based on the total weight of the rubber component, less than or equal to about 100 phr, less than or equal to about 90 phr, or even less than or equal to about 80 phr. In embodiments, the rubber component may comprise the statistical copolymer in an amount, based on the total weight of the rubber component, from about 20 phr to about 100 phr, from about 20 phr to about 90 phr, from about 20 phr to about 80 phr, from about 30 phr to about 100 phr, from about 30 phr to about 90 phr, from about 30 phr to about 80 phr, from about 40 phr to about 100 phr, from about 40 phr to about 90 phr, from about 40 phr to about 80 phr, from about 50 phr to about 100 phr, from about 50 phr to about 90 phr, or even from about 50 phr to about 80 phr or any and all sub-ranges formed from any of these endpoints.

[0046] The practice of the present invention also advantageously provides a method whereby a tire component is produced from a cured rubber matrix that has a relatively high content of sustainable constituents, which include recycled materials, naturally-derived materials, and / or materials synthesized from bio-synthesized feedstock or bio-based materials. For example, the tires or tire components of the present invention may include greater than 40 wt.%, in other embodiments greater than 50 wt.%, and in other embodiments greater than 60 wt.% sustainable materials. In these or other embodiments, the tire or tire components include from about 40 to about 90 wt.%, in other embodiments from about 45 to about 85 wt.%, and in other embodiments from about 50 to about 80 wt.% sustainable material. The cured rubber matrix with fdler dispersed therein may include greater than 40 wt.%, or 50 wt.%, or 60 wt.%, or 70 wt.%, or 80 wt.%, or 90 wt.%, or 99 wt.% of a statistical copolymer.

[0047] Curatives

[0048] As used herein, curatives are vulcanizing agents used in the vulcanization of the statistical copolymer. As described herein, the first stage cure is conducted in the presence of a traditional rubber curative. In embodiments, the traditional rubber curative may comprise a sulfurbased curative or a peroxide-based curative. In embodiments, the traditional rubber curative may comprise zinc oxide, sulfur, diphenylguanidine, fatty acids, benzothiazoles, sulfenamides, sulfenimides, thiurams, dithiocarbamates, or combinations thereof.

[0049] In embodiments, the curative may be a sustainable curative. Examples of specific suitable sulfur curatives include "rubbermaker's" soluble sulfur; sulfur donating curing agents, such as an amine disulfide, polymeric poly sulfide, or sulfur olefin adducts; and insoluble polymeric sulfur. In one embodiment, the sulfur curative may comprise soluble sulfur or a mixture of soluble and insoluble polymeric sulfur. For a general disclosure of suitable curatives and other components used in curing, e.g., vulcanizing inhibitor and anti- scorching agents, one may refer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, N.Y. 1982, Vol. 20, pp. 365 to 468, particularly Vulcanization Agents and Auxiliary Materials, pp. 390 to 402, or Vulcanization by A. Y. Coran, Encyclopedia of Polymer Science and Engineering, Second Edition (1989 John Wiley & Sons, Inc.), both of which are incorporated herein by reference. While various amounts are contemplated, the curatives may be used in an amount ranging from about 0.1 phr to about 10 phr, including from about 1 phr to about 7.5 phr, including from about 1 phr to about 5 phr, and preferably from about 1 phr to 3.5 phr.

[0050] Additional Rubbers

[0051] In embodiments, the rubber formulation may comprise additional rubbers that are not the statistical copolymer. In embodiments, the rubber formulation may further comprise a styrenebutadiene rubber, a butadiene rubber, butyl rubber, EPDM, natural rubber, polyisoprene, or combinations thereof, wherein the styrene -butadiene rubber and the butadiene rubber do not comprise a polymerized reaction product derived from vinylbenzocyclobutane.

[0052] These additional rubbers may also include other synthetic rubber, such as synthetic rubber that derives from petroleum-based raw materials, synthetic rubber that derives from other sustainable processes. As the skilled person understands, natural rubber is synthesized by and obtained from plant life. For example, natural rubber may be obtained from Hevea rubber trees, guayule shrub, gopher plant, mariola, rabbitbrush, milkweeds, goldenrods, pale Indian plantain, rubber vine, Russian dandelions, mountain mint, American germander, and tall bellflower.

[0053] Other synthetic polymers, if used, may include, without limitation, synthetic polyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene, poly(ethylene-co- propylene), poly(styrene-co-butadiene), poly(styrene-co-isoprene), poly(styrene-co-isoprene-co- butadiene), poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene), polysulfiderubber, and mixtures thereof. These elastomers may have a myriad of macromolecular structures including linear, branched, and star-shaped structures.

[0054] Generally, the rubber formulations may include from about 5 to about 45 wt.%, in other embodiments from about 15 to about 40 wt.%, and in other embodiments from about 20 to about 35 wt.% of elastomer, based on the total weight of the tire component.

[0055] Fillers

[0056] The rubber formulations may include fdlers such as organic and inorganic fdlers. Examples of organic fdlers include carbon black and starch. Examples of inorganic fdlers include silica, aluminum hydroxide, magnesium hydroxide, mica, talc (hydrated magnesium silicate), and clays (hydrated aluminum silicates). In certain embodiments, a mixture of different fdlers may be advantageously employed.

[0057] The amount of total fdler employed in the rubber compositions may be up to about 150 parts by weight per 100 parts by weight of rubber (phr), with about 30 to about 125 phr, or about 40 to about 110 phr being typical. In certain embodiments the total fdler content may be greater than about 100 phr. In other embodiments, the total fdler content may from about 50 to about 100 phr, and in in further embodiments from about 55 to about 95 phr.

[0058] Conventional carbon black may be used, which is generally known in the art. In one or more embodiments, carbon blacks include furnace blacks, channel blacks, and lamp blacks. More specific examples of carbon blacks include carcass grade blacks (e.g., N550), super abrasion furnace blacks, intermediate super abrasion furnace blacks, high abrasion furnace blacks, fast extrusion furnace blacks, fine furnace blacks, semi-reinforcing furnace blacks, medium processing channel blacks, hard processing channel blacks, conducting channel blacks, and acetylene blacks.

[0059] In particular embodiments, the carbon black may have a surface area (EMSA) of at least 20 m2 / g and in other embodiments at least 35 m2 / g; surface area values may be determined by ASTM D-1765 using the cetyltrimethylammonium bromide (CTAB) technique. The carbon black may be in a pelletized form or an unpelletized flocculent form. The preferred form of carbon black may depend upon the type of mixing equipment used to mix the rubber compound.

[0060] In one or more embodiments, carbon black may be sourced from a recycled material. Such recycled material may include reclaimed or recycled vulcanized rubber, whereby the vulcanized rubber is typically reclaimed from manufactured articles such as a pneumatic tire, an industrial conveyor belt, a power transmission belt, and a rubber hose. The recycled carbon black may be obtained by a pyrolysis process or other methods known for obtaining recycled carbon black. In an aspect, a recycled carbon black may be formed from incomplete combustion of recycled rubber feedstock or rubber articles. In another aspect, the recycled carbon black may be formed from the incomplete combustion of feedstock including oil resulting from the tire pyrolysis process. The carbon blacks utilized in the preparation of the vulcanizable elastomeric compositions may be in pelletized form or an unpelletized flocculent mass.

[0061] The amount of carbon black employed in the rubber compositions may be up to about 75 parts by weight per 100 parts by weight of rubber (phr), with about 5 to about 60 phr, or about 10 to about 55 phr being typical.

[0062] Commercially available silicas which may be used include Hi-Sil™ 215, Hi-Sil™ 233, and Hi-Sil™ 190 (PPG Industries, Inc.; Pittsburgh, Pa.). Other suppliers of commercially available silica include Grace Davison (Baltimore, Md.), Degussa Corp. (Parsippany, N.J.), Rhodia Silica Systems (Cranbury, N.J.), and J.M. Huber Corp. (Edison, N.J.). Such silicas may be considered as sustainable materials. Other sustainable silicas include those derived from rice husk ash.

[0063] In one or more embodiments, silicas may be characterized by their surface areas, which give a measure of their reinforcing character. The Brunauer, Emmet and Teller ("BET") method (described in J. Am. Chem. Soc., 1939, vol. 60, 2 p. 309-319) is a recognized method for determining the surface area. The BET surface area of silica is generally less than 450 m2 / g. Useful ranges of surface area include from about 32 to about 400 m2 / g, about 100 to about 250 m2 / g, about 130 to about 240 m2 / g, and about 170 to about 220 m2 / g. In certain embodiments, the silica may have a BET surface area of 190 to about 280 m2 / g. The pH's of the silicas are generally from about 5 to about 7 or slightly over 7, or in other embodiments from about 5.5 to about 6.8.

[0064] In one or more embodiments, where silica is employed as a fdler (alone or in combination with other fdlers), a coupling agent and / or a shielding agent may be added to the rubber compositions during mixing in order to enhance the interaction of silica with theelastomers. Useful coupling agents and shielding agents are disclosed in U.S. Patent Nos. 3,842,111; 3,873,489; 3,978,103; 3,997,581; 4,002,594; 5,580,919; 5,583,245; 5,663,396; 5,674,932; 5,684,171; 5,684,172; 5,696,197; 6,608,145; 6,667,362; 6,579,949; 6,590,017; 6,525,118; 6,342,552; and 6,683,135; which are incorporated herein by reference.

[0065] The amount of silica employed in the rubber compositions may be from about 1 to about 150 phr or in other embodiments from about 5 to about 130 phr. The useful upper range is limited by the high viscosity imparted by silicas. In certain embodiments, the silica employed in the rubber composition is derived from rice husk ash only, and in other embodiments the rubber compositions do not include silica from non-rice husk ash derived processes. When silica is used together with carbon black, the amount of the silica or carbon black individually may be as low as about 1 phr. Generally, the amounts of coupling agents and shielding agents range from about 4 wt.% to about 20 wt.% based on the weight of silica used. In one or more embodiments, where carbon black and silica are employed in combination as a fdler, the weight ratio or silica to total fdler may be from about 5 wt.% to about 99 wt.% of the total fdler, in other embodiments from about 10 wt.% to about 90 wt.% of the total fdler, or in yet other embodiments from about 50 wt.% to about 85 wt.% of the total fdler. In certain embodiments the silica and carbon black fdlers employed in the rubber composition are selected from the group consisting of sustainable pyrolysis carbon black and / or rice husk ash derived silica.

[0066] Other ingredients that are typically employed in rubber compounding may also be added to the rubber formulations. These include accelerators, accelerator activators, oils, plasticizer, waxes, scorch inhibiting agents, processing aids, zinc oxide, tackifying resins, reinforcing resins, fatty acids such as stearic acid, peptizers, and antidegradants such as antioxidants and antiozonants.

[0067] As described herein, in embodiments, the rubber formulation may comprise sulfur as a vulcanizing agent. A vulcanization accelerator may be used along with a vulcanizing agent to control the time and / or temperature required for vulcanization and to improve properties of the vulcanizate. The vulcanization accelerators suitable for use in the disclosed compositions are not particularly limited. Examples of vulcanization accelerator include thiazol vulcanization accelerators, such as 2-mercaptobenzothiazol, dibenzothiazyl disulfide, N-cyclohexyl-2- benzothiazyl-sulfenamide, N-tert-butyl-2-benzothiazyl sulfenamide, and the like; guanidinevulcanization accelerators, such as diphenylguanidine and the like; amines; disulfides; thiurams; sulfenamides; dithiocarbamates; xanthates; and thioureas; among others.

[0068] With regard to oils, sustainable oils, which include plant-based oils and bio-based oils, may be used. Plant-based oils may include plant-based triglycerides. Exemplary oils include, without limitation, palm oil, soybean oil (also referred to herein as soy oil), rapeseed oil, sunflower seed, peanut oil, cottonseed oil, oil produced from palm kernel, coconut oil, olive oil, corn oil, grape seed oil, hemp oil, linseed oil, rice oil, safflower oil, sesame oil, mustard oil, flax oil. Other examples include nut-derived oils such oils obtained from beech nuts, cashews, mongongo nuts, macadamia nuts, pine nuts, hazelnuts, chestnuts, acorns, almonds, pecans, pistachios, walnuts, or brazil nuts. As the skilled person will appreciate, these oils may be produced by any suitable process such as mechanical extraction (e.g., using an oil mill), chemical extraction (e.g., using a solvent, such as hexane or carbon dioxide), pressure extraction, distillation, leaching, maceration, purification, refining, hydrogenation, sparging, etc.

[0069] Bio-based oils, also referred to as bio-oils, may include oils produced by a recombinant cell. For example, bio-oils produced by recombinant cells may be produced using a select strain of algal cells that are fed with a supply of sugars (e.g., sucrose) and then allowed to ferment and produce a bio-oil with a selected profile; after sufficient growth or fermentation has taken place, the bio-oil is isolated from the cells and collected.

[0070] Generally, the rubber formulations may include from about 1 to about 70 parts by weight, or in other embodiments from about 5 to about 50 parts weight total oil per 100 parts by weight rubber. The amount of sustainable oil, relative to the total weight of oil included, may be from about 1 wt.% to about 99 wt.%, or in other embodiment from about 20 wt.% to about 80 wt.%.

[0071] With regard to waxes, the rubber compositions may include one or more sustainable waxes, which include natural waxes. A natural wax, or one with no petroleum as its raw material, may include carnauba wax, candelilla wax (e.g., extracted from candelilla flowers), rice wax (e.g., separated from rice bran oil) and Japan wax (e.g., extracted from Japanese wax tree).

[0072] Generally, the rubber formulations may include from about 1 to about 20 parts by weight, or in other embodiments from about 2 to about 15 parts by weight total wax per 100 partsby weight rubber. The amount of sustainable wax, relative to the total weight of wax included, may be from about 1 wt.% to about 99 wt.%, or in other embodiment from about 20 wt.% to about 80 wt.% of the total wax. In certain embodiments, the rubber composition may include sustainable waxes only.

[0073] In one or more embodiments, the rubber formulation may comprise at least one copper containing compound. Such copper compounds comprise acetates, acetylacetonates, aluminates, bicarbonates, borates, bromates, carbonates, chlorites, cyanides, diethylcitrates, halides, hexafluoroacetylacetonates, hexafluorophosphates, hexafluorosilicates, dihydrogen phosphates, hydrogen carbonates, hydrogen sulphates, hydrogen sulphides, hydrogen sulphites, hydroxides, hypochlorites, iodates, nitrates, nitrites, oxalates, oxides, perfluorophthalocyanines, peroxides, phosphates, phthalocyanines, pyrophosphates, silicates, sulphamates, sulphates, sulphides, sulphites, tartrates, tetrafluoroborates, thiocyanates, thiolates, thiosulphates, tosylates and triflates of these metals. Preferred compounds in this context include CuOCOCHs, Cu(OCOCH3)2, CU(OCOCH3)2XH2O, CU(C5H7O2)2, CuBr, CuBr2, CuCO3, CuCO3, Cu(OH)2, CuCl, CuCl2, CUC12XH2O, CU[CH3(CH2)3CH(C2H5)CO2]2, CUF2, CUF2XH2O, CU(HCO2)2, CU(HCO2)2XH2O, CU(OH)2, CU2(OH)PO4, Cui, CuFe2O4, Cu(NO3)2, Cu(NO3)2xH2O, Cu2O, CuO, Cu(C32Hi6N8), CU2P2O7XH2O, CuSO4, CUSO4XH2O, CUS, CU[O2CCH(OH)CH(OH)CO2]XH2O, CU(BF4)2, CU(BF4)XH2O, CU(SCN), CU(BF4)2, Cu(PFe)2, or CuF2. In embodiments, the copper containing compound may include Cu(BF4)2, Cu(PFe)2, or CuF2. Without being bound by theory, it is believed these copper compounds may reduce the temperature required to cure the rubber formulation by reducing the energy required for the VBCB in the statistical copolymer to form crosslinks.

[0074] The rubber composition may further include fdler in the form of one or more recycled rubbers in a particulate form. Recycled particulate rubber is typically broken down and reclaimed (or recycled) by any of a plurality of processes, which may include physical breakdown, grinding, chemical breakdown, devulcanization, cryogenic grinding, a combination thereof, etc. The term “recycled particulate rubber” may relate to both vulcanized and devulcanized rubber, where devulcanized recycle or recycled rubber (reclaim rubber) relates to rubber which has been vulcanized, ground into particulates and may have further undergone substantial or partial devulcanization. In an example, the recycled particulate rubber used in the rubber composition is essentially free of recycled rubber resulting from devulcanization. In a situation where thevulcanized rubber contains wire or textile fiber reinforcement, such wire or fiber reinforcement may be removed by any suitable process such as magnetic separation, air aspiration and / or air flotation step. In certain embodiments, the "recycled particulate rubber" may comprise cured, i.e., vulcanized (crosslinked) rubber that has been ground or pulverized into particulate matter.

[0075] Method of Making

[0076] Polymerization

[0077] In embodiments, the two-stage cured statistical copolymers of the present disclosure may be made by a method comprising polymerizing conjugated diene monomer and VBCB monomer, and optionally vinyl aromatic monomer, in the presence of an anionic initiator to produce polymer chains with a living end and a randomizing component to produce a statistical copolymer. The polymerization may produce a two-stage cured statistical copolymer as described herein.

[0078] In embodiments, an anionic initiator may be used during polymerization of the statistical copolymer of the rubber formulation. In embodiments, the anionic initiator may be a hydrocarbyl lithium compound. In embodiments, the anionic initiator may comprise ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, a reaction product of diisopropenylbenzene and butyl lithium, and combinations thereof. In embodiments, the anionic initiator may be n-butyl lithium.

[0079] In embodiments, a randomizing component may be used during the synthesis of the statistical copolymer of the rubber formulation. Without being bound by theory, it is believed that the randomizing component may influence the microstructure of the statistical copolymer allowing for a random distribution of monomer units of different compositions along the polymer chain.

[0080] In embodiments, the randomizing component may comprise those having an oxygen or nitrogen heteroatom and a non-bonded pair of electrons. Examples include linear and cyclic oligomeric oxolanyl alkanes; dialkyl ethers of mono and oligo alkylene glycols (also known as glyme ethers); “crown” ethers; tertiary amines; linear THF oligomers; and the like. Linear and cyclic oligomeric oxolanyl alkanes are described in U.S. Pat. No. 4,429,091 and 9,868,795, whichis incorporated herein by reference. Specific examples of compounds useful as randomizers include 2,2-bis(2'-tetrahydrofuryl)propane, 1,2-dimethoxyethane, N,N,N’,N’- tetramethylethylenediamine (TMEDA), tetrahydro furan (THF), 1,2-dipiperidylethane, dipiperidylmethane, hexamethylphosphoramide, A-A'-dimcthylpipcrazinc, diazabicyclooctane, dimethyl ether, diethyl ether, tri-n -butylamine, and mixtures thereof. In other embodiments, potassium alkoxides can be used to randomize the styrene distribution.

[0081] Curing

[0082] The two-stage cured statistical copolymer may undergo a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking. In embodiments, the first stage cure may cause the statistical copolymer to form crosslinks within the rubber formulation, leading to a vulcanized rubber formulation that may, for example, be used as a sidewall in a tire. For example, after the first stage cure, the rubber formulation may have a S' greater than or equal to 10 dNm. The first stage cure may be conducted in a controlled environment, such as during processing of the rubber formulation.

[0083] The first temperature should be above a threshold (e.g., greater than or equal to 110 °C) at which sulfur crosslinking occurs. The first temperature may be limited (e.g., less than or equal to about 180 °C) to preserve the VBCB monomer units for the subsequent second stage cure. If the first temperature was too high (e.g., greater than 180 °C), VBCB monomer units may be consumed during the first stage cure and may not be available for crosslinking in the subsequent second stage cure. In embodiments, the first temperature may be greater than or equal to about 110 °C and less than or equal to about 180 °C. In embodiments, the first temperature may be greater than or equal to about 110 °C, greater than or equal to about 130 °C, or even greater than or equal to about 150 °C. In embodiments, the first temperature may be less than or equal to about 180 °C or even less than or equal to about 170 °C. In embodiments, the first temperature may be from about 110 °C to about 180 °C, from about 110 °C to about 170 °C, from about 130 °C to about 180 °C, from about 130 °C to about 170 °C, from about 150 °C to about 180 °C, or even from about 150 °C to about 170 °C, or any and all sub-ranges formed from any of these endpoints.

[0084] In embodiments, a time period of the first stage cure may be from about 0.1 hour to about 2 hours, from about 0.1 hour to about 1.5 hours, from about 0.1 hour to about 1 hour, from about 0.1 hour to about 0.5 hour, about 0.2 hour to about 2 hours, from about 0.2 hour to about1.5 hours, from about 0.2 hour to about 1 hour, from about 0.2 hour to about 0.5 hour, about 0.3 hour to about 2 hours, from about 0.3 hour to about 1.5 hours, from about 0.3 hour to about 1 hour, or even from about 0.3 hour to about 0.5 hour, or any and all sub-ranges formed from any of these endpoints.

[0085] The two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking. The second stage cure may result from a puncture event. Specifically, when air inside a tire is released due to tire puncture, the tire is bent and its temperature becomes higher. The second stage cure may cause the statistical copolymer, particularly VBCB monomer units, to form further crosslinks within the rubber formulation, thereby increasing the overall stiffness of the rubber formulation. Further crosslinking may be evidenced if AS', accounting for temperature (i.e., Maximum S' at given temperature - S' at given temperature), is greater than or equal to 3 dNM, as further crosslinking due to VBCB results in higher torque values. In a traditional cure system (e.g., sulfurbased), an extended cure time and / or increased temperatures may lead to breakdown of the polymer or polymer network, which would lower S' and continued crosslinking, which would increase S'. This is in addition to the general relationship of S' decreasing when temperature is increased if no changes in crosslinking were to occur. Accordingly, when temperature is increased to drive a cure process for a VBCB system, additional crosslinking from traditional rubber curatives may still occur or current poly-sulfidic crosslinks may break apart to make a greater number of mono-sulfidic crosslinks, ultimately leading to more crosslinks. Nonetheless, after the subsequent second stage cure at a relatively higher temperature, a system with a traditional rubber curative and VBCB results in more crosslinks than a system with only a traditional rubber curative. Accordingly, AS' may be greater for the rubber formulations described herein including VBCB when compared to a corresponding rubber formulation that does not include VBCB.

[0086] While sulfur may not participate in the crosslinking that occurs during the second stage cure, other curatives that are still present in the rubber formulation, such as zinc oxide, may promote crosslinking.

[0087] In embodiments, the second temperature may be greater than or equal to about 190 °C and less than or equal to about 250 °C. In embodiments, the second temperature may greater than or equal to about 190 °C or even greater than or equal to about 200 °C. In embodiments, the second temperature may be less than or equal to about 250 °C, less than or equal to about 230 °C,or even less than or equal to about 210 °C. In embodiments, the second temperature may be from about 190 °C to about 250 °C, from about 190 °C to about 230 °C, from about 190 °C to about 210 °C, from about 200 °C to about 250 °C, from about 200 °C to about 230 °C, or even from about 200 °C to about 210 °C, or any and all sub-ranges formed from any of these endpoints.

[0088] As described herein, the second stage cure occurs when the rubber formulation is subjected to an elevated temperature, such as during a puncture event. Accordingly, the second stage cure of the Examples section herein, including the time period of the second stage cure, was simulated.

[0089] Rubber Formulation

[0090] The rubber formulations described herein have improved stiffness after a subsequent second stage cure (e.g., a puncture event), leading to maintained elasticity and mobility of a tire including the rubber formulation after the subsequent cure. For example, in embodiments, the rubber formulation may have a maximum displacement of less than or equal to about 0.003 m under a compression load of 150N on a cylinder with a diameter of 17.4 mm and a height of 24.6 mm.

[0091] In embodiments, the rubber formulation may be used in a run flat tire. For example, in embodiments, a tire sidewall may comprise a run flat insert, the run flat insert comprising the rubber formulation described herein. As such, the subsequent stage cure may occur during use of the tire sidewall. For example, in embodiments, the subsequent second stage cure may occur when air inside a tire is released due to tire puncture, the tire comprising the tire sidewall.

[0092] The rubber formulations of the present disclosure may also be utilized in other components and articles, which utilize rubber formulations, such as, for example, tire tread, inner- tubes and tire inner liners, air cushions, pneumatic sprays, air bags, tire-curing bladders, high temperature hoses and conveyor belts, damping mounts for engines and the like.

[0093] In one or more embodiments, the tires and / or other rubber containing components and articles may include fabric reinforcement made by using non-petroleum materials in place of synthetic fibers. For example, mechanical recycled fibers, chemical recycled fibers, or bio-based fibers may be used. Eikewise, the tires may include metal reinforcement made from recycled steel and / or other circular or sustainable metals. These non-petroleum fabrics and recycled metals maybe used exclusively within the tires or in combination with traditional fabric and / or metal reinforcement.EXAMPLES

[0094] The rubber formulations described herein will be further described in the following examples, which are not intended to restrict the rubber formulations.

[0095] Measurements

[0096] The number average molecular weight (Mn) and weight average molecular weight (Mw) were determined by gel permeation chromatography using a TOSOH Esosec HLC-8320 GPC system and TOSOH TSKgel GMHxl-BS columns with THF as the solvent. The system was calibrated using universal calibration with polystyrene standards and corrected using the Mark- Houwink constants for polybutadiene or poly(styrene-co-butadiene).

[0097] The vinylbenzocyclobutane content and vinyl content were determined by111-Nuclcar Magnetic Resonance spectroscopy in d-chloroform at 25 °C.

[0098] “Glass transition temperature Tg” was measured by differential scanning calorimetry. The differential scanning calorimetry method included a starting temperature of 23 °C, heating to 200 °C at a 10 °C / min ramp rate, cooling to -120 °C, and reheating to 200 °C at a 10 °C / min ramp rate.

[0099] Example 1 - Synthesis of Vinylbenzocyclobutane Copolymers

[0100] To a 7.57 L stainless steel reactor equipped with turbine agitator blades, 0.5 kg hexanes and 1.65 kg 20.7 wt% 1,3-butadiene in hexanes were added. To initiate polymerization, 0.91 mL of 0.80 M hexamethyleneimine in hexanes, 0.24 mL of 1.0M potassium t-amylate in hexanes, 34.0 mL of 1.0 M vinylbenzocyclobutane in hexanes, and 2.13 mL of 1.60 M n-butyl lithium in hexanes were added. The batch was then heated to an exotherm of 71 °C. Approximately 15 minutes after exotherm, the contents were discharged into nitrogen purged bottles and terminated with 0.15 mol tin tetrachloride / mol n-butyl lithium. The polymer was coagulated in isopropanol containing antioxidant and drum dried to yield Polymer 1. The properties of Polymer 1 are shown in Table 1.

[0101] Table 1- Property of Synthesized Polymer

[0102] Example 2 - Compounding Polymers with Carbon Black

[0103] In Example 2, polymers, including Polymer 1 synthesized in Example 1, were compounded to form rubber formulations. The formulations of the compound mixtures are shown in Tables 2 and 3 (in phr). Each rubber formulation was prepared in a master batch and then a final batch. In the master batch, the polymers were mixed with carbon black, stearic acid, antioxidant, and oil.

[0104] The master batch portion of the compound was mixed in a 65 g Banbury mixer operating with cam rotors at 60 rpm and 130 °C. First, polymer was placed in the mixer, and after 0.5 minutes, the remaining ingredients were added and mixed for a total of about 3 to 5 minutes. At the end of mixing, the temperatures were approximately 155 to 160 °C. The samples were transferred to an open mill operating at a temperature of 60 °C, where they were sheeted and subsequently cooled to room temperature.

[0105] The final batch portions were mixed by adding the master batch and the curative materials to the mixer simultaneously. The initial mixer temperature was 80 °C and it was operating at 50 RPM. The final material was removed from the mixer when the material temperature was between 100 °C and 105 °C. The final batch portions were sheeted and cured into Dynastat buttons and 7.62 cm x 15.24 cm x 0.19 cm sheets. The comparative formulations, Cl and C2, and example formulation E2 were cured at 171 °C for 3.5 minutes and example sample El was cured at 171 °C for 4.5 minutes.

[0106] Table 2 - Master Batch Formulation

[0107] Table 3 - Final Batch Formulation

[0108] Example 3 - Dynamic Mechanical Analysis

[0109] Final example formulations El and E2 and comparative formulations Cl and C2 were sheeted and cured into cylinders (H 24.6mm, D 17.4 mm) for dynamic mechanical analysis by using Metravib. All cylinders were cured at 171 °C for 10 minutes.

[0110] Referring now to FIG. 1 and Table 4, cure characteristics were measured by using a Rubber Process Analyzer (RPA) at 165 °C with the oscillating frequency at 1.667 Hz for the initial 20 minutes (i.e., zone “a” in FIG. 1) and resulting torques were recorded in dNm (i.e., S' at 20 minutes listed in Table 4). The torque values S' of example formulations El and E2 were greater than corresponding controls Cl and C2 after this first stage cure.

[0111] The temperature was raised in the next 5 minutes to 200 °C (i.e., zone “b” in FIG. 1) and the resulting torques were recorded (i.e., S' at 25 minutes listed in Table 4). All formulations had a decrease in torque value S', indicating that all of the formulations became softer. The curedrubbers were kept in the RPA cavity at 200 °C for additional 2 hours (i.e., zone “c” in FIG. 1) and the resulting torques were recorded (i.e., S' at 145 minutes listed in Table 4). As listed in Table 4, example formulations El and E2 had AS' values of 10.51 dNm and 5.25 dNm, respectively, indicating that VBCB present in example formulations El and E2 crosslinked at the elevated temperatures. The AS' values for comparative formulations Cl and C2 were 2.51 dNm and 1.37 dNm, respectively, indicating that the comparative formulations did not result in as much further crosslinking as the example formulations including VBCB. As exemplified by FIG. 1, rubber formulations including a two-stage cured statistical copolymer comprising VBCB provide increased stiffness at elevated temperatures.

[0112] Table 4 - Curing Characteristics

[0113] Embodiments of the invention include but are not limited to:

[0114] 1. A rubber formulation comprising: a two-stage cured statistical copolymer comprising a polymerized reaction product comprising a conjugated diene monomer and a monomer capable of crosslinking at a high-temperature, wherein: the two-stage cured statistical copolymer undergoes a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking; and the two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate nonsulfur crosslinking.

[0115] 2. The rubber formulation of any preceding clause, wherein the monomer capable of crosslinking at the high-temperature comprises vinylbenzocyclobutane.

[0116] 3. The rubber formulation of any preceding clause, wherein the first stage cure is conducted in the presence of a traditional rubber curative.

[0117] 4. The rubber formulation of any preceding clause, wherein the traditional rubber curative comprises zinc oxide, sulfur, diphenylguanidine, fatty acids, benzothiazoles, sulfenamides, sulfenimides, thiurams, dithiocarbamates, or combinations thereof.

[0118] 5. The rubber formulation of any preceding clause, wherein a rubber component of the rubber formulation comprises from about 20 phr to about 100 phr of the statistical copolymer, based on the total weight of the rubber component.

[0119] 6. The rubber formulation of any preceding clause, wherein the conjugated diene monomer is selected from the group consisting of 1,3 -butadiene, isoprene, 1,3 -pentadiene, 1,3- hexadiene, 2,3-dimethyl-l,3-butadiene, 2-ethyl- 1,3 -butadiene, 2-methyl- 1,3 -pentadiene, 3- methyl- 1,3 -pentadiene, 4-methyl-l,3-pentadiene, 2,4-hexadiene, 1,3 -cyclopentadiene, 1,3- cyclohexadiene, 1,3-cycloheptadiene, 1,3 -cyclooctadiene, and combinations thereof.

[0120] 7. The rubber formulation of any preceding clause, wherein the statistical copolymer comprises a polymerized, crosslinkable, reaction product derived from the conjugated diene monomer, the vinylbenzocyclobutane, and a vinyl aromatic monomer.

[0121] 8. The rubber formulation of any preceding clause, wherein the vinyl aromatic monomer is selected from the group consisting of styrene, alpha-methyl styrene, p-methylstyrene, o-methylstyrene, p-butyl styrene, vinylnapthalene, p-tertbutylstyrene, 4-vinylbiphenyl, 2- vinylnapthalene, 9-vinylanthracene, vinyl catechol, and combinations thereof.

[0122] 9. The rubber formulation of any preceding clause, wherein the conjugated diene monomer is 1,3-butadiene and the vinyl aromatic monomer is styrene.

[0123] 10. The rubber formulation of any preceding clause, wherein the first temperature is greater than or equal to about 110 °C and less than or equal to about 180 °C.

[0124] 11. The rubber formulation of any preceding clause, wherein the second temperature is greater than or equal to about 190 °C and less than or equal to about 250 °C.

[0125] 12. The rubber formulation of any preceding clause, wherein the rubber formulation has a maximum displacement of less than or equal to about 0.003 m under a compression load of 150N on a cylinder with a diameter of 17.4 mm and a height of 24.6 mm.

[0126] 13. The rubber formulation of any preceding clause, wherein the rubber formulation further comprises from about 5 to about 75 phr of carbon black.

[0127] 14. The rubber formulation of any preceding clause, wherein the carbon black comprises N550.

[0128] 15. The rubber formulation of any preceding clause, wherein the rubber formulation further comprises from about 1 phr to about 70 phr of oil.

[0129] 16. The rubber formulation of any preceding clause, wherein the rubber formulation further comprises from about 1 phr to about 150 phr of silica.

[0130] 17. The rubber formulation of any preceding clause, wherein the rubber formulation further comprises CuOCOCHs, Cu(OCOCH3)2, Cu(OCOCH3)2xH2O, Cu(C5H7O2)2, CuBr, CuB , CuCO3, CuCO3, CU(OH)2, CuCl, CuCl2, CuCbxfhO, Cu[CH3(CH2)3CH(C2H5)CO2]2, CuF2, CUF2XH2O, CU(HCO2)2, CU(HCO2)2XH2O, CU(OH)2, CU2(OH)PO4, Cui, CuFe2O4, Cu(NO3)2, CU(NO3)2XH2O, CU2O, CUO, Cu(C32Hi6N8), CU2P2O7XH2O, CuSO4, CuSO4xH2O, CuS, Cu[O2CCH(OH)CH(OH)CO2]xH2O, CU(BF4)2, CU(BF4)XH2O, CU(SCN), CU(BF4)2, CU(PF6)2, CUF2or combinations thereof.

[0131] 18. The rubber formulation of any preceding clause, wherein the rubber formulation further comprises a styrene-butadiene rubber, a butadiene rubber, butyl rubber, EPDM, natural rubber, polyisoprene, or combinations thereof, and wherein the styrene-butadiene rubber and the butadiene rubber do not comprise a polymerized reaction product derived from vinylbenzocyclobutane.

[0132] 19. The rubber formulation of any preceding clause, wherein the statistical copolymer has a weight average molecular weight of greater than or equal to about 100 kg / mol.

[0133] 20. The rubber formulation of any preceding clause, wherein the statistical copolymer comprises from about 0.02 wt.% to about 2 wt.% of the vinylbenzocyclobutane, based on the total weight of the statistical copolymer.

[0134] 21. The rubber formulation of any preceding clause, wherein the statistical copolymer comprises from 1 to 15 vinylbenzocyclobutane monomer units per chain of the statistical copolymer.

[0135] 22. The rubber formulation of any preceding clause, wherein the statistical copolymer comprises from about 50 wt.% to about 99.98 wt.% of the conjugated diene monomer, based on the total weight of the statistical copolymer.

[0136] 23. The rubber formulation of any preceding clause, wherein the statistical copolymer comprises from about 5 wt.% to about 50 wt.% of the vinyl aromatic monomer, based on the total weight of the statistical copolymer.

[0137] 24. The rubber formulation of any preceding clause, wherein the statistical copolymer has at least 1 vinylbenzocyclobutane monomer unit at an end of a polymer chain.

[0138] 25. A tire sidewall comprising a run flat insert, wherein the run flat insert comprises the rubber formulation of any preceding clause.

[0139] 26. The tire sidewall of any preceding clause, wherein the subsequent second stage cure occurs during use of the tire sidewall.

[0140] 27. The tire sidewall of any preceding clause, wherein the subsequent second stage cure occurs when air inside a tire is released due to tire puncture, the tire comprising the tire sidewall.

[0141] ft will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

CLAIMS1. A rubber formulation comprising: a two-stage cured statistical copolymer comprising a polymerized reaction product comprising a conjugated diene monomer and a monomer capable of crosslinking at a high- temperature, wherein: the two-stage cured statistical copolymer undergoes a first stage cure at a first temperature less than or equal to about 180 °C to initiate sulfur crosslinking; and the two-stage cured statistical copolymer undergoes a subsequent second stage cure at a second temperature greater than or equal to about 190 °C to initiate non-sulfur crosslinking.

2. The rubber formulation of claim 1, wherein the monomer capable of crosslinking at the high-temperature comprises vinylbenzocyclobutane.

3. The rubber formulation of claim 1 or claim 2, wherein the first stage cure is conducted in the presence of a traditional rubber curative.

4. The rubber formulation of claim 3, wherein the traditional rubber curative comprises zinc oxide, sulfur, diphenylguanidine, fatty acids, benzothiazoles, sulfenamides, sulfenimides, thiurams, dithiocarbamates, or combinations thereof.

5. The rubber formulation of claim 1 or claim 2, wherein a rubber component of the rubber formulation comprises from about 20 phr to about 100 phr of the statistical copolymer, based on the total weight of the rubber component.

6. The rubber formulation of claim 1 or claim 2, wherein the conjugated diene monomer is selected from the group consisting of 1,3 -butadiene, isoprene, 1,3 -pentadiene, 1,3 -hexadiene, 2,3- dimethyl- 1,3 -butadiene, 2-ethyl- 1,3 -butadiene, 2-methyl- 1,3 -pentadiene, 3 -methyl- 1,3- pentadiene, 4-methyl-l,3-pentadiene, 2,4-hexadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1,3 -cycloheptadiene, 1,3-cyclooctadiene, and combinations thereof.

7. The rubber formulation of claim 2, wherein the statistical copolymer comprises a polymerized, crosslinkable, reaction product derived from the conjugated diene monomer, the vinylbenzocyclobutane, and a vinyl aromatic monomer.

8. The rubber formulation of claim 7, wherein the vinyl aromatic monomer is selected from the group consisting of styrene, alpha-methyl styrene, p-methylstyrene, o-methylstyrene, p-butyl styrene, vinylnapthalene, p-tertbutylstyrene, 4-vinylbiphenyl, 2-vinylnapthalene, 9- vinylanthracene, vinyl catechol, and combinations thereof.

9. The rubber formulation of claim 7, wherein the conjugated diene monomer is 1,3- butadiene and the vinyl aromatic monomer is styrene.

10. The rubber formulation of claim 1 or claim 2, wherein the first temperature is greater than or equal to about 110 °C and less than or equal to about 180 °C.

11. The rubber formulation of claim 1 or claim 2, wherein the second temperature is greater than or equal to about 190 °C and less than or equal to about 250 °C.

12. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation has a maximum displacement of less than or equal to about 0.003 m under a compression load of 150N on a cylinder with a diameter of 17.4 mm and a height of 24.6 mm.

13. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation further comprises from about 5 to about 75 phr of carbon black.

14. The rubber formulation of claim 1 or claim 2, wherein the carbon black comprises N550.

15. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation further comprises from about 1 phr to about 70 phr of oil.

16. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation further comprises from about 1 phr to about 150 phr of silica.

17. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation further comprises CuOCOCHs, Cu(OCOCH3)2, Cu(OCOCH3)2xH2O, Cu(CsH7O2)2, CuBr, CuBn, CuCO3, CuCO3, CU(OH)2, CuCl, CuCl2, CuCbxfhO, Cu[CH3(CH2)3CH(C2H5)CO2]2, CuF2, CuF2xH2O, CU(HCO2)2, CU(HCO2)2XH2O, CU(OH)2, CU2(OH)PO4, Cui, CuFe2O4, Cu(NO3)2, CU(NO3)2XH2O, CU2O, CUO, Cu(C32Hi6N8), CU2P2O7XH2O, CuSO4, CuSO4xH2O, CuS, CU[O2CCH(OH)CH(OH)CO2]XH2O, CU(BF4)2, CU(BF4)XH2O, CU(SCN), CU(BF4)2, CU(PF6)2, CUF2or combinations thereof.

18. The rubber formulation of claim 1 or claim 2, wherein the rubber formulation further comprises a styrene-butadiene rubber, a butadiene rubber, butyl rubber, EPDM, natural rubber, polyisoprene, or combinations thereof, and wherein the styrene-butadiene rubber and the butadiene rubber do not comprise a polymerized reaction product derived from vinylbenzocyclobutane.

19. The rubber formulation of claim 1 or claim 2, wherein the statistical copolymer has a weight average molecular weight of greater than or equal to about 100 kg / mol.

20. The rubber formulation of claim 2, wherein the statistical copolymer comprises from about 0.02 wt.% to about 2 wt.% of the vinylbenzocyclobutane, based on the total weight of the statistical copolymer.

21. The rubber formulation of claim 2, wherein the statistical copolymer comprises from 1 to 15 vinylbenzocyclobutane monomer units per chain of the statistical copolymer.

22. The rubber formulation of claim 1 or claim 2, wherein the statistical copolymer comprises from about 50 wt.% to about 99.98 wt.% of the conjugated diene monomer, based on the total weight of the statistical copolymer.

23. The rubber formulation of claim 7, wherein the statistical copolymer comprises from about 5 wt.% to about 50 wt.% of the vinyl aromatic monomer, based on the total weight of the statistical copolymer.

24. The rubber formulation of claim 2, wherein the statistical copolymer has at least 1 vinylbenzocyclobutane monomer unit at an end of a polymer chain.

25. A tire sidewall comprising a run flat insert, wherein the run flat insert comprises the rubber formulation of claim 1 or claim 2.

26. The tire sidewall of claim 25, wherein the subsequent second stage cure occurs during use of the tire sidewall.

27. The tire sidewall of claim 26, wherein the subsequent second stage cure occurs when air inside a tire is released due to tire puncture, the tire comprising the tire sidewall.

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