JP7447447B2 - tire tread and tires - Google Patents

Description

The present invention relates to tire treads and tires.

Treads of tires (especially high-performance tires used in competitions) are generally required to have both high grip performance and wear resistance.

Conventionally, in order to obtain a rubber composition that exhibits high grip performance, for example, a rubber composition using styrene-butadiene rubber (SBR) with a high glass transition temperature (Tg) as a rubber component, a process oil as a high softening point resin, etc. Rubber compositions in which the amount of carbon black is substituted, rubber compositions highly filled with a softener or carbon black, rubber compositions using carbon black with a small particle size, and rubber compositions that combine these methods are known. However, rubber compositions using SBR with a high Tg tend to have a large temperature dependence and a large change in performance with respect to temperature changes. Furthermore, when an equal amount of process oil is replaced with a high softening point resin, if the replacement amount is large, temperature dependence tends to increase due to the influence of the high softening point resin. Furthermore, when carbon black with a small particle size or a large amount of softener is used, the dispersibility of the carbon black tends to deteriorate and the abrasion resistance tends to decrease.

In order to improve these points, Patent Document 1 proposes a rubber composition using low molecular weight SBR. Rubber compositions using partially hydrogenated low-molecular styrene-butadiene copolymers are also known, but the hydrogenation rate is limited due to bleeding of low-molecular components.

Here, as an index of wet grip performance and dry grip performance of rubber, for example, tan δ at a dynamic strain (amplitude) of 0.1% and a frequency of 10 Hz is used. Generally, the higher the tan δ at 0°C, the higher the wet skid performance, and the higher the tan δ at 50°C, the higher the dry grip property. Furthermore, in order to maintain grip performance, that is, to reduce the amount of change in initial grip, middle grip, and late grip, it is necessary to reduce the temperature dependence of the hardness of the rubber constituting the tread.

On the other hand, from the viewpoint of abrasion resistance, as the tan δ of the rubber increases, the hardness of the rubber at room temperature also increases, so the abrasion resistance tends to deteriorate. Therefore, wear resistance and grip performance are in a contradictory relationship, and it has been difficult to achieve both.

Publication No. 1983-101440

An object of the present invention is to solve the above-mentioned problems and provide a tire tread and tire with excellent wear resistance and grip performance.

The present invention provides a tire tread having a two-layer structure in which an upper layer rubber composition and a lower layer rubber composition are laminated, wherein the tan δ peak temperature at a dynamic strain of 2.5% of the upper layer rubber composition is 5° C. or less. The present invention relates to a tire tread in which tan δ and E ^* [MPa] of the upper layer rubber composition and the lower layer rubber composition at a dynamic strain of 2.5% and a temperature of 50° C. satisfy the following formulas (1) and (2).
(1) (tan δ/E ^* of upper layer rubber composition)×1000≧100
(2) tan δ/E ^* of upper layer rubber composition > tan δ/E ^* of lower layer rubber composition

In the lower layer rubber composition, the content of the plasticizer that does not contain a hetero element is preferably 5 parts by mass or more based on 100 parts by mass of the rubber component.

In the upper layer rubber composition, the content of a low molecular weight polymer having a weight average molecular weight of 300 to 100,000 as measured by gel permeation chromatography is preferably 5 parts by mass or more based on 100 parts by mass of the rubber component.

It is preferable that the monomer of the low molecular weight polymer is at least one type consisting of an aromatic vinyl monomer and its derivative, and a conjugated diene monomer and its derivative.

The upper layer rubber composition contains a high molecular weight polymer having a weight average molecular weight of 150,000 or more as measured by gel permeation chromatography, and in the upper layer rubber composition, the content of aromatic vinyl moieties in the high molecular weight polymer is It is also preferable that the content of the aromatic vinyl moiety in the low molecular weight polymer satisfies the following formula (3).
(3) Content of aromatic vinyl moieties in high molecular weight polymer - Content of aromatic vinyl moieties in low molecular weight polymer ≦20 [mass%]

In the upper layer rubber composition, the content of the plasticizer containing a hetero element is preferably 5 parts by mass or more based on 100 parts by mass of the rubber component.

In the upper layer rubber composition, the content of the resin having a glass transition temperature of 50° C. or higher as measured by differential scanning calorimetry is preferably 5 parts by mass or more based on 100 parts by mass of the rubber component.

In the upper layer rubber composition, the content of the component that is liquid at 160° C. or higher is preferably 70 parts by mass or more based on 100 parts by mass of the rubber component.

In the upper layer rubber composition, the content of the filler is preferably 40 parts by mass or more based on 100 parts by mass of the rubber component.

The invention also relates to a tire comprising said tire tread.

Preferably, the tire is a high performance tire.

According to the present invention, the tire tread has a two-layer structure in which an upper layer rubber composition and a lower layer rubber composition are laminated, and the tan δ peak temperature at a dynamic strain of 2.5% of the upper layer rubber composition is 5° C. or less. The tire tread has an excellent tan δ and E ^* [MPa] at a dynamic strain of 2.5% of the upper layer rubber composition and lower layer rubber composition and a temperature of 50°C that satisfy formulas (1) and (2). Provides wear resistance and grip performance.

The present invention provides a tire tread having a two-layer structure in which an upper layer rubber composition and a lower layer rubber composition are laminated, wherein the tan δ peak temperature at a dynamic strain of 2.5% of the upper layer rubber composition is 5° C. or less, The tire tread is a tire tread in which tan δ and E ^* [MPa] of the upper layer rubber composition and the lower layer rubber composition at a dynamic strain of 2.5% and a temperature of 50° C. satisfy formulas (1) and (2).

The present inventors have investigated the tan δ peak temperature of the upper layer rubber composition, and the tan δ peak temperature of the upper layer rubber composition and the lower layer rubber composition in a two-layer tire tread in which an upper layer rubber composition and a lower layer rubber composition are laminated. It has been found that excellent wear resistance and grip performance can be obtained by adjusting the tan δ and E ^* of the material within a specific range.

In the above tire tread, tan δ and E ^* of the upper layer rubber composition and the lower layer rubber composition satisfy formulas (1) and (2), so that the upper layer rubber composition has excellent grip performance and the lower layer rubber composition has excellent grip performance. It exhibits excellent wear resistance. Furthermore, when the tan δ peak temperature of the upper layer rubber composition is 5° C. or less, excellent grip performance can be obtained. It is thought that these effects make it possible to achieve both wear resistance and grip performance, which has been difficult in the past.

Note that the purpose of the present invention, that is, the problem to be solved by the present invention is to obtain excellent wear resistance and grip performance. A means to solve this problem is to adjust the tire tread so as to satisfy the relationships expressed by formulas (1) and (2), and to adjust the tan δ peak temperature of the upper layer rubber composition to a specific range. It is to adjust to.

When attached to a tire, the tire tread has a structure in which a lower layer rubber composition and an upper layer rubber composition are laminated in this order from the inner surface of the tire. Examples of such tire treads include treads with a two-layer structure in which a cap tread (upper layer rubber composition) and a base tread (lower layer rubber composition) are laminated.

The tan δ peak temperature of the upper layer rubber composition may be 5°C or lower, preferably 0°C or lower, more preferably -4°C or lower, even more preferably -8°C or lower, and preferably -20°C. Above, the temperature is more preferably -15°C or higher, still more preferably -10°C or higher. As the tan δ peak temperature increases, grip performance improves, but the embrittlement temperature increases and embrittlement tends to occur more easily. However, within the above range, both good grip performance and embrittlement temperature are achieved. There is a tendency to
Note that the tan δ peak temperature is measured with respect to the upper layer rubber composition after vulcanization under the condition of a dynamic strain of 2.5%, and can be measured by the method described in the Examples below.

The method for adjusting the tan δ peak temperature is not particularly limited, but for example, increasing the amount of styrene in the polymer, increasing the content of the resin component, decreasing the content of the plasticizer component, etc. can be used to increase the tan δ peak temperature. , it can be lowered by reducing the content of the resin component, increasing the content of the plasticizer component, etc.

The tan δ and E ^* of the upper layer rubber composition and the lower layer rubber composition satisfy the following formulas (1) and (2).
(1) (tan δ/E ^* of upper layer rubber composition)×1000≧100
(2) tan δ/E ^* of upper layer rubber composition > tan δ/E ^* of lower layer rubber composition
Note that tan δ and E ^* were measured for the upper layer rubber composition and the vulcanized rubber composition after vulcanization under the conditions of a dynamic strain of 2.5% and a temperature of 50°C, and were measured using the method described in the examples below. It can be measured by

In formula (1), "(tan δ/E ^* ) x 1000 of the upper layer rubber composition" may be 100 or more, preferably 115 or more, more preferably 130 or more, still more preferably 136 or more, and particularly preferably is 138 or more. Further, “(tan δ/E ^* )×1000 of the upper layer rubber composition” is preferably 200 or less, more preferably 180 or less, still more preferably 160 or less, particularly preferably 150 or less. Within the above range, good grip performance tends to be obtained.

The tan δ/E ^* of the lower layer rubber composition can be adjusted as appropriate within a range that satisfies formula (2), but "(tan δ/E ^* of the lower layer rubber composition) x 1000" is preferably 70 or more, more preferably is 80 or more, more preferably 90 or more, particularly preferably 97 or more, preferably 140 or less, more preferably 120 or less, still more preferably 110 or less, particularly preferably 100 or less. Within the above range, better effects tend to be obtained.

The difference x 1000 between tan δ/E ^* of the upper layer rubber composition and tan δ/E ^* of the lower layer rubber composition is preferably 20 or more, more preferably 35 or more, even more preferably 39 or more, particularly preferably 41 or more, Further, it is preferably 60 or less, more preferably 50 or less. Within the above range, better effects tend to be obtained.

In the upper layer rubber composition, tan δ and E ^* can be adjusted as appropriate within the range that satisfies formulas (1) and (2), but usually tan δ is 0.15 to 0.90 and E ^* is 2.0 to 2.0. It is 7.0 MPa.
Similarly, in the lower layer rubber composition, tan δ is usually 0.10 to 0.90 and E ^* is 2.0 to 10.0 MPa.

The method for adjusting tan δ is not particularly limited, but for example, tan δ can be increased by increasing the amount of styrene in the polymer, increasing the content of the resin component, increasing the content of carbon black, etc.; The carbon black content can be lowered by reducing the carbon black content.
Similarly, E ^* can be increased by increasing the molecular weight of the polymer, increasing the content of carbon black, decreasing the content of plasticizer components, etc.; It can be lowered by reducing the amount or increasing the content of the plasticizer component.

In the above tire tread, the gauge ratio (thickness ratio) of the upper layer rubber composition is preferably 90% or less, more preferably 80%, even more preferably 70% or less, and preferably 20% or more, more preferably It is 40% or more, more preferably 50% or more. Within the above range, better effects tend to be obtained.

Hereinafter, chemicals that can be used in each of the upper layer rubber composition and the lower layer rubber composition will be explained. Note that materials other than those described below can be used for the upper layer rubber composition and the lower layer rubber composition.

<Upper layer rubber composition>
The upper layer rubber composition preferably contains, as a rubber component, a high molecular weight polymer (component A in the Examples described below) having a weight average molecular weight (Mw) of 150,000 or more as measured by gel permeation chromatography (GPC). . This tends to produce better effects.

The Mw of the high molecular weight polymer is preferably 250,000 or more, more preferably 300,000 or more, even more preferably 350,000 or more, and preferably 1,000,000 or less, more preferably 700,000 or less, still more preferably 500,000 or less. It is. Within the above range, better effects tend to be obtained.

The molecular weight distribution (Mw/Mn) of the high molecular weight polymer is preferably 0.50 or more, more preferably 0.90 or more, even more preferably 1.12 or more, and preferably 2.50 or less, more preferably It is 1.50 or less, more preferably 1.25 or less. Within the above range, better effects tend to be obtained.

As the monomer component of the high molecular weight polymer, for example, at least one kind consisting of aromatic vinyl monomers and their derivatives, and conjugated diene monomers and their derivatives can be used.

Examples of the aromatic vinyl monomer include styrene and its derivatives α-methylstyrene, t-butoxystyrene, and the like. These may be used alone or in combination of two or more. Among them, styrene is preferred.

Examples of the conjugated diene monomer include butadiene and its derivatives such as isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, myrcene, and farnesene. These may be used alone or in combination of two or more. Among them, butadiene is preferred.

As the monomer component of the high molecular weight polymer, a combination of an aromatic vinyl monomer and a conjugated diene monomer is preferred, and a combination of styrene and butadiene is more preferred.

The method of polymerizing the high molecular weight polymer is not particularly limited, and known methods such as anionic polymerization, cationic polymerization, coordination polymerization, and emulsion polymerization can be used.

The content of aromatic vinyl moieties (content of structural units derived from aromatic vinyl monomers) in the high molecular weight polymer is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 38% by mass or more. The content is preferably 55% by mass or less, more preferably 48% by mass or less, even more preferably 45% by mass or less. Within the above range, better effects tend to be obtained.

The high molecular weight polymer may be modified by a known modification reaction such as a hydrogenation reaction, a graft reaction, or a terminal modification reaction.
The hydrogenation reaction is a reaction in which hydrogen is added to the double bond of the polymerized polymer by catalytic hydrogenation reaction in the presence of a transition metal and hydrogen.
The graft reaction is a reaction in which a grafting agent such as maleic anhydride is reacted with a double bond of a polymer.
The terminal modification reaction is a method of introducing a polar group at the terminal by adding a terminal modifier containing a hetero element at the time of termination of polymerization, and examples of the hetero element include silicon, nitrogen, oxygen, and the like.

Rubber components corresponding to high molecular weight polymers include natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), and styrene-isoprene-butadiene copolymer. Examples include diene rubbers such as rubber (SIBR). These may be used alone or in combination of two or more. Among these, SBR is preferred.

As commercially available SBR products, products from Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

The content of the high molecular weight polymer in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. Within the above range, better effects tend to be obtained.

The upper layer rubber composition preferably contains a low molecular weight polymer (component B in Examples described below) having an Mw of 300 to 100,000 as measured by GPC. This tends to provide particularly good grip performance.
Note that the low molecular weight polymer is not included in the rubber component.

The Mw of the low molecular weight polymer is preferably 1000 or more, more preferably 2000 or more, even more preferably 3000 or more from the viewpoint of improving grip performance, and from the viewpoint of ensuring good initial grip performance. It is 50,000 or less, more preferably 10,000 or less, even more preferably 6,000 or less.

The molecular weight distribution (Mw/Mn) of the low molecular weight polymer is preferably 0.50 or more, more preferably 0.90 or more, even more preferably 1.10 or more, and preferably 2.50 or less, more preferably It is 1.50 or less, more preferably 1.25 or less. Within the above range, better effects tend to be obtained.

As the low molecular weight polymer, at least one of the same monomer components as the above-mentioned high molecular weight polymer, ie, an aromatic vinyl monomer and its derivatives, and a conjugated diene monomer and its derivatives, can be used. Among these, combinations of aromatic vinyl monomers and conjugated diene monomers are preferred, and combinations of styrene and butadiene are more preferred.
Furthermore, the same polymerization methods and modification reactions as for high molecular weight polymers can be used.

The content of aromatic vinyl moieties (content of structural units derived from aromatic vinyl monomers) in the low molecular weight polymer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. The content is preferably 45% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less. Within the above range, better effects tend to be obtained.

It is preferable that the content of the aromatic vinyl moiety in the high molecular weight polymer and the content of the aromatic vinyl moiety in the low molecular weight polymer satisfy the following formula (3). Thereby, tread peeling caused by bleeding of the low molecular weight polymer can be suppressed.
(3) Content of aromatic vinyl moieties in high molecular weight polymer - Content of aromatic vinyl moieties in low molecular weight polymer ≦20 [mass%]

In formula (3), "content of aromatic vinyl moieties in high molecular weight polymer - content of aromatic vinyl moieties in low molecular weight polymer" may be 20% by mass or less, but preferably 15% by mass. The content is preferably 13% by mass or less. The lower limit is not particularly limited and may be 0. Within the above range, particularly good grip performance tends to be obtained.

The content of the low molecular weight polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 200 parts by mass or less, based on 100 parts by mass of the rubber component. , more preferably 175 parts by mass or less, still more preferably 155 parts by mass or less. Within the above range, better effects tend to be obtained.

The upper layer rubber composition preferably contains a plasticizer (component C in the Examples described below) that does not contain a hetero element. This tends to provide good workability and grip performance.

Examples of plasticizers that do not contain hetero elements include mineral oils, and examples of the mineral oils that can be used include aromatic mineral oils, naphthenic mineral oils, and paraffinic mineral oils. These may be used alone or in combination of two or more. Among these, aromatic mineral oils are preferred.

The content of the plasticizer that does not contain a hetero element is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. It is 80 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less. Within the above range, better effects tend to be obtained.

The upper layer rubber composition preferably contains a plasticizer containing a hetero element (component D in the Examples described below). This tends to provide good workability and grip performance (especially initial grip performance).

Examples of the hetero element include silicon, nitrogen, oxygen, sulfur, phosphorus, chlorine, iodine, and bromine. These may be one type or two or more types. Among them, oxygen is preferred.

Examples of plasticizers containing hetero elements include vegetable oils, ether plasticizers, ester plasticizers, phosphate ester plasticizers, and the like. Vegetable oils include linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, etc. as ether plasticizers. As the ester plasticizer, phthalate, adipate, etc. can be used, and as the phosphate plasticizer, tricresyl phosphate can be used. These may be used alone or in combination of two or more. Among these, ester plasticizers are preferred, adipate esters are more preferred, and bis[2-(2-butoxyethoxy)ethyl]adipate is even more preferred.

The content of the plasticizer containing a hetero element is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 40 parts by mass or less, more preferably 30 parts by mass, based on 100 parts by mass of the rubber component. It is not more than 20 parts by mass, more preferably not more than 20 parts by mass. Within the above range, better effects tend to be obtained.

Commercially available plasticizers that do not contain hetero elements and plasticizers that contain hetero elements include Daihachi Kagaku Kogyo Co., Ltd., Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Energy Corporation, and Orisoi Co., Ltd. , H&R, Toyokuni Sekiyu Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., etc. can be used.

The upper layer rubber composition preferably contains a resin (component E in the Examples described below) whose glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) is 50° C. or higher. As a result, good grip performance (especially late grip performance) tends to be obtained.

The Tg of the resin is preferably 50°C or higher, but preferably 90°C or lower, more preferably 80°C or lower. When the content is within the above range, better effects tend to be obtained.
Note that Tg is a value measured in accordance with JIS-K7121:1987 using a differential scanning calorimeter (Q200) manufactured by TA Instruments Japan under conditions of a heating rate of 10°C/min. .

Examples of the resin having a Tg of 50° C. or higher include hydrocarbon resins, terpene resins, coumaron indene resins, phenol resins, acrylic resins, and the like. Hydrocarbon resins include C5 and C9 petroleum resins, terpene resins include terpene resins, aromatic terpene resins, etc., and phenolic resins include terpene phenol resins, phenolacetylene condensates, and phenol-formalin condensates. As the acrylic resin, aromatic acrylic resin and the like can be used. These may be used alone or in combination of two or more. Among these, coumaron indene resin and aromatic terpene resin (particularly styrene terpene resin) are preferred.

Commercially available resins with a Tg of 50°C or higher include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, and Nichico. Kagaku Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Corporation, Nippon Zeon Co., Ltd., Harima Kasei Co., Ltd., Toagosei Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. You can use the product.

The content of the resin having a Tg of 50° C. or higher is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and more preferably 40 parts by mass or less, more preferably 40 parts by mass or less, based on 100 parts by mass of the rubber component. is 30 parts by mass or less, more preferably 20 parts by mass or less. Within the above range, better effects tend to be obtained.

It is preferable that the upper layer rubber composition has a content of a component that is liquid at 160° C. or higher within a specific range. This tends to provide good workability and grip performance.

Typical examples of components that are liquid at 160°C or higher include the above-mentioned low molecular weight polymer (component B), a plasticizer that does not contain a hetero element (component C), a plasticizer that contains a hetero element (component D), and a Tg of 60°C. The above resins (component E) can be mentioned. Note that some low molecular weight polymers and resins with a Tg of 60°C or higher are not liquid at 160°C or higher.

The content of the component that is liquid at 160° C. or higher is preferably 70 parts by mass or more, more preferably 80 parts by mass or more, and more preferably 250 parts by mass or less, more preferably 100 parts by mass of the rubber component. is 200 parts by mass or less, more preferably 185 parts by mass or less. Within the above range, better effects tend to be obtained.

The upper rubber composition preferably contains a filler. This tends to provide good wear resistance.

The content of the filler is preferably 40 parts by mass or more, more preferably 80 parts by mass or more, even more preferably 120 parts by mass or more, particularly preferably 130 parts by mass or more, based on 100 parts by mass of the rubber component. , preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 170 parts by mass or less. When the content is within the above range, better effects tend to be obtained.

Examples of the filler include carbon atom fillers and inorganic fillers. As the carbon atom filler, carbon black or the like can be used, and as the inorganic filler, silica, a metal salt of sulfuric acid, silicon carbide, a compound represented by the following formula, etc. can be used.
mM・xSiOy・zH ₂ O
(In the formula, M is at least one metal selected from the group consisting of Al, Mg, Ti, Ca, and Zr, an oxide or hydroxide of the metal, m is an integer from 1 to 5, and x is (Integer from 0 to 10, y is an integer from 2 to 5, and z is an integer from 0 to 10.)
Compounds represented by the above formula include alumina, alumina hydrate, aluminum hydroxide, magnesium hydroxide, talc, titanium white, titanium black, calcium oxide, calcium hydroxide, calcium aluminum oxide, clay, pyrophyllite, Examples include bentonite, aluminum silicate, calcium silicate, calcium aluminum silicate, magnesium silicate, zirconium, zirconium oxide, and the like.

These fillers may be used alone or in combination of two or more. Among them, carbon black and silica are preferred, and carbon black is more preferred.

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

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 75 m ² /g or more, more preferably 95 m ² /g or more, and preferably 120 m ² /g or less, more preferably 100 m ² /g. It is as follows. Within the above range, better effects tend to be obtained.
Note that the N ₂ SA of carbon black is a value measured in accordance with JIS K6217-2:2001.

Examples of the silica include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and wet process silica is preferable because it has a large number of silanol groups. As commercially available products, products from Evonik Degussa, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 100 m ² /g or more, more preferably 150 m ² /g or more, and preferably 250 m ² /g or less, more preferably 220 m ² /g or less. , more preferably 200 m ² /g or less. Within the above range, better effects tend to be obtained.
Note that the N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-81.

It is preferable to use silica together with a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide types such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto types such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, and vinyl triethoxysilane. Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Examples include nitro types such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro types such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Kasei Kogyo Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 12 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of silica. It is. Within the above range, better effects tend to be obtained.

The upper rubber composition may contain wax.
The wax is not particularly limited, and includes petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable waxes and animal waxes; and synthetic waxes such as polymers of ethylene and propylene. As commercially available products, products from Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the rubber component. It is. When the content is within the above range, better effects tend to be obtained.

The upper rubber composition may contain an anti-aging agent.
Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; -isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, etc. p-phenylenediamine-based anti-aging agents; quinoline-based anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methylphenol; Monophenolic anti-aging agents such as styrenated phenol; bis-, tris-, and polyphenol-based aging agents such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, etc. Examples include inhibitors. As commercially available products, products from Seiko Kagaku Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the anti-aging agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass, based on 100 parts by mass of the rubber component. below. When the content is within the above range, better effects tend to be obtained.

The upper rubber composition may contain stearic acid.
As stearic acid, conventionally known ones can be used, and commercially available products include products from NOF Corporation, NOF Inc., Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., and Chiba Fatty Acid Co., Ltd. Can be used. These may be used alone or in combination of two or more.

The content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass, based on 100 parts by mass of the rubber component. It is as follows. Within the above range, better effects tend to be obtained.

The upper rubber composition may contain zinc oxide.
As zinc oxide, conventionally known ones can be used, and commercially available products include Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. You can use products such as These may be used alone or in combination of two or more.

The content of zinc oxide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, based on 100 parts by mass of the rubber component. be. Within the above range, better effects tend to be obtained.

The upper layer rubber composition may contain sulfur.
Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. commonly used in the rubber industry. As commercially available products, products manufactured by Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis, Nippon Kanditsu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of sulfur is preferably 1 part by mass or more, more preferably 1.8 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. It is. Within the above range, better effects tend to be obtained.

The upper layer rubber composition may contain a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis (2-benzothiazolyl disulfide); Thiuram-based vulcanization accelerators such as -ethylhexyl)thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide ( TBBS), N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide, etc. Sulfurization accelerator: Guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolyl biguanidine can be mentioned. As commercially available products, products from Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 2.5 parts by mass or more, and preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. It is not more than 5 parts by mass, more preferably not more than 5 parts by mass. Within the above range, better effects tend to be obtained.

In addition to the above-mentioned components, the upper layer composition may further contain additives commonly used in the tire industry, such as organic peroxides. The content of these additives is preferably 0.1 to 200 parts by mass based on 100 parts by mass of the rubber component.

The upper layer rubber composition can be produced, for example, by a method in which the above-mentioned components are kneaded using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanized.

Regarding the kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the final kneading step of kneading the vulcanizing agent and vulcanization accelerator, the kneading temperature is usually 120°C or less, preferably 85 to 110°C. Further, a composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. Vulcanization time is usually 5 to 15 minutes.

<Lower rubber composition>
The lower layer rubber composition can be manufactured using the same chemicals and in the same manner as the upper layer rubber composition.
The preferred content of each chemical in the lower layer rubber composition will be described below, but the preferred content of chemicals not mentioned here is the same as that in the upper layer rubber composition.

In the lower layer rubber composition, the content of the low molecular weight polymer is preferably 5 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and Preferably it is 10 parts by mass or less. Within the above range, better effects tend to be obtained.

In the lower layer rubber composition, the content of the plasticizer that does not contain a hetero element is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, based on 100 parts by mass of the rubber component. It is particularly preferably 60 parts by mass or more, and preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. Within the above range, better effects tend to be obtained.

In the lower layer rubber composition, the content of the plasticizer containing a hetero element is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component. , 0 parts by mass. Within the above range, better effects tend to be obtained.

In the lower layer rubber composition, the content of the component that is liquid at 160° C. or higher is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, still more preferably 70 parts by mass or more, based on 100 parts by mass of the rubber component. The amount is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less. Within the above range, better effects tend to be obtained.

<Tires>
The tire of the present invention is manufactured by a conventional method using the above-mentioned upper layer rubber composition and lower layer rubber composition.
That is, the above-mentioned upper layer rubber composition and lower layer rubber composition are extruded in the unvulcanized stage to fit the shape of a cap tread, a base tread, etc., respectively, and then processed together with other tire components on a tire molding machine. A green tire is formed by molding in a conventional manner. By heating and pressurizing this unvulcanized tire in a vulcanizer, a tire having a tire tread in which an upper layer rubber composition and a lower layer rubber composition are laminated is obtained.

The above tire is not particularly limited, and includes, for example, a pneumatic tire, a solid tire, an airless tire, and the like. Among these, pneumatic tires are preferred.

The above tires include passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, high performance tires (competition tires, etc.), winter tires (studless tires, snow tires, studded tires). etc.), all-season tires, run-flat tires, aircraft tires, mining tires, etc. Among these, high-performance tires are preferred.

The present invention will be specifically explained based on examples, but the present invention is not limited to these examples.

Below, various chemicals used in the manufacturing examples will be explained. In addition, chemicals were purified according to standard methods as necessary.
Hexane: Anhydrous hexane manufactured by Kanto Chemical Co., Ltd. Isopropanol: Isopropanol manufactured by Kanto Chemical Co., Ltd. TMEDA: Tetramethylethylenediamine manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. n-Butyl Lithium: n-Butyl manufactured by Tosoh Corporation Lithium butadiene: 1,3-butadiene manufactured by Takachiho Chemical Industry Co., Ltd. Styrene: Styrene manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

The method for analyzing the polymer obtained in the production example is as follows.

(Weight average molecular weight (Mw), number average molecular weight (Mn))
The weight average molecular weight (Mw) and number average molecular weight (Mn) were determined using a GPC-8000 series device manufactured by Tosoh Corporation and a differential refractometer as a detector in terms of standard polystyrene.

(Content of aromatic vinyl moiety (styrene amount))
The content of aromatic vinyl moieties (styrene content) was calculated according to JIS-K-6239.

(Production Example 1-1: High molecular weight copolymer A-1)
0.02 mmol of TMEDA was charged into a 3 L pressure-resistant stainless steel polymerization container which was dried and purged with nitrogen, along with 900 g of hexane, 62 g of butadiene, and 38 g of styrene. Next, a small amount of n-butyllithium/hexane solution (n-butyllithium content: 0.3 mmol) was poured into the polymerization container as a scavenger in order to detoxify impurities that act on the deactivation of the polymerization initiator. . After further adding n-butyllithium/hexane solution, a polymerization reaction was carried out at 50°C for 3 hours. After 3 hours, 1.15 ml of 1M isopropanol/hexane solution was added dropwise to terminate the reaction. Next, the polymerization solution was evaporated at room temperature for 24 hours, and further dried under reduced pressure at 80° C. for 24 hours to obtain a high molecular weight copolymer A-1 (SBR). The polymerization conversion rate was approximately 100%. The obtained high molecular weight copolymer A-1 had a Mw of 350,000, a molecular weight distribution of 1.12, and an aromatic vinyl moiety content (styrene content) of 38% by mass.

(Production Example 1-2: High molecular weight copolymer A-2)
High molecular weight copolymer A-2 (SBR) was obtained by the same method as Production Example 1-1 except that the content of n-butyllithium in the n-butyllithium/hexane solution was 0.7 mmol. . The polymerization conversion rate was approximately 100%. The obtained high molecular weight copolymer A-2 had a Mw of 150,000, a molecular weight distribution of 1.12, and an aromatic vinyl moiety content (styrene content) of 38% by mass.

(Production Example 2-1: Low molecular weight copolymer B-1)
0.02 mmol of TMEDA was charged into a 3 L pressure-resistant stainless steel polymerization container that had been dried and purged with nitrogen, along with 900 g of hexane, 75 g of butadiene, and 25 g of styrene. Next, a small amount of n-butyllithium/hexane solution (n-butyllithium content: 30.0 mmol) was poured into the polymerization container as a scavenger in order to detoxify impurities that act on the deactivation of the polymerization initiator. . After further adding n-butyllithium/hexane solution, a polymerization reaction was carried out at 50°C for 3 hours. After 3 hours, 50 ml of 1M isopropanol/hexane solution was added dropwise to terminate the reaction. Next, the polymerization solution was evaporated at room temperature for 24 hours and further dried under reduced pressure at 80° C. for 24 hours to obtain a low molecular weight copolymer B-1 (SBR). The polymerization conversion rate was approximately 100%. The obtained low molecular weight copolymer B-1 had an Mw of 30,000, a molecular weight distribution of 1.10, and an aromatic vinyl moiety content (styrene content) of 25% by mass.

(Production Example 2-2: Low molecular weight copolymer B-2)
High molecular weight copolymer B-2 (SBR) was obtained by the same method as Production Example 2-1 except that the content of n-butyllithium in the n-butyllithium/hexane solution was 300.0 mmol. . The polymerization conversion rate was approximately 100%. The obtained high molecular weight copolymer B-2 had an Mw of 300, a molecular weight distribution of 1.10, and an aromatic vinyl moiety content (styrene content) of 25% by mass.

(Production Example 2-3: Low molecular weight copolymer B-3)
High molecular weight copolymer B-3 (SBR) was obtained by the same method as Production Example 2-1 except that the content of n-butyllithium in the n-butyllithium/hexane solution was 10.0 mmol. . The polymerization conversion rate was approximately 100%. The obtained high molecular weight copolymer B-3 had a Mw of 100,000, a molecular weight distribution of 1.10, and an aromatic vinyl moiety content (styrene content) of 25% by mass.

Below, various chemicals used in Examples and Comparative Examples will be explained.
(Component A)
High molecular weight copolymer A-1: Production example 1-1
High molecular weight copolymer A-2: Production example 1-2
(Component B)
Low molecular weight copolymer B-1: Production example 2-1
Low molecular weight copolymer B-2: Production example 2-2
Low molecular weight copolymer B-3: Production example 2-3
(Component C) Plasticizer that does not contain a hetero element Plasticizer C: X-140 manufactured by Japan Energy (aromatic mineral oil, liquid at room temperature (approximately 25°C) (Component D) Plasticizer that contains a hetero element Plasticizer D : BXAN (bis[2-(2-butoxyethoxy)ethyl]adipate) manufactured by Daihachi Kagaku Kogyo Co., Ltd., liquid at room temperature (approximately 25°C))
(Component E) Resin with Tg of 50°C or higher Resin E-1: G-90 (Coumaron indene resin, Tg: 50°C, liquid at 160°C) manufactured by Ninuri Kagaku Co., Ltd.
Resin E-2: TO125 manufactured by Yasuhara Chemical Co., Ltd. (styrene terpene resin, Tg: liquid at 65°C and 160°C)
(Other ingredients)
Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 111 m ² /g)
Stearic acid: Bead stearic acid manufactured by NOF Corporation. Camellia Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Metal Mining Co., Ltd. Vulcanization accelerator: Soccinol D manufactured by Sumitomo Chemical Co., Ltd.
Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

<Examples and comparative examples>
According to the formulation contents shown in Tables 1 and 2, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. obtained (Banbury process). Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition (open roll process). .
The obtained unvulcanized rubber composition was vulcanized at 150° C. for 30 minutes to obtain a vulcanized rubber composition.
Further, the unvulcanized rubber composition is molded into the shape of a cap tread and a base tread, and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and vulcanized at 150° C. for 30 minutes. A test tire was obtained.

The obtained unvulcanized rubber composition, vulcanized rubber composition, and test tire were evaluated by the following test method, and the results are shown in Tables 2 and 3.

(Rubber adhesion)
The degree of adhesion of the rubber in the Banbury process and the open roll process was evaluated in three grades based on the following criteria.
○: Almost no adhesion, no problem.
△: There is close contact, and it takes time to discharge the rubber compared to "○".
×: Poor adhesion, and it takes longer to discharge the rubber than in “△”.

(Workability index)
The Mooney viscosity of the unvulcanized rubber composition was measured at 100° C. according to JIS K6300 (1994), and expressed as an index with Comparative Example 1 set as 100. The larger the index, the lower the Mooney viscosity and the better the processability.

(tanδ/E ^* x1000)
A rectangular test piece with a width of 2 mm and a length of 40 mm was punched out from the above vulcanized rubber composition, and using a viscoelasticity measuring device (manufactured by Uejima Seisakusho Co., Ltd.), the initial strain was 0.5% and the dynamic strain was 2.5%. %, frequency of 10 Hz, and temperature of 50° C., tan δ and E ^* [MPa] were measured, and tan δ/E ^* x1000 was calculated.

(peak temperature of tanδ)
A rectangular test piece with a width of 2 mm and a length of 40 mm was punched out from the above vulcanized rubber composition, and using a viscoelasticity measuring device (manufactured by Uejima Seisakusho Co., Ltd.), the initial strain was 0.5% and the dynamic strain was 2.5%. %, frequency of 10 Hz, and temperature increase rate of 1° C./min, tan δ was measured in the temperature range from −50° C. to 150° C., and a temperature curve of tan δ was obtained. The peak temperature of tan δ was calculated from the temperature curve.

(Brittleness of tire surface)
The surface of the test tire was visually observed, and if there were any cracks on the surface, it was determined that the tire had become brittle. It should be noted that because tires with embrittlement cannot be driven on actual vehicles, the following tire evaluations were conducted only on tires without embrittlement.

(Peeling of tread upper layer (cap tread))
The above test tire was cut to create a tire section for observation, and the state of peeling of the upper layer of the tread was visually confirmed. Note that because tires with peeling cannot be driven on actual vehicles, the following tire evaluation was conducted only on tires with no peeling.

(Grip performance)
Using the above test tires, actual vehicle driving was carried out on a test course with a dry asphalt road surface. The stability of the steering control at that time was evaluated by a test driver using the following criteria, and expressed as an index with Comparative Example 1 set as 100. The larger the value, the better the grip performance.
Initial grip 1st lap lap time (index)
Mid-term grip 6th lap lap time (index)
Late grip 10th lap lap lime (index)
Absolute grip index (index average)

(wear resistance)
Using the above test tires, actual vehicle driving was performed on a test course with a dry asphalt road surface. The amount of remaining groove in the tire tread rubber at that time was measured and expressed as an index with Comparative Example 1 set as 100. The larger the value, the larger the amount of remaining grooves and the better the wear resistance.

From Tables 2 and 3, both grip performance and abrasion resistance of the example were better than that of Comparative Example 1, while Comparative Examples 2 and onwards were inferior to Comparative Example 1 in any of the items. .
Furthermore, in the examples, neither embrittlement of the tire surface nor peeling of the upper layer of the tread was observed.

Claims (10)

A tire tread having a two-layer structure in which an upper layer rubber composition and a lower layer rubber composition are laminated,
The tan δ peak temperature at a dynamic strain of 2.5% of the upper layer rubber composition is 5° C. or less,
tan δ and E ^* [MPa] of the upper layer rubber composition and the lower layer rubber composition at a dynamic strain of 2.5% and a temperature of 50° C. satisfy the following formulas (1) and (2),
In the upper layer rubber composition, the content of at least one plasticizer selected from the group consisting of vegetable oil, ether plasticizer, ester plasticizer, and phosphate ester plasticizer is 100 parts by mass of the rubber component. 5 parts by mass or more of tire tread.
(1) (tan δ/E ^* of upper layer rubber composition)×1000≧100
(2) tan δ/E ^* of upper layer rubber composition > tan δ/E ^* of lower layer rubber composition The tire tread according to claim 1, wherein the content of mineral oil in the lower layer rubber composition is 5 parts by mass or more based on 100 parts by mass of the rubber component. 1. In the upper rubber composition, the content of a low molecular weight polymer having a weight average molecular weight of 300 to 100,000 as measured by gel permeation chromatography is 5 parts by mass or more based on 100 parts by mass of the rubber component. The tire tread described in 2. The tire tread according to claim 3, wherein the monomer component of the low molecular weight polymer is at least one of an aromatic vinyl monomer and its derivatives, and a conjugated diene monomer and its derivatives. The upper layer rubber composition contains a high molecular weight polymer having a weight average molecular weight of 150,000 or more as measured by gel permeation chromatography,
In the upper layer rubber composition, the content of the aromatic vinyl moiety in the high molecular weight polymer and the content of the aromatic vinyl moiety in the low molecular weight polymer satisfy the following formula (3). tire tread.
(3) Content of aromatic vinyl moieties in high molecular weight polymer - Content of aromatic vinyl moieties in low molecular weight polymer ≦20 [mass%] In the upper layer rubber composition, the content of the resin having a glass transition temperature of 50° C. or higher as measured by differential scanning calorimetry is 5 parts by mass or more based on 100 parts by mass of the rubber component. Tire tread as described in either. The tire tread according to any one of claims 1 to 6 , wherein in the upper layer rubber composition, the content of a component that is liquid at 160° C. or higher is 70 parts by mass or more based on 100 parts by mass of the rubber component. The tire tread according to any one of claims 1 to 7 , wherein the content of the filler in the upper layer rubber composition is 40 parts by mass or more based on 100 parts by mass of the rubber component. A tire comprising the tire tread according to any one of claims 1 to 8 . The tire according to claim 9 , which is a high performance tire.