Tire

Abstract

The control stability in the high-speed driving process is improved, and particularly the responsiveness in the bending process is improved. The tire of the present invention includes a tread in which a crown rubber layer, which is a part of a tread portion, is made of a rubber composition containing 80 parts by mass to 100 parts by mass of a styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, and the rubber composition contains 100 parts by mass or less of silica per 100 parts by mass of the rubber component, and the complex modulus (30 DEG C E *) of the rubber composition measured in a tensile deformation mode under the conditions of a temperature of 30 DEG C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is greater than 8.0 MPa. The thickness of the tread portion is 8.5 mm or less.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] From a safety perspective, tires need to have excellent handling stability.

[0003] Therefore, various technologies have been proposed for improving the handling stability by, for example, improving the grip performance (eg, Patent Documents 1 to 4).

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] JP 2011-93386A

[0007] [Patent Document 2] JP 2013-79017A

[0008] [Patent Document 3] JP 2014-133845 A

[0009] [Patent Document 4] JP 2016-37100A Summary of the invention

[0010] [Problems to be solved by the invention]

[0011] However, with the construction of expressways in recent years, people often travel long distances on expressways. In this case, for the above-mentioned prior art, there is a strong need to further improve the handling stability during high-speed driving, especially the responsiveness when entering a curve.

[0012] The purpose of the present invention is to improve the handling stability during high-speed driving, especially the responsiveness when entering a corner.

[0013] [Methods used to solve the problem]

[0014] The present invention is a tire having a tread portion, wherein:

[0015] a cap rubber layer forming the tread portion formed of a rubber composition containing 80 parts by mass or more and 100 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, and containing 100 parts by mass or less of silica based on 100 parts by mass of the rubber component;

[0016] The complex modulus (30°C E * ) is greater than 8.0 MPa; and

[0017] The thickness of the tread portion is 8.5 mm or less.

[0018] [Effects of the Invention]

[0019] According to the present invention, the handling stability during high-speed driving, especially the responsiveness when entering a corner, can be improved. DETAILED DESCRIPTION

[0020] [1] Features of the tire of the present invention

[0021] First, the features of the tire of the present invention will be described.

[0022] 1. Overview

[0023] The tire of the present invention includes components containing fiber materials, etc., such as a carcass, a belt layer, a belt layer reinforcement layer and other components that are arranged between one and the other of a pair of bead portions that engage with the rim and form the skeleton of the tire; and a tread portion that is radially arranged outward on these components.

[0024] The tread portion includes a cap rubber layer which is disposed radially outward on the tire and forms a ground contact surface, and, if necessary, a base rubber layer which is disposed radially inward on the cap rubber layer.

[0025] The crown rubber layer forming the tread portion is formed of a rubber composition, wherein the rubber composition contains 80 parts by mass or more and 100 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of the rubber component, and contains 100 parts by mass or less of silica per 100 parts by mass of the rubber component. The complex modulus (30°C E * ) is greater than 8.0Mpa. The thickness of the tread portion is less than 8.5mm.

[0026] The cap rubber layer described herein is not limited to the rubber layer forming the outermost layer of the tread portion, and in the case where two or more layers exist within 5 mm inward from the tread surface, at least one of the layers must satisfy the requirements of the rubber composition.

[0027] As will be described below, these features can improve handling stability during high-speed driving, especially responsiveness when entering corners.

[0028] 2. Mechanism of the Effect of the Tire of the Present Invention

[0029] It is believed that the mechanism by which the above-mentioned effects are exhibited in the tire of the present invention is as follows.

[0030] (1) Low styrene SBR content

[0031] As described above, the cap rubber layer of the present invention is formed of a rubber composition containing 80 parts by mass or more and 100 parts by mass or less of SBR having a styrene content of 25% by mass or less per 100 parts by mass of the rubber component.

[0032] Since SBR having a low styrene content (specifically, 25% by mass or less) has a low glass transition temperature (Tg), by including 80 parts by mass or more and 100 parts by mass or less of this SBR per 100 parts by mass of the rubber component and forming a major part of the crown rubber layer, the Tg of the entire rubber composition can be lowered, and the fluidity of the polymer can be improved. Therefore, this is believed to improve road compliance, and improve handling stability during high-speed driving, especially responsiveness when entering a corner.

[0033] In addition, SBR with a low styrene content forms tiny styrene areas within the rubber matrix and, when input is applied from the road surface, heat is more easily generated due to friction in the areas, which is believed to improve road compliance and improve handling stability during high-speed driving, especially responsiveness when entering corners.

[0034] In the present invention, the styrene content is preferably 20% by mass or less, more preferably 15% by mass or less, while the lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, more preferably 8% by mass or more.

[0035] The phrase "80 parts by mass or more of SBR having a styrene content of 25% by mass or less is contained per 100 parts by mass of the rubber component" means that the amount of SBR in 100 parts by mass of the rubber component is 80 parts by mass or more and the amount of styrene in the entire SBR is 25% by mass or less.

[0036] In other words, when the rubber component contains only one styrene-containing polymer (SBR), this indicates that the styrene amount is 25% by mass or less; when the rubber component contains multiple styrene-containing polymers (SBR), this indicates that the styrene amount calculated by the sum of the products of the styrene amount (mass %) in each polymer and the mixing amount (mass parts) of the polymer in every 100 parts by mass of the rubber component is 25% by mass or less.

[0037] More specifically, when 100 parts by mass of the rubber component contains X1 parts by mass of SBR1 having a styrene content of S1% by mass and X2 parts by mass of SBR2 having a styrene content of S2% by mass, the styrene content calculated by the formula {(S1×X1)+(S2×X2)} / (X1+X2) is 25% by mass or less.

[0038] Furthermore, in the vulcanized rubber composition, the amount of styrene can also be calculated by measuring the amount of styrene contained in the rubber composition after acetone extraction using solid-state nuclear magnetic resonance (solid-state NMR) or Fourier transform infrared spectrometer (FTIR).

[0039] In the present invention, the amount of SBR per 100 parts by mass of the rubber component is more preferably 85 parts by mass or more, and more preferably 90 parts by mass or more.

[0040] (2) Silica content

[0041] In the crown rubber layer of the tire of the present invention, the content of silicon dioxide in every 100 parts by mass of the rubber component is less than 100 parts by mass, that is, not more than the content of the rubber component. This makes it easier for silicon dioxide to be evenly dispersed in the rubber matrix, making the rubber composition uniform and improving road compliance. In addition, a silicon dioxide network is easily formed in the rubber matrix, so that rubber reinforcement can be effectively obtained, and the force transmission inside the tire is improved. Therefore, it is believed that the handling stability during high-speed driving, especially the responsiveness when entering a corner, is improved.

[0042] In the present invention, in view of the reinforcing properties of rubber, the content of silica is more preferably 98 parts by mass or less per 100 parts by mass of the rubber component, while the lower limit is preferably 75 parts by mass or more, more preferably 80 parts by mass or more, and more preferably 90 parts by mass or more.

[0043] (3) Complex elastic modulus (30℃E * )

[0044] In the present invention, the rubber composition forming the cap rubber layer has a complex elastic modulus (30°C E*) greater than 8.0 MPa measured at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain rate of 1% and a tensile deformation mode.

[0045] The complex elastic modulus is a parameter indicating the rigidity of the rubber layer. * When the rigidity of the entire rubber exceeds 8.0 MPa, it is believed that a larger reaction force is exhibited from a macroscopic point of view, and the handling stability during high-speed driving, especially the responsiveness when entering a corner, is improved.

[0046] In the present invention, 30°C E *More preferably, it is 8.1 MPa or more, more preferably, it is 8.3 MPa or more, more preferably, it is greater than 8.5 MPa, more preferably, it is 8.7 MPa or more, more preferably, it is 8.8 MPa or more, more preferably, it is greater than 9.0 MPa, and more preferably, it is 9.2 MPa or more. On the other hand, in view of showing moderate compliance, the upper limit is preferably 11.0 MPa or less, more preferably 10.0 MPa or less, more preferably 9.5 MPa or less, and more preferably 9.4 MPa or less.

[0047] Here, the “complex elastic modulus” can be measured using a viscoelasticity measuring device (for example, “Eplexor (registered trademark)” manufactured by GABO Corporation).

[0048] Complex modulus of rubber layer (30℃E * ) can be appropriately adjusted by mixing the materials described later. Specifically, it can be adjusted by increasing the proportion of fillers (such as silica and carbon black), reducing the content of plasticizer components (such as oil), increasing the content of resin components or increasing the content of vulcanizing agents (such as sulfur and accelerators).

[0049] (4) Tread thickness

[0050] In addition, in the tire of the present invention, the thickness of the tread portion is reduced to less than 8.5 mm, which is believed to further improve the rigidity of the tread portion, increase force transmission inside the tire, and increase tangential rigidity, thereby improving handling stability during high-speed driving, especially responsiveness when entering a corner.

[0051] In the present invention, the thickness of the tread portion is more preferably 8.0 mm or less, while the lower limit is preferably 7.0 mm or more, and more preferably 7.5 mm or more.

[0052] In the present invention, the tread portion is a member in a region forming a ground contact surface of the tire, and refers to a portion radially outward of members including a fiber material such as a carcass, a belt layer, and a belt reinforcing layer.

[0053] "Thickness of tread" refers to the thickness of the tread on the equatorial plane of the tire in the radial section of the tire. When the tread is formed by a single rubber composition, it is the thickness of the rubber composition. When the tread is formed by a layered structure of multiple rubber compositions described later, it is the total thickness of these layers. When the tire has grooves on the equatorial plane, it refers to the thickness of the interface from the intersection of the straight line connecting the outermost end points of the grooves in the tire radial direction and the equatorial plane of the tire to the innermost part of the tread in the tire radial direction. The thickness of the tread portion can be measured by adjusting the bead portion to the standardized rim width in the cross section cut out in the tire radial direction.

[0054] In the above description, the "standardized rim" is a rim specified for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is a standard rim of applicable size described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tire and Rim Technical Organization), it is a "Measuring Rim" described in the "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it is a "Design Rim" described in the "YEAR BOOK". JATMA, ETRTO, and TRA are referred to in sequence, and if there is an applicable size when referring, the standard is followed. In the case of tires not specified in the standard, it refers to a rim that can be assembled and maintain internal pressure (i.e., a rim that does not cause air leakage from between the rim and the tire) and has the smallest rim diameter and the narrowest rim width.

[0055] As described above, in the tire of the present invention, the effects shown in (1) to (4) work together, so that slippage with the road surface is suppressed due to the microscopic fluidity, high heat generation and compliance of the rubber matrix itself, and at the same time, from a macroscopic perspective, a reaction force can be easily generated due to appropriate rigidity and easy force transmission. Therefore, when the steering angle is turned to enter a corner while running at high speed, the tire has excellent responsiveness, and it is believed that the handling stability during high-speed running is improved.

[0056] [2] More preferred embodiments of the tire of the present invention

[0057] The tire of the present invention can achieve better effects by adopting the following aspects.

[0058] 1. Loss tangent of the crown rubber layer at 30℃ (30℃tanδ)

[0059] In the present invention, the rubber composition forming the crown rubber layer has a loss tangent (30°C tan δ) measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5% and a dynamic strain rate of 1% that is preferably 0.26 or less, more preferably 0.25 or less, more preferably 0.24 or less, more preferably 0.22 or less, more preferably 0.21 or less, and more preferably 0.20 or less.

[0060] The loss tangent (tan δ) can be regarded as a parameter indicating the phase difference between the input and the response of the rubber, and by reducing the loss tangent corresponding to the frequency / temperature of the rotation (i.e., 30°C tan δ) to 0.25 or less, the phase difference between the input and the response is reduced, and the responsiveness is improved, which is considered to further improve the handling stability during high-speed running. The lower limit is not particularly limited, but is preferably 0.15 or more, more preferably 0.16 or more, and more preferably 0.18 or more.

[0061] Here, the “loss tangent (tan δ)” can be measured using a viscoelasticity measuring device (for example, “Eplexor (registered trademark)” manufactured by GABO Corporation) in the same manner as the measurement of the above-mentioned “complex elastic modulus”.

[0062] Furthermore, 30°C tan δ can be appropriately adjusted by mixing the components described later, and can be reduced by reducing the styrene content in the SBR component, reducing the resin component, reducing the amount of fillers such as silica and carbon black, or increasing the contents of sulfur and vulcanization accelerators.

[0063] 2. Multi-layer tread

[0064] In the present invention, the tread portion may be formed by only one crown rubber layer disposed on the outer side in the tire radial direction, or may be formed by two layers by disposing the base rubber layer on the inner side of the crown rubber layer in the tire radial direction, or may be formed by three layers, or may be formed by four or more layers. In this case, the thickness of the crown rubber layer in the entire tread portion is preferably 10% or more. This can generate sufficient friction between the tread surface and the road surface during high-speed driving, so that the friction can be fully transmitted to the inside of the tire, which is considered to further improve the handling stability during high-speed driving. More preferably, the thickness is 70% or more.

[0065] As described above, in the case where the tire is formed of a layered structure of multiple rubber compositions, the "thickness of the tread portion" refers to the total thickness of the stacked layers. In the case where the tire has grooves on the equatorial plane of the tire, the "thickness of the tread portion" refers to the thickness from the intersection of the straight line connecting the outermost end points of the grooves in the tire's radial direction and the equatorial plane of the tire to the innermost interface of the tread portion in the tire's radial direction.

[0066] The “thickness of the crown rubber layer” refers to the thickness of the crown rubber layer on the tire equatorial plane in the tire radial cross section, and when the tire has grooves on the equatorial plane, it refers to the thickness from the intersection of the straight line connecting the outermost end points of the grooves in the tire radial direction and the tire equatorial plane to the interface with the base rubber layer at the innermost part of the tread in the tire radial direction. The “thickness of the base rubber layer” refers to the thickness from the interface with the crown rubber layer to the innermost interface of the tread in the tire radial direction.

[0067] As described above, the thickness of the crown rubber layer and the thickness of the base rubber layer can be calculated by measuring the thickness of the crown rubber layer and the thickness of the base rubber layer in the thickness of the tread portion. When there are grooves on the equatorial plane of the tire, the thickness of the crown rubber layer and the thickness of the base rubber layer can be calculated at the center of the land portion of the tread portion closest to the equatorial plane, thereby calculating the thickness of the crown rubber layer and the thickness of the base rubber layer.

[0068] In the case of a multi-layer tread portion, it is preferred that the 30°C tanδ of the base rubber layer is smaller than that of the crown rubber layer. This is believed to improve the responsiveness by reducing the phase difference when a response is generated inside the tire relative to the grip performance generated by the crown rubber layer, thereby improving the handling stability during high-speed driving.

[0069] Furthermore, it is preferred that the 30°E of the base rubber layer * Less than 30℃E of the crown rubber layer * This makes it easier for deformation to occur inside the tread and for the entire tread surface to come into contact with the road surface, which is thought to help further improve handling stability during high-speed driving.

[0070] 30℃E of base rubber layer * and 30°C tan δ can be adjusted in the same manner as in the above-mentioned cap rubber layer.

[0071] 3. Particle size of silica contained in the crown rubber layer

[0072] In the present invention, from the viewpoint of improving the reinforcing property, the particle diameter (average primary particle diameter) of silica contained in the cap rubber layer is preferably 17 nm or less.

[0073] The average primary particle size can be calculated by directly observing silica particles extracted from a rubber composition cut out from a tire using a transmission electron microscope (TEM) or the like, calculating an equivalent cross-sectional diameter from the area of ​​each silica particle obtained, and calculating an average value.

[0074] 4. Resin component content in the crown rubber layer

[0075] In the present invention, the rubber composition forming the cap rubber layer preferably contains a resin component.

[0076] It is believed that by including the resin component in the rubber composition, the adhesion of the resin component ensures grip to the road surface even during high-speed running, thereby further improving the handling stability during high-speed running.

[0077] Preferred resin components include rosin resins, styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins and acrylic resins, which will be described later, and among these resins, styrene resins (e.g., α-methylstyrene) are more preferred. The content per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and more preferably 35 parts by mass or more. In consideration of the softening of the rubber, the upper limit is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and more preferably 40 parts by mass or less.

[0078] 5. Acetone extract of the crown rubber layer (AE)

[0079] In the present invention, from the viewpoint of exhibiting excellent handling stability through stable grip performance during high-speed running, the acetone extract (AE) of the cap rubber layer is preferably 10% by mass or more, more preferably 12% by mass or more, more preferably 13.4% by mass or more, more preferably 14% by mass or more, more preferably 14.5% by mass or more, and more preferably 16% by mass or more. On the other hand, the upper limit is preferably 23% by mass or less, more preferably 20% by mass or less, more preferably 19% by mass or less, more preferably 18.3% by mass or less, and more preferably 18% by mass or less.

[0080] The acetone extract (AE) can be considered as an indicator showing the amount of softener in the rubber composition, and can also be considered as an indicator showing the fluidity of the molecular chain of the rubber composition. Therefore, by properly controlling the amount of AE in the crown rubber layer, the tire can have a sufficient contact area with the road surface during high-speed driving, thereby showing stable grip performance and excellent handling stability during high-speed driving.

[0081] The acetone extract (AE) can be measured according to JIS K 6229: 2015. Specifically, a vulcanized rubber specimen cut out from a measurement site is immersed in acetone at room temperature and pressure for 72 hours, and the mass loss rate (%) of the specimen is measured to obtain AE (mass %).

[0082] More specifically, each vulcanized rubber specimen was immersed in acetone at room temperature and pressure for 72 hours to extract soluble components, the mass of each specimen before and after the extraction was measured, and the acetone extract (AE) could be calculated according to the following formula.

[0083] Acetone extract (%) = {(mass of rubber sample before extraction - mass of rubber sample after extraction) / (mass of rubber sample before extraction)} × 100

[0084] The acetone extract content can be appropriately changed by changing the compounding ratio of the plasticizer in the rubber composition.

[0085] 6. Landing rate

[0086] In the tire of the present invention, when mounted on a standardized rim and under a standardized internal pressure, the ground contact rate of the tread portion of the tire is preferably 55% or more, more preferably 60% or more, more preferably 63% or more, more preferably 65% ​​or more, and more preferably 68% or more.

[0087] The "ground contact ratio" is the ratio of the actual contact area to the hypothetical contact area that fills all the grooves on the tread surface. A larger ground contact ratio means a larger contact area with the road surface, which results in sufficient and stable grip performance and excellent handling stability.

[0088] The upper limit of the ground contact rate is not particularly limited, but is preferably 85% or less, more preferably 80% or less, and still more preferably 75% or less.

[0089] The ground contact ratio can be determined from the ground contact shape under standardized rim, standardized internal pressure and standardized load conditions.

[0090] Specifically, the tire is mounted on a standardized wheel hub, a standardized internal pressure is applied, and the tire is left at rest at 25°C for 24 hours. Then, the ink is applied to the tire tread surface, a standardized load is applied and pressed on a cardboard (camber angle is 0°), and the contact shape is transferred to the cardboard. The tire is rotated 72° in the circumferential direction, and the contact shape is transferred to 5 places. That is, 5 contact shapes are obtained. At this time, the 5 contact shapes are smoothly connected at the part interrupted by the groove in the outline of the contact shape, and the obtained shape is called a virtual contact surface.

[0091] The contact rate can be calculated as follows: (average area of ​​5 contact shapes (black parts) transferred to the cardboard / average area of ​​the virtual contact surface obtained from the 5 contact shapes)×100 (%).

[0092] "Standard internal pressure" refers to the air pressure specified for each tire in the above standards. In the case of JATMA, it refers to the maximum air pressure; in the case of ETRTO, it refers to the "INFLATION PRESSURE" table; in the case of TRA, it refers to the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLDINFLATION PRESSURES" table. As in the case of "standardized rim", it refers to referring to JATMA, ETRTO and TRA in sequence and following these standards. In the case of a tire not specified in the standard, it refers to the standardized internal pressure (above 250 KPa) of another tire size (specified in the standard) that specifies the standardized rim as a standard rim. In the case where multiple standard internal pressures of 250 KPa or more are specified, it refers to the minimum value among them.

[0093] The "standardized load" is a load specified for each tire by each standard in the standard system including the standards on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to the "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table. As in the case of the above-mentioned "standardized rim" and "standard internal pressure", refer to JATMA, ETRTO and TRA in sequence and follow their standards. In the case of a tire not specified by the standard, the standardized load W is calculated as follows L .

[0094] V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt

[0095] W L＝ 0.000011×V+175

[0096] W L :Standardized load (kg)

[0097] V: Imaginary volume of the tire (mm 3 )

[0098] Dt: Tire outer diameter Dt (mm)

[0099] Ht: Tire section height (mm)

[0100] Wt: tire section width (mm)

[0101] 7. The contact rate of the tread and the 30℃E of the crown rubber layer * The relationship between

[0102] In the tire of the present invention, the ground contact ratio R (%) of the tread portion and the complex modulus E of the crown rubber layer at 30°C are * The product of (MPa) is preferably 527 or more, more preferably 540 or more, and more preferably 560 or more. As described above, the ground contact ratio is the contact area ratio of the tread portion, and it is believed that by making this area ratio equal to the 30°E of the crown rubber layer, * The product of is 560 or more, the rigidity of the tread portion is improved, and the handling stability during high-speed driving can be easily improved.

[0103] The contact rate R and the 30℃E of the crown rubber layer * The product of is more preferably 566 or more, more preferably 572 or more, more preferably 580 or more, more preferably 598 or more, more preferably 600 or more, more preferably 611 or more, more preferably 617.5 or more, and more preferably 626 or more. On the other hand, the upper limit is not particularly limited, but is preferably 800 or less, more preferably 750 or less, and more preferably 700 or less.

[0104] 8. 30℃E of tread thickness and crown rubber layer * The relationship between

[0105] In the tire of the present invention, the 30°C E * Ratio to the thickness of the tread G (mm) (30℃E * / G) is preferably 0.95 or more, more preferably 0.98 or more, and more preferably 1.00 or more. It is believed that the greater the thickness G of the tread portion, the greater the deformation that occurs in the tread portion during cornering, and the worse the responsiveness. Therefore, it is believed that by making the 30°E of the crown rubber layer * The thickness G relative to the tread portion is sufficiently high, the rigidity of the tread portion is ensured, and good responsiveness can be exhibited.

[0106] 30℃E * / G is more preferably 1.02 or more, more preferably 1.04 or more, more preferably 1.05 or more, more preferably 1.08 or more, more preferably 1.10 or more, more preferably 1.11 or more, more preferably 1.12 or more, and more preferably 1.15 or more. There is no specific upper limit, but it is preferably 3.00 or less, more preferably 2.50 or less, and more preferably 2.00 or less.

[0107] 9. Flatness

[0108] The aspect ratio is the ratio of the section height to the section width of the tire, and the smaller the ratio, the smaller the proportion of the portion deformed in the tire width direction relative to the friction received by the tread portion, and the easier it is to transmit force, thereby improving stability and responsiveness, improving handling, and improving handling stability during high-speed driving. On the contrary, if the aspect ratio is small, the amount of bending of the side portion is small, which may lead to deterioration of ride comfort.

[0109] In consideration of these points, in the tire of the present invention, the specific aspect ratio is preferably 30% or more and 60% or less.

[0110] The aspect ratio (%) can be calculated by the following formula using the tire cross-sectional height Ht (mm), tire cross-sectional width Wt (mm), tire outer diameter Dt (mm) and rim radius R (mm) when the internal pressure is 250 kPa.

[0111] Flatness (%) = (Ht / Wt) × 100 (%)

[0112] Ht=(Dt-R) / 2

[0113] [3] Implementation Method

[0114] Hereinafter, the present invention will be described in detail according to embodiments.

[0115] 1. Rubber composition for forming a crown rubber layer

[0116] In the tire of the present invention, the rubber composition forming the cap rubber layer can be obtained by appropriately adjusting the kinds and contents of various compounding materials (eg, rubber component, filler, plasticizer, vulcanizing agent and vulcanization accelerator described below).

[0117] (1) Mixed materials

[0118] (a) Rubber component

[0119] In the present invention, the rubber component contains styrene-butadiene rubber (SBR) from the viewpoint of containing styrene in the rubber component, but may also contain styrene polymers other than SBR (e.g., styrene-butadiene-styrene block copolymer (SBS) and styrene-butadiene block copolymer (SB)).

[0120] Rubbers (polymers) commonly used for producing tires, such as diene rubbers (including isoprene rubbers, butadiene rubber (BR) and nitrile rubber (NBR)) and butyl rubbers (including butyl rubber) can be used in combination with the above-mentioned styrene polymers. For example, a combination of SBR and BR or a combination of SBR, BR and isoprene rubber is preferred. These rubbers may be oil-extended rubbers that have been previously filled with a plasticizer component (such as oil, resin or liquid rubber) described later.

[0121] (i) SBR

[0122] The weight average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. In the present invention, as described above, the amount of styrene in the SBR component is less than 25% by mass. The vinyl content (butadiene content of 1,2-bonding) of SBR is, for example, greater than 5% by mass and less than 70% by mass. The vinyl content of SBR refers to the butadiene content of 1,2-bonding relative to all butadiene parts in the SBR component. The structural identification of SBR can be carried out using, for example, the JNM-ECA series equipment manufactured by JEOL.

[0123] In the present invention, as described above, the SBR content per 100 parts by mass of the rubber component is 80 parts by mass or more and 100 parts by mass or less, more preferably 85 parts by mass or more, and more preferably 90 parts by mass or more.

[0124] SBR is not particularly limited, and for example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR) etc. can be used. SBR can be unmodified SBR or modified SBR. In addition, hydrogenated SBR obtained by hydrogenating the butadiene part of SBR. Hydrogenated SBR can be obtained by subsequently hydrogenating the BR part of SBR, or a similar structure can be obtained by copolymerizing styrene, ethylene and butadiene.

[0125] The modified SBR may be any SBR having a functional group that interacts with a filler (e.g., silica), and examples thereof include a terminal-modified SBR in which at least one end of the SBR is modified with a compound (modifier) ​​having a functional group (terminal-modified SBR having a functional group at the terminal); a main chain-modified SBR having a functional group in the main chain; a main chain-terminal-modified SBR having a functional group in the main chain and at least one terminal (e.g., an SBR having a functional group in the main chain and at least one terminal modified by a modifier); and a terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and into which a hydroxyl group or an epoxy group is introduced.

[0126] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a thioether group, a disulfide group, a sulfone group, a sulfoxide group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0127] As the modified SBR, for example, SBR modified with a compound (modifier) ​​represented by the following formula can be used.

[0128]

[0129] In the formula, R 1 , R 2 and R 3 are the same or different and represent an alkyl group, an alkoxy group, a silyl group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH) or a derivative thereof. 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 May bond to form a ring structure together with the nitrogen atom. "n" represents an integer.

[0130] As the SBR modified with the compound (modifier) ​​represented by the above formula, SBR whose polymerization end (active end) of solution-polymerized styrene-butadiene rubber (S-SBR) has been modified with the compound represented by the above formula (for example, modified SBR described in JP-A-2010-111753) can be used.

[0131] R 1 , R 2 and R 3 Preferably it is an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). "n" is preferably 1 to 5, more preferably 2 to 4, more preferably 3. When R 4 and R 5 When combined to form a ring structure together with a nitrogen atom, a 4- to 8-membered ring is preferred. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

[0132] Specific examples of the modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane and 3-diethylaminopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0133] As the modified SBR, a modified SBR modified by the following compounds (modifiers) can also be used. Examples of the modifier include: polyglycidyl ethers of polyols, such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidyl bisphenol A; polyepoxides, such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups, such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylamino compounds, such as diglycidyl Oleyl aniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl o-toluidine, tetraglycidyl m-phenylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides, such as bis(1-methylpropyl)carbamoyl chloride, 4-morpholinylphosgene, 1-pyrrolidinylphosgene, N,N-dimethylcarbamoyl chloride and N,N-diethylcarbamoyl chloride; epoxy group-containing silane compounds, such as 1,3-bis-(glycidyloxypropyl)-tetramethyl Silane compounds containing thioether groups, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, ] sulfide, (trimethylsilyl) [3- (methyldipropoxysilyl) propyl] sulfide and (trimethylsilyl) [3- (methyldibutoxysilyl) propyl] sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; alkoxysilanes such as methyltriethoxysilane, N,N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane, N,N-bis (trimethylsilyl) -3-aminopropyltriethoxysilane, N,N-bis (trimethylsilyl) aminoethyltrimethoxysilane and N,N-bis (trimethylsilyl) aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone and N,N,N',N'-bis-(tetraethylamino)benzophenone; (thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone and N,N,N',N'-bis-(tetraethylamino)benzophenone; N-substituted benzaldehyde compounds, such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2- piperidone and N-phenyl-2-piperidone; lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam and N-phenyl-β-propiolactam; and N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine -2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. The modification using the above compounds (modifiers) can be carried out by known methods. ;

[0134] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used. The SBR can be used alone or in combination of two or more.

[0135] (ii) BR

[0136] In the present invention, the rubber composition may contain BR as required. In this case, the BR content per 100 parts by mass of the rubber component is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

[0137] The weight average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The vinyl content of BR is, for example, greater than 1% by mass and less than 30% by mass. The cis content of BR is, for example, greater than 1% by mass and less than 98% by mass. The trans content of BR is, for example, greater than 1% by mass and less than 60% by mass.

[0138] BR is not particularly limited, and may be BR with a high cis content (90% or more cis content), BR with a low cis content, or BR containing syndiotactic polybutadiene crystals. BR may be unmodified or modified, and modified BR includes modified BR having the above-mentioned functional groups introduced therein. These may be used alone or in combination of two or more. The cis content may be measured by infrared absorption spectroscopy.

[0139] As BR, for example, products available from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, or the like can be used.

[0140] (iii) Isoprene rubber

[0141] In the present invention, the rubber composition may contain isoprene-based rubber as required. In this case, the content of the isoprene-based rubber per 100 parts by mass of the rubber component is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less.

[0142] Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0143] As NR, for example, SIR20, RSS#3, TSR20, SVR-L, etc., which are generally used in the tire industry, can be used. As IR, there is no particular limitation, and for example, IR2200, which is generally used in the tire industry, etc. can be used. As modified NR, deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), etc. can be mentioned; as modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. can be mentioned; as modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. can be mentioned. These can be used alone or in combination of two or more.

[0144] (iv) Other rubber components

[0145] Furthermore, as a rubber component other than the above-mentioned rubber components, a rubber (polymer) generally used for manufacturing tires, such as nitrile rubber (NBR), may be contained.

[0146] (b) Compounding materials other than rubber components

[0147] (i) Filling

[0148] In the present invention, as described above, the rubber composition contains silica as a filler, but may contain other fillers. Specific examples of fillers other than silica include carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, and biochar.

[0149] (i-1) Silicon dioxide

[0150] In the present invention, as described above, the content of silica per 100 parts by mass of the rubber component is 100 parts by mass or less, more preferably 98 parts by mass or less.

[0151] In the present invention, from the viewpoint of obtaining good durability performance, the BET specific surface area of ​​silica contained in the rubber composition is preferably greater than 140 m 2 / g, more preferably greater than 160m 2 / g, and more preferably greater than 180m 2 On the other hand, from the perspective of obtaining good rolling resistance during high-speed running, it is preferably less than 300 m 2 / g. The BET specific surface area is the value of N2 SA measured by the BET method according to ASTM D3037-93.

[0152] In the present invention, as described above, in the rubber composition, it is preferred to use silica having a particle size of 17 nm or less, and by using silica having a smaller particle size, the contact frequency with the polymer (styrene region) can be increased, thereby improving the reinforcement. The lower limit is not particularly limited, but from the perspective of dispersibility during mixing, it is preferably 10 nm or more.

[0153] Examples of silicon dioxide include dry-process silicon dioxide (anhydrous silicon dioxide) and wet-process silicon dioxide (hydrated silicon dioxide). Among them, wet-process silicon dioxide is preferred because it has a large number of silanol groups. In addition, silicon dioxide made from hydrated glass or silicon dioxide made from biomass materials (such as rice bran) can also be used.

[0154] As silica, for example, products of Evonik Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd., and the like can be used.

[0155] (i-2) Silane coupling agent

[0156] The rubber composition of the present invention preferably contains a silane coupling agent together with silica.

[0157] The silane coupling agent is not particularly limited. Specific examples of the silane coupling agent include sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)tetrasulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino Silane coupling agents of the group consisting of amino-based silane coupling agents such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more.

[0158] As the silane coupling agent, for example, products available from Evonik Industries, Momentive Corporation, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Dow Corning Toray Corporation, etc. can be used.

[0159] The content of the silane coupling agent is, for example, greater than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0160] (i-3) Carbon black

[0161] In the present invention, the rubber composition preferably contains carbon black from the viewpoint of reinforcement.

[0162] The specific content ratio of carbon black is preferably 5 parts by mass or more, and more preferably 15 parts by mass or more per 100 parts by mass of the rubber component. On the other hand, it is preferably 35 parts by mass or less, and more preferably 30 parts by mass or less.

[0163] Carbon black is not particularly limited, and examples thereof include furnace blacks (furnace blacks), such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal blacks), such as FT and MT; and channel blacks (channel blacks), such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0164] The CTAB specific surface area (cetyltrimethylammonium bromide) of carbon black is preferably 130 m 2 / g or more, more preferably 160m 2 / g or more, and more preferably 170 m 2 / g or more, on the other hand, it is preferably 250m 2 / g or less, and more preferably 200m 2 The CTAB specific surface area is a value measured according to ASTM D3765-92.

[0165] Specific carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Tanso Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Nippon Steel Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0166] (i-4) Other fillers

[0167] In addition to the above-mentioned silica and carbon black, the rubber composition may contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc., as required. The content of these fillers is, for example, greater than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0168] (ii) Plasticizer component

[0169] Rubber composition can comprise oil, liquid rubber and resin as the plasticizer component of softening rubber.Plasticizer component is the component that can be extracted with acetone from vulcanized rubber.When rubber composition comprises above-mentioned rubber filling component, the filling component contained therein is also included in these plasticizer components.Relative to the rubber component of 100 mass parts, the total content of plasticizer component is preferably more than 30 mass parts, more preferably more than 40 mass parts.On the other hand, it is preferably less than 55 mass parts, more preferably less than 50 mass parts.

[0170] (ii-1) Oil

[0171] The example of oil comprises mineral oil (commonly referred to as process oil), vegetable oil and its mixture.As mineral oil (process oil), paraffinic process oils, aromatic process oils, cycloparaffinic process oils etc. such as MES (gentle extraction solvate), DAE (distillation aromatic extract), TDAE (treated distillation aromatic extract), TRAE (treated residual aromatic extract) and RAE (residual aromatic extract) can be used.The example of vegetable oil comprises castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower seed oil, palm kernel oil, camellia oil, jojoba oil, macadamia oil and tung oil.These can be used alone or in combination of two or more.From the perspective of life cycle analysis, waste oil, waste cooking oil etc. as the lubricant in rubber mixer and automobile engine can be used as suitable material.

[0172] Examples of the process oil (mineral oil) include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., OLISOY Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., and the like.

[0173] (ii-2) Liquid rubber

[0174] The liquid rubber mentioned as the plasticizer is a polymer which is liquid at room temperature (25°C) and is a rubber component which can be extracted with acetone from a vulcanized tire. Examples of the liquid rubber include farnesene polymers, liquid diene polymers and hydrogenated products thereof.

[0175] Farnesene polymers are polymers obtained by polymerizing farnesene and have a farnesene-based structural unit. Farnesene includes isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodetetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0176] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0177] Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), and the like.

[0178] The weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) in terms of polystyrene is, for example, greater than 1.0×10 3 And less than 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0179] The content of the liquid rubber (the total content of the liquid farnesene polymer, the liquid diene polymer, etc.) relative to 100 parts by mass of the rubber component is, for example, more than 1 part by mass and less than 100 parts by mass.

[0180] As the liquid rubber, for example, products of Kuraray Co., Ltd. and Cray Valley Corporation can be used.

[0181] (ii-3) Resin component

[0182] The resin component also acts as a tackifier and can be solid or liquid at room temperature. Specific examples of the resin component include resins such as rosin resins, styrene resins, benzofuran resins, terpene resins, C5 resins, C9 resins, C5C9 resins, acrylic resins, and two or more thereof can also be used in combination. Relative to 100 parts by mass of the rubber component, the content of the resin component is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, and more preferably more than 35 parts by mass. Considering the softening of the rubber, the upper limit is preferably less than 50 parts by mass, more preferably less than 45 parts by mass, and more preferably less than 40 parts by mass.

[0183] Rosin resin is a resin whose main component is rosin acid obtained by processing rosin. These rosin resins (rosins) can be classified according to whether they are modified, and can be classified into unmodified rosin (non-modified rosin) and modified rosin (rosin derivative). The example of unmodified rosin includes tall oil rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, other chemically modified rosins, etc. Modified rosin is a modified substance of unmodified rosin, and the example of such modified rosin includes rosin ester, unsaturated carboxylic acid modified rosin, unsaturated carboxylic acid modified rosin ester, rosin amide compound and rosin amine salt.

[0184] The styrene resin is a polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers obtained by polymerizing a styrene monomer as a main component (50% by mass or more), etc. Specifically, it includes homopolymers obtained by polymerizing a styrene monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and further, copolymers obtained by copolymerizing a styrene monomer with other monomers copolymerizable with the styrene monomer.

[0185] Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene and isoprene; olefins such as 1-butene and 1-pentene; and α,β-unsaturated carboxylic acids and anhydrides thereof such as maleic anhydride and the like.

[0186] As the benzofuran resin, benzofuran-indene resin is preferably used. Benzene-indene resin is a resin containing benzofuran and indene as monomer components constituting the backbone (main chain) of the resin. Examples of monomer components other than benzofuran and indene contained in the backbone include styrene, α-methylstyrene, methylindene and vinyltoluene, etc.

[0187] The content of the coumarone-based resin is, for example, greater than 1.0 part by mass and less than 50.0 parts by mass relative to 100 parts by mass of the rubber component.

[0188] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl group when 1 g of the resin is acetylated, and is expressed in milligrams. It is a value measured by potentiometric titration (JIS K 0070: 1992).

[0189] The softening point of the coumarone-indene resin is, for example, higher than 30° C. and lower than 160° C. The softening point is a temperature at which a ball falls when the softening point specified in JIS K 6220-1:2001 is measured by a ring and ball softening point measuring apparatus.

[0190] Examples of terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins. Polyterpene is a resin obtained by polymerizing a terpene compound and its hydrogenate. A terpene compound is a terpene having (C5H8) n A hydrocarbon or an oxygen-containing derivative thereof, which is classified as a monoterpene (C10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) as a basic skeleton. Examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0191] Examples of polyterpenes include terpene resins made from the above-mentioned terpene compounds, such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin and β-pinene / limonene resin, and hydrogenated terpene resins obtained by hydrogenating the terpene resin. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins, specifically, resins formed by condensing the above-mentioned terpene compounds, phenolic compounds and formaldehyde. Examples of phenolic compounds include phenol, bisphenol A, cresol and xylenol, etc. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenol compounds such as phenol, alkylphenol, alkoxyphenol and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene and styrene containing an unsaturated hydrocarbon group; benzofuran; and indene.

[0192] C5 resin refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As the C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0193] C9 resin refers to a resin obtained by polymerizing a C9 fraction, and it can be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyl toluene, alkyl styrene, indene, methyl indene. As a specific example, it is preferred to use, for example, benzofuran-indene resin, benzofuran resin, indene resin and aromatic vinyl resin. As aromatic vinyl resin, preferably α-methylstyrene or a homopolymer of styrene or a copolymer of α-methylstyrene and styrene, because it is economical, easy to process and excellent in terms of heat generation. More preferably, a copolymer of α-methylstyrene and styrene. As aromatic vinyl resin, aromatic vinyl resins such as those commercially available from Clayton Company, Eastman Chemical Company, etc. can be used.

[0194] C5C9 resin refers to a resin obtained by copolymerizing the above-mentioned C5 fraction and the above-mentioned C9 fraction, and it may be hydrogenated or modified. Examples of C5 fraction and C9 fraction include the above-mentioned petroleum fraction. As C5C9 resin, for example, resins commercially available from Tosoh Corporation, LUHUA Corporation, etc. may be used.

[0195] The acrylic resin is not particularly limited, but for example, a solvent-free type acrylic resin may be used.

[0196] As the solvent-free acrylic resin, there can be mentioned a (meth)acrylic resin (polymer) synthesized by a high temperature continuous polymerization method (high temperature continuous bulk polymerization method, which is a method described in US 4414370 B, JP 84-6207A, JP 93-58805B, JP 89-313522A, US 5010166 B, ToaSynthetic Research Annual Report TREND2000 No.3p42-45, etc.), and a polymerization initiator, a chain transfer agent, an organic solvent, etc. are not used as auxiliary raw materials as much as possible. In the present invention, (meth)acrylic acid refers to methacrylic acid and acrylic acid.

[0197] Examples of monomer components constituting the acrylic resin include (meth)acrylic acid and (meth)acrylic acid derivatives such as (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, (meth)acrylamide derivatives, and the like.

[0198] In addition, as a monomer component constituting the above acrylic resin, an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0199] The acrylic resin may be a resin composed of only a (meth)acrylic component or a resin further having a component other than the (meth)acrylic component. In addition, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0200] As the resin component, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Co., Ltd., Nippon Paint Chemicals Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., etc. can be used.

[0201] (iii) Stearic acid

[0202] In the present invention, the rubber composition preferably contains stearic acid. For every 100 parts by mass of the rubber component, the content of stearic acid is, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass. As stearic acid, conventionally known products can be used. For example, products such as NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Co., Ltd., Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0203] (iv) Anti-aging agents

[0204] In the present invention, the rubber composition preferably contains an anti-aging agent. The content of the anti-aging agent is, for example, greater than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component.

[0205] Examples of anti-aging agents include naphthylamine anti-aging agents, such as phenyl-α-naphthylamine; diphenylamine anti-aging agents, such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine anti-aging agents, such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and N,N'-di-2-naphthyl-p-phenylenediamine; quinoline anti-aging agents, such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol anti-aging agents, such as 2,6-di-tert-butyl-4-methylphenol, styrenated phenol; bisphenol, triphenol, polyphenol anti-aging agents, such as tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate] methane. These can be used alone or in combination of two or more.

[0206] As the anti-aging agent, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis Corporation, etc. can be used.

[0207] (v) Wax

[0208] In the present invention, the rubber composition preferably contains wax. The content of the wax is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, and more preferably 1.5 to 10 parts by mass per 100 parts by mass of the rubber component.

[0209] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as vegetable wax and animal wax, synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0210] As the wax, products available from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., and the like can be used.

[0211] (vi) Zinc oxide

[0212] The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, greater than 0.5 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the rubber component. As zinc oxide, conventionally known products can be used, for example, products of Mitsui Mining and Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0213] (vii) Cross-linking agents and vulcanization accelerators

[0214] The rubber composition preferably contains a crosslinking agent (such as sulfur). The content of the crosslinking agent is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0215] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used in the rubber industry. These may be used alone or in combination of two or more.

[0216] As sulfur, products available from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanryu Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., and the like can be used.

[0217] Crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Industry Co., Ltd. and KA9188 (1,6-bis(N,N′-dibenzylthiocarbamoyldisulfide)hexane) manufactured by LANXESS, and organic peroxides such as dicumyl peroxide.

[0218] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, greater than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0219] Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazolyl sulfenamide; thiuram vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-ethylene oxide-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. These may be used alone or in combination of two or more.

[0220] (viii) Others

[0221] In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, reversion inhibitors, etc. The content of these additives is, for example, greater than 0.1 parts by mass and less than 50 parts by mass per 100 parts by mass of the rubber component.

[0222] (2) Preparation of rubber composition

[0223] The rubber composition forming the crown rubber layer is prepared by appropriately adjusting the various mixing materials mentioned above and using conventional methods, for example, a manufacturing method including the following steps: a basic mixing step of mixing the rubber component with a filler (such as silica), and a refined mixing step of mixing the mixed product obtained in the basic mixing step with a cross-linking agent.

[0224] The kneading can be carried out using a known (closed type) mixer such as a Banbury mixer, a kneader or an open roll mill.

[0225] The mixing temperature in the basic mixing step is, for example, greater than 50° C. and less than 200° C., and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In the basic mixing step, in addition to the above components, compounding agents commonly used in the rubber industry, such as plasticizer components (e.g., oil), zinc oxide, anti-aging agents, waxes, vulcanization accelerators, etc., may be appropriately added as needed and mixed.

[0226] In the refining and kneading step, the kneaded product obtained in the basic kneading step is kneaded with a crosslinking agent. The kneading temperature in the refining and kneading step is, for example, greater than room temperature and less than 80° C., and the kneading time is, for example, greater than 1 minute and less than 15 minutes. In the refining and kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added as needed and kneaded.

[0227] 2. Tire manufacturing

[0228] The tire of the present embodiment can be manufactured as an unvulcanized tire by molding the rubber composition obtained as described above into a tread rubber of a predetermined shape as a cap rubber layer, and then molding it together with other tire components on a tire molding machine in a conventional manner.

[0229] In the case where the tread portion has a multilayer structure provided with a base rubber layer, the rubber composition for forming the base rubber layer can be obtained by kneading the above-mentioned rubber component and compounding materials in the same manner while appropriately changing the compounding amount. Then, the rubber composition for forming the base rubber layer is extruded together with the crown rubber layer to form a tread rubber of a predetermined shape, and then molded on a tire molding machine in a conventional manner together with other tire components to produce an unvulcanized tire.

[0230] Specifically, the inner liner as a component for ensuring the airtightness of the tire, the carcass as a component for bearing the load, impact and filling pressure of the tire, and the belt layer component as a component for clamping the carcass to increase the rigidity of the tread are wound on the forming drum, and the two ends of the carcass are fixed to the edges on both sides, and the bead part as a component for fixing the tire on the rim is arranged and formed into a ring shape. Then, the tread is attached to the central part of the outer circumference, and the sidewall is attached to the radially outer side to form the side portion, thereby producing an unvulcanized tire.

[0231] Then, the unvulcanized tire thus produced is heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be performed by applying known vulcanization means. The vulcanization temperature is, for example, greater than 120° C. and less than 200° C., and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0232] As described above, due to the combined effects of the effects (1) to (4) described in "2. Mechanism of the effects of the tire of the present invention" above, the tire has the microscopic fluidity, high heat generation and easy force transmission of the rubber matrix itself. At the same time, from a macroscopic point of view, it has appropriate rigidity and thus has road compliance; from a force transmission point of view, it is easy to generate a reaction force. Therefore, when turning the steering angle while driving at high speed, the tire has excellent responsiveness and can substantially improve the handling stability during high-speed driving.

[0233] The tire of the present invention is not particularly limited in type and can be used as a passenger car tire, a heavy-duty vehicle (such as a truck and bus) tire, a two-wheel vehicle tire, a run-flat tire, a non-pneumatic tire, etc., but is preferably used as a passenger car tire. In addition, it is preferably a pneumatic tire.

[0234] [Example]

[0235] Examples (embodiments) considered to be preferred in the practice of the present invention are shown below, but the scope of the present invention is not limited to these examples. In the examples, pneumatic tires (tire size 225 / 45R17, aspect ratio: 45%) made from compositions obtained by changing the formulations according to the tables using various chemicals were examined, and the results calculated based on the following evaluation method are shown in Tables 2 to 4.

[0236] 1. Rubber composition for forming a crown rubber layer

[0237] (1) Mixed materials

[0238] (a) Rubber component

[0239] (i) SBR-1: Modified S-SBR (styrene content: 45% by mass, vinyl content: 35% by mass) obtained by the method shown in the following Production Example 1

[0240] (ii) SBR-2: Modified S-SBR (styrene content: 25 mass %, vinyl content: 25 mass %) obtained by the method shown in the following Production Example 2

[0241] (iii) SBR-3: HPR840 (S-SBR) manufactured by JSR Corporation (styrene content: 10% by mass, vinyl content: 42% by mass)

[0242] (iv) BR: Ubepol BR150B (Hicis BR) manufactured by Ube Industries, Ltd. (cis content: 97% by mass, trans content: 2% by mass, vinyl content: 1% by mass)

[0243] (Production Example 1)

[0244] SBR-1 was prepared according to the following process. Cyclohexane, tetrahydrofuran, styrene and 1,3-butadiene were first charged into a nitrogen-substituted autoclave reactor. The temperature of the reactor contents was adjusted to -20°C, and then n-butyl lithium was added to initiate the reaction. The polymerization was carried out under adiabatic conditions with a maximum temperature of 85°C. When the polymerization conversion reached 99%, butadiene was added, and the polymerization was further carried out for 5 minutes. Thereafter, methyltrimethoxysilane was added as a modifier and the reaction was carried out for 15 minutes. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by stripping, and the mixture was dried with a heating roller adjusted to 110°C to obtain SBR-1.

[0245] (Production Example 2)

[0246] SBR-2 was prepared according to the following process. First, two autoclaves with an internal volume of 10L, an inlet at the bottom and an outlet at the top, and equipped with a stirrer and a jacket were connected in series as reactors, and butadiene, styrene and cyclohexane were mixed in a predetermined ratio. The mixed solution was passed through a dehydration column filled with activated alumina, mixed with n-butyl lithium in a static mixer to remove impurities, and then continuously fed from the bottom of the first reactor. In addition, 2,2-bis(2-oxolane)propane as a polar substance and n-butyl lithium as a polymerization initiator were continuously fed from the bottom of the first reactor at a predetermined rate, respectively, and the temperature inside the reactor was maintained at 95°C. The polymer solution was continuously taken out from the head of the reactor and fed into the second reactor. The temperature of the second reactor was maintained at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and a monomer component was continuously added at a predetermined rate as a 1000-fold diluted cyclohexane solution to carry out a modification reaction. The polymer solution was continuously taken out from the reactor, an antioxidant was continuously added using a static mixer, and then the solvent was removed to obtain SBR-2.

[0247] The vinyl contents (unit: mass %) of the SBR-1 and SBR-2 obtained above were determined by infrared spectroscopy from about 910 cm -1 The absorption intensity at 100 nm (absorption peak of vinyl group) was measured, and the styrene content (unit: mass %) was measured from the refractive index according to JIS K6383:1995.

[0248] (b) Compounding materials other than rubber components

[0249] (i) Silica: Ultrasil VN3 (N2SA: 175 m 2 / g, average primary particle size: 15nm)

[0250] (ii) Carbon black: Diablack N220 (N2 SA: 115 m 2 / g)

[0251] (iii) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Industries

[0252] (iv) Resin: T-REZ PR801 manufactured by ENEOS Corporation (hydrogenated aromatic-modified alicyclic hydrocarbon resin)

[0253] (v) Oil: VIVATEC 500 (TDAE oil) manufactured by H&R

[0254] (vi) Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.

[0255] (vii) Antiaging agent-1: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.

[0256] (viii) Antiaging agent-2: Antigen RD (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) manufactured by Sumitomo Chemical Co., Ltd.

[0257] (ix) Wax: Sannok N (selected special wax) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0258] (x) Stearic acid: Bead stearic acid "Tsubaki" manufactured by NOF Corporation

[0259] (xi) Vulcanization accelerator-1: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0260] (xii) Vulcanization accelerator-2: Nocceler D (N,N'-diphenylguanidine (DPG) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0261] (xiii) Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd.

[0262] (2) Rubber composition for forming a crown rubber layer

[0263] According to the formulations shown in Tables 2 to 4, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a Banbury mixer to obtain kneaded mixtures. Each compounding amount is expressed in parts by mass.

[0264] Next, sulfur and a vulcanization accelerator were added to the kneaded mixture, and the mixture was kneaded at 80° C. for 5 minutes using an open roll mill to obtain a rubber composition for forming a cap rubber layer.

[0265] 2. Rubber composition for forming base rubber layer

[0266] Meanwhile, a rubber composition for forming a base rubber layer was obtained based on the formulation shown in Table 1 in the same manner as in the production of the rubber composition for forming a cap rubber layer.

[0267] [Table 1]

[0268]

[0269] 3. Manufacturing of pneumatic tires

[0270] Each rubber composition was extruded in a predetermined shape so that the ratio of (cap rubber layer / base rubber layer) was 70 / 30 to produce a tread portion having a thickness shown in Tables 2 to 4.

[0271] Thereafter, the tread portion was layered together with other tire components to form an unvulcanized tire, and the tire was then press-vulcanized at 170°C for 10 minutes to produce pneumatic tires (test tires) of Examples 1 to 11 shown in Tables 2 and 3 and pneumatic tires (test tires) of Comparative Examples 1 to 5 shown in Table 4.

[0272] 4. Calculation of parameters

[0273] (1) 30℃E *

[0274] The rubber sample for viscoelasticity measurement was prepared by cutting a piece of rubber with a length of 20 mm, a width of 4 mm, and a thickness of 2 mm (where the long side is in the tire circumferential direction) from the crown rubber layer of the tread portion of each test tire. The 30°C E of each rubber sample was then measured in the tensile deformation mode using the "Eplexor" series manufactured by GABO under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%. * .

[0275] 30℃E of base rubber layer * (MPa) is set to 4.0 MPa.

[0276] (2) tan δ at 30℃

[0277] The rubber sample for viscoelasticity measurement was prepared by cutting a piece of rubber of 20 mm in length × 4 mm in width × 2 mm in thickness (where the long side is in the tire circumferential direction) from the crown rubber layer of the tread portion of each test tire. Then, the 30°C tan δ of each rubber sample was measured using the "Eplexor" series manufactured by GABO under the conditions of temperature 30°C, frequency 10 Hz, initial strain 5%, dynamic strain rate 1% and tensile deformation mode.

[0278] The 30°C tan δ of the base rubber layer was set to 0.07.

[0279] (3)AE

[0280] Using a vulcanized rubber specimen prepared by cutting out from the cap rubber layer of the tread portion of each test tire, AE (mass %) was measured in accordance with JIS K 6229:2015.

[0281] (4) Landing rate

[0282] The ground contact rate R (%) is calculated using the above-mentioned method.

[0283] (5) 30℃E * × Landing Rate

[0284] 30℃E based on the crown rubber layer * (MPa) and the above ground contact rate R (%), calculate 30℃E * (MPa)×ground contact rate (%).

[0285] (6) 30℃E * ×Tread thickness G(mm)

[0286] 30℃E based on the crown rubber layer * (MPa) and the thickness of the tread G (mm), calculate 0℃E * / Thickness of tread portion G (mm).

[0287] 5. Performance evaluation test (evaluation of high-speed handling stability)

[0288] Each test tire was mounted on all wheels of a vehicle (a domestic front-engine, front-drive vehicle with a displacement of 2000cc), and the tire was filled with air so that the internal pressure was a standardized internal pressure. The vehicle was driven on a test track with a dry road surface for running-in, and then the vehicle was driven at about 120km / h. 20 drivers each made a sensory evaluation of the handling stability when entering a corner on a 5-point system (the higher the number, the better). The total score evaluated by the 20 drivers was then calculated.

[0289] Next, the result of Comparative Example 2 was set to 100 and indexed according to the following formula to evaluate the steering stability when running at high speed on a dry road surface. A larger value indicates better steering stability when running at high speed on a dry road surface.

[0290] Steering stability when running at high speed on a dry road = [(result of the test tire) / (result of Comparative Example 2)] × 100

[0291] [Table 2]

[0292]

[0293] [Table 3]

[0294]

[0295] [Table 4]

[0296]

[0297] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above embodiment within the scope of the same and equivalent to the present invention.

[0298] The present invention (1) is a tire having a tread portion, wherein:

[0299] a cap rubber layer forming the tread portion formed of a rubber composition containing 80 parts by mass or more and 100 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, and containing 100 parts by mass or less of silica based on 100 parts by mass of the rubber component;

[0300] The complex modulus (30°C E * ) is greater than 8.0 MPa; and

[0301] The thickness of the tread portion is 8.5 mm or less.

[0302] The present invention (2) is a tire according to the present invention (1), wherein 30°C E * Greater than 8.5MPa.

[0303] The present invention (3) is a tire according to the present invention (1), wherein 30°C E * Greater than 9.0MPa.

[0304] The present invention (4) is a tire according to any combination of the present inventions (1) to (3), wherein the thickness of the tread portion is 8.0 mm or less.

[0305] The present invention (5) is a tire as described in any combination of the present inventions (1) to (4), wherein the loss tangent (30°C tan δ) of the crown rubber layer measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5% and a dynamic strain rate of 1% is less than 0.25.

[0306] The present invention (6) is the tire according to the present invention (5), wherein tan δ at 30°C is 0.20 or less.

[0307] The present invention (7) is a tire as described in any combination of the present inventions (1) to (6), wherein the tread portion is a multilayer structure having a base rubber layer arranged inside the crown rubber layer, and the thickness of the crown rubber layer accounts for more than 70% of the thickness of the entire tread portion.

[0308] The present invention (8) is the tire according to any combination of the present inventions (1) to (7), wherein the particle size (average primary particle size) of the silica is 17 nm or less.

[0309] The present invention (9) is a tire according to any combination of the present inventions (1) to (8), wherein the acetone extract (AE) of the cap rubber layer is 20% by mass or less.

[0310] The present invention (10) is a tire according to any combination of the present inventions (1) to (9), wherein the acetone extract (AE) of the cap rubber layer is 18% by mass or more.

[0311] The present invention (11) is a tire according to any combination of the present inventions (1) to (10), wherein the ground contact ratio of the tread portion is 60% or more.

[0312] The present invention (12) is a tire according to any combination of the present inventions (1) to (11), wherein the ground contact ratio R (%) of the tread portion is * The product of (MPa) is 560 or more.

[0313] The present invention (13) is a tire according to any combination of the present inventions (1) to (12), wherein when the thickness of the tread portion is G (mm), 30°E * (MPa) and G satisfy the following relationship: 30℃E * / G≧1.0.

[0314] The present invention (14) is a tire according to any combination of the present inventions (1) to (13), wherein the aspect ratio is 30% or more and 60% or less.

Claims

1. A tire having a tread portion, wherein: a cap rubber layer forming the tread portion formed of a rubber composition containing 80 parts by mass or more and 100 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, and containing 100 parts by mass or less of silica based on 100 parts by mass of the rubber component; The complex modulus (30°C E * ) is greater than 8.0 MPa; and The tread portion has a thickness of 8.5 mm or less.

2. The tire according to claim 1, wherein: 30℃E * Greater than 8.5MPa.

3. The tire according to claim 1, wherein: 30℃E * Greater than 9.0MPa.

4. The tire according to any one of claims 1 to 3, wherein: The tread portion has a thickness of 8.0 mm or less.

5. The tire according to any one of claims 1 to 4, wherein: The crown rubber layer has a loss tangent (30°C tanδ) of 0.25 or less measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5% and a dynamic strain rate of 1%.

6. The tire according to claim 5, wherein: The 30°C tan δ is 0.20 or less.

7. The tire according to any one of claims 1 to 6, wherein: The tread portion is a multi-layer structure having a base rubber layer disposed inside the cap rubber layer, and the thickness of the cap rubber layer accounts for more than 70% of the thickness of the entire tread portion.

8. The tire according to any one of claims 1 to 7, wherein: The particle size (average primary particle size) of the silica is 17 nm or less.

9. The tire according to any one of claims 1 to 8, wherein: The acetone extract (AE) of the tread rubber layer is 20 mass % or less.

10. The tire according to any one of claims 1 to 9, wherein: The acetone extract (AE) of the tread rubber layer is 18% by mass or more.

11. The tire according to any one of claims 1 to 10, wherein: The ground contact ratio of the tread portion is 60% or more.

12. The tire according to any one of claims 1 to 11, wherein: The ground contact rate R (%) of the tread portion and the 30°E * The product of (MPa) is 560 or more.

13. The tire according to any one of claims 1 to 12, wherein: When the thickness of the tread portion is G (mm), the 30°E * (MPa) and G satisfy the following relationship: 30℃E * / G≧1.

0.

14. The tire according to any one of claims 1 to 13, wherein: The flatness is 30% or more and 60% or less.

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