JP2024097293A - tire - Google Patents

Abstract

The present invention provides a tire having improved durability after ozone degradation.
[Solution] A tire comprising a tread portion having at least one rubber layer, sidewall portions, and a carcass layer, wherein the tread portion and the sidewall portions are each made of a rubber composition containing a rubber component, and at least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having ethylene units and branched conjugated diene units, and wherein when the content of the phenylenediamine-based antiaging agent per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion is S1 (parts by mass), and the content of the phenylenediamine-based antiaging agent per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is S2 (parts by mass), S1 + S2 is less than 1.0 part by mass.
[Selection diagram] None

Description

The present invention relates to a tire.

In recent years, the wear resistance of tires has improved and their use in the market has become longer, so there is a demand for improvements in various tire performance characteristics, such as resistance to deterioration caused by long-term damage and degradation, and resistance to crack growth.

It is known that rubber compositions for tires contain antioxidants and waxes to suppress the occurrence and progression of cracks in the presence of ozone. For example, Patent Document 1 describes a rubber composition for tire treads that contains a specified wax and a specified surfactant.

JP 2018-177873 A

The present invention aims to provide a tire with improved durability after ozone degradation.

The present invention relates to the following tire.
A tire having a tread portion having at least one rubber layer, a sidewall portion, and a carcass layer,
the tread portion and the sidewall portion are each made of a rubber composition containing a rubber component,
At least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having an ethylene unit and a branched conjugated diene unit,
A tire in which, when the content of the phenylenediamine-based anti-aging agent per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion is S1 (parts by mass), and the content of the phenylenediamine-based anti-aging agent per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is S2 (parts by mass), S1 + S2 is less than 1.0 part by mass.

The present invention provides a tire with improved durability after ozone degradation.

1 is a schematic partial cross-sectional view of a tire according to one embodiment of the present invention. 1 is an enlarged cross-sectional view showing a portion of a tread portion of a tire according to one embodiment of the present invention.

The rubber composition for tires, which is one embodiment of the present invention, is a tire having a tread portion having at least one rubber layer, a sidewall portion, and a carcass layer, wherein the tread portion and the sidewall portion are each made of a rubber composition containing a rubber component, and at least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having ethylene units and branched conjugated diene units, and when the content of the phenylenediamine-based antiaging agent per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion is S1 (parts by mass), and the content of the phenylenediamine-based antiaging agent per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is S2 (parts by mass), S1 + S2 is less than 1.0 part by mass.

While not intending to be bound by theory, the mechanism by which durability performance after ozone degradation is improved in the tires of the present invention is believed to be as follows.

If a large amount of phenylenediamine-based antioxidant is blended to suppress the occurrence and progression of cracks in the presence of ozone, there is a concern that durability performance will deteriorate due to insufficient adhesion. On the other hand, if only a normal diene-based rubber is blended without blending a phenylenediamine-based antioxidant, there is a concern that it will deteriorate due to ozone. In the tire of the present invention, (1) at least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having an ethylene unit and a branched conjugated diene unit, which improves the compatibility of the rubber component and also improves the compatibility with the filler, which is thought to contribute to improving durability performance, and (2) by making the total content of the phenylenediamine-based antioxidant less than 1.0 part by mass per 100 parts by mass of the rubber component of the rubber composition constituting the tread portion and the rubber composition constituting the sidewall portion, the tread rubber maintains its ozone resistance while suppressing the migration of low molecular weight components to the rubber interface, which is thought to improve the adhesion between the tread portion and the sidewall portion and contribute to improving the durability of the tire. It is believed that the cooperation of the above (1) and (2) will achieve the remarkable effect of providing tires with improved durability after ozone degradation.

Copolymer A is preferably a random copolymer.

Being a random copolymer is thought to suppress intramolecular aggregation, further improving durability after ozone degradation.

The branched conjugated diene units in copolymer A are preferably 10 mol % or more and 30 mol % or less.

By having the branched conjugated diene units in copolymer A fall within the above range, it is believed that the progression of molecular chain scission of the copolymer caused by ozone during product use is suppressed while ensuring crosslinking reactivity during tire vulcanization, and durability performance after ozone degradation is further improved.

It is preferred that the branched conjugated diene units include a 3,4 configuration, and that the 3,4 configuration accounts for 70 mol % or more of the total branched conjugated diene units.

The branched conjugated diene units contain 3,4 configuration, and the 3,4 configuration accounts for 70 mol % or more of the total branched conjugated diene units. This is believed to suppress molecular chain scission of the copolymer by ozone during product use while ensuring crosslinking reactivity during tire vulcanization, and to further improve durability performance after ozone degradation.

The glass transition temperature of copolymer A is preferably -60°C or higher and -40°C or lower.

By having the glass transition temperature of copolymer A fall within the above range, it is believed that the temperature dependency of durability performance is reduced, and durability performance after ozone degradation is further improved.

The weight average molecular weight of copolymer A is preferably 10,000 or more.

It is believed that by having the weight-average molecular weight of copolymer A be 10,000 or more, the three-dimensional entanglement of the copolymer molecules increases, further improving durability performance after ozone degradation.

It is preferable that the breaking strength of the rubber composition constituting the sidewall portion of the present invention is 12 MPa or more, and the breaking elongation is 600% or more. By having the breaking strength and breaking elongation in the above ranges, it is believed that durability performance after ozone degradation will be further improved.

When the content of copolymer A in the rubber component constituting the sidewall portion of the present invention is C _SW (mass %) and the thickness of the surface rubber layer at the maximum width position of the tire is T (mm), it is preferable that C _SW /T is 10 or more and 60 or less.

When C _SW /T is in the above range, a certain amount of copolymer A is present even when the sidewall is thin, and it is believed that copolymer A improves the compatibility of the rubber component and further improves the durability performance after ozone degradation.

C _SW is preferably 50 mass% or more. When C _SW is in the above range, copolymer A is sufficiently present in the rubber component of the rubber composition constituting the sidewall portion, which is thought to improve the compatibility of the rubber components and further improve the durability performance after ozone degradation.

At least one rubber layer constituting the tread portion of the present invention preferably has a tan δ at 30° C. (30° C. tan δ _T ) of 0.40 or less.

It is believed that by setting 30° C. tan δ _T within the above range, heat build-up is reduced and durability is further improved.

The content _C of copolymer A in the rubber component of at least one rubber layer constituting the tread of the present invention is preferably 65% by mass or more. When _C is in the above range, copolymer A is sufficiently present in the rubber component of the rubber composition constituting the tread, which is believed to improve the compatibility of the rubber components and further improve the durability performance after ozone degradation.

It is preferable that S1 is 0.1 parts by mass or more. By having S1 0.1 parts by mass or more, it is believed that the occurrence and progression of cracks in the presence of ozone is suppressed, and the durability performance of the tire after ozone degradation is further improved.

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

"Regular internal pressure" is the air pressure set for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for ETRTO, it is "INFLATION PRESSURE," and for TRA, it is the "maximum value" listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference.

"Normal condition" means that the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. In the case of tires of sizes not specified in the above-mentioned standard system, it means that the tire is mounted on the smallest rim, inflated to 250 kPa, and unloaded.

"The thickness T of the surface rubber layer at the tire's maximum width position" is the distance (mm) from the sidewall surface to the carcass cord surface, measured along the normal line of the tire's maximum width position on the sidewall. "Maximum tire width position" refers to the maximum width position in the tire's widthwise cross section measured under normal conditions.

"The content S1 (parts by mass) of phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion" refers to the content of phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the rubber layer (the "first tread layer 6" described below) that is closest to the surface of the tread and has a thickness of 1 mm or more when the tread portion is made up of two or more rubber layers.

"Plasticizer content" includes the amount of plasticizer in the rubber component that has been extended by the plasticizer. Similarly, "oil content" includes the amount of oil contained in oil-extended rubber.

<Measurement method>
The "glass transition temperature of the copolymer" is measured in accordance with JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan, Ltd., while increasing the temperature at a rate of 10° C./min.

The "weight average molecular weight (Mw)" can be calculated based on the measured value obtained by gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) and converted into standard polystyrene. For example, it is applicable to rubber components, resin components, etc.

"30°C tan δ" is the loss tangent measured using a GABO Iplexer series under the following conditions: temperature 30°C, initial strain 5%, dynamic strain ±1%, frequency 10 Hz, and extension mode. The sample for measuring the loss tangent is a vulcanized rubber composition with a length of 20 mm, width 4 mm, and thickness of 1 mm. When cut out from the tread portion of a tire, the length direction is the circumferential direction of the tire.

The "breaking strength of the rubber composition" is measured in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile test properties" by conducting a tensile test at a tensile speed of 3.3 mm/sec in an atmosphere of 23°C. When preparing a test specimen for measurement from a tire, prepare a No. 7 dumbbell-shaped test specimen with a thickness of 1 mm so that the tire circumferential direction is the vertical direction.

The "breaking elongation of rubber composition" is measured by carrying out a tensile test in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile test properties" at a tensile speed of 3.3 mm/sec in an atmosphere of 23°C. When preparing a test specimen from a tire, prepare it in the same manner as for the "breaking strength of rubber composition".

The "styrene content" is a value calculated by ¹ H-NMR measurement, and is applied to, for example, rubber components having repeating units derived from styrene, such as SBR. The "vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied to, for example, rubber components having repeating units derived from butadiene, such as SBR and BR. The "cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied to, for example, rubber components having repeating units derived from butadiene, such as BR.

"Average primary particle size" is a value calculated by taking the arithmetic average of 400 particles when the particles are photographed with a transmission or scanning electron microscope, and taking the diameter of the sphere as the particle diameter if the particle shape is nearly spherical, the minor axis as the particle diameter if the particle shape is needle-like or rod-like, and the average of the minor axis and the diameter as the particle diameter if the particle shape is irregular. Note that if the particle shape is nearly spherical, the diameter of the sphere is taken as the particle diameter, if the particle shape is needle-like or rod-like, the minor axis as the particle diameter, and if the particle shape is irregular, the average of the minor axis and the major axis as the particle diameter.

"Nitrogen adsorption specific surface area (N ₂ SA) of carbon black" is measured in accordance with JIS K 6217-2: 2017. "Nitrogen adsorption specific surface area (N ₂ SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[tire]
Hereinafter, a tire according to an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example, and the tire of the present invention is not limited to the embodiment described below.

Figure 1 illustrates an example of a tire according to one embodiment of the present invention, but is not limited to this. Figure 1 shows a portion of a cross section perpendicular to the circumferential direction of the tire. In Figure 1, the up-down direction is the tire radial direction, the left-right direction is the tire axial direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

A tire having tire components made of the rubber composition of the present invention (hereinafter referred to as the tire of the present invention) includes a tread portion 1 extending in the circumferential direction to form an annular shape, a pair of sidewall portions 31 arranged on both sides of the tread portion, a pair of bead portions having bead cores 21, at least one layer of carcass 33 anchored to the bead cores 21, and at least one layer of belt 2 arranged radially outward of the carcass 33. In FIG. 1, the belt 2 is made up of two layers.

The bead portion of the tire of the present invention is located axially inside the sidewall portion 31. The bead portion includes a bead core 21 and a bead apex 22 that extends radially outward from the core. The bead apex 22 tapers radially outward.

In FIG. 1, the carcass 33 is folded around the bead core 21 from the inside to the outside in the tire axial direction. This folding forms a main portion and a folded portion in the carcass 33. The strip apex 25 generally extends in the tire radial direction. The strip apex 25 is laminated with the bead apex 22 near its radially inner end. The strip apex 25 is sandwiched between the main portion and the folded portion of the carcass 33 near its radially inner end.

"The thickness T of the surface rubber layer at the maximum tire width position" is the distance (mm) from the sidewall surface to the carcass 33 surface, measured along the normal line of the maximum tire width position PW of the sidewall portion 31. In the present invention, "the thickness T of the surface rubber layer at the maximum tire width position" is preferably 1.0 mm or more, more preferably 1.3 mm or more, even more preferably 1.5 mm or more, and particularly preferably 1.7 mm or more. From the viewpoint of the effects of the present invention, T (mm) is preferably 12.0 mm or less, more preferably 11.0 mm or less, even more preferably 10.0 mm or less, and particularly preferably 8.0 mm or less.

The ratio C _SW /T of the content C _SW (parts by mass) of copolymer A in the rubber component constituting the sidewall portion to the thickness T (mm) of the surface rubber layer at the maximum width position of the tire is preferably 50 or more, more preferably 55 or more, and even more preferably 60 or more. In addition, C _SW /T is preferably 100 or less, more preferably 90 or less, and even more preferably 80 or less.

<Breaking strength>
In the present invention, the breaking strength of the rubber composition constituting the sidewall portion 31 is preferably 10 MPa or more, more preferably 11 MPa or more, even more preferably 12 MPa or more, even more preferably more than 12 MPa, and particularly preferably more than 13 MPa. On the other hand, the upper limit of the breaking strength of the rubber composition constituting the sidewall portion 31 is not particularly limited, but can be, for example, 50 MPa or less, 45 MPa or less, or 40 MPa or less. The breaking strength can be adjusted by the amount of the rubber component or the type of the crosslinking agent. For example, the breaking strength can be increased by reducing the content of isoprene-based rubber.

<Elongation at break>
In the present invention, the breaking elongation of the rubber composition constituting the sidewall portion 31 is preferably 580% or more, more preferably 590% or more, even more preferably 600% or more, even more preferably 610% or more, even more preferably 615% or more, and particularly preferably 620% or more, from the viewpoint of the effects of the present invention. On the other hand, the upper limit of the breaking elongation is not particularly limited, but can be, for example, 900% or less, 850% or less, or 800% or less. The breaking elongation of the rubber composition can be adjusted by the amount of the rubber component, the amount of the resin component, the type of the resin component, and the like. For example, the breaking elongation can be increased by reducing the content of the isoprene-based rubber.

Figure 2 is a cross-sectional view showing a portion of the tread of a tire. In Figure 2, the up-down direction is the tire radial direction, the left-right direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

The tread portion of the tire of the present invention preferably has circumferential grooves 12 that extend continuously in the circumferential direction of the tire. The circumferential grooves 12 may extend linearly along the circumferential direction, or may extend in a zigzag pattern along the circumferential direction.

The tread portion of the tire of the present invention may be composed of a single rubber layer, or may be composed of two or more rubber layers. FIG. 2 shows a first layer 6 that constitutes the tread surface, and a second layer 7 that exists on the radially inner side of the first layer 6. The first layer 6 typically corresponds to a cap tread. One or more rubber layers may be present between the second layer 7 and the band.

In FIG. 2, the double-headed arrow t1 indicates the thickness of the first layer 6, and the double-headed arrow t2 indicates the thickness of the second layer 7. In FIG. 2, the midpoint of the land portion 3 in the tire width direction is indicated by the symbol P. The straight line indicated by the symbol N is a straight line (normal line) that passes through point P and is perpendicular to the tangent plane at point P. In this specification, the thicknesses t1 and t2 are measured along the normal line N drawn from point P on the tread surface at a position where no grooves exist in the cross section of FIG. 2.

In the present invention, the total thickness of the tread portion is not particularly limited, but is preferably 30 mm or less, more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 15 mm or less. The total thickness of the tread portion is more preferably 3.0 mm or more, more preferably 5.0 mm or more, and even more preferably 7.0 mm or more.

In the present invention, the thickness t1 of the first tread layer 6 is preferably 1.0 mm or more, more preferably 1.2 mm or more, even more preferably 1.5 mm or more, and particularly preferably 2.0 mm or more. The thickness t1 of the first tread layer 6 is not particularly limited, but is preferably 10.0 mm or less, more preferably 9.0 mm or less, and even more preferably 8.0 mm or less. In other words, in the present invention, the first tread layer 6 refers to the layer closest to the tread surface and having a thickness of 1.0 mm or more.

The ratio _Ct1 /t1 of the content Ct1 (parts by mass) of copolymer A in the rubber component constituting the first tread layer to the thickness t1 (mm) of the first tread layer 6 is preferably 60 or more, more preferably 65 or more, and _{even more preferably 70 or more. Also, Ct1/t1 is preferably 100 or less, more preferably 95 or less, and even more preferably 90 or less. By having Ct1 / t1} in the above range, a certain amount of copolymer A is present even when the first tread layer is thin, and it is believed that the compatibility of the rubber component is improved by copolymer A, and durability performance after ozone degradation is further improved.

In the present invention, the thickness t2 of the second tread layer 7 is not particularly limited, but is preferably 0.8 mm or more, more preferably 1.0 mm or more, even more preferably 1.5 mm or more, and particularly preferably 2.0 mm or more. The thickness t2 of the second tread layer 7 is not particularly limited, but is preferably 10.0 mm or less, more preferably 9.0 mm or less, and even more preferably 8.0 mm or less.

In the present invention, the 30°C tan δ (30°C tan δ _T ) of at least one rubber layer constituting the tread portion is preferably 0.22 or less, more preferably 0.21 or less, even more preferably 0.20 or less, and even more preferably 0.19 or less, from the viewpoint of the effects of the present invention. Also, from the viewpoint of grip performance, the 30°C tan δ _T is preferably 0.14 or more, more preferably 0.15 or more, and even more preferably 0.155 or more.

In the present invention, the 30°C tan δ (30°C tan δ _T1 ) of the first tread layer is preferably 0.22 or less, more preferably 0.21 or less, even more preferably 0.20 or less, and even more preferably 0.19 or less, from the viewpoint of the effects of the present invention. Also, from the viewpoint of grip performance, the 30°C tan δ _T1 is preferably 0.14 or more, more preferably 0.15 or more, and even more preferably 0.155 or more.

The 30°C tan δ of a rubber composition can be adjusted by standard methods used in the tire industry. For example, the 30°C tan δ can be increased by using a rubber component with a high glass transition temperature, increasing the amount of filler, decreasing the particle size, increasing the resin component as a plasticizer component, and decreasing the amount of sulfur and accelerator.

All tires of the present invention can be manufactured using the raw materials described below. The details are explained below.

<Rubber component>
In the present invention, it is preferred that at least one of the rubber compositions constituting the tread portion and the sidewall portion contains copolymer A, and that both of the rubber compositions constituting the tread portion and the sidewall portion contain copolymer A. Also, the rubber compositions constituting the tread portion and the sidewall portion may be rubber components consisting of copolymer A alone.

<Copolymer A>
Copolymer A is a diene rubber, a copolymer having ethylene units and branched conjugated diene units, and may have other monomer units, and is preferably a copolymer consisting of ethylene units and branched conjugated diene units, a ternary copolymer consisting of ethylene units, branched conjugated diene units and other monomer units, and a quaternary copolymer consisting of ethylene units, branched conjugated diene units and other monomer units.As long as copolymer A is a copolymer having ethylene units and branched conjugated diene units, there is no particular limitation on the arrangement of each unit, and it may be a random copolymer obtained by random copolymerization or a block copolymer obtained by block copolymerization, but a random copolymer is preferred.These copolymers A may be used alone or in combination of two or more.

The ethylene unit is a structural unit derived from ethylene in copolymer A. The ethylene unit may be formed by hydrogenating a structural unit derived from 1,3-butadiene (butadiene unit).

The branched conjugated diene unit refers to a structural unit in copolymer A that is derived from a branched conjugated diene compound.

The branched conjugated diene compound is preferably a 1,3-diene represented by the following formula:
CH ₂ =CR-CH=CH ₂
(wherein R represents a hydrocarbon having 1 to 20 carbon atoms).

R is preferably a hydrocarbon having 3 to 20 carbon atoms, more preferably a hydrocarbon having 3 to 15 carbon atoms, and even more preferably a hydrocarbon having 5 to 12 carbon atoms. In addition, although there are no particular limitations on the hydrocarbon, aliphatic hydrocarbons are preferred.

The branched conjugated diene compound may be used alone or in combination of two or more. As the branched conjugated diene compound, one or more selected from the group consisting of isoprene, myrcene, and farnesene are preferred, and myrcene and/or farnesene are more preferred. As the farnesene, either α-farnesene or β-farnesene may be used. Note that α-farnesene and β-farnesene may be used in combination.

The branched conjugated diene units may have a 1,2 configuration represented by the following formula (1), a 3,4 configuration represented by the following formula (2), or a 1,4 configuration represented by the following formula (3). In the present invention, the branched conjugated diene units of copolymer A preferably include a 3,4 configuration represented by the following formula (2), and the 3,4 configuration preferably accounts for 60 mol % or more of the entire branched conjugated diene units of copolymer A, more preferably 65 mol % or more, even more preferably 70 mol % or more, and particularly preferably 75 mol % or more.

From the viewpoint of co-crosslinking, the branched conjugated diene units in copolymer A are preferably 8 mol% or more, more preferably 10 mol% or more, even more preferably 12 mol% or more, and particularly preferably 15 mol% or more. From the viewpoint of suppressing the reaction with ozone, the branched conjugated diene units are preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less.

Other monomer units include butadiene units, aromatic vinyl units, non-conjugated olefin units, etc.

An aromatic vinyl unit refers to a structural unit in a copolymer that is derived from an aromatic vinyl compound. Here, an aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6-trimethylstyrene, with styrene being preferred. These may be used alone or in combination of two or more.

The term "non-conjugated olefin unit" refers to a structural unit in a copolymer derived from a non-conjugated olefin compound. Here, the term "non-conjugated olefin compound" refers to an unsaturated aliphatic hydrocarbon, a non-conjugated compound having one or more carbon-carbon double bonds. Examples of non-conjugated olefin compounds include α-olefins such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene; heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, and N-vinylpyrrolidone; and the like; with 1-butene being preferred. These may be used alone or in combination of two or more.

If desired, copolymer A can be treated with a modifying agent to form a modified product in which a functional group that interacts with silica has been introduced. Any functional group commonly used in this field can be suitably used as such a functional group, and examples of such functional groups include alkoxysilyl groups (e.g., trimethoxysilyl and triethoxysilyl groups). For example, if the copolymer is treated with chlorotriethoxysilane as a modifying agent before being hydrogenated after synthesis, a modified product in which a triethoxysilyl group has been introduced at the active end of the copolymer can be obtained.

From the viewpoint of the effects of the present invention, the glass transition temperature of copolymer A is preferably -80°C or higher, more preferably -70°C or higher, even more preferably -65°C or higher, and particularly preferably -60°C or higher. From the viewpoint of the effects of the present invention, the glass transition temperature of copolymer A is preferably -20°C or lower, more preferably -30°C or lower, and even more preferably -40°C or lower. The glass transition temperature of copolymer A is determined by the above-mentioned measurement method.

From the viewpoint of wet grip performance, the weight average molecular weight (Mw) of copolymer A is preferably 10,000 or more, more preferably 12,000 or more, and even more preferably 15,000 or more. From the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight average molecular weight of copolymer A is measured by the above-mentioned measurement method.

The Mw of copolymer A can be controlled by conventional methods, for example, by adjusting the amount of each monomer charged during polymerization relative to the catalyst. For example, the Mw can be increased by increasing the total monomer/anionic polymerization catalyst ratio or the total monomer/coordination polymerization catalyst ratio, and conversely, the Mw can be decreased by decreasing the ratio.

Copolymer A can be produced by subjecting each monomer component to a copolymerization reaction by an ordinary method, for example, anionic polymerization, coordination polymerization, etc., to produce a copolymer. Furthermore, the copolymer can be produced by hydrogenating the copolymer to produce a hydrogenated product. The hydrogenation reaction of the branched conjugated diene can be carried out by an ordinary method, and catalytic hydrogenation using a metal catalyst, a method using hydrazine, etc. can both be suitably used. For example, catalytic hydrogenation using a metal catalyst can be carried out by adding hydrogen under pressure in an organic solvent in the presence of a metal catalyst, and tetrahydrofuran, methanol, ethanol, etc. can both be suitably used as the organic solvent. These organic solvents can be used alone or in a mixture of two or more kinds. In addition, as the metal catalyst, for example, palladium, platinum, rhodium, ruthenium, nickel, etc. can both be suitably used, and these metal catalysts can be used alone or in a mixture of two or more kinds. The pressure when pressurizing is preferably, for example, 1 to 300 kgf/cm ² .

The presence of ethylene units and branched conjugated diene units in copolymer A can be confirmed by using techniques such as gel permeation chromatography (GPC), ¹ H-NMR, ¹³ C-NMR, etc. Furthermore, the presence of units derived from each monomer component can be confirmed based on the ¹ H-NMR spectrum and the ¹³ C-NMR spectrum.

The copolymerization reaction is not particularly limited in the order of copolymerization as long as each monomer component is copolymerized. For example, all monomers may be randomly copolymerized at once, or specific monomers may be copolymerized in advance and then the remaining monomers may be added and copolymerized, or specific monomers that have been copolymerized in advance may be block copolymerized. In the present invention, however, random copolymerization is preferred. There is also no particular restriction on the polymerization method, and any of solution polymerization, emulsion polymerization, gas phase polymerization, bulk polymerization, etc. may be used, with solution polymerization being preferred. The polymerization method may be either batch or continuous.

<Content of Copolymer A>
The content C _SW of copolymer A in the rubber component constituting the sidewall portion is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, and may be 100% by mass. The upper limit of the content C _SW of copolymer A in the rubber component constituting the sidewall portion may be 100% by mass, and is not particularly limited.

The content C _T of copolymer A in the rubber component constituting the tread portion is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. The upper limit of the content C _T of copolymer A in the rubber component constituting the tread portion may be 100% by mass, and is not particularly limited.

When the tread portion has two or more layers, the content _C of copolymer A in at least one layer constituting the tread portion is preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, still more preferably 90 mass% or more, and may be 100 mass%. Of the two or more rubber layers constituting the tread portion, it is more preferable that the first layer satisfies the above _C.

<Rubber Components Other Than Copolymer A>
As the rubber component other than copolymer A, a diene rubber other than copolymer A is suitably used. Examples of diene rubber other than copolymer A include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc. These other diene rubber components may be used alone or in combination of two or more.

(Isoprene rubber)
As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

There are no particular limitations on NR, and any commonly used NR in the tire industry can be used, such as SIR20, RSS#3, TSR20, etc.

The content of isoprene-based rubber in the rubber components constituting the tread and sidewall portions is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, from the viewpoint of wet grip performance and ensuring the content of copolymer A. On the other hand, the lower limit of the content is not particularly limited, but can be, for example, 5% by mass or more, 10% by mass or more, or 15% by mass or more.

(BR)
The BR is not particularly limited, and can be, for example, BR having a cis content of less than 50 mol% (low cis BR), BR having a cis content of 90 mol% or more (high cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high cis modified BR, low cis modified BR), etc. These BRs can be used alone or in combination of two or more.

As the high cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. By including high cis BR, it is possible to improve low temperature properties and wear resistance. The cis content is preferably 95 mol% or more, more preferably 96 mol% or more, even more preferably 97 mol% or more, and particularly preferably 98 mol% or more. The cis content is measured by the above-mentioned measurement method.

As the modified BR, a modified butadiene rubber (modified BR) in which the terminals and/or the main chain are modified with a functional group containing at least one element selected from the group consisting of silicon, nitrogen, and oxygen is preferably used.

Other modified BRs include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, in which the ends of the modified BR molecules are further bonded with tin-carbon bonds (tin-modified BR). In addition, the modified BR may be either non-hydrogenated or hydrogenated.

From the viewpoint of abrasion resistance, the weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The weight average molecular weight of BR can be determined by the above-mentioned measurement method.

The content of BR in the rubber components constituting the tread and sidewall is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, from the viewpoint of wet grip performance and ensuring the content of copolymer A. The lower limit of the content is not particularly limited, but can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more.

(SBR)
The SBR is not particularly limited, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of modified SBR include SBR whose ends and/or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin, silicon compounds, etc. Among these, S-SBR and modified SBR are preferred from the viewpoint of being able to satisfactorily improve fuel economy performance and abrasion resistance. These SBRs may be used alone or in combination of two or more types.

The SBR content in the rubber components constituting the tread and sidewall portions can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more. On the other hand, the SBR content in the diene rubber component is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less.

(Other rubber components)
The rubber component may contain other rubber components other than the diene rubber, as long as the effect of the present invention is not affected. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used, and examples thereof include butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, etc. These other rubber components may be used alone or in combination of two or more.

<Filler>
The rubber composition according to the present invention preferably contains a filler, and the filler preferably contains carbon black and/or silica.

(Carbon black)
The carbon black is not particularly limited, and for example, GPF, FEF, HAF, ISAF, SAF, and other carbon blacks commonly used in the tire industry can be used. In addition to carbon blacks produced by burning common mineral oils, carbon blacks made from biomass materials such as lignin can also be used. These carbon blacks can be used alone or in combination of two or more.

When the rubber composition constituting the tread portion contains carbon black, the nitrogen adsorption specific surface area ( _N2SA ) is preferably ³⁰ m2/g or more, more preferably ⁵⁰ m2/g or more, even more preferably ⁷⁰ m2/g or more, and particularly preferably ⁹⁰ m2/g or more from the viewpoint of reinforcement. Also, from the viewpoint of fuel efficiency and processability, it is preferably ²⁰⁰ m2/g or less, more preferably ¹⁵⁰ m2/g or less, and even more preferably 120 ^m2 /g or less. The _N2SA of carbon black is measured by the above-mentioned measurement method.

When the rubber composition constituting the sidewall portion contains carbon black, the nitrogen adsorption specific surface area ( _N2SA ) is preferably ²⁰ m2/g or more, more preferably 40 ^m2 /g or more, even more preferably ⁵⁰ m2/g or more, and particularly preferably ⁶⁰ m2/g or more, from the viewpoint of the effects of the present invention. Also, from the viewpoint of fuel efficiency and processability, it is preferably ²⁰⁰ m2/g or less, more preferably 150 ^m2 /g or less, and even more preferably 120 ^m2 /g or less. The _N2SA of carbon black is measured by the above-mentioned measurement method.

In the rubber composition constituting the tread portion, the content of carbon black 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, and even more preferably 15 parts by mass or more, from the viewpoint of abrasion resistance and wet grip performance. Also, from the viewpoint of fuel efficiency, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

In the rubber composition constituting the sidewall portion, the carbon black content per 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 45 parts by mass or more, from the viewpoint of the effects of the present invention. Also, from the viewpoint of durability performance, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 65 parts by mass or less.

The rubber composition constituting the sidewall preferably contains carbon black as a filler, and may contain only carbon black as a filler.

(silica)
The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. Among them, hydrated silica prepared by a wet method is preferred because it has a large number of silanol groups. In addition to the above silica, silica made from a biomass material such as rice husk may be used as appropriate. These silicas may be used alone or in combination of two or more. In addition to these silicas, silica made from a biomass material such as rice husk may also be used.

From the viewpoint of the effects of the present invention, the _N2SA of silica is preferably ¹²⁰ m2/g or more, more preferably ¹⁴⁰ m2/g or more, even more preferably ¹⁶⁰ m2/g or more, and particularly preferably ¹⁸⁰ m2/g or more. On the other hand, from the viewpoint of dispersibility, it is preferably ³⁵⁰ m2/g or less, more preferably ³⁰⁰ m2/g or less, and even more preferably ²⁵⁰ m2/g or less. The _N2SA of silica is measured by the above-mentioned measurement method.

From the viewpoint of the effects of the present invention, the average primary particle diameter of silica is preferably 22 nm or less, more preferably 20 nm or less, even more preferably 18 nm or less, and particularly preferably 17 nm or less. On the other hand, from the viewpoint of dispersibility, it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle diameter of silica is measured by the above-mentioned measurement method.

In the rubber composition constituting the tread portion, the content of silica per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and even more preferably more than 40 parts by mass. From the viewpoint of abrasion resistance performance, the content is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 130 parts by mass or less.

The rubber composition constituting the tread portion preferably contains carbon black and silica as fillers. In the rubber composition constituting the tread portion, the total content of carbon black and silica per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, even more preferably 50 parts by mass or more, and even more preferably more than 50 parts by mass. From the viewpoint of processability, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 130 parts by mass or less.

When the rubber composition constituting the tread portion contains carbon black and silica as fillers, the ratio of the silica content to the carbon black content is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.5 or less. The ratio of the silica content is preferably 0.8 or more, more preferably 1.0 or more, even more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 2.5 or more.

The rubber composition constituting the sidewall portion may not contain silica, and the amount of silica may be 0 parts by mass. When the rubber composition constituting the sidewall portion contains silica, the amount of silica per 100 parts by mass of the rubber component is not particularly limited, and may be, for example, more than 1 part by mass, more than 3 parts by mass, or more than 5 parts by mass.

(Other fillers)
As the filler, in addition to carbon black and silica, other fillers may be used. Such fillers are not particularly limited, and any filler commonly used in this field, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, etc., may be used. In addition to these fillers, biochar may be used as appropriate. These fillers may be used alone or in combination of two or more.

(Silane coupling agent)
Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used. Examples of the silane coupling agent include mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; Examples of the silane coupling agent include thioester-based silane coupling agents such as mercaptosilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, it is preferable to contain a sulfide-based silane coupling agent and/or a mercapto-based silane coupling agent. As the silane coupling agent, for example, those commercially available from Momentive, Inc. can be used. These silane coupling agents may be used alone or in combination of two or more.

When a silane coupling agent is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Also, from the viewpoint of preventing a decrease in abrasion resistance, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

The content of the silane coupling agent relative to 100 parts by mass of silica is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, from the viewpoint of increasing the dispersibility of the silica. Also, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

<Other compounding agents>
In addition to the above-mentioned components, the rubber composition according to the present invention may appropriately contain compounding agents generally used in the tire industry, such as plasticizers, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

(Plasticizer)
The rubber composition according to the present invention preferably contains a plasticizer, such as a resin, an oil, or a liquid rubber.

The resin is not particularly limited, but examples thereof include petroleum resins, terpene resins, rosin resins, and phenol resins commonly used in the tire industry, and these may be hydrogenated. These resins may be used alone or in combination of two or more types.

In this specification, "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5 petroleum resin, a cyclopentadiene resin is preferably used. Examples of cyclopentadiene resins include dicyclopentadiene resin (DCPD resin), cyclopentadiene resin, methylcyclopentadiene resin (non-hydrogenated cyclopentadiene resin), and these cyclopentadiene resins that have been subjected to a hydrogenation treatment (hydrogenated cyclopentadiene resin). As a cyclopentadiene resin, for example, commercially available products from ExxonMobil Chemical Corporation can be used.

In this specification, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are preferably used include coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin.

As the aromatic vinyl resin, a homopolymer of an α-methylstyrene derivative or a styrene derivative, or a copolymer of an α-methylstyrene derivative and a styrene derivative and/or indene is preferred because it is economical, easy to process, and has excellent heat generation properties. The above-mentioned "α-methylstyrene derivative" means an α-methylstyrene compound even if the benzene ring is substituted (preferably, an α-methylstyrene compound in which the benzene ring may be substituted with a saturated hydrocarbon group having 1 to 4 carbon atoms), and the above-mentioned "styrene derivative" means a styrene compound even if the benzene ring is substituted (preferably, a styrene compound in which the benzene ring may be substituted with a saturated hydrocarbon group having 1 to 4 carbon atoms). As the aromatic vinyl resin, for example, those commercially available from Mitsui Chemicals, Inc., Kraton, Eastman Chemical Co., etc. can be used.

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

Examples of terpene resins include polyterpene resins made of at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, and other terpene compounds; aromatic modified terpene resins made from the above terpene compounds and aromatic compounds; terpene phenolic resins made from terpene compounds and phenolic compounds; and terpene resins that have been subjected to hydrogenation treatment (hydrogenated terpene resins). Examples of aromatic compounds that are raw materials for aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that are raw materials for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. Examples of terpene resins that can be used include commercially available products from Yasuhara Chemical Co., Ltd., etc.

The rosin-based resin is not particularly limited, but examples thereof include natural rosin resin, modified rosin resin, etc. As the rosin-based resin, for example, those commercially available from Arakawa Chemical Industries Co., Ltd., Harima Chemical Co., Ltd., etc. can be used.

Phenol-based resins include, but are not limited to, phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, oil-modified phenol formaldehyde resin, etc.

The resin is preferably one or more selected from the group consisting of petroleum resins and terpene resins, and more preferably one or more selected from the group consisting of cyclopentadiene resins, aromatic vinyl resins, and terpene resins.

When resin is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. The content of resin is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

Examples of oils include process oil, vegetable oils and fats, and animal oils and fats. Examples of the process oil include paraffin-based process oil, naphthenic process oil, and aromatic process oil. In addition, as an environmental measure, process oil with a low content of polycyclic aromatic compound (PCA) compounds can be used. Examples of the low PCA content process oil include mild extract solvates (MES), treated distillate aromatic extracts (TDAE), and heavy naphthenic oil. In addition, from the viewpoint of life cycle assessment, waste oil after use in rubber mixers and engines, and refined waste edible oil used in restaurants may be used.

When oil is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 6 parts by mass or more, and particularly preferably 9 parts by mass or more, from the viewpoint of processability. Also, from the viewpoint of abrasion resistance, the content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less.

In the rubber composition of the present invention, the content of the plasticizer per 100 parts by mass of the rubber component (the total amount when multiple plasticizers are used in combination) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 18 parts by mass or more, and particularly preferably 25 parts by mass or more. The content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less.

When wax is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of weather resistance of the rubber. Also, from the viewpoint of preventing whitening of the tire due to bloom, the content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. Examples of processing aids that can be used include those commercially available from Schill+Seilacher, Performance Additives, etc.

When a processing aid is included, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of improving processability. Also, from the viewpoint of abrasion resistance and breaking strength, the content is preferably 10 parts by mass or less, and more preferably 8.0 parts by mass or less.

The tire of the present invention preferably contains an antioxidant to improve durability after ozone degradation.

Examples of antioxidants include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as antioxidants such as metal carbamates. Examples of amine-based antioxidants include amine-ketone-based and aromatic secondary amine-based compounds, and it is preferable to include aromatic secondary amine-based compounds. From the viewpoint of suppressing the occurrence and progression of cracks in the presence of ozone, it is more preferable to include a phenylenediamine-based antioxidant among aromatic secondary amine-based compounds. Examples of phenylenediamine-based antiaging agents include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and among these, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine is preferably used. These antiaging agents may be used alone or in combination of two or more.

The content S1 of the phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the rubber composition constituting the tread portion can be 0 parts by mass, but from the viewpoint of the durability performance of the tread portion, it is preferably 0.1 parts by mass or more, and more preferably more than 0.1 parts by mass. On the other hand, from the viewpoint of the effects of the present invention, the upper limit value of S1 is less than 1.0 part by mass, preferably less than 0.8 parts by mass, more preferably less than 0.7 parts by mass, even more preferably less than 0.6 parts by mass, and particularly preferably less than 0.5 parts by mass.

The content S2 of the phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is less than 1.0 part by mass, preferably less than 0.8 parts by mass, more preferably less than 0.6 parts by mass, even more preferably less than 0.5 parts by mass, even more preferably less than 0.4 parts by mass, and particularly preferably less than 0.3 parts by mass, from the viewpoint of the effects of the present invention. The lower limit value of S2 is not particularly limited, and can be, for example, 0 parts by mass, 0.1 parts by mass or more, more than 0.1 parts by mass, or more than 0.2 parts by mass.

In the present invention, S1+S2 is less than 1.0 part by mass, preferably less than 0.8 part by mass, more preferably less than 0.7 part by mass, even more preferably less than 0.6 part by mass, and particularly preferably less than 0.5 part by mass. The lower limit of S1+S2 can be set to 0 part by mass, but from the viewpoint of durability of the tread portion, it is preferably 0.1 part by mass or more, and more preferably more than 0.1 part by mass. By setting S1+S2 within the above range, it is possible to improve ozone durability while preventing deterioration of durability due to poor adhesion.

Quinoline-based antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, poly(2,2,4-trimethyl-1,2-dihydroquinoline), etc. In the present invention, the rubber composition constituting the tread portion preferably contains a quinoline-based antioxidant.

From the viewpoint of the effects of the present invention, the total content of the anti-aging agent per 100 parts by mass of the rubber component (the total amount of all the anti-aging agents when multiple anti-aging agents are used in combination) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more. Also, from the viewpoint of abrasion resistance and grip performance, it is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

When stearic acid is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Also, from the viewpoint of vulcanization speed, the content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability. Also, from the viewpoint of abrasion resistance, the content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

Sulfur is preferably used as a vulcanizing agent. Examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

When sulfur is used as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. From the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, even more preferably 3.0 parts by mass or less, and particularly preferably 2.5 parts by mass or less. Note that when oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur contained in the oil-containing sulfur.

Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. These vulcanizing agents other than sulfur can be commercially available from Taoka Chemical Co., Ltd., LANXESS Co., Ltd., Flexis, etc.

Examples of vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, or xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred, and sulfenamide-based vulcanization accelerators are more preferred.

Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS). Of these, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Of these, 2-mercaptobenzothiazole is preferred.

When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component (the total amount when multiple vulcanization accelerators are used in combination) is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 2.5 parts by mass or more. The content is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By keeping the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

<Manufacturing>
The rubber composition according to the present invention can be produced by a known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

The kneading process includes, for example, a base kneading process in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) process in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading process and kneaded. Furthermore, the base kneading process can be divided into multiple processes as desired.

The kneading conditions are not particularly limited, but examples include a method in which the base kneading process involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and in the final kneading process, kneading for 1 to 5 minutes at 70 to 110°C. The vulcanization conditions are not particularly limited, but examples include a method in which vulcanization is performed for 10 to 30 minutes at 150 to 200°C.

The tire of the present invention can be manufactured by a conventional method. That is, the unvulcanized rubber composition corresponding to each rubber layer obtained by the above method is extruded to match the shape of each rubber layer using an extruder equipped with a die of a predetermined shape, and then laminated together with other tire components on a tire building machine and molded by a conventional method to form an unvulcanized tire. The unvulcanized tire is then heated and pressurized in a vulcanizer to manufacture the tire. The vulcanization conditions are not particularly limited, and an example of the method is vulcanization at 150 to 200°C for 10 to 30 minutes.

<Applications>
The tire of the present invention can be suitably used as a passenger car tire, a truck/bus tire, a two-wheeled vehicle tire, or a racing tire, and is particularly preferably used as a passenger car tire. Note that a passenger car tire refers to a tire that is intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or less. The tire of the present invention can also be used as an all-season tire, a summer tire, or a winter tire such as a studless tire.

Tires having tread and sidewall portions made from rubber compositions obtained by varying the compounding using various chemicals shown below were examined, and the results calculated based on the evaluation method described below are shown below.
Copolymer A1: A copolymer produced in Production Example 1 described later (ethylene-farnesene copolymer, Mw: 450,000, Tg: -55°C)
Copolymer A2: A copolymer produced in Production Example 2 described later (ethylene-fernesene copolymer, Mw: 460,000, Tg: -64°C)
Copolymer A3: A copolymer produced in Production Example 3 described later (ethylene-myrcene copolymer, Mw: 450,000, Tg: -55°C)
Copolymer 1: A copolymer produced in Production Example 4 described later (farnesene polymer, Mw: 760,000, Tg: -70°C)
SBR: Nipol NS616 manufactured by ZS Elastomers Co., Ltd. (S-SBR, styrene content: 21.0% by mass, vinyl content: 61 mol%, Tg: -25°C, Mw: 510,000, non-oil extended)
BR: UBEPOL BR (registered trademark) 150B manufactured by UBE Co., Ltd. (cis content: 97 mol%, Mw: 440,000)
NR: TSR20
EPDM: Esprene (registered trademark) EPDM 505A manufactured by Sumitomo Chemical Co., Ltd. (ethylene content: 50%, diene content: 9.5%, non-oil extended)
Carbon black 1: Diablack (registered trademark) N220 ( _N2SA : 114 ^m2 /g) manufactured by Mitsubishi Chemical Corporation
Carbon black 2: Diablack (registered trademark) N330 ( _N2SA : 79 ^m2 /g) manufactured by Mitsubishi Chemical Corporation
Carbon black 3: Diablack (registered trademark) E (FEF, N550, _N2SA : 41 ^m2 /g) manufactured by Mitsubishi Chemical Corporation
Silica: ULTRASIL VN3 manufactured by Evonik Degussa ( _N2SA : 175 ^m2 /g, average primary particle size: 17 nm)
Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Evonik Degussa
Oil: H&R VivaTec 400 (TDAE oil)
Resin: Sylvares SA85 (a copolymer of α-methylstyrene and styrene) manufactured by Kraton
Wax: Ozoace 0355 by Nippon Seiro Co., Ltd.
Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corp. Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator 1: Noccela NS (N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Preparation Example 1: Preparation of Copolymer A1 Cocatalyst, butyroctylmagnesium (manufactured by Lanxess), and metallocene B are added to a reactor containing methylcyclohexane. The mixture is stirred at 20°C for 10 minutes to allow alkylation. Farnesene and ethylene are then continuously added in the amounts shown in Table 1, and the polymerization reaction is carried out at 40°C and 0.8 MPa. The polymerization reaction is terminated by cooling, degassing, and adding ethanol. An antioxidant is added to the polymer solution produced by the polymerization reaction, and the solution is dried in an oven under vacuum to obtain Copolymer A1.

Preparation Example 2: Preparation of Copolymer A2 Cocatalyst, butyroctylmagnesium (manufactured by Lanxess), and metallocene B are added to a reactor containing methylcyclohexane. The mixture is stirred at 20°C for 10 minutes to allow alkylation. Farnesene and ethylene are then added continuously in the amounts shown in Table 1, and the polymerization reaction is carried out at 40°C and 0.8 MPa. The polymerization reaction is terminated by cooling, degassing, and adding ethanol. An antioxidant is added to the polymer solution produced by the polymerization reaction, and the solution is dried in an oven under vacuum to obtain Copolymer A2.

Preparation Example 3: Preparation of Copolymer A3 Cocatalyst, butyroctylmagnesium (manufactured by Lanxess), and metallocene B are added to a reactor containing methylcyclohexane. The mixture is stirred at 20°C for 10 minutes to allow alkylation. Myrcene and ethylene are then added continuously in the amounts shown in Table 1, and the polymerization reaction is carried out at 80°C and 0.8 MPa. The polymerization reaction is stopped by cooling, degassing, and adding ethanol. An antioxidant is added to the polymer solution produced by the polymerization reaction, and the solution is dried in an oven under vacuum to obtain Copolymer A3.

Production Example 4: Production of Copolymer 1 In a nitrogen-substituted and dried pressure vessel, 9,500 g of cyclohexane as a solvent and 3.5 g of a 10.5 mass% cyclohexane solution of sec-butyllithium (0.37 g of sec-butyllithium) as an organometallic initiator are charged, and the temperature is raised to 70°C, and then 15.1 g of tetrahydrofuran is charged, and a mixture of 518 g of styrene and 777 g of butadiene prepared in advance is added at 10 mL/min to polymerize for 30 minutes. Next, 15.1 g of β-farnesene is added and polymerized for 30 minutes, and then 0.08 g of tetraethoxysilane is added as a coupling agent and reacted for 1 hour. 0.2 g of methanol is added to the obtained polymerization reaction solution to stop the polymerization reaction, and then 491 g of TDAE is added, and the mixture is dried with hot air at 70°C for 24 hours and dried under reduced pressure for 12 hours to obtain Copolymer 1.

The compositions of Copolymers A1 to A3 and Copolymer 1 are shown in Table 1.

Examples and Comparative Examples
According to the compounding recipes shown in Tables 2 and 3, chemicals other than sulfur and vulcanization accelerator are kneaded for 1 to 10 minutes using a 1.7 L closed type Banbury mixer until the discharge temperature reaches 150 to 160°C, to obtain a kneaded product. Next, sulfur and vulcanization accelerator are added to the kneaded product obtained using a two-screw open roll, and the mixture is kneaded for 4 minutes until the temperature reaches 105°C, to obtain an unvulcanized rubber composition. The unvulcanized rubber composition obtained is molded according to the shape of each layer of the tread part (thickness: 10.0 mm, in the case of two layers, the first layer thickness is 6.0 mm, the second layer thickness is 4.0 mm) or the sidewall part, and the rubber is laminated with other tire components as shown in Table 4 and press-vulcanized at 170°C for 12 minutes to obtain a test tire.

<Peel strength>
Each unvulcanized rubber composition is overlaid with an unvulcanized rubber composition containing C5, and press-vulcanized for 15 minutes at 170°C to obtain a vulcanized rubber composition. At this time, cellophane is sandwiched about 60 mm from the end to provide a grip for the tester, and the vulcanization is performed. The obtained vulcanized and bonded composition is subjected to an adhesion performance test in accordance with JIS K 6256 (peel test between cloth and vulcanized rubber). A test piece with a width of 25 mm is prepared and peeled at a speed of 50 mm/min, and the peel strength of the reference rubber (C5+C5) is expressed as an index, with 100 being the peel strength.

<Measurement of 30 tan δ _T >
Each vulcanized rubber test piece was cut out from the first layer of the tread portion of each test tire to a length of 20 mm, a width of 4 mm, and a thickness of 1 mm, with the long side in the tire circumferential direction. The loss tangent (tan δ) of each test piece was measured using a dynamic viscoelasticity measuring device (Iplexer series manufactured by GABO Corporation) under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode.

<Sidewall breaking strength and breaking elongation measurement>
A 1 mm-thick No. 7 dumbbell-shaped test piece was prepared from the sidewall of each test tire so that the tire circumferential direction was the vertical direction. A tensile test was carried out in accordance with JIS K 6251 "Vulcanized rubber and thermoplastic rubber - Determination of tensile test characteristics" at an atmosphere of 23°C and a tensile speed of 3.3 mm/sec to measure the breaking strength (TB) (MPa) and breaking elongation (EB) (%).

<Durability after ozone degradation>
Each test tire is left for 24 hours in a controlled room with a temperature of 40°C and an ozone concentration of 50±5 ppm, and exposed to ozone. Each test tire after exposure to ozone is mounted on four wheels of a domestic FF passenger car with an engine displacement of 2000cc, and the internal pressure is adjusted to 250 kPa. In an overloaded state, the tire runs 10 laps at a speed of 50 km/h on a test course with a dry road surface, and repeats the movement of climbing over unevenness on the road surface at a speed of 80 km/h 10 times. The tire is again run around at a speed of 50 km/h, and the speed is gradually increased and the speed at the time when the test driver feels something unusual is recorded. The speed of the target tire (Comparative Example 3) is set to 100, and the durability performance after ozone degradation of each tire is expressed as an index according to the following calculation formula. The higher the index, the better the durability performance after ozone degradation. Note that the tire of Comparative Example 2 is not indicated as an index, but is indicated as "-" because there is a concern that the tread part and the sidewall part may peel off.
(Durability index after ozone degradation) =
(speed of control tire)/(speed of each test tire) x 100

<Embodiment>
Examples of embodiments of the present invention are given below.
[1] A tire having a tread portion having at least one rubber layer, a sidewall portion, and a carcass layer,
the tread portion and the sidewall portion are each made of a rubber composition containing a rubber component,
At least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having an ethylene unit and a branched conjugated diene unit,
A tire in which, when the content of the phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion is S1 (parts by mass), and the content of the phenylenediamine-based antioxidant per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is S2 (parts by mass), S1 + S2 is less than 1.0 part by mass (preferably less than 0.8 part by mass, more preferably less than 0.7 part by mass, and even more preferably less than 0.6 part by mass).
[2] The tire according to the above [1], wherein the copolymer A is a random copolymer.
[3] The tire according to the above [1] or [2], wherein the branched conjugated diene unit in the copolymer A is 10 mol % or more (preferably 12 mol % or more, more preferably 15 mol % or more).
[4] The tire according to any one of the above [1] to [3], wherein the branched conjugated diene unit in the copolymer A is 30 mol % or less.
[5] The tire according to any one of the above [1] to [4], wherein the branched diene units contain a 3,4 configuration, and the 3,4 configuration accounts for 70 mol % or more (preferably 75 mol % or more) of all the branched conjugated diene units.
[6] The tire according to any one of the above [1] to [5], wherein the copolymer A has a glass transition temperature of −60° C. or higher.
[7] The tire according to any one of the above [1] to [6], wherein the copolymer A has a glass transition temperature of −40° C. or lower.
[8] The tire according to any one of the above [1] to [7], wherein the weight average molecular weight of the copolymer A is 10,000 or more (preferably 12,000 or more, more preferably 15,000 or more).
[9] The tire according to any one of the above [1] to [8], wherein the rubber composition constituting the sidewall portion has a breaking strength of 12 MPa or more and a breaking elongation of 600% or more.
[10] The tire according to any one of the above [1] to [9], wherein C _SW /T is 10 or more, where C _SW (mass %) is the content of copolymer A in the rubber component constituting the sidewall portion, and T (mm) is the thickness of the surface rubber layer at the maximum width position of the tire.
[11] The tire according to any one of the above [1] to [10], wherein C _SW /T is 60 or less, where C _SW (mass %) is the content of copolymer A in the rubber component constituting the sidewall portion, and T (mm) is the thickness of the surface rubber layer at the maximum width position of the tire.
[12] The tire according to any one of the above [1] to [11], wherein C _SW is 50 mass% or more (preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more).
[13] The tire according to any one of the above [1] to [12], wherein at least one rubber layer constituting the tread portion has a tan δ at 30° C. (30° C. tan δ _T ) of 0.35 or less (preferably 0.22 or less, more preferably 0.20 or less).
[14] _{The tire} according to any one of the above [1] to [13], wherein the content C of copolymer A in the rubber component of at least one rubber layer constituting the tread portion is 60 mass% or more (preferably 70 mass% or more, more preferably 80 mass% or more).
[15] The tire according to any one of [1] to [14] above, wherein S1 is 0.1 parts by mass or more.

Reference Signs List 1 Tread portion 2 Belt 3 Land portion 4 Line segment connecting tread surface ends 5 Extension of outer surface of second layer 6 First layer 7 Second layer 12 Circumferential groove 21 Bead core 22 Bead apex 25 Strip apex 31 Sidewall 32 Inner liner 33 Carcass CL Tire center line PW Normal line T at maximum tire width position Thickness P of surface rubber layer Midpoint N of land portion in tire width direction Normal line t1 drawn from point P Thickness t2 of first tread layer

Claims (15)

A tire having a tread portion having at least one rubber layer, a sidewall portion, and a carcass layer,
the tread portion and the sidewall portion are each made of a rubber composition containing a rubber component,
At least one of the rubber component constituting the tread portion and the rubber component constituting the sidewall portion contains a copolymer A having an ethylene unit and a branched conjugated diene unit,
A tire in which, when the content of the phenylenediamine-based anti-aging agent per 100 parts by mass of the rubber component of the tread rubber constituting the tread portion is S1 (parts by mass), and the content of the phenylenediamine-based anti-aging agent per 100 parts by mass of the rubber component of the rubber composition constituting the sidewall portion is S2 (parts by mass), S1 + S2 is less than 1.0 part by mass. The tire according to claim 1, wherein the copolymer A is a random copolymer. The tire according to claim 1 or 2, wherein the branched conjugated diene units in the copolymer A are 10 mol % or more. The tire according to claim 1 or 2, wherein the branched conjugated diene units in the copolymer A are 30 mol % or less. The tire according to claim 1 or 2, wherein the branched diene units include a 3,4 configuration, and the 3,4 configuration is 70 mol % or more of the total branched conjugated diene units. The tire according to claim 1 or 2, wherein the glass transition temperature of the copolymer A is -60°C or higher. The tire according to claim 1 or 2, wherein the glass transition temperature of the copolymer A is -40°C or lower. The tire according to claim 1 or 2, wherein the weight average molecular weight of the copolymer A is 10,000 or more. The tire according to claim 1 or 2, wherein the rubber composition constituting the sidewall portion has a breaking strength of 12 MPa or more and a breaking elongation of 600% or more. 3. The tire according to claim 1, wherein C _SW /T is 10 or more, where C _SW (mass %) is the content of copolymer A in the rubber component constituting the sidewall portion and T (mm) is the thickness of the surface rubber layer at the maximum width position of the tire. 3. The tire according to claim 1, wherein C _SW /T is 60 or less, where C _SW (mass %) is the content of copolymer A in the rubber component constituting the sidewall portion and T (mm) is the thickness of the surface rubber layer at the maximum width position of the tire. 3. The tire according to claim 1 or 2, wherein C _SW is 50 mass % or more. 3. The tire according to claim 1, wherein at least one rubber layer constituting the tread portion has a tan δ at 30° C. (30° C. tan δ _T ) of 0.35 or less. 3. The tire according to claim 1, wherein the content C _T of copolymer A in the rubber component of at least one rubber layer constituting the tread portion is 60% by mass or more. The tire according to claim 1 or 2, in which S1 is 0.1 parts by mass or more.

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