Tire

Abstract

To provide a tire improved in integrated performance of wet grip performance.SOLUTION: A tire comprises a tread part. The tread part has one or more circumferential grooves, and the tread part is constituted of rubber compositions containing rubber constituents and silica. The rubber constituents contain isoprene rubber and styrene-butadiene rubber. Contents of the isoprene rubber in the rubber constituents are 40 mass% or more. Contents of the styrene-butadiene rubber in the rubber constituents are 40 mass% or more. Contents of the silica with respect to 100 parts by mass of the rubber constituents are 90 parts by mass or more. Styrene contents S1 (mass%) of the styrene-butadiene rubber are 30 or less. When a land ratio of the tire is defined as R and tanδ at 0°C of the rubber compositions is defined as 0°Ctanδ, 0°Ctanδ×R is 0.30 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 describes that, with respect to 100 parts by mass of a rubber component containing 60 to 90 parts by mass of a specific conjugated diene rubber and 10 to 40 parts by mass of a conjugated diene polymer, 80 to 200 parts by mass of silica having a CTAB specific surface area of 150 to 300 m 2 / g and 0.1 to 5 parts by mass of a specific tetrazine compound are blended, and the specific conjugated diene rubber has an aromatic vinyl monomer content of 35 to 45% by mass and a vinyl bond content of less than 35 mol%, and the wet grip performance of the tire is improved by the rubber composition for a tire.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, further improvement in the wet grip performance of tires has been desired.

[0005] An object of the present invention is to provide a tire with improved wet grip performance.

Means for Solving the Problems

[0006] The present invention is a tire having a tread portion, the tread portion has one or more circumferential grooves, the tread portion is composed of a rubber composition containing a rubber component and silica, The rubber component contains isoprene rubber and styrene-butadiene rubber, the content of the isoprene rubber in the rubber component is 40% by mass or more, the content of the styrene-butadiene rubber in the rubber component is 40% by mass or more, the content of the silica is 90 parts by mass or more with respect to 100 parts by mass of the rubber component, the styrene content S1 (mass%) of the styrene-butadiene rubber is 30 or less, let the land ratio of the tire be R, when the tan δ at 0°C of the rubber composition is defined as 0°C tan δ, relates to a tire in which 0°C tan δ × R is 0.30 or more.

Advantages of the Invention

[0007] According to the present invention, a tire with improved wet grip performance is provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] A tire according to an embodiment of the present invention is a tire having a tread portion, wherein the tread portion has one or more circumferential grooves, the tread portion is composed of a rubber composition containing a rubber component and silica, the rubber component contains an isoprene-based rubber and a styrene-butadiene rubber, the content of the isoprene-based rubber in the rubber component is 40% by mass or more, the content of the styrene-butadiene rubber in the rubber component is 40% by mass or more, the content of the silica with respect to 100 parts by mass of the rubber component is 90 parts by mass or more, the styrene content S1 (% by mass) of the styrene-butadiene rubber is 30 or less, and when the land ratio of the tire is R and the tanδ at 0°C of the rubber composition is 0°C tanδ, 0°C tanδ × R is 0.30 or more.

[0010] Regarding the reason for the improvement in wet grip performance in the tire of this embodiment, although not intended to be restricted by theory, it is considered as follows.

[0011] The rubber composition constituting the tread portion of the tire of the present embodiment contains (1) 40% by mass or more of isoprene rubber, so a phase of isoprene rubber of a certain size or more is formed, and an interface with other rubber phases is generated, thereby relaxing the input to the tire during vehicle running. And since the interaction between isoprene rubber and silica is relatively weak, the isoprene rubber can move flexibly in the rubber matrix, and the followability of the tread portion to the road surface is improved, contributing to the improvement of wet grip performance. Also, (2) since it contains 40% by mass or more of styrene-butadiene rubber, the proportion of styrene domains in the rubber phase increases and heat generation becomes easier, contributing to the improvement of wet grip performance. Further, (3) since the content of silica with respect to 100 parts by mass of the rubber component is 90 parts by mass or more, the proportion of silica present on the tread surface increases, and an interaction occurs between the hydroxyl groups on the silica surface and the wet road surface, improving the followability of the tread portion to the road surface, and contributing to the improvement of wet grip performance. Also, (4) when the styrene content S1 of the styrene-butadiene rubber is 30% by mass or less, minute styrene domains are formed in the rubber phase, and the styrene domains move flexibly in the rubber phase. Then, the mobility of the entire polymer present in the rubber phase is improved, the followability of the tread portion to the road surface is improved, and it contributes to the improvement of wet grip performance.

[0012] Also, in the tread portion of the tire of the present embodiment, (5) the product of the 0°C tanδ and the land ratio R of the rubber composition constituting the tread portion, that is, 0°C tanδ × R is 0.30 or more, so that the total calorific value of the tread portion on the tread surface can be increased, contributing to the improvement of wet grip performance. And it is considered that the remarkable effect that the wet grip performance is greatly improved is achieved by the cooperation of the above (1) to (5).

[0013] It is preferable that the half-value width of the peak in the range of -20°C to -70°C in the tanδ temperature distribution curve of the rubber composition is 30°C or less. By narrowing the half-value width, more energy loss occurs in the frequency band when braking on a wet road surface, so it is considered that the wet grip performance is further improved.

[0014] When the acetone extraction amount of the rubber composition is AE (mass %), it is preferable that AE is 22.0 or more.

[0015] When the acetone extraction amount AE of the rubber composition is 22.0 mass % or more, a certain amount of plasticizer is contained in the rubber composition, the dispersibility of the filler is improved, and the distribution of the filler proceeds efficiently. Therefore, it is considered that the wet grip performance is further improved.

[0016] From the viewpoint of wet grip performance, 0 °C tan δ is preferably 0.45 or more.

[0017] It is preferable that 0 °C tan δ × H is 3.00 or more. This is because even when the groove depth of the circumferential groove is shallow, the hysteresis loss is improved and the wet grip performance is further improved.

[0018] When the total thickness of the tread portion is T (mm), it is preferable that 0 °C tan δ × T is 3.50 or more. This is because even when 0 °C tan δ of the rubber composition is low, by ensuring the total thickness of the tread portion, the heat generation property of the tread portion increases and the wet grip performance is improved.

[0019] It is preferable that AE amount × H is 140.0 or more. This is because the efficiency of filler dispersion and distribution is improved, the rigidity of the rubber composition can be reduced, the contact area with the road surface increases, and the followability of the tread portion to the road surface is improved. Therefore, it is considered that the wet grip performance is further improved.

[0020] The rubber composition preferably contains a resin component containing dicyclopentadiene, styrene, and indene as monomer components. By containing the resin component, the adhesiveness of the tread portion to the road surface is enhanced, and it is considered that the wet grip performance is improved.

[0021] From the perspective of wet grip performance, it is preferable that the rubber composition contains more than 100 parts by mass of silica with respect to 100 parts by mass of the rubber component.

[0022] From the perspective of wet grip performance, it is preferable that the rubber composition contains a mercapto-based silane coupling agent.

[0023] It is preferable that the total styrene amount S2 in the rubber component is 15% by mass or less. When the total styrene amount S2 is 15% by mass or less, minute styrene domains are formed in the rubber matrix, and since these minute domains have flexibility, the mobility of the polymer is improved, the followability of the rubber composition to the road surface is improved, and it is considered that the wet grip performance is further improved.

[0024] The tread portion has two or more land portions partitioned by the one or more circumferential grooves, and at least one of the land portions has a transverse groove extending toward the inner side in the tire radial direction. It is preferable that the transverse groove has a portion where the groove width in a cross section perpendicular to the extending direction is wider than the groove width on the tread surface.

[0025] By disposing the transverse groove in the land portion, it is considered that an increase in compression rigidity can be suppressed even when wear progresses, and wet grip performance can be ensured.

[0026] On the tread surface of the tread portion, when a region of 30% of the tread contact width centered on the tire equator is defined as the center region, and regions on both outer sides of the center region and within the tread contact width are defined as a pair of shoulder regions, it is preferable that the groove depth at the deepest part of the circumferential groove existing in the shoulder region is 6.0 mm or more.

[0027] With the above configuration, drainage performance can be enhanced, which is considered to contribute to an improvement in wet grip performance.

[0028] When the tire weight is G (kg), it is preferable that S1 / G is 3.0 or less. As the tire weight decreases, it is considered that by reducing S1, it becomes easier to improve the handling stability in a low-temperature environment. As the tire becomes lighter, the force pressing the land portion against the road surface becomes smaller. Therefore, as the tire becomes lighter, even a slight aggregation of the styrene portion has a greater impact on the tread surface.

[0029] It is preferable that S1×R is 11.0 or more. When S1×R is 11.0 or more, the minute styrene domains formed in the rubber phase move flexibly, improving the polymer motility. As a result, the tread portion with improved followability to the road surface has a larger contact area with the road surface, so it is considered that the wet grip performance is further improved.

[0030] [Definition] "Styrene content S1 (mass%) of styrene-butadiene rubber" is the styrene content (mass%) of styrene-butadiene rubber (SBR). When SBR is contained alone in the rubber component, it is the styrene content of that SBR. When a plurality of SBRs are contained in the rubber component, it is obtained by the sum of the products of the styrene content of each SBR and the blending amount (mass%) of that SBR when the total SBR is 100 mass%.

[0031] For example, when the rubber component consists of 20 mass% of the first SBR (styrene content: 25 mass%), 30 mass% of the second SBR (styrene content: 27.5 mass%), and 50 mass% of BR, the styrene content S1 of the styrene-butadiene rubber is 26.5 mass% (=(25×40 / 100)+(27.5×60 / 100)).

[0032] "Total styrene content S2 (mass %) in the rubber component" is the total content (mass %) of the styrene moiety contained in 100 mass % of the rubber component. For each rubber component, a value obtained by multiplying the styrene content (mass %) by the mass fraction in the rubber component is calculated, and the sum of these values is the total styrene content. Specifically, it is calculated by Σ (styrene content (mass %) of each styrene-containing rubber × content (mass %) of each styrene-containing rubber in the rubber component / 100).

[0033] For example, when the rubber component consists of 20 mass % of the first SBR (styrene content: 25 mass %), 30 mass % of the second SBR (styrene content: 27.5 mass %), and 50 mass % of BR, the total styrene content S2 in 100 mass % of the rubber component is approximately 13.3 mass % (=(25×20 / 100)+(27.5×30 / 100)+(0×10 / 100)).

[0034] "Tan δ at the peak position within the range of -20°C to -70°C in the tan δ temperature distribution curve of the rubber composition" can be obtained from the tan δ temperature distribution curve measured by the method disclosed in JP-A-2021-54377. That is, each vulcanized test piece is measured for the tan δ temperature distribution curve in the temperature range from -20°C to -70°C using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO) under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2°C / min. It is the tan δ at the peak position of the temperature dispersion curve with temperature on the X-axis and tan δ on the Y-axis.

[0035] The "half-width of the peak (half-width of the tanδ peak) within the range of -20°C to -70°C in the tanδ temperature distribution curve of the rubber composition" can be obtained from the temperature distribution curve of tanδ measured by the method disclosed in JP-A-2021-54377. That is, each vulcanized test piece is measured for the temperature distribution curve of tanδ in the temperature range from -20°C to -70°C under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2°C / min using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO), and a temperature dispersion curve with temperature on the X-axis and tanδ on the Y-axis is obtained. Let the tanδ at the peak position of the obtained temperature distribution curve be A, the intersection of the straight line parallel to the Y-axis passing through A and the X-axis be B, the midpoint of the line segment AB be C, the straight line parallel to the X-axis passing through C be D, and the two intersections of D and the temperature distribution curve be E and F. It is defined as the absolute value of the difference in temperature (°C) between E and F.

[0036] The "amount of acetone extraction (AE)" is a value obtained by immersing each vulcanized rubber test piece in acetone at room temperature (around 25°C) for 72 hours in accordance with JIS K 6229:2015 to extract soluble components, measuring the mass of each test piece before and after extraction, and calculating using the following formula. Amount of acetone extraction (mass%) = {(mass of the rubber test piece before extraction - mass of the rubber test piece after extraction) / (mass of the rubber test piece before extraction)} × 100

[0037] The "glass transition temperature (Tg) of the rubber composition" is the temperature (tanδ peak temperature) corresponding to the maximum value within the range of -60°C or higher and 40°C or lower in the temperature distribution curve of tanδ measured using a dynamic viscoelasticity measuring device (for example, the Implex series manufactured by GABO) under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2°C / min. In the measurement in the range of -60 to 40°C, when the tanδ value continuously increases or decreases with the increase in temperature, the glass transition temperature of the rubber composition is 40°C or -60°C, respectively. Also, when there are two or more points showing a maximum value in the range of -60°C or higher and 40°C or lower, the point with the lowest temperature is taken as the glass transition temperature.

[0038] "Tanδ at 0°C" is the loss tangent (tanδ) measured using a dynamic viscoelasticity measuring device (e.g., the Implex series manufactured by GABO) under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an elongation mode. The sample for measuring tanδ at 0°C is a vulcanized rubber composition with a length of 20 mm × a width of 4 mm × a thickness of 1 mm. When it is produced by cutting from a tire, it is cut out from the tread portion such that the circumferential direction of the tire is the long side and the radial direction of the tire is the thickness direction.

[0039] The "tread portion" is the part that forms the ground contact surface of the tire. In the radial cross-section of the tire, when it includes members that form the tire skeleton with steel or textile materials such as a belt layer, a belt reinforcing layer, and a carcass layer, it is the member outside these in the radial direction of the tire.

[0040] The "normal state" is a no-load state in which the tire is mounted on a normal rim and filled with air at a normal internal pressure.

[0041] The "dimensions of each part of the tire" are, unless otherwise specified, values specified in the normal state for those that appear on the outer surface of the tire, while for those existing inside the tire, they are values specified in a state where the cut tire piece is held in the rim width of the normal rim after cutting the tire with a plane including the tire rotation axis.

[0042] The "regular rim" is the rim defined for each tire in a standard system that includes the standards 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 during the reference. In the case of a tire not defined in the above standards, it refers to the rim with the narrowest width among the rims with the minimum diameter that can be assembled with the tire and can maintain the internal pressure (i.e., does not cause air leakage between the rim and the tire).

[0043] The "regular inflation pressure" is the air pressure defined for each tire in a standard system that includes the standards on which the tire is based. For example, in the case of JATMA, it refers to the "maximum air pressure"; in the case of ETRTO, it refers to the "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". Similar to the case of the regular rim, refer to JATMA, ETRTO, and TRA in this order, and follow the relevant standard if there is an applicable size during the reference. In the case of a tire not defined in the above standards, it refers to the regular inflation pressure (but not less than 250 kPa) of another tire size described with the regular rim as the standard rim (however, it must be defined in the standard), and if there are multiple regular inflation pressures not less than 250 kPa, it refers to the minimum value among them.

[0044] The "normal load" is the load defined 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 the "LOAD CAPACITY"; 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, similar to 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 defined in the above standards, the maximum load capacity W L calculated separately is taken as the normal load.

[0045] The "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 in the normal state (mm), "Ht" is the cross-sectional height of the tire in the cross-section of the tire by the plane including the tire rotation axis, in the tire radial direction (mm), and "Wt" is the cross-sectional width of the tire in the normal state (mm). When R is the rim diameter of the tire, Ht can be obtained by (Dt - R) / 2. Wt is the value obtained after excluding patterns, characters, etc. on the tire sidewall. Note that the maximum load capacity is synonymous with the above normal load.

[0046]

Equation

[0047] The "contact area" is the area of the tread obtained from the contour when the tire is pressed against the ground. After assembling the tire on the normal rim, applying the normal internal pressure, and leaving it static for 24 hours at 25°C, ink is applied to the tire tread surface, the tire is loaded with the normal load (maximum load capacity) and pressed vertically against cardboard (the camber angle is 0°), and the ink is transferred to obtain it. The area of the contact area is called the total contact area. The total contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72 degrees each time for a total of five locations.

[0048] The "effective contact area" is the area of the tread that comes into contact with the ground when the tire is pressed against the ground. It is obtained by assembling the tire on a standard rim, applying the standard internal pressure, allowing it to stand for 24 hours at 25°C, then painting ink on the tire tread surface, applying the standard load (maximum load capacity) to the tire and pressing it vertically against thick paper (the camber angle is 0°) to transfer the ink. The area of the effective contact area is referred to as the effective contact area. The effective contact area can be calculated as the average value of the five areas obtained by performing the above transfer operation while rotating the tire by 72 degrees each time for a total of five locations.

[0049] The "land ratio R" is calculated by the following formula from the total contact area of the contact area and the effective contact area of the effective contact area. It is represented by 0 to 1.0. Land ratio = (Effective contact area / Total contact area)

[0050] The "groove" refers to a recess extending inward in the tire radius direction formed on the tread surface of the tire, and the groove width (opening width) on the tread surface is 2.0 mm or more. Those less than 2.0 mm are referred to as "sipes". The "circumferential groove" refers to a groove extending continuously in the tire circumferential direction. The circumferential groove may extend linearly along the circumferential direction, or may extend in a wave shape, a sine shape, or a zigzag shape along the circumferential direction.

[0051] The "groove depth H (mm) at the deepest part of the circumferential groove" refers to the linear distance between the straight line connecting the ends of the groove on the tread surface and the lowest part of the groove in the tire radius direction in the cross-section of the tire by a plane including the tire rotation axis. When the groove depth of the groove varies in the tire width direction and / or the circumferential direction, the maximum value of the linear distance is taken as the groove depth of the groove (note that the depth at a point where multiple grooves intersect, such as a three-way intersection or more, is excluded from the definition of the groove depth in this specification).

[0052]

[0053] ​The "groove width" means the distance between the groove walls. The groove width can be recognized at each position along the extending direction of the groove from the tread surface to the groove bottom.

[0054] The "widened groove" refers to a groove whose groove width is wider on the inner side in the tire radius direction than the groove width (opening width) on the tread surface.

[0055] The "total thickness T (mm) of the tread portion" is the thickness of the tread portion measured along the normal line at the tire equator in the cross-section of the tire by a plane including the tire rotation axis. When there is a circumferential groove on the tire equator, it is the thickness measured along the normal line on the central portion in the tire width direction of the land portion that is closer to the tire equator among the land portions existing on both sides in the tire width direction of the groove. Note that the total thickness T of the tread portion is the average value of the total thicknesses of the tread portion obtained at five positions by rotating the tire by 72° in the circumferential direction.

[0056] The "weight G (kg) of the tire" refers to the weight of the tire alone, excluding the weight of the rim. On the other hand, when a member made of sponge or sealant or a sensor member, etc. is provided in the inner cavity of the tire, the weight including them is taken.

[0057] The "land portion" is the portion of the tread where the tire contacts the ground when the tire is pressed against the ground, and is the portion of the tread that constitutes the effective contact area.

[0058] The "depth of the deepest circumferential groove existing in the shoulder region" is the depth of the deepest circumferential groove existing in the shoulder region when the region centered on the tire equator on the tread surface is defined as the center region, and the regions on both outer sides of the center region and within the tire contact width are defined as a pair of shoulder regions.

[0059] 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.

[0060] The "glass transition temperature (Tg) of the rubber component" refers to the static glass transition temperature of each rubber component determined by a differential scanning calorimeter (for example, Q200 manufactured by TA Instruments Japan Co., Ltd.).

[0061] The "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 (styrene unit-containing rubber), for example.

[0062] The "vinyl content (1,2-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 SBR and BR, for example.

[0063] The "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, for example.

[0064] The "weight average molecular weight (Mw)" can be determined by standard polystyrene conversion based on the measured value by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation). For example, it is applicable to SBR, BR, plasticizers, etc.

[0065] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017. The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0066] The "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 shape of the particle is approximately circular, the diameter of the circle is taken as the particle diameter; when the particle is needle-shaped or rod-shaped, the minor axis is taken as the particle diameter; and 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.

[0067] The "plasticizer content" includes the amount of plasticizer contained in the stretched rubber component that has been stretched in advance by a plasticizer such as oil, resin component, liquid rubber component, etc. The same applies to the oil content, resin component content, and liquid rubber content. For example, when the stretching component is oil, the stretched oil is included in the oil content.

[0068] The "softening point of the resin component" is measured with a ring and ball softening point measuring device for the softening point defined in JIS K 6220-1:2015 7.7, and it is the temperature at which the ball drops.

[0069] [Tire] Hereinafter, with reference to the drawings, a tire according to an embodiment of the present invention will be described. Note that the following embodiment is merely an example, and the tire of this embodiment is not limited to the following embodiment.

[0070] FIG. 1 illustrates a tire according to an embodiment of the present invention. FIG. 1 shows a part of the cross-section when the tire is cut along a plane including the tire rotation axis. In FIG. 1, the vertical direction is the tire radial direction, the left-right direction is the tire axial direction, and the direction perpendicular to the paper surface is the tire circumferential direction. In FIG. 1, the dashed-dotted line CL represents the tire equator.

[0071] The tire of FIG. 1 has a tread portion 1 that contacts the ground during driving, a pair of sidewall portions 2 that extend outward in the tire radial direction, and a pair of bead portions 3.

[0072] As shown in Fig. 1, a belt layer 5 is provided on the inner side in the tire radial direction of the tread portion 1. Below the belt layer 5, a carcass 4 and an inner liner 7 are laminated. Further, a band layer 6 may be present between the tread portion 1 and the belt layer 5. The bead portion 3 includes a bead core 14 and a bead apex 13 extending radially outward in the tire direction from this core. The bead apex 13 tapers outward in the tire radial direction. In the bead portion 3, a clinch portion 10 that contacts the rim 8 when the rim 8 is mounted is provided outside the carcass 4, and the clinch portion 10 is composed of a rubber composition containing a rubber component. A rim chafer 9 may be present between the clinch portion 10 and the rim 8.

[0073] The tread portion 1 is composed of a rubber composition containing a rubber component and silica. The tread portion 1 may be a single rubber layer or may include two or more rubber layers. Among them, it is preferable to include a layer (cap rubber layer 11) whose outer surface constitutes the tread surface and a base rubber layer 12 on the outer side in the tire radial direction of the belt layer 5. One or more intermediate rubber layers may further be present between the cap rubber layer 11 and the base rubber layer 12. For each physical property value such as 0 °C tan δ of the rubber composition constituting the tread portion, when the tread portion includes two or more rubber layers, it is sufficient if any rubber layer satisfies the physical property value, but it is preferable that the layer (cap rubber layer) whose outer surface constitutes the tread surface satisfies it.

[0074] In Fig. 1, the double-headed arrow t1 is the thickness of the layer (cap rubber layer 11) whose outer surface constitutes the tread surface 16, and the double-headed arrow t2 is the thickness of the base rubber layer 12.

[0075] The total thickness T of the tread portion (t1 + t2 in Fig. 1) is preferably 4.0 mm or more, more preferably 5.0 mm or more, still more preferably 6.0 mm or more, particularly preferably 7.0 mm or more, and most preferably 8.0 mm or more. On the other hand, the upper limit is not particularly limited, but preferably 15.0 mm or less, more preferably 14.0 mm or less, still more preferably 12.0 mm or less, and particularly preferably 10.0 mm or less.

[0076] <<Tread Portion>> FIG. 2 is a cross-sectional view showing a cross-section passing through the tire rotation axis of the tread portion of the tire. In FIG. 2, the vertical direction is the tire radial direction, the left-right direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction. In FIG. 2, the midpoint of the land portion 20 in the tire width direction is shown as symbol P. The straight line indicated by symbol N passes through point P and is a straight line (normal line) perpendicular to the tangent plane at this point P.

[0077] The tread portion according to this embodiment has at least one or more circumferential grooves 15. The tread portion has land portions 20 partitioned by the circumferential grooves 15 in the tire width direction.

[0078] The groove depth H at the deepest part of the circumferential groove 15 refers to the linear distance between the straight line 17 connecting the ends of the circumferential grooves on the tread surface 16 and the extension line of the lowest part of the groove in the tire radial direction in FIG. 2. Note that, for example, when there are a plurality of circumferential grooves 15, the groove depth H refers to the linear distance between the straight line 17 and the extension line 19 of the lowest part of the circumferential groove 15 having the deepest groove depth among the plurality of circumferential grooves 15 (the left circumferential groove 15 in FIG. 2) in the tire radial direction.

[0079] From the viewpoint of wear resistance performance, the groove depth H at the deepest part in the circumferential direction is preferably 5.0 mm or more, more preferably 5.5 mm or more, still more preferably 6.0 mm or more, still more preferably 6.5 mm or more, and particularly preferably 7.0 mm or more. Also, from the viewpoint of wet grip performance, the groove depth H at the deepest part of the circumferential groove is preferably 10.0 mm or less, more preferably 8.0 mm or less, and still more preferably 7.5 mm or less.

[0080] As shown in FIGS. 1 and 2, the tread portion may have a layer (cap rubber layer 11) whose outer surface constitutes the tread surface 16, and a base rubber layer 12 adjacent to the inner side in the radial direction of the cap rubber layer 11. One of the circumferential grooves 15 shown on the left side of FIG. 2 is formed such that the deepest part of the groove bottom of the circumferential groove 15 is located on the inner side in the tire radial direction with respect to the outer surface of the base rubber layer 12. Specifically, the base rubber layer 12 has a recess recessed inward in the tire radial direction with respect to the outer surface, and a part of the cap rubber layer 11 is formed with a predetermined thickness in the recess of the base rubber layer 12. The circumferential groove 15 is formed so as to enter the inside of the recess of the base rubber layer 12 beyond the outer surface of the base rubber layer 12. Note that the circumferential groove 15 may be formed with a groove depth that does not reach the outer surface of the base rubber layer 12, like the circumferential groove 15 shown on the right side of FIG. 2.

[0081] From the viewpoint of improving the efficiency of filler dispersion and distribution and reducing the rigidity at low temperatures, the acetone extraction amount AE of the rubber composition constituting the tread portion is preferably 20.0% by mass or more, more preferably 22.0% by mass or more, and even more preferably 23.0% by mass or more. Further, from the viewpoint of durability performance, the acetone extraction amount (AE) is preferably less than 35.0% by mass, more preferably less than 33.0% by mass, and even more preferably less than 30.0% by mass.

[0082] From the viewpoint of wet grip performance, AE×H is preferably 140.0 or more, more preferably 142.0 or more, and even more preferably 145.0 or more. Further, from the viewpoint of durability performance, AE×H is preferably 210.0 or less, more preferably 190.0 or less, even more preferably 170.0 or less, and even more preferably 160.0 or less.

[0083] From the viewpoint of the effects of the present invention, the tanδ at the peak position within the range of -20°C to -70°C in the tanδ temperature distribution curve of the rubber composition constituting the tread portion is preferably -60°C or more, more preferably -50°C or more, and even more preferably -40°C or more.

[0084] The half-width of the peak (half-width of the tanδ peak) is preferably 45°C or lower, more preferably 40°C or lower, still more preferably 35°C or lower, and particularly preferably 30°C or lower from the viewpoint of causing energy loss in the frequency band when braking on a wet road surface and further improving wet grip performance. Further, since the half-width of the tanδ peak can cause energy loss in a wide frequency band and can release the input from the road surface as heat even in the deformation speed region of the rubber crack segments, crack growth can be suppressed, and from the viewpoint of improving wear resistance performance, 20°C or higher is preferable, more preferably 22°C or higher, and still more preferably 23°C or higher. Note that the temperature distribution curve of tanδ may have a plurality of peak tops, and in that case, it is sufficient that the half-width of the peak is within the above range for at least one peak (curve).

[0085] The 0°C tanδ of the rubber composition constituting the tread portion is preferably more than 0.40, more preferably more than 0.45, still more preferably more than 0.50, still more preferably more than 0.55, and particularly preferably more than 0.60 from the viewpoint of wet grip performance. Further, from the viewpoint of low fuel consumption performance, the 0°C tanδ is preferably less than 0.70, more preferably less than 0.65, and still more preferably less than 0.60.

[0086] 0°C tanδ × H is preferably more than 2.80, more preferably 3.00 or more, still more preferably more than 3.10, still more preferably more than 3.20, and particularly preferably more than 3.30 from the viewpoint of wet grip performance. Further, from the viewpoint of durability performance, 0°C tanδ × H is preferably less than 5.00, more preferably less than 4.50, and still more preferably less than 4.10.

[0087] 0°C tanδ × T is preferably more than 3.20, more preferably 3.50 or more, still more preferably more than 3.70, still more preferably more than 3.80, and particularly preferably more than 3.90 from the viewpoint of wet grip performance. Further, from the viewpoint of low fuel consumption performance, 0°C tanδ × T is preferably less than 5.00, more preferably 4.50 or less, and still more preferably 4.00 or less.

[0088] From the perspective of the effects of the present invention, the glass transition temperature (Tg) of the rubber composition constituting the tread portion is preferably above -70°C, more preferably above -60°C, still more preferably above -50°C, still more preferably above -40°C, and particularly preferably above -30°C. Further, from the perspective of low-temperature embrittlement, it is preferably below 0°C, more preferably below -10°C, and still more preferably below -20°C.

[0089] In addition, each physical property such as the 0°C tanδ of the rubber composition can be appropriately adjusted according to the types and blending amounts of the rubber component, filler, plasticizer, etc. described later. For example, the 0°C tanδ can be adjusted according to the type of resin component.

[0090] ≪Tread Pattern≫ FIG. 3 shows the tread pattern of a tire according to an embodiment of the present invention, but the tread pattern of the tire according to this embodiment is not limited to FIG. 3. In FIG. 3, the tread surface has three circumferential grooves extending continuously in the tire circumferential direction. The circumferential groove located in the center (central circumferential groove) extends in a zigzag shape, but is not limited to such a form, and the central circumferential groove may be linear. Also, a pair of circumferential grooves (a pair of outermost circumferential grooves) located on both sides thereof extend linearly, but are not limited to such a form, and the outermost circumferential groove may be linear. These circumferential grooves partition a pair of center land portions 21 and a pair of shoulder land portions 22. In the center land portion 21, lateral grooves 31 extending toward the inner side in the tire radial direction are arranged, and in the shoulder land portion 22, lateral grooves 32 extending toward the inner side in the tire diameter direction are arranged. The lateral groove 31 is a widened groove having a portion where the groove width spreads wider than the groove width on the tread surface in a cross section perpendicular to the extending direction. On the other hand, the lateral groove 32 has a constant groove width in a cross section perpendicular to the extending direction and is not a widened groove. Both ends of the lateral groove 31 are not in communication with the circumferential groove, but are not limited to such a form, and at least one of both ends thereof may be in communication with the circumferential groove. One end of the lateral groove 32 is in communication with the circumferential groove, and the other end extends to the tread contact end Te, but is not limited to such a mode. However, from the viewpoint of drainage, it is preferable that one end is in communication with the circumferential groove and the other end extends to the tread contact end Te, like the lateral groove 32.

[0091] The tread portion of the tire according to this embodiment preferably has two or more land portions partitioned by one or more circumferential grooves, and preferably has a plurality of lateral grooves extending toward the inner side in the tire radial direction in at least one of the land portions, and at least one of the lateral grooves is preferably a widened groove.

[0092] FIG. 4 shows a cross-sectional view taken along line C-C of the lateral groove 31 shown in FIG. 3. The cross section is a cross section perpendicular to the extending direction of the lateral groove 31 extending toward the inner side in the tire diameter direction.

[0093] The shape of the widened portion of the widened groove is not particularly limited as long as the drainage performance can be improved according to the wear of the tire, thereby improving the grip performance. For example, in the widened lateral grooves 31 of FIGS. 3 and 4, the widened portion has a groove width that uniformly expands from the tread surface to the groove bottom along the tire radial direction, that is, the widest groove width at the groove bottom. Therefore, as the tire wears, the drainage performance becomes higher.

[0094] In FIG. 4, the groove walls 42 on both sides of the lateral groove 31, which is a widened groove, are recessed from the groove edges of the tread surface to the groove bottom, and the amount of the recess is represented by C1 and C2. C1 and C2 are preferably each independently 0.05 times or more, more preferably 0.07 times or more, and even more preferably 0.10 times or more with respect to the groove width (groove width on the tread surface, opening width) W1, which is the distance between the groove edges of the lateral groove. On the other hand, the value is preferably 0.45 times or less, more preferably 0.40 times or less, and even more preferably 0.35 times.

[0095] From the viewpoint of the effects of the present invention, the land ratio R of the tire according to the present embodiment is preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less. Also, from the viewpoint of wear resistance performance, the land ratio R is preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.60 or more.

[0096] From the viewpoint of the effects of the present invention, 0 °C tanδ × R is 0.30 or more, preferably 0.31 or more, more preferably 0.32 or more, even more preferably 0.33 or more, particularly preferably 0.34 or more, and most preferably 0.35 or more. Also, 0 °C tanδ × R is preferably 0.42 or less, more preferably 0.40 or less, even more preferably 0.39 or less, and particularly preferably 0.38 or less.

[0097] In FIG. 3, the central circumferential groove is present within the center region, which is a region of 30% of the tread contact width centered on the tire equator on the tread surface, and its shape is a zigzag shape in which straight grooves repeatedly bend. It is preferable that the tread portion of the tire according to the present embodiment has a circumferential groove in the center region, which is a region of 30% of the tread contact width centered on the tire equator on the tread surface.

[0098] (Groove depth of the circumferential groove in the shoulder region) When the tread portion of the tire according to the present embodiment has a center region, which is a region of 30% of the tread contact width centered on the tire equator on the tread surface, and a pair of shoulder regions, which are regions outside both sides of the center region and within the tread contact width, it is preferable that the shoulder regions also have circumferential grooves. When there are circumferential grooves in the shoulder regions, the groove depth at the deepest part of the circumferential grooves is preferably 4.8 mm or more, more preferably 5.0 mm or more, still more preferably 5.5 mm or more, and particularly preferably 6.0 mm or more. With the above configuration, drainage performance can be improved, which is considered to contribute to the improvement of wet grip performance.

[0099] The circumferential grooves present in the shoulder regions are the circumferential grooves present on the tread surface other than the circumferential grooves present in the above-described center region. That is, the circumferential grooves present in the shoulder regions are the circumferential grooves in which, even if the grooves straddle both the center region and the shoulder regions, more than half of the grooves are present in the shoulder regions. Further, the groove depth at the deepest part of the circumferential grooves present in the shoulder regions means the groove depth of the circumferential groove having the deepest groove depth when there are a plurality of circumferential grooves present in the shoulder regions. Note that the groove depth at the deepest part of the circumferential grooves present in the shoulder regions here refers to the groove depth of the circumferential grooves when there are circumferential grooves in the shoulder regions, and is different from the deepest groove depth H (mm) that refers to the groove depth of the circumferential groove having the deepest groove depth among all the circumferential grooves.

[0100] The weight G of the tire is preferably 5.0 kg or more, more preferably 6.0 kg or more, and even more preferably 7.0 kg or more. The upper limit of the tire weight G is not particularly limited, but is usually 100 kg or less, and can be, for example, 80 kg or less, 60 kg or less, 40 kg or less, etc.

[0101] [Rubber composition] The rubber composition constituting the tread portion of the tire according to the present embodiment (hereinafter referred to as the rubber composition according to the present embodiment) will be described.

[0102] The rubber composition according to the present embodiment contains an isoprene rubber and a styrene-butadiene rubber. The rubber component according to the present embodiment preferably further contains a butadiene rubber as the rubber component, and more preferably contains an isoprene rubber, a styrene-butadiene rubber, and a butadiene rubber. The rubber component according to the present embodiment can also be a rubber component consisting only of an isoprene rubber and a styrene-butadiene rubber, or a rubber component consisting only of three components of an isoprene rubber, a styrene-butadiene rubber, and a butadiene rubber.

[0103] <Rubber component> (Isoprene rubber) As the isoprene rubber, for example, those common in the tire industry such as isoprene rubber (IR) and natural rubber can be used. Natural rubber includes, in addition to unmodified 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 rubbers may be used alone or in combination of two or more.

[0104] NR is not particularly limited, and those common in the tire industry can be used, and examples include SIR20, RSS#3, TSR20, etc.

[0105] From the perspective of the effects of the present invention, the content of isoprene rubber in the rubber component is 40% by mass or more, preferably more than 40% by mass, and more preferably 45% by mass or more. Further, the content of isoprene rubber is preferably less than 80% by mass, more preferably less than 70% by mass, still more preferably less than 60% by mass, and even more preferably 50% by mass or less.

[0106] (SBR) There is no particular limitation on 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 modified SBR include SBR modified at the terminal and / or main chain with a compound (modifying agent) having the following functional groups; modified SBR coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.). Further, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs can be used alone or in combination of two or more.

[0107] As the functional group of the modifying agent, a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen is preferred. Examples of such functional groups include, for example, amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, mercapto group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), hydroxyl group, oxy group, epoxy group, etc., and an amino group and / or an alkoxysilyl group is preferred. As the amino group, an amino group substituted with 1 to 2 alkyl groups having 1 to 6 carbon atoms is preferred. Specific examples of alkoxysilyl include, for example, trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, dimethoxymethylsilyl, diethoxymethylsilyl, dimethylmethoxysilyl, dimethylethoxysilyl, etc.

[0108] As the SBR, oil-extended SBR or non-oil-extended SBR can be used. As the SBR that can be used in this embodiment, those commercially available from JSR Corporation, Sumitomo Chemical Co., Ltd., UBE Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., ARLANXEO, etc. can be used.

[0109] From the viewpoint of the effects of the present invention, the styrene content S1 of the SBR is 30% by mass or less, preferably 28% by mass or less, more preferably 25% by mass or less, further preferably 23% by mass or less, still further preferably 20% by mass or less, still further preferably 18% by mass or less, and particularly preferably 15% by mass or less. Also, from the viewpoint of wet grip performance, S1 is preferably 5% by mass or more, more preferably 8% by mass or more, and further preferably 10% by mass or more.

[0110] From the viewpoint of wet grip performance, the vinyl content of the SBR is preferably more than 15 mol%, more preferably more than 18 mol%, and further preferably more than 20 mol%. Also, from the viewpoint of low fuel consumption performance, the vinyl content of the SBR is preferably less than 50 mol%, more preferably less than 45 mol%, and further preferably less than 30 mol%. In this specification, the vinyl content of the SBR is measured by the above measurement method.

[0111] From the viewpoint of the effects of the present invention, S1×R is preferably 10.0 or more, more preferably 11.0 or more, further preferably 12.0 or more, and particularly preferably 13.0 or more. Also, S1×R is preferably 20.0 or less, more preferably 18.0 or less, and further preferably 17.5 or less.

[0112] From the viewpoint of the effects of the present invention, S1 / G is preferably 1.0 or more, more preferably 1.5 or more, and further preferably 2.0 or more. Also, S1 / G is preferably 6.0 or less, more preferably 5.0 or less, and further preferably 4.0 or less.

[0113] From the perspective of the effects of the present invention, the glass transition temperature (Tg) of SBR is preferably -40°C or lower, more preferably -45°C or lower, still more preferably -50°C or lower, still more preferably -55°C or lower, and particularly preferably -60°C or lower. Also, from the perspective of abrasion resistance performance, it is preferably -90°C or higher, more preferably -80°C or higher, and still more preferably -70°C or higher.

[0114] From the perspective of the effects of the present invention, the weight average molecular weight (Mw) of SBR is preferably more than 80,000, more preferably more than 100,000, still more preferably more than 150,000, and particularly preferably more than 500,000. Also, from the perspective of crosslinking uniformity and the like, Mw is preferably less than 2,000,000, more preferably less than 1,500,000, and still more preferably less than 1,100,000. The Mw of SBR is measured by the above measurement method.

[0115] From the perspective of the effects of the present invention, the content in the rubber component of SBR is 40% by mass or more, preferably more than 40% by mass, more preferably 42% by mass or more, still more preferably 45% by mass or more, and particularly preferably 48% by mass or more. Also, the content in the rubber component of SBR is preferably 60% by mass or less, more preferably less than 60% by mass, and still more preferably 55% by mass or less.

[0116] (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.

[0117] As the 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 more than 95 mol%, more preferably more than 96 mol%, and even more preferably more than 97 mol%. The cis content of BR is measured by the above measurement method.

[0118] The rare-earth-based BR is synthesized using a rare-earth element-based catalyst, and the vinyl content is preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and even more preferably 1.5 mol% or less, and the cis content is preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. As the rare-earth-based BR, for example, those commercially available from Lanxess Co., Ltd., etc. can be used.

[0119] The SPB-containing BR is not simply one in which 1,2-syndiotactic polybutadiene crystals are dispersed in BR, but one in which they are dispersed after chemically bonding to BR. As such SPB-containing BR, those commercially available from UBE Industries, Ltd., etc. can be used.

[0120] Examples of the modified BR include BR modified with the same functional groups as those described for SBR above, and modified butadiene rubber (modified BR) modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen at the terminal and / or in the main chain can also be preferably used.

[0121] Examples of other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and those in which the terminal of the modified BR molecule is bonded by a tin-carbon bond (tin-modified BR), etc. The modified BR may be either unhydrogenated or hydrogenated.

[0122] The weight average molecular weight (Mw) of BR is preferably more than 300,000, more preferably more than 350,000, and even more preferably more than 400,000 from the viewpoint of abrasion resistance performance. Further, from the viewpoints such as crosslinking uniformity, etc., it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 500,000. Note that Mw can be determined by the above method.

[0123] The content in the rubber component of BR is not particularly limited, but is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 19% by mass or more. Further, the content in the rubber component of BR is preferably 20% by mass or less, more preferably less than 20% by mass, and even more preferably 15% by mass or less.

[0124] From the viewpoint of the effects of the present invention, the total styrene amount S2 in the rubber component is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. Further, S2 is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more.

[0125] (Other rubber components) The rubber component may contain rubber components other than isoprene rubber, SBR, and BR as long as it does not affect the effects of the present invention. As other rubber components, rubber components generally used in the tire industry can be used. For example, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. can be mentioned. These other rubber components may be used alone or in combination of two or more. Further, in addition to the above rubber components, a known thermoplastic elastomer may or may not be contained.

[0126] (Rubber components synthesized from recycled and biomass-derived raw materials) Monomers that are 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.

[0127] The method for producing recycled monomers is not particularly limited, and examples include being synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Also, 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.

[0128] Furthermore, monomers that are 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, plant-derived ethanol, biomass naphtha, and the like.

[0129] The biomass-derived monomers (biomass monomers) are not particularly limited, and examples thereof include biomass-derived butadiene and biomass-derived 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 thereof include styrene. Further, the method for producing the biomass monomer is not particularly limited, and examples thereof include those by biological and / or chemical and / or physical conversion of animals and plants. Fermentation by microorganisms is typical as the biological conversion, and examples of the chemical and / or physical conversion include those by a catalyst, high heat, high pressure, electromagnetic waves, a supercritical fluid, and combinations thereof.

[0130] The polymers synthesized from the biomass monomer components (biomass polymers) are not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl compounds. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0131] Whether the raw material of the polymer is derived from biomass can be determined by pMC (percent Modern Carbon) measured in accordance with ASTM D6866-10. pMC is the ratio of the 14 C concentration of the sample to the 14 C concentration of the standard modern carbon (modern standard reference), and is a value used as an index indicating the biomass ratio of the compound. The significance of this value will be described below.

[0132] In one mole (6.02 × 10 23 pieces) of carbon atoms, there are about 6.02 × 10 11 pieces of 14 C, which is about one trillionth of ordinary carbon atoms. 14The half-life of C is 5730 years, 14 and C decreases regularly. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been formed more than 226,000 years after carbon dioxide in the atmosphere was taken up and fixed by plants, etc., all of the 14 C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas 14 contain no C elements at all. Therefore, chemical substances produced from these fossil fuels 14 also contain no C elements at all.

[0133] On the other hand, 14 C is constantly generated by nuclear reactions of cosmic rays 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 earth's atmospheric environment, 14 the amount of C is constant. Therefore, the 14 C concentration of substances derived from biomass resources that are cycling in the current environment is about 1×10 -12 mol% with respect to the total number of carbon atoms as described above. Therefore, by utilizing the difference between these values, the biomass ratio in a certain compound can be calculated.

[0134] This 14 C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 the C concentration ( 13 C / 12 C), 14 the C concentration ( 14 C / 12 C) is measured. In the measurement, 14 as a modern standard reference for the concentration of C, the 14The C concentration 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 radioactivity intensity of 14 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 decay correction from 1950 AD to the measurement date is used as the value of the standard

[0135] C concentration (100%). The ratio of this value to the value of the actually measured sample is the pMC value. 14 Therefore, if the rubber is made of 100% biomass-derived substances, although there are regional differences and so on, 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 this

[0136] 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.

[0137] [Filler] The rubber composition according to this embodiment contains silica as a filler, and it is more preferable to contain silica and carbon black. Further, the filler may be a filler consisting only of carbon black and silica.

[0138] [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 of its large number of silanol groups. These silicas may be used alone or in combination of two or more.

[0139] Silica using a biomass material as a raw material can be obtained, for example, by extracting 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.

[0140] As the silica recycled from a product containing silica, for example, silica recovered from products containing silica such as electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth can be used. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among them, silica recovered from electronic components such as semiconductors or tires is preferred.

[0141] When silica crystallizes, it does not dissolve 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.).

[0142] Amorphous silica extracted from rice husk can be those commercially available from Wilmar Co., Ltd. and the like.

[0143] The nitrogen adsorption specific surface area (N2SA) of the silica is 110 m from the viewpoint of reinforcing property. 2 / g or more is preferred, 130 m 2 / g or more is more preferred, 150 m 2 / g or more is even more preferred, 170 m 2 / g or more is particularly preferred. Also, from the viewpoints of heat generation property and processability, 220 m 2 less than / g is preferred, 200 m 2 less than / g is more preferred, 180 m 2 less than / g is even more preferred. The N2SA of silica is measured by the above measurement method.

[0144] The average primary particle diameter of silica is preferably more than 10 nm, more preferably more than 12 nm, and even more preferably more than 14 nm from the viewpoint of the effects of the present invention. Also, the average primary particle diameter is preferably less than 20 nm, more preferably less than 18 nm, and even more preferably less than 17 nm. The average primary particle diameter of silica is measured by the above measurement method.

[0145] The content of silica with respect to 100 parts by mass of the rubber component is 90 parts by mass or more, preferably more than 90 parts by mass, and more preferably 95 parts by mass or more from the viewpoint of the effects of the present invention. Also, the content of silica with respect to 100 parts by mass of the rubber component is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 110 parts by mass or less.

[0146] The content of silica in the filler is preferably more than 60% by mass, more preferably more than 70% by mass, even more preferably more than 72% by mass, and particularly preferably more than 75% by mass from the viewpoint of the effects of the present invention. Also, from the viewpoint of wear resistance performance, it is preferably 95% by mass or less, more preferably 92% by mass or less, and even more preferably 90% by mass or less.

[0147] <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. Also, the manufacturing method of the carbon black may be by combustion such as the furnace method, may be by hydrothermal carbonization (HTC), or may be by thermal decomposition of methane such as the thermal black method. As commercially available products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., 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.

[0148] 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.

[0149] 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 component that does not burn (ash content) is 13% by mass or more. That is, the ratio of the mass of the weight loss amount (carbon amount) 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.

[0150] 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, pp. 408 - 449 (2012), especially pp. 438, 440, 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) 190 - 193).

[0151] 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, European Patent Application Publication No. 3173251 treats carbon black obtained from a pyrolysis process with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Also, Patent No. 6856781 treats carbon black obtained from a pyrolysis process 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.

[0152] Commercially available recycled carbon black from companies such as Strable Green Carbon and LDCarbon can be used.

[0153] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably more than 70 m 2 / g, and more preferably 100 m 2 / g or more is more preferable, and 120 m 2 / g or more is even more preferable, and 140 m 2 / g or more is particularly preferable. Further, from the viewpoints of heat generation property and processability, less than 250 m 2 / g is preferable, and less than 220 m 2 / g or less is more preferable, and less than 190 m 2 / g or less is even more preferable. The N2SA of carbon black is measured by the above measurement method.

[0154] The average primary particle diameter of carbon black is preferably less than 32 nm, more preferably less than 28 nm, even more preferably less than 24 nm, still more preferably less than 20 nm, particularly preferably less than 21 nm, and most preferably less than 18 nm. Further, the average primary particle diameter is preferably more than 8 nm, more preferably more than 10 nm, even more preferably more than 12 nm, and particularly preferably more than 14 nm. The average primary particle diameter of carbon black is measured by the above measurement method.

[0155] From the viewpoint of wear resistance performance, the content of carbon black with respect to 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably more than 9 parts by mass. Further, the content is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably 30 parts by mass or less.

[0156] <Other fillers> The filler 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.

[0157] The total content of the filler relative to 100 parts by mass of the rubber component is preferably more than 90 parts by mass, more preferably more than 95 parts by mass, and even more preferably more than 100 parts by mass. Also, the total content is preferably less than 200 parts by mass, more preferably less than 180 parts by mass, even more preferably less than 160 parts by mass, and particularly preferably less than 150 parts by mass.

[0158] <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. may be mentioned. 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.

[0159] The content of the silane coupling agent relative to 100 parts by mass of the rubber component (when using a plurality of silane coupling agents in combination, the total amount of all) 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 abrasion 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.

[0160] [Other compounding agents] In addition to the rubber component and the filler, the rubber composition according to the present embodiment may appropriately contain compounding agents generally used in the conventional tire industry, such as plasticizers, vulcanized rubber particles, processing aids, waxes, stearic acid, zinc oxide, anti-aging agents, vulcanizing agents, vulcanization accelerators, and the like.

[0161] [Plasticizer] A plasticizer is a material that imparts plasticity to the rubber component, and is a concept that includes both plasticizers that are liquid at 25°C and plasticizers that are solid at normal temperature (25°C). Examples of plasticizers include resin components, oils, liquid rubbers, ester-based plasticizers, and the like. These plasticizers may be derived from mineral resources such as petroleum and natural gas, or may be derived from biomass. Also, low-molecular-weight hydrocarbon components obtained by thermally decomposing and extracting used tires and products containing various components may be used as plasticizers. These plasticizers may be used alone or in combination of two or more.

[0162] (Resin component) The resin component is not particularly limited, but resin components commonly used in the tire industry can be used. For example, tackifying resins such as dicyclopentadiene-based resins, aromatic vinyl-based resins, coumarone-based resins, indene-based resins, C9-based resins, C5-based resins, C5C9-based resins, terpene-based resins, rosin-based resins, and phenol-based resins can be mentioned. These resin components may be used alone or in combination of two or more. The rubber composition according to the present embodiment preferably contains a resin component containing dicyclopentadiene, styrene, and indene as monomer components.

[0163] ≪Dicyclopentadiene resin≫ The "dicyclopentadiene resin" refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as a monomer component, and may be hydrogenated or modified thereof. Examples of the dicyclopentadiene resin include DCPD / C9 resins containing dicyclopentadiene and the C9 fraction described below as monomer components (the DCPD / C9 resin may be hydrogenated or modified thereof), and DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components are particularly preferred. As the dicyclopentadiene resin, for example, those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., etc. can be used. These dicyclopentadiene resins may be used alone or in combination of two or more.

[0164] ≪Aromatic vinyl resin≫ The "aromatic vinyl resin" refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. as the monomer component with the highest content, and may be hydrogenated or modified 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 Crayton, Eastman Chemical, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0165] ≪Coumarone resin≫ The term "coumarone resin" refers to a resin containing coumarone as a monomer component, which may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These coumarone resins may be used alone or in combination of two or more.

[0166] ≪Indene resin≫ The term "indene resin" refers to a resin containing indene as a monomer component, which may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These indene resins may be used alone or in combination of two or more.

[0167] ≪C9 resin≫ The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, which may be a polymer of 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, it may be hydrogenated or modified. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used alone or in combination of two or more.

[0168] ≪C5 resin≫ The term "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, which may be hydrogenated or modified. Examples of the C5 fraction include petroleum fractions corresponding to 4 to 5 carbon atoms such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used alone or in combination of two or more.

[0169] ≪C5C9 resin≫ The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, which may be hydrogenated or modified. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA Co., Ltd., etc. can be used. These C5C9 resins may be used alone or in combination of two or more.

[0170] ≪Terpene resin≫ The term "terpene resin" refers to a resin containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the monomer component with the highest content, which may be hydrogenated or modified. 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 aromatic compounds serving as monomer components of aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, divinyltoluene, etc. Examples of phenolic compounds serving as monomer components of terpene phenol resins include phenol, bisphenol A, cresol, xylenol, etc. These terpene resins may be used alone or in combination of two or more.

[0171] ≪Rosin resin≫ The "rosin resin" refers to a resin containing rosin acid compounds such as abietic acid, neoabietic acid, palustric acid, isopimaric acid, etc., and may be those obtained by hydrogenating or modifying them. The rosin resin is not particularly limited, and examples include natural resin rosin, rosin-modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. These rosin resins may be used alone or in combination of two or more.

[0172] ≪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. 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. These phenolic resins may be used alone or in combination of two or more.

[0173] ≪Softening point≫ From the viewpoint of wet grip performance, the softening point of the resin component is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. Further, 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 is measured by the above measurement method.

[0174] ≪Content≫ The total content of the resin component with respect to 100 parts by mass of the rubber component is preferably more than 10 parts by mass, more preferably more than 20 parts by mass, even more preferably more than 24 parts by mass, and particularly preferably 30 parts by mass or more. On the other hand, from the viewpoint of suppressing exothermicity, the content is preferably less than 100 parts by mass, more preferably less than 80 parts by mass, and even more preferably 45 parts by mass or less.

[0175] The content of the dicyclopentadiene-based resin 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, still more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. On the other hand, from the viewpoint of suppressing exothermicity, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 45 parts by mass or less.

[0176] (Oil) Examples of the oil include mineral oil, vegetable oil, animal oil, etc. Further, from the viewpoint of life cycle assessment, it is also possible to use waste oil after being used in a rubber mixer or an engine, or refined waste cooking oil used in a restaurant.

[0177] In this specification, the mineral oil refers to an oil derived from mineral resources such as petroleum and natural gas. Examples of the mineral oil include paraffinic oil (mineral oil), naphthenic oil, aromatic oil, etc. Specific examples of the 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, an oil with a low content of polycyclic aromatic (PCA) compounds can be used for environmental measures. Examples of the low PCA content oil include MES, TDAE, heavy naphthenic oil, etc.

[0178] As used herein, the term "vegetable oil" includes, 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, grapeseed oil, wood rosin, etc. Further, as vegetable oils, there may be mentioned refined oils (such as salad oil) obtained by refining the above oils, transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, heat-polymerized oils obtained by heat-polymerizing the above oils, oxidative-polymerized oils obtained by oxidizing the above oils, waste cooking oils recovered from those used as edible oils, etc. Note that the vegetable oil may be liquid or solid at normal temperature (25°C). These may be used alone or in combination of two or more. Further, the vegetable oil is a component contained in the above-mentioned plasticizer and may be used in combination with other plasticizers. Further, a part of the plasticizer component in a known rubber composition may be equivalently replaced with these vegetable oils so as to satisfy the relationship of the present invention.

[0179] The vegetable oil according to the present embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. As used herein, 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 heat polymerization, oxidative polymerization, etc. Further, the acylglycerol may be liquid or solid at normal temperature (25°C).

[0180] The method for confirming whether the acylglycerol is contained in the rubber composition is not particularly limited, but for example, the following 1It can be confirmed by 1H-NMR measurement. Specifically, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room 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 around 5.26 ppm, around 4.28 ppm, and around 4.15 ppm are observed. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester groups. In this paragraph, "around" means a range of ±0.10 ppm.

[0181] The fatty acid is not particularly limited and may be an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0182] Among them, it is desirable that the fatty acid contains 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. In addition, in order to produce a vegetable oil containing such a fatty acid, plants may be improved by variety improvement, genetic recombination, etc.

[0183] As the vegetable oil, for example, those commercially available from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kogyo Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0184] Examples of animal oils include fish oil, beef tallow, or oleyl alcohol that can be derived therefrom.

[0185] When contained, the content relative to 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, still more preferably more than 15 parts by mass, and particularly preferably 20 parts by mass or more from the viewpoint of processability. Further, from the viewpoint of abrasion resistance performance, it is preferably less than 100 parts by mass, more preferably less than 50 parts by mass, and still more preferably 30 parts by mass or less.

[0186] (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). For example, 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. can be mentioned. These liquid rubbers may be used alone or in combination of two or more.

[0187] (Ester plasticizer) Examples of the ester plasticizer 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.

[0188] The content of the plasticizer relative to 100 parts by mass of the rubber component (when using a plurality of plasticizers in combination, the total amount of all) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, further preferably 40 parts by mass or more, and particularly preferably more than 50 parts by mass from the viewpoint of wet grip performance. From the viewpoint of processability, it is preferably less than 110 parts by mass, more preferably less than 100 parts by mass, further preferably less than 80 parts by mass, and particularly preferably 70 parts by mass or less.

[0189] (Vulcanized rubber particles) Vulcanized rubber particles are particles made of vulcanized rubber. Specifically, rubber powder etc. defined 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 preferred. These may be used alone or in combination of two or more.

[0190] The vulcanized rubber particles are not particularly limited, and may be non-modified vulcanized rubber particles or modified vulcanized rubber particles.

[0191] As commercially available products of vulcanized rubber, for example, products of Lehigh, Murakami Rubber Industry Co., Ltd. etc. can be used.

[0192] (Processing aid) Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. As the processing aid, for example, those commercially available from Schill+Seilacher, Performance Additives etc. can be used.

[0193] When contained, 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 part by mass, and still more preferably more than 1.5 parts by mass from the viewpoint of exerting the effect of improving processability. Further, from the viewpoints of abrasion resistance and breaking strength, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and still more preferably less than 5.0 parts by mass.

[0194] (Wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be preferably used. Examples thereof include mineral waxes and plant-derived waxes. 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, for example, those commercially available from Ouchi Shinsei Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramoelt Co., etc. can be used. These waxes may be used alone or in combination of two or more.

[0195] When contained, 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 still more preferably more than 1.5 parts by mass from the viewpoint of the weather resistance of the rubber. Further, from the viewpoint of preventing 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 still more preferably less than 5.0 parts by mass.

[0196] (Stearic acid) When stearic acid is contained, 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 processability. Further, from the viewpoint of vulcanization rate, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0197] (Zinc oxide) When zinc oxide is contained, 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 processability. Further, from the viewpoint of abrasion resistance performance, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0198] (Antioxidant) 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 Co., etc. can be used. These anti-aging agents may be used alone or in combination of two or more.

[0199] When containing an anti-aging agent, the content per 100 parts by mass of the rubber component (the total amount of all when using a plurality of anti-aging agents in combination) is preferably more than 1.0 part by mass, more preferably more than 2.0 parts by mass, and even more preferably more than 2.5 parts by mass from the viewpoint of the ozone crack resistance of the rubber. Also, from the viewpoints of abrasion resistance performance and wet grip performance, it is preferably less than 10 parts by mass, more preferably less than 8.0 parts by mass, and even more preferably less than 5.0 parts by mass.

[0200] (Vulcanizing agent) 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.

[0201] From the viewpoint of ensuring a sufficient vulcanization reaction, the content of sulfur based on 100 parts by mass of the rubber component when sulfur is contained is preferably more than 0.5 part by mass, more preferably more than 1.5 parts by mass, still more preferably more than 1.0 part by mass, and particularly preferably 1.5 parts by mass or more. Further, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 3.0 parts by mass, and still more preferably less than 2.0 parts by mass. In addition, when oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0202] As a vulcanizing agent other than sulfur, known organic crosslinking agents can also be used. The organic crosslinking agent is not particularly limited as long as it can form a crosslinking chain other than a polysulfide bond. For example, alkylphenol sulfur chloride condensate, sodium 1,6-hexamethylene-dithiocarbonate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, dicumyl peroxide, etc. can be mentioned, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane is preferred. These organic crosslinking agents can be those commercially available from Taoka Chemical Industry Co., Ltd., Rancess Co., Ltd., Flexsys Co., etc.

[0203] (Vulcanization accelerator) The vulcanization accelerator is not particularly limited. For example, sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiourea-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, aldehyde-amine-based vulcanization accelerators, aldehyde-ammonia-based vulcanization accelerators, imidazoline-based vulcanization accelerators, xanthate-based vulcanization accelerators, caprolactam disulfide, etc. may be mentioned. These vulcanization accelerators may be used alone or in combination of two or more. Among them, from the viewpoint of more suitably obtaining the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators are preferred.

[0204] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc.

[0205] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salt, di-2-benzothiazolyldisulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, etc.

[0206] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc.

[0207] Examples of thiuram vulcanization accelerators include tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like.

[0208] Examples of thiourea vulcanization accelerators include thiourea compounds such as thiocarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, and diorthotolylthiourea, N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea, and the like.

[0209] Examples of dithiocarbamate vulcanization accelerators include piperidinium pentamethylenedithiocarbamate (PPDC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), zinc dibenzyldithiocarbamate (ZDBzC), zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), zinc N-pentamethylenedithiocarbamate (ZnPDC), sodium dibutyldithiocarbamate (NaBDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate (FeMDC), tellurium diethyldithiocarbamate (TeEDC), and the like.

[0210] When containing a vulcanization accelerator, the content with respect to 100 parts by mass of the rubber component (the total amount of all when using a plurality of vulcanization accelerators in combination) is preferably more than 3.0 parts by mass, more preferably more than 4.0 parts by mass, and still more preferably 5.0 parts by mass or more. Further, the content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably less than 8.0 parts by mass, more preferably less than 7.0 parts by mass, and still more preferably less than 6.0 parts by mass.

[0211] In this specification, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the various materials from carbon dioxide, the carbon dioxide may be directly converted, or the methane obtained through the methanation process of synthesizing methane from carbon dioxide may be converted.

[0212] [Manufacturing] The rubber composition according to this embodiment 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.).

[0213] The kneading process includes, for example, a base kneading process of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and a final kneading (F kneading) process of adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading process and kneading them. Furthermore, the base kneading process can also be divided into a plurality of processes if desired. In the case of dividing the base kneading process, the method may be (1) a method in which a part of the compounding agent and the additive are kneaded in advance to form a masterbatch, and then the remaining compounding agent and additive are added to the obtained masterbatch and kneaded, or (2) a method in which all the compounding agents and additives kneaded in the base kneading process are kneaded at once, and then the mill of the kneaded product is performed one or more times. In the method of (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.

[0214] The kneading conditions are not particularly limited. For example, in the base kneading process, kneading at a discharge temperature of 150 to 170°C for 3 to 10 minutes, and in the final kneading process, kneading at 70 to 110°C for 1 to 5 minutes can be mentioned. 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.

[0215] The tire of this embodiment having a tread portion composed of the rubber composition according to this embodiment can be manufactured by a conventional method. That is, the tire is produced by extruding an unvulcanized rubber composition prepared by blending each of the above components as required with respect to the rubber component into the shape of the tread portion, and then bonding and molding the thus obtained tread portion together with other tire members on a tire molding machine by a conventional method to form an unvulcanized tire, and then heating and pressurizing the thus obtained unvulcanized tire 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.

[0216] [Use] The tire of this embodiment 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 load tire, a run-flat tire. Note that a passenger car tire is a tire assumed to be mounted on an automobile that runs on four wheels, and refers to a tire having a maximum load capacity of less than 1400 kg. Further, a heavy load tire refers to a tire having a maximum load capacity of 1400 kg or more. Further, the tire of this embodiment can be used for winter tires such as studless tires in addition to all-season tires and summer tires.

Examples

[0217] Hereinafter, examples (Examples) considered to be preferable in carrying out the invention will be shown, but the scope of the present invention is not limited to the examples. Using the various chemicals shown below, the tires obtained according to Table 1 or Table 2 were examined, and the results calculated based on the following evaluation methods are shown in Tables 1 to 2.

[0218] [Various Chemicals] NR:TSR20 SBR1: SBR produced according to Production Example 1 below (S-SBR, Tg: -50 °C, styrene content: 25% by mass, vinyl content: 25 mol%, Mw: 1 million, non-oil extended) SBR2: SBR produced according to Production Example 2 below (S-SBR, Tg: -36 °C, styrene content: 38% by mass, vinyl content: 31 mol%, Mw: 1.127 million, non-oil extended) SBR3: HPR840 manufactured by JSR Corporation (S-SBR, Tg: -63 °C, styrene content: 10% by mass, vinyl content: 42 mol%, Mw: 160,000, non-oil extended) BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Industries, Ltd. (unmodified BR, cis content: 97% by mass, Mw: 440,000) Carbon black: Prototype (N2SA: 180 m 2 / g, average primary particle diameter: 16 nm) Silica: Ultrasil VN3 manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g, average primary particle diameter: 17 nm) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa GmbH Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Resin component 1: SYLVATRAXX 4401 manufactured by Cray Valley (α-methylstyrene resin, softening point: 85 °C) Resin component 2: SYLVATRAXX 4150 manufactured by Cray Valley (politerpene resin, softening point: 115 °C) Resin component 3: Oppera PR-395 manufactured by ExxonMobil (hydrogenated DCPD / C9 resin, resin containing dicyclopentadiene, styrene and indene as monomer components, softening point: 118 °C) Oil: VivaTec 500 manufactured by H&R Co., Ltd. (TDAE oil) Wax: Ozace 0355 (paraffin wax) manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Stearic acid: Bead stearic acid Camellia manufactured by NOF Corporation Zinc oxide: Zinc white No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powder sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Vulcanization accelerator 2: Nocceler D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0219] (Production Example 1: Production of SBR1) Charge cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene into a nitrogen-substituted autoclave reactor. Adjust the ratio of styrene and 1,3-butadiene so that the styrene content is 25% by mass. After adjusting the temperature of the contents of the reactor to 20°C, add n-butyllithium to initiate polymerization. Polymerize under adiabatic conditions, and the maximum temperature reaches 80°C. After confirming the formation of a polymer with Mw of 1,000,000 by GPC, pour the polymerization solution into 4 L of ethanol and recover the precipitate. After air-drying the obtained precipitate, perform vacuum drying at 80°C / 10 Pa or less until the loss on drying becomes 0.1% to obtain SBR1.

[0220] (Production Example 2: Production of SBR2) Charge cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene into a nitrogen-substituted autoclave reactor. Adjust the ratio of styrene and 1,3-butadiene so that the styrene content is 20% by mass. After adjusting the temperature of the contents of the reactor to 20°C, add n-butyllithium to initiate polymerization. Polymerize under adiabatic conditions, and the maximum temperature reaches 80°C. After confirming the formation of a polymer with Mw of 700,000 by GPC, pour the polymerization solution into 4 L of ethanol and recover the precipitate. After air-drying the obtained precipitate, perform vacuum drying at 80°C / 10 Pa or less until the loss on drying becomes 0.1% to obtain SBR2.

[0221] (Examples and Comparative Examples) According to the formulation shown in Table 1 or Table 2, using a 1.7 L sealed Banbury mixer, chemicals other than sulfur and vulcanization accelerators are kneaded at a discharge temperature of 160 °C for 4 minutes to obtain a kneaded product. Next, using an open roll, sulfur and vulcanization accelerators are added to the obtained kneaded product and kneaded until the temperature reaches 105 °C for 4 minutes to obtain an unvulcanized rubber composition. Using the obtained unvulcanized rubber composition, it is molded according to the shape of the tread portion and bonded together with other tire members to produce an unvulcanized tire, which is vulcanized at 170 °C to obtain each test tire (size: 205 / 65R15, rim: 15×6JJ, internal pressure: 230 kPa). The tread pattern of the tire with a land ratio of 0.68 is shown in Fig. 3 (the groove depth at the deepest part of the circumferential groove existing in the shoulder region is 6.0 mm).

[0222] (Measurement of Acetone Extraction Amount (AE)) Regarding the rubber test pieces prepared by cutting out from the tread portion of each test tire, the AE amount is measured for each of them. The AE amount can be obtained by immersing each rubber test piece in acetone at room temperature (around 25 °C) for 24 hours to extract the soluble components, measuring the mass of each test piece before and after extraction, and using the following formula. Acetone extraction amount (mass%) = {(mass of the vulcanized rubber test piece before extraction - mass of the vulcanized rubber test piece after extraction) / (mass of the rubber test piece before extraction)} × 100

[0223] (Temperature Distribution Curve of tanδ) Regarding each rubber test piece prepared by cutting out from the tread portion of each test tire with a length of 20 mm × width of 4 mm × thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction, using a dynamic viscoelasticity measuring device (E-Plexor series manufactured by GABO), under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2 °C / min, in the temperature range from -20 °C to 70 °C, the temperature distribution curve of tanδ is measured. Then, based on the obtained temperature distribution curve of tanδ, the tanδ and the half-width at the peak position within the range of -20 °C to -70 °C are measured.

[0224] <Measurement of tanδ at 0°C> For each rubber test piece prepared by cutting out from the tread portion of each test tire with a length of 20 mm × width of 4 mm × thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction, using a dynamic viscoelasticity measuring device (Implex series manufactured by GABO), measure the loss tangent tanδ under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2.5%, and an elongation mode.

[0225] <Measurement of glass transition temperature (Tg) of rubber composition> For each rubber test piece prepared by cutting out from the tread portion of each test tire with a length of 20 mm × width of 4 mm × thickness of 1 mm such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction, using a dynamic viscoelasticity measuring device (Implex series manufactured by GABO), measure the temperature distribution curve of tanδ in the range of -60°C to 40°C under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a heating rate of 2°C / min, and determine the temperature (tanδ peak temperature) corresponding to the largest tanδ value in the obtained temperature distribution curve as the Tg of the rubber composition.

[0226] <Wet grip performance> Mount each test tire on the four wheels of a FF passenger car with a displacement of 2000 cc, and measure the braking distance from the point where the brakes are applied at a speed of 100 km / h on a wet asphalt road surface. Taking the braking distance of the test tire of the reference comparative example (Comparative Example 2) as 100, express the wet grip performance of each tire in terms of an index according to the following calculation formula. The larger the index, the better the wet grip performance. (Wet grip performance index) = (Braking distance of the tire of the reference comparative example) / (Braking distance of each test tire) × 100

[0227]

Table 1

[0228]

Table 2

[0229] <Embodiment> Examples of embodiments of the present invention are shown below. 〔1〕A tire having a tread portion, wherein the tread portion has one or more circumferential grooves, the tread portion is composed of a rubber composition containing a rubber component and silica, the rubber component contains an isoprene-based rubber and a styrene-butadiene rubber, the content of the isoprene-based rubber in the rubber component is 40% by mass or more, the content of the styrene-butadiene rubber in the rubber component is 40% by mass or more, the content of the silica with respect to 100 parts by mass of the rubber component is 90 parts by mass or more, the styrene content S1 (mass%) of the styrene-butadiene rubber is 30 or less, let the land ratio of the tire be R, when the tanδ at 0 °C of the rubber composition is defined as 0 °C tanδ, a tire in which 0 °C tanδ × R is 0.30 or more. 〔2〕The tire according to 〔1〕 above, wherein the half-value width of the peak in the range of -20 °C to -70 °C in the tanδ temperature distribution curve of the rubber composition is 30 °C or less. 〔3〕The tire according to 〔1〕 or 〔2〕 above, when the acetone extraction amount of the rubber composition is AE (mass%), AE is 22.0 or more. 〔4〕The tire according to any one of 〔1〕 to 〔3〕 above, wherein 0 °C tanδ is 0.45 or more. 〔5〕The tire according to any one of 〔1〕 to 〔4〕 above, when the groove depth at the deepest part of the circumferential groove is H (mm), 0 °C tanδ × H is 3.00 or more. 〔6〕The tire according to any one of 〔1〕 to 〔5〕 above, when the total thickness of the tread portion is T (mm), 0 °C tanδ × T is 3.50 or more. 〔7〕When the groove depth at the deepest part of the circumferential groove is H (mm) and the acetone extraction amount of the rubber composition is AE (mass %), the tire according to any one of the above [1] to [6], wherein AE × H is 140.0 or more. 〔8〕The tire according to any one of the above [1] to [7], wherein the rubber composition contains a resin component containing dicyclopentadiene, styrene, and indene as monomer components. 〔9〕The tire according to any one of the above [1] to [8], wherein the rubber composition contains more than 100 parts of silica per 100 parts by mass of the rubber component. 〔10〕The tire according to any one of the above [1] to [9], wherein the rubber composition contains a mercapto-based silane coupling agent. 〔11〕The tread portion has two or more land portions partitioned by the one or more circumferential grooves, at least one of the land portions has a lateral groove extending radially inward of the tire, and the lateral groove has a portion where the groove width is wider than the groove width on the tread surface in a cross section perpendicular to the extending direction. The tire according to any one of the above [1] to

[10] . 〔12〕When a region of 30% of the tread contact width centered on the tire equator on the tread surface is defined as the center region, and regions on both outer sides of the center region and within the tread contact width are defined as a pair of shoulder regions, the groove depth at the deepest part of the circumferential groove present in the shoulder region is 6.0 mm or more. The tire according to any one of the above [1] to

[11] . 〔13〕The tire according to any one of the above [1] to

[12] , wherein when the tire weight is G (kg), S1 / G is 3.0 or less. 〔14〕The tire according to any one of the above [1] to

[13] , wherein S1 × R is 11.0 or more. 〔15〕The tire according to any one of the above [1] to

[14] , wherein 0℃ tanδ × R is 0.33 or more.

Explanation of Symbols

[0230] 1 Tread portion 2 Sidewall portion 3 Bead portion 4 Carcass 5 Belt layers 6 Band layers 7 Inner liner 8 Rim 9 Rim chafer 10 Clinch portion 11 Layer whose outer surface forms the tread surface (cap rubber layer) 12 Base rubber layer 13 Bead apex 14 Bead core CL Tire equator H Depth of the deepest part of the circumferential groove P Midpoint in the tire width direction N Line perpendicular to the tangent plane at point P T Total thickness of the tread portion B Thickness of the belt layer t1 Thickness of the layer whose outer surface forms the tread surface (cap rubber layer) t2 Thickness of the base rubber layer 15 Circumferential groove 16 Tread surface 17 Straight line connecting the ends of the circumferential groove 18 Extension line of the outer surface of the base rubber layer 19 Extension line of the lowest part of the circumferential groove 20 Land portion 21 Center land portion 22 Shoulder land portion 31 Lateral groove 32 Lateral groove TW Tread contact width CR Center region SR Shoulder region Te Tread contact end 40 Groove bottom 41 Groove edge 42 Groove wall W1 Opening width (groove width on the tread surface) C1 Amount of indentation from the groove edge at the groove bottom C2 Amount of indentation from the groove edge at the groove bottom

Claims

1. A tire having a tread portion, wherein the tread portion has one or more circumferential grooves, the tread portion is composed of a rubber composition containing a rubber component and silica, the rubber component contains an isoprene-based rubber and a styrene-butadiene rubber, the content of the isoprene-based rubber in the rubber component is 40% by mass or more, the content of the styrene-butadiene rubber in the rubber component is 40% by mass or more, the content of the silica relative to 100 parts by mass of the rubber component is 90 parts by mass or more, the styrene content S1 (mass%) of the styrene-butadiene rubber is 30 or less, the land ratio of the tire is R, when the tanδ of the rubber composition at 0°C is defined as 0°C tanδ, a tire wherein 0°C tanδ × R is 0.30 or more.

2. The tire according to claim 1, wherein the half-value width of the peak in the range of -20°C to -70°C in the tanδ temperature distribution curve of the rubber composition is 30°C or less.

3. The tire according to claim 1 or 2, wherein when the acetone extraction amount of the rubber composition is AE (mass%), AE is 22.0 or more.

4. The tire according to claim 1 or 2, wherein 0°C tanδ is 0.45 or more.

5. The tire according to claim 1 or 2, wherein when the groove depth at the deepest part of the circumferential groove is H (mm), 0°C tanδ × H is 3.00 or more.

6. The tire according to claim 1 or 2, wherein when the total thickness of the tread portion is T (mm), 0°C tanδ × T is 3.50 or more.

7. The tire according to claim 1 or 2, wherein when the groove depth at the deepest part of the circumferential groove is H (mm) and the acetone extraction amount of the rubber composition is AE (mass%), AE × H is 140.0 or more.

8. The tire according to claim 1 or 2, wherein the rubber composition contains a resin component containing dicyclopentadiene, styrene, and indene as monomer components.

9. The tire according to claim 1 or 2, wherein the rubber composition contains more than 100 parts of silica relative to 100 parts by mass of the rubber component.

10. The tire according to claim 1 or 2, wherein the rubber composition contains a mercapto-based silane coupling agent.

11. The tread portion has two or more land portions partitioned by the one or more circumferential grooves, at least one of the land portions has a transverse groove extending radially inward in the tire radius direction, and the transverse groove has a portion where the groove width is wider than the groove width on the tread surface in a cross section perpendicular to the extending direction. The tire according to claim 1 or 2.

12. When a region of 30% of the tread contact width centered on the tire equator on the tread surface is defined as a center region, and regions on both outer sides of the center region and within the tread contact width are defined as a pair of shoulder regions, the groove depth at the deepest part of the circumferential groove existing in the shoulder region is 6.0 mm or more. The tire according to claim 1 or 2.

13. When the tire weight is G (kg), S1 / G is 3.0 or less. The tire according to claim 1 or 2.

14. S1×R is 11.0 or more. The tire according to claim 1 or 2.

15. 0°C tanδ×R is 0.33 or more. The tire according to claim 1 or 2.

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