JP2023104871A - tire - Google Patents

Abstract

To provide a tire improved in uneven wear resistance performance.SOLUTION: A tire comprises a tread part in which a direction of mounting on a vehicle is designated. The tread part has an inner tread rubber layer that constitutes an inner end part side of the vehicle when the tread part is mounted on the vehicle and an outer tread rubber layer constituting an outer end part side of the vehicle. The inner tread rubber layer and the outer tread rubber layer are constituted of rubber compositions including rubber components. The rubber components constituting the outer tread rubber layer include copolymers in which aromatic vinyl compounds and conjugated diene compounds are copolymerized and some of the conjugated diene compounds are hydrogenated. Contents of carbon black with respect to 100 pts.mass of the rubber components of the rubber compositions constituting the outer tread rubber layer are larger than contents of carbon black with respect to 100 pts.mass of the rubber components of the rubber compositions forming the inner tread rubber layer.SELECTED DRAWING: None

Description

The present disclosure relates to tires.

A conventional pneumatic tire has a problem that uneven wear tends to occur in left and right shoulder land portions of the tire due to imbalance in rigidity between the vehicle inner region and the vehicle outer region when the tire is mounted on the vehicle. Patent Literature 1 discloses a tire in which uneven wear is suppressed by having a ground-contacting surface of a shoulder rib having an arcuate shape that protrudes inward in the tire radial direction when viewed in cross section in the tire meridian direction.

JP-A-5-77608

An object of the present disclosure is to provide a tire with improved uneven wear resistance performance.

As a result of intensive study, in a tire having a tread portion with a specified mounting direction to a vehicle, the tread portion is composed of an inner tread rubber layer constituting a vehicle inner end side when mounted on a vehicle and a vehicle outer end side. A specific hydrogenated rubber component is compounded in the outer tread rubber layer, and the carbon black content of the outer tread rubber layer is higher than the carbon black content of the inner tread rubber layer. It has been found that the above problems can be solved by increasing the

That is, the present disclosure is a tire having a tread portion with a specified mounting direction to a vehicle, wherein the tread portion includes an inner tread rubber layer forming a vehicle inner end side when mounted on a vehicle, and a vehicle outer end portion. the inner tread rubber layer and the outer tread rubber layer are composed of a rubber composition containing a rubber component; and the rubber component constituting the outer tread rubber layer is aromatic Carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer, which contains a copolymer obtained by copolymerizing a vinyl compound and a conjugated diene compound and partially hydrogenating the conjugated diene portion. is greater than the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer.

According to the present disclosure, a tire with improved uneven wear resistance performance is provided.

1 is a cross-sectional view of a tire according to one embodiment of the present disclosure; FIG.

A tire that is an embodiment of the present disclosure is a tire having a tread portion with a specified mounting direction to a vehicle, wherein the tread portion includes an inner tread rubber layer that constitutes an inner end side of the vehicle when mounted on the vehicle. and an outer tread rubber layer forming a vehicle outer end side, wherein the inner tread rubber layer and the outer tread rubber layer are made of a rubber composition containing a rubber component, and the rubber forming the outer tread rubber layer A rubber component 100 of a rubber composition comprising a copolymer in which an aromatic vinyl compound and a conjugated diene compound are copolymerized and a part of the conjugated diene portion is hydrogenated, and which constitutes the outer tread rubber layer. In the tire, the content of carbon black per part by mass is greater than the content of carbon black per 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer.

Obtained by blending a specific hydrogenated rubber component in the outer tread rubber layer and making the carbon black content of the outer tread rubber layer higher than the carbon black content of the inner tread rubber layer. The tire has improved uneven wear resistance performance. The reason for this is considered as follows, although it is not intended to be bound by theory.

During cornering, the outer side of the vehicle is mainly in contact with the ground, so the contact pressure on the outer side of the vehicle increases and uneven wear tends to occur. Since the hydrogenated copolymer has few double bonds and few cross-linking points, the density of cross-linking is less likely to occur and breakage due to stress concentration is less likely to occur. Therefore, it is considered that the wear resistance performance of the tread is improved by blending such a hydrogenated copolymer. In addition, during cornering, the temperature of the tread on the outside of the vehicle is higher than that on the inside of the vehicle, so the grip of the tread on the outside of the vehicle decreases and the amount of slip increases, which tends to cause uneven wear. Therefore, by making the content of carbon black in the outer tread rubber layer larger than the content of carbon black in the inner tread rubber layer, the heat generation of the outer tread rubber layer is relatively increased, and the grip on the outer side of the vehicle is increased. can. From this, it is considered that the amount of slippage on the vehicle outer side and the vehicle inner side of the tread can be made uniform, and uneven wear can be further suppressed. And it is thought that these work together to achieve a noteworthy effect of markedly improving uneven wear resistance performance.

The rubber composition constituting the outer tread rubber layer preferably contains 30 parts by mass or more of carbon black based on 100 parts by mass of the rubber component, from the viewpoint of increasing heat generation during cornering and suppressing slippage.

The rubber composition constituting the inner tread rubber layer should contain 90 parts by mass or more of silica with respect to 100 parts by mass of the rubber component from the viewpoint of improving wear resistance performance while lowering heat build-up than the outer tread rubber layer. is preferred.

The rubber composition forming the outer tread rubber layer preferably contains a hydrogenated petroleum resin from the viewpoint of homogenizing the inside of the rubber layer and suppressing uneven wear.

The tan δ at 30°C (30°C tan δ _out ) of the outer tread rubber layer is preferably greater than the tan δ at 30°C (30°C tan δ _in ) of the inner tread rubber layer.

By making the 30°C tan δ _out larger than the 30° C. tan δ _in , the heat generation of the outer tread rubber layer can be relatively increased, and the grip on the outer side of the vehicle can be increased. From this, it is considered that the amount of slippage on the vehicle outer side and the vehicle inner side of the tread can be made uniform, and uneven wear can be further suppressed.

The ratio of D from the outer vehicle edge to the interface between the inner tread rubber layer and the outer tread rubber layer to the distance W _L between the both edge edges ₍ D/WL) is preferably 0.50 or more.

By setting D/W _L within the above range, the outer rubber layer is likely to contact the ground during turning, and heat generation reduces slippage, thereby making it easier to improve uneven wear resistance.

The groove area ratio of the contact surface of the inner tread rubber layer is preferably larger than the groove area ratio of the contact surface of the outer tread rubber layer. Also, the difference between the groove area ratio of the contact surface of the inner tread rubber layer and the groove area ratio of the contact surface of the outer tread rubber layer (groove area ratio of the contact surface of the inner tread rubber layer - groove of the contact surface of the outer tread rubber layer area ratio) is preferably 2% or more and 10% or less.

By making the groove area ratio of the contact surface of the inner tread rubber layer larger than the groove area ratio of the contact surface of the outer tread rubber layer, the rigidity of the outer tread rubber layer can be increased, and the load on the outer tread rubber layer is high during cornering. deformation amount can be reduced. From this, it is considered that the wear of the outer tread rubber layer is suppressed, and thus uneven wear is easily suppressed.

The tread portion has land portions partitioned by two or more circumferential grooves extending continuously in the tire circumferential direction, and the land portion closest to the tire equatorial plane among the land portions has a width direction length on the tread surface. , preferably 18% or more of the contact width.

By setting the widthwise length of the land portion closest to the tire equatorial plane on the tread surface to the above range, buckling at the tread central portion is suppressed, and the outer tread layer tends to uniformly contact the ground. Conceivable.

30°C tan δ _out and D/W _L preferably satisfy the following formula (1).
30°C tan δ _out × (D/W _L )≧0.20 (1)

By setting the product of 30° C. tan δ _out and D/W _L within the above range, it is believed that sufficient rigidity and heat generation of the outer tread rubber layer can be ensured, and the effect of suppressing uneven wear is further improved.

<Definition>
"Regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. is “Measuring Rim”.

"Regular internal pressure" is the air pressure determined for each tire by each standard in the standard system including the standards on which tires are based. VARIOUS COLD INFLATION PRESSURES”, or “INFLATION PRESSURE” for ETRTO.

The "normal state" is a state in which the tire is mounted on a normal rim, is inflated to a normal internal pressure, and has no load. In this specification, unless otherwise specified, the dimensions of each part of the tire are measured in the normal condition.

"Normal load" is the load defined for each tire by each standard in the standard system including the standards on which tires are based. AT VARIOUS COLD INFLATION PRESSURES”, and for ETRTO, it is “LOAD CAPACITY”.

The "tread contact edge" is the outermost contact position in the tire width direction when the tire is in a normal condition and a normal load is applied and the tire contacts a flat surface with a camber angle of 0 degree.

"Distance D from the vehicle outer ground contact edge to the interface between the inner tread rubber layer and the outer tread rubber layer" is the distance between the vehicle outer contact edge on the ground contact surface and the inner tread rubber layer on the tread surface and the outer tread rubber layer. It refers to the straight line distance to the extended line of the rubber interface.

"Groove area ratio" is the ratio of all grooves to the total surface area assuming that all grooves are filled for each contact surface formed by the outer tread rubber layer and the inner tread rubber layer divided at the interface. It is the ratio of the total area.

"Aromatic vinyl unit" refers to a unit derived from an aromatic vinyl compound in a copolymer. Here, the aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group and does not include a conjugated diene compound described later. Specific examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4, Examples include 6-trimethylstyrene, and styrene is preferred. These may be used individually by 1 type, and may use 2 or more types together.

The "aromatic vinyl unit content in the rubber component" is the total content (% by mass) of aromatic vinyl units such as styrene units contained in 100% by mass of the rubber component, and for each rubber component, It is a value obtained by multiplying the aromatic vinyl unit content (% by mass) by the mass fraction in the rubber component, and summing the values. Specifically, it is calculated by Σ(aromatic vinyl unit content (% by mass) of each aromatic vinyl unit-containing rubber×content (% by mass) in the rubber component of each aromatic vinyl unit-containing rubber/100). When the aromatic vinyl unit-containing rubber is styrene-butadiene rubber, it is "styrene content".

"Oil content" also includes the amount of oil contained in the oil-extended rubber.

<Measurement method>
The "groove area ratio" is calculated from the contact shape when the tread is pressed against a flat surface under a normal load. After mounting the tire on the regular rim and maintaining the regular internal pressure, for example, ink is applied to the tread, the regular load is applied, and the tire is pressed vertically against cardboard or the like (camber angle is 0°). , is obtained by transferring the ink applied to the tread portion. Then, by dividing the obtained contact shape at the dividing interface between the outer tread rubber layer and the inner tread rubber layer, the groove area ratio of the contact surface of the outer tread rubber layer and the groove area of the contact surface of the inner tread rubber layer A ratio can be calculated for each.

“30° C. tan δ” is the loss tangent measured under the conditions of temperature of 30° C., frequency of 10 Hz, initial strain of 5%, dynamic strain of ±1%, and extension mode. A sample for loss tangent measurement is a vulcanized rubber composition of length 20 mm×width 4 mm×thickness 1 mm. When it is cut out from a tire, it is cut out from the tread portion of the tire such that the tire circumferential direction is the long side and the tire radial direction is the thickness direction.

"Aromatic vinyl unit content" is a value calculated by ¹ H-NMR measurement, and is, for example, a copolymer of an aromatic vinyl compound and a conjugated diene compound (including hydrogenated products of the copolymer). It is applied to a rubber component (aromatic vinyl unit-containing rubber) having a repeating unit derived from an aromatic vinyl compound such as.

"Cis content (cis-1,4-bonded butadiene unit amount)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2: 2017. For example, repeats derived from butadiene such as BR Applies to rubber components with units.

The glass transition temperature (Tg) of the hydrogenated copolymer and SBR was determined according to JIS K 7121 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan Co., Ltd. at a heating rate of 10 ° C. /min.

"Weight average molecular weight (Mw)" is measured by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ manufactured by Tosoh Corporation. -M), it can be determined by standard polystyrene conversion. For example, it is applied to SBR, BR, and the like.

“Nitrogen adsorption specific surface area (N ₂ SA) of carbon black” is measured according to JIS K 6217-2:2017. “Carbon black oil absorption (DBP oil absorption (OAN))” is measured according to JIS K6217-4:2017.

"Nitrogen adsorption specific surface area (N ₂ SA) of silica" is measured by the BET method according to ASTM D3037-93. The "average primary particle size of silica" can be obtained by observing with a transmission or scanning electron microscope, measuring 400 or more primary particles of silica observed in the field of view, and averaging them.

The "softening point of the resin component" is the temperature at which the softening point specified in JIS K 6220-1:2015 7.7 is measured with a ring and ball type softening point measuring device, and the sphere descends.

A procedure for making a tire that is an embodiment of the present disclosure will be described in detail below. However, the following description is an example for explaining the present disclosure, and is not intended to limit the technical scope of the present disclosure only to this description range.

<Tire>
A tire according to an embodiment of the present disclosure will be described below with reference to the drawings.

As shown in FIG. 1, a tire T includes a pair of bead portions 1 and sidewall portions 2 extending outward from each bead portion 1 in a tire radial direction RD (vertical direction in FIG. 1; hereinafter simply referred to as the tire radial direction). , a tread portion 3 connected to the tire radial direction RD outer ends of both sidewall portions 2 , and a toroidal carcass layer 4 extending from the tread portion 3 to the bead portion 1 via the sidewall portion 2 . A bead core 1 a and a bead filler 1 b are arranged in the bead portion 1 . The carcass layer 4 is provided between the pair of bead portions 1 and is composed of at least one carcass ply, and the end portion thereof is wound up through the bead core 1a and locked. The carcass ply is formed by covering a cord extending substantially perpendicular to the tire equator with a topping rubber. Inside the carcass layer 4, an inner liner rubber 4a for retaining air pressure is arranged. Furthermore, a sidewall rubber 6 is provided outside the carcass layer 4 in the sidewall portion 2 . A rim strip rubber 7 is provided on the outer side of the carcass layer 4 in the bead portion 1 so as to come into contact with a rim (not shown) when the tire is mounted on the rim.

The tire according to the present disclosure has a specified mounting direction with respect to the vehicle, and the mounting direction with respect to the vehicle (for example, indicating that it is the inner side or the outer side) is displayed on the side surface of the tire.

The tread portion 3 has an outer tread edge To and an inner tread edge Ti. The outer tread edge To is located on the outside of the vehicle (on the right side in FIG. 1) when the tire is mounted on the vehicle. The inner tread end Ti is positioned on the inner side of the vehicle (on the left side in FIG. 1) when the tire is mounted on the vehicle. Each tread edge To, Ti is the most in the tire width direction W (left and right direction in FIG. 1) when a normal load is applied to the tire in a normal state and the tire contacts a flat surface with a camber angle of 0 degrees. ) is the outer ground position.

In FIG. 1 , the tread portion 3 has a cap portion 50 forming a contact surface and a base portion 51 provided inside the cap portion 50 in the tire radial direction. The cap portion 50 has an inner tread rubber layer 52 forming a vehicle inner end side when mounted on a vehicle, and an outer tread rubber layer 53 forming a vehicle outer end side. A wing rubber may be provided on the outside of the inner tread rubber layer 52 and the outer tread rubber layer 53 . In addition, when the wing rubber is provided, or when the sidewall portion is in a form that covers the radially outer side of the tread, even if these form a contact surface, the inner tread rubber and the outer tread rubber of the present disclosure shall not apply. The interface P between the inner tread rubber layer and the outer tread rubber layer from the vehicle outer ground edge is located under the circumferential groove 5a in FIG. You can place it below. The term “land portion” refers to a region of the tread portion 3 partitioned by the tread edges To, Ti and a plurality of circumferential grooves 5a continuously extending in the tire circumferential direction.

The ratio (D/W _L ) of the distance D from the outer tread edge of the vehicle to the interface _P between the inner tread rubber layer and the outer tread rubber layer to the distance WL between the outer tread edge To and the inner tread edge Ti is , is preferably 0.40 or more, more preferably 0.45 or more, still more preferably 0.50 or more, and particularly preferably 0.55 or more. By setting D/W _L within the above range, it is believed that the outer rubber layer is more likely to contact the ground during turning, reducing slippage due to heat generation, and making it easier to improve uneven wear resistance. From the viewpoint of the effect of the present disclosure, D/W _L is preferably 0.90 or less, more preferably 0.86 or less, even more preferably 0.83 or less, and particularly preferably 0.80 or less.

The groove area ratio of the contact surface of the inner tread rubber layer is preferably larger than the groove area ratio of the contact surface of the outer tread rubber layer. By making the groove area ratio of the contact surface of the inner tread rubber layer larger than the groove area ratio of the contact surface of the outer tread rubber layer, the rigidity of the outer tread rubber layer can be increased, and the load on the outer tread rubber layer is high during cornering. deformation amount can be reduced. From this, it is considered that the wear of the outer tread rubber layer is suppressed, and thus uneven wear is easily suppressed.

The groove area ratio of the contact surface of the outer tread rubber layer is preferably 4% or more, more preferably 7% or more, and even more preferably 10% or more. Further, the groove area ratio of the contact surface of the outer tread rubber layer is preferably 40% or less, more preferably 35% or less, and even more preferably 30% or less.

The groove area ratio of the contact surface of the inner tread rubber layer is preferably 8% or more, more preferably 10% or more, and even more preferably 12% or more. Further, the groove area ratio of the contact surface of the inner tread rubber layer is preferably 45% or less, more preferably 40% or less, and even more preferably 35% or less.

From the viewpoint of the effect of the present disclosure, the difference between the groove area ratio of the contact surface of the inner tread rubber layer and the groove area ratio of the contact surface of the outer tread rubber layer is preferably 2% or more and 10% or less, and 3% or more and 9%. The following is more preferable, and 4% or more and 8% or less is even more preferable.

The tan δ at 30°C (30°C tan δ _out ) of the outer tread rubber layer is preferably greater than the tan δ at 30°C (30°C tan δ _in ) of the inner tread rubber layer. By making the 30°C tan δ _out larger than the 30° C. tan δ _in , the heat generation of the outer tread rubber layer can be relatively increased, and the grip on the outer side of the vehicle can be increased. From this, it is considered that the amount of slippage on the vehicle outer side and the vehicle inner side of the tread can be made uniform, and uneven wear can be further suppressed. The difference between 30° C. tan δ _out and 30° C. tan δ _in (30° C. tan δ _out −30° C. tan δ _in ) is preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more.

30°C tan δ _out is preferably 0.24 or more, more preferably 0.26 or more, still more preferably 0.28 or more, and particularly preferably 0.31 or more, from the viewpoint of improving grip and slipping. From the viewpoint of suppressing excessive heat generation, tan δ _out at 30°C is preferably 0.55 or less, more preferably 0.50 or less, still more preferably 0.48 or less, and particularly preferably 0.46 or less.

30°C tan δ _in is preferably 0.40 or less, more preferably 0.38 or less, and even more preferably 0.36 or less. Also, tan δ _in at 30° C. is preferably 0.12 or more, more preferably 0.15 or more, still more preferably 0.18 or more, and particularly preferably 0.21 or more.

The "30° C. tan δ" of the rubber composition of the present disclosure can be appropriately adjusted depending on the types and blending amounts of rubber components, fillers, softeners, etc. described later.

The product of 30° C. tan δ _out and D/W _L represented by the formula (1) is preferably 0.12 or more, more preferably 0.15 or more, further preferably 0.20 or more, and 0.25 or more. is more preferable, and 0.30 or more is particularly preferable. By setting the product of 30° C. tan δ _out and D/W _L within the above range, it is believed that sufficient rigidity and heat generation of the outer tread rubber layer can be ensured, and the effect of suppressing uneven wear is further improved. The product of tan δ _out at 30° C. and D/W _L is preferably 0.65 or less, more preferably 0.60 or less, still more preferably 0.50 or less, and particularly preferably 0.45 or less.

[Rubber composition]
Each rubber composition constituting the inner tread rubber layer 52 and the outer tread rubber layer 53 (hereinafter referred to as the rubber composition of the present disclosure unless otherwise specified) will be described in detail below. Unless otherwise specified, the following description of the rubber composition is common to both the inner tread rubber layer 52 and the outer tread rubber layer 53 .

<Rubber component>
In the rubber composition of the present disclosure, the rubber component constituting the outer tread rubber layer is a copolymer (hereinafter referred to as , sometimes simply referred to as a hydrogenated copolymer) as an essential component. Also, the rubber component of the present disclosure preferably contains a diene rubber. The rubber component constituting the outer tread rubber layer may be a rubber component consisting only of the hydrogenated copolymer and the diene rubber. The rubber component constituting the inner tread rubber layer may be a rubber component consisting only of diene rubber.

(Hydrogenated copolymer)
The hydrogenated copolymer of the present disclosure is obtained by polymerizing an aromatic vinyl compound and a conjugated diene compound by a known method (for example, the method described in JP-A-2020-79340). Can be synthesized by processing. The order of copolymerization is not particularly limited, and random copolymerization or block copolymerization may be used. Moreover, the hydrogenated copolymer may be synthesized by copolymerizing a monomer having a structure after hydrogenation.

An aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group and does not include a conjugated diene compound described later. Specific examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4, Examples include 6-trimethylstyrene, and styrene is preferred. These may be used individually by 1 type, and may use 2 or more types together.

Conjugated diene compounds include, for example, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. ,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. These may be used individually by 1 type, and may use 2 or more types together.

As a copolymer of an aromatic vinyl compound and a conjugated diene compound, a styrene-butadiene copolymer (SBR) is preferred. Therefore, as the hydrogenated copolymer, a copolymer (hydrogenated SBR) obtained by partially hydrogenating the conjugated diene portion of the styrene-butadiene copolymer is preferable.

The hydrogenation rate of the hydrogenated copolymer (preferably hydrogenated SBR) is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, and particularly preferably 70 mol% or more. Moreover, the hydrogenation rate of the hydrogenated copolymer is preferably 99 mol % or less, more preferably 98 mol % or less. Within the above range, the effects of the present disclosure tend to be obtained more favorably. The hydrogenation rate can be adjusted by adjusting reaction conditions such as hydrogen gas supply pressure and reaction temperature in the hydrogenation reaction as described in Production Examples 1 and 2 below. The degree of hydrogenation refers to the ratio of double bonds hydrogenated to the conjugated diene portion of the copolymer of the aromatic vinyl compound and the conjugated diene compound, and is obtained by measuring ¹ H-NMR. can be calculated from the spectral reduction rate of unsaturated bonds in the spectrum.

The aromatic vinyl unit content of the hydrogenated copolymer (styrene content when the hydrogenated copolymer is hydrogenated SBR) is appropriately selected, for example, so that the aromatic vinyl unit content in the rubber component satisfies the range described below. However, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The aromatic vinyl unit content of the hydrogenated copolymer 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 35% by mass or less. The aromatic vinyl unit content of the hydrogenated copolymer is measured by the measuring method described above.

From the viewpoint of the effects of the present disclosure, the weight average molecular weight (Mw) of the hydrogenated copolymer is preferably 100,000 or more, more preferably 200,000 or more, and even more preferably 300,000 or more. From the viewpoint of workability, the Mw of the multicomponent polymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, and even more preferably 800,000 or less.

The glass transition temperature (Tg) of the hydrogenated copolymer is preferably −90° C. or higher, more preferably −80° C. or higher, further preferably −70° C. or higher, and particularly −60° C. or higher, from the viewpoint of abrasion resistance performance. preferable. The Tg of the hydrogenated copolymer is preferably -10°C or lower, more preferably -15°C or lower, still more preferably -20°C or lower, and particularly preferably -25°C or lower.

The hydrogenated copolymer can also be modified into a functional group that interacts with silica. As such a functional group, any one commonly used in this field can be suitably used, and examples thereof include an amino group, a silanol group, an alkoxysilyl group and the like.

The content of the hydrogenated copolymer (preferably hydrogenated SBR, more preferably hydrogenated SBR with a hydrogenation rate of 50 mol% or more) in the rubber component constituting the outer tread rubber layer suppresses fracture due to stress concentration. However, from the viewpoint of improving the wear resistance performance of the tread, it is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The upper limit of the content is not particularly limited, but can be, for example, 100% by mass, 99% by mass or less, 95% by mass or less, or 90% by mass or less. The content of the hydrogenated copolymer in the rubber component that constitutes the inner tread rubber layer is not particularly limited, and may be appropriately selected, for example, so that the aromatic vinyl unit content in the rubber component satisfies the range described below. can be done.

(Diene rubber)
Examples of diene rubber include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber ( NBR) and the like. The rubber component constituting the outer tread rubber layer preferably contains at least one selected from the group consisting of isoprene rubber, BR, and SBR, and more preferably contains BR. The rubber component constituting the inner tread rubber layer preferably contains at least one selected from the group consisting of isoprene rubber, BR, and SBR, more preferably SBR, and contains SBR and BR. This is more preferable, and a rubber component consisting only of SBR and BR may be used. These diene rubbers may be used singly or in combination of two or more.

(SBR)
SBR is not particularly limited, and includes unmodified solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), modified SBR (modified S-SBR, modified E-SBR), and the like. Examples of the modified SBR include SBR whose terminal and/or main chain are modified, and modified SBR (condensate, branched structure, etc.) coupled with tin, a silicon compound, or the like.

The SBR listed above may be used singly or in combination of two or more. As the SBR listed above, for example, those commercially available from Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., ZS Elastomer Co., etc. can be used. can.

The styrene content of SBR can be appropriately selected, for example, so that the aromatic vinyl unit content in the rubber component satisfies the range described later, but is preferably 5% by mass or more, more preferably 10% by mass or more, and 15% by mass. % or more is more preferable. The styrene content of SBR is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. The styrene content of SBR is measured by the method for measuring aromatic vinyl unit content described above.

The glass transition temperature (Tg) of SBR is preferably −80° C. or higher, more preferably −70° C. or higher, and even more preferably −60° C. or higher, from the viewpoint of wear resistance performance. The Tg of SBR is preferably −20° C. or less, more preferably −25° C. or less, and even more preferably −30° C. or less.

The content of SBR in the rubber component constituting the inner tread rubber layer is preferably 40% by mass or more, more preferably 50% by mass or more, from the viewpoint of ensuring sufficient rigidity against heat transferred from the outer tread rubber layer. Preferably, 60% by mass or more is more preferable, and 70% by mass or more is particularly preferable. The upper limit of the content is not particularly limited, but can be, for example, 100% by mass, 99% by mass or less, 95% by mass or less, 90% by mass or less, and 85% by mass or less. The content of SBR in the rubber component constituting the outer tread rubber layer is not particularly limited, and can be appropriately selected, for example, so that the aromatic vinyl unit content in the rubber component satisfies the range described below.

(BR)
BR is not particularly limited, and 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), synthesized using a rare earth catalyst Rare earth-based butadiene rubber (rare earth-based BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc., which are commonly used in the tire industry can be used. can. These BRs may be used singly or in combination of two or more. The cis content of BR is measured by the above measuring method.

As Hi-cis BR, for example, those commercially available from Nippon Zeon Co., Ltd., Ube Industries, Ltd., JSR Corporation, etc. can be used. By containing high-cis BR, low-temperature characteristics and wear resistance performance can be improved. The cis content of high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, still more preferably 97 mol% or more, and particularly preferably 98 mol% or more. The cis content of BR is measured by the above measuring method.

The content of BR in the rubber component constituting the outer tread rubber layer is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less. 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 7% by mass or more.

The content of BR in the rubber component constituting the inner tread rubber layer is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less. 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 7% by mass or more.

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

When the isoprene-based rubber is contained, the content in the rubber component is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of the effects of the present disclosure. 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.

(Other rubber components)
The rubber component may contain rubber components other than the hydrogenated copolymer and the diene rubber within a range that does not affect the effects of the present disclosure. As other rubber components, crosslinkable rubber components commonly used in the tire industry can be used, such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, and chlorinated polyethylene. Rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. These other rubber components may be used singly or in combination of two or more. In addition to the above rubber component, it may or may not contain a known thermoplastic elastomer.

The aromatic vinyl unit content in the rubber component of the present disclosure is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 15% by mass or more, from the viewpoint of ensuring heat build-up in the tread portion and suppressing slippage. More preferred. In addition, from the viewpoint of the effect of the present disclosure, the aromatic vinyl unit content in the rubber component is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and further preferably 35% by mass or less. Preferably, 30% by mass or less is particularly preferable.

<Filler>
The rubber composition of the present disclosure preferably contains silica as a filler, and more preferably contains silica and carbon black. Moreover, it is good also as a filler which consists only of a silica and carbon black.

(Carbon black)
Carbon black is not particularly limited, and for example, those commonly used in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used. In addition to carbon black produced by burning general mineral oil, carbon black using biomass materials such as lignin may be used. These carbon blacks may be used singly or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 70 m ² /g or more, still more preferably 100 m ^{2 /g or more, and 120 m 2} /g or more, from the viewpoint of reinforcing properties and grip performance. ² /g or more is particularly preferred. From the viewpoint of dispersibility, it is preferably 250 m ² /g or less, more preferably 220 m ² /g or less. The N ₂ SA of carbon black is measured by the measuring method described above.

In the rubber composition of the present disclosure, the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer is carbon black relative to 100 parts by mass of the rubber component of the rubber composition constituting the inner tread rubber layer. It is characterized by having a higher content than black. By making the content of carbon black in the outer tread rubber layer higher than the content of carbon black in the inner tread rubber layer, heat generation in the outer tread rubber layer is relatively increased, and grip on the outer side of the vehicle can be increased. From this, it is considered that uneven wear can be further suppressed by suppressing slippage on the outer side of the vehicle and suppressing wear on the outer side where the load is large. The difference between the carbon black content per 100 parts by mass of the rubber component of the rubber composition forming the outer tread rubber layer and the carbon black content per 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer is , preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more. On the other hand, the ratio of the carbon black content per 100 parts by mass of the rubber component of the rubber composition forming the outer tread rubber layer to the carbon black content per 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer The upper limit of the difference is not particularly limited, but can be, for example, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less.

From the viewpoint of improving wear resistance and heat build-up, the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer is preferably 20 parts by mass or more, more preferably 25 parts by mass or more. , more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. Also, from the viewpoint of fuel economy performance, it is preferably 90 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 60 parts by mass or less.

From the viewpoint of reinforcing properties, the content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the inner tread rubber layer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and 3 parts by mass or more. More preferably, 4 parts by mass or more is particularly preferable. In addition, from the viewpoint of the effect of the present disclosure, the carbon black content per 100 parts by mass of the rubber component of the rubber composition constituting the inner tread rubber layer is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and 40 parts by mass. The amount is more preferably 20 parts by mass or less, further preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less.

(silica)
The silica is not particularly limited, and for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrous silica), and the like, commonly used in the tire industry can be used. Among them, hydrous silica prepared by a wet method is preferable because it contains many silanol groups. In addition to the silica described above, silica made from a biomass material such as rice husks may be used as appropriate. These silicas may be used individually by 1 type, and may use 2 or more types together.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 100 m ² /g or more, more preferably 120 m ² /g or more, and even more preferably 140 m ² /g or more, from the viewpoint of ensuring reinforcing properties and grip performance. 160 m ² /g or more is particularly preferred. From the viewpoint of heat build-up and workability, it is preferably 350 m ² /g or less, more preferably 300 m ² /g or less, and even more preferably 250 m ² /g or less. The N ₂ SA of silica is measured by the measuring method described above.

The average primary particle size of silica is preferably 10 nm or more, more preferably 12 nm or more, and even more preferably 14 nm or more. Also, the average primary particle size is preferably 22 nm or less, more preferably 20 nm or less, and even more preferably 18 nm or less. The average primary particle size of silica is measured by the above measuring method.

The silica content per 100 parts by mass of the rubber component of the rubber composition constituting the inner tread rubber layer is preferably 80 parts by mass or more from the viewpoint of ensuring rigidity and reinforcing properties without excessively increasing heat build-up. It is more preferably at least 90 parts by mass, particularly preferably at least 95 parts by mass. Moreover, from the viewpoint of reducing the specific gravity of the rubber to reduce the weight, it is preferably 140 parts by mass or less, more preferably 130 parts by mass or less, and even more preferably 120 parts by mass or less.

From the viewpoint of grip performance, the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and further preferably 55 parts by mass or more. Preferably, 60 parts by mass or more is particularly preferable. In addition, from the viewpoint of the effect of the present disclosure, the content of silica with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer is preferably 120 parts by mass or less, more preferably 105 parts by mass or less, and 90 parts by mass. Parts or less is more preferable, and 80 parts by mass or less is particularly preferable.

(other fillers)
As fillers other than silica and carbon black, aluminum hydroxide, calcium carbonate, alumina, clay, talc, and the like, which have been generally used in the tire industry, can be blended. In addition to these fillers, biochar (BIOCHAR) may be used as appropriate.

The total content of fillers relative to 100 parts by mass of the rubber component is preferably 70 parts by mass or more, more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, and 100 parts by mass or more, from the viewpoint of reinforcing properties and grip performance. Especially preferred. From the viewpoint of dispersibility, it is preferably 160 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 140 parts by mass or less, and particularly preferably 130 parts by mass or less.

(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, for example, 3-mercaptopropyltrimethoxysilane, 3-mercapto Mercapto-based silane coupling agents such as propyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; bis(3-triethoxysilylpropyl)disulfide, bis(3-triethoxysilylpropyl)tetra Sulfide-based silane coupling agents such as sulfide; Thioester-based silane cups such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane Ringing agent; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane amino-based silane coupling agents such as; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-silane coupling agents such as ethoxysilane; chloro-silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; and the like. Among them, 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, one commercially available from Momentive, etc. can be used. These silane coupling agents may be used singly or in combination of two or more.

In the case of containing a silane coupling agent, the content relative to 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 2.0 parts by mass, from the viewpoint of improving the dispersibility of silica. It is more preferably at least 4.0 parts by mass, and particularly preferably at least 4.0 parts by mass. Moreover, from the viewpoint of preventing deterioration of wear resistance performance, 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.

<Softener>
The rubber composition according to the present disclosure preferably contains a softening agent. Examples of softening agents include resin components, oils, liquid rubbers, ester plasticizers, and the like.

(resin component)
Examples of the resin component include, but are not limited to, petroleum resins, terpene-based resins, rosin-based resins, phenol-based resins, and the like commonly used in the tire industry. These resin components may be used individually by 1 type, and may use 2 or more types together.

Petroleum resins include C5 petroleum resins, aromatic petroleum resins, C5C9 petroleum resins, and the like.

As used herein, the term "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. Dicyclopentadiene resin (DCPD resin) is preferably used as the C5 petroleum resin.

As used herein, the term "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, which may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms such as vinyltoluene, alkylstyrene, indene, and methylindene. As specific examples of aromatic petroleum resins, coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins are preferably used. As the aromatic vinyl resin, α-methylstyrene, homopolymers of styrene, or copolymers of α-methylstyrene and styrene are preferable because they are economical, easy to process, and have excellent heat build-up properties. , a copolymer of α-methylstyrene and styrene is more preferred. As the aromatic vinyl resin, for example, those commercially available from Kraton, Eastman Chemical, Mitsui Chemicals, Inc., etc. can be used.

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

As the resin component, petroleum resin obtained by partially or completely hydrogenating the above petroleum resin can also be used. Such a hydrogenated petroleum resin is suitable for the rubber composition constituting the outer tread rubber layer from the viewpoint of excellent compatibility and good dispersion in the system due to the similarity of the hydrogenated structure. used for In the hydrogenated petroleum resin used in the present disclosure, the unsaturated bonds in the molecule are partially or completely hydrogenated, for example, aromatic rings such as benzene rings in the main chain or side chain is hydrogenated, the aromatic ring is reduced (for example, if the aromatic ring is a benzene ring, it is reduced to a cyclohexane ring, etc.).

Terpene-based resins include α-pinene, β-pinene, limonene, polyterpene resins made of at least one selected from terpene compounds such as dipentene; aromatic modified terpene resins made from the terpene compound and an aromatic compound; Terpene phenol resins made from a terpene compound and a phenolic compound as raw materials; and hydrogenated terpene resins obtained by hydrogenating these terpene resins (hydrogenated terpene resins). Examples of aromatic compounds used as 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 the rosin-based resin include, but are not limited to, natural resin rosin, and rosin-modified resin obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, and the like.

Phenol-based resins are not particularly limited, but include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, oil-modified phenol-formaldehyde resins, and the like.

From the viewpoint of grip performance, the softening point of the resin component is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher. From the viewpoint of workability and improvement of dispersibility between the rubber component and the filler, the temperature is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the resin component is measured by the measuring method described above.

When the resin component is contained, 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, still more preferably 15 parts by mass or more, and 20 parts by mass or more, from the viewpoint of grip performance. is more preferable, and 25 parts by mass or more is particularly preferable. From the viewpoint of suppressing heat generation, the amount is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less.

(oil)
Oils include, for example, process oils, vegetable oils, animal oils and the like. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. In addition, it is also possible to use a process oil with a low polycyclic aromatic compound (PCA) content for environmental protection. The low PCA content process oils include mild extractive solvates (MES), treated distillate aromatic extracts (TDAE), heavy naphthenic oils, and the like. Further, from the viewpoint of life cycle assessment, it is possible to use refined waste oil after being used in rubber mixers and engines, and waste cooking oil used in kitchens.

From the standpoint of workability, the content per 100 parts by mass of the rubber component when oil is contained is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and 15 parts by mass or more. Especially preferred. From the viewpoint of wear resistance performance, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 50 parts by mass or less.

(liquid rubber)
The liquid rubber is not particularly limited as long as it is a polymer in a liquid state at room temperature (25° C.). Examples include styrene isoprene rubber (liquid SIR) and liquid farnesene rubber. These liquid rubbers may be used singly or in combination of two or more.

When liquid rubber 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, and even more preferably 5 parts by mass or more. Also, the content of the liquid polymer 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.

From the viewpoint of grip performance, the content of the softening agent relative to 100 parts by mass of the rubber component (total amount of all softeners) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and 20 parts by mass. It is more preferably at least 25 parts by mass, and particularly preferably at least 25 parts by mass. Moreover, from the viewpoint of workability, it 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.

<Other compounding agents>
In addition to the above components, the rubber composition according to the present disclosure contains compounding agents commonly used in the conventional tire industry, such as waxes, processing aids, antioxidants, stearic acid, zinc oxide, vulcanizing agents, vulcanizing agents, A sulfur accelerator or the like can be appropriately contained.

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 more preferably 1.5 parts by mass or more, from the viewpoint of the weather resistance of the rubber. More preferred. From the viewpoint of preventing whitening of the tire due to bloom, the amount is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

The anti-aging agent is not particularly limited. -(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N' - phenylenediamine antioxidants such as di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and 2,2,4-trimethyl-1,2-dihydroquinoline heavy Quinoline anti-aging agents such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antioxidants may be used singly or in combination of two or more.

The content per 100 parts by mass of the rubber component when the anti-aging agent is contained is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass, from the viewpoint of the ozone crack resistance of the rubber. Part by mass or more is more preferable. From the viewpoint of wear resistance performance and wet grip performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

In the case of containing stearic acid, 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 further preferably 1.5 parts by mass or more, from the viewpoint of processability. preferable. From the viewpoint of the vulcanization rate, it is preferably 10 parts by mass or less, 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 further preferably 1.5 parts by mass or more, from the viewpoint of workability. preferable. Moreover, from the viewpoint of wear resistance performance, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less.

Sulfur is preferably used as the vulcanizing agent. As sulfur, powdered sulfur, oil treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used.

In the case of containing sulfur, 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, more preferably 0.5 parts by mass, from the viewpoint of ensuring a sufficient vulcanization reaction. Part or more is more preferable. From the viewpoint of preventing deterioration, it 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. The content of the vulcanizing agent when oil-containing sulfur is used as the cross-linking agent is the total content of pure sulfur contained in the oil-containing sulfur.

A known organic cross-linking agent can also be used as a vulcanizing agent other than sulfur. When an organic cross-linking agent is blended, the distance between cross-linking points becomes longer than in the case of cross-linking with sulfur, and a large amount of energy loss can occur, resulting in good peak grip performance.

The organic cross-linking agent is not particularly limited as long as it can form a cross-linking chain other than a polysulfide bond. ,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, dicumyl peroxide and the like.

Examples of vulcanization accelerators include sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, guanidine-based vulcanization accelerators, dithiocarbamate-based vulcanization accelerators, and caprolactam disulfide. etc. These vulcanization accelerators may be used singly or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, and guanidine-based vulcanization accelerators, since the desired effect can be obtained more preferably. A sulfenamide-based vulcanization accelerator and a guanidine-based vulcanization accelerator are more preferably used in combination.

Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N -dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) and the like. Among them, TBBS and CBS are preferred.

Thiazole-based vulcanization accelerators include, for example, 2-mercaptobenzothiazole (MBT) or salts thereof, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole and the like. Among them, MBTS and MBT are preferred, and MBTS is more preferred.

Guanidine-based vulcanization accelerators include, for example, 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 and the like. Among them, DPG is preferable.

When the vulcanization accelerator is contained, the content relative to 100 parts by mass of the rubber component is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more. The content of the vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, further preferably 6.0 parts by mass or less, and 5.0 parts by mass. Part or less is particularly preferred. By setting the content of the vulcanization accelerator within the above range, there is a tendency that breaking strength and elongation can be secured.

<Manufacturing>
A rubber composition according to the present disclosure can be produced by a known method. For example, it can be produced by kneading each of the above components using a rubber kneading device such as an open roll or closed type kneader (Banbury mixer, kneader, etc.).

The kneading step includes, for example, a base kneading step of kneading compounding agents and additives other than the vulcanizing agent and the vulcanization accelerator, and adding the vulcanizing agent and the vulcanization accelerator to the kneaded product obtained in the base kneading step. and a final kneading (F kneading) step of adding and kneading. Furthermore, the base kneading step can be divided into a plurality of steps as desired.

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

A tire of the present disclosure having a tread composed of the rubber composition can be manufactured by a conventional method. That is, an unvulcanized rubber composition obtained by blending each of the above components with a rubber component as necessary is extruded in accordance with the shape of each rubber layer constituting the tread, and is subjected to another tire on a tire building machine. A tire can be manufactured by laminating together the members and molding by a normal method to form an unvulcanized tire, and heating and pressurizing the unvulcanized tire in a vulcanizer. The vulcanization conditions are not particularly limited, and include, for example, vulcanization at 150 to 200° C. for 10 to 30 minutes.

<Application>
The tire of the present disclosure can be a general-purpose tire such as a tire for passenger cars, a tire for trucks and buses, a tire for two-wheeled vehicles, or a tire for racing. The passenger car tire is a tire that is intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or less. In addition, the tire of the present disclosure can be used for all-season tires, summer tires, winter tires such as studless tires.

Examples (embodiments) that are considered to be preferable when implementing are shown below, but the scope of the present disclosure is not limited to the examples.

Table 2 shows the results calculated based on the following evaluation methods, assuming a tire having a tread made of the rubber composition obtained according to Table 1 using various chemicals shown below.

Various chemicals used in Examples and Comparative Examples are listed below.
NR: TSR20
SBR: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, Tg: -56°C, Mw: 440,000, non-oil-extended)
Hydrogenated SBR: Hydrogenated SBR produced in Production Example 1 described later (hydrogenation rate: 80%, styrene content: 30% by mass, Tg: −30° C., Mw: 480,000)
BR: UBEPOL BR (registered trademark) 150B (unmodified BR, cis content: 97 mol%, Mw: 440,000) manufactured by Ube Industries, Ltd.
Carbon black: Diablack N220 (N ₂ SA: 114 m ² /g) manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 manufactured by Evonik Degussa (N ₂ SA: 175 m ² /g, average primary particle size: 15 nm)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Resin component 1: T-REZ PR801 (hydrogenated DCPD/C9 resin, softening point: 91°C) manufactured by ENEOS Corporation
Resin component 2: Sylvares SA85 manufactured by Kraton (a copolymer of α-methylstyrene and styrene, softening point: 85 ° C.)
Liquid rubber: RICON100 (liquid SBR) manufactured by Clay Valley
Oil: VivaTec500 (TDAE oil) manufactured by H&R Co., Ltd.
Zinc oxide: Zinc oxide type 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Bead stearic acid manufactured by NOF Corporation Tsubaki Antioxidant: Antigen 6C (N-(1,3- dimethylbutyl)-N'-phenyl-p-phenylenediamine)
Wax: Sannok N manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Sulfur: powdered sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. 1: Noxceler CZ-G (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxceler D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

Production Example 1: Production of hydrogenated SBR 2000 ml of n-hexane, 60 g of styrene, 140 g of 1,3-butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyllithium were added to a heat-resistant reaction vessel that had been sufficiently purged with nitrogen, and the mixture was heated to 50°C. for 5 hours to carry out the polymerization reaction. Next, while hydrogen gas is supplied at a pressure of 0.4 MPa-Gauge, the mixture is stirred for 20 minutes to react with unreacted polymer-terminated lithium to obtain lithium hydride. The hydrogen gas supply pressure is 0.7 MPa-Gauge, the reaction temperature is 90° C., and hydrogenation is carried out using a catalyst mainly composed of titanocene dichloride. When the total amount of hydrogen absorption reaches the desired hydrogenation rate, the reaction temperature is set to normal temperature, the hydrogen pressure is returned to normal pressure, the reaction solution is extracted from the reaction vessel, the reaction solution is stirred into water, and the solvent is steamed. Removal by stripping gives hydrogenated SBR.

(Examples and Comparative Examples)
According to the formulation shown in Table 1, using a 1.7 L closed Banbury mixer, chemicals other than sulfur and vulcanization accelerators were kneaded for 1 to 10 minutes until the discharge temperature reached 150 to 160 ° C., and the kneaded product was obtained. get Next, using a twin-screw open roll, sulfur and a vulcanization accelerator were added to the resulting kneaded material, and kneaded until the temperature reached 105° C. for 4 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition is extruded according to the shape of the inner tread rubber layer and the outer tread rubber layer (both thickness: 7.5 mm) using an extruder equipped with a mouthpiece of a predetermined shape. A composite of the tread layer and the inner tread layer is formed, laminated together with the base portion (thickness: 1.5 mm) and other tire members to produce an unvulcanized tire, and is pressed for 12 minutes at 170°C. Each test tire is made by vulcanization.

<Measurement of tan δ at 30°C>
Each rubber test piece after vulcanization was measured from each rubber layer of the tread portion of each test tire so that the tire circumferential direction was the long side and the tire radial direction was the thickness direction, and the length 20 mm × width 4 mm × thickness It is manufactured by cutting out with a thickness of 1 mm. For each rubber test piece, tan δ is measured under the conditions of temperature 30° C., frequency 10 Hz, initial strain 5%, dynamic strain ±1%, and elongation mode using the Xplexer series manufactured by GABO.

<Uneven wear resistance performance>
Each test tire is mounted on a domestic FR vehicle with a displacement of 2000cc. After running 5000 km on a dry asphalt test course at an average speed of 80 km/h, the wear amounts of the inner tread rubber layer and the outer tread rubber layer of the rear wheels are measured. Then, the difference in the amount of wear between the outer tread rubber layer and the inner tread rubber layer is determined, and the uneven wear resistance performance is expressed as an index according to the following formula. A larger index indicates better resistance to uneven wear.
(Wear index of each test tire)
= {(wear amount of outer tread rubber layer) - (wear amount of inner tread rubber layer)}/7.5 x 100
(Uneven wear resistance performance index of each test tire)
= {(100-wear index of each test tire)/(100-wear index of tire of Comparative Example 6)} x 100

<Embodiment>
Examples of embodiments of the present disclosure are provided below.

[1] A tire having a tread portion with a specified mounting direction to a vehicle, wherein the tread portion includes an inner tread rubber layer forming a vehicle inner end side when mounted on a vehicle, and a vehicle outer end side. The inner tread rubber layer and the outer tread rubber layer are composed of a rubber composition containing a rubber component, and the rubber component constituting the outer tread rubber layer is an aromatic vinyl compound. The content of carbon black with respect to 100 parts by mass of the rubber component of the rubber composition constituting the outer tread rubber layer, which contains a copolymer in which a conjugated diene compound is copolymerized and a part of the conjugated diene portion is hydrogenated. is greater than the carbon black content per 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer.
[2] The tire according to [1] above, wherein the rubber composition constituting the outer tread rubber layer contains 30 parts by mass or more of carbon black with respect to 100 parts by mass of the rubber component.
[3] The tire according to [1] or [2] above, wherein the rubber composition constituting the inner tread rubber layer contains 90 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.
[4] The tire according to any one of [1] to [3] above, wherein the rubber composition constituting the outer tread rubber layer contains a hydrogenated petroleum resin.
[5] Any one of [1] to [4] above, wherein the rubber component constituting the outer tread rubber layer contains 50% by mass or more of a hydrogenated styrene-butadiene rubber having a hydrogenation rate of 50 mol% or more. tires.
[6] The above [1] to [5], wherein the tan δ at 30° C. of the outer tread rubber layer (30° C. tan δ _out ) is greater than the tan δ at 30° C. of the inner tread rubber layer (30° C. tan δ _in ). A tire according to any one of the above.
[7] The above, wherein the ratio of D from the vehicle outer side contact edge to the interface between the inner tread rubber layer and the outer tread rubber layer to the distance W _L between the both side contact points (D/ _WL ) is 0.50 or more. [1] The tire according to any one of [6].
[8] The tire according to any one of [1] to [7] above, wherein the groove area ratio of the contact surface of the inner tread rubber layer is greater than the groove area ratio of the contact surface of the outer tread rubber layer.
[9] Any of the above [1] to [8], wherein the difference between the groove area ratio of the contact surface of the inner tread rubber layer and the groove area ratio of the contact surface of the outer tread rubber layer is 2% or more and 10% or less. A tire according to any one of the above.
[10] The tread portion has land portions partitioned by two or more circumferential grooves extending continuously in the tire circumferential direction, and the width of the land portion closest to the tire equatorial plane among the land portions on the tread surface. The tire according to any one of [1] to [9] above, wherein the directional length is 18% or more of the contact width.
[11] The tire according to any one of [1] to [10] above, wherein 30°C tan δ _out and D/W _L satisfy the following formula (1).
30°C tan δ _out × (D/W _L )≧0.20 (1)
[12] The tire according to [11] above, wherein the right side of formula (1) is 0.30.

DESCRIPTION OF SYMBOLS 1... Bead part 1a... Bead core 1b... Bead filler 2... Sidewall part 3... Tread part 4... Carcass layer 4a... Inner liner rubber 4b... Belt 4c. Belt reinforcing layer 5 Land portion 5a Circumferential groove 6 Side wall rubber 7 Rim strip rubber 50 Cap portion 51 Base portion 52 Inner tread Rubber layer 52: Outer tread rubber layer

Claims (12)

A tire having a tread portion with a specified mounting direction to a vehicle,
The tread portion has an inner tread rubber layer forming a vehicle inner end side when mounted on a vehicle, and an outer tread rubber layer forming a vehicle outer end side,
The inner tread rubber layer and the outer tread rubber layer are made of a rubber composition containing a rubber component,
The rubber component constituting the outer tread rubber layer includes a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, and a part of the conjugated diene portion thereof is hydrogenated,
The content of carbon black per 100 parts by mass of the rubber component of the rubber composition forming the outer tread rubber layer is higher than the content of carbon black per 100 parts by mass of the rubber component of the rubber composition forming the inner tread rubber layer. many tires. The tire according to claim 1, wherein the rubber composition constituting the outer tread rubber layer contains 30 parts by mass or more of carbon black with respect to 100 parts by mass of the rubber component. The tire according to claim 1 or 2, wherein the rubber composition constituting the inner tread rubber layer contains 90 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. The tire according to any one of claims 1 to 3, wherein the rubber composition that constitutes the outer tread rubber layer contains a hydrogenated petroleum resin. The tire according to any one of claims 1 to 4, wherein the rubber component constituting the outer tread rubber layer contains 50% by mass or more of hydrogenated styrene-butadiene rubber having a hydrogenation rate of 50 mol% or more. The tan δ at 30°C of the outer tread rubber layer (30°C tan δ _out ) is greater than the tan δ at 30°C of the inner tread rubber layer (30°C tan δ _in ). tires. Claims 1 to 2, wherein the ratio of D from the outer vehicle edge to the interface between the inner tread rubber layer and the outer tread rubber layer to the distance W _L between the both edge edges (D/W _L ) is 0.50 or more. 7. The tire according to any one of 6. The tire according to any one of claims 1 to 7, wherein the groove area ratio of the contact surface of the inner tread rubber layer is greater than the groove area ratio of the contact surface of the outer tread rubber layer. The difference between the groove area ratio of the contact surface of the inner tread rubber layer and the groove area ratio of the contact surface of the outer tread rubber layer is 2% or more and 10% or less. tires. The tread portion has land portions partitioned by two or more circumferential grooves extending continuously in the tire circumferential direction, and the width direction length on the tread surface of the land portion closest to the tire equatorial plane among the land portions is 18% or more of the contact width. The tire according to any one of claims 1 to 10, wherein 30°C tan δ _out and D/W _L satisfy the following formula (1).
30°C tan δ _out × (D/W _L )≧0.20 (1) 12. The tire of claim 11, wherein the right hand side of equation (1) is 0.30.

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