tire

Abstract

To provide a tire whose steering stability on a wet road surface can be maintained over the long term.SOLUTION: The tire comprises a tread part having at least one rubber layer and a side wall. The tread part and the side wall are constituted of rubber compositions containing rubber components and plant oil respectively. When an average value of contents of the plant oil with respect to 100 mass parts of rubber components of tread rubber constituting the tread part is defined as S1 (mass parts) and contents of the plant oil with respect to 100 mass% of the rubber compositions constituting the side wall are defined as S2 (mass parts), a ratio of S1 / S2 is over 1.0. When complex elastic modulus at 30°C of a cap rubber layer constituting a tread surface is defined as 30°CE*C(MPa) and complex elastic modulus at 70°C of the rubber compositions constituting the side wall is defined 70°CE*SW(MPa), 30°CE*C-70°CE*SW is equal to 3.0 MPa or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In Patent Document 1, in a tire having a tread portion including a cap rubber that contacts the road surface and a base rubber that is disposed radially inward of the cap rubber in the tire radius direction, the cap rubber is a relatively rigid rubber layer, the base rubber is a relatively low-rigidity rubber layer, and by inclining the thickness of the base rubber in the tire width direction, the difference in contact pressure is reduced and the braking performance is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the tire described in Patent Document 1 is likely to lose followability with respect to the road surface due to the relatively rigid cap rubber, and since the base rubber has low rigidity and cannot generate sufficient reaction force, there is room for improvement in the handling stability performance on a wet road surface.

[0005] An object of the present invention is to maintain the handling stability performance of a tire on a wet road surface over a long period.

Means for Solving the Problems

[0006] The present invention relates to a tire comprising a tread portion having at least one rubber layer and a sidewall, wherein the tread portion and the sidewall are each composed of a rubber composition containing a rubber component and a vegetable oil, and when S1 (parts by mass) is the average value of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber constituting the tread portion, and S2 (parts by mass) is the vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the sidewall, S1 / S2 is greater than 1.0, and the complex modulus of elasticity at 30°C of the cap rubber layer constituting the tread surface is 30°CE* C (MPa), the complex modulus of the rubber composition constituting the sidewall at 70°C is 70°CE* SW (MPa) when at 30℃E* C -70℃E* SW This pertains to tires with a pressure of 3.0 MPa or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to maintain the long-term handling stability performance of tires on wet road surfaces. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of an example of a tire according to one embodiment of the present invention. [Figure 2] This is an enlarged plan view of the main groove according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] This is an enlarged plan view of another main groove according to the present invention. [Figure 5] (a) is a cross-sectional view along line BB in Figure 4, and (b) is a cross-sectional view along line CC in Figure 4. [Modes for carrying out the invention]

[0009] A tire according to one embodiment of the present invention comprises a tread portion having at least one rubber layer and a sidewall, wherein the tread portion and the sidewall are each composed of a rubber composition containing a rubber component and a vegetable oil, and when S1 (parts by mass) is the average value of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber constituting the tread portion, and S2 (parts by mass) is the vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the sidewall, S1 / S2 is greater than 1.0, and the complex modulus of elasticity at 30°C of the cap rubber layer constituting the tread surface is 30°C E* C (MPa), the complex modulus of the rubber composition constituting the sidewall at 70°C is 70°CE* SW (MPa) when at 30℃E* C -70℃E* SW These are tires with a pressure of 3.0 MPa or less.

[0010] The reason why the tire according to this embodiment can maintain long-term handling stability on wet surfaces is, although we do not intend to be bound by theory, thought to be as follows.

[0011] By incorporating vegetable oil into the tread rubber and sidewall rubber, and by making the average content of vegetable oil per 100 parts by mass of rubber component in the tread rubber greater than the content of vegetable oil per 100 parts by mass of rubber component in the rubber composition constituting the sidewall, it is believed that the tread rubber can more easily follow the road surface, and appropriate rigidity can be ensured in the sidewall, thereby improving responsiveness. Furthermore, since vegetable oil has the property of not easily moving within rubber among rubber softeners used in rubber processing, it is possible to suppress the migration of the softener from the tread rubber to the sidewall. As a result, the tread becomes less prone to hardening, and the sidewall rubber becomes less prone to softening, so it is believed that the road surface following ability of the tread is maintained over time, and the rigidity of the sidewall is also more easily ensured.

[0012] Also, by reducing the rigidity difference between the tread rubber and the sidewall rubber, when cornering, the tread part and the sidewall part deform uniformly, and the whole twists from the tread part to the sidewall, making it easier for the tire to generate a reaction force.

[0013] And by these working together, it is considered that while maintaining the followability of the tread part to the road surface, a state where the tire easily generates a reaction force is maintained. As a result, it is considered that the remarkable effect that the tire maintains the handling stability performance on a wet road surface over a long period is achieved.

[0014] The content S2 of the vegetable oil with respect to 100 parts by mass of the rubber component of the rubber composition constituting the sidewall is preferably 5.0 parts by mass or less.

[0015] By setting S2 within the above range, it is considered that the rigidity can be increased in the sidewall part, making it easier to generate a reaction force.

[0016] The tanδ (30 °C tanδ C ) of the cap rubber layer is preferably not more than 0.13.

[0017] By setting 30 °C tanδ C within the above range, it is considered that the heat generation during running is reduced, and the aging of the cap rubber layer over time is suppressed.

[0018] The tanδ (70 °C tanδ SW ) of the rubber composition constituting the sidewall is preferably not more than 0.06.

[0019] By setting 70 °C tanδ SW within the above range, when the sidewall part is deformed so as to twist during cornering, it becomes easier to recover, the responsiveness is improved, and it is considered that it is easier to improve the handling stability performance on a wet road surface over a long period.

[0020] The complex modulus of elasticity of the cap rubber layer at 30°C (30°C E* C The pressure is preferably 5.0 MPa or higher.

[0021] 30℃E* C By setting the range to the aforementioned extent, it is believed that the tread portion will be able to more easily exert a restorative force against deformation after following the road surface, thereby improving responsiveness.

[0022] The glass transition temperature of the cap rubber layer is preferably -25°C or higher.

[0023] On wet surfaces, slippage occurs between the tread rubber surface and the road surface, and it is believed that this slippage, resulting in energy loss at temperatures lower than room temperature, contributes to the grip performance of the tread rubber surface. Therefore, by setting the glass transition temperature of the cap rubber layer to -25°C or higher, it is possible to improve energy loss at temperatures lower than room temperature, thereby improving the grip performance of the tread surface and making it easier to exhibit the effects of the present invention.

[0024] The Shore hardness (Hs) of the cap rubber layer is preferably between 40 and 70.

[0025] By setting the Shore hardness of the cap rubber layer within the aforementioned range, it is believed that handling stability and wet grip performance can be maintained.

[0026] Let t be the total thickness of the tread section (mm). Then, the tanδ of the cap rubber layer at 30°C (30°C tanδ) C ) and the product of t (30℃ tanδ C ×t) is preferably 1.50 or less.

[0027] The thicker the tread, the easier it is for heat to accumulate within the tread during driving, which is thought to lead to hardening of the tread. Also, 30℃ tanδ CThe higher the product of these factors, the more likely it is that heat will be generated by rolling during driving, which is likely to lead to hardening of the entire tread area. Therefore, by keeping the product of these factors below a certain level, it is possible to suppress heat generation and heat accumulation in the tread area, making it easier to suppress hardening of the tread area and thus making it easier to achieve the effects of the present invention.

[0028] The difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall (average amount of acetone extracted from the tread rubber - amount of acetone extracted from the rubber composition constituting the sidewall) is preferably 5.0% by mass or more.

[0029] By setting the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall within the aforementioned range, the diffusion of the softening agent from the tread rubber to the sidewall rubber can be appropriately controlled. From this, it is considered that the change in hardness of the cap rubber layer due to tire use can be appropriately controlled.

[0030] The average ash content of the tread rubber is preferably 7.5% by mass or more.

[0031] By setting the average value of the ash content of the tread rubber within the aforementioned range, it is believed that the ash component will adsorb the softening agent, suppressing the migration of the softening agent from the tread rubber to the sidewall rubber, and thereby suppressing the hardening phenomenon of the tread rubber over time.

[0032] The total amount of styrene in the rubber component constituting the cap rubber layer is preferably 3% by mass or more and 15% by mass or less.

[0033] By setting the total amount of styrene in the rubber component constituting the cap rubber layer to the aforementioned range, domains of styrene are created within the cap rubber layer, and it is believed that these styrene domains make it easier to obtain a scratching effect on the road surface. Furthermore, because the styrene portion has a bulky structure, it is thought that it becomes easier to prevent the softening agent from moving within the rubber, thus making it easier to exert the effects of the present invention.

[0034] The tread portion has circumferential grooves that extend continuously in the circumferential direction of the tire, and preferably the groove wall of at least one circumferential groove has a recess that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the total recess amount of the at least one circumferential groove relative to the groove width of the at least one circumferential groove is 0.10 to 0.90.

[0035] As the tread wears down, the opening area of ​​the circumferential grooves increases, which is thought to maintain handling stability on wet surfaces over a long period of time.

[0036] Preferably, the first groove wall, which is one groove wall of the circumferential groove, has a first recess that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the amount of recession from the groove edge gradually decreases from the deepest part that is recessed outward in the groove width direction toward both sides in the tire circumferential direction. Furthermore, it is preferable that the first groove wall has a second recess that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the amount of recession from the groove edge is constant in the tire circumferential direction.

[0037] By providing the aforementioned recess in at least one groove wall of the circumferential groove, it is believed that steering stability and wet performance will be improved in a balanced manner.

[0038] <Definition> A "standard rim" is the rim specified for each tire within the standards system that the tire is based on. For example, it refers to a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard.

[0039] The "cap rubber layer" refers to the outermost rubber layer of the tread, specifically one that is 2mm or thicker.

[0040] "Total tread thickness" refers to the overall thickness of the tread portion on the tire's equatorial plane when the tire is cut across a plane containing the tire's axis of rotation. The inner edge of the total tread thickness in the tire's radial direction is the inner interface of the rubber composition constituting the tread portion in the tire's radial direction. If the tire has a belt reinforcement layer, a belt layer, and a carcass layer, this refers to the total thickness of the rubber layers radially outside of the outermost layer in the tire's radial direction. Furthermore, if the tire has circumferential grooves on its equatorial plane, this refers to the total tread thickness from the intersection of a straight line connecting the tire widthwise ends of the tread surface on the tire's equatorial plane with the tire's equatorial plane.

[0041] "The thickness of each rubber layer constituting the tread" refers to the thickness of each rubber layer on the tire's equatorial plane in a cross-section obtained by cutting the tire with respect to the plane containing the tire's axis of rotation. For example, the thickness of the first layer refers to the straight-line distance in the tire's radial direction from the outermost surface of the tread to the inner radial interface of the first layer on the tire's equatorial plane. If the tire has circumferential grooves on its equatorial plane, the thickness of each rubber layer constituting the tread shall be the thickness of each rubber layer at the center of the tire's width direction of the land area closest to the tire's equatorial plane. "The land area closest to the tire's equatorial plane" refers to the land area of ​​a circumferential groove on the tire's equatorial plane that has the groove edge closest to the tire's equatorial plane. If such land areas exist on both sides in the tire's width direction, the thickness of each rubber layer constituting the tread shall be the average value of the thicknesses of each rubber layer at the center of the tire's width direction of the two land areas. Furthermore, if there are conductive members or the like on the land area of ​​the tire's equatorial plane and the interface is unclear, the interface obstructed by the conductive members or the like shall be virtually connected and measured.

[0042] The "average value of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber" is calculated by multiplying the vegetable oil content (in parts by mass) per 100 parts by mass of rubber component for each rubber layer constituting the tread by the ratio of the thickness of each rubber layer to the total thickness of the tread, and then summing these values. Specifically, it is calculated as Σ(vegetable oil content (in parts by mass) per 100 parts by mass of rubber component in each rubber layer × thickness of each rubber layer relative to the total thickness of the tread (%) / 100).

[0043] The "average amount of acetone extracted from the tread rubber" is calculated by multiplying the amount of acetone extracted (mass%) from each rubber layer that makes up the tread by the ratio of the thickness of each rubber layer to the total thickness of the tread, and then summing these values. Specifically, it is calculated as Σ(Acetone extracted from each rubber layer (mass%) × Thickness of each rubber layer relative to the total thickness of the tread (%) / 100).

[0044] The "average ash content of the tread rubber" is calculated by multiplying the ash content (mass%) of each rubber layer that makes up the tread by the ratio of the thickness of each rubber layer to the total thickness of the tread, and then summing these values. Specifically, it is calculated as Σ(ash content (mass%) of each rubber layer × thickness of each rubber layer (%) relative to the total thickness of the tread / 100).

[0045] 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. However, waxes and stearic acid commonly used in the tire industry are excluded.

[0046] "Softener content" includes the amount of softener contained in the stretchable rubber component that has been pre-stretched with softeners such as oil, resin components, and liquid rubber components. The same applies to the oil content, resin component content, and liquid rubber content; for example, if the stretchable component is oil, the stretchable oil is included in the oil content.

[0047] <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.

[0048] The "amount extracted with acetone" can be determined by immersing each vulcanized rubber test piece in acetone for 72 hours in accordance with JIS K 6229:2015 to extract soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. When preparing by cutting from a tire, cut 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

[0049] 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.

[0050] "30℃E*" is the complex modulus of elasticity measured using a dynamic viscoelasticity measuring device (e.g., GABO's Iplexer series) under the conditions of a temperature of 30℃, a frequency of 10Hz, an initial strain of 5%, a dynamic strain of 1%, and the extension mode. The sample used for this 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 tread portion so that the tire circumference is the longer side and the tire radius is the thickness direction.

[0051] "70℃E*" is the complex modulus of elasticity measured using a dynamic viscoelasticity measuring device (e.g., the Iplexer series from GABO) under the conditions of a temperature of 70℃, a frequency of 10Hz, an initial strain of 10%, a dynamic strain of 1%, and the extension mode. When fabricating by cutting from a tire, it is cut from the sidewall so that the tangent to the tire's circumferential direction is the longer side and the tire's width direction (normal direction to the sidewall surface) is the thickness direction.

[0052] "30℃tanδ" is the loss loss tangent measured using a dynamic viscoelasticity analyzer (e.g., GABO's Iplexer series) under the conditions of 30℃ temperature, 10Hz frequency, 5% initial strain, 1% dynamic strain, and extension mode. The sample for this measurement is prepared in the same manner as for 30℃E*.

[0053] "70℃tanδ" is the loss loss tangent measured using a dynamic viscoelasticity measuring instrument (e.g., the Iplexer series from GABO) under the conditions of a temperature of 70℃, a frequency of 10Hz, an initial strain of 10%, a dynamic strain of 1%, and extension mode. The sample for this measurement is prepared in the same manner as for 70℃E*.

[0054] 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.

[0055] The "Tg of the rubber composition" is determined by measuring the temperature distribution curve of tanδ in the range of -60°C to 40°C using a dynamic viscoelasticity measuring device (e.g., the Iplexer series from GABO) under conditions of frequency 10 Hz, initial strain 10%, amplitude ±0.5%, and heating rate 2°C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature) is determined as Tg. If there are two points with maximum values ​​of tanδ in the range of -60°C to 40°C, the one with the lower temperature is taken as Tg. Furthermore, if a temperature distribution curve is obtained in the range of -60°C to 40°C where tanδ gradually decreases with increasing temperature, Tg is set to -60°C according to the above definition. The sample for this measurement is prepared in the same manner as for 30°CE*.

[0056] The above physical properties and relationships of the present invention refer to values ​​and relationships for tires immediately after manufacture or for new, unused tires within one year of manufacture.

[0057] "Styrene content" is, 1The value is calculated by 1H-NMR measurement and applies, for example, to rubber components (styrene unit-containing rubber) that have repeating units derived from styrene, such as SBR. The "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, for example, to rubber components that have repeating units derived from butadiene, such as SBR and BR. The "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, for example, to rubber components that have repeating units derived from butadiene, such as BR.

[0058] "Total styrene content in rubber components" refers to the total amount of styrene units contained in 100% by mass of the rubber components (by mass%). For each rubber component, the value obtained by multiplying the styrene content (by mass%) by the mass fraction in the rubber components is calculated, and these values ​​are then summed up. Specifically, it is calculated as Σ(styrene content (by mass%) of each styrene-containing rubber × styrene content (by mass%) in the rubber components of each styrene-containing rubber / 100).

[0059] 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.

[0060] 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.

[0061] 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.

[0062] [tire] Figure 1 is a cross-sectional view showing a portion of the tread of a tire according to this embodiment, but is not limited to this configuration. The tire in Figure 1 comprises a tread portion 1, a sidewall 32, a bead portion 33, a carcass 34, a belt layer 35, a belt reinforcement layer 36, an inner liner 37, a rim 38, a clinch 39, and a wing 40. The bead portion 33 includes a bead core 31. The belt layer 35 is laminated in two layers, and a belt reinforcement layer 36 having a jointless structure is arranged between the base rubber layer 4 and the belt layer 35. The belt reinforcement layer 36 consists of an edge band 61 that covers only the edge portion of the belt layer 35 and a full band 62 that covers the entire area of ​​the belt layer 35.

[0063] The tread portion of the tire according to this embodiment has at least one rubber layer. The tread portion according to this embodiment may consist of a single rubber layer or may have two or more rubber layers, but it is preferable to have two or more rubber layers. The composition of the rubber layers is not particularly limited, but for example, it may have a base rubber layer 4 adjacent to the radially outer side of the belt reinforcement layer 36 (or belt layer 35 if there is no belt reinforcement layer) and a cap rubber layer 2 that constitutes the tread surface 5. There may also be one or more intermediate rubber layers between the cap rubber layer 2 and the base rubber layer 4.

[0064] In this embodiment, 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 preferably 3.0 mm or more, more preferably 5.0 mm or more, and even more preferably 7.0 mm or more.

[0065] From the viewpoint of the effects of the present invention, the thickness of the cap rubber layer 2 relative to the total thickness of the tread portion 1 is preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, and particularly preferably 60% or more. 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, 100%, 99% or less, 95% or less, or 90% or less.

[0066] When the base rubber layer 4 is present, its thickness relative to the total thickness of the tread portion 1 is preferably 1% or more, more preferably 5% or more, and even more preferably 10% or more, from the viewpoint of the effects of the present invention. 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.

[0067] In this embodiment, it is preferable that the groove wall of at least one circumferential groove 3 is provided with a recess that is recessed outward in the groove width direction from the groove edge 6 that appears on the tread surface of the tread portion 1.

[0068] Figure 2 shows an enlarged plan view of the circumferential groove 3 according to this embodiment. In Figure 2, the groove edge 6 of the circumferential groove 3 is shown by a solid line, and the contour 7 of the groove wall when the tread portion 2 is viewed from above is shown by a dashed line. In addition, the recessed area between the groove edge 6 of the circumferential groove 3 and the contour 7 of the groove wall is colored.

[0069] Figure 3 shows a cross-sectional view of the circumferential groove 3 shown in Figure 2, along line AA. As shown in Figure 3, the circumferential groove 3 has recesses 9 on both groove walls, with a constant amount of recession in the circumferential direction of the tire. The recesses 9 are configured such that, for example, a flat surface 15 is formed between the deepest part 13 of the recess and the groove edge 6, but the configuration is not limited to this.

[0070] Figure 4 shows an enlarged plan view of another circumferential groove 3 according to this embodiment. As shown in Figure 4, one of the groove walls of the circumferential groove 3, the first groove wall 10, is provided with at least one first recess 11.

[0071] In Figure 4, the groove edges 6 of the circumferential grooves 3 are shown as solid lines, and the contour 7 of the groove walls when the tread portion 2 is viewed from above is shown as a dashed line. The recessed area between the groove edges 6 of the circumferential grooves 3 and the contour 7 of the groove walls is colored. The first recess 11 is recessed outward in the groove width direction compared to the groove edges 6 that appear on the tread surface of the tread portion 2. As the tread portion 2 wears down, the opening area of ​​the circumferential grooves 3 increases, resulting in excellent wet performance over a long period of time.

[0072] The first recess 11 gradually decreases in depth from the groove edge 6 toward both sides in the tire circumferential direction, starting from the deepest part 13, which is recessed furthest outward in the groove width direction. As a result, the rigidity of the land portion divided into the circumferential groove 3 is ensured on both sides of the deepest part 13 in the tire circumferential direction, and the groove edge side portion 8 (shown in Figure 1) of the land portion is prevented from collapsing toward the groove center of the circumferential groove 3. Furthermore, because the first recess 11 smoothly changes the rigidity of the land portion in the tire circumferential direction, it prevents local deformation of the groove edge side portion 8. Therefore, excellent handling stability is obtained.

[0073] Generally, circumferential grooves that extend continuously in the circumferential direction of the tire discharge water to the rear in the direction of tire travel during wet driving. However, when there is a large amount of water on the road surface, they tend to push some of the water forward in the direction of tire travel. The circumferential grooves 3 according to this embodiment can push some of the water forward in the direction of tire travel and outward in the tire axial direction by the first recess 11 described above, thereby suppressing the water that has been pushed back from entering between the tread portion 2 and the road surface. Furthermore, as wear occurs, the groove area increases, so the decrease in groove volume due to wear is slower compared to conventional grooves.

[0074] Preferably, the first recess 11 has an arc-shaped contour portion 7 in a cross-section along the tread surface of the tread portion 2, and its curvature gradually increases toward the inner side in the tire radial direction. Such a first recess 11 can suppress deformation of the groove edge portion 8 while ensuring a large groove volume for the circumferential groove 3.

[0075] The radius of curvature r1 of the contour portion 7 is preferably 1.5 to 3.0 times the groove width W1. Also, the length L1 of the first recess 11 in the tire circumferential direction is preferably 2.0 to 3.0 times the groove width W1 of the circumferential groove 3.

[0076] Figure 5(a) is a cross-sectional view along line BB in Figure 4, and corresponds to a cross-sectional view of the groove passing through the deepest part 13 of the first recess 11 provided in the first groove wall 10. As shown in Figure 5(a), it is preferable that the first recess 11 is provided on the groove bottom side of the groove wall of the circumferential groove 3.

[0077] The first recess 11 according to this embodiment includes, for example, a concave portion 17 recessed outward in the groove width direction, and a convex portion 18 that extends radially outward from the concave portion 17 and protrudes toward the groove centerline of the circumferential groove 3. Preferably, the concave portion 17 and the convex portion 18 are each curved in a smooth arc shape. However, the first recess 11 is not limited to this configuration, and for example, a plane may be formed between the deepest part 13 and the groove edge 6.

[0078] In the groove cross-section passing through the deepest part 13, it is preferable that the amount of recess in the first recess 11 gradually decreases from the deepest part 13 toward the radially outward direction of the tire. In order to ensure the groove volume of the circumferential groove 3, the amount of recess d1 from the groove edge 6 at the deepest part 13 is preferably 0.10 times or more, more preferably 0.20 times or more, and even more preferably 0.30 times or more, the groove width W1 which is the length between the groove edges of the circumferential groove 3. Furthermore, although the above amount of recess d1 is not particularly limited, it is preferable that it be 0.50 times or less of the groove width W1 from the viewpoint of making it easier to remove the rib for forming the circumferential groove of the vulcanization mold from the tread portion.

[0079] As shown in Figure 4, it is preferable that the first groove wall 10 is further provided with at least one second recess 12. In a preferred embodiment, the first groove wall 10 is provided with a plurality of second recesses 12. In a more preferred embodiment, the first groove wall 10 according to this embodiment has first recesses 11 and second recesses 12 alternately provided in the tire circumferential direction. The second recesses 12 are recessed outward in the groove width direction from the groove edge 6, and the amount of recess from the groove edge 6 is constant in the tire circumferential direction.

[0080] The second recess 12 preferably has a shorter tire circumferential length than, for example, the first recess 11. The tire circumferential length L2 of the second recess 12 is preferably 0.45 to 0.60 times the tire circumferential length L1 of the first recess 11. Such a second recess 12 can improve both handling stability and wet performance in a balanced manner.

[0081] Figure 5(b) is a cross-sectional view along line CC in Figure 2, and corresponds to a cross-sectional view of the groove passing through the second recess 12 provided in the first groove wall 10. As shown in Figure 5(b), the second recess 12 has, for example, a plane 15 formed between the deepest part 14 of the recess and the groove edge 6, but is not limited to this configuration.

[0082] The angle θ1 of the plane 15 of the second recess 12 is preferably, for example, 5 to 15°. The angle θ1 is the angle between the tread normal passing through the groove edge 6 and the plane 15. Such a second recess 12 can improve wet performance after the tread portion has worn down.

[0083] It is preferable that the maximum recess amount d2 of the second recess 12 is smaller than the recess amount d1 of the deepest part 13 of the first recess 11.

[0084] As shown in Figure 4, the second groove wall 20, which is the other groove wall of the circumferential groove 3, is provided with at least one of the first recesses 11 described above. Furthermore, the second groove wall 20 is provided with at least one of the second recesses 12 described above. Figure 5(a) shows a cross-sectional view of the second recess 12 provided in the second groove wall 20, and Figure 5(b) shows a cross-sectional view of the first recess 11 provided in the second groove wall 20.

[0085] As shown in Figure 4, in a preferred embodiment, the second groove wall 20 is provided with a plurality of first recesses 11 and second recesses 12. In a more preferred embodiment, the second groove wall 20 according to this embodiment is provided with first recesses 11 and second recesses 12 alternately in the circumferential direction of the tire. This improves the handling stability and wet performance in a balanced manner after the tread has worn down.

[0086] In this embodiment, the first recess 11 provided in the second groove wall 20 faces, for example, the second recess 12 provided in the first groove wall 10. The second recess 12 provided in the second groove wall 20 faces, for example, the first recess 11 provided in the first groove wall 10. As a result, the first recess 11 provided in the first groove wall 10 and the first recess 11 provided in the second groove wall 20 are arranged alternately, for example, in the circumferential direction of the tire. This arrangement of recesses can suppress the increase in air column resonance noise in the circumferential grooves.

[0087] In order to ensure the groove volume of the circumferential groove 3, the total recess amount of the circumferential groove 3 is preferably 0.10 to 0.90 times the groove width W1 of the main groove 3, more preferably 0.15 to 0.80 times, and even more preferably 0.20 to 0.70 times. In this specification, "total recess amount of the circumferential groove" refers to c1 + c2 when the circumferential groove 3 is in the configuration shown in Figure 3, and refers to d1 + d2 when the circumferential groove 3 is in the configuration shown in Figure 5.

[0088] E* of the cap rubber layer at 30°C (30°C E* C ) is preferably 4.0 MPa or higher, more preferably 4.5 MPa or higher, even more preferably 5.0 MPa or higher, and particularly preferably 5.5 MPa or higher, from the viewpoint of exhibiting restorative force against deformation and improving responsiveness. On the other hand, 30℃E* C From the viewpoint of road surface following ability, a pressure of 30 MPa or less is preferred, 25 MPa or less is more preferred, 20 MPa or less is even more preferred, and 15 MPa or less is particularly preferred.

[0089] tanδ(30℃tanδ*) of the cap rubber layer at 30℃ CFrom the viewpoint of reducing heat generation during driving and suppressing hardening of the cap rubber layer over time, the 30°C tanδ of the base rubber layer is preferably 0.25 or less, more preferably 0.20 or less, even more preferably 0.18 or less, even more preferably 0.15 or less, even more preferably 0.13 or less, and particularly preferably 0.11 or less. Furthermore, if a base rubber layer is present, the 30°C tanδ of the base 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 and the base rubber layer is preferably 0.03 or more, more preferably 0.05 or more, and even more preferably 0.07 or more.

[0090] E* of the rubber composition constituting the sidewall at 70°C (70°C E* SW ) is preferably 2.0 MPa or higher, more preferably 3.0 MPa or higher, and even more preferably 4.0 MPa or higher, from the viewpoint of exhibiting restorative force against deformation and improving responsiveness. On the other hand, 70℃E* SW From the standpoint of ride comfort performance, a pressure of 10.0 MPa or less is preferable, 8.0 MPa or less is more preferable, and 6.0 MPa or less is even more preferable.

[0091] The tanδ(70℃tanδ) of the rubber composition constituting the sidewall at 70℃ SW From the viewpoint of reducing heat generation during driving and suppressing hardening of the cap rubber layer over time, the tanδ is preferably 0.20 or less, more preferably 0.15 or less, even more preferably 0.12 or less, even more preferably 0.10 or less, even more preferably 0.08 or less, and particularly preferably 0.06 or less. SW Preferably, the value is 0.02 or higher, more preferably 0.03 or higher, and even more preferably 0.04 or higher.

[0092] 30℃E* C -70℃E* SW From the viewpoint of the effects of the present invention, the pressure is 3.0 MPa or less, preferably 2.7 MPa or less, more preferably 2.4 MPa or less, and even more preferably 2.1 MPa or less. On the other hand, 30℃E* C -70℃E* SWThe lower limit is not particularly limited, but is preferably 0.1 MPa or higher, more preferably 0.3 MPa or higher, and even more preferably 0.5 MPa or higher.

[0093] The 30°C E*, 70°C E*, 30°C tanδ, and 70°C tanδ of the rubber composition can be appropriately adjusted depending on the type and amount of rubber components, fillers, and softeners described below.

[0094] 30℃ tanδ C The product of the total thickness of the tread section and t (mm) (30℃ tanδ C ×t) is preferably 2.10 or less, more preferably 1.90 or less, even more preferably 1.70 or less, and particularly preferably 1.50 or less. 30℃ tanδ C By setting ×t within the aforementioned range, it is thought that heat generation and heat accumulation in the tread portion can be more easily suppressed, making it easier to obtain the effects of the present invention. On the other hand, 30℃ tanδ C The lower limit of ×t is not particularly limited, but is preferably 0.20 or higher, more preferably 0.50 or higher, even more preferably 0.80 or higher, and particularly preferably 1.10 or higher.

[0095] The Tg of the cap rubber layer is preferably -40°C or higher, more preferably -35°C or higher, even more preferably -30°C or higher, and particularly preferably -25°C or higher. By setting the Tg within the above range, it is possible to improve energy loss at temperatures lower than room temperature, which is thought to improve grip performance on the tread surface and make it easier to exhibit the effects of the present invention. On the other hand, there is no particular upper limit to the Tg of the cap rubber layer, but it is preferably 20°C or lower, more preferably 10°C or lower, even more preferably 5°C or lower, and particularly preferably 0°C or lower. The Tg of the cap rubber layer can be appropriately adjusted depending on the type and amount of rubber components, fillers, softeners, etc.

[0096] The Shore hardness (Hs) of the cap rubber layer is preferably 40 or higher, more preferably 42 or higher, even more preferably 44 or higher, and particularly preferably 46 or higher. Furthermore, the Shore hardness (Hs) of the cap rubber layer is preferably 70 or lower, more preferably 65 or lower, and even more preferably 60 or lower. By setting the Shore hardness (Hs) of the cap rubber layer within the above range, it is believed that good handling stability and wet grip performance can be maintained. The Shore hardness of the cap rubber layer can be appropriately adjusted by changing the type and amount of rubber components, fillers, softeners, etc.

[0097] From the viewpoint of the effects of the present invention, the average amount of acetone extracted from the tread rubber is preferably 19% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less, and particularly preferably 13% by mass or less. Furthermore, the average amount of acetone extracted from the tread rubber is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and particularly preferably 6% by mass or more.

[0098] The amount of acetone extracted from the cap rubber layer is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less. Furthermore, the amount of acetone extracted from the cap rubber layer is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and particularly preferably 6% by mass or more.

[0099] If a base rubber layer is present, the amount of acetone extracted from the base rubber layer is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. Furthermore, the amount of acetone extracted from the base rubber layer is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and particularly preferably 6% by mass or more.

[0100] The amount of acetone extracted from the rubber composition constituting the sidewall is preferably 12% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and particularly preferably 7% by mass or less. Furthermore, there is no particular lower limit to the amount of acetone extracted from the rubber composition constituting the sidewall, but it is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and particularly preferably 4% by mass or more.

[0101] The difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall is preferably 12% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. By setting the difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall within the above range, the diffusion of the softening agent from the tread rubber to the sidewall rubber can be appropriately controlled. From this, it is considered that the change in hardness of the cap rubber layer due to tire use can be appropriately controlled. Furthermore, there is no particular lower limit to the difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the breaker topping rubber, but it is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more.

[0102] From the viewpoint of suppressing the migration of softeners, the average ash content of the tread rubber is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 16% by mass or more. Furthermore, from the viewpoint of rubber hardness, it is preferably 35% by mass or less, more preferably 33% by mass or less, even more preferably 31% by mass or less, and particularly preferably 29% by mass or less.

[0103] The ash content of the cap rubber layer is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 16% by mass or more. Furthermore, from the viewpoint of rubber hardness, it is preferably 35% by mass or less, more preferably 33% by mass or less, even more preferably 31% by mass or less, and particularly preferably 29% by mass or less.

[0104] If a base rubber layer is present, the ash content of the base rubber layer is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less. There is no particular lower limit to the ash content of the base rubber layer.

[0105] [Rubber composition] The rubber compositions constituting each layer of the tread and the rubber compositions constituting the sidewall can all be manufactured using the raw materials described below, according to the required 30°C E*, 70°C E*, 30°C tanδ, 70°C tanδ, etc. The rubber compositions according to this embodiment will be described below, and unless otherwise specified, they are applicable to both the rubber compositions constituting each layer of the tread and the rubber compositions constituting the sidewall.

[0106] <Rubber components> In the rubber composition according to this embodiment, diene rubber is preferably used 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). These rubber components may be used individually or in combination of two or more.

[0107] 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.

[0108] As the diene rubber component, at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR) is preferably used. The rubber component constituting the cap rubber layer preferably contains SBR, more preferably contains SBR and isoprene rubber, even more preferably contains SBR, BR, and isoprene rubber, and may consist only of SBR, BR, and isoprene rubber. The rubber component constituting the base rubber layer and sidewall rubber preferably contains isoprene rubber, more preferably contains isoprene rubber and BR, and may consist only of isoprene rubber and BR.

[0109] (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.

[0110] NR is not particularly limited and can be any tire that is common in the tire industry, such as SIR20, RSS#3, and TSR20.

[0111] From the viewpoint of wet grip performance, the content of isoprene-based rubber in the rubber component constituting the cap rubber layer 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 isoprene-based rubber content, 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.

[0112] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber components constituting the base rubber layer is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. Furthermore, there is no particular upper limit to the content of isoprene-based rubber, but it can be 100% by mass, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0113] From the viewpoint of the effects of the present invention, the content of isoprene-based rubber in the rubber component constituting the sidewall is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. Furthermore, there is no particular upper limit to the isoprene-based rubber content, but it can be 100% by mass, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0114] (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 thereof (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.

[0115] For SBR, either oil-expanded SBR or non-oil-expanded SBR can be used. When using oil-expanded SBR, the amount of oil expanded in the SBR, that is, the amount of oil-expanding oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of rubber solids in the SBR.

[0116] In this embodiment, commercially available S-SBRs from companies such as JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, and ZS Elastomer Co., Ltd. can be used.

[0117] The styrene content of SBR can be appropriately selected so that the total amount of styrene in the rubber component satisfies the range described below, but is preferably 36% by mass or less, more preferably 32% by mass or less, and even more preferably 28% by mass or less. Furthermore, the styrene content of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. The styrene content of SBR is measured by the measurement method described above.

[0118] 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.

[0119] The SBR content in the rubber component constituting the cap rubber layer can be appropriately selected so that the total styrene content in the rubber component satisfies the range described below, but is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more. On the other hand, the SBR content in the rubber component is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. The SBR content in the rubber component constituting the base rubber layer and the rubber component constituting the sidewall is not particularly limited.

[0120] (BR) BR is not particularly limited, and for example, BR with a cis content of less than 50% by mass (low-cis BR), BR with a cis content of 90% by mass or more (high-cis BR), rare-earth butadiene rubber synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are common in the tire industry, can be used. These BRs may be used individually or in combination of two or more types.

[0121] 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 of high-cis BR is preferably 95% by mass or more, more preferably 96% by mass or more, and even more preferably 97% by mass or more. The cis content of BR is measured by the measurement method described above.

[0122] 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.

[0123] 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.

[0124] 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 weight-average molecular weight of BR is measured by the measurement method described above.

[0125] From the viewpoint of wet grip performance, the BR content in the rubber component constituting the cap rubber layer 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.

[0126] From the viewpoint of the effects of the present invention, the BR content in the rubber component constituting the base rubber layer is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. Furthermore, there is no particular lower limit to the content, but for example, it can be 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more.

[0127] From the viewpoint of the effects of the present invention, the BR content in the rubber component constituting the sidewall is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. Furthermore, there is no particular lower limit to the content, but for example, it can be 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more.

[0128] (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. Examples of other rubber components besides diene rubber include 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), and hydrin rubber. These other rubber components may be used individually or in combination of two or more. Furthermore, known thermoplastic elastomers may or may not be included in addition to the above-mentioned rubber components.

[0129] <Filler> The rubber composition according to this embodiment preferably uses a filler containing carbon black and / or silica. The rubber composition constituting the cap rubber layer more preferably contains silica as a filler, and more preferably contains carbon black and silica. The rubber composition constituting the base rubber layer and the sidewall preferably contains carbon black as a filler.

[0130] (Carbon Black) As carbon black, commonly used in the tire industry can be used as appropriate, such as GPF, FEF, HAF, ISAF, and SAF. These carbon blacks may be used individually or in combination of two or more. Recycled carbon black obtained by thermally decomposing products containing carbon black, such as rubber products like tires or plastic products, may also be used as appropriate.

[0131] The nitrogen adsorption specific surface area (N2SA) of carbon black contained in the rubber composition constituting the cap rubber layer and the base rubber layer is 30m² from the viewpoint of reinforcement. 2 Preferably 50m 2 More preferably 70m 2 More preferably 90m / g or more. 2 A value of 200m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 200m 2 Preferably less than / g, 150m 2 Less than / g is more preferable, 120m 2 A value of less than / g is even more preferable. The N2SA of carbon black is measured by the measurement method described above.

[0132] The nitrogen adsorption specific surface area (N2SA) of carbon black contained in the rubber composition constituting the sidewall is 20 m², from the viewpoint of the effects of the present invention. 2 Preferably 40m / g or more. 2 More preferably 50m 2 More preferably 60m 2 A value of 200m or more is particularly preferred. Furthermore, from the viewpoint of low fuel consumption and processability, 200m 2 Preferably less than / g, 150m 2 Less than / g is more preferable, 120m 2 A value of less than or equal to / g is even more preferable.

[0133] From the viewpoint of the effects of the present invention, the carbon black content of the rubber composition constituting the cap rubber layer, relative to 100 parts by mass of rubber component, is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 9 parts by mass or less.

[0134] From the viewpoint of the effects of the present invention, the carbon black content of the rubber composition constituting the base rubber layer relative to 100 parts by mass of rubber components is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption performance, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0135] From the viewpoint of the effects of the present invention, the carbon black content per 100 parts by mass of rubber component in the rubber composition constituting the sidewall is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption performance, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less.

[0136] (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.

[0137] 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, 2More 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.

[0138] From the viewpoint of the effects of the present invention and the ash content, the silica content of the rubber composition constituting the cap rubber layer is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. Furthermore, from the viewpoint of the effects of the present invention, it is preferably 160 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 80 parts by mass or less. The silica content in the rubber composition constituting the base rubber layer and the rubber composition constituting the sidewall is not particularly limited.

[0139] From the viewpoint of the effects of the present invention, the total content of silica and carbon black per 100 parts by mass of rubber component in the rubber composition constituting the cap rubber layer is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more. Furthermore, from the viewpoint of low fuel consumption performance and elongation at break, it is preferably 170 parts by mass or less, more preferably 130 parts by mass or less, even more preferably 110 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0140] From the viewpoint of balancing handling stability and wet grip performance, the rubber composition constituting the cap rubber layer preferably has a silica content greater than the carbon black content per 100 parts by mass of rubber component. The ratio of silica to the total silica and carbon black content in the rubber composition constituting the cap rubber layer is preferably 51% by mass or more, more preferably 67% by mass or more, even more preferably 76% by mass or more, and particularly preferably 85% by mass or more. Furthermore, the ratio of silica to the total silica and carbon black content in the rubber composition constituting the cap rubber layer is preferably 99% by mass or less, more preferably 97% by mass or less, even more preferably 95% by mass or less, and particularly preferably 93% by mass or less.

[0141] (Other fillers) Other fillers besides silica and carbon black are not particularly limited and can include, for example, aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, and other materials commonly used in the tire industry. These other fillers may be used individually or in combination of two or more.

[0142] (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.

[0143] From the viewpoint of improving silica dispersibility, the content of the silane coupling agent per 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more. Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0144] <Vegetable oil> The vegetable oils usable in this embodiment are not particularly limited as long as they contain glycerides in which unsaturated fatty acids are ester-bonded (unsaturated fatty acid glycerides), and may also contain saturated fatty acid glycerides. Specific examples of vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, camellia oil, jojoba oil, coconut oil, peanut oil, grapeseed oil, rosin, etc., with sunflower oil and rapeseed oil being preferred. These vegetable oils may be used individually or in combination of two or more.

[0145] As for vegetable oils, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0146] Unsaturated fatty acids that make up unsaturated fatty acid glycerides include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid.

[0147] The content of unsaturated fatty acids in the constituent fatty acids of vegetable oil is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more.

[0148] The vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the cap rubber layer is preferably 3.0 parts by mass or more, more preferably 5.0 parts by mass or more, even more preferably 7.0 parts by mass or more, and particularly preferably 9.0 parts by mass or more. Furthermore, the content is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less. The vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the base rubber layer is not particularly limited.

[0149] The average value S1 of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber constituting the tread portion is preferably 3.0 parts by mass or more, more preferably 5.0 parts by mass or more, even more preferably 7.0 parts by mass or more, and particularly preferably 9.0 parts by mass or more. Furthermore, S1 is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less.

[0150] The content of vegetable oil S2 in the rubber composition constituting the sidewall, relative to 100 parts by mass of rubber component, is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 2.5 parts by mass or more. Furthermore, S2 is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, even more preferably 8.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less.

[0151] From the viewpoint of the effects of the present invention, S1 / S2 is greater than 1.0, preferably 1.1 or higher, more preferably 1.3 or higher, even more preferably 1.6 or higher, and particularly preferably 1.7 or higher. Furthermore, there is no particular upper limit to S1 / S2, but it is preferably less than 15, more preferably less than 10, even more preferably less than 8.0, and particularly preferably less than 5.0.

[0152] <Other compounding agents> In addition to the components mentioned above, the rubber composition according to this embodiment may appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0153] (Softener) The rubber composition according to this embodiment preferably contains a softening agent. Examples of softening agents include resin components, oils other than vegetable oils, and liquid rubber.

[0154] The resin components are not particularly limited, but examples include hydrocarbon resins commonly used in the tire industry, such as petroleum resins, terpene resins, rosin resins, and phenolic resins.

[0155] Examples of petroleum resins include C5-based petroleum resins, aromatic petroleum resins, and C5C9-based petroleum resins.

[0156] In this specification, "C5-based petroleum resin" refers to a resin obtained by polymerizing a C5 fraction, and may be hydrogenated or modified. 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-based petroleum resin.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] Rosin-based resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc.

[0161] Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, and oil-modified phenol-formaldehyde resin.

[0162] When a resin component is included, its content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, the content of the resin component is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0163] Other oils besides vegetable oils include, for example, paraffinic process oils (mineral oil), naphthenic process oils, and aromatic process oils. Specific examples of process oils include MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). 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 MES, TDAE, and heavy naphthenic oils. Additionally, from a life cycle assessment perspective, refined waste oil from rubber mixers and engines, or waste cooking oil used in restaurants, may be used.

[0164] When oils other than vegetable oils are included, the content per 100 parts by mass of rubber components is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0165] Liquid rubber 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 rubbers may be used individually or in combination of two or more.

[0166] When liquid rubber is included, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Furthermore, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0167] The amount of softener in the rubber composition constituting the cap rubber layer, relative to 100 parts by mass of rubber components (total amount including vegetable oil if multiple softeners are used in combination), can be appropriately selected such that the difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall satisfies the above range, but 3 parts by mass or more is preferred, 5 parts by mass or more is more preferred, 7 parts by mass or more is even more preferred, and 9 parts by mass or more is particularly preferred. Furthermore, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, and particularly preferably 40 parts by mass or less. The amount of softener in the rubber composition constituting the base rubber layer is not particularly limited.

[0168] The amount of softener in the rubber composition constituting the sidewall, relative to 100 parts by mass of rubber component (total amount including vegetable oil if multiple softeners are used in combination), can be appropriately selected such that the difference between the average amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall satisfies the above range, but is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. Furthermore, the content is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0169] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include petroleum-based waxes, mineral-based waxes, and synthetic waxes, with petroleum-based waxes being preferred. Examples of petroleum-based waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. These waxes may be used individually or in combination of two or more types.

[0170] When wax is included, the amount of wax per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, 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 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0171] 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.

[0172] When processing aids are included, the content per 100 parts by mass of rubber components is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture strength, it is preferably 10 parts by mass or less, and more preferably 8.0 parts by mass or less.

[0173] 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.

[0174] When an anti-aging agent is included, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, 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 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0175] When stearic acid is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0176] When zinc oxide is included, its content per 100 parts by mass of rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of wear resistance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0177] 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.

[0178] When sulfur is included as a vulcanizing agent, the amount of sulfur per 100 parts by mass of rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the amount of vulcanizing agent is the total amount of pure sulfur contained in the oil-containing sulfur.

[0179] 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.

[0180] Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiram-based vulcanization accelerators, guanidine-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, and caprolactam disulfide. 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-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred because they more favorably produce the desired effect.

[0181] 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, TBBS and CBS are preferred.

[0182] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, and 2-(2,6-diethyl-4-morpholinothio)benzothiazole. Among these, MBTS and MBT are preferred.

[0183] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, DPG is preferred.

[0184] When a vulcanization accelerator is included, the content per 100 parts by mass of the rubber component (total amount if multiple vulcanization accelerators are used in combination) is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more. Furthermore, the content is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, it tends to be possible to ensure fracture strength and elongation.

[0185] [Manufacturing of rubber compositions and tires] The rubber composition according to this embodiment 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.).

[0186] 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.

[0187] 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.

[0188] A tire comprising a tread and sidewall, including a cap rubber layer and a base rubber layer, can be manufactured by conventional methods using the corresponding rubber compositions. Specifically, the unvulcanized rubber compositions corresponding to the cap rubber layer, base rubber layer, and sidewall rubber obtained by the above method are extruded into their respective shapes using an extruder equipped with a die of a predetermined shape, bonded together with other tire components on a tire molding machine, and molded in a conventional method to form an unvulcanized tire. This unvulcanized tire can then be heated and pressurized in a vulcanizing machine to produce the tire according to this embodiment. The vulcanization conditions are not particularly limited, and examples include vulcanization at 150-200°C for 10-30 minutes.

[0189] [Tire Uses] The tire according to this embodiment can be suitably used for passenger car tires, truck and bus tires, motorcycle tires, and racing tires, and is particularly preferred for use as a passenger car tire. A passenger car tire is a tire intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or less. Furthermore, the tire according to this embodiment can be used for all-season tires, summer tires, and winter tires such as studless tires. [Examples]

[0190] The following examples (examples) are shown as preferred for implementation, but the scope of the present invention is not limited to these examples. Using the various chemicals shown below, we examined tires having a tread cap rubber layer, a base rubber layer, and a sidewall obtained according to the formulations in Tables 1 and 2, and the results calculated based on the evaluation method below are shown in Table 3.

[0191] The various chemicals used in the examples and comparative examples are summarized below. NR:TSR20 SBR: HPR850 manufactured by JSR Corporation (modified SBR, styrene content: 27.5% by mass, non-oil-based) BR: UBEPOL BR(registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass, Mw: 440,000) Carbon Black 1: Show Black N220 (N2SA: 111m) manufactured by Cabot Japan Co., Ltd. 2 / g) Carbon Black 2: Dia Black (registered trademark) E (FEF, N550, N2SA) manufactured by Mitsubishi Chemical Corporation: 41m 2 / g) Carbon Black 3: Show Black N330 (N2SA: 75m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica: Evonik Degussa's UltraSil VN3 (N2SA: 175m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa. Vegetable oil: Sunflower oil manufactured by Nisshin Oillio Group Ltd. (Oleic acid content in constituent fatty acids: 55% by mass, total polyunsaturated fatty acid content in constituent fatty acids: 8% by mass) Oil 1: Diana Process Oil AC-12 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Oil 2: Diana Process Oil PW-380 (paraffin-based process oil) manufactured by Idemitsu Kosan Co., Ltd. Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Wax: Ozoace 0355 (paraffin wax) from Nippon Seiro Co., Ltd. Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noxellar D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0192] (Examples and Comparative Examples) According to the formulations shown in Tables 1 and 2, 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, sulfur and vulcanization accelerator were added to the mixture using a twin-screw open roll mixer and mixed for 4 minutes until the temperature reached 105°C to obtain an unvulcanized rubber composition. Using this unvulcanized rubber composition, the cap rubber layer, base rubber layer, and sidewall were molded to the desired shape, and then bonded together with other tire components to produce an unvulcanized tire. The tire was then vulcanized at 170°C to obtain the test tires listed in Table 3 (size: 205 / 55R16, rim: 16×6.5J, internal pressure: 250kPa). The total thickness of the tread section was 11 mm in all cases. In Example 10 and Comparative Example 7, the thickness of the cap rubber layer was 7.5 mm and the thickness of the base rubber layer was 3.5 mm.

[0193] <Measurement of 30°C E* and 30°C tanδ> Each vulcanized rubber test piece, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, is prepared by cutting from within each rubber layer of the tread of each test tire, with the tire circumference being the longer side and the tire radius being the thickness direction. The complex modulus of elasticity E* and loss tangent tanδ are measured using a dynamic viscoelasticity measuring device (GABO's Iplexer series) under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and the extension mode.

[0194] <Measurement of 70°C E* and 70°C tanδ> Each vulcanized rubber test piece, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, is prepared by cutting from the inside of the sidewall rubber of each test tire, such that the tangent to the tire's circumferential direction is the longer side and the tire's width direction (normal direction to the sidewall surface) is the thickness direction. The complex modulus of elasticity E* and loss tangent tanδ are measured using a dynamic viscoelasticity measuring device (GABO's Iplexer series) under the conditions of a temperature of 70°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of 1%, and the extension mode.

[0195] <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, is prepared by cutting out pieces from within each rubber layer of the tread of each test tire, with the tire circumference being the longer side and the tire radius being the thickness direction. Using a dynamic viscoelasticity measuring device (GABO's Iplexer series), the temperature distribution curve of tanδ in the range of -60°C to 40°C is measured under conditions of frequency 10 Hz, initial strain 10%, amplitude ±0.5%, and heating rate 2°C / min. The temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature) is determined as the Tg of the rubber composition.

[0196] <Measurement of rubber hardness (Hs)> For each vulcanized rubber test specimen, which is prepared by cutting out a section from within each rubber layer of the tread of each test tire so that the tire radius is oriented in the thickness direction, the Shore hardness (Hs) of each rubber test specimen is measured at a temperature of 23°C using a durometer type A in accordance with JIS K6253-3:2012.

[0197] <Measurement of acetone extraction amount (AE amount)> The amount of AE (air-entraining) is measured for each vulcanized rubber test piece, which is prepared by cutting out each rubber layer from the tread of each test tire. The amount of AE is determined by immersing each vulcanized rubber test piece in acetone for 24 hours to extract soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. Acetone extraction amount (mass %) = {(mass of vulcanized rubber test piece before extraction - mass of vulcanized rubber test piece after extraction) / (mass of rubber test piece before extraction)} × 100

[0198] <Measurement of ash content> Vulcanized rubber test pieces, cut from each rubber layer of the tread of each test tire, are placed in an alumina crucible and heated in an electric furnace at 550°C for 4 hours. After that, the ash content (mass %) is calculated by (mass of test piece after heating / mass of test piece before heating) × 100.

[0199] <Wet handling stability performance> Each test tire, both new and worn, is mounted on the four wheels of a 2000cc front-wheel-drive passenger car, and the vehicle is driven on a wet asphalt test course. Handling characteristics are evaluated based on the feeling of straight driving, lane changes, and acceleration / deceleration while driving at 120 km / h by a test driver. The evaluation is given as an integer value from 1 to 5 points, with higher scores indicating superior handling characteristics. The total scores of 20 test drivers are calculated. The total score of the control tire (Comparative Example 2) when new is converted to a baseline value (100), and the evaluation results of each test tire after wear are indexed and displayed in proportion to the total score. The overall performance is then expressed by the sum of the wet handling stability performance index for new tires and the wet handling stability performance index for worn tires.

[0200] Each test tire after wear is prepared by first wearing down the tread along the tread radius so that the depth of the deepest circumferential groove of a new tire is 50% of that of a new tire, and then thermally degrading the tire at 80°C for 7 days.

[0201] [Table 1]

[0202] [Table 2]

[0203] [Table 3]

[0204] <Embodiment> Examples of embodiments of the present invention are shown below.

[0205] [1] A tire comprising a tread portion having at least one rubber layer and a sidewall, wherein the tread portion and the sidewall are each composed of a rubber composition containing a rubber component and a vegetable oil, and when the average value of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber constituting the tread portion is S1 (parts by mass), and the vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the sidewall is S2 (parts by mass), S1 / S2 is greater than 1.0, and the complex modulus of elasticity at 30°C of the cap rubber layer constituting the tread surface is 30°C E* C (MPa), the complex modulus of the rubber composition constituting the sidewall at 70°C is 70°CE* SW (MPa) when at 30℃E* C -70℃E* SW Tires with a pressure of 3.0 MPa or less. [2] The tire described in [1] above, wherein S2 is 5.0 parts by mass or less. [3] The tanδ of the cap rubber layer at 30°C (30°C tanδ C The tire described in [1] or [2] above, wherein the ratio is 0.13 or less. [4] The tanδ of the cap rubber layer at 30°C (30°C tanδ C The tire described in [1] or [2] above, wherein the ratio is 0.11 or less. [5] The tanδ(70°C tanδ) of the rubber composition constituting the sidewall at 70°C SW A tire as described in any of the above [1] to [4], wherein the ratio is 0.06 or less. [6] 30℃E* C A tire as described in any of the above [1] to [5], having a pressure of 5.0 MPa or higher. [7] The tire according to any one of [1] to [6] above, wherein the glass transition temperature of the cap rubber layer is -25°C or higher. [8] A tire according to any of [1] to [7] above, wherein the Shore hardness (Hs) of the cap rubber layer is 40 or more and 70 or less. [9] Let t (mm) be the total thickness of the tread section, and 30℃ tanδ C The product of (30°C tanδ) CA tire as described in any of the above [1] to [8], wherein ×t) is 1.50 or less.

[10] The tire according to any one of [1] to [9] above, wherein the difference between the average value of the amount of acetone extracted from the tread rubber and the amount of acetone extracted from the rubber composition constituting the sidewall is 5.0% by mass or more.

[11] A tire according to any of [1] to

[10] above, wherein the average value of the ash content of the tread rubber is 7.5% by mass or more.

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

[11] above, wherein the total amount of styrene in the rubber component constituting the cap rubber layer is 3% by mass or more and 15% by mass or less.

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

[12] above, wherein the tread portion has circumferential grooves that extend continuously in the circumferential direction of the tire, and the groove wall of at least one circumferential groove has a recess that is recessed outward in the groove width direction than the groove edge that appears on the tread surface of the tread portion, and the total recess amount of the at least one circumferential groove relative to the groove width of the at least one circumferential groove is 0.10 to 0.90.

[14] The tire according to

[13] , wherein one groove wall of the circumferential groove has a first recess that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the amount of recess from the groove edge gradually decreases toward both sides in the tire circumferential direction from the deepest part that is recessed outward in the groove width direction.

[15] The tire according to

[14] , wherein the first groove wall is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the amount of recess from the groove edge is constant in the tire circumferential direction. [Explanation of symbols]

[0206] 1. Tread section 2. Cap rubber layer 3 Circumferential groove 4. Base rubber layer 5. Tread surface 6 groove edge 7. Outline of the trench wall 8. The edge of the trench on land 9 recesses 10. First trench wall 11. First recess 12. Second recess 13, 14 Deepest part of the recess 15 plane 17 Concave portion 18 Convex portion 20 Second trench wall 21 Groove width gradual reduction section 31 Bead Core 32 Sidewall 33 Bead section 34 Carcass 35 Belt Layer 36 Belt reinforcement layer 37 Inner Liner 38 rim 39. Clinch 40 Wing 61 Edge Band 62 Full Band CL tire centerline

Claims

1. A tire comprising a tread section having at least one rubber layer and a sidewall, The tread portion and the sidewall are each made of a rubber composition containing rubber components and vegetable oil, When S1 (parts by mass) is the average value of the vegetable oil content per 100 parts by mass of rubber component in the tread rubber constituting the tread portion, and S2 (parts by mass) is the vegetable oil content per 100 parts by mass of rubber component in the rubber composition constituting the sidewall, S1 / S2 is greater than 1.0, The complex modulus of elasticity at 30°C for the cap rubber layer that makes up the tread surface is 30°C E* C (MPa), the complex modulus of the rubber composition constituting the sidewall at 70°C is 70°C E* SW When (MPa), at 30℃ E* C -70℃E* SW Tires with a pressure of 3.0 MPa or less.

2. The tire according to claim 1, wherein S2 is 5.0 parts by mass or less.

3. The tanδ of the cap rubber layer at 30°C (30°C tanδ C The tire according to claim 1 or 2, wherein the coefficient of gravity is 0.13 or less.

4. The tanδ of the cap rubber layer at 30°C (30°C tanδ C The tire according to claim 1 or 2, wherein the coefficient of force is 0.11 or less.

5. The tanδ of the rubber composition constituting the sidewall at 70°C (70°C tanδ SW The tire according to claim 1 or 2, wherein the coefficient of force is 0.06 or less.

6. 30℃E* C The tire according to claim 1 or 2, wherein the pressure is 5.0 MPa or more.

7. The tire according to claim 1 or 2, wherein the glass transition temperature of the cap rubber layer is -25°C or higher.

8. The tire according to claim 1 or 2, wherein the Shore hardness (Hs) of the cap rubber layer is 40 or more and 70 or less.

9. When the total thickness of the tread portion is t (mm), the product of 30°C tan δ C and t (30°C tan δ C × t) is 1.50 or less. The tire according to claim 1 or 2.

10. The tire according to claim 1 or 2, wherein the difference between the average value of the acetone extraction amount of the tread rubber and the acetone extraction amount of the rubber composition constituting the sidewall is 5.0% by mass or more.

11. The tire according to claim 1 or 2, wherein the average value of the ash content of the tread rubber is 7.5% by mass or more.

12. The tire according to claim 1 or 2, wherein the total amount of styrene in the rubber component constituting the cap rubber layer is 3% by mass or more and 15% by mass or less.

13. The tread portion has circumferential grooves that extend continuously in the circumferential direction of the tire, At least one circumferential groove has a groove wall that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, The tire according to claim 1 or 2, wherein the total recess amount of the at least one circumferential groove is 0.10 to 0.90 relative to the groove width of the at least one circumferential groove.

14. The first groove wall, which is one of the groove walls of the circumferential groove, has a first recess that is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion. The tire according to claim 13, wherein the first recess has a gradually decreasing amount of recess from the groove edge toward both sides in the tire circumferential direction, starting from the deepest part that is recessed furthest outward in the groove width direction.

15. The tire according to claim 14, wherein the first groove wall is recessed outward in the groove width direction from the groove edge that appears on the tread surface of the tread portion, and the amount of recess from the groove edge is constant in the tire circumferential direction.

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