tire

Abstract

To provide a tire improved in total performance of wet-grip performance and durability performance after the deterioration of the tire.SOLUTION: The tire comprises a tread part having two or more rubber layers and a belt layer. The tread part has a cap rubber layer constituting a tread surface and a base rubber layer existing inside in a tire radial direction of the cap rubber layer. The cap rubber layer and the base rubber layer are respectively constituted of rubber compositions containing rubber constituents. A ratio of a thickness of the cap rubber layer with respect to entire thicknesses of the tread part is 20% or higher. When acetone extraction amounts of the rubber composition constituting the cap rubber layer are defined as AE1, AE1 is less than 12.0 mass%. Ash contents of the rubber composition constituting the cap rubber layer are less than 7.5 mass%. The rubber composition constituting the cap rubber layer contains 5.0 mass parts or more of softener A whose weight average molecular weight is equal to 1000 or more, with respect to 100 mass parts of the rubber constituents. When acetone extraction amounts of the rubber composition constituting the base rubber layer are defined as AE2, AE2 / AE1 is equal to 0.6 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] The hardening phenomenon in the tread portion of a tire due to changes over time is a factor that causes a decrease in tire performance, such as wet grip performance. Patent Document 1 describes how, in a pneumatic tire having a tread portion comprising a cap rubber layer, an intermediate rubber layer, and a base rubber layer, the hardening phenomenon of the tread portion over time is effectively suppressed by setting the thickness of each rubber layer relative to the total thickness of the tread portion and the amount of acetone extracted from each rubber layer within a predetermined range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2005-67236 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a tire that suppresses the hardening phenomenon of the tread over time and improves wet grip performance after deterioration. [Means for solving the problem]

[0005] This invention relates to the following tires. A tire comprising a tread section having two or more rubber layers and a belt layer, The tread portion comprises a cap rubber layer that constitutes the tread surface, and a base rubber layer located radially inward of the cap rubber layer. The cap rubber layer and the base rubber layer are each composed of a rubber composition containing rubber components. The thickness of the cap rubber layer is 20% or more of the total thickness of the tread portion. When the amount of acetone extracted from the rubber composition constituting the cap rubber layer is denoted as AE1, AE1 is less than 12.0% by mass, The ash content of the rubber composition constituting the aforementioned cap rubber layer is less than 7.5% by mass. The rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of softener A having a weight-average molecular weight of 1000 or more, per 100 parts by mass of rubber component. When the amount of acetone extracted from the rubber composition constituting the base rubber layer is denoted as AE2, Tires with an AE2 / AE1 ratio of 0.6 or higher. [Effects of the Invention]

[0006] According to the present invention, a tire is provided in which the hardening phenomenon of the tread portion over time is suppressed, and the overall performance of wet grip performance and durability after deterioration is improved. [Brief explanation of the drawing]

[0007] [Figure 1] This is a partial cross-sectional view of the tire tread according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] One embodiment of the present invention is a tire comprising a tread portion having two or more rubber layers and a belt layer, wherein the tread portion has a cap rubber layer constituting the tread surface and a base rubber layer located radially inward of the cap rubber layer, the cap rubber layer and the base rubber layer are each composed of a rubber composition containing rubber components, the thickness of the cap rubber layer is 20% or more of the total thickness of the tread portion, when the amount of acetone extracted from the rubber composition constituting the cap rubber layer is AE1, AE1 is less than 12.0% by mass, the ash content of the rubber composition constituting the cap rubber layer is less than 7.5% by mass, the rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of a softener A having a weight-average molecular weight of 1000 or more per 100 parts by mass of rubber components, and when the amount of acetone extracted from the rubber composition constituting the base rubber layer is AE2, AE2 / AE1 is 0.6 or more.

[0009] When the thickness of the cap rubber layer relative to the total thickness of the tread, the amount of acetone extracted from the cap rubber layer, the amount of ash in the cap rubber layer, and the ratio of the amount of acetone extracted from the base rubber layer to the amount of acetone extracted from the cap rubber layer satisfy the above requirements, and the cap rubber layer contains a predetermined softening agent, the resulting tire suppresses the hardening phenomenon of the tread over time, and the overall performance of wet grip performance and durability after deterioration is improved. The reason for this is thought to be as follows, although we do not intend to be bound by theory.

[0010] One of the factors causing changes in tire hardness is that the concentration gradient of the softener inside the tread causes the softener to migrate from the tread side to the radially inward side of the tire, resulting in a decrease in the amount of softener in the cap rubber. The tire of the present invention has the following characteristics: (1) By setting the amount of acetone extracted from the cap rubber layer within the aforementioned range, the concentration of the softener in the rubber layer radially inward from the cap rubber layer becomes higher than the concentration of the softener in the cap rubber layer. (2) By setting the ratio of the amount of acetone extracted from the base rubber layer to the amount of acetone extracted from the cap rubber layer within the aforementioned range, the diffusion of the softener from the cap rubber layer to the base rubber layer can be appropriately controlled. As a result, the change in hardness of the rubber composition of the tread due to tire use can be appropriately controlled. Furthermore, (3) by setting the ash content of the cap rubber layer within the aforementioned range, the migration of the softener to the base rubber layer can be suppressed. In addition, (4) by having the cap rubber layer contain a predetermined amount of softener with a weight-average molecular weight of 1000 or more, the diffusion of the softener from the cap rubber layer to the base rubber layer can be appropriately controlled. Furthermore, it is believed that these factors working together will suppress the hardening of the tread rubber over time, significantly improve the decline in wet grip performance after tire deterioration, and achieve remarkable results in the overall performance of wet grip performance and durability after deterioration.

[0011] Preferably, the difference between the amount of acetone extracted from the rubber composition constituting the cap rubber layer and the amount of acetone extracted from the belt topping rubber is less than 5.0% by mass.

[0012] By setting the difference between the amount of acetone extracted from the rubber composition constituting the cap rubber layer and the amount of acetone extracted from the belt topping rubber within the aforementioned range, the diffusion of the softening agent from the tread rubber to the belt topping rubber can be appropriately controlled. Therefore, it is believed that the change in hardness of the tread surface rubber layer due to tire use can be appropriately controlled.

[0013] It is preferable that the rubber composition constituting the base rubber layer contains 5 parts by mass or more of softening agent A having a weight average molecular weight of 1000 or more.

[0014] It is considered that by the base rubber layer containing softening agent A, the diffusion of the softening agent from the cap rubber layer to the base rubber layer can be more appropriately controlled.

[0015] The shore hardness (Hs) of the cap rubber layer is preferably 50 or more and 70 or less. Further, the change rate of the shore hardness (Hs) of the cap rubber layer after standing at 80 °C for 2 months is preferably -10% or more and 10% or less.

[0016] By setting the shore hardness of the cap rubber layer within the above range, it is considered that the wet grip performance can be maintained even after deterioration.

[0017] The rubber component constituting the cap rubber layer preferably contains at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber.

[0018] By the rubber component constituting the cap rubber layer containing the above rubber, it is considered that the softening agent can migrate early to the adjacent rubber layer and the hardening of the rubber can be suppressed.

[0019] Softening agent A preferably contains at least one selected from the group consisting of terpene resins and liquid polymers.

[0020] By blending the above softening agent into the rubber composition constituting the cap rubber layer, it is considered that the softening agent can migrate early to the adjacent rubber layer and the hardening of the rubber can be suppressed.

[0021] The rubber composition constituting the cap rubber layer preferably contains 5.0 parts by mass or more of softening agent B having a weight average molecular weight of less than 1000 with respect to 100 parts by mass of the rubber component.

[0022] It is believed that by further including softener B in the rubber composition constituting the cap rubber layer, the diffusion of the softener from the cap rubber layer to the base rubber layer can be controlled more appropriately.

[0023] Preferably, the total content of the softener relative to 100 parts by mass of the rubber component in the rubber composition constituting the cap rubber layer is more than 10.0 parts by mass and less than 50.0 parts by mass.

[0024] It is believed that by keeping the total content of the softener in the rubber composition constituting the cap rubber layer within the above range, the diffusion of the softener from the cap rubber layer to the base rubber layer can be controlled more appropriately.

[0025] The tanδ of the cap rubber layer at 30°C is preferably 0.40 or less.

[0026] If the tanδ of the cap rubber layer is 0.40 or less, it is thought that the heat generated during driving will be reduced, and the hardening of the cap rubber layer over time will be suppressed.

[0027] From the viewpoint of wet grip performance, the 0°C E* of the cap rubber layer is preferably 5.0 MPa or higher.

[0028] The glass transition temperature of the cap rubber layer is preferably -40°C or higher.

[0029] If the glass transition temperature of the cap rubber layer is set to -40°C or higher, the loss tangent tanδ in the temperature range higher than Tg tends to be higher compared to the case where it is below -40°C, and it is thought that the effects of the present invention can be more easily demonstrated.

[0030] From the viewpoint of wet grip performance, the rubber composition constituting the cap rubber layer preferably contains more than 50 parts by mass of carbon black per 100 parts by mass of rubber component.

[0031] From the viewpoint of wet grip performance, the rubber composition constituting the base rubber layer preferably contains more than 50 parts by mass of carbon black per 100 parts by mass of rubber component.

[0032] <Definition> A "standard rim" is the rim specified for each tire within the standardization system that includes the standard on which the tire is based. For example, it is called a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0033] "Total tread thickness" refers to the straight-line distance from the outermost surface of the tread on the tire's equatorial plane to the outermost band (or the outermost belt layer if no band exists) in a cross-section of the tire cut along the plane containing the tire's axis of rotation. If the tire has circumferential grooves on its equatorial plane, this thickness is considered to be the thickness that fills those grooves.

[0034] The "thickness of each layer of the tread" is measured along the normal line drawn from the tire equator in a cross-section obtained by cutting the tire in the plane containing the tire's axis of rotation. If the tire has circumferential grooves on the equatorial plane, this is the thickness recognized as filling those grooves.

[0035] A "softener" is a material that imparts plasticity to rubber components and is extracted from rubber compositions using acetone. Softeners include those that are liquid at 25°C and those that are solid at 25°C, as well as softeners contained in stretchable rubber. However, waxes and stearic acid commonly used in the tire industry are excluded.

[0036] <Measurement method> The "total tread thickness" and the "thickness of each layer of the tread" are measured by cutting the tire across the plane containing the tire's rotation axis, with the width of the bead aligned to the width of the standard rim.

[0037] The "amount extracted with acetone" can be determined by immersing each vulcanized rubber test piece in acetone at room temperature (around 25°C) for 72 hours to extract soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. When preparing test pieces by cutting them from a tire, cut them from the tire tread so that the tire circumference is the longer side and the tire radius is the thickness direction. (Amount of acetone extracted (mass%)) = {(Mass of rubber test piece before extraction - Mass of rubber test piece after extraction) / (Mass of rubber test piece before extraction)} × 100

[0038] The "ash content (mass%)" indicates the ratio of the total mass of non-combustible components (ash) in the rubber composition to the total mass of the rubber composition, and is determined by the following method: A vulcanized rubber test piece cut from the tread of each test tire is placed in an alumina crucible and heated in an electric furnace at 550°C for 4 hours, and the mass of the vulcanized rubber test piece after heating is measured. The "ash content (mass%)" in the rubber composition can be determined by the mass of the vulcanized rubber test piece after heating, with the vulcanized rubber test piece before heating set to 100% by mass.

[0039] "tanδ at 30°C (30°C tanδ)" is the loss tangent measured in extension mode using a dynamic viscoelasticity measuring instrument (e.g., GABO's Iplexer series) under the conditions of 30°C temperature, 5% initial strain, 1% dynamic strain, and 10Hz frequency. The sample for loss tangent measurement is a vulcanized rubber composition measuring 20mm in length, 4mm in width, and 1mm in thickness. When preparing the sample by cutting it from a tire, it should be cut from the tire tread so that the tire circumference is the longer side and the tire radius is the thickness direction.

[0040] The complex modulus of elasticity at 0°C, E* (0°C E*), is measured using a dynamic viscoelasticity measuring instrument (e.g., the Iplexer series from GABO) under the conditions of 0°C, 10% initial strain, 2.5% dynamic strain, and 10 Hz frequency. The sample for this measurement is prepared in the same manner as for 30°C tanδ.

[0041] Shore hardness is measured in accordance with JIS K 6253-3:2012, using a durometer type A at a temperature of 23°C (Hs). The Shore hardness measurement sample is prepared by cutting a piece from the tread so that the tire radius is oriented in the thickness direction. The measurement is performed by pressing the measuring instrument against the sample from the contact surface side.

[0042] The "rate of change in Shore hardness (Hs) of the cap rubber layer after being left to stand at 80°C for two months" can be determined by measuring the Shore hardness (Hs) of the cap rubber layer in the tread area after leaving each test tire to stand at 80°C for two months after manufacture, and using the following formula. (Percentage change in Shore hardness (%)) = {(Shore hardness of the cap rubber layer after storage) / (Amount of acetone extracted from the cap rubber layer after tire manufacturing) × 100}-100

[0043] The Tg of a rubber composition is determined by measuring the temperature distribution curve of tanδ using a dynamic viscoelasticity analyzer (e.g., the Iplexer series from GABO) under conditions of a frequency of 10 Hz, initial strain of 10%, amplitude of ±0.5%, and heating rate of 2°C / min. The Tg is determined as the temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature). The sample for this measurement is prepared in the same manner as for 30°C tanδ.

[0044] The above physical properties and softening agent content of the present invention are those of a tire immediately after manufacture or a new, unused tire manufactured within one year.

[0045] "Styrene content" is, 1The value is calculated by 1H-NMR measurement and applies to rubber components having repeating units derived from styrene, such as SBR. "Vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017 and applies to rubber components having repeating units derived from butadiene, such as SBR and BR. "Cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017 and applies to rubber components having repeating units derived from butadiene, such as BR.

[0046] The "softening point of the resin component" can be defined as the temperature at which the sphere descends when the softening point specified in JIS K 6220-1:2001 is measured using a ring-type softening point measuring device.

[0047] The "weight-average molecular weight (Mw)" can be determined by converting the measured value using gel permeation chromatography (GPC) (for example, the GPC-8000 series from Tosoh Corporation, with a differential refractometer as the detector and TSKGEL SUPERMALTIPORE HZ-M column from Tosoh Corporation) to a standard polystyrene equivalent. This method is applicable, for example, to SBR, BR, and plasticizers.

[0048] The N2SA content of carbon black is measured according to JIS K 6217-2:2017. The N2SA content of silica is measured by the BET method according to ASTM D3037-93.

[0049] The "Tg of the softening agent" is a value measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 10°C / min, in accordance with JIS K 7121:2012.

[0050] The procedure for manufacturing a tire, which is one embodiment of the present invention, will be described in detail below. However, the following description is illustrative for explaining the present invention and is not intended to limit the technical scope of the present invention to this scope only.

[0051] [tire] Figure 1 is a cross-sectional view showing a portion of the tread of a tire according to the present invention, but the invention is not limited to this embodiment. The tire of the present invention has a tread portion 1 that contacts the ground when running, and a belt layer 8 on the radially inward side of the tread portion 1. The belt layer 8 is formed by covering with belt topping rubber. A carcass 9 and an inner liner 7 are laminated below the belt layer 8. A band may also be present between the tread portion 1 and the belt layer 8. In Figure 1, the belt layer 8 is laminated in two layers, and a band 11 having a jointless structure is arranged inside the base rubber layer 4. The belt layer 8 may be covered with belt topping rubber.

[0052] The tread portion of the present invention has at least two rubber layers. The composition of the rubber layers is not particularly limited, but for example, it has a cap rubber layer 2 whose outer surface constitutes the tread surface and a base rubber layer 4 between the cap rubber layer 2 and the belt layer 8. In the present invention, if there are two or more rubber layers between the cap rubber layer 2 and the belt layer 8, the layer closest to the belt layer with a thickness of 1 mm or more is designated as the base rubber layer. Furthermore, there may be one or more intermediate rubber layers between the cap rubber layer 2 and the base rubber layer 4.

[0053] In the present invention, the total thickness of the tread portion 1 is not particularly limited, but is preferably 30 mm or less, more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 15 mm or less. Furthermore, the total thickness of the tread is more preferably 3.0 mm or more, even more preferably 5.0 mm or more, and even more preferably 7.0 mm or more.

[0054] The thickness of the cap rubber layer 2 relative to the total thickness of the tread portion 1 is 20% or more, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and particularly preferably 60% or more, from the viewpoint of suppressing the migration of the softening agent within the tread portion and from the tread portion to the internal components. On the other hand, there is no particular upper limit to the thickness of the cap rubber layer 2 relative to the total thickness of the tread portion 1, but it can be, for example, 90% or less, or 85% or less.

[0055] From the viewpoint of the effects of the present invention, the thickness of the base rubber layer 4 relative to the total thickness of the tread portion 1 is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. On the other hand, the thickness of the base rubber layer 4 relative to the total thickness of the tread portion 1 is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, even more preferably 50% or less, and particularly preferably 40% or less.

[0056] The thickness of the tread portion 1 relative to the total thickness when an intermediate rubber layer is present is not particularly limited, but can be, for example, 1% or more, 5% or more, 10% or more, 60% or less, 40% or less, or 35% or less.

[0057] Amount of acetone extracted From the viewpoint of the effects of the present invention, the amount of acetone extracted from the rubber composition constituting the cap rubber layer 2, AE1, is less than 12.0% by mass, preferably less than 11.5% by mass, more preferably less than 11.0% by mass, even more preferably less than 10.5% by mass, even more preferably less than 10.0% by mass, and particularly preferably less than 9.5% by mass. Furthermore, AE1 can be appropriately selected to satisfy AE2 / AE1, but is preferably more than 3.0% by mass, more preferably more than 4.0% by mass, even more preferably more than 5.0% by mass, and particularly preferably more than 6.0% by mass.

[0058] The amount of acetone extracted from the rubber composition constituting the base rubber layer 4, AE2, is preferably less than 30.0% by mass, more preferably less than 27.0% by mass, even more preferably less than 24.0% by mass, and particularly preferably less than 21.0% by mass. Furthermore, AE2 can be appropriately selected to satisfy AE2 / AE1, but is preferably greater than 3.0% by mass, more preferably greater than 4.0% by mass, even more preferably greater than 5.0% by mass, and particularly preferably greater than 6.0% by mass.

[0059] AE2 / AE1 is 0.6 or higher, preferably 0.8 or higher, more preferably 0.9 or higher, even more preferably 1.0 or higher, even more preferably 1.1 or higher, and particularly preferably 1.2 or higher.

[0060] When an intermediate rubber layer is present, the amount of acetone extracted is preferably less than 40.0% by mass, more preferably less than 37.0% by mass, even more preferably less than 34.0% by mass, and particularly preferably less than 31.0% by mass. Furthermore, the amount of acetone extracted from the intermediate rubber layer is preferably greater than 10.0% by mass, more preferably greater than 13.0% by mass, even more preferably greater than 16.0% by mass, and particularly preferably greater than 19.0% by mass. From the viewpoint of suppressing the migration of the softener from the cap rubber layer to the base rubber layer, the amount of acetone extracted from the intermediate rubber layer is preferably greater than the amount of acetone extracted from the cap rubber layer AE1.

[0061] The amount of acetone extracted from the belt topping rubber, AE3, is preferably less than 10.0% by mass, more preferably less than 9.0% by mass, even more preferably less than 8.0% by mass, and particularly preferably less than 7.0% by mass. The lower limit of AE3 is not particularly limited, but it is preferably greater than 1.0% by mass, more preferably greater than 2.0% by mass, even more preferably greater than 3.0% by mass, and particularly preferably greater than 4.0% by mass.

[0062] The difference (AE1-AE3) between the acetone extraction amount of the rubber composition constituting the cap rubber layer 2 and the belt topping rubber is preferably less than 5.0% by mass, more preferably less than 4.5% by mass, even more preferably less than 4.0% by mass, even more preferably less than 3.1% by mass, and particularly preferably 3.0% by mass or less. By setting the difference between the acetone extraction amount of the cap rubber layer and the acetone extraction amount of the belt topping rubber within the above range, it is possible to appropriately control the hardness change of the tread surface rubber layer due to tire use, and the diffusion of the softening agent from the tread portion to the belt topping rubber is suppressed, thereby maintaining the durability performance of the tire. Furthermore, there is no particular limit to the lower limit of AE1-AE3, but it is preferably greater than 0.2% by mass, more preferably greater than 0.5% by mass, even more preferably greater than 1.0% by mass, and particularly preferably greater than 1.5% by mass.

[0063] When a band is present in the tire of the present invention, it is preferable that the amount of acetone extracted from the cap rubber layer is greater than the amount of acetone extracted from the band topping rubber. Furthermore, it is preferable that the amount of acetone extracted from the band topping rubber is greater than the amount of acetone extracted from the belt topping rubber.

[0064] ≪Ash content≫ From the viewpoint of rubber hardness, the ash content of the rubber composition constituting the cap rubber layer 2 is less than 7.5% by mass, preferably less than 7.0% by mass, more preferably less than 6.5% by mass, even more preferably less than 6.0% by mass, even more preferably less than 5.5% by mass, and particularly preferably 5.2% by mass or less. Furthermore, from the viewpoint of suppressing the migration of the softening agent, it is more than 1.0% by mass, more preferably more than 2.0% by mass, and even more preferably more than 3.0% by mass. Since the ash content consists of inorganic substances such as silica, the ash content of the rubber composition can be increased by increasing the content of inorganic substances such as silica, and conversely, it can be decreased by decreasing the content of inorganic substances such as silica.

[0065] The ash content of the rubber composition constituting the base rubber layer 4 is preferably less than 20.0% by mass, more preferably less than 15.0% by mass, and even more preferably less than 10.0% by mass. Furthermore, there is no particular lower limit to the ash content of the rubber composition constituting the base rubber layer 4, and it may be as low as 0.0% by mass.

[0066] When an intermediate rubber layer is present, the ash content is preferably less than 40.0% by mass, more preferably less than 35.0% by mass, even more preferably less than 30.0% by mass, and particularly preferably less than 25.0% by mass. Furthermore, there is no particular lower limit to the ash content of the intermediate rubber layer, but it can be, for example, 0.0% by mass, greater than 0.0% by mass, greater than 1.0% by mass, greater than 3.0% by mass, greater than 5.0% by mass, or greater than 7.0% by mass.

[0067] Shore hardness The Shore hardness (Hs) of the rubber composition constituting the cap rubber layer 2 is preferably 40 to 90, more preferably 50 to 80, and even more preferably 55 to 70. By setting the Shore hardness (Hs) of the cap rubber layer 2 within the above range, it is believed that good wet grip performance can be maintained even after tire deterioration. The Shore hardness (Hs) of the base rubber layer 4 and the intermediate rubber layer is not particularly limited, but is preferably 55 to 70, more preferably 57 to 68, and even more preferably 59 to 66. The Shore hardness of each rubber layer can be appropriately adjusted by changing the type and amount of rubber components, fillers, softeners, etc. For example, the rubber hardness can be lowered by increasing the amount of softener, and conversely, the rubber hardness can be lowered by decreasing the amount of softener.

[0068] The change in Shore hardness (Hs) of the cap rubber layer 2 after being left standing at 80°C for two months is preferably between -10% and 10%, more preferably between -8% and 8%, even more preferably between -6% and 6%, and particularly preferably between -4% and 4%. By keeping the change in Shore hardness (Hs) within the above range, it is believed that good wet grip performance can be maintained even after tire deterioration.

[0069] ≪30℃ tanδ≫ The 30°C tanδ of the rubber composition constituting the cap rubber layer 2 is preferably 0.30 or less, more preferably 0.25 or less, even more preferably 0.22 or less, and particularly preferably 0.20 or less, from the viewpoint of reducing heat generation during driving and suppressing hardening of the cap rubber layer over time. Furthermore, the 30°C tanδ of the rubber composition constituting the base rubber layer 4 and the intermediate rubber layer is preferably 0.40 or less, more preferably 0.35 or less, and even more preferably 0.30 or less. On the other hand, the 30°C tanδ of the cap rubber layer 2, base rubber layer 4, and intermediate rubber layer is preferably 0.05 or more, more preferably 0.07 or more, and even more preferably 0.09 or more. Note that the 30°C tanδ of each rubber layer can be appropriately adjusted depending on the type and amount of rubber components, fillers, softeners, etc. For example, the 30°C tanδ can be increased by increasing the amount of softener, and conversely, the 30°C tanδ can be decreased by decreasing the amount of softener.

[0070] ≪0℃E*≫ From the viewpoint of wet grip performance, the 0°C E* of the rubber composition constituting the cap rubber layer 2 is preferably 4.0 MPa or higher, more preferably 5.0 MPa or higher, even more preferably 6.0 MPa or higher, and particularly preferably 7.0 MPa or higher. Similarly, from the viewpoint of wet grip performance, the 0°C E* of the rubber composition constituting the base rubber layer 4 and the intermediate rubber layer is preferably 6.0 MPa or higher, and more preferably 7.0 MPa or higher. On the other hand, from the viewpoint of road surface following ability, the 0°C E* of the cap rubber layer 2 is preferably 100 MPa or lower, more preferably 80 MPa or lower, even more preferably 60 MPa or lower, and particularly preferably 40 MPa or lower. Furthermore, it is preferable that the 0°C E* value of the cap rubber layer 2 is greater than the 0°C E* values ​​of the base rubber layer 4 and the intermediate rubber layer. Note that the 0°C E* of each rubber layer can be appropriately adjusted by changing the type and amount of rubber components, fillers, softeners, etc. For example, the 0°C E* value can be lowered by increasing the amount of softening agent, and conversely, the 0°C E* value can be raised by decreasing the amount of softening agent.

[0071] ≪Glass transition temperature (Tg)≫ From the viewpoint of wet grip performance, the Tg of the rubber composition constituting the cap rubber layer 2 is preferably -60°C or higher, more preferably -50°C or higher, and even more preferably -40°C or higher. When the Tg is -40°C or higher, the loss tangent tanδ in the temperature range above Tg tends to be higher compared to when it is below -40°C. Furthermore, the Tg of the rubber composition constituting the base rubber layer 4 and the intermediate rubber layer is preferably -60°C or higher, more preferably -55°C or higher, and even more preferably -50°C or higher. On the other hand, there is no particular upper limit to the Tg of the cap rubber layer 2, base rubber layer 4 and intermediate rubber layer, but it is preferably 20°C or lower, more preferably 10°C or lower, even more preferably 0°C or lower, and particularly preferably -10°C or lower. Note that the Tg of each rubber layer can be appropriately adjusted depending on the type and amount of rubber components, fillers, softeners, etc.

[0072] [Tread rubber composition] The rubber compositions constituting the tread portion of the present invention (hereinafter referred to as "rubber compositions according to the present invention") can all be manufactured using the raw materials described below, according to the required amount of acetone extraction, etc. These will be described in detail below.

[0073] <Rubber components> The rubber composition according to the present invention preferably uses diene rubber as the rubber component. Examples of diene rubber include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Alternatively, it may be stretchable rubber that has been stretched in advance with a softening agent. These rubber components may be used individually or in combination of two or more.

[0074] The content of diene rubber in the rubber component is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Alternatively, the rubber component may consist solely of diene rubber.

[0075] The rubber composition according to the present invention preferably uses at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR) as the rubber component. The rubber component preferably contains isoprene rubber, more preferably contains isoprene rubber and SBR, even more preferably contains isoprene rubber, BR, and SBR, and may consist only of isoprene rubber, BR, and SBR.

[0076] (Isoprene rubber) As isoprene-based rubbers, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. Natural rubber includes not only unmodified natural rubber (NR), but also modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used individually or in combination of two or more types.

[0077] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0078] From the viewpoint of wet grip performance, the content of isoprene-based rubber in the rubber component of the rubber composition constituting the cap rubber layer 2 is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. Furthermore, there is no particular lower limit to the content of isoprene-based rubber, but it is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

[0079] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber composition constituting the base rubber layer 4 and the intermediate rubber layer, relative to 100 parts by mass of rubber components, is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 65% ​​by mass or less. Furthermore, there is no particular lower limit to the content of isoprene-based rubber, but it is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

[0080] (SBR) There are no particular limitations on SBR, and examples include unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs of these (modified S-SBR, modified E-SBR). Modified SBRs include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those with branched structures, etc.). Among these, S-SBR and modified SBRs are preferred. Furthermore, hydrogenated versions of these SBRs (hydrogenated SBRs) can also be used. These SBRs may be used individually or in combination of two or more types.

[0081] Either stretchable SBR or non-stretchable SBR can be used as the SBR. When stretchable SBR is used, the amount of stretchable SBR, that is, the amount of stretchable softener contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0082] S-SBRs that can be used in this invention are commercially available from companies such as JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, and ZS Elastomer Co., Ltd.

[0083] The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of wet grip performance and abrasion resistance. Furthermore, from the viewpoint of temperature dependence of grip performance and blow resistance, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. The styrene content of SBR is measured by the measurement method described above.

[0084] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, from the viewpoint of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Furthermore, the vinyl content of SBR is preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less, from the viewpoint of preventing increased temperature dependence, elongation at break, and abrasion resistance. The vinyl content of SBR is measured by the measurement method described above.

[0085] From the viewpoint of wet grip performance, the weight-average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. Furthermore, from the viewpoint of crosslinking uniformity, the Mw of SBR is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. The Mw of SBR is measured by the measurement method described above.

[0086] From the viewpoint of wet grip performance, the SBR content in the rubber component of the rubber composition constituting the cap rubber layer 2 is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. Furthermore, the content is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less.

[0087] The SBR content in the rubber components of the rubber composition constituting the base rubber layer 4 is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less. Furthermore, there is no particular lower limit to the content, and it may not contain SBR at all.

[0088] From the viewpoint of the effects of the present invention, the SBR content in the rubber component of the rubber composition constituting the intermediate rubber layer is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. Furthermore, the content is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0089] (BR) BR is not particularly limited, and common types used in the tire industry can be used, such as BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth butadiene rubber synthesized using rare-earth element catalysts (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). Modified BR can be BR modified with functional groups similar to those described for SBR above. These BRs may be used individually or in combination of two or more types.

[0090] High-cis BR can be commercially available from companies such as Nippon Zeon Co., Ltd., Ube Industries, Ltd., and JSR Corporation. Including high-cis BR can improve low-temperature properties and wear resistance. The cis content is preferably 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and particularly preferably 98 mol% or more.

[0091] Rare-earth BR is synthesized using a rare-earth element catalyst, and has a vinyl content of preferably 1.8 mol% or less, more preferably 1.0 mol% or less, and even more preferably 0.8 mol or less, and a cis content of preferably 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and particularly preferably 98 mol% or more. As rare-earth BR, commercially available products from companies such as Lanxess can be used. The vinyl content and cis content of BR are measured by the measurement method described above.

[0092] SPB-containing BR refers to a type in which 1,2-syndiotactic polybutadiene crystals are not simply dispersed in BR, but are chemically bonded to and dispersed in BR. Such SPB-containing BR can be commercially available from companies such as Ube Industries, Ltd.

[0093] As the modified BR, a modified butadiene rubber (modified BR) is preferably used in which the terminal and / or main chain is modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen.

[0094] Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the ends of the modified BR molecule are linked by a tin-carbon bond (tin-modified BR). Furthermore, the modified BR may be either unhydrogenated or hydrogenated.

[0095] The BRs listed above may be used individually or in combination of two or more.

[0096] From the viewpoint of wear resistance, the weight-average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The Mw of BR is measured by the measurement method described above.

[0097] From the viewpoint of wet grip performance, the BR content in the rubber component of the rubber composition constituting the cap rubber layer 2 is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less. Furthermore, the content is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

[0098] From the viewpoint of the effects of the present invention, the content of BR in the rubber components of the rubber composition constituting the base rubber layer 4 is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less. Furthermore, the content is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

[0099] (Other rubber components) The rubber component may contain other rubber components besides diene rubber, as long as they do not affect the effects of the present invention. Other rubber components besides diene rubber can be crosslinkable rubber components commonly used in the tire industry, such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, polyethylene chloride rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. These other rubber components may be used individually or in combination of two or more.

[0100] <Softener> The rubber composition according to the present invention contains a softening agent. A softening agent is a material that imparts plasticity to the rubber component, and the concept includes both softening agents that are liquid at room temperature (25°C) and softening agents that are solid at room temperature (25°C). Specifically, it is a component that can be extracted from the rubber composition using acetone. Suitable softening agents include, for example, oils, resin components, liquid polymers, and ester-based plasticizers. It is preferable that the softening agent contains at least one selected from the group consisting of resin components and liquid polymers. These softening agents may be used individually or in combination of two or more.

[0101] In this specification, a softening agent having a weight-average molecular weight (Mw) of 1000 or more is referred to as softening agent A, and a softening agent having a weight-average molecular weight (Mw) of less than 1000 is referred to as softening agent B.

[0102] The softening agent A is not particularly limited as long as its weight-average molecular weight (Mw) is less than 1000, but it is preferably at least one selected from the group consisting of resin components and liquid polymers, and more preferably at least one selected from the group consisting of terpene resins and liquid polymers.

[0103] From the viewpoint of the effects of the present invention, the total content of softener A per 100 parts by mass of rubber components in the rubber composition constituting the cap rubber layer 2 (the sum of the content of all softeners A if multiple softeners A are included) is 5.0 parts by mass or more, preferably more than 5.0 parts by mass, more preferably more than 5.5 parts by mass, even more preferably more than 6.0 parts by mass, even more preferably more than 7.0 parts by mass, and particularly preferably more than 8.0 parts by mass. Furthermore, from the viewpoint of rubber hardness, the total content of softener A per 100 parts by mass of rubber components in the rubber composition constituting the cap rubber layer 2 is preferably less than 50 parts by mass, more preferably less than 48 parts by mass, even more preferably less than 45 parts by mass, even more preferably less than 40 parts by mass, and particularly preferably less than 35 parts by mass.

[0104] The softening agent B is not particularly limited as long as its weight-average molecular weight (Mw) is less than 1000, but it is preferably at least one selected from the group consisting of resin components, oils, and ester-based plasticizers.

[0105] From the viewpoint of the effects of the present invention, the total content of softener B per 100 parts by mass of rubber component in the rubber composition constituting the cap rubber layer 2 is preferably more than 5.0 parts by mass, more preferably more than 7.0 parts by mass, even more preferably more than 10.0 parts by mass, and even more preferably more than 15.0 parts by mass. Furthermore, from the viewpoint of rubber hardness and processability, the total content of softener B per 100 parts by mass of rubber component in the rubber composition constituting the cap rubber layer 2 is preferably less than 60 parts by mass, more preferably less than 50 parts by mass, even more preferably less than 45 parts by mass, even more preferably less than 40 parts by mass, and particularly preferably less than 35 parts by mass.

[0106] In the present invention, the rubber composition constituting the base rubber layer 4 preferably contains a softening agent A, and the total content of softening agent A per 100 parts by mass of rubber components in the rubber composition containing the base rubber layer 4 is preferably 4.0 parts by mass or more, more preferably 5.0 parts by mass or more, even more preferably more than 5.0 parts by mass, and still more preferably more than 9.0 parts by mass.

[0107] Examples of resin components include petroleum resins, terpene resins, rosin resins, and phenolic resins commonly used in the tire industry, and it is preferable that the softening agent A contains a terpene resin. These resin components may be used individually or in combination of two or more.

[0108] Examples of terpene resins include polyterpene resins consisting of at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, etc.; aromatically modified terpene resins made from the terpene compound and an aromatic compound; terpene-phenol resins made from the terpene compound and a phenolic compound; and these terpene resins that have been hydrogenated (hydrogenated terpene resins). Examples of aromatic compounds used as raw materials for aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds used as raw materials for terpene-phenol resins include phenol, bisphenol A, cresol, and xylenol.

[0109] Examples of petroleum resins include C5-based petroleum resins, aromatic petroleum resins, and C5C9-based petroleum resins.

[0110] In this specification, "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as the C5 petroleum resin.

[0111] In this specification, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, and may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are preferably used include coumarone indene resin, coumarone resin, indene resin, and aromatic vinyl resins. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, for reasons of being economical, easy to process, and having excellent heat generation properties. As aromatic vinyl resins, commercially available products from companies such as Kraton, Eastman Chemical, etc., can be used.

[0112] In this specification, "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. Examples of the C5 fraction and C9 fraction include the petroleum fractions mentioned above. As C5C9 petroleum resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0113] Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc.

[0114] Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin.

[0115] The liquid polymer is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), but examples include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid polymers may be used individually or in combination of two or more.

[0116] From the viewpoint of processability, it is preferable that softener A exhibits fluidity at 130°C or higher, which is the processing temperature for rubber. For this reason, it is preferable that the glass transition temperature of softener A is 100°C or lower, and the softening temperature is 120°C or lower.

[0117] Examples of oils include process oils, vegetable oils, and animal oils. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Furthermore, for environmental reasons, process oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of low-PCA process oils include lightly extracted solvates (MES), processed distillate aromatic extracts (TDAEs), and heavy naphthenic oils.

[0118] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelaate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). These ester-based plasticizers may be used individually or in combination of two or more.

[0119] <Filler> The rubber composition constituting the cap rubber layer 2 preferably contains carbon black and / or silica as a filler, and more preferably contains carbon black. The rubber composition constituting the base rubber layer 4 preferably contains carbon black as a filler.

[0120] (Carbon black) As the carbon black, those commonly used in the tire industry can be appropriately used, for example, GPF, FEF, HAF, ISAF, SAF, etc. These carbon blacks may be used alone or in combination of two or more.

[0121] From the viewpoint of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 10 m 2 / g or more, more preferably 20 m 2 / g or more, still more preferably 35 m 2 / g or more, particularly preferably 50 m 2 / g or more. Also, from the viewpoints of low fuel consumption performance and processability, it is preferably 200 m 2 / g or less, more preferably 150 m 2 / g or less, still more preferably 100 m 2 / g or less, still more preferably 80 m 2 / g or less. The N2SA of carbon black is measured by the above measurement method.

[0122] From the viewpoints of wear resistance performance and wet grip performance, the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber layer 2 is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, still more preferably more than 40 parts by mass, still more preferably more than 50 parts by mass, and particularly preferably more than 55 parts by mass. Also, from the viewpoint of low fuel consumption performance, the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the cap rubber layer 2 is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, still more preferably less than 70 parts by mass, and particularly preferably less than 65 parts by mass.

[0123] In the present invention, the carbon black content per 100 parts by mass of rubber components in the rubber composition containing the base rubber layer 4 is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, even more preferably more than 40 parts by mass, even more preferably more than 50 parts by mass, and particularly preferably more than 55 parts by mass, from the viewpoint of wear resistance performance. Furthermore, the carbon black content per 100 parts by mass of rubber components in the rubber composition constituting the base rubber layer 4 is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, even more preferably less than 70 parts by mass, and particularly preferably less than 65 parts by mass, from the viewpoint of low fuel consumption performance.

[0124] (silica) The silica used is not particularly limited, and common silica used in the tire industry can be used, such as silica prepared by the dry method (anhydrous silica) or silica prepared by the wet method (hydrated silica). Among these, hydrated silica prepared by the wet method is preferred because it contains a large number of silanol groups. These silicas may be used individually or in combination of two or more types.

[0125] The nitrogen adsorption specific surface area (N2SA) of silica is 140 m², from the perspective of low fuel consumption and wear resistance. 2 Preferably 150m / g or more 2 More preferably 160m / g or more, 2 More preferably 170m / g or more. 2 A value of 350m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 350m 2 Preferably less than / g, 300m 2 More preferably less than / g, 250m 2 A value of less than / g is even more preferable. The N2SA of silica is measured by the measurement method described above.

[0126] From the viewpoint of ash content, the silica content of the rubber composition constituting the cap rubber layer 2 is preferably more than 5 parts by mass, more preferably more than 7 parts by mass, and even more preferably 10 parts by mass or more per 100 parts by mass of rubber components. Furthermore, from the viewpoint of rubber hardness, it is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 60 parts by mass or less.

[0127] From the viewpoint of rubber hardness, the silica content of the rubber composition constituting the base rubber layer 4 per 100 parts by mass of rubber components is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less. The lower limit of the silica content of the rubber composition constituting the base rubber layer 4 per 100 parts by mass of rubber components is not particularly limited, and silica may not be included.

[0128] From the viewpoint of wear resistance, the total content of silica and carbon black per 100 parts by mass of rubber components in the rubber composition constituting the cap rubber layer 2 is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption and elongation at break, it is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less.

[0129] From the viewpoint of balancing handling stability and wet grip performance, it is preferable that the rubber composition constituting the cap rubber layer 2 contains more carbon black per 100 parts by mass of rubber components than the silica content.

[0130] The ratio of carbon black to the total content of silica in the rubber composition constituting the cap rubber layer 2 is preferably 51% by mass or more, more preferably 54% by mass or more, even more preferably 57% by mass or more, and particularly preferably 60% by mass or more. Furthermore, there is no particular upper limit to the ratio of carbon black to the total content of silica in the rubber composition according to the present invention, and it can be, for example, 100% by mass, 95% by mass or less, 90% by mass or less, or 85% by mass or less.

[0131] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used, for example: mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane. Examples include thioester silane coupling agents such as lan; vinyl silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, it is preferable to contain a sulfide silane coupling agent and / or a mercapto silane coupling agent. As silane coupling agents, for example, those commercially available from Momentive, etc., can be used. These silane coupling agents may be used individually or in combination of two or more.

[0132] When a silane coupling agent is included, the content per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 part by mass, even more preferably more than 2.0 parts by mass, and particularly preferably more than 2.3 parts by mass, from the viewpoint of improving silica dispersibility. Furthermore, from the viewpoint of preventing a decrease in wear resistance, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, even more preferably less than 12 parts by mass, and particularly preferably less than 9.0 parts by mass.

[0133] From the viewpoint of improving silica dispersibility, the content of the silane coupling agent per 100 parts by mass of silica is preferably more than 1.0 part by mass, more preferably more than 3.0 parts by mass, and even more preferably more than 5.0 parts by mass. Furthermore, from the viewpoint of cost and processability, it is preferably less than 40 parts by mass, more preferably less than 35 parts by mass, and even more preferably less than 30 parts by mass.

[0134] In addition to carbon black and silica, other fillers may be used. Such fillers are not particularly limited; for example, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, and any other filler commonly used in this field can be used. These other fillers may be used individually or in combination of two or more.

[0135] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to the present invention may appropriately contain compounding agents commonly used in the tire industry, such as waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0136] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, and more preferably more than 1 part by mass, from the viewpoint of weather resistance of the rubber. Furthermore, from the viewpoint of preventing whitening of the tire due to bloom, it is preferably less than 10 parts by mass, and more preferably less than 5 parts by mass.

[0137] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids may be used individually or in combination of two or more. Examples of processing aids that can be used are those commercially available from companies such as Schill+Seilacher and Performance Additives.

[0138] When processing aids are included, the content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, and more preferably more than 1 part by mass, from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably less than 10 parts by mass, and more preferably less than 8 parts by mass.

[0139] While not particularly limited, examples of anti-aging agents include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts. Phenylenediamine-based anti-aging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine are preferred, as are quinoline-based anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. These anti-aging agents may be used individually or in combination of two or more.

[0140] When an anti-aging agent is included, the content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, and more preferably more than 1 part by mass, from the viewpoint of the rubber's resistance to ozone cracking. Furthermore, from the viewpoint of wear resistance and wet grip performance, it is preferably less than 10 parts by mass, and more preferably less than 5 parts by mass.

[0141] When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, and more preferably more than 1 part by mass, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably less than 10 parts by mass, and more preferably less than 5 parts by mass.

[0142] When stearic acid is included, its content per 100 parts by mass of rubber component is preferably more than 0.5 parts by mass, and more preferably more than 1 part by mass, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably less than 10 parts by mass, and more preferably less than 5 parts by mass.

[0143] Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0144] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably more than 0.1 parts by mass, more preferably more than 0.3 parts by mass, and even more preferably more than 0.5 parts by mass, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 3.0 parts by mass. When oil-containing sulfur is used as the vulcanizing agent, the amount of vulcanizing agent shall be the total amount of pure sulfur contained in the oil-containing sulfur.

[0145] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, 1,6-hexamethylene-dithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These non-sulfur vulcanizing agents can be purchased commercially from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0146] Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. These vulcanization accelerators may be used individually or in combination of two or more. Among these, one or more vulcanization accelerators selected from the group consisting of sulfenamide, guanidine, and thiazole vulcanization accelerators are preferred, with sulfenamide vulcanization accelerators being more preferred.

[0147] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) is preferred.

[0148] When a vulcanization accelerator is included, its content per 100 parts by mass of the rubber component (total amount if multiple vulcanization accelerators are used in combination) is preferably more than 0.5 parts by mass, more preferably more than 1 part by mass, and even more preferably 1.5 parts by mass or more. Furthermore, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably less than 8 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 6 parts by mass. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0149] The rubber composition according to the present invention can be manufactured by known methods. For example, it can be manufactured by kneading each of the above components using a rubber kneading device such as an open roll or a closed kneader (Banbury mixer, kneader, etc.).

[0150] The mixing process includes, for example, a base mixing process in which compounding agents and additives other than the vulcanizing agent and vulcanization accelerator are mixed, and a final mixing (F mixing) process in which the vulcanizing agent and vulcanization accelerator are added to the mixture obtained in the base mixing process and mixed. Furthermore, the base mixing process can be divided into multiple processes as desired.

[0151] There are no particular limitations on the mixing conditions, but for example, in the base mixing process, mixing is performed at a discharge temperature of 150-170°C for 3-10 minutes, and in the final mixing process, mixing is performed at 70-110°C for 1-5 minutes. There are no particular limitations on the vulcanization conditions, but for example, vulcanization is performed at 150-200°C for 10-30 minutes.

[0152] The tire of the present invention can be manufactured by conventional methods using the rubber composition described above. Specifically, an unvulcanized rubber composition, in which the above components are blended with the rubber component as needed, is extruded in an extruder equipped with a die of a predetermined shape to match the shape of each rubber layer of the tread portion, bonded together with other tire components on a tire molding machine, and molded in conventional methods to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to manufacture the tire.

[0153] <Application> The tire of the present invention can be suitably used for passenger car tires, truck and bus tires, motorcycle tires, and racing tires, and is particularly preferred for passenger car tires. By using it for passenger car tires, the effects of the present invention can be exhibited more effectively. A passenger car tire is defined as a tire intended to be mounted on a four-wheeled vehicle, with a maximum load capacity of 1000 kg or less. Furthermore, the tire of the present invention can be used for all-season tires, summer tires, and winter tires such as studless tires. [Examples]

[0154] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

[0155] We examined tires having treads made of rubber compositions obtained according to Table 1 using the various chemicals listed below, and the results calculated based on the various analysis and evaluation methods described below are shown in the lower part of Table 1 and in Tables 2 to 3.

[0156] NR:RSS#3 BR: Nipol BR1220 manufactured by Nippon Zeon Co., Ltd. (Sys1,4 content: 97%) SBR: SBR manufactured according to Manufacturing Example 1 below (styrene content: 25% by mass, vinyl content: 59 mol%, Mw: 250,000, non-stretchable) Carbon black: Diablack I (N220) (N2SA: 114m) manufactured by Mitsubishi Chemical Corporation. 2 / g, average primary particle diameter: 22nm) Silica: ULTRASIL(registered trademark) VN3 (N2SA: 175m) manufactured by Evonik Degussa. 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa. Oil: PS-32 (paraffin-based process oil, Mw: 400) manufactured by Idemitsu Kosan Co., Ltd. Resin component 1: Sylvatraxx 4401 manufactured by Kraton (a copolymer of α-methylstyrene and styrene, softening point: 85°C, Mw: 520) Resin component 2: PX1150N manufactured by Yasuhara Chemical Co., Ltd. (unhydrogenated polyterpene resin, Tg: 65℃, Mw: 3200) Liquid polymer: Liquid SBR (Tg: -25℃, Mw: 5000) produced according to Production Example 2 below. Anti-aging agent: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0157] (Manufacturing example 1: Manufacturing of SBR) In a nitrogen-purged autoclave reactor, 600 mL of hexane, 75 g of 1,3-butadiene, 25 g of styrene, and 60 mL of tetrahydrofuran were added and stirred at 40°C. After scavenging by adding 0.5 mL of 0.1 mol / L n-butyllithium / hexane solution at a time, 4 mL of 0.1 mol / L n-butyllithium / hexane solution was added, and the mixture was stirred at a stirring speed of 130 rpm and a jacket temperature of 80°C. After confirming the formation of polymers with an Mw of 250,000 by GPC, the polymerization solution was poured into 4 L of ethanol and the precipitate was collected. The obtained precipitate was air-dried, and then dried under reduced pressure at 80°C / 10 Pa or less until the drying loss was 0.1% to obtain SBR.

[0158] (Manufacturing Example 2: Manufacturing of Liquid Polymers) In a nitrogen-purged autoclave reactor, 20 mL of 1.0 mol / L n-butyllithium / hexane solution, 200 mL of hexane, and 60 mL of tetrahydrofuran were added. Then, a monomer solution prepared by dissolving 75 g of 1,3-butadiene and 25 g of styrene in 400 mL of hexane was added while stirring at a stirring speed of 80 rpm and a jacket temperature of 80°C, ensuring that the reaction mixture temperature did not exceed 90°C. After confirming the formation of a polymer with an Mw of 5000 by GPC, the polymerization solution was poured into 4 L of ethanol and the precipitate was collected. The obtained precipitate was air-dried, and then dried under reduced pressure at 80°C / 10 Pa or less until the loss on drying was 0.1%. The obtained liquid was analyzed by DSC and confirmed to have a Tg of -25°C.

[0159] According to the formulation shown in Table 1, the chemicals other than sulfur and vulcanization accelerator were mixed in a 1.7 L closed Banbury mixer for 1 to 10 minutes until the discharge temperature reached 150 to 160°C to obtain a mixture. Next, using a twin-screw open roll mixer, sulfur and vulcanization accelerator were added to the obtained mixture and mixed for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. Using the obtained unvulcanized rubber composition, the cap rubber layer, intermediate rubber layer, and base rubber layer of the tread section were molded to match their shapes, and the unvulcanized tires were bonded together with other tire components to produce an unvulcanized tire. The tires were then vulcanized at 170°C for 12 minutes to obtain the test tires listed in Table 2 (size: 165 / 65R15, rim: 15×5J, internal pressure: 230kPa). The total thickness of the tread section was 10 mm.

[0160] <Measurement of acetone extraction amount (AE amount)> The amount of AE (air-entraining) is measured for each test specimen cut from the tread and belt topping rubber of each test tire. The amount of AE can be determined by immersing each test specimen in acetone for 24 hours to extract soluble components, measuring the mass of each test specimen before and after extraction, and using the following formula. Acetone extraction amount (%) = {(Mass of vulcanized rubber test piece before extraction - Mass of vulcanized rubber test piece after extraction) / (Mass of rubber test piece before extraction)} × 100

[0161] <Measurement of ash content> Test specimens cut from the tread of each test tire are placed in an alumina crucible and heated in an electric furnace at 550°C for 4 hours. Then, the ash content (mass %) is calculated by (mass of test specimen after heating / mass of test specimen before heating) × 100.

[0162] <Measurement of tanδ at 30℃> Each vulcanized rubber test piece, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, was prepared by cutting from the rubber layer of the tread of each test tire, with the tire circumference as the longer side. The loss tangent tanδ was measured using a dynamic viscoelasticity analyzer (GABO Iplexer series) under the conditions of 30°C, 5% initial strain, 1% dynamic strain, and 10 Hz. The thickness direction of the sample was considered to be the tire radius direction.

[0163] <Measurement of 0℃E*> Each vulcanized rubber test piece, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, was prepared by cutting from the rubber layer of the tread of each test tire, with the tire circumference as the longer side. The complex modulus E* was measured using a dynamic viscoelasticity analyzer (GABO Iplexer series) under the conditions of 0°C, initial strain of 10%, dynamic strain of 2.5%, and frequency of 10 Hz. The thickness direction of the sample was considered to be the tire radius direction.

[0164] <Measurement of glass transition temperature (Tg)> Each vulcanized rubber test piece, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, was prepared by cutting a piece from the rubber layer of the tread of each test tire, with the tire circumference as the longer side. A dynamic viscoelasticity analyzer (GABO Iplexer series) was used to measure the temperature distribution curve of the loss tangent tanδ under conditions of a frequency of 10 Hz, initial strain of 10%, amplitude of ±0.5%, and heating rate of 2 °C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature) was defined as the glass transition temperature (Tg). The thickness direction of the sample was considered to be the tire radius direction.

[0165] <Measurement of rubber hardness (Hs)> In accordance with JIS K 6253-3:2012, the Shore hardness (Hs) of each rubber test specimen will be measured at a temperature of 23°C using a durometer type A. Each rubber test specimen will be cut from the inside of the rubber layer of the tread portion of each test tire.

[0166] <Hardness after storage> After each test tire is left to stand at 80°C for two months following manufacture, the Shore hardness (Hs) of the cap rubber layer on the tread is measured. The percentage change in the Shore hardness of the cap rubber layer is calculated using the following formula. (Percentage change in Shore hardness (%)) = {(Shore hardness of the cap rubber layer after storage) / (Shore hardness of the cap rubber layer after tire manufacturing) × 100} - 100

[0167] <Hardness after driving> Each test tire is mounted on one of the four wheels of a 2000cc front-wheel-drive passenger car, and after driving 20,000 km in urban areas, the Shore hardness (Hs) of the cap rubber layer on the tread is measured.

[0168] <Wet grip performance after deterioration> After thermally degrading the aforementioned tires at 80°C for 7 days, the tread is worn down along the tread radius until the tread thickness is 50% of that of a new tire. Each of these test tires is mounted on all wheels of a vehicle (Japanese-made FF 2000cc) and the braking distance is measured on a wet asphalt road surface at a speed of 100 km / h from the point of braking. The braking distance of the control tire (Comparative Example 1) is set to 100, and the reciprocal of the braking distance of each test tire is expressed as an index using the following formula. A higher index indicates that the wet grip performance after degradation is maintained. (Wet grip performance index) = (Braking distance of the control tire) / (Braking distance of each test tire)

[0169] <Durability> Each test tire was subjected to a drum test using a drum testing machine under internal pressure and load (normal load) of 200 kPa, and driven at 60 km / h. The distance traveled until damage was observed was measured, and the result was expressed as an index with the value of the control tire (Comparative Example 1) set to 100. A higher index value indicates superior durability.

[0170] <Overall Performance> The sum of the wet grip performance index and durability performance index after degradation is displayed as the overall performance index. A higher index indicates better overall performance.

[0171] [Table 1]

[0172] [Table 2]

[0173] [Table 3]

[0174] <Embodiment> Examples of embodiments of the present invention are shown below.

[0175] [1] A tire having a tread section having two or more rubber layers and a belt layer, The tread portion comprises a cap rubber layer that constitutes the tread surface, and a base rubber layer located radially inward of the cap rubber layer. The cap rubber layer and the base rubber layer are each composed of a rubber composition containing rubber components. The thickness of the cap rubber layer is 20% or more of the total thickness of the tread portion. When the amount of acetone extracted from the rubber composition constituting the cap rubber layer is denoted as AE1, AE1 is less than 12.0% by mass, The ash content of the rubber composition constituting the aforementioned cap rubber layer is less than 7.5% by mass. The rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of softener A having a weight-average molecular weight of 1000 or more, per 100 parts by mass of rubber component. When the amount of acetone extracted from the rubber composition constituting the base rubber layer is denoted as AE2, Tires with an AE2 / AE1 ratio of 0.6 or higher. [2] The tire described in [1] above, wherein when the amount of acetone extracted from the belt topping rubber is AE3, AE1-AE3 is less than 5.0% by mass. [3] The tire according to [1] or [2] above, wherein the rubber composition constituting the base rubber layer contains 5 parts by mass or more of softener A. [4] The tire according to any one of [1] to [3] above, wherein the Shore hardness (Hs) of the rubber composition constituting the cap rubber layer is 50 or more and 70 or less. [5] A tire according to any of [1] to [4] above, wherein the rate of change of the Shore hardness (Hs) of the cap rubber layer after being left standing at 80°C for two months is -10% or more and 10% or less. [6] The tire according to any one of [1] to [5] above, wherein the rubber component constituting the cap rubber layer includes at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber. [7] The tire according to any one of [1] to [6] above, wherein the softening agent A is at least one selected from the group consisting of terpene resins and liquid polymers. [8] The tire according to any one of [1] to [7] above, wherein the rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of a softener B having a weight-average molecular weight of less than 1000 per 100 parts by mass of the rubber component. [9] The tire according to any one of [1] to [8] above, wherein the total content of the softener per 100 parts by mass of rubber component in the rubber composition constituting the cap rubber layer is more than 10.0 parts by mass and less than 50.0 parts by mass.

[10] The tire according to any one of [1] to [9] above, wherein the tanδ of the cap rubber layer at 30°C is 0.40 or less.

[11] The tire according to any one of [1] to

[10] above, wherein the 0°C E* of the rubber composition constituting the cap rubber layer is 5.0 MPa or higher.

[12] The tire according to any one of [1] to

[11] above, wherein the glass transition temperature of the rubber composition constituting the cap rubber layer is -60°C or higher.

[13] The tire according to any one of [1] to

[12] above, wherein the rubber composition constituting the cap rubber layer contains more than 50 parts by mass of carbon black per 100 parts by mass of rubber component.

[14] The tire according to any one of [1] to

[13] above, wherein the rubber composition constituting the base rubber layer contains more than 50 parts by mass of carbon black per 100 parts by mass of rubber components.

[15] A tire as described in any of [1] to

[14] above, wherein the tire is a passenger car tire. [Explanation of symbols]

[0176] 1. Tread section 2. Cap rubber layer 4. Base rubber layer 7. Inner Liner 8 Belt Layer 9 Carcass 11 bands CL Tire Equatorial Plane

Claims

1. A tire comprising a tread section having two or more rubber layers and a belt layer, The tread portion comprises a cap rubber layer that constitutes the tread surface, and a base rubber layer located radially inward of the cap rubber layer. The cap rubber layer and the base rubber layer are each composed of a rubber composition containing rubber components. The thickness of the cap rubber layer is 20% or more of the total thickness of the tread portion. The amount of acetone extracted from the rubber composition constituting the cap rubber layer is AE 1 When this is the case, AE 1 It is less than 12.0% by mass, The ash content of the rubber composition constituting the aforementioned cap rubber layer is less than 7.5% by mass. The rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of softener A having a weight-average molecular weight of 1000 or more, per 100 parts by mass of rubber component. The amount of acetone extracted from the rubber composition constituting the base rubber layer is AE 2 In that case, AE 2 / AE 1 The value is 0.6 or higher, The aforementioned belt layer is covered with belt topping rubber, A tire in which, when the amount of acetone extracted from the belt topping rubber is AE3, AE1 - AE3 is less than 5.0% by mass.

2. The tire according to claim 1, wherein the rate of change in the Shore hardness (Hs) of the cap rubber layer after being left standing at 80°C for two months is -10% or more and 10% or less.

3. A tire comprising a tread portion having two or more rubber layers and a belt layer, The tread portion comprises a cap rubber layer that constitutes the tread surface, and a base rubber layer located radially inward of the cap rubber layer. The cap rubber layer and the base rubber layer are each composed of a rubber composition containing rubber components. The thickness of the cap rubber layer is 20% or more of the total thickness of the tread portion. When the amount of acetone extracted from the rubber composition constituting the cap rubber layer is defined as AE1, AE1 is less than 12.0% by mass, The ash content of the rubber composition constituting the aforementioned cap rubber layer is less than 7.5% by mass. The rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of softener A having a weight-average molecular weight of 1000 or more, per 100 parts by mass of rubber component. When the amount of acetone extracted from the rubber composition constituting the base rubber layer is AE2, AE2 / AE1 is 0.6 or higher, A tire in which the rate of change in the Shore hardness (Hs) of the cap rubber layer after being left standing at 80°C for two months is between -10% and 10%.

4. The tire according to claim 1 or 3, wherein the rubber composition constituting the base rubber layer contains 5 parts by mass or more of softener A.

5. The tire according to claim 1 or 3, wherein the Shore hardness (Hs) of the rubber composition constituting the cap rubber layer is 50 or more and 70 or less.

6. The tire according to claim 1 or 3, wherein the rubber component constituting the cap rubber layer includes at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber.

7. The tire according to claim 1 or 3, wherein the softening agent A is at least one selected from the group consisting of terpene resins and liquid polymers.

8. The tire according to claim 1 or 3, wherein the rubber composition constituting the cap rubber layer contains 5.0 parts by mass or more of a softener B having a weight-average molecular weight of less than 1000, per 100 parts by mass of the rubber component.

9. The tire according to claim 1 or 3, wherein the total content of the softener in the rubber composition constituting the cap rubber layer is more than 10.0 parts by mass and less than 50.0 parts by mass per 100 parts by mass of rubber component.

10. The tire according to claim 1 or 3, wherein the tanδ of the cap rubber layer at 30°C is 0.40 or less.

11. The tire according to claim 1 or 3, wherein the 0°C E* of the rubber composition constituting the cap rubber layer is 5.0 MPa or higher.

12. The tire according to claim 1 or 3, wherein the glass transition temperature of the rubber composition constituting the cap rubber layer is -60°C or higher.

13. The tire according to claim 1 or 3, wherein the rubber composition constituting the cap rubber layer contains more than 50 parts by mass of carbon black with respect to 100 parts by mass of rubber component.

14. The tire according to claim 1 or 3, wherein the rubber composition constituting the base rubber layer contains more than 50 parts by mass of carbon black with respect to 100 parts by mass of rubber components.

15. The tire according to claim 1 or 3, wherein the tire is a passenger car tire.

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