Rubber composition for tire sidewall

Abstract

A tire sidewall rubber composition comprising, per 100 parts by weight of rubber (phr): 90–100 phr natural or synthetic polyisoprene rubber and 0–10 phr of a second diene elastomer; 20–60 phr silica having a CTAB surface area of 20–200 m² / g; a silane coupling agent in an amount providing a silane‑to‑silica weight ratio of 5–20%; and 0–5 phr carbon black. Optionally, 2–10 phr of plasticizer and a covering agent selected from triethoxy(octyl)silane, diethoxy(methyl)octylsilane, diphenylguanidine, or polyethylene glycol is included at 0.25–2% by weight of silica. When cured, the composition exhibits a loss factor (tan δ_max) <0.15 and a shear modulus G* at 10% strain of 1.0–1.8 MPa (23 °C, 10 Hz).

Description

Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USRUBBER COMPOSITION FOR TIRE SIDEWALLFIELD OF THE INVENTION

[0001] The subject matter of the present invention relates to a rubber composition having a lower hysteresis and a higher cohesion comprised predominantly of natural rubber and silica for tire sidewall applications.BACKGROUND OF THE INVENTION

[0002] Tires and other articles that are made of rubber compositions are manufactured from elastomers, e.g., natural rubber, synthetic rubber, or combinations thereof; reinforcing fillers; vulcanizing agents; and other components that improve the physical mechanical characteristics of both the uncured and the cured rubber compositions.

[0003] For rubbers useful as tire sidewalls, the rubber compositions should possess several characteristics, for example, reasonable uncured viscosity for processing, decent cured flexibility for fatigue, great cohesion for endurance, excellent anti-ozonation for antidegradation, and low hysteresis for fuel consumption. Conventional rubber compositions are generally comprised of a blend of natural rubber (“NR”) and / or synthetic polyisoprene (“IR”) and polybutadiene rubber (“BR”), reinforcing carbon black, and other components for various purposes. Such rubber compositions are generally with some compromises between rigidity, cohesion, hysteresis, and endurance for tire applications, e.g., the coupling of higher tear resistance with higher hysteresis and higher tire rolling resistance and thus higher fuel consumption.

[0004] Recently, the rubber industry is developing more “sustainable” materials for tire applications. Along these lines, natural rubber is “sustainable”, and silica can be considered “sustainable” if made from sustainable feedstocks, e.g., rice husks, such as found in patent publication number USI0899914 by Bridgestone and US20230174743 by Goodyear.

[0005] For tire sidewall applications, the uses of an elastomer blend of NR (and / or IR) and BR and a filler blend of carbon black and silica is known and have been demonstrated previously. For example, European patent application number EP3233528 by Michelin discloses a rubber composition comprised of an elastomer blend of NR and BR with more than 20 phr BR. and a filler blend of carbon black and silica with no moreInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USthan 7 phr silica. United States patent publication US9446627 by Sumitomo discloses a composition with more than 30 phr BR and no more than 15 phr un-coupled silica. United States patent publications US7732522 and US8372910 by Bridgestone disclose a composition with more than 55 phr BR and no more than 9 phr silica. Still others teach the use of a NR / BR blend with more than 20 phr BR and predominantly silica, e.g., EP3233530 by Michelin, US10738179 by Continental, US8030392 by Sumitomo, and JP6992254 by Sumitomo.SUMMARY OF THE INVENTION

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] The present invention involves a rubber composition and the method making the same, where the rubber composition is comprised of predominantly natural rubber and / or synthetic polyisoprene rubber and predominantly silica filler coupled with silane; a method in the making such rubber composition by kneading the rubber and the filler system at temperatures of 120°C to 190°C, for example, for longer than 30 seconds at higher than 140°C temperature: the resultant rubber composition having a tan delta max of less than 0.15 and a G* at 10% strain in between 1 and 1.8 MPa at 23°C and 10Hz.Surprisingly, compared to the conventional sidewall compositions, at comparable rigidity', fatigue life, and antidegradation performances, the inventive rubber compositions showed lower hysteresis, improved tensile properties, and higher tearing resistance.

[0008] In one exemplary- embodiment, a rubber composition for a tire sideyvall is disclosed comprising, per 100 parts by weight of rubber (phr): a rubber component that is comprised of 90 to 100 phr natural or synthetic polyisoprene rubber and 0 to 10 phr of a second diene elastomer rubber; a reinforcing filler system that further comprises: a silica, the amount of silica present in a range from 20 to 60 phr, the silica having a CT AB surface area 20-200 m2 / g; a silane coupling agent, yvith the silane coupling agent present in an amount sufficient to form a silane to silica ratio 5% to 20% by weight; a de minimis amount of carbon black of approximately 0 to 5 phr; and wherein the sidewall rubber composition, when cured, has a tan delta max of less than 0.15 and a G* at 10% strain in between 1.0 and 1.8 MPa tested at 23°C and 10Hz.

[0009] In another exemplary embodiment, the sidewall rubber composition second diene elastomer may be a polybutadiene.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US

[0010] In a third exemplary embodiment, the sidewall rubber composition second diene elastomer is styrene butadiene rubber.

[0011] In yet another variation of one of the above embodiments wherein the styrene butadiene rubber is functionalized.

[0012] In another exemplary embodiment, which is a variant of one of the above embodiments wherein the coupling agent is selected from the group consisting of bis(triethoxysilyl)propyl tetrasulfide, and bis(triethoxysilylpropyl) disulfide.

[0013] In another exemplary embodiment, the sidewall rubber composition of any one of the above embodiments further comprising a covering agent with the covering agent present in an amount sufficient to form a covering agent to silica ratio of 0.2%-5%.

[0014] In another embodiment in which the immediate previous embodiment’s covering agent is selected from the group consisting of triethoxy(octyl)silane, diethoxy(methyl)octylsilane. diphenylguanidine, and polyethylene glycol.

[0015] In another embodiment in accordance with any one of the previous embodiments where the sidewall rubber composition, when cured, has a tan delta max of less than 0.15 and a G* at 10% strain in between 1.1 and 1.6 MPa tested at 23°C and 10Hz.

[0016] In another embodiment in accordance with any one of the previous embodiments where it further comprising from 2 phr to 10 phr of a plasticizer.

[0017] In another embodiment in accordance with any one of the previous embodiments where no more than 65 phr of a total amount of filler is present.

[0018] In another embodiment in accordance with any one of the previous embodiments where the sidewall composition further comprises a crosslinking system comprised of an accelerator and a sulfur.

[0019] In another embodiment in accordance with any one of the previous embodiments where the composition further comprising a protection system.

[0020] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention pertains to a rubber having a low er hysteresis and a higher cohesion with predominantly natural rubber and silica; wherein the rubber is used as a tire sidewall. For purposes of describing the invention, reference now will be made inInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USdetail to embodiments and / or methods of the invention. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features or steps illustrated or described as part of one embodiment, can be used with another embodiment or steps to yield a still further embodiments or methods. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0022] Methods that are embodiments of the present invention include methods for manufacturing a tire component, such methods comprising mixing together components of a rubber composition into a non-productive mix, the components including a natural rubber or a synthetic polyisoprene, and a reinforcing silica system. Such methods further include cooling the non-productive mix and mixing a vulcanizing package into the non-productive mix to convert the non-productive mix to a productive mix.

[0023] In the rubber composition comprising components such as elastomer, filler, plasticizer, and vulcanization will be further described below.

[0024] Elastomers: The rubber elastomers suitable for use with particular embodiments of the present invention include predominantly natural rubber (NR) and polyisoprene rubber (IR). Particular embodiments of the disclosed rubber compositions may include other dienic elastomers, for example, polybutadiene rubber (BR). Also suitable for use in particular embodiments of the present invention are rubber elastomers that are copolymers and include, for example, butadiene-styrene copolymers (SBR), butadiene-isoprene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-butadicnc-styrenc copolymers (SBIR) and mixtures thereof. Preferably, the rubber elastomer of this invention is comprised of at least 90 phr of NR or at least 90 phr of IR or at least 90 phr of a combination of NR and IR.

[0025] Reinforcing silicas: The reinforcing silicas of the present invention are comprised of a silica filler system that is comprised of a silica and its associated silane chemistry. The silica may be any reinforcing silica known to one having ordinary skill in the art including, for example, any precipitated silica from glassy materials, or pyrogenic silica from silicon tetrachloride, husk silica from rice husk. The silicas can be characterized as having a BET surface area and a specific CTAB surface area both of which are less than 450 m2 / g or alternatively, between 10 and 400 m2 / g may be suitable for particular embodiments based on the desired properties of the cured rubber composition.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USParticular embodiments of rubber compositions disclosed herein may include a silica having a CTAB of between 20 and 200 m2 / g, between 30 and 190 m2 / g, or between 140 and 180 m2 / g. CTAB is measured by an internal protocol in accordance with the standard NF ISO 5794-1 appendix G of June 2010 and described in US Patent number11,11 l,360B2.

[0026] Silanization: For the silica filler system, a proportional amount of a silane coupling agent is added to the rubber composition. The silane coupling agent is generally a sulfur-containing organosilicon compound that reacts with the silanol groups of the silica during mixing and with the elastomers during vulcanization to provide improved properties of the cured rubber composition, as summarized in Sang Yoon Lee, et al., The Investigation of the Silica-Reinforced Rubber Polymers with the Methoxy Type Silane Coupling Agents. Polymers. 12, 3058 (2020). DOI: 10.3390 / polyml2123058. A suitable coupling agent is one that is capable of establishing a sufficient chemical and / or physical bond between the inorganic filler and the diene elastomer; which is at least bifunctional, having, for example, the simplified general formula "Y-T-X", in which: Y represents a functional group ("Y" function) which is capable of bonding physically and / or chemically with the inorganic filler, such a bond being able to be established, for example, between a silicon atom of the coupling agent and the surface hydroxyl (OH) groups of the inorganic filler (for example, surface silanols in the case of silica); X represents a functional group ("X" function) which is capable of bonding physically and / or chemically with the diene elastomer, for example by means of a sulfur atom; T represents a divalent organic group making it possible to link Y and X.

[0027] Silane coupling agents: Useful silane coupling agents may include polysulfide organosilanes (symmetrical or asymmetrical) such as bis(3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT sold under the name “Si69” by Evonik or bis(tri ethoxysilylpropyl) disulfide, abbreviated to TESPD sold under the name “Si75” by Evonik, polyorganosiloxanes, mercaptosilanes, blocked mercaptosilanes, such as S-(3-(triethoxysilyl)propyl) octanethioate sold by Momentive Incorporated under the name “NXT Silane”. The silane coupling agent can be premixed with other materials such as carbon blacks or inert carriers. The amount of the coupling agent in the rubber composition is defined by the ratio of the silane coupling agent to the silica filler. One such ratio is expressed as the percentage of the silane weight to the silica weight, w%, and another as the percentage of the silane weight to the silica weighted CTAB surface area,Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USs%. Particular embodiments of rubber compositions disclosed herein may include a w% between 2% and 30%, between 3% to 20%, or between 5% to 15%.

[0028] Covering agents: For the silica filler system, a proportional amount of a covering agent is also added to the rubber composition such as described in United States Patent Application Publications US20090186961A1 and US20110009547A1 by Michelin and US9365699B2 by Bridgestone. The covering agent further blocks the silanol groups of on the silica surface to reduce Payne effect; it can also be chemically reactive to further aid the formation of “Y-T-X”. Suitable covering agent includes triethoxy(octyl)silane “TEO”, diethoxy(methyl)octylsilane “DEMO”, diphenylguanidine “DPG”, and polyethylene glycol “PEG”. While these agents may be added at different stages to act for other purposes such as accelerators for the vulcanization process, the covering agents named above and as use herein are added in the mixer with the silica filler during the non-productive phase of mixing. The amount of the covering agent is defined by the weight ratio of the covering agent to the silica filler, expressed as a percentage d%. This percentage d% in the rubber compositions disclosed herein is in the range from 0.1% to 10%, preferably from 0.2% to 5%, and more preferably from 0.5% to 3%.

[0029] Carbon blacks: Carbon blacks, which are organic fillers, are well known to those having ordinary skill in the rubber compounding field. The carbon black included in the rubber compositions produced by the methods disclosed herein may, in particular embodiments for example, be in an amount of less than 10 phr, and alternatively less than 5 phr. Suitable carbon blacks are any carbon blacks known in the art and suitable for the given purpose for example, any carbon black having a BET surface area or a specific CTAB surface area both of which are less than 400 m2 / g or alternatively, between 20 and 200 m2 / g may be suitable for particular embodiments based on the desired properties of the cured rubber composition. Suitable carbon blacks of the type HAF, ISAF and SAF, for example, are conventionally used in tire treads. Non-limitative examples of carbon blacks include, for example, the N115, N134, N234, N299, N326, N330, N339, N343, N347, N375, N550 and the 600 series of carbon blacks, including, but not limited to N630, N650, N660, and N683 carbon blacks.

[0030] Other fillers: For various purposes such as appearance coloring and properties modification, other reinforcing and / or non-reinforcing fillers may also be included in present invention, for example, graphene, graphite, zeolite, bentonite, aluminosilicate, clays, talc, chalk kaolin, fiber, coal, and so forth.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US

[0031] Plasticizers: Substances to increase flexibility and reduce viscosity' and increase plasticity are generally referred to as plasticizers. Plasticizers include oils, resins (from petroleum or other natural renewable resources, e.g., sunflower seeds, citrus orange peels). Processing oils are well known to one having ordinary’ skill in the art. are generally extracted from petroleum and are classified as being paraffinic, aromatic or naphthenic ty pe processing oil, including MES and TDAE oils. Processing oils are also know n to include, among other things: plant-based oils, such as sunflow er oil, rapeseed oil and vegetable oil.

[0032] Vulcanization system: The vulcanization system is preferably, for particular embodiments, one based on sulfur “S” and on an accelerator but other vulcanization agents known to one skilled in the art may be useful as well, for example, peroxide and ionic crosslinking agents. Vulcanization agents as used herein are those materials that cause the cross-linkage of the rubber and therefore may be added only to the productive mix so that premature curing does not occur, such agents including, for example, elemental sulfur, sulfur donating agents, and peroxides. Use may be made of any compound capable of acting as an accelerator of the vulcanization of elastomers in the presence of sulfur, in particular those chosen from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated to "MBTS"), N-cyclohexyl-2-benzothiazolesulphenamide (abbreviated to "CBS"), N,N-dicyclohexyl-2-benzothiazolesulphenamide (abbreviated to "DCBS"), N-tert-butyl-2-benzothiazolesulphenamide (abbreviated to "TBBS"). N-tert-butyl-2-benzothiazole-sulphenimide (abbreviated to "TBSI") and the mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used.

[0033] The rubber composition may also include vulcanization retarders, for a vulcanization system based, for example, on sulfur or on a peroxide, vulcanization activators, and so forth. The vulcanization system may further include various known secondary accelerators or vulcanization activators, such as zinc oxide “ZnO”, stearic acid “SAD” and guanidine derivatives.

[0034] Protective agents: The rubber compositions disclosed herein may further include, in addition to the compounds already described, all or part of the components often used in diene rubber compositions intended for the manufacture of tires, such as additional protective agents of the type that include antioxidants and / or antiozonants, such as N-1,3-dimethylbuty l-N'-pheny l-p-pheny lendiamine “6PPD”, N'-bis-(l ,4-dimethylpentyl)-p-Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USphenylenediamine “77PD”, N,N'-diphenyl-p-phenylenediamine “DPPD”, 2,2,4-Trimethyl-1,2-dihydroquinoline “TMQ”, hindered phenol, and wax.

[0035] Mixing: The rubber compositions that are embodiments of the present invention may be produced in suitable mixers in a manner known to those having ordinary skill in the art. Typically, the mixing may occur using two successive preparation phases, a first phase of thermo-mechanical working at high temperature followed by a second phase of mechanical working at a lower temperature.

[0036] The first phase, sometimes referred to as a "non-productive" phase, includes thoroughly mixing, typically by kneading, the various ingredients of the composition but excluding some of the vulcanization system such as the vulcanization agents, the accelerators, the retarders. This first phase is carried out in a suitable kneading device, such as an internal mixer of the Banbury type, until under the action of the mechanical working and the high shearing imposed on the mixture, a maximum temperature of generally between 120°C and 190°C is reached, indicating that the components are well dispersed.

[0037] After cooling the mixture, a second phase of mechanical working is implemented at a lower temperature. Sometimes referred to a "productive" phase, this finishing phase consists of incorporating some of the aforementioned vulcanization system that were not added in the “non-productive” phase, including the vulcanization agents, the accelerators, and the retarders into the rubber composition using a suitable device, such as an open mill or internal mixer. It is performed for an appropriate time (typically, for example, between 1 and 30 minutes or between 2 and 10 minutes), and at a sufficiently low temperature, i.e., lower than the vulcanization temperature of the mixture, so as to protect against premature vulcanization.

[0038] The rubber composition can be formed into useful articles, including tire components. Tire treads or sidewalls, for example, may be formed as tread bands and then later made a part of a tire or they be formed directly onto a tire carcass by, for example, extrusion and then cured in a mold. Other components such as those located in the bead area of the tire or in the sidewall may be formed and assembled into a green tire and then cured with the curing of the tire.

[0039] Measurements

[0040] The characterization methods of the rubber compositions disclosed in the examples were evaluated as described below'.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US

[0041] Mooney viscosity: Mooney viscosity is an indicator of the processability of a rubber composition at uncured stage in forming an article, for example, a tire. In general, the lower the Mooney viscosity, the easier the uncured products are to be processed.Mooney viscosity is measured in accordance with ASTM Standard D1646-19a. The composition in an uncured state is molded in a cylindrical enclosure and heated to 100°C. After 1 minute of preheating, the rotor turns within the test sample at 2 rpm, and the torque used for maintaining this movement is measured after 4 minutes of rotation. The Mooney viscosity is expressed in "Mooney units" (MU, with 1 MU=0.83 Newton-meter).

[0042] The elongational strain and stress were measured at 23 °C as the break elongation (%) and the elongation stress (MPa), respectively, in accordance with ASTM Standard D412-2006a using dumbbell test samples in accordance with the standard. An elongation index, a product of the break elongational strain and stress, is an indicator of the elongational cohesiveness of the rubber compositions, and the higher the values, the more the cohesion. The elongational index is calculated by the following formula.Elongation index — (elongation strain) * (elongation stress) / 100

[0043] The tearing strain and stress were measured on rectangular 145 mm long x 10 mm wide x 2.5 mm w ide test samples cut from a cured plaque. Three slits (perpendicular to the test direction) were created in the center of the samples (6 mm apart and 3 mm deep) on one side prior to testing. The stress and strain at break were measured using an Instron 5565 Uniaxial Testing System. The crosshead speed was 500 mm / min. Samples were tested at 23° C. The tearing index, a product of the tearing strain and stress, is an indicator for the cohesive tearing performance of a rubber composition; and the higher the index, the better the tearing cohesiveness. The tearing index is calculated by the following formula.tearing index = (tearing strain) * (tearing stress) / 100

[0044] The fatigue life, expressed as the number of cycles to break, is measured in a known manner on 12 test specimens subjected to repeated low frequency tensile deformations up to an elongation of 75%, at 23°C, using a Monsanto (MFTR) machine until the test specimen breaks, according to the ASTM D4482-11(2021) standards.

[0045] The dynamic properties tan delta max and G* 10% are measured on a viscosity analyzer (Viscoanalyseur VA4000) according to standard ASTM D 5992-96 (2018). The Double Shear Specimens were used, with each of the specimens beingInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USapproximately 2.0 mm in thickness and 79 mm2in cross section. The response of a sample of vulcanized composition subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz and at a temperature of 23°C, is recorded. A strain amplitude sweep is earned out from 0.1% to 50% (outward cycle) and then from 50% to 0.1% (return cycle). The results made use of are the shear modulus G* at 10% strain and the loss factor tan delta on the return curve. The maximum value of tan delta observed, tan delta max, between the values at 0.1% and at 50% strain (Payne effect) are shown for the return cycle. For rubber applications, e.g., tires. G*10% is generally accepted as an indicator for rigi di ty while tan delta max is an indicator for hysteresis.

[0046] The static ozone surface cracking is evaluated using a test in accordance with the ASTM 1149-99 Standard Test Method for rubber deterioration titled Surface Ozone Cracking in a Chamber with differences disclosed herein. The testing utilized in the examples that follow differs in the construction of the sample holder, which was a rod rather than a wooden block holder as required under the ASTM test method. Rectangular samples are made by sheeting the green rubber, molding into a specified mold, curing at a specified cure temp and time, cooling down, cutting with a die, then folding in half and stapling such that the curvature of the loop has a maximum local strain of 18%. These samples are hung on a rod for 2 days under ambient conditions before being placed in an ozone chamber. The ozone chamber conditions are set at 50 parts per hundred million ozone (pphm) and a temperature of 40°C for a specified duration. The samples are periodically evaluated for cracks. The surface cracks of the samples are then evaluated using the Rubber Deterioration Test Grades that consists of three numbers. The first number indicates the number of cracks in the sample, the second rates the width of the cracks and the third number is the depth of the crack. The higher the numbers, the more severe the ozone cracks. Zero indicates that no cracks are observed. The ozone cracking index is the product of the three numbers determined by the Rubber Deterioration Test Grades. A normalized index is used by normalizing the index of a ‘'comparative formulation” to that of the “witness formulation”.

[0047] The dynamic ozone cracking is evaluated according to ASTM D3395-99. The samples are subjected to a cyclic strain up to 25% at 30RPM for up to 2 days in the same ozone chamber as described for static ozone cracking test. The surface cracks and the cracking indices for dynamic ozone cracking are evaluated using a 10-point index with 0 denoting no cracking and 10 denoting large, multiple cracks.

[0048] ExamplesInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US

[0049] The invention is further illustrated by the following examples, which are to be regarded only as illustrations and not delimitative of the invention in any way.

[0050] Example 1

[0051] W1 is the primary’ comparative example of the invention, representing a traditional sidewall formulation known in the literature. Sidewall formulations are ty pically a blend of NR and BR with a semi -reinforcing or reinforcing carbon black and processing aids such as petroleum oils.

[0052] Other components, denoted ‘“Others"' in the table, were included including 3phr of TMQ, 3 phr of 6PPD, 1.5 phr of Wax, 2 phr of SAD, 3 phr of ZnO, 1.5 phr of sulfur and 1.5 phr of CBS for each of the samples.

[0053] Embodiments are shown having the presence of either 30 phr (Fl) or 50 phr (F2-F5) loading of silica (SIL160 from Solvay). Silane (Si69 TESPT from Hungpai New Materials, China) loading is proportional to the silica amount as is DPG which are added during the nonproductive phase. Embodiments F2, F3, F4 and F5 differ from one another in that they have increasing amounts of Naphthenic oil added, from 0 phr to 16 phr as shown below.

[0054] Table 1 summarizes the W1 comparative example versus the inventive examples. In particular, all F examples display significantly higher tearing performance than Wl. Fl and F2 demonstrate the range of rigidity7and hysteresis possible with unexpectedly excellent hysteresis, tearing performance, and rigidity for Fl compared to Wl. F3-F5 highlight the ability to manage rigidity and achieve a good balance of Mooney, tearing performance, rigidity, and hysteresis using plasticizer.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USTable 1. NR / BR with carbon black vs. NR with silicaExample 2

[0055] Table 2 shows the impact of NR / BR ratios from a ratio of 100% NR (F6) to 100% BR (Fl 1). In general, increasing BR in the NR / BR blend resulted in higher Mooney ML, lower tearing resistance, higher hysteresis, and higher rigidity7. Preferably, silica rubber mixes containing 10 phr or less of BR displayed the best performance with tearing resistance and hysteresis degraded at higher BR loadings.Table 2. NR / BR ratioInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US

[0056] Note (1): other ingredients are 3 TMQ, 3 6PPD, 1 Wax, 2 SAD, 3 ZnO, 1.5 S, and 1.5 CBSExample 3

[0057] Table 3 shows silica at various loadings from 30 phr (F12) to 60 phr (F15) at the same silane to silica ratio and at the same DPG to silica ratio. Higher loadings of silica show increasing Mooney properties and diminishing tearing resistance at loadings greater than 50 phr of silica. Additionally, hysteresis is shown to increase with increasing amounts of silica. While positive qualities can be seen with silica loading from 20 to 60 phr, preferably the inventive mix would have a silica loading of 30 to 50 phr of silica. Table 3. Silica loadingsNote (1): other ingredients are 3 TMQ, 3 6PPD, 1 Wax, 2 SAD, 3 ZnO, 1.5 S, and 1.5 CBSExample 4

[0058] Table 4 shows different silane to silica ratios from 7% by weight of silica (F16) to 16% by weight of silica (F 19). Surprisingly, an increase of tearing resistance and fatigue performance is found at 10% loading of silane to silica. Mooney decreases with additional silane. While positive properties can be observed across the samples for a silane to silica ratio of 7% to 16% by weight, 10% to 13% by weight of silica is preferred for increased tearing resistance and reasonable Mooney.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USTable 4. Coupling agent SI69 loadingInventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USExample 5%, and most beneficially between 1 to 2%.

[0059] Table 5 shows the effect of a varying amount of DPG used as a covering agent. The DPG covering agent is added to the mix during the non-productive phase of mixing. Covering agent loadings at 1.0% of the silica amount and up decreased the Mooney improving the industrial performance in the green state and improved the rolling resistance in the cured state as observed by the decreasing max tan delta values. Marginal changes in the elongation index and shear modulus (G*) and acceptable changes in the tear index show promising use of DPG as a covering agent up to 3% of the weight of the silica and beneficial use is observed in use of DPG as a covering agent at amounts of between 0.25% and 3% of the weight of silica, more beneficially between 0.25% and 2%, and most beneficially between 1 to 2%.

[0060] Table 5. Covering agent DPG loadingExample 6Table 6 shows the use of different silica grades with variable surface areas showing an acceptable silica surface area from approximately 20 to 200 CTAB value. Beneficially, a higher silica surface area is found with CTAB values between 50 to 160 as this represents an improvement in tearing resistance with acceptable shear modulus and a moderate change in the hysteresis as shown by the max tan delta of the rubber, which translates into an acceptable rolling resistance in the final tire product.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USTable 6. Silicas of different surface area

[0061] The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

Claims

Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 USWHAT IS CLAIMED IS:

1. A tire sidewall rubber composition comprising, per 100 parts by weight of rubber (phr):a rubber component that is comprised of 90 to 100 phr natural or synthetic polyisoprene rubber and 0 to 10 phr of a second diene elastomer rubber; a reinforcing filler system that further comprises:a silica, the amount of silica present in a range from 20 to 60 phr, the silica having a CT AB surface area of 20-200 m2 / g;a silane coupling agent, with the silane coupling agent present in an amount sufficient to form a silane to silica ratio 5% to 20% by weight;a carbon black in the amount of 0.1 to 5 phr;and the sidewall rubber composition that when cured, has a tan delta max of equal to or less than 0.17 and a G* at 10% strain in between 1.0 and 2.1 MPa tested at 23°C and 10Hz.

2. The sidewall rubber composition of claim 1 wherein the second diene elastomer is a polybutadiene.

3. The sidewall rubber composition of claim 1 wherein the second diene elastomer is sty rene butadiene rubber.

4. The sidewall rubber composition of claim 3 wherein the styrene butadiene rubber is functionalized.

5. The sidewall rubber composition of any one of the above claims wherein the coupling agent is selected from the group consisting of bis(triethoxysilyl)propyl tetrasulfide, and bis(triethoxysilylpropyl) disulfide.

6. The sidewall rubber composition of any one of the above claims further comprising a covering agent with the covering agent present in an amount sufficient to form a covering agent to silica ratio of 0.2%-5%.

7. The sidewall rubber composition of claim 6 wherein the covering agent is present in an amount sufficient to form a covering agent to silica ratio of 0.25%-2%.

8. The sidewall rubber composition of claim 6 wherein the covering agent is present in an amount sufficient to form a covering agent to silica ratio of 1 -2%.Inventor: Sean Hemp et al.Attorney Docket No.: 2022PAT00320 US9. The sidewall rubber composition of claim 6 or 7 wherein the covering agent is selected from the group consisting of triethoxy(octyl)silane, diethoxy(methyl)octylsilane, diphenylguanidine, and polyethylene glycol.

10. The sidewall rubber composition of any one of the above claims wherein the sidewall rubber composition, when cured, has a tan delta max of less than 0.15 and a G* at 10% strain in between 1.0 and 1.8 MPa tested at 23°C and 10Hz.

11. The sidewall rubber composition of claim 10 wherein the sidewall rubber composition, when cured, has a tan delta max of less than 0.15 and a G* at 10% strain in between 1.1 and 1.6 MPa tested at 23°C and 10Hz.

12. The sidewall rubber composition of any one of the above claims further comprising from 2 phr to 10 phr of a plasticizer.

13. The sidewall rubber composition of any one of the above claims wherein no more than 65 phr of a total amount of filler is present.

14. The sidewall rubber composition of any one of the above claims further comprising a crosslinking system comprised of an accelerator and a sulfur.

15. The sidewall rubber composition of any one of the above claims further comprising a protection system.

16. The sidewall rubber composition of any one of the above claims wherein the silane coupling agent present in an amount sufficient to form a silane to silica ratio 10% to 13% by weight.

17. The sidewall rubber composition of any one of the above claims wherein the silica has a CTAB surface area of 50 to 160 m2 / g.

Images