WO2023248828A1

WO2023248828A1 - Tire

Info

Publication number: WO2023248828A1
Application number: PCT/JP2023/021485
Authority: WO
Inventors: 亜由子山田; 健太郎中村
Original assignee: 住友ゴム工業株式会社
Priority date: 2022-06-24
Filing date: 2023-06-09
Publication date: 2023-12-28
Also published as: JP2024002386A

Abstract

The present invention improves wear resistance during high-speed travel. A tire comprising a tread section, wherein: a cap rubber layer forming the tread section is formed from a rubber composition containing 60-80 parts by mass of styrene butadiene rubber (SBR) having a styrene content of 25% by mass or less per 100 parts by mass of a rubber component, and also containing 100 parts by mass or less of silica per 100 parts by mass of the rubber component, the rubber composition being such that, at a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1%, the loss tangent (30°C tan δ) of the rubber composition measured in a tension deformation mode is greater than 0.25; and the thickness of the tread section is 6-15 mm.

Description

tire

The present invention relates to tires.

Since tires are subject to wear due to running, various techniques have been proposed to improve wear resistance (for example, Patent Documents 1 to 4).

JP2021-187860A WO2019/235526 publication WO2019/240226 publication

However, with the development of expressways in recent years, opportunities to travel long distances at high speeds have increased dramatically. is still not sufficient, and further improvements are strongly desired.

Therefore, an object of the present invention is to improve wear resistance during high-speed running.

The present invention
A tire including a tread portion,
The cap rubber layer forming the tread portion is
Containing styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, 60 parts by mass or more and 80 parts by mass or less,
Containing less than 100 parts by mass of silica with respect to 100 parts by mass of the rubber component,
Formed from a rubber composition whose loss tangent (30°C tan δ) measured in tensile deformation mode is more than 0.25 under the conditions of a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1%. and
The tire is characterized in that the thickness of the tread portion is 15 mm or less.

According to the present invention, it is possible to improve wear resistance during high-speed running.

[1] Features of the tire according to the present invention First, the features of the tire according to the present invention will be explained.

1. Summary The tire according to the present invention is a tire having a tread portion, in which the cap rubber layer forming the tread portion contains SBR containing 25% by mass or less of styrene, 60 parts by mass or more in 100 parts by mass of the rubber component, Contains 80 parts by mass or less, and contains less than 100 parts by mass of silica per 100 parts by mass of the rubber component, under the conditions of temperature 30 ° C., frequency 10 Hz, initial strain 5%, dynamic strain rate 1%, deformation mode: tensile. The rubber composition has a loss tangent (tan δ at 30°C) of more than 0.25. The thickness of the tread portion is 15 mm or less.

Note that the cap rubber layer referred to herein is not limited to the rubber layer that forms the outermost layer of the tread portion, but if there are two or more layers within 5 mm inward from the tread surface, at least one of the layers is It is sufficient as long as it satisfies the requirements of the rubber composition.

By having these characteristics, as will be described later, it is possible to improve the wear resistance during high-speed running.

2. Mechanism of the effect exerted in the tire according to the present invention The mechanism of the above-mentioned effect exerted in the tire according to the present invention is considered as follows.

As described above, the rubber composition forming the cap rubber layer of the tire according to the present invention contains 60 parts by mass or more and 80 parts by mass or less of SBR with a styrene content of 25% by mass or less in 100 parts by mass of the rubber component. In addition, silica is contained in an amount of 100 parts by mass or less based on 100 parts by mass of the rubber component.

By setting the SBR component in 100 parts by mass of the rubber component to 60 parts by mass or more and 80 parts by mass or less, it is possible to form a phase-separated structure in which the SBR phase is a continuous phase in the rubber matrix. By setting the amount of styrene in the rubber composition to 25% by mass or less, the silica contained in the rubber composition as a reinforcing agent can easily interact with the SBR phase in the rubber matrix, and the reinforcing effect of silica can be obtained. It is thought that it will become easier.

Furthermore, by containing an appropriate amount of SBR with a small amount of styrene (styrene amount of 25% by mass or less), minute styrene domains derived from the styrene portion can be appropriately formed in the rubber matrix system. These minute styrene domains that are formed tend to relax force at the interface with other polymer molecular chains, and are therefore thought to be able to ease deformation caused by friction with the road surface when the tire runs at high speed.

Note that the amount of styrene described above is more preferably 20% by mass or less, even more preferably 15% by mass or less, and even more preferably 10% by mass or less. On the other hand, the lower limit is preferably 4% by mass or more, more preferably 5% by mass or more, and even more preferably 6% by mass or more.

In the present invention, "containing 60 parts by mass or more and 80 parts by mass or less of SBR with an amount of styrene of 25 parts by mass or less in 100 parts by mass of the rubber component" means that the amount of SBR in 100 parts by mass of the rubber component is 60 parts by mass or less. The amount is 80 parts by mass or more, and 80 parts by mass or less, indicating that the amount of styrene in the entire SBR is 25% by mass or less.

That is, when a styrene-containing polymer (SBR) is contained alone in the rubber component, it indicates that the amount of styrene is 25% by mass or less, and if the rubber component contains multiple styrene-containing polymers (SBR). , the amount of styrene determined by the sum of the products of the amount of styrene (% by mass) in each polymer and the amount (parts by mass) of that polymer per 100 parts by mass of the rubber component is 25% by mass or less. It shows that.

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

In addition, in the rubber composition after vulcanization, the amount of styrene contained in the rubber component after acetone extraction can also be determined by solid-state nuclear magnetic resonance (solid-state NMR) or Fourier transform infrared spectrophotometer (FTIR). It is possible to calculate.

In the present invention, the rubber composition forming the cap rubber layer contains less than 100 parts by mass of silica per 100 parts by mass of the rubber component, which is not more than the rubber component. As a result, in addition to the reinforcing effect due to the interaction of silica, the minute styrene domains and silica create friction and generate heat, which makes it possible to release the energy of deformation, which improves wear resistance during high-speed running. It is thought that this can be sufficiently improved.

Furthermore, in the present invention, the deformation mode: loss tangent ( 30° C. tan δ) is set to exceed 0.25.

The loss tangent tan δ is a viscoelastic parameter indicating energy absorption performance, and the larger the value, the more energy can be absorbed and converted into heat. In the present invention, the tan δ of 30°C, which is close to the running temperature, is set to a high value exceeding 0.25, so even when running at high speeds where high-frequency vibrations occur, vibration energy is sufficiently absorbed and converted into heat. By releasing the energy, sufficient energy loss can be caused within the rubber composition, and the grip performance can be improved. In addition to improving the grip performance, it is possible to suppress the occurrence of slippage on the tread surface, so it is thought that the wear resistance during high-speed running can be sufficiently improved.

The 30°C tan δ is more preferably 0.28 or more, further preferably 0.30 or more, even more preferably 0.33 or more, even more preferably 0.34 or more, and 0.35 It is more preferable that it is 0.36 or more, and even more preferable that it is 0.36 or more. Although the upper limit is not particularly limited, it is preferably 0.50 or less, more preferably 0.45 or less, and even more preferably 0.40 or less.

In the above, the loss tangent (tan δ) can be measured, for example, using a viscoelasticity measuring device such as “Iplexer (registered trademark)” manufactured by GABO.

The method for adjusting tan δ is not particularly limited, but for example, tan δ can be increased by increasing the amount of styrene in the polymer, increasing the content of resin components, increasing the content of carbon black, etc.; It can be lowered by reducing the content of the components and the content of carbon black.

Furthermore, in the tire according to the present invention, as described above, the thickness of the tread portion is 15 mm or less. By controlling the thickness to an appropriate level in this way, it is possible to suppress the accumulation of heat generated by friction with the road surface in the tread, and to suppress the decline in wear resistance caused by the rise in temperature of the tread due to heat accumulation. it is conceivable that. The thickness of the tread portion is more preferably 13 mm or less, even more preferably 11 mm or less, even more preferably 10 mm or less, and even more preferably 9 mm or less. Although the lower limit is not particularly limited, it is preferably 4 mm or more, more preferably 5 mm or more, even more preferably 6 mm or more, and even more preferably 8 mm or more.

In addition, in the present invention, the thickness of the tread portion refers to the thickness of the tread portion on the tire equatorial plane in the tire radial cross section, and when the tread portion is formed of a single rubber composition, the thickness of the tread portion is This refers to the thickness of the composition, and in the case where it is formed of a laminated structure of a plurality of rubber compositions described below, it refers to the total thickness of these layers.

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

Note that the tread portion refers to a member in the region that forms the ground contact surface of the tire, and refers to a portion outside in the tire radial direction from members including fiber materials such as the carcass, belt layer, and belt reinforcing layer. The thickness of the tread portion described above can be measured by aligning the bead portion with the regular rim width in a cross section cut out of the tire in the radial direction.

In the above, "regular rim" is a rim specified for each tire by the standard in the standard system including the standard on which the tire is based, for example, in the case of JATMA (Japan Automobile Tire Association), "JATMA YEAR BOOK" For standard rims in the applicable sizes listed in ETRTO (The European Tire and Rim Technical Organization), "Measuring Rim" listed in "STANDARDS MANUAL", TRA (The Tire and Rim Association, Inc.) If there is, it refers to "Design Rim" described in "YEAR BOOK", and refers to JATMA, ETRTO, and TRA in that order, and if there is an applicable size at the time of reference, that standard is followed. In the case of a tire that is not specified by the standard, the rim that can be assembled into a rim and that can maintain internal pressure, that is, the rim that does not cause air leakage between the rim and the tire, has the smallest diameter, and then the rim. Refers to the narrowest width.

As described above, in the tire according to the present invention, the reinforcing effect of silica in the rubber composition, the moderating effect on deformation due to an appropriate amount of styrene, the suppressing effect on slipping on the tread surface due to an appropriate 30°C tan δ, and It is thought that wear resistance during high-speed running can be sufficiently improved due to the effect of suppressing heat accumulation through appropriate thickness control.

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

1. Relationship between the 30°C tan δ of the cap rubber layer and the thickness of the tread portion The present inventor has found that in order to improve wear resistance during high-speed running, there is a preferable relationship between the 30° C. tan δ and the thickness G (mm) of the tread portion. We considered that there is a possibility. As a result, if 30°C tan δ/G > 0.03, the effect of suppressing slippage on the tread surface due to the appropriate 30°C tan δ described above and the effect of suppressing heat accumulation due to appropriate thickness control will work together more fully. We believe that this will further improve wear resistance during high-speed driving. The 30° C. tan δ/G is more preferably 0.034 or more, even more preferably 0.035 or more, and even more preferably 0.036 or more. On the other hand, the upper limit is preferably 0.045 or less, more preferably 0.041 or less.

2. Glass transition temperature (Tg) of cap rubber layer
In the present invention, the glass transition temperature (Tg) of the cap rubber layer is preferably -10.8°C or lower, more preferably -12.6°C or lower, even more preferably -15°C or lower, The temperature is more preferably -19.1°C or lower, even more preferably -40°C or lower, even more preferably -40.8°C or lower, and even more preferably -41°C or lower. When the cap rubber layer is formed using a rubber composition with a high glass transition temperature (Tg), the tread portion becomes hard near the running temperature, and there is a risk that wear resistance may be reduced due to friction with the road surface. It is believed that by setting the Tg to -15°C or less, it is possible to suppress hardening of the tread portion and further improve wear resistance during high-speed running. Note that the lower limit of Tg is not particularly limited, but it is preferably -60°C or higher, and more preferably -50°C or higher.

The glass transition temperature (Tg) of the rubber composition described above was determined using a viscoelasticity measuring device such as the Iplexer series manufactured by GABO, and was measured at a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a temperature increase rate. It can be determined based on the temperature distribution curve of tan δ measured under the condition of 2 °C/min, and in the case of the present invention, in the range of -60 °C or more and 40 °C or less of the measured temperature distribution curve The temperature corresponding to the largest tan δ value is defined as the glass transition point (Tg). Note that if there are two or more points with the highest tan δ value within the range of −60° C. or higher and 40° C. or lower, the point with the lowest temperature is taken as Tg. For example, in the present invention, if the maximum value of tan δ is within the range of −60° C. or more and 40° C. or less, the temperature at which the maximum value occurs is Tg according to the above definition. Furthermore, if a temperature distribution curve is obtained in which the maximum value of tan δ is -60°C, for example, tanδ gradually decreases as the temperature rises within the range of -60°C or higher and 40°C or lower, based on the above definition. , the glass transition temperature (Tg) is -60°C.

The method for adjusting the glass transition temperature (Tg) described above is not particularly limited, but examples include increasing the proportion of a polymer component with a high Tg in the rubber component, increasing the amount of styrene in the rubber component, and increasing the content of the resin component. Conversely, it can be lowered by reducing the ratio of polymer components with high Tg in the rubber component, reducing the amount of styrene in the rubber component, or reducing the content of resin components. be able to.

3. Complex modulus of elasticity of cap rubber layer (E ^* )
In the present invention, the complex modulus of elasticity (30°C E*) of the cap rubber layer measured at a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, a dynamic strain rate of 1%, and a deformation mode in tension (30°C E ^* ) is 6.1 MPa or less. It is preferably 6.0 MPa or less, more preferably 5.9 MPa or less, even more preferably 5.6 MPa or less, even more preferably 5.5 MPa or less, and even more preferably 5.4 MPa or less. It is even more preferable. The complex modulus of elasticity E ^* is a parameter that indicates the rigidity of the rubber layer, and when E ^* at 30°C is set to 6.0 MPa or less, the rigidity is suppressed from becoming too high and the slippage with the road surface is reduced during high-speed driving. It is thought that this can suppress the wear resistance and further improve the wear resistance. Although the lower limit is not particularly limited, it is preferably 4.00 MPa or more, more preferably 5.00 MPa or more, and even more preferably 5.30 MPa or more.

The above 30°C E ^* (MPa) preferably satisfies (30°C E ^* /G)≧0.50 between the above-mentioned thickness G (mm) of the tread portion, and 0. It is more preferably .54 or more, even more preferably 0.55 or more, even more preferably 0.56 or more, even more preferably 0.59 or more, and even more preferably 0.61 or more. On the other hand, the upper limit is preferably 1.00 or less, more preferably 0.98 or less, even more preferably 0.77 or less, even more preferably 0.75 or less, and 0.65 or less. It is even more preferable. It is thought that the thicker the tread portion, the easier it is for heat to accumulate during rolling, the lower the strength of the rubber, the greater the amount of deformation during rolling, and the more likely it is to wear out. Therefore, in order to ensure sufficient rigidity for the thickness of the tread rubber, by appropriately controlling the relationship between 30℃E ^* and the thickness of the tread, the deformation of the tread during high-speed running can be optimized. It is believed that wear resistance can be further improved.

The above-mentioned complex modulus of elasticity can be measured, for example, using a viscoelasticity measuring device such as "Iprexor (registered trademark)" manufactured by GABO.

In addition, the above-mentioned method for adjusting 30℃E ^* is not particularly limited, but examples include increasing the amount of styrene in the polymer, increasing the amount of fillers such as silica and carbon black, decreasing the content of the plasticizer component, and increasing the amount of the resin component. The content can be increased by increasing the content, and the content can be lowered by reducing the amount of styrene in the polymer, reducing the amount of fillers such as silica and carbon black, increasing the content of plasticizer components, and reducing the content of resin components. can do.

4. Loss tangent at 0°C (0°C tan δ) and complex modulus of elasticity (0°C E ^* )
In the above, 30°C tan δ and 30°C E ^* are specified assuming that the tire is running, but the tire is in a cold state at the start of running, and considering running at low temperatures, the cap rubber layer is formed. The loss tangent (0°C tan δ) of the rubber composition measured in tensile deformation mode under the conditions of temperature 0°C, frequency 10Hz, initial strain 5%, and dynamic strain rate 1% must be 0.30 or more. is preferably 0.34 or more, more preferably 0.60 or more, even more preferably 0.70 or more, even more preferably 0.76 or more, and 0.77 or more. More preferably, it is 0.80 or more, even more preferably 0.83 or more, and even more preferably 0.84 or more. Although the upper limit is not particularly limited, it is preferably 1.00 or less, more preferably 0.95 or less, and even more preferably 0.90 or less.

Similarly, the complex modulus of elasticity (0°C E ^* ) of the cap rubber layer measured by temperature 0°C, frequency 10Hz, initial strain 5%, dynamic strain rate 1%, deformation mode: tension is 25.0 MPa or less. It is preferably 24.0 MPa or less, more preferably 23.8 MPa or less, even more preferably 23.5 MPa or less, and even more preferably 23.2 MPa or less. The lower limit is not particularly limited, but is preferably 9.4 MPa or higher, more preferably 9.5 MPa or higher, even more preferably 19.2 MPa or higher, even more preferably 20.0 MPa or higher, and 23.0 MPa or higher. It is more preferable that it is above.

There are no particular limitations on the method for adjusting the 0°C tan δ and 0°C E ^* described above, but for example, if it is 0°C tan δ, it can be increased by increasing the amount of styrene in the rubber component, increasing the content of the resin component, etc. It can be lowered by reducing the amount of styrene in the rubber component or by reducing the content of the resin component. In addition, if it is 0℃E ^* , you can increase the amount of styrene in the rubber component, increase the amount of fillers such as silica and carbon black, reduce the content of plasticizer components, and increase the content of resin components. It can be lowered by reducing the amount of styrene in the rubber component, reducing the amount of fillers such as silica and carbon black, increasing the content of plasticizer components, and reducing the content of resin components. Can be done.

5. Multi-layering of the tread portion In the present invention, the tread portion is preferably formed of only one layer of the cap rubber layer, but the tread portion is multi-layered by providing a base rubber layer inside the cap rubber layer. In this case, the thickness of the cap rubber layer over the entire tread portion is preferably 10% or more. This makes it easier to absorb the energy generated between the tread surface and the road surface at the interface between the cap rubber layer and the base rubber layer, further improving wear resistance during high-speed running. Conceivable. Note that the thickness of the cap rubber layer in the entire tread portion is more preferably 70% or more.

As described above, the thickness of the cap rubber layer and the thickness of the base rubber layer can be calculated by summing the thickness of the cap rubber layer and the thickness of the base rubber layer in the thickness of the tread portion.

In this case, it is preferable that the 30°C tan δ of the base rubber layer be smaller than the 30°C tan δ of the cap rubber layer. It is thought that this suppresses heat generation inside the tread portion, makes it easier to suppress softening of the tread portion due to heat accumulation, and further improves wear resistance during high-speed running.

In the case of a multi-layered tread part, the temperature of the base rubber layer is 30℃, the frequency is 10Hz, the initial strain is 5%, the dynamic strain rate is 1%, and the deformation mode is the complex modulus of elasticity measured in tension (30℃E ^* ) is preferably smaller than 30°C E ^* of the cap rubber layer, which is measured in the same manner.

6. Silica particle size

In the present invention, the particle size (average primary particle size) of silica is preferably 17 nm or less, considering ease of friction with the polymer.

The average primary particle diameter is calculated by directly observing silica taken out from a rubber composition cut from a tire using an electron microscope (TEM), etc., and calculating the equal cross-sectional area diameter from the area of each silica particle obtained. It can be calculated by finding the average value.

7. Containment of Resin Component in Cap Rubber Layer In the present invention, it is preferable that the rubber composition forming the cap rubber layer contains a resin component.

It is thought that by containing the resin component in the rubber composition, the adhesiveness of the resin component improves the ground contact with the road surface, and it is possible to sufficiently improve the wear resistance during high-speed running.

Preferred resin components include rosin resins, styrene resins, coumaron resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, which will be described later. Among these, α-methylstyrene, etc. More preferred are styrenic resins. The content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more. More preferably, the amount is 60 parts by mass or more, even more preferably 65 parts by mass or more, and even more preferably 70 parts by mass or more.

8. Acetone extract (AE) of cap rubber layer
In the present invention, the acetone extractable content (AE) of the cap rubber layer is preferably 28% by mass or more, more preferably 29.3% by mass or more, even more preferably 30% by mass or more, and 30% by mass or more. It is more preferably 7% by mass or more, even more preferably 31.5% by mass or more, and even more preferably 31.9% by mass or more. On the other hand, the upper limit is not particularly limited, but is preferably 35% by mass or less, more preferably 34% by mass or less, even more preferably 33.4% by mass or less, and even more preferably 33% by mass or less. preferable.

Acetone extractables (AE) can be considered as an indicator of the amount of softener, etc. in a rubber composition, and can also be considered as an indicator of the ease of movement of the molecular chains of the rubber component. For this reason, as described above in the cap rubber layer, when the amount of AE is increased to a certain extent, the area in which the tire contacts the road surface is sufficiently secured to improve ground contact and sufficiently improve wear resistance during high-speed driving. be able to.

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

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

Furthermore, the acetone extract described above can be changed as appropriate by changing the blending ratio of the plasticizer in the rubber composition.

9. Land Ratio In the tire according to the present invention, the land ratio in the tread portion of the tire is incorporated into a regular rim and has a regular internal pressure of 40% or more, and the styrene-butadiene rubber has a styrene content of 25% by mass or less in 100 parts by mass of the rubber component. The ratio of the content (parts by mass) of (SBR) to the land ratio (%) in the tread portion (SBR amount (parts by mass) with styrene content of 25% by mass or less/land ratio (%)) is 1.23 or less It is preferably 1.2 or less, more preferably 1.0 or less, and even more preferably 0.92 or less. On the other hand, the lower limit is not particularly limited, but is preferably 0.6 or more, more preferably 0.7 or more.

"Land ratio" is the ratio of the actual ground contact surface to the virtual ground contact surface that fills all the grooves arranged on the surface of the tread. If the land ratio is large, the area in contact with the road surface becomes large. It is possible to easily reduce the force generated per unit area when doing so. By setting the ratio of the SBR amount of 25% by mass or less of styrene to the land ratio to a certain level or less, it is possible to suppress excessive concentration of force on the styrene domains generated in the rubber composition, which become the starting point of wear. It is thought that this makes it easier to improve wear resistance during high-speed running.

Note that the lower limit of the ratio of the above-mentioned SBR content with a styrene content of 25% by mass or less and the land ratio is not particularly limited, but is preferably 0.2 or more, and more preferably 0.5 or more.

The land ratio described above can be determined from the ground contact shape under conditions of a regular rim, a regular internal pressure, and a regular load.

Specifically, the tire was assembled on a regular rim, the regular internal pressure was applied, and the tire was left to stand at 25°C for 24 hours.The tire tread surface was then painted with black ink, and the regular load was applied and the tire was pressed against cardboard (the camber angle was 0°). ), the ground contact shape can be obtained by transferring it to paper, so the tire is rotated by 72° in the circumferential direction and transferred at five locations. That is, the ground contact shape is obtained five times. At this time, for the five ground contact shapes, the interrupted portions of the contours of the ground contact shapes are smoothly connected by grooves, and the resulting shape is defined as a virtual ground contact surface.

Then, the land ratio can be calculated from (average area of the five ground contact shapes (black parts) transferred to the cardboard/average value of the area of the virtual ground contact surface obtained from the five ground contact shapes) x 100 (%). .

In addition, "regular internal pressure" is the air pressure specified for each tire by the above standard, and for JATMA it is the maximum air pressure, for ETRTO it is "INFLATION PRESSURE", and for TRA it is the air pressure shown in the table "TIRE LOAD LIMITS AT VARIOUS COLD". JATMA, ETRTO, and TRA are referred to in that order and the standards are followed, as in the case of the "regular rim." In the case of a tire that is not specified in the standard, it refers to the normal internal pressure (250 KPa or more) of another tire size (specified in the standard) in which the regular rim is described as a standard rim. In addition, when multiple normal internal pressures of 250 KPa or more are listed, it refers to the minimum value among them.

Here, the "regular load" is the load specified for each tire by each standard in the standard system, including the standard on which the above-mentioned tires are based, and is the maximum mass that is allowed to be loaded on the tire. For JATMA, it refers to the maximum load capacity, for ETRTO, it refers to "LOAD CAPACITY", for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and the above-mentioned "regular rim" As in the case of "regular internal pressure", refer to JATMA, ETRTO, and TRA in that order and follow their standards. In the case of tires that are not specified by the standard, the normal load _WL is determined by the following calculation.
V={(Dt/2) ² - (Dt/2-Ht) ² }×π×Wt
W _L =0.000011×V+175
W _L : Regular load (kg)
V: Virtual volume of tire (mm ³ )
Dt: Tire outer diameter Dt (mm)
Ht: Tire cross-sectional height (mm)
Wt: Tire cross-sectional width (mm)

The amount of styrene in 100 parts by mass of the rubber component is, for example, SBR1 having an amount of S1% by mass of styrene (X1 parts by mass) and SBR2 having an amount of S2% by mass of styrene (X2 parts by mass). If it is contained, it can be calculated from the formula {(S1×X1)+(S2×X2)}/100.

10. Oblateness In the tire according to the present invention, the oblateness is 80% or less, and the ratio of the content of silica (parts by mass) to the oblateness (%) with respect to 100 parts by mass of the rubber component (silica content (parts by mass) )/oblateness (%)) is preferably 0.5 or more, more preferably 0.6 or more, even more preferably 0.7 or more, even more preferably 0.8 or more, It is more preferably 0.9 or more, even more preferably 1.0 or more, even more preferably 1.2 or more, even more preferably 1.4 or more, even more preferably 1.64 or more, It is more preferably 1.7 or more, and even more preferably 1.73 or more. On the other hand, the upper limit is not particularly limited, but is preferably 3.5 or less, more preferably 3.3 or less, even more preferably 3.1 or less, even more preferably 2.9 or less, and 2. More preferably, it is .5 or less.

The aspect ratio is the cross-sectional height of the tire with respect to the cross-sectional width of the tire, and it is thought that the smaller this ratio is, the more easily the force from the rim is transmitted to the tread portion during rolling, and the easier it is for wear to progress in the tread portion. Therefore, by including a sufficient amount of silica in relation to the aspect ratio, it is possible to ensure the reinforcing properties of the silica network, making it easier to improve wear resistance during high-speed running. Conceivable.

In addition, the above-mentioned aspect ratio (%) is based on the cross-sectional height Ht (mm) of the tire, the cross-sectional width Wt (mm), the tire outer diameter Dt (mm), and the rim diameter R (mm) when the internal pressure is 250 kPa. It can be calculated using the following formula.
Oblateness (%) = (Ht/Wt) x 100 (%)
Ht=(Dt-R)/2

Further, the upper limit of the ratio of silica content to flatness is not particularly limited, but is preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less.

[3] Embodiments Hereinafter, the present invention will be specifically described based on embodiments.

1. Rubber Composition In the tire according to the present invention, the rubber composition forming the cap rubber layer includes various compounding materials such as the rubber component, filler, softener, vulcanizing agent, and vulcanization accelerator described below. It can be obtained by adjusting the type and amount as appropriate.

(1) Compounded materials (a) Rubber component The rubber component is not particularly limited, and may include isoprene rubber, diene rubber such as butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), butyl rubber, etc. Rubbers (polymers) commonly used in tire manufacturing can be used, such as thermoplastic elastomers such as butyl rubber, styrene-butadiene-styrene block copolymer (SBS), and styrene-butadiene block copolymer (SB). Note that, as these rubber components, extensible rubber that has been expanded in advance with oil, resin, liquid rubber component, etc., which will be described later, may be used.

In the present invention, among these, the rubber component contains SBR and other rubber components. Other rubber components are not particularly limited, but combinations of BR and BR and isoprene rubber are preferred.

(b) SBR
The weight average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. In the present invention, as described above, the amount of styrene in the SBR component is 25% by mass or less. The vinyl content (1,2-bonded butadiene content) of SBR is, for example, more than 5% by mass and less than 70% by mass. Note that the vinyl content of SBR refers to the 1,2-bonded butadiene content relative to the entire butadiene moiety in the SBR component. Further, structural identification of SBR (measurement of styrene content and vinyl content) can be performed using, for example, a JNM-ECA series device manufactured by JEOL Ltd.

In the present invention, the content of SBR in 100 parts by mass of the rubber component is, as described above, 60 parts by mass or more and 80 parts by mass or less, and more preferably 65 parts by mass or more and 75 parts by mass or less. In addition, in the case of extended SBR, the amount of pure rubber excluding the amount of extended components is the content of SBR.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR), etc. can be used. SBR may be either non-denatured SBR or modified SBR. Further, hydrogenated SBR obtained by hydrogenating the butadiene part in SBR may be used, and hydrogenated SBR may be obtained by subsequently hydrogenating the BR part in SBR, and styrene, ethylene, and butadiene can be hydrogenated. A similar structure may be obtained by copolymerization.

The modified SBR may be any SBR that has a functional group that interacts with a filler such as silica; for example, an end-modified SBR in which at least one end of the SBR is modified with a compound (modifier) having the above-mentioned functional group. SBR (terminally modified SBR having the above functional group at the end), main chain modified SBR having the above functional group in the main chain, main chain terminal modified SBR having the above functional group in the main chain and the end (e.g. The main chain end-modified SBR which has the above-mentioned functional group and has at least one end modified with the above-mentioned modifier, or is modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and has a hydroxyl group. and terminal-modified SBR into which an epoxy group has been introduced.

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

Furthermore, as the modified SBR, for example, SBR modified with a compound (modifier) represented by the following formula can be used.

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

The modified SBR modified with the compound (modifier) represented by the above formula includes a solution polymerized styrene butadiene rubber (S-SBR) whose polymerized end (active end) is modified with the compound represented by the above formula. SBR (modified SBR described in JP-A No. 2010-111753, etc.) can be used.

An alkoxy group is suitable as R ¹ , R ² and R ³ (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). As R ⁴ and R ⁵ , an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms) is suitable. n is preferably 1 to 5, more preferably 2 to 4, and still more preferably 3. Furthermore, when R ⁴ and R ⁵ combine to form a ring structure together with a nitrogen atom, it is preferably a 4- to 8-membered ring. Note that the alkoxy group also includes a cycloalkoxy group (cyclohexyloxy group, etc.) and an aryloxy group (phenoxy group, benzyloxy group, etc.).

Specific examples of the above modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltriethoxysilane, Examples include methoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These may be used alone or in combination of two or more.

Furthermore, as the modified SBR, modified SBR modified with the following compound (modifier) can also be used. Examples of modifiers include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; two or more of diglycidylated bisphenol A, etc. Polyglycidyl ethers of aromatic compounds having phenol groups; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; 4,4'-diglycidyl-diphenyl Epoxy group-containing tertiary amines such as methylamine, 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl orthotoluidine, tetraglycidyl metaxylene diamine , diglycidylamino compounds such as tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; bis-(1-methylpropyl)carbamic acid chloride; Amino group-containing acid chlorides such as 4-morpholine carbonyl chloride, 1-pyrrolidine carbonyl chloride, N,N-dimethylcarbamate acid chloride, N,N-diethylcarbamate acid chloride; 1,3-bis-(glycidyloxypropyl)-tetra Epoxy group-containing silane compounds such as methyldisiloxane, (3-glycidyloxypropyl)-pentamethyldisiloxane; (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, ( Sulfide groups such as (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide, etc. Containing silane compounds; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3- Alkoxysilanes such as aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltriethoxysilane; 4-N,N-dimethylaminobenzophenone, 4- N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'- (thio)benzophenone compounds having an amino group and/or substituted amino group such as bis(diphenylamino)benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone; 4-N,N-dimethylamino Benzaldehyde compounds having an amino group and/or substituted amino group such as benzaldehyde, 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde; N-methyl-2-pyrrolidone, N-vinyl-2- N-substituted pyrrolidone such as pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, N-methyl-2-piperidone, N-vinyl-2 - N-substituted piperidones such as piperidone, N-phenyl-2-piperidone; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurirolactam, N-vinyl-ω-lau N-substituted lactams such as lilolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-triones, N,N-diethyl Acetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl- 2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino) -4-heptanone and the like can be mentioned. Note that modification with the above compound (modifier) can be carried out by a known method.

As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used. Note that SBR may be used alone or in combination of two or more types.

(b) BR
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 20 parts by mass or more and 40 parts by mass or less, more preferably 25 parts by mass or more and 35 parts by mass or less.

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

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

As the BR, for example, products manufactured by Ube Industries, Ltd., ENEOS Materials, Asahi Kasei, Nippon Zeon, etc. can be used.

(iii) Isoprene-based rubber In the present invention, the rubber composition may contain isoprene-based rubber, if necessary. In this case, the content of the isoprene rubber in 100 parts by mass of the rubber component is preferably 20 parts by mass or more and 40 parts by mass or less, more preferably 25 parts by mass or more and 35 parts by mass or less.

Examples of isoprene rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like.

As the NR, those commonly used in the tire industry, such as SIR20, RSS#3, TSR20, and SVR-L, can be used. The IR is not particularly limited, and for example, one commonly used in the tire industry, such as IR2200, can be used. Modified NR includes deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), etc.; modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

(d) Other rubber components In addition, other rubber components may include rubbers (polymers) commonly used in tire manufacturing such as nitrile rubber (NBR).

(b) Compounded materials other than rubber components (a) Filler In the present invention, the rubber composition contains silica as a filler as described above, but it may also contain other fillers. good. Specific examples of fillers other than silica include carbon black, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica.

(i-1) Silica In the present invention, the BET specific surface area of the silica contained in the rubber composition is preferably more than 140 m ² /g, more preferably more than 160 m ² /g, from the viewpoint of obtaining good durability performance. On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed running, it is preferably less than 250 m ² /g, more preferably less than 220 m ² /g. Note that the BET specific surface area described above is the value of N ₂ SA measured by the BET method according to ASTM D3037-93.

In the present invention, as described above, it is preferable to use silica with a particle size of 17 nm or less, and by using silica with a small particle size, the frequency of contact with the polymer (styrene domain) can be increased. Since the mobility of the polymer can be increased and energy loss can be caused, wear resistance during high-speed running can be improved. Note that the lower limit is not particularly limited, but from the viewpoint of dispersibility during mixing, it is preferably 10 nm or more.

As mentioned above, the content of silica is 100 parts by mass or less per 100 parts by mass of the rubber component, which does not exceed the amount of the rubber component, but it is preferably 95 parts by mass or less, and 90 parts by mass or less. It is more preferable. The lower limit is not particularly limited, but in consideration of the reinforcing properties of silica, it is preferably 70 parts by mass or more, more preferably 80 parts by mass or more.

Examples of the silica include dry process silica (anhydrous silica), wet process silica (hydrated silica), and the like. Among these, wet process silica is preferred because it has a large number of silanol groups. Furthermore, silica made from hydrous glass or the like, silica made from biomass materials such as rice husks, etc. may be used.

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

(i-2) Silane coupling agent The rubber composition forming the cap rubber layer of the present invention preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide types such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto types such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, and vinyl triethoxysilane. Vinyl types such as methoxysilane, amino types such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, and glycidoxy types such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane. , 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, and other nitro types, and 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, and other chloro types. These may be used alone or in combination of two or more.

As the silane coupling agent, for example, products from Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Kasei Kogyo Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used.

The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass based on 100 parts by mass of silica.

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

The content of carbon black per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more. On the other hand, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less.

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

The CTAB specific surface area (Cetyl Tri-methyl Ammonium Bromide) of carbon black is preferably 130 m ² /g or more, more preferably 160 m ² /g or more, and even more preferably 170 m ² /g or more. On the other hand, it is preferably 250 m ² /g or less, more preferably 200 m ² /g or less. Note that the CTAB specific surface area is a value measured in accordance with ASTM D3765-92.

Specific carbon blacks are not particularly limited, and include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. Commercially available products include, for example, products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Nippon Kaya Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can be used. These may be used alone or in combination of two or more.

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

(B) Plasticizer component The rubber composition may contain oil (including extender oil), liquid rubber, and resin as plasticizer components, which soften the rubber. Note that the plasticizer component is a component that can be extracted from the vulcanized rubber with acetone. The total content of the plasticizer component is preferably 85 parts by mass or more, more preferably 100 parts by mass or more, based on 100 parts by mass of the rubber component. On the other hand, it is preferably 120 parts by mass or less, more preferably 110 parts by mass or less. Note that when extensible rubber is used as the rubber component, the amount of the extensible component is included in the amount of these plasticizer components.

(i) Oil Oils include, for example, mineral oils (generally referred to as process oils), vegetable oils, or mixtures thereof. As the mineral oil (process oil), for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Furthermore, from the viewpoint of life cycle assessment, waste oil that has been used as a lubricating oil for rubber mixing mixers, automobile engines, etc., waste cooking oil, etc. may be used as appropriate.

Furthermore, for environmental reasons, it is also possible to use process oil with a low content of polycyclic aromatic compound (PCA) compounds. The low PCA content process oils include mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), heavy naphthenic oils, and the like.

Specific process oils (mineral oils) include, for example, Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., and Showa Shell Sekiyu Co., Ltd. ), Fuji Kosan Co., Ltd., etc. can be used.

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

A farnesene-based polymer is a polymer obtained by polymerizing farnesene, and has a constituent unit based on farnesene. Farnesene includes 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).

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

Examples of liquid diene-based polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), etc. It will be done.

The weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) in terms of polystyrene is, for example, more than 1.0×10 ³ and less than 2.0×10 ⁵ . In this specification, the Mw of the liquid diene polymer is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

The content of liquid rubber (total content of liquid farnesene polymer, liquid diene polymer, etc.) is, for example, more than 1 part by mass and less than 100 parts by mass based on 100 parts by mass of the rubber component.

As the liquid rubber, for example, products from Kuraray Co., Ltd., Clay Valley Co., Ltd., etc. can be used.

(iii) Resin component The resin component also functions as a tackifying component and may be solid or liquid at room temperature. Specific resin components include rosin resin, styrene resin, etc. , coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, acrylic resin, etc., and two or more types may be used in combination. The content of the resin component is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more, based on 100 parts by mass of the rubber component. Note that these resin components may be provided with a modifying group capable of reacting with silica or the like, if necessary.

Rosin-based resin is a resin whose main component is rosin acid obtained by processing pine resin. This rosin-based resin (rosin) can be classified according to the presence or absence of modification, and can be classified into unmodified rosin (unmodified rosin) and modified rosin (rosin derivative). Examples of unmodified rosin include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. The modified rosin is a modified version of unmodified rosin, and includes rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, amide compounds of rosin, and amine salts of rosin.

Styrenic resins are polymers using styrene monomers as constituent monomers, and include polymers polymerized with styrene monomers as the main component (50% by mass or more). Specifically, styrenic monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, Homopolymers of o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), copolymers of two or more styrene monomers, and styrene monomers. and copolymers of other monomers that can be copolymerized therewith.

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

Among coumaron-based resins, coumaron indene resin is preferred. Coumarone indene resin is a resin containing coumaron and indene as monomer components constituting the skeleton (main chain) of the resin. In addition to coumaron and indene, monomer components contained in the skeleton include styrene, α-methylstyrene, methylindene, and vinyltoluene.

The content of the coumaron indene resin is, for example, more than 1.0 parts by mass and less than 50.0 parts by mass based on 100 parts by mass of the rubber component.

The hydroxyl value (OH value) of the coumaron indene resin is, for example, more than 15 mgKOH/g and less than 150 mgKOH/g. The OH number is the amount of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl group when acetylating 1 g of resin, expressed in milligrams, and is determined by the potentiometric titration method (JIS K 0070: (1992).

The softening point of the coumaron indene resin is, for example, higher than 30°C and lower than 160°C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring device.

Examples of terpene resins include polyterpenes, terpene phenols, aromatic modified terpene resins, and the like. Polyterpenes are resins obtained by polymerizing terpene compounds and hydrogenated products thereof. Terpene compounds are hydrocarbons and their oxygen-containing derivatives represented by the composition (C ₅ H ₈ ) _n , including monoterpenes (C ₁₀ H ₁₆ ), sesquiterpenes (C ₁₅ H ₂₄ ), and diterpenes (C ₂₀ H _{32 )} . ) and other compounds whose basic skeletons are terpenes, such as α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, and terpinolene. , 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, and the like.

Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene/limonene resin, which are made from the above-mentioned terpene compounds, as well as hydrogen obtained by hydrogenating the terpene resin. Also included are added terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds and phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Examples include resin. Note that examples of the phenolic compound include phenol, bisphenol A, cresol, xylenol, and the like. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the resins. The aromatic compound is not particularly limited as long as it has an aromatic ring, but examples include phenol compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, Naphthol compounds such as unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumaron, indene, and the like.

"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 the C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

"C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified resin. Examples of the C9 fraction include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples, for example, coumaron indene resin, coumaron resin, indene resin, and aromatic vinyl resin are preferably used. As the aromatic vinyl resin, α-methylstyrene, a styrene homopolymer, or a copolymer of α-methylstyrene and styrene is preferred because it is economical, easy to process, and has excellent heat generation properties. , a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from Clayton Co., Eastman Chemical Co., etc. can be used.

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

Although the acrylic resin is not particularly limited, for example, a solvent-free acrylic resin can be used.

Solvent-free acrylic resins are produced using a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (U.S. Patent No. 4,414,370), which uses as little as possible the use of auxiliary materials such as polymerization initiators, chain transfer agents, and organic solvents. specification, JP-A-59-6207, JP-A-5-58005, JP-A-1-313522, US Patent No. 5,010,166, Toagosei Research Annual Report TREND 2000 No. 3 p42 Examples include (meth)acrylic resins (polymers) synthesized by the method described in -45, etc. Note that in the present invention, (meth)acrylic means methacryl and acrylic.

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

In addition, as monomer components constituting the above acrylic resin, in addition to (meth)acrylic acid and (meth)acrylic acid derivatives, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc. aromatic vinyl may be used.

The above-mentioned acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component. Further, the acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

Examples of the resin component include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Co., Ltd., Ninuri Chemical Co., Ltd. ) Products from Nippon Shokubai, ENEOS Co., Ltd., Arakawa Chemical Industry Co., Ltd., Taoka Chemical Industry Co., Ltd., etc. can be used.

(c) Stearic acid In the present invention, the rubber composition preferably contains stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass based on 100 parts by mass of the rubber component. As the stearic acid, conventionally known ones can be used, and for example, products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

(d) Anti-aging agent In the present invention, the rubber composition preferably contains an anti-aging agent. The content of the anti-aging agent is, for example, more than 0.5 parts by mass and less than 10 parts by mass, and more preferably 1 part by mass or more, based on 100 parts by mass of the rubber component.

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

As the anti-aging agent, for example, products from Seiko Kagaku Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis Co., Ltd., etc. can be used.

(e) Wax In the present invention, the rubber composition preferably contains wax. The content of wax is, for example, 0.5 to 20 parts by weight, preferably 1.0 to 15 parts by weight, and more preferably 1.5 to 10 parts by weight, based on 100 parts by weight of the rubber component.

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

As the wax, for example, products manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

(f) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass based on 100 parts by mass of the rubber component. As zinc oxide, conventionally known ones can be used, such as products from Mitsui Kinzoku Kogyo Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

(g) Crosslinking agent and vulcanization accelerator The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass based on 100 parts by mass of the rubber component.

Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. commonly used in the rubber industry. These may be used alone or in combination of two or more.

As the sulfur, for example, products manufactured by Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis, Nippon Karidome Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used. .

Examples of cross-linking agents other than sulfur include sulfur atoms such as Tackirol V200 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.

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

Examples of vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; tetramethylthiuram disulfide (TMTD); ), thiuram-based vulcanization accelerators such as tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- Sulfenamide vulcanization accelerators such as 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine; Examples include guanidine-based vulcanization accelerators such as di-ortho-tolyl guanidine and ortho-tolyl biguanidine. These may be used alone or in combination of two or more.

(H) Others In addition to the above-mentioned components, the rubber composition may contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, and reversion (reversion). ) An inhibitor or the like may be further added as necessary. The content of these additives is, for example, more than 0.1 part by mass and less than 200 parts by mass based on 100 parts by mass of the rubber component.

(2) Preparation of rubber composition The rubber composition forming the cap rubber layer is prepared by appropriately adjusting the above-mentioned various compounding materials and kneading the rubber component and filler such as carbon black using a general method. It is produced by a manufacturing method including a base kneading step and a finishing kneading step of kneading the kneaded material obtained in the base kneading step and a crosslinking agent.

Kneading can be performed using a known (closed) kneader such as a Banbury mixer, kneader, or open roll.

The kneading temperature in the base kneading step is, for example, more than 50°C and less than 200°C, and the kneading time is, for example, more than 30 seconds and less than 30 minutes. In the base kneading process, in addition to the above ingredients, compounding agents conventionally used in the rubber industry, such as softeners such as oil, zinc oxide, anti-aging agents, wax, and vulcanization accelerators, are added as necessary. , may be kneaded.

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

2. Manufacture of Tire The tire according to the present invention is produced by molding the rubber composition obtained above as a cap rubber layer into a tread rubber having a predetermined shape, and then molding the rubber composition along with other tire members on a tire molding machine using a normal method. By molding it, it is possible to produce an unvulcanized tire.

In addition, when making the tread part a multilayer structure with the base rubber layer, basically, by using the above-mentioned rubber components and compounding materials, changing the compounding amounts as appropriate, and kneading in the same manner. , a rubber composition forming a base rubber layer can be obtained. Then, it is extruded together with the cap rubber layer and molded into a tread rubber of a predetermined shape, and then molded together with other tire components using a normal method on a tire molding machine to produce an unvulcanized tire. can.

Specifically, on the forming drum, there is an inner liner as a member to ensure airtightness of the tire, a carcass as a member to withstand the load, impact, and filling air pressure that the tire receives, and a carcass that is tightly tightened to increase the rigidity of the tread. A belt member that serves as a lifting member is wound around the carcass, and both ends of the carcass are fixed to both side edges, and a bead part that is a member that fixes the tire to the rim is placed to form a toroid shape. An unvulcanized tire is manufactured by laminating a tread to the center portion of the tire and a side wall to the outside in the radial direction to form a side portion.

Thereafter, a tire is obtained by heating and pressurizing the produced unvulcanized tire in a vulcanizer. The vulcanization process can be carried out by applying known vulcanization means. The vulcanization temperature is, for example, more than 120°C and less than 200°C, and the vulcanization time is, for example, more than 5 minutes and less than 15 minutes.

As mentioned above, the resulting tire has the reinforcing effect of silica in the rubber composition, the moderating effect on deformation due to an appropriate amount of styrene, the suppressing effect of slipping on the tread surface due to an appropriate 30°C tan δ, and the appropriate amount of styrene. Due to the effect of suppressing heat accumulation through thickness control, wear resistance during high-speed running can be sufficiently improved.

The tire according to the present invention is not particularly limited in category, and can be used as tires for passenger cars, tires for heavy-duty vehicles such as trucks and buses, tires for two-wheeled vehicles, run-flat tires, non-pneumatic tires, etc. However, it is preferable to use tires for passenger cars. Moreover, it is preferable to use a pneumatic tire.

In the following, examples (examples) that are considered preferable for implementation will be shown, but the scope of the present invention is not limited to these examples. In the examples, a pneumatic tire (tire size 205/55R16, flatness: 55%, land ratio: 65%) was manufactured from a composition obtained by changing the formulation according to each table using the various chemicals shown below. ) and calculated based on the following evaluation method are shown in Tables 2 and 3.

1. Rubber composition for forming the cap rubber layer (1) Compounding materials (a) Rubber component (a) SBR-1: Modified S-SBR obtained by the method shown in the next paragraph
(Styrene content: 25% by mass, vinyl content: 25% by mass)
(b) SBR-2: HPR850 (modified S-SBR) manufactured by ENEOS Materials Co., Ltd.
(Styrene content: 27.5% by mass, vinyl content: 59.0% by mass)
(c) SBR-3: HPR840 (S-SBR) manufactured by ENEOS Materials Co., Ltd.
(Styrene content: 10% by mass, vinyl content: 42% by mass)
(d) BR: Ubepol BR150B (Hisis BR) manufactured by Ube Industries, Ltd.
(Cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

(Manufacture of SBR-1)
The above SBR-1 is produced according to the following procedure. First, two autoclaves with an internal volume of 10 L, an inlet at the bottom and an outlet at the head, equipped with a stirrer and a jacket were connected in series as reactors, and butadiene, styrene, and cyclohexane were mixed in a predetermined ratio. do. This mixed solution is passed through a dehydration column packed with activated alumina, mixed with n-butyllithium in a static mixer to remove impurities, and then continuously fed from the bottom of the first reactor, and further 2,2-bis(2-oxolanyl)propane as a polar substance and n-butyllithium as a polymerization initiator were continuously supplied from the bottom of the first reactor at a predetermined rate, and the internal temperature of the reactor was brought to 95%. Keep at ℃. The polymer solution is continuously extracted 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 the oligomer component was diluted 1000 times with cyclohexane at a predetermined rate. The denaturation reaction is carried out by continuously adding as follows. This polymer solution is continuously extracted from the reactor, an antioxidant is continuously added using a static mixer, and then the solvent is removed to obtain the desired modified diene polymer (SBR-1).

The vinyl content (unit: mass %) of the SBR-1 is determined from the absorption intensity near 910 cm ⁻¹ , which is the absorption peak of vinyl groups, by infrared spectroscopy. Moreover, the amount of styrene (unit: mass %) is determined from the refractive index according to JIS K6383:1995.

(b) Compounding materials other than rubber components (a) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation
(N ₂ SA: 115 m ² /g)
(b) Silica: Ultrasil VN3 manufactured by Evonik Industries
(N ₂ SA: 175 m ² /g, average primary particle diameter: 17 nm)
(c) Silane coupling agent: Si266 manufactured by Evonik Industries
(Bis(3-triethoxysilylpropyl)disulfide)
(d) Resin: SYLVATRAXX4401 manufactured by Clayton
(α-methylstyrene resin)
(E) Oil: Diana Process NH-70S manufactured by Idemitsu Kosan Co., Ltd.
(Aromatic process oil)
(F) Stearic acid: Beaded stearic acid "Tsubaki" manufactured by NOF Corporation
(h) Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Mining Co., Ltd. (h) Anti-aging agent-1: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
(N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine)
(li) Anti-aging agent-2: Antigen RD manufactured by Sumitomo Chemical Co., Ltd.
(Polymer of 2,2,4-trimethyl-1,2-dihydroquinoline)
(nu) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
(Le) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. (contains 5% oil)
(w) Vulcanization accelerator-1: Noxeler CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
(N-cyclohexyl-2-benzothiazylsulfenamide (CBS))
(W) Vulcanization accelerator-2: Soxil D (DPG) manufactured by Sumitomo Chemical Co., Ltd.
(N,N'-diphenylguanidine)

(2) Rubber composition forming the cap rubber layer According to each formulation shown in Tables 2 and 3, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a Banbury mixer. to obtain a kneaded product. Note that each blending amount is in parts by mass.

Next, sulfur and a vulcanization accelerator are added to the kneaded product and kneaded for 5 minutes at 80° C. using open rolls to obtain a rubber composition that will form the cap rubber layer.

2. Rubber Composition Forming the Base Rubber Layer In parallel, a rubber composition forming the base rubber layer was prepared based on the formulation shown in Table 1 in the same manner as in the production of the rubber composition forming the cap rubber layer. A rubber composition forming a layer is obtained.

3. Manufacture of pneumatic tires Each rubber composition was extruded into a predetermined shape so that the ratio (thickness of cap rubber layer/thickness of base rubber layer) was 80/20. A tread portion having a thickness G (mm) shown in is formed.

Thereafter, an unvulcanized tire was formed by bonding with other tire members, and press vulcanization was performed for 10 minutes at 170°C. Examples 1 to 10 and Comparative Example 1 shown in Tables 2 and 3 - Each pneumatic tire (test tire) of Comparative Example 11 is manufactured.

4. Calculation of parameters After that, calculate the following parameters for each test tire.

(1) Loss tangent (tanδ)
A rubber test piece for measuring viscoelasticity was prepared by cutting out a piece measuring 20 mm long x 4 mm wide x 2 mm thick from the cap rubber layer of the tread of each test tire, with the long side in the tire circumferential direction. For the rubber test piece, tan δ was measured using the Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, initial strain of 5%, dynamic strain of 1%, deformation mode: tensile, and measurement temperature: 0 ° C. and 30 ° C. Then, 0°C tan δ and 30°C tan δ are determined, respectively. Note that the tan δ at 30° C. of the base rubber layer is 0.07.

Then, (30° C. tan δ/G) is calculated based on the 30° C. tan δ of the cap rubber layer and the thickness G (mm) of the tread portion.

(2) Tg
A rubber test piece for measuring viscoelasticity, which was cut out from the cap rubber layer in the same manner and produced, was measured using GABO's "Iplexer (registered trademark)" at a frequency of 10 Hz, an initial strain of 2%, an amplitude of ±1%, and a temperature increase rate of 2. ℃/min, temperature is changed from -60°C to 40°C, tan δ is measured, and Tg is determined by the method described above.

(3) Complex modulus of elasticity (E ^* )
A rubber test piece for measuring viscoelasticity, which was similarly cut out from the cap rubber layer, was tested using the Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and a deformation mode of tensile. , Measurement temperature: E ^* (MPa) is measured at 0°C and 30°C, and 0°C E ^* and 30°C E ^* are determined, respectively. Note that the 30°C E ^* of the base rubber layer is 4.0 MPa.

Then, (30°C E ^* ^/ G) is calculated based on 30°C E* (MPa) and the thickness G (mm) of the tread portion.

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

(5) (SBR content/land ratio), (Silica content/oblateness)
In addition, based on the specifications of each test tire and the formulation content, the content (parts by mass) of styrene-butadiene rubber (SBR) with an amount of styrene of 25% by mass or less in 100 parts by mass of the rubber component and the land in the tread part. Calculate the ratio (SBR content/land ratio) to the ratio (%) and the ratio of the silica content (parts by mass) to 100 parts by mass of the rubber component and the flatness (%) (silica content/flatness) .

5. Performance evaluation test (evaluation of wear resistance performance during high-speed driving)
Each test tire was attached to all wheels of a vehicle (domestic front-wheel drive vehicle, displacement 2000cc), filled with air to an internal pressure of 250kPa (regular internal pressure for passenger cars), and driven at 100km/h on a test course. After driving for 8,000 km, the groove depth of the tread was measured and the degree of decrease was determined. Then, the travel distance corresponding to a 1 mm decrease in groove depth is calculated.

Next, the result in Comparative Example 8 was set as 100, and the result was expressed as an index based on the formula below to evaluate the wear resistance performance during high-speed running. The larger the value, the better the wear resistance performance during high-speed running.
Wear resistance performance during high-speed running = [(results of test tires)/(results of comparative example 8)] x 100

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

The present invention (1) is
A tire including a tread portion,
The cap rubber layer forming the tread portion is
Containing styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, 60 parts by mass or more and 80 parts by mass or less,
Containing less than 100 parts by mass of silica with respect to 100 parts by mass of the rubber component,
Formed from a rubber composition whose loss tangent (30°C tan δ) measured in tensile deformation mode is more than 0.25 under the conditions of a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1%. and
The tire is characterized in that the thickness of the tread portion is 15 mm or less.

The present invention (2) is
The tire according to the present invention (1) is characterized in that the 30°C tan δ is 0.30 or more.

The present invention (3) is
The loss tangent (0°C tan δ) of the rubber composition forming the cap rubber layer measured under the conditions of a temperature of 0°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1% is as follows: The tire according to the present invention (1) or (2) is characterized in that it is 0.60 or more.

The present invention (4) is
The tire according to the present invention (3) is characterized in that the 0°C tan δ is 0.70 or more.

The present invention (5) is
The tire is characterized in that the cap rubber layer has a glass transition temperature (Tg) of −15° C. or lower, and is any combination of the present invention (1) to (4).

The present invention (6) is
The temperature of the cap rubber layer is 30°C, the frequency is 10Hz, the initial strain is 5%, the dynamic strain rate is 1%, and the deformation mode is that the complex modulus of elasticity (30°C E ^* ) measured in tension is 6.0 MPa or less. The present invention is characterized by a tire in any combination with any one of the present inventions (1) to (5).

The present invention (7) is
The present invention (1) is characterized in that the 30°C E ^* (MPa) and the thickness (mm) of the tread portion satisfy (30°C E ^* /thickness of the tread portion)≧0.50. It is a tire of any combination with any one of (6).

The present invention (8) is
The temperature of the cap rubber layer is 0°C, the frequency is 10Hz, the initial strain is 5%, the dynamic strain rate is 1%, the deformation mode is: the complex modulus of elasticity (0°C E ^* ) measured in tension is 25.0 MPa or less. The present invention is characterized by a tire in any combination with any one of the present inventions (1) to (7).

The present invention (9) is
The tire is characterized in that the thickness of the tread portion is 4 mm or more and 11 mm or less, and is any combination with any one of the present inventions (1) to (8).

The present invention (10) is
A tire according to any combination of the present invention (1) to (9), characterized in that the thickness of the cap rubber layer is 10% or more and less than 100% of the total thickness of the tread portion. It is.

The present invention (11) is
The cap rubber layer contains a resin component selected from the group of rosin resin, styrene resin, coumaron resin, terpene resin, C5 resin, C9 resin, C5C9 resin, and acrylic resin. , a tire in any combination with any one of the present inventions (1) to (10).

The present invention (12) is
The present invention (1) is characterized in that the 30°C tan δ of the cap rubber layer and the thickness (mm) of the tread portion satisfy (30°C tan δ/thickness of the tread portion)>0.03. (11) Any combination of tires.

The present invention (13) is
The land ratio in the tread portion is 40% or more,
The ratio of the content (parts by mass) of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component to the land ratio (%) in the tread portion (SBR having a styrene content of 25% by mass or less) The tire is characterized in that the content (parts by mass)/land ratio (%) is 1.2 or less, and is any combination of the present invention (1) to (12).

The present invention (14) is
The flattening ratio is 80% or less,
The ratio of the content (parts by mass) of the silica to 100 parts by mass of the rubber component and the oblateness (%) (silica content (parts by mass)/oblateness (%)) is 0.6 or more. It is a tire in any combination with any one of the present inventions (1) to (13).

Claims

A tire including a tread portion,
The cap rubber layer forming the tread portion is
Containing styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component, 60 parts by mass or more and 80 parts by mass or less,
Containing less than 100 parts by mass of silica with respect to 100 parts by mass of the rubber component,
Formed from a rubber composition whose loss tangent (30°C tan δ) measured in tensile deformation mode is more than 0.25 under the conditions of a temperature of 30°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1%. and
A tire characterized in that the thickness of the tread portion is 15 mm or less.
The tire according to claim 1, wherein the 30°C tan δ is 0.30 or more.
The loss tangent (0°C tan δ) of the rubber composition forming the cap rubber layer measured under the conditions of a temperature of 0°C, a frequency of 10Hz, an initial strain of 5%, and a dynamic strain rate of 1% is as follows: The tire according to claim 1 or 2, characterized in that it is 0.60 or more.
The tire according to claim 3, wherein the 0°C tan δ is 0.70 or more.
The tire according to any one of claims 1 to 4, wherein the cap rubber layer has a glass transition temperature (Tg) of -15°C or lower.
The temperature of the cap rubber layer is 30°C, the frequency is 10Hz, the initial strain is 5%, the dynamic strain rate is 1%, and the deformation mode is that the complex modulus of elasticity (30°C E * ) measured in tension is 6.0 MPa or less. The tire according to any one of claims 1 to 5, characterized in that:
The 30°C E * (MPa) and the thickness (mm) of the tread portion satisfy (30°C E * /thickness of the tread portion)≧0.50. The tire according to any one of item 6.
The temperature of the cap rubber layer is 0°C, the frequency is 10Hz, the initial strain is 5%, the dynamic strain rate is 1%, the deformation mode is: the complex modulus of elasticity (0°C E * ) measured in tension is 25.0 MPa or less. The tire according to any one of claims 1 to 7, characterized in that:
The tire according to any one of claims 1 to 8, wherein the tread portion has a thickness of 4 mm or more and 11 mm or less.
The tire according to any one of claims 1 to 9, wherein the thickness of the cap rubber layer is 10% or more and less than 100% of the thickness of the entire tread portion.
The cap rubber layer contains a resin component selected from the group of rosin resin, styrene resin, coumaron resin, terpene resin, C5 resin, C9 resin, C5C9 resin, and acrylic resin. The tire according to any one of claims 1 to 10.
30° C. tan δ of the cap rubber layer and the thickness (mm) of the tread portion satisfy (30° C. tan δ/thickness of tread portion)>0.03. 11. The tire according to any one of Item 11.
The land ratio in the tread portion is 40% or more,
The ratio of the content (parts by mass) of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component to the land ratio (%) in the tread portion (SBR having a styrene content of 25% by mass or less) The tire according to any one of claims 1 to 12, wherein the content (parts by mass)/land ratio (%) is 1.2 or less.
The flattening ratio is 80% or less,
The ratio of the content (parts by mass) of the silica to 100 parts by mass of the rubber component and the oblateness (%) (silica content (parts by mass)/oblateness (%)) is 0.6 or more. The tire according to any one of claims 1 to 13, characterized by: