TIRES

Abstract

An object of the present invention is to provide a tire that can achieve both wet grip performance during high-speed operation and abrasion resistance at low temperatures. A pneumatic tire is provided comprising a tread section, wherein the tread section is composed of a rubber composition comprising 50 parts by mass or more of silicon dioxide based on 100 parts by mass of a rubber component, wherein the rubber component comprises more than 50% by mass of a butadiene rubber and a styrene-butadiene rubber, wherein the total styrene content in the rubber component is 25% by mass or less, and wherein, when A BR A represents a mass % content of butadiene rubber in the rubber component, and L represents a percentage elevation of a tread surface of the tread section. BR and L satisfy the following inequality: A BR × L > 3000.

Description

TECHNICAL FIELD

[0001] The present invention relates to a tire. STATE OF THE ART

[0002] To date, various methods for improving wet grip performance and abrasion resistance have been investigated. For example, Patent Literature 1 discloses a tire rubber composition comprising a diene-based rubber (A) containing a predetermined amount of a specific conjugated diene-based rubber represented by a predetermined formula, silica whose CTAB adsorption specific surface area is within a predetermined range, and a silane coupling agent represented by a predetermined formula, and a pneumatic tire using the tire rubber composition for a tire tread. CITATION LISTPATENT LITERATURE

[0003] Patent Literature 1: JP 2017-141405 A SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0004] However, since wet grip performance and abrasion resistance are fundamentally contradictory, it is difficult to improve both performances simultaneously, and thus further improvements are required to achieve both performances.

[0005] An object of the present invention is to provide a tire that can achieve both wet grip performance during high-speed running and abrasion resistance at a low temperature. SOLUTION TO THE PROBLEM

[0006] The present invention relates to a tire below: Pneumatic tire comprising a tread portion, wherein the tread portion is constructed of a rubber composition comprising 50 parts by mass or more of silica based on 100 parts by mass of a rubber component, wherein the rubber component comprises more than 50% by mass of a butadiene rubber and a styrene-butadiene rubber, wherein a total amount of styrene in the rubber component is 25 mass% or less, and where, if A BR represents a content in mass% of butadiene rubber in the rubber component and L represents a projection ratio in % of a tread surface of the tread portion, A BR and L satisfy the following inequality: ABR×L>3000. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0007] According to the present invention, a tire can be provided which can achieve both wet grip performance during high-speed running and abrasion resistance at a low temperature. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is a view schematically illustrating an entire ground contact area of ​​a tread surface. Fig. 2 is a developed view of a portion of a tread of a tire having small holes in shoulder areas. Fig. 3 is a developed view of a portion of a tread of a tire having narrow circumferential grooves in shoulder areas. Fig. 4 is a developed view of a portion of a tread of a tire having widened circumferential grooves in land portions closest to a tire centerline. Fig. 5 is a view showing a cross section of the widened circumferential groove in Fig. 4 along a plane passing through a tire rotation axis. DESCRIPTION OF EMBODIMENTS

[0008] The tire which is an embodiment of the present invention is a pneumatic tire comprising a tread portion, wherein the tread portion is constructed of a rubber composition comprising 50 parts by mass or more of silica based on 100 parts by mass of a rubber component, wherein the rubber component comprises more than 50% by mass of a butadiene rubber and a styrene-butadiene rubber, wherein a total amount of styrene in the rubber component is 25 mass% or less, and where, if A BR represents a content in mass% of butadiene rubber in the rubber component and L represents a projection ratio in % of a tread surface of the tread portion, A BR and L satisfy the following inequality: ABR×L>3000.

[0009] Although not intended to be bound by theory, in the present invention, the following can be regarded as a mechanism by which both wet grip performance during high-speed running and abrasion resistance at a low temperature can be achieved.

[0010] That is, (1) in the rubber composition constituting the tread portion, abrasion resistance is improved by using a butadiene rubber (BR) as a main polymer of the rubber component; (2) following ability to a road surface of the tread portion is improved by including a certain amount or more of silica, thereby improving wet grip performance; (3) by further including a styrene-butadiene rubber (SBR) in the rubber component and setting the total styrene amount of the rubber component to a certain value or less, the SBR is made easily compatible with the BR, and SBR domains in which silicas are easily distributed are dispersed in a BR phase, thereby effectively reinforcing the BR to maintain abrasion resistance and improving wet grip performance; (4) the rubber composition,The rubber component comprising such a rubber component with a low total styrene content has a low glass transition temperature, and therefore, temperature dependence is reduced, and grip performance when the tire heats up due to high-speed running and abrasion resistance during a low-temperature period are less likely to decrease. (5) A ground contact area is increased by keeping a high elevation ratio of the tread surface, thereby dispersing abrasion energy introduced from the road surface to the tread surface, so that it is believed that tread wear can be suppressed. It is believed that with the cooperation of (1) to (5), both wet grip performance during high-speed running and abrasion resistance at a low temperature can be achieved.

[0011] If A STY represents a total amount of styrene in mass%, meet ABR , L and A STY prefers the following inequality: (ABR / ASTY)×L>130

[0012] Since A BR , L and A STY are restricted in an increase direction, an increase direction and a decrease direction respectively, they are believed to be advantageous for both wet grip performance during high-speed running and abrasion resistance at a low temperature.

[0013] It is preferable that the rubber composition comprises at least one type of hydrocarbon resin and that a content of the hydrocarbon resin in the rubber composition is 5 mass% or more.

[0014] Hydrocarbon resins, like silica, are easy to disperse in the SBR domains, and therefore, by further combining a certain amount or more of hydrocarbon resin, the SBR domains in which it is easy to disperse hydrocarbon resins are dispersed in the BR phase, which is considered beneficial for both wet grip performance and abrasion resistance.

[0015] A content of the silica based on 100 parts by mass of the rubber component is preferably 100 parts by mass or more.

[0016] It is believed that following ability against a road surface of the tread portion derived from the silica is further improved and wet grip performance is improved.

[0017] The glass transition temperature of the rubber composition described above is preferably lower than -30 °C.

[0018] This is because it is believed that temperature dependence of the rubber composition is reduced and grip performance when the tire heats up due to high-speed running and abrasion resistance during a period of low temperature are less likely to decrease.

[0019] The right-hand side of inequality (1) is preferably 3250, more preferably 3500.

[0020] It is believed that improvement in abrasion resistance can be expected by increasing a butadiene rubber content and a pitch ratio in a product.

[0021] A salary A BR of the butadiene rubber in the rubber component is preferably less than 70 mass%.

[0022] As the content of butadiene rubber in the rubber component increases, abrasion resistance at a low temperature tends to improve, but as the Tg decreases, a loss in a temperature range (0 °C-tanδ) generally considered to contribute to wet grip also decreases, which destroys a balance with wet grip performance during high-speed running, and it is therefore considered necessary to adjust the content to be less than 70 mass% to achieve both performances.

[0023] The glass transition temperature of the styrene-butadiene rubber is preferably lower than -30 °C.

[0024] It is believed that the glass transition temperature of the rubber composition is lowered and grip performance when the tire heats up due to high-speed running and abrasion resistance during a period of low temperature are further less likely to decrease.

[0025] It is preferable that the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and when a pair of land portions located on an outermost side in a tire width direction of the land portions are defined as shoulder land portions, the shoulder land portions have one or more small holes each having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 have.

[0026] Since the small holes contribute to improving drainage performance, drainage performance in a shoulder area improves, so it is believed that wet grip performance improves.

[0027] It is preferable that the tread surface has two or more circumferential main grooves extending in the tire circumferential direction and land portions separated by the circumferential main grooves, and when a pair of land portions located on the outermost side in the tire width direction of the land portions are defined as shoulder land portions, the shoulder land portions have at least one or more narrow circumferential grooves.

[0028] Since the narrow circumferential grooves contribute to improving drainage performance, drainage performance in the shoulder area improves, so it is believed that wet grip performance improves.

[0029] The tread surface has widened circumferential grooves whose groove width widens towards the inside in the tire radial direction.

[0030] Since the width of the widened circumferential groove increases as the tread portion is worn, drainage performance after tire wear improves, so it is expected that wet grip performance improves.

[0031] The widened circumferential groove is preferably at a land portion located on a tire centerline or, if a main circumferential groove is present on the tire centerline, at a land portion closest to the tire centerline.

[0032] It is believed that drainage performance after tire wear improves at a center portion in the tire width direction, so that wet grip performance improves. [Definitions]

[0033] A “standardized condition” is a condition in which a tire is rim-mounted on a standardized rim and inflated to a standardized internal pressure and no load is applied.

[0034] A "dimension of any part of the tire" is, unless otherwise specified, a value specified in a standardized condition for one occurring on the outer surface of the tire, while it is a value for one inside the tire specified in a condition in which the tire is cut along a plane containing a tire axis of rotation and the cut tire piece is held to a rim width of a standardized rim.

[0035] A "standardized rim" is a rim in a standards system containing a standard on which the tire is based, which is defined by the standard for each tire. For example, a "standardized rim" refers to a standard rim of an applicable size described in the "Jatma Year Book" of JATMA (The Japan Automobile Tire Manufacturers Association, Inc.), the "Measuring Rim" described in the "STANDARDS MANUAL" of ETRTO (The European Tire and Rim Technical Organization), or the "Design Rim" described in the "YEAR BOOK" of TRA (The Tire and Rim Association, Inc.), which are referred to in that order. If there is an applicable size at the time of reference, the rim conforms to its standard.In addition, in a case of tires not defined by the standard, the “standardized rim” refers to a rim that can be mounted and can maintain internal pressure, that is, one that has the smallest rim diameter among rims that do not cause air leakage between the rim and the tire, and secondly has the narrowest rim width.

[0036] A "standardized internal pressure" is an air pressure in a system of standards containing a standard on which the tire is based, which is defined by the standard for each tire. It refers, for example, to a "MAXIMUM AIR PRESSURE" at JATMA, "INFLATION PRESSURE" at ETRTO or a maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" at TRA, referred to in this order, as in the case of the standardized rim, and if there is an applicable size at the time of reference, the standardized internal pressure conforms to its standard.In addition, in the case of tires not defined by the standard, the standardized internal pressure shall refer to a standardized internal pressure (250 kPa or more) of another tire size (specified in the standard) for which the standardized rim is described as a standard rim, and if multiple standardized internal pressures of 250 kPa or more are described, it shall refer to a minimum value among them.

[0037] A "standardized load" is a load in a standard system containing a standard on which the tire is based, which is defined by the standard for each tire, for example, a "MAXIMUM LOAD CAPACITY" in JATMA, a "LOAD CAPACITY" in ETRTO, or a maximum value described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in TRA, which is referred to in this order, as in the case of a standardized rim and a standardized internal pressure, and if there is an applicable size at the time of reference, the load conforms to its standard. Then, in the case of tires not defined by the standard, a standardized load WL is calculated by the following equations. In addition, in the present specification, the "maximum load capacity" has the same meaning as the standardized load described above. WL=0.000011×V+175V=[(Dt / 2)2−(Dt / 2−Ht)2]×π×Wt V: virtual volume of tires (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: Tire section height (mm) Wt: Tire section width (mm)

[0038] A “lift ratio L (%)” is calculated from a total ground contact area and an effective ground contact area of ​​a tire by the following equation: Elevation ratio L (%) = (effective ground contact area / total ground contact area) × 100.

[0039] The "total ground contact area" is an area of ​​a tread region as obtained from a contour when a tire is pressed against the ground. The total ground contact area can be obtained by mounting a tire on a standardized rim, applying a standardized internal pressure, and allowing the tire to stand at 25°C for 24 hours, followed by painting the tire tread surface with ink, applying a standardized load (of the maximum load capacity) to the tire to press the tire vertically against a cardboard (a camber angle of 0°), and transferring the ink. The total ground contact area is determined as an average value of five areas obtained by performing the transfer process described above at a total of five locations by rotating a tire by 72°.

[0040] The "effective ground contact area" is the area of ​​a tread region where a tire contacts the ground when the tire is pressed against the ground. The effective ground contact area can be obtained by mounting a tire on a standardized rim, applying a standardized internal pressure, and allowing the tire to stand at 25°C for 24 hours. This is followed by painting the tire tread surface with ink, applying a standardized load (of maximum load capacity) to the tire to press the tire vertically against a cardboard (a camber angle of 0°), and transferring the ink. The effective ground contact area is determined as an average value of five areas obtained by performing the transfer process described above at a total of five locations by rotating a tire by 72°.

[0041] A “total styrene content (mass %)” is a total content of styrene parts contained in a total amount of rubber components, which can be calculated by Σ(styrene content (mass %) in each rubber component × content (mass %) of each rubber component in total amount of rubber components / 100). For example, if 100 mass% of a rubber component consists of 85 mass% of a styrene-butadiene rubber with 40 mass% of a styrene content, 5 mass% of a styrene-butadiene rubber with 25 mass% of a styrene content and 10 mass% of a butadiene rubber with 0 mass% of a styrene content, a total amount of styrene in the rubber component is 35.25 mass% (= 40 × 85 / 100 + 25 × 5 / 100 + 0 × 10 / 100).

[0042] A “hydrocarbon resin content” refers to a total content of all of at least one type of hydrocarbon resin contained in a rubber composition.

[0043] A "plasticizer content" also includes an amount of a plasticizer in a rubber component extended by the plasticizer. Similarly, an "oil content" also includes an amount of oil contained in the oil-extended rubber.

[0044] A "circumferential main groove" refers to a circumferential groove having a groove width of 4 mm or more in a tire width direction on a tread surface, among circumferential grooves extending continuously in a tire circumferential direction. The circumferential main groove may extend linearly along the circumferential direction, or may extend in a wave-like, sinusoidal, or zigzag shape along the circumferential direction. However, widened circumferential grooves, which will be described later, are not included.

[0045] A "land portion" is an area on a tread surface defined by a circumferential main groove, which is a portion where a tire contacts a road surface. Among land portions, a pair of land portions located on the outermost side in the tire width direction are called shoulder land portions, and a land portion present in an area sandwiched by the shoulder land portions is called a center land portion. When there is a circumferential main groove, only shoulder land portions are present, and no center land portion is present.

[0046] A "pinhole" is a small hole present on a tread surface that extends from the inner side of a tread and opens into the tread surface. Pinholes exist independently and do not communicate with circumferential grooves, lateral grooves, and the like.

[0047] A "narrow circumferential groove" refers to a circumferential groove having a groove width of less than 4 mm in a tire width direction on a tread surface, among circumferential grooves that extend continuously in a tire circumferential direction. The narrow circumferential groove may extend linearly along the circumferential direction, or may extend in a wave-like, sinusoidal, or zigzag shape along the circumferential direction. However, widened circumferential grooves, which will be described later, are not included.

[0048] A "widened circumferential groove" is a groove configured such that a groove width in a tire width direction on a tread surface is minimal and widens toward an inner side in a tire radial direction, among circumferential grooves that extend continuously in a tire circumferential direction. The widened circumferential groove may extend linearly along the circumferential direction, or may extend in a wave-like, sinusoidal, or zigzag shape along the circumferential direction. [Measurement method]

[0049] A “styrene content (mass %)” is determined by 1 H-NMR measurement calculated.

[0050] A “Vinyl content (1,2-bonded butadiene unit amount) (mol%)” is calculated by infrared absorption spectrometry according to JIS K 6239-2:2017.

[0051] A “cis content (cis-1,4-bonded butadiene unit amount) (mol%)” is calculated by infrared absorption spectrometry according to JIS K 6239-2:2017.

[0052] A "glass transition temperature (Tg) (°C)" is measured by measuring while raising the temperature at a temperature rise rate of 10 °C / min using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Inc. according to JIS K 7121. In the present invention, specifically, a Tg of each of a styrene-butadiene rubber, a butadiene rubber, and the like is measured.

[0053] The "glass transition temperature (Tg) of a rubber composition" is a temperature corresponding to a maximum value (tan δ peak temperature) within a range of -60°C or higher and 40°C or lower on a temperature distribution curve of tan δ obtained by measurement under conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±0.5%, and a temperature rise rate of 2°C / min using a dynamic viscosity measuring device (e.g., EPLEXOR series, manufactured by gabo Systemtechnik GmbH). Furthermore, when measured in the range of -60 to 40°C, if the tan δ value continues to gradually increase or decrease as the temperature rises, the glass transition temperature of the rubber composition shall be 40°C or -60°C, respectively.In addition, in the range of -60 °C or higher and 40 °C or lower, if there are two or more points indicating the maximum value, a point with the lowest temperature shall be a glass transition temperature.

[0054] A “weight-average molecular weight (Mw)” can be calculated with respect to a standard polystyrene based on measured values ​​obtained by gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0055] An “N2SA of soot” is measured according to JIS K 2.

[0056] An “N2SA of silica” is measured by the BET method according to ASTM D3037-93.

[0057] An "average primary particle size" is calculated by taking the arithmetic mean of particle sizes of 400 particles photographed with a transmission or scanning electron microscope. Regarding particle size, in a case where the particle is substantially circular, a diameter of the circle is defined as a particle size; in a case where it is needle- or rod-shaped, a minor axis is defined as a particle size; and in other cases, an equivalent circle diameter calculated from an electron microscope image is defined as a particle size. The equivalent circle diameter is calculated as "the positive square root of 4 × (particle area) / n." The average primary particle size is applied to silica, carbon black, etc.

[0058] A “softening point” is specified as a temperature at which a ball falls when the softening point defined in JIS K 6220-1:2001 is measured with a ring-and-ball softening point measuring device. [Tires]

[0059] The pneumatic tire of the present invention will be appropriately described below with reference to the drawings. However, the drawings are merely illustrative, and the present invention should not be interpreted as limited based on the drawings.

[0060] The pneumatic tire of the present invention is a tire comprising a tread portion, wherein the tread portion is composed of a predetermined rubber composition, and wherein in the rubber composition, when A BRrepresents a content in mass% of butadiene rubber in the rubber component and L represents a projection ratio in % of a tread surface at the tread portion, A BR and L satisfy the following inequality: ABR×L>3000. <Ungleichung (1)>

[0061] In the pneumatic tire of the present invention, a bump ratio L in % of a tread surface is defined as described above and calculated from a total ground contact area and an effective ground contact area of ​​the tire.

[0062] Fig.Figure 1 shows a tread area for calculating a total ground contact area obtained from a contour when the tire is pressed against the ground. As described above, the contour can be obtained by mounting a tire on a standardized rim, applying a standardized internal pressure, and allowing the tire to stand at 25°C for 24 hours, followed by painting the tire tread surface with ink, applying a standardized load (the maximum load capacity) to the tire to press the tire vertically against a cardboard (a camber angle of 0°), and transferring the ink. Fig. 1 CL is a tire centerline.

[0063] The elevation ratio is preferably 60% or more, more preferably 61% or more, even more preferably 62% or more, even more preferably 63% or more, even more preferably 64% or more, and even more preferably 65% ​​or more. Furthermore, the elevation ratio is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less.

[0064] The right-hand side of inequality (1) is preferably 3250, more preferably 3500, even more preferably 3750, and even more preferably 4000. On the other hand, an upper limit of the value of A BR × L is not particularly restricted, but can be, for example, 6500, 6000 or 5000. <Ungleichung (2)>

[0065] In the pneumatic tire of the present invention, when A STY represents a total amount of styrene in mass% in the rubber component contained in the rubber composition, A BR , L and ASTY prefers the following inequality: (ABR / ASTY)×L>130.

[0066] The right-hand side of inequality (2) is preferably 200, more preferably 300, even more preferably 360, even more preferably 450, even more preferably 550, and even more preferably 600. On the other hand, an upper limit of the value of (A BR / A STY ) × L is not particularly restricted, but can be, for example, 750, 700 or 650. <Glasübergangstemperatur von Kautschukzusammensetzung>

[0067] In the rubber composition constituting the tread portion of the pneumatic tire of the present invention, a glass transition temperature in °C of the rubber composition is preferably lower than -30 °C.

[0068] The glass transition temperature is preferably lower than -33°C, more preferably lower than -37°C, even more preferably lower than -40°C, and even more preferably lower than -42°C from the viewpoint of reducing temperature dependence of the rubber composition. On the other hand, a lower limit of the glass transition temperature is not particularly limited, but may be, for example, higher than -50°C, higher than -47°C, or higher than -45°C.

[0069] The glass transition temperature can be appropriately adjusted depending on the types and compounding amounts of the rubber component constituting the rubber composition and the types and compounding amounts of additives other than the rubber component. <Kleines Loch>

[0070] In the pneumatic tire of the present invention, it is preferable that the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and among the land portions, a pair of land portions located on an outermost side in a tire width direction are called shoulder land portions, the shoulder land portions have one or more small holes each having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 have.

[0071] Fig. Figure 2 illustrates an embodiment in which the pneumatic tire of the present invention has the small holes described above. Fig.2, small holes 4 are formed on the pair of land portions 3 present in the shoulder region of the tread surface. Since the small holes contribute to improving drainage performance, drainage performance in the shoulder region is improved, which contributes to improving wet grip performance. For example, in actual use, even if a shoulder land portion or center land portion on one side is preferentially abraded and the remaining shoulder land portion hardens over time, it is believed that with the small holes, drainage performance can be ensured and wet grip performance can be slightly improved after abrasion. The opening area of ​​the small hole to the tread surface is preferably greater than 0.1 mm. 2 , more preferably larger than 0.5 mm 2 , even more preferably greater than 1.0 mm 2 and particularly preferably larger than 1.5 mm 2. In addition, the opening area of ​​the small hole to the tread surface is preferably less than 15 mm 2 , more preferably less than 10 mm 2 , even more preferably less than 7.0 mm 2 and particularly preferably less than 5.0 mm 2 The depth of the deepest part of the small hole is preferably 3% or more, and more preferably 5% or more, of the depth of the deepest part of the circumferential main groove. Furthermore, the depth of the deepest part of the small hole is preferably 80% or less, more preferably 60% or less, and even more preferably 40% or less, of the depth of the deepest part of the circumferential main groove. <Schmale Umfangsrille>

[0072] In the pneumatic tire of the present invention, it is preferable that the tread surface has two or more circumferential main grooves extending in the tire circumferential direction and land portions separated by the circumferential main grooves, and when a pair of land portions located on the outermost side in the tire width direction of the land portions are defined as shoulder land portions, the shoulder land portions have at least one or more narrow circumferential grooves.

[0073] Fig. Figure 3 illustrates an embodiment in which the pneumatic tire of the present invention has the narrow circumferential grooves described above. Fig.3, narrow circumferential grooves 5 are formed on the pair of land portions 3 present in the shoulder region of the tread surface. Since the narrow circumferential grooves contribute to improving drainage performance, drainage performance in the shoulder region improves, which contributes to improving wet grip performance. <Verbreiterte Umfangsrille>

[0074] In the pneumatic tire of the present invention, the tread surface has widened circumferential grooves whose groove width widens toward the inside in the tire radial direction.

[0075] Fig. Figure 4 illustrates an embodiment in which the pneumatic tire of the present invention has the widened circumferential grooves described above. Fig.4, line-shaped circumferential widened grooves 6 are formed on two land portions 3, which abut a main circumferential groove 2 extending on the tire centerline. The circumferential widened groove may extend, for example, in a wave shape, a sinusoidal shape, or a zigzag shape along the circumferential direction. Furthermore, land portions at which the circumferential widened grooves are formed are not particularly limited, but the circumferential widened grooves are preferably formed on land portions located on the tire centerline, or preferably formed on a land portion closest to the tire centerline, such as the circumferential widened grooves 6 in Fig.4, when a circumferential main groove is present on the tire centerline. In addition, the land portion closest to the tire centerline is a land portion in which a distance between the end on the inside of the land portion in the tire width direction and the tire centerline is minimal.

[0076] Fig. 5 shows a cross-section of the widened circumferential groove 6. In Fig. 5, the groove width of the widened circumferential groove increases smoothly toward the inside in the tire radial direction, but the increase of groove width is not limited to such an aspect, and the groove width may, for example, increase while repeating small increases and decreases in a curved or stepped shape. [Rubber composition]

[0077] The rubber composition constituting the tread portion of the pneumatic tire of the present invention is described below.

[0078] The rubber composition according to the present invention comprises 50 parts by mass or more of silica based on 100 parts by mass of the rubber component. <kautschukkomponente>

[0079] The rubber component comprises more than 50 mass% of a butadiene rubber (BR) and a styrene-butadiene rubber (SBR). Furthermore, the rubber component may comprise rubber components other than BR and SBR, such as an isoprene-based rubber (IR-based rubber). Furthermore, the rubber component may consist of more than 50 mass% of a BR and an SBR. (SBR)

[0080] The SBR is not particularly limited; examples include a solution-polymerized SBR (S-SBR), an emulsion-polymerized SBR (E-SBR), modified SBRs (a modified S-SBR, a modified E-SBR) thereof, and the like. Examples of the modified SBR include an SBR modified at its terminal and / or main chain, a modified SBR coupled with tin, a silicon compound, etc. (a modified SBR of condensate or having a branched structure, etc.), and the like. Among them, an S-SBR and a modified SBR are preferable. Furthermore, hydrogenated SBRs (hydrogenated SBRs) and the like can also be used. The SBR can be used alone, or two or more of them can be used in combination.

[0081] Examples of the S-SBR that can be used in the present invention include S-SBRs manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomer Co., Ltd., etc.

[0082] A styrene content of an SBR is preferably low from the viewpoint of suppressing temperature dependence of the rubber composition, for example, less than 40 mass%, more preferably less than 30 mass%, more preferably 20 mass% or less, and even more preferably 15 mass% or less. A lower limit of the styrene content is not particularly limited, but is usually approximately greater than 1 mass%, greater than 3 mass%, or greater than 5 mass%. Furthermore, the styrene content of the SBR is measured by the measurement method described above.

[0083] A vinyl content of the SBR is preferably greater than 10 mol%, more preferably greater than 13 mol%, and even more preferably greater than 15 mol% from the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Furthermore, from the viewpoints of preventing an increase in temperature dependence, elongation at break, and abrasion resistance, the vinyl content of the SBR is preferably less than 50 mol%, more preferably less than 40 mol%, and even more preferably less than 30 mol%. Furthermore, the vinyl content of the SBR (1,2-bonded butadiene unit amount) is measured by the measurement method described above.

[0084] A glass transition temperature (Tg) of an SBR is preferably lower than -30°C from the viewpoint of suppressing temperature dependence of the rubber composition. The Tg of the SBR is preferably lower than -40°C, more preferably lower than -50°C, and even more preferably lower than -55°C. Moreover, the Tg is usually higher than -80°C, higher than -70°C, or higher than -65°C. In addition, the Tg of the SBR is measured by the measurement method described above.

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

[0086] From the viewpoint of wet grip performance, the content of SBR in the rubber component is preferably more than 25 mass%, more preferably more than 30 mass%, and even more preferably 35 mass% or more. On the other hand, from the viewpoint of effects of the invention, the content of SBR in the rubber component is preferably 50 mass% or less, more preferably less than 48 mass%, and even more preferably 45 mass% or less. (BR)

[0087] The BR is not particularly limited, and those commonly used in the tire industry can be used, such as a BR with a cis content of less than 50 mol% (a low-cis BR), a BR with a cis content of more than 90 mol% (a high-cis BR), a rare earth-based butadiene rubber synthesized using a rare earth element-based catalyst (a rare earth-based BR), a BR containing a syndiotactic polybutadiene crystal (a SPB-containing BR), a modified BR (a modified high-cis BR, a modified low-cis BR), and the like. Examples of the modified BR include BRs modified with similar functional groups as explained in the above-described SBR, and the like. Among them, the modified BR is preferable. The BR can be used alone, or two or more of them can be used in combination.

[0088] As the cis-rich BR, for example, those commercially available from Zeon Corporation, Ube Industries, Ltd., JSR Corporation, etc. can be used. When the cis-rich BR is bonded, low-temperature properties and abrasion resistance can be improved. The cis content is preferably greater than 95 mol%, more preferably greater than 96 mol%, and even more preferably 97 mol% or more. Furthermore, in the present specification, the cis content (cis-1,4-bonded butadiene unit amount) is a value calculated by infrared absorption spectrometry.

[0089] The rare earth-based BR includes those synthesized using a rare earth element-based catalyst and having a vinyl content of preferably less than 1.8 mol%, more preferably less than 1.6 mol%, and even more preferably 1.5 mol% or less, and a cis content of preferably more than 95 mol%, more preferably more than 96 mol%, and even more preferably 97 mol% or more. For the rare earth-based BR, for example, those commercially available from LANXESS, etc., can be used.

[0090] Examples of the SPB-containing BR include those in which a 1,2-syndiotactic polybutadiene crystal is chemically bonded and dispersed with BR, but not those in which the crystal is simply dispersed in the BR. As such SPB-containing BR, those commercially available from Ube Industries, Ltd., etc., can be used.

[0091] As the modified BR, a modified butadiene rubber (modified BR) modified at its terminal and / or main chain with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen can be suitably used.

[0092] Examples of other modified BRs include those obtained by adding a tin compound after polymerizing 1,3-butadiene with a lithium initiator, the end of which is further bonded by a tin-carbon bond (tin-modified BR), and the like. Furthermore, the modified BR can be either non-hydrogenated or hydrogenated.

[0093] A weight-average molecular weight (Mw) of the BR is preferably greater than 300,000, more preferably greater than 350,000, and even more preferably greater than 400,000 from the viewpoint of abrasion resistance. Furthermore, it is preferably less than 2,000,000, more preferably less than 1,000,000, and even more preferably less than 500,000 from the viewpoint of crosslinking uniformity, etc. In addition, the Mw can be calculated by the measurement method described above.

[0094] The rubber component according to the present invention comprises more than 50 mass% of a BR. A content A BR of the BR in the rubber component is preferably more than 51 mass%, more preferably more than 53 mass%, and even more preferably 55 mass% or more from the viewpoint of abrasion resistance. In addition, A BR In one embodiment, from the point of view of wet grip performance, preferably less than 90 mass%, more preferably less than 85 mass%, even more preferably less than 80 mass%, and even more preferably less than 75 mass%. Furthermore, A BR in another embodiment preferably less than 70 mass%, more preferably less than 65 mass% and even more preferably less than 60 mass%. (Other rubber components)

[0095] The rubber component according to the present invention may include rubber components other than SBR and BR. As other rubber components, crosslinkable rubber components commonly used in the tire industry may be used, such as an isoprene-based rubber (IR-based rubber), a styrene-isoprene-butadiene copolymer rubber (SIBR), a styrene-isobutylene-styrene block copolymer (SIBS), a chloroprene rubber (CR), an acrylonitrile-butadiene rubber (NBR), a hydrogenated nitrile rubber (HNBR), a butyl rubber (IIR), an ethylene-propylene rubber, a polynorbornene rubber, a silicone rubber, a polyethylene chloride rubber, a fluororubber (FKM), an acrylic rubber (ACM), a hydrin rubber, and the like. Other rubber components may be used alone, or two or more of them may be used in combination.

[0096] As an IR-based rubber, for example, those commonly used in the tire industry can be used, such as isoprene rubber (IR), natural rubber, and the like. Examples of natural rubber include unreformed natural rubber (NR), and refined natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), ultrapure natural rubber, grafted natural rubber, and the like. The isoprene-based rubber can be used alone, or two or more of them can be used in combination.

[0097] The NR is not particularly limited, and those commonly used in the tire industry can be used, examples of which include SIR20, RSS#3, TSR20 and the like.

[0098] From the viewpoint of the effects of the present invention, the content of the other rubber components when combined in the rubber component is preferably less than 15 mass%, more preferably 10 mass% or less, and even more preferably less than 5 mass%. On the other hand, the lower limit of the content of the other rubber components in the rubber component is not particularly limited and may be 0 mass%, but may also be, for example, greater than 1 mass%, greater than 2 mass%, or greater than 3 mass%. (Total styrene amount)

[0099] A total amount of styrene (A STY ) is a total content in mass % of styrene parts contained in a total amount of rubber components as defined above. In the present invention, the total amount of styrene in the rubber component is 25 mass % or less. The total amount of styrene is preferably less than 20 mass %, more preferably less than 15 mass % and even more preferably less than 10 mass %. Furthermore, the total amount of styrene is normally about 3 mass % or more, 4 mass % or more, or 5 mass % or more. <Füllstoff>

[0100] The rubber composition forming the sidewall according to the present invention comprises 50 parts by mass or more of silica based on 100 parts by mass of the rubber component as a filler.

[0101] The rubber composition according to the present invention may comprise carbon black as a filler in addition to silica. The rubber composition preferably comprises silica and carbon black as fillers, and a filler may be one consisting of silica and carbon black. (silicon dioxide)

[0102] Silica is not particularly limited, and those commonly used in the tire industry can be used, such as silica produced by a dry process (anhydrous silica), silica produced by a wet process (hydrous silica), and the like. Furthermore, from the viewpoint of environmental impact, silica from a biomass material (for example, amorphous silica purified from rice husks) can be used. Among them, hydrous silica produced by a wet process is preferred because it has many silanol groups. Silica can be used alone, or two or more of them can be used in combination.

[0103] For example, silicon dioxide from a biomass material can be obtained by burning rice husks to obtain rice husk ash, extracting silicate from the rice husk ash using a sodium hydroxide solution, generating silicon dioxide by reacting the silicate with sulfuric acid in the same manner as for conventional wet silicon dioxide, and filtering, washing with water, drying, and pulverizing precipitates of the silicon dioxide. When silicon dioxide crystallizes, it is insoluble in water, and silicic acid, which is a component thereof, cannot be used. By controlling the firing temperature and firing time, crystallization of silicon dioxide in rice husk ash can be suppressed (JP 2009-2594 A, Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222, etc.). As an amorphous silicon dioxide extracted from rice husks, those produced by Wilmar, etc., can be used.are commercially available.

[0104] A specific nitrogen adsorption surface area (N2SA) of silica is preferably greater than 140 m from the perspective of fuel efficiency and abrasion resistance 2 / g, more preferably greater than 150 m 2 / g, even more preferably greater than 160 m 2 / g and even more preferably 175 m 2 / g or greater. In addition, from the perspective of fuel efficiency and processability, it is preferably less than 350 m 2 / g, more preferably less than 300 m 2 / g and even more preferably less than 250 m 2 / g. In addition, the N2SA of silicon dioxide is measured using the measurement method described above.

[0105] An average primary particle size of silicon dioxide is preferably greater than 10 nm, more preferably greater than 12 nm, and even more preferably greater than 14 nm. Furthermore, the average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or smaller. Furthermore, the average primary particle size of silicon dioxide is measured by the measurement method described above.

[0106] A silica content based on 100 parts by mass of the rubber component is preferably greater than 70 parts by mass, more preferably 80 parts by mass or more, even more preferably greater than 90 parts by mass, and even more preferably 100 parts by mass or more from the viewpoint of wet grip performance. Furthermore, from the viewpoint of abrasion resistance, it is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, and even more preferably less than 130 parts by mass. (Soot)

[0107] As the carbon black, those commonly used in the tire industry can be suitably used. Examples include, for example, GPF, FEF, HAF, ISAF, SAF, and the like. Furthermore, in addition to the above-mentioned carbon black, carbon black made from lignin or a reclaimed carbon black obtained by pyrolysis or the like from a product containing carbon black, such as a tire, and the like, can be used from the viewpoint of environmental performance. Carbon black can be used alone, or two or more of them can be used in combination.

[0108] A specific nitrogen adsorption surface area (N2SA) of carbon black is preferably larger than 10 m from the viewpoint of reinforcement property 2 / g, more preferably larger than 30 m 2 / g and even more preferably greater than 50 m 2 / g. In addition, from the perspective of fuel efficiency and processability, it is preferably less than 200 m 2 / g, more preferably less than 175 m 2 / g and even more preferably less than 150 m 2 / g. In addition, the N2SA of soot is measured using the method described above.

[0109] An average primary particle size of carbon black is preferably greater than 10 nm, more preferably greater than 12 nm, and even more preferably greater than 14 nm. Furthermore, the average primary particle size is preferably less than 26 nm, more preferably less than 24 nm, and even more preferably 22 nm or smaller. Furthermore, the average primary particle size of carbon black is measured by the measurement method described above.

[0110] The content of carbon black when combined, based on 100 parts by mass of the rubber component, is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably 5 parts by mass or more from the viewpoints of abrasion resistance and wet grip performance. Furthermore, from the viewpoint of fuel efficiency, it is preferably less than 50 parts by mass, more preferably less than 30 parts by mass, and even more preferably less than 10 parts by mass.

[0111] When both silica and carbon black are combined, the silica content is preferably greater than the carbon black content from the perspective of balancing fuel efficiency, wet grip performance, and abrasion resistance. The ratio of the silica content to the total content of silica and carbon black is preferably more than 80 mass%, more preferably more than 90 mass%, and even more preferably more than 95 mass%. (Other fillers)

[0112] In addition to carbon black and silica, other fillers may also be used as the filler. Such fillers are not particularly limited, and for example, any fillers conventionally and commonly used in the tire industry can be used, such as aluminum hydroxide, aluminum oxide (alumina), calcium carbonate, magnesium sulfate, talc, clay, biochar (BIO CHAR), and the like. Other fillers may be used alone, or two or more of them may be used in combination.

[0113] The total filler content based on 100 parts by mass of the rubber component is preferably more than 40 parts by mass, more preferably more than 60 parts by mass, and even more preferably more than 80 parts by mass from the viewpoint of abrasion resistance. Furthermore, from the viewpoints of fuel efficiency and elongation at break, it is preferably less than 250 parts by mass, more preferably less than 200 parts by mass, and even more preferably less than 150 parts by mass. (silane coupling agent)

[0114] Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agents conventionally used in the tire industry in combination with silica can be used. Examples thereof include, for example, thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, 3-octanoylthio-1-propyltrimethoxysilane, and the like; mercapto-based silane coupling agents such as those shown below in the following chemical formulas, and the like; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetrasulfide, and the like; vinyl-based silane coupling agents such as vinyltriethoxysilane, vinyltrimethoxysilane, and the like.Amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, and the like; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, and the like; chlorine-based silane coupling agents such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and the like; and the like. Among them, thioester-based silane coupling agents and / or sulfide-based silane coupling agents are preferred. The silane coupling agent can be used alone, or two or more of them can be used in combination.

[0115] It is preferable that the mercapto-based silane coupling agent is a compound represented by the following chemical formula (1) and / or a compound comprising a bonding unit A represented by the following chemical formula (2) and a bonding unit B represented by the following chemical formula (3). (wherein R 101 , R 102 and R 103 each independently represents an alkyl having 1 to 12 carbon atoms, an alkoxy having 1 to 12 carbon atoms or a group substituted by -O-(R 111 - O) zR 112 (z pieces by R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 represents an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms, an aryl having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms; and z represents an integer from 1 to 30); and R 104 an alkylene having 1 to 6 carbon atoms.) (where x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 hydrogen atom or an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms or an alkynyl having 2 to 30 carbon atoms, which are optionally replaced by a halogen atom, hydroxyl or carboxyl; and R 202 an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms or an alkynylene having 2 to 30 carbon atoms; where R 201 and R 202 together can form a ring structure.)

[0116] Examples of the compound represented by chemical formula (1) include, for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, a compound represented by the following chemical formula (4) (Si363, manufactured by Evonik Degussa GmbH), and the like. Among them, the compound represented by the following chemical formula (4) can be suitably used. They can be used alone, or two or more of them can be used in combination.

[0117] Examples of the compound containing the bonding unit A represented by the chemical formula (2) and the bonding unit B represented by the chemical formula (3) include, for example, those manufactured and sold by Momentive Performance Materials, etc.

[0118] A content of the silane coupling agent when combined based on 100 parts by mass of the rubber component (a total amount of all of a plurality of silane coupling agents when used in combination) is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, even more preferably greater than 2.0 parts by mass, and even more preferably greater than 4.0 parts by mass from the viewpoint of enhancing silica dispersibility. Moreover, from the viewpoint of preventing a decrease in abrasion resistance, it is preferably less than 20 parts by mass, more preferably less than 12 parts by mass, even more preferably less than 10 parts by mass, and even more preferably less than 9.0 parts by mass.

[0119] The content of the silane coupling agent based on 100 parts by mass of silica is preferably greater than 1.0 parts by mass, more preferably greater than 3.0 parts by mass, and even more preferably greater than 5.0 parts by mass from the viewpoint of enhancing the dispersibility of silica. Furthermore, from the viewpoints of cost and processability, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 12 parts by mass. <plastifizierungsmittel>

[0120] The rubber composition relating to the present invention preferably comprises a plasticizer. Examples of the plasticizer include, for example, a hydrocarbon resin, oil, a liquid rubber, an ester-based plasticizer, and the like. (hydrocarbon resin)

[0121] A hydrocarbon resin refers to a polymer having a skeleton formed from a hydrocarbon that is solid at 25°C. The hydrocarbon resin may generally include an oxygen element derived from a carboxyl group, a hydroxyl group, coumarone, or the like. The hydrocarbon resin is not particularly limited, and examples thereof include a petroleum resin, a terpene-based resin, a rosin-based resin, a phenol-based resin, and the like, which are commonly used in the tire industry. As the hydrocarbon resin, for example, those manufactured by Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Corporation, Eastman Chemical Company, Nitto Chemical Co., Ltd., Zibo Luhua Hongjin New Material Group Co., Ltd., Nippon Shokubai Co., Ltd. can be used., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., etc. The hydrocarbon resin can be used alone, or two or more of them can be used in combination. <<Erdölharz> >

[0122] As a petroleum resin, a C5-based petroleum resin, an aromatic petroleum resin, a C5 / C9-based petroleum resin, and the like can be used. The petroleum resin can be used alone, or two or more of them can be used in combination.

[0123] A C5-based petroleum resin refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include, for example, a petroleum fraction having 4 to 5 carbon atoms, such as cyclopentadiene, a pentene, a pentadiene, isoprene, and the like, and may be one obtained by hydrogenation or modification thereof. A dicyclopentadiene resin (DCPD resin) is suitably used as the C5-based petroleum resin.

[0124] The aromatic petroleum resin refers to a resin obtained by polymerizing a C9 fraction and may be hydrogenated or modified. Examples of the C9 fraction include, for example, a petroleum fraction having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, methylindene, and the like. Specific examples of the aromatic petroleum resin include, for example, a coumarone-indene resin, a coumarone resin, an indene resin, and an aromatic vinyl-based resin.

[0125] As the aromatic vinyl-based resin, 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 because it is economical, easy to process, and excellent in heat generation.

[0126] A C5 / C9-based petroleum resin refers to a resin obtained by polymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. Examples of the C5 fraction and the C9 fraction include the petroleum fractions described above. <<Harz auf Terpen-Basis> >

[0127] Examples of a terpene-based resin include a polyterpene resin consisting of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, dipentene, and the like; an aromatic-modified terpene resin made from a terpene compound among the above-described terpene compounds and an aromatic compound; a terpene-phenolic resin made from a terpene compound and a phenol-based compound; and those in which these terpene-based resins are hydrogenated (hydrogenated terpene-based resins). Examples of the aromatic compound used as a raw material for the aromatic-modified terpene resin include, for example, styrene, α-methylstyrene, vinyltoluene, divinyltoluene, and the like.Examples of the phenol-based compound used as a raw material for the terpene phenolic resin include, for example, phenol, bisphenol A, cresol, xylenol, and the like. The terpene-based resin can be used alone, or two or more of them can be used in combination. <<Harz auf Kolophonium-Basis> >

[0128] Examples of a rosin-based resin include, for example, but are not particularly limited to: a natural resin rosin; and a rosin-modified resin obtained by modifying it through hydrogenation, disproportionation, dimerization, esterification, or the like; etc. The rosin-based resin may be used alone, or two or more of them may be used in combination. <<Harz auf Phenol-Basis> >

[0129] Examples of a phenol-based resin include, but are not particularly limited to, a phenol-formaldehyde resin, an alkylphenol-formaldehyde resin, an alkylphenol-acetylene resin, an oil-modified phenol-formaldehyde resin, and the like. The phenol-based resin can be used alone, or two or more of them can be used in combination. < <erweichungspunkt>>

[0130] A softening point of the hydrocarbon resin is preferably higher than 60°C, more preferably higher than 70°C, and even more preferably higher than 80°C from the viewpoint of wet grip performance. Furthermore, it is preferably lower than 150°C, more preferably lower than 140°C, and even more preferably lower than 130°C from the viewpoints of processability and improvement of dispersibility of a rubber component with a filler. In addition, the softening point is measured by the measurement method described above. <<Glasübergangstemperatur (Tg)> >

[0131] A Tg of the hydrocarbon resin is preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 100°C or lower from the viewpoint of excellent compatibility with the rubber component. Furthermore, the Tg is preferably -35°C or higher, more preferably 0°C or higher, and even more preferably 30°C or higher from the viewpoint of excellent compatibility with the rubber component. Furthermore, the Tg is measured by the above-described measurement method using a differential scanning calorimeter. < <Gewichtsmittleres Molekulargewicht (Mw) »

[0132] The Mw of the hydrocarbon resin is preferably more than 500, more preferably more than 600, and even more preferably more than 650 from the viewpoints of less volatilization and good adhesion performance. Furthermore, from the viewpoint that the hydrocarbon resin easily entangles with a polymer and is less detached therefrom and thus is excellent in dry adhesion performance, the Mw is preferably less than 15,000, more preferably less than 13,000, and even more preferably less than 11,000. When the Mw is within the above-described ranges, a rubber composition to be obtained has excellent processability and can have improved heat generation and elongation at break. In addition, the Mw is measured by the above-described measurement method. < <gehalt>>

[0133] The rubber composition according to the present invention preferably comprises at least one type of hydrocarbon resin from the viewpoints of wet grip performance, etc., and in the rubber composition of the present invention, a content of the hydrocarbon resin in the rubber composition is preferably 5 mass% or more. A content of the resin in the rubber composition is more preferably more than 6 mass%, even more preferably more than 7 mass%, even more preferably more than 10 mass%, and even more preferably more than 12 mass%. In addition, the content of the hydrocarbon resin in the rubber composition is from the viewpoints of suppressing heat generation, etc.preferably less than 100 mass%, more preferably less than 80 mass%, even more preferably less than 60 mass%, particularly preferably less than 50 mass%, most preferably less than 35 mass% and most preferably less than 25 mass%. (Oil)

[0134] Examples of oil include, for example, a process oil, vegetable fats and oils, animal fats and oils, and the like. Examples of the process oil include a paraffin-based process oil, a naphthene-based process oil, an aromatic-based process oil, and the like. In addition, as an environmental measure, a process oil having a low content of a polycyclic aromatic compound (PCA) can also be used. Examples of the process oil having a low content of a PCA include an MES (mild extraction solvent), a TDAE (treated distillate aromatic extract), a heavy naphthenic oil, and the like. The oil can be used alone, or two or more of them can be used in combination.

[0135] The oil content when combined, based on 100 parts by mass of the rubber component, is preferably more than 5 parts by mass from the viewpoint of processability, more preferably more than 10 parts by mass, and even more preferably more than 15 parts by mass. Furthermore, from the viewpoint of abrasion resistance, it is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 40 parts by mass. Furthermore, in the present specification, the oil content also includes an amount of oil contained in an oil-extended rubber. (liquid rubber)

[0136] The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at normal temperature (25°C). Examples include, for example, a liquid butadiene rubber (a liquid BR), a liquid styrene-butadiene rubber (a liquid SBR), a liquid isoprene rubber (a liquid IR), a liquid styrene-isoprene rubber (a liquid SIR), a liquid farnesene rubber, and the like. The liquid rubber can be used alone, or two or more of them can be used in combination.

[0137] The content of the liquid rubber when combined, based on 100 parts by mass of the rubber component, is preferably greater than 1 part by mass, more preferably greater than 2 parts by mass, even more preferably greater than 3 parts by mass, and even more preferably greater than 5 parts by mass. Furthermore, the content of the liquid rubber is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 20 parts by mass. (Ester-based plasticizer)

[0138] Examples of the ester-based plasticizer include, for example, 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), and the like. The ester-based plasticizer can be used alone, or two or more of them can be used in combination. (Plasticizer content)

[0139] A plasticizer content based on 100 parts by mass of the rubber component is preferably greater than 5 parts by mass from the viewpoint of wet grip performance, more preferably greater than 10 parts by mass, and even more preferably greater than 15 parts by mass. Furthermore, from the viewpoint of processability, it is preferably less than 120 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 60 parts by mass. (Other connecting devices)

[0140] The rubber composition according to the present invention may suitably comprise, in addition to the components described above, coupling agents conventionally and commonly used in the tire industry, for example, processing aids, zinc oxide, stearic acid, wax, an antioxidant, a vulcanizing agent, a vulcanization accelerator and the like. (processing aids)

[0141] Examples of processing aids include, for example, a fatty acid metal salt, a fatty acid amide, an amide ester, a silica surface activator, a fatty acid ester, a mixture of a fatty acid metal salt and an amide ester, a mixture of a fatty acid metal salt and a fatty acid amide, and the like. Processing aids can be used alone, or two or more of them can be used in combination. Examples of processing aids that can be used include those commercially available from Schill+Seilacher GmbH, Performance Additives, etc.

[0142] The content of the processing aid when combined, based on 100 parts by mass of the rubber component, is preferably greater than 0.5 parts by mass, more preferably greater than 1 part by mass, and even more preferably greater than 1.5 parts by mass from the viewpoint of exhibiting an effect of improving processability. Furthermore, from the viewpoint of abrasion resistance and fracture toughness, it is preferably less than 10 parts by mass, more preferably less than 8 parts by mass, and even more preferably less than 5 parts by mass. (Zinc oxide)

[0143] The content of zinc oxide when combined, based on 100 parts by mass of the rubber component, is preferably more than 0.5 parts by mass from the viewpoint of processability, more preferably more than 1.0 parts by mass, and even more preferably more than 1.5 parts by mass. Furthermore, from the viewpoint of abrasion resistance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass. (Stearic acid)

[0144] The content of stearic acid when combined, based on 100 parts by mass of the rubber component, is preferably 0.5 parts by mass or more from the viewpoint of processability, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more. Furthermore, from the viewpoint of vulcanization rate, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less. (Wax)

[0145] A wax content when combined based on 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 parts by mass, and even more preferably more than 1.3 parts by mass from the viewpoint of weather resistance of a rubber. Furthermore, from the viewpoint of preventing tire whitening due to blooming, it is preferably less than 10 parts by mass, more preferably less than 7.0 parts by mass, and even more preferably less than 5.0 parts by mass. (antioxidant)

[0146] Examples of the antioxidant include, but are not particularly limited to, for example, amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, a carbamic acid metal salt, and the like, preferably phenylenediamine-based antioxidants such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and the like, and quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and the like. The antioxidant can be used alone, or two or more of them can be used in combination.

[0147] A content of the antioxidant when combined based on 100 parts by mass of the rubber component is preferably greater than 0.5 parts by mass, more preferably greater than 1.0 parts by mass, and even more preferably greater than 1.5 parts by mass from the viewpoint of ozone cracking resistance of a rubber. Furthermore, from the viewpoints of abrasion resistance and wet grip performance, it is preferably less than 10 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass. (vulcanizing agent)

[0148] Sulfur is suitably used as a vulcanizing agent. Powdered sulfur, oil-processing sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and the like can be used as the sulfur. The vulcanizing agent can be used alone, or two or more of them can be used in combination.

[0149] A content of sulfur when combined as a vulcanizing agent based on 100 parts by mass of the rubber component is preferably greater than 0.1 part by mass, more preferably greater than 0.3 parts by mass, and even more preferably greater than 0.5 parts by mass from the viewpoint of ensuring a sufficient vulcanization reaction. Moreover, from the viewpoint of preventing deterioration, it is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 3.0 parts by mass. In addition, when an oil-containing sulfur is used as the vulcanizing agent, a content of the vulcanizing agent should be a total content of pure sulfur contained in the oil-containing sulfur.

[0150] Examples of vulcanizing agents other than sulfur include, for example, an alkylphenol sulfur chloride condensate, sodium hexamethylene 1,6-bisthiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, and the like. As these vulcanizing agents other than sulfur, those commercially available from Taoka Chemical Co., Ltd., LANXESS, Flexsys, etc. can be used. (vulcanization accelerator)

[0151] Examples of the vulcanization accelerator include, for example, sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators, and the like. The vulcanization accelerator can be used alone, or two or more of them can be used in combination.

[0152] Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based and thiazole-based vulcanization accelerators are preferably combined, and the vulcanization accelerator is more preferably composed of a sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator.

[0153] Examples of the sulfenamide-based vulcanization accelerator include, for example, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and the like. Among them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0154] Examples of the guanidine-based vulcanization accelerator include, for example, 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicachol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and the like. Among them, 1,3-diphenylguanidine (DPG) is preferred.

[0155] Examples of the thiazole-based vulcanization accelerator include, for example, 2-mercaptobenzothiazole, a cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and the like. Among them, 2-mercaptobenzothiazole is preferred.

[0156] The content of the vulcanization accelerator when combined, based on 100 parts by mass of the rubber component, is preferably greater than 1 part by mass, more preferably greater than 1.5 parts by mass, and even more preferably greater than 2 parts by mass. Furthermore, the content of the vulcanization accelerator based on 100 parts by mass of the rubber component is preferably less than 8 parts by mass, more preferably less than 7 parts by mass, and even more preferably less than 6 parts by mass. When the content of the vulcanization accelerator is within the above-described ranges, fracture strength and elongation tend to be ensured. [Production]

[0157] Each of the rubber compositions according to the present invention can be produced by a known method. For example, it can be produced by kneading each of the above-described components using a rubber kneading device such as an open roll, a closed-type kneader (Bunbury mixer, kneader, etc.), and the like.

[0158] The kneading step includes, for example, a basic kneading step of kneading coupling agents and additives other than vulcanizing agents and vulcanization accelerators, and a final kneading step (F-kneading) of adding vulcanizing agents and vulcanization accelerators to the kneaded product obtained by the basic kneading step and kneading them. Furthermore, the basic kneading step can be divided into multiple steps if desired.

[0159] Kneading conditions are not particularly limited. Examples of kneading include, for example, a method of kneading at a discharge temperature of 150 to 170 °C for 3 to 10 minutes in the initial kneading step and a method of kneading at 70 to 110 °C for 1 to 5 minutes in the final kneading step.

[0160] The pneumatic tire of the present invention can be manufactured by a conventional method using the above-described unvulcanized rubber composition. That is, the pneumatic tire of the present invention can be manufactured by extruding an unvulcanized rubber composition into a shape of a predetermined tread with an extruder equipped with a die having a predetermined shape, assembling it with other tire elements on a tire molding machine, and molding it by a conventional method to form an unvulcanized tire, followed by heating and pressurizing this unvulcanized tire in a vulcanizing machine. A vulcanization condition is not particularly limited. Examples of vulcanization include, for example, a method of vulcanizing at 150 to 200°C for 10 to 30 minutes. [Application]

[0161] The pneumatic tire of the present invention can be used for any application, such as a passenger car tire, a large passenger car tire, a light truck tire, a large SUV tire, a racing tire, or a motorcycle tire. Among them, a passenger car tire and a light truck tire are preferable. Here, the passenger car tire is a tire provided it is mounted on a car that runs on four wheels and refers to one with a maximum load capacity of 1,000 kg or less, while the light truck tire refers to one with a maximum load capacity of less than 1,400 kg.

[0162] Furthermore, the tire of the present invention can be used as a summer tire, a winter tire, or a studless tire for any of the tires described above. Among them, a winter tire and a studless tire used at low temperatures are preferred. EXAMPLES

[0163] Although the present invention is described based on examples, it is not limited to the examples. [Various chemicals]

[0164] Various chemicals used in examples and comparative examples are shown collectively below. No.: TSR20 SBR1: SLR6430, manufactured by Trinseo PLC (S-SBR, styrene content: 40 mass%, vinyl bond amount: 24 mol%, Tg: -30 °C, Mw: 1,010,000, oil-extended product comprising 37.5 parts by mass of oil content based on 100 parts by mass of rubber component) SBR2: Styrene-butadiene rubber, synthesized in Production Example 1 below (modified S-SBR, Styrene content: 20 mass%, vinyl content: 20 mol%, Tg: - 60 °C, Mw: 800,000) SBR3: Styrene-butadiene rubber, synthesized in Production Example 2 below (modified S-SBR, styrene content: 15 mass%, vinyl content: 30 mol%, Tg: -60 °C, Mw: 800,000) BR1: Ubepol BR (registered trademark) 150B, manufactured by Ube Industries, Ltd. (Vinyl content: 1.5 mol%, cis content: 97 mol%, Tg: -108 °C, Mw: 440,000) BR2: ASAPRENE N103, manufactured by Asahi Kasei Corporation (modified BR whose end is modified with a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane and its oligomer component, vinyl content: 12 mol%, cis content: 36 mass%, Tg: -90 °C, Mw: 550,000) CB (Carbon black): Show Black N134, manufactured by Cabot Japan KK (N2SA: 148 m 2 / g, average primary particle size: 18 nm) Silicon dioxide: Ultrasil (registered trademark) VN3, manufactured by Evonik Degussa GmbH (N2SA: 175 m 2 / g, average primary particle size: 18 nm) Coupling agent (silane coupling agent): Si266, manufactured by Evonik Degussa GmbH (bis(3-triethoxysilylpropyl) disulfide) Oil: VivaTec 500, manufactured by H&R Group (TDAE oil) Hydrocarbon resin 1: Sylvatraxx 4401, manufactured by Kraton Corporation (aromatic vinyl-based resin (copolymer of styrene and α-methylstyrene), Mw: 700, softening point: 85 °C, Tg: 34 °C) Hydrocarbon resin 2: PR395, manufactured by Exxon Mobil Corporation (C5 / C9-based resin, Mw: 880, softening point 117.8 °C, Tg: 68 °C) Zinc Oxide: Zinc Oxide No. 2, manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid "CAMELLIA", manufactured by NOF CORPORATION Wax: SUNNOC N, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 1: Antigen 6C, manufactured by Sumitomo Chemical Co., Ltd. (6PPD, N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine) Antioxidant 2: Nocrac 224, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (TMQ, 2,2,4-trimethyl-1,2-dihydroquinoline polymer) Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co, Ltd. Vulcanization accelerator 1: Nocceler CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (CBS, N-cyclohexyl-2-benzothiazolylsulfenamide) Vulcanization accelerator 2: Nocceler D, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (DPG, 1,3-diphenylguanidine) [Production examples]Production example 1: Synthesis of SBR2

[0165] The ratio of styrene to 1,3-butadiene is adjusted so that the styrene content of the target product is 20 mass%. Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the contents in the reactor to 20°C, n-butyllithium is added to initiate polymerization. Polymerization is carried out under an adiabatic condition, and when the polymerization conversion rate reaches 99%, 1,3-butadiene is added. After further polymerization, methyltriethoxysilane is added as a modifier to conduct a modification reaction. After the reaction is complete, 2,6-ditert-butyl-p-cresol is added. Next, the mixture is subjected to steam stripping to remove the solvent and dried by a heat roller whose temperature is adjusted to 110°C to obtain SBR2. Production example 2: Synthesis of SBR3

[0166] The ratio of styrene to 1,3-butadiene is adjusted so that the styrene content of the target product is 15 mass%. Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene are charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the contents in the reactor to 20°C, n-butyllithium is added to initiate polymerization. Polymerization is carried out under adiabatic conditions, and when the polymerization conversion rate reaches 99%, 1,3-butadiene is added. After further polymerization, 3-[bis(trimethylsilyl)amino]propyltriethoxysilane is added as a modifier to conduct a modification reaction. After the reaction is complete, 2,6-ditert-butyl-p-cresol is added. Next, the mixture is subjected to solvent removal by steam stripping and dried by a heat roller whose temperature is adjusted to 110 °C to obtain SBR3. [Examples and comparative examples]

[0167] According to the compound recipes shown in each table, using a 1.7-liter closed-loop Banbury mixer, all chemicals other than sulfur and vulcanization accelerator are kneaded for 1 to 10 minutes until a discharge temperature of 150°C to 160°C is reached to obtain a kneaded product. Next, using an open-roll twin-screw mixer, sulfur and vulcanization accelerator are added to the resulting kneaded product, and the mixture is kneaded for 4 minutes until the temperature reaches 105°C to obtain an unvulcanized rubber composition.The obtained unvulcanized rubber composition is molded into a shape of a predetermined tread according to each table and assembled with other tire elements to prepare an unvulcanized tire, followed by press vulcanization under a condition of 170 °C for 12 minutes to obtain each test tire (Tire 1: 225 / 60R16 98H, Tire 2: 275 / 55R20 117T XL).

[0168] The tread surface of each test tire has at least two circumferential main grooves and two lateral grooves. The number of circumferential main grooves is three, one of which runs along the tire centerline, and the remaining two are installed at positions equally spaced from the circumferential main grooves running along the tire centerline on the outer side in the tire width direction. Furthermore, the tread surface has no pinholes, narrow circumferential grooves, or wide circumferential grooves. <bewertung>

[0169] For each test tire, results measured by the following procedure are also described in the corresponding columns of tables below. (collection ratio)

[0170] For each test tire, a total ground contact area and an effective ground contact area, as defined above, are determined by calculating a bump ratio (%). (Wet grip performance at high speed)

[0171] Each test tire is mounted on all wheels of a vehicle (Tire 1: domestic FF vehicle, displacement of 2000 cc; Tire 2: domestic 4WD vehicle, displacement of 3000 cc) driven on a test track of a wet asphalt road surface at a speed of 100 km / h. The grip performance during driving is evaluated by 20 test drivers with a rating from 1 to 5, calculating an overall rating. The results are given as indicators, with the reference comparative example being 100. The results show that the higher the indicator, the better the steering stability during driving and the better the wet grip performance at high speed. (Abrasion resistance at low temperatures)

[0172] Each test tire is mounted on all wheels of a vehicle (Tire 1: domestic FF vehicle, displacement of 2000 cc; Tire 2: domestic 4WD vehicle, displacement of 3000 cc) driven on a test track on an asphalt road surface for 20,000 km at an outside air temperature of 10 °C or lower, and a reduction amount of a tread thickness is measured from the start of driving. The results are given as indicators, with the reference comparative example being 100. The results show that the larger the indicator, the smaller the reduction amount and the more excellent the low-temperature abrasion resistance. Table 1 (Tire 1: 225 / 60R16 98H) Example 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 Composite quantity (mass part) NR - - - - - - - - 10 SBR1 - - - - - - - - - SBR2 45 45 45 45 - 45 45 35 35 SBR3 - - - - 45 - - - - BR1 55 55 55 - 55 55 55 65 55 BR2 - - - 55 - - - - - (extending oil) (0) (0) (0) (0) (0) (0) (0) (0) (0) CB 5 5 5 5 5 5 5 5 5 Silicon dioxide 80 80 80 80 80 100 80 100 80 coupling agent 6, 4 6, 4 6, 4 6, 4 6, 4 8 6, 4 8 6, 4 Öl 10 - - - - 25 10 15 - Hydrocarbon resin 1 20 30 - 30 30 20 20 30 30 Hydrocarbon resin 2 - - 30 - - - - - - zinc oxide 3 3 3 3 3 3 3 3 3 Stearic acid 3 3 3 3 3 3 3 3 3 (Continued on the next page) wax 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Antioxidant 1 2 2 2 2 2 2 2 2 2 Antioxidants 2 1 1 1 1 1 1 1 1 1 sulfur 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 2 1,8 1,8 1,8 1,8 1,8 2,2 1,8 2,2 1,8 BR content (mass%) (A BR ) 55 55 55 55 55 55 55 65 55 Total styrene amount (mass%) (A sty ) 9,0 9,0 9,0 9,0 6,8 9,0 9,0 7,0 7,0 Survey ratio (%) (L) 60 60 60 60 60 60 65 65 60 Hydrocarbon resin content (mass%) 8 13 13 13 13 7 8 11 13 Tg of rubber component (°C) -43 -38 -38 -34 -38 -43 -43 -41 -35 Inequality (1) A BR × L 3300 3300 3300 3300 3300 3300 3575 4225 3300 Inequality (2) (A BR / A stY ) × L 367 367 367 367 489 367 397 604 471 Wet grip performance at high speed 108 110 112 114 112 116 108 118 106 Abrasion resistance at low temperatures 112 112 112 110 112 112 114 117 112 Total performance 220 222 224 224 224 228 222 235 218 (Continued on the next page) Composite quantity (mass part) NR - - - - - - 45 SBR1 96,25 96,25 - - 72,88 - - SBR2 - - 70 70 - 45 - SBR3 - - - - - - - BR1 30 30 30 30 47 55 55 BR2 - - - - - - - (extending oil) (26, 25) (26,25) (0) (0) (19, 88) (0) (0) CB 5 5 5 5 5 55 5 Silicon dioxide 80 80 80 80 80 30 80 coupling agent 6, 4 6, 4 6, 4 6, 4 6, 4 2,4 6,4 Öl 10 10 30 20 30 30 10 Hydrocarbon resin 1 - - - 10 - - - Hydrocarbon resin 2 - - - - - - - zinc oxide 3 3 3 3 3 3 3 Stearic acid 3 3 3 3 3 3 3 wax 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Antioxidant 1 2 2 2 2 2 2 2 Antioxidants 2 1 1 1 1 1 1 1 (Continued on the next page) sulfur 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 2 2 2 2 2 2 2 Vulcanization accelerator 2 1,8 1,8 1,8 1,8 1,8 1,8 1,8 BR content (mass%) (A BR ) 30 30 30 30 47 55 55 Total styrene amount (mass%) (A sty ) 28,0 28,0 14,0 14,0 21,2 9,0 - Survey ratio (%) (L) 57 60 57 57 65 60 60 Hydrocarbon resin content (mass%) 0 0 0 4 0 0 0 Tg of rubber component (°C) -23 -23 -47 -43 -28 -53 -48 Inequality (1) A BR × L 1710 1800 1710 1710 3055 3300 3300 Inequality (2) (A BR / A sty ) × L 61 64 122 122 144 367 - Wet grip performance at high speed 100 100 102 104 102 90 86 Abrasion resistance at low temperatures 100 102 103 103 105 108 109 Total performance 200 202 205 207 207 198 195 Table 2 (Tire 2: 275 / 55R20 117T XL) Example 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 Composite quantity (mass part) NR - - - - - - - - 10 SBR1 - - - - - - - - - SBR2 45 45 45 45 - 45 45 35 35 SBR3 - - - - 45 - - - - BR1 55 55 55 - 55 55 55 65 55 BR2 - - - 55 - - - - - (extending oil) (0) (0) (0) (0) (0) (0) (0) (0) (0) CB 5 5 5 5 5 5 5 5 5 Silicon dioxide 80 80 80 80 80 100 80 100 80 coupling agent 6, 4 6, 4 6, 4 6, 4 6, 4 8 6, 4 8 6, 4 Öl 10 - - - - 25 10 15 - Hydrocarbon resin 1 20 30 - 30 30 20 20 30 30 Hydrocarbon resin 2 - - 30 - - - - - - zinc oxide 3 3 3 3 3 3 3 3 3 Stearic acid 3 3 3 3 3 3 3 3 3 (Continued on the next page) wax 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Antioxidant 1 2 2 2 2 2 2 2 2 2 Antioxidants 2 1 1 1 1 1 1 1 1 1 sulfur 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 2 2 2 2 2 2 2 2 2 Vulcanization accelerator 2 1,8 1,8 1,8 1,8 1,8 2,2 1,8 2,2 1,8 BR content (mass%) (A BR ) 55 55 55 55 55 55 55 65 55 Total styrene amount (mass%) (A sty ) 9,0 9,0 9,0 9,0 6,8 9,0 9,0 7,0 7,0 Survey ratio (%) (L) 60 60 60 60 60 60 65 65 60 Hydrocarbon resin content (mass%) 8 13 13 13 13 7 8 11 13 Tg of rubber component (°C) -43 -38 -38 -34 -38 -43 -43 -41 -35 Inequality (1) A BR × L 3300 3300 3300 3300 3300 3300 3575 4225 3300 Inequality (2) (A BR / A sty ) × L 367 367 367 367 489 367 397 604 471 Wet grip performance at high speed 108 110 112 114 112 116 108 118 106 Abrasion resistance at low temperatures 112 112 112 110 112 112 114 117 112 Total performance 220 222 224 224 224 228 222 235 218 (Continued on the next page) Composite quantity (mass part) NR - - - - - - 45 SBR1 96,25 96,25 - - 72,88 - - SBR2 - - 70 70 - 45 - SBR3 - - - - - - - BR1 30 30 30 30 47 55 55 BR2 - - - - - - - (extending oil) (26, 25) (26,25) (0) (0) ( 19,88) (0) (0) CB 5 5 5 5 5 55 5 Silicon dioxide 80 80 80 80 80 30 80 coupling agent 6,4 6,4 6,4 6,4 6,4 2,4 6,4 Öl 10 10 30 20 30 30 10 Hydrocarbon resin 1 - - - 10 - - - Hydrocarbon resin 2 - - - - - - - zinc oxide 3 3 3 3 3 3 3 Stearic acid 3 3 3 3 3 3 3 wax 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Antioxidant 1 2 2 2 2 2 2 2 Antioxidants 2 1 1 1 1 1 1 1 (Continued on the next page) sulfur 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Vulcanization accelerator 1 2 2 2 2 2 2 2 Vulcanization accelerator 2 1,8 1,8 1,8 1,8 1,8 1,8 1,8 BR content (mass%) (A BR ) 30 30 30 30 47 55 55 Total styrene amount (mass%) (A sty ) 28,0 28,0 14,0 14,0 21,2 9,0 - Survey ratio (%) (L) 57 60 57 57 65 60 60 Hydrocarbon resin content (mass%) 0 0 0 4 0 0 0 Tg of rubber component (°C) -23 -23 -47 -43 -28 -53 -48 Inequality (1) A BR × L 1710 1800 1710 1710 3055 3300 3300 Inequality (2) (A BR / A sty ) × L 61 64 122 122 144 367 - Wet grip performance at high speed 100 100 102 104 102 90 86 Abrasion resistance at low temperatures 100 102 103 103 105 108 109 Total performance 200 202 205 207 207 198 195 [Embodiments]

[0173] Preferred embodiments are shown below.

[0174] [1] A pneumatic tire comprising a tread portion wherein the tread portion is composed of a rubber composition comprising 50 parts by mass or more, preferably 70 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 90 parts by mass or more of silica based on 100 parts by mass of a rubber component, wherein the rubber component comprises more than 50% by mass of a butadiene rubber and a styrene-butadiene rubber, wherein a total amount of styrene in the rubber component is 25 mass% or less, and where, if A BR represents a content in mass% of butadiene rubber in the rubber component and L represents a projection ratio in % of a tread surface of the tread portion, A BR and L satisfy the following inequality: ABR×L>3000.

[0175] [2] The pneumatic tire of [1], where, if A STY represents the total amount of styrene in mass%, A BR , L and A STY satisfy the following inequality: (ABR / ASTY)×L>130, wherein the right-hand side of inequality (2) is preferably 200, more preferably 300, even more preferably 360, even more preferably 450, even more preferably 550 and even more preferably 600.

[0176] [3] The pneumatic tire of [1] or [2], wherein the rubber composition comprises at least one type of hydrocarbon resin, and wherein a content of the hydrocarbon resin in the rubber composition is 5 mass% or more, preferably more than 6 mass%, more preferably more than 7 mass%, even more preferably more than 10 mass%, and even more preferably more than 12 mass%.

[0177] [4] The pneumatic tire of any one of [1] to [3], wherein a content of the silica based on 100 parts by mass of the rubber component is more than 70 parts by mass, preferably 80 parts by mass or more, more preferably more than 90 parts by mass, and even more preferably 100 parts by mass or more.

[0178] [5] The pneumatic tire of any one of [1] to [4], wherein a glass transition temperature of the rubber composition is lower than -30 °C, preferably lower than -33 °C, more preferably lower than -37 °C, even more preferably lower than -40 °C, and even more preferably lower than -42 °C.

[0179] [6] The pneumatic tire of one of [1] to [5], where the right-hand side of inequality (1) is 3250.

[0180] [7] The pneumatic tire of any one of [1] to [5], wherein the right-hand side of inequality (1) is 3500, preferably 3750, and more preferably 4000.

[0181] [8] The pneumatic tire of one of [1] to [7], wherein the content A BR of the butadiene rubber in the rubber component is less than 70 mass%, preferably less than 65 mass% and more preferably less than 60 mass%.

[0182] [9] The pneumatic tire of any one of [1] to [8], wherein a glass transition temperature of the styrene-butadiene rubber is lower than -30 °C, preferably lower than -40 °C, more preferably lower than -50 °C, and even more preferably lower than -55 °C.

[0183]

[10] The pneumatic tire of one of [1] to [9], wherein the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and wherein, when a pair of land portions located on an outermost side in a tire width direction are defined among the land portions as shoulder land portions, the shoulder land portions have one or more small holes each having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 , preferably larger than 0.5 mm 2 and smaller than 10 mm 2 , more preferably larger than 0.5 mm 2 and less than 7.0 mm 2 and even more preferably greater than 1.0 mm 2 and less than 5.0 mm 2 have, have.

[0184]

[11] The pneumatic tire of one of [1] to

[10] , wherein the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and wherein, when a pair of land portions located on an outermost side in a tire width direction are defined as shoulder land portions among the land portions, the shoulder land portions have at least one or more narrow circumferential grooves.

[0185]

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

[11] , wherein the tread surface has widened circumferential grooves whose groove width widens toward an inner side in a tire radial direction.

[0186]

[13] The pneumatic tire of

[12] , wherein the widened circumferential groove is provided at a land portion located on a tire centerline or, when a main circumferential groove is provided on the tire centerline, at a land portion closest to the tire centerline. LIST OF REFERENCE SYMBOLS CL tire centerline The tread end W Tire width direction C Tire circumferential direction 1 tire 2 main circumferential grooves 3 bridge section 4 small hole 5 narrow circumferential grooves 6 widened circumferential groove QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2017-141405 A

[0003] JP 2009-2594 A

[0103] Cited non-patent literature

[0000] JIS K 6239-2:2017

[0050] JIS K 6220-1:2001

[0058] Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222 etc

[0103] Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Corporation, Eastman Chemical Company, Nitto Chemical Co., Ltd., Zibo Luhua Hongjin New Material Group Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd. etc

[0121] < / bewertung> < / gehalt> < / erweichungspunkt> < / plastifizierungsmittel> < / kautschukkomponente>

Claims

[1] Pneumatic tire comprising a tread portion, wherein the tread portion is constructed of a rubber composition comprising 50 parts by mass or more of silica based on 100 parts by mass of a rubber component, wherein the rubber component comprises more than 50% by mass of a butadiene rubber and a styrene-butadiene rubber, wherein a total amount of styrene in the rubber component is 25 mass% or less, and where, if A BR represents a content in mass% of butadiene rubber in the rubber component and L represents a projection ratio in % of a tread surface of the tread portion, A BR and L satisfy the following inequality: ABR×L>3000. [2] A pneumatic tire according to claim 1, wherein when A STY represents the total amount of styrene in mass%, A BR , L and A STY satisfy the following inequality: (ABR / ASTY)×L>130. [3] Pneumatic tyre according to claim 1 or 2, wherein the rubber composition comprises at least one type of hydrocarbon resin, and wherein a content of the hydrocarbon resin in the rubber composition is 5 mass% or more. [4] The pneumatic tire according to any one of claims 1 to 3, wherein a content of the silica based on 100 parts by mass of the rubber component is 100 parts by mass or more. [5] A pneumatic tire according to any one of claims 1 to 4, wherein a glass transition temperature of the rubber composition is lower than -30°C. [6] A pneumatic tire according to any one of claims 1 to 5, wherein the right side of the inequality (1) is 3250. [7] A pneumatic tire according to any one of claims 1 to 5, wherein the right side of the inequality (1) is 3500. [8] A pneumatic tire according to any one of claims 1 to 7, wherein the content A BRof the butadiene rubber in the rubber component is less than 70 mass%. [9] A pneumatic tire according to any one of claims 1 to 8, wherein a glass transition temperature of the styrene-butadiene rubber is lower than -30°C. [10] Pneumatic tyre according to one of claims 1 to 9, wherein the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and wherein, when a pair of land portions located on an outermost side in a tire width direction are defined among the land portions as shoulder land portions, the shoulder land portions have one or more small holes each having an opening area of ​​greater than 0.1 mm 2 and smaller than 15 mm 2 have, have. [11] Pneumatic tyre according to one of claims 1 to 10, wherein the tread surface has two or more circumferential main grooves extending in a tire circumferential direction and land portions separated by the circumferential main grooves, and wherein, when a pair of land portions located on an outermost side in a tire width direction are defined as shoulder land portions among the land portions, the shoulder land portions have at least one or more narrow circumferential grooves. [12] A pneumatic tire according to any one of claims 1 to 11, wherein the tread surface has widened circumferential grooves whose groove width widens toward an inner side in a tire radial direction. [13] A pneumatic tire according to claim 12, wherein the widened circumferential groove is provided at a land portion located on a tire centerline, or, when a main circumferential groove is provided on the tire centerline, at a land portion closest to the tire centerline.

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