tire

Abstract

To improve the off-road performance of a tire.SOLUTION: A tire includes a tread part having a circumferential groove continuously extending in a circumferential direction. A cap rubber layer forming the tread part is formed from a rubber composition which contains 40 pts.mass or more and 80 pts.mass or less of styrene-butadiene rubber (SBR) with a styrene content of 25 mass% or less, in 100 pts.mass of a rubber component, and which contains 60 pts.mass or more of a filler with respect to 100 pts.mass of the rubber component. The rubber composition has a loss tangent 10°C tanδ of 0.28 or greater as measured in a deformation mode of tension under the conditions of a temperature of 10°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, and has a glass transition temperature Tg (°C) of -40°C or lower. Further, the glass transition temperature Tg (°C) and a depth G (mm) of the circumferential groove satisfy the following (formula 1): Tg≤-0.5×G-35 ... (formula 1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] Tires used for off-road driving require off-road propulsion performance, including the ability to dig up sand and soil from the off-road surface (soil removal performance) and the ability to suppress chipping during off-road driving (chipping resistance performance). Conventionally, improvements to off-road performance have been proposed by modifying the rubber composition that makes up the tire tread and the surface shape of the tread (for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-129214 [Patent Document 2] Japanese Patent Publication No. 2005-119614 [Patent Document 3] Japanese Patent Publication No. 2012-218652 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the off-road performance of tires manufactured based on the conventional technology described above is still insufficient, and further improvements are desired.

[0005] Therefore, the objective of this invention is to improve the off-road performance of tires. [Means for solving the problem]

[0006] The present invention A tire having a tread portion with circumferential grooves that communicate in the circumferential direction, The cap rubber layer that forms the tread portion The tire contains 40 parts by mass or more and 80 parts by mass or less of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, and contains 60 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component. Under the conditions of a temperature of 10°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, the loss tangent 10°C tanδ measured in the deformation mode of tension is at least 0.28. The tire is formed from a rubber composition having a glass transition temperature Tg (°C) of -40°C or less. Furthermore, the tire is characterized in that the glass transition temperature Tg (°C) and the depth G (mm) of the circumferential groove satisfy the following formula (1). Tg ≤ -0.5×G - 35 ········· (Formula 1) [Advantages of the Invention]

[0007] According to the present invention, the off-performance of the tire can be improved. [Embodiments for Carrying Out the Invention]

[0008] [1] Features of the Tire According to the Present Invention First, the features of the tire according to the present invention will be described.

[0009] 1. Overview The tire according to the present invention is a tire provided with a tread portion having circumferential grooves (hereinafter also simply referred to as "grooves") communicating in the circumferential direction. The cap rubber layer forming the tread portion is formed from a rubber composition containing 40 parts by mass or more and 80 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 containing 60 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component. And this rubber composition has a loss tangent 10°C tanδ measured in the deformation mode of tension under the conditions of a temperature of 10°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% of at least 0.28, and a glass transition temperature Tg (°C) of -40°C or less. Furthermore, in the tire according to the present invention, the glass transition temperature Tg (°C) and the depth G (mm) of the circumferential groove satisfy the following formula (1). Tg≦-0.5×G-35 (Formula 1)

[0010] The tread portion refers to the area that forms the contact surface of the tire, and specifically the portion radially outward from the carcass, belt layer, belt reinforcement layer, and other components containing fibrous materials. Furthermore, the cap rubber layer is not limited to the outermost cap rubber layer of the tread portion; if there are two or more layers within 5 mm inward from the tread surface, it is sufficient that at least one of the layers satisfies the requirements of the rubber composition.

[0011] These features allow for improved off-road performance, as will be discussed later.

[0012] 2. Mechanism of effect in the tire according to the present invention The mechanism by which the above-mentioned effects are manifested in the tire according to the present invention is thought to be as follows.

[0013] As mentioned above, when tires travel on off-road surfaces, they need to scrape up sand and dirt from the surface. It is thought that in this case, the tires compact the sand and dirt on the road surface, take it into the grooves of the tread, and then expel it through the rotation of the tires to generate propulsion.

[0014] The tire cap rubber layer according to the present invention is formed from a rubber composition containing 40 to 80 parts by mass of SBR with a styrene content of 25% by mass or less per 100 parts by mass of rubber component, and containing 60 parts by mass or more of filler per 100 parts by mass of rubber component.

[0015] By including 40 to 80 parts by mass of SBR with a styrene content of 25% by mass or less in 100 parts by mass of rubber component, a network of small amounts of styrene domains can be appropriately formed within the rubber matrix.

[0016] The formation of this styrene domain network mitigates the strain caused by rubber deformation, allowing for smooth force transmission in the tread area. This enables the tread to easily deform and recover, efficiently compacting sand and soil trapped in the grooves between the blocks on the tread surface.

[0017] Furthermore, the amount of styrene is more preferably 20% by mass or less, and even more preferably 15% by mass or less. On the other hand, 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.

[0018] In this invention, "containing 40 parts by mass or more and 80 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" means that the amount of SBR in 100 parts by mass of the rubber component is 40 parts by mass or more and 80 parts by mass or less, and the amount of styrene in the total SBR is 25% by mass or less.

[0019] In other words, when styrene-containing polymer (SBR) is contained alone in the rubber component, it indicates that the amount of styrene is 25% by mass or less. When multiple styrene-containing polymers (SBR) are contained in the rubber component, it indicates that the amount of styrene, calculated by the sum of the products of the amount of styrene (by mass) in each polymer and the amount of that polymer blended per 100 parts by mass of the rubber component (parts by mass), is 25% by mass or less.

[0020] More specifically, if 100 parts by mass of rubber component contain SBR1 (X1 parts by mass) with a styrene content of S1% by mass and SBR2 (X2 parts by mass) with a styrene content of S2% by mass, then the amount of styrene calculated from the formula {(S1 × X1) + (S2 × X2)} / (X1 + X2) is 25% by mass or less.

[0021] Furthermore, in the rubber composition after vulcanization, the amount of styrene can also be calculated by determining the amount of styrene contained in the rubber component after acetone extraction using solid-state nuclear magnetic resonance (solid-state NMR) or Fourier transform infrared spectrophotometer (FTIR).

[0022] Furthermore, the tire according to the present invention contains a large amount of filler, 60 parts by mass or more per 100 parts by mass of rubber component. This allows for the formation of a network of filler in addition to the styrene domain network described above within the cap rubber layer, thereby facilitating the transmission of force within the cap layer. As a result, the deformation and recovery of the cap layer are more adequate, and sand and soil taken into the grooves can be efficiently compacted and discharged from the grooves. It is more preferable to have 90 parts by mass or more, and even more preferable to have 120 parts by mass or more. On the other hand, there is no particular upper limit, but considering the processability, it is preferable to have 180 parts by mass or less, more preferable to have 160 parts by mass or less, and even more preferable to have 140 parts by mass or less.

[0023] In the tire according to the present invention, the loss tangent 10°C tanδ of the rubber composition forming the cap rubber layer, measured in tensile deformation mode under conditions of a temperature of 10°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1%, is further increased to 0.28 or higher.

[0024] The loss tangent tanδ is a viscoelastic parameter that indicates the energy absorption performance, and the larger the value, the more heat generation due to rubber deformation can be promoted. In the present invention, as described above, this 10°C tanδ is made large, to 0.28 or more, so that the energy applied to the tread can be easily dissipated as heat, making it difficult for the rubber to chip and sufficiently suppressing the occurrence of chipping. In addition, because the rubber can easily recover from deformation, sand and soil taken into the grooves can be efficiently compacted. A value of 0.31 or more is more preferable, and a value of 0.35 or more is even more preferable. There is no particular upper limit, but a value of 0.45 or less is preferable, a value of 0.43 or less is more preferable, and a value of 0.40 or less is even more preferable.

[0025] Although the above only specifies the tanδ at 10°C, it is preferable for tanδ to be large over a wide temperature range, as this allows more energy to escape as heat, further suppressing chipping. Specifically, the loss tangent at 0°C (0°C tanδ) is preferably 0.30 or higher, more preferably 0.35 or higher, and even more preferably 0.40 or higher. Furthermore, the loss tangent at 30°C (30°C tanδ) is preferably 0.27 or higher, more preferably 0.30 or higher, and even more preferably 0.33 or higher.

[0026] Furthermore, the loss tangent (tanδ) in the above can be measured using a viscoelasticity measuring device such as the "Iprexor®" manufactured by GABO.

[0027] On the other hand, when viewed from the perspective of grooves provided around the tread (circumferential grooves), the deeper the grooves, the larger the groove volume and the more sand and soil are taken in. However, the force required to compact the sand and soil is more easily dispersed, making it difficult to obtain propulsion efficiently.

[0028] Therefore, in the present invention, the glass transition temperature Tg (°C) of the rubber composition is set to be -40°C or lower, and the glass transition temperature Tg (°C) is set to be sufficiently low relative to the groove depth. Specifically, the relationship between the glass transition temperature Tg (°C) and the depth G (mm) of the circumferential groove is set to Tg ≤ -0.5 × G - 35.

[0029] As a result, even in deep grooves, the tread can flexibly deform and recover, suppressing the dispersion of force used to compact sand and soil. This allows for the incorporation and compaction of more sand and soil, resulting in more efficient propulsion. It is even more preferable that Tg ≤ -0.5 × G - 40.

[0030] The glass transition temperature (Tg) of the rubber composition described above can be determined based on the temperature distribution curve of tanδ measured using a viscoelasticity measuring device such as the Iplexer series manufactured by GABO, under conditions of frequency 10 Hz, initial strain 10%, amplitude ±0.5%, and heating rate 2°C / min. In the case of the present invention, the temperature corresponding to the largest tanδ value in the range of -60°C to 40°C of the measured temperature distribution curve is defined as the glass transition temperature (Tg). If there are two or more points with the largest tanδ value within the range of -60°C to 40°C, the point with the lowest temperature is defined as Tg. For example, in the present invention, if the maximum value of tanδ is within the range of -60°C to 40°C, then according to the above definition, the temperature at which that maximum value is shown is Tg. Also, for example, if a temperature distribution curve is obtained in which tanδ gradually decreases with increasing temperature within the range of -60°C to 40°C, and the temperature at which tanδ is shown to be the maximum value is -60°C, then according to the above definition, the glass transition temperature (Tg) is -60°C.

[0031] In this invention, "circumferential groove" refers to a groove with a width of 3 mm or more that is in communication with the tire in the circumferential direction and is the groove closest to the tire's equatorial plane. Any groove that extends continuously in the circumferential direction, including zigzag or wavy grooves, is included in the definition of a circumferential groove.

[0032] Furthermore, "groove depth" refers to the height from the bottom of the groove to the opening in the radial direction of the tire under normal conditions and no load. Normal conditions refer to the state when the tire is mounted on a normal rim and subjected to normal internal pressure. In the case of grooves that are not straight or stepped grooves, the maximum depth from the opening is defined as the "groove depth."

[0033] Furthermore, "standard rim" refers to the rim specified for each tire within the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standard, it refers to the rim with the smallest diameter and the narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage from between the rim and tire.

[0034] Furthermore, "standard internal pressure" refers to the air pressure specified for each tire by the aforementioned standards. For JATMA, it refers to the maximum air pressure; for ETRTO, it refers to "INFLATION PRESSURE"; and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Similar to the case of "standard rim," refer to JATMA, ETRTO, and TRA in that order and follow the respective standards. In the case of tires not specified in the standards, it refers to the standard internal pressure (but 250 kPa or higher) of another tire size (specified in the standards) that uses the aforementioned standard rim as the standard rim. If multiple standard internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0035] [2] More preferred embodiment of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following embodiments.

[0036] 1. Filler As described above, in the tire according to the present invention, by incorporating a large amount of filler into the cap rubber layer, at a ratio of 60 parts by mass or more per 100 parts by mass of rubber component, a network of filler is formed within the cap rubber layer, thereby facilitating further force transmission within the cap layer.

[0037] In the present invention, it is preferable to use carbon black and silica as specific fillers, and in this case, the carbon black content may be greater than the silica content, that is, (silica content / carbon black content) may be less than 1.

[0038] This allows the carbon black to provide reinforcement, improving chipping resistance. A value of 0.8 or less is more preferable, and 0.6 or less is even more preferable.

[0039] 2. Thickness and multi-layering of the tread section In the present invention, the tread portion may be formed of only one cap rubber layer, or it may be made of two layers by providing a base rubber layer inside the cap rubber layer, or it may be made of three layers, or four or more layers. In this case, considering sufficient intake of sand and soil into the groove, the thickness of the cap rubber layer relative to the entire tread portion is preferably 10% or more, and more preferably 70% or more.

[0040] In this invention, the tread thickness refers to the thickness of the tread on the tire's equatorial plane in the tire's radial cross-section. When the tread is formed from a single rubber composition, it refers to the thickness of that rubber composition. When it is formed from a laminated structure of multiple rubber compositions, as described later, it refers to the total thickness of these layers.

[0041] In the case of a tire with grooves on its equatorial plane, this refers to the thickness from the intersection of the straight line connecting the outermost endpoints of the grooves in the tire's radial direction with the tire's equatorial plane, to the innermost interface of the tread portion in the tire's radial direction.

[0042] The tread portion refers to the area that forms the contact surface of the tire, specifically the part radially outside the carcass, belt layer, belt reinforcement layer, and other components containing fibrous materials. The thickness of the tread portion can be measured by cutting a section of the tire radially and aligning the bead portion with the standard rim width.

[0043] Furthermore, when the tread section is composed of a cap rubber layer and a base rubber layer, considering handling stability, it is preferable that the tanδ of the base rubber layer at each of the above temperatures (0°C, 10°C, 30°C) be smaller than the tanδ of the cap rubber layer.

[0044] The tanδ of the cap rubber layer and base rubber layer at each temperature can be adjusted as appropriate by the amount and type of compounding materials described later. For example, it can be increased by increasing the amount of styrene in the rubber component, increasing the SBR content in the rubber component, increasing the amount of styrene in the SBR component, increasing the content of fillers such as silica and carbon black, or increasing the content of resin components. Conversely, it can be lowered by decreasing the amount of styrene in the rubber component, decreasing the SBR content in the rubber component, decreasing the amount of styrene in the SBR component, decreasing the content of fillers such as silica and carbon black, or decreasing the content of resin components.

[0045] 3. Acetone extract (AE) from the cap rubber layer In the present invention, the acetone extract (AE) in the cap rubber layer is preferably 10% by mass or more, more preferably 12% by mass or more, and even more preferably 14% by mass or more. On the other hand, there is no particular upper limit, but it is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 17% by mass or less.

[0046] Acetone extract (AE) can be considered an indicator of the amount of softeners and other substances in a rubber composition, and can also be considered an indicator of the softness of the rubber composition. Therefore, by controlling the amount of AE in the cap rubber layer as described above, the cap rubber layer can deform appropriately, making it easier to obtain the force to compact sand and soil.

[0047] The acetone extract (AE) can be measured in accordance with JIS K 6229:2015. Specifically, a vulcanized rubber test piece cut from the measurement site is immersed in acetone for 72 hours at room temperature and atmospheric pressure, and the AE (mass%) can be obtained by determining the mass loss rate (%) of the test piece.

[0048] More specifically, the soluble components can be extracted by immersing each vulcanized rubber test piece in acetone for 72 hours at room temperature and atmospheric pressure, measuring the mass of each test piece before and after extraction, and then determining the result using the following formula. Acetone extraction amount (%) = {(Mass of rubber test piece before extraction - Mass of rubber test piece after extraction)} / (mass of rubber test piece before extraction)} × 100

[0049] Furthermore, the aforementioned acetone extract can be appropriately modified by changing the blending ratio of plasticizers in the rubber composition.

[0050] 4. Rand ratio In the tire according to the present invention, it is preferable that the land ratio in the tread portion of the tire, when mounted on a regular rim and subjected to regular internal pressure, is 40% or more.

[0051] The "land ratio" is the ratio of the actual contact area to the hypothetical contact area where all the grooves on the tread surface are filled. By setting the land ratio to 40% or more, the contact area with the road surface is increased, allowing for stable and sufficient grip performance. On the other hand, it is preferable to set the land ratio to 95% or less. This allows sufficient sand and soil to be incorporated into the grooves of the tread.

[0052] Furthermore, if the product of the styrene-butadiene rubber (SBR) content (parts by mass) with a styrene content of 25% by mass or less per 100 parts by mass of rubber component and the land ratio (%) in the tread area is 4400 or less, the effects of the styrene domain network work together to further improve off-road performance.

[0053] The above-mentioned land ratio can be determined from the contact patch shape under normal rim, normal internal pressure, and normal load conditions.

[0054] Specifically, the tire is mounted on a standard rim, the standard internal pressure is applied, and it is left to stand at 25°C for 24 hours. Then, ink is applied to the surface of the tire tread, and the standard load is applied and it is pressed onto cardboard (camber angle is 0°). By transferring the image to the paper, the contact shape can be obtained. The tire is rotated 72° in the circumferential direction, and the image is transferred at five locations. In other words, the contact shape is obtained five times. At this time, for each of the five contact shapes, the parts that are interrupted by grooves in the contour are smoothly connected, and the resulting shape is considered the virtual contact surface.

[0055] The land ratio can then be calculated from (average area of ​​the five contact shapes (inked areas) transferred to the cardboard / (average area of ​​the virtual contact surface obtained from the five contact shapes) × 100 (%).

[0056] Furthermore, "standard load" refers to the load specified for each tire in the standards system, including the standard on which the aforementioned tire is based, and represents the maximum mass that the tire is allowed to be loaded with. For JATMA, it refers to the maximum load capacity; for ETRTO, it refers to "LOAD CAPACITY"; and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As with the aforementioned "standard rim" and "standard internal pressure", refer to JATMA, ETRTO, and TRA in that order and follow their respective standards. In the case of tires not specified in the standards, the standard load W is calculated as follows: L We seek. V = {(Dt / 2)} 2-(Dt / 2-Ht) 2} × π × Wt W L = 0.000011 × V + 175 W L :Normal load (kg) V: Virtual volume of the tire (mm) 3 ) Dt: Tire outer diameter Dt (mm) Ht: Tire section height (mm) Wt: Tire section width (mm)

[0057] 5. Flatness The aspect ratio indicates the ratio of the cross-sectional height to the cross-sectional width of the tire. The smaller this ratio, the larger the contact area can be secured, allowing the tread to take in and expel more sand and soil, thus improving off-road performance. In this invention, the specific aspect ratio is preferably 80% or less.

[0058] Furthermore, if the product of the filler content (parts by mass) per 100 parts by mass of rubber component and the aspect ratio is 9100 or less, the network effect of the filler works together to further improve the off-road performance.

[0059] The aspect ratio (%) mentioned above can be calculated using the following formula, with the tire's cross-sectional height Ht (mm), cross-sectional width Wt (mm), tire outer diameter Dt (mm), and rim diameter R (mm) assuming an internal pressure of 250 kPa. Oblateness (%)=(Ht / Wt)×100(%) Ht = (Dt - R) / 2

[0060] [3] Embodiment The present invention will be specifically described below based on embodiments.

[0061] 1. Rubber composition that forms the cap layer In the tire according to 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 rubber components, fillers, softeners, vulcanizing agents, and vulcanization accelerators described below.

[0062] (1) Compounding materials (a) Rubber component The rubber component is not particularly limited, and any rubber (polymer) commonly used in tire manufacturing can be used, such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), butyl rubber, and thermoplastic elastomers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-butadiene block copolymer (SB).

[0063] In this embodiment, among these, the rubber component contains styrene, and it is preferable to include one of the styrene-based polymers such as SBR, SBS, and SB. Furthermore, these styrene-based polymers may be used in combination with other rubber components; for example, a combination of SBR and BR, or a combination of SBR, BR, and isoprene-based rubber is preferred.

[0064] (i) SBR The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. In the present invention, as described above, the amount of styrene in the SBR component is 25% by mass or less. More preferably 20% by mass or less, and even more preferably 15% by mass or less. On the other hand, 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.

[0065] The vinyl content (1,2-bonded butadiene content) of SBR is, for example, more than 5% by mass and less than 70% by mass. Note that the vinyl content of SBR refers to the 1,2-bonded butadiene content relative to the total butadiene portion within the SBR component. Furthermore, the structural identification of SBR (measurement of styrene content and vinyl content) can be performed, for example, using the JNM-ECA series instrument manufactured by JEOL Ltd.

[0066] As mentioned above, the SBR content in 100 parts by mass of rubber component is preferably 40 parts by mass or more and 80 parts by mass or less, more preferably 50 parts by mass or more and 70 parts by mass or less, and even more preferably 55 parts by mass or more and 65 parts by mass or less.

[0067] The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc., can be used. The SBR may be either unmodified SBR or modified SBR. Furthermore, hydrogenated SBR, in which the butadiene portion of the SBR is hydrogenated, may be used. Hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of the SBR, or a similar structure may be obtained by copolymerizing styrene, ethylene, and butadiene.

[0068] Modified SBRs can be any SBR having a functional group that interacts with a packing material such as silica. Examples include terminally modified SBRs (terminally modified SBRs having the functional group at the terminal) in which at least one end of the SBR is modified with a compound having the functional group (modifying agent), main-chain modified SBRs having the functional group in the main chain, main-chain terminally modified SBRs having the functional group in both the main chain and the terminal (for example, main-chain terminally modified SBRs having the functional group in the main chain and at least one end modified with the modifying agent), and terminally modified SBRs that are modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and in which hydroxyl groups or epoxy groups are introduced.

[0069] 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 substituents.

[0070] Further, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0071]

Chemical formula

[0072] 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 derivatives thereof. R 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. R 4 and R 5 may combine to form a ring structure together with the nitrogen atom. n represents an integer.

[0073] As the modified SBR modified with the compound (modifying agent) represented by the above formula, SBR obtained by modifying the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) with the compound represented by the above formula (modified SBR described in JP-A-2010-111753, etc.) can be used.

[0074] R 1 , R 2 and R 3A suitable alkoxy group is used (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 A suitable alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is used. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Also, R 4 and R 5 When the alkoxy group is bonded to form a ring structure with the nitrogen atom, it is preferably a 4- to 8-membered ring. Note that the alkoxy group also includes cycloalkoxy groups (such as cyclohexyloxy group) and aryloxy groups (such as phenoxy group and benzyloxy group).

[0075] Specific examples of the above-mentioned denaturing agents include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These may be used individually or in combination of two or more.

[0076] Furthermore, modified SBR can also be modified using the following compounds (modifying agents): For example, 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 diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxylated liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, Diglycidylamino compounds such as diglycidyl orthotoluidine, tetraglycidylmetoxylendiamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamate chloride, 4-morpholine carbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamate chloride, and N,N-diethylcarbamate 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-(tributoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (Trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide Sulfide group-containing silane compounds such as [sisilyl)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)aminoethyl Alkoxysilanes such as tiltriethoxysilane; (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; 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-triones. Examples include 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-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone. Modification using the above compounds (modifiers) can be carried out by known methods.

[0077] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used. SBR may be used alone or in combination of two or more types.

[0078] (b)BR In the present invention, BR may be further included as needed. In this case, the BR content in 100 parts by mass of the rubber component is preferably more than 20 parts by mass, and more preferably more than 30 parts by mass. On the other hand, it is preferably less than 50 parts by mass, and more preferably less than 45 parts by mass.

[0079] 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.

[0080] The BR is not particularly limited, and can be high-cis content BR (cis content of 90% or more), low-cis content BR, or BR containing syndiotactic polybutadiene crystals. The BR can be either unmodified or modified, and modified BR can be modified BR into which the aforementioned functional groups have been introduced. These can be used individually or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0081] For example, products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used as BRs.

[0082] (h) Isoprene rubber In the present invention, isoprene rubber may be included as needed. In this case, the content of isoprene rubber in 100 parts by mass of rubber component is preferably 20 parts by mass or more and 40 parts by mass or less.

[0083] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0084] For NR, common types used in the tire industry can be used, such as SIR20, RSS#3, and TSR20. For IR, there are no particular limitations, and common types used in the tire industry can be used, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity 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 individually or in combination of two or more types.

[0085] (ii) Other rubber components Furthermore, other rubber components may include rubbers (polymers) commonly used in tire manufacturing, such as nitrile rubber (NBR).

[0086] (b) Compounding materials other than rubber components (i) Filler In the present invention, the rubber composition preferably contains a filler. Specific fillers include, for example, silica, carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. As mentioned above, among these, the use of silica and carbon black in combination is preferable. Furthermore, the ratio of (silica content / carbon black content) may be less than 1.

[0087] (i-1) Silica In the present invention, the rubber composition preferably contains silica, and more preferably contains a silane coupling agent together with the silica.

[0088] The BET specific surface area of ​​silica is 140 m² from the perspective of obtaining good durability performance. 2 Preferably more than / g, 160m 2 A value greater than / g is preferable. On the other hand, from the viewpoint of obtaining good rolling resistance at high speeds, 300m 2 Less than / g is preferable. The BET specific surface area mentioned above is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0089] In the present invention, as described above, it is preferable to use silica with a particle size of 17 nm or less in the rubber composition. By using silica with a small particle size, the frequency of contact with the polymer can be increased. The lower limit is not particularly limited, but from the viewpoint of dispersibility during mixing, it is preferable to be 10 nm or more.

[0090] When silica is used, the silica content is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, per 100 parts by mass of rubber component. On the other hand, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 60 parts by mass or less.

[0091] Examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Among these, wet-process silica is preferred because it contains a large number of silanol groups. Silica made from hydrated glass or silica made from biomass materials such as rice husks may also be used.

[0092] For example, silica products from companies such as Evonik Industries, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Ltd., and Tokuyama Corporation can be used.

[0093] (i-2) Silane coupling agent When silica is used, it is preferable that the rubber composition contains a silane coupling agent along with the silica. The silane coupling agent is not particularly limited and includes, for example, 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-dimethylthioca Examples include sulfide compounds such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z from Momentive; vinyl compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used individually or in combination of two or more.

[0094] Examples of silane coupling agents that can be used include products from Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd.

[0095] The silane coupling agent content is, for example, more than 3 parts by mass and less than 25 parts by mass per 100 parts by mass of silica.

[0096] (ii) Carbon Black In the present invention, the rubber composition preferably contains carbon black from the viewpoint of reinforcing properties.

[0097] The specific content ratio of carbon black to 100 parts by mass of rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more. On the other hand, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0098] Carbon black is not particularly limited and can 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 individually or in combination of two or more types.

[0099] The specific surface area (CTAB) of carbon black (Cetyl Tri-methyl Ammonium Bromide) is 130 m². 2 Preferably 160m / g or more. 2 It is more preferable that it is 170m or more / g. 2 It is even more preferable if it is 1 / g or more. On the other hand, 250m 2 Preferably less than / g, 200m 2It is more preferable that the value is less than or equal to / g. Note that the CTAB specific surface area is a value measured in accordance with ASTM D3765-92.

[0100] There are no specific limitations on the carbon black used, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon Corporation. These can be used individually or in combination of two or more types.

[0101] (iii) Other fillers The rubber composition may, if necessary, further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, in addition to the silica and carbon black mentioned above. The amount of these fillers 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.

[0102] (b) Plasticizer components The rubber composition may contain oil, liquid rubber, and resin as plasticizer components to soften the rubber. The plasticizer components are those that can be extracted from vulcanized rubber with acetone. The total content of the plasticizer components is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, it is preferably 55 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. If the rubber component is an oil-dispersed rubber component, the amount of oil used in the oil dispersion is included in the oil content.

[0103] (i) oil Examples of oils include mineral oil (generally called process oil), vegetable oils, or mixtures thereof. Examples of mineral oils (process oils) include paraffinic process oil, aromatic process oil, and naphthenic process oil. 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 oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used individually or in combination of two or more. Furthermore, from a life cycle assessment perspective, waste oil used as lubricant in rubber mixers or automobile engines, or waste cooking oil may be used as appropriate.

[0104] Specific process oils (mineral oils) that can be used include products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kosan Co., Ltd.

[0105] (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 from vulcanized tires by acetone extraction. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and their hydrogenated derivatives.

[0106] Farnesene polymers are polymers obtained by polymerizing farnesene and have constituent 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).

[0107] The farnesene polymer may be a farnesene homopolymer (farnesene homopolymer) or a farnesene-vinyl monomer copolymer (farnesene-vinyl monomer copolymer).

[0108] 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).

[0109] The liquid diene polymer has a weight-average molecular weight (Mw) on a polystyrene basis, measured by gel permeation chromatography (GPC), for example, 1.0 × 10⁻⁶. 3 Super, 2.0×10 5 It is less than. In this specification, the Mw of the liquid diene polymer is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0110] The liquid rubber content (total content of liquid farnesene polymers, liquid diene polymers, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass per 100 parts by mass of rubber components.

[0111] As for liquid rubber, products from companies such as Kuraray Co., Ltd. and Clay Valley Corporation can be used.

[0112] (iii) Resin components The resin component also functions as a tackifying agent and may be solid or liquid at room temperature. Specific resin components include, for example, rosin resins, styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more may be used in combination. The resin component content is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component. These resin components may be given modified groups that can react with silica or the like, as needed.

[0113] Rosin resins are resins whose main component is rosin acid, obtained by processing pine resin. These rosin resins (rosins) can be classified according to whether or not they are modified, and can be classified into unmodified rosin and rosin derivatives. Examples of unmodified rosin include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionate rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Rosin derivatives are modified forms of unmodified rosin and include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, rosin amide compounds, and rosin amine salts.

[0114] Styrene resins are polymers that use styrene monomers as constituent monomers, and include polymers polymerized with styrene monomers as the main component (50% by mass or more). Specifically, 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 copolymerize with them.

[0115] Examples of the aforementioned 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; and α,β-unsaturated carboxylic acids such as maleic anhydride or their acid anhydrides.

[0116] Among coumarone-based resins, coumarone-indene resin is preferred. Coumarone-indene resin is a resin that contains coumarone and indene as monomer components that constitute the resin's backbone (main chain). Other monomer components that can be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0117] The coumaron indene resin content is, for example, more than 1.0 part by mass and less than 50.0 parts by mass per 100 parts by mass of rubber component.

[0118] The hydroxyl value (OH value) of coumarone indene resin is, for example, greater than 15 mg KOH / g and less than 150 mg KOH / g. The OH value is expressed in milligrams as the amount of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl groups when acetylating 1 g of resin, and is measured by potentiometric titration (JIS K 0070:1992).

[0119] The softening point of coumaron indene resin is, for example, above 30°C and below 160°C. The softening point is determined by measuring the softening point as specified in JIS K 6220-1:2001 using a ring-type softening point measuring device, and it is the temperature at which the sphere descends.

[0120] Examples of terpene resins include polyterpenes, terpene phenols, and aromatically modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n A hydrocarbon represented by the following composition and its oxygen-containing derivative, a monoterpene (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpene (C 20 H 32These are compounds with a terpene as their basic skeleton, classified as such, and examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0121] 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 terpene compounds mentioned above, as well as hydrogenated terpene resins obtained by hydrogenating these terpene resins. Terpene phenols include resins obtained by copolymerizing the above terpene compounds with phenolic compounds, and resins obtained by hydrogenating these resins. Specifically, resins obtained by condensing the above terpene compounds, phenolic compounds, and formalin are included. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Aromatically modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating these resins. The aromatic compounds are not particularly limited as long as they are compounds having an aromatic ring, but examples include phenol 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; coumarone, indene, and others.

[0122] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5-based petroleum resin.

[0123] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples include coumarone indene resin, coumarone resin, indene resin, and aromatic vinyl resins, which are suitably used. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, due to their economical nature, ease of processing, and excellent heat generation properties. Aromatic vinyl resins that are commercially available from companies such as Kraton and Eastman Chemical can be used.

[0124] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified. Examples of the C5 and C9 fractions include the petroleum fractions mentioned above. As for the C5C9 resin, commercially available products from companies such as Tosoh Corporation and LUHUA can be used.

[0125] While there are no particular limitations on the acrylic resin used, for example, a solvent-free acrylic resin can be used.

[0126] Solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous mass polymerization) (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, Toa Gosei Research Annual Report TREND2000 No. 3 pp. 42-45, etc.) with minimal use of polymerization initiators, chain transfer agents, organic solvents, etc. as auxiliary raw materials. In this invention, (meth)acrylic means methacrylic and acrylic.

[0127] Examples of monomer components constituting the above-mentioned 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.

[0128] Furthermore, as monomer components constituting the above-mentioned acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used along with (meth)acrylic acid and (meth)acrylic acid derivatives.

[0129] The above-mentioned acrylic resin may be a resin composed solely of (meth)acrylic components, or a resin that also contains components other than (meth)acrylic components. Furthermore, the above-mentioned acrylic resin may have hydroxyl groups, carboxyl groups, silanol groups, etc.

[0130] As resin components, products from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0131] (H) Stearic acid In the present invention, the rubber composition preferably contains stearic acid. The stearic acid content 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. Conventional known stearic acid can be used, for example, products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, Chiba Fatty Acid Co., Ltd., etc.

[0132] (ii) Anti-aging agents In the present invention, it is preferable that the rubber composition contains an anti-aging agent. The amount of the anti-aging agent 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.

[0133] Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers and other quinoline-based antioxidants; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane. These may be used individually or in combination of two or more types.

[0134] Furthermore, as an anti-aging agent, products from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. can be used.

[0135] (Ho) Wax In the present invention, the rubber composition preferably contains wax. The wax-off content 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, per 100 parts by mass of the rubber component.

[0136] The waxes are not particularly limited and include petroleum-based waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant-based waxes and animal-based waxes; and synthetic waxes such as polymers of ethylene and propylene. These may be used individually or in combination of two or more types.

[0137] For example, waxes from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used.

[0138] (f) Zinc oxide The rubber composition may contain zinc oxide. The zinc oxide content 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. Conventionally known zinc oxides 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.

[0139] (t) Processing aid The rubber composition may contain processing aids. Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. Products from companies such as Rhein Chemie and Structol can be used. These may be used individually or in combination of two or more. Among these, fatty acid metal salts are preferred.

[0140] Examples of fatty acids that make up fatty acid metal salts include saturated or unsaturated fatty acids (preferably saturated or unsaturated fatty acids having 6 to 28 carbon atoms (more preferably 10 to 25 carbon atoms, and even more preferably 14 to 20 carbon atoms)), such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, and nervonic acid. These can be used individually or in combination of two or more. Among these, saturated fatty acids are preferred, and saturated fatty acids having 14 to 20 carbon atoms are more preferred.

[0141] Examples of metals that make up fatty acid metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel, and molybdenum. These may be used individually or in combination of two or more. Among these, zinc is preferred.

[0142] The content of the processing aid is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, it is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 4 parts by mass or less.

[0143] (h) Crosslinking agents and vulcanization accelerators The rubber composition preferably contains a crosslinking agent such as sulfur. The crosslinking agent content 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.

[0144] Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. These may be used individually or in combination of two or more types.

[0145] For sulfur, products from companies such as Tsurumi Chemical Industries, Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industries Co., Ltd. can be used.

[0146] Other crosslinking agents besides sulfur include, for example, sulfur-containing vulcanizing agents such as Tackyrol V200 manufactured by Taoka Chemical Industries, Ltd. and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Lanxess, as well as organic peroxides such as dicumyl peroxide.

[0147] The rubber composition preferably contains a vulcanization accelerator. The amount of 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.

[0148] Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; 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-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotrilguanidine, and orthotrilbiguanidine. These may be used individually or in combination of two or more.

[0149] (Ri) Others In addition to the above-mentioned components, the rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylate metal salts, organic peroxides, and reversion (vulcanization reversal) inhibitors, as needed. 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.

[0150] (2) Preparation of rubber composition The rubber composition that forms the cap rubber layer is produced by appropriately adjusting the various compounding materials described above, using a general method that includes a base mixing step of mixing rubber components with a filler such as carbon black, and a finish mixing step of mixing the mixture obtained in the base mixing step with a crosslinking agent.

[0151] Mixing can be carried out using known (closed) mixers such as Banbury mixers, kneaders, and open roll mixers.

[0152] The mixing temperature in the base mixing process is, for example, more than 50°C and less than 200°C, and the mixing time is, for example, more than 30 seconds and less than 30 minutes. In the base mixing process, in addition to the above components, compounding agents conventionally used in the rubber industry, such as softeners such as oils, zinc oxide, antioxidants, waxes, and vulcanization accelerators, may be added and mixed as needed.

[0153] In the final mixing step, the mixture obtained in the base mixing step and the crosslinking agent are mixed together. The mixing temperature in the final mixing step is, for example, above room temperature but below 80°C, and the mixing time is, for example, more than 1 minute but less than 15 minutes. In the final mixing step, in addition to the above components, vulcanization accelerators, zinc oxide, etc., may be added and mixed as needed.

[0154] 2. Tire manufacturing The tire according to the present invention can be manufactured as an unvulcanized tire by first forming the rubber composition obtained above as a cap rubber layer into a tread rubber of a predetermined shape, and then molding it together with other tire components on a tire molding machine in a conventional manner.

[0155] Furthermore, when the tread section is to have a multi-layer structure with the base rubber layer, a rubber composition for forming the base rubber layer can be obtained by using the above-mentioned rubber components and compounding materials, appropriately changing their proportions, and kneading them in the same manner. Then, after extruding it together with the cap rubber layer to form a tread rubber of a predetermined shape, it can be manufactured as an unvulcanized tire by molding it together with other tire components on a tire molding machine in a normal manner.

[0156] Specifically, an inner liner (a component to ensure the airtightness of the tire), a carcass (a component to withstand the load, impact, and air pressure of the tire), and a belt (a component to tightly fasten the carcass and increase the rigidity of the tread) are wound onto a molding drum. The ends of the carcass are fixed to both side edges, and a bead (a component to fix the tire to the rim) is placed to form a toroid shape. After forming the toroid, the tread is attached to the center of the outer circumference, and the sidewall is attached to the radially outward side to form the side section, thereby creating an unvulcanized tire.

[0157] Subsequently, the prepared unvulcanized tire is heated and pressurized in a vulcanizing machine to obtain a tire. The vulcanization process can be carried out by applying known vulcanization methods. The vulcanization temperature is, for example, above 120°C and below 200°C, and the vulcanization time is, for example, above 5 minutes and below 15 minutes.

[0158] As described above, the resulting tire can generate propulsion by compacting sand and soil on the off-road surface, incorporating them into the grooves of the tread, and then expelling them from the grooves through the rotation of the tire. Therefore, it is possible to significantly improve off-road performance.

[0159] The tire according to the present invention is not particularly limited to any category and can be used as a passenger car tire, a heavy-duty vehicle tire such as a truck or bus, a motorcycle tire, a run-flat tire, a non-pneumatic tire, etc., but it is preferable to use it as a passenger car tire. Furthermore, it is preferable to use it as a pneumatic tire. [Examples]

[0160] The following examples (case studies) are shown as preferred for implementation, but the scope of the present invention is not limited to these examples. In the examples, pneumatic tires (tire size: LT315 / 70R17 (aspect ratio: 70%, land ratio: 52%)) made from compositions obtained by changing the formulation according to each table using the various chemicals shown below were examined, and the results calculated based on the evaluation method below are shown in Tables 2 to 4.

[0161] 1. Rubber composition for forming the cap rubber layer (1) Compounding materials (a) Rubber component (i) SBR-1: Modified S-SBR obtained by the method described in the next paragraph. (Styrene content: 25% by mass, Vinyl content: 25% by mass) (b) SBR-2: HPR840 (S-SBR) manufactured by JSR Corporation (Styrene content: 10% by mass, vinyl content: 42% by mass) (H)NR:TSR20 (ii) BR: Ube Pole BR150B (High-Sys BR) manufactured by Ube Industries, Ltd. (Cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

[0162] (Manufacturing of SBR-1) The above SBR-1 is prepared according to the following procedure. First, two autoclaves with a total volume of 10 L, an inlet at the bottom and an outlet at the top, equipped with a stirrer and a jacket, are connected in series as reactors, and butadiene, styrene, and cyclohexane are mixed in predetermined ratios. This mixed solution is passed through a dehydration column packed with activated alumina, and after mixing with n-butyllithium in a static mixer to remove impurities, it is continuously supplied from the bottom of the first reactor. Furthermore, 2,2-bis(2-oxolanil)propane as a polar substance and n-butyllithium as a polymerization initiator are continuously supplied from the bottom of the first reactor at predetermined rates, and the reactor temperature is maintained at 95°C. The polymer solution is continuously withdrawn from the top of the reactor and supplied to the second reactor. The temperature of the second reactor is maintained at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) and the oligomer component is continuously added at a predetermined rate as a 1000-fold dilution of cyclohexane to carry out the modification reaction. This polymer solution is continuously withdrawn from the reactor, an antioxidant is continuously added using a static mixer, and then the solvent is removed to obtain the desired oil-expanding modified diene polymer (SBR-1).

[0163] The amount of vinyl bond in SBR-1 (in mole percent) was determined by infrared spectroscopy to be at the absorption peak of the vinyl group, 910 cm⁻¹. -1 The absorption intensity in the vicinity is used to determine the amount of styrene (unit: mass%), which is determined from the refractive index according to JIS K6383 (1995).

[0164] (b) Compounding materials other than rubber components (i) Carbon Black: Show Black N134 manufactured by Cabot Japan Co., Ltd. (CTAB specific surface area: 135m 2 / g) (b) Silica: UltraSil VN3 manufactured by Evonik Industries (N2SA:175m 2 ( / g, 18nm) (h) Silane coupling agent: Si266 manufactured by Evonik Industries (Bis(3-triethoxysilylpropyl) disulfide) (ii) Resin: PetroTac 90 (C5 / C9 copolymer petroleum resin) manufactured by Tosoh Corporation (H) Oil: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. (H) Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (T) Anti-aging agent-1: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) (C) Anti-aging agent-2: Antigen RD manufactured by Sumitomo Chemical Co., Ltd. (polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) (Re)Stearic acid: Beads stearic acid "Tsubaki" manufactured by NOF Corporation (Nu) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. (L) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries Co., Ltd. (containing 5% oil) (Wo) Vulcanization accelerator: Noxellar CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiadylsulfenamide (CBS))

[0165] (2) Rubber composition for forming the cap rubber layer According to the formulations shown in Tables 2-4, the materials other than sulfur and vulcanization accelerator were mixed in a Banbury mixer for 5 minutes at 150°C to obtain the mixture. The amounts of each ingredient are in parts by mass.

[0166] Next, sulfur and a vulcanization accelerator are added to the mixture, and the mixture is kneaded using an open roll at 80°C for 5 minutes to obtain a rubber composition that forms the cap rubber layer.

[0167] 2. Rubber composition forming the base rubber layer In parallel, a rubber composition for forming the base rubber layer is obtained based on the formulation shown in Table 1, in the same manner as in the production of the rubber composition for forming the cap rubber layer.

[0168] [Table 1]

[0169] 3. Rubber caps and pneumatic tires Each rubber composition is used to manufacture the tread portion by extruding it into a predetermined shape with a (thickness of the cap rubber layer / thickness of the base rubber layer) ratio of 90 / 10 and a total thickness of 20.5 mm.

[0170] Subsequently, the tire components are bonded together to form an unvulcanized tire, which is then press-vulcanized for 10 minutes under conditions of 170°C to produce the pneumatic tires (test tires) for Examples 1 to 16 and Comparative Examples 1 to 5.

[0171] 4. Calculation of parameters (1) tanδ From the cap rubber layer of the tread of each test tire, a rubber test piece measuring 20 mm in length, 4 mm in width, and 2 mm in thickness was cut out so that the longer side was circumferential to the tire. For each rubber test piece, the tanδ was measured using a GABO Iplexer series at a frequency of 10 Hz, initial strain of 5%, dynamic strain of 1%, deformation mode: tensile, and measurement temperatures of 0°C, 10°C, and 30°C. The tanδ values ​​for 0°C, 10°C, and 30°C were determined accordingly. The tanδ value for the base rubber layer at 30°C was assumed to be 0.07.

[0172] (2) Tg Furthermore, for each measurement sample cut from the cap rubber layer of the tread portion of each test tire, with the tire circumference as the longer side, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, the temperature was varied from -60°C to 40°C using a GABO "Iplexer®" under the conditions of a frequency of 10 Hz, initial strain of 2%, amplitude of ±1%, and heating rate of 2°C / min, and Tg(°C) was determined by the method described above.

[0173] (3) Groove depth Each test tire is brought to its normal state, and the height from the bottom of the circumferential main groove to the opening is measured under no load, and this is defined as the groove depth G (mm).

[0174] Subsequently, using the obtained groove depth G (mm), [-0.5 × G-35] and [-0.5 × G-40] are calculated. In addition, (SBR content × land ratio) and (filler content × flattening ratio) are calculated.

[0175] 5. Performance evaluation (off-screen performance) (1) Evaluation of soil excavation capacity Each test tire is mounted on all four wheels of a test vehicle (4600cc engine, four-wheel drive), inflated to the correct internal pressure, and then driven through muddy terrain (30cm deep). Twenty drivers then provide a sensory evaluation of the mud-clearing performance on a 5-point scale (higher numbers indicate better performance). The total score from the 20 drivers' evaluations is then calculated.

[0176] Next, the results in Comparative Example 5 are set to 100 and indexed based on the following formula to evaluate the soil excavation performance. A higher numerical value indicates better soil excavation performance. Soil-removing capacity = [(Results for test tire) / (Results for comparative example 5)] × 100

[0177] (2) Chipping resistance Using the same test vehicle as described above, after spinning the tires on a gravel road, 20 drivers each visually evaluate the number and size of chipped blocks on the tire tread on a 5-point scale (higher numbers indicate better performance). The total score from the 20 drivers' evaluations is then calculated.

[0178] Next, the results in Comparative Example 5 are set to 100 and indexed based on the following formula to evaluate the chipping resistance performance. A higher numerical value indicates better chipping resistance. Chipping resistance = [(Results of the test tire) / (Results of Comparative Example 5)] × 100

[0179] (3) Evaluation of overall off-road performance Next, the evaluation results from (1) and (2) above are totaled to determine the overall off-road performance. A higher number indicates better overall off-road performance.

[0180] [Table 2]

[0181] [Table 3]

[0182] [Table 4]

[0183] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equivalent scope as the present invention.

[0184] The present invention (1) is, A tire having a tread portion with circumferential grooves that communicate in the circumferential direction, The cap rubber layer that forms the tread portion The rubber component contains 40 to 80 parts by mass of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less per 100 parts by mass, and also contains 60 parts by mass or more of filler per 100 parts by mass of the rubber component. Under conditions of temperature 10°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1%, the loss loss tangent 10°C tanδ measured in the deformation mode: tensile is 0.28 or greater, and It is formed from a rubber composition with a glass transition temperature Tg (°C) of -40°C or lower. Furthermore, the tire is characterized in that the glass transition temperature Tg (°C) and the depth G (mm) of the circumferential grooves satisfy the following equation (Equation 1). Tg≦-0.5×G-35 (Formula 1)

[0185] The present invention (2) is, The tire described in (1) of the present invention is characterized in that the amount of styrene in the styrene-butadiene rubber (SBR) is 20% by mass or less.

[0186] The present invention (3) is, The tire is characterized in that the amount of the filler is 90 parts by mass or more per 100 parts by mass of the rubber component, as described in (1) or (2) of the present invention.

[0187] The present invention (4) is, The present invention (1) is characterized in that the tanδ at 10°C is 0.31 or greater. Or as described in (2) It is a tire.

[0188] The present invention (5) is, The loss loss tangent 0°C tanδ of the aforementioned cap rubber layer, measured under the conditions of temperature 0°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1%, in tensile deformation mode, is 0.30 or greater, and the present invention (1) Or as described in (2) It is a tire.

[0189] The present invention (6) is, The tire is characterized in that the tanδ at 0°C is 0.35 or greater, as described in (5) of the present invention.

[0190] The present invention (7) is, The aforementioned cap rubber layer is characterized in that the loss loss tangent 30°C tanδ, measured under the conditions of temperature 30°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1%, in tensile deformation mode, is 0.27 or greater, and the present invention (1) Or as described in (2) It is a tire.

[0191] The present invention (8) is, The present invention (1) is characterized by satisfying the following (Equation 2) Or as described in (2) It is a tire. Tg≦-0.5×G-40 (Formula 2)

[0192] The present invention (9) is, The present invention (1) is characterized in that the thickness of the cap rubber layer is 10% or more of the entire tread portion. Or as described in (2) It is a tire.

[0193] The present invention (10) is, The land ratio in the tread portion is 40% or more. The present invention (1) is characterized in that the product of the content (parts by mass) of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less in 100 parts by mass of rubber component and the land ratio (%) in the tread portion is 4400 or less. Or as described in (2) It is a tire.

[0194] The present invention (11) is, The aspect ratio is 80% or less. The present invention (1) is characterized in that the product of the content (parts by mass) of the filler relative to 100 parts by mass of the rubber component and the flattening ratio is 9100 or less. Or as described in (2) It is a tire.

Claims

1. A tire having a tread portion with circumferential grooves that communicate in the circumferential direction, The cap rubber layer that forms the tread portion The rubber component contains 40 to 80 parts by mass of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less per 100 parts by mass, and also contains 60 parts by mass or more of filler per 100 parts by mass of the rubber component. Under conditions of temperature 10°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1%, the loss loss tangent 10°C tanδ measured in the deformation mode: tensile is 0.28 or greater, It is formed from a rubber composition with a glass transition temperature Tg (°C) of -40°C or lower. Furthermore, the tire is characterized in that the glass transition temperature Tg (°C) and the depth G (mm) of the circumferential groove satisfy the following equation (Equation 1). Tg≦-0.5×G-35 (Formula 1)

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 1 or 2, characterized in that the amount of the filler is 90 parts by mass or more per 100 parts by mass of the rubber component.

4. The tire according to claim 1 or 2, characterized in that the tanδ at 10°C is 0.31 or greater.

5. The tire according to claim 1 or 2, characterized in that the loss loss tangent 0°C tanδ of the cap rubber layer, measured under the conditions of temperature 0°C, frequency 10 Hz, initial strain 5%, and dynamic strain rate 1%, in the deformation mode: tensile, is 0.30 or more.

6. The tire according to claim 5, characterized in that the tanδ at 0°C is 0.35 or more.

7. The tire according to claim 1 or 2, characterized in that the loss loss tangent 30°C tanδ of the cap rubber layer, measured under the conditions of temperature 30°C, frequency 10 Hz, initial strain 5%, and dynamic strain rate 1%, in the deformation mode: tensile, is 0.27 or more.

8. A tire according to claim 1 or 2, characterized in that it satisfies the following (formula 2). Tg≦-0.5×G-40 (Formula 2)

9. The tire according to claim 1 or 2, characterized in that the thickness of the cap rubber layer relative to the entire tread portion is 10% or more.

10. The land ratio in the tread portion is 40% or more. The tire according to claim 1 or 2, characterized in that the product of the content (parts by mass) of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less in 100 parts by mass of rubber component and the land ratio (%) in the tread portion is 4400 or less.

11. The aspect ratio is 80% or less. The tire according to claim 1 or 2, characterized in that the product of the content (parts by mass) of the filler relative to 100 parts by mass of rubber component and the aspect ratio is 9100 or less.

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