PNEUMATIC TIRES

Abstract

Pneumatic tire formed by molding a rubber composition for a tire, wherein the rubber composition contains: from 70 to 150 parts by mass of silica per 100 parts by mass of diene rubber formed from two kinds of modified styrene-butadiene rubbers and a butadiene rubber and an oil, and from 5 to 15% by mass of 3-octanoylthio-1-propyltriethoxysilane with respect to a mass of the silica, wherein the diene rubber contains a total of 75% by mass or more and less than 100% by mass of the two types of modified styrene-butadiene rubbers and more than 0% by mass and 25% by mass or less of the butadiene rubber, wherein a total amount of oil component containing the oil is from 25 to 45 mass% of a total mass of the filler containing the silicon dioxide, wherein a glass transition temperature of the rubber composition is -50°C or less, wherein a difference between glass transition temperatures of the two kinds of modified styrene-butadiene rubbers is 20°C or more, and wherein a first modification group of a first modified styrene-butadiene rubber and a second modification group of a second modified styrene-butadiene rubber of the two types of modified styrene-butadiene rubbers are selected from the group comprising: epoxy group, carboxy group, amino group, hydroxy group, alkoxy group, silyl group, alkoxysilyl group, amide group, oxysilyl group, silanol group, isocyanate group, isothiocyanate group, carbonyl group, aldehyde group.

Description

Technical field

[0001] The present invention relates to a pneumatic tire having excellent dry grip performance, wet grip performance, low rolling resistance and snow performance. State of the art

[0002] All-season tires mounted on high-performance vehicles are required to have excellent dry grip and wet grip performance, as well as high snow performance to improve safety and low rolling resistance to improve fuel economy. However, it is difficult to provide these properties to a high degree in a compatible manner because these properties contradict each other. For example, there are cases where a high content of butadiene rubber is included to lower the glass transition temperature of a rubber composition to improve snow performance. However, problems arise in that the dispersibility of silica is reduced, and dry grip performance, wet grip performance, and low rolling resistance are deteriorated.

[0003] JP 6329187 B describes an all-season tire that prioritizes wet grip performance, ice grip performance, and low rolling resistance, manufactured from a rubber composition containing a natural rubber, a butadiene rubber, a styrene-butadiene rubber, silica, and a plasticizer, in which their contents satisfy a formula with a specific relationship. However, the performance required for an all-season pneumatic tire required by consumers is even higher, and thus, further improvement is required.

[0004] DE 10 2010 062 557 A1 describes a rubber composition for use in tires, comprising 60 to 120 parts by weight of silica with a CTAB specific surface area of ​​70 to 175 m2 / g, from 3 to 25 parts by weight of an aromatic modified terpene resin per 100 parts by weight of a diene rubber, 30 to 80% by weight of a modified styrene-butadiene rubber, and from 10 to 80% by weight of a butadiene rubber.

[0005] DE 11 2013 002 176 T5 relates to a rubber composition for tires comprising: 100 parts by weight of diene rubber containing 5 to 50 wt.% of modified S-SBR, 2 to 50 parts by weight of an aromatically modified terpene resin with a softening point of 100°C or higher, and a total content of 60 to 130 parts by weight of two types of silica. One functional group of the modified S-SBR has reactivity with a silanol group. Brief description of the inventionTechnical problem

[0006] An object of the present invention is to provide a pneumatic tire having excellent dry grip performance, wet grip performance, low rolling resistance and snow performance. Solution to the problem

[0007] A pneumatic tire according to the present invention which achieves the above-described object is formed by forming a rubber composition for a tire, the rubber composition containing: from 70 to 150 parts by mass of silicon dioxide per 100 parts by mass of diene rubber formed from two kinds of modified styrene-butadiene rubbers and a butadiene rubber and an oil, and from 5 to 15 mass% of 3-octanoylthio-1-propyltriethoxysilane with respect to a mass of silicon dioxide, wherein the diene rubber contains a total of 75% by mass or more and less than 100% by mass of the two types of modified styrene-butadiene rubbers and more than 0% by mass and 25% by mass or less of the butadiene rubber, wherein a total amount of oil component containing the oil is from 25 to 45 mass% of a total mass of the filler containing the silicon dioxide, wherein a glass transition temperature of the rubber composition is -50°C or less, wherein a difference between glass transition temperatures of the two kinds of modified styrene-butadiene rubbers is 20°C or more, and wherein a first modification group of a first modified styrene-butadiene rubber and a second modification group of a second modified styrene-butadiene rubber of the two types of modified styrene-butadiene rubbers are selected from the group comprising: epoxy group, carboxy group, amino group, hydroxy group, alkoxy group, silyl group, alkoxysilyl group, amide group, oxysilyl group, silanol group, isocyanate group, isothiocyanate group, carbonyl group, aldehyde group. Advantageous effects of the invention

[0008] According to a pneumatic tire according to an embodiment of the present invention, since a tread portion is formed by molding the above-described rubber composition for a tire, even better dispersibility of silica can be achieved, and thus a rubber composition for a tire having excellent dry grip performance, wet grip performance, low rolling resistance, and snow performance can be obtained.

[0009] In the rubber composition for a tire, preferably both weight average molecular weights of the two kinds of modified styrene-butadiene rubbers are 400000 or more, and a difference between the glass transition temperatures of the two kinds of modified styrene-butadiene rubbers is 20°C or higher, and an even better balance of dry grip performance, wet grip performance, low rolling resistance, and snow performance can be achieved.

[0010] In the rubber composition for a tire, preferably at least one of the two kinds of modified styrene-butadiene rubbers has an alkoxysilyl group, and an even better balance of dry grip performance, wet grip performance, low rolling resistance, and snow performance can be achieved.

[0011] In the rubber composition for a tire, the silica used is preferably silica with a specific CTAB adsorption surface area of ​​140 m 2 / g or more and less than 180 m 2 / g and silicon dioxide with a specific CTAB adsorption surface of 180 m 2 / g up to 250 m 2 / g, and an even lower rolling resistance can be achieved.

[0012] The pneumatic tire according to an embodiment of the present invention has excellent performances as a pneumatic tire for all seasons, and in particular can provide dry grip performance, wet grip performance, low rolling resistance, and snow performance highly in a compatible manner by forming the tread portion by molding the rubber composition for a tire. Brief description of the drawings Fig. 1 is a partial cross-sectional view illustrating an example of a pneumatic tire according to an embodiment of the present invention in the tire meridian direction. Description of embodiments

[0013] Fig. 1 is a partial cross-sectional view illustrating an example of a pneumatic tire according to an embodiment in the tire meridian direction. The pneumatic tire includes a tread portion 1, a side portion 2, and a bead portion 3.

[0014] In Fig.1, two carcass layers 4 in which reinforcing cords extending in the tire radial direction are arranged at a predetermined pitch in the tire circumferential direction and embedded in a rubber layer extend between left- and right-side bead portions 3, and both ends of the two carcass layers 4 are folded back from the inner side to the outer side in the tire axial direction around a bead core 5 embedded in each of the bead portions 3, so that a bead filler 6 is wrapped. An inner liner layer 7 is arranged inside the carcass layers 4. Two belt layers 8 in which reinforcing cords extending at an inclination with respect to the tire circumferential direction are arranged at a predetermined pitch in the tire axial direction and embedded in the rubber layer are arranged on the outer peripheral side of the carcass layers 4 of the tread portion 1.These reinforcing cords of the two belt layers 8 are arranged crosswise with opposite inclination directions with respect to the tire circumferential direction. Furthermore, a belt cover layer 9 is arranged on the outer peripheral side of the belt layer 8. A tread rubber 10 is arranged on an outer peripheral side of the belt cover layer 9, forming the tread portion 1. Furthermore, a side rubber is arranged on the outer side in the tire width direction of the carcass layer 4, forming the side portion 2.

[0015] In a pneumatic tire according to an embodiment of the present invention, a rubber composition constituting the tread portion 1 and / or the side portion 2 contains from 70 to 150 mass parts of silica per 100 mass parts of diene rubber formed from two kinds of modified styrene-butadiene rubbers and a butadiene rubber and an oil, and from 5 to 15 mass% of 3-octanoylthio-1-propyltriethoxysilane with respect to a mass of the silica, wherein the diene rubber contains 75 mass% or more and less than 100 mass% of the two kinds of modified styrene-butadiene rubbers and more than 0 mass% and 25 mass% or less of the butadiene rubber, wherein a total amount of oil component containing the oil is from 25 to 45 mass% of a total mass of filler containing the Contains silicon dioxide and has a glass transition temperature of -50°C or less.

[0016] Diene rubber is formed from two types of modified styrene-butadiene rubbers and a butadiene rubber. There are no specific restrictions on the butadiene rubber, as long as the butadiene rubber is a butadiene rubber generally used in tire rubber compositions. Because butadiene rubber has a low glass transition temperature, blending it into tire rubber compositions can improve snow performance. However, blending butadiene rubber may impair the dispersibility of silica, and thus may not achieve sufficient improvement in dry grip performance, wet grip performance, and low rolling resistance.Meanwhile, by using the configuration of the present invention, the dispersibility of silica can be made excellent even in the presence of butadiene rubber, and an excellent balance of dry grip performance, wet grip performance, low rolling resistance, and snow performance can be achieved.

[0017] The butadiene rubber content is more than 0 mass% and 25 mass% or less, preferably from 6 to 23 mass%, and more preferably from 10 to 21 mass% per 100 mass% of diene rubber. Without butadiene rubber, snow performance cannot be sufficiently improved. If the butadiene rubber content exceeds 25 mass%, dry grip performance will deteriorate.

[0018] The diene rubber contains two types of modified styrene-butadiene rubbers. The two types of modified styrene-butadiene rubbers refer to two types of modified styrene-butadiene rubbers, at least one of which is selected from the type of modification group, the degree of modification, and the type of styrene-butadiene rubber (e.g., polymerization method, catalyst, styrene content, vinyl content, and molecular weight) differing. The two types of modified styrene-butadiene rubbers in which the type of modification group and the type of styrene-butadiene rubber differ are preferred.

[0019] The modification group of a first modified styrene-butadiene rubber and a second modification group of a second modified styrene-butadiene rubber of the two types of modified styrene-butadiene rubbers are selected from the group consisting of: epoxy group, carboxyl group, amino group, hydroxy group, alkoxy group, silyl group, alkoxysilyl group, amide group, oxysilyl group, silanol group, isocyanate group, isothiocyanate group, carbonyl group, and aldehyde group. For example, an alkoxysilyl group, amino group, hydroxy group, alkoxy group, silyl group, aminosilyl group, and glycidyl group are preferred. Furthermore, at least one of the two types of modified styrene-butadiene rubbers preferably has a hydroxy group. By allowing a styrene-butadiene rubber containing a hydroxy group to be included, even better dispersibility of silica can be achieved.

[0020] The weight-average molecular weight of each of the two types of modified styrene-butadiene rubbers is preferably 400,000 or more, and more preferably from 420,000 to 1,400,000. Setting both weight-average molecular weights of the modified styrene-butadiene rubbers to 400,000 or more is preferable because even lower rolling resistance can be achieved. Furthermore, high abrasion resistance can also be achieved. The weight-average molecular weights of the modified styrene-butadiene rubbers can be increased or decreased, for example, by polymerization conditions. The weight-average molecular weights of the modified styrene-butadiene rubbers can be measured by gel permeation chromatography (GPC) based on calibration with polystyrene standards.

[0021] The glass transition temperatures of the two types of modified styrene-butadiene rubbers differ from each other, and the difference between the two glass transition temperatures is 20°C or more, and preferably from 25°C to 50°C. By adjusting the difference between the glass transition temperatures of the modified styrene-butadiene rubbers to 20°C or more, the on-snow performance can be improved. The glass transition temperatures of the modified styrene-butadiene rubbers can be adjusted by changing, for example, the styrene amounts, vinyl amounts, and weight-average molecular weight. The glass transition temperature of each of the modified styrene-butadiene rubbers can be measured using a differential scanning calorimeter (DSC) at a temperature elevation rate of 10°C / min and calculated based on the intersection point method.It should be noted that when each of the modified styrene-butadiene rubbers contains an oil-extending ingredient, the glass transition temperature of the modified styrene-butadiene rubber is determined without the oil-extending ingredient or before the addition of the oil-extending ingredient.

[0022] In the two types of modified styrene-butadiene rubbers, the combination of the types of modification groups and glass transition temperatures is not subject to any specific restrictions. For example, the glass transition temperature of styrene-butadiene rubber containing an alkoxysilyl group is preferably lower than the glass transition temperature of styrene-butadiene rubber containing a modification group other than the alkoxysilyl group, and this can achieve even better silica dispersibility.

[0023] The total content of the two types of modified styrene-butadiene rubbers is 75 mass% or more and less than 100 mass%, preferably from 76 to 92 mass%, and more preferably from 77 to 90 mass% per 100 mass% of diene rubber. If the total content of the two types of modified styrene-butadiene rubbers is less than 75 mass%, the dispersibility of silica cannot be sufficiently improved. If the diene rubber is formed only from the two types of modified styrene-butadiene rubbers, the on-snow performance cannot be sufficiently improved.

[0024] Regarding the contents of the two types of modified styrene-butadiene rubbers, the mass ratio thereof is not particularly limited; however, the ratio of the content of the modified styrene-butadiene rubber having a higher glass transition temperature (M1 mass part) to the content of the modified styrene-butadiene rubber having a lower glass transition temperature (M2 mass part) (M1 / M2) is preferably from 25 / 75 to 75 / 25, and more preferably from 40 / 60 to 60 / 40. By setting the mass ratio (M1 / M2) of the contents of the two types of modified styrene-butadiene rubbers to such a range, even better silica dispersibility can be achieved.

[0025] For the rubber composition for a tire, in the diene rubber, the sum of the two types of modified styrene-butadiene rubbers and the butadiene rubber is 100 mass %. However, a pneumatic tire according to an embodiment of the present invention does not prevent reuse in its compounding process or molding process. For example, when a tread portion is green-molded by winding an unvulcanized layer formed from the rubber composition around a predetermined position on a molding drum, a small piece of the unvulcanized layer cut off before and after winding the unvulcanized layer is sometimes reused in the process. At this time, the small piece of the unvulcanized layer can be compounded during the production of the rubber composition for a tire as long as the objects of the present invention are not hindered.In the rubber composition for a tire, the amount of another diene rubber contained in the small piece of the unvulcanized layer (e.g., natural rubber and unmodified styrene-butadiene rubber) is preferably 5 mass% or less, and more preferably 3 mass% or less, per 100 mass% of diene rubber.

[0026] The rubber composition for a tire contains silica. Examples of silica include wet silica (aqueous silica), dry silica (silicic anhydride), calcium silicate, and aluminum silicate. One of these materials can be used alone, or a combination of two or more can be used. Surface-treated silica, in which the surface of the silica is treated with a silane coupling agent, can also be used.

[0027] The specific CTAB adsorption surface of the silica is not subject to any special restrictions and is preferably from 140 to 300 m 2 / g and more preferably from 160 to 260 m 2 / g. By adjusting the specific CTAB adsorption surface area of ​​silica to 140 m 2 / g or more, the wet grip performance of the rubber composition can be ensured. In addition, by adjusting the specific CTAB adsorption surface area of ​​silica to 300 m 2 / g or less, excellent dry grip performance, wet grip performance, and low rolling resistance can be achieved. In this specification, the CTAB specific surface area of ​​silica is a value measured according to ISO 5794.

[0028] As the silica, two types of silica with different specific CTAB adsorption surface areas can preferably be used. The two types of silica have different specific CTAB adsorption surface areas, and the difference between the specific CTAB adsorption surface areas is preferably 20 m 2 / g or more and more preferably from 25 to 50 m 2 / g. By setting the difference between the specific CTAB adsorption surfaces to 20 m 2 / g or more, even better dispersibility of silicon dioxide can be achieved.

[0029] The silica with the smaller specific CTAB adsorption surface area preferably has a specific CTAB adsorption surface area of ​​preferably 140 m 2 / g or more and less than 180 m 2 / g and more preferably from 150 to 175 m 2 / g. On the other hand, the silica with the larger specific CTAB adsorption surface area preferably has a specific CTAB adsorption surface area of ​​180 m 2 / g up to 250 m 2 / g and more preferably from 190 to 240 m 2 / g. Adjusting the specific CTAB adsorption surfaces of the two types of silica to such ranges can make rolling resistance low and improve wet grip performance.

[0030] Silica is blended at a rate of 70 to 150 parts by mass, and preferably 80 to 140 parts by mass, per 100 parts by mass of diene rubber. By adjusting the blended amount of silica to 70 parts by mass or more, dry grip performance, wet grip performance, and low rolling resistance can be improved. Furthermore, adjusting the blended amount of silica to 150 parts by mass or less can improve the dispersibility of silica.

[0031] The rubber composition for a tire may contain another filler besides silica. Examples of such another filler include carbon black, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, and calcium sulfate. Of these, carbon black is preferred. One type of these other fillers may be used alone, or a combination of two or more of these types may be used.

[0032] By allowing 3-octanoylthio-1-propyltriethoxysilane to be blended as a silane coupling agent, the rubber composition for a tire can improve the dispersibility of silica. 3-octanoylthio-1-propyltriethoxysilane is blended at from 5 to 15 mass%, and preferably from 6 to 14 mass%, based on the mass of silica. Blending 5 mass% or more of 3-octanoylthio-1-propyltriethoxysilane can improve the dispersibility of silica. In addition, blending 15 mass% or less of 3-octanoylthio-1-propyltriethoxysilane can suppress the condensation of silane coupling agents and can provide a rubber composition with desired hardness and strength.

[0033] The rubber composition for a tire contains an oil. Examples of the oil include natural oils, synthetic oils, and oils added during production of a rubber composition, such as plasticizers. In addition, an oil-extending component contained in the diene rubber is also an oil. In the rubber composition for a tire, the total amount of the oil component, including an oil added during production, is determined with respect to the total mass of fillers including silica. That is, the total amount of the oil component including an oil is from 25 to 45 mass%, and preferably from 27 to 43 mass%, with respect to the total mass of the filler including silica. If the total amount of the oil component is less than 25 mass%, the on-snow performance will deteriorate.In addition, if the total amount is greater than 45 mass%, the dry grip performance will deteriorate and the steering stability may also be insufficient.

[0034] The rubber composition for a tire has a glass transition temperature of -50°C or lower, and preferably from -50 to -65°C. If the glass transition temperature of the rubber composition for a tire is higher than -50°C, the performance on snow deteriorates. The glass transition temperature of the rubber composition for a tire can be measured using a differential scanning calorimeter (DSC) at a temperature elevation rate of 10°C / min and calculated based on the intersection point method.The glass transition temperature of the rubber composition for a tire can be calculated as the sum of the products obtained by multiplying a glass transition temperature of each of the two types of modified styrene-butadiene rubbers, the butadiene rubber, and the oil, and a mass fraction (a real number greater than 0 and less than 1) of each of the components when the total content of these components is 1 (weighted average). Note that when components each having a glass transition temperature, such as a liquid polymer or a terpene resin, are optionally included, the glass transition temperature of the rubber composition for a tire is calculated by adding the glass transition temperatures and the mass fractions of these optional components.

[0035] The rubber composition for a tire may also contain various additives commonly used in the rubber composition for a tire within a range that does not impair the object of the present invention. Examples thereof include a vulcanizing or crosslinking agent, a vulcanization accelerator, an aging retarder, a plasticizer, a processing aid, a liquid polymer, a terpene resin, and a thermosetting resin. These additives can be kneaded by any publicly known method to form a rubber composition and can be used for vulcanization or crosslinking. Blended amounts of these additives can be any known conventional amounts as long as the objects of the present invention are not hindered.

[0036] The pneumatic tire according to one embodiment of the present invention has, for example, a tread portion or side portion formed by molding the above-described rubber composition for a tire, and highly exhibits an excellent balance of dry grip performance, wet grip performance, low rolling resistance, and snow performance. The pneumatic tire preferably exhibits excellent performance as an all-season pneumatic tire, and in particular, its tread portion is formed by molding the rubber composition for a tire. The pneumatic tire is a tire with significantly high performance as an all-season pneumatic tire with excellent dry grip performance, wet grip performance, low rolling resistance, and snow performance.

[0037] Embodiments according to the present invention will be further described below by way of examples. However, the scope of the present invention is not limited to these examples. Example

[0038] Each of the rubber compositions for a tire (Examples 1 to 10, Standard Example, and Comparative Examples 1 to 7) was prepared according to the formulations shown in Tables 1 and 2, using the compounding agents shown in Table 3 as common ingredients. Except for the sulfur and the vulcanization accelerator, the ingredients were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, then discharged from the mixer and cooled at room temperature. This was added to the 1.7-liter sealed Banbury mixer, and the sulfur and the vulcanization accelerators were then added and mixed, thus preparing a rubber composition for a tire.Note that in the modified styrene-butadiene rubber (modified SBR-2) rows in Tables 1 and 2, the net blended amount of modified SBR, excluding the amount of the oil extender, is written in parentheses in addition to the blended amount of the product. In addition, the blended amounts of the compounding agents shown in Table 3 are expressed as values ​​in parts by mass per 100 parts by mass of diene rubber shown in Tables 1 and 2.

[0039] A vulcanization test piece was prepared by subjecting the obtained tire rubber composition to press vulcanization at 160 °C for 20 minutes using a predetermined mold. The glass transition temperature thereof was measured using a differential scanning calorimeter (DSC) at a temperature elevation rate of 10 °C / min and calculated based on the intersection point method. The glass transition temperatures are also shown in Tables 1 and 2.

[0040] Eighteen types of pneumatic radial tires in which the rubber composition for a tire obtained as described above was used in a tread rubber (tire size: 195 / 65R15) were vulcanization-molded, and dry grip performance, wet grip performance, snow performance, steering stability, and rolling resistance were measured by the following test methods. Dry grip performance

[0041] The pneumatic tire obtained as described above was mounted on a standard rim, inflated to an air pressure of 250 kPa, and mounted on a test vehicle. The test vehicle ran on a dry road surface with comparatively fewer bumps and valleys, and a braking distance when the test vehicle was braked at an initial speed of 100 km / h was measured. Each of the obtained results is expressed as an index value obtained by calculating a reciprocal thereof, with the standard example assigned a value of 100, and shown in the "Dry Grip Performance" rows in Tables 1 and 2. A larger index value indicates a shorter braking distance, and an index value of 102 or greater indicates excellent dry grip performance. Wet grip performance

[0042] The pneumatic tire obtained as described above was mounted on a standard rim, inflated to an air pressure of 250 kPa, and mounted on a test vehicle. The test vehicle ran on a wet road surface with comparatively fewer bumps and valleys, and a braking distance when the test vehicle was braked at an initial speed of 100 km / h was measured. Each of the obtained results is expressed as an index value obtained by calculating a reciprocal thereof, with the standard example assigned a value of 100, and shown in the "Wet Grip Performance" rows in Tables 1 and 2. A larger index value indicates a shorter braking distance, and an index value of 102 or greater indicates excellent wet grip performance. Performance on snow

[0043] The pneumatic tire obtained as described above was mounted on a standard rim, inflated to an air pressure of 250 kPa, and mounted on a test vehicle. The test vehicle ran on a road surface covered with compressed snow, and a braking distance when the test vehicle was braked at an initial speed of 40 km / h was measured. Each of the obtained results is expressed as an index value obtained by calculating a reciprocal thereof, with the standard example assigned a value of 100, and shown in the "Performance on Snow" rows in Tables 1 and 2. A larger index value indicates a shorter braking distance, and an index value of 102 or greater indicates excellent performance on snow. Steering stability

[0044] The pneumatic tire obtained as described above was mounted on a standard rim, inflated to an air pressure of 250 kPa, and mounted on a test vehicle. The test vehicle drove on a dry road surface with comparatively fewer bumps and valleys, and a sensory evaluation was conducted for the steering response on a scale of one to five. The results obtained are shown in the "Steering Stability" rows in Tables 1 and 2. Larger scores indicate superior steering stability. A score of 4 or higher is preferred. Rolling resistance

[0045] The pneumatic tire obtained as described above was mounted on a standard rim, inflated to an air pressure of 210 kPa, and mounted on an indoor drum testing machine with a drum diameter of 1707 mm according to JIS D 4230. The resistance was measured as rolling resistance under a test load of 4.82 kN at a speed of 80 km / h. The obtained results are shown in the "Rolling Resistance" rows in Tables 1 and 2, with the value 100 assigned to the standard example. A smaller index value indicates lower rolling resistance, and an index value of 98 or less indicates excellent low rolling resistance. [Table 1-I] Standard example Example 1 Example 2 Example 3 Example 4 Modified SBR 1 Mass part 40 40 50 35 40 Modified SBR 2 Mass part 55 (40) 55 (40) 55 (40) 55 (40) 55 (40) Modified SBR 3 Mass part BR Mass part 20 20 10 25 20 soot Mass part 20 20 20 20 40 Silicon dioxide 1 Mass part 100 100 100 100 80 Silicon dioxide 2 Mass part Adhesion promoter 1 Mass part 10 Adhesion promoter 2 Mass part 10 10 10 8 Aroma oil Mass part 25 25 25 25 25 Total amount of filler (mass part) (120) (120) (120) (120) (120) Total amount of oil component (mass part) (40) (40) (40) (40) (40) Ratio (oil / filler) Mass% 33 33 33 33 33 Glass transition temperature ° C -54 -54 -51 -56 -54 Dry grip performance Index value 100 105 108 103 110 Wet grip performance Index value 100 110 115 108 106 Performance on snow Index value 100 105 102 109 105 Steering stability Evaluation 3 4 4 4 5 Rolling resistance Index value 100 90 87 93 97 [Table 1-II] Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Modified SBR 1 Mass part 40 40 40 40 40 40 Modified SBR 2 Mass part 55 (40) 55 (40) 55 (40) 55 (40) 55 (40) Modified SBR 3 Mass part 40 BR Mass part 20 20 20 20 20 20 soot Mass part 10 20 20 20 20 20 Silicon dioxide 1 Mass part 110 100 100 20 40 100 Silicon dioxide 2 Mass part 80 60 Adhesion promoter 1 Mass part Adhesion promoter 2 Mass part 11 10 10 10 10 10 Aroma oil Mass part 25 20 35 25 25 40 Total amount of filler (mass part) (120) (120) (120) (120) (120) (120) Total amount of oil component (mass part) (40) (35) (50) (40) (40) (40) Ratio (oil / filler) Mass% 33 29 42 33 33 33 Glass transition temperature ° C -54 -54 -54 -54 -54 -51 Dry grip performance Index value 104 107 102 105 105 103 Wet grip performance Index value 112 112 108 106 108 108 Performance on snow Index value 105 103 112 105 105 103 Steering stability Evaluation 4 5 4 4 4 4 Rolling resistance Index value 88 92 88 85 88 93 [Table 2-I] Comparison example 1 Comparison example 2 Comparison example 3 Comparison example 4 Modified SBR 1 Mass part 30 55 40 40 Modified SBR 2 Mass part 55 (40) 55 (40) 55 (40) 55 (40) BR Mass part 30 5 20 20 NR Mass part soot Mass part 20 20 60 20 Silicon dioxide 1 Mass part 100 100 60 100 Adhesion promoter 2 Mass part 10 10 6 10 Aroma oil Mass part 25 25 25 10 Total amount of filler (mass part) (120) (120) (120) (120) Total amount of oil component (mass part) (40) (40) (40) (25) Ratio (oil / filler) Mass% 33 33 33 21 Glass transition temperature ° C -57 -49 -54 -54 Dry grip performance Index value 100 110 115 110 Wet grip performance Index value 102 118 103 114 Performance on snow Index value 113 98 105 99 Steering stability Evaluation 3 4 5 5 Rolling resistance Index value 96 85 103 95 [Table 2-II] Comparison example 5 Comparison example 6 Comparison example 7 Modified SBR 1 Mass part 40 60 32 Modified SBR 2 Mass part 55 (40) 55 (40) 55 (40) BR Mass part 20 20 NR Mass part 8 soot Mass part 20 20 20 Silicon dioxide 1 Mass part 100 100 100 Adhesion promoter 2 Mass part 10 10 10 Aroma oil Mass part 45 25 25 Total amount of filler (mass part) (120) (120) (120) Total amount of oil component (mass part) (60) (40) (40) Ratio (oil / filler) Mass% 50 33 33 Glass transition temperature ° C -54 -48 -54 Dry grip performance Index value 99 112 102 Wet grip performance Index value 104 120 108 Performance on snow Index value 115 95 105 Steering stability Evaluation 3 4 3 Rolling resistance Index value 86 84 95 [Table 3] Common formulation of rubber compositions zinc oxide 2,0 Mass part Stearic acid 1,0 Mass part Anti-aging agent 1 3,0 Mass part Anti-aging agent 2 2,0 Mass part sulfur 2,4 Mass part Vulcanization accelerator-1 2,0 Mass part Vulcanization accelerator-1 1,0 Mass part

[0046] For Table 3, the types of raw materials used are as follows. • Modified SBR 1: Modified styrene-butadiene rubber, NS612, available from Zeon Corporation, the modification group is a hydroxy group, styrene amount: 15%, vinyl amount: 31%, weight average molecular weight: 440,000, glass transition temperature: -61°C • Modified SBR 2: Modified styrene-butadiene rubber, TUFDENE E581, available from Asahi Kasei Corporation, the modification group is a hydroxy group, styrene amount: 36%, vinyl amount: 38%, weight average molecular weight: 1260000, glass transition temperature: -34°C • Modified SBR 3: Modified styrene-butadiene rubber, NS116R, available from Zeon Corporation, the modification group is an amino group, styrene amount: 22%, vinyl amount: 63%, weight average molecular weight: 390,000, glass transition temperature: -23°C BR: Butadiene rubber; Nipol BR1220, available from Zeon Corporation, glass transition temperature: -106°C • NR: Natural rubber, STR 20, glass transition temperature: -70 ° C • Carbon black: N-134, available from Thai Tokai Carbon • Silica-1: 9000GR, available from Evonik, specific CTAB adsorption surface is 200 m 2 / G • Silica-2: ULTRASIL 7000 GR, available from Evonik, specific CTAB adsorption surface area is 158 m 2 / G • Adhesion Promoter-1: Sulfide-based silane adhesion promoter, Si69, available from Evonik Degussa, bis(triethoxysilylpropyl)tetrasulfide • Adhesion promoter 2: NXT silane, available from Evonik Degussa, 3-octanoylthio-1-propyltriethoxysilane • Aroma oil: VivaTec 500, available from H&R Chemical • Zinc oxide: Zinc oxide III, available from Seido Chemical Industry Co., Ltd. • Stearic acid: Stearic acid beads, available from NOF Corporation • Age retarder 1: Santoflex 6PPD, available from Solutia Europe • Age retarder 2: Pilnox TDQ, available from Nocil Limited • Sulfur: Oil-treated sulfur powder “Golden Flower” (sulfur content: 95.24 mass%), available from Tsurumi Chemical Industry Co., Ltd. • Vulcanization accelerator-1: NOCCELER CZ-G (CZ), available from Ouchi Shinko Chemical Industrial Co., Ltd. • Vulcanization accelerator-2: Soxinol DG (DPG), available from Sumitomo Chemical Co., Ltd.

[0047] As can be seen from Tables 1 and 2, it was confirmed that the pneumatic tire obtained by rubber compositions of Examples 1 to 10, respectively, achieved excellent dry grip performance, wet grip performance, snow performance, steering stability, and low rolling resistance.

[0048] Since the pneumatic tire obtained in Comparative Example 1 contained a total amount of the two kinds of modified styrene-butadiene rubbers of less than 75 mass% and contained more than 25 mass% of butadiene rubber, the pneumatic tire had poor dry grip performance and steering stability.

[0049] Since the pneumatic tire of Comparative Example 2 had a glass transition temperature of the rubber composition for a tire of more than -50 °C, the pneumatic tire had poor performance on snow.

[0050] Since the pneumatic tire of Comparative Example 3 had the blended amount of silica less than 70 parts by mass, the pneumatic tire had a high rolling resistance.

[0051] Since the pneumatic tire of Comparative Example 4 had a ratio of the total amount of the oil component to the total mass of the filler including silica (in the tables “Ratio (Oil / Filler)”) of less than 25 mass %, the pneumatic tire exhibited poor performance on snow.

[0052] Since the pneumatic tire of Comparative Example 5 had a ratio of the total amount of the oil component to the total mass of the filler including silica (in the tables “Ratio (Oil / Filler)”) of more than 45 mass %, the pneumatic tire had poor dry grip performance and steering stability.

[0053] Since the pneumatic tire of Comparative Example 6 did not contain butadiene rubber, the pneumatic tire exhibited poor snow performance. Since the pneumatic tire of Comparative Example 7 contained less than 75 mass% of the total amount of the two types of modified styrene-butadiene rubbers and 8 mass% of the natural rubber, the pneumatic tire exhibited poor steering stability. List of reference symbols 1 tread section 2 page section

Claims

A pneumatic tire formed by molding a rubber composition for a tire, wherein the rubber composition contains from 70 to 150 parts by mass of silica per 100 parts by mass of diene rubber formed from two kinds of modified styrene-butadiene rubbers and a butadiene rubber and an oil, and from 5 to 15 mass% of 3-octanoylthio-1-propyltriethoxysilane with respect to a mass of the silica, wherein the diene rubber contains a total of 75 mass% or more and less than 100 mass% of the two kinds of modified styrene-butadiene rubbers and more than 0 mass% and 25 mass% or less of the butadiene rubber, wherein a total amount of oil component containing the oil is from 25 to 45 mass% of a total mass of the filler containing the silica, wherein a glass transition temperature of the rubber composition is -50°C or less,wherein a difference between glass transition temperatures of the two types of modified styrene-butadiene rubbers is 20°C or more, and wherein a first modification group of a first modified styrene-butadiene rubber and a second modification group of a second modified styrene-butadiene rubber of the two types of modified styrene-butadiene rubbers are selected from the group consisting of: epoxy group, carboxy group, amino group, hydroxy group, alkoxy group, silyl group, alkoxysilyl group, amide group, oxysilyl group, silanol group, isocyanate group, isothiocyanate group, carbonyl group, and aldehyde group. A pneumatic tire according to claim 1, wherein both weight average molecular weights of the two kinds of modified styrene-butadiene rubbers are 400,000 or more. A pneumatic tire according to any one of claims 1 to 2, wherein, as the silica, silica having a specific CTAB adsorption surface area of ​​140 m2 / g or more and less than 180 m2 / g and silica having a specific CTAB adsorption surface area of ​​180 m2 / g to 250 m2 / g are mixed. A pneumatic tire for all seasons, the pneumatic tire being a pneumatic tire according to any one of claims 1 to 3 and comprising a tread portion formed by molding the rubber composition for a tire.

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