Tire

Abstract

The purpose of the present invention is to improve riding comfort during high-speed travel. A tire provided with a tread portion, in which a crown rubber layer forming the tread portion is formed from a rubber composition containing 40 parts by mass or less of a styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, the loss tangent (0 DEG C tan [delta]) measured by deformation mode: stretching under the conditions of a temperature of 0 DEG C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.10 or more, and the thickness of the tread portion is 10-20 mm.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Good ride comfort is required of tires, and various techniques have been proposed in the past for improving ride comfort (for example, Patent Documents 1 to 4).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-263175

[0006] Patent Document 2: Japanese Patent Application Publication No. 2010-132772

[0007] Patent Document 3: Japanese Patent Application Publication No. 2019-065270

[0008] Patent Document 4: Japanese Patent Application Publication No. 2021-172248 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, with the recent expansion of expressways, opportunities for traveling long distances at high speeds have increased dramatically. Under these circumstances, the ride comfort performance of tires manufactured based on the above-mentioned prior art during high-speed travel is still not sufficient, and further improvement is strongly desired.

[0011] Therefore, an object of the present invention is to improve the riding comfort during high-speed driving.

[0012] Means for solving problems

[0013] The present invention relates to a tire having a tread portion, wherein:

[0014] The cap rubber layer forming the tread portion is formed of a rubber composition.

[0015] The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component.

[0016] The loss tangent (0℃tanδ) measured in the deformation mode: tension under the conditions of temperature 0℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more,

[0017] The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

[0018] Effects of the Invention

[0019] According to the present invention, it is possible to improve the riding comfort performance during high-speed traveling. DETAILED DESCRIPTION

[0020] [1] Features of the tire of the present invention

[0021] First, the features of the tire of the present invention will be described.

[0022] 1. Summary

[0023] The tire of the present invention comprises: a carcass, which is spanned between one and the other of a pair of bead portions as a portion engaged with a wheel rim and serves as a tire skeleton; a belt layer, which is arranged at a position radially outward of the carcass; a belt reinforcement layer, which is arranged radially outward of the belt layer; and a tread portion, which is arranged radially outward of the carcass, the belt layer, and the belt reinforcement layer. The tread portion comprises a cap rubber layer, which is arranged radially outward of the tire and serves as a contact surface, and further comprises a base rubber layer, which is arranged radially inward of the tire than the cap rubber layer, as required.

[0024] Furthermore, the cap rubber layer forming the tread portion is formed of a rubber composition, the rubber composition contains 40 parts by mass or less of SBR with a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, and the loss tangent (0°C tanδ) measured in a deformation mode: tension under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.10 or more. Furthermore, the thickness of the tread portion is 10 mm or more and 20 mm or less.

[0025] It should be noted that the cap rubber layer mentioned here is not limited to the outermost rubber layer forming the tread portion, and when there are two or more layers within 5 mm from the tread surface toward the inside, at least one layer satisfies the above-mentioned conditions of the rubber composition.

[0026] By having these features, as described later, it is possible to improve the riding comfort performance during high-speed running.

[0027] 2. Mechanism of the Effects of the Tire of the Present Invention

[0028] The mechanism by which the above-mentioned effects are exhibited in the tire of the present invention is considered to be as follows.

[0029] As described above, the cap rubber layer of the tire of the present invention contains 40 parts by mass or less of SBR having a styrene amount of 25% by mass or less in 100 parts by mass of the rubber component.

[0030] The glass transition temperature (Tg) of SBR with a small amount of styrene, specifically, 25% by mass or less of styrene, is low, so by including such a low styrene amount SBR in the rubber component, an interface can be formed between the styrene part in the SBR and other polymers. In addition, the formed interface can absorb and mitigate the impact from the outside (road surface) on the tire during high-speed driving.

[0031] At the same time, by containing less than 40 parts by mass of SBR with a small amount of styrene (less than 25% by mass of styrene), tiny styrene domains can be appropriately formed on the rubber surface. In addition, the formed tiny styrene domains can improve the mobility of the polymer and move flexibly, so that the impact from the outside (road surface) on the tire during high-speed driving can be absorbed and mitigated.

[0032] It should be noted that the above-mentioned styrene amount is more preferably 20% by mass or less, further preferably 15% by mass or less, further preferably 10% by mass or less. On the other hand, as the lower limit, it is preferably 4% by mass or more, more preferably 5% by mass or more, further preferably 6% by mass or more.

[0033] Furthermore, in the present invention, “SBR containing 40 parts by mass or less and 25% by mass or less of styrene in 100 parts by mass of the rubber component” means that the amount of SBR in 100 parts by mass of the rubber component is 40 parts by mass or less and the amount of styrene in the entire SBR is 25% by mass or less.

[0034] That is, when the styrene-containing polymer (SBR) is contained alone in the rubber component, it means that the styrene amount is 25% by mass or less, and when a plurality of styrene-containing polymers (SBR) are contained in the rubber component, it means that the styrene amount calculated by the sum of the products of the styrene amount (mass %) in each polymer and the blending amount (mass parts) of the polymer relative to 100 parts by mass of the rubber component is 25% by mass or less.

[0035] More specifically, when 100 parts by mass of the rubber component contains SBR1 (X1 parts by mass) containing S1% by mass of styrene and SBR2 (X2 parts by mass) containing S2% by mass of styrene, the amount of styrene calculated by the formula {(S1×X1)+(S2×X2)} / (X1+X2) is less than 25% by mass.

[0036] In addition, in the vulcanized rubber composition, the amount of styrene contained in the rubber component after acetone extraction is determined by solid nuclear magnetic resonance (solid NMR) or Fourier transform infrared spectrophotometry (FTIR), and the amount of styrene can be calculated from this.

[0037] Furthermore, in the present invention, the rubber composition forming the cap rubber layer has a loss tangent (0°C tanδ) of 0.10 or more measured in a deformation mode: tension under the conditions of temperature 0°C, frequency 10 Hz, initial strain 5%, and dynamic strain rate 1%.

[0038] The loss tangent tanδ is a viscoelastic parameter indicating the energy absorption performance, and the larger its value is, the more energy can be absorbed and converted into heat. In the present invention, since the 0°C tanδ is increased to 0.10 or more, even when driving at high speed with high-frequency vibration, the energy of the vibration can be fully absorbed and converted into heat and released. It is more preferably 0.30 or more, more preferably 0.33 or more, more preferably 0.36 or more, more preferably 0.37 or more, more preferably 0.40 or more, more preferably 0.44 or more, more preferably 0.46 or more, and more preferably 0.50 or more. The upper limit is not particularly limited, and is preferably 0.85 or less, more preferably 0.80 or less, and more preferably 0.75 or less.

[0039] Furthermore, the loss tangent tanδ is preferably 0.33 or less, more preferably 0.31 or less, further preferably 0.30 or less, further preferably 0.28 or less, and further preferably 0.25 or less, measured in the deformation mode: tension under the conditions of temperature 30°C, frequency 10 Hz, initial strain 5%, and dynamic strain rate 1%. It is believed that by appropriately controlling 30°C tanδ to such a value, the tread portion bent due to contact with the road surface during rolling can easily return to its original shape when leaving the road surface, and can easily bend again when contacting the ground again, thereby improving ride comfort performance.

[0040] In the above, the loss tangent (tan δ) can be measured using a viscoelasticity measuring device such as “EPLEXOR (registered trademark)” manufactured by GABO Corporation.

[0041] In addition, in the tire of the present invention, as described above, the thickness of the tread portion is set to be 10 mm to 20 mm. It is believed that by controlling the thickness to be appropriate, the tread portion as a whole is easily deformed by bending, and the riding comfort performance is improved. It is more preferably 12 mm to 18 mm, further preferably 14 mm to 16 mm, and particularly preferably 15 mm.

[0042] The thickness of the tread portion mentioned above refers to the thickness of the tread portion on the equatorial plane of the tire in the radial cross section of the tire. When the tread portion is formed by a single rubber composition, it is the thickness of the rubber composition. When it is formed by a layered structure of multiple rubber compositions described later, it refers to the total thickness of these layers.

[0043] When the tire has a groove on the equatorial plane, it means the thickness from the intersection of a straight line connecting the outermost end points of the groove in the tire radial direction and the tire equatorial plane to the innermost interface of the tread portion in the tire radial direction.

[0044] It should be noted that the tread portion is a component forming the contact surface of the tire, and refers to a portion that is closer to the outside of the tire in the radial direction than components including fiber materials such as the carcass, belt layer, and belt reinforcement layer. The thickness of the tread portion can be measured by making the bead portion consistent with the normal rim width in a cross section cut out of the tire in the radial direction.

[0045] It should be noted that "regular rim" refers to a rim that specifies the standard for each tire in a standard system including the standard to which the tire is based. For example, if it is JATMA (Japan Automobile Tire Association), it refers to the standard rim in the applicable size recorded in "JATMAYEARBOOK"; if it is ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" recorded in "STANDARDS MANUAL"; if it is TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" recorded in "YEARBOOK". JATMA, ETRTO, and TRA are referenced in this order. If there is an applicable size when referencing, the standard is followed. In addition, in the case of a tire not specified in the standard, it refers to a rim that can be mounted in a rim-type manner and can maintain the internal pressure, that is, it refers to a rim with the smallest rim diameter and the narrowest rim width among the rims that do not cause air leakage between the rim and the tire.

[0046] As described above, in the tire of the present invention, the entire rubber of the tread portion is easily bent, and input from the road surface can be sufficiently absorbed and released as heat even during high-speed running, so it is believed that the ride comfort during high-speed running can be sufficiently improved.

[0047] [2] A more preferred embodiment of the tire of the present invention

[0048] The tire of the present invention can obtain greater effects by adopting the following aspects.

[0049] 1. Glass transition temperature (Tg) of the crown rubber layer

[0050] In the present invention, the glass transition temperature (Tg) of the cap rubber layer is preferably -41°C or higher, more preferably higher than -40°C, further preferably -38°C or higher, further preferably -34°C or higher, further preferably -32°C or higher, further preferably -29°C or higher, further preferably -28°C or higher. It is considered that by setting the Tg higher than -40°C, tanδ near 0°C is likely to be high, so that the ride comfort performance during high-speed driving is further improved.

[0051] It should be noted that the glass transition temperature (Tg) of the rubber composition can be obtained from the temperature distribution curve of tanδ measured using a viscoelasticity measuring device such as the "EPLEXOR (registered trademark)" series manufactured by GABO. Specifically, the temperature distribution curve of tanδ is measured under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a heating rate of 2°C / min, and the temperature corresponding to the maximum tanδ value in the range of -60°C to 40°C of the measured temperature distribution curve is taken as the glass transition temperature (Tg). It should be noted that when there are two or more points with the maximum tanδ value in the range of -60°C to 40°C, the point with the lowest temperature is taken as Tg. For example, in the present invention, if the maximum value of tanδ is within the range of -60°C to 40°C, the temperature showing the maximum value is the glass transition temperature (Tg) according to the above definition. For example, when a temperature distribution curve is obtained in which tan δ gradually decreases as the temperature rises in the range of -60°C to 40°C and the temperature at which the maximum value of tan δ is -60°C is obtained, the glass transition temperature (Tg) is -60°C according to the above definition.

[0052] 2. Multi-layer tread

[0053] In the present invention, the tread portion may be formed by only one crown rubber layer, or a base rubber layer may be provided inside the crown rubber layer to make it two layers, or three layers, or four layers or more. In this case, the thickness of the crown rubber layer in the entire tread portion is preferably 10% or more. As a result, the friction generated between the tread surface and the road surface can be fully transmitted to the inside of the tire, so it is believed that the ride comfort performance during high-speed driving is further improved. It should be noted that the thickness of the crown rubber layer in the entire tread portion is more preferably 70% or more.

[0054] As described above, the thickness of the cap rubber layer and the thickness of the base rubber layer can be calculated by adding up the thickness of the cap rubber layer and the thickness of the base rubber layer in the thickness of the tread portion.

[0055] In this case, the 0°C tanδ of the base rubber layer is preferably smaller than that of the cap rubber layer. This improves the responsiveness of the cap rubber layer to the grip performance, thereby sufficiently improving the ride comfort during high-speed running.

[0056] The 0°C tanδ of the cap rubber layer and the base rubber layer can be appropriately adjusted by the amount and type of the compounding materials described later, for example, by increasing the styrene content in the rubber component, increasing the SBR content in the rubber component, increasing the styrene content in the SBR component, increasing the content of fillers such as silica and carbon black, increasing the content of the resin component, etc. On the contrary, it can be reduced by reducing the styrene content in the rubber component, reducing the SBR content in the rubber component, reducing the styrene content in the SBR component, reducing the content of fillers such as silica and carbon black, reducing the content of the resin component, etc.

[0057] Furthermore, in the case of a multi-layered tread portion, the complex elastic modulus of the base rubber layer measured under the conditions of temperature 0°C, frequency 10 Hz, initial strain 5%, dynamic strain rate 1%, and deformation mode: tension is preferably smaller than the complex elastic modulus of the cap rubber layer measured in the same manner. It should be noted that these complex elastic moduli can be measured using a viscoelasticity measuring device such as "EPLEXOR (registered trademark)" manufactured by GABO, for example.

[0058] The complex elastic modulus is a parameter that indicates the rigidity of the rubber layer. By making the complex elastic modulus of the base rubber layer smaller than the complex elastic modulus of the crown rubber layer, the tread portion as a whole deforms from the inside during driving, and the road surface and the tread surface can be roughly evenly grounded, thereby improving the ground contact performance and being able to fully improve the ride comfort performance during high-speed driving.

[0059] 3. Content of silica in the crown rubber layer

[0060] In the present invention, the rubber composition forming the crown rubber layer preferably contains silica. By containing silica, the microscopic styrene domains that move flexibly and the silica are easily rubbed, which can further increase the heat generation and release the energy of vibration, thereby fully improving the ride comfort performance during high-speed driving.

[0061] As a specific content, it is preferably 90 parts by mass or more, more preferably 100 parts by mass or more, and further preferably 110 parts by mass or more, relative to 100 parts by mass of the rubber component. The upper limit is not particularly limited, but in consideration of the kneading processability and molding processability of the rubber composition, it is preferably 140 parts by mass or less, more preferably 130 parts by mass or less, and further preferably 120 parts by mass or less.

[0062] Furthermore, in the present invention, the particle size (average primary particle size) of silica is preferably 17 nm or less in consideration of the ease of friction with the polymer.

[0063] It should be noted that the average primary particle size can be calculated as follows: a rubber composition is cut out from a tire, and the silica taken out from the rubber composition is directly observed using an electron microscope (TEM) or the like, and the equal cross-sectional area diameter is calculated from the particle area of ​​each silica obtained, and the average value is obtained for calculation.

[0064] 4. Content of resin components in the crown rubber layer

[0065] In the present invention, the rubber composition forming the cap rubber layer preferably contains a resin component.

[0066] By including a resin component in the rubber composition, the adhesion of the resin component can improve the ground contact with the road surface, and the ride comfort during high-speed running can be sufficiently improved.

[0067] As the preferred resin component, rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc., which are described later, are preferred, and styrene resins such as α-methylstyrene are more preferred. Moreover, as the content relative to 100 parts by mass of the rubber component, it is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 25 parts by mass or more.

[0068] 5. Acetone extract of crown rubber layer (AE)

[0069] In the present invention, the acetone extractable component (AE) of the cap rubber layer is preferably 10.4% by mass or more, more preferably 11% by mass or more, further preferably 11.1% by mass or more, further preferably 12% by mass or more, further preferably 13% by mass or more, further preferably 13.3% by mass or more. On the other hand, the upper limit is not particularly limited, but is preferably 17% by mass or less, more preferably 15% by mass or less, further preferably 14% by mass or less, further preferably 13.9% by mass or less, further preferably 13.7% by mass or less.

[0070] The acetone extract (AE) can be considered as an index indicating the amount of softener etc. in the rubber composition, and can also be considered as an index indicating the softness of the rubber composition. Therefore, in the cap rubber layer, when the amount of AE is increased to a certain extent as described above, the area in contact with the road surface of the tire can be sufficiently ensured, the ground contact performance is improved, and the ride comfort performance during high-speed driving can be sufficiently improved.

[0071] The acetone extractable component (AE) can be measured in accordance with JIS K 6229: 2015. Specifically, a vulcanized rubber test piece cut out from a measurement site is immersed in acetone for a predetermined time and the mass reduction rate (%) of the test piece is determined to obtain AE (mass %).

[0072] More specifically, each vulcanized rubber test piece is immersed in acetone at normal temperature and pressure for 72 hours to extract the soluble component, and the mass of each test piece before and after the extraction is measured to determine the acetone extraction amount by the following formula.

[0073] Acetone extraction amount (%) = {(mass of the rubber test piece before extraction - mass of the rubber test piece after extraction) / (mass of the rubber test piece before extraction)} × 100

[0074] The above-mentioned acetone extractable component can be appropriately changed by changing the blending ratio of the plasticizer in the rubber composition.

[0075] 6. Land Ratio

[0076] In the tire of the present invention, when assembled on a regular rim and set to a regular internal pressure, the land ratio of the tread portion of the tire is preferably 55% or more, more preferably 60% or more, and even more preferably 63% or more.

[0077] The “land ratio” is the ratio of the actual contact surface to the virtual contact surface in which all the grooves arranged on the tread surface are filled. If the land ratio is large, the area in contact with the road surface will increase, thereby improving the ground contact performance and fully improving the ride comfort performance during high-speed driving.

[0078] In addition, the upper limit of the land ratio is not particularly limited, but is preferably 85% or less, more preferably 80% or less, and further preferably 75% or less.

[0079] The above-mentioned land ratio can be obtained from the ground contact shape under the conditions of a regular rim, a regular internal pressure, and a regular load.

[0080] Specifically, the tire is mounted on a regular rim, a regular internal pressure is applied, and after standing at 25°C for 24 hours, ink is applied to the tire tread surface, a regular load is applied, and the tire is pressed against a thick paper (camber angle is 0°) and transferred to the paper. Thus, the contact shape can be obtained, so the tire is rotated 72° in the circumferential direction and transferred at 5 locations. That is, 5 contact shapes are obtained. At this time, for the 5 contact shapes, the parts of the contour of the contact shape interrupted by the groove are smoothly connected, and the obtained shape is used as the virtual contact surface.

[0081] The land ratio can be calculated from (average area of ​​five ground contact shapes (ink portions) transferred onto thick paper / average area of ​​virtual ground contact surfaces obtained from the five ground contact shapes)×100 (%).

[0082] "Normal internal pressure" refers to the air pressure specified in the above standards for each tire. If it is JATMA, it refers to the maximum air pressure. If it is ETRTO, it refers to "INFLATION PRESSURE". If it is TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". As in the case of "regular rims", reference is made in the order of JATMA, ETRTO, and TRA, and the standards are followed. In addition, in the case of tires not specified in the standard, it refers to the normal internal pressure (of which 250KPa or more) of other tire sizes (tire sizes specified in the standard) that record the above-mentioned normal rims as standard rims. It should be noted that when there are multiple normal internal pressures of 250KPa or more, it refers to the minimum value among them.

[0083] In addition, "regular load" refers to the load specified for each standard for each tire in the standard system including the standards based on the above tires, and refers to the maximum mass allowed to be loaded by the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUSCOLD INFLATION PRESSURES". As in the case of the above "regular rim" and "regular internal pressure", reference is made in the order of JATMA, ETRTO, and TRA, and the standards are followed. In addition, in the case of a tire not specified in the standard, the regular load W is calculated by the following calculation: L .

[0084] V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt

[0085] W L =0.000011×V+175

[0086] W L :Normal load(kg)

[0087] V: Imaginary volume of the tire (mm 3 )

[0088] Dt: Tire outer diameter Dt (mm)

[0089] Ht: Tire section height (mm)

[0090] Wt: tire section width (mm)

[0091] And, at this time, the ratio of the content (mass parts) of styrene-butadiene rubber (SBR) with a styrene amount of 25% or less in 100 parts by mass of the rubber component to the land ratio (%) of the tread portion (SBR amount (mass parts) with a styrene amount of 25% or less / land ratio (%)) is preferably 0.75 or less, more preferably 0.72 or less, further preferably 0.70 or less, further preferably 0.68 or less, further preferably 0.65 or less, more preferably 0.62 or less, and further preferably 0.60 or less. Thus, the synergistic effect brought about by the network based on the styrene domain can further improve the ride comfort performance during high-speed driving. It should be noted that the lower limit is not particularly limited, and is preferably 0.15 or more, more preferably 0.20 or more, further preferably 0.25 or more, further preferably 0.30 or more, further preferably 0.40 or more, further preferably 0.45 or more, further preferably 0.50 or more, further preferably 0.54 or more, and further preferably 0.55 or more.

[0092] 7. Flatness

[0093] The aspect ratio is the height of the cross section relative to the width of the tire cross section. The smaller the ratio, the better the ground contact with the road surface, which can fully improve the ride comfort performance when driving at high speeds. On the other hand, if the aspect ratio is reduced, the flexure of the side portion is reduced, which may lead to a deterioration in ride comfort performance.

[0094] It should be noted that the above-mentioned aspect ratio (%) can be obtained by the following formula using the tire's cross-sectional height Ht (mm), cross-sectional width Wt (mm), tire outer diameter Dt (mm) and rim diameter R (mm) when the internal pressure is set to 250 kPa.

[0095] Flatness (%) = (Ht / Wt) × 100 (%)

[0096] Ht=(Dt-R) / 2

[0097] Moreover, at this time, the ratio of the content (mass part) of silica to the flatness (%) relative to 100 parts by mass of the rubber component (silicon dioxide content (mass part) / flatness (%)) is preferably 1.0 or more, more preferably 1.1 or more, more preferably 1.3 or more, further preferably 1.5 or more, further preferably 1.64 or more, further preferably 1.7 or more, further preferably 1.82 or more, further preferably 2.0 or more, further preferably 2.1 or more, further preferably 2.2 or more. Thus, the synergistic effect brought about by the silica-based network can further improve the ride comfort performance during high-speed driving. It should be noted that the upper limit is not particularly limited, and is preferably 7.5 or less, more preferably 7.0 or less, further preferably 6.5 or less, further preferably 6.0 or less, and further preferably 5.5 or less.

[0098] [3] Implementation Method

[0099] The present invention will be described in detail below based on embodiments.

[0100] 1. Rubber composition

[0101] In the tire of the present invention, the rubber composition forming the cap rubber layer can be obtained by appropriately adjusting the types and amounts of various compounding materials such as the rubber component, filler, softener, vulcanizer, and vulcanization accelerator described below.

[0102] (1) Mixed materials

[0103] (a) Rubber component

[0104] The rubber component is not particularly limited, and rubbers (polymers) commonly used in the manufacture of tires, such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), diene rubbers such as nitrile rubber (NBR), butyl rubbers such as butyl rubber, thermoplastic elastomers such as styrene-butadiene-styrene block copolymers (SBS), and styrene-butadiene block copolymers (SB), can be used.

[0105] In the present invention, among these components, any one of styrene polymers such as SBR, SBS, and SB is included from the aspect of including styrene in the rubber component, and SBR is preferably included. In addition, these styrene polymers can be used in combination with other rubber components, for example, the combination of SBR and BR, and the combination of SBR, BR, and isoprene rubber are preferred.

[0106] (A)SBR

[0107] The weight average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. In addition, in the present invention, as described above, the amount of styrene in the SBR component is made to be less than 25% by mass. The vinyl content (1,2-bonded butadiene content) of SBR is, for example, greater than 5% by mass and less than 70% by mass. It should be noted that the vinyl content of SBR refers to the 1,2-bonded butadiene content of all butadiene parts in the SBR component. In addition, the structural identification of SBR (styrene amount, determination of vinyl content) can be carried out using, for example, the device of the JNM-ECA series manufactured by JEOL Ltd.

[0108] In the present invention, as described above, the content of SBR in 100 parts by mass of the rubber component is 40 parts by mass or less, more preferably 35 parts by mass or less, and further preferably 30 parts by mass or less. On the other hand, as the lower limit, it is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 25 parts by mass or more.

[0109] As SBR, there is no particular limitation, for example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR) etc. can be used. SBR can be any one of non-modified SBR and modified SBR. In addition, hydrogenated SBR formed by hydrogenating the butadiene portion in SBR can also be used, and hydrogenated SBR can be obtained by hydrogenating the BR portion in SBR later, and styrene, ethylene, butadiene can be copolymerized to obtain the same structure.

[0110] As the modified SBR, any SBR having a functional group that interacts with a filler such as silica may be used, and examples thereof include: a terminal-modified SBR in which at least one terminal of the SBR is modified with a compound (modifier) ​​having the above-mentioned functional group (a terminal-modified SBR having the above-mentioned functional group at the terminal); a main chain-modified SBR having the above-mentioned functional group in the main chain; a main chain-terminal-modified SBR having the above-mentioned functional group in the main chain and at the terminal (for example, a main chain-terminal-modified SBR having the above-mentioned functional group in the main chain and at least one terminal modified with the above-mentioned modifier); a terminal-modified SBR having a hydroxyl group or an epoxy group introduced therein by modification (coupling) with a polyfunctional compound having two or more epoxy groups in the molecule, and the like.

[0111] Examples of the functional group include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazole, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, 1,2-hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, and epoxy groups. It should be noted that these functional groups may have substituents.

[0112] Moreover, as a modified SBR, for example, SBR modified with the compound (modifying agent) represented by the following formula can be used.

[0113] [Chemistry 1]

[0114]

[0115] It should be noted that, in the formula, R 1 , R 2 and R 3 are 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 It may be bonded to form a ring structure together with the nitrogen atom. n represents an integer.

[0116] As the modified SBR modified with the compound (modifier) ​​represented by the above formula, there can be used SBR in which the polymerization end (active end) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified with the compound represented by the above formula (modified SBR described in JP-A-2010-111753, etc.).

[0117] As R 1 , R 2 and R 3 , 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 , 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. 4 and R 5 When the ring structure is formed by bonding with a nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

[0118] Specific examples of the above-mentioned modifiers include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These can be used alone or in combination of two or more.

[0119] In addition, as modified SBR, modified SBR modified with the following compounds (modifiers) may also be used. Examples of the modifier include: polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'- Diglycidylamino compounds such as diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-phenylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane; acyl chlorides containing amino groups such as bis-(1-methylpropyl)carbamoyl chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylurea chloride, N,N-diethylurea chloride; 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-tetramethyldisiloxane, )-pentamethyldisiloxane and other epoxy-containing silane compounds; (trimethylsilyl) [3-(trimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(triethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tripropoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) Silane compounds containing a thioether group, such as [3-(methyldipropoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds, such as ethyleneimine and propyleneimine; alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-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-dimethylaminobenzaldehyde Benzaldehyde compounds having an amino group and / or a substituted amino group, such as 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, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone; N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone, etc. N-substituted piperidones; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, N-phenyl-β-propiolactam and other N-substituted lactams; and N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine- 2,4,6-triones, 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-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. It should be noted that the modification using the above compounds (modifiers) can be carried out by a known method. ;

[0120] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. In addition, SBR can be used alone or in combination of two or more.

[0121] (B)BR

[0122] In the present invention, the rubber composition may contain BR. In this case, the content of BR in 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more. On the other hand, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less.

[0123] The weight average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The vinyl content of BR is, for example, greater than 1% by mass and less than 30% by mass. The cis content of BR is, for example, greater than 1% by mass and less than 98% by mass. The trans content of BR is, for example, greater than 1% by mass and less than 60% by mass.

[0124] There is no particular limitation on BR, and BR with a high cis content (a cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR can be any of unmodified BR and modified BR. As modified BR, modified BR introduced with the above-mentioned functional groups can be cited. They can be used alone or in combination of two or more. It should be noted that the cis content can be measured by infrared absorption spectroscopy.

[0125] As BR, for example, products of Ube Industries, Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0126] (C) Isoprene rubber

[0127] In the present invention, the rubber composition may contain isoprene-based rubber. In this case, the content of the isoprene-based rubber in 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 50 parts by mass or more. On the other hand, it is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and further preferably less than 60 parts by mass.

[0128] Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0129] As NR, for example, SIR20, RSS#3, TSR20, SVR-L and other common substances in the tire industry can be used. There is no particular limitation on IR, for example, IR2200 and other common substances in the tire industry can be used. As modified NR, deproteinized natural rubber (DPNR), high purity natural rubber (UPNR) and the like can be cited. As modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber and the like can be cited. As modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber and the like can be cited. These substances can be used alone or in combination of two or more.

[0130] (D) Other rubber components

[0131] Furthermore, as other rubber components, rubber (polymer) generally used in the production of tires, such as nitrile rubber (NBR), may be contained.

[0132] (b) Compounding materials other than rubber components

[0133] (A) Filler

[0134] 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.

[0135] (i-1) Silicon dioxide

[0136] In the present invention, the rubber composition preferably contains silica, and preferably contains a silane coupling agent together with silica.

[0137] The BET specific surface area of ​​silica is preferably greater than 140 m 2 / g, more preferably greater than 160m 2 On the other hand, from the perspective of obtaining good rolling resistance during high-speed running, it is preferably less than 250 m 2 / g, more preferably less than 220m 2 It should be noted that the above-mentioned BET specific surface area is the value of N2SA measured by the BET method according to ASTM D3037-93.

[0138] In the present invention, as described above, silica having a particle size of 17 nm or less is preferably used in the rubber composition forming the outer crown rubber layer. By using silica having a small particle size, the contact frequency with the polymer (styrene domain) can be increased, the mobility of the polymer can be improved, and thus the ride comfort performance can be improved. The lower limit is not particularly limited, but is preferably 10 nm or more from the perspective of dispersibility during mixing.

[0139] When silica is used as a filler reinforcing agent, as described above, the content is preferably 90 parts by mass or more, more preferably 100 parts by mass or more, further preferably greater than 100 parts by mass, and further preferably 110 parts by mass or more, relative to 100 parts by mass of the rubber component. In addition, the upper limit is not particularly limited, but is preferably 140 parts by mass or less, more preferably 130 parts by mass or less, and further preferably 120 parts by mass or less.

[0140] As silicon dioxide, for example, dry silicon dioxide (anhydrous silicon dioxide), wet silicon dioxide (hydrous silicon dioxide), etc. can be cited. Among them, for the reason of many silanol groups, wet silicon dioxide is preferred. In addition, silicon dioxide using water-containing glass as raw material, silicon dioxide using biomass materials such as rice husk as raw material, etc. can be used.

[0141] As silica, for example, products of Evonik Industries, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd., etc. can be used.

[0142] (i-2) Silane coupling agent

[0143] When silica is used as a filler reinforcing agent, 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-triethoxysilylbutyl)tetrasulfide, bis(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-trimethoxysilane Sulfide-based silanes include 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes include 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based silanes include vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes include γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based silanes include 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more.

[0144] As the silane coupling agent, for example, products of Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Toray-Dow Corning Co., Ltd., etc. can be used.

[0145] The content of the silane coupling agent is, for example, greater than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0146] (ii) Carbon black

[0147] In the present invention, carbon black is preferably contained in the rubber composition from the viewpoint of reinforcement.

[0148] The specific content of carbon black relative to 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

[0149] The carbon black is not particularly limited, and examples thereof include furnace blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black; thermal blacks such as FT and MT; channel blacks such as EPC, MPC, and CC, etc. These may be used alone or in combination of two or more.

[0150] The CTAB specific surface area of ​​carbon black (Cetyl Tri-methyl Ammonium Bromide) is preferably 130 m 2 / g or more, more preferably 160m 2 / g or more, more preferably 170m 2 / g or more. On the other hand, it is preferably 250m 2 / g or less, more preferably 200m 2 In addition, the CTAB specific surface area is a value measured according to ASTM D3765-92.

[0151] As specific carbon black, there is no particular limitation, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Tanso Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin Nichika Carbon Co., Ltd., and Columbian Carbon Co., Ltd. can be used. They can be used alone or in combination of two or more.

[0152] (iii) Other fillers

[0153] In addition to the above-mentioned silica and carbon black, the rubber composition may further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc., as required. The content of these fillers is, for example, greater than 0.1 parts by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0154] (B) Plasticizer ingredients

[0155] In the rubber composition, as a component for softening the rubber, oil (including filler oil), liquid rubber and resin can be included in the form of a plasticizer component. It should be noted that the plasticizer component is a component that can be extracted from vulcanized rubber using acetone. The total content of the plasticizer component is preferably more than 25 mass parts, more preferably more than 40 mass parts relative to 100 mass parts of the rubber component. On the other hand, it is preferably less than 50 mass parts, more preferably less than 45 mass parts. It should be noted that when using oil-filled rubber as the rubber component, the amount of filler oil is also included in the content of the oil.

[0156] (i)Oil

[0157] As oil, for example, mineral oil (commonly referred to as process oil), vegetable oil, or a mixture thereof can be cited. As mineral oil (process oil), for example, paraffinic process oil, aromatic process oil, cycloparaffinic process oil, etc. can be used. As vegetable oil, 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 oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil (jojoba oil), macadamia oil, tung oil, etc. can be cited. They can be used alone or in combination of two or more. In addition, from the aspect of life cycle assessment, waste oil, waste cooking oil, etc. after use as lubricating oil for rubber mixing mixers, automotive engines, etc. can be suitably used.

[0158] As specific process oil (mineral oil), for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., etc. can be used.

[0159] (ii) Liquid rubber

[0160] Liquid rubber as a plasticizer is a polymer in a liquid state at room temperature (25° C.) and is a rubber component that can be extracted from a vulcanized tire by acetone extraction. Examples of the liquid rubber include farnesene polymers, liquid diene polymers, and hydrogenated products thereof.

[0161] Farnesene polymers are polymers obtained by polymerizing farnesene, and have a structural unit 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).

[0162] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0163] Examples of the liquid diene polymer include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), and liquid styrene-isoprene copolymers (liquid SIR).

[0164] The polystyrene-equivalent weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) is, for example, greater than 1.0×10 3 , less than 2.0×10 5 In addition, in this specification, Mw of a liquid diene polymer is a polystyrene conversion value measured by gel permeation chromatography (GPC).

[0165] The content of the liquid rubber (the total content of the liquid farnesene polymer, the liquid diene polymer, etc.) is, for example, greater than 1 part by mass and less than 100 parts by mass relative to 100 parts by mass of the rubber component.

[0166] As the liquid rubber, for example, products of KURARAY Co., Ltd., Cray Valley Corporation, etc. can be used.

[0167] (iii) Resin component

[0168] The resin component also plays a role as an adhesiveness imparting component, which can be solid or liquid at room temperature. As a specific resin component, for example, resins such as rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc. can be cited, and two or more resins can also be used in combination. The content of the resin component is greater than 2 mass parts relative to 100 mass parts of the rubber component, preferably less than 45 mass parts, and more preferably less than 30 mass parts. It should be noted that these resin components can also be given modified groups that can react with silica etc. as needed.

[0169] Rosin resin is a resin with rosin acid obtained by processing rosin as the main component. The rosin resin (rosin) can be classified by whether it is modified or not, and can be classified into unmodified rosin (unmodified rosin) and rosin modified products (rosin derivatives). As unmodified rosin, tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, other chemically modified rosins, etc. can be cited. Rosin modified products are modified products of unmodified rosin, and rosin esters, unsaturated carboxylic acid modified rosins, unsaturated carboxylic acid modified rosin esters, amide compounds of rosin, amine salts of rosin, etc. can be cited.

[0170] Styrene resins are polymers using styrene monomers as constituent monomers, and examples include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more). Specifically, in addition to homopolymers obtained by homopolymerizing 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.), copolymers obtained by copolymerizing two or more styrene monomers, copolymers of styrene monomers and other monomers copolymerizable therewith can also be mentioned.

[0171] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene and isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or their anhydrides, etc.

[0172] Among the coumarone resins, coumarone indene resins are preferred. Coumarone indene resins are resins containing coumarone and indene as monomer components constituting the backbone (main chain) of the resin. Examples of monomer components contained in the backbone in addition to coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, and the like.

[0173] The content of the coumarone indene resin is, for example, greater than 1.0 part by mass and less than 50.0 parts by mass relative to 100 parts by mass of the rubber component.

[0174] The hydroxyl value (OH value) of the coumarone indene resin is, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is a value expressed in milligrams as the amount of potassium hydroxide required to neutralize acetic acid bound to hydroxyl groups when 1 g of the resin is acetylated, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0175] The softening point of the coumarone indene resin is, for example, higher than 30° C. and lower than 160° C. The softening point is the softening point specified in JIS K 6220-1:2001 and is measured using a ring and ball softening point measuring apparatus, and is the temperature at which a ball falls.

[0176] Examples of 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 composed of (C5H8) n The hydrocarbons and their oxygenated derivatives are classified as monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) and the like as a basic skeleton, for example, 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, γ-terpineol, etc. can be mentioned.

[0177] As polyterpenes, in addition to terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, etc., which use the above-mentioned terpene compounds as raw materials, hydrogenated terpene resins obtained by hydrogenating the terpene resins can also be cited. As terpene phenols, resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds and resins obtained by hydrogenating the resins can be cited. Specifically, resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds and formaldehyde can be cited. It should be noted that, as phenolic compounds, for example, phenol, bisphenol A, cresol, xylenol, etc. can be cited. As aromatic modified terpene resins, resins obtained by modifying terpene resins using aromatic compounds and resins obtained by hydrogenating the resins can be cited. It should be noted that 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 phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and styrene containing an unsaturated hydrocarbon group; benzofuran, indene, etc.

[0178] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) can be appropriately used.

[0179] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may also be a resin obtained by hydrogenating or modifying them. As the C9 fraction, for example, petroleum fractions having 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene can be cited. As specific examples, for example, benzofuran indene resin, benzofuran resin, indene resin, and aromatic vinyl resin can be appropriately used. As an aromatic vinyl resin, for reasons of economy, easy processing, and excellent heat generation, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As an aromatic vinyl resin, for example, commercially available substances from Kraton, Eastman Chemical, etc. can be used.

[0180] "C5C9 resin" refers to a resin obtained by copolymerizing the above-mentioned C5 fraction and the above-mentioned C9 fraction, and may also be a substance obtained by hydrogenating or modifying them. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 resin, for example, a substance commercially available from Tosoh Corporation, LUHUA Corporation, etc. may be used.

[0181] The acrylic resin is not particularly limited, and for example, a solvent-free acrylic resin can be used.

[0182] Solvent-free acrylic resins include (meth) acrylic resins (polymers) synthesized by a high temperature continuous polymerization method (high temperature continuous bulk polymerization method) (methods described in U.S. Patent No. 4,414,370, Japanese Patent Publication No. 59-6207, Japanese Patent Publication No. 5-58005, Japanese Patent Publication No. 1-313522, U.S. Patent No. 5,010,166, East Asia Synthesis Research Annual Report TREND 2000 No. 3, p. 42-45, etc.) without using a polymerization initiator, a chain transfer agent, an organic solvent, etc. as secondary raw materials as much as possible. It should be noted that in the present invention, (meth) acrylic acid refers to methacrylic acid and acrylic acid.

[0183] Examples of the monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, arylalkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0184] As monomer components constituting the acrylic resin, 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.

[0185] The acrylic resin may be a resin composed only of a (meth)acrylic acid component, or may be a resin containing components other than the (meth)acrylic acid component as constituent elements. In addition, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0186] As the resin component, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakery Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Co., Ltd., Nippon Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., etc. can be used.

[0187] (C) Stearic acid

[0188] In the present invention, stearic acid is preferably included in the rubber composition. The content of stearic acid is, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component. As stearic acid, conventionally known substances can be used, for example, products of NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0189] (D) Anti-aging agent

[0190] In the present invention, the rubber composition preferably contains an antioxidant, and the content of the antioxidant is, for example, greater than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, based on 100 parts by mass of the rubber component.

[0191] Examples of the anti-aging agent include naphthylamine antioxidants such as phenyl-α-naphthylamine; diphenylamine antioxidants such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine antioxidants such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; bisphenol, triphenol, and polyphenol antioxidants such as tetrakis-[methylene-3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl)propionate]methane; and the like. These may be used alone or in combination of two or more.

[0192] As the antioxidant, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., FlexSys Co., Ltd., and the like can be used.

[0193] (E) Wax

[0194] In the present invention, the rubber composition preferably contains wax. The content of the wax 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, based on 100 parts by mass of the rubber component.

[0195] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as plant wax and animal wax, and synthetic waxes such as polymers of ethylene and propylene, etc. These may be used alone or in combination of two or more.

[0196] As the wax, for example, products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0197] (F) Zinc Oxide

[0198] The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, greater than 0.5 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the rubber component. As zinc oxide, conventionally known substances may be used, for example, products of Mitsui Mining and Smelting Co., Ltd., Toho Asia Lead Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. may be used.

[0199] (G) Crosslinking agent and vulcanization accelerator

[0200] The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0201] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur generally used in the rubber industry. These may be used alone or in combination of two or more.

[0202] As sulfur, for example, products of Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., FlexSys Co., Ltd., Nippon Kanryu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used.

[0203] Examples of the crosslinking agent other than sulfur include sulfur-containing vulcanizing agents such as TACKROLV200 manufactured by Taoka Chemical Industry Co., Ltd. and KA9188 (1,6-bis(N,N′-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS, and organic peroxides such as dicumyl peroxide.

[0204] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, greater than 0.3 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0205] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazolyl 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, N-tert-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. These may be used alone or in combination of two or more.

[0206] (H) Others

[0207] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, anti-reversion (vulcanization reversion) agents, etc. The content of these additives is, for example, greater than 0.1 parts by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0208] (2) Preparation of rubber composition

[0209] The rubber composition forming the crown rubber layer can be produced by appropriately adjusting the above-mentioned various mixed materials through common methods, for example, by a manufacturing method including the following steps: a basic mixing step of mixing the rubber component with fillers such as carbon black; and a final mixing step of mixing the mixture obtained in the above-mentioned basic mixing step with a cross-linking agent.

[0210] Kneading can be performed using a known (closed type) kneading machine such as a Banbury mixer, a kneader, or an open roll mill.

[0211] The mixing temperature of the basic mixing step is, for example, greater than 50° C. and less than 200° C., and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In the basic mixing step, in addition to the above-mentioned components, compounding agents used in the existing rubber industry, such as softeners such as oil, zinc oxide, anti-aging agents, waxes, vulcanization accelerators, etc., may be appropriately added and mixed as needed.

[0212] In the final kneading step, the kneaded product obtained in the above-mentioned basic kneading step is kneaded with a crosslinking agent. The kneading temperature of the final kneading step is, for example, greater than room temperature and less than 80° C., and the kneading time is, for example, greater than 1 minute and less than 15 minutes. In the final kneading step, in addition to the above-mentioned components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added as needed.

[0213] 2. Tire manufacturing

[0214] The tire of the present invention can be produced as follows: the rubber composition obtained above is used as a cap rubber layer, molded into a tread rubber of a specified shape, and then molded together with other tire components on a tire molding machine by a common method, thereby producing a tire in the form of an unvulcanized tire.

[0215] It should be noted that, in the case of making the tread portion a multilayer structure with the base rubber layer, the above-mentioned rubber components and compounding materials can be basically used, and the compounding amounts thereof can be appropriately changed and kneaded in the same manner to obtain a rubber composition for forming the base rubber layer. Furthermore, the tread rubber is extruded together with the cap rubber layer to be molded into a predetermined shape, and then molded together with other tire components on a tire molding machine by a common method, thereby manufacturing a tire in the form of an unvulcanized tire.

[0216] 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 filling air pressure borne by the tire, a belt component as a component for strongly fastening the carcass to increase the rigidity of the tread, etc. are wound on a forming drum, and a bead portion as a component for fixing the two ends of the carcass to the edge portions on both sides and fixing the tire to the rim is arranged and formed into a ring shape, and then the tread is adhered to the central portion of the outer periphery and the sidewall is adhered to the radial outside to form a side portion, thereby producing an unvulcanized tire.

[0217] The unvulcanized tire prepared as described above is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be implemented by applying 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.

[0218] As described above, the rubber of the tread portion of the obtained tire is easily bent as a whole, and input from the road surface can be sufficiently absorbed and released as heat even during high-speed running, so that the ride comfort performance during high-speed running can be sufficiently improved.

[0219] Furthermore, the tire of the present invention can be appropriately used as a tire for passenger cars, a tire for large passenger cars, a tire for large SUVs, a tire for trucks and buses, a tire for two-wheeled vehicles, a tire for racing cars, a studless tire (a winter tire), a four-season tire, a run-flat tire, a tire for aircraft, a tire for mining, a non-pneumatic tire, etc., and is particularly preferably used as a tire for passenger cars. In addition, it is preferably used as a pneumatic tire.

[0220] Example

[0221] The following are examples (embodiments) that are considered to be preferred when implementing the invention, but the scope of the invention is not limited to these examples. In the examples, various chemicals shown below were used and the proportions were changed according to the tables to obtain compositions, and pneumatic tires (tire size: 205 / 55R16, aspect ratio: 55%, land ratio: 65%) made from the obtained compositions were studied, and the results calculated based on the following evaluation method are shown in Tables 2 to 4.

[0222] 1. Rubber composition forming the crown rubber layer

[0223] (1) Mixed materials

[0224] (a) Rubber component

[0225] (A)NR:SVR-L

[0226] (B) SBR-1: Modified S-SBR obtained by the method described in the following paragraph

[0227] (Styrene content: 25 mass%, vinyl content: 25 mass%)

[0228] (C) SBR-2: HPR840 manufactured by ENEOS Materials Co., Ltd.

[0229] (S-SBR) (styrene content: 10% by mass, vinyl content: 42% by mass)

[0230] (D) SBR-3: HPR850 manufactured by ENEOS Materials Co., Ltd.

[0231] (Modified S-SBR) (Styrene content: 27.5 mass%, vinyl content: 59.0 mass%)

[0232] (E)BR: UbepolBR150B (high cis BR) from Ube Kosan Co., Ltd.

[0233] (cis content 97 mass %, trans content 2 mass %, vinyl content 1 mass %)

[0234] (Manufacture of SBR-1)

[0235] The above-mentioned SBR-1 was prepared according to the following steps. First, an autoclave with an internal volume of 10 L, an inlet at the bottom, an outlet at the head, a stirrer and a jacket was used as a reactor, and two of them were connected in series, and butadiene, styrene and cyclohexane were mixed in a specified ratio. The mixed solution was passed through a dehydration column filled with activated alumina. In order to remove impurities, n-butyl lithium was mixed in a static mixer and then continuously supplied from the bottom of the first reactor. Furthermore, 2,2-bis(2-oxacyclopentyl)propane as a polar substance and n-butyl lithium as a polymerization initiator were continuously supplied from the bottom of the first reactor at a specified speed, respectively, and the temperature in the reactor was maintained at 95°C. The polymer solution was continuously discharged from the head of the reactor and supplied to 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 an oligomer component was continuously added at a predetermined rate in the form of a 1000-fold dilution of cyclohexane to carry out a modification reaction. The polymer solution was continuously discharged from the reactor, and an antioxidant was continuously added using a static mixer, and then the solvent was removed to obtain the target modified diene polymer (SBR-1).

[0236] By infrared spectroscopy, the absorption peak of vinyl group was 910 cm -1The vinyl content (unit: mass %) of the SBR was determined from the absorption intensity near 1.3447 W / m2. The styrene content (unit: mass %) was determined from the refractive index in accordance with JIS K 6383:1995.

[0237] (b) Compounding materials other than rubber components

[0238] (A) Carbon black: DIABLACK N220 manufactured by Mitsubishi Chemical Corporation

[0239] (N2SA: 115m 2 / g)

[0240] (B) Silica: Ultrasil VN3 manufactured by Evonik Industries

[0241] (N2SA: 175m 2 / g, average primary particle size: 17nm)

[0242] (C) Silane coupling agent: Si266 manufactured by Evonik Industries

[0243] (Bis(3-triethoxysilylpropyl) disulfide)

[0244] (D) Resin: SYLVATRAXX4401 manufactured by Arizona Chemical

[0245] (α-Methylstyrene resin)

[0246] (E) Oil: Vivatec 500 manufactured by H&R

[0247] (Aromatic operating oil: TDAE oil)

[0248] (F) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining and Smelting Co., Ltd.

[0249] (G) Antiaging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.

[0250] (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)

[0251] (H) Stearic acid: Beads Stearic Acid "Tsubaki" manufactured by NOF Corporation

[0252] (I) Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd.

[0253] (J) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. (containing 5% oil)

[0254] (K) Vulcanization accelerator: NOCCELER CZ (CBS) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0255] (N-cyclohexyl-2-benzothiazolylsulfenamide)

[0256] (2) Rubber composition forming the cap rubber layer

[0257] According to the compounding contents shown in Tables 2 to 4, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a Banbury mixer to obtain a kneaded product. The compounding amounts are parts by mass.

[0258] Next, sulfur and a vulcanization accelerator were added to the kneaded product, and kneaded for 5 minutes at 80° C. using an open roll mill to obtain a rubber composition for forming a cap rubber layer.

[0259] 2. Rubber composition forming the base rubber layer

[0260] In parallel, a rubber composition for forming a base rubber layer was prepared based on the formulation shown in Table 1 in the same manner as the rubber composition for forming a cap rubber layer.

[0261] [Table 1]

[0262] Mixed materials Mixing amount (mass parts) NR(TSR20) 70 BR (UBEPOL-BR150B manufactured by Ube Industries, Ltd.) 30 Carbon black (Show Black N330T manufactured by Cabot Japan Co., Ltd.) 35 Stearic acid (Stearic acid "Tsubaki" manufactured by NOF Corporation) 2 Zinc oxide (Zinc White No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd.) 4 Wax (Sunnoc Wax manufactured by Ouchi Shinko Chemical Co., Ltd.) 2 Anti-aging agent (NOCRAC 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) 3 Antiaging agent (ANTAGE RD manufactured by Kawaguchi Chemical Industry Co., Ltd.) 1 Sulfur (powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.) 1.7 Vulcanization accelerator (NOCCELERCZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) 1.2

[0263] 3. Manufacturing of pneumatic tires

[0264] Each rubber composition was extruded and processed into a predetermined shape having a total thickness shown in Tables 2 to 4 so that (cap rubber layer thickness / base rubber layer thickness) = 90 / 10 to produce a tread portion.

[0265] Thereafter, the unvulcanized tire was formed by laminating the tire together with other tire components and press-vulcanizing was performed at 170° C. for 10 minutes to manufacture the pneumatic tires (test tires) of Examples 1 to 10 shown in Tables 2 and 3 and the pneumatic tires (test tires) of Comparative Examples 1 to 6 shown in Table 4.

[0266] 4. Calculation of parameters

[0267] Thereafter, the following parameters were obtained for each test tire.

[0268] (1)tanδ

[0269] The rubber test piece for viscoelasticity measurement was prepared by cutting the crown rubber layer of the tread portion of each test tire into a length of 20 mm × width of 4 mm × thickness of 2 mm in the manner that the tire circumferential direction becomes the long side. For each rubber test piece, the EPLEXOR series manufactured by GABO was used to measure tanδ at a measurement temperature of 0°C and 30°C under the conditions of frequency of 10 Hz, initial strain of 5%, dynamic strain of 1%, and deformation mode: tension, and the 0°C tanδ and 30°C tanδ were obtained respectively. It should be noted that the 0°C tanδ of the base rubber layer is 0.07.

[0270] (2)Tg

[0271] For the rubber test piece for viscoelasticity measurement, which was similarly cut from the crown rubber layer, "EPLEXOR (registered trademark)" manufactured by GABO was used. Under the conditions of frequency 10 Hz, initial strain 2%, amplitude ±1% and heating rate 2°C / min, the temperature was changed from -60°C to 40°C, and tanδ was measured. The temperature corresponding to the maximum tanδ value in the obtained temperature distribution curve was determined as Tg.

[0272] (3) Complex elastic modulus

[0273] The rubber test piece for viscoelasticity measurement similarly cut from the crown rubber layer was measured using the EPLEXOR series manufactured by GABO, and the complex elastic modulus (MPa) was measured in the deformation mode: tension under the conditions of temperature 0°C, frequency 10 Hz, initial strain 5%, and dynamic strain 1%. It should be noted that the complex elastic modulus of the base rubber layer was 12.0 MPa.

[0274] (4) Acetone extract of the crown rubber layer (AE)

[0275] Using a vulcanized rubber test piece cut out from the cap rubber layer of the tread portion of each test tire, AE (mass %) was determined in accordance with JISK 6229:2015.

[0276] (5) (SBR content / land ratio), (silicon dioxide content / flatness ratio)

[0277] At the same time, based on the specifications and mixing contents of each test tire, the ratio of the content (mass part) of styrene-butadiene rubber (SBR) with a styrene amount of less than 25 mass% in 100 mass parts of the rubber component to the land ratio (%) of the tread portion (SBR content / land ratio), and the ratio of the content (mass part) of silica relative to 100 mass parts of the rubber component to the aspect ratio (%) (silica content / aspect ratio) were calculated.

[0278] 5. Performance evaluation test (evaluation of riding comfort performance)

[0279] Each test tire was installed on all wheels of a vehicle (a domestic FF car with a displacement of 2000cc), and filled with air to an internal pressure of 250kPa (the normal internal pressure of a passenger car). The vehicle was then driven at 180km / h on a test course on a dry asphalt road, and 20 drivers performed a sensory evaluation of the ride comfort during driving in five stages (the larger the value, the better). The total score based on the evaluations of the 20 drivers was then calculated.

[0280] Next, the result of Comparative Example 1 was set to 100, and the index was calculated based on the following formula to evaluate the riding comfort performance during high-speed running. A larger numerical value indicates a better riding comfort performance during high-speed running.

[0281] Ride comfort performance during high-speed driving = [(result of the test tire) / (result of Comparative Example 1)] × 100

[0282] [Table 2]

[0283]

[0284] [Table 3]

[0285]

[0286] [Table 4]

[0287]

[0288] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications may be made to the above-described embodiments within the scope of the same or equivalent aspects of the present invention.

[0289] The present invention (1) relates to a tire having a tread portion, characterized in that:

[0290] The cap rubber layer forming the tread portion is formed of a rubber composition.

[0291] The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component.

[0292] The loss tangent (0℃tanδ) measured in the deformation mode: tension under the conditions of temperature 0℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more,

[0293] The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

[0294] The present invention (2) is directed to the tire according to the present invention (1), wherein the amount of styrene in the styrene-butadiene rubber (SBR) is 20% by mass or less.

[0295] The present invention (3) is directed to the tire according to the present invention (2), wherein the amount of styrene in the styrene-butadiene rubber (SBR) is 15% by mass or less.

[0296] The present invention (4) relates to a tire in combination with any one of the present inventions (1) to (3), characterized in that the content of the styrene-butadiene rubber (SBR) is 35 parts by mass or less.

[0297] The present invention (5) is directed to the tire according to the present invention (4), characterized in that the content of the styrene-butadiene rubber (SBR) is 30 parts by mass or less.

[0298] The present invention (6) relates to a tire in combination with any one of the present inventions (1) to (5), wherein the 0°C tan δ is 0.30 or more.

[0299] The present invention (7) is directed to the tire according to the present invention (6), wherein the 0°C tanδ is 0.40 or more.

[0300] The present invention (8) relates to a tire in any combination with any one of the present inventions (1) to (7), characterized in that the loss tangent (30°C tanδ) of the crown rubber layer measured in a deformation mode: tension under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is less than 0.30.

[0301] The present invention (9) relates to the tire according to the present invention (8), wherein the 30°C tanδ is 0.25 or less.

[0302] The present invention (10) relates to a tire in combination with any one of the present inventions (1) to (9), characterized in that the glass transition temperature (Tg) of the cap rubber layer is greater than -40°C.

[0303] The present invention (11) relates to a tire in any combination with any one of the present inventions (1) to (10), characterized in that the tread portion is formed of a cap rubber layer forming an outermost layer and a base rubber layer forming an inner layer,

[0304] The cap rubber layer has a thickness of 10% or more and less than 100% of the entire tread portion thickness.

[0305] The present invention (12) relates to a tire in any combination with any one of the present inventions (1) to (11), characterized in that the rubber composition forming the above-mentioned crown rubber layer contains silica, and the content of silica in the above-mentioned rubber composition is greater than 90 parts by mass relative to 100 parts by mass of the rubber component.

[0306] The present invention (13) relates to the tire described in the present invention (12), characterized in that the content of silica in the rubber composition forming the cap rubber layer is 100 parts by mass or more relative to 100 parts by mass of the rubber component.

[0307] The present invention (14) relates to a tire in any combination with any one of the present inventions (1) to (13), characterized in that:

[0308] The land ratio of the tread portion is 60% or more.

[0309] The ratio of the content (mass parts) of styrene-butadiene rubber (SBR) with a styrene content of less than 25 mass% in 100 mass parts of the rubber component of the above-mentioned cap rubber layer to the land ratio (%) of the tread portion [the amount (mass parts) of SBR with a styrene content of less than 25 mass% / land ratio (%)] is less than 0.7.

[0310] The present invention (15) relates to a tire in any combination with any one of the present inventions (1) to (14), characterized in that the ratio of the silica content (parts by mass) to the aspect ratio (%) relative to 100 parts by mass of the rubber component [silica content (parts by mass) / aspect ratio (%)] is greater than 1.5.

Claims

1. A tire having a tread portion, characterized in that: The cap rubber layer forming the tread portion is formed of a rubber composition, The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component. The loss tangent (0℃tanδ) measured in the deformation mode: tension under the conditions of temperature 0℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more, The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

2. The tire according to claim 1, characterized in that The amount of styrene in the styrene-butadiene rubber (SBR) is 20% by mass or less.

3. The tire according to claim 2, characterized in that The amount of styrene in the styrene-butadiene rubber (SBR) is 15% by mass or less.

4. The tire according to any one of claims 1 to 3, characterized in that The content of the styrene-butadiene rubber (SBR) is 35 parts by mass or less.

5. The tire according to claim 4, characterized in that The content of the styrene-butadiene rubber (SBR) is 30 parts by mass or less.

6. The tire according to any one of claims 1 to 5, characterized in that The 0°C tanδ is greater than or equal to 0.

30.

7. The tire according to claim 6, characterized in that The 0°C tanδ is greater than or equal to 0.

40.

8. The tire according to any one of claims 1 to 7, characterized in that The cap rubber layer has a loss tangent (30°C tan δ) of 0.30 or less when measured in a deformation mode: tension under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%.

9. The tire according to claim 8, characterized in that The 30°C tanδ is 0.25 or less.

10. The tire according to any one of claims 1 to 9, characterized in that The cap rubber layer has a glass transition temperature (Tg) greater than -40°C.

11. The tire according to any one of claims 1 to 10, characterized in that The tread portion is formed of a cap rubber layer forming an outermost layer and a base rubber layer forming an inner layer. The thickness of the cap rubber layer is not less than 10% and less than 100% of the thickness of the entire tread portion.

12. The tire according to any one of claims 1 to 11, characterized in that The rubber composition forming the cap rubber layer contains silica, and the content of silica in the rubber composition is 90 parts by mass or more based on 100 parts by mass of the rubber component.

13. The tire according to claim 12, characterized in that The content of silica in the rubber composition forming the cap rubber layer is 100 parts by mass or more relative to 100 parts by mass of the rubber component.

14. The tire according to any one of claims 1 to 13, characterized in that The land ratio of the tread portion is 60% or more, The ratio of the content (mass parts) of styrene-butadiene rubber (SBR) with a styrene content of less than 25 mass% in 100 mass parts of the rubber component of the cap rubber layer to the land ratio (%) of the tread portion [amount (mass parts) of SBR with a styrene content of less than 25 mass% / land ratio (%)] is less than 0.

7.

15. The tire according to any one of claims 1 to 14, characterized in that The ratio of the content (parts by mass) of silica to 100 parts by mass of the rubber component and the oblateness (%) [silica content (parts by mass) / oblateness (%)] is 1.5 or more.

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