Tire

Abstract

The road gripping performance on ice and snow covered roads is improved. A tire provided with a tread portion, in which a crown rubber layer forming the tread portion is formed from a rubber composition containing 40 parts by mass or less of a styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, the loss tangent (-30 DEG C tan [delta]) measured by deformation mode: stretching under the conditions of a temperature of-30 DEG C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.10 or more, and the thickness of the tread portion is 10-20 mm (inclusive).

Description

Technical Field

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

[0002] From the viewpoint of safety, tires are required to have high braking performance (gripping performance), and various techniques have been proposed for improving the gripping performance (for example, Patent Documents 1 to 3).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-93386

[0006] Patent Document 2: Japanese Patent Application Publication No. 2013-79017

[0007] Patent Document 3: Japanese Patent Application Publication No. 2016-37100 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, tires manufactured based on the above-mentioned conventional technologies cannot yet be said to have sufficient grip performance on icy and snowy roads, and further improvement is strongly desired.

[0010] Therefore, an object of the present invention is to improve the grip performance on icy and snowy roads.

[0011] Means for solving problems

[0012] The present invention relates to a tire having a tread portion, wherein:

[0013] The cap rubber layer forming the tread portion is formed of a rubber composition.

[0014] The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component.

[0015] The loss tangent (-30℃ tanδ) measured in the deformation mode: tension under the conditions of temperature -30℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more,

[0016] The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to improve the grip performance on icy and snowy roads. DETAILED DESCRIPTION

[0019] [1] Features of the tire of the present invention

[0020] First, the features of the tire of the present invention will be described.

[0021] 1. Summary

[0022] The tire of the present invention comprises: a carcass, which is mounted between one and the other of a pair of bead portions as a portion engaged with a wheel rim and serves as a tire skeleton; a belt layer; a belt reinforcing layer and other components including fiber materials; and a tread portion, which is arranged at a position further outward in the tire radial direction than the carcass, the belt layer, and the belt reinforcing layer. In addition, the tread portion comprises a crown rubber layer which is arranged at the outer side in the tire radial direction and serves as a contact surface, and further comprises a base rubber layer which is arranged at a position further inward in the tire radial direction than the crown rubber layer as required.

[0023] Furthermore, the crown rubber layer forming the tread portion is formed of a rubber composition, the rubber composition contains 40 parts by mass or less of SBR with a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, and the loss tangent (-30°C tanδ) measured in a deformation mode: tension under the conditions of a temperature of -30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.10 or more. In addition, the thickness of the tread portion is 10 mm or more and 20 mm or less.

[0024] It should be noted that the cap rubber layer mentioned here is not limited to the outermost rubber layer forming the tread portion, and when there are two or more layers within 5 mm from the tread surface toward the inside, at least one layer satisfies the above-mentioned conditions of the rubber composition.

[0025] By having these features, as described later, it is possible to improve the grip performance on icy and snowy roads.

[0026] 2. Mechanism of the Effects of the Tire of the Present Invention

[0027] The mechanism by which the above-mentioned effects are exhibited in the tire of the present invention is considered to be as follows.

[0028] As described above, the cap rubber layer of the tire of the present invention contains 40 parts by mass or less of SBR having a styrene amount of 25% by mass or less in 100 parts by mass of the rubber component.

[0029] SBR with a low styrene content, specifically, a styrene content of 25% by mass or less, has a low glass transition temperature (Tg). Therefore, by including such a low styrene content SBR in the rubber component, the flexibility of the rubber can be maintained even at low temperatures, and the followability on icy and snowy roads is improved.

[0030] At the same time, by containing 40 parts by mass or less of SBR having a low styrene content (styrene content 25% by mass or less), fine styrene domains can be appropriately formed on the rubber surface, so that the rubber easily bites into the road surface.

[0031] In addition, the presence of tiny styrene domains is believed to cause friction with other polymer molecular chains, allowing moderate heat generation even at low temperatures, thereby facilitating friction on icy and snowy roads. Furthermore, the tiny styrene domains can also provide a scratching effect on icy and snowy roads.

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

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

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

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

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

[0037] Furthermore, in the present invention, the rubber composition forming the cap rubber layer has a loss tangent (-30°C tanδ) of 0.10 or more measured in a deformation mode: tension under the conditions of temperature -30°C, frequency 10 Hz, initial strain 5%, and dynamic strain rate 1%.

[0038] The loss tangent tanδ is a viscoelastic parameter that indicates the energy absorption performance. The larger the value, the more energy can be absorbed and converted into heat. In the present invention, since the -30°C tanδ, which is lower than the temperature of the icy and snowy road surface, is increased to 0.10 or more, even in a low temperature atmosphere, the energy during rolling can be fully absorbed and converted into heat, heat generation is ensured, and the grip performance is improved. It is more preferably 0.33 or more, more preferably 0.42 or more, more preferably 0.50 or more, more preferably 0.55 or more, more preferably 0.56 or more, more preferably 0.65 or more, and more preferably 0.68 or more. The upper limit is not particularly limited, preferably 0.85 or less, more preferably 0.80 or less, more preferably 0.75 or less, and more preferably 0.73 or less.

[0039] It should be noted that, considering that the atmospheric temperature of the icy and snowy road surface is around 0°C, the loss tangent (0°C tanδ) measured in the deformation mode: stretching under the conditions of temperature 0°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1% is preferably 0.24 or more, more preferably 0.26 or more, further preferably 0.28 or more, further preferably 0.30 or more, further preferably 0.35 or more, further preferably 0.37 or more, further preferably 0.38 or more, further preferably 0.45 or more, further preferably 0.46 or more, further preferably 0.48 or more. The higher the 0°C tanδ, the greater the energy loss of the above-mentioned icy and snowy road surface, the higher the heat generation, and thus the improved grip performance.

[0040] On the other hand, if the tread portion is overheated, the ice melts and may cause slipping. Therefore, under a certain degree of heating, it is preferred to reduce tanδ in advance. For example, the loss tangent (30℃ tanδ) measured in the deformation mode: tension at a temperature of 30℃, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1% is preferably 0.28 or less, more preferably 0.26 or less, further preferably 0.25 or less, further preferably 0.23 or less, further preferably 0.22 or less, further preferably 0.20 or less, further preferably 0.13 or less, and further preferably 0.12 or less.

[0041] In the above, the loss tangent (tan δ) can be measured using a viscoelasticity measuring device such as “EPLEXOR (registered trademark)” manufactured by GABO Corporation.

[0042] It should be noted that the above-mentioned -30°C tanδ, 0°C tanδ and 30°C tanδ can be adjusted by appropriately changing the content of each compounding material described later. For example, if it is -30°C tanδ, it can be increased by increasing the styrene content in SBR, increasing the styrene content in the rubber component, increasing the amount of resin components, etc. On the contrary, it can be reduced by reducing the styrene content in SBR, reducing the styrene content in the rubber component, reducing the amount of resin components, etc. For 0°C tanδ and 30°C tanδ, it can also be increased by increasing the amount of styrene in SBR, increasing the styrene content in the rubber component, increasing the amount of resin components, increasing the amount of fillers such as silica and carbon black, etc. On the contrary, it can be reduced by reducing the styrene content in SBR, reducing the styrene content in the rubber component, reducing the amount of resin components, reducing silica and carbon black, etc.

[0043] In addition, in the tire of the present invention, as described above, the thickness of the tread portion is set to 10 mm to 20 mm. As a result, the tread portion as a whole is easily bent and deformed, and the ground contact is improved, thereby improving the grip performance. More preferably, it is 12 mm to 18 mm, further preferably 14 mm to 16 mm, and particularly preferably 15 mm.

[0044] The thickness of the tread portion mentioned above refers to the thickness of the tread portion on the equatorial plane of the tire in the radial cross section of the tire. When the tread portion is formed by a single rubber composition, it is the thickness of the rubber composition. When it is formed by a layered structure of multiple rubber compositions described later, it refers to the total thickness of these layers.

[0045] When the tire has a groove on the equatorial plane, it means the thickness from the intersection of a straight line connecting the outermost end points of the groove in the tire radial direction and the tire equatorial plane to the innermost interface of the tread portion in the tire radial direction.

[0046] The thickness of the tread portion can be measured by making the bead portion coincide with the normal rim width in a cross section of the tire cut out in the radial direction.

[0047] In the above, "regular rim" means a rim that specifies the standard for each tire in a standard system including the standard to which the tire is based, for example, in the case of JATMA (Japan Automobile Tire Association), it means a standard rim in the applicable size described in "JATMA YEARBOOK"; in the case of ETRTO (The European Tyre and Rim Technical Organization), it means "Measuring Rim" described in "STANDARDS MANUAL"; in the case of TRA (The Tire and Rim Association, Inc.), it means "Design Rim" described in "YEAR BOOK", and reference is made in the order of JATMA, ETRTO, and TRA. If there is an applicable size when referencing, the standard is followed. In addition, in the case of a tire not specified in the standard, it means a rim that can be mounted in a rim-type manner and can maintain the internal pressure, that is, it means a rim with the smallest rim diameter and the narrowest rim width among the rims that do not cause air leakage between the rim and the tire.

[0048] As described above, in the tire of the present invention, the grip and friction of ice or snow due to the styrene domain can be obtained while improving the ground contact performance, so it is considered that the grip performance on icy and snowy roads can be improved.

[0049] [2] A more preferred embodiment of the tire of the present invention

[0050] The tire of the present invention can obtain greater effects by adopting the following aspects.

[0051] 1. Glass transition temperature (Tg) of the crown rubber layer

[0052] When a rubber composition with a high glass transition temperature (Tg) is used to form the cap rubber layer, the tread portion becomes hard near the driving temperature, so the road following performance may be deteriorated. Therefore, in order to achieve improved grip performance on icy and snowy roads, it is preferred to lower the glass transition temperature (Tg) of the rubber composition and reduce the hardness of the rubber in the low temperature region.

[0053] In the present invention, the specific glass transition temperature (Tg) of the rubber composition is preferably -32°C or lower, more preferably -34°C or lower, further preferably -37°C or lower, further preferably -38°C or lower, further preferably -40°C or lower, further preferably -41°C or lower.

[0054] The glass transition temperature (Tg) of the rubber composition can be obtained based on the temperature distribution curve of tanδ measured under the conditions of frequency 10 Hz, initial strain 10%, amplitude ±0.5% and heating rate 2°C / min using a viscoelasticity measuring device such as the EPLEXOR series manufactured by GABO. In the case of the present invention, the temperature corresponding to the maximum tanδ value in the range of -70°C to 30°C of the measured temperature distribution curve is taken as the glass transition temperature (Tg). It should be noted that when there are two or more points with the maximum tanδ value in the range of -70°C to 30°C, the point with the lowest temperature is taken as Tg. For example, in the present invention, if the maximum value of tanδ is in the range of -70°C to 30°C, the temperature showing the maximum value is Tg according to the above definition. In addition, when a temperature distribution curve showing the maximum value of tanδ is -70°C, such as tanδ gradually decreases as the temperature rises in the range of -70°C to 30°C, the glass transition temperature (Tg) is -70°C according to the above definition.

[0055] In addition, the glass transition temperature (Tg) of the rubber composition can be adjusted by appropriately changing the content of each compounding material described later, similarly to the above-mentioned tanδ. For example, it can be increased by increasing the amount of SBR in the rubber component, increasing the styrene content in the SBR component, increasing the amount of the resin component, using a resin component with a high softening point, etc. On the contrary, it can be reduced by reducing the amount of SBR in the rubber component, reducing the styrene content in the SBR component, reducing the amount of the resin component, using a resin component with a low softening point, etc.

[0056] 2. Relationship between tanδ of the crown rubber layer at -30℃ and the thickness of the tread

[0057] As described above, in the present invention, by setting the tread thickness to 10 mm or more, it is easy to obtain ground contact performance on the tread surface. Among them, it is preferable to increase the tan δ of the cap rubber layer at low temperatures relative to the tread thickness.

[0058] Specifically, the quotient of tanδ (tanδ at -30℃) of the crown rubber at -30℃ relative to the thickness T (mm) of the tread (tanδ at -30℃ / T) is preferably 0.022 or more, more preferably 0.028 or more, further preferably 0.037 or more, further preferably greater than 0.04, further preferably 0.043 or more, further preferably 0.045 or more, further preferably 0.046 or more, further preferably 0.049 or more, further preferably 0.054 or more. Thus, it is possible to easily obtain greater surface grip performance while improving ground contact. It should be noted that the upper limit is not particularly limited, for example, it is preferably less than 0.1.

[0059] 3. Multi-layer tread

[0060] In the present invention, the tread portion may be formed by only one crown rubber layer arranged on the outer side in the radial direction of the tire, or a base rubber layer may be arranged on the inner side in the radial direction of the crown rubber layer to make it two layers. In addition, it may be three layers, or even four layers or more. In this case, the thickness of the crown rubber layer of the entire tread portion is preferably 10% or more. As a result, sufficient friction can be generated between the surface of the tread portion and the road surface and the friction force can be fully transmitted to the inside of the tire, thereby sufficiently improving the grip performance on icy and snowy roads. It should be noted that if the friction between the surface of the tread portion and the road surface is taken into account, the thickness of the crown rubber layer of the entire tread portion is more preferably 50% or more, and further preferably 70% or more.

[0061] As described above, the thickness of the cap rubber layer and the thickness of the base rubber layer can be calculated by adding up the thickness of the cap rubber layer and the thickness of the base rubber layer in the thickness of the tread portion.

[0062] Furthermore, the "thickness of the cap rubber layer" refers to the thickness of the cap rubber layer on the tire equatorial plane in the tire radial cross section. If there is a groove on the tire equatorial plane, it refers to the thickness from the intersection 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 with the innermost base rubber layer in the tire radial direction of the tread portion. Furthermore, the "thickness of the base rubber layer" refers to the thickness from the interface with the cap rubber layer to the innermost interface in the tire radial direction of the tread portion.

[0063] As described above, the thickness of the cap rubber layer and the thickness of the base rubber layer can be calculated by finding the thickness of the cap rubber layer and the thickness of the base rubber layer in the thickness of the tread portion. It should be noted that, in the case where there are grooves on the equatorial plane of the tire, the thickness of the cap rubber layer at the center of the land portion of the tread portion closest to the equatorial plane and the thickness of the base rubber layer can be calculated.

[0064] It should be noted that in the case of a multi-layered tread portion, it is preferred that the 30°C tanδ of the base rubber layer is greater than the 30°C tanδ of the cap rubber layer. As described above, from the perspective of suppressing the increase in tread surface temperature and melting ice on the road surface to cause skidding, it is desirable that the 30°C tanδ of the cap rubber layer is low. It is believed that this increases the heat generation of the base rubber layer present inside, and energy loss is easily generated inside the tire, thereby making it easy to generate energy loss in the entire tread portion, thereby obtaining excellent grip performance.

[0065] In the case of a multi-layered tread portion, the complex elastic modulus (-30°C E * B) is preferably greater than the complex elastic modulus of the cap rubber layer at -30°C (-30°C E * C), that is, (-30℃E * C / -30℃E * B) < 1. These complex elastic moduli can be measured using a viscoelasticity measuring device such as “EPLEXOR (registered trademark)” manufactured by GABO Corporation.

[0066] The complex elastic modulus is a parameter that indicates the rigidity of the rubber layer. It is believed that the temperature inside the tire, such as the base rubber layer, is higher than the surface during driving. Therefore, by setting (-30°C E * C / -30℃E * B) <1, the complex elastic modulus of the base rubber layer at 30°C is greater than the complex elastic modulus of the cap rubber layer at -30°C, which can prevent the tread rubber from excessively deforming in the inner base rubber layer after the tread surface follows the road surface during driving, and easily generate reaction force, thereby obtaining excellent grip performance. It should be noted that as a specific (-30°C E * C / -30℃E * B), preferably 0.36 or less, more preferably 0.33 or less, further preferably 0.32 or less, further preferably 0.20 or less, further preferably 0.16 or less, further preferably 0.13 or less. The lower limit is not particularly limited, but is, for example, preferably 0.05 or more, and more preferably 0.10 or more.

[0067] 4. The content of silica in the crown rubber layer

[0068] In the present invention, the rubber composition forming the cap rubber layer preferably contains silica. By containing silica, the flexible and moving microscopic styrene domains and silica are more likely to rub against each other, which can further increase heat generation and improve the grip performance on icy and snowy roads.

[0069] As a specific content, relative to 100 parts by mass of the rubber component, it is preferably 50 parts by mass or more, more preferably more than 50 parts by mass, further preferably 55 parts by mass or more, further preferably more than 75 parts by mass, further preferably 80 parts by mass or more, further preferably 85 parts by mass or more, further preferably 90 parts by mass or more. The upper limit is not particularly limited, but in consideration of the kneading processability and molding processability of the rubber composition, it is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, further preferably 110 parts by mass or less.

[0070] Furthermore, in the present invention, the particle size (average primary particle size) of silica is preferably 17 nm or less in consideration of the ease of friction with the polymer.

[0071] It should be noted that the average primary particle size can be calculated as follows: a rubber composition is cut out from a tire, and the silica taken out from the rubber composition is directly observed using an electron microscope (TEM) or the like, and the equal cross-sectional area diameter is calculated from the particle area of ​​each silica obtained, and the average value is obtained for calculation.

[0072] 5. Content of resin components in the crown rubber layer

[0073] In the present invention, the rubber composition forming the cap rubber layer preferably contains a resin component.

[0074] It is considered that by including a resin component in the rubber composition, the grip on the road surface can be ensured by utilizing the adhesiveness of the resin component.

[0075] As the preferred resin component, rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc., which are described later, are preferred, and styrene resins such as α-methylstyrene are more preferred. In addition, the content relative to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, further preferably 13 parts by mass or more, further preferably 15 parts by mass or more, further preferably 17 parts by mass or more, further preferably 25 parts by mass or more.

[0076] 6. Acetone extract of crown rubber layer (AE)

[0077] In the present invention, the acetone extractable component (AE) of the cap rubber layer is preferably 1.7% by mass or more, more preferably 2.8% by mass or more, further preferably 5% by mass or more, further preferably 6% by mass or more, further preferably 8% by mass or more, further preferably 9.4% by mass or more, further preferably 9.6% by mass or more, further preferably 10.4% by mass or more, further preferably 11% by mass or more, further preferably 11.1% by mass or more. On the other hand, the upper limit is not particularly limited, but is preferably 17% by mass or less, more preferably 15% by mass or less, further preferably 14% by mass or less.

[0078] The acetone extract (AE) can be considered as an index of the amount of softener etc. in the rubber composition, and it can be considered that the greater the amount, the easier it is for the rubber molecules to move flexibly, and the better the road-following performance. Therefore, in the cap rubber layer, when the amount of AE is increased to a certain extent as described above, the area in contact with the road surface can be sufficiently ensured, and excellent grip performance can be stably exerted.

[0079] The acetone extractable component (AE) can be measured in accordance with JIS K 6229: 2015. Specifically, a vulcanized rubber test piece cut out from a measurement site is immersed in acetone for a predetermined time and the mass reduction rate (%) of the test piece is determined to obtain AE (mass %).

[0080] More specifically, each vulcanized rubber test piece is immersed in acetone at normal temperature and pressure for 72 hours to extract the soluble component, and the mass of each test piece before and after the extraction is measured to determine the acetone extraction amount by the following formula.

[0081] Acetone extraction amount (%) = {(mass of the rubber test piece before extraction - mass of the rubber test piece after extraction) / (mass of the rubber test piece before extraction)} × 100

[0082] The above-mentioned acetone extractable component can be appropriately changed by changing the blending ratio of the plasticizer in the rubber composition.

[0083] 7. Styrene content and land ratio in rubber components

[0084] (1) Land ratio

[0085] In the tire of the present invention, when assembled on a regular rim and set to a regular internal pressure, the land ratio of the tread portion of the tire is preferably 55% or more, more preferably 60% or more, and even more preferably 63% or more.

[0086] The “land ratio” is the ratio of the actual contact surface to the virtual contact surface in which all the grooves arranged on the tread surface are filled. If the land ratio is large, the area in contact with the road surface increases, so sufficient grip performance can be stably obtained.

[0087] In addition, the upper limit of the land ratio is not particularly limited, but is preferably 85% or less, more preferably 80% or less, and further preferably 75% or less.

[0088] The above-mentioned land ratio can be obtained from the ground contact shape under the conditions of a regular rim, a regular internal pressure, and a regular load.

[0089] Specifically, the tire is mounted on a regular rim, a regular internal pressure is applied, and after standing at 25°C for 24 hours, ink is applied to the tire tread surface, a regular load is applied, and the tire is pressed against a thick paper (camber angle is 0°) and transferred to the paper. Thus, the contact shape can be obtained, so the tire is rotated 72° in the circumferential direction and transferred at 5 locations. That is, 5 contact shapes are obtained. At this time, for the 5 contact shapes, the parts of the contour of the contact shape interrupted by the groove are smoothly connected, and the obtained shape is used as the virtual contact surface.

[0090] The land ratio can be calculated from (average area of ​​five ground contact shapes (ink portions) transferred onto thick paper / average area of ​​virtual ground contact surfaces obtained from the five ground contact shapes)×100 (%).

[0091] It should be noted that the above-mentioned "regular internal pressure" refers to the air pressure specified for each standard for each tire in the standard system including the standard on which the above-mentioned tire is based. If it is JATMA, it refers to the maximum air pressure, if it is ETRTO, it refers to "INFLATION PRESSURE", and if it is TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLDINFLATION PRESSURES". As in the case of "regular rims", reference is made in the order of JATMA, ETRTO, and TRA, and the standards are followed. And, in the case of tires not specified in the standard, it refers to the regular internal pressure (of which 250KPa or more) of other tire sizes (tire sizes specified in the standard) that record the above-mentioned regular rims as standard rims. It should be noted that, in the case of multiple regular internal pressures of 250KPa or more, it refers to the minimum value among them.

[0092] Furthermore, "regular load" refers to the load specified for each standard for each tire in the standard system including the standards based on the above tires, and refers to the maximum mass allowed to be loaded by the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUSCOLD INFLATION PRESSURES". As in the case of the above "regular rim" and "regular internal pressure", reference is made in the order of JATMA, ETRTO, and TRA, and the standards are followed. In the case of a tire not specified in the standard, the regular load W is calculated by the following calculation: L .

[0093] V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt

[0094] W L =0.000011×V+175

[0095] W L :Normal load(kg)

[0096] V: Imaginary volume of the tire (mm 3 )

[0097] Dt: Tire outer diameter Dt (mm)

[0098] Ht: Tire section height (mm)

[0099] Wt: tire section width (mm)

[0100] (2) Amount of styrene in the rubber component

[0101] In addition, in the present invention, the amount of styrene contained in 100 parts by mass of the rubber component is preferably 15% by mass or less, more preferably 12% by mass or less, further preferably 10% by mass or less, further preferably 7.5% by mass or less. In addition, the lower limit is not particularly limited, but is preferably 2% by mass or more, more preferably 3% by mass or more, further preferably 4% by mass or more.

[0102] The above-mentioned "amount of styrene in the rubber component" refers to the amount of styrene from the rubber component contained in 100 parts by mass of the rubber component, and is the amount of styrene components excluding components soluble in acetone such as resin components. In the case where the rubber component has a plurality of polymers containing styrene, it can be obtained by multiplying the content of each styrene by the content of the polymer. For example, in the case where 100 parts by mass of the rubber component contains X1 parts by mass of SBR with a styrene content of A1 and X2 parts by mass of SBR with a styrene content of A2, it can be obtained as (A1×X1+A2×X2) / 100.

[0103] (3) Relationship between the amount of styrene in the rubber component and the land ratio

[0104] In the present invention, the ratio of the amount of styrene in the rubber component (mass %) to the land ratio (%) (amount of styrene in the rubber component / land ratio) is preferably 0.15 or less, more preferably 0.13 or less, further preferably 0.12 or less, further preferably 0.11 or less, further preferably 0.10 or less, further preferably 0.09 or less, further preferably 0.08 or less, further preferably 0.06 or less, further preferably 0.05 or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.05 or more, and more preferably 0.06 or more.

[0105] It is believed that the styrene portion in the rubber component forms domains derived from the styrene portion, which bite into the road surface, thereby improving the grip performance on icy and snowy roads. However, it is believed that if the styrene domains are excessively formed on the tread surface, it is difficult to bite into the road surface. Therefore, it is believed that by making the styrene amount in the rubber component less than a certain land ratio, which is the actual contact area ratio, the styrene domains are easy to bite into icy and snowy roads, and the grip performance is easy to improve.

[0106] 8. The amount of styrene in the rubber component and the thickness of the tread

[0107] In the tire of the present invention, the product of the amount of styrene (mass %) in the rubber component and the thickness T (mm) of the tread (amount of styrene × thickness T) is preferably 180 or less, more preferably 150 or less, further preferably 120 or less, further preferably 112.5 or less, further preferably 100 or less, further preferably 80 or less, further preferably 60 or less. On the other hand, the lower limit is not particularly limited, but is preferably 5 or more, more preferably 10 or more, further preferably 15 or more, further preferably 20 or more, further preferably 36 or more, further preferably 45 or more, further preferably 48 or more.

[0108] The friction between the styrene domain formed in the rubber component and other rubber molecular chains can be expected to generate heat, but if it is excessive, it will generate excessive heat during rolling, which may increase the tread surface temperature. Therefore, it is believed that by making the product of the thickness of the tread portion less than a certain value, the heat of the tread portion can be easily released, and heat storage can be suppressed, so that the grip performance on icy and snowy roads can be easily improved.

[0109] 9. Flatness

[0110] The aspect ratio is the height of the cross section relative to the width of the tire. The smaller the ratio, the smaller the ratio of the part deformed in the tire width direction to the friction obtained in the tread portion, and the easier it is to transmit force, so the grip performance is improved. On the other hand, if the aspect ratio is reduced, the flexure of the side portion is reduced, which may lead to a deterioration in ride comfort.

[0111] Taking these points into consideration, in the tire of the present invention, the specific aspect ratio is preferably 30% to 60%.

[0112] It should be noted that the above-mentioned aspect ratio (%) can be calculated using the tire's cross-sectional height Ht (mm), cross-sectional width Wt (mm), tire outer diameter Dt (mm) and rim diameter R (mm) when the internal pressure is set to 250 kPa using the following formula.

[0113] Flatness (%) = (Ht / Wt) × 100 (%)

[0114] Ht=(Dt-R) / 2

[0115] [3] Implementation Method

[0116] The present invention will be described in detail below based on embodiments.

[0117] 1. Rubber composition

[0118] In the tire of the present invention, the rubber composition forming the cap rubber layer can be obtained by appropriately adjusting the types and amounts of various compounding materials such as the rubber component, filler, softener, vulcanizer, and vulcanization accelerator described below.

[0119] (1) Mixed materials

[0120] (a) Rubber component

[0121] The rubber component is not particularly limited, and can be a rubber (polymer) commonly used in the manufacture of tires such as isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), diene rubber such as acrylonitrile-butadiene rubber (NBR), butyl rubber such as butyl rubber, styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene block copolymer (SB) and other thermoplastic elastomers. As described later, these rubber components can be modified. In addition, filler rubbers pre-filled with plasticizer components such as oil, resin, and liquid rubber in these rubber components can also be used.

[0122] In the present invention, among these components, any one of styrene polymers such as SBR, SBS, and SB is included from the aspect of including styrene in the rubber component, and SBR is preferably included. In addition, these styrene polymers can be used in combination with other rubber components, for example, the combination of SBR and BR, and the combination of SBR, BR, and isoprene rubber are preferred.

[0123] (A)SBR

[0124] The weight average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. In addition, in the present invention, as described above, the amount of styrene in the SBR component is made to be less than 25% by mass. The vinyl content (1,2-bonded butadiene content) of SBR is, for example, greater than 5% by mass and less than 70% by mass. It should be noted that the vinyl content of SBR refers to the 1,2-bonded butadiene content of all butadiene parts in the SBR component. In addition, the structural identification of SBR (styrene amount, determination of vinyl content) can be carried out using, for example, the device of the JNM-ECA series manufactured by JEOL Ltd.

[0125] In the present invention, as described above, the content of SBR in 100 parts by mass of the rubber component is 40 parts by mass or less, more preferably 35 parts by mass or less, and further preferably 30 parts by mass or less. On the other hand, as the lower limit, it is preferably 1 part by mass or more, more preferably 3 parts by mass or more, further preferably 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 15 parts by mass or more, further preferably 20 parts by mass or more, and further preferably 25 parts by mass or more.

[0126] As SBR, there is no particular limitation, for example, emulsion polymerization styrene-butadiene rubber (E-SBR), solution polymerization styrene-butadiene rubber (S-SBR) etc. can be used. SBR can be any one of non-modified SBR and modified SBR. In addition, hydrogenated SBR formed by hydrogenating the butadiene portion in SBR can also be used, and hydrogenated SBR can be obtained by hydrogenating the BR portion in SBR later, and styrene, ethylene, butadiene can be copolymerized to obtain the same structure.

[0127] As the modified SBR, any SBR having a functional group that interacts with a filler such as silica may be used, and examples thereof include: a terminal-modified SBR in which at least one terminal of the SBR is modified with a compound (modifier) ​​having the above-mentioned functional group (a terminal-modified SBR having the above-mentioned functional group at the terminal); a main chain-modified SBR having the above-mentioned functional group in the main chain; a main chain-terminal-modified SBR having the above-mentioned functional group in the main chain and at the terminal (for example, a main chain-terminal-modified SBR having the above-mentioned functional group in the main chain and at least one terminal modified with the above-mentioned modifier); a terminal-modified SBR having a hydroxyl group or an epoxy group introduced therein by modification (coupling) with a polyfunctional compound having two or more epoxy groups in the molecule, and the like.

[0128] Examples of the functional group include amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazole, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, 1,2-hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, and epoxy groups. It should be noted that these functional groups may have substituents.

[0129] Moreover, as a modified SBR, for example, SBR modified with the compound (modifying agent) represented by the following formula can be used.

[0130] [Chemistry 1]

[0131]

[0132] It should be noted that, in the formula, R 1 , R 2 and R 3 are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH) or a derivative thereof. 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 It may be bonded to form a ring structure together with the nitrogen atom. n represents an integer.

[0133] As the modified SBR modified with the compound (modifier) ​​represented by the above formula, there can be used SBR in which the polymerization end (active end) of solution-polymerized styrene-butadiene rubber (S-SBR) is modified with the compound represented by the above formula (modified SBR described in JP-A-2010-111753, etc.).

[0134] As R 1 , R 2 and R 3 , preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 , preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. 4 and R 5 When the ring structure is formed by bonding with a nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

[0135] Specific examples of the above-mentioned modifiers include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These can be used alone or in combination of two or more.

[0136] In addition, as modified SBR, modified SBR modified with the following compounds (modifiers) may also be used. Examples of the modifier include: polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'- Diglycidylamino compounds such as diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-phenylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane; acyl chlorides containing amino groups such as bis-(1-methylpropyl)carbamoyl chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylurea chloride, N,N-diethylurea chloride; 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyloxypropyl)-tetramethyldisiloxane, )-pentamethyldisiloxane and other epoxy-containing silane compounds; (trimethylsilyl) [3-(trimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(triethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tripropoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) Silane compounds containing a thioether group, such as [3-(methyldipropoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds, such as ethyleneimine and propyleneimine; alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N-dimethylaminobenzaldehyde Benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-diphenylaminobenzaldehyde and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone; N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone, etc. N-substituted piperidones; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, N-phenyl-β-propiolactam and other N-substituted lactams; and N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine- 2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. It should be noted that the modification using the above compounds (modifiers) can be carried out by a known method. ;

[0137] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. In addition, SBR can be used alone or in combination of two or more.

[0138] (B)BR

[0139] In the present invention, the rubber composition may contain BR. In this case, the content of BR in 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 15 parts by mass or more. On the other hand, it is preferably 30 parts by mass or less, more preferably 25 parts by mass or less.

[0140] 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.

[0141] There is no particular limitation on BR, and BR with a high cis content (a cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. BR can be any of unmodified BR and modified BR. As modified BR, modified BR introduced with the above-mentioned functional groups can be cited. They can be used alone or in combination of two or more. It should be noted that the cis content can be measured by infrared absorption spectroscopy.

[0142] As BR, for example, products of Ube Industries, Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0143] (C) Isoprene rubber

[0144] In the present invention, the rubber composition may contain isoprene-based rubber. In this case, the content of isoprene-based rubber in 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 50 parts by mass or more. On the other hand, it is preferably 70 parts by mass or less, more preferably less than 60 parts by mass.

[0145] Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0146] As NR, for example, SIR20, RSS#3, TSR20, SVR-L and other common substances in the tire industry can be used. There is no particular limitation on IR, for example, IR2200 and other common substances in the tire industry can be used. As modified NR, deproteinized natural rubber (DPNR), high purity natural rubber (UPNR) and the like can be cited. As modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber and the like can be cited. As modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber and the like can be cited. These substances can be used alone or in combination of two or more.

[0147] (D) Other rubber components

[0148] Furthermore, as other rubber components, rubber (polymer) generally used in the production of tires, such as nitrile rubber (NBR), may be contained.

[0149] (b) Compounding materials other than rubber components

[0150] (A) Filler

[0151] In the present embodiment, the rubber composition preferably contains a filler. Specific examples of the filler include silica, carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica.

[0152] (i-1) Silicon dioxide

[0153] In the present invention, the rubber composition preferably contains silica, and preferably contains a silane coupling agent together with silica.

[0154] The BET specific surface area of ​​silica is preferably greater than 140 m 2 / g, more preferably greater than 160m 2 On the other hand, from the perspective of obtaining good rolling resistance during high-speed running, it is preferably less than 250 m 2 / g, more preferably less than 220m 2 It should be noted that the above-mentioned BET specific surface area is the value of N2SA measured by the BET method according to ASTM D3037-93.

[0155] In the present invention, as described above, silica having a particle size of 17 nm or less is preferably used in the rubber composition forming the outer crown rubber layer. By using silica having a small particle size, the contact frequency with the polymer (styrene domain) can be increased, thereby improving the grip performance. The lower limit is not particularly limited, but is preferably 10 nm or more from the perspective of dispersibility during mixing.

[0156] When silica is used as a filler and reinforcing agent, the amount is preferably greater than 50 parts by mass, more preferably greater than 75 parts by mass, and even more preferably greater than 85 parts by mass relative to 100 parts by mass of the rubber component. It should be noted that, as described above, in consideration of the kneading processability and molding processability of the rubber composition, the amount is preferably less than 150 parts by mass, more preferably less than 130 parts by mass, and even more preferably less than 110 parts by mass.

[0157] As silicon dioxide, for example, dry silicon dioxide (anhydrous silicon dioxide), wet silicon dioxide (hydrous silicon dioxide), etc. can be cited. Among them, for the reason of many silanol groups, wet silicon dioxide is preferred. In addition, silicon dioxide using water-containing glass as raw material, silicon dioxide using biomass materials such as rice husk as raw material, etc. can be used.

[0158] As silica, for example, products of Evonik Industries, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd., etc. can be used.

[0159] (i-2) Silane coupling agent

[0160] When silica is used as a filler reinforcing agent, the rubber composition preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilane Sulfide-based silanes include 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes include 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based silanes include vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes include 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes include γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based silanes include 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These may be used alone or in combination of two or more.

[0161] As the silane coupling agent, for example, products of Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Toray-Dow Corning Co., Ltd., etc. can be used.

[0162] The content of the silane coupling agent is, for example, greater than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0163] (ii) Carbon black

[0164] In the present invention, carbon black is preferably contained in the rubber composition from the viewpoint of reinforcement.

[0165] The specific content ratio of carbon black to 100 parts by mass of the rubber component is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less.

[0166] The carbon black is not particularly limited, and examples thereof include furnace blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black; thermal blacks such as FT and MT; channel blacks such as EPC, MPC, and CC, etc. These may be used alone or in combination of two or more.

[0167] The CTAB specific surface area of ​​carbon black (Cetyl Tri-methyl Ammonium Bromide) is preferably 130 m 2 / g or more, more preferably 160m 2 / g or more, more preferably 170m 2 / g or more. On the other hand, it is preferably 250m 2 / g or less, more preferably 200m 2 In addition, the CTAB specific surface area is a value measured according to ASTM D3765-92.

[0168] As specific carbon black, there is no particular limitation, and N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. can be cited. As commercially available products, for example, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Shin Nichia Carbon Co., Ltd., Columbian Carbon Co., Ltd., etc. can be used. They can be used alone or in combination of two or more. In addition, in addition to the above-mentioned carbon black using mineral oil as raw material, carbon using lignin, etc. as raw material can also be suitably used.

[0169] (iii) Other fillers

[0170] In addition to the above-mentioned silica and carbon black, the rubber composition may further contain fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, biochar, etc., as required. The content of these fillers is, for example, greater than 0.1 parts by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0171] (B) Plasticizer ingredients

[0172] In the rubber composition, as a component that softens the rubber, oil, liquid rubber and resin can be included in the form of a plasticizer component. It should be noted that the plasticizer component is a component that can be extracted from vulcanized rubber using acetone. The total content of the plasticizer component is preferably more than 2 mass parts, more preferably more than 20 mass parts relative to 100 mass parts of the rubber component. On the other hand, it is preferably less than 40 mass parts, more preferably less than 30 mass parts. It should be noted that, when using filling rubber as a rubber component, the filling component amount is also included in the content of the plasticizer. And, for example, if it is oil-filled, the filling oil is also included in the amount of oil described later.

[0173] (i)Oil

[0174] As oil, for example, mineral oil (commonly referred to as process oil), vegetable oil, or a mixture thereof can be cited. As mineral oil (process oil), for example, paraffinic process oil, aromatic process oil, cycloparaffinic process oil, etc. such as MES (mild extract solvent), DAE (distillate aromatic extract), TDAE (treated distillate aromatic extract), TRAE (treated residual aromatic extract), and RAE (residual aromatic extract) can be used. As vegetable oil, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower seed oil, palm kernel oil, camellia oil, jojoba oil, macadamia oil, tung oil, etc. can be cited. These may be used alone or in combination of two or more. In addition, from the perspective of life cycle assessment, waste oil used as lubricating oil for rubber mixing mixers, automobile engines, etc., waste cooking oil, etc. may be suitably used.

[0175] As specific process oil (mineral oil), for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Olisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., etc. can be used.

[0176] (ii) Liquid rubber

[0177] Liquid rubber as a plasticizer is a polymer in a liquid state at room temperature (25° C.) and is a rubber component that can be extracted from a vulcanized tire by acetone extraction. Examples of the liquid rubber include farnesene polymers, liquid diene polymers, and hydrogenated products thereof.

[0178] Farnesene polymers are polymers obtained by polymerizing farnesene, and have a structural unit based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0179] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0180] Examples of the liquid diene polymer include liquid styrene-butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), and liquid styrene-isoprene copolymers (liquid SIR).

[0181] The polystyrene-equivalent weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) is, for example, greater than 1.0×10 3 , less than 2.0×10 5 In addition, in this specification, Mw of a liquid diene polymer is a polystyrene conversion value measured by gel permeation chromatography (GPC).

[0182] The content of the liquid rubber (the total content of the liquid farnesene polymer, the liquid diene polymer, etc.) is, for example, greater than 1 part by mass and less than 100 parts by mass relative to 100 parts by mass of the rubber component.

[0183] As the liquid rubber, for example, products of KURARAY Co., Ltd., Cray Valley Corporation, etc. can be used.

[0184] (iii) Resin component

[0185] The resin component also plays a role as an adhesiveness imparting component, which can be solid or liquid at room temperature. As a specific resin component, for example, resins such as rosin resin, styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc. can be cited, and two or more resins can also be used in combination. The content of the resin component is greater than 2 mass parts relative to 100 mass parts of the rubber component, preferably less than 45 mass parts, and more preferably less than 30 mass parts. It should be noted that these resin components can also be given modified groups that can react with silica etc. as needed.

[0186] Rosin resin is a resin with rosin acid obtained by processing rosin as the main component. The rosin resin (rosin) can be classified by whether it is modified or not, and can be classified into unmodified rosin (unmodified rosin) and rosin modified products (rosin derivatives). As unmodified rosin, tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, other chemically modified rosins, etc. can be cited. Rosin modified products are modified products of unmodified rosin, and rosin esters, unsaturated carboxylic acid modified rosins, unsaturated carboxylic acid modified rosin esters, amide compounds of rosin, amine salts of rosin, etc. can be cited.

[0187] Styrene resins are polymers using styrene monomers as constituent monomers, and examples include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more). Specifically, in addition to homopolymers obtained by homopolymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), copolymers obtained by copolymerizing two or more styrene monomers, copolymers of styrene monomers and other monomers copolymerizable therewith can also be mentioned.

[0188] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate; dienes such as chloroprene, butadiene and isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride or their anhydrides, etc.

[0189] Among the coumarone resins, coumarone indene resins are preferred. Coumarone indene resins are resins containing coumarone and indene as monomer components constituting the backbone (main chain) of the resin. Examples of monomer components contained in the backbone in addition to coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, and the like.

[0190] The content of the coumarone indene resin is, for example, greater than 1.0 part by mass and less than 50.0 parts by mass relative to 100 parts by mass of the rubber component.

[0191] The hydroxyl value (OH value) of the coumarone indene resin is, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is a value expressed in milligrams as the amount of potassium hydroxide required to neutralize acetic acid bound to hydroxyl groups when 1 g of the resin is acetylated, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0192] The softening point of the coumarone indene resin is, for example, higher than 30° C. and lower than 160° C. The softening point is the softening point specified in JIS K 6220-1:2001 and is measured using a ring and ball softening point measuring apparatus, and is the temperature at which a ball falls.

[0193] Examples of terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are composed of (C5H8) n The hydrocarbons and their oxygenated derivatives are classified as monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) and the like as a basic skeleton, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. can be mentioned.

[0194] As polyterpenes, in addition to terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin, etc., which use the above-mentioned terpene compounds as raw materials, hydrogenated terpene resins obtained by hydrogenating the terpene resins can also be cited. As terpene phenols, resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds and resins obtained by hydrogenating the resins can be cited. Specifically, resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds and formaldehyde can be cited. It should be noted that, as phenolic compounds, for example, phenol, bisphenol A, cresol, xylenol, etc. can be cited. As aromatic modified terpene resins, resins obtained by modifying terpene resins using aromatic compounds and resins obtained by hydrogenating the resins can be cited. It should be noted that the aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and styrene containing an unsaturated hydrocarbon group; benzofuran, indene, etc.

[0195] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of the C5 fraction include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5-based petroleum resin, dicyclopentadiene resin (DCPD resin) can be appropriately used.

[0196] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may also be a resin obtained by hydrogenating or modifying them. As the C9 fraction, for example, petroleum fractions having 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene can be cited. As specific examples, for example, benzofuran indene resin, benzofuran resin, indene resin, and aromatic vinyl resin can be appropriately used. As an aromatic vinyl resin, for reasons of economy, easy processing, and excellent heat generation, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred. As an aromatic vinyl resin, for example, commercially available substances from Kraton, Eastman Chemical, etc. can be used.

[0197] "C5C9 resin" refers to a resin obtained by copolymerizing the above-mentioned C5 fraction and the above-mentioned C9 fraction, and may also be a substance obtained by hydrogenating or modifying them. Examples of the C5 fraction and the C9 fraction include the above-mentioned petroleum fractions. As the C5C9 resin, for example, a substance commercially available from Tosoh Corporation, LUHUA Corporation, etc. may be used.

[0198] The acrylic resin is not particularly limited, and for example, a solvent-free acrylic resin can be used.

[0199] Solvent-free acrylic resins include (meth) acrylic resins (polymers) synthesized by a high temperature continuous polymerization method (high temperature continuous bulk polymerization method) (methods described in U.S. Patent No. 4,414,370, Japanese Patent Publication No. 59-6207, Japanese Patent Publication No. 5-58005, Japanese Patent Publication No. 1-313522, U.S. Patent No. 5,010,166, East Asia Synthesis Research Annual Report TREND 2000 No. 3, p. 42-45, etc.) without using a polymerization initiator, a chain transfer agent, an organic solvent, etc. as secondary raw materials as much as possible. It should be noted that in the present invention, (meth) acrylic acid refers to methacrylic acid and acrylic acid.

[0200] Examples of the monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, arylalkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0201] As monomer components constituting the acrylic resin, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0202] The acrylic resin may be a resin composed only of a (meth)acrylic acid component, or may be a resin containing components other than the (meth)acrylic acid component as constituent elements. In addition, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0203] As the resin component, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakery Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF Corporation, Arizona Chemical Co., Ltd., Nippon Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., etc. can be used.

[0204] (C) Stearic acid

[0205] In the present invention, stearic acid is preferably included in the rubber composition. The content of stearic acid is, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component. As stearic acid, conventionally known substances can be used, for example, products of NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0206] (D) Anti-aging agent

[0207] In the present invention, the rubber composition preferably contains an antioxidant, and the content of the antioxidant is, for example, greater than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, based on 100 parts by mass of the rubber component.

[0208] Examples of the anti-aging agent include naphthylamine antioxidants such as phenyl-α-naphthylamine; diphenylamine antioxidants such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine antioxidants such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; bisphenol, triphenol, and polyphenol antioxidants such as tetrakis-[methylene-3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl)propionate]methane; and the like. These may be used alone or in combination of two or more.

[0209] As the antioxidant, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., FlexSys Co., Ltd., and the like can be used.

[0210] (E) Wax

[0211] In the present invention, the rubber composition preferably contains wax. The content of the wax is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, and more preferably 1.5 to 10 parts by mass, based on 100 parts by mass of the rubber component.

[0212] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as plant wax and animal wax, and synthetic waxes such as polymers of ethylene and propylene, etc. These may be used alone or in combination of two or more.

[0213] As the wax, for example, products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0214] (F) Zinc Oxide

[0215] The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, greater than 0.5 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the rubber component. As zinc oxide, conventionally known substances may be used, for example, products of Mitsui Mining and Smelting Co., Ltd., Toho Asia Lead Co., Ltd., HakusuiTech Co., Ltd., Shodo Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. may be used.

[0216] (G) Crosslinking agent and vulcanization accelerator

[0217] The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0218] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur generally used in the rubber industry. These may be used alone or in combination of two or more.

[0219] As sulfur, for example, products of Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., FlexSys Co., Ltd., Nippon Kanryu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used.

[0220] Examples of the crosslinking agent other than sulfur include sulfur-containing vulcanizing agents such as TACKROLV200 manufactured by Taoka Chemical Industry Co., Ltd. and KA9188 (1,6-bis(N,N′-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS, and organic peroxides such as dicumyl peroxide.

[0221] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, greater than 0.3 parts by mass and less than 10.0 parts by mass relative to 100 parts by mass of the rubber component.

[0222] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazolyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. These may be used alone or in combination of two or more.

[0223] (H) Others

[0224] In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, anti-reversion (vulcanization reversion) agents, etc. The content of these additives is, for example, greater than 0.1 parts by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0225] (2) Preparation of rubber composition

[0226] The rubber composition forming the crown rubber layer can be produced by appropriately adjusting the above-mentioned various mixed materials through common methods, for example, by a manufacturing method including the following steps: a basic mixing step of mixing the rubber component with fillers such as carbon black; and a final mixing step of mixing the mixture obtained in the above-mentioned basic mixing step with a cross-linking agent.

[0227] The kneading can be performed using a known kneading machine such as a Banbury mixer, a kneader, or an open roll mill.

[0228] The mixing temperature of the basic mixing process is, for example, greater than 50°C and less than 200°C, and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In the basic mixing process, in addition to the above-mentioned components, compounding agents used in the existing rubber industry, such as softeners such as oil, zinc oxide, anti-aging agents, wax, vulcanization accelerators, etc., can be appropriately added and mixed as needed. It should be noted that there is no particular restriction on the order of inputting the materials during mixing. The rubber component can be crushed in a mixer and then the filler and softener can be added, or the filler and softener can be mixed in the mixer in advance and then the rubber component can be added.

[0229] In the final kneading step, the kneaded product obtained in the above-mentioned basic kneading step is kneaded with a crosslinking agent. The kneading temperature of the final kneading step is, for example, greater than room temperature and less than 80° C., and the kneading time is, for example, greater than 1 minute and less than 15 minutes. In the final kneading step, in addition to the above-mentioned components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added as needed.

[0230] 2. Tire manufacturing

[0231] The tire of the present invention can be produced as follows: the rubber composition obtained above is used as a cap rubber layer, molded into a tread rubber of a specified shape, and then molded together with other tire components on a tire molding machine by a common method, thereby producing a tire in the form of an unvulcanized tire.

[0232] It should be noted that, in the case of making the tread portion a multilayer structure with the base rubber layer, the above-mentioned rubber components and compounding materials can be basically used, and the compounding amounts thereof can be appropriately changed and kneaded in the same manner to obtain a rubber composition for forming the base rubber layer. Furthermore, the tread rubber is extruded together with the cap rubber layer to be molded into a predetermined shape, and then molded together with other tire components on a tire molding machine by a common method, thereby manufacturing a tire in the form of an unvulcanized tire.

[0233] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and filling air pressure borne by the tire, a belt component as a component for strongly fastening the carcass to increase the rigidity of the tread, etc. are wound on a forming drum, and a bead portion as a component for fixing the two ends of the carcass to the edge portions on both sides and fixing the tire to the rim is arranged and formed into a ring shape, and then the tread is adhered to the central portion of the outer periphery and the sidewall is adhered to the radial outside to form a side portion, thereby producing an unvulcanized tire.

[0234] The unvulcanized tire prepared as described above is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be implemented by applying a known vulcanization method. The vulcanization temperature is, for example, greater than 120° C. and less than 200° C., and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0235] As described above, the obtained tire can improve the ground contact performance and realize the bite into ice and snow based on the styrene domain, so the grip performance on icy and snowy roads can be sufficiently improved.

[0236] It should be noted that the category of the tire of the present invention is not particularly limited, and can be used as a heavy-duty vehicle tire such as a passenger car tire, a truck, a bus, a tire for a two-wheel vehicle, a puncture-proof tire, a non-pneumatic tire, etc., but is preferably used as a passenger car tire. In addition, it is preferably used as a pneumatic tire.

[0237] Example

[0238] The following are examples (embodiments) that are considered to be preferred when implementing the invention, but the scope of the invention is not limited to these examples. In the examples, various chemicals shown below were used and the proportions were changed according to the tables to obtain compositions, and pneumatic tires (tire size: 205 / 55R16, aspect ratio: 55%, land ratio: 65%) made from the obtained compositions were studied, and the results calculated based on the following evaluation method are shown in Tables 2 to 5.

[0239] 1. Rubber composition forming the crown rubber layer

[0240] (1) Mixed materials

[0241] (a) Rubber component

[0242] (A)NR:TSR20

[0243] (B) SBR-1: Modified S-SBR obtained by the method described in the following paragraph

[0244] (Styrene content: 25 mass%, vinyl content: 25 mass%)

[0245] (C) SBR-2: HPR840 manufactured by ENEOS Materials Co., Ltd.

[0246] (Styrene content: 10 mass %, vinyl content: 42 mass %)

[0247] (D) BR: Ubepol BR150B (high cis BR) manufactured by Ube Industries, Ltd.

[0248] (cis content 97 mass %, trans content 2 mass %, vinyl content 1 mass %)

[0249] (Manufacture of SBR-1)

[0250] The above-mentioned SBR-1 was prepared according to the following steps. First, an autoclave with an internal volume of 10 L, an inlet at the bottom, an outlet at the head, a stirrer and a jacket was used as a reactor, and two of them were connected in series, and butadiene, styrene and cyclohexane were mixed in a specified ratio. The mixed solution was passed through a dehydration column filled with activated alumina. In order to remove impurities, n-butyl lithium was mixed in a static mixer and then continuously supplied from the bottom of the first reactor. Furthermore, 2,2-bis(2-oxacyclopentyl)propane as a polar substance and n-butyl lithium as a polymerization initiator were continuously supplied from the bottom of the first reactor at a specified speed, respectively, and the temperature in the reactor was maintained at 95°C. The polymer solution was continuously discharged from the head of the reactor and supplied to the second reactor. The temperature of the second reactor was maintained at 95°C, and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and an oligomer component was continuously added at a predetermined rate in the form of a 1000-fold dilution of cyclohexane to carry out a modification reaction. The polymer solution was continuously discharged from the reactor, and an antioxidant was continuously added using a static mixer, and then the solvent was removed to obtain the target modified diene polymer (SBR-1).

[0251] By infrared spectroscopy, the absorption peak of vinyl group was 910 cm -1 The vinyl content (unit: mass %) of the SBR-1 was determined from the absorption intensity near 1.5 Å / min. The styrene content (unit: mass %) was determined from the refractive index in accordance with JIS K6383 (1995).

[0252] (b) Compounding materials other than rubber components

[0253] (A) Carbon black: DIABLACK N220 manufactured by Mitsubishi Chemical Corporation

[0254] (N2SA: 115m 2 / g)

[0255] (B) Silica: Ultrasil VN3 manufactured by Evonik Industries

[0256] (N2SA: 175m 2 / g, average primary particle size: 17nm)

[0257] (C) Silane coupling agent: Si266 manufactured by Evonik Industries

[0258] (Bis(3-triethoxysilylpropyl) disulfide)

[0259] (D) Resin: SYLVATRAXX4401 manufactured by Kraton

[0260] (α-Methylstyrene resin)

[0261] (E) Oil: Vivatec 500 manufactured by H&R

[0262] (Aromatic operating oil: TDAE oil)

[0263] (F) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining and Smelting Co., Ltd.

[0264] (G) Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.

[0265] (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)

[0266] (H) Stearic acid: Beads Stearic Acid "Tsubaki" manufactured by NOF Corporation

[0267] (I) Wax: Sunnoc N manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0268] (J) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. (containing 5% oil)

[0269] (K) Vulcanization accelerator: NOCCELERCZ (CBS) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0270] (N-cyclohexyl-2-benzothiazolylsulfenamide)

[0271] (2) Rubber composition forming the cap rubber layer

[0272] According to the compounding contents shown in Tables 2 to 5, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a Banbury mixer to obtain a kneaded product.

[0273] Next, sulfur and a vulcanization accelerator were added to the kneaded product obtained above, and kneaded for 5 minutes at 80° C. using an open roll mill to obtain a rubber composition for forming a cap rubber layer.

[0274] 2. Rubber composition forming the base rubber layer

[0275] In parallel, a rubber composition for forming a base rubber layer was prepared based on the formulation shown in Table 1 in the same manner as the rubber composition for forming a cap rubber layer.

[0276] [Table 1]

[0277]

[0278] 3. Manufacturing of pneumatic tires

[0279] Each rubber composition obtained above was extruded into a predetermined shape so that the ratio of (cap rubber layer thickness / base rubber layer thickness) was 6 / 4 to form a tread portion having a thickness T (mm) shown in Tables 2 to 5.

[0280] Thereafter, the unvulcanized tire was laminated together with other tire components and press-vulcanized at 170° C. for 10 minutes to produce pneumatic tires (test tires) of Examples 1 to 14 and Comparative Examples 1 to 6 shown in Tables 2 to 5.

[0281] 4. Calculation of parameters

[0282] Thereafter, the following parameters were obtained for each test tire.

[0283] (1)tanδ

[0284] The rubber test piece for viscoelasticity measurement was prepared by cutting the crown rubber layer of the tread portion of each test tire in a manner that the long side becomes the tire circumferential direction, with a length of 20 mm × a width of 4 mm × a thickness of 2 mm. For each rubber test piece, the EPLEXOR series manufactured by GABO was used, and tanδ was measured at a measurement temperature of -30°C, 0°C, and 30°C under the conditions of frequency 10 Hz, initial strain 5%, dynamic strain 1%, and deformation mode: tension, and the -30°C tanδ, 0°C tanδ, and 30°C tanδ were obtained respectively. It should be noted that the 30°C tanδ of the base rubber layer is 0.22.

[0285] Next, -30°C tanδ / T (mm) was determined from the -30°C tanδ of the cap rubber layer and the thickness T (mm) of the tread portion.

[0286] (2)Tg

[0287] For the rubber test piece for viscoelasticity measurement, which was similarly cut from the crown rubber layer, "EPLEXOR (registered trademark)" manufactured by GABO was used. Under the conditions of frequency 10 Hz, initial strain 2%, amplitude ±1% and heating rate 2°C / min, the temperature was changed from -70°C to 30°C, and tanδ was measured. The temperature corresponding to the maximum tanδ value in the obtained temperature distribution curve was determined as Tg.

[0288] (3) Complex elastic modulus

[0289] The rubber test piece for viscoelasticity measurement, which was similarly cut from the crown rubber layer, was measured using the EPLEXOR series manufactured by GABO under the conditions of temperature -30°C, frequency 10 Hz, initial strain 5%, and dynamic strain 1% in the deformation mode: tensile for complex elastic modulus (MPa) (-30°C E * C). It should be noted that the complex elastic modulus of the base rubber layer at 30°C (-30°C E * B) is 12.0 MPa.

[0290] (4) Acetone extract of the crown rubber layer (AE)

[0291] Using a vulcanized rubber test piece cut out from the cap rubber layer of the tread portion of each test tire, AE (mass %) was determined in accordance with JIS K 6229:2015.

[0292] (5) Other parameters

[0293] The styrene amount (mass %) in the rubber component was determined, and the styrene amount (mass %) in the rubber component × the thickness T (mm) of the tread portion and the styrene amount (mass %) in the rubber component / land ratio (%) were determined.

[0294] 5. Performance evaluation test (evaluation of grip performance on icy and snowy roads)

[0295] Each test tire was installed on all wheels of a vehicle (a domestic FF car with a displacement of 2000cc), and filled with air to a pressure of 250kPa (the normal pressure of a passenger car). The vehicle was then driven at 60km / h on a test route on an icy and snowy road, and 20 drivers performed a sensory evaluation of the grip performance during driving in five stages (the larger the value, the better). The total score based on the evaluations of the 20 drivers was then calculated.

[0296] Next, the result of Comparative Example 4 was set to 100, and the index was converted into an evaluation of the grip performance on an icy and snowy road surface (ice and snow grip performance) based on the following formula. A larger numerical value indicates a better ice and snow grip performance.

[0297] Ice and snow grip performance = [(result of test tire) / (result of comparative example 4)] × 100

[0298] [Table 2]

[0299]

[0300] [Table 3]

[0301]

[0302] [Table 4]

[0303]

[0304] [Table 5]

[0305]

[0306] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications may be made to the above-described embodiments within the scope of the same or equivalent aspects of the present invention.

[0307] The present invention (1) relates to a tire having a tread portion, characterized in that:

[0308] The cap rubber layer forming the tread portion is formed of a rubber composition.

[0309] The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component.

[0310] The loss tangent (-30℃ tanδ) measured in the deformation mode: tension under the conditions of temperature -30℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more,

[0311] The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

[0312] The present invention (2) is directed to the tire according to the present invention (1), wherein the content of the styrene-butadiene rubber (SBR) is 35 parts by mass or less.

[0313] The present invention (3) relates to the tire described in the present invention (1) or (2), characterized in that the loss tangent (0℃tanδ) of the above-mentioned crown rubber layer measured in the deformation mode: tension under the conditions of temperature 0℃, frequency 10Hz, initial strain 5%, and dynamic strain rate 1% is greater than 0.30.

[0314] The present invention (4) relates to a tire in any combination with any one of the present inventions (1) to (3), characterized in that the loss tangent (30°C tanδ) of the above-mentioned crown rubber layer measured in a deformation mode: tension under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is less than 0.20.

[0315] The present invention (5) relates to a tire in combination with any one of the present inventions (1) to (4), characterized in that the thickness T of the tread portion is not less than 12 mm and not more than 18 mm.

[0316] The present invention (6) relates to a tire in any combination with any one of the present inventions (1) to (5), characterized in that the tread thickness T and the tan δ of the cap rubber layer at -30°C satisfy the following formula.

[0317] -30℃tanδ / T>0.04

[0318] The present invention (7) relates to a tire in combination with any one of the present inventions (1) to (6), characterized in that the glass transition temperature (Tg) of the cap rubber layer is -40°C or lower.

[0319] The present invention (8) relates to a tire in any combination with any one of the present inventions (1) to (7), characterized in that the tread portion is formed by the cap rubber layer and a base rubber layer provided on the inner side of the cap rubber layer.

[0320] The present invention (9) relates to the tire according to the present invention (8), characterized in that the thickness of the cap rubber layer is 50% or more of the thickness of the entire tread portion.

[0321] The present invention (10) relates to the tire described in the present invention (8) or (9), characterized in that the 30°C tanδ of the above-mentioned base rubber layer is larger than the 30°C tanδ of the above-mentioned cap rubber layer.

[0322] The present invention (11) relates to a tire in any combination with any one of the present inventions (8) to (10), characterized in that the complex elastic modulus (-30°C E * B) and the complex elastic modulus of the cap rubber layer at -30°C (-30°C E * C) satisfies the following formula.

[0323] (-30℃E * C / -30℃E * B) <1

[0324] The present invention (12) relates to a tire in any combination with any one of the present inventions (1) to (11), characterized in that the above-mentioned cap rubber layer contains a resin component selected from the group consisting of rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins.

[0325] The present invention (13) relates to a tire in combination with any one of the present inventions (1) to (12), characterized in that the acetone extractable component (AE) of the cap rubber layer is 8 mass % or more.

[0326] The present invention (14) relates to a tire in any combination with any one of the present inventions (1) to (13), characterized in that the ratio of the amount of styrene in the rubber component (mass %) to the land ratio (%) in the above-mentioned tread portion (amount of styrene in the rubber component / land ratio) is less than 0.13.

[0327] The present invention (15) relates to a tire in any combination with any one of the present inventions (1) to (14), characterized in that the product of the amount of styrene in the rubber component (mass %) and the thickness T (mm) of the above-mentioned tread portion (styrene amount × thickness T) is less than 180.

Claims

1. A tire having a tread portion, characterized in that: The cap rubber layer forming the tread portion is formed of a rubber composition, The rubber composition contains 40 parts by mass or less of styrene and 25% by mass or less of styrene-butadiene rubber (SBR) in 100 parts by mass of the rubber component. The loss tangent (-30℃ tanδ) measured in the deformation mode: tension under the conditions of temperature -30℃, frequency 10Hz, initial strain 5%, dynamic strain rate 1% is 0.10 or more, The tread portion has a thickness of not less than 10 mm and not more than 20 mm.

2. The tire according to claim 1, characterized in that The content of the styrene-butadiene rubber (SBR) is 35 parts by mass or less.

3. The tire according to claim 1 or 2, characterized in that: The cap rubber layer has a loss tangent (0°C tan δ) of 0.30 or more when measured in a deformation mode: tension 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%.

4. The tire according to any one of claims 1 to 3, characterized in that The cap rubber layer has a loss tangent (30°C tan δ) of 0.20 or less when measured in a deformation mode: tension under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%.

5. The tire according to any one of claims 1 to 4, characterized in that The thickness T of the tread portion is not less than 12 mm and not more than 18 mm.

6. The tire according to any one of claims 1 to 5, characterized in that The tread thickness T and the tanδ of the cap rubber layer at -30°C satisfy the following formula: -30℃tanδ / T>0.

04.

7. The tire according to any one of claims 1 to 6, characterized in that The cap rubber layer has a glass transition temperature (Tg) of -40°C or less.

8. The tire according to any one of claims 1 to 7, characterized in that The tread portion is formed of the cap rubber layer and a base rubber layer provided on the inner side of the cap rubber layer.

9. The tire according to claim 8, characterized in that The cap rubber layer has a thickness of 50% or more relative to the entire tread portion thickness.

10. The tire according to claim 8 or 9, characterized in that The tan δ at 30° C. of the base rubber layer is greater than the tan δ at 30° C. of the cap rubber layer.

11. The tire according to any one of claims 8 to 10, characterized in that The complex elastic modulus (-30°C E * B) and the complex elastic modulus of the cap rubber layer at -30°C (-30°C E * C) satisfies the following formula, (-30℃E * C / -30℃E * B)<1。 12. The tire according to any one of claims 1 to 11, characterized in that The cap rubber layer includes a resin component selected from the group consisting of rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins.

13. The tire according to any one of claims 1 to 12, characterized in that The cap rubber layer has an acetone extractable component (AE) of 8 mass % or more.

14. The tire according to any one of claims 1 to 13, characterized in that The ratio of the amount of styrene in the rubber component (mass %) to the land ratio (%) of the tread portion (amount of styrene in the rubber component / land ratio) is 0.13 or less.

15. The tire according to any one of claims 1 to 14, characterized in that The product of the amount of styrene (mass %) in the rubber component and the thickness T (mm) of the tread portion (the amount of styrene×the thickness T) is 180 or less.

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