pneumatic tires

Abstract

To provide a pneumatic tire sufficiently improved in wet-grip performance during high-speed steering.SOLUTION: In a pneumatic tire 1 in which a direction of mounting in mounting the tire on a vehicle is designated, a cap rubber layer 21 of an outermost layer of a tread part is divided in a tire width direction, and a cap rubber layer 21a positioned outside the vehicle is formed of a rubber composition which contains 25 mass% or less of styrene in rubber constituents and has a glass-transition temperature of -18°C or higher. When a content ratio of silica in the cap rubber layer 21a positioned outside the vehicle is defined as SOUT (mass%), a ground contact area ratio is defined as LOUT, a content ratio of silica in a cap rubber layer 21b positioned inside the vehicle is defined as SIN (mass%) and a ground contact area ratio is defined as LIN, the following (formula 1) and (formula 2) are satisfied: SIN<SOUT (formula 1) and 0≤(SOUT×LOUT)-(SIN×LIN) (formula 2).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a pneumatic tire, and more particularly to a pneumatic tire with improved wet grip performance during high-speed cornering. [Background technology]

[0002] Pneumatic tires (hereinafter simply referred to as "tires") are required to have high braking performance (grip performance) from the standpoint of safety, and various techniques have been proposed to improve grip performance (for example, Patent Documents 1 to 3).

[0003] In particular, with the recent development of expressways, it is not uncommon to travel long distances on expressways, and there is an increasing demand for improved grip performance when making high-speed turns on wet roads (wet grip performance during high-speed turns). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-93386 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-79017 [Patent Document 3] JP 2016-37100 A Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, an object of the present disclosure is to provide a pneumatic tire with sufficiently improved wet grip performance during high-speed cornering. [Means for solving the problem]

[0006] The present inventors have conducted extensive research into solving the above problems, and have found that the problems can be solved by the disclosure described below, leading to the completion of the present disclosure.

[0007] This disclosure (1) A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN Then, the following (Equation 1) and (Equation 2) are satisfied. And, Furthermore, the acetone extractable content in the cap rubber layer located on the outside of the vehicle is 22% by mass or more. The pneumatic tire is characterized by the following: S IN OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2) And, this disclosure (2) is, A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied: Furthermore, the pneumatic tire is characterized in that an external apex is provided on the outside of the carcass. S IN <S OUT ...(Formula 1) 0≦(S ​OUT ×L OUT )-(S IN ×L IN )...(Formula 2) In addition, this disclosure (3) A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied: Furthermore, in the pneumatic tire, the rubber component of the rubber composition contains a styrene-butadiene rubber component, and the styrene-butadiene rubber component has a styrene content of 20 mass % or less. S IN <S OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2) [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a pneumatic tire with sufficiently improved wet grip performance during high-speed cornering. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a tire according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view showing a configuration example of a bead portion of a tire according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [1] Characteristics of the tire according to the present disclosure First, the features of the tire according to the present disclosure will be described.

[0011] 1. Overview The tire according to the present disclosure is a pneumatic tire in which the tire mounting direction when mounted on a vehicle is specified, and the cap rubber layer of the outermost layer of the tread portion is divided in the tire width direction. In the tire according to the present disclosure, the cap rubber layer located on the outer side of the vehicle (outer cap rubber layer) is formed from a rubber composition containing 25 mass % or less of styrene in the rubber component and having a glass transition temperature (Tg) of -18°C or higher. In addition, the tire according to the present disclosure has a silica content ratio in the outer cap rubber layer of S OUT (mass%), the contact area ratio is L OUT The silica content ratio in the cap rubber layer located on the inside of the vehicle (inner cap rubber layer) is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied. S IN OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2) Furthermore, the tire according to the present disclosure is any one of the following (1) to (3). (1) The acetone extractable content in the cap rubber layer located on the outside of the vehicle is 22% by mass or more. (2) An external apex is provided on the outside of the carcass. (3) The rubber component of the rubber composition contains a styrene-butadiene rubber component, and the styrene content in the styrene-butadiene rubber component is 20% by mass or less.

[0012] These features make it possible to provide a pneumatic tire with sufficiently improved wet grip performance during high-speed cornering, as will be described later.

[0013] 2. Mechanism of effect manifestation in tires according to the present disclosure The mechanism by which the above-described effects of the tire according to the present disclosure are exhibited is believed to be as follows.

[0014] ​When a tire is mounted on a vehicle, the inner part of the tread comes into contact with the road surface with high contact pressure when the vehicle is traveling straight, but when the vehicle turns, it is subjected to lateral forces and the outer part of the tread tends to come into contact with the road surface, and this tendency is more pronounced when the vehicle is traveling at high speeds.

[0015] Therefore, in the tire according to the present disclosure, as described above, the outer cap rubber layer is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a Tg of -18°C or higher, thereby improving wet grip performance during high-speed cornering.

[0016] In other words, by forming the outer cap rubber layer with the styrene content in the rubber component of the rubber composition being 25 mass% or less, the interaction and cohesion between the styrene parts in the outer cap rubber layer is weakened, allowing the polymer molecules to move flexibly and increasing the contact area between the road surface and the polymer, which is thought to improve wet grip performance during high-speed cornering.

[0017] In addition, because a certain amount of styrene is contained in the rubber component, the styrene moieties in the polymer, which move flexibly, tend to generate heat due to friction with each other, which further promotes the movement of the polymer molecules and improves wet grip performance during high-speed cornering.

[0018] In addition, rubber compositions with a high Tg of -18°C or higher are prone to heat generation, which further promotes the movement of polymer molecules and improves wet grip performance during high-speed cornering.

[0019] The glass transition temperature (Tg) of the rubber composition can be determined from a temperature distribution curve of tan δ measured using a viscoelasticity measuring device such as the "Iplexer (registered trademark)" series manufactured by GABO. Specifically, the temperature corresponding to the largest tan δ value in the obtained temperature distribution curve of tan δ (tan δ peak temperature) is defined as the glass transition temperature (Tg). It is more preferably -16°C or higher, and even more preferably -15°C or higher. On the other hand, the upper limit is not particularly limited, but is preferably 0°C or lower, more preferably -8°C or lower, and even more preferably -10°C or lower.

[0020] The Tg can be adjusted as appropriate by adjusting the ratio of the rubber component contained in the rubber composition, the amount of styrene in the rubber component, the plasticizer component, etc., and it is possible to increase the Tg by increasing the amount of styrene in the rubber component or by using a plasticizer component such as a resin with a high Tg.

[0021] Furthermore, in the present disclosure, the silica content ratio in the outer cap rubber layer is S OUT (mass%), the contact area ratio is L OUT The silica content in the inner cap rubber layer is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied. S IN OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2)

[0022] S IN OUT ​​That is, by making the outer cap rubber layer contain more silica than the inner cap rubber layer, when a load is applied to the outer cap rubber layer during high-speed cornering, the temperature of the outer cap rubber layer is more likely to rise due to friction between the silica and the polymer, which further promotes the movement of the polymer and improves wet grip performance during high-speed cornering.

[0023] On the other hand, the inner cap rubber layer has a small amount of silica, which suppresses heat generation and ensures the rigidity of the inner cap rubber layer, which is more likely to come into contact with the ground at the beginning of a turn, making it easier to apply load to the outer cap rubber layer during a turn. As a result, the temperature of the outer cap rubber layer increases more easily, further promoting the movement of the polymer and improving wet grip performance during high-speed turns.

[0024] In addition, S OUT and S IN The specific difference between OUT -S IN ) is preferably more than 6% by mass, more preferably more than 7% by mass, and even more preferably more than 8% by mass. On the other hand, although there is no particular upper limit, it is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less.

[0025] Furthermore, since the size of the contact area ratio is related to the size of the area where the polymer comes into contact with the road surface during high-speed cornering, increasing the contact area ratio of the outer cap rubber layer also leads to an increase in the area where the polymer comes into contact with the road surface, which is thought to be advantageous in improving wet grip performance during high-speed cornering.

[0026] In the present disclosure, the ground contact area ratio L of the outer cap rubber layer OUT and the contact area ratio L of the inner cap rubber layer IN The specific difference between OUT -L IN ) is preferably 0.1 or more, more preferably 0.2 or more. On the other hand, although there is no particular upper limit, it is preferably 0.8 or less, more preferably 0.7 or less.

[0027] Then, experiments and studies were conducted to determine the desirable relationship between the silica content and the size of the ground contact area ratio between the outer cap rubber layer and the inner cap rubber layer, and as a result, it was found that 0≦[(S OUT ×L OUT )-(S IN ×L IN )] (Equation 2) is satisfied. OUT ×L OUT )-(S IN ×L IN ) is more preferably 1.0 or more, and even more preferably 8.0 or more. On the other hand, although there is no particular upper limit, it is preferably 20.0 or less, more preferably 18.0 or less, and even more preferably 15.0 or less.

[0028] In the above description, the content of silica indicates the content ratio (mass %) of silica relative to the entire rubber composition, and can be calculated by thermal analysis or the like.

[0029] In the above description, the ground contact area ratio can be determined from the ground contact shape and the division positions of the cap rubber layers under normal rim, normal internal pressure, and normal load conditions.

[0030] Specifically, the tire is mounted on a standard rim, pressurized to the standard internal pressure, and left to stand at 25°C for 24 hours. After that, ink is applied to the surface of the tire tread, and the standard load is applied and pressed against cardboard (camber angle 0°). The contact shape can be obtained by transferring the shape to the paper, and the tire is rotated 72° in circumferential directions and transferred at five locations. In other words, the contact shape is obtained five times.

[0031] And the ground contact area ratio (L OUT ) and the contact area ratio of the inner cap rubber layer (L IN ) can be obtained by calculating the percentage of the area occupied by each cap rubber layer out of the average area of ​​the five contact shapes (black areas) transferred onto the cardboard. LOUT = Average value of the contact area of ​​the outer cap rubber layer / Average value of the entire contact area L IN = Average value of the contact area of ​​the inner cap rubber layer / Average value of the entire contact area

[0032] "Regular rim" refers to the rim specified for each tire by the standard system that includes the standard on which the tire is based, such as the standard rim for the applicable size listed in the "JATMA YEAR BOOK" for JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" listed in the "STANDARDS MANUAL" for ETRTO (The European Tyre and Rim Technical Organization), and the "Design Rim" listed in the "YEAR BOOK" for TRA (The Tire and Rim Association, Inc.). For tires not specified by a standard, it refers to the rim that can be mounted on a rim and can maintain internal pressure, i.e., the rim with the smallest rim diameter and the next narrowest rim width, among rims that do not leak air between the rim and tire.

[0033] "Normal internal pressure" refers to the air pressure specified for each tire by the standard, and in the case of JATMA it refers to the maximum air pressure, in the case of TRA it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO it refers to "INFLATION PRESSURE".

[0034] Furthermore, "normal load" refers to the load determined for each tire by each standard in the standard system, including the standard on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, this is the maximum load capacity, in the case of TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and in the case of ETRTO, it is "LOAD CAPACITY."

[0035] The width of each cap rubber layer when obtaining the contact area of ​​each cap rubber layer can be calculated from the tire width direction length of each cap rubber layer at the outermost surface of the tread in the radial cross section of the tire, with the bead portion aligned to the normal rim width.

[0036] [2] More preferred embodiments of the tire according to the present disclosure The tire according to the present disclosure can achieve even greater effects by adopting the following aspects.

[0037] 1. The boundary surface between the outer cap rubber layer and the inner cap rubber layer Fig. 1 is a schematic cross-sectional view showing the configuration of a tire according to an embodiment of the present disclosure. In Fig. 1, the left side of the page is the inside and the right side is the outside. 5 is a carcass, 6 is an inner tread, 23 is an inner tread edge of a cap rubber layer 21, 24 is an outer tread edge of the cap rubber layer 21, 26 is a belt, 31 is a sidewall, and C is the tire equatorial plane.

[0038] As shown in Fig. 1, a tire 1 includes a tread portion 2, a sidewall portion 3, and a bead portion 4. The tread portion 2 includes an outermost cap rubber layer 21 and an inner base rubber layer 25. In the present disclosure, the cap rubber layer 21 is composed of an outer cap rubber layer 21a and an inner cap rubber layer 21b, and the outer cap rubber layer 21a and the inner cap rubber layer 21b are joined together at an interface 22 to form an integrated body.

[0039] In the present disclosure, the boundary surface 22 is a predetermined region D inside the equatorial plane C, specifically, a distance D from the inner ground edge 23 of the cap rubber layer 21 to the equatorial plane C. IN It is preferable that the tread portion is formed in an area of ​​5% to 80% of the total area of ​​the tire. This allows for an appropriate balance between frictional force and reaction force in the tread portion, further improving wet grip performance during high-speed cornering.

[0040] 2. Particle size of silica contained in the outer cap rubber layer In the present disclosure, the particle size (average primary particle size) of the silica contained in the outer cap rubber layer is preferably 17 nm or less, taking into consideration the ease of friction with the polymer described above.

[0041] The average primary particle diameter can be calculated by directly observing silica particles extracted from a rubber composition cut out from a tire using a transmission electron microscope (TEM) or the like, calculating the equivalent cross-sectional area diameter from the area of ​​each silica particle obtained, and determining the average value.

[0042] 3. Styrene content in the rubber component of the outer cap rubber layer As described above, the rubber component of the outer cap rubber layer contains 25% by mass or less of styrene, preferably 20% by mass or less, and even more preferably 15% by mass or less. On the other hand, the lower limit is preferably 4% by mass or more, more preferably 5% by mass or more, and even more preferably 6% by mass or more.

[0043] The styrene content in the rubber component is the mass % of the styrene portion in 100 mass % of the rubber component, and in the case of a rubber composition after vulcanization, it can be calculated by determining the amount of styrene contained in the rubber component after acetone extraction.

[0044] The styrene content may be obtained from a single styrene-containing polymer or from multiple styrene-containing polymers. When multiple styrene-containing polymers are used, the styrene content can be calculated by summing the product of the styrene content (mass%) in each polymer and the blending amount of that polymer relative to 100 mass% of the rubber component.

[0045] 4. Acetone extractables (AE) of the outer cap rubber layer In the present disclosure, the acetone extractables (AE) of the outer cap rubber layer is preferably 22% by mass or more, more preferably 23% by mass or more, and even more preferably 24% by mass or more, from the viewpoint of exhibiting stable wet grip performance during high-speed cornering. On the other hand, although there is no particular upper limit, it is preferably 35% by mass or less, more preferably 33% by mass or less, and even more preferably 30% by mass or less.

[0046] Acetone extractables (AE) can be considered an indicator of the amount of easily migrating components, such as softeners, in a rubber composition, and can also be considered an indicator of the softness of the rubber composition. Therefore, an outer cap rubber layer with a high amount of AE can ensure a sufficient area for the tire to come into contact with the road surface, allowing it to consistently demonstrate wet grip performance during high-speed cornering.

[0047] The acetone extractables (AE) can be measured in accordance with JIS K 6229: 2015. Specifically, the AE (mass%) can be obtained by immersing a vulcanized rubber test piece cut out from the measurement site in acetone for a predetermined time and determining the mass loss rate (%) of the test piece.

[0048] The acetone extractable content can be appropriately changed by changing the compounding ratio of the plasticizer in the rubber composition.

[0049] 5. Sulfur content (TS) in the outer and inner cap rubber layers In the tire according to the present disclosure, the sulfur amount TS in the outer cap rubber layer OUT (mass%) is the sulfur content TS in the inner cap rubber layer IN (mass%), i.e., TS OUT <TS IN It is preferable that:

[0050] By using sulfur as a vulcanizing agent, the molecular chains of the rubber component are chemically bonded and easily cross-linked, which allows the rubber to maintain its rigidity even at high temperatures. Therefore, the sulfur content TS in the outer cap rubber layer OUT The sulfur content in the inner cap rubber layer is TS IN If the value is smaller than this, cross-linking by sulfur is more easily formed in the inner cap rubber layer, and sufficient rigidity can be obtained in the inner cap rubber layer. As a result, load is more easily applied to the outer cap rubber layer during turning, promoting the movement of polymer molecules in the cap rubber layer, and thus better cornering performance can be obtained.

[0051] The TS is measured using a test piece cut out from the measurement site using an oxygen combustion flask method or the like in accordance with JIS-K6233.

[0052] 6. External Apex The tire according to the present disclosure preferably has an external apex attached to the bead portion.

[0053] 2A and 2B are schematic cross-sectional views showing examples of the configuration of a bead portion of a tire according to an embodiment of the present disclosure, in which (a) is an example without an external apex attached to the outside of the carcass, and (b) is an example with an external apex attached to the outside of the carcass. In Fig. 2, 41 is a bead core, 42 is a bead apex, 43 is a clinch, and 44 is a chafer.

[0054] By providing an external apex 45 on the outside of the carcass 5, even if a large force acts outward on the bead portion 4 during high-speed cornering, the rigidity of the bead portion 4 is sufficiently maintained, deformation of the outer cap rubber layer is prevented, a sufficient contact area is secured, and sufficient grip function can be maintained.

[0055] [3] Implementation form Hereinafter, the present disclosure will be specifically described based on embodiments.

[0056] 1. Rubber composition The rubber composition forming the tread portion (outer cap rubber layer and inner cap rubber layer) of the tire according to the present disclosure can be obtained by appropriately adjusting the types and amounts of various compounding materials such as the rubber components, fillers, softeners, vulcanizing agents, and vulcanization accelerators described below.

[0057] (1) Compounding materials (a) Rubber component In the present embodiment, the rubber component is not particularly limited, and rubbers (polymers) that are generally used in tire manufacturing can be used, such as diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), and nitrile rubber (NBR), butyl rubbers such as butyl rubber, and thermoplastic elastomers such as styrene butadiene styrene block copolymer (SBS) and styrene butadiene copolymer (SB).

[0058] Among these, the outer cap rubber layer contains one of styrene-based polymers such as SBR, SBS, and SB, preferably SBR, in order to include styrene in the rubber component. Furthermore, these styrene-based polymers may be used in combination with other rubber components, and for example, a combination of SBR and BR, or a combination of SBR, BR, and isoprene-based rubber is preferred.

[0059] On the other hand, the rubber component used in the inner cap rubber layer is not particularly limited, but preferably contains any one of isoprene-based rubber, SBR, and BR, and more preferably contains two or more of these in combination.

[0060] (a) SBR The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. In the present disclosure, as described above, the rubber composition forming the outer cap rubber layer has a styrene content of 25% by mass or less in the rubber component. While the styrene content in the SBR component is not particularly limited, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. Meanwhile, the lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more.

[0061] On the other hand, in the rubber composition forming the inner cap rubber layer, the styrene content in the rubber component is not particularly limited, but is, for example, preferably more than 10% by mass, more preferably more than 20% by mass. On the other hand, it is preferably less than 40% by mass, more preferably less than 35% by mass. In this case, the styrene content in the SBR component is, for example, preferably more than 15% by mass, more preferably more than 20% by mass. On the other hand, it is preferably less than 50% by mass, more preferably less than 45% by mass.

[0062] The vinyl bond content (amount of 1,2-bonded butadiene units) of the SBR is, for example, more than 5 mol% and less than 70 mol% in both the rubber composition forming the outer cap rubber layer and the rubber composition forming the inner cap rubber layer. The structure of the SBR (measurement of the styrene content and vinyl bond content) can be performed using, for example, a JNM-ECA series device manufactured by JEOL Ltd.

[0063] As described above, the content of SBR in 100 parts by mass of the rubber component is preferably 65 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 90 parts by mass or more in the rubber composition forming the outer cap rubber layer, while the content of SBR in the rubber composition forming the inner cap rubber layer is preferably 70 parts by mass or more, and more preferably 75 parts by mass or more.

[0064] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR). The SBR may be either unmodified or modified. Hydrogenated SBR, which is obtained by hydrogenating the butadiene portion of SBR, may also be used. Hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of SBR, or a similar structure may be obtained by copolymerizing styrene, ethylene, and butadiene.

[0065] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifier) ​​having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain terminal-modified SBR in which the main chain and terminals have the above functional group (for example, main-chain terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR in which the SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and in which a hydroxyl group or epoxy group has been introduced.

[0066] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0067] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0068] [ka]

[0069] In the formula, R 1 , R 2 and R 3 R may be the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0070] As the modified SBR modified with a compound (modifier) ​​represented by the above formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0071] R 1 , R 2 and R 3 R is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0072] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0073] Modified SBR may also be modified with the following compounds (modifiers): Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N- Benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; and N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0074] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. The SBR may be used alone or in combination of two or more types.

[0075] (b)BR In the present disclosure, both the rubber compositions forming the outer cap rubber layer and the inner cap rubber layer may further contain BR, as necessary. In this case, the content of BR per 100 parts by mass of the rubber composition forming the outer cap rubber layer is preferably more than 20 parts by mass, more preferably more than 25 parts by mass. On the other hand, it is preferably less than 40 parts by mass, more preferably less than 35 parts by mass. And, in the rubber composition forming the inner cap rubber layer, it is preferably more than 10 parts by mass, more preferably more than 15 parts by mass. On the other hand, it is preferably less than 30 parts by mass, more preferably less than 25 parts by mass.

[0076] The weight-average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl bond content of the BR is, for example, more than 1% by mass and less than 30% by mass. The cis content of the BR is, for example, more than 1% by mass and less than 98% by mass. The trans content of the BR is, for example, more than 1% by mass and less than 60% by mass.

[0077] The BR is not particularly limited, and can be a BR with a high cis content (cis content of 90% or more), a BR with a low cis content, or a BR containing syndiotactic polybutadiene crystals. The BR can be either unmodified or modified, and examples of modified BR include modified BRs into which the above-mentioned functional groups have been introduced. These can be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0078] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0079] (c) Isoprene rubber In the present disclosure, the rubber compositions forming the outer cap rubber layer and the inner cap rubber layer may further contain an isoprene-based rubber, if necessary. In this case, the content of the isoprene-based rubber per 100 parts by mass of the rubber component is preferably more than 20 parts by mass and less than 35 parts by mass.

[0080] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0081] As the NR, for example, SIR20, RSS#3, TSR20, and other commonly used rubbers in the tire industry can be used. As the IR, there are no particular limitations, and for example, IR2200, and other commonly used rubbers in the tire industry can be used. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0082] (d) Other rubber components Furthermore, other rubber components may include rubbers (polymers) that are generally used in the manufacture of tires, such as nitrile rubber (NBR).

[0083] (b) Compounding materials other than rubber components (a) Filler In the present embodiment, the rubber composition preferably contains a filler. Specific examples of the filler include silica, carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica.

[0084] (i-1) Silica In the present disclosure, the rubber compositions forming the outer cap rubber layer and the inner cap rubber layer each preferably contain silica. In this case, the outer cap rubber layer has a higher silica content than the inner cap rubber layer, from the viewpoint of improving wet grip performance during high-speed cornering with the outer cap rubber layer, while suppressing heat generation with the inner cap rubber layer and improving rigidity. In this case, it is preferable to contain a silane coupling agent together with silica.

[0085] The BET specific surface area of ​​silica is 140m from the viewpoint of obtaining good durability. 2 / g or more is preferable, and 160m 2On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed running, a value of 250m 2 / g or less is preferable, and 220m 2 / g or less. The BET specific surface area is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0086] In the present disclosure, it is preferable to use silica having a particle size of 17 nm or less in the rubber composition forming the outer cap rubber layer. By using silica with a small particle size, the frequency of contact with the polymer can be increased, thereby improving wet grip performance during high-speed cornering.

[0087] When silica is used as a filling reinforcing agent, the content of silica per 100 parts by mass of the rubber component in the rubber composition forming the outer cap rubber layer is preferably 95 parts by mass or more and 180 parts by mass or less, and more preferably 100 parts by mass or more and 125 parts by mass or less, while in the rubber composition forming the inner cap rubber layer, the content of silica is preferably 70 parts by mass or more and 90 parts by mass or less, and more preferably 75 parts by mass or more and 85 parts by mass or less.

[0088] Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Among them, wet process silica is preferred because it has a large number of silanol groups. Silica made from hydrous glass or silica made from biomass materials such as rice husks may also be used.

[0089] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0090] (i-2) Silane coupling agent When silica is used as the reinforcing filler, the rubber composition preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocathanide, Examples of suitable silanes include sulfide-based silanes such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These silanes may be used alone or in combination of two or more.

[0091] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0092] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0093] (ii) Carbon black In the present disclosure, each rubber composition preferably contains carbon black from the viewpoint of improving rigidity and responsiveness during high-speed driving.

[0094] The specific content ratio of carbon black per 100 parts by mass of the rubber component is preferably 5 parts by mass or more and 25 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or less, in the rubber composition forming the outer cap rubber layer, while it is preferably 5 parts by mass or more and 30 parts by mass or less, and more preferably 10 parts by mass or more and 25 parts by mass or less, in the rubber composition forming the inner cap rubber layer.

[0095] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon blacks) such as FT and MT; and channel blacks (channel carbon blacks) such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0096] The specific surface area of ​​carbon black CTAB (Cetyl Tri-methyl Ammonium Bromide) is 130m 2 / g or more is preferable, and 160m 2 / g or more is more preferable, and 170m 2 / g or more is more preferable. 2 / g or less is preferable, and 200m 2 / g or less is more preferable. The CTAB specific surface area is a value measured in accordance with ASTM D3765-92.

[0097] Specific carbon blacks are not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination of two or more.

[0098] (iii) Other fillers In addition to the silica and carbon black described above, the rubber composition may further contain, as necessary, fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these fillers is, for example, more than 0.1 part by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0099] (b) Plasticizer component The rubber composition may contain oil (including extender oil), liquid rubber, and resin as plasticizers to soften the rubber. The plasticizer component is a component that can be extracted from vulcanized rubber with acetone. The total content of the plasticizer component in the outer cap rubber layer is preferably 40 parts by mass or more and 80 parts by mass or less, and more preferably 50 parts by mass or more and 75 parts by mass or less, per 100 parts by mass of the rubber component. Meanwhile, the total content of the plasticizer component in the inner cap rubber layer is preferably 50 parts by mass or more and 80 parts by mass or less, and more preferably 60 parts by mass or more and 70 parts by mass or less. The oil content includes the amount of oil contained in the rubber (oil-extended rubber).

[0100] (i) Oil Examples of oils include mineral oils (commonly referred to as process oils), vegetable oils, and mixtures thereof. Examples of mineral oils (process oils) that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These oils may be used alone or in combination. From the perspective of life cycle assessment, waste oils used as lubricants in rubber mixers and automobile engines, as well as waste edible oils, may also be used as appropriate.

[0101] Specific examples of process oils (mineral oils) that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like.

[0102] (ii) Liquid rubber The liquid rubber mentioned as a plasticizer is a polymer that is in a liquid state at room temperature (25°C) and is a rubber component that can be extracted by acetone from a vulcanized tire. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and hydrogenated products thereof.

[0103] Farnesene polymers are polymers obtained by polymerizing farnesene, which has structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0104] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0105] Examples of liquid diene polymers include liquid styrene butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene isoprene copolymer (liquid SIR).

[0106] The liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0 × 10 in terms of polystyrene measured by gel permeation chromatography (GPC). 3 Super, 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0107] The amount of the liquid rubber (total amount of the liquid farnesene polymer, liquid diene polymer, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass per 100 parts by mass of the rubber component.

[0108] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0109] (iii) Resin component The resin component also functions as a tackifier and may be solid or liquid at room temperature. Specific examples of the resin component include rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more types may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component. These resin components may be provided with a modifying group capable of reacting with silica, etc., as needed.

[0110] Rosin-based resins are resins whose main component is rosin acid, which is obtained by processing pine resin. These rosin-based resins (rosins) can be classified based on whether they are modified or not, and can be divided into unmodified rosin (unmodified rosin) and modified rosin (rosin derivatives). Examples of unmodified rosins include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Modified rosin is a modification of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosin esters, unsaturated carboxylic acid-modified rosin esters, rosin amide compounds, and rosin amine salts.

[0111] Styrenic resins are polymers that use styrene monomers as constituent monomers, and examples thereof include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more).Specific examples include homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) individually, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of styrene monomers and other monomers that can be copolymerized with them.

[0112] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof, and the like.

[0113] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins containing coumarone and indene as monomer components that constitute the resin skeleton (main chain). Monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0114] The amount of the coumarone-indene resin per 100 parts by mass of the rubber component is, for example, more than 1.0 part by mass and less than 50.0 parts by mass.

[0115] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide, expressed in milligrams, required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0116] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0117] Terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0118] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Specific examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0119] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5 petroleum resin.

[0120] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable aromatic vinyl resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation properties. Examples of aromatic vinyl resins that can be used include those commercially available from Kraton, Eastman Chemical Company, and the like.

[0121] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5 fractions and C9 fractions include the petroleum fractions mentioned above. As the C5C9 resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0122] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0123] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyusho TREND 2000 Vol. 3, pp. 42-45, etc.), with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In this disclosure, (meth)acrylic refers to both methacrylic and acrylic.

[0124] Examples of the monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0125] Furthermore, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative as a monomer component constituting the acrylic resin.

[0126] The acrylic resin may be a resin composed solely of a (meth)acrylic component, or a resin containing components other than a (meth)acrylic component, and may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0127] As the resin component, for example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Nippon Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., etc. can be used.

[0128] (c) Stearic acid In the present disclosure, the rubber composition preferably contains stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. Conventionally known stearic acids can be used, such as those available from NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0129] (d) Antiaging agents In the present disclosure, the rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, more than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component.

[0130] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine antioxidants such as quinolone; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more.

[0131] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0132] (E) Wax In the present disclosure, the rubber composition preferably contains wax. The content of the wax per 100 parts by mass of the rubber component is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, and more preferably 1.5 to 10 parts by mass.

[0133] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0134] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0135] (f) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0136] (g) Crosslinking agents and vulcanization accelerators The rubber composition preferably contains a crosslinking agent such as sulfur, etc. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0137] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0138] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0139] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd. and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Lanxess, and organic peroxides, such as dicumyl peroxide.

[0140] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0141] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

[0142] (H) Other In addition to the above components, the rubber composition may further contain, as necessary, additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, reversion (reversion) inhibitors, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0143] (2) Preparation of rubber composition Each rubber composition forming the outer cap rubber layer and the inner cap rubber layer is prepared by appropriately adjusting the various compounding materials described above and using a general method, for example, a manufacturing method including a base kneading step in which a rubber component and a filler such as carbon black are kneaded together, and a finish kneading step in which the kneaded product obtained in the base kneading step is kneaded together with a crosslinking agent.

[0144] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0145] The kneading temperature in the base kneading step is, for example, higher than 50° C. and lower than 200° C., and the kneading time is, for example, higher than 30 seconds and lower than 30 minutes. In the base kneading step, in addition to the above components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0146] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80°C, and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0147] 2. Tire manufacturing The tire according to the present disclosure can be produced as an unvulcanized tire by molding the two types of rubber compositions obtained above into a tread rubber of a predetermined shape as an outer cap rubber layer and an inner cap rubber layer, and then molding it together with other tire components in a tire building machine using a conventional method.

[0148] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and inflation pressure to which the tire is subjected, and a belt component as a component for tightly fastening the carcass and increasing the rigidity of the tread are wound around a forming drum, and both ends of the carcass are fixed to both side edges, and bead portions as components for fixing the tire to the rim are arranged. After forming into a toroidal shape, a tread is attached to the center of the outer periphery and sidewalls are attached to the radially outer sides to form side portions, thereby producing an unvulcanized tire.

[0149] The unvulcanized tire is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization process can be carried out by using a known vulcanization method. The vulcanization temperature is, for example, greater than 120°C and less than 200°C, and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0150] The above-mentioned tires can be suitably used as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, studless tires (winter tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc., and are particularly preferably used as passenger car tires. [Example]

[0151] The present disclosure will be described in more detail below with reference to examples. In these examples, tires having a tire size of 225 / 45R18 were produced and evaluated.

[0152] 1. Production of rubber composition First, a rubber composition was produced to form an outer cap rubber layer located on the outer side of the vehicle and an inner cap rubber layer located on the inner side of the vehicle when the tire is mounted on the vehicle.

[0153] (1) Compounding materials First, the following ingredients were prepared.

[0154] (a) Rubber component (A) SBR-1: Modified S-SBR obtained by the method described in the next paragraph (Styrene content: 25% by mass, vinyl bond content: 59 mol%, 25% oil-extended) (b) SBR-2: HPR840 manufactured by JSR Corporation (Styrene content: 10%, vinyl bond content: 42 mol%, non-oil extended) (c) SBR-3: SLR6430 (S-SBR) manufactured by Trinseo (Styrene content: 40% by mass, vinyl bond content: 18% by mole, 37.5% oil-extended) (d) SBR-4: Tufuden 4850 (unmodified S-SBR) manufactured by Asahi Kasei Corporation (Styrene content: 40% by mass, vinyl content: 46% by mole, 50% oil-extended) (E) BR: Ubepol BR150B (High-Sys BR) from Ube Industries, Ltd. (cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

[0155] (Production of SBR-1) The SBR-1 was prepared according to the following procedure. First, two 10 L reactors, each consisting of a 10 L inlet at the bottom, an outlet at the top, and a jacket, were connected in series. Butadiene, styrene, and cyclohexane were mixed in the specified ratios. This mixture was passed through a dehydration column packed with activated alumina and mixed with n-butyllithium in a static mixer to remove impurities. The mixture was then continuously fed into the bottom of the first reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance and n-butyllithium as a polymerization initiator were continuously fed into the bottom of the first reactor at specified rates, while the reactor temperature was maintained at 95°C. The polymer solution was continuously withdrawn from the top of the reactor and fed into the second reactor. The temperature of the second reactor was maintained at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and the oligomer component was continuously added at a predetermined rate as a 1000-fold diluted solution with cyclohexane to carry out the modification reaction. The polymer solution was continuously withdrawn from the reactor, and an antioxidant was continuously added using a static mixer. 25 parts by mass of Japan Energy NC140 extender oil per 100 parts by mass of polymer was then added to the polymer solution and mixed, after which the solvent was removed to obtain the desired oil-extended, modified diene polymer (SBR-1).

[0156] The vinyl bond content (unit: mol%) of the obtained SBR-1 was determined by infrared spectroscopy at 910 cm, which is the absorption peak of the vinyl group. -1 The styrene content (unit: mass %) was determined from the refractive index in accordance with JIS K6383 (1995).

[0157] (b) Compounding materials other than rubber components (a) Carbon black: Show Black N220 manufactured by Cabot Japan Co., Ltd. (CTAB specific surface area: 111m 2 / g) (b) Silica-1: Ultrasil 9100GR manufactured by Evonik Degussa (BET specific surface area: 235m 2 / g, average primary particle diameter: 15nm) (c) Silica-2: Ultrasil VN3 manufactured by Evonik Degussa (BET specific surface area: 175m 2 / g, average primary particle diameter: 18nm) (d) Silane coupling agent-1: NXT manufactured by Momentive (8-mercaptooctanoyltriethoxysilane) (e) Silane coupling agent-2: Si998 manufactured by Nanjing Shuguang Chemical (Bis-(3-triethoxysilylpropyl) disulfide) (F) Resin-1: SYLVATRAXX 4401 manufactured by Arizona Chemical Company (α-methylstyrene resin) (G) Resin-2: ExxonMobil PR120 (Hydrogenated DCPD resin, softening point: 120℃) (H) Resin-3: RICON 340 manufactured by Cray Valley (C5 / C9 resin, Mw:240) (l) Oil: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. (J) Liquid SBR: Cray Valley RICON 100 (random copolymer, styrene content: 25% by mass, vinyl content: 70%, Mn: 4500) (K) Liquid BR: Kuraray Co., Ltd.'s Kuraplane LBR-302 (Mn: 5500) (l) Stearic acid: Beaded stearic acid "Tsubaki" manufactured by NOF Corporation (W) Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) (Ka) Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (Y) Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. (T) Sulfur: Powdered sulfur (containing 5% oil) manufactured by Tsurumi Chemical Industry Co., Ltd. (L) Vulcanization accelerator 1: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazylsulfenamide (CBS)) (S) Vulcanization accelerator 2: Soksil D (DPG) manufactured by Sumitomo Chemical Co., Ltd. (N,N'-diphenylguanidine)

[0158] (2) Preparation of the rubber composition for forming the outer cap rubber layer and the inner cap rubber layer According to the formulations shown in Tables 1 to 3, materials other than sulfur and the vulcanization accelerator were kneaded for 5 minutes at 150°C using a Banbury mixer to obtain kneaded materials. Each blend amount is in parts by mass.

[0159] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain a rubber composition for forming the outer cap rubber layer and the inner cap rubber layer.

[0160] 2. Tire manufacturing Using each of the obtained rubber compositions, an outer cap rubber layer and an inner cap rubber layer were extruded into a predetermined shape so that the boundary surface between the outer cap rubber layer and the inner cap rubber layer was formed at a position inward from the equatorial plane of the tire, at a distance from the inner ground contact end of the cap rubber layer to the equatorial plane as shown in Tables 1 to 3, to form a tread portion.

[0161] The division positions (%) shown in Tables 1 to 3 are (distance from the equatorial plane to the division position / distance from the equatorial plane to the ground edge), and a positive value indicates that the division interface is on the inside of the vehicle relative to the equatorial plane when installed on the vehicle, while a negative value indicates that the division interface is on the outside of the vehicle relative to the equatorial plane when installed on the vehicle.

[0162] Thereafter, the tire was laminated together with other tire components to form an unvulcanized tire, which was then press-vulcanized for 10 minutes under a condition of 170°C to produce test tires of Examples 1 to 16 shown in Tables 1 and 2, and test tires of Comparative Examples 1 to 10 shown in Table 3. In Examples 8 to 16, externally laminated apex-type test tires were produced.

[0163] The rubber compositions used for the outer apex and bead apex were the same in each comparative example and example, and the distance from the lower end of the bead portion to the tip of the bead apex and the tip of the outer apex was 35% of the cross-sectional height.

[0164] 3. Calculation of parameters Thereafter, using each of the obtained test tires, the contact area ratio L was calculated for each of the outer cap rubber layer and the inner cap rubber layer based on the method described in "1. Overview" of "[1] Features of Tire According to the Present Disclosure." OUT , L IN Then, using test pieces cut out from each of the outer cap rubber layer and the inner cap rubber layer, the sulfur content (mass%) in the test pieces (TS) was measured by the oxygen combustion flask method in accordance with JIS K6233. OUT , T.S. IN asked for.

[0165] In addition, a viscoelasticity measurement sample measuring 20 mm in length, 4 mm in width, and 1 mm in thickness was taken from the outer cap rubber layer so that the long side was in the tire circumferential direction. Using an "IPLEXER (registered trademark)" manufactured by GABO, tan δ was measured by changing the temperature from -50°C to 5°C under the conditions of a frequency of 10 Hz, an initial strain of 2%, an amplitude of ±1%, and a heating rate of 2°C / min. The temperature corresponding to the largest tan δ value in the obtained temperature distribution curve (tan δ peak temperature) was defined as Tg OUT was requested as follows.

[0166] Also, [(S OUT ×L OUT )-(S IN ×L IN )] was calculated.

[0167] The results are shown in Tables 1 to 3.

[0168] 4. Performance evaluation test (evaluation of wet grip performance during high-speed cornering) Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and inflated to an internal pressure of 250 kPa (normal internal pressure for a passenger car). The vehicle was then driven at 100 km / h on a test course with a wet road surface, and 20 drivers each performed a sensory evaluation of the cornering performance when entering a corner on a 5-point scale (the higher the number, the better). The total score of the 20 drivers' evaluations was then calculated.

[0169] The results for Comparative Example 9 were then set to 100 and indexed according to the following formula to evaluate wet grip performance during high-speed cornering. A larger value indicates better wet grip performance during high-speed cornering. The results are shown in Tables 1 to 3. Wet grip performance during high-speed cornering = [(Test tire results) / (Comparative example 9 results)] × 100

[0170] [Table 1]

[0171] [Table 2]

[0172] [Table 3]

[0173] From the results shown in Tables 1 to 3, it can be seen that the outer cap rubber layer is formed using a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher, and S IN OUT (Equation 1) and 0≦(S OUT ×L OUT )-(S IN ​×L IN ) (Equation 2) can be satisfied to provide a pneumatic tire with sufficiently improved wet grip performance during high-speed cornering.

[0174] Furthermore, it has been found that by appropriately controlling the particle size of the silica and the amount of sulfur contained in the outer cap rubber layer, or by providing an external apex, it is possible to provide a pneumatic tire with even improved wet grip performance during high-speed cornering.

[0175] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiments within the scope of the same or equivalent to the present disclosure.

[0176] This disclosure (1) A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN Then, the following (Equation 1) and (Equation 2) are satisfied. And, Furthermore, the acetone extractable content in the cap rubber layer located on the outside of the vehicle is 22% by mass or more. The pneumatic tire is characterized by the following: S IN OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2) ​ This disclosure (2) A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied: Furthermore, the pneumatic tire is characterized in that an external apex is provided on the outside of the carcass. S IN <S OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2) This disclosure (3) A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outside of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of -18°C or higher; The silica content in the cap rubber layer located on the outside of the vehicle is S OUT (mass%), the contact area ratio is L OUT year, The silica content in the cap rubber layer located on the inside of the vehicle is S IN (mass%), the contact area ratio is L IN When this is the case, the following (Equation 1) and (Equation 2) are satisfied: Furthermore, in the pneumatic tire, the rubber component of the rubber composition contains a styrene-butadiene rubber component, and the styrene-butadiene rubber component has a styrene content of 20 mass % or less. S IN <S OUT ...(Formula 1) 0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 2)

[0177] This disclosure ( 4 )teeth, The present disclosure (1) is characterized by satisfying the following (formula 3): Any combination of (1) to (3) It is a pneumatic tire. 6<(S OUT -S IN )...(Formula 3)

[0178] This disclosure ( 5 )teeth, The present disclosure is characterized by satisfying the following (Formula 4): 4 ) is a pneumatic tire described in 8<(S OUT -S IN )...(Formula 4)

[0179] This disclosure ( 6 )teeth, The following formula (5) is satisfied, and the present disclosure (1) to ( 5 ) and any combination of pneumatic tires. 0.1≦(L OUT -L IN )...(Formula 5)

[0180] This disclosure ( 7 )teeth, The present disclosure is characterized by satisfying the following (Formula 6): 6 ) is a pneumatic tire described in 0.2≦(L OUT -L IN )...(Formula 6)

[0181] This disclosure ( 8 )teeth, The following formula (7) is satisfied, and the present disclosure (1) to ( 7 ) and any combination of pneumatic tires. 1.0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 7)

[0182] This disclosure ( 9)teeth, The present disclosure is characterized by satisfying the following (Equation 8): 8 ) is a pneumatic tire described in 8.0≦(S OUT ×L OUT )-(S IN ×L IN )...(Formula 8) The present disclosure (10) The pneumatic tire is characterized in that the styrene content in the rubber component is 15% by mass or less, and is any combination with any of the present disclosures (1) to (9).

[0183] This disclosure ( 11 )teeth, The boundary surface between the cap rubber layer located on the outside of the vehicle and the cap rubber layer located on the inside of the vehicle is formed inward from the equatorial plane by a distance of 5% or more and 80% or less of the distance from the inner ground contact end of the cap rubber layer to the equatorial plane, and 10 ) and any combination of pneumatic tires.

[0184] This disclosure ( 12 )teeth, The particle diameter of the silica contained in the cap rubber layer located on the outside of the vehicle is 17 nm or less, and 11 ) and any combination of pneumatic tires.

[0185] This disclosure ( 13 )teeth, The cap rubber layer located on the outer side of the vehicle contains 100 parts by mass of a rubber component, and the content of the styrene butadiene rubber is 65% by mass or more. 12 ) and any combination of pneumatic tires. This disclosure (14) The pneumatic tire is characterized in that the content of butadiene rubber is more than 15 mass% out of 100 parts by mass of the rubber component contained in the cap rubber layer located on the inside of the vehicle, and is any combination with any of the present disclosures (1) to (13).

[0187] This disclosure ( 15 )teeth, The cap rubber layer positioned on the outside of the vehicle has an acetone extractable content of 24% by mass or more, and14 ) and any combination of pneumatic tires.

[0188] This disclosure ( 16 )teeth, The amount of sulfur in the cap rubber layer located on the outside of the vehicle is calculated by TS OUT (mass%), the sulfur content in the cap rubber layer located on the inside of the vehicle is TS IN (mass%), TS OUT <TS IN The present disclosure (1) to ( 15 ) and any combination of pneumatic tires. [Explanation of symbols]

[0190] 1 tire 2 Tread section 3 Sidewall 4 Bead section 5. Carcass 6 Innerwear 21 Cap rubber layer 21a Outer cap rubber layer 21b Inner cap rubber layer 22 Boundary 23 Inner ground edge of cap rubber layer 24 Outer ground edge of cap rubber layer 25 base rubber layer 26 Belt 31 Sidewall 41 Bead core 42 Bead Apex 43 Clinch 44 Chafer 45 External Apex C Tire equatorial plane D area D IN Distance from the inner contact edge of the cap rubber layer to the equator

Claims

1. A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outer side of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of −18° C. or higher; The silica content in the cap rubber layer located on the outer side of the vehicle is S ＯＵＴ (mass%), and the ground contact area ratio is L ＯＵＴ year, The silica content in the cap rubber layer located on the inside of the vehicle is S ＩＮ (mass%), and the ground contact area ratio is L ＩＮ When this is the case, the following (Equation 1) and (Equation 2) are satisfied: Furthermore, the pneumatic tire is characterized in that the acetone extractable content in the cap rubber layer located on the outer side of the vehicle is 22 mass % or more. S ＩＮ <S ＯＵＴ ・・・・・(Formula 1) 0≦(S ＯＵＴ ×L ＯＵＴ )-(S ＩＮ ×L ＩＮ )・・・・・(Formula 2)

2. A pneumatic tire for which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outer side of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of −18° C. or higher; The silica content in the cap rubber layer located on the outer side of the vehicle is defined as S OUT (mass %), and the ground contact area ratio is defined as L OUT ; When the silica content ratio in the cap rubber layer located on the inside of the vehicle is S IN (mass %) and the ground contact area ratio is L IN , the following (Equation 1) and (Equation 2) are satisfied: The pneumatic tire further comprises an outer apex attached to the outside of the carcass. S IN < S OUT (Formula 1) 0≦(S OUT ×L OUT )−(S IN ×L IN )・・・(Formula 2)

3. A pneumatic tire in which the tire mounting direction when mounted on a vehicle is specified, The cap rubber layer, which is the outermost layer of the tread portion, is divided in the tire width direction, a cap rubber layer located on the outer side of the vehicle is formed from a rubber composition containing 25% by mass or less of styrene in the rubber component and having a glass transition temperature of −18° C. or higher; The silica content in the cap rubber layer located on the outer side of the vehicle is defined as S OUT (mass %), and the ground contact area ratio is defined as L OUT ; When the silica content ratio in the cap rubber layer located on the inside of the vehicle is S IN (mass %) and the ground contact area ratio is L IN , the following (Equation 1) and (Equation 2) are satisfied: Furthermore, the pneumatic tire is characterized in that the rubber component of the rubber composition contains a styrene-butadiene rubber component, and the styrene-butadiene rubber component has a styrene content of 20 mass % or less. S IN < S OUT (Formula 1) 0≦(S OUT ×L OUT )−(S IN ×L IN )・・・(Formula 2)

4. 4. The pneumatic tire according to claim 1, wherein the following formula (3) is satisfied: 6<(S ＯＵＴ -S ＩＮ )・・・・・(Formula 3)

5. 5. The pneumatic tire according to claim 4, wherein the following formula (4) is satisfied: 8<(S ＯＵＴ -S ＩＮ )・・・・・(Formula 4)

6. 6. The pneumatic tire according to claim 1, wherein the following formula (5) is satisfied: 0.1≦(L ＯＵＴ -L ＩＮ )・・・・・(Formula 5)

7. 7. The pneumatic tire according to claim 6, wherein the following formula (6) is satisfied: 0.2≦(L ＯＵＴ -L ＩＮ )・・・・・(Formula 6)

8. 8. The pneumatic tire according to claim 1, wherein the following formula (7) is satisfied: 1.0≦(S ＯＵＴ ×L ＯＵＴ )-(S ＩＮ ×L ＩＮ )・・・・・(Formula 7)

9. 9. The pneumatic tire according to claim 8, wherein the following formula (8) is satisfied: 8.0≦(S ＯＵＴ ×L ＯＵＴ )-(S ＩＮ ×L ＩＮ )・・・・・(Formula 8)

10. A pneumatic tire described in any one of claims 1 to 9, characterized in that the styrene content in the rubber component is 15 mass% or less.

11. 11. The pneumatic tire according to claim 1, wherein the boundary surface between the cap rubber layer located on the outer side of the vehicle and the cap rubber layer located on the inner side of the vehicle is formed inward from the equatorial plane at a distance of 5% to 80% of the distance from the inner ground contact end of the cap rubber layer to the equatorial plane.

12. 12. The pneumatic tire according to claim 1, wherein the particle diameter of silica contained in the cap rubber layer located on the outer side of the vehicle is 17 nm or less.

13. 13. The pneumatic tire according to claim 1, wherein a content of the styrene-butadiene rubber is 65 parts by mass or more per 100 parts by mass of a rubber component contained in the cap rubber layer located on the outer side of the vehicle.

14. A pneumatic tire described in any one of claims 1 to 13, characterized in that the butadiene rubber content is more than 15 mass% out of 100 mass parts of rubber components contained in the cap rubber layer located inside the vehicle.

15. 15. The pneumatic tire according to claim 1, wherein the cap rubber layer located on the outer side of the vehicle has an acetone extractable content of 24% by mass or more.

16. The amount of sulfur in the cap rubber layer located on the outer side of the vehicle is TS ＯＵＴ (mass%), the amount of sulfur in the cap rubber layer located on the inside of the vehicle is TS ＩＮ (mass%), TS ＯＵＴ <TS ＩＮ The pneumatic tire according to any one of claims 1 to 15, wherein

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