Tire tread

Abstract

A tread comprising at least one elastomer and at least 15 phr of silica is disclosed herein, the tread having a low total concentration of defects and / or voids resulting from particles (e.g., silica, carbon black).

Description

[Technical Field]

[0001] A silica-containing tire tread having a low defect concentration is disclosed herein. [Background technology]

[0002] Many commercially important products are formed from elastomer compositions in which a reinforcing filler is dispersed in one or more elastomers, such as synthetic elastomers, natural rubber, or mixtures of such elastomers. The compositions or masterbatches formed by mixing the reinforcing filler with elastomers are then formulated with processing and curing additives. Various products are cured to produce, for example, pneumatic and non-pneumatic or solid tires for vehicles, including tread portions such as caps, bases, and undertreads.

[0003] Carbon black is often incorporated into tires, for example, as a reinforcing filler for rubber compounds incorporated as tire treads. Silica is also commonly used in tire applications and can offer certain performance advantages over carbon black-based tire treads, such as improved rolling resistance. However, with respect to silica-based compounds, there is a trade-off in that these compounds exhibit poorer wear performance compared to, for example, natural rubber-containing compounds. Therefore, there is a need to provide silica-containing rubber compounds that can optimize both wear characteristics and rolling resistance characteristics. [Overview of the Initiative]

[0004] One embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is defined by a value A, which is the area ratio of defects in a 1 μm thick rubber slice. T It has a low total defect concentration as indicated by A T (i)~(vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, A T ≤2.7%, (ii) For defects having an area equivalent diameter of at least 3 μm, A T ≤ 1.4%, (iii) For defects having an area equivalent diameter of at least 4 μm, A T ≤ 0.75%, (iv) For defects having an area equivalent diameter of at least 5 μm, A T ≤ 0.5%, (v) For defects having an area equivalent diameter of at least 6 μm, A T ≤ 0.33%, and (vi) For defects having an area equivalent diameter of at least 10 μm, A T ≤ 0.15% satisfies at least one of the above.

[0005] Another aspect is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread has a low total defect density determined as the number of defects per area of a 1 - μm thick rubber slice, N T which is represented by N T and N satisfies (i) - (vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, N T ≤ 1700 / mm 2 , (ii) For defects having an area equivalent diameter of at least 3 μm, N T ≤ 950 / mm 2 , (iii) For defects having an area equivalent diameter of at least 4 μm, N T ≤ 250 / mm 2 , (iv) For defects having an area equivalent diameter of at least 5 μm, N T ≤ 100 / mm 2 , and (v) For defects having an area equivalent diameter of at least 6 μm, N T ≤ 50 / mm 2 satisfies at least one of the above.

[0006] Another embodiment is a tread comprising at least one elastomer and at least one silica of at least 15 phr, wherein the tread is defined by a value A, which is the area ratio of the voids in a rubber slice with a thickness of 1 μm. V It has a low void concentration as indicated by A V (i)~(vi), that is, (i) For a void having an area equivalent diameter of at least 2 μm, A V ≤0.6%, and (ii) For a void having an area equivalent diameter of at least 3 μm, A V ≤0.4% It satisfies at least one of the following conditions.

[0007] Another embodiment is a tread comprising at least one elastomer and at least one silica of at least 15 phr, wherein the tread is defined by a value N, which is the number of voids per unit area of ​​a 1 μm thick rubber slice. V It has a low void concentration as indicated by N V (i)~(vi), that is, (i) For a void having an area equivalent diameter of at least 2 μm, N V ≤500 / mm 2 , (ii) For a void having an area equivalent diameter of at least 3 μm, N V ≤150 / mm 2 , and (iii) For a void having an area equivalent diameter of at least 4 μm, N V ≤65 / mm 2 It satisfies at least one of the following conditions.

[0008] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is based on formula A T ≦a·e -bx It has a low total defect concentration as shown by +c, where x = silica packing amount (phr), and A T This represents the area ratio of defects in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a=4, b=0.08, and c=1.9, (ii) For defects having an area equivalent diameter of at least 3 μm, a=2.4, b=0.07, and c=1, (iii) For defects having an area equivalent diameter of at least 4 μm, a=0.8, b=0.008, and c=0.09, (iv) For defects having an area equivalent diameter of at least 5 μm, a = -0.73, b = 0.15, and c = 0.93, and (v) For defects with an area equivalent diameter of at least 6 μm, a = -5.26, b = 0.001, and c = 5.38 It satisfies at least one of the following conditions.

[0009] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is of formula N T ≦a·e -bx It has a low total defect concentration as shown by +c, where x = silica packing amount (phr), and N T This is the number of defects per unit area in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a=2500, b=0.007, and c=0, (ii) For defects having an area equivalent diameter of at least 3 μm, a=1500, b=0.018, and c=0, (iii) For defects having an area equivalent diameter of at least 4 μm, a=580, b=0.14, and c=240, (iv) For defects having an area equivalent diameter of at least 5 μm, a=-30, b=0.01, and c=120, (v) For defects with an area equivalent diameter of at least 6 μm, a = -590, b = 0.0014, and c = 611 It satisfies at least one of the following conditions.

[0010] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is based on formula A V ≦a·e -bx It has a low void concentration as shown by +c, where x = silica packing amount (phr), and A V This is the area ratio of voids in a tread slice with a thickness of 1 μm, where (i) and (ii) are, (i) For voids having an area equivalent diameter of at least 2 μm, a=3.3, b=0.037, and c=0.1, (ii) For voids having an area equivalent diameter of at least 3 μm, a=2.3, b=0.075, and c=0.28 It satisfies at least one of the following conditions.

[0011] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is of formula N V ≦a·e -bx It has a low void concentration as shown by +c, where x = silica packing amount (phr), and N V This is the number of voids per unit area in a tread slice with a thickness of 1 μm, i.e., (i) and (ii), (i) For voids having an area equivalent diameter of at least 2 μm, a=800, b=0.02, and c=400, (ii) For voids having an area equivalent diameter of at least 3 μm, a=480, b=0.1, and c=170 It satisfies at least one of the following conditions.

[0012] In any embodiment disclosed herein, the total defect concentration satisfies at least one of (i) to (v), at least one of (i) to (iv), at least one of (i) to (iii), or (i) or (ii).

[0013] Another embodiment is a tread comprising at least one elastomer and at least one silica in an amount of at least 15 phr, wherein a tire having the tread has one or more of the following: a rolling resistance coefficient of RRc of 7 N / kN or less, a normalized rolling resistance coefficient of 95 or less, a normalized rolling resistance reduced by 10% compared to an equivalent design tire tread having an equivalent amount of carbon black filler, an equivalent or reduced tread wear rate compared to an equivalent design tire tread having an equivalent amount of carbon black filler, a normalized rolling resistance reduced by 10% compared to a tire tread obtained from a dry mixed equivalent prepared from a dry filler and a solid elastomer, and an equivalent or reduced tread wear rate compared to a tire tread obtained from a dry mixed equivalent prepared from a dry filler and a solid elastomer.

[0014] With respect to any aspect or embodiment disclosed herein, where applicable, the tire tread is, in the following embodiments, namely, silica present in an amount of at least 20 phr, silica being precipitated silica, silica being rice husk silica, silica being 80 m 2 / g to 350m 2 The CTAB surface area must be in the range of up to / g, and the silica must be 140m 2 / g to 250m 2 This may further include having a CTAB surface area in the range of up to / g.

[0015] With respect to any aspect or embodiment disclosed herein, where applicable, the tire tread may further include, namely, one or more of the following embodiments: the tire tread further comprises at least one additional filler selected from carbonaceous materials, carbon black, nanocellulose, lignin, clay, nanoclay, metal oxides, metal carbonates, pyrolysis carbon, recycled carbon, recovered carbon black, graphene, graphene oxide, reduced graphene oxide, high-density reduced graphene oxide granules, carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanostructures, fibrous fillers, hydrothermal carbon, nanocrystalline cellulose starch particles, polysaccharides, glucans, dextran, microfibrillated cellulose, starch, siliceous earth, crumb rubber, and functionalized crumb rubber, or combinations thereof, and coated and treated materials, with silica present in an amount ranging from 25% to 99% by weight, and at least one additional filler present in an amount ranging from 1% to 75% by weight relative to the total weight of the fillers.

[0016] With respect to any aspect or embodiment disclosed herein, where applicable, the tire tread is, in the following embodiments, namely, at least one elastomer is natural rubber, functionalized natural rubber, styrene-butadiene rubber, functionalized styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, polybutadiene rubber, functionalized polybutadiene rubber, polyisoprene rubber, ethylene-propylene rubber, isobutylene-based elastomer, polychloroprene rubber, nitrile rubber, hydrogenated nitrile rubber, polysulfide rubber, polyacrylate elastomer, fluoroelastomer, perfluoroelastomer, silico The material may further include one or more of the following: being selected from elastomers, thermoplastic block copolymers, and mixtures thereof; at least one elastomer being selected from natural rubber, styrene-butadiene rubber, polybutadiene rubber, and mixtures thereof; at least one elastomer containing natural rubber in an amount of at least 20% by weight relative to the total weight of the elastomers; at least one elastomer being natural rubber; or at least one elastomer being a mixture containing natural rubber and at least one of styrene-butadiene rubber and polybutadiene rubber.

[0017] With respect to any aspect or embodiment disclosed herein, where applicable, the tire tread may further include one or more of the following embodiments, namely, the tire tread being selected from truck and bus radial (TBR) tire treads, off-road (OTR) tire treads, passenger car tire treads, performance car tire treads, light truck tire treads, motorcycle tire treads, electric vehicle tire treads, and heavy equipment tire treads.

[0018] With respect to any aspect or embodiment disclosed herein, where applicable, the tire tread may further include one or more of the following embodiments, namely, the tire tread being obtained from a composite formed by mixing silica as wet silica with at least one elastomer as a solid elastomer. [Modes for carrying out the invention]

[0019] A silica-containing tire tread (containing silica filler dispersed in at least one elastomer) is disclosed herein, which provides excellent rolling resistance performance in a tire. Surprisingly, the tire tread also provides wear performance at least equivalent to that of an equivalent tread having carbon black filler.

[0020] Tires and tire treads contain a rubber compound selected according to the desired tire size, grade, and purpose. Treads are typically manufactured from an elastomer compound reinforced with fillers such as carbon black and / or silica. While many known mixing techniques exist to optimize the dispersion of fillers in the elastomer, most commercially available mixing techniques fail to achieve the excellent uniformity of filler dispersion that can provide performance benefits. As a result, a significant amount of undispersed filler remains in the rubber compound, acting as a source of defects in the rubber that can reduce one or more of the following: rubber fatigue life, tear strength, and abrasion resistance.

[0021] While the quantification of carbon black dispersion (e.g., macrodispersion) is of great interest, numerous rubber compounds exist that contain significant amounts of particles other than carbon black. For example, many rubber products, including tire treads, incorporate silica as a filler. Zinc oxide (ZnO) is a common active ingredient and is present in many rubber formulations. Like carbon black, certain portions of these other particle types remain undispersed. Light transmission microscope images of thin rubber slices containing carbon black, silica, and other particles may show numerous dark spots, gray spots, and bright spots. Because carbon black has high light absorption properties, dark spots resulting from undispersed carbon black usually provide sufficient contrast against the background (gray). This contrast provides clues for measuring carbon black dispersion through image analysis. However, silica and zinc oxide have poor light absorption properties, posing challenges in their measurement and analysis through light microscopy. These particles, much like undispersed carbon black, have the potential to act as sources of defects. As a result, for more complex rubber formulations containing components other than carbon black, a more complete picture of the macrodispersion may not be observed by optical microscopy. It has been found that undispersed silica and zinc oxide can be quantified using electron microscopy, as described below.

[0022] Furthermore, surprisingly, it has been found that numerous defect types, including undispersed carbon black, undispersed silica, zinc oxide, and voids (cracks, fissures, cavities, and similar), can be prevalent in reinforced elastomer materials, including commercial tire treads. Undispersed carbon black, undispersed silica, zinc oxide, and voids are all defects in rubber materials, and voids can be considered an additional defect type to particulate defects (e.g., undispersed carbon black, silica, and zinc oxide). Since voids are essentially empty spaces without solid or liquid, they can be identified and quantified as bright objects in light transmission microscope images of thin rubber slices. Overall, all defects described herein—namely, undispersed carbon black, undispersed silica, zinc oxide, and voids—are defects that can lead to larger cracks, fractures, and cavities, resulting in degradation of the rubber compound. Combinations of such defects in treads can lead to poor performance, such as wear.

[0023] A novel tire tread is disclosed herein, comprising silica filler having the low-concentration defect type described herein. Such low-concentration defects have not been observed to date in any known tire tread.

[0024] One embodiment is a tire tread having a low total defect concentration. As used herein, “total defect concentration” refers to the measured amount of defects in the tread resulting from a combination of particles and voids. More specifically, the total defect concentration may be the sum of undispersed fillers (e.g., carbon black and / or silica), zinc oxide, and particle filler defects such as voids. The total defect concentration may be determined by a combination of light microscopy and electron microscopy.

[0025] While we do not wish to be bound by any theory, undispersed carbon black, undispersed silica, zinc oxide, and voids can have a significant impact on performance (e.g., tread performance). Particle defects can lead to cracks and cavities, and voids can be considered pre-existing cracks and cavities in the compound, representing progression steps toward rubber degradation. While we do not wish to be bound by any theory, cracks and cavities due to particle defects and voids are expected to increase in size due to concentrated stress under the widespread compressive stresses repeatedly experienced by tire rolling on the road, leading to increased cracking on the tire surface and resulting in rubber tread loss. While we do not wish to be bound by any theory, a reduction in total defect concentration or voids alone can lead to improved rubber properties and performance. Therefore, tire treads with low concentrations of total defects and / or voids, i.e., low void concentration, are disclosed herein.

[0026] Alternatively, the defect concentration (total defect concentration and / or void concentration) can be determined by analyzing microtome sections of the tread. Microtome sections may have a thickness of 2 μm or less, 1.5 μm or less, or 1 μm or less, for example, 0.5 μm to 2 μm, 0.5 μm to 1.5 μm, for example, about 1 μm. Any part of the tread can be measured. Alternatively, the total defect concentration can be measured by sampling the center of the tread. The center of the tread can refer to the geometric center, i.e., the radial center of the tire (i.e., half the tread depth) and the lateral center (the center of the lateral cross-section). For example, the sample may be taken from the center of the lateral cross-section at half the tread depth, e.g., ±20%, ±10%, or ±5% of the tread depth. Alternatively, the center of the tread may refer to the geometric center of the tread block, which is the center of a continuous block without grooves at half the tread depth, e.g., the center of a rib or lug. Typically, tire treads have thicknesses ranging from 4 mm to 150 mm. Other thicknesses may range from 9 mm to 33 mm for TBR tire treads, from 9 mm to 150 mm (e.g., 60 mm to 150 mm) for OTR tire treads, and from 4 mm to 15 mm for passenger car tire treads. While we do not wish to be bound by any theory, it is believed that voids are created, at least partially, by the formation of vapor from residual moisture during the curing process. While we do not wish to be bound by any theory, it can be assumed that the center of the tread or tread block usually contains the highest concentration of voids relative to the outer portion of the tread, at least partially, because the paths required for vapor to diffuse from the rubber are longer. Reducing the void concentration, and therefore the total defect concentration, from the center of the tread may consequently result in a reduction in the number of void defects from the rest (e.g., outer) portion of the tread.

[0027] Alternatively, the concentration of defects can be determined by microscopy. For example, undispersed carbon black and voids can be determined by light microscopy of microtome sections of the tread. Light microscopy can be performed in transmission mode, e.g., light transmission microscopy (TLM). The light image (in transmission mode) of a microtome section typically shows a light background where dark objects exist, each object being the result of an aggregate of carbon black aggregates. When the image is viewed in two-dimensional space, each dark object covers an area that can be likened to a type of “particle.” (For carbon black, the term “particle” is intended to represent the area coverage of carbon black aggregates and is distinguished from “primary particles” that form a single carbon black aggregate.) This particle “diameter” is defined herein as the “area equivalent circle diameter” of the filler and is typically in the micron size range. Thus, the dispersion state can be indicated by the form of the particle size distribution, whether it be the area coverage of particles or the number of particles per unit area of ​​a particular size.

[0028] The concentration or amount of undispersed carbon black and voids can be determined by optical microscopy, such as light transmission microscopy. Alternatively, void concentration can be determined by optical microscopy in transmission mode on a microtome section of the tread, as it appears as a bright object. Alternatively, the amounts of undispersed silica, zinc oxide, and voids can also be measured by scanning electron microscopy (SEM) using a backscatter electron detector on a microtome section of the tread placed on an indium tin oxide (ITO) coated slide. The use of an ITO substrate can alter or improve the contrast of undispersed silica, zinc oxide, and voids against the background in SEM images. Alternatively, after cooling the tread to a temperature around or below the rubber-glass transition temperature, for example, below approximately -20°C, for example, below approximately -30°C, below approximately -50°C, below approximately -100°C, for example, between -20°C and -130°C, between -50°C and -130°C, or between -100°C and -130°C, the tread may be cut into microtome sections. The cooled microtome sections may then be placed on an ITO-coated slide and warmed to room temperature before measurement by light microscope or SEM.

[0029] Undispersed silica and / or zinc oxide cannot be reliably detected by optical microscopy due to insufficient contrast; however, they can be detected by scanning electron microscopy (SEM). Alternatively, SEM measurements can be performed using a backscattered electron (BSE) detector, i.e., SEM / BSE, which provides high contrast between the metal oxides and carbon black or rubber due to the much higher electron backscattering efficiency of silicon and zinc atoms, which have a much higher number of atoms than carbon atoms. This mechanism allows silica and zinc oxide to be detected as light gray objects against a darker rubber and carbon black background. The electron beam acceleration voltage can be adjusted so that the beam has a penetration depth in the rubber that is longer than the thickness of the rubber slice, in order to detect all undispersed silica and zinc oxide in a thin rubber slice from their backscattered electrons. This is very similar to optical transmission microscopy, which detects all undispersed carbon black in a rubber slice rather than just undispersed silica and zinc oxide on the rubber surface using a conventional secondary electron detector. As an alternative, contrast can be further improved by placing rubber on a slide with an indium tin oxide (ITO) coating, as backscattering from the ITO coating beneath the rubber slice can increase the overall backscattered electron intensity, allowing the void to be detected as a very bright object in the SEM / BSE image.

[0030] In one embodiment, the tread may be characterized by the total concentration of (at least) the following sources: undispersed fillers (e.g., carbon black and / or silica), zinc oxide particles, and defects arising from voids. Alternatively, the tread may be characterized by the total concentration of undispersed carbon black, undispersed silica, zinc oxide, and defects arising from voids. In another embodiment, the tread may be characterized by the concentration of void defects alone.

[0031] One embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica (the silica is dispersed in at least one elastomer), wherein the tread is defined by a value A, which is the area ratio of defects in a 1 μm thick rubber slice. T It has a low total defect concentration as indicated by A T (i)~(vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, A T ≤2.7%, (ii) For defects having an area equivalent diameter of at least 3 μm, A T ≤1.4%, (iii) For defects having an area equivalent diameter of at least 4 μm, A T ≤0.75%, (iv) For defects having an area equivalent diameter of at least 5 μm, A T ≤0.5%, (v) For defects having an area equivalent diameter of at least 6 μm, A T ≤0.33%, and (vi) For defects having an area equivalent diameter of at least 10 μm, A T ≤0.15% It satisfies at least one of the following conditions.

[0032] A T As options regarding this, (i) For defects having an area equivalent diameter of at least 2 μm, A T For defects with an area equivalent diameter of ≤2.5% or at least 2 μm, A T For defects with an area equivalent diameter of ≤2% or at least 2 μm, A T For defects with an area equivalent diameter of ≤1.5% or at least 2 μm, A T For defects with an area equivalent diameter of ≤1% or at least 2 μm, A T ≤0.9% (ii) For defects having an area equivalent diameter of at least 3 μm, A T For defects with an area equivalent diameter of ≤1% or at least 3 μm, AT For defects with an area equivalent diameter of ≤0.9% or at least 3 μm, A T For defects with an area equivalent diameter of ≤0.8% or at least 3 μm, A T ≤0.7% (iii) For defects having an area equivalent diameter of at least 4 μm, A T ≤0.6% (iv) For defects having an area equivalent diameter of at least 5 μm, A T ≤0.4% (v) For defects having an area equivalent diameter of at least 6 μm, A T ≤0.3%, or (vi) For defects having an area equivalent diameter of at least 10 μm, A T The percentage is ≤0.1%.

[0033] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is defined by a value N, which is the number of defects per unit area of ​​a 1 μm thick rubber slice. T It has a low total defect concentration as indicated by N T (i)~(vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, N T ≤1700 / mm 2 , (ii) For defects having an area equivalent diameter of at least 3 μm, N T ≤950 / mm 2 , (iii) For defects having an area equivalent diameter of at least 4 μm, N T ≤250 / mm 2 , (iv) For defects having an area equivalent diameter of at least 5 μm, N T ≤100 / mm 2 , and (v) For defects having an area equivalent diameter of at least 6 μm, N T ≤50 / mm 2 It satisfies at least one of the following conditions.

[0034] Alternatively, N T can generally be defined (for any rubber slice thickness) as the number of defects per unit volume (number / mm 2 -μm).

[0035] N T As an option for N (i) For defects having an area equivalent diameter of at least 2 μm, N T ≤ 1600 / mm 2 or, for defects having an area equivalent diameter of at least 2 μm, N T ≤ 1500 / mm 2 or, for defects having an area equivalent diameter of at least 2 μm, N T ≤ 1200 / mm 2 or, for defects having an area equivalent diameter of at least 2 μm, N T ≤ 1000 / mm 2 or, for defects having an area equivalent diameter of at least 2 μm, N T ≤ 900 / mm 2 or, or for defects having an area equivalent diameter of at least 2 μm, N T ≤ 800 / mm 2 , (ii) For defects having an area equivalent diameter of at least 3 μm, N T ≤ 900 / mm 2 or, for defects having an area equivalent diameter of at least 3 μm, N T ≤ 800 / mm 2 or, for defects having an area equivalent diameter of at least 3 μm, N T ≤ 700 / mm 2 or, for defects having an area equivalent diameter of at least 3 μm, N T ≤ 600 / mm 2 or, for defects having an area equivalent diameter of at least 3 μm, N T ≤ 500 / mm 2 or, for defects having an area equivalent diameter of at least 3 μm, N T ≤ 400 / mm 2 or, or for defects having an area equivalent diameter of at least 3 μm, N T≤300 / mm 2 , (iii) For defects having an area equivalent diameter of at least 4 μm, N T ≤200 / mm 2 Or, for defects having an area equivalent diameter of at least 4 μm, N T ≤150 / mm 2 , (iv) For defects having an area equivalent diameter of at least 5 μm, N T ≤100 / mm 2 Or, for defects having an area equivalent diameter of at least 5 μm, N T ≤90 / mm 2 Or, for defects having an area equivalent diameter of at least 5 μm, N T ≤80 / mm 2 .

[0036] Another embodiment is a tread comprising at least one elastomer and at least one silica of at least 15 phr, wherein the tread is defined by a value A, which is the area ratio of the voids in a rubber slice with a thickness of 1 μm. V It has a low void concentration as indicated by A V (i) and (ii), that is, (i) For a void having an area equivalent diameter of at least 2 μm, A V ≤0.6%, and (ii) For a void having an area equivalent diameter of at least 3 μm, A V ≤0.4% It satisfies at least one of the following conditions.

[0037] A V As options regarding this, (i) For a void having an area equivalent diameter of at least 2 μm, A V For voids having an area equivalent diameter of ≤0.5% or at least 2 μm, A V ≤0.4%, (ii) For a void having an area equivalent diameter of at least 3 μm, A V The percentage is ≤0.3%.

[0038] Another embodiment is a tread comprising at least one elastomer and at least one silica of at least 15 phr, wherein the tread is defined by a value N, which is the number of voids per unit area of ​​a 1 μm thick rubber slice. V It has a low void concentration as indicated by N V (i)~(vi), that is, (i) For a void having an area equivalent diameter of at least 2 μm, N V ≤500 / mm 2 , (ii) For a void having an area equivalent diameter of at least 3 μm, N V ≤150 / mm 2 , and (iii) For a void having an area equivalent diameter of at least 4 μm, N V ≤65 / mm 2 It satisfies at least one of the following conditions.

[0039] N V As options regarding this, (i) For a void having an area equivalent diameter of at least 2 μm, N V ≤400 / mm 2 , (ii) For a void having an area equivalent diameter of at least 3 μm, N V ≤140 / mm 2 Or, for a void having an area equivalent diameter of at least 3 μm, N V ≤130 / mm 2 , (iii) For a void having an area equivalent diameter of at least 4 μm, N V ≤60 / mm 2 That is the case.

[0040] As an alternative, N V Generally speaking (for any thickness of rubber slice), the number of voids per unit volume (number / mm) 2 It can be defined as -μm).

[0041] Another embodiment is a tread comprising at least one elastomer and at least one silica in an amount of at least 15 phr, wherein the tread has a low total defect or void concentration defined as a function of silica filler (phr). The total defect or void concentration per unit area in a tread slice with a thickness of 1 μm is given by the following formula, i.e., a·e -bx It can be expressed as +c, where x = silica filler (phr), and a, b, and c are variables depending on the type and size of the defect.

[0042] One embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is based on formula A T ≦a·e -bx It has a low total defect concentration as shown by +c, where x = silica packing amount (phr), and A T This represents the area ratio of defects in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a=4, b=0.08, and c=1.9, (ii) For defects having an area equivalent diameter of at least 3 μm, a=2.4, b=0.07, and c=1, (iii) For defects having an area equivalent diameter of at least 4 μm, a=0.8, b=0.008, and c=0.09, (iv) For defects having an area equivalent diameter of at least 5 μm, a = -0.73, b = 0.15, and c = 0.93, and (v) For defects with an area equivalent diameter of at least 6 μm, a = -5.26, b = 0.001, and c = 5.38 It satisfies at least one of the following conditions.

[0043] The options are as follows, namely, (i) For defects having an area equivalent diameter of at least 2 μm, a=3.5, b=0.8, and c=1.5, (ii) For defects having an area equivalent diameter of at least 3 μm, a=2.1, b=0.07, and c=0.79, (iii) For defects having an area equivalent diameter of at least 4 μm, a=0.7, b=0.008, and c=0.08, (iv) For defects having an area equivalent diameter of at least 5 μm, a=0.5, b=0.002, and c=0, (v) For defects with an area equivalent diameter of at least 6 μm, a = -5.3, b = 0.001, and c = 5.35 At least one of them is A T This applies to the following.

[0044] Another embodiment is a tread comprising at least one elastomer and at least one silica of at least 15 phr, wherein the tread is of formula N T ≦a·e -bx It has a low total defect concentration as shown by +c, where x = silica packing amount (phr), and N T This is the number of defects per unit area in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a=2500, b=0.007, and c=0, (ii) For defects having an area equivalent diameter of at least 3 μm, a=1500, b=0.018, and c=0, (iii) For defects having an area equivalent diameter of at least 4 μm, a=580, b=0.14, and c=240, (iv) For defects having an area equivalent diameter of at least 5 μm, a=-30, b=0.01, and c=120, (v) For defects with an area equivalent diameter of at least 6 μm, a = -590, b = 0.0014, and c = 611 It satisfies at least one of the following conditions.

[0045] The options are as follows, namely, (i) For defects having an area equivalent diameter of at least 2 μm, a=2100, b=0.009, and c=0, (ii) For defects having an area equivalent diameter of at least 3 μm, a=1400, b=0.022, and c=0, (iii) For defects having an area equivalent diameter of at least 4 μm, a=450, b=0.14, and c=180, (iv) For defects having an area equivalent diameter of at least 5 μm, a=-30, b=0.01, and c=105, and (v) For defects with an area equivalent diameter of at least 6 μm, a = -590, b = 0.0013, and c = 600 At least one of them is N T This applies to the following.

[0046] Another embodiment is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is based on formula A V ≦a·e -bx It has a low void concentration as shown by +c, where x = silica packing amount (phr), and A V This is the area ratio of voids in a tread slice with a thickness of 1 μm, where (i) and (ii) are, (i) For voids having an area equivalent diameter of at least 2 μm, a=3.3, b=0.037, and c=0.1, (ii) For voids having an area equivalent diameter of at least 3 μm, a=2.3, b=0.075, and c=0.28 It satisfies at least one of the following conditions.

[0047] The options are as follows, namely, (i) For voids having an area equivalent diameter of at least 2 μm, a=2.5, b=0.037, and c=0.1, (ii) For voids having an area equivalent diameter of at least 3 μm, a=1.9, b=0.075, and c=0.25 At least one of them is A V This applies to the following.

[0048] Another option is a tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is of formula N V ≦a·e -bx It has a low void concentration as shown by +c, where x = silica packing amount (phr), and N V This is the number of voids per unit area in a tread slice with a thickness of 1 μm, i.e., (i) and (ii), (i) For voids having an area equivalent diameter of at least 2 μm, a=800, b=0.02, and c=400, (ii) For voids having an area equivalent diameter of at least 3 μm, a=480, b=0.1, and c=170 It satisfies at least one of the following conditions.

[0049] The options are as follows, namely, (i) For voids having an area equivalent diameter of at least 2 μm, a=720, b=0.05, and c=370, (ii) For voids having an area equivalent diameter of at least 3 μm, a=430, b=0.12, and c=140 At least one of them is A V This applies to the following.

[0050] As an option, the total defect or void concentration in the tire tread is A T , N T , A V , or N VRegardless of how it is shown, where applicable, the tire tread may satisfy at least one of (i)-(v) or at least one of (i)-(iv) or at least one of (i)-(iii), or it may satisfy (i) or (ii). Alternatively, the total defect and / or void concentration may satisfy two, three, four, five, or all of (i)-(vi). For example, the total defect and / or void concentration may satisfy all of (i)-(v), all of (i)-(iv), all of (i)-(iii), or (i) and (ii), where applicable. Another option is that the total defect and / or void concentration may satisfy all of (ii)-(v), all of (ii)-(iv), or (ii) and (iii), where applicable.

[0051] For a slice with a thickness of 1 μm, A T and A V It can have a minimum value of 0.1%, 0.05%, 0.01%, 0.005%, 0.001%, 0.0005%, or 0.0001%. For example, A T For defects having an area equivalent diameter of at least 2 μm, the percentage may range from 0.0001% to 2.7%, or A V For voids having an area equivalent diameter of at least 2 μm, this can be in the range of 0.0001% to 0.6% (or any range in between). T and N V is 1 / mm 2 or 0.5 / mm 2 0.1 / mm 2 or 0.09 / mm 2 It can have a minimum value of N. For example, N T For defects with an area equivalent diameter of at least 2 μm, the rate is 0.09 / mm 2 From 1700 / mm 2 It may be within the range of N V For voids with an area equivalent diameter of at least 2 μm, the rate is 0.09 / mm 2 From 500 / mm 2It could be within the range up to (or any range in between). Another option for a 1 μm thick slide is A T It may have a minimum value of 0.1% or 0.05% (for example, for defects with an area equivalent diameter of at least 2 μm, at least 3 μm, at least 4 μm, at least 5 μm, at least 6 μm, or at least 10 μm), or N T Where applicable, 100 / mm 2 (For example, for defects having an area equivalent diameter of at least 2 μm, at least 3 μm, or at least 4 μm) or 10 / mm 2 or 1 / mm 2 (For example, for defects having an area equivalent diameter of at least 2 μm, at least 3 μm, at least 4 μm, at least 5 μm, or at least 6 μm) may have a minimum value of A V It may have a minimum value of 0.01%, 0.005%, 0.001%, 0.0005%, or 0.0001% (for example, for defects with an area equivalent diameter of at least 2 μm or at least 3 μm), or N V Where applicable, 100 / mm 2 (For example, for a void with an area equivalent diameter of at least 2 μm or at least 3 μm) or 10 / mm 2 or, 1 / mm 2 or 0.5 / mm 2 0.1 / mm 2 or 0.09 / mm 2 (For example, for voids having an area equivalent diameter of at least 2 μm, at least 3 μm, or at least 4 μm) it may have a minimum value.

[0052] As another option, the defect concentration is A T , N T , A V , and N V It is possible to satisfy two or more combinations of the following. For example, the defect concentration is A T and N T It can satisfy (i.e., the tire tread has a low total defect concentration as determined by area ratio or number density), or A Vand N V It can satisfy (i.e., the tire tread has a low void concentration as determined by area ratio or number density), or A T , N T , and A V Can it satisfy A T , N T , and N V The tire tread may satisfy the condition, or it may have both a low total defect concentration and a low void concentration, as determined by area ratio or number density.

[0053] The tire treads disclosed herein contain a significant amount of silica as a reinforcing filler. Optionally, the silica is present in the tread in amounts of at least 15 phr, e.g., at least 20 phr, at least 25 phr, at least 30 phr, at least 35 phr, or at least 40 phr. Optionally, the amount of silica present in the tread is in the range of 15 phr to 250 phr, 15 phr to 200 phr, 15 phr to 150 phr, 15 phr to 120 phr, 15 phr to 100 phr, 15 phr to 80 phr, 15 phr to 70 phr, 15 phr to 60 phr, 15 phr to 50 phr, or 20 phr to 250 phr. The range is up to 1, the range is from 20phr to 200phr, the range is from 20phr to 150phr, the range is from 20phr to 120phr, the range is from 20phr to 100phr, the range is from 20phr to 80phr, the range is from 20phr to 70phr, the range is from 20phr to 60phr, the range is from 20phr to 50phr, the range is from 30phr to 250phr, the range is from 30phr to 200phr, the range is from 30phr to 150phr Range up to hr, range from 30phr to 100phr, range from 30phr to 80phr, range from 30phr to 70phr, range from 30phr to 60phr, range from 30phr to 50phr, range from 25phr to 150phr, range from 25phr to 100phr, range from 25phr to 80phr, range from 25phr to 70phr, range from 25phr to 60phr, range from 25phr to 50phr The ranges may be up to 1, 35 phr to 150 phr, 35 phr to 100 phr, 35 phr to 80 phr, 35 phr to 70 phr, 40 phr to 150 phr, 40 phr to 100 phr, 40 phr to 90 phr, 40 phr to 80 phr, 40 phr to 70 phr, 40 phr to 60 phr, and similar ranges.

[0054] As an option, the tire tread further comprises at least one additional filler, resulting in a filler mixture dispersed in at least one elastomer. For example, the at least one additional filler may be selected from carbonaceous materials, carbon black, nanocellulose, lignin, clay, nanoclay, metal oxides, metal carbonates, pyrolysis carbon, recycled carbon, recovered carbon black, graphene, graphene oxide, reduced graphene oxide, high-density reduced graphene oxide granules, carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanostructures, fibrous fillers, hydrothermal carbon, nanocrystalline cellulose starch particles, polysaccharides, glucans, dextran, microfibrillated cellulose, starch, siliceous earth, crumb rubber, and functionalized crumb rubber, or combinations thereof, as well as coated and treated versions of these materials (for example, silicon-treated carbon black such as Ecoblack® silicon-treated carbon black is available from Cabot Corporation or as described in U.S. Patent No. 6,028,137, the disclosure of which is incorporated herein by reference). The fibrous filler may have a ratio of 2:1 or higher, 3:1 or higher, 4:1 or higher, or even higher, such as 5:1 or 10:1, 100:1, 200:1, or up to 10 6 It may have an aspect ratio of :1. Fillers typically used to reinforce elastomers have dimensions that are micro (less than several hundred microns) or nanoscale (less than 1 micron). When present in a composite, fibrous fillers may be present in amounts ranging from 1% to 10% by weight relative to the total amount of fillers containing at least 15 phr of silica. At least one additional filler may be incorporated into the composite as a wet or dry filler, or a combination of wet and dry fillers.

[0055] The amount of at least one additional filler may vary as long as the amount of silica in the elastomer is at least 15 phr or any other amount disclosed herein. For example, silica may be present in an amount ranging from 25% to 99% by weight relative to the total weight of the fillers, and at least one additional filler (which may include one or more filler types other than silica) constitutes the remaining filler content. For example, the amount of silica relative to the total weight of the filler mixture is in the range of 25% to 95%, 25% to 85%, 25% to 80%, 25% to 75%, 25% to 70%, 25% to 65%, 25% to 60%, 25% to 55%, 25% to 50%, 25% to 45%, 25% to 40%, or 25% to 35%, and at least one additional filler constitutes the remainder (for example, 1% to 75% by weight relative to the total weight of the filler mixture, or other ranges in between, depending on the amount of silica in the selected range).

[0056] For example, at least one additional filler may be carbon black, and the tread may contain a filler mixture of silica and carbon black, where the amount of silica ranges from 25% to 99% by weight and the amount of carbon black ranges from 1% to 75% by weight (e.g., 1% to 60% or 1% to 50%), or the amount of silica ranges from 25% to 95% by weight and the amount of carbon black ranges from 5% to 75% by weight (e.g., 5% to 60% or 5% to 50%). As long as silica is present in an amount of at least 15 phr, silica may represent the majority or minority of the fillers. If silica is the majority filler in a filler mixture with at least one additional filler such as carbon black, then, for example, when resin or oil is present (e.g., resin and / or oil may be present in amounts ranging from 10 phr to 100 phr), silica may be present in amounts of up to 200 phr, 150 phr, or 100 phr. For example, silica may be present in amounts ranging from 30 phr to 150 phr or from 35 phr to 100 phr, e.g., from 35 phr to 90 phr, from 35 phr to 80 phr, or from 35 phr to 70 phr, and carbon black may be present in amounts ranging from 1 phr to 30 phr, from 2 phr to 30 phr, from 3 phr to 30 phr, or from 5 phr to 30 phr, e.g., from 5 phr to 20 phr or from 5 phr to 10 phr. If silica is a small amount of filler, silica may be present in amounts ranging from 15 phr to 30 phr (or from 15 phr to 25 phr), and carbon black may be present in amounts ranging from 20 phr to 50 phr, from 20 phr to 45 phr, from 20 phr to 40 phr, for example, from 20 phr to 35 phr, from 25 phr to 50 phr, from 25 phr to 40 phr, or from 25 phr to 35 phr.

[0057] One or more types of silica, or any combination of silica, may be used in any embodiment disclosed herein. Silica may include or be composed of precipitated silica, fumed silica, silica gel, and / or colloidal silica. Silica may be untreated silica and / or chemically treated silica, or may be composed of these. Silica may be rice husk silica, or silica obtained from rice husk ash or other biogenic sources. Silica may be suitable for reinforcing elastomer composites, and 80m 2 / g to 350m 2 A range up to / g, for example, 80m 2 / g to 250m 2 Range up to / g, 100m 2 / g to 350m 2 Range up to / g, 100m 2 / g to 250m 2 Range up to / g, 120m 2 / g to 350m 2 Range up to / g, 120m 2 / g to 250m 2 Range up to / g, 140m 2 / g to 350m 2 Range up to / g, or 140m 2 / g to 250m 2 It can be characterized by the CTAB surface area in the range up to / g.

[0058] Alternatively, silica is 20m 2 / g to 700m 2 The range is up to / g, or 20m 2 / g to 500m 2 The range is up to / g, or 20m 2 / g to 450m 2 The range is up to / g, or 20m 2 / g to 200m 2 The range is up to / g, or 20m 2 / g to 150m 2 Up to / g, or 30m 2 / g to 450m 2 Up to / g, or 30m 2 / g to 400m 2 The range is up to / g, or 6m 2 / g to 250m 2 The range is up to / g, or 6m 2 / g to 250m 2 The range is up to / g, or 80m 2 / g to 700m 2 The range is up to / g, or 80m 2 / g to 500m 2 The range is up to / g, or 80m 2 / g to 300m 2 The range is up to / g, or 80m 2 / g to 200m 2 It can be characterized by the Brunaur Emmett Teller surface area (multipoint BET nitrogen adsorption, as defined by ASTM D1993) in the range of up to / g.

[0059] Highly dispersed precipitated silica can be used as a filler in this method. Highly dispersed precipitated silica ("HDS") is understood to mean any silica that has substantial ability to non-aggregate and disperse in the elastomer matrix. Such dispersion quantification can be observed in known ways by electron microscopy or optical microscopy in thin sections of the elastomer composite. Examples of commercial-grade HDS include Perkasil® GT3000GRAN silica from WR Grace & Co., Ultrasil® 7000 silica from Evonik Industries, Zeosil® 1165MP, 1115MP, Premium, and 1200MP silica from Solvay SA, Hi-Sil® EZ160G silica from PPG Industries, Inc., and Zeopol® 8741 or 8745 silica from Evonik Industries. Conventional non-HDS precipitated silica can also be used. Examples of conventional commercially grade precipitated silica include Perkasil® KS408 silica from WR Grace & Co., Zeosil® 175GR silica from Solvay SA, Ultrasil® VN3 silica from Evonik Industries, and Hi-Sil® 243 silica from PPG Industries, Inc. Precipitated silica with surface-bonding silane coupling agents may also be used. Examples of commercially grade chemically treated precipitated silica include Agilon® 400, 454, or 458 silica from PPG Industries, Inc., and Coupsil silica from Evonik Industries, e.g., Coupsil® 6109 silica. Other examples of chemically treated silica include those marketed as Efficium® highly dispersed silica from Solvay SA, and those disclosed in U.S. Patent Application Publication 2017 / 0058111, the disclosure of which is incorporated herein by reference.

[0060] As additional fillers, the carbon black used in any of the methods disclosed herein may be any grade of reinforced or semi-reinforced carbon black. Examples of ASTM grade reinforced grades are N110, N121, N134, N220, N231, N234, N299, N326, N330, N339, N347, N351, N358, and N375 carbon black. Examples of ASTM grade semi-reinforced grades are N539, N550, N650, N660, N683, N762, N765, N774, N787, N990 carbon black, and / or N990 grade thermal black.

[0061] Carbon black, 30m 2 / g to 200m 2 A range up to / g, for example, 60m 2 / g to 200m 2 Range up to / g or 60m 2 / g to 170m 2 The carbon black may have a statistical thickness surface area (STSA) in the range of up to 1 / g. The carbon black may have a compressed oil absorption number (COAN) in the range of 30 mL / 100g to 150 mL / 100g, for example, from 60 mL / 100g to 120 mL / 100g. STSA (statistical thickness surface area) is determined based on ASTM Test Procedure D-5816 (measured by nitrogen adsorption). Compressed oil absorption number (COAN) is determined according to ASTM D3493. As an alternative, the carbon black may have a COAN of 70 mL / 100g to 115 mL / 100g, and may be 60 m 2 / g to 150m 2 It may have an STSA in the range of up to / g.

[0062] As stated, carbon black may be rubber black, particularly reinforced or semi-reinforced grade carbon black. Carbon blacks available from Cabot Corporation, sold under the trademarks Regal®, Black Pearls®, Spheron®, Sterling®, Propel®, Endure®, and Vulcan®; carbon blacks available from Birla Carbon (formerly available from Columbia Chemicals), sold under the trademarks Raven®, Statex®, Furnex®, and Neotex®, and the CD and HV lines; carbon blacks available from Orion Engineered Carbons (formerly Evonik and Degussa Industries), sold under the trademarks Corax®, Durax®, Ecorax®, and Purex®, and the CK line; and other fillers suitable for use in rubber or tire applications may also be utilized for use in various mounting configurations. Suitable chemically functionalized carbon blacks include those disclosed in International Publication No. 96 / 18688 and U.S. Patent Application Publication No. 2013 / 0165560, the disclosures of which are incorporated herein by reference. Mixtures of any of these carbon blacks may be employed. Carbon blacks having surface area and structure exceeding ASTM grade and typical values, selected for mixing with rubber, such as those described in U.S. Patent Application Publication No. 2018 / 0282523, the disclosures of which are incorporated herein by reference, may be used in wet fillers and composites made by any of the methods disclosed herein.

[0063] The tread is made from natural rubber (NR), synthetic elastomers such as styrene-butadiene rubber (SBR, e.g., solution SBR (SSBR), emulsion SBR (ESBR), or oil-extracted SSBR (OESSBR)), polybutadiene (BR), polyisoprene rubber (IR), functionalized SBR, functionalized BR, functionalized NR, ethylene-propylene rubber (e.g., EPDM), isobutylene-based elastomers (e.g., butyl rubber), halogenated butyl rubber, polychloroprene rubber (CR), nitrile rubber (NBR), and hydrogenated nitrile rubber (HNBR). ), fluoroelastomers, perfluoroelastomers, and silicone rubbers, for example, natural rubber, functionalized natural rubber, styrene-butadiene rubber, functionalized styrene-butadiene rubber, polybutadiene rubber, functionalized polybutadiene rubber, polyisoprene rubber, ethylene-propylene rubber, nitrile rubber, hydrogenated nitrile rubber, and mixtures thereof, or one or more elastomer types, for example, natural rubber, styrene-butadiene rubber, polybutadiene rubber, and mixtures thereof, for example, a mixture of the first and second elastomers. Other synthetic polymers that may be used in this method (whether alone or in mixtures) include hydrogenated SBR and thermoplastic block copolymers (for example, recyclable ones). Synthetic polymers include copolymers of ethylene, propylene, styrene, butadiene, and isoprene. Other synthetic elastomers include those synthesized in metallocene chemistry in which the metal is selected from Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Co, Ni, and Ti. Polymers made from bio-based monomers such as modern carbon-containing monomers as defined by ASTM D6866, for example, polymers made from bio-based styrene monomers disclosed in U.S. Patent No. 9,868,853, the disclosure of which is incorporated herein by reference, or polymers made from bio-based monomers such as butadiene, isoprene, ethylene, propylene, farnesene, and their comonomers may also be used.

[0064] When two or more elastomers are used, the two or more elastomers may be filled into the mixer simultaneously as a mixture (as one or more fills), or the elastomers may be added separately in any order and amount. For example, at least one elastomer may include natural rubber. Alternatively, at least one elastomer may include natural rubber mixed with one or more of the elastomers disclosed herein, such as butadiene rubber and / or styrene-butadiene rubber.

[0065] The tread may contain an elastomer that is or may contain natural rubber. If the elastomer is a mixture, the elastomer may contain at least 20% by weight, at least 30% by weight, at least 40% by weight, at least 50% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight of natural rubber. The mixture may further contain synthetic elastomers such as styrene-butadiene rubber, functionalized styrene-butadiene rubber, and polybutadiene rubber, and / or one or more of any other elastomers disclosed herein. The final tread may contain natural rubber in an amount of at least 20% by weight, e.g., at least 30%, at least 40%, at least 50%, at least 70%, at least 80%, at least 90%, or at least 95% by weight, relative to the total weight of the elastomer, or the final tread may contain an elastomer that is substantially all natural rubber (e.g., up to 99% or up to 100% by weight, relative to the total weight of the elastomer).As an option, the elastomer in the tread can be in the range of 20% to 99% of the total weight of the elastomer, 20% to 95%, 20% to 90%, for example, 20% to 80%, 20% to 70%, 20% to 60%, 20% to 50%, 30% to 99%, 30% to 95%, 30% to 90%, 30% to 80%, 30% to 70%, 30% to 60%, 30% to 50%, 40% to 99%, 40% to 95%, 40% to 90%, 40% to 80% A mixture comprising natural rubber in amounts ranging from 1% by weight, from 40% by weight to 70% by weight, from 40% by weight to 60% by weight, from 40% by weight to 50% by weight, from 50% by weight to 99% by weight, from 50% by weight to 95% by weight, from 50% by weight to 90% by weight, from 50% by weight to 80% by weight, from 50% by weight to 70% by weight, from 60% by weight to 99% by weight, from 60% by weight to 95% by weight, from 60% by weight to 90% by weight, from 60% by weight to 80% by weight, and from 60% by weight to 70% by weight, the remainder being a different elastomer, such as styrene-butadiene rubber, functionalized styrene-butadiene rubber, and polybutadiene rubber, and / or at least one of any other elastomers disclosed herein. For example, the tread may be a mixture containing natural rubber, styrene-butadiene rubber, and polybutadiene rubber in amounts of 50% to 80% by weight of natural rubber, 10% to 40% by weight of styrene-butadiene rubber, and 5% to 30% by weight of polybutadiene rubber, respectively.

[0066] In other embodiments, the elastomer may contain a small amount of natural rubber relative to the total weight of at least one elastomer, for example, from 0.1% to 10% by weight, or may not contain natural rubber at all (0% by weight). In certain embodiments, at least one elastomer may contain at least 50% by weight, for example, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, and up to 99% by weight, 95% by weight, or 90% by weight of polybutadiene rubber, with the remainder being any elastomer disclosed herein, for example, at least one of natural rubber and styrene-butadiene rubber. In certain embodiments, the elastomer may be 100% polybutadiene rubber. In certain embodiments, the elastomer may comprise at least 50% styrene-butadiene rubber, for example, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, and up to 99% by weight, 95% by weight, or 90% by weight of styrene-butadiene rubber, with the remainder comprising at least one of any elastomer disclosed herein, for example, natural rubber and polybutadiene rubber. In certain embodiments, the elastomer may comprise 100% styrene-butadiene rubber. In yet other embodiments, the elastomer may comprise a mixture of styrene-butadiene rubber and butadiene rubber in ratios ranging from 5:1 to 1:1, 4:1 to 1:1, 3:1 to 1:1, 1:1 to 3:1, 1:1 to 4:1, or 1:1 to 5:1.

[0067] Natural rubber can also be chemically modified in some way. For example, natural rubber can be treated to chemically or enzymatically modify or reduce various non-rubber components, or the rubber molecule itself can be modified with various monomers or other chemical groups, such as chlorine. Other examples include epoxidized natural rubber and natural rubber having a nitrogen content of at most 0.3% by weight, as described in International Publication No. 2017 / 207912.

[0068] Other preferred elastomers include, but are not limited to, rubber, polymers (e.g., homopolymers, copolymers, and / or terpolymers) such as 1,3-butadiene, styrene, isoprene, isobutylene, 2,3-dialkyl-1,3-butadiene, acrylonitrile, ethylene, propylene, and the like.

[0069] Other applicable solid elastomers that may be used in the methods of this disclosure are disclosed in International Publication No. 2020 / 247663, which is incorporated herein by reference.

[0070] Silica-containing tire treads (tire treads containing silica dispersed in at least one elastomer) are known to provide tires with excellent rolling resistance characteristics. However, such treads exhibit poorer wear performance compared to carbon black-reinforced treads, and until now, excellent wear performance has not been achievable for such treads, for example, treads containing natural rubber. However, this silica-containing tread may offer better wear performance than previously achieved for its equivalent, and in some cases, carbon black-containing treads.

[0071] The wear performance of this tire tread can be measured against an equivalent tread as a control, i.e., a tread with an equivalent tread pattern having an equivalent amount of carbon black as a reinforcing filler (equivalent tread control). While we do not wish to be bound by any theory, it can be assumed that superior wear performance is achieved by a tread with a lower total defect concentration and / or void concentration, which can lead to a reduction in cracks and cavities and similar structures that can cause rubber degradation. This tread, having at least 15 phr of silica, may provide an equivalent or reduced tread wear rate compared to an equivalent tread (reinforced, for example, with an equivalent amount of carbon black filler). As an alternative, the equivalent amount of carbon black replaces silica with an equivalent volume fraction of carbon black. For example, if this tire tread has 55 phr of silica, the control tread has an equivalent tread design with an equivalent volume fraction of carbon black (e.g., about 50 phr of carbon black). Alternatively, an equivalent amount of carbon black can replace silica with an equivalent amount of carbon black to achieve equivalent stiffness / hardness properties. For example, an equivalent amount of carbon black will give equivalent Shore A hardness.

[0072] As an option, the indication of tread wear may be a tread wear rate, which is a measure of tread depth loss per kilometer (mm / km). Alternatively, the tread wear rate may be a measure of normalized tread depth loss per kilometer (%). For example, an equivalent tire tread control may be assigned a normalized tread depth loss per kilometer equal to 100%. This tire tread, containing at least 15 phr of silica, may match the tread depth loss indicated by a normalized tread depth loss per kilometer of 100%, or this tread may exhibit improved performance (reduced tread wear rate) indicated by a normalized tread depth loss per kilometer of less than 100%, for example, less than 95%.

[0073] Because this tread contains a significant amount of silica as a filler, tires with silica-containing treads may also have superior rolling resistance characteristics compared to equivalent tread controls containing carbon black as a filler. Rolling resistance characteristics can be determined by the rolling resistance coefficient range, which can be determined by the test protocol ECE Regulation Number 117 Annex 6. Alternatively, tires with this tread may have a rolling resistance coefficient of RRc of 7 N / kN or less, for example, RRc of 6.5 N / kN or less or RRc of 6 N / kN or less.

[0074] Alternatively, tires with this silica-containing tread may have improved rolling resistance characteristics, as indicated by the normalized rolling resistance coefficient. The normalized rolling resistance coefficient can be measured against a tire with a control tire tread of equivalent design and equivalent amount of carbon black filler. If the normalized rolling resistance coefficient of the control tire is assigned a value of 100%, tires with this tread may have a normalized rolling resistance coefficient of 95% or less, 90% or less, 85% or less, or 80% or less. Alternatively, tires with this tread may have normalized rolling resistance at least 10% lower compared to a tire tread of equivalent design containing equivalent amount of carbon black filler.

[0075] As described herein, the tire tread may be prepared from an initial elastomer composite formed by mixing at least one filler with at least one elastomer. This initial composite may be considered an uncured mixture of the filler and elastomer. The formed composite may optionally be considered a mixture or masterbatch which may be an intermediate product used in subsequent rubber compounding and one or more vulcanization processes. The composite prior to compounding and vulcanization may also undergo additional processes, such as one or more holding or further mixing steps, one or more additional drying steps, one or more extrusion steps, one or more calendering steps, one or more milling steps, one or more granulation steps, one or more baling steps, one or more twin-screw discharge extrusion steps, or one or more rubber processing steps, in order to obtain a rubber compound or rubber article.

[0076] International Publication No. 2020 / 247663, whose disclosure is incorporated herein by reference, describes a mixing process using solid elastomers and wet fillers (including, for example, fillers and liquids) that enables control of batch time and temperature beyond what is achievable with known dry mixing processes. Options include composites such as, namely, (a) filling a mixer having one or more rotors with a wet filler comprising at least a solid elastomer and a wet filler, wherein the wet filler is present in an amount of at least 15% by weight based on the total weight of the filler and the wet filler; and (b) in one or more mixing steps, mixing at least the solid elastomer and the wet filler to form a mixture, removing at least a portion of the liquid from the mixture by evaporation, and performing the mixing in at least one of the mixing steps, i.e., (i) The mixer has at least one temperature control means that is set to a temperature Tz of 65°C or higher, and The composite may be prepared by a method comprising: (ii) at least one of the following: one or more rotors operating at a tip speed of at least 0.6 m / s for at least 50% of the mixing time; and (c) discharging from the mixer a composite comprising a filler dispersed in an elastomer at a packing amount of at least 20 phr, including at least 15 phr of at least one silica, wherein the composite has a liquid content of 10% by weight or less based on the total weight of the composite. Mixing may be carried out in one, two, three, or more mixing steps.

[0077] As an option, the tire tread comprises an elastomer compound (vulcanized product) prepared by curing a composite in the presence of at least one curing agent, the composite being formed by mixing a wet filler (e.g., wet silica) with a liquid present in an amount of at least 15% by weight based on the total weight of the filler and wet filler (e.g., at least 20% by weight, at least 30% by weight, at least 40% by weight, or in an amount ranging from 15% to 80% by weight, from 20% to 70% by weight, from 30% to 60% by weight, or from 40% to 60% by weight based on the total weight of the wet filler, e.g., wet silica). The wet filler or wet silica may be in the form of a powder paste, pellets, cake, or slurry. As an option, the mixture of at least a solid elastomer and a wet filler (e.g., wet silica) is prepared at a temperature of 50°C or higher, 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and a maximum of 100°C, a maximum of 95°C, or a maximum of 90°C T z The mixing is carried out in a mixer having at least one temperature control means set to [value]. As an alternative or additional option, the mixing of at least a solid elastomer and a wet filler (e.g., wet silica) is carried out in a mixer by one or more rotors of the mixer operating at a tip speed of at least 0.6 m / s for at least 50% of the mixing time.

[0078] The composites may be formed by single-stage mixing or multi-stage mixing (e.g., two-stage mixing, three-stage mixing, etc.). The resulting composite discharged from the mixer contains a filler (e.g., silica) dispersed in the elastomer at a packing volume of at least 20 phr (containing at least 15 phr of silica), and the composite has a liquid content of 10% by weight or less (e.g., 5% by weight or less) based on the total weight of the composite. Further details regarding the mixing of solid elastomers with wet fillers are disclosed in International Publication No. 2020 / 247663, which is incorporated herein by reference.

[0079] Alternatively, one or more rotors may be mechanically connected to the mixer motor, and at least a portion of the mixing in step (b) may be performed under output control, where the rotational speed of one or more rotors is controlled by a controller, which is described in International Publication No. 2023 / 034575, and its disclosure is incorporated herein by reference, (i) calculates the difference between the measured mixer motor output and the output setpoint (e.g., automatically calculates the difference), and (ii) adjusts the rotational speed of one or more rotors if the measured mixer motor output deviates from the output setpoint. Further options may be performed under PID output control. The controller may continuously calculate the difference between the measured mixer motor output and the output setpoint, for example, at time intervals ranging from 0.05 seconds to 5 seconds or from 0.05 seconds to 1 second. Optionally, one or more stages of mixing (e.g., the first and second stages of mixing) may be performed under output control.

[0080] A composite resulting from the mixing of a solid elastomer with a wet filler may be referred to as a wet-mix composite. Optionally, the tire tread contains an elastomer compound formed from a wet-mix composite and has at least one of improved tread wear (e.g., reduced tread wear rate) and rolling resistance performance compared to a control tire tread containing an elastomer compound formed from a dry-mix equivalent composite. A dry-mix equivalent composite has a composite equivalent to a wet-mix composite (e.g., equivalent filler, filler content, elastomer, and compound), except that the dry-mix equivalent composite is formed by a known dry-mixing method, e.g., mixing a dry filler and a solid elastomer.

[0081] Therefore, as an option, a tire having this tire tread has improved rolling resistance characteristics (e.g., a normalized rolling resistance coefficient of 90 or less) compared to a control tire having an equivalent tread obtained or formed from a dry mixed equivalent of the control rubber compound. Alternatively, this tire tread has the same or improved wear characteristics (reduced wear rate) compared to an equivalent tread having a rubber compound formed or obtained from a dry mixed equivalent of the control tire tread.

[0082] The composite used to form the tire tread may further include one or more additives, including a degradation inhibitor (e.g., N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine or "6PPD" and Antioxidant DQ or "TMQ"), a coupling agent, and one or more rubber chemicals, in order to enable the dispersion of fillers into the elastomer. Rubber chemicals as defined herein include processing aids (e.g., various oils and plasticizers, waxes that facilitate the mixing and processing of rubber), activators (e.g., zinc oxide and fatty acids that activate the vulcanization process), accelerators (e.g., N,N'-diphenylguanidine or "DPG" powder, sulfenamides, and thiazoles that accelerate the vulcanization process), vulcanizing agents (or curing agents that crosslink rubber, e.g., sulfur, peroxides), and one or more other rubber additives, including but not limited to retarders, crosslinking aids, peptizers, adhesion promoters, tackifiers, resins, flame retardants, colorants, and foaming agents. Optionally, rubber chemicals may include processing aids and activators. Alternatively, one or more other rubber chemicals may be selected from zinc oxide, fatty acids, zinc salts of fatty acids, waxes, accelerators, resins, and process oils.

[0083] With respect to silica fillers, if a coupling agent is used, the coupling agent may be introduced in any (or more) steps or locations of the mixing process, insofar as it has the opportunity to become dispersed in the composite. The coupling agent may be one or more silane coupling agents, one or more zirconate coupling agents, one or more titanate coupling agents, one or more nitro coupling agents, or any combination thereof, or may include these. The coupling agents are bis(3-triethoxysilylpropyl)tetrasulfan (e.g., Si69 from Evonik Industries, Struktol SCA98 from Struktol Company), bis(3-triethoxysilylpropyl)disulfan (e.g., Si75 and Si266 from Evonik Industries, Struktol SCA985 from Struktol Company), 3-thiocyanatopropyl-triethoxysilane (e.g., Si264 from Evonik Industries), gamma-mercaptopropyl-trimethoxysilane (e.g., VP Si163 from Evonik Industries, Struktol SCA989 from Struktol Company), gamma-mercaptopropyl-triethoxysilane (e.g., VP from Evonik Industries) The coupling agents may include, or may include, Si263), zirconium dineoalkanolatodi(3-mercapto)propionato-O,N,N'-bis(2-methyl-2-nitropropyl)-1,6-diaminohexane, S-(3-(triethoxysilyl)propyl)octanthioate (e.g., Momentive, Friendly, WV's NXT coupling agent), and / or coupling agents that are chemically similar or have one or more of the same chemical groups. Alternatively, the coupling agent may be triethoxysilylpropyl)tetrasulfan (Si69). Additional specific examples of coupling agents include, but are not limited to, VP Si363 from Evonik Industries and NXT Z and NXT Z-50 silanes from Momentive, trade names.The coupling agents described herein may be used to provide hydrophobic surface-modified silica (pre-coupled or pre-treated silica) before using silica in any of the processes disclosed herein. It should be understood that any combination of elastomers, additives, and additional composites may be added to the elastomer composite, for example, in the compounding step.

[0084] Tire treads may be formed by any one or a combination of the processes described herein. Generally, tire treads may be formed by mixing a filler with an elastomer to form an elastomer composite, which is then formulated into a tire tread compound that is cured to form a rubber compound. The compound may be molded and cured in the desired tread pattern. The tread may be applied to a tire and autoclaved to produce a finished tire.

[0085] Tire treads can be selected from truck / bus radial (TBR) tire treads, off-road (OTR) tire treads, passenger car tire treads, performance car tire treads, light truck tire treads, motorcycle tire treads, electric vehicle tire treads, aircraft tire treads, and heavy equipment tire treads. A tread may include a cap, a base, and an undertread. [Examples]

[0086] The examples describe the preparation of composites, compounds (vulcanized products), and tire treads, where performance (tread wear, rolling resistance) is evaluated against a control tread.

[0087] Example 1 The composite was prepared by mixing a wet filler with natural rubber (Composite 1). For comparison, the comparative carbon black and silica composite was prepared by a conventional dry mixing method (Comparative CB and Comparative Silica Composite). The elastomer used was TSR20 (Technical Grade Rubber), standard grade natural rubber RSS#3 with a maximum of 0.2% Dirt retained through a 45 μm sieve. A technical description of this natural rubber is widely available, for example, in Rubber World Magazine's Blue Book published by Lippincott and Peto, Inc. (Akron, Ohio, USA). The carbon black (CB) used was supplied as VULCAN® 7H carbon black. The silica used was ZEOSIL® Z1165MP precipitated silica ("Z1165MP") from Solvay USA Inc., Cranbury, NJ. The silane coupling agents used were X50S and Si-69 ("Si69") coupling agents, both from Evonik Industries.

[0088] Preparation of wet silica: Dry silica with a moisture content of 7.5 wt% was supplied to a continuous FEECO pin mixer at a rate of 460 lbs / hour (approximately 208.65 kg / hour). Water was sprayed using two fan nozzles within the pin mixer, positioned immediately after the dry silica entered the mixer. The water spray rate was 486 lbs / hour (approximately 220.4 kg / hour). Uniform wet silica pellets between 60 mesh and 120 mesh were discharged with 52.5 wt% water.

[0089] The compound formulations (amounts in PHR) are shown in Table 1. [Table 1]

[0090] The comparative composites were prepared in two steps by dry mixing. The protocols for steps 1 and 2 forming the comparative carbon black composite ("comparative CB composite") are shown in Tables 2 and 3, respectively, and the protocols for steps 1 and 2 forming the comparative silica composite ("comparative silica composite") are shown in Tables 4 and 5, respectively. Both mixing processes in steps 1 and 2 were carried out at a TCU temperature of 40°C using a 320L meshing mixer (Harburg Feudenberger GK320) equipped with a PES5 rotor. [Table 2] [Table 3] [Table 4] [Table 5]

[0091] Composite 1 was formed by mixing a wet filler with a solid elastomer, followed by two subsequent steps of adding chemicals in a third stage. The first stage of mixing was performed using a Kobelco BB-16 tangent mixer (Kobelco Kobe Steel Group) with a 6WI rotor, with a TCU temperature setpoint of 83°C and a filler density of 66%. The protocol for the first stage of mixing is shown in Table 6. In steps 5, 9, and 13, mixing was performed under output PID control (proportional, integral, and derivative). The proportionality constant was 200%, the integral constant was 5 seconds, and derivative control was not used. The output setpoint (kW) and maximum rotor speed setting are shown in Table 6. The output input signal used by the output PID control loop was filtered by using a Kalman filter with a K2 constant of 0.005. Further details regarding output PID control and mixing with a Kalman filter are provided in International Publication No. 2023 / 034575, the disclosure of which is incorporated herein by reference. [Table 6]

[0092] The composite material was processed using a TSR-125 twin-screw discharge extruder (Kobelco Kobe Steel Group) equipped with a fixed knife.

[0093] The second stage of mixing to prepare composite 1 was performed using a BB-72 tangential mixer (Kobelco Kobe Steel Group) equipped with a 6WI rotor, with a TCU temperature setpoint of 75°C and a packing density of 40%. The protocol for the second stage of mixing is shown in Table 7. After initial kneading with the ram down, mixing was performed under PID temperature control with the ram raised, allowing for automatic control of the batch temperature via a feedback loop. A thermocouple inserted through the mixer drop door measures the batch temperature, which is transmitted to the PID controller. The controller output is used to control the speed of the mixer rotor. [Table 7]

[0094] The composite was passed through a TSR-125 twin-screw discharge extruder (Kobelco Kobe Steel Group) equipped with a roller head. A third mixing step, adding chemicals, was performed using a 320L mesh mixer (Harburg Feudenberger GK320) equipped with a PES5 rotor at a TCU setpoint of 40°C. The protocol is shown in Table 8. [Table 8]

[0095] Compound (vulcanizate) Comparative carbon black and silica vulcanized compounds (prepared from comparative CB composites and comparative silica composites, respectively), and Compound 1 (prepared from Composite 1) were prepared. All preparations were carried out using a 320L meshing mixer (Harburg Feudenberger GK320) equipped with a PES5 rotor at the TCU setting point at 40°C.

[0096] The formulations are shown in Table 9 (amount of phr), where the comparative CB and silica compounds were prepared from the comparative dry-mixed compound, and compound 1 was prepared from compound 1. TBBS = accelerator BBTS, TBzTD = accelerator TBzTD, and CTP = retarder CTP, all of which are available from Akrochem, Akron, and Ohio. [Table 9]

[0097] The formulation protocol for preparing the comparative CB compound is shown in Table 10. [Table 10]

[0098] The formulation protocol for preparing the comparative silica compound is shown in Table 11. [Table 11]

[0099] The protocols for the first and second steps of compound preparation are shown in Tables 12 and 13. [Table 12] [Table 13]

[0100] The curing of the sample was carried out under heated pressing (150°C) for a time determined by a conventional rubber rheometer, for example, between T90 and T90+50%, where T90 is the time to achieve 90% vulcanization (pressure = 2500 lb).

[0101] Tire tread A retreading process using a pre-cured tread was used to produce a tire (tire size: 315 / 70R22.5). The tire was produced and cured by standard techniques known in the art, including the following steps: (1) a used commercial tire was buffed to remove the tread compound; (2) the rubber compound was extruded into a camelback and molded and cured in a lug tread pattern at 170°C and 230 bar (approximately 23 MPa) (final pressure release = 15 minutes, curing time ranging from 19.2 to 21.7 minutes); (3) the pre-cured tread was buffed and sprayed with rubber cement; and (4) a cushion gum compound was applied to the buffed tire, the tread was placed on top of the cushion gum, and the tire was autoclaved to produce the finished tire. The tread pattern is a lug-type design with aggressive shoulders and excellent block stability. The tread depth was 20 mm.

[0102] Defect concentration The total defect concentration observed in the tire tread was determined from the following defect types larger than 2 μm: undispersed carbon black particles, undispersed silica, zinc oxide, and voids. These defects can be identified and quantified from a combination of light transmission microscopy (TLM) and scanning electron microscopy (SEM) images of thin rubber microtome slices.

[0103] Thin microtome rubber slices were prepared using the following procedure. Pieces of rubber tire tread were trimmed and placed in a sample holder. The rubber sample was placed in an ultramicrotome instrument and cooled to a temperature ranging from -100°C to -130°C. The rubber slices were then cut at -50°C using an RMC Boeckeler PowerTome ultramicrotome instrument with a diamond knife to a thickness setting of 1 μm. Each slice was suspended away from the knife edge in a trough containing a 60 / 40 DMSO / water viscous liquid mixture held at -50°C. The resulting ribbons of cut sections were then transferred to ITO-coated glass slides. Typically, 30 to 40 rubber slices were collected for one sample, and the slices were dried at room temperature before imaging. Rubber samples were collected from the geometric center of the tread block in both the radial (half the tread depth, or 10 mm + / - 1 mm) and lateral (center of the lateral cross-section at half the tread depth) directions.

[0104] An Olympus optical microscope was used to acquire light transmission microscopy (TLM) images of rubber slices by using an image pixel size of 0.645 μm / pixel and a total of 1360 × 1024 pixels in a field of view of 0.877 mm × 0.660 mm. Typically, only a single image was collected for each rubber slice, with a total of 20 to 40 images collected for one sample. Typical TLM images have a gray background with both dark and bright objects. The dark objects are due to undispersed CB particles, caused by the high attenuation coefficient of carbon black, while the bright objects are due to voids within the rubber.

[0105] A Zeiss scanning electron microscope (SEM) was used to acquire SEM images of rubber slices on ITO glass slides using a backscattered electron (BSE) detector with an electron acceleration voltage of 10 kV. SEM images were collected using a 0.933 mm × 0.700 mm field of view, a pixel size of 0.456 μm / pixel, and 2048 × 1536 pixels. The light gray objects in the SEM images are due to undispersed silica and zinc oxide particles.

[0106] TLM and SEM images were analyzed using suitable software programs based on the NIH ImageJ macro language and Excel macros based on Microsoft Visual Basic for Applications (VBA). The distribution of undispersed carbon black particles and voids was obtained from the analysis of TLM images, while the distribution of undispersed silica and zinc oxide particles was measured using SEM images. The total defect distribution was obtained by combining the distributions of undispersed carbon black particles, undispersed silica and zinc oxide particles, and voids.

[0107] The TLM images were first processed by correcting the non-uniform background of the images using a pseudo-flat-field correction algorithm based on Gaussian blur. Image noise was reduced using an edge-preserving bilateral filter, and image contrast enhancement was applied as needed. Objects were separated from the image by image segmentation using a preferred combination of global and local thresholding methods, resulting in two binary images representing particles and voids, respectively. Image filtering and segmentation were optimized to ensure that the boundaries between voids and particles were sufficiently defined by visual comparison between the segmented image and the original image. The SEM images were processed and analyzed in the same way as the TLM images, thereby generating binary images of undispersed silica and zinc oxide particles. Subsequently, both the area-weighted and number-weighted size distributions of undispersed carbon black, undispersed silica and zinc oxide particles, and voids were analyzed and calculated from their respective binary images.

[0108] The particle size is determined from the area-equivalent circle diameter of the corresponding object in the binary image, where area-equivalent diameter = (4 * area of ​​dark object / π) 1 / 2

[0109] The smallest area-equivalent diameter that can be reliably quantified is 2 μm. Both the number-weighted and area-weighted distributions of defects were calculated. The absolute number of particles per unit image area and the area ratio of particles in the image were calculated.

[0110] The total defect concentration (defects due to undispersed carbon black, undispersed silica, ZnO, and voids) based on the minimum size in μm (e.g., at least 2 μm, at least 3 μm, at least 4 μm, at least 5 μm, at least 6 μm, and at least 10 μm) was obtained for numerous commercial tire treads, as well as pre-cured treads made from comparative CB and silica compounds and compound 1 (comparative CB tread, comparative silica tread, and tread 1, respectively). The commercial tire treads analyzed were Bridgestone® R284ECOPIA® tires ("R284"), Firestone® FS561® tires ("FS561"), Goodyear Endurance® LHS® tires ("LHS"), Michelin® X® Line Energy tires ("XLE"), Michelin X® LINE® ENERGY® D2 tires ("XLE D2"), Michelin X® LINE® ENERGY® Z2 tires ("XLE Z2"), Bridgestone ECOPIA H-STEER002 tires ("H-Steer"), Bridgestone ECOPIA H-DRIVE002 tires ("H-Drive"), Goodyear FUELMAX PERFORMANCE S tires ("FM S"), Goodyear FUELMAX PERFORMANCE D tires ("FM D"), and Continental The tires were Conti EfficientPro D ("PRO D"). The R284, FS561, and LHS treads are carbon black treads. The remaining treads contain a mixture of silica and carbon black fillers with silica:carbon black ratios of 1:5 (PRO D, XLE), 1:2 (H-Drive), 5:1 (H-Steer), 6.7:1 (XLE D2), 11.5:1 (XLE Z2, FM S), and 15.7:1 (FM D). All commercial tires have filler content of 47 phr to 60 phr, except for the XLE (40 phr).It should be noted that the treads of the H-Steer, Pro D, H-Drive, XLE D2, and XLE Z2 were sampled 2mm to 3mm below the tread surface, and the number of defects would likely be even higher if sampled at the geometric center.

[0111] The total number of defects by area and number are listed in Table 14, and Table 15 lists the corresponding void data. [Table 14] [Table 15]

[0112] From Tables 14 and 15, it can be seen that the comparative tread had a defect concentration similar to other commercially available tires on the market. In contrast, the preferred tread disclosed herein (Tread 1) has significantly lower total defect and void concentrations compared to commercial tire treads and comparative tire treads for a wide range of defect sizes (ranging from at least 2 μm to at least 10 μm).

[0113] Tread wear and rolling resistance Tread wear tests were performed on finished tires from vehicles transporting goods within Europe for regional / long-distance transport applications. The current freight vehicles used in the tests had a 4x4 axle configuration with a single trailer delivering goods in Western Europe, and the tires were evaluated for wear rate at the driving position. Tread depth measurements were taken every two months until the tires were removed for service. A total of 28 tires were measured for tread depth loss relative to comparison CB (14 tires) and tire 1 (14 tires). The results are shown using an index with the following formula: Normalized tread depth loss per mile = (Tread depth loss per mile in the example) / Tread depth loss per mile relative to comparison CB tires) × 100. The results indicate that a smaller index indicates a lower wear rate and longer tire life. The tires tested were prepared from comparison CB treads (comparison CB tires) and tread 1 (tire 1).

[0114] Rolling resistance tests were completed in accordance with DIN ECE R117 Annex 6. Data regarding rolling resistance and tread wear performance are shown in Table 16. [Table 16]

[0115] From Table 16, it can be seen that the wear performance of tire 1, including tread 1, was superior to that of the comparative CB control tire. This is a surprising result, given that the tread wear rate of silica-containing TBR tires is generally considered to be inferior to that of treads made from carbon black-based compounds. It can be hypothesized that the low defect concentration in the tire tread is effective in improving the tread wear performance of silica-containing tread compounds.

[0116] The use of the terms “a” and “an” and “the” should be interpreted as covering both singular and plural, unless otherwise specifically indicated herein or unless clearly contradicted by the context. The terms “comprising,” “having,” “including,” and “containing” should be interpreted as open-ended terms (i.e., “including, but not limited to”), unless otherwise specifically indicated herein. The descriptions of value ranges herein are merely intended to function as abbreviations for each distinct value within the range, unless otherwise specifically indicated herein, and each distinct value is incorporated herein as if it were individually listed herein. All methods described herein may be performed in any preferred order, unless otherwise specifically indicated herein or unless clearly contradicted by the context. The use of any and all example or illustrative terms provided herein (e.g., “etc.”) is merely intended to make the invention more fully clear and does not impose any limitation on the scope of the invention unless specifically claimed. The terms used herein should not be construed as indicating that any unclaimed element is essential for the implementation of the invention.

Claims

1. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is defined as a value A, which is the area ratio of defects in a tread slice with a thickness of 1 μm. Ｔ It has a low total defect concentration as indicated by A Ｔ (i) to (vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, A Ｔ ≤2.7%, (ii) For defects having an area equivalent diameter of at least 3 μm, A Ｔ ≤1.4%, (iii) For defects having an area equivalent diameter of at least 4 μm, A Ｔ ≤0.75%, (iv) For defects having an area equivalent diameter of at least 5 μm, A Ｔ ≤0.5%, (v) For defects having an area equivalent diameter of at least 6 μm, A Ｔ ≤0.33%, and (vi) For defects having an area equivalent diameter of at least 10 μm, A Ｔ ≤0.15% A tire tread that satisfies at least one of the following conditions.

2. For defects having an area equivalent diameter of at least 2 μm, A Ｔ The tire tread according to claim 1, wherein A ≤ 2.5%.

3. For defects having an area equivalent diameter of at least 3 μm, A Ｔ A tire tread according to claim 1 or 2, wherein the percentage is ≤1%.

4. For defects having an area equivalent diameter of at least 4 μm, A Ｔ A tire tread according to any one of claims 1 to 3, wherein the percentage is ≤0.6%.

5. For defects with an area equivalent diameter of at least 5 μm, A Ｔ A tire tread according to any one of claims 1 to 4, wherein the percentage is ≤0.4%.

6. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is made of a material of formula A Ｔ ≤ a・e －ｂｘ Having a low total defect concentration as indicated by +c, x = silica packing amount (phr), A Ｔ This represents the area ratio of defects in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a = 4, b = 0.08, and c = 1.9, (ii) For defects having an area equivalent diameter of at least 3 μm, a = 2.4, b = 0.07, and c = 1, (iii) For defects having an area equivalent diameter of at least 4 μm, a = 0.8, b = 0.008, and c = 0.09, (iv) For defects having an area equivalent diameter of at least 5 μm, a = -0.73, b = 0.15, and c = 0.93, (v) For defects with an area equivalent diameter of at least 6 μm, a = -5.26, b = 0.001, and c = 5.38 A tire tread that satisfies at least one of the following conditions.

7. A Ｔ (i) to (v), that is, (i) For defects having an area equivalent diameter of at least 2 μm, a = 3.5, b = 0.8, and c = 1.5, (ii) For defects having an area equivalent diameter of at least 3 μm, a = 2.1, b = 0.07, and c = 0.79, (iii) For defects having an area equivalent diameter of at least 4 μm, a = 0.7, b = 0.008, and c = 0.08, (iv) For defects having an area equivalent diameter of at least 5 μm, a = 0.5, b = 0.002, and c = 0, (v) For defects having an area equivalent diameter of at least 6 μm, a = -5.3, b = 0.001, and c = 5.35 A tire tread according to claim 6, satisfying at least one of the following conditions.

8. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is defined as a value N, which is the number of defects per unit area in a tread slice with a thickness of 1 μm. Ｔ It has a low total defect concentration as indicated by N Ｔ (i) to (vi), that is, (i) For defects having an area equivalent diameter of at least 2 μm, N Ｔ ≤1700 / mm ２ , (ii) For defects having an area equivalent diameter of at least 3 μm, N Ｔ ≤950 / mm ２ , (iii) For defects having an area equivalent diameter of at least 4 μm, N Ｔ ≤250 / mm ２ , (iv) For defects having an area equivalent diameter of at least 5 μm, N Ｔ ≤100 / mm ２ , and (v) For defects having an area equivalent diameter of at least 6 μm, N Ｔ ≤ 50 / mm ２ A tire tread that satisfies at least one of the following conditions.

9. For defects having an area equivalent diameter of at least 2 μm, N Ｔ ≤1600 / mm ２ The tire tread according to claim 8.

10. For defects having an area equivalent diameter of at least 3 μm, N Ｔ ≤900 / mm ２ The tire tread according to claim 8 or 9.

11. For defects having an area equivalent diameter of at least 4 μm, N Ｔ ≤200 / mm ２ The tire tread according to any one of claims 8 to 10.

12. For defects having an area equivalent diameter of at least 5 μm, N Ｔ ≤100 / mm ２ The tire tread according to any one of claims 8 to 11.

13. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is a material of formula N Ｔ ≤ a・e －ｂｘ Having a low total defect concentration as indicated by +c, x = silica packing amount (phr), N Ｔ This is the number of defects per unit area in a tread slice with a thickness of 1 μm, i.e., (i) to (v), (i) For defects having an area equivalent diameter of at least 2 μm, a = 2500, b = 0.007, and c = 0. (ii) For defects having an area equivalent diameter of at least 3 μm, a = 1500, b = 0.018, and c = 0. (iii) For defects having an area equivalent diameter of at least 4 μm, a = 580, b = 0.14, and c = 240, (iv) For defects having an area equivalent diameter of at least 5 μm, a = -30, b = 0.01, and c = 120, (v) For defects with an area equivalent diameter of at least 6 μm, a = -590, b = 0.0014, and c = 611 A tire tread that satisfies at least one of the following conditions.

14. N Ｔ (i) to (v), that is, (i) For defects having an area equivalent diameter of at least 2 μm, a = 2100, b = 0.009, and c = 0. (ii) For defects having an area equivalent diameter of at least 3 μm, a = 1400, b = 0.022, and c = 0, (iii) For defects having an area equivalent diameter of at least 4 μm, a = 450, b = 0.14, and c = 180, (iv) For defects having an area equivalent diameter of at least 5 μm, a = -30, b = 0.01, and c = 105, (v) For defects having an area equivalent diameter of at least 6 μm, a = -590, b = 0.0013, and c = 600 A tire tread according to claim 13, satisfying at least one of the following conditions.

15. The tire tread according to any one of claims 1 to 14, wherein the total defect concentration satisfies at least one of (i) to (iv).

16. The tire tread according to any one of claims 1 to 14, wherein the total defect concentration satisfies at least one of (i) to (iii).

17. The tire tread according to any one of claims 1 to 14, wherein the total defect concentration satisfies (i) or (ii).

18. A tire tread comprising at least one elastomer and at least one silica in an amount of at least 15 phr, wherein the tread is defined as a value A, which is the area ratio of voids in a tread slice with a thickness of 1 μm. Ｖ It has a low void concentration as indicated by A Ｖ (i) and (ii), that is, (i) For a void having an area equivalent diameter of at least 2 μm, A Ｖ ≤0.6%, and (ii) For a void having an area equivalent diameter of at least 3 μm, A Ｖ ≤0.4% A tire tread that satisfies at least one of the following conditions.

19. For a void having an area equivalent diameter of at least 2 μm, A Ｖ The tire tread according to claim 18, wherein the percentage is ≤0.5%.

20. For a void having an area equivalent diameter of at least 3 μm, A Ｖ The tire tread according to claim 18 or 19, wherein the percentage is ≤0.3%.

21. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is made of a material of formula A Ｖ ≤ a・e －ｂｘ Having a low void concentration as indicated by +c, x = silica packing amount (phr), A Ｖ This is the area ratio of voids in a tread slice with a thickness of 1 μm, where (i) and (ii) are, (i) For voids having an area equivalent diameter of at least 2 μm, a = 3.3, b = 0.037, and c = 0.1, (ii) For voids having an area equivalent diameter of at least 3 μm, a = 2.3, b = 0.075, and c = 0.28 A tire tread that satisfies at least one of the following conditions.

22. A Ｖ (i) and (ii), that is, (i) For voids having an area equivalent diameter of at least 2 μm, a = 2.5, b = 0.037, and c = 0.1, (ii) For voids having an area equivalent diameter of at least 3 μm, a = 1.9, b = 0.075, and c = 0.25 A tire tread according to claim 21, satisfying at least one of the following conditions.

23. A tire tread comprising at least one elastomer and at least one silica in an amount of at least 15 phr, wherein the tread is defined by a value N, which is the number of voids per unit area in a tread slice with a thickness of 1 μm. Ｖ It has a low void concentration as indicated by N Ｖ (i) to (iii), that is, (i) For a void having an area equivalent diameter of at least 2 μm, N Ｖ ≤500 / mm ２ , (ii) For a void having an area equivalent diameter of at least 3 μm, N Ｖ ≤150 / mm ２ , and (iii) For a void having an area equivalent diameter of at least 4 μm, N Ｖ ≤65 / mm ２ A tire tread that satisfies at least one of the following conditions.

24. For a void having an area equivalent diameter of at least 2 μm, N Ｖ ≤400 / mm ２ The tire tread according to claim 23.

25. For a void having an area equivalent diameter of at least 3 μm, N Ｖ ≤140 / mm ２ The tire tread according to claim 23 or 24.

26. A tire tread comprising at least one elastomer and at least 15 phr of silica, wherein the tread is a material of formula N Ｖ ≤ a・e －ｂｘ Having a low void concentration as indicated by +c, x = silica packing amount (phr), N Ｖ This is the number of voids per unit area in a tread slice with a thickness of 1 μm, where (i) and (ii), i.e., (i) For voids having an area equivalent diameter of at least 2 μm, a = 800, b = 0.02, and c = 400, (ii) For voids having an area equivalent diameter of at least 3 μm, a = 480, b = 0.1, and c = 170 A tire tread that satisfies at least one of the following conditions.

27. N Ｖ (i) and (ii), that is, (i) For voids having an area equivalent diameter of at least 2 μm, a = 720, b = 0.05, and c = 370, (ii) For voids having an area equivalent diameter of at least 3 μm, a = 430, b = 0.12, and c = 140 A tire tread according to claim 26, satisfying at least one of the following conditions.

28. The tire tread according to any one of claims 1 to 27, wherein the silica is present in an amount of at least 20 phr.

29. The tire tread according to any one of claims 1 to 27, wherein the silica is present in an amount ranging from 15 phr to 200 phr.

30. The tire tread according to any one of claims 1 to 27, wherein the silica is present in an amount ranging from 15 phr to 100 phr.

31. The tire tread according to any one of claims 1 to 30, wherein the silica is precipitated silica.

32. The tire tread according to any one of claims 1 to 30, wherein the silica is rice husk silica.

33. The aforementioned silica is 80 m ２ / g to 350m ２ A tire tread according to any one of claims 1 to 32, having a CTAB surface area in the range of up to / g.

34. The silica mentioned above is 140 m ２ / g to 250m ２ A tire tread according to any one of claims 1 to 32, having a CTAB surface area in the range of up to / g.

35. The tire tread according to any one of claims 1 to 34, further comprising carbonaceous material, carbon black, nanocellulose, lignin, clay, nanoclay, metal oxide, metal carbonate, pyrolysis carbon, recycled carbon, recovered carbon black, graphene, graphene oxide, reduced graphene oxide, high-density reduced graphene oxide granules, carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanostructures, fibrous fillers, hydrothermal carbon, nanocrystalline cellulose starch particles, polysaccharides, glucans, dextran, microfibrillated cellulose, starch, siliceous soil, crumb rubber, and functionalized crumb rubber, or combinations thereof, and at least one additional filler selected from these materials that have been coated and treated.

36. The tire tread according to claim 35, wherein silica is present in an amount ranging from 25% to 99% by weight, and at least one additional filler is present in an amount ranging from 1% to 75% by weight relative to the total weight of the fillers.

37. The tire tread according to claim 35 or 36, wherein the at least one additional filler is carbon black.

38. The tire tread according to claim 37, wherein the total filler content is in the range of 30 phr to 100 phr, the silica is present in an amount in the range of 30 phr to 99 phr, and the carbon black is present in an amount in the range of 1 phr to 30 phr.

39. The tire tread according to claim 37, wherein the total filler content is 80 phr, the silica is present in an amount ranging from 15 phr to 30 phr, and the carbon black is present in an amount ranging from 20 phr to 40 phr.

40. The tire tread according to any one of claims 1 to 39, wherein the tread has a thickness ranging from 4 mm to 150 mm.

41. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer is selected from natural rubber, functionalized natural rubber, styrene-butadiene rubber, functionalized styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, polybutadiene rubber, functionalized polybutadiene rubber, polyisoprene rubber, ethylene-propylene rubber, isobutylene-based elastomer, polychloroprene rubber, nitrile rubber, hydrogenated nitrile rubber, polysulfide rubber, polyacrylate elastomer, fluoroelastomer, perfluoroelastomer, silicone elastomer, thermoplastic block copolymer, and mixtures thereof.

42. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer is selected from natural rubber, styrene-butadiene rubber, polybutadiene rubber, and mixtures thereof.

43. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer comprises natural rubber in an amount of at least 20% by weight relative to the total weight of the elastomer.

44. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer comprises natural rubber in an amount of at least 50% by weight relative to the total weight of the elastomer.

45. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer is natural rubber.

46. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer is a mixture comprising natural rubber and at least one of styrene-butadiene rubber and polybutadiene rubber.

47. The tire tread according to any one of claims 1 to 40, wherein the at least one elastomer comprises styrene-butadiene rubber and polybutadiene rubber.

48. The tire tread according to claim 47, wherein the at least one elastomer further comprises natural rubber in an amount ranging from 0.1% to 10% by weight relative to the total weight of the at least one elastomer.

49. The tire tread is selected from truck and bus radial (TBR) tire treads, off-road (OTR) tire treads, passenger car tire treads, performance car tire treads, light truck tire treads, motorcycle tire treads, electric vehicle tire treads, and heavy equipment tire treads, as described in any one of claims 1 to 48.

50. The tire tread is selected from truck and bus radial (TBR) tire treads, as described in any one of claims 1 to 48.

51. The tire tread is obtained from a composite formed by mixing the silica as wet silica with the at least one elastomer as a solid elastomer, according to any one of claims 1 to 50.

52. A tire having the tread described in any one of claims 1 to 51.

53. A tire having a tread as described in any one of claims 1 to 51, wherein the tire has a rolling resistance coefficient of RRc of 7 N / kN or less.

54. A tire having a tread as described in any one of claims 1 to 51, wherein the tire has a normalized rolling resistance coefficient of 95 or less.

55. A tire having a tread according to any one of claims 1 to 51, wherein the tire has a normalized rolling resistance that is 10% lower than that of an equivalent design tire tread having an equivalent amount of carbon black filler.

56. A tire having a tread according to any one of claims 1 to 51, wherein the tire has an equivalent tread wear rate or a reduced tread wear rate compared to a tire tread of equivalent design having an equivalent amount of carbon black filler.

57. A tire having a tread according to any one of claims 1 to 51, wherein the tire has a normalized rolling resistance that is 10% lower than that of a tire tread obtained from a dry mixed equivalent prepared from a dry filler and a solid elastomer.

58. A tire having a tread according to any one of claims 1 to 51, wherein the tire has an equivalent tread wear rate or a reduced tread wear rate compared to a tire tread obtained from a dry mixed equivalent prepared from a dry filler and a solid elastomer.

Images