tire

Abstract

To improve propulsion performance on a snow-covered road surface.SOLUTION: A tire includes a tread part having a groove. 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 less than 0.28 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 groove satisfy the following (formula 1): Tg≤-0.5×G-35 ... (formula 1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] In order to ensure safe driving even in winter, it has been proposed to improve the rubber composition and surface shape constituting the tread portion of winter tires and all-weather (all-season) tires (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-107502 [Patent Document 2] JP 2019-104877 A [Patent Document 3] JP 2020-164107 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with the above proposals, there is still room for improvement in vehicle driving performance in winter. In particular, even with recent improvements in vehicle performance, there is concern that tires may spin when there is a large amount of snowfall and the tread portion does not come into contact with the road surface base material such as asphalt, making it impossible to escape from snowy areas, and further improvement in propulsion performance on snowy roads is desired.

[0005] Therefore, an object of the present invention is to improve propulsion performance on snow-covered road surfaces. [Means for solving the problem]

[0006] The present invention relates to A tire having a tread portion having grooves, A cap rubber layer forming the tread portion is A styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less is contained in 40 parts by mass or more and 80 parts by mass or less per 100 parts by mass of a rubber component, and a filler is contained in an amount of 60 parts by mass or more per 100 parts by mass of the rubber component, The loss tangent 10℃ tanδ measured under the conditions of temperature 10℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1%, and deformation mode: tension is less than 0.28. The rubber composition has 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 groove depth G (mm) satisfy the following (Formula 1). Tg≦-0.5×G-35 (Formula 1) Effect of the Invention

[0007] According to the present invention, it is possible to improve propulsion performance on snow-covered road surfaces. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [1] Characteristics 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 having a tread portion having grooves, and the cap rubber layer forming the tread portion 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 the rubber component, and 60 parts by mass or more of a filler per 100 parts by mass of the rubber component. The rubber composition has a loss tangent 10°C tan δ of less than 0.28 and a glass transition temperature Tg (°C) of -40°C or less, measured under conditions of a temperature of 10°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, in a deformation mode: tension. Furthermore, the glass transition temperature Tg (°C) and the groove depth G (mm) of the tire according to the present invention satisfy the following (Formula 1). Tg≦-0.5×G-35 (Formula 1)

[0010] The cap rubber layer referred to here is not limited to the cap rubber layer that forms the outermost layer of the tread portion, and if there are two or more layers within 5 mm from the tread surface toward the inside, at least one of the layers must satisfy the requirements of the rubber composition.

[0011] These features make it possible to improve propulsion performance on snow-covered roads, as will be described later.

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

[0013] When a tire travels on a snowy road, it is thought that the tire needs to scrape off the snow on the road surface in order to travel. At this time, the tire compacts the snow on the road surface and collects it into the grooves of the tread part as snow pillars, and then expels the snow pillars from the grooves by rotating the tire, thereby obtaining propulsive force.

[0014] The cap rubber layer of the tire according to the present invention 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 per 100 parts by mass of the rubber component, and containing 60 parts by mass or more of a filler per 100 parts by mass of the rubber component.

[0015] By incorporating 40 parts by mass or more and 80 parts by mass or less of SBR having a styrene content of 25% by mass or less per 100 parts by mass of the rubber component, a network of a small amount of styrene domains can be appropriately formed in the rubber matrix.

[0016] The formation of this styrene domain network allows for smooth transmission of force in the tread, so that the tread can easily deform and return to its original shape, and snow that has gotten into the grooves can be efficiently packed down on the tread surface.

[0017] On the other hand, the styrene domains generate heat in microscopic areas due to friction with other molecular chains in the rubber matrix, which can melt the surface of the snow pillars trapped in the grooves and make it difficult for them to be removed from the grooves.

[0018] In the present invention, as described above, a network is appropriately formed using a small amount of styrene domains, which maintains the ease of force transmission in the tread portion while suppressing heat generation in microscopic areas and suppressing melting of the surfaces of snow pillars trapped in the grooves, making it possible to easily expel the snow pillars from the grooves, thereby achieving an improvement on snow-covered road surfaces.

[0019] The styrene content is more preferably 20% by mass or less, and even more preferably 15% by mass or less, while 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.

[0020] In the present 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 per 100 parts by mass of the rubber component" means that the amount of SBR per 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.

[0021] In other words, when the rubber component contains only a styrene-containing polymer (SBR), it indicates that the styrene content is 25 mass% or less. When the rubber component contains multiple styrene-containing polymers (SBR), it indicates that the styrene content calculated by the sum of the product of the styrene content (mass%) in each polymer and the blending amount (parts by mass) of that polymer per 100 parts by mass of the rubber component is 25 mass% or less.

[0022] More specifically, when 100 parts by mass of the rubber component contains SBR1 (X1 parts by mass) having a styrene content of S1% by mass and SBR2 (X2 parts by mass) having a styrene content of S2% by mass, the styrene content calculated from the formula {(S1×X1)+(S2×X2)} / (X1+X2) is 25% by mass or less.

[0023] In addition, in the case of a 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 a Fourier transform infrared spectrophotometer (FTIR).

[0024] In the tire according to the present invention, the filler is contained in a large amount of 60 parts by mass or more per 100 parts by mass of the rubber component, and thus, in addition to the network of the styrene domain, a network of the filler can be formed in the cap rubber layer, so that the force in the cap layer is more easily transmitted. As a result, the deformation and restoration of the cap layer are more sufficiently performed, and the snow that has entered the groove can be efficiently compressed and discharged from the groove. It is more preferable that the filler content is 80 parts by mass or more, and even more preferable that the filler content is 90 parts by mass or more. On the other hand, the upper limit is not particularly limited, but considering the kneading processability, it is preferably 180 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less.

[0025] In the tire according to the present invention, the loss tangent 10°C tan δ of the rubber composition forming the cap rubber layer, measured 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%, in a deformation mode of tension, is further reduced to less than 0.28.

[0026] The loss tangent tanδ is a viscoelastic parameter that indicates the energy absorption performance, and the smaller the value, the more heat generation due to the deformation of the rubber can be suppressed. In the present invention, the temperature inside the rubber when driving on a snow-covered road surface during snowfall is also taken into consideration, and 10°C tanδ, which is a temperature lower than room temperature, is set to be smaller than 0.28 as described above. This sufficiently suppresses heat generation due to deformation of the rubber at low temperatures, and the temperature of the tread part increases, suppressing the melting of the surface of the snow pillars taken into the grooves, and making it easy to scrape them out and discharge them from the grooves. It is more preferable that it is 0.25 or less, and even more preferable that it is 0.23 or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.11 or more.

[0027] As described above, the tire according to the present invention is intended to improve the propulsion performance on snowy roads, but in actual driving, driving on normal road surfaces and snowy and icy road surfaces is also assumed. Therefore, in the tire according to the present invention, the loss tangent assuming driving on normal road surfaces is preferably 0.26 or less, more preferably 0.24 or less, and even more preferably 0.22 or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.11 or more. Also, the loss tangent assuming driving on snowy and icy road surfaces is preferably 0.30 or less, more preferably 0.28 or less, and even more preferably 0.26 or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.06 or more, more preferably 0.10 or more, and even more preferably 0.13 or more.

[0028] In the above, the loss tangent (tan δ) can be measured using a viscoelasticity measuring device such as "IPLEXER (registered trademark)" manufactured by GABO.

[0029] The tan δ at 0°C, 10°C, and 30°C can be adjusted as appropriate by adjusting the amounts and types of the compounded materials described below. For example, it is possible to lower the tan δ at each temperature by reducing the SBR content in the rubber component, reducing the styrene content in the SBR component, reducing the filler content, reducing the resin component content, increasing the content of vulcanizing agents such as sulfur and accelerators, etc. On the other hand, it is possible to increase the tan δ at each temperature by increasing the SBR content in the rubber component, increasing the styrene content in the SBR component, increasing the filler content, increasing the resin component content, reducing the content of sulfur, accelerators, etc.

[0030] On the other hand, the deeper the grooves in the tread section, the larger the groove volume and the more snow can be taken in. This increases the shear stress on the snow pillars packed inside the grooves when the snow is discharged. However, this also makes it more difficult to obtain efficient propulsion force as the force packing the snow into snow pillars tends to disperse.

[0031] Therefore, in the present invention, the glass transition temperature Tg (°C) of the rubber composition is -40°C or lower, and the glass transition temperature Tg (°C) is a value that is sufficiently low compared to the groove depth, specifically, the glass transition temperature Tg (°C) and the groove depth G (mm) satisfy the relationship Tg≦-0.5×G-35.

[0032] This allows the tread to flexibly deform and restore even with deep grooves, suppressing the dispersion of the force used to pack the snow, allowing more snow to be taken in and packed down, and providing efficient propulsion. It is more preferable that Tg≦−0.5×G-42. There is no particular limit to the lower limit of the glass transition temperature Tg (°C), but it is preferably −75°C or higher, more preferably −65°C or higher, and even more preferably −55°C or higher.

[0033] The glass transition temperature (Tg) of the rubber composition described above can be determined based on a temperature distribution curve of tan δ measured under conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a temperature rise rate of 2°C / min using a viscoelasticity measuring device such as the Iplexer series manufactured by GABO Co., Ltd. In the case of the present invention, the temperature corresponding to the largest tan δ value in the range of -80°C to 40°C in the measured temperature distribution curve is taken as the glass transition point (Tg). In addition, if there are two or more points of the largest tan δ value in the range of -80°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 tan δ is in the range of -80°C to 40°C, the temperature showing the maximum value is Tg according to the above definition. In addition, for example, if tan δ gradually decreases with increasing temperature in the range of -80°C to 40°C, and a temperature distribution curve showing the maximum value of tan δ is obtained at -80°C, the glass transition temperature (Tg) is -80°C according to the above definition.

[0034] The glass transition temperature (Tg) of the rubber composition can be adjusted appropriately by mixing the materials described below. For example, Tg can be lowered by reducing the SBR content in the rubber component, reducing the styrene content in the SBR component, or reducing the amount of resin component mixed. On the other hand, Tg can be increased by increasing the SBR content in the rubber component, increasing the styrene content in the SBR component, or increasing the amount of resin component mixed.

[0035] In the present invention, the term "groove" refers to a groove having an opening width of 3 mm or more at the outermost surface of the tread portion and a depth of 3 mm or more. It is preferable that a plurality of grooves are provided on the tread surface, and when a plurality of grooves are provided, the deepest groove among those grooves is defined as the "groove depth".

[0036] The grooves may be grooves that are continuous in the tire circumferential direction, or may be angled or curved with respect to the tire circumferential direction. From the viewpoint of compacting snow on a snow-covered road surface and facilitating scraping out, if the grooves are continuous in the circumferential direction, it is preferable that the grooves are zigzag, curved, or wavy, formed by grooves that are angled with respect to the circumferential direction. In addition, if the tread portion has a circumferential groove, it is preferable that the tread portion has a groove that crosses the groove and a plurality of land portions separated by the ground contact edge.

[0037] "Groove depth" refers to the height from the bottom of the groove to the opening in the radial direction of the tire in a normal state and with no load. The normal state refers to the state in which the tire is mounted on a normal rim and pressurized with normal internal pressure. In the case of non-linear grooves or stepped grooves, the "groove depth" refers to the maximum depth from the opening.

[0038] In addition, the term "genuine rim" refers to a rim that is specified for each tire by the standard system including the standard on which the tire is based, for example, the standard rim for the applicable size described in the "JATMA YEAR BOOK" for JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" described in the "STANDARDS MANUAL" for ETRTO (The European Tire and Rim Technical Organisation), and the "Design Rim" described in the "YEAR BOOK" for TRA (The Tire and Rim Association, Inc.), referring to JATMA, ETRTO, and TRA in that order, and following the standard if there is an applicable size at the time of reference. In the case of a tire not specified in the standard, it refers to a rim that can be assembled to a rim and can hold internal pressure, that is, a rim that does not leak air from between the rim / tire, with the smallest rim diameter and the next narrowest rim width.

[0039] "Regular internal pressure" refers to the air pressure specified for each tire by the standard, which is the maximum air pressure for JATMA, the "INFLATION PRESSURE" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with "regular rims," ​​JATMA, ETRTO, and TRA are referenced in that order and the standards are followed. For tires not specified in the standard, the regular internal pressure refers to the regular internal pressure (250 KPa or more) of another tire size (specified in the standard) that is specified with the regular rim as the standard rim. Note that if multiple regular internal pressures of 250 KPa or more are specified, the minimum value among them is specified.

[0040] The "ground contact end" refers to the end that provides the maximum ground contact width when the tire is assembled to a regular rim, filled with air at the regular internal pressure, and subjected to a regular load. The regular rim and regular internal pressure are as described above.

[0041] In addition, "normal load" refers to the load determined for each tire by each standard in the standard system, including the standard on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to the "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As in the case of "normal rim" and "normal internal pressure" mentioned above, JATMA, ETRTO, and TRA are referred to in that order and their standards are followed. In the case of tires not specified in the standard, the normal load W is calculated as follows: L Request. 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: Section height of the tire (mm) Wt: tire section width (mm)

[0042] [2] More preferred embodiments of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following aspects.

[0043] 1. Filler As described above, in the tire of the present invention, a large amount of filler, 60 parts by mass or more per 100 parts by mass of the rubber component, is contained, so that a filler network is formed within the cap rubber layer, making it easier to transmit force within the cap layer.

[0044] In the present invention, it is preferable to use carbon black and silica as specific fillers, and in this case, the content of carbon black may be greater than that of silica, that is, the ratio (silica content / carbon black content) may be less than 1.

[0045] By including silica, the cap rubber layer becomes flexible and easily deformed, so that snow can be easily taken into the groove. However, if the content of silica is greater than the content of carbon black, the reinforcing effect of carbon black is reduced, the cap rubber layer becomes too flexible, and the force for compacting snow is reduced. For this reason, it is preferable to have a content of carbon black greater than that of silica, which makes it easier for the cap rubber layer to deform minutely and to obtain the force for compacting snow. The silica content / carbon black content is more preferably 0.8 or less, and even more preferably 0.6 or less. The lower limit is not particularly limited, but is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.3 or more.

[0046] 2. Multi-layered tread In the present invention, the tread portion may be formed of only one layer, the cap rubber layer, or may be formed of two layers by providing a base rubber layer inside the cap rubber layer, or may be formed of three layers, four layers or more. In this case, in consideration of sufficient snow intake, the thickness of the cap rubber layer occupies preferably 10% or more of the entire tread portion, and more preferably 70% or more.

[0047] In the present invention, the thickness of the tread portion refers to the thickness of the tread portion on the tire equatorial plane in the tire radial cross section. When the tread portion is formed of a single rubber composition, it is the thickness of the rubber composition. When the tread portion is formed of a laminated structure of a plurality of rubber compositions described later, it is the total thickness of these layers. When the tire has a groove on the tire equatorial plane, it refers to the thickness from the intersection point of the straight line connecting the outermost end points of the groove in the tire radial direction and the tire equatorial plane to the interface of the innermost part in the tire radial direction of the tread portion. The tread portion is a member of the region that forms the ground contact surface of the tire, and refers to the part radially outward of the members containing fiber materials such as the carcass, belt layer, and belt reinforcing layer. The thickness of the tread portion can be measured by adjusting the bead portion to the normal rim width in a cross section cut out in the radial direction of the tire.

[0048] In this case, in order to compact the snow on the snow-covered road surface, from the viewpoint of improving the restoring ability of the tread portion against deformation, it is preferable that the tan δ of the base rubber layer at each of the above temperatures (0°C, 10°C, 30°C) be smaller than the tan δ of the cap rubber layer.

[0049] 3. Acetone extractables (AE) from the cap rubber layer In the present invention, the acetone extractables (AE) of the cap rubber layer is preferably 11% by mass or more, more preferably 13% by mass or more, and even more preferably 15% by mass or more. On the other hand, although there is no particular upper limit, it is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 17% by mass or less.

[0050] The acetone extractables (AE) can be considered as an index showing the amount of softeners in the rubber composition, and can also be considered as an index showing 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 be appropriately deformed, making it easier to obtain the force to compact snow.

[0051] The acetone extractables (AE) can be measured in accordance with JIS K 6229: 2015. Specifically, the AE (mass%) can be obtained by immersing a vulcanized rubber test piece cut out from the measurement site in acetone at room temperature and normal pressure for 72 hours and determining the mass loss rate (%) of the test piece.

[0052] More specifically, each vulcanized rubber test piece is immersed in acetone for 72 hours at room temperature and normal pressure to extract the soluble components, and the mass of each test piece before and after extraction is measured, and the mass can be calculated according to the following formula. Acetone extractable amount (%) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction)} / (mass of rubber test piece before extraction)}×100

[0053] The acetone extractable content can be appropriately changed by changing the compounding ratio of the plasticizer in the rubber composition.

[0054] 4. Ratio of 10℃ tan δ to groove depth In the tire according to the present invention, the ratio of 10°C tan δ to the groove depth G (mm) (10°C tan δ / G) is preferably 0.025 or less. When obtaining propulsive force on a snowy road surface, it is considered necessary to compact the snow pillars taken into the grooves with the cap rubber layer and discharge them. 10°C tan δ indicates heat generation at low temperatures and is also considered to be a phase difference in response to deformation. Therefore, it is considered that by sufficiently reducing the value of 10°C tan δ to the groove depth, it is possible to efficiently compact the snow on the snowy road surface and make it easier to discharge the snow pillars. 10°C tan δ / G is more preferably 0.022 or less, and even more preferably 0.020 or less. There is no particular limit to the lower limit, but it is preferably 0.008 or more, more preferably 0.010 or more, and even more preferably 0.012 or more.

[0055] 5. Land Ratio In the tire according to the present invention, it is preferable that the land ratio in the tread portion of the tire mounted on a regular rim and with the regular internal pressure is 40% or more.

[0056] "Land ratio" is the ratio of the actual contact area to the virtual contact area when all the grooves on the surface of the tread are filled. By setting the land ratio at 40% or more, it becomes easier to compact snow on snowy roads, and sufficient propulsion performance can be obtained stably. On the other hand, it is preferable to set the land ratio at 95% or less. This allows snow to be sufficiently taken in by the grooves of the tread.

[0057] In addition, when the product of the content (parts by mass) of styrene butadiene rubber (SBR) having a styrene content of 25 mass% or less in 100 parts by mass of the rubber component and the land ratio (%) in the tread portion is 4,000 or less, this works in conjunction with the effect of the network of the styrene domains to further improve the propulsion performance on snow-covered roads.

[0058] The product of the content of the styrene butadiene rubber having a styrene content of 25% by mass or less and the land ratio in the tread portion is more preferably 3900 or less, and even more preferably 3800 or less. There is no particular restriction on the lower limit, but it is preferably 2500 or more, more preferably 2700 or more, and even more preferably 3000 or more.

[0059] The above-mentioned land ratio can be obtained from the ground contact shape under normal rim, normal internal pressure, and normal load conditions.

[0060] Specifically, the tire is mounted on a standard rim, the standard internal pressure is applied, and the tire is left to stand at 25°C for 24 hours. Then, ink is applied to the tire tread surface, and the standard load is applied and pressed against cardboard (camber angle is 0°), and the contact shape is transferred to the paper, so the tire is rotated 72° in the circumferential direction and transferred at five locations. In other words, five contact shapes are obtained. At this time, the parts of the five contact shapes that are interrupted by the grooves in the contour are smoothly connected, and the resulting shape is called the virtual contact surface.

[0061] The land ratio can be calculated by (average area of ​​five contact shapes (black parts) transferred to cardboard) / (average area of ​​virtual contact surface obtained from five contact shapes)×100(%).

[0062] 6. Flatness The aspect ratio indicates the ratio of the section height to the section width of the tire, and the smaller this ratio is, the larger the contact area can be secured, and the more snow can be taken in and discharged from the tread portion, thereby improving the propulsion performance on snowy roads. In the present invention, the specific aspect ratio is preferably 80% or less.

[0063] In addition, when the product of the silica content (parts by mass) per 100 parts by mass of the rubber component and the aspect ratio is 4,000 or less, the propulsion performance on snow-covered roads can be further improved in cooperation with the effect of the silica network.

[0064] The product of the silica content and the flatness is more preferably 3500 or less, and even more preferably 2500 or less. On the other hand, the lower limit is not particularly limited, but is preferably 500 or more, preferably 1000 or more, and even more preferably 1500 or more.

[0065] The above-mentioned aspect ratio (%) can be calculated by the following formula using the tire 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 250 kPa. Oblateness (%)=(Ht / Wt)×100(%) Ht = (Dt - R) / 2

[0066] [3] Implementation form Hereinafter, the present invention will be described in detail based on the embodiments.

[0067] 1. Rubber composition forming 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 the rubber components, fillers, softeners, vulcanizing agents and vulcanization accelerators described below.

[0068] (1) Compounding materials (a) Rubber component The rubber component is not particularly limited, and rubbers (polymers) commonly used in tire production can be used, such as isoprene-based rubber, diene-based rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), and nitrile rubber (NBR), butyl-based rubbers such as butyl rubber, and thermoplastic elastomers such as styrene-butadiene-styrene block copolymer (SBS) and styrene-butadiene copolymer (SB).

[0069] In the present invention, from the viewpoint of including styrene in the rubber component, it is preferable to include any one of styrene-based polymers such as SBR, SBS, and SB, and to include SBR. Furthermore, these styrene-based polymers may be used in combination with other rubber components, and for example, a combination of SBR and BR, or a combination of SBR, BR, and isoprene-based rubber is preferable.

[0070] (a) SBR The weight average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. As described above, in the present invention, the amount of styrene in the SBR component is set to 25% by mass or less. It 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.

[0071] The vinyl content (1,2-bonded butadiene content) of SBR is, for example, more than 5% by mass and less than 70% by mass. More preferably, it is 10% by mass or more and 45% by mass or less, and even more preferably, it is 15% by mass or more and 30% by mass or less. The vinyl content of SBR refers to the 1,2-bonded butadiene content relative to the total butadiene portion in the SBR component. The structure of SBR (measurement of styrene amount and vinyl content) can be identified using, for example, a JNM-ECA series device manufactured by JEOL Ltd.

[0072] As described above, the content of SBR in 100 parts by mass of the 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.

[0073] There are no particular limitations on the SBR, 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. In addition, hydrogenated SBR obtained by hydrogenating the butadiene portion of SBR may be used, and hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of SBR, or a similar structure may be obtained by copolymerizing styrene, ethylene, and butadiene.

[0074] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one end of SBR has been modified with a compound (modifying agent) having the above-mentioned functional group (terminal-modified SBR having the above-mentioned functional group at the end), main-chain-modified SBR in which the main chain has the above-mentioned functional group, main-chain-terminal-modified SBR in which the main chain and at least one end are modified with the above-mentioned modifier, and terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0075] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0076] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0077] [ka]

[0078] In the formula, R 1 , R 2 and R 3 R may be the same or different and represents 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 R may be the same or different and represents a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0079] As the modified SBR modified with a compound (modifier) ​​represented by the above formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0080] R 1 , R 2 and R 3 R is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and further preferably 3. In addition, R 4 and R 5 When the nitrogen atom and the nitrogen atom are bonded to each other to form a ring structure, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group and a benzyloxy group).

[0081] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0082] In addition, modified SBR modified with the following compounds (modifiers) can also be used as the modified SBR. Examples of the modifiers include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (thio)benzophenone compounds having amino groups and / or substituted amino groups, 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; Benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde, etc.; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, etc.; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone, etc.;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione. , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0083] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. may be used. The SBR may be used alone or in combination of two or more kinds.

[0084] (b) BR In the present invention, BR may be further contained as necessary. In this case, the content of BR in 100 parts by mass of the rubber component is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, and is preferably less than 50 parts by mass, more preferably less than 45 parts by mass.

[0085] The weight average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl content of the BR is, for example, more than 1 mass% and less than 30 mass%. The cis content of the BR is, for example, more than 1 mass% and less than 98 mass%. The trans content of the BR is, for example, more than 1 mass% and less than 60 mass%.

[0086] The BR is not particularly limited, and BR with a high cis content (cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. The BR may be either unmodified BR or modified BR, and the modified BR may be modified BR into which the above-mentioned functional groups have been introduced. These may be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0087] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used.

[0088] (c) Isoprene rubber In the present invention, an isoprene-based rubber may be further contained as necessary. In this case, the content of the isoprene-based rubber in 100 parts by mass of the rubber component is preferably 20 parts by mass or more and 40 parts by mass or less.

[0089] Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0090] As the NR, for example, SIR20, RSS♯3, TSR20, etc., which are common in the tire industry, can be used. As the IR, there is no particular limitation, and for example, IR2200, etc., which are common in the tire industry can be used. As the modified NR, deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), etc. can be used. As the modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. can be used. As the modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. can be used. These may be used alone or in combination of two or more kinds.

[0091] (D) Other rubber components Furthermore, as other rubber components, rubbers (polymers) that are generally used in the manufacture of tires, such as nitrile rubber (NBR), may be included.

[0092] (b) Compounding materials other than rubber components (a) Filler In the present invention, 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. As described above, it is preferable to use silica and carbon black in combination. Furthermore, the ratio of (silica content / carbon black content) may be less than 1.

[0093] (i-1) Silica In the present invention, the rubber composition preferably contains silica, and preferably contains a silane coupling agent together with silica.

[0094] The BET specific surface area of ​​silica is set to 140 m from the viewpoint of obtaining good durability. 2 / g or more is preferable, and 160m 2 On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed running, a rolling resistance of 300 m 2 The BET specific surface area is preferably less than N2SA / g.

[0095] In the present invention, when silica is contained in the rubber composition, the average particle size is preferably 20 nm or less. By using silica having an average particle size of 20 nm or less, the frequency of contact with the polymer can be increased. Although the lower limit is not particularly limited, it is preferably 10 nm or more from the viewpoint of dispersibility during mixing.

[0096] When silica is used, the content of silica 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, based on 100 parts by mass of the rubber component, while 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.

[0097] Examples of silica include dry silica (anhydrous silica) and wet silica (hydrated silica). Among them, wet silica is preferred because it has a large number of silanol groups. In addition, silica made from hydrated glass or silica made from biomass materials such as rice husk may also be used.

[0098] As the silica, for example, products available from Evonik Industries, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

[0099] (i-2) Silane coupling agent When silica is used, the rubber composition preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl silane, and the like. Examples of such silanes include sulfide-based silanes such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based silanes such as vinyl triethoxysilane and vinyl trimethoxysilane; amino-based silanes such as 3-aminopropyl triethoxysilane and 3-aminopropyl trimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro-based silanes such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; and chloro-based silanes such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. These may be used alone or in combination of two or more.

[0100] As the silane coupling agent, for example, products available from Evonik Industries, Momentive, Shin-Etsu Silicones, Tokyo Chemical Industry, Azumax, Dow Corning Toray, etc. can be used.

[0101] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0102] (ii) Carbon black In the present invention, the rubber composition preferably contains carbon black from the viewpoint of further reinforcing properties.

[0103] The specific content ratio of carbon black per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, while it is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less.

[0104] The carbon black is not particularly limited, and examples thereof include furnace black (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF; acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC and CC. In addition to carbon black obtained by burning conventional mineral oil, carbon black derived from vegetable oil or lignin may be used as appropriate, and recycled carbon black obtained by decomposing waste tires and other rubber products may be used. These may be used alone or in combination of two or more.

[0105] The CTAB specific surface area of ​​carbon black (Cetyl Tri-methyl Ammonium Bromide) is 130m 2 / g or more is preferable, and 160m 2 / g or more is more preferable, and 170m2 / g or more is more preferable. 2 / g or less is preferable, and 200m 2 / g or less. The CTAB specific surface area is a value measured in accordance with ASTM D3765-92.

[0106] Specific carbon black is not particularly limited, and examples thereof 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 Co., Ltd., Lion Co., Ltd., Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more kinds.

[0107] (iii) Other fillers In addition to the above-mentioned silica and carbon black, the rubber composition may further contain, as necessary, fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these fillers is, for example, more than 0.1 part by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0108] (b) Plasticizer components The rubber composition may contain oil, liquid rubber, and resin as plasticizer components that soften rubber. The plasticizer components are components 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 more preferably 35 parts by mass or more, relative to 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 more preferably 45 parts by mass or less. When the rubber component contains an extension rubber that has been previously extended with oil, resin, liquid rubber component, etc., the extension component is included in the plasticizer component, and for example, if it is oil extension, the amount of the oil is included in the oil content.

[0109] (i) Oil Examples of the oil include mineral oil (generally called process oil), vegetable oil, and mixtures thereof. Examples of the mineral oil (process oil) that can be used include paraffin-based process oil, aromatic process oil, and naphthenic process oil. Examples of the vegetable oil 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 alone or in combination of two or more. In addition, from the viewpoint of life cycle assessment, waste oil after being used as a lubricating oil for rubber mixers and automobile engines, waste edible oil, and the like may be appropriately used.

[0110] Specific examples of process oils (mineral oils) that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Corporation, H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like.

[0111] (ii) Liquid rubber The liquid rubber mentioned as a plasticizer is a polymer that is in a liquid state at room temperature (25°C) and is a rubber component that can be extracted by acetone extraction from a vulcanized tire. Examples of liquid rubber include farnesene-based polymers, liquid diene-based polymers, and hydrogenated products thereof.

[0112] Farnesene polymers are polymers obtained by polymerizing farnesene and contain structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0113] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0114] 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).

[0115] The liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0×10 3 Super, 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0116] The amount of the liquid rubber (total amount of the liquid farnesene polymer, the liquid diene polymer, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass per 100 parts by mass of the rubber component.

[0117] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0118] (iii) Resin component The resin component also functions as a tackifier and may be solid or liquid at room temperature. Specific examples of the resin component include rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, and acrylic resin, and two or more of them may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass, based on 100 parts by mass of the rubber component. In addition, these resin components may be provided with a modified group capable of reacting with silica, etc., as necessary.

[0119] Rosin-based resins are resins whose main component is rosin acid obtained by processing rosin. These rosin-based resins (rosins) can be classified according to whether they have been modified or not, and can be classified into unmodified rosin (unmodified rosin) and modified rosin (rosin derivatives). Examples of unmodified rosins include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Modified rosin is a modification of unmodified rosin, and examples of such modified rosin include rosin esters, unsaturated carboxylic acid modified rosin esters, unsaturated carboxylic acid modified rosin esters, rosin amide compounds, and rosin amine salts.

[0120] The styrene resin is a polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers polymerized with a styrene monomer as the main component (50% by mass or more).Specific examples thereof include homopolymers obtained by polymerizing each of the 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.) alone, copolymers obtained by copolymerizing two or more kinds of styrene monomers, and copolymers of a styrene monomer and another monomer that can be copolymerized therewith.

[0121] Examples of the other monomer include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene-isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof, and the like.

[0122] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins that contain coumarone and indene as monomer components that constitute the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0123] The amount of the coumarone-indene resin per 100 parts by mass of the rubber component is, for example, more than 1.0 part by mass and less than 50.0 parts by mass.

[0124] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, expressed in milligrams, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0125] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0126] Terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: Monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0127] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins, and specifically include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include, for example, phenol, bisphenol A, cresol, and xylenol. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenols, alkoxyphenols, and phenols containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthols, alkoxynaphthols, and naphthols containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrenes, alkoxystyrenes, and styrenes containing an unsaturated hydrocarbon group; coumarone, indene, and the like.

[0128] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0129] The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a resin obtained by hydrogenating or modifying the resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. 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, because they are economical, easy to process, and have excellent heat generation properties. As aromatic vinyl resins, for example, those commercially available from Kraton, Eastman Chemical, etc. can be used.

[0130] The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of the C5 fraction and the C9 fraction include the petroleum fractions. As the C5C9 resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0131] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0132] Examples of the solvent-free acrylic resin include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, p. 42-45, etc.) using as little secondary raw material as possible, such as polymerization initiators, chain transfer agents, and organic solvents. In the present invention, (meth)acrylic means methacryl and acrylic.

[0133] Examples of monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0134] In addition, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative as a monomer component constituting the acrylic resin.

[0135] The acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component as constituent elements. The acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0136] Examples of the resin component that can be used include products from 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 Co., Ltd.

[0137] (C) Stearic acid In the present invention, the rubber composition preferably contains stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. As the stearic acid, a conventionally known product can be used, for example, a product from NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0138] (D) Anti-aging agents In the present invention, the rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, more than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component.

[0139] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as quinolinone, quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, 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 alone or in combination of two or more.

[0140] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0141] (E) Wax 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, per 100 parts by mass of the rubber component.

[0142] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as vegetable wax and animal wax, synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more kinds.

[0143] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0144] (F) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass with respect to 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, for example, a product of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0145] (G) Processing aids The rubber composition may contain a processing aid. Examples of the processing aid that can be used include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, and the like. For example, products of Rhein Chemie, Struktol, and the like can be used. These may be used alone or in combination of two or more. Among them, fatty acid metal salts are preferred.

[0146] Examples of fatty acids constituting the fatty acid metal salt 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 alone or in combination of two or more. Of these, saturated fatty acids are preferred, and saturated fatty acids having 14 to 20 carbon atoms are more preferred.

[0147] Examples of metals constituting fatty acid metal salts include alkali metals such as potassium and sodium, alkaline earth metals such as magnesium, calcium and barium, zinc, nickel, molybdenum, etc. These may be used alone or in combination of two or more. Among these, zinc is preferred.

[0148] 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, relative to 100 parts by mass of the rubber component, while 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.

[0149] (H) Crosslinking agents and vulcanization accelerators The rubber composition preferably contains a crosslinking agent such as sulfur, etc. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0150] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more kinds.

[0151] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0152] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd. and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS, and organic peroxides, such as dicumyl peroxide.

[0153] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0154] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more.

[0155] (R) Other 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, carboxylate metal salts, organic peroxides, reversion (reversion) inhibitors, etc., as necessary. 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.

[0156] (2) Preparation of rubber composition The rubber composition that forms the cap rubber layer is prepared by appropriately adjusting the various compounding materials described above and using a general method, for example, a manufacturing method that includes a base kneading process in which the rubber component is kneaded with a filler such as carbon black, and a finish kneading process in which the kneaded product obtained in the base kneading process is kneaded with a crosslinking agent.

[0157] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0158] The kneading temperature in the base kneading step is, for example, more than 50° C. and less than 200° C., and the kneading time is, for example, more than 30 seconds and less than 30 minutes. In the base kneading step, in addition to the above-mentioned components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as necessary.

[0159] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80° C., and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0160] 2. Tire manufacturing The tire according to the present invention can be produced as an unvulcanized tire by molding the rubber composition obtained above into a tread rubber of a predetermined shape as a cap rubber layer, and then molding the tread rubber together with other tire components in a normal manner on a tire building machine.

[0161] In the case where the tread portion has a multi-layer structure with a base rubber layer, the rubber composition for forming the base rubber layer can be obtained by kneading the above-mentioned rubber components and compounding materials in the same manner while appropriately changing the compounding amounts. Then, the rubber composition for forming the base rubber layer can be extruded together with the cap rubber layer to form a tread rubber of a predetermined shape, and then molded together with other tire components in a normal manner on a tire building machine to produce an unvulcanized tire.

[0162] Specifically, an inner liner as a member for ensuring the airtightness of the tire, a carcass as a member for enduring the load, impact, and filled air pressure received by the tire, and a belt member as a member for tightly tightening the carcass and increasing the rigidity of the tread are wound around a molding drum, and both ends of the carcass are fixed to both side edges, and bead portions as members for fixing the tire to the rim are arranged. After molding into a toroidal shape, a tread is attached to the center of the outer periphery, and a sidewall is attached to the radially outside to form the side portion, thereby producing an unvulcanized tire.

[0163] The unvulcanized tire thus produced is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be carried out by applying a known vulcanization method. The vulcanization temperature is, for example, more than 120°C and less than 200°C, and the vulcanization time is, for example, more than 5 minutes and less than 15 minutes.

[0164] As described above, the resulting tire compacts snow on the road surface, traps it in the grooves of the tread as snow pillars, and then expels the snow pillars from the grooves as the tire rotates, thereby generating propulsive force, thereby improving propulsive performance on snow-covered roads.

[0165] The tire according to the present invention is not particularly limited in category and can be used as a passenger car tire, a tire for heavy load vehicles such as trucks and buses, a two-wheeled vehicle tire, a run-flat tire, a non-pneumatic tire, etc., but is preferably a passenger car tire. Also, it is preferably a pneumatic tire. EXAMPLES

[0166] The following examples (working examples) are considered to be preferable for carrying out the present invention, but the scope of the present invention is not limited to these working examples. In the working examples, a pneumatic tire (tire size: LT275 / 70R18, aspect ratio: 70%, land ratio: 63%) manufactured from a composition obtained by varying the blending according to each table using various chemicals shown below was examined, and the results calculated based on the following evaluation method are shown in Tables 2 to 4.

[0167] 1. Rubber composition for forming the cap rubber layer (1) Compounding materials (a) Rubber component (a) 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) made by JSR Corporation (styrene content: 10% by mass, vinyl content: 42% by mass) (c) NR:TSR20 (d) BR: Ubepol BR150B (High Sys BR) manufactured by Ube Industries, Ltd. (cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

[0168] (Production of SBR-1) The above SBR-1 is produced according to the following procedure. First, two autoclaves with an internal volume of 10 L, an inlet at the bottom and an outlet at the top, and an agitator and a jacket are connected in series as reactors, and butadiene, styrene, and cyclohexane are mixed in a predetermined ratio. This mixed solution is passed through a dehydration column filled with activated alumina, and after mixing with n-butyllithium in a static mixer to remove impurities, it is continuously fed from the bottom of the first reactor, and further 2,2-bis(2-oxolanyl)propane as a polar substance and n-butyllithium as a polymerization initiator are continuously fed from the bottom of the first reactor at a predetermined rate, respectively, and the temperature inside the reactor is maintained at 95°C. The polymer solution is continuously withdrawn from the head of the reactor and fed to the second reactor. The temperature of the second reactor is kept at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and oligomer components is continuously added as a 1000-fold diluted solution of cyclohexane at a specified rate to carry out the modification reaction. This polymer solution is continuously withdrawn from the reactor, and after the antioxidant is continuously added using a static mixer, the solvent is removed to obtain the desired modified diene polymer (SBR-1).

[0169] The vinyl content of the SBR-1 (unit: mass%) was determined by infrared spectroscopy at the absorption peak of the vinyl group at 910 cm -1 The amount of styrene (unit: mass%) is determined from the refractive index in accordance with JIS K6383 (1995).

[0170] (b) Compounding materials other than rubber components (a) 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) (c) Silane coupling agent: Si266 manufactured by Evonik Industries (Bis(3-triethoxysilylpropyl) disulfide) (d) Resin: Petrotac 90 (C5 / C9 copolymer petroleum resin) manufactured by Tosoh Corporation (E) Oil: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. (F) Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (G) Anti-aging agent-1: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) (H) Anti-aging agent-2: Antigen RD manufactured by Sumitomo Chemical Co., Ltd. (Polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) (i) Stearic acid: Bead stearic acid "Tsubaki" manufactured by NOF Corporation (J) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. (k) Processing aid: EF44 (zinc salt of saturated fatty acid) manufactured by Struktol (L) Sulfur: Powdered sulfur (containing 5% oil) manufactured by Tsurumi Chemical Industry Co., Ltd. (W) Vulcanization accelerator: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-Cyclohexyl-2-benzothiazylsulfenamide (CBS))

[0171] (2) Rubber composition for forming the cap rubber layer According to the blending contents shown in Tables 2 to 4, materials other than sulfur and vulcanization accelerator are mixed for 5 minutes at 150° C. using a Banbury mixer to obtain a blend. Each blending amount is in parts by mass.

[0172] Next, sulfur and a vulcanization accelerator are added to the kneaded mixture, and the mixture is kneaded for 5 minutes under the condition of 80° C. using an open roll to obtain a rubber composition for forming the cap rubber layer.

[0173] 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.

[0174] [Table 1]

[0175] 3. Cap rubber and pneumatic tires Using each rubber composition, a tread portion is manufactured by extruding into a predetermined shape having a total thickness of 17.5 mm with (thickness of cap rubber layer / thickness of base rubber layer)=90 / 10.

[0176] Thereafter, the tire is laminated together with other tire components to form an unvulcanized tire, which is then press-vulcanized for 10 minutes under a condition of 170°C to produce each of the pneumatic tires (test tires) of Examples 1 to 15 and Comparative Examples 1 to 5.

[0177] 4. Calculation of parameters (1) tan δ A rubber test piece for viscoelasticity measurement is prepared by cutting out a piece of rubber with a length of 20 mm, width of 4 mm, and thickness of 2 mm from the cap rubber layer of the tread portion of each test tire, with the long side being in the tire circumferential direction, and measuring tan δ for each rubber test piece using an Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, initial strain of 5%, dynamic strain of 1%, deformation mode: tension, and measuring temperatures: 0°C, 10°C, and 30°C, respectively, to obtain tan δ at 0°C, tan δ at 10°C, and tan δ at 30°C. The tan δ at 30°C of the base rubber layer is set to 0.07.

[0178] (2) Tg In addition, for each measurement sample cut out from the cap rubber layer of the tread portion of each test tire with a size of 20 mm in length x 4 mm in width x 1 mm in thickness, with the long side in the tire circumferential direction, GABO's "IPLEXER (registered trademark)" was used to measure tan δ by changing the temperature from -80°C to 40°C under conditions of a frequency of 10 Hz, initial strain of 2%, amplitude of ±1% and a heating rate of 2°C / min, and the temperature corresponding to the largest tan δ value in the obtained temperature distribution curve was determined as Tg (°C).

[0179] (3)AE Using a vulcanized rubber test piece cut out from the cap rubber layer of the tread portion of each test tire, the AE (mass%) is determined in accordance with JIS K 6229:2015.

[0180] (4) Groove depth Each test tire is put in a normal state, and the height from the bottom of the groove to the opening of the groove is measured under no load, and the maximum value is calculated and regarded as the groove depth G (mm).

[0181] Then, using the obtained groove depth G (mm), [-0.5×G-35] and [-0.5×G-42] are calculated. In addition, [10°C tan δ / G (mm)] is calculated from 10°C tan δ and the groove depth G (mm).

[0182] (5) Other parameters Then, the silica content / carbon black content (silica / CB) of each test tire is calculated. Based on the specifications and compounding contents of each test tire, (SBR content x land ratio) and (silica content x aspect ratio) are calculated.

[0183] 5. Performance evaluation (propulsion performance on snow-covered roads) Each test tire was fitted to all wheels of a test vehicle (2400cc displacement, four-wheel drive vehicle) and inflated to the normal internal pressure, after which the vehicle was driven on a snow-covered road and the propulsion performance at that time was evaluated by 20 drivers on a 5-point scale (the higher the number, the better).The total score of the evaluations by the 20 drivers was then calculated.

[0184] Next, the result of Comparative Example 2 was set as 100 and indexed according to the following formula to evaluate the propulsion performance on snow-covered road surfaces. A larger value indicates better propulsion performance on snow-covered road surfaces. Propulsion performance on snowy roads = [(Test tire results) / (Comparative example 2 results)]×100

[0185] [Table 2]

[0186] [Table 3]

[0187] [Table 4]

[0188] Although the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

[0189] The present invention (1) is A tire having a tread portion having grooves, A cap rubber layer forming the tread portion is A styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less is contained in 40 parts by mass or more and 80 parts by mass or less per 100 parts by mass of a rubber component, and a filler is contained in an amount of 60 parts by mass or more per 100 parts by mass of the rubber component, The loss tangent 10℃ tanδ measured under the conditions of temperature 10℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1%, and deformation mode: tension is less than 0.28. The rubber composition has 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 groove depth G (mm) satisfy the following (Formula 1). Tg≦-0.5×G-35 (Formula 1)

[0190] The present invention (2) is The tire according to the present invention (1) is characterized in that the content of the filler is 80 parts by mass or more per 100 parts by mass of the rubber component.

[0191] The present invention (3) is The tire according to the present invention (1) or (2) is characterized in that the 10° C. tan δ is 0.25 or less.

[0192] The present invention (4) is The cap rubber layer has a loss tangent 0°C tan δ of 0.30 or less, measured in a deformation mode of 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%, and is a tire in any combination with any of the present inventions (1) to (3).

[0193] The present invention (5) is The tire according to the present invention (4) is characterized in that the 0° C. tan δ is 0.28 or less.

[0194] The present invention (6) is The cap rubber layer has a loss tangent 30°C tan δ of 0.26 or less, measured in a deformation mode of 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%, and is a tire in any combination with any of the present inventions (1) to (5).

[0195] The present invention (7) is The tire is characterized by satisfying the following formula 2 and can be arbitrarily combined with any of the present inventions (1) to (6). Tg≦-0.5×G-42 (Formula 2)

[0196] The present invention (8) is The tire is characterized in that the ratio of the 10° C. tan δ to the groove depth G (mm) (10° C. tan δ / G) is 0.025 or less, and is any combination with any of the present inventions (1) to (7).

[0197] The present invention (9) is The tire is characterized in that the thickness of the cap rubber layer accounts for 10% or more of the entire tread portion, and is an arbitrary combination with any of the present inventions (1) to (8).

[0198] The present invention (10) is The land ratio in the tread portion is 40% or more, The tire is characterized in that the product of the content (parts by mass) of styrene butadiene rubber (SBR) having a styrene content of 25 mass% or less in 100 parts by mass of the rubber component and the land ratio (%) in the tread portion is 4000 or less, and is any combination with any of the present inventions (1) to (9).

[0199] The present invention (11) is The aspect ratio is 80% or less, The cap layer contains silica, and the product of the content (parts by mass) of the silica per 100 parts by mass of the rubber component and the aspect ratio is 4000 or less. The tire is any combination with any of the present inventions (1) to (10).

Claims

1. A tire having a tread portion having grooves, A cap rubber layer forming the tread portion is A styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less is contained in 40 parts by mass or more and 80 parts by mass or less per 100 parts by mass of a rubber component, and a filler is contained in an amount of 60 parts by mass or more per 100 parts by mass of the rubber component, The loss tangent 10°C tan δ measured 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%, in a deformation mode of tension, is less than 0.28; The rubber composition has a glass transition temperature Tg (°C) of -40°C or lower. The tire is further characterized in that the glass transition temperature Tg (°C) and the groove depth G (mm) satisfy the following (Formula 1): Tg≦-0.5×G-35 (Formula 1)

2. 2. The tire according to claim 1, wherein a content of the filler is 80 parts by mass or more based on 100 parts by mass of the rubber component.

3. 3. The tire according to claim 1, wherein the 10° C. tan δ is 0.25 or less.

4. The tire according to any one of claims 1 to 3, characterized in that the cap rubber layer has a loss tangent 0°C tan δ of 0.30 or less, measured under conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, in a deformation mode: tension.

5. 5. The tire according to claim 4, wherein the 0° C. tan δ is 0.28 or less.

6. The tire according to any one of claims 1 to 5, characterized in that the cap rubber layer has a loss tangent 30°C tan δ of 0.26 or less, measured 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%, in a deformation mode of tension.

7. 7. The tire according to claim 1, wherein the following formula 2 is satisfied: Tg≦-0.5×G-42 (Formula 2)

8. The tire according to any one of claims 1 to 7, characterized in that a ratio (10°C tan δ / G) of the 10°C tan δ to the groove depth G (mm) is 0.025 or less.

9. The tire according to any one of claims 1 to 8, wherein a thickness of the cap rubber layer occupies 10% or more of the entire tread portion.

10. A land ratio in the tread portion is 40% or more, 10. The tire according to claim 1, wherein a product of a content (parts by mass) of the styrene butadiene rubber (SBR) having a styrene amount of 25 mass% or less in 100 parts by mass of the rubber component and a land ratio (%) in the tread portion is 4000 or less.

11. The aspect ratio is 80% or less, 11. The tire according to claim 1, wherein the cap layer contains silica, and a product of a content (parts by mass) of the silica per 100 parts by mass of a rubber component and an aspect ratio is 4000 or less.

Images