tire

Abstract

To provide a pneumatic tire with improved steering stability during high speed travelling.SOLUTION: There is provided a pneumatic tire having a tread part. The tread part is composed of a rubber composition containing a rubber component and silica. In the pneumatic tire, the content of isoprene-based rubber in the rubber component is more than 40 mass%; the content of silica with respect to 100 pts.mass of the rubber component in the rubber composition is more than 30 pts.mass; a difference between a complex elastic modulus at a dynamic strain of 0.25% and that at a dynamic strain of 1.0%, measured under conditions of a temperature of 30°C, a frequency of 10 Hz, and an initial strain of 5% for the rubber composition, is defined as 30°CΔE*(0.25%-1.0%); and when a thickness of the tread part is defined as T (mm), 30°CΔE*(0.25%-1.0%) is 6.0 MPa or more, and 30°CΔE*(0.25%-1.0%) / T is 0.45 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Recently, in pneumatic tires, from the viewpoint of low fuel consumption performance and the like, attempts have been made to compound modified styrene-butadiene rubber and silica to reduce the heat generation of the tires (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, these days with the progress of highway construction, it is not uncommon to move long distances at high speeds, and in pneumatic tires, handling stability during high-speed driving is required.

[0005] An object of the present invention is to provide a pneumatic tire with improved handling stability performance during high-speed driving.

Means for Solving the Problems

[0006] The present invention is a pneumatic tire having a tread portion, wherein the tread portion is composed of a rubber composition containing a rubber component and silica, the content of isoprene-based rubber in the rubber component is more than 40% by mass, the content of silica with respect to 100 parts by mass of the rubber component in the rubber composition is more than 30 parts by mass, The difference between the complex modulus of dynamic strain of 0.25% and the complex modulus of dynamic strain of 1.0% measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, and an initial strain of 5% of the rubber composition is denoted as 30°C ΔE*(0.25% - 1.0%). When the thickness of the tread portion is T (mm), 30°C ΔE*(0.25% - 1.0%) is 6.0 MPa or more, and 30°C ΔE*(0.25% - 1.0%) / T is 0.45 or more, relating to a pneumatic tire.

Advantages of the Invention

[0007] According to the present invention, a pneumatic tire with improved handling stability performance during high-speed driving is provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a pneumatic tire having a tread portion. The tread portion is composed of a rubber composition containing a rubber component and silica. The content of the isoprene rubber in the rubber component is more than 40% by mass, and the content of silica with respect to 100 parts by mass of the rubber component in the rubber composition is more than 30 parts by mass. The difference between the complex elastic modulus at a dynamic strain of 0.25% and the complex elastic modulus at a dynamic strain of 1.0% measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, and an initial strain of 5% of the rubber composition is designated as 30°CΔE*(0.25% - 1.0%). When the thickness of the tread portion is T (mm), 30°CΔE*(0.25% - 1.0%) is 6.0 MPa or more, and 30°CΔE*(0.25% - 1.0%) / T is 0.45 or more. It is a pneumatic tire.

[0010] Although not intended to be bound by theory, as a mechanism for improving the handling stability performance during high-speed driving in the pneumatic tire of the present invention, it can be considered as follows, for example.

[0011] Since silica is a hydrophilic filler, (1) when the isoprene rubber is contained in the rubber component and the content of silica with respect to 100 parts by mass of the rubber component exceeds 30 parts by mass, when the silica is blended with the isoprene rubber, it can reinforce the polymer chains existing around the silica and form a region where the silicas aggregate with each other. Therefore, it becomes possible to increase 30°CΔE*(0.25% - 1.0%).

[0012] During high-speed driving, the contact surface of the tread portion in contact with the road surface has a large deformation amount because the vehicle weight is applied to the unevenness of the road surface. On the other hand, the deformation amount is relatively small inside the tread portion because the time when the vehicle weight is applied is short due to driving at high speed. Therefore, by making (2) 30°C ΔE*(0.25% - 1.0%) 6.0 MPa or more, it is possible to maintain a state where the complex elastic modulus is high for small deformations and a state where the complex elastic modulus is low for large deformations, while enhancing the followability of the tread portion contact surface to the road surface and also enhancing the responsiveness. In addition, since isoprene rubber has a high strength of rubber molecules, by making (3) the content of isoprene rubber in the rubber component exceed 40% by mass, the reaction force during response becomes large. Furthermore, by increasing 30°C ΔE*(0.25% - 1.0%) with respect to the thickness T (mm) of the tread portion and making 30°C ΔE*(0.25% - 1.0%) / T 0.45 or more, it is possible to shorten the force transmission distance from input to response while also increasing the rigidity of the entire tread portion.

[0013] And it is considered that the remarkable effect that the handling stability performance during high-speed driving is improved is achieved by the cooperation of the above (1) to (4).

[0014] The rubber composition contains carbon black, and it is preferable that the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition exceeds 1 part by mass and is less than 25 parts by mass.

[0015] By setting the content of carbon black within the above range, the content of silica can be increased, and the effect of reinforcing the polymer chain by silica can be easily obtained, and it is considered that the handling stability performance during high-speed driving is further improved.

[0016] It is preferable that the rubber hardness of the rubber composition exceeds 50 and is less than 80. By setting the rubber hardness within the above range, it is considered that the handling stability performance during high-speed driving is further improved.

[0017] The tread portion has one or more lateral grooves extending in the tire width direction, and it is preferable that the total volume of the one or more lateral grooves is 2.0% or more and 5.0% or less of the volume of the tread portion. Thereby, it is considered that the movement of the tread portion is suppressed and the handling stability during high-speed driving is further improved.

[0018] The tread portion has one or more circumferential grooves extending in the tire circumferential direction, and in any one of the one or more circumferential grooves, at the 80% position of the groove depth of the deepest part of the circumferential groove with respect to the groove width L0 at the ground contact surface of the tread portion, the groove width L 80 of the ratio (L 80 / L0) is preferably 0.3 or more and 0.7 or less. Thereby, it is possible to suppress the movement of the entire land portion at the bottom surface of the land portion of the tread portion, and it is considered that the handling stability during high-speed driving is further improved.

[0019] The tread portion has grooves inclined in the tire circumferential direction or the tire width direction, and it is preferable that the maximum width L of the grooves inclined in the tire circumferential direction or the tire width direction is more than 7.0 mm and less than 20.0 mm.

[0020] By providing the tread portion with grooves inclined in the tire circumferential direction or the tire width direction, it is possible to enhance the followability to the road surface of the tread portion ground contact surface while also enhancing the responsiveness, and it is considered that the handling stability performance during high-speed driving is further improved.

[0021] It is preferable that T is more than 6 mm and less than 12 mm. When the thickness of the tread portion is within the above range, it is possible to enhance the followability to the road surface of the tread ground contact surface while also enhancing the responsiveness, and it is considered that the handling stability performance during high-speed driving is further improved.

[0022] <Definition> The "normal state" is a no-load state in which it is mounted on a normal rim and filled with a normal internal pressure.

[0023] "Dimensions of each part of the tire" are, unless otherwise specified, values specified in a normal state for those appearing on the outer surface of the tire, while those existing inside the tire or on the tire cut surface are values specified in a state where, for example, the tire is cut by a plane including the tire rotation axis and the cut tire piece is held in the rim width of a normal rim.

[0024] "Normal rim" is the rim defined for each tire in a standard system including the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it refers to the standard rim in the applicable sizes described in the "JATMA YEAR BOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" described in the "STANDARDS MANUAL"; and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" described in the "YEAR BOOK". Refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size at the time of reference. In the case of a tire not defined in the above standards, it refers to the narrowest rim among the rims with the smallest diameter that can be assembled with the tire and can hold the internal pressure (i.e., does not cause air leakage between the rim and the tire).

[0025] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum air pressure"; in the case of ETRTO, it is "INFLATION PRESSURE"; and in the case of TRA, it refers to the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order as in the case of the normal rim, and follow the relevant standard if there is an applicable size during the reference. For tires not specified in the standard, it refers to the normal internal pressure (however, 250 kPa or more) of another tire size described with the said normal rim as the standard rim (however, those specified in the standard). If there are multiple normal internal pressures of 250 kPa or more described, the minimum value among them shall be referred to.

[0026] "Normal load" refers to the load specified for each tire in the standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of ETRTO, it is "LOAD CAPACITY"; and in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Refer to JATMA, ETRTO, and TRA in this order as in the case of the normal rim and normal internal pressure, and follow the relevant standard if there is an applicable size during the reference. For tires not specified in the standard, the maximum load capacity W L calculated separately shall be taken as the normal load.

[0027] "Maximum load capacity W L " is calculated by the following formula. "V" is the virtual volume of the tire (mm 3)、「Dt」 is the outer diameter of the tire (mm) in the normal state, 「Ht」 is the cross-sectional height of the tire in the cross-section of the tire by the plane including the tire rotation axis (mm) in the tire radial direction, and 「Wt」 is the cross-sectional width of the tire (mm) in the normal state. When the rim diameter of the tire is R, Ht can be obtained by (Dt - R) / 2. Wt is the value obtained excluding patterns, letters, etc. on the tire sidewall. Note that the maximum load capacity is synonymous with the above-mentioned normal load.

[0028]

Number

[0029] The 「thickness T (mm) of the tread portion」 is the total thickness of the tread portion measured along the normal line to the tread contact surface on the tire equator in the cross-section passing through the tire rotation axis. When there are circumferential grooves on the tire equator, among the land portions existing on both sides in the tire width direction of the groove, it is the thickness measured along the normal line to the tread contact surface on the central portion in the tire width direction of the land portion where the central portion in the tire width direction of the land portion is closer to the tire equatorial plane.

[0030] The 「groove」 refers to a recessed portion formed in the tread portion of the tire, and among them, those with an opening width on the tread contact surface of the groove of 2.0 mm or more. Among the recessed portions, those with an opening width on the tread contact surface of less than 2.0 mm are called 「sipes」.

[0031] The 「circumferential groove」 refers to a groove extending in the tire circumferential direction. The circumferential groove may extend linearly along the circumferential direction, or may extend in a wave shape, sine shape, or zigzag shape along the circumferential direction.

[0032] The 「groove depth」 refers to the maximum value of the distance between the straight line connecting the ends of the groove on the tread contact surface and the deepest part of the groove in the tire radial direction. When the groove depth of the groove changes in the tire width direction or circumferential direction, this maximum value is taken as the groove depth of the groove. Also, the depth at a point where multiple grooves intersect, such as a three-way intersection or above, is excluded from the groove depth.

[0033] A "lateral groove" refers to a groove extending in the tire width direction. Here, "extending in the tire width direction" means that the angle formed by the line segment connecting its starting point and ending point and the tire width direction is less than 45°. When the groove extends to the tread edge, the tread edge is taken as the starting point or the ending point. The "volume of the lateral groove" is the value of the volume formed by the surface connecting the end portions of the lateral groove in the tire width direction and the groove wall in a tire in the normal state. The "total volume of the lateral grooves" can be calculated by obtaining the volumes of the individual lateral grooves.

[0034] The "volume of the tread portion" is the volume of the tread portion assuming that all the grooves in the tread portion are filled. Here, the "tread portion" is the portion that forms the ground contact surface of the tire. In the cross-section in the tire radial direction, when it includes members that form the tire skeleton with steel or textile materials such as the belt layer, belt reinforcing layer, carcass layer, etc., it is the member outside these in the tire radial direction.

[0035] The "groove width L0 of the circumferential groove on the ground contact surface of the tread portion" is the width (mm) in the tire rotation axis direction on the tread ground contact surface of the circumferential groove, and is measured in the normal state. The "groove width L 80 " at the 80% position of the groove depth at the deepest part of the circumferential groove is the width (mm) in the tire rotation axis direction at the 80% position of the groove depth at the deepest part of the circumferential groove, and is measured in the normal state.

[0036] The "groove depth at the deepest part of the circumferential groove", when there are multiple circumferential grooves, is the groove depth of the circumferential groove having the deepest groove depth.

[0037] The "maximum width of the inclined groove" refers to the largest one among the opening widths of the groove on the tread ground contact surface in the cross-section perpendicular to the center line of both ends of the tread extending in the groove extension direction. The opening width is the distance from one end of the tread piece to the other end on the tread ground contact surface. Here, the "groove extension direction" refers to the direction in which the groove continuously extends. For example, for a circumferential groove, it is the circumferential direction, and for a groove inclined in the tire width direction, it is the direction along the inclination in the tire width direction.

[0038] "Styrene content (mass %) of the rubber component" means that for each rubber constituting the entire rubber component (100 mass %), the value obtained by multiplying its styrene content by its content rate in the entire rubber component is calculated, and all of these values are summed up.

[0039] "Vinyl content (mass %) of the rubber component" means that for each rubber constituting the entire rubber component (100 mass %), the value obtained by multiplying the vinyl butadiene unit content derived from its 1,2-butadiene bond by its content rate in the entire rubber component is calculated, and all of these values are summed up.

[0040] "The rubber component of the rubber composition" is a component that contributes to crosslinking within the rubber composition, and generally has a weight average molecular weight (Mw) of 10,000 or more.

[0041] <Measurement method> "E* at 30°C with a dynamic strain of 0.25%" is the complex elastic modulus measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±0.25%, and an elongation mode using a viscoelasticity measuring device (for example, the Implex series manufactured by GABO). When the sample for measuring the complex elastic modulus is prepared by cutting it out from a tire, it is cut out from the tread part of the tire so that the tire radius direction becomes the thickness direction.

[0042] "E* at 30°C with a dynamic strain of 1.0%" is the complex elastic modulus measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1.0%, and an elongation mode using a viscoelasticity measuring device (for example, the Implex series manufactured by GABO). The sample for measurement is prepared in the same manner as in the case of E* at 30°C with a dynamic strain of 0.25%.

[0043] "ΔE* at 30°C (0.25% - 1.0%)" can be obtained from the difference between E* at 30°C with a dynamic strain of 0.25% and E* at 30°C with a dynamic strain of 1.0%.

[0044] "Rubber hardness" is a value measured by cutting out a tread portion to form a hardness measurement sample so that the tire radial direction from the tread portion forming the ground contact surface becomes the thickness direction, and pressing a type A durometer against the ground contact surface side of the sample at 23°C in accordance with JIS K 6253.

[0045] "Glass transition temperature (Tg) of rubber component" is measured by heating at a rate of 10°C / min using a differential scanning calorimeter (Q200) of TA Instruments Japan Co., Ltd. in accordance with JIS K 7121 while raising the temperature.

[0046] "Average primary particle diameter" is obtained by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of 400 particle diameters. When the particle shape is approximately circular, the diameter of the circle is taken as the particle diameter; when it is needle-shaped or rod-shaped, the minor axis is taken as the particle diameter; in other cases, the equivalent circle diameter is calculated from the electron microscope image and taken as the particle diameter. The equivalent circle diameter is obtained as the "positive square root of 4×(particle area) / π". The average primary particle diameter is applicable to silica, carbon black, etc.

[0047] "Nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0048] "Nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0049] "Styrene content" is 1 a value calculated by 1H-NMR measurement and is applicable to rubber components having repeating units derived from styrene such as SBR. "Cis content (cis-1,4-bonded butadiene unit amount)" is a value calculated by infrared absorption spectrum analysis in accordance with JIS K 6239-2:2017 and is applicable to rubber components having repeating units derived from butadiene such as BR.

[0050] The "softening point of the resin component" is the temperature at which the ball drops when measured with a ring and ball softening point measuring device for the softening point defined in JIS K 6220-1:2015, 7.7.

[0051] The "content of the softening agent" includes the amount of the softening agent contained in the extended rubber component previously extended with a softening agent such as oil, resin component, and liquid rubber component. The same applies to the content of oil, the content of resin component, and the content of liquid rubber. For example, when the extended component is oil, the extended oil is included in the content of oil.

[0052] The manufacturing procedure of the pneumatic tire which is one embodiment of the present invention will be described in detail below. However, the following description is an exemplification for explaining the present invention, and is not intended to limit the technical scope of the present invention only to this description range. In this specification, when a numerical range is indicated using "~", the numerical values at both ends are included.

[0053] <Tire> Fig. 1 shows a schematic view of the contact surface when the tread portion of the tire according to one embodiment of the present invention is pressed against a plane. The tread portion 10 has a plurality of circumferential grooves 1. In Fig. 1, three circumferential grooves 1 are provided, but the number of circumferential grooves is not particularly limited, and may be, for example, 2 to 5.

[0054] The tread portion 10 has land portions 2 partitioned by a plurality of circumferential grooves 1 in the tire width direction W. The shoulder land portions 11 are a pair of land portions formed between the circumferential groove 1 and the tread edge Te. The center land portion 12 is a land portion formed between the pair of shoulder land portions 11. In Fig. 1, two center land portions 12 are provided, but the number of center land portions is not particularly limited, and may be, for example, 1 to 5.

[0055] Figure 2 shows a schematic diagram of a developed view of a tread portion of a tire, which is another embodiment of the present invention. In Figure 2, the tread portion 10 has a plurality of zigzag circumferential grooves 1 that continuously extend in the circumferential direction. The lateral groove 5 is inclined so as to shift toward one side in the circumferential direction of the tire as it approaches the center in the tire width direction. And at the bent portion of the circumferential groove 1, the lateral groove 5 intersects and extends across the circumferential groove 1. Further, the shoulder land portion 11 is provided with a plurality of linear shoulder sipe 22 having one end opening into the circumferential groove 1, and the center land portion 12 is provided with a plurality of linear center sipe 23 having one end opening into the circumferential groove 1. Note that in the present embodiment, it is not essential that the circumferential groove 1 is continuous without interruption in the circumferential direction, and it may be divided by the lateral groove 5.

[0056] From the viewpoint of handling stability during high-speed driving, the tread portion according to the present embodiment preferably has one or more lateral grooves. The total volume of the one or more lateral grooves is preferably 1.5% or more, more preferably 2.0% or more, and even more preferably 2.5% or more of the volume of the tread portion. Also, the total volume of the one or more lateral grooves is preferably 10.0% or less, more preferably 8.0% or less, and even more preferably 5.0% or less of the volume of the tread portion. By setting the total volume of the lateral grooves in the volume of the tread portion within the above range, it is considered that the handling stability during high-speed driving is further improved.

[0057] From the viewpoint of handling stability during high-speed driving, the maximum width L of the groove inclined in the tire circumferential direction or the tire width direction is preferably more than 7.0 mm, more preferably more than 8.0 mm, and even more preferably more than 9.0 mm. On the other hand, the upper limit is not particularly limited, but preferably less than 20.0 mm, more preferably less than 15.0 mm.

[0058] Figure 3 is a cross-sectional view passing through the tire rotation axis of the tire according to the present embodiment, showing a part of the tread portion. In Figure 3, the tread portion is composed of a first layer 3 and a second layer 4, but it is not limited to such a mode. For example, the tread portion may be a single rubber layer or may be three or more rubber layers.

[0059] The thickness T of the tread portion of the pneumatic tire according to the present embodiment is preferably more than 6.0 mm, more preferably more than 8.0 mm, still more preferably 10.0 mm or more, and even more preferably 12.0 mm or more. Also, the thickness T of the tread portion is preferably 18.0 mm or less, more preferably 15.0 mm or less, and still more preferably 14.0 mm or less.

[0060] From the viewpoint of handling stability during high-speed driving, in any of the circumferential grooves of the tread portion according to the present embodiment, it is preferable that the groove width on the inner side in the tire radial direction is narrower than the groove width on the ground contact surface 6 of the tread portion. The groove width L at the 80% position of the groove depth of the deepest part of the circumferential groove with respect to the groove width L0 of the circumferential groove where the groove width on the inner side in the tire radial direction is narrower than the groove width on the ground contact surface 6 of the tread portion 80 of the ratio (L 80 / L0) is preferably 0.20 or more, more preferably 0.30 or more, still more preferably 0.40 or more. Also, L 80 / L0 is preferably 0.80 or less, more preferably 0.70 or less, and still more preferably 0.60 or less.

[0061] The dynamic strain ±0.25% 30°C E* of the rubber composition constituting the tread portion according to the present embodiment is preferably 19.0 MPa or more, more preferably 20.0 MPa or more, still more preferably 22.0 MPa or more, and even more preferably 23.0 MPa or more. Also, the dynamic strain ±0.25% 30°C E* is preferably 28.0 MPa or less, more preferably 26.0 MPa or less, and still more preferably 25.0 MPa or less.

[0062] The dynamic strain ±1.0% 30°C E* of the rubber composition constituting the tread portion according to the present embodiment is preferably 13.0 MPa or more, more preferably 14.0 MPa or more, still more preferably 15.0 MPa or more, and even more preferably 16.0 MPa or more. Also, the dynamic strain ±1.00% 30°C E* is preferably 20.0 MPa or less, more preferably 18.0 MPa or less, and still more preferably 17.0 MPa or less.

[0063] The 30°C ΔE*(0.25% - 1.0%) of the rubber composition constituting the tread part according to this embodiment is 6.0 MPa or more, preferably 6.5 MPa or more, more preferably 6.8 MPa or more, still more preferably 7.0 MPa or more, still more preferably 7.2 MPa or more, still more preferably 7.5 MPa or more, still more preferably 7.8 MPa or more, and particularly preferably 8.0 MPa or more. Also, the upper limit value of the 30°C ΔE*(0.25% - 1.0%) of the rubber composition constituting the tread part according to this embodiment is not particularly limited, but for example, it can be 12.0 MPa or less, 10.0 MPa or less, 9.0 MPa or less, etc.

[0064] Note that the 30°C E* can be appropriately adjusted according to the types and compounding amounts of the rubber component, filler, softening agent, etc. described later. For example, the 30°C E* can be increased by increasing the amount of the filler in the rubber composition, reducing the content of the softening agent, etc.

[0065] The 30°C ΔE*(0.25% - 1.0%) / T of the rubber composition constituting the tread part according to this embodiment is 0.45 or more, preferably 0.50 or more, more preferably 0.60 or more, still more preferably 0.70 or more, and particularly preferably 0.75 or more. Also, the upper limit value of the 30°C ΔE*(0.25% - 1.0%) / T is not particularly limited, but for example, it can be 1.00 or less, 0.95 or less, 0.90 or less, etc.

[0066] The rubber hardness of the rubber composition constituting the tread part according to this embodiment is preferably more than 50, more preferably more than 55, and still more preferably more than 60 from the viewpoint of riding comfort performance. Also, from the viewpoint of handling stability performance, the rubber hardness is preferably less than 80, more preferably less than 75, and still more preferably less than 70.

[0067] Note that the rubber hardness can be appropriately adjusted according to the types and compounding amounts of the rubber component, filler, softening agent, etc. described later. For example, the rubber hardness can be increased by increasing the amount of the filler in the rubber composition and reducing the content of the softening agent.

[0068] The tread portion of the present invention has at least one rubber layer. The rubber layer may be formed by a single rubber layer, and preferably has a rubber layer (first layer) that contacts the road surface during use of the tire and a rubber layer (second layer) adjacent to the belt layer. It may further have one or more rubber layers between the first layer and the second layer.

[0069] When the tread portion includes two or more rubber layers, for each physical property value such as 30 °C ΔE*(0.25%-1.0%) of the rubber composition constituting the tread portion, it is sufficient if the physical property value is satisfied in any of the rubber layers, but it is preferably satisfied in the first layer.

[0070] <Rubber component> The rubber composition constituting the tread portion according to the present embodiment (hereinafter, referred to as the rubber composition according to the present embodiment unless otherwise specified) contains an isoprene-based rubber as a rubber component, and preferably contains an isoprene-based rubber and a butadiene rubber (BR), and more preferably contains an isoprene-based rubber, BR, and a styrene-butadiene rubber (SBR). Further, other rubber components other than these may be contained. Also, the rubber component may be a rubber component consisting only of an isoprene-based rubber, BR, and SBR.

[0071] (Isoprene-based rubber) As the isoprene-based rubber, for example, those commonly used in the tire industry such as isoprene rubber (IR) and natural rubber can be used. Natural rubber includes, in addition to non-modified natural rubber (NR), 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 alone or in combination of two or more.

[0072] NR is not particularly limited, and those commonly used in the tire industry can be used, and examples include SIR20, RSS#3, and TSR20.

[0073] From the perspective of the effects of the present invention, the content of isoprene rubber in the rubber component is more than 40% by mass, preferably 45% by mass or more, more preferably 48% by mass or more, and even more preferably 50% by mass or more. On the other hand, the content of isoprene rubber in the rubber component is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0074] (BR) BR is not particularly limited. For example, BR with a cis content of less than 50 mol% (low-cis BR), BR with a cis content of 90 mol% or more (high-cis BR), rare-earth-based butadiene rubber synthesized using a rare-earth element-based catalyst (rare-earth-based 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 can be used alone or in combination of two or more.

[0075] As high-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., UBE Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, the low-temperature properties and abrasion resistance can be improved. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 97 mol% or more. The cis content of BR is measured by the above measurement method.

[0076] From the perspective of the effects of the present invention, when BR is contained, the content in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. On the other hand, when BR is contained, the content in the rubber component is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

[0077] (SBR) There are no particular limitations on the SBR, and examples include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of the modified SBR include SBRs with modified terminals and / or main chains, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Among them, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs can be used alone or in combination of two or more.

[0078] The styrene content of the SBR is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, and particularly preferably 45% by mass or less. Also, the styrene content of the SBR is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, further preferably 30% by mass or more, and particularly preferably 35% by mass or more. Note that the styrene content of the SBR is measured by the aforementioned measurement method.

[0079] From the perspective of wear resistance performance, the glass transition temperature (Tg) of the SBR is preferably -60°C or higher, more preferably -50°C or higher, and still more preferably -40°C or higher. Also, the Tg of the SBR is preferably -20°C or lower, more preferably -25°C or lower, and still more preferably -30°C or lower.

[0080] When containing SBR, the content in the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 32% by mass or more. On the other hand, the content of SBR in the rubber component is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, further preferably 35% by mass or less, and particularly preferably 30% by mass or less.

[0081] (Other rubber components) The rubber component may also contain rubber components other than those described above, as long as the effects of the present invention are not impaired. Examples of such rubber components include non-diene rubbers such as hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber.

[0082] (Rubber component synthesized from recycled and biomass-derived raw materials) The monomers that are the constituent units of synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or may be recycled from rubber products such as tires and non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, and examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Among them, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0083] The method for producing recycled monomers is not particularly limited, and examples include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and high pressure, decomposed by microwaves, or extracted after mechanical pulverization.

[0084] Furthermore, the monomers that are the constituent units of polymers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, and examples include agricultural and forestry products, sugars, wood chips, plant residues after obtaining useful components, ethanol derived from plants, biomass naphtha, and the like.

[0085] The monomers derived from biomass (biomass monomers) are not particularly limited, and examples include butadiene derived from biomass and aromatic vinyl compounds derived from biomass. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. The aromatic vinyl compound is not particularly limited, and examples include styrene. Also, the method for producing biomass monomers is not particularly limited, and examples include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical of biological conversion, and examples of chemical and / or physical conversion include those by catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof.

[0086] The polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples include polybutadiene rubber synthesized from butadiene derived from biomass and aromatic vinyl / butadiene copolymers synthesized from butadiene derived from biomass and / or aromatic vinyl compounds derived from biomass. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from butadiene derived from biomass and / or styrene derived from biomass.

[0087] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D 6866-10. pMC is the 14 C concentration of the sample relative to that of 14It is the ratio of C concentration, and this value is used as an index indicating the biomass ratio of the compound (rubber). The significance of this value is described below.

[0088] In 1 mole (6.02×10 23 pieces) of carbon atoms, there are approximately 6.02×10 11 pieces, which is about one trillionth of the normal carbon atoms, of 14 C present. 14 The half-life of 14 C is 5730 years, and 14 C decreases regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are considered to have passed more than 226,000 years after the carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 C elements that were originally contained in them have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain any 14 C elements at all. Therefore, chemical substances produced from these fossil fuels also do not contain any

[0089] On the other hand, 14 C is constantly generated by cosmic rays undergoing nuclear reactions in the atmosphere. Therefore, 14 C is in equilibrium between the decrease due to radioactive decay and the generation due to nuclear reactions, and in the atmospheric environment of the earth, the amount of 14 C is constant. Therefore, the 14 C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the entire C atoms as described above. Therefore, the biomass ratio in a certain compound can be calculated using the difference between these values.

[0090] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12Measure (C). In the measurement, 14 As reference standards for the concentration of C, the 14 C concentration in the circulating carbon in nature in 1950 is adopted. As a specific reference material, the oxalic acid standard provided by NIST (National Institute of Standards and Technology) is used. The specific activity of carbon in this oxalic acid (the 14 radioactivity intensity of C per 1 g of carbon) is separated for each carbon isotope, 13 For 14 C, it is corrected to a constant value, and the value after applying the decay correction from 1950 AD to the measurement date is used as the standard

[0091] Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences, etc., it usually does not reach 100 under normal conditions at present, so it will show a value of about 110 pMC. On the other hand, for chemical substances derived from fossil fuels such as petroleum, when the 14 C concentration is measured, it will show a value of about 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% mentioned above.

[0092] From the above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in the rubber composition is suitable from the perspective of environmental protection.

[0093] <Filler> The rubber composition according to this embodiment contains silica as a filler, and preferably contains silica and carbon black.

[0094] (Silica) The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), etc., which are common in the tire industry, can be used. The raw material of the silica is not particularly limited, and for example, it may be a raw material derived from a mineral such as quartz, or a raw material derived from a living organism such as rice husk (for example, silica using a biomass material such as rice husk as a raw material), or silica recycled from a product containing silica may be used. Among them, hydrous silica prepared by a wet method is preferred because it has many silanol groups. These silicas may be used alone or in combination of two or more.

[0095] From the viewpoint of ensuring reinforcing property and grip performance, the nitrogen adsorption specific surface area (N2SA) of the silica is preferably 100 m 2 / g or more, more preferably 120 m 2 / g or more, still more preferably 140 m 2 / g or more, still more preferably 160 m 2 / g or more, particularly preferably 180 m 2 / g or more. Further, from the viewpoints of heat generation property and processability, it is preferably 350 m 2 / g or less, more preferably 300 m 2 / g or less, still more preferably 250 m 2 / g or less. The N2SA of the silica is measured by the above measurement method.

[0096] Silica using a biomass material as a raw material can be obtained, for example, by extracting a silicate from rice husk ash obtained by burning rice husk using a sodium hydroxide solution, and reacting the silicate with sulfuric acid in the same manner as conventional wet silica to precipitate silicon dioxide, followed by filtration, washing with water, drying, and pulverization.

[0097] Silica recycled from products containing silica can be, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. The method of recovery is not particularly limited, and examples include pyrolysis and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0098] When silica crystallizes, it becomes insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash can be suppressed (see, for example, JP-A-2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.). Amorphous silica extracted from rice husks can be those commercially available from companies such as Wilmar.

[0099] The average primary particle diameter of the silica is preferably 10 nm or more, more preferably 12 nm or more, and even more preferably 14 nm or more. Also, the average primary particle diameter is preferably 22 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. The average primary particle diameter of the silica is measured by the above-described measurement method.

[0100] From the viewpoint of the effects of the present invention, the content of silica relative to 100 parts by mass of the rubber component is more than 30 parts by mass, preferably more than 40 parts by mass, more preferably more than 50 parts by mass, even more preferably more than 60 parts by mass, even more preferably more than 70 parts by mass, even more preferably more than 80 parts by mass, and particularly preferably more than 90 parts by mass. Also, from the viewpoint of low fuel consumption performance, it is preferably less than 150 parts by mass, more preferably less than 130 parts by mass, even more preferably less than 120 parts by mass, and particularly preferably less than 110 parts by mass.

[0101] (Carbon black) The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw material of the carbon black may be a biomass material such as lignin or vegetable oil, or may be a pyrolysis oil obtained by pyrolyzing waste tires. Further, the manufacturing method of the carbon black may be by combustion such as the furnace method, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black method. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbian Carbon Company, etc. can be used. These carbon blacks may be used alone or in combination of two or more.

[0102] In addition to the above, from the perspective of life cycle assessment and the like, carbon black made from biomass materials such as lignin as a raw material, or recycled carbon black obtained by pyrolyzing and purifying products containing carbon black such as tires may also be used as the carbon black.

[0103] In this specification, "recycled carbon black" refers to carbon black obtained by pulverizing used products such as tires containing carbon black and firing the pulverized product, and when oxidized and burned by heating in air by a thermogravimetric method conforming to JIS K 6226-2:2003, it refers to carbon black in which the ratio of the mass of the ash content (ash amount), which is the component that does not burn, is 13% by mass or more. That is, the ratio of the mass (carbon amount) of the weight loss due to the oxidative combustion of the recycled carbon black is 87% by mass or less. Recycled carbon black may also be represented by rCB.

[0104] Recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975 refers to "Rubber Chemistry and Technology", Vol. 85, No. 3, pages 408-449 (2012), particularly pages 438, 440, and 442, and describes that it can be obtained by pyrolysis of organic materials at 550-800 °C with oxygen excluded or vacuum pyrolysis at relatively low temperatures (

[0027] ). The carbon black obtained from such a pyrolysis process usually lacks functional groups on its surface, as mentioned in

[0004] of Patent No. 6856781 (Comparison of the surface morphology and chemistry of pyrolytic carbon black and commercially available carbon black, Powder Technology 160 (2005) pages 190-193).

[0105] Recycled carbon black may lack functional groups on its surface, or may be treated to contain functional groups on its surface. The treatment to make the recycled carbon black contain functional groups on its surface can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black obtained from the pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, in Patent No. 6856781, carbon black obtained from the pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes such carbon black treated to contain functional groups on its surface.

[0106] Commercially available recycled carbon black from companies such as Strable Green Carbon and LDCarbon can be used.

[0107] The average primary particle diameter of the carbon black is preferably 12 nm or more, more preferably 15 nm or more, still more preferably 18 nm or more, and particularly preferably 20 nm or more. On the other hand, from the viewpoint of obtaining reinforcing properties, the average primary particle diameter is preferably 80 nm or less, more preferably 50 nm or less, and still more preferably 30 nm or less. The average primary particle diameter of the carbon black is measured by the above measurement method.

[0108] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 200 m 2 / g or less, more preferably 180 m 2 / g or less, and still more preferably 150 m 2 / g or less, from the viewpoint of the effects of the present invention. Also, the N2SA is preferably 100 m 2 / g or more, more preferably 120 m 2 / g or more, and still more preferably 130 m 2 / g or more. The N2SA of the carbon black is measured by the above measurement method.

[0109] From the viewpoint of the effects of the present invention, the content of the carbon black with respect to 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, still more preferably more than 5 parts by mass, still more preferably more than 9 parts by mass, and particularly preferably more than 15 parts by mass. Also, from the viewpoint of obtaining flexibility and relaxing stress, it is preferably less than 80 parts by mass, more preferably less than 60 parts by mass, still more preferably less than 40 parts by mass, still more preferably less than 30 parts by mass, and particularly preferably less than 25 parts by mass.

[0110] (Other fillers) The rubber composition may contain other fillers other than silica and carbon black. The other fillers are not particularly limited, and for example, those commonly used in the tire industry such as aluminum hydroxide, calcium carbonate, alumina, clay, talc, etc. can be blended.

[0111] <Silane coupling agent> Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited. For example, sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, etc. Among them, it is preferable to contain a sulfide-based silane coupling agent and / or a mercapto-based silane coupling agent. As the silane coupling agent, for example, those commercially available from Evonik Degussa, Momentive, etc. can be used. These silane coupling agents may be used alone or in combination of two or more.

[0112] The content of the silane coupling agent with respect to 100 parts by mass of the rubber component (the total amount of all when using a plurality of silane coupling agents in combination) is preferably more than 3.0 parts by mass, more preferably more than 5.0 parts by mass, and even more preferably 6.0 parts by mass or more from the viewpoint of enhancing the dispersibility of silica. Also, from the viewpoint of preventing a decrease in wear resistance performance, it is preferably less than 15 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 8.0 parts by mass.

[0113] <Other compounding agents> In addition to the rubber component and the filler, the rubber composition may appropriately contain compounding agents generally used in the conventional tire industry, such as softeners, processing aids, vulcanized rubber particles, waxes, stearic acid, zinc oxide, antioxidants, vulcanizing agents, vulcanization accelerators, and the like.

[0114] <Softener> A softener is a material that imparts plasticity to the rubber component, and is a concept that includes both softeners that are liquid at 25°C and softeners that are solid at room temperature (25°C). Examples of softeners include resins, oils, liquid rubbers, ester plasticizers, and the like. These softeners may be derived from mineral resources such as petroleum and natural gas, or may be derived from biomass. In addition, low-molecular-weight hydrocarbon components obtained by pyrolyzing and extracting used tires and products containing various components may be used as softeners. Softeners may be used alone or in combination of two or more.

[0115] (Oil) Examples of oils include mineral oils, vegetable oils, animal oils, and the like. Also, from the perspective of life cycle assessment, waste oils used in rubber mixers and engines, or refined waste cooking oils used in restaurants may be used. Oils may be used alone or in combination of two or more.

[0116] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of mineral oil include, for example, MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), RAE (Residual Aromatic Extract), etc. Also, oil with a low content of polycyclic aromatic (PCA) compounds can be used for environmental protection. Examples of the low-PCA-content oil include MES, TDAE, heavy naphthenic oil, etc.

[0117] In this specification, vegetable oil refers to, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grape seed oil, wood wax, etc. Furthermore, vegetable oil includes refined oil (such as salad oil) obtained by refining the above oil, transesterified oil obtained by transesterifying the above oil, hydrogenated oil obtained by hydrogenating the above oil, thermally polymerized oil obtained by thermally polymerizing the above oil, oxidatively polymerized oil obtained by oxidizing the above oil, waste cooking oil recovered from those used as edible oil, etc. Note that vegetable oil may be liquid or solid at room temperature (25°C).

[0118] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxy group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Further, the acylglycerol may be a monomer, a dimer, or a multimer of trimer or higher. Note that acylglycerols of dimer or higher can be obtained by thermal polymerization, oxidative polymerization, or the like. Also, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0119] As a method for confirming whether the acylglycerol is contained in the rubber composition, it is not particularly limited, but 1 it can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at normal temperature (25°C) for 24 hours. After removing the rubber composition, 1 1H-NMR is measured. When the signal of tetramethylsilane (TMS) is set to 0.00 ppm, signals are observed around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" means a range of ±0.10 ppm.

[0120] The fatty acid is not particularly limited and may be an unsaturated fatty acid or a saturated fatty acid. Examples of the unsaturated fatty acid include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of the saturated fatty acid include butyric acid and lauric acid.

[0121] Among these, as the fatty acid, it is desirable to contain a fatty acid with few double bonds, that is, a saturated fatty acid or a monounsaturated fatty acid, and oleic acid is preferred. As the vegetable oil containing such a fatty acid, for example, a vegetable oil containing a saturated fatty acid or a monounsaturated fatty acid may be used, or a vegetable oil subjected to modification such as transesterification may be used. Further, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by varietal improvement, gene recombination, or the like.

[0122] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0123] Examples of the animal oil include fish oil, beef tallow, or oleyl alcohol that can be derived therefrom.

[0124] From the viewpoint of processability, the content with respect to 100 parts by mass of the rubber component when containing oil is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more. Also, the content is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and further preferably 60 parts by mass or less. As described above, the oil content includes the amount of oil contained in the oil-extended rubber.

[0125] (Resin component) The resin component is not particularly limited, but resins commonly used in the tire industry can be used. For example, aromatic vinyl resins, dicyclopentadiene resins, C9 resins, C5 resins, C5C9 resins, terpene resins, rosin resins, phenolic resins, etc. can be mentioned. Among these, petroleum resins, aromatic vinyl resins, dicyclopentadiene resins, C9 resins, and terpene resins are preferred. The resin component may be used alone or in combination of two or more.

[0126] ≪Aromatic vinyl resin≫ "Aromatic vinyl resin" refers to a resin containing at least one aromatic vinyl compound selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc., with the monomer component having the highest content, preferably containing 50 mol% or more, and may be a hydrogenated or modified product thereof. As the aromatic vinyl resin, due to economic reasons, ease of processing, and excellent heat generation properties, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from companies such as Kreton, Eastman Chemical, and Mitsui Chemicals, Inc. can be used. The resin may be used alone or in combination of two or more.

[0127] ≪Dicyclopentadiene-based resin≫ "Dicyclopentadiene-based resin" refers to a resin containing dicyclopentadiene (DCPD) as the monomer component with the highest content, and may be a hydrogenated or modified product thereof. Examples of the dicyclopentadiene-based resin include DCPD / C9 resins obtained by copolymerizing dicyclopentadiene and the above-mentioned C9 fraction, and DCPD / C9 resins are preferred. As the DCPD resin, for example, those commercially available from companies such as ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., and Maruzen Petrochemical Co., Ltd. can be used. The resin may be used alone or in combination of two or more.

[0128] ≪C9-based resin≫ The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction. It may be a resin obtained by polymerizing the C9 fraction alone or a copolymer obtained by copolymerizing the C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. Also, those that are hydrogenated or modified may be used. Examples of the C9 fraction include at least one petroleum fraction having 8 to 10 carbon atoms selected from the group consisting of vinyltoluene, alkylstyrene, coumarone, indene, methylindene, dicyclopentadiene, and the like. Specific examples of the C9 resin include, for example, coumarone-indene resin, coumarone resin, indene resin, and the like. The resin may be used alone or in combination of two or more.

[0129] ≪C5 resin≫ The term "C5 resin" refers to a resin obtained by polymerizing a C5 fraction other than dicyclopentadiene, and those that are hydrogenated or modified may be used. Examples of the C5 fraction other than dicyclopentadiene include at least one petroleum fraction having 4 to 5 carbon atoms selected from the group consisting of cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, pentadiene, and the like. The resin may be used alone or in combination of two or more.

[0130] ≪C5C9 resin≫ The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and those that are hydrogenated or modified may be used. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Co., Ltd., and the like can be used. The resin may be used alone or in combination of two or more.

[0131] ≪Terpene resin≫ A terpene resin refers to a resin that contains, as the monomer component with the highest content, at least one terpene compound selected from the group consisting of α-pinene, β-pinene, limonene, dipentene, etc., preferably containing 50 mol% or more. It may be a hydrogenated or modified one. Specific examples of terpene resins include, for example, polyterpene resins containing only one or more of the above terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compounds and aromatic compounds as monomer components; terpene phenol resins containing the terpene compounds and phenolic compounds as monomer components, etc. Examples of the aromatic compounds that are monomer components of aromatic-modified terpene resins include at least one selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of the phenolic compounds that are monomer components of terpene phenol resins include at least one selected from the group consisting of phenol, bisphenol A, cresol, xylenol, etc. The resin may be used alone or in combination of two or more.

[0132] ≪Rosin Resin≫ A rosin resin refers to a resin that contains at least one rosin acid compound selected from the group consisting of abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., preferably containing it as the monomer component with the highest content, more preferably containing 50 mol% or more. It may be a hydrogenated or modified one. The rosin resin is not particularly limited, and examples thereof include natural resin rosin, rosin-modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. The resin may be used alone or in combination of two or more.

[0133] ≪Phenolic Resin≫ The phenolic resin refers to a resin containing a phenolic compound such as phenol or cresol as the monomer component with the highest content, preferably containing 50 mol% or more. The phenolic resin is not particularly limited, and examples include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc. The resin may be used alone or in combination of two or more.

[0134] From the viewpoint of grip performance, the softening point of the resin component is preferably 60 °C or higher, more preferably 70 °C or higher, and even more preferably 80 °C or higher. Also, from the viewpoints of processability and improvement of the dispersibility of the rubber component and the filler, it is preferably 150 °C or lower, more preferably 140 °C or lower, and even more preferably 130 °C or lower. The softening point of the resin component is measured by the above measurement method.

[0135] When containing a resin component, the content with respect to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and particularly preferably 18 parts by mass or more. Also, from the viewpoint of suppressing heat generation, it 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.

[0136] (Liquid rubber) The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25 °C). 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. The liquid rubber may be used alone or in combination of two or more.

[0137] When containing a liquid rubber, the content with respect to 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. Also, the content of the liquid rubber is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0138] (Ester plasticizer) Examples of ester plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), bis(2-ethylhexyl) azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. The ester plasticizer may be used alone or in combination of two or more kinds.

[0139] (Vulcanized rubber particles) Vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. specified in JIS K 6316:2017 can be used. From the viewpoints of environmental consideration and cost, recycled rubber powder produced from crushed waste tires etc. is preferable. The vulcanized rubber particles may be used alone or in combination of two or more kinds.

[0140] The vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles.

[0141] As commercially available products of vulcanized rubber, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used.

[0142] (Wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. Examples include mineral waxes, plant-derived waxes, etc. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among them, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, candelilla wax, etc. Examples of mineral waxes include paraffin wax, microcrystalline wax, and their selected special waxes, etc., and paraffin wax is preferred. Note that the wax according to this embodiment does not contain stearic acid. As the wax, commercially available products from, for example, Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramoelt Co., etc. can be used. The wax may be used alone or in combination of two or more.

[0143] When containing wax, the content relative to 100 parts by mass of the rubber component is preferably more than 0.5 part by mass, more preferably more than 1.0 part by mass, and even more preferably more than 1.5 part by mass from the viewpoint of the weather resistance of the rubber. Also, from the viewpoint of preventing the whitening of the tire due to blooming, it is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0144] The anti-aging agent is not particularly limited, but examples include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents such as N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditoly-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based anti-aging agents such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; bis, tris, polyphenol-based anti-aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Among them, p-phenylenediamine-based anti-aging agents and quinoline-based anti-aging agents are preferred, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and polymers of 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Industry Co., Ltd., Flexsys, etc. can be used. The anti-aging agent may be used alone or in combination of two or more kinds.

[0145] When containing an anti-aging agent, from the viewpoint of the ozone crack resistance of the rubber, the content per 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more. Also, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0146] When contained, the content of stearic acid relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Also, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0147] When contained, the content of zinc oxide relative to 100 parts by mass of the rubber component is preferably 0.5 part by mass or more, more preferably 1.0 part by mass or more, and still more preferably 1.5 part by mass or more from the viewpoint of processability. Also, from the viewpoint of abrasion resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

[0148] Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, etc. can be used.

[0149] When contained, the content of sulfur as the vulcanizing agent relative to 100 parts by mass of the rubber component is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and still more preferably 1.0 part by mass or more from the viewpoint of ensuring a sufficient vulcanization reaction. Also, from the viewpoint of deterioration prevention, it is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and still more preferably 3.5 parts by mass or less. In addition, when using oil-containing sulfur as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0150] Examples of vulcanizing agents other than sulfur include alkylphenol sulfur chloride condensates, sodium 1,6 - hexamethylenedithiocarbamate dihydrate, 1,6 - bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. Commercially available products from companies such as Taoka Chemical Co., Ltd., Ransburg Co., Ltd., and Flexsys can be used as these vulcanizing agents other than sulfur.

[0151] Examples of the vulcanization accelerator include sulfenamide - based, thiazole - based, thiuram - based, thiourea - based, guanidine - based, dithiocarbamic acid - based, aldehyde - amine - based or aldehyde - ammonia - based, imidazoline - based, or xanthate - based vulcanization accelerators, etc. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint of more preferably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide - based, guanidine - based, and thiazole - based vulcanization accelerators are preferred, and sulfenamide - based vulcanization accelerators are more preferred.

[0152] Examples of the sulfenamide - based vulcanization accelerator include N - tert - butyl - 2 - benzothiazolylsulfenamide (TBBS), N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS), N,N - dicyclohexyl - 2 - benzothiazolylsulfenamide (DCBS), etc. Among them, N - tert - butyl - 2 - benzothiazolylsulfenamide (TBBS) and N - cyclohexyl - 2 - benzothiazolylsulfenamide (CBS) are preferred.

[0153] Examples of the guanidine - based vulcanization accelerator include 1,3 - diphenylguanidine (DPG), 1,3 - di - o - tollylguanidine, 1 - o - tollylbiguanide, di - o - tollylguanidine salt of dicatecholborate, 1,3 - di - o - cumenylguanidine, 1,3 - di - o - biphenylguanidine, 1,3 - di - o - cumenyl - 2 - propionylguanidine, etc. Among them, 1,3 - diphenylguanidine (DPG) is preferred.

[0154] Examples of the thiazole - based vulcanization accelerator include 2 - mercaptobenzothiazole, cyclohexylamine salt of 2 - mercaptobenzothiazole, di - 2 - benzothiazolyldisulfide, etc. Among them, 2 - mercaptobenzothiazole is preferred.

[0155] When contained, the content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and still more preferably 2.0 parts by mass or more. Also, the content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 6.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, the breaking strength and elongation tend to be ensured.

[0156] In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, anti-aging agent, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the blend of the various materials from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process of synthesizing methane from carbon dioxide may be converted.

[0157] [Manufacturing] The rubber composition can be manufactured by a known method. For example, it can be manufactured by kneading the above-mentioned respective components using a rubber kneading device such as an open roll, a closed kneader (Banbury mixer, kneader, etc.).

[0158] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than vulcanizing agents and vulcanization accelerators, and a final kneading (F kneading) process of adding vulcanizing agents and vulcanization accelerators to the kneaded material obtained in the base kneading process and kneading them. Further, the base kneading process can also be divided into a plurality of processes if desired. When dividing the base kneading process, the method may be (1) a method in which a part of the compounding agents and additives is kneaded in advance to form a masterbatch, and then the remaining compounding agents and additives are added to the obtained masterbatch and kneaded, or (2) a method in which all the compounding agents and additives to be kneaded in the base kneading process are kneaded at once, and then the remixing of the kneaded material is performed one or more times. In the method (1) above, the number of masterbatches is not limited and may be 2 or more. Also, when the number of masterbatches is 2 or more, all the compounding agents and additives used in the base kneading process may be allocated to any one of the masterbatches.

[0159] The kneading conditions are not particularly limited. For example, in the base kneading process, kneading is performed at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading is performed at 70 to 110°C for 1 to 5 minutes. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be mentioned.

[0160] A tire provided with a tread portion composed of a rubber composition can be manufactured by a normal method. That is, the tire is obtained by extruding an unvulcanized rubber composition prepared by blending the above components with the rubber component as needed according to the shape of the tread portion, and then laminating and molding the obtained unvulcanized tread portion together with other tire members on a tire molding machine by a normal method to form an unvulcanized tire, and the unvulcanized tire thus obtained can be manufactured by heating and pressurizing it in a vulcanizer. The vulcanization conditions are not particularly limited, and for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes can be mentioned.

[0161] [Use] In this specification, the tire can be used for any application, regardless of whether it is a pneumatic tire or a non-pneumatic tire, and can be used as a passenger car tire, a large passenger car tire, a large SUV tire, a racing tire, a motorcycle tire, a heavy-duty tire, a run-flat tire. Among them, it is preferably a passenger car tire. Note that a passenger car tire is a tire that is assumed to be mounted on an automobile that runs on four wheels and has a maximum load capacity of less than 1400 kg. Also, in this specification, the tire can be used for all-season tires, summer tires, and winter tires such as studless tires in addition to summer tires.

Examples

[0162] The following shows examples (Examples) that are considered preferable for implementation, but the scope of the present invention is not limited to the Examples.

[0163] The results calculated based on the following evaluation methods were examined for pneumatic tires having a tread portion produced using a rubber composition obtained by changing the formulation according to Table 1 using the various chemicals shown below and are shown in Table 2. NR: TSR20 SBR: SLR6430 manufactured by Dow Chemical (S-SBR, styrene content: 40% by mass, vinyl content: 20 mol%, Tg -36°C, containing 37.5 parts by weight of oil-extended oil per 100 parts by weight of rubber component) BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (cis content: 97 mol%) Carbon black: SHOW BLACK N134 manufactured by Cabot Japan Ltd. (N2SA: 148m 2 / g, average primary particle diameter: 18 nm) Silica 1: ULTRASIL (registered trademark) VN3 manufactured by Evonik Degussa (N2SA: 175m 2 / g, average primary particle diameter: 18 nm) Silica 2: ULTRASIL (registered trademark) 9100GR manufactured by Evonik Degussa (N2SA: 230m 2 / g, average primary particle size: 15 nm) Coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Resin component: SYLVATRAXX 4401 (α-methylstyrene resin, Mw: 700, softening point: 85°C) manufactured by Kraton Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Tsubaki Bead Stearic Acid manufactured by NOF Corporation Wax: Oz Ace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: No Crack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: No Crack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Seimi OT (10% oil-containing insoluble sulfur) manufactured by Nippon Karyu Kogyo Co., Ltd. Vulcanization accelerator 1: No Celer CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: No Celer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0164] (Examples and Comparative Examples) According to the formulation shown in Table 1, using a 1.7 L closed Banbury mixer, chemicals other than sulfur and vulcanization accelerators are kneaded for 5 minutes until the discharge temperature reaches 170°C to obtain a kneaded product. Next, using a twin-screw open roll, sulfur and vulcanization accelerators are added to the obtained kneaded product and kneaded for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is extruded into the shapes of the first layer and the second layer of the tread part using an extruder equipped with a die of a predetermined shape, and laminated together with other tire members to form an unvulcanized tire, which is press-vulcanized at 170°C for 12 minutes to manufacture each test tire.

[0165] <Measurement of 30℃E*> From the first layer of the tread of each test tire, rubber test pieces are prepared by cutting out a piece with a length of 20 mm, a width of 4 mm, and a thickness of 1 mm such that the tire circumferential direction is the long side and the tire width direction is the thickness direction. For each rubber test piece, using an Iplexer series manufactured by GABO, the complex elastic modulus (30℃E*) at a dynamic strain of ±0.25% and a dynamic strain of 1.0% is measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and an elongation mode. 30℃ΔE*(0.25%-1.0%) is calculated from the difference between 30℃E* at a dynamic strain of ±0.25% and 30℃E* at a dynamic strain of 1.0%.

[0166] <Measurement of rubber hardness> The tread part is cut out so that the tire radial direction from the first layer of the tread part is the thickness direction to create a sample for hardness measurement. For the sample, a type A durometer is pressed from the ground contact side at 23°C in accordance with JIS K 6253 to measure the rubber hardness.

[0167] <Handling stability performance during high-speed driving> Each test tire is mounted on all four wheels of a vehicle (domestic FF2000cc), and a real vehicle test drive of 10 laps is performed on a test course on a dry asphalt road surface at about 120 km / h. Regarding the wobbling during cornering entry, turning, and exit at that time, 20 test drivers conduct sensory evaluations. The evaluation is performed with integer values from 1 to 5 points (the smaller the wobbling, the higher the score), and the total score of the 20 test drivers is calculated. The total score of the reference comparative example (Comparative Example 4) is converted to a reference value (100), and the evaluation results of each test tire are indexed and displayed in proportion to the total score. The larger the numerical value, the better the handling stability performance during high-speed driving.

[0168]

Table 1

[0169]

Table 2

[0170] <Embodiment> Examples of embodiments of the present invention are shown below. 〔1〕A pneumatic tire having a tread portion, The tread portion is composed of a rubber composition containing a rubber component and silica, The content of isoprene rubber in the rubber component exceeds 40% by mass, The content of silica with respect to 100 parts by mass of the rubber component in the rubber composition exceeds 30 parts by mass, The difference between the complex elastic modulus at a dynamic strain of 0.25% and the complex elastic modulus at a dynamic strain of 1.0%, measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, and an initial strain of 5% of the rubber composition, is designated as 30°C ΔE*(0.25% - 1.0%), When the thickness of the tread portion is T (mm), 30°C ΔE*(0.25% - 1.0%) is 6.0 MPa or more, A pneumatic tire in which 30°C ΔE*(0.25% - 1.0%) / T is 0.45 or more. 〔2〕The pneumatic tire according to the above 〔1〕, wherein the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition exceeds 60 parts by mass. 〔3〕The pneumatic tire according to the above 〔1〕 or 〔2〕, wherein the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition exceeds 90 parts by mass. 〔4〕The pneumatic tire according to any one of the above 〔1〕 to 〔3〕, wherein 30°C ΔE*(0.25% - 1.0%) is 7.0 MPa or more. 〔5〕The pneumatic tire according to any one of the above 〔1〕 to 〔4〕, wherein 30°C ΔE*(0.25% - 1.0%) is 8.0 MPa or more. 〔6〕The pneumatic tire according to any one of the above 〔1〕 to 〔5〕, wherein 30°C ΔE*(0.25% - 1.0%) / T is 0.60 or more. 〔7〕The pneumatic tire according to any one of the above 〔1〕 to 〔6〕, wherein 30°C ΔE*(0.25% - 1.0%) / T is 0.75 or more. [8] The pneumatic tire according to any one of [1] to [7] above, wherein the rubber composition contains carbon black, and the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition is more than 1 part by mass and less than 25 parts by mass. [9] The pneumatic tire according to any one of [1] to [8] above, wherein the rubber hardness of the rubber composition is more than 50 and less than 80.

[10] The pneumatic tire according to any one of [1] to [9] above, wherein the tread portion has one or more lateral grooves extending in the tire width direction, and the total volume of the one or more lateral grooves is 2.0% or more and 5.0% or less of the volume of the tread portion.

[11] In the tread portion, there is one or more circumferential grooves extending in the tire circumferential direction, and in any one of the one or more circumferential grooves, at the 80% position of the groove depth of the deepest part of the circumferential groove with respect to the groove width L0 at the ground contact surface of the tread portion, the groove width L 80 of the ratio (L 80 / L0) is 0.3 or more and 0.7 or less. The pneumatic tire according to any one of [1] to

[10] above.

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

[11] above, wherein the tread portion has a groove inclined in the tire circumferential direction or the tire width direction, and the maximum width L of the groove inclined in the tire circumferential direction or the tire width direction is more than 7.0 mm and less than 20.0 mm.

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

[12] above, wherein T is more than 6 mm and less than 12 mm.

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

[13] above, which is for a passenger car.

Explanation of Signs

[0171] 1 Circumferential groove 2 Land portion 3 First layer 4 Second layer 5 Inclined lateral groove 6 Tread ground contact surface 10 Tread portion 11 Shoulder land portion 12 Center land portion 21 Lateral groove 22 Shoulder sipe 23 Center size C Tire equator W Tire width direction Te Tread edge T Thickness of tread part N Normal line to the tread contact surface on the tire equator H Groove depth at the deepest part of the circumferential groove L0 Groove width on the contact surface L 80 Groove width at the 80% position of the deepest groove depth

Claims

1. A pneumatic tire having a tread portion, wherein the tread portion is composed of a rubber composition containing a rubber component and silica, the content of isoprene rubber in the rubber component exceeds 40% by mass, the content of silica relative to 100 parts by mass of the rubber component in the rubber composition exceeds 30 parts by mass, the difference between the complex elastic modulus at a dynamic strain of 0.25% and the complex elastic modulus at a dynamic strain of 1.0%, measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, and an initial strain of 5% of the rubber composition, is denoted as 30°C ΔE*(0.25% - 1.0%), when the thickness of the tread portion is T (mm), 30°C ΔE*(0.25% - 1.0%) is 6.0 MPa or more, and 30°C ΔE*(0.25% - 1.0%) / T is 0.45 or more, a pneumatic tire.

2. The pneumatic tire according to claim 1, wherein the content of silica relative to 100 parts by mass of the rubber component of the rubber composition exceeds 60 parts by mass.

3. The pneumatic tire according to claim 1 or 2, wherein the content of silica relative to 100 parts by mass of the rubber component of the rubber composition exceeds 90 parts by mass.

4. The pneumatic tire according to claim 1 or 2, wherein 30°C ΔE*(0.25% - 1.0%) is 7.0 MPa or more.

5. The pneumatic tire according to claim 1 or 2, wherein 30°C ΔE*(0.25% - 1.0%) is 8.0 MPa or more.

6. The pneumatic tire according to claim 1 or 2, wherein 30°C ΔE*(0.25% - 1.0%) / T is 0.60 or more.

7. The pneumatic tire according to claim 1 or 2, wherein 30°C ΔE*(0.25% - 1.0%) / T is 0.75 or more.

8. The pneumatic tire according to claim 1 or 2, wherein the rubber composition contains carbon black, and the content of carbon black relative to 100 parts by mass of the rubber component of the rubber composition exceeds 1 part by mass and is less than 25 parts by mass.

9. The pneumatic tire according to claim 1 or 2, wherein the rubber hardness of the rubber composition is more than 50 and less than 80.

10. The pneumatic tire according to claim 1 or 2, wherein the tread portion has one or more transverse grooves extending in the tire width direction, and the total volume of the one or more transverse grooves is 2.0% or more and 5.0% or less of the volume of the tread portion.

11. The tread portion has one or more circumferential grooves extending in the tire circumferential direction, and in any one of the one or more circumferential grooves, the groove width L at the ground contact surface of the tread portion 0 at the 80% position of the groove depth of the deepest part of the circumferential groove with respect to the groove width L 80 The ratio (L 80 / L 0 ) is 0.3 or more and 0.7 or less. The pneumatic tire according to claim 1 or 2

12. The pneumatic tire according to claim 1 or 2, wherein the tread portion has grooves inclined in the tire circumferential direction or the tire width direction, and a maximum width L of the grooves inclined in the tire circumferential direction or the tire width direction is more than 7.0 mm and less than 20.0 mm.

13. The pneumatic tire according to claim 1 or 2, wherein T is more than 6 mm and less than 12 mm.

14. The pneumatic tire according to claim 1 or 2, which is for a passenger car.

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