Modulus recovery in silica-containing tire treads.

Abstract

A tire tread for heavy vehicles, comprising a rubber component and a reinforcing filler comprising silica and a second filler. The first and second vulcanization accelerators are used in the tire tread together with sulfur and a silane coupling agent, and the tire tread has a 300% modulus of elasticity of 8 MPa or more. The silane coupling agent, sulfur, and total reinforcing filler content in the tire tread composition are present in a ratio range of 1:0.4:0.4 to 1:1.4:1.4.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to heavy vehicle tire treads having silica content, and more particularly to heavy vehicle tire treads having selective modulus properties comparable to tire treads that do not contain silica fillers. [Background technology]

[0002] The improvement of tire tread performance and wear characteristics is often a compromise between them, since an increase in wear resistance can reduce performance, rolling resistance, and heat resistance. The raw materials of the composition are selected for their potential impact on the properties of the tire. For heavy vehicle tire treads, the selection of reinforcing fillers has focused on carbon black, and less frequently, silica is utilized for the desired performance properties. Silica can retard the rubber curing reaction compared to the use of carbon black, which can affect the performance properties of the tire tread. Summary of the Invention [Problem to be solved by the invention]

[0003] There is a need for a rubber composition that provides a heavy vehicle tire tread with an improved combination of wear performance and rolling resistance. The present invention uses a combination of materials that provides a silica-containing heavy vehicle tire tread with similar performance characteristics of non-silica tread compositions.

[0004] In a first aspect, a heavy duty vehicle tire tread is disclosed formed from a rubber composition having a rubber component, a reinforcing filler having less than 30 phr of silica per 100 parts by weight of rubber, a silane coupling agent, 0.5-2.5 phr of sulfur, and 0.5 phr or more of a first vulcanization accelerator, and optionally a second vulcanization accelerator, wherein a ratio of silane coupling agent to sulfur to total accelerator content is in the range of 1:0.6:0.6 to 1:1.4:1.4, and wherein the tire tread has a modulus of elasticity at 300% elongation of the tire tread of 8 MPa or greater.

[0005] In one example of embodiment 1, the reinforcing filler comprises up to 28 phr of silica, such as 1 to 28 phr of silica.

[0006] In another example of aspect 1, the ratio of silane coupling agent to total sulfur (e.g., free sulfur) is greater than 1:0.6, and the ratio of total sulfur to total accelerator content is from 1:0.9 to 1:1.3, or from 1:0.95 to 1:1.25, or greater than 1:1.

[0007] In another example of aspect 1, the sulfur is present at 1-2 phr and the silane coupling agent is present at 0.5-4.5 phr, 0.6-4 phr, 0.7-3 phr, or 0.8-2.5 phr.

[0008] In another example of aspect 1, the primary accelerator is a sulfenamide and the ratio of sulfur to sulfenamide is from 1:0.65 to 1:1.2.

[0009] In another example of embodiment 1, the second accelerator is present in an amount greater than or equal to 0.35 phr.

[0010] In another example of Aspect 1, the first vulcanization accelerator and the second vulcanization accelerator are present in a ratio of 1:1 to 4:1.

[0011] In another example of embodiment 1, the ratio of silane coupling agent to sulfur is from 0.75:1 to 3:1.

[0012] In another example of Aspect 1, the reinforcing filler further comprises carbon black, and the reinforcing filler has a ratio of silica to carbon black from 1:1 to 12.5:1.

[0013] In another example of the first aspect, the reinforcing filler comprises 1 to 35 phr of carbon black.

[0014] In another example of the first embodiment, the total content of the first vulcanization accelerator and the second vulcanization accelerator is in the range of 1.5 to 2.5 phr.

[0015] In another example of the first embodiment, the rubber component contains 40 to 100 parts by mass of natural rubber or polyisoprene rubber.

[0016] In another example of embodiment 1, the rubber component further contains a diene elastomer, such as polybutadiene rubber or polystyrene-butadiene rubber.

[0017] In another example of embodiment 1, the tire tread is a truck tire tread or a bus tire tread.

[0018] In a second aspect, there is provided a heavy duty vehicle tire tread formed from a rubber composition, the rubber composition comprising a rubber component, the rubber component comprising 50-90 phr of natural rubber or polyisoprene rubber, 10-50 phr of diene elastomer, and a reinforcing filler comprising, per 100 parts by weight of rubber, 30-50 phr of silica, 2-4 phr of a silane coupling agent, 1-2.5 phr of sulfur, 1 phr or more of a first vulcanization accelerator and a second vulcanization accelerator, wherein the ratio of the silane coupling agent to the sulfur to the total accelerator content in the composition is in the range of 1:0.4:0.4 to 1:0.8:0.8, and the tire tread has a modulus of elasticity at 300% elongation of 8 MPa or more.

[0019] In one example of embodiment 2, the reinforcing filler contains up to 35 phr of carbon black.

[0020] In another example of the second aspect, the first vulcanization accelerator and the second vulcanization accelerator are present in a ratio of 1.2:1 to 2.5:1.

[0021] In another example of aspect 2, the primary accelerator is a sulfenamide and the ratio of sulfur to sulfenamide is from 1:0.6 to 1:0.9.

[0022] In another example of embodiment 2, the sulfenamide is present at 1 to 1.5 phr.

[0023] In another example of embodiment 2, the sulfur is present at 1.5 to 2 phr and the silane coupling agent is present at 2.8 to 3.8 phr.

[0024] In another example of the second embodiment, the total content of the first vulcanization accelerator and the second vulcanization accelerator is in the range of 1.5 to 2.5 phr.

[0025] Any one of the above aspects (or examples of these aspects) may be provided alone or in combination with any one or more of the example aspects discussed above, e.g., the first aspect may be provided alone or in combination with any one or more of the example aspects of the first aspect discussed above, the second aspect may be provided alone or in combination with any one or more of the example aspects of the second aspect discussed above, etc.

[0026] Additional features and advantages are set forth in the following Detailed Description, and in part will be readily apparent to those skilled in the art from this description or will be recognized by practicing the embodiments described herein, including the following Detailed Description, and the claims. It should be understood that both the foregoing general description and the following Detailed Description are exemplary only and are intended to provide an overview or framework for understanding the nature and characteristics of the claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The terminology used herein is for the purpose of describing the embodiments only and is not to be construed as limiting the invention as a whole.

[0028] As used herein, when a range is given, such as 5 to 25 (or from 5 to 25), this range preferably means at least 5 or greater than 5, and separately and independently preferably no greater than 25. In one example, such a range independently specifies at least 5, and separately and independently no greater than 25.

[0029] As used herein, the terms "substantial," "substantially," and variations thereof are intended to refer to a described characteristic being equal or equivalent to a value or description. For example, a "substantially planar" surface is intended to mean a surface that is planar or nearly planar. Additionally, it should be noted that the terms "substantially" and "about" may be utilized herein to express the degree of inherent uncertainty that may result from any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to express the extent to which a quantitative representation may vary from the stated basis without resulting in a change in the basic functionality of the object in question.

[0030] The present disclosure relates to a tire tread for heavy vehicle tires. The tire tread can be a tread portion that contacts the road surface or an undertread portion that is disposed immediately below the surface contacting tread, for example adjacent to a belt area in the crown. The tire tread is suitable for use in heavy vehicle tires. Heavy vehicles include, but are not limited to, trucks (e.g., tractor-trailer semi-trucks), tractors, agricultural equipment, trailers, buses, aircraft, off-road vehicles (e.g., earth movers, dump trucks), and the like. In one or more embodiments, the tire tread for heavy vehicles does not include, is not suitable for, or is not intended for use with, passenger cars (e.g., passenger cars, vans, motorcycles) and conventional light vehicles.

[0031] Heavy vehicle tire treads are made from rubber compositions. Tire tread compositions have a rubber component that includes, for example, one, two or more rubber compounds. Both synthetic and natural rubbers may be used in the rubber composition of tire treads. These rubbers, which may also be referred to as elastomers, include, but are not limited to, natural or synthetic poly(isoprene) (natural polyisoprene is preferred), and elastomeric diene polymers including polybutadiene and copolymers of conjugated diene monomers with at least one monoolefin monomer. Synthetic polyisoprenes include, for example, synthetic cis-1,4 polyisoprene. An exemplary polybutadiene rubber is elastomeric and has a 1,2-vinyl content of about 1 to 3 percent and a cis-1,4 content of 96 to 98 percent. Another exemplary polybutadiene rubber has a low cis-1,4 content (e.g., less than 95 or 90 percent). Other butadiene rubbers having a 1,2-content up to 12 percent may also be suitable with appropriate adjustment in the levels of other components, so that virtually any high vinyl, elastomeric polybutadiene may be used. The copolymers may be derived from conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene-(isoprene), 2,3-dimethyl-1,2-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like, and mixtures of the foregoing dienes. The preferred conjugated diene is 1,3-butadiene.

[0032] With respect to the monoolefin monomers, they include vinyl aromatic monomers such as styrene, alpha-methylstyrene, vinyl naphthalene, vinyl pyridine, and the like, and mixtures of the foregoing. The copolymers may contain up to 50 weight percent monoolefins, based on the total weight of the copolymer. Preferred copolymers are those of conjugated dienes, particularly butadiene, and vinyl aromatic hydrocarbons, particularly styrene (e.g., polystyrene-butadiene rubber).

[0033] The copolymers of conjugated dienes described above and their preparation methods are well known in the art of rubber and polymers. Many of the polymers and copolymers are commercially available. It is understood that the practice of the present invention is not limited to any particular rubber included or excluded above.

[0034] In one or more embodiments, the heavy vehicle tire tread can include a rubber component containing natural rubber or polyisoprene rubber. In one example, the natural rubber, synthetic polyisoprene rubber, or combination thereof is present in the rubber component in an amount of 40-100, 50-90, 60-85, or 65-80 parts by weight, or parts by weight per 100 parts by weight of total elastomer (phr) of the rubber component, and optionally, one or more other elastomers. In another example, the rubber component of the heavy vehicle tire tread includes natural rubber in an amount of 50-90 phr or parts by weight of the rubber component, and optionally, one or more non-natural rubber elastomers (e.g., diene elastomers). In another example, the rubber component of the heavy vehicle tire tread includes a first component of natural rubber, synthetic polyisoprene rubber, or combination thereof, and a second component of a diene elastomer. The diene elastomer or combination of diene elastomers may be present in the rubber component of the heavy vehicle tire tread in an amount of from 5 to 50, 10 to 45, 15 to 40, or 20 to 35 phr or parts by weight of the rubber component.

[0035] The heavy vehicle tire tread comprises one or more reinforcing fillers or a blend of reinforcing fillers. In one or more embodiments, the heavy vehicle tire tread is made from a composition having a total reinforcing filler content in an amount of 30-80 phr, 35-65 phr, or 40, 45, 50, 55, or 60 phr. The reinforcing filler content in the tire tread composition can comprise two or more reinforcing fillers, such as at least two fillers, such as a first reinforcing filler and a second reinforcing filler, one of the reinforcing fillers being silica. The first reinforcing filler and the second reinforcing filler can be different from each other. The first reinforcing filler (e.g., silica) can be present in an amount within the range of 1-60 phr, 5-50 phr, 10-40 phr, 15-30 phr, or 20, or 25 phr. The second reinforcing filler (eg, carbon black) may be present in an amount within the range of 1 to 50 phr, 5 to 40 phr, 10 to 30 phr, or 15, 20, or 25 phr.

[0036] The surface of the carbon black and / or silica may optionally be treated or modified to improve compatibility with certain types of polymers. Such surface treatments and modifications are well known to those skilled in the art.

[0037] Additional fillers may also be utilized, including, but not limited to, mineral fillers such as clay, talc, aluminum hydrate, aluminum hydroxide, and mica. The aforementioned additional fillers are optional and may be utilized in amounts ranging from 1 phr to 40 phr.

[0038] In one or more embodiments, the reinforcing filler can include one or more suitable carbon blacks. Suitable carbon blacks are any conventional carbon blacks, such as HAF, ISAF, and SAF type carbon blacks. Further examples of carbon blacks include N115, N134, N234, N299, N330, N339, N343, N347, and N375 type carbon blacks. Carbon black fillers can be, for example, 70-150m 2The carbon black reinforcing filler has a nitrogen specific surface area N2SA in the range of 100 ml / 100 g. In another example, the carbon black reinforcing filler has a dibutyl phthalate absorption of, for example, 60 to 140 ml / 100 g. Reinforcing fillers can be selected that have one or more of the above characteristics, for example, all of the recited characteristics or various combinations thereof. When present in the reinforcing filler, the carbon black is in an amount of 1 to 50, 5 to 45, 10 to 40, or 15 to 35 phr.

[0039] Reinforcing fillers include, for example, silica, optionally in combination with a non-silica filler such as carbon black. The silica can be any conventional suitable silica. Examples of suitable silica include precipitated or pyrogenic silica, wet-process silica (hydrated silicic acid), dry-process silica (anhydrous silicic acid), calcium silicate, and the like. Of these, precipitated amorphous wet-process hydrated silica is preferred. The silica can be, for example, 500 ml 2 / g or less, or 50-400, or 100-200m 2 The silica may have a BET surface area and a specific CTAB surface area in the range of 1 / g. Some of the commercially available silicas that may be used include, but are not limited to, HiSil 190, HiSil 210, HiSil 215, HiSil 233, HiSil 243, and the like, produced by PPG Industries (Pittsburgh, Pa.). Several useful commercial grades of different silicas are also available from DeGussa Corporation (e.g., VN2, VN3), Rhone Poulenc (e.g., Zeosil 1165 MP0), and JM Huber Corporation. In one example, the silica is present in the reinforcing filler in an amount of 1-30 phr, 2-28 phr, 5-25 phr, 10-20 phr, or 15 phr, optionally in combination with another non-silica reinforcing filler. In other examples, silica is present in the reinforcing filler in an amount of 30 to 50 phr, 30 to 45 phr, or 35 to 40 phr, optionally in combination with another non-silica reinforcing filler.

[0040] In one or more embodiments, the blend of reinforcing fillers may be present in the heavy vehicle tire tread composition in a selected weight percent or phr ratio, for example, a first reinforcing filler (e.g., silica) may be present in a phr ratio to a second reinforcing filler (e.g., carbon black) that is in the range of 9:1 to 0.25:1, 4:1 to 0.5:1, 3:1 to 1.5:1, or 1:1.

[0041] Heavy vehicle tire treads may include a coupling agent, such as a silane, when silica or some other type of inorganic particles are used as reinforcing fillers. In such embodiments, the silane coupling agent may help to aid in bonding the filler (e.g., silica) to the elastomer. Examples of suitable silane coupling agents include, but are not limited to, functional polysulfide silanes, organosulfide polysulfides, and organoalkoxymercaptosilanes, bis(trialkoxysilylorgano)polysulfide silanes, and thiocarboxylate functional silanes. The amount of coupling agent in the rubber composition may be based on the weight of the silica in the composition and may be from about 0.1% to about 20% by weight of silica, from about 1% to about 15% by weight of silica, or alternatively, from about 1% to about 10% by weight of silica. In another example, the coupling agent may be present in the rubber composition in the range of 0.1 to 5 phr, 0.3 to 4.5 phr, 0.5 to 4 phr, 0.5 to 3.6 phr, 0.8 to 3 phr, or 1, 1.5, 2, 2.2, or 2.5 phr.

[0042] Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanizate. When the rubber composition contains silica, the surface chemical structure of the silica can interact with the curing reaction. The use of accelerators in non-heavy vehicle rubber compositions can be used to reduce the interactions that the silica may cause to provide comparable cure rates to rubber compositions having only carbon black as a filler. For heavy vehicle tread compositions, the use of accelerators has been found to be less effective, and the static modulus can be up to 50 percent lower compared to the same rubber composition containing all carbon black filler. It has been found that the addition of sulfur (e.g., free sulfur) at a ratio of about 20 percent of the silane coupling agent filler in combination with the accelerator can substantially maintain the static modulus of silica-containing heavy vehicle tread compositions compared to the same composition containing carbon black instead of the silica reinforcing filler.

[0043] The rubber composition may include the presence of a sulfur vulcanizing agent, such as elemental sulfur or free sulfur. The sulfur agent is used in an amount ranging from 0.5 to 4 phr, 0.8 to 3 phr, 1 to 2.5 phr, 1.2 to 2.2 phr, or 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or 2.1 phr. In one or more embodiments, the amount of sulfur vulcanizing agent present in the rubber composition is related to the content of the silane coupling agent. For example, the ratio of silane coupling agent to sulfur vulcanizing agent is in the range of 0.75:1 to 3:1, 0.8:1 to 2.75:1, 0.85:1 to 2.5:1, 0.9:1 to 2:1, 1:1.4 to 1:0.6, or 2.1:1.65, 2.1:1.35, 2:1.5, 1:1.3, 3:1.7, or 3.5:2.

[0044] As mentioned above, the sulfur vulcanizing agent is used in combination with one or more accelerators or vulcanization accelerators. In one embodiment, a single vulcanization accelerator system can be used, in which case it includes a first vulcanization accelerator or primary vulcanization accelerator. The primary vulcanization accelerator is used in a total amount ranging from, for example, 0.3 to 2.5 phr, 0.5 to 2 phr, 0.8 to 1.8 phr, or 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7 phr. In one or more embodiments, the primary vulcanization accelerator present in the rubber composition relates to the content of the sulfur vulcanizing agent. For example, the ratio of the primary vulcanization accelerator to the sulfur vulcanizing agent is in the range of 1:0.6 to 1:1.2, 1:0.7 to 1:1.1, or 1:0.8 to 1:1. The primary accelerator may be any suitable type of accelerator, such as amines, disulfides, guanidines (DPG), thioureas, thiurams, sulfenamides, dithiocarbamates, xanthates, and sulfenamides. The primary accelerator may also be a thiazole, such as a benzothiazole accelerator. Exemplary benzothiazole vulcanization accelerators may include N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), 4-oxydiethylene-2-benzothiazole sulfenamide (OBTS), N,N'-dicyclohexyll-2-benzothiazole sulfonamide (OCBS), 2-mercaptobenzothiazole (MBT), and dibenzothiazole disulfide (MBTS).

[0045] In another embodiment, a combination of a primary vulcanization accelerator and a secondary or secondary vulcanization accelerator may be used, with the secondary vulcanization accelerator being used in an equal or lesser amount compared to the primary vulcanization accelerator. The secondary vulcanization accelerator is used, for example, in a range of 0.1-1.5 phr, 0.2-1.2 phr, 0.3-1.1 phr, or in a total amount of 0.4, 0.5, 0.6, 0.7, 0.9, or 1 phr. In one or more embodiments, the secondary vulcanization accelerator present in the rubber composition is related to the content of the primary vulcanization accelerator. For example, the ratio of the primary vulcanization accelerator to the secondary vulcanization accelerator is in the range of 1:1-4:1, 1.5:1-3.5:1, or 2:1-3:1. The secondary vulcanization accelerator may be any suitable type of accelerator, such as those listed above for the primary vulcanization accelerator. In one or more embodiments, the secondary accelerator can be a guanidine compound such as diphenyl guanidine (DPG), a thiuram accelerator, a carbamate accelerator, or the like.

[0046] The total amount of vulcanization accelerators (e.g., primary and secondary vulcanization accelerators), excluding any free sulfur, in the rubber composition may be in the range of 0.8-5 phr, 1-4 phr, 1.2-3 phr, or in the range of 1.4, 1.5, 1.6, 1.8, 2, 2.2, 2.4, 2.5, 2.6, or 2.8 phr. The total amount of vulcanization accelerators may be expressed relative to the amount of silane coupling agent and sulfur (free sulfur present) in the rubber composition. For example, the ratio of silane coupling agent to sulfur to total vulcanization accelerator content is in the range of 1:0.4:0.4-1:1.4:1.4, 1:0.6:0.6-1:1.2:1.2, or 1:0.8:0.8-1:1:1.

[0047] Other ingredients that may be used in the rubber compositions of certain embodiments disclosed herein are well known to those skilled in the art and include oils (for processing and extension), waxes, processing aids, tackifying resins, reinforcing resins, peptizers, and one or more additional rubbers.

[0048] Various types of processing and extending oils may be utilized, including, but not limited to, aromatic, naphthenic, and low PCA oils. In one or more embodiments, the total amount of oil (processing and extending oils) used in the rubber compositions and methods disclosed herein ranges from 1 to 70 phr, 2 to 60 phr, or 3 to 50 phr.

[0049] Various antioxidants are known to those skilled in the art and may be utilized in the rubber compositions of certain embodiments, including, but not limited to, phenolic antioxidants, amine phenolic antioxidants, hydroquinone antioxidants, alkyl diamine antioxidants, and amine compound antioxidants such as N-phenyl-N'-isopropyl-p-phenylenediamine (IPPD) or N-(1,3-dimethylbutyl)-N'-phenyl-phenylenediamine (6PPD). In certain embodiments, one or more types may be utilized, with the total amount of antioxidants used being between 0.1 and 6 phr.

[0050] Further disclosed herein are methods for preparing rubber compositions. The rubber compositions can generally be formed by mixing together the raw materials of the rubber composition (as disclosed above) by methods known in the art, such as, for example, compounding the raw materials in a Banbury mixer or a roll mill. These methods generally include at least one non-productive masterbatch mix stage and a final productive mix stage. The term non-productive masterbatch stage is known to those skilled in the art and is generally understood to be a mix stage in which no vulcanizing agents or vulcanization accelerators are added. In certain embodiments of the compositions and methods disclosed herein, two or more non-productive masterbatch mix stages may be used. The term final productive mix stage is also known to those skilled in the art and is generally understood to be a mix stage in which vulcanizing agents and vulcanization accelerators are added in the rubber composition.

[0051] In certain embodiments of the method for preparing a rubber composition according to embodiments disclosed herein, the non-productive masterbatch mix stage may be carried out at a temperature of about 130° C. to about 200° C. In certain embodiments, the final productive mix stage may be carried out at a temperature below the vulcanization temperature to avoid undesired pre-curing of the rubber composition. Thus, the temperature of the productive mix stage should not exceed about 120° C., and is typically about 40° C. to about 120° C., or about 60° C. to about 110° C., and particularly about 75° C. to about 100° C.

[0052] For certain embodiments disclosed herein, the list of ingredients should be understood to include ingredients that are mixed to form the rubber composition. For other embodiments disclosed herein (i.e., rubber compositions that have been subjected to curing), the list of ingredients should be understood to include ingredients that are present in the cured rubber composition.

[0053] As previously discussed, certain embodiments disclosed herein include tires and tire treads comprising the rubber composition of the second embodiment as otherwise disclosed herein, i.e., comprising at least one rubber, silica (e.g., greater than 30 phr), a silane coupling agent, 0.5 to 2.5 phr sulfur, and one or more vulcanization accelerators, with the ratio of silane coupling agent to sulfur to total accelerator content being in the range of 1:0.6:0.6 to 1:1.4:1.4. More specifically, the disclosure includes tires comprising the rubber composition of the embodiments as otherwise disclosed herein, tires with tire treads comprising the rubber composition of the embodiments as otherwise disclosed herein, and tire treads comprising the rubber composition of the embodiments as otherwise disclosed herein. Generally, when the rubber compositions of the embodiments disclosed herein are utilized in tires, tire treads, or other components, these compositions are processed into tire components by conventional tire manufacturing techniques, including standard rubber shaping, molding, and curing techniques. Any of a variety of rubber tire components may be made, including, but not limited to, treads. Typically, vulcanization of tire components is accomplished by heating the vulcanizable composition in a mold, which may be heated, for example, to about 140°C to about 180°C. The cured or crosslinked rubber composition may be referred to as a vulcanizate, which generally contains a thermoset three-dimensional polymer network. Other ingredients, such as processing aids and fillers, may be uniformly dispersed throughout the vulcanized network. In certain embodiments, pneumatic tires containing the rubber compositions disclosed herein may be manufactured as discussed in U.S. Pat. Nos. 5,866,171, 5,876,527, 5,931,211, and 5,971,046, which are incorporated herein by reference.

[0054] The following examples have been prepared and tested to demonstrate the practice of the present invention. However, these examples should not be considered as limiting the scope of the present invention. Many modifications to these specific examples are possible without departing from the spirit and scope of the embodiments of the present disclosure. More specifically, the specific rubbers, fillers, and other ingredients (e.g., curative package ingredients and accelerators) utilized in the following examples should not be construed as limiting, since other such ingredients consistent with the disclosure in the detailed description of the invention can be utilized instead. In other words, the specific rubbers, fillers, and other ingredients in the following examples, as well as their amounts and their relative amounts, should be understood to apply more general contents than those in the detailed description of the invention.

[0055] Example 1 Table 1 below lists the components of sample tread rubber compositions made to determine composition properties at various loadings of silica, silane coupling agent, sulfur, and vulcanization accelerator. Composition A is a reference composition containing only carbon black filler and no silica compared to compositions B-F. Compositions B-F contain constant amounts of both carbon black and silica. All loadings are listed as parts per hundred parts rubber (phr). All compounded final sample stocks were sheeted and subsequently cured at 145°C for 33 minutes.

[0056] [Table 1]

[0057] Table 2 below lists the post-cure properties (e.g., tensile) of the sample tread rubber compositions (compositions A-F) of Table 1. The abbreviations Eb and Tb are used for elongation at break and stress at break, respectively, and these measurements provide an indication of the tear resistance of the rubber composition, which is of particular concern when incorporated into a tire tread. The abbreviations M50 and M300 are used for tensile stress or modulus at 50% and 300% elongation. The abbreviation E' is used for dynamic storage modulus, which provides a measure of the hardness of the rubber composition.

[0058] [Table 2]

[0059] Compositions C, E, and F exhibited M50 and M300 moduli comparable to the silica-free reference composition A, thus demonstrating that the addition of free sulfur with additional accelerator can bring the modulus of a silica-containing composition (e.g., 20-30 phr) back closer to that of a carbon black composition. More specifically, compositions C, E, and F had silane coupling agent:free sulfur:total accelerator ratios of about 1:0.8:0.8, about 1:0.8:1, and about 1:0.65:0.9. Compositions C, E, and F each had an M50 modulus equal to or greater than composition A, and an M300 modulus greater than 8 MPa and within about 24, about 6, and about 25 percent, respectively, of that measured for composition A.

[0060] Table 3 below lists the components of sample tread rubber compositions made to determine the composition properties at various loadings of silica, silane coupling agent, sulfur, and vulcanization accelerator. In comparison to compositions H-M, composition G is a reference composition containing only carbon black filler and no silica. Compositions H-M contain both carbon black and silica in various ratios, e.g., 3:1 to 1:9. All loadings are listed as parts per hundred parts of rubber (phr). All compounded final sample stocks were sheeted and subsequently cured at 145°C for 33 minutes.

[0061] [Table 3]

[0062] Table 4 below lists the post-cure properties (eg, tensile strength) of the sample tread rubber compositions of Table 3 (Compositions G through M).

[0063] [Table 4]

[0064] Compositions H, J, L, and M exhibited M50 and M300 moduli comparable to the silica-free reference composition G, thus demonstrating that the addition of free sulfur with additional accelerator can bring the modulus of a silica-containing composition back closer to that of a carbon black composition. More specifically, compositions H, J, L, and M had silane coupling agent:free sulfur:total accelerator ratios of about 1:1.3:1.3, about 1:0.75:0.75, about 1:0.6:0.6, and about 1:0.5:0.5 for compositions containing silica contents of 10 to 50 phr. Compositions H, J, L, and M had M50 moduli approximately equal to or greater than composition G, and M300 moduli greater than 8.5 MPa and within 10 to 20 percent of that measured for composition G. Specifically, composition H exhibited M300 and M50 moduli less than 1% and less than about 3%, respectively, compared to composition G. Composition J exhibited M300 and M50 moduli within about 10% and about 4%, respectively, compared to composition G. Composition L exhibited M300 and M50 moduli within about 10% and more than about 2%, respectively, compared to composition G. Finally, composition M exhibited M300 and M50 moduli within and equal to about 18%, respectively, compared to composition G.

[0065] In contrast, compositions I and K exhibited M300 less than 8 MPa and 25% lower than composition G. Compositions I and K also exhibited lower M50 modulus compared to composition G, which was 10% lower than composition G. Compositions I and K had silane coupling agent:free sulfur:total accelerator ratios of about 1:0.55:0.8 and about 1:0.35:0.65, respectively, showing that when the silane coupling agent to sulfur ratio falls below 1:0.6, the modulus is undesirably reduced in silica-containing compositions compared to the same compositions in which silica is replaced with carbon black as a filler, even when the total accelerator content is greater than the free sulfur.

[0066] While various aspects and embodiments of the compositions and methods have been disclosed herein, other aspects and embodiments will be apparent to those of ordinary skill in the art. The various aspects and embodiments disclosed herein are for illustrative purposes only and are not intended to limit the true scope and spirit of the invention, as set forth in the appended claims. [1] 1. A heavy duty vehicle tire tread formed from a rubber composition, the rubber composition comprising a rubber component and, per 100 parts by weight of rubber: a. a reinforcing filler comprising silica, said silica being present at less than 30 phr; b. a silane coupling agent; c. 0.5 to 2.5 phr of sulfur; d. 0.5 phr or more of a first vulcanization accelerator; e. optionally, a second vulcanization accelerator; the ratio of the silane coupling agent to the sulfur to the total accelerator content in the rubber composition is within a range of 1:0.6:0.6 to 1:1.4:1.4; A tire tread for large vehicles, wherein the tire tread has an elastic modulus of 8 MPa or more at 300% elongation. [2] 2. The tire tread for heavy vehicles according to claim 1, wherein the reinforcing filler comprises 28 phr or less of silica. [3] 2. The tire tread for heavy vehicles according to claim 1, wherein the sulfur is present in an amount of 1 to 2 phr and the silane coupling agent is present in an amount of 0.8 to 4.5 phr. [4] The tire tread for heavy vehicles according to the above [1], wherein the first vulcanization accelerator is a sulfenamide, and the ratio of the sulfur to the sulfonamide is 1:0.65 to 1:1.2. [5] 2. The tire tread for heavy vehicles according to claim 1, wherein the second vulcanization accelerator is present in an amount of 0.35 phr or more. [6] The tire tread for heavy vehicles according to the above [1], wherein the first vulcanization accelerator and the second vulcanization accelerator are present in a ratio of 1:1 to 4:1. [7] The tire tread for large vehicles according to the above [1], wherein the ratio of the silane coupling agent to the sulfur is from 0.75:1 to 3:1. [8] 2. The tire tread for heavy vehicles according to claim 1, wherein the reinforcing filler further comprises carbon black, and the reinforcing filler comprises a ratio of the silica to the carbon black of 1:1 to 12.5:1. [9] 9. The tire tread for heavy vehicles according to claim 8, wherein the reinforcing filler comprises 1 to 35 phr of carbon black.

[10] The tire tread for large vehicles according to the above [1], wherein a total content of the first vulcanization accelerator and the second vulcanization accelerator is within a range of 1.5 to 2.5 phr.

[11] The tire tread for large vehicles according to the above [1], wherein the rubber component comprises 40 to 100 parts by mass of natural rubber or polyisoprene rubber and 5 to 50 parts by mass of polybutadiene rubber or polystyrene-butadiene rubber.

[12] A heavy-duty vehicle tire tread formed from a rubber composition, the rubber composition comprising a rubber component, the rubber component comprising 50 to 90 phr of natural rubber or polyisoprene rubber, 5 to 50 phr of a diene elastomer, and per 100 parts by weight of rubber: a. 30 to 50 phr of a reinforcing filler containing silica; b. 2 to 4 phr of a silane coupling agent; c. 1 to 2.5 phr of sulfur; d. 1 phr or more of a first vulcanization accelerator; e. a second vulcanization accelerator; the ratio of the silane coupling agent to the sulfur to the total accelerator content in the rubber composition is within a range of 1:0.4:0.4 to 1:0.8:0.8; A tire tread for large vehicles, wherein the tire tread has an elastic modulus of 8 MPa or more at 300% elongation.

[13] The tire tread for heavy vehicles according to the above

[12] , wherein the first vulcanization accelerator and the second vulcanization accelerator are present in a ratio of 1.2:1 to 2.5:1.

[14] 13. The heavy vehicle tire tread according to claim 12, wherein the primary accelerator is a sulfenamide, the sulfenamide being present at 1 to 1.5 phr and the ratio of the sulfur to the sulfenamide is from 1:0.6 to 1:0.9.

[15] The tire tread for heavy vehicles according to the above

[12] , wherein the sulfur is present in an amount of 1.5 to 2 phr, the silane coupling agent is present in an amount of 2.8 to 3.8 phr, and the total content of the first vulcanization accelerator and the second vulcanization accelerator is in the range of 1.5 to 2.5 phr.

Claims

1. 1. A heavy duty vehicle tire tread formed from a rubber composition comprising: The rubber composition comprises a rubber component and, per 100 parts by weight of rubber, a. a reinforcing filler comprising silica and carbon black, wherein the ratio of said silica to said carbon black is in the range of 9:1 to 1:1; b. a silane coupling agent; c. 0.5 to 2.5 phr sulfur; d. 0.5 phr or more of a first vulcanization accelerator; e. optionally, a second vulcanization accelerator; the ratio of the silane coupling agent to the sulfur to the total vulcanization accelerator content in the rubber composition is within a range of 1:0.6:0.6 to 1:1.2:1.2; The elastic modulus of the tire tread at 300% elongation is 8 MPa or more, The heavy vehicle tire tread, wherein the heavy vehicle is one selected from the group consisting of trucks, tractors, agricultural equipment, trailers, buses, aircraft, and off-road vehicles.

2. 2. The heavy vehicle tire tread of claim 1, wherein said sulfur is present from 1 to 2 phr, said silane coupling agent is present from 0.8 to 4.5 phr, and said reinforcing filler comprises up to 28 phr of silica.

3. 2. Heavy vehicle tire tread according to claim 1, wherein said first vulcanization accelerator is a sulfenamide and the ratio of said sulfur to said sulfenamide is from 1:0.65 to 1:1.

2.

4. 2. The heavy vehicle tire tread according to claim 1, wherein said first vulcanization accelerator and said second vulcanization accelerator are present in a ratio of 1:1 to 4:

1.

5. 2. Heavy vehicle tire tread according to claim 1, wherein said rubber component comprises 40 to 100 parts by weight of natural rubber or polyisoprene rubber and 5 to 50 parts by weight of polybutadiene rubber or polystyrene-butadiene rubber.

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